Design of Super-Paramagnetic Core-Shell Nanoparticles for Enhanced Performance of Inverted Polymer Solar Cells.

PubMed

Jaramillo, Johny; Boudouris, Bryan W; Barrero, César A; Jaramillo, Franklin

2015-11-18

Controlling the nature and transfer of excited states in organic photovoltaic (OPV) devices is of critical concern due to the fact that exciton transport and separation can dictate the final performance of the system. One effective method to accomplish improved charge separation in organic electronic materials is to control the spin state of the photogenerated charge-carrying species. To this end, nanoparticles with unique iron oxide (Fe3O4) cores and zinc oxide (ZnO) shells were synthesized in a controlled manner. Then, the structural and magnetic properties of these core-shell nanoparticles (Fe3O4@ZnO) were tuned to ensure superior performance when they were incorporated into the active layers of OPV devices. Specifically, small loadings of the core-shell nanoparticles were blended with the previously well-characterized OPV active layer of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Upon addition of the core-shell nanoparticles, the performance of the OPV devices was increased up to 25% relative to P3HT-PCBM active layer devices that contained no nanoparticles; this increase was a direct result of an increase in the short-circuit current densities of the devices. Furthermore, it was demonstrated that the increase in photocurrent was not due to enhanced absorption of the active layer due to the presence of the Fe3O4@ZnO core-shell nanoparticles. In fact, this increase in device performance occurred because of the presence of the superparamagnetic Fe3O4 in the core of the nanoparticles as incorporation of ZnO only nanoparticles did not alter the device performance. Importantly, however, the ZnO shell of the nanoparticles mitigated the negative optical effect of Fe3O4, which have been observed previously. This allowed the core-shell nanoparticles to outperform bare Fe3O4 nanoparticles when the single-layer nanoparticles were incorporated into the active layer of OPV devices. As such, the new materials described here present a tangible pathway toward the development of enhanced design schemes for inorganic nanoparticles such that magnetic and energy control pathways can be tailored for flexible electronic applications.

Platform for efficient switching between multiple devices in the intensive care unit.

PubMed

De Backere, F; Vanhove, T; Dejonghe, E; Feys, M; Herinckx, T; Vankelecom, J; Decruyenaere, J; De Turck, F

2015-01-01

This article is part of the Focus Theme of METHODS of Information in Medicine on "Managing Interoperability and Complexity in Health Systems". Handheld computers, such as tablets and smartphones, are becoming more and more accessible in the clinical care setting and in Intensive Care Units (ICUs). By making the most useful and appropriate data available on multiple devices and facilitate the switching between those devices, staff members can efficiently integrate them in their workflow, allowing for faster and more accurate decisions. This paper addresses the design of a platform for the efficient switching between multiple devices in the ICU. The key functionalities of the platform are the integration of the platform into the workflow of the medical staff and providing tailored and dynamic information at the point of care. The platform is designed based on a 3-tier architecture with a focus on extensibility, scalability and an optimal user experience. After identification to a device using Near Field Communication (NFC), the appropriate medical information will be shown on the selected device. The visualization of the data is adapted to the type of the device. A web-centric approach was used to enable extensibility and portability. A prototype of the platform was thoroughly evaluated. The scalability, performance and user experience were evaluated. Performance tests show that the response time of the system scales linearly with the amount of data. Measurements with up to 20 devices have shown no performance loss due to the concurrent use of multiple devices. The platform provides a scalable and responsive solution to enable the efficient switching between multiple devices. Due to the web-centric approach new devices can easily be integrated. The performance and scalability of the platform have been evaluated and it was shown that the response time and scalability of the platform was within an acceptable range.

Metalorganic chemical vapor deposition of AlGaAs and InGaP heterojunction bipolar transistors

NASA Astrophysics Data System (ADS)

Pan, N.; Welser, R. E.; Lutz, C. R.; DeLuca, P. M.; Han, B.; Hong, K.

2001-05-01

Heterojunction bipolar transistors (HBT) are now beginning to be widely incorporated as power amplifiers, laser drivers, multiplexers, clock data recovery circuits, as well as transimpedance and broadband amplifiers in high performance millimeter wave circuits (MMICs). The increasing acceptance of this device is principally due to advancements in metalorganic chemical vapor deposition (MOCVD), device processing, and circuit design technologies. Many of the DC electrical characteristics of large area devices can be directly correlated to the DC performance of small area RF devices. A precise understanding of the growth parameters and their relationship to device characteristics is critical for ensuring the high degree of reproducibility required for low cost high-yield volume manufacturing. Significant improvements in the understanding of the MOCVD growth process have been realized through the implementation of statistical process control on the key HBT device parameters. This tool has been successfully used to maintain the high quality of the device characteristics in high-volume production of 4″ GaAs-based HBTs. There is a growing demand to migrate towards 6″ diameter wafer size due to the potential cost reductions and increased volume production that can be realized. Preliminary results, indicating good heterostructure layer characteristics, demonstrate the feasibility of 6″ InGaP-based HBT devices.

Cardiac implantable electronic device infection due to Mycobacterium species: a case report and review of the literature.

PubMed

Al-Ghamdi, Bandar; Widaa, Hassan El; Shahid, Maie Al; Aladmawi, Mohammed; Alotaibi, Jawaher; Sanei, Aly Al; Halim, Magid

2016-08-24

Infection of cardiac implantable electronic devices is a serious cardiovascular disease and it is associated with a high mortality. Mycobacterium species may rarely cause cardiac implantable electronic devices infection. We are reporting a case of miliary tuberculosis in an Arab patient with dilated cardiomyopathy and a cardiac resynchronization therapy-defibrillator device that was complicated with infection of his cardiac resynchronization therapy-defibrillator device. To our knowledge, this is the third case in the literature with such a presentation and all patients died during the course of treatment. This underscores the importance of early diagnosis and management. We also performed a literature review of reported cases of cardiac implantable electronic devices infection related to Mycobacterium species. Cardiac implantable electronic devices infection due to Mycobacterium species is an uncommon but a well-known entity. Early diagnosis and prompt management may result in a better outcome.

Plasmon Enhanced Hetero-Junction Solar Cell

NASA Astrophysics Data System (ADS)

Long, Gen; Ching, Levine; Sadoqi, Mostafa; Xu, Huizhong

2015-03-01

Here we report a systematic study of plasmon-enhanced hetero-junction solar cells made of colloidal quantum dots (PbS) and nanowires (ZnO), with/without metal nanoparticles (Au). The structure of solar cell devices was characterized by AFM, SEM and profilometer, etc. The power conversion efficiencies of solar cell devices were characterized by solar simulator (OAI TriSOL, AM1.5G Class AAA). The enhancement in the photocurrent due to introduction of metal nanoparticles was obvious. We believe this is due to the plasmonic effect from the metal nanoparticles. The correlation between surface roughness, film uniformity and device performance was also studied.

Correlating Microstructure and Optoelectronic Performance of Carbon-Based Nanomaterials

NASA Astrophysics Data System (ADS)

Rochford, Caitlin

There is a great deal of interest in carbon nanostructures such as graphene and various forms of carbon nanotubes due to their exceptional physical, electronic, and optical properties. Many technological applications have been proposed for these nanostructures, but despite the promise many carbon nanostructure-based optoelectronic devices fail to compete with their conventional counterparts. This is often due in large part to a non-optimized material or device microstructure. Factors such as crystallinity, contact quality, defect structure, and device configuration can critically affect device performance due to the high sensitivity and extreme surface to volume ratio of carbon nanostructures. In order for the exceptional intrinsic properties of the nanostructures to be exploited, a clear understanding of the microstructure and its correlation with device-relevant optoelectronic properties is needed. This dissertation presents four projects which demonstrate this principle. First, a TiO 2-coated carbon nanofiber is studied in order to optimize its structure for use in a novel dye-sensitized solar cell. Second, the electrode configuration of an individual multiwall carbon nanotube infrared sensor is investigated in order to surpass the limitations of disordered nanotube film-based infrared sensors. Third, the properties of defect structures in large area transferred graphene films grown by chemical vapor deposition are correlated with carrier diffusion in order to understand the film's low mobility compared to exfoliated graphene. Fourth, the effect of deposition conditions on graphene-metal contact was studied with the goal of achieving sufficiently transparent contacts for investigation of the superconducting proximity effect. All four projects highlight the unique properties of carbon nanostructures as well as the need to correlate their optoelectronic properties with microstructural details in order to achieve the desired device performance.

A New Device for Alveolar Bone Transportation

PubMed Central

Vega, Omar; Pérez, Daniel; Páramo, Viviana; Falcón, Jocelyn

2011-01-01

We present a retrospective review of a new technique for the transportation of alveolar bone using a Hyrax device modified by the principal author (O.A.V.). There were seven patients (five males and two females), including five patients with cleft palate and lip diagnosis, one patient with a high-speed gunshot wound, and one patient with facial trauma sequel due to mandibular fracture. They were all treated with an alveolar bone transportation technique (ABT) through the use of the modified Hyrax device (VEGAX). Before surgery, distraction osteogenesis of the bifocal type was performed on four patients, and the trifocal type was performed on the other three patients. However, in one case, direct dental anchorage was not used, only orthodontic appliances. In all the cases, new bone formation and gingival tissue around the defect were obtained, posterior to the alveolar distraction process; no complications were observed in any patient. In one case, two teeth involved in the disk of the ABT were extracted, due to a previous condition of periodontal disease. The alveolar bone transport with the VEGAX device is an accessible technique for almost every patient with alveolar defects due to diverse causes. In all the presented cases, predictability and success were demonstrated. PMID:22655120

Advanced analytical modeling of double-gate Tunnel-FETs - A performance evaluation

NASA Astrophysics Data System (ADS)

Graef, Michael; Hosenfeld, Fabian; Horst, Fabian; Farokhnejad, Atieh; Hain, Franziska; Iñíguez, Benjamín; Kloes, Alexander

2018-03-01

The Tunnel-FET is one of the most promising devices to be the successor of the standard MOSFET due to its alternative current transport mechanism, which allows a smaller subthreshold slope than the physically limited 60 mV/dec of the MOSFET. Recently fabricated devices show smaller slopes already but mostly not over multiple decades of the current transfer characteristics. In this paper the performance limiting effects, occurring during the fabrication process of the device, such as doping profiles and midgap traps are analyzed by physics-based analytical models and their performance limiting abilities are determined. Additionally, performance enhancing possibilities, such as hetero-structures and ambipolarity improvements are introduced and discussed. An extensive double-gate n-Tunnel-FET model is presented, which meets the versatile device requirements and shows a good fit with TCAD simulations and measurement data.

Error reduction by combining strapdown inertial measurement units in a baseball stitch

NASA Astrophysics Data System (ADS)

Tracy, Leah

A poor musical performance is rarely due to an inferior instrument. When a device is under performing, the temptation is to find a better device or a new technology to achieve performance objectives; however, another solution may be improving how existing technology is used through a better understanding of device characteristics, i.e., learning to play the instrument better. This thesis explores improving position and attitude estimates of inertial navigation systems (INS) through an understanding of inertial sensor errors, manipulating inertial measurement units (IMUs) to reduce that error and multisensor fusion of multiple IMUs to reduce error in a GPS denied environment.

Effects of Various Passivation Layers on Electrical Properties of Multilayer MoS₂ Transistors.

PubMed

Ma, Jiyeon; Yoo, Geonwook

2018-09-01

So far many of research on transition metal dichalcogenides (TMDCs) are based on a bottomgate device structure due to difficulty with depositing a dielectric film on top of TMDs channel layer. In this work, we study different effects of various passivation layers on electrical properties of multilayer MoS2 transistors: spin-coated CYTOP, SU-8, and thermal evaporated MoOX. The SU-8 passivation layer alters device performance least significantly, and MoOX induces positive threshold voltage shift of ~8.0 V due to charge depletion at the interface, and the device with CYTOP layer exhibits decreased field-effect mobility by ~50% due to electric dipole field effect of C-F bonds in the end groups. Our results imply that electrical properties of the multilayer MoS2 transistors can be modulated using a passivation layer, and therefore a proper passivation layer should be considered for MoS2 device structures.

Characterization of crosstalk in stereoscopic display devices.

PubMed

Zafar, Fahad; Badano, Aldo

2014-12-01

Many different types of stereoscopic display devices are used for commercial and research applications. Stereoscopic displays offer the potential to improve performance in detection tasks for medical imaging diagnostic systems. Due to the variety of stereoscopic display technologies, it remains unclear how these compare with each other for detection and estimation tasks. Different stereo devices have different performance trade-offs due to their display characteristics. Among them, crosstalk is known to affect observer perception of 3D content and might affect detection performance. We measured and report the detailed luminance output and crosstalk characteristics for three different types of stereoscopic display devices. We recorded the effect of other issues on recorded luminance profiles such as viewing angle, use of different eye wear, and screen location. Our results show that the crosstalk signature for viewing 3D content can vary considerably when using different types of 3D glasses for active stereo displays. We also show that significant differences are present in crosstalk signatures when varying the viewing angle from 0 degrees to 20 degrees for a stereo mirror 3D display device. Our detailed characterization can help emulate the effect of crosstalk in conducting computational observer image quality assessment evaluations that minimize costly and time-consuming human reader studies.

Analysis of electrical characteristics and proposal of design guide for ultra-scaled nanoplate vertical FET and 6T-SRAM

NASA Astrophysics Data System (ADS)

Seo, Youngsoo; Kim, Shinkeun; Ko, Kyul; Woo, Changbeom; Kim, Minsoo; Lee, Jangkyu; Kang, Myounggon; Shin, Hyungcheol

2018-02-01

In this paper, electrical characteristics of gate-all-around (GAA) nanoplate (NP) vertical FET (VFET) were analyzed for single transistor and 6T-SRAM cell through 3D technology computer-aided design (TCAD) simulation. In VFET, gate and extension lengths are not limited by the area of device because theses lengths are vertically located. The height of NP is assumed in 40 nm considering device fabrication method (top-down approach). According to the sizes of devices, we analyzed the performances of device such as total resistance, capacitance, intrinsic gate delay, sub-threshold swing (S.S), drain-induced barrier lowering (DIBL) and static noise margin (SNM). As the gate length becomes larger, the resistance should be smaller because the total height of NP is fixed in 40 nm. Also, when the channel thickness becomes thicker, the total resistance becomes smaller since the sheet resistances of channel and extension become smaller and the contact resistance becomes smaller due to the increasing contact area. In addition, as the length of channel pitch increases, the parasitic capacitance comes to be larger due to the increasing area of gate-drain and gate-source. The performance of RC delay is best in the shortest gate length (12 nm), the thickest channel (6 nm) and the shortest channel pitch (17 nm) owing to the reduced resistance and parasitic capacitance. However, the other performances such as DIBL, S.S, on/off ratio and SNM are worst because the short channel effect is highest in this situation. Also, we investigated the performance of the multi-channel device. As the number of channels increases, the performance of device and the reliability of SRAM improve because of reduced contact resistance, increased gate dimension and multi-channel compensation effect.

High Performance Polymer Memory and Its Formation

DTIC Science & Technology

2007-04-26

the retention time of the device was performed to estimate the barrier height of the charge trap . The activation energy was approximated to be about...characteristics and presented a model to explain the mechanism of electrical switching in the device. By exploiting an electric-field induced charge transfer...electrical current in the high conductivity state would be due to some temperature-independent charge tunneling processes. The IV curves could be

Restorative effect of oxygen annealing on device performance in HfIZO thin-film transistors

NASA Astrophysics Data System (ADS)

Ha, Tae-Jun

2015-03-01

Metal-oxide based thin-film transistors (oxide-TFTs) are very promising for use in next generation electronics such as transparent displays requiring high switching and driving performance. In this study, we demonstrate an optimized process to secure excellent device performance with a favorable shift of the threshold voltage toward 0V in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs by using post-treatment with oxygen annealing. This enhancement results from the improved interfacial characteristics between gate dielectric and semiconductor layers due to the reduction in the density of interfacial states related to oxygen vacancies afforded by oxygen annealing. The device statistics confirm the improvement in the device-to-device and run-to-run uniformity. We also report on the photo-induced stability in such oxide-TFTs against long-term UV irradiation, which is significant for transparent displays.

The effect of reactive ion etch (RIE) process conditions on ReRAM device performance

NASA Astrophysics Data System (ADS)

Beckmann, K.; Holt, J.; Olin-Ammentorp, W.; Alamgir, Z.; Van Nostrand, J.; Cady, N. C.

2017-09-01

The recent surge of research on resistive random access memory (ReRAM) devices has resulted in a wealth of different materials and fabrication approaches. In this work, we describe the performance implications of utilizing a reactive ion etch (RIE) based process to fabricate HfO2 based ReRAM devices, versus a more unconventional shadow mask fabrication approach. The work is the result of an effort to increase device yield and reduce individual device size. Our results show that choice of RIE etch gas (SF6 versus CF4) is critical for defining the post-etch device profile (cross-section), and for tuning the removal of metal layers used as bottom electrodes in the ReRAM device stack. We have shown that etch conditions leading to a tapered profile for the device stack cause poor electrical performance, likely due to metal re-deposition during etching, and damage to the switching layer. These devices exhibit nonlinear I-V during the low resistive state, but this could be improved to linear behavior once a near-vertical etch profile was achieved. Device stacks with vertical etch profiles also showed an increase in forming voltage, reduced switching variability and increased endurance.

Distributed processing for features improvement in real-time portable medical devices.

PubMed

Mercado, Erwin John Saavedra

2008-01-01

Portable biomedical devices are being developed and incorporated in daily life. Nevertheless, their standalone capacity is diminished due to the lack of processing power required to face such duties as for example, signal artifacts robustness in EKG monitor devices. The following paper presents a multiprocessor architecture made from simple microcontrollers to provide an increase in processing performance, power consumption efficiency and lower cost.

Improving performance of armchair graphene nanoribbon field effect transistors via boron nitride doping

NASA Astrophysics Data System (ADS)

Goharrizi, A. Yazdanpanah; Sanaeepur, M.; Sharifi, M. J.

2015-09-01

Device performance of 10 nm length armchair graphene nanoribbon field effect transistors with 1.5 nm and 4 nm width (13 and 33 atoms in width respectively) are compared in terms of Ion /Ioff , trans-conductance, and sub-threshold swing. While narrow devices suffer from edge roughness wider devices are subject to more substrate surface roughness and reduced bandgap. Boron Nitride doping is employed to compensate reduced bandgap in wider devices. Simultaneous effects of edge and substrate surface roughness are considered. Results show that in the presence of both the edge and substrate surface roughness the 4 nm wide device with boron nitride doping shows improved performance with respect to the 1.5 nm one (both of which incorporate the same bandgap AGNR as channel material). Electronic simulations are performed via NEGF method along with tight-binding Hamiltonian. Edge and surface roughness are created by means of one and two dimensional auto correlation functions respectively. Electronic characteristics are averaged over a large number of devices due to statistic nature of both the edge and surface roughness.

The roles of carrier concentration and interface, bulk, and grain-boundary recombination for 25% efficient CdTe solar cells

DOE PAGES

Kanevce, A.; Reese, Matthew O.; Barnes, T. M.; ...

2017-06-06

CdTe devices have reached efficiencies of 22% due to continuing improvements in bulk material properties, including minority carrier lifetime. Device modeling has helped to guide these device improvements by quantifying the impacts of material properties and different device designs on device performance. One of the barriers to truly predictive device modeling is the interdependence of these material properties. For example, interfaces become more critical as bulk properties, particularly, hole density and carrier lifetime, increase. We present device-modeling analyses that describe the effects of recombination at the interfaces and grain boundaries as lifetime and doping of the CdTe layer change. Themore » doping and lifetime should be priorities for maximizing open-circuit voltage (V oc) and efficiency improvements. However, interface and grain boundary recombination become bottlenecks for device performance at increased lifetime and doping levels. In conclusion, this work quantifies and discusses these emerging challenges for next-generation CdTe device efficiency.« less

Regulatory science based approach in development of novel medical devices.

PubMed

Sakuma, Ichiro

2015-08-01

For development rational evaluation method for medical devices' safety and efficacy, regulatory science studies are important. Studies on regulatory affairs related to a medical device under development should be conducted as well as its technological development. Clinical performance of a medical device is influenced by performance of the device, medical doctors' skill, pathological condition of a patient, and so on. Thus it is sometimes difficult to demonstrate superiority of the device in terms of clinical outcome although its efficacy as a medical device is accepted. Setting of appropriate end points is required to evaluate a medical device appropriately. Risk assessment and risk management are the basis of medical device safety assurance. In case of medical device software, there are difficulties in identifying the risk due to its complexity of user environment and different design and manufacturing procedure compared with conventional hardware based medical devices. Recent technological advancement such as information and communication technologies (ICT) for medical devices and wireless network has raised new issue on risk management: cybersecurity. We have to watch closely the progress of safety standard development.

Interdigitated electrode (IDE) for porcine detection based on titanium dioxide (TiO2) thin films

NASA Astrophysics Data System (ADS)

Nordin, N.; Hashim, U.; Azizah, N.

2016-07-01

Interdigited Electrode (IDE) porcine detection can be accomplished to authenticate the halal issue that has been a concern to Muslim not only in Malaysia but all around the world. The method used is photolithography that used the p-type photoresist on the spin coater with 2500 rpm. Bare IDEs device is deposited with Titanium Dioxide (TiO2) to improve the performance of the device. The result indicates that current-voltage (I-V) measurement of porcine probe line slightly above porcine target due to negative charges repelled each other. The IDE device can detect the porcine presence in food as lowest as 1.0 µM. Better performance of the device can be achieved with the replacement of gold deposited to trigger more sensitivity of the device.

Towards Scalable Graph Computation on Mobile Devices.

PubMed

Chen, Yiqi; Lin, Zhiyuan; Pienta, Robert; Kahng, Minsuk; Chau, Duen Horng

2014-10-01

Mobile devices have become increasingly central to our everyday activities, due to their portability, multi-touch capabilities, and ever-improving computational power. Such attractive features have spurred research interest in leveraging mobile devices for computation. We explore a novel approach that aims to use a single mobile device to perform scalable graph computation on large graphs that do not fit in the device's limited main memory, opening up the possibility of performing on-device analysis of large datasets, without relying on the cloud. Based on the familiar memory mapping capability provided by today's mobile operating systems, our approach to scale up computation is powerful and intentionally kept simple to maximize its applicability across the iOS and Android platforms. Our experiments demonstrate that an iPad mini can perform fast computation on large real graphs with as many as 272 million edges (Google+ social graph), at a speed that is only a few times slower than a 13″ Macbook Pro. Through creating a real world iOS app with this technique, we demonstrate the strong potential application for scalable graph computation on a single mobile device using our approach.

Towards Scalable Graph Computation on Mobile Devices

PubMed Central

Chen, Yiqi; Lin, Zhiyuan; Pienta, Robert; Kahng, Minsuk; Chau, Duen Horng

2015-01-01

Mobile devices have become increasingly central to our everyday activities, due to their portability, multi-touch capabilities, and ever-improving computational power. Such attractive features have spurred research interest in leveraging mobile devices for computation. We explore a novel approach that aims to use a single mobile device to perform scalable graph computation on large graphs that do not fit in the device's limited main memory, opening up the possibility of performing on-device analysis of large datasets, without relying on the cloud. Based on the familiar memory mapping capability provided by today's mobile operating systems, our approach to scale up computation is powerful and intentionally kept simple to maximize its applicability across the iOS and Android platforms. Our experiments demonstrate that an iPad mini can perform fast computation on large real graphs with as many as 272 million edges (Google+ social graph), at a speed that is only a few times slower than a 13″ Macbook Pro. Through creating a real world iOS app with this technique, we demonstrate the strong potential application for scalable graph computation on a single mobile device using our approach. PMID:25859564

Temperature dependent simulation of diamond depleted Schottky PIN diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hathwar, Raghuraj; Dutta, Maitreya; Chowdhury, Srabanti

2016-06-14

Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco{sup ®} Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond.more » The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures.« less

Inkjet-printing of non-volatile organic resistive devices and crossbar array structures

NASA Astrophysics Data System (ADS)

Sax, Stefan; Nau, Sebastian; Popovic, Karl; Bluemel, Alexander; Klug, Andreas; List-Kratochvil, Emil J. W.

2015-09-01

Due to the increasing demand for storage capacity in various electronic gadgets like mobile phones or tablets, new types of non-volatile memory devices have gained a lot of attention over the last few years. Especially multilevel conductance switching elements based on organic semiconductors are of great interest due to their relatively simple device architecture and their small feature size. Since organic semiconductors combine the electronic properties of inorganic materials with the mechanical characteristics of polymers, this class of materials is suitable for solution based large area device preparation techniques. Consequently, inkjet based deposition techniques are highly capable of facing preparation related challenges. By gradually replacing the evaporated electrodes with inkjet printed silver, the preparation related influence onto device performance parameters such as the ON/OFF ratio was investigated with IV measurements and high resolution transmission electron microscopy. Due to the electrode surface roughness the solvent load during the printing of the top electrode as well as organic layer inhomogeneity's the utilization in array applications is hampered. As a prototypical example a 1diode-1resistor element and a 2×2 subarray from 5×5 array matrix were fully characterized demonstrating the versatility of inkjet printing for device preparation.

Notebook input devices put to the age test: the usability of trackpoint and touchpad for middle-aged adults.

PubMed

Armbrüster, C; Sutter, C; Ziefle, M

2007-03-01

In two experiments, the usability of input devices integrated into computer notebooks was under study. The most common input devices, touchpad (experiment 1) and trackpoint (experiment 2) were examined. So far, the evaluation of mobile input devices has been restricted to younger users. However, due to ongoing demographic change, the main target group of mobile devices will be older users. Therefore, the present study focused on ageing effects. A total of 14 middle-aged (40-65 years) and 20 younger (20-32 years) users were compared regarding speed and accuracy of cursor control in a point-click and a point-drag-drop task. Moreover, the effects of training were addressed by examining the performance increase over time. In total, 640 trials per task and input device were executed. The results show that ageing is a central factor to be considered in input device design. Middle-aged users were significantly slower than younger users when executing the different tasks. Over time, a significant training effect was observed for both devices and both age groups, although the benefit of training was greater for the middle-aged group. Generally, the touchpad performance was higher than the trackpoint performance in both age groups, but the age-related performance decrements were less distinct when using the touchpad.

ECG R-R peak detection on mobile phones.

PubMed

Sufi, F; Fang, Q; Cosic, I

2007-01-01

Mobile phones have become an integral part of modern life. Due to the ever increasing processing power, mobile phones are rapidly expanding its arena from a sole device of telecommunication to organizer, calculator, gaming device, web browser, music player, audio/video recording device, navigator etc. The processing power of modern mobile phones has been utilized by many innovative purposes. In this paper, we are proposing the utilization of mobile phones for monitoring and analysis of biosignal. The computation performed inside the mobile phone's processor will now be exploited for healthcare delivery. We performed literature review on RR interval detection from ECG and selected few PC based algorithms. Then, three of those existing RR interval detection algorithms were programmed on Java platform. Performance monitoring and comparison studies were carried out on three different mobile devices to determine their application on a realtime telemonitoring scenario.

Hybrid thermionic-photovoltaic converter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datas, A.

2016-04-04

A conceptual device for the direct conversion of heat into electricity is presented. This concept hybridizes thermionic (TI) and thermophotovoltaic (TPV) energy conversion in a single thermionic-photovoltaic (TIPV) solid-state device. This device transforms into electricity both the electron and photon fluxes emitted by an incandescent surface. This letter presents an idealized analysis of this device in order to determine its theoretical potential. According to this analysis, the key advantage of this converter, with respect to either TPV or TI, is the higher power density in an extended temperature range. For low temperatures, TIPV performs like TPV due to the negligiblemore » electron flux. On the contrary, for high temperatures, TIPV performs like TI due to the great enhancement of the electron flux, which overshadows the photon flux contribution. At the intermediate temperatures, ∼1650 K in the case of this particular study, I show that the power density potential of TIPV converter is twice as great as that of TPV and TI. The greatest impact concerns applications in which the temperature varies in a relatively wide range, for which averaged power density enhancement above 500% is attainable.« less

Performance analysis of junction-less double Gate n-p-n impact ionization MOS transistor (JLDG n-IMOS)

NASA Astrophysics Data System (ADS)

Chauhan, Manvendra Singh; Chauhan, R. K.

2018-04-01

This paper demonstrates a Junction-less Double Gate n-p-n Impact ionization MOS transistor (JLDG n-IMOS) on a very light doped p-type silicon body. Device structure proposed in the paper is based on charge plasma concept. There is no metallurgical junctions in the proposed device and does not need any impurity doping to create the drain and source regions. Due to doping-less nature, the fabrication process is simple for JLDG n-IMOS. The double gate engineering in proposed device leads to reduction in avalanche breakdown via impact ionization, generating large number of carriers in drain-body junction, resulting high ION current, small IOFF current and great improvement in ION/IOFF ratio. The simulation and examination of the proposed device have been performed on ATLAS device simulatorsoftware.

Interdigitated electrode (IDE) for porcine detection based on titanium dioxide (TiO{sub 2}) thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nordin, N.; Azizah, N.; Hashim, U., E-mail: uda@unimap.edu.my

2016-07-06

Interdigited Electrode (IDE) porcine detection can be accomplished to authenticate the halal issue that has been a concern to Muslim not only in Malaysia but all around the world. The method used is photolithography that used the p-type photoresist on the spin coater with 2500 rpm. Bare IDEs device is deposited with Titanium Dioxide (TiO{sub 2}) to improve the performance of the device. The result indicates that current-voltage (I-V) measurement of porcine probe line slightly above porcine target due to negative charges repelled each other. The IDE device can detect the porcine presence in food as lowest as 1.0 µM.more » Better performance of the device can be achieved with the replacement of gold deposited to trigger more sensitivity of the device.« less

Rapid, all dry microfabrication of three-dimensional Co3O4/Pt nanonetworks for high-performance microsupercapacitors.

PubMed

Ma, Xinyu; Feng, Shuxuan; He, Liang; Yan, Mengyu; Tian, Xiaocong; Li, Yanxi; Tang, Chunjuan; Hong, Xufeng; Mai, Liqiang

2017-08-17

On-chip electrochemical energy storage devices have attracted growing attention due to the decreasing size of electronic devices. Various approaches have been applied for constructing the microsupercapacitors. However, the microfabrication of high-performance microsupercapacitors by conventional and fully compatible semiconductor microfabrication technologies is still a critical challenge. Herein, unique three-dimensional (3D) Co 3 O 4 nanonetwork microelectrodes formed by the interconnection of Co 3 O 4 nanosheets are constructed by controllable physical vapor deposition combined with rapid thermal annealing. This construction process is an all dry and rapid (≤5 minutes) procedure. Afterward, by sputtering highly electrically conductive Pt nanoparticles on the microelectrodes, the 3D Co 3 O 4 /Pt nanonetworks based microsupercapacitor is fabricated, showing a high volume capacitance (35.7 F cm -3 ) at a scan rate of 20 mV s -1 due to the unique interconnected structures, high electrical conductivity and high surface area of the microelectrodes. This microfabrication process is also used to construct high-performance flexible microsupercapacitors, and it can be applied in the construction of wearable devices. The proposed strategy is completely compatible with the current semiconductor microfabrication and shows great potential in the applications of the large-scale integration of micro/nano and wearable devices.

Permittivity and temperature effects on rectification performance of self-switching diodes with different geometrical structures using two-dimensional device simulator

NASA Astrophysics Data System (ADS)

Zakaria, N. F.; Kasjoo, S. R.; Zailan, Z.; Isa, M. M.; Taking, S.; Arshad, M. K. M.

2017-12-01

Characterization on an InGaAs-based self-switching diode (SSD) using technology computer aided design (TCAD) aimed for optimizing the electrical rectification performance of the device is reported. The rectifying performance is mainly contributed by a parameter known as the curvature coefficient which is derived from the current-voltage (I-V) behavior of the device. As such, the curvature coefficient of SSD was analyzed in this work, not only by varying the device's geometrical structure, but also by implementing different dielectric relative permittivity of the device's trenches, ranging from 1.0 to 10. Furthermore, the simulations were performed under temperature range of 300-600 K. The results showed that increased temperature degraded the SSD's rectifying performance due to increased reverse current which can deteriorate the nonlinearity of the device's I-V characteristic. Moreover, an improved curvature coefficient can be achieved using silicon dioxide (∼3.9) as the SSD trenches. The cut-off frequency of SSD with zero-bias curvature coefficient of ∼30 V-1 attained in this work was approximately 80 GHz, operating at unbiased condition. The results obtained can assist the design of SSD to efficiently operate as rectifiers at microwave and terahertz frequencies.

Electron and Phonon Engineered Nano- and Heterostructures for Increased Speed and Performance Enhancement of the Electronic and Optoelectronic Devices

DTIC Science & Technology

2011-01-01

doped source and drain form ohmic contact to metal silicide [2]-[6] due to their immunity to short channel effect [7]-[10]. In this project, we...investigated the hole mobility of SB Si NW. II. Device Fabrication Technology We prepared SiNWs by Au-catalyzed vapor-transport as described in Ref. [11...overlapping Ti/Au (70/50 nm) top gate is defined. Devices are characterized at this stage and also after annealing. III. Silicide Formation Our devices

Low-temperature phase transitions in a soluble oligoacene and their effect on device performance and stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ward, J. W.; Goetz, K. P.; Obaid, A.

The use of organic semiconductors in high-performance organic field-effect transistors requires a thorough understanding of the effects that processing conditions, thermal, and bias-stress history have on device operation. Here, we evaluate the temperature dependence of the electrical properties of transistors fabricated with 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene, a material that has attracted much attention recently due to its exceptional electrical properties. We have discovered a phase transition at T = 205 K and discuss its implications on device performance and stability. We examined the impact of this low-temperature phase transition on the thermodynamic, electrical, and structural properties of both single crystals and thin films of this material.more » Our results show that while the changes to the crystal structure are reversible, the induced thermal stress yields irreversible degradation of the devices.« less

An E-Book Hub Service Based on a Cloud Platform

ERIC Educational Resources Information Center

Cheng, Jinn-Shing; Huang, Echo; Lin, Chuan-Lang

2012-01-01

Due to the constant performance upgrades and regular price reductions of mobile devices in recent years, users are able to take advantage of the various devices to obtain digital content regardless of the limitations of time and place. The increasing use of e-books has stimulated new e-learning approaches. This research project developed an e-book…

Rational design of metal-organic electronic devices: A computational perspective

NASA Astrophysics Data System (ADS)

Chilukuri, Bhaskar

Organic and organometallic electronic materials continue to attract considerable attention among researchers due to their cost effectiveness, high flexibility, low temperature processing conditions and the continuous emergence of new semiconducting materials with tailored electronic properties. In addition, organic semiconductors can be used in a variety of important technological devices such as solar cells, field-effect transistors (FETs), flash memory, radio frequency identification (RFID) tags, light emitting diodes (LEDs), etc. However, organic materials have thus far not achieved the reliability and carrier mobility obtainable with inorganic silicon-based devices. Hence, there is a need for finding alternative electronic materials other than organic semiconductors to overcome the problems of inferior stability and performance. In this dissertation, I research the development of new transition metal based electronic materials which due to the presence of metal-metal, metal-pi, and pi-pi interactions may give rise to superior electronic and chemical properties versus their organic counterparts. Specifically, I performed computational modeling studies on platinum based charge transfer complexes and d 10 cyclo-[M(mu-L)]3 trimers (M = Ag, Au and L = monoanionic bidentate bridging (C/N~C/N) ligand). The research done is aimed to guide experimental chemists to make rational choices of metals, ligands, substituents in synthesizing novel organometallic electronic materials. Furthermore, the calculations presented here propose novel ways to tune the geometric, electronic, spectroscopic, and conduction properties in semiconducting materials. In addition to novel material development, electronic device performance can be improved by making a judicious choice of device components. I have studied the interfaces of a p-type metal-organic semiconductor viz cyclo-[Au(mu-Pz)] 3 trimer with metal electrodes at atomic and surface levels. This work was aimed to guide the device engineers to choose the appropriate metal electrodes considering the chemical interactions at the interface. Additionally, the calculations performed on the interfaces provided valuable insight into binding energies, charge redistribution, change in the energy levels, dipole formation, etc., which are important parameters to consider while fabricating an electronic device. The research described in this dissertation highlights the application of unique computational modeling methods at different levels of theory to guide the experimental chemists and device engineers toward a rational design of transition metal based electronic devices with low cost and high performance.

Recent advances in polymer solar cells: realization of high device performance by incorporating water/alcohol-soluble conjugated polymers as electrode buffer layer.

PubMed

He, Zhicai; Wu, Hongbin; Cao, Yong

2014-02-01

This Progress Report highlights recent advances in polymer solar cells with special attention focused on the recent rapid-growing progress in methods that use a thin layer of alcohol/water-soluble conjugated polymers as key component to obtain optimized device performance, but also discusses novel materials and device architectures made by major prestigious institutions in this field. We anticipate that due to drastic improvements in efficiency and easy utilization, this method opens up new opportunities for PSCs from various material systems to improve towards 10% efficiency, and many novel device structures will emerge as suitable architectures for developing the ideal roll-to-roll type processing of polymer-based solar cells. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficiency limits for photoelectrochemical water-splitting

DOE PAGES

Fountaine, Katherine T.; Lewerenz, Hans Joachim; Atwater, Harry A.

2016-12-02

Theoretical limiting efficiencies have a critical role in determining technological viability and expectations for device prototypes, as evidenced by the photovoltaics community’s focus on detailed balance. However, due to their multicomponent nature, photoelectrochemical devices do not have an equivalent analogue to detailed balance, and reported theoretical efficiency limits vary depending on the assumptions made. Here we introduce a unified framework for photoelectrochemical device performance through which all previous limiting efficiencies can be understood and contextualized. Ideal and experimentally realistic limiting efficiencies are presented, and then generalized using five representative parameters—semiconductor absorption fraction, external radiative efficiency, series resistance, shunt resistance andmore » catalytic exchange current density—to account for imperfect light absorption, charge transport and catalysis. Finally, we discuss the origin of deviations between the limits discussed herein and reported water-splitting efficiencies. This analysis provides insight into the primary factors that determine device performance and a powerful handle to improve device efficiency.« less

Velocity overshoot decay mechanisms in compound semiconductor field-effect transistors with a submicron characteristic length

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jyegal, Jang, E-mail: jjyegal@inu.ac.kr

Velocity overshoot is a critically important nonstationary effect utilized for the enhanced performance of submicron field-effect devices fabricated with high-electron-mobility compound semiconductors. However, the physical mechanisms of velocity overshoot decay dynamics in the devices are not known in detail. Therefore, a numerical analysis is conducted typically for a submicron GaAs metal-semiconductor field-effect transistor in order to elucidate the physical mechanisms. It is found that there exist three different mechanisms, depending on device bias conditions. Specifically, at large drain biases corresponding to the saturation drain current (dc) region, the velocity overshoot suddenly begins to drop very sensitively due to the onsetmore » of a rapid decrease of the momentum relaxation time, not the mobility, arising from the effect of velocity-randomizing intervalley scattering. It then continues to drop rapidly and decays completely by severe mobility reduction due to intervalley scattering. On the other hand, at small drain biases corresponding to the linear dc region, the velocity overshoot suddenly begins to drop very sensitively due to the onset of a rapid increase of thermal energy diffusion by electrons in the channel of the gate. It then continues to drop rapidly for a certain channel distance due to the increasing thermal energy diffusion effect, and later completely decays by a sharply decreasing electric field. Moreover, at drain biases close to a dc saturation voltage, the mechanism is a mixture of the above two bias conditions. It is suggested that a large secondary-valley energy separation is essential to increase the performance of submicron devices.« less

PIN architecture for ultrasensitive organic thin film photoconductors.

PubMed

Jin, Zhiwen; Wang, Jizheng

2014-06-17

Organic thin film photoconductors (OTFPs) are expected to have wide applications in the field of optical communications, artificial vision and biomedical sensing due to their great advantages of high flexibility and low-cost large-area fabrication. However, their performances are not satisfactory at present: the value of responsivity (R), the parameter that measures the sensitivity of a photoconductor to light, is below 1 AW(-1). We believe such poor performance is resulted from an intrinsic self-limited effect of present bare blend based device structure. Here we designed a PIN architecture for OTFPs, the PIN device exhibits a significantly improved high R value of 96.5 AW(-1). The PIN architecture and the performance the PIN device shows here should represent an important step in the development of OTFPs.

PIN architecture for ultrasensitive organic thin film photoconductors

PubMed Central

Jin, Zhiwen; Wang, Jizheng

2014-01-01

Organic thin film photoconductors (OTFPs) are expected to have wide applications in the field of optical communications, artificial vision and biomedical sensing due to their great advantages of high flexibility and low-cost large-area fabrication. However, their performances are not satisfactory at present: the value of responsivity (R), the parameter that measures the sensitivity of a photoconductor to light, is below 1 AW−1. We believe such poor performance is resulted from an intrinsic self-limited effect of present bare blend based device structure. Here we designed a PIN architecture for OTFPs, the PIN device exhibits a significantly improved high R value of 96.5 AW−1. The PIN architecture and the performance the PIN device shows here should represent an important step in the development of OTFPs. PMID:24936952

Development of low-cost technology for the next generation of high efficiency solar cells composed of earth abundant elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrawal, Rakesh

2014-09-28

The development of renewable, affordable, and environmentally conscious means of generating energy on a global scale represents a grand challenge of our time. Due to the “permanence” of radiation from the sun, solar energy promises to remain a viable and sustainable power source far into the future. Established single-junction photovoltaic technologies achieve high power conversion efficiencies (pce) near 20% but require complicated manufacturing processes that prohibit the marriage of large-scale throughput (e.g. on the GW scale), profitability, and quality control. Our approach to this problem begins with the synthesis of nanocrystals of semiconductor materials comprising earth abundant elements and characterizedmore » by material and optoelectronic properties ideal for photovoltaic applications, namely Cu2ZnSn(S,Se)4 (CZTSSe). Once synthesized, such nanocrystals are formulated into an ink, coated onto substrates, and processed into completed solar cells in such a way that enables scale-up to high throughput, roll-to-roll manufacturing processes. This project aimed to address the major limitation to CZTSSe solar cell pce’s – the low open-circuit voltage (Voc) reported throughout literature for devices comprised of this material. Throughout the project significant advancements have been made in fundamental understanding of the CZTSSe material and device limitations associated with this material system. Additionally, notable improvements have been made to our nanocrystal based processing technique to alleviate performance limitations due to the identified device limitations. Notably, (1) significant improvements have been made in reducing intra- and inter-nanoparticle heterogeneity, (2) improvements in device performance have been realized with novel cation substitution in Ge-alloyed CZTGeSSe absorbers, (3) systematic analysis of absorber sintering has been conducted to optimize the selenization process for large grain CZTSSe absorbers, (4) novel electrical characterization analysis techniques have been developed to identify significant limitations to traditional electrical characterization of CZTSSe devices, and (5) the developed electrical analysis techniques have been used to identify the role that band gap and electrostatic potential fluctuations have in limiting device performance for this material system. The device modeling and characterization of CZTSSe undertaken with this project have significant implications for the CZTSSe research community, as the identified limitations due to potential fluctuations are expected to be a performance limitation to high-efficiency CZTSSe devices fabricated from all current processing techniques. Additionally, improvements realized through enhanced absorber processing conditions to minimize nanoparticle and large-grain absorber heterogeneity are suggested to be beneficial processing improvements which should be applied to CZTSSe devices fabricated from all processing techniques. Ultimately, our research has indicated that improved performance for CZTSSe will be achieved through novel absorber processing which minimizes defect formation, elemental losses, secondary phase formation, and compositional uniformity in CZTSSe absorbers; we believe this novel absorber processing can be achieved through nanocrystal based processing of CZTSSe which is an active area of research at the conclusion of this award. While significant fundamental understanding of CZTSSe and the performance limitations associated with this material system, as well as notable improvements in the processing of nanocrystal based CZTSSe absorbers, have been achieved under this project, the limitation of two years of research funding towards our goals prevents further significant advancements directly identified through pce. improvements relative to those reported herein. As the characterization and modeling subtask of this project has been the main driving force for understanding device limitations, the conclusions of this analysis have just recently been applied to the processing of nanocrystal based CZTSSe absorbers -- with notable success. We expect the notable fundamental understanding of device limitations and absorber sintering achieved under this project will lead to significant improvements in device performance for CZTSSe devices in the near future for devices fabricated from a variety of processing techniques« less

Auger compositional depth profiling of the metal contact-TlBr interface

NASA Astrophysics Data System (ADS)

Nelson, A. J.; Swanberg, E. L.; Voss, L. F.; Graff, R. T.; Conway, A. M.; Nikolic, R. J.; Payne, S. A.; Kim, H.; Cirignano, L.; Shah, K.

2015-08-01

Degradation of room temperature operation of TlBr radiation detectors with time is thought to be due to electromigration of Tl and Br vacancies within the crystal as well as the metal contacts migrating into the TlBr crystal itself due to electrochemical reactions at the metal/TlBr interface. Scanning Auger electron spectroscopy (AES) in combination with sputter depth profiling was used to investigate the metal contact surface/interfacial structure on TlBr devices. Device-grade TlBr was polished and subjected to a 32% HCl etch to remove surface damage and create a TlBr1-xClx surface layer prior to metal contact deposition. Auger compositional depth profiling results reveal non-equilibrium interfacial diffusion after device operation in both air and N2 at ambient temperature. These results improve our understanding of contact/device degradation versus operating environment for further enhancing radiation detector performance.

Enhancing light emission in flexible AC electroluminescent devices by tetrapod-like zinc oxide whiskers.

PubMed

Wen, Li; Liu, Nishuang; Wang, Siliang; Zhang, Hui; Zhao, Wanqiu; Yang, Zhichun; Wang, Yumei; Su, Jun; Li, Luying; Long, Fei; Zou, Zhengguang; Gao, Yihua

2016-10-03

Flexible alternating current electroluminescent devices (ACEL) are more and more popular and widely used in liquid-crystal display back-lighting, large-scale architectural and decorative lighting due to their uniform light emission, low power consumption and high resolution. However, presently how to acquire high brightness under a certain voltage are confronted with challenges. Here, we demonstrate an electroluminescence (EL) enhancing strategy that tetrapod-like ZnO whiskers (T-ZnOw) are added into the bottom electrode of carbon nanotubes (CNTs) instead of phosphor layer in flexible ACEL devices emitting blue, green and orange lights, and the brightness is greatly enhanced due to the coupling between the T-ZnOw and ZnS phosphor dispersed in the flexible polydimethylsiloxane (PDMS) layer. This strategy provides a new routine for the development of high performance, flexible and large-area ACEL devices.

NASA Flexible Screen Propellant Management Device (PMD) Demonstration With Cryogenic Liquid

NASA Technical Reports Server (NTRS)

Wollen, Mark; Bakke, Victor; Baker, James

2012-01-01

While evaluating various options for liquid methane and liquid oxygen propellant management for lunar missions, Innovative Engineering Solutions (IES) conceived the flexible screen device as a potential simple alternative to conventional propellant management devices (PMD). An apparatus was designed and fabricated to test flexible screen devices in liquid nitrogen. After resolution of a number of issues (discussed in detail in the paper), a fine mesh screen (325 by 2300 wires per inch) spring return assembly was successfully tested. No significant degradation in the screen bubble point was observed either due to the screen stretching process or due to cyclic fatigue during testing. An estimated 30 to 50 deflection cycles, and approximately 3 to 5 thermal cycles, were performed on the final screen specimen, prior to and between formally recorded testing. These cycles included some "abusive" pressure cycling, where gas or liquid was driven through the screen at rates that produced differential pressures across the screen of several times the bubble point pressure. No obvious performance degradation or other changes were observed over the duration of testing. In summary, it is felt by the author that these simple tests validated the feasibility of the flexible screen PMD concept for use with cryogenic propellants.

A case report of laparoscopic duodenal atresia repair in a neonate using a novel miniature stapling device.

PubMed

Boo, Yoon Jung; Gödeke, Jan; Engel, Veronika; Muensterer, Oliver J

2017-01-01

Laparoscopic duodenal atresia repair is an advanced procedure performed in select pediatric surgical centers. Recently, sub-6mm endosurgical staplers have been introduced, facilitating and accelerating the creation of intracorporeal intestinal anastomoses. We performed a laparoscopic duodenojejunostomy in a one-day-old child with duodenal atresia due to annular pancreas using a novel 5.8mm articulating endostapler with excellent outcome. The technical details are reported. Laparoscopic duodenojejunostomy is a technically demanding procedure due to difficulty in hand-sewn anastomosis in a small and restricted space. With this novel 5.8mm articulating endostapler, we were able to perform a quicker and easier anastomosis. We report a case of laparoscopic duodenal atresia repair in a neonate using a novel miniature stapling device. This new technique is a safe, quick and easier way to perform laparoscopic duodenal atresia repair. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Analysis of DC and analog/RF performance on Cyl-GAA-TFET using distinct device geometry

NASA Astrophysics Data System (ADS)

Vishvakarma, S. K.; Beohar, Ankur; Vijayvargiya, Vikas; Trivedi, Priyal

2017-07-01

In this paper, analysis of DC and analog/RF performance on cylindrical gate-all-around tunnel field-effect transistor (TFET) has been made using distinct device geometry. Firstly, performance parameters of GAA-TFET are analyzed in terms of drain current, gate capacitances, transconductance, source-drain conductance at different radii and channel length. Furthermore, we also produce the geometrical analysis towards the optimized investigation of radio frequency parameters like cut-off frequency, maximum oscillation frequency and gain bandwidth product using a 3D technology computer-aided design ATLAS. Due to band-to-band tunneling based current mechanism unlike MOSFET, gate-bias dependence values as primary parameters of TFET differ. We also analyze that the maximum current occurs when radii of Si is around 8 nm due to high gate controllability over channel with reduced fringing effects and also there is no change in the current of TFET on varying its length from 100 to 40 nm. However current starts to increase when channel length is further reduced for 40 to 30 nm. Both of these trades-offs affect the RF performance of the device. Project supported by the Council of Scientific and Industrial Research (CSIR) Funded Research Project, Grant No. 22/0651/14/EMR-II, Government of India.

Comparative study of graphene and its derivative materials as an electrode in OLEDs

NASA Astrophysics Data System (ADS)

Srivastava, Anshika; Kumar, Brijesh

2018-04-01

In current scenario, the organic materials have given a revolutionary evolution in the electronics industry. As, the organic light emitting diodes (OLEDs) have almost replaced the conventional technologies due to the use of organic based materials. However, the next generations OLEDs are intensively desired nowadays for high definition display technology. There are various concern involved in the successful design of OLEDs. Electrodes are one of the electrical conductors, which play a vital role in the construction of OLEDs. The performance of OLED is majorly affected by the material used for electrodes. Due to the requirement of transparent, flexible and inexpensive anodes in bottom emissive OLEDs, ITO was replaced by graphene material. Graphene is a single layer 2-dimensional transparent carbon allotrope which showed prodigious potential to escalate the device performance. Although graphene demonstrated impressive characteristics in various applications, it showed unfavorable work function for many other devices. Thus, derivative materials of graphene such as graphene oxide, graphane and β - graphdiyne were synthesized by several researchers. By comparing graphene and its derivatives as an anode of OLEDs, it has been found that graphene oxide showed the preeminent performance among all. In this paper, all the comparisons are investigated by using a standard device constructed by piling layers of anode/ m_MTDATA/ NPB/ Alq3: QAD/ Alq3/ cathode in TCAD ATLAS device simulator.

Hetero-Material Gate Doping-Less Tunnel FET and Its Misalignment Effects on Analog/RF Parameters

NASA Astrophysics Data System (ADS)

Anand, Sunny; Sarin, R. K.

2018-03-01

In this paper, with the use of a hetero-material gate technique, a tunnel field-effect transistor (TFET) subject to charge plasma technique is proposed, named as hetero-material gate doping-less tunnel FET (HMG-DLTFET) and a brief study has been done on the effects due to misalignment of the bottom gate towards drain (GMAD) and towards source (GMAS). The proposed devices provide better performance as the drive current increased by three times as compared to conventional doping-less TFET (DLTFET). The results are then analyzed and compared with conventional doped hetero-material gate double-gate tunnel FET (HMG-DGTFET). The analog/radiofrequency (RF) performance has been studied for both devices and comparative analysis has been done for different parameters such as drain current (I D), transconductance (g m), output conductance (g d), total gate capacitance (C gg) and cutoff frequency (f T). Both devices performed similarly in different misalignment configurations. When the bottom gate is perfectly aligned, the best performance is observed for both devices, but the doping-less device gives slightly more freedom for fabrication engineers as the amount of tolerance for HMG-DLTFET is better than that of HMG-DGTFET.

Performance investigation of bandgap, gate material work function and gate dielectric engineered TFET with device reliability improvement

NASA Astrophysics Data System (ADS)

Raad, Bhagwan Ram; Nigam, Kaushal; Sharma, Dheeraj; Kondekar, P. N.

2016-06-01

This script features a study of bandgap, gate material work function and gate dielectric engineering for enhancement of DC and Analog/RF performance, reduction in the hot carriers effect (HCEs) and drain induced barrier lowering (DIBL) for better device reliability. In this concern, the use of band gap and gate material work function engineering improves the device performance in terms of the ON-state current and suppressed ambipolar behaviour with maintaining the low OFF-state current. With these advantages, the use of gate material work function engineering imposes restriction on the high frequency performance due to increment in the parasitic capacitances and also introduces the hot carrier effects. Hence, the gate dielectric engineering with bandgap and gate material work function engineering are used in this paper to overcome the cons of the gate material work function engineering by obtaining a superior performance in terms of the current driving capability, ambipolar conduction, HCEs, DIBL and high frequency parameters of the device for ultra-low power applications. Finally, the optimization of length for different work function is performed to get the best out of this.

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

DOE PAGES

Coltrin, Michael E.; Baca, Albert G.; Kaplar, Robert J.

2017-10-26

In this paper, predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-of-merit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet chargemore » density of 1 × 10 13 cm –2. However, at higher temperatures at which AlGaN power devices are anticipated to operate, this “breakeven” composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.« less

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coltrin, Michael E.; Baca, Albert G.; Kaplar, Robert J.

In this paper, predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-of-merit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet chargemore » density of 1 × 10 13 cm –2. However, at higher temperatures at which AlGaN power devices are anticipated to operate, this “breakeven” composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.« less

Charge plasma based source/drain engineered Schottky Barrier MOSFET: Ambipolar suppression and improvement of the RF performance

NASA Astrophysics Data System (ADS)

Kale, Sumit; Kondekar, Pravin N.

2018-01-01

This paper reports a novel device structure for charge plasma based Schottky Barrier (SB) MOSFET on ultrathin SOI to suppress the ambipolar leakage current and improvement of the radio frequency (RF) performance. In the proposed device, we employ dual material for the source and drain formation. Therefore, source/drain is divided into two parts as main source/drain and source/drain extension. Erbium silicide (ErSi1.7) is used as main source/drain material and Hafnium metal is used as source/drain extension material. The source extension induces the electron plasma in the ultrathin SOI body resulting reduction of SB width at the source side. Similarly, drain extension also induces the electron plasma at the drain side. This significantly increases the SB width due to increased depletion at the drain end. As a result, the ambipolar leakage current can be suppressed. In addition, drain extension also reduces the parasitic capacitances of the proposed device to improve the RF performance. The optimization of length and work function of metal used in the drain extension is performed to achieve improvement in device performance. Moreover, the proposed device makes fabrication simpler, requires low thermal budget and free from random dopant fluctuations.

Solution processed ternary blend nano-composite charge regulation layer to enhance inverted OLED performances

NASA Astrophysics Data System (ADS)

Kaçar, Rifat; Mucur, Selin Pıravadılı; Yıldız, Fikret; Dabak, Salih; Tekin, Emine

2018-04-01

Inverted bottom-emission organic light emitting diodes (IBOLEDs) have attracted increasing attention due to their exceptional air stability and applications in active-matrix displays. For gaining high IBOLED device efficiencies, it is crucial to develop an effective strategy to make the bottom electrode easy for charge injection and transport. Charge selectivity, blocking the carrier flow towards the unfavourable side, plays an important role in determining charge carrier balance and accordingly radiative recombination efficiency. It is therefore highly desirable to functionalize an interfacial layer which will perform many different tasks simultaneously. Here, we contribute to the hole-blocking ability of the zinc oxide/polyethyleneimine (ZnO:PEI) nano-composite (NC) interlayer with the intention of increasing the OLED device efficiency. With this purpose in mind, a small amount of 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBi) was added as a hole-blocking molecule into the binary blend of ZnO and PEI solution. The device with a ternary ZnO:PEI:TPBi NC interlayer achieved a maximum current efficiency of 38.20 cd A-1 and a power efficiency of 34.29 lm W-1 with a luminance of 123 200 cd m-2, which are high performance parameters for inverted device architecture. The direct comparisons of device performances incorporating ZnO only, ZnO/PEI bilayers, and ZnO:PEI binary NC counterparts were also performed, which shed light on the origin of device performance enhancement.

"Power-on resets" in cardiac implantable electronic devices during magnetic resonance imaging.

PubMed

Higgins, John V; Sheldon, Seth H; Watson, Robert E; Dalzell, Connie; Acker, Nancy; Cha, Yong-Mei; Asirvatham, Samuel J; Kapa, Suraj; Felmlee, Joel P; Friedman, Paul A

2015-03-01

Magnetic resonance imaging (MRI) has been safely performed in some patients with cardiac implantable electronic devices (CIEDs) under careful monitoring and prespecified conditions. Pacemaker-dependent patients are often excluded, partly because of the potential for "power-on reset" (PoR), which can lead to a change from asynchronous to inhibited pacing with consequent inhibition of pacing due to electromagnetic interference during MRI. The purpose of this study was to review risk factors for PoR during MRI. A prospective study was performed between January 2008 and May 2013 in patients with CIEDs undergoing clinically indicated MRI. Eligible patients were not pacemaker dependent. Devices were interrogated before and after MRI, programmed to an asynchronous mode or an inhibition mode with tachyarrhythmia therapies turned off, and reprogrammed to their original settings after MRI. MRI scans (n = 256) were performed in 198 patients with non-MRI-conditional CIEDs between 2008 and 2013 (median age 66 years; interquartile range 57-77 years; 59% men). PoR occurred during 9 MRI scans (3.5%) in 8 patients. PoR was more frequent with Medtronic devices than with other generator brands (n = 9/139 vs 0/117 [6% vs 0%]; P = .005). Devices with PoR were all released before 2002 and were implanted from 1999 to 2004. Effects of PoR included a decrease in heart rate during MRI (n = 4) and transient anomalous battery life indication (n = 1). All devices functioned normally after MRI. PoR occurs infrequently but can cause deleterious changes in pacing mode and heart rate. MRI should not be performed in pacemaker-dependent patients with older at-risk generators. Continuous monitoring during MRI is essential because unrecognized PoR may inhibit pacing or accelerate battery depletion due to high pacing output. Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Prosthetic Jamming Terminal Device: A Case Study of Untethered Soft Robotics

PubMed Central

Amend, John; Farrell, Todd; Latour, Debra; Martinez, Carlos; Johansson, Jen; McNicoll, Anthony; Wartenberg, Marek; Naseef, Samuel; Hanson, William; Culley, William

2016-01-01

Abstract This article illuminates the major and often overlooked challenge of untethering soft robotic systems through the context of recent work, in which soft robotic gripper technology enabled by jamming of granular media was applied to a prosthetic jamming terminal device (PJTD). The PJTD's technical and market feasibility was evaluated in a pilot study with two upper-limb amputees. A PJTD prototype was tested against a commercial device (Motion Control electric terminal service with a one degree-of-freedom pinching mechanism) using two existing hand function tests: the first quantified the device's speed in picking and placing small blocks and the second evaluated a person's ability to perform activities of daily living (ADLs). The PJTD prototype performed slightly slower than its commercial counterpart in the first test. While both participants successfully completed all the ADLs with both devices in the second test, the commercial device scored marginally higher. Results suggested that PJTD can have potential benefits over existing terminal devices, such as providing the capability to firmly grasp tools due to the ability of PJTD to conform to arbitrary surfaces and reducing compensatory shoulder movements due to its axisymmetric design. Some downsides were that users reported fatigue while operating the PJTD, as most operations require pushing the PJTD against target objects to adequately conform to them. The greatest drawback for the PJTD is also a major roadblock preventing a number of soft robotic research projects from making an impact in real-world applications: pneumatic technology required for operating the PJTD is currently too large and heavy to enable compact untethered operation. PMID:28078196

Electrorheological Fluid Based Force Feedback Device

NASA Technical Reports Server (NTRS)

Pfeiffer, Charles; Bar-Cohen, Yoseph; Mavroidis, Constantinos; Dolgin, Benjamin

1999-01-01

Parallel to the efforts to develop fully autonomous robots, it is increasingly being realized that there are applications where it is essential to have a fully controlled robot and "feel" its operating conditions, i.e. telepresence. This trend is a result of the increasing efforts to address tasks where humans can perform significantly better but, due to associated hazards, distance, physical limitations and other causes, only robots can be employed to perform these tasks. Such robots need to be assisted by a human that remotely controls the operation. To address the goal of operating robots as human surrogates, the authors launched a study of mechanisms that provide mechanical feedback. For this purpose, electrorheological fluids (ERF) are being investigated for the potential application as miniature haptic devices. This family of electroactive fluids has the property of changing the viscosity during electrical stimulation. Consequently, ERF can be used to produce force feedback haptic devices for tele-operated control of medical and space robotic systems. Forces applied at the robot end-effector due to a compliant environment are reflected to the user using an ERF device where a change in the system viscosity will occur proportionally to the transmitted force. Analytical model and control algorithms are being developed taking into account the non-linearities of these type of devices. This paper will describe the concept and the developed mechanism of ERF based force feedback. The test process and the physical properties of this device will be described and the results of preliminary tests will be presented.

Floating compression of Ag nanowire networks for effective strain release of stretchable transparent electrodes

NASA Astrophysics Data System (ADS)

Pyo, Jun Beom; Kim, Byoung Soo; Park, Hyunchul; Kim, Tae Ann; Koo, Chong Min; Lee, Jonghwi; Son, Jeong Gon; Lee, Sang-Soo; Park, Jong Hyuk

2015-10-01

Manipulation of the configuration of Ag nanowire (NW) networks has been pursued to enhance the performance of stretchable transparent electrodes. However, it has remained challenging due to the high Young's modulus and low yield strain of Ag NWs, which lead to their mechanical failure when subjected to structural deformation. We demonstrate that floating a Ag NW network on water and subsequent in-plane compression allows convenient development of a wavy configuration in the Ag NW network, which can release the applied strain. A greatly enhanced electromechanical stability of Ag NW networks can be achieved due to their wavy configuration, while the NW networks maintain the desirable optical and electrical properties. Moreover, the produced NW networks can be transferred to a variety of substrates, offering flexibility for device fabrication. The Ag NW networks with wavy configurations are used as compliant electrodes for dielectric elastomer actuators. The study demonstrates their promising potential to provide improved performance for soft electronic devices.Manipulation of the configuration of Ag nanowire (NW) networks has been pursued to enhance the performance of stretchable transparent electrodes. However, it has remained challenging due to the high Young's modulus and low yield strain of Ag NWs, which lead to their mechanical failure when subjected to structural deformation. We demonstrate that floating a Ag NW network on water and subsequent in-plane compression allows convenient development of a wavy configuration in the Ag NW network, which can release the applied strain. A greatly enhanced electromechanical stability of Ag NW networks can be achieved due to their wavy configuration, while the NW networks maintain the desirable optical and electrical properties. Moreover, the produced NW networks can be transferred to a variety of substrates, offering flexibility for device fabrication. The Ag NW networks with wavy configurations are used as compliant electrodes for dielectric elastomer actuators. The study demonstrates their promising potential to provide improved performance for soft electronic devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03814f

Low-voltage back-gated atmospheric pressure chemical vapor deposition based graphene-striped channel transistor with high-κ dielectric showing room-temperature mobility > 11,000 cm(2)/V·s.

PubMed

Smith, Casey; Qaisi, Ramy; Liu, Zhihong; Yu, Qingkai; Hussain, Muhammad Mustafa

2013-07-23

Utilization of graphene may help realize innovative low-power replacements for III-V materials based high electron mobility transistors while extending operational frequencies closer to the THz regime for superior wireless communications, imaging, and other novel applications. Device architectures explored to date suffer a fundamental performance roadblock due to lack of compatible deposition techniques for nanometer-scale dielectrics required to efficiently modulate graphene transconductance (gm) while maintaining low gate capacitance-voltage product (CgsVgs). Here we show integration of a scaled (10 nm) high-κ gate dielectric aluminum oxide (Al2O3) with an atmospheric pressure chemical vapor deposition (APCVD)-derived graphene channel composed of multiple 0.25 μm stripes to repeatedly realize room-temperature mobility of 11,000 cm(2)/V·s or higher. This high performance is attributed to the APCVD graphene growth quality, excellent interfacial properties of the gate dielectric, conductivity enhancement in the graphene stripes due to low tox/Wgraphene ratio, and scaled high-κ dielectric gate modulation of carrier density allowing full actuation of the device with only ±1 V applied bias. The superior drive current and conductance at Vdd = 1 V compared to other top-gated devices requiring undesirable seed (such as aluminum and poly vinyl alcohol)-assisted dielectric deposition, bottom gate devices requiring excessive gate voltage for actuation, or monolithic (nonstriped) channels suggest that this facile transistor structure provides critical insight toward future device design and process integration to maximize CVD-based graphene transistor performance.

Field Performance versus Standard Test Condition Efficiency of Tandem Solar Cells and the Singular Case of Perovskites/Silicon Devices.

PubMed

Dupré, Olivier; Niesen, Bjoern; De Wolf, Stefaan; Ballif, Christophe

2018-01-18

Multijunction cells may offer a cost-effective route to boost the efficiency of industrial photovoltaics. For any technology to be deployed in the field, its performance under actual operating conditions is extremely important. In this perspective, we evaluate the impact of spectrum, light intensity, and module temperature variations on the efficiency of tandem devices with crystalline silicon bottom cells with a particular focus on perovskite top cells. We consider devices with different efficiencies and calculate their energy yields using field data from Denver. We find that annual losses due to differences between operating conditions and standard test conditions are similar for single-junction and four-terminal tandem devices. The additional loss for the two-terminal tandem configuration caused by current mismatch reduces its performance ratio by only 1.7% when an optimal top cell bandgap is used. Additionally, the unusual bandgap temperature dependence of perovskites is shown to have a positive, compensating effect on current mismatch.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors.

PubMed

Giusi, G; Giordano, O; Scandurra, G; Rapisarda, M; Calvi, S; Ciofi, C

2016-04-01

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz(1/2), while DC performances are limited only by the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giusi, G.; Giordano, O.; Scandurra, G.

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz{sup 1/2}, while DC performances are limited only bymore » the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.« less

Gold nanoparticle-embedded silk protein-ZnO nanorod hybrids for flexible bio-photonic devices

NASA Astrophysics Data System (ADS)

Gogurla, Narendar; Kundu, Subhas C.; Ray, Samit K.

2017-04-01

Silk protein has been used as a biopolymer substrate for flexible photonic devices. Here, we demonstrate ZnO nanorod array hybrid photodetectors on Au nanoparticle-embedded silk protein for flexible optoelectronics. Hybrid samples exhibit optical absorption at the band edge of ZnO as well as plasmonic energy due to Au nanoparticles, making them attractive for selective UV and visible wavelength detection. The device prepared on Au-silk protein shows a much lower dark current and a higher photo to dark-current ratio of ∼105 as compared to the control sample without Au nanoparticles. The hybrid device also exhibits a higher specific detectivity due to higher responsivity arising from the photo-generated hole trapping by Au nanoparticles. Sharp pulses in the transient photocurrent have been observed in devices prepared on glass and Au-silk protein substrates due to the light induced pyroelectric effect of ZnO, enabling the demonstration of self-powered photodetectors at zero bias. Flexible hybrid detectors have been demonstrated on Au-silk/polyethylene terephthalate substrates, exhibiting characteristics similar to those fabricated on rigid glass substrates. A study of the performance of photodetectors with different bending angles indicates very good mechanical stability of silk protein based flexible devices. This novel concept of ZnO nanorod array photodetectors on a natural silk protein platform provides an opportunity to realize integrated flexible and self-powered bio-photonic devices for medical applications in near future.

A Study on Organic-Metal Halide Perovskite Film Morphology, Interfacial Layers, Tandem Applications, and Encapsulation

NASA Astrophysics Data System (ADS)

Fisher, Dallas A.

Organic-metal halide perovskites have brought about a new wave of research in the photovoltaic community due to their ideally suited optical and electronic parameters. In less than a decade, perovskite solar cell performance has skyrocketed to unprecedented efficiencies with numerous reported methodologies. Perovskites face many challenges with high-quality film morphology, interfacial layers, and long-term stability. In this work, these active areas are explored through a combination of studies. First, the importance of perovskite film precursor ratios is explored with an in-depth study of carrier lifetime and solvent-grain effects. It was found that excess lead iodide precursor greatly improves the film morphology by reducing pinholes in the solar absorber. Dimethyl sulfoxide (DMSO) solvent was found to mend grains, as well as improve carrier lifetime and device performance, possibly by passivation of grain boundary traps. Second, applications of perovskite with tandem cells is investigated, with an emphasis for silicon devices. Perovskites can easily be integrated with silicon, which already has strong market presence. Additionally, both materials' bandgaps are ideally suited for maximum tandem efficiency. The silicon/perovskite tandem device structure necessitated the optimization of inverted (p-i-n) structure devices. PEDOT:PSS, copper oxide, and nickel oxide p-type layers were explored through a combination of photoluminescent, chemical reactivity, and solar simulation results. Results were hindered due to resistive ITO and rough silicon substrates, but tandem devices displayed Voc indicative of proper monolithic performance. Third, replacement of titanium dioxide n-type layer with iron oxide (Fe 2O3, common rust) was studied. Iron oxide experiences less ultraviolet instability than that of titanium dioxide under solar illumination. It was found that current density slightly decreased due to parasitic absorption from the rust, but that open circuit voltage decreased drastically due to poor band alignment. Fe2O3 appears to be better suited to a narrower band gap material than methylammonium lead iodide perovskite. Finally, encapsulation of perovskite devices with epoxy coatings is explored as a method to improve long-term stability. Perovskites are sensitive to a variety of conditions, but most importantly water and polar molecules. Encapsulants act as a moisture/oxygen barrier, but also prevent outgassing of the organic components. Three epoxies were tested in high heat and high humidity conditions. Important factors in the curing process were uncovered such as the sensitivity of UV-epoxies to amine functional groups found in common p-type dopants and perovskite layers. Moisture ingress was the failure point for high-humidity/heat devices which was confirmed through conversion to yellow lead iodide. A revised device fabrication method is proposed to reduce moisture ingress for future experiments.

Increasing operational life of brush-contact device in the turbine generator due to using lubricating molybdenum disulphide brushes

NASA Astrophysics Data System (ADS)

Izotov, A. I.; Fominykh, A. A.; Nikulin, S. V.; Prokoshev, D. K.; Legoti, A. B.; Timina, N. V.

2018-01-01

A way of reducing irregular current distribution in multi-brush systems of sliding current transfer with its wear reduction due to installing lubricating molybdenum disulphide brushes on slip rings to ensure a greasing nano-sized cover on the slip ring surface is proposed. The authors give the results of industrial tests estimated on the performance effectiveness of lubricating brushes on slip rings of the TBB-320-2UZ-type turbine generator. The results showed that the lubricating brushes reduce a) the wear of 6110 OM+M and EG2AF+M brushes by 1.2 and 2.1 times respectively, b) current distribution irregularity in parallel operating brushes due to stabilizing the contact arc, and c) the temperature of the electrical brush-contact device due to the friction reduction in brushes.

Effect of the intra-layer potential distributions and spatial currents on the performance of graphene SymFETs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasan, Mehdi; Sensale-Rodriguez, Berardi, E-mail: berardi.sensale@utah.edu

2015-09-15

In this paper, a two-dimensional (2-D) model for a graphene symmetric field effect transistor (SymFET), which considers (a) the intra-graphene layer potential distributions and (b) the internal current flows through the device, is presented and discussed. The local voltages along the graphene electrodes as well as the current-voltage characteristics of the device are numerically calculated based on a single-particle tunneling model. Our numerical results show that: (i) when the tunneling current is small, due to either a large tunneling thickness (≥ 2 atomic layers of BN) or a small coherence length, the voltage distributions along the graphene electrodes have almostmore » zero variations upon including these distributed effects, (ii) when the tunnel current is large, due to either a small tunneling thickness (∼ 1 atomic layer of BN) or due to a large coherence length, the local voltage distributions along the graphene electrodes become appreciable and the device behavior deviates from that predicted by a 1-D approximation. These effects, which are not captured in one-dimensional SymFET models, can provide a better understanding about the electron dynamics in the device and might indicate potential novel applications for this proposed device.« less

The Aortic Bifurcation Angle as a Factor in Application of the Outback for Femoropopliteal Lesions in Ipsilateral Versus Contralateral Approaches.

PubMed

Raskin, Daniel; Khaitovich, Boris; Balan, Shmuel; Silverberg, Daniel; Halak, Moshe; Rimon, Uri

2018-01-01

To assess the technical success of the Outback reentry device in contralateral versus ipsilateral approaches for femoropopliteal arterial occlusion. A retrospective review of patients treated for critical limb ischemia (CLI) using the Outback between January 2013 and July 2016 was performed. Age, gender, length and site of the occlusion, approach site, aortic bifurcation angle, and reentry site were recorded. Calcification score was assigned at both aortic bifurcation and reentry site. Technical success was assessed. During the study period, a total of 1300 endovascular procedures were performed on 489 patients for CLI. The Outback was applied on 50 femoropopliteal chronic total occlusions. Thirty-nine contralateral and 11 ipsilateral antegrade femoral were accessed. The device was used successfully in 41 patients (82%). There were nine failures, all in the contralateral approach group. Six due to inability to deliver the device due to acute aortic bifurcation angle and three due to failure to achieve luminal reentry. Procedural success was significantly affected by the aortic bifurcation angle (p = 0.013). The Outback has high technical success rates in treatment of femoropopliteal occlusion, when applied from either an ipsi- or contralateral approach. When applied in contralateral access, acute aortic bifurcation angle predicts procedural failure.

Characterization and reliability of aluminum gallium nitride/gallium nitride high electron mobility transistors

NASA Astrophysics Data System (ADS)

Douglas, Erica Ann

Compound semiconductor devices, particularly those based on GaN, have found significant use in military and civilian systems for both microwave and optoelectronic applications. Future uses in ultra-high power radar systems will require the use of GaN transistors operated at very high voltages, currents and temperatures. GaN-based high electron mobility transistors (HEMTs) have proven power handling capability that overshadows all other wide band gap semiconductor devices for high frequency and high-power applications. Little conclusive research has been reported in order to determine the dominating degradation mechanisms of the devices that result in failure under standard operating conditions in the field. Therefore, it is imperative that further reliability testing be carried out to determine the failure mechanisms present in GaN HEMTs in order to improve device performance, and thus further the ability for future technologies to be developed. In order to obtain a better understanding of the true reliability of AlGaN/GaN HEMTs and determine the MTTF under standard operating conditions, it is crucial to investigate the interaction effects between thermal and electrical degradation. This research spans device characterization, device reliability, and device simulation in order to obtain an all-encompassing picture of the device physics. Initially, finite element thermal simulations were performed to investigate the effect of device design on self-heating under high power operation. This was then followed by a study of reliability of HEMTs and other tests structures during high power dc operation. Test structures without Schottky contacts showed high stability as compared to HEMTs, indicating that degradation of the gate is the reason for permanent device degradation. High reverse bias of the gate has been shown to induce the inverse piezoelectric effect, resulting in a sharp increase in gate leakage current due to crack formation. The introduction of elevated temperatures during high reverse gate bias indicated that device failure is due to the breakdown of an unintentional gate oxide. RF stress of AlGaN/GaN HEMTs showed comparable critical voltage breakdown regime as that of similar devices stressed under dc conditions. Though RF device characteristics showed stability up to a drain bias of 20 V, Schottky diode characteristics degraded substantially at all voltages investigated. Results from both dc and RF stress conditions, under several bias regimes, confirm that the primary root for stress induced degradation was due to the Schottky contact. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

The Importance of Moisture in Hybrid Lead Halide Perovskite Thin Film Fabrication.

PubMed

Eperon, Giles E; Habisreutinger, Severin N; Leijtens, Tomas; Bruijnaers, Bardo J; van Franeker, Jacobus J; deQuilettes, Dane W; Pathak, Sandeep; Sutton, Rebecca J; Grancini, Giulia; Ginger, David S; Janssen, Rene A J; Petrozza, Annamaria; Snaith, Henry J

2015-09-22

Moisture, in the form of ambient humidity, has a significant impact on methylammonium lead halide perovskite films. In particular, due to the hygroscopic nature of the methylammonium component, moisture plays a significant role during film formation. This issue has so far not been well understood and neither has the impact of moisture on the physical properties of resultant films. Herein, we carry out a comprehensive and well-controlled study of the effect of moisture exposure on methylammonium lead halide perovskite film formation and properties. We find that films formed in higher humidity atmospheres have a less continuous morphology but significantly improved photoluminescence, and that film formation is faster. In photovoltaic devices, we find that exposure to moisture, either in the precursor solution or in the atmosphere during formation, results in significantly improved open-circuit voltages and hence overall device performance. We then find that by post-treating dry films with moisture exposure, we can enhance photovoltaic performance and photoluminescence in a similar way. The enhanced photoluminescence and open-circuit voltage imply that the material quality is improved in films that have been exposed to moisture. We determine that this improvement stems from a reduction in trap density in the films, which we postulate to be due to the partial solvation of the methylammonium component and "self-healing" of the perovskite lattice. This work highlights the importance of controlled moisture exposure when fabricating high-performance perovskite devices and provides guidelines for the optimum environment for fabrication. Moreover, we note that often an unintentional water exposure is likely responsible for the high performance of solar cells produced in some laboratories, whereas careful synthesis and fabrication in a dry environment will lead to lower-performing devices.

Adjustable Focus Optical Correction Lens (AFOCL)

NASA Technical Reports Server (NTRS)

Peters, Bruce R.

2001-01-01

This report describes the activities and accomplishments along with the status of the characterization of a PLZT-based Adjustable Focus Optical Correction Lens (AFOCL) test device. The activities described in this report were undertaken by members of the Center for Applied Optics (CAO) at the University of Alabama in Huntsville (UAH) under NASA Contract NAS8-00188. The effort was led by Dr. Bruce Peters as the Principal Investigator and supported by Dr. Patrick Reardon, Ms. Deborah Bailey, and graduate student Mr. Jeremy Wong. The activities outlined for the first year of the contract were to identify vendors and procure a test device along with performing the initial optical characterization of the test device. This activity has been successfully executed and test results are available and preliminary information was published at the SPIE Photonics West Conference in San Jose, January 2001. The paper, "Preliminary investigation of an active PLZT lens," was well received and generated response with several questions from the audience. A PLZT test device has been commercially procured from an outside vendor: The University of California in San Diego (UCSD) in partnership with New Interconnect Packaging Technologies (NIPT) Inc. The device has been subjected to several tests to characterize the optical performance of the device at wavelengths of interest. The goal was to evaluate the AFOCL similar to a conventional lens and measure any optical aberrations present due to the PLZT material as a deviation in the size of the diffraction limited spot (blur), the presence of diffracted energy into higher orders surrounding the focused spot (a variation in Strehl), and/or a variation or spread in the location of the focused energy away from the optical axis (a bias towards optical wedge, spherical, comma, or other higher order aberrations). While data has been collected indicative of the imaging quality of the AFOCL test device, it was not possible to fully characterize the optical performance of the AFOCL alone because there were significant optical distortions due to fabrication related issues.

Normally-off AlGaN/GaN-based MOS-HEMT with self-terminating TMAH wet recess etching

NASA Astrophysics Data System (ADS)

Son, Dong-Hyeok; Jo, Young-Woo; Won, Chul-Ho; Lee, Jun-Hyeok; Seo, Jae Hwa; Lee, Sang-Heung; Lim, Jong-Won; Kim, Ji Heon; Kang, In Man; Cristoloveanu, Sorin; Lee, Jung-Hee

2018-03-01

Normally-off AlGaN/GaN-based MOS-HEMT has been fabricated by utilizing damage-free self-terminating tetramethyl ammonium hydroxide (TMAH) recess etching. The device exhibited a threshold voltage of +2.0 V with good uniformity, extremely small hysteresis of ∼20 mV, and maximum drain current of 210 mA/mm. The device also exhibited excellent off-state performances, such as breakdown voltage of ∼800 V with off-state leakage current as low as ∼10-12 A and high on/off current ratio (Ion/Ioff) of 1010. These excellent device performances are believed to be due to the high quality recessed surface, provided by the simple self-terminating TMAH etching.

Bridge to transplantation with a left ventricular assist device.

PubMed

Jung, Jae Jun; Sung, Kiick; Jeong, Dong Seop; Kim, Wook Sung; Lee, Young Tak; Park, Pyo Won

2012-04-01

A 61-year-old female patient was diagnosed with dilated cardiomyopathy with severe left ventricle dysfunction. Two days after admission, continuous renal replacement therapy was performed due to oliguria and lactic acidosis. On the fifth day, an intra-aortic balloon pump was inserted due to low cardiac output syndrome. Beginning 4 days after admission, she was supported for 15 days thereafter with an extracorporeal left ventricular assist device (LVAD) because of heart failure with multi-organ failure. A heart transplant was performed while the patient was stabilized with the LVAD. She developed several complications after the surgery, such as cytomegalovirus pneumonia, pulmonary tuberculosis, wound dehiscence, and H1N1 infection. On postoperative day 19, she was discharged from the hospital with close follow-up and treatment for infection. She received follow-up care for 10 months without any immune rejection reaction.

Planar junctionless phototransistor: A potential high-performance and low-cost device for optical-communications

NASA Astrophysics Data System (ADS)

Ferhati, H.; Djeffal, F.

2017-12-01

In this paper, a new junctionless optical controlled field effect transistor (JL-OCFET) and its comprehensive theoretical model is proposed to achieve high optical performance and low cost fabrication process. Exhaustive study of the device characteristics and comparison between the proposed junctionless design and the conventional inversion mode structure (IM-OCFET) for similar dimensions are performed. Our investigation reveals that the proposed design exhibits an outstanding capability to be an alternative to the IM-OCFET due to the high performance and the weak signal detection benefit offered by this design. Moreover, the developed analytical expressions are exploited to formulate the objective functions to optimize the device performance using Genetic Algorithms (GAs) approach. The optimized JL-OCFET not only demonstrates good performance in terms of derived drain current and responsivity, but also exhibits superior signal to noise ratio, low power consumption, high-sensitivity, high ION/IOFF ratio and high-detectivity as compared to the conventional IM-OCFET counterpart. These characteristics make the optimized JL-OCFET potentially suitable for developing low cost and ultrasensitive photodetectors for high-performance and low cost inter-chips data communication applications.

Zinc oxide integrated area efficient high output low power wavy channel thin film transistor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanna, A. N.; Ghoneim, M. T.; Bahabry, R. R.

2013-11-25

We report an atomic layer deposition based zinc oxide channel material integrated thin film transistor using wavy channel architecture allowing expansion of the transistor width in the vertical direction using the fin type features. The experimental devices show area efficiency, higher normalized output current, and relatively lower power consumption compared to the planar architecture. This performance gain is attributed to the increased device width and an enhanced applied electric field due to the architecture when compared to a back gated planar device with the same process conditions.

Buried homojunction in CdS/Sb2Se3 thin film photovoltaics generated by interfacial diffusion

NASA Astrophysics Data System (ADS)

Zhou, Ying; Li, Yang; Luo, Jiajun; Li, Dengbing; Liu, Xinsheng; Chen, Chao; Song, Huaibing; Ma, Jingyuan; Xue, Ding-Jiang; Yang, Bo; Tang, Jiang

2017-07-01

Antimony selenide (Sb2Se3) emerges as a very promising non-toxic absorber material for thin film photovoltaics, and most of the devices, either in the superstrate or substrate configuration, employed CdS as the buffer layer. Due to the peculiar one-dimensional crystal structure of Sb2Se3, severe interfacial diffusion would be expected. In this letter, the interfacial diffusion in CdS/Sb2Se3 photovoltaics was carefully characterized from a combined material and device physics characterization. The results indicated that a buried homojunction located deep inside the Sb2Se3 absorber layer due to Cd diffusion, instead of the apparent CdS/Sb2Se3 heterojunction, dictated charge separation and device performance in Sb2Se3 thin film solar cells. Cd diffusion converted p-type Sb2Se3 into n-type by introducing a donor level with an activation energy of 0.22 eV. Our studies deepen the understanding of Sb2Se3 photovoltaics and shed light on their further performance optimization.

Evaluation of Adaptive Subdivision Method on Mobile Device

NASA Astrophysics Data System (ADS)

Rahim, Mohd Shafry Mohd; Isa, Siti Aida Mohd; Rehman, Amjad; Saba, Tanzila

2013-06-01

Recently, there are significant improvements in the capabilities of mobile devices; but rendering large 3D object is still tedious because of the constraint in resources of mobile devices. To reduce storage requirement, 3D object is simplified but certain area of curvature is compromised and the surface will not be smooth. Therefore a method to smoother selected area of a curvature is implemented. One of the popular methods is adaptive subdivision method. Experiments are performed using two data with results based on processing time, rendering speed and the appearance of the object on the devices. The result shows a downfall in frame rate performance due to the increase in the number of triangles with each level of iteration while the processing time of generating the new mesh also significantly increase. Since there is a difference in screen size between the devices the surface on the iPhone appears to have more triangles and more compact than the surface displayed on the iPad. [Figure not available: see fulltext.

Water Uptake Performance of Hygroscopic Heat and Moisture Exchangers after 24-Hour Tracheostoma Application.

PubMed

van den Boer, Cindy; Vas Nunes, Jonathan H; Muller, Sara H; van der Noort, Vincent; van den Brekel, Michiel W M; Hilgers, Frans J M

2014-06-01

After total laryngectomy, patients suffer from pulmonary complaints due to the shortcut of the upper airways that results in decreased warming and humidification of inspired air. Laryngectomized patients are advised to use a heat and moisture exchanger (HME) to optimize the inspired air. According to manufacturers' guidelines, these medical devices should be replaced every 24 hours. The aim of this study is to determine whether HMEs still function after 24-hour tracheostoma application. Assessment of residual water uptake capacity of used HMEs by measuring the difference between wet and dry core weight. Tertiary comprehensive cancer center. Three hygroscopic HME types were tested after use by laryngectomized patients in long-term follow-up. Water uptake of 41 used devices (including 10 prematurely replaced devices) was compared with that of control (unused) devices of the same type and with a control device with a relatively low performance. After 24 hours, the mean water uptake of the 3 device types had decreased compared with that of the control devices. For only one type was this difference significant. None of the used HMEs had a water uptake lower than that of the low-performing control device. The water uptake capacity of hygroscopic HEMs is clinically acceptable although no longer optimal after 24-hour tracheostoma application. From a functional point of view, the guideline for daily device replacement is therefore justified. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014.

Impact of combined hydrogen plasma and transient heat loads on the performance of tungsten as plasma facing material

NASA Astrophysics Data System (ADS)

Wirtz, M.; Bardin, S.; Huber, A.; Kreter, A.; Linke, J.; Morgan, T. W.; Pintsuk, G.; Reinhart, M.; Sergienko, G.; Steudel, I.; De Temmerman, G.; Unterberg, B.

2015-11-01

Experiments were performed in three different facilities in order to investigate the impact of combined steady state deuterium plasma exposure and ELM-like thermal shock events on the performance of ultra high purity tungsten. The electron beam facility JUDITH 1 was used to simulate pure thermal loads. In addition the linear plasma devices PSI-2 and Pilot-PSI have been used for successive as well as simultaneous exposure where the transient heat loads were applied by a high energy laser and the pulsed plasma operation, respectively. The results show that the damage behaviour strongly depends on the loading conditions and the sequence of the particle and heat flux exposure. This is due to hydrogen embrittlement and/or a higher defect concentration in the tungsten near surface region due to supersaturation of hydrogen. The different results in terms of damage formation from both linear plasma devices indicate that also the plasma parameters such as particle energy, flux and fluence, plasma impurities and the pulse shape have a strong influence on the damage performance. In addition, the different loading methods such as the scanning with the electron beam in contrast to the homogeneous exposure by the laser leads to an faster increase of the surface roughness due to plastic deformation.

An optical microfluidic platform for spatiotemporal biofilm treatment monitoring

NASA Astrophysics Data System (ADS)

Kim, Young Wook; Mosteller, Matthew P.; Subramanian, Sowmya; Meyer, Mariana T.; Bentley, William E.; Ghodssi, Reza

2016-01-01

Bacterial biofilms constitute in excess of 65% of clinical microbial infections, with the antibiotic treatment of biofilm infections posing a unique challenge due to their high antibiotic tolerance. Recent studies performed in our group have demonstrated that a bioelectric effect featuring low-intensity electric signals combined with antibiotics can significantly improve the efficacy of biofilm treatment. In this work, we demonstrate the bioelectric effect using sub-micron thick planar electrodes in a microfluidic device. This is critical in efforts to develop microsystems for clinical biofilm infection management, including both in vivo and in vitro applications. Adaptation of the method to the microscale, for example, can enable the development of localized biofilm infection treatment using microfabricated medical devices, while augmenting existing capabilities to perform biofilm management beyond the clinical realm. Furthermore, due to scale-down of the system, the voltage requirement for inducing the electric field is reduced further below the media electrolysis threshold. Enhanced biofilm treatment using the bioelectric effect in the developed microfluidic device elicited a 56% greater reduction in viable cell density and 26% further decrease in biomass growth compared to traditional antibiotic therapy. This biofilm treatment efficacy, demonstrated in a micro-scale device and utilizing biocompatible voltage ranges, encourages the use of this method for future clinical biofilm treatment applications.

Haptic device development based on electro static force of cellulose electro active paper

NASA Astrophysics Data System (ADS)

Yun, Gyu-young; Kim, Sang-Youn; Jang, Sang-Dong; Kim, Dong-Gu; Kim, Jaehwan

2011-04-01

Haptic is one of well-considered device which is suitable for demanding virtual reality applications such as medical equipment, mobile devices, the online marketing and so on. Nowadays, many of concepts for haptic devices have been suggested to meet the demand of industries. Cellulose has received much attention as an emerging smart material, named as electro-active paper (EAPap). The EAPap is attractive for mobile haptic devices due to its unique characteristics in terms of low actuation power, suitability for thin devices and transparency. In this paper, we suggest a new concept of haptic actuator with the use of cellulose EAPap. Its performance is evaluated depending on various actuation conditions. As a result, cellulose electrostatic force actuator shows a large output displacement and fast response, which is suitable for mobile haptic devices.

Biomechanical Modeling of the Deadlift Exercise on the HULK Device to Improve the Efficacy of Resistive Exercise Microgravity Countermeasures

NASA Technical Reports Server (NTRS)

Jagodnik, K. M.; Thompson, W. K.; Gallo, C. A.; Crentsil, L.; Funk, J. H.; Funk, N. W.; Perusek, G. P.; Sheehan, C. C.; Lewandowski, B. E.

2016-01-01

Extended spaceflight typically results in the loss of muscular strength and bone density due to exposure to microgravity. Resistive exercise countermeasures have been developed to maintain musculoskeletal health during spaceflight. The Advanced Resistive Exercise Device (ARED) is the "gold standard" of available devices; however, its footprint and volume are too large for use in space capsules employed in exploration missions. The Hybrid Ultimate Lifting Kit (HULK) device, with its smaller footprint, is a prototype exercise device for exploration missions. This work models the deadlift exercise being performed on the HULK device using biomechanical simulation, with the long-term goal to improve and optimize astronauts' exercise prescriptions, to maximize the benefit of exercise while minimizing time and effort invested.

Oxidation/reduction reactions at the metal contact-TlBr interface: an x-ray photoelectron spectroscopy study

NASA Astrophysics Data System (ADS)

Nelson, A. J.; Swanberg, E. L.; Voss, L. F.; Graff, R. T.; Conway, A. M.; Nikolic, R. J.; Payne, S. A.; Kim, H.; Cirignano, L.; Shah, K.

2014-09-01

TlBr radiation detector operation degrades with time at room temperature and is thought to be due to electromigration of Tl and Br vacancies within the crystal as well as the metal contacts migrating into the TlBr crystal itself due to electrochemical reactions at the metal/TlBr interface. X-ray photoemission spectroscopy (XPS) was used to investigate the metal contact surface/interfacial structure on TlBr devices. Device-grade TlBr was polished and subjected to a 32% HCl etch to remove surface damage prior to Mo or Pt contact deposition. High-resolution photoemission measurements on the Tl 4f, Br 3d, Cl 2p, Mo 3d and Pt 4f core lines were used to evaluate surface chemistry and non-equilibrium interfacial diffusion. Results indicate that anion substitution at the TlBr surface due to the HCl etch forms TlBr1-xClx with consequent formation of a shallow heterojunction. In addition, a reduction of Tl1+ to Tl0 is observed at the metal contacts after device operation in both air and N2 at ambient temperature. Understanding contact/device degradation versus operating environment is useful for improving radiation detector performance.

Proton irradiation effects on gallium nitride-based devices

NASA Astrophysics Data System (ADS)

Karmarkar, Aditya P.

Proton radiation effects on state-of-the-art gallium nitride-based devices were studied using Schottky diodes and high electron-mobility transistors. The device degradation was studied over a wide range of proton fluences. This study allowed for a correlation between proton irradiation effects between different types of devices and enhanced the understanding of the mechanisms responsible for radiation damage in GaN-based devices. Proton irradiation causes reduced carrier concentration and increased series resistance and ideality factor in Schottky diodes. 1.0-MeV protons cause greater degradation than 1.8-MeV protons because of their higher non-ionizing energy loss. The displacement damage in Schottky diodes recovers during annealing. High electron-mobility transistors exhibit extremely high radiation tolerance, continuing to perform up to a fluence of ˜1014 cm-2 of 1.8-MeV protons. Proton irradiation creates defect complexes in the thin-film structure. Decreased sheet carrier mobility due to increased carrier scattering and decreased sheet carrier density due to carrier removal by the defect centers are the primary damage mechanisms. Interface disorder at either the Schottky or the Ohmic contact plays a relatively unimportant part in overall device degradation in both Schottky diodes and high electron-mobility transistors.

Probing scattering mechanisms with symmetric quantum cascade lasers.

PubMed

Deutsch, Christoph; Detz, Hermann; Zederbauer, Tobias; Andrews, Aaron M; Klang, Pavel; Kubis, Tillmann; Klimeck, Gerhard; Schuster, Manfred E; Schrenk, Werner; Strasser, Gottfried; Unterrainer, Karl

2013-03-25

A characteristic feature of quantum cascade lasers is their unipolar carrier transport. We exploit this feature and realize nominally symmetric active regions for terahertz quantum cascade lasers, which should yield equal performance with either bias polarity. However, symmetric devices exhibit a strongly bias polarity dependent performance due to growth direction asymmetries, making them an ideal tool to study the related scattering mechanisms. In the case of an InGaAs/GaAsSb heterostructure, the pronounced interface asymmetry leads to a significantly better performance with negative bias polarity and can even lead to unidirectionally working devices, although the nominal band structure is symmetric. The results are a direct experimental proof that interface roughness scattering has a major impact on transport/lasing performance.

Improving acute care through use of medical device data.

PubMed

Kennelly, R J

1998-02-01

The Medical Information Bus (MIB) is a data communications standard for bedside patient connected medical devices. It is formally titled IEEE 1073 Standard for Medical Device Communications. MIB defines a complete seven layer communications stack for devices in acute care settings. All of the design trade-offs in writing the standard were taken to optimize performance in acute care settings. The key clinician based constraints on network performance are: (1) the network must be able to withstand multiple daily reconfigurations due to patient movement and condition changes; (2) the network must be 'plug-and-play' to allow clinicians to set up the network by simply plugging in a connector, taking no other actions; (3) the network must allow for unambiguous associations of devices with specific patients. A network of this type will be used by clinicians, thus giving complete, accurate, real time data from patient connected devices. This capability leads to many possible improvements in patient care and hospital cost reduction. The possible uses for comprehensive automatic data capture are only limited by imagination and creativity of clinicians adapting to the new hospital business paradigm.

Patterning of conjugated polymers for organic optoelectronic devices.

PubMed

Xu, Youyong; Zhang, Fan; Feng, Xinliang

2011-05-23

Conjugated polymers have been attracting more and more attention because they possess various novel electrical, magnetical, and optical properties, which render them useful in modern organic optoelectronic devices. Due to their organic nature, conjugated polymers are light-weight and can be fabricated into flexible appliances. Significant research efforts have been devoted to developing new organic materials to make them competitive with their conventional inorganic counterparts. It is foreseeable that when large-scale industrial manufacture of the devices made from organic conjugated polymers is feasible, they would be much cheaper and have more functions. On one hand, in order to improve the performance of organic optoelectronic devices, it is essential to tune their surface morphologies by techniques such as patterning. On the other hand, patterning is the routine requirement for device processing. In this review, the recent progress in the patterning of conjugated polymers for high-performance optoelectronic devices is summarized. Patterning based on the bottom-up and top-down methods are introduced. Emerging new patterning strategies and future trends for conventional patterning techniques are discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controllable Spatial Configuration on Cathode Interface for Enhanced Photovoltaic Performance and Device Stability.

PubMed

Li, Jiangsheng; Duan, Chenghao; Wang, Ning; Zhao, Chengjie; Han, Wei; Jiang, Li; Wang, Jizheng; Zhao, Yingjie; Huang, Changshui; Jiu, Tonggang

2018-05-08

The molecular structure of cathode interface modification materials can affect the surface morphology of the active layer and key electron transfer processes occurring at the interface of polymer solar cells in inverted structures mostly due to the change of molecular configuration. To investigate the effects of spatial configuration of the cathode interfacial modification layer on polymer solar cells device performances, we introduced two novel organic ionic salts (linear NS2 and three-dimensional (3D) NS4) combined with the ZnO film to fabricate highly efficient inverted solar cells. Both organic ionic salts successfully decreased the surface traps of the ZnO film and made its work function more compatible. Especially NS4 in three-dimensional configuration increased the electron mobility and extraction efficiency of the interfacial film, leading to a significant improvement of device performance. Power conversion efficiency (PCE) of 10.09% based on NS4 was achieved. Moreover, 3D interfacial modification could retain about 92% of its initial PCE over 160 days. It is proposed that 3D interfacial modification retards the element penetration-induced degradation without impeding the electron transfer from the active layer to the ZnO film, which significantly improves device stability. This indicates that inserting three-dimensional organic ionic salt is an efficient strategy to enhance device performance.

Atlantoaxial Joint Distraction with a New Expandable Device for the Treatment of Basilar Invagination with Preservation of the C2 Nerve Root: A Cadaveric Anatomical Study.

PubMed

Polli, Filippo Maria; Trungu, Sokol; Miscusi, Massimo; Forcato, Stefano; Visocchi, Massimiliano; Raco, Antonino

2017-01-01

Atlantoaxial joint distraction has been advocated for the decompression of the brain stem in patients affected by basilar invagination, avoiding direct transoral decompression. This technique requires C2 ganglion resection and it is often impossible to perform due to the peculiar bony anatomy. We describe a cadaveric anatomical study supporting the feasibility of C1-C2 distraction performed with an expandable device, allowing easier insertion of the tool and preservation of the C2 nerve root. In five adult cadaveric specimens, posterior atlantoaxial surgical exposure was performed and an expandable system was inserted within the C1-C2 joint. The expansion of the device, leading to active distraction of the joint space, together with all the surgical steps of the technique was recorded with anatomical pictures and the final results were checked with a computed tomography (CT) scan. Insertion of the device was easily performed in all cases without anatomical conflict with the C2 ganglion; CT scans confirmed the distraction of the C1-C2 joint. This cadaveric anatomical study confirms the feasibility of the introduction of an expandable and flexible device within the C1-C2 joint, allowing it's distraction and preservation of the C2 ganglion.

Study of the properties of new SPM detectors

NASA Astrophysics Data System (ADS)

Stewart, A. G.; Greene-O'Sullivan, E.; Herbert, D. J.; Saveliev, V.; Quinlan, F.; Wall, L.; Hughes, P. J.; Mathewson, A.; Jackson, J. C.

2006-02-01

The operation and performance of multi-pixel, Geiger-mode APD structures referred to as Silicon Photomultiplier (SPM) are reported. The SPM is a solid state device that has emerged over the last decade as a promising alternative to vacuum PMTs. This is due to their comparable performance in addition to their lower bias operation and power consumption, insensitivity to magnetic fields and ambient light, smaller size and ruggedness. Applications for these detectors are numerous and include life sciences, nuclear medicine, particle physics, microscopy and general instrumentation. With SPM devices, many geometrical and device parameters can be adjusted to optimize their performance for a particular application. In this paper, Monte Carlo simulations and experimental results for 1mm2 SPM structures are reported. In addition, trade-offs involved in optimizing the SPM in terms of the number and size of pixels for a given light intensity, and its affect on the dynamic range are discussed.

Progress and Challenges in Macroencapsulation Approaches for Type 1 Diabetes (T1D) Treatment: Cells, Biomaterials, and Devices

PubMed Central

Song, Shang; Roy, Shuvo

2018-01-01

Macroencapsulation technology has been an attractive topic in the field of treatment for Type 1 diabetes due to mechanical stability, versatility, and retrievability of the macrocapsule design. Macro-capsules can be categorized into extravascular and intravascular devices, in which solute transport relies either on diffusion or convection, respectively. Failure of macroencapsulation strategies can be due to limited regenerative capacity of the encased insulin-producing cells, sub-optimal performance of encapsulation biomaterials, insufficient immunoisolation, excessive blood thrombosis for vascular perfusion devices, and inadequate modes of mass transfer to support cell viability and function. However, significant technical advancements have been achieved in macroencapsulation technology, namely reducing diffusion distance for oxygen and nutrients, using pro-angiogenic factors to increase vascularization for islet engraftment, and optimizing membrane permeability and selectivity to prevent immune attacks from host’s body. This review presents an overview of existing macroencapsulation devices and discusses the advances based on tissue-engineering approaches that will stimulate future research and development of macroencapsulation technology. PMID:26615050

Development of a new instrument for direct skin friction measurements

NASA Technical Reports Server (NTRS)

Vakili, A. D.; Wu, J. M.

1986-01-01

A device developed for the direct measurement of wall shear stress generated by flows is described. Simple and symmetric in design with optional small moving mass and no internal friction, the features employed in the design eliminate most of the difficulties associated with the traditional floating element balances. The device is basically small and can be made in various sizes. Vibration problems associated with the floating element skin friction balances were found to be minimized due to the design symmetry and optional damping provided. The design eliminates or reduces the errors associated with conventional floating element devices: such as errors due to gaps, pressure gradient, acceleration, heat transfer, and temperature change. The instrument is equipped with various sensing systems and the output signal is a linear function of the wall shear stress. Dynamic measurements could be made in a limited range and measurements in liquids could be performed readily. Measurement made in the three different tunnels show excellent agreement with data obtained by the floating element devices and other techniques.

Atomic Scale Understanding of Poly-Si/SiO2/c-Si Passivated Contacts: Passivation Degradation Due to Metallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aguiar, Jeffery A.; Young, David; Lee, Benjamin

2016-11-21

The key attributes for achieving high efficiency crystalline silicon solar cells include class leading developments in the ability to approach the theoretical limits of silicon solar technology (29.4% efficiency). The push for high efficiency devices is further compounded with the clear need for passivation to reduce recombination at the metal contacts. At the same time there is stringent requirement to retain the same material device quality, surface passivation, and performance characteristics following subsequent processing. The development of passivated silicon cell structures that retain active front and rear surface passivation and overall material cell quality is therefore a relevant and activemore » area of development. To address the potential outcomes of metallization on passivated silicon stack, we report on some common microstructural features of degradation due to metallization for a series of silicon device stacks. A fundamental materials understanding of the metallization process on retaining high-efficiency passivated Si devices is therefore gained over these series of results.« less

Resonant Pulse Combustors: A Reliable Route to Practical Pressure Gain Combustion

NASA Technical Reports Server (NTRS)

Paxson, Dan

2017-01-01

A particular type of pressure gain combustion (PGC) device is described, which is under investigation at GRC. The Resonant Pulse Combustor (RPC) has been largely overlooked due to its theoretically low performance. However, its practical performance is quite competitive with other PGC systems, and its physical simplicity is unmatched.

Determining the Effects of Environment and Atmospheric Parameters on PV Field Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Micheli, Leonardo; Muller, Matthew; Kurtz, Sarah

2016-11-21

The performance losses due to soiling occurring on any photovoltaic (PV) device are caused by a complex mechanism that involves numerous factors and their interactions. For this reason, the present work analyzes the outputs of reference PV cells installed in various locations, with the aim of contributing to the identification of the most important factors influencing the accumulation of dust on a PV surface. Parameters such as the air-quality indexes, the recurrence and the amount of rainfall and the climate zone are investigated and related to the soiling losses of the PV device.

Self-aligned photolithography for the fabrication of fully transparent high-voltage devices

NASA Astrophysics Data System (ADS)

Zhang, Yonghui; Mei, Zengxia; Huo, Wenxing; Wang, Tao; Liang, Huili; Du, Xiaolong

2018-05-01

High-voltage devices, working in the range of hundreds of volts, are indispensable elements in the driving or readout circuits for various kinds of displays, integrated microelectromechanical systems and x-ray imaging sensors. However, the device performances are found hardly uniform or repeatable due to the misalignment issue, which are extremely common for offset drain high-voltage devices. To resolve this issue, this article reports a set of self-aligned photolithography technology for the fabrication of high-voltage devices. High-performance fully-transparent high-voltage thin film transistors, diodes and logic inverters are successfully fabricated with this technology. Unlike other self-aligned routes, opaque masks are introduced on the backside of the transparent substrate to facilitate proximity exposure method. The photolithography process is simulated and analyzed with technology computer aided design simulation to explain the working principle of the proximity exposure method. The substrate thickness is found to be vital for the implementation of this technology based on both simulation and experimental results. The electrical performance of high-voltage devices is dependent on the offset length, which can be delicately modulated by changing the exposure dose. The presented self-aligned photolithography technology is proved to be feasible in high-voltage circuits, demonstrating its huge potential in practical industrial applications.

Inverted organic electronic and optoelectronic devices

NASA Astrophysics Data System (ADS)

Small, Cephas E.

The research and development of organic electronics for commercial application has received much attention due to the unique properties of organic semiconductors and the potential for low-cost high-throughput manufacturing. For improved large-scale processing compatibility and enhanced device stability, an inverted geometry has been employed for devices such as organic light emitting diodes and organic photovoltaic cells. These improvements are attributed to the added flexibility to incorporate more air-stable materials into the inverted device geometry. However, early work on organic electronic devices with an inverted geometry typically showed reduced device performance compared to devices with a conventional structure. In the case of organic light emitting diodes, inverted devices typically show high operating voltages due to insufficient carrier injection. Here, a method for enhancing hole injection in inverted organic electronic devices is presented. By incorporating an electron accepting interlayer into the inverted device, a substantial enhancement in hole injection efficiency was observed as compared to conventional devices. Through a detailed carrier injection study, it is determined that the injection efficiency enhancements in the inverted devices are due to enhanced charge transfer at the electron acceptor/organic semiconductor interface. A similar situation is observed for organic photovoltaic cells, in which devices with an inverted geometry show limited carrier extraction in early studies. In this work, enhanced carrier extraction is demonstrated for inverted polymer solar cells using a surface-modified ZnO-polymer composite electron-transporting layer. The insulating polymer in the composite layer inhibited aggregation of the ZnO nanoparticles, while the surface-modification of the composite interlayer improved the electronic coupling with the photoactive layer. As a result, inverted polymer solar cells with power conversion efficiencies of over 8% were obtained. To further study carrier extraction in inverted polymer solar cells, the active layer thickness dependence of the efficiency was investigated. For devices with active layer thickness < 200 nm, power conversion efficiencies over 8% was obtained. This result is important for demonstrating improved large-scale processing compatibility. Above 200 nm, significant reduction in cell efficiency were observed. A detailed study of the loss processes that contributed to the reduction in efficiency for thick-film devices are presented.

Collection-limited theory interprets the extraordinary response of single semiconductor organic solar cells

PubMed Central

Ray, Biswajit; Baradwaj, Aditya G.; Khan, Mohammad Ryyan; Boudouris, Bryan W.; Alam, Muhammad Ashraful

2015-01-01

The bulk heterojunction (BHJ) organic photovoltaic (OPV) architecture has dominated the literature due to its ability to be implemented in devices with relatively high efficiency values. However, a simpler device architecture based on a single organic semiconductor (SS-OPV) offers several advantages: it obviates the need to control the highly system-dependent nanoscale BHJ morphology, and therefore, would allow the use of broader range of organic semiconductors. Unfortunately, the photocurrent in standard SS-OPV devices is typically very low, which generally is attributed to inefficient charge separation of the photogenerated excitons. Here we show that the short-circuit current density from SS-OPV devices can be enhanced significantly (∼100-fold) through the use of inverted device configurations, relative to a standard OPV device architecture. This result suggests that charge generation may not be the performance bottleneck in OPV device operation. Instead, poor charge collection, caused by defect-induced electric field screening, is most likely the primary performance bottleneck in regular-geometry SS-OPV cells. We justify this hypothesis by: (i) detailed numerical simulations, (ii) electrical characterization experiments of functional SS-OPV devices using multiple polymers as active layer materials, and (iii) impedance spectroscopy measurements. Furthermore, we show that the collection-limited photocurrent theory consistently interprets typical characteristics of regular SS-OPV devices. These insights should encourage the design and OPV implementation of high-purity, high-mobility polymers, and other soft materials that have shown promise in organic field-effect transistor applications, but have not performed well in BHJ OPV devices, wherein they adopt less-than-ideal nanostructures when blended with electron-accepting materials. PMID:26290582

Collection-limited theory interprets the extraordinary response of single semiconductor organic solar cells.

PubMed

Ray, Biswajit; Baradwaj, Aditya G; Khan, Mohammad Ryyan; Boudouris, Bryan W; Alam, Muhammad Ashraful

2015-09-08

The bulk heterojunction (BHJ) organic photovoltaic (OPV) architecture has dominated the literature due to its ability to be implemented in devices with relatively high efficiency values. However, a simpler device architecture based on a single organic semiconductor (SS-OPV) offers several advantages: it obviates the need to control the highly system-dependent nanoscale BHJ morphology, and therefore, would allow the use of broader range of organic semiconductors. Unfortunately, the photocurrent in standard SS-OPV devices is typically very low, which generally is attributed to inefficient charge separation of the photogenerated excitons. Here we show that the short-circuit current density from SS-OPV devices can be enhanced significantly (∼100-fold) through the use of inverted device configurations, relative to a standard OPV device architecture. This result suggests that charge generation may not be the performance bottleneck in OPV device operation. Instead, poor charge collection, caused by defect-induced electric field screening, is most likely the primary performance bottleneck in regular-geometry SS-OPV cells. We justify this hypothesis by: (i) detailed numerical simulations, (ii) electrical characterization experiments of functional SS-OPV devices using multiple polymers as active layer materials, and (iii) impedance spectroscopy measurements. Furthermore, we show that the collection-limited photocurrent theory consistently interprets typical characteristics of regular SS-OPV devices. These insights should encourage the design and OPV implementation of high-purity, high-mobility polymers, and other soft materials that have shown promise in organic field-effect transistor applications, but have not performed well in BHJ OPV devices, wherein they adopt less-than-ideal nanostructures when blended with electron-accepting materials.

Gallium nitride vertical power devices on foreign substrates: a review and outlook

NASA Astrophysics Data System (ADS)

Zhang, Yuhao; Dadgar, Armin; Palacios, Tomás

2018-07-01

Vertical gallium nitride (GaN) power devices have attracted increased attention due to their superior high-voltage and high-current capacity as well as easier thermal management than lateral GaN high electron mobility transistors. Vertical GaN devices are promising candidates for next-generation power electronics in electric vehicles, data centers, smart grids and renewable energy process. The use of low-cost foreign substrates such as silicon (Si) substrates, instead of the expensive free-standing GaN substrates, could greatly trim material cost and enable large-diameter wafer processing while maintaining high device performance. This review illustrates recent progress in material epitaxy, device design, device physics and processing technologies for the development of vertical GaN power devices on low-cost foreign substrates. Although the device technologies are still at the early stage of development, state-of-the-art vertical GaN-on-Si power diodes have already shown superior Baliga’s figure of merit than commercial SiC and Si power devices at the voltage classes beyond 600 V. Furthermore, we unveil the design space of vertical GaN power devices on native and different foreign substrates, from the analysis of the impact of dislocation and defects on device performance. We conclude by identifying the application space, current challenges and exciting research opportunities in this very dynamic research field.

Titanium MEMS Technology Development for Drug Delivery and Microfluidic Applications

NASA Astrophysics Data System (ADS)

Khandan, Omid

The use of microelectromechanical systems (MEMS) technology in medical and biological applications has increased dramatically in the past decade due to the potential for enhanced sensitivity, functionality, and performance associated with the miniaturization of devices, as well as the market potential for low-cost, personalized medicine. However, the utility of such devices in clinical medicine is ultimately limited due to factors associated with prevailing micromachined materials such as silicon, as it poses concerns of safety and reliability due to its intrinsically brittle properties, making it prone to catastrophic failure. Recent advances in titanium (Ti) micromachining provides an opportunity to create devices with enhanced safety and performance due to its proven biocompatibility and high fracture toughness, which causes it to fail by means of graceful, plasticity-based deformation. Motivated by this opportunity, we discuss our efforts to advance Ti MEMS technology in two ways: 1) Through the development of titanium-based microneedles (MNs) that seek to provide a safer, simpler, and more efficacious means of ocular drug delivery, and 2) Through the advancement of Ti anodic bonding for future realization of robust microfluidic devices for photocatalysis applications. As for the first of these thrusts, we show that MN devices with in-plane geometry and through-thickness fenestrations that serve as drug reservoirs for passive delivery via diffusive transport from fast-dissolving coatings can be fabricated utilizing Ti deep reactive ion etching (Ti DRIE). Our mechanical testing and finite element analysis (FEA) results suggest that these devices possess sufficient stiffness for reliable corneal insertion. Our MN coating studies show that, relative to solid MNs of identical shank dimension, fenestrated devices can increase drug carrying capacity by 5-fold. Furthermore, we demonstrate that through-etched fenestrations provide a protective cavity for delivering drugs subsurface, thereby enhancing delivery efficiencies in an ex vivo rabbit cornea model. Collectively, these results show the potential embodied in developing Ti MNs for effective, minimally invasive, and low-cost ocular drug delivery. Additionally, or the second of these thrusts, we report the development of an anodic bonding process that allows, for the first time, high-strength joining of bulk Ti and glass substrates at the wafer-scale, without need for interlayers or adhesives. We demonstrate that uniform, full-wafer bonding can be achieved at temperatures as low as 250°C, and that failure during burst pressure testing occurs via crack propagation through the glass, rather than the Ti/glass interface, thus demonstrating the robustness of the bonding. Moreover, using optimized bonding conditions, we demonstrate the fabrication of rudimentary Ti/glass-based microfluidic devices at the wafer-scale, and their leak-free operation under pressure-driven flow. Finally, we demonstrate the monolithic integration of nanoporous titanium dioxide within such devices, thus illustrating the promise embodied in Ti anodic bonding for future realization of robust microfluidic devices for photocatalysis applications. Together, these results demonstrate the potential embodied in utilizing Ti MEMS technology for the fabrication of novel drug delivery and microfluidic systems with enhanced robustness, safety, and performance.

Performance analysis of resistive switching devices based on BaTiO3 thin films

NASA Astrophysics Data System (ADS)

Samardzic, Natasa; Kojic, Tijana; Vukmirovic, Jelena; Tripkovic, Djordjije; Bajac, Branimir; Srdic, Vladimir; Stojanovic, Goran

2016-03-01

Resitive switching devices, memristors, have recenty attracted much attention due to promising performances and potential applications in the field of logic and memory devices. Here, we present thin film BaTiO3 based memristor fabricated using ink-jet printing technique. Active material is a single layer barium titanate film with thickness of ̴100 nm, sandwitched between metal electodes. Printing parameters were optimized aiming to achieve stable drop flow and uniform printed layer. Current-voltage characteristics show typical memristive behavior with pinched hysteresis loop crossed at the origin, with marked differences between High Resistive State (HRS) and Low Resistive State (LRS). Obtained resistive states are stable during numerous switching processes. The device also shows unipolar switching effect for negative voltage impulses. Variable voltage impulse amplitudes leads to the shifting of the energy levels of electode contacts resulting in changing of the overall current through the device. Structural charcterization have been performed using XRD analysis and SEM micrography. High-temperature current-voltage measurements combined with transport parameter analysis using Hall efect measurement system (HMS 3000) and Impedance Analyzer AC measurements allows deeper insigth into conduction mechanism of ferroelectric memristors.

Evaluation of input devices for teleoperation of concentric tube continuum robots for surgical tasks

NASA Astrophysics Data System (ADS)

Fellmann, Carolin; Kashi, Daryoush; Burgner-Kahrs, Jessica

2015-03-01

For those minimally invasive surgery where conventional surgical instruments cannot reach the surgical site due to their straight structure and rigidity, concentric tube continuum robots are a promising technology because of their small size (comparable to a needle) and maneuverability. These flexible, compliant manipulators can easily access hard to reach anatomical structures, e.g. by turning around corners. By teleoperating the robot the surgeon stays in direct control at any time. In this paper, three off-the-shelf input devices are considered for teleoperation of a concentric tube continuum robot: a 3D mouse, a gamepad, and a 3 degrees of freedom haptic input device. Three tasks which mimic relevant surgical maneuvers are performed by 12 subjects using each input device: reaching specific locations, picking and placing objects from one location to another, and approaching the surgical site through a restricted pathway. We present quantitative results (task completion time, accuracy, etc.), a statistical analysis, and empirical results (questionnaires). Overall, the performance of subjects using the 3D mouse was superior to the performance using the other input devices. The subjective ranking of the 3D mouse by the subjects confirms this result.

Performance of an SOI Boot-Strapped Full-Bridge MOSFET Driver, Type CHT-FBDR, under Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2009-01-01

Electronic systems designed for use in deep space and planetary exploration missions are expected to encounter extreme temperatures and wide thermal swings. Silicon-based devices are limited in their wide-temperature capability and usually require extra measures, such as cooling or heating mechanisms, to provide adequate ambient temperature for proper operation. Silicon-On-Insulator (SOI) technology, on the other hand, lately has been gaining wide spread use in applications where high temperatures are encountered. Due to their inherent design, SOI-based integrated circuit chips are able to operate at temperatures higher than those of the silicon devices by virtue of reducing leakage currents, eliminating parasitic junctions, and limiting internal heating. In addition, SOI devices provide faster switching, consume less power, and offer improved radiation-tolerance. Very little data, however, exist on the performance of such devices and circuits under cryogenic temperatures. In this work, the performance of an SOI bootstrapped, full-bridge driver integrated circuit was evaluated under extreme temperatures and thermal cycling. The investigations were carried out to establish a baseline on the functionality and to determine suitability of this device for use in space exploration missions under extreme temperature conditions.

Initial Experience of an Anesthesiology-based Service for Perioperative Management of Pacemakers and Implantable Cardioverter Defibrillators.

PubMed

Rooke, G Alec; Lombaard, Stefan A; Van Norman, Gail A; Dziersk, Jörg; Natrajan, Krishna M; Larson, Lyle W; Poole, Jeanne E

2015-11-01

Management of cardiovascular implantable electronic devices (CIEDs), including pacemakers and implantable cardioverter defibrillators, for surgical procedures is challenging due to the increasing number of patients with CIEDs and limited availability of trained providers. At the authors' institution, a small group of anesthesiologists were trained to interrogate CIEDs, devise a management plan, and perform preoperative and postoperative programming and device testing whenever necessary. Patients undergoing surgery between October 1, 2009 and June 30, 2013 at the University of Washington Medical Center were included in a retrospective chart review to determine the number of devices actively managed by the Electrophysiology/Cardiology Service (EPCS) versus the Anesthesiology Device Service (ADS), changes in workload over time, surgical case delays due to device management, and errors and problems encountered in device programming. The EPCS managed 254 CIEDs, the ADS managed 548, and 227 by neither service. Over time, the ADS providers managed an increasing percentage of devices with decreasing supervision from the EPCS. Only two CIEDs managed by the ADS required immediate assistance from the EPCS. Patients who were unstable postoperatively were referred to the EPCS. Although numerous issues in programming were encountered, primarily when restoring demand pacing after programming asynchronous pacing for surgery, no patient harm resulted from ADS or EPCS management of CIEDs. An ADS can provide safe CIED management for surgery, but it requires specialized provider training and strong support from the EPCS. Due to the complexity of CIED management, an ADS will likely only be feasible in high-volume settings.

Use of cryopoor plasma for albumin replacement and continuous antimicrobial infusion for treatment of septic peritonitis in a dog.

PubMed

Ropski, Meaghan K; Guillaumin, Julien; Monnig, Andrea A; Townsend, Katy; McLoughlin, Mary A

2017-05-01

To report the successful management of a dog with septic peritonitis and septic shock secondary to enterectomy dehiscence using novel techniques for identification of intestinal dehiscence and for septic shock treatment. A 5-year-old castrated male Bernese Mountain Dog presented for lethargy 6 days following enterotomy for foreign body obstruction. Septic peritonitis was identified due to dehiscence of the enterotomy site, and resection and anastomosis were performed using a gastrointestinal anastomosis and thoracoabdominal stapling device. Postoperatively the patient experienced severe hypotension, which responded to norepinephrine constant rate infusion (CRI) after failing to improve with fluid therapy or dopamine CRI. Further treatment included antimicrobial CRI and supportive care including careful fluid therapy. Due to low effective circulating volume paired with intersititial fluid overload and large volume abdominal effusion, fluid therapy consisted of a combination of human serum albumin, canine albumin, synthetic colloids, and isotonic crystalloids. Cryopoor plasma (CPP) was used as a source of canine albumin and intravascular volume. On Day 4, food dye was given through a nasogastric tube due to suspicion of dehiscence of the anastomosis site. Dehiscence was confirmed during abdominal exploratory, and a second resection and anastomosis was performed. Abdominal partial closure with vacuum-assisted closure device was performed. Supportive care was continued with CPP CRI and imipenem CRI. Planned relaparotomy to change the vacuum-assisted closure device was performed 48 hours later, with abdominal closure 96 hours after anastomosis. The patient was discharged on Day 15. Recheck 12 months later was normal. This case includes novel techniques such food dye via nasogastric tube to identify anastomosis dehiscence, use of CPP as a source of canine albumin, and antimicrobial CRI in a dog with septic peritonitis. © Veterinary Emergency and Critical Care Society 2017.

Application of Localized Surface Plasmons for the Enhancement of Thin-Film Amorphous Silicon Solar Cells

NASA Astrophysics Data System (ADS)

Hungerford, Chanse D.

Photovoltaics (PV) is a rapidly growing electricity source and new PV technologies are continually being developed. Increasing the efficiency of PV will continue to drive down the costs of solar installations. One area of research that is necessary for increasing PV performance is light management. This is especially true for thin-film devices that are unable to maximize absorption of the solar spectrum in a single pass. Methods for light trapping include texturing, high index nanostructures, nanophotonic structures, and plasmonics. This research focus on the use of plasmonic structures, in this case metallic nanoparticles, to increase the power conversion efficiency of solar cells. Three different designs are investigated. First was an a-Si:H solar cell, approximately 300nm thick, with a rear reflector consisting of metallic nanoparticles and a mirror. This structure is referred to as a plasmonic back reflector. Simulations indicate that a maximum absorption increase of 7.2% in the 500nm to 800nm wavelength range is possible versus a flat reference. Experiments did not show enhancement, likely due to absorption in the transparent conducting oxide and the parasitic absorption in the small metallic nanoparticles. The second design was an a-Si:H solar cell with embedded metal nanoparticles. Experimental devices were successfully fabricated by breaking the i-layer deposition into two steps and introducing colloidal nanoparticles between the two depositions. These devices performed worse than the controls, but the results provide proof that fabrication of such a device is possible and may be improved in the future. Suggestions for improvements are discussed. The final device investigated was an ultra-thin, undoped solar cell. The device used an absorber layer < 100nm thick, with the thinnest device using an i-layer of only approximately 15nm. Loses due to the doped layers in the standard p-i-n structure can be reduced by replacing the doped layers with MoO 3 and LiF. While the efficiency and open circuit voltage of the test devices was lower than the controls, the short circuit current was increased by 27.3%. Incorporation of nanoparticles into the device caused shorting between the layers, resulting in non-functional solar cells. This is likely due to fabrication issues that can be solved and suggestions are discussed.

Influence of Hybrid Perovskite Fabrication Methods on Film Formation, Electronic Structure, and Solar Cell Performance

PubMed Central

Schnier, Tobias; Emara, Jennifer; Olthof, Selina; Meerholz, Klaus

2017-01-01

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to achieve device efficiencies exceeding other thin film device technologies. Yet, large variations in device efficiency and basic physical properties are reported. This is due to unintentional variations during film processing, which have not been sufficiently investigated so far. We therefore conducted an extensive study of the morphology and electronic structure of a large number of CH3NH3PbI3 perovskite where we show how the preparation method as well as the mixing ratio of educts methylammonium iodide and lead(II) iodide impact properties like film formation, crystal structure, density of states, energy levels, and ultimately the solar cell performance. PMID:28287555

Response of surge protection devices to fast rising pulses

NASA Technical Reports Server (NTRS)

Mindel, I. N.

1980-01-01

Two types of lightning protection modules incorporating leadless (pill type) Zener like devices were evaluated with regard to their ability to suppress EMP induced transients. Two series of tests were performed to evaluate the ability of these modules to react to fast rate of rise ( 1Kv/ns) transients, and the attenuation introduced and the ability to limit damped sinusoid pulses which may be induced due to an EMP resulting from a nuclear detonation.

Performance evaluation of a high power DC-DC boost converter for PV applications using SiC power devices

NASA Astrophysics Data System (ADS)

Almasoudi, Fahad M.; Alatawi, Khaled S.; Matin, Mohammad

2016-09-01

The development of Wide band gap (WBG) power devices has been attracted by many commercial companies to be available in the market because of their enormous advantages over the traditional Si power devices. An example of WBG material is SiC, which offers a number of advantages over Si material. For example, SiC has the ability of blocking higher voltages, reducing switching and conduction losses and supports high switching frequency. Consequently, SiC power devices have become the affordable choice for high frequency and power application. The goal of this paper is to study the performance of 4.5 kW, 200 kHz, 600V DC-DC boost converter operating in continuous conduction mode (CCM) for PV applications. The switching behavior and turn on and turn off losses of different switching power devices such as SiC MOSFET, SiC normally ON JFET and Si MOSFET are investigated and analyzed. Moreover, a detailed comparison is provided to show the overall efficiency of the DC-DC boost converter with different switching power devices. It is found that the efficiency of SiC power switching devices are higher than the efficiency of Si-based switching devices due to low switching and conduction losses when operating at high frequencies. According to the result, the performance of SiC switching power devices dominate the conventional Si power devices in terms of low losses, high efficiency and high power density. Accordingly, SiC power switching devices are more appropriate for PV applications where a converter of smaller size with high efficiency, and cost effective is required.

Labour time required for piglet castration with isoflurane-anaesthesia using shared and stationary inhaler devices.

PubMed

Weber, Sabrina; Das, Gürbüz; Waldmann, Karl-Heinz; Gauly, Matthias

2014-01-01

Isoflurane-anaesthesia combined with an analgesic represents a welfare-friendly method of pain mitigation for castration of piglets. However, it requires an inhaler device, which is uneconomic for small farms. Sharing a device among farms may be an economical option if the shared use does not increase labour time and the resulting costs. This study aimed to investigate the amount and components of labour time required for piglet castration with isoflurane anaesthesia performed with stationary and shared devices. Piglets (N = 1579) were anaesthetised with isoflurane (using either stationary or shared devices) and castrated.The stationary devices were used in a group (n = 5) of larger farms (84 sows/farm on an average), whereas smaller farms (n = 7; 32 sows/farm on an average) shared one device. Each farm was visited four times and labour time for each process-step was recorded. The complete process included machine set-up, anaesthesia and castration by a practitioner, and preparation, collection and transport of piglets by a farmer. Labour time of the complete process was increased (P = 0.012) on farms sharing a device (266 s/piglet) compared to farms using stationary devices (177 s/ piglet), due to increased time for preparation (P = 0.055), castration (P = 0.026) and packing (P = 0.010) when sharing a device. However, components of the time budget of farms using stationary or shared devices did not differ significantly (P > 0.05). Cost arising from time spent by farmers did not differ considerably between the use of stationary (0.28 Euro per piglet) and shared (0.26 Euro) devices. It is concluded that costs arising from the increased labour time due to sharing a device can be considered marginal, since the high expenses originating from purchasing an inhaler device are shared among several farms.

Analysis of high-k spacer on symmetric underlap DG-MOSFET with Gate Stack architecture

NASA Astrophysics Data System (ADS)

Das, Rahul; Chakraborty, Shramana; Dasgupta, Arpan; Dutta, Arka; Kundu, Atanu; Sarkar, Chandan K.

2016-09-01

This paper shows the systematic study of underlap double gate (U-DG) NMOSFETs with Gate Stack (GS) under the influence of high-k spacers. In highly scaled devices, underlap is used at the Source and Drain side so as to reduce the short channel effects (SCE's), however, it significantly reduces the on current due to the increased channel resistance. To overcome these drawbacks, the use of high-k spacers is projected as one of the remedies. In this paper, the analog performance of the devices is studied on the basis of parameters like transconductance (gm), transconductance generation factor (gm/Id) and intrinsic gain (gmro). The RF performance is analyzed on the merits of intrinsic capacitance (Cgd, Cgs), resistance (Rgd, Rgs), transport delay (τm), inductance (Lsd), cutoff frequency (fT), and the maximum frequency of oscillation (fmax). The circuit performance of the devices are studied by implementing the device as the driver MOSFET in a Single Stage Common Source Amplifier. The Gain Bandwidth Product (GBW) has been analyzed from the frequency response of the circuit.

The role of inelastic deformations in the mechanical response of endovascular shape memory alloy devices.

PubMed

Petrini, Lorenza; Bertini, Alessandro; Berti, Francesca; Pennati, Giancarlo; Migliavacca, Francesco

2017-05-01

Nickel-titanium alloys are commonly adopted for producing cardiovascular minimally invasive devices such as self-expandable stents, aortic valves and stent-grafts. These devices are subjected to cyclic loads (due to blood pulsatility, leg or heart movements), that can induce fatigue fracture, and may also be subjected to very large deformations (due to crimping procedure, a tortuous physiological path or overloads), that can induce material yield. Recently, the authors developed a new constitutive model that considers inelastic strains due to not-completed reverse phase transformation (not all the stress-induced martensite turns back to austenite) or/and plasticity and their accumulation during cyclic loads. In this article, the model is implemented in the finite element code ABAQUS/Standard and it is used to investigate the effects of inelastic strain accumulation on endovascular nickel-titanium devices. In particular, the behavior of a transcatheter aortic valve is studied considering the following steps: (1) crimping, (2) expansion in a tube resembling a durability test chamber and (3) cyclic loads due to pressure variation applied on the inner surface of the tube. The analyses are performed twice, activating and not activating that part of the new model which describes the development of irreversible strain. From the results, it is interesting to note that plasticity has a very significant effect on the local material response, inducing stress modification from compression to tension. However, permanent deformations are concentrated in few zones of the stent frame and their presence does not affect the global behavior of the device that maintains its capability of recovering the original shape. In conclusion, this work suggests that at least for cardiovascular devices where the crimping is high (local strain may reach values of 8%-9%), taking into account inelastic effects due to plasticity and not-completed reverse phase transformation can be important, and hence using a suitable constitutive model is recommended.

Objective and perceptual comparisons of two bluetooth hearing aid assistive devices.

PubMed

Clark, Jackie L; Pustejovsky, Carmen; Vanneste, Sven

2017-08-01

With the advent of Bluetooth technology, many of the assistive listening devices for hearing have become manufacturer specific, with little objective information about the performance provided. Thirty native English-speaking adults (mean age 29.8) with normal hearing were tested pseudo-randomly with two major hearing aid manufacturers' proprietary Bluetooth connectivity devices paired to the accompanying manufacturer's specific hearing aids. Sentence recognition performance was objectively measured for each system with signals transmitted via a land-line to the same iPhone in two conditions. There was a significant effect of participant's performance according to listening condition. There was no significant effect between device manufacturers according to listening condition, but there was a significant effect in participant's perception of "quality of sound". Despite differences in signal transmission for each devise, when worn by participants both the systems performed equally. In fact, participants expressed personal preferences for specific technology that was largely due to their perceived quality of sound while listening to recorded signals. While further research is necessary to investigate other measures of benefit for Bluetooth connectivity devices, preliminary data suggest that in order to ensure comfort and compatibility, not only should objective measures of the patient benefit be completed, but also assessing the patient's perception of benefit is equally important. Implications for Rehabilitation All professionals who work with individuals with hearing loss, become aware of the differences in the multiple choices for assistive technology readily available for hearing loss. With the ever growing dispensing of Bluetooth connectivity devices coupled to hearing aids, there is an increased burden to determine whether performance differences could exist between manufacturers. There is a growing need to investigate other measures of benefit for Bluetooth hearing aid connectivity devices that not only include objective measures, but also patient perception of benefit.

In-plane Schottky-barrier field-effect transistors based on 1T/2H heterojunctions of transition-metal dichalcogenides

NASA Astrophysics Data System (ADS)

Fan, Zhi-Qiang; Jiang, Xiang-Wei; Luo, Jun-Wei; Jiao, Li-Ying; Huang, Ru; Li, Shu-Shen; Wang, Lin-Wang

2017-10-01

As Moore's law approaches its end, two-dimensional (2D) materials are intensely studied for their potentials as one of the "More than Moore' (MM) devices. However, the ultimate performance limits and the optimal design parameters for such devices are still unknown. One common problem for the 2D-material-based device is the relative weak on-current. In this study, two-dimensional Schottky-barrier field-effect transistors (SBFETs) consisting of in-plane heterojunctions of 1T metallic-phase and 2H semiconducting-phase transition-metal dichalcogenides (TMDs) are studied following the recent experimental synthesis of such devices at a much larger scale. Our ab initio simulation reveals the ultimate performance limits of such devices and offers suggestions for better TMD materials. Our study shows that the Schottky-barrier heights (SBHs) of the in-plane 1T/2H contacts are smaller than the SBHs of out-of-plane contacts, and the contact coupling is also stronger in the in-plane contact. Due to the atomic thickness of the monolayer TMD, the average subthreshold swing of the in-plane TMD-SBFETs is found to be close to the limit of 60 mV/dec, and smaller than that of the out-of-plane TMD-SBFET device. Different TMDs are considered and it is found that the in-plane WT e2-SBFET provides the best performance and can satisfy the performance requirement of the sub-10-nm high-performance transistor outlined by the International Technology Roadmap for Semiconductors, and thus could be developed into a viable sub-10-nm MM device in the future.

Performance issues for iterative solvers in device simulation

NASA Technical Reports Server (NTRS)

Fan, Qing; Forsyth, P. A.; Mcmacken, J. R. F.; Tang, Wei-Pai

1994-01-01

Due to memory limitations, iterative methods have become the method of choice for large scale semiconductor device simulation. However, it is well known that these methods still suffer from reliability problems. The linear systems which appear in numerical simulation of semiconductor devices are notoriously ill-conditioned. In order to produce robust algorithms for practical problems, careful attention must be given to many implementation issues. This paper concentrates on strategies for developing robust preconditioners. In addition, effective data structures and convergence check issues are also discussed. These algorithms are compared with a standard direct sparse matrix solver on a variety of problems.

Radiation Test Challenges for Scaled Commerical Memories

NASA Technical Reports Server (NTRS)

LaBel, Kenneth A.; Ladbury, Ray L.; Cohn, Lewis M.; Oldham, Timothy

2007-01-01

As sub-100nm CMOS technologies gather interest, the radiation effects performance of these technologies provide a significant challenge. In this talk, we shall discuss the radiation testing challenges as related to commercial memory devices. The focus will be on complex test and failure modes emerging in state-of-the-art Flash non-volatile memories (NVMs) and synchronous dynamic random access memories (SDRAMs), which are volatile. Due to their very high bit density, these device types are highly desirable for use in the natural space environment. In this presentation, we shall discuss these devices with emphasis on considerations for test and qualification methods required.

Deaths and cardiovascular injuries due to device-assisted implantable cardioverter–defibrillator and pacemaker lead extraction

PubMed Central

Hauser, Robert G.; Katsiyiannis, William T.; Gornick, Charles C.; Almquist, Adrian K.; Kallinen, Linda M.

2010-01-01

Aims An estimated 10 000–15 000 pacemaker and implantable cardioverter–defibrillator (ICD) leads are extracted annually worldwide using specialized tools that disrupt encapsulating fibrous tissue. Additional information is needed regarding the safety of the devices that have been approved for lead extraction. The aim of this study was to determine whether complications due to device-assisted lead extraction might be more hazardous than published data suggest, and whether procedural safety precautions are effective. Methods and results We searched the US Food and Drug Administration's (FDA) Manufacturers and User Defined Experience (MAUDE) database from 1995 to 2008 using the search terms ‘lead extraction and death’ and ‘lead extraction and injury’. Additional product specific searches were performed for the terms ‘death’ and ‘injury’. Between 1995 and 2008, 57 deaths and 48 serious cardiovascular injuries associated with device-assisted lead extraction were reported to the FDA. Owing to underreporting, the FDA database does not contain all adverse events that occurred during this period. Of the 105 events, 27 deaths and 13 injuries occurred in 2007–2008. During these 2 years, 23 deaths were linked with excimer laser or mechanical dilator sheath extractions. The majority of deaths and injuries involved ICD leads, and most were caused by lacerations of the right atrium, superior vena cava, or innominate vein. Overall, 62 patients underwent emergency surgical repair of myocardial perforations and venous lacerations and 35 (56%) survived. Conclusion These findings suggest that device-assisted lead extraction is a high-risk procedure and that serious complications including death may not be mitigated by emergency surgery. However, skilled standby cardiothoracic surgery is essential when performing pacemaker and ICD lead extractions. Although the incidence of these complications is unknown, the results of our study imply that device-assisted lead extractions should be performed by highly qualified physicians and their teams in specialized centres. PMID:19946113

78 FR 24817 - Visual-Manual NHTSA Driver Distraction Guidelines for In-Vehicle Electronic Devices

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-26

...The National Highway Traffic Safety Administration (NHTSA) is concerned about the effects of distraction on motor vehicle safety due to drivers' use of electronic devices. Consequently, NHTSA is issuing nonbinding, voluntary Driver Distraction Guidelines (NHTSA Guidelines) to promote safety by discouraging the introduction of excessively distracting devices in vehicles. This notice announces the issuance of the final version of the first phase of the NHTSA Guidelines. This first phase applies to original equipment (OE) in-vehicle electronic devices used by the driver to perform secondary tasks (communications, entertainment, information gathering, navigation tasks, etc. are considered secondary tasks) through visual-manual means (i.e., the driver looks at a device, manipulates a device-related control with his or her hand, and/or watches for visual feedback). The NHTSA Guidelines list certain secondary tasks believed by the agency to interfere inherently with a driver's ability to safely control the vehicle. The NHTSA Guidelines recommend that in-vehicle devices be designed so that they cannot be used by the driver to perform these inherently distracting secondary tasks while driving. For all other visual-manual secondary tasks, the NHTSA Guidelines specify a test method for measuring eye glance behavior during those tasks. Eye glance metrics are compared to acceptance criteria to evaluate whether a task interferes too much with driver attention, rendering it unsuitable for a driver to perform while driving. If a task does not meet the acceptance criteria, the NHTSA Guidelines recommend that the task be made inaccessible for performance by the driver while driving. In addition, the NHTSA Guidelines contain several recommendations to limit and reduce the potential for distraction associated with the use of OE in-vehicle electronic devices.

37 CFR 385.12 - Calculation of royalty payments in general.

Code of Federal Regulations, 2010 CFR

2010-07-01

... accounting period under its agreements with performing rights societies as defined in 17 U.S.C. 101, it will... information due to bona fide limitations of the available technology for services of that nature or of devices...

37 CFR 385.12 - Calculation of royalty payments in general.

Code of Federal Regulations, 2011 CFR

2011-07-01

... accounting period under its agreements with performing rights societies as defined in 17 U.S.C. 101, it will... information due to bona fide limitations of the available technology for services of that nature or of devices...

Carbon nanotube and graphene device modeling and simulation

NASA Astrophysics Data System (ADS)

Yoon, Young Ki

The performance of the semiconductors has been improved and the price has gone down for decades. It has been continuously scaled down in size year by year, and now it encounters the fundamental scaling limit. We, therefore, should prepare a new era beyond the conventional semiconductor technologies. One of the most promising devices is possible by carbon nanotube (CNT) or graphene nanoribbon (GNR) in terms of its excellent charge transport properties. Their fundamental material properties and device physics are totally different to those of the conventional devices. In this nano-regime, more sophisticated device modeling and simulation are really needed to elucidate nano-device operation and to save our resources from errors. The numerical simulation works in this dissertation will provide novel view points on the emerging devices. In this dissertation, CNT and GNR devices are numerically studied. The first part of this work is on CNT devices, and a common structure of CNT device has CNT channel, metal source and drain contacts, and gate electrode. We investigate the strain, geometry, and scattering effects on the device performance of CNT field-effect transistors (FETs). It is shown that even a small amount of strain can result in a large effect on the performance of CNTFETs due to the variation of the bandgap and band-structure-limited velocity. A type of strain which produces a larger bandgap results in increased Schottky barrier (SB) height and decreased band-structure-limited velocity, and hence a smaller minimum leakage current, smaller on current, larger maximum achievable Ion/Ioff, and larger intrinsic delay. We also examine geometry effect of partial gate CNTFETs. In the growth process of vertical CNT, underlap between the gate and the bottom electrode is advantageous for transistor operation because it suppresses ambipolar conduction of SBFETs. Both n-type and p-type transistor operations with balanced performance metrics can be achieved on a single partial gate FET by using proper bias schemes. The effect of phonon scattering on the intrinsic delay and cut-off frequency of Schottky barrier CNTFETs is also examined. Carriers are mostly scattered by optical and zone boundary phonons beyond the beginning of the channel. The scattering has a small direct effect on the DC on current of the CNTFET, but it results in significant decrease of intrinsic cut-off frequency and increase of intrinsic delay. Semiconducting CNT is useful for the channel in CNTFETs, whereas metallic CNT can be used as an electrode. If a porous CNT film is used as a source electrode, vertical thin-film transistors (TFTs) can be constructed. Vertical organic FET (OFET) shows clear transistor switching behavior allowing orders of magnitude modulation of the source-drain current even in the presence of electrostatic screening by the source electrode. The channel length should be carefully engineered due to the trade-off between device characteristics in the subthreshold and above-threshold regions. The second subject is device simulations of GNRFETs. Even though GNR is also graphene-based quasi-1D nanostructure like CNT, the differences in shape, boundary condition, and existence of edges and dangling bonds make it operate in a different way. Atomistic 3D simulation study of the performance of GNR SBFETs is presented. The impacts of non-idealities on device performance have been investigated. The edges of GNR, which do not exist in CNT, can be advantages or disadvantages. If an appropriate control by different edge atoms is possible, it would be definitely positive. Totally new electronic band structure is obtained by different edge-termination atoms. In addition, only a fraction of impurity atom can also much affect on the material properties of GNR. In order to perform device simulations of non-uniform GNR devices, multiscale simulation scheme can be used in non-equilibrium Green's function (NEGF) formalism and density-functional method.

Hadoop-MCC: Efficient Multiple Compound Comparison Algorithm Using Hadoop.

PubMed

Hua, Guan-Jie; Hung, Che-Lun; Tang, Chuan Yi

2018-01-01

In the past decade, the drug design technologies have been improved enormously. The computer-aided drug design (CADD) has played an important role in analysis and prediction in drug development, which makes the procedure more economical and efficient. However, computation with big data, such as ZINC containing more than 60 million compounds data and GDB-13 with more than 930 million small molecules, is a noticeable issue of time-consuming problem. Therefore, we propose a novel heterogeneous high performance computing method, named as Hadoop-MCC, integrating Hadoop and GPU, to copy with big chemical structure data efficiently. Hadoop-MCC gains the high availability and fault tolerance from Hadoop, as Hadoop is used to scatter input data to GPU devices and gather the results from GPU devices. Hadoop framework adopts mapper/reducer computation model. In the proposed method, mappers response for fetching SMILES data segments and perform LINGO method on GPU, then reducers collect all comparison results produced by mappers. Due to the high availability of Hadoop, all of LINGO computational jobs on mappers can be completed, even if some of the mappers encounter problems. A comparison of LINGO is performed on each the GPU device in parallel. According to the experimental results, the proposed method on multiple GPU devices can achieve better computational performance than the CUDA-MCC on a single GPU device. Hadoop-MCC is able to achieve scalability, high availability, and fault tolerance granted by Hadoop, and high performance as well by integrating computational power of both of Hadoop and GPU. It has been shown that using the heterogeneous architecture as Hadoop-MCC effectively can enhance better computational performance than on a single GPU device. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Effects of Lightning Injection on Power-MOSFETs

NASA Technical Reports Server (NTRS)

Celaya, Jose; Saha, Sankalita; Wysocki, Phil; Ely, Jay; Nguyen, Truong; Szatkowski, George; Koppen, Sandra; Mielnik, John; Vaughan, Roger; Goebel, Kai

2009-01-01

Lightning induced damage is one of the major concerns in aircraft health monitoring. Such short-duration high voltages can cause significant damage to electronic devices. This paper presents a study on the effects of lightning injection on power metal-oxide semiconductor field effect transistors (MOSFETs). This approach consisted of pin-injecting lightning waveforms into the gate, drain and/or source of MOSFET devices while they were in the OFF-state. Analysis of the characteristic curves of the devices showed that for certain injection modes the devices can accumulate considerable damage rendering them inoperable. Early results demonstrate that a power MOSFET, even in its off-state, can incur considerable damage due to lightning pin injection, leading to significant deviation in its behavior and performance, and to possibly early device failures.

Collection-limited theory interprets the extraordinary response of single semiconductor organic solar cells

DOE PAGES

Ray, Biswajit; Baradwaj, Aditya G.; Khan, Mohammad Ryyan; ...

2015-08-19

The bulk heterojunction (BHJ) organic photovoltaic (OPV) architecture has dominated the literature due to its ability to be implemented in devices with relatively high efficiency values. However, a simpler device architecture based on a single organic semiconductor (SS-OPV) offers several advantages: it obviates the need to control the highly system-dependent nanoscale BHJ morphology, and therefore, would allow the use of broader range of organic semiconductors. Unfortunately, the photocurrent in standard SS-OPV devices is typically very low, which generally is attributed to inefficient charge separation of the photogenerated excitons. In this paper, we show that the short-circuit current density from SS-OPVmore » devices can be enhanced significantly (~100-fold) through the use of inverted device configurations, relative to a standard OPV device architecture. This result suggests that charge generation may not be the performance bottleneck in OPV device operation. Instead, poor charge collection, caused by defect-induced electric field screening, is most likely the primary performance bottleneck in regular-geometry SS-OPV cells. We justify this hypothesis by: ( i) detailed numerical simulations, ( ii) electrical characterization experiments of functional SS-OPV devices using multiple polymers as active layer materials, and ( iii) impedance spectroscopy measurements. Furthermore, we show that the collection-limited photocurrent theory consistently interprets typical characteristics of regular SS-OPV devices. Finally, these insights should encourage the design and OPV implementation of high-purity, high-mobility polymers, and other soft materials that have shown promise in organic field-effect transistor applications, but have not performed well in BHJ OPV devices, wherein they adopt less-than-ideal nanostructures when blended with electron-accepting materials.« less

Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films

DOE PAGES

Berweger, Samuel; MacDonald, Gordon A.; Yang, Mengjin; ...

2017-02-02

We perform scanning microwave microscopy (SMM) to study the spatially varying electronic properties and related morphology of pristine and degraded methylammonium lead-halide (MAPI) perovskite films fabricated under different ambient humidity. Here, we find that higher processing humidity leads to the emergence of increased conductivity at the grain boundaries but also correlates with the appearance of resistive grains that contain PbI 2. Deteriorated films show larger and increasingly insulating grain boundaries as well as spatially localized regions of reduced conductivity within grains. These results suggest that while humidity during film fabrication primarily benefits device properties due to the passivation of trapsmore » at the grain boundaries and self-doping, it also results in the emergence of PbI 2-containing grains. We further establish that MAPI film deterioration under ambient conditions proceeds via the spatially localized breakdown of film conductivity, both at grain boundaries and within grains, due to local variations in susceptibility to deterioration. These results confirm that PbI 2 has both beneficial and adverse effects on device performance and provide new means for device optimization by revealing spatial variations in sample conductivity as well as morphological differences in resistance to sample deterioration.« less

Structural design considerations for micromachined solid-oxide fuel cells

NASA Astrophysics Data System (ADS)

Srikar, V. T.; Turner, Kevin T.; Andrew Ie, Tze Yung; Spearing, S. Mark

Micromachined solid-oxide fuel cells (μSOFCs) are among a class of devices being investigated for portable power generation. Optimization of the performance and reliability of such devices requires robust, scale-dependent, design methodologies. In this first analysis, we consider the structural design of planar, electrolyte-supported, μSOFCs from the viewpoints of electrochemical performance, mechanical stability and reliability, and thermal behavior. The effect of electrolyte thickness on fuel cell performance is evaluated using a simple analytical model. Design diagrams that account explicitly for thermal and intrinsic residual stresses are presented to identify geometries that are resistant to fracture and buckling. Analysis of energy loss due to in-plane heat conduction highlights the importance of efficient thermal isolation in microscale fuel cell design.

Polymer-based doping control for performance enhancement of wet-processed short-channel CNTFETs

NASA Astrophysics Data System (ADS)

Hartmann, Martin; Schubel, René; Claus, Martin; Jordan, Rainer; Schulz, Stefan E.; Hermann, Sascha

2018-01-01

The electrical transport properties of short-channel transistors based on single-walled carbon nanotubes (CNT) are significantly affected by bundling along with solution processing. We report that especially high off currents of CNT transistors are not only related to the incorporation of metallic CNTs but also to the incorporation of CNT bundles. By applying device passivation with poly(4-vinylpyridine), the impact of CNT bundling on the device performance can be strongly reduced due to increased gate efficiency as well as reduced oxygen and water-induced p-type doping, boosting essential field-effect transistor performance parameters by several orders of magnitude. Moreover, this passivation approach allows the hysteresis and threshold voltage of CNT transistors to be tuned.

Nanoparticle-Enhanced Silver-Nanowire Plasmonic Electrodes for High-Performance Organic Optoelectronic Devices.

PubMed

Kim, Taehyo; Kang, Saewon; Heo, Jungwoo; Cho, Seungse; Kim, Jae Won; Choe, Ayoung; Walker, Bright; Shanker, Ravi; Ko, Hyunhyub; Kim, Jin Young

2018-05-21

Improved performance in plasmonic organic solar cells (OSCs) and organic light-emitting diodes (OLEDs) via strong plasmon-coupling effects generated by aligned silver nanowire (AgNW) transparent electrodes decorated with core-shell silver-silica nanoparticles (Ag@SiO 2 NPs) is demonstrated. NP-enhanced plasmonic AgNW (Ag@SiO 2 NP-AgNW) electrodes enable substantially enhanced radiative emission and light absorption efficiency due to strong hybridized plasmon coupling between localized surface plasmons (LSPs) and propagating surface plasmon polaritons (SPPs) modes, which leads to improved device performance in organic optoelectronic devices (OODs). The discrete dipole approximation (DDA) calculation of the electric field verifies a strongly enhanced plasmon-coupling effect caused by decorating core-shell Ag@SiO 2 NPs onto the AgNWs. Notably, an electroluminescence efficiency of 25.33 cd A -1 (at 3.2 V) and a power efficiency of 25.14 lm W -1 (3.0 V) in OLEDs, as well as a power conversion efficiency (PCE) value of 9.19% in OSCs are achieved using hybrid Ag@SiO 2 NP-AgNW films. These are the highest values reported to date for optoelectronic devices based on AgNW electrodes. This work provides a new design platform to fabricate high-performance OODs, which can be further explored in various plasmonic and optoelectronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intimate effects of surface functionalization of porous silicon microcavities on biosensing performance

NASA Astrophysics Data System (ADS)

Martin, M.; Massif, L.; Estephan, E.; Saab, M.-b.; Cloitre, T.; Larroque, C.; Agarwal, V.; Cuisinier, F. J. G.; Le Lay, G.; Gergely, C.

2011-10-01

We study the effect of different surface functionalization methods on the sensing performances of porous silicon (PSi) microcavities when used for detection of biomolecules. Previous research on porous silicon demonstrated versatility of these devices for sensor applications based on their photonic responses. The interface between biological molecules and the Si semiconductor surface is a key issue for improving biomolecular recognition in these devices. PSi microcavities were fabricated to reveal reflectivity pass-band spectra in the visible and near-infrared domain. To assure uniform infiltration of proteins the number of layers of Bragg mirrors was limited to five, the first layer being of high porosity. In one approach the devices were thermally oxidized and functionalized to assure covalent binding of molecules. Secondly, the as etched PSi surface was modified with adhesion peptides isolated via phage display technology and presenting high binding capacity for Si. Functionalization and molecular binding events were monitored via reflectometric interference spectra as shifts in the resonance peaks of the cavity structure due to changes in the refractive index when a biomolecule is attached to the large internal surface of PSi. Improved sensitivity is obtained due to the peptide interface linkers between the PSi and biological molecules compared to the silanized devices. We investigate the formation of peptide-Si interface layer via X-ray photoelectron spectroscopy, scanning tunneling microscopy and scanning electron microscopy.

Surface modification of biomaterials and biomedical devices using additive manufacturing.

PubMed

Bose, Susmita; Robertson, Samuel Ford; Bandyopadhyay, Amit

2018-01-15

The demand for synthetic biomaterials in medical devices, pharmaceutical products and, tissue replacement applications are growing steadily due to aging population worldwide. The use for patient matched devices is also increasing due to availability and integration of new technologies. Applications of additive manufacturing (AM) or 3D printing (3DP) in biomaterials have also increased significantly over the past decade towards traditional as well as innovative next generation Class I, II and III devices. In this review, we have focused our attention towards the use of AM in surface modified biomaterials to enhance their in vitro and in vivo performances. Specifically, we have discussed the use of AM to deliberately modify the surfaces of different classes of biomaterials with spatial specificity in a single manufacturing process as well as commented on the future outlook towards surface modification using AM. It is widely understood that the success of implanted medical devices depends largely on favorable material-tissue interactions. Additive manufacturing has gained traction as a viable and unique approach to engineered biomaterials, for both bulk and surface properties that improve implant outcomes. This review explores how additive manufacturing techniques have been and can be used to augment the surfaces of biomedical devices for direct clinical applications. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A Voice and Mouse Input Interface for 3D Virtual Environments

NASA Technical Reports Server (NTRS)

Kao, David L.; Bryson, Steve T.

2003-01-01

There have been many successful stories on how 3D input devices can be fully integrated into an immersive virtual environment. Electromagnetic trackers, optical trackers, gloves, and flying mice are just some of these input devices. Though we can use existing 3D input devices that are commonly used for VR applications, there are several factors that prevent us from choosing these input devices for our applications. One main factor is that most of these tracking devices are not suitable for prolonged use due to human fatigue associated with using them. A second factor is that many of them would occupy additional office space. Another factor is that many of the 3D input devices are expensive due to the unusual hardware that are required. For our VR applications, we want a user interface that would work naturally with standard equipment. In this paper, we demonstrate applications or our proposed muitimodal interface using a 3D dome display. We also show that effective data analysis can be achieved while the scientists view their data rendered inside the dome display and perform user interactions simply using the mouse and voice input. Though the sphere coordinate grid seems to be ideal for interaction using a 3D dome display, we can also use other non-spherical grids as well.

Ab initio modeling of transport and thermodynamic stability for hafnia memristive devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Xiaoliang; Rungger, Ivan; Zapol, Peter

HfO 2-based memristive switching devices are currently under intensive investigation due to their high performance and mature fabrication techniques. However, several critical issues have to be addressed to bring them from lab to market. We have recently looked into two important issues with the use of density functional theory methods. One is the wide distribution of device resistance in off-states. We have modeled the switching process of a Pt-HfO 2-Pt structure for which quantized conductance was observed. Oxygen atoms moving inside a conductive oxygen vacancy filament divide the filament into several quantum wells. Device conductance changes exponentially when one oxygenmore » atom moves away from interface into filament. We propose that the high sensitivity of device conductance to the position of oxygen atoms results in the large variation of device off-state resistance. Another issue that we have recently addressed is the poor switching performance of devices based on a TiN-HfO 2-TiN structure. While recent experiments have shown that by inserting an "oxygen scavenger" metal between positive electrode and oxide significantly improves device performance, the fundamental understanding of the improvement is lacking.We provide detailed understanding how scavenger layers improve device performance. First, we show that Ta insertion facilitates formation of on-states by reducing the formation energy. Second, the inserted Ta layer reduces the Schottky barrier height in the off-states by changing interface electric dipole at the oxide electrode interface. Nevertheless, the device maintains a high on/off resistance ratio. Finally, with Ta insertion the on-state conductance becomes much less sensitive to the specific location from which the oxygen was removed from the oxide. In conclusion, our studies provide fundamental understanding needed for enabling realization of a non-volatile memory technology with reduced energy consumption.« less

Ab initio modeling of transport and thermodynamic stability for hafnia memristive devices

DOE PAGES

Zhong, Xiaoliang; Rungger, Ivan; Zapol, Peter; ...

2017-09-05

HfO 2-based memristive switching devices are currently under intensive investigation due to their high performance and mature fabrication techniques. However, several critical issues have to be addressed to bring them from lab to market. We have recently looked into two important issues with the use of density functional theory methods. One is the wide distribution of device resistance in off-states. We have modeled the switching process of a Pt-HfO 2-Pt structure for which quantized conductance was observed. Oxygen atoms moving inside a conductive oxygen vacancy filament divide the filament into several quantum wells. Device conductance changes exponentially when one oxygenmore » atom moves away from interface into filament. We propose that the high sensitivity of device conductance to the position of oxygen atoms results in the large variation of device off-state resistance. Another issue that we have recently addressed is the poor switching performance of devices based on a TiN-HfO 2-TiN structure. While recent experiments have shown that by inserting an "oxygen scavenger" metal between positive electrode and oxide significantly improves device performance, the fundamental understanding of the improvement is lacking.We provide detailed understanding how scavenger layers improve device performance. First, we show that Ta insertion facilitates formation of on-states by reducing the formation energy. Second, the inserted Ta layer reduces the Schottky barrier height in the off-states by changing interface electric dipole at the oxide electrode interface. Nevertheless, the device maintains a high on/off resistance ratio. Finally, with Ta insertion the on-state conductance becomes much less sensitive to the specific location from which the oxygen was removed from the oxide. In conclusion, our studies provide fundamental understanding needed for enabling realization of a non-volatile memory technology with reduced energy consumption.« less

Hybrid Power Management (HPM)

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2007-01-01

The NASA Glenn Research Center s Avionics, Power and Communications Branch of the Engineering and Systems Division initiated the Hybrid Power Management (HPM) Program for the GRC Technology Transfer and Partnership Office. HPM is the innovative integration of diverse, state-of-the-art power devices in an optimal configuration for space and terrestrial applications. The appropriate application and control of the various power devices significantly improves overall system performance and efficiency. The advanced power devices include ultracapacitors and fuel cells. HPM has extremely wide potential. Applications include power generation, transportation systems, biotechnology systems, and space power systems. HPM has the potential to significantly alleviate global energy concerns, improve the environment, and stimulate the economy. One of the unique power devices being utilized by HPM for energy storage is the ultracapacitor. An ultracapacitor is an electrochemical energy storage device, which has extremely high volumetric capacitance energy due to high surface area electrodes, and very small electrode separation. Ultracapacitors are a reliable, long life, maintenance free, energy storage system. This flexible operating system can be applied to all power systems to significantly improve system efficiency, reliability, and performance. There are many existing and conceptual applications of HPM.

Thermal-Responsive Polymers for Enhancing Safety of Electrochemical Storage Devices.

PubMed

Yang, Hui; Leow, Wan Ru; Chen, Xiaodong

2018-03-01

Thermal runway constitutes the most pressing safety issue in lithium-ion batteries and supercapacitors of large-scale and high-power density due to risks of fire or explosion. However, traditional strategies for averting thermal runaway do not enable the charging-discharging rate to change according to temperature or the original performance to resume when the device is cooled to room temperature. To efficiently control thermal runaway, thermal-responsive polymers provide a feasible and reversible strategy due to their ability to sense and subsequently act according to a predetermined sequence when triggered by heat. Herein, recent research progress on the use of thermal-responsive polymers to enhance the thermal safety of electrochemical storage devices is reviewed. First, a brief discussion is provided on the methods of preventing thermal runaway in electrochemical storage devices. Subsequently, a short review is provided on the different types of thermal-responsive polymers that can efficiently avoid thermal runaway, such as phase change polymers, polymers with sol-gel transitions, and polymers with positive temperature coefficients. The results represent the important development of thermal-responsive polymers toward the prevention of thermal runaway in next-generation smart electrochemical storage devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Performance of re-used pacemakers and implantable cardioverter defibrillators compared with new devices at Groote Schuur Hospital in Cape Town, South Africa

PubMed Central

Jama, Zimasa V; Chin, Ashley; Mayosi, Bongani M; Badri, Motasim

2015-01-01

Objectives Little is known about the performance of re-used pacemakers and implantable cardioverter defibrillators (ICDs) in Africa. We sought to compare the risk of infection and the rate of malfunction of re-used pacemakers and ICDs with new devices implanted at Groote Schuur Hospital in Cape Town, South Africa. Methods This was a retrospective case comparison study of the performance of re-used pacemakers and ICDs in comparison with new devices implanted at Groote Schuur Hospital over a 10-year period. The outcomes were incidence of device infection, device malfunction, early battery depletion, and device removal due to infection, malfunction, or early battery depletion. Results Data for 126 devices implanted in 126 patients between 2003 and 2013 were analysed, of which 102 (81%) were pacemakers (51 re-used and 51 new) and 24 (19%) were ICDs (12 re-used and 12 new). There was no device infection, malfunction, early battery depletion or device removal in either the re-used or new pacemaker groups over the median follow up of 15.1 months [interquartile range (IQR), 1.3–36.24 months] for the re-used pacemakers, and 55.8 months (IQR, 20.3–77.8 months) for the new pacemakers. In the ICD group, no device infection occurred over a median follow up of 35.9 months (IQR, 17.0–70.9 months) for the re-used ICDs and 45.7 months (IQR, 37.6–53.7 months) for the new ICDs. One device delivered inappropriate shocks, which resolved without intervention and with no harm to the patient. This re-used ICD subsequently needed generator replacement 14 months later. In both the pacemaker and ICD groups, there were no procedure-non-related infections documented for the respective follow-up periods. Conclusion No significant differences were found in performance between re-used and new pacemakers and ICDs with regard to infection rates, device malfunction, battery life and device removal for complications. Pacemaker and ICD re-use is feasible and safe and is a viable option for patients with bradyarrhythmias and tachyarrthythmias. PMID:26407220

Trends In Susceptibility To Single-Event Upset

NASA Technical Reports Server (NTRS)

Nichols, Donald K.; Price, William E.; Kolasinski, Wojciech A.; Koga, Rukotaro; Waskiewicz, Alvin E.; Pickel, James C.; Blandford, James T.

1989-01-01

Report provides nearly comprehensive body of data on single-event upsets due to irradiation by heavy ions. Combines new test data and previously published data from governmental and industrial laboratories. Clear trends emerge from data useful in predicting future performances of devices.

Fabrication and properties of light-emitting diodes based on self-assembled multilayers of poly(phenylene vinylene)

NASA Astrophysics Data System (ADS)

Fou, A. C.; Onitsuka, O.; Ferreira, M.; Rubner, M. F.; Hsieh, B. R.

1996-05-01

Light-emitting diodes have been fabricated from self-assembled multilayers of poly(p-phenylene vinylene) (PPV) and two different polyanions; polystyrene sulfonic acid (SPS) and polymethacrylic acid (PMA). The type of polyanion used to assemble the multilayer thin films was found to dramatically influence the behavior and performance of devices fabricated with indium tin oxide and aluminum electrodes. Light-emitting devices fabricated from PMA/PPV multilayers were found to exhibit luminance levels in the range of 20-60 cd/m2, a thickness dependent turn-on voltage and classical rectifying behavior with rectification ratios greater than 105. In sharp contrast, the devices based on SPS/PPV exhibited near symmetric current-voltage curves, thickness independent turn-on voltages and much lower luminance levels. The significant difference in device behavior observed between these two systems is primarily due to a doping effect induced either chemically or electrochemically by the sulfonic acid groups of SPS. It was also found that the performance of these devices depends on the type of layer that is in contact with the Al top electrode thereby making it possible to manipulate device efficiency at the molecular level.

Metal oxide resistive random access memory based synaptic devices for brain-inspired computing

NASA Astrophysics Data System (ADS)

Gao, Bin; Kang, Jinfeng; Zhou, Zheng; Chen, Zhe; Huang, Peng; Liu, Lifeng; Liu, Xiaoyan

2016-04-01

The traditional Boolean computing paradigm based on the von Neumann architecture is facing great challenges for future information technology applications such as big data, the Internet of Things (IoT), and wearable devices, due to the limited processing capability issues such as binary data storage and computing, non-parallel data processing, and the buses requirement between memory units and logic units. The brain-inspired neuromorphic computing paradigm is believed to be one of the promising solutions for realizing more complex functions with a lower cost. To perform such brain-inspired computing with a low cost and low power consumption, novel devices for use as electronic synapses are needed. Metal oxide resistive random access memory (ReRAM) devices have emerged as the leading candidate for electronic synapses. This paper comprehensively addresses the recent work on the design and optimization of metal oxide ReRAM-based synaptic devices. A performance enhancement methodology and optimized operation scheme to achieve analog resistive switching and low-energy training behavior are provided. A three-dimensional vertical synapse network architecture is proposed for high-density integration and low-cost fabrication. The impacts of the ReRAM synaptic device features on the performances of neuromorphic systems are also discussed on the basis of a constructed neuromorphic visual system with a pattern recognition function. Possible solutions to achieve the high recognition accuracy and efficiency of neuromorphic systems are presented.

Soft shape-adaptive gripping device made from artificial muscle

NASA Astrophysics Data System (ADS)

Hamburg, E.; Vunder, V.; Johanson, U.; Kaasik, F.; Aabloo, A.

2016-04-01

We report on a multifunctional four-finger gripper for soft robotics, suitable for performing delicate manipulation tasks. The gripping device is comprised of separately driven gripping and lifting mechanisms, both made from a separate single piece of smart material - ionic capacitive laminate (ICL) also known as artificial muscle. Compared to other similar devices the relatively high force output of the ICL material allows one to construct a device able to grab and lift objects exceeding multiple times its own weight. Due to flexible design of ICL grips, the device is able to adapt the complex shapes of different objects and allows grasping single or multiple objects simultaneously without damage. The performance of the gripper is evaluated in two different configurations: a) the ultimate grasping strength of the gripping hand; and b) the maximum lifting force of the lifting actuator. The ICL is composed of three main layers: a porous membrane consisting of non-ionic polymer poly(vinylidene fluoride-co-hexafluoropropene) (PVdF-HFP), ionic liquid 1-ethyl-3-methylimidazolium trifluoromethane-sulfonate (EMITFS), and a reinforcing layer of woven fiberglass cloth. Both sides of the membrane are coated with a carbonaceous electrode. The electrodes are additionally covered with thin gold layers, serving as current collectors. Device made of this material operates silently, requires low driving voltage (<3 V), and is suitable for performing tasks in open air environment.

Reduced contact resistance of a-IGZO thin film transistors with inkjet-printed silver electrodes

NASA Astrophysics Data System (ADS)

Chen, Jianqiu; Ning, Honglong; Fang, Zhiqiang; Tao, Ruiqiang; Yang, Caigui; Zhou, Yicong; Yao, Rihui; Xu, Miao; Wang, Lei; Peng, Junbiao

2018-04-01

In this study, high performance amorphous In–Ga–Zn–O (a-IGZO) TFTs were successfully fabricated with inkjet-printed silver source-drain electrodes. The results showed that increased channel thickness has an improving trend in the properties of TFTs due to the decreased contact resistance. Compared with sputtered silver TFTs, devices with printed silver electrodes were more sensitive to the thickness of active layer. Furthermore, the devices with optimized active layer showed high performances with a maximum saturation mobility of 8.73 cm2 · V‑1 · S‑1 and an average saturation mobility of 6.97 cm2 · V‑1 · S‑1, I on/I off ratio more than 107 and subthreshold swing of 0.28 V/decade, which were comparable with the analogous devices with sputtered electrodes.

Palmprint Recognition Across Different Devices.

PubMed

Jia, Wei; Hu, Rong-Xiang; Gui, Jie; Zhao, Yang; Ren, Xiao-Ming

2012-01-01

In this paper, the problem of Palmprint Recognition Across Different Devices (PRADD) is investigated, which has not been well studied so far. Since there is no publicly available PRADD image database, we created a non-contact PRADD image database containing 12,000 grayscale captured from 100 subjects using three devices, i.e., one digital camera and two smart-phones. Due to the non-contact image acquisition used, rotation and scale changes between different images captured from a same palm are inevitable. We propose a robust method to calculate the palm width, which can be effectively used for scale normalization of palmprints. On this PRADD image database, we evaluate the recognition performance of three different methods, i.e., subspace learning method, correlation method, and orientation coding based method, respectively. Experiments results show that orientation coding based methods achieved promising recognition performance for PRADD.

Palmprint Recognition across Different Devices

PubMed Central

Jia, Wei; Hu, Rong-Xiang; Gui, Jie; Zhao, Yang; Ren, Xiao-Ming

2012-01-01

In this paper, the problem of Palmprint Recognition Across Different Devices (PRADD) is investigated, which has not been well studied so far. Since there is no publicly available PRADD image database, we created a non-contact PRADD image database containing 12,000 grayscale captured from 100 subjects using three devices, i.e., one digital camera and two smart-phones. Due to the non-contact image acquisition used, rotation and scale changes between different images captured from a same palm are inevitable. We propose a robust method to calculate the palm width, which can be effectively used for scale normalization of palmprints. On this PRADD image database, we evaluate the recognition performance of three different methods, i.e., subspace learning method, correlation method, and orientation coding based method, respectively. Experiments results show that orientation coding based methods achieved promising recognition performance for PRADD. PMID:22969380

Optimization of material/device parameters of CdTe photovoltaic for solar cells applications

NASA Astrophysics Data System (ADS)

Wijewarnasuriya, Priyalal S.

2016-05-01

Cadmium telluride (CdTe) has been recognized as a promising photovoltaic material for thin-film solar cell applications due to its near optimum bandgap of ~1.5 eV and high absorption coefficient. The energy gap is near optimum for a single-junction solar cell. The high absorption coefficient allows films as thin as 2.5 μm to absorb more than 98% of the above-bandgap radiation. Cells with efficiencies near 20% have been produced with poly-CdTe materials. This paper examines n/p heterostructure device architecture. The performance limitations related to doping concentrations, minority carrier lifetimes, absorber layer thickness, and surface recombination velocities at the back and front interfaces is assessed. Ultimately, the paper explores device architectures of poly- CdTe and crystalline CdTe to achieve performance comparable to gallium arsenide (GaAs).

CVD growth of large-area and high-quality HfS2 nanoforest on diverse substrates

NASA Astrophysics Data System (ADS)

Zheng, Binjie; Wang, Zegao; Qi, Fei; Wang, Xinqiang; Yu, Bo; Zhang, Wanli; Chen, Yuanfu

2018-03-01

Two-dimensional layered transition metal dichalcogenides (TMDs) have attracted burgeoning attention due to their various properties and wide potential applications. As a new TMD, hafnium disulfide (HfS2) is theoretically predicted to have better electrical performance than widely studied MoS2. The experimental researches also confirmed the extraordinary feature in electronics and optoelectronics. However, the maximal device performance may not be achieved due to its own limitation of planar structure and challenge of transfer without contamination. Here, through the chemical vapor deposition (CVD) technique, inch-size HfS2 nanoforest has been directly grown on diverse objective substrates covering insulating, semiconducting and conducting substrates. This direct CVD growth without conventional transfer process avoids contamination and degradation in quality, suggesting its promising and wide applications in high-quality and multifarious devices. It is noted that all the HfS2 nanoforests grown on diverse substrates are constructed with vertically aligned few-layered HfS2 nanosheets with high crystalline quality and edge orientation. Moreover, due to its unique structure, the HfS2 nanoforest owns abundant exposed edge sites and large active surface area, which is essential to apply in high-performance catalyst, sensor, and energy storage or field emitter.

A Two-Step Absorber Deposition Approach To Overcome Shunt Losses in Thin-Film Solar Cells: Using Tin Sulfide as a Proof-of-Concept Material System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steinmann, Vera; Chakraborty, Rupak; Rekemeyer, Paul H.

2016-08-31

As novel absorber materials are developed and screened for their photovoltaic (PV) properties, the challenge remains to reproducibly test promising candidates for high-performing PV devices. Many early-stage devices are prone to device shunting due to pinholes in the absorber layer, producing 'false-negative' results. Here, we demonstrate a device engineering solution toward a robust device architecture, using a two-step absorber deposition approach. We use tin sulfide (SnS) as a test absorber material. The SnS bulk is processed at high temperature (400 degrees C) to stimulate grain growth, followed by a much thinner, low-temperature (200 degrees C) absorber deposition. At a lowermore » process temperature, the thin absorber overlayer contains significantly smaller, densely packed grains, which are likely to provide a continuous coating and fill pinholes in the underlying absorber bulk. We compare this two-step approach to the more standard approach of using a semi-insulating buffer layer directly on top of the annealed absorber bulk, and we demonstrate a more than 3.5x superior shunt resistance Rsh with smaller standard error ..sigma..Rsh. Electron-beam-induced current (EBIC) measurements indicate a lower density of pinholes in the SnS absorber bulk when using the two-step absorber deposition approach. We correlate those findings to improvements in the device performance and device performance reproducibility.« less

III-V HEMTs: low-noise devices for high-frequency applications

NASA Astrophysics Data System (ADS)

Mateos, Javier

2003-05-01

With the recent development of broadband and satellite communications, one of the main engines for the advance of modern Microelectronics is the fabrication of devices with increasing cutoff frequency and lowest possible level of noise. Even if heterojunction bipolar devices (HBTs) have reached a good frequency performance, the top end of high frequency low-noise applications is monopolized by unipolar devices, mainly HEMTs (High Electron Mobility Transistors). In particular, within the vast family of heterojunction devices, the best results ever reported in the W-band have been obtained with InP based HEMTs using the AlInAs/InGaAs material system, improving those of usual GaAs based pseudomorphic HEMTs. In field effect devices, the reduction of the gate length (Lg) up to the technological limit is the main way to achieve the maximum performances. But the design of the devices is not so simple, when reducing the gate length it is convenient to keep constant the aspect ratio (gate length over gate-to-channel distance) in order to limit short channel effects. This operation can lead to the appearance of other unwanted effects, like the depletion of the channel due to the surface potential or the tunneling of electrons from the channel to the gate. Therefore, in order to optimize the high frequency or the low-noise behavior of the devices (that usually can not be reached together) not only the gate-to-channel distance must be chosen carefully, but also many other technological parameters (both geometrical and electrical): composition of materials, width of the device, length, depth and position of the recess, thickness and doping of the different layers, etc. Historically, these parameters have been optimized by classical simulation techniques or, when such simulations are not physically applicable, by the expensive 'test and error' procedure. With the use of computer simulation, the design optimization can be made in a short time and with no money spent. However, classical modelling of electronic devices meets important difficulties when dealing with advanced transistors, mainly due to their small size, and the Monte Carlo technique appears as the only possible choice

Preclinical assessment of a modified Occlutech left atrial appendage closure device in a canine model.

PubMed

Kim, Jung-Sun; Lee, Seul-Gee; Bong, Sung-Kyung; Park, Se-Il; Hong, Sung-Yu; Shin, Sanghoon; Shim, Chi Young; Hong, Geu-Ru; Choi, Donghoon; Jang, Yangsoo; Park, Jai-Wun

2016-10-15

LAA occlusion has a similar stroke prevention efficacy compared to anticoagulation treatment for non-valvular atrial fibrillation. The objective of this study was to assess the feasibility and safety of a modified Occlutech® left atrial appendage (LAA) closure device in a canine model. The device was implanted in 10 dogs (33±1kg) using fluoroscopy and transesophageal echocardiography (TEE) guidance. The modified Occlutech® LAA occlusion device was compared with the current version, the Watchman device, and the Amplazter cardiac plug (ACP). LAA occlusion and anchoring to the LAA were evaluated. All dogs were assessed using angiography, TEE, and a gross anatomy examination. The 10 LAA occlusion devices were to be implanted into 10 dogs (5 modified Occlutech devices, 3 current version of Occlutech devices, 1 Watchman, and 1 ACP). LAA implantation was not performed in one dog due to transeptal puncture failure. The three current version of Occlutech devices were embolized immediately after implantation, so three modified devices of the same size were implanted securely without embolization. The mean implant size was 20.1±2.0mm. The devices chosen were a mean of 23.3±10.6% larger than the measured landing zone diameters. Post-implant angiography and TEE revealed well-positioned devices without pericardial effusion or impingement on surrounding structures. The results of this acute animal study suggested that a modified Occlutech® LAA occlusion device was feasible and had greater anchoring performance in canines. Additional large clinical studies are needed to evaluate safety and efficacy. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Efficient and mechanically robust stretchable organic light-emitting devices by a laser-programmable buckling process

PubMed Central

Yin, Da; Feng, Jing; Ma, Rui; Liu, Yue-Feng; Zhang, Yong-Lai; Zhang, Xu-Lin; Bi, Yan-Gang; Chen, Qi-Dai; Sun, Hong-Bo

2016-01-01

Stretchable organic light-emitting devices are becoming increasingly important in the fast-growing fields of wearable displays, biomedical devices and health-monitoring technology. Although highly stretchable devices have been demonstrated, their luminous efficiency and mechanical stability remain impractical for the purposes of real-life applications. This is due to significant challenges arising from the high strain-induced limitations on the structure design of the device, the materials used and the difficulty of controlling the stretch-release process. Here we have developed a laser-programmable buckling process to overcome these obstacles and realize a highly stretchable organic light-emitting diode with unprecedented efficiency and mechanical robustness. The strained device luminous efficiency −70 cd A−1 under 70% strain - is the largest to date and the device can accommodate 100% strain while exhibiting only small fluctuations in performance over 15,000 stretch-release cycles. This work paves the way towards fully stretchable organic light-emitting diodes that can be used in wearable electronic devices. PMID:27187936

Cathode Degradation in Thallium Bromide Devices

NASA Astrophysics Data System (ADS)

Datta, Amlan; Motakef, Shariar

2015-06-01

Thallium bromide (TlBr) is a wide bandgap, compound semiconductor with high gamma-ray stopping power and promising physical properties. However, performance degradation and the eventual irreversible failure of TlBr devices can occur rapidly at room temperature, due to “polarization”, caused by the electromigration of Tl+ and Br- ions to the electrical contacts across the device. Using the Accelerated Device Degradation (ADD) experiment, the degradation phenomena in TlBr devices have been visualized and recorded. This paper focuses on “ageing” of the device cathode at various temperatures. ADD is a fast and reliable direct characterization technique that can be used to identify the effects of various growth and post-growth process modifications on device degradation. Using this technique we have identified cathode degradation with the migration of Br- ions and an associated generation and growth of Thallium-rich fractal “ferns” from the cathode. Its effect on the radiation response of the device has also been discussed in this paper. The chemical changes in the cathode were characterized using Energy-dispersive X-ray spectroscopy.

Quantum funneling in blended multi-band gap core/shell colloidal quantum dot solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neo, Darren C. J.; Assender, Hazel E.; Watt, Andrew A. R., E-mail: Andrew.watt@materials.ox.ac.uk

2015-09-07

Multi-band gap heterojunction solar cells fabricated from a blend of 1.2 eV and 1.4 eV PbS colloidal quantum dots (CQDs) show poor device performance due to non-radiative recombination. To overcome this, a CdS shell is epitaxially formed around the PbS core using cation exchange. From steady state and transient photoluminescence measurements, we understand the nature of charge transfer between these quantum dots. Photoluminescence decay lifetimes are much longer in the PbS/CdS core/shell blend compared to PbS only, explained by a reduction in non-radiative recombination resulting from CdS surface passivation. PbS/CdS heterojunction devices sustain a higher open-circuit voltage and lower reverse saturation currentmore » as compared to PbS-only devices, implying lower recombination rates. Further device performance enhancement is attained by modifying the composition profile of the CQD species in the absorbing layer resulting in a three dimensional quantum cascade structure.« less

Cu(In,Ga)Se2 solar cells with In2S3 buffer layer deposited by thermal evaporation

NASA Astrophysics Data System (ADS)

Kim, SeongYeon; Rana, Tanka R.; Kim, JunHo; Yun, JaeHo

2017-12-01

We report on physical vapor deposition of indium sulfide (In2S3) buffer layers and its application to Cu(In,Ga)Se2 (CIGSe) thin film solar cell. The Indium sulfide buffer layers were evaporated onto CIGSe at various substrate temperatures from room temperature (RT) to 350 °C. The effect of deposition temperature of buffer layers on the solar cell device performance were investigated by analyzing temperature dependent current-voltage ( J- V- T), external quantum efficiency (EQE) and Raman spectroscopy. The fabricated device showed the highest power conversion efficiency of 6.56% at substrate temperature of 250 °C, which is due to the decreased interface recombination. However, the roll-over in J- V curves was observed for solar cell device having buffer deposited at substrate temperature larger than 250 °C. From the measurement results, the interface defect and roll-over related degradation were found to have limitation on the performance of solar cell device.

Opportunity of spinel ferrite materials in nonvolatile memory device applications based on their resistive switching performances.

PubMed

Hu, Wei; Qin, Ni; Wu, Guangheng; Lin, Yanting; Li, Shuwei; Bao, Dinghua

2012-09-12

The opportunity of spinel ferrites in nonvolatile memory device applications has been demonstrated by the resistive switching performance characteristics of a Pt/NiFe(2)O(4)/Pt structure, such as low operating voltage, high device yield, long retention time (up to 10(5) s), and good endurance (up to 2.2 × 10(4) cycles). The dominant conduction mechanisms are Ohmic conduction in the low-resistance state and in the lower-voltage region of the high-resistance state and Schottky emission in the higher-voltage region of the high-resistance state. On the basis of measurements of the temperature dependence of the resistances and magnetic properties in different resistance states, we explain the physical mechanism of resistive switching of Pt/NiFe(2)O(4)/Pt devices using the model of formation and rupture of conducting filaments by considering the thermal effect of oxygen vacancies and changes in the valences of cations due to the redox effect.

[Methodologic and clinical comparison of four different ergospirometry systems].

PubMed

Winter, U J; Fritsch, J; Gitt, A K; Pothoff, G; Berge, P G; Hilger, H H

1994-01-01

The clinician who uses cardio-pulmonary exercise testing (CPX) systems relies on the technical informations from the device producers. In this paper, the practicability, the accuracy and the safety of four different, available CPX systems are compared in the clinical area, using clinically orientated criteria. The exercise tests were performed in healthy subjects, in patients with cardiac and/or pulmonary disease as well as in young or old people. The comparison study showed, that there were partially large differences in device design and measurement accuracy. Furthermore, our investigation demonstrated that beneath repetitive calibrations of the CPX systems a frequent validation of the devices by means of a metabolic simulator is necessary. Problems in calibration can be caused by an inadequate performance or by unclean calibration gases. Problems in validation can be due to incompatibility of the CPX device and the validator. The comparison study of the four different systems showed that in the future standards for CPX testing should be defined.

MEMS-based tunable gratings and their applications

NASA Astrophysics Data System (ADS)

Yu, Yiting; Yuan, Weizheng; Qiao, Dayong

2015-03-01

The marriage of optics and MEMS has resulted in a new category of optical devices and systems that have unprecedented advantages compared with their traditional counterparts. As an important spatial light modulating technology, diffractive optical MEMS obtains a wide variety of successful commercial applications, e.g. projection displays, optical communication and spectral analysis, due to its features of highly compact, low-cost, IC-compatible, excellent performance, and providing possibilities for developing totally new, yet smart devices and systems. Three most successful MEMS diffraction gratings (GLVs, Polychromator and DMDs) are briefly introduced and their potential applications are analyzed. Then, three different MEMS tunable gratings developed by our group, named as micro programmable blazed gratings (μPBGs) and micro pitch-tunable gratings (μPTGs) working in either digital or analog mode, are demonstrated. The strategies to largely enhance the maximum blazed angle and grating period are described. Some preliminary application explorations based on the developed grating devices are also shown. For our ongoing research focus, we will further improve the device performance to meet the engineering application requirements.

Morphology control of polymer: Fullerene solar cells by nanoparticle self-assembly

NASA Astrophysics Data System (ADS)

Zhang, Wenluan

During the past two decades, research in the field of polymer based solar cells has attracted great effort due to their simple processing, mechanical flexibility and potential low cost. A standard polymer solar cell is based on the concept of a bulk-heterojunction composed of a conducting polymer as the electron donor and a fullerene derivative as the electron acceptor. Since the exciton lifetime is limited, this places extra emphasis on control of the morphology to obtain improved device performance. In this thesis, detailed characterization and novel morphological design of polymer solar cells was studied, in addition, preliminary efforts to transfer laboratory scale methods to industrialized device fabrication was made. Magnetic contrast neutron reflectivity was used to study the vertical concentration distribution of fullerene nanoparticles within poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2- b]thiophene (pBTTT) thin film. Due to the wide space between the side chains of polymer, these fullerene nanoparticles intercalate between them creating a stable co-crystal structure. Therefore, a high volume fraction of fullerene was needed to obtain optimal device performance as phase separated conductive pathways are required and resulted in a homogeneous fullerene concentration profile through the film. Small angle neutron scattering was used to find there is amorphous fullerene even at lower concentration since it was previously believed that all fullerene formed a co-crystal. These fullerene molecules evolve into approximately 15 nm sized agglomerates at higher concentrations to improve electron transport. Unfortunately, thermal annealing gives these agglomerates mobility to form micrometer sized crystals and reduce the device performance. In standard poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCMBM) solar cells, a higher concentration of PCBM at the cathode interface is desired due to the band alignment structure. This was achieved by having a sparse mono-layer of Fe3O4 nanoparticles (NPs) that formed a polymer depletion zone excluding P3HT away from cathode interface. Convective outflow and surface energy ordering were hypothesized to promote the NPs toward the cathode interface. By proper tuning of the NPs volume fraction added to the films the distance between two NPs can be made to be smaller than the P3HT radius of gyration to form the polymer depletion zone. PCBM molecules can then fill the space left by P3HT and help build electron transport pathways improving electron collection at cathode. The addition of NPs does not affect the PCBM agglomerate morphology, but does decrease the degree of P3HT crystallinity, so a balance between this NP effect and P3HT crystallinity has to be reached to obtain optimum device performance. To assess this NP effect in industrialized device fabrication, the rod coating method was used for a preliminary study. It is found that, the NPs do not move upward and are kinetically trapped with random a distribution within the film. In addition, the P3HT crystallinity was also reduced by adding NPs, so the device performance actually is even lower. It is hyposized that the slower drying rate in rod coating compared to spin coating traps the NPs in the film perhaps due to les convective flow. Hence, further effort is needed to realize this NP effect in large scalable device fabrication. Considering the low cost of NPs and the simple process applied to achieve this improvement, it is remarkably beneficial to organic photovoltaic industry. Further study could combine light management by using colloid particles and this NP effect to further modify morphology to obtain better solar cells. It is believed that this NP effect could be broadly applicable to other organic electronic devices like light emitting diodes, and batteries for lighting and energy storage.

Performance evaluation of photoacoustic oximetry imaging systems using a dynamic blood flow phantom with tunable oxygen saturation

NASA Astrophysics Data System (ADS)

Vogt, William C.; Zhou, Xuewen; Andriani, Rudy; Wear, Keith A.; Garra, Brian S.; Pfefer, Joshua

2018-02-01

Photoacoustic Imaging (PAI) is an emerging technology with strong potential for broad clinical applications from breast cancer detection to cerebral monitoring due to its ability to compute maps of blood oxygen saturation (SO2) distribution in deep tissues using multispectral imaging. However, no well-validated consensus test methods currently exist for evaluating oximetry-specific performance characteristics of PAI devices. We have developed a phantombased flow system capable of rapid SO2 adjustment to serve as a test bed for elucidation of factors impacting SO2 measurement and quantitative characterization of device performance. The flow system is comprised of a peristaltic pump, membrane oxygenator, oxygen and nitrogen gas, and in-line oxygen, pH, and temperature sensors that enable real-time estimation of SO2 reference values. Bovine blood was delivered through breast-relevant tissue phantoms containing vessel-mimicking fluid channels, which were imaged using a custom multispectral PAI system. Blood was periodically drawn for SO2 measurement in a clinical-grade CO-oximeter. We used this flow phantom system to evaluate the impact of device parameters (e.g.,wavelength-dependent fluence corrections) and tissue parameters (e.g. fluid channel depth, blood SO2, spectral coloring artifacts) on oximetry measurement accuracy. Results elucidated key challenges in PAI oximetry and device design trade-offs, which subsequently allowed for optimization of system performance. This approach provides a robust benchtop test platform that can support PAI oximetry device optimization, performance validation, and clinical translation, and may inform future development of consensus test methods for performance assessment of photoacoustic oximetry imaging systems.

Fermi Level Manipulation through Native Doping in the Topological Insulator Bi2Se3.

PubMed

Walsh, Lee A; Green, Avery J; Addou, Rafik; Nolting, Westly; Cormier, Christopher R; Barton, Adam T; Mowll, Tyler R; Yue, Ruoyu; Lu, Ning; Kim, Jiyoung; Kim, Moon J; LaBella, Vincent P; Ventrice, Carl A; McDonnell, Stephen; Vandenberghe, William G; Wallace, Robert M; Diebold, Alain; Hinkle, Christopher L

2018-06-08

The topologically protected surface states of three-dimensional (3D) topological insulators have the potential to be transformative for high-performance logic and memory devices by exploiting their specific properties such as spin-polarized current transport and defect tolerance due to suppressed backscattering. However, topological insulator based devices have been underwhelming to date primarily due to the presence of parasitic issues. An important example is the challenge of suppressing bulk conduction in Bi 2 Se 3 and achieving Fermi levels ( E F ) that reside in between the bulk valence and conduction bands so that the topologically protected surface states dominate the transport. The overwhelming majority of the Bi 2 Se 3 studies in the literature report strongly n-type materials with E F in the bulk conduction band due to the presence of a high concentration of selenium vacancies. In contrast, here we report the growth of near-intrinsic Bi 2 Se 3 with a minimal Se vacancy concentration providing a Fermi level near midgap with no extrinsic counter-doping required. We also demonstrate the crucial ability to tune E F from below midgap into the upper half of the gap near the conduction band edge by controlling the Se vacancy concentration using post-growth anneals. Additionally, we demonstrate the ability to maintain this Fermi level control following the careful, low-temperature removal of a protective Se cap, which allows samples to be transported in air for device fabrication. Thus, we provide detailed guidance for E F control that will finally enable researchers to fabricate high-performance devices that take advantage of transport through the topologically protected surface states of Bi 2 Se 3 .

Subperiosteal preparation using a new piezoelectric device: a histological examination.

PubMed

Stoetzer, Marcus; Magel, Anja; Kampmann, Andreas; Lemound, Juliana; Gellrich, Nils-Claudius; von See, Constantin

2014-01-01

Subperiosteal preparation using a periosteal elevator leads to disturbances of local immunohistochemistry and periosteal histology due to a microtrauma. Usually soft-tissue damage can be considerably reduced by using piezoelectric technology. For this reason, the effects of a novel piezoelectric device on immunohistochemistry and periosteal histology were examined and compared to conventional preparation of the periosteum using a periosteal elevator. Lewis rats were randomly assigned to one of five groups (n=50). Subperiosteal preparation was performed using either a piezoelectric device or a periosteal elevator. Immunohistochemical and histological analyses were performed immediately after preparation as well as three and eight days postoperatively. A statistical analysis of the histological colouring was performed offline using analysis of variance (ANOVA) on ranks (p<0.05). At all times, immunohistochemical and histological analysis demonstrated a significantly more homogenous tissue structure in the group of rats that underwent piezosurgery than in the group of rats that underwent treatment with a periosteal elevator. The use of a piezoelectric device for subperiosteal preparation is associated with more harmonious immunohistochemical and histological results for the periosteum than the use of a conventional periosteal elevator. As a result, piezoelectric devices can be expected to have a positive effect primarily on soft tissue, in particular of the periosteal as well as on surrounding tissues.

Controllable Growth of Perovskite Films by Room-Temperature Air Exposure for Efficient Planar Heterojunction Photovoltaic Cells

DOE PAGES

Yang, Bin; Dyck, Ondrej; Poplawsky, Jonathan; ...

2015-12-01

A two-step-solution-processing approach has been established to grow void-free perovskite films for low-cost and high-performance planar heterojunction photovoltaic devices. We generally applied a high-temperature thermal annealing treatment in order to drive the diffusion of CH 3NH 3I precursor molecules into the compact PbI 2 layer to form perovskite films. But, thermal annealing for extended periods would lead to degraded device performance due to the defects generated by decomposition of perovskite into PbI 2. In this work, we explored a controllable layer-by-layer spin-coating method to grow bilayer CH 3NH 3I/PbI 2 films, and then drive the interdiffusion between PbI 2 andmore » CH 3NH 3I layers by a simple room-temperature-air-exposure for making well-oriented, highly-crystalline perovskite films without thermal annealing. This high degree of crystallinity resulted in a carrier diffusion length of ~ 800 nm and high device efficiency of 15.6%, which is comparable to the reported values from thermally-annealed perovskite films based counterparts. Finally, the simplicity and high device performance of this processing approach is highly promising for direct integration into industrial-scale device manufacture.« less

Symmetric supercapacitor: Sulphurized graphene and ionic liquid.

PubMed

Shaikh, Jasmin S; Shaikh, Navajsharif S; Kharade, Rohini; Beknalkar, Sonali A; Patil, Jyoti V; Suryawanshi, Mahesh P; Kanjanaboos, Pongsakorn; Hong, Chang Kook; Kim, Jin Hyeok; Patil, Pramod S

2018-10-01

Symmetric supercapacitor is advanced over simple supercapacitor device due to their stability over a large potential window and high energy density. Graphene is a desired candidate for supercapacitor application since it has a high surface area, good electronic conductivity and high electro chemical stability. There is a pragmatic use of ionic liquid electrolyte for supercapacitor due to its stability over a large potential window, good ionic conductivity and eco-friendly nature. For high performance supercapacitor, the interaction between ionic liquid electrolyte and graphene are crucial for better charge transportation. In respect of this, a three-dimensional (3D) nanoporous honeycomb shaped sulfur embedded graphene (S-graphene) has been synthesized by simple chemical method. Here, the fabrication of high performance symmetric supercapacitor is done by using S-graphene as an electrode and [BMIM-PF 6 ] as an electrolyte. The particular architecture of S-graphene benefited to reduce the ion diffusion resistance, providing the large surface area for charge transportation and efficient charge storage. The S-graphene and ionic liquid-based symmetric supercapacitor device showed the large potential window of 3.2 V with high energy density 124 Wh kg -1 at 0.2 A g -1 constant applied current density. Furthermore, this device shows good cycling performance (stability) with a capacitive retention of 95% over 20,000 cycles at a higher current density of 2 A g -1 . Copyright © 2018 Elsevier Inc. All rights reserved.

Cotton-textile-enabled flexible self-sustaining power packs via roll-to-roll fabrication

PubMed Central

Gao, Zan; Bumgardner, Clifton; Song, Ningning; Zhang, Yunya; Li, Jingjing; Li, Xiaodong

2016-01-01

With rising energy concerns, efficient energy conversion and storage devices are required to provide a sustainable, green energy supply. Solar cells hold promise as energy conversion devices due to their utilization of readily accessible solar energy; however, the output of solar cells can be non-continuous and unstable. Therefore, it is necessary to combine solar cells with compatible energy storage devices to realize a stable power supply. To this end, supercapacitors, highly efficient energy storage devices, can be integrated with solar cells to mitigate the power fluctuations. Here, we report on the development of a solar cell-supercapacitor hybrid device as a solution to this energy requirement. A high-performance, cotton-textile-enabled asymmetric supercapacitor is integrated with a flexible solar cell via a scalable roll-to-roll manufacturing approach to fabricate a self-sustaining power pack, demonstrating its potential to continuously power future electronic devices. PMID:27189776

Metastable defect response in CZTSSe from admittance spectroscopy

DOE PAGES

Koeper, Mark J.; Hages, Charles J.; Li, Jian V.; ...

2017-10-02

Admittance spectroscopy is a useful tool used to study defects in semiconductor materials. However, metastable defect responses in non-ideal semiconductors can greatly impact the measurement and therefore the interpretation of results. Here, admittance spectroscopy was performed on Cu2ZnSn(S,Se) 4 where metastable defect response is illustrated due to the trapping of injected carriers into a deep defect state. To investigate the metastable response, admittance measurements were performed under electrically and optically relaxed conditions in comparison to a device following a low level carrier-injection pretreatment. The relaxed measurement demonstrates a single capacitance signature while two capacitance signatures are observed for the devicemore » measured following carrier-injection. The deeper level signature, typically reported for kesterites, is activated by charge trapping following carrier injection. Both signatures are attributed to bulk level defects. The significant metastable response observed on kesterites due to charge trapping obscures accurate interpretation of defect levels from admittance spectroscopy and indicates that great care must be taken when performing and interpreting this measurement on non-ideal devices.« less

Surface Modification of Cu(In,Ga)Se2 Grains

NASA Astrophysics Data System (ADS)

Alruqobah, Essam H.

Nearly all of the world’s energy demand today is being met by the use of non-renewable energy sources. With the worldwide energy demand projected to increase in the coming years, it is vital to find alternative and renewable energy sources. Among the available renewable energy sources, solar energy is the most promising in meeting the worldwide energy demand. Recently, thin film solar cells have garnered attention due to their thinner architecture and relatively high optical absorption coefficients, as opposed to the conventional crytslline silicon solar cells. One of the most promising thin-film solar cell absorber materials is Cu(In,Ga)Se2 (CIGSe), achieving power conversion efficiencies approaching those of crystalline Si. The highest efficiency CIGSe devices were made via costly vacuum-based co-evaporation process. CIGSe devices made from solution-processed methods have also garnered attention due to their lower costs, and their efficiencies have increased considerably in recent years. In this thesis, CIGSe absorber layers are fabricated via the solution-processed from nanoparticle-based sulfide CIGS. The most important step in fabrication of a CIGSe solar cell absorber layer is the selenization step, which is the thermal sintering of a CIGSe precursor layer in the presence of selenium vapor to achieve large, dense selenide grains that are required for adequate PV performance. It is determined that maintaining adequate selenium vapor pressure on the substrate during the selenization and subsequent cooldown is crucial in producing high efficiency solar cell devices. Furthermore, exposing the CIGSe grains to a Se-deficient atmosphere causes Se to evaporate from the grains, and subsequently modifying the CIGSe grain surface. The modified grain surface adversely impacts the PV performance of the final solar cell device by forming defects due to the decrease in selenium concentration. These defects are manifested in increased current shunting, and decrease the overall efficiency of the device.

Computer simulation of heterogeneous polymer photovoltaic devices

NASA Astrophysics Data System (ADS)

Kodali, Hari K.; Ganapathysubramanian, Baskar

2012-04-01

Polymer-based photovoltaic devices have the potential for widespread usage due to their low cost per watt and mechanical flexibility. Efficiencies close to 9.0% have been achieved recently in conjugated polymer based organic solar cells (OSCs). These devices were fabricated using solvent-based processing of electron-donating and electron-accepting materials into the so-called bulk heterojunction (BHJ) architecture. Experimental evidence suggests that a key property determining the power-conversion efficiency of such devices is the final morphological distribution of the donor and acceptor constituents. In order to understand the role of morphology on device performance, we develop a scalable computational framework that efficiently interrogates OSCs to investigate relationships between the morphology at the nano-scale with the device performance. In this work, we extend the Buxton and Clarke model (2007 Modelling Simul. Mater. Sci. Eng. 15 13-26) to simulate realistic devices with complex active layer morphologies using a dimensionally independent, scalable, finite-element method. We incorporate all stages involved in current generation, namely (1) exciton generation and diffusion, (2) charge generation and (3) charge transport in a modular fashion. The numerical challenges encountered during interrogation of realistic microstructures are detailed. We compare each stage of the photovoltaic process for two microstructures: a BHJ morphology and an idealized sawtooth morphology. The results are presented for both two- and three-dimensional structures.

Communication target object recognition for D2D connection with feature size limit

NASA Astrophysics Data System (ADS)

Ok, Jiheon; Kim, Soochang; Kim, Young-hoon; Lee, Chulhee

2015-03-01

Recently, a new concept of device-to-device (D2D) communication, which is called "point-and-link communication" has attracted great attentions due to its intuitive and simple operation. This approach enables user to communicate with target devices without any pre-identification information such as SSIDs, MAC addresses by selecting the target image displayed on the user's own device. In this paper, we present an efficient object matching algorithm that can be applied to look(point)-and-link communications for mobile services. Due to the limited channel bandwidth and low computational power of mobile terminals, the matching algorithm should satisfy low-complexity, low-memory and realtime requirements. To meet these requirements, we propose fast and robust feature extraction by considering the descriptor size and processing time. The proposed algorithm utilizes a HSV color histogram, SIFT (Scale Invariant Feature Transform) features and object aspect ratios. To reduce the descriptor size under 300 bytes, a limited number of SIFT key points were chosen as feature points and histograms were binarized while maintaining required performance. Experimental results show the robustness and the efficiency of the proposed algorithm.

A comparative study of spin coated and floating film transfer method coated poly (3-hexylthiophene)/poly (3-hexylthiophene)-nanofibers based field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiwari, Shashi; Balasubramanian, S. K.; Takashima, Wataru

2014-09-07

A comparative study on electrical performance, optical properties, and surface morphology of poly(3-hexylthiophene) (P3HT) and P3HT-nanofibers based “normally on” type p-channel field effect transistors (FETs), fabricated by two different coating techniques has been reported here. Nanofibers are prepared in the laboratory with the approach of self-assembly of P3HT molecules into nanofibers in an appropriate solvent. P3HT (0.3 wt. %) and P3HT-nanofibers (∼0.25 wt. %) are used as semiconductor transport materials for deposition over FETs channel through spin coating as well as through our recently developed floating film transfer method (FTM). FETs fabricated using FTM show superior performance compared to spin coated devices;more » however, the mobility of FTM films based FETs is comparable to the mobility of spin coated one. The devices based on P3HT-nanofibers (using both the techniques) show much better performance in comparison to P3HT FETs. The best performance among all the fabricated organic field effect transistors are observed for FTM coated P3HT-nanofibers FETs. This improved performance of nanofiber-FETs is due to ordering of fibers and also due to the fact that fibers offer excellent charge transport facility because of point to point transmission. The optical properties and structural morphologies (P3HT and P3HT-nanofibers) are studied using UV-visible absorption spectrophotometer and atomic force microscopy , respectively. Coating techniques and effect of fiber formation for organic conductors give information for fabrication of organic devices with improved performance.« less

High-Performance Flexible All-Solid-State Supercapacitor from Large Free-Standing Graphene-PEDOT/PSS Films.

PubMed

Liu, Yuqing; Weng, Bo; Razal, Joselito M; Xu, Qun; Zhao, Chen; Hou, Yuyang; Seyedin, Shayan; Jalili, Rouhollah; Wallace, Gordon G; Chen, Jun

2015-11-20

Although great attention has been paid to wearable electronic devices in recent years, flexible lightweight batteries or supercapacitors with high performance are still not readily available due to the limitations of the flexible electrode inventory. In this work, highly flexible, bendable and conductive rGO-PEDOT/PSS films were prepared using a simple bar-coating method. The assembled device using rGO-PEDOT/PSS electrode could be bent and rolled up without any decrease in electrochemical performance. A relatively high areal capacitance of 448 mF cm(-2) was achieved at a scan rate of 10 mV s(-1) using the composite electrode with a high mass loading (8.49 mg cm(-2)), indicating the potential to be used in practical applications. To demonstrate this applicability, a roll-up supercapacitor device was constructed, which illustrated the operation of a green LED light for 20 seconds when fully charged.

High-Performance Flexible All-Solid-State Supercapacitor from Large Free-Standing Graphene-PEDOT/PSS Films

NASA Astrophysics Data System (ADS)

Liu, Yuqing; Weng, Bo; Razal, Joselito M.; Xu, Qun; Zhao, Chen; Hou, Yuyang; Seyedin, Shayan; Jalili, Rouhollah; Wallace, Gordon G.; Chen, Jun

2015-11-01

Although great attention has been paid to wearable electronic devices in recent years, flexible lightweight batteries or supercapacitors with high performance are still not readily available due to the limitations of the flexible electrode inventory. In this work, highly flexible, bendable and conductive rGO-PEDOT/PSS films were prepared using a simple bar-coating method. The assembled device using rGO-PEDOT/PSS electrode could be bent and rolled up without any decrease in electrochemical performance. A relatively high areal capacitance of 448 mF cm-2 was achieved at a scan rate of 10 mV s-1 using the composite electrode with a high mass loading (8.49 mg cm-2), indicating the potential to be used in practical applications. To demonstrate this applicability, a roll-up supercapacitor device was constructed, which illustrated the operation of a green LED light for 20 seconds when fully charged.

Investigation of Short Channel Effects on Device Performance for 60nm NMOS Transistor

NASA Astrophysics Data System (ADS)

Chinnappan, U.; Sanudin, R.

2017-08-01

In the aggressively scaled complementary metal oxide semiconductor (CMOS) devices, shallower p-n junctions and low sheet resistances are essential for short-channel effect (SCE) control and high device performance. The SCE are attributed to two physical phenomena that are the limitation imposed on electron drift characteristics in channel and the modification of the threshold voltage (Vth) due to the shortening channel length. The decrement of Vth with decrement in gate length is a well-known attribute in SCE known as “threshold voltage roll-off’. In this research, the Technology Computer Aided Design (TCAD) was used to model the SCE phenomenon effect on 60nm n-type metal oxide semiconductor (NMOS) transistor. There are three parameters being investigated, which are the oxide thickness (Tox), gate length (L), acceptor concentration (Na). The simulation data were used to visualise the effect of SCE on the 60nm NMOS transistor. Simulation data suggest that all three parameters have significant effect on Vth, and hence on the transistor performance. It is concluded that there is a trade-off among these three parameters to obtain an optimized transistor performance.

Performance limit of daytime radiative cooling in warm humid environment

NASA Astrophysics Data System (ADS)

Suichi, Takahiro; Ishikawa, Atsushi; Hayashi, Yasuhiko; Tsuruta, Kenji

2018-05-01

Daytime radiative cooling potentially offers efficient passive cooling, but the performance is naturally limited by the environment, such as the ambient temperature and humidity. Here, we investigate the performance limit of daytime radiative cooling under warm and humid conditions in Okayama, Japan. A cooling device, consisting of alternating layers of SiO2 and poly(methyl methacrylate) on an Al mirror, is fabricated and characterized to demonstrate a high reflectance for sunlight and a selective thermal radiation in the mid-infrared region. In the temperature measurement under the sunlight irradiation, the device shows 3.4 °C cooler than a bare Al mirror, but 2.8 °C warmer than the ambient of 35 °C. The corresponding numerical analyses reveal that the atmospheric window in λ = 16 ˜ 25 μm is closed due to a high humidity, thereby limiting the net emission power of the device. Our study on the humidity influence on the cooling performance provides a general guide line of how one can achieve practical passive cooling in a warm humid environment.

Two-dimensional crystals: managing light for optoelectronics.

PubMed

Eda, Goki; Maier, Stefan A

2013-07-23

Semiconducting two-dimensional (2D) crystals such as MoS2 and WSe2 exhibit unusual optical properties that can be exploited for novel optoelectronics ranging from flexible photovoltaic cells to harmonic generation and electro-optical modulation devices. Rapid progress of the field, particularly in the growth area, is beginning to enable ways to implement 2D crystals into devices with tailored functionalities. For practical device performance, a key challenge is to maximize light-matter interactions in the material, which is inherently weak due to its atomically thin nature. Light management around the 2D layers with the use of plasmonic nanostructures can provide a compelling solution.

Experimental Microfluidic System

NASA Technical Reports Server (NTRS)

Culbertson, Christopher; Gonda, Steve; Ramsey, John Michael

2005-01-01

The ultimate goal of this project is to integrate microfluidic devices with NASA's space bioreactor systems. In such a system, the microfluidic device would provide realtime feedback control of the bioreactor by monitoring pH, glucose, and lactate levels in the cell media; and would provide an analytical capability to the bioreactor in exterrestrial environments for monitoring bioengineered cell products and health changes in cells due to environmental stressors. Such integrated systems could be used as biosentinels both in space and on planet surfaces. The objective is to demonstrate the ability of microfabricated devices to repeatedly and reproducibly perform bead cytometry experiments in micro, lunar, martian, and hypergravity (1.8g).

High performance superconducting devices enabled by three dimensionally ordered nanodots and/or nanorods

DOEpatents

Goyal, Amit

2013-09-17

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

Verification, Validation and Credibility Assessment of a Computational Model of the Advanced Resistive Exercise Device (ARED)

NASA Technical Reports Server (NTRS)

Werner, C. R.; Humphreys, B. T.; Mulugeta, L.

2014-01-01

The Advanced Resistive Exercise Device (ARED) is the resistive exercise device used by astronauts on the International Space Station (ISS) to mitigate bone loss and muscle atrophy due to extended exposure to microgravity (micro g). The Digital Astronaut Project (DAP) has developed a multi-body dynamics model of biomechanics models for use in spaceflight exercise physiology research and operations. In an effort to advance model maturity and credibility of the ARED model, the DAP performed verification, validation and credibility (VV and C) assessment of the analyses of the model in accordance to NASA-STD-7009 'Standards for Models and Simulations'.

High performance electrical, magnetic, electromagnetic and electrooptical devices enabled by three dimensionally ordered nanodots and nanorods

DOEpatents

Goyal, Amit , Kang; Sukill, [Knoxville, TN

2012-02-21

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

High performance devices enabled by epitaxial, preferentially oriented, nanodots and/or nanorods

DOEpatents

Goyal, Amit [Knoxville, TN

2011-10-11

Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic, superconducting and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

Hand VR Exergame for Occupational Health Care.

PubMed

Ortiz, Saskia; Uribe-Quevedo, Alvaro; Kapralos, Bill

2016-01-01

The widespread use and ubiquity of mobile computing technologies such as smartphones, tablets, laptops and portable gaming consoles has led to an increase in musculoskeletal disorders due to overuse, bad posture, repetitive movements, fixed postures and physical de-conditioning caused by low muscular demands while using (and over-using) these devices. In this paper we present the development of a hand motion-based virtual reality-based exergame for occupational health purposes that allows the user to perform simple exercises using a cost-effective non-invasive motion capture device to help overcome and prevent some of the muskoloskeletal problems associated with the over-use of keyboards and mobile devices.

Recent Advancements in Functionalized Paper-Based Electronics.

PubMed

Lin, Yang; Gritsenko, Dmitry; Liu, Qian; Lu, Xiaonan; Xu, Jie

2016-08-17

Building electronic devices on ubiquitous paper substrates has recently drawn extensive attention due to its light weight, low cost, environmental friendliness, and ease of fabrication. Recently, a myriad of advancements have been made to improve the performance of paper electronics for various applications, such as basic electronic components, energy storage devices, generators, antennas, and electronic circuits. This review aims to summarize this progress and discuss different perspectives of paper electronics as well as the remaining challenges yet to be overcome in this field. Other aspects included in this review are the fundamental characteristics of paper, modification of paper with functional materials, and various methods for device fabrication.

Device Performance and Reliability Improvements of AlGaBN/GaN/Si MOSFET

DTIC Science & Technology

2016-02-04

Metal insulator semiconductor AlGaN /GaN high electron mobility transistors (MISHEMTs) are promising for power device applications due to a lower leakage...current than the conventional Schottky AlGaN/GaN HEMTs.1–3 Among a large number of insulator materials, an Al2O3 dielectric layer, deposited by...atomic layer deposition (ALD), is often employed as the gate insulator because of a large band gap (and the resultant high conduction band offset on

Fixation of operating point and measurement of turn on characteristics of IGBT F4-75R06W1E3

NASA Astrophysics Data System (ADS)

Haseena, A.; Subhash Joshi T., G.; George, Saly

2018-05-01

For the proficient operation of the Power electronic circuit, signal level performance of power electronic devices are very important. For getting good signal level characteristics, fixing operating point is very critical. Device deviates from the typical characteristics given in the datasheet due to the presence of stray components in the circuit lay out. Fixation of operating point of typical silicon IGBT and its turn on characteristics is discussed in this paper.

Transseptal Guidewire Stabilization for Device Closure of a Large Pulmonary Arteriovenous Malformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joseph, George, E-mail: joseph59@gmail.com; Kunwar, Brajesh Kumar, E-mail: kunwar_brajesh@yahoo.com

A 46-year-old man presenting with massive hemoptysis was found to have a large pulmonary arteriovenous malformation (PAVM) in the right lung. Closure of the PAVM with an Amplatzer-type duct occluder was hampered by inability to advance the device delivery sheath into the PAVM due to vessel tortuosity and inadequate guidewire support. Atrial septal puncture was performed and a femorofemoral arteriovenous guidewire loop through the right pulmonary artery, PAVM, and left atrium was created. Traction on both ends of the guidewire loop allowed advancement of the device delivery sheath into the PAVM and successful completion of the procedure. Transseptal guidewire stabilizationmore » can be a valuable option during device closure of large PAVMs when advancement, stability, or kinking of the device delivery sheath is an issue.« less

Highly tunable local gate controlled complementary graphene device performing as inverter and voltage controlled resistor.

PubMed

Kim, Wonjae; Riikonen, Juha; Li, Changfeng; Chen, Ya; Lipsanen, Harri

2013-10-04

Using single-layer CVD graphene, a complementary field effect transistor (FET) device is fabricated on the top of separated back-gates. The local back-gate control of the transistors, which operate with low bias at room temperature, enables highly tunable device characteristics due to separate control over electrostatic doping of the channels. Local back-gating allows control of the doping level independently of the supply voltage, which enables device operation with very low VDD. Controllable characteristics also allow the compensation of variation in the unintentional doping typically observed in CVD graphene. Moreover, both p-n and n-p configurations of FETs can be achieved by electrostatic doping using the local back-gate. Therefore, the device operation can also be switched from inverter to voltage controlled resistor, opening new possibilities in using graphene in logic circuitry.

Direct evaluation of influence of electron damage on the subcell performance in triple-junction solar cells using photoluminescence decays.

PubMed

Tex, David M; Nakamura, Tetsuya; Imaizumi, Mitsuru; Ohshima, Takeshi; Kanemitsu, Yoshihiko

2017-05-16

Tandem solar cells are suited for space applications due to their high performance, but also have to be designed in such a way to minimize influence of degradation by the high energy particle flux in space. The analysis of the subcell performance is crucial to understand the device physics and achieve optimized designs of tandem solar cells. Here, the radiation-induced damage of inverted grown InGaP/GaAs/InGaAs triple-junction solar cells for various electron fluences are characterized using conventional current-voltage (I-V) measurements and time-resolved photoluminescence (PL). The conversion efficiencies of the entire device before and after damage are measured with I-V curves and compared with the efficiencies predicted from the time-resolved method. Using the time-resolved data the change in the carrier dynamics in the subcells can be discussed. Our optical method allows to predict the absolute electrical conversion efficiency of the device with an accuracy of better than 5%. While both InGaP and GaAs subcells suffered from significant material degradation, the performance loss of the total device can be completely ascribed to the damage in the GaAs subcell. This points out the importance of high internal electric fields at the operating point.

Temperature coefficients and radiation induced DLTS spectra of MOCVD grown n(+)p InP solar cells

NASA Technical Reports Server (NTRS)

Walters, Robert J.; Statler, Richard L.; Summers, Geoffrey P.

1991-01-01

The effects of temperature and radiation on n(+)p InP solar cells and mesa diodes grown by metallorganic chemical vapor deposition (MOCVD) were studied. It was shown that MOCVD is capable of consistently producing good quality InP solar cells with Eff greater than 19 percent which display excellent radiation resistance due to minority carrier injection and thermal annealing. It was also shown that universal predictions of InP device performance based on measurements of a small group of test samples can be expected to be quite accurate, and that the degradation of an InP device due to any incident particle spectrum should be predictable from a measurement following a single low energy proton irradiation.

Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide /PEDOT:PSS double decked hole transport layer

PubMed Central

Rafique, Saqib; Abdullah, Shahino Mah; Shahid, Muhammad Mehmood; Ansari, Mohammad Omaish; Sulaiman, Khaulah

2017-01-01

This work demonstrates the high performance graphene oxide (GO)/PEDOT:PSS doubled decked hole transport layer (HTL) in the PCDTBT:PC71BM based bulk heterojunction organic photovoltaic device. The devices were tested on merits of their power conversion efficiency (PCE), reproducibility, stability and further compared with the devices with individual GO or PEDOT:PSS HTLs. Solar cells employing GO/PEDOT:PSS HTL yielded a PCE of 4.28% as compared to either of individual GO or PEDOT:PSS HTLs where they demonstrated PCEs of 2.77 and 3.57%, respectively. In case of single GO HTL, an inhomogeneous coating of ITO caused the poor performance whereas PEDOT:PSS is known to be hygroscopic and acidic which upon direct contact with ITO reduced the device performance. The improvement in the photovoltaic performance is mainly ascribed to the increased charge carriers mobility, short circuit current, open circuit voltage, fill factor, and decreased series resistance. The well matched work function of GO and PEDOT:PSS is likely to facilitate the charge transportation and an overall reduction in the series resistance. Moreover, GO could effectively block the electrons due to its large band-gap of ~3.6 eV, leading to an increased shunt resistance. In addition, we also observed the improvement in the reproducibility and stability. PMID:28084304

Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide /PEDOT:PSS double decked hole transport layer.

PubMed

Rafique, Saqib; Abdullah, Shahino Mah; Shahid, Muhammad Mehmood; Ansari, Mohammad Omaish; Sulaiman, Khaulah

2017-01-13

This work demonstrates the high performance graphene oxide (GO)/PEDOT:PSS doubled decked hole transport layer (HTL) in the PCDTBT:PC 71 BM based bulk heterojunction organic photovoltaic device. The devices were tested on merits of their power conversion efficiency (PCE), reproducibility, stability and further compared with the devices with individual GO or PEDOT:PSS HTLs. Solar cells employing GO/PEDOT:PSS HTL yielded a PCE of 4.28% as compared to either of individual GO or PEDOT:PSS HTLs where they demonstrated PCEs of 2.77 and 3.57%, respectively. In case of single GO HTL, an inhomogeneous coating of ITO caused the poor performance whereas PEDOT:PSS is known to be hygroscopic and acidic which upon direct contact with ITO reduced the device performance. The improvement in the photovoltaic performance is mainly ascribed to the increased charge carriers mobility, short circuit current, open circuit voltage, fill factor, and decreased series resistance. The well matched work function of GO and PEDOT:PSS is likely to facilitate the charge transportation and an overall reduction in the series resistance. Moreover, GO could effectively block the electrons due to its large band-gap of ~3.6 eV, leading to an increased shunt resistance. In addition, we also observed the improvement in the reproducibility and stability.

Significantly improved photovoltaic performance in polymer bulk heterojunction solar cells with graphene oxide /PEDOT:PSS double decked hole transport layer

NASA Astrophysics Data System (ADS)

Rafique, Saqib; Abdullah, Shahino Mah; Shahid, Muhammad Mehmood; Ansari, Mohammad Omaish; Sulaiman, Khaulah

2017-01-01

This work demonstrates the high performance graphene oxide (GO)/PEDOT:PSS doubled decked hole transport layer (HTL) in the PCDTBT:PC71BM based bulk heterojunction organic photovoltaic device. The devices were tested on merits of their power conversion efficiency (PCE), reproducibility, stability and further compared with the devices with individual GO or PEDOT:PSS HTLs. Solar cells employing GO/PEDOT:PSS HTL yielded a PCE of 4.28% as compared to either of individual GO or PEDOT:PSS HTLs where they demonstrated PCEs of 2.77 and 3.57%, respectively. In case of single GO HTL, an inhomogeneous coating of ITO caused the poor performance whereas PEDOT:PSS is known to be hygroscopic and acidic which upon direct contact with ITO reduced the device performance. The improvement in the photovoltaic performance is mainly ascribed to the increased charge carriers mobility, short circuit current, open circuit voltage, fill factor, and decreased series resistance. The well matched work function of GO and PEDOT:PSS is likely to facilitate the charge transportation and an overall reduction in the series resistance. Moreover, GO could effectively block the electrons due to its large band-gap of ~3.6 eV, leading to an increased shunt resistance. In addition, we also observed the improvement in the reproducibility and stability.

Inert gas annealing effect in solution-processed amorphous indium-gallium-zinc-oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Lee, Seungwoon; Jeong, Jaewook

2017-08-01

In this paper, the annealing effect of solution-processed amorphous indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs), under ambient He (He-device), is systematically analyzed by comparison with those under ambient O2 (O2-device) and N2 (N2-device), respectively. The He-device shows high field-effect mobility and low subthreshold slope owing to the minimization of the ambient effect. The degradation of the O2- and N2-device performances originate from their respective deep acceptor-like and shallow donor-like characteristics, which can be verified by comparison with the He-device. However, the three devices show similar threshold voltage instability under prolonged positive bias stress due to the effect of excess oxygen. Therefore, annealing in ambient He is the most suitable method for the fabrication of reference TFTs to study the various effects of the ambient during the annealing process in solution-processed a-IGZO TFTs.

Performance Evaluation of an Automotive-Grade, High Speed Gate Driver for SiC FETs, Type UCC27531, Over a Wide Temperature Range

NASA Technical Reports Server (NTRS)

Boomer, Kristen; Hammoud, Ahmad

2015-01-01

Silicon carbide (SiC) devices are becoming widely used in electronic power circuits as replacement for conventional silicon parts due to their attractive properties that include low on-state resistance, high temperature tolerance, and high frequency operation. These attributes have a significant impact by reducing system weight, saving board space, and conserving power. In this work, the performance of an automotive-grade high speed gate driver with potential use in controlling SiC FETs (field-Effect Transistors) in converters or motor control applications was evaluated under extreme temperatures and thermal cycling. The investigations were carried out to assess performance and to determine suitability of this device for use in space exploration missions under extreme temperature conditions.

The effects of human finger and Chinese character on Chinese handwriting performance on mobile touch devices.

PubMed

Chen, Zhe; Rau, Pei-Luen Patrick; Chen, Cuiling

2014-05-01

The aim of the present study is to investigate Chinese handwriting on mobile touch devices, considering the effects of three characteristics of the human finger (type, length, and width) and three characteristics of Chinese characters (direction of the first stroke, number of strokes, and structure). Due to the popularity of touch devices in recent years, finger input for Chinese characters has attracted more attention from both industry and academia. However, previous studies have no systematical consideration on the effects of human finger and Chinese characters on Chinese handwriting performance. An experiment was reported in this article to illustrate the effects of the human finger and Chinese characters on the Chinese handwriting performance (i.e., input time, accuracy, number of protruding strokes, mental workload, satisfaction, and physical fatigue). The experiment results indicated that all six factors have significant effects on Chinese handwriting performance, especially on the input time, accuracy, and number of protruding strokes. Finger type, finger length, finger width, direction of the first stroke, number of strokes, and character structures are significantly influencing Chinese handwriting performance. These factors should be taken into more consideration in future research and the practical design for Chinese handwriting systems.

In Vivo Self-Powered Wireless Cardiac Monitoring via Implantable Triboelectric Nanogenerator.

PubMed

Zheng, Qiang; Zhang, Hao; Shi, Bojing; Xue, Xiang; Liu, Zhuo; Jin, Yiming; Ma, Ye; Zou, Yang; Wang, Xinxin; An, Zhao; Tang, Wei; Zhang, Wei; Yang, Fan; Liu, Yang; Lang, Xilong; Xu, Zhiyun; Li, Zhou; Wang, Zhong Lin

2016-07-26

Harvesting biomechanical energy in vivo is an important route in obtaining sustainable electric energy for powering implantable medical devices. Here, we demonstrate an innovative implantable triboelectric nanogenerator (iTENG) for in vivo biomechanical energy harvesting. Driven by the heartbeat of adult swine, the output voltage and the corresponding current were improved by factors of 3.5 and 25, respectively, compared with the reported in vivo output performance of biomechanical energy conversion devices. In addition, the in vivo evaluation of the iTENG was demonstrated for over 72 h of implantation, during which the iTENG generated electricity continuously in the active animal. Due to its excellent in vivo performance, a self-powered wireless transmission system was fabricated for real-time wireless cardiac monitoring. Given its outstanding in vivo output and stability, iTENG can be applied not only to power implantable medical devices but also possibly to fabricate a self-powered, wireless healthcare monitoring system.

Pectoral nerves (PECS) and intercostal nerve block for cardiac resynchronization therapy device implantation.

PubMed

Fujiwara, Atsushi; Komasawa, Nobuyasu; Minami, Toshiaki

2014-01-01

A 71-year-old man was scheduled to undergo cardiac resynchronization therapy device (CRTD) implantation. He was combined with severe chronic heart failure due to ischemic heart disease. NYHA class was 3 to 4 and electrocardiogram showed non-sustained ventricular. Ejection fraction was about 20% revealed by transthoracic echocardiogram. He was also on several anticoagulation medications. We planned to implant the device under the greater pectoral muscle. As general anesthesia was considered risky, monitored anesthesia care utilizing peripheral nerve block and slight sedation was scheduled. Pectoral nerves (PECS) block and intercostal block was performed under ultrasonography with ropivacaine. For sedation during the procedure, continuous infusion of dexmedetomidine without a loading dose was performed. The procedure lasted about 3 hours, but the patient showed no pain or restlessness. Combination of PECS block and intercostal block may provide effective analgesia for CRTD implantation.

The Influence of Unsteadiness on the Analysis of Pressure Gain Combustion Devices

NASA Technical Reports Server (NTRS)

Paxson, Daniel E.; Kaemming, Tom

2013-01-01

Pressure gain combustion (PGC) has been the object of scientific study for over a century due to its promise of improved thermodynamic efficiency. In many recent application concepts PGC is utilized as a component in an otherwise continuous, normally steady flow system, such as a gas turbine or ram jet engine. However, PGC is inherently unsteady. Failure to account for the effects of this periodic unsteadiness can lead to misunderstanding and errors in performance calculations. This paper seeks to provide some clarity by presenting a consistent method of thermodynamic cycle analysis for a device utilizing PGC technology. The incorporation of the unsteady PGC process into the conservation equations for a continuous flow device is presented. Most importantly, the appropriate method for computing the conservation of momentum is presented. It will be shown that proper, consistent analysis of cyclic conservation principles produces representative performance predictions.

Characterization of Stress in Thallium Bromide Devices

NASA Astrophysics Data System (ADS)

Datta, Amlan; Motakef, Shariar

2015-04-01

Thallium bromide (TlBr) is a wide bandgap, compound semiconductor with high gamma-ray stopping power and promising physical properties. Several surface modification techniques have been demonstrated to increase the lifetime of TlBr devices at room temperature. However, absence of reproducibility in the performance of TlBr detectors (even with low ionic conduction at -20°C) suggests presence of unexplored bulk phenomena. Stress in the TlBr crystal due to various intrinsic (e.g. grain boundaries and dislocations networks) in conjunction with external factors such as thermal, mechanical, and electrical loadings explains detector-to-detector variations. Photoelasticity and opto-electrical techniques were applied to visualize and qualitatively correlate the device performance with stress. Changes in stress patterns with variations in ambient temperature were clearly demonstrated. Electric field fluctuations in TlBr detectors with time were for the first time observed using the Pockels effect.

High Performance Perovskite Solar Cells

PubMed Central

Tong, Xin; Lin, Feng; Wu, Jiang

2015-01-01

Perovskite solar cells fabricated from organometal halide light harvesters have captured significant attention due to their tremendously low device costs as well as unprecedented rapid progress on power conversion efficiency (PCE). A certified PCE of 20.1% was achieved in late 2014 following the first study of long‐term stable all‐solid‐state perovskite solar cell with a PCE of 9.7% in 2012, showing their promising potential towards future cost‐effective and high performance solar cells. Here, notable achievements of primary device configuration involving perovskite layer, hole‐transporting materials (HTMs) and electron‐transporting materials (ETMs) are reviewed. Numerous strategies for enhancing photovoltaic parameters of perovskite solar cells, including morphology and crystallization control of perovskite layer, HTMs design and ETMs modifications are discussed in detail. In addition, perovskite solar cells outside of HTMs and ETMs are mentioned as well, providing guidelines for further simplification of device processing and hence cost reduction. PMID:27774402

Combining Charge Couple Devices and Rate Sensors for the Feedforward Control System of a Charge Coupled Device Tracking Loop.

PubMed

Tang, Tao; Tian, Jing; Zhong, Daijun; Fu, Chengyu

2016-06-25

A rate feed forward control-based sensor fusion is proposed to improve the closed-loop performance for a charge couple device (CCD) tracking loop. The target trajectory is recovered by combining line of sight (LOS) errors from the CCD and the angular rate from a fiber-optic gyroscope (FOG). A Kalman filter based on the Singer acceleration model utilizes the reconstructive target trajectory to estimate the target velocity. Different from classical feed forward control, additive feedback loops are inevitably added to the original control loops due to the fact some closed-loop information is used. The transfer function of the Kalman filter in the frequency domain is built for analyzing the closed loop stability. The bandwidth of the Kalman filter is the major factor affecting the control stability and close-loop performance. Both simulations and experiments are provided to demonstrate the benefits of the proposed algorithm.

Gold and iodine diffusion in large area perovskite solar cells under illumination.

PubMed

Cacovich, S; Ciná, L; Matteocci, F; Divitini, G; Midgley, P A; Di Carlo, A; Ducati, C

2017-04-06

Operational stability is the main issue hindering the commercialisation of perovskite solar cells. Here, a long term light soaking test was performed on large area hybrid halide perovskite solar cells to investigate the morphological and chemical changes associated with the degradation of photovoltaic performance occurring within the devices. Using Scanning Transmission Electron Microscopy (STEM) in conjunction with EDX analysis on device cross sections, we observe the formation of gold clusters in the perovskite active layer as well as in the TiO 2 mesoporous layer, and a severe degradation of the perovskite due to iodine migration into the hole transporter. All these phenomena are associated with a drastic drop of all the photovoltaic parameters. The use of advanced electron microscopy techniques and data processing provides new insights on the degradation pathways, directly correlating the nanoscale structure and chemistry to the macroscopic properties of hybrid perovskite devices.

Analysis of casing treatment’s impact on the axial compressor model stage characteristics

NASA Astrophysics Data System (ADS)

Tribunskaia, K.; Kozhukhov, Y. V.

2017-08-01

There are special requirements for the compressors of aircraft engines. They must ensure maximum efficiency in a maximally large stable work zone Due to a high pressure ratio these stages are more susceptible to the losses from radial clearance. One of the approaches to reduce such losses is the application of above-rotor devices. In the following study there is considered the impact of such treatments on the compressor stage performance. Despite the fact that there is a sufficient amount of research about this issue, their results are contradictory. The use of these devices can affect the characteristics of compressor stage performance both positively and negatively. This study was conducted using the methods of computational fluid dynamics and was based on the NASA Rotor-37 geometry model stage. Results were obtained through the comparison of the characteristics of stages with and without above-rotor devices.

77 FR 11199 - Visual-Manual NHTSA Driver Distraction Guidelines for In-Vehicle Electronic Devices

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-24

...The National Highway Traffic Safety Administration (NHTSA) is concerned about the effects of distraction due to drivers' use of electronic devices on motor vehicle safety. Consequently, NHTSA is issuing nonbinding, voluntary NHTSA Driver Distraction Guidelines (NHTSA Guidelines) to promote safety by discouraging the introduction of excessively distracting devices in vehicles. This notice details the contents of the first phase of the NHTSA Driver Distraction Guidelines. These NHTSA Guidelines cover original equipment in-vehicle device secondary tasks (communications, entertainment, information gathering, and navigation tasks not required to drive are considered secondary tasks) performed by the driver through visual-manual means (meaning the driver looking at a device, manipulating a device-related control with the driver's hand, and watching for visual feedback). The proposed NHTSA Guidelines list certain secondary, non-driving related tasks that, based on NHTSA's research, are believed by the agency to interfere inherently with a driver's ability to safely control the vehicle. The Guidelines recommend that those in-vehicle devices be designed so that they cannot be used by the driver to perform such tasks while the driver is driving. For all other secondary, non-driving-related visual-manual tasks, the NHTSA Guidelines specify a test method for measuring the impact of task performance on driving safety while driving and time-based acceptance criteria for assessing whether a task interferes too much with driver attention to be suitable to perform while driving. If a task does not meet the acceptance criteria, the NHTSA Guidelines recommend that in- vehicle devices be designed so that the task cannot be performed by the driver while driving. In addition to identifying inherently distracting tasks and providing a means for measuring and evaluating the level of distraction associated with other non-driving-related tasks, the NHTSA Guidelines contain several design recommendations for in-vehicle devices in order to minimize their potential for distraction. NHTSA seeks comments on these NHTSA Guidelines and any suggestions for how to improve them so as to better enhance motor vehicle safety.

Graphene base heterojunction transistor: An explorative study on device potential, optimization, and base parasitics

NASA Astrophysics Data System (ADS)

Di Lecce, Valerio; Grassi, Roberto; Gnudi, Antonio; Gnani, Elena; Reggiani, Susanna; Baccarani, Giorgio

2015-12-01

The Graphene-Base Heterojunction Transistor (GBHT) is a novel device concept with a high potential for analog high-frequency RF operation, in which the current is due to both thermionic emission and tunneling. In this paper we study through numerical simulations the influence of previously uninvestigated aspects of Si- and Ge-based GBHTs-namely, crystallographic orientation and doping density values-on the device performance; a comparison with an aggressively scaled HBT structure is then reported. The simulations are carried out with an in-house developed code based on a 1-D quantum transport model within the effective mass approximation and the assumptions of ballistic transport with non-parabolic corrections and ideal semiconductor-graphene interface. We show that crystallographic orientation has a negligible effect on the GBHT performance. The doping density values in the GBHT emitter and collector regions can be tailored to maximize the device performance: the Si device shows better overall performance than the Ge one, yielding a peak cut-off frequency fT higher than 4 THz together with an intrinsic voltage gain above 10, or even higher fT at the cost of a lower gain. The Si-based GBHT can potentially outperform the SiGe HBT by a 2.8 higher fT . For a Si-based GBHT with a circular active region of diameter 50-100 nm, a theoretical balanced value for fT and fmax above 2 THz can be achieved, provided the base parasitics are carefully minimized.

Unified Numerical Solver for Device Metastabilities in CdTe Thin-Film PV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasileska, Dragica

Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. Manufacturers de-vote significant empirical efforts to study these phenomena and to improve semiconduc-tor device stability. Still, understanding the underlying reasons of these instabilities re-mains clouded due to the lack of ability to characterize materials at atomistic levels and the lack of interpretation from the most fundamental material science. The most com-monly alleged causes of metastability in CdTe device, such as “migration of Cu,” have been investigated rigorously overmore » the past fifteen years. Still, the discussion often ended prematurely with stating observed correlations between stress conditions and changes in atomic profiles of impurities or CV doping concentration. Multiple hypotheses sug-gesting degradation of CdTe solar cell devices due to interaction and evolution of point defects and complexes were proposed, and none of them received strong theoretical or experimental confirmation. It should be noted that atomic impurity profiles in CdTe pro-vide very little intelligence on active doping concentrations. The same elements could form different energy states, which could be either donors or acceptors, depending on their position in crystalline lattice. Defects interact with other extrinsic and intrinsic de-fects; for example, changing the state of an impurity from an interstitial donor to a sub-stitutional acceptor often is accompanied by generation of a compensating intrinsic in-terstitial donor defect. Moreover, all defects, intrinsic and extrinsic, interact with the elec-trical potential and free carriers so that charged defects may drift in the electric field and the local electrical potential affects the formation energy of the point defects. Such complexity of interactions in CdTe makes understanding of temporal changes in device performance even more challenging and a closed solution that can treat the entire sys-tem and its interactions is required.« less

Motion compensation for MRI-compatible patient-mounted needle guide device: estimation of targeting accuracy in MRI-guided kidney cryoablations

NASA Astrophysics Data System (ADS)

Tokuda, Junichi; Chauvin, Laurent; Ninni, Brian; Kato, Takahisa; King, Franklin; Tuncali, Kemal; Hata, Nobuhiko

2018-04-01

Patient-mounted needle guide devices for percutaneous ablation are vulnerable to patient motion. The objective of this study is to develop and evaluate a software system for an MRI-compatible patient-mounted needle guide device that can adaptively compensate for displacement of the device due to patient motion using a novel image-based automatic device-to-image registration technique. We have developed a software system for an MRI-compatible patient-mounted needle guide device for percutaneous ablation. It features fully-automated image-based device-to-image registration to track the device position, and a device controller to adjust the needle trajectory to compensate for the displacement of the device. We performed: (a) a phantom study using a clinical MR scanner to evaluate registration performance; (b) simulations using intraoperative time-series MR data acquired in 20 clinical cases of MRI-guided renal cryoablations to assess its impact on motion compensation; and (c) a pilot clinical study in three patients to test its feasibility during the clinical procedure. FRE, TRE, and success rate of device-to-image registration were mm, mm, and 98.3% for the phantom images. The simulation study showed that the motion compensation reduced the targeting error for needle placement from 8.2 mm to 5.4 mm (p  <  0.0005) in patients under general anesthesia (GA), and from 14.4 mm to 10.0 mm () in patients under monitored anesthesia care (MAC). The pilot study showed that the software registered the device successfully in a clinical setting. Our simulation study demonstrated that the software system could significantly improve targeting accuracy in patients treated under both MAC and GA. Intraprocedural image-based device-to-image registration was feasible.

Processing and Characterization of Thin Cadmium Telluride Solar Cells

NASA Astrophysics Data System (ADS)

Wojtowicz, Anna

Cadmium telluride (CdTe) has the highest theoretical limit to conversion efficiency of single-junction photovoltaic (PV) technologies today. However, despite a maximum theoretical open-circuit voltage of 1.20 V, record devices have historically had voltages pinned around only 900 mV. Voltage losses due to high recombination rates remains to be the most complex hurdle to CdTe technology today, and the subject of on-going research in the physics PV group at Colorado State University. In this work, an ultrathin CdTe device architecture is proposed in an effort to reduce bulk recombination and boost voltages. By thinning the CdTe layer, a device's internal electric field extends fully towards the back contact. This quickly separates electrons-hole pairs throughout the bulk of the device and reduces overall recombination. Despite this advantage, very thin CdTe layers also present a unique set of optical and electrical challenges which result in performance losses not as prevalent in thicker devices. When fabricating CdTe solar cells, post-deposition treatments applied to the absorber layer are a critical step for achieving high efficiency devices. Exposure of the polycrystalline CdTe film to a chlorine species encourages the passivation of dangling bonds and larger grain formation, while copper-doping improves device uniformity and voltages. This work focuses on experiments conducted via close-space sublimation to optimize CdCl2 and CuCl treatments for thin CdTe solar cells. Sweeps of both exposure and anneal time were performed for both post-deposition treatments on CdTe devices with 1.0 mum absorber layers. The results demonstrate that thin CdTe devices require substantially less post-deposition processing than standard thicker devices as expected. Additionally, the effects of CdTe growth temperature on thin devices is briefly investigated. The results suggest that higher growth temperatures lead to both electrical and stoichiometric changes in CdTe closely associated with lower carrier lifetimes and poorer overall performance.

Electrocautery device does not provide adequate pulmonary vessel sealing in transumbilical anatomic pulmonary lobectomy.

PubMed

Liu, Hung-Ping; Chu, Yen; Wu, Yi-Cheng; Hsieh, Ming-Ju; Liu, Chieng-Ying; Chen, Tzu-Ping; Chao, Yin-Kai; Wu, Ching-Yang; Yeh, Chi-Ju; Ko, Po-Jen; Liu, Yun-Hen

2016-05-01

Safe pulmonary vessel sealing device plays a crucial role in anatomic lung resection. In 2014, we reported high rates of massive bleeding complications during transumbilical lobectomy in a canine model due to difficulty in managing the pulmonary vessel with an endostapler. In this animal survival series, we aimed to evaluate the outcome of pulmonary vessel sealing with an electrocautery device to simplify the transumbilical thoracic surgery. Under general anesthesia, a 3-cm longitudinal incision was made over the umbilicus. Under video guidance, a bronchoscope was inserted through the incision for exploration. The diaphragmatic wound was created with an electrocautery knife and used as the entrance into the thoracic cavity. Using the transumbilical technique, anatomic lobectomy was performed with electrosurgical devices and endoscopic vascular staplers in 15 canines. Transumbilical endoscopic anatomic lobectomy was successfully completed in 12 of the 15 animals. Intraoperative bleeding developed in three animals during pulmonary hilum dissection, where one animal was killed due to hemodynamic instability and the other two animals required thoracotomy to complete the operation. There were five delayed bleeding and surgical mortality cases caused by inadequate vessel sealing by electrosurgical devices. Postmortem examination confirmed correct transumbilical lobectomy in the twelve animals that survived the operations. Transumbilical anatomic lobectomy is technically feasible in a canine model; however, the electrosurgical devices were not effective in sealing the pulmonary vessel in the current canine model.

Low permanent pacemaker rates following Lotus device implantation for transcatheter aortic valve replacement due to modified implantation protocol.

PubMed

Krackhardt, Florian; Kherad, Behrouz; Krisper, Maximilian; Pieske, Burkert; Laule, Michael; Tschöpe, Carsten

2017-01-01

Conduction disturbances requiring permanent pacemaker implantation following transcatheter aortic valve replacement (TAVR) are a common problem. Pacemaker implantation rates after TAVR appear to be higher compared to conventional aortic valve replacement. The aim of this study was to analyze whether a high annulus implantation conveys the benefit of a decreased rate of permanent pacemaker implantation while being safe and successful according to Valve Academic Research Consortium 2 (VARC2)-criteria. A total of 23 patients with symptomatic severe aortic valve stenosis, an aortic annulus of 19-27 mm and at high risk for surgery were treated with the Lotus valve. In all patients the valve was implanted in a high annulus position via femoral access. The primary device performance endpoint was VARC2-defined device success after 30 days and the primary safety endpoint was the need for permanent pacemaker implantation. The mean age was 73.23 ± 7.65 years, 46% were female, 38% were New York Heart Association class III/IV at baseline. Thirty-day follow-up data were available for all patients. The VARC2-defined device success rate after 30 days was 22/23 (96%). 2/21 (10%) patients required a newly implanted pacemaker due to 3rd degree atrioventricular block. 25% of the patients developed a new left bundle branch block after valvuloplasty or device implantation. 21 of the 23 patients (96%) had no other signs of conduction disturbances after 30 days. The approach of the modified implantation technique of Lotus TAVR device was safe and effective. The incidence of need for a permanent pacemaker following TAVR could be significantly reduced due to adopted implantation protocol.

Single-layer MoS2 - electrical transport properties, devices and circuits

NASA Astrophysics Data System (ADS)

Kis, Andras

2013-03-01

After quantum dots, nanotubes and nanowires, two-dimensional materials in the shape of sheets with atomic-scale thickness represent the newest addition to the diverse family of nanoscale materials. Single-layer molybdenum disulphide (MoS2) , a direct-gap semiconductor is a typical example of these new graphene-like materials that can be produced using the adhesive-tape based cleavage technique originally developed for graphene. The presence of a band gap in MoS2 allowed us to fabricate transistors that can be turned off and operate with negligible leakage currents. Furthermore, our transistors can be used to build simple integrated circuits capable of performing logic operations and amplifying small signals. I will report here on our latest 2D MoS2 transistors with improved performance due to enhanced electrostatic control, showing improved currents and transconductance as well as current saturation. We also record electrical breakdown of our devices and find that MoS2 can support very high current densities, exceeding the current carrying capacity of copper by a factor of fifty. Furthermore, I will show optoelectronic devices incorporating MoS2 with sensitivity that surpasses similar graphene devices by several orders of magnitude. Finally, I will present temperature-dependent electrical transport and mobility measurements that show clear mobility enhancement due to the suppression of the influence of charge impurities with the deposition of an HfO2 capping layer. Financially supported by grants from Swiss National Science Foundation, EU-FP7, EU-ERC and Swiss Nanoscience Institute.

Aerosol can puncture device operational test plan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leist, K.J.

1994-05-03

Puncturing of aerosol cans is performed in the Waste Receiving and Processing Facility Module 1 (WRAP 1) process as a requirement of the waste disposal acceptance criteria for both transuranic (TRU) waste and low-level waste (LLW). These cans have contained such things as paints, lubricating oils, paint removers, insecticides, and cleaning supplies which were used in radioactive facilities. Due to Westinghouse Hanford Company (WHC) Fire Protection concerns of the baseline system`s fire/explosion proof characteristics, a study was undertaken to compare the baseline system`s design to commercially available puncturing devices. While the study found no areas which might indicate a riskmore » of fire or explosion, WHC Fire Protection determined that the puncturing system must have a demonstrated record of safe operation. This could be obtained either by testing the baseline design by an independent laboratory, or by substituting a commercially available device. As a result of these efforts, the commercially available Aerosolv can puncturing device was chosen to replace the baseline design. Two concerns were raised with the system. Premature blinding of the coalescing/carbon filter, due to its proximity to the puncture and draining operation; and overpressurization of the collection bottle due to its small volume and by blinding of the filter assembly. As a result of these concerns, testing was deemed necessary. The objective of this report is to outline test procedures for the Aerosolv.« less

Metal-insulator-semiconductor heterostructures for plasmonic hot-carrier optoelectronics.

PubMed

García de Arquer, F Pelayo; Konstantatos, Gerasimos

2015-06-01

Plasmonic hot-electron devices are attractive candidates for light-energy harvesting and photodetection applications. For solid state devices, the most compact and straightforward architecture is the metal-semiconductor Schottky junction. However convenient, this structure introduces limitations such as the elevated dark current associated to thermionic emission, or constraints for device design due to the finite choice of materials. In this work we theoretically consider the metal-insulator-semiconductor heterojunction as a candidate for plasmonic hot-carrier photodetection and solar cells. The presence of the insulating layer can significantly reduce the dark current, resulting in increased device performance with predicted solar power conversion efficiencies up to 9%. For photodetection, the sensitivity can be extended well into the infrared by a judicious choice of the insulating layer, with up to 300-fold expected enhancement in detectivity.

A new method for overhead drilling.

PubMed

Rempel, David; Star, Demetra; Barr, Alan; Gibbons, Billy; Janowitz, Ira

2009-12-01

In the construction sector, overhead drilling into concrete or metal ceilings is a strenuous task associated with shoulder, neck and back musculoskeletal disorders due to the large applied forces and awkward arm postures. Two intervention devices, an inverted drill press and a foot lever design, were developed then compared to the usual method by construction workers performing their normal overhead drilling activities (n = 14). While the intervention devices were rated as less fatiguing than the usual method, their ratings on usability measures were worse than the usual method. The study demonstrates that the intervention devices can reduce fatigue; however, additional modifications are necessary in order to improve usability and productivity. Devices designed to improve workplace safety may need to undergo several rounds of field testing and modification prior to implementation.

Effects of ultrathin oxides in conducting MIS structures on GaAs

NASA Technical Reports Server (NTRS)

Childs, R. B.; Ruths, J. M.; Sullivan, T. E.; Fonash, S. J.

1978-01-01

Schottky barrier-type GaAs baseline devices (semiconductor surface etched and then immediately metalized) and GaAs conducting metal oxide-semiconductor devices are fabricated and characterized. The baseline surfaces (no purposeful oxide) are prepared by a basic or an acidic etch, while the surface for the MIS devices are prepared by oxidizing after the etch step. The metallizations used are thin-film Au, Ag, Pd, and Al. It is shown that the introduction of purposeful oxide into these Schottky barrier-type structures examined on n-type GaAs modifies the barrier formation, and that thin interfacial layers can modify barrier formation through trapping and perhaps chemical reactions. For Au- and Pd-devices, enhanced photovoltaic performance of the MIS configuration is due to increased barrier height.

Bluetooth Communication for Battery Powered Medical Devices

NASA Astrophysics Data System (ADS)

Babušiak, Branko; Borik, Štefan

2016-01-01

wireless communication eliminates obtrusive cables associated with wearable sensors and considerably increases patient comfort during measurement and collection of medical data. Wireless communication is very popular in recent years and plays a significant role in telemedicine and homecare applications. Bluetooth technology is one of the most commonly used wireless communication types in medicine. This paper describes the design of a universal wireless communication device with excellent price/performance ratio. The said device is based on the low-cost RN4020 Bluetooth module with Microchip Low-energy Data Profile (MLDP) and due to low-power consumption is especially suitable for the transmission of biological signals (ECG, EMG, PPG, etc.) from wearable medical/personal health devices. A unique USB dongle adaptor was developed for wireless communication via UART interface and power consumption was evaluated under various conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Hyekyoung; Kim, Sungwoo; Luther, Joseph M.

Silver dimetal chalcogenide (Ag-V-VI 2) ternary quantum dots (QDs) are emerging lead-free materials for optoelectronic devices due to their NIR band gaps, large absorption coefficients, and superior electronic properties. However, thin film-based devices of the ternary QDs still lag behind due to the lack of understanding of the surface chemistry, compared to that of lead chalcogenide QDs even with the same crystal structure. Here in this paper, the surface ligand interactions of AgSbS 2 QDs, synthesized with 1-dodecanethiol used as a stabilizer, are studied. For nonpolar (1 0 0) surfaces, it is suggested that the thiolate ligands are associated withmore » the crystal lattices, thus preventing surface oxidation by protecting sulfur after air-exposure, as confirmed through optical and surface chemical analysis. Otherwise, silver rich (1 1 1) surfaces are passivated by thiolate ligands, allowing ligand exchange processes for the conductive films. This in-depth investigation of the surface chemistry of ternary QDs will prompt the performance enhancement of their optoelectronic devices.« less

Bio-sorbable, liquid electrolyte gated thin-film transistor based on a solution-processed zinc oxide layer.

PubMed

Singh, Mandeep; Palazzo, Gerardo; Romanazzi, Giuseppe; Suranna, Gian Paolo; Ditaranto, Nicoletta; Di Franco, Cinzia; Santacroce, Maria Vittoria; Mulla, Mohammad Yusuf; Magliulo, Maria; Manoli, Kyriaki; Torsi, Luisa

2014-01-01

Among the metal oxide semiconductors, ZnO has been widely investigated as a channel material in thin-film transistors (TFTs) due to its excellent electrical properties, optical transparency and simple fabrication via solution-processed techniques. Herein, we report a solution-processable ZnO-based thin-film transistor gated through a liquid electrolyte with an ionic strength comparable to that of a physiological fluid. The surface morphology and chemical composition of the ZnO films upon exposure to water and phosphate-buffered saline (PBS) are discussed in terms of the operation stability and electrical performance of the ZnO TFT devices. The improved device characteristics upon exposure to PBS are associated with the enhancement of the oxygen vacancies in the ZnO lattice due to Na(+) doping. Moreover, the dissolution kinetics of the ZnO thin film in a liquid electrolyte opens the possible applicability of these devices as an active element in "transient" implantable systems.

Optimal micro-mirror tilt angle and sync mark design for digital micro-mirror device based collinear holographic data storage system.

PubMed

Liu, Jinpeng; Horimai, Hideyoshi; Lin, Xiao; Liu, Jinyan; Huang, Yong; Tan, Xiaodi

2017-06-01

The collinear holographic data storage system (CHDSS) is a very promising storage system due to its large storage capacities and high transfer rates in the era of big data. The digital micro-mirror device (DMD) as a spatial light modulator is the key device of the CHDSS due to its high speed, high precision, and broadband working range. To improve the system stability and performance, an optimal micro-mirror tilt angle was theoretically calculated and experimentally confirmed by analyzing the relationship between the tilt angle of the micro-mirror on the DMD and the power profiles of diffraction patterns of the DMD at the Fourier plane. In addition, we proposed a novel chess board sync mark design in the data page to reduce the system bit error rate in circumstances of reduced aperture required to decrease noise and median exposure amount. It will provide practical guidance for future DMD based CHDSS development.

3D direct writing fabrication of electrodes for electrochemical storage devices

NASA Astrophysics Data System (ADS)

Wei, Min; Zhang, Feng; Wang, Wei; Alexandridis, Paschalis; Zhou, Chi; Wu, Gang

2017-06-01

Among different printing techniques, direct ink writing is commonly used to fabricate 3D battery and supercapacitor electrodes. The major advantages of using the direct ink writing include effectively building 3D structure for energy storage devices and providing higher power density and higher energy density than traditional techniques due to the increased surface area of electrode. Nevertheless, direct ink writing has high standards for the printing inks, which requires high viscosity, high yield stress under shear and compression, and well-controlled viscoelasticity. Recently, a number of 3D-printed energy storage devices have been reported, and it is very important to understand the printing process and the ink preparation process for further material design and technology development. We discussed current progress of direct ink writing technologies by using various electrode materials including carbon nanotube-based material, graphene-based material, LTO (Li4Ti5O12), LFP (LiFePO4), LiMn1-xFexPO4, and Zn-based metallic oxide. Based on achieve electrochemical performance, these 3D-printed devices deliver performance comparable to the energy storage device fabricated using traditional methods still leaving large room for further improvement. Finally, perspectives are provided on the potential future direction of 3D printing for all solid-state electrochemical energy storage devices.

Si-Doping Effects in Cu(In,Ga)Se2 Thin Films and Applications for Simplified Structure High-Efficiency Solar Cells.

PubMed

Ishizuka, Shogo; Koida, Takashi; Taguchi, Noboru; Tanaka, Shingo; Fons, Paul; Shibata, Hajime

2017-09-13

We found that elemental Si-doped Cu(In,Ga)Se 2 (CIGS) polycrystalline thin films exhibit a distinctive morphology due to the formation of grain boundary layers several tens of nanometers thick. The use of Si-doped CIGS films as the photoabsorber layer in simplified structure buffer-free solar cell devices is found to be effective in enhancing energy conversion efficiency. The grain boundary layers formed in Si-doped CIGS films are expected to play an important role in passivating CIGS grain interfaces and improving carrier transport. The simplified structure solar cells, which nominally consist of only a CIGS photoabsorber layer and a front transparent and a back metal electrode layer, demonstrate practical application level solar cell efficiencies exceeding 15%. To date, the cell efficiencies demonstrated from this type of device have remained relatively low, with values of about 10%. Also, Si-doped CIGS solar cell devices exhibit similar properties to those of CIGS devices fabricated with post deposition alkali halide treatments such as KF or RbF, techniques known to boost CIGS device performance. The results obtained offer a new approach based on a new concept to control grain boundaries in polycrystalline CIGS and other polycrystalline chalcogenide materials for better device performance.

Developing improved silica materials and devices for integrated optics applications

NASA Astrophysics Data System (ADS)

Maker, Ashley Julia

Due to their favorable optical and material properties, silica-based materials and devices have found many important applications throughout science and engineering, especially in sensing, communications, lasers, and integrated optics. Often, silica's properties ultimately limit the performance of these applications. To address this limitation, this thesis investigates the development of improved silica materials and optical devices, including silica films, coatings, waveguides, resonators, lasers, and sensors. Using sol-gel chemistry and microfabrication procedures, custom silica materials and devices are developed to benefit many applications. In this thesis, it is first demonstrated how the low optical loss of silica enables fabrication of low loss integrated waveguides and toroidal resonators with ultra-high quality factors. Then, by adding various rare earth and metal dopants to sol-gel silica, hybrid silica materials and devices are made with custom properties such as high refractive index and lasing capabilities. Finally, several applications are demonstrated, including the use of high refractive index coatings to control the behavior of light, development of Raman and ultra-low threshold rare earth microlasers, and a heterodyned microlaser sensor with significantly improved sensing performance. Future applications and directions of this research are also discussed.

Development of Magnetorheological Resistive Exercise Device for Rowing Machine

PubMed Central

Žiliukas, Pranas

2016-01-01

Training equipment used by professional sportsmen has a great impact on their sport performance. Most universal exercisers may help only to improve the general physical condition due to the specific kinematics and peculiar resistance generated by their loading units. Training of effective techniques and learning of psychomotor skills are possible only when exercisers conform to the movements and resistance typical for particular sports kinematically and dynamically. Methodology of developing a magnetorheological resistive exercise device for generating the desired law of passive resistance force and its application in a lever-type rowing machine are described in the paper. The structural parameters of a controllable hydraulic cylinder type device were found by means of the computational fluid dynamics simulation performed by ANSYS CFX software. Parameters describing the magnetorheological fluid as non-Newtonian were determined by combining numerical and experimental research of the resistance force generated by the original magnetorheological damper. A structural scheme of the device control system was developed and the variation of the strength of magnetic field that affects the magnetorheological fluid circulating in the device was determined, ensuring a variation of the resistance force on the oar handle adequate for the resistance that occurs during a real boat rowing stroke. PMID:27293479

Development of Magnetorheological Resistive Exercise Device for Rowing Machine.

PubMed

Grigas, Vytautas; Šulginas, Anatolijus; Žiliukas, Pranas

2015-01-01

Training equipment used by professional sportsmen has a great impact on their sport performance. Most universal exercisers may help only to improve the general physical condition due to the specific kinematics and peculiar resistance generated by their loading units. Training of effective techniques and learning of psychomotor skills are possible only when exercisers conform to the movements and resistance typical for particular sports kinematically and dynamically. Methodology of developing a magnetorheological resistive exercise device for generating the desired law of passive resistance force and its application in a lever-type rowing machine are described in the paper. The structural parameters of a controllable hydraulic cylinder type device were found by means of the computational fluid dynamics simulation performed by ANSYS CFX software. Parameters describing the magnetorheological fluid as non-Newtonian were determined by combining numerical and experimental research of the resistance force generated by the original magnetorheological damper. A structural scheme of the device control system was developed and the variation of the strength of magnetic field that affects the magnetorheological fluid circulating in the device was determined, ensuring a variation of the resistance force on the oar handle adequate for the resistance that occurs during a real boat rowing stroke.

Enhancing Thermoelectric Performance Using Nonlinear Transport Effects

NASA Astrophysics Data System (ADS)

Jiang, Jian-Hua; Imry, Yoseph

2017-06-01

We study nonlinear transport effects on the maximum efficiency and power for both inelastic and elastic thermoelectric generators. The former device refers to phonon-assisted hopping in double quantum dots, while the latter device is represented by elastic tunneling through a single quantum dot. We find that nonlinear thermoelectric transport can lead to enhanced efficiency and power for both types of devices. A comprehensive survey of various quantum-dot energy, temperature, and parasitic heat conduction reveals that the nonlinear transport-induced improvements of the maximum efficiency and power are overall much more significant for inelastic devices than for elastic devices, even for temperature biases as small as Th=1.2 Tc (Th and Tc are the temperatures of the hot and cold reservoirs, respectively). The underlying mechanism is revealed as due to the fact that, unlike the Fermi distribution, the Bose distribution is not bounded when the temperature bias increases. A large flux density of absorbed phonons leads to a great enhancement of the electrical current, output power, and energy efficiency, dominating over the concurrent increase of the parasitic heat current. Our study reveals that nonlinear transport effects can be a useful tool for improving thermoelectric performance.

Efficacy of a new device to optimize positive pressure ventilation via face mask in edentulous patients: a randomized trial.

PubMed

Niño, Maria C; Pauwels, Andres; Raffan, Fernando; Arango, Enrique; Romero, David J; Benitez, Daniel

2017-04-01

Mask ventilation is routinely performed during anesthesia. Under some circumstances, it might be difficult to perform, such as in edentulous patients, due to inadequate mask seal. We developed a new device called NIPARA and studied its use For ventilation optimization in edentulous patients. This randomized controlled trial included edentulous adults who had no other predictors of difficult airway, scheduled to undergo general anesthesia. Patients were assigned either to the NIPARA device group or to the control group (oral airway only). The primary outcomes were peak inspiratory pressure and tidal volume values of the first 14 breaths. The secondary outcome was the incidence of complications. Data from 37 patients were collected during a one-year period (twenty in the NIPARA device group and 17 in the control group). The difference in mean PIP was not statistically significant. The tidal volume was 1.5 times greater in the NIPARA group than in the control group. One patient from the intervention group had minimal oral trauma. In the administration of face mask ventilation, NIPARA is an effective device that significantly improves the tidal volume administered in edentulous patients.

Design of Mechanism for Assisting Standing Movement Using Planar Linkage and Gear Train

NASA Astrophysics Data System (ADS)

Nango, Jun; Yoshizawa, Hisato; Liu, Jiajun

The number of people who are in need of nursing care due to difficulties they experience with performing various activities of daily living is increasing. In particular, the action of standing up is performed frequently in daily life, and this action starts to induce pain in joints as people age. In this research, we develop a device whose seat plate follows the movement of the thigh in the action of standing up for the purpose of relieving the burden from the joints and reducing the effort associated with nursing care. The device is designed by using a planar five-link mechanism and a gear train, and only a single input is needed to drive the device. The respective lengths of the links are determined by comparing the movement of the seat plate of the device with the movement of the human thigh in the action of standing up. In addition, this device is expected to be useful for assisting users in standing up in a natural manner, including in the case when the body remains supported by the seat plate, as well as for guiding the individual movements of users in the action of standing up.

Solution processed ZnO hybrid nanocomposite with tailored work function for improved electron transport layer in organic photovoltaic devices.

PubMed

Lee, Yun-Ju; Wang, Jian; Cheng, Samuel R; Hsu, Julia W P

2013-09-25

We demonstrate improved organic photovoltaic device performance using solution processed electron transport layers of ZnO nanoparticle (NP) films containing organic additives, poly(vinylpyrrolidone) (PVP), or diethanolamine (DEA), that do not require post processing after film deposition. Inclusion of PVP or DEA decreased the ZnO work function by 0.4 eV through interfacial dipole formation. While PVP did not change the ZnO NP shape or size, DEA modified the ZnO shape from 5 nm × 15 nm nanorods to 5 nm nanoparticles. At an optimized PVP concentration of 0.7 wt %, ZnO NP:PVP electron transport layers (ETLs) improved the efficiency of inverted P3HT:PCBM devices by 37%, primarily through higher fill factor. ZnO NP:PVP and ZnO NP:DEA ETLs increased the open circuit voltage of inverted P3HT:ICBA devices by 0.07 V due to decreasing ETL work function, leading to enhanced built-in field. The relationship between ZnO nanocomposite ETL work function, donor-acceptor energy offset, and device performance is discussed. The effects of the two additives are compared.

Finite element analysis of a percussion device for pulmonary diagnostics

NASA Astrophysics Data System (ADS)

Dhar, Aneesh

A pneumothorax is a medical condition where one or both lungs are unable to remain expanded due to air in the pleural space. Finite Element Analysis simulations were conducted on a Percussion Device, which is able to diagnose a pneumothorax using an automated percussion technique. The simulations helped determine the natural modes of vibration of the Percussion Device. These modes were then compared to the motion experimentally measured by an accelerometer on the Percussion Device. It was observed that the modes of the percussion head occurred in the range of 0 to 100 Hz, while the sensor membrane modes occurred in the range of 600 to 900 Hz. Most of these modes were found to match with peaks in the experimental spectra. The simulations performed are reliable and provide an understanding of the contribution of the normal modes to the complex signals measured using the Percussion Device.

Thin and small form factor cells : simulated behavior.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clews, Peggy Jane; Pluym, Tammy; Grubbs, Robert K.

Thin and small form factor cells have been researched lately by several research groups around the world due to possible lower assembly costs and reduced material consumption with higher efficiencies. Given the popularity of these devices, it is important to have detailed information about the behavior of these devices. Simulation of fabrication processes and device performance reveals some of the advantages and behavior of solar cells that are thin and small. Three main effects were studied: the effect of surface recombination on the optimum thickness, efficiency, and current density, the effect of contact distance on the efficiency for thin cells,more » and lastly the effect of surface recombination on the grams per Watt-peak. Results show that high efficiency can be obtained in thin devices if they are well-passivated and the distance between contacts is short. Furthermore, the ratio of grams per Watt-peak is greatly reduced as the device is thinned.« less

Kesterite Cu2ZnSn(S,Se)4 Solar Cells with beyond 8% Efficiency by a Sol-Gel and Selenization Process.

PubMed

Liu, Fangyang; Zeng, Fangqin; Song, Ning; Jiang, Liangxing; Han, Zili; Su, Zhenghua; Yan, Chang; Wen, Xiaoming; Hao, Xiaojing; Liu, Yexiang

2015-07-08

A facile sol-gel and selenization process has been demonstrated to fabricate high-quality single-phase earth abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic absorbers. The structure and band gap of the fabricated CZTSSe can be readily tuned by varying the [S]/([S] + [Se]) ratios via selenization condition control. The effects of [S]/([S] + [Se]) ratio on device performance have been presented. The best device shows 8.25% total area efficiency without antireflection coating. Low fill factor is the main limitation for the current device efficiency compared to record efficiency device due to high series resistance and interface recombination. By improving film uniformity, eliminating voids, and reducing the Mo(S,Se)2 interfacial layer, a further boost of the device efficiency is expected, enabling the proposed process for fabricating one of the most promising candidates for kesterite solar cells.

The plasmatron: Advanced mode thermionic energy conversion

NASA Technical Reports Server (NTRS)

Hansen, L. K.; Hatch, G. L.; Rasor, N. S.

1976-01-01

A theory of the plasmatron was developed. Also, a wide range of measurements were obtained with two versatile, research devices. To gain insight into plasmatron performance, the experimental results are compared with calculations based on the theoretical model of plasmatron operation. Results are presented which show that the plasma arc drop of the conventional arc (ignited) mode converter can be suppressed by use of an auxiliary ion source. The improved performance, however, is presently limited to low current densities because of voltage losses due to plasma resistance. This resistance loss could be suppressed by an increase in the plasma electron temperature or a decrease in spacing. Plasmatron performance characteristics for both argon and cesium are reported. The argon plasmatron has superior performance. Results are also presented for magnetic cutoff effects and for current distributing effects. These are shown to be important factors for the design of practical devices.

Low power, compact charge coupled device signal processing system

NASA Technical Reports Server (NTRS)

Bosshart, P. W.; Buss, D. D.; Eversole, W. L.; Hewes, C. R.; Mayer, D. J.

1980-01-01

A variety of charged coupled devices (CCDs) for performing programmable correlation for preprocessing environmental sensor data preparatory to its transmission to the ground were developed. A total of two separate ICs were developed and a third was evaluated. The first IC was a CCD chirp z transform IC capable of performing a 32 point DFT at frequencies to 1 MHz. All on chip circuitry operated as designed with the exception of the limited dynamic range caused by a fixed pattern noise due to interactions between the digital and analog circuits. The second IC developed was a 64 stage CCD analog/analog correlator for performing time domain correlation. Multiplier errors were found to be less than 1 percent at designed signal levels and less than 0.3 percent at the measured smaller levels. A prototype IC for performing time domain correlation was also evaluated.

Numerical simulation and characterization of trapping noise in InGaP-GaAs heterojunctions devices at high injection

NASA Astrophysics Data System (ADS)

Nallatamby, Jean-Christophe; Abdelhadi, Khaled; Jacquet, Jean-Claude; Prigent, Michel; Floriot, Didier; Delage, Sylvain; Obregon, Juan

2013-03-01

Commercially available simulators present considerable advantages in performing accurate DC, AC and transient simulations of semiconductor devices, including many fundamental and parasitic effects which are not generally taken into account in house-made simulators. Nevertheless, while the TCAD simulators of the public domain we have tested give accurate results for the simulation of diffusion noise, none of the tested simulators perform trap-assisted GR noise accurately. In order to overcome the aforementioned problem we propose a robust solution to accurately simulate GR noise due to traps. It is based on numerical processing of the output data of one of the simulators available in the public-domain, namely SENTAURUS (from Synopsys). We have linked together, through a dedicated Data Access Component (DAC), the deterministic output data available from SENTAURUS and a powerful, customizable post-processing tool developed on the mathematical SCILAB software package. Thus, robust simulations of GR noise in semiconductor devices can be performed by using GR Langevin sources associated to the scalar Green functions responses of the device. Our method takes advantage of the accuracy of the deterministic simulations of electronic devices obtained with SENTAURUS. A Comparison between 2-D simulations and measurements of low frequency noise on InGaP-GaAs heterojunctions, at low as well as high injection levels, demonstrates the validity of the proposed simulation tool.

Efficient double-emitting layer inverted organic light-emitting devices with different spacer layers

NASA Astrophysics Data System (ADS)

Nie, Qu-yang; Zhang, Fang-hui

2017-09-01

Double-emitting layer inverted organic light-emitting devices (IOLEDs) with different spacer layers were investigated, where 2,20,7,70-tetrakis(carbazol-9-yl)-9,9-spirobifluorene (CBP), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 4,40,400-tris(N-carbazolyl)-triphenylamine (TCTA) were used as spacer layers, respectively, and GIr1 and R-4b were used as green and red guest phosphorescent materials, respectively. The results show that the device with BCP spacer layer has the best performance. The maximum current efficiency of the BCP spacer layer device reaches up to 24.15 cd·A-1 when the current density is 3.99 mA·cm-2, which is 1.23 times bigger than that of the CBP spacer layer device. The performance is better than that of corresponding conventional device observably. The color coordinate of the device with BCP spacer layer only changes from (0.625 1, 0.368 0) to (0.599 5, 0.392 8) when the driving voltage increases from 6 V to 10 V, so it shows good stability in color coordinate, which is due to the adoption of the co-doping evaporation method for cladding luminous layer and the effective restriction of spacer layer to carriers in emitting layer.

Image quality degradation by light-scattering processes in high-performance display devices for medical imaging

NASA Astrophysics Data System (ADS)

Badano, Aldo

1999-11-01

This thesis addresses the characterization of light scattering processes that degrade image quality in high performance electronic display devices for digital radiography. Using novel experimental and computational tools, we study the lateral diffusion of light in emissive display devices that causes extensive veiling glare and significant reduction of the physical contrast. In addition, we examine the deleterious effects of ambient light reflections that affect the contrast of low luminance regions, and superimpose unwanted structured signal. The analysis begins by introducing the performance limitations of the human visual system to define high fidelity requirements. It is noted that current devices severely suffer from image quality degradation due to optical transport processes. To model the veiling glare and reflectance characteristics of display devices, we introduce a Monte Carlo light transport simulation code, DETECT-II, that tracks individual photons through multiple scattering events. The simulation accounts for the photon polarization state at each scattering event, and provides descriptions for rough surfaces and thin film coatings. A new experimental method to measure veiling glare is described next, based on a conic collimated probe that minimizes contamination from bright areas. The measured veiling glare ratio is taken to be the luminance in the surrounding bright field divided by the luminance in the dark circle. We show that veiling glare ratios in the order of a few hundreds can be measured with an uncertainty of a few percent. The veiling glare response function is obtained by measuring the small spot contrast ratio of test patterns having varying dark spot radius. Using DETECT-II, we then estimate the ring response functions for a high performance medical imaging monitor of current design, and compare the predictions of the model with the experimentally measured response function. The data presented in this thesis demonstrate that although absorption in the faceplate of high performance monochrome cathode-ray tube monitors have reduced glare, a black matrix design is needed for high fidelity applications. For a high performance medical imaging monitor with anti-reflective coating, the glare ratio for a 1 cm diameter dark spot was measured to be 240. Finally, we introduce experimental techniques for measurements of specular and diffuse display reflectance, and we compare measured reflection coefficients with Monte Carlo estimates. A specular reflection coefficient of 0.0012, and a diffuse coefficient of 0.005 nits/lux are required to minimize degradation from ambient light in rooms with 100 lux illumination. In spite of having comparable reflection coefficients, the low maximum luminance of current devices worsens the effect of ambient light reflections when compared to radiographic film. Flat panel technologies with optimized designs can perform even better than film due to a thin faceplate, increased light absorption, and high brightness.

Comparisons of Auditory Performance and Speech Intelligibility after Cochlear Implant Reimplantation in Mandarin-Speaking Users

PubMed Central

Hwang, Chung-Feng; Ko, Hui-Chen; Tsou, Yung-Ting; Chan, Kai-Chieh; Fang, Hsuan-Yeh; Wu, Che-Ming

2016-01-01

Objectives. We evaluated the causes, hearing, and speech performance before and after cochlear implant reimplantation in Mandarin-speaking users. Methods. In total, 589 patients who underwent cochlear implantation in our medical center between 1999 and 2014 were reviewed retrospectively. Data related to demographics, etiologies, implant-related information, complications, and hearing and speech performance were collected. Results. In total, 22 (3.74%) cases were found to have major complications. Infection (n = 12) and hard failure of the device (n = 8) were the most common major complications. Among them, 13 were reimplanted in our hospital. The mean scores of the Categorical Auditory Performance (CAP) and the Speech Intelligibility Rating (SIR) obtained before and after reimplantation were 5.5 versus 5.8 and 3.7 versus 4.3, respectively. The SIR score after reimplantation was significantly better than preoperation. Conclusions. Cochlear implantation is a safe procedure with low rates of postsurgical revisions and device failures. The Mandarin-speaking patients in this study who received reimplantation had restored auditory performance and speech intelligibility after surgery. Device soft failure was rare in our series, calling attention to Mandarin-speaking CI users requiring revision of their implants due to undesirable symptoms or decreasing performance of uncertain cause. PMID:27413753

The use of hormonal treatments to improve reproductive performance of anestrous beef cattle in tropical climates.

PubMed

Baruselli, P S; Reis, E L; Marques, M O; Nasser, L F; Bó, G A

2004-07-01

Most of the world's bovine herd is found in tropical regions. Bos indicus predominates, due to their adaptation to the climate and management conditions. Anestrous is the main factor that negatively affects reproductive performance of animals bred in these regions of the globe. Several factors affect postpartum anestrous, including suckling and maternal-offspring bond, and pre- and postpartum nutritional status. The short duration of estrus and the tendency to show estrus during the night, greatly affect the efficiency of artificial insemination (AI) programs in B. indicus cattle managed in tropical areas. Several restricted suckling or weaning procedures (temporary or permanent), and hormonal treatments have been used to induce ovulation and cyclicity in postpartum cows. Most hormonal treatments are based on progesterone/progestogen (P4) releasing devices associated with estradiol benzoate (EB), or a combination of GnRH/PGF(2alpha)/GnRH (Ovsynch). Treatments with GnRH/PGF(2alpha)/GnRH has presented inconsistent results, probably due to the variable number of cows in anestrous. Treatments using P4 devices and EB have resulted in apparently more consistent results than Ovsynch programs in B. indicus cattle; however, pregnancy rates are low in herds presenting high anestrous rates and moderate to low body condition. The addition of an eCG treatment at the time of device removal, which increased plasma progesterone concentrations and pregnancy rates in anestrous postpartum suckled B. indicus cows, may be useful to improve reproductive performance of beef cattle in tropical climates.

Carbon nanotubes and graphene towards soft electronics

NASA Astrophysics Data System (ADS)

Chae, Sang Hoon; Lee, Young Hee

2014-04-01

Although silicon technology has been the main driving force for miniaturizing device dimensions to improve cost and performance, the current application of Si to soft electronics (flexible and stretchable electronics) is limited due to material rigidity. As a result, various prospective materials have been proposed to overcome the rigidity of conventional Si technology. In particular, nano-carbon materials such as carbon nanotubes (CNTs) and graphene are promising due to outstanding elastic properties as well as an excellent combination of electronic, optoelectronic, and thermal properties compared to conventional rigid silicon. The uniqueness of these nano-carbon materials has opened new possibilities for soft electronics, which is another technological trend in the market. This review covers the recent progress of soft electronics research based on CNTs and graphene. We discuss the strategies for soft electronics with nano-carbon materials and their preparation methods (growth and transfer techniques) to devices as well as the electrical characteristics of transparent conducting films (transparency and sheet resistance) and device performances in field effect transistor (FET) (structure, carrier type, on/off ratio, and mobility). In addition to discussing state of the art performance metrics, we also attempt to clarify trade-off issues and methods to control the trade-off on/off versus mobility). We further demonstrate accomplishments of the CNT network in flexible integrated circuits on plastic substrates that have attractive characteristics. A future research direction is also proposed to overcome current technological obstacles necessary to realize commercially feasible soft electronics.

Carbon nanotubes and graphene towards soft electronics.

PubMed

Chae, Sang Hoon; Lee, Young Hee

2014-01-01

Although silicon technology has been the main driving force for miniaturizing device dimensions to improve cost and performance, the current application of Si to soft electronics (flexible and stretchable electronics) is limited due to material rigidity. As a result, various prospective materials have been proposed to overcome the rigidity of conventional Si technology. In particular, nano-carbon materials such as carbon nanotubes (CNTs) and graphene are promising due to outstanding elastic properties as well as an excellent combination of electronic, optoelectronic, and thermal properties compared to conventional rigid silicon. The uniqueness of these nano-carbon materials has opened new possibilities for soft electronics, which is another technological trend in the market. This review covers the recent progress of soft electronics research based on CNTs and graphene. We discuss the strategies for soft electronics with nano-carbon materials and their preparation methods (growth and transfer techniques) to devices as well as the electrical characteristics of transparent conducting films (transparency and sheet resistance) and device performances in field effect transistor (FET) (structure, carrier type, on/off ratio, and mobility). In addition to discussing state of the art performance metrics, we also attempt to clarify trade-off issues and methods to control the trade-off on/off versus mobility). We further demonstrate accomplishments of the CNT network in flexible integrated circuits on plastic substrates that have attractive characteristics. A future research direction is also proposed to overcome current technological obstacles necessary to realize commercially feasible soft electronics.

Computational fluid dynamics (CFD) simulations of molten steel flow patterns and particle-wall adhesion in continuous casting of steels

NASA Astrophysics Data System (ADS)

Mohammadi-Ghaleni, Mahdi

The Sun has long been the most important energy source for planet Earth. Sunlight offers the potential to function as a source of clean, renewable energy; photovoltaic (PV) cells have been designed to tap into this abundant solar energy to generate electricity. Organic photovoltaic (OPV) devices show promise as technologies capable of lightweight, low cost and flexible alternatives to traditional silicon PV but the nature of conjugated organic and polymeric semiconductors have limited performance and, therefore, application. However, recent advances have shown that the addition of pristine graphene (PG) to the active layer of OPV devices can yield three-fold performance improvements in blends of P3HT (poly(3-hexylthiophene-2,5-diyl) & PCBM (phenyl C 61 butyric acid methyl ester) and, later, in all-polymer blends of P3HT & F8BT (poly(9,9-dioctylfluorene-alt-benzothiadiazole). In both OPV systems, increased performance is believed to be due to high charge carrier mobility imparted by the PG additive to the composite active layer blend. In this work, the effect of addition of PG to the active layer blend of P3HT & PCPDTBT (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) systems was investigated. PV devices were designed, fabricated and tested using standard processing methods and testing procedures. Although PG increased OPV device performance relative to samples without PG, power conversion efficiency (eta) on an absolute scale was lower than expected despite the otherwise complementary properties of these materials. Based on the literature, the low performance of these devices was hypothesized to result from non-ideal active layer morphology, lacking charge carried percolation pathways to the electrodes. Small angle neutron scattering (SANS) was employed to probe the active layer morphology in polymer blend films similar to the active layers of the cells. Deuterated P3HT (d-P3HT) was used to exploit the large scattering length density (SLD) contrast between hydrogen and deuterium. Rigorous analysis of the SANS data allowed the nanostructure to be determined and a model of disk-like d-P3HT crystallites dispersed in a matrix of the amorphous polymers was constructed. This structure shows limited interfacial area for exciton dissociation and exhibits a lack of charge percolation pathways to the electrodes. Morphological insight offered by SANS analysis along with literature review allowed higher performance all-polymer photovoltaic cells to be designed and tested using the same semiconducting polymers. By introducing a co-solvent and modifying the thermal annealing procedure, significant performance gains were realized for subsequent devices. The increased performance observed following the change in procedure is believed to be due to enhanced active layer morphology and formation of a bulk heterojunction (BHJ) structure, to be studied in future work. Although there is room for further performance gains in P3HT-PCPDTBT devices as well as application to other OPV systems in future work, the methods, results and discussion presented here highlight the importance of structure-property relationships in all-polymer photovoltaic cells.

SnO2-based memristors and the potential synergies of integrating memristors with MEMS

NASA Astrophysics Data System (ADS)

Zubia, David; Almeida, Sergio; Talukdar, Arka; Mireles, Jose; MacDonald, Eric

2012-06-01

Memristors, usually in the form metal/metal-oxide/metal, have attracted much attention due to their potential application for non-volatile memory. Their simple structure and ease of fabrication make them good candidates for dense memory with projections of 22 terabytes per wafer. Excellent switching times of ~10 ns, memory endurance of >109 cycles, and extrapolated retention times of >10 yrs have been reported. Interestingly, memristors use the migration of ions to change their resistance in response to charge flow, and can therefore measure and remember the amount of current that has flowed. This is similar to many MEMS devices in which the motion of mass is an operating principle of the device. Memristors are also similar to MEMS in the sense that they can both be resistant to radiation effects. Memristors are radiation tolerant since information is stored as a structural change and not as electronic charge. Functionally, a MEMS device's sensitivity to radiation is concomitant to the role that the dielectric layers play in the function of the device. This is due to radiation-induced trapped charge in the dielectrics which can alter device performance and in extreme cases cause failure. Although different material systems have been investigated for memristors, SnO2 has received little attention even though it demonstrates excellent electronic properties and a high resistance to displacement damage from radiation due to a large Frenkel defect energy (7 eV) compared its bandgap (3.6 eV). This talk discusses recent research on SnO2-based memristors and the potential synergies of integrating memristors with MEMS.

Resistive switching in ZnO/ZnO:In nanocomposite

NASA Astrophysics Data System (ADS)

Khakhulin, D. A.; Vakulov, Z. E.; Smirnov, V. A.; Tominov, R. V.; Yoon, Jong-Gul; Ageev, O. A.

2017-11-01

A lot of effort nowadays is put into development of new approaches to processing and storage of information in integrated circuits due to limitations in miniaturisation. Our research is dedicated to one of actively developed concepts - oxide based resistive memory devices. A material that draws interest due to its promising technological properties is ZnO but pure ZnO lacks in performance in comparison with some other transition metal oxides. Thus our work is focused on improvement of resistive switching parameters in ZnO films by creation of complex nanocomposites. In this work we report characterisation of a nanocomposite based on PLD grown ZnO films with inclusions of In. Such solution allows us to achieve improvements of main parameters that are critical for ReRAM device: RHRS/RLRS ratio, endurance and retention.

Physical interface dynamics alter how robotic exosuits augment human movement: implications for optimizing wearable assistive devices.

PubMed

Yandell, Matthew B; Quinlivan, Brendan T; Popov, Dmitry; Walsh, Conor; Zelik, Karl E

2017-05-18

Wearable assistive devices have demonstrated the potential to improve mobility outcomes for individuals with disabilities, and to augment healthy human performance; however, these benefits depend on how effectively power is transmitted from the device to the human user. Quantifying and understanding this power transmission is challenging due to complex human-device interface dynamics that occur as biological tissues and physical interface materials deform and displace under load, absorbing and returning power. Here we introduce a new methodology for quickly estimating interface power dynamics during movement tasks using common motion capture and force measurements, and then apply this method to quantify how a soft robotic ankle exosuit interacts with and transfers power to the human body during walking. We partition exosuit end-effector power (i.e., power output from the device) into power that augments ankle plantarflexion (termed augmentation power) vs. power that goes into deformation and motion of interface materials and underlying soft tissues (termed interface power). We provide empirical evidence of how human-exosuit interfaces absorb and return energy, reshaping exosuit-to-human power flow and resulting in three key consequences: (i) During exosuit loading (as applied forces increased), about 55% of exosuit end-effector power was absorbed into the interfaces. (ii) However, during subsequent exosuit unloading (as applied forces decreased) most of the absorbed interface power was returned viscoelastically. Consequently, the majority (about 75%) of exosuit end-effector work over each stride contributed to augmenting ankle plantarflexion. (iii) Ankle augmentation power (and work) was delayed relative to exosuit end-effector power, due to these interface energy absorption and return dynamics. Our findings elucidate the complexities of human-exosuit interface dynamics during transmission of power from assistive devices to the human body, and provide insight into improving the design and control of wearable robots. We conclude that in order to optimize the performance of wearable assistive devices it is important, throughout design and evaluation phases, to account for human-device interface dynamics that affect power transmission and thus human augmentation benefits.

Microengineering of magnetic bearings and actuators

NASA Astrophysics Data System (ADS)

Ghantasala, Muralihar K.; Qin, LiJiang; Sood, Dinesh K.; Zmood, Ronald B.

2000-06-01

Microengineering has evolved in the last decade as a subject of its own with the current research encompassing every possible area of devices from electromagnetic to optical and bio-micro electromechanical systems (MEMS). The primary advantage of the micro system technology is its small size, potential to produce high volume and low cost devices. However, the major impediments in the successful realization of many micro devices in practice are the reliability, packaging and integration with the existing microelectronics technology. Microengineering of actuators has recently grown tremendously due to its possible applicability to a wide range of devices of practical importance and the availability of a choice of materials. Selection of materials has been one of the important aspects of the design and fabrication of many micro system and actuators. This paper discusses the issues related to the selection of materials and subsequently their effect on the performance of the actuator. These will be discussed taking micro magnetic actuators and bearings, in particular, as examples. Fabrication and processing strategies and performance evaluation methods adopted will be described. Current status of the technology and projected futuristic applications in this area will be reviewed.

Printable Fabrication of Nanocoral-Structured Electrodes for High-Performance Flexible and Planar Supercapacitor with Artistic Design.

PubMed

Lin, Yuanjing; Gao, Yuan; Fan, Zhiyong

2017-11-01

Planar supercapacitors with high flexibility, desirable operation safety, and high performance are considered as attractive candidates to serve as energy-storage devices for portable and wearable electronics. Here, a scalable and printable technique is adopted to construct novel and unique hierarchical nanocoral structures as the interdigitated electrodes on flexible substrates. The as-fabricated flexible all-solid-state planar supercapacitors with nanocoral structures achieve areal capacitance up to 52.9 mF cm -2 , which is 2.5 times that of devices without nanocoral structures, and this figure-of-merit is among the highest in the literature for the same category of devices. More interestingly, due to utilization of the inkjet-printing technique, excellent versatility on electrode-pattern artistic design is achieved. Particularly, working supercapacitors with artistically designed patterns are demonstrated. Meanwhile, the high scalability of such a printable method is also demonstrated by fabrication of large-sized artistic supercapacitors serving as energy-storage devices in a wearable self-powered system as a proof of concept. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Defect-induced instability mechanisms of sputtered amorphous indium tin zinc oxide thin-film transistors

NASA Astrophysics Data System (ADS)

Park, Jinhee; Rim, You Seung; Li, Chao; Wu, Jiechen; Goorsky, Mark; Streit, Dwight

2018-04-01

We report the device performance and stability of sputtered amorphous indium-tin-zinc-oxide (ITZO) thin-film transistors as a function of oxygen ratio [O2/(Ar + O2)] during growth. Increasing the oxygen ratio enhanced the incorporation of oxygen during ITZO film growth and reduced the concentration of deep-level defects associated with oxygen vacancies. Under illumination with no bias stress, device stability and persistent photocurrent were improved with increased oxygen ratio. Bias stress tests of the devices were also performed with and without illumination. While high oxygen ratio growth conditions resulted in decreased deep-level oxygen vacancies in the ITZO material, the same conditions resulted in degradation of the interfacial layer between the ITZO channel and dielectric due to the migration of energetic oxygen ions to the interface. Therefore, when bias stress was applied, increased carrier trap density at the interface led to a decrease in device stability that offsets any improvement in the material itself. In order to take advantage of the improved ITZO material growth at a high oxygen ratio, the interface-related problems must be solved.

High power, gel polymer lithium-ion cells with improved low temperature performance for NASA and DoD applications

NASA Technical Reports Server (NTRS)

Smart, M. C.; Ratnakumar, B. V.; Whitcanack, L. D.; Chin, K. B.; Surampudi, S.; Narayanan, S. R.; Alamgir, Mohamed; Yu, Ji-Sang; Plichta, Edward P.

2004-01-01

Both NASA and the U.S. Army have interest in developing secondary energy storage devices that are capable of meeting the demanding performance requirements of aerospace and man-portable applications. In order to meet these demanding requirements, gel-polymer electrolyte-based lithium-ion cells are being actively considered, due to their promise of providing high specific energy and enhanced safety aspects.

An electron transporting unit linked multifunctional Ir(III) complex: a promising strategy to improve the performance of solution-processed phosphorescent organic light-emitting diodes.

PubMed

Giridhar, Thota; Saravanan, Chinnusamy; Cho, Woosum; Park, Young Geun; Lee, Jin Yong; Jin, Sung-Ho

2014-04-18

An oxadiazole based electron transporting (ET) unit was glued to the heteroleptic Ir(III) complex (TPQIr-ET) and used as a dopant for phosphorescent organic light-emitting diodes (PhOLEDs). It shows superior device performance than the dopant without the ET unit (TPQIr) due to the balanced charge carrier injection by the ET unit.

Development of Micro-Scale Assays of Mammary Stem and Progenitor Cells

DTIC Science & Technology

2008-07-01

visualization via phase contrast along the length of the channel. Additionally, most devices can be placed on any substrate, allowing glass to be...microenvironment composition due to increases in surface area to volume ratios as the scale of the culture is reduced. Purcell provided a very useful account...cultures are performed in polysytrene (or glass bottomed) tissue culture flasks, dishes and plates. While many microfluidic cultures are performed

High thermoelectricpower factor in graphene/hBN devices

PubMed Central

Duan, Junxi; Wang, Xiaoming; Lai, Xinyuan; Li, Guohong; Taniguchi, Takashi; Zebarjadi, Mona; Andrei, Eva Y.

2016-01-01

Fast and controllable cooling at nanoscales requires a combination of highly efficient passive cooling and active cooling. Although passive cooling in graphene-based devices is quite effective due to graphene’s extraordinary heat conduction, active cooling has not been considered feasible due to graphene’s low thermoelectric power factor. Here, we show that the thermoelectric performance of graphene can be significantly improved by using hexagonal boron nitride (hBN) substrates instead of SiO2. We find the room temperature efficiency of active cooling in the device, as gauged by the power factor times temperature, reaches values as high as 10.35 W⋅m−1⋅K−1, corresponding to more than doubling the highest reported room temperature bulk power factors, 5 W⋅m−1⋅K−1, in YbAl3, and quadrupling the best 2D power factor, 2.5 W⋅m−1⋅K−1, in MoS2. We further show that the Seebeck coefficient provides a direct measure of substrate-induced random potential fluctuations and that their significant reduction for hBN substrates enables fast gate-controlled switching of the Seebeck coefficient polarity for applications in integrated active cooling devices. PMID:27911824

High power microwave source with a three dimensional printed metamaterial slow-wave structure.

PubMed

French, David M; Shiffler, Don

2016-05-01

For over the last decade, the concept of metamaterials has led to new approaches for considering the interaction of radiation with complex structures. However, practical manifestations of such a device operating at high power densities have proven difficult to achieve due to the resonant nature of metamaterials and the resultant high electric fields, which place severe constraints on manufacturing the slow wave structures. In this paper, we describe the first experimental manifestation of a high power microwave device utilizing a metallic slow wave structure (metamaterial-like) fabricated using additive manufacturing. The feasibility of utilizing additive manufacturing as a technique for building these relatively complicated structures has thus been demonstrated. The MW class microwave source operates in the C-band and shows frequency tunablility with electron beam voltage. The basic electromagnetic characteristics of this device, the construction using additive manufacturing, and the basic performance as a microwave oscillator are considered. Due to the tunable nature of the device, it shows promise not only as an oscillator but also as a microwave amplifier. Therefore, the dispersive characteristics and a discussion of the anticipated gain is included as it relates to an amplifier configuration.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Riley E.; Mangan, Niall M.; Li, Jian V.

The development of new thin-film photovoltaic (PV) absorbers is often hindered by the search for an optimal heterojunction contact; an unoptimized contact may be mistaken for poor quality of the underlying absorber, making it difficult to assess the reasons for poor performance. Therefore, quantifying the loss in device efficiency and open-circuit voltage (VOC) as a result of the interface is a critical step in evaluating a new material. In the present work, we fabricate thin-film PV devices using cuprous oxide (Cu2O), with several different n-type heterojunction contacts. Their current-voltage characteristics are measured over a range of temperatures and illumination intensitiesmore » (JVTi). We quantify the loss in VOC due to the interface and determine the effective energy gap at the interface. The effective interface gap measured by JVTi matches the gap measured by X-ray photoelectron spectroscopy, albeit with higher energy resolution and an order of magnitude faster. We discuss potential artifacts in JVTi measurements and areas where analytical models are insufficient. Applying JVTi to complete devices, rather than incomplete material stacks, suggests that it can be a quick, accurate method to assess the loss due to unoptimized interface band offsets in thin-film PV devices.« less

Selecting and designing with the right thermoplastic polymer for your microfluidic chip: a close look into cyclo-olefin polymer

NASA Astrophysics Data System (ADS)

Nevitt, Mark

2013-03-01

Engineers who are developing microfluidic devices and bioMEMs for life science applications have many aspects to consider when selecting the proper base materials for constructing a device. While glass and polydimethylsiloxane (PDMS) are the staple materials for proof-of-concept and prototype chip fabrication, they are not a feasible solution for commercial production due to their slow, labor-intensive production rate. Alternatively, a molded or extruded thermoplastic solution can deliver the precision, consistency, and high volume capability required for commercial scale production. Traditional thermoplastics, such as polymethylmethacrylate (PMMA), polycarbonate (PC), and polystyrene (PS), are well known by development engineers in the bioscience community; however, cyclo-olefin polymer (COP), a relative newcomer in the world of plastics, is gaining increasing attention for use in microfluidic devices due to its unique balance of key properties compared to conventional thermoplastics. In this paper, we provide a comprehensive look at the properties which make COP an excellent candidate for providing the flow cell support and reagent storage functions in microfluidic assays. We also explore the processing attributes and capabilities of COP resin and film which are crucial for manufacturing high-performance microfluidic devices.

High power microwave source with a three dimensional printed metamaterial slow-wave structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

French, David M.; Shiffler, Don

2016-05-15

For over the last decade, the concept of metamaterials has led to new approaches for considering the interaction of radiation with complex structures. However, practical manifestations of such a device operating at high power densities have proven difficult to achieve due to the resonant nature of metamaterials and the resultant high electric fields, which place severe constraints on manufacturing the slow wave structures. In this paper, we describe the first experimental manifestation of a high power microwave device utilizing a metallic slow wave structure (metamaterial-like) fabricated using additive manufacturing. The feasibility of utilizing additive manufacturing as a technique for buildingmore » these relatively complicated structures has thus been demonstrated. The MW class microwave source operates in the C-band and shows frequency tunablility with electron beam voltage. The basic electromagnetic characteristics of this device, the construction using additive manufacturing, and the basic performance as a microwave oscillator are considered. Due to the tunable nature of the device, it shows promise not only as an oscillator but also as a microwave amplifier. Therefore, the dispersive characteristics and a discussion of the anticipated gain is included as it relates to an amplifier configuration.« less

The role of the substrate in Graphene/Silicon photodiodes

NASA Astrophysics Data System (ADS)

Luongo, G.; Giubileo, F.; Iemmo, L.; Di Bartolomeo, A.

2018-01-01

The Graphene/Silicon (Gr/Si) junction can function as a Schottky diode with performances strictly related to the quality of the interface. Here, we focus on the substrate geometry and on its effects on Gr/Si junction physics. We fabricate and study the electrical and optical behaviour of two types of devices: one made of a Gr/Si planar junction, the second realized with graphene on an array of Si nanotips. We show that the Gr/Si flat device exhibits a reverse photocurrent higher than the forward current and achieves a photoresponsivity of 2.5 A/W. The high photoresponse is due to the charges photogenerated in Si below a parasitic graphene/SiO2/Si structure, which are injected into the Gr/Si junction region. The other device with graphene on Si-tips displays a reverse current that grows exponentially with the bias. We explain this behaviour by taking into account the tip geometry of the substrate, which magnifies the electric field and shifts the Fermi level of graphene, thus enabling fine-tuning of the Schottky barrier height. The Gr/Si-tip device achieves a higher photoresponsivity, up to 3 A/W, likely due to photocharge internal multiplication.

Optical recording materials

NASA Astrophysics Data System (ADS)

Savant, Gajendra D.; Jannson, Joanna L.

1991-07-01

The increased emphasis on speed of operation, wavelength selectivity, compactness, and ruggedization has focused a great deal of attention on the solutions offered by all-optic devices and by hybrid electro-optic systems. In fact, many photonic devices are being considered for use as partial replacements for electronic systems. Optical components, which include modulators, switches, 3-D memory storage devices, wavelength division multiplexers, holographic optical elements, and others, are examples of such devices. The success or failure of these modern optical devices depends, to a great extent, on the performance and survivability of the optical materials used. This is particularly true for volume holographic filters, organic memory media, second- and third-order nonlinear material-based processors and neural networks. Due to the critical importance of these materials and their lack of availability, Physical Optics Corporation (POC) undertook a global advanced optical materials program which has enabled it to introduce several optical devices, based on the new and improved materials which will be described in this article.

High-performance shape-engineerable thermoelectric painting

PubMed Central

Park, Sung Hoon; Jo, Seungki; Kwon, Beomjin; Kim, Fredrick; Ban, Hyeong Woo; Lee, Ji Eun; Gu, Da Hwi; Lee, Se Hwa; Hwang, Younghun; Kim, Jin-Sang; Hyun, Dow-Bin; Lee, Sukbin; Choi, Kyoung Jin; Jo, Wook; Son, Jae Sung

2016-01-01

Output power of thermoelectric generators depends on device engineering minimizing heat loss as well as inherent material properties. However, the device engineering has been largely neglected due to the limited flat or angular shape of devices. Considering that the surface of most heat sources where these planar devices are attached is curved, a considerable amount of heat loss is inevitable. To address this issue, here, we present the shape-engineerable thermoelectric painting, geometrically compatible to surfaces of any shape. We prepared Bi2Te3-based inorganic paints using the molecular Sb2Te3 chalcogenidometalate as a sintering aid for thermoelectric particles, with ZT values of 0.67 for n-type and 1.21 for p-type painted materials that compete the bulk values. Devices directly brush-painted onto curved surfaces produced the high output power of 4.0 mW cm−2. This approach paves the way to designing materials and devices that can be easily transferred to other applications. PMID:27834369

Game theory-based mode cooperative selection mechanism for device-to-device visible light communication

NASA Astrophysics Data System (ADS)

Liu, Yuxin; Huang, Zhitong; Li, Wei; Ji, Yuefeng

2016-03-01

Various patterns of device-to-device (D2D) communication, from Bluetooth to Wi-Fi Direct, are emerging due to the increasing requirements of information sharing between mobile terminals. This paper presents an innovative pattern named device-to-device visible light communication (D2D-VLC) to alleviate the growing traffic problem. However, the occlusion problem is a difficulty in D2D-VLC. This paper proposes a game theory-based solution in which the best-response dynamics and best-response strategies are used to realize a mode-cooperative selection mechanism. This mechanism uses system capacity as the utility function to optimize system performance and selects the optimal communication mode for each active user from three candidate modes. Moreover, the simulation and experimental results show that the mechanism can attain a significant improvement in terms of effectiveness and energy saving compared with the cases where the users communicate via only the fixed transceivers (light-emitting diode and photo diode) or via only D2D.

Guide Catheter Extension Device Is Effective in Renal Angioplasty for Severely Calcified Lesions.

PubMed

Sugimoto, Takeshi; Nomura, Tetsuya; Hori, Yusuke; Yoshioka, Kenichi; Kubota, Hiroshi; Miyawaki, Daisuke; Urata, Ryota; Kikai, Masakazu; Keira, Natsuya; Tatsumi, Tetsuya

2017-05-23

BACKGROUND The GuideLiner catheter extension device is a monorail-type "Child" support catheter that facilitates coaxial alignment with the guide catheter and provides an appropriate back-up force. This device has been developed in the field of coronary intervention, and now is becoming widely applied in the field of endovascular treatment. However, there has been no report on the effectiveness of the guide catheter extension device in percutaneous transluminal renal angioplasty (PTRA). CASE REPORT We encountered a case of atherosclerotic subtotal occlusion at the ostium of the left renal artery. Due to the severely calcified orifice and weaker back-up force provided by a JR4 guide catheter, we could not pass any guidewires through the target lesion. Therefore, we introduced a guide catheter extension device, the GuideLiner catheter, through the guide catheter and achieved good guidewire maneuverability. We finally deployed 2 balloon-expandable stents and successfully performed all PTRA procedures. CONCLUSIONS The guide catheter extension device can be effective in PTRA for severely calcified subtotal occlusion.

The study of VOPc thin film transistors on modified substrates

NASA Astrophysics Data System (ADS)

Song, De; Xu, Qi; Cheng, Hongcang; Li, Bao-zeng; Shang, Yubin

2018-02-01

The vanadyl phthalocyanine (VOPc) organic thin film transistors (OTFTs) were fabricated on the various organosilane self-assembled monolayer (SAM) modified substrates. And the effect of the surface properties on the performance of these transistors was studied. The atomic force morphologies and X-ray diffraction (XRD) spectrums of vanadyl phthalocyanine films on different SAM-modified surfaces were studied. They reveal that the terminal functional groups of organosilane affect the growth of VOPc film and device performance. The VOPc film on octadecyltrichlorosilane (OTS) modified substrate has larger crystal size and effective crystal thickness than those on phenyltrichlorosilane (PTS), 1H,1H,2H,2H-Perfluorodec-yltrichlorosilane (FDTS) as well as non-modified substrate, which contributes the mobility of corresponding device several and several dozen times relative to other ones. The effective crystal thickness and crystal grain size of VOPc film on PTS is between that on OTS treated and that on non-modified substrate due to the stronger attractive force between VOPc and SiO2. The VOPc films' performance and effective crystal thickness on FDTS treated are worse than that on PTS due to the existents of attractive force between -CF3 and VOPc.

Multiphoton microscopy of transdermal quantum dot delivery using two photon polymerization-fabricated polymer microneedles

PubMed Central

Gittard, Shaun D; Miller, Philip R; Boehm, Ryan D; Ovsianikov, Aleksandr; Chichkov, Boris N; Heiser, Jeremy; Gordon, John; Monteiro-Riviere, Nancy A; Narayan, Roger J

2010-01-01

Due to their ability to serve as fluorophores and drug delivery vehicles, quantum dots are a powerful tool for theranostics-based clinical applications. In this study, microneedle devices for transdermal drug delivery were fabricated by means of two-photon polymerization of an acrylate-based polymer. We examined proliferation of cells on this polymer using neonatal human epidermal keratinocytes and human dermal fibroblasts. The microneedle device was used to inject quantum dots into porcine skin; imaging of the quantum dots was performed using multiphoton microscopy. PMID:21413181

Alarm!!! A UFO inside the heart.

PubMed

Santoro, Giuseppe; Castaldi, Biagio; Iacono, Carola; Giugno, Luca; Gaio, Gianpiero; Russo, Maria G

2012-10-01

An 8-year-old asymptomatic child was referred for surgical repair of coronary sinus atrial septal defect resulting in significant left-to-right shunt and right chamber volume overload. The septal fenestration was located near to its drainage site into the right atrium. Due to this seemingly favourable anatomy, transcatheter closure of the septal defect was performed using an Amplatzer Septal Occluder device. The echocardiographic postprocedural evaluation imaged the occluding device almost perpendicular to the atrial septum, seemingly floating above the mitral valve orifice, like an alien spaceship inside the heart.

Paper-based batteries: a review.

PubMed

Nguyen, Thu H; Fraiwan, Arwa; Choi, Seokheun

2014-04-15

There is an extensively growing interest in using paper or paper-like substrates for batteries and other energy storage devices. Due to their intrinsic characteristics, paper (or paper-like) batteries show outstanding performance while retaining low cost, multifunctionality, versatility, flexibility and disposability. In this overview, we review recent achievements in paper (or paper-like) batteries as well as their applications. Various types of paper power devices are discussed including electrochemical batteries, biofuel cells, lithium-ion batteries, supercapacitors, and nanogenerators. Further scientific and technological challenges in this field are also discussed. © 2013 Elsevier B.V. All rights reserved.

Highly efficient organic light-emitting diodes with a quantum dot interfacial layer.

PubMed

Ryu, Seung Yoon; Hwang, Byoung Har; Park, Ki Wan; Hwang, Hyeon Seok; Sung, Jin Woo; Baik, Hong Koo; Lee, Chang Ho; Song, Seung Yong; Lee, Jun Yeob

2009-02-11

Advanced organic light-emitting diodes (OLEDs), based on a multiple structure, were achieved in combination with a quantum dot (QD) interfacial layer. The authors used core/shell CdSe/ZnS QDs passivated with trioctylphosphine oxide (TOPO) and TOPO-free QDs as interlayers. Multiple-structure OLEDs (MOLEDs) with TOPO-free QDs showed higher device efficiency because of a well-defined interfacial monolayer formation. Additionally, the three-unit MOLED showed high performance for device efficiency with double-structured QD interfacial layers due to the enhanced charge balance and recombination probability.

Origin of the performances degradation of two-dimensional-based metal-oxide-semiconductor field effect transistors in the sub-10 nm regime: A first-principles study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Anh Khoa Augustin; IMEC, 75 Kapeldreef, B-3001 Leuven; Pourtois, Geoffrey

2016-01-25

The impact of the scaling of the channel length on the performances of metal-oxide-semiconductor field effect transistors, based on two-dimensional (2D) channel materials, is theoretically investigated, using density functional theory combined with the non-equilibrium Green's function method. It is found that the scaling of the channel length below 10 nm leads to strong device performance degradations. Our simulations reveal that this degradation is essentially due to the tunneling current flowing between the source and the drain in these aggressively scaled devices. It is shown that this electron tunneling process is modulated by the effective mass of the 2D channel material, andmore » sets the limit of the scaling in future transistor designs.« less

Comparing performance of mothers using simplified mid-upper arm circumference (MUAC) classification devices with an improved MUAC insertion tape in Isiolo County, Kenya.

PubMed

Grant, Angeline; Njiru, James; Okoth, Edgar; Awino, Imelda; Briend, André; Murage, Samuel; Abdirahman, Saida; Myatt, Mark

2018-01-01

A novel approach for improving community case-detection of acute malnutrition involves mothers/caregivers screening their children for acute malnutrition using a mid-upper arm circumference (MUAC) insertion tape. The objective of this study was to test three simple MUAC classification devices to determine whether they improved the sensitivity of mothers/caregivers at detecting acute malnutrition. Prospective, non-randomised, partially-blinded, clinical diagnostic trial describing and comparing the performance of three "Click-MUAC" devices and a MUAC insertion tape. The study took place in twenty-one health facilities providing integrated management of acute malnutrition (IMAM) services in Isiolo County, Kenya. Mothers/caregivers classified their child ( n =1040), aged 6-59 months, using the "Click-MUAC" devices and a MUAC insertion tape. These classifications were compared to a "gold standard" classification (the mean of three measurements taken by a research assistant using the MUAC insertion tape). The sensitivity of mother/caregiver classifications was high for all devices (>93% for severe acute malnutrition (SAM), defined by MUAC < 115 mm, and > 90% for global acute malnutrition (GAM), defined by MUAC < 125 mm). Mother/caregiver sensitivity for SAM and GAM classification was higher using the MUAC insertion tape (100% sensitivity for SAM and 99% sensitivity for GAM) than using "Click-MUAC" devices. Younden's J for SAM classification, and sensitivity for GAM classification, were significantly higher for the MUAC insertion tape (99% and 99% respectively). Specificity was high for all devices (>96%) with no significant difference between the "Click-MUAC" devices and the MUAC insertion tape. The results of this study indicate that, although the "Click-MUAC" devices performed well, the MUAC insertion tape performed best. The results for sensitivity are higher than found in previous studies. The high sensitivity for both SAM and GAM classification by mothers/caregivers with the MUAC insertion tape could be due to the use of an improved MUAC tape design which has a number of new design features. The one-on-one demonstration provided to mothers/caregivers on the use of the devices may also have helped improve sensitivity. The results of this study provide evidence that mothers/caregivers can perform sensitive and specific classifications of their child's nutritional status using MUAC. Clinical trials registration number: NCT02833740.

Physical mechanisms affecting hot carrier-induced degradation in gallium nitride HEMTs

NASA Astrophysics Data System (ADS)

Mukherjee, Shubhajit

Gallium Nitride or GaN-based high electron mobility transistors (HEMTs) is currently the most promising device technology in several key military and civilian applications due to excellent high-power as well as high-frequency performance. Even though the performance figures are outstanding, GaN-based HEMTs are not as mature as some competing technologies, which means that establishing the reliability of the technology is important to enable use in critical applications. The objective of this research is to understand the physical mechanisms affecting the reliability of GaN HEMTs at moderate drain biases (typically VDS < 30 V in the devices considered here). The degradation in device performance is believed to be due to the formation or modification of charged defects near the interface by hydrogen depassivation processes (due to electron-activated hydrogen removal) from energetic carriers. A rate-equation describing the defect generation process is formulated based on this assumption. A combination of ensemble Monte-Carlo (EMC) simulation statistics, ab-initio density functional theory (DFT) calculations, and accelerated stress experiments is used to relate the candidate defects to the overall degradation behavior (VT and gm). The focus of this work is on the 'semi-ON' mode of transistor operation in which the degradation is usually observed to be at its highest. This semi-ON state is reasonably close to the biasing region of class-AB high power amplifiers, which are popular because of the combination of high efficiency and low distortion that is associated with this configuration. The carrier-energy distributions are obtained using an EMC simulator that was developed specifically for III-V HFETs. The rate equation is used to model the degradation at different operating conditions as well as longer stress times from the result of one short duration stress test, by utilizing the carrier-energy distribution obtained from EMC simulations for one baseline condition. This work also attempts to identify the spatial location of these defects, and how this impacts the V T shift and gm degradation of the devices.

Modeling of organic solar cell using response surface methodology

NASA Astrophysics Data System (ADS)

Suliman, Rajab; Mitul, Abu Farzan; Mohammad, Lal; Djira, Gemechis; Pan, Yunpeng; Qiao, Qiquan

Polymer solar cells have drawn much attention during the past few decades due to their low manufacturing cost and incompatibility for flexible substrates. In solution-processed organic solar cells, the optimal thickness, annealing temperature, and morphology are key components to achieving high efficiency. In this work, response surface methodology (RSM) is used to find optimal fabrication conditions for polymer solar cells. In order to optimize cell efficiency, the central composite design (CCD) with three independent variables polymer concentration, polymer-fullerene ratio, and active layer spinning speed was used. Optimal device performance was achieved using 10.25 mg/ml polymer concentration, 0.42 polymer-fullerene ratio, and 1624 rpm of active layer spinning speed. The predicted response (the efficiency) at the optimum stationary point was found to be 5.23% for the Poly(diketopyrrolopyrrole-terthiophene) (PDPP3T)/PC60BM solar cells. Moreover, 97% of the variation in the device performance was explained by the best model. Finally, the experimental results are consistent with the CCD prediction, which proves that this is a promising and appropriate model for optimum device performance and fabrication conditions.

Polarization-mediated Debye-screening of surface potential fluctuations in dual-channel AlN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Deen, David A.; Miller, Ross A.; Osinsky, Andrei V.; Downey, Brian P.; Storm, David F.; Meyer, David J.; Scott Katzer, D.; Nepal, Neeraj

2016-12-01

A dual-channel AlN/GaN/AlN/GaN high electron mobility transistor (HEMT) architecture is proposed, simulated, and demonstrated that suppresses gate lag due to surface-originated trapped charge. Dual two-dimensional electron gas (2DEG) channels are utilized such that the top 2DEG serves as an equipotential that screens potential fluctuations resulting from surface trapped charge. The bottom channel serves as the transistor's modulated channel. Two device modeling approaches have been performed as a means to guide the device design and to elucidate the relationship between the design and performance metrics. The modeling efforts include a self-consistent Poisson-Schrodinger solution for electrostatic simulation as well as hydrodynamic three-dimensional device modeling for three-dimensional electrostatics, steady-state, and transient simulations. Experimental results validated the HEMT design whereby homo-epitaxial growth on free-standing GaN substrates and fabrication of the same-wafer dual-channel and recessed-gate AlN/GaN HEMTs have been demonstrated. Notable pulsed-gate performance has been achieved by the fabricated HEMTs through a gate lag ratio of 0.86 with minimal drain current collapse while maintaining high levels of dc and rf performance.

Transparent and stretchable high-performance supercapacitors based on wrinkled graphene electrodes.

PubMed

Chen, Tao; Xue, Yuhua; Roy, Ajit K; Dai, Liming

2014-01-28

Transparent and/or stretchable energy storage devices have attracted intense attention due to their unique optical and/or mechanical properties as well as their intrinsic energy storage function. However, it remains a great challenge to integrate transparent and stretchable properties into an energy storage device because the currently developed electrodes are either transparent or stretchable, but not both. Herein, we report a simple method to fabricate wrinkled graphene with high stretchability and transparency. The resultant wrinkled graphene sheets were used as both current collector and electrode materials to develop transparent and stretchable supercapacitors, which showed a high transparency (57% at 550 nm) and can be stretched up to 40% strain without obvious performance change over hundreds of stretching cycles.

Temperature- and Intensity-Dependent Photovoltaic Measurements to Identify Dominant Recombination Pathways

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, Riley E.; Mangan, Niall M.; Li, Jian V.

2016-11-21

In novel photovoltaic absorbers, it is often difficult to assess the root causes of low open-circuit voltages, which may be due to bulk recombination or sub-optimal contacts. In the present work, we discuss the role of temperature- and illumination-dependent device electrical measurements in quantifying and distinguishing these performance losses - in particular, for determining bounds on interface recombination velocities, band alignment, and minority carrier lifetime. We assess the accuracy of this approach by direct comparison to photoelectron spectroscopy. Then, we demonstrate how more computationally intensive model parameter fitting approaches can draw more insights from this broad measurement space. We applymore » this measurement and modeling approach to high-performance III-V and thin-film chalcogenide devices.« less

Ferroelectric nanoparticle-embedded sponge structure triboelectric generators

NASA Astrophysics Data System (ADS)

Park, Daehoon; Shin, Sung-Ho; Yoon, Ick-Jae; Nah, Junghyo

2018-05-01

We report high-performance triboelectric nanogenerators (TENGs) employing ferroelectric nanoparticles (NPs) embedded in a sponge structure. The ferroelectric BaTiO3 NPs inside the sponge structure play an important role in increasing surface charge density by polarized spontaneous dipoles, enabling the packaging of TENGs even with a minimal separation gap. Since the friction surfaces are encapsulated in the packaged device structure, it suffers negligible performance degradation even at a high relative humidity of 80%. The TENGs also demonstrated excellent mechanical durability due to the elasticity and flexibility of the sponge structure. Consequently, the TENGs can reliably harvest energy even under harsh conditions. The approach introduced here is a simple, effective, and reliable way to fabricate compact and packaged TENGs for potential applications in wearable energy-harvesting devices.

Ferroelectric nanoparticle-embedded sponge structure triboelectric generators.

PubMed

Park, Daehoon; Shin, Sung-Ho; Yoon, Ick-Jae; Nah, Junghyo

2018-05-04

We report high-performance triboelectric nanogenerators (TENGs) employing ferroelectric nanoparticles (NPs) embedded in a sponge structure. The ferroelectric BaTiO 3 NPs inside the sponge structure play an important role in increasing surface charge density by polarized spontaneous dipoles, enabling the packaging of TENGs even with a minimal separation gap. Since the friction surfaces are encapsulated in the packaged device structure, it suffers negligible performance degradation even at a high relative humidity of 80%. The TENGs also demonstrated excellent mechanical durability due to the elasticity and flexibility of the sponge structure. Consequently, the TENGs can reliably harvest energy even under harsh conditions. The approach introduced here is a simple, effective, and reliable way to fabricate compact and packaged TENGs for potential applications in wearable energy-harvesting devices.

Non-Platinum Group Metal OER/ORR Catalysts for Alkaline Membrane Fuel Cells and Electrolyzers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Danilovic, Nemanja; Ayers, Katherine

Regenerative fuel cells (RFC) are energy storage devices that capture electrical energy in the form of hydrogen, with potential application for backup power and energy storage in remote locations, unmanned missions, and renewable energy capture. A unitized regenerative fuel cell (URFC) combines two separate electrochemical devices (fuel cell and electrolyzer) into one stack. The stack cost is driven by the platinum group metal (PGM) catalysts and the flow field components designed to withstand high potentials in acidic environments. Since the stack is the most expensive subcomponent of both the fuel cell and electrolyzer system, combining the two devices results inmore » substantial reduction in capital cost. However, in the past, combining the two stacks sacrificed device performance (operating cost) largely because the fuel cell had to operate with the thick electrolysis membranes in a URFC configuration, and due to water management issues in switching modes. Recent work in membrane-based electrolysis has resulted in more mechanically robust designs and materials that allow much thinner membranes, and work in flow cell design such as flow batteries has shown improved water transport through channel design and wet-proofing approaches. Therefore, the URFC concept is worth revisiting. At the same time, alkaline exchange membrane (AEM) devices are gathering attention due to the promise of PGM and valve metal elimination from the stack and a resulting strategic and capital cost benefit as compared with proton exchange membrane (PEM) systems. The result is a lower capital cost system that has half the precious metal group (PGM) catalysts, membrane and other stack component materials compared with discrete RFCs, although at the sacrifice of performance (operating cost). Proton has identified innovative AEM based RFC's to fulfill the role of low capital cost energy storage device owing to the use of non-precious metal containing electrodes, that enables certain markets where higher operating costs can be tolerated.« less

Photovoltaic performance and stability of fullerene/cerium oxide double electron transport layer superior to single one in p-i-n perovskite solar cells

NASA Astrophysics Data System (ADS)

Xing, Zhou; Li, Shu-Hui; Wu, Bao-Shan; Wang, Xin; Wang, Lu-Yao; Wang, Tan; Liu, Hao-Ran; Zhang, Mei-Lin; Yun, Da-Qin; Deng, Lin-Long; Xie, Su-Yuan; Huang, Rong-Bin; Zheng, Lan-Sun

2018-06-01

Interface engineering that involves in the metal cathodes and the electron transport layers (ETLs) facilitates the simultaneous improvement of device performances and stability in perovskite solar cells (PSCs). Herein, low-temperature solution-processed cerium oxide (CeOx) films are prepared by a facile sol-gel method and employed as the interface layers between [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and an Ag back contact to form PC61BM/CeOx double ETLs. The introduction of CeOx enables electron extraction to the Ag electrode and protects the underlying perovskite layer and thus improves the device performance and stability of the p-i-n PSCs. The p-i-n PSCs with double PC61BM/CeOx ETLs demonstrate a maximum power conversion efficiency (PCE) of 17.35%, which is superior to those of the devices with either PC61BM or CeOx single ETLs. Moreover, PC61BM/CeOx devices exhibit excellent stability in light soaking, which is mainly due to the chemically stable CeOx interlayer. The results indicate that CeOx is a promising interface modification layer for stable high-efficiency PSCs.

Poor chest compression quality with mechanical compressions in simulated cardiopulmonary resuscitation: a randomized, cross-over manikin study.

PubMed

Blomberg, Hans; Gedeborg, Rolf; Berglund, Lars; Karlsten, Rolf; Johansson, Jakob

2011-10-01

Mechanical chest compression devices are being implemented as an aid in cardiopulmonary resuscitation (CPR), despite lack of evidence of improved outcome. This manikin study evaluates the CPR-performance of ambulance crews, who had a mechanical chest compression device implemented in their routine clinical practice 8 months previously. The objectives were to evaluate time to first defibrillation, no-flow time, and estimate the quality of compressions. The performance of 21 ambulance crews (ambulance nurse and emergency medical technician) with the authorization to perform advanced life support was studied in an experimental, randomized cross-over study in a manikin setup. Each crew performed two identical CPR scenarios, with and without the aid of the mechanical compression device LUCAS. A computerized manikin was used for data sampling. There were no substantial differences in time to first defibrillation or no-flow time until first defibrillation. However, the fraction of adequate compressions in relation to total compressions was remarkably low in LUCAS-CPR (58%) compared to manual CPR (88%) (95% confidence interval for the difference: 13-50%). Only 12 out of the 21 ambulance crews (57%) applied the mandatory stabilization strap on the LUCAS device. The use of a mechanical compression aid was not associated with substantial differences in time to first defibrillation or no-flow time in the early phase of CPR. However, constant but poor chest compressions due to failure in recognizing and correcting a malposition of the device may counteract a potential benefit of mechanical chest compressions. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

On neoclassical impurity transport in stellarator geometry

NASA Astrophysics Data System (ADS)

García-Regaña, J. M.; Kleiber, R.; Beidler, C. D.; Turkin, Y.; Maaßberg, H.; Helander, P.

2013-07-01

The impurity dynamics in stellarators has become an issue of moderate concern due to the inherent tendency of the impurities to accumulate in the core when the neoclassical ambipolar radial electric field points radially inwards (ion root regime). This accumulation can lead to collapse of the plasma due to radiative losses, and thus limit high performance plasma discharges in non-axisymmetric devices. A quantitative description of the neoclassical impurity transport is complicated by the breakdown of the assumption of small E × B drift and trapping due to the electrostatic potential variation on a flux surface \\tilde{\\Phi} compared with those due to the magnetic field gradient. This work examines the impact of this potential variation on neoclassical impurity transport in the Large Helical Device heliotron. It shows that the neoclassical impurity transport can be strongly affected by \\tilde{\\Phi} . The central numerical tool used is the δf particle in cell Monte Carlo code EUTERPE. The \\tilde{\\Phi} used in the calculations is provided by the neoclassical code GSRAKE. The possibility of obtaining a more general \\tilde{\\Phi} self-consistently with EUTERPE is also addressed and a preliminary calculation is presented.

Integrated MEMS-based variable optical attenuator and 10Gb/s receiver

NASA Astrophysics Data System (ADS)

Aberson, James; Cusin, Pierre; Fettig, H.; Hickey, Ryan; Wylde, James

2005-03-01

MEMS devices can be successfully commercialized in favour of competing technologies only if they offer an advantage to the customer in terms of lower cost or increased functionality. There are limited markets where MEMS can be manufactured cheaper than similar technologies due to large volumes: automotive, printing technology, wireless communications, etc. However, success in the marketplace can also be realized by adding significant value to a system at minimal cost or leverging MEMS technology when other solutions simply will not work. This paper describes a thermally actuated, MEMS based, variable optical attenuator that is co-packaged with existing opto-electronic devices to develop an integrated 10Gb/s SONET/SDH receiver. The configuration of the receiver opto-electronics and relatively low voltage availability (12V max) in optical systems bar the use of LCD, EO, and electro-chromic style attenuators. The device was designed and fabricated using a silicon-on-insulator (SOI) starting material. The design and performance of the device (displacement, power consumption, reliability, physical geometry) was defined by the receiver parameters geometry. This paper will describe how these design parameters (hence final device geometry) were determined in light of both the MEMS device fabrication process and the receiver performance. Reference will be made to the design tools used and the design flow which was a joint effort between the MEMS vendor and the end customer. The SOI technology offered a robust, manufacturable solution that gave the required performance in a cost-effective process. However, the singulation of the devices required the development of a new singulation technique that allowed large volumes of silicon to be removed during fabrication yet still offer high singulation yields.

In-situ device integration of large-area patterned organic nanowire arrays for high-performance optical sensors

PubMed Central

Wu, Yiming; Zhang, Xiujuan; Pan, Huanhuan; Deng, Wei; Zhang, Xiaohong; Zhang, Xiwei; Jie, Jiansheng

2013-01-01

Single-crystalline organic nanowires (NWs) are important building blocks for future low-cost and efficient nano-optoelectronic devices due to their extraordinary properties. However, it remains a critical challenge to achieve large-scale organic NW array assembly and device integration. Herein, we demonstrate a feasible one-step method for large-area patterned growth of cross-aligned single-crystalline organic NW arrays and their in-situ device integration for optical image sensors. The integrated image sensor circuitry contained a 10 × 10 pixel array in an area of 1.3 × 1.3 mm2, showing high spatial resolution, excellent stability and reproducibility. More importantly, 100% of the pixels successfully operated at a high response speed and relatively small pixel-to-pixel variation. The high yield and high spatial resolution of the operational pixels, along with the high integration level of the device, clearly demonstrate the great potential of the one-step organic NW array growth and device construction approach for large-scale optoelectronic device integration. PMID:24287887

Fixed Junction Light Emitting Electrochemical Cells based on Polymerizable Ionic Liquids

NASA Astrophysics Data System (ADS)

Brown, Erin; Limanek, Austin; Bauman, James; Leger, Janelle

Organic photovoltaic (OPV) devices are of interest due to ease of fabrication, which increases their cost-effectiveness. OPV devices based on fixed-junction light emitting electrochemical cells (LECs) in particular have shown promising results. LECs are composed of a layer of polymer semiconductor blended with a salt sandwiched between two electrodes. As a forward bias is applied, the ions within the polymer separate, migrate to the electrodes, and enable electrochemical doping, thereby creating a p-n junction analog. In a fixed junction device, the ions are immobilized after the desired distribution has been established, allowing for operation under reverse bias conditions. Fixed junctions can be established using various techniques, including chemically by mixing polymerizable salts that will bond to the polymer under a forward bias. Previously we have demonstrated the use of the polymerizable ionic liquid allyltrioctylammonium allysulfonate (ATOAAS) as an effective means of creating a chemically fixed junction in an LEC. Here we present the application of this approach to the creation of photovoltaic devices. Devices demonstrate higher open circuit voltages, faster charging, and an overall improved device performance over previous chemically-fixed junction PV devices.

SiC Technology

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.

1998-01-01

Silicon carbide (SiC)-based semiconductor electronic devices and circuits are presently being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot adequately perform. Silicon carbide's ability to function under such extreme conditions is expected to enable significant improvements to a far-ranging variety of applications and systems. These range from greatly improved high-voltage switching [1- 4] for energy savings in public electric power distribution and electric motor drives to more powerful microwave electronics for radar and communications [5-7] to sensors and controls for cleaner-burning more fuel-efficient jet aircraft and automobile engines. In the particular area of power devices, theoretical appraisals have indicated that SiC power MOSFET's and diode rectifiers would operate over higher voltage and temperature ranges, have superior switching characteristics, and yet have die sizes nearly 20 times smaller than correspondingly rated silicon-based devices [8]. However, these tremendous theoretical advantages have yet to be realized in experimental SiC devices, primarily due to the fact that SiC's relatively immature crystal growth and device fabrication technologies are not yet sufficiently developed to the degree required for reliable incorporation into most electronic systems [9]. This chapter briefly surveys the SiC semiconductor electronics technology. In particular, the differences (both good and bad) between SiC electronics technology and well-known silicon VLSI technology are highlighted. Projected performance benefits of SiC electronics are highlighted for several large-scale applications. Key crystal growth and device-fabrication issues that presently limit the performance and capability of high temperature and/or high power SiC electronics are identified.

Passive thermal management using phase change materials

NASA Astrophysics Data System (ADS)

Ganatra, Yash Yogesh

The trend of enhanced functionality and reducing thickness of mobile devices has. led to a rapid increase in power density and a potential thermal bottleneck since. thermal limits of components remain unchanged. Active cooling mechanisms are not. feasible due to size, weight and cost constraints. This work explores the feasibility. of a passive cooling system based on Phase Change Materials (PCMs) for thermal. management of mobile devices. PCMs stabilize temperatures due to the latent heat. of phase change thus increasing the operating time of the device before threshold. temperatures are exceeded. The primary contribution of this work is the identification. of key parameters which influence the design of a PCM based thermal management. system from both the experiments and the numerical models. This work first identifies strategies for integrating PCMs in an electronic device. A. detailed review of past research, including experimental techniques and computational. models, yields key material properties and metrics to evaluate the performance of. PCMs. Subsequently, a miniaturized version of a conventional thermal conductivity. measurement technique is developed to characterize thermal resistance of PCMs. Further, latent heat and transition temperatures are also characterized for a wide. range of PCMs. In-situ measurements with PCMs placed on the processor indicate that some. PCMs can extend the operating time of the device by as much as a factor of 2.48. relative to baseline tests (with no PCMs). This increase in operating time is investigated. by computational thermal models that explore various integration locations, both at the package and device level.

A Reliable Data Transmission Model for IEEE 802.15.4e Enabled Wireless Sensor Network under WiFi Interference.

PubMed

Sahoo, Prasan Kumar; Pattanaik, Sudhir Ranjan; Wu, Shih-Lin

2017-06-07

The IEEE 802.15.4e standard proposes Medium Access Control (MAC) to support collision-free wireless channel access mechanisms for industrial, commercial and healthcare applications. However, unnecessary wastage of energy and bandwidth consumption occur due to inefficient backoff management and collisions. In this paper, a new channel access mechanism is designed for the buffer constraint sensor devices to reduce the packet drop rate, energy consumption and collisions. In order to avoid collision due to the hidden terminal problem, a new frame structure is designed for the data transmission. A new superframe structure is proposed to mitigate the problems due to WiFi and ZigBee interference. A modified superframe structure with a new retransmission opportunity for failure devices is proposed to reduce the collisions and retransmission delay with high reliability. Performance evaluation and validation of our scheme indicate that the packet drop rate, throughput, reliability, energy consumption and average delay of the nodes can be improved significantly.

A Reliable Data Transmission Model for IEEE 802.15.4e Enabled Wireless Sensor Network under WiFi Interference

PubMed Central

Sahoo, Prasan Kumar; Pattanaik, Sudhir Ranjan; Wu, Shih-Lin

2017-01-01

The IEEE 802.15.4e standard proposes Medium Access Control (MAC) to support collision-free wireless channel access mechanisms for industrial, commercial and healthcare applications. However, unnecessary wastage of energy and bandwidth consumption occur due to inefficient backoff management and collisions. In this paper, a new channel access mechanism is designed for the buffer constraint sensor devices to reduce the packet drop rate, energy consumption and collisions. In order to avoid collision due to the hidden terminal problem, a new frame structure is designed for the data transmission. A new superframe structure is proposed to mitigate the problems due to WiFi and ZigBee interference. A modified superframe structure with a new retransmission opportunity for failure devices is proposed to reduce the collisions and retransmission delay with high reliability. Performance evaluation and validation of our scheme indicate that the packet drop rate, throughput, reliability, energy consumption and average delay of the nodes can be improved significantly. PMID:28590434

Fabrication and Characterization of Thermo-Optic Mach-Zehnder Silicon Modulator

NASA Astrophysics Data System (ADS)

Park, Yeongho

This thesis focuses on the modeling, design, and fabrication of the Thermo-Optic Mach-Zehnder Modulator, which is one of the simple active devices in silicon photonics. The Mach-Zehnder interferometer (MZI) was formed as an optical path on a silicon on insulator (SOI) wafer of 2040+/-80 nm thick, and the thermo-optic effect was used to modulate the infrared light of 1553 nm wavelength by controlling the temperature of the one arm of the MZI. To fabricate and understand the Si photonic device, the whole process from theory to the measurement setup is introduced. Additionally, all the fabrication details and some informative experiments which were performed during the fabrication are discussed for students who will study the more developed devices. The width of the designed waveguide is 4 mum, but the width of the fabricated waveguide is 3.0+/-0.2 mum due to the isotropic etching. For the lithography for both patterning waveguides and metal contacts, the AZ 5214 photoresist was used, and the details of the lithography was discussed. Furthermore, the lift-off method was performed and introduced to solve the over-etching problem. The fabricated metal contacts can withstand up to 1.6W, and the electric power 0.3W is required to make Pi phase difference according to the simulation result by the simulation software Lumerical. The optical output of the device was not detected due to the huge losses from the sidewall roughness and the insertion loss, so it is discussed in the experimental measurement chapter.

A computational fluid dynamics (CFD) study of WEB-treated aneurysms: Can CFD predict WEB "compression" during follow-up?

PubMed

Caroff, Jildaz; Mihalea, Cristian; Da Ros, Valerio; Yagi, Takanobu; Iacobucci, Marta; Ikka, Léon; Moret, Jacques; Spelle, Laurent

2017-07-01

Recent reports have revealed a worsening of aneurysm occlusion between WEB treatment baseline and angiographic follow-up due to "compression" of the device. We utilized computational fluid dynamics (CFD) in order to determine whether the underlying mechanism of this worsening is flow related. We included data from all consecutive patients treated in our institution with a WEB for unruptured aneurysms located either at the middle cerebral artery or basilar tip. The CFD study was performed using pre-operative 3D rotational angiography. From digital subtraction follow-up angiographies patients were dichotomized into two groups: one with WEB "compression" and one without. We performed statistical analyses to determine a potential correlation between WEB compression and CFD inflow ratio. Between July 2012 and June 2015, a total of 22 unruptured middle cerebral artery or basilar tip aneurysms were treated with a WEB device in our department. Three patients were excluded from the analysis and the mean follow-up period was 17months. Eleven WEBs presented "compression" during follow-up. Interestingly, device "compression" was statistically correlated to the CFD inflow ratio (P=0.018), although not to aneurysm volume, aspect ratio or neck size. The mechanisms underlying the worsening of aneurysm occlusion in WEB-treated patients due to device compression are most likely complex as well as multifactorial. However, it is apparent from our pilot study that a high arterial inflow is, at least, partially involved. Further theoretical and animal research studies are needed to increase our understanding of this phenomenon. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Carbon Based Transistors and Nanoelectronic Devices

NASA Astrophysics Data System (ADS)

Rouhi, Nima

Carbon based materials (carbon nanotube and graphene) has been extensively researched during the past decade as one of the promising materials to be used in high performance device technology. In long term it is thought that they may replace digital and/or analog electronic devices, due to their size, near-ballistic transport, and high stability. However, a more realistic point of insertion into market may be the printed nanoelectronic circuits and sensors. These applications include printed circuits for flexible electronics and displays, large-scale bendable electrical contacts, bio-membranes and bio sensors, RFID tags, etc. In order to obtain high performance thin film transistors (as the basic building block of electronic circuits) one should be able to manufacture dense arrays of all semiconducting nanotubes. Besides, graphene synthesize and transfer technology is in its infancy and there is plenty of room to improve the current techniques. To realize the performance of nanotube and graphene films in such systems, we need to economically fabricate large-scale devices based on these materials. Following that the performance control over such devices should also be considered for future design variations for broad range of applications. Here we have first investigated carbon nanotube ink as the base material for our devices. The primary ink used consisted of both metallic and semiconducting nanotubes which resulted in networks suitable for moderate-resistivity electrical connections (such as interconnects) and rfmatching circuits. Next, purified all-semiconducting nanotube ink was used to fabricate waferscale, high performance (high mobility, and high on/off ratio) thin film transistors for printed electronic applications. The parameters affecting device performance were studied in detail to establish a roadmap for the future of purified nanotube ink printed thin film transistors. The trade of between mobility and on/off ratio of such devices was studied and the effect of nanotube network density was explained in detail. On the other hand, graphene transfer technology was explored here as well. Annealing techniques were utilized to deposit clean graphene on arbitrary substrates. Raman spectroscopy and Raman data analysis was used to confirm the clean process. Furthermore, suspended graphene membrane was fabricated using single and multi-layer graphene films. This can make a major impact on graphene based transistors and bio-nano sensors technology.

Organic mixed conductors for bioelectronic applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Rivnay, Jonathan

2016-09-01

Direct measurement and stimulation of electrophysiological activity is a staple of neural and cardiac health monitoring, diagnosis and/or therapy. The ability to sensitively detect these signals can be enhanced by organic electronic materials that show mixed conduction properties (both electronic and ionic transport) in order to bridge the inherent mismatch that is prevalent between biological systems and traditional microelectronic materials/devices. Organic electrochemical transistors (OECTs) are one class of devices that utilize organic mixed conductors as the transistor channel, and have shown considerable promise as amplifying transducers due to their stability in aqueous conditions and high transconductance. These devices are fabricated in flexible, conformable form factors for in vivo recordings of epileptic activity, and for cutaneous EEG and ECG recordings in human subjects. The majority of high performance devices are based on conducting polymers such as poly(3,4-ethylenedioxythiophene) :poly(styrenesulfonate), PEDOT:PSS. By investigating PEDOT-based materials and devices, we are able to construct design rules for new formulations/materials. Introducing glycolated side chains to carefully selected semiconducting polymer backbones has enabled a new class high performance bioelectronic materials that feature high volumetric capacitance, transconductance >10mS (device dimensions ca. 10um), and steep subthreshold switching characteristics. A sub-set of these materials outperform PEDOT:PSS and shows significant promise for low power in vitro and in vivo biosensing applications.

Significance of coupling device for vessel anastomosis in esophageal reconstruction.

PubMed

Watanabe, Y; Horiuchi, A; Yamamoto, Y; Kikkawa, H; Kusunose, H; Sugishita, H; Sato, K; Yoshida, M; Yukumi, S; Kawachi, K

2005-01-01

To prevent an anastomotic failure due to impaired blood supply, several trials have been performed such as preoperative ischemic conditioning by transarterial embolization of the left gastric, right gastric and splenic arteries or microvascular anastomosis. We assess the significance of an automatic anastomotic coupling device for vessel anastomosis, which we have continuously utilized, to simplify the task and shorten the anastomotic time since March 1999. 8 patients who underwent venous anastomosis by an automatic anastomotic coupling device were evaluated for the time of anastomosis, total ischemic time and outcomes. Venous anastomosis was completed within 5 minutes on average. Microscopic arterial anastomosis by hand took 35 minutes on average. For gastric tube reconstruction, venous anastomosis by an automatic coupling device took only 5 minutes. The top of the gastric tube showed congestion before venous anastomosis, but rapidly recovered from it after anastomosis. Postoperative endoscopic observation of the mucosal color of the replaced intestine or gastric tube was started 3 days after surgery and revealed no ischemia or congestion. The postoperative course was uneventful except one case suffering from pneumonia but leakage was not observed in any case. An automatic anastomotic coupling device can perform an easy and reliable vascular anastomosis for patients who undergo esophageal reconstruction. The device may shorten the operating time and consequently the ischemic time of the gastric tube or jejunal or colonic graft, which in turn may lead to a decrease of complications.

Electronic voltage and current transformers testing device.

PubMed

Pan, Feng; Chen, Ruimin; Xiao, Yong; Sun, Weiming

2012-01-01

A method for testing electronic instrument transformers is described, including electronic voltage and current transformers (EVTs, ECTs) with both analog and digital outputs. A testing device prototype is developed. It is based on digital signal processing of the signals that are measured at the secondary outputs of the tested transformer and the reference transformer when the same excitation signal is fed to their primaries. The test that estimates the performance of the prototype has been carried out at the National Centre for High Voltage Measurement and the prototype is approved for testing transformers with precision class up to 0.2 at the industrial frequency (50 Hz or 60 Hz). The device is suitable for on-site testing due to its high accuracy, simple structure and low-cost hardware.

Conducting Polymers for Neural Prosthetic and Neural Interface Applications

PubMed Central

2015-01-01

Neural interfacing devices are an artificial mechanism for restoring or supplementing the function of the nervous system lost as a result of injury or disease. Conducting polymers (CPs) are gaining significant attention due to their capacity to meet the performance criteria of a number of neuronal therapies including recording and stimulating neural activity, the regeneration of neural tissue and the delivery of bioactive molecules for mediating device-tissue interactions. CPs form a flexible platform technology that enables the development of tailored materials for a range of neuronal diagnostic and treatment therapies. In this review the application of CPs for neural prostheses and other neural interfacing devices are discussed, with a specific focus on neural recording, neural stimulation, neural regeneration, and therapeutic drug delivery. PMID:26414302

Optimizing Aspect-Oriented Mechanisms for Embedded Applications

NASA Astrophysics Data System (ADS)

Hundt, Christine; Stöhr, Daniel; Glesner, Sabine

As applications for small embedded mobile devices are getting larger and more complex, it becomes inevitable to adopt more advanced software engineering methods from the field of desktop application development. Aspect-oriented programming (AOP) is a promising approach due to its advanced modularization capabilities. However, existing AOP languages tend to add a substantial overhead in both execution time and code size which restricts their practicality for small devices with limited resources. In this paper, we present optimizations for aspect-oriented mechanisms at the level of the virtual machine. Our experiments show that these optimizations yield a considerable performance gain along with a reduction of the code size. Thus, our optimizations establish the base for using advanced aspect-oriented modularization techniques for developing Java applications on small embedded devices.

Solvents induced ZnO nanoparticles aggregation associated with their interfacial effect on organic solar cells.

PubMed

Li, Pandeng; Jiu, Tonggang; Tang, Gang; Wang, Guojie; Li, Jun; Li, Xiaofang; Fang, Junfeng

2014-10-22

ZnO nanofilm as a cathode buffer layer has surface defects due to the aggregations of ZnO nanoparticles, leading to poor device performance of organic solar cells. In this paper, we report the ZnO nanoparticles aggregations in solution can be controlled by adjusting the solvents ratios (chloroform vs methanol). These aggregations could influence the morphology of ZnO film. Therefore, compact and homogeneous ZnO film can be obtained to help achieve a preferable power conversion efficiency of 8.54% in inverted organic solar cells. This improvement is attributed to the decreased leakage current and the increased electron-collecting efficiency as well as the improved interface contact with the active layer. In addition, we find the enhanced maximum exciton generation rate and exciton dissociation probability lead to the improvement of device performance due to the preferable ZnO dispersion. Compared to other methods of ZnO nanofilm fabrication, it is the more convenient, moderate, and effective to get a preferable ZnO buffer layer for high-efficiency organic solar cells.

Radio-frequency flexible and stretchable electronics: the need, challenges and opportunities

NASA Astrophysics Data System (ADS)

Jung, Yei Hwan; Seo, Jung-Hun; Zhang, Huilong; Lee, Juhwan; Cho, Sang June; Chang, Tzu-Hsuan; Ma, Zhenqiang

2017-05-01

Successful integration of ultrathin flexible or stretchable systems with new applications, such as medical devices and biodegradable electronics, have intrigued many researchers and industries around the globe to seek materials and processes to create high-performance, non-invasive and cost-effective electronics to match those of state-of-the-art devices. Nevertheless, the crucial concept of transmitting data or power wirelessly for such unconventional devices has been difficult to realize due to limitations of radio-frequency (RF) electronics in individual components that form a wireless circuitry, such as antenna, transmission line, active devices, passive devices etc. To overcome such challenges, these components must be developed in a step-by-step manner, as each component faces a number of different challenges in ultrathin formats. Here, we report on materials and design considerations for fabricating flexible and stretchable electronics systems that operate in the microwave level. High-speed flexible active devices, including cost effective Si-based strained MOSFETs, GaAs-based HBTs and GaN-based HEMTs, performing at multi-gigahertz frequencies are presented. Furthermore, flexible or stretchable passive devices, including capacitors, inductors and transmission lines that are vital parts of a microwave circuitry are also demonstrated. We also present unique applications using the presented flexible or stretchable RF components, including wearable RF electronics and biodegradable RF electronics, which were impossible to achieve using conventional rigid, wafer-based technology. Further opportunities like implantable systems exist utilizing such ultrathin RF components, which are discussed in this report as well.

Performance of an adjustable, threaded inertance tube

NASA Astrophysics Data System (ADS)

Zhou, W. J.; Pfotenhauer, J. M.; Nellis, G. F.; Liu, S. Y.

2015-12-01

The performance of the Stirling type pulse tube cryocooler depends strongly on the design of the inertance tube. The phase angle produced by the inertance tube is very sensitive to its diameter and length. Recent developments are reported here regarding an adjustable inertance device that can be adjusted in real time. The inertance passage is formed by the root of a concentric cylindrical threaded device. The depth of the threads installed on the outer screw varies. In this device, the outer screw can be rotated four and half turns. At the zero turn position the length of the passage is 1.74 m and the hydraulic diameter is 7 mm. By rotating the outer screw, the inner threaded rod engages with additional, larger depth threads. Therefore, at its upper limit of rotation, the inertance passage includes both the original 1.74 m length with 7mm hydraulic diameter plus an additional 1.86 m length with a 10 mm hydraulic diameter. A phase shift change of 24° has been experimentally measured by changing the position of outer screw while operating the device at a frequency of 60 Hz. This phase angle shift is less than the theoretically predicted value due to the presence of a relatively large leak through the thread clearance. Therefore, the distributed component model of the inertance tube was modified to account for the leak path causing the data to agree with the model. Further, the application of vacuum grease to the threads causes the performance of the device to improve substantially.

Quantitative experimental assessment of hot carrier-enhanced solar cells at room temperature

NASA Astrophysics Data System (ADS)

Nguyen, Dac-Trung; Lombez, Laurent; Gibelli, François; Boyer-Richard, Soline; Le Corre, Alain; Durand, Olivier; Guillemoles, Jean-François

2018-03-01

In common photovoltaic devices, the part of the incident energy above the absorption threshold quickly ends up as heat, which limits their maximum achievable efficiency to far below the thermodynamic limit for solar energy conversion. Conversely, the conversion of the excess kinetic energy of the photogenerated carriers into additional free energy would be sufficient to approach the thermodynamic limit. This is the principle of hot carrier devices. Unfortunately, such device operation in conditions relevant for utilization has never been evidenced. Here, we show that the quantitative thermodynamic study of the hot carrier population, with luminance measurements, allows us to discuss the hot carrier contribution to the solar cell performance. We demonstrate that the voltage and current can be enhanced in a semiconductor heterostructure due to the presence of the hot carrier population in a single InGaAsP quantum well at room temperature. These experimental results substantiate the potential of increasing photovoltaic performances in the hot carrier regime.

Review of Combustion-acoustic Instabilities

NASA Technical Reports Server (NTRS)

Oyediran, Ayo; Darling, Douglas; Radhakrishnan, Krishnan

1995-01-01

Combustion-acoustic instabilities occur when the acoustic energy increase due to the unsteady heat release of the flame is greater than the losses of acoustic energy from the system. The problem of combustion-acoustic instability is a concern in many devices for various reasons, as each device may have a unique mechanism causing unsteady heat release rates and many have unique boundary conditions. To accurately predict and quantify combustion-acoustic stabilities, the unsteady heat release rate and boundary conditions need to be accurately determined. The present review brings together work performed on a variety of practical combustion devices. Many theoretical and experimental investigations of the unsteady heat release rate have been performed, some based on perturbations in the fuel delivery system particularly for rocket instabilities, while others are based on hydrodynamic processes as in ramjet dump combustors. The boundary conditions for rocket engines have been analyzed and measured extensively. However, less work has been done to measure acoustic boundary conditions in many other combustion systems.

Ternary solution-processed organic solar cells incorporating 2D materials

NASA Astrophysics Data System (ADS)

Stylianakis, Minas M.; Konios, Dimitrios; Petridis, Constantinos; Kakavelakis, George; Stratakis, Emmanuel; Kymakis, Emmanuel

2017-12-01

Recently, the study of ternary organic solar cells (OSCs) has attracted the efforts of the scientific community, leading to significantly higher performance due to the enhanced harvesting of incoming irradiation. Here, for the first time, and in order to promote this OSC architecture, we review the progress implemented by the application of two-dimensional (2D) materials in the field of blend bulk heterojunction ternary OSCs. Power conversion efficiency (PCE) improvements of the order of 40% compared to the reference binary devices, and PCEs in excess of 8% have been reported by incorporating graphene-based or other 2D materials as a third element inside the active layer. These OSCs combine the synergetic advantages of ternary devices and the superb properties of the 2D material family. In conclusion, the incorporation of the unique properties of graphene and other 2D materials inside the active layer opens up a very promising pathway in the design and construction of high-performance, simply fabricated and low- cost photovoltaic devices.

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

NASA Astrophysics Data System (ADS)

Liu, Yu-Hsin; Yan, Lujiang; Zhang, Alex Ce; Hall, David; Niaz, Iftikhar Ahmad; Zhou, Yuchun; Sham, L. J.; Lo, Yu-Hwa

2015-08-01

Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanism based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.

Don't Mess with the NEST

NASA Astrophysics Data System (ADS)

Larson, Michael

2012-03-01

This presentation will describe the history of the Nuclear Emergency Support Team (NEST) and its evolution over the years. NEST was formed due to a number of nuclear extortion threats received in the early 1970s. From the beginning NEST developed an extensive exercise program to test and expand capabilities. The Nuclear Assessment Program (NAP) was developed, in part, to determine if NEST deployments were required. A major revamp of the NEST program occurred in 1994. Many other organizations work in conjunction with NEST in particular the FBI and DOD. Considerable research and development has been performed in the areas of Access, Search, Diagnostics, Device Assessment, and Disablement. Extensive searches of material appearing in the unclassified literature have been and are being performed to see what is being said about nuclear materials and devices. A comprehensive study of Improvised Nuclear Devices (IND) is ongoing to determine what a terrorist can and cannot do. NEST now consists of four phases with the latest additions of Phase III, Disposition and Phase IV, Nuclear Forensics. LLNL-ABS-521775

Is hexagonal boron nitride always good as a substrate for carbon nanotube-based devices?

PubMed

Kang, Seoung-Hun; Kim, Gunn; Kwon, Young-Kyun

2015-02-21

Hexagonal boron nitride sheets have been noted especially for their enhanced properties as substrates for sp(2) carbon-based nanodevices. To evaluate whether such enhanced properties would be retained under various realistic conditions, we investigate the structural and electronic properties of semiconducting carbon nanotubes on perfect and defective hexagonal boron nitride sheets under an external electric field as well as with a metal impurity, using density functional theory. We verify that the use of a perfect hexagonal boron nitride sheet as a substrate indeed improves the device performances of carbon nanotubes, compared with the use of conventional substrates such as SiO2. We further show that even the hexagonal boron nitride with some defects can show better performance as a substrate. Our calculations, on the other hand, also suggest that some defective boron nitride layers with a monovacancy and a nickel impurity could bring about poor device behavior since the imperfections impair electrical conductivity due to residual scattering under an applied electric field.

Printable Functional Chips Based on Nanoparticle Assembly.

PubMed

Huang, Yu; Li, Wenbo; Qin, Meng; Zhou, Haihua; Zhang, Xingye; Li, Fengyu; Song, Yanlin

2017-01-01

With facile manufacturability and modifiability, impressive nanoparticles (NPs) assembly applications were performed for functional patterned devices, which have attracted booming research attention due to their increasing applications in high-performance optical/electrical devices for sensing, electronics, displays, and catalysis. By virtue of easy and direct fabrication to desired patterns, high throughput, and low cost, NPs assembly printing is one of the most promising candidates for the manufacturing of functional micro-chips. In this review, an overview of the fabrications and applications of NPs patterned assembly by printing methods, including inkjet printing, lithography, imprinting, and extended printing techniques is presented. The assembly processes and mechanisms on various substrates with distinct wettabilities are deeply discussed and summarized. Via manipulating the droplet three phase contact line (TCL) pinning or slipping, the NPs contracted in ink are controllably assembled following the TCL, and generate novel functional chips and correlative integrate devices. Finally, the perspective of future developments and challenges is presented and widely exhibited. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of hollow corner retroreflectors for use in a synchronous orbit

NASA Technical Reports Server (NTRS)

Yoder, P. R., Jr.

1975-01-01

The performance of a hollow corner cube retroreflector made up of three mutually perpendicular optically flat mirrors when undergoing the thermal-mechanical strains induced by a spacecraft environment was studied. Of particular interest was a device of 200 square centimeter optical aperture used on a satellite in a synchronous orbit. It was assumed that the reflector always faces the earth. The effects of direct solar irradiance, earthshine, and albedo were considered. The results included the maximum mirror surface temperature during the orbit as well as the worst-case loss of optical performance due to thermally-induced mirror distortions. It was concluded that a device made of three suitably coated flat ULE mirrors, optically contacted to each other and supported mechanically in a nonrigid mount, would be expected to concentrate over 80 percent of the theoretical maximum energy in the central of the far field diffraction pattern. Continued development of the device through a detailed design, fabrication, and test phase was recommended.

Hybrid Perovskite/Perovskite Heterojunction Solar Cells.

PubMed

Hu, Yinghong; Schlipf, Johannes; Wussler, Michael; Petrus, Michiel L; Jaegermann, Wolfram; Bein, Thomas; Müller-Buschbaum, Peter; Docampo, Pablo

2016-06-28

Recently developed organic-inorganic hybrid perovskite solar cells combine low-cost fabrication and high power conversion efficiency. Advances in perovskite film optimization have led to an outstanding power conversion efficiency of more than 20%. Looking forward, shifting the focus toward new device architectures holds great potential to induce the next leap in device performance. Here, we demonstrate a perovskite/perovskite heterojunction solar cell. We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion efficiency due to reduced recombination losses, as well as improved moisture stability in the resulting photovoltaic devices.

A new adjustable parallel drill guide for internal fixation of femoral neck fracture: a developmental and experimental study.

PubMed

Yuenyongviwat, Varah; Tuntarattanapong, Pakjai; Tangtrakulwanich, Boonsin

2016-01-11

Internal fixation is one treatment for femoral neck fracture. Some devices and techniques reported improved accuracy and decreased fluoroscopic time. However, these are not widely used nowadays due to the lack of available special instruments and techniques. To improve the surgical procedure, the authors designed a new adjustable drill guide and tested the efficacy of the device. The authors developed a new adjustable drill guide for cannulated screw guide wire insertion for multiple screw fixation. Eight orthopaedic surgeons performed the experimental study to evaluate the efficacy of this device. Each surgeon performed guide wire insertion for multiple screw fixation in six synthetic femurs: three times with the new device and three times with the conventional technique. The fluoroscopic time, operative time and surgeon satisfaction were evaluated. In the operations with the new adjustable drill guide, the fluoroscopic and operative times were significantly lower than the operations with the conventional technique (p < 0.05). The mean score for the level of satisfaction of this device was also statistically significantly better (p = 0.02) than the conventional technique. The fluoroscopic and operative times with the new adjustable drill guide were reduced for multiple screw fixation of femoral neck fracture and the satisfaction of the surgeons was good.

Fiber optic tracheal detection device

NASA Astrophysics Data System (ADS)

Souhan, Brian E.; Nawn, Corinne D.; Shmel, Richard; Watts, Krista L.; Ingold, Kirk A.

2017-02-01

Poorly performed airway management procedures can lead to a wide variety of adverse events, such as laryngeal trauma, stenosis, cardiac arrest, hypoxemia, or death as in the case of failed airway management or intubation of the esophagus. Current methods for confirming tracheal placement, such as auscultation, direct visualization or capnography, may be subjective, compromised due to clinical presentation or require additional specialized equipment that is not always readily available during the procedure. Consequently, there exists a need for a non-visual detection mechanism for confirming successful airway placement that can give the provider rapid feedback during the procedure. Based upon our previously presented work characterizing the reflectance spectra of tracheal and esophageal tissue, we developed a fiber-optic prototype to detect the unique spectral characteristics of tracheal tissue. Device performance was tested by its ability to differentiate ex vivo samples of tracheal and esophageal tissue. Pig tissue samples were tested with the larynx, trachea and esophagus intact as well as excised and mounted on cork. The device positively detected tracheal tissue 18 out of 19 trials and 1 false positive out of 19 esophageal trials. Our proof of concept device shows great promise as a potential mechanism for rapid user feedback during airway management procedures to confirm tracheal placement. Ongoing studies will investigate device optimizations of the probe for more refined sensing and in vivo testing.

Functionalized Graphitic Carbon Nitride for Metal-free, Flexible and Rewritable Nonvolatile Memory Device via Direct Laser-Writing

NASA Astrophysics Data System (ADS)

Zhao, Fei; Cheng, Huhu; Hu, Yue; Song, Long; Zhang, Zhipan; Jiang, Lan; Qu, Liangti

2014-07-01

Graphitic carbon nitride nanosheet (g-C3N4-NS) has layered structure similar with graphene nanosheet and presents unusual physicochemical properties due to the s-triazine fragments. But their electronic and electrochemical applications are limited by the relatively poor conductivity. The current work provides the first example that atomically thick g-C3N4-NSs are the ideal candidate as the active insulator layer with tunable conductivity for achieving the high performance memory devices with electrical bistability. Unlike in conventional memory diodes, the g-C3N4-NSs based devices combined with graphene layer electrodes are flexible, metal-free and low cost. The functionalized g-C3N4-NSs exhibit desirable dispersibility and dielectricity which support the all-solution fabrication and high performance of the memory diodes. Moreover, the flexible memory diodes are conveniently fabricated through the fast laser writing process on graphene oxide/g-C3N4-NSs/graphene oxide thin film. The obtained devices not only have the nonvolatile electrical bistability with great retention and endurance, but also show the rewritable memory effect with a reliable ON/OFF ratio of up to 105, which is the highest among all the metal-free flexible memory diodes reported so far, and even higher than those of metal-containing devices.

A New Cuffless Device for Measuring Blood Pressure: A Real-Life Validation Study.

PubMed

Schoot, Tessa S; Weenk, Mariska; van de Belt, Tom H; Engelen, Lucien J L P G; van Goor, Harry; Bredie, Sebastian J H

2016-05-05

Cuffless blood pressure (BP) monitoring devices, based on pulse transit time, are being developed as an easy-to-use, more convenient, fast, and relatively cheap alternative to conventional BP measuring devices based on cuff occlusion. Thereby they may provide a great alternative to BP self-measurement. The objective of our study was to evaluate the performance of the first release of the Checkme Health Monitor (Viatom Technology), a cuffless BP monitor, in a real-life setting. Furthermore, we wanted to investigate whether the posture of the volunteer and the position of the device relative to the heart level would influence its outcomes. Study volunteers fell into 3 BP ranges: high (>160 mmHg), normal (130-160 mmHg), and low (<130 mmHg). All requirements for test environment, observer qualification, volunteer recruitment, and BP measurements were met according to the European Society of Hypertension International Protocol (ESH-IP) for the validation of BP measurement devices. After calibrating the Checkme device, we measured systolic BP with Checkme and a validated, oscillometric reference BP monitor (RM). Measurements were performed in randomized order both in supine and in sitting position, and with Checkme at and above heart level. We recruited 52 volunteers, of whom we excluded 15 (12 due to calibration failure with Checkme, 3 due to a variety of reasons). The remaining 37 volunteers were divided into low (n=14), medium (n=13), and high (n=10) BP ranges. There were 18 men and 19 women, with a mean age of 54.1 (SD 14.5) years, and mean recruitment systolic BP of 141.7 (SD 24.7) mmHg. BP results obtained by RM and Checkme correlated well. In the supine position, the difference between the RM and Checkme was >5 mmHg in 17 of 37 volunteers (46%), of whom 9 of 37 (24%) had a difference >10 mmHg and 5 of 37 (14%) had a difference >15 mmHg. BP obtained with Checkme correlated well with RM BP, particularly in the position (supine) in which the device was calibrated. These preliminary results are promising for conducting further research on cuffless BP measurement in the clinical and outpatient settings.

Magnetoresistive sensors based on the elasticity of domain walls.

PubMed

Zhang, Xueying; Vernier, Nicolas; Cao, Zhiqiang; Leng, Qunwen; Cao, Anni; Ravelosona, Dafine; Zhao, Weisheng

2018-06-19

Magnetic sensors based on the magnetoresistance effects have a promising application prospect due to their excellent sensitivity and advantages in terms of the integration. However, competition between higher sensitivity and larger measuring range remains a problem. Here, we propose a novel mechanism for the design of magnetoresistive sensors: probing the perpendicular field by detecting the expansion of the elastic magnetic Domain Wall (DW) in the free layer of a spin valve or a magnetic tunnel junction. Performances of devices based on this mechanism, such as the sensitivity and the measuring range can be tuned by manipulating the geometry of the device, without changing the intrinsic properties of the material, thus promising a higher integration level and a better performance. The mechanism is theoretically explained based on the experimental results. Two examples are proposed and their functionality and performances are verified via micromagnetic simulation. © 2018 IOP Publishing Ltd.

Performance characteristics of a nanoscale double-gate reconfigurable array

NASA Astrophysics Data System (ADS)

Beckett, Paul

2008-12-01

The double gate transistor is a promising device applicable to deep sub-micron design due to its inherent resistance to short-channel effects and superior subthreshold performance. Using both TCAD and SPICE circuit simulation, it is shown that the characteristics of fully depleted dual-gate thin-body Schottky barrier silicon transistors will not only uncouple the conflicting requirements of high performance and low standby power in digital logic, but will also allow the development of a locally-connected reconfigurable computing mesh. The magnitude of the threshold shift effect will scale with device dimensions and will remain compatible with oxide reliability constraints. A field-programmable architecture based on the double gate transistor is described in which the operating point of the circuit is biased via one gate while the other gate is used to form the logic array, such that complex heterogeneous computing functions may be developed from this homogeneous, mesh-connected organization.

Integration of a photonic crystal polarization beam splitter and waveguide bend.

PubMed

Zheng, Wanhua; Xing, Mingxin; Ren, Gang; Johnson, Steven G; Zhou, Wenjun; Chen, Wei; Chen, Lianghui

2009-05-11

In this work, we present the design of an integrated photonic-crystal polarization beam splitter (PC-PBS) and a low-loss photonic-crystal 60 degrees waveguide bend. Firstly, the modal properties of the PC-PBS and the mechanism of the low-loss waveguide bend are investigated by the two-dimensional finite-difference time-domain (FDTD) method, and then the integration of the two devices is studied. It shows that, although the individual devices perform well separately, the performance of the integrated circuit is poor due to the multi-mode property of the PC-PBS. By introducing deformed airhole structures, a single-mode PC-PBS is proposed, which significantly enhance the performance of the circuit with the extinction ratios remaining above 20 dB for both transverse-electric (TE) and transverse-magnetic (TM) polarizations. Both the specific result and the general idea of integration design are promising in the photonic crystal integrated circuits in the future.

CMOS compatible fabrication process of MEMS resonator for timing reference and sensing application

NASA Astrophysics Data System (ADS)

Huynh, Duc H.; Nguyen, Phuong D.; Nguyen, Thanh C.; Skafidas, Stan; Evans, Robin

2015-12-01

Frequency reference and timing control devices are ubiquitous in electronic applications. There is at least one resonator required for each of this device. Currently electromechanical resonators such as crystal resonator, ceramic resonator are the ultimate choices. This tendency will probably keep going for many more years. However, current market demands for small size, low power consumption, cheap and reliable products, has divulged many limitations of this type of resonators. They cannot be integrated into standard CMOS (Complement metaloxide- semiconductor) IC (Integrated Circuit) due to material and fabrication process incompatibility. Currently, these devices are off-chip and they require external circuitries to interface with the ICs. This configuration significantly increases the overall size and cost of the entire electronic system. In addition, extra external connection, especially at high frequency, will potentially create negative impacts on the performance of the entire system due to signal degradation and parasitic effects. Furthermore, due to off-chip packaging nature, these devices are quite expensive, particularly for high frequency and high quality factor devices. To address these issues, researchers have been intensively studying on an alternative for type of resonator by utilizing the new emerging MEMS (Micro-electro-mechanical systems) technology. Recent progress in this field has demonstrated a MEMS resonator with resonant frequency of 2.97 GHz and quality factor (measured in vacuum) of 42900. Despite this great achievement, this prototype is still far from being fully integrated into CMOS system due to incompatibility in fabrication process and its high series motional impedance. On the other hand, fully integrated MEMS resonator had been demonstrated but at lower frequency and quality factor. We propose a design and fabrication process for a low cost, high frequency and a high quality MEMS resonator, which can be integrated into a standard CMOS IC. This device is expected to operate in hundreds of Mhz frequency range; quality factor surpasses 10000 and series motional impedance low enough that could be matching into conventional system without enormous effort. This MEMS resonator can be used in the design of many blocks in wireless and RF (Radio Frequency) systems such as low phase noise oscillator, band pass filter, power amplifier and in many sensing application.

RSTensorFlow: GPU Enabled TensorFlow for Deep Learning on Commodity Android Devices

PubMed Central

Alzantot, Moustafa; Wang, Yingnan; Ren, Zhengshuang; Srivastava, Mani B.

2018-01-01

Mobile devices have become an essential part of our daily lives. By virtue of both their increasing computing power and the recent progress made in AI, mobile devices evolved to act as intelligent assistants in many tasks rather than a mere way of making phone calls. However, popular and commonly used tools and frameworks for machine intelligence are still lacking the ability to make proper use of the available heterogeneous computing resources on mobile devices. In this paper, we study the benefits of utilizing the heterogeneous (CPU and GPU) computing resources available on commodity android devices while running deep learning models. We leveraged the heterogeneous computing framework RenderScript to accelerate the execution of deep learning models on commodity Android devices. Our system is implemented as an extension to the popular open-source framework TensorFlow. By integrating our acceleration framework tightly into TensorFlow, machine learning engineers can now easily make benefit of the heterogeneous computing resources on mobile devices without the need of any extra tools. We evaluate our system on different android phones models to study the trade-offs of running different neural network operations on the GPU. We also compare the performance of running different models architectures such as convolutional and recurrent neural networks on CPU only vs using heterogeneous computing resources. Our result shows that although GPUs on the phones are capable of offering substantial performance gain in matrix multiplication on mobile devices. Therefore, models that involve multiplication of large matrices can run much faster (approx. 3 times faster in our experiments) due to GPU support. PMID:29629431

RSTensorFlow: GPU Enabled TensorFlow for Deep Learning on Commodity Android Devices.

PubMed

Alzantot, Moustafa; Wang, Yingnan; Ren, Zhengshuang; Srivastava, Mani B

2017-06-01

Mobile devices have become an essential part of our daily lives. By virtue of both their increasing computing power and the recent progress made in AI, mobile devices evolved to act as intelligent assistants in many tasks rather than a mere way of making phone calls. However, popular and commonly used tools and frameworks for machine intelligence are still lacking the ability to make proper use of the available heterogeneous computing resources on mobile devices. In this paper, we study the benefits of utilizing the heterogeneous (CPU and GPU) computing resources available on commodity android devices while running deep learning models. We leveraged the heterogeneous computing framework RenderScript to accelerate the execution of deep learning models on commodity Android devices. Our system is implemented as an extension to the popular open-source framework TensorFlow. By integrating our acceleration framework tightly into TensorFlow, machine learning engineers can now easily make benefit of the heterogeneous computing resources on mobile devices without the need of any extra tools. We evaluate our system on different android phones models to study the trade-offs of running different neural network operations on the GPU. We also compare the performance of running different models architectures such as convolutional and recurrent neural networks on CPU only vs using heterogeneous computing resources. Our result shows that although GPUs on the phones are capable of offering substantial performance gain in matrix multiplication on mobile devices. Therefore, models that involve multiplication of large matrices can run much faster (approx. 3 times faster in our experiments) due to GPU support.

High Performance Transparent Transistor Memory Devices Using Nano-Floating Gate of Polymer/ZnO Nanocomposites

NASA Astrophysics Data System (ADS)

Shih, Chien-Chung; Lee, Wen-Ya; Chiu, Yu-Cheng; Hsu, Han-Wen; Chang, Hsuan-Chun; Liu, Cheng-Liang; Chen, Wen-Chang

2016-02-01

Nano-floating gate memory devices (NFGM) using metal nanoparticles (NPs) covered with an insulating polymer have been considered as a promising electronic device for the next-generation nonvolatile organic memory applications NPs. However, the transparency of the device with metal NPs is restricted to 60~70% due to the light absorption in the visible region caused by the surface plasmon resonance effects of metal NPs. To address this issue, we demonstrate a novel NFGM using the blends of hole-trapping poly (9-(4-vinylphenyl) carbazole) (PVPK) and electron-trapping ZnO NPs as the charge storage element. The memory devices exhibited a remarkably programmable memory window up to 60 V during the program/erase operations, which was attributed to the trapping/detrapping of charge carriers in ZnO NPs/PVPK composite. Furthermore, the devices showed the long-term retention time (>105 s) and WRER test (>200 cycles), indicating excellent electrical reliability and stability. Additionally, the fabricated transistor memory devices exhibited a relatively high transparency of 90% at the wavelength of 500 nm based on the spray-coated PEDOT:PSS as electrode, suggesting high potential for transparent organic electronic memory devices.

Design of nanostructured-based glucose biosensors

NASA Astrophysics Data System (ADS)

Komirisetty, Archana; Williams, Frances; Pradhan, Aswini; Konda, Rajini B.; Dondapati, Hareesh; Samantaray, Diptirani

2012-04-01

This paper presents the design of glucose sensors that will be integrated with advanced nano-materials, bio-coatings and electronics to create novel devices that are highly sensitive, inexpensive, accurate, and reliable. In the work presented, a glucose biosensor and its fabrication process flow have been designed. The device is based on electrochemical sensing using a working electrode with bio-functionalized zinc oxide (ZnO) nano-rods. Among all metal oxide nanostructures, ZnO nano-materials play a significant role as a sensing element in biosensors due to their properties such as high isoelectric point (IEP), fast electron transfer, non-toxicity, biocompatibility, and chemical stability which are very crucial parameters to achieve high sensitivity. Amperometric enzyme electrodes based on glucose oxidase (GOx) are used due to their stability and high selectivity to glucose. The device also consists of silicon dioxide and titanium layers as well as platinum working and counter electrodes and a silver/silver chloride reference electrode. Currently, the biosensors are being fabricated using the process flow developed. Once completed, the sensors will be bio-functionalized and tested to characterize their performance, including their sensitivity and stability.

Comparison of microtweezers based on three lateral thermal actuator configurations

NASA Astrophysics Data System (ADS)

Luo, J. K.; Flewitt, A. J.; Spearing, S. M.; Fleck, N. A.; Milne, W. I.

2005-06-01

Thermal actuator-based microtweezers with three different driving configurations have been designed, fabricated and characterized. Finite element analysis has been used to model the device performance. It was found that one configuration of microtweezer, based on two lateral bimorph thermal actuators, has a small displacement (tip opening of the tweezers) and a very limited operating power range. An alternative configuration consisting of two horizontal hot bars with separated beams as the arms can deliver a larger displacement with a much-extended operating power range. This structure can withstand a higher temperature due to the wider beams used, and has flexible arms for increased displacement. Microtweezers driven by a number of chevron structures in parallel have similar maximum displacements but at a cost of higher power consumption. The measured temperature of the devices confirms that the device with the chevron structure can deliver the largest displacement for a given working temperature, while the bimorph thermal actuator design has the highest operating temperature at the same power due to its thin hot arm, and is prone to structural failure.

Bleeding with the artificial heart: Gastrointestinal hemorrhage in CF-LVAD patients.

PubMed

Gurvits, Grigoriy E; Fradkov, Elena

2017-06-14

Continuous-flow left ventricular assist devices (CF-LVADs) have significantly improved outcomes for patients with end-stage heart failure when used as a bridge to cardiac transplantation or, more recently, as destination therapy. However, its implantations carries a risk of complications including infection, device malfunction, arrhythmias, right ventricular failure, thromboembolic disease, postoperative and nonsurgical bleeding. A significant number of left ventricular assist devices (LVAD) recipients may experience recurrent gastrointestinal hemorrhage, mainly due to combination of antiplatelet and vitamin K antagonist therapy, activation of fibrinolytic pathway, acquired von Willebrand factor deficiency, and tendency to develop small intestinal angiodysplasias due to increased rotary speed of the pump. Gastrointestinal bleeding in LVAD patients remains a source of increased morbidity including the need for blood transfusions, extended hospital stays, multiple readmissions, and overall mortality. Management of gastrointestinal bleeding in LVAD patients involves multidisciplinary approach in stabilizing the patients, addressing risk factors and performing structured endoluminal evaluation with focus on upper gastrointestinal tract including jejunum to find and eradicate culprit lesion. Medical and procedural intervention is largely successful and universal bleeding cessation occurs in transplanted patients.

Facet-Specific Ligand Interactions on Ternary AgSbS 2 Colloidal Quantum Dots

DOE PAGES

Choi, Hyekyoung; Kim, Sungwoo; Luther, Joseph M.; ...

2017-11-07

Silver dimetal chalcogenide (Ag-V-VI 2) ternary quantum dots (QDs) are emerging lead-free materials for optoelectronic devices due to their NIR band gaps, large absorption coefficients, and superior electronic properties. However, thin film-based devices of the ternary QDs still lag behind due to the lack of understanding of the surface chemistry, compared to that of lead chalcogenide QDs even with the same crystal structure. Here in this paper, the surface ligand interactions of AgSbS 2 QDs, synthesized with 1-dodecanethiol used as a stabilizer, are studied. For nonpolar (1 0 0) surfaces, it is suggested that the thiolate ligands are associated withmore » the crystal lattices, thus preventing surface oxidation by protecting sulfur after air-exposure, as confirmed through optical and surface chemical analysis. Otherwise, silver rich (1 1 1) surfaces are passivated by thiolate ligands, allowing ligand exchange processes for the conductive films. This in-depth investigation of the surface chemistry of ternary QDs will prompt the performance enhancement of their optoelectronic devices.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newman, Jennifer; Clifton, Andrew; Bonin, Timothy

As wind turbine sizes increase and wind energy expands to more complex and remote sites, remote-sensing devices such as lidars are expected to play a key role in wind resource assessment and power performance testing. The switch to remote-sensing devices represents a paradigm shift in the way the wind industry typically obtains and interprets measurement data for wind energy. For example, the measurement techniques and sources of uncertainty for a remote-sensing device are vastly different from those associated with a cup anemometer on a meteorological tower. Current IEC standards for quantifying remote sensing device uncertainty for power performance testing considermore » uncertainty due to mounting, calibration, and classification of the remote sensing device, among other parameters. Values of the uncertainty are typically given as a function of the mean wind speed measured by a reference device and are generally fixed, leading to climatic uncertainty values that apply to the entire measurement campaign. However, real-world experience and a consideration of the fundamentals of the measurement process have shown that lidar performance is highly dependent on atmospheric conditions, such as wind shear, turbulence, and aerosol content. At present, these conditions are not directly incorporated into the estimated uncertainty of a lidar device. In this presentation, we describe the development of a new dynamic lidar uncertainty framework that adapts to current flow conditions and more accurately represents the actual uncertainty inherent in lidar measurements under different conditions. In this new framework, sources of uncertainty are identified for estimation of the line-of-sight wind speed and reconstruction of the three-dimensional wind field. These sources are then related to physical processes caused by the atmosphere and lidar operating conditions. The framework is applied to lidar data from a field measurement site to assess the ability of the framework to predict errors in lidar-measured wind speed. The results show how uncertainty varies over time and can be used to help select data with different levels of uncertainty for different applications, for example, low uncertainty data for power performance testing versus all data for plant performance monitoring.« less

Wafer-Scale Integration of Graphene-based Electronic, Optoelectronic and Electroacoustic Devices

PubMed Central

Tian, He; Yang, Yi; Xie, Dan; Cui, Ya-Long; Mi, Wen-Tian; Zhang, Yuegang; Ren, Tian-Ling

2014-01-01

In virtue of its superior properties, the graphene-based device has enormous potential to be a supplement or an alternative to the conventional silicon-based device in varies applications. However, the functionality of the graphene devices is still limited due to the restriction of the high cost, the low efficiency and the low quality of the graphene growth and patterning techniques. We proposed a simple one-step laser scribing fabrication method to integrate wafer-scale high-performance graphene-based in-plane transistors, photodetectors, and loudspeakers. The in-plane graphene transistors have a large on/off ratio up to 5.34. And the graphene photodetector arrays were achieved with photo responsivity as high as 0.32 A/W. The graphene loudspeakers realize wide-band sound generation from 1 to 50 kHz. These results demonstrated that the laser scribed graphene could be used for wafer-scale integration of a variety of graphene-based electronic, optoelectronic and electroacoustic devices. PMID:24398542

Identification of Bodies by Unique Serial Numbers on Implanted Medical Devices.

PubMed

Blessing, Melissa M; Lin, Peter T

2018-05-01

Visual identification is the most common identification method used by medical examiners but is not always possible. Alternative methods include X-ray, fingerprint, or DNA comparison, but these methods require additional resources. Comparison of serial numbers on implanted medical devices is a rapid and definitive method of identification. To assess the practicality of using this method, we reviewed 608 consecutive forensic autopsies performed at a regional medical examiner office. Of these, 56 cases required an alternative method of identification due to decomposition (n = 35), gunshot wound (n = 9), blunt trauma (n = 6), or charring (n = 6). Of these 56 cases, eight (14.3%) were known to have an implanted medical device. Of these eight cases, five (63%) could be positively identified by comparing serial numbers. If an implanted medical device is known to be present, and medical records are available, identification by medical device serial number should be a first-line method. © 2017 American Academy of Forensic Sciences.

Flexible Light Emission Diode Arrays Made of Transferred Si Microwires-ZnO Nanofilm with Piezo-Phototronic Effect Enhanced Lighting.

PubMed

Li, Xiaoyi; Liang, Renrong; Tao, Juan; Peng, Zhengchun; Xu, Qiming; Han, Xun; Wang, Xiandi; Wang, Chunfeng; Zhu, Jing; Pan, Caofeng; Wang, Zhong Lin

2017-04-25

Due to the fragility and the poor optoelectronic performances of Si, it is challenging and exciting to fabricate the Si-based flexible light-emitting diode (LED) array devices. Here, a flexible LED array device made of Si microwires-ZnO nanofilm, with the advantages of flexibility, stability, lightweight, and energy savings, is fabricated and can be used as a strain sensor to demonstrate the two-dimensional pressure distribution. Based on piezo-phototronic effect, the intensity of the flexible LED array can be increased more than 3 times (under 60 MPa compressive strains). Additionally, the device is stable and energy saving. The flexible device can still work well after 1000 bending cycles or 6 months placed in the atmosphere, and the power supplied to the flexible LED array is only 8% of the power of the surface-contact LED. The promising Si-based flexible device has wide range application and may revolutionize the technologies of flexible screens, touchpad technology, and smart skin.

Optimal placement of FACTS devices using optimization techniques: A review

NASA Astrophysics Data System (ADS)

Gaur, Dipesh; Mathew, Lini

2018-03-01

Modern power system is dealt with overloading problem especially transmission network which works on their maximum limit. Today’s power system network tends to become unstable and prone to collapse due to disturbances. Flexible AC Transmission system (FACTS) provides solution to problems like line overloading, voltage stability, losses, power flow etc. FACTS can play important role in improving static and dynamic performance of power system. FACTS devices need high initial investment. Therefore, FACTS location, type and their rating are vital and should be optimized to place in the network for maximum benefit. In this paper, different optimization methods like Particle Swarm Optimization (PSO), Genetic Algorithm (GA) etc. are discussed and compared for optimal location, type and rating of devices. FACTS devices such as Thyristor Controlled Series Compensator (TCSC), Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM) are considered here. Mentioned FACTS controllers effects on different IEEE bus network parameters like generation cost, active power loss, voltage stability etc. have been analyzed and compared among the devices.

Development of Deposition and Characterization Systems for Thin Film Solar Cells

NASA Astrophysics Data System (ADS)

Cimaroli, Alexander J.

Photovoltaic (PV) devices are becoming more important due to a number of economic and environmental factors. PV research relies on the ability to quickly fabricate and characterize these devices. While there are a number of deposition methods that are available in a laboratory setting, they are not necessarily able to be scaled to provide high throughput in a commercial setting. A close-space sublimation (CSS) system was developed to provide a means of depositing thin films in a very controlled and scalable manner. Its viability was explored by using it to deposit the absorber layer in Zn3P2 and CdTe solar cell devices. Excellent control over morphology and growth conditions and a high level of repeatability was demonstrated in the study of textured Zn3P2 thin films. However, some limitations imposed by the structure of Zn3P 2-based PV devices showed that CSS may not be the best approach for depositing Zn3P2 thin films. Despite the inability to make Zn3P2 solar cell devices, high efficiency CdTe solar cells were fabricated using CSS. With the introduction of Perovskite-based solar cell devices, the viability of data collected from conventional J-V measurements was questioned due to the J-V hysteresis that Perovskite devices exhibited. New methods of solar cell characterization were developed in order to accurately and quickly assess the performance of hysteretic PV devices. Both J-V measurements and steady-state efficiency measurements are prone to errors due to hysteresis and maximum power point drift. To resolve both of these issues, a maximum power point tracking (MPPT) system was developed with two algorithms: a simple algorithm and a predictive algorithm. The predictive algorithm showed increased resistance to the effects of hysteresis because of its ability to predict the steady-state current after a bias step with a double exponential decay model fit. Some publications have attempted to quantify the degree of J-V hysteresis present in fabricated Perovskite-based devices, but the analysis relied on J-V measurements. The sweep rate, starting bias, illumination time, etc. would affect the value of the calculated degree of hysteresis. A method of using transient photocurrent measurements is presented to accurately quantify the degree of hysteresis for all solar cells: not just Perovskite-based devices. According to this method, almost all solar cell devices exhibit several forms of J-V hysteresis. This method may open new ways of analyzing the defects in fabricated PV devices.

Natural Environment Illumination: Coherent Interactive Augmented Reality for Mobile and Non-Mobile Devices.

PubMed

Rohmer, Kai; Jendersie, Johannes; Grosch, Thorsten

2017-11-01

Augmented Reality offers many applications today, especially on mobile devices. Due to the lack of mobile hardware for illumination measurements, photorealistic rendering with consistent appearance of virtual objects is still an area of active research. In this paper, we present a full two-stage pipeline for environment acquisition and augmentation of live camera images using a mobile device with a depth sensor. We show how to directly work on a recorded 3D point cloud of the real environment containing high dynamic range color values. For unknown and automatically changing camera settings, a color compensation method is introduced. Based on this, we show photorealistic augmentations using variants of differential light simulation techniques. The presented methods are tailored for mobile devices and run at interactive frame rates. However, our methods are scalable to trade performance for quality and can produce quality renderings on desktop hardware.

Towards Efficient Spectral Converters through Materials Design for Luminescent Solar Devices.

PubMed

McKenna, Barry; Evans, Rachel C

2017-07-01

Single-junction photovoltaic devices exhibit a bottleneck in their efficiency due to incomplete or inefficient harvesting of photons in the low- or high-energy regions of the solar spectrum. Spectral converters can be used to convert solar photons into energies that are more effectively captured by the photovoltaic device through a photoluminescence process. Here, recent advances in the fields of luminescent solar concentration, luminescent downshifting, and upconversion are discussed. The focus is specifically on the role that materials science has to play in overcoming barriers in the optical performance in all spectral converters and on their successful integration with both established (e.g., c-Si, GaAs) and emerging (perovskite, organic, dye-sensitized) cell types. Current challenges and emerging research directions, which need to be addressed for the development of next-generation luminescent solar devices, are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymer-based actuators for virtual reality devices

NASA Astrophysics Data System (ADS)

Bolzmacher, Christian; Hafez, Moustapha; Benali Khoudja, Mohamed; Bernardoni, Paul; Dubowsky, Steven

2004-07-01

Virtual Reality (VR) is gaining more importance in our society. For many years, VR has been limited to the entertainment applications. Today, practical applications such as training and prototyping find a promising future in VR. Therefore there is an increasing demand for low-cost, lightweight haptic devices in virtual reality (VR) environment. Electroactive polymers seem to be a potential actuation technology that could satisfy these requirements. Dielectric polymers developed the past few years have shown large displacements (more than 300%). This feature makes them quite interesting for integration in haptic devices due to their muscle-like behaviour. Polymer actuators are flexible and lightweight as compared to traditional actuators. Using stacks with several layers of elatomeric film increase the force without limiting the output displacement. The paper discusses some design methods for a linear dielectric polymer actuator for VR devices. Experimental results of the actuator performance is presented.

Exploring the Short-Channel Characteristics of Asymmetric Junctionless Double-Gate Silicon-on-Nothing MOSFET

NASA Astrophysics Data System (ADS)

Saha, Priyanka; Banerjee, Pritha; Dash, Dinesh Kumar; Sarkar, Subir Kumar

2018-03-01

This paper presents an analytical model of an asymmetric junctionless double-gate (asymmetric DGJL) silicon-on-nothing metal-oxide-semiconductor field-effect transistor (MOSFET). Solving the 2-D Poisson's equation, the expressions for center potential and threshold voltage are calculated. In addition, the response of the device toward the various short-channel effects like hot carrier effect, drain-induced barrier lowering and threshold voltage roll-off has also been examined along with subthreshold swing and drain current characteristics. Performance analysis of the present model is also demonstrated by comparing its short-channel behavior with conventional DGJL MOSFET. The effect of variation of the device features due to the variation of device parameters is also studied. The simulated results obtained using 2D device simulator, namely ATLAS, are in good agreement with the analytical results, hence validating our derived model.

On the Efficacy of Isolating Shoulder and Elbow Movements with a Soft, Portable, and Wearable Robotic Device

NASA Technical Reports Server (NTRS)

Kadivar, Zahra; Beck, Christopher E.; Rovekamp, Roger N.; O'Malley, Marcia K.; Joyce, Charles A.

2016-01-01

Treatment intensity has a profound effect on motor recovery following neurological injury. The use of robotics has potential to automate these labor-intensive therapy procedures that are typically performed by physical therapists. Further, the use of wearable robotics offers an aspect of portability that may allow for rehabilitation outside the clinic. The authors have developed a soft, portable, lightweight upper extremity wearable robotic device to provide motor rehabilitation of patients with affected upper limbs due to traumatic brain injury (TBI). A key feature of the device demonstrated in this paper is the isolation of shoulder and elbow movements necessary for effective rehabilitation interventions. Herein is presented a feasibility study with one subject and demonstration of the device's ability to provide safe, comfortable, and controlled upper extremity movements. Moreover, it is shown that by decoupling shoulder and elbow motions, desired isolated joint actuation can be achieved.

Particle-in-Cell Modeling of Magnetron Sputtering Devices

NASA Astrophysics Data System (ADS)

Cary, John R.; Jenkins, T. G.; Crossette, N.; Stoltz, Peter H.; McGugan, J. M.

2017-10-01

In magnetron sputtering devices, ions arising from the interaction of magnetically trapped electrons with neutral background gas are accelerated via a negative voltage bias to strike a target cathode. Neutral atoms ejected from the target by such collisions then condense on neighboring material surfaces to form a thin coating of target material; a variety of industrial applications which require thin surface coatings are enabled by this plasma vapor deposition technique. In this poster we discuss efforts to simulate various magnetron sputtering devices using the Vorpal PIC code in 2D axisymmetric cylindrical geometry. Field solves are fully self-consistent, and discrete models for sputtering, secondary electron emission, and Monte Carlo collisions are included in the simulations. In addition, the simulated device can be coupled to an external feedback circuit. Erosion/deposition profiles and steady-state plasma parameters are obtained, and modifications due to self consistency are seen. Computational performance issues are also discussed. and Tech-X Corporation.

Performance analysis of SOI MOSFET with rectangular recessed channel

NASA Astrophysics Data System (ADS)

Singh, M.; Mishra, S.; Mohanty, S. S.; Mishra, G. P.

2016-03-01

In this paper a two dimensional (2D) rectangular recessed channel-silicon on insulator metal oxide semiconductor field effect transistor (RRC-SOI MOSFET), using the concept of groove between source and drain regions, which is one of the channel engineering technique to suppress the short channel effect (SCE). This suppression is mainly due to corner potential barrier of the groove and the simulation is carried out by using ATLAS 2D device simulator. To have further improvement of SCE in RRC-SOI MOSFET, three more devices are designed by using dual material gate (DMG) and gate dielectric technique, which results in formation of devices i.e. DMRRC-SOI,MLSMRRC-SOI, MLDMRRC-SOI MOSFET. The effect of different structures of RRC-SOI on AC and RF parameters are investigated and the importance of these devices over RRC MOSFET regarding short channel effect is analyzed.

Nanoelectronics: Opportunities for future space applications

NASA Technical Reports Server (NTRS)

Frazier, Gary

1995-01-01

Further improvements in the performance of integrated electronics will eventually halt due to practical fundamental limits on our ability to downsize transistors and interconnect wiring. Avoiding these limits requires a revolutionary approach to switching device technology and computing architecture. Nanoelectronics, the technology of exploiting physics on the nanometer scale for computation and communication, attempts to avoid conventional limits by developing new approaches to switching, circuitry, and system integration. This presentation overviews the basic principles that operate on the nanometer scale that can be assembled into practical devices and circuits. Quantum resonant tunneling (RT) is used as the center-piece of the overview since RT devices already operate at high temperature (120 degrees C) and can be scaled, in principle, to a few nanometers in semiconductors. Near- and long-term applications of GaAs and silicon quantum devices are suggested for signal and information processing, memory, optoelectronics, and radio frequency (RF) communication.

Impact of in-band interference on a wake-up radio system in wireless sensor networks

NASA Astrophysics Data System (ADS)

Lebreton, J. M.; Murad, N. M.; Lorion, R.

2017-05-01

The energy efficiency of Wireless Sensor Networks (WSNs) is considerably improved with Wake-up Radio (WuR) systems. However, their resilience to interference is often neglected in the literature. This might be an issue due to the proliferation of wireless devices and the growing field of internet of things. In this paper, we evaluate the impact of in-band interference from wireless devices on a WuR system. The approach proves that WuR systems are still performing well when coexisting with external wireless networks, even if the energy-efficiency is slightly reduced.

Temperature Dependence of Photoluminescence in InGaAs/InP Strained MQW Heterostructures

NASA Technical Reports Server (NTRS)

Raisky, O. Y.; Wang, W. B.; Alfano, R. R.; Reynolds, C. L., Jr.; Swaminathan, V.

1996-01-01

Multiple quantum well (MQW) InGaAsP/InP heterostructure systems have been drawn considerable research interest in recent years due to its suitability for long wavelength optoelectronic devices. The performance of such devices is strongly affected by peculiarities of recombination processes in the quantum wells (QW). The goal of this study was to investigate the effect of barrier width on the radiative recombination of carriers. In our study, the photoluminescence spectra from InGaAsP/lnP MQW double heterostructures have been measured in the 77-290 K temperature range with different excitation intensities.

A cross-stacked plasmonic nanowire network for high-contrast femtosecond optical switching.

PubMed

Lin, Yuanhai; Zhang, Xinping; Fang, Xiaohui; Liang, Shuyan

2016-01-21

We report an ultrafast optical switching device constructed by stacking two layers of gold nanowires into a perpendicularly crossed network, which works at a speed faster than 280 fs with an on/off modulation depth of about 22.4%. The two stacks play different roles in enhancing consistently the optical switching performance due to their different dependence on the polarization of optical electric fields. The cross-plasmon resonance based on the interaction between the perpendicularly stacked gold nanowires and its Fano-coupling with Rayleigh anomaly is the dominant mechanism for such a high-contrast optical switching device.

Multifunctional 2D- Materials: Selenides and Halides

NASA Technical Reports Server (NTRS)

Singh, N. B.; Su, Ching Hua; Arnold, Brad; Choa, Fow-Sen; Bohorfous, Sara

2016-01-01

Material is the key component and controls the performance of the detectors, devices and sensors. The materials design, processing, growth and fabrication of bulk and nanocrystals and fabrication into devices and sensors involve multidisciplinary team of experts. This places a large burden on the cost of the novel materials development. Due to this reason there is a big thrust for the prediction of multifunctionality of materials before design and development. Up to some extent design can achieve certain properties. In multinary materials processing is also a big factor. In this presentation, examples of two classes of industrially important materials will be described.

Graphene and Carbon Quantum Dot-Based Materials in Photovoltaic Devices: From Synthesis to Applications

PubMed Central

Paulo, Sofia; Palomares, Emilio; Martinez-Ferrero, Eugenia

2016-01-01

Graphene and carbon quantum dots have extraordinary optical and electrical features because of their quantum confinement properties. This makes them attractive materials for applications in photovoltaic devices (PV). Their versatility has led to their being used as light harvesting materials or selective contacts, either for holes or electrons, in silicon quantum dot, polymer or dye-sensitized solar cells. In this review, we summarize the most common uses of both types of semiconducting materials and highlight the significant advances made in recent years due to the influence that synthetic materials have on final performance. PMID:28335285

[Natural orifice trans-luminal endoscopic surgery (notes)--a new era in general surgery].

PubMed

Elazary, Ram; Horgan, Santiago; Talamini, Mark A; Rivkind, Avraham I; Mintz, Yoav

2008-10-01

Four years ago, a new surgical technique was presented, the natural orifice trans-luminal endoscopic surgery (NOTES). This technique provides an incisionless operation. The surgical devices are inserted into the peritoneal cavity through the gastrointestinal or the urogenital tracts. Today, a cholecystectomy can be performed using an advanced endoscope inserted through the stomach or the vagina. The advantages of NOTES are: reduced post operative pain, no hernias, no surgical wounds infections and better cosmetic results. The disadvantages are: difficulties in achieving safe enterotomy closure or a leak proof anastomosis, it necessitates performing more operations compared to open or laparoscopic operations in order to obtain the skills for performing these operations, and difficulties of acquiring satisfactory endoscopic vision due to lack of advanced technology. Several NOTES operations have already been performed in humans. However, many other surgical procedures were tested in laboratory animals. Development and improvement of surgical devices may promote this surgical modality in the future.

Recent Progress on Flexible and Wearable Supercapacitors.

PubMed

Xue, Qi; Sun, Jinfeng; Huang, Yan; Zhu, Minshen; Pei, Zengxia; Li, Hongfei; Wang, Yukun; Li, Na; Zhang, Haiyan; Zhi, Chunyi

2017-12-01

Recently, wearable electronic devices including electrical sensors, flexible displays, and health monitors have received considerable attention and experienced rapid progress. Wearable supercapacitors attract tremendous attention mainly due to their high stability, low cost, fast charging/discharging, and high efficiency; properties that render them value for developing fully flexible devices. In this Concept, the recent achievements and advances made in flexible and wearable supercapacitors are presented, especially highlighting the promising performances of yarn/fiber-shaped and planar supercapacitors. On the basis of their working mechanism, electrode materials including carbon-based materials, metal oxide-based materials, and conductive polymers with an emphasis on the performance-optimization method are introduced. The latest representative techniques and active materials of recently developed supercapacitors with superior performance are summarized. Furthermore, the designs of 1D and 2D electrodes are discussed according to their electrically conductive supporting materials. Finally, conclusions, challenges, and perspective in optimizing and developing the electrochemical performance and function of wearable supercapacitors for their practical utility are addressed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and properties of silicon nanowire devices

NASA Astrophysics Data System (ADS)

Byon, Kumhyo

Silicon nanowire (SiNW) is a very attractive one-dimensional material for future nanoelectronic applications. Reliable control of key field effect transistor (FET) parameters such as conductance, mobility, threshold voltage and on/off ratio is crucial to the applications of SiNW to working logic devices and integrated circuits. In this thesis, we fabricated silicon nanowire field effect transistors (SiNW FETs) and studied the dependence of their electrical transport properties upon various parameters including SiNW growth conditions, post-growth doping, and contact annealing. From these studies, we found how different processes control important FET characteristics. Key accomplishments of this thesis include p-channel enhancement mode FETs, n-channel FETs by post-growth vapor doping and high performance ambipolar devices. In the first part of this work, single crystalline SiNWs were synthesized by thermal evaporation without gold catalysts. FETs were fabricated using both as-grown SiNWs and post-growth n-doped SiNWs. FET from p-type source materials behaves as a p-channel enhancement mode FET which is predominant in logic devices due to its fast operation and low power consumption. Using bismuth vapor, the as-grown SiNWs were doped into n-type materials. The majority carriers in SiNWs can therefore be controlled by proper choice of the vapor phase dopant species. Post-growth doping using vapor phase is applicable to other nanowire systems. In the second part, high performance ambipolar FETs were fabricated. A two step annealing process was used to control the Schottky barrier between SiNW and metal contacts in order to enhance device performance. Initial p-channel SiNW FETs were converted into ambipolar SiNW FETs after contact annealing. Furthermore, significant increases in both on/off ratio and channel mobilities were achieved after contact annealing. Promising device structures to implement ambipolar devices into large scale integrated circuits were proposed. The contributions of this study are to further understanding of the electrical transport properties of SiNWs and to provide optimized processes to fabricate emerging high performance nanoelectronic devices using SiNWs for future generation beyond bulk silicon.

Direct Search for Low Mass Dark Matter Particles with CCDs

DOE PAGES

Barreto, J.; Cease, H.; Diehl, H. T.; ...

2012-05-15

A direct dark matter search is performed using fully-depleted high-resistivity CCD detectors. Due to their low electronic readout noise (RMS ~7 eV) these devices operate with a very low detection threshold of 40 eV, making the search for dark matter particles with low masses (~5 GeV) possible. The results of an engineering run performed in a shallow underground site are presented, demonstrating the potential of this technology in the low mass region.

Utility of point of care test devices for infectious disease testing of blood and oral fluid and application to rapid testing in the field

NASA Astrophysics Data System (ADS)

Lee, Stephen R.; Kardos, Keith W.; Yearwood, Graham D.; Guillon, Geraldine B.; Kurtz, Lisa A.; Mokkapati, Vijaya K.

2008-04-01

Rapid, point of care (POC) testing has been increasingly deployed as an aid in the diagnosis of infectious disease, due to its ability to deliver rapid, actionable results. In the case of HIV, a number of rapid test devices have been FDA approved and CLIA-waived in order to enable diagnosis of HIV infection outside of traditional laboratory settings. These settings include STD clinics, community outreach centers and mobile testing units, as well as identifying HIV infection among pregnant women and managing occupational exposure to infection. The OraQuick ® rapid test platform has been widely used to identify HIV in POC settings, due to its simplicity, ease of use and the ability to utilize oral fluid as an alternative specimen to blood. More recently, a rapid test for antibodies to hepatitis C virus (HCV) has been developed on the same test platform which uses serum, plasma, finger-stick blood, venous blood and oral fluid. Clinical testing using this POC test device has shown that performance is equivalent to state of the art, laboratory based tests. These devices may be suitable for rapid field testing of blood and other body fluids for the presence of infectious agents.

Design and simulation study of high frequency response for surface acoustic wave device by using CST software

NASA Astrophysics Data System (ADS)

Zakaria, M. R.; Hashim, U.; Amin, Mohd Hasrul I. M.; Ayub, R. Mat; Hashim, M. N.; Adam, T.

2015-05-01

This paper focuses on the enhancement and improvement of the Surface Acoustic Wave (SAW) device performance. Due to increased demand in the international market for biosensor product, the product must be emphasized in terms of quality. However, within the technological advances, demand for device with low cost, high efficiency and friendly-user preferred. Surface Acoustic Wave (SAW) device with the combination of pair electrode know as Interdigital Transducer (IDT) was fabricated on a piezoelectric substrate. The design of Interdigital Transducer (IDT) parameter is changes in several sizes and values for which it is able to provide greater efficiency in sensing sensitivity by using process simulation with CST STUDIO Suite software. In addition, Interdigital Transducer (IDT) parameters also changed to be created the products with a smaller size and easy to handle where it also reduces the cost of this product. Parameter values of an Interdigital Transducer (IDT) will be changed in the design is the total number of fingers pair, finger length, finger width and spacing, aperture and also the thickness of the Interdigital Transducer (IDT). From the result, the performance of the sensor is improved significantly after modification is done.

GaAs Photovoltaics on Polycrystalline Ge Substrates

NASA Technical Reports Server (NTRS)

Wilt, David M.; Pal, AnnaMaria T.; McNatt, Jeremiah S.; Wolford, David S.; Landis, Geoffrey A.; Smith, Mark A.; Scheiman, David; Jenkins, Phillip P.; McElroy Bruce

2007-01-01

High efficiency III-V multijunction solar cells deposited on metal foil or even polymer substrates can provide tremendous advantages in mass and stowage, particularly for planetary missions. As a first step towards that goal, poly-crystalline p/i/n GaAs solar cells are under development on polycrystalline Ge substrates. Organo Metallic Vapor Phase Epitaxy (OMVPE) parameters for pre-growth bake, nucleation and deposition have been examined. Single junction p/i/n GaAs photovoltaic devices, incorporating InGaP front and back window layers, have been grown and processed. Device performance has shown a dependence upon the thickness of a GaAs buffer layer deposited between the Ge substrate and the active device structure. A thick (2 m) GaAs buffer provides for both increased average device performance as well as reduced sensitivity to variations in grain size and orientation. Illumination under IR light (lambda > 1 micron), the cells showed a Voc, demonstrating the presence of an unintended photoactive junction at the GaAs/Ge interface. The presence of this junction limited the efficiency to approx.13% (estimated with an anti-refection coating) due to the current mismatch and lack of tunnel junction interconnect.

Unraveling the High Open Circuit Voltage and High Performance of Integrated Perovskite/Organic Bulk-Heterojunction Solar Cells.

PubMed

Dong, Shiqi; Liu, Yongsheng; Hong, Ziruo; Yao, Enping; Sun, Pengyu; Meng, Lei; Lin, Yuze; Huang, Jinsong; Li, Gang; Yang, Yang

2017-08-09

We have demonstrated high-performance integrated perovskite/bulk-heterojunction (BHJ) solar cells due to the low carrier recombination velocity, high open circuit voltage (V OC ), and increased light absorption ability in near-infrared (NIR) region of integrated devices. In particular, we find that the V OC of the integrated devices is dominated by (or pinned to) the perovskite cells, not the organic photovoltaic cells. A Quasi-Fermi Level Pinning Model was proposed to understand the working mechanism and the origin of the V OC of the integrated perovskite/BHJ solar cell, which following that of the perovskite solar cell and is much higher than that of the low bandgap polymer based organic BHJ solar cell. Evidence for the model was enhanced by examining the charge carrier behavior and photovoltaic behavior of the integrated devices under illumination of monochromatic light-emitting diodes at different characteristic wavelength. This finding shall pave an interesting possibility for integrated photovoltaic devices to harvest low energy photons in NIR region and further improve the current density without sacrificing V OC , thus providing new opportunities and significant implications for future industry applications of this kind of integrated solar cells.

A graphene based frequency quadrupler

NASA Astrophysics Data System (ADS)

Cheng, Chuantong; Huang, Beiju; Mao, Xurui; Zhang, Zanyun; Zhang, Zan; Geng, Zhaoxin; Xue, Ping; Chen, Hongda

2017-04-01

Benefit from exceptional electrical transport properties, graphene receives worldwide attentions, especially in the domain of high frequency electronics. Due to absence of effective bandgap causing off-state the device, graphene material is extraordinarily suitable for analog circuits rather than digital applications. With this unique ambipolar behavior, graphene can be exploited and utilized to achieve high performance for frequency multipliers. Here, dual-gated graphene field-effect transistors have been firstly used to achieve frequency quadrupling. Two Dirac points in the transfer curves of the designed GFETs can be observed by tuning top-gate voltages, which is essential to generate the fourth harmonic. By applying 200 kHz sinusoid input, arround 50% of the output signal radio frequency power is concentrated at the desired frequency of 800 kHz. Additionally, in suitable operation areas, our devices can work as high performance frequency doublers and frequency triplers. Considered both simple device structure and potential superhigh carrier mobility of graphene material, graphene-based frequency quadruplers may have lots of superiorities in regards to ultrahigh frequency electronic applications in near future. Moreover, versatility of carbon material system is far-reaching for realization of complementary metal-oxide-semiconductor compatible electrically active devices.

A Flexible High-Performance Photoimaging Device Based on Bioinspired Hierarchical Multiple-Patterned Plasmonic Nanostructures.

PubMed

Lee, Yoon Ho; Lee, Tae Kyung; Kim, Hongki; Song, Inho; Lee, Jiwon; Kang, Saewon; Ko, Hyunhyub; Kwak, Sang Kyu; Oh, Joon Hak

2018-03-01

In insect eyes, ommatidia with hierarchical structured cornea play a critical role in amplifying and transferring visual signals to the brain through optic nerves, enabling the perception of various visual signals. Here, inspired by the structure and functions of insect ommatidia, a flexible photoimaging device is reported that can simultaneously detect and record incoming photonic signals by vertically stacking an organic photodiode and resistive memory device. A single-layered, hierarchical multiple-patterned back reflector that can exhibit various plasmonic effects is incorporated into the organic photodiode. The multiple-patterned flexible organic photodiodes exhibit greatly enhanced photoresponsivity due to the increased light absorption in comparison with the flat systems. Moreover, the flexible photoimaging device shows a well-resolved spatiotemporal mapping of optical signals with excellent operational and mechanical stabilities at low driving voltages below half of the flat systems. Theoretical calculation and scanning near-field optical microscopy analyses clearly reveal that multiple-patterned electrodes have much stronger surface plasmon coupling than flat and single-patterned systems. The developed methodology provides a versatile and effective route for realizing high-performance optoelectronic and photonic systems. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Battery‐Supercapacitor Hybrid Devices: Recent Progress and Future Prospects

PubMed Central

Zuo, Wenhua; Li, Ruizhi; Zhou, Cheng; Xia, Jianlong

2017-01-01

Design and fabrication of electrochemical energy storage systems with both high energy and power densities as well as long cycling life is of great importance. As one of these systems, Battery‐supercapacitor hybrid device (BSH) is typically constructed with a high‐capacity battery‐type electrode and a high‐rate capacitive electrode, which has attracted enormous attention due to its potential applications in future electric vehicles, smart electric grids, and even miniaturized electronic/optoelectronic devices, etc. With proper design, BSH will provide unique advantages such as high performance, cheapness, safety, and environmental friendliness. This review first addresses the fundamental scientific principle, structure, and possible classification of BSHs, and then reviews the recent advances on various existing and emerging BSHs such as Li‐/Na‐ion BSHs, acidic/alkaline BSHs, BSH with redox electrolytes, and BSH with pseudocapacitive electrode, with the focus on materials and electrochemical performances. Furthermore, recent progresses in BSH devices with specific functionalities of flexibility and transparency, etc. will be highlighted. Finally, the future developing trends and directions as well as the challenges will also be discussed; especially, two conceptual BSHs with aqueous high voltage window and integrated 3D electrode/electrolyte architecture will be proposed. PMID:28725528

Effect of the substitution of F on the photoswitching behavior in single molecular device

NASA Astrophysics Data System (ADS)

Bian, Baoan; Zheng, Yapeng; Yuan, Peipei; Liao, Bin; Chen, Wei; An, Xiuhua; Mo, Xiaotong; Ding, Yuqiang

2017-09-01

We carry out first-principles calculations based on density functional theory and non-equilibrium Green's function to investigate the electronic transport properties of a 5-arylidenehydantoin molecule sandwiched between two Au electrodes. A reversible switching behavior between E and Z isomerization can be observed in the device through light irradiation, and their currents display different characteristic. Furthermore, it is found that the substitution of F in the molecule enlarges the switching ratio of device. The different characteristics of currents for E/Z forms and E/Z with the substitution of F are discussed by the transmission spectra and the molecular projected self-consistent Hamiltonian states. We discuss the change of Fermi level alignment due to the substitution of F, and the polarization effect under bias. We find the negative differential resistance effect in the E form with the substitution of F, which is explained by change of molecule-electrode coupling with the varied bias. The results suggest that the 5-arylidenehydantoin molecule with the substitution of F that improves the performance of device, becoming one of the methods for improving single molecular photoswitching performance in the future.

A graphene based frequency quadrupler

PubMed Central

Cheng, Chuantong; Huang, Beiju; Mao, Xurui; Zhang, Zanyun; Zhang, Zan; Geng, Zhaoxin; Xue, Ping; Chen, Hongda

2017-01-01

Benefit from exceptional electrical transport properties, graphene receives worldwide attentions, especially in the domain of high frequency electronics. Due to absence of effective bandgap causing off-state the device, graphene material is extraordinarily suitable for analog circuits rather than digital applications. With this unique ambipolar behavior, graphene can be exploited and utilized to achieve high performance for frequency multipliers. Here, dual-gated graphene field-effect transistors have been firstly used to achieve frequency quadrupling. Two Dirac points in the transfer curves of the designed GFETs can be observed by tuning top-gate voltages, which is essential to generate the fourth harmonic. By applying 200 kHz sinusoid input, arround 50% of the output signal radio frequency power is concentrated at the desired frequency of 800 kHz. Additionally, in suitable operation areas, our devices can work as high performance frequency doublers and frequency triplers. Considered both simple device structure and potential superhigh carrier mobility of graphene material, graphene-based frequency quadruplers may have lots of superiorities in regards to ultrahigh frequency electronic applications in near future. Moreover, versatility of carbon material system is far-reaching for realization of complementary metal-oxide-semiconductor compatible electrically active devices. PMID:28418013

Nanostructured manganese oxide thin films as electrode material for supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Hui; Lai, Man On; Lu, Li

2011-01-01

Electrochemical capacitors, also called supercapacitors, are alternative energy storage devices, particularly for applications requiring high power densities. Recently, manganese oxides have been extensively evaluated as electrode materials for supercapacitors due to their low cost, environmental benignity, and promising supercapacitive performance. In order to maximize the utilization of manganese oxides as the electrode material for the supercapacitors and improve their supercapacitive performance, the nanostructured manganese oxides have therefore been developed. This paper reviews the synthesis of the nanostructured manganese oxide thin films by different methods and the supercapacitive performance of different nanostructures.

Novel nano materials for high performance logic and memory devices

NASA Astrophysics Data System (ADS)

Das, Saptarshi

After decades of relentless progress, the silicon CMOS industry is approaching a stall in device performance for both logic and memory devices due to fundamental scaling limitations. In order to reinforce the accelerating pace, novel materials with unique properties are being proposed on an urgent basis. This list includes one dimensional nanotubes, quasi one dimensional nanowires, two dimensional atomistically thin layered materials like graphene, hexagonal boron nitride and the more recently the rich family of transition metal di-chalcogenides comprising of MoS2, WSe2, WS2 and many more for logic applications and organic and inorganic ferroelectrics, phase change materials and magnetic materials for memory applications. Only time will tell who will win, but exploring these novel materials allow us to revisit the fundamentals and strengthen our understanding which will ultimately be beneficial for high performance device design. While there has been growing interest in two-dimensional (2D) crystals other than graphene, evaluating their potential usefulness for electronic applications is still in its infancies due to the lack of a complete picture of their performance potential. The fact that the 2-D layered semiconducting di-chalcogenides need to be connected to the "outside" world in order to capitalize on their ultimate potential immediately emphasizes the importance of a thorough understanding of the contacts. This thesis demonstrate that through a proper understanding and design of source/drain contacts and the right choice of number of MoS2 layers the excellent intrinsic properties of this 2D material can be harvested. A comprehensive experimental study on the dependence of carrier mobility on the layer thickness of back gated multilayer MoS 2 field effect transistors is also provided. A resistor network model that comprises of Thomas-Fermi charge screening and interlayer coupling is used to explain the non-monotonic trend in the extracted field effect mobility with the layer thickness. The non-monotonic trend suggests that in order to harvest the maximum potential of MoS2 for high performance device applications, a layer thickness in the range of 6-12 nm would be ideal. Finally using scandium contacts on 10nm thick exfoliated MoS2 flakes that are covered by a 15nm ALD grown Al2O3 film, record high mobility of 700cm2/Vs is achieved at room-temperature which is extremely encouraging for the design of high performance logic devices. The destructive nature of the readout process in Ferroelectric Random Access Memories (FeRAMs) is one of the major limiting factors for their wide scale commercialization. Utilizing Ferroelectric Field-Effect Transistor RAM (FeTRAM) instead solves the destructive read out problem, but at the expense of introducing crystalline ferroelectrics that are hard to integrate into CMOS. In order to address these challenges a novel, fully functional, CMOS compatible, One-Transistor-One-Transistor (1T1T) memory cell architecture using an organic ferroelectric -- PVDF-TrFE -- as the memory storage unit (gate oxide) and a silicon nanowire as the memory read out unit (channel material) is proposed and experimentally demonstrated. While evaluating the scaling potential of the above mentioned organic FeTRAM, it is found that the switching time and switching voltage of this organic copolymer PVDF-TrFE exhibits an unexpected scaling behavior as a function of the lateral device dimensions. The phenomenological theory, that explains this abnormal scaling trend, involves in-plane interchain and intrachain interaction of the copolymer - resulting in a power-law dependence of the switching field on the device area (ESW alpha ACH0.1) that is ultimately responsible for the decrease in the switching time and switching voltage. These findings are encouraging since they indicate that scaling the switching voltage and switching time without aggressively scaling the copolymer thickness occurs naturally while scaling the device area -- in this way ultimately improving the packing density and leading towards high performance memory devices.

Growth and characterization of In1-xGaxAs/InAs0.65Sb0.35 strained layer superlattice infrared detectors

NASA Astrophysics Data System (ADS)

Ariyawansa, G.; Duran, J. M.; Reyner, C. J.; Steenbergen, E. H.; Yoon, N.; Wasserman, D.; Scheihing, J. E.

2017-02-01

Type-II strained layer superlattices (SLS) are an active research topic in the infrared detector community and applications for SLS detectors continue to grow. SLS detector technology has already reached the commercial market due to improvements in material quality, device design, and device fabrication. Despite this progress, the optimal superlattice design has not been established, and at various times has been believed to be InAs/GaSb, InAs/InGaSb, or InAs/InAsSb. Building on these, we investigate the properties of a new mid-wave infrared SLS material: InGaAs/InAsSb SLS. The ternary InGaAs/InAsSb SLS has three main advantages over other SLS designs: greater support for strain compensation, enhanced absorption due to increased electron-hole wavefunction overlap, and improved vertical hole mobility due to reduced hole effective mass. Here, we compare three ternary SLSs, with approximately the same bandgap (0.240 eV at 150 K), comprised of Ga fractions of 5%, 10%, and 20% to a reference sample with 0% Ga. Enhanced absorption is both theoretically predicted and experimentally realized. Furthermore, the characteristics of ternary SLS infrared detectors based on an nBn architecture are reported and exhibit nearly state-of-the-art dark current performance with minimal growth optimization. We report standard material and device characterization information, including dark current and external quantum efficiency, and provide further analysis that indicates improved quantum efficiency and vertical hole mobility. Finally, a 320×256 focal plane array built based on the In0.8Ga0.2As/InAs0.65Sb0.35 SLS design is demonstrated with promising performance.

Appdaptivity: An Internet of Things Device-Decoupled System for Portable Applications in Changing Contexts

PubMed Central

Díaz, Manuel; Rubio, Bartolomé; Van den Abeele, Floris

2018-01-01

Currently, applications in the Internet of Things (IoT) are tightly coupled to the underlying physical devices. As a consequence, upon adding a device, device replacement or user’s relocation to a different physical space, application developers have to re-perform installation and configuration processes to reconfigure applications, which bears costs in time and knowledge of low-level details. In the emerging IoT field, this issue is even more challenging due to its current unpredictable growth in term of applications and connected devices. In addition, IoT applications can be personalised to each end user and can be present in different environments. As a result, IoT scenarios are very changeable, presenting a challenge for IoT applications. In this paper we present Appdaptivity, a system that enables the development of portable device-decoupled applications that can be adapted to changing contexts. Through Appdaptivity, application developers can intuitively create portable and personalised applications, disengaging from the underlying physical infrastructure. Results confirms a good scalability of the system in terms of connected users and components involved. PMID:29701698

Implementation of light extraction improvements of GaN-based light-emitting diodes with specific textured sidewalls

NASA Astrophysics Data System (ADS)

Chen, Chun-Yen; Chen, Wei-Cheng; Chang, Ching-Hong; Lee, Yu-Lin; Liu, Wen-Chau

2018-05-01

Textured-sidewall GaN-based light-emitting diodes (LEDs) with various sidewall angles (15-90°) and convex or concave sidewalls prepared using an inductively-coupled-plasma approach are comprehensively fabricated and studied. The device with 45° sidewalls (Device F) and that with convex sidewalls (Device B) show significant improvements in optical properties. Experiments show that, at an injection current of 350 mA, the light output power, external quantum efficiency, wall-plug efficiency, and luminous flux of Device F (Device B) are greatly improved by 18.3% (18.2%), 18.2% (18.2%), 17.3% (19.8%), and 16.6% (18.4%), respectively, compared to those of a conventional LED with flat sidewalls. In addition, negligible degradation in electrical properties is found. The enhanced optical performance is mainly attributed to increased light extraction in the horizontal direction due to a significant reduction in total internal reflection at the textured sidewalls. Therefore, the reported specific textured-sidewall structures (Devices B and F) are promising for high-power GaN-based LED applications.

Appdaptivity: An Internet of Things Device-Decoupled System for Portable Applications in Changing Contexts.

PubMed

Martín, Cristian; Hoebeke, Jeroen; Rossey, Jen; Díaz, Manuel; Rubio, Bartolomé; Van den Abeele, Floris

2018-04-26

Currently, applications in the Internet of Things (IoT) are tightly coupled to the underlying physical devices. As a consequence, upon adding a device, device replacement or user’s relocation to a different physical space, application developers have to re-perform installation and configuration processes to reconfigure applications, which bears costs in time and knowledge of low-level details. In the emerging IoT field, this issue is even more challenging due to its current unpredictable growth in term of applications and connected devices. In addition, IoT applications can be personalised to each end user and can be present in different environments. As a result, IoT scenarios are very changeable, presenting a challenge for IoT applications. In this paper we present Appdaptivity, a system that enables the development of portable device-decoupled applications that can be adapted to changing contexts. Through Appdaptivity, application developers can intuitively create portable and personalised applications, disengaging from the underlying physical infrastructure. Results confirms a good scalability of the system in terms of connected users and components involved.

Metastability and reliability of CdTe solar cells

NASA Astrophysics Data System (ADS)

Guo, Da; Brinkman, Daniel; Shaik, Abdul R.; Ringhofer, Christian; Vasileska, Dragica

2018-04-01

Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. Manufacturers devote significant empirical efforts to study these phenomena and to improve semiconductor device stability. Still, understanding the underlying reasons of these instabilities remains clouded due to the lack of ability to characterize materials at atomistic levels and the lack of interpretation from the most fundamental material science. The most commonly alleged causes of metastability in CdTe devices, such as ‘migration of Cu’, have been investigated rigorously over the past fifteen years. Still, the discussion often ended prematurely with stating observed correlations between stress conditions and changes in atomic profiles of impurities or CV doping concentration. Multiple hypotheses suggesting degradation of CdTe solar cell devices due to interaction and evolution of point defects and complexes were proposed, and none of them received strong theoretical or experimental confirmation. It should be noted that atomic impurity profiles in CdTe provide very little intelligence on active doping concentrations. The same elements could form different energy states, which could be either donors or acceptors, depending on their position in crystalline lattice. Defects interact with other extrinsic and intrinsic defects; for example, changing the state of an impurity from an interstitial donor to a substitutional acceptor often is accompanied by generation of a compensating intrinsic interstitial donor defect. Moreover, all defects, intrinsic and extrinsic, interact with the electrical potential and free carriers so that charged defects may drift in the electric field and the local electrical potential affects the formation energy of the point defects. Such complexity of interactions in CdTe makes understanding of temporal changes in device performance even more challenging and a closed solution that can treat the entire system and its interactions is required.

Design of Amorphous Manganese Oxide@Multiwalled Carbon Nanotube Fiber for Robust Solid-State Supercapacitor.

PubMed

Shi, Peipei; Li, Li; Hua, Li; Qian, Qianqian; Wang, Pengfei; Zhou, Jinyuan; Sun, Gengzhi; Huang, Wei

2017-01-24

Solid-state fiber-based supercapacitors have been considered promising energy storage devices for wearable electronics due to their lightweight and amenability to be woven into textiles. Efforts have been made to fabricate a high performance fiber electrode by depositing pseudocapacitive materials on the outer surface of carbonaceous fiber, for example, crystalline manganese oxide/multiwalled carbon nanotubes (MnO 2 /MWCNTs). However, a key challenge remaining is to achieve high specific capacitance and energy density without compromising the high rate capability and cycling stability. In addition, amorphous MnO 2 is actually preferred due to its disordered structure and has been proven to exhibit superior electrochemical performance over the crystalline one. Herein, by incorporating amorphous MnO 2 onto a well-aligned MWCNT sheet followed by twisting, we design an amorphous MnO 2 @MWCNT fiber, in which amorphous MnO 2 nanoparticles are distributed in MWCNT fiber uniformly. The proposed structure gives the amorphous MnO 2 @MWCNT fiber good mechanical reliability, high electrical conductivity, and fast ion-diffusion. Solid-state supercapacitor based on amorphous MnO 2 @MWCNT fibers exhibits improved energy density, superior rate capability, exceptional cycling stability, and excellent flexibility. This study provides a strategy to design a high performance fiber electrode with microstructure control for wearable energy storage devices.

Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures.

PubMed

Liang, Xiaoguang; Shu, Lei; Lin, Hao; Fang, Ming; Zhang, Heng; Dong, Guofa; Yip, SenPo; Xiu, Fei; Ho, Johnny C

2016-09-27

Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices.

SSVEP-based BCI for manipulating three-dimensional contents and devices

NASA Astrophysics Data System (ADS)

Mun, Sungchul; Cho, Sungjin; Whang, Mincheol; Ju, Byeong-Kwon; Park, Min-Chul

2012-06-01

Brain Computer Interface (BCI) studies have been done to help people manipulate electronic devices in a 2D space but less has been done for a vigorous 3D environment. The purpose of this study was to investigate the possibility of applying Steady State Visual Evoked Potentials (SSVEPs) to a 3D LCD display. Eight subjects (4 females) ranging in age between 20 to 26 years old participated in the experiment. They performed simple navigation tasks on a simple 2D space and virtual environment with/without 3D flickers generated by a Flim-Type Patterned Retarder (FPR). The experiments were conducted in a counterbalanced order. The results showed that 3D stimuli enhanced BCI performance, but no significant effects were found due to the small number of subjects. Visual fatigue that might be evoked by 3D stimuli was negligible in this study. The proposed SSVEP BCI combined with 3D flickers can allow people to control home appliances and other equipment such as wheelchairs, prosthetics, and orthotics without encountering dangerous situations that may happen when using BCIs in real world. 3D stimuli-based SSVEP BCI would motivate people to use 3D displays and vitalize the 3D related industry due to its entertainment value and high performance.

Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures

PubMed Central

Liang, Xiaoguang; Shu, Lei; Lin, Hao; Fang, Ming; Zhang, Heng; Dong, Guofa; Yip, SenPo; Xiu, Fei; Ho, Johnny C.

2016-01-01

Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices. PMID:27671709

Mechanical Energy Harvesting Performance of Ferroelectric Polymer Nanowires Grown via Template‐Wetting

PubMed Central

Whiter, Richard A.; Boughey, Chess; Smith, Michael

2018-01-01

Abstract Nanowires of the ferroelectric co‐polymer poly(vinylidenefluoride‐co‐triufloroethylene) [P(VDF‐TrFE)] are fabricated from solution within nanoporous templates of both “hard” anodic aluminium oxide (AAO) and “soft” polyimide (PI) through a facile and scalable template‐wetting process. The confined geometry afforded by the pores of the templates leads directly to highly crystalline P(VDF‐TrFE) nanowires in a macroscopic “poled” state that precludes the need for external electrical poling procedure typically required for piezoelectric performance. The energy‐harvesting performance of nanogenerators based on these template‐grown nanowires are extensively studied and analyzed in combination with finite element modelling. Both experimental results and computational models probing the role of the templates in determining overall nanogenerator performance, including both materials and device efficiencies, are presented. It is found that although P(VDF‐TrFE) nanowires grown in PI templates exhibit a lower material efficiency due to lower crystallinity as compared to nanowires grown in AAO templates, the overall device efficiency was higher for the PI‐template‐based nanogenerator because of the lower stiffness of the PI template as compared to the AAO template. This work provides a clear framework to assess the energy conversion efficiency of template‐grown piezoelectric nanowires and paves the way towards optimization of template‐based nanogenerator devices.

Comparison of high-performance liquid chromatography and supercritical fluid chromatography using evaporative light scattering detection for the determination of plasticizers in medical devices.

PubMed

Lecoeur, Marie; Decaudin, Bertrand; Guillotin, Yoann; Sautou, Valérie; Vaccher, Claude

2015-10-23

Recently, interest in supercritical fluid chromatography (SFC) has increased due to its high throughput and the development of new system improving chromatographic performances. However, most papers dealt with fundamental studies and chiral applications and only few works described validation process of SFC method. Likewise, evaporative light scattering detection (ELSD) has been widely employed in liquid chromatography but only a few recent works presented its quantitative performances hyphenated with SFC apparatus. The present paper discusses about the quantitative performances of SFC-ELSD compared to HPLC-ELSD, for the determination of plasticizers (ATBC, DEHA, DEHT and TOTM) in PVC tubing used as medical devices. After the development of HPLC-ELSD, both methods were evaluated based on the total error approach using accuracy profile. The results show that HPLC-ELSD was more precise than SFC-ELSD but lower limits of quantitation were obtained by SFC. Hence, HPLC was validated in the ± 10% acceptance limits whereas SFC lacks of accuracy to quantify plasticizers. Finally, both methods were used to determine the composition of plasticized-PVC medical devices. Results demonstrated that SFC and HPLC both hyphenated with ELSD provided similar results. Copyright © 2015 Elsevier B.V. All rights reserved.

Highly conductive and flexible nano-structured carbon-based polymer nanocomposites with improved electromagnetic-interference-shielding performance

NASA Astrophysics Data System (ADS)

Mondal, Subhadip; Ghosh, Sabyasachi; Ganguly, Sayan; Das, Poushali; Ravindren, Revathy; Sit, Subhashis; Chakraborty, Goutam; Das, Narayan Ch

2017-10-01

Widespread usage and development of electrical/electronic devices can create severe problems for various other devices and in our everyday lives due to harmful exposure to electromagnetic (EM) radiation. Herein, we report on the electromagnetic interference (EMI)-shielding performance of highly flexible and conductive chlorinated polyethylene (CPE)/carbon nanofiber (CNF) nanocomposites fabricated by a probe-sonication-assisted simple solution-mixing process. The dispersion of CNF nanofillers inside the CPE matrix has been studied by electron micrographs. This dispersion is reflected in the formation of continuous conductive networks at a low percolation-threshold value of 2.87 wt% and promising EMI-shielding performance of 41.5 dB for 25 wt% CNF in the X-band frequency (8.2-12.4 GHz). Such an intriguing performance mainly depends on the unique filler-filler or filler-polymer networks in CPE nanocomposites. In addition, the composite material displays a superior EMI efficiency of 47.5 dB for 2.0 mm thickness at 8.2 GHz. However, we have been encouraged by the promotion of highly flexible and lightweight CPE/CNF nanocomposite as a superior EMI shield, which can protect electronic devices against harm caused by EM radiation and offers an adaptable solution in advanced EMI-shield applications.

Role of bond adaptability in the passivation of colloidal quantum dot solids.

PubMed

Thon, Susanna M; Ip, Alexander H; Voznyy, Oleksandr; Levina, Larissa; Kemp, Kyle W; Carey, Graham H; Masala, Silvia; Sargent, Edward H

2013-09-24

Colloidal quantum dot (CQD) solids are attractive materials for photovoltaic devices due to their low-cost solution-phase processing, high absorption cross sections, and their band gap tunability via the quantum size effect. Recent advances in CQD solar cell performance have relied on new surface passivation strategies. Specifically, cadmium cation passivation of surface chalcogen sites in PbS CQDs has been shown to contribute to lowered trap state densities and improved photovoltaic performance. Here we deploy a generalized solution-phase passivation strategy as a means to improving CQD surface management. We connect the effects of the choice of metal cation on solution-phase surface passivation, film-phase trap density of states, minority carrier mobility, and photovoltaic power conversion efficiency. We show that trap passivation and midgap density of states determine photovoltaic device performance and are strongly influenced by the choice of metal cation. Supported by density functional theory simulations, we propose a model for the role of cations, a picture wherein metals offering the shallowest electron affinities and the greatest adaptability in surface bonding configurations eliminate both deep and shallow traps effectively even in submonolayer amounts. This work illustrates the importance of materials choice in designing a flexible passivation strategy for optimum CQD device performance.

Engineering of Metal Oxide Nanoparticles for Application in Electrochemical Devices

NASA Astrophysics Data System (ADS)

Santos, Lidia Sofia Leitao

The growing demand for materials and devices with new functionalities led to the increased interest in the field of nanomaterials and nanotechnologies. Nanoparticles, not only present a reduced size as well as high reactivity, which allows the development of electronic and electrochemical devices with exclusive properties, when compared with thin films. This dissertation aims to explore the development of several nanostructured metal oxides by solvothermal synthesis and its application in different electrochemical devices. Within this broad theme, this study has a specific number of objectives: a) research of the influence of the synthesis parameters to the structure and morphology of the nanoparticles; b) improvement of the performance of the electrochromic devices with the application of the nanoparticles as electrode; c) application of the nanoparticles as probes to sensing devices; and d) production of solution-pro-cessed transistors with a nanostructured metal oxide semiconductor. Regarding the results, several conclusions can be exposed. Solvothermal synthesis shows to be a very versatile method to control the growth and morphology of the nanoparticles. The electrochromic device performance is influenced by the different structures and morphologies of WO3 nanoparticles, mainly due to the surface area and conductivity of the materials. The deposition of the electrochromic layer by inkjet printing allows the patterning of the electrodes without wasting material and without any additional steps. Nanostructured WO3 probes were produced by electrodeposition and drop casting and applied as pH sensor and biosensor, respectively. The good performance and sensitivity of the devices is explained by the high number of electrochemical reactions occurring at the surface of the na-noparticles. GIZO nanoparticles were deposited by spin coating and used in electrolyte-gated transistors, which promotes a good interface between the semiconductor and the dielectric. The produced transistors work at low potential and with improved ON-OFF current ratio, up to 6 orders of mag-nitude. To summarize, the low temperatures used in the production of the devices are compatible with flexible substrates and additionally, the low cost of the techniques involved can be adapted for disposable devices.

Ground Reaction Force and Mechanical Differences Between the Interim Resistive Exercise Device (iRED) and Smith Machine While Performing a Squat

NASA Technical Reports Server (NTRS)

Amonette, William E.; Bentley, Jason R.; Lee, Stuart M. C.; Loehr, James A.; Schneider, Suzanne

2004-01-01

Musculoskeletal unloading in microgravity has been shown to induce losses in bone mineral density, muscle cross-sectional area, and muscle strength. Currently, an Interim Resistive Exercise Device (iRED) is being flown on board the ISS to help counteract these losses. Free weight training has shown successful positive musculoskeletal adaptations. In biomechanical research, ground reaction forces (GRF) trajectories are used to define differences between exercise devices. The purpose of this evaluation is to quantify the differences in GRF between the iRED and free weight exercise performed on a Smith machine during a squat. Due to the differences in resistance properties, inertial loading and load application to the body between the two devices, we hypothesize that subjects using iRED will produce GRF that are significantly different from the Smith machine. There will be differences in bar/harness range of motion and the time when peak GRF occurred in the ROMbar. Three male subjects performed three sets of ten squats on the iRED and on the Smith Machine on two separate days at a 2-second cadence. Statistically significant differences were found between the two devices in all measured GRF variables. Average Fz and Fx during the Smith machine squat were significantly higher than iRED. Average Fy (16.82 plus or minus.23; p less than .043) was significantly lower during the Smith machine squat. The mean descent/ascent ratio of the magnitude of the resultant force vector of all three axes for the Smith machine and iRED was 0.95 and 0.72, respectively. Also, the point at which maximum Fz occurred in the range of motion (Dzpeak) was at different locations with the two devices.

Electronic device for endosurgical skills training (EDEST): study of reliability.

PubMed

Pagador, J B; Uson, J; Sánchez, M A; Moyano, J L; Moreno, J; Bustos, P; Mateos, J; Sánchez-Margallo, F M

2011-05-01

Minimally Invasive Surgery procedures are commonly used in many surgical practices, but surgeons need specific training models and devices due to its difficulty and complexity. In this paper, an innovative electronic device for endosurgical skills training (EDEST) is presented. A study on reliability for this device was performed. Different electronic components were used to compose this new training device. The EDEST was focused on two basic laparoscopic tasks: triangulation and coordination manoeuvres. A configuration and statistical software was developed to complement the functionality of the device. A calibration method was used to assure the proper work of the device. A total of 35 subjects (8 experts and 27 novices) were used to check the reliability of the system using the MTBF analysis. Configuration values for triangulation and coordination exercises were calculated as 0.5 s limit threshold and 800-11,000 lux range of light intensity, respectively. Zero errors in 1,050 executions (0%) for triangulation and 21 errors in 5,670 executions (0.37%) for coordination were obtained. A MTBF of 2.97 h was obtained. The results show that the reliability of the EDEST device is acceptable when used under previously defined light conditions. These results along with previous work could demonstrate that the EDEST device can help surgeons during first training stages.

Design and Fabrication of Ta filled microcavites in the delay paths of SAW devices for improved power transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richardson, Mandek; Sankaranarayanan, S. K. R. S.; Bhethanabotla, V. R.

2015-03-01

The authors report the design and fabrication of a surface acoustic wave (SAW) device with improved power transfer due to modification of its delay path. Typically, SAW delay-line devices suffer from relatively high insertion loss (IL) (similar to 10-30 dB). Our approach is to incorporate an array of microcavities, having square cross-sectional area (lambda/2 x lambda/2) and filled with tantalum, within the delay path to maximize acoustic confinement to the surface and reduce IL. To determine the effectiveness of the cavities without expending too many resources and to explain trends found in actual devices, a finite element model of amore » SAW device with tantalum filled cavities having various depths was utilized. For each depth simulated, IL was decreased compared to a standard SAW device. Microcavities 2.5 mu m deep filled with tantalum showed the best performance (Delta IL = 17.93 dB). To validate simulated results, the authors fabricated a SAW device on ST 90 degrees-X quartz with microcavities etched into its delay path using deep reactive ion etching and filled with tantalum. Measurement of fabricated devices showed inclusion of tantalum filled microcavities increased power transfer compared to a device without cavities. (C) 2015 American Vacuum Society.« less

Japanese Ubiquotous Network Project: Ubila

NASA Astrophysics Data System (ADS)

Ohashi, Masayoshi

Recently, the advent of sophisticated technologies has stimulated ambient paradigms that may include high-performance CPU, compact real-time operating systems, a variety of devices/sensors, low power and high-speed radio communications, and in particular, third generation mobile phones. In addition, due to the spread of broadband ccess networks, various ubiquitous terminals and sensors can be connected closely.

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals.

PubMed

Varghese, Tony; Hollar, Courtney; Richardson, Joseph; Kempf, Nicholas; Han, Chao; Gamarachchi, Pasindu; Estrada, David; Mehta, Rutvik J; Zhang, Yanliang

2016-09-12

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstrate a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm(2) with 60 °C temperature difference between the hot side and cold side. The highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varghese, Tony; Hollar, Courtney; Richardson, Joseph

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstratemore » a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm 2 with 60°C temperature difference between the hot side and cold side. In conclusion, the highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.« less

Electrical Performance and Reliability Improvement of Amorphous-Indium-Gallium-Zinc-Oxide Thin-Film Transistors with HfO₂ Gate Dielectrics by CF₄ Plasma Treatment.

PubMed

Fan, Ching-Lin; Tseng, Fan-Ping; Tseng, Chiao-Yuan

2018-05-17

In this work, amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) with a HfO₂ gate insulator and CF₄ plasma treatment was demonstrated for the first time. Through the plasma treatment, both the electrical performance and reliability of the a-IGZO TFT with HfO₂ gate dielectric were improved. The carrier mobility significantly increased by 80.8%, from 30.2 cm²/V∙s (without treatment) to 54.6 cm²/V∙s (with CF₄ plasma treatment), which is due to the incorporated fluorine not only providing an extra electron to the IGZO, but also passivating the interface trap density. In addition, the reliability of the a-IGZO TFT with HfO₂ gate dielectric has also been improved by the CF₄ plasma treatment. By applying the CF₄ plasma treatment to the a-IGZO TFT, the hysteresis effect of the device has been improved and the device's immunity against moisture from the ambient atmosphere has been enhanced. It is believed that the CF₄ plasma treatment not only significantly improves the electrical performance of a-IGZO TFT with HfO₂ gate dielectric, but also enhances the device's reliability.

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

DOE PAGES

Varghese, Tony; Hollar, Courtney; Richardson, Joseph; ...

2016-09-12

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstratemore » a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm 2 with 60°C temperature difference between the hot side and cold side. In conclusion, the highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.« less

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

PubMed Central

Varghese, Tony; Hollar, Courtney; Richardson, Joseph; Kempf, Nicholas; Han, Chao; Gamarachchi, Pasindu; Estrada, David; Mehta, Rutvik J.; Zhang, Yanliang

2016-01-01

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstrate a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm2 with 60 °C temperature difference between the hot side and cold side. The highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications. PMID:27615036

Hybrid Organic-Inorganic Perovskite Photodetectors.

PubMed

Tian, Wei; Zhou, Huanping; Li, Liang

2017-11-01

Hybrid organic-inorganic perovskite materials garner enormous attention for a wide range of optoelectronic devices. Due to their attractive optical and electrical properties including high optical absorption coefficient, high carrier mobility, and long carrier diffusion length, perovskites have opened up a great opportunity for high performance photodetectors. This review aims to give a comprehensive summary of the significant results on perovskite-based photodetectors, focusing on the relationship among the perovskite structures, device configurations, and photodetecting performances. An introduction of recent progress in various perovskite structure-based photodetectors is provided. The emphasis is placed on the correlation between the perovskite structure and the device performance. Next, recent developments of bandgap-tunable perovskite and hybrid photodetectors built from perovskite heterostructures are highlighted. Then, effective approaches to enhance the stability of perovskite photodetector are presented, followed by the introduction of flexible and self-powered perovskite photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. A comprehensive summary of the research status on perovskite photodetectors is hoped to push forward the development of this field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of 3D printing method for GRIN micro-optics devices

NASA Astrophysics Data System (ADS)

Wang, P. J.; Yeh, J. A.; Hsu, W. Y.; Cheng, Y. C.; Lee, W.; Wu, N. H.; Wu, C. Y.

2016-03-01

Conventional optical elements are based on either refractive or reflective optics theory to fulfill the design specifications via optics performance data. In refractive optical lenses, the refractive index of materials and radius of curvature of element surfaces determine the optical power and wavefront aberrations so that optical performance can be further optimized iteratively. Although gradient index (GRIN) phenomenon in optical materials is well studied for more than a half century, the optics theory in lens design via GRIN materials is still yet to be comprehensively investigated before realistic GRIN lenses are manufactured. In this paper, 3D printing method for manufacture of micro-optics devices with special features has been studied based on methods reported in the literatures. Due to the additive nature of the method, GRIN lenses in micro-optics devices seem to be readily achievable if a design methodology is available. First, derivation of ray-tracing formulae is introduced for all possible structures in GRIN lenses. Optics simulation program is employed for characterization of GRIN lenses with performance data given by aberration coefficients in Zernike polynomial. Finally, a proposed structure of 3D printing machine is described with conceptual illustration.

Selectivity Enhancement by Using Double-Layer MOX-Based Gas Sensors Prepared by Flame Spray Pyrolysis (FSP).

PubMed

Rebholz, Julia; Grossmann, Katharina; Pham, David; Pokhrel, Suman; Mädler, Lutz; Weimar, Udo; Barsan, Nicolae

2016-09-06

Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX)-based sensor device. Direct current (DC) electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of highly porous metal oxide double- and single-layer sensors obtained by flame spray pyrolysis. The results show that the calculated resistance ratios of the single- and double-layer sensors are a good indicator for the presence of specific gases in the atmosphere, and can constitute some building blocks for the development of chemical logic devices. Due to the inherent lack of selectivity of SMOX-based gas sensors, such devices could be especially relevant for domestic applications.

Selectivity Enhancement by Using Double-Layer MOX-Based Gas Sensors Prepared by Flame Spray Pyrolysis (FSP)

PubMed Central

Rebholz, Julia; Grossmann, Katharina; Pham, David; Pokhrel, Suman; Mädler, Lutz; Weimar, Udo; Barsan, Nicolae

2016-01-01

Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX)-based sensor device. Direct current (DC) electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of highly porous metal oxide double- and single-layer sensors obtained by flame spray pyrolysis. The results show that the calculated resistance ratios of the single- and double-layer sensors are a good indicator for the presence of specific gases in the atmosphere, and can constitute some building blocks for the development of chemical logic devices. Due to the inherent lack of selectivity of SMOX-based gas sensors, such devices could be especially relevant for domestic applications. PMID:27608028

Junctionless tri-gate InGaAs MOSFETs

NASA Astrophysics Data System (ADS)

Zota, Cezar B.; Borg, Mattias; Wernersson, Lars-Erik; Lind, Erik

2017-12-01

We demonstrate and characterize junctionless tri-gate InGaAs MOSFETs, fabricated using a simplified process with gate lengths down to L g = 25 nm at a nanowire dimension of 7 × 16 nm2. These devices use a single 7-nm-thick In0.80Ga0.20As (N D = 1 × 1019 cm-3) layer as both channel and contacts. The devices show SSsat = 76 mV/dec, peak g m = 1.6 mS/µm and I ON = 160 µA/µm (at I OFF = 100 nA/µm and V DD = 0.5 V), the latter which is the highest reported value for a junctionless FET. We also show that device performance is mainly limited by high parasitic access resistance due to the narrow and thin contact layer.

Trellis Tone Modulation Multiple-Access for Peer Discovery in D2D Networks

PubMed Central

Lim, Chiwoo; Kim, Sang-Hyo

2018-01-01

In this paper, a new non-orthogonal multiple-access scheme, trellis tone modulation multiple-access (TTMMA), is proposed for peer discovery of distributed device-to-device (D2D) communication. The range and capacity of discovery are important performance metrics in peer discovery. The proposed trellis tone modulation uses single-tone transmission and achieves a long discovery range due to its low Peak-to-Average Power Ratio (PAPR). The TTMMA also exploits non-orthogonal resource assignment to increase the discovery capacity. For the multi-user detection of superposed multiple-access signals, a message-passing algorithm with supplementary schemes are proposed. With TTMMA and its message-passing demodulation, approximately 1.5 times the number of devices are discovered compared to the conventional frequency division multiple-access (FDMA)-based discovery. PMID:29673167

Graphene nanopore devices for DNA sensing.

PubMed

Merchant, Chris A; Drndić, Marija

2012-01-01

We describe here a method for detecting the translocation of individual DNA molecules through nanopores created in graphene membranes. The devices consist of 1-5-nm thick graphene membranes with electron-beam sculpted nanopores from 5 to 10 nm in diameter. Due to the thin nature of the graphene membranes, and the reduced electrical resistance, we observe larger blocked currents than for traditional solid-state nanopores. We also show how ionic current noise levels can be reduced with the atomic-layer deposition of a few nanometers of titanium dioxide over the graphene surface. Unlike traditional solid-state nanopore materials that are insulating, graphene is an excellent electrical conductor, and its use opens the door to a new future class of nanopore devices in which electronic sensing and control is performed directly at the pore.

DNA translocation through graphene nanopores.

PubMed

Merchant, Christopher A; Healy, Ken; Wanunu, Meni; Ray, Vishva; Peterman, Neil; Bartel, John; Fischbein, Michael D; Venta, Kimberly; Luo, Zhengtang; Johnson, A T Charlie; Drndić, Marija

2010-08-11

We report on DNA translocations through nanopores created in graphene membranes. Devices consist of 1-5 nm thick graphene membranes with electron-beam sculpted nanopores from 5 to 10 nm in diameter. Due to the thin nature of the graphene membranes, we observe larger blocked currents than for traditional solid-state nanopores. However, ionic current noise levels are several orders of magnitude larger than those for silicon nitride nanopores. These fluctuations are reduced with the atomic-layer deposition of 5 nm of titanium dioxide over the device. Unlike traditional solid-state nanopore materials that are insulating, graphene is an excellent electrical conductor. Use of graphene as a membrane material opens the door to a new class of nanopore devices in which electronic sensing and control are performed directly at the pore.

Electronic Voltage and Current Transformers Testing Device

PubMed Central

Pan, Feng; Chen, Ruimin; Xiao, Yong; Sun, Weiming

2012-01-01

A method for testing electronic instrument transformers is described, including electronic voltage and current transformers (EVTs, ECTs) with both analog and digital outputs. A testing device prototype is developed. It is based on digital signal processing of the signals that are measured at the secondary outputs of the tested transformer and the reference transformer when the same excitation signal is fed to their primaries. The test that estimates the performance of the prototype has been carried out at the National Centre for High Voltage Measurement and the prototype is approved for testing transformers with precision class up to 0.2 at the industrial frequency (50 Hz or 60 Hz). The device is suitable for on-site testing due to its high accuracy, simple structure and low-cost hardware. PMID:22368510

Technological choices for mobile clinical applications.

PubMed

Ehrler, Frederic; Issom, David; Lovis, Christian

2011-01-01

The rise of cheaper and more powerful mobile devices make them a new and attractive platform for clinical applications. The interaction paradigm and portability of the device facilitates bedside human-machine interactions. The better accessibility to information and decision-support anywhere in the hospital improves the efficiency and the safety of care processes. In this study, we attempt to find out what are the most appropriate Operating System (OS) and Software Development Kit (SDK) to support the development of clinical applications on mobile devices. The Android platform is a Linux-based, open source platform that has many advantages. Two main SDKs are available on this platform: the native Android and the Adobe Flex SDK. Both of them have interesting features, but the latter has been preferred due its portability at comparable performance and ease of development.

Trellis Tone Modulation Multiple-Access for Peer Discovery in D2D Networks.

PubMed

Lim, Chiwoo; Jang, Min; Kim, Sang-Hyo

2018-04-17

In this paper, a new non-orthogonal multiple-access scheme, trellis tone modulation multiple-access (TTMMA), is proposed for peer discovery of distributed device-to-device (D2D) communication. The range and capacity of discovery are important performance metrics in peer discovery. The proposed trellis tone modulation uses single-tone transmission and achieves a long discovery range due to its low Peak-to-Average Power Ratio (PAPR). The TTMMA also exploits non-orthogonal resource assignment to increase the discovery capacity. For the multi-user detection of superposed multiple-access signals, a message-passing algorithm with supplementary schemes are proposed. With TTMMA and its message-passing demodulation, approximately 1.5 times the number of devices are discovered compared to the conventional frequency division multiple-access (FDMA)-based discovery.

Graphene/Pentacene Barristor with Ion-Gel Gate Dielectric: Flexible Ambipolar Transistor with High Mobility and On/Off Ratio.

PubMed

Oh, Gwangtaek; Kim, Jin-Soo; Jeon, Ji Hoon; Won, EunA; Son, Jong Wan; Lee, Duk Hyun; Kim, Cheol Kyeom; Jang, Jingon; Lee, Takhee; Park, Bae Ho

2015-07-28

High-quality channel layer is required for next-generation flexible electronic devices. Graphene is a good candidate due to its high carrier mobility and unique ambipolar transport characteristics but typically shows a low on/off ratio caused by gapless band structure. Popularly investigated organic semiconductors, such as pentacene, suffer from poor carrier mobility. Here, we propose a graphene/pentacene channel layer with high-k ion-gel gate dielectric. The graphene/pentacene device shows both high on/off ratio and carrier mobility as well as excellent mechanical flexibility. Most importantly, it reveals ambipolar behaviors and related negative differential resistance, which are controlled by external bias. Therefore, our graphene/pentacene barristor with ion-gel gate dielectric can offer various flexible device applications with high performances.

A multispectral, high-speed, low-cost device in the UV-MWIR spectral range

NASA Astrophysics Data System (ADS)

Svensson, Thomas; Lindell, Roland; Carlsson, Leif

2011-10-01

This paper presents the design and performance of a multispectral, high-speed, low-cost device. It is composed of six separate single element detectors covering the spectral range from UV to MWIR. Due to the wide spectral ranges of the detectors, these are used in conjunction with spectral filters. The device is a tool to spectrally and temporally resolve large field of view angularly integrated signatures from very fast events and get a total amplitude measure. One application has been to determine the maximal amplitude signal in muzzle flashes. Since the pulse width of a muzzle flash is on the order of 1 ms, a sensor with a bandwidth significantly higher than 1000 Hz is needed to resolve the flash. Examples from experimental trials are given.

Fabrication of three-dimensional hybrid nanostructure-embedded ITO and its application as a transparent electrode for high-efficiency solution processable organic photovoltaic devices.

PubMed

Kim, Jeong Won; Jeon, Hwan-Jin; Lee, Chang-Lyoul; Ahn, Chi Won

2017-03-02

Well-aligned, high-resolution (10 nm), three-dimensional (3D) hybrid nanostructures consisting of patterned cylinders and Au islands were fabricated on ITO substrates using an ion bombardment process and a tilted deposition process. The fabricated 3D hybrid nanostructure-embedded ITO maintained its excellent electrical and optical properties after applying a surface-structuring process. The solution processable organic photovoltaic device (SP-OPV) employing a 3D hybrid nanostructure-embedded ITO as the anode displayed a 10% enhancement in the photovoltaic performance compared to the photovoltaic device prepared using a flat ITO electrode, due to the improved charge collection (extraction and transport) efficiency as well as light absorbance by the photo-active layer.

Development of High-k Dielectric for Antimonides and a sub 350 degree Celsius III-V pMOSFET Outperforming Germanium

DTIC Science & Technology

2010-12-01

due to BTBT was observed in the surface channel device (Figure 23). Buried channel device moves the maximum E-field due to VGD in the WB cap (Figure...23(inset)) suppressing BTBT which might be the dominant component of IOFF in scaled devices [10]. Lastly, a 4.3% increase in ID was observed when...inset : SS with T). Fig. 21 : Temp Dependence of mobility. Fig. 23 :GIDL due to BTBT seen in surface channel device at 80K. Use of wide bandgap (WB

Enhanced electrical properties of oxide semiconductor thin-film transistors with high conductivity thin layer insertion for the channel region

NASA Astrophysics Data System (ADS)

Nguyen, Cam Phu Thi; Raja, Jayapal; Kim, Sunbo; Jang, Kyungsoo; Le, Anh Huy Tuan; Lee, Youn-Jung; Yi, Junsin

2017-02-01

This study examined the performance and the stability of indium tin zinc oxide (ITZO) thin film transistors (TFTs) by inserting an ultra-thin indium tin oxide (ITO) layer at the active/insulator interface. The electrical properties of the double channel device (ITO thickness of 5 nm) were improved in comparison with the single channel ITZO or ITO devices. The TFT characteristics of the device with an ITO thickness of less than 5 nm were degraded due to the formation of an island-like morphology and the carriers scattering at the active/insulator interface. The 5 nm-thick ITO inserted ITZO TFTs (optimal condition) exhibited a superior field effect mobility (∼95 cm2/V·s) compared with the ITZO-only TFTs (∼34 cm2/V·s). The best characteristics of the TFT devices with double channel layer are due to the lowest surface roughness (0.14 nm) and contact angle (50.1°) that result in the highest hydrophicility, and the most effective adhesion at the surface. Furthermore, the threshold voltage shifts for the ITO/ITZO double layer device decreased to 0.80 and -2.39 V compared with 6.10 and -6.79 V (for the ITZO only device) under positive and negative bias stress, respectively. The falling rates of EA were 0.38 eV/V and 0.54 eV/V for the ITZO and ITO/ITZO bi-layer devices, respectively. The faster falling rate of the double channel devices suggests that the trap density, including interface trap and semiconductor bulk trap, can be decreased by the ion insertion of a very thin ITO film into the ITZO/SiO2 reference device. These results demonstrate that the double active layer TFT can potentially be applied to the flat panel display.

Silicon Germanium Strained Layers and Heterostructures

NASA Astrophysics Data System (ADS)

Willander, M.; Nur, O.; Jain, S. C.

2004-01-01

The integration of strained-Si1 xGex into Si technology has enhanced the performance and extended the functionality of Si based circuits. The improvement of device performance is observed in both AC as well as DC characteristics of these devices. The category of such devices includes field effect as well as bipolar families. Speed performance in some based circuits has reached limits previously dominated by III-V heterostructures based devices. In addition, for some optoelectronics applications including photodetectors it is now possible to easily integrate strained-Si1 xGex based optical devices into standard Silicon technology. The impact of integrating strained and relaxed Si1 xGex alloys into Si technology is important. It has lead to stimulate Si research as well as offers easy options for performances that requires very complicated and costly process if pure Si has to be used. In this paper we start by discussing the strain and stability of Si1 xGex alloys. The origin and the process responsible for transient enhanced diffusion (TED) in highly doped Si containing layers will be mentioned. Due to the importance of TED for thin highly doped Boron strained-Si1 xGex layers and its degrading consequences, possible suppression design methods will be presented. Quantum well pchannel MOSFETs (QW-PMOSFETs) based on thin buried QW are solution to the low speed and weak current derivability. Different aspects of designing these devices for a better performance are briefly reviewed. Other FETs based on tensile strained Si on relaxed Si1 xGex for n-channel and modulation doped field effect transistors (MODFETs) showed excellent performance. Record AC performance well above 200GHz for fmax is already observed and this record is expected to increase in the coming years. Heterojunction bipolar transistors (HPTs) with thin strained-Si1 xGex highly doped base have lead to optimize the performance of the bipolar technology for many applications easily. The strategies of design and the most important designs of HBTs for optimum AC as well as DC are discussed in details. This technology is now mature enough and that is manifested in the appearance in the market nowadays. Si1 xGex based FETs circuits compatible with standard Si CMOS processes are soon expected to appear in the market. Finally, we briefly discuss the recent advances in Si1 xGex based infrared photodetectors.

Flashing characters with famous faces improves ERP-based brain-computer interface performance

NASA Astrophysics Data System (ADS)

Kaufmann, T.; Schulz, S. M.; Grünzinger, C.; Kübler, A.

2011-10-01

Currently, the event-related potential (ERP)-based spelling device, often referred to as P300-Speller, is the most commonly used brain-computer interface (BCI) for enhancing communication of patients with impaired speech or motor function. Among numerous improvements, a most central feature has received little attention, namely optimizing the stimulus used for eliciting ERPs. Therefore we compared P300-Speller performance with the standard stimulus (flashing characters) against performance with stimuli known for eliciting particularly strong ERPs due to their psychological salience, i.e. flashing familiar faces transparently superimposed on characters. Our results not only indicate remarkably increased ERPs in response to familiar faces but also improved P300-Speller performance due to a significant reduction of stimulus sequences needed for correct character classification. These findings demonstrate a promising new approach for improving the speed and thus fluency of BCI-enhanced communication with the widely used P300-Speller.

Gate length scaling optimization of FinFETs

NASA Astrophysics Data System (ADS)

Chen, Shoumian; Shang, Enming; Hu, Shaojian

2018-06-01

This paper introduces a device performance optimization approach for the FinFET through optimization of the gate length. As a result of reducing the gate length, the leakage current (Ioff) increases, and consequently, the stress along the channel enhances which leads to an increase in the drive current (Isat) of the PMOS. In order to sustain Ioff, work function is adjusted to offset the effect of the increased stress. Changing the gate length of the transistor yields different drive currents when the leakage current is fixed by adjusting the work function. For a given device, an optimal gate length is found to provide the highest drive current. As an example, for a standard performance device with Ioff = 1 nA/um, the best performance Isat = 856 uA/um is at L = 34 nm for 14 nm FinFET and Isat = 1130 uA/um at L = 21 nm for 7 nm FinFET. A 7 nm FinFET will exhibit performance boost of 32% comparing with 14 nm FinFET. However, applying the same method to a 5 nm FinFET, the performance boosting is out of expectance comparing to the 7 nm FinFET, which is due to the severe short-channel-effect and the exhausted channel stress in the FinFET.

Evolution and update on current devices for prosthetic breast reconstruction

PubMed Central

2015-01-01

Over the past decade, the leading breast reconstruction modality has shifted from autologous tissue to implants. This trend reversal is multi-factorial but includes increasing bilateral mastectomies and the more widespread acceptance of implants due to stringent quality and safety regulatory surveillance by the US Food and Drug Administration (FDA). Since 2012, the US FDA has approved several new implant styles, shapes and textures, increasing the choices for patients and surgeons. Predictable, superior aesthetic results after prosthetic breast reconstruction are attainable, but require thoughtful planning, precise surgical technique and appropriate device selection based on several different patient and surgeon parameters, such as patient desires, body mass index, breast shape, mastectomy flap quality and tissue based bio-dimensional assessment. This article briefly reviews historic devices used in prosthetic breast reconstruction beginning in the 1960s through the modern generation devices used today. We reflect on the rigorous hurdles endured over the last several decades leading to the approval of silicone gel devices, along with their well-established safety and efficacy. The various implant characteristics can affect feel and performance of the device. The many different styles and features of implants and expanders are described emphasizing surgical indications, advantages and disadvantages of each device. PMID:26005642

Analysis of higher harmonics on bidirectional heat pulse propagation experiment in helical and tokamak plasmas

NASA Astrophysics Data System (ADS)

Kobayashi, T.; Ida, K.; Inagaki, S.; Tsuchiya, H.; Tamura, N.; Choe, G. H.; Yun, G. S.; Park, H. K.; Ko, W. H.; Evans, T. E.; Austin, M. E.; Shafer, M. W.; Ono, M.; López-bruna, D.; Ochando, M. A.; Estrada, T.; Hidalgo, C.; Moon, C.; Igami, H.; Yoshimura, Y.; Tsujimura, T. Ii.; Itoh, S.-I.; Itoh, K.

2017-07-01

In this contribution we analyze modulation electron cyclotron resonance heating (MECH) experiment and discuss higher harmonic frequency dependence of transport coefficients. We use the bidirectional heat pulse propagation method, in which both inward propagating heat pulse and outward propagating heat pulse are analyzed at a radial range, in order to distinguish frequency dependence of transport coefficients due to hysteresis from that due to other reasons, such as radially dependent transport coefficients, a finite damping term, or boundary effects. The method is applied to MECH experiments performed in various helical and tokamak devices, i.e. Large Helical Device (LHD), TJ-II, Korea Superconducting Tokamak Advanced Research (KSTAR), and Doublet III-D (DIII-D) with different plasma conditions. The frequency dependence of transport coefficients are clearly observed, showing a possibility of existence of transport hysteresis in flux-gradient relation.

Titanium-based, fenestrated, in-plane microneedles for passive ocular drug delivery.

PubMed

Khandan, Omid; Famili, Amin; Kahook, Malik Y; Rao, Masaru P

2012-01-01

Drug delivery to the eye remains a key challenge, due to limitations inherent to prevailing delivery techniques. For example, while topical delivery offers simplicity and safety, its efficacy is often limited by poor bioavailability, due to natural transport barriers and clearance mechanisms. Similarly, while intravitreal injections performed across the ocular tunic provide means for circumventing such limitations, non-negligible potential for retinal detachment and other complications adversely affects safety. Herein, we discuss our initial efforts to address these limitations through development of titanium-based microneedles (MNs) which seek to provide a safer, simpler, and more efficacious means of ocular drug delivery. Devices with in-plane geometry and through-thickness fenestrations that serve as drug reservoirs for passive delivery via diffusive transport from fast-dissolving coatings are demonstrated. Details regarding device design, fabrication, and mechanical testing are presented, as are results from preliminary coating characterization and insertion testing in ex vivo rabbit cornea.

Transport and breakdown analysis for improved figure-of-merit for AlGaN power devices

NASA Astrophysics Data System (ADS)

Coltrin, Michael E.; Kaplar, Robert J.

2017-02-01

Mobility and critical electric field for bulk AlxGa1-xN alloys across the full composition range (0 ≤ x ≤ 1) are analyzed to address the potential application of this material system for power electronics. Calculation of the temperature-dependent electron mobility includes the potential limitations due to different scattering mechanisms, including alloy, optical polar phonon, deformation potential, and piezoelectric scattering. The commonly used unipolar figure of merit (appropriate for vertical-device architectures), which increases strongly with increasing mobility and critical electric field, is examined across the alloy composition range to estimate the potential performance in power electronics applications. Alloy scattering is the dominant limitation to mobility and thus also for the unipolar figure of merit. However, at higher alloy compositions, the limitations due to alloy scattering are overcome by increased critical electric field. These trade-offs, and their temperature dependence, are quantified in the analysis.

Technical feasibility of personalized articulating knee joint distraction for treatment of tibiofemoral osteoarthritis.

PubMed

Struik, T; Jaspers, J E N; Besselink, N J; van Roermund, P M; Plomp, S; Rudert, M J; Lafeber, F P J G; Mastbergen, S C

2017-11-01

Knee osteoarthritis is a highly prevalent degenerative joint disorder characterized by joint tissue damage and pain. Knee joint distraction has been introduced as a joint preserving surgical procedure to postpone knee arthroplasty. An often used standard externally fixation device for distraction poses a burden to patients due to the absence of joint flexion during the 6weeks treatment. Therefore, a personalized articulating distraction device was developed. The aim of this study was to test technical feasibility of this device. Based on an often applied rigid device, using equal bone pin positions and connectors, a hinge mechanism was developed consisting of a cam-following system for reproducing the complex joint-specific knee kinematics. In support, a device was developed for capturing the joint-specific sagittal plane articulation. The obtained kinematic data were translated into joint-specific cam shapes that were installed bilaterally in the hinge mechanism of the distraction device, as such providing personalized knee motion. Distraction of 5mm was performed within a range of motion of 30deg. joint flexion. Pre-clinical evaluation of the working principle was performed on human cadaveric legs and system stiffness characteristics were biomechanically evaluated. The desired range of motion was obtained and distraction was maintained under physiologically representative loading. Moreover, the joint-specific approach demonstrated tolerance of deviations from anatomical and alignment origin during initial placement of the developed distraction device. Articulation during knee distraction is considered technically feasible and has potential to decrease burden and improve acceptance of distraction therapy. Testing of clinical feasibility is warranted. Copyright © 2017 Elsevier Ltd. All rights reserved.

Turning a cylindrical treadmill with feet: an MR-compatible device for assessment of the neural correlates of lower-limb movement.

PubMed

Toyomura, Akira; Yokosawa, Koichi; Shimojo, Atsushi; Fujii, Tetsunoshin; Kuriki, Shinya

2018-06-17

Locomotion, which is one of the most basic motor functions, is critical for performing various daily-life activities. Despite its essential function, assessment of brain activity during lower-limb movement is still limited because of the constraints of existing brain imaging methods. Here, we describe an MR-compatible, cylindrical treadmill device that allows participants to perform stepping movements on an MRI scanner table. The device was constructed from wood and all of the parts were handmade by the authors. We confirmed the MR-compatibility of the device by evaluating the temporal signal-to-noise ratio of 64 voxels of a phantom during scanning. Brain activity was measured while twenty participants turned the treadmill with feet in sync with metronome sounds. The rotary speed of the cylinder was encoded by optical fibers. The post/pre-central gyrus and cerebellum showed significant activity during the movements, which was comparable to the activity patterns reported in previous studies. Head movement on the y- and z-axes was influenced more by lower-limb movement than was head movement on the x-axis. Among the 60 runs (3 runs × 20 participants), head movement during two of the runs (3.3%) was excessive due to the lower-limb movement. Compared to MR-compatible devices proposed in the previous studies, the advantage of this device may be simple structure and replicability to realize stepping movement with a supine position. Collectively, our results suggest that the treadmill device is useful for evaluating lower-limb-related neural activity. Copyright © 2018. Published by Elsevier B.V.

Achieving high performance polymer optoelectronic devices for high efficiency, long lifetime and low fabrication cost

NASA Astrophysics Data System (ADS)

Huang, Jinsong

This thesis described three types of organic optoelectronic devices: polymer light emitting diodes (PLED), polymer photovoltaic solar cell, and organic photo detector. The research in this work focuses improving their performance including device efficiency, operation lifetime simplifying fabrication process. With further understanding in PLED device physics, we come up new device operation model and improved device architecture design. This new method is closely related to understanding of the science and physics at organic/metal oxide and metal oxide/metal interface. In our new device design, both material and interface are considered in order to confine and balance all injected carriers, which has been demonstrated very be successful in increasing device efficiency. We created two world records in device efficiency: 18 lm/W for white emission fluorescence PLED, 22 lm/W for red emission phosphorescence PLED. Slow solvent drying process has been demonstrated to significantly increase device efficiency in poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C 61-butyric acid methyl ester (PCBM) mixture polymer solar cell. From the mobility study by time of flight, the increase of efficiency can be well correlated to the improved carrier transport property due to P3HT crystallization during slow solvent drying. And it is found that, similar to PLED, balanced carrier mobility is essential in high efficient polymer solar cell. There is also a revolution in our device fabrication method. A unique device fabrication method is presented by an electronic glue based lamination process combined with interface modification as a one-step polymer solar cell fabrication process. It can completely skip the thermal evaporation process, and benefit device lifetime by several merits: no air reactive. The device obtained is metal free, semi-transparent, flexible, self-encapsulated, and comparable efficiency with that by regular method. We found the photomultiplication (PM) phenomenon in C60 based device accidentally. The high PM factor makes it good candidate for photo detector. The high gain was assigned to the trapped-charge induced enhanced-injection at C60/PEDOT:PSS interface.

Nanometer-scale oxide thin film transistor with potential for high-density image sensor applications.

PubMed

Jeon, Sanghun; Park, Sungho; Song, Ihun; Hur, Ji-Hyun; Park, Jaechul; Kim, Hojung; Kim, Sunil; Kim, Sangwook; Yin, Huaxiang; Chung, U-In; Lee, Eunha; Kim, Changjung

2011-01-01

The integration of electronically active oxide components onto silicon circuits represents an innovative approach to improving the functionality of novel devices. Like most semiconductor devices, complementary-metal-oxide-semiconductor image sensors (CISs) have physical limitations when progressively scaled down to extremely small dimensions. In this paper, we propose a novel hybrid CIS architecture that is based on the combination of nanometer-scale amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) and a conventional Si photo diode (PD). With this approach, we aim to overcome the loss of quantum efficiency and image quality due to the continuous miniaturization of PDs. Specifically, the a-IGZO TFT with 180 nm gate length is probed to exhibit remarkable performance including low 1/f noise and high output gain, despite fabrication temperatures as low as 200 °C. In particular, excellent device performance is achieved using a double-layer gate dielectric (Al₂O₃/SiO₂) combined with a trapezoidal active region formed by a tailored etching process. A self-aligned top gate structure is adopted to ensure low parasitic capacitance. Lastly, three-dimensional (3D) process simulation tools are employed to optimize the four-pixel CIS structure. The results demonstrate how our stacked hybrid device could be the starting point for new device strategies in image sensor architectures. Furthermore, we expect the proposed approach to be applicable to a wide range of micro- and nanoelectronic devices and systems.

Spring-action Apparatus for Fixation of Eyeball (SAFE): a novel, cost-effective yet simple device for ophthalmic wet-lab training.

PubMed

Ramakrishnan, Seema; Baskaran, Prabu; Fazal, Romana; Sulaiman, Syed Mohammad; Krishnan, Tiruvengada; Venkatesh, Rengaraj

2016-10-01

Achieving a formed and firm eyeball which is stably fixed in a holding device is a major challenge of surgical wet-lab training. Our innovation, the 'Spring-action Apparatus for Fixation of Eyeball (SAFE)' is a robust, simple and economical device to solve this problem. It consists of a hollow iron cylinder to which a spring-action syringe is attached. The spring-action syringe generates vacuum and enables reliable fixation of a human or animal cadaveric eye on the iron cylinder. The rise in intraocular pressure due to vacuum fixation can be varied as per need or nature of surgery being practised. A mask-fixed version of this device is also designed to train surgeons for appropriate hand positioning. An experienced surgeon performed various surgeries including manual small incision cataract surgery (MSICS), phacoemulsification, laser in situ keratomileusis (LASIK), femtosecond LASIK docking, Descemet's stripping endothelial keratoplasty, deep anterior lamellar keratoplasty, penetrating keratoplasty and trabeculectomy on this device, while a trainee surgeon practised MSICS and wound suturing. Skill-appropriate comfort level was much higher with SAFE than with conventional globe holders for both surgeons. Due to its stability, pressure adjustability, portability, cost-efficiency and simplicity, we recommend SAFE as the basic equipment for every wet lab. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

A design of Si-based nanoplasmonic structure as an antenna and reception amplifier for visible light communication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, J. H.; Lin, Z. Y.; Liu, P.

2014-10-21

Visible light communication has been widely investigated due to its larger bandwidth and higher bit rate, and it can combine with the indoor illumination system that makes it more convenient to carry out. Receiving and processing the visible light signal on chip request for nanophotonics devices performing well. However, conventional optical device cannot be used for light-on-chip integration at subwavelength dimensions due to the diffraction limit. Herein, we propose a design of Si-based nanoplasmonic structure as an antenna and reception amplifier for visible light communication based on the interaction between Si nanoparticle and Au nanorod. This device integrates the uniquemore » scattering property of high-refractive index dielectric Si nanoparticles, whose scattering spectrum is dependent on the particle size, with the localized surface plasmon resonance of Au nanorod. We calculated the spectra collected by plane detector and near field distribution of nanostructure, and theoretically demonstrate that the proposed device can act as good receiver, amplifier and superlens during the visible light signal receiving and processing. Besides, unlike some other designs of nanoantenna devices focused less on how to detect the signals, our hybrid nanoantenna can realize the transfer between the scattering source and the detector effectively by Au nanorod waveguides. These findings suggest that the designed nanoplasmonic structure is expected to be used in on-chip nanophotonics as antenna, spectral splitter and demultiplexer for visible light communication.« less

BlueDetect: An iBeacon-Enabled Scheme for Accurate and Energy-Efficient Indoor-Outdoor Detection and Seamless Location-Based Service

PubMed Central

Zou, Han; Jiang, Hao; Luo, Yiwen; Zhu, Jianjie; Lu, Xiaoxuan; Xie, Lihua

2016-01-01

The location and contextual status (indoor or outdoor) is fundamental and critical information for upper-layer applications, such as activity recognition and location-based services (LBS) for individuals. In addition, optimizations of building management systems (BMS), such as the pre-cooling or heating process of the air-conditioning system according to the human traffic entering or exiting a building, can utilize the information, as well. The emerging mobile devices, which are equipped with various sensors, become a feasible and flexible platform to perform indoor-outdoor (IO) detection. However, power-hungry sensors, such as GPS and WiFi, should be used with caution due to the constrained battery storage on mobile device. We propose BlueDetect: an accurate, fast response and energy-efficient scheme for IO detection and seamless LBS running on the mobile device based on the emerging low-power iBeacon technology. By leveraging the on-broad Bluetooth module and our proposed algorithms, BlueDetect provides a precise IO detection service that can turn on/off on-board power-hungry sensors smartly and automatically, optimize their performances and reduce the power consumption of mobile devices simultaneously. Moreover, seamless positioning and navigation services can be realized by it, especially in a semi-outdoor environment, which cannot be achieved by GPS or an indoor positioning system (IPS) easily. We prototype BlueDetect on Android mobile devices and evaluate its performance comprehensively. The experimental results have validated the superiority of BlueDetect in terms of IO detection accuracy, localization accuracy and energy consumption. PMID:26907295

Performance analysis of a miniature turbine generator for intracorporeal energy harvesting.

PubMed

Pfenniger, Alois; Vogel, Rolf; Koch, Volker M; Jonsson, Magnus

2014-05-01

Replacement intervals of implantable medical devices are commonly dictated by battery life. Therefore, intracorporeal energy harvesting has the potential to reduce the number of surgical interventions by extending the life cycle of active devices. Given the accumulated experience with intravascular devices such as stents, heart valves, and cardiac assist devices, the idea to harvest a small fraction of the hydraulic energy available in the cardiovascular circulation is revisited. The aim of this article is to explore the technical feasibility of harvesting 1 mW electric power using a miniature hydrodynamic turbine powered by about 1% of the cardiac output flow in a peripheral artery. To this end, numerical modelling of the fluid mechanics and experimental verification of the overall performance of a 1:1 scale friction turbine are performed in vitro. The numerical flow model is validated for a range of turbine configurations and flow conditions (up to 250 mL/min) in terms of hydromechanic efficiency; up to 15% could be achieved with the nonoptimized configurations of the study. Although this article does not entail the clinical feasibility of intravascular turbines in terms of hemocompatibility and impact on the circulatory system, the numerical model does provide first estimates of the mechanical shear forces relevant to blood trauma and platelet activation. It is concluded that the time-integrated shear stress exposure is significantly lower than in cardiac assist devices due to lower flow velocities and predominantly laminar flow. Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Development of SiC Large Tapered Crystal Growth

NASA Technical Reports Server (NTRS)

Neudeck, Phil

2010-01-01

Majority of very large potential benefits of wide band gap semiconductor power electronics have NOT been realized due in large part to high cost and high defect density of commercial wafers. Despite 20 years of development, present SiC wafer growth approach is yet to deliver majority of SiC's inherent performance and cost benefits to power systems. Commercial SiC power devices are significantly de-rated in order to function reliably due to the adverse effects of SiC crystal dislocation defects (thousands per sq cm) in the SiC wafer.

Aluminium alloyed iron-silicide/silicon solar cells: A simple approach for low cost environmental-friendly photovoltaic technology.

PubMed

Kumar Dalapati, Goutam; Masudy-Panah, Saeid; Kumar, Avishek; Cheh Tan, Cheng; Ru Tan, Hui; Chi, Dongzhi

2015-12-03

This work demonstrates the fabrication of silicide/silicon based solar cell towards the development of low cost and environmental friendly photovoltaic technology. A heterostructure solar cells using metallic alpha phase (α-phase) aluminum alloyed iron silicide (FeSi(Al)) on n-type silicon is fabricated with an efficiency of 0.8%. The fabricated device has an open circuit voltage and fill-factor of 240 mV and 60%, respectively. Performance of the device was improved by about 7 fold to 5.1% through the interface engineering. The α-phase FeSi(Al)/silicon solar cell devices have promising photovoltaic characteristic with an open circuit voltage, short-circuit current and a fill factor (FF) of 425 mV, 18.5 mA/cm(2), and 64%, respectively. The significant improvement of α-phase FeSi(Al)/n-Si solar cells is due to the formation p(+-)n homojunction through the formation of re-grown crystalline silicon layer (~5-10 nm) at the silicide/silicon interface. Thickness of the regrown silicon layer is crucial for the silicide/silicon based photovoltaic devices. Performance of the α-FeSi(Al)/n-Si solar cells significantly depends on the thickness of α-FeSi(Al) layer and process temperature during the device fabrication. This study will open up new opportunities for the Si based photovoltaic technology using a simple, sustainable, and los cost method.

Functionalized Graphitic Carbon Nitride for Metal-free, Flexible and Rewritable Nonvolatile Memory Device via Direct Laser-Writing

PubMed Central

Zhao, Fei; Cheng, Huhu; Hu, Yue; Song, Long; Zhang, Zhipan; Jiang, Lan; Qu, Liangti

2014-01-01

Graphitic carbon nitride nanosheet (g-C3N4-NS) has layered structure similar with graphene nanosheet and presents unusual physicochemical properties due to the s-triazine fragments. But their electronic and electrochemical applications are limited by the relatively poor conductivity. The current work provides the first example that atomically thick g-C3N4-NSs are the ideal candidate as the active insulator layer with tunable conductivity for achieving the high performance memory devices with electrical bistability. Unlike in conventional memory diodes, the g-C3N4-NSs based devices combined with graphene layer electrodes are flexible, metal-free and low cost. The functionalized g-C3N4-NSs exhibit desirable dispersibility and dielectricity which support the all-solution fabrication and high performance of the memory diodes. Moreover, the flexible memory diodes are conveniently fabricated through the fast laser writing process on graphene oxide/g-C3N4-NSs/graphene oxide thin film. The obtained devices not only have the nonvolatile electrical bistability with great retention and endurance, but also show the rewritable memory effect with a reliable ON/OFF ratio of up to 105, which is the highest among all the metal-free flexible memory diodes reported so far, and even higher than those of metal-containing devices. PMID:25073687

Fluorescence particle detection using microfluidics and planar optoelectronic elements

NASA Astrophysics Data System (ADS)

Kettlitz, Siegfried W.; Moosmann, Carola; Valouch, Sebastian; Lemmer, Uli

2014-05-01

Detection of fluorescent particles is an integral part of flow cytometry for analysis of selectively stained cells. Established flow cytometer designs achieve great sensitivity and throughput but require bulky and expensive components which prohibit mass production of small single-use point-of-care devices. The use of a combination of innovative technologies such as roll-to-roll printed microuidics with integrated optoelectronic components such as printed organic light emitting diodes and printed organic photodiodes enables tremendous opportunities in cost reduction, miniaturization and new application areas. In order to harvest these benefits, the optical setup requires a redesign to eliminate the need for lenses, dichroic mirrors and lasers. We investigate the influence of geometric parameters on the performance of a thin planar design which uses a high power LED as planar light source and a PIN-photodiode as planar detector. Due to the lack of focusing optics and inferior optical filters, the device sensitivity is not yet on par with commercial state of the art flow cytometer setups. From noise measurements, electronic and optical considerations we deduce possible pathways of improving the device performance. We identify that the sensitivity is either limited by dark noise for very short apertures or by noise from background light for long apertures. We calculate the corresponding crossover length. For the device design we conclude that a low device thickness, low particle velocity and short aperture length are necessary to obtain optimal sensitivity.

Low-Temperature Solution-Processed ZnSe Electron Transport Layer for Efficient Planar Perovskite Solar Cells with Negligible Hysteresis and Improved Photostability.

PubMed

Li, Xin; Yang, Junyou; Jiang, Qinghui; Lai, Hui; Li, Shuiping; Xin, Jiwu; Chu, Weijing; Hou, Jingdi

2018-05-15

For a typical perovskite solar cell (PKSC), the electron transport layer (ETL) has a great effect on device performance and stability. Herein, we manifest that low-temperature solution-processed ZnSe can be used as a potential ETL for PKSCs. Our optimized device with ZnSe ETL has achieved a high power conversion efficiency (PCE) of 17.78% with negligible hysteresis, compared with the TiO 2 based cell (13.76%). This enhanced photovoltaic performance is attributed to the suitable band alignment, high electron mobility, and reduced charge accumulation at the interface of ETL/perovskite. Encouraging results were obtained when the thin layer of ZnSe cooperated with TiO 2 . It shows that the device based on the TiO 2 /ZnSe ETL with cascade conduction band level can effectively reduce the interfacial charge recombination and promote carrier transfer with the champion PCE of 18.57%. In addition, the ZnSe-based device exhibits a better photostability than the control device due to the greater ultraviolet (UV) light harvesting of the ZnSe layer, which can efficiently prevent the perovskite film from intense UV-light exposure to avoid associated degradation. Consequently, our results present that a promising ETL can be a potential candidate of the n-type ETL for commercialization of efficient and photostable PKSCs.

Memristive effects in oxygenated amorphous carbon nanodevices

NASA Astrophysics Data System (ADS)

Bachmann, T. A.; Koelmans, W. W.; Jonnalagadda, V. P.; Le Gallo, M.; Santini, C. A.; Sebastian, A.; Eleftheriou, E.; Craciun, M. F.; Wright, C. D.

2018-01-01

Computing with resistive-switching (memristive) memory devices has shown much recent progress and offers an attractive route to circumvent the von-Neumann bottleneck, i.e. the separation of processing and memory, which limits the performance of conventional computer architectures. Due to their good scalability and nanosecond switching speeds, carbon-based resistive-switching memory devices could play an important role in this respect. However, devices based on elemental carbon, such as tetrahedral amorphous carbon or ta-C, typically suffer from a low cycling endurance. A material that has proven to be capable of combining the advantages of elemental carbon-based memories with simple fabrication methods and good endurance performance for binary memory applications is oxygenated amorphous carbon, or a-CO x . Here, we examine the memristive capabilities of nanoscale a-CO x devices, in particular their ability to provide the multilevel and accumulation properties that underpin computing type applications. We show the successful operation of nanoscale a-CO x memory cells for both the storage of multilevel states (here 3-level) and for the provision of an arithmetic accumulator. We implement a base-16, or hexadecimal, accumulator and show how such a device can carry out hexadecimal arithmetic and simultaneously store the computed result in the self-same a-CO x cell, all using fast (sub-10 ns) and low-energy (sub-pJ) input pulses.

Ultra-Sensitive Humidity Sensor Based on Optical Properties of Graphene Oxide and Nano-Anatase TiO2.

PubMed

Ghadiry, Mahdiar; Gholami, Mehrdad; Lai, C K; Ahmad, Harith; Chong, W Y

2016-01-01

Generally, in a waveguide-based humidity sensors, increasing the relative humidity (RH) causes the cladding refractive index (RI) to increase due to cladding water absorption. However, if graphene oxide (GO) is used, a reverse phenomenon is seen due to a gap increase in graphene layers. In this paper, this interesting property is applied in order to fabricate differential humidity sensor using the difference between RI of reduced GO (rGO) and nano-anatase TiO2 in a chip. First, a new approach is proposed to prepare high quality nano-anatase TiO2 in solution form making the fabrication process simple and straightforward. Then, the resulted solutions (TiO2 and GO) are effortlessly drop casted and reduced on SU8 two channels waveguide and extensively examined against several humid conditions. Investigating the sensitivity and performance (response time) of the device, reveals a great linearity in a wide range of RH (35% to 98%) and a variation of more than 30 dB in transmitted optical power with a response time of only ~0.7 sec. The effect of coating concentration and UV treatment are studied on the performance and repeatability of the sensor and the attributed mechanisms explained. In addition, we report that using the current approach, devices with high sensitivity and very low response time of only 0.3 sec can be fabricated. Also, the proposed device was comprehensively compared with other state of the art proposed sensors in the literature and the results were promising. Since high sensitivity ~0.47dB/%RH and high dynamic performances were demonstrated, this sensor is a proper choice for biomedical applications.

Ultra-Sensitive Humidity Sensor Based on Optical Properties of Graphene Oxide and Nano-Anatase TiO2

PubMed Central

Ghadiry, Mahdiar; Gholami, Mehrdad; Lai, C. K.; Ahmad, Harith; Chong, W. Y.

2016-01-01

Generally, in a waveguide-based humidity sensors, increasing the relative humidity (RH) causes the cladding refractive index (RI) to increase due to cladding water absorption. However, if graphene oxide (GO) is used, a reverse phenomenon is seen due to a gap increase in graphene layers. In this paper, this interesting property is applied in order to fabricate differential humidity sensor using the difference between RI of reduced GO (rGO) and nano-anatase TiO2 in a chip. First, a new approach is proposed to prepare high quality nano-anatase TiO2 in solution form making the fabrication process simple and straightforward. Then, the resulted solutions (TiO2 and GO) are effortlessly drop casted and reduced on SU8 two channels waveguide and extensively examined against several humid conditions. Investigating the sensitivity and performance (response time) of the device, reveals a great linearity in a wide range of RH (35% to 98%) and a variation of more than 30 dB in transmitted optical power with a response time of only ~0.7 sec. The effect of coating concentration and UV treatment are studied on the performance and repeatability of the sensor and the attributed mechanisms explained. In addition, we report that using the current approach, devices with high sensitivity and very low response time of only 0.3 sec can be fabricated. Also, the proposed device was comprehensively compared with other state of the art proposed sensors in the literature and the results were promising. Since high sensitivity ~0.47dB/%RH and high dynamic performances were demonstrated, this sensor is a proper choice for biomedical applications. PMID:27101247

A Study of Dip-Coatable, High-Capacitance Ion Gel Dielectrics for 3D EWOD Device Fabrication

PubMed Central

Clement, Carlos E.; Jiang, Dongyue; Thio, Si Kuan; Park, Sung-Yong

2017-01-01

We present a dip-coatable, high-capacitance ion gel dielectric for scalable fabrication of three-dimensional (3D) electrowetting-on-dielectric (EWOD) devices such as an n × n liquid prism array. Due to the formation of a nanometer-thick electric double layer (EDL) capacitor, an ion gel dielectric offers two to three orders higher specific capacitance (c ≈ 10 μF/cm2) than that of conventional dielectrics such as SiO2. However, the previous spin-coating method used for gel layer deposition poses several issues for 3D EWOD device fabrication, particularly when assembling multiple modules. Not only does the spin-coating process require multiple repetitions per module, but the ion gel layer also comes in risks of damage or contamination due to handling errors caused during assembly. In addition, it was observed that the chemical formulation previously used for the spin-coating method causes the surface defects on the dip-coated gel layers and thus leads to poor EWOD performance. In this paper, we alternatively propose a dip-coating method with modified gel solutions to obtain defect-free, functional ion gel layers without the issues arising from the spin-coating method for 3D device fabrication. A dip-coating approach offers a single-step coating solution with the benefits of simplicity, scalability, and high throughput for deposition of high-capacitance gel layers on non-planar EWOD devices. An ion gel solution was prepared by combining the [EMIM][TFSI] ionic liquid and the [P(VDF-HFP)] copolymer at various wt % ratios in acetone solvent. Experimental studies were conducted to fully understand the effects of chemical composition ratios in the gel solution and how varying thicknesses of ion gel and Teflon layers affects EWOD performance. The effectiveness and potentiality of dip-coatable gel layers for 3D EWOD devices have been demonstrated through fabricating 5 × 1 arrayed liquid prisms using a single-step dip-coating method. Each prism module has been individually controlled to achieve spatial beam steering without the need for bulky mechanical moving parts. PMID:28772400

A Study of Dip-Coatable, High-Capacitance Ion Gel Dielectrics for 3D EWOD Device Fabrication.

PubMed

Clement, Carlos E; Jiang, Dongyue; Thio, Si Kuan; Park, Sung-Yong

2017-01-05

We present a dip-coatable, high-capacitance ion gel dielectric for scalable fabrication of three-dimensional (3D) electrowetting-on-dielectric (EWOD) devices such as an n × n liquid prism array. Due to the formation of a nanometer-thick electric double layer (EDL) capacitor, an ion gel dielectric offers two to three orders higher specific capacitance ( c ≈ 10 μF/cm²) than that of conventional dielectrics such as SiO₂. However, the previous spin-coating method used for gel layer deposition poses several issues for 3D EWOD device fabrication, particularly when assembling multiple modules. Not only does the spin-coating process require multiple repetitions per module, but the ion gel layer also comes in risks of damage or contamination due to handling errors caused during assembly. In addition, it was observed that the chemical formulation previously used for the spin-coating method causes the surface defects on the dip-coated gel layers and thus leads to poor EWOD performance. In this paper, we alternatively propose a dip-coating method with modified gel solutions to obtain defect-free, functional ion gel layers without the issues arising from the spin-coating method for 3D device fabrication. A dip-coating approach offers a single-step coating solution with the benefits of simplicity, scalability, and high throughput for deposition of high-capacitance gel layers on non-planar EWOD devices. An ion gel solution was prepared by combining the [EMIM][TFSI] ionic liquid and the [P(VDF-HFP)] copolymer at various wt % ratios in acetone solvent. Experimental studies were conducted to fully understand the effects of chemical composition ratios in the gel solution and how varying thicknesses of ion gel and Teflon layers affects EWOD performance. The effectiveness and potentiality of dip-coatable gel layers for 3D EWOD devices have been demonstrated through fabricating 5 × 1 arrayed liquid prisms using a single-step dip-coating method. Each prism module has been individually controlled to achieve spatial beam steering without the need for bulky mechanical moving parts.

Usability Tests in Medicine: A Cost-Benefit Analysis for Hospitals Before Acquiring Medical Devices for Theatre.

PubMed

Gonser, Phillipp; Fuchsberger, Thomas; Matern, Ulrich

2017-08-01

The use of active medical devices in clinical routine should be as safe and efficient as possible. Usability tests (UTs) help improve these aspects of medical devices during their development, but UTs can be of use for hospitals even after a product has been launched. The present pilot study examines the costs and possible benefits of UT for hospitals before buying new medical devices for theatre. Two active medical devices with different complexity were tested in a standardized UT and a cost-benefit analysis was carried out assuming a different device bought at the same price with a higher usability could increase the efficiency of task solving and due to that save valuable theatre time. The cost of the UT amounted up to €19.400. Hospitals could benefit from UTs before buying new devices for theatre by reducing time-consuming operator errors and thereby increase productivity and patient safety. The possible benefits amounted from €23.300 to €1.570.000 (median = €797.000). Not only hospitals could benefit economically from investing in a UT before deciding to buy a medical device, but especially patients would profit from a higher usability by reducing possible operator errors and increase safety and performance of use.

Embedded Volttron specification - benchmarking small footprint compute device for Volttron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanyal, Jibonananda; Fugate, David L.; Woodworth, Ken

An embedded system is a small footprint computing unit that typically serves a specific purpose closely associated with measurements and control of hardware devices. These units are designed for reasonable durability and operations in a wide range of operating conditions. Some embedded systems support real-time operations and can demonstrate high levels of reliability. Many have failsafe mechanisms built to handle graceful shutdown of the device in exception conditions. The available memory, processing power, and network connectivity of these devices are limited due to the nature of their specific-purpose design and intended application. Industry practice is to carefully design the softwaremore » for the available hardware capability to suit desired deployment needs. Volttron is an open source agent development and deployment platform designed to enable researchers to interact with devices and appliances without having to write drivers themselves. Hosting Volttron on small footprint embeddable devices enables its demonstration for embedded use. This report details the steps required and the experience in setting up and running Volttron applications on three small footprint devices: the Intel Next Unit of Computing (NUC), the Raspberry Pi 2, and the BeagleBone Black. In addition, the report also details preliminary investigation of the execution performance of Volttron on these devices.« less

Resistive switching effect of N-doped MoS2-PVP nanocomposites films for nonvolatile memory devices

NASA Astrophysics Data System (ADS)

Wu, Zijin; Wang, Tongtong; Sun, Changqi; Liu, Peitao; Xia, Baorui; Zhang, Jingyan; Liu, Yonggang; Gao, Daqiang

2017-12-01

Resistive memory technology is very promising in the field of semiconductor memory devices. According to Liu et al, MoS2-PVP nanocomposite can be used as an active layer material for resistive memory devices due to its bipolar resistive switching behavior. Recent studies have also indicated that the doping of N element can reduce the band gap of MoS2 nanosheets, which is conducive to improving the conductivity of the material. Therefore, in this paper, we prepared N-doped MoS2 nanosheets and then fabricated N-doped MoS2-PVP nanocomposite films by spin coating. Finally, the resistive memory [C. Tan et al., Chem. Soc. Rev. 44, 2615 (2015)], device with ITO/N-doped MoS2-PVP/Pt structure was fabricated. Study on the I-V characteristics shows that the device has excellent resistance switching effect. It is worth mentioning that our device possesses a threshold voltage of 0.75 V, which is much better than 3.5 V reported previously for the undoped counterparts. The above research shows that N-doped MoS2-PVP nanocomposite films can be used as the active layer of resistive switching memory devices, and will make the devices have better performance.

Synthesis of graphene and related two-dimensional materials for bioelectronics devices.

PubMed

Zhang, Tao; Liu, Jilun; Wang, Cheng; Leng, Xuanye; Xiao, Yao; Fu, Lei

2017-03-15

In recent years, graphene and related two-dimensional (2D) materials have emerged as exotic materials in nearly every fields of fundamental science and applied engineering. The latest progress has shown that these 2D materials could have a profound impact on bioelectronics devices. For the construction of these bioelectronics devices, these 2D materials were generally synthesized by the processes of exfoliation and chemical vapor deposition. In particular, the macrostructures of these 2D materials have also been realized by these two processes, which have shown great potentials in the self-supported and special-purpose biosensors. Due to the high specific surface area, subtle electron properties, abundant surface atoms of these 2D materials, the as-constructed bioelectronics devices have exhibited enhanced performance in the sensing of small biomolecules, heavy metals, pH, protein and DNA. The aim of this review article is to provide a comprehensive scientific progress in the synthesis of 2D materials for the construction of five typical bioelectronics devices (electrochemical biosensors, FET-based biosensors, piezoelectric devices, electrochemiluminescence devices and supercapacitors) and to overview the present status and future perspective of the applications of these bioelectronics devices based on 2D materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Comprehensive electrocardiogram-to-device time for primary percutaneous coronary intervention in ST-segment elevation myocardial infarction: A report from the American Heart Association mission: Lifeline program.

PubMed

Shavadia, Jay S; French, William; Hellkamp, Anne S; Thomas, Laine; Bates, Eric R; Manoukian, Steven V; Kontos, Michael C; Suter, Robert; Henry, Timothy D; Dauerman, Harold L; Roe, Matthew T

2018-03-01

Assessing hospital-related network-level primary percutaneous coronary intervention (PCI) performance for ST-segment elevation myocardial infarction (STEMI) is challenging due to differential time-to-treatment metrics based on location of diagnostic electrocardiogram (ECG) for STEMI. STEMI patients undergoing primary PCI at 588 PCI-capable hospitals in AHA Mission: Lifeline (2008-2013) were categorized by initial STEMI identification location: PCI-capable hospitals (Group 1); pre-hospital setting (Group 2); and non-PCI-capable hospitals (Group 3). Patient-specific time-to-treatment categories were converted to minutes ahead of or behind their group-specific mean; average time-to-treatment difference for all patients at a given hospital was termed comprehensive ECG-to-device time. Hospitals were then stratified into tertiles based on their comprehensive ECG-to-device times with negative values below the mean representing shorter (faster) time intervals. Of 117,857 patients, the proportion in Groups 1, 2, and 3 were 42%, 33%, and 25%, respectively. Lower rates of heart failure and cardiac arrest at presentation are noted within patients presenting to high-performing hospitals. Median comprehensive ECG-to-device time was shortest at -9 minutes (25th, 75th percentiles: -13, -6) for the high-performing hospital tertile, 1 minute (-1, 3) for middle-performing, and 11 minutes (7, 16) for low-performing. Unadjusted rates of in-hospital mortality were 2.3%, 2.6%, and 2.7%, respectively, but the adjusted risk of in-hospital mortality was similar across tertiles. Comprehensive ECG-to-device time provides an integrated hospital-related network-level assessment of reperfusion timing metrics for primary PCI, regardless of the location for STEMI identification; further validation will delineate how this metric can be used to facilitate STEMI care improvements. Copyright © 2017 Elsevier Inc. All rights reserved.

Broadband absorption enhancement in amorphous Si solar cells using metal gratings and surface texturing

NASA Astrophysics Data System (ADS)

Magdi, Sara; Swillam, Mohamed A.

2017-02-01

The efficiencies of thin film amorphous silicon (a-Si) solar cells are restricted by the small thickness required for efficient carrier collection. This thickness limitations result in poor light absorption. In this work, broadband absorption enhancement is theoretically achieved in a-Si solar cells by using nanostructured back electrode along with surface texturing. The back electrode is formed of Au nanogratings and the surface texturing consists of Si nanocones. The results were then compared to random texturing surfaces. Three dimensional finite difference time domain (FDTD) simulations are used to design and optimize the structure. The Au nanogratings achieved absorption enhancement in the long wavelengths due to sunlight coupling to surface plasmon polaritons (SPP) modes. High absorption enhancement was achieved at short wavelengths due to the decreased reflection and enhanced scattering inside the a-Si absorbing layer. Optimizations have been performed to obtain the optimal geometrical parameters for both the nanogratings and the periodic texturing. In addition, an enhancement factor (i.e. absorbed power in nanostructured device/absorbed power in reference device) was calculated to evaluate the enhancement obtained due to the incorporation of each nanostructure.

Investigation of the Semicoa 2N7616 and 2N7425 and the Microsemi 2N7480 for Single-Event Gate Rupture and Single-Event Burnout

NASA Technical Reports Server (NTRS)

Scheick, Leif

2014-01-01

Single-event-effect test results for hi-rel total-dose-hardened power MOSFETs are presented in this report. The 2N7616 and the 2N7425 from Semicoa and the 2N7480 from International Rectifier were tested to NASA test condition standards and requirements. The 2N7480 performed well and the data agree with the manufacture's data. The 2N7616 and 2N7425 were entry parts from Semicoa using a new device architecture. Unfortunately, the device performed poorly and Semicoa is withdrawing power MOSFETs from it line due to these data. Vertical metal-oxide-semiconductor field-effect transistors (MOSFETs) are the most commonly used power transistor. MOSFETs are typically employed in power supplies and high current switching applications. Due to the inherent high electric fields in the device, power MOSFETs are sensitive to heavy ion irradiation and can fail catastrophically as a result of single-event gate rupture (SEGR) or single-event burnout (SEB). Manufacturers have designed radiation-hardened power MOSFETs for space applications. See [1] through [5] for more information. The objective of this effort was to investigate the SEGR and SEB responses of two power MOSFETs recently produced. These tests will serve as a limited verification of these parts. It is acknowledged that further testing on the respective parts may be needed for some mission profiles.

Strain effects in low-dimensional silicon MOS and AlGaN/GaN HEMT devices

NASA Astrophysics Data System (ADS)

Baykan, Mehmet Onur

Strained silicon technology is a well established method to enhance sub-100nm MOSFET performance. With the scalability of process-induced strain, strained silicon channels have been used in every advanced CMOS technology since the 90nm node. At the 22nm node, due to the detrimental short channel effects, non-planar silicon CMOS has emerged as a viable solution to sustain transistor scaling without compromising the device performance. Therefore, it is necessary to conduct a physics based investigation of the effects of mechanical strain in silicon MOS device performance enhancement, as the transverse and longitudinal device dimensions scale down for future technology nodes. While silicon is widely used as the material basis for logic transistors, AlGaN/GaN HEMTs promise a superior device platform over silicon based power MOSFETs for high-frequency and high-power applications. In contrast to the mature Si crystal growth technology, the abundance of defects in the GaN material system creates obstacles for the realization of a reliable AlGaN/GaN HEMT device technology. Due to the high levels of internal mechanical strain present in AlGaN/GaN HEMTs, it is of utmost importance to understand the impact of mechanical stress on AlGaN/GaN trap generation. First, we have investigated the underlying physics of the comparable electron mobility observed in (100) and (110) sidewall silicon double-gate FinFETs, which is different from the observed planar (100) and (110) electron mobility. By conducting a systematic experimental study, it is shown that the undoped body, metal gate induced stress, and volume-inversion effects do not explain the comparable electron mobility. Using a self-consistent double-gate FinFET simulator, we have showed that for (110) FinFETs, an increased population of electrons is obtained for the Delta2 valley due to the heavy nonparabolic confinement mass, leading to a comparable average electron transport effective mass for both orientations. The width dependent strain response of tri-gate p-type FinFETs are experimentally extracted using a 4-point bending jig. It is found that the low-field piezoresistance coefficient of p-type FinFETs can be modeled by using a weighted conductance average of the top and sidewall bulk piezoresistance coefficients. Next, the strain enhancement of p-type ballistic silicon nanowire MOSFETs is studied using sp3d 5s* basis nearest-neighbor tight-binding simulations coupled with a semiclassical top-of-the-barrier transport model. Size and orientation dependent strain enhancement of ballistic hole transport is explained by the strain-induced modification of the 1D nanowire valence band density-of-states. Further insights are provided for future p-type high-performance silicon nanowire logic devices. A physics based investigation is conducted to understand the strain effects on surface roughness limited electron mobility in silicon inversion layers. Based on the evidence from electrical and material characterization, a strain-induced surface morphology change is hypothesized. To model the observed electrical characteristics, we have employed a self-consistent MOSFET mobility simulator coupled with an ad hoc strain-induced roughness modification. The strain induced surface morphology change is found to be consistent among electrical and materials characterization, as well as transport simulations. In order to bridge the gap between the drift-diffusion based models for long-channel devices and the quasi-ballistic models for nanoscale channels, a unified carrier transport model is developed using an updated one-flux theory. Including the high-field and carrier confinement effects, a surface-potential based analytical transmission expression is obtained for the entire MOSFET operation range. With the new channel transmission equation and average carrier drift velocity, a new expression for channel ballisticity is defined. Impact of mechanical strain on carrier transport for both nMOSFETs and pMOSFETs in both linear and saturation regimes is explained using the new channel transmission definitions. To understand the impact of mechanical strain on AlGaN/GaN HEMT trap generation, we have devised an experimental method to obtain the photon flux-normalized relative areal trap density distribution using photoionization spectroscopy technique. The details of the trap extraction method and the experimental setup are given. Using this setup, the trap characteristics are extracted for both ungated transmission line module (TLM) and gated HEMT devices from both Si and SiC substrates. The changes in the device trap characteristics are emphasized before and after electrical stressing. It is found through the step-voltage stressing of the AlGaN/GaN HEMT gate stack that the device degradation is due to the near bandgap trap generation, which are shown to be related to the structural defects in GaN.

Variability in syringe components and its impact on functionality of delivery systems.

PubMed

Rathore, Nitin; Pranay, Pratik; Eu, Bruce; Ji, Wenchang; Walls, Ed

2011-01-01

Prefilled syringes and autoinjectors are becoming increasingly common for parenteral drug administration primarily due to the convenience they offer to the patients. Successful commercialization of such delivery systems requires thorough characterization of individual components. Complete understanding of various sources of variability and their ranking is essential for robust device design. In this work, we studied the impact of variability in various primary container and device components on the delivery forces associated with syringe injection. More specifically, the effects of barrel size, needle size, autoinjector spring force, and frictional forces have been evaluated. An analytical model based on underlying physics is developed that can be used to fully characterize the design space for a product delivery system. Use of prefilled syringes (syringes prefilled with active drug) is becoming increasingly common for injectable drugs. Compared to vials, prefilled syringes offer higher dose accuracy and ease of use due to fewer steps required for dosage. Convenience to end users can be further enhanced through the use of prefilled syringes in combination with delivery devices such as autoinjectors. These devices allow patients to self-administer the drug by following simple steps such as pressing a button. These autoinjectors are often spring-loaded and are designed to keep the needle tip shielded prior to injection. Because the needle is not visible to the user, such autoinjectors are perceived to be less invasive than syringes and help the patient overcome the hesitation associated with self-administration. In order to successfully develop and market such delivery devices, we need to perform an in-depth analysis of the components that come into play during the activation of the device and dose delivery. Typically, an autoinjector is activated by the press of a button that releases a compressed spring; the spring relaxes and provides the driving force to push the drug out of the syringe and into the site of administration. Complete understanding of the spring force, syringe barrel dimensions, needle size, and drug product properties is essential for robust device design. It is equally important to estimate the extent of variability that exists in these components and the resulting impact it could have on the performance of the device. In this work, we studied the impact of variability in syringe and device components on the delivery forces associated with syringe injection. More specifically, the effect of barrel size, needle size, autoinjector spring force, and frictional forces has been evaluated. An analytical model based on underlying physics is developed that can be used to predict the functionality of the autoinjector.

Device- and system-independent personal touchless user interface for operating rooms : One personal UI to control all displays in an operating room.

PubMed

Ma, Meng; Fallavollita, Pascal; Habert, Séverine; Weidert, Simon; Navab, Nassir

2016-06-01

In the modern day operating room, the surgeon performs surgeries with the support of different medical systems that showcase patient information, physiological data, and medical images. It is generally accepted that numerous interactions must be performed by the surgical team to control the corresponding medical system to retrieve the desired information. Joysticks and physical keys are still present in the operating room due to the disadvantages of mouses, and surgeons often communicate instructions to the surgical team when requiring information from a specific medical system. In this paper, a novel user interface is developed that allows the surgeon to personally perform touchless interaction with the various medical systems, switch effortlessly among them, all of this without modifying the systems' software and hardware. To achieve this, a wearable RGB-D sensor is mounted on the surgeon's head for inside-out tracking of his/her finger with any of the medical systems' displays. Android devices with a special application are connected to the computers on which the medical systems are running, simulating a normal USB mouse and keyboard. When the surgeon performs interaction using pointing gestures, the desired cursor position in the targeted medical system display, and gestures, are transformed into general events and then sent to the corresponding Android device. Finally, the application running on the Android devices generates the corresponding mouse or keyboard events according to the targeted medical system. To simulate an operating room setting, our unique user interface was tested by seven medical participants who performed several interactions with the visualization of CT, MRI, and fluoroscopy images at varying distances from them. Results from the system usability scale and NASA-TLX workload index indicated a strong acceptance of our proposed user interface.

Architectures for Improved Organic Semiconductor Devices

NASA Astrophysics Data System (ADS)

Beck, Jonathan H.

Advancements in the microelectronics industry have brought increasing performance and decreasing prices to a wide range of users. Conventional silicon-based electronics have followed Moore's law to provide an ever-increasing integrated circuit transistor density, which drives processing power, solid-state memory density, and sensor technologies. As shrinking conventional integrated circuits became more challenging, researchers began exploring electronics with the potential to penetrate new applications with a low price of entry: "Electronics everywhere." The new generation of electronics is thin, light, flexible, and inexpensive. Organic electronics are part of the new generation of thin-film electronics, relying on the synthetic flexibility of carbon molecules to create organic semiconductors, absorbers, and emitters which perform useful tasks. Organic electronics can be fabricated with low energy input on a variety of novel substrates, including inexpensive plastic sheets. The potential ease of synthesis and fabrication of organic-based devices means that organic electronics can be made at very low cost. Successfully demonstrated organic semiconductor devices include photovoltaics, photodetectors, transistors, and light emitting diodes. Several challenges that face organic semiconductor devices are low performance relative to conventional devices, long-term device stability, and development of new organic-compatible processes and materials. While the absorption and emission performance of organic materials in photovoltaics and light emitting diodes is extraordinarily high for thin films, the charge conduction mobilities are generally low. Building highly efficient devices with low-mobility materials is one challenge. Many organic semiconductor films are unstable during fabrication, storage, and operation due to reactions with water, oxygen and hydroxide. A final challenge facing organic electronics is the need for new processes and materials for electrodes, semiconductors and substrates compatible with low-temperature, flexible, and oxygenated and aromatic solvent-free fabrication. Materials and processes must be capable of future high volume production in order to enable low costs. In this thesis we explore several techniques to improve organic semiconductor device performance and enable new fabrication processes. In Chapter 2, I describe the integration of sub-optical-wavelength nanostructured electrodes that improve fill factor and power conversion efficiency in organic photovoltaic devices. Photovoltaic fill factor performance is one of the primary challenges facing organic photovoltaics because most organic semiconductors have poor charge mobility. Our electrical and optical measurements and simulations indicate that nanostructured electrodes improve charge extraction in organic photovoltaics. In Chapter 3, I describe a general method for maximizing the efficiency of organic photovoltaic devices by simultaneously optimizing light absorption and charge carrier collection. We analyze the potential benefits of light trapping strategies for maximizing the overall power conversion efficiency of organic photovoltaic devices. This technique may be used to improve organic photovoltaic materials with low absorption, or short exciton diffusion and carrier-recombination lengths, opening up the device design space. In Chapter 4, I describe a process for high-quality graphene transfer onto chemically sensitive, weakly interacting organic semiconductor thin-films. Graphene is a promising flexible and highly transparent electrode for organic electronics; however, transferring graphene films onto organic semiconductor devices was previously impossible. We demonstrate a new transfer technique based on an elastomeric stamp coated with an fluorinated polymer release layer. We fabricate three classes of organic semiconductor devices: field effect transistors without high temperature annealing, transparent organic light-emitting diodes, and transparent small-molecule organic photovoltaic devices.

Field evaluation of a prototype paper-based point-of-care fingerstick transaminase test.

PubMed

Pollock, Nira R; McGray, Sarah; Colby, Donn J; Noubary, Farzad; Nguyen, Huyen; Nguyen, The Anh; Khormaee, Sariah; Jain, Sidhartha; Hawkins, Kenneth; Kumar, Shailendra; Rolland, Jason P; Beattie, Patrick D; Chau, Nguyen V; Quang, Vo M; Barfield, Cori; Tietje, Kathy; Steele, Matt; Weigl, Bernhard H

2013-01-01

Monitoring for drug-induced liver injury (DILI) via serial transaminase measurements in patients on potentially hepatotoxic medications (e.g., for HIV and tuberculosis) is routine in resource-rich nations, but often unavailable in resource-limited settings. Towards enabling universal access to affordable point-of-care (POC) screening for DILI, we have performed the first field evaluation of a paper-based, microfluidic fingerstick test for rapid, semi-quantitative, visual measurement of blood alanine aminotransferase (ALT). Our objectives were to assess operational feasibility, inter-operator variability, lot variability, device failure rate, and accuracy, to inform device modification for further field testing. The paper-based ALT test was performed at POC on fingerstick samples from 600 outpatients receiving HIV treatment in Vietnam. Results, read independently by two clinic nurses, were compared with gold-standard automated (Roche Cobas) results from venipuncture samples obtained in parallel. Two device lots were used sequentially. We demonstrated high inter-operator agreement, with 96.3% (95% C.I., 94.3-97.7%) agreement in placing visual results into clinically-defined "bins" (<3x, 3-5x, and >5x upper limit of normal), >90% agreement in validity determination, and intraclass correlation coefficient of 0.89 (95% C.I., 0.87-0.91). Lot variability was observed in % invalids due to hemolysis (21.1% for Lot 1, 1.6% for Lot 2) and correlated with lots of incorporated plasma separation membranes. Invalid rates <1% were observed for all other device controls. Overall bin placement accuracy for the two readers was 84% (84.3%/83.6%). Our findings of extremely high inter-operator agreement for visual reading-obtained in a target clinical environment, as performed by local practitioners-indicate that the device operation and reading process is feasible and reproducible. Bin placement accuracy and lot-to-lot variability data identified specific targets for device optimization and material quality control. This is the first field study performed with a patterned paper-based microfluidic device and opens the door to development of similar assays for other important analytes.

Variable friction device for structural control based on duo-servo vehicle brake: Modeling and experimental validation

NASA Astrophysics Data System (ADS)

Cao, Liang; Downey, Austin; Laflamme, Simon; Taylor, Douglas; Ricles, James

2015-07-01

Supplemental damping can be used as a cost-effective method to reduce structural vibrations. In particular, passive systems are now widely accepted and have numerous applications in the field. However, they are typically tuned to specific excitations and their performances are bandwidth-limited. A solution is to use semi-active devices, which have shown to be capable of substantially enhanced mitigation performance. The authors have recently proposed a new type of semi-active device, which consists of a variable friction mechanism based on a vehicle duo-servo drum brake, a mechanically robust and reliable technology. The theoretical performance of the proposed device has been previously demonstrated via numerical simulations. In this paper, we further the understanding of the device, termed Modified Friction Device (MFD) by fabricating a small scale prototype and characterizing its dynamic behavior. While the dynamics of friction is well understood for automotive braking technology, we investigate for the first time the dynamic behavior of this friction mechanism at low displacements and velocities, in both forward and backward directions, under various hydraulic pressures. A modified 3-stage dynamic model is introduced. A LuGre friction model is used to characterize the friction zone (Stage 1), and two pure stiffness regions to characterize the dynamics of the MFD once the rotation is reversed and the braking shoes are sticking to the drum (Stage 2) and the rapid build up of forces once the shoes are held by the anchor pin (Stage 3). The proposed model is identified experimentally by subjecting the prototype to harmonic excitations. It is found that the proposed model can be used to characterize the dynamics of the MFD, and that the largest fitting error arises at low velocity under low pressure input. The model is then verified by subjecting the MFD to two different earthquake excitations under different pressure inputs. The model is capable of tracking the device's response, despite a lower fitting performance under low pressure and small force output, as it was found in the harmonic tests due to the possible nonlinearity in Stage 2 of the model.

Electronic structure of clathrates Bax@AlySi46-y ; thermoelectric devices

NASA Astrophysics Data System (ADS)

Eguchi, Haruki; Nagano, Takatoshi; Takenaka, Hiroyuki; Tsumuraya, Kazuo

2002-03-01

Clathrates have received much attention as a candidate of high performance thermoelectric devices. This is because they have a) low thermal conductivity due to rattle effect of the alkali or heavy alkali-earth metals such as Ba atoms in the cages of clusters of the clathrates, and b) adjustablity of the Fermi levels through replacement of frame Si atoms with acceptor Al atoms and addition of the cage atoms as donors. We present the dispersion curves with LDA and GGA approximations for the exchange correlation of electrons using the planewave based pseudopotential methods and predict the electronic properties of the clathrates.

Less severe processing improves carbon nanotube photovoltaic performance

NASA Astrophysics Data System (ADS)

Shea, Matthew J.; Wang, Jialiang; Flach, Jessica T.; Zanni, Martin T.; Arnold, Michael S.

2018-05-01

Thin film semiconducting single walled carbon nanotube (s-SWCNT) photovoltaics suffer losses due to trapping and quenching of excitons by defects induced when dispersing s-SWCNTs into solution. We study these aspects by preparing photovoltaic devices from (6,5) carbon nanotubes isolated by different processes: extended ultrasonication, brief ultrasonication, and shear force mixing. Peak quantum efficiency increases from 28% to 38% to 49% as the processing harshness decreases and is attributed to both increasing s-SWCNT length and reducing sidewall defects. Fill-factor and open-circuit voltage also improve with shear force mixing, highlighting the importance of obtaining long, defect-free s-SWCNTs for efficient photoconversion devices.

Suppression of the self-heating effect in GaN HEMT by few-layer graphene heat spreading elements

NASA Astrophysics Data System (ADS)

Volcheck, V. S.; Stempitsky, V. R.

2017-11-01

Self-heating has an adverse effect on characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs). Various solutions to the problem have been proposed, however, a temperature rise due to dissipated electrical power still hinders the production of high power and high speed GaN devices. In this paper, thermal management of GaN HEMT via few-layer graphene (FLG) heat spreading elements is investigated. It is shown that integration of the FLG elements on top of the device structure considerably reduces the maximum temperature and improves the DC and small signal AC performance.

Assessment of Safety and Effectiveness of the Extracorporeal Continuous-Flow Ventricular Assist Device (BR16010) Use as a Bridge-to-Decision Therapy for Severe Heart Failure or Refractory Cardiogenic Shock: Study Protocol for Single-Arm Non-randomized, Uncontrolled, and Investigator-Initiated Clinical Trial.

PubMed

Fukushima, Norihide; Tatsumi, Eisuke; Seguchi, Osamu; Takewa, Yoshiaki; Hamasaki, Toshimitsu; Onda, Kaori; Yamamoto, Haruko; Hayashi, Teruyuki; Fujita, Tomoyuki; Kobayashi, Junjiro

2018-06-08

The management of heart failure patients presenting in a moribund state remains challenging, despite significant advances in the field of ventricular assist systems. Bridge to decision involves using temporary devices to stabilize the hemodynamic state of such patients while further assessment is performed and a decision can be made regarding patient management. The purpose of this study (NCVC-BTD_01, National Cerebral and Cardiovascular Center-Bridge to Dicision_01) is to assess the safety and effectiveness of the newly developed extracorporeal continuous-flow ventricular assist system employing a disposable centrifugal pump with a hydrodynamically levitated bearing (BR16010) use as a bridge-to-decision therapy for patients with severe heart failure or refractory cardiogenic shock. NCVC-BTD_01 is a single-center, single-arm, open-label, exploratory, medical device, investigator-initiated clinical study. It is conducted at the National Cerebral and Cardiovascular Center in Japan. A total of nine patients will be enrolled in the study. The study was planned using Simon's minimax two-stage phase design. The primary endpoint is a composite of survival free of device-related serious adverse events and complications during device support. For left ventricular assistance, withdrawal of a trial device due to cardiac function recovery or exchange to other ventricular assist devices (VADs) for the purpose of bridge to transplantation (BTT) during 30 days after implantation will be considered study successes. For right ventricular assistance, withdrawal of tal device due to right ventricular function recovery within 30 days after implantation will be considered a study success. Secondary objectives include changes in brain natriuretic peptide levels (7 days after implantation of a trial device and the day of withdrawal of a trial device), period of mechanical ventricular support, changes in left ventricular ejection fraction (7 days after implantation of a trial device and the day of withdrawal of a trial device), and changes in left ventricular diastolic dimension (7 days after implantation of a trial device and the day of withdrawal of a trial device). We will disseminate the findings through regional, national, and international conferences and through peer-reviewed journals. UMIN Clinical Trials Registry (UMIN-CTR; R000033243) registered on 8 September 2017.

Epidermal Inorganic Optoelectronics for Blood Oxygen Measurement.

PubMed

Li, Haicheng; Xu, Yun; Li, Xiaomin; Chen, Ying; Jiang, Yu; Zhang, Changxing; Lu, Bingwei; Wang, Jian; Ma, Yinji; Chen, Yihao; Huang, Yin; Ding, Minquang; Su, Honghong; Song, Guofeng; Luo, Yi; Feng, X

2017-05-01

Flexible and stretchable optoelectronics, built-in inorganic semiconductor materials, offer a wide range of unprecedented opportunities and will redefine the conventional rigid optoelectronics in biological application and medical measurement. However, a significant bottleneck lies in the brittleness nature of rigid semiconductor materials and the performance's extreme sensitivity to the light intensity variation due to human skin deformation while measuring physical parameters. In this study, the authors demonstrate a systematic strategy to design an epidermal inorganic optoelectronic device by using specific strain-isolation design, nanodiamond thinning, and hybrid transfer printing. The authors propose all-in-one suspension structure to achieve the stretchability and conformability for surrounding environment, and they propose a two-step transfer printing method for hybrid integrating III-V group emitting elements, Si-based photodetector, and interconnects. Owing to the excellent flexibility and stretchability, such device is totally conformal to skin and keeps the constant light transmission between emitting element and photodetector as well as the signal stability due to skin deformation. This method opens a route for traditional inorganic optoelectronics to achieve flexibility and stretchability and improve the performance of optoelectronics for biomedical application. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Slotted Photonic Crystal Sensors

PubMed Central

Scullion, Mark G.; Krauss, Thomas F.; Di Falco, Andrea

2013-01-01

Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them results in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This review article presents a new platform for optical biosensors, namely slotted photonic crystals, which provide higher sensitivities due to their ability to confine, spatially and temporally, the optical mode peak within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. Higher sensitivities were observed in smaller structures than possible with most competing devices reported in the literature. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study. PMID:23503295

Boolean and brain-inspired computing using spin-transfer torque devices

NASA Astrophysics Data System (ADS)

Fan, Deliang

Several completely new approaches (such as spintronic, carbon nanotube, graphene, TFETs, etc.) to information processing and data storage technologies are emerging to address the time frame beyond current Complementary Metal-Oxide-Semiconductor (CMOS) roadmap. The high speed magnetization switching of a nano-magnet due to current induced spin-transfer torque (STT) have been demonstrated in recent experiments. Such STT devices can be explored in compact, low power memory and logic design. In order to truly leverage STT devices based computing, researchers require a re-think of circuit, architecture, and computing model, since the STT devices are unlikely to be drop-in replacements for CMOS. The potential of STT devices based computing will be best realized by considering new computing models that are inherently suited to the characteristics of STT devices, and new applications that are enabled by their unique capabilities, thereby attaining performance that CMOS cannot achieve. The goal of this research is to conduct synergistic exploration in architecture, circuit and device levels for Boolean and brain-inspired computing using nanoscale STT devices. Specifically, we first show that the non-volatile STT devices can be used in designing configurable Boolean logic blocks. We propose a spin-memristor threshold logic (SMTL) gate design, where memristive cross-bar array is used to perform current mode summation of binary inputs and the low power current mode spintronic threshold device carries out the energy efficient threshold operation. Next, for brain-inspired computing, we have exploited different spin-transfer torque device structures that can implement the hard-limiting and soft-limiting artificial neuron transfer functions respectively. We apply such STT based neuron (or 'spin-neuron') in various neural network architectures, such as hierarchical temporal memory and feed-forward neural network, for performing "human-like" cognitive computing, which show more than two orders of lower energy consumption compared to state of the art CMOS implementation. Finally, we show the dynamics of injection locked Spin Hall Effect Spin-Torque Oscillator (SHE-STO) cluster can be exploited as a robust multi-dimensional distance metric for associative computing, image/ video analysis, etc. Our simulation results show that the proposed system architecture with injection locked SHE-STOs and the associated CMOS interface circuits can be suitable for robust and energy efficient associative computing and pattern matching.

Highly Efficient Solution-Processed Deep-Red Organic Light-Emitting Diodes Based on an Exciplex Host Composed of a Hole Transporter and a Bipolar Host.

PubMed

Huang, Manli; Jiang, Bei; Xie, Guohua; Yang, Chuluo

2017-10-19

With the aim to achieve highly efficient deep-red emission, we introduced an exciplex forming cohost, 4,4',4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA): 2,5-bis(2-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o-CzOXD) (1:1). Due to the efficient triplet up-conversion processes upon the exciplex forming cohost, excellent performances of the devices were achieved with deep-red emission. Using the heteroleptic iridium complexes as the guest dopants, the solution-processed deep-red phosphorescent organic light-emitting diodes (PhOLEDs) with the iridium(III) bis(6-(4-(tert-butyl)phenyl)phenanthridine)acetylacetonate [(TP-BQ) 2 Ir(acac)]-based phosphorescent emitter exhibited an electroluminescent peak at 656 nm and a maximum external quantum efficiency (EQE) of 11.9%, which is 6.6 times that of the device based on the guest emitter doped in the polymer-based cohost. The unique exciplex with a typical hole transporter and a bipolar material is ideal and universal for hosting the red PhOLEDs and tremendously improves the device performances.

Cycling excitation process: An ultra efficient and quiet signal amplification mechanism in semiconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yu-Hsin; Yan, Lujiang; Zhang, Alex Ce

2015-08-03

Signal amplification, performed by transistor amplifiers with its merit rated by the efficiency and noise characteristics, is ubiquitous in all electronic systems. Because of transistor thermal noise, an intrinsic signal amplification mechanism, impact ionization was sought after to complement the limits of transistor amplifiers. However, due to the high operation voltage (30-200 V typically), low power efficiency, limited scalability, and, above all, rapidly increasing excess noise with amplification factor, impact ionization has been out of favor for most electronic systems except for a few applications such as avalanche photodetectors and single-photon Geiger detectors. Here, we report an internal signal amplification mechanismmore » based on the principle of the phonon-assisted cycling excitation process (CEP). Si devices using this concept show ultrahigh gain, low operation voltage, CMOS compatibility, and, above all, quantum limit noise performance that is 30 times lower than devices using impact ionization. Established on a unique physical effect of attractive properties, CEP-based devices can potentially revolutionize the fields of semiconductor electronics.« less

All 2D materials as electrodes for high power hybrid energy storage applications

NASA Astrophysics Data System (ADS)

Kato, Keiko; Sayed, Farheen N.; Babu, Ganguli; Ajayan, Pulickel M.

2018-04-01

Achieving both high energy and power densities from energy storage devices is a core strategy to meet the increasing demands of high performance portable electronics and electric transportation systems. Li-ion capacitor is a promising hybrid technology that strategically exploits high energy density from a Li-ion battery electrode and high power density from a supercapacitor electrode. However, the performance and safety of hybrid devices are still major concerns due to the use of graphite anodes which form passivation layers with organic electrolytes at lower potentials. Here, we explore 2D nanosheets as both anode and cathode electrodes to build a high power system without compromising energy density. Owing to the high electrical conductivity and multivalent redox activity at higher potentials, the Li-ion intercalation electrode is capable of maintaining large energy density at higher current rates with less safety risk than conventional systems. Hybrid devices consisting of all in all 2D electrodes deliver energy density as high as 121 Wh g-1 (at 240 W kg-1) and retains 29 Wh g-1 at high power density of 3600 W kg-1.

Side effects of intraoral devices for OSAS treatment.

PubMed

Teixeira, Andressa Otranto de Britto; Andrade, Ana Luiza Ladeia; Almeida, Rhita Cristina da Cunha; Almeida, Marco Antonio de Oliveira

2017-10-14

Intraoral devices have increasingly assumed a key role in the treatment of obstructive sleep apnea syndrome, but there are limitations to their indication and side effects that result from their continuous use, as well as the use of the continuous positive airway pressure device. To evaluate the changes in dental positioning caused by the continuous use of mandibular advancement devices. A prospective longitudinal study with a sample of 15 patients, with evaluation of complete documentation after a mean time of 6.47 months, assessed changes in dental positioning due to the use of the Twin Block oral device for the treatment of patients with apnea. The following variables were evaluated: overjet, overbite, upper and lower intermolar distances, upper and lower intercanine distances, Little's irregularity index and the incisor mandibular plane angle. An intraclass correlation test was performed and a correlation index>0.08 was accepted. After verifying the normal sample distribution (Shapiro-Wilks), a parametric test was used (t test), with a significance level set at 5%. There was a decrease in the values of overjet, overbite and Little's irregularity index, whereas there was an increase in the lower intercanine distance and IMPA values. All these variables are influenced, at different levels, by the forward inclination of the lower incisors, an action that can be expected due to the force applied by the device on the dentition. The other variables did not show statistically significant differences. After a mean time of 6.47 months of use of the mandibular advancement device, there were statistically significant changes in the dental positioning, but they were not clinically relevant. However, it is relevant that this device is commonly in use over long periods of time, making the monitoring of these patients of the utmost importance for the duration of their therapy. Copyright © 2017 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

User acceptance of location-tracking technologies in health research: Implications for study design and data quality.

PubMed

Hardy, Jean; Veinot, Tiffany C; Yan, Xiang; Berrocal, Veronica J; Clarke, Philippa; Goodspeed, Robert; Gomez-Lopez, Iris N; Romero, Daniel; Vydiswaran, V G Vinod

2018-03-01

Research regarding place and health has undergone a revolution due to the availability of consumer-focused location-tracking devices that reveal fine-grained details of human mobility. Such research requires that participants accept such devices enough to use them in their daily lives. There is a need for a theoretically grounded understanding of acceptance of different location-tracking technology options, and its research implications. Guided by an extended Unified Theory of Acceptance and Use of Technology (UTAUT), we conducted a 28-day field study comparing 21 chronically ill people's acceptance of two leading, consumer-focused location-tracking technologies deployed for research purposes: (1) a location-enabled smartphone, and (2) a GPS watch/activity tracker. Participants used both, and completed two surveys and qualitative interviews. Findings revealed that all participants exerted effort to facilitate data capture, such as by incorporating devices into daily routines and developing workarounds to keep devices functioning. Nevertheless, the smartphone was perceived to be significantly easier and posed fewer usability challenges for participants than the watch. Older participants found the watch significantly more difficult to use. For both devices, effort expectancy was significantly associated with future willingness to participate in research although prosocial motivations overcame some concerns. Social influence, performance expectancy and use behavior were significantly associated with intentions to use the devices in participants' personal lives. Data gathered via the smartphone was significantly more complete than data gathered via the watch, primarily due to usability challenges. To make longer-term participation in location tracking research a reality, and to achieve complete data capture, researchers must minimize the effort involved in participation; this requires usable devices. For long-term location-tracking studies using similar devices, findings indicate that only smartphone-based tracking is up to the challenge. Copyright © 2018 Elsevier Inc. All rights reserved.

DOE FES FY2017 Joint Research Target Fourth Quarter Milestone Report for theNational Spherical Torus Experiment Upgrade.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soukhanovskii, V. A.

2017-09-13

A successful high-performance plasma operation with a radiative divertor has been demonstrated on many tokamak devices, however, significant uncertainty remains in accurately modeling detachment thresholds, and in how detachment depends on divertor geometry. Whereas it was originally planned to perform dedicated divertor experiments on the National Spherical Tokamak Upgrade to address critical detachment and divertor geometry questions for this milestone, the experiments were deferred due to technical difficulties. Instead, existing NSTX divertor data was summarized and re-analyzed where applicable, and additional simulations were performed.

Study of performance and propagation characteristics of wire and planar structures around human body.

PubMed

Aroul, A L Praveen; Bhatia, Dinesh

2011-01-01

Continued miniaturization of electronic devices and technological advancements in wireless communications has made wearable body-centric telemedicine systems viable. Antennas play a crucial role in characterizing the efficiency and reliability of these systems. The performance characteristics such as the radiation pattern, gain, efficiency of the antennas get adversely affected due to the presence of lossy human body tissues. In this paper we investigate the above mentioned performance parameters and radio frequency transmission properties of wire and planar structures operating at ISM frequency band of 2.40-2.50 GHz in the proximity of human body.

Determining the Impact of Steady-State PV Fault Current Injections on Distribution Protection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seuss, John; Reno, Matthew J.; Broderick, Robert Joseph

This report investigates the fault current contribution from a single large PV system and the impact it has on existing distribution overcurrent protection devices. Assumptions are made about the modeling of the PV system under fault to perform exhaustive steady - state fault analyses throughout distribution feeder models. Each PV interconnection location is tested to determine how the size of the PV system affects the fault current measured by each protection device. This data is then searched for logical conditions that indicate whether a protection device has operated in a manner that will cause more customer outages due to themore » addition of the PV system. This is referred to as a protection issue , and there are four unique types of issues that have been identified in the study. The PV system size at which any issues occur are recorded to determine the feeder's PV hosting capacity limitations due to interference with protection settings. The analysis is carried out on six feeder models. The report concludes with a discussion of the prevalence and cause of each protection issue caused by PV system fault current.« less

Identification and validation of nebulized aerosol devices for sputum induction

PubMed Central

Davidson, Warren J; Dennis, John; The, Stephanie; Litoski, Belinda; Pieron, Cora; Leigh, Richard

2014-01-01

Induced sputum cell count measurement has proven reliability for evaluating airway inflammation in patients with asthma and other airway diseases. Although the use of nebulizer devices for sputum induction is commonplace, they are generally labelled as single-patient devices by the manufacturer and, therefore, cannot be used for multiple patients in large clinical sputum induction programs due to infect ion-control requirements. Accordingly, this study investigated the aerosol characteristics of alternative devices that could be used in such programs. BACKGROUND: Induced sputum cell counts are a noninvasive and reliable method for evaluating the presence, type and degree of airway inflammation in patients with asthma. Currently, standard nebulizer devices used for sputum induction in multiple patients are labelled as single-patient devices by the manufacturer, which conflicts with infection prevention and control requirements. As such, these devices cannot feasibly be used in a clinical sputum induction program. Therefore, there is a need to identify alternative nebulizer devices that are either disposable or labelled for multi-patient use. OBJECTIVE: To apply validated rigorous, scientific testing methods to identify and validate commercially available nebulizer devices appropriate for use in a clinical sputum induction program. METHODS: Measurement of nebulized aerosol output and size for the selected nebulizer designs followed robust International Organization for Standardization methods. Sputum induction using two of these nebulizers was successfully performed on 10 healthy adult subjects. The cytotechnologist performing sputum cell counts was blinded to the type of nebulizer used. RESULTS: The studied nebulizers had variable aerosol outputs. The AeroNeb Solo (Aerogen, Ireland), Omron NE-U17 (Omron, Japan) and EASYneb II (Flaem Nuova, Italy) systems were found to have similar measurements of aerosol size. There was no significant difference in induced sputum cell results between the AeroNeb Solo and EASYneb II devices. DISCUSSION: There is a need for rigorous, scientific evaluation of nebulizer devices for clinical applications, including sputum induction, for measurement of cell counts. CONCLUSION: The present study was the most comprehensive analysis of different nebulizer devices for sputum induction to measure cell counts, and provides a framework for appropriate evaluation of nebulizer devices for induced sputum testing. PMID:24288700

Multi-shape memory polymers achieved by the spatio-assembly of 3D printable thermoplastic building blocks.

PubMed

Li, Hongze; Gao, Xiang; Luo, Yingwu

2016-04-07

Multi-shape memory polymers were prepared by the macroscale spatio-assembly of building blocks in this work. The building blocks were methyl acrylate-co-styrene (MA-co-St) copolymers, which have the St-block-(St-random-MA)-block-St tri-block chain sequence. This design ensures that their transition temperatures can be adjusted over a wide range by varying the composition of the middle block. The two St blocks at the chain ends can generate a crosslink network in the final device to achieve strong bonding force between building blocks and the shape memory capacity. Due to their thermoplastic properties, 3D printing was employed for the spatio-assembly to build devices. This method is capable of introducing many transition phases into one device and preparing complicated shapes via 3D printing. The device can perform a complex action via a series of shape changes. Besides, this method can avoid the difficult programing of a series of temporary shapes. The control of intermediate temporary shapes was realized via programing the shapes and locations of building blocks in the final device.

Electromechanically generating electricity with a gapped-graphene electric generator

NASA Astrophysics Data System (ADS)

Dressen, Donald; Golovchenko, Jene

2015-03-01

We demonstrate the fabrication and operation of a gapped-graphene electric generator (G-GEG) device. The G-GEG generates electricity from the mechanical oscillation of droplets of electrolytes and ionic liquids. The spontaneous adsorption of ionic species on graphene charges opposing electric double-layer capacitors (EDLCs) on each half of the device. Modulating the area of contact between the droplet and graphene leads to adsorption/desorption of ions, effectively charging/discharging each EDLC and generating a current. The flow of current supports a potential difference across the G-GEG due to the device's internal impedance. Both the magnitude and polarity of the induced current and voltage show a strong dependence on the type of ionic species used, suggesting that certain ions interact more strongly with graphene than others. We find that a simple model circuit consisting of an AC current source in series with a resistor and a time-varying capacitor accurately predicts the device's dynamic behavior. Additionally, we discuss the effect of graphene's intrinsic quantum capacitance on the G-GEG's performance and speculate on the utility of the device in the context of energy harvesting.

Multi-Level Bitmap Indexes for Flash Memory Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Kesheng; Madduri, Kamesh; Canon, Shane

2010-07-23

Due to their low access latency, high read speed, and power-efficient operation, flash memory storage devices are rapidly emerging as an attractive alternative to traditional magnetic storage devices. However, tests show that the most efficient indexing methods are not able to take advantage of the flash memory storage devices. In this paper, we present a set of multi-level bitmap indexes that can effectively take advantage of flash storage devices. These indexing methods use coarsely binned indexes to answer queries approximately, and then use finely binned indexes to refine the answers. Our new methods read significantly lower volumes of data atmore » the expense of an increased disk access count, thus taking full advantage of the improved read speed and low access latency of flash devices. To demonstrate the advantage of these new indexes, we measure their performance on a number of storage systems using a standard data warehousing benchmark called the Set Query Benchmark. We observe that multi-level strategies on flash drives are up to 3 times faster than traditional indexing strategies on magnetic disk drives.« less

Characterization of perovskite solar cells: Towards a reliable measurement protocol

NASA Astrophysics Data System (ADS)

Zimmermann, Eugen; Wong, Ka Kan; Müller, Michael; Hu, Hao; Ehrenreich, Philipp; Kohlstädt, Markus; Würfel, Uli; Mastroianni, Simone; Mathiazhagan, Gayathri; Hinsch, Andreas; Gujar, Tanaji P.; Thelakkat, Mukundan; Pfadler, Thomas; Schmidt-Mende, Lukas

2016-09-01

Lead halide perovskite solar cells have shown a tremendous rise in power conversion efficiency with reported record efficiencies of over 20% making this material very promising as a low cost alternative to conventional inorganic solar cells. However, due to a differently severe "hysteretic" behaviour during current density-voltage measurements, which strongly depends on scan rate, device and measurement history, preparation method, device architecture, etc., commonly used solar cell measurements do not give reliable or even reproducible results. For the aspect of commercialization and the possibility to compare results of different devices among different laboratories, it is necessary to establish a measurement protocol which gives reproducible results. Therefore, we compare device characteristics derived from standard current density-voltage measurements with stabilized values obtained from an adaptive tracking of the maximum power point and the open circuit voltage as well as characteristics extracted from time resolved current density-voltage measurements. Our results provide insight into the challenges of a correct determination of device performance and propose a measurement protocol for a reliable characterisation which is easy to implement and has been tested on varying perovskite solar cells fabricated in different laboratories.

Development master arm of 2-DOF planar parallel manipulator for In-Vitro Fertilization

NASA Astrophysics Data System (ADS)

Thamrongaphichartkul, Kitti; Vongbunyong, Supachai; Nuntakarn, Lalana

2018-01-01

Micromanipulator is a mechanical device used for manipulating miniature objects in the order of micron. It is widely used in In-Vitro Fertilization (IVF) in which sperms will be held in a micro-needle and penetrate to an oocyte for fertilization. IVF needs to be performed by high skill embryologists to control the movement of the needle accurately due to the lack of tactile perception of the user. Haptic device is a device that can transmit and simulate position, velocity and force in order to enhance interaction between the user and system. However, commercially available haptic devices have unnecessary degrees of freedom and limited workspace which are inappropriate for IVF process. This paper focuses on development of a haptic device for using in IVF process. It will be used as a master arm for the master-slave system for IVF process in order to enhance the ability of users to control the micromanipulator. As a result, the embryologist is able to carry out the IVF process more effectively with having tactile perception.

High to ultra-high power electrical energy storage.

PubMed

Sherrill, Stefanie A; Banerjee, Parag; Rubloff, Gary W; Lee, Sang Bok

2011-12-14

High power electrical energy storage systems are becoming critical devices for advanced energy storage technology. This is true in part due to their high rate capabilities and moderate energy densities which allow them to capture power efficiently from evanescent, renewable energy sources. High power systems include both electrochemical capacitors and electrostatic capacitors. These devices have fast charging and discharging rates, supplying energy within seconds or less. Recent research has focused on increasing power and energy density of the devices using advanced materials and novel architectural design. An increase in understanding of structure-property relationships in nanomaterials and interfaces and the ability to control nanostructures precisely has led to an immense improvement in the performance characteristics of these devices. In this review, we discuss the recent advances for both electrochemical and electrostatic capacitors as high power electrical energy storage systems, and propose directions and challenges for the future. We asses the opportunities in nanostructure-based high power electrical energy storage devices and include electrochemical and electrostatic capacitors for their potential to open the door to a new regime of power energy.

A vacuum manifold for rapid world-to-chip connectivity of complex PDMS microdevices.

PubMed

Cooksey, Gregory A; Plant, Anne L; Atencia, Javier

2009-05-07

The lack of simple interfaces for microfluidic devices with a large number of inlets significantly limits production and utilization of these devices. In this article, we describe the fabrication of a reusable manifold that provides rapid world-to-chip connectivity. A vacuum network milled into a rigid manifold holds microdevices and prevents leakage of fluids injected into the device from ports in the manifold. A number of different manifold designs were explored, and all performed similarly, yielding an average of 100 kPa (15 psi) fluid holding pressure. The wide applicability of this manifold concept is demonstrated by interfacing with a 51-inlet microfluidic chip containing 144 chambers and hundreds of embedded pneumatic valves. Due to the speed of connectivity, the manifolds are ideal for rapid prototyping and are well suited to serve as "universal" interfaces.

Upper limb functional electrical stimulation devices and their man-machine interfaces.

PubMed

Venugopalan, L; Taylor, P N; Cobb, J E; Swain, I D

2015-01-01

Functional Electrical Stimulation (FES) is a technique that uses electricity to activate the nerves of a muscle that is paralysed due to hemiplegia, multiple sclerosis, Parkinson's disease or spinal cord injury (SCI). FES has been widely used to restore upper limb functions in people with hemiplegia and C5-C7 tetraplegia and has improved their ability to perform their activities of daily living (ADL). At the time of writing, a detailed literature review of the existing upper limb FES devices and their man-machine interfaces (MMI) showed that only the NESS H200 was commercially available. However, the rigid arm splint doesn't fit everyone and prevents the use of a tenodesis grip. Hence, a robust and versatile upper limb FES device that can be used by a wider group of people is required.

Study and characterization of a MEMS micromirror device

NASA Astrophysics Data System (ADS)

Furlong, Cosme; Pryputniewicz, Ryszard J.

2004-08-01

In this paper, advances in our study and characterization of a MEMS micromirror device are presented. The micromirror device, of 510 mm characteristic length, operates in a dynamic mode with a maximum displacement on the order of 10 mm along its principal optical axis and oscillation frequencies of up to 1.3 kHz. Developments are carried on by analytical, computational, and experimental methods. Analytical and computational nonlinear geometrical models are developed in order to determine the optimal loading-displacement operational characteristics of the micromirror. Due to the operational mode of the micromirror, the experimental characterization of its loading-displacement transfer function requires utilization of advanced optical metrology methods. Optoelectronic holography (OEH) methodologies based on multiple wavelengths that we are developing to perform such characterization are described. It is shown that the analytical, computational, and experimental approach is effective in our developments.

A novel thin-film transistor with step gate-overlapped lightly doped drain and raised source/drain design

NASA Astrophysics Data System (ADS)

Chien, Feng-Tso; Chen, Jian-Liang; Chen, Chien-Ming; Chen, Chii-Wen; Cheng, Ching-Hwa; Chiu, Hsien-Chin

2017-11-01

In this paper, a novel step gate-overlapped lightly doped drain (GOLDD) with raised source/drain (RSD) structure (SGORSD) is proposed for TFT electronic device application. The new SGORSD structure could obtain a low electric field at channel near the drain side owing to a step GOLDD design. Compared to the conventional device, the SGORSD TFT exhibits a better kink effect and higher breakdown performance due to the reduced drain electric field (D-EF). In addition, the leakage current also can be suppressed. Moreover, the device stability, such as the threshold voltage shift and drain current degradation under a high gate bias, is improved by the design of SGORSD structure. Therefore, this novel step GOLDD structure can be a promising design to be used in active-matrix flat panel electronics.

High operation temperature of HgCdTe photodiodes by bulk defect passivation

NASA Astrophysics Data System (ADS)

Boieriu, Paul; Velicu, S.; Bommena, R.; Buurma, C.; Blisset, C.; Grein, C.; Sivananthan, S.; Hagler, P.

2013-01-01

Spatial noise and the loss of photogenerated current due material non-uniformities limit the performance of long wavelength infrared (LWIR) HgCdTe detector arrays. Reducing the electrical activity of defects is equivalent to lowering their density, thereby allowing detection and discrimination over longer ranges. Infrared focal plane arrays (IRFPAs) in other spectral bands will also benefit from detectivity and uniformity improvements. Larger signal-to-noise ratios permit either improved accuracy of detection/discrimination when an IRFPA is employed under current operating conditions, or provide similar performance with the IRFPA operating under less stringent conditions such as higher system temperature, increased system jitter or damaged read out integrated circuit (ROIC) wells. The bulk passivation of semiconductors with hydrogen continues to be investigated for its potential to become a tool for the fabrication of high performance devices. Inductively coupled plasmas have been shown to improve the quality and uniformity of semiconductor materials and devices. The retention of the benefits following various aging conditions is discussed here.

GaAs MOEMS Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

SPAHN, OLGA B.; GROSSETETE, GRANT D.; CICH, MICHAEL J.

2003-03-01

Many MEMS-based components require optical monitoring techniques using optoelectronic devices for converting mechanical position information into useful electronic signals. While the constituent piece-parts of such hybrid opto-MEMS components can be separately optimized, the resulting component performance, size, ruggedness and cost are substantially compromised due to assembly and packaging limitations. GaAs MOEMS offers the possibility of monolithically integrating high-performance optoelectronics with simple mechanical structures built in very low-stress epitaxial layers with a resulting component performance determined only by GaAs microfabrication technology limitations. GaAs MOEMS implicitly integrates the capability for radiation-hardened optical communications into the MEMS sensor or actuator component, a vitalmore » step towards rugged integrated autonomous microsystems that sense, act, and communicate. This project establishes a new foundational technology that monolithically combines GaAs optoelectronics with simple mechanics. Critical process issues addressed include selectivity, electrochemical characteristics, and anisotropy of the release chemistry, and post-release drying and coating processes. Several types of devices incorporating this novel technology are demonstrated.« less

Mobile Videoconferencing Apps for Telemedicine

PubMed Central

Liu, Wei-Li; Locatis, Craig; Ackerman, Michael

2016-01-01

Abstract Introduction: The quality and performance of several videoconferencing applications (apps) tested on iOS (Apple, Cupertino, CA) and Android™ (Google, Mountain View, CA) mobile platforms using Wi-Fi (802.11), third-generation (3G), and fourth-generation (4G) cellular networks are described. Materials and Methods: The tests were done to determine how well apps perform compared with videoconferencing software installed on computers or with more traditional videoconferencing using dedicated hardware. The rationale for app assessment and the testing methodology are described. Results: Findings are discussed in relation to operating system platform (iOS or Android) for which the apps were designed and the type of network (Wi-Fi, 3G, or 4G) used. The platform, network, and apps interact, and it is impossible to discuss videoconferencing experienced on mobile devices in relation to one of these factors without referencing the others. Conclusions: Apps for mobile devices can vary significantly from other videoconferencing software or hardware. App performance increased over the testing period due to improvements in network infrastructure and how apps manage bandwidth. PMID:26204322

Aqueous rechargeable zinc/sodium vanadate batteries with enhanced performance from simultaneous insertion of dual carriers.

PubMed

Wan, Fang; Zhang, Linlin; Dai, Xi; Wang, Xinyu; Niu, Zhiqiang; Chen, Jun

2018-04-25

Rechargeable aqueous zinc-ion batteries are promising energy storage devices due to their high safety and low cost. However, they remain in their infancy because of the limited choice of positive electrodes with high capacity and satisfactory cycling performance. Furthermore, their energy storage mechanisms are not well established yet. Here we report a highly reversible zinc/sodium vanadate system, where sodium vanadate hydrate nanobelts serve as positive electrode and zinc sulfate aqueous solution with sodium sulfate additive is used as electrolyte. Different from conventional energy release/storage in zinc-ion batteries with only zinc-ion insertion/extraction, zinc/sodium vanadate hydrate batteries possess a simultaneous proton, and zinc-ion insertion/extraction process that is mainly responsible for their excellent performance, such as a high reversible capacity of 380 mAh g -1 and capacity retention of 82% over 1000 cycles. Moreover, the quasi-solid-state zinc/sodium vanadate hydrate battery is also a good candidate for flexible energy storage device.

Application of hybrid supercapacitor using granule Li4Ti5O12/activated carbon with variation of current density

NASA Astrophysics Data System (ADS)

Lee, Byung-Gwan; Lee, Seung-Hwan

2017-03-01

We report the electrochemical performance of asymmetric hybrid supercapacitors composed of granule Li4Ti5O12 as an anode and activated carbon as a cathode with different current densities. It is demonstrated that the hybrid supercapacitors show good initial discharge capacities were ranged from 39.8 to 46.4 F g-1 in the current densities range of 0.3-1 A g-1. The performance degradation is proportional to the current density due to quick gassing, resulting from H2O and HF formation. In particular, the hybrid supercapacitors show the pretty good cycling stability of 97.4%, even at the high current density of 0.8 A g-1, which are among most important performance in the real application for energy storage devices. Therefore, we believe that hybrid supercapacitors using granule Li4Ti5O12/activated carbon are eligible for the promising next generation energy devices.

Mobile Videoconferencing Apps for Telemedicine.

PubMed

Zhang, Kai; Liu, Wei-Li; Locatis, Craig; Ackerman, Michael

2016-01-01

The quality and performance of several videoconferencing applications (apps) tested on iOS (Apple, Cupertino, CA) and Android (Google, Mountain View, CA) mobile platforms using Wi-Fi (802.11), third-generation (3G), and fourth-generation (4G) cellular networks are described. The tests were done to determine how well apps perform compared with videoconferencing software installed on computers or with more traditional videoconferencing using dedicated hardware. The rationale for app assessment and the testing methodology are described. Findings are discussed in relation to operating system platform (iOS or Android) for which the apps were designed and the type of network (Wi-Fi, 3G, or 4G) used. The platform, network, and apps interact, and it is impossible to discuss videoconferencing experienced on mobile devices in relation to one of these factors without referencing the others. Apps for mobile devices can vary significantly from other videoconferencing software or hardware. App performance increased over the testing period due to improvements in network infrastructure and how apps manage bandwidth.

A New Cuffless Device for Measuring Blood Pressure: A Real-Life Validation Study

PubMed Central

Schoot, Tessa S; Weenk, Mariska; van de Belt, Tom H; Engelen, Lucien JLPG; van Goor, Harry

2016-01-01

Background Cuffless blood pressure (BP) monitoring devices, based on pulse transit time, are being developed as an easy-to-use, more convenient, fast, and relatively cheap alternative to conventional BP measuring devices based on cuff occlusion. Thereby they may provide a great alternative to BP self-measurement. Objective The objective of our study was to evaluate the performance of the first release of the Checkme Health Monitor (Viatom Technology), a cuffless BP monitor, in a real-life setting. Furthermore, we wanted to investigate whether the posture of the volunteer and the position of the device relative to the heart level would influence its outcomes. Methods Study volunteers fell into 3 BP ranges: high (>160 mmHg), normal (130–160 mmHg), and low (<130 mmHg). All requirements for test environment, observer qualification, volunteer recruitment, and BP measurements were met according to the European Society of Hypertension International Protocol (ESH-IP) for the validation of BP measurement devices. After calibrating the Checkme device, we measured systolic BP with Checkme and a validated, oscillometric reference BP monitor (RM). Measurements were performed in randomized order both in supine and in sitting position, and with Checkme at and above heart level. Results We recruited 52 volunteers, of whom we excluded 15 (12 due to calibration failure with Checkme, 3 due to a variety of reasons). The remaining 37 volunteers were divided into low (n=14), medium (n=13), and high (n=10) BP ranges. There were 18 men and 19 women, with a mean age of 54.1 (SD 14.5) years, and mean recruitment systolic BP of 141.7 (SD 24.7) mmHg. BP results obtained by RM and Checkme correlated well. In the supine position, the difference between the RM and Checkme was >5 mmHg in 17 of 37 volunteers (46%), of whom 9 of 37 (24%) had a difference >10 mmHg and 5 of 37 (14%) had a difference >15 mmHg. Conclusions BP obtained with Checkme correlated well with RM BP, particularly in the position (supine) in which the device was calibrated. These preliminary results are promising for conducting further research on cuffless BP measurement in the clinical and outpatient settings. PMID:27150527

Home-based Computer Assisted Arm Rehabilitation (hCAAR) robotic device for upper limb exercise after stroke: results of a feasibility study in home setting.

PubMed

Sivan, Manoj; Gallagher, Justin; Makower, Sophie; Keeling, David; Bhakta, Bipin; O'Connor, Rory J; Levesley, Martin

2014-12-12

Home-based robotic technologies may offer the possibility of self-directed upper limb exercise after stroke as a means of increasing the intensity of rehabilitation treatment. The current literature has a paucity of robotic devices that have been tested in a home environment. The aim of this research project was to evaluate a robotic device Home-based Computer Assisted Arm Rehabilitation (hCAAR) that can be used independently at home by stroke survivors with upper limb weakness. hCAAR device comprises of a joystick handle moved by the weak upper limb to perform tasks on the computer screen. The device provides assistance to the movements depending on users ability. Nineteen participants (stroke survivors with upper limb weakness) were recruited. Outcome measures performed at baseline (A0), at end of 8-weeks of hCAAR use (A1) and 1 month after end of hCAAR use (A2) were: Optotrak kinematic variables, Fugl Meyer Upper Extremity motor subscale (FM-UE), Action Research Arm Test (ARAT), Medical Research Council (MRC) and Modified Ashworth Scale (MAS), Chedoke Arm and Hand Activity Inventory (CAHAI) and ABILHAND. Two participants were unable to use hCAAR: one due to severe paresis and the other due to personal problems. The remaining 17 participants were able to use the device independently in their home setting. No serious adverse events were reported. The median usage time was 433 minutes (IQR 250 - 791 min). A statistically significant improvement was observed in the kinematic and clinical outcomes at A1. The median gain in the scores at A1 were by: movement time 19%, path length 15% and jerk 19%, FM-UE 1 point, total MAS 1.5 point, total MRC 2 points, ARAT 3 points, CAHAI 5.5 points and ABILHAND 3 points. Three participants showed clinically significant improvement in all the clinical outcomes. The hCAAR feasibility study is the first clinical study of its kind reported in the current literature; in this study, 17 participants used the robotic device independently for eight weeks in their own homes with minimal supervision from healthcare professionals. Statistically significant improvements were observed in the kinematic and clinical outcomes in the study.

A rhythm-based authentication scheme for smart media devices.

PubMed

Lee, Jae Dong; Jeong, Young-Sik; Park, Jong Hyuk

2014-01-01

In recent years, ubiquitous computing has been rapidly emerged in our lives and extensive studies have been conducted in a variety of areas related to smart devices, such as tablets, smartphones, smart TVs, smart refrigerators, and smart media devices, as a measure for realizing the ubiquitous computing. In particular, smartphones have significantly evolved from the traditional feature phones. Increasingly higher-end smartphone models that can perform a range of functions are now available. Smart devices have become widely popular since they provide high efficiency and great convenience for not only private daily activities but also business endeavors. Rapid advancements have been achieved in smart device technologies to improve the end users' convenience. Consequently, many people increasingly rely on smart devices to store their valuable and important data. With this increasing dependence, an important aspect that must be addressed is security issues. Leaking of private information or sensitive business data due to loss or theft of smart devices could result in exorbitant damage. To mitigate these security threats, basic embedded locking features are provided in smart devices. However, these locking features are vulnerable. In this paper, an original security-locking scheme using a rhythm-based locking system (RLS) is proposed to overcome the existing security problems of smart devices. RLS is a user-authenticated system that addresses vulnerability issues in the existing locking features and provides secure confidentiality in addition to convenience.

A Rhythm-Based Authentication Scheme for Smart Media Devices

PubMed Central

Lee, Jae Dong; Park, Jong Hyuk

2014-01-01

In recent years, ubiquitous computing has been rapidly emerged in our lives and extensive studies have been conducted in a variety of areas related to smart devices, such as tablets, smartphones, smart TVs, smart refrigerators, and smart media devices, as a measure for realizing the ubiquitous computing. In particular, smartphones have significantly evolved from the traditional feature phones. Increasingly higher-end smartphone models that can perform a range of functions are now available. Smart devices have become widely popular since they provide high efficiency and great convenience for not only private daily activities but also business endeavors. Rapid advancements have been achieved in smart device technologies to improve the end users' convenience. Consequently, many people increasingly rely on smart devices to store their valuable and important data. With this increasing dependence, an important aspect that must be addressed is security issues. Leaking of private information or sensitive business data due to loss or theft of smart devices could result in exorbitant damage. To mitigate these security threats, basic embedded locking features are provided in smart devices. However, these locking features are vulnerable. In this paper, an original security-locking scheme using a rhythm-based locking system (RLS) is proposed to overcome the existing security problems of smart devices. RLS is a user-authenticated system that addresses vulnerability issues in the existing locking features and provides secure confidentiality in addition to convenience. PMID:25110743

A two-axis micromachined silicon actuator with micrometer range electrostatic actuation and picometer sensitive capacitive detection

NASA Astrophysics Data System (ADS)

Ayela, F.; Bret, J. L.; Chaussy, J.; Fournier, T.; Ménégaz, E.

2000-05-01

This article presents an innovative micromachined silicon actuator. A 50-μm-thick silicon foil is anodically bonded onto a broached Pyrex substrate. A free standing membrane and four coplanar electrodes in close proximity are then lithographied and etched. The use of phosphorus doped silicon with low electrical resistivity allows the application of an electrostatic force between one electrode and the moving diaphragm. This plane displacement and the induced interelectrode variation are capacitively detected. Due to the very low electrical resistivity of the doped silicon, there is no need to metallize the vertical trenches of the device. No piezoelectric transducer takes place so that the mechanical device is free from any hysteretic or temperature dependance. The range of the possible actuation along the x and y axis is around 5 μm. The actual sensitivity is xn=0.54 Å/Hz1/2 and yn=0.14 Å/Hz1/2. The microengineering steps and the electronic setup devoted to design the actuator and to perform relative capacitive measurements ΔC/C=10-6 from an initial value C≈10-13 F are described. The elaborated tests and performances of the device are presented. As a conclusion, some experimental projects using this subnanometric sensitive device are mentioned.

An Electrochemical Capacitor with Applicable Energy Density of 7.4 Wh/kg at Average Power Density of 3000 W/kg.

PubMed

Zhai, Teng; Lu, Xihong; Wang, Hanyu; Wang, Gongming; Mathis, Tyler; Liu, Tianyu; Li, Cheng; Tong, Yexiang; Li, Yat

2015-05-13

Electrochemical capacitors represent a new class of charge storage devices that can simultaneously achieve high energy density and high power density. Previous reports have been primarily focused on the development of high performance capacitor electrodes. Although these electrodes have achieved excellent specific capacitance based on per unit mass of active materials, the gravimetric energy densities calculated based on the weight of entire capacitor device were fairly small. This is mainly due to the large mass ratio between current collector and active material. We aimed to address this issue by a 2-fold approach of minimizing the mass of current collector and increasing the electrode performance. Here we report an electrochemical capacitor using 3D graphene hollow structure as current collector, vanadium sulfide and manganese oxide as anode and cathode materials, respectively. 3D graphene hollow structure provides a lightweight and highly conductive scaffold for deposition of pseudocapacitive materials. The device achieves an excellent active material ratio of 24%. Significantly, it delivers a remarkable energy density of 7.4 Wh/kg (based on the weight of entire device) at the average power density of 3000 W/kg. This is the highest gravimetric energy density reported for asymmetric electrochemical capacitors at such a high power density.

Potassium-induced surface modification of Cu(In,Ga)Se2 thin films for high-efficiency solar cells.

PubMed

Chirilă, Adrian; Reinhard, Patrick; Pianezzi, Fabian; Bloesch, Patrick; Uhl, Alexander R; Fella, Carolin; Kranz, Lukas; Keller, Debora; Gretener, Christina; Hagendorfer, Harald; Jaeger, Dominik; Erni, Rolf; Nishiwaki, Shiro; Buecheler, Stephan; Tiwari, Ayodhya N

2013-12-01

Thin-film photovoltaic devices based on chalcopyrite Cu(In,Ga)Se2 (CIGS) absorber layers show excellent light-to-power conversion efficiencies exceeding 20%. This high performance level requires a small amount of alkaline metals incorporated into the CIGS layer, naturally provided by soda lime glass substrates used for processing of champion devices. The use of flexible substrates requires distinct incorporation of the alkaline metals, and so far mainly Na was believed to be the most favourable element, whereas other alkaline metals have resulted in significantly inferior device performance. Here we present a new sequential post-deposition treatment of the CIGS layer with sodium and potassium fluoride that enables fabrication of flexible photovoltaic devices with a remarkable conversion efficiency due to modified interface properties and mitigation of optical losses in the CdS buffer layer. The described treatment leads to a significant depletion of Cu and Ga concentrations in the CIGS near-surface region and enables a significant thickness reduction of the CdS buffer layer without the commonly observed losses in photovoltaic parameters. Ion exchange processes, well known in other research areas, are proposed as underlying mechanisms responsible for the changes in chemical composition of the deposited CIGS layer and interface properties of the heterojunction.

Materials Design and System Construction for Conventional and New‐Concept Supercapacitors

PubMed Central

Wu, Zhong; Li, Lin

2017-01-01

With the development of renewable energy and electrified transportation, electrochemical energy storage will be more urgent in the future. Supercapacitors have received extensive attention due to their high power density, fast charge and discharge rates, and long‐term cycling stability. During past five years, supercapacitors have been boomed benefited from the development of nanostructured materials synthesis and the promoted innovation of devices construction. In this review, we have summarized the current state‐of‐the‐art development on the fabrication of high‐performance supercapacitors. From the electrode material perspective, a variety of materials have been explored for advanced electrode materials with smart material‐design strategies such as carbonaceous materials, metal compounds and conducting polymers. Proper nanostructures are engineered to provide sufficient electroactive sites and enhance the kinetics of ion and electron transport. Besides, new‐concept supercapacitors have been developed for practical application. Microsupercapacitors and fiber supercapacitors have been explored for portable and compact electronic devices. Subsequently, we have introduced Li‐/Na‐ion supercapacitors composed of battery‐type electrodes and capacitor‐type electrode. Integrated energy devices are also explored by incorporating supercapacitors with energy conversion systems for sustainable energy storage. In brief, this review provides a comprehensive summary of recent progress on electrode materials design and burgeoning devices constructions for high‐performance supercapacitors. PMID:28638780

Performance optimization in electric field gradient focusing.

PubMed

Sun, Xuefei; Farnsworth, Paul B; Tolley, H Dennis; Warnick, Karl F; Woolley, Adam T; Lee, Milton L

2009-01-02

Electric field gradient focusing (EFGF) is a technique used to simultaneously separate and concentrate biomacromolecules, such as proteins, based on the opposing forces of an electric field gradient and a hydrodynamic flow. Recently, we reported EFGF devices fabricated completely from copolymers functionalized with poly(ethylene glycol), which display excellent resistance to protein adsorption. However, the previous devices did not provide the predicted linear electric field gradient and stable current. To improve performance, Tris-HCl buffer that was previously doped in the hydrogel was replaced with a phosphate buffer containing a salt (i.e., potassium chloride, KCl) with high mobility ions. The new devices exhibited stable current, good reproducibility, and a linear electric field distribution in agreement with the shaped gradient region design due to improved ion transport in the hydrogel. The field gradient was calculated based on theory to be approximately 5.76 V/cm(2) for R-phycoerythrin when the applied voltage was 500 V. The effect of EFGF separation channel dimensions was also investigated; a narrower focused band was achieved in a smaller diameter channel. The relationship between the bandwidth and channel diameter is consistent with theory. Three model proteins were resolved in an EFGF channel of this design. The improved device demonstrated 14,000-fold concentration of a protein sample (from 2 ng/mL to 27 microg/mL).

Materials Design and System Construction for Conventional and New-Concept Supercapacitors.

PubMed

Wu, Zhong; Li, Lin; Yan, Jun-Min; Zhang, Xin-Bo

2017-06-01

With the development of renewable energy and electrified transportation, electrochemical energy storage will be more urgent in the future. Supercapacitors have received extensive attention due to their high power density, fast charge and discharge rates, and long-term cycling stability. During past five years, supercapacitors have been boomed benefited from the development of nanostructured materials synthesis and the promoted innovation of devices construction. In this review, we have summarized the current state-of-the-art development on the fabrication of high-performance supercapacitors. From the electrode material perspective, a variety of materials have been explored for advanced electrode materials with smart material-design strategies such as carbonaceous materials, metal compounds and conducting polymers. Proper nanostructures are engineered to provide sufficient electroactive sites and enhance the kinetics of ion and electron transport. Besides, new-concept supercapacitors have been developed for practical application. Microsupercapacitors and fiber supercapacitors have been explored for portable and compact electronic devices. Subsequently, we have introduced Li-/Na-ion supercapacitors composed of battery-type electrodes and capacitor-type electrode. Integrated energy devices are also explored by incorporating supercapacitors with energy conversion systems for sustainable energy storage. In brief, this review provides a comprehensive summary of recent progress on electrode materials design and burgeoning devices constructions for high-performance supercapacitors.

Enhanced performance of inverted organic photovoltaic cells using CNTs-TiO(X) nanocomposites as electron injection layer.

PubMed

Zhang, Hong; Xu, Meifeng; Cui, Rongli; Guo, Xihong; Yang, Shangyuan; Liao, Liangsheng; Jia, Quanjie; Chen, Yu; Dong, Jinquan; Sun, Baoyun

2013-09-06

In this study, we fabricated inverted organic photovoltaic cells with the structure ITO/carbon nanotubes (CNTs)-TiO(X)/P3HT:PCBM/MoO₃/Al by spin casting CNTs-TiO(X) nanocomposite (CNTs-TiO(X)) as the electron injection layer onto ITO/glass substrates. The power conversion efficiency (PCE) of the 0.1 wt% single-walled nanotubes (SWNTs)-TiO(X) nanocomposite device was almost doubled compared with the TiO(X) device, but with increasing concentration of the incorporated SWNTs in the TiO(X) film, the performance of the devices appeared to decrease rapidly. Devices with multi-walled NTs in the TiO(X) film have a similar trend. This phenomenon mainly depends on the inherent physical and chemical characteristics of CNTs such as their high surface area, their electron-accepting properties and their excellent carrier mobility. However, with increasing concentration of CNTs, CNTs-TiO(X) current leakage pathways emerged and also a recombination of charges at the interfaces. In addition, there was a significant discovery. The incorporated CNTs were highly conducive to enhancing the degree of crystallinity and the ordered arrangement of the P3HT in the active layers, due to the intermolecular π-π stacking interactions between CNTs and P3HT.

Flexible and Robust Thermoelectric Generators Based on All-Carbon Nanotube Yarn without Metal Electrodes.

PubMed

Choi, Jaeyoo; Jung, Yeonsu; Yang, Seung Jae; Oh, Jun Young; Oh, Jinwoo; Jo, Kiyoung; Son, Jeong Gon; Moon, Seung Eon; Park, Chong Rae; Kim, Heesuk

2017-08-22

As practical interest in flexible/or wearable power-conversion devices increases, the demand for high-performance alternatives to thermoelectric (TE) generators based on brittle inorganic materials is growing. Herein, we propose a flexible and ultralight TE generator (TEG) based on carbon nanotube yarn (CNTY) with excellent TE performance. The as-prepared CNTY shows a superior electrical conductivity of 3147 S/cm due to increased longitudinal carrier mobility derived from a highly aligned structure. Our TEG is innovative in that the CNTY acts as multifunctions in the same device. The CNTY is alternatively doped into n- and p-types using polyethylenimine and FeCl 3 , respectively. The highly conductive CNTY between the doped regions is used as electrodes to minimize the circuit resistance, thereby forming an all-carbon TEG without additional metal deposition. A flexible TEG based on 60 pairs of n- and p-doped CNTY shows the maximum power density of 10.85 and 697 μW/g at temperature differences of 5 and 40 K, respectively, which are the highest values among reported TEGs based on flexible materials. We believe that the strategy proposed here to improve the power density of flexible TEG by introducing highly aligned CNTY and designing a device without metal electrodes shows great potential for the flexible/or wearable power-conversion devices.

Adaptive Transcutaneous Power Transfer to Implantable Devices: A State of the Art Review

PubMed Central

Bocan, Kara N.; Sejdić, Ervin

2016-01-01

Wireless energy transfer is a broad research area that has recently become applicable to implantable medical devices. Wireless powering of and communication with implanted devices is possible through wireless transcutaneous energy transfer. However, designing wireless transcutaneous systems is complicated due to the variability of the environment. The focus of this review is on strategies to sense and adapt to environmental variations in wireless transcutaneous systems. Adaptive systems provide the ability to maintain performance in the face of both unpredictability (variation from expected parameters) and variability (changes over time). Current strategies in adaptive (or tunable) systems include sensing relevant metrics to evaluate the function of the system in its environment and adjusting control parameters according to sensed values through the use of tunable components. Some challenges of applying adaptive designs to implantable devices are challenges common to all implantable devices, including size and power reduction on the implant, efficiency of power transfer and safety related to energy absorption in tissue. Challenges specifically associated with adaptation include choosing relevant and accessible parameters to sense and adjust, minimizing the tuning time and complexity of control, utilizing feedback from the implanted device and coordinating adaptation at the transmitter and receiver. PMID:26999154

Adaptive Transcutaneous Power Transfer to Implantable Devices: A State of the Art Review.

PubMed

Bocan, Kara N; Sejdić, Ervin

2016-03-18

Wireless energy transfer is a broad research area that has recently become applicable to implantable medical devices. Wireless powering of and communication with implanted devices is possible through wireless transcutaneous energy transfer. However, designing wireless transcutaneous systems is complicated due to the variability of the environment. The focus of this review is on strategies to sense and adapt to environmental variations in wireless transcutaneous systems. Adaptive systems provide the ability to maintain performance in the face of both unpredictability (variation from expected parameters) and variability (changes over time). Current strategies in adaptive (or tunable) systems include sensing relevant metrics to evaluate the function of the system in its environment and adjusting control parameters according to sensed values through the use of tunable components. Some challenges of applying adaptive designs to implantable devices are challenges common to all implantable devices, including size and power reduction on the implant, efficiency of power transfer and safety related to energy absorption in tissue. Challenges specifically associated with adaptation include choosing relevant and accessible parameters to sense and adjust, minimizing the tuning time and complexity of control, utilizing feedback from the implanted device and coordinating adaptation at the transmitter and receiver.

Guide Catheter Extension Device Is Effective in Renal Angioplasty for Severely Calcified Lesions

PubMed Central

Sugimoto, Takeshi; Nomura, Tetsuya; Hori, Yusuke; Yoshioka, Kenichi; Kubota, Hiroshi; Miyawaki, Daisuke; Urata, Ryota; Kikai, Masakazu; Keira, Natsuya; Tatsumi, Tetsuya

2017-01-01

Patient: Male, 69 Final Diagnosis: Atherosclerotic renal artery stenosis Symptoms: None Medication: — Clinical Procedure: — Specialty: Radiology Objective: Unusual setting of medical care Background: The GuideLiner catheter extension device is a monorail-type “Child” support catheter that facilitates coaxial alignment with the guide catheter and provides an appropriate back-up force. This device has been developed in the field of coronary intervention, and now is becoming widely applied in the field of endovascular treatment. However, there has been no report on the effectiveness of the guide catheter extension device in percutaneous transluminal renal angioplasty (PTRA). Case Report: We encountered a case of atherosclerotic subtotal occlusion at the ostium of the left renal artery. Due to the severely calcified orifice and weaker back-up force provided by a JR4 guide catheter, we could not pass any guide-wires through the target lesion. Therefore, we introduced a guide catheter extension device, the GuideLiner catheter, through the guide catheter and achieved good guidewire maneuverability. We finally deployed 2 balloon-expandable stents and successfully performed all PTRA procedures. Conclusions: The guide catheter extension device can be effective in PTRA for severely calcified subtotal occlusion. PMID:28533503

Multifunctional tunneling devices based on graphene/h-BN/MoSe2 van der Waals heterostructures

NASA Astrophysics Data System (ADS)

Cheng, Ruiqing; Wang, Feng; Yin, Lei; Xu, Kai; Ahmed Shifa, Tofik; Wen, Yao; Zhan, Xueying; Li, Jie; Jiang, Chao; Wang, Zhenxing; He, Jun

2017-04-01

The vertically stacked devices based on van der Waals heterostructures (vdWHs) of two-dimensional layered materials (2DLMs) have attracted considerable attention due to their superb properties. As a typical structure, graphene/hexagonal boron nitride (h-BN)/graphene vdWH has been proved possible to make tunneling devices. Compared with graphene, transition metal dichalcogenides possess intrinsic bandgap, leading to high performance of electronic devices. Here, tunneling devices based on graphene/h-BN/MoSe2 vdWHs are designed for multiple functions. On the one hand, the device shows a typical tunneling field-effect transistor behavior. A high on/off ratio of tunneling current (5 × 103) and an ultrahigh current rectification ratio (7 × 105) are achieved, which are attributed to relatively small electronic affinity of MoSe2 and optimized thickness of h-BN. On the other hand, the same structure also realizes 2D non-volatile memory with a high program/erase current ratio (>105), large memory window (˜150 V from ±90 V), and good retention characteristic. These results could enhance the fundamental understanding of tunneling behavior in vdWHs and contribute to the design of ultrathin rectifiers and memory based on 2DLMs.

[Optical Care in Low Vision Patients].

PubMed

von Livonius, Bettina

2018-05-17

The numbers of low vision patients will steadily increase because of increasing longevity. It is important to be aware of those patients so that visual rehabilitation can be started as soon as possible and needed. Before the adjustment of low vision devices a diagnosis should be confirmed in order to check any therapeutic option and to ensure the best individual rehabilitation. If there is no further therapeutic option left a detailed anamnesis of the problems due to low vision should be made to ensure that every patient gets the optical or electronic device he really needs in his everyday life. The first step of the adjustment is to get the best subjective refraction for the far distance and the magnification needed for reading. Thereafter, the testing of different devices can start. It is important to know the advantages and disadvantages of the different devices. Besides the optical devices a counceling of the best light and of edge filters should be made. For the prescription of the devices certain criteria must be performed. That way it is possible to reach the main target namely to improve the quality of life of our low vision patients. Georg Thieme Verlag KG Stuttgart · New York.

Potential Space Applications for Body-Centric Wireless and E-Textile Antennas

NASA Technical Reports Server (NTRS)

Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.; Studor, George F.

2007-01-01

Space environment benefits of body-centric wireless communications are numerous, particularly in the context of long duration Lunar and Martian outposts that are in planning stages at several space agencies around the world. Since crew time for such missions is a scarce commodity, seamless integration of body-centric wireless from various sources is paramount. Sources include traditional data, such as audio, video, tracking, and biotelemetry. Newer data sources include positioning, orientation, and status of handheld tools and devices, as well as management and status of on-body inventories. In addition to offering lighter weight and flexibility, performance benefits of e-textile antennas are anticipated due to advantageous use of the body s surface area. In creating e-textile antennas and RF devices, researchers are faced with the challenge of transferring conventional and novel designs to textiles. Lack of impedance control, limited conductivity, and the inability to automatically create intricate designs are examples of limitations frequently attributed to e-textiles. Reliable interfaces between e-textiles and conventional hardware also represent significant challenges. Addressing these limitations is critical to the continued development and acceptance of fabric-based circuits for body-centric wireless applications. Here we present several examples of e-textile antennas and RF devices, created using a NASA-developed process, that overcome several of these limitations. The design and performance of an equiangular spiral, miniaturized spiral-loaded slot antenna, and a hybrid coupler are considered, with the e-textile devices showing comparable performance to like designs using conventional materials.

Interparticle coupling effect of silver-gold heterodimer to enhance light harvesting in ultrathin perovskite solar cell

NASA Astrophysics Data System (ADS)

Hu, Zhaosheng; Ma, Tingli; Hayase, Shuzi

2018-01-01

Thin perovskite solar cells are under intensive interest since they reduce the amount of absorber layer, especially toxic lead in methylammonium lead iodide (MAPbI3) devices and have wide application in semitransparent and tandem solar cells. However, due to the decrease of the layer thickness, thin perovskite devices with weak light-harvesting have poor performance. Moreover, the performance of plasmonic thin perovskite devices by incorporating noncoupling metal NPs cannot give comparable performance with normal devices. In this perspective, we discuss the implication of employing random silver-gold heterodimers in MAPbI3 solar cells with the aim of establishing some guidelines for the efficient ultrathin perovskite solar cells. This method induces an extraordinarily high light-harvesting for ultrathin perovskite film. And the underlying physical mechanism behind the enhanced absorption is deeply investigated by plasmon hybridization, dipolar-dipolar coupling method and FDTD simulation. We notice that perovskite embedded silver-gold heterodimer overcomes the vanished antibonding plasmon resononse (σ * ) in nonjunction area of gold/silver homodimer. A 150-nm perovskite film with embedded random silver-gold heterodimers with 80 nm size and 25 nm gap distance processes 28.15% absorption enhancement compared to the reference film, which is higher than the reported 10% for gold homodimers. And we also predict a realistic solution-processed, easy, and low-cost fabrication method, which provide a means to realize highly efficient ultrathin perovskite solar cell including other absorber-based photovoltaics.

Incomplete Ionization of a 110 meV Unintentional Donor in β-Ga2O3 and its Effect on Power Devices.

PubMed

Neal, Adam T; Mou, Shin; Lopez, Roberto; Li, Jian V; Thomson, Darren B; Chabak, Kelson D; Jessen, Gregg H

2017-10-16

Understanding the origin of unintentional doping in Ga 2 O 3 is key to increasing breakdown voltages of Ga 2 O 3 based power devices. Therefore, transport and capacitance spectroscopy studies have been performed to better understand the origin of unintentional doping in Ga 2 O 3 . Previously unobserved unintentional donors in commercially available [Formula: see text] Ga 2 O 3 substrates have been electrically characterized via temperature dependent Hall effect measurements up to 1000 K and found to have a donor energy of 110 meV. The existence of the unintentional donor is confirmed by temperature dependent admittance spectroscopy, with an activation energy of 131 meV determined via that technique, in agreement with Hall effect measurements. With the concentration of this donor determined to be in the mid to high 10 16  cm -3 range, elimination of this donor from the drift layer of Ga 2 O 3 power electronics devices will be key to pushing the limits of device performance. Indeed, analytical assessment of the specific on-resistance (R onsp ) and breakdown voltage of Schottky diodes containing the 110 meV donor indicates that incomplete ionization increases R onsp and decreases breakdown voltage as compared to Ga 2 O 3 Schottky diodes containing only the shallow donor. The reduced performance due to incomplete ionization occurs in addition to the usual tradeoff between R onsp and breakdown voltage.

Rational Design of Molecular Hole-Transporting Materials for Perovskite Solar Cells: Direct versus Inverted Device Configurations.

PubMed

Grisorio, Roberto; Iacobellis, Rosabianca; Listorti, Andrea; De Marco, Luisa; Cipolla, Maria Pia; Manca, Michele; Rizzo, Aurora; Abate, Antonio; Gigli, Giuseppe; Suranna, Gian Paolo

2017-07-26

Due to a still limited understanding of the reasons making 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) the state-of-the-art hole-transporting material (HTM) for emerging photovoltaic applications, the molecular tailoring of organic components for perovskite solar cells (PSCs) lacks in solid design criteria. Charge delocalization in radical cationic states can undoubtedly be considered as one of the essential prerequisites for an HTM, but this aspect has been investigated to a relatively minor extent. In marked contrast with the 3-D structure of Spiro-OMeTAD, truxene-based HTMs Trux1 and Trux2 have been employed for the first time in PSCs fabricated with a direct (n-i-p) or inverted (p-i-n) architecture, exhibiting a peculiar behavior with respect to the referential HTM. Notwithstanding the efficient hole extraction from the perovskite layer exhibited by Trux1 and Trux2 in direct configuration devices, their photovoltaic performances were detrimentally affected by their poor hole transport. Conversely, an outstanding improvement of the photovoltaic performances in dopant-free inverted configuration devices compared to Spiro-OMeTAD was recorded, ascribable to the use of thinner HTM layers. The rationalization of the photovoltaic performances exhibited by different configuration devices discussed in this paper can provide new and unexpected prospects for engineering the interface between the active layer of perovskite-based solar cells and the hole transporters.

Solution processible MoOx-incorporated graphene anode for efficient polymer light-emitting diodes

NASA Astrophysics Data System (ADS)

Lee, Dongchan; Kim, Donghyuk; Lee, Yonghee; Jeon, Duk Young

2017-06-01

Graphene has attracted great attention owing to its superb properties as an anode of organic or polymer light-emitting diodes (OLEDs or PLEDs). However, there are still barriers for graphene to replace existing indium tin oxide (ITO) due to relatively high sheet resistance and work function mismatch. In this study, PLEDs using molybdenum oxide (MoOx) nanoparticle-doped graphene are demonstrated on a plastic substrate to have a low sheet resistance and high work function. Also, this work shows how the doping amount influences the electronic properties of the graphene anode and the PLED performance. A facile and scalable spin coating process was used for doping graphene with MoOx. After doping, the sheet resistance and the optical transmittance of five-layer graphene were ˜180 Ω sq-1 and ˜88%, respectively. Moreover, the surface roughness of MoOx-doped graphene becomes smoother than that of pristine graphene. Furthermore, a nonlinear relationship was observed between the MoOx doping level and device performance. Therefore, a modified stacking structure of graphene electrode is presented to further enhance device performance. The maximum external quantum efficiency (EQE) and power efficiency of the PLED using the MoOx-doped graphene anode were 4.7% and 13.3 lm W-1, respectively. The MoOx-doped graphene anode showed enhanced device performance (261% for maximum EQE, 255% for maximum power efficiency) compared with the pristine graphene.