37 CFR 211.4 - Registration of claims of protection in mask works.

Code of Federal Regulations, 2014 CFR

2014-07-01

... version of a mask work fixed in an intermediate or final form of any semiconductor chip product. However... registration per work, owners of mask works in final forms of semiconductor chip products that are produced by... chip product that includes a plurality of circuit elements that are adaptable to be personalized into a...

37 CFR 211.4 - Registration of claims of protection in mask works.

Code of Federal Regulations, 2013 CFR

2013-07-01

... version of a mask work fixed in an intermediate or final form of any semiconductor chip product. However... registration per work, owners of mask works in final forms of semiconductor chip products that are produced by... chip product that includes a plurality of circuit elements that are adaptable to be personalized into a...

The ATLAS SemiConductor Tracker operation and performance

NASA Astrophysics Data System (ADS)

Pater, J. R.

2012-04-01

The ATLAS SemiConductor Tracker (SCT) is a key precision tracking detector in the ATLAS experiment at CERN's Large Hadron Collider. The SCT is composed of 4088 planar p-in-n silicon micro-strip detectors. The signals from the strips are processed in the front-end ABCD3TA ASICs, which operate in binary readout mode; data are transferred to the off-detector readout electronics via optical fibres. The SCT was completed in 2007. An extensive commissioning phase followed, during which calibration data were collected and analysed to determine the noise performance of the system, and further performance parameters of the detector were determined using cosmic ray data, both with and without magnetic field. After the commissioning phase, the SCT was ready for the first LHC proton-proton collisions in December 2009. From the beginning of data taking, the completed SCT has been in very good shape with more than 99% of its 6.3 million strips operational; the detector is well timed-in and the operational channels are 99.9% efficient in data acquisition. The noise occupancy and hit efficiency are better than the design specifications. The detector geometry is monitored continuously with a laser-based alignment system and is stable to the few-micron level; the alignment accuracy as determined by tracks is near specification and improving as statistics increase. The sensor behaviour in the 2T solenoidal magnetic field has been studied by measuring the Lorentz angle. Radiation damage in the silicon is monitored by periodic measurements of the leakage current; these measurements are in reasonable agreement with predictions.

The Mu2e undoped CsI crystal calorimeter

NASA Astrophysics Data System (ADS)

Atanov, N.; Baranov, V.; Budagov, J.; Cervelli, F.; Colao, F.; Cordelli, M.; Corradi, G.; Davydov, Y. I.; Di Falco, S.; Diociaiuti, E.; Donati, S.; Donghia, R.; Echenard, B.; Giovannella, S.; Glagolev, V.; Grancagnolo, F.; Happacher, F.; Hitlin, D. G.; Martini, M.; Miscetti, S.; Miyashita, T.; Morescalchi, L.; Murat, P.; Pedreschi, E.; Pezzullo, G.; Porter, F.; Raffaelli, F.; Ricci, M.; Saputi, A.; Sarra, I.; Spinella, F.; Tassielli, G.; Tereshchenko, V.; Usubov, Z.; Zhu, R. Y.

2018-02-01

The Mu2e experiment at Fermilab will search for Charged Lepton Flavor Violating conversion of a muon to an electron in an atomic field. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external system, surrounding the solenoid, to veto cosmic rays. The calorimeter plays an important role to provide: a) excellent particle identification capabilities; b) a fast trigger filter; c) an easier tracker track reconstruction. Two disks, located downstream of the tracker, contain 674 pure CsI crystals each. Each crystal is read out by two arrays of UV-extended SiPMs. The choice of the crystals and SiPMs has been finalized after a thorough test campaign. A first small scale prototype consisting of 51 crystals and 102 SiPM arrays has been exposed to an electron beam at the BTF (Beam Test Facility) in Frascati. Although the readout electronics were not final, results show that the current design is able to meet the timing and energy resolution required by the Mu2e experiment.

Processing approach towards the formation of thin-film Cu(In,Ga)Se2

DOEpatents

Beck, Markus E.; Noufi, Rommel

2003-01-01

A two-stage method of producing thin-films of group IB-IIIA-VIA on a substrate for semiconductor device applications includes a first stage of depositing an amorphous group IB-IIIA-VIA precursor onto an unheated substrate, wherein the precursor contains all of the group IB and group IIIA constituents of the semiconductor thin-film to be produced in the stoichiometric amounts desired for the final product, and a second stage which involves subjecting the precursor to a short thermal treatment at 420.degree. C.-550.degree. C. in a vacuum or under an inert atmosphere to produce a single-phase, group IB-III-VIA film. Preferably the precursor also comprises the group VIA element in the stoichiometric amount desired for the final semiconductor thin-film. The group IB-IIIA-VIA semiconductor films may be, for example, Cu(In,Ga)(Se,S).sub.2 mixed-metal chalcogenides. The resultant supported group IB-IIIA-VIA semiconductor film is suitable for use in photovoltaic applications.

Performance verification of the CMS Phase-1 Upgrade Pixel detector

NASA Astrophysics Data System (ADS)

Veszpremi, V.

2017-12-01

The CMS tracker consists of two tracking systems utilizing semiconductor technology: the inner pixel and the outer strip detectors. The tracker detectors occupy the volume around the beam interaction region between 3 cm and 110 cm in radius and up to 280 cm along the beam axis. The pixel detector consists of 124 million pixels, corresponding to about 2 m 2 total area. It plays a vital role in the seeding of the track reconstruction algorithms and in the reconstruction of primary interactions and secondary decay vertices. It is surrounded by the strip tracker with 10 million read-out channels, corresponding to 200 m 2 total area. The tracker is operated in a high-occupancy and high-radiation environment established by particle collisions in the LHC . The current strip detector continues to perform very well. The pixel detector that has been used in Run 1 and in the first half of Run 2 was, however, replaced with the so-called Phase-1 Upgrade detector. The new system is better suited to match the increased instantaneous luminosity the LHC would reach before 2023. It was built to operate at an instantaneous luminosity of around 2×1034 cm-2s-1. The detector's new layout has an additional inner layer with respect to the previous one; it allows for more efficient tracking with smaller fake rate at higher event pile-up. The paper focuses on the first results obtained during the commissioning of the new detector. It also includes challenges faced during the first data taking to reach the optimal measurement efficiency. Details will be given on the performance at high occupancy with respect to observables such as data-rate, hit reconstruction efficiency, and resolution.

Exposure Time Optimization for Highly Dynamic Star Trackers

PubMed Central

Wei, Xinguo; Tan, Wei; Li, Jian; Zhang, Guangjun

2014-01-01

Under highly dynamic conditions, the star-spots on the image sensor of a star tracker move across many pixels during the exposure time, which will reduce star detection sensitivity and increase star location errors. However, this kind of effect can be compensated well by setting an appropriate exposure time. This paper focuses on how exposure time affects the star tracker under highly dynamic conditions and how to determine the most appropriate exposure time for this case. Firstly, the effect of exposure time on star detection sensitivity is analyzed by establishing the dynamic star-spot imaging model. Then the star location error is deduced based on the error analysis of the sub-pixel centroiding algorithm. Combining these analyses, the effect of exposure time on attitude accuracy is finally determined. Some simulations are carried out to validate these effects, and the results show that there are different optimal exposure times for different angular velocities of a star tracker with a given configuration. In addition, the results of night sky experiments using a real star tracker agree with the simulation results. The summarized regularities in this paper should prove helpful in the system design and dynamic performance evaluation of the highly dynamic star trackers. PMID:24618776

Spacecraft angular velocity estimation algorithm for star tracker based on optical flow techniques

NASA Astrophysics Data System (ADS)

Tang, Yujie; Li, Jian; Wang, Gangyi

2018-02-01

An integrated navigation system often uses the traditional gyro and star tracker for high precision navigation with the shortcomings of large volume, heavy weight and high-cost. With the development of autonomous navigation for deep space and small spacecraft, star tracker has been gradually used for attitude calculation and angular velocity measurement directly. At the same time, with the dynamic imaging requirements of remote sensing satellites and other imaging satellites, how to measure the angular velocity in the dynamic situation to improve the accuracy of the star tracker is the hotspot of future research. We propose the approach to measure angular rate with a nongyro and improve the dynamic performance of the star tracker. First, the star extraction algorithm based on morphology is used to extract the star region, and the stars in the two images are matched according to the method of angular distance voting. The calculation of the displacement of the star image is measured by the improved optical flow method. Finally, the triaxial angular velocity of the star tracker is calculated by the star vector using the least squares method. The method has the advantages of fast matching speed, strong antinoise ability, and good dynamic performance. The triaxial angular velocity of star tracker can be obtained accurately with these methods. So, the star tracker can achieve better tracking performance and dynamic attitude positioning accuracy to lay a good foundation for the wide application of various satellites and complex space missions.

HVMUX, a high voltage multiplexing for the ATLAS Tracker upgrade

NASA Astrophysics Data System (ADS)

Giulio Villani, E.; Phillips, P.; Matheson, J.; Zhang, Z.; Lynn, D.; Kuczewski, P.; Hommels, L. B. A.; Gregor, I.; Bessner, M.; Tackmann, K.; Newcomer, F. M.; Spencer, E.; Greenall, A.

2017-01-01

The HV biasing solution adopted in the current ATLAS detector uses one HV conductor for each sensor. This approach easily allows disabling of malfunctioning sensors without affecting the others, but space constraints and material budget considerations renders this approach impractical for the Upgraded detector. In fact, the increased luminosity of the Upgraded LHC will require more channels in the upgraded ATLAS Tracker, as a result of the finer detector segmentation. Different approaches to bring the HV biasing to the detectors, including the use of a shared HV line to bias several sensors and employing semiconductor switches for the HV routing (HVMUX), have been investigated. Beside the size constraints, particular attention must be paid to the radiation tolerance of any proposed solution, which, for the strips detector, requires proper operation up to fluences of the order of 2ṡ 1015 1MeV neq/cm2 and TID in excess of 300 kGy. In this paper, a description of the proposed HVMUX solution, along with electrical and radiation tests results will be presented and discussed.

High efficiency, low cost, thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

2001-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, Bhushan L.

1999-01-01

A semiconductor device having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer.

Individual Differences in the Attribution of Incentive Salience to a Pavlovian Alcohol Cue.

PubMed

Villaruel, Franz R; Chaudhri, Nadia

2016-01-01

Individual differences exist in the attribution of incentive salience to conditioned stimuli associated with food. Here, we investigated whether individual differences also manifested with a Pavlovian alcohol conditioned stimulus (CS). We compiled data from five experiments that used a Pavlovian autoshaping paradigm and tests of conditioned reinforcement. In all experiments, male, Long-Evans rats with unrestricted access to food and water were acclimated to 15% ethanol. Next, rats received Pavlovian autoshaping training, in which a 10 s presentation of a retractable lever served as the CS and 0.2 mL of 15% ethanol served as the unconditioned stimulus (US). Finally, rats underwent conditioned reinforcement tests in which nose-pokes to an active aperture led to brief presentations of the lever-CS, but nose-pokes to an inactive aperture had no consequence. Rats were categorized as sign-trackers, goal-trackers and intermediates based on a response bias score that reflected their tendencies to sign-track or goal-track at different times during training. We found that distinct groups of rats either consistently interacted with the lever-CS ("sign-trackers") or routinely approached the port during the lever-CS ("goal-trackers") across a majority of the training sessions. However, some individuals ("shifted sign-trackers") with an early tendency to goal-track later shifted to comparable asymptotic levels of sign-tracking as the group identified as sign-trackers. The lever-CS functioned as a conditioned reinforcer for sign-trackers and shifted sign-trackers, but not for goal-trackers. These results provide evidence of robust individual differences in the extent to which a Pavlovian alcohol cue gains incentive salience and functions as a conditioned reinforcer.

The Mu2e undoped CsI crystal calorimeter

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

Atanov, N.; Baranov, V.; Budagov, J.

We present the Mu2e experiment at Fermilab will search for Charged Lepton Flavor Violating conversion of a muon to an electron in an atomic field. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external system, surrounding the solenoid, to veto cosmic rays. The calorimeter plays an important role to provide: a) excellent particle identification capabilities; b) a fast trigger filter; c) an easier tracker track reconstruction. Two disks, located downstream of the tracker, contain 674 pure CsI crystals each. Each crystal is read out by two arrays of UV-extended SiPMs. The choice of the crystalsmore » and SiPMs has been finalized after a thorough test campaign. A first small scale prototype consisting of 51 crystals and 102 SiPM arrays has been exposed to an electron beam at the BTF (Beam Test Facility) in Frascati. Lastly, although the readout electronics were not final, results show that the current design is able to meet the timing and energy resolution required by the Mu2e experiment.« less

The Mu2e undoped CsI crystal calorimeter

DOE PAGES

Atanov, N.; Baranov, V.; Budagov, J.; ...

2018-02-22

We present the Mu2e experiment at Fermilab will search for Charged Lepton Flavor Violating conversion of a muon to an electron in an atomic field. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external system, surrounding the solenoid, to veto cosmic rays. The calorimeter plays an important role to provide: a) excellent particle identification capabilities; b) a fast trigger filter; c) an easier tracker track reconstruction. Two disks, located downstream of the tracker, contain 674 pure CsI crystals each. Each crystal is read out by two arrays of UV-extended SiPMs. The choice of the crystalsmore » and SiPMs has been finalized after a thorough test campaign. A first small scale prototype consisting of 51 crystals and 102 SiPM arrays has been exposed to an electron beam at the BTF (Beam Test Facility) in Frascati. Lastly, although the readout electronics were not final, results show that the current design is able to meet the timing and energy resolution required by the Mu2e experiment.« less

Core x-ray spectra in semiconductors and the Mahan-Nozieres-De Dominicis model

NASA Astrophysics Data System (ADS)

Livins, Peteris

1998-10-01

The Mahan-Nozières-De Dominicis (MND) model of core x-ray spectra is examined for semiconductors. Due to the finite band gap, the Anderson orthogonality does not occur, and thus spectra near the band edge can be calculated without the shakeup contribution. For semiconductors, and not only for metals, we investigate whether the remaining many-particle dynamic exchange effect of the MND model, or so-called replacement, can significantly alter x-ray spectral shapes near the band edge from those obtained from a straightforward final-state rule. For both emission and absorption, in the absence of shakeup, an exact formulation suitable for materials with band structure is discussed. A numerical model for a semiconductor with a 1-eV band gap demonstrates the band-edge modifications, and shows a 50% effect at the band edge, indicating that this dynamic exchange effect can be significant and should be considered in any specific emission or absorption calculation for a semiconductor. Although the ineffectiveness of the orthogonality theorem in semiconductors is emphasized, a suppression near the band edge also remains a possibility. Included is a discussion on the breakdown of the final-state rule. In addition, connection is made to the determinantal approach of Ohtaka and Tanabe.

Centro-Apical Self-Organization of Organic Semiconductors in a Line-Printed Organic Semiconductor: Polymer Blend for One-Step Printing Fabrication of Organic Field-Effect Transistors

PubMed Central

Jin Lee, Su; Kim, Yong-Jae; Young Yeo, So; Lee, Eunji; Sun Lim, Ho; Kim, Min; Song, Yong-Won; Cho, Jinhan; Ah Lim, Jung

2015-01-01

Here we report the first demonstration for centro-apical self-organization of organic semiconductors in a line-printed organic semiconductor: polymer blend. Key feature of this work is that organic semiconductor molecules were vertically segregated on top of the polymer phase and simultaneously crystallized at the center of the printed line pattern after solvent evaporation without an additive process. The thickness and width of the centro-apically segregated organic semiconductor crystalline stripe in the printed blend pattern were controlled by varying the relative content of the organic semiconductors, printing speed, and solution concentrations. The centro-apical self-organization of organic semiconductor molecules in a printed polymer blend may be attributed to the combination of an energetically favorable vertical phase-separation and hydrodynamic fluids inside the droplet during solvent evaporation. Finally, a centro-apically phase-separated bilayer structure of organic semiconductor: polymer blend was successfully demonstrated as a facile method to form the semiconductor and dielectric layer for OFETs in one- step. PMID:26359068

Centro-Apical Self-Organization of Organic Semiconductors in a Line-Printed Organic Semiconductor: Polymer Blend for One-Step Printing Fabrication of Organic Field-Effect Transistors.

PubMed

Lee, Su Jin; Kim, Yong-Jae; Yeo, So Young; Lee, Eunji; Lim, Ho Sun; Kim, Min; Song, Yong-Won; Cho, Jinhan; Lim, Jung Ah

2015-09-11

Here we report the first demonstration for centro-apical self-organization of organic semiconductors in a line-printed organic semiconductor: polymer blend. Key feature of this work is that organic semiconductor molecules were vertically segregated on top of the polymer phase and simultaneously crystallized at the center of the printed line pattern after solvent evaporation without an additive process. The thickness and width of the centro-apically segregated organic semiconductor crystalline stripe in the printed blend pattern were controlled by varying the relative content of the organic semiconductors, printing speed, and solution concentrations. The centro-apical self-organization of organic semiconductor molecules in a printed polymer blend may be attributed to the combination of an energetically favorable vertical phase-separation and hydrodynamic fluids inside the droplet during solvent evaporation. Finally, a centro-apically phase-separated bilayer structure of organic semiconductor: polymer blend was successfully demonstrated as a facile method to form the semiconductor and dielectric layer for OFETs in one- step.

High efficiency low cost thin film silicon solar cell design and method for making

DOEpatents

Sopori, B.L.

1999-04-27

A semiconductor device is described having a substrate, a conductive intermediate layer deposited onto said substrate, wherein the intermediate layer serves as a back electrode, an optical reflector, and an interface for impurity gettering, and a semiconductor layer deposited onto said intermediate layer, wherein the semiconductor layer has a grain size at least as large as the layer thickness, and preferably about ten times the layer thickness. The device is formed by depositing a metal layer on a substrate, depositing a semiconductive material on the metal-coated substrate to produce a composite structure, and then optically processing the composite structure by illuminating it with infrared electromagnetic radiation according to a unique time-energy profile that first produces pits in the backside surface of the semiconductor material, then produces a thin, highly reflective, low resistivity alloy layer over the entire area of the interface between the semiconductor material and the metal layer, and finally produces a grain-enhanced semiconductor layer. The time-energy profile includes increasing the energy to a first energy level to initiate pit formation and create the desired pit size and density, then ramping up to a second energy level in which the entire device is heated to produce an interfacial melt, and finally reducing the energy to a third energy level and holding for a period of time to allow enhancement in the grain size of the semiconductor layer. 9 figs.

75 FR 62462 - Additions to the List of Validated End-Users in the People's Republic of China: Hynix...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-12

...In this final rule, the Bureau of Industry and Security amends the Export Administration Regulations (EAR) to add three end-users, Hynix Semiconductor (China) Ltd., Hynix Semiconductor (Wuxi) Ltd. and Lam Research Corporation to the list of validated end-users in the People's Republic of China (PRC). With this rule, exports, reexports and transfers (in-country) of certain items to one facility of Hynix Semiconductor (China) Ltd., one facility of Hynix Semiconductor (Wuxi) Ltd. and nine facilities of Lam Research Corporation in the PRC are now authorized under Authorization Validated End-User (VEU).

"Sturdy as a house with four windows," the star tracker of the future

NASA Astrophysics Data System (ADS)

Duivenvoorde, Tom; Leijtens, Johan; van der Heide, Erik J.

2017-11-01

Ongoing miniaturization of spacecraft demands the reduction in size of Attitude and Orbit Control Systems (AOCS). Therefore TNO has created a new design of a multi aperture, high performance, and miniaturized star tracker. The innovative design incorporates the latest developments in camera technology, attitude calculation and mechanical design into a system with 5 arc seconds accuracy, making the system usable for many applications. In this paper the results are presented of the system design and analysis, as well as the performance predictions for the Multi Aperture Baffled Star Tracker (MABS). The highly integrated system consists of multiple apertures without the need for external baffles, resulting in major advantages in mass, volume, alignment with the spacecraft and relative aperture stability. In the analysis part of this paper, the thermal and mechanical stability are discussed. In the final part the simulation results will be described that have lead to the predicted accuracy of the star tracker system and a peek into the future of attitude sensors is given.

Fast front-end electronics for semiconductor tracking detectors: Trends and perspectives

NASA Astrophysics Data System (ADS)

Rivetti, Angelo

2014-11-01

In the past few years, extensive research efforts pursued by both the industry and the academia have lead to major improvements in the performance of Analog to Digital Converters (ADCs) and Time to Digital Converters (TDCs). ADCs achieving 8-10 bit resolution, 50-100 MHz conversion frequency and less than 1 mW power consumption are the today's standard, while TDCs have reached sub-picosecond time resolution. These results have been made possible by architectural upgrades combined with the use of ultra deep submicron CMOS technologies with minimum feature size of 130 nm or smaller. Front-end ASICs in which a prompt digitization is followed by signal conditioning in the digital domain can now be envisaged also within the tight power budget typically available in high density tracking systems. Furthermore, tracking detectors embedding high resolution timing capabilities are gaining interest. In the paper, ADC's and TDC's developments which are of particular relevance for the design front-end electronics for semiconductor trackers are discussed along with the benefits and challenges of exploiting such high performance building blocks in implementing the next generation of ASICs for high granularity particle detectors.

Semiconductor Laser Low Frequency Noise Characterization

NASA Technical Reports Server (NTRS)

Maleki, Lute; Logan, Ronald T.

1996-01-01

This work summarizes the efforts in identifying the fundamental noise limit in semiconductor optical sources (lasers) to determine the source of 1/F noise and it's associated behavior. In addition, the study also addresses the effects of this 1/F noise on RF phased arrays. The study showed that the 1/F noise in semiconductor lasers has an ultimate physical limit based upon similar factors to fundamental noise generated in other semiconductor and solid state devices. The study also showed that both additive and multiplicative noise can be a significant detriment to the performance of RF phased arrays especially in regard to very low sidelobe performance and ultimate beam steering accuracy. The final result is that a noise power related term must be included in a complete analysis of the noise spectrum of any semiconductor device including semiconductor lasers.

Recent progress in magnetic iron oxide-semiconductor composite nanomaterials as promising photocatalysts

NASA Astrophysics Data System (ADS)

Wu, Wei; Changzhong Jiang, Affc; Roy, Vellaisamy A. L.

2014-11-01

Photocatalytic degradation of toxic organic pollutants is a challenging tasks in ecological and environmental protection. Recent research shows that the magnetic iron oxide-semiconductor composite photocatalytic system can effectively break through the bottleneck of single-component semiconductor oxides with low activity under visible light and the challenging recycling of the photocatalyst from the final products. With high reactivity in visible light, magnetic iron oxide-semiconductors can be exploited as an important magnetic recovery photocatalyst (MRP) with a bright future. On this regard, various composite structures, the charge-transfer mechanism and outstanding properties of magnetic iron oxide-semiconductor composite nanomaterials are sketched. The latest synthesis methods and recent progress in the photocatalytic applications of magnetic iron oxide-semiconductor composite nanomaterials are reviewed. The problems and challenges still need to be resolved and development strategies are discussed.

Semiconductor millimeter wavelength electronics

NASA Astrophysics Data System (ADS)

Rosenbaum, F. J.

1985-12-01

This final report summarizes the results of research carried out on topics in millimeter wavelength semiconductor electronics under an ONR Selected Research Opportunity program. Study areas included III-V compound semiconductor growth and characterization, microwave and millimeter wave device modeling, fabrication and testing, and the development of new device concepts. A new millimeter wave mixer and detector, the Gap diode was invented. Topics reported on include ballistic transport, Zener oscillations, impurities in GaAs, electron velocity-electric field calculation and measurements, etc., calculations.

SED16 autonomous star tracker night sky testing

NASA Astrophysics Data System (ADS)

Foisneau, Thierry; Piriou, Véronique; Perrimon, Nicolas; Jacob, Philippe; Blarre, Ludovic; Vilaire, Didier

2017-11-01

The SED16 is an autonomous multi-missions star tracker which delivers three axis satellite attitude in an inertial reference frame and the satellite angular velocity with no prior information. The qualification process of this star sensor includes five validation steps using optical star simulator, digitized image simulator and a night sky tests setup. The night sky testing was the final step of the qualification process during which all the functions of the star tracker were used in almost nominal conditions : Autonomous Acquisition of the attitude, Autonomous Tracking of ten stars. These tests were performed in Calern in the premises of the OCA (Observatoire de la Cote d'Azur). The test set-up and the test results are described after a brief review of the sensor main characteristics and qualification process.

Technician Training for the Semiconductor Microdevices Industry. Final Report.

ERIC Educational Resources Information Center

Center for Occupational Research and Development, Inc., Waco, TX.

The Center for Occupational Research and Development (CORD) carried out four activities to foster semiconductor manufacturing technician (SMT) training: (1) collaboration with industry experts and educators while developing a curriculum to train SMTs; (2) implementation and testing of the curriculum at a technical college; (3) dissemination of…

77 FR 65878 - Application for Final Commitment for a Long-term Loan or Financial Guarantee in Excess of $100...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-31

... export of semiconductor manufacturing equipment to Germany. Brief non-proprietary description of the anticipated use of the items being exported: Equipment supports the manufacture of logic semiconductors. To... United States industry. Parties: Principal Suppliers: Applied Materials, Inc., KLA-Tencor Corporation...

Nanopatterning of Group V Elements for Tailoring the Electronic Properties of Semiconductors by Monolayer Doping.

PubMed

Thissen, Peter; Cho, Kyeongjae; Longo, Roberto C

2017-01-18

Control of the electronic properties of semiconductors is primarily achieved through doping. While scaling down the device dimensions to the molecular regime presents an increasing number of difficulties, doping control at the nanoscale is still regarded as one of the major challenges of the electronic industry. Within this context, new techniques such as monolayer doping (MLD) represent a substantial improvement toward surface doping with atomic and specific doping dose control at the nanoscale. Our previous work has explained in detail the atomistic mechanism behind MLD by means of density-functional theory calculations (Chem. Mater. 2016, 28, 1975). Here, we address the key questions that will ultimately allow one to optimize the scalability of the MLD process. First, we show that dopant coverage control cannot be achieved by simultaneous reaction of several group V elements, but stepwise reactions make it possible. Second, using ab initio molecular dynamics, we investigate the thermal decomposition of the molecular precursors, together with the stability of the corresponding binary and ternary dopant oxides, prior to the dopant diffusion into the semiconductor surface. Finally, the effect of the coverage and type of dopant on the electronic properties of the semiconductor is also analyzed. Furthermore, the atomistic characterization of the MLD process raises unexpected questions regarding possible crystal damage effects by dopant exchange with the semiconductor ions or the final distribution of the doping impurities within the crystal structure. By combining all our results, optimization recipes to create ultrashallow doped junctions at the nanoscale are finally proposed.

Cosmology of a covariant Galilean field.

PubMed

De Felice, Antonio; Tsujikawa, Shinji

2010-09-10

We study the cosmology of a covariant scalar field respecting a Galilean symmetry in flat space-time. We show the existence of a tracker solution that finally approaches a de Sitter fixed point responsible for cosmic acceleration today. The viable region of model parameters is clarified by deriving conditions under which ghosts and Laplacian instabilities of scalar and tensor perturbations are absent. The field equation of state exhibits a peculiar phantomlike behavior along the tracker, which allows a possibility to observationally distinguish the Galileon gravity from the cold dark matter model with a cosmological constant.

Toward designing semiconductor-semiconductor heterojunctions for photocatalytic applications

NASA Astrophysics Data System (ADS)

Zhang, Liping; Jaroniec, Mietek

2018-02-01

Semiconductor photocatalysts show a great potential for environmental and energy-related applications, however one of the major disadvantages is their relatively low photocatalytic performance due to the recombination of electron-hole pairs. Therefore, intensive research is being conducted toward design of heterojunctions, which have been shown to be effective for improving the charge-transfer properties and efficiency of photocatalysts. According to the type of band alignment and direction of internal electric field, heterojunctions are categorized into five different types, each of which is associated with its own charge transfer characteristics. Since the design of heterojunctions requires the knowledge of band edge positions of component semiconductors, the commonly used techniques for the assessment of band edge positions are reviewed. Among them the electronegativity-based calculation method is applied for a large number of popular visible-light-active semiconductors, including some widely investigated bismuth-containing semiconductors. On basis of the calculated band edge positions and the type of component semiconductors reported, heterojunctions composed of the selected bismuth-containing semiconductors are proposed. Finally, the most popular synthetic techniques for the fabrication of heterojunctions are briefly discussed.

76 FR 2336 - Dynamic Random Access Memory Semiconductors From the Republic of Korea: Final Results of...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-13

... DEPARTMENT OF COMMERCE International Trade Administration [C-580-851] Dynamic Random Access Memory... administrative review of the countervailing duty order on dynamic random access memory semiconductors from the... following events have occurred since the publication of the preliminary results of this review. See Dynamic...

Ionic Liquid Activation of Amorphous Metal-Oxide Semiconductors for Flexible Transparent Electronic Devices

DOE PAGES

Pudasaini, Pushpa Raj; Noh, Joo Hyon; Wong, Anthony T.; ...

2016-02-09

To begin this abstract, amorphous metal-oxide semiconductors offer the high carrier mobilities and excellent large-area uniformity required for high performance, transparent, flexible electronic devices; however, a critical bottleneck to their widespread implementation is the need to activate these materials at high temperatures which are not compatible with flexible polymer substrates. The highly controllable activation of amorphous indium gallium zinc oxide semiconductor channels using ionic liquid gating at room temperature is reported. Activation is controlled by electric field-induced oxygen migration across the ionic liquid-semiconductor interface. In addition to activation of unannealed devices, it is shown that threshold voltages of a transistormore » can be linearly tuned between the enhancement and depletion modes. Finally, the first ever example of transparent flexible thin film metal oxide transistor on a polyamide substrate created using this simple technique is demonstrated. Finally, this study demonstrates the potential of field-induced activation as a promising alternative to traditional postdeposition thermal annealing which opens the door to wide scale implementation into flexible electronic applications.« less

Low-Frequency Error Extraction and Compensation for Attitude Measurements from STECE Star Tracker

PubMed Central

Lai, Yuwang; Gu, Defeng; Liu, Junhong; Li, Wenping; Yi, Dongyun

2016-01-01

The low frequency errors (LFE) of star trackers are the most penalizing errors for high-accuracy satellite attitude determination. Two test star trackers- have been mounted on the Space Technology Experiment and Climate Exploration (STECE) satellite, a small satellite mission developed by China. To extract and compensate the LFE of the attitude measurements for the two test star trackers, a new approach, called Fourier analysis, combined with the Vondrak filter method (FAVF) is proposed in this paper. Firstly, the LFE of the two test star trackers’ attitude measurements are analyzed and extracted by the FAVF method. The remarkable orbital reproducibility features are found in both of the two test star trackers’ attitude measurements. Then, by using the reproducibility feature of the LFE, the two star trackers’ LFE patterns are estimated effectively. Finally, based on the actual LFE pattern results, this paper presents a new LFE compensation strategy. The validity and effectiveness of the proposed LFE compensation algorithm is demonstrated by the significant improvement in the consistency between the two test star trackers. The root mean square (RMS) of the relative Euler angle residuals are reduced from [27.95′′, 25.14′′, 82.43′′], 3σ to [16.12′′, 15.89′′, 53.27′′], 3σ. PMID:27754320

EyeTribe Tracker Data Accuracy Evaluation and Its Interconnection with Hypothesis Software for Cartographic Purposes.

PubMed

Popelka, Stanislav; Stachoň, Zdeněk; Šašinka, Čeněk; Doležalová, Jitka

2016-01-01

The mixed research design is a progressive methodological discourse that combines the advantages of quantitative and qualitative methods. Its possibilities of application are, however, dependent on the efficiency with which the particular research techniques are used and combined. The aim of the paper is to introduce the possible combination of Hypothesis with EyeTribe tracker. The Hypothesis is intended for quantitative data acquisition and the EyeTribe is intended for qualitative (eye-tracking) data recording. In the first part of the paper, Hypothesis software is described. The Hypothesis platform provides an environment for web-based computerized experiment design and mass data collection. Then, evaluation of the accuracy of data recorded by EyeTribe tracker was performed with the use of concurrent recording together with the SMI RED 250 eye-tracker. Both qualitative and quantitative results showed that data accuracy is sufficient for cartographic research. In the third part of the paper, a system for connecting EyeTribe tracker and Hypothesis software is presented. The interconnection was performed with the help of developed web application HypOgama. The created system uses open-source software OGAMA for recording the eye-movements of participants together with quantitative data from Hypothesis. The final part of the paper describes the integrated research system combining Hypothesis and EyeTribe.

EyeTribe Tracker Data Accuracy Evaluation and Its Interconnection with Hypothesis Software for Cartographic Purposes

PubMed Central

Stachoň, Zdeněk; Šašinka, Čeněk; Doležalová, Jitka

2016-01-01

The mixed research design is a progressive methodological discourse that combines the advantages of quantitative and qualitative methods. Its possibilities of application are, however, dependent on the efficiency with which the particular research techniques are used and combined. The aim of the paper is to introduce the possible combination of Hypothesis with EyeTribe tracker. The Hypothesis is intended for quantitative data acquisition and the EyeTribe is intended for qualitative (eye-tracking) data recording. In the first part of the paper, Hypothesis software is described. The Hypothesis platform provides an environment for web-based computerized experiment design and mass data collection. Then, evaluation of the accuracy of data recorded by EyeTribe tracker was performed with the use of concurrent recording together with the SMI RED 250 eye-tracker. Both qualitative and quantitative results showed that data accuracy is sufficient for cartographic research. In the third part of the paper, a system for connecting EyeTribe tracker and Hypothesis software is presented. The interconnection was performed with the help of developed web application HypOgama. The created system uses open-source software OGAMA for recording the eye-movements of participants together with quantitative data from Hypothesis. The final part of the paper describes the integrated research system combining Hypothesis and EyeTribe. PMID:27087805

Centroid tracker and aimpoint selection

NASA Astrophysics Data System (ADS)

Venkateswarlu, Ronda; Sujata, K. V.; Venkateswara Rao, B.

1992-11-01

Autonomous fire and forget weapons have gained importance to achieve accurate first pass kill by hitting the target at an appropriate aim point. Centroid of the image presented by a target in the field of view (FOV) of a sensor is generally accepted as the aimpoint for these weapons. Centroid trackers are applicable only when the target image is of significant size in the FOV of the sensor but does not overflow the FOV. But as the range between the sensor and the target decreases the image of the target will grow and finally overflow the FOV at close ranges and the centroid point on the target will keep on changing which is not desirable. And also centroid need not be the most desired/vulnerable point on the target. For hardened targets like tanks, proper aimpoint selection and guidance up to almost zero range is essential to achieve maximum kill probability. This paper presents a centroid tracker realization. As centroid offers a stable tracking point, it can be used as a reference to select the proper aimpoint. The centroid and the desired aimpoint are simultaneously tracked to avoid jamming by flares and also to take care of the problems arising due to image overflow. Thresholding of gray level image to binary image is a crucial step in centroid tracker. Different thresholding algorithms are discussed and a suitable algorithm is chosen. The real-time hardware implementation of centroid tracker with a suitable thresholding technique is presented including the interfacing to a multimode tracker for autonomous target tracking and aimpoint selection. The hardware uses very high speed arithmetic and programmable logic devices to meet the speed requirement and a microprocessor based subsystem for the system control. The tracker has been evaluated in a field environment.

Southeast Alaska Native Land Entitlement Finalization and Jobs Protection Act

THOMAS, 113th Congress

Sen. Murkowski, Lisa [R-AK

2013-02-14

Senate - 09/10/2013 Placed on Senate Legislative Calendar under General Orders. Calendar No. 176. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Visible light active 2D C3N4-CdS hetero-junction photocatalyst for effective removal of azo dye by photodegradation

NASA Astrophysics Data System (ADS)

Ghosh Chaudhuri, Rajib; Chaturvedi, Ashwin; Iype, Eldhose

2018-03-01

A hetero-junction two dimensional photocatalyst that consists of organic semiconductor carbon nitride (C3N4) and inorganic semiconductor CdS, which acts as the light harvesting units and heterogeneous catalyst, was developed for the degradation of azo dye methyl orange (MO). Both materials are visible light active semiconductor. So the effective band gap of this heterojunction materials does not significantly change the visible light activity, but the injection of electrons from excited C3N4 to CdS increases the stability of hole-electron pair and that ultimately enhances the photocatalytic activity. This heterojunction catalyst finally can remove 97% of dyes and that is comparatively higher than individual pure materials. Finally, by using DFT analysis the band structure and the level diagrams of this photocatalyst are also analyzed.

Using CarbonTracker carbon flux estimates to improve a terrestrial carbon cycle model

NASA Astrophysics Data System (ADS)

Peters, W.; Krol, M.; Miller, J. B.; Tans, P. P.; Carvalhais, N.; Schaefer, K.

2009-12-01

Estimates of net ecosystem exchange (NEE) from NOAA’s CarbonTracker CO2 data assimilation system show patterns of annual net uptake not represented in most terrestrial carbon cycle models. This is mainly because such models lack information on the land-use history of individual ecosystems, which is the main driver of long-term mean carbon exchange. Instead, they assume the biosphere to be in steady-state, with annual gross photosynthesis equalling ecosystem respiration everywhere. This limits their use in interpreting observations of carbon dynamics such as with eddy-covariance techniques or through atmospheric CO2 records. We have implemented a method that takes the long-term mean NEE estimates from CarbonTracker to derive the size of the dominant carbon pool in each ecosystem of the SIBCASA biosphere model. With the new pool sizes, the SIBCASA model is no longer in steady-state and reproduces annual carbon uptake patterns from CarbonTracker. We will show that the non steady-state SIBCASA model is not only much more consistent with the atmospheric CO2 record, but also with independent data on standing wood biomass and forest age from the Forest Inventory and Analysis (FIA) Program of the U.S. Forest Service. Four years of CarbonTracker NEE are needed to reliably derive a long term mean for this process, and we use three other years from CarbonTracker to evaluate the non steady state SIBCASA NEE. We will furthermore show that the non steady-state SIBCASA NEE is a much better first-guess for the CarbonTracker data assimilation process, allowing more confidence in its final NEE estimate, and reducing a systematic bias in CarbonTracker modeled atmospheric CO2. This overcomes a long standing issue in inverse modeling, and opens the way for further assessment and improvement of carbon cycle models such as SIBCASA.

Verification of an on line in vivo semiconductor dosimetry system for TBI with two TLD procedures.

PubMed

Sánchez-Doblado, F; Terrón, J A; Sánchez-Nieto, B; Arráns, R; Errazquin, L; Biggs, D; Lee, C; Núñez, L; Delgado, A; Muñiz, J L

1995-01-01

This work presents the verification of an on line in vivo dosimetry system based on semiconductors. Software and hardware has been designed to convert the diode signal into absorbed dose. Final verification was made in the form of an intercomparison with two independent thermoluminiscent (TLD) dosimetry systems, under TBI conditions.

78 FR 42777 - Application for Final Commitment for a Long-Term Loan or Financial Guarantee in Excess of $100...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-17

... the transaction: To support the export of U.S. manufactured semiconductor manufacturing equipment to... supports the manufacture of NAND flash semiconductors. To the extent that Ex-Im Bank is reasonably aware... exportation of goods or provision of services by a United States industry. Parties: Principal Supplier...

To validate final patent number 27-2005-0081, and for other purposes.

THOMAS, 111th Congress

Rep. Heller, Dean [R-NV-2

2009-01-28

Senate - 08/05/2010 Placed on Senate Legislative Calendar under General Orders. Calendar No. 542. (All Actions) Tracker: This bill has the status Passed HouseHere are the steps for Status of Legislation:

CosmoQuest Transient Tracker: Opensource Photometry & Astrometry software

NASA Astrophysics Data System (ADS)

Myers, Joseph L.; Lehan, Cory; Gay, Pamela; Richardson, Matthew; CosmoQuest Team

2018-01-01

CosmoQuest is moving from online citizen science, to observational astronomy with the creation of Transient Trackers. This open source software is designed to identify asteroids and other transient/variable objects in image sets. Transient Tracker’s features in final form will include: astrometric and photometric solutions, identification of moving/transient objects, identification of variable objects, and lightcurve analysis. In this poster we present our initial, v0.1 release and seek community input.This software builds on the existing NIH funded ImageJ libraries. Creation of this suite of opensource image manipulation routines is lead by Wayne Rasband and is released primarily under the MIT license. In this release, we are building on these libraries to add source identification for point / point-like sources, and to do astrometry. Our materials released under the Apache 2.0 license on github (http://github.com/CosmoQuestTeam) and documentation can be found at http://cosmoquest.org/TransientTracker.

Angle-depended photocurrent characteristics of cascade photoelectric converters on the base of homogeneous semiconductor

NASA Astrophysics Data System (ADS)

Arbuzov, Yuri D.; Evdokimov, Vladimir M.; Shepovalova, Olga V.

2018-05-01

Angle-dependent spectral photoresponse characteristics for theoretically perfect and physically implementable tunnel cascade (multi-junction) photoelectric converters (PC), for example high-voltage planar PV cells, have been studied as functions of technological parameters and number of single PCs in cascade. Angle-dependent spectral photoresponse characteristics values for real cascade silicon structures have been determined in visible and ultraviolet radiation spectra. Characteristic values of radiation incidence angle corresponding to the twofold photocurrent reduction in relation to normal incidence have been found depending on the number of single PCs in cascade, `dead' layer thickness of tunnel junction and photosensitivity of the base PC. The possibility and practicability of solar trackers use in PV systems with proposed PCs under study have been evaluated.

Hole-cyclotron instability in semiconductor quantum plasmas

NASA Astrophysics Data System (ADS)

Areeb, F.; Rasheed, A.; Jamil, M.; Siddique, M.; Sumera, P.

2018-01-01

The excitation of electrostatic hole-cyclotron waves generated by an externally injected electron beam in semiconductor plasmas is examined using a quantum hydrodynamic model. The quantum effects such as tunneling potential, Fermi degenerate pressure, and exchange-correlation potential are taken care of. The growth rate of the wave is analyzed on varying the parameters normalized by hole-plasma frequency, like the angle θ between propagation vector and B0∥z ̂ , speed of the externally injected electron beam v0∥k , thermal temperature of the electron beam τ, external magnetic field B0∥z ̂ that modifies the hole-cyclotron frequency, and finally, the semiconductor electron number density. The instability of the hole-cyclotron wave seeks its applications in semiconductor devices.

Hybrid organic semiconductor lasers for bio-molecular sensing.

PubMed

Haughey, Anne-Marie; Foucher, Caroline; Guilhabert, Benoit; Kanibolotsky, Alexander L; Skabara, Peter J; Burley, Glenn; Dawson, Martin D; Laurand, Nicolas

2014-01-01

Bio-functionalised luminescent organic semiconductors are attractive for biophotonics because they can act as efficient laser materials while simultaneously interacting with molecules. In this paper, we present and discuss a laser biosensor platform that utilises a gain layer made of such an organic semiconductor material. The simple structure of the sensor and its operation principle are described. Nanolayer detection is shown experimentally and analysed theoretically in order to assess the potential and the limits of the biosensor. The advantage conferred by the organic semiconductor is explained, and comparisons to laser sensors using alternative dye-doped materials are made. Specific biomolecular sensing is demonstrated, and routes to functionalisation with nucleic acid probes, and future developments opened up by this achievement, are highlighted. Finally, attractive formats for sensing applications are mentioned, as well as colloidal quantum dots, which in the future could be used in conjunction with organic semiconductors.

An on-line acoustic fluorocarbon coolant mixture analyzer for the ATLAS silicon tracker

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

Bates, R.; Battistin, M.; Berry, S.

2011-07-01

The ATLAS silicon tracker community foresees an upgrade from the present octafluoro-propane (C{sub 3}F{sub 8}) evaporative cooling fluid - to a composite fluid with a probable 10-20% admixture of hexafluoro-ethane (C{sub 2}F{sub 6}). Such a fluid will allow a lower evaporation temperature and will afford the tracker silicon substrates a better safety margin against leakage current-induced thermal runaway caused by cumulative radiation damage as the luminosity profile at the CERN Large Hadron Collider increases. Central to the use of this new fluid is a new custom-developed speed-of-sound instrument for continuous real-time measurement of the C{sub 3}F{sub 8}/C{sub 2}F{sub 6} mixturemore » ratio and flow. An acoustic vapour mixture analyzer/flow meter with new custom electronics allowing ultrasonic frequency transmission through gas mixtures has been developed for this application. Synchronous with the emission of an ultrasound 'chirp' from an acoustic transmitter, a fast readout clock (40 MHz) is started. The clock is stopped on receipt of an above threshold sound pulse at the receiver. Sound is alternately transmitted parallel and anti-parallel with the vapour flow for volume flow measurement from transducers that can serve as acoustic transmitters or receivers. In the development version, continuous real-time measurement of C{sub 3}F{sub 8}/C{sub 2}F{sub 6} flow and calculation of the mixture ratio is performed within a graphical user interface developed in PVSS-II, the Supervisory, Control and Data Acquisition standard chosen for LHC and its experiments at CERN. The described instrument has numerous potential applications - including refrigerant leak detection, the analysis of hydrocarbons, vapour mixtures for semiconductor manufacture and anesthetic gas mixtures. (authors)« less

An On-Line Acoustic Fluorocarbon Coolant Mixture Analyzer for the ATLAS Silicon Tracker

NASA Astrophysics Data System (ADS)

Bates, R.; Battistin, M.; Berry, S.; Bitadze, A.; Bonneau, P.; Bousson, N.; Boyd, G.; Botelho-Direito, J.; DiGirolamo, B.; Doubek, M.; Egorov, K.; Godlewski, J.; Hallewell, G.; Katunin, S.; Mathieu, M.; McMahon, S.; Nagai, K.; Perez-Rodriguez, E.; Rozanov, A.; Vacek, V.; Vitek, M.

2012-10-01

The ATLAS silicon tracker community foresees an upgrade from the present octafluoropropane (C3F8) evaporative cooling fluid to a composite fluid with a probable 10-20% admixture of hexafluoroethane (C2F6). Such a fluid will allow a lower evaporation temperature and will afford the tracker silicon substrates a better safety margin against leakage current-induced thermal runaway caused by cumulative radiation damage as the luminosity profile at the CERN Large Hadron Collider increases. Central to the use of this new fluid is a new custom-developed speed-of-sound instrument for continuous real-time measurement of the C3F8/C2F6 mixture ratio and flow. An acoustic vapour mixture analyzer/flow meter with new custom electronics allowing ultrasonic frequency transmission through gas mixtures has been developed for this application. Synchronous with the emission of an ultrasound `chirp' from an acoustic transmitter, a fast readout clock (40 MHz) is started. The clock is stopped on receipt of an above threshold sound pulse at the receiver. Sound is alternately transmitted parallel and anti-parallel with the vapour flow for volume flow measurement from transducers that can serve as acoustic transmitters or receivers. In the development version, continuous real-time measurement of C3F8/C2F6 flow and calculation of the mixture ratio is performed within a graphical user interface developed in PVSS-II, the Supervisory, Control and Data Acquisition standard chosen for LHC and its experiments at CERN. The described instrument has numerous potential applications - including refrigerant leak detection, the analysis of hydrocarbons, vapour mixtures for semi-conductor manufacture and anesthetic gas mixtures.

Alternative glues for the production of ATLAS silicon strip modules for the Phase-II upgrade of the ATLAS Inner Detector

NASA Astrophysics Data System (ADS)

Poley, L.; Bloch, I.; Edwards, S.; Friedrich, C.; Gregor, I.-M.; Jones, T.; Lacker, H.; Pyatt, S.; Rehnisch, L.; Sperlich, D.; Wilson, J.

2016-05-01

The Phase-II upgrade of the ATLAS detector for the High Luminosity Large Hadron Collider (HL-LHC) includes the replacement of the current Inner Detector with an all-silicon tracker consisting of pixel and strip detectors. The current Phase-II detector layout requires the construction of 20,000 strip detector modules consisting of sensor, circuit boards and readout chips, which are connected mechanically using adhesives. The adhesive used initially between readout chips and circuit board is a silver epoxy glue as was used in the current ATLAS SemiConductor Tracker (SCT). However, this glue has several disadvantages, which motivated the search for an alternative. This paper presents a study of six ultra-violet (UV) cure glues and a glue pad for possible use in the assembly of silicon strip detector modules for the ATLAS upgrade. Trials were carried out to determine the ease of use, thermal conduction and shear strength. Samples were thermally cycled, radiation hardness and corrosion resistance were also determined. These investigations led to the exclusion of three UV cure glues as well as the glue pad. Three UV cure glues were found to be possible better alternatives than silver loaded glue. Results from electrical tests of first prototype modules constructed using these glues are presented.

Southeast Alaska Native Land Entitlement Finalization Act

THOMAS, 111th Congress

Sen. Murkowski, Lisa [R-AK

2009-04-23

Senate - 10/08/2009 Committee on Energy and Natural Resources Subcommittee on Public Lands and Forests. Hearings held. With printed Hearing: S.Hrg. 111-285. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Semiconductor Phase Conjugation

DTIC Science & Technology

1992-05-01

PL-TR--91- 1082 PL-TR-- AD-A253 684 91- 1082 SEMICONDUCTOR PHASE CONJUGATION lam-Choon Khoo Pennsylvania State University Electrical and Computer... 1082 This final report was prepared by Pennsylvania State University, University Park, Pennsylvania, under Contract F29601-88-K-0028, Job Order 33261B18...10. SPONSORING/ MONITORING AGENCY REPORT NUMBER Phill ips Laboratory PL-TR--91- 1082 Kirtland AFB, NM 87117-6008 11. SUPPLEMENTARY NOTES 12a

Aptamer-Modified Semiconductor Quantum Dots for Biosensing Applications

PubMed Central

Wen, Lin; Qiu, Liping; Wu, Yongxiang; Hu, Xiaoxiao; Zhang, Xiaobing

2017-01-01

Semiconductor quantum dots have attracted extensive interest in the biosensing area because of their properties, such as narrow and symmetric emission with tunable colors, high quantum yield, high stability and controllable morphology. The introduction of various reactive functional groups on the surface of semiconductor quantum dots allows one to conjugate a spectrum of ligands, antibodies, peptides, or nucleic acids for broader and smarter applications. Among these ligands, aptamers exhibit many advantages including small size, high chemical stability, simple synthesis with high batch-to-batch consistency and convenient modification. More importantly, it is easy to introduce nucleic acid amplification strategies and/or nanomaterials to improve the sensitivity of aptamer-based sensing systems. Therefore, the combination of semiconductor quantum dots and aptamers brings more opportunities in bioanalysis. Here we summarize recent advances on aptamer-functionalized semiconductor quantum dots in biosensing applications. Firstly, we discuss the properties and structure of semiconductor quantum dots and aptamers. Then, the applications of biosensors based on aptamer-modified semiconductor quantum dots by different signal transducing mechanisms, including optical, electrochemical and electrogenerated chemiluminescence approaches, is discussed. Finally, our perspectives on the challenges and opportunities in this promising field are provided. PMID:28788080

Aptamer-Modified Semiconductor Quantum Dots for Biosensing Applications.

PubMed

Wen, Lin; Qiu, Liping; Wu, Yongxiang; Hu, Xiaoxiao; Zhang, Xiaobing

2017-07-28

Semiconductor quantum dots have attracted extensive interest in the biosensing area because of their properties, such as narrow and symmetric emission with tunable colors, high quantum yield, high stability and controllable morphology. The introduction of various reactive functional groups on the surface of semiconductor quantum dots allows one to conjugate a spectrum of ligands, antibodies, peptides, or nucleic acids for broader and smarter applications. Among these ligands, aptamers exhibit many advantages including small size, high chemical stability, simple synthesis with high batch-to-batch consistency and convenient modification. More importantly, it is easy to introduce nucleic acid amplification strategies and/or nanomaterials to improve the sensitivity of aptamer-based sensing systems. Therefore, the combination of semiconductor quantum dots and aptamers brings more opportunities in bioanalysis. Here we summarize recent advances on aptamer-functionalized semiconductor quantum dots in biosensing applications. Firstly, we discuss the properties and structure of semiconductor quantum dots and aptamers. Then, the applications of biosensors based on aptamer-modified semiconductor quantum dots by different signal transducing mechanisms, including optical, electrochemical and electrogenerated chemiluminescence approaches, is discussed. Finally, our perspectives on the challenges and opportunities in this promising field are provided.

Individual Differences in the Attribution of Incentive Salience to a Pavlovian Alcohol Cue

PubMed Central

Villaruel, Franz R.; Chaudhri, Nadia

2016-01-01

Individual differences exist in the attribution of incentive salience to conditioned stimuli associated with food. Here, we investigated whether individual differences also manifested with a Pavlovian alcohol conditioned stimulus (CS). We compiled data from five experiments that used a Pavlovian autoshaping paradigm and tests of conditioned reinforcement. In all experiments, male, Long-Evans rats with unrestricted access to food and water were acclimated to 15% ethanol. Next, rats received Pavlovian autoshaping training, in which a 10 s presentation of a retractable lever served as the CS and 0.2 mL of 15% ethanol served as the unconditioned stimulus (US). Finally, rats underwent conditioned reinforcement tests in which nose-pokes to an active aperture led to brief presentations of the lever-CS, but nose-pokes to an inactive aperture had no consequence. Rats were categorized as sign-trackers, goal-trackers and intermediates based on a response bias score that reflected their tendencies to sign-track or goal-track at different times during training. We found that distinct groups of rats either consistently interacted with the lever-CS (“sign-trackers”) or routinely approached the port during the lever-CS (“goal-trackers”) across a majority of the training sessions. However, some individuals (“shifted sign-trackers”) with an early tendency to goal-track later shifted to comparable asymptotic levels of sign-tracking as the group identified as sign-trackers. The lever-CS functioned as a conditioned reinforcer for sign-trackers and shifted sign-trackers, but not for goal-trackers. These results provide evidence of robust individual differences in the extent to which a Pavlovian alcohol cue gains incentive salience and functions as a conditioned reinforcer. PMID:28082877

77 FR 11486 - Fresh Garlic From the People's Republic of China: Partial Final Results and Partial Final...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-27

... between grades are based on color, size, sheathing, and level of decay. The scope of the order does not... Less than Fair Value: Static Random Access Memory Semiconductors From Taiwan, 63 FR 8909, 8911...

Equipment for Topographical Preparation and Analysis of Various Semiconductor Infrared Detector Samples

DTIC Science & Technology

2015-11-13

P Wijewarnasuriya at the Army Research Lab to understand the bandd offsets of HgCdTe infrared detector structures. Especially when a sample is not...Final Report: Equipment for Topographical Preparation and Analysis of Various Semiconductor Infrared Detector Samples Report Title A used calibrated...structures i. G15-38 and G15-38 Quantum Dot ---------------------------- 16 Infrared Detector Samples ii. GSU13-MPD-GB1 Heterostructure

A review of carrier thermoelectric-transport theory in organic semiconductors.

PubMed

Lu, Nianduan; Li, Ling; Liu, Ming

2016-07-20

Carrier thermoelectric-transport theory has recently become of growing interest and numerous thermoelectric-transport models have been proposed for organic semiconductors, due to pressing current issues involving energy production and the environment. The purpose of this review is to provide a theoretical description of the thermoelectric Seebeck effect in organic semiconductors. Special attention is devoted to the carrier concentration, temperature, polaron effect and dipole effect dependence of the Seebeck effect and its relationship to hopping transport theory. Furthermore, various theoretical methods are used to discuss carrier thermoelectric transport. Finally, an outlook of the remaining challenges ahead for future theoretical research is provided.

Absorption of light dark matter in semiconductors

DOE PAGES

Hochberg, Yonit; Lin, Tongyan; Zurek, Kathryn M.

2017-01-01

Semiconductors are by now well-established targets for direct detection of MeV to GeV dark matter via scattering off electrons. We show that semiconductor targets can also detect significantly lighter dark matter via an absorption process. When the dark matter mass is above the band gap of the semiconductor (around an eV), absorption proceeds by excitation of an electron into the conduction band. Below the band gap, multiphonon excitations enable absorption of dark matter in the 0.01 eV to eV mass range. Energetic dark matter particles emitted from the sun can also be probed for masses below an eV. We derivemore » the reach for absorption of a relic kinetically mixed dark photon or pseudoscalar in germanium and silicon, and show that existing direct detection results already probe new parameter space. Finally, with only a moderate exposure, low-threshold semiconductor target experiments can exceed current astrophysical and terrestrial constraints on sub-keV bosonic dark matter.« less

Southeast Alaska Native Land Entitlement Finalization and Jobs Protection Act

THOMAS, 112th Congress

Sen. Murkowski, Lisa [R-AK

2011-04-05

Senate - 05/25/2011 Committee on Energy and Natural Resources Subcommittee on Public Lands and Forests. Hearings held. With printed Hearing: S.Hrg. 112-131. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

A joint resolution calling upon the President to issue a proclamation recognizing the 35th anniversary of the Helsinki Final Act.

THOMAS, 111th Congress

Sen. Cardin, Benjamin L. [D-MD

2010-08-02

Senate - 12/21/2010 Placed on Senate Legislative Calendar under General Orders. Calendar No. 726. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

On-Orbit Solar Dynamics Observatory (SDO) Star Tracker Warm Pixel Analysis

NASA Technical Reports Server (NTRS)

Felikson, Denis; Ekinci, Matthew; Hashmall, Joseph A.; Vess, Melissa

2011-01-01

This paper describes the process of identification and analysis of warm pixels in two autonomous star trackers on the Solar Dynamics Observatory (SDO) mission. A brief description of the mission orbit and attitude regimes is discussed and pertinent star tracker hardware specifications are given. Warm pixels are defined and the Quality Index parameter is introduced, which can be explained qualitatively as a manifestation of a possible warm pixel event. A description of the algorithm used to identify warm pixel candidates is given. Finally, analysis of dumps of on-orbit star tracker charge coupled devices (CCD) images is presented and an operational plan going forward is discussed. SDO, launched on February 11, 2010, is operated from the NASA Goddard Space Flight Center (GSFC). SDO is in a geosynchronous orbit with a 28.5 inclination. The nominal mission attitude points the spacecraft X-axis at the Sun, with the spacecraft Z-axis roughly aligned with the Solar North Pole. The spacecraft Y-axis completes the triad. In attitude, SDO moves approximately 0.04 per hour, mostly about the spacecraft Z-axis. The SDO star trackers, manufactured by Galileo Avionica, project the images of stars in their 16.4deg x 16.4deg fields-of-view onto CCD detectors consisting of 512 x 512 pixels. The trackers autonomously identify the star patterns and provide an attitude estimate. Each unit is able to track up to 9 stars. Additionally, each tracker calculates a parameter called the Quality Index, which is a measure of the quality of the attitude solution. Each pixel in the CCD measures the intensity of light and a warns pixel is defined as having a measurement consistently and significantly higher than the mean background intensity level. A warns pixel should also have lower intensity than a pixel containing a star image and will not move across the field of view as the attitude changes (as would a dim star image). It should be noted that the maximum error introduced in the star tracker attitude solution during suspected warm pixel corruptions is within the specified 36 attitude error budget requirement of [35, 70, 70] arcseconds. Thus, the star trackers provided attitude accuracy within the specification for SDO. The star tracker images are intentionally defocused so each star image is detected in more than one CCD pixel. The position of each star is calculated as an intensity-weighted average of the illuminated pixels. The exact method of finding the positions is proprietary to the tracker manufacturer. When a warm pixel happens to be in the vicinity of a star, it can corrupt the calculation of the position of that particular star, thereby corrupting the estimate of the attitude.

A resolution congratulating the Miami Heat for winning the 2013 National Basketball Association Finals.

THOMAS, 113th Congress

Sen. Rubio, Marco [R-FL

2013-06-25

Senate - 06/25/2013 Submitted in the Senate, considered, and agreed to without amendment and with a preamble by Unanimous Consent. (All Actions) Tracker: This bill has the status Agreed to in SenateHere are the steps for Status of Legislation:

Optoelectronics of supported and suspended 2D semiconductors

NASA Astrophysics Data System (ADS)

Bolotin, Kirill

2014-03-01

Two-dimensional semiconductors, materials such monolayer molybdenum disulfide (MoS2) are characterized by strong spin-orbit and electron-electron interactions. However, both electronic and optoelectronic properties of these materials are dominated by disorder-related scattering. In this talk, we investigate approaches to reduce scattering and explore physical phenomena arising in intrinsic 2D semiconductors. First, we discuss fabrication of pristine suspended monolayer MoS2 and use photocurrent spectroscopy measurements to study excitons in this material. We observe band-edge and van Hove singularity excitons and estimate their binding energies. Furthermore, we study dissociation of these excitons and uncover the mechanism of their contribution to photoresponse of MoS2. Second, we study strain-induced modification of bandstructures of 2D semiconductors. With increasing strain, we find large and controllable band gap reduction of both single- and bi-layer MoS2. We also detect experimental signatures consistent with strain-induced transition from direct to indirect band gap in monolayer MoS2. Finally, we fabricate heterostructures of dissimilar 2D semiconductors and study their photoresponse. For closely spaced 2D semiconductors we detect charge transfer, while for separation larger than 10nm we observe Forster-like energy transfer between excitations in different layers.

Two-Dimensional Semiconductor Optoelectronics Based on van der Waals Heterostructures.

PubMed

Lee, Jae Yoon; Shin, Jun-Hwan; Lee, Gwan-Hyoung; Lee, Chul-Ho

2016-10-27

Two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDCs) and black phosphorous have drawn tremendous attention as an emerging optical material due to their unique and remarkable optical properties. In addition, the ability to create the atomically-controlled van der Waals (vdW) heterostructures enables realizing novel optoelectronic devices that are distinct from conventional bulk counterparts. In this short review, we first present the atomic and electronic structures of 2D semiconducting TMDCs and their exceptional optical properties, and further discuss the fabrication and distinctive features of vdW heterostructures assembled from different kinds of 2D materials with various physical properties. We then focus on reviewing the recent progress on the fabrication of 2D semiconductor optoelectronic devices based on vdW heterostructures including photodetectors, solar cells, and light-emitting devices. Finally, we highlight the perspectives and challenges of optoelectronics based on 2D semiconductor heterostructures.

Two-Dimensional Semiconductor Optoelectronics Based on van der Waals Heterostructures

PubMed Central

Lee, Jae Yoon; Shin, Jun-Hwan; Lee, Gwan-Hyoung; Lee, Chul-Ho

2016-01-01

Two-dimensional (2D) semiconductors such as transition metal dichalcogenides (TMDCs) and black phosphorous have drawn tremendous attention as an emerging optical material due to their unique and remarkable optical properties. In addition, the ability to create the atomically-controlled van der Waals (vdW) heterostructures enables realizing novel optoelectronic devices that are distinct from conventional bulk counterparts. In this short review, we first present the atomic and electronic structures of 2D semiconducting TMDCs and their exceptional optical properties, and further discuss the fabrication and distinctive features of vdW heterostructures assembled from different kinds of 2D materials with various physical properties. We then focus on reviewing the recent progress on the fabrication of 2D semiconductor optoelectronic devices based on vdW heterostructures including photodetectors, solar cells, and light-emitting devices. Finally, we highlight the perspectives and challenges of optoelectronics based on 2D semiconductor heterostructures. PMID:28335321

The Physics of Semiconductors

NASA Astrophysics Data System (ADS)

Brennan, Kevin F.

1999-02-01

Modern fabrication techniques have made it possible to produce semiconductor devices whose dimensions are so small that quantum mechanical effects dominate their behavior. This book describes the key elements of quantum mechanics, statistical mechanics, and solid-state physics that are necessary in understanding these modern semiconductor devices. The author begins with a review of elementary quantum mechanics, and then describes more advanced topics, such as multiple quantum wells. He then disusses equilibrium and nonequilibrium statistical mechanics. Following this introduction, he provides a thorough treatment of solid-state physics, covering electron motion in periodic potentials, electron-phonon interaction, and recombination processes. The final four chapters deal exclusively with real devices, such as semiconductor lasers, photodiodes, flat panel displays, and MOSFETs. The book contains many homework exercises and is suitable as a textbook for electrical engineering, materials science, or physics students taking courses in solid-state device physics. It will also be a valuable reference for practicing engineers in optoelectronics and related areas.

A bill to validate final patent number 27-2005-0081, and for other purposes.

THOMAS, 112th Congress

Sen. Ensign, John [R-NV

2011-04-05

Senate - 05/18/2011 Committee on Energy and Natural Resources Subcommittee on Public Lands and Forests. Hearings held. With printed Hearing: S.Hrg. 112-39. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Fiscal Year 2011 Director’s Strategic Initiative Final Report Heterogeneous Device Architectures Incorporating Nitride Semiconductors for Enhanced Functionality of Optoelectronic Devices

DTIC Science & Technology

2014-03-01

electromagnetic radiation across the spectrum from the ultraviolet ( UV ) to terahertz, heterogeneous integration of these materials with others having different...weak absorption that limit the QE of homogenous SiC-based photodetectors in the deep UV and near UV regions, respectively. Furthermore, we have...Polarization-Enhanced III-Nitride-SiC Avalanche Photodiodes Semiconductor-based ultraviolet ( UV ) avalanche photodetectors (APDs) have significant promise

Molecular-Beam Epitaxial Growth and Device Potential of Polar/Nonpolar Semiconductor Heterostructures.

DTIC Science & Technology

1985-06-24

research , and perhaps the most far-reaching one * A GaP -on-Si transistor was achieved, vastly better than any previous or concurrent effort towards this...the numerous conceptual and technological developments that had accumulated during the research . e) Defects in GaP -on-Si(211) Layers. With the help...Growth and Device Potential of Polar/Nonpolar Semiconductor Heterostructures Final Report by A Herbert Kroemer June 1985 -..2-- U. S. Army Research

Magneto-Transpots in Interband Resonant Tunneling Diodes (I-RTDs) and Dilute Magnetic Semiconductor (DMS) I-RTDs

DTIC Science & Technology

2011-03-02

Woolard, "Far- infrared and Terahertz lasing based upon resonant and interband tunneling in InAs/GaSb heterostructure," Applied Physics Letter, vol. 98...REPORT FINAL REPORT: Magneto-Transpots in interband Resonant Tunneling Diodes (I-RTDs) and Dilute Magnetic Semiconductor (DMS) I-RTDs 14. ABSTRACT 16...diodes (RTDs). This DB-BG-RTD device will utilizes two distinct innovations. First, ultra-fast heavy-hole (HH) interband tunneling is leveraged to

A Review of Activity Trackers for Senior Citizens: Research Perspectives, Commercial Landscape and the Role of the Insurance Industry.

PubMed

Tedesco, Salvatore; Barton, John; O'Flynn, Brendan

2017-06-03

The objective assessment of physical activity levels through wearable inertial-based motion detectors for the automatic, continuous and long-term monitoring of people in free-living environments is a well-known research area in the literature. However, their application to older adults can present particular constraints. This paper reviews the adoption of wearable devices in senior citizens by describing various researches for monitoring physical activity indicators, such as energy expenditure, posture transitions, activity classification, fall detection and prediction, gait and balance analysis, also by adopting consumer-grade fitness trackers with the associated limitations regarding acceptability. This review also describes and compares existing commercial products encompassing activity trackers tailored for older adults, thus providing a comprehensive outlook of the status of commercially available motion tracking systems. Finally, the impact of wearable devices on life and health insurance companies, with a description of the potential benefits for the industry and the wearables market, was analyzed as an example of the potential emerging market drivers for such technology in the future.

Dynamic imaging model and parameter optimization for a star tracker.

PubMed

Yan, Jinyun; Jiang, Jie; Zhang, Guangjun

2016-03-21

Under dynamic conditions, star spots move across the image plane of a star tracker and form a smeared star image. This smearing effect increases errors in star position estimation and degrades attitude accuracy. First, an analytical energy distribution model of a smeared star spot is established based on a line segment spread function because the dynamic imaging process of a star tracker is equivalent to the static imaging process of linear light sources. The proposed model, which has a clear physical meaning, explicitly reflects the key parameters of the imaging process, including incident flux, exposure time, velocity of a star spot in an image plane, and Gaussian radius. Furthermore, an analytical expression of the centroiding error of the smeared star spot is derived using the proposed model. An accurate and comprehensive evaluation of centroiding accuracy is obtained based on the expression. Moreover, analytical solutions of the optimal parameters are derived to achieve the best performance in centroid estimation. Finally, we perform numerical simulations and a night sky experiment to validate the correctness of the dynamic imaging model, the centroiding error expression, and the optimal parameters.

Tracking instrument and control for solar concentrators. Final technical report, October 1979-January 1981

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

Gray, J; Kuhlman, J

1981-01-31

The tracker uses a single photo sensor, and a rotating aperature to obtain tracking accuracies better than 1.5 mrads (0.1 degs). Peak signal detection is used to eliminate tracking of false sources, i.e., clouds, etc. A prism is employed to obtain an extended field of view (150 degs axially - 360 degs radially). The tracker digitally measures the Suns displacement angle relative to the concentrator axis, and repositions it incrementally. This arrangement permits the use of low cost non-servo motors. The local controller contains microprocessor based electronics, incorporating digital signal processing. A single controller may be time shared by amore » maximum of sixteen trackers, providing a high performance, cost effective solar tracking system, suitable for both line and point focus concentrators. An installation may have the local controller programmed as a standalone unit or slaved to a central controller. When used with a central controller, dynamic data monitoring and logging is available, together with the ability to change system modes and parameters, as desired.« less

A Review of Activity Trackers for Senior Citizens: Research Perspectives, Commercial Landscape and the Role of the Insurance Industry

PubMed Central

Tedesco, Salvatore; Barton, John; O’Flynn, Brendan

2017-01-01

The objective assessment of physical activity levels through wearable inertial-based motion detectors for the automatic, continuous and long-term monitoring of people in free-living environments is a well-known research area in the literature. However, their application to older adults can present particular constraints. This paper reviews the adoption of wearable devices in senior citizens by describing various researches for monitoring physical activity indicators, such as energy expenditure, posture transitions, activity classification, fall detection and prediction, gait and balance analysis, also by adopting consumer-grade fitness trackers with the associated limitations regarding acceptability. This review also describes and compares existing commercial products encompassing activity trackers tailored for older adults, thus providing a comprehensive outlook of the status of commercially available motion tracking systems. Finally, the impact of wearable devices on life and health insurance companies, with a description of the potential benefits for the industry and the wearables market, was analyzed as an example of the potential emerging market drivers for such technology in the future. PMID:28587188

Evaluating CMEMS products in the Western Mediterranean using multiplatform in situ data and an eddy tracker

NASA Astrophysics Data System (ADS)

Mason, Evan; Burgoa, Nadia; Pascual, Ananda; Sánchez-Román, Antonio; Tintoré, Joaquín; Ruiz, Simón

2017-04-01

Assessment of three CMEMS forecast modelling products (MEDSEA, IBI and GLOBAL) available for the Western Mediterranean has been done for the period 2013-2016. The final objective is to contribute to the improvement of these products by providing feedback to the Monitoring and Forecasting Centers (MFCs). To achieve this objective, a multiplatform approach, combining in-situ and satellite data in synergy with numerical simulations is followed. We present new results on the mesoscale content of three operational models operating in the Western Mediterranean, based on standard statistical analysis and an automated eddy tracker (py-eddy-tracker, v2.1.0; Mason et al., 2014). Properties such as eddy radius, amplitude, polarity, eddy center and tracks have been produced for the three products. For each product the eddy tracker is run over the same period, at a sampling frequency of 1 day. The parameters used for the tracking are the same for each product. Eddy tracks reveal clear areas of dominance of either cyclones or anticyclones. These patterns are visible in all three products. In addition, CMEMS products have been evaluated for specific dates, using high-resolution multiplatform observations from different field experiments carried out in the Western Mediterranean. This study is a contribution to the MedSUB project, funded by Copernicus Marine Service within the Service Evolution 21-SE-CALL1.

Tracking Multiple Video Targets with an Improved GM-PHD Tracker

PubMed Central

Zhou, Xiaolong; Yu, Hui; Liu, Honghai; Li, Youfu

2015-01-01

Tracking multiple moving targets from a video plays an important role in many vision-based robotic applications. In this paper, we propose an improved Gaussian mixture probability hypothesis density (GM-PHD) tracker with weight penalization to effectively and accurately track multiple moving targets from a video. First, an entropy-based birth intensity estimation method is incorporated to eliminate the false positives caused by noisy video data. Then, a weight-penalized method with multi-feature fusion is proposed to accurately track the targets in close movement. For targets without occlusion, a weight matrix that contains all updated weights between the predicted target states and the measurements is constructed, and a simple, but effective method based on total weight and predicted target state is proposed to search the ambiguous weights in the weight matrix. The ambiguous weights are then penalized according to the fused target features that include spatial-colour appearance, histogram of oriented gradient and target area and further re-normalized to form a new weight matrix. With this new weight matrix, the tracker can correctly track the targets in close movement without occlusion. For targets with occlusion, a robust game-theoretical method is used. Finally, the experiments conducted on various video scenarios validate the effectiveness of the proposed penalization method and show the superior performance of our tracker over the state of the art. PMID:26633422

A review of the physics and response models for burnout of semiconductor devices

NASA Astrophysics Data System (ADS)

Orvis, W. J.; Khanaka, G. H.; Yee, J. H.

1984-12-01

Physical mechanisms that cause semiconductor devices to fail from electrical overstress--particularly, EMP-induced electrical stress--are described in light of the current literature and the authors' own research. A major concern is the cause and effects of second breakdown phenomena in p-n junction devices. Models of failure thresholds are evaluated for their inherent errors and for their ability to represent the relevant physics. Finally, the response models that relate electromagnetic stress parameters to appropriate failure-threshold parameters are discussed.

Review of betavoltaic energy conversion

NASA Astrophysics Data System (ADS)

Olsen, Larry C.

1993-05-01

Betavoltaic energy conversion refers to the generation of power by coupling a beta source to a semiconductor junction device. The theory of betavoltaic energy conversion and some past studies of the subject are briefly reviewed. Calculations of limiting efficiencies for semiconductor cells versus bandgap are presented along with specific studies for Pm-147 and Ni-63 fueled devices. The approach used for fabricating Pm-147 fueled batteries by the author in the early 1970's is reviewed. Finally, the potential performance of advanced betavoltaic power sources is considered.

The Effects of Temperature and Electron Radiation on the Electrical Properties of AlGaN/GaN Heterostructure Field Effect Transistors

DTIC Science & Technology

2009-03-01

focus of much semiconductor research. GaN alloyed materials have moved 2 to the forefront of modern semiconductor device technology owing to their...LEDs are used in place of incandescent light bulbs, they consume 80-90% less power and provide lifetimes over 10 times longer than incandescent light...of various lengths of time . Finally, comparisons are made between the results of this research and those from other researchers. Chapter 6

Review of betavoltaic energy conversion

NASA Technical Reports Server (NTRS)

Olsen, Larry C.

1993-01-01

Betavoltaic energy conversion refers to the generation of power by coupling a beta source to a semiconductor junction device. The theory of betavoltaic energy conversion and some past studies of the subject are briefly reviewed. Calculations of limiting efficiencies for semiconductor cells versus bandgap are presented along with specific studies for Pm-147 and Ni-63 fueled devices. The approach used for fabricating Pm-147 fueled batteries by the author in the early 1970's is reviewed. Finally, the potential performance of advanced betavoltaic power sources is considered.

Final Technical Report

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

Li, Lian

2017-03-08

Our BES supported program integrates molecular beam epitaxy growth with in situ atomic scale imaging using scanning tunneling microscopy/spectroscopy and atomic force microscopy. Aided by density functional theory calculations, we explore enhanced functionalities emerging from the interplay of strain, proximity, and spin-orbit interactions in heterostructures of wide band gap semiconductors, graphene, and Dirac materials, focusing on three thrusts: 1) doping wide bandgap semiconductors and graphene; 2) graphene nanoribbons and graphene-semiconductor heterostructures; and 3) Dirac materials. Our findings and discoveries have led to the publication of one book chapter and twenty-three refereed journal articles, including several in high impact journals suchmore » as Nature Communications, Physical Review Letters, and Nano Letters. Highlights of each thrust are provided in the report.« less

Majorana zero modes in superconductor-semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Lutchyn, R. M.; Bakkers, E. P. A. M.; Kouwenhoven, L. P.; Krogstrup, P.; Marcus, C. M.; Oreg, Y.

2018-05-01

Realizing topological superconductivity and Majorana zero modes in the laboratory is a major goal in condensed-matter physics. In this Review, we survey the current status of this rapidly developing field, focusing on proposals for the realization of topological superconductivity in semiconductor-superconductor heterostructures. We examine materials science progress in growing InAs and InSb semiconductor nanowires and characterizing these systems. We then discuss the observation of robust signatures of Majorana zero modes in recent experiments, paying particular attention to zero-bias tunnelling conduction measurements and Coulomb blockade experiments. We also outline several next-generation experiments probing exotic properties of Majorana zero modes, including fusion rules and non-Abelian exchange statistics. Finally, we discuss prospects for implementing Majorana-based topological quantum computation.

Recent progress in high-mobility thin-film transistors based on multilayer 2D materials

NASA Astrophysics Data System (ADS)

Hong, Young Ki; Liu, Na; Yin, Demin; Hong, Seongin; Kim, Dong Hak; Kim, Sunkook; Choi, Woong; Yoon, Youngki

2017-04-01

Two-dimensional (2D) layered semiconductors are emerging as promising candidates for next-generation thin-film electronics because of their high mobility, relatively large bandgap, low-power switching, and the availability of large-area growth methods. Thin-film transistors (TFTs) based on multilayer transition metal dichalcogenides or black phosphorus offer unique opportunities for next-generation electronic and optoelectronic devices. Here, we review recent progress in high-mobility transistors based on multilayer 2D semiconductors. We describe the theoretical background on characterizing methods of TFT performance and material properties, followed by their applications in flexible, transparent, and optoelectronic devices. Finally, we highlight some of the methods used in metal-semiconductor contacts, hybrid structures, heterostructures, and chemical doping to improve device performance.

Increasing the Endurance and Payload Capacity of Unmanned Vehicles with Thin-Film Photovoltaics

DTIC Science & Technology

2014-06-01

25  1.  Maximum Power Point Tracker .......................................................25  2.  DC-DC Power Conversion...An example of the amorphous silicon cell (from [28]). ...................................20  Figure 15.  The structure of a copper indium gallium ...for the final solar array with the maximum power point indicated

Continuing Appropriations Act, 2014

THOMAS, 113th Congress

Rep. Black, Diane [R-TN-6

2013-07-22

10/17/2013 Became Public Law No: 113-46. (TXT | PDF) (All Actions) Notes: The final version of the bill makes continuing appropriations through January 15, 2014, thus ending the government shutdown, and increases the debt limit through February 7, 2014. Tracker: This bill has the status Became LawHere are the steps for Status of Legislation:

Singlet fission/silicon solar cell exceeding 100% EQE (Conference Presentation)

NASA Astrophysics Data System (ADS)

Pazos, Luis M.; Lee, Jumin; Kirch, Anton; Tabachnyk, Maxim; Friend, Richard H.; Ehrler, Bruno

2016-09-01

Current matching limits the commercialization of tandem solar cells due to their instability over spectral changes, leading to the need of using solar concentrators and trackers to keep the spectrum stable. We demonstrate that voltage-matched systems show far higher performance over spectral changes; caused by clouds, dust and other variations in atmospheric conditions. Singlet fission is a process in organic semiconductors which has shown very efficient, 200%, down-conversion yield and the generated excitations are long-lived, ideal for solar cells. As a result, the number of publications has grown exponentially in the past 5 years. Yet, so far no one has achieved to combine singlet fission with most low bandgap semiconductors, including crystalline silicon, the dominating solar cell material with a 90% share of the PV Market. Here we show that singlet fission can facilitate the fabrication of voltage-matched systems, opening a simple design route for the effective implementation of down-conversion in commercially available photovoltaic technologies, with no modification of the electronic circuitry of such. The implemention of singlet fission is achieved simply by decoupling the fabrication of the individual subcells. For this demonstration we used an ITO/PEDOT/P3HT/Pentacene/C60/Ag wide-bandgap subcell, and a commercial silicon solar cell as the low-bandgap component. We show that the combination of the two leads to the first tandem silicon solar cell which exceeds 100% external quantum efficiency.

Zero suppression logic of the ALICE muon forward tracker pixel chip prototype PIXAM and associated readout electronics development

NASA Astrophysics Data System (ADS)

Flouzat, C.; Değerli, Y.; Guilloux, F.; Orsini, F.; Venault, P.

2015-05-01

In the framework of the ALICE experiment upgrade at HL-LHC, a new forward tracking detector, the Muon Forward Tracker (MFT), is foreseen to overcome the intrinsic limitations of the present Muon Spectrometer and will perform new measurements of general interest for the whole ALICE physics. To fulfill the new detector requirements, CMOS Monolithic Active Pixel Sensors (MAPS) provide an attractive trade-off between readout speed, spatial resolution, radiation hardness, granularity, power consumption and material budget. This technology has been chosen to equip the Muon Forward Tracker and also the vertex detector: the Inner Tracking System (ITS). Since few years, an intensive R&D program has been performed on the design of MAPS in the 0.18 μ m CMOS Image Sensor (CIS) process. In order to avoid pile up effects in the experiment, the classical rolling shutter readout system of MAPS has been improved to overcome the readout speed limitation. A zero suppression algorithm, based on a 3 by 3 cluster finding (position and data), has been chosen for the MFT. This algorithm allows adequate data compression for the sensor. This paper presents the large size prototype PIXAM, which represents 1/3 of the final chip, and will focus specially on the zero suppression block architecture. This chip is designed and under fabrication in the 0.18 μ m CIS process. Finally, the readout electronics principle to send out the compressed data flow is also presented taking into account the cluster occupancy per MFT plane for a single central Pb-Pb collision.

Imaging the motion of electrons in 2D semiconductor heterostructures

NASA Astrophysics Data System (ADS)

Dani, Keshav

Technological progress since the late 20th century has centered on semiconductor devices, such as transistors, diodes, and solar cells. At the heart of these devices, is the internal motion of electrons through semiconductor materials due to applied electric fields or by the excitation of photocarriers. Imaging the motion of these electrons would provide unprecedented insight into this important phenomenon, but requires high spatial and temporal resolution. Current studies of electron dynamics in semiconductors are generally limited by the spatial resolution of optical probes, or by the temporal resolution of electronic probes. In this talk, we combine femtosecond pump-probe techniques with spectroscopic photoemission electron microscopy to image the motion of photoexcited electrons from high-energy to low-energy states in a 2D InSe/GaAs heterostructure exhibiting a type-II band alignment. At the instant of photoexcitation, energy-resolved photoelectron images reveal a highly non-equilibrium distribution of photocarriers in space and energy. Thereafter, in response to the out-of-equilibrium photocarriers, we observe the spatial redistribution of charges, thus forming internal electric fields, bending the semiconductor bands, and finally impeding further charge transfer. By assembling images taken at different time-delays, we make a movie lasting a few tens of picoseconds of the electron transfer process in the photoexcited type-II heterostructure - a fundamental phenomenon in semiconductor devices like solar cells. Quantitative analysis and theoretical modeling of spatial variations in the video provide insight into future solar cells, electron dynamics in 2D materials, and other semiconductor devices.

Imaging the motion of electrons across semiconductor heterojunctions.

PubMed

Man, Michael K L; Margiolakis, Athanasios; Deckoff-Jones, Skylar; Harada, Takaaki; Wong, E Laine; Krishna, M Bala Murali; Madéo, Julien; Winchester, Andrew; Lei, Sidong; Vajtai, Robert; Ajayan, Pulickel M; Dani, Keshav M

2017-01-01

Technological progress since the late twentieth century has centred on semiconductor devices, such as transistors, diodes and solar cells. At the heart of these devices is the internal motion of electrons through semiconductor materials due to applied electric fields or by the excitation of photocarriers. Imaging the motion of these electrons would provide unprecedented insight into this important phenomenon, but requires high spatial and temporal resolution. Current studies of electron dynamics in semiconductors are generally limited by the spatial resolution of optical probes, or by the temporal resolution of electronic probes. Here, by combining femtosecond pump-probe techniques with spectroscopic photoemission electron microscopy, we imaged the motion of photoexcited electrons from high-energy to low-energy states in a type-II 2D InSe/GaAs heterostructure. At the instant of photoexcitation, energy-resolved photoelectron images revealed a highly non-equilibrium distribution of photocarriers in space and energy. Thereafter, in response to the out-of-equilibrium photocarriers, we observed the spatial redistribution of charges, thus forming internal electric fields, bending the semiconductor bands, and finally impeding further charge transfer. By assembling images taken at different time-delays, we produced a movie lasting a few trillionths of a second of the electron-transfer process in the photoexcited type-II heterostructure-a fundamental phenomenon in semiconductor devices such as solar cells. Quantitative analysis and theoretical modelling of spatial variations in the movie provide insight into future solar cells, 2D materials and other semiconductor devices.

Imaging the motion of electrons across semiconductor heterojunctions

NASA Astrophysics Data System (ADS)

Man, Michael K. L.; Margiolakis, Athanasios; Deckoff-Jones, Skylar; Harada, Takaaki; Wong, E. Laine; Krishna, M. Bala Murali; Madéo, Julien; Winchester, Andrew; Lei, Sidong; Vajtai, Robert; Ajayan, Pulickel M.; Dani, Keshav M.

2017-01-01

Technological progress since the late twentieth century has centred on semiconductor devices, such as transistors, diodes and solar cells. At the heart of these devices is the internal motion of electrons through semiconductor materials due to applied electric fields or by the excitation of photocarriers. Imaging the motion of these electrons would provide unprecedented insight into this important phenomenon, but requires high spatial and temporal resolution. Current studies of electron dynamics in semiconductors are generally limited by the spatial resolution of optical probes, or by the temporal resolution of electronic probes. Here, by combining femtosecond pump-probe techniques with spectroscopic photoemission electron microscopy, we imaged the motion of photoexcited electrons from high-energy to low-energy states in a type-II 2D InSe/GaAs heterostructure. At the instant of photoexcitation, energy-resolved photoelectron images revealed a highly non-equilibrium distribution of photocarriers in space and energy. Thereafter, in response to the out-of-equilibrium photocarriers, we observed the spatial redistribution of charges, thus forming internal electric fields, bending the semiconductor bands, and finally impeding further charge transfer. By assembling images taken at different time-delays, we produced a movie lasting a few trillionths of a second of the electron-transfer process in the photoexcited type-II heterostructure—a fundamental phenomenon in semiconductor devices such as solar cells. Quantitative analysis and theoretical modelling of spatial variations in the movie provide insight into future solar cells, 2D materials and other semiconductor devices.

Peptides for functionalization of InP semiconductors.

PubMed

Estephan, Elias; Saab, Marie-belle; Larroque, Christian; Martin, Marta; Olsson, Fredrik; Lourdudoss, Sebastian; Gergely, Csilla

2009-09-15

The challenge is to achieve high specificity in molecular sensing by proper functionalization of micro/nano-structured semiconductors by peptides that reveal specific recognition for these structures. Here we report on surface modification of the InP semiconductors by adhesion peptides produced by the phage display technique. An M13 bacteriophage library has been used to screen 10(10) different peptides against the InP(001) and the InP(111) surfaces to finally isolate specific peptides for each orientation of the InP. MALDI-TOF/TOF mass spectrometry has been employed to study real affinity of the peptide towards the InP surfaces. The peptides serve for controlled placement of biotin onto InP to bind then streptavidin. Our Atomic Force Microscopy study revealed a total surface coverage of molecules when the InP surface was functionalized by its specific biotinylated peptide (YAIKGPSHFRPS). Finally, fluorescence microscopy has been employed to demonstrate the preferential attachment of the peptide onto a micro-patterned InP surface. Use of substrate specific peptides could present an alternative solution for the problems encountered in the actually existing sensing methods and molecular self-assembly due to the unwanted unspecific interactions.

Elucidating the electron transport in semiconductors via Monte Carlo simulations: an inquiry-driven learning path for engineering undergraduates

NASA Astrophysics Data System (ADS)

Persano Adorno, Dominique; Pizzolato, Nicola; Fazio, Claudio

2015-09-01

Within the context of higher education for science or engineering undergraduates, we present an inquiry-driven learning path aimed at developing a more meaningful conceptual understanding of the electron dynamics in semiconductors in the presence of applied electric fields. The electron transport in a nondegenerate n-type indium phosphide bulk semiconductor is modelled using a multivalley Monte Carlo approach. The main characteristics of the electron dynamics are explored under different values of the driving electric field, lattice temperature and impurity density. Simulation results are presented by following a question-driven path of exploration, starting from the validation of the model and moving up to reasoned inquiries about the observed characteristics of electron dynamics. Our inquiry-driven learning path, based on numerical simulations, represents a viable example of how to integrate a traditional lecture-based teaching approach with effective learning strategies, providing science or engineering undergraduates with practical opportunities to enhance their comprehension of the physics governing the electron dynamics in semiconductors. Finally, we present a general discussion about the advantages and disadvantages of using an inquiry-based teaching approach within a learning environment based on semiconductor simulations.

Tungsten coating for improved wear resistance and reliability of microelectromechanical devices

DOEpatents

Fleming, James G.; Mani, Seethambal S.; Sniegowski, Jeffry J.; Blewer, Robert S.

2001-01-01

A process is disclosed whereby a 5-50-nanometer-thick conformal tungsten coating can be formed over exposed semiconductor surfaces (e.g. silicon, germanium or silicon carbide) within a microelectromechanical (MEM) device for improved wear resistance and reliability. The tungsten coating is formed after cleaning the semiconductor surfaces to remove any organic material and oxide film from the surface. A final in situ cleaning step is performed by heating a substrate containing the MEM device to a temperature in the range of 200-600 .degree. C. in the presence of gaseous nitrogen trifluoride (NF.sub.3). The tungsten coating can then be formed by a chemical reaction between the semiconductor surfaces and tungsten hexafluoride (WF.sub.6) at an elevated temperature, preferably about 450.degree. C. The tungsten deposition process is self-limiting and covers all exposed semiconductor surfaces including surfaces in close contact. The present invention can be applied to many different types of MEM devices including microrelays, micromirrors and microengines. Additionally, the tungsten wear-resistant coating of the present invention can be used to enhance the hardness, wear resistance, electrical conductivity, optical reflectivity and chemical inertness of one or more semiconductor surfaces within a MEM device.

PIFCGT: A PIF autopilot design program for general aviation aircraft

NASA Technical Reports Server (NTRS)

Broussard, J. R.

1983-01-01

This report documents the PIFCGT computer program. In FORTRAN, PIFCGT is a computer design aid for determing Proportional-Integral-Filter (PIF) control laws for aircraft autopilots implemented with a Command Generator Tracker (CGT). The program uses Linear-Quadratic-Regulator synthesis algorithms to determine feedback gains, and includes software to solve the feedforward matrix equation which is useful in determining the command generator tracker feedforward gains. The program accepts aerodynamic stability derivatives and computes the corresponding aerodynamic linear model. The nine autopilot modes that can be designed include four maneuver modes (ROLL SEL, PITCH SEL, HDG SEL, ALT SEL), four final approach models (APR GS, APR LOCI, APR LOCR, APR LOCP), and a BETA HOLD mode. The program has been compiled and executed on a CDC computer.

Beam collimation and focusing and error analysis of LD and fiber coupling system based on ZEMAX

NASA Astrophysics Data System (ADS)

Qiao, Lvlin; Zhou, Dejian; Xiao, Lei

2017-10-01

Laser diodde has many advantages, such as high efficiency, small volume, low cost and easy integration, so it is widely used. Because of its poor beam quality, the application of semiconductor laser has also been seriously hampered. In view of the poor beam quality, the ZEMAX optical design software is used to simulate the far field characteristics of the semiconductor laser beam, and the coupling module of the semiconductor laser and the optical fiber is designed and optimized. And the beam is coupled into the fiber core diameter d=200µm, the numerical aperture NA=0.22 optical fiber, the output power can reach 95%. Finally, the influence of the three docking errors on the coupling efficiency during the installation process is analyzed.

Semiconductor ferroelectric compositions and their use in photovoltaic devices

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

Rappe, Andrew M; Davies, Peter K; Spanier, Jonathan E

Disclosed herein are ferroelectric perovskites characterized as having a band gap, Egap, of less than 2.5 eV. Also disclosed are compounds comprising a solid solution of KNbO3 and BaNi1/2Nb1/2O3-delta, wherein delta is in the range of from 0 to about 1. The specification also discloses photovoltaic devices comprising one or more solar absorbing layers, wherein at least one of the solar absorbing layers comprises a semiconducting ferroelectric layer. Finally, this patent application provides solar cell, comprising: a heterojunction of n- and p-type semiconductors characterized as comprising an interface layer disposed between the n- and p-type semiconductors, the interface layer comprisingmore » a semiconducting ferroelectric absorber layer capable of enhancing light absorption and carrier separation.« less

Surface Plasmon-Assisted Solar Energy Conversion.

PubMed

Dodekatos, Georgios; Schünemann, Stefan; Tüysüz, Harun

2016-01-01

The utilization of localized surface plasmon resonance (LSPR) from plasmonic noble metals in combination with semiconductors promises great improvements for visible light-driven photocatalysis, in particular for energy conversion. This review summarizes the basic principles of plasmonic photocatalysis, giving a comprehensive overview about the proposed mechanisms for enhancing the performance of photocatalytically active semiconductors with plasmonic devices and their applications for surface plasmon-assisted solar energy conversion. The main focus is on gold and, to a lesser extent, silver nanoparticles in combination with titania as semiconductor and their usage as active plasmonic photocatalysts. Recent advances in water splitting, hydrogen generation with sacrificial organic compounds, and CO2 reduction to hydrocarbons for solar fuel production are highlighted. Finally, further improvements for plasmonic photocatalysts, regarding performance, stability, and economic feasibility, are discussed for surface plasmon-assisted solar energy conversion.

A resolution observing Juneteenth Independence Day, June 19, 1865, the day on which slavery finally came to an end in the United States.

THOMAS, 113th Congress

Sen. Levin, Carl [D-MI

2013-06-19

Senate - 06/19/2013 Submitted in the Senate, considered, and agreed to without amendment and with a preamble by Unanimous Consent. (All Actions) Tracker: This bill has the status Agreed to in SenateHere are the steps for Status of Legislation:

Customer Satisfaction: Fiscal Year 2007, Survey of Missouri Adults : Tracker Measures : 5a, 12j, 13c, 17d and 18b.

DOT National Transportation Integrated Search

2007-06-01

Using the 2006 survey as a baseline, the investigators collaborated with MoDOT to finalize the survey questions to be asked. A professional calling center was contracted to obtain a representative sample of each of the 10 MoDOT Districts, with a mini...

A bill to require the Bureau of Consumer Financial Protection to conduct a small business review panel on the qualified mortgage rule before the Bureau can go forward with a final rule.

THOMAS, 112th Congress

Sen. Crapo, Mike [R-ID

2012-09-19

Senate - 09/19/2012 Read twice and referred to the Committee on Banking, Housing, and Urban Affairs. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Reinventing the PN Junction: Dimensionality Effects on Tunneling Switches

DTIC Science & Technology

2012-05-11

Figure 4.7. Finally we need to define the band tail density of states:    > < = −− Vp qVEE Vp p EEe EE ED OVp , ,1 )( /)( (4.3.10...Cn qVEE Cn n EEe EE ED OCn , ,1 )( /)( (4.3.11) Here EVp is the valence band edge on the p side and ECn is the conduction band...semiconductor will occur at the oxide semiconductor interface and is given by the boundary condition SSOXOX EE  εε = . This means that the maximum

Electrically coupling complex oxides to semiconductors: A route to novel material functionalities

DOE PAGES

Ngai, J. H.; Ahmadi-Majlan, K.; Moghadam, J.; ...

2017-01-12

Complex oxides and semiconductors exhibit distinct yet complementary properties owing to their respective ionic and covalent natures. By electrically coupling complex oxides to traditional semiconductors within epitaxial heterostructures, enhanced or novel functionalities beyond those of the constituent materials can potentially be realized. Essential to electrically coupling complex oxides to semiconductors is control of the physical structure of the epitaxially grown oxide, as well as the electronic structure of the interface. In this paper, we discuss how composition of the perovskite A- and B-site cations can be manipulated to control the physical and electronic structure of semiconductor—complex oxide heterostructures. Two prototypicalmore » heterostructures, Ba 1-xSr xTiO 3/Ge and SrZr xTi 1-xO 3/Ge, will be discussed. In the case of Ba 1-xSr xTiO 3/Ge, we discuss how strain can be engineered through A-site composition to enable the re-orientable ferroelectric polarization of the former to be coupled to carriers in the semiconductor. In the case of SrZr xTi 1-xO 3/Ge we discuss how B-site composition can be exploited to control the band offset at the interface. Finally, analogous to heterojunctions between compound semiconducting materials, control of band offsets, i.e., band-gap engineering, provides a pathway to electrically couple complex oxides to semiconductors to realize a host of functionalities.« less

Electrically coupling complex oxides to semiconductors: A route to novel material functionalities

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

Ngai, J. H.; Ahmadi-Majlan, K.; Moghadam, J.

Complex oxides and semiconductors exhibit distinct yet complementary properties owing to their respective ionic and covalent natures. By electrically coupling complex oxides to traditional semiconductors within epitaxial heterostructures, enhanced or novel functionalities beyond those of the constituent materials can potentially be realized. Essential to electrically coupling complex oxides to semiconductors is control of the physical structure of the epitaxially grown oxide, as well as the electronic structure of the interface. In this paper, we discuss how composition of the perovskite A- and B-site cations can be manipulated to control the physical and electronic structure of semiconductor—complex oxide heterostructures. Two prototypicalmore » heterostructures, Ba 1-xSr xTiO 3/Ge and SrZr xTi 1-xO 3/Ge, will be discussed. In the case of Ba 1-xSr xTiO 3/Ge, we discuss how strain can be engineered through A-site composition to enable the re-orientable ferroelectric polarization of the former to be coupled to carriers in the semiconductor. In the case of SrZr xTi 1-xO 3/Ge we discuss how B-site composition can be exploited to control the band offset at the interface. Finally, analogous to heterojunctions between compound semiconducting materials, control of band offsets, i.e., band-gap engineering, provides a pathway to electrically couple complex oxides to semiconductors to realize a host of functionalities.« less

Four wave mixing oscillation in a semiconductor microcavity: generation of two correlated polariton populations.

PubMed

Romanelli, M; Leyder, C; Karr, J Ph; Giacobino, E; Bramati, A

2007-03-09

We demonstrate a novel kind of polariton four wave mixing oscillation. Two pump polaritons scatter towards final states that emit two beams of equal intensity, separated both spatially and in polarization with respect to the pumps. The measurement of the intensity fluctuations of the emitted light demonstrates that the final states are strongly correlated.

Oxide semiconductor thin-film transistors: a review of recent advances.

PubMed

Fortunato, E; Barquinha, P; Martins, R

2012-06-12

Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CMOS/SOS processing

NASA Technical Reports Server (NTRS)

Ramondetta, P.

1980-01-01

Report describes processes used in making complementary - metal - oxide - semiconductor/silicon-on-sapphire (CMOS/SOS) integrated circuits. Report lists processing steps ranging from initial preparation of sapphire wafers to final mapping of "good" and "bad" circuits on a wafer.

Online Hierarchical Sparse Representation of Multifeature for Robust Object Tracking

PubMed Central

Qu, Shiru

2016-01-01

Object tracking based on sparse representation has given promising tracking results in recent years. However, the trackers under the framework of sparse representation always overemphasize the sparse representation and ignore the correlation of visual information. In addition, the sparse coding methods only encode the local region independently and ignore the spatial neighborhood information of the image. In this paper, we propose a robust tracking algorithm. Firstly, multiple complementary features are used to describe the object appearance; the appearance model of the tracked target is modeled by instantaneous and stable appearance features simultaneously. A two-stage sparse-coded method which takes the spatial neighborhood information of the image patch and the computation burden into consideration is used to compute the reconstructed object appearance. Then, the reliability of each tracker is measured by the tracking likelihood function of transient and reconstructed appearance models. Finally, the most reliable tracker is obtained by a well established particle filter framework; the training set and the template library are incrementally updated based on the current tracking results. Experiment results on different challenging video sequences show that the proposed algorithm performs well with superior tracking accuracy and robustness. PMID:27630710

Synchronization of discrete-time neural networks with delays and Markov jump topologies based on tracker information.

PubMed

Yang, Xinsong; Feng, Zhiguo; Feng, Jianwen; Cao, Jinde

2017-01-01

In this paper, synchronization in an array of discrete-time neural networks (DTNNs) with time-varying delays coupled by Markov jump topologies is considered. It is assumed that the switching information can be collected by a tracker with a certain probability and transmitted from the tracker to controller precisely. Then the controller selects suitable control gains based on the received switching information to synchronize the network. This new control scheme makes full use of received information and overcomes the shortcomings of mode-dependent and mode-independent control schemes. Moreover, the proposed control method includes both the mode-dependent and mode-independent control techniques as special cases. By using linear matrix inequality (LMI) method and designing new Lyapunov functionals, delay-dependent conditions are derived to guarantee that the DTNNs with Markov jump topologies to be asymptotically synchronized. Compared with existing results on Markov systems which are obtained by separately using mode-dependent and mode-independent methods, our result has great flexibility in practical applications. Numerical simulations are finally given to demonstrate the effectiveness of the theoretical results. Copyright © 2016 Elsevier Ltd. All rights reserved.

Linear electro-optic effect in semiconductors: Ab initio description of the electronic contribution

NASA Astrophysics Data System (ADS)

Prussel, Lucie; Véniard, Valérie

2018-05-01

We propose an ab initio framework to derive the electronic part of the second-order susceptibility tensor for the electro-optic effect in bulk semiconductors. We find a general expression for χ(2 ) evaluated within time-dependent density-functional theory, including explicitly the band-gap corrections at the level of the scissors approximation. Excitonic effects are accounted for, on the basis of a simple scalar approximation. We apply our formalism to the computation of the electro-optic susceptibilities for several semiconductors, such as GaAs, GaN, and SiC. Taking into account the ionic contribution according to the Faust-Henry coefficient, we obtain a good agreement with experimental results. Finally, using different types of strain to break centrosymmetry, we show that high electro-optic coefficients can be obtained in bulk silicon for a large range of frequencies.

Computational modeling of properties

NASA Technical Reports Server (NTRS)

Franz, Judy R.

1994-01-01

A simple model was developed to calculate the electronic transport parameters in disordered semiconductors in strong scattered regime. The calculation is based on a Green function solution to Kubo equation for the energy-dependent conductivity. This solution together with a rigorous calculation of the temperature-dependent chemical potential allows the determination of the dc conductivity and the thermopower. For wise-gap semiconductors with single defect bands, these transport properties are investigated as a function of defect concentration, defect energy, Fermi level, and temperature. Under certain conditions the calculated conductivity is quite similar to the measured conductivity in liquid II-VI semiconductors in that two distinct temperature regimes are found. Under different conditions the conductivity is found to decrease with temperature; this result agrees with measurements in amorphous Si. Finally the calculated thermopower can be positive or negative and may change sign with temperature or defect concentration.

Computational modeling of properties

NASA Technical Reports Server (NTRS)

Franz, Judy R.

1994-01-01

A simple model was developed to calculate the electronic transport parameters in disordered semiconductors in strong scattered regime. The calculation is based on a Green function solution to Kubo equation for the energy-dependent conductivity. This solution together with a rigorous calculation of the temperature-dependent chemical potential allows the determination of the dc conductivity and the thermopower. For wide-gap semiconductors with single defect bands, these transport properties are investigated as a function of defect concentration, defect energy, Fermi level, and temperature. Under certain conditions the calculated conductivity is quite similar to the measured conductivity in liquid 2-6 semiconductors in that two distinct temperature regimes are found. Under different conditions the conductivity is found to decrease with temperature; this result agrees with measurements in amorphous Si. Finally the calculated thermopower can be positive or negative and may change sign with temperature or defect concentration.

Excitons in atomically thin 2D semiconductors and their applications

NASA Astrophysics Data System (ADS)

Xiao, Jun; Zhao, Mervin; Wang, Yuan; Zhang, Xiang

2017-06-01

The research on emerging layered two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS2), reveals unique optical properties generating significant interest. Experimentally, these materials were observed to host extremely strong light-matter interactions as a result of the enhanced excitonic effect in two dimensions. Thus, understanding and manipulating the excitons are crucial to unlocking the potential of 2D materials for future photonic and optoelectronic devices. In this review, we unravel the physical origin of the strong excitonic effect and unique optical selection rules in 2D semiconductors. In addition, control of these excitons by optical, electrical, as well as mechanical means is examined. Finally, the resultant devices such as excitonic light emitting diodes, lasers, optical modulators, and coupling in an optical cavity are overviewed, demonstrating how excitons can shape future 2D optoelectronics.

Expressing the sense of the House of Representatives that the President of the United States should not issue pardons to senior members of his administration during the final 90 days of his term of office.

THOMAS, 111th Congress

Rep. Nadler, Jerrold [D-NY-8

2009-01-06

House - 09/14/2009 Referred to the Subcommittee on the Constitution, Civil Rights, and Civil Liberties. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Substrate induced changes in atomically thin 2-dimensional semiconductors: Fundamentals, engineering, and applications

NASA Astrophysics Data System (ADS)

Sun, Yinghui; Wang, Rongming; Liu, Kai

2017-03-01

Substrate has great influences on materials syntheses, properties, and applications. The influences are particularly crucial for atomically thin 2-dimensional (2D) semiconductors. Their thicknesses are less than 1 nm; however, the lateral sizes can reach up to several inches or more. Therefore, these materials must be placed onto a variety of substrates before subsequent post-processing techniques for final electronic or optoelectronic devices. Recent studies reveal that substrates have been employed as ways to modulate the optical, electrical, mechanical, and chemical properties of 2D semiconductors. In this review, we summarize recent progress upon the effects of substrates on properties of 2D semiconductors, mostly focused on 2D transition metal dichalcogenides, through viewpoints of both fundamental physics and device applications. First, we discuss various effects of substrates, including interface strain, charge transfer, dielectric screening, and optical interference. Second, we show the modulation of 2D semiconductors by substrate engineering, including novel substrates (patterned substrates, 2D-material substrates, etc.) and active substrates (phase transition materials, ferroelectric materials, flexible substrates, etc.). Last, we present prospectives and challenges in this research field. This review provides a comprehensive understanding of the substrate effects, and may inspire new ideas of novel 2D devices based on substrate engineering.

Quantum dot-decorated semiconductor micro- and nanoparticles: A review of their synthesis, characterization and application in photocatalysis.

PubMed

Bajorowicz, Beata; Kobylański, Marek P; Gołąbiewska, Anna; Nadolna, Joanna; Zaleska-Medynska, Adriana; Malankowska, Anna

2018-06-01

Quantum dot (QD)-decorated semiconductor micro- and nanoparticles are a new class of functional nanomaterials that have attracted considerable interest for their unique structural, optical and electronic properties that result from the large surface-to-volume ratio and the quantum confinement effect. In addition, because of QDs' excellent light-harvesting capacity, unique photoinduced electron transfer, and up-conversion behaviour, semiconductor nanoparticles decorated with quantum dots have been used widely in photocatalytic applications for the degradation of organic pollutants in both the gas and aqueous phases. This review is a comprehensive overview of the recent progress in synthesis methods for quantum dots and quantum dot-decorated semiconductor composites with an emphasis on their composition, morphology and optical behaviour. Furthermore, various approaches used for the preparation of QD-based composites are discussed in detail with respect to visible and UV light-induced photoactivity. Finally, an outlook on future development is proposed with the goal of overcoming challenges and stimulating further research into this promising field. Copyright © 2018 Elsevier B.V. All rights reserved.

Semiconductor-Insulator-Semiconductor Diode Consisting of Monolayer MoS2, h-BN, and GaN Heterostructure.

PubMed

Jeong, Hyun; Bang, Seungho; Oh, Hye Min; Jeong, Hyeon Jun; An, Sung-Jin; Han, Gang Hee; Kim, Hyun; Kim, Ki Kang; Park, Jin Cheol; Lee, Young Hee; Lerondel, Gilles; Jeong, Mun Seok

2015-10-27

We propose a semiconductor-insulator-semiconductor (SIS) heterojunction diode consisting of monolayer (1-L) MoS2, hexagonal boron nitride (h-BN), and epitaxial p-GaN that can be applied to high-performance nanoscale optoelectronics. The layered materials of 1-L MoS2 and h-BN, grown by chemical vapor deposition, were vertically stacked by a wet-transfer method on a p-GaN layer. The final structure was verified by confocal photoluminescence and Raman spectroscopy. Current-voltage (I-V) measurements were conducted to compare the device performance with that of a more classical p-n structure. In both structures (the p-n and SIS heterojunction diode), clear current-rectifying characteristics were observed. In particular, a current and threshold voltage were obtained for the SIS structure that was higher compared to that of the p-n structure. This indicated that tunneling is the predominant carrier transport mechanism. In addition, the photoresponse of the SIS structure induced by the illumination of visible light was observed by photocurrent measurements.

Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring

PubMed Central

Fine, George F.; Cavanagh, Leon M.; Afonja, Ayo; Binions, Russell

2010-01-01

Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. PMID:22219672

Surface Stability and Growth Kinetics of Compound Semiconductors: An Ab Initio-Based Approach

PubMed Central

Kangawa, Yoshihiro; Akiyama, Toru; Ito, Tomonori; Shiraishi, Kenji; Nakayama, Takashi

2013-01-01

We review the surface stability and growth kinetics of III-V and III-nitride semiconductors. The theoretical approach used in these studies is based on ab initio calculations and includes gas-phase free energy. With this method, we can investigate the influence of growth conditions, such as partial pressure and temperature, on the surface stability and growth kinetics. First, we examine the feasibility of this approach by comparing calculated surface phase diagrams of GaAs(001) with experimental results. In addition, the Ga diffusion length on GaAs(001) during molecular beam epitaxy is discussed. Next, this approach is systematically applied to the reconstruction, adsorption and incorporation on various nitride semiconductor surfaces. The calculated results for nitride semiconductor surface reconstructions with polar, nonpolar, and semipolar orientations suggest that adlayer reconstructions generally appear on the polar and the semipolar surfaces. However, the stable ideal surface without adsorption is found on the nonpolar surfaces because the ideal surface satisfies the electron counting rule. Finally, the stability of hydrogen and the incorporation mechanisms of Mg and C during metalorganic vapor phase epitaxy are discussed. PMID:28811438

Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

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

Le Breton, J.-C., E-mail: jean-christophe.lebreton@univ-rennes1.fr; Tricot, S.; Delhaye, G.

2016-08-01

The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron–graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that themore » hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.« less

Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Le Breton, J.-C.; Tricot, S.; Delhaye, G.; Lépine, B.; Turban, P.; Schieffer, P.

2016-08-01

The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron-graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.

Modelling individual differences in the form of Pavlovian conditioned approach responses: a dual learning systems approach with factored representations.

PubMed

Lesaint, Florian; Sigaud, Olivier; Flagel, Shelly B; Robinson, Terry E; Khamassi, Mehdi

2014-02-01

Reinforcement Learning has greatly influenced models of conditioning, providing powerful explanations of acquired behaviour and underlying physiological observations. However, in recent autoshaping experiments in rats, variation in the form of Pavlovian conditioned responses (CRs) and associated dopamine activity, have questioned the classical hypothesis that phasic dopamine activity corresponds to a reward prediction error-like signal arising from a classical Model-Free system, necessary for Pavlovian conditioning. Over the course of Pavlovian conditioning using food as the unconditioned stimulus (US), some rats (sign-trackers) come to approach and engage the conditioned stimulus (CS) itself - a lever - more and more avidly, whereas other rats (goal-trackers) learn to approach the location of food delivery upon CS presentation. Importantly, although both sign-trackers and goal-trackers learn the CS-US association equally well, only in sign-trackers does phasic dopamine activity show classical reward prediction error-like bursts. Furthermore, neither the acquisition nor the expression of a goal-tracking CR is dopamine-dependent. Here we present a computational model that can account for such individual variations. We show that a combination of a Model-Based system and a revised Model-Free system can account for the development of distinct CRs in rats. Moreover, we show that revising a classical Model-Free system to individually process stimuli by using factored representations can explain why classical dopaminergic patterns may be observed for some rats and not for others depending on the CR they develop. In addition, the model can account for other behavioural and pharmacological results obtained using the same, or similar, autoshaping procedures. Finally, the model makes it possible to draw a set of experimental predictions that may be verified in a modified experimental protocol. We suggest that further investigation of factored representations in computational neuroscience studies may be useful.

Modelling Individual Differences in the Form of Pavlovian Conditioned Approach Responses: A Dual Learning Systems Approach with Factored Representations

PubMed Central

Lesaint, Florian; Sigaud, Olivier; Flagel, Shelly B.; Robinson, Terry E.; Khamassi, Mehdi

2014-01-01

Reinforcement Learning has greatly influenced models of conditioning, providing powerful explanations of acquired behaviour and underlying physiological observations. However, in recent autoshaping experiments in rats, variation in the form of Pavlovian conditioned responses (CRs) and associated dopamine activity, have questioned the classical hypothesis that phasic dopamine activity corresponds to a reward prediction error-like signal arising from a classical Model-Free system, necessary for Pavlovian conditioning. Over the course of Pavlovian conditioning using food as the unconditioned stimulus (US), some rats (sign-trackers) come to approach and engage the conditioned stimulus (CS) itself – a lever – more and more avidly, whereas other rats (goal-trackers) learn to approach the location of food delivery upon CS presentation. Importantly, although both sign-trackers and goal-trackers learn the CS-US association equally well, only in sign-trackers does phasic dopamine activity show classical reward prediction error-like bursts. Furthermore, neither the acquisition nor the expression of a goal-tracking CR is dopamine-dependent. Here we present a computational model that can account for such individual variations. We show that a combination of a Model-Based system and a revised Model-Free system can account for the development of distinct CRs in rats. Moreover, we show that revising a classical Model-Free system to individually process stimuli by using factored representations can explain why classical dopaminergic patterns may be observed for some rats and not for others depending on the CR they develop. In addition, the model can account for other behavioural and pharmacological results obtained using the same, or similar, autoshaping procedures. Finally, the model makes it possible to draw a set of experimental predictions that may be verified in a modified experimental protocol. We suggest that further investigation of factored representations in computational neuroscience studies may be useful. PMID:24550719

77 FR 27249 - Certain Semiconductor Chips and Products Containing Same; Review of a Final Initial Determination...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-09

... review, as set forth below. 2. Validity a. The motivation to combine and secondary indicia of... the motivation to apply the teachings of asynchronous art to synchronous systems. (Barth patents) c...

System and method for calibrating inter-star-tracker misalignments in a stellar inertial attitude determination system

NASA Technical Reports Server (NTRS)

Li, Rongsheng (Inventor); Wu, Yeong-Wei Andy (Inventor); Hein, Douglas H. (Inventor)

2004-01-01

A method and apparatus for determining star tracker misalignments is disclosed. The method comprises the steps of defining a defining a reference frame for the star tracker assembly according to a boresight of the primary star tracker and a boresight of a second star tracker wherein the boresight of the primary star tracker and a plane spanned by the boresight of the primary star tracker and the boresight of the second star tracker at least partially define a datum for the reference frame for the star tracker assembly; and determining the misalignment of the at least one star tracker as a rotation of the defined reference frame.

The influence of crystalline lens accommodation on post-saccadic oscillations in pupil-based eye trackers.

PubMed

Nyström, Marcus; Andersson, Richard; Magnusson, Måns; Pansell, Tony; Hooge, Ignace

2015-02-01

It is well known that the crystalline lens (henceforth lens) can oscillate (or 'wobble') relative to the eyeball at the end of saccades. Recent research has proposed that such wobbling of the lens is a source of post-saccadic oscillations (PSOs) seen in data recorded by eye trackers that estimate gaze direction from the location of the pupil. Since the size of the lens wobbles increases with accommodative effort, one would predict a similar increase of PSO-amplitude in data recorded with a pupil based eye tracker. In four experiments, we investigated the role of lens accommodation on PSOs in a video-based eye tracker. In Experiment 1, we replicated previous results showing that PSO-amplitudes increase at near viewing distances (large vergence angles), when the lens is highly accommodated. In Experiment 2a, we manipulated the accommodative state of the lens pharmacologically using eye drops at a fixed viewing distance and found, in contrast to Experiment 1, no significant difference in PSO-amplitude related to the accommodative state of the lens. Finally, in Experiment 2b, the effect of vergence angle was investigated by comparing PSO-amplitudes at near and far while maintaining a fixed lens accommodation. Despite the pharmacologically fixed degree of accommodation, PSO-amplitudes were systematically larger in the near condition. In summary, PSOs cannot exhaustively be explained by lens wobbles. Possible confounds related to pupil size and eye-camera angle are investigated in Experiments 3 and 4, and alternative mechanisms behind PSOs are probed in the discussion. Copyright © 2014 Elsevier Ltd. All rights reserved.

Molecular level control of nanoscale composition and morphology: Toward photocatalytic nanocomposites for solar-to-chemical energy conversion of biomass

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

Ruberu, Thanthrige P.

2013-01-01

Understanding the factors influencing nanocrystal formation is a challenge yet to be realized. In comparison to the large number of studies on nanocrystal synthesis and their applications, the number of studies on the effect of the precursor chemistry on nanocrystal composition and shape remains low. Although photochemical fabrication of metalsemiconductor nano-heterostructures is reported in literature, control over the free particle formation and the site of metal deposition have not been achieved. Moreover, utilization of metal- semiconductor nano-heterostructures in photocatalytic reactions other than water splitting is hardly explored. In this thesis, we studied the effect of chalcogenide precursor reactivity on themore » composition, morphology and the axial anisotropy of cadmiumchalcogenide nanocrystals. We also investigated the influence of the irradiation wavelength in synthesizing metal-semiconductor nano-heterostructures. Finally, we showed that metal semiconductor nano-heterostructures can be used as a photocatalyst for alcohol dehydrogenation reactions. We explored the pathways for the formation of Pt and Pd nanoparticles on CdS and CdS{sub 0.4}Se{sub 0.6} nanorods. This study revealed that the wavelength of irradiation is critical to control free-standing vs. bound metal (Pt and Pd) nanoparticles to semiconductor. Additionally, we observed that metal photodeposition occurs on specific segments of axially anisotropic, compositionally graded CdS0.4Se0.6 nanorods due to the band-gap differential between their nano-domains. We used semiconductor-metal heterostructures for sunlightdriven dehydrogenation and hydrogenolysis of benzyl alcohol. Heterostructure composition dictates activity (turnovers) and product distribution. A few metal (Pt, Pd) islands on the semiconductor surface significantly enhance activity and selectivity and also greatly stabilize the semiconductor against photoinduced etching and degradation.« less

A resolution to provide for the approval of final regulations issued by the Office of Compliance to implement the Veterans Employment Opportunities Act of 1998 that apply to the Senate and employees of the Senate.

THOMAS, 111th Congress

Sen. Schumer, Charles E. [D-NY

2010-12-10

Senate - 12/10/2010 Submitted in the Senate, considered, and agreed to without amendment by Unanimous Consent. (All Actions) Tracker: This bill has the status Agreed to in SenateHere are the steps for Status of Legislation:

A resolution honoring the men and women of the National Aeronautics and Space Administration Space Shuttle Program on reaching the historic milestone of the 135th and final flight of the Space Transportation System.

THOMAS, 112th Congress

Sen. Nelson, Bill [D-FL

2011-07-13

Senate - 07/13/2011 Submitted in the Senate, considered, and agreed to without amendment and with a preamble by Unanimous Consent. (All Actions) Tracker: This bill has the status Agreed to in SenateHere are the steps for Status of Legislation:

A resolution congratulating the Navy and the current and former officers and crew of the U.S.S. Enterprise (CVN 65) on completion of the 26th and final deployment of the vessel.

THOMAS, 112th Congress

Sen. Warner, Mark R. [D-VA

2013-01-02

Senate - 01/02/2013 Submitted in the Senate, considered, and agreed to without amendment and with a preamble by Unanimous Consent. (All Actions) Tracker: This bill has the status Agreed to in SenateHere are the steps for Status of Legislation:

Recent Advances of Solution-Processed Metal Oxide Thin-Film Transistors.

PubMed

Xu, Wangying; Li, Hao; Xu, Jian-Bin; Wang, Lei

2018-03-06

Solution-processed metal oxide thin-film transistors (TFTs) are considered as one of the most promising transistor technologies for future large-area flexible electronics. This review surveys the recent advances in solution-based oxide TFTs, including n-type oxide semiconductors, oxide dielectrics and p-type oxide semiconductors. Firstly, we provide an introduction on oxide TFTs and the TFT configurations and operating principles. Secondly, we present the recent progress in solution-processed n-type transistors, with a special focus on low-temperature and large-area solution processed approaches as well as novel non-display applications. Thirdly, we give a detailed analysis of the state-of-the-art solution-processed oxide dielectrics for low-voltage electronics. Fourthly, we discuss the recent progress in solution-based p-type oxide semiconductors, which will enable the highly desirable future low-cost large-area complementary circuits. Finally, we draw the conclusions and outline the perspectives over the research field.

Three- and Two-Dimensional Tin and Lead Halide Perovskite Semiconductors: Synthesis and Application in Photovoltaics

NASA Astrophysics Data System (ADS)

Cao, Duyen Hanh

Halide perovskites, AMX3 (A = monocation, B = Ge, Sn, or Pb, and X = halogen), present a versatile class of solution-processable semiconductors made from earth abundant materials with outstanding electrical and optical properties. Their solar cell efficiencies have dramatically increased from 9% to 22% in less than five years since 2012, a rate that has never been seen before in photovoltaic research. Critical to the final goal of commercializing perovskite solar cell technology is achieving device long-term stability and eliminating toxic elements in device components. This thesis uses 3D AMX 3 perovskites as a stand-in to develop a new class of lead-free, moisture stable, functional and highly tunable 2D Ruddlesden-Popper (BA) 2(MA)n-1SnnI3n+1 (n is an integer) perovskite semiconductors. Synthesis, thin film fabrication, extensive characterization, and solar cell device structure-performance relationships are presented throughout the entire thesis.

Opto-valleytronic imaging of atomically thin semiconductors

DOE PAGES

Neumann, Andre; Lindlau, Jessica; Colombier, Léo; ...

2017-01-16

Transition metal dichalcogenide semiconductors represent elementary components of layered heterostructures for emergent technologies beyond conventional opto-electronics. In their monolayer form they host electrons with quantized circular motion and associated valley polarization and valley coherence as key elements of opto-valleytronic functionality. Here, we introduce two-dimensional polarimetry as means of direct imaging of the valley pseudospin degree of freedom in monolayer transition metal dichalcogenides. Using MoS 2 as a representative material with valley-selective optical transitions, we establish quantitative image analysis for polarimetric maps of extended crystals, and identify valley polarization and valley coherence as sensitive probes of crystalline disorder. Moreover, we findmore » site-dependent thermal and non-thermal regimes of valley-polarized excitons in perpendicular magnetic fields. Finally, we demonstrate the potential of widefield polarimetry for rapid inspection of opto-valleytronic devices based on atomically thin semiconductors and heterostructures.« less

Opto-valleytronic imaging of atomically thin semiconductors

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

Neumann, Andre; Lindlau, Jessica; Colombier, Léo

Transition metal dichalcogenide semiconductors represent elementary components of layered heterostructures for emergent technologies beyond conventional opto-electronics. In their monolayer form they host electrons with quantized circular motion and associated valley polarization and valley coherence as key elements of opto-valleytronic functionality. Here, we introduce two-dimensional polarimetry as means of direct imaging of the valley pseudospin degree of freedom in monolayer transition metal dichalcogenides. Using MoS 2 as a representative material with valley-selective optical transitions, we establish quantitative image analysis for polarimetric maps of extended crystals, and identify valley polarization and valley coherence as sensitive probes of crystalline disorder. Moreover, we findmore » site-dependent thermal and non-thermal regimes of valley-polarized excitons in perpendicular magnetic fields. Finally, we demonstrate the potential of widefield polarimetry for rapid inspection of opto-valleytronic devices based on atomically thin semiconductors and heterostructures.« less

Excitons in atomically thin 2D semiconductors and their applications

DOE PAGES

Xiao, Jun; Zhao, Mervin; Wang, Yuan; ...

2017-01-01

The research on emerging layered two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS 2), reveals unique optical properties generating significant interest. Experimentally, these materials were observed to host extremely strong light-matter interactions as a result of the enhanced excitonic effect in two dimensions. Thus, understanding and manipulating the excitons are crucial to unlocking the potential of 2D materials for future photonic and optoelectronic devices. Here in this review, we unravel the physical origin of the strong excitonic effect and unique optical selection rules in 2D semiconductors. In addition, control of these excitons by optical, electrical, as well as mechanical meansmore » is examined. Finally, the resultant devices such as excitonic light emitting diodes, lasers, optical modulators, and coupling in an optical cavity are overviewed, demonstrating how excitons can shape future 2D optoelectronics.« less

Articulated Arm Coordinate Measuring Machine Calibration by Laser Tracker Multilateration

PubMed Central

Majarena, Ana C.; Brau, Agustín; Velázquez, Jesús

2014-01-01

A new procedure for the calibration of an articulated arm coordinate measuring machine (AACMM) is presented in this paper. First, a self-calibration algorithm of four laser trackers (LTs) is developed. The spatial localization of a retroreflector target, placed in different positions within the workspace, is determined by means of a geometric multilateration system constructed from the four LTs. Next, a nonlinear optimization algorithm for the identification procedure of the AACMM is explained. An objective function based on Euclidean distances and standard deviations is developed. This function is obtained from the captured nominal data (given by the LTs used as a gauge instrument) and the data obtained by the AACMM and compares the measured and calculated coordinates of the target to obtain the identified model parameters that minimize this difference. Finally, results show that the procedure presented, using the measurements of the LTs as a gauge instrument, is very effective by improving the AACMM precision. PMID:24688418

Command generator tracker based direct model reference adaptive tracking guidance for Mars atmospheric entry

NASA Astrophysics Data System (ADS)

Li, Shuang; Peng, Yuming

2012-01-01

In order to accurately deliver an entry vehicle through the Martian atmosphere to the prescribed parachute deployment point, active Mars entry guidance is essential. This paper addresses the issue of Mars atmospheric entry guidance using the command generator tracker (CGT) based direct model reference adaptive control to reduce the adverse effect of the bounded uncertainties on atmospheric density and aerodynamic coefficients. Firstly, the nominal drag acceleration profile meeting a variety of constraints is planned off-line in the longitudinal plane as the reference model to track. Then, the CGT based direct model reference adaptive controller and the feed-forward compensator are designed to robustly track the aforementioned reference drag acceleration profile and to effectively reduce the downrange error. Afterwards, the heading alignment logic is adopted in the lateral plane to reduce the crossrange error. Finally, the validity of the guidance algorithm proposed in this paper is confirmed by Monte Carlo simulation analysis.

Scene-Aware Adaptive Updating for Visual Tracking via Correlation Filters

PubMed Central

Zhang, Sirou; Qiao, Xiaoya

2017-01-01

In recent years, visual object tracking has been widely used in military guidance, human-computer interaction, road traffic, scene monitoring and many other fields. The tracking algorithms based on correlation filters have shown good performance in terms of accuracy and tracking speed. However, their performance is not satisfactory in scenes with scale variation, deformation, and occlusion. In this paper, we propose a scene-aware adaptive updating mechanism for visual tracking via a kernel correlation filter (KCF). First, a low complexity scale estimation method is presented, in which the corresponding weight in five scales is employed to determine the final target scale. Then, the adaptive updating mechanism is presented based on the scene-classification. We classify the video scenes as four categories by video content analysis. According to the target scene, we exploit the adaptive updating mechanism to update the kernel correlation filter to improve the robustness of the tracker, especially in scenes with scale variation, deformation, and occlusion. We evaluate our tracker on the CVPR2013 benchmark. The experimental results obtained with the proposed algorithm are improved by 33.3%, 15%, 6%, 21.9% and 19.8% compared to those of the KCF tracker on the scene with scale variation, partial or long-time large-area occlusion, deformation, fast motion and out-of-view. PMID:29140311

The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

NASA Astrophysics Data System (ADS)

Watanabe, Shin; Tajima, Hiroyasu; Fukazawa, Yasushi; Ichinohe, Yuto; Takeda, Shin`ichiro; Enoto, Teruaki; Fukuyama, Taro; Furui, Shunya; Genba, Kei; Hagino, Kouichi; Harayama, Atsushi; Kuroda, Yoshikatsu; Matsuura, Daisuke; Nakamura, Ryo; Nakazawa, Kazuhiro; Noda, Hirofumi; Odaka, Hirokazu; Ohta, Masayuki; Onishi, Mitsunobu; Saito, Shinya; Sato, Goro; Sato, Tamotsu; Takahashi, Tadayuki; Tanaka, Takaaki; Togo, Atsushi; Tomizuka, Shinji

2014-11-01

The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60-600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm×12 cm×12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13,312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0-2.0 keV (FWHM) at 60 keV and 1.6-2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype.

A lysinated thiophene-based semiconductor as a multifunctional neural bioorganic interface.

PubMed

Bonetti, Simone; Pistone, Assunta; Brucale, Marco; Karges, Saskia; Favaretto, Laura; Zambianchi, Massimo; Posati, Tamara; Sagnella, Anna; Caprini, Marco; Toffanin, Stefano; Zamboni, Roberto; Camaioni, Nadia; Muccini, Michele; Melucci, Manuela; Benfenati, Valentina

2015-06-03

Lysinated molecular organic semiconductors are introduced as valuable multifunctional platforms for neural cells growth and interfacing. Cast films of quaterthiophene (T4) semiconductor covalently modified with lysine-end moieties (T4Lys) are fabricated and their stability, morphology, optical/electrical, and biocompatibility properties are characterized. T4Lys films exhibit fluorescence and electronic transport as generally observed for unsubstituted oligothiophenes combined to humidity-activated ionic conduction promoted by the charged lysine-end moieties. The Lys insertion in T4 enables adhesion of primary culture of rat dorsal root ganglion (DRG), which is not achievable by plating cells on T4. Notably, on T4Lys, the number on adhering neurons/area is higher and displays a twofold longer neurite length than neurons plated on glass coated with poly-l-lysine. Finally, by whole-cell patch-clamp, it is shown that the biofunctionality of neurons cultured on T4Lys is preserved. The present study introduces an innovative concept for organic material neural interface that combines optical and iono-electronic functionalities with improved biocompatibility and neuron affinity promoted by Lys linkage and the softness of organic semiconductors. Lysinated organic semiconductors could set the scene for the fabrication of simplified bioorganic devices geometry for cells bidirectional communication or optoelectronic control of neural cells biofunctionality. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

First-principles calculations reveal controlling principles for carrier mobilities in semiconductors

DOE PAGES

Wu, Yu -Ning; Zhang, Xiaoguang; Pantelides, Sokrates T.; ...

2016-10-11

It has long been believed that carrier mobilities in semiconductors can be calculated by Fermi s golden rule (Born approximation). Phenomenological models for scattering amplitudes are typically used for engineering- level device modeling. Here we introduce a parameter-free, first-principles approach based on complex- wavevector energy bands that does not invoke the Born approximation. We show that phonon-limited mobility is controlled by low-resistivity percolation paths and that in ionized-impurity scattering one must account for the effect of the screening charge, which cancels most of the Coulomb tail.Finally, calculated electron mobilities in silicon are in agreement with experimental data.

Optimal convolution SOR acceleration of waveform relaxation with application to semiconductor device simulation

NASA Technical Reports Server (NTRS)

Reichelt, Mark

1993-01-01

In this paper we describe a novel generalized SOR (successive overrelaxation) algorithm for accelerating the convergence of the dynamic iteration method known as waveform relaxation. A new convolution SOR algorithm is presented, along with a theorem for determining the optimal convolution SOR parameter. Both analytic and experimental results are given to demonstrate that the convergence of the convolution SOR algorithm is substantially faster than that of the more obvious frequency-independent waveform SOR algorithm. Finally, to demonstrate the general applicability of this new method, it is used to solve the differential-algebraic system generated by spatial discretization of the time-dependent semiconductor device equations.

Recent Progress in Photocatalysis Mediated by Colloidal II-VI Nanocrystals

PubMed Central

Wilker, Molly B; Schnitzenbaumer, Kyle J; Dukovic, Gordana

2012-01-01

The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This review focuses on recent research efforts to understand and control the photocatalytic processes mediated by colloidal II-VI nanocrystalline materials, such as cadmium and zinc chalcogenides. First, we highlight how nanocrystal properties govern the rates and efficiencies of charge-transfer processes relevant to photocatalysis. We then describe the use of nanocrystal catalyst heterostructures for fuel-forming reactions, most commonly H2 generation. Finally, we review the use of nanocrystal photocatalysis as a synthetic tool for metal–semiconductor nano-heterostructures. PMID:24115781

Effect of point defects on the electronic density states of SnC nanosheets: First-principles calculations

NASA Astrophysics Data System (ADS)

Majidi, Soleyman; Achour, Amine; Rai, D. P.; Nayebi, Payman; Solaymani, Shahram; Beryani Nezafat, Negin; Elahi, Seyed Mohammad

In this work, we investigated the electronic and structural properties of various defects including single Sn and C vacancies, double vacancy of the Sn and C atoms, anti-sites, position exchange and the Stone-Wales (SW) defects in SnC nanosheets by using density-functional theory (DFT). We found that various vacancy defects in the SnC monolayer can change the electronic and structural properties. Our results show that the SnC is an indirect band gap compound, with the band gap of 2.10 eV. The system turns into metal for both structure of the single Sn and C vacancies. However, for the double vacancy contained Sn and C atoms, the structure remains semiconductor with the direct band gap of 0.37 eV at the G point. We also found that for anti-site defects, the structure remains semiconductor and for the exchange defect, the structure becomes indirect semiconductor with the K-G point and the band gap of 0.74 eV. Finally, the structure of SW defect remains semiconductor with the direct band gap at K point with band gap of 0.54 eV.

Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: A new design space for organic light-emitting diodes.

PubMed

Keum, Chang-Min; Liu, Shiyi; Al-Shadeedi, Akram; Kaphle, Vikash; Callens, Michiel Koen; Han, Lu; Neyts, Kristiaan; Zhao, Hongping; Gather, Malte C; Bunge, Scott D; Twieg, Robert J; Jakli, Antal; Lüssem, Björn

2018-01-15

Liquid-crystalline organic semiconductors exhibit unique properties that make them highly interesting for organic optoelectronic applications. Their optical and electrical anisotropies and the possibility to control the alignment of the liquid-crystalline semiconductor allow not only to optimize charge carrier transport, but to tune the optical property of organic thin-film devices as well. In this study, the molecular orientation in a liquid-crystalline semiconductor film is tuned by a novel blading process as well as by different annealing protocols. The altered alignment is verified by cross-polarized optical microscopy and spectroscopic ellipsometry. It is shown that a change in alignment of the liquid-crystalline semiconductor improves charge transport in single charge carrier devices profoundly. Comparing the current-voltage characteristics of single charge carrier devices with simulations shows an excellent agreement and from this an in-depth understanding of single charge carrier transport in two-terminal devices is obtained. Finally, p-i-n type organic light-emitting diodes (OLEDs) compatible with vacuum processing techniques used in state-of-the-art OLEDs are demonstrated employing liquid-crystalline host matrix in the emission layer.

Spin cat state generation for quadrupolar nuclei in semiconductor quantum dots or defect centers

NASA Astrophysics Data System (ADS)

Bulutay, Ceyhun

Implementing spin-based quantum information encoding schemes in semiconductors has a high priority. The so-called cat codes offer a paradigm that enables hardware-efficient error correction. Their inauguration to semiconductor-based nuclear magnetic resonance framework hinges upon the realization of coherent spin states (CSS). In this work, we show how the crucial superpositions of CSS can be generated for the nuclear spins. This is through the intrinsic electric quadrupole interaction involving a critical role by the biaxiality term that is readily available, as in strained heterostructures of semiconductors, or defect centers having nearby quadrupolar spins. The persistence of the cat states is achieved using a rotation pulse so as to harness the underlying fixed points of the classical Hamiltonian. We classify the two distinct types as polar- and equator-bound over the Bloch sphere with respect to principal axes. Their optimal performance as well as sensitivity under numerous parameter deviations are analyzed. Finally, we present how these modulo-2 cat states can be extended to modulo-4 by a three-pulse scheme. This work was supported by TUBITAK, The Scientific and Technological Research Council of Turkey through the project No. 114F409.

The measurement of alpha particle emissions from semiconductor memory materials

NASA Astrophysics Data System (ADS)

Bouldin, D. P.

1981-07-01

With the increasing concern for the affects of alpha particles on the reliability of semiconductor memories, an interest has arisen in characterizing semiconductor manufacturing materials for extremely low-level alpha-emitting contaminants. It is shown that four elements are of primary concern: uranium, thorium, radium, and polonium. Measurement of contamination levels are given relevance by first correlating them with alpha flux emission levels and then corre1ating these flux values with device soft error rates. Measurement techniques involve either measurements of elemental concentrations-applicable to only uranium and thorium - or direct measurements of alpha emission fluxes. Alpha fluxes are most usefully measured by means of ZnS scintillation counting, practical details of which are discussed. Materials measurements are reported for ceramics, solder, silicon, quartz, and various metals and organic materials. Ceramics and most metals have contamination levels of concern, but the high temperature processing normally used in semiconductor manufacturing and low total amounts reduce problems, at least for metals. Silicon, silicon compounds, and organic materials have been found to have no detectable alpha emitters. Finally, a brief discussion of the calibration of alpha sources for accelerated device testing is given, including practical details on the affects of source/chip separation and alignment variations.

Technology Roadmaps for Compound Semiconductors

PubMed Central

Bennett, Herbert S.

2000-01-01

The roles cited for compound semiconductors in public versions of existing technology roadmaps from the National Electronics Manufacturing Initiative, Inc., Optoelectronics Industry Development Association, Microelectronics Advanced Research Initiative on Optoelectronic Interconnects, and Optoelectronics Industry and Technology Development Association (OITDA) are discussed and compared within the context of trends in the Si CMOS industry. In particular, the extent to which these technology roadmaps treat compound semiconductors at the materials processing and device levels will be presented for specific applications. For example, OITDA’s Optical Communications Technology Roadmap directly connects the information demand of delivering 100 Mbit/s to the home to the requirement of producing 200 GHz heterojunction bipolar transistors with 30 nm bases and InP high electron mobility transistors with 100 nm gates. Some general actions for progress towards the proposed International Technology Roadmap for Compound Semiconductors (ITRCS) and methods for determining the value of an ITRCS will be suggested. But, in the final analysis, the value added by an ITRCS will depend on how industry leaders respond. The technical challenges and economic opportunities of delivering high quality digital video to consumers provide concrete examples of where the above actions and methods could be applied. PMID:27551615

Characteristics of a Power Line Used as a VLF Antenna.

DTIC Science & Technology

1982-05-01

were glass melamine . Assemblies of 12 layers were fabricated at El Segundo, CA and shipped by air to Tromso, Norway for final assembly of the full 120...sciences, applied electronics, semiconductor crystal and device physics, radiometric Imaging; millimeter-wave and microwave technology. Information

Local atomic and magnetic structure of dilute magnetic semiconductor ( Ba , K ) ( Zn , Mn ) 2 As 2

DOE PAGES

Frandsen, Benjamin A.; Gong, Zizhou; Terban, Maxwell W.; ...

2016-09-06

We studied the atomic and magnetic structure of the dilute ferromagnetic semiconductor system (Ba,K)(Zn,Mn) 2As 2 through atomic and magnetic pair distribution function analysis of temperature-dependent x-ray and neutron total scattering data. Furthermore, we detected a change in curvature of the temperature-dependent unit cell volume of the average tetragonal crystallographic structure at a temperature coinciding with the onset of ferromagnetic order. We also observed the existence of a well-defined local orthorhombic structure on a short length scale of ≲5Å, resulting in a rather asymmetrical local environment of the Mn and As ions. Finally, the magnetic PDF revealed ferromagnetic alignment ofmore » Mn spins along the crystallographic c axis, with robust nearest-neighbor ferromagnetic correlations that exist even above the ferromagnetic ordering temperature. Finally, we discuss these results in the context of other experiments and theoretical studies on this system.« less

To confer upon the United States Court of Federal Claims jurisdiction to hear, determine, and render final judgment on any legal or equitable claim against the United States to receive just compensation for the taking of certain lands in the State of Missouri, and for other purposes.

THOMAS, 111th Congress

Rep. Carnahan, Russ [D-MO-3

2009-07-08

House - 08/19/2009 Referred to the Subcommittee on Immigration, Citizenship, Refugees, Border Security, and International Law. (All Actions) Tracker: This bill has the status IntroducedHere are the steps for Status of Legislation:

Department of Defense Appropriations Act, 2010

THOMAS, 111th Congress

Rep. Murtha, John P. [D-PA-12

2009-07-24

12/19/2009 Became Public Law No: 111-118. (TXT | PDF) (All Actions) Notes: Because the FY2010 DOD Appropriations Act was approved by both chambers by exchanging different versions of H.R. 3326, no conference report was issued. Section 1014 of the final version provides that the explanatory statement inserted in the Congressional Record on December 16... Tracker: This bill has the status Became LawHere are the steps for Status of Legislation:

PREFACE: Theory, Modelling and Computational methods for Semiconductors

NASA Astrophysics Data System (ADS)

Migliorato, Max; Probert, Matt

2010-04-01

These conference proceedings contain the written papers of the contributions presented at the 2nd International Conference on: Theory, Modelling and Computational methods for Semiconductors. The conference was held at the St Williams College, York, UK on 13th-15th Jan 2010. The previous conference in this series took place in 2008 at the University of Manchester, UK. The scope of this conference embraces modelling, theory and the use of sophisticated computational tools in Semiconductor science and technology, where there is a substantial potential for time saving in R&D. The development of high speed computer architectures is finally allowing the routine use of accurate methods for calculating the structural, thermodynamic, vibrational and electronic properties of semiconductors and their heterostructures. This workshop ran for three days, with the objective of bringing together UK and international leading experts in the field of theory of group IV, III-V and II-VI semiconductors together with postdocs and students in the early stages of their careers. The first day focused on providing an introduction and overview of this vast field, aimed particularly at students at this influential point in their careers. We would like to thank all participants for their contribution to the conference programme and these proceedings. We would also like to acknowledge the financial support from the Institute of Physics (Computational Physics group and Semiconductor Physics group), the UK Car-Parrinello Consortium, Accelrys (distributors of Materials Studio) and Quantumwise (distributors of Atomistix). The Editors Acknowledgements Conference Organising Committee: Dr Matt Probert (University of York) and Dr Max Migliorato (University of Manchester) Programme Committee: Dr Marco Califano (University of Leeds), Dr Jacob Gavartin (Accelrys Ltd, Cambridge), Dr Stanko Tomic (STFC Daresbury Laboratory), Dr Gabi Slavcheva (Imperial College London) Proceedings edited and compiled by Dr Max Migliorato and Dr Matt Probert

Semiconductor Quantum Electron Wave Transport, Diffraction, and Interference: Analysis, Device, and Measurement.

NASA Astrophysics Data System (ADS)

Henderson, Gregory Newell

Semiconductor device dimensions are rapidly approaching a fundamental limit where drift-diffusion equations and the depletion approximation are no longer valid. In this regime, quantum effects can dominate device response. To increase further device density and speed, new devices must be designed that use these phenomena to positive advantage. In addition, quantum effects provide opportunities for a new class of devices which can perform functions previously unattainable with "conventional" semiconductor devices. This thesis has described research in the analysis of electron wave effects in semiconductors and the development of methods for the design, fabrication, and characterization of quantum devices based on these effects. First, an exact set of quantitative analogies are presented which allow the use of well understood optical design and analysis tools for the development of electron wave semiconductor devices. Motivated by these analogies, methods are presented for modeling electron wave grating diffraction using both an exact rigorous coupled-wave analysis and approximate analyses which are useful for grating design. Example electron wave grating switch and multiplexer designs are presented. In analogy to thin-film optics, the design and analysis of electron wave Fabry-Perot interference filters are also discussed. An innovative technique has been developed for testing these (and other) electron wave structures using Ballistic Electron Emission Microscopy (BEEM). This technique uses a liquid-helium temperature scanning tunneling microscope (STM) to perform spectroscopy of the electron transmittance as a function of electron energy. Experimental results show that BEEM can resolve even weak quantum effects, such as the reflectivity of a single interface between materials. Finally, methods are discussed for incorporating asymmetric electron wave Fabry-Perot filters into optoelectronic devices. Theoretical and experimental results show that such structures could be the basis for a new type of electrically pumped mid - to far-infrared semiconductor laser.

MEDEA+ project 2T302 MUSCLE: masks through user's supply chain: leadership by excellence

NASA Astrophysics Data System (ADS)

Torsy, Andreas

2008-04-01

The rapid evolution of our information society depends on the continuous developments and innovations of semiconductor products. The cost per chip functionality keeps reducing by a factor of 2 every 18 month. However, this performance and success of the semiconductor industry critically depends on the quality of the lithographic photomasks. The need for the high quality of photomask drives lithography costs sensitively, which is a key factor in the manufacture of microelectronics devices. Therefore, the aim is to reduce production costs while overcoming challenges in terms of feature sizes, complexity and cycle times. Consequently, lithography processes must provide highest possible quality at reasonable prices. This way, the leadership in the lithographic area can be maintained and European chipmakers can stay competitive with manufacturers in the Far East and the USA. Under the umbrella of MEDEA+, a project called MUSCLE (<< Masks through User's Supply Chain: Leadership by Excellence >>) has been started among leading semiconductor companies in Europe: ALTIS Semiconductor (Project Leader), ALCATEL Vacuum, ATMEL, CEA/LETI, Entegris, NXP Semiconductors, TOPPAN Photomasks, AMTC, Carl ZEISS SMS, DMS, Infineon Technologies, VISTEC Semiconductor, NIKON Precision, SCHOTT Lithotec, ASML, PHOTRONICS, IMEC, DCE, DNP Photomask, STMicroelectronics, XYALIS and iCADA. MUSCLE focuses particularly on mask data flow, photomask carrier, photomask defect characterization and photomask data handling. In this paper, we will discuss potential solutions like standardization and automation of the photomask data flow based on SEMI P10, the performance and the impact of the supply chain parameter within the photomask process, the standardization of photomask defect characterization and a discussion of the impact of new Reticle Enhancement Technologies (RET) such as mask process correction and finally a generic model to describe the photomasks key performance indicators for prototype photomasks.

Technology Development of Miniaturized Far-Infrared Sources for Biomolecular Spectroscopy

NASA Technical Reports Server (NTRS)

Kono, Junichiro

2003-01-01

The objective of this project was to develop a purely solid-state based, thus miniaturized, far-infrared (FIR) (also known as terahertz (THz)) wave source using III-V semiconductor nanostructures for biomolecular detection and sensing. Many biomolecules, such as DNA and proteins, have distinct spectroscopic features in the FIR wavelength range as a result of vibration-rotation-tunneling motions and various inter- and intra-molecule collective motions. Spectroscopic characterization of such molecules requires narrow linewidth, sufficiently high power, tunable (in wavelength), and coherent FIR sources. Unfortunately, the FIR frequency is one of the least technologically developed ranges in the electromagnetic spectrum. Currently available FIR sources based on non-solid state technology are bulky, inefficient, and very often incoherent. In this project we investigated antimonide based compound semiconductor (ABCS) nanostructures as the active medium to generate FIR radiation. The final goal of this project was to demonstrate a semiconductor THz source integrated with a pumping diode laser module to achieve a compact system for biomolecular applications.

First Principles Electronic Structure of Mn doped GaAs, GaP, and GaN Semiconductors

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

Schulthess, Thomas C; Temmerman, Walter M; Szotek, Zdzislawa

We present first-principles electronic structure calculations of Mn doped III-V semiconductors based on the local spin-density approximation (LSDA) as well as the self-interaction corrected local spin density method (SIC-LSD). We find that it is crucial to use a self-interaction free approach to properly describe the electronic ground state. The SIC-LSD calculations predict the proper electronic ground state configuration for Mn in GaAs, GaP, and GaN. Excellent quantitative agreement with experiment is found for magnetic moment and p-d exchange in (GaMn)As. These results allow us to validate commonly used models for magnetic semiconductors. Furthermore, we discuss the delicate problem of extractingmore » binding energies of localized levels from density functional theory calculations. We propose three approaches to take into account final state effects to estimate the binding energies of the Mn-d levels in GaAs. We find good agreement between computed values and estimates from photoemisison experiments.« less

Interfacial engineering of metal-insulator-semiconductor junctions for efficient and stable photoelectrochemical water oxidation

PubMed Central

Digdaya, Ibadillah A.; Adhyaksa, Gede W. P.; Trześniewski, Bartek J.; Garnett, Erik C.; Smith, Wilson A.

2017-01-01

Solar-assisted water splitting can potentially provide an efficient route for large-scale renewable energy conversion and storage. It is essential for such a system to provide a sufficiently high photocurrent and photovoltage to drive the water oxidation reaction. Here we demonstrate a photoanode that is capable of achieving a high photovoltage by engineering the interfacial energetics of metal–insulator–semiconductor junctions. We evaluate the importance of using two metals to decouple the functionalities for a Schottky contact and a highly efficient catalyst. We also illustrate the improvement of the photovoltage upon incidental oxidation of the metallic surface layer in KOH solution. Additionally, we analyse the role of the thin insulating layer to the pinning and depinning of Fermi level that is responsible to the resulting photovoltage. Finally, we report the advantage of using dual metal overlayers as a simple protection route for highly efficient metal–insulator–semiconductor photoanodes by showing over 200 h of operational stability. PMID:28660883

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

Maughan, Bret; Zahl, Percy; Sutter, Peter

Switching the magnetic properties of organic semiconductors on a metal surface has thus far largely been limited to molecule-by-molecule tip-induced transformations in scanned probe experiments. Here we demonstrate with molecular resolution that collective control of activated Kondo screening can be achieved in thin-films of the organic semiconductor titanyl phthalocyanine on Cu(110) to obtain tunable concentrations of Kondo impurities. Using low-temperature scanning tunneling microscopy and spectroscopy, we show that a thermally activated molecular distortion dramatically shifts surface–molecule coupling and enables ensemble-level control of Kondo screening in the interfacial spin system. This is accompanied by the formation of a temperature-dependent Abrikosov–Suhl–Kondo resonancemore » in the local density of states of the activated molecules. This enables coverage-dependent control over activation to the Kondo screening state. Finally, our study thus advances the versatility of molecular switching for Kondo physics and opens new avenues for scalable bottom-up tailoring of the electronic structure and magnetic texture of organic semiconductor interfaces at the nanoscale.« less

Ensemble control of Kondo screening in molecular adsorbates

DOE PAGES

Maughan, Bret; Zahl, Percy; Sutter, Peter; ...

2017-04-06

Switching the magnetic properties of organic semiconductors on a metal surface has thus far largely been limited to molecule-by-molecule tip-induced transformations in scanned probe experiments. Here we demonstrate with molecular resolution that collective control of activated Kondo screening can be achieved in thin-films of the organic semiconductor titanyl phthalocyanine on Cu(110) to obtain tunable concentrations of Kondo impurities. Using low-temperature scanning tunneling microscopy and spectroscopy, we show that a thermally activated molecular distortion dramatically shifts surface–molecule coupling and enables ensemble-level control of Kondo screening in the interfacial spin system. This is accompanied by the formation of a temperature-dependent Abrikosov–Suhl–Kondo resonancemore » in the local density of states of the activated molecules. This enables coverage-dependent control over activation to the Kondo screening state. Finally, our study thus advances the versatility of molecular switching for Kondo physics and opens new avenues for scalable bottom-up tailoring of the electronic structure and magnetic texture of organic semiconductor interfaces at the nanoscale.« less

Electronic properties of semiconductor-water interfaces: Predictions from ab-initio molecular dynamics and many-body perturbation theory

NASA Astrophysics Data System (ADS)

Pham, Tuan Anh

2015-03-01

Photoelectrochemical cells offer a promising avenue for hydrogen production from water and sunlight. The efficiency of these devices depends on the electronic structure of the interface between the photoelectrode and liquid water, including the alignment between the semiconductor band edges and the water redox potential. In this talk, we will present the results of first principles calculations of semiconductor-water interfaces that are obtained with a combination of density functional theory (DFT)-based molecular dynamics simulations and many-body perturbation theory (MBPT). First, we will discuss the development of an MBPT approach that is aimed at improving the efficiency and accuracy of existing methodologies while still being applicable to complex heterogeneous interfaces consisting of hundreds of atoms. We will then present studies of the electronic structure of liquid water and aqueous solutions using MBPT, which represent an essential step in establishing a quantitative framework for computing the energy alignment at semiconductor-water interfaces. Finally, using a combination of DFT-based molecular dynamics simulations and MBPT, we will describe the relationship between interfacial structure, electronic properties of semiconductors and their reactivity in aqueous solutions through a number of examples, including functionalized Si surfaces and GaP/InP surfaces in contact with liquid water. T.A.P was supported by the U.S. Department of Energy at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and by the Lawrence Fellowship Program.

LysoTracker and MitoTracker Red are transport substrates of P-glycoprotein: implications for anticancer drug design evading multidrug resistance.

PubMed

Zhitomirsky, Benny; Farber, Hodaya; Assaraf, Yehuda G

2018-04-01

LysoTracker and MitoTracker Red are fluorescent probes widely used for viable cell staining of lysosomes and mitochondria, respectively. They are utilized to study organelle localization and their resident proteins, assess organelle functionality and quantification of organelle numbers. The ATP-driven efflux transporter P-glycoprotein (P-gp) is expressed in normal and malignant tissues and extrudes structurally distinct endogenous and exogenous cytotoxic compounds. Thus, once aromatic hydrophobic compounds such as the above-mentioned fluorescent probes are recognized as transport substrates, efflux pumps including P-gp may abolish their ability to reach their cellular target organelles. Herein, we show that LysoTracker and MitoTracker Red are expelled from P-gp-overexpressing cancer cells, thus hindering their ability to fluorescently mark target organelles. We further demonstrate that tariquidar, a potent P-gp transport inhibitor, restores LysoTracker and MitoTracker Red cell entry. We conclude that LysoTracker and MitoTracker Red are P-gp transport substrates, and therefore, P-gp expression must be taken into consideration prior to cellular applications using these probes. Importantly, as MitoTracker was a superior P-gp substrate than LysoTracker Red, we discuss the implications for the future design of chemotherapeutics evading cancer multidrug resistance. Furthermore, restoration of MitoTracker Red fluorescence in P-gp-overexpressing cells may facilitate the identification of potent P-gp transport inhibitors (i.e. chemosensitizers). © 2018 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Extended Bright Bodies - Flight and Ground Software Challenges on the Cassini Mission at Saturn

NASA Technical Reports Server (NTRS)

Sung, Tina S.; Burk, Thomas A.

2016-01-01

Extended bright bodies in the Saturn environment such as Saturn's rings, the planet itself, and Saturn's satellites near the Cassini spacecraft may interfere with the star tracker's ability to find stars. These interferences can create faulty spacecraft attitude knowledge, which would decrease the pointing accuracy or even trip a fault protection response on board the spacecraft. The effects of the extended bright body interference were observed in December of 2000 when Cassini flew by Jupiter. Based on this flight experience and expected star tracker behavior at Saturn, the Cassini AACS operations team defined flight rules to suspend the star tracker during predicted interference windows. The flight rules are also implemented in the existing ground software called Kinematic Predictor Tool to create star identification suspend commands to be uplinked to the spacecraft for future predicted interferences. This paper discusses the details of how extended bright bodies impact Cassini's acquisition of attitude knowledge, how the observed data helped the ground engineers in developing flight rules, and how automated methods are used in the flight and ground software to ensure the spacecraft is continuously operated within these flight rules. This paper also discusses how these established procedures will continue to be used to overcome new bright body challenges that Cassini will encounter during its dips inside the rings of Saturn for its final orbits of a remarkable 20-year mission at Saturn.

Sensing and perception research for space telerobotics at JPL

NASA Technical Reports Server (NTRS)

Gennery, Donald B.; Litwin, Todd; Wilcox, Brian; Bon, Bruce

1987-01-01

PIFLEX is a pipelined-image processor that can perform elaborate computations whose exact nature is not fixed in the hardware, and that can handle multiple images. A wire-wrapped prototype PIFEX module has been produced and debugged, using a version of the convolver composed of three custom VLSI chips (plus the line buffers). A printed circuit layout is being designed for use with a single-chip convolver, leading to production of a PIFEX with about 120 modules. A high-level language for programming PIFEX has been designed, and a compiler will be written for it. The camera calibration software has been completed and tested. Two more terms in the camera model, for lens distortion, probably will be added later. The acquisition and tracking system has been designed and most of it has been coded in Pascal for the MicroVAX-II. The feature tracker, motion stereo module and stereo matcher have executed successfully. The model matcher is still under development, and coding has begun on the tracking initializer. The object tracker was running on a different computer from the VAX, and preliminary runs on real images have been performed there. Once all modules are working, optimization and integration will begin. Finally, when a sufficiently large PIFEX is available, appropriate parts of acquisition and tracking, including much of the feature tracker, will be programmed into PIFEX, thus increasing the speed and robustness of the system.

A new star tracker concept for satellite attitude determination based on a multi-purpose panoramic camera

NASA Astrophysics Data System (ADS)

Opromolla, Roberto; Fasano, Giancarmine; Rufino, Giancarlo; Grassi, Michele; Pernechele, Claudio; Dionisio, Cesare

2017-11-01

This paper presents an innovative algorithm developed for attitude determination of a space platform. The algorithm exploits images taken from a multi-purpose panoramic camera equipped with hyper-hemispheric lens and used as star tracker. The sensor architecture is also original since state-of-the-art star trackers accurately image as many stars as possible within a narrow- or medium-size field-of-view, while the considered sensor observes an extremely large portion of the celestial sphere but its observation capabilities are limited by the features of the optical system. The proposed original approach combines algorithmic concepts, like template matching and point cloud registration, inherited from the computer vision and robotic research fields, to carry out star identification. The final aim is to provide a robust and reliable initial attitude solution (lost-in-space mode), with a satisfactory accuracy level in view of the multi-purpose functionality of the sensor and considering its limitations in terms of resolution and sensitivity. Performance evaluation is carried out within a simulation environment in which the panoramic camera operation is realistically reproduced, including perturbations in the imaged star pattern. Results show that the presented algorithm is able to estimate attitude with accuracy better than 1° with a success rate around 98% evaluated by densely covering the entire space of the parameters representing the camera pointing in the inertial space.

A robust star identification algorithm with star shortlisting

NASA Astrophysics Data System (ADS)

Mehta, Deval Samirbhai; Chen, Shoushun; Low, Kay Soon

2018-05-01

A star tracker provides the most accurate attitude solution in terms of arc seconds compared to the other existing attitude sensors. When no prior attitude information is available, it operates in "Lost-In-Space (LIS)" mode. Star pattern recognition, also known as star identification algorithm, forms the most crucial part of a star tracker in the LIS mode. Recognition reliability and speed are the two most important parameters of a star pattern recognition technique. In this paper, a novel star identification algorithm with star ID shortlisting is proposed. Firstly, the star IDs are shortlisted based on worst-case patch mismatch, and later stars are identified in the image by an initial match confirmed with a running sequential angular match technique. The proposed idea is tested on 16,200 simulated star images having magnitude uncertainty, noise stars, positional deviation, and varying size of the field of view. The proposed idea is also benchmarked with the state-of-the-art star pattern recognition techniques. Finally, the real-time performance of the proposed technique is tested on the 3104 real star images captured by a star tracker SST-20S currently mounted on a satellite. The proposed technique can achieve an identification accuracy of 98% and takes only 8.2 ms for identification on real images. Simulation and real-time results depict that the proposed technique is highly robust and achieves a high speed of identification suitable for actual space applications.

Silicon carbide, a semiconductor for space power electronics

NASA Technical Reports Server (NTRS)

Powell, J. Anthony; Matus, Lawrence G.

1991-01-01

After many years of promise as a high temperature semiconductor, silicon carbide (SiC) is finally emerging as a useful electronic material. Recent significant progress that has led to this emergence has been in the areas of crystal growth and device fabrication technology. High quality single-crystal SiC wafers, up to 25 mm in diameter, can now be produced routinely from boules grown by a high temperature (2700 K) sublimation process. Device fabrication processes, including chemical vapor deposition (CVD), in situ doping during CVD, reactive ion etching, oxidation, metallization, etc. have been used to fabricate p-n junction diodes and MOSFETs. The diode was operated to 870 K and the MOSFET to 770 K.

Test Standard Revision Update: JESD57, "Procedures for the Measurement of Single-Event Effects in Semiconductor Devices from Heavy-Ion Irradiation"

NASA Technical Reports Server (NTRS)

Lauenstein, Jean-Marie

2015-01-01

The JEDEC JESD57 test standard, Procedures for the Measurement of Single-Event Effects in Semiconductor Devices from Heavy-Ion Irradiation, is undergoing its first revision since 1996. In this talk, we place this test standard into context with other relevant radiation test standards to show its importance for single-event effect radiation testing for space applications. We show the range of industry, government, and end-user party involvement in the revision. Finally, we highlight some of the key changes being made and discuss the trade-space in which setting standards must be made to be both useful and broadly adopted.

78 FR 51737 - Notice of Issuance of Final Determination Concerning Certain Hard Disk Drives and Self-Encrypting...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-21

... the HDA incorporate semiconductor, magnetic, mechanical, and manufacturing process design into an..., mechanical surface design and manufacturing process design. It takes approximately [xxx] hours to design... brand names ``Barracuda'' and ``Desktop''. HDDs are designed in the United States and assembled either...

Microwave Sintering of Ceramic Materials for Industrial Application Final Report CRADA No. TC-1116-95

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

Caplan, M.; Tandon, R.; Callis, R.

The goal of this project was to develop the commercial capability in the US to sinter alumina oxide ceramic parts for the semiconductor manufacturing equipment industry. We planned to use the millimeter microwave (30 GHz) sintering system first developed by IAP in Russia.

Can a Free Wearable Activity Tracker Change Behavior? The Impact of Trackers on Adults in a Physician-Led Wellness Group.

PubMed

Gualtieri, Lisa; Rosenbluth, Sandra; Phillips, Jeffrey

2016-11-30

Wearable activity trackers (trackers) are increasingly popular devices used to track step count and other health indicators. Trackers have the potential to benefit those in need of increased physical activity, such as adults who are older and face significant health challenges. These populations are least likely to purchase trackers and most likely to face challenges in using them, yet may derive educational, motivational, and health benefits from their use once these barriers are removed. The aim of this pilot research is to investigate the use of trackers by adults with chronic medical conditions who have never used trackers previously. Specifically, we aim to determine (1) if participants would accept and use trackers to increase their physical activity; (2) if there were barriers to use besides cost and training; (3) if trackers would educate participants on their baseline and ongoing activity levels and support behavior change; and (4) if clinical outcomes would show improvements in participants' health. This study was conducted with patients (N=10) in a 12-week physician-led wellness group offered by Family Doctors, LLC. Patients were given trackers in the second week of The Wellness Group and were interviewed 2 to 4 weeks after it ended. The study investigators analyzed the interview notes to extract themes about the participants' attitudes and behavior changes and collected and analyzed participants' clinical data, including weight and low-density lipoprotein (LDL) cholesterol over the course of the study. Over the 12 to 14 weeks of tracker use, improvements were seen in clinical outcomes, attitudes towards the trackers, and physical activity behaviors. Participants lost an average of 0.5 lbs per week (SD 0.4), with a mean total weight loss of 5.97 lbs (P=.004). Other short-term clinical outcomes included a 9.2% decrease in LDL levels (P=.038). All participants reported an increase in well-being and confidence in their ability to lead more active lives. We identified the following 6 major attitudinal themes from our qualitative analysis of the interview notes: (1) barriers to tracker purchase included cost, perceived value, and choice confusion; (2) attitudes towards the trackers shifted for many, from half of the participants expressing excitement and hope and half expressing hesitation or trepidation, to all participants feeling positive towards their tracker at the time of the interviews; (3) trackers served as educational tools for baseline activity levels; (4) trackers provided concrete feedback on physical activity, which motivated behavior change; (5) tracker use reinforced wellness group activities and goals; and (6) although commitment to tracker use did not waver, external circumstances influenced some participants' ongoing use. Our findings suggest that adding trackers to wellness groups comprising primarily older adults with chronic medical conditions can support education and behavior change to be more physically active. The trackers increased participant self-efficacy by providing a tangible, visible reminder of a commitment to increasing activity and immediate feedback on step count and progress towards a daily step goal. While acceptance was high and attitudes ultimately positive, training and support are needed and short-term drop-off in participant use is to be expected. Future research will further consider the potential of trackers in older adults with chronic medical conditions who are unlikely to purchase them, and studies will use larger samples, continue over a longer period of time, and evaluate outcomes independent of a wellness group. ©Lisa Gualtieri, Sandra Rosenbluth, Jeffrey Phillips. Originally published in JMIR Research Protocols (http://www.researchprotocols.org), 30.11.2016.

Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process.

PubMed

Swain, Basudev; Mishra, Chinmayee; Lee, Chan Gi; Park, Kyung-Soo; Lee, Kun-Jae

2015-07-01

Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga0.97N0.9O0.09 is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga0.97N0.9O0.09 of the MOCVD dust is leached at the optimum condition. Subsequently, the leach residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4M HCl, 100°C and pulp density of 100 kg/m(3,) respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition. Copyright © 2015 Elsevier Inc. All rights reserved.

A full time-domain approach to spatio-temporal dynamics of semiconductor lasers. II. Spatio-temporal dynamics

NASA Astrophysics Data System (ADS)

Böhringer, Klaus; Hess, Ortwin

The spatio-temporal dynamics of novel semiconductor lasers is discussed on the basis of a space- and momentum-dependent full time-domain approach. To this means the space-, time-, and momentum-dependent Full-Time Domain Maxwell Semiconductor Bloch equations, derived and discussed in our preceding paper I [K. Böhringer, O. Hess, A full time-domain approach to spatio-temporal dynamics of semiconductor lasers. I. Theoretical formulation], are solved by direct numerical integration. Focussing on the device physics of novel semiconductor lasers that profit, in particular, from recent advances in nanoscience and nanotechnology, we discuss the examples of photonic band edge surface emitting lasers (PBE-SEL) and semiconductor disc lasers (SDLs). It is demonstrated that photonic crystal effects can be obtained for finite crystal structures, and leading to a significant improvement in laser performance such as reduced lasing thresholds. In SDLs, a modern device concept designed to increase the power output of surface-emitters in combination with near-diffraction-limited beam quality, we explore the complex interplay between the intracavity optical fields and the quantum well gain material in SDL structures. Our simulations reveal the dynamical balance between carrier generation due to pumping into high energy states, momentum relaxation of carriers, and stimulated recombination from states near the band edge. Our full time-domain approach is shown to also be an excellent framework for the modelling of the interaction of high-intensity femtosecond and picosecond pulses with semiconductor nanostructures. It is demonstrated that group velocity dispersion, dynamical gain saturation and fast self-phase modulation (SPM) are the main causes for the induced changes and asymmetries in the amplified pulse shape and spectrum of an ultrashort high-intensity pulse. We attest that the time constants of the intraband scattering processes are critical to gain recovery. Moreover, we present new insight into the physics of nonlinear coherent pulse propagation phenomena in active (semiconductor) gain media. Our numerical full time-domain simulations are shown to generally agree well with analytical predictions, while in the case of optical pulses with large pulse areas or few-cycle pulses they reveal the limits of analytic approaches. Finally, it is demonstrated that coherent ultrafast nonlinear propagation effects become less distinctive if we apply a realistic model of the quantum well semiconductor gain material, consider characteristic loss channels and take into account de-phasing processes and homogeneous broadening.

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

DOE PAGES

Dalal, Shakeel S.; Walters, Diane M.; Lyubimov, Ivan; ...

2015-03-23

Physical vapor deposition is commonly used to prepare organic glasses that serve as the active layers in light-emitting diodes, photovoltaics, and other devices. Recent work has shown that orienting the molecules in such organic semiconductors can significantly enhance device performance. In this paper, we apply a high-throughput characterization scheme to investigate the effect of the substrate temperature (T substrate) on glasses of three organic molecules used as semiconductors. The optical and material properties are evaluated with spectroscopic ellipsometry. We find that molecular orientation in these glasses is continuously tunable and controlled by T substrate/T g, where T g is themore » glass transition temperature. All three molecules can produce highly anisotropic glasses; the dependence of molecular orientation upon substrate temperature is remarkably similar and nearly independent of molecular length. All three compounds form “stable glasses” with high density and thermal stability, and have properties similar to stable glasses prepared from model glass formers. Simulations reproduce the experimental trends and explain molecular orientation in the deposited glasses in terms of the surface properties of the equilibrium liquid. Finally, by showing that organic semiconductors form stable glasses, these results provide an avenue for systematic performance optimization of active layers in organic electronics.« less

Preparation methodologies and nano/microstructural evaluation of metal/semiconductor thin films.

PubMed

Chen, Zhiwen; Jiao, Zheng; Wu, Minghong; Shek, Chan-Hung; Wu, C M Lawrence; Lai, Joseph K L

2012-01-01

Metal/semiconductor thin films are a class of unique materials that are widespread technological applications, particularly in the field of microelectronic devices. Assessment strategies of fractal and tures are of fundamental importance in the development of nano/microdevices. This review presents the preparation methodologies and nano/microstructural evaluation of metal/semiconductor thin films including Au/Ge bilayer films and Pd-Ge alloy thin films, which show in the form of fractals and nanocrystals. Firstly, the extended version of Au/Ge thin films for the fractal crystallization of amorphous Ge and the formation of nanocrystals developed with improved micro- and nanostructured features are described in Section 2. Secondly, the nano/microstructural characteristics of Pd/Ge alloy thin films during annealing have been investigated in detail and described in Section 3. Finally, we will draw the conclusions from the present work as shown in Section 4. It is expected that the preparation methodologies developed and the knowledge of nano/microstructural evolution gained in metal/semiconductor thin films, including Au/Ge bilayer films and Pd-Ge alloy thin films, will provide an important fundamental basis underpinning further interdisciplinary research in these fields such as physics, chemistry, materials science, and nanoscience and nanotechnology, leading to promising exciting opportunities for future technological applications involving these thin films.

Discrete Electronic Bands in Semiconductors and Insulators: Potential High-Light-Yield Scintillators

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

Shi, Hongliang; Du, Mao-Hua

Bulk semiconductors and insulators typically have continuous valence and conduction bands. In this paper, we show that valence and conduction bands of a multinary semiconductor or insulator can be split to narrow discrete bands separated by large energy gaps. This unique electronic structure is demonstrated by first-principles calculations in several quaternary elpasolite compounds, i.e., Cs 2NaInBr 6, Cs 2NaBiCl 6, and Tl 2NaBiCl 6. The narrow discrete band structure in these quaternary elpasolites is due to the large electronegativity difference among cations and the large nearest-neighbor distances in cation sublattices. We further use Cs 2NaInBr 6 as an example tomore » show that the narrow bands can stabilize self-trapped and dopant-bound excitons (in which both the electron and the hole are strongly localized in static positions on adjacent sites) and promote strong exciton emission at room temperature. The discrete band structure should further suppress thermalization of hot carriers and may lead to enhanced impact ionization, which is usually considered inefficient in bulk semiconductors and insulators. Finally, these characteristics can enable efficient room-temperature light emission in low-gap scintillators and may overcome the light-yield bottleneck in current scintillator research.« less

Discrete Electronic Bands in Semiconductors and Insulators: Potential High-Light-Yield Scintillators

DOE PAGES

Shi, Hongliang; Du, Mao-Hua

2015-05-12

Bulk semiconductors and insulators typically have continuous valence and conduction bands. In this paper, we show that valence and conduction bands of a multinary semiconductor or insulator can be split to narrow discrete bands separated by large energy gaps. This unique electronic structure is demonstrated by first-principles calculations in several quaternary elpasolite compounds, i.e., Cs 2NaInBr 6, Cs 2NaBiCl 6, and Tl 2NaBiCl 6. The narrow discrete band structure in these quaternary elpasolites is due to the large electronegativity difference among cations and the large nearest-neighbor distances in cation sublattices. We further use Cs 2NaInBr 6 as an example tomore » show that the narrow bands can stabilize self-trapped and dopant-bound excitons (in which both the electron and the hole are strongly localized in static positions on adjacent sites) and promote strong exciton emission at room temperature. The discrete band structure should further suppress thermalization of hot carriers and may lead to enhanced impact ionization, which is usually considered inefficient in bulk semiconductors and insulators. Finally, these characteristics can enable efficient room-temperature light emission in low-gap scintillators and may overcome the light-yield bottleneck in current scintillator research.« less

Optoelectronic Devices and Materials

NASA Astrophysics Data System (ADS)

Sweeney, Stephen; Adams, Alfred

Unlike the majority of electronic devices, which are silicon based, optoelectronic devices are predominantly made using III-V semiconductor compounds such as GaAs, InP, GaN and GaSb and their alloys due to their direct band gap. Understanding the properties of these materials has been of vital importance in the development of optoelectronic devices. Since the first demonstration of a semiconductor laser in the early 1960s, optoelectronic devices have been produced in their millions, pervading our everyday lives in communications, computing, entertainment, lighting and medicine. It is perhaps their use in optical-fibre communications that has had the greatest impact on humankind, enabling high-quality and inexpensive voice and data transmission across the globe. Optical communications spawned a number of developments in optoelectronics, leading to devices such as vertical-cavity surface-emitting lasers, semiconductor optical amplifiers, optical modulators and avalanche photodiodes. In this chapter we discuss the underlying theory of operation of the most important optoelectronic devices. The influence of carrier-photon interactions is discussed in the context of producing efficient emitters and detectors. Finally we discuss how the semiconductor band structure can be manipulated to enhance device properties using quantum confinement and strain effects, and how the addition of dilute amounts of elements such as nitrogen is having a profound effect on the next generation of optoelectronic devices.

Interface Energetics and Chemical Doping of Organic Electronic Materials

NASA Astrophysics Data System (ADS)

Kahn, Antoine

2014-03-01

The energetics of organic semiconductors and their interfaces are central to the performance of organic thin film devices. The relative positions of charge transport states across the many interfaces of multi-layer OLEDs, OPV cells and OFETs determine in great part the efficiency and lifetime of these devices. New experiments are presented here, that look in detail at the position of these transport states and associated gap states and electronic traps that tail into the energy gap of organic molecular (e.g. pentacene) or polymer (P3HT, PBDTTT-C) semiconductors, and which directly affect carrier mobility in these materials. Disorder, sometime caused by simple exposure to an inert gas, impurities and defects are at the origin of these electronic gap states. Recent efforts in chemical doping in organic semiconductors aimed at mitigating the impact of electronic gap states are described. An overview of the reducing or oxidizing power of several n- and p-type dopants for vacuum- or solution-processed films, and their effect on the electronic structure and conductivity of both vacuum- and solution-processed organic semiconductor films is given. Finally, the filling (compensation) of active gap states via doping is investigated on the electron-transport materials C60 and P(NDI2OD-T2) , and the hole-transport polymer PBDTTT-C.

3D Band Diagram and Photoexcitation of 2D–3D Semiconductor Heterojunctions

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

Li, Bo; Shi, Gang; Lei, Sidong

2015-08-17

The emergence of a rich variety of two-dimensional (2D) layered semiconductor materials has enabled the creation of atomically thin heterojunction devices. Junctions between atomically thin 2D layers and 3D bulk semiconductors can lead to junctions that are fundamentally electronically different from the covalently bonded conventional semiconductor junctions. In this paper, we propose a new 3D band diagram for the heterojunction formed between n-type monolayer MoS 2 and p-type Si, in which the conduction and valence band-edges of the MoS 2 monolayer are drawn for both stacked and in-plane directions. This new band diagram helps visualize the flow of charge carriersmore » inside the device in a 3D manner. Our detailed wavelength-dependent photocurrent measurements fully support the diagrams and unambiguously show that the band alignment is type I for this 2D-3D heterojunction. Photogenerated electron–hole pairs in the atomically thin monolayer are separated and driven by an external bias and control the “on/off” states of the junction photodetector device. Finally, two photoresponse regimes with fast and slow relaxation are also revealed in time-resolved photocurrent measurements, suggesting the important role played by charge trap states.« less

Improved performance of the LHCb Outer Tracker in LHC Run 2

NASA Astrophysics Data System (ADS)

d'Argent, P.; Dufour, L.; Grillo, L.; de Vries, J. A.; Ukleja, A.; Aaij, R.; Archilli, F.; Bachmann, S.; Berninghoff, D.; Birnkraut, A.; Blouw, J.; De Cian, M.; Ciezarek, G.; Färber, C.; Demmer, M.; Dettori, F.; Gersabeck, E.; Grabowski, J.; Hulsbergen, W. D.; Khanji, B.; Kolpin, M.; Kucharczyk, M.; Malecki, B. P.; Merk, M.; Mulder, M.; Müller, J.; Mueller, V.; Pellegrino, A.; Pikies, M.; Rachwal, B.; Schmelzer, T.; Spaan, B.; Szczekowski, M.; van Tilburg, J.; Tolk, S.; Tuning, N.; Uwer, U.; Wishahi, J.; Witek, M.

2017-11-01

The LHCb Outer Tracker is a gaseous detector covering an area of 5 × 6 m2 with 12 double layers of straw tubes. The performance of the detector is presented based on data of the LHC Run 2 running period from 2015 and 2016. Occupancies and operational experience for data collected in pp, pPb and PbPb collisions are described. An updated study of the ageing effects is presented showing no signs of gain deterioration or other radiation damage effects. In addition several improvements with respect to LHC Run 1 data taking are introduced. A novel real-time calibration of the time-alignment of the detector and the alignment of the single monolayers composing detector modules are presented, improving the drift-time and position resolution of the detector by 20%. Finally, a potential use of the improved resolution for the timing of charged tracks is described, showing the possibility to identify low-momentum hadrons with their time-of-flight.

Cyclometalated Iridium(III) Complexes as AIE Phosphorescent Probes for Real-Time Monitoring of Mitophagy in Living Cells

NASA Astrophysics Data System (ADS)

Jin, Chengzhi; Liu, Jiangping; Chen, Yu; Guan, Ruilin; Ouyang, Cheng; Zhu, Yanjiao; Ji, Liangnian; Chao, Hui

2016-02-01

Mitophagy, which is a special autophagy that removes damaging mitochondria to maintain sufficient healthy mitochondria, provides an alternative path for addressing dysfunctional mitochondria and avoiding cellular death. In the present study, by coupling the triphenylamine group with 2-phenylimidazo[4,5-f][1,10]phenanthroline derivatives, we synthesized five Ir(III) complexes with an AIE property that are expected to fulfill requirements for real-time monitoring of mitophagy. Ir1-Ir5 were exploited to image mitochondria with a short incubation time by confocal microscopy and inductive coupled plasma-mass spectrometry (ICP-MS). Due to aggregation-induced emission (AIE), Ir1-Ir5 exhibited excellent photostability compared to MitoTracker Green (MTG). Moreover, Ir1-Ir5 manifested satisfactory photostability in the mitochondrial physiological pH range. In addition, the uptake mechanism of Ir1 was investigated using confocal microscopy and flow cytometry analysis. Finally, using both Ir1 and LysoTracker Green, we were able to achieve real-time monitoring of mitophagy.

Sun-Relative Pointing for Dual-Axis Solar Trackers Employing Azimuth and Elevation Rotations

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

Riley, Daniel; Hansen, Clifford W.

Dual axis trackers employing azimuth and elevation rotations are common in the field of photovoltaic (PV) energy generation. Accurate sun-tracking algorithms are widely available. However, a steering algorithm has not been available to accurately point the tracker away from the sun such that a vector projection of the sun beam onto the tracker face falls along a desired path relative to the tracker face. We have developed an algorithm which produces the appropriate azimuth and elevation angles for a dual axis tracker when given the sun position, desired angle of incidence, and the desired projection of the sun beam ontomore » the tracker face. Development of this algorithm was inspired by the need to accurately steer a tracker to desired sun-relative positions in order to better characterize the electro-optical properties of PV and CPV modules.« less

Hall Effect Spintronics

DTIC Science & Technology

2014-01-01

ferromagnetic films with perpendicular anisotropy were examined, and finally, the magnetoresistance and Hall effect in Manganese- doped Germanium was...interest in ferromagnetic semiconductors. Germanium doped with Mn is particularly interesting Distribution A: Approved for public release...unavoidable, and doped films are strongly inhomogeneous with GexMny, metallic precipitates coexisting with Mn-rich regions and Mn dilute matrix

Lower Merrimack Valley Workplace Education Project. Final Report.

ERIC Educational Resources Information Center

Norris, Cynthia Zylkuski; Breen, Patricia K.

A description is provided of the Lower Merrimack Valley Workplace Education Project (WEP), an educational project that offers English-as-a-Second-Language (ESL) and job-specific education classes to hourly employees in the Semiconductor Division of Alpha Industries. The challenge of the project was to create a WEP that could accommodate the…

Which cue to ‘want’? Opioid stimulation of central amygdala makes goal-trackers show stronger goal-tracking, just as sign-trackers show stronger sign-tracking

PubMed Central

DiFeliceantonio, Alexandra G.; Berridge, Kent C.

2012-01-01

Pavlovian cues that have been paired with reward can gain incentive salience. Drug addicts find drug cues motivationally attractive and binge eaters are attracted by food cues. But the level of incentive salience elicited by a cue re-encounter still varies across time and brain states. In an animal model, cues become attractive and ‘wanted’ in an ‘autoshaping’ paradigm, where different targets of incentive salience emerge for different individuals. Some individuals (sign-trackers) find a predictive discrete cue attractive while others find a reward contiguous and goal cue more attractive (location where reward arrives: goal-trackers). Here we assessed whether central amygdala mu opioid receptor stimulation enhances the phasic incentive salience of the goal-cue for goal-trackers during moments of predictive cue presence (expressed in both approach and consummatory behaviors to goal cue), just as it enhances the attractiveness of the predictive cue target for sign-trackers. Using detailed video analysis we measured the approaches, nibbles, sniffs, and bites directed at their preferred target for both sign-trackers and goal-trackers. We report that DAMGO microinjections in central amygdala made goal-trackers, like sign-trackers, show phasic increases in appetitive nibbles and sniffs directed at the goal-cue expressed selectively whenever the predictive cue was present. This indicates enhancement of incentive salience attributed by both goal trackers and sign-trackers, but attributed in different directions: each to their own target cue. For both phenotypes, amygdala opioid stimulation makes the individual’s prepotent cue into a stronger motivational magnet at phasic moments triggered by a CS that predicts the reward UCS. PMID:22391118

Molecular Electrical Doping of Organic Semiconductors: Fundamental Mechanisms and Emerging Dopant Design Rules.

PubMed

Salzmann, Ingo; Heimel, Georg; Oehzelt, Martin; Winkler, Stefanie; Koch, Norbert

2016-03-15

Today's information society depends on our ability to controllably dope inorganic semiconductors, such as silicon, thereby tuning their electrical properties to application-specific demands. For optoelectronic devices, organic semiconductors, that is, conjugated polymers and molecules, have emerged as superior alternative owing to the ease of tuning their optical gap through chemical variability and their potential for low-cost, large-area processing on flexible substrates. There, the potential of molecular electrical doping for improving the performance of, for example, organic light-emitting devices or organic solar cells has only recently been established. The doping efficiency, however, remains conspicuously low, highlighting the fact that the underlying mechanisms of molecular doping in organic semiconductors are only little understood compared with their inorganic counterparts. Here, we review the broad range of phenomena observed upon molecularly doping organic semiconductors and identify two distinctly different scenarios: the pairwise formation of both organic semiconductor and dopant ions on one hand and the emergence of ground state charge transfer complexes between organic semiconductor and dopant through supramolecular hybridization of their respective frontier molecular orbitals on the other hand. Evidence for the occurrence of these two scenarios is subsequently discussed on the basis of the characteristic and strikingly different signatures of the individual species involved in the respective doping processes in a variety of spectroscopic techniques. The critical importance of a statistical view of doping, rather than a bimolecular picture, is then highlighted by employing numerical simulations, which reveal one of the main differences between inorganic and organic semiconductors to be their respective density of electronic states and the doping induced changes thereof. Engineering the density of states of doped organic semiconductors, the Fermi-Dirac occupation of which ultimately determines the doping efficiency, thus emerges as key challenge. As a first step, the formation of charge transfer complexes is identified as being detrimental to the doping efficiency, which suggests sterically shielding the functional core of dopant molecules as an additional design rule to complement the requirement of low ionization energies or high electron affinities in efficient n-type or p-type dopants, respectively. In an extended outlook, we finally argue that, to fully meet this challenge, an improved understanding is required of just how the admixture of dopant molecules to organic semiconductors does affect the density of states: compared with their inorganic counterparts, traps for charge carriers are omnipresent in organic semiconductors due to structural and chemical imperfections, and Coulomb attraction between ionized dopants and free charge carriers is typically stronger in organic semiconductors owing to their lower dielectric constant. Nevertheless, encouraging progress is being made toward developing a unifying picture that captures the entire range of doping induced phenomena, from ion-pair to complex formation, in both conjugated polymers and molecules. Once completed, such a picture will provide viable guidelines for synthetic and supramolecular chemistry that will enable further technological advances in organic and hybrid organic/inorganic devices.

Molecular detection via hybrid peptide-semiconductor photonic devices

NASA Astrophysics Data System (ADS)

Estephan, E.; Saab, M.-b.; Martin, M.; Cloitre, T.; Larroque, C.; Cuisinier, F. J. G.; Malvezzi, A. M.; Gergely, C.

2011-03-01

The aim of this work was to investigate the possibilities to support device functionality that includes strongly confined and localized light emission and detection processes within nano/micro-structured semiconductors for biosensing applications. The interface between biological molecules and semiconductor surfaces, yet still under-explored is a key issue for improving biomolecular recognition in devices. We report on the use of adhesion peptides, elaborated via combinatorial phage-display libraries for controlled placement of biomolecules, leading to user-tailored hybrid photonic systems for molecular detection. An M13 bacteriophage library has been used to screen 1010 different peptides against various semiconductors to finally isolate specific peptides presenting a high binding capacity for the target surfaces. When used to functionalize porous silicon microcavities (PSiM) and GaAs/AlGaAs photonic crystals, we observe the formation of extremely thin (<1nm) peptide layers, hereby preserving the nanostructuration of the crystals. This is important to assure the photonic response of these tiny structures when they are functionalized by a biotinylated peptide layer and then used to capture streptavidin. Molecular detection was monitored via both linear and nonlinear optical measurements. Our linear reflectance spectra demonstrate an enhanced detection resolution via PSiM devices, when functionalized with the Si-specific peptide. Molecular capture at even lower concentrations (femtomols) is possible via the second harmonic generation of GaAs/AlGaAs photonic crystals when functionalized with GaAs-specific peptides. Our work demonstrates the outstanding value of adhesion peptides as interface linkers between semiconductors and biological molecules. They assure an enhanced molecular detection via both linear and nonlinear answers of photonic crystals.

Development of high yielding photonic light delivery system for photodynamic therapy of esophageal carcinomas

NASA Astrophysics Data System (ADS)

Premasiri, Amaranath; Happawana, Gemunu; Rosen, Arye

2007-02-01

Photodynamic therapy (PDT) is an approved treatment modality for Barrett's and invasive esophageal carcinoma. Proper Combination of photosentizing agent, oxygen, and a specific wavelength of light to activate the photosentizing agents is necessary for the cytotoxic destruction of cancerous cells by PDT. As a light source expensive solid-state laser sources currently are being used for the treatment. Inexpensive semiconductor lasers have been suggested for the light delivery system, however packaging of semiconductor lasers for optimal optical power output is challenging. In this paper, we present a multidirectional direct water-cooling of semiconductor lasers that provides a better efficiency than the conventional unidirectional cooling. AlGaAsP lasers were tested under de-ionized (DI) water and it is shown that the optical power output of the lasers under the DI water is much higher than that of the uni-directional cooling of lasers. Also, in this paper we discuss how direct DI water-cooling can optimize power output of semiconductor lasers. Thereafter an optimal design of the semiconductor laser package is shown with the DI water-cooling system. Further, a microwave antenna is designed which is to be imprinted on to a balloon catheter in order to provide local heating of esophagus, leading to an increase in local oxygenation of the tumor to generate an effective level of singlet oxygen for cellular death. Finally the optimal level of light energy that is required to achieve the expected level of singlet oxygen is modeled to design an efficient PDT protocol.

Optimum design on refrigeration system of high-repetition-frequency laser

NASA Astrophysics Data System (ADS)

Li, Gang; Li, Li; Jin, Yezhou; Sun, Xinhua; Mao, Shaojuan; Wang, Yuanbo

2014-12-01

A refrigeration system with fluid cycle, semiconductor cooler and air cooler is designed to solve the problems of thermal lensing effect and unstable output of high-repetition-frequency solid-state lasers. Utilizing a circulating water pump, water recycling system carries the water into laser cavity to absorb the heat then get to water cooling head. The water cooling head compacts cold spot of semiconductor cooling chips, so the heat is carried to hot spot which contacts the radiating fins, then is expelled through cooling fan. Finally, the cooled water return to tank. The above processes circulate to achieve the purposes of highly effective refrigeration in miniative solid-state lasers.The refrigeration and temperature control components are designed strictly to ensure refrigeration effect and practicability. we also set up a experiment to test the performances of this refrigeration system, the results show that the relationship between water temperature and cooling power of semiconductor cooling chip is linear at 20°C-30°C (operating temperature range of Nd:YAG), the higher of the water temperature, the higher of cooling power. According to the results, cooling power of single semiconductor cooling chip is above 60W, and the total cooling power of three semiconductor cooling chips achieves 200W that will satisfy the refrigeration require of the miniative solid-state lasers.The performance parameters of laser pulse are also tested, include pulse waveform, spectrogram and laser spot. All of that indicate that this refrigeration system can ensure the output of high-repetition-frequency pulse whit high power and stability.

Autonomous star tracker based on active pixel sensors (APS)

NASA Astrophysics Data System (ADS)

Schmidt, U.

2017-11-01

Star trackers are opto-electronic sensors used onboard of satellites for the autonomous inertial attitude determination. During the last years, star trackers became more and more important in the field of the attitude and orbit control system (AOCS) sensors. High performance star trackers are based up today on charge coupled device (CCD) optical camera heads. The Jena-Optronik GmbH is active in the field of opto-electronic sensors like star trackers since the early 80-ties. Today, with the product family ASTRO5, ASTRO10 and ASTRO15, all marked segments like earth observation, scientific applications and geo-telecom are supplied to European and Overseas customers. A new generation of star trackers can be designed based on the APS detector technical features. The measurement performance of the current CCD based star trackers can be maintained, the star tracker functionality, reliability and robustness can be increased while the unit costs are saved.

Surprising stability of neutral interstitial hydrogen in diamond and cubic BN

DOE PAGES

Lyons, J. L.; Van de Walle, C. G.

2016-01-21

We report that in virtually all semiconductors and insulators, hydrogen interstitials (H i) act as negative-U centers, implying that hydrogen is never stable in the neutral charge state. Using hybrid density functional calculations, we find a different behavior for H i in diamond and cubic BN. In diamond, H i is a very strong positive-U center, and the H 0 icharge state is stable over a Fermi-level range of more than 2 eV. In cubic BN, a III-V compound similar to diamond, we also find positive-U behavior, though over a much smaller Fermi-level range. Finally, these results highlight the uniquemore » behavior of Hi in these covalent wide-band-gap semiconductors.« less

Implicit versus explicit momentum relaxation time solution for semiconductor nanowires

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

Marin, E. G., E-mail: egmarin@ugr.es; Ruiz, F. G., E-mail: franruiz@ugr.es; Godoy, A., E-mail: agodoy@ugr.es

2015-07-14

We discuss the necessity of the exact implicit Momentum Relaxation Time (MRT) solution of the Boltzmann transport equation in order to achieve reliable carrier mobility results in semiconductor nanowires. Firstly, the implicit solution for a 1D electron gas with a isotropic bandstructure is presented resulting in the formulation of a simple matrix system. Using this solution as a reference, the explicit approach is demonstrated to be inaccurate for the calculation of inelastic anisotropic mechanisms such as polar optical phonons, characteristic of III-V materials. Its validity for elastic and isotropic mechanisms is also evaluated. Finally, the implications of the MRT explicitmore » approach inaccuracies on the total mobility of Si and III-V NWs are studied.« less

Gatemon Benchmarking and Two-Qubit Operation

NASA Astrophysics Data System (ADS)

Casparis, Lucas; Larsen, Thorvald; Olsen, Michael; Petersson, Karl; Kuemmeth, Ferdinand; Krogstrup, Peter; Nygard, Jesper; Marcus, Charles

Recent experiments have demonstrated superconducting transmon qubits with semiconductor nanowire Josephson junctions. These hybrid gatemon qubits utilize field effect tunability singular to semiconductors to allow complete qubit control using gate voltages, potentially a technological advantage over conventional flux-controlled transmons. Here, we present experiments with a two-qubit gatemon circuit. We characterize qubit coherence and stability and use randomized benchmarking to demonstrate single-qubit gate errors of ~0.5 % for all gates, including voltage-controlled Z rotations. We show coherent capacitive coupling between two gatemons and coherent SWAP operations. Finally, we perform a two-qubit controlled-phase gate with an estimated fidelity of ~91 %, demonstrating the potential of gatemon qubits for building scalable quantum processors. We acknowledge financial support from Microsoft Project Q and the Danish National Research Foundation.

Interest and preferences for using advanced physical activity tracking devices: results of a national cross-sectional survey

PubMed Central

Alley, Stephanie; Schoeppe, Stephanie; Guertler, Diana; Jennings, Cally; Vandelanotte, Corneel

2016-01-01

Objectives Pedometers are an effective self-monitoring tool to increase users' physical activity. However, a range of advanced trackers that measure physical activity 24 hours per day have emerged (eg, Fitbit). The current study aims to determine people's current use, interest and preferences for advanced trackers. Design and participants A cross-sectional national telephone survey was conducted in Australia with 1349 respondents. Outcome measures Regression analyses were used to determine whether tracker interest and use, and use of advanced trackers over pedometers is a function of demographics. Preferences for tracker features and reasons for not wanting to wear a tracker are also presented. Results Over one-third of participants (35%) had used a tracker, and 16% are interested in using one. Multinomial regression (n=1257) revealed that the use of trackers was lower in males (OR=0.48, 95% CI 0.36 to 0.65), non-working participants (OR=0.43, 95% CI 0.30 to 0.61), participants with lower education (OR=0.52, 95% CI 0.38 to 0.72) and inactive participants (OR=0.52, 95% CI 0.39 to 0.70). Interest in using a tracker was higher in younger participants (OR=1.73, 95% CI 1.15 to 2.58). The most frequently used tracker was a pedometer (59%). Logistic regression (n=445) revealed that use of advanced trackers compared with pedometers was higher in males (OR=1.67, 95% CI 1.01 to 2.79) and younger participants (OR=2.96, 95% CI 1.71 to 5.13), and lower in inactive participants (OR=0.35, 95% CI 0.19 to 0.63). Over half of current or interested tracker users (53%) prefer to wear it on their wrist, 31% considered counting steps the most important function and 30% regarded accuracy as the most important characteristic. The main reasons for not wanting to use a tracker were, ‘I don't think it would help me’ (39%), and ‘I don't want to increase my activity’ (47%). Conclusions Activity trackers are a promising tool to engage people in self-monitoring a physical activity. Trackers used in physical activity interventions should align with the preferences of target groups, and should be able to be worn on the wrist, measure steps and be accurate. PMID:27388359

Precision Pointing Control System (PPCS) star tracker test

NASA Technical Reports Server (NTRS)

1972-01-01

Tests performed on the TRW precision star tracker are described. The unit tested was a two-axis gimballed star tracker designed to provide star LOS data to an accuracy of 1 to 2 sec. The tracker features a unique bearing system and utilizes thermal and mechanical symmetry techniques to achieve high precision which can be demonstrated in a one g environment. The test program included a laboratory evaluation of tracker functional operation, sensitivity, repeatibility, and thermal stability.

Small star trackers for modern space vehicles

NASA Astrophysics Data System (ADS)

Kouzmin, Vladimir; Jushkov, Vladimir; Zaikin, Vladimir

2017-11-01

Based on experience of many years creation of spacecrafts' star trackers with diversified detectors (from the first star trackers of 60's to tens versions of star trackers in the following years), using technological achievements in the field of optics and electronics the NPP "Geofizika-Cosmos" has provided celestial orientation for all the space vehicles created in Russia and now has developed a series of new star trackers with CCD matrix and special processors, which are able to meet needs in celestial orientation of the modern spacecrafts for the nearest 10-15 years. In the given article the main characteristics and description of some star trackers' versions are presented. The star trackers have various levels of technical characteristics and use both combined (Russian and foreign) procurement parts, and only national (Russian) procurement parts for the main units.

ASPOD modifications of 1993-1994

NASA Technical Reports Server (NTRS)

Jackson, Jennifer J. (Editor); Fogarty, Paul W.; Muller, Matthew; Martucci, Thomas A., III; Williams, Daniel; Rowney, David A.

1994-01-01

ASPOD, Autonomous Space Processors for Orbital Debris, provides a unique way of collecting the space debris that has built up over the past 37 years. For the past several years, ASPOD has gone through several different modifications. This year's concentrations were on the solar cutting array, the solar tracker, the earth based main frame/tilt table, the controls for the two robotic arms, and accurate autocad drawings of ASPOD. This final report contains the reports written by the students who worked on the ASPOD project this year.

Improved semi-supervised online boosting for object tracking

NASA Astrophysics Data System (ADS)

Li, Yicui; Qi, Lin; Tan, Shukun

2016-10-01

The advantage of an online semi-supervised boosting method which takes object tracking problem as a classification problem, is training a binary classifier from labeled and unlabeled examples. Appropriate object features are selected based on real time changes in the object. However, the online semi-supervised boosting method faces one key problem: The traditional self-training using the classification results to update the classifier itself, often leads to drifting or tracking failure, due to the accumulated error during each update of the tracker. To overcome the disadvantages of semi-supervised online boosting based on object tracking methods, the contribution of this paper is an improved online semi-supervised boosting method, in which the learning process is guided by positive (P) and negative (N) constraints, termed P-N constraints, which restrict the labeling of the unlabeled samples. First, we train the classification by an online semi-supervised boosting. Then, this classification is used to process the next frame. Finally, the classification is analyzed by the P-N constraints, which are used to verify if the labels of unlabeled data assigned by the classifier are in line with the assumptions made about positive and negative samples. The proposed algorithm can effectively improve the discriminative ability of the classifier and significantly alleviate the drifting problem in tracking applications. In the experiments, we demonstrate real-time tracking of our tracker on several challenging test sequences where our tracker outperforms other related on-line tracking methods and achieves promising tracking performance.

Plasmon‐Mediated Solar Energy Conversion via Photocatalysis in Noble Metal/Semiconductor Composites

PubMed Central

Wang, Mengye; Ye, Meidan; Iocozzia, James

2016-01-01

Plasmonics has remained a prominent and growing field over the past several decades. The coupling of various chemical and photo phenomenon has sparked considerable interest in plasmon‐mediated photocatalysis. Given plasmonic photocatalysis has only been developed for a relatively short period, considerable progress has been made in improving the absorption across the full solar spectrum and the efficiency of photo‐generated charge carrier separation. With recent advances in fundamental (i.e., mechanisms) and experimental studies (i.e., the influence of size, geometry, surrounding dielectric field, etc.) on plasmon‐mediated photocatalysis, the rational design and synthesis of metal/semiconductor hybrid nanostructure photocatalysts has been realized. This review seeks to highlight the recent impressive developments in plasmon‐mediated photocatalytic mechanisms (i.e., Schottky junction, direct electron transfer, enhanced local electric field, plasmon resonant energy transfer, and scattering and heating effects), summarize a set of factors (i.e., size, geometry, dielectric environment, loading amount and composition of plasmonic metal, and nanostructure and properties of semiconductors) that largely affect plasmonic photocatalysis, and finally conclude with a perspective on future directions within this rich field of research. PMID:27818901

Electron energy loss spectroscopy on semiconductor heterostructures for optoelectronics and photonics applications.

PubMed

Eljarrat, A; López-Conesa, L; Estradé, S; Peiró, F

2016-05-01

In this work, we present characterization methods for the analysis of nanometer-sized devices, based on silicon and III-V nitride semiconductor materials. These methods are devised in order to take advantage of the aberration corrected scanning transmission electron microscope, equipped with a monochromator. This set-up ensures the necessary high spatial and energy resolution for the characterization of the smallest structures. As with these experiments, we aim to obtain chemical and structural information, we use electron energy loss spectroscopy (EELS). The low-loss region of EELS is exploited, which features fundamental electronic properties of semiconductor materials and facilitates a high data throughput. We show how the detailed analysis of these spectra, using theoretical models and computational tools, can enhance the analytical power of EELS. In this sense, initially, results from the model-based fit of the plasmon peak are presented. Moreover, the application of multivariate analysis algorithms to low-loss EELS is explored. Finally, some physical limitations of the technique, such as spatial delocalization, are mentioned. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

Controlling of the optical properties of the solutions of the PTCDI-C8 organic semiconductor

NASA Astrophysics Data System (ADS)

Erdoğan, Erman; Gündüz, Bayram

2016-09-01

N,N'-Dioctyl-3,4,9,10 perylenedicarboximide (PTCDI-C8) organic semiconductor have vast applications in solar cells, thermoelectric generators, thin film photovoltaics and many other optoelectronic devices. These applications of the materials are based on their spectral and optical properties. The solutions of the PTCDI-C8 for different molarities were prepared and the spectral and optical mesaurements were analyzed. Effects of the molarities on optical properties were investigated. Vibronic structure has been observed based on the absorption bands of PTCDI-C8 semiconductor with seven peaks at 2.292, 2.451, 2.616, 3.212, 3.851, 4.477 and 4.733 eV. The important spectral parameteres such as molar/mass extinction coefficients, absorption coefficient of the PTCDI-C8 molecule were calculated. Optical properties such as angle of incidence/refraction, optical band gap, real and imaginary parts of dielectric constant, loss factor and electrical susceptibility of the the PTCDI-C8 were obtained. Finally, we discussed these parameters for optoelectronic applications and compared with related parameters in literature.

Testing and Further Development of Improved Etches and Etching Methods for the Analysis of Bridgman Grown Semiconductor Crystals with an Emphasis on Lead-Tin-Telluride

NASA Technical Reports Server (NTRS)

Barber, Patrick G.

1998-01-01

The goals outlined for the research project for this year have been completed, and the following supporting documentation is attached: 1. A copy of the proposal outlining the principal goals: (a) Improve the characterization of semiconductor crystals through new etches and etching procedures. (b) Developed a novel voltammetric method to characterize semiconductor crystals as a result of searching for improved etches for lead-tin-telluride. (c) Presented paper at ACCG- 10. (d) Prepared manuscripts for publication. Completed additional testing suggested by reviewers and re-submitted manuscripts. (e) Worked with an undergraduate student on this project to provide her an opportunity to have a significant research experience prior to graduation. 2. In addition to the anticipated goals the following were also accomplished: (a) Submitted the newly developed procedures for consideration as a patent or a NASA Tech Brief. (b) Submitted a paper for presentation at the forthcoming ICCG- 12 conference. 3. A copy of the final draft of the publication as submitted to the editors of the Journal of Crystal Growth.

Plasmon-Mediated Solar Energy Conversion via Photocatalysis in Noble Metal/Semiconductor Composites.

PubMed

Wang, Mengye; Ye, Meidan; Iocozzia, James; Lin, Changjian; Lin, Zhiqun

2016-06-01

Plasmonics has remained a prominent and growing field over the past several decades. The coupling of various chemical and photo phenomenon has sparked considerable interest in plasmon-mediated photocatalysis. Given plasmonic photocatalysis has only been developed for a relatively short period, considerable progress has been made in improving the absorption across the full solar spectrum and the efficiency of photo-generated charge carrier separation. With recent advances in fundamental (i.e., mechanisms) and experimental studies (i.e., the influence of size, geometry, surrounding dielectric field, etc.) on plasmon-mediated photocatalysis, the rational design and synthesis of metal/semiconductor hybrid nanostructure photocatalysts has been realized. This review seeks to highlight the recent impressive developments in plasmon-mediated photocatalytic mechanisms (i.e., Schottky junction, direct electron transfer, enhanced local electric field, plasmon resonant energy transfer, and scattering and heating effects), summarize a set of factors (i.e., size, geometry, dielectric environment, loading amount and composition of plasmonic metal, and nanostructure and properties of semiconductors) that largely affect plasmonic photocatalysis, and finally conclude with a perspective on future directions within this rich field of research.

Directional interlayer spin-valley transfer in two-dimensional heterostructures

DOE PAGES

Schaibley, John R.; Rivera, Pasqual; Yu, Hongyi; ...

2016-12-14

Van der Waals heterostructures formed by two different monolayer semiconductors have emerged as a promising platform for new optoelectronic and spin/valleytronic applications. In addition to its atomically thin nature, a two-dimensional semiconductor heterostructure is distinct from its three-dimensional counterparts due to the unique coupled spin-valley physics of its constituent monolayers. In this paper, we report the direct observation that an optically generated spin-valley polarization in one monolayer can be transferred between layers of a two-dimensional MoSe 2–WSe 2 heterostructure. Using non-degenerate optical circular dichroism spectroscopy, we show that charge transfer between two monolayers conserves spin-valley polarization and is only weaklymore » dependent on the twist angle between layers. Finally, our work points to a new spin-valley pumping scheme in nanoscale devices, provides a fundamental understanding of spin-valley transfer across the two-dimensional interface, and shows the potential use of two-dimensional semiconductors as a spin-valley generator in two-dimensional spin/valleytronic devices for storing and processing information.« less

Plasmonic Enhancement Mechanisms in Solar Energy Harvesting

NASA Astrophysics Data System (ADS)

Cushing, Scott K.

Semiconductor photovoltaics (solar-to-electrical) and photocatalysis (solar-to-chemical) requires sunlight to be converted into excited charge carriers with sufficient lifetimes and mobility to drive a current or photoreaction. Thin semiconductor films are necessary to reduce the charge recombination and mobility losses, but thin films also limit light absorption, reducing the solar energy conversion efficiency. Further, in photocatalysis, the band edges of semiconductor must straddle the redox potentials of a photochemical reaction, reducing light absorption to half the solar spectrum in water splitting. Plasmonics transforms metal nanoparticles into antennas with resonances tuneable across the solar spectrum. If energy can be transferred from the plasmon to the semiconductor, light absorption in the semiconductor can be increased in thin films and occur at energies smaller than the band gap. This thesis investigates why, despite this potential, plasmonic solar energy harvesting techniques rarely appear in top performing solar architectures. To accomplish this goal, the possible plasmonic enhancement mechanisms for solar energy conversion were identified, isolated, and optimized by combining systematic sample design with transient absorption spectroscopy, photoelectrochemical and photocatalytic testing, and theoretical development. Specifically, metal semiconductor nanostructures were designed to modulate the plasmon's scattering, hot carrier, and near field interactions as well as remove heating and self-catalysis effects. Transient absorption spectroscopy then revealed how the structure design affected energy and charge carrier transfer between metal and semiconductor. Correlating this data with wavelength-dependent photoconversion efficiencies and theoretical developments regarding metal-semiconductor interactions identified the origin of the plasmonic enhancement. Using this methodology, it has first been proven that three plasmonic enhancement routes are possible: i) increasing light absorption in the semiconductor by light trapping through scattering, ii) transferring hot carriers from metal to semiconductor after light absorption in the metal, and iii) non-radiative excitation of interband transitions in the semiconductor by plasmon-induced resonant energy transfer (PIRET). The effects of the metal on charge transport and carrier recombination were also revealed. Next, it has been shown that the strength and balance of the three enhancement mechanisms is rooted in the plasmon's dephasing time, or how long it takes the collective electron oscillations to stop being collective. The importance of coherent effects in plasmonic enhancement is also shown. Based on these findings, a thermodynamic balance framework has been used to predict the theoretical maximum efficiency of solar energy conversion in plasmonic metal-semiconductor heterojunctions. These calculations have revealed how plasmonics is best used to address the different light absorption problems in semiconductors, and that not taking into account the plasmon's dephasing is the origin of low plasmonic enhancement Finally, to prove these guidelines, each of the three enhancement mechanisms has been translated into optimal device geometries, showing the plasmon's potential for solar energy harvesting. This dissertation identifies the three possible plasmonic enhancement mechanisms for the first time, discovering a new enhancement mechanism (PIRET) in the process. It has also been shown for the first time that the various plasmon-semiconductor interactions could be rooted in the plasmon's dephasing. This has allowed for the first maximum efficiency estimates which have combined all three enhancement mechanisms to be performed, and revealed that changes in the plasmon's dephasing leads to the disparity in reported plasmonic enhancements. These findings are combined to create optimal device design guidelines, which are proven by fabrication of several devices with top efficiencies in plasmonic solar energy conversion. The knowledge obtained will guide the design of efficient photovoltaics and photocatalysts, helping usher in a renewable energy economy and address current needs of climate change.

Two-Photon-Absorption Scheme for Optical Beam Tracking

NASA Technical Reports Server (NTRS)

Ortiz, Gerardo G.; Farr, William H.

2011-01-01

A new optical beam tracking approach for free-space optical communication links using two-photon absorption (TPA) in a high-bandgap detector material was demonstrated. This tracking scheme is part of the canonical architecture described in the preceding article. TPA is used to track a long-wavelength transmit laser while direct absorption on the same sensor simultaneously tracks a shorter-wavelength beacon. The TPA responsivity was measured for silicon using a PIN photodiode at a laser beacon wavelength of 1,550 nm. As expected, the responsivity shows a linear dependence with incident power level. The responsivity slope is 4.5 x 10(exp -7) A/W2. Also, optical beam spots from the 1,550-nm laser beacon were characterized on commercial charge coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) imagers with as little as 13.7 microWatts of optical power (see figure). This new tracker technology offers an innovative solution to reduce system complexity, improve transmit/receive isolation, improve optical efficiency, improve signal-to-noise ratio (SNR), and reduce cost for free-space optical communications transceivers.

Improved charge injection device and a focal plane interface electronics board for stellar tracking

NASA Technical Reports Server (NTRS)

Michon, G. J.; Burke, H. K.

1984-01-01

An improved Charge Injection Device (CID) stellar tracking sensor and an operating sensor in a control/readout electronics board were developed. The sensor consists of a shift register scanned, 256x256 CID array organized for readout of 4x4 subarrays. The 4x4 subarrays can be positioned anywhere within the 256x256 array with a 2 pixel resolution. This allows continuous tracking of a number of stars simultaneously since nine pixels (3x3) centered on any star can always be read out. Organization and operation of this sensor and the improvements in design and semiconductor processing are described. A hermetic package incorporating an internal thermoelectric cooler assembled using low temperature solders was developed. The electronics board, which contains the sensor drivers, amplifiers, sample hold circuits, multiplexer, analog to digital converter, and the sensor temperature control circuits, is also described. Packaged sensors were evaluated for readout efficiency, spectral quantum efficiency, temporal noise, fixed pattern noise, and dark current. Eight sensors along with two tracker electronics boards were completed, evaluated, and delivered.

Dual mode scanner-tracker

NASA Astrophysics Data System (ADS)

Mongeon, R. J.

1984-11-01

The beam of a laser radar is moved over the field of view by means of a pair of scanner/trackers arranged in cascade along the laser beam. One of the scanner/trackers operates at high speed, with high resolution and a wide field and is located in the demagnified portion of the laser beam. The two scanner/trackers complement each other to achieve high speed, high resolution scanning as well as tracking of moving targets. A beam steering telescope for an airborne laser radar which incorporates the novel dual mode scanner/tracker is also shown. The other scanner/tracker operates at low speed with low resolution and a wide field and is located in the magnified portion of the laser beam.

Metal oxide semiconductor thin-film transistors for flexible electronics

NASA Astrophysics Data System (ADS)

Petti, Luisa; Münzenrieder, Niko; Vogt, Christian; Faber, Hendrik; Büthe, Lars; Cantarella, Giuseppe; Bottacchi, Francesca; Anthopoulos, Thomas D.; Tröster, Gerhard

2016-06-01

The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular, the realization of large-area digital circuitry like flexible near field communication tags and analog integrated circuits such as bendable operational amplifiers is presented. The last topic of this review is devoted for emerging flexible electronic systems, from foldable displays, power transmission elements to integrated systems for large-area sensing and data storage and transmission. Finally, the conclusions are drawn and an outlook over the field with a prediction for the future is provided.

Metal oxide semiconductor thin-film transistors for flexible electronics

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

Petti, Luisa; Vogt, Christian; Büthe, Lars

The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This reviewmore » reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular, the realization of large-area digital circuitry like flexible near field communication tags and analog integrated circuits such as bendable operational amplifiers is presented. The last topic of this review is devoted for emerging flexible electronic systems, from foldable displays, power transmission elements to integrated systems for large-area sensing and data storage and transmission. Finally, the conclusions are drawn and an outlook over the field with a prediction for the future is provided.« less

On the Effect of Confinement on the Structure and Properties of Small-Molecular Organic Semiconductors

DOE PAGES

Martín, Jaime; Dyson, Matthew; Reid, Obadiah G.; ...

2017-12-11

Many typical organic optoelectronic devices, such as light-emitting diodes, field-effect transistors, and photovoltaic cells, use an ultrathin active layer where the organic semiconductor is confined within nanoscale dimensions. However, the question of how this spatial constraint impacts the active material is rarely addressed, although it may have a drastic influence on the phase behavior and microstructure of the active layer and hence the final performance. Here, the small-molecule semiconductor p-DTS(FBTTh 2) 2 is used as a model system to illustrate how sensitive this class of material can be to spatial confinement on device-relevant length scales. It is also shown thatmore » this effect can be exploited; it is demonstrated, for instance, that spatial confinement is an efficient tool to direct the crystal orientation and overall texture of p-DTS(FBTTh 2) 2 structures in a controlled manner, allowing for the manipulation of properties including photoluminescence and charge transport characteristics. This insight should be widely applicable as the temperature/confinement phase diagrams established via differential scanning calorimetry and grazing-incidence X-ray diffraction are used to identify specific processing routes that can be directly extrapolated to other functional organic materials, such as polymeric semiconductors, ferroelectrics or high-refractive-index polymers, to induce desired crystal textures or specific (potentially new) polymorphs.« less

On the Effect of Confinement on the Structure and Properties of Small-Molecular Organic Semiconductors

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

Martín, Jaime; Dyson, Matthew; Reid, Obadiah G.

Many typical organic optoelectronic devices, such as light-emitting diodes, field-effect transistors, and photovoltaic cells, use an ultrathin active layer where the organic semiconductor is confined within nanoscale dimensions. However, the question of how this spatial constraint impacts the active material is rarely addressed, although it may have a drastic influence on the phase behavior and microstructure of the active layer and hence the final performance. Here, the small-molecule semiconductor p-DTS(FBTTh 2) 2 is used as a model system to illustrate how sensitive this class of material can be to spatial confinement on device-relevant length scales. It is also shown thatmore » this effect can be exploited; it is demonstrated, for instance, that spatial confinement is an efficient tool to direct the crystal orientation and overall texture of p-DTS(FBTTh 2) 2 structures in a controlled manner, allowing for the manipulation of properties including photoluminescence and charge transport characteristics. This insight should be widely applicable as the temperature/confinement phase diagrams established via differential scanning calorimetry and grazing-incidence X-ray diffraction are used to identify specific processing routes that can be directly extrapolated to other functional organic materials, such as polymeric semiconductors, ferroelectrics or high-refractive-index polymers, to induce desired crystal textures or specific (potentially new) polymorphs.« less

Functionalization of semiconductors for biosensing applications

NASA Astrophysics Data System (ADS)

Estephan, E.; Larroque, C.; Martineau, P.; Cloitre, T.; Gergely, Cs.

2007-05-01

Functionalization of semiconductors (SC) has been widely used for various electronic, photonic and biomedical applications. In this paper, we report on selective functionalization achieved by peptides that reveal specific recognition of the SC surfaces. A M13 bacteriophage library was used to screen 10 10 different 12-mer peptide on various SC substrates to successfully isolate after 3 cycles one specific peptide for the majority of semiconductors. Our results conclude that GaAs(100) and GaN(0001) retain the same sequence of 12-mer peptide, suggesting that the specificity does not depend on the crystallographic structure but it depends on the chemical composition and the electronegativity of the surface, thus on the orientation of the material. We also note the presence of at least one proline (Pro) amino acid in each peptide, and the presence of the histidine (His) in the specific peptides for the II-VI class SC. Pro imprints a constraint to the peptide to facilitate adhesion to the surface, whereas the basic side chain His is known for its affinity towards some of the elements of class II SC. Finally, fluorescence microscopy has been employed to demonstrate the preferential attachment of the peptide to their specific SC surface in close proximity to a surface of different chemical and structural composition. The use of selected peptides expressed by phage display can be extended to encompass a variety of nanostructured semiconductor based devices.

Conjugated polymers/semiconductor nanocrystals hybrid materials--preparation, electrical transport properties and applications.

PubMed

Reiss, Peter; Couderc, Elsa; De Girolamo, Julia; Pron, Adam

2011-02-01

This critical review discusses specific preparation and characterization methods applied to hybrid materials consisting of π-conjugated polymers (or oligomers) and semiconductor nanocrystals. These materials are of great importance in the quickly growing field of hybrid organic/inorganic electronics since they can serve as active components of photovoltaic cells, light emitting diodes, photodetectors and other devices. The electronic energy levels of the organic and inorganic components of the hybrid can be tuned individually and thin hybrid films can be processed using low cost solution based techniques. However, the interface between the hybrid components and the morphology of the hybrid directly influences the generation, separation and transport of charge carriers and those parameters are not easy to control. Therefore a large variety of different approaches for assembling the building blocks--conjugated polymers and semiconductor nanocrystals--has been developed. They range from their simple blending through various grafting procedures to methods exploiting specific non-covalent interactions between both components, induced by their tailor-made functionalization. In the first part of this review, we discuss the preparation of the building blocks (nanocrystals and polymers) and the strategies for their assembly into hybrid materials' thin films. In the second part, we focus on the charge carriers' generation and their transport within the hybrids. Finally, we summarize the performances of solar cells using conjugated polymer/semiconductor nanocrystals hybrids and give perspectives for future developments.

A Novel Performance Evaluation Methodology for Single-Target Trackers.

PubMed

Kristan, Matej; Matas, Jiri; Leonardis, Ales; Vojir, Tomas; Pflugfelder, Roman; Fernandez, Gustavo; Nebehay, Georg; Porikli, Fatih; Cehovin, Luka

2016-11-01

This paper addresses the problem of single-target tracker performance evaluation. We consider the performance measures, the dataset and the evaluation system to be the most important components of tracker evaluation and propose requirements for each of them. The requirements are the basis of a new evaluation methodology that aims at a simple and easily interpretable tracker comparison. The ranking-based methodology addresses tracker equivalence in terms of statistical significance and practical differences. A fully-annotated dataset with per-frame annotations with several visual attributes is introduced. The diversity of its visual properties is maximized in a novel way by clustering a large number of videos according to their visual attributes. This makes it the most sophistically constructed and annotated dataset to date. A multi-platform evaluation system allowing easy integration of third-party trackers is presented as well. The proposed evaluation methodology was tested on the VOT2014 challenge on the new dataset and 38 trackers, making it the largest benchmark to date. Most of the tested trackers are indeed state-of-the-art since they outperform the standard baselines, resulting in a highly-challenging benchmark. An exhaustive analysis of the dataset from the perspective of tracking difficulty is carried out. To facilitate tracker comparison a new performance visualization technique is proposed.

Module Fifteen: Special Topics; Basic Electricity and Electronics Individualized Learning System.

ERIC Educational Resources Information Center

Bureau of Naval Personnel, Washington, DC.

The final module emphasizes utilizing the information learned in modules 1-14 to analyze and evaluate the power supply constructed in Module 0. The module contains the following narrative--power supply evaluation; experiment 1--resistance analysis of the half-wave and semiconductor power supply; experiment 2--voltage analysis of the half-wave and…

Wellbeing in the Making: Peoples' Experiences with Wearable Activity Trackers.

PubMed

Karapanos, Evangelos; Gouveia, Rúben; Hassenzahl, Marc; Forlizzi, Jodi

Wearable activity trackers have become a viable business opportunity. Nevertheless, research has raised concerns over their potentially detrimental effects on wellbeing. For example, a recent study found that while counting steps with a pedometer increased steps taken throughout the day, at the same time it decreased the enjoyment people derived from walking. This poses a serious threat to the incorporation of healthy routines into everyday life. Most studies aim at proving the effectiveness of activity trackers. In contrast, a wellbeing-oriented perspective calls for a deeper understanding of how trackers create and mediate meaningful experiences in everyday life. We present a study of real life experiences with three wearable activity trackers: Fitbit , Jawbone Up and Nike  +  Fuelband . Using need fulfillment as a theoretical lens, we study recent, memorable experiences submitted by 133 users of activity trackers. We reveal a two-dimensional structure of users' experience driven by the needs of physical thriving or relatedness. Our qualitative findings further show a nuanced picture of the adoption of activity trackers and their impact on wellbeing. For instance, while reflection about own exercising practices lost its relevance over time, users continued to wear the tracker to document and collect their runs. More than just supporting behavioral change, we find trackers to provide multiple psychological benefits. For instance, they enhance feelings of autonomy as people gain more control about their exercising regime. Others experience relatedness, when family members purchase a tracker for relatives and join them in their efforts towards a better, healthier self. The study highlights that activity trackers can be more than "tools" to change behavior. Through incorporation in daily life, they offer new social experiences, new ways of boosting our self-esteem and getting closer to our ideal selves.

Light-matter Interactions in Semiconductors and Metals: From Nitride Optoelectronics to Quantum Plasmonics

NASA Astrophysics Data System (ADS)

Narang, Prineha

This thesis puts forth a theory-directed approach coupled with spectroscopy aimed at the discovery and understanding of light-matter interactions in semiconductors and metals. The first part of the thesis presents the discovery and development of Zn-IV nitride materials. The commercial prominence in the optoelectronics industry of tunable semiconductor alloy materials based on nitride semiconductor devices, specifically InGaN, motivates the search for earth-abundant alternatives for use in efficient, high-quality optoelectronic devices. II-IV-N2 compounds, which are closely related to the wurtzite-structured III-N semiconductors, have similar electronic and optical properties to InGaN namely direct band gaps, high quantum efficiencies and large optical absorption coefficients. The choice of different group II and group IV elements provides chemical diversity that can be exploited to tune the structural and electronic properties through the series of alloys. The first theoretical and experimental investigation of the ZnSnxGe1--xN2 series as a replacement for III-nitrides is discussed here. The second half of the thesis shows ab-initio calculations for surface plasmons and plasmonic hot carrier dynamics. Surface plasmons, electromagnetic modes confined to the surface of a conductor-dielectric interface, have sparked renewed interest because of their quantum nature and their broad range of applications. The decay of surface plasmons is usually a detriment in the field of plasmonics, but the possibility to capture the energy normally lost to heat would open new opportunities in photon sensors, energy conversion devices and switching. A theoretical understanding of plasmon-driven hot carrier generation and relaxation dynamics in the ultrafast regime is presented here. Additionally calculations for plasmon-mediated upconversion as well as an energy-dependent transport model for these non-equilibrium carriers are shown. Finally, this thesis gives an outlook on the potential of non-equilibrium phenomena in metals and semiconductors for future light-based technologies.

How Accurate Is Your Activity Tracker? A Comparative Study of Step Counts in Low-Intensity Physical Activities

PubMed Central

2017-01-01

Background As commercially available activity trackers are being utilized in clinical trials, the research community remains uncertain about reliability of the trackers, particularly in studies that involve walking aids and low-intensity activities. While these trackers have been tested for reliability during walking and running activities, there has been limited research on validating them during low-intensity activities and walking with assistive tools. Objective The aim of this study was to (1) determine the accuracy of 3 Fitbit devices (ie, Zip, One, and Flex) at different wearing positions (ie, pants pocket, chest, and wrist) during walking at 3 different speeds, 2.5, 5, and 8 km/h, performed by healthy adults on a treadmill; (2) determine the accuracy of the mentioned trackers worn at different sites during activities of daily living; and (3) examine whether intensity of physical activity (PA) impacts the choice of optimal wearing site of the tracker. Methods We recruited 15 healthy young adults to perform 6 PAs while wearing 3 Fitbit devices (ie, Zip, One, and Flex) on their chest, pants pocket, and wrist. The activities include walking at 2.5, 5, and 8 km/h, pushing a shopping cart, walking with aid of a walker, and eating while sitting. We compared the number of steps counted by each tracker with gold standard numbers. We performed multiple statistical analyses to compute descriptive statistics (ie, ANOVA test), intraclass correlation coefficient (ICC), mean absolute error rate, and correlation by comparing the tracker-recorded data with that of the gold standard. Results All the 3 trackers demonstrated good-to-excellent (ICC>0.75) correlation with the gold standard step counts during treadmill experiments. The correlation was poor (ICC<0.60), and the error rate was significantly higher in walker experiment compared to other activities. There was no significant difference between the trackers and the gold standard in the shopping cart experiment. The wrist worn tracker, Flex, counted several steps when eating (P<.01). The chest tracker was identified as the most promising site to capture steps in more intense activities, while the wrist was the optimal wearing site in less intense activities. Conclusions This feasibility study focused on 6 PAs and demonstrated that Fitbit trackers were most accurate when walking on a treadmill and least accurate during walking with a walking aid and for low-intensity activities. This may suggest excluding participants with assistive devices from studies that focus on PA interventions using commercially available trackers. This study also indicates that the wearing site of the tracker is an important factor impacting the accuracy performance. A larger scale study with a more diverse population, various activity tracker vendors, and a larger activity set are warranted to generalize our results. PMID:28801304

Precision Attitude Determination System (PADS) system design and analysis: Single-axis gimbal star tracker

NASA Technical Reports Server (NTRS)

1974-01-01

The feasibility is evaluated of an evolutionary development for use of a single-axis gimbal star tracker from prior two-axis gimbal star tracker based system applications. Detailed evaluation of the star tracker gimbal encoder is considered. A brief system description is given including the aspects of tracker evolution and encoder evaluation. System analysis includes evaluation of star availability and mounting constraints for the geosynchronous orbit application, and a covariance simulation analysis to evaluate performance potential. Star availability and covariance analysis digital computer programs are included.

Validation of an Electronic System for Recording Medical Student Patient Encounters

PubMed Central

Nkoy, Flory L.; Petersen, Sarah; Matheny Antommaria, Armand H.; Maloney, Christopher G.

2008-01-01

The Liaison Committee for Medical Education requires monitoring of the students’ clinical experiences. Student logs, typically used for this purpose, have a number of limitations. We used an electronic system called Patient Tracker to passively generate student encounter data. The data contained in Patient Tracker was compared to the information reported on student logs and data abstracted from the patients’ charts. Patient Tracker identified 30% more encounters than the student logs. Compared to the student logs, Patient Tracker contained a higher average number of diagnoses per encounter (2.28 vs. 1.03, p<0.01). The diagnostic data contained in Patient Tracker was also more accurate under 4 different definitions of accuracy. Only 1.3% (9/677) of diagnoses in Patient Tracker vs. 16.9% (102/601) diagnoses in the logs could not be validated in patients’ charts (p<0.01). Patient Tracker is a more effective and accurate tool for documenting student clinical encounters than the conventional student logs. PMID:18999155

Pre-service teachers’ approaches to a historical problem in mechanics

NASA Astrophysics Data System (ADS)

Malgieri, Massimiliano; Onorato, Pasquale; Mascheretti, Paolo; De Ambrosis, Anna

2014-09-01

In this paper we report on an activity sequence with a group of 29 pre-service physics teachers based on the reconstruction and analysis of a thought experiment that was crucial for Huygens’ derivation of the formula for the centre of oscillation of a physical pendulum. The sequence starts with student teachers approaching the historical problem and culminates in a guided inquiry activity in a video-based laboratory (VBL) setting using Tracker software. We collected data before, during and after the experimental activity by means of written questions, oral discussions and final reports. These documents provide insights into students’ initial and evolving conceptions, as well as their attitudes towards the activity. The analysis of data allows us to uncover and focus on relevant difficulties for future teachers in mastering the concepts of centre of mass and conservation of energy. Moreover, we find indications that the VBL environment makes a positive contribution by stimulating and improving students’ modelling abilities. In particular, we find a sharp increase in the percentage of students capable of producing coherent explanations and physical analyses for the Huygens’ pendulum system after the Tracker activity.

How Accurate Is Your Activity Tracker? A Comparative Study of Step Counts in Low-Intensity Physical Activities.

PubMed

Alinia, Parastoo; Cain, Chris; Fallahzadeh, Ramin; Shahrokni, Armin; Cook, Diane; Ghasemzadeh, Hassan

2017-08-11

As commercially available activity trackers are being utilized in clinical trials, the research community remains uncertain about reliability of the trackers, particularly in studies that involve walking aids and low-intensity activities. While these trackers have been tested for reliability during walking and running activities, there has been limited research on validating them during low-intensity activities and walking with assistive tools. The aim of this study was to (1) determine the accuracy of 3 Fitbit devices (ie, Zip, One, and Flex) at different wearing positions (ie, pants pocket, chest, and wrist) during walking at 3 different speeds, 2.5, 5, and 8 km/h, performed by healthy adults on a treadmill; (2) determine the accuracy of the mentioned trackers worn at different sites during activities of daily living; and (3) examine whether intensity of physical activity (PA) impacts the choice of optimal wearing site of the tracker. We recruited 15 healthy young adults to perform 6 PAs while wearing 3 Fitbit devices (ie, Zip, One, and Flex) on their chest, pants pocket, and wrist. The activities include walking at 2.5, 5, and 8 km/h, pushing a shopping cart, walking with aid of a walker, and eating while sitting. We compared the number of steps counted by each tracker with gold standard numbers. We performed multiple statistical analyses to compute descriptive statistics (ie, ANOVA test), intraclass correlation coefficient (ICC), mean absolute error rate, and correlation by comparing the tracker-recorded data with that of the gold standard. All the 3 trackers demonstrated good-to-excellent (ICC>0.75) correlation with the gold standard step counts during treadmill experiments. The correlation was poor (ICC<0.60), and the error rate was significantly higher in walker experiment compared to other activities. There was no significant difference between the trackers and the gold standard in the shopping cart experiment. The wrist worn tracker, Flex, counted several steps when eating (P<.01). The chest tracker was identified as the most promising site to capture steps in more intense activities, while the wrist was the optimal wearing site in less intense activities. This feasibility study focused on 6 PAs and demonstrated that Fitbit trackers were most accurate when walking on a treadmill and least accurate during walking with a walking aid and for low-intensity activities. This may suggest excluding participants with assistive devices from studies that focus on PA interventions using commercially available trackers. This study also indicates that the wearing site of the tracker is an important factor impacting the accuracy performance. A larger scale study with a more diverse population, various activity tracker vendors, and a larger activity set are warranted to generalize our results. ©Parastoo Alinia, Chris Cain, Ramin Fallahzadeh, Armin Shahrokni, Diane Cook, Hassan Ghasemzadeh. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 11.08.2017.

An analysis of automatic human detection and tracking

NASA Astrophysics Data System (ADS)

Demuth, Philipe R.; Cosmo, Daniel L.; Ciarelli, Patrick M.

2015-12-01

This paper presents an automatic method to detect and follow people on video streams. This method uses two techniques to determine the initial position of the person at the beginning of the video file: one based on optical flow and the other one based on Histogram of Oriented Gradients (HOG). After defining the initial bounding box, tracking is done using four different trackers: Median Flow tracker, TLD tracker, Mean Shift tracker and a modified version of the Mean Shift tracker using HSV color space. The results of the methods presented in this paper are then compared at the end of the paper.

A multi-hypothesis tracker for clicking whales.

PubMed

Baggenstoss, Paul M

2015-05-01

This paper describes a tracker specially designed to track clicking beaked whales using widely spaced bottom-mounted hydrophones, although it can be adapted to different species and sensors. The input to the tracker is a sequence of static localization solutions obtained using time difference of arrival information at widely spaced hydrophones. To effectively handle input localizations with high ambiguity, the tracker is based on multi-hypothesis tracker concepts, so it considers all potential association hypotheses and keeps a large number of potential tracks in memory. The method is demonstrated on actual data and shown to successfully track multiple beaked whales at depth.

Trusted Silicon Stratus (TSS) Workshop

DTIC Science & Technology

2011-02-01

business case for a proposed Infrastructure-as-a- Service (IaaS)/ Software -as-a- Service ( SaaS ) cloud architecture. User desires for innovative pricing and...Public Physically Unclonable Function PUF Physically Unclonable Function SaaS Software -as-a- Service SIP Semiconductor Intellectual Property SNL...WORKSHOP NIMBIS SERVICES INCORPORATED FEBRUARY 2011 FINAL TECHNICAL REPORT  ROME, NY 13441 UNITED STATES AIR FORCE  AIR FORCE

Modifying the Interface Edge to Control the Electrical Transport Properties of Nanocontacts to Nanowires.

PubMed

Lord, Alex M; Ramasse, Quentin M; Kepaptsoglou, Despoina M; Evans, Jonathan E; Davies, Philip R; Ward, Michael B; Wilks, Steve P

2017-02-08

Selecting the electrical properties of nanomaterials is essential if their potential as manufacturable devices is to be reached. Here, we show that the addition or removal of native semiconductor material at the edge of a nanocontact can be used to determine the electrical transport properties of metal-nanowire interfaces. While the transport properties of as-grown Au nanocatalyst contacts to semiconductor nanowires are well-studied, there are few techniques that have been explored to modify the electrical behavior. In this work, we use an iterative analytical process that directly correlates multiprobe transport measurements with subsequent aberration-corrected scanning transmission electron microscopy to study the effects of chemical processes that create structural changes at the contact interface edge. A strong metal-support interaction that encapsulates the Au nanocontacts over time, adding ZnO material to the edge region, gives rise to ohmic transport behavior due to the enhanced quantum-mechanical tunneling path. Removal of the extraneous material at the Au-nanowire interface eliminates the edge-tunneling path, producing a range of transport behavior that is dependent on the final interface quality. These results demonstrate chemically driven processes that can be factored into nanowire-device design to select the final properties.

Correlation tracking study for meter-class solar telescope on space shuttle. [solar granulation

NASA Technical Reports Server (NTRS)

Smithson, R. C.; Tarbell, T. D.

1977-01-01

The theory and expected performance level of correlation trackers used to control the pointing of a solar telescope in space using white light granulation as a target were studied. Three specific trackers were modeled and their performance levels predicted for telescopes of various apertures. The performance of the computer model trackers on computer enhanced granulation photographs was evaluated. Parametric equations for predicting tracker performance are presented.

In-flight evaluation of an optical head motion tracker III

NASA Astrophysics Data System (ADS)

Tawada, Kazuho; Okamoto, Masakazu

2011-06-01

We have presented a new approach for Optical HMT (Head Motion Tracker) past years [1]-[4]. In existing Magnetic HMT, it is inevitable to conduct pre-mapping in order to obtain sufficient accuracy because of magnetic field's distortion caused by metallic material around HMT, such as cockpit and helmet. Optical HMT is commonly known as mapping-free tracker; however, it has some disadvantages on accuracy, stability against sunlight conditions, in terms of comparison with Magnetic HMT. We had succeeded to develop new HMT system, which can overcome particular disadvantages by integration with two area cameras, optical markers, image processing techniques and inertial sensors with simple algorithm in laboratory level environment (2008). We have also reported some experimental results conducted in flight test, which proved good accuracy even in the sunlight condition (2009). We have also reported some experimental results conducted in flight test, which proved good performance even in the night flight (2010). Shimadzu Corp. and JAXA (Japan Aerospace Exploration Agency) are conducting joint research named SAVERH (Situation Awareness and Visual Enhancer for Rescue Helicopter) [2]-[4] that aims at inventing method of presenting suitable information to the pilot to support search and rescue missions by helicopters. The HMT system has been evaluated through a series of flight evaluation in SAVERH and demonstrated the operation concept. In this report, we show result of the final evaluation of the HMD system through 12 flights including night flight. Also, those evaluation was done by integrated HMT system that was newly developed for the tests in this year.

Optimization of detectors for the ILC

NASA Astrophysics Data System (ADS)

Suehara, Taikan; ILD Group; SID Group

2016-04-01

International Linear Collider (ILC) is a next-generation e+e- linear collider to explore Higgs, Beyond-Standard-Models, top and electroweak particles with great precision. We are optimizing our two detectors, International Large Detector (ILD) and Silicon Detector (SiD) to maximize the physics reach expected in ILC with reasonable detector cost and good reliability. The optimization study on vertex detectors, main trackers and calorimeters is underway. We aim to conclude the optimization to establish final designs in a few years, to finish detector TDR and proposal in reply to expected ;green sign; of the ILC project.

Evidence of Coherent K+ Meson Production in Neutrino-Nucleus Scattering

NASA Astrophysics Data System (ADS)

Wang, Z.; Marshall, C. M.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; da Motta, H.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Endress, E.; Felix, J.; Fields, L.; Fine, R.; Galindo, R.; Gallagher, H.; Ghosh, A.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Hurtado, K.; Kiveni, M.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Martinez Caicedo, D. A.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Paolone, V.; Park, J.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ransome, R. D.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Schmitz, D. W.; Simon, C.; Solano Salinas, C. J.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Wospakrik, M.; Zavala, G.; Zhang, D.; Minerva Collaboration

2016-08-01

Neutrino-induced charged-current coherent kaon production νμA →μ-K+A is a rare, inelastic electroweak process that brings a K+ on shell and leaves the target nucleus intact in its ground state. This process is significantly lower in rate than the neutrino-induced charged-current coherent pion production because of Cabibbo suppression and a kinematic suppression due to the larger kaon mass. We search for such events in the scintillator tracker of MINERvA by observing the final state K+, μ-, and no other detector activity, and by using the kinematics of the final state particles to reconstruct the small momentum transfer to the nucleus, which is a model-independent characteristic of coherent scattering. We find the first experimental evidence for the process at 3 σ significance.

Measurement of Muon Neutrino Quasielastic Scattering on a Hydrocarbon Target at E ν~3.5 GeV

DOE PAGES

Fiorentini, G. A.; Schmitz, D. W.; Rodrigues, P. A.; ...

2013-07-11

We report a study of ν μ charged-current quasielastic events in the segmented scintillator inner tracker of the MINERvA experiment running in the NuMI neutrino beam at Fermilab. The events were selected by requiring a μ⁻ and low calorimetric recoil energy separated from the interaction vertex. We measure the flux-averaged differential cross section, dσ/dQ², and study the low energy particle content of the final state. Deviations are found between the measured dσ/dQ² and the expectations of a model of independent nucleons in a relativistic Fermi gas. We also observe an excess of energy near the vertex consistent with multiple protonsmore » in the final state.« less

Technology transfer: Imaging tracker to robotic controller

NASA Technical Reports Server (NTRS)

Otaguro, M. S.; Kesler, L. O.; Land, Ken; Erwin, Harry; Rhoades, Don

1988-01-01

The transformation of an imaging tracker to a robotic controller is described. A multimode tracker was developed for fire and forget missile systems. The tracker locks on to target images within an acquisition window using multiple image tracking algorithms to provide guidance commands to missile control systems. This basic tracker technology is used with the addition of a ranging algorithm based on sizing a cooperative target to perform autonomous guidance and control of a platform for an Advanced Development Project on automation and robotics. A ranging tracker is required to provide the positioning necessary for robotic control. A simple functional demonstration of the feasibility of this approach was performed and described. More realistic demonstrations are under way at NASA-JSC. In particular, this modified tracker, or robotic controller, will be used to autonomously guide the Man Maneuvering Unit (MMU) to targets such as disabled astronauts or tools as part of the EVA Retriever efforts. It will also be used to control the orbiter's Remote Manipulator Systems (RMS) in autonomous approach and positioning demonstrations. These efforts will also be discussed.

Software and mathematical support of Kazakhstani star tracker

NASA Astrophysics Data System (ADS)

Akhmedov, D.; Yelubayev, S.; Ten, V.; Bopeyev, T.; Alipbayev, K.; Sukhenko, A.

2016-10-01

Currently the specialists of Kazakhstan have been developing the star tracker that is further planned to use on Kazakhstani satellites of various purposes. At the first stage it has been developed the experimental model of star tracker that has following characteristics: field of view 20°, update frequency 2 Hz, exclusion angle 40°, accuracy of attitude determination of optical axis/around optical axis 15/50 arcsec. Software and mathematical support are the most high technology parts of star tracker. The results of software and mathematical support development of experimental model of Kazakhstani star tracker are represented in this article. In particular, there are described the main mathematical models and algorithms that have been used as a basis for program units of preliminary image processing of starry sky, stars identification and star tracker attitude determination. The results of software and mathematical support testing with the help of program simulation complex using various configurations of defects including image sensor noises, point spread function modeling, optical system distortion up to 2% are presented. Analysis of testing results has shown that accuracy of attitude determination of star tracker is within the permissible range

Breadboard stellar tracker system test report, volume 1

NASA Technical Reports Server (NTRS)

Kollodge, J. C.; Hubbard, M. W.; Jain, S.; Schons, C. A.

1981-01-01

The performance of a star tracker equipped with a focal plane detector was evaluated. The CID board is an array of 256 x 256 pixels which are 20 x 20 micrometers in dimension. The tracker used for test was a breadboard tracker system developed by BASD. Unique acquisition and tracking algorithms are employed to enhance performance. A pattern recognition process is used to test for proper image spread function and to avoid false acquisition on noise. A very linear, high gain, interpixel transfer function is derived for interpolating star position. The lens used in the tracker has an EFL of 100 mm. The tracker has an FOV of 2.93 degrees resulting in a pixel angular subtense of 41.253 arc sec in each axis. The test procedure used for the program presented a star to the tracker in a circular pattern of positions; the pattern was formed by projecting a simulated star through a rotatable deviation wedge. Further tests determined readout noise, Noise Equivalent Displacement during track, and spatial noise during acquisition by taking related data and reducing it.

Optical System Error Analysis and Calibration Method of High-Accuracy Star Trackers

PubMed Central

Sun, Ting; Xing, Fei; You, Zheng

2013-01-01

The star tracker is a high-accuracy attitude measurement device widely used in spacecraft. Its performance depends largely on the precision of the optical system parameters. Therefore, the analysis of the optical system parameter errors and a precise calibration model are crucial to the accuracy of the star tracker. Research in this field is relatively lacking a systematic and universal analysis up to now. This paper proposes in detail an approach for the synthetic error analysis of the star tracker, without the complicated theoretical derivation. This approach can determine the error propagation relationship of the star tracker, and can build intuitively and systematically an error model. The analysis results can be used as a foundation and a guide for the optical design, calibration, and compensation of the star tracker. A calibration experiment is designed and conducted. Excellent calibration results are achieved based on the calibration model. To summarize, the error analysis approach and the calibration method are proved to be adequate and precise, and could provide an important guarantee for the design, manufacture, and measurement of high-accuracy star trackers. PMID:23567527

Recovery of hazardous semiconductor-industry sludge as a useful resource.

PubMed

Lee, Tzen-Chin; Liu, Feng-Jiin

2009-06-15

Sludge, a solid waste recovered from wastewater of semiconductor-industries composes of agglomerates of nano-particles like SiO(2) and CaF(2). This sludge deflocculates in acidic and alkaline aqueous solutions into nano-particles smaller than 100 nm. Thus, this sludge is potentially hazardous to water resources when improperly dumped. It can cause considerable air-pollution when fed into rotary-kilns as a raw material for cement production. In this study, dried and pulverized sludge was used to replace 5-20 wt.% Portland cement in cement mortar. The compressive strength of the modified mortar was higher than that of plain cement mortar after curing for 3 days and more. In particular, the strength of mortar with 10 wt.% substitution improved by 25-35% after curing for 7-90 days. TCLP studies reveal no detectable release of heavy metals. Preliminary studies showed that nano-particles deflocculated from the sludge, when cured for up to 3 days retain in the modified mortar their nano-size, which become large-sized hydration compounds that contribute to the final mortar strength. Semiconductor sludge can thus be utilized as a useful resource to replace portion of cement in cement mortar, thereby avoiding their potential hazard on the environment.

Liquid phase epitaxy of binary III–V nanocrystals in thin Si layers triggered by ion implantation and flash lamp annealing

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

Wutzler, Rene, E-mail: r.wutzler@hzdr.de; Rebohle, Lars; Prucnal, Slawomir

2015-05-07

The integration of III–V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III–V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO{sub 2}/Si/SiO{sub 2} layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of themore » III–V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.« less

Schottky-barrier-free contacts with two-dimensional semiconductors by surface-engineered MXenes

DOE PAGES

Liu, Yuanyue; Xiao, Hai; Goddard, III, William A.

2016-11-22

Two-dimensional (2D) metal carbides and nitrides, called MXenes, have attracted great interest for applications such as energy storage. Here we demonstrate their potential as Schottky-barrier-free metal contacts to 2D semiconductors, providing a solution to the contact-resistance problem in 2D electronics. Based on first principles calculations, we find that the surface chemistry strongly affects the Fermi level of MXenes: O termination always increases the work function with respect to that of bare surface, OH always decreases it, while F exhibits either trend depending on the specific material. This phenomenon originates from the effect of surface dipoles, which together with the weakmore » Fermi level pinning, enable Schottky-barrier-free hole (or electron) injection into 2D semiconductors through van der Waals junctions with some of the O-terminated (or all the OH-terminated) MXenes. Furthermore, we suggest synthetic routes to control the surface terminations based on the calculated formation energies. Finally, this study enhances the understanding of the correlation between surface chemistry and electronic/transport properties of 2D materials, and also gives practical predictions for improving 2D electronics.« less

Optical bandgap of single- and multi-layered amorphous germanium ultra-thin films

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

Liu, Pei; Zaslavsky, Alexander; Longo, Paolo

2016-01-07

Accurate optical methods are required to determine the energy bandgap of amorphous semiconductors and elucidate the role of quantum confinement in nanometer-scale, ultra-thin absorbing layers. Here, we provide a critical comparison between well-established methods that are generally employed to determine the optical bandgap of thin-film amorphous semiconductors, starting from normal-incidence reflectance and transmittance measurements. First, we demonstrate that a more accurate estimate of the optical bandgap can be achieved by using a multiple-reflection interference model. We show that this model generates more reliable results compared to the widely accepted single-pass absorption method. Second, we compare two most representative methods (Taucmore » and Cody plots) that are extensively used to determine the optical bandgap of thin-film amorphous semiconductors starting from the extracted absorption coefficient. Analysis of the experimental absorption data acquired for ultra-thin amorphous germanium (a-Ge) layers demonstrates that the Cody model is able to provide a less ambiguous energy bandgap value. Finally, we apply our proposed method to experimentally determine the optical bandgap of a-Ge/SiO{sub 2} superlattices with single and multiple a-Ge layers down to 2 nm thickness.« less

Electronic Structure, Surface Doping, and Optical Response in Epitaxial WSe2 Thin Films.

PubMed

Zhang, Yi; Ugeda, Miguel M; Jin, Chenhao; Shi, Su-Fei; Bradley, Aaron J; Martín-Recio, Ana; Ryu, Hyejin; Kim, Jonghwan; Tang, Shujie; Kim, Yeongkwan; Zhou, Bo; Hwang, Choongyu; Chen, Yulin; Wang, Feng; Crommie, Michael F; Hussain, Zahid; Shen, Zhi-Xun; Mo, Sung-Kwan

2016-04-13

High quality WSe2 films have been grown on bilayer graphene (BLG) with layer-by-layer control of thickness using molecular beam epitaxy. The combination of angle-resolved photoemission, scanning tunneling microscopy/spectroscopy, and optical absorption measurements reveal the atomic and electronic structures evolution and optical response of WSe2/BLG. We observe that a bilayer of WSe2 is a direct bandgap semiconductor, when integrated in a BLG-based heterostructure, thus shifting the direct-indirect band gap crossover to trilayer WSe2. In the monolayer limit, WSe2 shows a spin-splitting of 475 meV in the valence band at the K point, the largest value observed among all the MX2 (M = Mo, W; X = S, Se) materials. The exciton binding energy of monolayer-WSe2/BLG is found to be 0.21 eV, a value that is orders of magnitude larger than that of conventional three-dimensional semiconductors, yet small as compared to other two-dimensional transition metal dichalcogennides (TMDCs) semiconductors. Finally, our finding regarding the overall modification of the electronic structure by an alkali metal surface electron doping opens a route to further control the electronic properties of TMDCs.

n-Channel semiconductor materials design for organic complementary circuits.

PubMed

Usta, Hakan; Facchetti, Antonio; Marks, Tobin J

2011-07-19

Organic semiconductors have unique properties compared to traditional inorganic materials such as amorphous or crystalline silicon. Some important advantages include their adaptability to low-temperature processing on flexible substrates, low cost, amenability to high-speed fabrication, and tunable electronic properties. These features are essential for a variety of next-generation electronic products, including low-power flexible displays, inexpensive radio frequency identification (RFID) tags, and printable sensors, among many other applications. Accordingly, the preparation of new materials based on π-conjugated organic molecules or polymers has been a central scientific and technological research focus over the past decade. Currently, p-channel (hole-transporting) materials are the leading class of organic semiconductors. In contrast, high-performance n-channel (electron-transporting) semiconductors are relatively rare, but they are of great significance for the development of plastic electronic devices such as organic field-effect transistors (OFETs). In this Account, we highlight the advances our team has made toward realizing moderately and highly electron-deficient n-channel oligomers and polymers based on oligothiophene, arylenediimide, and (bis)indenofluorene skeletons. We have synthesized and characterized a "library" of structurally related semiconductors, and we have investigated detailed structure-property relationships through optical, electrochemical, thermal, microstructural (both single-crystal and thin-film), and electrical measurements. Our results reveal highly informative correlations between structural parameters at various length scales and charge transport properties. We first discuss oligothiophenes functionalized with perfluoroalkyl and perfluoroarene substituents, which represent the initial examples of high-performance n-channel semiconductors developed in this project. The OFET characteristics of these compounds are presented with an emphasis on structure-property relationships. We then examine the synthesis and properties of carbonyl-functionalized oligomers, which constitute second-generation n-channel oligothiophenes, in both vacuum- and solution-processed FETs. These materials have high carrier mobilities and good air stability. In parallel, exceptionally electron-deficient cyano-functionalized arylenediimide derivatives are discussed as early examples of thermodynamically air-stable, high-performance n-channel semiconductors; they exhibit record electron mobilities of up to 0.64 cm(2)/V·s. Furthermore, we provide an overview of highly soluble ladder-type macromolecular semiconductors as OFET components, which combine ambient stability with solution processibility. A high electron mobility of 0.16 cm(2)/V·s is obtained under ambient conditions for solution-processed films. Finally, examples of polymeric n-channel semiconductors with electron mobilities as high as 0.85 cm(2)/V·s are discussed; these constitute an important advance toward fully printed polymeric electronic circuitry. Density functional theory (DFT) computations reveal important trends in molecular physicochemical and semiconducting properties, which, when combined with experimental data, shed new light on molecular charge transport characteristics. Our data provide the basis for a fundamental understanding of charge transport in high-performance n-channel organic semiconductors. Moreover, our results provide a road map for developing functional, complementary organic circuitry, which requires combining p- and n-channel transistors.

A protocol for evaluating video trackers under real-world conditions.

PubMed

Nawaz, Tahir; Cavallaro, Andrea

2013-04-01

The absence of a commonly adopted performance evaluation framework is hampering advances in the design of effective video trackers. In this paper, we present a single-score evaluation measure and a protocol to objectively compare trackers. The proposed measure evaluates tracking accuracy and failure, and combines them for both summative and formative performance assessment. The proposed protocol is composed of a set of trials that evaluate the robustness of trackers on a range of test scenarios representing several real-world conditions. The protocol is validated on a set of sequences with a diversity of targets (head, vehicle and person) and challenges (occlusions, background clutter, pose changes and scale changes) using six state-of-the-art trackers, highlighting their strengths and weaknesses on more than 187000 frames. The software implementing the protocol and the evaluation results are made available online and new results can be included, thus facilitating the comparison of trackers.

Determinants for Sustained Use of an Activity Tracker: Observational Study

PubMed Central

Moons, Jonas; Kerkhof, Peter; Wiekens, Carina; De Groot, Martijn

2017-01-01

Background A lack of physical activity is considered to cause 6% of deaths globally. Feedback from wearables such as activity trackers has the potential to encourage daily physical activity. To date, little research is available on the natural development of adherence to activity trackers or on potential factors that predict which users manage to keep using their activity tracker during the first year (and thereby increasing the chance of healthy behavior change) and which users discontinue using their trackers after a short time. Objective The aim of this study was to identify the determinants for sustained use in the first year after purchase. Specifically, we look at the relative importance of demographic and socioeconomic, psychological, health-related, goal-related, technological, user experience–related, and social predictors of feedback device use. Furthermore, this study tests the effect of these predictors on physical activity. Methods A total of 711 participants from four urban areas in France received an activity tracker (Fitbit Zip) and gave permission to use their logged data. Participants filled out three Web-based questionnaires: at start, after 98 days, and after 232 days to measure the aforementioned determinants. Furthermore, for each participant, we collected activity data tracked by their Fitbit tracker for 320 days. We determined the relative importance of all included predictors by using Random Forest, a machine learning analysis technique. Results The data showed a slow exponential decay in Fitbit use, with 73.9% (526/711) of participants still tracking after 100 days and 16.0% (114/711) of participants tracking after 320 days. On average, participants used the tracker for 129 days. Most important reasons to quit tracking were technical issues such as empty batteries and broken trackers or lost trackers (21.5% of all Q3 respondents, 130/601). Random Forest analysis of predictors revealed that the most influential determinants were age, user experience–related factors, mobile phone type, household type, perceived effect of the Fitbit tracker, and goal-related factors. We explore the role of those predictors that show meaningful differences in the number of days the tracker was worn. Conclusions This study offers an overview of the natural development of the use of an activity tracker, as well as the relative importance of a range of determinants from literature. Decay is exponential but slower than may be expected from existing literature. Many factors have a small contribution to sustained use. The most important determinants are technical condition, age, user experience, and goal-related factors. This finding suggests that activity tracking is potentially beneficial for a broad range of target groups, but more attention should be paid to technical and user experience–related aspects of activity trackers. PMID:29084709

Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

PubMed Central

Gu, Haoshuang; Wang, Zhao; Hu, Yongming

2012-01-01

Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors. PMID:22778599

Electronic structure of the organic semiconductor Alq3 (aluminum tris-8-hydroxyquinoline) from soft x-ray spectroscopies and density functional theory calculations.

PubMed

DeMasi, A; Piper, L F J; Zhang, Y; Reid, I; Wang, S; Smith, K E; Downes, J E; Peltekis, N; McGuinness, C; Matsuura, A

2008-12-14

The element-specific electronic structure of the organic semiconductor aluminum tris-8-hydroxyquinoline (Alq(3)) has been studied using a combination of resonant x-ray emission spectroscopy, x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and density functional theory (DFT) calculations. Resonant and nonresonant x-ray emission spectroscopy were used to measure directly the carbon, nitrogen and oxygen 2p partial densities of states in Alq(3), and good agreement was found with the results of DFT calculations. Furthermore, resonant x-ray emission at the carbon K-edge is shown to be able to measure the partial density of states associated with individual C sites. Finally, comparison of previous x-ray emission studies and the present data reveal the presence of clear photon-induced damage in the former.

Semiconductor adiabatic qubits

DOEpatents

Carroll, Malcolm S.; Witzel, Wayne; Jacobson, Noah Tobias; Ganti, Anand; Landahl, Andrew J.; Lilly, Michael; Nguyen, Khoi Thi; Bishop, Nathaniel; Carr, Stephen M.; Bussmann, Ezra; Nielsen, Erik; Levy, James Ewers; Blume-Kohout, Robin J.; Rahman, Rajib

2016-12-27

A quantum computing device that includes a plurality of semiconductor adiabatic qubits is described herein. The qubits are programmed with local biases and coupling terms between qubits that represent a problem of interest. The qubits are initialized by way of a tuneable parameter, a local tunnel coupling within each qubit, such that the qubits remain in a ground energy state, and that initial state is represented by the qubits being in a superposition of |0> and |1> states. The parameter is altered over time adiabatically or such that relaxation mechanisms maintain a large fraction of ground state occupation through decreasing the tunnel coupling barrier within each qubit with the appropriate schedule. The final state when tunnel coupling is effectively zero represents the solution state to the problem represented in the |0> and |1> basis, which can be accurately read at each qubit location.

Radio-frequency measurement in semiconductor quantum computation

NASA Astrophysics Data System (ADS)

Han, TianYi; Chen, MingBo; Cao, Gang; Li, HaiOu; Xiao, Ming; Guo, GuoPing

2017-05-01

Semiconductor quantum dots have attracted wide interest for the potential realization of quantum computation. To realize efficient quantum computation, fast manipulation and the corresponding readout are necessary. In the past few decades, considerable progress of quantum manipulation has been achieved experimentally. To meet the requirements of high-speed readout, radio-frequency (RF) measurement has been developed in recent years, such as RF-QPC (radio-frequency quantum point contact) and RF-DGS (radio-frequency dispersive gate sensor). Here we specifically demonstrate the principle of the radio-frequency reflectometry, then review the development and applications of RF measurement, which provides a feasible way to achieve high-bandwidth readout in quantum coherent control and also enriches the methods to study these artificial mesoscopic quantum systems. Finally, we prospect the future usage of radio-frequency reflectometry in scaling-up of the quantum computing models.

Particulate photocatalysts for overall water splitting

NASA Astrophysics Data System (ADS)

Chen, Shanshan; Takata, Tsuyoshi; Domen, Kazunari

2017-10-01

The conversion of solar energy to chemical energy is a promising way of generating renewable energy. Hydrogen production by means of water splitting over semiconductor photocatalysts is a simple, cost-effective approach to large-scale solar hydrogen synthesis. Since the discovery of the Honda-Fujishima effect, considerable progress has been made in this field, and numerous photocatalytic materials and water-splitting systems have been developed. In this Review, we summarize existing water-splitting systems based on particulate photocatalysts, focusing on the main components: light-harvesting semiconductors and co-catalysts. The essential design principles of the materials employed for overall water-splitting systems based on one-step and two-step photoexcitation are also discussed, concentrating on three elementary processes: photoabsorption, charge transfer and surface catalytic reactions. Finally, we outline challenges and potential advances associated with solar water splitting by particulate photocatalysts for future commercial applications.

Transport and release of colloidal 3-mercaptopropionic acid-coated CdSe–CdS/ZnS core-multishell quantum dots in human umbilical vein endothelial cells

PubMed Central

Fontana, Jacopo M; Yin, Huijuan; Chen, Yun; Florez, Ricardo; Brismar, Hjalmar; Fu, Ying

2017-01-01

Colloidal semiconductor quantum dots (QDs) have been extensively researched and developed for biomedical applications, including drug delivery and biosensing assays. Hence, it is pivotal to understand their behavior in terms of intracellular transport and toxicological effects. In this study, we focused on 3-mercaptopropionic acid-coated CdSe-CdS/ZnS core-multishell quantum dots (3MPA-QDs) converted from the as-grown octadecylamine-coated quantum dots (ODA-QDs) and their direct and dynamic interactions with human umbilical vein endothelial cells (HUVECs). Live cell imaging using confocal fluorescence microscopy showed that 3MPA-QDs first attached to and subsequently aggregated on HUVEC plasma membrane ~25 min after QD deposition. The aggregated QDs started being internalized at ~2 h and reached their highest internalization degree at ~24 h. They were released from HUVECs after ~48 h. During the 48 h period, the HUVECs responded normally to external stimulations, grew, proliferated and wound healed without any perceptible apoptosis. Furthermore, 1) 3MPA-QDs were internalized in newly formed LysoTracker-stained early endosomes; 2) adenosine 5′-triphosphate-induced [Ca2+]i modulation caused a transient decrease in the fluorescence of 3MPA-QDs that were attached to the plasma membrane but a transient increase in the internalized 3MPA-QDs; and 3) fluorescence signal modulations of co-stained LysoTracker and QDs induced by the lysosomotropic agent Gly-Phe-β-naphthylamide were spatially co-localized and temporally synchronized. Our findings suggest that 3MPA-QDs converted from ODA-QDs are a potential nontoxic fluorescent probe for future use in clinical applications. Moreover, the photophysical strategy and techniques reported in this work are easily applicable to study of direct interactions between other nanoparticles and live cells; contributing to awareness and implementation of the safe applications of nanoparticles. PMID:29270011

Transport and release of colloidal 3-mercaptopropionic acid-coated CdSe-CdS/ZnS core-multishell quantum dots in human umbilical vein endothelial cells.

PubMed

Fontana, Jacopo M; Yin, Huijuan; Chen, Yun; Florez, Ricardo; Brismar, Hjalmar; Fu, Ying

2017-01-01

Colloidal semiconductor quantum dots (QDs) have been extensively researched and developed for biomedical applications, including drug delivery and biosensing assays. Hence, it is pivotal to understand their behavior in terms of intracellular transport and toxicological effects. In this study, we focused on 3-mercaptopropionic acid-coated CdSe-CdS/ZnS core-multishell quantum dots (3MPA-QDs) converted from the as-grown octadecylamine-coated quantum dots (ODA-QDs) and their direct and dynamic interactions with human umbilical vein endothelial cells (HUVECs). Live cell imaging using confocal fluorescence microscopy showed that 3MPA-QDs first attached to and subsequently aggregated on HUVEC plasma membrane ~25 min after QD deposition. The aggregated QDs started being internalized at ~2 h and reached their highest internalization degree at ~24 h. They were released from HUVECs after ~48 h. During the 48 h period, the HUVECs responded normally to external stimulations, grew, proliferated and wound healed without any perceptible apoptosis. Furthermore, 1) 3MPA-QDs were internalized in newly formed LysoTracker-stained early endosomes; 2) adenosine 5'-triphosphate-induced [Ca 2+ ] i modulation caused a transient decrease in the fluorescence of 3MPA-QDs that were attached to the plasma membrane but a transient increase in the internalized 3MPA-QDs; and 3) fluorescence signal modulations of co-stained LysoTracker and QDs induced by the lysosomotropic agent Gly-Phe-β-naphthylamide were spatially co-localized and temporally synchronized. Our findings suggest that 3MPA-QDs converted from ODA-QDs are a potential nontoxic fluorescent probe for future use in clinical applications. Moreover, the photophysical strategy and techniques reported in this work are easily applicable to study of direct interactions between other nanoparticles and live cells; contributing to awareness and implementation of the safe applications of nanoparticles.

Optical Alignment of the Global Precipitation Measurement (GPM) Star Trackers

NASA Technical Reports Server (NTRS)

Hetherington, Samuel; Osgood, Dean; McMann, Joe; Roberts, Viki; Gill, James; Mclean, Kyle

2013-01-01

The optical alignment of the star trackers on the Global Precipitation Measurement (GPM) core spacecraft at NASA Goddard Space Flight Center (GSFC) was challenging due to the layout and structural design of the GPM Lower Bus Structure (LBS) in which the star trackers are mounted as well as the presence of the star tracker shades that blocked line-of-sight to the primary star tracker optical references. The initial solution was to negotiate minor changes in the original LBS design to allow for the installation of a removable item of ground support equipment (GSE) that could be installed whenever measurements of the star tracker optical references were needed. However, this GSE could only be used to measure secondary optical reference cube faces not used by the star tracker vendor to obtain the relationship information and matrix transformations necessary to determine star tracker alignment. Unfortunately, due to unexpectedly large orthogonality errors between the measured secondary adjacent cube faces and the lack of cube calibration data, we required a method that could be used to measure the same reference cube faces as originally measured by the vendor. We describe an alternative technique to theodolite auto-collimation for measurement of an optical reference mirror pointing direction when normal incidence measurements are not possible. This technique was used to successfully align the GPM star trackers and has been used on a number of other NASA flight projects. We also discuss alignment theory as well as a GSFC-developed theodolite data analysis package used to analyze angular metrology data.

Elliptically framed tip-tilt mirror optimized for stellar tracking

NASA Astrophysics Data System (ADS)

Clark, James H.; Penado, F. E.; Petak, Jeremy

2015-09-01

We compare a design innovation of an elliptically framed tip-tilt optical tracker with an existing circularly framed tracker for the Navy Precision Optical Interferometer. The tracker stabilizes a 12.5 cm stellar beam on a target hundreds of meters away and requires an increase in operational frequency. We reduced mass and size by integrating an elliptical mirror as one of the rotating components, which eliminated a rotating frame. We used the same materials as the existing tracker; however, light-weighted both the aluminum frame and Zerodur® mirror. We generated a computer-aided design model, converted it into a finite element model and performed modal analysis on two load cases. In load case 1, we tied down three points on the bottom surface of the tracker corresponding to the tie-down points of the comparison tracker. This reveals a first mode (lowest) frequency of 140 Hz, a factor of two over the baseline tracker's first mode frequency of 67 Hz. In load case 2, we constrained four additional points inboard of the corners of the tracker base, for a total of seven tie-downs, simulating a firmly bolted and secured mount. The first mode of vibration for this case is 211 Hz, an increase over load case 1 by a factor of 1.5 and more than three times the fundamental frequency of the existing tracker. We conclude that these geometrical changes with the additional tie-down bolts are a viable solution path forward to improve steering speed and recommend a continuation with this effort.

PREFACE: Proceedings of the First Workshop of the EU RT Network `Photon-Mediated Phenomena in Semiconductor Nanostructures' (Gregynog, Wales, UK, 28--31 March 2003)

NASA Astrophysics Data System (ADS)

Ivanov, Alexei L.

2004-09-01

The EU Research Training Network `Photon-Mediated Phenomena in Semiconductor Nanostructures' (HPRN-CT-2002-00298) comprises seven teams from across Europe: Cambridge, Cardiff, Dortmund, Heraklion, Grenoble, Lund and Paderborn (for details see the Network website http://www.astro.cardiff.ac.uk/research/PMPnetwork/index.html). The first workshop of the Network was held at Gregynog Hall, a conference centre in the beautiful countryside of mid-Wales. There were 44 participants who attended the meeting (7 from France, 2 from Japan, 3 from Germany, 1 from Greece, 2 from Russia, 3 from Sweden, 23 from UK and 3 from USA). Of these, 57% were students and young postdoctoral research associates. The talks presented at the meeting were mainly devoted to linear and nonlinear optics of semiconductor nanostructures. Thus the review and research papers included in this special issue of Journal of Physics: Condensed Matter deal with the exciton-mediated optical phenomena in semiconductor quantum wires, quantum wells, planar and spherical microcavities and self-assembled quantum dots. The specific topics covered by the proceedings are exciton-mediated optics, including lasing, of semiconductor quantum wires Bose-Einstein condensation of excitons and microcavity polaritons diffusion, thermalization and photoluminescence of free carriers and excitons in GaAs coupled quantum wells polaritons in semiconductor microcavities exciton-mediated optics of semiconductor photonic dots optical nonlinearities of biexciton waves optics of self-assembled quantum dots photosensitive metal oxides films On the first day of the workshop, a special session on presentation skills, lead by Mike Edmunds, was organized for the young researchers. The meeting concluded with a round-table discussion at which key questions on research, organization and management of the Network were identified and discussed. The second workshop of the Network, organized and chaired by George Kiriakidis, took place at Hersonissos (Crete, Greece) in October 2003. The forthcoming third workshop, organized by Detlef Schikora and Ulrike Woggon, will be held in Paderborn (conference part) and Dortmund (training part) from 4 October 4 through 7 October 2004 (for details visit the Network website). Finally, I would like to thank my colleagues, Celestino Creatore, Nikolay Nikolaev, Lois Smallwood and Andrew Smith, for their help with preparation of the Proceedings.

Diode and method of making the same

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

Dickerson, Jeramy Ray; Wierer, Jr., Jonathan; Kaplar, Robert

2018-03-13

A diode includes a second semiconductor layer over a first semiconductor layer. The diode further includes a third semiconductor layer over the second semiconductor layer, where the third semiconductor layer includes a first semiconductor element over the second semiconductor layer. The third semiconductor layer additionally includes a second semiconductor element over the second semiconductor layer, wherein the second semiconductor element surrounds the first semiconductor element. Further, the third semiconductor layer includes a third semiconductor element over the second semiconductor element. Furthermore, a hole concentration of the second semiconductor element is less than a hole concentration of the first semiconductor element.

Validity, reliability and feasibility of commercially available activity trackers in physical therapy for people with a chronic disease: a study protocol of a mixed methods research.

PubMed

Beekman, Emmylou; Braun, Susy M; Ummels, Darcy; van Vijven, Kim; Moser, Albine; Beurskens, Anna J

2017-01-01

For older people and people with a chronic disease, physical activity provides health benefits. Patients and healthcare professionals can use commercially available activity trackers to objectively monitor (alterations in) activity levels and patterns and to support physical activity. However, insight in the validity, reliability, and feasibility of these trackers in people with a chronic disease is needed. In this article, a study protocol is described in which the validity, reliability (part A), and feasibility from a patient and therapist's point of view (part B) of commercially available activity trackers in daily life and health care is investigated. In part A, a quantitative cross-sectional study, an activity protocol that simulates everyday life activities will be used to determine the validity and reliability of nine commercially available activity trackers. Video recordings will act as the gold standard. In part B, a qualitative participatory action research study will be performed to gain insight in the use of activity trackers in peoples' daily life and therapy settings. Objective feasibility of the activity trackers will be measured with questionnaires, and subjective feasibility (experiences) will be explored in a community of practice. Physical therapists ( n  = 8) will regularly meet during 6 months to learn from each other regarding the actual use of activity trackers in therapy. Therapists and patients ( n  = 48) will decide together which tracker will be used in therapy and for which purpose (e.g., monitoring, goal setting). Data from the therapist' and patients' experiences will be collected by interviews (individual and focus groups) and analyzed by a directed content analysis. At the time of submission, selection of activity trackers, development of the activity protocol, and the ethical approval process are finished. Data collection and data processing are ongoing. The relevance of the study as well as the advantages and disadvantages of several aspects of the chosen design are discussed. The results acquired from both study parts can be used to create decision aids that may assist therapists and people with a chronic disease in choosing a suitable activity tracker, and to facilitate use of these activity trackers in health care settings. Ethical approval has been obtained from two medical-ethical committees (nr. 15-N-109, 15-N-48 and MEC-15-07).

Grumman S2F-1 Tracker at NACA Lewis

NASA Image and Video Library

1956-08-21

The NACA’s Lewis Flight Propulsion Laboratory acquired the Grumman S2F-1 Tracker from the Navy in 1955 to study icing instrumentation. Lewis’s icing research program was winding down at the time. The use of jet engines was increasing thus reducing the threat of ice accumulation. Nonetheless Lewis continued research on the instrumentation used to detect icing conditions. The S2F-1 Tracker was a carrier-based submarine hunter for the Navy. Grumman developed the Tracker as a successor to its Korean War-era Guardian patrol aircraft. Prototypes first flew in late 1952 and battle-ready versions entered Naval service in early 1954. The Navy utilized the Trackers to protect fleets from attack.

Geometric Model for Tracker-Target Look Angles and Line of Slight Distance

DTIC Science & Technology

2015-10-20

412TW-PA-15239 Geometric Model for Tracker -Target Look Angles and Line of Slight Distance DANIEL T. LAIRD AIR FORCE TEST CENTER EDWARDS...15 – 23 OCT 15 4. TITLE AND SUBTITLE Geometric Model for Tracker -Target Look Angles and Line of Slight Distance 5a. CONTRACT...include area code) 661-277-8615 Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 GEOMETRIC MODEL FOR TRACKER -TARGET LOOK ANGLES

Integration of an Apple II Plus Computer into an Existing Dual Axis Sun Tracker System.

DTIC Science & Technology

1984-06-01

Identify by block number) S, tpec l Sun Tracker System Solar Energy Apple II Plus Computer 20. ABSTRACT (’ ntlnue on reveree ide If neceesery end...14 4. Dual Axis Sun Tracker (Side View) ----------------- 15 5. Solar Tracker System Block Diagram ---------------- 17 6. Plug Wiring Diagram for Top...sources will be competitive. Already many homes have solar collectors and other devices designed to decrease the consumption of gas, oil, and

Counting Steps in Activities of Daily Living in People With a Chronic Disease Using Nine Commercially Available Fitness Trackers: Cross-Sectional Validity Study.

PubMed

Ummels, Darcy; Beekman, Emmylou; Theunissen, Kyra; Braun, Susy; Beurskens, Anna J

2018-04-02

Measuring physical activity with commercially available activity trackers is gaining popularity. People with a chronic disease can especially benefit from knowledge about their physical activity pattern in everyday life since sufficient physical activity can contribute to wellbeing and quality of life. However, no validity data are available for this population during activities of daily living. The aim of this study was to investigate the validity of 9 commercially available activity trackers for measuring step count during activities of daily living in people with a chronic disease receiving physiotherapy. The selected activity trackers were Accupedo (Corusen LLC), Activ8 (Remedy Distribution Ltd), Digi-Walker CW-700 (Yamax), Fitbit Flex (Fitbit inc), Lumoback (Lumo Bodytech), Moves (ProtoGeo Oy), Fitbit One (Fitbit inc), UP24 (Jawbone), and Walking Style X (Omron Healthcare Europe BV). In total, 130 persons with chronic diseases performed standardized activity protocols based on activities of daily living that were recorded on video camera and analyzed for step count (gold standard). The validity of the trackers' step count was assessed by correlation coefficients, t tests, scatterplots, and Bland-Altman plots. The correlations between the number of steps counted by the activity trackers and the gold standard were low (range: -.02 to .33). For all activity trackers except for Fitbit One, a significant systematic difference with the gold standard was found for step count. Plots showed a wide range in scores for all activity trackers; Activ8 showed an average overestimation and the other 8 trackers showed underestimations. This study showed that the validity of 9 commercially available activity trackers is low measuring steps while individuals with chronic diseases receiving physiotherapy engage in activities of daily living. ©Darcy Ummels, Emmylou Beekman, Kyra Theunissen, Susy Braun, Anna J Beurskens. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 02.04.2018.

An Overview of Plume Tracker: Mapping Volcanic Emissions with Interactive Radiative Transfer Modeling

NASA Astrophysics Data System (ADS)

Realmuto, V. J.; Berk, A.; Guiang, C.

2014-12-01

Infrared remote sensing is a vital tool for the study of volcanic plumes, and radiative transfer (RT) modeling is required to derive quantitative estimation of the sulfur dioxide (SO2), sulfate aerosol (SO4), and silicate ash (pulverized rock) content of these plumes. In the thermal infrared, we must account for the temperature, emissivity, and elevation of the surface beneath the plume, plume altitude and thickness, and local atmospheric temperature and humidity. Our knowledge of these parameters is never perfect, and interactive mapping allows us to evaluate the impact of these uncertainties on our estimates of plume composition. To enable interactive mapping, the Jet Propulsion Laboratory is collaborating with Spectral Sciences, Inc., (SSI) to develop the Plume Tracker toolkit. This project is funded by a NASA AIST Program Grant (AIST-11-0053) to SSI. Plume Tracker integrates (1) retrieval procedures for surface temperature and emissivity, SO2, NH3, or CH4 column abundance, and scaling factors for H2O vapor and O3 profiles, (2) a RT modeling engine based on MODTRAN, and (3) interactive visualization and analysis utilities under a single graphics user interface. The principal obstacle to interactive mapping is the computational overhead of the RT modeling engine. Under AIST-11-0053 we have achieved a 300-fold increase in the performance of the retrieval procedures through the use of indexed caches of model spectra, optimization of the minimization procedures, and scaling of the effects of surface temperature and emissivity on model radiance spectra. In the final year of AIST-11-0053 we will implement parallel processing to exploit multi-core CPUs and cluster computing, and optimize the RT engine to eliminate redundant calculations when iterating over a range of gas concentrations. These enhancements will result in an additional 8 - 12X increase in performance. In addition to the improvements in performance, we have improved the accuracy of the Plume Tracker retrievals through refinements in the description of surface emissivity and use of vector projection to define the misfit between model and observed spectra. Portions of this research were conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

Co-training Framework of Generative and Disciminative Trackers with Partial Occlusion Handling

DTIC Science & Technology

2011-01-01

ARO W911NF-06-1-0094. The first author was also supported by the Vietnam Education Foundation. We thank Zdenek Kalal for his help with the P-N Tracker...handling challenging situations with cluttered background. Recently, Kalal et al. [11] proposed the P-N Tracker us- ing positive and negative constraints to...Vietnam Education Foundation. We thank Zdenek Kalal for his help with the P-N Tracker [11]. References [1] A. Adam, E. Rivlin, and I. Shimshoni. Robust

Measuring Scale Errors in a Laser Tracker’s Horizontal Angle Encoder Through Simple Length Measurement and Two-Face System Tests

PubMed Central

Muralikrishnan, B.; Blackburn, C.; Sawyer, D.; Phillips, S.; Bridges, R.

2010-01-01

We describe a method to estimate the scale errors in the horizontal angle encoder of a laser tracker in this paper. The method does not require expensive instrumentation such as a rotary stage or even a calibrated artifact. An uncalibrated but stable length is realized between two targets mounted on stands that are at tracker height. The tracker measures the distance between these two targets from different azimuthal positions (say, in intervals of 20° over 360°). Each target is measured in both front face and back face. Low order harmonic scale errors can be estimated from this data and may then be used to correct the encoder’s error map to improve the tracker’s angle measurement accuracy. We have demonstrated this for the second order harmonic in this paper. It is important to compensate for even order harmonics as their influence cannot be removed by averaging front face and back face measurements whereas odd orders can be removed by averaging. We tested six trackers from three different manufacturers. Two of those trackers are newer models introduced at the time of writing of this paper. For older trackers from two manufacturers, the length errors in a 7.75 m horizontal length placed 7 m away from a tracker were of the order of ± 65 μm before correcting the error map. They reduced to less than ± 25 μm after correcting the error map for second order scale errors. Newer trackers from the same manufacturers did not show this error. An older tracker from a third manufacturer also did not show this error. PMID:27134789

Counting Steps in Activities of Daily Living in People With a Chronic Disease Using Nine Commercially Available Fitness Trackers: Cross-Sectional Validity Study

PubMed Central

Beekman, Emmylou; Theunissen, Kyra; Braun, Susy; Beurskens, Anna J

2018-01-01

Background Measuring physical activity with commercially available activity trackers is gaining popularity. People with a chronic disease can especially benefit from knowledge about their physical activity pattern in everyday life since sufficient physical activity can contribute to wellbeing and quality of life. However, no validity data are available for this population during activities of daily living. Objective The aim of this study was to investigate the validity of 9 commercially available activity trackers for measuring step count during activities of daily living in people with a chronic disease receiving physiotherapy. Methods The selected activity trackers were Accupedo (Corusen LLC), Activ8 (Remedy Distribution Ltd), Digi-Walker CW-700 (Yamax), Fitbit Flex (Fitbit inc), Lumoback (Lumo Bodytech), Moves (ProtoGeo Oy), Fitbit One (Fitbit inc), UP24 (Jawbone), and Walking Style X (Omron Healthcare Europe BV). In total, 130 persons with chronic diseases performed standardized activity protocols based on activities of daily living that were recorded on video camera and analyzed for step count (gold standard). The validity of the trackers’ step count was assessed by correlation coefficients, t tests, scatterplots, and Bland-Altman plots. Results The correlations between the number of steps counted by the activity trackers and the gold standard were low (range: –.02 to .33). For all activity trackers except for Fitbit One, a significant systematic difference with the gold standard was found for step count. Plots showed a wide range in scores for all activity trackers; Activ8 showed an average overestimation and the other 8 trackers showed underestimations. Conclusions This study showed that the validity of 9 commercially available activity trackers is low measuring steps while individuals with chronic diseases receiving physiotherapy engage in activities of daily living. PMID:29610110

Reliability and Validity of Ten Consumer Activity Trackers Depend on Walking Speed.

PubMed

Fokkema, Tryntsje; Kooiman, Thea J M; Krijnen, Wim P; VAN DER Schans, Cees P; DE Groot, Martijn

2017-04-01

To examine the test-retest reliability and validity of ten activity trackers for step counting at three different walking speeds. Thirty-one healthy participants walked twice on a treadmill for 30 min while wearing 10 activity trackers (Polar Loop, Garmin Vivosmart, Fitbit Charge HR, Apple Watch Sport, Pebble Smartwatch, Samsung Gear S, Misfit Flash, Jawbone Up Move, Flyfit, and Moves). Participants walked three walking speeds for 10 min each; slow (3.2 km·h), average (4.8 km·h), and vigorous (6.4 km·h). To measure test-retest reliability, intraclass correlations (ICC) were determined between the first and second treadmill test. Validity was determined by comparing the trackers with the gold standard (hand counting), using mean differences, mean absolute percentage errors, and ICC. Statistical differences were calculated by paired-sample t tests, Wilcoxon signed-rank tests, and by constructing Bland-Altman plots. Test-retest reliability varied with ICC ranging from -0.02 to 0.97. Validity varied between trackers and different walking speeds with mean differences between the gold standard and activity trackers ranging from 0.0 to 26.4%. Most trackers showed relatively low ICC and broad limits of agreement of the Bland-Altman plots at the different speeds. For the slow walking speed, the Garmin Vivosmart and Fitbit Charge HR showed the most accurate results. The Garmin Vivosmart and Apple Watch Sport demonstrated the best accuracy at an average walking speed. For vigorous walking, the Apple Watch Sport, Pebble Smartwatch, and Samsung Gear S exhibited the most accurate results. Test-retest reliability and validity of activity trackers depends on walking speed. In general, consumer activity trackers perform better at an average and vigorous walking speed than at a slower walking speed.

Precision Attitude Determination System (PADS) design and analysis. Two-axis gimbal star tracker

NASA Technical Reports Server (NTRS)

1973-01-01

Development of the Precision Attitude Determination System (PADS) focused chiefly on the two-axis gimballed star tracker and electronics design improved from that of Precision Pointing Control System (PPCS), and application of the improved tracker for PADS at geosynchronous altitude. System design, system analysis, software design, and hardware design activities are reported. The system design encompasses the PADS configuration, system performance characteristics, component design summaries, and interface considerations. The PADS design and performance analysis includes error analysis, performance analysis via attitude determination simulation, and star tracker servo design analysis. The design of the star tracker and electronics are discussed. Sensor electronics schematics are included. A detailed characterization of the application software algorithms and computer requirements is provided.

Sun tracker for clear or cloudy weather

NASA Technical Reports Server (NTRS)

Scott, D. R.; White, P. R.

1979-01-01

Sun tracker orients solar collector so that they absorb maximum possible sunlight without being fooled by bright clouds, holes in cloud cover, or other atmospheric conditions. Tracker follows sun within 0.25 deg arc and is accurate within + or - 5 deg when sun is hidden.

Advantages and Limitations of Wearable Activity Trackers: Considerations for Patients and Clinicians.

PubMed

Walker, Rachel K; Hickey, Amanda M; Freedson, Patty S

2016-12-01

Exercise, light physical activity, and decreased sedentary time all have been associated with health benefits following cancer diagnoses. Commercially available wearable activity trackers may help patients monitor and self-manage their behaviors to achieve these benefits. This article highlights some advantages and limitations clinicians should be aware of when discussing the use of activity trackers with cancer survivors. Limited research has assessed the accuracy of commercially available activity trackers compared to research-grade devices. Because most devices use confidential, proprietary algorithms to convert accelerometry data to meaningful output like total steps, assessing whether these algorithms account for differences in gait abnormalities, functional limitations, and different body morphologies can be difficult. Quantification of sedentary behaviors and light physical activities present additional challenges. The global market for activity trackers is growing, which presents clinicians with a tremendous opportunity to incorporate these devices into clinical practice as tools to promote activity. This article highlights important considerations about tracker accuracy and usage by cancer survivors.

Experimental predictions drawn from a computational model of sign-trackers and goal-trackers.

PubMed

Lesaint, Florian; Sigaud, Olivier; Clark, Jeremy J; Flagel, Shelly B; Khamassi, Mehdi

2015-01-01

Gaining a better understanding of the biological mechanisms underlying the individual variation observed in response to rewards and reward cues could help to identify and treat individuals more prone to disorders of impulsive control, such as addiction. Variation in response to reward cues is captured in rats undergoing autoshaping experiments where the appearance of a lever precedes food delivery. Although no response is required for food to be delivered, some rats (goal-trackers) learn to approach and avidly engage the magazine until food delivery, whereas other rats (sign-trackers) come to approach and engage avidly the lever. The impulsive and often maladaptive characteristics of the latter response are reminiscent of addictive behaviour in humans. In a previous article, we developed a computational model accounting for a set of experimental data regarding sign-trackers and goal-trackers. Here we show new simulations of the model to draw experimental predictions that could help further validate or refute the model. In particular, we apply the model to new experimental protocols such as injecting flupentixol locally into the core of the nucleus accumbens rather than systemically, and lesioning of the core of the nucleus accumbens before or after conditioning. In addition, we discuss the possibility of removing the food magazine during the inter-trial interval. The predictions from this revised model will help us better understand the role of different brain regions in the behaviours expressed by sign-trackers and goal-trackers. Copyright © 2014 Elsevier Ltd. All rights reserved.

Evidence of coherent $$K^{+}$$ meson production in neutrino-nucleus scattering

DOE PAGES

Wang, Z.

2016-08-05

Neutrino-induced charged-current coherent kaon production ν μA→μ -K +A is a rare, inelastic electroweak process that brings a K + on shell and leaves the target nucleus intact in its ground state. This process is significantly lower in rate than the neutrino-induced charged-current coherent pion production because of Cabibbo suppression and a kinematic suppression due to the larger kaon mass. We search for such events in the scintillator tracker of MINERvA by observing the final state K +, μ -, and no other detector activity, and by using the kinematics of the final state particles to reconstruct the small momentummore » transfer to the nucleus, which is a model-independent characteristic of coherent scattering. Furthermore, we find the first experimental evidence for the process at 3σ significance.« less

High- k Gate Dielectrics for Emerging Flexible and Stretchable Electronics.

PubMed

Wang, Binghao; Huang, Wei; Chi, Lifeng; Al-Hashimi, Mohammed; Marks, Tobin J; Facchetti, Antonio

2018-05-22

Recent advances in flexible and stretchable electronics (FSE), a technology diverging from the conventional rigid silicon technology, have stimulated fundamental scientific and technological research efforts. FSE aims at enabling disruptive applications such as flexible displays, wearable sensors, printed RFID tags on packaging, electronics on skin/organs, and Internet-of-things as well as possibly reducing the cost of electronic device fabrication. Thus, the key materials components of electronics, the semiconductor, the dielectric, and the conductor as well as the passive (substrate, planarization, passivation, and encapsulation layers) must exhibit electrical performance and mechanical properties compatible with FSE components and products. In this review, we summarize and analyze recent advances in materials concepts as well as in thin-film fabrication techniques for high- k (or high-capacitance) gate dielectrics when integrated with FSE-compatible semiconductors such as organics, metal oxides, quantum dot arrays, carbon nanotubes, graphene, and other 2D semiconductors. Since thin-film transistors (TFTs) are the key enablers of FSE devices, we discuss TFT structures and operation mechanisms after a discussion on the needs and general requirements of gate dielectrics. Also, the advantages of high- k dielectrics over low- k ones in TFT applications were elaborated. Next, after presenting the design and properties of high- k polymers and inorganic, electrolyte, and hybrid dielectric families, we focus on the most important fabrication methodologies for their deposition as TFT gate dielectric thin films. Furthermore, we provide a detailed summary of recent progress in performance of FSE TFTs based on these high- k dielectrics, focusing primarily on emerging semiconductor types. Finally, we conclude with an outlook and challenges section.

Novel Approach to Evaluation of Charging on Semiconductor Surface by Noncontact, Electrode-Free Capacitance/Voltage Measurement

NASA Astrophysics Data System (ADS)

Hirae, Sadao; Kohno, Motohiro; Okada, Hiroshi; Matsubara, Hideaki; Nakatani, Ikuyoshi; Kusuda, Tatsufumi; Sakai, Takamasa

1994-04-01

This paper describes a novel approach to the quantitative characterization of semiconductor surface charging caused by plasma exposures and ion implantations. The problems in conventional evaluation of charging are also discussed. Following the discussions above, the necessity of unified criteria is suggested for efficient development of systems or processes without charging damage. Hence, the charging saturation voltage between a top oxide surface and substrate, V s, and the charging density per unit area per second, ρ0, should be taken as criteria of charging behavior, which effectively represent the charging characteristics of both processes. The unified criteria can be obtained from the exposure time dependence of a net charging density on the thick field oxide. In order to determine V s and ρ0, the analysis using the C-V curve measured in a noncontact method with the metal-air-insulator-semiconductor (MAIS) technique is employed. The total space-charge density in oxide and its centroid can be determined at the same time by analyzing the flat-band voltage (V fb) of the MAIS capacitor as a function of the air gap. The net charge density can be obtained by analyzing the difference between the total space-charge density in oxide before and after charging. Finally, it is shown that charge damage of the large area metal-oxide-semiconductor (MOS) capacitor can be estimated from both V s and ρ0 which are obtained from results for a thick field oxide implanted with As+ and exposed to oxygen plasma.

Electronic structure of metals and semiconductors: bulk, surface, and interface properties

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

Louie, S.G.S.

1976-09-01

A theoretical study of the electronic structure of various metals and semiconductors is presented with the emphasis on understanding the properties of these materials when they are subjected to extreme conditions and in various different configurations. Among the bulk systems studied, the properties of cesium under high pressure are discussed in terms of the electronic structure calculated at various cell volumes using the pseudopotential method. Local fields or umklapp processes in semiconductors are studied within the random phase approximation (RPA). Specifically the dielectric response matrix epsilon/sub GG'/ (q = 0,omega) is evaluated numerically to determine the effects of local-field correctionsmore » in the optical spectrum of Si. Also, some comments on the excitonic mechanism of superconductivity are presented and the role of local fields is discussed. The pseudo-potential method is next extended to calculate the electronic structure of a transition metal Nb. The calculation is performed self-consistently with the use of a non-local ionic potential determined from atomic spectra. Finally the theory of the superconducting transition temperature T/sub c/ is discussed in the strong-coupling formulation of the BCS theory. The Eliashberg equations in the Matsubara representation are solved analytically and a general T/sub c/ equation is obtained. A new method is developed using pseudopotentials in a self-consistent manner to describe non-periodic systems. The method is applicable to localized configurations such as molecules, surfaces, impurities, vacancies, finite chains of atoms, adsorbates, and solid interfaces. Specific applications to surfaces, metal-semiconductor interfaces and vacancies are presented.« less

Gate tunneling current and quantum capacitance in metal-oxide-semiconductor devices with graphene gate electrodes

NASA Astrophysics Data System (ADS)

An, Yanbin; Shekhawat, Aniruddh; Behnam, Ashkan; Pop, Eric; Ural, Ant

2016-11-01

Metal-oxide-semiconductor (MOS) devices with graphene as the metal gate electrode, silicon dioxide with thicknesses ranging from 5 to 20 nm as the dielectric, and p-type silicon as the semiconductor are fabricated and characterized. It is found that Fowler-Nordheim (F-N) tunneling dominates the gate tunneling current in these devices for oxide thicknesses of 10 nm and larger, whereas for devices with 5 nm oxide, direct tunneling starts to play a role in determining the total gate current. Furthermore, the temperature dependences of the F-N tunneling current for the 10 nm devices are characterized in the temperature range 77-300 K. The F-N coefficients and the effective tunneling barrier height are extracted as a function of temperature. It is found that the effective barrier height decreases with increasing temperature, which is in agreement with the results previously reported for conventional MOS devices with polysilicon or metal gate electrodes. In addition, high frequency capacitance-voltage measurements of these MOS devices are performed, which depict a local capacitance minimum under accumulation for thin oxides. By analyzing the data using numerical calculations based on the modified density of states of graphene in the presence of charged impurities, it is shown that this local minimum is due to the contribution of the quantum capacitance of graphene. Finally, the workfunction of the graphene gate electrode is extracted by determining the flat-band voltage as a function of oxide thickness. These results show that graphene is a promising candidate as the gate electrode in metal-oxide-semiconductor devices.

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.

Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) Nanorods Superlattice (SL)

DTIC Science & Technology

2006-03-29

Final Report (Technical) 3. DATES COVERED 29-03-2005 to 29-05-2006 4. TITLE AND SUBTITLE Indium Gallium Nitride/ Gallium Nitride (InGaN/GaN...Institution: Quantum functional Semiconductor Research Center (QSRC), Dongguk University - Title of project: Indium Gallium Nitride/ Gallium Nitride...Accepted with minor revision Indium Gallium Nitride / Gallium Nitride (InGaN/ GaN) Nanorods Superlattice (SL) Abstract The growth condition, electrical

Final Report: High Power Semiconductor Laser Sources,

DTIC Science & Technology

1989-01-01

Mittelstein, Yasuhiko Arakawa, ) Anders Larssonb) and Amnon Yariv California Institute of Technology, Pasadena, California 91 125~412 (Received 7 July...Electronics and Commu- nication Engineers of Japan. He is a member of the Institute of Electronics Yasuhiko Arakawa S󈨑-M󈨔) was born in Ai- and...Gain, Modulation Response, and Spectral Linewidth in AlGaAs Quantum Well Lasers YASUHIKO ARAKAWA. MEMBER, IEEE. AND AMNON YARIV. FELLOW. IEEE Abstract

Materials Science and Physics at Micro/Nano-Scales. FINAL REPORT

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

Wu, Judy Z.

2009-09-07

The scope of this project is to study nanostructures of semiconductors and superconductors, which have been regarded as promising building blocks for nanoelectronic and nanoelectric devices. The emphasis of this project is on developing novel synthesis approaches for fabrication of nanostructures with desired physical properties. The ultimate goal is to achieve a full control of the nanostructure growth at microscopic scales. The major experimental achievements obtained are summarized

Quantum Entanglement of Quantum Dot Spin Using Flying Qubits

DTIC Science & Technology

2015-05-01

QUANTUM ENTANGLEMENT OF QUANTUM DOT SPIN USING FLYING QUBITS UNIVERSITY OF MICHIGAN MAY 2015 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE...To) SEP 2012 – DEC 2014 4. TITLE AND SUBTITLE QUANTUM ENTANGLEMENT OF QUANTUM DOT SPIN USING FLYING QUBITS 5a. CONTRACT NUMBER FA8750-12-2-0333...been to advance the frontier of quantum entangled semiconductor electrons using ultrafast optical techniques. The approach is based on

Low-Energy Tunable Self-Modulated Nanolasers (1.1 SHORT-TERM INNOVATIVE RESEARCH (STIR) PROGRAM)

DTIC Science & Technology

2016-09-28

Optoelectronics: Low -Energy Tunable Self- Modulated Nanolasers (1.1 SHORT-TERM INNOVATIVE RESEARCH (STIR) PROGRAM) Our goal was to exploit Quantum...reviewed journals: Final Report: Optoelectronics: Low -Energy Tunable Self-Modulated Nanolasers (1.1 SHORT-TERM INNOVATIVE RESEARCH (STIR) PROGRAM...metal layer. By optimizing the thickness of the low index shield between the metal and semiconductor, the gain threshold of the laser can be

Macro Pixel ASIC (MPA): the readout ASIC for the pixel-strip (PS) module of the CMS outer tracker at HL-LHC

NASA Astrophysics Data System (ADS)

Ceresa, D.; Marchioro, A.; Kloukinas, K.; Kaplon, J.; Bialas, W.; Re, V.; Traversi, G.; Gaioni, L.; Ratti, L.

2014-11-01

The CMS tracker at HL-LHC is required to provide prompt information on particles with high transverse momentum to the central Level 1 trigger. For this purpose, the innermost part of the outer tracker is based on a combination of a pixelated sensor with a short strip sensor, the so-called Pixel-Strip module (PS). The readout of these sensors is carried out by distinct ASICs, the Strip Sensor ASIC (SSA), for the strip layer, and the Macro Pixel ASIC (MPA) for the pixel layer. The processing of the data directly on the front-end module represents a design challenge due to the large data volume (30720 pixels and 1920 strips per module) and the limited power budget. This is the reason why several studies have been carried out to find the best compromise between ASICs performance and power consumption. This paper describes the current status of the MPA ASIC development where the logic for generating prompt information on particles with high transverse momentum is implemented. An overview of the readout method is presented with particular attention on the cluster reduction, position encoding and momentum discrimination logic. Concerning the architectural studies, a software test bench capable of reading physics Monte-Carlo generated events has been developed and used to validate the MPA design and to evaluate the MPA performance. The MPA-Light is scheduled to be submitted for fabrication this year and will include the full analog functions and a part of the digital logic of the final version in order to qualify the chosen VLSI technology for the analog front-end, the module assembly and the low voltage digital supply.

Involvement of lysosomal dysfunction in silver nanoparticle-induced cellular damage in A549 human lung alveolar epithelial cells.

PubMed

Miyayama, Takamitsu; Matsuoka, Masato

2016-01-01

While silver nanoparticles (AgNPs) are widely used in consumer and medical products, the mechanism by which AgNPs cause pulmonary cytotoxicity is not clear. AgNP agglomerates are found in endo-lysosomal structures within the cytoplasm of treated cells. In this study, the functional role of lysosomes in AgNP-induced cellular damage was examined in A549 human lung alveolar epithelial cells. We evaluated the intracellular distribution of AgNPs, lysosomal pH, cellular viability, Ag dissolution, and metallothionein (MT) mRNA levels in AgNP-exposed A549 cells that were treated with bafilomycin A1, the lysosomal acidification inhibitor. Exposure of A549 cells to citrate-coated AgNPs (20 nm diameter) for 24 h induced cellular damage and cell death at 100 and 200 μg Ag/ml, respectively. Confocal laser microscopic examination of LysoTracker-stained cells showed that AgNPs colocalized with lysosomes and their agglomeration increased in a dose-dependent manner (50-200 μg Ag/ml). In addition, the fluorescence signals of LysoTracker were reduced following exposure to AgNPs, suggesting the elevation of lysosomal pH. Treatment of A549 cells with 200 nM bafilomycin A1 and AgNPs (50 μg Ag/ml) further reduced the fluorescence signals of LysoTracker. AgNP-induced cell death was also increased by bafilomycin A1 treatment. Finally, treatment with bafilomycin A1 suppressed the dissolution of Ag and decreased the mRNA expression levels of MT-I and MT-II following exposure to AgNPs. The perturbation of lysosomal pH by AgNP exposure may play a role in AgNP agglomeration and subsequent cellular damage in A549 cells.

Electronic Structure of the Organic Semiconductor Alq3 (aluminum tris-8-hydroxyquinoline) from Soft X-ray Spectroscopies and Density Functional Theory Calculations

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

DeMasi, A.; Piper, L; Zhang, Y

2008-01-01

The element-specific electronic structure of the organic semiconductor aluminum tris-8-hydroxyquinoline (Alq3) has been studied using a combination of resonant x-ray emission spectroscopy, x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and density functional theory (DFT) calculations. Resonant and nonresonant x-ray emission spectroscopy were used to measure directly the carbon, nitrogen and oxygen 2p partial densities of states in Alq3, and good agreement was found with the results of DFT calculations. Furthermore, resonant x-ray emission at the carbon K-edge is shown to be able to measure the partial density of states associated with individual C sites. Finally, comparison of previous x-ray emission studiesmore » and the present data reveal the presence of clear photon-induced damage in the former.« less

Electronic Properties, Screening, and Efficient Carrier Transport in NaSbS 2

DOE PAGES

Sun, Jifeng; Singh, David J.

2017-02-13

NaSbS 2 is a semiconductor that was recently shown to have remarkable efficacy as a solar absorber indicating efficient charge collection even in material containing defects. We report first-principles calculations of properties that show (1) an indirect gap only slightly smaller than the direct gap, which may impede the recombination of photoexcited carriers, (2) highly anisotropic electronic and optical properties reflecting a layered crystal structure, (3) a pushed-up valence-band maximum due to repulsion from the Sb 5s states, and (4) cross-gap hybridization between the S p—derived valence bands and the Sb 5p states. This latter feature leads to enhanced Bornmore » effective charges that can provide local screening and, therefore, defect tolerance. Finally, these features are discussed in relation to the performance of the compound as a semiconductor with efficient charge collection.« less

Luminescent hyperbolic metasurfaces

NASA Astrophysics Data System (ADS)

Smalley, J. S. T.; Vallini, F.; Montoya, S. A.; Ferrari, L.; Shahin, S.; Riley, C. T.; Kanté, B.; Fullerton, E. E.; Liu, Z.; Fainman, Y.

2017-01-01

When engineered on scales much smaller than the operating wavelength, metal-semiconductor nanostructures exhibit properties unobtainable in nature. Namely, a uniaxial optical metamaterial described by a hyperbolic dispersion relation can simultaneously behave as a reflective metal and an absorptive or emissive semiconductor for electromagnetic waves with orthogonal linear polarization states. Using an unconventional multilayer architecture, we demonstrate luminescent hyperbolic metasurfaces, wherein distributed semiconducting quantum wells display extreme absorption and emission polarization anisotropy. Through normally incident micro-photoluminescence measurements, we observe absorption anisotropies greater than a factor of 10 and degree-of-linear polarization of emission >0.9. We observe the modification of emission spectra and, by incorporating wavelength-scale gratings, show a controlled reduction of polarization anisotropy. We verify hyperbolic dispersion with numerical simulations that model the metasurface as a composite nanoscale structure and according to the effective medium approximation. Finally, we experimentally demonstrate >350% emission intensity enhancement relative to the bare semiconducting quantum wells.

Local atomic and magnetic structure of dilute magnetic semiconductor (Ba ,K ) (Zn,Mn ) 2As2

NASA Astrophysics Data System (ADS)

Frandsen, Benjamin A.; Gong, Zizhou; Terban, Maxwell W.; Banerjee, Soham; Chen, Bijuan; Jin, Changqing; Feygenson, Mikhail; Uemura, Yasutomo J.; Billinge, Simon J. L.

2016-09-01

We have studied the atomic and magnetic structure of the dilute ferromagnetic semiconductor system (Ba ,K )(Zn ,Mn )2As2 through atomic and magnetic pair distribution function analysis of temperature-dependent x-ray and neutron total scattering data. We detected a change in curvature of the temperature-dependent unit cell volume of the average tetragonal crystallographic structure at a temperature coinciding with the onset of ferromagnetic order. We also observed the existence of a well-defined local orthorhombic structure on a short length scale of ≲5 Å , resulting in a rather asymmetrical local environment of the Mn and As ions. Finally, the magnetic PDF revealed ferromagnetic alignment of Mn spins along the crystallographic c axis, with robust nearest-neighbor ferromagnetic correlations that exist even above the ferromagnetic ordering temperature. We discuss these results in the context of other experiments and theoretical studies on this system.

Etching of semiconductors and metals by the photonic jet with shaped optical fiber tips

NASA Astrophysics Data System (ADS)

Pierron, Robin; Lecler, Sylvain; Zelgowski, Julien; Pfeiffer, Pierre; Mermet, Frédéric; Fontaine, Joël

2017-10-01

The etching of semiconductors and metals by a photonic jet (PJ) generated with a shaped optical fiber tip is studied. Etched marks with a diameter of 1 μm have been realized on silicon, stainless steel and titanium with a 35 kHz pulsed laser, emitting 100 ns pulses at 1064 nm. The selection criteria of the fiber and its tip are discussed. We show that a 100/140 silica fiber is a good compromise which takes into account the injection, the working distance and the energy coupled in the higher-order modes. The energy balance is performed on the basis of the known ablation threshold of the material. Finally, the dependence between the etching depth and the number of pulses is studied. Saturation is observed probably due to a redeposition of the etched material, showing that a higher pulse energy is required for deeper etchings.

Electro-optical interfacial effects on a graphene/π-conjugated organic semiconductor hybrid system

PubMed Central

Araujo, Karolline A S; Cury, Luiz A; Matos, Matheus J S; Fernandes, Thales F D; Cançado, Luiz G

2018-01-01

The influence of graphene and retinoic acid (RA) – a π-conjugated organic semiconductor – interface on their hybrid system is investigated. The physical properties of the interface are assessed via scanning probe microscopy, optical spectroscopy (photoluminescence and Raman) and ab initio calculations. The graphene/RA interaction induces the formation of a well-organized π-conjugated self-assembled monolayer (SAM) at the interface. Such structural organization leads to the high optical emission efficiency of the RA SAM, even at room temperature. Additionally, photo-assisted electrical force microscopy, photo-assisted scanning Kelvin probe microscopy and Raman spectroscopy indicate a RA-induced graphene doping and photo-charge generation. Finally, the optical excitation of the RA monolayer generates surface potential changes on the hybrid system. In summary, interface-induced organized structures atop 2D materials may have an important impact on both design and operation of π-conjugated nanomaterial-based hybrid systems. PMID:29600157

Low-Cost Approaches to III–V Semiconductor Growth for Photovoltaic Applications

DOE PAGES

Greenaway, Ann L.; Boucher, Jason W.; Oener, Sebastian Z.; ...

2017-08-31

III–V semiconductors form the most efficient single- and multijunction photovoltaics. Metal–organic vapor-phase epitaxy, which uses toxic and pyrophoric gas-phase precursors, is the primary commercial growth method for these materials. In order for the use of highly efficient III–V-based devices to be expanded as the demand for renewable electricity grows, a lower-cost approach to the growth of these materials is needed. This Review focuses on three deposition techniques compatible with current device architectures: hydride vapor-phase epitaxy, close-spaced vapor transport, and thin-film vapor–liquid–solid growth. Here, we consider recent advances in each technique, including the available materials space, before providing an in-depth comparisonmore » of growth technology advantages and limitations and considering the impact of modifications to the method of production on the cost of the final photovoltaics.« less

Research and Design on a Product Data Definition System of Semiconductor Packaging Industry

NASA Astrophysics Data System (ADS)

Shi, Jinfei; Ma, Qingyao; Zhou, Yifan; Chen, Ruwen

2017-12-01

This paper develops a product data definition (PDD) system for a semiconductor packaging and testing company with independent intellectual property rights. The new PDD system can solve the problems such as, the effective control of production plans, the timely feedback of production processes, and the efficient schedule of resources. Firstly, this paper introduces the general requirements of the PDD system and depicts the operation flow and the data flow of the PDD system. Secondly, the overall design scheme of the PDD system is put forward. After that, the physical data model is developed using the Power Designer15.0 tool, and the database system is built. Finally, the function realization and running effects of the PDD system are analysed. The successful operation of the PDD system can realize the information flow among various production departments of the enterprise to meet the standard of the enterprise manufacturing integration and improve the efficiency of production management.

Light-Emitting GaAs Nanowires on a Flexible Substrate.

PubMed

Valente, João; Godde, Tillmann; Zhang, Yunyan; Mowbray, David J; Liu, Huiyun

2018-06-18

Semiconductor nanowire-based devices are among the most promising structures used to meet the current challenges of electronics, optics and photonics. Due to their high surface-to-volume ratio and excellent optical and electrical properties, devices with low power, high efficiency and high density can be created. This is of major importance for environmental issues and economic impact. Semiconductor nanowires have been used to fabricate high performance devices, including detectors, solar cells and transistors. Here, we demonstrate a technique for transferring large-area nanowire arrays to flexible substrates while retaining their excellent quantum efficiency in emission. Starting with a defect-free self-catalyzed molecular beam epitaxy (MBE) sample grown on a Si substrate, GaAs core-shell nanowires are embedded in a dielectric, removed by reactive ion etching and transferred to a plastic substrate. The original structural and optical properties, including the vertical orientation, of the nanowires are retained in the final plastic substrate structure. Nanowire emission is observed for all stages of the fabrication process, with a higher emission intensity observed for the final transferred structure, consistent with a reduction in nonradiative recombination via the modification of surface states. This transfer process could form the first critical step in the development of flexible nanowire-based light-emitting devices.

Extended vertical range roughness measurements in non-ideal environments

NASA Astrophysics Data System (ADS)

Creath, Katherine

2011-09-01

This paper describes recent research into developing an extended range dynamic interferometry technique where the range is extended vertically to enhance surface roughness measurements made in non-ideal environments. Utilizing short pulses from two sources on either side of a frame transfer in a CCD sensor, data can be taken fast enough in noisy shop environments to make measurements in the presence of vibration, and air turbulence. A key application of this technique is monitoring of surface roughness of large optics during the polishing process by making in situ measurements from fine grind through to the final polish. It is anticipated that this monitoring can help speed up what is now a very lengthy process. This same technique is applicable to many other types of measurements including MEMS devices, as it is not affected by dispersion in windows covering devices, and for measuring features on flat panel display glass or semiconductor wafers. This paper describes the technique, and presents results of a variety of sample measurements including: bare glass in various states of polish from fine grind to final polish, scratches and pits in a roughened semiconductor wafer, a DMD MEMS device, and various calibration standards. Performance in terms of repeatabilitity of step heights and roughness for this proof of concept is in the +/-2% range.

Removal of fluoride, SDS, ammonia and turbidity from semiconductor wastewater by combined electrocoagulation-electroflotation.

PubMed

Aoudj, S; Khelifa, A; Drouiche, N

2017-08-01

Semiconductor industry effluents contain organic and inorganic pollutants, such as sodium dodecyl sulfate (SDS), fluoride and ammonia, at high levels which consists a major environmental issue. A combined EC-EF process is proposed as a post-treatment after precipitation for simultaneous clarification and removal of pollutants. In EC step, a hybrid Fe-Al was used as the soluble anode in order to avoid supplementary EC step. EC-Fe is more suitable for SDS removal; EC-Al is more suitable for fluoride removal, while EC with hybrid Al-Fe makes a good compromise. Clarification and ammonia oxidation were achieved in the EF step. Effects of anodic material, initial pH, current, anion nature, chloride concentration and initial pollutant concentration were studied. The final concentrations may reach 0.27, 6.23 and 0.22 mg L -1 for SDS, fluoride and ammonia respectively. These concentrations are far lower than the correspondent discharge limits. Similarly, the final turbidity was found 4.35 NTU which is lower than 5NTU and the treated water does not need further filtration before discharge. Furthermore, the EC-EF process proves to be sufficiently energy-efficient with less soluble electrode consumption. Copyright © 2017 Elsevier Ltd. All rights reserved.

Visual tracking using objectness-bounding box regression and correlation filters

NASA Astrophysics Data System (ADS)

Mbelwa, Jimmy T.; Zhao, Qingjie; Lu, Yao; Wang, Fasheng; Mbise, Mercy

2018-03-01

Visual tracking is a fundamental problem in computer vision with extensive application domains in surveillance and intelligent systems. Recently, correlation filter-based tracking methods have shown a great achievement in terms of robustness, accuracy, and speed. However, such methods have a problem of dealing with fast motion (FM), motion blur (MB), illumination variation (IV), and drifting caused by occlusion (OCC). To solve this problem, a tracking method that integrates objectness-bounding box regression (O-BBR) model and a scheme based on kernelized correlation filter (KCF) is proposed. The scheme based on KCF is used to improve the tracking performance of FM and MB. For handling drift problem caused by OCC and IV, we propose objectness proposals trained in bounding box regression as prior knowledge to provide candidates and background suppression. Finally, scheme KCF as a base tracker and O-BBR are fused to obtain a state of a target object. Extensive experimental comparisons of the developed tracking method with other state-of-the-art trackers are performed on some of the challenging video sequences. Experimental comparison results show that our proposed tracking method outperforms other state-of-the-art tracking methods in terms of effectiveness, accuracy, and robustness.

Post flight analysis of NASA standard star trackers recovered from the solar maximum mission

NASA Technical Reports Server (NTRS)

Newman, P.

1985-01-01

The flight hardware returned after the Solar Maximum Mission Repair Mission was analyzed to determine the effects of 4 years in space. The NASA Standard Star Tracker would be a good candidate for such analysis because it is moderately complex and had a very elaborate calibration during the acceptance procedure. However, the recovery process extensively damaged the cathode of the image dissector detector making proper operation of the tracker and a comparison with preflight characteristics impossible. Otherwise, the tracker functioned nominally during testing.

Personal Activity Trackers and the Quantified Self.

PubMed

Hoy, Matthew B

2016-01-01

Personal activity trackers are an inexpensive and easy way for people to record their physical activity and simple biometric data. As these devices have increased in availability and sophistication, their use in daily life and in medicine has grown. This column will briefly explore what these devices are, what types of data they can track, and how that data can be used. It will also discuss potential problems with trackers and how librarians can help patients and physicians manage and protect activity data. A brief list of currently available activity trackers is also included.

One-kilohertz eye tracker and active intraoperative torsion detection in the NIDEK CXIII and Quest excimer lasers.

PubMed

Waring, George O

2009-10-01

To describe recent technological additions to the NIDEK CXIII and Quest excimer lasers. A summary article with data from previous published studies outlining the benefits of newer technology. The addition of a 1-kHz infrared eye tracker decreased the spread of laser spot placement from a mean of 228.79 microm without a tracker to 38.47 microm with the eye tracker. The addition of real-time torsion error correction produced a statistically significantly lower cylinder dispersion, mean manifest refractive cylinder, and error of angle postoperatively in eyes that underwent LASIK. The incorporation of an ultrahigh speed eye tracker and active cyclotorsion correction surpasses the minimal technology criteria required for accurate wavefront-based ablations. Copyright 2009, SLACK Incorporated.

Log-polar mapping-based scale space tracking with adaptive target response

NASA Astrophysics Data System (ADS)

Li, Dongdong; Wen, Gongjian; Kuai, Yangliu; Zhang, Ximing

2017-05-01

Correlation filter-based tracking has exhibited impressive robustness and accuracy in recent years. Standard correlation filter-based trackers are restricted to translation estimation and equipped with fixed target response. These trackers produce an inferior performance when encountered with a significant scale variation or appearance change. We propose a log-polar mapping-based scale space tracker with an adaptive target response. This tracker transforms the scale variation of the target in the Cartesian space into a shift along the logarithmic axis in the log-polar space. A one-dimensional scale correlation filter is learned online to estimate the shift along the logarithmic axis. With the log-polar representation, scale estimation is achieved accurately without a multiresolution pyramid. To achieve an adaptive target response, a variance of the Gaussian function is computed from the response map and updated online with a learning rate parameter. Our log-polar mapping-based scale correlation filter and adaptive target response can be combined with any correlation filter-based trackers. In addition, the scale correlation filter can be extended to a two-dimensional correlation filter to achieve joint estimation of the scale variation and in-plane rotation. Experiments performed on an OTB50 benchmark demonstrate that our tracker achieves superior performance against state-of-the-art trackers.

Materials Science and Device Physics of 2-Dimensional Semiconductors

NASA Astrophysics Data System (ADS)

Fang, Hui

Materials and device innovations are the keys to future technology revolution. For MOSFET scaling in particular, semiconductors with ultra-thin thickness on insulator platform is currently of great interest, due to the potential of integrating excellent channel materials with the industrially mature Si processing. Meanwhile, ultra-thin thickness also induces strong quantum confinement which in turn affect most of the material properties of these 2-dimensional (2-D) semiconductors, providing unprecedented opportunities for emerging technologies. In this thesis, multiple novel 2-D material systems are explored. Chapter one introduces the present challenges faced by MOSFET scaling. Chapter two covers the integration of ultrathin III V membranes with Si. Free standing ultrathin III-V is studied to enable high performance III-V on Si MOSFETs with strain engineering and alloying. Chapter three studies the light absorption in 2-D membranes. Experimental results and theoretical analysis reveal that light absorption in the 2-D quantum membranes is quantized into a fundamental physical constant, where we call it the quantum unit of light absorption, irrelevant of most of the material dependent parameters. Chapter four starts to focus on another 2-D system, atomic thin layered chalcogenides. Single and few layered chalcogenides are first explored as channel materials, with focuses in engineering the contacts for high performance MOSFETs. Contact treatment by molecular doping methods reveals that many layered chalcogenides other than MoS2 exhibit good transport properties at single layer limit. Finally, Chapter five investigated 2-D van der Waals heterostructures built from different single layer chalcogenides. The investigation in a WSe2/MoS2 hetero-bilayer shows a large Stokes like shift between photoluminescence peak and lowest absorption peak, as well as strong photoluminescence intensity, consistent with spatially indirect transition in a type II band alignment in this van der Waals heterostructure. This result enables new family of semiconductor heterostructures having tunable optoelectronic properties with customized composite layers and highlights the ability to build van der Waals semiconductor heterostructure lasers/LEDs.

Hybrid semiconductor fiber lasers for telecommunications

NASA Astrophysics Data System (ADS)

Khalili, Alireza

2006-12-01

Highly stable edge emitting semiconductor lasers are of utmost importance in most telecommunications applications where high-speed data transmission sets strict limits on the purity of the laser signal. Unfortunately, most edge emitting semiconductor lasers, unlike gaseous or solid-state laser sources, operate with many closely spaced axial modes, which accounts for the observed instability and large spikes in the output spectrum of such lasers. Consequently, in most telecom applications distributed feedback (DFB) or distributed Bragg reflector (DBR) techniques are used to ensure stability and single-frequency operation, further adding to the cost and complexity of such lasers. Additionally, coupling of the highly elliptical output beam of these lasers to singlemode fibers complicates the packaging procedure and sub-micron alignment of various optical components is often necessary. Utilizing the evanescent coupling between a semiconductor antiresonant reflecting optical waveguide (ARROW) and a side polished fiber, this thesis presents an alternative side-coupled laser module that eliminates the need for the cumbersome multi-component alignment processes of conventional laser packages, and creates an inherent mode selection mechanism that guarantees singlemode radiation into the fiber without any gratings. We have been able to demonstrate the first side-coupled fiber semiconductor laser in this technology, coupling more than 3mW of power at 850nm directly into a 5/125mum singlemode fiber. This mixed-cavity architecture yields a high thermal stability (˜0.06nm/°C), and negligible spectral spikes are observed. Theoretical background and simulation results, as well as several supplementary materials are also presented to further rationalize the experimental data. A side-coupled light-emitter and pre-amplifier are also proposed and discussed. We also study different architectures for attaining higher efficiency, higher output power, and wavelength tunability in such lasers. Finally, we discuss possible venues for integration of these side-coupled devices in a telecommunication system. Approved for publication.

Theoretical study of new potential semiconductor surfaces performance for dye sensitized solar cell usage: TiO2-B (001), (100) and H2Ti3O7 (100)

NASA Astrophysics Data System (ADS)

German, Estefania; Faccio, Ricardo; Mombrú, Álvaro W.

2017-12-01

Hydrogen titanate (H2Ti3O7) and TiO2-B polymorph are potential surfaces identified experimentally in the last years, which need to be analyzed. To study their performance as surfaces for dye sensitized solar cells (DSSC), a set of dye adsorption configurations were evaluated on them, as model dye the small and organic catechol molecule was used. We have calculated adsorption geometry, energy, electronic transfer from dye to semiconductor adsorbent and frontier orbitals by means of density functional theory (DFT). Results show that vacancy-like defected H2Ti3O7 (100) and TiO2-B (100) surfaces present favorable adsorption energies. Finally, an adequate energy level alignment make both surfaces prone to be adequate for direct electron transfer upon excitation, from catechol to the conduction band of the semiconductors, with bands located in the Visible region of the electromagnetic spectrum. Additionally, the band structure alignment indicates an increase in the open circuit voltage, in reference to I2/I3- redox pair potential. All these characteristics make hydrogen titanate (H2Ti3O7) and TiO2-B polymorph promising for DSSC applications.

Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111)

PubMed Central

Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E.; Sanchez, Ana M.; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W.; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M.; Hasnip, Philip J.; Hase, Thomas; Bell, Gavin R.; Hirohata, Atsufumi; Lazarov, Vlado K.

2016-01-01

Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors. PMID:27869132

Shuttle Mission STS-50: Orbital Processing of High-Quality CdTe Compound Semiconductors Experiment: Final Flight Sample Characterization Report

NASA Technical Reports Server (NTRS)

Larson, David J.; Casagrande, Luis G.; DiMarzio, Don; Alexander, J. Iwan D.; Carlson, Fred; Lee, Taipo; Dudley, Michael; Raghathamachar, Balaji

1998-01-01

The Orbital Processing of High-Quality Doped and Alloyed CdTe Compound Semiconductors program was initiated to investigate, quantitatively, the influences of gravitationally dependent phenomena on the growth and quality of bulk compound semiconductors. The objective was to improve crystal quality (both structural and compositional) and to better understand and control the variables within the crystal growth production process. The empirical effort entailed the development of a terrestrial (one-g) experiment baseline for quantitative comparison with microgravity (mu-g) results. This effort was supported by the development of high-fidelity process models of heat transfer, fluid flow and solute redistribution, and thermo-mechanical stress occurring in the furnace, safety cartridge, ampoule, and crystal throughout the melting, seeding, crystal growth, and post-solidification processing. In addition, the sensitivity of the orbital experiments was analyzed with respect to the residual microgravity (mu-g) environment, both steady state and g-jitter. CdZnTe crystals were grown in one-g and in mu-g. Crystals processed terrestrially were grown at the NASA Ground Control Experiments Laboratory (GCEL) and at Grumman Aerospace Corporation (now Northrop Grumman Corporation). Two mu-g crystals were grown in the Crystal Growth Furnace (CGF) during the First United States Microgravity Laboratory Mission (USML-1), STS-50, June 24 - July 9, 1992.

A novel image encryption algorithm based on synchronized random bit generated in cascade-coupled chaotic semiconductor ring lasers

NASA Astrophysics Data System (ADS)

Li, Jiafu; Xiang, Shuiying; Wang, Haoning; Gong, Junkai; Wen, Aijun

2018-03-01

In this paper, a novel image encryption algorithm based on synchronization of physical random bit generated in a cascade-coupled semiconductor ring lasers (CCSRL) system is proposed, and the security analysis is performed. In both transmitter and receiver parts, the CCSRL system is a master-slave configuration consisting of a master semiconductor ring laser (M-SRL) with cross-feedback and a solitary SRL (S-SRL). The proposed image encryption algorithm includes image preprocessing based on conventional chaotic maps, pixel confusion based on control matrix extracted from physical random bit, and pixel diffusion based on random bit stream extracted from physical random bit. Firstly, the preprocessing method is used to eliminate the correlation between adjacent pixels. Secondly, physical random bit with verified randomness is generated based on chaos in the CCSRL system, and is used to simultaneously generate the control matrix and random bit stream. Finally, the control matrix and random bit stream are used for the encryption algorithm in order to change the position and the values of pixels, respectively. Simulation results and security analysis demonstrate that the proposed algorithm is effective and able to resist various typical attacks, and thus is an excellent candidate for secure image communication application.

Combined soft and hard X-ray ambient pressure photoelectron spectroscopy studies of semiconductor/electrolyte interfaces

DOE PAGES

Starr, David E.; Favaro, Marco; Abdi, Fatwa F.; ...

2017-05-18

The development of solar fuel generating materials would greatly benefit from a molecular level understanding of the semiconductor/electrolyte interface and changes in the interface induced by an applied potential and illumination by solar light. Ambient pressure photoelectron spectroscopy techniques with both soft and hard X-rays, AP-XPS and AP-HAXPES respectively, have the potential to markedly contribute to this understanding. In this paper we initially provide two examples of current challenges in solar fuels material development that AP-XPS and AP-HAXPES can directly a ddress. This will be followed by a brief description of the distinguishing and complementary characteristics of soft and hardmore » X-ray AP-XPS and AP-HAXPES and best approaches to achieving monolayer sensitivity in solid/aqueous electrolyte studies. In particular we focus on the detection of surface adsorbed hydroxyl groups in the presence of aqueous hydroxide anions in the electrolyte, a common situation when investigating photoanodes for solar fuel generating applications. Finally, the article concludes by providing an example of a combined AP-XPS and AP-HAXPES study of a semiconductor/aqueous electrolyte interface currently used in water splitting devices specifically the BiVO 4/aqueous potassium phosphate electrolyte interface.« less

Electrical control of second-harmonic generation in a WSe 2 monolayer transistor

DOE PAGES

Seyler, Kyle L.; Schaibley, John R.; Gong, Pu; ...

2015-04-20

Nonlinear optical frequency conversion, in which optical fields interact with a nonlinear medium to produce new field frequencies, is ubiquitous in modern photonic systems. However, the nonlinear electric susceptibilities that give rise to such phenomena are often challenging to tune in a given material and, so far, dynamical control of optical nonlinearities remains confined to research laboratories as a spectroscopic tool. In this paper, we report a mechanism to electrically control second-order optical nonlinearities in monolayer WSe 2, an atomically thin semiconductor. We show that the intensity of second-harmonic generation at the A-exciton resonance is tunable by over an ordermore » of magnitude at low temperature and nearly a factor of four at room temperature through electrostatic doping in a field-effect transistor. Such tunability arises from the strong exciton charging effects in monolayer semiconductors, which allow for exceptional control over the oscillator strengths at the exciton and trion resonances. The exciton-enhanced second-harmonic generation is counter-circularly polarized to the excitation laser due to the combination of the two-photon and one-photon valley selection rules, which have opposite helicity in the monolayer. Finally, our study paves the way towards a new platform for chip-scale, electrically tunable nonlinear optical devices based on two-dimensional semiconductors.« less

Terahertz plasmon-induced transparency based on asymmetric dual-disk resonators coupled to a semiconductor InSb waveguide and its biosensor application

NASA Astrophysics Data System (ADS)

Shahamat, Yadollah; Vahedi, Mohammad

2017-06-01

An ultracompact double eight-shaped plasmonic structure for the realization of plasmon-induced transparency (PIT) in the terahertz (THz) region has been studied. The device consists of a semiconductor-insulator-semiconductor bus waveguide coupled to the dual-disk resonators. Indium antimonide is employed to excite SPP in the THz region. The transmission characteristics of the proposed device are simulated numerically by the finite-difference time-domain method. In addition, a theoretical analysis based on the coupled-mode theory for transmission features is presented and compared with the numerical results. Results are in good agreement. Also, the dependence of PIT frequency characteristics on the radius of the outer disk is discussed in detail. In addition, by removing one of the outer disk resonators, double-PIT peaks can be observed in the transmission spectrum, and the physical mechanism of the appeared peaks is investigated. Finally, an application of the proposed structure for distinguishing different states of DNA molecules is discussed. Results show that the maximum sensitivity with 654 GHz/RIU-1 could be obtained for a single PIT structure. The frequency shifts equal to 37 and 99 GHz could be observed for the denatured and the hybridized DNA states, respectively.

Infant Eyes: A Window on Cognitive Development

ERIC Educational Resources Information Center

Aslin, Richard N.

2012-01-01

Eye-trackers suitable for use with infants are now marketed by several commercial vendors. As eye-trackers become more prevalent in infancy research, there is the potential for users to be unaware of dangers lurking "under the hood" if they assume the eye-tracker introduces no errors in measuring infants' gaze. Moreover, the influx of voluminous…

Analyzing Virtual Physics Simulations with Tracker

ERIC Educational Resources Information Center

Claessens, Tom

2017-01-01

In the physics teaching community, Tracker is well known as a user-friendly open source video analysis software, authored by Douglas Brown. With this tool, the user can trace markers indicated on a video or on stroboscopic photos and perform kinematic analyses. Tracker also includes a data modeling tool that allows one to fit some theoretical…

Space Shuttle Star Tracker Challenges

NASA Technical Reports Server (NTRS)

Herrera, Linda M.

2010-01-01

The space shuttle fleet of avionics was originally designed in the 1970's. Many of the subsystems have been upgraded and replaced, however some original hardware continues to fly. Not only fly, but has proven to be the best design available to perform its designated task. The shuttle star tracker system is currently flying as a mixture of old and new designs, each with a unique purpose to fill for the mission. Orbiter missions have tackled many varied missions in space over the years. As the orbiters began flying to the International Space Station (ISS), new challenges were discovered and overcome as new trusses and modules were added. For the star tracker subsystem, the growing ISS posed an unusual problem, bright light. With two star trackers on board, the 1970's vintage image dissector tube (IDT) star trackers track the ISS, while the new solid state design is used for dim star tracking. This presentation focuses on the challenges and solutions used to ensure star trackers can complete the shuttle missions successfully. Topics include KSC team and industry partner methods used to correct pressurized case failures and track system performance.

A low-cost, CCD solid state star tracker

NASA Technical Reports Server (NTRS)

Chmielowski, M.; Wynne, D.

1992-01-01

Applied Research Corporation (ARC) has developed an engineering model of a multi-star CCD-based tracker for space applications requiring radiation hardness, high reliability and low power consumption. The engineering unit compared favorably in functional performance tests to the standard NASA single-star tracker. Characteristics of the ARC star tracker are: field of view = 10 deg x 7.5 deg, sensitivity range of -1 to +5 star magnitude, NEA = 3 in x 3 in, linearity = 5 in x 5 in, and power consumption of 1-3 W (operating mode dependent). The software is upgradable through a remote link. The hardware-limited acquisition rate is 1-5 Hz for stars of +2 to +5 magnitude and 10-30 Hz for -1 to +2 magnitude stars. Mechanical and electrical interfaces are identical to the standard NASA star tracker.

Deep UV LEDs

NASA Astrophysics Data System (ADS)

Han, Jung; Amano, Hiroshi; Schowalter, Leo

2014-06-01

Deep ultraviolet (DUV) photons interact strongly with a broad range of chemical and biological molecules; compact DUV light sources could enable a wide range of applications in chemi/bio-sensing, sterilization, agriculture, and industrial curing. The much shorter wavelength also results in useful characteristics related to optical diffraction (for lithography) and scattering (non-line-of-sight communication). The family of III-N (AlGaInN) compound semiconductors offers a tunable energy gap from infrared to DUV. While InGaN-based blue light emitters have been the primary focus for the obvious application of solid state lighting, there is a growing interest in the development of efficient UV and DUV light-emitting devices. In the past few years we have witnessed an increasing investment from both government and industry sectors to further the state of DUV light-emitting devices. The contributions in Semiconductor Science and Technology 's special issue on DUV devices provide an up-to-date snapshot covering many relevant topics in this field. Given the expected importance of bulk AlN substrate in DUV technology, we are pleased to include a review article by Hartmann et al on the growth of AlN bulk crystal by physical vapour transport. The issue of polarization field within the deep ultraviolet LEDs is examined in the article by Braut et al. Several commercial companies provide useful updates in their development of DUV emitters, including Nichia (Fujioka et al ), Nitride Semiconductors (Muramoto et al ) and Sensor Electronic Technology (Shatalov et al ). We believe these articles will provide an excellent overview of the state of technology. The growth of AlGaN heterostructures by molecular beam epitaxy, in contrast to the common organo-metallic vapour phase epitaxy, is discussed by Ivanov et al. Since hexagonal boron nitride (BN) has received much attention as both a UV and a two-dimensional electronic material, we believe it serves readers well to include the article by Jiang et al on using BN for UV devices; potentially as a p-type wide band gap semiconductor contact. Finally, an in-depth discussion of one DUV application in defense, the non-line-of-sight (NLOS) communication, is given by Drost and Sadler. Overall, we believe that this special issue of Semiconductor Science and Technology provides a useful overview of the state-of-art in the field on DUV materials and devices. In view of the rapidly growing interest in this field, the demonstrated enhanced device performance, and the wide range of applications, this special issue can be considered a very timely contribution. Finally, we would like to thank the IOP editorial staff, in particular Alice Malhador, for their support and also like to thank all contributors for their efforts to make this special issue possible.

The chemical deposition of semiconductor thin-films for photovoltaic devices

NASA Astrophysics Data System (ADS)

Breen, Marc Louis

Initially, possible precursors to metal sulfide films formed by metal-organic chemical vapor deposition (MOCVD), the standard commercial technique for manufacturing photovoltaic semiconductors, were synthesized. Triple-junction GaInP 2/GaAs/Ge solar cells, prepared by this method, were studied to understand how chemical properties and material defects can effect the performance of photovoltaic devices. Finally, novel methods for the low-temperature, solution growth of CdS, CdSe, and CuInSe2 photovoltaic materials were targeted which will reduce manufacturing costs and increase the economic feasibility of solar energy conversion. A series of dialkyldithiocarbamate copper, gallium and indium compounds were studied as possible metal sulfide MOCVD precursors. Metal powders were oxidized by dialkylthiurams in 3- or 4-methylpyridine using standard techniques for handling air and moisture-sensitive compounds. Metal chlorides reacted directly with the sodium dialkyldithiocarbamate salts. In these complexes, the metal was found in a roughly octahedral orientation, surrounded by dithiocarbamate ligands and/or solvent molecules. Triple-junction GaInP2/GaAs/Ge cells were composed of thin-films of GaInP2 and GaAs grown monolithically on top of a germanium substrate. Each layer of semiconductor material had a different bandgap and absorbed a different portion of the solar spectrum, thus improving the overall efficiency of the cell. Work focused on dark current-voltage behavior which is known to limit solar cell open-circuit voltage, fill factor, and conversion efficiency. Cells were studied using microscopic and spectroscopic techniques to correlate the effect of physical defects in the materials with poor performance of the devices as evaluated through current vs. voltage measurements. Films of US and CdSe were readily prepared in solution through an "ion-by-ion" deposition of Cd2+ and S2- (or Se 2-) generated from the slow hydrolysis of thiourea (or dimethylthiourea). The bath chemistry was carefully controlled by the adjustment of pH to slow hydrolysis and with chelating agents to sequester the cadmium ions. Triethanolamine and ethylenediamine were both effective chelators with the latter producing thicker, clearer films. Finally, US films were grown over electrodeposited CuInSe2 to form working photovoltaic devices. In summary, contributions were made which (a) advance current methods for manufacturing photovoltaic semiconductors and (b) offer an alternative route to producing new forms of thin-film solar cell devices.

Intelligent error correction method applied on an active pixel sensor based star tracker

NASA Astrophysics Data System (ADS)

Schmidt, Uwe

2005-10-01

Star trackers are opto-electronic sensors used on-board of satellites for the autonomous inertial attitude determination. During the last years star trackers became more and more important in the field of the attitude and orbit control system (AOCS) sensors. High performance star trackers are based up today on charge coupled device (CCD) optical camera heads. The active pixel sensor (APS) technology, introduced in the early 90-ties, allows now the beneficial replacement of CCD detectors by APS detectors with respect to performance, reliability, power, mass and cost. The company's heritage in star tracker design started in the early 80-ties with the launch of the worldwide first fully autonomous star tracker system ASTRO1 to the Russian MIR space station. Jena-Optronik recently developed an active pixel sensor based autonomous star tracker "ASTRO APS" as successor of the CCD based star tracker product series ASTRO1, ASTRO5, ASTRO10 and ASTRO15. Key features of the APS detector technology are, a true xy-address random access, the multiple windowing read out and the on-chip signal processing including the analogue to digital conversion. These features can be used for robust star tracking at high slew rates and under worse conditions like stray light and solar flare induced single event upsets. A special algorithm have been developed to manage the typical APS detector error contributors like fixed pattern noise (FPN), dark signal non-uniformity (DSNU) and white spots. The algorithm works fully autonomous and adapts to e.g. increasing DSNU and up-coming white spots automatically without ground maintenance or re-calibration. In contrast to conventional correction methods the described algorithm does not need calibration data memory like full image sized calibration data sets. The application of the presented algorithm managing the typical APS detector error contributors is a key element for the design of star trackers for long term satellite applications like geostationary telecom platforms.

Reliability and validity of ten consumer activity trackers.

PubMed

Kooiman, Thea J M; Dontje, Manon L; Sprenger, Siska R; Krijnen, Wim P; van der Schans, Cees P; de Groot, Martijn

2015-01-01

Activity trackers can potentially stimulate users to increase their physical activity behavior. The aim of this study was to examine the reliability and validity of ten consumer activity trackers for measuring step count in both laboratory and free-living conditions. Healthy adult volunteers (n = 33) walked twice on a treadmill (4.8 km/h) for 30 min while wearing ten different activity trackers (i.e. Lumoback, Fitbit Flex, Jawbone Up, Nike+ Fuelband SE, Misfit Shine, Withings Pulse, Fitbit Zip, Omron HJ-203, Yamax Digiwalker SW-200 and Moves mobile application). In free-living conditions, 56 volunteers wore the same activity trackers for one working day. Test-retest reliability was analyzed with the Intraclass Correlation Coefficient (ICC). Validity was evaluated by comparing each tracker with the gold standard (Optogait system for laboratory and ActivPAL for free-living conditions), using paired samples t-tests, mean absolute percentage errors, correlations and Bland-Altman plots. Test-retest analysis revealed high reliability for most trackers except for the Omron (ICC .14), Moves app (ICC .37) and Nike+ Fuelband (ICC .53). The mean absolute percentage errors of the trackers in laboratory and free-living conditions respectively, were: Lumoback (-0.2, -0.4), Fibit Flex (-5.7, 3.7), Jawbone Up (-1.0, 1.4), Nike+ Fuelband (-18, -24), Misfit Shine (0.2, 1.1), Withings Pulse (-0.5, -7.9), Fitbit Zip (-0.3, 1.2), Omron (2.5, -0.4), Digiwalker (-1.2, -5.9), and Moves app (9.6, -37.6). Bland-Altman plots demonstrated that the limits of agreement varied from 46 steps (Fitbit Zip) to 2422 steps (Nike+ Fuelband) in the laboratory condition, and 866 steps (Fitbit Zip) to 5150 steps (Moves app) in the free-living condition. The reliability and validity of most trackers for measuring step count is good. The Fitbit Zip is the most valid whereas the reliability and validity of the Nike+ Fuelband is low.

Development of the FitSight Fitness Tracker to Increase Time Outdoors to Prevent Myopia.

PubMed

Verkicharla, Pavan K; Ramamurthy, Dharani; Nguyen, Quang Duc; Zhang, Xinquan; Pu, Suan-Hui; Malhotra, Rahul; Ostbye, Truls; Lamoureux, Ecosse L; Saw, Seang-Mei

2017-06-01

To develop a fitness tracker (FitSight) to encourage children to increase time spent outdoors. To evaluate the wear pattern for this tracker and outdoor time pattern by estimating light illumination levels among children. The development of the FitSight fitness tracker involved the designing of two components: (1) the smartwatch with custom-made FitSight watch application (app) to log the instant light illuminance levels the wearer is exposed to, and (2) a companion smartphone app that synchronizes the time outdoors recorded by the smartwatch to smartphone via Bluetooth communication. Smartwatch wear patterns and tracker-recorded daily light illuminance levels data were gathered over 7 days from 23 Singapore children (mean ± standard deviation age: 9.2 ± 1.4 years). Feedback about the tracker was obtained from 14 parents using a three-level rating scale: very poor/poor/good. Of the 14 parents, 93% rated the complete "FitSight fitness tracker" as good and 64% rated its wearability as good. While 61% of 23 children wore the watch on all study days (i.e., 0 nonwear days), 26% had 1 nonwear day, and 4.5% children each had 3, 4, and 5 nonwear days, respectively. On average, children spent approximately 1 hour in light levels greater than 1000 lux on weekdays and 1.3 hours on weekends (60 ± 46 vs. 79 ± 53 minutes, P = 0.19). Mean number of outdoor "spurts" (light illuminance levels >1000 lux) per day was 8 ± 3 spurts with spurt duration of 34 ± 32 minutes. The FitSight tracker with its novel features may motivate children to increase time outdoors and play an important role in supplementing community outdoor programs to prevent myopia. If the developed noninvasive, wearable, smartwatch-based fitness tracker, FitSight, promotes daytime outdoor activity among children, it will be beneficial in addressing the epidemic of myopia.

Compensation for Time-Dependent Star Tracker Thermal Deformation on the Aqua Spacecraft

NASA Technical Reports Server (NTRS)

Hashmall, Joseph A.; Natanson, Gregory; Glickman, Jonathan; Sedlak, Joseph

2004-01-01

Analysis of attitude sensor data from the Aqua mission showed small but systematic differences between batch least-squares and extended Kalman filter attitudes. These differences were also found to be correlated with star tracker residuals, gyro bias estimates, and star tracker baseplate temperatures. This paper describes the analysis that shows that these correlations are all consistent with a single cause: time-dependent thermal deformation of star tracker alignments. These varying alignments can be separated into relative and common components. The relative misalignments can be determined and compensated for. The common misalignments can only be determined in special cases.

Users' experiences of wearable activity trackers: a cross-sectional study.

PubMed

Maher, Carol; Ryan, Jillian; Ambrosi, Christina; Edney, Sarah

2017-11-15

Wearable activity trackers offer considerable promise for helping users to adopt healthier lifestyles. This study aimed to explore users' experience of activity trackers, including usage patterns, sharing of data to social media, perceived behaviour change (physical activity, diet and sleep), and technical issues/barriers to use. A cross-sectional online survey was developed and administered to Australian adults who were current or former activity tracker users. Results were analysed descriptively, with differences between current and former users and wearable brands explored using independent samples t-tests, Mann-Whitney, and chi square tests. Participants included 200 current and 37 former activity tracker users (total N = 237) with a mean age of 33.1 years (SD 12.4, range 18-74 years). Fitbit (67.5%) and Garmin devices (16.5%) were most commonly reported. Participants typically used their trackers for sustained periods (5-7 months) and most intended to continue usage. Participants reported they had improved their physical activity (51-81%) more commonly than they had their diet (14-40%) or sleep (11-24%), and slightly more participants reported to value the real time feedback (89%) compared to the long-term monitoring (78%). Most users (70%) reported they had experienced functionality issues with their devices, most commonly related to battery life and technical difficulties. Results suggest users find activity trackers appealing and useful tools for increasing perceived physical activity levels over a sustained period.

Analysis of the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery☆

PubMed Central

Arba-Mosquera, Samuel; Aslanides, Ioannis M.

2012-01-01

Purpose To analyze the effects of Eye-Tracker performance on the pulse positioning errors during refractive surgery. Methods A comprehensive model, which directly considers eye movements, including saccades, vestibular, optokinetic, vergence, and miniature, as well as, eye-tracker acquisition rate, eye-tracker latency time, scanner positioning time, laser firing rate, and laser trigger delay have been developed. Results Eye-tracker acquisition rates below 100 Hz correspond to pulse positioning errors above 1.5 mm. Eye-tracker latency times to about 15 ms correspond to pulse positioning errors of up to 3.5 mm. Scanner positioning times to about 9 ms correspond to pulse positioning errors of up to 2 mm. Laser firing rates faster than eye-tracker acquisition rates basically duplicate pulse-positioning errors. Laser trigger delays to about 300 μs have minor to no impact on pulse-positioning errors. Conclusions The proposed model can be used for comparison of laser systems used for ablation processes. Due to the pseudo-random nature of eye movements, positioning errors of single pulses are much larger than observed decentrations in the clinical settings. There is no single parameter that ‘alone’ minimizes the positioning error. It is the optimal combination of the several parameters that minimizes the error. The results of this analysis are important to understand the limitations of correcting very irregular ablation patterns.

Collaborative engineering and design management for the Hobby-Eberly Telescope tracker upgrade

NASA Astrophysics Data System (ADS)

Mollison, Nicholas T.; Hayes, Richard J.; Good, John M.; Booth, John A.; Savage, Richard D.; Jackson, John R.; Rafal, Marc D.; Beno, Joseph H.

2010-07-01

The engineering and design of systems as complex as the Hobby-Eberly Telescope's* new tracker require that multiple tasks be executed in parallel and overlapping efforts. When the design of individual subsystems is distributed among multiple organizations, teams, and individuals, challenges can arise with respect to managing design productivity and coordinating successful collaborative exchanges. This paper focuses on design management issues and current practices for the tracker design portion of the Hobby-Eberly Telescope Wide Field Upgrade project. The scope of the tracker upgrade requires engineering contributions and input from numerous fields including optics, instrumentation, electromechanics, software controls engineering, and site-operations. Successful system-level integration of tracker subsystems and interfaces is critical to the telescope's ultimate performance in astronomical observation. Software and process controls for design information and workflow management have been implemented to assist the collaborative transfer of tracker design data. The tracker system architecture and selection of subsystem interfaces has also proven to be a determining factor in design task formulation and team communication needs. Interface controls and requirements change controls will be discussed, and critical team interactions are recounted (a group-participation Failure Modes and Effects Analysis [FMEA] is one of special interest). This paper will be of interest to engineers, designers, and managers engaging in multi-disciplinary and parallel engineering projects that require coordination among multiple individuals, teams, and organizations.

WDM Nanoscale Laser Diodes for Si Photonic Interconnects

DTIC Science & Technology

2016-07-25

mounting on silicon. The nanoscale VCSELs can achieve small optical modes and present a compact laser diode that is also robust. In this work we have used...Distribution Unlimited UU UU UU UU 25-07-2016 1-Feb-2012 31-Dec-2015 Final Report: WDM Nanoscale Laser Diodes for Si Photonic Interconnects The views...P.O. Box 12211 Research Triangle Park, NC 27709-2211 VCSEL, optical interconnect, laser diode , semiconductor laser, microcavity REPORT DOCUMENTATION

Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy

NASA Technical Reports Server (NTRS)

Mazuruk, Konstantin; Ramachandran, Narayanan; Grugel, Richard; Curreri, Peter A. (Technical Monitor)

2002-01-01

The Traveling Magnetic Field (TMF) technique, recently proposed to control meridional flow in electrically conducting melts, is reviewed. In particular, the natural convection damping capability of this technique has been numerically demonstrated with the implication of significantly improving crystal quality. Advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, are discussed. Finally, results of experiments with mixing metallic alloys in long ampoules using TMF is presented

User Acceptance of Wrist-Worn Activity Trackers Among Community-Dwelling Older Adults: Mixed Method Study

PubMed Central

Puri, Arjun; Kim, Ben; Nguyen, Olivier; Stolee, Paul; Tung, James

2017-01-01

Background Wearable activity trackers are newly emerging technologies with the anticipation for successfully supporting aging-in-place. Consumer-grade wearable activity trackers are increasingly ubiquitous in the market, but the attitudes toward, as well as acceptance and voluntary use of, these trackers in older population are poorly understood. Objective The aim of this study was to assess acceptance and usage of wearable activity trackers in Canadian community-dwelling older adults, using the potentially influential factors as identified in literature and technology acceptance model. Methods A mixed methods design was used. A total of 20 older adults aged 55 years and older were recruited from Southwestern Ontario. Participants used 2 different wearable activity trackers (Xiaomi Mi Band and Microsoft Band) separately for each segment in the crossover design study for 21 days (ie, 42 days total). A questionnaire was developed to capture acceptance and experience at the end of each segment, representing 2 different devices. Semistructured interviews were conducted with 4 participants, and a content analysis was performed. Results Participants ranged in age from 55 years to 84 years (mean age: 64 years). The Mi Band gained higher levels of acceptance (16/20, 80%) compared with the Microsoft Band (10/20, 50%). The equipment characteristics dimension scored significantly higher for the Mi Band (P<.05). The amount a participant was willing to pay for the device was highly associated with technology acceptance (P<.05). Multivariate logistic regression with 3 covariates resulted in an area under the curve of 0.79. Content analysis resulted in the formation of the following main themes: (1) smartphones as facilitators of wearable activity trackers; (2) privacy is less of a concern for wearable activity trackers, (3) value proposition: self-awareness and motivation; (4) subjective norm, social support, and sense of independence; and (5) equipment characteristics matter: display, battery, comfort, and aesthetics. Conclusions Older adults were mostly accepting of wearable activity trackers, and they had a clear understanding of its value for their lives. Wearable activity trackers were uniquely considered more personal than other types of technologies, thereby the equipment characteristics including comfort, aesthetics, and price had a significant impact on the acceptance. Results indicated that privacy was less of concern for older adults, but it may have stemmed from a lack of understanding of the privacy risks and implications. These findings add to emerging research that investigates acceptance and factors that may influence acceptance of wearable activity trackers among older adults. PMID:29141837

Cross modality registration of video and magnetic tracker data for 3D appearance and structure modeling

NASA Astrophysics Data System (ADS)

Sargent, Dusty; Chen, Chao-I.; Wang, Yuan-Fang

2010-02-01

The paper reports a fully-automated, cross-modality sensor data registration scheme between video and magnetic tracker data. This registration scheme is intended for use in computerized imaging systems to model the appearance, structure, and dimension of human anatomy in three dimensions (3D) from endoscopic videos, particularly colonoscopic videos, for cancer research and clinical practices. The proposed cross-modality calibration procedure operates this way: Before a colonoscopic procedure, the surgeon inserts a magnetic tracker into the working channel of the endoscope or otherwise fixes the tracker's position on the scope. The surgeon then maneuvers the scope-tracker assembly to view a checkerboard calibration pattern from a few different viewpoints for a few seconds. The calibration procedure is then completed, and the relative pose (translation and rotation) between the reference frames of the magnetic tracker and the scope is determined. During the colonoscopic procedure, the readings from the magnetic tracker are used to automatically deduce the pose (both position and orientation) of the scope's reference frame over time, without complicated image analysis. Knowing the scope movement over time then allows us to infer the 3D appearance and structure of the organs and tissues in the scene. While there are other well-established mechanisms for inferring the movement of the camera (scope) from images, they are often sensitive to mistakes in image analysis, error accumulation, and structure deformation. The proposed method using a magnetic tracker to establish the camera motion parameters thus provides a robust and efficient alternative for 3D model construction. Furthermore, the calibration procedure does not require special training nor use expensive calibration equipment (except for a camera calibration pattern-a checkerboard pattern-that can be printed on any laser or inkjet printer).

Development and evaluation of a hand tracker using depth images captured from an overhead perspective.

PubMed

Czarnuch, Stephen; Mihailidis, Alex

2015-03-27

We present the development and evaluation of a robust hand tracker based on single overhead depth images for use in the COACH, an assistive technology for people with dementia. The new hand tracker was designed to overcome limitations experienced by the COACH in previous clinical trials. We train a random decision forest classifier using ∼5000 manually labeled, unbalanced, training images. Hand positions from the classifier are translated into task actions based on proximity to environmental objects. Tracker performance is evaluated using a large set of ∼24 000 manually labeled images captured from 41 participants in a fully-functional washroom, and compared to the system's previous colour-based hand tracker. Precision and recall were 0.994 and 0.938 for the depth tracker compared to 0.981 and 0.822 for the colour tracker with the current data, and 0.989 and 0.466 in the previous study. The improved tracking performance supports integration of the depth-based tracker into the COACH toward unsupervised, real-world trials. Implications for Rehabilitation The COACH is an intelligent assistive technology that can enable people with cognitive disabilities to stay at home longer, supporting the concept of aging-in-place. Automated prompting systems, a type of intelligent assistive technology, can help to support the independent completion of activities of daily living, increasing the independence of people with cognitive disabilities while reducing the burden of care experienced by caregivers. Robust motion tracking using depth imaging supports the development of intelligent assistive technologies like the COACH. Robust motion tracking also has application to other forms of assistive technologies including gaming, human-computer interaction and automated assessments.

Behavior Change Techniques Present in Wearable Activity Trackers: A Critical Analysis

PubMed Central

Mercer, Kathryn; Li, Melissa; Giangregorio, Lora; Burns, Catherine

2016-01-01

Background Wearable activity trackers are promising as interventions that offer guidance and support for increasing physical activity and health-focused tracking. Most adults do not meet their recommended daily activity guidelines, and wearable fitness trackers are increasingly cited as having great potential to improve the physical activity levels of adults. Objective The objective of this study was to use the Coventry, Aberdeen, and London-Refined (CALO-RE) taxonomy to examine if the design of wearable activity trackers incorporates behavior change techniques (BCTs). A secondary objective was to critically analyze whether the BCTs present relate to known drivers of behavior change, such as self-efficacy, with the intention of extending applicability to older adults in addition to the overall population. Methods Wearing each device for a period of 1 week, two independent raters used CALO-RE taxonomy to code the BCTs of the seven wearable activity trackers available in Canada as of March 2014. These included Fitbit Flex, Misfit Shine, Withings Pulse, Jawbone UP24, Spark Activity Tracker by SparkPeople, Nike+ FuelBand SE, and Polar Loop. We calculated interrater reliability using Cohen's kappa. Results The average number of BCTs identified was 16.3/40. Withings Pulse had the highest number of BCTs and Misfit Shine had the lowest. Most techniques centered around self-monitoring and self-regulation, all of which have been associated with improved physical activity in older adults. Techniques related to planning and providing instructions were scarce. Conclusions Overall, wearable activity trackers contain several BCTs that have been shown to increase physical activity in older adults. Although more research and development must be done to fully understand the potential of wearables as health interventions, the current wearable trackers offer significant potential with regard to BCTs relevant to uptake by all populations, including older adults. PMID:27122452

Behavior Change Techniques Present in Wearable Activity Trackers: A Critical Analysis.

PubMed

Mercer, Kathryn; Li, Melissa; Giangregorio, Lora; Burns, Catherine; Grindrod, Kelly

2016-04-27

Wearable activity trackers are promising as interventions that offer guidance and support for increasing physical activity and health-focused tracking. Most adults do not meet their recommended daily activity guidelines, and wearable fitness trackers are increasingly cited as having great potential to improve the physical activity levels of adults. The objective of this study was to use the Coventry, Aberdeen, and London-Refined (CALO-RE) taxonomy to examine if the design of wearable activity trackers incorporates behavior change techniques (BCTs). A secondary objective was to critically analyze whether the BCTs present relate to known drivers of behavior change, such as self-efficacy, with the intention of extending applicability to older adults in addition to the overall population. Wearing each device for a period of 1 week, two independent raters used CALO-RE taxonomy to code the BCTs of the seven wearable activity trackers available in Canada as of March 2014. These included Fitbit Flex, Misfit Shine, Withings Pulse, Jawbone UP24, Spark Activity Tracker by SparkPeople, Nike+ FuelBand SE, and Polar Loop. We calculated interrater reliability using Cohen's kappa. The average number of BCTs identified was 16.3/40. Withings Pulse had the highest number of BCTs and Misfit Shine had the lowest. Most techniques centered around self-monitoring and self-regulation, all of which have been associated with improved physical activity in older adults. Techniques related to planning and providing instructions were scarce. Overall, wearable activity trackers contain several BCTs that have been shown to increase physical activity in older adults. Although more research and development must be done to fully understand the potential of wearables as health interventions, the current wearable trackers offer significant potential with regard to BCTs relevant to uptake by all populations, including older adults.

IMM tracking of a theater ballistic missile during boost phase

NASA Astrophysics Data System (ADS)

Hutchins, Robert G.; San Jose, Anthony

1998-09-01

Since the SCUD launches in the Gulf War, theater ballistic missile (TBM) systems have become a growing concern for the US military. Detection, tracking and engagement during boost phase or shortly after booster cutoff are goals that grow in importance with the proliferation of weapons of mass destruction. This paper addresses the performance of tracking algorithms for TBMs during boost phase and across the transition to ballistic flight. Three families of tracking algorithms are examined: alpha-beta-gamma trackers, Kalman-based trackers, and the interactive multiple model (IMM) tracker. In addition, a variation on the IMM to include prior knowledge of a booster cutoff parameter is examined. Simulated data is used to compare algorithms. Also, the IMM tracker is run on an actual ballistic missile trajectory. Results indicate that IMM trackers show significant advantage in tracking through the model transition represented by booster cutoff.

Robust object tacking based on self-adaptive search area

NASA Astrophysics Data System (ADS)

Dong, Taihang; Zhong, Sheng

2018-02-01

Discriminative correlation filter (DCF) based trackers have recently achieved excellent performance with great computational efficiency. However, DCF based trackers suffer boundary effects, which result in the unstable performance in challenging situations exhibiting fast motion. In this paper, we propose a novel method to mitigate this side-effect in DCF based trackers. We change the search area according to the prediction of target motion. When the object moves fast, broad search area could alleviate boundary effects and reserve the probability of locating object. When the object moves slowly, narrow search area could prevent effect of useless background information and improve computational efficiency to attain real-time performance. This strategy can impressively soothe boundary effects in situations exhibiting fast motion and motion blur, and it can be used in almost all DCF based trackers. The experiments on OTB benchmark show that the proposed framework improves the performance compared with the baseline trackers.

Sign-tracking predicts increased choice of cocaine over food in rats.

PubMed

Tunstall, Brendan J; Kearns, David N

2015-03-15

The purpose of this study was to determine whether the tendency to sign-track to a food cue was predictive of rats' choice of cocaine over food. First, rats were trained on a procedure where insertion of a retractable lever was paired with food. A sub-group of rats - sign-trackers - primarily approached and contacted the lever, while another sub-group - goal-trackers - approached the site of food delivery. Rats were then trained on a choice task where they could choose between an infusion of cocaine (1.0 mg/kg) and a food pellet (45 mg). Sign-trackers chose cocaine over food significantly more often than did goal-trackers. These results support the incentive-salience theory of addiction and add to a growing number of studies which suggest that sign-trackers may model an addiction-prone phenotype. Copyright © 2014 Elsevier B.V. All rights reserved.

Mechanical stability of the CMS strip tracker measured with a laser alignment system

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

Sirunyan, A. M.; Tumasyan, A.; Adam, W.

Here, the CMS tracker consists of 206 m 2 of silicon strip sensors assembled on carbon fibre composite structures and is designed for operation in the temperature range from –25 to +25°C. The mechanical stability of tracker components during physics operation was monitored with a few μm resolution using a dedicated laser alignment system as well as particle tracks from cosmic rays and hadron-hadron collisions. During the LHC operational period of 2011–2013 at stable temperatures, the components of the tracker were observed to experience relative movements of less than 30μm. In addition, temperature variations were found to cause displacements ofmore » tracker structures of about 2μm°C, which largely revert to their initial positions when the temperature is restored to its original value.« less

Mechanical stability of the CMS strip tracker measured with a laser alignment system

DOE PAGES

Sirunyan, A. M.; Tumasyan, A.; Adam, W.; ...

2017-04-21

Here, the CMS tracker consists of 206 m 2 of silicon strip sensors assembled on carbon fibre composite structures and is designed for operation in the temperature range from –25 to +25°C. The mechanical stability of tracker components during physics operation was monitored with a few μm resolution using a dedicated laser alignment system as well as particle tracks from cosmic rays and hadron-hadron collisions. During the LHC operational period of 2011–2013 at stable temperatures, the components of the tracker were observed to experience relative movements of less than 30μm. In addition, temperature variations were found to cause displacements ofmore » tracker structures of about 2μm°C, which largely revert to their initial positions when the temperature is restored to its original value.« less

Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process

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

Swain, Basudev, E-mail: Swain@iae.re.kr; Mishra, Chinmayee; Lee, Chan Gi

2015-07-15

Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga{sub 0.97}N{sub 0.9}O{sub 0.09} is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga{sub 0.97}N{sub 0.9}O{sub 0.09} of the MOCVD dust is leached at the optimum condition. Subsequently, the leachmore » residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4 M HCl, 100 °C and pulp density of 100 kg/m{sup 3,} respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition. - Highlights: • Waste MOCVD dust is treated through mechanochemical leaching. • GaN is hardly leached, and converted to NaGaO{sub 2} through ball milling and annealing. • Process for gallium recovery from waste MOCVD dust has been developed. • Thermal analysis and phase properties of GaN to Ga{sub 2}O{sub 3} and GaN to NaGaO{sub 2} is revealed. • Solid-state chemistry involved in this process is reported.« less

Adaptive Neural Star Tracker Calibration for Precision Spacecraft Pointing and Tracking

NASA Technical Reports Server (NTRS)

Bayard, David S.

1996-01-01

The Star Tracker is an essential sensor for precision pointing and tracking in most 3-axis stabilized spacecraft. In the interest (of) improving pointing performance by taking advantage of dramatic increases in flight computer power and memory anticipated over the next decade, this paper investigates the use of a neural net for adaptive in-flight calibration of the Star Tracker.

Improvement of Hungarian Joint Terminal Attack Program

DTIC Science & Technology

2013-06-13

LST Laser Spot Tracker NVG Night Vision Goggle ROMAD Radio Operator Maintainer and Driver ROVER Remotely Operated Video Enhanced Receiver TACP...visual target designation. The other component consists of a laser spot tracker (LST), which identifies targets by tracking laser energy reflecting...capability for every type of night time missions, laser spot tracker for laser spot search missions, remotely operated video enhanced receiver

An accuracy measurement method for star trackers based on direct astronomic observation

PubMed Central

Sun, Ting; Xing, Fei; Wang, Xiaochu; You, Zheng; Chu, Daping

2016-01-01

Star tracker is one of the most promising optical attitude measurement devices and it is widely used in spacecraft for its high accuracy. However, how to realize and verify such an accuracy remains a crucial but unsolved issue until now. The authenticity of the accuracy measurement method of a star tracker will eventually determine the satellite performance. A new and robust accuracy measurement method for a star tracker based on the direct astronomical observation is proposed here. In comparison with the conventional method with simulated stars, this method utilizes real navigation stars as observation targets which makes the measurement results more authoritative and authentic. Transformations between different coordinate systems are conducted on the account of the precision movements of the Earth, and the error curves of directional vectors are obtained along the three axes. Based on error analysis and accuracy definitions, a three-axis accuracy evaluation criterion has been proposed in this paper, which could determine pointing and rolling accuracy of a star tracker directly. Experimental measurements confirm that this method is effective and convenient to implement. Such a measurement environment is close to the in-orbit conditions and it can satisfy the stringent requirement for high-accuracy star trackers. PMID:26948412

An accuracy measurement method for star trackers based on direct astronomic observation.

PubMed

Sun, Ting; Xing, Fei; Wang, Xiaochu; You, Zheng; Chu, Daping

2016-03-07

Star tracker is one of the most promising optical attitude measurement devices and it is widely used in spacecraft for its high accuracy. However, how to realize and verify such an accuracy remains a crucial but unsolved issue until now. The authenticity of the accuracy measurement method of a star tracker will eventually determine the satellite performance. A new and robust accuracy measurement method for a star tracker based on the direct astronomical observation is proposed here. In comparison with the conventional method with simulated stars, this method utilizes real navigation stars as observation targets which makes the measurement results more authoritative and authentic. Transformations between different coordinate systems are conducted on the account of the precision movements of the Earth, and the error curves of directional vectors are obtained along the three axes. Based on error analysis and accuracy definitions, a three-axis accuracy evaluation criterion has been proposed in this paper, which could determine pointing and rolling accuracy of a star tracker directly. Experimental measurements confirm that this method is effective and convenient to implement. Such a measurement environment is close to the in-orbit conditions and it can satisfy the stringent requirement for high-accuracy star trackers.

Analyzing Virtual Physics Simulations with Tracker

NASA Astrophysics Data System (ADS)

Claessens, Tom

2017-12-01

In the physics teaching community, Tracker is well known as a user-friendly open source video analysis software, authored by Douglas Brown. With this tool, the user can trace markers indicated on a video or on stroboscopic photos and perform kinematic analyses. Tracker also includes a data modeling tool that allows one to fit some theoretical equations of motion onto experimentally obtained data. In the field of particle mechanics, Tracker has been effectively used for learning and teaching about projectile motion, "toss up" and free-fall vertical motion, and to explain the principle of mechanical energy conservation. Also, Tracker has been successfully used in rigid body mechanics to interpret the results of experiments with rolling/slipping cylinders and moving rods. In this work, I propose an original method in which Tracker is used to analyze virtual computer simulations created with a physics-based motion solver, instead of analyzing video recording or stroboscopic photos. This could be an interesting approach to study kinematics and dynamics problems in physics education, in particular when there is no or limited access to physical labs. I demonstrate the working method with a typical (but quite challenging) problem in classical mechanics: a slipping/rolling cylinder on a rough surface.

TE-Tracker: systematic identification of transposition events through whole-genome resequencing.

PubMed

Gilly, Arthur; Etcheverry, Mathilde; Madoui, Mohammed-Amin; Guy, Julie; Quadrana, Leandro; Alberti, Adriana; Martin, Antoine; Heitkam, Tony; Engelen, Stefan; Labadie, Karine; Le Pen, Jeremie; Wincker, Patrick; Colot, Vincent; Aury, Jean-Marc

2014-11-19

Transposable elements (TEs) are DNA sequences that are able to move from their location in the genome by cutting or copying themselves to another locus. As such, they are increasingly recognized as impacting all aspects of genome function. With the dramatic reduction in cost of DNA sequencing, it is now possible to resequence whole genomes in order to systematically characterize novel TE mobilization in a particular individual. However, this task is made difficult by the inherently repetitive nature of TE sequences, which in some eukaryotes compose over half of the genome sequence. Currently, only a few software tools dedicated to the detection of TE mobilization using next-generation-sequencing are described in the literature. They often target specific TEs for which annotation is available, and are only able to identify families of closely related TEs, rather than individual elements. We present TE-Tracker, a general and accurate computational method for the de-novo detection of germ line TE mobilization from re-sequenced genomes, as well as the identification of both their source and destination sequences. We compare our method with the two classes of existing software: specialized TE-detection tools and generic structural variant (SV) detection tools. We show that TE-Tracker, while working independently of any prior annotation, bridges the gap between these two approaches in terms of detection power. Indeed, its positive predictive value (PPV) is comparable to that of dedicated TE software while its sensitivity is typical of a generic SV detection tool. TE-Tracker demonstrates the benefit of adopting an annotation-independent, de novo approach for the detection of TE mobilization events. We use TE-Tracker to provide a comprehensive view of transposition events induced by loss of DNA methylation in Arabidopsis. TE-Tracker is freely available at http://www.genoscope.cns.fr/TE-Tracker . We show that TE-Tracker accurately detects both the source and destination of novel transposition events in re-sequenced genomes. Moreover, TE-Tracker is able to detect all potential donor sequences for a given insertion, and can identify the correct one among them. Furthermore, TE-Tracker produces significantly fewer false positives than common SV detection programs, thus greatly facilitating the detection and analysis of TE mobilization events.

Fabrication of Semiconductor ZnO Nanostructures for Versatile SERS Application

PubMed Central

Yang, Lili; Yang, Yong; Ma, Yunfeng; Li, Shuai; Wei, Yuquan; Huang, Zhengren; Long, Nguyen Viet

2017-01-01

Since the initial discovery of surface-enhanced Raman scattering (SERS) in the 1970s, it has exhibited a huge potential application in many fields due to its outstanding advantages. Since the ultra-sensitive noble metallic nanostructures have increasingly exposed themselves as having some problems during application, semiconductors have been gradually exploited as one of the critical SERS substrate materials due to their distinctive advantages when compared with noble metals. ZnO is one of the most representative metallic oxide semiconductors with an abundant reserve, various and cost-effective fabrication techniques, as well as special physical and chemical properties. Thanks to the varied morphologies, size-dependent exciton, good chemical stability, a tunable band gap, carrier concentration, and stoichiometry, ZnO nanostructures have the potential to be exploited as SERS substrates. Moreover, other distinctive properties possessed by ZnO such as biocompatibility, photocatcalysis and self-cleaning, and gas- and chemo-sensitivity can be synergistically integrated and exerted with SERS activity to realize the multifunctional potential of ZnO substrates. In this review, we discuss the inevitable development trend of exploiting the potential semiconductor ZnO as a SERS substrate. After clarifying the root cause of the great disparity between the enhancement factor (EF) of noble metals and that of ZnO nanostructures, two specific methods are put forward to improve the SERS activity of ZnO, namely: elemental doping and combination of ZnO with noble metals. Then, we introduce a distinctive advantage of ZnO as SERS substrate and illustrate the necessity of reporting a meaningful average EF. We also summarize some fabrication methods for ZnO nanostructures with varied dimensions (0–3 dimensions). Finally, we present an overview of ZnO nanostructures for the versatile SERS application. PMID:29156600

Evaluating electrically insulating films deposited on V-4% Cr-4% Ti by reactive CVD

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

Park, J.H.; Cho, W.D.

1997-04-01

Previous CaO coatings on V-4%Cr-4%Ti exhibited high-ohmic insulator behavior even though a small amount of vanadium from the alloy was incorporated in the coating. However, when the vanadium concentration in the coatings is > 15 wt%, the coating becomes conductive. When the vanadium concentration is high in localized areas, a calcium vanadate phase that exhibits semiconductor behavior can form. To explore this situation, CaO and Ca-V-O coatings were produced on vanadium alloys by chemical vapor deposition (CVD) and by a metallic-vapor process to investigate the electrical resistance of the coatings. Initially, the vanadium alloy specimens were either charged with oxygenmore » in argon that contained trace levels of oxygen, or oxidized for 1.5-3 h in a 1% CO-CO{sub 2} gas mixture or in air to form vanadium oxide at 625-650{degrees}C. Most of the specimens were exposed to calcium vapor at 800-850{degrees}C. Initial and final weights were obtained to monitor each step, and surveillance samples were removed for examination by optical and scanning electron microscopy and electron-energy-dispersive and X-ray diffraction analysis; the electrical resistivity was also measured. The authors found that Ca-V-O films exhibited insulator behavior when the ratio of calcium concentration to vanadium concentration R in the film was > 0.9, and semiconductor or conductor behavior for R < 0.8. However, in some cases, semiconductor behavior was observed when CaO-coated samples with R > 0.98 were exposed in liquid lithium. Based on these studies, the authors conclude that semiconductor behavior occurs if a conductive calcium vanadate phase is present in localized regions in the CaO coating.« less

X-ray Characterization of Oxide-based Magnetic Semiconductors

NASA Astrophysics Data System (ADS)

Idzerda, Yves

2008-05-01

Although the evidence for magnetic semiconductors (not simply semiconductors which are ferromagnetic) is compelling, there is much uncertainty in the mechanism for the polarization of the carriers, suggesting that it must be quite novel. Recent experimental evidence suggests that this mechanism is similar to the polaron percolation theory proposed by Kaminski and Das Sarma,ootnotetextKaminski and S. Das Sarma, Physical Review Letters 88, 247202 (2002). which was recently applied specifically to doped oxides by Coey et al.ootnotetextJ. M. D. Coey, M. Venkatesan, and C. B. Fitzgerald, Nature Materials 4, 173 (2005). where the ferromagnetism is driven by the percolation of polarons generated by defects or dopants. We have used X-ray absorption spectroscopy at the L-edges and K-edges for low concentrations transition metal (TM) doped magnetic oxides (including TiO2, La1-xSrxO3, HfO2, and In2O3). We have found that in most cases, the transition metal assumes a valence consistent with being at a substitutional, and not interstitial site. We have also measured the X-ray Magnetic Circular Dichroism spectra. Although these materials show strong bulk magnetization, we are unable to detect a robust dichroism feature associated with magnetic elements in the host semiconductor. In the cases where a dichroism signal was observed, it was very weak and could be ascribed to a distinct ferromagnetic phase (TM metal cluster, TM oxide particulate, etc.) separate from the host material. This fascinating absence of a dichroic signal and its significant substantiation of important features of the polaron percolation model may help to finally resolve the issue of ferromagnetism in magnetically doped oxides.

Specific peptide for functionalization of GaN

NASA Astrophysics Data System (ADS)

Estephan, E.; Larroque, C.; Cloitre, T.; Cuisinier, F. J. G.; Gergely, C.

2008-04-01

Nanobiotechnology aims to exploit biomolecular recognition and self-assembly capabilities for integrating advanced materials into medicine and biology. However frequent problems are encountered at the interface of substrate-biological molecule, as the direct physical adsorption of biological molecules is dependent of unpredictable non-specific interactions with the surface, often causing their denaturation. Therefore, a proper functionalization of the substrate should avoid a loss of biological activity. In this work we address the functionalization of the semiconductor GaN (0001) for biosensing applications. The basic interest of using III-V class semiconductors is their good light emitting properties and a fair chemical stability that allows various applications of these materials. The technology chosen to elaborate GaN-specific peptides is the combinatorial phage-display method, a biological screening procedure based on affinity selection. An M13 bacteriophage library has been used to screen 10 10 different peptides against the GaN (0001) surface to finally isolate one specific peptide. The preferential attachment of the biotinylated selected peptide onto the GaN (0001), in close proximity to a surface of different chemical and structural composition has been demonstrated by fluorescence microscopy. Further physicochemical studies have been initiated to evaluate the semiconductor-peptide interface and understand the details in the specific recognition of peptides for semiconductor substrates. Fourier Transform Infrared spectroscopy in Attenuated Total Reflection mode (FTIR-ATR) has been employed to prove the presence of peptides on the surface. Our Atomic Force Microscopy (AFM) studies on the morphology of the GaN surface after functionalization revealed a total surface coverage by a very thin, homogeneous peptide layer. Due to its good biocompatibility, functionalized GaN devices might evolve in a new class of implantable biosensors for medical applications.

Collective Poisson process with periodic rates: applications in physics from micro-to nanodevices.

PubMed

da Silva, Roberto; Lamb, Luis C; Wirth, Gilson Inacio

2011-01-28

Continuous reductions in the dimensions of semiconductor devices have led to an increasing number of noise sources, including random telegraph signals (RTS) due to the capture and emission of electrons by traps at random positions between oxide and semiconductor. The models traditionally used for microscopic devices become of limited validity in nano- and mesoscale systems since, in such systems, distributed quantities such as electron and trap densities, and concepts like electron mobility, become inadequate to model electrical behaviour. In addition, current experimental works have shown that RTS in semiconductor devices based on carbon nanotubes lead to giant current fluctuations. Therefore, the physics of this phenomenon and techniques to decrease the amplitudes of RTS need to be better understood. This problem can be described as a collective Poisson process under different, but time-independent, rates, τ(c) and τ(e), that control the capture and emission of electrons by traps distributed over the oxide. Thus, models that consider calculations performed under time-dependent periodic capture and emission rates should be of interest in order to model more efficient devices. We show a complete theoretical description of a model that is capable of showing a noise reduction of current fluctuations in the time domain, and a reduction of the power spectral density in the frequency domain, in semiconductor devices as predicted by previous experimental work. We do so through numerical integrations and a novel Monte Carlo Markov chain (MCMC) algorithm based on microscopic discrete values. The proposed model also handles the ballistic regime, relevant in nano- and mesoscale devices. Finally, we show that the ballistic regime leads to nonlinearity in the electrical behaviour.

Solar hydrogen production by tandem cell system composed of metal oxide semiconductor film photoelectrode and dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Arakawa, H.; Shiraishi, C.; Tatemoto, M.; Kishida, H.; Usui, D.; Suma, A.; Takamisawa, A.; Yamaguchi, T.

2007-09-01

Photocatalytic and photoelectrochemical approaches to solar hydrogen production in our group were introduced. In photocatalytic water splitting system using NiO x/ TiO II powder photocatalyst with concentrated Na IICO 3 aqueous solution, solar energy conversion efficiency to H II and O II production (STH efficiency) was 0.016%. In addition, STH efficiency of visible light responding photocatalyst, NiOx/ promoted In 0.9Ni 0.1TaO 4, was estimated at 0.03%. In photoelectrochemical system using an oxide semiconductor film phptoelectrode, STH efficiencies of meosporous TiO II (Anatase) , mesoporous visible light responding S-doped TiO II (Anatase) and WO 3 film were 0.32-0.44% at applied potential of 0.35 V vs NHE, 0.14% at 0.55 V and 0.44% at 0.9 V, respectively. Finally, solar hydrogen production by tandem cell system composed of an oxide semiconductor photoelectrode, a Pt wire counter electrode and a dye-sensitized solar cell (DSC) was investigated. As photoelectrodes, meosporous TiO II (Anatase), mesoporous S-doped TiO II (Anatase), WO 3, BiVO 4 and Fe IIO 3 film were tested. STH efficiency of tandem cell system composed of a WO 3 film photoelectrode, and a two-series-connected DSC (Voc = 1.4 V) was 2.5-2.8%. In conclusion, it is speculated that more than 5% STH efficiency will be obtained by tandem cell system composed of an oxide semiconductor photoelectrode and a two-series-connected DSC in near future. This suggests a cost-effective and practical application of this system for solar hydrogen production.

A star tracker insensitive to stray light generated by radiation sources close to the field of view

NASA Astrophysics Data System (ADS)

Romoli, A.; Gambicorti, L.; Simonetti, F.; Zuccaro Marchi, A.

2017-11-01

Aim of this work is to propose an innovative star tracker, practically insensitive to the radiation coming from the sun or from other strong planetary sources out of (but near) the Field of View. These sources need to be stopped in some way. The classical solution to reject the unwanted radiation is to place a shadow (or baffle) before the star tracker objective. The shadow size depends on the Field of View and on the minimum angle subtended by the source (i.e. the sun) with respect to the optical axis of the star tracker. The lower is this angle the larger is the shadow. Requests for star trackers able to work with the sun as close as possible to the Field of View are increasing, due to the need of maximum mission flexibility. The innovation of this proposed star tracker is conceived by using spatial filtering with a concept complementary to that of coronagraph for sun corona observation, allowing to drastically reduce the size of the shadow. It can also work close to antennas and other part of the platform, which, when illuminated by the sun, become secondary sources capable to blind the star tracker. This kind of accommodation offers three main advantages: no cumbersome shadows (baffle), maximum flexibility in terms of mission profile, less platform location constraints. This new star sensor concept, dated 2007, is now patent pending. Galileo Avionica (now Selex Galileo) is the owner of the patent.

Direct laser writing of topographic features in semiconductor-doped glass

NASA Astrophysics Data System (ADS)

Smuk, Andrei Y.

2000-11-01

Patterning of glass and silica surfaces is important for a number of modern technologies, which depend on these materials for manufacturing of both final products, such as optics, and prototypes for casting and molding. Among the fields that require glass processing on microscopic scale are optics (lenses and arrays, diffractive/holographic elements, waveguides), biotechnology (capillary electrophoresis chips and biochemical libraries) and magnetic media (landing zones for magnetic heads). Currently, standard non-laser techniques for glass surface patterning require complex multi-step processes, such as photolithography. Work carried out at Brown has shown that semiconductor- doped glasses (SDG) allow a single-step patterning process using low power continuous-wave visible lasers. SDG are composite materials, which consist of semiconductor crystallites embedded into glass matrix. In this study, borosilicate glasses doped with CdSxSe1-x nanocrystals were used. Exposure of these materials to a low-power above- the-energy gap laser beam leads to local softening, and subsequent expansion and rapid solidification of the exposed volume, resulting in a nearly spherical topographic feature on the surface. The effects of the incident power, beam configuration, and the exposure time on the formation and final parameters of the microlens were studied. Based on the numerical simulation of the temperature distribution produced by the absorbed Gaussian beam, and the ideas of viscous flow at the temperatures around the glass transition point, a model of lens formation is suggested. The light intensity distribution in the near-field of the growing lens is shown to have a significant effect on the final lens height. Fabrication of dense arrays of microlenses is shown, and the thermal and structural interactions between the neighboring lenses were also studied. Two-dimensional continuous-profile topographic features are achieved by exposure of the moving substrates to the writing beam. By controlling the translation speed and the position of the sample, predefined extended structures, such as diffractive optical elements (blazed gratings, Dammann generators, Fresnel zone plates) can be produced with resolution of ~1μm. Below-the-surface patterning is achieved due to a selective etching of laser-written structures in hydrofluoric acid. Similar selective etching technique was developed for undoped borosilicate glasses by exposure to intense visible and UV radiation.

Organic Donor-Acceptor Complexes as Novel Organic Semiconductors.

PubMed

Zhang, Jing; Xu, Wei; Sheng, Peng; Zhao, Guangyao; Zhu, Daoben

2017-07-18

Organic donor-acceptor (DA) complexes have attracted wide attention in recent decades, resulting in the rapid development of organic binary system electronics. The design and synthesis of organic DA complexes with a variety of component structures have mainly focused on metallicity (or even superconductivity), emission, or ferroelectricity studies. Further efforts have been made in high-performance electronic investigations. The chemical versatility of organic semiconductors provides DA complexes with a great number of possibilities for semiconducting applications. Organic DA complexes extend the semiconductor family and promote charge separation and transport in organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). In OFETs, the organic complex serves as an active layer across extraordinary charge pathways, ensuring the efficient transport of induced charges. Although an increasing number of organic semiconductors have been reported to exhibit good p- or n-type properties (mobilities higher than 1 or even 10 cm 2 V -1 s -1 ), critical scientific challenges remain in utilizing the advantages of existing semiconductor materials for more and wider applications while maintaining less complicated synthetic or device fabrication processes. DA complex materials have revealed new insight: their unique molecular packing and structure-property relationships. The combination of donors and acceptors could offer practical advantages compared with their unimolecular materials. First, growing crystals of DA complexes with densely packed structures will reduce impurities and traps from the self-assembly process. Second, complexes based on the original structural components could form superior mixture stacking, which can facilitate charge transport depending on the driving force in the coassembly process. Third, the effective use of organic semiconductors can lead to tunable band structures, allowing the operation mode (p- or n-type) of the transistor to be systematically controlled by changing the components. Finally, theoretical calculations based on cocrystals with unique stacking could widen our understanding of structure-property relationships and in turn help us design high-performance semiconductors based on DA complexes. In this Account, we focus on discussing organic DA complexes as a new class of semiconducting materials, including their design, growth methods, packing modes, charge-transport properties, and structure-property relationships. We have also fabricated and investigated devices based on these binary crystals. This interdisciplinary work combines techniques from the fields of self-assembly, crystallography, condensed-matter physics, and theoretical chemistry. Researchers have designed new complex systems, including donor and acceptor compounds that self-assemble in feasible ways into highly ordered cocrystals. We demonstrate that using this crystallization method can easily realize ambipolar or unipolar transport. To further improve device performance, we propose several design strategies, such as using new kinds of donors and acceptors, modulating the energy alignment of the donor (ionization potential, IP) and acceptor (electron affinity, EA) components, and extending the π-conjugated backbones. In addition, we have found that when we use molecular "doping" (2:1 cocrystallization), the charge-transport nature of organic semiconductors can be switched from hole-transport-dominated to electron-transport-dominated. We expect that the formation of cocrystals through the complexation of organic donor and acceptor species will serve as a new strategy to develop semiconductors for organic electronics with superior performances over their corresponding individual components.

Tracker-on-C for cone-beam CT-guided surgery: evaluation of geometric accuracy and clinical applications

NASA Astrophysics Data System (ADS)

Reaungamornrat, S.; Otake, Y.; Uneri, A.; Schafer, S.; Mirota, D. J.; Nithiananthan, S.; Stayman, J. W.; Khanna, A. J.; Reh, D. D.; Gallia, G. L.; Taylor, R. H.; Siewerdsen, J. H.

2012-02-01

Conventional surgical tracking configurations carry a variety of limitations in line-of-sight, geometric accuracy, and mismatch with the surgeon's perspective (for video augmentation). With increasing utilization of mobile C-arms, particularly those allowing cone-beam CT (CBCT), there is opportunity to better integrate surgical trackers at bedside to address such limitations. This paper describes a tracker configuration in which the tracker is mounted directly on the Carm. To maintain registration within a dynamic coordinate system, a reference marker visible across the full C-arm rotation is implemented, and the "Tracker-on-C" configuration is shown to provide improved target registration error (TRE) over a conventional in-room setup - (0.9+/-0.4) mm vs (1.9+/-0.7) mm, respectively. The system also can generate digitally reconstructed radiographs (DRRs) from the perspective of a tracked tool ("x-ray flashlight"), the tracker, or the C-arm ("virtual fluoroscopy"), with geometric accuracy in virtual fluoroscopy of (0.4+/-0.2) mm. Using a video-based tracker, planning data and DRRs can be superimposed on the video scene from a natural perspective over the surgical field, with geometric accuracy (0.8+/-0.3) pixels for planning data overlay and (0.6+/-0.4) pixels for DRR overlay across all C-arm angles. The field-of-view of fluoroscopy or CBCT can also be overlaid on real-time video ("Virtual Field Light") to assist C-arm positioning. The fixed transformation between the x-ray image and tracker facilitated quick, accurate intraoperative registration. The workflow and precision associated with a variety of realistic surgical tasks were significantly improved using the Tracker-on-C - for example, nearly a factor of 2 reduction in time required for C-arm positioning, reduction or elimination of dose in "hunting" for a specific fluoroscopic view, and confident placement of the x-ray FOV on the surgical target. The proposed configuration streamlines the integration of C-arm CBCT with realtime tracking and demonstrated utility in a spectrum of image-guided interventions (e.g., spine surgery) benefiting from improved accuracy, enhanced visualization, and reduced radiation exposure.

A Bit of Fit: Minimalist Intervention in Adolescents Based on a Physical Activity Tracker

PubMed Central

Gaudet, Jeffrey; Gallant, François

2017-01-01

Background Only 5% of Canadian youth meet the recommended 60 minutes of moderate to vigorous physical activity (MVPA) per day, with leisure time being increasingly allocated to technology usage. Direct-to-consumer mHealth devices that promote physical activity, such as wrist-worn physical activity trackers, have features with potential appeal to youth. Objective The primary purpose of this study was to determine whether a minimalist physical activity tracker-based intervention would lead to an increase in physical activity in young adolescents. A secondary aim of this study was to assess change in physical activity across a 7-week intervention, as measured by the tracker. Methods Using a quasi-experimental crossover design, two groups of 23 young adolescents (aged 13-14 years) were randomly assigned to immediate intervention or delayed intervention. The intervention consisted of wearing a Fitbit-Charge-HR physical activity tracker over a 7-week period. Actical accelerometers were used to measure participants’ levels of MVPA before and at the end of intervention periods for each group. Covariates such as age, sex, stage of change for physical activity behavior, and goal commitment were also measured. Results There was an increase in physical activity over the course of the study period, though it was not related to overall physical activity tracker use. An intervention response did, however, occur in a subset of participants. Specifically, exposure to the physical activity tracker was associated with an average daily increase in MVPA by more than 15 minutes (P=.01) among participants who reported being in the action and maintenance stages of behavior change in relation to participation in physical activity. Participants in the precontemplation, contemplation, and preparation stages of behavior change had no change in their level of MVPA (P=.81). Conclusions These results suggest that physical activity trackers may elicit improved physical activity related behavior in young adolescents demonstrating a readiness to be active. Future studies should seek to investigate if integrating physical activity trackers as part of more intensive interventions leads to greater increases in physical activity across different levels of stages of behavior change and if these changes can be sustained over longer periods of time. PMID:28684384

TlBr[sub x]I[sub (1[minus]x)] photodetectors for scintillation spectroscopy

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

Shah, K.S.; Lund, J.C.; Olschner, F.

1994-12-01

This paper reports on the evaluation of photodetectors fabricated from a ternary semiconductor, TlBr[sub x]I[sub 1[minus]x] for application in scintillation spectroscopy. These photodetectors are characterized in terms of their resistivity, charge transport parameters, quantum efficiency as a function of wavelength, and finally their performance as scintillation spectrometers. The details about TlBr[sub x]I[sub 1[minus]x] purification, crystal growth and device fabrication are also addressed.

Reduced Auger Recombination in Mid-Infrared Semiconductor Lasers (POSTPRINT)

DTIC Science & Technology

2013-02-01

restricted at the longer wavelengths , compared to QCLs due to band filling.9 In the short-wave and mid-wave infrared wavelengths , their low T0...the conduction subband positions are plotted relative to the lowest electronic subband in Fig. 1(b). In the infrared wavelength regime, Eg is...although the noise floor of this detector is 0.01 on this arbitrary scale. Finally, we also record spectra at each temperature and pump level to confirm

Thermophysical Properties of Te-based II-VI Semiconductors: Reduced Algorithms for Thermal Diffusivity Determination

NASA Technical Reports Server (NTRS)

Banish, R. Michael; Brantschen, Segolene; Pourpoint, Timothee L.; Wessling, Francis; Sekerka, Robert F.

2003-01-01

This paper presents methodologies for measuring the thermal diffusivity using the difference between temperatures measured at two, essentially independent, locations. A heat pulse is applied for an arbitrary time to one region of the sample; either the inner core or the outer wall. Temperature changes are then monitored versus time. The thermal diffusivity is calculated from the temperature difference versus time. No initial conditions are used directly in the final results.

Feasibility studies for the Forward Spectrometer

NASA Astrophysics Data System (ADS)

Biernat, Jacek; P¯ANDA Collaboration

2015-04-01

The Forward Spectrometer designed for the P¯ANDA detector will consist of many different detector systems allowing for precise track reconstruction and particle identification. Feasibility studies for Forward Spectrometer done by means of specific reactions will be presented. In the first part of the paper, results of simulations focussing on rate estimates of the tracking stations based on straw tubes will be presented. Next, the importance of the Forward Tracker will be demonstrated through the reconstruction of the ψ(4040) → DD¯ decay. Finally, results from the analysis of the experimental data collected with a straw tube prototype designed and constructed at the Research Center in Juelich will be discussed.

User Acceptance of Wrist-Worn Activity Trackers Among Community-Dwelling Older Adults: Mixed Method Study.

PubMed

Puri, Arjun; Kim, Ben; Nguyen, Olivier; Stolee, Paul; Tung, James; Lee, Joon

2017-11-15

Wearable activity trackers are newly emerging technologies with the anticipation for successfully supporting aging-in-place. Consumer-grade wearable activity trackers are increasingly ubiquitous in the market, but the attitudes toward, as well as acceptance and voluntary use of, these trackers in older population are poorly understood. The aim of this study was to assess acceptance and usage of wearable activity trackers in Canadian community-dwelling older adults, using the potentially influential factors as identified in literature and technology acceptance model. A mixed methods design was used. A total of 20 older adults aged 55 years and older were recruited from Southwestern Ontario. Participants used 2 different wearable activity trackers (Xiaomi Mi Band and Microsoft Band) separately for each segment in the crossover design study for 21 days (ie, 42 days total). A questionnaire was developed to capture acceptance and experience at the end of each segment, representing 2 different devices. Semistructured interviews were conducted with 4 participants, and a content analysis was performed. Participants ranged in age from 55 years to 84 years (mean age: 64 years). The Mi Band gained higher levels of acceptance (16/20, 80%) compared with the Microsoft Band (10/20, 50%). The equipment characteristics dimension scored significantly higher for the Mi Band (P<.05). The amount a participant was willing to pay for the device was highly associated with technology acceptance (P<.05). Multivariate logistic regression with 3 covariates resulted in an area under the curve of 0.79. Content analysis resulted in the formation of the following main themes: (1) smartphones as facilitators of wearable activity trackers; (2) privacy is less of a concern for wearable activity trackers, (3) value proposition: self-awareness and motivation; (4) subjective norm, social support, and sense of independence; and (5) equipment characteristics matter: display, battery, comfort, and aesthetics. Older adults were mostly accepting of wearable activity trackers, and they had a clear understanding of its value for their lives. Wearable activity trackers were uniquely considered more personal than other types of technologies, thereby the equipment characteristics including comfort, aesthetics, and price had a significant impact on the acceptance. Results indicated that privacy was less of concern for older adults, but it may have stemmed from a lack of understanding of the privacy risks and implications. These findings add to emerging research that investigates acceptance and factors that may influence acceptance of wearable activity trackers among older adults. ©Arjun Puri, Ben Kim, Olivier Nguyen, Paul Stolee, James Tung, Joon Lee. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 15.11.2017.

Combinations of 148 navigation stars and the star tracker

NASA Technical Reports Server (NTRS)

Duncan, R.

1980-01-01

The angular separation of all star combinations for 148 nav star on the onboard software for space transportation system-3 flight and following missions is presented as well as the separation of each pair that satisfies the viewing constraints of using both star trackers simultaneously. Tables show (1) shuttle star catalog 1980 star position in M 1950 coordinates; (2) two star combination of 148 nav stars; and (3) summary of two star-combinations of the star tracker 5 deg filter. These 148 stars present 10,875 combinations. For the star tracker filters of plus or minus 5 deg, there are 875 combinations. Formalhaut (nav star 26) has the best number of combinations, which is 33.

Robust Visual Tracking Revisited: From Correlation Filter to Template Matching.

PubMed

Liu, Fanghui; Gong, Chen; Huang, Xiaolin; Zhou, Tao; Yang, Jie; Tao, Dacheng

2018-06-01

In this paper, we propose a novel matching based tracker by investigating the relationship between template matching and the recent popular correlation filter based trackers (CFTs). Compared to the correlation operation in CFTs, a sophisticated similarity metric termed mutual buddies similarity is proposed to exploit the relationship of multiple reciprocal nearest neighbors for target matching. By doing so, our tracker obtains powerful discriminative ability on distinguishing target and background as demonstrated by both empirical and theoretical analyses. Besides, instead of utilizing single template with the improper updating scheme in CFTs, we design a novel online template updating strategy named memory, which aims to select a certain amount of representative and reliable tracking results in history to construct the current stable and expressive template set. This scheme is beneficial for the proposed tracker to comprehensively understand the target appearance variations, recall some stable results. Both qualitative and quantitative evaluations on two benchmarks suggest that the proposed tracking method performs favorably against some recently developed CFTs and other competitive trackers.

Chemoreception of hunger levels alters the following behaviour of a freshwater snail.

PubMed

Larcher, Marie; Crane, Adam L

2015-12-01

Chemically-mediated orientation is essential for many animals that must locate sites containing resources such as mates or food. One way to find these areas is by using publically-available information from other individuals. We tested a freshwater snail, Physa gyrina, for chemoreception of conspecific cues and predicted they could discriminate between cues based on information regarding hunger levels. We placed 'tracker' snails into a 2-arm arena where they could either follow or avoid an area previously used by a 'marker' snail. The hunger levels of both trackers and markers was manipulated, being either starved or fed. Starved and fed trackers did not differ in their following response when markers were hungry, but starved trackers were significantly more likely to follow fed markers, compared to fed trackers that tended to avoid areas used by fed markers. This outcome suggests that P. gyrina uses conspecific chemical cues to find food and potentially in some situations to avoid intra-specific food competition. Copyright © 2015 Elsevier B.V. All rights reserved.

Star tracker operation in a high density proton field

NASA Technical Reports Server (NTRS)

Miklus, Kenneth J.; Kissh, Frank; Flynn, David J.

1993-01-01

Algorithms that reject transient signals due to proton effects on charge coupled device (CCD) sensors have been implemented in the HDOS ASTRA-l Star Trackers to be flown on the TOPEX mission scheduled for launch in July 1992. A unique technique for simulating a proton-rich environment to test trackers is described, as well as the test results obtained. Solar flares or an orbit that passes through the South Atlantic Anomaly can subject the vehicle to very high proton flux levels. There are three ways in which spurious proton generated signals can impact tracker performance: the many false signals can prevent or extend the time to acquire a star; a proton-generated signal can compromise the accuracy of the star's reported magnitude and position; and the tracked star can be lost, requiring reacquisition. Tests simulating a proton-rich environment were performed on two ASTRA-1 Star Trackers utilizing these new algorithms. There were no false acquisitions, no lost stars, and a significant reduction in reported position errors due to these improvements.

Method of producing strained-layer semiconductor devices via subsurface-patterning

DOEpatents

Dodson, Brian W.

1993-01-01

A method is described for patterning subsurface features in a semiconductor device, wherein the semiconductor device includes an internal strained layer. The method comprises creating a pattern of semiconductor material over the semiconductor device, the semiconductor material having a predetermined thickness which stabilizes areas of the strained semiconductor layer that lie beneath the pattern. Subsequently, a heating step is applied to the semiconductor device to cause a relaxation in areas of the strained layer which do not lie beneath the semiconductor material pattern, whereby dislocations result in the relaxed areas and impair electrical transport therethrough.

Optical and structural properties of carbon dots/TiO2 nanostructures prepared via DC arc discharge in liquid

NASA Astrophysics Data System (ADS)

Biazar, Nooshin; Poursalehi, Reza; Delavari, Hamid

2018-01-01

Synthesis and development of visible active catalysts is an important issue in photocatalytic applications of nanomaterials. TiO2 nanostructures coupled with carbon dots demonstrate a considerable photocatalytic activity in visible wavelengths. Extending optical absorption of a wide band gap semiconductor such as TiO2 with carbon dots is the origin of the visible activity of carbon dots modified semiconductor nanostructures. In addition, carbon dots exhibit high photostability, appropriate electron transport and chemical stability without considerable toxicity or environmental footprints. In this study, optical and structural properties of carbon dots/TiO2 nanostructures prepared via (direct current) DC arc discharge in liquid were investigated. Crystal structure, morphology and optical properties of the samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy respectively. SEM images show formation of spherical nanoparticles with an average size of 27 nm. In comparison with pristine TiO2, optical transmission spectrum of carbon dots/TiO2 nanostructures demonstrates an absorption edge at longer wavelengths as well a high optical absorption in visible wavelengths which is significant for visible activity of nanostructures as a photocatalyst. Finally, these results can provide a flexible and versatile pathway for synthesis of carbon dots/oxide semiconductor nanostructures with an appropriate activity under visible light.

OPS laser EPI design for different wavelengths

NASA Astrophysics Data System (ADS)

Moloney, J. V.; Hader, J.; Li, H.; Kaneda, Y.; Wang, T. S.; Yarborough, M.; Koch, S. W.; Stolz, W.; Kunert, B.; Bueckers, C.; Chaterjee, S.; Hardesty, G.

2009-02-01

Design of optimized semiconductor optically-pumped semiconductor lasers (OPSLs) depends on many ingredients starting from the quantum wells, barrier and cladding layers all the way through to the resonant-periodic gain (RPG) and high reflectivity Bragg mirror (DBR) making up the OPSL active mirror. Accurate growth of the individual layers making up the RPG region is critical if performance degradation due to cavity misalignment is to be avoided. Optimization of the RPG+DBR structure requires knowledge of the heat generation and heating sinking of the active mirror. Nonlinear Control Strategies SimuLaseTM software, based on rigorous many-body calculations of the semiconductor optical response, allows for quantum well and barrier optimization by correlating low intensity photoluminescence spectra computed for the design, with direct experimentally measured wafer-level edge and surface PL spectra. Consequently, an OPSL device optimization procedure ideally requires a direct iterative interaction between designer and grower. In this article, we discuss the application of the many-body microscopic approach to OPSL devices lasing at 850nm, 1040nm and 2μm. The latter device involves and application of the many-body approach to mid-IR OPSLs based on antimonide materials. Finally we will present results on based on structural modifications of the epitaxial structure and/or novel material combinations that offer the potential to extend OPSL technology to new wavelength ranges.

Growth rates and interface shapes in germanium and lead tin telluride observed in-situ, real-time in vertical Bridgman furnaces

NASA Technical Reports Server (NTRS)

Barber, P. G.; Berry, R. F.; Debnam, W. J.; Fripp, A. L.; Woodell, G.; Simchick, R. T.

1995-01-01

Using the advanced technology developed to visualize the melt-solid interface in low Prandtl number materials, crystal growth rates and interface shapes have been measured in germanium and lead tin telluride semiconductors grown in vertical Bridgman furnaces. The experimental importance of using in-situ, real time observations to determine interface shapes, to measure crystal growth rates, and to improve furnace and ampoule designs is demonstrated. The interface shapes observed in-situ, in real-time were verified by quenching and mechanically induced interface demarcation, and they were also confirmed using machined models to ascertain the absence of geometric distortions. Interface shapes depended upon the interface position in the furnace insulation zone, varied with the nature of the crystal being grown, and were dependent on the extent of transition zones at the ends of the ampoule. Actual growth rates varied significantly from the constant translation rate in response to the thermophysical properties of the crystal and its melt and the thermal conditions existing in the furnace at the interface. In the elemental semiconductor germanium the observed rates of crystal growth exceeded the imposed translation rate, but in the compound semiconductor lead tin telluride the observed rates of growth were less than the translation rate. Finally, the extent of ampoule thermal loading influenced the interface positions, the shapes, and the growth rates.

Simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewater by zero-valent iron.

PubMed

Yoshino, Hiroyuki; Tokumura, Masahiro; Kawase, Yoshinori

2014-01-01

The zero-valent iron (ZVI) wastewater treatment has been applied to simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewaters. The simultaneous removal occurs by the reactions performed due to the sequential transformation of ZVI under the acidic condition. Fortunately the solution pH of semiconductor acidic wastewaters is low which is effective for the sequential transformation of ZVI. Firstly the reduction of nitrate is taken place by electrons generated by the corrosion of ZVI under acidic conditions. Secondly the ferrous ion generated by the corrosion of ZVI reacts with hydrogen peroxide and generates ·OH radical (Fenton reaction). The Fenton reaction consists of the degradation of hydrogen peroxide and the generation of ferric ion. Finally phosphate precipitates out with iron ions. In the simultaneous removal process, 1.6 mM nitrate, 9.0 mM hydrogen peroxide and 1.0 mM phosphate were completely removed by ZVI within 100, 15 and 15 min, respectively. The synergy among the reactions for the removal of nitrate, hydrogen peroxide and phosphate was found. In the individual pollutant removal experiment, the removal of phosphate by ZVI was limited to 80% after 300 min. Its removal rate was considerably improved in the presence of hydrogen peroxide and the complete removal of phosphate was achieved after 15 min.

Final Scientific/Technical Report -- Single-Junction Organic Solar Cells with >15% Efficiency

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

Starkenburg, Daken; Weldeab, Asmerom; Fagnani, Dan

Organic solar cells have the potential to offer low-cost solar energy conversion due to low material costs and compatibility with low-temperature and high throughput manufacturing processes. This project aims to further improve the efficiency of organic solar cells by applying a previously demonstrated molecular self-assembly approach to longer-wavelength light-absorbing organic materials. The team at the University of Florida designed and synthesized a series of low-bandgap organic semiconductors with functional hydrogen-bonding groups, studied their assembly characteristics and optoelectronic properties in solid-state thin film, and fabricated organic solar cells using solution processing. These new organic materials absorb light up 800 nm wavelength,more » and provide a maximum open-circuit voltage of 1.05 V in the resulted solar cells. The results further confirmed the effectiveness in this approach to guide the assembly of organic semiconductors in thin films to yield higher photovoltaic performance for solar energy conversion. Through this project, we have gained important understanding on designing, synthesizing, and processing organic semiconductors that contain appropriately functionalized groups to control the morphology of the organic photoactive layer in solar cells. Such fundamental knowledge could be used to further develop new functional organic materials to achieve higher photovoltaic performance, and contribute to the eventual commercialization of the organic solar cell technology.« less

Donor impurity incorporation during layer growth of Zn II-VI semiconductors

NASA Astrophysics Data System (ADS)

Barlow, D. A.

2017-12-01

The maximum halogen donor concentration in Zn II-VI semiconductors during layer growth is studied using a standard model from statistical mechanics. Here the driving force for incorporation is an increase in entropy upon mixing of the donor impurity into the available anion lattice sites in the host binary. A formation energy opposes this increase and thus equilibrium is attained at some maximum concentration. Considering the halogen donor impurities within the Zn II-VI binary semiconductors ZnO, ZnS, ZnSe and ZnTe, a heat of reaction obtained from reported diatomic bond strengths is shown to be directly proportional to the log of maximum donor concentration. The formation energy can then be estimated and an expression for maximum donor concentration derived. Values for the maximum donor concentration with each of the halogen impurities, within the Zn II-VI compounds, are computed. This model predicts that the halogens will serve as electron donors in these compounds in order of increasing effectiveness as: F, Br, I, Cl. Finally, this result is taken to be equivalent to an alternative model where donor concentration depends upon impurity diffusion and the conduction band energy shift due to a depletion region at the growing crystal's surface. From this, we are able to estimate the diffusion activation energy for each of the impurities mentioned above. Comparisons are made with reported values and relevant conclusions presented.

Design and status of the Mu2e electromagnetic calorimeter

DOE PAGES

Atanov, N.; Baranov, V.; Budagov, J.; ...

2015-10-02

Here, the Mu2e experiment at Fermilab aims at measuring the neutrinoless conversion of a negative muon into an electron and reach a single event sensitivity of 2.5×10 –17 after three years of data taking. The monoenergetic electron produced in the final state, is detected by a high precision tracker and a crystal calorimeter, all embedded in a large superconducting solenoid (SD) surrounded by a cosmic ray veto system. The calorimeter is complementary to the tracker, allowing an independent trigger and powerful particle identification, while seeding the track reconstruction and contributing to remove background tracks mimicking the signal. In order tomore » match these requirements, the calorimeter should have an energy resolution of O(5)% and a time resolution better than 500 ps at 100 MeV. The baseline solution is a calorimeter composed of two disks of BaF 2 crystals read by UV extended, solar blind, Avalanche Photodiode (APDs), which are under development from a JPL, Caltech, RMD consortium. In this paper, the calorimeter design, the R&D; studies carried out so far and the status of engineering are described. A backup alternative setup consisting of a pure CsI crystal matrix read by UV extended Hamamatsu MPPC's is also presented.« less

ν{sub μ} CCπ° reaction in the tracker of the ND280 detector in the T2K experiment

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

Batkiewicz, Marcela

A good knowledge of both inclusive and exclusive neutrino interaction cross sections is one of the key issues for a precise determination of the neutrino oscillation parameters in the T2K experiment. These studies are performed at the near detector (ND280). Its central tracker part equipped with a water target is used, among others, to study the ν{sub μ}CCπ° reaction. At the energies of the T2K neutrino beam its contribution to the total cross section is relatively large, so the reaction is a potential source of the background for the quasi-elastic ν{sub μ}CC reaction. Two different production mechanisms contribute to ν{submore » μ}CCπ°: single pion resonance production and Deep Inelastic Scattering (DIS). In addition, Final State Interactions (FSI) have to be considered. Thus, the analysis of the ν{sub μ}CCπ° reaction aims also at a better tuning of the Monte Carlo (MC) models used to describe neutrino interactions in T2K. This paper describes selection criteria leading to the determination of the inclusive and exclusive cross sections for the π° production in the ν{sub μ}CC interactions.« less

Utilizing Maximum Power Point Trackers in Parallel to Maximize the Power Output of a Solar (Photovoltaic) Array

DTIC Science & Technology

2012-12-01

photovoltaic (PV) system to use a maximum power point tracker ( MPPT ) to increase... photovoltaic (PV) system to use a maximum power point tracker ( MPPT ) to increase the power output of the solar array. Currently, most military... MPPT ) is an optimizing circuit that is used in conjunction with photovoltaic (PV) arrays to achieve the maximum delivery of power from the array

A Methodology to Analyze Photovoltaic Tracker Uptime

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

Muller, Matthew T; Ruth, Dan

A metric is developed to analyze the daily performance of single-axis photovoltaic (PV) trackers. The metric relies on comparing correlations between the daily time series of the PV power output and an array of simulated plane-of-array irradiances for the given day. Mathematical thresholds and a logic sequence are presented, so the daily tracking metric can be applied in an automated fashion on large-scale PV systems. The results of applying the metric are visually examined against the time series of the power output data for a large number of days and for various systems. The visual inspection results suggest that overall,more » the algorithm is accurate in identifying stuck or functioning trackers on clear-sky days. Visual inspection also shows that there are days that are not classified by the metric where the power output data may be sufficient to identify a stuck tracker. Based on the daily tracking metric, uptime results are calculated for 83 different inverters at 34 PV sites. The mean tracker uptime is calculated at 99% based on 2 different calculation methods. The daily tracking metric clearly has limitations, but as there is no existing metrics in the literature, it provides a valuable tool for flagging stuck trackers.« less

Use of a Remote Eye-Tracker for the Analysis of Gaze during Treadmill Walking and Visual Stimuli Exposition.

PubMed

Serchi, V; Peruzzi, A; Cereatti, A; Della Croce, U

2016-01-01

The knowledge of the visual strategies adopted while walking in cognitively engaging environments is extremely valuable. Analyzing gaze when a treadmill and a virtual reality environment are used as motor rehabilitation tools is therefore critical. Being completely unobtrusive, remote eye-trackers are the most appropriate way to measure the point of gaze. Still, the point of gaze measurements are affected by experimental conditions such as head range of motion and visual stimuli. This study assesses the usability limits and measurement reliability of a remote eye-tracker during treadmill walking while visual stimuli are projected. During treadmill walking, the head remained within the remote eye-tracker workspace. Generally, the quality of the point of gaze measurements declined as the distance from the remote eye-tracker increased and data loss occurred for large gaze angles. The stimulus location (a dot-target) did not influence the point of gaze accuracy, precision, and trackability during both standing and walking. Similar results were obtained when the dot-target was replaced by a static or moving 2D target and "region of interest" analysis was applied. These findings foster the feasibility of the use of a remote eye-tracker for the analysis of gaze during treadmill walking in virtual reality environments.

Contradictions in digital health engagement: An activity tracker's ambiguous influence on vulnerable young adults' engagement in own health.

PubMed

Kanstrup, Anne Marie; Bertelsen, Pernille; Jensen, Martin B

2018-01-01

Activity trackers are designed to support individuals in monitoring and increasing their physical activity. The use of activity trackers among individuals diagnosed with depression and anxiety has not yet been examined. This pilot study investigates how this target group engages with an activity tracker during a 10-week health intervention aimed to increase their physical activity level and improve their physical and mental health. Two groups of 11 young adults (aged 18-29 years) diagnosed with depression or anxiety participated in the digital health intervention. The study used mixed methods to investigate the research question. Quantitative health data were used to assess the intervention's influence on the participants' health and qualitative data provided insights into the participants' digital health experience. The study demonstrated an ambiguous influence from the use of an activity tracker with positive physical and mental health results, but a fading and even negative digital health engagement and counterproductive competition. The ambiguous results identify a need for (1) developing strategies for health professionals to provide supervised use of activity trackers and support the target groups' abilities to convert health information about physical activity into positive health strategies, and (2) designing alternatives for health promoting IT targeted users who face challenges and need motivation beyond self-tracking and competition.

Star Tracker Performance Estimate with IMU

NASA Technical Reports Server (NTRS)

Aretskin-Hariton, Eliot D.; Swank, Aaron J.

2015-01-01

A software tool for estimating cross-boresight error of a star tracker combined with an inertial measurement unit (IMU) was developed to support trade studies for the Integrated Radio and Optical Communication project (iROC) at the National Aeronautics and Space Administration Glenn Research Center. Typical laser communication systems, such as the Lunar Laser Communication Demonstration (LLCD) and the Laser Communication Relay Demonstration (LCRD), use a beacon to locate ground stations. iROC is investigating the use of beaconless precision laser pointing to enable laser communication at Mars orbits and beyond. Precision attitude knowledge is essential to the iROC mission to enable high-speed steering of the optical link. The preliminary concept to achieve this precision attitude knowledge is to use star trackers combined with an IMU. The Star Tracker Accuracy (STAcc) software was developed to rapidly assess the capabilities of star tracker and IMU configurations. STAcc determines the overall cross-boresight error of a star tracker with an IMU given the characteristic parameters: quantum efficiency, aperture, apparent star magnitude, exposure time, field of view, photon spread, detector pixels, spacecraft slew rate, maximum stars used for quaternion estimation, and IMU angular random walk. This paper discusses the supporting theory used to construct STAcc, verification of the program and sample results.

Tracker-assisted versus manual ablation zone centration in laser in situ keratomileusis for myopia and astigmatism.

PubMed

Pineros, Oscar E

2002-01-01

Eye tracker systems have been developed concomitantly with small scanning beams to theoretically reduce ablation zone decentration and for accurate registration of all the laser pulses on the cornea. The purpose of the study was to compare the tracker-assisted with the manual centration method. Twenty-five patients (48 eyes) with myopia and/or astigmatism had laser in situ keratomileusis (LASIK) between August 1998 and February 1999 with the Technolas 117C laser. Twenty patients (38 eyes, 80%) were available for follow-up at 3 months after surgery. Eyes were assigned randomly to one of two ablation zone centration methods: Group 1: Tracker-assisted (20 eyes), Group 2: Manual (18 eyes). Mean distance between the ablation zone center and the pupillary center in the tracker-assisted centration group was 0.55 +/- 0.30 mm (range, 0.10 to 1.4 mm), and in the manual centration group, 0.43 +/- 0.23 mm (range, 0.10 to 1.0 mm) (P = .177). There was no statistically significant difference in postoperative contrast sensitivity, glare, and Topographical Corneal Surface Regularity Index (SRI) between the two groups. We obtained good results with both centration methods. We did not find superiority of the tracker-assisted over manual regarding ablation zone centration, vision quality, or regularity of the ablation.

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High Efficiency Thin Film CdTe and a-Si Based Solar Cells: Final Technical Report, 4 March 1998--15 October 2001

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

Compaan, A. D.; Deng, X.; Bohn, R. G.

2003-10-01

This is the final report covering about 42 months of this subcontract for research on high-efficiency CdTe-based thin-film solar cells and on high-efficiency a-Si-based thin-film solar cells. Phases I and II have been extensively covered in two Annual Reports. For this Final Report, highlights of the first two Phases will be provided and then detail will be given on the last year and a half of Phase III. The effort on CdTe-based materials is led by Prof. Compaan and emphasizes the use of sputter deposition of the semiconductor layers in the fabrication of CdS/CdTe cells. The effort on high-efficiency a-Simore » materials is led by Prof. Deng and emphasizes plasma-enhanced chemical vapor deposition for cell fabrication with major efforts on triple-junction devices.« less

Youth Oriented Activity Trackers: Comprehensive Laboratory- and Field-Based Validation

PubMed Central

2017-01-01

Background Commercial activity trackers are growing in popularity among adults and some are beginning to be marketed to children. There is, however, a paucity of independent research examining the validity of these devices to detect physical activity of different intensity levels. Objectives The purpose of this study was to determine the validity of the output from 3 commercial youth-oriented activity trackers in 3 phases: (1) orbital shaker, (2) structured indoor activities, and (3) 4 days of free-living activity. Methods Four units of each activity tracker (Movband [MB], Sqord [SQ], and Zamzee [ZZ]) were tested in an orbital shaker for 5-minutes at three frequencies (1.3, 1.9, and 2.5 Hz). Participants for Phase 2 (N=14) and Phase 3 (N=16) were 6-12 year old children (50% male). For Phase 2, participants completed 9 structured activities while wearing each tracker, the ActiGraph GT3X+ (AG) research accelerometer, and a portable indirect calorimetry system to assess energy expenditure (EE). For Phase 3, participants wore all 4 devices for 4 consecutive days. Correlation coefficients, linear models, and non-parametric statistics evaluated the criterion and construct validity of the activity tracker output. Results Output from all devices was significantly associated with oscillation frequency (r=.92-.99). During Phase 2, MB and ZZ only differentiated sedentary from light intensity (P<.01), whereas the SQ significantly differentiated among all intensity categories (all comparisons P<.01), similar to AG and EE. During Phase 3, AG counts were significantly associated with activity tracker output (r=.76, .86, and .59 for the MB, SQ, and ZZ, respectively). Conclusions Across study phases, the SQ demonstrated stronger validity than the MB and ZZ. The validity of youth-oriented activity trackers may directly impact their effectiveness as behavior modification tools, demonstrating a need for more research on such devices. PMID:28724509

Optically switched graphene/4H-SiC junction bipolar transistor

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

Chandrashekhar, MVS; Sudarshan, Tangali S.; Omar, Sabih U.

A bi-polar device is provided, along with methods of making the same. The bi-polar device can include a semiconductor substrate doped with a first dopant, a semiconductor layer on the first surface of the semiconductor substrate, and a Schottky barrier layer on the semiconductor layer. The method of forming a bi-polar device can include: forming a semiconductor layer on a first surface of a semiconductor substrate, where the semiconductor substrate comprises a first dopant and where the semiconductor layer comprises a second dopant that has an opposite polarity than the first dopant; and forming a Schottky barrier layer on amore » first portion of the semiconductor layer while leaving a second portion of the semiconductor layer exposed.« less

Free-carrier-induced soliton fission unveiled by in situ measurements in nanophotonic waveguides

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

Husko, Chad; Wulf, Matthias; Lefrancois, Simon

Solitons are localized waves formed by a balance of focusing and defocusing effects. These nonlinear waves exist in diverse forms of matter yet exhibit similar properties including stability, periodic recurrence and particle-like trajectories. One important property is soliton fission, a process by which an energetic higher-order soliton breaks apart due to dispersive or nonlinear perturbations. Here we demonstrate through both experiment and theory that nonlinear photocarrier generation can induce soliton fission. Using near-field measurements, we directly observe the nonlinear spatial and temporal evolution of optical pulses in situ in a nanophotonic semiconductor waveguide. We develop an analytic formalism describing themore » free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude. We confirm these observations with a numerical nonlinear Schrodinger equation model. Finally, these results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.« less

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

De Geronimo, G.; Li, S.; D'Andragora, A.

We present a front-end application-specific integrated circuit (ASIC) for a wire based time-projection-chamber (TPC) operating in liquid Argon (LAr). The LAr TPC will be used for long baseline neutrino oscillation experiments. The ASIC must provide a low-noise readout of the signals induced on the TPC wires, digitization of those signals at 2 MSamples/s, compression, buffering and multiplexing. A resolution of better than 1000 rms electrons at 200 pF input capacitance for an input range of 300 fC is required, along with low power and operation in LAr (at 87 K). We include the characterization of a commercial technology for operationmore » in the cryogenic environment and the first experimental results on the analog front end. The results demonstrate that complementary metal-oxide semiconductor transistors have lower noise and much improved dc characteristics at LAr temperature. Finally, we introduce the concept of '1/f equivalent' to model the low-frequency component of the noise spectral density, for use in the input metal-oxide semiconductor field-effect transistor optimization.« less

Vertical electro-absorption modulator design and its integration in a VCSEL

NASA Astrophysics Data System (ADS)

Marigo-Lombart, L.; Calvez, S.; Arnoult, A.; Thienpont, H.; Almuneau, G.; Panajotov, K.

2018-04-01

Electro-absorption modulators, either embedded in CMOS technology or integrated with a semiconductor laser, are of high interest for many applications such as optical communications, signal processing and 3D imaging. Recently, the integration of a surface-normal electro-absorption modulator into a vertical-cavity surface-emitting laser has been considered. In this paper we implement a simple quantum well electro-absorption model and design and optimize an asymmetric Fabry-Pérot semiconductor modulator while considering all physical properties within figures of merit. We also extend this model to account for the impact of temperature on the different parameters involved in the calculation of the absorption, such as refractive indices and exciton transition broadening. Two types of vertical modulator structures have been fabricated and experimentally characterized by reflectivity and photocurrent measurements demonstrating a very good agreement with our model. Finally, preliminary results of an electro-absorption modulator vertically integrated with a vertical-cavity surface-emitting laser device are presented, showing good modulation performances required for high speed communications.

The Power of Materials Science Tools for Gaining Insights into Organic Semiconductors

NASA Astrophysics Data System (ADS)

Treat, Neil D.; Westacott, Paul; Stingelin, Natalie

2015-07-01

The structure of organic semiconductors can be complex because features from the molecular level (such as molecular conformation) to the micrometer scale (such as the volume fraction and composition of phases, phase distribution, and domain size) contribute to the definition of the optoelectronic landscape of the final architectures and, hence, to device performance. As a consequence, a detailed understanding of how to manipulate molecular ordering, e.g., through knowledge of relevant phase transitions, of the solidification process, of relevant solidification mechanisms, and of kinetic factors, is required to induce the desired optoelectronic response. In this review, we discuss relevant structural features of single-component and multicomponent systems; provide a case study of the multifaceted structure that polymer:fullerene systems can adopt; and highlight relevant solidification mechanisms such as nucleation and growth, liquid-liquid phase separation, and spinodal decomposition. In addition, cocrystal formation, solid solutions, and eutectic systems are treated and their relevance within the optoelectronic area emphasized.

Mixing-Induced Anisotropic Correlations in Molecular Crystalline Systems: Rationalizing the Behavior of Organic Semiconductor Blends

NASA Astrophysics Data System (ADS)

Broch, Katharina; Aufderheide, Antje; Novak, Jiri; Hinderhofer, Alexander; Gerlach, Alexander; Banerjee, Rupak; Schreiber, Frank

2013-03-01

Binary mixtures of organic semiconductors (OSCs) have recently become an important field of research, as they find applications in opto-electronic devices. In these systems, the mixing (intermixing vs. phase separation) and ordering behavior is crucial, since it affects the optical and electronic properties. We present a comprehensive study of binary mixtures of the three prototypical OSCs pentacene (PEN), perfluoropentacene (PFP) and diindenoperlyene (DIP) in all possible combinations. Using X-ray reflectivity and grazing incidence X-ray diffraction we investigate the stuctural properties of the mixed films as well as their impact on the optical spectra obtained by spectroscopic ellipsometry. For PEN:DIP we find an anisotropic ordering behavior, comparable to that observed in some liquid crystals, which is fundamentally new for OSCs. The influence of sterical compatibility and the strength of the intermolecular interactions on the mixing and ordering behavior in the different blends will be discussed by extending a conventional mean-field model. Finally, we discuss general rules for the targeted preparation of blends of OSCs.

Theoretical studies of the transport properties in compound semiconductors

NASA Technical Reports Server (NTRS)

Segall, Benjamin

1994-01-01

This final report is an overview of the work done on Cooperative Agreement NCC 3-55 with the Solid State Technology Branch of the NASA-Lewis Research Center (LeRC). Over the period of time that the agreement was in effect, the principal investigator and, in the last three years, the co-principal investigator worked on a significant number of projects and interacted with members of the Solid State Technology (SST) branch in a number of different ways. For the purpose of this report, these efforts will be divided into five categories: 1) work directly with experimental electrical transport studies conducted by members of the SST branch; 2) theoretical work on electrical transport in compound semiconductors; 3) electronic structure calculations which are relevant to the electrical transport in polytypes of SiC and SiC-AlN alloys; 4) the electronic structure calculations of polar interfaces; and 5) consultative and supportive activities related to experiments and other studies carried out by SST branch members. Work in these categories is briefly discussed.

Free-carrier-induced soliton fission unveiled by in situ measurements in nanophotonic waveguides

DOE PAGES

Husko, Chad; Wulf, Matthias; Lefrancois, Simon; ...

2016-04-15

Solitons are localized waves formed by a balance of focusing and defocusing effects. These nonlinear waves exist in diverse forms of matter yet exhibit similar properties including stability, periodic recurrence and particle-like trajectories. One important property is soliton fission, a process by which an energetic higher-order soliton breaks apart due to dispersive or nonlinear perturbations. Here we demonstrate through both experiment and theory that nonlinear photocarrier generation can induce soliton fission. Using near-field measurements, we directly observe the nonlinear spatial and temporal evolution of optical pulses in situ in a nanophotonic semiconductor waveguide. We develop an analytic formalism describing themore » free-carrier dispersion (FCD) perturbation and show the experiment exceeds the minimum threshold by an order of magnitude. We confirm these observations with a numerical nonlinear Schrodinger equation model. Finally, these results provide a fundamental explanation and physical scaling of optical pulse evolution in free-carrier media and could enable improved supercontinuum sources in gas based and integrated semiconductor waveguides.« less

General low-temperature reaction pathway from precursors to monomers before nucleation of compound semiconductor nanocrystals

PubMed Central

Yu, Kui; Liu, Xiangyang; Qi, Ting; Yang, Huaqing; Whitfield, Dennis M.; Y. Chen, Queena; Huisman, Erik J. C.; Hu, Changwei

2016-01-01

Little is known about the molecular pathway to monomers of semiconductor nanocrystals. Here we report a general reaction pathway, which is based on hydrogen-mediated ligand loss for the precursor conversion to ‘monomers' at low temperature before nucleation. We apply 31P nuclear magnetic resonance spectroscopy to monitor the key phosphorous-containing products that evolve from MXn+E=PPh2H+HY mixtures, where MXn, E=PPh2H, and HY are metal precursors, chalcogenide precursors, and additives, respectively. Surprisingly, the phosphorous-containing products detected can be categorized into two groups, Ph2P–Y and Ph2P(E)–Y. On the basis of our experimental and theoretical results, we propose two competing pathways to the formation of M2En monomers, each of which is accompanied by one of the two products. Our study unravels the pathway of precursor evolution into M2En monomers, the stoichiometry of which directly correlates with the atomic composition of the final compound nanocrystals. PMID:27531507

Effect of forming gas annealing on the degradation properties of Ge-based MOS stacks

NASA Astrophysics Data System (ADS)

Aguirre, F.; Pazos, S.; Palumbo, F. R. M.; Fadida, S.; Winter, R.; Eizenberg, M.

2018-04-01

The influence of forming gas annealing on the degradation at a constant stress voltage of multi-layered germanium-based Metal-Oxide-Semiconductor capacitors (p-Ge/GeOx/Al2O3/High-K/Metal Gate) has been analyzed in terms of the C-V hysteresis and flat band voltage as a function of both negative and positive stress fields. Significant differences were found for the case of negative voltage stress between the annealed and non-annealed samples, independently of the stressing time. It was found that the hole trapping effect decreases in the case of the forming gas annealed samples, indicating strong passivation of defects with energies close to the valence band existing in the oxide-semiconductor interface during the forming gas annealing. Finally, a comparison between the degradation dynamics of Germanium and III-V (n-InGaAs) MOS stacks is presented to summarize the main challenges in the integration of reliable Ge-III-V hybrid devices.

High-pressure phase transition makes B 4.3 C boron carbide a wide-gap semiconductor

DOE PAGES

Hushur, Anwar; Manghnani, Murli H.; Werheit, Helmut; ...

2016-01-11

Single-crystal B4.3C boron carbide is investigated concerning the pressure-dependence of optical properties and of Raman-active phonons up to ~70 GPa. The high concentration of structural defects determining the electronic properties of boron carbide at ambient conditions initially decrease and finally vanish with pressure increasing. We obtain this immediately from transparency photos, allowing to estimate the pressure-dependent variation of the absorption edge rapidly increasing around 55 GPa. Glass-like transparency at pressures exceeding 60 GPa indicate that the width of the band exceeds ~3.1 eV thus making boron carbide a wide-gap semiconductor. Furthermore, the spectra of Raman–active phonons indicate a pressure-dependent phasemore » transition in single-crystal natB4.3C boron carbide near 35 GPa., particularly related to structural changes in connection with the C-B-C chains, while the basic icosahedral structure remains largely unaffected.« less

Magneto-electronic properties and spin-resolved I-V curves of a Co/GeSe heterojunction diode: an ab initio study

NASA Astrophysics Data System (ADS)

Makinistian, Leonardo; Albanesi, Eduardo A.

2013-06-01

We present ab initio calculations of magnetoelectronic and transport properties of the interface of hcp Cobalt (001) and the intrinsic narrow-gap semiconductor germanium selenide (GeSe). Using a norm-conserving pseudopotentials scheme within DFT, we first model the interface with a supercell approach and focus on the spin-resolved densities of states and the magnetic moment (spin and orbital components) at the different atomic layers that form the device. We also report a series of cuts (perpendicular to the plane of the heterojunction) of the electronic and spin densities showing a slight magnetization of the first layers of the semiconductor. Finally, we model the device with a different scheme: using semiinfinite electrodes connected to the heterojunction. These latter calculations are based upon a nonequilibrium Green's function approach that allows us to explore the spin-resolved electronic transport under a bias voltage (spin-resolved I-V curves), revealing features of potential applicability in spintronics.

Reconfiguring crystal and electronic structures of MoS 2 by substitutional doping

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

Suh, Joonki; Tan, Teck Leong; Zhao, Weijie

Doping of traditional semiconductors has enabled technological applications in modern electronics by tailoring their chemical, optical and electronic properties. However, substitutional doping in two-dimensional semiconductors is at a comparatively early stage, and the resultant effects are less explored. In this work, we report unusual effects of degenerate doping with Nb on structural, electronic and optical characteristics of MoS 2 crystals. The doping readily induces a structural transformation from naturally occurring 2H stacking to 3R stacking. Electronically, a strong interaction of the Nb impurity states with the host valence bands drastically and nonlinearly modifies the electronic band structure with the valencemore » band maximum of multilayer MoS 2 at the Γ point pushed upward by hybridization with the Nb states. Finally, when thinned down to monolayers, in stark contrast, such significant nonlinear effect vanishes, instead resulting in strong and broadband photoluminescence via the formation of exciton complexes tightly bound to neutral acceptors.« less

Reconfiguring crystal and electronic structures of MoS 2 by substitutional doping

DOE PAGES

Suh, Joonki; Tan, Teck Leong; Zhao, Weijie; ...

2018-01-15

Doping of traditional semiconductors has enabled technological applications in modern electronics by tailoring their chemical, optical and electronic properties. However, substitutional doping in two-dimensional semiconductors is at a comparatively early stage, and the resultant effects are less explored. In this work, we report unusual effects of degenerate doping with Nb on structural, electronic and optical characteristics of MoS 2 crystals. The doping readily induces a structural transformation from naturally occurring 2H stacking to 3R stacking. Electronically, a strong interaction of the Nb impurity states with the host valence bands drastically and nonlinearly modifies the electronic band structure with the valencemore » band maximum of multilayer MoS 2 at the Γ point pushed upward by hybridization with the Nb states. Finally, when thinned down to monolayers, in stark contrast, such significant nonlinear effect vanishes, instead resulting in strong and broadband photoluminescence via the formation of exciton complexes tightly bound to neutral acceptors.« less

Single-Cell Semiconductor Sequencing

PubMed Central

Kohn, Andrea B.; Moroz, Tatiana P.; Barnes, Jeffrey P.; Netherton, Mandy; Moroz, Leonid L.

2014-01-01

RNA-seq or transcriptome analysis of individual cells and small-cell populations is essential for virtually any biomedical field. It is especially critical for developmental, aging, and cancer biology as well as neuroscience where the enormous heterogeneity of cells present a significant methodological and conceptual challenge. Here we present two methods that allow for fast and cost-efficient transcriptome sequencing from ultra-small amounts of tissue or even from individual cells using semiconductor sequencing technology (Ion Torrent, Life Technologies). The first method is a reduced representation sequencing which maximizes capture of RNAs and preserves transcripts’ directionality. The second, a template-switch protocol, is designed for small mammalian neurons. Both protocols, from cell/tissue isolation to final sequence data, take up to 4 days. The efficiency of these protocols has been validated with single hippocampal neurons and various invertebrate tissues including individually identified neurons within a simpler memory-forming circuit of Aplysia californica and early (1-, 2-, 4-, 8-cells) embryonic and developmental stages from basal metazoans. PMID:23929110

Single-electron-occupation metal-oxide-semiconductor quantum dots formed from efficient poly-silicon gate layout

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

Carroll, Malcolm S.; rochette, sophie; Rudolph, Martin

We introduce a silicon metal-oxide-semiconductor quantum dot structure that achieves dot-reservoir tunnel coupling control without a dedicated barrier gate. The elementary structure consists of two accumulation gates separated spatially by a gap, one gate accumulating a reservoir and the other a quantum dot. Control of the tunnel rate between the dot and the reservoir across the gap is demonstrated in the single electron regime by varying the reservoir accumulation gate voltage while compensating with the dot accumulation gate voltage. The method is then applied to a quantum dot connected in series to source and drain reservoirs, enabling transport down tomore » the single electron regime. Finally, tuning of the valley splitting with the dot accumulation gate voltage is observed. This split accumulation gate structure creates silicon quantum dots of similar characteristics to other realizations but with less electrodes, in a single gate stack subtractive fabrication process that is fully compatible with silicon foundry manufacturing.« less

Noble-Metal-Free Molybdenum Disulfide Cocatalyst for Photocatalytic Hydrogen Production.

PubMed

Yuan, Yong-Jun; Lu, Hong-Wei; Yu, Zhen-Tao; Zou, Zhi-Gang

2015-12-21

Photocatalytic water splitting using powered semiconductors as photocatalysts represents a promising strategy for clean, low-cost, and environmentally friendly production of H2 utilizing solar energy. The loading of noble-metal cocatalysts on semiconductors can significantly enhance the solar-to-H2 conversion efficiency. However, the high cost and scarcity of noble metals counter their extensive utilization. Therefore, the use of alternative cocatalysts based on non-precious metal materials is pursued. Nanosized MoS2 cocatalysts have attracted considerable attention in the last decade as a viable alternative to improve solar-to-H2 conversion efficiency because of its superb catalytic activity, excellent stability, low cost, availability, environmental friendliness, and chemical inertness. In this perspective, the design, structures, synthesis, and application of MoS2 -based composite photocatalysts for solar H2 generation are summarized, compared, and discussed. Finally, this Review concludes with a summary and remarks on some challenges and opportunities for the future development of MoS2 -based photocatalysts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Semiconductor nanowires: A platform for nanoscience and nanotechnology

PubMed Central

Lieber, Charles M.

2012-01-01

Advances in nanoscience and nanotechnology critically depend on the development of nanostructures whose properties are controlled during synthesis. We focus on this critical concept using semiconductor nanowires, which provide the capability through design and rational synthesis to realize unprecedented structural and functional complexity in building blocks as a platform material. First, a brief review of the synthesis of complex modulated nanowires in which rational design and synthesis can be used to precisely control composition, structure, and, most recently, structural topology is discussed. Second, the unique functional characteristics emerging from our exquisite control of nanowire materials are illustrated using several selected examples from nanoelectronics and nano-enabled energy. Finally, the remarkable power of nanowire building blocks is further highlighted through their capability to create unprecedented, active electronic interfaces with biological systems. Recent work pushing the limits of both multiplexed extracellular recording at the single-cell level and the first examples of intracellular recording is described, as well as the prospects for truly blurring the distinction between nonliving nanoelectronic and living biological systems. PMID:22707850

Graphene/h-BN/GaAs sandwich diode as solar cell and photodetector.

PubMed

Li, Xiaoqiang; Lin, Shisheng; Lin, Xing; Xu, Zhijuan; Wang, Peng; Zhang, Shengjiao; Zhong, Huikai; Xu, Wenli; Wu, Zhiqian; Fang, Wei

2016-01-11

In graphene/semiconductor heterojunction, the statistic charge transfer between graphene and semiconductor leads to decreased junction barrier height and limits the Fermi level tuning effect in graphene, which greatly affects the final performance of the device. In this work, we have designed a sandwich diode for solar cells and photodetectors through inserting 2D hexagonal boron nitride (h-BN) into graphene/GaAs heterostructure to suppress the static charge transfer. The barrier height of graphene/GaAs heterojunction can be increased from 0.88 eV to 1.02 eV by inserting h-BN. Based on the enhanced Fermi level tuning effect with interface h-BN, through adopting photo-induced doping into the device, power conversion efficiency (PCE) of 10.18% has been achieved for graphene/h-BN/GaAs compared with 8.63% of graphene/GaAs structure. The performance of graphene/h-BN/GaAs based photodetector is also improved with on/off ratio increased by one magnitude compared with graphene/GaAs structure.

Methods of producing free-standing semiconductors using sacrificial buffer layers and recyclable substrates

DOEpatents

Ptak, Aaron Joseph; Lin, Yong; Norman, Andrew; Alberi, Kirstin

2015-05-26

A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a spinel substrate using a sacrificial buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The sacrificial buffer material and semiconductor materials may be deposited using lattice-matching epitaxy or coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The sacrificial buffer layer may be dissolved using an epitaxial liftoff technique in order to separate the semiconductor device from the spinel substrate, and the spinel substrate may be reused in the subsequent fabrication of other semiconductor devices. The low-defect density semiconductor materials produced using this method result in the enhanced performance of the semiconductor devices that incorporate the semiconductor materials.

Patterns of Fitbit Use and Activity Levels Throughout a Physical Activity Intervention: Exploratory Analysis from a Randomized Controlled Trial

PubMed Central

Nelson, Sandahl H; Weiner, Lauren S

2018-01-01

Background There has been a rapid increase in the use of technology-based activity trackers to promote behavior change. However, little is known about how individuals use these trackers on a day-to-day basis or how tracker use relates to increasing physical activity. Objective The aims were to use minute level data collected from a Fitbit tracker throughout a physical activity intervention to examine patterns of Fitbit use and activity and their relationships with success in the intervention based on ActiGraph-measured moderate to vigorous physical activity (MVPA). Methods Participants included 42 female breast cancer survivors randomized to the physical activity intervention arm of a 12-week randomized controlled trial. The Fitbit One was worn daily throughout the 12-week intervention. ActiGraph GT3X+ accelerometer was worn for 7 days at baseline (prerandomization) and end of intervention (week 12). Self-reported frequency of looking at activity data on the Fitbit tracker and app or website was collected at week 12. Results Adherence to wearing the Fitbit was high and stable, with a mean of 88.13% of valid days over 12 weeks (SD 14.49%). Greater adherence to wearing the Fitbit was associated with greater increases in ActiGraph-measured MVPA (binteraction=0.35, P<.001). Participants averaged 182.6 minutes/week (SD 143.9) of MVPA on the Fitbit, with significant variation in MVPA over the 12 weeks (F=1.91, P=.04). The majority (68%, 27/40) of participants reported looking at their tracker or looking at the Fitbit app or website once a day or more. Changes in Actigraph-measured MVPA were associated with frequency of looking at one’s data on the tracker (b=−1.36, P=.07) but not significantly associated with frequency of looking at one’s data on the app or website (P=.36). Conclusions This is one of the first studies to explore the relationship between use of a commercially available activity tracker and success in a physical activity intervention. A deeper understanding of how individuals engage with technology-based trackers may enable us to more effectively use these types of trackers to promote behavior change. Trial Registration ClinicalTrials.gov NCT02332876; https://clinicaltrials.gov/ct2/show/NCT02332876?term=NCT02332876 &rank=1 (Archived by WebCite at http://www.webcitation.org/6wplEeg8i). PMID:29402761

Patterns of Fitbit Use and Activity Levels Throughout a Physical Activity Intervention: Exploratory Analysis from a Randomized Controlled Trial.

PubMed

Hartman, Sheri J; Nelson, Sandahl H; Weiner, Lauren S

2018-02-05

There has been a rapid increase in the use of technology-based activity trackers to promote behavior change. However, little is known about how individuals use these trackers on a day-to-day basis or how tracker use relates to increasing physical activity. The aims were to use minute level data collected from a Fitbit tracker throughout a physical activity intervention to examine patterns of Fitbit use and activity and their relationships with success in the intervention based on ActiGraph-measured moderate to vigorous physical activity (MVPA). Participants included 42 female breast cancer survivors randomized to the physical activity intervention arm of a 12-week randomized controlled trial. The Fitbit One was worn daily throughout the 12-week intervention. ActiGraph GT3X+ accelerometer was worn for 7 days at baseline (prerandomization) and end of intervention (week 12). Self-reported frequency of looking at activity data on the Fitbit tracker and app or website was collected at week 12. Adherence to wearing the Fitbit was high and stable, with a mean of 88.13% of valid days over 12 weeks (SD 14.49%). Greater adherence to wearing the Fitbit was associated with greater increases in ActiGraph-measured MVPA (b interaction =0.35, P<.001). Participants averaged 182.6 minutes/week (SD 143.9) of MVPA on the Fitbit, with significant variation in MVPA over the 12 weeks (F=1.91, P=.04). The majority (68%, 27/40) of participants reported looking at their tracker or looking at the Fitbit app or website once a day or more. Changes in Actigraph-measured MVPA were associated with frequency of looking at one's data on the tracker (b=-1.36, P=.07) but not significantly associated with frequency of looking at one's data on the app or website (P=.36). This is one of the first studies to explore the relationship between use of a commercially available activity tracker and success in a physical activity intervention. A deeper understanding of how individuals engage with technology-based trackers may enable us to more effectively use these types of trackers to promote behavior change. ClinicalTrials.gov NCT02332876; https://clinicaltrials.gov/ct2/show/NCT02332876?term=NCT02332876 &rank=1 (Archived by WebCite at http://www.webcitation.org/6wplEeg8i). ©Sheri J Hartman, Sandahl H Nelson, Lauren S Weiner. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 05.02.2018.

Tracking Detectors in the STAR Experiment at RHIC

NASA Astrophysics Data System (ADS)

Wieman, Howard

2015-04-01

The STAR experiment at RHIC is designed to measure and identify the thousands of particles produced in 200 Gev/nucleon Au on Au collisions. This talk will focus on the design and construction of two of the main tracking detectors in the experiment, the TPC and the Heavy Flavor Tracker (HFT) pixel detector. The TPC is a solenoidal gas filled detector 4 meters in diameter and 4.2 meters long. It provides precise, continuous tracking and rate of energy loss in the gas (dE/dx) for particles at + - 1 units of pseudo rapidity. The tracking in a half Tesla magnetic field measures momentum and dE/dX provides particle ID. To detect short lived particles tracking close to the point of interaction is required. The HFT pixel detector is a two-layered, high resolution vertex detector located at a few centimeters radius from the collision point. It determines origins of the tracks to a few tens of microns for the purpose of extracting displaced vertices, allowing the identification of D mesons and other short-lived particles. The HFT pixel detector uses detector chips developed by the IPHC group at Strasbourg that are based on standard IC Complementary Metal-Oxide-Semiconductor (CMOS) technology. This is the first time that CMOS pixel chips have been incorporated in a collider application.

Electric field induced spin-polarized current

DOEpatents

Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

2006-05-02

A device and a method for generating an electric-field-induced spin current are disclosed. A highly spin-polarized electric current is generated using a semiconductor structure and an applied electric field across the semiconductor structure. The semiconductor structure can be a hole-doped semiconductor having finite or zero bandgap or an undoped semiconductor of zero bandgap. In one embodiment, a device for injecting spin-polarized current into a current output terminal includes a semiconductor structure including first and second electrodes, along a first axis, receiving an applied electric field and a third electrode, along a direction perpendicular to the first axis, providing the spin-polarized current. The semiconductor structure includes a semiconductor material whose spin orbit coupling energy is greater than room temperature (300 Kelvin) times the Boltzmann constant. In one embodiment, the semiconductor structure is a hole-doped semiconductor structure, such as a p-type GaAs semiconductor layer.

Highly Enhanced Many-Body Interactions in Anisotropic 2D Semiconductors.

PubMed

Sharma, Ankur; Yan, Han; Zhang, Linglong; Sun, Xueqian; Liu, Boqing; Lu, Yuerui

2018-05-15

Atomically thin two-dimensional (2D) semiconductors have presented a plethora of opportunities for future optoelectronic devices and photonics applications, made possible by the strong light matter interactions at the 2D quantum limit. Many body interactions between fundamental particles in 2D semiconductors are strongly enhanced compared with those in bulk semiconductors because of the reduced dimensionality and, thus, reduced dielectric screening. These enhanced many body interactions lead to the formation of robust quasi-particles, such as excitons, trions, and biexcitons, which are extremely important for the optoelectronics device applications of 2D semiconductors, such as light emitting diodes, lasers, and optical modulators, etc. Recently, the emerging anisotropic 2D semiconductors, such as black phosphorus (termed as phosphorene) and phosphorene-like 2D materials, such as ReSe 2 , 2D-perovskites, SnS, etc., show strong anisotropic optical and electrical properties, which are different from conventional isotropic 2D semiconductors, such as transition metal dichalcogenide (TMD) monolayers. This anisotropy leads to the formation of quasi-one-dimensional (quasi-1D) excitons and trions in a 2D system, which results in even stronger many body interactions in anisotropic 2D materials, arising from the further reduced dimensionality of the quasi-particles and thus reduced dielectric screening. Many body interactions have been heavily investigated in TMD monolayers in past years, but not in anisotropic 2D materials yet. The quasi-particles in anisotropic 2D materials have fractional dimensionality which makes them perfect candidates to serve as a platform to study fundamental particle interactions in fractional dimensional space. In this Account, we present our recent progress related to 2D phosphorene, a 2D system with quasi-1D excitons and trions. Phosphorene, because of its unique anisotropic properties, provides a unique 2D platform for investigating the dynamics of excitons, trions, and biexcitons in reduced dimensions and fundamental many body interactions. We begin by explaining the fundamental reasons for the highly enhanced interactions in the 2D systems influenced by dielectric screening, resulting in high binding energies of excitons and trions, which are supported by theoretical calculations and experimental observations. Phosphorene has shown much higher binding energies of excitons and trions than TMD monolayers, which allows robust quasi-particles in anisotropic materials at room temperature. We also discuss the role of extrinsic defects induced in phosphorene, resulting in localized excitonic emissions in the near-infrared range, making it suitable for optical telecommunication applications. Finally, we present our vision of the exciting device applications based on the highly enhanced many body interactions in phosphorene, including exciton-polariton devices, polariton lasers, single-photon emitters, and tunable light emitting diodes (LEDs).

PREFACE: 19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON'19)

NASA Astrophysics Data System (ADS)

González, T.; Martín-Martínez, M. J.; Mateos, J.

2015-10-01

The 19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON'19) was held at the Hospedería Fonseca (Universidad de Salamanca, Spain), on 29 June - 2 July, 2015, and was organized by the Electronics Area from the University of Salamanca. The Conference is held biannually and covers the recent progress in the field of electron dynamics in solid-state materials and devices. This was the 19th meeting of the international conference series formerly named Hot Carriers in Semiconductors (HCIS), first held in Modena in 1973. In the edition of 1997 in Berlin the name of the conference changed to International Conference on Nonequilibrium Carrier Dynamics in Semiconductors, keeping the same acronym, HCIS; and finally in the edition of Montpellier in 2009 the name was again changed to the current one, International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON). The latest editions took place in Santa Barbara, USA, in 2011 and Matsue, Japan, in 2013. Research work on electron dynamics involves quite different disciplines, and requires both fundamental and technological scientific efforts. Attendees to the conference come mostly from academic institutions, belonging to both theoretical and experimental groups working in a variety of fields, such as solid-state physics, electronics, optics, electrical engineering, material science, laser physics, etc. In this framework, events like the EDISON conference become a basic channel for the progress in the field. Here, researchers working in different areas can meet, present their latest advances and exchange their ideas. The program of EDISON'19 included 13 invited papers, 61 oral contributions and 73 posters. These contributions originated from scientists in more than 30 different countries. The Conference gathered 140 participants, coming from 24 different countries, most from Europe, but also with a significant participation from Japan and USA. The two topics receiving more abstracts correspond to fields attracting a lot of attention and research activity in the last years: electron dynamics in graphene and related materials and devices, and THz phenomena in nanostructures. Other topics like coherent dynamics in ultrafast optical phenomena or quantum processing, and semiconductor-based spintronics, had also an important presence in the program. Thanks are given to the members of the International and Scientific Program Committees for their valuable and qualified assistance in the selection of invited speakers and the review of the submitted contributions; and also to those attendees who assisted us in the review process of the papers included in this volume. We would like also to thank the institutions and sponsors that contributed to support the conference. Firstly the University of Salamanca, one of the oldest in the world, commemorating within three years, in 2018, the 8th century of its foundation in 1218. EDISON'19 can be considered as one more of the events taking place to celebrate such centennial. The Salamanca City Council also contributed in the organization of the conference. We acknowledge as well the support from the Spanish Ministry of Economy and Competitiveness, and from our sponsors and exhibitors, Oxford Instruments and Rohde&Schwarz. Finally, we would like to thank all participants and authors of the proceedings for their support and contributions to the conference. We devote this volume to the memory of Prof. Daniel Pardo, our dear boss in Salamanca for many years, who passed away in 2013. He was the pioneer of our activity in the field of the conference and would have enjoyed a lot the celebration of EDISON in Salamanca.

High resolution energy-sensitive digital X-ray

DOEpatents

Nygren, David R.

1995-01-01

An apparatus and method for detecting an x-ray and for determining the depth of penetration of an x-ray into a semiconductor strip detector. In one embodiment, a semiconductor strip detector formed of semiconductor material is disposed in an edge-on orientation towards an x-ray source such that x-rays From the x-ray source are incident upon and substantially perpendicular to the front edge of the semiconductor strip detector. The semiconductor strip detector is formed of a plurality of segments. The segments are coupled together in a collinear arrangement such that the semiconductor strip detector has a length great enough such that substantially all of the x-rays incident on the front edge of the semiconductor strip detector interact with the semiconductor material which forms the semiconductor strip detector. A plurality of electrodes are connected to the semiconductor strip detect or such that each one of the of semiconductor strip detector segments has at least one of the of electrodes coupled thereto. A signal processor is also coupled to each one of the electrodes. The present detector detects an interaction within the semiconductor strip detector, between an x-ray and the semiconductor material, and also indicates the depth of penetration of the x-ray into the semiconductor strip detector at the time of the interaction.

High resolution energy-sensitive digital X-ray

DOEpatents

Nygren, D.R.

1995-07-18

An apparatus and method for detecting an x-ray and for determining the depth of penetration of an x-ray into a semiconductor strip detector. In one embodiment, a semiconductor strip detector formed of semiconductor material is disposed in an edge-on orientation towards an x-ray source such that x-rays from the x-ray source are incident upon and substantially perpendicular to the front edge of the semiconductor strip detector. The semiconductor strip detector is formed of a plurality of segments. The segments are coupled together in a collinear arrangement such that the semiconductor strip detector has a length great enough such that substantially all of the x-rays incident on the front edge of the semiconductor strip detector interact with the semiconductor material which forms the semiconductor strip detector. A plurality of electrodes are connected to the semiconductor strip detector such that each one of the semiconductor strip detector segments has at least one of the of electrodes coupled thereto. A signal processor is also coupled to each one of the electrodes. The present detector detects an interaction within the semiconductor strip detector, between an x-ray and the semiconductor material, and also indicates the depth of penetration of the x-ray into the semiconductor strip detector at the time of the interaction. 5 figs.

Breadboard stellar tracker system test report, volume 2

NASA Technical Reports Server (NTRS)

1981-01-01

Complete data from a test program designed to evaluate the performance of a star tracker, a breadboard tracker system, is presented in tabular form. All data presented was normalized to the pixel dimension of 20 micrometers. Data from determination of maximum spatial noise as it applies to the coarse and fine acquisition modes is presented. Pointing accuracy test data, raw pixel data for the track cycle, and data from equipment related tests is also presented.

S-band range tracker and Surveillance Lab interface

NASA Astrophysics Data System (ADS)

Bush, B. D.

1983-09-01

This report documents the design, construction, test and laboratory integration of the range tracker and associated subsystems for the RADC/OC Surveillance Laboratory's S-Band tracking radar. This development was accomplished over the period from December 1981 to November 1983 and was designed, constructed and tested entirely in-house. This report contains information on the use of the range tracker, its interfaces to other laboratory equipment, the philosophy behind its design, the detailed design of the hardware (including schematics, timing and cabling diagrams), the detailed software design (including flowcharts), and the mathematical description of its algorithms. The range tracker will be used in conjunction with other equipment in the OC Surveillance Lab in the taking and recording of radar data during flight tests.

A comparison of VLSI architecture of finite field multipliers using dual, normal or standard basis

NASA Technical Reports Server (NTRS)

Hsu, I. S.; Truong, T. K.; Shao, H. M.; Deutsch, L. J.; Reed, I. S.

1987-01-01

Three different finite field multipliers are presented: (1) a dual basis multiplier due to Berlekamp; (2) a Massy-Omura normal basis multiplier; and (3) the Scott-Tavares-Peppard standard basis multiplier. These algorithms are chosen because each has its own distinct features which apply most suitably in different areas. Finally, they are implemented on silicon chips with nitride metal oxide semiconductor technology so that the multiplier most desirable for very large scale integration implementations can readily be ascertained.

Deep-UV Emitters and Detectors Based on Lattice-Matched Cubic Oxide Semiconductors (4.2 Optoelectronics)

DTIC Science & Technology

2015-05-14

calculated   by   dividing   photo-­‐‑ generated  current  by  the  optical  power  spectrum  of  the   lamp .    A   UV ...the optimized parameters for growth. Efforts led to significant increases in solar?blind detector responsivity (up to 0.1 A/W) with sub-­ nanoamp...Aug-2014 Approved for Public Release; Distribution Unlimited Final Report: Deep- UV Emitters and Detectors Based on Lattice- Matched Cubic Oxide

The Effect of Thermal Annealing on Charge Transport in Organolead Halide Perovskite Microplate Field-Effect Transistors.

PubMed

Li, Dehui; Cheng, Hung-Chieh; Wang, Yiliu; Zhao, Zipeng; Wang, Gongming; Wu, Hao; He, Qiyuan; Huang, Yu; Duan, Xiangfeng

2017-01-01

Transformation of unipolar n-type semiconductor behavior to ambipolar and finally to unipolar p-type behavior in CH 3 NH 3 PbI 3 microplate field-effect transistors by thermal annealing is reported. The photoluminescence spectra essentially maintain the same features before and after the thermal annealing process, demonstrating that the charge transport measurement provides a sensitive way to probe low-concentration defects in perovskite materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

CONJUGATED POLYMERS AND POLYELECTROLYTES IN SOLAR PHOTOCONVERSION, Final Technical Report

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

Schanze, Kirk S

2014-08-05

This DOE-supported program investigated the fundamental properties of conjugated polyelectrolytes, with emphasis placed on studies of excited state energy transport, self-assembly into conjugated polyelectroyte (CPE) based films and colloids, and exciton transport and charge injection in CPE films constructed atop wide bandgap semiconductors. In the most recent grant period we have also extended efforts to examine the properties of low-bandgap donor-acceptor conjugated polyelectrolytes that feature strong visible light absorption and the ability to adsorb to metal-oxide interfaces.

A Strain-Sonde Technique for the Measurement of Mechanical Time-Delay Fuze Function Times and Performance

DTIC Science & Technology

1983-09-01

AD IV) MEMORANDUM REPORT ARBRL-MR-03309 N(Supersedes IMR No. 760) A STRAIN -SONDE TECHNIQUE FOR THE MEASUREMENT OF MECHANICAL TIME- DELAY FUZE...and BkuWel) S. TYPE OF REPORT & PERIOD COVERED A STRAIN -SONDE TECHNIQUE FOR THE MEASUREMENT OF Final MECHANICAL TIME-DELAY FUZE FUNCTION TIMES AND S...nmber) M577 Mechanical Time-Delay Fuze F"/FM Telemeter Interlock Pin Release Semiconductor Strain Gage Rotor Signal Condition Amplifier Firing Pin In

Highly Efficient Nd:yag Lasers for Free-space Optical Communications

NASA Technical Reports Server (NTRS)

Sipes, D. L., Jr.

1985-01-01

A highly efficient Nd:YAG laser end-pumped by semiconductor lasers as a possible free-space optical communications source is discussed. Because this concept affords high pumping densities, a long absorption length, and excellent mode-matching characteristics, it is estimated that electrical-to-optical efficiencies greater than 5% could be achieved. Several engineering aspects such as resonator size and configuration, pump collecting optics, and thermal effects are also discussed. Finally, possible methods for combining laser-diode pumps to achieve higher output powers are illustrated.

Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon [Pinole, CA; Bruchez, Jr., Marcel; Alivisatos, Paul [Oakland, CA

2008-01-01

A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) an affinity molecule linked to the semiconductor nanocrystal. The semiconductor nanocrystal is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Exposure of the semiconductor nanocrystal to excitation energy will excite the semiconductor nanocrystal causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

tkLayout: a design tool for innovative silicon tracking detectors

NASA Astrophysics Data System (ADS)

Bianchi, G.

2014-03-01

A new CMS tracker is scheduled to become operational for the LHC Phase 2 upgrade in the early 2020's. tkLayout is a software package developed to create 3d models for the design of the CMS tracker and to evaluate its fundamental performance figures. The new tracker will have to cope with much higher luminosity conditions, resulting in increased track density, harsher radiation exposure and, especially, much higher data acquisition bandwidth, such that equipping the tracker with triggering capabilities is envisaged. The design of an innovative detector involves deciding on an architecture offering the best trade-off among many figures of merit, such as tracking resolution, power dissipation, bandwidth, cost and so on. Quantitatively evaluating these figures of merit as early as possible in the design phase is of capital importance and it is best done with the aid of software models. tkLayout is a flexible modeling tool: new performance estimates and support for different detector geometries can be quickly added, thanks to its modular structure. Besides, the software executes very quickly (about two minutes), so that many possible architectural variations can be rapidly modeled and compared, to help in the choice of a viable detector layout and then to optimize it. A tracker geometry is generated from simple configuration files, defining the module types, layout and materials. Support structures are automatically added and services routed to provide a realistic tracker description. The tracker geometries thus generated can be exported to the standard CMS simulation framework (CMSSW) for full Monte Carlo studies. tkLayout has proven essential in giving guidance to CMS in studying different detector layouts and exploring the feasibility of innovative solutions for tracking detectors, in terms of design, performance and projected costs. This tool has been one of the keys to making important design decisions for over five years now and has also enabled project engineers and simulation experts to focus their efforts on other important or specific issues. Even if tkLayout was designed for the CMS tracker upgrade project, its flexibility makes it experiment-agnostic, so that it could be easily adapted to model other tracking detectors. The technology behind tkLayout is presented, as well as some of the results obtained in the context of the CMS silicon tracker design studies.

A Bit of Fit: Minimalist Intervention in Adolescents Based on a Physical Activity Tracker.

PubMed

Gaudet, Jeffrey; Gallant, François; Bélanger, Mathieu

2017-07-06

Only 5% of Canadian youth meet the recommended 60 minutes of moderate to vigorous physical activity (MVPA) per day, with leisure time being increasingly allocated to technology usage. Direct-to-consumer mHealth devices that promote physical activity, such as wrist-worn physical activity trackers, have features with potential appeal to youth. The primary purpose of this study was to determine whether a minimalist physical activity tracker-based intervention would lead to an increase in physical activity in young adolescents. A secondary aim of this study was to assess change in physical activity across a 7-week intervention, as measured by the tracker. Using a quasi-experimental crossover design, two groups of 23 young adolescents (aged 13-14 years) were randomly assigned to immediate intervention or delayed intervention. The intervention consisted of wearing a Fitbit-Charge-HR physical activity tracker over a 7-week period. Actical accelerometers were used to measure participants' levels of MVPA before and at the end of intervention periods for each group. Covariates such as age, sex, stage of change for physical activity behavior, and goal commitment were also measured. There was an increase in physical activity over the course of the study period, though it was not related to overall physical activity tracker use. An intervention response did, however, occur in a subset of participants. Specifically, exposure to the physical activity tracker was associated with an average daily increase in MVPA by more than 15 minutes (P=.01) among participants who reported being in the action and maintenance stages of behavior change in relation to participation in physical activity. Participants in the precontemplation, contemplation, and preparation stages of behavior change had no change in their level of MVPA (P=.81). These results suggest that physical activity trackers may elicit improved physical activity related behavior in young adolescents demonstrating a readiness to be active. Future studies should seek to investigate if integrating physical activity trackers as part of more intensive interventions leads to greater increases in physical activity across different levels of stages of behavior change and if these changes can be sustained over longer periods of time. ©Jeffrey Gaudet, François Gallant, Mathieu Bélanger. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 06.07.2017.

Healthy Weight

MedlinePlus

... certain health conditions External Resources Weight loss, weight management, nutrition, meal planning tools… Super Tracker SuperTracker: My Plan Food Diary [PDF – 34KB] Physical Activity Diary [PDF – 52KB] ...

Use of LysoTracker dyes: a flow cytometric study of autophagy.

PubMed

Chikte, Shaheen; Panchal, Neelam; Warnes, Gary

2014-02-01

The flow cytometric use of LysoTracker dyes was employed to investigate the autophagic process and to compare this with the upregulation of autophagy marker, the microtubule-associated protein LC3B. Although the mechanism of action of LysoTracker dyes is not fully understood, they have been used in microscopy to image acidic spherical organelles, and their use in flow cytometry has not been thoroughly investigated in the study of autophagy. This investigation uses numerous autophagy-inducing agents including chloroquine (CQ), rapamycin, low serum (<1%) RPMI, and nutrient starvation to induce autophagy in Jurkat T-cell leukemia and K562 erythromyeloid cell lines. LC3B showed an increase with CQ treatment although this was different to LysoTracker signals in terms of dose and time. Rapamycin, low serum (<1%) RPMI, and nutrient starvation induction of autophagy also induced an increase in LysoTracker and LC3B signals. CQ also induced apoptosis in cell lines, which was blocked by pan-caspase inhibitor z-VAD resulting in a reduction in cells undergoing apoptosis and a subsequent upregulation of autophagic markers LC3B and lysosomal dye signals. Given that LC3B and LysoTracker are measuring different biological events in the autophagic process, they surprisingly both upregulated during autophagic process. This study, however, shows that although LysoTracker dyes do not specifically label lysosomes or autophagosomes within the cell, they allow the simultaneous measurement of an autophagy-related process and other live-cell functions, which are not possible with the standard LC3B antibody-labeling technique. This method has the advantage of other live-cell LCB-GFP-tagged experiments in that be used to analyze patient cells as well as easier to use and significantly less costly. Copyright © 2013 International Society for Advancement of Cytometry.

Using analog instruments in Tracker video-based experiments to understand the phenomena of electricity and magnetism in physics education

NASA Astrophysics Data System (ADS)

Aguilar-Marín, Pablo; Chavez-Bacilio, Mario; Jáuregui-Rosas, Segundo

2018-05-01

Tracker is a piece of freeware software, designed to use video recorded images of the motion of objects as input data, and has been mostly applied in physics education to analyse and simulate physical phenomena in mechanics. In this work we report the application of Tracker to the study of experiments in electricity and magnetism using analog instruments for electrical signal measurements. As we are unable to directly video-track the motion of electrons in electric circuits, the angular deflections of the instruments’ pointers were video captured instead. The kinematic variables (angular position as a function of time) had to be related to the electrical ones (voltages and currents as a function of time). Two well-known experiments in physics teaching, the RC circuit for charging and discharging a capacitor and Faraday electromagnetic induction, were chosen to illustrate the procedures. The third experiment analysed and modeled with Tracker was the rather well-known electromagnetic retardation of disk- or cylinder-shaped magnets falling inside non-magnetic metallic pipes. Instead of metallic pipes we used an aluminum plate with an arrangement of a couple of parallelepiped-shaped magnets falling parallel to the plate. In the three cases studied, the experimental and the Tracker simulation results were in very good agreement. These outcomes show that it is possible to exploit the potential of Tracker software in areas other than mechanics, in areas where electrical signals are involved. The experiments are inexpensive and simple to perform, and are suitable for high school and introductory undergraduate courses in electricity, magnetism and electronics. We propose the use of Tracker combined with analog measuring devices to explore further its applications in electricity, magnetism, electronics and in other experimental sciences where electrical signals are involved.

Characterization of functional variables in epididymal alpaca (Vicugna pacos) sperm using imaging flow cytometry.

PubMed

Santiani, Alexei; Ugarelli, Alejandra; Evangelista-Vargas, Shirley

2016-10-01

Epididymal alpaca sperm represent an alternative model for the study of alpaca semen. The objective of this study was to characterize the normal values of some functional variables in epididymal alpaca sperm using imaging flow cytometry. Alpaca testicles (n=150) were processed and sperm were recovered from the cauda epididymides. Only 76 samples with acceptable motility and sperm count were considered for assessment by imaging flow cytometry. Acrosome integrity and integrity/viability were assessed by FITC-PSA/PI and FITC-PNA/PI. Mitochondrial membrane potential (MMP) was assessed by MitoTracker CMXRos and MitoTracker Deep Red FM. Lipid peroxidation was evaluated using BODIPY 581/591 C11. Results show that the mean values for acrosome-intact sperm were 95.03±6.39% and 93.34±7.96%, using FITC-PSA and FITC-PNA, respectively. The mean values for acrosome-intact viable sperm were 60.58±12.12% with FITC-PSA/PI and 58.81±12.94% with FITC-PNA/PI. Greater MMP was detected in 65.03±15.92% and 59.52±19.19%, using MitoTracker CMXRos and MitoTracker Deep Red FM, respectively. Lipid peroxidation was 0.84±0.95%. Evaluation of acrosome-intact and acrosome-intact viable sperm with FITC-PSA/PI compared with. FITC-PNA/PI or MMP with MitoTracker CMXRos compared with MitoTracker Deep Red FM were correlated (P<0.05). The MMP using MitoTracker CMXRos was the only variable correlated (P<0.05) with sperm motility (r=0.3979). This report provides a basis for future research related to alpaca semen using the epididymal sperm model. Copyright © 2016 Elsevier B.V. All rights reserved.

Minimum Error Bounded Efficient L1 Tracker with Occlusion Detection (PREPRINT)

DTIC Science & Technology

2011-01-01

Minimum Error Bounded Efficient `1 Tracker with Occlusion Detection Xue Mei\\ ∗ Haibin Ling† Yi Wu†[ Erik Blasch‡ Li Bai] \\Assembly Test Technology...proposed BPR-L1 tracker is tested on several challenging benchmark sequences involving chal- lenges such as occlusion and illumination changes. In all...point method de - pends on the value of the regularization parameter λ. In the experiments, we found that the total number of PCG is a few hundred. The

Long-life 3-axis satellite attitude sensing, phase 1

NASA Technical Reports Server (NTRS)

Arild, Tor

1987-01-01

The purpose was to investigate the feasibility of new, moderate-cost, high reliability navigation sensors for high-altitude satellites, using stellar sources to obviate the use of gyroscopic devices. The primary investigation focused on the need for developing a star tracker model to replace an old star tracker which is still needed for current probe and satellite programs. One innovative element of the proposed star tracker was the design, development, and testing of technology components related to a phase scrambler plate. The purpose of the phase scrambler plate is to convert the impulse response of the optical system from a point image to a uniformly bright, square, angularly large, in-focus image of the star source. A collimated star source was built and tested. A breadboard star tracker with an 8 x 8 degree field of view was designed and built. It was tested in normal quad-cell mode (without the phase scrambler plate) and with the phase scrambler plate. Although the phase scrambler plate was crudely made, the performance of the star tracker breadboard was greatly improved using the phase scrambler plate, instead of system defocus. If further developed, the phase scrambler plate may be added as a low-cost retroconversion to any objective lens to greatly improve quad-cell or CCD array tracking; applications include star trackers, laser metrology, laser machining optics, and surveying instrumentation.

Development of a digital mobile solar tracker

NASA Astrophysics Data System (ADS)

Baidar, S.; Kille, N.; Ortega, I.; Sinreich, R.; Thomson, D.; Hannigan, J.; Volkamer, R.

2015-11-01

We have constructed and deployed a fast digital solar tracker aboard a moving ground-based platform. The tracker consists of two rotating mirrors, a lens, an imaging camera, and a motion compensation system that provides the Euler angles of the mobile platform in real time. The tracker can be simultaneously coupled to UV-Vis and FTIR spectrometers making it a versatile tool to measure the absorption of trace gases using solar incoming radiation. The integrated system allows the tracker to operate autonomously while the mobile laboratory is in motion. Mobile direct sun Differential Optical Absorption Spectroscopy (mobile DS-DOAS) observations using this tracker were conducted during summer 2014 as part of the Front Range Photochemistry and Pollution Experiment (FRAPPE) in Colorado, USA. We demonstrate an angular precision of 0.052° (about 1/10 of the solar disk diameter) during research drives, and verify this tracking precision from measurements of the center to limb darkening (CLD, the changing appearance of Fraunhofer lines) in the mobile DS-DOAS spectra. The high photon flux from direct sun observation enables measurements of nitrogen dioxide (NO2) slant columns with high temporal resolution, and reveals spatial detail in the variations of NO2 vertical column densities (VCDs). The NO2 VCD from DS-DOAS is compared with a co-located MAX-DOAS instrument. Overall good agreement is observed amid a highly heterogeneous air mass.

Development of a digital mobile solar tracker

NASA Astrophysics Data System (ADS)

Baidar, Sunil; Kille, Natalie; Ortega, Ivan; Sinreich, Roman; Thomson, David; Hannigan, James; Volkamer, Rainer

2016-03-01

We have constructed and deployed a fast digital solar tracker aboard a moving ground-based platform. The tracker consists of two rotating mirrors, a lens, an imaging camera, and a motion compensation system that provides the Euler angles of the mobile platform in real time. The tracker can be simultaneously coupled to UV-Vis and Fourier transform infrared spectrometers, making it a versatile tool to measure the absorption of trace gases using solar incoming radiation. The integrated system allows the tracker to operate autonomously while the mobile laboratory is in motion. Mobile direct sun differential optical absorption spectroscopy (mobile DS-DOAS) observations using this tracker were conducted during summer 2014 as part of the Front Range Air Pollution and Photochemistry Experiment (FRAPPE) in Colorado, USA. We demonstrate an angular precision of 0.052° (about 1/10 of the solar disk diameter) during research drives and verify this tracking precision from measurements of the center to limb darkening (CLD, the changing appearance of Fraunhofer lines) in the mobile DS-DOAS spectra. The high photon flux from direct sun observation enables measurements of nitrogen dioxide (NO2) slant columns with high temporal resolution and reveals spatial detail in the variations of NO2 vertical column densities (VCDs). The NO2 VCD from DS-DOAS is compared with a co-located MAX-DOAS instrument. Overall good agreement is observed amid a highly heterogeneous air mass.

Utility of the T2 Mood Tracker mobile application among army warrior transition unit service members.

PubMed

Bush, Nigel E; Ouellette, Gary; Kinn, Julie

2014-12-01

Many military personnel returning from deployment experience increases in psychological symptoms, including post-traumatic stress disorder (PTSD), depression, and mood changes. Patient health diaries are commonly used for self-reporting over time away from the clinic. "T2 Mood Tracker" is an application ("app") for smartphones and other mobile devices that enables users to rate their moods, to self-monitor across time, and to report their emotional experiences to health providers. We designed T2 Mood Tracker to track symptoms associated with deployment-related behavioral health issues, including PTSD, Head Injury, Stress, Depression, Anxiety, and General Well-Being. We field-tested T2 Mood Tracker with a small sample of redeployed soldiers under treatment for behavioral health issues at a Warrior Transition Unit. Participants used the app an average of 10 different days over the 2- to 3-week test period. Consensus was that T2 Mood Tracker was easy to use, useful and beneficial. The majority said they would use the app in the future, would recommend it to other service members, and would use the app to share their mood information with a provider. Warrior Transition Unit providers were enthusiastic about the potential of T2 Mood Tracker as a tool for use with their patients. Reprint & Copyright © 2014 Association of Military Surgeons of the U.S.

Application of virtual distances methodology to laser tracker verification with an indexed metrology platform

NASA Astrophysics Data System (ADS)

Acero, R.; Santolaria, J.; Pueo, M.; Aguilar, J. J.; Brau, A.

2015-11-01

High-range measuring equipment like laser trackers need large dimension calibrated reference artifacts in their calibration and verification procedures. In this paper, a new verification procedure for portable coordinate measuring instruments based on the generation and evaluation of virtual distances with an indexed metrology platform is developed. This methodology enables the definition of an unlimited number of reference distances without materializing them in a physical gauge to be used as a reference. The generation of the virtual points and reference lengths derived is linked to the concept of the indexed metrology platform and the knowledge of the relative position and orientation of its upper and lower platforms with high accuracy. It is the measuring instrument together with the indexed metrology platform one that remains still, rotating the virtual mesh around them. As a first step, the virtual distances technique is applied to a laser tracker in this work. The experimental verification procedure of the laser tracker with virtual distances is simulated and further compared with the conventional verification procedure of the laser tracker with the indexed metrology platform. The results obtained in terms of volumetric performance of the laser tracker proved the suitability of the virtual distances methodology in calibration and verification procedures for portable coordinate measuring instruments, broadening and expanding the possibilities for the definition of reference distances in these procedures.

Miniature Laser Tracker

DOEpatents

Vann, Charles S.

2003-09-09

This small, inexpensive, non-contact laser sensor can detect the location of a retroreflective target in a relatively large volume and up to six degrees of position. The tracker's laser beam is formed into a plane of light which is swept across the space of interest. When the beam illuminates the retroreflector, some of the light returns to the tracker. The intensity, angle, and time of the return beam is measured to calculate the three dimensional location of the target. With three retroreflectors on the target, the locations of three points on the target are measured, enabling the calculation of all six degrees of target position. Until now, devices for three-dimensional tracking of objects in a large volume have been heavy, large, and very expensive. Because of the simplicity and unique characteristics of this tracker, it is capable of three-dimensional tracking of one to several objects in a large volume, yet it is compact, light-weight, and relatively inexpensive. Alternatively, a tracker produces a diverging laser beam which is directed towards a fixed position, and senses when a retroreflective target enters the fixed field of view. An optically bar coded target can be read by the tracker to provide information about the target. The target can be formed of a ball lens with a bar code on one end. As the target moves through the field, the ball lens causes the laser beam to scan across the bar code.

Semiconductor structure and recess formation etch technique

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

Lu, Bin; Sun, Min; Palacios, Tomas Apostol

2017-02-14

A semiconductor structure has a first layer that includes a first semiconductor material and a second layer that includes a second semiconductor material. The first semiconductor material is selectively etchable over the second semiconductor material using a first etching process. The first layer is disposed over the second layer. A recess is disposed at least in the first layer. Also described is a method of forming a semiconductor structure that includes a recess. The method includes etching a region in a first layer using a first etching process. The first layer includes a first semiconductor material. The first etching processmore » stops at a second layer beneath the first layer. The second layer includes a second semiconductor material.« less

Real-Time Detection and Tracking of Multiple People in Laser Scan Frames

NASA Astrophysics Data System (ADS)

Cui, J.; Song, X.; Zhao, H.; Zha, H.; Shibasaki, R.

This chapter presents an approach to detect and track multiple people ro bustly in real time using laser scan frames. The detection and tracking of people in real time is a problem that arises in a variety of different contexts. Examples in clude intelligent surveillance for security purposes, scene analysis for service robot, and crowd behavior analysis for human behavior study. Over the last several years, an increasing number of laser-based people-tracking systems have been developed in both mobile robotics platforms and fixed platforms using one or multiple laser scanners. It has been proved that processing on laser scanner data makes the tracker much faster and more robust than a vision-only based one in complex situations. In this chapter, we present a novel robust tracker to detect and track multiple people in a crowded and open area in real time. First, raw data are obtained that measures two legs for each people at a height of 16 cm from horizontal ground with multiple registered laser scanners. A stable feature is extracted using accumulated distribu tion of successive laser frames. In this way, the noise that generates split and merged measurements is smoothed well, and the pattern of rhythmic swinging legs is uti lized to extract each leg. Second, a probabilistic tracking model is presented, and then a sequential inference process using a Bayesian rule is described. A sequential inference process is difficult to compute analytically, so two strategies are presented to simplify the computation. In the case of independent tracking, the Kalman fil ter is used with a more efficient measurement likelihood model based on a region coherency property. Finally, to deal with trajectory fragments we present a concise approach to fuse just a little visual information from synchronized video camera to laser data. Evaluation with real data shows that the proposed method is robust and effective. It achieves a significant improvement compared with existing laser-based trackers.

Motion Tracker: Camera-Based Monitoring of Bodily Movements Using Motion Silhouettes

PubMed Central

Westlund, Jacqueline Kory; D’Mello, Sidney K.; Olney, Andrew M.

2015-01-01

Researchers in the cognitive and affective sciences investigate how thoughts and feelings are reflected in the bodily response systems including peripheral physiology, facial features, and body movements. One specific question along this line of research is how cognition and affect are manifested in the dynamics of general body movements. Progress in this area can be accelerated by inexpensive, non-intrusive, portable, scalable, and easy to calibrate movement tracking systems. Towards this end, this paper presents and validates Motion Tracker, a simple yet effective software program that uses established computer vision techniques to estimate the amount a person moves from a video of the person engaged in a task (available for download from http://jakory.com/motion-tracker/). The system works with any commercially available camera and with existing videos, thereby affording inexpensive, non-intrusive, and potentially portable and scalable estimation of body movement. Strong between-subject correlations were obtained between Motion Tracker’s estimates of movement and body movements recorded from the seat (r =.720) and back (r = .695 for participants with higher back movement) of a chair affixed with pressure-sensors while completing a 32-minute computerized task (Study 1). Within-subject cross-correlations were also strong for both the seat (r =.606) and back (r = .507). In Study 2, between-subject correlations between Motion Tracker’s movement estimates and movements recorded from an accelerometer worn on the wrist were also strong (rs = .801, .679, and .681) while people performed three brief actions (e.g., waving). Finally, in Study 3 the within-subject cross-correlation was high (r = .855) when Motion Tracker’s estimates were correlated with the movement of a person’s head as tracked with a Kinect while the person was seated at a desk (Study 3). Best-practice recommendations, limitations, and planned extensions of the system are discussed. PMID:26086771

A novel design of dual-channel optical system of star-tracker based on non-blind area PAL system

NASA Astrophysics Data System (ADS)

Luo, Yujie; Bai, Jian

2016-07-01

Star-tracker plays an important role in satellite navigation. Considering the satellites on near-Earth orbit, the system usually has two optical systems: one for observing the profile of Earth and the other for capturing the positions of stars. In this paper, we demonstrate a novel kind of dual-channel optical observation system of star-tracker with non-blind area PAL imaging system based on dichroic filter, which can combine both different observation channels into an integrated structure and realize the feature of miniaturization. According to the practical usage of star-tracker and the features of dichroic filter, we set the ultraviolet band as the PAL channel to observe the Earth with the FOV ranging from 40°-60°, and set the visible band as the front imaging channel to capture the stars far away from this system with the FOV ranging from 0°-20°. Consequently, the rays of both channels are converged on the same image plane, improving the efficiency of pixels of detector and reducing the weight and size of whole star-tracker system.

Ground Testing Strategies for Verifying the Slew Rate Tolerance of Star Trackers

PubMed Central

Dzamba, Tom; Enright, John

2014-01-01

The performance of a star tracker is largely based on the availability of its attitude solution. Several methods exist to assess star tracker availability under both static and dynamic imaging conditions. However, these methods typically make various idealizations that can limit the accuracy of these results. This study aims to increase the fidelity of star tracker availability modeling by accounting for the effects of detection logic and pixel saturation on star detection. We achieve this by developing an analytical model for the focal plane intensity distribution of a star in the presence of sensor slew. Using the developed model, we examine the effects of slew rate on star detection using simulations and lab tests. The developed approach allows us to determine the maximum slew rate for which a star of a given stellar magnitude can still be detected. This information can then be used to describe the availability of a star tracker attitude solution as a function of slew rate, both spatially, across the entire celestial sphere, or locally, along a specified orientation track. PMID:24577522

Effective Visual Tracking Using Multi-Block and Scale Space Based on Kernelized Correlation Filters

PubMed Central

Jeong, Soowoong; Kim, Guisik; Lee, Sangkeun

2017-01-01

Accurate scale estimation and occlusion handling is a challenging problem in visual tracking. Recently, correlation filter-based trackers have shown impressive results in terms of accuracy, robustness, and speed. However, the model is not robust to scale variation and occlusion. In this paper, we address the problems associated with scale variation and occlusion by employing a scale space filter and multi-block scheme based on a kernelized correlation filter (KCF) tracker. Furthermore, we develop a more robust algorithm using an appearance update model that approximates the change of state of occlusion and deformation. In particular, an adaptive update scheme is presented to make each process robust. The experimental results demonstrate that the proposed method outperformed 29 state-of-the-art trackers on 100 challenging sequences. Specifically, the results obtained with the proposed scheme were improved by 8% and 18% compared to those of the KCF tracker for 49 occlusion and 64 scale variation sequences, respectively. Therefore, the proposed tracker can be a robust and useful tool for object tracking when occlusion and scale variation are involved. PMID:28241475

Effective Visual Tracking Using Multi-Block and Scale Space Based on Kernelized Correlation Filters.

PubMed

Jeong, Soowoong; Kim, Guisik; Lee, Sangkeun

2017-02-23

Accurate scale estimation and occlusion handling is a challenging problem in visual tracking. Recently, correlation filter-based trackers have shown impressive results in terms of accuracy, robustness, and speed. However, the model is not robust to scale variation and occlusion. In this paper, we address the problems associated with scale variation and occlusion by employing a scale space filter and multi-block scheme based on a kernelized correlation filter (KCF) tracker. Furthermore, we develop a more robust algorithm using an appearance update model that approximates the change of state of occlusion and deformation. In particular, an adaptive update scheme is presented to make each process robust. The experimental results demonstrate that the proposed method outperformed 29 state-of-the-art trackers on 100 challenging sequences. Specifically, the results obtained with the proposed scheme were improved by 8% and 18% compared to those of the KCF tracker for 49 occlusion and 64 scale variation sequences, respectively. Therefore, the proposed tracker can be a robust and useful tool for object tracking when occlusion and scale variation are involved.

Development and Testing of the AMEGO Silicon Tracker System

NASA Astrophysics Data System (ADS)

Griffin, Sean; Amego Team

2018-01-01

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe-class mission in consideration for the 2020 decadal review designed to operate at energies from ˜ 200 keV to > 10 GeV. Operating a detector in this energy regime is challenging due to the crossover in the interaction cross-section for Compton scattering and pair production. AMEGO is made of four major subsystems: a plastic anticoincidence detector for rejecting cosmic-ray events, a silicon tracker for measuring the energies of Compton scattered electrons and pair-production products, a CZT calorimeter for measuring the energy and location of Compton scattered photons, and a CsI calorimeter for measuring the energy of the pair-production products at high energies. The tracker comprises layers of dual-sided silicon strip detectors which provide energy and localization information for Compton scattering and pair-production events. A prototype tracker system is under development at GSFC; in this contribution we provide details on the verification, packaging, and testing of the prototype tracker, as well as present plans for the development of the front-end electronics, beam tests, and a balloon flight.

Long Term Outdoor Testing of Low Concentration Solar Modules

NASA Astrophysics Data System (ADS)

Fraas, Lewis; Avery, James; Minkin, Leonid; Huang, H. X.; Hebrink, Tim; Hurt, Rik; Boehm, Robert

2011-12-01

A 1-axis carousel tracker equipped with four 3-sun low-concentration mirror modules has now been under test outdoors at the University of Nevada in Las Vegas (UNLV) for three years. There are three unique features associated with this unit. First, simple linear mirrors are used to reduce the amount of expensive single crystal silicon in order to potentially lower the module cost while potentially maintaining cell efficiencies over 20% and high module efficiency. Simple linear mirrors also allow the use of a single axis tracker. Second, the azimuth carousel tracker is also unique allowing trackers to be used on commercial building rooftops. Third, an experiment is underway comparing aluminum based mirrors with novel 3M Company multilayer polymeric mirrors which are potentially very low cost. Comparing the data from March of 2008 through March of 2011 shows that the aluminum mirror degradation to date is negligible and that the carousel tracker has been operating continuously and reliable. Also, no degradation has been observed for the 3M brand cool mirrors after one year in use.

Robust visual tracking via multiscale deep sparse networks

NASA Astrophysics Data System (ADS)

Wang, Xin; Hou, Zhiqiang; Yu, Wangsheng; Xue, Yang; Jin, Zefenfen; Dai, Bo

2017-04-01

In visual tracking, deep learning with offline pretraining can extract more intrinsic and robust features. It has significant success solving the tracking drift in a complicated environment. However, offline pretraining requires numerous auxiliary training datasets and is considerably time-consuming for tracking tasks. To solve these problems, a multiscale sparse networks-based tracker (MSNT) under the particle filter framework is proposed. Based on the stacked sparse autoencoders and rectifier linear unit, the tracker has a flexible and adjustable architecture without the offline pretraining process and exploits the robust and powerful features effectively only through online training of limited labeled data. Meanwhile, the tracker builds four deep sparse networks of different scales, according to the target's profile type. During tracking, the tracker selects the matched tracking network adaptively in accordance with the initial target's profile type. It preserves the inherent structural information more efficiently than the single-scale networks. Additionally, a corresponding update strategy is proposed to improve the robustness of the tracker. Extensive experimental results on a large scale benchmark dataset show that the proposed method performs favorably against state-of-the-art methods in challenging environments.

Method of making photovoltaic cell

DOEpatents

Cruz-Campa, Jose Luis; Zhou, Xiaowang; Zubia, David

2017-06-20

A photovoltaic solar cell comprises a nano-patterned substrate layer. A plurality of nano-windows are etched into an intermediate substrate layer to form the nano-patterned substrate layer. The nano-patterned substrate layer is positioned between an n-type semiconductor layer composed of an n-type semiconductor material and a p-type semiconductor layer composed of a p-type semiconductor material. Semiconductor material accumulates in the plurality of nano-windows, causing a plurality of heterojunctions to form between the n-type semiconductor layer and the p-type semiconductor layer.

Developmental Milestones

MedlinePlus

... 3 years 4 years 5 years Milestone Tracker App Milestones in Action: Photos & Videos 2 months 4 ... milestone checklists (PDF) Download the Milestone Tracker mobile app View the Milestones in Action photo and video ...

75 FR 5996 - Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-05

... and OMB Number: Synchronized Predeployment and Operational Tracker (SPOT) System; OMB Control Number... Operational Tracker (SPOT) System before deployment outside the United States. Data collection on contractors...

Intelligent robotic tracker

NASA Technical Reports Server (NTRS)

Otaguro, W. S.; Kesler, L. O.; Land, K. C.; Rhoades, D. E.

1987-01-01

An intelligent tracker capable of robotic applications requiring guidance and control of platforms, robotic arms, and end effectors has been developed. This packaged system capable of supervised autonomous robotic functions is partitioned into a multiple processor/parallel processing configuration. The system currently interfaces to cameras but has the capability to also use three-dimensional inputs from scanning laser rangers. The inputs are fed into an image processing and tracking section where the camera inputs are conditioned for the multiple tracker algorithms. An executive section monitors the image processing and tracker outputs and performs all the control and decision processes. The present architecture of the system is presented with discussion of its evolutionary growth for space applications. An autonomous rendezvous demonstration of this system was performed last year. More realistic demonstrations in planning are discussed.

Context Aware Programmable Trackers for the Next Generation Internet

NASA Astrophysics Data System (ADS)

Sousa, Pedro

This work introduces and proposes the concept of context aware programmable trackers for the next generation Internet. The proposed solution gives ground for the development of advanced applications based on the P2P paradigm and will foster collaborative efforts among several network entities (e.g. P2P applications and ISPs). The proposed concept of context aware programmable trackers allows that several peer selection strategies might be supported by a P2P tracker entity able to improve the peer selection decisions according with pre-defined objectives and external inputs provided by specific services. The flexible, adaptive and enhanced peer selection semantics that might be achieved by the proposed solution will contribute for devising novel P2P based services and business models for the future Internet.

Optical orientation in ferromagnet/semiconductor hybrids

NASA Astrophysics Data System (ADS)

Korenev, V. L.

2008-11-01

The physics of optical pumping of semiconductor electrons in ferromagnet/semiconductor hybrids is discussed. Optically oriented semiconductor electrons detect the magnetic state of a ferromagnetic film. In turn, the ferromagnetism of the hybrid can be controlled optically with the help of a semiconductor. Spin-spin interactions near the ferromagnet/semiconductor interface play a crucial role in the optical readout and the manipulation of ferromagnetism.

Fabrication of Metallic Hollow Nanoparticles

NASA Technical Reports Server (NTRS)

Lillehei, Peter T. (Inventor); Chu, Sang-Hyon (Inventor); Park, Yeonjoon (Inventor); Kim, Jae-Woo (Inventor); Choi, Sr., Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

2016-01-01

Metal and semiconductor nanoshells, particularly transition metal nanoshells, are fabricated using dendrimer molecules. Metallic colloids, metallic ions or semiconductors are attached to amine groups on the dendrimer surface in stabilized solution for the surface seeding method and the surface seedless method, respectively. Subsequently, the process is repeated with additional metallic ions or semiconductor, a stabilizer, and NaBH.sub.4 to increase the wall thickness of the metallic or semiconductor lining on the dendrimer surface. Metallic or semiconductor ions are automatically reduced on the metallic or semiconductor nanoparticles causing the formation of hollow metallic or semiconductor nanoparticles. The void size of the formed hollow nanoparticles depends on the dendrimer generation. The thickness of the metallic or semiconductor thin film around the dendrimer depends on the repetition times and the size of initial metallic or semiconductor seeds.

78 FR 38695 - Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-27

..., Associated Form and OMB Number: Synchronized Predeployment and Operational Tracker (SPOT) System; OMB Control... Operational Tracker (SPOT) System before deployment outside of the United States. Data collection on...

Optical contacting for gravity probe star tracker

NASA Technical Reports Server (NTRS)

Wright, J. J.; Zissa, D. E.

1984-01-01

A star-tracker telescope, constructed entirely of fused silica elements optically contacted together, has been proposed to provide submilliarc-second pointing accuracy for Gravity Probe. A bibliography and discussion on optical contacting (the bonding of very flat, highly polished surfaces without the use of adhesives) are presented. Then results from preliminary experiments on the strength of optical contacts including a tensile strength test in liquid helium are discussed. Suggestions are made for further study to verify an optical contacting method for the Gravity Probe star-tracker telescope.

Which Eye Tracker is Right for Your Research Performance Evaluation of Several Cost Variant Eye Trackers

DTIC Science & Technology

2016-09-19

REPORT TYPE 3. DATES COVERED (From - To) 21-10-16 Conference Proceedings 10/2015 – 03/2016 4. TITLE AND SUBTITLE Which eye tracker is right for...Force Research Laboratory 711th Human Performance Wing Airman Systems Directorate Warfighter Interface Division Applied Neuroscience Branch Wright...88ABW-2016-1334; Human Factors and Ergonomics Society 2016 Annual Meeting 19 – 23 Sept 2016 14. Though not often mentioned, the price point of many

Radiation-Hard Breadboard Star Tracker. Attachment 1.

DTIC Science & Technology

1985-09-01

fdL RETURN DONE !! * . *• , . -+., -• -: . . E+ . . .. j , ’ - - V.r.*r - , It - ’Cjf0 Q -****r.. ... " * *. " . -. tu ’ * Checkadapt 3- 2"Jj...TRACK POSITION, it will use the 3 70! CURRENT STAR #, X POSITION, Y POSITION for 5180 ! information sent to the tracker interface. 7_390 5t0 0 Track _it...CRITERIA which is currently defines as the number of times 57 20 ! the tracker will try and track the star before it is dropped, 5730 it will also

Star tracker error analysis: Roll-to-pitch nonorthogonality

NASA Technical Reports Server (NTRS)

Corson, R. W.

1979-01-01

An error analysis is described on an anomaly isolated in the star tracker software line of sight (LOS) rate test. The LOS rate cosine was found to be greater than one in certain cases which implied that either one or both of the star tracker measured end point unit vectors used to compute the LOS rate cosine had lengths greater than unity. The roll/pitch nonorthogonality matrix in the TNB CL module of the IMU software is examined as the source of error.

Spectroscopic characterization of III-V semiconductor nanomaterials

NASA Astrophysics Data System (ADS)

Crankshaw, Shanna Marie

III-V semiconductor materials form a broad basis for optoelectronic applications, including the broad basis of the telecom industry as well as smaller markets for high-mobility transistors. In a somewhat analogous manner as the traditional silicon logic industry has so heavily depended upon process manufacturing development, optoelectronics often relies instead on materials innovations. This thesis focuses particularly on III-V semiconductor nanomaterials, detailed characterization of which is invaluable for translating the exhibited behavior into useful applications. Specifically, the original research described in these thesis chapters is an investigation of semiconductors at a fundamental materials level, because the nanostructures in which they appear crystallize in quite atypical forms for the given semiconductors. Rather than restricting the experimental approaches to any one particular technique, many different types of optical spectroscopies are developed and applied where relevant to elucidate the connection between the crystalline structure and exhibited properties. In the first chapters, for example, a wurtzite crystalline form of the prototypical zincblende III-V binary semiconductor, GaAs, is explored through polarization-dependent Raman spectroscopy and temperature-dependent photoluminescence, as well as second-harmonic generation (SHG). The altered symmetry properties of the wurtzite crystalline structure are particularly evident in the Raman and SHG polarization dependences, all within a bulk material realm. A rather different but deeply elegant aspect of crystalline symmetry in GaAs is explored in a separate study on zincblende GaAs samples quantum-confined in one direction, i.e. quantum well structures, whose quantization direction corresponds to the (110) direction. The (110) orientation modifies the low-temperature electron spin relaxation mechanisms available compared to the usual (001) samples, leading to altered spin coherence times explored through a novel spectroscopic technique first formulated for the rather different purpose of dispersion engineering for slow-light schemes. The frequency-resolved technique combined with the unusual (110) quantum wells in a furthermore atypical waveguide experimental geometry has revealed fascinating behavior of electron spin splitting which points to the possibility of optically orienting electron spins with linearly polarized light---an experimental result supporting a theoretical description of the phenomenon itself only a few years old. Lastly, to explore a space of further-restricted dimensionality, the final chapters describe InP semiconductor nanowires with dimensions small enough to be considered truly one-dimensional. Like the bulk GaAs of the first few chapters, the InP nanowires here crystallize in a wurtzite structure. In the InP nanowire case, though, the experimental techniques explored for characterization are temperature-dependent time-integrated photoluminescence at the single-wire level (including samples with InAsP insertions) and time-resolved photoluminescence at the ensemble level. The carrier dynamics revealed through these time-resolved studies are the first of their kind for wurtzite InP nanowires. The chapters are thus ordered as a progression from three (bulk), to two (quantum well), to one (nanowire), to zero dimensions (axially-structured nanowire), with the uniting theme the emphasis on connecting the semiconductor nanomaterials' crystallinity to its exhibited properties by relevant experimental spectroscopic techniques, whether these are standard methods or effectively invented for the case at hand.

Method of physical vapor deposition of metal oxides on semiconductors

DOEpatents

Norton, David P.

2001-01-01

A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.

Semiconductor Lasers and Their Application in Optical Fiber Communication.

ERIC Educational Resources Information Center

Agrawal, Govind P.

1985-01-01

Working principles and operating characteristics of the extremely compact and highly efficient semiconductor lasers are explained. Topics include: the p-n junction; Fabry-Perot cavity; heterostructure semiconductor lasers; materials; emission characteristics; and single-frequency semiconductor lasers. Applications for semiconductor lasers include…

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

Dahal, Rajendra P.; Bhat, Ishwara B.; Chow, Tat-Sing

Methods for facilitating fabricating semiconductor structures are provided which include: providing a multilayer structure including a semiconductor layer, the semiconductor layer including a dopant and having an increased conductivity; selectively increasing, using electrochemical processing, porosity of the semiconductor layer, at least in part, the selectively increasing porosity utilizing the increased conductivity of the semiconductor layer; and removing, at least in part, the semiconductor layer with the selectively increased porosity from the multilayer structure. By way of example, the selectively increasing porosity may include selectively, anodically oxidizing, at least in part, the semiconductor layer of the multilayer structure.

Method for removing semiconductor layers from salt substrates

DOEpatents

Shuskus, Alexander J.; Cowher, Melvyn E.

1985-08-27

A method is described for removing a CVD semiconductor layer from an alkali halide salt substrate following the deposition of the semiconductor layer. The semiconductor-substrate combination is supported on a material such as tungsten which is readily wet by the molten alkali halide. The temperature of the semiconductor-substrate combination is raised to a temperature greater than the melting temperature of the substrate but less than the temperature of the semiconductor and the substrate is melted and removed from the semiconductor by capillary action of the wettable support.

Photovoltaic cell with nano-patterned substrate

DOEpatents

Cruz-Campa, Jose Luis; Zhou, Xiaowang; Zubia, David

2016-10-18

A photovoltaic solar cell comprises a nano-patterned substrate layer. A plurality of nano-windows are etched into an intermediate substrate layer to form the nano-patterned substrate layer. The nano-patterned substrate layer is positioned between an n-type semiconductor layer composed of an n-type semiconductor material and a p-type semiconductor layer composed of a p-type semiconductor material. Semiconductor material accumulates in the plurality of nano-windows, causing a plurality of heterojunctions to form between the n-type semiconductor layer and the p-type semiconductor layer.

Convolutional Deep Belief Networks for Single-Cell/Object Tracking in Computational Biology and Computer Vision.

PubMed

Zhong, Bineng; Pan, Shengnan; Zhang, Hongbo; Wang, Tian; Du, Jixiang; Chen, Duansheng; Cao, Liujuan

2016-01-01

In this paper, we propose deep architecture to dynamically learn the most discriminative features from data for both single-cell and object tracking in computational biology and computer vision. Firstly, the discriminative features are automatically learned via a convolutional deep belief network (CDBN). Secondly, we design a simple yet effective method to transfer features learned from CDBNs on the source tasks for generic purpose to the object tracking tasks using only limited amount of training data. Finally, to alleviate the tracker drifting problem caused by model updating, we jointly consider three different types of positive samples. Extensive experiments validate the robustness and effectiveness of the proposed method.

Convolutional Deep Belief Networks for Single-Cell/Object Tracking in Computational Biology and Computer Vision

PubMed Central

Pan, Shengnan; Zhang, Hongbo; Wang, Tian; Du, Jixiang; Chen, Duansheng; Cao, Liujuan

2016-01-01

In this paper, we propose deep architecture to dynamically learn the most discriminative features from data for both single-cell and object tracking in computational biology and computer vision. Firstly, the discriminative features are automatically learned via a convolutional deep belief network (CDBN). Secondly, we design a simple yet effective method to transfer features learned from CDBNs on the source tasks for generic purpose to the object tracking tasks using only limited amount of training data. Finally, to alleviate the tracker drifting problem caused by model updating, we jointly consider three different types of positive samples. Extensive experiments validate the robustness and effectiveness of the proposed method. PMID:27847827

MIT's role in project Apollo. Volume 2: Optical, radar, and candidate subsystems

NASA Technical Reports Server (NTRS)

1972-01-01

The development of optical, radar, and candidate subsystems for Project Apollo is discussed. The design and development of the optical subsystems for both the Apollo command and lunar spacecraft are described. Design approaches, problems, and solutions are presented. The evolution of radar interfaces with the GN&C system is discussed; these interfaces involved both hardware and software in a relatively complex interrelationship. The design and development of three candidate subsystems are also described. The systems were considered for use in Apollo, but were not incorporated into the final GN&C system. The three subsystems discussed are the star tracker-horizon photometer, the map and data viewer and the lunar module optical rendezvous system.

A viscosity sensitive fluorescent dye for real-time monitoring of mitochondria transport in neurons.

PubMed

Baek, Yeonju; Park, Sang Jun; Zhou, Xin; Kim, Gyungmi; Kim, Hwan Myung; Yoon, Juyoung

2016-12-15

We present here a viscosity sensitive fluorescent dye, namely thiophene dihemicyanine (TDHC), that enables the specific staining of mitochondria. In comparison to the common mitochondria tracker (Mitotracker Deep Red, MTDR), this dye demonstrated its unique ability for robust staining of mitochondria with high photostability and ultrahigh signal-to-noise ratio (SNR). Moreover, TDHC also showed high sensitivity towards mitochondria membrane potential (ΔΨm) and intramitochondria viscosity change. Consequently, this dye was utilized in real-time monitoring of mitochondria transport in primary cortical neurons. Finally, the Two-Photon Microscopy (TPM) imaging ability of TDHC was also demonstrated. Copyright © 2016 Elsevier B.V. All rights reserved.

Separating semiconductor devices from substrate by etching graded composition release layer disposed between semiconductor devices and substrate including forming protuberances that reduce stiction

DOEpatents

Tauke-Pedretti, Anna; Nielson, Gregory N; Cederberg, Jeffrey G; Cruz-Campa, Jose Luis

2015-05-12

A method includes etching a release layer that is coupled between a plurality of semiconductor devices and a substrate with an etch. The etching includes etching the release layer between the semiconductor devices and the substrate until the semiconductor devices are at least substantially released from the substrate. The etching also includes etching a protuberance in the release layer between each of the semiconductor devices and the substrate. The etch is stopped while the protuberances remain between each of the semiconductor devices and the substrate. The method also includes separating the semiconductor devices from the substrate. Other methods and apparatus are also disclosed.

Reducing leakage current in semiconductor devices

DOEpatents

Lu, Bin; Matioli, Elison de Nazareth; Palacios, Tomas Apostol

2018-03-06

A semiconductor device includes a first region having a first semiconductor material and a second region having a second semiconductor material. The second region is formed over the first region. The semiconductor device also includes a current blocking structure formed in the first region between first and second terminals of the semiconductor device. The current blocking structure is configured to reduce current flow in the first region between the first and second terminals.

Autonomous star sensor ASTRO APS: flight experience on Alphasat

NASA Astrophysics Data System (ADS)

Schmidt, U.; Fiksel, T.; Kwiatkowski, A.; Steinbach, I.; Pradarutti, B.; Michel, K.; Benzi, E.

2015-06-01

Jena-Optronik GmbH, located in Jena/Germany, has profound experience in designing and manufacturing star trackers since the early 80s. Today the company has a worldwide leading position in supplying geo-stationary and Earth observation satellites with robust and reliable star tracker systems. In the first decade of the new century Jena-Optronik received a development contract (17317/2003/F/WE) from the European Space Agency to establish the technologically challenging elements for which advanced star tracker technologies as CMOS Active Pixel Sensors were being introduced or were considered strategic. This activity was performed in the frame of the Alphabus large platform pre-development lead by ESA and the industrial Joint Project Team consisting of Astrium (now Airbus Defence and Space), Thales Alenia Space and CNES (Centre national d'études spatiales). The new autonomous star tracker, ASTRO APS (Active Pixel Sensor), extends the Jena-Optronik A stro-series CCD-based star tracker products taken the full benefit of the CMOS APS technology. ASTRO APS is a fully autonomous compact star tracker carrying either the space-qualified radiation hard STAR1000 or the HAS2 APS detectors. The star tracker is one of four Technology Demonstration Payloads (TDP6) carried by Alphasat as hosted payload in the frame of a successful Private Public Partnership between ESA and Inmarsat who owns and operates the satellite as part of its geo-stationary communication satellites fleet. TDP6 supports also directly TDP1, a Laser Communication Terminal, for fine pointing tasks. Alphasat was flawlessly brought in orbit at the end of July 2013 by a European Ariane 5 launcher. Only a few hours after launch the star tracker received its switch ON command and acquired nominally within 6 s the inertial 3-axes attitude. In the following days of the early in-orbit operations of Alphasat the TDP6 unit tracked reliably all the spacecraft maneuvers including the 0.1 and 0.2°/s spin stabilization for Sun pointing, all of the apogee engine thrusts, Moon field of view transits and recovered to stable tracking after several Earth and Sun blindings before the spacecraft entered a preliminary Earth pointing in a nominal geo-stationary attitude. The Jena-Optronik TDP6 operation center received daily the star tracker status and attitude data. The huge amount of acquired raw data has been evaluated to characterize the ASTRO APS (STAR1000) star tracker in-orbit performance. The paper will present in detail these data processing activities and will show the extraordinary good results. Due to the diverse transfer orbit satellite operations the key performance star tracker data like attitude random noise, single star noise, star brightness measurement, baffle Sun exclusion angle, temperature control, etc., could be derived and have been compared to the ground based laboratory and field measurements. The ultimate performance parameters achieved and verified as well as the lessons learned from the comparison to the ground test data are summarized in the conclusion of the paper.

Internal structure of acceptor-bound excitons in wide-band-gap wurtzite semiconductors

NASA Astrophysics Data System (ADS)

Gil, Bernard; Bigenwald, Pierre; Paskov, Plamen P.; Monemar, Bo

2010-02-01

We describe the internal structure of acceptor-bound excitons in wurtzite semiconductors. Our approach consists in first constructing, in the context of angular momentum algebra, the wave functions of the two-hole system that fulfill Pauli’s exclusion’s principle. Second, we construct the acceptor-bound exciton states by adding the electron states in a similar manner that two-hole states are constructed. We discuss the optical selection rules for the acceptor-bound exciton recombination. Finally, we compare our theory with experimental data for CdS and GaN. In the specific case of CdS for which much experimental information is available, we demonstrate that, compared with cubic semiconductors, the sign of the short-range hole-exchange interaction is reversed and more than one order of magnitude larger. The whole set of data is interpreted in the context of a large value of the short-range hole-exchange interaction Ξ0=3.4±0.2meV . This value dictates the splitting between the ground-state line I1 and the other transitions. The values we find for the electron-hole spin-exchange interaction and of the crystal-field splitting of the two-hole state are, respectively, -0.4±0.1 and 0.2±0.1meV . In the case of GaN, the experimental data for the acceptor-bound excitons in the case of Mg and Zn acceptors, show more than one bound-exciton line. We discuss a possible assignment of these states.

Features of the piezo-phototronic effect on optoelectronic devices based on wurtzite semiconductor nanowires.

PubMed

Yang, Qing; Wu, Yuanpeng; Liu, Ying; Pan, Caofeng; Wang, Zhong Lin

2014-02-21

The piezo-phototronic effect, a three way coupling effect of piezoelectric, semiconductor and photonic properties in non-central symmetric semiconductor materials, utilizing the piezo-potential as a "gate" voltage to tune the charge transport/generation/recombination and modulate the performance of optoelectronic devices, has formed a new field and attracted lots of interest recently. The mechanism was verified in various optoelectronic devices such as light emitting diodes (LEDs), photodetectors and solar cells etc. The fast development and dramatic increasing interest in the piezo-phototronic field not only demonstrate the way the piezo-phototronic effects work, but also indicate the strong need for further research in the physical mechanism and potential applications. Furthermore, it is important to distinguish the contribution of the piezo-phototronic effect from other factors induced by external strain such as piezoresistance, band shifting or contact area change, which also affect the carrier behaviour and device performance. In this perspective, we review our recent progress on piezo-phototronics and especially focus on pointing out the features of piezo-phototronic effect in four aspects: I-V characteristics; c-axis orientation; influence of illumination; and modulation of carrier behaviour. Finally we proposed several criteria for describing the contribution made by the piezo-phototronic effect to the performance of optoelectronic devices. This systematic analysis and comparison will not only help give an in-depth understanding of the piezo-phototronic effect, but also work as guide for the design of devices in related areas.

Star Identification Without Attitude Knowledge: Testing with X-Ray Timing Experiment Data

NASA Technical Reports Server (NTRS)

Ketchum, Eleanor

1997-01-01

As the budget for the scientific exploration of space shrinks, the need for more autonomous spacecraft increases. For a spacecraft with a star tracker, the ability to determinate attitude from a lost in space state autonomously requires the capability to identify the stars in the field of view of the tracker. Although there have been efforts to produce autonomous star trackers which perform this function internally, many programs cannot afford these sensors. The author previously presented a method for identifying stars without a priori attitude knowledge specifically targeted for onboard computers as it minimizes the necessary computer storage. The method has previously been tested with simulated data. This paper provides results of star identification without a priori attitude knowledge using flight data from two 8 by 8 degree charge coupled device star trackers onboard the X-Ray Timing Experiment.

A Brightness-Referenced Star Identification Algorithm for APS Star Trackers

PubMed Central

Zhang, Peng; Zhao, Qile; Liu, Jingnan; Liu, Ning

2014-01-01

Star trackers are currently the most accurate spacecraft attitude sensors. As a result, they are widely used in remote sensing satellites. Since traditional charge-coupled device (CCD)-based star trackers have a limited sensitivity range and dynamic range, the matching process for a star tracker is typically not very sensitive to star brightness. For active pixel sensor (APS) star trackers, the intensity of an imaged star is valuable information that can be used in star identification process. In this paper an improved brightness referenced star identification algorithm is presented. This algorithm utilizes the k-vector search theory and adds imaged stars' intensities to narrow the search scope and therefore increase the efficiency of the matching process. Based on different imaging conditions (slew, bright bodies, etc.) the developed matching algorithm operates in one of two identification modes: a three-star mode, and a four-star mode. If the reference bright stars (the stars brighter than three magnitude) show up, the algorithm runs the three-star mode and efficiency is further improved. The proposed method was compared with other two distinctive methods the pyramid and geometric voting methods. All three methods were tested with simulation data and actual in orbit data from the APS star tracker of ZY-3. Using a catalog composed of 1500 stars, the results show that without false stars the efficiency of this new method is 4∼5 times that of the pyramid method and 35∼37 times that of the geometric method. PMID:25299950

A brightness-referenced star identification algorithm for APS star trackers.

PubMed

Zhang, Peng; Zhao, Qile; Liu, Jingnan; Liu, Ning

2014-10-08

Star trackers are currently the most accurate spacecraft attitude sensors. As a result, they are widely used in remote sensing satellites. Since traditional charge-coupled device (CCD)-based star trackers have a limited sensitivity range and dynamic range, the matching process for a star tracker is typically not very sensitive to star brightness. For active pixel sensor (APS) star trackers, the intensity of an imaged star is valuable information that can be used in star identification process. In this paper an improved brightness referenced star identification algorithm is presented. This algorithm utilizes the k-vector search theory and adds imaged stars' intensities to narrow the search scope and therefore increase the efficiency of the matching process. Based on different imaging conditions (slew, bright bodies, etc.) the developed matching algorithm operates in one of two identification modes: a three-star mode, and a four-star mode. If the reference bright stars (the stars brighter than three magnitude) show up, the algorithm runs the three-star mode and efficiency is further improved. The proposed method was compared with other two distinctive methods the pyramid and geometric voting methods. All three methods were tested with simulation data and actual in orbit data from the APS star tracker of ZY-3. Using a catalog composed of 1500 stars, the results show that without false stars the efficiency of this new method is 4~5 times that of the pyramid method and 35~37 times that of the geometric method.

Spontaneous emission of semiconductor quantum dots in inverse opal SiO2 photonic crystals at different temperatures.

PubMed

Yang, Peng; Yang, Yingshu; Wang, Yinghui; Gao, Jiechao; Sui, Ning; Chi, Xiaochun; Zou, Lu; Zhang, Han-Zhuang

2016-02-01

The photoluminescence (PL) characteristics of CdSe quantum dots (QDs) infiltrated into inverse opal SiO2 photonic crystals (PCs) are systemically studied. The special porous structure of inverse opal PCs enhanced the thermal exchange rate between the CdSe QDs and their surrounding environment. Finally, inverse opal SiO2 PCs suppressed the nonlinear PL enhancement of CdSe QDs in PCs excited by a continuum laser and effectively modulated the PL characteristics of CdSe QDs in PCs at high temperatures in comparison with that of CdSe QDs out of PCs. The final results are of benefit in further understanding the role of inverse opal PCs on the PL characteristics of QDs. Copyright © 2015 John Wiley & Sons, Ltd.

Focused ion beam system

DOEpatents

Leung, Ka-Ngo; Gough, Richard A.; Ji, Qing; Lee, Yung-Hee Yvette

1999-01-01

A focused ion beam (FIB) system produces a final beam spot size down to 0.1 .mu.m or less and an ion beam output current on the order of microamps. The FIB system increases ion source brightness by properly configuring the first (plasma) and second (extraction) electrodes. The first electrode is configured to have a high aperture diameter to electrode thickness aspect ratio. Additional accelerator and focusing electrodes are used to produce the final beam. As few as five electrodes can be used, providing a very compact FIB system with a length down to only 20 mm. Multibeamlet arrangements with a single ion source can be produced to increase throughput. The FIB system can be used for nanolithography and doping applications for fabrication of semiconductor devices with minimum feature sizes of 0.1 .mu.m or less.

Focused ion beam system

DOEpatents

Leung, K.; Gough, R.A.; Ji, Q.; Lee, Y.Y.

1999-08-31

A focused ion beam (FIB) system produces a final beam spot size down to 0.1 {mu}m or less and an ion beam output current on the order of microamps. The FIB system increases ion source brightness by properly configuring the first (plasma) and second (extraction) electrodes. The first electrode is configured to have a high aperture diameter to electrode thickness aspect ratio. Additional accelerator and focusing electrodes are used to produce the final beam. As few as five electrodes can be used, providing a very compact FIB system with a length down to only 20 mm. Multibeamlet arrangements with a single ion source can be produced to increase throughput. The FIB system can be used for nanolithography and doping applications for fabrication of semiconductor devices with minimum feature sizes of 0.1 m or less. 13 figs.

Unitary lens semiconductor device

DOEpatents

Lear, Kevin L.

1997-01-01

A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.

Method of doping a semiconductor

DOEpatents

Yang, Chiang Y.; Rapp, Robert A.

1983-01-01

A method for doping semiconductor material. An interface is established between a solid electrolyte and a semiconductor to be doped. The electrolyte is chosen to be an ionic conductor of the selected impurity and the semiconductor material and electrolyte are jointly chosen so that any compound formed from the impurity and the semiconductor will have a free energy no lower than the electrolyte. A potential is then established across the interface so as to allow the impurity ions to diffuse into the semiconductor. In one embodiment the semiconductor and electrolyte may be heated so as to increase the diffusion coefficient.

Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers

DOEpatents

Norman, Andrew

2016-08-23

A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.

Stable surface passivation process for compound semiconductors

DOEpatents

Ashby, Carol I. H.

2001-01-01

A passivation process for a previously sulfided, selenided or tellurated III-V compound semiconductor surface. The concentration of undesired mid-gap surface states on a compound semiconductor surface is reduced by the formation of a near-monolayer of metal-(sulfur and/or selenium and/or tellurium)-semiconductor that is effective for long term passivation of the underlying semiconductor surface. Starting with the III-V compound semiconductor surface, any oxidation present thereon is substantially removed and the surface is then treated with sulfur, selenium or tellurium to form a near-monolayer of chalcogen-semiconductor of the surface in an oxygen-free atmosphere. This chalcogenated surface is then contacted with a solution of a metal that will form a low solubility chalcogenide to form a near-monolayer of metal-chalcogen-semiconductor. The resulting passivating layer provides long term protection for the underlying surface at or above the level achieved by a freshly chalcogenated compound semiconductor surface in an oxygen free atmosphere.

Acceptance of Commercially Available Wearable Activity Trackers Among Adults Aged Over 50 and With Chronic Illness: A Mixed-Methods Evaluation.

PubMed

Mercer, Kathryn; Giangregorio, Lora; Schneider, Eric; Chilana, Parmit; Li, Melissa; Grindrod, Kelly

2016-01-27

Physical inactivity and sedentary behavior increase the risk of chronic illness and death. The newest generation of "wearable" activity trackers offers potential as a multifaceted intervention to help people become more active. To examine the usability and usefulness of wearable activity trackers for older adults living with chronic illness. We recruited a purposive sample of 32 participants over the age of 50, who had been previously diagnosed with a chronic illness, including vascular disease, diabetes, arthritis, and osteoporosis. Participants were between 52 and 84 years of age (mean 64); among the study participants, 23 (72%) were women and the mean body mass index was 31 kg/m(2). Participants tested 5 trackers, including a simple pedometer (Sportline or Mio) followed by 4 wearable activity trackers (Fitbit Zip, Misfit Shine, Jawbone Up 24, and Withings Pulse) in random order. Selected devices represented the range of wearable products and features available on the Canadian market in 2014. Participants wore each device for at least 3 days and evaluated it using a questionnaire developed from the Technology Acceptance Model. We used focus groups to explore participant experiences and a thematic analysis approach to data collection and analysis. Our study resulted in 4 themes: (1) adoption within a comfort zone; (2) self-awareness and goal setting; (3) purposes of data tracking; and (4) future of wearable activity trackers as health care devices. Prior to enrolling, few participants were aware of wearable activity trackers. Most also had been asked by a physician to exercise more and cited this as a motivation for testing the devices. None of the participants planned to purchase the simple pedometer after the study, citing poor accuracy and data loss, whereas 73% (N=32) planned to purchase a wearable activity tracker. Preferences varied but 50% felt they would buy a Fitbit and 42% felt they would buy a Misfit, Jawbone, or Withings. The simple pedometer had a mean acceptance score of 56/95 compared with 63 for the Withings, 65 for the Misfit and Jawbone, and 68 for the Fitbit. To improve usability, older users may benefit from devices that have better compatibility with personal computers or less-expensive Android mobile phones and tablets, and have comprehensive paper-based user manuals and apps that interpret user data. For older adults living with chronic illness, wearable activity trackers are perceived as useful and acceptable. New users may need support to both set up the device and learn how to interpret their data.

Acceptance of Commercially Available Wearable Activity Trackers Among Adults Aged Over 50 and With Chronic Illness: A Mixed-Methods Evaluation

PubMed Central

Mercer, Kathryn; Giangregorio, Lora; Schneider, Eric; Chilana, Parmit; Li, Melissa

2016-01-01

Background Physical inactivity and sedentary behavior increase the risk of chronic illness and death. The newest generation of “wearable” activity trackers offers potential as a multifaceted intervention to help people become more active. Objective To examine the usability and usefulness of wearable activity trackers for older adults living with chronic illness. Methods We recruited a purposive sample of 32 participants over the age of 50, who had been previously diagnosed with a chronic illness, including vascular disease, diabetes, arthritis, and osteoporosis. Participants were between 52 and 84 years of age (mean 64); among the study participants, 23 (72%) were women and the mean body mass index was 31 kg/m2. Participants tested 5 trackers, including a simple pedometer (Sportline or Mio) followed by 4 wearable activity trackers (Fitbit Zip, Misfit Shine, Jawbone Up 24, and Withings Pulse) in random order. Selected devices represented the range of wearable products and features available on the Canadian market in 2014. Participants wore each device for at least 3 days and evaluated it using a questionnaire developed from the Technology Acceptance Model. We used focus groups to explore participant experiences and a thematic analysis approach to data collection and analysis. Results Our study resulted in 4 themes: (1) adoption within a comfort zone; (2) self-awareness and goal setting; (3) purposes of data tracking; and (4) future of wearable activity trackers as health care devices. Prior to enrolling, few participants were aware of wearable activity trackers. Most also had been asked by a physician to exercise more and cited this as a motivation for testing the devices. None of the participants planned to purchase the simple pedometer after the study, citing poor accuracy and data loss, whereas 73% (N=32) planned to purchase a wearable activity tracker. Preferences varied but 50% felt they would buy a Fitbit and 42% felt they would buy a Misfit, Jawbone, or Withings. The simple pedometer had a mean acceptance score of 56/95 compared with 63 for the Withings, 65 for the Misfit and Jawbone, and 68 for the Fitbit. To improve usability, older users may benefit from devices that have better compatibility with personal computers or less-expensive Android mobile phones and tablets, and have comprehensive paper-based user manuals and apps that interpret user data. Conclusions For older adults living with chronic illness, wearable activity trackers are perceived as useful and acceptable. New users may need support to both set up the device and learn how to interpret their data. PMID:26818775

A retrospective analysis of real-world use of the eaTracker® My Goals website by adults from Ontario and Alberta, Canada.

PubMed

Lieffers, Jessica R L; Haresign, Helen; Mehling, Christine; Hanning, Rhona M

2016-09-15

Little is known about use of goal setting and tracking tools within online programs to support nutrition and physical activity behaviour change. In 2011, Dietitians of Canada added "My Goals," a nutrition and physical activity behaviour goal setting and tracking tool to their free publicly available self-monitoring website (eaTracker® ( http://www.eaTracker.ca/ )). My Goals allows users to: a) set "ready-made" SMART (Specific, Measurable, Attainable, Realistic, Time-related) goals (choice of n = 87 goals from n = 13 categories) or "write your own" goals, and b) track progress using the "My Goals Tracker." The purpose of this study was to characterize: a) My Goals user demographics, b) types of goals set, and c) My Goals Tracker use. Anonymous data on all goals set using the My Goals feature from December 6/2012-April 28/2014 by users ≥19y from Ontario and Alberta, Canada were obtained. This dataset contained: anonymous self-reported user demographic data, user set goals, and My Goals Tracker use data. Write your own goals were categorized by topic and specificity. Data were summarized using descriptive statistics. Multivariate binary logistic regression was used to determine associations between user demographics and a) goal topic areas and b) My Goals Tracker use. Overall, n = 16,511 goal statements (75.4 % ready-made; 24.6 % write your own) set by n = 8,067 adult users 19-85y (83.3 % female; mean age 41.1 ± 15.0y, mean BMI 28.8 ± 7.6kg/m(2)) were included for analysis. Overall, 33.1 % of ready-made goals were from the "Managing your Weight" category. Of write your own goal entries, 42.3 % were solely distal goals (most related to weight management); 38.6 % addressed nutrition behaviour change (16.6 % had unspecific general eating goals); 18.1 % addressed physical activity behaviour change (47.3 % had goals without information on exercise amount and type). Many write your own goals were poor quality (e.g., non-specific (e.g., missing amounts)), and possibly unrealistic (e.g., no sugar). Few goals were tracked (<10 %). Demographic variables had statistically significant relations with goal topic areas and My Goals Tracker use. eaTracker® users had high interest in goal setting and the My Goals feature, however, self-written goals were often poor quality and goal tracking was rare. Further research is needed to better support users.

Connecting Interface Structure to Energy Level Alignment at Aqueous Semiconductor Interfaces

NASA Astrophysics Data System (ADS)

Hybertsen, Mark

Understanding structure-function relationships at aqueous semiconductor interfaces presents fundamental challenges, including the discovery of the key interface structure motifs themselves. Important examples include the alignment of electrochemical redox levels with the semiconductor band edges and the identification of catalytic active sites. We have developed a multistep approach, initially demonstrated for GaN, ZnO and their alloys, motivated by measured high efficiency for photocatalytic water oxidation. The interface structure is simulated using ab initio molecular dynamics (AIMD). The calculated, average interface dipole is combined with the GW approach from many-body perturbation theory to calculate the energy level alignment between the semiconductor band edges and the centroid of the occupied 1b1 energy level of water and thus, the electrochemical levels. Cluster models are used to study reaction pathways. The emergent interface motif is the full (GaN) or partial (ZnO) dissociated interface water layer. Here I will focus on the aqueous interfaces to the stable TiO2 anatase (101) and rutile (110) facets. The AIMD calculations reveal interface water dissociation and reassociation processes through distinct pathways: one direct at the interface and the other via a spectator water molecule from the hydration layer. Comparisons between the two interfaces shows that the energy landscape for these pathways depends on the local hydrogen bonding patterns and the interplay with the interface template. Combined results from different initial conditions and AIMD temperatures demonstrate a partially dissociated interface water layer in both cases. Specifically for rutile, structure and the GW-based analysis of the interface energy level alignment agree with experiment. Finally, hole localization at different interface structure motifs will be discussed. Work performed in collaboration with J. Lyons, N. Kharche, M. Ertem and J. Muckerman, done in part at the CFN, which is a U.S. DOE Office of Science Facility, at BNL under Contract No. DE-SC0012704 and with resources from NERSC under Contract No. DE-AC02-05CH11231.

Hole localization, water dissociation mechanisms, and band alignment at aqueous-titania interfaces

NASA Astrophysics Data System (ADS)

Lyons, John L.

Photocatalytic water splitting is a promising method for generating clean energy, but materials that can efficiently act as photocatalysts are scarce. This is in part due to the fact that exposure to water can strongly alter semiconductor surfaces and therefore photocatalyst performance. Many materials are not stable in aqueous environments; in other cases, local changes in structure may occur, affecting energy-level alignment. Even in the simplest case, dynamic fluctuations modify the organization of interface water. Accounting for such effects requires knowledge of the dominant local structural motifs and also accurate semiconductor band-edge positions, making quantitative prediction of energy-level alignments computationally challenging. Here we employ a combined theoretical approach to study the structure, energy alignment, and hole localization at aqueous-titania interfaces. We calculate the explicit aqueous-semiconductor interface using ab initio molecular dynamics, which provides the fluctuating atomic structure, the extent of water dissociation, and the resulting electrostatic potential. For both anatase and rutile TiO2 we observe spontaneous water dissociation and re-association events that occur via distinct mechanisms. We also find a higher-density water layer occurring on anatase. In both cases, we find that the second monolayer of water plays a crucial role in controlling the extent of water dissociation. Using hybrid functional calculations, we then investigate the propensity for dissociated waters to stabilize photo-excited carriers, and compare the results of rutile and anatase aqueous interfaces. Finally, we use the GW approach from many-body perturbation theory to obtain the position of semiconductor band edges relative to the occupied 1b1 level and thus the redox levels of water, and examine how local structural modifications affect these offsets. This work was performed in collaboration with N. Kharche, M. Z. Ertem, J. T. Muckerman, and M. S. Hybertsen. It made use of resources at the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Lab.

jTracker and Monte Carlo Comparison

NASA Astrophysics Data System (ADS)

Selensky, Lauren; SeaQuest/E906 Collaboration

2015-10-01

SeaQuest is designed to observe the characteristics and behavior of `sea-quarks' in a proton by reconstructing them from the subatomic particles produced in a collision. The 120 GeV beam from the main injector collides with a fixed target and then passes through a series of detectors which records information about the particles produced in the collision. However, this data becomes meaningful only after it has been processed, stored, analyzed, and interpreted. Several programs are involved in this process. jTracker (sqerp) reads wire or hodoscope hits and reconstructs the tracks of potential dimuon pairs from a run, and Geant4 Monte Carlo simulates dimuon production and background noise from the beam. During track reconstruction, an event must meet the criteria set by the tracker to be considered a viable dimuon pair; this ensures that relevant data is retained. As a check, a comparison between a new version of jTracker and Monte Carlo was made in order to see how accurately jTracker could reconstruct the events created by Monte Carlo. In this presentation, the results of the inquest and their potential effects on the programming will be shown. This work is supported by U.S. DOE MENP Grant DE-FG02-03ER41243.