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1

Stresa, Italy, 26-28 April 2006 A SILICON-BASED MICRO GAS TURBINE ENGINE FOR POWER GENERATION  

E-print Network

gas turbine engine consists of a micro combustor, a turbine and a centrifugal compressor and a piezoelectric converter, as illustrated in Fig. 1 [6]. The micro gas turbine engine is composed of a centrifugalStresa, Italy, 26-28 April 2006 A SILICON-BASED MICRO GAS TURBINE ENGINE FOR POWER GENERATION X. C

Paris-Sud XI, Université de

2

Experimental Investigation of Silicon-Based Micro-Pulsating Heat Pipe for Cooling Electronics  

Microsoft Academic Search

A simultaneous temperature measurement and flow visualization experiment was performed to investigate the thermal and flow behaviors of a silicon-based micro-pulsating heat pipe (micro-PHP) with trapezoidal microchannels with a hydraulic diameter of 352 ?m. FC-72 and R113 were used as working fluids. Variations in temperature versus time at different locations of the micro-PHP under different power inputs and typical flow

Jian Qu; Hui-Ying Wu; Qian Wang

2012-01-01

3

Study of energy transfer in silicon-based micro-ring resonators  

NASA Astrophysics Data System (ADS)

Physical model, time-domain model, transmission spectra and energy transfer diagram of silicon-based micro-ring resonators based on the parallel waveguide structure are analyzed in this paper, in which transmission spectrum is obtained by Matlab, and the energy transfer process is analyzed by Rsoft. According to the analyses of the models and results, the energy transfer process in this type of resonator is clear to a great extent. The experimental results show that when the input signal is stable, the energy of the micro-ring resonator and the drop port tends to be steady after the input optical signal is coupled in the coupling region, which proves that the silicon-based micro-ring resonators can select specific optical signal if the input optical signal satisfies the resonance condition. However, if the resonance condition is not met, filtering function, optical switch function and signal selection function can be realized. Therefore, the analysis and simulation of energy transfer in silicon-based micro-ring resonators can not only enrich the silicon micro-ring resonator theory, but also provide new theoretical basis and method for the design and optimization of existing optoelectronic devices.

Li, Xin-juan; Wu, Rong; Hu, Yu-feng; Hu, Li-xin; Guo, Jian-cheng

2014-09-01

4

Realization of optical pickup head by using stacked silicon-based micro-optical system  

NASA Astrophysics Data System (ADS)

We have developed a novel stacked silicon-based microoptical system, which is optical-on-axis and transmissible in both visible and infrared ranges. By using the new microoptical system techniques, we fabricated a miniaturized optical pickup head module. This optical pickup head consisted of a 650nm laser diode, a 45 degrees silicon reflector, a grating, a holographic optical element, and some aspherical Fresnel lenses. These optical phase elements fabricated on a SiNx membrane were free-standing on Si chips. Each element was then stacked by chip bonding. We could obtain a circular focusing spot on the optical disc as small as 3.1um.

Wang, Chih Ming; Lan, Hsiao-Chin; Chang, Jenq Yang; Lee, Chien Chieh

2004-10-01

5

Monolithic integration of elliptic-symmetry diffractive optical element on silicon-based 45 degrees micro-reflector.  

PubMed

A monolithically integrated micro-optical element consisting of a diffractive optical element (DOE) and a silicon-based 45 degrees micro-reflector is experimentally demonstrated to facilitate the optical alignment of non-coplanar fiber-to-fiber coupling. The slanted 45 degrees reflector with a depth of 216 microm is fabricated on a (100) silicon wafer by anisotropic wet etching. The DOE with a diameter of 174.2 microm and a focal length of 150 microm is formed by means of dry etching. Such a compact device is suitable for the optical micro-system to deflect the incident light by 90 degrees and to focus it on the image plane simultaneously. The measured light pattern with a spot size of 15 microm has a good agreement with the simulated result of the elliptic-symmetry DOE with an off-axis design for eliminating the strongly astigmatic aberration. The coupling efficiency is enhanced over 10-folds of the case without a DOE on the 45 degrees micro-reflector. This device would facilitate the optical alignment of non-coplanar light coupling and further miniaturize the volume of microsystem. PMID:19997331

Lan, Hsiao-Chin; Hsiao, Hsu-Liang; Chang, Chia-Chi; Hsu, Chih-Hung; Wang, Chih-Ming; Wu, Mount-Learn

2009-11-01

6

Porous silicon based orientation independent, self-priming micro direct ethanol fuel cell  

Microsoft Academic Search

The design, fabrication and testing of an orientation independent, self-priming micro direct ethanol fuel cell (DEFC) is presented. The electrodes of the fuel cell are fabricated using macro-porous silicon technology. The capillary force generated by the pores has the ability of “wicking” the fuel towards the electrode irrespective of the orientation of the cell, resulting in a uniform and regulated

Shyam Aravamudhan; Abdur Rub Abdur Rahman; Shekhar Bhansali

2005-01-01

7

Wettability modification of polysilicon for stiction reduction in silicon based micro-electromechanical structures  

NASA Astrophysics Data System (ADS)

Surface micromachining using deposited polysilicon films is a technology that is widely used for the fabrication of micro-electromechanical structures. One of the biggest yield and reliability problems in the fabrication of such structures is "stiction" or adhesion to the substrate. This may occur during the drying step that is required after wet processing and/or during use of a device. Deposition of self-assembled monolayer coatings is one of the most successful approaches to chemical modification of silicon surfaces to reduce stiction. This approach involves making the surfaces of pre-oxidized polysilicon highly hydrophobic. As a result, microstructures come out of the final water rinse extremely dry without being broken or adhered to the substrate. Available technology requires that these coatings are applied from organic media . However, increasing pressure on semiconductor companies to reduce the generation of organic wastes has sparked interest in the feasibility of applying these coatings from aqueous media. The objective of this research was to develop the chemistry and techniques for the application of hydrophobic coatings on polysilicon from aqueous media. The results obtained from three commercially available water dispersible silanes and cationic alkoxysilanes are discussed. Key experimental variables that were investigated are concentration of reactive silane, type of oxidation pretreatment of polysilicon, pH and temperature of the silane dispersion and curing temperature of the coating. The stability of the dispersions was characterized by viscosity measurements. The formation and quality of the films were studied using atomic force microscopy (AFM), ellipsometry, dynamic contact angle measurements and electrochemical impedance spectroscopy (EIS). The coatings showed contact angles greater than 100°. It was found using AFM that the structure of these films is a continuous film with some particulates attributed to bulk polymerization of the precursor molecule in water. EIS results indicated that the coatings had low porosity as well as high charge transfer resistance across the silicon/HF interface. Ellipsometric analysis showed that thickness of these coatings is roughly a (statistical) monolayer. The stability improvement of the dispersions by the addition of quaternary ammonium cationic surfactants is also discussed.

Almanza-Workman, Angeles Marcia

8

Modification of inkjet printer for polymer sensitive layer preparation on silicon-based gas sensors  

NASA Astrophysics Data System (ADS)

Inkjet printing is a versatile, low cost deposition technology with the capabilities for the localized deposition of high precision, patterned deposition in a programmable way, and the parallel deposition of a variety of materials. This paper demonstrates a new method of modifying the consumer inkjet printer to prepare polymer-sensitive layers on silicon wafer for gas sensor applications. A special printing tray for the modified inkjet printer to support a 4-inch silicon wafer is designed. The positioning accuracy of the deposition system is tested, based on the newly modified printer. The experimental data show that the positioning errors in the horizontal direction are negligibly small, while the positioning errors in the vertical direction rise with the increase of the printing distance of the wafer. The method for making suitable ink to be deposited to form the polymer-sensitive layer is also discussed. In the testing, a solution of 0.1 wt% polyvinyl alcohol (PVA) was used as ink to prepare a sensitive layer with certain dimensions at a specific location on the surface of the silicon wafer, and the results prove the feasibility of the methods presented in this article.

Li, Tianjian; Dong, Ying; Yuan, Dengpeng; Liu, Yujin

2015-04-01

9

MEMS micropump for a Micro Gas Analyzer  

E-print Network

This thesis presents a MEMS micro-vacuum pump designed for use in a portable gas analysis system. It is designed to be pneumatically-driven and as such does not have self-contained actuation (the focus of future work). ...

Sharma, Vikas, 1979-

2009-01-01

10

Analyses of gas flows in micro- and nanochannels  

Microsoft Academic Search

Micro- and nanoscale gas flows are analyzed theoretically and numerically. The analyses of gas flow similarity show that the gas flows at different scales can be similar only when the gas is treated as a prefect gas. If the gas density is so high that the density effect cannot be ignored, the three dimensionless parameters, Re, Ma, and Kn, which

Moran Wang; Xudong Lan; Zhixin Li

2008-01-01

11

Tilting pad gas bearing design for micro gas turbines  

NASA Astrophysics Data System (ADS)

This paper presents the results of a dynamic stability investigation of a micro gas turbine supported by two flexible tilting pad bearings. The pad flexibility allows centrifugal and thermal shaft growth of the rotor but can also introduce undesirable rotor instabilities. An eigenvalue analysis on the linearised rotor-bearing dynamics is performed to estimate the required pad stiffness and damping for stability. Results of the eigenvalue analysis are evaluated by fully nonlinear orbit simulations.

Nabuurs, M. J. H. W.; Al-Bender, F.; Reynaerts, D.

2013-12-01

12

Micro-combustor for gas turbine engine  

DOEpatents

An improved gas turbine combustor (20) including a basket (26) and a multiplicity of micro openings (29) arrayed across an inlet wall (27) for passage of a fuel/air mixture for ignition within the combustor. The openings preferably have a diameter on the order of the quenching diameter; i.e. the port diameter for which the flame is self-extinguishing, which is a function of the fuel mixture, temperature and pressure. The basket may have a curved rectangular shape that approximates the shape of the curved rectangular shape of the intake manifolds of the turbine.

Martin, Scott M. (Oviedo, FL)

2010-11-30

13

Silicon-based nanoenergetic composites  

SciTech Connect

Fundamental combustion properties of silicon-based nano-energetic composites was studied by performing equilibrium calculations, 'flame tests', and instrumented burn-tube tests. That the nominal maximum flame temperature and for many Si-oxidizer systems is about 3000 K, with exceptions. Some of these exceptions are Si-metal oxides with temperatures ranging from 2282 to 2978 K. Theoretical maximum gas production of the Si composites ranged from 350-6500 cm{sup 3}/g of reactant with NH{sub 4}ClO{sub 4} - Si producing the most gas at 6500 cm{sup 3}/g and Fe{sub 2}O{sub 3} producing the least. Of the composites tested NH{sub 4}ClO{sub 4} - Si showed the fastest burning rates with the fastest at 2.1 km/s. The Si metal oxide burning rates where on the order of 0.03-75 mls the slowest of which was nFe{sub 2}O{sub 3} - Si.

Asay, Blaine [Los Alamos National Laboratory; Son, Steven [PURDUE UNIV; Mason, Aaron [PURDUE UNIV; Yarrington, Cole [PURDUE UNIV; Cho, K Y [PURDUE UNIV; Gesner, J [PSU; Yetter, R A [PSU

2009-01-01

14

Simulation of gas flows through micro-constrictions  

E-print Network

A series of numerical simulations based on a spectral element formulation of compressible Navier-Stokes equations are performed for gas flows through micro-constrictions, and the thermal/fluidic transport through these devices is studied in detail...

Ahmed, Imtiaz

2001-01-01

15

Recent advancements in the gas-phase MicroChemLab  

NASA Astrophysics Data System (ADS)

Sandia's hand-held MicroChemLabTM system uses a micromachined preconcentrator (PC), a gas chromatography channel (GC) and a quartz surface acoustic wave array (SAW) detector for sensitive/selective detection of gas-phase chemical analytes. Requisite system size, performance, power budget and time response mandate microfabrication of the key analytical system components. In the fielded system hybrid integration has been employed, permitting optimization of the individual components. Recent improvements in the hybrid-integrated system, using plastic, metal or silicon/glass manifolds, is described, as is system performance against semivolatile compounds and toxic industrial chemicals. The design and performance of a new three-dimensional micropreconcentrator is also introduced. To further reduce system dead volume, eliminate unheated transfer lines and simplify assembly, there is an effort to monolithically integrate the silicon PC and GC with a suitable silicon-based detector, such as a magnetically-actuated flexural plate wave sensor (magFPW) or a magnetically-actuated pivot plate resonator (PPR).

Manginell, Ronald P.; Lewis, Patrick R.; Adkins, Douglas R.; Kottenstette, Richard J.; Wheeler, David; Sokolowski, Sara; Trudell, Dan; Byrnes, Joy; Okandan, Murat; Bauer, Joseph M.; Manley, Robert G.

2004-12-01

16

Silicon-based micro-Fourier spectrometer  

Microsoft Academic Search

A novel Fourier spectrometer based on a partly transparent thin-film detector in combination with a tunable silicon micromachined mirror was developed. The operation principle based on the detection of an intensity profile of a standing-wave by introducing a partly transparent detector in the standing-wave. Varying the position of the mirror results in a phase shift of the standing-wave and thus

Dietmar Knipp; Helmut Stiebig; Sameer R. Bhalotra; Eerke Bunte; Helen L. Kung; David A. B. Miller

2005-01-01

17

Measuring micro-organism gas production  

NASA Technical Reports Server (NTRS)

Transducer, which senses pressure buildup, is easy to assemble and use, and rate of gas produced can be measured automatically and accurately. Method can be used in research, in clinical laboratories, and for environmental pollution studies because of its ability to detect and quantify rapidly the number of gas-producing microorganisms in water, beverages, and clinical samples.

Wilkins, J. R.; Pearson, A. O.; Mills, S. M.

1973-01-01

18

Design of micro-sensor-array detector for toxic gas  

NASA Astrophysics Data System (ADS)

To quickly measure the trace concentration of the single component toxic gas (e.g. sarin), a micro-array toxic gas detector is designed. A 3 x 3 gas sensor array with metalloporphyrins as sensitive materials is introduced. A micro-capsule that can be easy to be loaded and unloaded is designed for the gas reaction. A fiber-array optical path is designed, which is based on the principle that gas sensors will show different colors after reaction with the toxic gas. The tricolor information about the concentration of gas is collected by the color liner CCD. A control handling system with C8051F021 MCU as the core is implemented and embedded into the detector to perform the functions of gas sampling, data collection and analysis calculation. Data acquisition experimental results show that the proposed scheme can effectively collect the color information after gas reaction. Moreover, the system has many important advantages, such as small size, compact structure, high degree of automation, fast detection speed and high performance-cost ratio, etc.

Liao, Hai-yang; Tian, Peng

2010-08-01

19

PREDICTION OF THE FLOW INSIDE A MICRO GAS TURBINE COMBUSTOR  

Microsoft Academic Search

The main purpose of this study is to predict the flow dynamics inside a micro gas turbine combustor model. The flow field inside the combustor is controlled by the liner shape and size, wall side holes shape, size and arrangement (primary, secondary and dilution holes), and primary air swirler configuration. Air swirler adds sufficient swirling to the inlet flow to

Yehia A. Eldrainy; Johann Jeffrie; Muhamad Ridzwan; Mohammad Nazri Mohd Jaafar

2008-01-01

20

Stirling engines for gas fired micro-cogen and cooling  

SciTech Connect

This paper describes the design and performance of free-piston Stirling engine-alternators particularly suited for use as natural gas fired micro-cogen and cooling devices. Stirling based cogen systems offer significant potential advantages over internal combustion engines in efficiency, to maintain higher efficiencies at lower power levels than than combustion engines significantly expands the potential for micro-cogen. System cost reduction and electric prices higher than the U.S. national average will have a far greater effect on commercial success than any further increase in Stirling engine efficiency. There exist niche markets where Stirling engine efficiency. There exist niche markets where Stirling based cogen systems are competitive. Machines of this design are being considered for production in the near future as gas-fired units for combined heat and power in sufficiently large quantities to assure competitive prices for the final unit.

Lane, N.W.; Beale, W.T. [Sunpower, Inc., Athens, OH (United States)

1996-12-31

21

PREFACE: 1st European Conference on Gas Micro Flows (GasMems 2012)  

NASA Astrophysics Data System (ADS)

The aim of the 1st European Conference on Gas Micro Flows is to advance research in Europe and worldwide in the field of gas micro flows as well as to improve global fundamental knowledge and to enable technological applications. Gas flows in microsystems are of great importance and touch almost every industrial field (e.g. fluidic microactuators for active control of aerodynamic flows, vacuum generators for extracting biological samples, mass flow and temperature micro-sensors, pressure gauges, micro heat-exchangers for the cooling of electronic components or for chemical applications, and micro gas analyzers or separators). The main characteristic of gas microflows is their rarefaction, which for device design often requires modelling and simulation both by continuous and molecular approaches. In such flows various non-equilibrium transport phenomena appear, while the role played by the interaction between the gas and the solid device surfaces becomes essential. The proposed models of boundary conditions often need an empirical adjustment strongly dependent on the micro manufacturing technique. The 1st European Conference on Gas Micro Flows is organized under the umbrella of the recently established GASMEMS network (www.gasmems.eu/) consisting of 13 participants and six associate members. The main objectives of the network are to structure research and train researchers in the fields of micro gas dynamics, measurement techniques for gaseous flows in micro experimental setups, microstructure design and micro manufacturing with applications in lab and industry. The conference takes place on June 6-8 2012, at the Skiathos Palace Hotel, on the beautiful island of Skiathos, Greece. The conference has received funding from the European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement ITN GASMEMS no. 215504. It owes its success to many people. We would like to acknowledge the support of all members of the Scientific Committee and of all referees for their thorough reviews and evaluation of the full papers. Above all, we would like to sincerely thank all authors for their valuable contributions to these proceedings as well as all the participants for creating a stimulating atmosphere through their presentations and discussions and making this conference a great success. Dr Arjan Frijns Editor and Event Coordinator Prof. Dimitris Valougeorgis Local Organizer Prof. Stéphane Colin Network Coordinator Dr Lucien Baldas Assistant Network Coordinator The PDF also contains details of the Conference Organizers.

Frijns, Arjan; Valougeorgis, Dimitris; Colin, Stéphane; Baldas, Lucien

2012-05-01

22

A gas bubble-based parallel micro manipulator: conceptual design and kinematics model  

NASA Astrophysics Data System (ADS)

The parallel mechanism has become an alternative solution when micro manipulators are demanded in the fields of micro manipulation and micro assembly. In this technical note, a three-degree-of-freedom (3-DOF) parallel micro manipulator is presented, which is directly driven by three micro gas bubbles. Since the micro gas bubbles are generated and maintained due to the surface tension between the gas and liquid media, the proposed novel system can be used in the liquid environment which allows for rotation about the X and Y axes and translation along the Z axis. In this technical note, the conceptual design of micro gas bubble-based parallel manipulator is introduced and the input/output characteristic of the actuator is analyzed in detail. The kinematics model of the parallel micro manipulator is also established, based on which the workspace and the system motion resolution are analyzed as a criterion and reference for future prototype development.

Dong, Wei; Gauthier, Michaël; Lenders, Cyrille; Lambert, Pierre

2012-05-01

23

Development of a catalytic combustion system for the MIT Micro Gas Turbine Engine  

E-print Network

As part of the MIT micro-gas turbine engine project, the development of a hydrocarbon-fueled catalytic micro-combustion system is presented. A conventionally-machined catalytic flow reactor was built to simulate the ...

Peck, Jhongwoo, 1976-

2003-01-01

24

A passive micro gas regulator for hydrogen flow control  

NASA Astrophysics Data System (ADS)

This paper presents the design, fabrication process, experimental characterizations and simulations of a novel passive micro gas regulator. The device is to be used in a miniature fuel cell for portable electronic applications in order to regulate the hydrogen flow feeding the fuel cell from a high-pressure tank. Its structure and working principle are similar to some macroscopic devices. Using MEMS technologies, e.g., deep-RIE etching and multiple wafer bonding, the dimensions of the device have been made less than 8 × 8 × 1 mm3. Moreover, as it is passive, it consumes no power from the fuel cell. Thanks to these two features, it is well suited for portable applications. To our knowledge, this is the first passive micro gas regulator, except those actuated by hydrogels. The experimental characterization shows that the opening and closing are controlled by the released gas pressure. Up to an input pressure of 8 atm, the device has been successfully driven and the leakage has been measured to be below 0.1 sccm nitrogen. Analytical models for the moving part and for the flow rate show a good agreement when compared to the experimental data.

Debray, A.; Nakakubo, T.; Ueda, K.; Mogi, S.; Shibata, M.; Fujita, H.

2005-09-01

25

Amorphous Silicon Based Neutron Detector  

SciTech Connect

Various large-scale neutron sources already build or to be constructed, are important for materials research and life science research. For all these neutron sources, neutron detectors are very important aspect. However, there is a lack of a high-performance and low-cost neutron beam monitor that provides time and temporal resolution. The objective of this SBIR Phase I research, collaboratively performed by Midwest Optoelectronics, LLC (MWOE), the University of Toledo (UT) and Oak Ridge National Laboratory (ORNL), is to demonstrate the feasibility for amorphous silicon based neutron beam monitors that are pixilated, reliable, durable, fully packaged, and fabricated with high yield using low-cost method. During the Phase I effort, work as been focused in the following areas: 1) Deposition of high quality, low-defect-density, low-stress a-Si films using very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) at high deposition rate and with low device shunting; 2) Fabrication of Si/SiO2/metal/p/i/n/metal/n/i/p/metal/SiO2/ device for the detection of alpha particles which are daughter particles of neutrons through appropriate nuclear reactions; and 3) Testing of various devices fabricated for alpha and neutron detection; As the main results: · High quality, low-defect-density, low-stress a-Si films have been successfully deposited using VHF PECVD on various low-cost substrates; · Various single-junction and double junction detector devices have been fabricated; · The detector devices fabricated have been systematically tested and analyzed. · Some of the fabricated devices are found to successfully detect alpha particles. Further research is required to bring this Phase I work beyond the feasibility demonstration toward the final prototype devices. The success of this project will lead to a high-performance, low-cost, X-Y pixilated neutron beam monitor that could be used in all of the neutron facilities worldwide. In addition, the technologies developed here could be used to develop X-ray and neutron monitors that could be used in the future for security checks at the airports and other critical facilities. The project would lead to devices that could significantly enhance the performance of multi-billion dollar neutron source facilities in the US and bring our nation to the forefront of neutron beam sciences and technologies which have enormous impact to materials, life science and military research and applications.

Xu, Liwei

2004-12-12

26

Hot gas stream application in micro-bonding technique  

NASA Astrophysics Data System (ADS)

This paper presents a new concept for bonding micro-parts with dimensions in the range of 50 ?m to 300 ?m. Two different kinds of adhesives - polyurethane adhesive foil and hot melt glue - were applied to a basic substrate by different techniques. The focused and concentrated hot gas stream softened glue which had been applied in a solid state. Micro-parts were then embossed in the softened glue, or covered and shielded by it. In this way, a rigid and compact bond was obtained after cooling. For the positioning of micro-parts (optical fibers), it has been necessary to manufacture adequate V-grooves. Finite element analyses using the ANSYS TM program package were performed in order to evaluate parameters which govern the heat transfer to the adhesive and substrate respectively. Experimental results are in good agreement with results obtained by the numerical simulations. The advantages of this new approach are small system size, low capital costs, simple usage, applicability to many material combinations, easy integration into existing production lines, etc.

Andrijasevic, Daniela; Giouroudi, Ioanna; Smetana, Walter; Boehm, Stefan; Brenner, Werner

2006-01-01

27

Integrated Micro-Machined Hydrogen Gas Sensor. Final Report  

SciTech Connect

This report details our recent progress in developing novel MEMS (Micro-Electro-Mechanical Systems) based hydrogen gas sensors. These sensors couple novel thin films as the active layer on a device structure known as a Micro-HotPlate. This coupling has resulted in a gas sensor that has several unique advantages in terms of speed, sensitivity, stability and amenability to large scale manufacture. This Phase-I research effort was focused on achieving the following three objectives: (1) Investigation of sensor fabrication parameters and their effects on sensor performance. (2) Hydrogen response testing of these sensors in wet/dry and oxygen-containing/oxygen-deficient atmospheres. (3) Investigation of the long-term stability of these thin film materials and identification of limiting factors. We have made substantial progress toward achieving each of these objectives, and highlights of our phase I results include the demonstration of signal responses with and without oxygen present, as well as in air with a high level of humidity. We have measured response times of <0.5 s to 1% H{sub 2} in air, and shown the ability to detect concentrations of <200 ppm. These results are extremely encouraging and suggest that this technology has substantial potential for meeting the needs of a hydrogen based economy. These achievements demonstrate the feasibility of using micro-hotplates structures in conjunction with palladium+coated metal-hydride films for sensing hydrogen in many of the environments required by a hydrogen based energy economy. Based on these findings, they propose to continue and expand the development of this technology in Phase II.

Frank DiMeo, Jr.

2000-10-02

28

Silicon-based wire electrode array for neural interfaces  

NASA Astrophysics Data System (ADS)

Objectives. Metal-wire electrode arrays are widely used to record and stimulate neurons. Commonly, these devices are fabricated from a long insulated metal wire by cutting it into the proper length and using the cross-section as the electrode site. The assembly of a micro-wire electrode array with regular spacing is difficult. With the help of micro-machine technology, a silicon-based wire electrode array (SWEA) is proposed to simplify the assembling process and provide a wire-type electrode with tapered tips. Approach. Silicon wires with regular spacing coated with metal are generated from a silicon wafer through micro-fabrication and are ordered into a 3D array. A silicon wafer is cut into a comb-like structure with hexagonal teeth on both sides by anisotropic etching. To establish an array of silicon-based linear needles through isotropic wet etching, the diameters of these hexagonal teeth are reduced; their sharp edges are smoothed out and their tips are sharpened. The needle array is coated with a layer of parylene after metallization. The tips of the needles are then exposed to form an array of linear neural electrodes. With these linear electrode arrays, an array of area electrodes can be fabricated. Main results. A 6? × ?6 array of wire-type electrodes based on silicon is developed using this method. The time required to manually assemble the 3D array decreases significantly with the introduction of micro-fabricated 2D array. Meanwhile, the tip intervals in the 2D array are accurate and are controlled at no more than 1%. The SWEA is effective both in vitro and in vivo. Significance. Using this method, the SWEA can be batch-prepared in advance along with its parameters, such as spacing, length, and diameter. Thus, neural scientists can assemble proper electrode arrays in a short time.

Pei, Weihua; Zhao, Hui; Zhao, Shanshan; Fang, Xiaolei; Chen, Sanyuan; Gui, Qiang; Tang, Rongyu; Chen, Yuanfang; Hong, Bo; Gao, Xiaorong; Chen, Hongda

2014-09-01

29

Development of Micro-Heaters with Optimized Temperature Compensation Design for Gas Sensors  

PubMed Central

One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature is required over a wide area of the heater. On the other hand, for the NDIR gas sensor, the micro-heater needs high levels of infrared radiation in order to increase sensitivity. In this study, a novel design of a poly-Si micro-heater is proposed to improve the uniformity of heat dissipation on the heating plate. Temperature uniformity of the micro-heater is achieved by compensating for the variation in power consumption around the perimeter of the heater. With the power compensated design, the uniform heating area is increased by 2.5 times and the average temperature goes up by 40 °C. Therefore, this power compensated micro-heater design is suitable for a semiconductor gas sensor. Meanwhile, the poly-Si micro-heater without compensation shows a higher level of infrared radiation under equal power consumption conditions. This indicates that the micro-heater without compensation is more suitable for a NDIR gas sensor. Furthermore, the micro-heater shows a short response time of less than 20ms, indicating a very high efficiency of pulse driving. PMID:22163756

Hwang, Woo-Jin; Shin, Kyu-Sik; Roh, Ji-Hyoung; Lee, Dae-Sung; Choa, Sung-Hoon

2011-01-01

30

Computational and experimental investigation on the performance characteristics of the micro gas compressor  

Microsoft Academic Search

This paper describes the performance characteristics of a micro gas compressor, which is fabricated on the silicon substrates. The micro gas compressor consists of silicon membrane, compression chamber, port holes and cantilever check valves. The compressor is driven by a piezoelectric actuator, which is a bimorphemic structure of a silicon membrane and a piezoelectric ceramic plate. The actuator pulsates and

Jae Sung Yoon; Jong Won Choi; Min Soo Kim

2009-01-01

31

SHIRTBUTTON-SIZED GAS TURBINES: THE ENGINEERING CHALLENGES OF MICRO HIGH SPEED ROTATING MACHINERY  

Microsoft Academic Search

MIT is developing micro-electro-mechanical systems (MEMS)-based gas turbine engines, turbogenerators, and rocket engines. Fabricated in large numbers in parallel using semicon- ductor manufacturing techniques, these engines-on-a-chip are based on micro-high speed rotating machinery with power den- sities approaching those of their more familiar, full-sized breth- ren. The micro-gas turbine is a 2 cm diameter by 3 mm thick Si or

Alan H. Epstein; Stuart A. Jacobson; Jon M. Protz; Luc G. Frechette

2000-01-01

32

Toward silicon-based longwave integrated optoelectronics (LIO)  

NASA Astrophysics Data System (ADS)

The vision of longwave silicon photonics articulated in the Journal of Optics A, vol. 8, pp 840-848, 2006 has now come into sharper focus. There is evidence that newly designed silicon-based optoelectronic circuits will operate at any wavelength within the wide 1.6 to 200 ?m range. Approaches to that LWIR operation are reviewed here. A long-range goal is to manufacture LWIR OEIC chips in a silicon foundry by integrating photonics on-chip with CMOS, bipolar, or BiCMOS micro-electronics. A principal LWIR application now emerging is the sensing of chemical and biological agents with an OE laboratory-on-a-chip. Regarding on-chip IR sources, the hybrid evanescent-wave integration of III-V interband-cascade lasers and quantum-cascade lasers on silicon (or Ge/Si) waveguides is a promising technique, although an alternative all-group-IV solution is presently taking shape in the form of silicon-based Ge/SiGeSn band-to-band and inter-subband lasers. There is plenty of room for creativity in developing a complete suite of LWIR components. Materials modification, device innovation, and scaling of waveguide dimensions are needed to implement microphotonic, plasmonic and photonic-crystal LWIR devices, both active and passive. Such innovation will likely lead to significant LIO applications.

Soref, Richard

2008-02-01

33

Development of Pressure-Sensitive Channel Chip for Micro Gas Flows  

NASA Astrophysics Data System (ADS)

Optical measurement techniques are useful for experimental studies on micro gas flows, which enable us to non-intrusively measure the flows with a high spatial resolution. The pressure-sensitive paint (PSP) technique, which is based on the emission of photons from luminophore, is a potential diagnostic tool for pressure measurement of micro gas flows. However, measurements by conventional PSPs are limited to the sub-millimeter order spatial resolution of ca. 200 ?m, indicating the difficulty of the micro scale measurements. The present study proposes pressure-sensitive channel chip (PSCC) which is a micro channel with the capability of measuring pressure. We focused on the poly (dimethylsiloxane) (PDMS) micro-molding technique, which is one of the most popular techniques to fabricate a micro channel easily. Moreover, PDMS is a polymer used as a binder in PSP because of high optical transparency, gas permeability, and gas diffusivity. Thus, we developed a micro channel by the PDMS micro-molding technique with mixing a pressure-sensitive luminophore into PDMS: i.e. a micro channel fabricated by PSP, which is named PSCC. A flow through a micro converging-diverging nozzle with the throat width of 120 ?m was demonstrated. The pressure distribution on the nozzle surface was successfully obtained by PSCC.

Matsuda, Yu; Yamaguchi, Hiroki; Niimi, Tomohide

2012-05-01

34

Process characteristics of pretreatment system under H 2 S circumstance for bio-gas micro gas turbine power generation  

Microsoft Academic Search

As distributed generation becomes more reliable and economically feasible, it is expected that a higher application of the\\u000a distributed generation such as Micro Gas Turbine Power system would be interconnected to the existing grids. This paper describes\\u000a the results for the mechanical and environmental tests of pretreatment system for Livestock bio-energy Micro Gas Turbine (MGT)\\u000a Combined Heat & power. It

Kwang-Beom Hur; Sang-Kyu Rhim; Jung-Keuk Park; Jae-Hoon Kim

2010-01-01

35

Micro-miniature gas chromatograph column disposed in silicon wafers  

DOEpatents

A micro-miniature gas chromatograph column is fabricated by forming matching halves of a circular cross-section spiral microcapillary in two silicon wafers and then bonding the two wafers together using visual or physical alignment methods. Heating wires are deposited on the outside surfaces of each wafer in a spiral or serpentine pattern large enough in area to cover the whole microcapillary area inside the joined wafers. The visual alignment method includes etching through an alignment window in one wafer and a precision-matching alignment target in the other wafer. The two wafers are then bonded together using the window and target. The physical alignment methods include etching through vertical alignment holes in both wafers and then using pins or posts through corresponding vertical alignment holes to force precision alignment during bonding. The pins or posts may be withdrawn after curing of the bond. Once the wafers are bonded together, a solid phase of very pure silicone is injected in a solution of very pure chloroform into one end of the microcapillary. The chloroform lowers the viscosity of the silicone enough that a high pressure hypodermic needle with a thumbscrew plunger can force the solution into the whole length of the spiral microcapillary. The chloroform is then evaporated out slowly to leave the silicone behind in a deposit.

Yu, Conrad M. (Antioch, CA)

2000-01-01

36

Investigations of Slip Effect on the Performance of Micro Gas Bearings and Stability of Micro Rotor-Bearing Systems  

PubMed Central

Incorporating the velocity slip effect of the gas flow at the solid boundary, the performance and dynamic response of a micro gas-bearing-rotor system are investigated in this paper. For the characteristic length scale of the micro gas bearing, the gas flow in the bearing resides in the slip regime rather than in the continuum regime. The modified Reynolds equations of different slip models are presented. Gas pressure distribution and load carrying capacity are obtained by solving the Reynolds equations with finite different method (FDM). Comparing results from different models, it is found that the second order slip model agrees reasonably well with the benchmarked solutions obtained from the linearized Boltzmann equation. Therefore, dynamic coefficients derived from the second order slip model are employed to evaluate the linear dynamic stability and vibration characteristics of the system. Compared with the continuum flow model, the slip effect reduces dynamic coefficients of the micro gas bearing, and the threshold speed for stable operation is consequently raised. Also, dynamic analysis shows that the system responses change with variation of the operating parameters including the eccentricity ratio, the rotational speed, and the unbalance ratio.

Huang, Hai; Meng, Guang; Chen, Jieyu

2007-01-01

37

Investigation of H2/CH4 mixed gas plasma post-etching process for ZnO:B front contacts grown by LP-MOCVD method in silicon-based thin-film solar cells  

NASA Astrophysics Data System (ADS)

A new plasma post-etching method, H2/CH4 mixed gas plasma, is introduced to modify ZnO:B films grown by LP-MOCVD technique, successfully relaxing the double trade-offs, i.e., transparency/conductivity trade-off and surface texture/Voc and FF trade-off. To deeply evaluate the post-etching process, optical emission spectroscopy technique is applied to diagnose the plasma condition. Upon different etching power, three distinct possible etching mechanisms are identified by analyzing the evolution of H?*, H?*, CH* emission species in the plasma space. It is demonstrated that H?* and CH* species are responsible for the physical etching process and chemical etching process, respectively, from which a new “soft” surface morphology is formed with a combination of micro- and nano-sized texture. Additionally, H?* species can bond with ZnO and also passivate the grains boundaries, thereby making both the carrier concentration and hall mobility increase. This process is defined as chemical bonding process. Finally, pin-type a-Si:H single-junction solar cells with an optimized device structure is grown on the etched ZnO:B substrate. The corresponding electrical parameters, such as Jsc, Voc and FF, are simultaneously improved compared with the solar cell deposited on as-grown ZnO:B substrate with the same fabrication process. As a consequence, a noteworthy 8.85% conversion-efficiency is achieved with an absorber layer thickness only 160 nm.

Wang, Li; Zhang, Xiaodan; Zhao, Ying; Yamada, Takuto; Naito, Yusuke

2014-10-01

38

Storage sizing for embedding of local gas production in a micro gas grid  

NASA Astrophysics Data System (ADS)

In this paper we study the optimal control of a micro grid of biogas producers. The paper considers the possibility to have a local storage device for each producer, who partly consumes his own production, i.e. prosumer. In addition, connected prosumers can sell stored gas to create revenue from it. An optimization model is employed to derive the size of storage device and to provide a pricing mechanism in an effort to value the stored gas. Taking into account physical grid constraints, the model is constructed in a centralized scheme of model predictive control. Case studies show that there is a relation between the demand and price profiles in terms of peaks and lows. The price profiles generally follow each other. The case studies are employed as well to to study the impacts of model parameters on deriving the storage size.

Alkano, D.; Nefkens, W. J.; Scherpen, J. M. A.; Volkerts, M.

2014-12-01

39

New Concept of Micro-Gas-Turbine-Based Cogeneration Package for Performance Improvement in Practical Use  

NASA Astrophysics Data System (ADS)

As energy consumption is rapidly increasing in the commercial sector in Japan, the market potential for a micro-gas turbine is expected to grow significantly if thermal efficiency is improved further. One way of improving thermal efficiency is to introduce a steam injection system that uses steam from the heat recovery steam generator. We have recently carried out several tests using a micro-gas turbine (Capstone C60). Test results show that this new device utilizing steam injection can improve some key performance parameters for output, thermal efficiency and emissions. The stable operation of the micro-gas turbine with steam injection was confirmed under various operating conditions. On the basis of the above findings, we hereby propose the use of a micro-gas-turbine-based cogeneration package with steam injection driven by a heat recovery steam generator (HRSG) with supplementary firing.

Mochizuki, Kenichiro; Shibata, Satoshi; Inoue, Umeo; Tsuchiya, Toshiaki; Sotouchi, Hiroko; Okamoto, Masanori

40

In2O3-based micro gas sensor for detecting NO x gases  

NASA Astrophysics Data System (ADS)

In this study, NO x micro gas sensors for monitoring the indoor atmosphere of automobile were fabricated using MEMS (microelectromechanical system) technology and a sol-gel process. The sensing electrode and micro heater were designed to have a co-planar typed structure in a Pt thin film layer. The thermal characteristics of a micro heater array were analyzed using a finite element method (FEM). The chip size of the gas sensor was approximately 2 mm × 2 mm. Indium oxide as a sensing material for NO x gas was synthesized by a sol-gel process with indium isopropoxide as a precursor. Field emission Scanning electron microscopy and x-ray diffraction showed that particle size of the synthesized In2O3 was approximately 17-45 nm. The maximum gas sensitivity as the relative resistance ( R s = R gas / R air ) was observed at 275°C with a value of 8.0 at 1 ppm NO2 gas. The response (80% saturation) and recovery times were within 1 min. The sensing properties of NO2 gas exhibited linear behavior with increasing gas concentration. The sensing mechanism of the gas sensor was explained by the variations in the electron depletion layers and the adsorption of gas molecules on the In2O3 particle surface. These results suggest that in the future, MEMS-based gas sensors can be used as automotive-exhaust-gas sensors.

Kim, Bum-Joon; Song, In-Gyu; Kim, Jung-Sik

2014-03-01

41

CO2 Emission Reduction from Power Plant Flue Gas by MicroAlgae: A Preliminary Study  

Microsoft Academic Search

CO2 fixation by marine micro-algae cultivation has the potential to diminish the emission of CO2. To select the proponent micro-algae species this is vital to realize workable biological CO2 fixation systems, three kinds of candidate energy marine algal strain were cultivated and tested for bio-fixation of CO2 from power plant flue gas. It was found that Chlorella was the most

Yixin Zhang; Bingtao Zhao; Kaibin Xiong; Zhongxiao Zhang; Tao Liu

2010-01-01

42

Gas transport by thermal transpiration in micro-channels -- A numerical study  

SciTech Connect

A reliable micro gas pump is an essential element to the development of many micro-systems for chemical gas analyses. At Sandia, the authors are exploring a different pumping mechanism, gas transport by thermal transpiration. Thermal transpiration refers to the rarefied gas dynamics developed in a micro-channel with a longitudinal temperature gradient. To investigate the potential of thermal transpiration for gas pumping in micro-systems, the authors have performed simulations and model analysis to design micro-devices and to assess their design performance before the fabrication process. The effort is to apply ICARUS (a Direct Simulation Monte Carlo code developed at Sandia) to characterize the fluid transport and evaluate the design performance. The design being considered has two plenums at different temperatures (hot and cold) separated by a micro-channel of 0.1 micron wide and 1 micron long. The temperature difference between the two plenums is 30 kelvin. ICARUS results, a quasi-steady analysis, predicts a net flow through the micro-channel with a velocity magnitude of about 0.4 m/s due to temperature gradient at the wall (thermal creep flow) at the early time. Later as the pressure builds up in the hot plenum, flow is reversed. Eventually when the system reaches steady state equilibrium, the net flow becomes zero. The thermal creep effect is compensated by the thermo-molecular pressure effect. This result demonstrates that it is important to include the thermo-molecular pressure effect when designing a pumping mechanism based on thermal transpiration. The DSMC technique can model this complex thermal transpiration problem.

Wong, C.C.; Hudson, M.L.; Potter, D.L.; Bartel, T.J.

1998-08-01

43

Preconcentration modeling for the optimization of a micro gas preconcentrator applied to environmental monitoring.  

PubMed

This paper presents the optimization of a micro gas preconcentrator (?-GP) system applied to atmospheric pollution monitoring, with the help of a complete modeling of the preconcentration cycle. Two different approaches based on kinetic equations are used to illustrate the behavior of the micro gas preconcentrator for given experimental conditions. The need for high adsorption flow and heating rate and for low desorption flow and detection volume is demonstrated in this paper. Preliminary to this optimization, the preconcentration factor is discussed and a definition is proposed. PMID:25810264

Camara, Malick; Breuil, Philippe; Briand, Danick; Viricelle, Jean-Paul; Pijolat, Christophe; de Rooij, Nico F

2015-04-21

44

Deng & Schiff, Amorphous Silicon Based Solar Cells rev. 7/30/2002, Page 1 Amorphous Silicon Based Solar Cells  

E-print Network

Deng & Schiff, Amorphous Silicon Based Solar Cells rev. 7/30/2002, Page 1 Amorphous Silicon Based Solar Cells Xunming Deng and Eric A. Schiff Table of Contents 1 Overview 3 1.1 Amorphous Silicon: The First Bipolar Amorphous Semiconductor 3 1.2 Designs for Amorphous Silicon Solar Cells: A Guided Tour 6

Deng, Xunming

45

A six-wafer combustion system for a silicon micro gas turbine engine  

Microsoft Academic Search

As part of a program to develop a micro gas turbine engine capable of producing 10-50 W of electrical power in a package less than one cubic centimeter in volume, we present the design, fabrication, packaging, and experimental test results for the 6-wafer combustion system for a silicon microengine. Comprising the main nonrotating functional components of the engine, the device

A. Mehra; Xin Zhang; A. A. Ayon; I. A. Waitz; M. A. Schmidt; C. M. Spadaccini

2000-01-01

46

Thermomechanical analysis of micro-drop coated gas sensors  

Microsoft Academic Search

The paper discusses the mechanical and thermal behaviour of drop-coated micromachined gas sensors. A laboratory optimised micromachined hotplate has been developed and coated with SnO2 sensing pastes by means of microdropping technology. Different drop dimensions and geometries have been investigated with regard to their influence on the power consumption, the time response and the mechanical behaviour of the whole sensor.

J. Puigcorbé; A. Vilà; J. Cerdà; A. Cirera; I. Gràcia; C. Cané; J. R. Morante

2002-01-01

47

Design and simulation of a small polygeneration plant cofiring biomass and natural gas in a dual combustion micro gas turbine (BIO_MGT)  

Microsoft Academic Search

The operation and performances of an innovative small scale polygeneration system (BIO_MGT), which combines biomass and natural gas in a micro gas turbine, has been simulated in the present work by means of a thermodynamic matching analysis. The BIO_MGT unit matches an externally fired cycle with a commercial Micro Gas Turbine (MGT, 100kWe). A significant share of the total energy

G. Riccio; D. Chiaramonti

2009-01-01

48

Growth of carbon nanotubes by Fe-catalyzed chemical vapor processes on silicon-based substrates  

NASA Astrophysics Data System (ADS)

In this paper, a site-selective catalytic chemical vapor deposition synthesis of carbon nanotubes on silicon-based substrates has been developed in order to get horizontally oriented nanotubes for field effect transistors and other electronic devices. Properly micro-fabricated silicon oxide and polysilicon structures have been used as substrates. Iron nanoparticles have been obtained both from a thin Fe film evaporated by e-gun and from iron nitrate solutions accurately dispersed on the substrates. Single-walled nanotubes with diameters as small as 1 nm, bridging polysilicon and silicon dioxide “pillars”, have been grown. The morphology and structure of CNTs have been characterized by SEM, AFM and Raman spectroscopy.

Angelucci, Renato; Rizzoli, Rita; Vinciguerra, Vincenzo; Fortuna Bevilacqua, Maria; Guerri, Sergio; Corticelli, Franco; Passini, Mara

2007-03-01

49

Micro-size gas turbines create market opportunities  

SciTech Connect

Power plants in the 25 to 250 kW-size range will enable utilities, IPPs and ESCOs to provide economic power for a variety of applications. Small, low-cost, highly efficient gas turbines provide the utility industry with a four-generation technology that features numerous benefits and potential applications. These include firm power to isolated communities, commercial centers and industries; peak shaving for utility systems to reduce the incremental cost of additional loads; peak shaving for large commercial and industrial establishments to reduce demand charges, as well as standby, emergency power and uninterruptible power supply (UPS).

Scott, W.G. [International Power and Light (United States)

1997-09-01

50

Silicon rich nitride for silicon based laser devices  

E-print Network

Silicon based light sources, especially laser devices, are the key components required to achieve a complete integrated silicon photonics system. However, the fundamental physical limitation of the silicon material as light ...

Yi, Jae Hyung

2008-01-01

51

Plasma-Sprayed Refractory Oxide Coatings on Silicon-Base Ceramics  

NASA Technical Reports Server (NTRS)

Silicon-base ceramics are promising candidate materials for high temperature structural applications such as heat exchangers, gas turbines and advanced internal combustion engines. Composites based on these materials are leading candidates for combustor materials for HSCT gas turbine engines. These materials possess a combination of excellent physical and mechanical properties at high temperatures, for example, high strength, high toughness, high thermal shock resistance, high thermal conductivity, light weight and excellent oxidation resistance. However, environmental durability can be significantly reduced in certain conditions such as when molten salts, H2 or water vapor are present. The oxidation resistance of silicon-base materials is provided by SiO2 protective layer. Molten salt reacts with SiO2 and forms a mixture of SiO2 and liquid silicate at temperatures above 800C. Oxygen diffuses more easily through the chemically altered layer, resulting in a catastrophic degradation of the substrate. SiC and Si3N4 are not stable in pure H2 and decompose to silicon and gaseous species such as CH4, SiH, SiH4, N2, and NH3. Water vapor is known to slightly increase the oxidation rate of SiC and Si3N4. Refractory oxides such as alumina, yttria-stabilized zirconia, yttria and mullite (3Al2O3.2SiO2) possess excellent environmental durability in harsh conditions mentioned above. Therefore, refractory oxide coatings on silicon-base ceramics can substantially improve the environmental durability of these materials by acting as a chemical reaction barrier. These oxide coatings can also serve as a thermal barrier. The purpose of this research program has been to develop refractory oxide chemical/thermal barrier coatings on silicon-base ceramics to provide extended temperature range and lifetime to these materials in harsh environments.

Tewari, Surendra

1997-01-01

52

Current-Voltage Characteristics of DC Discharge in Micro Gas Jet Injected into Vacuum Environment  

NASA Astrophysics Data System (ADS)

A current-voltage characteristic of direct current (DC) gas discharge operated in a micro gas jet injected into a secondary electron microscope (SEM) chamber is presented. Ar gas was injected through a 30 ?m orifice gas nozzle (OGN) and was evacuated by an additional pump to keep the high vacuum environment. Gas discharges were ignited between the OGN as anode and a counter electrode of Si wafer. The discharge was self-pulsating in most of the cases while it was stable at lower pressure, larger gap length, and larger time averaged current. The self-pulsating discharge was oscillated by the RC circuit consisting of a stray capacitor and a large ballast resistor. The real time plots of voltage and current during the pulsating was investigated using a discharge model.

Matra, K.; Furuta, H.; Hatta, A.

2013-06-01

53

Applications of Gas Imaging Micro-Well Detectors to an Advanced Compton Telescope  

E-print Network

We present a concept for an Advanced Compton Telescope (ACT) based on the use of pixelized gas micro-well detectors to form a three-dimensional electron track imager. A micro-well detector consists of an array of individual micro-patterned proportional counters opposite a planar drift electrode. When combined with thin film transistor array readouts, large gas volumes may be imaged with very good spatial and energy resolution at reasonable cost. The third dimension is determined from the drift time of the ionization electrons. The primary advantage of this approach is the excellent tracking of the Compton recoil electron that is possible in a gas volume. Such good electron tracking allows us to reduce the point spread function of a single incident photon dramatically, greatly improving the imaging capability and sensitivity. The polarization sensitivity, which relies on events with large Compton scattering angles, is particularly enhanced. We describe a possible ACT implementation of this technique, in which the gas tracking volume is surrounded by a CsI calorimeter, and present our plans to build and test a small prototype over the next three years.

P. F. Bloser; S. D. Hunter; J. M. Ryan; M. L. McConnell; R. S. Miller; T. N. Jackson; B. Bai; S. Jung

2003-09-26

54

Applications of Gas Imaging Micro-Well Detectors to an Advanced Compton Telescope  

NASA Technical Reports Server (NTRS)

We present a concept for an Advanced Compton Telescope (ACT) based on the use of pixelized gas micro-well detectors to form a three-dimensional electron track imager. A micro-well detector consists of an array of individual micro-patterned proportional counters opposite a planar drift electrode. When combined with thin film transistor array readouts, large gas volumes may be imaged with very good spatial and energy resolution at reasonable cost. The third dimension is determined by timing the drift of the ionization electrons. The primary advantage of this approach is the excellent tracking of the Compton recoil electron that is possible in a gas volume. Such good electron tracking allows us to reduce the point spread function of a single incident photon dramatically, greatly improving the imaging capability and sensitivity. The polarization sensitivity, which relies on events with large Compton scattering angles, is particularly enhanced. We describe a possible ACT implementation of this technique, in which the gas tracking volume is surrounded by a CsI calorimeter, and present our plans to build and test a small prototype over the next three years.

Bloser, P. F.; Hunter, S. D.; Ryan, J. M.; McConnell, M. L.; Miller, R. S.; Jackson, T. N.; Bai, B.; Jung, S.

2003-01-01

55

Simulation of gas flows in micro/nano systems using the Burnett equations  

NASA Astrophysics Data System (ADS)

The gaseous flow characteristics in micro/nano systems are studied using the Burnett equations. The Burnett equations are the second-order approximation of the Chapman-Enskog solution to the Boltzmann equation. This set of equation is appropriate to describe the rarefied gas flows. Velocity slip and temperature jump boundary conditions are applied on solid surface. Several techniques, including the usage of relaxation method on slip values and Burnett terms, are introduced to increase the stability of the Burnett equations. Hence, convergent results at Knudsen number up to 0.5 are achieved for the first time. The results of the Burnett equations are first verified using the corresponding experimental and the DSMC data. The Navier-Stokes and the Burnett equations give almost the same result when the flow is in slip regime (Kn<0.0l). But when the flow is in transition regime (0.1micro/nano systems. The pressure driven plane Poiseuille and the backward-facing step flows, the flows through micro filters are then studied. Different inlet to outlet pressure ratios, size effects, shape effects and boundary conditions are analyzed. The competitive relations of rarefied and compressible effects in micro gas flows are discussed.

Bao, Fubing; Yu, Xia; Lin, Jianzhong

2012-05-01

56

Transient Flow Dynamics in Optical Micro Well Involving Gas Bubbles  

NASA Technical Reports Server (NTRS)

The Lab-On-a-Chip Application Development (LOCAD) team at NASA s Marshall Space Flight Center is utilizing Lab-On-a-Chip to support technology development specifically for Space Exploration. In this paper, we investigate the transient two-phase flow patterns in an optic well configuration with an entrapped bubble through numerical simulation. Specifically, the filling processes of a liquid inside an expanded chamber that has bubbles entrapped. Due to the back flow created by channel expansion, the entrapped bubbles tend to stay stationary at the immediate downstream of the expansion. Due to the huge difference between the gas and liquid densities, mass conservation issues associated with numerical diffusion need to be specially addressed. The results are presented in terms of the movement of the bubble through the optic well. Bubble removal strategies are developed that involve only pressure gradients across the optic well. Results show that for the bubble to be moved through the well, pressure pulsations must be utilized in order to create pressure gradients across the bubble itself.

Johnson, B.; Chen, C. P.; Jenkins, A.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-01-01

57

Heat recovery from a micro-gas turbine by vapour jet refrigeration systems  

Microsoft Academic Search

The coproduction of electrical, thermal and refrigerating power is a well-known strategy which can significantly improve the efficiency of energy systems. Often in such tri-generation systems the refrigerating power is obtained by means of absorption cycles. This paper deals with the potential use of ejector-powered refrigerating cycles for heat recovery from a micro-gas turbine. At first, ejector performance is analyzed

Costante Invernizzi; Paolo Iora

2005-01-01

58

Mini and micro-gas turbines for combined heat and power  

Microsoft Academic Search

The use of mainframe gas turbines for power generation has increased in recent years and is likely to continue to increase. The proportion of power generation using combined heat and power is also growing mainly due to efficiency improvements and environmental benefits.Mini- and micro-turbines offer a number of potential advantages compared to other technologies for small-scale power generation, particularly for

P. A. Pilavachi

2002-01-01

59

Scale Effect on Gaseous Flow around a Micro-Scaled Gas Turbine Blade  

Microsoft Academic Search

Two-dimensional compressible momentum and energy equations are solved on gaseous flows around a micro-scaled gas turbine blade (GE-E) for which the axial chord length ranges from 86.1 ? m to 86.1 mm to obtain the scale effect. The numerical methodology is based on Arbitrary-Lagrangian-Eulerian (ALE) method. The flow is assumed to be “no heat conduction” flow. The computations were performed

Toru Yamada; Yutaka Asako

2007-01-01

60

MICRO-HEAT ENGINES, GAS TURBINES, AND ROCKET ENGINES THE MIT MICROENGINE PROJECT  

Microsoft Academic Search

This is a report on work in progress on microelectrical and mechanical systems (MEMS)-based gas turbine en- gines, turbogenerators, and rocket engines currently un- der development at MIT. Fabricated in large numbers in parallel using semiconductor manufacturing techniques, these engines are based on micro-high speed rotating machinery with the same power density as that achieved in their more familiar, full-sized

A. H. Epstein; S. D. Senturia; O. Al-Midani; A. Ayon; K. Breuer; K-S Chen; F. E. Ehrich; E. Esteve; L. Frechette; G. Gauba; R. Ghodssi; C. Groshenry; S. Jacobson; J. L. Kerrebrock; J. H. Lang; J. Lopata; A. Mehra; J. O. Mur Miranda; S. Nagle; D. J. Orr; E. Piekos; M. A. Schmidt; G. Shirley; S. M. Spearing; C. S. Tan; I. A. Waitz

1997-01-01

61

Xenon Additives Detection in Helium Micro-Plasma Gas Analytical Sensor  

NASA Astrophysics Data System (ADS)

Electron energy spectra of Xe atoms at He filled micro-plasma afterglow gas analyzer were observed using Collisional Electron Spectroscopy (CES) method [1]. According to CES, diffusion path confinement for characteristic electrons makes it possible to measure electrons energy distribution function (EEDF) at a high (up to atmospheric) gas pressure. Simple geometry micro-plasma CES sensor consists of two plane parallel electrodes detector and microprocessor-based acquisition system providing current-voltage curve measurement in the afterglow of the plasma discharge. Electron energy spectra are deduced as 2-nd derivative of the measured current-voltage curve to select characteristic peaks of the species to be detected. Said derivatives were obtained by the smoothing-differentiating procedure using spline least-squares approximation of a current-voltage curve. Experimental results on CES electron energy spectra at 10-40 Torr in pure He and in admixture with 0.3% Xe are discussed. It demonstrates a prototype of the new miniature micro-plasma sensors for industry, safety and healthcare applications. [1]. A.A.Kudryavtsev, A.B.Tsyganov. US Patent 7,309,992. Gas analysis method and ionization detector for carrying out said method, issued December 18, 2007.

Tsyganov, Alexander; Kudryavtsev, Anatoliy; Mustafaev, Alexander

2012-10-01

62

Efficient gas sensitivity in mixed bismuth ferrite micro (cubes) and nano (plates) structures  

SciTech Connect

Graphical abstract: Display Omitted Highlights: ? Micro (cubes) structure embedded in nano (plates) of bismuth ferrite was prepared by a chemical method. ? These structures were characterized by XRD and SEM. ? LPG, CO{sub 2} and NH{sub 4} gases were exposed. ? Properties related to gas sensors were measured and reported. -- Abstract: Mixed micro (cubes) and nano (plates) structures of bismuth ferrite (BFO) have been synthesized by a simple and cost-effective wet-chemical method. Structural, morphological and phase confirmation characteristics are measured using X-ray diffraction, field-emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis techniques. The digital FE-SEM photo-images of BFO sample confirmed an incubation of discrete micro-cubes into thin and regularly placed large number of nano-plates. The bismuth ferrite, with mixed structures, films show considerable performance when used in liquefied petroleum (LPG), carbon dioxide (CO{sub 2}) and ammonium (NH{sub 3}) gas sensors application. Different chemical entities in LPG have made it more efficient with higher sensitivity, recovery and response times compared to CO{sub 2} and NH{sub 3} gases. Furthermore, effect of palladium surface treatment on the gas sensitivity and the charge transfer resistances of BFO mixed structures is investigated and reported.

Waghmare, Shivaji D.; Jadhav, Vijaykumar V.; Gore, Shaym K. [Center for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra (India)] [Center for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra (India); Yoon, Seog-Joon; Ambade, Swapnil B. [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of)] [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of); Lokhande, B.J. [Department of Physics, Solapur University, Solapur (India)] [Department of Physics, Solapur University, Solapur (India); Mane, Rajaram S., E-mail: rsmane_2000@yahoo.com [Center for Nanomaterials and Energy Devices, School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra (India); Han, Sung-Hwan, E-mail: shhan@hanyang.ac.kr [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of)] [Inorganic Nanomaterials Laboratory, Department of Chemistry, Hanyang University, Seoul 133-1791 (Korea, Republic of)

2012-12-15

63

Pore size determination in modified micro- and mesoporous materials. Pitfalls and limitations in gas adsorption data analysis  

Microsoft Academic Search

Physical gas adsorption is extensively used in the characterization of micro- and mesoporous materials and is often considered as a straightforward-to-interpret technique. However, physical phenomena like the tensile strength effect, adsorbate phase transitions, and monolayer formation in combined micro- and mesoporous materials frequently lead to extra contributions in the adsorption isotherm. Models for pore size determination mostly do not account

Johan C. Groen; Louk A. A. Peffer; Javier Pérez-Ram??rez

2003-01-01

64

A comparison of ground source heat pumps and micro-combined heat and power as residential greenhouse gas reduction strategies  

E-print Network

Both ground source heat pumps operating on electricity and micro-combined heat and power systems operating on fossil fuels offer potential for the reduction of green house gas emissions in comparison to the conventional ...

Guyer, Brittany (Brittany Leigh)

2009-01-01

65

Treatment to Control Adhesion of Silicone-Based Elastomers  

NASA Technical Reports Server (NTRS)

Seals are used to facilitate the joining of two items, usually temporarily. At some point in the future, it is expected that the items will need to be separated. This innovation enables control of the adhesive properties of silicone-based elastomers. The innovation may also be effective on elastomers other than the silicone-based ones. A technique has been discovered that decreases the level of adhesion of silicone- based elastomers to negligible levels. The new technique causes less damage to the material compared to alternative adhesion mitigation techniques. Silicone-based elastomers are the only class of rubber-like materials that currently meet NASA s needs for various seal applications. However, silicone-based elastomers have natural inherent adhesive properties. This stickiness can be helpful, but it can frequently cause problems as well, such as when trying to get items apart. In the past, seal adhesion was not always adequately addressed, and has caused in-flight failures where seals were actually pulled from their grooves, preventing subsequent spacecraft docking until the seal was physically removed from the flange via an extravehicular activity (EVA). The primary method used in the past to lower elastomer seal adhesion has been the application of some type of lubricant or grease to the surface of the seal. A newer method uses ultraviolet (UV) radiation a mixture of UV wavelengths in the range of near ultraviolet (NUV) and vacuum ultraviolet (VUV) wavelengths.

deGroh, Henry C., III; Puleo, Bernadette J.; Waters, Deborah L.

2013-01-01

66

Evolution of Bubbles through Gas Injection from a Micro-Tube into Liquid Cross-Flow  

NASA Astrophysics Data System (ADS)

Generation of small-size bubbles is of importance in many processes such as chemical, medical and food industries. The most common method of bubble generation is injection of gas from an orifice into the liquid phase. In spite of simplicity of this method, appropriate conditions should exist to avoid bubble growth and obtain required small-size bubbles. Thorough understanding of the bubble formation and growth can reveal the required conditions and ensure detachment of the bubbles from the orifice with desired timing to control their size. In this work, evolution of bubbles from a micro-size gas injection tube into liquid cross-flow is investigated. Special attention has been devoted to optimize the conditions to generate micro-size bubbles. Specifically, the influence of gas injection tube size and location, gas and liquid Reynolds numbers and the geometry of the mixing chamber on the bubbles evolution is studied. High-speed shadowgraphy technique is applied to investigate bubbles size and shape. A Particle Tracking Velocimetry algorithm is also applied to calculate bubbles velocity. The velocity field of the liquid flow surrounding the bubbles is also characterized using a Mirco-Stereo-Particle Image Velocimetry technique.

Ghaemi, Sina; Rahimi, Payam; Nobes, David

2008-11-01

67

Transition regime analytical solution to gas mass flow rate in a rectangular micro channel  

NASA Astrophysics Data System (ADS)

We present an analytical model predicting the experimentally observed gas mass flow rate in rectangular micro channels over slip and transition regimes without the use of any fitting parameter. Previously, Sone reported a class of pure continuum regime flows that requires terms of Burnett order in constitutive equations of shear stress to be predicted appropriately. The corrective terms to the conventional Navier-Stokes equation were named the ghost effect. We demonstrate in this paper similarity between Sone ghost effect model and newly so-called 'volume diffusion hydrodynamic model'. A generic analytical solution to gas mass flow rate in a rectangular micro channel is then obtained. It is shown that the volume diffusion hydrodynamics allows to accurately predict the gas mass flow rate up to Knudsen number of 5. This can be achieved without necessitating the use of adjustable parameters in boundary conditions or parametric scaling laws for constitutive relations. The present model predicts the non-linear variation of pressure profile along the axial direction and also captures the change in curvature with increase in rarefaction.

Dadzie, S. Kokou; Dongari, Nishanth

2012-11-01

68

Integration of a wave rotor to an ultra-micro gas turbine (UmuGT)  

NASA Astrophysics Data System (ADS)

Wave rotor technology has shown a significant potential for performance improvement of thermodynamic cycles. The wave rotor is an unsteady flow machine that utilizes shock waves to transfer energy from a high energy fluid to a low energy fluid, increasing both the temperature and the pressure of the low energy fluid. Used initially as a high pressure stage for a gas turbine locomotive engine, the wave rotor was commercialized only as a supercharging device for internal combustion engines, but recently there is a stronger research effort on implementing wave rotors as topping units or pressure gain combustors for gas turbines. At the same time, Ultra Micro Gas Turbines (UmuGT) are expected to be a next generation of power source for applications from propulsion to power generation, from aerospace industry to electronic industry. Starting in 1995, with the MIT "Micro Gas Turbine" project, the mechanical engineering research world has explored more and more the idea of "Power MEMS". Microfabricated turbomachinery like turbines, compressors, pumps, but also electric generators, heat exchangers, internal combustion engines and rocket engines have been on the focus list of researchers for the past 10 years. The reason is simple: the output power is proportional to the mass flow rate of the working fluid through the engine, or the cross-sectional area while the mass or volume of the engine is proportional to the cube of the characteristic length, thus the power density tends to increase at small scales (Power/Mass=L -1). This is the so-called "cube square law". This work investigates the possibilities of incorporating a wave rotor to an UmuGT and discusses the advantages of wave rotor as topping units for gas turbines, especially at microscale. Based on documented wave rotor efficiencies at larger scale and subsidized by both, a gasdynamic model that includes wall friction, and a CFD model, the wave rotor compression efficiency at microfabrication scale could be estimated at about 70%, which is much higher than the obtained efficiency obtained for centrifugal compressors in a microfabricated gas turbine. This dissertation also proposes several designs of ultra-micro wave rotors, including the novel concept of a radial-flow configuration. It describes a new and simplified design procedure as well as numerical simulations of these wave rotors. Results are obtained using FLUENT, a Computational Fluid Dynamics (CFD) commercial code. The vast information about the unsteady processes occurring during simulation is visualized. Last, two designs for experimental tests have been created, one for a micro shock tube and one for the ultra-micro wave rotor. Theoretical and numerical results encourage the idea that at microscale, compression by shock waves may be more efficient than by conventional centrifugal compressors, thus making the ultra-micro wave rotor (UmuWR) a feasible idea for enhancing (upgrading) UmuGT.

Iancu, Florin

2005-12-01

69

Moment equations and gas-kinetic scheme application to numerical simulation of gas flows in micro scale devices  

NASA Astrophysics Data System (ADS)

This study is devoted to the comparison of continuous and kinetic approaches for two-dimensional numerical simulation of the gas flow transition regime. Regularized 13-moment Grad's set of equations (R13) is used as continuum mathematical model and Unified Gas-Kinetic Scheme (UGKS) is used as kinetic method. The variant of explicit high resolution Godunov scheme with linear flow parameter reconstruction is chosen for numerical solution of the R13 set of equations. Five so-called kinetic boundary conditions are taken as a base of mathematical model of isothermal solid wall. The complete set of the wall boundary conditions is obtained by an approximation of the selected subset of the R13 bulk equations. The resulted set of nonlinear equations for the wall is solved with Newton's numerical method. Our implementation of the UGKS follows in the basic details, and allows calculating continuous and rarefied flows in geometrically complex regions. Except well-known test cases, some complex shape micro device gas flows are used as examples of application of both approaches for various gas flow regimes (from continuous to moderately rarefied).

Timokhin, M. Yu.; Ivanov, I. E.; Kryukov, I. A.

2014-12-01

70

THETRIS: A MICRO-SCALE TEMPERATURE AND GAS RELEASE MODEL FOR TRISO FUEL  

SciTech Connect

The dominating mechanism in the passive safety of gas-cooled, graphite-moderated, high-temperature reactors (HTRs) is the Doppler feedback effect. These reactor designs are fueled with sub-millimeter sized kernels formed into TRISO particles that are imbedded in a graphite matrix. The best spatial and temporal representation of the feedback effect is obtained from an accurate approximation of the fuel temperature. Most accident scenarios in HTRs are characterized by large time constants and slow changes in the fuel and moderator temperature fields. In these situations a meso-scale, pebble and compact scale, solution provides a good approximation of the fuel temperature. Micro-scale models are necessary in order to obtain accurate predictions in faster transients or when parameters internal to the TRISO are needed. Since these coated particles constitute one of the fundamental design barriers for the release of fission products, it becomes important to understand the transient behavior inside this containment system. An explicit TRISO fuel temperature model named THETRIS has been developed and incorporated into the CYNOD-THERMIX-KONVEK suite of coupled codes. The code includes gas release models that provide a simple predictive capability of the internal pressure during transients. The new model yields similar results to those obtained with other micro-scale fuel models, but with the added capability to analyze gas release, internal pressure buildup, and effects of a gap in the TRISO. The analyses show the instances when the micro-scale models improve the predictions of the fuel temperature and Doppler feedback. In addition, a sensitivity study of the potential effects on the transient behavior of high-temperature reactors due to the presence of a gap is included. Although the formation of a gap occurs under special conditions, its consequences on the dynamic behavior of the reactor can cause unexpected responses during fast transients. Nevertheless, the strong Doppler feedback forces the reactor to quickly stabilize.

J. Ortensi; A.M. Ougouag

2011-12-01

71

Specific features of the formation of vanadium oxide micro- and nanocrystals during gas-phase synthesis  

NASA Astrophysics Data System (ADS)

A modified method of gas-phase synthesis of vanadium oxide micro- and nanocrystals was developed. The morphology of the crystals obtained and its dependence on the synthesis conditions are analyzed. The method is shown to permit the growth of rod-shaped crystals rectangular in cross section, whiskers, crystals with a rectangular cavity, and also lamellar crystals and planar ordered textures consisting of oriented rodshaped crystals. The microcrystals synthesized were used to study the mutual reversible transformation of various vanadium oxides using oxidation and reduction reactions.

Vinogradova, O. P.; Sidorov, A. I.; Klimov, V. A.; Shadrin, E. B.; Nashchekin, A. V.; Khanin, S. D.; Lyubimov, V. Yu.

2008-07-01

72

Micro gas bearings fabricated by deep X-ray lithography D. Kim, S. Lee, Y. Jin, Y. Desta, M. D. Bryant, J. Goettert  

E-print Network

] demonstrated an electrostatic induction motor supported by externally pressurized hydrostatic gas bearingsMicro gas bearings fabricated by deep X-ray lithography D. Kim, S. Lee, Y. Jin, Y. Desta, M. D, frictionless bearings are needed, and in practice, micro gas bearings approach the ideal. Typically, bearings

Bryant, Michael D.

73

Ultrafast silicon-based active plasmonics at telecom wavelengths  

E-print Network

Ultrafast silicon-based active plasmonics at telecom wavelengths Jan N. Caspers,1,2,* Nir Rotenberg pulses we demonstrate an ultrafast spectral shift to a surface plasmon polariton coupling resonance recombination. ©2010 Optical Society of America OCIS codes: (230.4110) Modulators; (240.6680) Surface plasmons

Van Driel, Henry M.

74

Optoelectrical Detection System Using Porous Silicon-Based Optical Multilayers  

Microsoft Academic Search

Porous silicon-based multilayer structures for optical sensors have been simulated, fabricated and tested. The proper- ties of optical sensors using porous silicon multilayers can be ad- justed by appropriate substrate material, morphology, process pa- rameters in the pore formation process and by surface treatment (thermal oxidation). Heavily and lightly doped p-doped substrates have been used to realize porous silicon layers

Andras Kovacs; Prasad Jonnalagadda; Ulrich Mescheder

2011-01-01

75

Experimental Investigation of A Twin Shaft Micro Gas-Turbine System  

NASA Astrophysics Data System (ADS)

Due to the fast depletion of fossil fuels and its negative impact on the environment, more attention has been concentrated to find new resources, policies and technologies, which meet the global needs with regard to fuel sustainability and emissions. In this paper, as a step to study the effect of burning low calorific value fuels on gas-turbine performance; a 50 kW slightly pressurized non-premixed tubular combustor along with turbocharger based twin shaft micro gas-turbine was designed and fabricated. A series of tests were conducted to characterize the system using LPG fuel. The tests include the analysis of the temperature profile, pressure and combustor efficiency as well as air fuel ratio and speed of the second turbine. The tests showed a stable operation with acceptable efficiency, air fuel ratio, and temperature gradient for the single and twin shaft turbines.

Sadig, Hussain; Sulaiman, Shaharin Anwar; Ibrahim, Idris

2013-06-01

76

Micro computed tomography and CFD simulation of drop deposition on gas diffusion layers  

NASA Astrophysics Data System (ADS)

Fuel cells are electrochemical power generation system which may achieve high energy efficiencies with environmentally friendly emissions. Among the different types, Proton Exchange Membrane fuel cells (PEMFC) seem at present one of the most promising choices. A very important component of a PEMFC is the gas diffusion layer (GDL), which has the primary role of managing water in the cell, allowing reactant gases transport to the catalyst layer while keeping the membrane correctly hydrated and preventing electrode flooding. Therefore, GDLs have to be porous and very hydrophobic. Carbon clothes or carbon papers coated with a hydrophobizing agent – typically a fluoropolymer – are used. Given the complex chemistry and morphology of the GDLs, wettability analyses on them present some critical issues when using the conventional contact angle measurement techniques. In this paper, the deposition of a drop on a GDL (produced using polytetrafluoroethylene-co-perfluoroalcoxy vinyl ether as the fluorinated polymer) was investigated by means of micro computed tomography (microCT) and numerical simulation. The microCT facility operational at the University of Bergamo was used to acquire a 3D tomography of a water drop deposed on a sample GDL. The reconstructed drop dataset allows thorough understanding of the real drop shape, of its contact area and contact line. The GDL dataset was used to create a realistic mesh for the numerical simulation of the drop deposition, which was performed using the OpenFOAM® interFOAM solver.

Guilizzoni, M.; Santini, M.; Lorenzi, M.; Knisel, V.; Fest-Santini, S.

2014-11-01

77

Light from Silicon-Based Nanostructures  

NASA Astrophysics Data System (ADS)

Si-nanocrystals (Si-nc) embedded in SiO2 glass matrices shows undoubtedly efficient room temperature light emission under optical pumping and sizable optical gain and light amplification have been demonstrated [1]. However, the presence of an insulating SiO2 matrix prevents the fabrication of reliable and efficient electrically-driven devices and the efficiency of light emission is severely curtailed by the slow radiative lifetime of Si-nc. An alternative possibility is offered by the nucleation of Si-nc in dielectric hosts with smaller band-gaps. In this talk we will show our results on light-emitting Si-rich silicon nitride films (SRN) and photonic structures obtained by Plasma Enhanced Chemical Vapor Deposition (PE-CVD) followed by low temperature (500-900 C) thermal annealing[2]. The optical properties of SRNfilms are studied by micro-Raman and photoluminescence spectroscopy and demonstrate the presence of small Si-clusters with nanosecond recombination time and negligible emission thermal quenching. The electrical transport properties of SRN films are also investigated and efficient charge injection at low bias voltages is demonstrated. Additionally, we show that SRN matrices are suitable for efficient energy sensitization of Er ions emitting at 1.54 ?m. The light emission mechanism in SRN nanostructures is studied by DFT-LDA first principles calculations showing that, largely Stokes-shifted, nanosecond-fast and efficient light emission in PE-CVD deposited SRN samples originates from strongly localized excitons transitions at the surface of small Si-nc (˜ 1-2 nm) embedded in Silicon nitride[3]. Additionally, we show that the presence of bridging nitrogen groups at the surface of small Si nanocrystals can explain the origin of the experimentally measured Stokes-shift and the nanosecond relaxation times[3]. *L. Pavesi, L. Dal Negro, C. Mazzoleni, G. Franzo, F. Priolo ``Optical gain in Si nanocrystals'', Nature 408, 440, 23 November 2000. *L. Dal Negro, J.H. Yi, V. Nguyen, Y. Yi, J. Michel, L.C. Kimerling, ``Spectrally enhanced light emission from aperiodic photonic structures'', Appl. Phys. Lett., 86, 261905, (2005) *L. Dal Negro, J. H. Yi, L. C. Kimerling, S. Hamel, A. Williamson, G. Galli, Light Emission from Silicon-rich Nitride Nanostructures, Appl. Phys. Lett., submitted 2005

Dal Negro, Luca

2006-03-01

78

Numerical analysis of micro-/nanoscale gas-film lubrication of sliding surface with complicated structure  

NASA Astrophysics Data System (ADS)

It has been reported that the friction between a partially polished diamond-coated surface and a metal surface was drastically reduced to zero when they are slid at a few m/s. Since the sliding was noiseless, it seems that the diamond-coated surface was levitated over the counter surface and the sliding mechanism was the gas film lubrication. Recently, the mechanism of levitation of a slider with a micro/nanoscale surface structure on a rotating disk was theoretically clarified [S. Yonemura et al., Tribol. Lett., (2014), doi:10.1007/s11249-014-0368-2]. Probably, the partially polished diamond-coated surface may be levitated by high gas pressure generated by the micro/nanoscale surface structure on it. In this study, in order to verify our deduction, we performed numerical simulations of sliding of partially polished diamond-coated surface by reproducing its complicated surface structure using the data measured by an atomic force microscope (AFM). As a result, we obtained the lift force which is large enough to levitate the slider used in the experiment.

Kawagoe, Yoshiaki; Yonemura, Shigeru; Isono, Susumu; Takeno, Takanori; Miki, Hiroyuki; Takagi, Toshiyuki

2014-12-01

79

Quantitative measurement of gas pressure drop along T-shaped micro channels by interferometry  

NASA Astrophysics Data System (ADS)

The study of gas flows in microchannels has received considerably more attention in the literature from a simulation perspective than an experimental. The majority of the experimental work has emphasis on the global measurements at the inlet or exit of the microchannel instead locally along it. In this paper some efforts were made to measure the pressure drop along T-shaped micro channel by using interferometry. The two side channels were served as gas entrances and they were both open to air and the channel outlet was being vacuumed during experiments. A Mach-Zehnder interference microscopy was built for the measurement of gas pressure drop along the mixing channel. Some points along the mixing channel were selected for interferometric measurements. Simulations were first developed in unsteady condition by using Ansys Fluent to verify the nonexistence of transient phenomena of gas flow in the defined condition and then run again in steady condition to get the theoretical pressure drop that was would be used for comparison with experimental results.

Li, Y.; Joseph, S.; Colin, S.; Baldas, L.; Barrot, C.; Orieux, S.; Newport, D.; Brandner, J. J.

2012-05-01

80

78 FR 21100 - Grant of Authority for Subzone Status; Dow Corning Corporation (Silicon-Based Products); Midland, MI  

Federal Register 2010, 2011, 2012, 2013, 2014

...Subzone Status; Dow Corning Corporation (Silicon-Based Products); Midland, MI Pursuant...certain manufacturing authority at the silicon- based products manufacturing facility...activity related to the manufacturing of silicon-based products at the facility of...

2013-04-09

81

Visualisation by high resolution synchrotron X-ray phase contrast micro-tomography of gas films on submerged superhydrophobic leaves.  

PubMed

Floods can completely submerge terrestrial plants but some wetland species can sustain O2 and CO2 exchange with the environment via gas films forming on superhydrophobic leaf surfaces. We used high resolution synchrotron X-ray phase contrast micro-tomography in a novel approach to visualise gas films on submerged leaves of common cordgrass (Spartina anglica). 3D tomograms enabled a hitherto unmatched level of detail regarding the micro-topography of leaf gas films. Gas films formed only on the superhydrophobic adaxial leaf side (water droplet contact angle, ?=162°) but not on the abaxial side (?=135°). The adaxial side of the leaves of common cordgrass is plicate with a longitudinal system of parallel grooves and ridges and the vast majority of the gas film volume was found in large ?180?m deep elongated triangular volumes in the grooves and these volumes were connected to each neighbouring groove via a fine network of gas tubules (?1.7?m diameter) across the ridges. In addition to the gas film retained on the leaf exterior, the X-ray phase contrast micro-tomography also successfully distinguished gas spaces internally in the leaf tissues, and the tissue porosity (gas volume per unit tissue volume) ranged from 6.3% to 20.3% in tip and base leaf segments, respectively. We conclude that X-ray phase contrast micro-tomography is a powerful tool to obtain quantitative data of exterior gas features on biological samples because of the significant difference in electron density between air, biological tissues and water. PMID:25175398

Lauridsen, Torsten; Glavina, Kyriaki; Colmer, Timothy David; Winkel, Anders; Irvine, Sarah; Lefmann, Kim; Feidenhans'l, Robert; Pedersen, Ole

2014-10-01

82

A novel implantable multichannel silicon-based microelectrode  

NASA Astrophysics Data System (ADS)

Silicon-based microelectrodes have been confirmed to be helpful in neural prostheses. The fabricated 7-channel silicon-based microelectrode was feasible to be implanted into the brain cortex. The manufacturing process by microelectromechanical system (MEMS) technology was detailed with four photolithographic masks. The microscopic photographs and SEM images indicated that the probe shank was 3 mm long, 100 ?m wide and 20 ?m thick with the recording sites spaced 120 ?m apart for good signal isolation. To facilitate the insertion and minimize the trauma, the microelectrode is narrowed down gradually near the tip with the tip taper angle of 6 degrees. Curve of the single recording site impedance versus frequency was shown by test in vitro and the impedance declined from 150.5k? to 6.0 k? with frequency changing from 10 k to 10 MHz.

Sui, Xiao-Hong; Zhang, Ruo-Xin; Pei, Wei-Hua; Chen, Hong-Da

2007-07-01

83

Outdoor degradation of thin film amorphous silicon based PV modules  

NASA Astrophysics Data System (ADS)

One of the main problems in thin film silicon based modules is the deterioration of their performance upon exposure to light. The presented work focuses on a methodology for evaluation of thin-film photovoltaic module degradation behavior under real operating conditions. The outdoor degradation of double junction a-Si:H/a-Si:H modules was investigated using automated measurement setup for a period of two years. A deterioration of the module's maximum power was observed due to the well known Staebler-Wronski effect, which main causes are the decrease of open circuit voltage and the fill factor of the module. The obtained results can be correlated to the technology and construction of the thin film silicon based modules.

Berov, M.; Ivanov, P.; Tuytuyndziev, N.; Vitanov, P.

2014-12-01

84

Silicon Based Anodes for Li-Ion Batteries  

SciTech Connect

Silicon is environmentally benign and ubiquitous. Because of its high specific capacity, it is considered one of the most promising candidates to replace the conventional graphite negative electrode used in today's Li ion batteries. Silicon has a theoretical specific capacity of nearly 4200 mAh/g (Li21Si5), which is 10 times larger than the specific capacity of graphite (LiC6, 372 mAh/g). However, the high capacity of silicon is associated with huge volume changes (more than 300 percent) when alloyed with lithium, which can cause severe cracking and pulverization of the electrode and lead to significant capacity loss. Significant scientific research has been conducted to circumvent the deterioration of silicon based anode materials during cycling. Various strategies, such as reduction of particle size, generation of active/inactive composites, fabrication of silicon based thin films, use of alternative binders, and the synthesis of 1-D silicon nanostructures have been implemented by a number of research groups. Fundamental mechanistic research has also been performed to better understand the electrochemical lithiation and delithiation process during cycling in terms of crystal structure, phase transitions, morphological changes, and reaction kinetics. Although efforts to date have not attained a commercially viable Si anode, further development is expected to produce anodes with three to five times the capacity of graphite. In this chapter, an overview of research on silicon based anodes used for lithium-ion battery applications will be presented. The overview covers electrochemical alloying of the silicon with lithium, mechanisms responsible for capacity fade, and methodologies adapted to overcome capacity degradation observed during cycling. The recent development of silicon nanowires and nanoparticles with significantly improved electrochemical performance will also be discussed relative to the mechanistic understanding. Finally, future directions on the development of silicon based anodes will be considered.

Zhang, Jiguang; Wang, Wei; Xiao, Jie; Xu, Wu; Graff, Gordon L.; Yang, Zhenguo; Choi, Daiwon; Li, Xiaolin; Wang, Deyu; Liu, Jun

2012-06-15

85

Silicon-based microfilters for whole blood cell separation  

Microsoft Academic Search

This paper reports on the comparison analysis of four main types of silicon-based microfilter for isolation of white blood\\u000a cells (WBCs) from red blood cells (RBCs) in a given whole blood. The microfilter designs, namely, weir, pillar, crossflow,\\u000a and membrane, all impose the same cut-off size of 3.5 ?m to selectively trap WBCs. Using human whole blood, the microfilters\\u000a have been

Hong Miao Ji; Victor Samper; Yu Chen; Chew Kiat Heng; Tit Meng Lim; Levent Yobas

2008-01-01

86

Toward silicon-based longwave integrated optoelectronics (LIO)  

Microsoft Academic Search

The vision of longwave silicon photonics articulated in the Journal of Optics A, vol. 8, pp 840-848, 2006 has now come into sharper focus. There is evidence that newly designed silicon-based optoelectronic circuits will operate at any wavelength within the wide 1.6 to 200 mum range. Approaches to that LWIR operation are reviewed here. A long-range goal is to manufacture

Richard Soref

2008-01-01

87

Response of silicon-Based Linear Energy Transfer Spectrometers  

NASA Technical Reports Server (NTRS)

Silicon-based linear energy transfer (LET) telescope,(e. g., DOSTEL and RRMD) have recently been flown in space. LET spectra measured using tissue equivalent proportional counters show differences that need to be fully understood. A Monte Carlo technique based on: 1. radiation transport cluster intra-cascade model. 2. Landau-Vavilov distribution, 3. telescope geometry and detector coincidence & discriminator settings, 4. spacecraft shielding geometry, and 5. the external free space radiation environment, including recent albedo measurements, was developed.

Aman, A.; Bman, B.; Badhwar, G. D.; ONeill, P. M. O.

2000-01-01

88

Physics of amorphous silicon based alloy field-effect transistors  

Microsoft Academic Search

In this paper we develop a new theory to describe the characteristics of amorphous silicon based alloy field-effect transistors. We show that the transition from below to above threshold operation occurs when the Fermi level in the accumulation region moves from the deep to tail localized states in the energy gap. The current-voltage and capacitance-voltage characteristics are related to the

M. Shur; M. Hack

1984-01-01

89

Silicon-Based Plasmonics for On-Chip Photonics  

Microsoft Academic Search

Silicon-based photonic devices dissipate substantially less power and provide a significantly greater information bandwidth than electronic components. Unfortunately, large-scale integration of photonic devices has been limited by their large, wavelength-scale size and the weak optical response of Si. Surface plasmons may overcome these two limitations. Combining the high localization of electronic waves with the propagation properties of optical waves, plasmons

Jennifer A. Dionne; Luke A. Sweatlock; Matthew T. Sheldon; A. Paul Alivisatos; Harry A. Atwater

2010-01-01

90

Corrosion of silicon-based ceramics in combustion environments  

Microsoft Academic Search

Silicon-based ceramics and composites are prime candidates for heat engines and heat exchanger structural components. In such applications these materials are exposed to combustion gases and deposit-forming corrodents. In this paper combustion environments are defined for various applications. These environments lead to five main types of corrosive degradation: passive oxidation, deposit-induced corrosion, active oxidation, scale\\/substrate interactions, and scale volatility. Each

Nathan S. Jacobson

1993-01-01

91

Porous silicon-based biosensor for pathogen detection  

Microsoft Academic Search

A porous silicon-based biosensor for rapid detection of bacteria was fabricated. Silicon (0.01ohmcm, p-type) was anodized electrochemically in an electrochemical Teflon cell containing ethanoic hydrofluoric acid solution to produce sponge-like porous layer of silicon. Anodizing conditions of 5mA\\/cm2 for 85min proved best for biosensor fabrication. A single-tube chemiluminescence-based assay, previously developed, was adapted to the biosensor for detection of Escherichia

Finny P. Mathew; Evangelyn C. Alocilja

2005-01-01

92

Fault Diagnosis for Micro-Gas Turbine Engine Sensors via Wavelet Entropy  

PubMed Central

Sensor fault diagnosis is necessary to ensure the normal operation of a gas turbine system. However, the existing methods require too many resources and this need can’t be satisfied in some occasions. Since the sensor readings are directly affected by sensor state, sensor fault diagnosis can be performed by extracting features of the measured signals. This paper proposes a novel fault diagnosis method for sensors based on wavelet entropy. Based on the wavelet theory, wavelet decomposition is utilized to decompose the signal in different scales. Then the instantaneous wavelet energy entropy (IWEE) and instantaneous wavelet singular entropy (IWSE) are defined based on the previous wavelet entropy theory. Subsequently, a fault diagnosis method for gas turbine sensors is proposed based on the results of a numerically simulated example. Then, experiments on this method are carried out on a real micro gas turbine engine. In the experiment, four types of faults with different magnitudes are presented. The experimental results show that the proposed method for sensor fault diagnosis is efficient. PMID:22163734

Yu, Bing; Liu, Dongdong; Zhang, Tianhong

2011-01-01

93

Analytical estimation of neutron yield in a micro gas-puff X pinch  

SciTech Connect

In this paper, we present the basic concepts for developing a micro x pinch as a small-scale neutron source. For compact sources, these concepts offer repetitive function at higher yields and pulsing rates than competing methods. The uniqueness of these concepts arises from the use of microelectronic technology to reduce the size of the target plasma and to efficiently heat the target gas. The use of repetitive microelectromechanical systems (MEMs) gas puff technology, as compared to cryogenic wires or solid targets (for the beam-target alternatives), has the potential to be robust and have a long lifetime because the plasma is not created from solid surfaces. The modeling suggests that a 50 J at the wall plug pulse could provide >10{sup 5} tritium (DT) neutrons and 10{sup 3} deuterium (DD) neutrons at temperatures of a few keV. At 1 kHz, this would be >10{sup 8} and 10{sup 6} neutrons per second, DT and DD, respectively, with a 250 {mu}m anode-cathode gap. DT gas puff devices may provide >10{sup 12} neutrons/s operating at 1 kHz and requiring 100 kW. The MEMs approach offers potentially high pulse rates and yields.

Derzon, M. S.; Galambos, P. C. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Hagen, E. C. [NSTec, North Las Vegas, Nevada 89031 (United States)

2012-12-01

94

Fault diagnosis for micro-gas turbine engine sensors via wavelet entropy.  

PubMed

Sensor fault diagnosis is necessary to ensure the normal operation of a gas turbine system. However, the existing methods require too many resources and this need can't be satisfied in some occasions. Since the sensor readings are directly affected by sensor state, sensor fault diagnosis can be performed by extracting features of the measured signals. This paper proposes a novel fault diagnosis method for sensors based on wavelet entropy. Based on the wavelet theory, wavelet decomposition is utilized to decompose the signal in different scales. Then the instantaneous wavelet energy entropy (IWEE) and instantaneous wavelet singular entropy (IWSE) are defined based on the previous wavelet entropy theory. Subsequently, a fault diagnosis method for gas turbine sensors is proposed based on the results of a numerically simulated example. Then, experiments on this method are carried out on a real micro gas turbine engine. In the experiment, four types of faults with different magnitudes are presented. The experimental results show that the proposed method for sensor fault diagnosis is efficient. PMID:22163734

Yu, Bing; Liu, Dongdong; Zhang, Tianhong

2011-01-01

95

Development of Electron Tracking Compton Camera using micro pixel gas chamber for medical imaging  

NASA Astrophysics Data System (ADS)

We have developed the Electron Tracking Compton Camera (ETCC) with reconstructing the 3-D tracks of the scattered electron in Compton process for both sub-MeV and MeV gamma rays. By measuring both the directions and energies of not only the recoil gamma ray but also the scattered electron, the direction of the incident gamma ray is determined for each individual photon. Furthermore, a residual measured angle between the recoil electron and scattered gamma ray is quite powerful for the kinematical background rejection. For the 3-D tracking of the electrons, the Micro Time Projection Chamber (?-TPC) was developed using a new type of the micro pattern gas detector. The ETCC consists of this ?-TPC (10×10×8 cm 3) and the 6×6×13 mm 3 GSO crystal pixel arrays with a flat panel photo-multiplier surrounding the ?-TPC for detecting recoil gamma rays. The ETCC provided the angular resolution of 6.6° (FWHM) at 364 keV of 131I. A mobile ETCC for medical imaging, which is fabricated in a 1 m cubic box, has been operated since October 2005. Here, we present the imaging results for the line sources and the phantom of human thyroid gland using 364 keV gamma rays of 131I.

Kabuki, Shigeto; Hattori, Kaori; Kohara, Ryota; Kunieda, Etsuo; Kubo, Atsushi; Kubo, Hidetoshi; Miuchi, Kentaro; Nakahara, Tadaki; Nagayoshi, Tsutomu; Nishimura, Hironobu; Okada, Yoko; Orito, Reiko; Sekiya, Hiroyuki; Shirahata, Takashi; Takada, Atsushi; Tanimori, Toru; Ueno, Kazuki

2007-10-01

96

200 The Institute of Electrical Engineers of Japan. 1 Micro gas preconcentrator made of a film of single-walled carbon nanotubes  

E-print Network

technology have resulted in low values of the concentration factor, the conventional figure of merit embedded in the micro gas preconcentrators by using the hot water-assisted detachment method. The small size of the fabricated micro gas preconcentrator and the use of SWNTs as the adsorbent material allow

Maruyama, Shigeo

97

Gas transport evaluation in lithium-air batteries with micro/nano-structured cathodes  

NASA Astrophysics Data System (ADS)

Inefficient gas transport in the porous cathode is disastrous for the lithium-air battery to achieve a high electrochemical performance. Previous evaluation of the cathode diffusivity relies on indirect calculations based on multiple V-I data obtained over the intact battery system, which inevitably induces evaluation uncertainty and material waste. In this report, an electrochemical device is designed for the out-of-cell diffusivity measurement in the lithium-air battery with micro/nano-sized cathodes. With the measured diffusivity, a few electrochemical parameters including the limiting current density and the concentration polarization associated with the porous cathodes can thus be directly evaluated. The work facilitates the development of highly-efficient cathode materials in the general field of metal-air battery field.

Wang, Xiaoning; Wen, Kechun; Song, Yuanqiang; Ye, Luhan; Zhang, Kelvin H. L.; Pan, Yu; Lv, Weiqiang; Liao, Yulong; He, Weidong

2015-01-01

98

Fabrication of functional mesoscopic ceramic parts for micro gas turbine engines  

NASA Astrophysics Data System (ADS)

The demand for small-size energy sources with high power densities is increasing with the development of miniature devices. New materials and novel manufacturing techniques are essential for developing these energy sources for miniature devices. Micro gas turbine engines can have higher power density per volume and weight due to their higher operating frequencies, which is made possible by the scaling effect. Higher power densities can also lead to redundant systems that have higher reliability than single engine systems. By replacing metal parts with lighter ceramics, power generated per unit mass can be increased further. However, since the ceramic parts are brittle, they suffer from lower reliability. Mesoscopic ceramic parts have higher reliability due to their smaller volume. This can be predicted by Weibull statistics. A fist-size miniature gas turbine engine with silicon nitride parts called "Firefly" is being developed at the Rapid Prototyping Laboratory (RPL), Stanford University and its industrial partners. Firefly's rotor-group and turbine inlet nozzle are made of silicon nitride to achieve light weight and increased efficiency. The Firefly engine's ceramic parts require smooth surface but their complex geometry prevents grinding. The Mold Shape Deposition Manufacturing (Mold SDM) process and its derivative, therefore, are used to fabricate the ceramic parts. Since the process was not fully developed for the fabrication of functional ceramic parts, several process improvements have been made. The manufacturing processes and the fabricated parts are characterized in terms of surface quality, strength, accuracy and build time. The results show that the processes have been developed to the extent that they produce functional ceramic parts for micro gas turbine engines. The functionality of the Mold SDM silicon nitride parts for the Firefly engine is tested. The ceramic inlet nozzles were tested with high temperature gas. The ceramic turbine has been spin tested and it achieved 456,000 rpm. The ceramic compressor was characterized up to 420,000 rpm and the effect of compressor clearance gap for the compressor functionality was measured. Noticeable increases of compression ratio, mass flow rate and efficiency have been observed as the compressor clearance gap decreases from 180 mum to 120 mum.

Kang, Sangkyun

99

Pressure Drop Measurements in Rectangular Micro-Channel Using Gas Flow  

E-print Network

Abstract: Due to the need for practical cooling technologies which could dissipate high heat fluxes, an experimental study of pressure drop in micro-channel was performed. In this work, laminar flow friction factors were determined using gas (air) as flow medium. Pressure drop vs flow rate data were used to evaluate friction factors in two parallel microchannels, namely MCP1 and MCP2 (1.0 mm deep x 0.240 mm width and 0.9 mm deep x 0.2 mm width, respectively). Each channel of length 192 mm fabricated on a 304 Stainless Steel substrate by chemical milling Reynolds number was covered between 24 – 5398 for MCP1 and 26 – 6233 for MCP2. Transient pressure drops measured within the channel itself to exclude entrance and exit losses. Friction factor – Reynolds number analyses show that the friction constant are identical as normal channels for gas flow in the laminar region. Transition region lies in Re> 500 and transition set off at lower Re ~ 500 in comparison to normal channel. The discontinuity in f – Re data identified as transition. Further, it may be possible to identify transition (from laminar region) as the deviation of non-dimensional pressure drop (NDPD) values.

100

Mass flow rate prediction of pressure-temperature-driven gas flows through micro/nanoscale channels  

NASA Astrophysics Data System (ADS)

In this paper, we study mass flow rate of rarefied gas flow through micro/nanoscale channels under simultaneous thermal and pressure gradients using the direct simulation Monte Carlo (DSMC) method. We first compare our DSMC solutions for mass flow rate of pure temperature-driven flow with those of Boltzmann-Krook-Walender equation and Bhatnagar-Gross-Krook solutions. Then, we focus on pressure-temperature-driven flows. The effects of different parameters such as flow rarefaction, channel pressure ratio, wall temperature gradient and flow bulk temperature on the thermal mass flow rate of the pressure-temperature-driven flow are examined. Based on our analysis, we propose a correlated relation that expresses normalized mass flow rate increment due to thermal creep as a function of flow rarefaction, normalized wall temperature gradient and pressure ratio over a wide range of Knudsen number. We examine our predictive relation by simulation of pressure-driven flows under uniform wall heat flux (UWH) boundary condition. Walls under UWH condition have non-uniform temperature distribution, that is, thermal creep effects exist. Our investigation shows that developed analytical relation could predict mass flow rate of rarefied pressure-driven gas flows under UWH condition at early transition regime, that is, up to Knudsen numbers of 0.5.

Akhlaghi, Hassan; Roohi, Ehsan

2014-01-01

101

Thermal/environmental barrier coating system for silicon-based materials  

NASA Technical Reports Server (NTRS)

A coating system for a substrate containing a silicon-based material, such as silicon carbide-containing ceramic matrix materials containing silicon carbide and used to form articles exposed to high temperatures, including the hostile thermal environment of a gas turbine engine. The coating system includes a layer of barium strontium aluminosilicate (BSAS) as a bond coat for a thermal-insulating top coat. As a bond coat, the BSAS layer serves to adhere the top coat to a SiC-containing substrate. The BSAS bond coat exhibits sufficient environmental resistance such that, if the top coat should spall, the BSAS bond coat continues to provide a level of environmental protection to the underlying SiC-containing substrate.

Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor)

1999-01-01

102

A silicon-based cluster state quantum computer  

E-print Network

It has been over ten years since Kane's influential proposal for a silicon-based nuclear spin quantum computer using phosphorous donors. Since then, silicon-based architectures have been refined as the experimental challenges associated with the original proposal have become better understood, while simultaneously a number of powerful and generic models for quantum computation have emerged. Here, I discuss how the cluster state or "one-way" model for quantum computing might be advantageously applied to donors in silicon, with the potential to substantially reduce the practical requirements of a successful implementation. The essence of the scheme is to use the electron spin associated with a donor to weave an entangled network between 31P donor nuclear spins. This resource has been shown to have exceptional coherence times and supports universal quantum computation through local measurements on the nuclear spins. Some of the key ingredients, such as global spin manipulation, have been robustly established, while others, such as single spin measurement, have seen much progress in recent years. A key challenge will be the demonstration of electron transfer between donors that preserves spin coherence.

John J. L. Morton

2009-05-25

103

Porous silicon-based biosensor for pathogen detection.  

PubMed

A porous silicon-based biosensor for rapid detection of bacteria was fabricated. Silicon (0.01 ohmcm, p-type) was anodized electrochemically in an electrochemical Teflon cell containing ethanoic hydrofluoric acid solution to produce sponge-like porous layer of silicon. Anodizing conditions of 5 mA/cm2 for 85 min proved best for biosensor fabrication. A single-tube chemiluminescence-based assay, previously developed, was adapted to the biosensor for detection of Escherichia coli. Porous silicon chips were functionalized with a dioxetane-Polymyxin B (cell wall permeabilizer) mixture by diffusion and adsorption on to the porous surface. The reaction of beta-galactosidase enzyme from E. coli with the dioxetane substrate generated light at 530 nm. Light emission for the porous silicon biosensor chip with E. coli was significantly greater than that of the control and planar silicon chip with E. coli (P<0.01). Sensitivity of the porous silicon biosensor was determined to be 101-102 colony forming units (CFU) of E. coli. The porous silicon-based biosensor was fabricated and functionalized to successfully detect E. coli and has potential applications in food and environmental testing. PMID:15626624

Mathew, Finny P; Alocilja, Evangelyn C

2005-02-15

104

Micro-machined planar field asymmetric ion mobility spectrometer as a gas chromatographic detector  

NASA Technical Reports Server (NTRS)

A planar high field asymmetric waveform ion mobility spectrometer (PFAIMS) with a micro-machined drift tube was characterized as a detector for capillary gas chromatography. The performance of the PFAIMS was compared directly to that of a flame ionization detector (FID) for the separation of a ketone mixture from butanone to decanone. Effluent from the column was continuously sampled by the detector and mobility scans could be obtained throughout the chromatographic analysis providing chemical inforrmation in mobility scans orthogonal to retention time. Limits of detection were approximately I ng for measurement of positive ions and were comparable or slightly better than those for the FID. Direct comparison of calibration curves for the FAIMS and the FID was possible over four orders of magnitude with a semi-log plot. The concentration dependence of the PFAIMS mobility scans showed the dependence between ion intensity and ion clustering, evident in other mobility spectrometers and atmospheric pressure ionization technologies. Ions were identified using mass spectrometry as the protonated monomer and the proton bound dimer of the ketones. Residence time for column effluent in the PFAIMS was calculated as approximately 1 ms and a 36% increase in extra-column broadening versus the FID occurred with the PFAIMS.

Eiceman, G. A.; Nazarov, E. G.; Miller, R. A.; Krylov, E. V.; Zapata, A. M.

2002-01-01

105

Solidphase micro-extraction–gas chromatography–mass spectrometry and headspace-gas chromatography of tetrahydrocannabinol, amphetamine, methamphetamine, cocaine and ethanol in saliva samples  

Microsoft Academic Search

In the present work, a method was developed aiming at the serial detection of tetrahydrocannabinol (THC), amphetamine, methamphetamine, cocaine and ethanol in saliva. Saliva samples were submitted to an initial headspace procedure for ethanol determination by gas chromatography\\/flame ionization detector (GC–FID). After this step, two consecutive solid-phase micro-extractions (SPME) were carried out: THC was extracted by submersing a polydimethylsiloxane fiber

Mauricio Yonamine; Nadia Tawil; Regina Lucia de Moraes Moreau; Ovandir Alves Silva

2003-01-01

106

Study of Influence of Diffuser Meridian Channel Shape on Performance of Micro-Gas Turbine Centrifugal Compressor  

Microsoft Academic Search

Three-dimensional viscous flow numerical simulation was conducted to study influence of diffuser meridional-section shape with different width ratio on micro-gas turbine centrifugal compressor. Then, the curves of efficiency, total pressure recovery coefficient, total pressure ratio and static pressure ratio were compared under different width ratio. Moreover, the velocity vector in diffuser flow channels, the magnitude distribution of absolute velocity near

Yong Yang; Rong Xie; Lu-yuan Gong; Yang Hai

2011-01-01

107

Silicon-Based Optical Modulator with Ferroelectric Layer  

NASA Technical Reports Server (NTRS)

According to a proposal, a silicon dioxide layer in a high-speed, low-power, silicon- based electro-optical modulator would be replaced by a layer of lead zirconate titanate or other ferroelectric oxide material. The purpose of this modification is to enhance the power performance and functionality of the modulator. In its unmodified form, the particular silicon- based electro-optical modulator is of an advanced design that overcomes the speed limitation of prior silicon-based electro- optical modulators. Whereas modulation frequencies of such devices had been limited to about 20 MHz, this modulator can operate at modulation frequencies as high as 1 GHz. This modulator can be characterized as a silicon-waveguide-based metal oxide/semiconductor (MOS) capacitor phase shifter in which modulation of the index of refraction in silicon is obtained by exploiting the free-charge-carrier-plasma dispersion effect. As shown in the figure, the modulator includes an n-doped crystalline silicon slab (the silicon layer of a silicon- on-insulator wafer) and a p-doped polycrystalline silicon rib with a gate oxide layer (the aforementioned silicon dioxide layer) sandwiched between them. Under accumulation conditions, the majority charge carriers in the silicon waveguide modify the index of refraction so that a phase shift is induced in the optical mode propagating in the waveguide. The advantage of using an MOS capacitor phase shifter is that it is possible to achieve high modulation speed because there are no slow carrier-generation or -recombination processes involved in the accumulation operation. The main advantage of the proposed substitution of a ferroelectric oxide layer for the silicon dioxide layer would arise from the spontaneous polarization effect of the ferroelectric layer: This spontaneous polarization would maintain accumulation conditions in the absence of applied voltage. Consequently, once the device had been switched to a given optical state, it would remain in that state, even in the absence of applied voltage (in other words, even with power turned off). A secondary advantage is that because the ferroelectric layer would have an index of refraction larger than that of silicon dioxide, there could be some reduction of optical losses attributable to fabrication of the modulator

Sheldon, Douglas

2006-01-01

108

Measurement of Gas-Liquid Two-Phase Flow in Micro-Pipes by a Capacitance Sensor  

PubMed Central

A capacitance measurement system is developed for the measurement of gas-liquid two-phase flow in glass micro-pipes with inner diameters of 3.96, 2.65 and 1.56 mm, respectively. As a typical flow regime in a micro-pipe two-phase flow system, slug flow is chosen for this investigation. A capacitance sensor is designed and a high-resolution and high-speed capacitance measurement circuit is used to measure the small capacitance signals based on the differential sampling method. The performance and feasibility of the capacitance method are investigated and discussed. The capacitance signal is analyzed, which can reflect the voidage variation of two-phase flow. The gas slug velocity is determined through a cross-correlation technique using two identical capacitance sensors. The simulation and experimental results show that the presented capacitance measurement system is successful. Research work also verifies that the capacitance sensor is an effective method for the measurement of gas liquid two-phase flow parameters in micro-pipes. PMID:25587879

Ji, Haifeng; Li, Huajun; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing

2014-01-01

109

Measurement of gas-liquid two-phase flow in micro-pipes by a capacitance sensor.  

PubMed

A capacitance measurement system is developed for the measurement of gas-liquid two-phase flow in glass micro-pipes with inner diameters of 3.96, 2.65 and 1.56 mm, respectively. As a typical flow regime in a micro-pipe two-phase flow system, slug flow is chosen for this investigation. A capacitance sensor is designed and a high-resolution and high-speed capacitance measurement circuit is used to measure the small capacitance signals based on the differential sampling method. The performance and feasibility of the capacitance method are investigated and discussed. The capacitance signal is analyzed, which can reflect the voidage variation of two-phase flow. The gas slug velocity is determined through a cross-correlation technique using two identical capacitance sensors. The simulation and experimental results show that the presented capacitance measurement system is successful. Research work also verifies that the capacitance sensor is an effective method for the measurement of gas liquid two-phase flow parameters in micro-pipes. PMID:25587879

Ji, Haifeng; Li, Huajun; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing

2014-01-01

110

Effect of surrounding gas condition on surface integrity in micro-drilling of SiC by ns pulsed laser  

NASA Astrophysics Data System (ADS)

The influence of the surrounding gas conditions on the surface integrity in the micro-drilling of silicon carbide was experimentally investigated using ns pulsed laser of 266 nm wavelength. Moreover, micro-machining characteristics were observed using high-speed shutter and video cameras in the micro-drilling of silicon carbide. The size and intensity of the laser-induced plasma were larger, and the plasma affected area was larger and deeper in argon than that in air. Although the intensity of the plasma was lower in helium than that in other gases, the surface around the drilled hole was roughened by the spread of the plasma in the vicinity of the drilled hole. Debris was removed along the flow field generated by laser shot in the opposite direction to the laser irradiation. The gas flow behavior and the spectrum and intensity of the laser-induced plasma were influenced by the surrounding gas type and pressure. The appearance of plasma generation affected the surface integrity at the circumference of the drilled hole, and the surface integrity was improved by reducing the pressure.

Okamoto, Yasuhiro; Asako, Kiichi; Nishi, Norio; Sakagawa, Tomokazu; Okada, Akira

2015-03-01

111

Gas transport through nano and micro composites of natural rubber (NR) and their blends with carboxylated styrene butadiene rubber (XSBR) latex membranes  

Microsoft Academic Search

The gas permeability coefficient of nano and micro composites of natural rubber, carboxylated styrene butadiene rubber and 70:30 natural rubber\\/carboxylated styrene butadiene rubber blend membranes has been investigated with special reference to type of filler, gases, filler loading and pressure. The layered silicates such as sodium bentonite and sodium fluorohectorite were the nanofillers used and the conventional micro fillers were

Ranimol Stephen; C. Ranganathaiah; Siby Varghese; Kuruvilla Joseph; Sabu Thomas

2006-01-01

112

Silicon-based sleeve devices for chemical reactions  

DOEpatents

A silicon-based sleeve type chemical reaction chamber that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis.

Northrup, M. Allen (Berkeley, CA); Mariella, Jr., Raymond P. (Danville, CA); Carrano, Anthony V. (Livermore, CA); Balch, Joseph W. (Livermore, CA)

1996-01-01

113

Silicon-based sleeve devices for chemical reactions  

DOEpatents

A silicon-based sleeve type chemical reaction chamber is described that combines heaters, such as doped polysilicon for heating, and bulk silicon for convection cooling. The reaction chamber combines a critical ratio of silicon and silicon nitride to the volume of material to be heated (e.g., a liquid) in order to provide uniform heating, yet low power requirements. The reaction chamber will also allow the introduction of a secondary tube (e.g., plastic) into the reaction sleeve that contains the reaction mixture thereby alleviating any potential materials incompatibility issues. The reaction chamber may be utilized in any chemical reaction system for synthesis or processing of organic, inorganic, or biochemical reactions, such as the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction, which are examples of a synthetic, thermal-cycling-based reaction. The reaction chamber may also be used in synthesis instruments, particularly those for DNA amplification and synthesis. 32 figs.

Northrup, M.A.; Mariella, R.P. Jr.; Carrano, A.V.; Balch, J.W.

1996-12-31

114

Theory for hydrostatic gas journal bearings for micro-electro-mechanical systems  

E-print Network

The goal of the MIT micro-engine project is to develop high-speed rotating Power MEMS (Micro-Electro-Mechanical Systems) using computer chip fabrication technologies. To produce high power (10-50 W) in a small volume (less ...

Liu, Lixian, Ph. D. Massachusetts Institute of Technology

2005-01-01

115

Microfabricated thermal modulator for comprehensive two-dimensional micro gas chromatography: design, thermal modeling, and preliminary testing.  

PubMed

In comprehensive two-dimensional gas chromatography (GC x GC), a modulator is placed at the juncture between two separation columns to focus and re-inject eluting mixture components, thereby enhancing the resolution and the selectivity of analytes. As part of an effort to develop a microGC x microGC prototype, in this report we present the design, fabrication, thermal operation, and initial testing of a two-stage microscale thermal modulator (microTM). The microTM contains two sequential serpentine Pyrex-on-Si microchannels (stages) that cryogenically trap analytes eluting from the first-dimension column and thermally inject them into the second-dimension column in a rapid, programmable manner. For each modulation cycle (typically 5 s for cooling with refrigeration work of 200 J and 100 ms for heating at 10 W), the microTM is kept approximately at -50 degrees C by a solid-state thermoelectric cooling unit placed within a few tens of micrometres of the device, and heated to 250 degrees C at 2800 degrees C s(-1) by integrated resistive microheaters and then cooled back to -50 degrees C at 250 degrees C s(-1). Thermal crosstalk between the two stages is less than 9%. A lumped heat transfer model is used to analyze the device design with respect to the rates of heating and cooling, power dissipation, and inter-stage thermal crosstalk as a function of Pyrex-membrane thickness, air-gap depth, and stage separation distance. Experimental results are in agreement with trends predicted by the model. Preliminary tests using a conventional capillary column interfaced to the microTM demonstrate the capability for enhanced sensitivity and resolution as well as the modulation of a mixture of alkanes. PMID:20556268

Kim, Sung-Jin; Reidy, Shaelah M; Block, Bruce P; Wise, Kensall D; Zellers, Edward T; Kurabayashi, Katsuo

2010-07-01

116

Finesse of silicon-based terahertz Fabry-Perot spectrometer Justin W. Cleary, Robert E. Peale  

E-print Network

. A high finesse Fabry-Perot could be operated in low resonance order to achieve high resolving powerFinesse of silicon-based terahertz Fabry-Perot spectrometer Justin W. Cleary, Robert E. Peale achievable finesse for a recently demonstrated silicon-based scanning Fabry- Perot transmission filter

Peale, Robert E.

117

In-situ formation of nanoparticles within a silicon-based matrix  

DOEpatents

A method for encapsulating nanoparticles with an encapsulating matrix that minimizes aggregation and maintains favorable properties of the nanoparticles. The matrix comprises silicon-based network-forming compounds such as ormosils and polysiloxanes. The nanoparticles are synthesized from precursors directly within the silicon-based matrix.

Thoma, Steven G. (Albuquerque, NM); Wilcoxon, Jess P. (Albuquerque, NM); Abrams, Billie L. (Albuquerque, NM)

2008-06-10

118

A Highly Tunable Silicone-Based Magnetic Elastomer with Nanoscale Homogeneity  

PubMed Central

Magnetic elastomers have been widely pursued for sensing and actuation applications. Silicone-based magnetic elastomers have a number of advantages over other materials such as hydrogels, but aggregation of magnetic nanoparticles within silicones is difficult to prevent. Aggregation inherently limits the minimum size of fabricated structures and leads to non-uniform response from structure to structure. We have developed a novel material which is a complex of a silicone polymer (polydimethylsiloxane-co-aminopropylmethylsiloxane) adsorbed onto the surface of magnetite (?-Fe203) nanoparticles 7–10 nm in diameter. The material is homogenous at very small length scales (< 100 nm) and can be crosslinked to form a flexible, magnetic material which is ideally suited for the fabrication of micro- to nanoscale magnetic actuators. The loading fraction of magnetic nanoparticles in the composite can be varied smoothly from 0 – 50% wt. without loss of homogeneity, providing a simple mechanism for tuning actuator response. We evaluate the material properties of the composite across a range of nanoparticle loading, and demonstrate a magnetic-field-induced increase in compressive modulus as high as 300%. Furthermore, we implement a strategy for predicting the optimal nanoparticle loading for magnetic actuation applications, and show that our predictions correlate well with experimental findings. PMID:22184482

Evans, Benjamin A.; Fiser, Briana L.; Prins, Willem J.; Rapp, Daniel J.; Shields, Adam R.; Glass, Daniel R.; Superfine, R.

2011-01-01

119

Evaluation of micro flat-tube solid-oxide fuel cell modules using simple gas heating apparatus  

NASA Astrophysics Data System (ADS)

Micro flat-tube solid-oxide fuel cell (SOFC) modules consisting of 1 mm thick, 1.2 cm wide micro flat-tube SOFCs, gas manifold, and insulator have been fabricated and evaluated using simple gas heating apparatus. The cell consists of NiO - yttria stabilized zirconia (YSZ) as an anode (flat-tube support), scandia stabilized zirconia (ScSZ) as an electrolyte, gadolinia doped ceria (GDC) for an interlayer, and (La, Sr)(Fe, Co)O3 (LSCF) - GDC as a cathode, which has been fabricated using cost effective extrusion technique and dip-coating technique. The cell has been investigated between 600 and 650 °C operating temperature and showed the power density at 0.75 V of 0.19 and 0.385 W cm-2, respectively. Using the cell, a five and ten-series modules were assembled and stored in insulator with small gas heaters powered by a 24 V power source for start-up. The module successfully operated using hydrogen and methane fuel.

Suzuki, Toshio; Yamaguchi, Toshiaki; Sumi, Hirofumi; Hamamoto, Koichi; Shimada, Hiroyuki; Fujishiro, Yoshinobu

2014-12-01

120

The information of oil and gas micro-seepage in Dongsheng region of inner Mongolia based on the airborne hyperspectral remote sensing image  

NASA Astrophysics Data System (ADS)

The technology of hyper-spectral remote sensing which has higher spatial resolution characteristic, and optimizes the qualification of identifying and extracting salt mines, not only enhances the capacity of natural scenes detection and recognition, but also advances the level of quantitative remote sensing. It has important meaning for using the technology of hyper-spectral remote sensing to quantitative extraction. The paper investigate gas micro-seepage based on the Airborne Hyper-spectral Remote Sensing in Dongsheng of Inner Mongolia on the basis of gas micro-seepage theory using EO-1 Hyperion data collected by Satellite-Borne Sensor which has highest spatial resolution presently in the world. On the basis of data pretreated this paper adopts band math extracted the distribution of oil and gas micro-seepage using diagnostic assimilating spectrum of alteration minerals by the numbers. With eigenvector length model evaluates the research area comprehensive index, oil and gas micro-seepage information model of the research area is established and key regions of oil and gas micro-seepage are confirmed, which offers academic gist for oil and gas resource exploitation of Dongsheng.

Tian, Shu-Fang; Chen, Jian-Ping; Zhou, Mi

2008-11-01

121

Compact polarization rotator for silicon-based slot waveguide structures.  

PubMed

A compact polarization rotator (PR) for silicon-based slot waveguides is proposed, where the slot region including the upper claddings is filled with liquid crystals (LCs). With the anisotropic features of the LCs, the transverse field components of eigenmodes have almost identical amplitudes, leading to a high modal hybridness. As a result, the TE (TM) polarization can be rotated efficiently to the TM (TE) polarization within a short length. The numerical results show that a PR 11.3 ?m in length at an operating wavelength of 1.55 ?m is achieved with an extinction ratio (ER) (insertion loss) of 12.6 (0.22) dB for TE-to-TM and 11.5 (0.30) dB for TM-to-TE. Moreover, the optical bandwidth for TE-to-TM (TM-to-TE) mode must be ?64(?29)??nm to keep the ER over 12 (10) dB. In addition, fabrication tolerances to the structural parameters are investigated, and field evolution along the propagation distance through the PR is also demonstrated. PMID:24787409

Xiao, Jinbiao; Xu, Yin; Wang, Jiayuan; Sun, Xiaohan

2014-04-10

122

Investigation on the heat transfer characteristics during flow boiling of liquefied natural gas in a vertical micro-fin tube  

NASA Astrophysics Data System (ADS)

This paper presents an experimental investigation on the heat transfer characteristics of liquefied natural gas flow boiling in a vertical micro-fin tube. The effect of heat flux, mass flux and inlet pressure on the flow boiling heat transfer coefficients was analyzed. The Kim, Koyama, and two kinds of Wellsandt correlations with different Ftp coefficients were used to predict the flow boiling heat transfer coefficients. The predicted results showed that the Koyama correlation was the most accurate over the range of experimental conditions.

Xu, Bin; Shi, Yumei; Chen, Dongsheng

2014-03-01

123

Development of new method of ?(13)C measurement for trace hydrocarbons in natural gas using solid phase micro-extraction coupled to gas chromatography isotope ratio mass spectrometry.  

PubMed

Compound specific isotope analysis (CSIA) of normal-level hydrocarbons (C1-C4) in natural gas is often successfully used in natural gas origin identification and classification, but little progress so far has been made for trace level hydrocarbons (C5-C14) in natural gas. In this study, we developed a method for rapid analysis of carbon isotopic ratios for trace hydrocarbons in natural gas samples. This method can be described as a combined approach characterized by solid phase micro-extraction (SPME) technique coupled to gas chromatography isotope ratio mass spectrometry (GC/IRMS). In this study, the CAR-PDMS fiber was chosen as the SPME adsorptive material after comparative experiments with other four fibers, and the parameters, including equilibration time, extraction temperature and desorption time, for efficient extraction of trace hydrocarbons were systematically optimized. The results showed the carbon isotopic fractionation was not observed as a function of equilibration time and extraction temperature. And the ?(13)C signatures determined by SPME-GC/IRMS were in good agreement with the known ?(13)C values of C5-C14 measured by GC-IRMS, and the accuracy is generally within ±0.5‰. Five natural gas samples were analyzed using this method, and the ?(13)C values for C5-C14 components were obtained with satisfied repeatability. The SPME-GC/IRMS approach fitted with CAR-PDMS fiber is well suited for the preconcentration of trace hydrocarbons and provides so far the most reliable carbon isotopic analysis for trace compounds in natural gas. PMID:25465020

Li, Zhongping; Wang, Xibin; Li, Liwu; Zhang, Mingjie; Tao, Mingxin; Xing, Lantian; Cao, Chunhui; Xia, Yanqing

2014-11-01

124

Micro-fabricated membrane gas valves with a non-stiction coating deposited by C4F8/Ar plasma  

NASA Astrophysics Data System (ADS)

Micro-fabricated gas valves with C4F8/Ar treatment at the sealing interface are designed, fabricated and characterized to passively control gases in a micro gas analysis system. The check valves form a seal between a polished Si/SiO2 substrate and a smooth polyimide (PI) membrane. The smooth PI membrane touches the SiO2 surface, giving rise to relatively strong van der Waals adhesion, and under humid conditions hydrogen-bonded stiction can occur at the interface between PI and SiO2. To prevent stiction from dominating adhesion, the valve-seat surface was treated with a hydrophobic CFn thin film, which was formed by exposing the surface to C4F8/Ar inductively coupled plasma (ICP) at low power. The valves without a non-stiction coating did not open with inlet pressures up to 210 kPa. With a non-stiction coating, the valves showed an average initial opening pressure of 59.25 kPa. In order to further reduce the opening pressure, 40% of the valve-seat area is reduced. After modification, the average opening pressure is reduced to 32.5 kPa. After the initial opening, the average in-use opening pressure was 16.9 kPa before area modification, and 13.1 kPa after the modification. The valve has been tested up to 10 000 open/close cycles under dry N2 gas flow, and an additional 3000 open/close cycles under humid N2 gas flow. The average forward flow conductance of the valves before modification was 1.1 sccm kPa-1, and the conductance after modification was 1.41 sccm kPa-1. The measured leakage is between 0.0003 and 0.004 sccm up to 35 kPa reverse pressure.

Han, Jeahyeong; Flachsbart, Bruce; Masel, Rich I.; Shannon, Mark A.

2008-09-01

125

Silicon-based microfabricated microbial fuel cell toxicity sensor.  

PubMed

Microbial fuel cells (MFCs) have been used for several years as biosensors for measuring environmental parameters such as biochemical oxygen demand and water toxicity. The present study is focused on the detection of toxic matter using a novel silicon-based MFC. Like other existing toxicity sensors based on MFCs, this device is capable of detecting the variation on the current produced by the cell when toxic compounds are present in the medium. The MFC approach presented in this work aims to obtain a simple, compact and planar device for its further application as a biosensor in the design and fabrication of equipment for toxicity monitoring. It consists on a proton exchange membrane placed between two microfabricated silicon plates that act as current collectors. An array of square 80 ?m × 80 ?m vertical channels, 300 ?m deep, have been defined trough the plates over an area of 6 mm × 6 mm. The final testing assembly incorporates two perspex pieces positioned onto the plates as reservoirs with a working volume of 144 ?L per compartment. The operation of the microdevice as a direct electron transfer MFC has been validated by comparing its performance against a larger scale MFC, run under the same conditions. The device has been tested as a toxicity sensor by setting it at a fixed current while monitoring changes in the output power. A drop in the power production is observed when a toxic compound is added to the anode compartment. The compact design of the device makes it suitable for its incorporation into measurement equipment either as an individual device or as an array of sensors for high throughput processing. PMID:21074397

Dávila, D; Esquivel, J P; Sabaté, N; Mas, J

2011-01-15

126

Nested potassium hydroxide etching and protective coatings for silicon-based microreactors  

NASA Astrophysics Data System (ADS)

We have developed a multilayer, multichannel silicon-based microreactor that uses elemental fluorine as a reagent and generates hydrogen fluoride as a byproduct. Nested potassium hydroxide etching (using silicon nitride and silicon oxide as masking materials) was developed to create a large number of channels (60 reaction channels connected to individual gas and liquid distributors) of significantly different depths (50-650 µm) with sloped walls (54.7° with respect to the (1?0?0) wafer surface) and precise control over their geometry. The wetted areas were coated with thermally grown silicon oxide and electron-beam evaporated nickel films to protect them from the corrosive fluorination environment. Up to four Pyrex layers were anodically bonded to three silicon layers in a total of six bonding steps to cap the microchannels and stack the reaction layers. The average pinhole density in as-evaporated films was 3 holes cm-2. Heating during anodic bonding (up to 350 °C for 4 min) did not significantly alter the film composition. Upon fluorine exposure, nickel films (160 nm thick) deposited on an adhesion layer of Cr (10 nm) over an oxidized silicon substrate (up to 500 nm thick SiO2) led to the formation of a nickel fluoride passivation layer. This microreactor was used to investigate direct fluorinations at room temperature over several hours without visible signs of film erosion.

de Mas, Nuria; Schmidt, Martin A.; Jensen, Klavs F.

2014-03-01

127

Nested potassium hydroxide etching and protective coatings for silicon-based microreactors  

E-print Network

We have developed a multilayer, multichannel silicon-based microreactor that uses elemental fluorine as a reagent and generates hydrogen fluoride as a byproduct. Nested potassium hydroxide etching (using silicon nitride ...

de Mas, Nuria

128

Fabrication of silicon-based shape memory alloy micro-actuators  

NASA Technical Reports Server (NTRS)

Thin film shape memory alloy has been integrated with silicon in a new actuation mechanism for microelectromechanical systems. This paper compares nickel-titanium film with other actuators, describes recent results of chemical milling processes developed to fabricate shape memory alloy microactuators in silicon, and describes simple actuation mechanisms which have been fabricated and tested.

Johnson, A. David; Busch, John D.; Ray, Curtis A.; Sloan, Charles L.

1992-01-01

129

Characterization and Modeling of Segmental Dynamics in Silicone Based Nanocomposites  

SciTech Connect

The addition of nano-particles with novel chemical, optical, or barrier properties further opens the door to the development of so-called multifunctional materials (1). Key to developing robust, tailored composites is a detailed understanding of the structural contributions to the engineering properties of the composite and how they may change with time in harsh service conditions. The segmental dynamics and local order underlie much of the fundamental physics that influence the performance of elastomers and can serve as important diagnostics for reinforcement and other fundamental properties (e.g., network topology, cross-link density, the number and distance between chemical and physical (entanglements) cross-links, the type and volume fraction of filler) and thus provide a route to this fundamental understanding. {sup 1}H MQ-NMR spectroscopy has shown the ability to provide more reliable and quantitative information regarding the elastomer network structure and heterogeneities (2). {sup 1}H MQ-NMR methods allow for the measurement of absolute residual dipolar couplings (<{Omega}{sub d}>) and thus the segmental/cooperative dynamics Thus, the MQ-NMR method allows for the direct measure of network topology and in many cases, filler-particle interactions. The ability of MD methods to uncover structural motifs and dynamics at the atomistic scale is well known. In polymer systems, however, the relationship to bulk material properties can be somewhat tenuous due to often limited number of atoms and short time durations that can be studied. Extending these MD simulations to large assemblies of atoms and extending them to longer times using state of the art computational resources has allowed us to probe some useful relationships. MD provides static and dynamic properties for a collection of particles that allow atomic scale insights that are difficult to gain otherwise. We have been exploiting these methods to characterize the effects of network structure and filler content on a number of silicone based nanocomposite systems. This data is providing improved insight into the structural contributions to the changes in segmental dynamics. Here we provide an overview of our ongoing work toward understanding the influence of the network structure on the physical and chemical properties of advanced composite elastomers, including material performance in severe environments (high temperature, high strains, high radiation fluxes).

Maxwell, R S; Baumann, T; Gee, R; Maiti, A; Patel, M; Lewicki, J

2009-03-27

130

Recent Progress in Silicon-Based MEMS Field Emission Thrusters  

NASA Astrophysics Data System (ADS)

The Indium Field Emission Thruster (In-FET) is a highly characterized and space-proven device based on space-qualified liquid metal ion sources. There is also extensive experience with liquid metal ion sources for high-brightness semiconductor fabrications and inspection Like gridded ion engines, In-FETs efficiently accelerate ions through a series of high voltage electrodes. Instead of a plasma discharge to generate ions, which generates a mixture of singly and doubly charged ions as well as neutrals, indium metal is melted (157°C) and fed to the tip of a capillary tube where very high local electric fields perform more-efficient field emission ionization, providing nearly 100% singly charged species. In-FETs do not have the associated losses or lifetime concerns of a magnetically confined discharge and hollow cathode in ion thrusters. For In-FETs, propellant efficiencies ˜100% stipulate single-emitter currents ?10?A, perhaps as low as 5?A of current. This low emitter current results in ?0.5 W/emitter. Consequently, if the In-FET is to be used for future Human and Robotic missions under President Bush's Exploration plan, a mechanism to generate very high power levels is necessary. Efficient high-power operation requires many emitter/extractor pairs. Conventional fabrication techniques allow 1-10 emitters in a single module, with pain-staking precision required. Properly designed and fabricated In-FETs possess electric-to-jet efficiency >90% and a specific mass <0.25 kg/kWe. MEMS techniques allow reliable batch processing with ˜160,000 emitters in a 10×10-cm array. Developing a 1.5kW 10×10-cm module is a necessary stepping-stone for >500 kWe systems where groups of 9 or 16 modules, with a single PPU/feed system, form the building blocks for even higher-power exploration systems. In 2003, SNL and ARCS produced a MEMS-based In-FET 5×5 emitter module with individually addressable emitter/extractor pairs on a 15×15mm wafer. The first MEMS thruster prototype has already been tested to demonstrate the proof-of-concept in laboratory-scale testing. In this paper we discuss progress that has been achieved in the past year on fabricating silicon-based MEMS In-FETs.

Lenard, Roger X.; Kravitz, Stanley H.; Tajmar, Martin

2005-02-01

131

Start-up and Self-sustain Test of 500 W Ultra-Micro Gas Turbine Generator  

NASA Astrophysics Data System (ADS)

This paper provides the performance test for start-up and self-sustaining of 500W ultra-micro gas turbine (UMGT) generator. Each component of UMGT, a centrifugal compressor, a radial turbine, an annular combustor and a shaft is already designed, manufactured and tested to meet design requirements in previous researches. However, they are not tested to work in an integrate system. Currently, integrated test unit with a compressor, a combustor and a turbine, is developed to find the proper condition of start-up and self-sustain. Ignition sequence depending on rotating speed is designed. Performance test for start-up and self-sustain is designed based on the ignition possible condition. An air impingement starter and a hot bulb inginer are applied. LPG is used as main fuel.

Seo, Jeong Min; Park, Jun Young; Seog Choi, Bum

2013-12-01

132

Solidphase micro-extraction–gas chromatography–(tandem) mass spectrometry as a tool for pesticide residue analysis in water samples at high sensitivity and selectivity with confirmation capabilities  

Microsoft Academic Search

Gas chromatography–mass spectrometry (GC–MS) has been widely applied for pesticide monitoring because of its high sensitivity and specificity and for the potential of multi-residue and multi-class analysis. An analytical procedure was developed for the determination of pesticide multi-residues in water samples combining solid-phase micro-extraction (SPME) and gas chromatography–ion trap mass spectrometry. For SPME extraction a poly(dimethylsiloxane)–divinylbenzene coated fibre was selected

C Gonçalves; M. F Alpendurada

2004-01-01

133

Numerical analysis of gas separator with thermal transpiration in micro channels II  

NASA Astrophysics Data System (ADS)

A membrane gas separator which operates with only a small temperature difference across a membrane is designed, and its capability is numerically proved. The separator system consists of three Knudsen pumps - a motionless pump that utilizes the thermal transpiration of the rarefied gas. Each pump is composed of a porous membrane and one channel along each of the two surfaces of the membrane. Two of the pumps induce a variation of mole fraction using a combination of the thermal transpiration and pressure driven flow through the membrane, and the other one provides the former two pumps with a required pressure difference. This paper reports the first numerical calculations that demonstrate a neon-argon binary gas mixture can be separated into pure neon gas and argon gas with the proposed design. The temperature difference is no more than 90 K, and the total length of the membrane is ˜ 15 cm at standard ambient temperature and pressure. The production rate of the separator is proportional to the width of the membrane. For example, when the width is 10 cm, the flow rates of the product gases are 0.8 sccm for argon and 1.9 sccm for neon.

Nakaye, Shoeji; Sugimoto, Hiroshi

2014-12-01

134

Silicon-based semimetals and semiconductors for thermoelectric applications  

NASA Astrophysics Data System (ADS)

The direct conversion between heat and electricity can be achieved by thermoelectric devices. Thus, thermoelectricity is considered as not only an environmentally friendly substitute for compressor-based refrigerators but also a promising energy solution to harvest waste heat. State-of-the-art thermoelectric materials are often comprised of expensive tellurium or germanium elements and hence are hardly suitable for mass production. The silicon-based thermoelectrics, e.g. semimetallic CoSi and semiconducting beta -FeSi2 materials we study here, are composed of abundant elements in nature. They are also chemically stable, non-toxic, and mechanically robust. Despite the above benefits, they exhibit relatively lower efficiencies compared to state-of-the-art materials. In this dissertation, we have intended to understand the thermal and electrical transport in these materials and enhance their thermoelectric performance. CoSi possesses one of the highest power factors among thermoelectrics due to the sharp features around the Fermi level in its electronic density of states. In order to improve the performance, the effects of p-type dopants, isoelectronic substitutions, n-type dopants, and double doping were systematically studied for arc-melted CoSi samples. The results show that p-type dopants like iron and gallium and n-type dopants like nickel and palladium deteriorate the electrical properties due to the introduction of excess holes and electrons, respectively. Boron and platinum have very limited solubility in CoSi and the segregated impurity phases at grain boundaries are helpful to improve the electrical properties. The isoelectronic substitutions influence the power factor slightly; however, they result in a drastic decrease in the lattice thermal conductivity and hence an enhancement in the figure of merit. In addition, CoSi samples prepared by powder processing were investigated to further reduce the lattice thermal conductivity. Unfortunately, all the consolidated samples show worse performance than the arc-melted CoSi. beta-FeSi2 is one of the most cost-efficient thermoelectric materials. Its thermoelectric performance can be tuned by cobalt doping and the highest figure of merit is close to 0.4 at 1000 K. Grain size reduction was also used to reduce the lattice thermal conductivity. However, no improvement has been obtained yet. SiC nanoparticles were dispersed into beta-FeSi2 matrix to form a composite structure. With addition of the nanoparticles, the thermal conductivity is slightly decreased associated with a decrease in the power factor. Although the figure of merit is less than that of some Te-based materials, beta-FeSi2-based thermoelectrics may be suitable in large-scale applications where material abundance and cost are concerns.

Sun, Hui

135

Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High-T and Dynamic Gas Pressure in Harsh Environments  

SciTech Connect

This is the final report for the program “Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High Temperature and Dynamic Gas Pressure in Harsh Environments”, funded by NETL, and performed by Missouri University of Science and Technology, Clemson University and University of Cincinnati from October 1, 2009 to September 30, 2014. Securing a sustainable energy economy by developing affordable and clean energy from coal and other fossil fuels is a central element to the mission of The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). To further this mission, NETL funds research and development of novel sensor technologies that can function under the extreme operating conditions often found in advanced power systems. The main objective of this research program is to conduct fundamental and applied research that will lead to successful development and demonstration of robust, multiplexed, microstructured silica and single-crystal sapphire fiber sensors to be deployed into the hot zones of advanced power and fuel systems for simultaneous measurements of high temperature and gas pressure. The specific objectives of this research program include: 1) Design, fabrication and demonstration of multiplexed, robust silica and sapphire fiber temperature and dynamic gas pressure sensors that can survive and maintain fully operational in high-temperature harsh environments. 2) Development and demonstration of a novel method to demodulate the multiplexed interferograms for simultaneous measurements of temperature and gas pressure in harsh environments. 3) Development and demonstration of novel sapphire fiber cladding and low numerical aperture (NA) excitation techniques to assure high signal integrity and sensor robustness.

Xiao, Hai; Tsai, Hai-Lung; Dong, Junhang

2014-09-30

136

Design and part-load performance of a hybrid system based on a solid oxide fuel cell reactor and a micro gas turbine  

Microsoft Academic Search

This paper addresses the design and off-design analysis of a hybrid system (HS) based on the coupling of a recuperated micro gas turbine (MGT) with a high temperature solid oxide fuel cell (SOFC) reactor. The SOFC reactor model is presented and discussed, taking into account the influence of the reactor lay-out, the current density, the air utilisation factor, the cell

P. Costamagna; L. Magistri; A. F. Massardo

2001-01-01

137

Original Research Article Influence of anodic gas recirculation on solid oxide fuel cells in a micro  

E-print Network

-oxide fuel cells systems are ideally suited to operate on hydrocarbons, directly converting fuelOriginal Research Article Influence of anodic gas recirculation on solid oxide fuel cells January 2014 Revised 23 July 2014 Accepted 5 August 2014 Keywords: SOFC Steam reforming Fuel processing

Nielsen, Mads Pagh

138

Gas Detection with a Micro FTIR Spectrometer in the MIR Region  

Microsoft Academic Search

We report on the application of a silicon micromachined lamellar grating interferometer in a Fourier Transform Infrared (FTIR) spectrometer for the detection of gases in the mid-infrared (MIR) region. The FTIR spectrometer was equipped with MIR optical fibers for light coupling. Gas measurements in the MIR region were focused on specific gases (CO2, CH4) in order to determine the limit

T. Scharf; D. Briand; S. Bühler; O. Manzardo; H. P. Herzig; N. F. de Rooij

2009-01-01

139

MACRO- MICRO-PURGE SOIL GAS SAMPLING METHODS FOR THE COLLECTION OF CONTAMINANT VAPORS  

EPA Science Inventory

Purging influence on soil gas concentrations for volatile organic compounds (VOCs), as affected by sampling tube inner diameter and sampling depth (i.e., dead-space purge volume), was evaluated at different field sites. A macro-purge sampling system consisted of a standard hollo...

140

Gas flows in rectangular microchannels and a capacitive micro flow sensor using differential pressure  

Microsoft Academic Search

Flows often behave differently at small length scales than macroscopic intuition. These behavior changes can have serious implications for microfluidic devices. In gas flows, these differences are rarefaction and compressibility, among others. The goal of this thesis is to derive the theoretical mass flow rate and pressure distribution in rectangular microchannels considering those differences. These results are applied to designing

Jaesung Jang

2004-01-01

141

High-speed bearings for micro gas turbines: stability analysis of foil bearings  

Microsoft Academic Search

Mesoscopic or microscopic gas turbines can be an interesting replacement for batteries as mobile energy supplies. A difficult consequence of small-scale turbomachinery is an increased rotor speed, in the order of 500 000 rpm and higher, turning bearing design into a challenging task. Air bearings are the only bearing type able to withstand the severe conditions of high speed and

P. Vleugels; T. Waumans; J. Peirs; F. Al-Bender; D. Reynaerts

2006-01-01

142

Development of High Precision Metal Micro-Electro-Mechanical-Systems Column for Portable Surface Acoustic Wave Gas Chromatograph  

NASA Astrophysics Data System (ADS)

In the field of environmental measurement and security, a portable gas chromatograph (GC) is required for the on-site analysis of multiple hazardous gases. Although the gas separation column has been downsized using micro-electro-mechanical-systems (MEMS) technology, an MEMS column made of silicon and glass still does not have sufficient robustness and a sufficiently low fabrication cost for a portable GC. In this study, we fabricated a robust and inexpensive high-precision metal MEMS column by combining diffusion-bonded etched stainless-steel plates with alignment evaluation using acoustic microscopy. The separation performance was evaluated using a desktop GC with a flame ionization detector and we achieved the high separation performance comparable to the best silicon MEMS column fabricated using a dynamic coating method. As an application, we fabricated a palm-size surface acoustic wave (SAW) GC combining this column with a ball SAW sensor and succeeded in separating and detecting a mixture of volatile organic compounds.

Iwaya, Takamitsu; Akao, Shingo; Sakamoto, Toshihiro; Tsuji, Toshihiro; Nakaso, Noritaka; Yamanaka, Kazushi

2012-07-01

143

Stresa, Italy, 26-28 April 2006 RECENT DEVELOPMENTS IN MEMS-BASED MICRO FUEL CELLS  

E-print Network

Stresa, Italy, 26-28 April 2006 RECENT DEVELOPMENTS IN MEMS-BASED MICRO FUEL CELLS Tristan Pichonat ABSTRACT Micro fuel cells (µ-FC) represent promising power sources for portable applications. Today, one describes the latest developments of a new porous silicon- based miniature fuel cell. Using a silane grafted

Boyer, Edmond

144

A programmable palm-size gas analyzer for use in micro-autonomous systems  

NASA Astrophysics Data System (ADS)

Gas analysis systems having small size, low power, and high selectivity are badly needed for defense (detection of explosives and chemical warfare agents), homeland security, health care, and environmental applications. This paper presents a palm-size gas chromatography system having analysis times of 5-50sec, detection limits less than 1ppb, and an average power dissipation less than one watt. It uses no consumables. The three-chip fluidic system consists of a preconcentrator, a 25cm-3m separation column, and a chemi-resistive detector and is supported by a microcomputer and circuitry for programmable temperature control. The entire system, including the mini-pump and battery, occupies less than 200cc and is configured for use on autonomous robotic vehicles.

Gordenker, Robert J. M.; Wise, Kensall D.

2012-06-01

145

Thermal balance analysis of a micro-thermoelectric gas sensor using catalytic combustion of hydrogen.  

PubMed

A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Q(catalyst) required for 1 mV of ?V(gas) was calculated to be 46.1 ?W. Using these parameters, we find from simulations for the device performance that the expected Q(catalyst) for 200 and 1,000 ppm H? was 3.69 ?W and 11.7 ?W, respectively. PMID:24451468

Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

2014-01-01

146

Silicon-based two dimensional tunable photonic crystal devices  

NASA Astrophysics Data System (ADS)

Photonic crystal devices are capable of controlling the flow of light in ultra compact scales. Silicon two dimensional (2D) nanostructures are well developed in the integrated circuit (IC) industry. Silicon is transparent to infrared light and has high refractive index which makes silicon an ideal material for photonic crystals in the infrared spectrum. Silicon 2D photonic crystals have attracted a lot of interest for showing feasibility of photonic integrated circuits. Typical photonic crystal devices are waveguides or cavities, which were developed as mostly passive devices. Various methods can be used to make photonic crystals tunable. In this work, silicon 2D tunable photonic crystal devices are studied using thermo-optic effect of silicon. In addition, this research presents one-step lithography to form micro and nano combined structures for the two-dimensional slab photonic crystals.

Choi, Kyung-Hak

147

Tin oxide gas sensor fabricated using CMOS micro-hotplates and in-situ processing  

Microsoft Academic Search

A monolithic tin oxide (SnO2) gas sensor realized by commercial CMOS foundry fabrication (MOSIS) and postfabrication processing techniques is reported. The device is composed of a sensing film that is sputter-deposited on a silicon micromachined hotplate. The fabrication technique requires no masking and utilizes in situ process control and monitoring of film resistivity during film growth. Microhotplate temperature is controlled

John S. Suehle; Richard E. Cavicchi; Michael Gaitan; Steve Semancik

1993-01-01

148

Effect of boundary conditions on the performances of gas-lubricated micro journal bearing  

NASA Astrophysics Data System (ADS)

As significant components of micromechanics, gas-lubricated microbearings are more prevalent for their special advantages than other types. The fluid dynamics of the microbearing is different from their larger cousins due to the noncontinuum effect and surface-dominated effect, which may make the Navier-Stokes equations invalid. In this paper, by considering the accommodation coefficients on journal (? i) and that on bearing (? o) separately, the microbearings with different bearing numbers under the assumption of large L/D (length to diameter) are simulated using direct simulation Monte Carlo (DSMC) program incorporated with a Volume-CAD software. The diffuse reflection model and Cercignani-Lampis-Lord (CLL) model are applied to model the molecule-surface interaction. The flow field characteristics, as well as the performances of gas-lubricated journal bearings including load-carrying capacity, attitude angle and bearing drag are obtained. The results reveal that ?i and ?o have different effects to flow field characteristics and bearing performances. The bearing number has significantly impact on the bearing performances. The method developed in this paper would be very useful for designing and evaluating the gas-lubricated journal microbearing.

Wang, Sheng; Lei, Kangbin; Luo, Xilian; Gu, Zhaolin; Kiwamu, Kase

2010-06-01

149

Laboratory simulations of fluid/gas induced micro-earthquakes: application to volcano seismology.  

NASA Astrophysics Data System (ADS)

Understanding different seismic signals recorded in active volcanic regions allows geoscientists to derive insight into the processes that generate them. A key type is known as Low Frequency or Long Period (LP) event, generally understood to be generated by different fluid types resonating in cracks and faults. The physical mechanisms of these signals have been linked to either resonance/turbulence within fluids, or as a result of fluids ‘sloshing’ due to a mixture of gas and fluid being present in the system. Less well understood, however, is the effect of the fluid type (phase) on the measured signal. To explore this, we designed an experiment in which we generated a precisely controlled liquid to gas transition in a closed system by inducing rapid decompression of fluid-filled fault zones in a sample of basalt from Mt. Etna Volcano, Italy. We find that fluid phase transition is accompanied by a marked frequency shift in the accompanying microseismic dataset that can be compared to volcano seismic data. Moreover, our induced seismic activity occurs at pressure conditions equivalent to hydrostatic depths of 200 to 750 meters. This is consistent with recently measured dominant frequencies of LP events and with numerous models.

Benson, Philip; Vinciguerra, Sergio; Nasseri, Mohamed; Young, R.

2014-11-01

150

Toward a Micro Gas Chromatograph/Mass Spectrometer (GC/MS) System  

NASA Technical Reports Server (NTRS)

Miniature mass filters (e.g., quadrupoles, ion traps) have been the subject of several miniaturization efforts. A project is currently in progress at JPL to develop a miniaturized Gas Chromatograph/Mass Spectrometer (GC/MS) system, incorporating and/or developing miniature system components including turbomolecular pumps, scroll type roughing pump, quadrupole mass filter, gas chromatograph, precision power supply and other electronic components. The preponderance of the system elements will be fabricated using microelectromechanical systems (MEMS) techniques. The quadrupole mass filter will be fabricated using an X-ray lithography technique producing high precision, 5x5 arrays of quadrupoles with pole lengths of about 3 mm and a total volume of 27 cubic mm. The miniature scroll pump will also be fabricated using X-ray lithography producing arrays of scroll stages about 3 mm in diameter. The target detection range for the mass spectrometer is 1 to 300 atomic mass units (AMU) with are solution of 0.5 AMU. This resolution will allow isotopic characterization for geochronology, atmospheric studies and other science efforts dependant on the understanding of isotope ratios of chemical species. This paper will discuss the design approach, the current state-of-the art regarding the system components and the progress toward development of key elements. The full system is anticipated to be small enough in mass, volume and power consumption to allow in situ chemical analysis on highly miniaturized science craft for geochronology, atmospheric characterization and detection of life experiments applicable to outer planet roadmap missions.

Wiberg, D. V.; Eyre, F. B.; Orient, O.; Chutjian, A.; Garkarian, V.

2001-01-01

151

Modeling Transport in Gas Chromatography Columns for the Micro-ChemLab  

SciTech Connect

The gas chromatography (GC) column is a critical component in the microsystem for chemical detection ({mu}ChemLab{trademark}) being developed at Sandia. The goal is to etch a meter-long GC column onto a 1-cm{sup 2} silicon chip while maintaining good chromatographic performance. Our design strategy is to use a modeling and simulation approach. We have developed an analytical tool that models the transport and surface interaction process to achieve an optimized design of the GC column. This analytical tool has a flow module and a separation module. The flow module considers both the compressibility and slip flow effects that may significantly influence the gas transport in a long and narrow column. The separation module models analyte transport and physico-chemical interaction with the coated surface in the GC column. It predicts the column efficiency and performance. Results of our analysis will be presented in this paper. In addition to the analytical tool, we have also developed a time-dependent adsorption/desorption model and incorporated this model into a computational fluid dynamics (CFD) code to simulate analyte transport and separation process in GC columns. CFD simulations can capture the complex three-dimensional flow and transport dynamics, whereas the analytical tool cannot. Different column geometries have been studied, and results will be presented in this paper. Overall we have demonstrated that the modeling and simulation approach can guide the design of the GC column and will reduce the number of iterations in the device development.

ADKINS,DOUGLAS R.; FRYE-MASON,GREGORY CHARLES; HUDSON,MARY L.; KOTTENSTETTE,RICHARD; MATZKE,CAROLYN M.; SALINGER,ANDREW G.; SHADID,JOHN N.; WONG, CHUNGNIN CHANN

1999-09-01

152

Hybrid preconcentrator/focuser module for determinations of explosive marker compounds with a micro-scale gas chromatograph.  

PubMed

This article describes the development and characterization of a partially selective preconcentrator/focuser (PCF) module for a field-portable micro-scale gas chromatograph (?GC) designed to rapidly determine trace levels of two vapor-phase markers of the explosive trinitrotoluene (TNT): 2,3-dimethyl-2,3-dinitrobutane (DMNB) and 2,4-dinitrotoluene (2,4-DNT). The PCF module has three primary components. The first is a high-volume sampler, comprising a resistively-heated 6-cm long stainless steel tube packed with tandem beds of the graphitized carbons Carbopack B (C-B, 30 mg) and Carbopack Y (C-Y, 15 mg), which traps the markers but permits more volatile interferences to pass through largely unretained. The second component is a microfocuser (?F), comprising a 4.2×9.8 mm Si chip containing a deep-reactive-ion-etched (DRIE) cavity packed with 2mg of C-B, a Pyrex cap, integrated heaters, and etched fluidic channels. The third component is a commercial polymer-membrane filter used as a pre-trap to remove particles and adsorbed low volatility interferences. Markers captured in the sampler are thermally desorbed and transferred to the ?F, and then thermally desorbed/injected from the ?F into a downstream separation (micro)column and detected. Scrubbed ambient air is used as carrier gas. The adsorbent capacities, baseline temperatures, sampling and desorption flow rates, and heating profiles were optimized for each PCF module component while minimizing the analysis time. An overall transfer efficiency of 86% was achieved at marker concentrations of ~0.2-2.6 ppb. In the final configuration the PCF module requires just 60s to collect a 1-L sample (3 L/min), focus (40 mL/min), and inject the markers (3 mL/min), producing half-maximum injection peak widths of ~2 and 5 s, and preconcentration factors of 4500 and 1800, for DMNB and 2,4-DNT, respectively. PMID:23357747

Serrano, Gustavo; Sukaew, Thitiporn; Zellers, Edward T

2013-03-01

153

Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen-containing species in chemically reactive, high temperature environments. For fast and stable sensor response measurements, a gate activation process is required. Activation of all sensors took place by switching back and forth between oxidizing (1.0% oxygen in nitrogen) and reducing (10% hydrogen in nitrogen) gases for several hours at a sensor temperature {ge}620 C. All 52 devices on the sensor chip were activated simultaneously by flooding the entire chip with gas. The effects of activation on surface morphology and structure of Pt gates before and after activation were investigated. The optical images obtained from Pt gates demonstrated a clear transition from a smooth and shiny surface to a grainy and cloudy surface morphology. XRD scans collected from Pt gates suggest the presence of an amorphous layer and species other than Pt (111) after activation. The reliability of the gate insulator of our metal-oxide-SiC sensors for long-term device operation at 630 C was studied. We find that the dielectric is stable against breakdown due to electron injection from the substrate with gate leakage current densities as low at 5nA/cm{sup 2} at 630 C. We also designed and constructed a new nano-reactor capable of high gas flow rates at elevated pressure. Our reactor, which is a miniature version of an industrial reactor, is designed to heat the flowing gas up to 700 C. Measurements in ultrahigh vacuum demonstrated that hydrogen sulfide readily deposits sulfur on the gate surface, even at the very high hydrogen/hydrogen sulfide ratios (10{sup 3}-10{sup 5}) expected in applications. Once deposited, the sulfur adversely affects sensor response, and could not be removed by exposure to hydrogen at the temperatures and pressures accessible in the ultrahigh vacuum experiments. Oxygen exposures, however, were very effective at removing sulfur, and the device performance after sulfur removal was indistinguishable from performance before exposure to H{sub 2}S.

Ruby N. Ghosh; Reza Loloee; Roger G. Tobin; Yung Ho Kahng

2006-04-01

154

Heterogeneous metal-oxide nanowire micro-sensor array for gas sensing  

NASA Astrophysics Data System (ADS)

Vanadium oxide, manganese oxide, tungsten oxide, and nickel oxide nanowires were investigated for their applicability as chemiresistive gas sensors. Nanowires have excellent surface-to-volume ratios which yield higher sensitivities than bulk materials. Sensing elements consisting of these materials were assembled in an array to create an electronic nose platform. Dielectrophoresis was used to position the nanomaterials onto a microfabricated array of electrodes, which was subsequently mounted onto a leadless chip carrier and printed circuit board for rapid testing. Samples were tested in an enclosed chamber with vapors of acetone, isopropanol, methanol, and aqueous ammonia. The change in resistance of each assembly was measured. Responses varied between nanowire compositions, each demonstrating unique and repeatable responses to different gases; this enabled direct detection of the gases from the ensemble response. Sensitivities were calculated based on the fractional resistance change in a saturated environment and ranged from 6 × 10-4 to 2 × 10-5%change ppm-1.

DeMeo, Dante; MacNaughton, Sam; Wang, Zhilong; Zhang, Xinjie; Sonkusale, Sameer; Vandervelde, Thomas E.

2014-04-01

155

Thermal Balance Analysis of a Micro-Thermoelectric Gas Sensor Using Catalytic Combustion of Hydrogen  

PubMed Central

A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Qcatalyst required for 1 mV of ?Vgas was calculated to be 46.1 ?W. Using these parameters, we find from simulations for the device performance that the expected Qcatalyst for 200 and 1,000 ppm H2 was 3.69 ?W and 11.7 ?W, respectively. PMID:24451468

Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

2014-01-01

156

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 22, NO. 1, JANUARY 1, 2010 21 Silicon-Based Thermo-Optically Tunable  

E-print Network

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 22, NO. 1, JANUARY 1, 2010 21 Silicon-Based ThermoFarlane, and Jeong-Bong Lee Abstract--We report an extremely compact (30 m 7 m) silicon-based 2-D thermo) with transverse-magnetic-like polarization light. A honeycomb lattice array of high index silicon rods with 340 nm

Lee, Jeong-Bong

157

A Comparative Efficiency Study of Silicon-based Solid State Transformers  

E-print Network

A Comparative Efficiency Study of Silicon-based Solid State Transformers Hengsi Qin and Jonathan W of power flow. However, they are not as efficient as traditional 60 Hz transformers because of the presence Terms--Solid State Transformer, Efficiency, Soft Switch- ing I. INTRODUCTION Power electronic converter

Kimball, Jonathan W.

158

Local Heating of Discrete Droplets Using Magnetic Porous Silicon-Based Photonic Crystals  

E-print Network

Local Heating of Discrete Droplets Using Magnetic Porous Silicon-Based Photonic Crystals Ji-Ho Park (FRET). The magnetic porous Si microparticles were prepared as photonic crystals, containing spectral surrounding the experiment) generates heat in the superpara- magnetic particles that can raise the temperature

Bhatia, Sangeeta

159

Surface adhesion between hexagonal boron nitride nanotubes and silicon based on lateral force microscopy  

Microsoft Academic Search

This study presents the surface adhesion between hexagonal boron nitride nanotube (BNNT) and silicon based on lateral manipulation in an atomic force microscope (AFM). The BNNT was mechanically manipulated by the lateral force of an AFM pyramidal silicon probe using the scan mechanism in the imaging mode. With a controlled normal force of the AFM probe and the lateral motion,

Jung-Hui Hsu; Shuo-Hung Chang

2010-01-01

160

Effect of Nanocrystalline Diamond Coatings on Micro-End Milling  

Microsoft Academic Search

The growing interest in high precision machining to fabricate miniaturized parts for medical devices, micro-satellites, and the optical industry with meso-scale machine tool systems (mMTs) requires high-performance micro-end mills with diameters ranging from 10 to 500 microns. This technology complements standard silicon-based microfabrication proc- esses with its ability to directly produce true 3D structures with high accuracy, low cost, and

Patrick Heaney; Chris Torres; Anirudha Sumant; Robert W. Carpick; Frank Pfefferkorn

161

Quadruple-junction thin-film silicon-based solar cells with high open-circuit voltage  

NASA Astrophysics Data System (ADS)

We have fabricated a-SiOx:H/a-Si:H/nc-Si:H/nc-Si:H quadruple-junction thin-film silicon-based solar cells (4J TFSSCs) to obtain high spectral utilization and high voltages. By processing the solar cells on micro-textured superstrates, extremely high open-circuit voltages for photovoltaic technology based on thin-film silicon alloys up to 2.91 V have been achieved. Optical simulations of quadruple-junction solar cells using an advanced in-house model are a crucial tool to effectively tackle the challenging task of current matching among the individual sub-cells in such devices. After optimizing the optical design of the device and the absorber thicknesses, an energy conversion efficiency of 11.4% has been achieved. The open-circuit voltage, short-circuit current density, and fill factor were 2.82 V, 5.49 mA/cm2, and 73.9%, respectively. Based on this demonstration, strategies for further development of highly efficient 4J TFSSCs are proposed.

Si, Fai Tong; Kim, Do Yun; Santbergen, Rudi; Tan, Hairen; van Swaaij, René A. C. M. M.; Smets, Arno H. M.; Isabella, Olindo; Zeman, Miro

2014-08-01

162

Silicon Carbide Micro-devices for Combustion Gas Sensing under Harsh Conditions  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device, Pt/SiO{sub 2}/SiC that can detect hydrogen-containing species in chemically reactive, high temperature (600 C) environments. We demonstrate that the device can be used as a hydrogen monitor in syngas applications of common interferants as well as sulfur and water vapor. These measurements were made in the Catalyst Screening Unit at NETL, Morgantown under atmospheric conditions. The sensor response to hydrogen gas at 350 C is 240 mV/decade, this is significantly higher than the device response to room temperature gas or that predicted from vacuum chamber studies. The enhanced catalytic activity of the platinum sensing film under energy plant operating conditions was investigated via AFM, x-ray diffraction, TEM and x-ray photoelectron spectroscopy. Our characterization indicated that exposure to high temperature gases significantly modifies the morphology of the Pt catalytic film and the Pt/SiO{sub 2} interfacial region, which we tentatively attribute to the enhanced hydrogen sensitivity of the sensing film. A model for the hydrogen/oxygen response of the SiC device under atmospheric conditions was developed. It is based on two independent phenomena: a chemically induced shift in the metal-semiconductor work function difference and the passivation/creation of charged states at the SiO{sub 2}-SiC interface. The optimum operating set point for the SiC sensor with respect to response time and long term reliability was determined to be close to mid-gap. Ultrahigh vacuum (UHV) techniques were used to investigate the effects of sulfur contamination on the Pt gate. Exposure to hydrogen sulfide, even in the presence of hydrogen or oxygen at partial pressures of 20-600 times greater than the H2S level, rapidly coated the gate with a monolayer of sulfur. Although hydrogen exposure could not remove the adsorbed sulfur, oxygen was effective at removing sulfur with no evidence of irreversible changes in device behavior. The role of oxygen in the functioning of the SiC sensors was also investigated. All of the results are consistent with oxygen acting through its surface reactions with hydrogen, including the need for oxygen to reset the device to a fully hydrogen-depleted state and competition between hydrogen oxidation and hydrogen diffusion to metal/oxide interface sites. A strong sensor response to the unsaturated linear hydrocarbon propene (C{sub 3}H{sub 6}) was observed.

Ruby Ghosh; Reza Loloee; Roger Tobin

2008-09-30

163

SILICON CARBIDE MICRO-DEVICES FOR COMBUSTION GAS SENSING UNDER HARSH CONDITIONS  

SciTech Connect

A sensor based on the wide bandgap semiconductor, silicon carbide (SiC), has been developed for the detection of combustion products in power plant environments. The sensor is a catalytic gate field effect device that can detect hydrogen containing species in chemically reactive, high temperature environments. For these capacitive sensors we have determined that the optimum sensor operating point in terms of sensor lifetime and response time is at midgap. Detailed measurements of the oxide leakage current as a function of temperature were performed to investigate the high temperature reliability of the devices. In addition, robust metallization and electrical contacting techniques have been developed for device operation at elevated temperatures. To characterize the time response of the sensor responses in the millisecond range, a conceptually new apparatus has been built. Using laser induced fluorescence imaging techniques we have shown that the gas underneath the sensor can be completely exchanged with a time constant under 1 millisecond. Ultrahigh vacuum studies of the surface chemistry of the platinum gate have shown that sensor deactivation by adsorbed sulfur is a possible problem. Investigations on the chemical removal of sulfur by catalytic oxidation or reduction are continuing.

Ruby N. Ghosh; Peter Tobias; Roger G. Tobin

2004-10-01

164

Miniaturized GC/MS instrumentation for in situ measurements: micro gas chromatography coupled with miniature quadrupole array and paul ion trap mass spectrometers  

NASA Technical Reports Server (NTRS)

Miniaturized chemical instrumentation is needed for in situ measurements in planetary exploration and other spaceflight applications where factors such as reduction in payload requirements and enhanced robustness are important. In response to this need, we are 'continuing to develop miniaturized GC/MS instrumentation which combines chemical separations by gas chromatography (GC) with mass spectrometry (MS) to provide positive identification of chemical compounds in complex mixtures of gases, such as those found in the International Space Station's cabin atmosphere. Our design approach utilizes micro gas chromatography components coupled with either a miniature quadrupole mass spectrometer array (QMSA) or compact, high-resolution Paul ion trap.

Holland, P.; Chutjian, A.; Darrach, M.; Orient, O.

2002-01-01

165

Positron annihilation studies of silicon-based materials  

NASA Astrophysics Data System (ADS)

Positron Annihilation Spectroscopy (PAS) is used as a defect-profiling tool in the characterization of Si-based materials. PAS, in conjunction with variable energy positron beams, is a non-destructive depth-profiling probe, ideally suited for studying thin films, multi-layered structures, and buried interfaces. Its sensitivity to open-volume defects covers a wide range of defect sizes and concentrations, and surpasses that of most other techniques. This dissertation presents PAS investigations of electrical, chemical and mechanical properties of a number of advanced materials for future use by the semiconductor industry. Among the subjects of this work are: hydrogenated amorphous silicon (a-Si:H) for use in solar cells and flat-panel displays; low dielectric constant materials (low-k) for interlayer dielectrics; and thin-gate transistors, focusing on the defects at the Si/SiO 2 interface, which limit the device reliability. Results from extensive research on various possibilities to enhance the PAS capability by increasing its efficiency are presented in the appendices. The recognition of different dangling bond defects for low defect densities is achieved in these first PAS studies of void-free a-Si:H. Direct evidence of the existence of dopant-defect complexes is obtained for the first time. This research lays the foundation for future studies of the role of the impurities in light- and thermal degradation of a-Si:H PAS was applied to the characterization of porous low-k dielectrics. The annihilation observables are correlated with the dielectric properties of the material and their preparation conditions. PAS is the only non-destructive local k-probe, and the only tool for measuring void densities and sizes. The method is also sensitive to the chemical environment of the voids, seen during oxidation, water absorption, and forming gas anneal. Industrial research, partially based on these results, is currently in progress at IBM. A decade-old controversy, involving different models of defect states at Si/SiO2 interfaces, has been resolved. The two-defect model was confirmed and previous results were reevaluated. Research in this area will promote the use of PAS as an on-line diagnostic tool in the manufacturing of integrated circuits.

Petkov, Mihail Petkov

166

Some recent advances in multi-material micro- and nano-manufacturing  

Microsoft Academic Search

The increasing demand for micro-products and components can be met only partly by the lithography-based micro-electromechanical\\u000a systems fabrication processes that originated from the silicon-based microelectronics revolution of the late twentieth century.\\u000a In particular, such processes have limitations when applied to new micro-devices which require the use of a variety of materials\\u000a and complex 3D microstructures with high aspect ratios. In

E. B. Brousseau; S. S. Dimov; D. T. Pham

2010-01-01

167

A contribution to spectroscopic diagnostics and cathode sheath modeling of micro-hollow gas discharge in argon  

SciTech Connect

In this paper, the hydrogen Balmer beta line shape from a micro-hollow gas discharge (MHGD) in argon with traces of hydrogen is used for simultaneous diagnostics of plasma and cathode sheath (CS) parameters. For this purpose, a simple model of relevant processes responsible for the line broadening is introduced and applied to the Balmer beta profile recorded from a MHGD generated in the microhole (diameter 100 {mu}m at narrow side and 130 {mu}m at wider side) of a gold-alumina-gold sandwich in the pressure range (100-900 mbar). The electron number density N{sub e} in the range (0.4-4.5) x 10{sup 20} m{sup -3} is determined from the width of the central part of the Balmer beta line profile, while, from the extended wings of the Balmer beta profile, induced by dc Stark effect, the next three parameters are determined: the average value E{sub a} of electric field strength in the CS in the range (16-95 kV/cm), the electric field strength E{sub 0} at the cathode surface in the range (32-190 kV/cm), and the CS thickness z{sub g} in the range (18-70 {mu}m). All four MHGD parameters, N{sub e}, E{sub a}, E{sub 0}, and z{sub g}, compare reasonably well with results of the modeling experiment by M. J. Kushner [J. Phys. D: Appl. Phys. 38, 1633 (2005)]. The results for N{sub e} are compared with other emission experiments.

Cvejic, M.; Spasojevic, Dj.; Sisovic, N. M.; Konjevic, N. [Faculty of Physics, University of Belgrade, P.O. Box 368, Belgrade 11001 (Serbia)

2011-08-01

168

Hybrid micro-technologies for medical applications.  

PubMed

Medical applications have long provided an impetus for research in silicon-based microsystems. This paper explores micro-technologies that complement and extend conventional manufacturing approaches and applications. For example, lithographic microfabrication methods can be used to fabricate stents and integrated microsensors that can monitor lumen patency in cardiac and biliary applications. These methods can also be extended to the fabrication of ceramic-based piezoelectric transducers. One potential application is to provide tissue density measurements at the tip of a biopsy needle. Piezo-thermal elements may additionally provide the means for precise cauterization and tissue ablation. Other examples of hybrid micro-technologies are also provided. PMID:19964176

Gianchandani, Yogesh B

2009-01-01

169

Syngas generation from n-butane with an integrated MEMS assembly for gas processing in micro-solid oxide fuel cell systems.  

PubMed

An integrated system of a microreformer and a carrier allowing for syngas generation from liquefied petroleum gas (LPG) for micro-SOFC application is discussed. The microreformer with an overall size of 12.7 mm × 12.7 mm × 1.9 mm is fabricated with micro-electro-mechanical system (MEMS) technologies. As a catalyst, a special foam-like material made from ceria-zirconia nanoparticles doped with rhodium is used to fill the reformer cavity of 58.5 mm(3). The microreformer is fixed onto a microfabricated structure with built-in fluidic channels and integrated heaters, the so-called functional carrier. It allows for thermal decoupling of the cold inlet gas and the hot fuel processing zone. Two methods for heating the microreformer are compared in this study: a) heating in an external furnace and b) heating with the two built-in heaters on the functional carrier. With both methods, high butane conversion rates of 74%-85% are obtained at around 550 °C. In addition, high hydrogen and carbon monoxide yields and selectivities are achieved. The results confirm those from classical lab reformers built without MEMS technology (N. Hotz et al., Chem. Eng. Sci., 2008, 63, 5193; N. Hotz et al., Appl. Catal., B, 2007, 73, 336). The material combinations and processing techniques enable syngas production with the present MEMS based microreformer with high performance for temperatures up to 700 °C. The functional carrier is the basis for a new platform, which can integrate the micro-SOFC membranes and the gas processing unit as subsystem of an entire micro-SOFC system. PMID:23044760

Bieberle-Hütter, A; Santis-Alvarez, A J; Jiang, B; Heeb, P; Maeder, T; Nabavi, M; Poulikakos, D; Niedermann, P; Dommann, A; Muralt, P; Bernard, A; Gauckler, L J

2012-11-21

170

Single-Crystalline Silicon-Based Heterojunction Photodiode Arrays on Flexible Plastic Substrates  

Microsoft Academic Search

A silicon-based photodiode array was fabricated on a flexible polyethylene terephthalate substrate using a trans- fer printing technique. A heterojunction structure composed of a 15-nm-thick highly doped hydrogenated amorphous-silicon (n + a-Si:H) layer and a 3-µm-thick p-type single-crystal silicon (p c-Si) membrane layer was adopted as the active layer of the flexible photodiode. The highly ordered photodiode array formed on

Sangwook Lee; Juree Hong; Ja Hoon Koo; Seulah Lee; Kwanghyun Lee; Seongil Im; Taeyoon Lee

2011-01-01

171

High-speed silicon-based integrated optical modulators for optical-fiber telecommunications  

NASA Astrophysics Data System (ADS)

A monolithically integrated silicon-based optical modulator is reviewed with respect to design and high-speed performance. The integrated silicon-based optical modulator consists of nested in-phase/quadrature Mach-Zehnder modulator operated in quadrature phase-shift keying formats. Design and performance of high-speed silicon ribwaveguide phase shifters and high-frequency coplanar-waveguide traveling-wave electrode are presented as key modulator elements which allow high-speed zero-chirp operation of the integrated optical modulator in the quadrature phase-shift keying formats. Transmission performance of the integrated optical modulator in differential quadrature phase-shift keying format is characterized in direct-detection constellation-diagram and bit-error-rate measurements towards 44.6-Gbit/s optical-fiber transmission. High-speed quadrature phase-shift keying operation is characterized in coherent-detection constellation-diagram measurements in C and L bands, and QPSK at bit rates up to 64-Gbit/s is presented. A partial-rib-waveguide polarization rotator, which is essential for 128-Gbit/s small-footprint silicon-based optical modulator for digital coherent communication, is described and high-extinction ratio low-loss polarization conversion over C and L bands is evidenced.

Ogawa, Kensuke

2014-03-01

172

Deformation-induced bandgap tuning of 2D silicon-based photonic crystals.  

PubMed

We address the issue of tuning the absolute bandgap in 2D silicon-based photonic crystals by mechanical deformation. The moving least-square (MLS) method, recently proposed by the authors for photonic bandgap materials, is employed for the real-space computation of band structures. The uniaxial tension mode is shown to be more effective for bandgap tuning than both pure and simple shear deformations. We verify that bandgap modifications are strongly influenced by the deformation-induced distortion of interfaces between inclusions and matrix. This result ensures the usefulness of real-space technique for the accurate calculation of strained photonic bandgap materials. PMID:19471392

Jun, Sukky; Cho, Young-Sam

2003-10-20

173

Etching process for improving the strength of a laser-machined silicon-based ceramic article  

DOEpatents

A process for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength.

Copley, Stephen M. (Palos Verdes, CA); Tao, Hongyi (Covina, CA); Todd-Copley, Judith A. (Palos Verdes, CA)

1991-01-01

174

Etching process for improving the strength of a laser-machined silicon-based ceramic article  

DOEpatents

A process is disclosed for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength. 1 figure.

Copley, S.M.; Tao, H.; Todd-Copley, J.A.

1991-06-11

175

Neutron and X-ray irradiation of silicon based Mach-Zehnder modulators  

NASA Astrophysics Data System (ADS)

We report on our recent investigation into the potential for using silicon-based Mach-Zehnder modulators in the harshest radiation environments of the High-Luminosity LHC. The effect of ionizing and non-ionizing radiation on the performance of the devices have been investigated using the 20 MeV neutron beam line at the Cyclotron Resource Centre in Louvain-La-Neuve and the X-ray irradiation facility in the CERN PH department. The devices were exposed to a total fluence and ionizing dose of 1.2×1015 n cm?2 and 1.3 MGy respectively.

El Nasr-Storey, S. S.; Détraz, S.; Olanterä, L.; Sigaud, C.; Soós, C.; Pezzullo, G.; Troska, J.; Vasey, F.; Zeiler, Marcel

2015-03-01

176

Silicon-Based Thermoelectrics: Harvesting Low Quality Heat Using Economically Printed Flexible Nanostructured Stacked Thermoelectric Junctions  

SciTech Connect

Broad Funding Opportunity Announcement Project: UIUC is experimenting with silicon-based materials to develop flexible thermoelectric devices—which convert heat into energy—that can be mass-produced at low cost. A thermoelectric device, which resembles a computer chip, creates electricity when a different temperature is applied to each of its sides. Existing commercial thermoelectric devices contain the element tellurium, which limits production levels because tellurium has become increasingly rare. UIUC is replacing this material with microscopic silicon wires that are considerably cheaper and could be equally effective. Improvements in thermoelectric device production could return enough wasted heat to add up to 23% to our current annual electricity production.

None

2010-03-01

177

Performance of a Micro-Strip Gas Chamber for event wise, high rate thermal neutron detection with accurate 2D position determination  

NASA Astrophysics Data System (ADS)

A two-dimensional (2D) position sensitive detector for neutron scattering applications based on low-pressure gas amplification and micro-strip technology was built and tested with an innovative readout electronics and data acquisition system. This detector contains a thin solid neutron converter and was developed for time- and thus wavelength-resolved neutron detection in single-event counting mode, which improves the image contrast in comparison with integrating detectors. The prototype detector of a Micro-Strip Gas Chamber (MSGC) was built with a solid natGd/CsI thermal neutron converter for spatial resolutions of about 100 ?m and counting rates up to 107 neutrons/s. For attaining very high spatial resolutions and counting rates via micro-strip readout with centre-of-gravity evaluation of the signal amplitude distributions, a fast, channel-wise, self-triggering ASIC was developed. The front-end chips (MSGCROCs), which are very first signal processing components, are read out into powerful ADC-FPGA boards for on-line data processing and thereafter via Gigabit Ethernet link into the data receiving PC. The workstation PC is controlled by a modular, high performance dedicated software suite. Such a fast and accurate system is crucial for efficient radiography/tomography, diffraction or imaging applications based on high flux thermal neutron beam. In this paper a brief description of the detector concept with its operation principles, readout electronics requirements and design together with the signals processing stages performed in hardware and software are presented. In more detail the neutron test beam conditions and measurement results are reported. The focus of this paper is on the system integration, two dimensional spatial resolution, the time resolution of the readout system and the imaging capabilities of the overall setup. The detection efficiency of the detector prototype is estimated as well.

Mindur, B.; Alimov, S.; Fiutowski, T.; Schulz, C.; Wilpert, T.

2014-12-01

178

Novel silicone-based polymer containing active methylene designed for the removal of indoor formaldehyde.  

PubMed

Indoor air pollution is caused inevitably due to complicated home decoration, in which formaldehyde is one of the most typical pollutants. It will be a convenient, economical and effective strategy to remove indoor formaldehyde if imparting a feature of formaldehyde removal to decorative coatings. We have successfully explored a novel silicone-based polymer containing active methylene used as a formaldehyde absorbent in coatings via a straightforward transesterification process using inexpensive and easily available chemicals. The polymer has been characterized by (13)C NMR, FTIR, GC and GPC. Formaldehyde removal capacity of the coating films containing different contents of the polymer has been investigated. The results indicated that coatings incorporating 4wt% of the polymer could make the coating films exhibit significant improvement on formaldehyde removal including purificatory performance (>85%) and durability of purificatory effect (>60%), compared to those consisting of absorbents without any silicon, and improve yellowing resistance performance, while other properties, such as gloss, adhesion, pencil hardness, flexibility and impact resistance, were kept almost unaffected. The chemical absorption process of the silicone-based polymer filled in interior decorative coatings is demonstrated as a promising technology to purify indoor formaldehyde and thus can reduce the harm to individuals. PMID:25661173

Niu, Song; Yan, Hongxia

2015-04-28

179

Next Generation Silicon Based Detector Characterization in the LASI Lab at Arizona State University  

NASA Astrophysics Data System (ADS)

We present preliminary results of comprehensive characterization we performed on a Cassini flight spare 1024 x 1024 silicon based CCD, to ensure that our methods are accurate, and a 1024 x 1024 NIR/Red optimized delta-doped, anti-reflection coated silicon based CCD provided by the Nanoscience and Advanced Detector Arrays Group at JPL. We also present here a new facility for CCD calibration and testing at the Laboratory of Astronomical and Space Instrumentation (LASI) at Arizona State University. The current process includes calibration from the optical to near-infrared with future considerations to calibrate into the ultraviolet. We measure several important CCD characterization parameters including, but not limited to; the quantum efficiency, optimum operating temperature, read noise, dark current, gain, linearity and reproducibility. A unique feature of the calibration is the coplanar positioning of the photodiode and CCD. The CCD is stabilized at optimum operating temperature while the photodiode is held at the equilibrium ambient temperature inside an Infrared Laboratories ND-5 Series Dewar. FITS image acquisition is done using the Voodoo software provided with the LEACH controller while control of the monochrometer is done using LABVIEW. All of the image processing is done using an IDL and LABVIEW interface. This work is supported by the Jet Propulsion Laboratory under Award Number 1275804.

Veach, Todd; Scowen, P.; Nikzad, S.

2007-05-01

180

Heterobimetallic cuprates consisting of a redox-switchable, silicon-based metalloligand: synthesis, structures, and electronic properties.  

PubMed

A series of bimetallic silyl halido cuprates consisting of the new tripodal silicon-based metalloligand [?(3)N-Si(3,5-Me2pz)3Mo(CO)3](-) is presented (pz = pyrazolyl). This metalloligand is straightforwardly accessible by reacting the ambidentate ligand tris(3,5-dimethylpyrazolyl)silanide ({Si(3,5-Me2pz)3}(-)) with [Mo(CO)3(?(6)-toluene)]. The compound features a fac-coordinated tripodal chelating ligand and an outward pointing, "free" pyramidal silyl donor, which is easily accessible for a secondary coordination to other metal centers. Several bimetallic silyl halido cuprates of the general formula [CuX{?-?(1)Si:?(3)N-Si(3,5-Me2pz)3Mo(CO)3}](-) (X = Cl, Br, I) have been synthesized. The electronic and structural properties of these complexes were probed in detail by X-ray diffraction analysis, electrospray mass spectrometry, infrared-induced multiphoton dissociation studies, cyclic voltammetry, spectroelectrochemistry, gas-phase photoelectron spectroscopy, as well as UV/Vis and fluorescence spectroscopy. The heterobimetallic complexes contain linear two-coordinate copper(I) entities with the shortest silicon-copper distances reported so far. Oxidation of the anionic complexes in methylene chloride and acetonitrile solutions at E(1/2)(0( = -0.60 and -0.44?V (vs. ferrocene/ferrocenium (Fc/Fc(+))), respectively, shows substantial reversibility. Based on various results obtained from different characterization methods, as well as density functional theory calculations, these oxidation events were attributed to the Mo(0)/Mo(I) redox couple. PMID:23737399

Styra, Steffen; González-Gallardo, Sandra; Armbruster, Felix; Oña-Burgos, Pascual; Moos, Eric; Vonderach, Matthias; Weis, Patrick; Hampe, Oliver; Grün, Anneken; Schmitt, Yvonne; Gerhards, Markus; Menges, Fabian; Gaffga, Maximilian; Niedner-Schatteburg, Gereon; Breher, Frank

2013-06-24

181

Gas-Phase Transport and Redeposition of Nano and Micro-Particulates During Laser Cleaning from Solid Substrates  

Microsoft Academic Search

Theoretical modeling and experimental studies were performed to investigate basic processes underlying transport of model submicron spherical particles in still air and thin liquid layers of variable thickness after their laser-assisted detachment from dry and 2-propanol–dosed Si surfaces. Viscous drag and diffusive Brownian motion were found to mostly affect transport of nano- and micro-particles removed from solid substrates in the

Sergey I. Kudryashov; Susan D. Allen

2008-01-01

182

Application of Micro Scanning Laser Doppler Vibrometer for Vibrational Velocity and Resonance Frequency Measurement on Micro Electro Mechanical Devices (MEMS)  

Microsoft Academic Search

Micro-Electro-Mechanical Systems (MEMS) represent the integration of mechanical elements, sensors, actuators, and electronics\\u000a on a common silicon substrate through the utilization of microfabrication technology. The “micromachining” processes selectively\\u000a etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. MEMS\\u000a promises to revolutionize nearly every product category by bringing together silicon-based microelectronics

Paolo Castellini; Barbara Marchetti; E. P. Tomasini

183

Design, Fabrication and Prototype testing of a Chip Integrated Micro PEM Fuel Cell Accumulator combined On-Board Range Extender  

NASA Astrophysics Data System (ADS)

In this work we present the design, fabrication and prototype testing of Chip Integrated Micro PEM Fuel Cell Accumulator (CI?-PFCA) combined On-Board Range Extender (O-BRE). CI?-PFCA is silicon based micro-PEM fuel cell system with an integrated hydrogen storage feature (palladium metal hydride), the run time of CI?-PFCA is dependent on the stored hydrogen, and in order to extend its run time an O-BRE is realized (catalytic hydrolysis of chemical hydride, NaBH4. Combining the CI?-PFCA and O-BRE on a system level have few important design requirements to be considered; hydrogen regulation, gas -liquid separator between the CI?-PFCA and the O-RE. The usage of traditional techniques to regulate hydrogen (tubes), gas-liquid phase membranes (porous membrane separators) are less desirable in the micro domain, due to its space constraint. Our approach is to use a passive hydrogen regulation and gas-liquid phase separation concept; to use palladium membrane. Palladium regulates hydrogen by concentration diffusion, and its property to selectively adsorb only hydrogen is used as a passive gas-liquid phase separator. Proof of concept is shown by realizing a prototype system. The system is an assembly of CI?-PFCA, palladium membrane and the O-BRE. The CI?-PFCA consist of 2 individually processed silicon chips, copper supported palladium membrane realized by electroplating followed by high temperature annealing process under inter atmosphere and the O-BRE is realized out of a polymer substrate by micromilling process with platinum coated structures, which functions as a catalyst for the hydrolysis of NaBH4. The functionality of the assembled prototype system is demonstrated by the measuring a unit cell (area 1 mm2) when driven by the catalytic hydrolysis of chemical hydride (NaBH4 and the prototype system shows run time more than 15 hours.

Balakrishnan, A.; Mueller, C.; Reinecke, H.

2014-11-01

184

Improved performance of micro-fabricated preconcentrators using silica nanoparticles as a surface template.  

PubMed

A new approach of enhancing the adsorption capability of the widely used polymer adsorbent Tenax TA poly(2,6-diphenylene oxide) through its deposition on a nano-structured template is reported. The modified Tenax TA-coated silica nanoparticles (SNP) are incorporated as an adsorbent bed in silicon based micro-thermal preconcentrator (?TPC) chips with an array of square microposts embedded inside the cavity and sealed with a Pyrex cover. The interior surface of the chip is first modified by depositing SNP using a layer-by-layer self-assembly technique followed by coating with Tenax TA. The adsorption capacity of the SNP-Tenax TA ?TPC is enhanced by as much as a factor of three compared to the one coated solely with thin film Tenax TA for the compounds tested. The increased adsorption ability of the Tenax TA is attributed to the higher surface area provided by the underlying porous SNP coating and the pores between SNPs affecting the morphology of deposited Tenax TA film by bringing nano-scale features into the polymer. In addition, the adsorption ability of the SNP coating as a pseudo-selective inorganic adsorption bed for polar compounds was also observed. The modified Tenax TA-coated SNP ?TPC is a promising development toward integrated micro-gas chromatography systems. PMID:24268363

Akbar, Muhammad; Wang, Dong; Goodman, Ryan; Hoover, Ashley; Rice, Gary; Heflin, James R; Agah, Masoud

2013-12-27

185

Silicon-based reproducible and active surface-enhanced Raman scattering substrates for sensitive, specific, and multiplex DNA detection  

NASA Astrophysics Data System (ADS)

Silicon-based active and reproducible surface-enhanced Raman scattering (SERS) substrate, i.e., silver nanoparticles decorated-silicon wafers (AgNPs@Si), is employed for constructing high-performance sensors. Significantly, the AgNPs@Si, facilely prepared via in situ AgNPs growth on silicon wafers, features excellent SERS reproducibility and high enhancement factor. Our experiment further demonstrates such resultant silicon-based SERS substrate is efficacious for multiplex, sensitive, and specific DNA detection. In particular, single-base mismatched DNA with low concentrations is readily discriminated by using the AgNPs@Si. Moreover, the silicon-based sensor exhibits adequate multiplexing capacity, enabling unambiguous identification of the dual-target DNA detection.

Jiang, Z. Y.; Jiang, X. X.; Su, S.; Wei, X. P.; Lee, S. T.; He, Y.

2012-05-01

186

Preparation of rich handles soft cellulosic fabric using amino silicone based softener. Part-I: Surface smoothness and softness properties.  

PubMed

A series of amino silicone based softeners with different emulsifiers were prepared and adsorbed onto the surfaces of cotton and blends of cotton/polyester fabrics. Factors affecting the performance properties of the finished substrate such as post-treatment with amino functional silicone based softener varying different emulsifiers in their formulations and its concentration on different processed fabrics were studied. Fixation of the amino-functional silicone softener onto/or within the cellulose structure is accompanied by the formation of semi-inter-penetrated network structure thereby enhancing both the extent of crosslinking and networking as well as providing very high softness. The results of the experiments indicate that the amino silicone can form a hydrophobic film on both cotton and blends of cotton/polyester fabrics and its coating reduces the surface roughness significantly. Furthermore, the roughness becomes lesser with an increase in the applied strength of amino silicone based softener. PMID:21255604

Zia, Khalid Mahmood; Tabassum, Shazia; Barkaat-ul-Hasin, Syed; Zuber, Mohammad; Jamil, Tahir; Jamal, Muhammad Asghar

2011-04-01

187

Speciation analysis of organotin compounds in human urine by headspace solid-phase micro-extraction and gas chromatography with pulsed flame photometric detection.  

PubMed

A new headspace solid-phase micro-extraction (HS-SPME) method followed by gas chromatography with pulsed flame photometric detection (GC-PFPD) analysis has been developed for the simultaneous determination of 11 organotin compounds, including methyl-, butyl-, phenyl- and octyltin derivates, in human urine. The methodology has been validated by the analysis of urine samples fortified with all analytes at different concentration levels, and recovery rates above 87% and relative precisions between 2% and 7% were obtained. Additionally, an experimental-design approach has been used to model the storage stability of organotin compounds in human urine, demonstrating that organotins are highly degraded in this medium, although their stability is satisfactory during the first 4 days of storage at 4 °C and pH=4. Finally, this methodology was applied to urine samples collected from harbor workers exposed to antifouling paints; methyl- and butyltins were detected, confirming human exposure in this type of work environment. PMID:24840433

Valenzuela, Aníbal; Lespes, Gaëtane; Quiroz, Waldo; Aguilar, Luis F; Bravo, Manuel A

2014-07-01

188

Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method.  

PubMed

A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range. PMID:22824206

Dang, Zhiya; Breese, Mark Bh; Recio-Sánchez, Gonzalo; Azimi, Sara; Song, Jiao; Liang, Haidong; Banas, Agnieszka; Torres-Costa, Vicente; Martín-Palma, Raúl José

2012-01-01

189

Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method  

NASA Astrophysics Data System (ADS)

A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range.

Dang, Zhiya; Breese, Mark BH; Recio-Sánchez, Gonzalo; Azimi, Sara; Song, Jiao; Liang, Haidong; Banas, Agnieszka; Torres-Costa, Vicente; Martín-Palma, Raúl José

2012-07-01

190

Nanostructuring surfaces with conjugated silica colloids deposited using silicon-based microcantilevers  

NASA Astrophysics Data System (ADS)

In this paper, the assembly and stability of locally spotted spherical nanoparticles onto various substrates are studied. Arrays of silicon-based microcantilevers, combined with an automated three-stage spotter, are used to deposit picolitre droplets containing 300 nm diameter polyethylene glycol and 150 nm diameter amino conjugated silica nanospheres onto silicon, allylamine and acrylic acid surfaces. Matrices of colloid spots ranging from 10 to 100 µm in diameter have been successfully patterned. SEM characterizations of the nanoparticles' geometry and spatial distribution within the spots were carried out, showing the colloid aggregation at the droplet's rim and the selective stability of the printed patterns. The expected substrate functionalization was assessed by XPS characterizations of the nanoparticles' surfaces. Finally, polyethylene glycol-SiO2 nanoparticle conjugates were used as masks during a selective reactive ion etching of the silicon substrate, and silicon nanopillars have been obtained. This work opens up possibilities of high spatial resolution nanopatterning with nanoparticle conjugates.

Leïchlé, Thierry; Manso Silvan, Miguel; Belaubre, Pascal; Valsesia, Andrea; Ceccone, Giacomo; Rossi, François; Saya, Daisuke; Pourciel, Jean-Bernard; Nicu, Liviu; Bergaud, Christian

2005-04-01

191

Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method  

PubMed Central

A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared range. PMID:22824206

2012-01-01

192

Preparation of rich handles soft cellulosic fabric using amino silicone based softener, part II: colorfastness properties.  

PubMed

The preparation of amino silicone based softeners with different emulsifiers was carried out and adsorbed onto the surfaces of cotton and blends of cotton/polyester fabrics. The softened fabrics have high surface area, so poorly performance in washing and rubbing fastness. It is obvious from the results of colorfastness to rubbing and washing that some of the samples of the dyed fabric treated with prepared softeners have shown some poor rating as compared to the untreated fabrics. However the other two samples have shown acceptable rubbing fastness results without losing softness and permanent handle. It can be observed that washing of the printed treated fabric remains unaffected almost in all the studied samples. Moreover, the application of the prepared softeners has imparted anti pilling property to the fabric. It can be seen that there is a remarkable increase in weights of treated fabrics as compared to the untreated fabrics. PMID:21300085

Zuber, Mohammad; Zia, Khalid Mahmood; Tabassum, Shazia; Jamil, Tahir; Barkaat-Ul-Hasin, Syed; Khosa, Muhammad Kaleem

2011-07-01

193

Silicon-based spin quantum computation and the shallow donor exchange gate  

NASA Astrophysics Data System (ADS)

Proposed silicon-based quantum-computer architectures have attracted attention because of their promise for scalability and their potential for synergetically utilizing the available resources associated with the existing Si technology infrastructure. Electronic and nuclear spins of shallow donors (e.g. phosphorus) in Si are ideally suited candidates for qubits in such proposals, where shallow donor exchange gates are frequently invoked to perform two-qubit operations. An important potential problem in this context is that intervalley interference originating from the degeneracy in the Si conduction-band edge causes fast oscillations in donor exchange coupling, which imposes significant constraints on the Si quantum-computer architecture. We discuss the theoretical origin of such oscillations. Considering two substitutional donors in Si, we present a systematic statistical study of the correlation between relative position distributions and the resulting exchange distributions.

Koiller, Belita; Capaz, R. B.; Hu, Xuedong; Das Sarma, S.

2005-06-01

194

Corrosion-Prevention Capabilities of a Water-Borne, Silicone-Based, Primerless Coating  

NASA Technical Reports Server (NTRS)

Comparative tests have been performed to evaluate the corrosion-prevention capabilities of an experimental paint of the type described in Water-Borne, Silicone-Based, Primerless Paints, NASA Tech Briefs, Vol. 26, No. 11 (November 2002), page 30. To recapitulate: these paints contain relatively small amounts of volatile organic solvents and were developed as substitutes for traditional anticorrosion paints that contain large amounts of such solvents. An additional desirable feature of these paints is that they can be applied without need for prior application of primers to ensure adhesion. The test specimens included panels of cold-rolled steel, stainless steel 316, and aluminum 2024-T3. Some panels of each of these alloys were left bare and some were coated with the experimental water-borne, silicone-based, primerless paint. In addition, some panels of aluminum 2024-T3 and some panels of a fourth alloy (stainless steel 304) were coated with a commercial solvent-borne paint containing aluminum and zinc flakes in a nitrile rubber matrix. In the tests, the specimens were immersed in an aerated 3.5-weight-percent aqueous solution of NaCl for 168 hours. At intervals of 24 hours, the specimens were characterized by electrochemical impedance spectroscopy (EIS) and measurements of corrosion potentials. The specimens were also observed visually. As indicated by photographs of specimens taken after the 168-hour immersion (see figure), the experimental primerless silicone paint was effective in preventing corrosion of stainless steel 316, but failed to protect aluminum 2024-T3 and cold-rolled steel. The degree of failure was greater in the case of the cold-rolled steel. On the basis of visual observations, EIS, and corrosion- potential measurements, it was concluded that the commercial aluminum and zinc-filled nitrile rubber coating affords superior corrosion protection to aluminum 2024-T3 and is somewhat less effective in protecting stainless steel 304.

Calle, Luz Marina; MacDowell, Louis G.; Vinje, Rubie D.

2005-01-01

195

Effects of shear work on non-equilibrium heat transfer characteristics of rarefied gas flow through micro/nanochannels  

NASA Astrophysics Data System (ADS)

In the current work, the impact of shear work due to the slip velocity on non-equilibrium heat transfer in a pressure driven micro/nanochannel is evaluated under constant wall heat flux boundary condition. The DSMC method is employed as numerical tool. Implementation of the wall heat flux in the DSMC method is performed using the "modified Iterative" technique which in general eliminates any difficulty of implementation in adiabatic conditions and improves the solution convergence. We investigate the effects of rarefaction, property variations and compressibility. The numerical results show that shear stress on the walls significantly affects all aspects of the flow behavior and heat transfer through micro/nano channels such as heat flux rates. We also analyze the counter gradient heat flow phenomenon appearing at the cooling conditions. It is observed that viscous dissipation affects the heat flux applied to the walls and may overcome the wall heat flux, .i.e., in the case of low cooling wall heat flux condition, shear work may completely heat the flow field.

Balaj, Mojtaba; Roohi, Ehsan; Akhlaghi, Hassan

2014-12-01

196

Direct water balance analysis on a polymer electrolyte fuel cell (PEFC): Effects of hydrophobic treatment and micro-porous layer addition to the gas diffusion layer of a PEFC on its performance during a simulated start-up operation  

Microsoft Academic Search

Effects of hydrophobic treatment and micro-porous layer (MPL) addition to a gas diffusion layer (GDL) in a polymer electrolyte fuel cell (PEFC) have been investigated from water balance analysis at the electrode (catalyst layer), GDL and flow channel in the cathode after a simulated start-up operation. The water balance is directly analyzed by measuring the weight of the adherent water

Hironori Nakajima; Toshiaki Konomi; Tatsumi Kitahara

2007-01-01

197

MicroSimulation Models of Urban Regions: Anticipating Greenhouse Gas Emissions from Transport and Housing in Austin, Texas  

Microsoft Academic Search

To be presented at the 88th Annual Meeting of the Transportation Research Board and under review for publication in Transportation Research Record ABSTRACT Anthropogenic greenhouse gas (GHG) emissions are largely attributable to household and firm travel and building decisions. This paper demonstrates the development and application of a microsimulation model for household and firm evolution and location choices overtime, along

Sumala Tirumalachetty; Kara M. Kockelman; Saurabh Kumar

198

Fabrication and design of an auto ventilation controller using micro gas sensor for the clean room\\/building environment  

Microsoft Academic Search

With the growing attention to environmental problems and the increase of standard of living, there are imperative needs for gas sensors with high sensitivity and excellent selectivity in air quality monitoring. Domestic environmental monitoring is an important aspect nowadays. We have tried to develop a sensor that can help to monitor the presence of harmful gases. An auto ventilation controller

Ii Jin Kim; Sang Do Han; Hi Dock Lee; Jin Suk Wang

2005-01-01

199

Neutral gas temperature maps of the pin-to-plate Argon micro discharge into the ambient air  

E-print Network

This study is designed to explore the two dimensional temperature maps of the atmospheric argon discharge consisting of pin-to-plane electrodes supplied by a high voltage DC source. After checking the stability of the micro discharge, the two dimensional image plane focused by a quartz lens was scanned by the fiber probe driven by a 3D Mobile Platform. The rotational and vibrational temperatures are calculated using nitrogen emissions collected by the high resolution spectrometer and high sensitive intensified charge coupled device (ICCD). The rotational temperature varies from 1558.15 K to 2621.14 K and vibrational temperature varies from 3010.38 K to 3774.69 K, indicating a great temperature gradient due to small discharge size. The temperature maps show a lateral expansion and a sharp truncation in the radial direction. A double layers discharge is identified, where an arc discharge coats the glow discharge.

Xu, Shaofeng; Majeed, Asif

2015-01-01

200

Neutral gas temperature maps of the pin-to-plate argon micro discharge into the ambient air  

NASA Astrophysics Data System (ADS)

This study is designed to explore the two dimensional temperature maps of the atmospheric argon discharge consisting of pin-to-plane electrodes supplied by a high voltage DC source. After checking the stability of the micro discharge, the two dimensional image plane focused by a quartz lens was scanned by the fiber probe driven by a 3D Mobile Platform. The rotational and vibrational temperatures are calculated using nitrogen emissions collected by the high resolution spectrometer and high sensitive intensified charge coupled device. The rotational temperature varies from 1558.15 K to 2621.14 K and vibrational temperature varies from 3010.38 K to 3774.69 K, indicating a great temperature gradient due to small discharge size. The temperature maps show a lateral expansion and a sharp truncation in the radial direction. A double layers discharge is identified, where an arc discharge coats the glow discharge.

Xu, S. F.; Zhong, X. X.; Majeed, Asif

2015-03-01

201

The synthesis of porous Co{sub 3}O{sub 4} micro cuboid structures by solvothermal approach and investigation of its gas sensing properties and catalytic activity  

SciTech Connect

Graphical abstract: - Highlights: • Micro cuboid Co{sub 3}O{sub 4} particle prepared by solvothermal method. • Study of morphology of synthesized cuboids before and after calcinations. • Investigation of formation mechanism of porous Co{sub 3}O{sub 4} from cuboid CoCO{sub 3}. • Investigation of gas sensing properties of porous Co{sub 3}O{sub 4}. • Study of catalytic activity of product. - Abstract: The cobalt carbonate cuboids are prepared by adopting a simple solvothermal approach by using diethylene glycol and water in specific ratio as solvent. The prepared cobalt carbonate is subjected to different instrumentation to investigate its morphology and other properties. It is clear from the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the product is distinct cuboid in shape with a size of approximately 3 ?m from each face of the cube. Each particle of cuboid cobalt carbonate seems to comprise of layer by layer assembly of unit cells that consequently leads to a cuboid geometry. The cuboid cobalt carbonate was calcined at 700 °C in a furnace under argon atmosphere that decompose cobalt carbonate into porous Co{sub 3}O{sub 4} with the loosely packed arrangement of nano architectures. The gas sensing properties and catalytic activity of porous cuboids Co{sub 3}O{sub 4} are also investigated.

Jamil, Saba, E-mail: saba_hrb@yahoo.com [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, 150001 (China); Jing, Xiaoyan [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, 150001 (China); Institute of Advanced Marine Materials, Harbin Engineering University, 150001 (China); Wang, Jun, E-mail: zhqw1888@sohu.com [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, 150001 (China); Li, Songnan; Liu, Jingyuan [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, 150001 (China); Zhang, Milin [Key Laboratory of Superlight Material and Surface Technology, Ministry of Education, Harbin Engineering University, 150001 (China); Institute of Advanced Marine Materials, Harbin Engineering University, 150001 (China)

2013-11-15

202

The effect of a micro bubble dispersed gas phase on hydrogen isotope transport in liquid metals under nuclear irradiation  

E-print Network

The present work intend to be a first step towards the understanding and quantification of the hydrogen isotope complex phenomena in liquid metals for nuclear technology. Liquid metals under nuclear irradiation in,e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles. Other liquid metal systems of a nuclear reactor involve hydrogen isotope absorption processes, e.g., tritium extraction system. Hence, hydrogen isotope absorption into gas bubbles modelling and control may have a capital importance regarding design, operation and safety. Here general models for hydrogen isotopes transport in liquid metal and absorption into gas phase, that do not depend on the mass transfer limiting regime, are exposed and implemented in OpenFOAMR CFD tool for 0D to 3D simulations. Results for a 0D case show the impact of a He dispersed phase of na...

Fradera, Jorge

2013-01-01

203

Silicon Based Microchemical Concepts for Miniature Fuel Keyur Shah, R.S. Besser  

E-print Network

Ox Microfabricated Vacuum Insulation d: thickness of insulation Kp: Thermal conductivity at given pressure Insulation bonding under vacuum) ANSYS Thermal Simulation of Insulator Packaged with SR Microreactor Micro Steam Jersey Center for Microchemical Systems, Department of Chemical, Biomedical, & Materials Engineering

Besser, Ronald S.

204

Porous silicon based all-optical modulator using asymmetrical Mach-Zehnder interferometer configuration  

NASA Astrophysics Data System (ADS)

In this paper, nonlinear porous silicon based all-optical modulator is proposed and investigated by utilizing an asymmetrical Mach-Zehnder Interferometer (MZI) configuration consisted of two couplers with equal splitting ratio, and two unbalance arms, in which a porous silicon (PS) waveguide as the nonlinear element is only placed in one arm of MZI, and another arm is short fiber delay line. Results show that both a pulsed pump and continuous probe wave are simultaneously launched into the input port with the result that an outcome signal with ~14.10 dB modulation depth at probe wavelength is obtained at the end of the device under the conditions of an initial pulsed pump with 47.07 dB m peak, 10.88 extinction ratio and 100 ps duration, continuous probe wave of 0 dB m power, and 3-mm long PS waveguide. Extinction ratio and eye opening ratio of eye diagram are observed for various operation speeds.

Xiao, Lei; Wu, Jian-Wei

2015-03-01

205

Chemical stability of the fiber coating/matrix interface in silicon-based ceramic matrix composites  

SciTech Connect

Carbon and boron nitride are used as fiber coatings in silicon-based composites. In order to assess the long-term stability of these materials, reactions of carbon/Si3N4 and BN/SiC were studied at high temperatures with Knudsen effusion, coupon tests, and microstructural examination. In the carbon/Si3N4 system, carbon reacted with Si3N4 to form gaseous N2 and SiC. The formation of SiC limited further reaction by physically separating the carbon and Si3N4. Consequently, the development of high p(N2) at the interface, predicted from thermochemical calculations, did not occur, thus limiting the potential deleterious effects of the reaction on the composite. Strong indications of a reaction between BN and SiC were shown by TEM and SIMS analysis of the BN/SiC interface. In long-term exposures, this reaction can lead to a depletion of a BN coating and/or an unfavorable change of the interfacial properties, limiting the beneficial effects of the coating.

Lee, K.N.; Jacobson, N.S.

1995-01-01

206

Angular dependence of the magnetoresistance effect in a silicon based p-n junction device.  

PubMed

We report a pronounced angular dependence of the magnetoresistance (MR) effect in a silicon based p-n junction device at room temperature by manipulating the space charge region of the p-n junction under a magnetic field. For the p-n junction device with various space charge region configurations, we find that all the angular dependence of the MR effect is proportional to sin(2)(?), where the ? is the angle between the magnetic field and the driving current. With increasing the magnetic field and driving current, the anisotropic MR effect is obviously improved. At room temperature, under a magnetic field 2 T and driving current 20 mA, the MR ratio is about 50%, almost one order of amplitude larger than that in the magnetic material permalloy. Our results reveal an interpretation of the MR effect in the non-magnetic p-n junction in terms of the Lorentz force and give a new way for the development of future magnetic sensors with non-magnetic p-n junctions. PMID:24561960

Wang, Tao; Si, Mingsu; Yang, Dezheng; Shi, Zhong; Wang, Fangcong; Yang, Zhaolong; Zhou, Shiming; Xue, Desheng

2014-04-21

207

18F-Labeled Silicon-Based Fluoride Acceptors: Potential Opportunities for Novel Positron Emitting Radiopharmaceuticals  

PubMed Central

Background. Over the recent years, radiopharmaceutical chemistry has experienced a wide variety of innovative pushes towards finding both novel and unconventional radiochemical methods to introduce fluorine-18 into radiotracers for positron emission tomography (PET). These “nonclassical” labeling methodologies based on silicon-, boron-, and aluminium-18F chemistry deviate from commonplace bonding of an [18F]fluorine atom (18F) to either an aliphatic or aromatic carbon atom. One method in particular, the silicon-fluoride-acceptor isotopic exchange (SiFA-IE) approach, invalidates a dogma in radiochemistry that has been widely accepted for many years: the inability to obtain radiopharmaceuticals of high specific activity (SA) via simple IE. Methodology. The most advantageous feature of IE labeling in general is that labeling precursor and labeled radiotracer are chemically identical, eliminating the need to separate the radiotracer from its precursor. SiFA-IE chemistry proceeds in dipolar aprotic solvents at room temperature and below, entirely avoiding the formation of radioactive side products during the IE. Scope of Review. A great plethora of different SiFA species have been reported in the literature ranging from small prosthetic groups and other compounds of low molecular weight to labeled peptides and most recently affibody molecules. Conclusions. The literature over the last years (from 2006 to 2014) shows unambiguously that SiFA-IE and other silicon-based fluoride acceptor strategies relying on 18F? leaving group substitutions have the potential to become a valuable addition to radiochemistry. PMID:25157357

Bernard-Gauthier, Vadim; Wängler, Carmen; Wängler, Bjoern; Schirrmacher, Ralf

2014-01-01

208

High-frequency, silicon-based ultrasonic nozzles using multiple Fourier horns.  

PubMed

This paper presents the design, simulation, and characterization of microfabricated 0.5 MHz, silicon-based, ultrasonic nozzles. Each nozzle is made of a piezoelectric drive section and a silicon resonator consisting of multiple Fourier horns, each with half wavelength design and twice amplitude magnification. Results of finite element three-dimensional (3-D) simulation using a commercial program predicted existence of one resonant frequency of pure longitudinal vibration. Both impedance analysis and measurement of longitudinal vibration confirmed the simulation results with one pure longitudinal vibration mode at the resonant frequency in excellent agreement with the design value. Furthermore, at the resonant frequency, the measured longitudinal vibration amplitude at the nozzle tip increases as the number of Fourier horns (n) increases in good agreement with the theoretical values of 2(n). Using this design, very high vibration amplitude gain at the nozzle tip can be achieved with no reduction in the tip cross-sectional area for contact of liquid to be atomized. Therefore, the required electric drive power should be drastically reduced, decreasing the likelihood of transducer failure in ultrasonic atomization. PMID:15128214

Tsai, Shirley C; Song, Yu L; Tseng, Terry K; Chou, Yuan F; Chen, Wei J; Tsai, Chen S

2004-03-01

209

Surface adhesion between hexagonal boron nitride nanotubes and silicon based on lateral force microscopy  

NASA Astrophysics Data System (ADS)

This study presents the surface adhesion between hexagonal boron nitride nanotube (BNNT) and silicon based on lateral manipulation in an atomic force microscope (AFM). The BNNT was mechanically manipulated by the lateral force of an AFM pyramidal silicon probe using the scan mechanism in the imaging mode. With a controlled normal force of the AFM probe and the lateral motion, the lateral force applied to the BNNT could overcome the surface adhesion between BNNT and silicon surface. The individual BNNT is forced to slide and rotate on the silicon surface. Based on the recorded force curve, the calculated shear stress due to surface adhesion is 0.5 GPa. And the specific sliding energy loss is 0.2 J/m 2. Comparing BNNTs and carbon nanotube (CNT), the shear stress and specific sliding energy loss of BNNT are an order of magnitude larger than that of CNT. Therefore, the results show that the surface adhesion between BNNT and silicon surface is higher than that of CNT.

Hsu, Jung-Hui; Chang, Shuo-Hung

2010-01-01

210

Silicon-based optoelectronic integrated circuit for label-free bio/chemical sensor.  

PubMed

We demonstrate a silicon-based optoelectronic integrated circuit (OEIC) for label-free bio/chemical sensing application. Such on-chip OEIC sensor system consists of optical grating couplers for vertical light coupling into silicon waveguides, a thermal-tunable microring as a tunable filter, an exposed microring as an optical label-free sensor, and a Ge photodetector for a direct electrical readout. Different from the conventional wavelength-scanning method, we adopt low-cost broadband ASE light source, together with the on-chip tunable filter to generate sliced light source. The effective refractive index change of the sensing microring induced by the sensing target is traced by scanning the supplied electrical power applied onto the tracing microring, and the detected electrical signal is read out by the Ge photodetector. For bulk refractive index sensing, we demonstrate using such OEIC sensing system with a sensitivity of ~15 mW/RIU and a detection limit of 3.9 ?-RIU, while for surface sensing of biotin-streptavidin, we obtain a surface mass sensitivity of S(m) = ~192 µW/ng?mm(-2) and a surface detection limit of 0.3 pg/mm(2). The presented OEIC sensing system is suitable for point-of-care applications. PMID:23938665

Song, Junfeng; Luo, Xianshu; Kee, Jack Sheng; Han, Kyungsup; Li, Chao; Park, Mi Kyoung; Tu, Xiaoguang; Zhang, Huijuan; Fang, Qing; Jia, Lianxi; Yoon, Yong-Jin; Liow, Tsung-Yang; Yu, Mingbin; Lo, Guo-Qiang

2013-07-29

211

On-Wafer Measurement of a Silicon-Based CMOS VCO at 324 GHz  

NASA Technical Reports Server (NTRS)

The world s first silicon-based complementary metal oxide/semiconductor (CMOS) integrated-circuit voltage-controlled oscillator (VCO) operating in a frequency range around 324 GHz has been built and tested. Concomitantly, equipment for measuring the performance of this oscillator has been built and tested. These accomplishments are intermediate steps in a continuing effort to develop low-power-consumption, low-phase-noise, electronically tunable signal generators as local oscillators for heterodyne receivers in submillimeter-wavelength (frequency > 300 GHz) scientific instruments and imaging systems. Submillimeter-wavelength imaging systems are of special interest for military and law-enforcement use because they could, potentially, be used to detect weapons hidden behind clothing and other opaque dielectric materials. In comparison with prior submillimeter- wavelength signal generators, CMOS VCOs offer significant potential advantages, including great reductions in power consumption, mass, size, and complexity. In addition, there is potential for on-chip integration of CMOS VCOs with other CMOS integrated circuitry, including phase-lock loops, analog- to-digital converters, and advanced microprocessors.

Samoska, Lorene; Man Fung, King; Gaier, Todd; Huang, Daquan; Larocca, Tim; Chang, M. F.; Campbell, Richard; Andrews, Michael

2008-01-01

212

Moment tensor inversion for two micro-earthquakes occurring inside the Háje gas storage facilities, Czech Republic  

NASA Astrophysics Data System (ADS)

Broadband data from the P?íbram seismological network was used to investigate the source of two earthquakes, with magnitudes M w = 0.2 and 0.4 respectively, occurring in the period of October-November 2009 in the Háje natural gas storage area (Czech Republic). Both events were located inside the limits of the storage area and at depths similar to those of the underground caverns where the gas is stored. We applied an inversion technique using the software ISOLA for moment tensor retrieval in order to assess the source process of both events and recognize whether a significant isotropic component existed that could be interpreted as a possible cavern collapse. We also performed an uncertainty analysis so as to confirm the reliability of the focal mechanism solutions and we controlled the consistency between the inverted focal mechanisms and those calculated using the P-waves first motions. Our results showed that the nodal plane orientation, the centroid depth, and the magnitude remained stable. Furthermore, we calculated synthetic waveforms for collapse-type ruptures and compared them with the original records. The match between the synthetic and the original data was very poor supporting the interpretation of the shear character of the events. The combination of the inversion results, which indicated significant double-couple components and of the synthetic tests, which supported the inexistence of an isotropic component at the source, led to the conclusion that the possibility of rocks falling from the ceiling of the caverns or a cavern collapse is highly unlikely.

Benetatos, Christoforos; Málek, Ji?í; Verga, Francesca

2013-04-01

213

Monitoring the emission of volatile organic compounds from flowers of Jasminum sambac using solid-phase micro-extraction fibers and gas chromatography with mass spectrometry detection.  

PubMed

Solid-phase micro-extraction (SPME) was studied as a solvent free alternative method for the extraction and characterization of volatile compounds in intact and plucked flowers of Jasminum sambac at different day time intervals using gas chromatography (GC-FID) and gas chromatography-quadrupole mass spectrometry. The analytes identified included alcohols, esters, phenolic compounds, and terpenoids. The main constituents identified in the flower aroma using different fibers were cis-3-hexenyl acetate, (E)-beta-ocimene, linalool, benzyl acetate, and (E,E)-alpha-farnesene. The benzyl acetate proportion decreased from morning to afternoon and then increased in evening collections. PDMS fiber showed a high proportion of (E,E)-alpha-farnesene in jasmine floral aroma. Among other constituents identified, cis-3-hexenyl acetate, linalool, and benzyl acetate were major aroma contributors in plucked and living flowers extracts using PDMS/DVB, Carboxen/PDMS, and DVB/Carboxen/PDMS fibers. PDMS/DVB recorded the highest emission for benzyl acetate while the (E)-beta-ocimene proportion was highest in DVB/Carboxen/PDMS when compared with the rest. The highest linalool content, with increasing proportion from morning to noon, was found using mixed coating fibers. Almost negligible volatile adsorption was recorded for the polyacrylate fiber for intact flower aroma, whereas it was most effective for benzyl acetate, followed by indole under plucked conditions. Moreover, the highest amounts extracted, evaluated from the sum of peak areas, were achieved using Carboxen/PDMS, and DVB/Carboxen/PDMS. Introduction of a rapid, and solvent free SPME method for the analysis of multicomponent volatiles can be successfully employed to monitor the extraction and characterization of flower aroma constituents. PMID:21941909

Pragadheesh, Vppalayam Shanmugam; Yadav, Anju; Chanotiya, Chandan Singh; Rout, Prasanta Kumar; Uniyal, Girish Chandra

2011-09-01

214

In vivo silicon-based flexible radio frequency integrated circuits monolithically encapsulated with biocompatible liquid crystal polymers.  

PubMed

Biointegrated electronics have been investigated for various healthcare applications which can introduce biomedical systems into the human body. Silicon-based semiconductors perform significant roles of nerve stimulation, signal analysis, and wireless communication in implantable electronics. However, the current large-scale integration (LSI) chips have limitations in in vivo devices due to their rigid and bulky properties. This paper describes in vivo ultrathin silicon-based liquid crystal polymer (LCP) monolithically encapsulated flexible radio frequency integrated circuits (RFICs) for medical wireless communication. The mechanical stability of the LCP encapsulation is supported by finite element analysis simulation. In vivo electrical reliability and bioaffinity of the LCP monoencapsulated RFIC devices are confirmed in rats. In vitro accelerated soak tests are performed with Arrhenius method to estimate the lifetime of LCP monoencapsulated RFICs in a live body. The work could provide an approach to flexible LSI in biointegrated electronics such as an artificial retina and wireless body sensor networks. PMID:23617401

Hwang, Geon-Tae; Im, Donggu; Lee, Sung Eun; Lee, Jooseok; Koo, Min; Park, So Young; Kim, Seungjun; Yang, Kyounghoon; Kim, Sung June; Lee, Kwyro; Lee, Keon Jae

2013-05-28

215

Rapid analysis of tile industry gaseous emissions by ion mobility spectrometry and comparison with solid phase micro-extraction/gas chromatography/mass spectrometry.  

PubMed

The present paper reports on a rapid method for the analysis of gaseous emissions from ceramic industry, based on ion mobility spectrometry (IMS) as a means for on-site monitoring of volatile organic compounds (VOCs) produced during tile baking. IMS was calibrated with a set of reference compounds (i.e. ethyl acetate, ethanol, ethylene glycol, diethylene glycol, acetaldehyde, formaldehyde, 2-methyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 1,3-dioxolane, 1,4-dioxane, benzene, toluene, cyclohexane, acetone, acetic acid) via air-flow permeation. The technique was tested on a laboratory-scale kiln and tiles prepared with selected glycol- and resin-based additives. Finally, the analytical method was applied to emissions from two industries in the Modena (Italy) ceramic area. The results of all experimental phases were compared to those obtained by solid phase micro-extraction/gas chromatography/mass spectrometry (SPME/GC/MS). IMS showed potential as a real-time monitoring device for quality assessment in ceramic industry emissions. IMS spectra, SPME/GC/MS data, relationship between additives/baking conditions and produced VOCs and advantages and limitations of both techniques will be discussed. PMID:17133278

Pozzi, R; Bocchini, P; Pinelli, F; Galletti, G C

2006-12-01

216

High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents.  

PubMed

To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-?m-deep, and 60-?m-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m. PMID:24899869

Li, Yi; Du, Xiaosong; Wang, Yang; Tai, Huiling; Qiu, Dong; Lin, Qinghao; Jiang, Yadong

2014-01-01

217

Performance Analysis and Optimum Operation Planning of Distributed Energy System Based on Micro Gas Turbine-Solid Oxide Fuel Cell Hybrid Power Generation  

NASA Astrophysics Data System (ADS)

In this paper, the economical and energy saving advantages of the distributed energy system, which consists of a micro gas turbine-solid oxide fuel cell hybrid power generation system, waste heat recovery devices and air-conditioning equipments, are investigated. Firstly, the thermodynamical performance evaluation of the hybrid system with the heat recovery devices is discussed to estimate the energy conversion efficiency of the whole system. Secondly, by using 1inear programming technique, the optimum operation planning of the cogeneration plant based on the hybrid system is discussed to predict the reduction of the primary fuel consumption and utility cost. Throughout detailed investigation, it is found that the energy conversion efficiency, which includes the waste heat utilization, reaches over 80% (LHV). In addition, the optimum operation of the hybrid system, of which power generation capacity is appropriate for the energy demand, achieve the highly effective energy saving against the traditional energy supply scheme, that is, the fuel reduction reaches around 40% to the conventional value.

Morita, Aina; Kimijima, Shinji

218

4E analysis and multi objective optimization of a micro gas turbine and solid oxide fuel cell hybrid combined heat and power system  

NASA Astrophysics Data System (ADS)

Energy, exergy, economic and environmental (4E) analysis and optimization of a hybrid solid oxide fuel cell and micro gas turbine (SOFC-MGT) system for use as combined generation of heat and power (CHP) is investigated in this paper. The hybrid system is modeled and performance related results are validated using available data in literature. Then a multi-objective optimization approach based on genetic algorithm is incorporated. Eight system design parameters are selected for the optimization procedure. System exergy efficiency and total cost rate (including capital or investment cost, operational cost and penalty cost of environmental emissions) are the two objectives. The effects of fuel unit cost, capital investment and system power output on optimum design parameters are also investigated. It is observed that the most sensitive and important design parameter in the hybrid system is fuel cell current density which has a significant effect on the balance between system cost and efficiency. The selected design point from the Pareto distribution of optimization results indicates a total system exergy efficiency of 60.7%, with estimated electrical energy cost 0.057 $kW-1 h-1, and payback period of about 6.3 years for the investment.

Sanaye, Sepehr; Katebi, Arash

2014-02-01

219

High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents  

NASA Astrophysics Data System (ADS)

To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-?m-deep, and 60-?m-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m.

Li, Yi; Du, Xiaosong; Wang, Yang; Tai, Huiling; Qiu, Dong; Lin, Qinghao; Jiang, Yadong

2014-05-01

220

Features of the gas discharge in the narrow gap micro-pattern gas detectors (MPGD) at a high level of alpha-particles background  

E-print Network

In given article preliminary results of the research of the electron multiplication in MPGD are presented at a high level of alpha-particles background. This work has expanded borders of understanding of the streamer mode nature. It is seen as a complex from electrostatic and electromagnetic interactions which begin with appearance of the precursor in plasma state. In an inter-electrode gap the plasma oscillations occur, accompanied by longitudinal elastic waves of ionization, which can reach the cathode surface with induced negative charge. With the release of this charge due to previously established conducting channel there is a strong current pulse, accompanied by the emission due to recombination of positive and negative ions and a thin cord or streamer derive. In the aim of the MPGD protection from the spark breakdown at a high level of the alpha-particle background the next gas composition from a buffer, cooling and electronegative components are offered: 70% He +28% CF4 +2% SF6.

V. I. Razin; A. I. Reshetin

2010-09-15

221

Interaction of silicon-based quantum dots with gibel carp liver: oxidative and structural modifications  

PubMed Central

Quantum dots (QDs) interaction with living organisms is of central interest due to their various biological and medical applications. One of the most important mechanisms proposed for various silicon nanoparticle-mediated toxicity is oxidative stress. We investigated the basic processes of cellular damage by oxidative stress and tissue injury following QD accumulation in the gibel carp liver after intraperitoneal injection of a single dose of 2 mg/kg body weight Si/SiO2 QDs after 1, 3, and 7 days from their administration. QDs gradual accumulation was highlighted by fluorescence microscopy, and subsequent histological changes in the hepatic tissue were noted. After 1 and 3 days, QD-treated fish showed an increased number of macrophage clusters and fibrosis, while hepatocyte basophilia and isolated hepatolytic microlesions were observed only after substantial QDs accumulation in the liver parenchyma, at 7 days after IP injection. Induction of oxidative stress in fish liver was revealed by the formation of malondialdehyde and advanced oxidation protein products, as well as a decrease in protein thiol groups and reduced glutathione levels. The liver enzymatic antioxidant defense was modulated to maintain the redox status in response to the changes initiated by Si/SiO2 QDs. So, catalase and glutathione peroxidase activities were upregulated starting from the first day after injection, while the activity of superoxide dismutase increased only after 7 days. The oxidative damage that still occurred may impair the activity of more sensitive enzymes. A significant inhibition in glucose-6-phosphate dehydrogenase and glutathione-S-transferase activity was noted, while glutathione reductase remained unaltered. Taking into account that the reduced glutathione level had a deep decline and the level of lipid peroxidation products remained highly increased in the time interval we studied, it appears that the liver antioxidant defense of Carassius gibelio does not counteract the oxidative stress induced 7 days after silicon-based QDs exposure in an efficient manner. PMID:23718202

2013-01-01

222

Probing silicon based molecular electronics with ultrahigh vacuum scanning tunneling microscopy  

NASA Astrophysics Data System (ADS)

A variable temperature ultra-high vacuum (UHV) scanning tunneling microscope (STM) is utilized for measuring the electrical properties of isolated organic molecules adsorbed to the degenerately doped n- and p-type silicon surfaces at room temperature and 80 K. Current-voltage curves taken under these conditions show negative differential resistance (NDR) at positive sample bias for p-type doping and negative bias for n-type doping. These results qualitatively agree with a theoretical model proposed by Supriyo Datta (Purdue University). Due to the enhanced stability of the STM at cryogenic temperatures, repeated measurements can be routinely taken over the same molecule. Taking advantage of this improved stability, current-voltage curves on isolated cyclopentene molecules are demonstrated to be repeatable and possess negligible hysteresis for a given tip-molecule distance. On the other hand, subsequent measurements with variable tip position show that the NDR voltage increases with increasing tip-molecule distance. Using a one-dimensional capacitive equivalent circuit and a resonant tunneling model, this behavior can be quantitatively explained, thus providing insight into the electrostatic potential distribution across a semiconductor-molecule-vacuum-metal tunnel junction. This model also provides a quantitative estimate for the alignment of the highest occupied molecular orbital (HOMO) of cyclopentene with respect to the Fermi level of the silicon substrate, thus suggesting that this experimental approach can be used for performing chemical spectroscopy at the single molecule level on semiconductor surfaces. Overall, these results serve as the basis for a series of design rules that can be applied to silicon-based molecular electronic devices.

Guisinger, Nathan Paul

223

Interaction of silicon-based quantum dots with gibel carp liver: oxidative and structural modifications  

NASA Astrophysics Data System (ADS)

Quantum dots (QDs) interaction with living organisms is of central interest due to their various biological and medical applications. One of the most important mechanisms proposed for various silicon nanoparticle-mediated toxicity is oxidative stress. We investigated the basic processes of cellular damage by oxidative stress and tissue injury following QD accumulation in the gibel carp liver after intraperitoneal injection of a single dose of 2 mg/kg body weight Si/SiO2 QDs after 1, 3, and 7 days from their administration. QDs gradual accumulation was highlighted by fluorescence microscopy, and subsequent histological changes in the hepatic tissue were noted. After 1 and 3 days, QD-treated fish showed an increased number of macrophage clusters and fibrosis, while hepatocyte basophilia and isolated hepatolytic microlesions were observed only after substantial QDs accumulation in the liver parenchyma, at 7 days after IP injection. Induction of oxidative stress in fish liver was revealed by the formation of malondialdehyde and advanced oxidation protein products, as well as a decrease in protein thiol groups and reduced glutathione levels. The liver enzymatic antioxidant defense was modulated to maintain the redox status in response to the changes initiated by Si/SiO2 QDs. So, catalase and glutathione peroxidase activities were upregulated starting from the first day after injection, while the activity of superoxide dismutase increased only after 7 days. The oxidative damage that still occurred may impair the activity of more sensitive enzymes. A significant inhibition in glucose-6-phosphate dehydrogenase and glutathione-S-transferase activity was noted, while glutathione reductase remained unaltered. Taking into account that the reduced glutathione level had a deep decline and the level of lipid peroxidation products remained highly increased in the time interval we studied, it appears that the liver antioxidant defense of Carassius gibelio does not counteract the oxidative stress induced 7 days after silicon-based QDs exposure in an efficient manner.

Stanca, Loredana; Petrache, Sorina Nicoleta; Serban, Andreea Iren; Staicu, Andrea Cristina; Sima, Cornelia; Munteanu, Maria Cristina; Z?rnescu, Otilia; Dinu, Diana; Dinischiotu, Anca

2013-05-01

224

A silicon integrated micro nano-positioning XY-stage for nano-manipulation  

Microsoft Academic Search

An integrated micro XY-stage with a 2 × 2 mm2 movable table is designed and fabricated for application in nanometer-scale operation and nanometric positioning precision. The device integrates the functions of both actuating and sensing in a monolithic chip and is mainly composed of a silicon-based XY-stage, comb-drive actuator and a displacement sensor, which are developed by using double-sided bulk-micromachining

Lining Sun; Jiachou Wang; Weibin Rong; Xinxin Li; Haifei Bao

2008-01-01

225

Identification of metabolites from liquid chromatography-coulometric array detection profiling: gas chromatography-mass spectrometry and refractionation provide essential information orthogonal to LC-MS/microNMR.  

PubMed

Liquid chromatography-coulometric array detection (LC-EC) is a sensitive, quantitative, and robust metabolomics profiling tool that complements the commonly used mass spectrometry (MS) and nuclear magnetic resonance (NMR)-based approaches. However, LC-EC provides little structural information. We recently demonstrated a workflow for the structural characterization of metabolites detected by LC-EC profiling combined with LC-electrospray ionization (ESI)-MS and microNMR. This methodology is now extended to include (i) gas chromatography (GC)-electron ionization (EI)-MS analysis to fill structural gaps left by LC-ESI-MS and NMR and (ii) secondary fractionation of LC-collected fractions containing multiple coeluting analytes. GC-EI-MS spectra have more informative fragment ions that are reproducible for database searches. Secondary fractionation provides enhanced metabolite characterization by reducing spectral overlap in NMR and ion suppression in LC-ESI-MS. The need for these additional methods in the analysis of the broad chemical classes and concentration ranges found in plasma is illustrated with discussion of four specific examples: (i) characterization of compounds for which one or more of the detectors is insensitive (e.g., positional isomers in LC-MS, the direct detection of carboxylic groups and sulfonic groups in (1)H NMR, or nonvolatile species in GC-MS), (ii) detection of labile compounds, (iii) resolution of closely eluting and/or coeluting compounds, and (iv) the capability to harness structural similarities common in many biologically related, LC-EC-detectable compounds. PMID:24657819

Gathungu, Rose M; Bird, Susan S; Sheldon, Diane P; Kautz, Roger; Vouros, Paul; Matson, Wayne R; Kristal, Bruce S

2014-06-01

226

A novel approach to mixed field dosimetry utilizing prototype silicon based P-I-N diodes  

NASA Astrophysics Data System (ADS)

Novel approaches to mixed beam dosimetry are presented, utilizing silicon based semiconductor detectors. The forward voltage drop across the diode is proportional to neutron induced damage caused by the non-ionizing energy losses (NIEL) and correlates with neutron dose. On the other hand, the current produced in the diode is due to both neutron and gamma interactions (ionizing energy losses IEL) and may be correlated with the total dose. A single diode operated in these two modes of operation thus may be used as a twin detector in mixed fields. A special circuitry has been built to read out the voltage drop increase associated with neutron damage. The circuitry allows online monitoring of voltage drop across the diode and the beam target current simultaneously. A pulsed constant current is used to reduce signal variation due to temperature effects. A modified lead attenuation method has been adopted and successfully applied to determine the neutron sensitivity of PIN diodes of different geometry. The sensitivity is given in mV cGy-1 when the diode is operated in voltage drop mode, or in nC cGy-1 when the diode is operated in charge mode. Sensitivity of the diodes to gamma rays was determined from measurements in a 60Co beam. Neutron and gamma doses were measured at 17 different points. The diodes demonstrated good accuracy in measuring neutron and total dose, agreeing to within the stated uncertainties with results obtained with the twin detector method for 14 of the measured points. Discrepancies were noted in the penumbra, where the dose gradient is highest. In measuring the gamma component all methods agree to within stated uncertainties. The largest uncertainty in the measurements is observed when the gamma dose is very small relative to the neutron dose. The proposed detectors offer the advantages of high spatial resolution, simple instrumentation and immediate availability of the measured dose. Most importantly, a single detector can be used for separating dose components in the mixed beam. These features make the diode detectors well suited for a number of applications including in-vivo dosimetry, intensity modulated neutron radiation therapy (IMNRT) and measurements of penumbra.

Alyousef, Khalid A.

227

Silicon based nano-architectures for high power lithium-ion battery anodes  

NASA Astrophysics Data System (ADS)

Lithium-ion batteries have now become an inseparable part of modern day society as the power source for several portable electronics like cell phones, digital cameras and laptops. Their high energy density compared with other electrochemical battery systems has been their most attractive feature. This has lead to a great interest in developing lithium-ion batteries for hybrid and all-electric vehicles. Eventually such vehicles will help drastically reduce the carbon footprint making the environment cleaner and healthier. In spite of their high energy density, Li-ion batteries are known to have poor power densities. This forms a major limitation in their deployment as a power source on vehicles. Electric vehicles need power sources that can provide both high energy and power densities. This requires the development of anode, cathode and electrolyte materials that would transform the capabilities of existing Li-ion batteries. Among anode materials silicon has received great attention because of its very large theoretical capacity of ˜4200 mAh/g based on the alloy Li22Si5. It should be noted that storage of charge in the anode occurs through the alloying of Li with the host anode material. However, the large specific capacity of silicon also results in a ˜400% volume expansion which could lead to pulverization and delamination reducing the cycle life of the electrode. These failure processes are exacerbated at high rates making it extremely difficult to use silicon for high-power Li-ion battery anodes. The major research thrust supporting this Ph.D. thesis involved exploring silicon based nano-architectures that would provide high energy and power densities over a long cycle life. The key technique used to design different nano-architectures was DC Magnetron sputtering with oblique angle deposition. The main development of this research was a functionally strain graded Carbon-Aluminum-Silicon nanoscoop architecture for high-power Li-ion battery anodes. This consisted of Carbon nanorods with an intermediate Aluminum layer finally capped by a nanoscoop of Silicon. The strain gradation arises from the fact that each of these materials has differential volumetric expansions due to different extents of Li uptake. Such a strain gradation from Carbon towards Silicon would provide for a less abrupt transition across the material interfaces thereby reducing interfacial mismatch and improving the tolerance to delamination at very high rates. This nano-architecture provided average capacities of ˜412 mAh/g with a power output of ˜100 kW/kg electrode continuously over 100 cycles. Even when the power output was as high as ˜250 kW/kgelectrode, the average capacity over 100 cycles is still ˜90 mAh/g. Furthermore, scanning electron microscopy and X-ray photoelectron spectroscopy investigations revealed that the functionally strain graded nanostructures were being partially lithiated in the bulk even at high rates. The fact that charge storage was not merely a surface phenomenon supported the high energy densities obtained at high charge/discharge rates. In an attempt to improve the mass loading density of Silicon based nano-architectures, a nano-compliant layer (NCL) supported thin film architecture was also explored. This consisted of an array of oblique nanorods (the nano-compliant layer) sandwiched between the substrate and the thin film. The NCL layer was used to improve the stress tolerance of the thin film thereby allowing the use of bulk thin films as opposed to nanostructures. This would directly improve the mass loading density. Silicon films with Carbon NCLs and Carbon films with Silicon NCLs were both deposited and tested. It was found that Li+ diffusivity is higher in carbon than in silicon by at least two orders of magnitude. This was calculated from cyclic voltammetry tests using the Randles-Sevcik equation. This difference in Li+ diffusivity within the two materials was found to be the C-rate limiting factor for a given nano-architecture design.

Krishnan, Rahul

228

Micro-machined resonator  

DOEpatents

A micro-machined resonator, typically quartz, with upper and lower micro-machinable support members, or covers, having etched wells which may be lined with conductive electrode material, between the support members is a quartz resonator having an energy trapping quartz mesa capacitively coupled to the electrode through a diaphragm; the quartz resonator is supported by either micro-machined cantilever springs or by thin layers extending over the surfaces of the support. If the diaphragm is rigid, clock applications are available, and if the diaphragm is resilient, then transducer applications can be achieved. Either the thin support layers or the conductive electrode material can be integral with the diaphragm. In any event, the covers are bonded to form a hermetic seal and the interior volume may be filled with a gas or may be evacuated. In addition, one or both of the covers may include oscillator and interface circuitry for the resonator.

Godshall, Ned A. (Albuquerque, NM); Koehler, Dale R. (Albuquerque, NM); Liang, Alan Y. (Albuquerque, NM); Smith, Bradley K. (Albuquerque, NM)

1993-01-01

229

Micro-machined resonator  

DOEpatents

A micro-machined resonator, typically quartz, with upper and lower micro-machinable support members, or covers, having etched wells which may be lined with conductive electrode material, between the support members is a quartz resonator having an energy trapping quartz mesa capacitively coupled to the electrode through a diaphragm; the quartz resonator is supported by either micro-machined cantilever springs or by thin layers extending over the surfaces of the support. If the diaphragm is rigid, clock applications are available, and if the diaphragm is resilient, then transducer applications can be achieved. Either the thin support layers or the conductive electrode material can be integral with the diaphragm. In any event, the covers are bonded to form a hermetic seal and the interior volume may be filled with a gas or may be evacuated. In addition, one or both of the covers may include oscillator and interface circuitry for the resonator.

Godshall, N.A.; Koehler, D.R.; Liang, A.Y.; Smith, B.K.

1993-03-30

230

A review: mid-infrared photonic crystals in silicon and porous silicon based on ion beam irradiation  

NASA Astrophysics Data System (ADS)

Silicon and porous silicon based photonic crystals are key aspects of photonic circuits with good compatibility with integrated circuits. Here a brief review is carried out on the fabrication of mid infrared photonic crystals using experimental processes of combining ion beam irradiation and electrochemical anodisation of silicon. Experimental processes have been developed to fabricate high aspect ratio trenches in porous silicon, high aspect ratio silicon pillars, buried channels in porous silicon, and multilevel freestanding silicon wires. These structures have the potential to be used for photonic crystals. Several 2D, quasi-3D and 3D mid infrared photonic crystals in porous silicon and silicon have been designed and fabricated.

Dang, Zhiya; Breese, Mark; Liu, Dongqing; Turaga, Shuvan Prashant; Azimi, Sara; Song, Jiao; Banas, Agnieszka; Recio-Sánchez, Gonzalo

2014-11-01

231

Preparation of 2,3-Disubstituted Indoles by Sequential Larock Heteroannulation and Silicon-Based Cross-Coupling Reactions  

PubMed Central

A simple and convergent synthesis of 2,3-disubstituted indoles has been developed using a sequential Larock indole synthesis and silicon-based, cross-coupling reaction. Substituted 2-iodoanilines reacted with an alkynyldimethylsilyl tert-butyl ether to afford indole-2-silanols under the Larock heteroannulation conditions after hydrolysis. The corresponding sodium 2-indolylsilanolate salts successfully engaged in cross-coupling with aryl bromides and chlorides to afford multi-substituted indoles. The development of an alkynyldimethylsilyl tert-butyl ether as a masked silanol equivalent enabled a smooth heteroannulation process and the identification of a suitable catalyst/ligand combination provided for a facile cross-coupling reaction. PMID:19784400

Baird, John D.

2009-01-01

232

Gas Producing Micro-Reaction  

NSDL National Science Digital Library

In this chemistry activity, learners use common chemicals and metals to examine reactions that produce gaseous substances. Learners will identify the gases produced and write a balanced equation for each reaction. Use this activity to also introduce learners to single displacement and double displacement reactions, two types of chemical reactions.

2014-01-28

233

Design and evaluation of a low nitrogen oxides natural gas-fired conical wire-mesh duct burner for a micro-cogeneration unit  

NASA Astrophysics Data System (ADS)

A novel low NOx conical wire-mesh duct burner was designed, built and tested in the present research. This thesis documents the design process and the in-depth evaluation of this novel duct burner for the development of a more efficient micro-cogeneration unit. This duct burner provides the thermal energy necessary to raise the microturbine exhaust gases temperature to increase the heat recovery capability. The duct burner implements both lean-premixed and surface combustion techniques to achieve low NOx and CO emissions. The design of the duct burner was supported by a qualitative flow visualization study for the duct burner premixer to provide insight into the premixer flow field (mixing process). Different premixer geometries were used to control the homogeneity of the fuel-oxidant mixture at the exit of the duct burner premixer. Laser sheet illumination (LSI) technique was used to capture images of the mixing process, for each configuration studied. A quasi-quantitative analysis technique was developed to rank the different premixer geometries in terms of mixing effectiveness. The premixer geometries that provided better mixing were selected and used for the combustion tests. The full-scale gas-fired duct burner was installed in the exhaust duct of a micro-cogeneration unit for the evaluation. Three wire-mesh burners with different pressure drops were used. Each burner has a conical shape made from FeCrAL alloy mat and was designed based on a heat release per unit area of 2500 kW/m2 and a total heat release of 240kW at 100 percent excess air. The local momentum of the gaseous mixture introduced through the wire-mesh was adjusted so that the flame stabilized outside the burner mesh (surface combustion). Cold flow tests (i.e., the duct burner was off, but the microturbine was running) were conducted to measure the effect of different duct burner geometrical parameters on flow split between the combustion zone and the bypass channel, and on pressure drop across the duct burner. A considerable amount of detailed parametric experimental data was collected to investigate the performance characteristics of the duct burner. The variables studied (firing rate, mass flow ratio, conical burner pressure drop, blockage ratio, conical burner shield length, premixer geometry and inlet conditions) were all found to play an important role on emissions (NOx and CO), overall duct burner pressure drop and flame stability. The range of firing rates at which surface combustion was maintained for the duct burner was defined by direct observation of the burner surface and monitoring of the temperature in the combustion zone. Flame images were captured for qualitative assessment. The combustion tests results presented in this thesis proved that the design procedures that were implemented to design this novel microturbine conical wire-mesh duct burner were successful. During the course of the combustion tests, the duct burner displayed stable, low emissions operation throughout the surface firing rate range of 148 kW to 328 kW (1574 kW/m 2 to 3489 kW/m2). Emissions of less than 5 ppm (corrected to 15 percent 02) for NOx and CO emissions were recorded, while the duct burner successfully raised the microturbine exhaust gases temperature from about 227°C to as high as 700°C. The overall duct burner pressure drop throughout was consistently below the design limit of 249 Pa.

Ramadan, Omar Barka Ab

234

Micro heat barrier  

DOEpatents

A highly effective, micron-scale micro heat barrier structure and process for manufacturing a micro heat barrier based on semiconductor and/or MEMS fabrication techniques. The micro heat barrier has an array of non-metallic, freestanding microsupports with a height less than 100 microns, attached to a substrate. An infrared reflective membrane (e.g., 1 micron gold) can be supported by the array of microsupports to provide radiation shielding. The micro heat barrier can be evacuated to eliminate gas phase heat conduction and convection. Semi-isotropic, reactive ion plasma etching can be used to create a microspike having a cusp-like shape with a sharp, pointed tip (<0.1 micron), to minimize the tip's contact area. A heat source can be placed directly on the microspikes. The micro heat barrier can have an apparent thermal conductivity in the range of 10.sup.-6 to 10.sup.-7 W/m-K. Multiple layers of reflective membranes can be used to increase thermal resistance.

Marshall, Albert C.; Kravitz, Stanley H.; Tigges, Chris P.; Vawter, Gregory A.

2003-08-12

235

Study of silicone-based materials for the packaging of optoelectronic devices  

NASA Astrophysics Data System (ADS)

The first part of this work is to evaluate the main materials used for the packaging of high power light-emitting diodes (LEDs), i.e., the die attach materials, the encapsulant materials, and high color rendering index(CRI) sol-gel composite materials. All of these materials had been discussed the performance, reliability, and issues in high power LED packages. High power white LEDs are created either from blue or near-ultraviolet chips encapsulated with a yellow phosphor, or from red-green-blue LED light mixing systems. The phosphor excited by blue LED chip was mostly used in experiment of this dissertation. The die attach materials contains filler particles possessing a maximum particle size less than 1.5 mum in diameter blended with epoxy polymer matrix. Such compositions enable thin bond line thickness, which decreases thermal resistance that exists between thermal interface materials and the corresponding mating surfaces. The thermal conductivity of nano silver die attach materials is relatively low, the thermal resistance from the junction to board is just 1.6 KW-1 in the bond line thickness of 5.3 mum, which is much lower than the thermal resistance using conventional die attach materials. The silicone die attach adhesive made in the lab cures through the free radical reaction of epoxy-functional organopolysiloxane and through the hydrosilylation reaction between alkenyl-functional organopolysiloxane and silicone-boned hydrogen-functional organopolysiloxane. By the combination of the free radical reaction and the hydrosilylation reaction, the low-molecular-weight silicone oil will not be out-migrated and not contaminate wire bondability to the LED chip and lead frame. Hence, the silicone die attach adhesive made in the lab can pass all reliability tests, such as operating life test JEDEC 85°C/85RH and room temperature operating life test. For LED encapsulating materials, most of commercial silicone encapsulants still suffer thermal/radiation induced degradations, and thus cause reliability issues and shorten the lifetime. A new high performance silicone has been developed and its performance has been compared with other commercial silicone products in the packaging of high power white LEDs. The high performance silicone also has better results than commercial high refractive index silicone and optical grade epoxy under JEDEC reliability standard for moisture sensitivity test. In synthesis of red dye-doped particles by sol-gel method, it is a novel method to get high color rendering index (CRI) LEDs. These red dye-doped particles, with average diameter of 5 mum, can be mixed with liquid encapsulants to form a uniform distribution in polymer matrix. The red dye-doped particles can be excited by phosphor-emitted yellow light instead of blue light from LED chip. Therefore, warm white LEDs with high CRI can be gotten at high lumen efficiency. The second part of this work is silicone elastomer for biomedical applications, especially in making urological implantable devices. A cross-linked, heat curable, addition-reaction silicone material is prepared. The material may be molded or formed into one or more medical devices. One such medical device could be a catheter used in urological applications. The material is a long term indwelling material that resists encrustation like a metal stent, but is more comfortable because it is silicone-based. The material can be made relatively cheaply compared to metal stents. Furthermore, the material is biocompatible with bladder epithelial cells.

Lin, Yeong-Her

236

Micro Navigator  

NASA Astrophysics Data System (ADS)

Miniature high-performance low-mass space avionics systems are desired for planned future outer planetary exploration missions (i.e. Europa Orbiter/Lander, Pluto-Kuiper Express). The spacecraft fuel and mass requirements enabling orbit insertion is the driving requirement. The Micro Navigator is an integrated autonomous Guidance, Navigation & Control (GN&C)micro-system that would provide the critical avionics function for navigation, pointing, and precision landing. The Micro Navigator hardware and software allow fusion of data from multiple sensors to provide a single integrated vehicle state vector necessary for six degrees of freedom GN&C. The benefits of this MicroNavigator include: 1) The Micro Navigator employs MEMS devices that promise orders of magnitude reductions in mass power and volume of inertial sensors (accelerometers and gyroscopes), celestial sensing devices (startracker, sun sensor), and computing element; 2) The highly integrated nature of the unit will reduce the cost of flight missions. a) The advanced miniaturization technologies employed by the Micro Navigator lend themselves to mass production, and therefore will reduce production cost of spacecraft. b) The integral approach simplifies interface issues associated with discrete components and reduces cost associated with integration and test of multiple components; and 3) The integration of sensors and processing elements into a single unit will allow the Micro Navigator to encapsulate attitude information and determination functions into a single object. This is particularly beneficial for object-oriented software architectures that are used in advanced spacecraft. Additional information is contained in the original extended abstract.

Blaes, B. R.; Kia, T.; Chau, S. N.

2001-01-01

237

Silicon Based Solid Oxide Fuel Cell Chip for Portable Consumer Electronics -- Final Technical Report  

SciTech Connect

LSI’s fuel cell uses efficient Solid Oxide Fuel Cell (“SOFC”) technology, is manufactured using Micro Electrical Mechanical System (“MEMS”) fabrication methods, and runs on high energy fuels, such as butane and ethanol. The company’s Fuel Cell on a Chip™ technology enables a form-factor battery replacement for portable electronic devices that has the potential to provide an order-of-magnitude run-time improvement over current batteries. Further, the technology is clean and environmentally-friendly. This Department of Energy funded project focused on accelerating the commercialization and market introduction of this technology through improvements in fuel cell chip power output, lifetime, and manufacturability.

Alan Ludwiszewski

2009-06-29

238

Structural and Oxidative Changes in the Kidney of Crucian Carp Induced by Silicon-Based Quantum Dots  

PubMed Central

Silicon-based quantum dots were intraperitoneally injected in Carassius auratus gibelio specimens and, over one week, the effects on renal tissue were investigated by following their distribution and histological effects, as well as antioxidative system modifications. After three and seven days, detached epithelial cells from the basal lamina, dilated tubules and debris in the lumen of tubules were observed. At day 7, nephrogenesis was noticed. The reduced glutathione (GSH) concentration decreased in the first three days and started to rise later on. The superoxide dismutase (SOD) activity increased only after one week, whereas catalase (CAT) was up-regulated in a time-dependent manner. The activities of glutathione reductase (GR) and glutathione peroxidise (GPX) decreased dramatically by approximately 50% compared to control, whereas the glutathione-S-transferase (GST) and glucose-6-phosphate dehydrogenase (G6PDH) increased significantly after 3 and 7 days of treatment. Oxidative modifications of proteins and the time-dependent increase of Hsp70 expression were also registered. Our data suggest that silicon-based quantum dots induced oxidative stress followed by structural damages. However, renal tissue is capable of restoring its integrity by nephron development. PMID:22949855

Petrache, Sorina Nicoleta; Stanca, Loredana; Serban, Andreea Iren; Sima, Cornelia; Staicu, Andreia Cristina; Munteanu, Maria Cristina; Costache, Marieta; Burlacu, Radu; Zarnescu, Otilia; Dinischiotu, Anca

2012-01-01

239

Research on high-efficiency, multiple-gap, multijunction, amorphous-silicon-based alloy thin-film solar cells  

SciTech Connect

This report presents results of research on advancing our understanding of amorphous-silicon-based alloys and their use in small-area multijunction solar cells. The principal objectives of the program are to develop a broad scientific base for the chemical, structural, optical, and electronic properties of amorphous-silicon-based alloys; to determine the optimum properties of these alloy materials as they relate to high-efficiency cells; to determine the optimum device configuration for multijunction cells; and to demonstrate proof-of-concept, multijunction, a-Si-alloy-based solar cells with 18% efficiency under standard AM1.5 global insolation conditions and with an area of at least 1 cm{sup 2}. A major focus of the work done during this reporting period was the optimization of a novel, multiple-graded structure that enhances cell efficiency through band-gap profiling. The principles of the operation of devices incorporating such a structure, computer simulations of those, and experimental results for both single- and multijunction cells prepared by using the novel structure are discussed in detail. 14 refs., 35 figs., 7 tabs.

Guha, S. (Energy Conversion Devices, Inc., Troy, MI (USA))

1989-06-01

240

A Silicon-Based Two-Dimensional Chalcogenide: Growth of Si2Te3 Nanoribbons and Nanoplates.  

PubMed

We report the synthesis of high-quality single-crystal two-dimensional, layered nanostructures of silicon telluride, Si2Te3, in multiple morphologies controlled by substrate temperature and Te seeding. Morphologies include nanoribbons formed by VLS growth from Te droplets, vertical hexagonal nanoplates through vapor-solid crystallographically oriented growth on amorphous oxide substrates, and flat hexagonal nanoplates formed through large-area VLS growth in liquid Te pools. We show the potential for doping through the choice of substrate and growth conditions. Vertical nanoplates grown on sapphire substrates, for example, can incorporate a uniform density of Al atoms from the substrate. We also show that the material may be modified after synthesis, including both mechanical exfoliation (reducing the thickness to as few as five layers) and intercalation of metal ions including Li(+) and Mg(2+), which suggests applications in energy storage materials. The material exhibits an intense red color corresponding to its strong and broad interband absorption extending from the red into the infrared. Si2Te3 enjoys chemical and processing compatibility with other silicon-based material including amorphous SiO2 but is very chemically sensitive to its environment, which suggests applications in silicon-based devices ranging from fully integrated thermoelectrics to optoelectronics to chemical sensors. PMID:25764295

Keuleyan, Sean; Wang, Mengjing; Chung, Frank R; Commons, Jeffrey; Koski, Kristie J

2015-04-01

241

A high efficient micro-proton exchange membrane fuel cell by integrating micro-nano synergical structures  

NASA Astrophysics Data System (ADS)

A silicon-based micro-proton exchange membrane fuel cell (?-PEMFC) which carries out an outstanding cell performance and high efficient catalyst utilization ratio is proposed in this paper by the employment of three micro-nano synergical techniques. Firstly, a novel design incorporating multi-walled carbon nano-tubes (MWCNTs) on radial shaped micro-channel walls to form micro/nano reaction chambers which significantly enhance the reaction surface areas for the performance improvement. In the second, the dispensing of ionomer onto the three-phase zones in the reaction chambers is controlled by different rotation speed and the optimized distribution can therefore be achieved for the improvement of catalyst utilization. In the third, the cell interfacial strength is greatly enhanced by the employment of micro-interlocks for maintaining excellent interface between Nafion membrane and reaction chambers while minimizing the system size. A ?-PEMFC is successfully fabricated by integrating aforementioned synergical micro/nano structures altogether. The best cell efficiency is 26 mW cm-2 which corresponds to a catalyst utilization ratio of 38.2 W g-pt-1, and can be considered among the best performed micro-fuel cells.

Peng, Hsien-Chih; Wang, Chung-Nan; Yeh, Tsung-Kuang; Su, Yu-Chuan; Pan, Chin; Tseng, Fan-Gang

2013-03-01

242

Biocompatibility Assessment of Si-based Nano- and Micro-particles  

PubMed Central

Silicon is one of the most abundant chemical elements found on the Earth. Due to its unique chemical and physical properties, silicon based materials and their oxides (e.g. silica) have been used in several industries such as building and construction, electronics, food industry, consumer products and biomedical engineering/medicine. This review summarizes studies on effects of silicon and silica nano- and micro-particles on cells and organs following four main exposure routes, namely, intravenous, pulmonary, dermal and oral. Further, possible genotoxic effects of silica based nanoparticles are discussed. The review concludes with an outlook on improving and standardizing biocompatibility assessment for nano- and micro-particles. PMID:22634160

Jaganathan, Hamsa; Godin, Biana

2012-01-01

243

A thermally self-sustained micro-power plant with integrated micro-solid oxide fuel cells, micro-reformer and functional micro-fluidic carrier  

NASA Astrophysics Data System (ADS)

Low temperature micro-solid oxide fuel cell (micro-SOFC) systems are an attractive alternative power source for small-size portable electronic devices due to their high energy efficiency and density. Here, we report on a thermally self-sustainable reformer-micro-SOFC assembly. The device consists of a micro-reformer bonded to a silicon chip containing 30 micro-SOFC membranes and a functional glass carrier with gas channels and screen-printed heaters for start-up. Thermal independence of the device from the externally powered heater is achieved by exothermic reforming reactions above 470 °C. The reforming reaction and the fuel gas flow rate of the n-butane/air gas mixture controls the operation temperature and gas composition on the micro-SOFC membrane. In the temperature range between 505 °C and 570 °C, the gas composition after the micro-reformer consists of 12 vol.% to 28 vol.% H2. An open-circuit voltage of 1.0 V and maximum power density of 47 mW cm-2 at 565 °C is achieved with the on-chip produced hydrogen at the micro-SOFC membranes.

Scherrer, Barbara; Evans, Anna; Santis-Alvarez, Alejandro J.; Jiang, Bo; Martynczuk, Julia; Galinski, Henning; Nabavi, Majid; Prestat, Michel; Tölke, René; Bieberle-Hütter, Anja; Poulikakos, Dimos; Muralt, Paul; Niedermann, Philippe; Dommann, Alex; Maeder, Thomas; Heeb, Peter; Straessle, Valentin; Muller, Claude; Gauckler, Ludwig J.

2014-07-01

244

Focused ion beam high resolution grayscale lithography for silicon-based nanostructures  

SciTech Connect

Nanofabrication techniques providing a fine control over the profile of silicon structures are of great importance for nanophotonics, plasmonics, sensing, micro- and nano fluidics, and biomedical applications. We report on the applicability of focused ion beam for the fine grayscale lithography, which yields surface profiles that are customized at nanoscale. The approach is based on a correlation between the ion beam irradiation dose of inorganic resist and the mask etching rate in the reactive ion etching. An exceptional property of this method is the number of gray tones that are not limited by the resist characteristics. We apply the process to fabricate unique periodic nanostructures with a slope angle varying across the structure and a period as small as 200?nm.

Erdmanis, M., E-mail: mikhail.erdmanis@aalto.fi; Tittonen, I. [Department of Micro- and Nanosciences, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland)

2014-02-17

245

InGaAlAsPN: A Materials System for Silicon Based Optoelectronics and Heterostructure Device Technologies  

NASA Technical Reports Server (NTRS)

A new material system is proposed for silicon based opto-electronic and heterostructure devices; the silicon lattice matched compositions of the (In,Ga,Al)-(As,P)N 3-5 compounds. In this nitride alloy material system, the bandgap is expected to be direct at the silicon lattice matched compositions with a bandgap range most likely to be in the infrared to visible. At lattice constants ranging between those of silicon carbide and silicon, a wider bandgap range is expected to be available and the high quality material obtained through lattice matching could enable applications such as monolithic color displays, high efficiency multi-junction solar cells, opto-electronic integrated circuits for fiber communications, and the transfer of existing 3-5 technology to silicon.

Broekaert, T. P. E.; Tang, S.; Wallace, R. M.; Beam, E. A., III; Duncan, W. M.; Kao, Y. -C.; Liu, H. -Y.

1995-01-01

246

High temperature electrical conductivity and thermal decomposition of phenolic- and silicon-based dielectrics for fireset housings  

SciTech Connect

The temperature dependence of the electrical conductivity and thermal decomposition characteristics of several phenolic- and silicone-based materials of interest for fireset case housings have been measured to 600 to 700/sup 0/C. The materials are phenolic or silicone resins reinforced with glass chopped fabric or cloth. The conductivity temperature dependence was measured during decomposition in a nitrogen atmosphere at a heating rate of approx. 10/sup 0/C/minute. Applied electric fields were from 4 x 10/sup 2/ to 4 x 10/sup 3/ volts/cm. Thermal decomposition characteristics were investigated by mass spectroscopy in vacuum and thermal gravimetric analysis in nitrogen and air. Nearly ohmic voltage-current characteristics were obtained, except where decomposition and/or outgassing was pronounced.

Johnson, R.T. Jr.; Biefeld, R.M.

1981-08-01

247

High yield fabrication of hollow vesica-like silicon based on the Kirkendall effect and its application to energy storage.  

PubMed

Recently, a unique process based on the Kirkendall effect was employed to generate hollow nanostructures with a wide variety of materials. However, a similar hollow structure of silicon based on the fabrication mechanism of the Kirkendall effect is still not proposed. Here, we provide an extensible synthesis method for the high yield fabrication of a uniform vesica-like hollow Si material from SiO2 based on the Kirkendall effect in a molten salt reduction process. Significantly, without further modification, the as-prepared hollow vesica-like Si exhibits a high electrochemical storage capacity and long cycling properties (?712 mA h g(-1) at 0.36 A g(-1) over 200 cycles). PMID:25644942

Liang, Jianwen; Li, Xiaona; Cheng, Qiushi; Hou, Zhiguo; Fan, Long; Zhu, Yongchun; Qian, Yitai

2015-02-12

248

Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof  

DOEpatents

An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al.sub.x N.sub.y O.sub.z layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al.sub.x N.sub.y O.sub.z layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

Sarin, Vinod K. (Lexington, MA)

1990-01-01

249

Fabrication and direct transmission measurement of high-aspect-ratio two-dimensional silicon-based photonic crystal chips  

SciTech Connect

We report the fabrication and characterization of two-dimensional silicon-based photonic crystal (PhC) structures realized by a combination of electron-beam lithography and dry-etching techniques. PhCs of various lattices with very high aspect ratios up to 20 have been achieved, and PhC chips were prepared by standard semiconductor technologies, including thinning and cleaving. The chips consisting of high-aspect-ratio air rods or dielectric rods permit a direct transmission measurement, and they were observed to demonstrate pronounced photonic bandgap effects. Several photonic bandgap behaviors were identified by comparing transmission with reflection and experimental results with numerical results, and by considering detecting beam property. {copyright} 2001 Optical Society of America

Xu, Ying; Sun, Hong-Bo; Ye, Jia-Yu; Matsuo, Shigeki; Misawa, Hiroaki

2001-08-01

250

THz-wave generation via difference frequency mixing in strained silicon based waveguide utilizing its second order susceptibility ?((2)).  

PubMed

Terahertz (THz) wave generation via difference frequency mixing (DFM) process in strain silicon membrane waveguides by introducing the straining layer is theoretically investigated. The Si(3)N(4) straining layer induces anisotropic compressive strain in the silicon core and results in the appearance of the bulk second order nonlinear susceptibility ?((2)) by breaking the crystal symmetry. We have proposed waveguide structures for THz wave generation under the DFM process by .using the modal birefringence in the waveguide core. Our simulations show that an output power of up to 0.95 mW can be achieved at 9.09 THz. The strained silicon optical device may open a widow in the field of the silicon-based active THz photonic device applications. PMID:25090484

Saito, Kyosuke; Tanabe, Tadao; Oyama, Yutaka

2014-07-14

251

High yield fabrication of hollow vesica-like silicon based on the Kirkendall effect and its application to energy storage  

NASA Astrophysics Data System (ADS)

Recently, a unique process based on the Kirkendall effect was employed to generate hollow nanostructures with a wide variety of materials. However, a similar hollow structure of silicon based on the fabrication mechanism of the Kirkendall effect is still not proposed. Here, we provide an extensible synthesis method for the high yield fabrication of a uniform vesica-like hollow Si material from SiO2 based on the Kirkendall effect in a molten salt reduction process. Significantly, without further modification, the as-prepared hollow vesica-like Si exhibits a high electrochemical storage capacity and long cycling properties (~712 mA h g-1 at 0.36 A g-1 over 200 cycles).Recently, a unique process based on the Kirkendall effect was employed to generate hollow nanostructures with a wide variety of materials. However, a similar hollow structure of silicon based on the fabrication mechanism of the Kirkendall effect is still not proposed. Here, we provide an extensible synthesis method for the high yield fabrication of a uniform vesica-like hollow Si material from SiO2 based on the Kirkendall effect in a molten salt reduction process. Significantly, without further modification, the as-prepared hollow vesica-like Si exhibits a high electrochemical storage capacity and long cycling properties (~712 mA h g-1 at 0.36 A g-1 over 200 cycles). Electronic supplementary information (ESI) available: Experimental section; detail analysis of silica aerogel and the resulting production before wash; auxiliary analysis such as different magnification SEM images, TEM images and Raman spectra of SiNV; TEM image of the SiNV after 100 cycles. See DOI: 10.1039/c4nr07642g

Liang, Jianwen; Li, Xiaona; Cheng, Qiushi; Hou, Zhiguo; Fan, Long; Zhu, Yongchun; Qian, Yitai

2015-02-01

252

Local Heating of Discrete Droplets Using Magnetic Porous Silicon-Based Photonic Crystals  

PubMed Central

This paper describes a method for local heating of discrete micro-liter scale liquid droplets. The droplets are covered with magnetic porous Si microparticles, and heating is achieved by application of an external alternating electromagnetic field. The magnetic porous Si microparticles consist of two layers: the top layer contains a photonic code and it is hydrophobic, with surface-grafted dodecyl moieties. The bottom layer consists of a hydrophilic Si oxide host layer that is infused with Fe3O4 nanoparticles. The amphiphilic microparticles spontaneously align at the interface of a water droplet immersed in mineral oil, allowing manipulation of the droplets by application of a magnetic field. Application of an oscillating magnetic field (338 kHz, 18A RMS current in a coil surrounding the experiment) generates heat in the superparamagnetic particles that can raise the temperature of the enclosed water droplet to >80 °C within 5 min. A simple microfluidics application is demonstrated: combining complementary DNA strands contained in separate droplets and then thermally inducing dehybridization of the conjugate. The complementary oligonucleotides were conjugated with the cyanine dye fluorophores Cy3 and Cy5 to quantify the melting/re-binding reaction by fluorescence resonance energy transfer (FRET). The magnetic porous Si microparticles were prepared as photonic crystals, containing spectral codes that allowed the identification of the droplets by reflectivity spectroscopy. The technique demonstrates the feasibility of tagging, manipulating, and heating small volumes of liquids without the use of conventional microfluidic channel and heating systems. PMID:16771508

Park, Ji-Ho; Derfus, Austin M.; Segal, Ester; Vecchio, Kenneth S.; Bhatia, Sangeeta N.; Sailor, Michael J.

2012-01-01

253

Forum on micro fluid mechanics 1991  

Microsoft Academic Search

This book includes the following topics in micro-fluid mechanics: simulation of rarefied gas flows, analysis of dust particles, methods for studying cavitation bubble dynamics, and electroosmosis for removal of chemicals in clay soil.

Trefethen

1991-01-01

254

IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 52, NO. 11, NOVEMBER 2005 2489 Analysis of the Kirk Effect in Silicon-Based Bipolar  

E-print Network

Effect in Silicon-Based Bipolar Transistors With a Nonuniform Collector Profile Raymond J. E. Hueting- icon-based bipolar transistors (BJTs) with a nonuniform collector profile. We show that, for any for optimizing future BJTs. Index Terms--Heterojunction bipolar transistors (HBTs), high- frequency (HF

Technische Universiteit Delft

255

Design and evaluation of a low nitrogen oxides natural gas-fired conical wire-mesh duct burner for a micro-cogeneration unit  

Microsoft Academic Search

A novel low NOx conical wire-mesh duct burner was designed, built and tested in the present research. This thesis documents the design process and the in-depth evaluation of this novel duct burner for the development of a more efficient micro-cogeneration unit. This duct burner provides the thermal energy necessary to raise the microturbine exhaust gases temperature to increase the heat

Omar Barka Ab Ramadan

2008-01-01

256

Development of a liquid-fueled micro-combustor  

E-print Network

Advances in Micro-Electro-Mechanical Systems (MEMS) have made possible the development of shirtbutton-sized gas turbine engines for use as portable power sources. As part of an effort to develop a microscale gas turbine ...

Peck, Jhongwoo, 1976-

2008-01-01

257

Deviations of the results for the properties of a dense hard-sphere gas near the walls of a micro channel using the hybrid molecular dynamics—Monte Carlo simulation method ? ? A preliminary version of this paper was presented at ICMM05: Third International Conference on Microchannels and Minichannels, held at University of Toronto, June 13–15, 2005, organized by S.G. Kandlikar and M. Kawaji, CD-ROM Proceedings, ISBN: 0-7918-3758-0, ASME, New York  

Microsoft Academic Search

We study the deviations for the results of the properties of a hard-sphere gas near the walls of a micro\\/nano channel using the hybrid MD–MC simulation method compared to the pure MD and MC results. Our model for the micro channel consists of two parallel infinite plates situated at distance L apart from each other, and of gas molecules confined

S. V. Nedea; A. J. H. Frijns; A. A. van Steenhoven; A. J. Markvoort; P. A. J. Hilbers

2006-01-01

258

A self-regulating hydrogen generator for micro fuel cells  

Microsoft Academic Search

The ever-increasing power demands and miniaturization of portable electronics, micro-sensors and actuators, and emerging technologies such as cognitive arthropods have created a significant interest in development of micro fuel cells. One of the major challenges in development of hydrogen micro fuel cells is the fabrication and integration of auxiliary systems for generating, regulating, and delivering hydrogen gas to the membrane

Saeed Moghaddam; Eakkachai Pengwang; Richard I. Masel; Mark A. Shannon

2008-01-01

259

PREFACE: E-MRS 2012 Spring Meeting, Symposium M: More than Moore: Novel materials approaches for functionalized Silicon based Microelectronics  

NASA Astrophysics Data System (ADS)

More than Moore explores a new area of Silicon based microelectronics, which reaches beyond the boundaries of conventional semiconductor applications. Creating new functionality to semiconductor circuits, More than Moore focuses on motivating new technological possibilities. In the past decades, the main stream of microelectronics progresses was mainly powered by Moore's law, with two focused development arenas, namely, IC miniaturization down to nano scale, and SoC based system integration. While the microelectronics community continues to invent new solutions around the world to keep Moore's law alive, there is increasing momentum for the development of 'More than Moore' technologies which are based on silicon technologies but do not simply scale with Moore's law. Typical examples are RF, Power/HV, Passives, Sensor/Actuator/MEMS or Bio-chips. The More than Moore strategy is driven by the increasing social needs for high level heterogeneous system integration including non-digital functions, the necessity to speed up innovative product creation and to broaden the product portfolio of wafer fabs, and the limiting cost and time factors of advanced SoC development. It is believed that More than Moore will add value to society on top of and beyond advanced CMOS with fast increasing marketing potentials. Important key challenges for the realization of the 'More than Moore' strategy are: perspective materials for future THz devices materials systems for embedded sensors and actuators perspective materials for epitaxial approaches material systems for embedded innovative memory technologies development of new materials with customized characteristics The Hot topics covered by the symposium M (More than Moore: Novel materials approaches for functionalized Silicon based Microelectronics) at E-MRS 2012 Spring Meeting, 14-18 May 2012 have been: development of functional ceramics thin films New dielectric materials for advanced microelectronics bio- and CMOS compatible material systems piezoelectric films and nanostructures Atomic Layer Deposition (ALD) of oxides and nitrides characterization and metrology of very thin oxide layers We would like to take this opportunity to thank the Scientific Committee and Local Committee for bringing together a coherent and high quality Symposium at E-MRS 2012 Spring Meeting. Christian Wenger, Jean Fompeyrine, Christophe Vallée and Jean-Pierre Locquet Organizing Committee of Symposium M September 2012

Wenger, Christian; Fompeyrine, Jean; Vallée, Christophe; Locquet, Jean-Pierre

2012-12-01

260

Thermal conductivity of a graphite bipolar plate (BPP) and its thermal contact resistance with fuel cell gas diffusion layers: Effect of compression, PTFE, micro porous layer (MPL), BPP out-of-flatness and cyclic load  

NASA Astrophysics Data System (ADS)

This paper reports on measurements of thermal conductivity of a graphite bipolar plate (BPP) as a function of temperature and its thermal contact resistance (TCR) with treated and untreated gas diffusion layers (GDLs). The thermal conductivity of the BPP decreases with temperature and its thermal contact resistance with GDLs, which has been overlooked in the literature, is found to be dominant over a relatively wide range of compression. The effects of PTFE loading, micro porous layer (MPL), compression, and BPP out-of-flatness are also investigated experimentally. It is found that high PTFE loadings, MPL and even small BPP out-of-flatness increase the BPP-GDL thermal contact resistance dramatically. The paper also presents the effect of cyclic load on the total resistance of a GDL-BPP assembly, which sheds light on the behavior of these materials under operating conditions in polymer electrolyte membrane fuel cells.

Sadeghifar, Hamidreza; Djilali, Ned; Bahrami, Majid

2015-01-01

261

Connecting the Micro-dynamics to the Emergent Macro-variables: Self-Organized Criticality and Absorbing Phase Transitions in the Deterministic Lattice Gas  

E-print Network

We reinvestigate the Deterministic Lattice Gas introduced as a paradigmatic model of the 1/f spectra (Phys. Rev. Lett. V26, 3103 (1990)) arising according to the Self-Organized Criticality scenario. We demonstrate that the density fluctuations exhibit an unexpected dependence on systems size and relate the finding to effective Langevin equations. The low density behavior is controlled by the critical properties of the gas at the absorbing state phase transition. We also show that the Deterministic Lattice Gas is in the Manna universality class of absorbing state phase transitions. This is in contrast to expectations in the literature which suggested that the entirely deterministic nature of the dynamics would put the model in a different universality class. To our knowledge this is the first fully deterministic member of the Manna universality class.

Andrea Giometto; Henrik Jeldtoft Jensen

2011-10-12

262

Connecting the Micro-dynamics to the Emergent Macro-variables: Self-Organized Criticality and Absorbing Phase Transitions in the Deterministic Lattice Gas  

E-print Network

We reinvestigate the Deterministic Lattice Gas introduced as a paradigmatic model of the 1/f spectra (Phys. Rev. Lett. V26, 3103 (1990)) arising according to the Self-Organized Criticality scenario. We demonstrate that the density fluctuations exhibit an unexpected dependence on systems size and relate the finding to effective Langevin equations. The low density behavior is controlled by the critical properties of the gas at the absorbing state phase transition. We also show that the Deterministic Lattice Gas is in the Manna universality class of absorbing state phase transitions. This is in contrast to expectations in the literature which suggested that the entirely deterministic nature of the dynamics would put the model in a different universality class. To our knowledge this is the first fully deterministic member of the Manna universality class.

Giometto, Andrea

2011-01-01

263

Response of Silicon-Based Linear Energy Transfer Spectrometers: Implication for Radiation Risk Assessment in Space Flights  

NASA Technical Reports Server (NTRS)

There is considerable interest in developing silicon-based telescopes because of their compactness and low power requirements. Three such telescopes have been flown on board the Space Shuttle to measure the linear energy transfer spectra of trapped, galactic cosmic ray, and solar energetic particles. Dosimeters based on single silicon detectors have also been flown on the Mir orbital station. A comparison of the absorbed dose and radiation quality factors calculated from these telescopes with that estimated from measurements made with a tissue equivalent proportional counter show differences which need to be fully understood if these telescopes are to be used for astronaut radiation risk assessments. Instrument performance is complicated by a variety of factors. A Monte Carlo-based technique was developed to model the behavior of both single element detectors in a proton beam, and the performance of a two-element, wide-angle telescope, in the trapped belt proton field inside the Space Shuttle. The technique is based on: (1) radiation transport intranuclear-evaporation model that takes into account the charge and angular distribution of target fragments, (2) Landau-Vavilov distribution of energy deposition allowing for electron escape, (3) true detector geometry of the telescope, (4) coincidence and discriminator settings, (5) spacecraft shielding geometry, and (6) the external space radiation environment, including albedo protons. The value of such detailed modeling and its implications in astronaut risk assessment is addressed. c2001 Elsevier Science B.V. All rights reserved.

Badhwar, G. D.; O'Neill, P. M.

2001-01-01

264

Titanium dioxide/silicon hole-blocking selective contact to enable double-heterojunction crystalline silicon-based solar cell  

NASA Astrophysics Data System (ADS)

In this work, we use an electron-selective titanium dioxide (TiO2) heterojunction contact to silicon to block minority carrier holes in the silicon from recombining at the cathode contact of a silicon-based photovoltaic device. We present four pieces of evidence demonstrating the beneficial effect of adding the TiO2 hole-blocking layer: reduced dark current, increased open circuit voltage (VOC), increased quantum efficiency at longer wavelengths, and increased stored minority carrier charge under forward bias. The importance of a low rate of recombination of minority carriers at the Si/TiO2 interface for effective blocking of minority carriers is quantitatively described. The anode is made of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) heterojunction to silicon which forms a hole selective contact, so that the entire device is made at a maximum temperature of 100 °C, with no doping gradients or junctions in the silicon. A low rate of recombination of minority carriers at the Si/TiO2 interface is crucial for effective blocking of minority carriers. Such a pair of complementary carrier-selective heterojunctions offers a path towards high-efficiency silicon solar cells using relatively simple and near-room temperature fabrication techniques.

Nagamatsu, Ken A.; Avasthi, Sushobhan; Sahasrabudhe, Girija; Man, Gabriel; Jhaveri, Janam; Berg, Alexander H.; Schwartz, Jeffrey; Kahn, Antoine; Wagner, Sigurd; Sturm, James C.

2015-03-01

265

Optimizing performance of silicon-based p-n junction photodetectors by the piezo-phototronic effect.  

PubMed

Silicon-based p-n junction photodetectors (PDs) play an essential role in optoelectronic applications for photosensing due to their outstanding compatibility with well-developed integrated circuit technology. The piezo-phototronic effect, a three-way coupling effect among semiconductor properties, piezoelectric polarizations, and photon excitation, has been demonstrated as an effective approach to tune/modulate the generation, separation, and recombination of photogenerated electron-hole pairs during optoelectronic processes in piezoelectric-semiconductor materials. Here, we utilize the strain-induced piezo-polarization charges in a piezoelectric n-ZnO layer to modulate the optoelectronic process initiated in a p-Si layer and thus optimize the performances of p-Si/ZnO NWs hybridized photodetectors for visible sensing via tuning the transport property of charge carriers across the Si/ZnO heterojunction interface. The maximum photoresponsivity R of 7.1 A/W and fastest rising time of 101 ms were obtained from these PDs when applying an external compressive strain of -0.10‰ on the ZnO NWs, corresponding to relative enhancement of 177% in R and shortening to 87% in response time, respectively. These results indicate a promising method to enhance/optimize the performances of non-piezoelectric semiconductor material (e.g., Si) based optoelectronic devices by the piezo-phototronic effect. PMID:25470314

Wang, Zhaona; Yu, Ruomeng; Wen, Xiaonan; Liu, Ying; Pan, Caofeng; Wu, Wenzhuo; Wang, Zhong Lin

2014-12-23

266

Full breast digital mammography with an amorphous silicon-based flat panel detector: physical characteristics of a clinical prototype.  

PubMed

The physical characteristics of a clinical prototype amorphous silicon-based flat panel imager for full-breast digital mammography have been investigated. The imager employs a thin thallium doped CsI scintillator on an amorphous silicon matrix of detector elements with a pixel pitch of 100 microm. Objective criteria such as modulation transfer function (MTF), noise power spectrum, detective quantum efficiency (DQE), and noise equivalent quanta were employed for this evaluation. The presampling MTF was found to be 0.73, 0.42, and 0.28 at 2, 4, and 5 cycles/mm, respectively. The measured DQE of the current prototype utilizing a 28 kVp, Mo-Mo spectrum beam hardened with 4.5 cm Lucite is approximately 55% at close to zero spatial frequency at an exposure of 32.8 mR, and decreases to approximately 40% at a low exposure of 1.3 mR. Detector element nonuniformity and electronic gain variations were not significant after appropriate calibration and software corrections. The response of the imager was linear and did not exhibit signal saturation under tested exposure conditions. PMID:10757607

Vedantham, S; Karellas, A; Suryanarayanan, S; Albagli, D; Han, S; Tkaczyk, E J; Landberg, C E; Opsahl-Ong, B; Granfors, P R; Levis, I; D'Orsi, C J; Hendrick, R E

2000-03-01

267

In Vivo Validation of Custom-Designed Silicon-Based Microelectrode Arrays for Long-Term Neural Recording and Stimulation  

PubMed Central

We developed and validated silicon-based neural probes for neural stimulating and recording in long-term implantation in the brain. The probes combine the deep reactive ion etching process and mechanical shaping of their tip region, yielding a mechanically sturdy shank with a sharpened tip to reduce insertion force into the brain and spinal cord, particularly, with multiple shanks in the same array. The arrays’ insertion forces have been quantified in vitro. Five consecutive chronically-implanted devices were fully functional from 3 to 18 months. The microelectrode sites were electroplated with iridium oxide, and the charge injection capacity measurements were performed both in vitro and after implantation in the adult feline brain. The functionality of the chronic array was validated by stimulating in the cochlear nucleus and recording the evoked neuronal activity in the central nucleus of the inferior colliculus. The arrays’ recording quality has also been quantified in vivo with neuronal spike activity recorded up to 566 days after implantation. Histopathology evaluation of neurons and astrocytes using immunohistochemical stains indicated minimal alterations of tissue architecture after chronic implantation. PMID:22020666

Manoonkitiwongsa, Panya S.; Wang, Cindy X.; McCreery, Douglas B.

2012-01-01

268

Nonlinear phenomenon in monocrystalline silicon based PV module for low power system: Lead acid battery for low energy storage  

NASA Astrophysics Data System (ADS)

In the present work, we report the indoor photo-electrical measurements of monocrystalline silicon based photovoltaic (PV) module associated with 4 Ah lead acid battery as a storage unit for low power PV system applications. Concerning the PV module, our measurements show, at low illumination regime, that the short circuit current ISC increases linearly with the illumination power levels. Moreover, for high illumination levels, the mechanism of bimolecular recombination and space charge limitation may be intensified and hence the short current of the PV module ISCMod depends sublinearly on the incident optical power; the behavior is nonlinear. For the open circuit voltage of the PV module VOCMod measurements, a linear variation of the VOCMod versus the short circuit current in semi-logarithmic scale has been noticed. The diode ideality factor n and diode saturation current Is have been investigated; the values of n and Is are approximately of 1.3 and 10-9 A, respectively. In addition, we have shown, for different discharging-charging currents rates (i.e. 0.35 A, 0.2 A and 0.04 A), that the battery voltage decreases with discharging time as well as discharging battery capacity, and on the other hand it increases with the charging time and will rise up until it maximized value. The initial result shows the possibility to use such lead acid battery for low power PV system, which is generally designed for the motorcycle battery.

El Amrani, A.; El Amraoui, M.; El Abbassi, A.; Messaoudi, C.

2014-11-01

269

Reaction mechanisms in silicon-based resist materials: polysilanes for deep-UV, EUV, and x-ray lithography  

NASA Astrophysics Data System (ADS)

The present paper describes mechanisms of photo- and radiation induced reactions in silicon based resist materials: polysilanes with Si-branchings and Si-H bondings, as a candidate for EUV and X-ray resist materials. Polysilanes have been previously confirmed to show positive-type resist properties for UV light, electron beams (EB), X-rays, etc. at any conditions. However the cross-linking reaction of the polymer became dominant in the polysilane with Si-branchings upon irradiation to UV light, EB, and ion beams. The efficiency of the cross-linking reaction strongly depended on the ratio of Si-branching giving polymer gels in the polysilane with higher amount of Si-branching than 5% even for (gamma) -ray irradiation. Polyhydrosilanes containing vinyl groups revealed to cause efficient cross-linking reactions with the presence of catalysts for hydrosilylation upon exposure to deep UV or X-rays, leading to high-sensitive negative resist materials for EUV lithography.

Seki, Shu; Sakurai, Yusuke; Maeda, Kazuki; Kunimi, Yoshihisa; Nagahara, Seiji; Tagawa, Seiichi

2000-06-01

270

Silicon Based System for Single-Nucleotide-Polymorphism Detection: Chip Fabrication and Thermal Characterization of Polymerase Chain Reaction Microchamber  

NASA Astrophysics Data System (ADS)

A single nucleotide polymorphism (SNP) is a difference in the DNA sequence of one nucleotide only. We recently proposed a lab-on-a-chip (LoC) system which has the potentiality of fast, sensitive and highly specific SNP detection. Most of the chip components are silicon based and fabricated within a single process. In this paper, the newly developed fabrication method for the silicon chip is presented. The robust and reliable process allows etching structures on the same chip with very different aspect ratios. The characterization of a crucial component to the LoC SNP detector, the microreactor where DNA amplification is performed, is also detailed. Thanks to innovative design and fabrication methodologies, the microreactor has an excellent thermal isolation from the surrounding silicon substrate. This allows for highly localized temperature control. Furthermore, the microreactor is demonstrated to have rapid heating and cooling rates, allowing for rapid amplification of the target DNA fragments. Successful DNA amplification in the microreactor is demonstrated.

Majeed, Bivragh; Jones, Ben; Tezcan, Deniz S.; Tutunjyan, Nina; Haspeslagh, Luc; Peeters, Sara; Fiorini, Paolo; de Beeck, Maaike Op; Van Hoof, Chris; Hiraoka, Maki; Tanaka, Hiroyuki; Yamashita, Ichiro

2012-04-01

271

Gas-surface interactions using accommodation coefficients for a dilute and a dense gas in a micro- or nanochannel: heat flux predictions using combined molecular dynamics and Monte Carlo techniques.  

PubMed

The influence of gas-surface interactions of a dilute gas confined between two parallel walls on the heat flux predictions is investigated using a combined Monte Carlo (MC) and molecular dynamics (MD) approach. The accommodation coefficients are computed from the temperature of incident and reflected molecules in molecular dynamics and used as effective coefficients in Maxwell-like boundary conditions in Monte Carlo simulations. Hydrophobic and hydrophilic wall interactions are studied, and the effect of the gas-surface interaction potential on the heat flux and other characteristic parameters like density and temperature is shown. The heat flux dependence on the accommodation coefficient is shown for different fluid-wall mass ratios. We find that the accommodation coefficient is increasing considerably when the mass ratio is decreased. An effective map of the heat flux depending on the accommodation coefficient is given and we show that MC heat flux predictions using Maxwell boundary conditions based on the accommodation coefficient give good results when compared to pure molecular dynamics heat predictions. The accommodation coefficients computed for a dilute gas for different gas-wall interaction parameters and mass ratios are transferred to compute the heat flux predictions for a dense gas. Comparison of the heat fluxes derived using explicit MD, MC with Maxwell-like boundary conditions based on the accommodation coefficients, and pure Maxwell boundary conditions are discussed. A map of the heat flux dependence on the accommodation coefficients for a dense gas, and the effective accommodation coefficients for different gas-wall interactions are given. In the end, this approach is applied to study the gas-surface interactions of argon and xenon molecules on a platinum surface. The derived accommodation coefficients are compared with values of experimental results. PMID:25353885

Nedea, S V; van Steenhoven, A A; Markvoort, A J; Spijker, P; Giordano, D

2014-05-01

272

An automated method for the analysis of phenolic acids in plasma based on ion-pairing micro-extraction coupled on-line to gas chromatography/mass spectrometry with in-liner derivatisation.  

PubMed

A new method is presented for the analysis of phenolic acids in plasma based on ion-pairing 'Micro-extraction in packed sorbent' (MEPS) coupled on-line to in-liner derivatisation-gas chromatography-mass spectrometry (GC-MS). The ion-pairing reagent served a dual purpose. It was used both to improve extraction yields of the more polar analytes and as the methyl donor in the automated in-liner derivatisation method. In this way, a fully automated procedure for the extraction, derivatisation and injection of a wide range of phenolic acids in plasma samples has been obtained. An extensive optimisation of the extraction and derivatisation procedure has been performed. The entire method showed excellent repeatabilities of under 10% and linearities of 0.99 or better for all phenolic acids. The limits of detection of the optimised method for the majority of phenolic acids were 10ng/mL or lower with three phenolic acids having less-favourable detection limits of around 100 ng/mL. Finally, the newly developed method has been applied in a human intervention trial in which the bioavailability of polyphenols from wine and tea was studied. Forty plasma samples could be analysed within 24h in a fully automated method including sample extraction, derivatisation and gas chromatographic analysis. PMID:22099223

Peters, Sonja; Kaal, Erwin; Horsting, Iwan; Janssen, Hans-Gerd

2012-02-24

273

Facile and scalable synthesis of silicon-based nanocomposites with slitlike nanopores: a solid-state exfoliation reaction using layered CaSi?.  

PubMed

Silicon-based nanocomposites with slitlike nanopores were prepared by heating a mixture of layered CaSi2 and NiCl2. The formation mechanism is based on a solid-state exfoliation reaction wherein the formation of CaCl2 promotes the extraction of Ca from CaSi2, thereby exfoliating the layered structure. The nanocomposites showed anode capacity for lithium ion batteries up to 804?mA?h?g(-1). PMID:25145780

Oh, Song-Yul; Imagawa, Haruo; Itahara, Hiroshi

2014-11-01

274

Preparation and characterisation of silicone-based coatings filled with carbon nanotubes and natural sepiolite and their application as marine fouling-release coatings  

Microsoft Academic Search

This article reports on the preparation and partial characterisation of silicone-based coatings filled with low levels of either synthetic multiwall carbon nanotubes (MWCNTs) or natural sepiolite (NS). The antifouling and fouling-release properties of these coatings were explored through laboratory assays involving representative soft-fouling (Ulva) and hard-fouling (Balanus) organisms. The bulk mechanical properties of the coatings appeared unchanged by the addition

Alexandre Beigbeder; Philippe Degee; Sheelagh L. Conlan; Robert J. Mutton; Anthony S. Clare; Michala E. Pettitt; Maureen E. Callow; James A. Callow; Philippe Dubois

2008-01-01

275

Effect of materials for micro-electro-mechanical systems on PCR yield  

Microsoft Academic Search

In this study we analyzed the surface properties of different silicon-based materials used for micro-electro-mechanical systems\\u000a (MEMS) production, such as thermally grown silicon oxide, plasma-enhanced chemical vapor deposition (PECVD)-treated silicon\\u000a oxide, reactive-ion etch (RIE)-treated silicon oxide, and Pyrex. Substrates were characterized by atomic force microscopy\\u000a (AFM) and X-ray photoelectron spectroscopy (XPS) to define the surface chemical and morphological properties, and

Cristina Potrich; Lorenzo Lunelli; Stefania Forti; Diego Vozzi; Laura Pasquardini; Lia Vanzetti; Cristina Panciatichi; Mariano Anderle; Cecilia Pederzolli

2010-01-01

276

Diamond single micro-crystals and graphitic micro-balls’ formation in plasmoids under atmospheric pressure  

NASA Astrophysics Data System (ADS)

Plasmoids are produced in the argon filamentary discharge. By going through hydrocarbon gas, the plasmoids collect carbon material. These plasmoids produce diamond single micro-crystals upon contact on the inner surface of cavity in air atmosphere. When the plasmoid’s contact point on the substrate is in inert atmosphere, they deposit their material as micro-balls with a graphite core. The dimension and nature of the micro-materials deposited by the plasmoids are analysed using scanning electron microscopy and Raman microspectroscopy. The compressive residual stress in the deposited micro-diamonds varies in the range ?7 to ?21?GPa.

Pothiraja, Ramasamy; Kartaschew, Konstantin; Bibinov, Nikita; Havenith, Martina; Awakowicz, Peter

2015-03-01

277

Breast imaging using an amorphous silicon-based full-field digital mammographic system: stability of a clinical prototype.  

PubMed

An amorphous silicon-based full-breast imager for digital mammography was evaluated for detector stability over a period of 1 year. This imager uses a structured CsI:TI scintillator coupled to an amorphous silicon layer with a 100-micron pixel pitch and read out by special purpose electronics. The stability of the system was characterized using the following quantifiable metrics: conversion factor (mean number of electrons generated per incident x-ray), presampling modulation transfer function (MTF), detector linearity and sensitivity, detector signal-to-noise ratio (SNR), and American College of Radiology (ACR) accreditation phantom scores. Qualitative metrics such as flat field uniformity, geometric distortion, and Society of Motion Picture and Television Engineers (SMPTE) test pattern image quality were also used to study the stability of the system. Observations made over this 1-year period indicated that the maximum variation from the average of the measurements were less than 0.5% for conversion factor, 3% for presampling MTF over all spatial frequencies, 5% for signal response, linearity and sensitivity, 12% for SNR over seven locations for all 3 target-filter combinations, and 0% for ACR accreditation phantom scores. ACR mammographic accreditation phantom images indicated the ability to resolve 5 fibers, 4 speck groups, and 5 masses at a mean glandular dose of 1.23 mGy. The SMPTE pattern image quality test for the display monitors used for image viewing indicated ability to discern all contrast steps and ability to distinguish line-pair images at the center and corners of the image. No bleeding effects were observed in the image. Flat field uniformity for all 3 target-filter combinations displayed no artifacts such as gridlines, bad detector rows or columns, horizontal or vertical streaks, or bad pixels. Wire mesh screen images indicated uniform resolution and no geometric distortion. PMID:11110258

Vedantham, S; Karellas, A; Suryanarayanan, S; D'Orsi, C J; Hendrick, R E

2000-11-01

278

A method to detect diphenylamine contamination of apple fruit and storages using headspace solid phase micro-extraction and gas chromatography/mass spectroscopy.  

PubMed

Analysis of headspace concentrations of diphenylamine using solid phase micro-extraction (SPME) was examined for its suitability to detect DPA contamination and off-gassing in apple (Malus domestica) fruit, storage rooms and storage materials. Four SPME fibre coatings including polydimethylsiloxane (PDMS, 100 ?m), PDMS/divinylbenzene (PDMS/DVB), Polyacrylate (PA) and PDMS 7 ?m were evaluated. The average limits of detection and of quantification for head space DPA ranged from 0.13 to 0.72 ?g L(-1) and 0.42 to 2.35 ?g L(-1), respectively. Polyacrylate was identified to be the most suitable and compatible fibre for DPA analysis in apple samples, because of its high sensitivity to DPA and low fruit volatile interferences. SPME techniques were further applied to study contamination of DPA in apples, storage rooms and packaging materials. DPA was found in the air of storage rooms containing apples that were not treated with DPA. Wood and plastic bin material, bin liners, and foam insulation all adsorbed and off-gassed DPA and could be potential sources of contamination of untreated apples. PMID:24799236

Song, Jun; Forney, Charles F; Jordan, Michael A

2014-10-01

279

Integrated Microfluidic Gas Sensors for Water Monitoring  

NASA Technical Reports Server (NTRS)

A silicon-based microhotplate tin oxide (SnO2) gas sensor integrated into a polymer-based microfluidic system for monitoring of contaminants in water systems is presented. This device is designed to sample a water source, control the sample vapor pressure within a microchannel using integrated resistive heaters, and direct the vapor past the integrated gas sensor for analysis. The sensor platform takes advantage of novel technology allowing direct integration of discrete silicon chips into a larger polymer microfluidic substrate, including seamless fluidic and electrical interconnects between the substrate and silicon chip.

Zhu, L.; Sniadecki, N.; DeVoe, D. L.; Beamesderfer, M.; Semancik, S.; DeVoe, D. L.

2003-01-01

280

Silicon-based optoelectronics  

Microsoft Academic Search

The decade of the 1990's is an opportune time for scientists and engineers to create cost-effective silicon “superchips” that merge silicon photonics with advanced silicon electronics on a silicon substrate. We can expect significant electrooptical devices from Column IV materials (Si, Ge, C and Sn) for a host of applications. The best devices will use strained-layer epitaxy, doped heterostructures, and

R. A. Soref

1993-01-01

281

Stresa, Italy, 26-28 April 2006 A MICRO TURBINE DEVICE WITH ENHANCED  

E-print Network

engine [3], which consists of a combustor, a radial inflow turbine and a centrifugal compressor. A micro in micro gas turbine engine, which will generate power output and drive the compressor. The critical

Paris-Sud XI, Université de

282

In situ deposition behavior of silica-based layers and its effect on thermal degradation of IN713 turbine blades during operation of a micro-gas turbine  

NASA Astrophysics Data System (ADS)

This study examined the in situ deposition behavior of silica-based layers on IN713 turbine blades during the operation of a 13 kgf-class gas turbine at a rotation speed of 20,000/min as well as its effect on the degradation of the metallic substrate. Tetraethylorthosilicate (TEOS) was mixed with the fuel (liquid petroleum gas, LPG) and burned to generate silica-based coating precursors for deposition from the flame. Two deposition conditions were adopted. For condition 1 (C1), the silicon-to-carbon ratio in the mixed fuel was set at 0.1 mol% for the first 5 min and at zero mol% for the final 95 min in a 100-min operation. For condition 2 (C2), the ratio was set at 0.005 mol% during the entire 100 min operation. The total TEOS feed was the same under both conditions. C1 resulted in a rather uniform and thicker (5-10 ?m on the pressure side) porous silica-based coating on the blade than C2. The in situ deposited layer of C1 was well preserved on the blade and protected the underlying metallic substrate from oxidation during the entire 100 min operation. The layer on the C2 blades was ˜5 ?m thick at the region near to root, but was too thin in the other areas on the blade to be protective. The early build-up of a porous layer to an effective thickness on the blades produced a thermal barrier toward the substrate as well as a diffusion barrier toward the oxidizing elements during operation.

Kim, Min Tae; Kim, Doo Soo; Oh, Won Young

2010-09-01

283

Micro-machined thermo-conductivity detector  

DOEpatents

A micro-machined thermal conductivity detector for a portable gas chromatograph. The detector is highly sensitive and has fast response time to enable detection of the small size gas samples in a portable gas chromatograph which are in the order of nanoliters. The high sensitivity and fast response time are achieved through micro-machined devices composed of a nickel wire, for example, on a silicon nitride window formed in a silicon member and about a millimeter square in size. In addition to operating as a thermal conductivity detector, the silicon nitride window with a micro-machined wire therein of the device can be utilized for a fast response heater for PCR applications.

Yu, Conrad (Antioch, CA)

2003-01-01

284

Micro-cogeneration with fuel cells  

NASA Astrophysics Data System (ADS)

The article is aimed at perspective and fast developing field of micro-cogeneration with small performance. Fuel cell application which uses natural gas as a fuel is high sophisticated technology of combined produce of heat and electric power. The aim of article is analysis of operation parameters of micro-cogeneration unit with fuel cell which as a fuel uses natural gas. The device is installed in University of Zilina laboratory. Measured parameters were electric input and output, thermal energy and electric, thermal and overall efficiency.

Patsch, Marek; ?ierny, Jaroslav

2014-08-01

285

Micro direct methanol fuel cell with perforated silicon-plate integrated ionomer membrane  

NASA Astrophysics Data System (ADS)

This article describes the fabrication and characterization of a silicon based micro direct methanol fuel cell using a Nafion ionomer membrane integrated into a perforated silicon plate. The focus of this work is to provide a platform for micro- and nanostructuring of a combined current collector and catalytic electrode. AC impedance spectroscopy is utilized alongside IV characterization to determine the influence of the plate perforation geometries on the cell performance. It is found that higher ratios of perforation increases peak power density, with the highest achieved being 2.5 mW cm-2 at a perforation ratio of 40.3%. The presented fuel cells also show a high volumetric peak power density of 2  mW cm-3 in light of the small system volume of 480  ?L, while being fully self contained and passively feed.

Larsen, J. V.; Dalslet, B. T.; Johansson, A.-C.; Kallesøe, C.; Thomsen, E. V.

2014-07-01

286

Boiling of nuclear liquid in the micro-canonical ensemble  

E-print Network

Boiling of nuclear liquid in the micro-canonical ensemble K. Miyazaki E-mail: miyazakiro@rio.odn.ne.jp Abstract New calculus of the liquid-gas phase transition is developed for the boiling of nuclear liquid-dependence of the nuclear symmetry energy and the critical temperature of 1 #12;Boiling of nuclear liquid in the micro

287

Room temperature micro-hydrogen-generator  

Microsoft Academic Search

A new compact and cost-effective hydrogen-gas generator has been made that is well suited for supplying hydrogen to a fuel-cell for providing base electrical power to hand-carried appliances. This hydrogen-generator operates at room temperature, ambient pressure and is orientation-independent. The hydrogen-gas is generated by the heterogeneous catalytic hydrolysis of aqueous alkaline borohydride solution as it flows into a micro-reactor. This

Don Gervasio; Sonja Tasic; Frederic Zenhausern

2005-01-01

288

Graphene oxide-based dispersive micro-solid phase extraction for separation and preconcentration of nicotine from biological and environmental water samples followed by gas chromatography-flame ionization detection.  

PubMed

Graphene oxide (GO) has showed great potential to use as an adsorbent in sample preparation procedures. In this research, GO was used as an effective adsorbent in a simple GO-based dispersive micro-solid phase extraction (GO-D-µ-SPE) method for isolation and preconcentration of nicotine prior to gas chromatography-flame ionization detection (GC-FID). The prepared GO was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), thermogravimetric analysis/differential thermal analysis (TGA/DTA), and ultraviolet-visible (UV-vis) absorption spectroscopy techniques. Various experimental parameters affecting the extraction recovery, including the amount of GO, extraction time, pH of the sample solution, salt concentration, and desorption conditions were investigated and optimized. Under the optimized conditions, a linear response was obtained in the concentration range of 5-2000 ng mL(-1) with a determination coefficient of 0.9987. The limit of detection (LOD) of the method at a signal to noise ratio of 3 was 1.5 ng mL(-1). The linearity was in the concentration range of 5-2000 ng mL(-1) with a determination coefficient of 0.9987. Intraday and inter-day precisions were obtained equal to 2.7% and 5.2%, respectively. The method was successfully applied to the nicotine analysis in biological and water samples with the recoveries in the range of 88.7-109.7%. PMID:25159381

Mahpishanian, Shokouh; Sereshti, Hassan

2014-12-01

289

Comparison of air-agitated liquid-liquid microextraction technique and conventional dispersive liquid-liquid micro-extraction for determination of triazole pesticides in aqueous samples by gas chromatography with flame ionization detection.  

PubMed

Two micro-extraction methods, air-agitated liquid-liquid microextraction (AALLME) and dispersive liquid-liquid microextraction (DLLME), have been compared with each other by applying them for the analysis of five triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole and triticonazole) in aqueous samples by gas chromatography with flame ionization detection (GC-FID). In the AALLME method, which excludes any disperser solvent, much less volume of organic solvent is used. In order to form fine and dispersed organic droplets in the aqueous phase, the mixture of aqueous sample solution and extraction solvent is repeatedly aspirated and dispensed with a syringe. In the DLLME method, an appropriate mixture of extraction solvent and disperser solvent is rapidly injected by a syringe into the aqueous sample. Effect of the pertinent experimental factors on DLLME (i.e. identity and volume of the extraction and disperser solvents and ionic strength) and on AALLME (identity and volume of the extraction solvent, number of agitations, and ionic strength) were investigated. Under optimal conditions, limits of detection for the five target pesticides obtained by AALLME-GC-FID and DLLME-GC-FID ranged from 0.20 to 1.1ngmL(-1) and 1.9 to 5.9ngmL(-1), respectively. The relative standard deviations (RSDs, n=5) were in the range of 1-4% and 3-5% with the enrichment factors of 449-504 and 79-143 for AALLME-GC-FID and DLLME-GC-FID, respectively. Both of the compared methods are simple, fast, efficient, inexpensive and can be applied to the analysis of the five pesticides in different aqueous samples in which penconazole and hexaconazole were found. For spiked samples, the recoveries were in the ranges of 92-105%, and 92-104% for AALLME and DLLME, respectively. PMID:23473511

Farajzadeh, Mir Ali; Mogaddam, Mohammad Reza Afshar; Aghdam, Abdollah Abdollahi

2013-07-26

290

Fabrication of a flexible micro CO sensor for micro reformer applications.  

PubMed

Integration of a reformer and a proton exchange membrane fuel cell (PEMFC) is problematic due to the presence in the gas from the reforming process of a slight amount of carbon monoxide. Carbon monoxide poisons the catalyst of the proton exchange membrane fuel cell subsequently degrading the fuel cell performance, and necessitating the sublimation of the reaction gas before supplying to fuel cells. Based on the use of micro-electro-mechanical systems (MEMS) technology to manufacture flexible micro CO sensors, this study elucidates the relation between a micro CO sensor and different SnO2 thin film thicknesses. Experimental results indicate that the sensitivity increases at temperatures ranging from 100-300 °C. Additionally, the best sensitivity is obtained at a specific temperature. For instance, the best sensitivity of SnO2 thin film thickness of 100 nm at 300 °C is 59.3%. Moreover, a flexible micro CO sensor is embedded into a micro reformer to determine the CO concentration in each part of a micro reformer in the future, demonstrating the inner reaction of a micro reformer in depth and immediate detection. PMID:22163494

Lee, Chi-Yuan; Chang, Chi-Chung; Lo, Yi-Man

2010-01-01

291

Fabrication of a Flexible Micro CO Sensor for Micro Reformer Applications  

PubMed Central

Integration of a reformer and a proton exchange membrane fuel cell (PEMFC) is problematic due to the presence in the gas from the reforming process of a slight amount of carbon monoxide. Carbon monoxide poisons the catalyst of the proton exchange membrane fuel cell subsequently degrading the fuel cell performance, and necessitating the sublimation of the reaction gas before supplying to fuel cells. Based on the use of micro-electro-mechanical systems (MEMS) technology to manufacture flexible micro CO sensors, this study elucidates the relation between a micro CO sensor and different SnO2 thin film thicknesses. Experimental results indicate that the sensitivity increases at temperatures ranging from 100–300 °C. Additionally, the best sensitivity is obtained at a specific temperature. For instance, the best sensitivity of SnO2 thin film thickness of 100 nm at 300 °C is 59.3%. Moreover, a flexible micro CO sensor is embedded into a micro reformer to determine the CO concentration in each part of a micro reformer in the future, demonstrating the inner reaction of a micro reformer in depth and immediate detection. PMID:22163494

Lee, Chi-Yuan; Chang, Chi-Chung; Lo, Yi-Man

2010-01-01

292

Design, fabrication and characterization of an air-driven micro turbine device  

Microsoft Academic Search

Micro turbine is one of the important components in a micro gas turbine engine. This paper reports on the development and investigations of a micro turbine device driven by compressed air, which consists of three layers of silicon wafers and two layers of acrylic plates. The rotor has an outer diameter of 8.4 mm with a thickness of 0.76 mm.

X. C. Shan; Qide Zhang; Yaofeng Sun; Zhenfeng Wang

2006-01-01

293

Experimental studies of micromegas detectors with different micro-meshes  

NASA Astrophysics Data System (ADS)

The structure of micromegas (micro-mesh gaseous structure) detectors with different micro-meshes of stainless steel wire woven netting and Ni foil has been presented. The counting rates, energy resolution, gain, discharge probability and time resolution have been measured. Wider counter plateaus and gain for the developed detector were obtained. Excellent energy resolution of the micromegas detector, 17% (FWHM) based on Ni foil micro-mesh and 25% (FWHM) based on stainless steel wire woven netting micro-mesh, has been obtained for the 5.9 keV photon peak of the 55Fe X-ray source in an Ar/CO2(10%) gas mixture. The best time resolution at -620 V micro-mesh voltage and -870 V drift voltage is 14.8 ns for cosmic rays in an Ar/CO2 (10%) gas mixture. These results satisfy the basic demand of the micromegas detector preliminary design.

Yang, He-Run; Hu, Bi-Tao; Zhang, Xiao-Dong; Zou, Chun-Yan

2011-02-01

294

Increasing Stabilized Performance Of Amorphous Silicon Based Devices Produced By Highly Hydrogen Diluted Lower Temperature Plasma Deposition.  

DOEpatents

High quality, stable photovoltaic and electronic amorphous silicon devices which effectively resist light-induced degradation and current-induced degradation, are produced by a special plasma deposition process. Powerful, efficient single and multi-junction solar cells with high open circuit voltages and fill factors and with wider bandgaps, can be economically fabricated by the special plasma deposition process. The preferred process includes relatively low temperature, high pressure, glow discharge of silane in the presence of a high concentration of hydrogen gas.

Li, Yaun-Min (Langhorne, PA); Bennett, Murray S. (Langhorne, PA); Yang, Liyou (Plainsboro, NJ)

1999-08-24

295

Increased Stabilized Performance Of Amorphous Silicon Based Devices Produced By Highly Hydrogen Diluted Lower Temperature Plasma Deposition.  

DOEpatents

High quality, stable photovoltaic and electronic amorphous silicon devices which effectively resist light-induced degradation and current-induced degradation, are produced by a special plasma deposition process. Powerful, efficient single and multi-junction solar cells with high open circuit voltages and fill factors and with wider bandgaps, can be economically fabricated by the special plasma deposition process. The preferred process includes relatively low temperature, high pressure, glow discharge of silane in the presence of a high concentration of hydrogen gas.

Li, Yaun-Min (Langhorne, PA); Bennett, Murray S. (Langhorne, PA); Yang, Liyou (Plainsboro, NJ)

1997-07-08

296

Electrical and luminescence properties of silicon-based tunnel transit-time light-emitting diodes p{sup +}/n{sup +}/n-Si:Er  

SciTech Connect

The electrical and luminescence properties of silicon-based tunnel transit-time light-emitting diodes (LEDs) p{sup +}/n{sup +}/n-Si:Er, emitting under reverse bias on the p{sup +}/n{sup +} junction in the breakdown regime, have been investigated. The room-temperature emission power at the wavelength {lambda} {approx} 1.5 {mu}m ({approx}5 {mu}W), external quantum efficiency ({approx}10{sup -5}), and excitation efficiency of erbium ions ({approx}2 x 10{sup -20} cm{sup 2} s) have been determined. At the same excitation efficiency, tunnel transit-time LEDs exhibit higher emission power in comparison with p{sup +}/n-Si:Er diode structures. The experimental results are compared with the model predictions for these structures. The factors limiting the electroluminescence intensity and impact excitation efficiency for erbium ions in tunnel transit-time LEDs are discussed.

Shmagin, V. B., E-mail: shm@ipm.sci-nnov.ru [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Kuznetsov, V. P. [Lobachevsky State University, Physicotechnical Research Institute (Russian Federation); Kudryavtsev, K. E. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Obolensky, S. V. [Lobachevsky State University (Russian Federation); Kozlov, V. A.; Krasil'nik, Z. F. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

2010-11-15

297

Sensitive detection of protein and miRNA cancer biomarkers using silicon-based photonic crystals and a resonance coupling laser scanning platform.  

PubMed

Enhancement of the fluorescent output of surface-based fluorescence assays by performing them upon nanostructured photonic crystal (PC) surfaces has been demonstrated to increase signal intensities by >8000×. Using the multiplicative effects of optical resonant coupling to the PC in increasing the electric field intensity experienced by fluorescent labels ("enhanced excitation") and the spatially biased funneling of fluorophore emissions through coupling to PC resonances ("enhanced extraction"), PC enhanced fluorescence (PCEF) can be adapted to reduce the limits of detection of disease biomarker assays, and to reduce the size and cost of high sensitivity detection instrumentation. In this work, we demonstrate the first silicon-based PCEF detection platform for multiplexed biomarker assay. The sensor in this platform is a silicon-based PC structure, comprised of a SiO2 grating that is overcoated with a thin film of high refractive index TiO2 and is produced in a semiconductor foundry for low cost, uniform, and reproducible manufacturing. The compact detection instrument that completes this platform was designed to efficiently couple fluorescence excitation from a semiconductor laser to the resonant optical modes of the PC, resulting in elevated electric field strength that is highly concentrated within the region <100 nm from the PC surface. This instrument utilizes a cylindrically focused line to scan a microarray in <1 min. To demonstrate the capabilities of this sensor-detector platform, microspot fluorescent sandwich immunoassays using secondary antibodies labeled with Cy5 for two cancer biomarkers (TNF-? and IL-3) were performed. Biomarkers were detected at concentrations as low as 0.1 pM. In a fluorescent microarray for detection of a breast cancer miRNA biomarker miR-21, the miRNA was detectable at a concentration of 0.6 pM. PMID:23963502

George, Sherine; Chaudhery, Vikram; Lu, Meng; Takagi, Miki; Amro, Nabil; Pokhriyal, Anusha; Tan, Yafang; Ferreira, Placid; Cunningham, Brian T

2013-10-21

298

Performance of a time-projection chamber with a large-area micro-pixel-chamber readout  

Microsoft Academic Search

A micro-time-projection chamber (micro-TPC) with a detection volume of 23×28×31cm3 was developed, and its fundamental performance was examined. The micro-TPC consists of a micro-pixel chamber with a detection area of 31×31cm2 as a two-dimensional imaging device and a gas electron multiplier (GEM) with an effective area of 23×28cm2 as a pre-gas-multiplier. The micro-TPC was operated at a gas gain of

Kentaro Miuchi; Kaori Hattori; Shigeto Kabuki; Hidetoshi Kubo; Shunsuke Kurosawa; Hironobu Nishimura; Atsushi Takada; Ken’ichi Tsuchiya; Yoko Okada; Toru Tanimori; Kazuki Ueno

2007-01-01

299

Performance of a Time-Projection-Chamber with a Large-Area Micro-Pixel-Chamber Readout  

E-print Network

A micro time-projection-chamber (micro-TPC) with a detection volume of 23*28*31 cm^3 was developed, and its fundamental performance was examined. The micro-TPC consists of a micro pixel chamber with a detection area of 31*31 cm^2 as a two-dimensional imaging device and a gas electron multiplier with an effective area of 23*28 cm^2 as a pre-gas-multiplier. The micro-TPC was operated at a gas gain of 50,000, and energy resolutions and spatial resolutions were measured.

Miuchi, K; Kabuki, S; Kubo, H; Kurosawa, S; Nishimura, H; Takada, A; Tsuchiya, K; Okada, Y; Tanimori, T; Ueno, K; Miuchi, Kentaro; Hattori, Kaori; Kabuki, Shigeto; Kubo, Hidetoshi; Kurosawa, Shunsuke; Nishimura, Hironobu; Takada, Atsushi; Tsuchiya, Ken'ichi; Okada, Yoko; Tanimori, Toru; Ueno, Kazuki

2007-01-01

300

The Ultra-micro Wave Rotor Research at Michigan State University Florin Iancu, Janusz Piechna*  

E-print Network

turbines (UµGT) are appropriate solutions for powering small unmanned air- vehicles (UAV) and electronical University of Technology 24 Nowowiejska Str., 00-665 Warsaw, Poland ABSTRACT Ultra Micro Gas Turbines (Uµ concepts of incorporating a wave rotor to an ultra-micro gas turbine and the advantages of wave rotors

Müller, Norbert

301

Integrated Micro Nano Systems Integrated Micro Nano Systems  

E-print Network

#12;Integrated Micro Nano Systems 2 #12;Integrated Micro Nano Systems 3 Val Jones (Ed.) Symposium on Integrated Micro Nano Systems: Convergence of bio and nanotechnologies, Enschede, The Netherlands, June 2006 Micro Nano Systems 4 #12;Integrated Micro Nano Systems 5 Preface In order to explore the convergence

Al Hanbali, Ahmad

302

MicroSight Optics  

SciTech Connect

MicroSight is an innovative gunsight technology that allows a marksman's eye to focus on both the front gunsight and the intended target. The MicroSight improves both firearm safety and performance by imaging two objects at different focal distances. The MicroSight was developed at Idaho National Laboratory, and has been licensed by Apollo Optical Systems. You can learn more about INL's research programs at http://www.facebook.com/idahonationallaboratory.

None

2010-01-01

303

MicroSight Optics  

ScienceCinema

MicroSight is an innovative gunsight technology that allows a marksman's eye to focus on both the front gunsight and the intended target. The MicroSight improves both firearm safety and performance by imaging two objects at different focal distances. The MicroSight was developed at Idaho National Laboratory, and has been licensed by Apollo Optical Systems. You can learn more about INL's research programs at http://www.facebook.com/idahonationallaboratory.

None

2013-05-28

304

Process for the deposition of high temperature stress and oxidation resistant coatings on silicon-based substrates  

DOEpatents

A process is disclosed for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900--1500 C and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist. The gases and their partial pressures are varied according to a predetermined time schedule and the halide and other reactant gases are selected so that the layers include (a) an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or an aluminum oxynitride material, over and chemically bonded to the substrate body, and (b) an adherent, continuous first outer layer about 0.5-900 microns thick including an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Sarin, V.K.

1991-07-30

305

Micro-Organ Device  

NASA Technical Reports Server (NTRS)

A method for fabricating a micro-organ device comprises providing a microscale support having one or more microfluidic channels and one or more micro-chambers for housing a micro-organ and printing a micro-organ on the microscale support using a cell suspension in a syringe controlled by a computer-aided tissue engineering system, wherein the cell suspension comprises cells suspended in a solution containing a material that functions as a three-dimensional scaffold. The printing is performed with the computer-aided tissue engineering system according to a particular pattern. The micro-organ device comprises at least one micro-chamber each housing a micro-organ; and at least one microfluidic channel connected to the micro-chamber, wherein the micro-organ comprises cells arranged in a configuration that includes microscale spacing between portions of the cells to facilitate diffusion exchange between the cells and a medium supplied from the at least one microfluidic channel.

Gonda, Steve R. (Inventor); Chang, Robert C. (Inventor); Starly, Binil (Inventor); Culbertson, Christopher (Inventor); Holtorf, Heidi L. (Inventor); Sun, Wei (Inventor); Leslie, Julia (Inventor)

2013-01-01

306

Micro-organ device  

NASA Technical Reports Server (NTRS)

A method for fabricating a micro-organ device comprises providing a microscale support having one or more microfluidic channels and one or more micro-chambers for housing a micro-organ and printing a micro-organ on the microscale support using a cell suspension in a syringe controlled by a computer-aided tissue engineering system, wherein the cell suspension comprises cells suspended in a solution containing a material that functions as a three-dimensional scaffold. The printing is performed with the computer-aided tissue engineering system according to a particular pattern. The micro-organ device comprises at least one micro-chamber each housing a micro-organ; and at least one microfluidic channel connected to the micro-chamber, wherein the micro-organ comprises cells arranged in a configuration that includes microscale spacing between portions of the cells to facilitate diffusion exchange between the cells and a medium supplied from the at least one microfluidic channel.

Gonda, Steve R. (Inventor); von Gustedt-Gonda, legal representative, Iris (Inventor); Chang, Robert C. (Inventor); Starly, Binil (Inventor); Culbertson, Christopher (Inventor); Holtorf, Heidi L. (Inventor); Sun, Wei (Inventor); Leslie, Julia (Inventor)

2013-01-01

307

High-speed thin-film transistors on single-crystalline, unstrained- and strained-silicon-based nanomembranes  

NASA Astrophysics Data System (ADS)

This research focuses on developing high-performance single-crystal Si-based nanomembranes and high-frequency thin-film transistors (TFTs) using these nanomembranes on flexible plastic substrates. Unstrained Si or SiGe nanomembranes with thickness of several tens to a couple of hundred nanometers are derived from silicon-on-insulator (SOI) or silicon-germanium-on-insulator (SGOI) and are subsequently transferred and integrated with flexible plastic host substrates via a one-step dry printing technique. Biaxial tensile-strained Si membranes that utilize elastic strain-sharing between Si and additionally grown SiGe thin films are also successfully integrated with plastic host substrates and exhibit predicted strain status and negligible density of dislocations. Biaxial tensile strain enhances electron mobility and lowers Schottky contact resistance. As a result, flexible TFTs built on the strained Si-membranes demonstrate much higher electron effective mobility and higher drive current than the unstrained counterpart. The dependence of drive current and transconductance on uniaxial tensile strain introducing by mechanical bending is also discussed. A novel combined "hot-and-cold" TFT fabrication process is developed specifically for realizing a wide spectrum of micro-electronics that can exhibit RF performance and can be integrated on low-temperature plastic substrate. The "hot" process that consists of ion implant and high-temperature annealing for desired doping type, profile, and concentration is realized on the bulk SOI/SGOI substrates followed by the "cold" process that includes room-temperature silicon-monoxide (SiO) deposition as gate dielectric layer to ensure the process compatibility with low-temperature, low-cost plastics. With these developments flexible Si-membrane n-type RF TFTs for analog applications and complementary TFTs for digital applications are demonstrated for the first time. RF TFTs with 1.5-mum channel length have demonstrated record-high f T and fmax values of 2.04 and 7.8 GHz, respectively. A small-signal equivalent circuit model study on the RF TFTs reveals the physics of how device layout affects fT and f max, which paves the way for further performance optimization and realization of integrated circuit on flexible substrate in the future.

Yuan, Hao-Chih

308

Effect of structural heat conduction on the performance of micro-combustors and micro-thrusters  

NASA Astrophysics Data System (ADS)

This thesis investigates the effect of gas-structure interaction on the design and performance of miniaturized combustors with characteristic dimensions less than a few millimeters. These are termed 'micro-combustors' and are intended for use in devices ranging from micro-scale rocket motors for micro, nano, and pico-satellite propulsion, to micro-scale engines for micro-Unmanned Air Vehicle (UAV) propulsion and compact power generation. Analytical models for the propagation of a premixed laminar flame in a micro-channel are developed. The models' predictions are compared to the results of more detailed numerical simulations that incorporate multi-step chemistry, distributed heat transfer between the reacting gas and the combustor structure, heat transfer between the combustor and the environment, and heat transfer within the combustor structure. The results of the modeling and simulation efforts are found to be in good qualitative agreement and demonstrate that the behavior of premixed laminar flames in micro-channels is governed by heat transfer within the combustor structure and heat loss to the environment. The key findings of this work are as follows: First, heat transfer through the micro-combustor's structure tends to increase the flame speed and flame thickness. The increase in flame thickness with decreasing passage height suggests that micro-scale combustors will need to be longer than their conventional-scale counterparts. However, the increase in flame speed more than compensates for this effect and the net effect is that miniaturizing a combustor can increase its power density substantially. Second, miniaturizing chemical rocket thrusters can substantially increase thrust/weight ratio but comes at the price of reduced specific impulse (i.e. overall efficiency). Third, heat transfer through the combustor's structure increases steady-state and transient flame stability. This means that micro-scale combustors will be more stable than their conventional-scale counterparts. Fourth and finally, the extended temperature profile associated with the broadened flame causes a different set of elementary reactions to dominate the operation of the overall reaction mechanism at the micro-scale. This suggests that new chemical mechanisms may need to be developed in order to accurately simulate combustion at small-scales. It also calls into question the efficacy of single-step mechanisms presently used by other researchers.

Leach, Timothy Thierry

309

OIL & GAS INSTITUTE Introduction  

E-print Network

Corrosion and erosion Power, micro-grid and control systems Fluid Flow, measurement and assurance Decision of fixed and floating offshore platforms as well as the structural health monitoring of platforms and shipsOIL & GAS INSTITUTE CONTENTS Introduction Asset Integrity Underpinning Capabilities 2 4 4 6 8 9 10

Mottram, Nigel

310

Search for Bs0 --> micro+ micro- and B0 --> micro+ micro- decays with 2 fb-1 of pp collisions.  

PubMed

We have performed a search for B(s)(0) --> micro(+) micro(-) and B(0) --> micro(+) micro(-) decays in pp collisions at square root s = 1.96 TeV using 2 fb(-1) of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron Collider. The observed number of B(s)(0) and B0 candidates is consistent with background expectations. The resulting upper limits on the branching fractions are B(B(s)0) --> micro(+) micro(-)) <5.8 x 10(-8) and B(B(0) --> micro(+) micro(-))<1.8 x 10(-8) at 95% C.L. PMID:18352173

Aaltonen, T; Adelman, J; Akimoto, T; Albrow, M G; Alvarez González, B; Amerio, S; Amidei, D; Anastassov, A; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Apresyan, A; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Aurisano, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Beauchemin, P-H; Bedeschi, F; Bednar, P; Behari, S; Bellettini, G; Bellinger, J; Belloni, A; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Bizjak, I; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Bridgeman, A; Brigliadori, L; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Buzatu, A; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carlsmith, D; Carosi, R; Carrillo, S; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, K; Chokheli, D; Chou, J P; Choudalakis, G; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Cuenca Almenar, C; Cuevas, J; Culbertson, R; Cully, J C; Dagenhart, D; Datta, M; Davies, T; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; De Lorenzo, G; Dell'orso, M; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Di Giovanni, G P; Dionisi, C; Di Ruzza, B; Dittmann, J R; D'Onofrio, M; Donati, S; Dong, P; Donini, J; Dorigo, T; Dube, S; Efron, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Ferrazza, C; Field, R; Flanagan, G; Forrest, R; Forrester, S; Franklin, M; Freeman, J C; Furic, I; Gallinaro, M; Galyardt, J; Garberson, F; Garcia, J E; Garfinkel, A F; Genser, K; Gerberich, H; Gerdes, D; Giagu, S; Giakoumopolou, V; Giannetti, P; Gibson, K; Gimmell, J L; Ginsburg, C M; Giokaris, N; Giordani, M; Giromini, P; Giunta, M; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Golossanov, A; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Goulianos, K; Gresele, A; Grinstein, S; Grosso-Pilcher, C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, K; Hahn, S R; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, D; Hare, M; Harper, S; Harr, R F; Harris, R M; Hartz, M; Hatakeyama, K; Hauser, J; Hays, C; Heck, M; Heijboer, A; Heinemann, B; Heinrich, J; Henderson, C; Herndon, M; Heuser, J; Hewamanage, S; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Husemann, U; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ivanov, A; Iyutin, B; James, E; Jayatilaka, B; Jeans, D; Jeon, E J; Jindariani, S; Johnson, W; Jones, M; Joo, K K; Jun, S Y; Jung, J E; Junk, T R; Kamon, T; Kar, D; Karchin, P E; Kato, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kimura, N; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Koay, S A; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kraus, J; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kubo, T; Kuhlmann, S E; Kuhr, T; Kulkarni, N P; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; Lecompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Linacre, J; Lindgren, M; Lipeles, E; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Lovas, L; Lu, R-S; Lucchesi, D; Lueck, J; Luci, C; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; Macqueen, D; Madrak, R; Maeshima, K; Makhoul, K; Maki, T; Maksimovic, P; Malde, S; Malik, S; Manca, G; Manousakis, A; Margaroli, F; Marino, C; Marino, C P; Martin, A; Martin, M; Martin, V; Martínez, M; Martínez-Ballarín, R; Maruyama, T; Mastrandrea, P; Masubuchi, T; Mattson, M E; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Mehtala, P; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; Miao, T; Miladinovic, N; Miles, J; Miller, R; Mills, C; Milnik, M; Mitra, A; Mitselmakher, G; Miyake, H; Moed, S; Moggi, N; Moon, C S; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Mussini, M; Nachtman, J; Nagai, Y; Nagano, A; Naganoma, J; Nakamura, K; Nakano, I; Napier, A; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nodulman, L; Norman, M; Norniella, O; Nurse, E; Oh, S H

2008-03-14

311

Analysis of Membrane Lipids of Airborne Micro-Organisms  

NASA Technical Reports Server (NTRS)

A method of characterization of airborne micro-organisms in a given location involves (1) large-volume filtration of air onto glass-fiber filters; (2) accelerated extraction of membrane lipids of the collected micro-organisms by use of pressurized hot liquid; and (3) identification and quantitation of the lipids by use of gas chromatography and mass spectrometry. This method is suitable for use in both outdoor and indoor environments; for example, it can be used to measure airborne microbial contamination in buildings ("sick-building syndrome"). The classical approach to analysis of airborne micro-organisms is based on the growth of cultureable micro-organisms and does not provide an account of viable but noncultureable micro-organisms, which typically amount to more than 90 percent of the micro-organisms present. In contrast, the present method provides an account of all micro-organisms, including cultureable, noncultureable, aerobic, and anaerobic ones. The analysis of lipids according to this method makes it possible to estimate the number of viable airborne micro-organisms present in the sampled air and to obtain a quantitative profile of the general types of micro-organisms present along with some information about their physiological statuses.

MacNaughton, Sarah

2006-01-01

312

Methods for fabricating a micro heat barrier  

DOEpatents

Methods for fabricating a highly effective, micron-scale micro heat barrier structure and process for manufacturing a micro heat barrier based on semiconductor and/or MEMS fabrication techniques. The micro heat barrier has an array of non-metallic, freestanding microsupports with a height less than 100 microns, attached to a substrate. An infrared reflective membrane (e.g., 1 micron gold) can be supported by the array of microsupports to provide radiation shielding. The micro heat barrier can be evacuated to eliminate gas phase heat conduction and convection. Semi-isotropic, reactive ion plasma etching can be used to create a microspike having a cusp-like shape with a sharp, pointed tip (<0.1 micron), to minimize the tip's contact area. A heat source can be placed directly on the microspikes. The micro heat barrier can have an apparent thermal conductivity in the range of 10.sup.-6 to 10.sup.-7 W/m-K. Multiple layers of reflective membranes can be used to increase thermal resistance.

Marshall, Albert C.; Kravitz, Stanley H.; Tigges, Chris P.; Vawter, Gregory A.

2004-01-06

313

Development of a Silicon Based Electron Beam Transmission Window for Use in a KrF Excimer Laser System  

SciTech Connect

The Princeton Plasma Physics Laboratory (PPPL), in collaboration with the Naval Research Laboratory (NRL), is currently investigating various novel materials (single crystal silicon, <100>, <110> and <111>) for use as electron-beam transmission windows in a KrF excimer laser system. The primary function of the window is to isolate the active medium (excimer gas) from the excitation mechanism (field-emission diodes). Chosen window geometry must accommodate electron energy transfer greater than 80% (750 keV), while maintaining structural integrity during mechanical load (1.3 to 2.0 atm base pressure differential, approximate 0.5 atm cyclic pressure amplitude, 5 Hz repetition rate) and thermal load across the entire hibachi area (approximate 0.9 W {center_dot} cm superscript ''-2''). In addition, the window must be chemically resistant to attack by fluorine free-radicals (hydrofluoric acid, secondary). In accordance with these structural, functional, and operational parameters, a 22.4 mm square silicon prototype window, coated with 500 nm thin-film silicon nitride (Si{sub 3}N{sub 4}), has been fabricated. The window consists of 81 square panes with a thickness of 0.019 mm {+-} 0.001 mm. Stiffened (orthogonal) sections are 0.065 mm in width and 0.500 mm thick (approximate). Appended drawing (Figure 1) depicts the window configuration. Assessment of silicon (and silicon nitride) material properties and CAD modeling and analysis of the window design suggest that silicon may be a viable solution to inherent parameters and constraints.

C.A. Gentile; H.M. Fan; J.W. Hartfield; R.J. Hawryluk; F. Hegeler; P.J. Heitzenroeder; C.H. Jun; L.P. Ku; P.H. LaMarche; M.C. Myers; J.J. Parker; R.F. Parsells; M. Payen; S. Raftopoulos; J.D. Sethian

2002-11-21

314

Collective Motion of Micro-organisms from Field Theoretical Viewpoint  

E-print Network

We analyze the collective motion of micro-organisms in the fluid and consider the problem of the red tide. The red tide is produced by the condensation of the micro-organisms, which might be a similar phenomenon to the condensation of the strings. We propose a model of the generation of the red tide. By considering the interaction between the micro- organisms mediated by the velocity fields in the fluid, we derive the Van der Waals type equation of state, where the generation of the red tide can be regarded as a phase transition from the gas of micro-organisms to the liquid. (The number density of micro-organisms which generates the red tide is order estimated.)

Shin'ichi Nojiri; Masako Kawamura; Akio Sugamoto

1995-12-13

315

Thermal characterisation of micro-hotplates used in sensor structures  

NASA Astrophysics Data System (ADS)

Micro-hotplates operated at elevated temperature form the basic element in several sensor devices, such as integrated calorimetric or Taguchi-type gas sensors and flow-rate sensors. In all of these applications thermal properties of the sensing elements play a determining role in functional operation, therefore, their accurate characterisation is essential. The micro-hotplates investigated were developed by one side porous silicon micro-machining technology, forming Pt micro-filaments embedded in non-stoichiometric silicon nitride, and suspended across a cavity. This work is dealing with the accurate temperature detection in the micro-scale by different measurement methods for the deduction of steady state and transient thermal properties from the results. Transient properties of the structure were investigated by application of a simplified thermal equivalent circuit model.

Fürjes, P.; Dücs?, Cs.; Ádám, M.; Zettner, J.; Bársony, I.

2004-03-01

316

Paclitaxel release from micro-porous PLGA disks  

Microsoft Academic Search

Micro-porous biodegradable polymeric foams have potential applications in tissue engineering and drug delivery systems. A two-stage fabrication process combining spray drying and supercritical gas foaming is presented for the encapsulation of paclitaxel in micro-porous PLGA (poly lactic glycolic acid) foams. Encapsulation of paclitaxel in the PLGA polymer matrix was achieved and these foams have potential application as a new type

Lai Yeng Lee; Sudhir Hulikal Ranganath; Yilong Fu; Jasmine Limin Zheng; How Sung Lee; Chi-Hwa Wang; Kenneth A. Smith

2009-01-01

317

Study of surface treatment processes for improvement in the wettability of silicon-based materials used in high aspect ratio through-via copper electroplating  

NASA Astrophysics Data System (ADS)

We report the improvements in wetting characteristics of silicon-based materials with copper electrolyte by various surface treatments to achieve uniform and void free copper deposition in high aspect ratio through-via electroplating. The contact angles of samples such as native silicon, thermally oxidized silicon, silicon nitride, deep reactive ion etched silicon etc, with copper electrolyte, were measured before and after the surface treatments. The wetting of copper electrolyte with silicon nitride coated silicon samples was found to be more than that with thermally oxidized samples. Due to its better wettability, silicon nitride was later used as an insulating layer instead of commonly used silicon oxide in the electroplating experiments. After the SC1 wet surface treatment, the contact angles of all the samples were found to be significantly lower, thus making the surface more suitable for electroplating applications. X-ray photoelectron spectroscopy results verified the presence of polar functional groups on the samples surface, which has helped to improve wetting with copper electrolyte. The conclusions drawn by the experimental results were employed in the high aspect ratio through-via copper electroplating; and void free copper interconnects, having aspect ratio as high as 20, were fabricated.

Dixit, Pradeep; Chen, Xiaofeng; Miao, Jianmin; Divakaran, Sheeja; Preisser, Robert

2007-08-01

318

The Response of the silicon-based Linear Energy Transfer Spectrometer (RRMD-III) to Protons from 1 to 70 MeV  

NASA Astrophysics Data System (ADS)

Experiments have been performed to measure the response of the silicon-based linear energy transfer (LET) spectrometer (RRMD-III) to protons with energies ranging from 1 to 70 MeV. The beam energies incident upon RRMD-III were obtained using plastic polycarbonate degraders with mono-energetic proton beams that were extracted at 70, 40 and 25 MeV from a cyclotron. The energy loss in the degraders never exceeded 70% of the incident energy in order that the energy spread of the emerging protons created by straggling and scattering effects could be suppressed. Estimates of the LET were influenced by the asymmetric energy distribution of the degraded beam. Protons with energies less than 12.2 MeV did not reach the second Si detector in RRMD-III and were not measured. Measured values of LET were within ± 7% of the expected value for incident protons that had an energy sufficient to penetrate the second Si detector in RRMD-III (E>15.4 MeV). The LET of stopping particles was computed using a lookup table listing LET vs E, and a simple stopping power formula for a particle with charge Z and energy ER, where ER is the energy of the stopping particle measured in the second Si detector.

Terasawa, Kazuhiro; Borak, Thomas B.; Doke, Tadayoshi; Fuse, Tetsuhito; Hara, Ken-ichiro; Kikuchi, Jun; Kitamura, Hisashi; Suzuki, Satoshi; Uchihori, Yukio

2005-10-01

319

A micromachined gas chromatographic column to optimize the gas selectivity for a resistive thin film gas sensor  

Microsoft Academic Search

Indoor air quality monitoring applications require both high selectivity and sensitivity, which are difficult to reach with solid state gas sensors. An ultra small packed gas chromatographic column designed for a micro total analyzing system (?TAS) based on a solid state gas sensor as a detector and used to determine the concentration of benzene, toluene and xylene (BTX) in indoor

Jorg Sturmann; W. Benecke; S. Zampolli; I. Elmi; G. C. Cardinali; W. Lang

2005-01-01

320

Continuous flowing micro-reactor for aqueous reaction at temperature higher than 100?°C.  

PubMed

Some aqueous reactions in biological or chemical fields are accomplished at a high temperature. When the reaction temperature is higher than 100?°C, an autoclave reactor is usually required to elevate the boiling point of the water by creating a high-pressure environment in a closed system. This work presented an alternative continuous flowing microfluidic solution for aqueous reaction with a reaction temperature higher than 100?°C. The pressure regulating function was successfully fulfilled by a small microchannel based on a delicate hydrodynamic design. Combined with micro heater and temperature sensor that integrated in a single chip by utilizing silicon-based microfabrication techniques, this pressure regulating microchannel generated a high-pressure/high-temperature environment in the upstream reaction zone when the reagents continuously flow through the chip. As a preliminary demonstration, thermal digestion of aqueous total phosphorus sample was achieved in this continuous flowing micro-reactor at a working pressure of 990?kPa (under the working flow rate of 20 nl/s) along with a reaction temperature of 145?°C. This continuous flowing microfluidic solution for high-temperature reaction may find applications in various micro total analysis systems. PMID:24404024

Xie, Fei; Wang, Baojun; Wang, Wei; Dong, Tian; Tong, Jianhua; Xia, Shanhong; Wu, Wengang; Li, Zhihong

2013-01-01

321

The role of the substrate in micro-scale scratching of epoxy-polyester films  

NASA Astrophysics Data System (ADS)

The present investigation analyzes the deformation response of electrostatically sprayed epoxy-polyester powder coatings by 'in situ' micro-mechanical tests. The characterization of the performance of the coatings was carried out by micro-scale scratching, by varying the indenter type, the applied load and the sliding speed. The tests were carried out on polymeric coatings deposited on as-received, micro and macro-corrugated AISI 304 stainless steel substrates and 'rigidly adhered' to them. Further tests were performed on 'free-standing' coatings, that is, on the as-received metal substrates pre-coated with an intermediate layer of silicon-based heat curable release coating. Experimental data allow us to evaluate the influence of the contact conditions between substrate and indenter and the role of the loading conditions on the scratch and penetration resistance of the epoxy-polyester coatings. The different responses of the polymeric coatings when deposited on untreated or pre-treated substrates as well as on an intermediate layer of release coating, contribute to a better understanding of the intrinsic roles of the polymeric material and substrate as well as the influence of the interfacial adhesion between coating and substrate.

Barletta, M.; Gisario, A.

2011-02-01

322

A silicon-based photocathode for water reduction with an epitaxial SrTiO3 protection layer and a nanostructured catalyst.  

PubMed

The rapidly increasing global demand for energy combined with the environmental impact of fossil fuels has spurred the search for alternative sources of clean energy. One promising approach is to convert solar energy into hydrogen fuel using photoelectrochemical cells. However, the semiconducting photoelectrodes used in these cells typically have low efficiencies and/or stabilities. Here we show that a silicon-based photocathode with a capping epitaxial oxide layer can provide efficient and stable hydrogen production from water. In particular, a thin epitaxial layer of strontium titanate (SrTiO3) was grown directly on Si(001) by molecular beam epitaxy. Photogenerated electrons can be transported easily through this layer because of the conduction-band alignment and lattice match between single-crystalline SrTiO3 and silicon. The approach was used to create a metal-insulator-semiconductor photocathode that, under a broad-spectrum illumination at 100?mW cm(-2), exhibits a maximum photocurrent density of 35?mA?cm(-2) and an open circuit potential of 450?mV; there was no observable decrease in performance after 35 hours of operation in 0.5?M H2SO4. The performance of the photocathode was also found to be highly dependent on the size and spacing of the structured metal catalyst. Therefore, mesh-like Ti/Pt nanostructured catalysts were created using a nanosphere lithography lift-off process and an applied-bias photon-to-current efficiency of 4.9% was achieved. PMID:25437745

Ji, Li; McDaniel, Martin D; Wang, Shijun; Posadas, Agham B; Li, Xiaohan; Huang, Haiyu; Lee, Jack C; Demkov, Alexander A; Bard, Allen J; Ekerdt, John G; Yu, Edward T

2015-01-01

323

A silicon-based photocathode for water reduction with an epitaxial SrTiO3 protection layer and a nanostructured catalyst  

NASA Astrophysics Data System (ADS)

The rapidly increasing global demand for energy combined with the environmental impact of fossil fuels has spurred the search for alternative sources of clean energy. One promising approach is to convert solar energy into hydrogen fuel using photoelectrochemical cells. However, the semiconducting photoelectrodes used in these cells typically have low efficiencies and/or stabilities. Here we show that a silicon-based photocathode with a capping epitaxial oxide layer can provide efficient and stable hydrogen production from water. In particular, a thin epitaxial layer of strontium titanate (SrTiO3) was grown directly on Si(001) by molecular beam epitaxy. Photogenerated electrons can be transported easily through this layer because of the conduction-band alignment and lattice match between single-crystalline SrTiO3 and silicon. The approach was used to create a metal–insulator–semiconductor photocathode that, under a broad-spectrum illumination at 100?mW cm?2, exhibits a maximum photocurrent density of 35?mA?cm?2 and an open circuit potential of 450?mV there was no observable decrease in performance after 35 hours of operation in 0.5?M H2SO4. The performance of the photocathode was also found to be highly dependent on the size and spacing of the structured metal catalyst. Therefore, mesh-like Ti/Pt nanostructured catalysts were created using a nanosphere lithography lift-off process and an applied-bias photon-to-current efficiency of 4.9% was achieved.

Ji, Li; McDaniel, Martin D.; Wang, Shijun; Posadas, Agham B.; Li, Xiaohan; Huang, Haiyu; Lee, Jack C.; Demkov, Alexander A.; Bard, Allen J.; Ekerdt, John G.; Yu, Edward T.

2015-01-01

324

Method of fabricating a micro machine  

DOEpatents

A micro machine may be in or less than the micrometer domain. The micro machine may include a micro actuator and a micro shaft coupled to the micro actuator. The micro shaft is operable to be driven by the micro actuator. A tool is coupled to the micro shaft and is operable to perform work in response to at least motion of the micro shaft.

Stalford, Harold L

2014-11-11

325

Preliminary development of a hydrocarbon-fueled catalytic micro-combustor  

Microsoft Academic Search

This paper reports development of a hydrocarbon-fueled micro-combustion system for a micro-scale gas turbine engine for power generation and micro-propulsion applications. A three-wafer catalytic combustor was fabricated and tested. Efficiencies in excess of 40% were achieved for ethylene–air and propane–air combustion. A fabrication process for a six-wafer catalytic combustor was developed and this device was successfully constructed.

Christopher M. Spadaccini; Xin Zhang; Christopher P. Cadou; Norihisa Miki; Ian A. Waitz

2003-01-01

326

Silicon micro-mold  

DOEpatents

The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

Morales, Alfredo M. (Livermore, CA)

2006-10-24

327

Micro-Organ Devices  

NASA Technical Reports Server (NTRS)

Micro-organ devices (MODs) are being developed to satisfy an emerging need for small, lightweight, reproducible, biological-experimentati on apparatuses that are amenable to automated operation and that imp ose minimal demands for resources (principally, power and fluids). I n simplest terms, a MOD is a microfluidic device containing a variety of microstructures and assemblies of cells, all designed to mimic a complex in vivo microenvironment by replicating one or more in vivo micro-organ structures, the architectures and composition of the extr acellular matrices in the organs of interest, and the in vivo fluid flows. In addition to microscopic flow channels, a MOD contains one or more micro-organ wells containing cells residing in microscopic e xtracellular matrices and/or scaffolds, the shapes and compositions o f which enable replication of the corresponding in vivo cell assembl ies and flows.

Gonda, Steven R.; Leslie, Julia; Chang, Robert C.; Starly, Binil; Sun, Wei; Culbertson, Christopher; Holtorf, Heidi

2009-01-01

328

Structure of catalase determined by MicroED  

PubMed Central

MicroED is a recently developed method that uses electron diffraction for structure determination from very small three-dimensional crystals of biological material. Previously we used a series of still diffraction patterns to determine the structure of lysozyme at 2.9 Å resolution with MicroED (Shi et al., 2013). Here we present the structure of bovine liver catalase determined from a single crystal at 3.2 Å resolution by MicroED. The data were collected by continuous rotation of the sample under constant exposure and were processed and refined using standard programs for X-ray crystallography. The ability of MicroED to determine the structure of bovine liver catalase, a protein that has long resisted atomic analysis by traditional electron crystallography, demonstrates the potential of this method for structure determination. DOI: http://dx.doi.org/10.7554/eLife.03600.001 PMID:25303172

Nannenga, Brent L; Shi, Dan; Hattne, Johan; Reyes, Francis E; Gonen, Tamir

2014-01-01

329

MicroBooNE  

E-print Network

The MicroBooNE experiment is a 170 ton Liquid Argon Time Projection Chamber (LArTPC) that will begin running at Fermilab in 2013. Its primary physics goal is to explore the low energy excess of events seen by the MiniBooNE experiment and it is the next step in the R&D to make LAr a viable option for future large neutrino detectors. This talk presented an overview of the MicroBooNE experiment with an emphasis on the light collection system and recent technical advances.

C. M. Ignarra

2011-10-07

330

Surface tension effects on adiabatic gasliquid flow across micro pillars Santosh Krishnamurthy, Yoav Peles *  

E-print Network

, Yoav Peles * Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic-chemical reactors (Losey et al., 2002), micro-rockets (Hitt et al., 2001; Lon- don, 2000), micro-biological systems- phase flow characteristics in small length scales. Kawahara et al. (2005) in their study on gas

Peles, Yoav

331

Analysis of a fuel cell micro-grid with a small-scale wind turbine generator  

Microsoft Academic Search

If electric power is supplied using an independent micro-grid connected to renewable energy, it can flexibly match the energy demand characteristics of a local area. And an independent micro-grid is expected to be effective in cutting greenhouse gas discharge and energy costs, as well as in eliminating the need for an emergency power supply system. Since the output of renewable

Shin’ya Obara

2007-01-01

332

Method of Manufacturing Micro-Disperse Particles of Sodium Borohydride  

DOEpatents

A compact solid source of hydrogen gas, where the gas is generated by contacting water with micro-disperse particles of sodium borohydride in the presence of a catalyst, such as cobalt or ruthenium. The micro-disperse particles can have a substantially uniform diameter of 1-10 microns, and preferably about 3-5 microns. Ruthenium or cobalt catalytic nanoparticles can be incorporated in the micro-disperse particles of sodium borohydride, which allows a rapid and complete reaction to occur without the problems associated with caking and scaling of the surface by the reactant product sodium metaborate. A closed loop water management system can be used to recycle wastewater from a PEM fuel cell to supply water for reacting with the micro-disperse particles of sodium borohydride in a compact hydrogen gas generator. Capillary forces can wick water from a water reservoir into a packed bed of micro-disperse fuel particles, eliminating the need for using an active pump.

Kravitz, Stanley H. (Placitas, NM); Hecht, Andrew M. (Sandia Park, NM); Sylwester. Alan P. (Albuquerque, NM); Bell, Nelson S. (Albuquerque, NM)

2008-09-23

333

Micro acoustic spectrum analyzer  

DOEpatents

A micro acoustic spectrum analyzer for determining the frequency components of a fluctuating sound signal comprises a microphone to pick up the fluctuating sound signal and produce an alternating current electrical signal; at least one microfabricated resonator, each resonator having a different resonant frequency, that vibrate in response to the alternating current electrical signal; and at least one detector to detect the vibration of the microfabricated resonators. The micro acoustic spectrum analyzer can further comprise a mixer to mix a reference signal with the alternating current electrical signal from the microphone to shift the frequency spectrum to a frequency range that is a better matched to the resonant frequencies of the microfabricated resonators. The micro acoustic spectrum analyzer can be designed specifically for portability, size, cost, accuracy, speed, power requirements, and use in a harsh environment. The micro acoustic spectrum analyzer is particularly suited for applications where size, accessibility, and power requirements are limited, such as the monitoring of industrial equipment and processes, detection of security intrusions, or evaluation of military threats.

Schubert, W. Kent; Butler, Michael A.; Adkins, Douglas R.; Anderson, Larry F.

2004-11-23

334

Micro-PROUST.  

ERIC Educational Resources Information Center

This detailed description of a microcomputer version of PROUST (Program Understander for Students), a knowledge-based system that finds nonsyntactic bugs in Pascal programs written by novice programmers, presents the inner workings of Micro-PROUST, which was written in Golden LISP for the IBM-PC (512K). The contents include: (1) a reprint of an…

Johnson, W. Lewis; Soloway, Elliot

335

Autonomous, agile micro-satellites and supporting technologies  

SciTech Connect

This paper updates the on-going effort at Lawrence Livermore National Laboratory to develop autonomous, agile micro-satellites (MicroSats). The objective of this development effort is to develop MicroSats weighing only a few tens of kilograms, that are able to autonomously perform precision maneuvers and can be used telerobotically in a variety of mission modes. The required capabilities include satellite rendezvous, inspection, proximity-operations, docking, and servicing. The MicroSat carries an integrated proximity-operations sensor-suite incorporating advanced avionics. A new self-pressurizing propulsion system utilizing a miniaturized pump and non-toxic mono-propellant hydrogen peroxide was successfully tested. This system can provide a nominal 25 kg MicroSat with 200-300 m/s delta-v including a warm-gas attitude control system. The avionics is based on the latest PowerPC processor using a CompactPCI bus architecture, which is modular, high-performance and processor-independent. This leverages commercial-off-the-shelf (COTS) technologies and minimizes the effects of future changes in processors. The MicroSat software development environment uses the Vx-Works real-time operating system (RTOS) that provides a rapid development environment for integration of new software modules, allowing early integration and test. We will summarize results of recent integrated ground flight testing of our latest non-toxic pumped propulsion MicroSat testbed vehicle operated on our unique dynamic air-rail.

Breitfeller, E; Dittman, M D; Gaughan, R J; Jones, M S; Kordas, J F; Ledebuhr, A G; Ng, L C; Whitehead, J C; Wilson, B

1999-07-19

336

Characteristics of Ozone Generation using a Micro Hollow Cathode Discharge  

Microsoft Academic Search

A new type of ozone generator using a micro hollow cathode discharge has been developed and evaluated on its operating characteristics. The electrode system consists of two thin metal cathodes and a ceramic spacer with a center hole of a few 100 µm diameter. By feeding high- pressure oxygen gas through the center hole, the residence time of the oxygen

Yasunobu Endo; Koichi Yasuoka; Shozo Ishii

2003-01-01

337

Breakthrough: micro-electronic photovoltaics  

ScienceCinema

Sandia developed tiny glitter-sized photovoltaic (PV) cells that could revolutionize solar energy collection. The crystalline silicon micro-PV cells will be cheaper and have greater efficiencies than current PV collectors. Micro-PV cells require relatively little material to form well-controlled, highly efficient devices. Cell fabrication uses common microelectric and micro-electromechanical systems (MEMS) techniques.

Okandan, Murat; Gupta, Vipin

2014-06-23

338

Research on high-band-gap materials and amorphous-silicon-based solar cells. Annual subcontract report, May 15, 1994--May 14, 1995  

SciTech Connect

We have conducted a survey of thin BP:H and BPC:H films prepared by plasma deposition using phosphine, diborane, tri-methylboron, and hydrogen as precursor gases. The objective of this research is to find out whether such films might offer a superior window layer film for application to wide bandgap a-Si solar cells. The research has shown good optical properties in a-BP:H films, but electrical properties acceptable for use in window layers have not been demonstrated yet. We have also found an interesting, conductive and transparent BPC:H film in a remote deposition region of the reactor, but have been unable to transfer deposition of this film to the standard interelectrode region. We have developed our capability to deposit nip sequence amorphous silicon based solar cells, and have demonstrated an open circuit voltage greater than 0.7 V. We have continued our studies of built-in potentials in a-Si based solar cells using the electroabsorption technique, extending our measurements to include cells with wider bandgap intrinsic layers and Schottky barrier test structures. We have made the first time-of-flight drift mobility measurements on a-Si:H prepared by hot wire (HW) deposition. Initial work has shown that light-soaked HW material can have much better ambipolar diffusion lengths than the plasma-deposited material following extended light soaking. We have performed some theoretical work which addresses a difficulty in understanding photocarrier recombination in a-Si:H first identified by Marvin Silver. In particular, electron-hole recombination is much slower than expected from the well-known {open_quotes}diffusion-controlled{close_quotes} models for Onsager (geminate) recombination and Langevin recombination. This slowness is essential to the success of a-Si in solar cells, but is unexplained. We have done work on high field electron drift mobilities in a-Si:H and on the validity of the Einstein relation connecting the diffusion and drift of holes in a-Si:H.

Schiff, E.A.; Gu, Q.; Jiang, L.; Wang, Q. [Syracuse Univ., NY (United States)

1995-12-01

339

Fabrication and evaluation of a free molecule micro-resistojet with thick silicon dioxide insulation and suspension  

NASA Astrophysics Data System (ADS)

A silicon free molecule micro-resistojet (FMMR) with a thermally insulating suspension frame composed of silicon dioxide has been designed, fabricated and tested. The concept was developed to increase the efficiency of FMMRs, especially in silicon-based integrated systems. Fabrication of the thick insulating frame was performed through oxidation of high-aspect ratio silicon trenches. The thermal properties of the 1 cm2 thruster were evaluated using an IR camera, and it was found that when the volume inside the frame is heated more than 200 °C using integrated nickel heaters, the temperature increase in the volume outside the frame is less than 50 °C. During operation in vacuum, the thrust range was calculated to be about 13-1070 µN and the maximum specific impulse 54 s. At maximum thrust, and a power consumption of 1.6 W, the total efficiency of the thruster was 17%. Designs of more efficient and versatile systems are discussed.

Palmer, Kristoffer; Nguyen, Hugo; Thornell, Greger

2013-06-01

340

Methods and systems for micro transmissions  

DOEpatents

Methods and systems for micro transmissions for a micro machine may comprise an input shaft assembly coupled to a micro actuator, an output shaft assembly coupled to a micro shaft, and one or more power conversion elements operable to convert a first type of movement from the micro actuator into a second, disparate type of movement for the micro shaft.

Stalford, Harold L

2014-12-23

341

Methods and systems for micro bearings  

DOEpatents

A micro drive assembly may comprise a substrate, a micro shall oriented in-plane with the substrate and at least one micro bearing to support rotation of the micro shaft. The micro shaft and micro bearing may be in or less than the micrometer domain.

Stalford, Harold L.

2012-10-09

342

Simulation studies of RF excited micro-cavity discharges for micro-propulsion applications  

NASA Astrophysics Data System (ADS)

A detailed computational modelling study of the micro-cavity discharge (MCD) thruster is presented. The MCD thruster concept incorporates a microdischarge with dielectric covered electrodes operated using alternating current (ac) excitation. The thruster geometry comprises a constant area pipe section followed by a divergent micro-nozzle. Two ring electrodes are embedded in the wall of the pipe section with the downstream electrode close to the pipe-micronozzle intersection. A microdischarge plasma is generated in argon propellant gas flowing through the thruster. A detailed plasma dynamics model coupled with the compressible Navier-Stokes equations is used to study the flow and plasma phenomenon in the thruster. Results show a highly pulsed microdischarge with plasma densities of ˜1019 m-3 and current densities ˜700 mA cm-2 for an ac excitation in the radio frequency (RF) regime of 10 and 20 MHz. The dominant gas heating mechanism in these discharges is through ion Joule heating. Higher electron densities and spatially dominant thermal source terms are observed for the 20 MHz excitation compared with 10 MHz excitation. The addition of 20% nitrogen to the flow resulted in much better performance compared with the pure argon cases. A peak gas temperature rise ˜200 K is seen for a cycle-averaged power deposition of 76 mW. For the conditions explored in this study, the overall specific impulse of the thruster operating with the microdischarge plasma is found to be about 25% higher than a corresponding cold gas case.

Sitaraman, H.; Raja, L. L.

2012-05-01

343

Micro pulse lidar  

SciTech Connect

An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering has been demonstrated. The transmitter of the micro pulse lidar is a diode pumped [mu]J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view (FOV) and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited by optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that systems built on the micro pulse lidar concept are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

Spinhirne, J.D. (Goddard Space Flight Center, Greenbelt, MD (United States))

1993-01-01

344

Micro-Geomechanics  

NSDL National Science Digital Library

This paper discusses the neglect of micro-mechanics in soil mechanics, and seeks to establish a role that will benefit both the research worker and the practitioner. In support of the mathematical construct of "plasticity", micro-mechanics introduces observations of grain crushing and re-arrangement. Not only does this help to explain the dimensionally inconsistent concept of the normal compression line, it goes some way to unifying our understanding ofsands and clays. Indeed, bridging the grain-continuum duality is the key to raising the confidence of practitioners both in the meaningfulness of certain constitutive modeling parameters and in the scaling rules applied to the behavior of small scale physical models.

Bolton, M.D.

345

Micro pulse laser radar  

NASA Technical Reports Server (NTRS)

An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering is disclosed. The transmitter of the micro pulse lidar is a diode pumped micro-J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited to optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that micropulse lider systems are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

Spinhirne, James D. (inventor)

1993-01-01

346

Performance analysis and design optimization of micro-jet impingement heat sink  

NASA Astrophysics Data System (ADS)

This study evaluated a silicon-based micro-jet impingement heat sink for electronic cooling applications. First, the pressure-drop and thermal characteristics were investigated for steady incompressible and laminar flow by solving three-dimensional Navier-Stokes equations, and the performance enhancement was carried out through parametric and optimization studies. Several parallel and staggered micro-jet configurations consisting of a maximum of 16 jet impingements were tested. The effectiveness of the micro-jet configurations, i.e. inline 2 × 2, 3 × 3 and 4 × 4 jets, and staggered 5-jet and 13-jet arrays with nozzle diameters 50, 76, and 100 ?m, were analyzed at various flow rates for the maximum temperature-rise and pressure-drop characteristics. A design with a staggered 13-jet array showed the best performance among the various configurations investigated in the present study. The design optimization based on three-dimensional numerical analysis, surrogate modeling and a multi-objective evolutionary algorithm were carried out to understand the thermal resistance and pumping power correlation of the micro-jet impingement heat sink. Two design variables, the ratio of height of the channel and nozzle diameter, and the ratio of nozzle diameter and interjet spacing, were chosen for design optimization. The global Pareto-optimal front was achieved for overall thermal resistance and required pumping power of the heat sink. The Pareto-optimal front revealed existing correlation between pumping power and thermal resistance of the heat sink. Of the range of Pareto-optimal designs available, some representative designs were selected and their functional relationships among the objective functions and design variables were examined to understand the Pareto-optimal sensitivity and optimal design space. A minimum of 66 °C of maximum-temperature-rise was obtained for a heat flux of 100 W/cm2 at a pressure drop of about 24 kPa.

Husain, Afzal; Kim, Sun-Min; Kim, Kwang-Yong

2013-11-01

347

Scanning micro-sclerometer  

DOEpatents

A scanning micro-sclerometer measures changes in contact stiffness and correlates these changes to characteristics of a scratch. A known force is applied to a contact junction between two bodies and a technique employing an oscillating force is used to generate the contact stiffness between the two bodies. As the two bodies slide relative to each other, the contact stiffness changes. The change is measured to characterize the scratch.

Oliver, Warren C. (Knoxville, TN); Blau, Peter J. (Oak Ridge, TN)

1994-01-01

348

Scanning micro-sclerometer  

DOEpatents

A scanning micro-sclerometer measures changes in contact stiffness and correlates these changes to characteristics of a scratch. A known force is applied to a contact junction between two bodies and a technique employing an oscillating force is used to generate the contact stiffness between the two bodies. As the two bodies slide relative to each other, the contact stiffness changes. The change is measured to characterize the scratch. 2 figs.

Oliver, W.C.; Blau, P.J.

1994-11-01

349

Micro pulse lidar  

Microsoft Academic Search

An eye safe, compact, solid-state lidar for profiling atmospheric cloud and aerosol scattering is described. The transmitter of the micro pulse lidar is a diode pumped microjoule pulse energy, high-repetition-rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver uses a photon counting solid-state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler.

J. D. Spinhirne

1993-01-01

350

Micro coring apparatus  

NASA Technical Reports Server (NTRS)

A micro-coring apparatus for lunar exploration applications, that is compatible with the other components of the Walking Mobile Platform, was designed. The primary purpose of core sampling is to gain an understanding of the geological composition and properties of the prescribed environment. This procedure has been used extensively for Earth studies and in limited applications during lunar explorations. The corer is described and analyzed for effectiveness.

Collins, David; Brooks, Marshall; Chen, Paul; Dwelle, Paul; Fischer, Ben

1989-01-01

351

Micro borehole drilling platform  

SciTech Connect

This study by CTES, L.C. meets two main objectives. First, evaluate the feasibility of using coiled tubing (CT) to drill 1.0 inches-2.5 inches diameter directional holes in hard rocks. Second, develop a conceptual design for a micro borehole drilling platform (MBDP) meeting specific size, weight, and performance requirements. The Statement of Work (SOW) in Appendix A contains detailed specifications for the feasibility study and conceptual design.

NONE

1996-10-01

352

Micro-column plasma emission liquid chromatograph  

DOEpatents

In a direct current plasma emission spectrometer for use in combination with a micro-column liquid chromatograph, an improved plasma source unit. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

Gay, Don D. (Aiken, SC)

1984-01-01

353

Micro-optical instrumentation for process spectroscopy  

NASA Astrophysics Data System (ADS)

Traditional laboratory ultraviolet/visible/near-infrared spectroscopy instruments are tabletop-sized pieces of equipment that exhibit very high performance, but are generally too large and costly to be widely distributed for process control applications or used as spectroscopic sensors. Utilizing a unique, and proven, micro-optical technology platform origi-nally developed, qualified and deployed in the telecommunications industry, we have developed a new class of spectro-scopic micro-instrumentation that has laboratory quality resolution and spectral range, with superior speed and robust-ness. The fundamentally lower cost and small form factor of the technology will enable widespread use in process moni-toring and control. This disruption in the ground rules of spectroscopic analysis in these processes is enabled by the re-placement of large optics and detector arrays with a high-finesse, high-speed micro electro mechanical system (MEMS) tunable filter and a single detector, that enable the manufacture of a high performance and extremely rugged spectrome-ter in the footprint of a credit card. Specific process monitoring and control applications discussed in the paper include pharmaceutical, gas sensing and chemical processing applications.

Crocombe, Richard A.; Flanders, Dale C.; Atia, Walid

2004-12-01

354

Furanic compounds and furfural in different coffee products by headspace liquid-phase micro-extraction followed by gas chromatography-mass spectrometry: survey and effect of brewing procedures.  

PubMed

In this study, the levels of furan, 2-methylfuran, 2,5-dimethylfuran, vinyl furan, 2-methoxymethyl-furan and furfural in different coffee products were evaluated. Simultaneous determination of these six furanic compounds was performed by a head space liquid-phase micro-extraction (HS-LPME) method. A total of 67 coffee powder samples were analysed. The effects of boiling and espresso-making procedures on the levels of furanic compounds were investigated. The results showed that different types of coffee samples contained different concentrations of furanic compounds, due to the various processing conditions such as temperature, degree of roasting and fineness of grind. Among the different coffee samples, the highest level of furan (6320 µg kg(-1)) was detected in ground coffee, while coffee-mix samples showed the lowest furan concentration (10 µg kg(-1)). Levels in brewed coffees indicated that, except for furfural, brewing by an espresso machine caused significant loss of furanic compounds. PMID:25356540

Chaichi, Maryam; Ghasemzadeh-Mohammadi, Vahid; Hashemi, Maryam; Mohammadi, Abdorreza

2015-01-01

355

Automated headspace-solid-phase micro extraction-retention time locked-isotope dilution gas chromatography-mass spectrometry for the analysis of organotin compounds in water and sediment samples.  

PubMed

An automated method for the simultaneous determination of six important organotin compounds namely monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), diphenyltin (DPhT) and triphenyltin (TPhT) in water and sediment samples is described. The method is based on derivatization with sodium tetraethylborate followed by automated headspace-solid-phase micro extraction (SPME) combined with GC-MS under retention time locked (RTL) conditions. Home-synthesized deuterated organotin analogues were used as internal standards. Two high abundant fragment ions corresponding to the main tin isotopes Sn118 and Sn120 were chosen; one for quantification and one as qualifier ion. The method was validated and excellent figures of merit were obtained. Limits of quantification (LOQs) are from 1.3 to 15 ng l(-1) (ppt) for water samples and from 1.0 to 6.3 microg kg(-1) (ppb) for sediment samples. Accuracy for sediment samples was tested on spiked real-life sediment samples and on a reference PACS-2 marine harbor sediment. The developed method was used in a case-study at the harbor of Antwerp where sediment samples in different areas were taken and subsequently screened for TBT contamination. Concentrations ranged from 15 microg kg(-1) in the port of Antwerp up to 43 mg kg(-1) near a ship repair unit. PMID:16038329

Devosa, Christophe; Vliegen, Maarten; Willaert, Bart; David, Frank; Moens, Luc; Sandra, Pat

2005-06-24

356

Gas-Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon  

E-print Network

1 Gas-Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon #12;2 ABSTRACT Since gas flows in micro/nano devices are dominated by the interaction of gas molecules accommodation of gas molecules on surfaces. The scattering of gas molecules on quartz surfaces covered with VA

Maruyama, Shigeo

357

Advanced Micro Turbine System (AMTS) -C200 Micro Turbine -Ultra-Low Emissions Micro Turbine  

SciTech Connect

In September 2000 Capstone Turbine Corporation commenced work on a US Department of Energy contract to develop and improve advanced microturbines for power generation with high electrical efficiency and reduced pollutants. The Advanced MicroTurbine System (AMTS) program focused on: (1) The development and implementation of technology for a 200 kWe scale high efficiency microturbine system (2) The development and implementation of a 65 kWe microturbine which meets California Air Resources Board (CARB) emissions standards effective in 2007. Both of these objectives were achieved in the course of the AMTS program. At its conclusion prototype C200 Microturbines had been designed, assembled and successfully completed field demonstration. C65 Microturbines operating on natural, digester and landfill gas were also developed and successfully tested to demonstrate compliance with CARB 2007 Fossil Fuel Emissions Standards for NOx, CO and VOC emissions. The C65 Microturbine subsequently received approval from CARB under Executive Order DG-018 and was approved for sale in California. The United Technologies Research Center worked in parallel to successfully execute a RD&D program to demonstrate the viability of a low emissions AMS which integrated a high-performing microturbine with Organic Rankine Cycle systems. These results are documented in AMS Final Report DOE/CH/11060-1 dated March 26, 2007.

Capstone Turbine Corporation

2007-12-31

358

MicroMAPS Missions for CO Detection  

NASA Astrophysics Data System (ADS)

The ultimate goal of MicroMaps is to detect CO and N2O from an orbital platform. The instrument is equipped with CO and N2O gas cells configured to observe the earth's IR radiance in a band centered at 4.67 microns. Utilizing these gas cells in a selective chopper, the instrument produces its signal by forming the difference between the incoming energy as seen though one of the gas cells and a second cell that is either evacuated or contains a non-absorbing gas. From the chopper the beams are directed to a detector where they are electronically differenced. The resulting signals will be used with pre- and post-flight calibration for data reduction. A test flight for MicroMAPS is planned on the Proteus aircraft. To prepare for this flight a full-scale theoretical model of the data Proteus is expected to obtain is produced. This model includes total upwelling radiance of the earth in the wavenumber range of 2080 cm-1 to 2280cm-1 transmission of the earth's radiance through the optical window, the band pass filter, and the optical chopper which includes transmission through and emission of the gas in the gas cells. The model produces 5K increments in the range of 280.15K to 310.15K for the blackbody source. Each source temperature includes a model of instrument temperatures with the same range. This upwelling radiance vs. wavenumber data is then integrated over wavenumber for all the temperatures to give us a theoretical model of total radiance vs. temperature of the target for multiple instrument temperatures. The atmospheric radiance was obtained using Line By Line Radiative Transfer Model (LBLRTM) with the HITRAN 1992 database. Gas cell transmissions were obtained via HITRAN-PC, which uses the same database. For comparison, the atmospheric radiance was also generated using HITRAN 1996 with LBLRTM and using HITRAN 2000 with an independent program written in MATLAB with the GENSPECT toolbox. This theoretical model will be used in conjunction with preflight calibration data to give a theoretical prediction of CO concentration. Once the Proteus flies, the post-flight calibration data will be used to reduce the in-flight difference signals. This result will be compared with the predictions of CO concentrations based on theoretical models.

Hopkins, P. E.; Tangen, S. A.; Ribando, R. J.; Wood, H. G.; Connors, V. S.

2003-12-01

359

Stringy and Membranic Theory of Swimming of Micro-organisms  

E-print Network

When the swimming of micro-organisms is viewed from the string and membrane theories coupled to the velocity field of the fluid, a number of interesting results are derived; 1) importance of the area (or volume) preserving algebra, 2) usefulness of the $N$-point Reggeon (membranic) amplitudes, and of the gas to liquid transition in case of the red tide issues, 3) close relation between the red tide issue and the generation of Einstein gravity, and 4) possible understanding of the three different swimming ways of micro-organisms from the singularity structure of the shape space.

Masako Kawamura; Shin'ichi Nojiri; Akio Sugamoto

1996-03-21

360

Micro-/nanofluidics based cell electroporation  

PubMed Central

Non-viral gene delivery has been extensively explored as the replacement for viral systems. Among various non-viral approaches, electroporation has gained increasing attention because of its easy operation and no restrictions on probe or cell type. Several effective systems are now available on the market with reasonably good gene delivery performance. To facilitate broader biological and medical applications, micro-/nanofluidics based technologies were introduced in cell electroporation during the past two decades and their advances are summarized in this perspective. Compared to the commercially available bulk electroporation systems, they offer several advantages, namely, (1) sufficiently high pulse strength generated by a very low potential difference, (2) conveniently concentrating, trapping, and regulating the position and concentration of cells and probes, (3) real-time monitoring the intracellular trafficking at single cell level, and (4) flexibility on cells to be transfected (from single cell to large scale cell population). Some of the micro-devices focus on cell lysis or fusion as well as the analysis of cellular properties or intracellular contents, while others are designed for gene transfection. The uptake of small molecules (e.g., dyes), DNA plasmids, interfering RNAs, and nanoparticles has been broadly examined on different types of mammalian cells, yeast, and bacteria. A great deal of progress has been made with a variety of new micro-/nanofluidic designs to address challenges such as electrochemical reactions including water electrolysis, gas bubble formation, waste of expensive reagents, poor cell viability, low transfection efficacy, higher throughput, and control of transfection dosage and uniformity. Future research needs required to advance micro-/nanofluidics based cell electroporation for broad life science and medical applications are discussed. PMID:23405056

Wang, Shengnian; Lee, L. James

2013-01-01

361

Micro-/nanofluidics based cell electroporation.  

PubMed

Non-viral gene delivery has been extensively explored as the replacement for viral systems. Among various non-viral approaches, electroporation has gained increasing attention because of its easy operation and no restrictions on probe or cell type. Several effective systems are now available on the market with reasonably good gene delivery performance. To facilitate broader biological and medical applications, micro-/nanofluidics based technologies were introduced in cell electroporation during the past two decades and their advances are summarized in this perspective. Compared to the commercially available bulk electroporation systems, they offer several advantages, namely, (1) sufficiently high pulse strength generated by a very low potential difference, (2) conveniently concentrating, trapping, and regulating the position and concentration of cells and probes, (3) real-time monitoring the intracellular trafficking at single cell level, and (4) flexibility on cells to be transfected (from single cell to large scale cell population). Some of the micro-devices focus on cell lysis or fusion as well as the analysis of cellular properties or intracellular contents, while others are designed for gene transfection. The uptake of small molecules (e.g., dyes), DNA plasmids, interfering RNAs, and nanoparticles has been broadly examined on different types of mammalian cells, yeast, and bacteria. A great deal of progress has been made with a variety of new micro-/nanofluidic designs to address challenges such as electrochemical reactions including water electrolysis, gas bubble formation, waste of expensive reagents, poor cell viability, low transfection efficacy, higher throughput, and control of transfection dosage and uniformity. Future research needs required to advance micro-/nanofluidics based cell electroporation for broad life science and medical applications are discussed. PMID:23405056

Wang, Shengnian; Lee, L James

2013-01-01

362

Micro CVD diamond heat sink  

NASA Astrophysics Data System (ADS)

Chemical vapor deposition (CVD) diamond film has broad application prospect as heat sink in microelectronic field for its excellent thermal conductivity. The micro CVD diamond heat sinks with the size of 50?m×100?m×2000?m were prepared using mould copy technique. The micro silicon moulds for deposition of micro CVD diamond heat sinks were fabricated using inductivity coupling plasma (ICP) etching process. Micro CVD diamond heat sinks were synthesized under 2% methane and 98% hydrogen by hot filament CVD (HFCVD) method. The micro CVD diamond heat sinks were investigated by SEM, Raman and photo thermal deflection. The results show that favorable micro CVD heat sinks having a thermal conductivity of 960W·m-1·K-1 can be prepared by mould copy technique.

Lu, Wenzhuang; Ai, Guoping; Li, Pin; Sun, Yuli; Zhang, Dan; Zuo, Dunwen

2013-08-01

363

Gas sensor with attenuated drift characteristic  

DOEpatents

A sensor with an attenuated drift characteristic, including a layer structure in which a sensing layer has a layer of diffusional barrier material on at least one of its faces. The sensor may for example be constituted as a hydrogen gas sensor including a palladium/yttrium layer structure formed on a micro-hotplate base, with a chromium barrier layer between the yttrium layer and the micro-hotplate, and with a tantalum barrier layer between the yttrium layer and an overlying palladium protective layer. The gas sensor is useful for detection of a target gas in environments susceptible to generation or incursion of such gas, and achieves substantial (e.g., >90%) reduction of signal drift from the gas sensor in extended operation, relative to a corresponding gas sensor lacking the diffusional barrier structure of the invention

Chen, Ing-Shin (Danbury, CT) [Danbury, CT; Chen, Philip S. H. (Bethel, CT) [Bethel, CT; Neuner, Jeffrey W. (Bethel, CT) [Bethel, CT; Welch, James (Fairfield, CT) [Fairfield, CT; Hendrix, Bryan (Danbury, CT) [Danbury, CT; Dimeo, Jr., Frank [Danbury, CT

2008-05-13

364

Micro-fluidic interconnect  

DOEpatents

An apparatus for simultaneously aligning and interconnecting microfluidic ports is presented. Such interconnections are required to utilize microfluidic devices fabricated in Micro-Electromechanical-Systems (MEMS) technologies, that have multiple fluidic access ports (e.g. 100 micron diameter) within a small footprint, (e.g. 3 mm.times.6 mm). Fanout of the small ports of a microfluidic device to a larger diameter (e.g. 500 microns) facilitates packaging and interconnection of the microfluidic device to printed wiring boards, electronics packages, fluidic manifolds etc.

Okandan, Murat (Albuquerque, NM); Galambos, Paul C. (Albuquerque, NM); Benavides, Gilbert L. (Los Ranchos, NM); Hetherington, Dale L. (Albuquerque, NM)

2006-02-28

365

FUEL CELL/MICRO-TURBINE COMBINED CYCLE  

SciTech Connect

A wide variety of conceptual design studies have been conducted that describe ultra-high efficiency fossil power plant cycles. The most promising of these ultra-high efficiency cycles incorporate high temperature fuel cells with a gas turbine. Combining fuel cells with a gas turbine increases overall cycle efficiency while reducing per kilowatt emissions. This study has demonstrated that the unique approach taken to combining a fuel cell and gas turbine has both technical and economic merit. The approach used in this study eliminates most of the gas turbine integration problems associated with hybrid fuel cell turbine systems. By using a micro-turbine, and a non-pressurized fuel cell the total system size (kW) and complexity has been reduced substantially from those presented in other studies, while maintaining over 70% efficiency. The reduced system size can be particularly attractive in the deregulated electrical generation/distribution environment where the market may not demand multi-megawatt central stations systems. The small size also opens up the niche markets to this high efficiency, low emission electrical generation option.

Larry J. Chaney; Mike R. Tharp; Tom W. Wolf; Tim A. Fuller; Joe J. Hartvigson

1999-12-01

366

Dynamic Characteristics of PEM-FC\\/Woody Biomass Engine Hybrid Micro Grid  

Microsoft Academic Search

The combustion exhaust heat of woody biomass engine using Stirling cycle is high temperature. This exhaust heat is used for the city gas reforming reaction of a proton exchange membrane fuel cell (PEM-FC) system. The woody biomass engine generator has the characteristic that the greenhouse gas amount of emission with power generation is greatly reducible. In this paper, the micro

Shin'ya Obara; Shunsuke Kito; Akira Hoshi; Seizi Sasaki

2007-01-01

367

Calorimetric gas sensor  

DOEpatents

A combustible gas sensor is described that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 {micro}m thick {times} 10{micro}m wide {times} 100, 250, 500, or 1000 {micro}m-long polycrystalline Si; some are overcoated with a 0.25 {micro}m-thick protective CVD Si{sub 3}N{sub 4} layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac){sub 2} onto microfilaments resistively heated to approximately 500 C; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300 C (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H{sub 2} concentrations between 100 ppm and 1% in an 80/20 N{sub 2}/O{sub 2} mixture. Other catalytic materials can also be used. 11 figs.

Ricco, A.J.; Hughes, R.C.; Smith, J.H.; Moreno, D.J.; Manginell, R.P.; Senturia, S.D.; Huber, R.J.

1998-11-10

368

Current State and Prospect of MicroMachining  

Microsoft Academic Search

Micro-machining is a delicate process that requires pinpoint accuracy. Researchers in academia and industry worldwide are striving to develop efficient fabrication techniques for features in ranges of a few micrometers and even nanometers. The current leading micro-machining processes are micro drilling, micro milling, and micro turning, micro EDM, micro USM, micro LBM, micro ECM and LIGA. In this paper, the

Xiaoxia Li; Jiuhe Wang; Wen Li

2007-01-01

369

Modeling Micro-Damage Healing Mechanism at Micro-Scale  

E-print Network

This thesis demonstrates the effect of micro-damage healing on stress and displacement fields in the vicinity of a crack tip in the material that tend to self-heal. The micro-damage healing model is modeled by incorporating time-dependent traction...

Arastoo, Mahsa

2013-08-06

370

Infrared micro-optics technologies  

NASA Astrophysics Data System (ADS)

Bodenseewerk GmbH generally works on challenging projects comprising Microsystems, e.g. micro-optics (micro-lenses, micro-mirrors). We utilize state-of-the-art laboratory equipment and simulation software (e.g. optical design with ZEMAX, ASAP and GLAD). Our recent activities on the development of several infrared micro-optical devices focus on high speed imaging of scenes with high angular resolution including the analysis of physical properties of the detected light (e.g. spectral content, polarization) utilizing staring IR sensors with focal-plane-arrays operating in a snap shot mode at high frame rates. We report about the development of so called micro-optical multiplexers which: (a) comprise micro-optical arrays and electro-mechanical micro-actuators, (b) image several fields of view with high resolution onto a single focal-plane-array, (c) image several fields of view with enhanced spatial resolution [by the factor of four compared to (b)] in a modified realization onto one focal-plane-array and (d) analyze the spectral content of an image using a single-band photon detector-array and multi-frame processing. The micro-opto-electro-mechanical multiplexer (MOEM) systems all consist of a primary objective, a MOEM image-steering respectively image coding device and a secondary objective. The primary objective images one or more suitable formed individual fields of view onto a common intermediate image plane. The MOEM devices comprise combinations of focusing and defocusing micro-lens-arrays, micro-shutter-arrays and micro-filter-arrays which are mounted parallel to each other near the intermediate image plane. The MOEM devices exhibit their above mentioned function modes by laterally displacing the micro-arrays with the help of modern micro-actuators. The secondary objective is utilized as relay optical stage. A modern common focal-plane-array is used as detector device. The micro-actuators responsible for the relative displacement of the micro-arrays are highly miniaturized while maintaining large displacement ranges and high linearity, reproducable positioning and reliability. This paper outlines the general sensor concept, explains the underlying principles and delineates the optical systems layout. Recent hardware realizations useful in military applications concerning image and laser beam steering are presented.

Krogmann, Dirk; Tholl, Hans D.

2004-08-01

371

A Micro-Ultrastable Oscillator (micro-US0) for Micro/Nano Sciencecraft  

NASA Technical Reports Server (NTRS)

Syntonics LLC developed a prototype micro-Ultra Stable Oscillator (micro-USO) under a Space Base Technology Grant (NAGS-10395). Syntonics conducted the micro-USO Program in two phases. In Phase I, we developed a set of verified analytical models (including thermal, electrical, and control models) for a baseline USO, conducted a series of six technology studies, and built three approx.9OOg prototype units. These prototypes provided a tool for evaluating competing design topologies. In Phase II we prepared the conceptual design of a approx.100-15Og micro-USO.

2003-01-01

372

A Reinnervating MicroRNA  

NSDL National Science Digital Library

Over the past 15 years, critical roles for microRNA have been established in regulating cell proliferation, differentiation and development, and death. Williams et al. define a role for a microRNA (miR-206) in reinnervating the neuromuscular junction after injury and improving survival in a mouse model of the neurodegenerative disease amyotrophic lateral sclerosis (ALS).

Robert Brown (University of Massachusetts Medical School; )

2009-12-11

373

Microsystems Micro and Nano Technologies  

E-print Network

· Adaptive and ophthalmic optics · Metrology 8 RESEARCH GROUPS 82 RESEARCHERS 133 PhD STUDENTS The Research · Micro-nanofluidics, nanobiosystems · Optical sources and functions for photonic integration, nanophotonics, MOEMS and micro-optics · Power-electronics components, electrical and photovoltaic energy

Ingrand, François

374

Micro-porous Paclitaxel-Loaded PLGA Foams -- a New Implant Material for Controlled Release of Chemotherapeutic Agents  

E-print Network

Supercritical gas foaming using CO? was used to fabricate blank poly DL lactide-co-glycolide (PLGA) micro-porous foams. Paclitaxel-loaded PLGA foams were also produced for the first time using a modification of the ...

Lee, Lai Yeng

375

Micro thrust and heat generator  

DOEpatents

A micro thrust and heat generator have a means for providing a combustion fuel source to an ignition chamber of the micro thrust and heat generator. The fuel is ignited by a ignition means within the micro thrust and heat generator`s ignition chamber where it burns and creates a pressure. A nozzle formed from the combustion chamber extends outward from the combustion chamber and tappers down to a narrow diameter and then opens into a wider diameter where the nozzle then terminates outside of said combustion chamber. The pressure created within the combustion chamber accelerates as it leaves the chamber through the nozzle resulting in pressure and heat escaping from the nozzle to the atmosphere outside the micro thrust and heat generator. The micro thrust and heat generator can be microfabricated from a variety of materials, e.g., of polysilicon, on one wafer using surface micromachining batch fabrication techniques or high aspect ratio micromachining techniques (LIGA). 30 figs.

Garcia, E.J.

1998-11-17

376

Chemical micro-sensor  

DOEpatents

An integrated optical capillary electrophoresis system for analyzing an analyte. A modulated optical pump beam impinges on an capillary containing the analyte/buffer solution which is separated by electrophoresis. The thermally-induced change in the index of refraction of light in said electrophoresis capillary is monitored using an integrated micro-interferometer. The interferometer includes a first interferometer arm intersecting the electrophoresis capillary proximate the excitation beam and a second, reference interferometer arm. Changes in index of refraction in the analyte measured by interrogating the interferometer state using white light interferometry and a phase-generated carrier demodulation technique. Background thermo-optical activity in the buffer solution is cancelled by splitting the pump beam and exciting pure buffer solution in a second section of capillary where it crosses the reference arm of the interferometer.

Ruggiero, Anthony J.

2005-05-03

377

Micro Environmental Concrete  

NASA Astrophysics Data System (ADS)

Reactive powder concretes (RPC) are characterized by a particle diameter not exceeding 600 ?m and having very high compressive and tensile strengths. This paper describes a new generation of micro concrete, which has an initial as well as a final high physicomechanical performance. To achieve this, 15% by weight of the Portland cement have been substituted by materials rich in Silica (Slag and Dune Sand). The results obtained from the tests carried out on the RPC show that compressive and tensile strengths increase when incorporating the addition, thus improving the compactness of mixtures through filler and pozzolanic effects. With a reduction in the aggregate phase in the RPC and the abundance of the dune sand (southern of Algeria) and slag (industrial by-product of the blast furnace), the use of the RPC will allow Algeria to fulfil economical as well as ecological requirements.

Lanez, M.; Oudjit, M. N.; Zenati, A.; Arroudj, K.; Bali, A.

378

Micro UV detector  

NASA Astrophysics Data System (ADS)

A lightweight, tactical biological agent detection network offers the potential for a detect-to-warn capability against biological aerosol attacks. Ideally, this capability can be achieved by deploying the sensors upwind from the protected assets. The further the distance upwind, the greater the warning time. The technological challenge to this concept is the biological detection technology. Here, cost, size and power are major factors in selecting acceptable technologies. This is in part due to the increased field densities needed to cover the upwind area and the fact that the sensors, when deployed forward, must operate autonomously for long periods of time with little or no long-term logistical support. The Defense Advanced Research Project Agency"s (DARPA) Solid-state Ultraviolet Optical Source (SUVOS) program offers an enabling technology to achieving a detector compatible with this mission. As an optical source, these devices emit excitation wavelengths known to be useful in the detection of biological aerosols. The wavelength band is absorbed by the biological aerosol and results in visible fluorescence. Detection of a biological aerosol is based on the observed intensity of this fluorescence signal compared to a background reference. Historically this has been accomplished with emission sources that are outside the boundaries for low cost, low power sensors. The SUVOS technology, on the other hand, provides the same basic wavelengths needed for the detection process in a small, low power package. ECBC has initiated an effort to develop a network array based on micro UV detectors that utilize the SUVOS technology. This paper presents an overview of the micro UV detector and some of the findings to date. This includes the overall design philosophy, fluid flow calculations to maximize presentation of aerosol particles to the sources, and the fluorescence measurements.

Cabalo, Jerry B.; Sickenberger, Richard; Underwood, William J.; Sickenberger, David W.

2004-09-01

379

Micro-UV detector  

NASA Astrophysics Data System (ADS)

A lightweight, tactical biological agent detection network offers the potential for a detect-to-warn capability against biological aerosol attacks. Ideally, this capability can be achieved by deploying the sensors upwind from the protected assets. The further the distance upwind, the greater the warning time. The technological challenge to this concept is the biological detection technology. Here, cost, size and power are major factors in selecting acceptable technologies. This is in part due to the increased field densities needed to cover the upwind area and the fact that the sensors, when deployed forward, must operate autonomously for long periods of time with little or no long-term logistical support. The Defense Advanced Research Project Agency"s (DARPA) Solid-state Ultraviolet Optical Source (SUVOS) program offers an enabling technology to achieving a detector compatible with this mission. As an optical source, these devices emit excitation wavelengths known to be useful in the detection of biological aerosols. The wavelength band is absorbed by the biological aerosol and results in visible fluorescence. Detection of a biological aerosol is based on the observed intensity of this fluorescence signal compared to a background reference. Historically this has been accomplished with emission sources that are outside the boundaries for low cost, low power sensors. The SUVOS technology, on the other hand, provides the same basic wavelengths needed for the detection process in a small, low power package. ECBC has initiated an effort to develop a network array based on micro UV detectors that utilize the SUVOS technology. This paper presents an overview of the micro UV detector and some of the findings to date. This includes the overall design philosophy, fluid flow calculations to maximize presentation of aerosol particles to the sources, and the fluorescence measurements.

Cabalo, Jerry B.; Sickenberger, Richard; Underwood, William J.; Sickenberger, David W.

2004-12-01

380

Simulations for gas flows in microgeometries using the direct simulation Monte Carlo method  

Microsoft Academic Search

Micro gas flows are often encountered in MEMS devices and classical CFD could not accurately predict the flow and thermal behavior due to the high Knudsen number. Therefore, the gas flow in microgeometries was investigated using the direct simulation Monte Carlo (DSMC) method. New treatments for boundary conditions are verified by simulations of micro-Poiseuille flow, compared with the previous boundary

Moran Wang; Zhixin Li

2004-01-01

381

A Microcantilever-based Gas Flow Sensor for Flow Rate and Direction Detection  

Microsoft Academic Search

The purpose of this paper is to apply characteristics of residual stress that causes cantilever beams to bend for manufacturing a micro-structured gas flow sensor. This study uses a silicon wafer deposited silicon nitride layers, reassembled the gas flow sensor with four cantilever beams that perpendicular to each other and manufactured piezoresistive structure on each micro-cantilever by MEMS technologies, respectively.

Yu-hsiang Wang; Tzu-Han Hsueh; Rong-Hua Ma; Chia-Yen Lee; Lung-Ming Fu; Po-cheng Chou; Chien-Hsiung Tsai

2008-01-01

382

Dual liquid and gas chromatograph system  

DOEpatents

A chromatographic system that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a non-transparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extremely low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

Gay, Don D. (Aiken, SC)

1985-01-01

383

Electrohydrodynamically augmented micro heat pipes  

NASA Astrophysics Data System (ADS)

For high power density dissipation, micro heat pipes and micro grooves have demonstrated much promise. Several experimental investigations were conducted to evaluate the potential benefits of electrohydrodynamic (EHD) forces on the operation of micro heat pipes. In these experiments, electric fields were used to orient and guide the flow of the dielectric liquid within the micro heat pipes from the condenser to the evaporator. The first series of experiments indicate that the heat transport capability of the EHD micro heat pipes is increased by up to 6 times of that of conventional ones. Simultaneously, a theoretical model was developed to predict the maximum heat transport capability for various electric field intensities and micro heat pipe geometries. The analytical model agrees well with the experimental results. The model shows that large pore sizes are optimal from a heat transport capacity perspective. Finally, a critical assessment of the experimental results suggest an alternative design capable of achieving as much as a 240 times improvement in the heat transport capacity in comparison to traditional micro heat pipes. Another means to augment the heat transport capacity of micro heat pipes is to employ an ion-drag pumping. An analytical model is developed to evaluate the maximum heat transport capacity as a function of the applied electric field. The predictions indicate that ion drag pumping can achieve a four times increase in heat transport capacity under the application of an electric field relative to what would exist in the absence of a field. A transient analytical model was developed to permit variation of the electric field with applied thermal load. A proportional-integral-derivative controller was used to simulate active temperature control. The feasibility of achieving active temperature control was demonstrated experimentally. Finally, a simpler EHD enhanced micro groove model was constructed and tested. A pair of electrodes was used as a liquid artery to convey the working liquid from the condenser to the evaporator. A six times increase of the heat transport capability was obtained.

Yu, Zhiquan

2001-12-01

384

Micro-environmental Modelling  

Microsoft Academic Search

\\u000a “Indoor air quality” is a wide subject with different social, economic, and health aspects. In developed countries, people\\u000a spend more than 80% of their time indoors where they are exposed to many kinds of air pollutants either from outdoor origin\\u000a or produced indoors. An air pollutant can be a gas or an aerosol particle (solid, liquid, radioactive, bio-aerosols, etc.).\\u000a Indoor

Tareq Hussein; Markku Kulmala

385

Nano-scale NiSi and n-type silicon based Schottky barrier diode as a near infra-red detector for room temperature operation  

NASA Astrophysics Data System (ADS)

The fabrication of nano-scale NiSi/n-Si Schottky barrier diode by rapid thermal annealing process is reported. The characterization of the nano-scale NiSi film was performed using Micro-Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The thickness of the film (27 nm) has been measured by cross-sectional Secondary Electron Microscopy and XPS based depth profile method. Current-voltage (I-V) characteristics show an excellent rectification ratio (ION/IOFF = 105) at a bias voltage of ±1 V. The diode ideality factor is 1.28. The barrier height was also determined independently based on I-V (0.62 eV) and high frequency capacitance-voltage technique (0.76 eV), and the correlation between them has explained. The diode photo-response was measured in the range of 1.35-2.5 ?m under different reverse bias conditions (0.0-1.0 V). The response is observed to increase with increasing reverse bias. From the photo-responsivity study, the zero bias barrier height was determined to be 0.54 eV.

Roy, S.; Midya, K.; Duttagupta, S. P.; Ramakrishnan, D.

2014-09-01

386

Multiplexed Specific Label-Free Detection of NCI-H358 Lung Cancer Cell Line Lysates with Silicon Based Photonic Crystal Microcavity Biosensors  

PubMed Central

We experimentally demonstrate label-free photonic crystal (PC) microcavity biosensors in silicon-on-insulator (SOI) to detect the epithelial-mesenchymal transition (EMT) transcription factor, ZEB1, in minute volumes of sample. Multiplexed specific detection of ZEB1 in lysates from NCI-H358 lung cancer cells down to an estimated concentration of 2 cells per micro-liter is demonstrated. L13 photonic crystal microcavities, coupled to W1 photonic crystal waveguides, are employed in which resonances show high Q in the bio-ambient phosphate buffered saline (PBS). When the sensor surface is derivatized with a specific antibody, the binding of the corresponding antigen from a complex whole-cell lysate generates a change in refractive index in the vicinity of the photonic crystal microcavity, leading to a change in the resonance wavelength of the resonance modes of the photonic crystal microcavity. The shift in the resonance wavelength reveals the presence of the antigen. The sensor cavity has a surface area of ~11 ?m2. Multiplexed sensors permit simultaneous detection of many binding interactions with specific immobilized antibodies from the same bio-sample at the same instant of time. Specificity was demonstrated using a sandwich assay which further amplifies the detection sensitivity at low concentrations. The device represents a proof-of-concept demonstration of label-free, high throughput, multiplexed detection of cancer cells with specificity and sensitivity on a silicon chip platform. PMID:23274197

Chakravarty, Swapnajit; Lai, Wei-Cheng; Zou, Yi; Drabkin, Harry A.; Gemmill, Robert M.; Simon, George R.; Chin, Steve H.; Chen, Ray T.

2012-01-01

387

Nano-scale NiSi and n-type silicon based Schottky barrier diode as a near infra-red detector for room temperature operation  

SciTech Connect

The fabrication of nano-scale NiSi/n-Si Schottky barrier diode by rapid thermal annealing process is reported. The characterization of the nano-scale NiSi film was performed using Micro-Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The thickness of the film (27?nm) has been measured by cross-sectional Secondary Electron Microscopy and XPS based depth profile method. Current–voltage (I–V) characteristics show an excellent rectification ratio (I{sub ON}/I{sub OFF}?=?10{sup 5}) at a bias voltage of ±1?V. The diode ideality factor is 1.28. The barrier height was also determined independently based on I–V (0.62?eV) and high frequency capacitance–voltage technique (0.76?eV), and the correlation between them has explained. The diode photo-response was measured in the range of 1.35–2.5??m under different reverse bias conditions (0.0–1.0?V). The response is observed to increase with increasing reverse bias. From the photo-responsivity study, the zero bias barrier height was determined to be 0.54?eV.

Roy, S. [Centre for Nanotechnology and Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Centre of Excellence in Nanoelectronics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Midya, K.; Duttagupta, S. P., E-mail: sdgupta@ee.iitb.ac.in [Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); Centre of Excellence in Nanoelectronics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Ramakrishnan, D. [Department of Earth Science, Indian Institute of Technology Bombay, Mumbai 400076 (India)

2014-09-28

388

Development of a catalytic silicon micro-combustor for hydrocarbon-fueled power MEMS  

Microsoft Academic Search

This paper reports the development of a high efficiency, hydrocarbon-fueled micro-combustion system for a microscale gas turbine engine for power generation and micro-propulsion applications. A three-wafer catalytic combustor was fabricated and tested. Efficiencies in excess of 40% were achieved for ethylene-air and propane-air combustion. A fabrication process for a six-wafer catalytic combustor was developed and this device was successfully constructed

C. M. Spadaccini; X. Zhangt; C. P. CadouS; N. Miki; I. A. Waitz

2002-01-01

389

Statistical characteristic and parameter characterization of 3D surface micro-topography on micro-EDM  

Microsoft Academic Search

The characteristic of three-dimensional (3D) surface micro-topography of micro-EDM plays an important role on the component function properties. In this paper, two types of 3D surface micro-topography, which machined by micro-electrical discharge machining forming (micro-EDMF) and micro-wire electrical discharge machining (micro-WEDM), have been measured by the atomic force microscope (AFM) instrument after the surface data have been reshaped and denoised

Haijuan Ding; Libin Guo; Hai Cui

2009-01-01

390

Micro-EDM Milling of Micro Platinum Hemisphere  

Microsoft Academic Search

Micro-EDM milling has become one of the powerful means of 3D micromachining for MEMS. However, for micro- EDM milling, there isn't a general electrode wear compensation strategy matched to arbitrary materials of workpiece and electrode. In this paper, the machinability of platinum metal is evaluated by taking latent heat of fusion and evaporation into account firstly. And then, a general

Guanrong Hang; Guohui Cao; Zaicheng Wang; Jing Tang; Zhenlong Wang; Wansheng Zhao

2006-01-01

391

Micro-sensors for space applications  

SciTech Connect

Important factors in the application of sensing technology to space applications are low mass, small size, and low power. All of these attributes are enabled by the application of MEMS and micro-fabrication technology to microsensors. Two types of sensors are utilized in space applications: remotes sensing from orbit around the earth or another planetary body, and point sensing in the spacecraft or external to it. Several Sandia projects that apply microfabrication technologies to the development of new sensing capabilities having the potential for space applications will be briefly described. The Micro-Navigator is a project to develop a MEMS-based device to measure acceleration and rotation in all three axes for local area navigation. The Polychromator project is a joint project with Honeywell and MIT to develop an electrically programmable diffraction grating that can be programmed to synthesize the spectra of molecules. This grating will be used as the reference cell in a gas correlation radiometer to enable remote chemical detection of most chemical species. Another area of research where microfabrication is having a large impact is the development of a lab on a chip. Sandia's efforts to develop the {mu}ChemLab{trademark} will be described including the development of microfabricated pre-concentrators, chromatographic columns, and detectors. Smart sensors that allow the spacecraft independent decision making capabilities depend on pattern recognition. Sandia's development of a new pattern recognition methodology that can be used to interpret sensor response as well as for target recognition applications will be described.

Butler, M.A.; Frye-Mason, G.C.; Osbourn, G.C.

1999-12-08

392

MICRO SCALE PURIFICATION SYSTEMS FOR BIOLOGICAL SAMPLE PREPARATION  

E-print Network

include the micro electrophysiological characterization system; the micro thermal field flow fractionation system; and the micro electrical field flow fractionation system. The micro cellular electrophysiological leukocytes). The micro thermal field flow fractionation system is a chromatographic separation technique

393

Patterned graphene functionalization via mask-free scanning of micro-plasma jet under ambient condition  

SciTech Connect

In this work, a mask-free method is introduced for patterned nitrogen doping of graphene using a micro-plasma jet under ambient condition. Raman and X-ray photoelectron spectroscopy spectra indicate that nitrogen atoms are incorporated into the graphene lattice with the two-dimensional spatial distribution precisely controlled in the range of mm down to 10??m. Since the chemistry of the micro-plasma jet can be controlled by the choice of the gas mixture, this direct writing process with micro-plasma jet can be a versatile approach for patterned functionalization of graphene with high spatial resolution. This could have promising applications in graphene-based electronics.

Ye, Dong; Yu, Yao, E-mail: ensiyu@mail.hust.edu.cn; Liu, Lin [School of Materials Science and Engineering, Huazhong University of Science and Technology, 430074 Wuhan (China)] [School of Materials Science and Engineering, Huazhong University of Science and Technology, 430074 Wuhan (China); Wu, Shu-Qun; Lu, Xin-Pei [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China)] [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); Wu, Yue [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3255 (United States)] [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3255 (United States)

2014-03-10

394

Perfectly monodisperse micro-bubble production by novel mechanical means. Scaling laws.  

NASA Astrophysics Data System (ADS)

A continuous stream of controllable, perfectly homogeneous size micro-bubbles (of the order of some microns and larger) can be produced by a novel, extremely simple mechanical means that we call "Flow Focusing" (e.g. see Ganan-Calvo 1998, Phys. Rev. Lett. vol. 80, 285). Using this technique, a capillary gas micro-jet is formed ("focused") by a co-flowing stream of liquid forced through a sub-millimetric orifice. This gas micro-jet undergoes a rapid capillary breakup (e.g. Chandrasekhar 1961 "Hydrodynamic and Hydromagnetic Stability", p. 541) with a strong frequency "self-locking" effect. In this work we present a theoretical model which predicts the micro-bubble size as a function of the physical and geometrical parameters of the system. A complete experimental study is also provided, and the raw data are collapsed into a universal scaling law given by our theoretical model. This novel micro-fluidics phenomenon may have a wide variety of applications ranging from bio-medicine, pharmaceutical specialities, food industry, and even for the mesoscale micro-templating of micro-engineered materials (i.e. photonic crystals, smart materials, etc.).

Ganan-Calvo, Alfonso M.; Gordillo, Jose M.; Ouarti, Nawel; Prevost, Thomas; Sampedro, Jose L.

2000-11-01

395

Gas gangrene  

MedlinePLUS

Tissue infection - Clostridial; Gangrene - gas; Myonecrosis; Clostridial infection of tissues ... Gas gangrene is most often caused by a bacterium called Clostridium perfringens. It also can be caused ...

396

Micro Injection Moulding of Polymeric Components  

Microsoft Academic Search

Micro components and micro devices are strongly used in several fields: IT components, biomedical and medical products, automotive industry, telecommunication area and aerospace. A micro component is characterized by small dimensions of the product itself or small dimensions of the functional features. The development of new micro parts is highly dependent on manufacturing systems that can reliably and economically produce

G. Trotta; R. Surace; F. Modica; R. Spina; I. Fassi

2011-01-01

397

Micro Linear Pump with Electromagnetic Actuator  

Microsoft Academic Search

In recent years, research and development of the micro-fluid systems have been activated in the field of chemical technology and biotechnology. Micro-fluid systems are realized by micromachine technology and MEMS technology. Micro pump is an essential element for miniaturization of chemical analysis reaction systems. The aim of this research is development of a micro linear pump which will be built

Koichi Suzumori; Hiroaki Furusawa; Takefumi Kanda; Yoshiaki Yamada; Takashi Nagata

2005-01-01

398

Development of Micro UAV Swarms  

Microsoft Academic Search

\\u000a Some complex application scenarios for micro UAVs (Unmanned Aerial Vehicles) call for the formation of swarms of multiple\\u000a drones. In this paper a platform for the creation of such swarms is presented. It consists of modified commercial quadrocopters\\u000a and a self-made ground control station software architecture. Autonomy of individual drones is generated through a micro controller\\u000a equipped video camera. Currently

Axel Bürkle; Sandro Leuchter

2009-01-01

399

Unconventional Shale-Gas Resource Systems and Processes Affecting Gas Generation, Retention, Storage, and Flow Rates  

NASA Astrophysics Data System (ADS)

Geochemical and petrophysical characterization of various shale-gas systems in the U.S. indicates a variety of unconventional shale-gas system types. The most basic distinction is gas type: biogenic and thermogenic, although there can also be mixtures of the two gas types. Thermogenic shale-gas systems are further segregated into various sub-types depending on geochemistry and geology. The shale-gas system categories are: (1) high thermal maturity shale; (2) low thermal maturity shales; (3) mixed lithology intra-formational systems containing shale, sands, and silts; (4) inter-formational systems where gas is generated in a mature shale and stored in a less mature shale, and (5) mixed systems. A key difference among these shale-gas systems are initial gas flow rates. High thermal maturity systems tend to have much higher gas flow rates than low maturity systems because of gas charge and storage mechanisms. Certainly other non-geochemical factors, such as shale mineralogy, are extremely important in being able to stimulate these shales to flow gas. Geochemical comparison of the Antrim Shale (Michigan Basin), New Albany Shale (Illinois Basin), and Barnett Shale (Fort Worth Basin) are used to illustrate these different systems as well as other systems. These systems show significant differences in gas type, organic richness, thermal maturity, and gas flow rates. Gas flow rates are then dependent upon the amount of gas stored (or generated) and the ability to release gas from adsorption sites as well as connecting to micro-reservoir compartments.

Jarvie, D. M.; Philp, R. P.; Jarvie, B. M.

2009-04-01

400

The Carbon Nanotube Based Micro Bubble Generator in Micro Channel with Dynamic Fluid  

Microsoft Academic Search

Based on the previous study of micro bubble generation using carbon nanotube heating elements with uW power input in static droplet of water, the dynamic characteristic of micro bubble generated by CNTs heater draw us much attention. In this summary, the micro bubble transportation, diameter control in micro channel and the departure of micro bubble from CNTs heater by pulse

Peng Xiao; Wai Kit Chan; Ho Shing Poon; Yu Zhang; Wen J. Li; R. Du

2008-01-01

401

Micro manipulation based on micro physics-strategy based on attractive force reduction and stress measurement  

Microsoft Academic Search

Micro manipulation is required for assembling and maintenance works of micro machines and their parts. This paper proposes a handling strategy for micro objects based on micro physics. Attractive forces are modeled and their reduction methods are presented. The authors show experimental results of reducing these forces. Based on the proposed reduction methods, the authors present a new micro manipulation

F. Arai; D. Ando; T. Fukuda; Y. Nonoda; T. Oota

1995-01-01

402

Hard and Soft Micro- and Nanofabrication: An Integrated Approach to Hydrogel Based Biosensing and Drug Delivery  

PubMed Central

We review efforts to produce microfabricated glucose sensors and closed loop insulin delivery systems. These devices function due to the swelling and shrinking of glucose-sensitive microgels that are incorporated into silicon-based microdevices. The glucose response of the hydrogel is due to incorporated phenylboronic acid (PBA) side chains. It is shown that in the presence of glucose, these polymers alter their swelling properties, either by ionization or by formation of glucose-mediated reversible crosslinks. Swelling pressures impinge on microdevice structures, leading either to a change in resonant frequency of a microcircuit, or valving action. Potential areas for future development and improvement are described. Finally, an asymmetric nano-microporous membrane, which may be integrated with the glucose sensitive devices, is described. This membrane, formed using photolithography and block polymer assembly techniques, can be functionalized to enhance its biocompatibility and solute size selectivity. The work described here features the interplay of design considerations at the supramolecular, nano, and micro scales. PMID:20036310

Siegel, Ronald A.; Gu, Yuandong; Lei, Ming; Baldi, Antonio; Nuxoll, Eric E.; Ziaie, Babak

2010-01-01

403

A silicon integrated micro nano-positioning XY-stage for nano-manipulation  

NASA Astrophysics Data System (ADS)

An integrated micro XY-stage with a 2 × 2 mm2 movable table is designed and fabricated for application in nanometer-scale operation and nanometric positioning precision. The device integrates the functions of both actuating and sensing in a monolithic chip and is mainly composed of a silicon-based XY-stage, comb-drive actuator and a displacement sensor, which are developed by using double-sided bulk-micromachining technology. The high-aspect-ratio comb-driven XY-stage is achieved by deep reactive ion etching (DRIE) on both sides of the wafer. The displacement sensor is formed on four vertical sidewall surface piezoresistors with a full Wheatstone bridge circuit, where a novel fabrication process of a vertical sidewall surface piezoresistor is proposed. Comprehensive design and analysis of the comb actuator, the piezoresistive displacement sensor and the XY-stage are given in full detail, and the experimental results verify the design and fabrication of the device. The final realization of the device shows that the sensitivity of the fabricated piezoresistive sensors is better than 1.17 mV µm-1 without amplification, and the linearity is better than 0.814%. Under 28.5 V driving voltage, a ±10 µm single-axis displacement is measured without crosstalk and the resonant frequency is measured at 983 Hz in air.

Sun, Lining; Wang, Jiachou; Rong, Weibin; Li, Xinxin; Bao, Haifei

2008-12-01

404

A secure WDM ring access network employing silicon micro-ring based remote node  

NASA Astrophysics Data System (ADS)

A secure and scalable wavelength-division-multiplexing (WDM) ring-based access network is proposed and demonstrated using proof-of-concept experiments. In the remote node (RN), wavelength hopping for specific optical networking unit (ONU) is deployed by using silicon micro-ring resonators (SMR). Using silicon-based devices could be cost-effective for the cost-sensitive access network. Hence the optical physical layer security is introduced. The issues of denial of service (DOS) attacks, eavesdropping and masquerading can be made more difficult in the proposed WDM ring-based access network. Besides, the SMRs with different dropped wavelengths can be cascaded, such that the signals pass through the preceding SMRs can be dropped by a succeeding SMR. This can increase the scalability of the RN for supporting more ONUs for future upgrade. Here, error-free 10 Gb/s downlink and 1.25 Gb/s uplink transmission are demonstrated to show the feasibility of the proposed network.

Sung, Jiun-Yu; Chow, Chi-Wai; Yeh, Chien-Hung; Xu, Ke; Hsu, Chin-Wei; Su, Hong-Quan; Tsang, Hon-Ki

2014-08-01

405

Micro electret power generators  

NASA Astrophysics Data System (ADS)

The taming of electricity and its widespread use allows people to see in the dark, to speak to one another instantaneously across the earth, and it allows retrieval of data from instruments sent out of the solar system. It is right to expect that the uses and demand for electricity will continue to grow, and to extend the ability to generate electricity; here two new micromachined devices for converting mechanical energy into electrical energy are presented. Aided by the wealth of micromachining process technology, generators that use an oscillatory motion to modify the physical structure of a capacitor with a built-in electric field provided by a permanent electret have been designed, built, and tested. The electret creates an electric field inside the capacitor structure, which induces mirror charge at some potential. The modification of the capacitor then generates an alternating displacement current through an external circuit, which provides useful electrical power. The electret microphone is a similar well known device for converting pressure waves into electrical signals by varying the distance between two charged capacitive plates. This work explores and proves feasible the ability to use mechanical forces to change the overlapping area of a charged capacitor structure and using mechanical forces to move a liquid into the gap of a charged capacitor structure, changing its permittivity to produce electricity. This work demonstrates 2.5mW of power from a 2cm diameter rotary generator at 12kRPM and 10[micro]w for a 0.1cm3 linear shaking generator at 60Hz.

Boland, Justin

406

Micro-spherical probes machining by EDM  

Microsoft Academic Search

This paper describes a new hybrid micro-machining method, which combines wire electro discharge grinding technology with one pulse electro discharge, to fabricate micro-spherical probes and micro-spherical cavities. The results show that a burnished micro-spherical probe with about 40 µm diameter could be formed instantaneously with the hybrid machining process, which is not available in the conventional micro-machining method. The deviation

Dong-Yea Sheu

2005-01-01

407

Silicon Carbide-Based Hydrogen and Hydrocarbon Gas Detection  

NASA Technical Reports Server (NTRS)

Hydrogen and hydrocarbon detection in aeronautical applications is important for reasons of safety and emissions control. The use of silicon carbide as a semiconductor in a metal-semiconductor or metal-insulator-semiconductor structure opens opportunities to measure hydrogen and hydrocarbons in high temperature environments beyond the capabilities of silicon-based devices. The purpose of this paper is to explore the response and stability of Pd-SiC Schottky diodes as gas sensors in the temperature range from 100 to 400 C. The effect of heat treating on the diode properties as measured at 100 C is explored. Subsequent operation at 400 C demonstrates the diodes' sensitivity to hydrogen and hydrocarbons. It is concluded that the Pd-SiC Schottky diode has potential as a hydrogen and hydrocarbon sensor over a wide range of temperatures but further studies are necessary to determine the diodes' long term stability.

Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, D.; Liu, C. C.; Wu, Q. H.R

1995-01-01

408

Ultra-high mobility two-dimensional electron gas in a SiGe/Si/SiGe quantum well  

NASA Astrophysics Data System (ADS)

We report the observation of an electron gas in a SiGe/Si/SiGe quantum well with maximum mobility up to 240 m2/Vs, which is noticeably higher than previously reported results in silicon-based structures. Using SiO, rather than Al2O3, as an insulator, we obtain strongly reduced threshold voltages close to zero. In addition to the predominantly small-angle scattering well known in the high-mobility heterostructures, the observed linear temperature dependence of the conductivity reveals the presence of a short-range random potential.

Melnikov, M. Yu.; Shashkin, A. A.; Dolgopolov, V. T.; Huang, S.-H.; Liu, C. W.; Kravchenko, S. V.

2015-03-01

409

In vitro and transdermal penetration of PHBV micro/nanoparticles.  

PubMed

The purpose of this study was to develop micro and nano sized drug carriers from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and study the cell and skin penetration of these particles. PHBV micro/nanospheres were prepared by o/w emulsion method and were stained with a fluorescent dye, Nile Red. The particles were fractionated by centrifugation to produce different sized populations. Topography was studied by SEM and average particle size and its distribution were determined with particle sizer. Cell viability assay (MTT) was carried out using L929 fibroblastic cell line, and particle penetration into the cells were studied. Transdermal permeation of PHBV micro/nanospheres and tissue reaction were studied using a BALB/c mouse model. Skin response was evaluated histologically and amount of PHBV in skin was determined by gas chromatography-mass spectrometry. The average diameters of the PHBV micro/nanosphere batches were found to be 1.9 ?m, 426 and 166 nm. Polydispersity indices showed that the size distribution of micro sized particles was broader than the smaller ones. In vitro studies showed that the cells had a normal growth trend. MTT showed no signs of particle toxicity. The 426 and 166 nm sized PHBV spheres were seen to penetrate the cell membrane. The histological sections revealed no adverse effects. In view of this data nano and micro sized PHBV particles appeared to have potential to serve as topical and transdermal drug delivery carriers for use on aged or damaged skin or in cases of skin diseases such as psoriasis, and may even be used in gene transfer to cells. PMID:24510225

Eke, G; Kuzmina, A M; Goreva, A V; Shishatskaya, E I; Hasirci, N; Hasirci, V

2014-06-01

410

Natural gas  

NSDL National Science Digital Library

Natural gas is used as a means of power in households. Natural gas has no natural odor, so an odor is added to the gas. This is useful because gas leaks can be detected better and it also reduces the risk of accidents in homes.

N/A N/A (None; )

2003-07-27

411

Predicting the pressure driven flow of gases through micro-capillaries and micro-orifices  

SciTech Connect

A large body of experimentally measured gas flow rates were obtained from the literature and then compared to the predictions obtained with constitutive flow equations. This was done to determine whether the equations apply to the predictions of gas flow rates from leaking containment vessels used to transport radioactive materials. The experiments consisted of measuring the volumetric pressure-driven flow of gases through micro-capillaries and micro-orifices. The experimental results were compared to the predictions obtained with the equations given in ANSI N14.5 the American National Standard for Radioactive Materials-Leakage Tests on Package for Shipment. The equations were applied to both (1) the data set according to the recommendations given in ANSI N14.5 and (2) globally to the complete data set. It was found that: The continuum and molecular flow equation provided good agreement between the experimental and calculated flow rates for flow rates less than about 1 atm{center_dot}cm{sup 3}/s. The choked flow equation resulted in over-prediction of the flow rates for flow rates less than about 1 atm-cm{sup 3}/s. For flow rates higher than 1 atm{center_dot}cm{sup 3}/s, the molecular and continuum flow equation over-predicted the measured flow rates and the predictions obtained with the choked flow equation agreed well with the experimental values. Since the flow rates of interest for packages used to transport radioactive materials are almost always less than 1 atm{center_dot}cm{sup 3}/s, it is suggested that the continuum and molecular flow equation be used for gas flow rate predictions related to these applications.

Anderson, B.L.; Carlson, R.W.; Fischer, L.E. [Lawrence Livermore National Lab., CA (United States)

1994-11-01

412

Using a helical micro-tool in micro-EDM combined with ultrasonic vibration for micro-hole machining  

NASA Astrophysics Data System (ADS)

This paper presents a novel process using micro-electro-discharge- machining (micro-EDM) combined with ultrasonic vibration by a helical micro-tool electrode to drill and finish micro-holes. During the machining processes, a micro-tool is directly fabricated by wire electro-discharge grinding (WEDG) using micro-EDM combined with various methods for machining the micro-hole and by ultrasonic vibration to finish the hole wall. In this work, circular micro-holes are machined in a high nickel alloy by cylindrical and helical electrodes. Using a helical micro-tool electrode for micro-EDM combined with ultrasonic vibration (HE-MEDM-UV) can substantially reduce the EDM gap, taper and machining time for deep micro-hole drilling. In addition, using a helical micro-tool with micro ultrasonic vibration finishing (HE-MUVF), good surface quality and less taper of the hole wall can be obtained by applying a suitable electrode step variation, rotational speed and ultrasonic amplitude with a machining time of approximately 25 min. According to scanning electron microscopy (SEM) micrographs and atomic force microscopy (AFM) measurement, HE-MUVF can indeed improve the surface roughness from 1.345 µm Rmax before finishing to 0.58 µm Rmax after HE-MUVF. This result demonstrates that using HE-MEDM-UV combined with MUVF can yield micro-holes of precise shape and smooth surface.

Hung, Jung-Chou; Lin, Jui-Kuan; Yan, Biing-Hwa; Liu, Hung-Sung; Ho, Ping-Hsing

2006-12-01

413

Compact solid source of hydrogen gas  

DOEpatents

A compact solid source of hydrogen gas, where the gas is generated by contacting water with micro-disperse particles of sodium borohydride in the presence of a catalyst, such as cobalt or ruthenium. The micro-disperse particles can have a substantially uniform diameter of 1-10 microns, and preferably about 3-5 microns. Ruthenium or cobalt catalytic nanoparticles can be incorporated in the micro-disperse particles of sodium borohydride, which allows a rapid and complete reaction to occur without the problems associated with caking and scaling of the surface by the reactant product sodium metaborate. A closed loop water management system can be used to recycle wastewater from a PEM fuel cell to supply water for reacting with the micro-disperse particles of sodium borohydride in a compact hydrogen gas generator. Capillary forces can wick water from a water reservoir into a packed bed of micro-disperse fuel particles, eliminating the need for using an active pump.

Kravitz, Stanley H.; Hecht, Andrew M.; Sylwester, Alan P.; Bell, Nelson S.

2004-06-08

414

Elemental analyses of hypervelocity micro-particle impact sites on interplanetary dust experiment sensor surfaces  

NASA Technical Reports Server (NTRS)

The Interplanetary Dust Experiment (IDE) had over 450 electrically active ultra-high purity metal-oxide-silicon impact detectors located on the six primary sides of the Long Duration Exposure Facility (LDEF). Hypervelocity micro-particles that struck the active sensors with enough energy to breakdown the 0.4 to 1.0 micron thick SiO2 insulator layer separating the silicon base (the negative electrode), and the 1000 A thick surface layer of aluminum (the positive electrode) caused electrical discharges that were recorded for the first year of orbit. These discharge features, which include 50 micron diameter areas where the aluminum top layer has been vaporized, facilitate the location of the impacts. The high purity Al-SiO2-Si substrates allow detection of trace (ppm) amounts of hypervelocity impactor residues. After sputtering through a layer of surface contamination, secondary ion mass spectrometry (SIMS) is used to create two-dimensional elemental ion intensity maps of micro-particle impact sites on the IDE sensors. The element intensities in the central craters of the impacts are corrected for relative ion yields and instrumental conditions and then normalized to silicon. The results are used to classify the particles' origins as 'manmade', 'natural' or 'indeterminate'. The last classification results from the presence of too little impactor residue (a frequent occurrence on leading edge impacts), analytical interference from high background contamination, the lack of information on silicon residue, the limited usefulness of data on aluminum in the central craters, or a combination of these circumstances. Several analytical 'blank' discharges were induced on flight sensors by pressing down on the sensor surface with a pure silicon shard. Analyses of these blank discharges showed that the discharge energy blasts away the layer of surface contamination. Only Si and Al were detected inside the discharge zones, including the central craters, of these features. A total of 35 impacts on leading edge sensors and 22 impacts on trailing edge sensors were analyzed.

Simon, Charles G.; Hunter, J. L.; Griffis, D. P.; Misra, V.; Ricks, D. R.; Wortman, Jim J.

1992-01-01

415

Micro-Resistojet for Small Satellites  

NASA Technical Reports Server (NTRS)

An efficient micro-resistojet has been developed with thrust in the millinewton level, with a specific impulse of approximately 250 seconds and power input of 20 watts or less that is useful for applications of up to 1,000 hours of operation or more. The essential feature of this invention is a gas-carrying tube surrounding a central heating element. The propellant is flashed into vapor and then passes through a narrow annulus between the tube and the heater where it is cracked (in the case of methanol, into CO and H2) before being discharged through a de Laval nozzle to produce thrust. A multi-layer radiation shield around the gas tube minimizes heat loss. Also, if methanol is used as the propellant, the simultaneous heating and cracking does not need an additional device. This unit would be especially useful for small satellites, with mass up to 100 kg, and for delta v up to 500 m/sec, and is suited for use with green methanol as the propellant where a specific impulse of 220 seconds is expected. Noble metal alloys are the optimal materials of construction. While the microresistojet is especially suited to methanol, many other propellants may be used such as water or, in the case of de-orbiting, many other residual liquids onboard the vehicle.

Brogan, Thomas; Robin, Mike; Delichatsios, Mary; Duggan, John; Hohman, Kurt; Hruby,Vlad

2008-01-01

416

High-resolution structure determination by continuous rotation data collection in MicroED  

PubMed Central

MicroED uses very small three-dimensional protein crystals and electron diffraction for structure determination. An improved data collection protocol for MicroED called “continuous rotation” is presented. Here microcrystals are continuously rotated during data collection yielding improved data, and allowing data processing with MOSFLM resulting in improved resolution for the model protein lysozyme. These improvements pave the way for the implementation and application of MicroED with wide applicability in structural biology. PMID:25086503

Leslie, Andrew G. W.; Gonen, Tamir

2014-01-01

417

Mechano-micro/nano systems  

NASA Astrophysics Data System (ADS)

In recent years, the researches about Micro/Nano Systems are down actively in the bio-medical research fields, DNA research fields, chemical analysis systems fields, etc. In the results, a new materials and new functions in the systems are developed. In this invited paper, Mechano-Micro/Nano Systems, especially, motion systems are introduced. First, the research activities concerning the Mechano-Micro/Nano Systems in the world(MST2003, MEMS2003 and MEMS2004) and in Japan(Researech Projects on Nanotechnology and Materials in Ministry of Education, Culture, Sports, Science and Technology) are shown. Secondary, my research activities are introduced. As my research activities, (1) a comb-drive static actuator for the motion convert mechanisms, (2) a micro-nano fabrication method by use of FAB(Fast Atom Beam) machines, (3) a micro optical mirror manipulator for inputs-outputs optical switches, (4) a miniature pantograph mechanism with large-deflective hinges and links made of plastics are discussed and their performances are explained.

Horie, Mikio

2004-10-01

418

The multiphase flow system used in exploiting depleted reservoirs: water-based Micro-bubble drilling fluid  

Microsoft Academic Search

Water-based micro-bubble drilling fluid, which is used to exploit depleted reservoirs, is a complicated multiphase flow system that is composed of gas, water, oil, polymer, surfactants and solids. The gas phase is separate from bulk water by two layers and three membranes. They are \\

Zheng Li-hui; He Xiao-qing; Fu Li-xia; Wang Xiang-chun

2009-01-01

419

Pharmaceutical micro-particles give amorphous sucrose higher physical stability.  

PubMed

The aim of this study was to explore how pharmaceutical micro-sized filler particles affect the amorphous stability of sucrose in sucrose/filler particle composites produced by freeze-drying. Focus was put on the filler particles' properties crystallinity, hygroscopicity, hydrophobicity, and surface area, and their influence on physical stability of the amorphous phase. The micro-sized filler particles were examined with Blaine permeametry, gas adsorption, pycnometry, gravimetric vapour sorption, X-ray diffraction, and light microscopy before composites of sucrose and micro-sized filler particles were prepared by freeze-drying. The stability of the composites was examined with X-ray diffraction, differential scanning calorimetry (DSC), and microcalorimetry. All composites were amorphous and showed higher stability compared to pure amorphous sucrose, which was evident from a delay in heat and moisture-induced crystallization. However, calcium carbonate and oxazepam micro-sized filler particles lost their ability to stabilize the amorphous sucrose when exposed to humidity. The dry glass transition temperature (T(g)) was higher for the composites, indicating the stabilization was mediated by a reduced molecular mobility of the amorphous phase. PMID:21356288

Hellrup, Joel; Mahlin, Denny

2011-05-16

420

Experimental study of micro electrical discharge machining discharges  

NASA Astrophysics Data System (ADS)

Micro electrical discharge machining (?EDM) is an atmospheric-pressure plasma-assisted technology that uses point-to-plane discharges in liquid dielectrics to remove microscopic quantities of electrically conductive materials. In this work, an innovative ?EDM prototype machine was specifically designed and fabricated to produce and control single spark discharges, thus, resolving the typical limitations of (multi-discharge) commercial machines. The work analyses the type of discharge and the micro-plasma electron-density values obtained for 0.5-38 ?m gap sizes, 3-10 000 ?s pulse durations, 75-250 V low breakdown voltages, and 1-20 A discharge currents, using different combinations of metallic electrodes in oil and in water. Results allow fitting, for micro-scale and low voltages, an empirical law between the maximum gap-size for breakdown, the breakdown voltage, and the effective stress-time. The electron density ne is obtained by optical emission spectroscopy diagnostics of the H?-line Stark broadening (yielding ne˜1016-1017 cm-3, i.e., ionization degrees of ˜2×10-5-10-4) and by a semi-empirical resistive plasma model. The model uses the experimental values of several electrical and geometrical quantities, and of the gas pressure estimated as ˜60 bar-2 kbar from measurements of the plasma mechanical action, obtained using a force sensor. The quantitative information of this phenomenological study can assist the optimization of this micro-fabrication technique.

Bragança, I. M. F.; Rosa, P. A. R.; Dias, F. M.; Martins, P. A. F.; Alves, L. L.

2013-06-01

421

Micro flame-based detector suite for universal gas sensing.  

SciTech Connect

A microflame-based detector suit has been developed for sensing of a broad range of chemical analytes. This detector combines calorimetry, flame ionization detection (FID), nitrogen-phosphorous detection (NPD) and flame photometric detection (FPD) modes into one convenient platform based on a microcombustor. The microcombustor consists in a micromachined microhotplate with a catalyst or low-work function material added to its surface. For the NPD mode a low work function material selectively ionizes chemical analytes; for all other modes a supported catalyst such as platinum/alumina is used. The microcombustor design permits rapid, efficient heating of the deposited film at low power. To perform calorimetric detection of analytes, the change in power required to maintain the resistive microhotplate heater at a constant temperature is measured. For FID and NPD modes, electrodes are placed around the microcombustor flame zone and an electrometer circuit measures the production of ions. For FPD, the flame zone is optically interrogated to search for light emission indicative of deexcitation of flame-produced analyte compounds. The calorimetric and FID modes respond generally to all hydrocarbons, while sulfur compounds only alarm in the calorimetric mode, providing speciation. The NPD mode provides 10,000:1 selectivity of nitrogen and phosphorous compounds over hydrocarbons. The FPD can distinguish between sulfur and phosphorous compounds. Importantly all detection modes can be established on one convenient microcombustor platform, in fact the calorimetric, FID and FPD modes can be achieved simultaneously on only one microcombustor. Therefore, it is possible to make a very universal chemical detector array with as little as two microcombustor elements. A demonstration of the performance of the microcombustor in each of the detection modes is provided herein.

Hamilton, Thomas Warren; Washburn, Cody M.; Moorman, Matthew Wallace; Manley, Robert George; Lewis, Patrick Raymond; Miller, James Edward; Clem, Paul Gilbert; Shelmidine, Gregory J.; Manginell, Ronald Paul; Okandan, Murat

2005-11-01

422

The growth and harvesting of algae in a micro-gravity environment  

NASA Technical Reports Server (NTRS)

Algae growth in a micro-gravity environment is an important factor in supporting man's permanent presence in space. Algae can be used to produce food, oxygen, and pure water in a manned space station. A space station is one example of a situation where a Controlled Ecological Life Support System (CELSS) is imperative. In setting up a CELSS with an engineering approach at the Aerospace department of the University of Colorado, questions concerning algae growth in micro-g have arisen. The Get Away Special (GAS) Fluids Management project is a means through which many questions about the effects of a micro-g environment on the adequacy of growth rates, the viability of micro-organisms, and separation of gases and solids for harvesting purposes can be answered. In order to be compatible with the GAS tests, the algae must satisfy the following criteria: (1) rapid growth rates, (2) sustain viability over long periods of non-growth storage, and (3) very brief latency from storage to rapid growth. Testing indicates that the overall growth characteristics of Anacystis Nidulans satisfy the specifications of GAS's design constraints. In addition, data acquisition and the method of growth instigation are two specific problems being examined, as they will be encountered in interfacing with the GAS project. Flight testing will be two-fold, measurement of algae growth in micro-g and separation of algae from growth medium in an artificial gravitation field. Post flight results will provide information on algae viability in a micro-g environment as reflected by algal growth rates in space. Other post flight results will provide a basis for evaluating techniques for harvesting algae. The results from the GAS project will greatly assist the continuing effort of developing the CELSS and its applications for space.

Wiltberger, Nancy L.

1987-01-01

423

Development of Micro UAV Swarms  

NASA Astrophysics Data System (ADS)

Some complex application scenarios for micro UAVs (Unmanned Aerial Vehicles) call for the formation of swarms of multiple drones. In this paper a platform for the creation of such swarms is presented. It consists of modified commercial quadrocopters and a self-made ground control station software architecture. Autonomy of individual drones is generated through a micro controller equipped video camera. Currently it is possible to fly basic maneuvers autonomously, such as take-off, fly to position, and landing. In the future the camera's image processing capabilities will be used to generate additional control information. Different co-operation strategies for teams of UAVs are currently evaluated with an agent based simulation tool. Finally complex application scenarios for multiple micro UAVs are presented.

Bürkle, Axel; Leuchter, Sandro

424

Zeolite-dye micro lasers  

E-print Network

We present a new class of micro lasers based on nanoporous molecular sieve host-guest systems. Organic dye guest molecules of 1-Ethyl-4-(4-(p-Dimethylaminophenyl)-1,3-butadienyl)-pyridinium Perchlorat were inserted into the 0.73-nm-wide channel pores of a zeolite AlPO$_4$-5 host. The zeolitic micro crystal compounds where hydrothermally synthesized according to a particular host-guest chemical process. The dye molecules are found not only to be aligned along the host channel axis, but to be oriented as well. Single mode laser emission at 687 nm was obtained from a whispering gallery mode oscillating in a 8-$\\mu$m-diameter monolithic micro resonator, in which the field is confined by total internal reflection at the natural hexagonal boundaries inside the zeolitic microcrystals.

Vietze, U; Laeri, F; Ihlein, G; Schüth, F; Limburg, B; Abraham, M

1998-01-01

425

Job Title BIOLOGY GENETICS MICRO TOX TOTAL BIOLOGY GENETICS MICRO TOX TOTAL BIOLOGY GENETICS MICRO TOX TOTAL T/TT Faculty  

E-print Network

Job Title BIOLOGY GENETICS MICRO TOX TOTAL BIOLOGY GENETICS MICRO TOX TOTAL BIOLOGY GENETICS MICRO.00 Job Title NTT Faculty BIOLOGY GENETICS MICRO TOX TOTAL BIOLOGY GENETICS MICRO TOX TOTAL BIOLOGY GENETICS MICRO TOX TOTAL Lecturer 3.76 2.00 5.76 3.76 2.00 - - 5.76 Teaching Asst Professor 8.57 2.00 10

Liu, Paul

426

Micro electric propulsion feasibility  

NASA Technical Reports Server (NTRS)

Miniature, 50 kg class, strategic satellites intended for extended deployment in space require an on-board propulsion capability to perform needed attitude control adjustments and drag compensation maneuvers. Even on such very small spacecraft, these orbit maintenance functions can be significant and result in a substantial propellant mass requirement. Development of advanced propulsion technology could reduce this propellant mass significantly, and thereby maximize the payload capability of these spacecraft. In addition, spacecraft maneuverability could be enhanced and/or multi-year mission lifetimes realized. These benefits cut spacecraft replacement costs, and reduce services needed to maintain the launch vehicles. For SDIO brilliant pebble spacecraft, a miniaturized hydrazine propulsion system provides both boost and divert thrust control. This type of propulsion system is highly integrated and is capable of delivering large thrust levels for short time periods. However, orbit maintenance functions such as drag make-up require only very small velocity corrections. Using the boost and/or divert thrusters for these small corrections exposes this highly integrated propulsion system to continuous on/off cycling and thereby increases the risk of system failure. Furthermore, since drag compensation velocity corrections would be orders of magnitude less than these thrusters were designed to deliver, their effective specific impulse would be expected to be lower when operated at very short pulse lengths. The net result of these effects would be a significant depletion of the on-board hydrazine propellant supply throughout the mission, and a reduced propulsion system reliability, both of which would degrade the interceptors usefulness. In addition to SDIO brilliant pebble spacecraft, comparably small spacecraft can be anticipated for other future strategic defense applications such as surveillance and communication. For such spacecraft, high capability and reliability, minimal detectability and low cost are requirements. All these miniature spacecraft share a common characteristic: because of their on-board electronic equipment they have, by design, solar order 50-100 W. In a relative sense, such spacecraft are power rich when compared to other larger spacecraft. This power rich situation is offset by very tight mass budgets, which make reductions in propellant mass requirements a key issue in meeting overall spacecraft minimum mass goals. In principle, power rich and propellant poor brilliant pebbles class spacecraft can benefit from using high specific impulse electric propulsion to reduce chemical propellant mass requirements. However, at power levels of order 50 W, arcjets cannot be made to function, ion thrusters are too complex and heavy and resistojets have too low a specific impulse. Recognizing these capability limitations in existing electric propulsion technology, the SDIO/IST sponsored the Phase I SBIR Micro Electric Propulsion (MEP) thruster study described in this report. The objective of this study was to examine the feasibility of developing a very simple, low mass and small volume, electric thruster for operation on hydrazine at less than 100 W of input power. The feasibility of developing such a MEP thruster was successfully demonstrated by EPL by the discovery of a novel plasma acceleration process. The sections in this report summarize the approach, test results and major accomplishments of this proof-of-concept program.

Aston, Graeme; Aston, Martha

1992-01-01

427

Greenhouse Gas Emission Analysis for Distributed Energy System  

Microsoft Academic Search

Greenhouse effect directly affects human health. The literature firstly introduces greenhouse effect and the distributed energy system. Four systems including one natural gas micro-turbine system, one internal combustion biogas engine system, one Phosphoric Acid Fuel Cell combined heat and power system and one Proton Exchange Membrane Fuel Cell system are taken as the targets. Greenhouse gas concentration and emission rate

Zhai Rong-rong; Yang Yong-ping; Duan Li-qiang

2008-01-01

428

Simple gas chromatographic system for analysis of microbial respiratory gases  

NASA Technical Reports Server (NTRS)

Dual column ambient temperature system, consisting of pair of capillary columns, microbead thermistor detector and micro gas-sampling valve, is used in remote life-detection equipment for space experiments. Performance outweighs advantage gained by utilizing single-column systems to reduce weight, conserve carrier gas and operate at lower power levels.

Carle, G. C.

1972-01-01

429

Micro-machined calorimetric biosensors  

DOEpatents

A method and apparatus are provided for detecting and monitoring micro-volumetric enthalpic changes caused by molecular reactions. Micro-machining techniques are used to create very small thermally isolated masses incorporating temperature-sensitive circuitry. The thermally isolated masses are provided with a molecular layer or coating, and the temperature-sensitive circuitry provides an indication when the molecules of the coating are involved in an enthalpic reaction. The thermally isolated masses may be provided singly or in arrays and, in the latter case, the molecular coatings may differ to provide qualitative and/or quantitative assays of a substance.

Doktycz, Mitchel J. (Knoxville, TN); Britton, Jr., Charles L. (Alcoa, TN); Smith, Stephen F. (Loudon, TN); Oden, Patrick I. (Plano, TX); Bryan, William L. (Knoxville, TN); Moore, James A. (Powell, TN); Thundat, Thomas G. (Knoxville, TN); Warmack, Robert J. (Knoxville, TN)

2002-01-01

430

Evaluation of stability and size distribution of sunflower oil-coated micro bubbles for localized drug delivery  

PubMed Central

Background Micro bubbles were initially introduced as contrast agents for ultrasound examinations as they are able to modify the signal-to-noise ratio in imaging, thus improving the assessment of clinical information on human tissue. Recent developments have demonstrated the feasibility of using these bubbles as drug carriers in localized delivery. In micro fluidics devices for generation of micro bubbles, the bubbles are formed at interface of liquid gas through a strangulation process. A device that uses these features can produce micro bubbles with small size dispersion in a single step. Methods A T-junction micro fluidic device constructed using 3D prototyping was made for the production of mono dispersed micro bubbles. These micro bubbles use sunflower oil as a lipid layer. Stability studies for micro bubbles with diameters different generated from a liquid phase of the same viscosity were conducted to evaluate whether micro bubbles can be used as drug carriers. The biocompatibility of coating layer, the ability to withstand environmental pressure variations combined with echogenicity, are key factors that they can safely play the role of drug transporters. Results The normal distribution curve with small dispersion of the diameter of bubbles validates the process of generating micro bubbles with low value of variation coefficient, i.e., 0.381 at 1.90%. The results also showed the feasibility of using sunflower oil as the lipid matrix with stable population of bubbles over 217 minutes for micro bubbles with an average diameter of 313.04 ?m and 121 minutes for micro bubbles with an average diameter of 73.74 ?m, considering bubbles with air as gaseous phase. Conclusion The results indicate that the micro fluidic device designed can be used for producing micro bubbles with low variation coefficient using sunflower oil as a coating of micro bubbles. These carriers were stable for periods of time that are long enough for clinical applications even when regular air is used as the gas phase. Improved stability can be achieved when biocompatible gas with lower permeability is used. PMID:22995578

2012-01-01

431

Fabrication of a Flexible Micro Temperature Sensor for Micro Reformer Applications  

PubMed Central

Micro reformers still face obstacles in minimizing their size, decreasing the concentration of CO, conversion efficiency and the feasibility of integrated fabrication with fuel cells. By using a micro temperature sensor fabricated on a stainless steel-based micro reformer, this work attempts to measure the inner temperature and increase the conversion efficiency. Micro temperature sensors on a stainless steel substrate are fabricated using micro-electro-mechanical systems (MEMS) and then placed separately inside the micro reformer. Micro temperature sensors are characterized by their higher accuracy and sensitivity than those of a conventional thermocouple. To the best of our knowledge, micro temperature sensors have not been embedded before in micro reformers and commercial products, therefore, this work presents a novel approach to integrating micro temperature sensors in a stainless steel-based micro reformer in order to evaluate inner local temperature distributions and enhance reformer performance. PMID:22163817

Lee, Chi-Yuan; Lin, Chien-Hen; Lo, Yi-Man

2011-01-01

432

Design of a Micro Reciprocating Engine for Power Generation  

NASA Astrophysics Data System (ADS)

A reciprocating engine was designed for a micro power generator. It is expected to be used for a portable micro power generator with high energy density. The proposed reciprocating engine has the spring system, which is composed of opposite-pistons supported by an elastic spring. Combination of resonance of the spring system by the combustion pressure and an induction coil generates electricity due to generated voltage. Working cycle analysis, structural analysis, vibration analysis, and generated voltage calculations were carried out. Adopting H2 gas as a fuel and Si as a structural material, the theoretical output was found to be 41 mW under the conditions that compression ratio is 5, the maximum combustion temperature is 850 K and resonance frequency of the spring system is 582 Hz.

Sugiyama, Susumu; Toriyama, Toshiyuki