30 CFR 56.12017 - Work on power circuits.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Work on power circuits. 56.12017 Section 56.12017 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Electricity § 56...

30 CFR 56.12017 - Work on power circuits.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Work on power circuits. 56.12017 Section 56.12017 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Electricity § 56...

Reference reactor module for NASA's lunar surface fission power system

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

Poston, David I; Kapernick, Richard J; Dixon, David D

Surface fission power systems on the Moon and Mars may provide the first US application of fission reactor technology in space since 1965. The Affordable Fission Surface Power System (AFSPS) study was completed by NASA/DOE to determine the cost of a modest performance, low-technical risk surface power system. The AFSPS concept is now being further developed within the Fission Surface Power (FSP) Project, which is a near-term technology program to demonstrate system-level TRL-6 by 2013. This paper describes the reference FSP reactor module concept, which is designed to provide a net power of 40 kWe for 8 years on themore » lunar surface; note, the system has been designed with technologies that are fully compatible with a Martian surface application. The reactor concept uses stainless-steel based. UO{sub 2}-fueled, pumped-NaK fission reactor coupled to free-piston Stirling converters. The reactor shielding approach utilizes both in-situ and launched shielding to keep the dose to astronauts much lower than the natural background radiation on the lunar surface. The ultimate goal of this work is to provide a 'workhorse' power system that NASA can utilize in near-term and future Lunar and Martian mission architectures, with the eventual capability to evolve to very high power, low mass systems, for either surface, deep space, and/or orbital missions.« less

30 CFR 77.703 - Grounding frames of stationary high-voltage equipment receiving power from ungrounded delta systems.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Grounding frames of stationary high-voltage..., SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Grounding § 77.703 Grounding frames of stationary high-voltage equipment receiving power from ungrounded delta systems. The frames of all stationary...

High performance ZnO:Al films deposited on PET substrates using facing target sputtering

NASA Astrophysics Data System (ADS)

Guo, Tingting; Dong, Guobo; Gao, Fangyuan; Xiao, Yu; Chen, Qiang; Diao, Xungang

2013-10-01

ZnO:Al (ZAO) thin films have been deposited on flexible PET substrates using a plasma damage-free facing target sputtering system at room temperature. The structure, surface morphology, electrical and optical properties were investigated as a function of working power. All the samples have a highly preferred orientation of the c-axis perpendicular to the PET substrate and have a high quality surface. With increased working power, the carrier concentration changes slightly, the mobility increases at the beginning and decreases after it reaches a maximum value, in line with electrical conductivity. The figure of merit has been significantly improved with increasing of the working power. Under the optimized condition, the lowest resistivity of 1.3 × 10-3 Ω cm with a sheet resistance of 29 Ω/□ and the relative visible transmittance above 93% in the visible region were obtained.

A Summary of NASA Architecture Studies Utilizing Fission Surface Power Technology

NASA Technical Reports Server (NTRS)

Mason, Lee; Poston, Dave

2010-01-01

Beginning with the Exploration Systems Architecture Study in 2005, NASA has conducted various mission architecture studies to evaluate implementation options for the U.S. Space Policy (formerly the Vision for Space Exploration). Several of the studies examined the use of Fission Surface Power (FSP) systems for human missions to the lunar and Martian surface. This paper summarizes the FSP concepts developed under four different NASA-sponsored architecture studies: Lunar Architecture Team, Mars Architecture Team, Lunar Surface Systems/Constellation Architecture team, and International Architecture Working Group-Power Function team. The results include a summary of FSP design characteristics, a compilation of mission-compatible FSP configuration options, and an FSP concept-of-operations that is consistent with the overall mission objectives.

Fission Surface Power Technology Development Update

NASA Technical Reports Server (NTRS)

Palac, Donald T.; Mason, Lee S.; Houts, Michael G.; Harlow, Scott

2011-01-01

Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and places beyond. Nuclear power is an important option, especially for locations in the solar system where sunlight is limited or environmental conditions are challenging (e.g., extreme cold, dust storms). NASA and the Department of Energy are maintaining the option for fission surface power for the Moon and Mars by developing and demonstrating technology for a fission surface power system. The Fission Surface Power Systems project has focused on subscale component and subsystem demonstrations to address the feasibility of a low-risk, low-cost approach to space nuclear power for surface missions. Laboratory demonstrations of the liquid metal pump, reactor control drum drive, power conversion, heat rejection, and power management and distribution technologies have validated that the fundamental characteristics and performance of these components and subsystems are consistent with a Fission Surface Power preliminary reference concept. In addition, subscale versions of a non-nuclear reactor simulator, using electric resistance heating in place of the reactor fuel, have been built and operated with liquid metal sodium-potassium and helium/xenon gas heat transfer loops, demonstrating the viability of establishing system-level performance and characteristics of fission surface power technologies without requiring a nuclear reactor. While some component and subsystem testing will continue through 2011 and beyond, the results to date provide sufficient confidence to proceed with system level technology readiness demonstration. To demonstrate the system level readiness of fission surface power in an operationally relevant environment (the primary goal of the Fission Surface Power Systems project), a full scale, 1/4 power Technology Demonstration Unit (TDU) is under development. The TDU will consist of a non-nuclear reactor simulator, a sodium-potassium heat transfer loop, a power conversion unit with electrical controls, and a heat rejection system with a multi-panel radiator assembly. Testing is planned at the Glenn Research Center Vacuum Facility 6 starting in 2012, with vacuum and liquid-nitrogen cold walls to provide simulation of operationally relevant environments. A nominal two-year test campaign is planned including a Phase 1 reactor simulator and power conversion test followed by a Phase 2 integrated system test with radiator panel heat rejection. The testing is expected to demonstrate the readiness and availability of fission surface power as a viable power system option for NASA's exploration needs. In addition to surface power, technology development work within this project is also directly applicable to in-space fission power and propulsion systems.

Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

2008-01-01

Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a SNAP derivative reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

Atmospheric pressure plasma jet's characterization and surface wettability driven by neon transformer

NASA Astrophysics Data System (ADS)

Elfa, R. R.; Nafarizal, N.; Ahmad, M. K.; Sahdan, M. Z.; Soon, C. F.

2017-03-01

Atmospheric pressure plasma driven by Neon transformer power supply argon is presented in this paper. Atmospheric pressure plasma system has attracted researcher interest over low pressure plasma as it provides a flexibility process, cost-efficient, portable device and vacuum-free device. Besides, another golden key of this system is the wide promising application in the field of work cover from industrial and engineering to medical. However, there are still numbers of fundamental investigation that are necessary such as device configuration, gas configuration and its effect. Dielectric barrier discharge which is also known as atmospheric pressure plasma discharge is created when there is gas ionization process occur which enhance the movement of atom and electron and provide energetic particles. These energetic particles can provide modification and cleaning property to the sample surface due to the bombardment of the high reactive ion and radicals to the sample surface. In order to develop atmospheric pressure plasma discharge, a high voltage and high frequency power supply is needed. In this work, we used a neon transformer power supply as the power supply. The flow of the Ar is feed into 10 mm cylinder quartz tube with different treatment time in order to investigate the effect of the plasma discharge. The analysis of each treatment time is presented by optical emission spectroscopy (OES) and water contact angle (WCA) measurement. The increase of gas treatment time shows increases intensity of reactive Ar and reduces the angle of water droplets in water contact angle. Treatment time of 20 s microslide glass surface shows that the plasma needle discharges have modified the sample surface from hydrophilic surface to superhydrophilic surface. Thus, this leads to another interesting application in reducing sample surface adhesion to optimize productivity in the industry of paintings, semiconductor and more.

29 CFR 1910.30 - Other working surfaces.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) Dockboards (bridge plates). (1) Portable and powered dockboards shall be strong enough to carry the load... vats on which men are working and a portable railing shall be placed at this point to protect the...

Triboelectrification-Enabled Self-Powered Data Storage.

PubMed

Kuang, Shuang Yang; Zhu, Guang; Wang, Zhong Lin

2018-02-01

Data storage by any means usually requires an electric driving power for writing or reading. A novel approach for self-powered, triboelectrification-enabled data storage (TEDS) is presented. Data are incorporated into a set of metal-based surface patterns. As a probe slides across the patterned surface, triboelectrification between the scanning probe and the patterns produces alternatively varying voltage signal in quasi-square wave. The trough and crest of the quasi-square wave signal are coded as binary bits of "0" and "1," respectively, while the time span of the trough and the crest is associated with the number of bits. The storage of letters and sentences is demonstrated through either square-shaped or disc-shaped surface patterns. Based on experimental data and numerical calculation, the theoretically predicted maximum data storage density could reach as high as 38.2 Gbit in -2 . Demonstration of real-time data retrieval is realized with the assistance of software interface. For the TEDS reported in this work, the measured voltage signal is self-generated as a result of triboelectrification without the reliance on an external power source. This feature brings about not only low power consumption but also a much more simplified structure. Therefore, this work paves a new path to a unique approach of high-density data storage that may have widespread applications.

Megawatt solar power systems for lunar surface operations

NASA Technical Reports Server (NTRS)

Adams, B.; Alhadeff, S.; Beard, S.; Carlile, D.; Cook, D.; Douglas, C.; Garcia, D.; Gillespie, D.; Golingo, R.; Gonzalez, D.

1990-01-01

The work presented here shows that a solar power system can provide power on the order of one megawatt to a lunar base with a fairly high specific power. The main drawback to using solar power is still the high mass, and therefore, cost of supplying energy storage through the solar night. The use of cryogenic reactant storage in a fuel cell system, however, greatly reduces the total system mass over conventional energy storage schemes.

Quantifying surface roughness effects on phonon transport in silicon nanowires.

PubMed

Lim, Jongwoo; Hippalgaonkar, Kedar; Andrews, Sean C; Majumdar, Arun; Yang, Peidong

2012-05-09

Although it has been qualitatively demonstrated that surface roughness can reduce the thermal conductivity of crystalline Si nanowires (SiNWs), the underlying reasons remain unknown and warrant quantitative studies and analysis. In this work, vapor-liquid-solid (VLS) grown SiNWs were controllably roughened and then thoroughly characterized with transmission electron microscopy to obtain detailed surface profiles. Once the roughness information (root-mean-square, σ, correlation length, L, and power spectra) was extracted from the surface profile of a specific SiNW, the thermal conductivity of the same SiNW was measured. The thermal conductivity correlated well with the power spectra of surface roughness, which varies as a power law in the 1-100 nm length scale range. These results suggest a new realm of phonon scattering from rough interfaces, which restricts phonon transport below the Casimir limit. Insights gained from this study can help develop a more concrete theoretical understanding of phonon-surface roughness interactions as well as aid the design of next generation thermoelectric devices.

Performance and Mass Modeling Subtleties in Closed-Brayton-Cycle Space Power Systems

NASA Technical Reports Server (NTRS)

Barrett, Michael J.; Johnson, Paul K.

2005-01-01

Contents include the following: 1. Closed-Brayton-cycle (CBC) thermal energy conversion is one available option for future spacecraft and surface systems. 2. Brayton system conceptual designs for milliwatt to megawatt power converters have been developed 3. Numerous features affect overall optimized power conversion system performance: Turbomachinery efficiency. Heat exchanger effectiveness. Working-fluid composition. Cycle temperatures and pressures.

Europa Small Lander Design Concepts

NASA Astrophysics Data System (ADS)

Zimmerman, W. F.

2005-12-01

Title: Europa Small Lander Design Concepts Authors: Wayne F. Zimmerman, James Shirley, Robert Carlson, Tom Rivellini, Mike Evans One of the primary goals of NASA's Outer Planets Program is to revisit the Jovian system. A new Europa Geophysical Explorer (EGE) Mission has been proposed and is under evaluation. There is in addition strong community interest in a surface science mission to Europa. A Europa Lander might be delivered to the Jovian system with the EGE orbiter. A Europa Astrobiology Lander (EAL) Mission has also been proposed; this would launch sometime after 2020. The primary science objectives for either of these would most likely include: Surface imaging (both microscopic and near-field), characterization of surface mechanical properties (temperature, hardness), assessment of surface and near-surface organic and inorganic chemistry (volatiles, mineralogy, and compounds), characterization of the radiation environment (total dose and particles), characterization of the planetary seismicity, and the measurement of Europa's magnetic field. The biggest challenges associated with getting to the surface and surviving to perform science investigations revolve around the difficulty of landing on an airless body, the ubiquitous extreme topography, the harsh radiation environment, and the extreme cold. This presentation reviews some the recent design work on drop-off probes, also called "hard landers". Hard lander designs have been developed for a range of science payload delivery systems spanning small impactors to multiple science pods tethered to a central hub. In addition to developing designs for these various payload delivery systems, significant work has been done in weighing the relative merits of standard power systems (i.e., batteries) against radioisotope power systems. A summary of the power option accommodation benefits and issues will be presented. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract from NASA,

Self-Powered Wireless Smart Sensor Node Enabled by an Ultrastable, Highly Efficient, and Superhydrophobic-Surface-Based Triboelectric Nanogenerator.

PubMed

Zhao, Kun; Wang, Zhong Lin; Yang, Ya

2016-09-27

Wireless sensor networks will be responsible for a majority of the fast growth in intelligent systems in the next decade. However, most of the wireless smart sensor nodes require an external power source such as a Li-ion battery, where the labor cost and environmental waste issues of replacing batteries have largely limited the practical applications. Instead of using a Li-ion battery, we report an ultrastable, highly efficient, and superhydrophobic-surface-based triboelectric nanogenerator (TENG) to scavenge wind energy for sustainably powering a wireless smart temperature sensor node. There is no decrease in the output voltage and current of the TENG after continuous working for about 14 h at a wind speed of 12 m/s. Through a power management circuit, the TENG can deliver a constant output voltage of 3.3 V and a pulsed output current of about 100 mA to achieve highly efficient energy storage in a capacitor. A wireless smart temperature sensor node can be sustainably powered by the TENG for sending the real-time temperature data to an iPhone under a working distance of 26 m, demonstrating the feasibility of the self-powered wireless smart sensor networks.

Ambient Noise and Surface Wave Dissipation in the Ocean

DTIC Science & Technology

1993-06-21

computed frmn a one hour wave gauge record with U10 = 8 m/s. a ) Power spectrum computed rom 1024-point FFr. used throughout this work . b) Power specttrum...this work , equations relating U and N in the form of Equation 1.3 will be referred to as WOTAN equations’. Figure 1.2 shows a figure taken from Evans et...the found that a significant proportion of the dissipated energy (up to 50%) is due to work done by the liquid in entraining air against buoyancy

Milliwatt radioisotope power supply for the PASCAL Mars surface stations

NASA Astrophysics Data System (ADS)

Allen, Daniel T.; Murbach, Marcus S.

2001-02-01

A milliwatt power supply is being developed based on the 1 watt Light-Weight Radioisotope Heater Unit (RHU), which has already been used to provide heating alone on numerous spacecraft. In the past year the power supply has been integrated into the design of the proposed PASCAL Mars Network Mission, which is intended to place 24 surface climate monitoring stations on Mars. The PASCAL Mars mission calls for the individual surface stations to be transported together in one spacecraft on a trajectory direct from launch to orbit around Mars. From orbit around Mars each surface station will be deployed on a SCRAMP (slotted compression ramp) probe and, after aerodynamic and parachute deceleration, land at a preselected location on the planet. During descent sounding data and still images will be accumulated, and, once on the surface, the station will take measurements of pressure, temperature and overhead atmospheric optical depth for a period of 10 Mars years (18.8 Earth years). Power for periodic data acquisition and transmission to orbital then to Earth relay will come from a bank of ultracapacitors which will be continuously recharged by the radioisotope power supply. This electronic system has been designed and a breadboard built. In the ultimate design the electronics will be arrayed on the exterior surface of the radioisotope power supply in order to take advantage of the reject heat. This assembly in turn is packaged within the SCRAMP, and that assembly comprises the surface station. An electrically heated but otherwise prototypical power supply was operated in combination with the surface station breadboard system, which included the ultracapacitors. Other issues addressed in this work have been the capability of the generator to withstand the mechanical shock of the landing on Mars and the effectiveness of the generator's multi-foil vacuum thermal insulation. .

Theoretical Investigation For The Effect of Fuel Quality on Gas Turbine Power Plants

NASA Astrophysics Data System (ADS)

AbdulRazzak khudair, Omar; Alwan Abass, Khetam; Saadi Abed, Noor; Hussain Ali, Khalid; AbdulAziz, Saad; Chlaib Shaboot, Ali

2018-05-01

Gas turbine engine power generation is declined dramatically because of the reduction in thermodynamic parameters as a work of turbine, compressor ratio, compressor work, and air mass flow rate and fuel consumption. There are two main objectives of this work, the first is related with the effect of fuel kinds and their quality on the operation of fuel flow divider and its performance specifically gear pump displacement and fuel flow rate to the combustion chambers of gas power plant. AL-DORA gas turbine power plant 35MW was chosen to predict these effects on its performance MATLAB Software program is used to perform thermodynamic calculations. Fuel distribution stage before the process of combustion and as a result of the kind and its quality, chemical reaction will occur between the fuel and the parts of the gear system of each pump of the flow divider, which causes the erosion of the internal pump wall and the teeth of the gear system, thus hampering the pump operation in terms of fuel discharge. The discharge of fuel form the eight external gates of flow divider is decreased and varied when going to the combustion chambers, so that, flow divider does not give reliable mass flow rate due to absence of accurate pressure in each of eight exit pipes. The second objective deals with the stage of fuel combustion process inside the combustion chamber. A comparative study based upon performance parameters, such as specific fuel consumption for gas and gasoil and power generation. Fuel poor quality causes incomplete combustion and increased its consumption, so that combustion products are interacted with the surface of the turbine blades, causing the erosion and create surface roughness of the blade and disruption of gas flow. As a result of this situation, turbulence flow of these gases will increase causing the separation of gas boundary layers over the suction surface of the blade. Therefore the amount of extracted gas will decrease causing retreat work done by turbine, as a result decline of power and gas turbine power plant efficiency causing the drop in the level of electric generation. The fuel quality is found to be a strong function of specific fuel consumption and its effects on the power generation and the efficiency of the gas turbine power plants and hence, the cycle performance shifts towards favorable conditions.

Ocean thermal gradient as a generator of electricity. OTEC power plant

NASA Astrophysics Data System (ADS)

Enrique, Luna-Gomez Victor; Angel, Alatorre-Mendieta Miguel

2016-04-01

The OTEC (Ocean Thermal Energy Conversion) is a power plant that uses the thermal gradient of the sea water between the surface and a depth of about 700 meters. It works by supplying the heat to a steam machine, for evaporation, with sea water from the surface and cold, to condense the steam, with deep sea water. The energy generated by the power plant OTEC can be transferred to the electric power grid, another use is to desalinate seawater. During the twentieth century in some countries experimental power plants to produce electricity or obtaining drinking water they were installed. On the Mexico's coast itself this thermal gradient, as it is located in tropical seas it occurs, so it has possibilities of installing OTEC power plant type. In this paper one type OTEC power plant operation is represented in most of its components.

Significance of the contacting and no contacting thermoelectric power measurements applied to grit blasted medical Ti6Al4V.

PubMed

Carreon, H; Barriuso, S; Lieblich, M; González-Carrasco, J L; Jimenez, J A; Caballero, F G

2013-04-01

Grit blasting is a surface plastic deformation technique aimed to increase the surface area available for bone/implant apposition, which contributes to improve fixation and mechanical stability of Ti-6Al-4V implants. Besides roughening, grit blasting also causes surface contamination with embedded grit particles and subtle subsurface microstructural changes that, although does not challenge their biocompatibility, might influence other surface dominated properties like corrosion and ion release. Additional benefits are expected due to the induced compressive residual stresses, hence enhancing fatigue strength. The net effect depends on the type of particles used for blasting, but also on the amount of the subsurface cold work associated to the severe surface plastic deformation. In this work we study the potential of the non-contacting and contacting thermoelectric power (TEP) measurements in the analysis of the global changes induced in the Ti6Al4V when blasting the alloy with Al2O3 or ZrO2 particles, which yields a coarse and a fine rough surface, respectively. To reveal the effect of residual stresses, a set of specimens were thermally treated. The study proves that the non-contacting technique is more sensitive to the presence of residual stresses, whereas the contact technique is strongly influenced by the grain size refinements, work hardening and changes in solute. Copyright © 2012 Elsevier B.V. All rights reserved.

Influence of diligent disintegration on anaerobic biomass and performance of microbial fuel cell.

PubMed

Divyalakshmi, Palanisamy; Murugan, Devaraj; Rai, Chockalingam Lajapathi

2017-12-01

To enhance the performance of microbial fuel cells (MFC) by increasing the surface area of cathode and diligent mechanical disintegration of anaerobic biomass. Tannery effluent and anaerobic biomass were used. The increase in surface area of the cathode resulted in 78% COD removal, with the potential, current density, power density and coulombic efficiency of 675 mV, 147 mA m -2 , 33 mW m -2 and 3.5%, respectively. The work coupled with increased surface area of the cathode with diligent mechanical disintegration of the biomass, led to a further increase in COD removal of 82% with the potential, current density, power density and coulombic efficiency of 748 mV, 229 mA m -2 , 78 mW m -2 and 6% respectively. Mechanical disintegration of the biomass along with increased surface area of cathode enhances power generation in vertical MFC reactors using tannery effluent as fuel.

Local digital control of power electronic converters in a dc microgrid based on a-priori derivation of switching surfaces

NASA Astrophysics Data System (ADS)

Banerjee, Bibaswan

In power electronic basedmicrogrids, the computational requirements needed to implement an optimized online control strategy can be prohibitive. The work presented in this dissertation proposes a generalized method of derivation of geometric manifolds in a dc microgrid that is based on the a-priori computation of the optimal reactions and trajectories for classes of events in a dc microgrid. The proposed states are the stored energies in all the energy storage elements of the dc microgrid and power flowing into them. It is anticipated that calculating a large enough set of dissimilar transient scenarios will also span many scenarios not specifically used to develop the surface. These geometric manifolds will then be used as reference surfaces in any type of controller, such as a sliding mode hysteretic controller. The presence of switched power converters in microgrids involve different control actions for different system events. The control of the switch states of the converters is essential for steady state and transient operations. A digital memory look-up based controller that uses a hysteretic sliding mode control strategy is an effective technique to generate the proper switch states for the converters. An example dcmicrogrid with three dc-dc boost converters and resistive loads is considered for this work. The geometric manifolds are successfully generated for transient events, such as step changes in the loads and the sources. The surfaces corresponding to a specific case of step change in the loads are then used as reference surfaces in an EEPROM for experimentally validating the control strategy. The required switch states corresponding to this specific transient scenario are programmed in the EEPROM as a memory table. This controls the switching of the dc-dc boost converters and drives the system states to the reference manifold. In this work, it is shown that this strategy effectively controls the system for a transient condition such as step changes in the loads for the example case.

Development of a Direct Contact Heat Exchanger, Phase 1 Study Report

NASA Technical Reports Server (NTRS)

Manvi, R.

1978-01-01

Electric power generation from geothermal brine requires, first, bringing the hot brine to the surface and then converting the heat to electric power. Binary conversion schemes were proposed, with the heat transfer between the brine and the working organic fluid taking place in a conventional tube and shell heat exchanger. If the brine is heavily laden with dissolved solids, however, solids buildup on the heat exchanger surfaces leads to a considerable degree of fouling and an accompanying drop in performance is experienced. A possible solution to this problem is the use of a direct contact exchanger with the secondary fluid power cycle. The proposed concept involves the formation of fluid sheets and bells as heat angles. Results of a study concerning the fluid mechanics of such surfaces are given.

Wavelength specific excitation of gold nanoparticle thin-films

NASA Astrophysics Data System (ADS)

Lucas, Thomas M.; James, Kurtis T.; Beharic, Jasmin; Moiseeva, Evgeniya V.; Keynton, Robert S.; O'Toole, Martin G.; Harnett, Cindy K.

2014-01-01

Advances in microelectromechanical systems (MEMS) continue to empower researchers with the ability to sense and actuate at the micro scale. Thermally driven MEMS components are often used for their rapid response and ability to apply relatively high forces. However, thermally driven MEMS often have high power consumption and require physical wiring to the device. This work demonstrates a basis for designing light-powered MEMS with a wavelength specific response. This is accomplished by patterning surface regions with a thin film containing gold nanoparticles that are tuned to have an absorption peak at a particular wavelength. The heating behavior of these patterned surfaces is selected by the wavelength of laser directed at the sample. This method also eliminates the need for wires to power a device. The results demonstrate that gold nanoparticle films are effective wavelength-selective absorbers. This "hybrid" of infrared absorbent gold nanoparticles and MEMS fabrication technology has potential applications in light-actuated switches and other mechanical structures that must bend at specific regions. Deposition methods and surface chemistry will be integrated with three-dimensional MEMS structures in the next phase of this work. The long-term goal of this project is a system of light-powered microactuators for exploring cellular responses to mechanical stimuli, increasing our fundamental understanding of tissue response to everyday mechanical stresses at the molecular level.

Power ultrasound irradiation during the alkaline etching process of the 2024 aluminum alloy

NASA Astrophysics Data System (ADS)

Moutarlier, V.; Viennet, R.; Rolet, J.; Gigandet, M. P.; Hihn, J. Y.

2015-11-01

Prior to any surface treatment on an aluminum alloy, a surface preparation is necessary. This commonly consists in performing an alkaline etching followed by acid deoxidizing. In this work, the use of power ultrasound irradiation during the etching step on the 2024 aluminum alloy was studied. The etching rate was estimated by weight loss, and the alkaline film formed during the etching step was characterized by glow discharge optical emission spectrometry (GDOES) and scanning electron microscope (SEM). The benefit of power ultrasound during the etching step was confirmed by pitting potential measurement in NaCl solution after a post-treatment (anodizing).

Mars manned transportation vehicle

NASA Technical Reports Server (NTRS)

Perez-Davis, Marla E.; Faymon, Karl A.

1987-01-01

A viable power system technology for a surface transportation vehicle to explore the planet Mars is presented. A number of power traction systems were investigated, and it was found that a regenerative hydrogen-oxygen fuel cell appears to be attractive for a manned Mars rover application. Mission requirements were obtained from the Manned Mars Mission Working Group. Power systems weights, power, and reactants requirements were determined as a function of vehicle weights for vehicles weighing from 6,000 to 16,000 lb (2,722 to 7,257 kg), (Earth weight). The vehicle performance requirements were: velocity, 10 km/hr; range, 100 km; slope climbing capability, 30 deg uphill for 50 km; mission duration, 5 days; and crew, 5. Power requirements for the operation of scientific equipment and support system capabilities were also specified and included in this study. The concept developed here would also be applicable to a Lunar based vehicle for Lunar exploration. The reduced gravity on the Lunar surface, (over that on the Martian surface), would result in an increased range or capability over that of the Mars vehicle since many of the power and energy requirements for the vehicle are gravity dependent.

Study on on-machine defects measuring system on high power laser optical elements

NASA Astrophysics Data System (ADS)

Luo, Chi; Shi, Feng; Lin, Zhifan; Zhang, Tong; Wang, Guilin

2017-10-01

The influence of surface defects on high power laser optical elements will cause some harm to the performances of imaging system, including the energy consumption and the damage of film layer. To further increase surface defects on high power laser optical element, on-machine defects measuring system was investigated. Firstly, the selection and design are completed by the working condition analysis of the on-machine defects detection system. By designing on processing algorithms to realize the classification recognition and evaluation of surface defects. The calibration experiment of the scratch was done by using the self-made standard alignment plate. Finally, the detection and evaluation of surface defects of large diameter semi-cylindrical silicon mirror are realized. The calibration results show that the size deviation is less than 4% that meet the precision requirement of the detection of the defects. Through the detection of images the on-machine defects detection system can realize the accurate identification of surface defects.

Nano-scale investigations of electric-dipole-layer enhanced field and thermionic emission from high current density cathodes

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios

Cesium iodide coated graphitic fibers and scandate cathodes are two important electron emission technologies. The coated fibers are utilized as field emitters for high power microwave sources. The scandate cathodes are promising thermionic cathode materials for pulsed power vacuum electron devices. This work attempts to understand the fundamental physical and chemical relationships between the atomic structure of the emitting cathode surfaces and the superior emission characteristics of these cathodes. Ab initio computational modeling in conjunction with experimental investigations was performed on coated fiber cathodes to understand the origin of their very low turn on electric field, which can be reduced by as much as ten-fold compared to uncoated fibers. Copious amounts of cesium and oxygen were found co-localized on the fiber, but no iodine was detected on the surface. Additional ab initio studies confirmed that cesium oxide dimers could lower the work function significantly. Surface cesium oxide dipoles are therefore proposed as the source of the observed reduction in the turn on electric field. It is also proposed that emission may be further enhanced by secondary electrons from cesium oxide during operation. Thermal conditioning of the coated cathode may be a mechanism by which surface cesium iodide is converted into cesium oxide, promoting the depletion of iodine by formation of volatile gas. Ab initio modeling was also utilized to investigate the stability and work functions of scandate structures. The work demonstrated that monolayer barium-scandium-oxygen surface structures on tungsten can dramatically lower the work function of the underlying tungsten substrate from 4.6 eV down to 1.16 eV, by the formation of multiple surface dipoles. On the basis of this work, we conclude that high temperature kinetics force conventional dispenser cathodes (barium-oxygen monolayers on tungsten) to operate in a non-equilibrium compositional steady state with higher than optimal work functions of ˜2 eV. We hypothesize that scandium enables the barium-oxygen surface monolayer kinetics to access a more thermodynamically stable phase with reported work functions as low as ˜1.3 eV.

Thermomechanical modelling of laser surface glazing for H13 tool steel

NASA Astrophysics Data System (ADS)

Kabir, I. R.; Yin, D.; Tamanna, N.; Naher, S.

2018-03-01

A two-dimensional thermomechanical finite element (FE) model of laser surface glazing (LSG) has been developed for H13 tool steel. The direct coupling technique of ANSYS 17.2 (APDL) has been utilised to solve the transient thermomechanical process. A H13 tool steel cylindrical cross-section has been modelled for laser power 200 W and 300 W at constant 0.2 mm beam width and 0.15 ms residence time. The model can predict temperature distribution, stress-strain increments in elastic and plastic region with time and space. The crack formation tendency also can be assumed by analysing the von Mises stress in the heat-concentrated zone. Isotropic and kinematic hardening models have been applied separately to predict the after-yield phenomena. At 200 W laser power, the peak surface temperature achieved is 1520 K which is below the melting point (1727 K) of H13 tool steel. For laser power 300 W, the peak surface temperature is 2523 K. Tensile residual stresses on surface have been found after cooling, which are in agreement with literature. Isotropic model shows higher residual stress that increases with laser power. Conversely, kinematic model gives lower residual stress which decreases with laser power. Therefore, both plasticity models could work in LSG for H13 tool steel.

Closed Brayton Cycle Power Conversion Unit for Fission Surface Power Phase I Final Report

NASA Technical Reports Server (NTRS)

Fuller, Robert L.

2010-01-01

A Closed Brayton cycle power conversion system has been developed to support the NASA fission surface power program. The goal is to provide electricity from a small nuclear reactor heat source for surface power production for lunar and Mars environments. The selected media for a heat source is NaK 78 with water as a cooling source. The closed Brayton cycle power was selected to be 12 kWe output from the generator terminals. A heat source NaK temperature of 850 K plus or minus 25 K was selected. The cold source water was selected at 375 K plus or minus 25 K. A vacuum radiation environment of 200 K is specified for environmental operation. The major components of the system are the power converter, the power controller, and the top level data acquisition and control unit. The power converter with associated sensors resides in the vacuum radiation environment. The power controller and data acquisition system reside in an ambient laboratory environment. Signals and power are supplied across the pressure boundary electrically with hermetic connectors installed on the vacuum vessel. System level analyses were performed on working fluids, cycle design parameters, heater and cooling temperatures, and heat exchanger options that best meet the needs of the power converter specification. The goal is to provide a cost effective system that has high thermal-to-electric efficiency in a compact, lightweight package.

Space solar power stations. Problems of energy generation and using its on the earth surface and nearest cosmos

NASA Astrophysics Data System (ADS)

Sinkevich, OA; Gerasimov, DN; Glazkov, VV

2017-11-01

Three important physical and technical problems for solar power stations (SPS) are considered: collection of solar energy and effective conversion of this energy to electricity in space power stations, energy transportation by the microwave beam to the Earth surface and direct utilization of the microwave beam energy for global environmental problems. Effectiveness of solar energy conversion into electricity in space power stations using gas and steam turbines plants, and magneto-hydrodynamic generator (MHDG) are analyzed. The closed cycle MHDG working on non-equilibrium magnetized plasmas of inert gases seeded with the alkaline metal vapors are considered. The special emphases are placed on MHDG and gas-turbine installations that are operating without compressor. Also opportunities for using the produced by space power stations energy for ecological needs on Earth and in Space are discussed.

Thermoelectric-Driven Autonomous Sensors for a Biomass Power Plant

NASA Astrophysics Data System (ADS)

Rodríguez, A.; Astrain, D.; Martínez, A.; Gubía, E.; Sorbet, F. J.

2013-07-01

This work presents the design and development of a thermoelectric generator intended to harness waste heat in a biomass power plant, and generate electric power to operate sensors and the required electronics for wireless communication. The first objective of the work is to design the optimum thermoelectric generator to harness heat from a hot surface, and generate electric power to operate a flowmeter and a wireless transmitter. The process is conducted by using a computational model, presented in previous papers, to determine the final design that meets the requirements of electric power consumption and number of transmissions per minute. Finally, the thermoelectric generator is simulated to evaluate its performance. The final device transmits information every 5 s. Moreover, it is completely autonomous and can be easily installed, since no electric wires are required.

Study of RF breakdown and multipacting in accelerator components

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

Pande, Manjiri; Singh, P., E-mail: manjiri@barc.gov.in, E-mail: psingh@barc.gov.in

2014-07-01

Radio frequency (RF) structures that are part of accelerators and energy sources, operate with sinusoidally varying electromagnetic fields under high RF energy. Here, RF breakdown and multipacting take place in RF structures and limit their performance. Electron field emission processes in a RF structure are precursors for breakdown processes. RF breakdown is a major phenomena affecting and causing the irreversible damage to RF structures. Breakdown rate and the damage induced by the breakdowns are its important properties. The damage is related to power absorbed during breakdown, while the breakdown rate is determined by the amplitudes of surface electric and magneticmore » fields, geometry, metal surface preparation and conditioning history. It limits working power and produces irreversible surface damage. The breakdown limit depends on the RF circuit, structure geometry, RF frequency, input RF power, pulse width, materials used, surface processing technique and surface electric and magnetic fields. Multipactor (MP) is a low power, electron multiplication based resonance breakdown phenomenon in vacuum and is often observed in RF structures. A multipactor discharge is undesirable, as it can create a reactive component that detunes the resonant cavities and components, generates noise in communication system and induces gas desorption from the conductor surfaces. In RF structures, certain conditions are required to generate multipacting. (author)« less

[Test of thermal deformation for electronic devices of high thermal reliability].

PubMed

Li, Hai-yuan; Li, Bao-ming

2002-06-01

Thermal deformation can be caused by high partial heat flux and greatly reduce thermal reliability of electronic devices. In this paper, an attempt is made to measure the thermal deformation of high power electronic devices under working condition using laser holographic interferometry with double exposure. Laser holographic interferometry is an untouched measurement with measurement precision up to micron dimension. The electronic device chosen for measurement is a type of solid state relay which is used for ignition of rockets. The output circuit of the solid state relay is made up of a MOSFET chip and the power density of the chip can reach high value. In particular situations thermal deformation and stress may significantly influence working performance of the solid state relay. The bulk deformation of the chip and its mount is estimated by number of interferential stripes on chip surface. While thermal stress and deformation can be estimated by curvature of interferential stripes on chip surface. Experimental results indicate that there are more interferential stripes on chip surface and greater flexural degree of stripes under high power. Therefore, these results reflect large out-of-plain displacement and deformed size of the chip with the increase of load current.

Reflectors with directional-mixed reflection properties for application in luminaries with high-power LED diodes

NASA Astrophysics Data System (ADS)

Zaremba, Krzysztof

2008-06-01

Application of directional-mixed reflectors results in a luminance decrease of the apparent image of light emitting diodes (LEDs), which is advantageous as far as glare reduction is concerned. On the other hand, reflectors have a negative impact on luminous intensity curves of the luminaries. This work analyzes an impact of surfaces with directional-mixed reflection properties in a mirror reflector designed for a luminary equipped with high-power LEDs. We present an algorithm used to determine the shape of the reflector of the surface with small scattering, where the axis twist angle for a parabolic reflector varies in a predefined range and follows a power function.

Measuring Plasma Formation Field Strength and Current Loss in Pulsed Power Diodes

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

Johnston, Mark D.; Patel, Sonal G.; Falcon, Ross Edward

This LDRD investigated plasma formation, field strength, and current loss in pulsed power diodes. In particular the Self-Magnetic Pinch (SMP) e-beam diode was studied on the RITS-6 accelerator. Magnetic fields of a few Tesla and electric fields of several MV/cm were measured using visible spectroscopy techniques. The magnetic field measurements were then used to determine the current distribution in the diode. This distribution showed that significant beam current extends radially beyond the few millimeter x-ray focal spot diameter. Additionally, shielding of the magnetic field due to dense electrode surface plasmas was observed, quantified, and found to be consistent with themore » calculated Spitzer resistivity. In addition to the work on RITS, measurements were also made on the Z-machine looking to quantify plasmas within the power flow regions. Measurements were taken in the post-hole convolute and final feed gap regions on Z. Dopants were applied to power flow surfaces and measured spectroscopically. These measurements gave species and density/temperature estimates. Preliminary B-field measurements in the load region were attempted as well. Finally, simulation work using the EMPHASIS, electromagnetic particle in cell code, was conducted using the Z MITL conditions. The purpose of these simulations was to investigate several surface plasma generations models under Z conditions for comparison with experimental data.« less

Anode power deposition in quasi-steady MPD arcs. [accelerator anode heat flux measurement

NASA Technical Reports Server (NTRS)

Saber, A. J.; Jahn, R. G.

1973-01-01

The power deposited in the anode of a quasi-steady MPD accelerator has been measured directly by thermocouples attached to the inside surface of a shell anode which provide a local measurement of anode heat flux. The results over a range of arc currents from 5.5 to 44 kiloamperes and argon mass flows from 1 g/sec to 48 g/sec show that the fraction of the total input power deposited in the anode decreases drastically from 50% at an arc power of 200 kW to 10% at 20 MW, and that anode power is not uniformly deposited in the anode. A theoretical model of the anode heat transfer, including effects of anode work function, electron thermal energy, and anode sheath, can be brought into reasonable agreement with the measurements, provided the effective range of the conduction electrons from within the discharge plasma to the anode surface is properly acknowledged.

Heating power at the substrate, electron temperature, and electron density in 2.45 GHz low-pressure microwave plasma

NASA Astrophysics Data System (ADS)

Kais, A.; Lo, J.; Thérèse, L.; Guillot, Ph.

2018-01-01

To control the temperature during a plasma treatment, an understanding of the link between the plasma parameters and the fundamental process responsible for the heating is required. In this work, the power supplied by the plasma onto the surface of a glass substrate is measured using the calorimetric method. It has been shown that the powers deposited by ions and electrons, and their recombination at the surface are the main contributions to the heating power. Each contribution is estimated according to the theory commonly used in the literature. Using the corona balance, the Modified Boltzmann Plot (MBP) is employed to determine the electron temperature. A correlation between the power deposited by the plasma and the results of the MBP has been established. This correlation has been used to estimate the electron number density independent of the Langmuir probe in considered conditions.

Advanced underground Vehicle Power and Control: The locomotive Research Platform

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

Vehicle Projects LLC

2003-01-28

Develop a fuelcell mine locomotive with metal-hydride hydrogen storage. Test the locomotive for fundamental limitations preventing successful commercialization of hydride fuelcells in underground mining. During Phase 1 of the DOE-EERE sponsored project, FPI and its partner SNL, completed work on the development of a 14.4 kW fuelcell power plant and metal-hydride energy storage. An existing battery-electric locomotive with similar power requirements, minus the battery module, was used as the base vehicle. In March 2001, Atlas Copco Wagner of Portland, OR, installed the fuelcell power plant into the base vehicle and initiated integration of the system into the vehicle. The entiremore » vehicle returned to Sandia in May 2001 for further development and integration. Initial system power-up took place in December 2001. A revision to the original contract, Phase 2, at the request of DOE Golden Field Office, established Vehicle Projects LLC as the new prime contractor,. Phase 2 allowed industry partners to conduct surface tests, incorporate enhancements to the original design by SNL, perform an extensive risk and safety analysis, and test the fuelcell locomotive underground under representative production mine conditions. During the surface tests one of the fuelcell stacks exhibited reduced power output resulting in having to replace both fuelcell stacks. The new stacks were manufactured with new and improved technology resulting in an increase of the gross power output from 14.4 kW to 17 kW. Further work by CANMET and Hatch Associates, an engineering consulting firm specializing in safety analysis for the mining industry, both under subcontract to Vehicle Projects LLC, established minimum requirements for underground testing. CANMET upgraded the Programmable Logic Control (PLC) software used to monitor and control the fuelcell power plant, taking into account locomotive operator's needs. Battery Electric, a South Africa manufacturer, designed and manufactured (at no cost to the project) a new motor controller capable of operating the higher rpm motor and different power characteristics of the fuelcells. In early August 2002, CANMET, with the technical assistance of Nuvera Fuel Cells and Battery Electric, installed the new PLC software, installed the new motor controller, and installed the new fuelcell stacks. After minor adjustments, the fuelcell locomotive pulled its first fully loaded ore cars on a surface track. The fuelcell-powered locomotive easily matched the battery powered equivalent in its ability to pull tonnage and equaled the battery-powered locomotive in acceleration. The final task of Phase 2, testing the locomotive underground in a production environment, occurred in early October 2002 in a gold mine. All regulatory requirements to allow the locomotive underground were completed and signed off by Hatch Associates prior to going underground. During the production tests, the locomotive performed flawlessly with no failures or downtime. The actual tests occurred during a 2-week period and involved moving both gold ore and waste rock over a 1,000 meter track. Refueling, or recharging, of the metal-hydride storage took place on the surface. After each shift, the metal-hydride storage module was removed from the locomotive, transported to surface, and filled with hydrogen from high-pressure tanks. The beginning of each shift started with taking the fully recharged metal-hydride storage module down into the mine and re-installing it onto the locomotive. Each 8 hour shift consumed approximately one half to two thirds of the onboard hydrogen. This indicates that the fuelcell-powered locomotive can work longer than a similar battery-powered locomotive, which operates about 6 hours, before needing a recharge.« less

Fission Surface Power Systems (FSPS) Project Final Report for the Exploration Technology Development Program (ETDP): Fission Surface Power, Transition Face to Face

NASA Technical Reports Server (NTRS)

Palac, Donald T.

2011-01-01

The Fission Surface Power Systems Project became part of the ETDP on October 1, 2008. Its goal was to demonstrate fission power system technology readiness in an operationally relevant environment, while providing data on fission system characteristics pertinent to the use of a fission power system on planetary surfaces. During fiscal years 08 to 10, the FSPS project activities were dominated by hardware demonstrations of component technologies, to verify their readiness for inclusion in the fission surface power system. These Pathfinders demonstrated multi-kWe Stirling power conversion operating with heat delivered via liquid metal NaK, composite Ti/H2O heat pipe radiator panel operations at 400 K input water temperature, no-moving-part electromagnetic liquid metal pump operation with NaK at flight-like temperatures, and subscale performance of an electric resistance reactor simulator capable of reproducing characteristics of a nuclear reactor for the purpose of system-level testing, and a longer list of component technologies included in the attached report. Based on the successful conclusion of Pathfinder testing, work began in 2010 on design and development of the Technology Demonstration Unit (TDU), a full-scale 1/4 power system-level non-nuclear assembly of a reactor simulator, power conversion, heat rejection, instrumentation and controls, and power management and distribution. The TDU will be developed and fabricated during fiscal years 11 and 12, culminating in initial testing with water cooling replacing the heat rejection system in 2012, and complete testing of the full TDU by the end of 2014. Due to its importance for Mars exploration, potential applicability to missions preceding Mars missions, and readiness for an early system-level demonstration, the Enabling Technology Development and Demonstration program is currently planning to continue the project as the Fission Power Systems project, including emphasis on the TDU completion and testing.

An underground nuclear power station using self-regulating heat-pipe controlled reactors

DOEpatents

Hampel, V.E.

1988-05-17

A nuclear reactor for generating electricity is disposed underground at the bottom of a vertical hole that can be drilled using conventional drilling technology. The primary coolant of the reactor core is the working fluid in a plurality of thermodynamically coupled heat pipes emplaced in the hole between the heat source at the bottom of the hole and heat exchange means near the surface of the earth. Additionally, the primary coolant (consisting of the working fluid in the heat pipes in the reactor core) moderates neutrons and regulates their reactivity, thus keeping the power of the reactor substantially constant. At the end of its useful life, the reactor core may be abandoned in place. Isolation from the atmosphere in case of accident or for abandonment is provided by the operation of explosive closures and mechanical valves emplaced along the hole. This invention combines technology developed and tested for small, highly efficient, space-based nuclear electric power plants with the technology of fast- acting closure mechanisms developed and used for underground testing of nuclear weapons. This invention provides a nuclear power installation which is safe from the worst conceivable reactor accident, namely, the explosion of a nuclear weapon near the ground surface of a nuclear power reactor. 5 figs.

Underground nuclear power station using self-regulating heat-pipe controlled reactors

DOEpatents

Hampel, Viktor E.

1989-01-01

A nuclear reactor for generating electricity is disposed underground at the bottom of a vertical hole that can be drilled using conventional drilling technology. The primary coolant of the reactor core is the working fluid in a plurality of thermodynamically coupled heat pipes emplaced in the hole between the heat source at the bottom of the hole and heat exchange means near the surface of the earth. Additionally, the primary coolant (consisting of the working flud in the heat pipes in the reactor core) moderates neutrons and regulates their reactivity, thus keeping the power of the reactor substantially constant. At the end of its useful life, the reactor core may be abandoned in place. Isolation from the atmosphere in case of accident or for abandonment is provided by the operation of explosive closures and mechanical valves emplaced along the hole. This invention combines technology developed and tested for small, highly efficient, space-based nuclear electric power plants with the technology of fast-acting closure mechanisms developed and used for underground testing of nuclear weapons. This invention provides a nuclear power installation which is safe from the worst conceivable reactor accident, namely, the explosion of a nuclear weapon near the ground surface of a nuclear power reactor.

30 CFR 77.902-3 - Attachment of ground conductors and ground check wires to equipment frames; use of separate...

Code of Federal Regulations, 2012 CFR

2012-07-01

... SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.902-3 Attachment of ground conductors and ground check wires to... equipment receiving power from resistance grounded systems, separate connections shall be used. ...

30 CFR 77.902-3 - Attachment of ground conductors and ground check wires to equipment frames; use of separate...

Code of Federal Regulations, 2014 CFR

2014-07-01

... SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.902-3 Attachment of ground conductors and ground check wires to... equipment receiving power from resistance grounded systems, separate connections shall be used. ...

30 CFR 77.902-3 - Attachment of ground conductors and ground check wires to equipment frames; use of separate...

Code of Federal Regulations, 2013 CFR

2013-07-01

... SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.902-3 Attachment of ground conductors and ground check wires to... equipment receiving power from resistance grounded systems, separate connections shall be used. ...

Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module

DTIC Science & Technology

2015-02-01

executed with SolidWorks Flow Simulation , a computational fluid-dynamics code. The graph in Fig. 2 shows the timing and amplitudes of power pulses...defined a convective flow of air perpendicular to the bottom surface of the mounting plate, with a velocity of 10 ft/s. The thermal simulations were...Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module by Gregory K Ovrebo ARL-TR-7210

The Principle and the Application of Self-cleaning Anti-pollution Coating in Power System

NASA Astrophysics Data System (ADS)

Zhao, Y. J.; Zhang, Z. B.; Liu, Y.; Wang, J. H.; Teng, J. L.; Wu, L. S.; Zhang, Y. L.

2017-11-01

The common problem existed in power system is analyzed in this paper. The main reason for the affection of the safe and stable operation to power equipment is flash-over caused by dirt and discharge. Using the self-cleaning anti-pollution coating in the power equipment surface is the key to solve the problem. In the work, the research progress and design principle about the self-cleaning anti-pollution coating was summarized. Furthermore, the preparation technology was also studied. Finally, the application prospect of hard self-cleaning anti-pollution coating in power system was forecast.

Design and Build of Reactor Simulator for Fission Surface Power Technology Demonstrator Unit

NASA Technical Reports Server (NTRS)

Godfroy, Thomas; Dickens, Ricky; Houts, Michael; Pearson, Boise; Webster, Kenny; Gibson, Marc; Qualls, Lou; Poston, Dave; Werner, Jim; Radel, Ross

2011-01-01

The Nuclear Systems Team at NASA Marshall Space Flight Center (MSFC) focuses on technology development for state of the art capability in non-nuclear testing of nuclear system and Space Nuclear Power for fission reactor systems for lunar and Mars surface power generation as well as radioisotope power systems for both spacecraft and surface applications. Currently being designed and developed is a reactor simulator (RxSim) for incorporation into the Technology Demonstrator Unit (TDU) for the Fission Surface Power System (FSPS) Program, which is supported by multiple national laboratories and NASA centers. The ultimate purpose of the RxSim is to provide heated NaK to a pair of Stirling engines in the TDU. The RxSim includes many different systems, components, and instrumentation that have been developed at MSFC while working with pumped NaK systems and in partnership with the national laboratories and NASA centers. The main components of the RxSim are a core, a pump, a heat exchanger (to mimic the thermal load of the Stirling engines), and a flow meter for tests at MSFC. When tested at NASA Glenn Research Center (GRC) the heat exchanger will be replaced with a Stirling power conversion engine. Additional components include storage reservoirs, expansion volumes, overflow catch tanks, safety and support hardware, instrumentation (temperature, pressure, flow) for data collection, and power supplies. This paper will discuss the design and current build status of the RxSim for delivery to GRC in early 2012.

Design and Build of Reactor Simulator for Fission Surface Power Technology Demonstrator Unit

NASA Astrophysics Data System (ADS)

Godfroy, T.; Dickens, R.; Houts, M.; Pearson, B.; Webster, K.; Gibson, M.; Qualls, L.; Poston, D.; Werner, J.; Radel, R.

The Nuclear Systems Team at Marshall Space Flight Center (MSFC) focuses on technology development for state of the art capability in non-nuclear testing of nuclear system and Space Nuclear Power for fission reactor systems for lunar and mars surface power generation as well as radioisotope power systems for both spacecraft and surface applications. Currently being designed and developed is a reactor simulator (RxSim) for incorporation into the Technology Demonstrator Unit (TDU) for the Fission Surface Power System (FSPS) Program which is supported by multiple national laboratories and NASA centers. The ultimate purpose of the RxSim is to provide heated NaK to a pair of Stirling engines in the TDU. The RxSim includes many different systems, components, and instrumentation that have been developed at MSFC while working with pumped NaK systems and in partnership with the national laboratories and NASA centers. The main components of the RxSim are a core, a pump, a heat exchanger (to mimic the thermal load of the Stirling engines), and a flow meter when being tested at MSFC. When tested at GRC the heat exchanger will be replaced with a Stirling power conversion engine. Additional components include storage reservoirs, expansion volumes, overflow catch tanks, safety and support hardware, instrumenta- tion (temperature, pressure, flow) data collection, and power supplies. This paper will discuss the design and current build status of the RxSim for delivery to GRC in early 2012.

Continued Investigation of Leakage and Power Loss Test Results for Competing Turbine Engine Seals

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.; Proctor, Margaret P.

2006-01-01

Secondary seal leakage in jet engine applications results in power losses to the engine cycle. Likewise, seal power loss in jet engines not only result in efficiency loss but also increase the heat input into the engine resulting in reduced component lives. Experimental work on labyrinth and annular seals was performed at NASA Glenn Research Center to quantify seal leakage and power loss at various temperatures, seal pressure differentials, and surface speeds. Data from annular and labyrinth seals are compared with previous brush and finger seal test results. Data are also compared to literature. Annular and labyrinth seal leakage rates are 2 to 3 times greater than brush and finger seal rates. Seal leakage decreases with increasing speed but increases with increasing test temperature due to thermal expansion mismatch. Also seal power loss increases with surface speed, seal pressure differential, mass flow rate, and radial clearance. Annular and labyrinth seal power losses were higher than those of brush or finger seal data. The brush seal power loss was 15 to 30 percent lower than annular and labyrinth seal power loss.

Work function and surface stability of tungsten-based thermionic electron emission cathodes

NASA Astrophysics Data System (ADS)

Jacobs, Ryan; Morgan, Dane; Booske, John

2017-11-01

Materials that exhibit a low work function and therefore easily emit electrons into vacuum form the basis of electronic devices used in applications ranging from satellite communications to thermionic energy conversion. W-Ba-O is the canonical materials system that functions as the thermionic electron emitter commercially used in a range of high-power electron devices. However, the work functions, surface stability, and kinetic characteristics of a polycrystalline W emitter surface are still not well understood or characterized. In this study, we examined the work function and surface stability of the eight lowest index surfaces of the W-Ba-O system using density functional theory methods. We found that under the typical thermionic cathode operating conditions of high temperature and low oxygen partial pressure, the most stable surface adsorbates are Ba-O species with compositions in the range of Ba0.125O-Ba0.25O per surface W atom, with O passivating all dangling W bonds and Ba creating work function-lowering surface dipoles. Wulff construction analysis reveals that the presence of O and Ba significantly alters the surface energetics and changes the proportions of surface facets present under equilibrium conditions. Analysis of previously published data on W sintering kinetics suggests that fine W particles in the size range of 100-500 nm may be at or near equilibrium during cathode synthesis and thus may exhibit surface orientation fractions well described by the calculated Wulff construction.

Method of processing a substrate

DOEpatents

Babayan, Steven E [Huntington Beach, CA; Hicks, Robert F [Los Angeles, CA

2008-02-12

The invention is embodied in a plasma flow device or reactor having a housing that contains conductive electrodes with openings to allow gas to flow through or around them, where one or more of the electrodes are powered by an RF source and one or more are grounded, and a substrate or work piece is placed in the gas flow downstream of the electrodes, such that said substrate or work piece is substantially uniformly contacted across a large surface area with the reactive gases emanating therefrom. The invention is also embodied in a plasma flow device or reactor having a housing that contains conductive electrodes with openings to allow gas to flow through or around them, where one or more of the electrodes are powered by an RF source and one or more are grounded, and one of the grounded electrodes contains a means of mixing in other chemical precursors to combine with the plasma stream, and a substrate or work piece placed in the gas flow downstream of the electrodes, such that said substrate or work piece is contacted by the reactive gases emanating therefrom. In one embodiment, the plasma flow device removes organic materials from a substrate or work piece, and is a stripping or cleaning device. In another embodiment, the plasma flow device kills biological microorganisms on a substrate or work piece, and is a sterilization device. In another embodiment, the plasma flow device activates the surface of a substrate or work piece, and is a surface activation device. In another embodiment, the plasma flow device etches materials from a substrate or work piece, and is a plasma etcher. In another embodiment, the plasma flow device deposits thin films onto a substrate or work piece, and is a plasma-enhanced chemical vapor deposition device or reactor.

Surface Tension Mediated Conversion of Light to Work

PubMed Central

Okawa, David; Pastine, Stefan J.; Zettl, Alex; Fréchet, Jean M. J.

2009-01-01

As energy demands increase, new, more direct, energy collection and utilization processes must be explored. We present a system that intrinsically combines the absorption of sunlight with the production of useful work in the form of locomotion of objects on liquids. Focused sunlight is locally absorbed by a nanostructured composite, creating a thermal surface tension gradient and, subsequently, motion. Controlled linear motion and rotational motion are demonstrated. The system is scale independent, with remotely powered and controlled motion shown for objects in the milligram to tens of grams range. PMID:20560635

Keep Laptop Cool with Simple Custom Riser

ERIC Educational Resources Information Center

Rynone, William

2012-01-01

Although the author's netbook computer--a diminished capacity laptop computer--uses less power than its big brother, when working with it on his lap, his thighs are roasted, even in the winter. When using the unit on a flat surface, such as a table top, the bottom surface of the computer and table top become quite warm--and it is generally…

A metamaterial electromagnetic energy rectifying surface with high harvesting efficiency

NASA Astrophysics Data System (ADS)

Duan, Xin; Chen, Xing; Zhou, Lin

2016-12-01

A novel metamaterial rectifying surface (MRS) for electromagnetic energy capture and rectification with high harvesting efficiency is presented. It is fabricated on a three-layer printed circuit board, which comprises an array of periodic metamaterial particles in the shape of mirrored split rings, a metal ground, and integrated rectifiers employing Schottky diodes. Perfect impedance matching is engineered at two interfaces, i.e. one between free space and the surface, and the other between the metamaterial particles and the rectifiers, which are connected through optimally positioned vias. Therefore, the incident electromagnetic power is captured with almost no reflection by the metamaterial particles, then channeled maximally to the rectifiers, and finally converted to direct current efficiently. Moreover, the rectifiers are behind the metal ground, avoiding the disturbance of high power incident electromagnetic waves. Such a MRS working at 2.45 GHz is designed, manufactured and measured, achieving a harvesting efficiency up to 66.9% under an incident power density of 5 mW/cm2, compared with a simulated efficiency of 72.9%. This high harvesting efficiency makes the proposed MRS an effective receiving device in practical microwave power transmission applications.

Effect of Laser Power on Metallurgical, Mechanical and Tribological Characteristics of Hardfaced Surfaces of Nickel-Based Alloy

NASA Astrophysics Data System (ADS)

Gnanasekaran, S.; Padmanaban, G.; Balasubramanian, V.

2017-12-01

In this present work, nickel based alloy was deposited on 316 LN austenitic stainless steel (ASS) by a laser hardfacing technique to investigate the influence of laser power on macrostructure, microstructure, microhardness, dilution and wear characteristics. The laser power varied from 1.1 to 1.9 kW. The phase constitution, microstructure and microhardness were examined by optical microscope, scanning electron microscopy, energy dispersion spectroscopy and Vickers microhardness tester. The wear characteristics of the hardfaced surfaces and substrate were evaluated at room temperature (RT) under dry sliding wear condition (pin-on-disc). The outcome demonstrates that as the laser power increases, dilution increases and hardness of the deposit decreases. This is because excess heat melts more volume of substrate material and increases the dilution; subsequently it decreases the hardness of the deposit. The microstructure of the deposit is characterized by Ni-rich carbide, boride and silicide.

Application of the mobility power flow approach to structural response from distributed loading

NASA Technical Reports Server (NTRS)

Cuschieri, J. M.

1988-01-01

The problem of the vibration power flow through coupled substructures when one of the substructures is subjected to a distributed load is addressed. In all the work performed thus far, point force excitation was considered. However, in the case of the excitation of an aircraft fuselage, distributed loading on the whole surface of a panel can be as important as the excitation from directly applied forces at defined locations on the structures. Thus using a mobility power flow approach, expressions are developed for the transmission of vibrational power between two coupled plate substructures in an L configuration, with one of the surfaces of one of the plate substructures being subjected to a distributed load. The types of distributed loads that are considered are a force load with an arbitrary function in space and a distributed load similar to that from acoustic excitation.

Tunneling of spoof surface plasmon polaritons through magnetoinductive metamaterial channels

NASA Astrophysics Data System (ADS)

Xu, Zhixia; Liu, Siyuan; Li, Shunli; Zhao, Hongxin; Liu, Leilei; Yin, Xiaoxing

2018-04-01

In this work, we realize tunneling propagation through spoof surface plasmon polariton transmission lines loaded with magnetoinductive metamaterial channels above a high cutoff frequency. Magnetoinductive metamaterial channels consist of split-ring resonators, and two different structures are proposed. Samples are fabricated, and both measurements and simulations indicate a near-perfect tunneling propagation around 17 GHz. The proposed methodology could be exploited as a powerful platform for investigating tunneling surface plasmons from radio frequencies to optical frequencies.

A large-eddy simulation based power estimation capability for wind farms over complex terrain

NASA Astrophysics Data System (ADS)

Senocak, I.; Sandusky, M.; Deleon, R.

2017-12-01

There has been an increasing interest in predicting wind fields over complex terrain at the micro-scale for resource assessment, turbine siting, and power forecasting. These capabilities are made possible by advancements in computational speed from a new generation of computing hardware, numerical methods and physics modelling. The micro-scale wind prediction model presented in this work is based on the large-eddy simulation paradigm with surface-stress parameterization. The complex terrain is represented using an immersed-boundary method that takes into account the parameterization of the surface stresses. Governing equations of incompressible fluid flow are solved using a projection method with second-order accurate schemes in space and time. We use actuator disk models with rotation to simulate the influence of turbines on the wind field. Data regarding power production from individual turbines are mostly restricted because of proprietary nature of the wind energy business. Most studies report percentage drop of power relative to power from the first row. There have been different approaches to predict power production. Some studies simply report available wind power in the upstream, some studies estimate power production using power curves available from turbine manufacturers, and some studies estimate power as torque multiplied by rotational speed. In the present work, we propose a black-box approach that considers a control volume around a turbine and estimate the power extracted from the turbine based on the conservation of energy principle. We applied our wind power prediction capability to wind farms over flat terrain such as the wind farm over Mower County, Minnesota and the Horns Rev offshore wind farm in Denmark. The results from these simulations are in good agreement with published data. We also estimate power production from a hypothetical wind farm in complex terrain region and identify potential zones suitable for wind power production.

30 CFR 75.705-1 - Work on high-voltage lines.

Code of Federal Regulations, 2011 CFR

2011-07-01

... wye-connected systems, the neutral wire is the system-grounding medium. In the case of an ungrounded power system, either the steel armor or conduit enclosing the system or a surface grounding field is a...

30 CFR 75.705-1 - Work on high-voltage lines.

Code of Federal Regulations, 2010 CFR

2010-07-01

... wye-connected systems, the neutral wire is the system-grounding medium. In the case of an ungrounded power system, either the steel armor or conduit enclosing the system or a surface grounding field is a...

Synthesis of Ag and Au nanoparticles embedded in carbon film: Optical, crystalline and topography analysis

NASA Astrophysics Data System (ADS)

Gholamali, Hediyeh; Shafiekhani, Azizollah; Darabi, Elham; Elahi, Seyed Mohammad

2018-03-01

Atomic force microscopy (AFM) images give valuable information about surface roughness of thin films based on the results of power spectral density (PSD) through the fast Fourier transform (FFT) algorithms. In the present work, AFM data are studied for silver and gold nanoparticles (Ag NPs a-C: H and Au NPs a-C: H) embedded in amorphous hydrogenated carbon films and co-deposited on glass substrate via of RF-Sputtering and RF-Plasma Enhanced Chemical Vapor Deposition methods. Here, the working gas is acetylene and the targets are Ag and Au. While time and power are constant, the only variable parameter in this study is initial pressure. In addition, the crystalline structure of Ag NPs a-C: H and Au NPs a-C: H are studied using X-ray diffraction (XRD). UV-visible spectrophotometry will also investigate optical properties and localized surface plasmon resonance (LSPR) of samples.

Surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding

NASA Astrophysics Data System (ADS)

Abd El-Rahman, A. M.; Maitz, M. F.; Kassem, M. A.; El-Hossary, F. M.; Prokert, F.; Reuther, H.; Pham, M. T.; Richter, E.

2007-09-01

The present work describes the surface improvement and biocompatibility of TiAl 24Nb 10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400 W to 650 W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400 W.

An efficient computational method for characterizing the effects of random surface errors on the average power pattern of reflectors

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.

1983-01-01

Based on the works of Ruze (1966) and Vu (1969), a novel mathematical model has been developed to determine efficiently the average power pattern degradations caused by random surface errors. In this model, both nonuniform root mean square (rms) surface errors and nonuniform illumination functions are employed. In addition, the model incorporates the dependence on F/D in the construction of the solution. The mathematical foundation of the model rests on the assumption that in each prescribed annular region of the antenna, the geometrical rms surface value is known. It is shown that closed-form expressions can then be derived, which result in a very efficient computational method for the average power pattern. Detailed parametric studies are performed with these expressions to determine the effects of different random errors and illumination tapers on parameters such as gain loss and sidelobe levels. The results clearly demonstrate that as sidelobe levels decrease, their dependence on the surface rms/wavelength becomes much stronger and, for a specified tolerance level, a considerably smaller rms/wavelength is required to maintain the low sidelobes within the required bounds.

Modulation of joint moments and work in the goat hindlimb with locomotor speed and surface grade

PubMed Central

Arnold, Allison S.; Lee, David V.; Biewener, Andrew A.

2013-01-01

SUMMARY Goats and other quadrupeds must modulate the work output of their muscles to accommodate the changing mechanical demands associated with locomotion in their natural environments. This study examined which hindlimb joint moments goats use to generate and absorb mechanical energy on level and sloped surfaces over a range of locomotor speeds. Ground reaction forces and the three-dimensional locations of joint markers were recorded as goats walked, trotted and galloped over 0, +15 and −15 deg sloped surfaces. Net joint moments, powers and work were estimated at the goats' hip, knee, ankle and metatarsophalangeal joints throughout the stance phase via inverse dynamics calculations. Differences in locomotor speed on the level, inclined and declined surfaces were characterized and accounted for by fitting regression equations to the joint moment, power and work data plotted versus non-dimensionalized speed. During level locomotion, the net work generated by moments at each of the hindlimb joints was small (less than 0.1 J kg−1 body mass) and did not vary substantially with gait or locomotor speed. During uphill running, by contrast, mechanical energy was generated at the hip, knee and ankle, and the net work at each of these joints increased dramatically with speed (P<0.05). The greatest increases in positive joint work occurred at the hip and ankle. During downhill running, mechanical energy was decreased in two main ways: goats generated larger knee extension moments in the first half of stance, absorbing energy as the knee flexed, and goats generated smaller ankle extension moments in the second half of stance, delivering less energy. The goats' hip extension moment in mid-stance was also diminished, contributing to the decrease in energy. These analyses offer new insight into quadrupedal locomotion, clarifying how the moments generated by hindlimb muscles modulate mechanical energy at different locomotor speeds and grades, as needed to accommodate the demands of variable terrain. PMID:23470662

Broadband changes in the cortical surface potential track activation of functionally diverse neuronal populations

PubMed Central

Miller, Kai J; Honey, Christopher J; Hermes, Dora; Rao, Rajesh PN; denNijs, Marcel; Ojemann, Jeffrey G

2013-01-01

We illustrate a general principal of electrical potential measurements from the surface of the cerebral cortex, by revisiting and reanalyzing experimental work from the visual, language and motor systems. A naïve decomposition technique of electrocorticographic power spectral measurements reveals that broadband spectral changes reliably track task engagement. These broadband changes are shown to be a generic correlate of local cortical function across a variety of brain areas and behavioral tasks. Furthermore, they fit a power-law form that is consistent with simple models of the dendritic integration of asynchronous local population firing. Because broadband spectral changes covary with diverse perceptual and behavioral states on the timescale of 20–50ms, they provide a powerful and widely applicable experimental tool. PMID:24018305

Analysis of key factors influencing the evaporation performances of an oriented linear cutting copper fiber sintered felt

NASA Astrophysics Data System (ADS)

Pan, Minqiang; Zhong, Yujian

2018-01-01

Porous structure can effectively enhance the heat transfer efficiency. A kind of micro vaporizer using the oriented linear cutting copper fiber sintered felt is proposed in this work. Multiple long cutting copper fibers are firstly fabricated with a multi-tooth tool and then sintered together in parallel to form uniform thickness metal fiber sintered felts that provided a characteristic of oriented microchannels. The temperature rise response and thermal conversion efficiency are experimentally investigated to evaluate the influences of porosity, surface structure, feed flow rate and input power on the evaporation characteristics. It is indicated that the temperature rise response of water is mainly affected by input power and feed flow rate. High input power and low feed flow rate present better temperature rise response of water. Porosity rather than surface structure plays an important role in the temperature rise response of water at a relatively high input power. The thermal conversion efficiency is dominated by the input power and surface structure. The oriented linear cutting copper fiber sintered felts for three kinds of porosities show better thermal conversion efficiency than that of the oriented linear copper wire sintered felt when the input power is less than 115 W. All the sintered felts have almost the same performance of thermal conversion at a high input power.

Carbon Nanotube-Silicon Nanowire Heterojunction Solar Cells with Gas-Dependent Photovoltaic Performances and Their Application in Self-Powered NO2 Detecting.

PubMed

Jia, Yi; Zhang, Zexia; Xiao, Lin; Lv, Ruitao

2016-12-01

A multifunctional device combining photovoltaic conversion and toxic gas sensitivity is reported. In this device, carbon nanotube (CNT) membranes are used to cover onto silicon nanowire (SiNW) arrays to form heterojunction. The porous structure and large specific surface area in the heterojunction structure are both benefits for gas adsorption. In virtue of these merits, gas doping is a feasible method to improve cell's performance and the device can also work as a self-powered gas sensor beyond a solar cell. It shows a significant improvement in cell efficiency (more than 200 times) after NO2 molecules doping (device working as a solar cell) and a fast, reversible response property for NO2 detection (device working as a gas sensor). Such multifunctional CNT-SiNW structure can be expected to open a new avenue for developing self-powered, efficient toxic gas-sensing devices in the future.

The interaction of spacecraft high voltage power systems with the space plasma environment

NASA Technical Reports Server (NTRS)

Domitz, S.; Grier, N. T.

1974-01-01

Research work has shown that the interaction of a spacecraft and its high voltage power systems with the space plasma environment can result in harmful power loss and damage to insulators and metal surfaces. Insulator and solar panel tests were performed and flight tests are planned. High voltage power processing equipment was shown to be affected by power loss, and by transients due to plasma interactions. Power loss was determined to be roughly proportional to the square of the voltage and increases approximately as the square root of the area. Kapton, Teflon, and glass were found to be satisfactory insulating materials and it is concluded that for large space power stations should consider the effect of large pinhole currents.

A revolutionary concept to improve the efficiency of IC antennas

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

Milanesio, D.; Maggiora, R.

2014-02-12

The successful design of an Ion Cyclotron (IC) antenna mainly relies on the capability of coupling high power to the plasma (MW), feature that is currently reached by allowing rather high voltages (tens of kV) on the unavoidable unmatched part of the feeding lines. This requirement is often responsible of arcs along the transmission lines and other unwanted phenomena that considerably limit the usage of IC launchers. In this work, we suggest and describe a revolutionary approach based on high impedance surfaces, which allows to increase the antenna radiation efficiency and, hence, to highly reduce the imposed voltages to couplemore » the same level of power to the plasma. High-impedance surfaces are periodic metallic structures (patches) displaced usually on top of a dielectric substrate and grounded by means of vertical posts usually embedded inside a dielectric, in a mushroom-like shape. In terms of working properties, high impedance surfaces are electrically thin in-phase reflectors, i.e. they present a high impedance, within a given frequency band, such that the image currents are in-phase with the currents of the antenna itself, thus determining a significant efficiency increase. While the usual design of a high impedance surface requires the presence of a dielectric layer, some alternative solutions can be realized in vacuum, taking advantage of double layers ofmetallic patches. After an introductory part on the properties of high impedance surfaces, this work documents both their design by means of numerical codes and their implementation on a scaled mock-up.« less

A revolutionary concept to improve the efficiency of ion cyclotron antennas

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

Milanesio, D., E-mail: daniele.milanesio@polito.it; Maggiora, R., E-mail: riccardo.maggiora@polito.it

2014-06-15

The successful design of an ion cyclotron (IC) antenna mainly relies on the capability of coupling high power to the plasma (MW), feature that is currently reached by allowing rather high voltages (tens of kV) on the unavoidable unmatched part of the feeding lines. This requirement is often responsible of arcs along the transmission lines and other unwanted phenomena, such as rectification discharges or hotspots, that considerably limit the usage of IC launchers. In this work, we suggest and describe a revolutionary approach based on high impedance surfaces, which allows to increase the antenna radiation efficiency and, hence, to highlymore » reduce the imposed voltages to couple the same level of power to the plasma. High-impedance surfaces are periodic metallic structures (patches) displaced usually on top of a dielectric substrate and grounded by means of vertical posts usually embedded inside a dielectric, in a mushroom-like shape. In terms of working properties, high impedance surfaces are electrically thin in-phase reflectors, i.e., they present a high impedance, within a given frequency band, such that the image currents are in-phase with the currents of the antenna itself, thus determining a significant efficiency increase. While the usual design of a high impedance surface requires the presence of a dielectric layer, some alternative solutions can be realised in vacuum, taking advantage of double layers of metallic patches. After an introductory part on the properties of high impedance surfaces, this work documents both their design by means of numerical codes and their implementation on a scaled mock-up.« less

Barium-Dispenser Thermionic Cathode

NASA Technical Reports Server (NTRS)

Wintucky, Edwin G.; Green, M.; Feinleib, M.

1989-01-01

Improved reservoir cathode serves as intense source of electrons required for high-frequency and often high-output-power, linear-beam tubes, for which long operating lifetime important consideration. High emission-current densities obtained through use of emitting surface of relatively-low effective work function and narrow work-function distribution, consisting of coat of W/Os deposited by sputtering. Lower operating temperatures and enhanced electron emission consequently possible.

30 CFR 77.704-1 - Work on high-voltage lines.

Code of Federal Regulations, 2011 CFR

2011-07-01

... grounded or solid wye-connected systems, the neutral wire is the system grounding medium. In the case of an ungrounded power system, either the steel armor or conduit enclosing the system or a surface grounding field...

30 CFR 77.704-1 - Work on high-voltage lines.

Code of Federal Regulations, 2010 CFR

2010-07-01

... grounded or solid wye-connected systems, the neutral wire is the system grounding medium. In the case of an ungrounded power system, either the steel armor or conduit enclosing the system or a surface grounding field...

Design considerations for space radiators based on the liquid sheet (LSR) concept

NASA Technical Reports Server (NTRS)

Juhasz, Albert J.; Chubb, Donald L.

1991-01-01

Concept development work on space heat rejection subsystems tailored to the requirements of various space power conversion systems is proceeding over a broad front of technologies at NASA LeRC. Included are orbital and planetary surface based radiator concepts utilizing pumped loops, a variety of heat pipe radiator concepts, and the innovative liquid sheet radiator (LSR). The basic feasibility of the LSR concept was investigated in prior work which generated preliminary information indicating the suitability of the LSR concept for space power systems requiring cycle reject heat to be radiated to the space sink at low-to-mid temperatures (300 to 400 K), with silicon oils used for the radiator working fluid. This study is directed at performing a comparative examination of LSR characteristics as they affect the basic design of low earth orbit solar dynamic power conversion systems. The power systems considered were based on the closed Brayton (CBC) and the Free Piston Stirling (FPS) cycles, each with a power output of 2 kWe and using previously tested silicone oil (Dow-Corning Me2) as the radiator working fluid. Conclusions indicate that, due to its ability for direct cold end cooling, an LSR based heat rejection subsystem is far more compatible with a Stirling space power system than with a CBC, which requires LSR coupling by means of an intermediate gas/liquid heat exchanger and adjustment of cycle operating conditions.

The Separation of Blood Components Using Standing Surface Acoustic Waves (SSAWs) Microfluidic Devices: Analysis and Simulation.

PubMed

Soliman, Ahmed M; Eldosoky, Mohamed A; Taha, Taha E

2017-03-29

The separation of blood components (WBCs, RBCs, and platelets) is important for medical applications. Recently, standing surface acoustic wave (SSAW) microfluidic devices are used for the separation of particles. In this paper, the design analysis of SSAW microfluidics is presented. Also, the analysis of SSAW force with Rayleigh angle effect and its attenuation in liquid-loaded substrate, viscous drag force, hydrodynamic force, and diffusion force are explained and analyzed. The analyses are provided for selecting the piezoelectric material, width of the main microchannel, working area of SAW, wavelength, minimum input power required for the separation process, and widths of outlet collecting microchannels. The design analysis of SSAW microfluidics is provided for determining the minimum input power required for the separation process with appropriated the displacement contrast of the particles.The analyses are applied for simulation the separation of blood components. The piezoelectric material, width of the main microchannel, working area of SAW, wavelength, and minimum input power required for the separation process are selected as LiNbO₃, 120 μm, 1.08 mm², 300 μm, 371 mW. The results are compared to other published results. The results of these simulations achieve minimum power consumption, less complicated setup, and high collecting efficiency. All simulation programs are built by MATLAB.

The Separation of Blood Components Using Standing Surface Acoustic Waves (SSAWs) Microfluidic Devices: Analysis and Simulation

PubMed Central

Soliman, Ahmed M.; Eldosoky, Mohamed A.; Taha, Taha E.

2017-01-01

The separation of blood components (WBCs, RBCs, and platelets) is important for medical applications. Recently, standing surface acoustic wave (SSAW) microfluidic devices are used for the separation of particles. In this paper, the design analysis of SSAW microfluidics is presented. Also, the analysis of SSAW force with Rayleigh angle effect and its attenuation in liquid-loaded substrate, viscous drag force, hydrodynamic force, and diffusion force are explained and analyzed. The analyses are provided for selecting the piezoelectric material, width of the main microchannel, working area of SAW, wavelength, minimum input power required for the separation process, and widths of outlet collecting microchannels. The design analysis of SSAW microfluidics is provided for determining the minimum input power required for the separation process with appropriated the displacement contrast of the particles.The analyses are applied for simulation the separation of blood components. The piezoelectric material, width of the main microchannel, working area of SAW, wavelength, and minimum input power required for the separation process are selected as LiNbO3, 120 μm, 1.08 mm2, 300 μm, 371 mW. The results are compared to other published results. The results of these simulations achieve minimum power consumption, less complicated setup, and high collecting efficiency. All simulation programs are built by MATLAB. PMID:28952506

Sol-gel derived electrode materials for supercapacitor applications

NASA Astrophysics Data System (ADS)

Lin, Chuan

1998-12-01

Electrochemical capacitors have been receiving increasing interest in recent years for use in energy storage systems because of their high energy and power density and long cycle lifes. Possible applications of electrochemical capacitors include high power pulsed lasers, hybrid power system for electric vehicles, etc. In this dissertation, the preparation of electrode materials for use as electrochemical capacitors has been studied using the sol-gel process. The high surface area electrode materials explored in this work include a synthetic carbon xerogel for use in a double-layer capacitor, a cobalt oxide xerogel for use in a pseudocapacitor, and a carbon-ruthenium xerogel composite, which utilizes both double-layer and faradaic capacitances. The preparation conditions of these materials were investigated in detail to maximize the surface area and optimize the pore size so that more energy could be stored while minimizing mass transfer limitations. The microstructures of the materials were also correlated with their performance as electrochemical capacitors to improve their energy and power densities. Finally, an idealistic mathematical model, including both double-layer and faradaic processes, was developed and solved numerically. This model can be used to perform the parametric studies of an electrochemical capacitor so as to gain a better understanding of how the capacitor works and also how to improve cell operations and electrode materials design.

Reasons for service failure of an ÉKG-20 power shovel bogie wheel

NASA Astrophysics Data System (ADS)

Yakovleva, S. P.; Milokhin, S. E.

1985-10-01

Early failure of a bogie wheel is caused by the occurrence after heat treatment of a working surface structure with insufficient resistance to plastic deformation, which under the specific conditions of contact loading causes flattening of it with the formation of accumulations of material on the side surfaces. This leads to the occurrence of significant stresses on the faces of the wheel which intensify the nonuniformity of the structure obtained after machining of the side surface.

Cylindrical stationary striations in surface wave produced plasma columns of argon

NASA Astrophysics Data System (ADS)

Kumar, Rajneesh; Kulkarni, Sanjay V.; Bora, Dhiraj

2007-12-01

Striations are a good example of manifestation of a glow discharge. In the present investigation, stationary striations in the surface wave produced plasma column are formed. Physical parameters (length, number, etc.) of such striations can be controlled by operating parameters. With the help of bifurcation theory, experimental results are explained by considering two-step ionization in the surface wave discharge mechanism in argon gas. It is also observed that the bifurcation parameter is a function of input power, working pressure, and tube radius.

Immersion Condensation on Oil-Infused Heterogeneous Surfaces for Enhanced Heat Transfer

PubMed Central

Xiao, Rong; Miljkovic, Nenad; Enright, Ryan; Wang, Evelyn N.

2013-01-01

Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems. Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected. In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil. The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles. Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases. This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer. PMID:23759735

Experimental investigation on the thermal performance of a closed oscillating heat pipe in thermal management

NASA Astrophysics Data System (ADS)

Rao, Zhonghao; Wang, Qingchao; Zhao, Jiateng; Huang, Congliang

2017-10-01

To investigate the thermal performance of the closed oscillating heat pipe (OHP) as a passive heat transfer device in thermal management system, the gravitation force, surface tension, cooling section position and inclination angle were discussed with applied heating power ranging from 5 to 65 W. The deionized water was chosen as the working fluid and liquid-filling ratio was 50 ± 5%. The operation of the OHP mainly depends on the phase change of the working fluid. The working fluid within the OHP was constantly evaporated and cooled. The results show that the movement of the working fluid was similar to the forced damped mechanical vibration, it has to overcome the capillary resistance force and the stable oscillation should be that the OHP could successful startup. The oscillation frequency slowed and oscillation amplitude decreased when the inclination angle of the OHP increased. However, the thermal resistance increased. With the increment of the heating power, the average temperature of the evaporation and condensation section would be close. If the heating power was further increased, dry-out phenomenon within the OHP would appeared. With the decrement of the L, the start-up heating power also decreased and stable oscillation would be formed.

Laser treatment of white China surface

NASA Astrophysics Data System (ADS)

Osvay, K.; Képíró, I.; Berkesi, O.

2006-04-01

The surface of gloss fired porcelain with and without raw glaze coating was radiated by a CO 2 laser working at 10.6 μm, a choice resulted from spectroscopic studies of suspensions made of China. The shine of the untreated sample was defined as the distribution of micro-droplets on the surface. The surface alterations due to laser heating were classified by the diameter of the completely melted surface, the ring of the surface at the threshold of melting, and the size of microscopic cracks. The diameter of the laser treated area was in the range of 3 mm, while the incident laser power and the duration of laser heating were varied between 1 and 10 W and 1-8 min, respectively. The different stages of surface modifications were attributed primarily to the irradiating laser power and proved to be rather insensitive to the duration of the treatment. We have found a range of parameters under which the white China surface coated with raw glaze and followed by laser induced melting exhibited very similar characteristics to the untreated porcelain. This technique seems prosperous for laser assisted reparation of small surface defects of unique China samples after the firing process.

Overview of bureau research directed towards surface powered haulage safety

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

May, J.P.; Aldinger, J.A.

1995-12-31

Surface mining operations, including mills and preparation plants, employ over 260,000 people. This represents a significant contribution to our nation`s economy and an important source of skilled and well-paying jobs. As mine production has shifted from underground to surface, and with continuing advances in underground mine safety, surface mining has unfortunately become the leader in mine fatalities. In 1994 surface mining accidents accounted for 49% of all mine fatalities, followed by underground mining with 37% and mills and preparation plants with 14%. The U.S. Bureau of Mines (USBM) has targeted surface mining as an important research priority to reduce themore » social and economic costs associated with fatalities and lost-work-time injuries. USBM safety research focuses on the development of technologies that can enhance productivity and reduce mining costs through a reduction in the number and severity of mining accidents. This report summarizes a number of completed and ongoing research programs directed towards surface powered haulage--the single largest category of fatalities in surface mining and a major cause of lost workdays. Research products designed for industry are highlighted and future USBM surface mining safety research is discussed.« less

Impacts of propagating, frustrated and surface modes on radiative, electrical and thermal losses in nanoscale-gap thermophotovoltaic power generators.

PubMed

Bernardi, Michael P; Dupré, Olivier; Blandre, Etienne; Chapuis, Pierre-Olivier; Vaillon, Rodolphe; Francoeur, Mathieu

2015-06-26

The impacts of radiative, electrical and thermal losses on the performances of nanoscale-gap thermophotovoltaic (nano-TPV) power generators consisting of a gallium antimonide cell paired with a broadband tungsten and a radiatively-optimized Drude radiator are analyzed. Results reveal that surface mode mediated nano-TPV power generation with the Drude radiator outperforms the tungsten radiator, dominated by frustrated modes, only for a vacuum gap thickness of 10 nm and if both electrical and thermal losses are neglected. The key limiting factors for the Drude- and tungsten-based devices are respectively the recombination of electron-hole pairs at the cell surface and thermalization of radiation with energy larger than the cell absorption bandgap. A design guideline is also proposed where a high energy cutoff above which radiation has a net negative effect on nano-TPV power output due to thermal losses is determined. It is shown that the power output of a tungsten-based device increases by 6.5% while the cell temperature decreases by 30 K when applying a high energy cutoff at 1.45 eV. This work demonstrates that design and optimization of nano-TPV devices must account for radiative, electrical and thermal losses.

Impacts of propagating, frustrated and surface modes on radiative, electrical and thermal losses in nanoscale-gap thermophotovoltaic power generators

PubMed Central

Bernardi, Michael P.; Dupré, Olivier; Blandre, Etienne; Chapuis, Pierre-Olivier; Vaillon, Rodolphe; Francoeur, Mathieu

2015-01-01

The impacts of radiative, electrical and thermal losses on the performances of nanoscale-gap thermophotovoltaic (nano-TPV) power generators consisting of a gallium antimonide cell paired with a broadband tungsten and a radiatively-optimized Drude radiator are analyzed. Results reveal that surface mode mediated nano-TPV power generation with the Drude radiator outperforms the tungsten radiator, dominated by frustrated modes, only for a vacuum gap thickness of 10 nm and if both electrical and thermal losses are neglected. The key limiting factors for the Drude- and tungsten-based devices are respectively the recombination of electron-hole pairs at the cell surface and thermalization of radiation with energy larger than the cell absorption bandgap. A design guideline is also proposed where a high energy cutoff above which radiation has a net negative effect on nano-TPV power output due to thermal losses is determined. It is shown that the power output of a tungsten-based device increases by 6.5% while the cell temperature decreases by 30 K when applying a high energy cutoff at 1.45 eV. This work demonstrates that design and optimization of nano-TPV devices must account for radiative, electrical and thermal losses. PMID:26112658

Flexible Hybrid Battery/Pseudocapacitor

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Paley, Steven

2015-01-01

Batteries keep devices working by utilizing high energy density, however, they can run down and take tens of minutes to hours to recharge. For rapid power delivery and recharging, high-power density devices, i.e., supercapacitors, are used. The electrochemical processes which occur in batteries and supercapacitors give rise to different charge-storage properties. In lithium ion (Li+) batteries, the insertion of Li+, which enables redox reactions in bulk electrode materials, is diffusion controlled and can be slow. Supercapacitor devices, also known as electrical double-layer capacitors (EDLCs) store charge by adsorption of electrolyte ions onto the surface of electrode materials. No redox reactions are necessary, so the response to changes in potential without diffusion limitations is rapid and leads to high power. However, the charge in EDLCs is confined to the surface, so the energy density is lower than that of batteries.

Discharge Characteristic of VHF-DC Superimposed Magnetron Sputtering System

NASA Astrophysics Data System (ADS)

Toyoda, Hirotaka; Fukuoka, Yushi; Fukui, Takashi; Takada, Noriharu; Sasai, Kensuke

2014-10-01

Magnetron plasmas are one of the most important tools for sputter deposition of thin films. However, energetic particles from the sputtered target such as backscattered rare gas atoms or oxygen negative ions from oxide targets sometimes induce physical and chemical damages as well as surface roughening to the deposited film surface during the sputtering processes. To suppress kinetic energy of such particles, superposition of RF or VHF power to the DC power has been investigated. In this study, influence of the VHF power superposition on the DC target voltage, which is important factor to determine kinetic energy of high energy particles, is investigated. In the study, 40 MHz VHF power was superimposed to an ITO target and decrease in the target DC voltage was measured as well as deposited film deposition properties such as deposition rate or electrical conductivity. From systematic measurement of the target voltage, it was revealed that the target voltage can be determined by a very simple parameter, i.e., a ratio of VHF power to the total input power (DC and VHF powers) in spite of the DC discharge current. Part of this work was supported by ASTEP, JST.

UUGM Code Development

DTIC Science & Technology

1993-07-26

atmospheres of at this time. certain solar system planets. The JPL work was directed at very specific applications; however, the Studi"ss-1 7 WorkRe ported in...pressure atmospheres of certain 1-60 Hz. The spark plug power output was varied inversely solar system planets. The JPL work was directed at very with...general case of explosive dust diaper - deposited as a thin layer over the surface area of the sion. We will consider particle density variation from 4

Operational Results From a High Power Alternator Test Bed

NASA Technical Reports Server (NTRS)

Birchenough, Arthur; Hervol, David

2007-01-01

The Alternator Test Unit (ATU) in the Lunar Power System Facility (LPSF) located at the NASA Glenn Research Center (GRC) in Cleveland, Ohio was used to simulate the operating conditions and evaluate the performance of the ATU and its interaction with various LPSF components in accordance with the current Fission Surface Power System (FSPS) requirements. The testing was carried out at the breadboard development level. These results successfully demonstrated excellent ATU power bus characteristics and rectified user load power quality during steady state and transient conditions. Information gained from this work could be used to assist the design and primary power quality considerations for a possible future FSPS. This paper describes the LPSF components and some preliminary test results.

Experimental investigations on the effect of process parameters with the use of minimum quantity solid lubrication in turning

NASA Astrophysics Data System (ADS)

Makhesana, Mayur A.; Patel, K. M.; Mawandiya, B. K.

2018-04-01

Turning process is a very basic process in any field of mechanical application. During turning process, most of the energy is converted into heat because of the friction between work piece and tool. Heat generation can affect the surface quality of the work piece and tool life. To reduce the heat generation, Conventional Lubrication process is used in most of the industry. Minimum quantity lubrication has been an effective alternative to improve the performance of machining process. In this present work, effort has been made to study the effect of various process parameters on the surface roughness and power consumption during turning of EN8 steel material. Result revealed the effect of depth of cut and feed on the obtained surface roughness value. Further the effect of solid lubricant has been also studied and optimization of process parameters is also done for the turning process.

Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter

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

Tom, Nathan M.; Yu, Yi-Hsiang; Wright, Alan D.

The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of themore » controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.« less

Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter: Preprint

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

Tom, Nathan M.; Yu, Yi-Hsiang; Wright, Alan D.

The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of themore » controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.« less

Summary of aerospace and nuclear engineering activities

NASA Technical Reports Server (NTRS)

1988-01-01

The Texas A&M Nuclear and Aerospace engineering departments have worked on five different projects for the NASA/USRA Advanced Design Program during the 1987/88 year. The aerospace department worked on two types of lunar tunnelers that would create habitable space. The first design used a heated cone to melt the lunar regolith, and the second used a conventional drill to bore its way through the crust. Both used a dump truck to get rid of waste heat from the reactor as well as excess regolith from the tunneling operation. The nuclear engineering department worked on three separate projects. The NEPTUNE system is a manned, outer-planetary explorer designed with Jupiter exploration as the baseline mission. The lifetime requirement for both reactor and power-conversion systems was twenty years. The second project undertaken for the power supply was a Mars Sample Return Mission power supply. This was designed to produce 2 kW of electrical power for seven years. The design consisted of a General Purpose Heat Source (GPHS) utilizing a Stirling engine as the power conversion unit. A mass optimization was performed to aid in overall design. The last design was a reactor to provide power for propulsion to Mars and power on the surface. The requirements of 300 kW of electrical power output and a mass of less than 10,000 Rg were set. This allowed the reactor and power conversion unit to fit within the Space Shuttle cargo bay.

A novel carbon electrode material for highly improved EDLC performance.

PubMed

Fang, Baizeng; Binder, Leo

2006-04-20

Porous materials, developed by grafting functional groups through chemical surface modification with a surfactant, represent an innovative concept in energy storage. This work reports, in detail, the first practical realization of a novel carbon electrode based on grafting of vinyltrimethoxysilane (vtmos) functional group for energy storage in electric double layer capacitor (EDLC). Surface modification with surfactant vtmos enhances the hydrophobisation of activated carbon and the affinity toward propylene carbonate (PC) solvent, which improves the wettability of activated carbon in the electrolyte solution based on PC solvent, resulting in not only a lower resistance to the transport of electrolyte ions within micropores of activated carbon but also more usable surface area for the formation of electric double layer, and accordingly, higher specific capacitance, energy density, and power capability available from the capacitor based on modified carbon. Especially, the effects from surface modification become superior at higher discharge rate, at which much better EDLC performance (i.e., much higher energy density and power capability) has been achieved by the modified carbon, suggesting that the modified carbon is a novel and very promising electrode material of EDLC for large current applications where both high energy density and power capability are required.

The effect of oxygen molecule adsorption on lead iodide perovskite surface by first-principles calculation

NASA Astrophysics Data System (ADS)

Ma, Xia-Xia; Li, Ze-Sheng

2018-01-01

Oxygen molecule has a negative effect on perovskite solar cells, which has been investigated experimentally. However, detailed theoretical research is still rare. This study presents a microscopic view to reveal the interaction mechanism between O2 and perovskite based on the first-principles calculation. The results show that O2 is adsorbed on the (100) surface of MAPbI3 perovskite mainly by Van der Waals force. O2 adsorption makes the MAPbI3 surface generate a small number of positive charges, which leads to the increase of the work function of the MAPbI3 surface. This is in agreement with the experimental measurement. And increased work function of MAPbI3 surface is not beneficial to electron transfer from perovskite to electronic extraction layer (such as TiO2). Comparison of the density of states (DOS) of the clean (100) surface and the adsorbed system shows that an in-gap state belonging to O2 appears, which can explain the phenomenon observed from experiments that electron transfers from the surface of perovskite to O2 to form superoxide. The theoretical power conversion efficiency of the system with and without O2 adsorption is evaluated, and it turns out that the power conversion efficiency of the system with O2 adsorption is slightly lower than that of the system without O2 adsorption. This result indicates that avoiding the introduction of O2 molecules between perovskite and electronic extraction layer is beneficial to the perovskite solar cell.

Experimental assessment of spanwise-oscillating dielectric electroactive surfaces for turbulent drag reduction in an air channel flow

NASA Astrophysics Data System (ADS)

Gatti, Davide; Güttler, Andreas; Frohnapfel, Bettina; Tropea, Cameron

2015-05-01

In the present work, wall oscillations for turbulent skin friction drag reduction are realized in an air turbulent duct flow by means of spanwise-oscillating active surfaces based on dielectric electroactive polymers. The actuator system produces spanwise wall velocity oscillations of 820 mm/s semi-amplitude at its resonance frequency of 65 Hz while consuming an active power of a few 100 mW. The actuators achieved a maximum integral drag reduction of 2.4 %. The maximum net power saving, budget of the power benefit and cost of the control, was measured for the first time with wall oscillations. Though negative, the net power saving is order of magnitudes higher than what has been estimated in previous studies. Two new direct numerical simulations of turbulent channel flow show that the finite size of the actuator only partially explains the lower values of integral drag reduction typically achieved in laboratory experiments compared to numerical simulations.

Graphene transparent electrode for enhanced optical power and thermal stability in GaN light-emitting diodes.

PubMed

Youn, Doo-Hyeb; Yu, Young-Jun; Choi, Hongkyw; Kim, Suck-Hwan; Choi, Sung-Yool; Choi, Choon-Gi

2013-02-22

We report an improvement of the optical power and thermal stability of GaN LEDs using a chemically doped graphene transparent conducting layer (TCL) and a low-resistance contact structure. In order to obtain low contact resistance between the TCL and p-GaN surface, a patterned graphene TCL with Cr/Au electrodes is suggested. A bi-layer patterning method of a graphene TCL was utilized to prevent the graphene from peeling off the p-GaN surface. To improve the work function and the sheet resistance of graphene, CVD (chemical vapor deposition) graphene was doped by a chemical treatment using a HNO(3) solution. The effect of the contact resistance on the power degradation of LEDs at a high injection current level was investigated. In addition, the enhancement of the optical power via an increase in the current spreading and a decrease in the potential barrier of the graphene TCL was investigated.

Graphene transparent electrode for enhanced optical power and thermal stability in GaN light-emitting diodes

NASA Astrophysics Data System (ADS)

Youn, Doo-Hyeb; Yu, Young-Jun; Choi, HongKyw; Kim, Suck-Hwan; Choi, Sung-Yool; Choi, Choon-Gi

2013-02-01

We report an improvement of the optical power and thermal stability of GaN LEDs using a chemically doped graphene transparent conducting layer (TCL) and a low-resistance contact structure. In order to obtain low contact resistance between the TCL and p-GaN surface, a patterned graphene TCL with Cr/Au electrodes is suggested. A bi-layer patterning method of a graphene TCL was utilized to prevent the graphene from peeling off the p-GaN surface. To improve the work function and the sheet resistance of graphene, CVD (chemical vapor deposition) graphene was doped by a chemical treatment using a HNO3 solution. The effect of the contact resistance on the power degradation of LEDs at a high injection current level was investigated. In addition, the enhancement of the optical power via an increase in the current spreading and a decrease in the potential barrier of the graphene TCL was investigated.

Rotary-Atomizer Electric Power Generator

NASA Astrophysics Data System (ADS)

Nguyen, Trieu; Tran, Tuan; de Boer, Hans; van den Berg, Albert; Eijkel, Jan C. T.

2015-03-01

We report experimental and theoretical results on a ballistic energy-conversion method based on a rotary atomizer working with a droplet acceleration-deceleration cycle. In a rotary atomizer, liquid is fed onto the center of a rotating flat surface, where it spreads out under the action of the centrifugal force and creates "atomized" droplets at its edge. The advantage of using a rotary atomizer is that the centrifugal force exerted on the fluid on a smooth, large surface is not only a robust form of acceleration, as it avoids clogging, but also easily allows high throughput, and produces high electrical power. We successfully demonstrate an output power of 4.9 mW and a high voltage up to 3120 V. At present, the efficiency of the system is still low (0.14%). However, the conversion mechanism of the system is fully interpreted in this paper, permitting a conceptual understanding of system operation and providing a roadmap for system optimization. This observation will open up a road for building power-generation systems in the near future.

Inductance and resistance measurement method for vessel detection and coil powering in all-surface inductive heating systems composed of outer squircle coils

NASA Astrophysics Data System (ADS)

Kilic, Veli Tayfun; Unal, Emre; Demir, Hilmi Volkan

2017-05-01

In this work, we investigate a method proposed for vessel detection and coil powering in an all-surface inductive heating system composed of outer squircle coils. Besides conventional circular coils, coils with different shapes such as outer squircle coils are used for and enable efficient all-surface inductive heating. Validity of the method, which relies on measuring inductance and resistance values of a loaded coil at different frequencies, is experimentally demonstrated for a coil with shape different from conventional circular coil. Simple setup was constructed with a small coil to model an all-surface inductive heating system. Inductance and resistance maps were generated by measuring coil's inductance and resistance values at different frequencies loaded by a plate made of different materials and located at various positions. Results show that in an induction hob for various coil geometries it is possible to detect a vessel's presence, to identify its material type and to specify its position on the hob surface by considering inductance and resistance of the coil measured on at least two different frequencies. The studied method is important in terms of enabling safe, efficient and user flexible heating in an all-surface inductive heating system by automatically detecting the vessel's presence and powering on only the coils that are loaded by the vessel with predetermined current levels.

A methodology for constraining power in finite element modeling of radiofrequency ablation.

PubMed

Jiang, Yansheng; Possebon, Ricardo; Mulier, Stefaan; Wang, Chong; Chen, Feng; Feng, Yuanbo; Xia, Qian; Liu, Yewei; Yin, Ting; Oyen, Raymond; Ni, Yicheng

2017-07-01

Radiofrequency ablation (RFA) is a minimally invasive thermal therapy for the treatment of cancer, hyperopia, and cardiac tachyarrhythmia. In RFA, the power delivered to the tissue is a key parameter. The objective of this study was to establish a methodology for the finite element modeling of RFA with constant power. Because of changes in the electric conductivity of tissue with temperature, a nonconventional boundary value problem arises in the mathematic modeling of RFA: neither the voltage (Dirichlet condition) nor the current (Neumann condition), but the power, that is, the product of voltage and current was prescribed on part of boundary. We solved the problem using Lagrange multiplier: the product of the voltage and current on the electrode surface is constrained to be equal to the Joule heating. We theoretically proved the equality between the product of the voltage and current on the surface of the electrode and the Joule heating in the domain. We also proved the well-posedness of the problem of solving the Laplace equation for the electric potential under a constant power constraint prescribed on the electrode surface. The Pennes bioheat transfer equation and the Laplace equation for electric potential augmented with the constraint of constant power were solved simultaneously using the Newton-Raphson algorithm. Three problems for validation were solved. Numerical results were compared either with an analytical solution deduced in this study or with results obtained by ANSYS or experiments. This work provides the finite element modeling of constant power RFA with a firm mathematical basis and opens pathway for achieving the optimal RFA power. Copyright © 2016 John Wiley & Sons, Ltd.

Robotics

NASA Technical Reports Server (NTRS)

Ambrose, Robert O.

2007-01-01

Lunar robotic functions include: 1. Transport of crew and payloads on the surface of the moon; 2. Offloading payloads from a lunar lander; 3. Handling the deployment of surface systems; with 4. Human commanding of these functions from inside a lunar vehicle, habitat, or extravehicular (space walk), with Earth-based supervision. The systems that will perform these functions may not look like robots from science fiction. In fact, robotic functions may be automated trucks, cranes and winches. Use of this equipment prior to the crew s arrival or in the potentially long periods without crews on the surface, will require that these systems be computer controlled machines. The public release of NASA's Exploration plans at the 2nd Space Exploration Conference (Houston, December 2006) included a lunar outpost with as many as four unique mobility chassis designs. The sequence of lander offloading tasks involved as many as ten payloads, each with a unique set of geometry, mass and interface requirements. This plan was refined during a second phase study concluded in August 2007. Among the many improvements to the exploration plan were a reduction in the number of unique mobility chassis designs and a reduction in unique payload specifications. As the lunar surface system payloads have matured, so have the mobility and offloading functional requirements. While the architecture work continues, the community can expect to see functional requirements in the areas of surface mobility, surface handling, and human-systems interaction as follows: Surface Mobility 1. Transport crew on the lunar surface, accelerating construction tasks, expanding the crew s sphere of influence for scientific exploration, and providing a rapid return to an ascent module in an emergency. The crew transport can be with an un-pressurized rover, a small pressurized rover, or a larger mobile habitat. 2. Transport Extra-Vehicular Activity (EVA) equipment and construction payloads. 3. Transport habitats and power modules over long distances, pre-positioning them for the arrival of crew on a subsequent lander. Surface Handling 1. Offload surface system payloads from the lander, breaking launch restraints and power/data connections. Payloads may be offloaded to a wheeled vehicle for transport. 2. Deploy payloads from a wheeled vehicle at a field site, placing the payloads in their final use site on the ground or mating them with existing surface systems. 3. Support regolith collection, site preparation, berm construction, or other civil engineering tasks using tools and implements attached to rovers. Human-Systems Interaction 1. Provide a safe command and control interface for suited EVA to ride on and drive the vehicles, making sure that the systems are also safe for working near dismounted crew. 2. Provide an effective control system for IV crew to tele-operate vehicles, cranes and other equipment from inside the surface habitats with evolving independence from Earth. .. Provide a supervisory system that allows machines to be commanded from the ground, working across the Earth-Lunar time delays on the order of 5-10 seconds (round trip) to support operations when crew are not resident on the surface. Technology Development Needs 1. Surface vehicles that can dock, align and mate with outpost equipment such as landers, habitats and fluid/power interfaces. 2. Long life motors, drive trains, seals, motor electronics, sensors, processors, cable harnesses, and dash board displays. 3. Active suspension control, localization, high speed obstacle avoidance, and safety systems for operating near dismounted crew. 4. High specific energy and specific power batteries that are safe, rechargeable, and long lived.

Design and evaluation of a high temperature/pressure supercritical carbon dioxide direct tubular receiver for concentrating solar power applications

NASA Astrophysics Data System (ADS)

Ortega, Jesus Daniel

This work focuses on the development of a solar power thermal receiver for a supercritical-carbon dioxide (sCO2), Brayton power-cycle to produce ~1 MWe. Closed-loop sCO2 Brayton cycles are being evaluated in combination with concentrating solar power to provide higher thermal-to-electric conversion efficiencies relative to conventional steam Rankine cycles. High temperatures (923--973 K) and pressures (20--25 MPa) are required in the solar receiver to achieve thermal efficiencies of ~50%, making concentrating solar power (CSP) technologies a competitive alternative to current power generation methods. In this study, the CSP receiver is required to achieve an outlet temperature of 923 K at 25 MPa or 973 K at 20 MPa to meet the operating needs. To obtain compatible receiver tube material, an extensive material review was performed based the ASME Boiler and Pressure Vessel Code, ASME B31.1 and ASME B313.3 codes respectively. Subsequently, a thermal-structural model was developed using a commercial computational fluid (CFD) dynamics and structural mechanics software for designing and analyzing the tubular receiver that could provide the heat input for a ~2 MWth plant. These results were used to perform an analytical cumulative damage creep-fatigue analysis to estimate the work-life of the tubes. In sequence, an optical-thermal-fluid model was developed to evaluate the resulting thermal efficiency of the tubular receiver from the NSTTF heliostat field. The ray-tracing tool SolTrace was used to obtain the heat-flux distribution on the surfaces of the receiver. The K-ω SST turbulence model and P-1 radiation model used in Fluent were coupled with SolTrace to provide the heat flux distribution on the receiver surface. The creep-fatigue analysis displays the damage accumulated due to the cycling and the permanent deformation of the tubes. Nonetheless, they are able to support the required lifetime. The receiver surface temperatures were found to be within the safe operational limit while exhibiting a receiver thermal efficiency of ~85%. Future work includes the completion of a cyclic loading analysis to be performed using the Larson-Miller creep model in nCode Design Life to corroborate the structural integrity of the receiver over the desired lifetime of ~10,000 cycles.

A global plasma model for reactive deposition of compound films by modulated pulsed power magnetron sputtering discharges

NASA Astrophysics Data System (ADS)

Zheng, B. C.; Wu, Z. L.; Wu, B.; Li, Y. G.; Lei, M. K.

2017-05-01

A spatially averaged, time-dependent global plasma model has been developed to describe the reactive deposition of a TiAlSiN thin film by modulated pulsed power magnetron sputtering (MPPMS) discharges in Ar/N2 mixture gas, based on the particle balance and the energy balance in the ionization region, and considering the formation and erosion of the compound at the target surface. The modeling results show that, with increasing the N2 partial pressure from 0% to 40% at a constant working pressure of 0.3 Pa, the electron temperature during the strongly ionized period increases from 4 to 7 eV and the effective power transfer coefficient, which represents the power fraction that effectively heats the electrons and maintains the discharge, increases from about 4% to 7%; with increasing the working pressure from 0.1 to 0.7 Pa at a constant N2 partial pressure of 25%, the electron temperature decreases from 10 to 4 eV and the effective power transfer coefficient decreases from 8% to 5%. Using the modeled plasma parameters to evaluate the kinetic energy of arriving ions, the ion-to-neutral flux ratio of deposited species, and the substrate heating, the variations of process parameters that increase these values lead to an enhanced adatom mobility at the target surface and an increased input energy to the substrate, corresponding to the experimental observation of surface roughness reduction, the microstructure transition from the columnar structure to the dense featureless structure, and the enhancement of phase separation. At higher N2 partial pressure or lower working pressure, the modeling results demonstrate an increase in electron temperature, which shifts the discharge balance of Ti species from Ti+ to Ti2+ and results in a higher return fraction of Ti species, corresponding to the higher Al/Ti ratio of deposited films at these conditions. The modeling results are well correlated with the experimental observation of the composition variation and the microstructure transition of deposited TiAlSiN compound films, demonstrating the applicability of this approach in understanding the characteristics of reactive MPPMS discharges as well as the composition and microstructure of deposited compound films. The model for reactive MPPMS discharges has no special limitations and is applicable to high power impulse magnetron sputtering discharges as well.

Theoretical studies of thermionic conversion of solar energy with graphene as emitter and collector

NASA Astrophysics Data System (ADS)

Olawole, Olukunle C.; De, Dilip Kumar

2018-01-01

Thermionic energy conversion (TEC) using nanomaterials is an emerging field of research. It is known that graphene can withstand temperatures as high as 4600 K in vacuum, and it has been shown that its work function can be engineered from a high value (for monolayer/bilayer) of 4.6 eV to as low as 0.7 eV. Such attractive electronic properties (e.g., good electrical conductivity and high dielectric constant) make engineered graphene a good candidate as an emitter and collector in a thermionic energy converter for harnessing solar energy efficiently. We have used a modified Richardson-Dushman equation and have adopted a model where the collector temperature could be controlled through heat extraction in a calculated amount and a magnet can be attached on the back surface of the collector for future control of the space-charge effect. Our work shows that the efficiency of solar energy conversion also depends on power density falling on the emitter surface, and that a power conversion efficiency of graphene-based solar TEC as high as 55% can be easily achieved (in the absence of the space-charge effect) through proper choice of work functions, collector temperature, and emissivity of emitter surfaces. Such solar energy conversion would reduce our dependence on silicon solar panels and offers great potential for future renewable energy utilization.

Neutron Reflectivity and Grazing Angle Diffraction

PubMed Central

Ankner, J. F.; Majkrzak, C. F.; Satija, S. K.

1993-01-01

Over the last 10 years, neutron reflectivity has emerged as a powerful technique for the investigation of surface and interfacial phenomena in many different fields. In this paper, a short review of some of the work on neutron reflectivity and grazing-angle diffraction as well as a description of the current and planned neutron rcflectometers at NIST is presented. Specific examples of the characterization of magnetic, superconducting, and polymeric surfaces and interfaces are included. PMID:28053457

Surface properties of magnetite in high temperature aqueous electrolyte solutions: A review.

PubMed

Vidojkovic, Sonja M; Rakin, Marko P

2017-07-01

Deposits and scales formed on heat transfer surfaces in power plant water/steam circuits have a significant negative impact on plant reliability, availability and performance, causing tremendous economic consequences and subsequent increases in electricity cost. Consequently, the improvement of the understanding of deposition mechanisms on power generating surfaces is defined as a high priority in the power industry. The deposits consist principally of iron oxides, which are steel corrosion products and usually present in colloidal form. Magnetite (Fe 3 O 4 ) is the predominant and most abundant compound found in water/steam cycles of all types of power plants. The crucial factor that governs the deposition process and influences the deposition rate of magnetite is the electrostatic interaction between the metal wall surfaces and the suspended colloidal particles. However, there is scarcity of data on magnetite surface properties at elevated temperatures due to difficulties in their experimental measurement. In this paper a generalized overview of existing experimental data on surface characteristics of magnetite at high temperatures is presented with particular emphasis on possible application in the power industry. A thorough analysis of experimental techniques, mathematical models and results has been performed and directions for future investigations have been considered. The state-of-the-art assessment showed that for the characterization of magnetite/aqueous electrolyte solution interface at high temperatures acid-base potentiometric titrations and electrophoresis were the most beneficial and dependable techniques which yielded results up to 290 and 200°C, respectively. Mass titrations provided data on magnetite surface charge up to 320°C, however, this technique is highly sensitive to the minor concentrations of impurities present on the surface of particle. Generally, fairly good correlation between the isoelectric point (pH iep ) and point of zero charge (pH pzc ) values has been obtained. All obtained results showed that the surface of magnetite particles is negatively charged in typical high temperature thermal power plant water, which indicates the low probability of aggregation and deposition on plant metal surfaces. The results also gave strong evidence on decline of pH iep and pH pzc with temperature in the same manner as neutral pH of water. The thermodynamic parameters of magnetite surface protonation reactions were in good agreement with each other and obtained using one site/two pK and mainly one site/one pK model. All collected data provided evidences for interaction between particles, probability of deposition and eventual attachment to the steel surface at various pH and temperatures and can serve as a foundation for future surface studies aimed at optimizing plant performances and reducing of magnetite deposition. In future works it would be indispensable to provide the surface experimental data for extended temperature ranges, typical solution chemistries and metal surfaces of power plant structural components and thus obtain entire set of results useful in modeling the surface behavior and control of deposition process in power reactors and thermal plant circuits. Moreover, the acquired results will be applicable and greatly valuable to all other types of power plants, industrial facilities and technological processes using the high temperature water medium. Copyright © 2016 Elsevier B.V. All rights reserved.

Luneburg lens with extended flat focal surface for electronic scan applications.

PubMed

Li, Ying; Zhu, Qi

2016-04-04

Luneburg lens with flat focal surface has been developed to work together with planar antenna feeds for beam steering applications. According to our analysis of the conventional flattened Luneburg lens, it cannot accommodate enough feeding elements which can cover its whole scan range with half power beamwidths (HPBWs). In this paper, a novel Luneburg lens with extended flat focal surface is proposed based on the theory of Quasi-Conformal Transformation Optics (QCTO), with its beam steering features reserved. To demonstrate this design, a three-dimensional (3D) prototype of this novel extend-flattened Luneburg lens working at Ku band is fabricated based on 3D printing techniques, whose flat focal surface is attached to a 9-element microstrip antenna array to achieve different scan angles. Our measured results show that, with different antenna elements being fed, the HPBWs can cover the whole scan range.

Optimisation Of Cutting Parameters Of Composite Material Laser Cutting Process By Taguchi Method

NASA Astrophysics Data System (ADS)

Lokesh, S.; Niresh, J.; Neelakrishnan, S.; Rahul, S. P. Deepak

2018-03-01

The aim of this work is to develop a laser cutting process model that can predict the relationship between the process input parameters and resultant surface roughness, kerf width characteristics. The research conduct is based on the Design of Experiment (DOE) analysis. Response Surface Methodology (RSM) is used in this work. It is one of the most practical and most effective techniques to develop a process model. Even though RSM has been used for the optimization of the laser process, this research investigates laser cutting of materials like Composite wood (veneer)to be best circumstances of laser cutting using RSM process. The input parameters evaluated are focal length, power supply and cutting speed, the output responses being kerf width, surface roughness, temperature. To efficiently optimize and customize the kerf width and surface roughness characteristics, a machine laser cutting process model using Taguchi L9 orthogonal methodology was proposed.

Nanotexturing of polystyrene surface in fluorocarbon plasmas: from sticky to slippery superhydrophobicity.

PubMed

Mundo, Rosa Di; Palumbo, Fabio; d'Agostino, Riccardo

2008-05-06

In this work plasma etching processes have been studied to roughen and fluorinate polystyrene surface as an easy method to achieve a superhydrophobic slippery character. Radiofrequency discharges have been fed with CF(4)/O(2) mixtures and the effect of the O(2):CF(4) ratio, the input power, and the treatment duration have been investigated in terms of wettability, with focus on sliding performances. For this purpose, surface morphological variations, evaluated by means of scanning electron microscopy and atomic force microscopy, together with the chemical assessment by X-ray photoelectron spectroscopy, have been correlated with water contact angle hysteresis and volume resolved sliding angle measurements. Results indicate that by increasing the height and decreasing the density of the structures formed by etching, within a tailored range, a transition from sticky to slippery superhydrophobicity occurs. A short treatment time (5 min) is sufficient to obtain such an effect, provided that a high power input is utilized. Optimized surfaces show a unaltered transparency to visible light according to the low roughness produced.

Gas Surface Interactions Occurring on Materials Within Ultrahigh Vacuum. Ph.D. Thesis - va. Polytechnic Inst.

NASA Technical Reports Server (NTRS)

Outlaw, R. A.

1972-01-01

The physical adsorption of nitrogen on the chemically cleaned surfaces of Pyrex, 347 stainless steel and polycrystalline nickel was investigated over the pressure range 1 x 10 to the minus 12th power to 3 x 10 to the minus 7th power torr and for temperatures 77.4 and 87.4 K. The adsorption data were linearized by the Dubinin-Radushkevich equation. The metal surfaces were cleaned by electron impact desorption (EID) and the desorbed gases analyzed by mass spectrometry. Work function measurements were also used to indicate changes in the surface condition following an EID dose. At least a monolayer of gas was observed to desorb from the metal surfaces. The isotherms revealed that the metal surfaces were very heterogeneous and that the Pyrex surface had been leached. The calculated isosteric heats of adsorption indicated that the relative order of the physical binding of nitrogen to the solids was 347 stainless steel Pyrex nickel. A relationship was observed to exist in the dynamic technique between the equilibration time and the pressure above the absorbed layer. The slope of the log-log plot of these parameters was found to be sensitive to the surface heterogeneity and may be related to the activation energy for surface diffusion of physically absorbed molecules.

Laser dispersing of ceramic powders into Al-alloys

NASA Astrophysics Data System (ADS)

Jendrzejewski, Rafał; Van Acker, Karel; Vanhoyweghen, Dirk

2007-02-01

The general objective of the work was formation of highly wear resistant metal matrix composite (MMC) surface layers on aluminium based Al 6061 alloy by means of laser dispersing. The surface of the substrate is locally melted by the high power diode laser beam and simultaneously powder particles are injected into molten material. The optimal process parameter window for the laser dispersing of SiC in Al 6061 has been found. The measured values of the wear rates of the sample with dispersed SiC particles are about seven times lower than that of the reference Al-substrates. Results show that laser dispersing is highly promising technology to improve the surface, mainly wear properties of light metals. However the possibilities of industrial application are still limited due to considerable laser beam power and preheating temperature applied as well low productivity because of low scanning speed, and therefore further investigations are required.

Ge nanopillar solar cells epitaxially grown by metalorganic chemical vapor deposition

PubMed Central

Kim, Youngjo; Lam, Nguyen Dinh; Kim, Kangho; Park, Won-Kyu; Lee, Jaejin

2017-01-01

Radial junction solar cells with vertically aligned wire arrays have been widely studied to improve the power conversion efficiency. In this work, we report the first Ge nanopillar solar cell. Nanopillar arrays are selectively patterned on p-type Ge (100) substrates using nanosphere lithography and deep reactive ion etching processes. Nanoscale radial and planar junctions are realized by an n-type Ge emitter layer which is epitaxially grown by MOCVD using isobutylgermane. In situ epitaxial surface passivation is employed using an InGaP layer to avoid high surface recombination rates and Fermi level pinning. High quality n-ohmic contact is realized by protecting the top contact area during the nanopillar patterning. The short circuit current density and the power conversion efficiency of the Ge nanopillar solar cell are demonstrated to be improved up to 18 and 30%, respectively, compared to those of the Ge solar cell with a planar surface. PMID:28209964

Broadband absorption enhancement in amorphous Si solar cells using metal gratings and surface texturing

NASA Astrophysics Data System (ADS)

Magdi, Sara; Swillam, Mohamed A.

2017-02-01

The efficiencies of thin film amorphous silicon (a-Si) solar cells are restricted by the small thickness required for efficient carrier collection. This thickness limitations result in poor light absorption. In this work, broadband absorption enhancement is theoretically achieved in a-Si solar cells by using nanostructured back electrode along with surface texturing. The back electrode is formed of Au nanogratings and the surface texturing consists of Si nanocones. The results were then compared to random texturing surfaces. Three dimensional finite difference time domain (FDTD) simulations are used to design and optimize the structure. The Au nanogratings achieved absorption enhancement in the long wavelengths due to sunlight coupling to surface plasmon polaritons (SPP) modes. High absorption enhancement was achieved at short wavelengths due to the decreased reflection and enhanced scattering inside the a-Si absorbing layer. Optimizations have been performed to obtain the optimal geometrical parameters for both the nanogratings and the periodic texturing. In addition, an enhancement factor (i.e. absorbed power in nanostructured device/absorbed power in reference device) was calculated to evaluate the enhancement obtained due to the incorporation of each nanostructure.

Rotational reorganization of doped cholesteric liquid crystalline films.

PubMed

Eelkema, Rienk; Pollard, Michael M; Katsonis, Nathalie; Vicario, Javier; Broer, Dirk J; Feringa, Ben L

2006-11-08

In this paper an unprecedented rotational reorganization of cholesteric liquid crystalline films is described. This rotational reorganization results from the conversion of a chiral molecular motor dopant to an isomer with a different helical twisting power, leading to a change in the cholesteric pitch. The direction of this reorganization is correlated to the sign of the change in helical twisting power of the dopant. The rotational reorganization of the liquid crystalline film was used to rotate microscopic objects 4 orders of magnitude larger than the bistable dopants in the film, which shows that molecular motors and switches can perform work. The surface of the doped cholesteric liquid crystalline films was found to possess a regular surface relief, whose periodicity coincides with typical cholesteric polygonal line textures. These surface features originate from the cholesteric superstructure in the liquid crystalline film, which in turn is the result of the presence of the chiral dopant. As such, the presence of the dopant is expressed in these distinct surface structures. A possible mechanism at the origin of the rotational reorganization of liquid crystalline films and the cholesteric surface relief is discussed.

Lunar base thermal management/power system analysis and design

NASA Technical Reports Server (NTRS)

Mcghee, Jerry R.

1992-01-01

A compilation of several lunar surface thermal management and power system studies completed under contract and IR&D is presented. The work includes analysis and preliminary design of all major components of an integrated thermal management system, including loads determination, active internal acquisition and transport equipment, external transport systems (active and passive), passive insulation, solar shielding, and a range of lunar surface radiator concepts. Several computer codes were utilized in support of this study, including RADSIM to calculate radiation exchange factors and view factors, RADIATOR (developed in-house) for heat rejection system sizing and performance analysis over a lunar day, SURPWER for power system sizing, and CRYSTORE for cryogenic system performance predictions. Although much of the work was performed in support of lunar rover studies, any or all of the results can be applied to a range of surface applications. Output data include thermal loads summaries, subsystem performance data, mass, and volume estimates (where applicable), integrated and worst-case lunar day radiator size/mass and effective sink temperatures for several concepts (shielded and unshielded), and external transport system performance estimates for both single and two-phase (heat pumped) transport loops. Several advanced radiator concepts are presented, along with brief assessments of possible system benefits and potential drawbacks. System point designs are presented for several cases, executed in support of the contract and IR&D studies, although the parametric nature of the analysis is stressed to illustrate applicability of the analysis procedure to a wide variety of lunar surface systems. The reference configuration(s) derived from the various studies will be presented along with supporting criteria. A preliminary design will also be presented for the reference basing scenario, including qualitative data regarding TPS concerns and issues.

Analytical close-form solutions to the elastic fields of solids with dislocations and surface stress

NASA Astrophysics Data System (ADS)

Ye, Wei; Paliwal, Bhasker; Ougazzaden, Abdallah; Cherkaoui, Mohammed

2013-07-01

The concept of eigenstrain is adopted to derive a general analytical framework to solve the elastic field for 3D anisotropic solids with general defects by considering the surface stress. The formulation shows the elastic constants and geometrical features of the surface play an important role in determining the elastic fields of the solid. As an application, the analytical close-form solutions to the stress fields of an infinite isotropic circular nanowire are obtained. The stress fields are compared with the classical solutions and those of complex variable method. The stress fields from this work demonstrate the impact from the surface stress when the size of the nanowire shrinks but becomes negligible in macroscopic scale. Compared with the power series solutions of complex variable method, the analytical solutions in this work provide a better platform and they are more flexible in various applications. More importantly, the proposed analytical framework profoundly improves the studies of general 3D anisotropic materials with surface effects.

Impact of uneven sample morphology on mass resolving power in linear MALDI-TOF mass spectrometry: A comprehensive theoretical investigation.

PubMed

Cai, Yi-Hong; Wang, Yi-Sheng

2018-04-01

This work discusses the correlation between the mass resolving power of matrix-assisted laser desorption/ionization time-of-flight mass analyzers and extraction condition with an uneven sample morphology. Previous theoretical calculations show that the optimum extraction condition for flat samples involves an ideal ion source design and extraction delay. A general expression of spectral feature takes into account ion initial velocity, and extraction delay is derived in the current study. The new expression extends the comprehensive calculation to uneven sample surfaces and above 90% Maxell-Boltzmann initial velocity distribution of ions to account for imperfect ionization condition. Calculation shows that the impact of uneven sample surface or initial spatial spread of ions is negligible when the extraction delay is away from the ideal value. When the extraction delay approaches the optimum value, the flight-time topology shows a characteristic curve shape, and the time-domain mass spectral feature broadens with an increase in initial spatial spread of ions. For protonated 2,5-dihydroxybenzoic acid, the mass resolving power obtained from a sample of 3-μm surface roughness is approximately 3.3 times lower than that of flat samples. For ions of m/z 3000 coexpanded with 2,5-dihydroxybenzoic acid, the mass resolving power in the 3-μm surface roughness case only reduces roughly 7%. Comprehensive calculations also show that the mass resolving power of lighter ions is more sensitive to the accuracy of the extraction delay than heavier ions. Copyright © 2018 John Wiley & Sons, Ltd.

Communications Transceivers for Venus Surface Missions

NASA Technical Reports Server (NTRS)

Force, Dale A.

2004-01-01

The high temperature of the surface of Venus poses many difficulties. Previous Venus landers have only operated for short durations before succumbing to the heat. NASA Glenn Research Center conducted a study on communications for long duration Venus surface missions. I report the findings in this presentation. Current technology allows production of communications transceivers that can operate on the surface of Venus, at temperatures above 450 C and pressures of over 90 atmospheres. While these transceivers would have to be relatively simple, without much of the advanced signal processing often used in modern transceivers, since current and near future integrated circuits cannot operate at such high temperatures, the transceivers will be able to meet the requirements of proposed Venus Surface mission. The communication bands of interest are High Frequency or Very High Frequency (HFNHF) for communication between Venus surface and airborne probes (including surface to surface and air to air), and Ultra High Frequency (UHF) to Microwave bands for communication to orbiters. For HFNHF, transceivers could use existing vacuum tube technology. The packaging of the vacuum tubes may need modification, but the internal operating structure already operates at high temperatures. Using metal vacuum structures instead of glass, allows operation at high pressure. Wide bandgap transistors and diodes may be able to replace some of the thermionic components. VHF communications would be useful for line-of- sight operations, while HF would be useful for short-wave type communications using the Venusian ionosphere. UHF and microwave communications use magnetically focused thermionic devices, such as traveling wave tubes (TWTs), magnetron (M-type) amplifiers, and klystrons for high power amplifiers, and backward wave oscillators (BWOs) and reflex klystrons for oscillators. Permanent magnets are already in use in industry that can operate at 500 C. These magnets could focus electron beam tubes on the surface of Venus. While microwave windows will need to be designed for the high pressure, diamond windows have already been demonstrated, so high-pressure microwave windows can be designed and built. Thus, all of these devices could be useful for Venus surface missions. Current electronic power conditioners to supply the high voltages used in these microwave devices cannot operate at high temperatures, but earlier electronic power conditioners that used vacuum tubes can be modified to work at high temperature. Evaluating the various devices in this study, the M-type traveling wave tube (where a traveling wave structure is used in a crossed-field device, similar to the Amplitron used on the Apollo missions) stood out for the high power amplifier since it requires a single high voltage, simplifying the power supply design. Since the receiver amplifier is a low power amplifier, the loss of efficiency in linear beam devices without a depressed collector (and thus needing a single high voltage) is not important; a low noise TWT is a possible solution. Before solid-state microwave amplifiers were available, such TWTs were built with a 1-2 dB noise figure. A microwave triode or transistor made from a wide bandgap material may be preferable, if available. Much of the development work needed for Venusian communication devices will need to focus on the packaging of the devices, and their connections, but the technology is available to build transceivers that can operate on the surface of Venus indefinitely.

Terahertz wave manipulation based on multi-bit coding artificial electromagnetic surfaces

NASA Astrophysics Data System (ADS)

Li, Jiu-Sheng; Zhao, Ze-Jiang; Yao, Jian-Quan

2018-05-01

A polarization insensitive multi-bit coding artificial electromagnetic surface is proposed for terahertz wave manipulation. The coding artificial electromagnetic surfaces composed of four-arrow-shaped particles with certain coding sequences can generate multi-bit coding in the terahertz frequencies and manipulate the reflected terahertz waves to the numerous directions by using of different coding distributions. Furthermore, we demonstrate that our coding artificial electromagnetic surfaces have strong abilities to reduce the radar cross section with polarization insensitive for TE and TM incident terahertz waves as well as linear-polarized and circular-polarized terahertz waves. This work offers an effectively strategy to realize more powerful manipulation of terahertz wave.

Ultra Low Temperature Ultra Low Power Instrument Packages for Planetary Surfaces

NASA Technical Reports Server (NTRS)

Clark, P. E.; Millar, P. S.; Beaman, B.; Yeh, P. S.; Cooper, L.; Feng, S.; Young, E.

2010-01-01

Achievement of solar system exploration roadmap goals will involve robotic or human deployment and longterm operation of surface science packages remote from human presence, thus requiring autonomous, self-powered operation. The major challenge such packages face will be operating during long periods of darkness in extreme cold potentially without the Pu238 based power and thermal systems available to Apollo era packages (ALSEP). Development of such science payloads will thus require considerable optimization of instrument and subsystem design, packaging and integration for a variety of planetary surface environments in order to support solar system exploration fully. Our work supports this process through the incorporation of low temperature operational components and design strategies which radically minimize power, mass, and cost while maximizing the performance under extreme surface conditions that are in many cases more demanding than those routinely experienced by spacecraft in deep space. Chief instruments/instrument package candidates include those which could provide long-term monitoring of the surface and subsurface environments for fundamental science and human crew safety. The initial attempt to design a 10 instrument environmental monitoring package with a solar/battery based power system led to a package with a unacceptably large mass (500 kg) of which over half was battery mass. In phase 1, a factor of 5 reduction in mass was achieved, first through the introduction of high performance electronics capable of operating at far lower temperature and then through the use of innovative thermal balance strategies involving the use of multi-layer thin materials and gravity-assisted heat pipes. In phase 2, reported here, involves strategies such as universal incorporation of ULT/ULP digital and analog electronics, and distributed or non-conventionally packaged power systems. These strategies will be required to meet the far more challenging thermal requirements of operating through a normal 28 day diurnal cycle. The limited temperature range of efficient battery operation remains the largest obstacle.

Optical analysis of high power free electron laser resonators

NASA Astrophysics Data System (ADS)

Knapp, C. E.; Viswanathan, V. K.; Appert, Q. D.; Bender, S. C.; McVey, B. D.

1987-06-01

The first part of this paper briefly describes the optics code used at Los Alamos National Laboratory to do optical analyses of various components of a free electron laser. The body of the paper then discusses the recent results in modeling low frequency gratings and ripple on the surfaces of liquid-cooled mirrors. The ripple is caused by structural/thermal effects in the mirror surface due to heating by optical absorption in high power resonators. Of interest is how much ripple can be permitted before diffractive losses or optical mode distortions become unacceptable. Preliminary work is presented involving classical diffraction problems to support the ripple study. The limitations of the techniques are discussed and the results are compared to experimental results where available.

A flexible, stretchable and shape-adaptive approach for versatile energy conversion and self-powered biomedical monitoring.

PubMed

Yang, Po-Kang; Lin, Long; Yi, Fang; Li, Xiuhan; Pradel, Ken C; Zi, Yunlong; Wu, Chih-I; He, Jr-Hau; Zhang, Yue; Wang, Zhong Lin

2015-07-01

A flexible triboelectric nanogenerator (FTENG) based on wavy-structured Kapton film and a serpentine electrode on stretchable substrates is presented. The as-fabricated FTENG is capable of harvesting ambient mechanical energy via both compressive and stretching modes. Moreover, the FTENG can be a bendable power source to work on curved surfaces; it can also be adaptively attached onto human skin for monitoring gentle body motions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of organic solar cells using various power O2 plasma treatments on the indium tin oxide substrate.

PubMed

Ke, Jhong-Ciao; Wang, Yeong-Her; Chen, Kan-Lin; Huang, Chien-Jung

2016-03-01

The effect of organic solar cells (OSCs) by using different power O2 plasma treatments on indium tin oxide (ITO) substrate was studied. The power of O2 plasma treatment on ITO substrate was varied from 20W to 80W, and the power conversion efficiency of device was improved from 1.18% to 1.93% at 20W O2 plasma treatment. The function of O2 plasma treatment on ITO substrate was to remove the surface impurity and to improve the work function of ITO, which can reduce the energy offset between the ITO and SubPc layer and depress the leakage current of device, leading to the shunt resistance increased from 897 to 1100Ωcm(2). The surface roughness of ITO decreased from 3.81 to 3.33nm and the work function of ITO increased from 4.75 to 5.2eV after 20W O2 plasma treatment on ITO substrate. As a result, the open circuit voltage and the fill factor were improved from 0.46 to 0.70V and from 0.56 to 0.61, respectively. However, the series resistance of device was dramatically increased as the power of O2 plasma treatment exceeds 40W, leading to the efficiency reduction. The result is attributed to the variation of oxygen vacancies in ITO film after the 60, 80W O2 plasma treatment. As a consequence, the power of O2 plasma treatment on ITO substrate for the OSCs application should be controlled below 40W to avoid affecting the electricity of ITO film. Copyright © 2015 Elsevier Inc. All rights reserved.

Tipjet 80-inch Model Rotor Hover Test: Test No. 1198

DTIC Science & Technology

1993-09-01

primarily working papers Intended for internal use. They I carry an Identifying number which indicates their type and the numerical code of the oriwginatn...rotor lifting system, while exhbitin the highes aumntbnratio eve recorded for a CC rotor, sufer an induced power penalty due to the norilifting regon...INFORMATION This work was conducted by the Ship Systems and Programs DirectorateI (Code 22) of the Carderock Division, Naval Surface Warfare Center

30 CFR 75.1905-1 - Diesel fuel piping systems.

Code of Federal Regulations, 2010 CFR

2010-07-01

... storage facility. (h) The diesel fuel piping system must not be located in a borehole with electric power... Diesel fuel piping systems. (a) Diesel fuel piping systems from the surface must be designed and operated...) Capable of withstanding working pressures and stresses; (2) Capable of withstanding four times the static...

30 CFR 77.508 - Lightning arresters, ungrounded and exposed power conductors and telephone wires.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Lightning arresters, ungrounded and exposed... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Electrical Equipment-General § 77.508 Lightning... conductors and telephone wires shall be equipped with suitable lightning arresters which are adequately...

30 CFR 77.508 - Lightning arresters, ungrounded and exposed power conductors and telephone wires.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Lightning arresters, ungrounded and exposed... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Electrical Equipment-General § 77.508 Lightning... conductors and telephone wires shall be equipped with suitable lightning arresters which are adequately...

30 CFR 77.508 - Lightning arresters, ungrounded and exposed power conductors and telephone wires.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Lightning arresters, ungrounded and exposed... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Electrical Equipment-General § 77.508 Lightning... conductors and telephone wires shall be equipped with suitable lightning arresters which are adequately...

Hydrophobic Surface Modification of Silk Fabric Using Plasma-Polymerized Hmdso

NASA Astrophysics Data System (ADS)

Rani, K. Vinisha; Chandwani, Nisha; Kikani, Purvi; Nema, S. K.; Sarma, Arun Kumar; Sarma, Bornali

In this work, we study the hydrophobic properties of silk fabrics by deposition of plasma-polymerized (pp) hexamethyldisiloxane (HMDSO) using low-pressure plasma-enhanced chemical vapor deposition. Recently, hydrophobic properties are under active research in textile industry. The effects of coating time and power on the HMDSO-coated silk fabrics are investigated. Water contact angle of pp-HMDSO-coated silk fabric surface is measured as a function of power and coating time. Fabric surface shows an enhancement in hydrophobicity after coating. Attenuated total reflectance-Fourier transform infrared spectroscopy reveals the surface chemistry, and scanning electron microscopy shows the surface morphology of the uncoated and HMDSO-coated fabrics, respectively. In the case of uncoated fabric, water droplet absorbs swiftly, whereas in the case of HMDSO-coated fabric, water droplet remains on the fabric surface with a maximum contact angle of 140∘. The HMDSO-deposited silk surface is found to be durable after detergent washing. Common stains such as ink, tea, milk, turmeric and orange juice are tested on the surface of both fabrics. In HMDSO-coated fabrics, all the stains are bedded like ball droplet. In order to study the self-cleaning property, the fabric is tilted to 45∘ angle; stain droplets easily roll off from the fabric.

Surface morphology effects in a vibration based triboelectric energy harvester

NASA Astrophysics Data System (ADS)

Nafari, A.; Sodano, H. A.

2018-01-01

Despite the abundance of ambient mechanical energy in our environment, it is often neglected and left unused. However, recent studies have demonstrated that mechanical vibrations can be harvested and used to power small wireless electronic devices, such as micro electromechanical sensors (MEMS) and actuators. Most commonly, these energy harvesters convert vibration into electrical energy by utilizing piezoelectric, electromagnetic or electrostatic effects. Recently, triboelectric based energy harvesters have shown to be among the simplest and most cost-effective techniques for scavenging mechanical energy. The basis of triboelectric energy harvesters is the periodic contact and separation of two surfaces with opposite triboelectric properties which results in induced charge flow through an external load. Here, a vibration driven triboelectric nanogenerator (TENG) is fabricated and the effect of micro/nano scale surface modification is studied. The TENG produces electrical energy on the basis of periodic out-of-plane charge separation between gold and polydimethylsiloxane (PDMS) with opposite triboelectric charge polarities. By introducing micro/nano scale surface modifications to the PDMS and gold, the TENG’s power output is further enhanced. This work demonstrates that the morphology of the surfaces in a TENG device is important and by increasing the effective surface area through micro/nano scale modification, the power output of the device can increase by 118%. Moreover, it is shown that unlike many TENGs proposed in the literature, the fabricated device has a high RMS open circuit voltage and short circuit current and can perform for an extended period of time.

Surface-to-surface biofilm transfer: a quick and reliable startup strategy for mixed culture microbial fuel cells.

PubMed

Vogl, Andreas; Bischof, Franz; Wichern, Marc

2016-01-01

The startup of microbial fuel cells (MFCs) is known to be prone to failure or result in erratic performance impeding the research. The aim of this study was to advise a quick launch strategy for laboratory-scale MFCs that ensures steady operation performance in a short period of time. Different startup strategies were investigated and compared with membraneless single chamber MFCs. A direct surface-to-surface biofilm transfer (BFT) in an operating MFC proved to be the most efficient method. It provided steady power densities of 163 ± 13 mWm(-2) 4 days after inoculation compared to 58 ± 15 mWm(-2) after 30 days following a conventional inoculation approach. The in situ BFT eliminates the need for microbial acclimation during startup and reduces performance fluctuations caused by shifts in microbial biodiversity. Anaerobic pretreatment of the substrate and addition of suspended enzymes from an operating MFC into the new MFC proved to have a beneficial effect on startup and subsequent operation. Polarization methods were applied to characterize the startup phase and the steady state operation in terms of power densities, internal resistance and power overshoot during biofilm maturation. Applying this method a well-working MFC can be multiplied into an array of identically performing MFCs.

Radiation heat transfer simulation in a window for a small particle solar receiver using the Monte Carlo method

NASA Astrophysics Data System (ADS)

Whitmore, Alexander Jason

Concentrating solar power systems are currently the predominant solar power technology for generating electricity at the utility scale. The central receiver system, which is a concentrating solar power system, uses a field of mirrors to concentrate solar radiation onto a receiver where a working fluid is heated to drive a turbine. Current central receiver systems operate on a Rankine cycle, which has a large demand for cooling water. This demand for water presents a challenge for the current central receiver systems as the ideal locations for solar power plants have arid climates. An alternative to the current receiver technology is the small particle receiver. The small particle receiver has the potential to produce working fluid temperatures suitable for use in a Brayton cycle which can be more efficient when pressurized to 0.5 MPa. Using a fused quartz window allows solar energy into the receiver while maintaining a pressurized small particle receiver. In this thesis, a detailed numerical investigation for a spectral, three dimensional, cylindrical glass window for a small particle receiver was performed. The window is 1.7 meters in diameter and 0.0254 meters thick. There are three Monte Carlo Ray Trace codes used within this research. The first MCRT code, MIRVAL, was developed by Sandia National Laboratory and modified by a fellow San Diego State University colleague Murat Mecit. This code produces the solar rays on the exterior surface of the window. The second MCRT code was developed by Steve Ruther and Pablo Del Campo. This code models the small particle receiver, which creates the infrared spectral direction flux on the interior surface of the window used in this work. The third MCRT, developed for this work, is used to model radiation heat transfer within the window itself and is coupled to an energy equation solver to produce a temperature distribution. The MCRT program provides a source term to the energy equation. This in turn, produces a new temperature field for the MCRT program; together the equations are solved iteratively. These iterations repeat until convergence is reached for a steady state temperature field. The energy equation was solved using a finite volume method. The window's thermal conductivity is modeled as a function of temperature. This thermal model is used to investigate the effects of different materials, receiver geometries, interior convection coefficients and exterior convection coefficients. To prevent devitrification and the ultimate failure of the window, the window needs to stay below the devitrification temperature of the material. In addition, the temperature gradients within the window need to be kept to a minimum to prevent thermal stresses. A San Diego State University colleague E-Fann Saung uses these temperature maps to insure that the mounting of the window does not produce thermal stresses which can cause cracking in the brittle fused quartz. The simulations in this thesis show that window temperatures are below the devitrification temperature of the window when there are cooling jets on both surfaces of the window. Natural convection on the exterior window surface was explored and it does not provide adequate cooling; therefore forced convection is required. Due to the low thermal conductivity of the window, the edge mounting thermal boundary condition has little effect on the maximum temperature of the window. The simulations also showed that the solar input flux absorbed less than 1% of the incoming radiation while the window absorbed closer to 20% of the infrared radiation emitted by the receiver. The main source of absorbed power in the window is located directly on the interior surface of the window where the infrared radiation is absorbed. The geometry of the receiver has a large impact on the amount of emitted power which reached the interior surface of the window, and using a conical shaped receiver dramatically reduced the receiver's infrared flux on the window. The importance of internal emission is explored within this research. Internal emission produces a more even emission field throughout the receiver than applying radiation surface emission only. Due to a majority of the infrared receiver re-radiation being absorbed right at the interior surface, the surface emission only approximation method produces lower maximum temperatures.

Regolith Advanced Surface Systems Operations Robot (RASSOR) Phase 2 and Smart Autonomous Sand-Swimming Excavator

NASA Technical Reports Server (NTRS)

Sandy, Michael

2015-01-01

The Regolith Advanced Surface Systems Operations Robot (RASSOR) Phase 2 is an excavation robot for mining regolith on a planet like Mars. The robot is programmed using the Robotic Operating System (ROS) and it also uses a physical simulation program called Gazebo. This internship focused on various functions of the program in order to make it a more professional and efficient robot. During the internship another project called the Smart Autonomous Sand-Swimming Excavator was worked on. This is a robot that is designed to dig through sand and extract sample material. The intern worked on programming the Sand-Swimming robot, and designing the electrical system to power and control the robot.

Laser Induced Aluminum Surface Breakdown Model

NASA Technical Reports Server (NTRS)

Chen, Yen-Sen; Liu, Jiwen; Zhang, Sijun; Wang, Ten-See (Technical Monitor)

2002-01-01

Laser powered propulsion systems involve complex fluid dynamics, thermodynamics and radiative transfer processes. Based on an unstructured grid, pressure-based computational aerothermodynamics; platform, several sub-models describing such underlying physics as laser ray tracing and focusing, thermal non-equilibrium, plasma radiation and air spark ignition have been developed. This proposed work shall extend the numerical platform and existing sub-models to include the aluminum wall surface Inverse Bremsstrahlung (IB) effect from which surface ablation and free-electron generation can be initiated without relying on the air spark ignition sub-model. The following tasks will be performed to accomplish the research objectives.

Heat Transfer Enhancement During Water and Hydrocarbon Condensation on Lubricant Infused Surfaces.

PubMed

Preston, Daniel J; Lu, Zhengmao; Song, Youngsup; Zhao, Yajing; Wilke, Kyle L; Antao, Dion S; Louis, Marcel; Wang, Evelyn N

2018-01-11

Vapor condensation is routinely used as an effective means of transferring heat or separating fluids. Dropwise condensation, where discrete droplets form on the condenser surface, offers a potential improvement in heat transfer of up to an order of magnitude compared to filmwise condensation, where a liquid film covers the surface. Low surface tension fluid condensates such as hydrocarbons pose a unique challenge since typical hydrophobic condenser coatings used to promote dropwise condensation of water often do not repel fluids with lower surface tensions. Recent work has shown that lubricant infused surfaces (LIS) can promote droplet formation of hydrocarbons. In this work, we confirm the effectiveness of LIS in promoting dropwise condensation by providing experimental measurements of heat transfer performance during hydrocarbon condensation on a LIS, which enhances heat transfer by ≈450% compared to an uncoated surface. We also explored improvement through removal of noncondensable gases and highlighted a failure mechanism whereby shedding droplets depleted the lubricant over time. Enhanced condensation heat transfer for low surface tension fluids on LIS presents the opportunity for significant energy savings in natural gas processing as well as improvements in thermal management, heating and cooling, and power generation.

Potential for natural evaporation as a reliable renewable energy resource.

PubMed

Cavusoglu, Ahmet-Hamdi; Chen, Xi; Gentine, Pierre; Sahin, Ozgur

2017-09-26

About 50% of the solar energy absorbed at the Earth's surface drives evaporation, fueling the water cycle that affects various renewable energy resources, such as wind and hydropower. Recent advances demonstrate our nascent ability to convert evaporation energy into work, yet there is little understanding about the potential of this resource. Here we study the energy available from natural evaporation to predict the potential of this ubiquitous resource. We find that natural evaporation from open water surfaces could provide power densities comparable to current wind and solar technologies while cutting evaporative water losses by nearly half. We estimate up to 325 GW of power is potentially available in the United States. Strikingly, water's large heat capacity is sufficient to control power output by storing excess energy when demand is low, thus reducing intermittency and improving reliability. Our findings motivate the improvement of materials and devices that convert energy from evaporation.The evaporation of water represents an alternative source of renewable energy. Building on previous models of evaporation, Cavusoglu et al. show that the power available from this natural resource is comparable to wind and solar power, yet it does not suffer as much from varying weather conditions.

Plasmonic photothermal accumulation of particles by a microfiber decorated with gold nanostructures

NASA Astrophysics Data System (ADS)

Li, Ying; Hu, Yanjun; Wu, Xingda

2017-08-01

This paper introduces an efficient method for accumulation of particles via thermophoresis and thermal convection sustained by localized surface plasmon energy. Gold nanorods were deposited on the designated surface of a microfiber, when a 808 nm laser at an optical power of 12 mV launched into the microfiber, particles dispersed in the water were massively trapped and aggregated on the substrate. This work is envisioned to have application in photothermal cancer therapy, photothermal imaging, and targeted drug delivery.

Screen printed silver top electrode for efficient inverted organic solar cells

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

Kim, Junwoo; Duraisamy, Navaneethan; Lee, Taik-Min

2015-10-15

Highlights: • Screen printing of silver pattern. • X-ray diffraction pattern confirmed the face centered cubic structure of silver. • Uniform surface morphology of silver pattern with sheet resistance of 0.06 Ω/sq. • The power conversion efficiency of fabricated solar cell is found to be 2.58%. - Abstract: The present work is mainly focused on replacement of the vacuum process for top electrode fabrication in organic solar cells. Silver top electrode deposited through solution based screen printing on pre-deposited polymeric thin film. The solution based printing technology provides uniform top electrode without damaging the underlying organic layers. The surface crystallinitymore » and surface morphology of silver top electrode are examined through X-ray diffraction, field-emission scanning electron microscope and atomic force microscope. The purity of silver is examined through X-ray energy dispersive spectroscopy. The top electrode exhibits face centered cubic structure with homogeneous morphology. The sheet resistance of top electrode is found to be 0.06 Ω/sq and an average pattern thickness of ∼15 μm. The power conversion efficiency is 2.58%. Our work demonstrates that the solution based screen printing is a significant role in the replacement of vacuum process for the fabrication of top electrode in organic solar cells.« less

Electronic materials high-T(sub c) superconductivity polymers and composites structural materials surface science and catalysts industry participation

NASA Technical Reports Server (NTRS)

1988-01-01

The fifth year of the Center for Advanced Materials was marked primarily by the significant scientific accomplishments of the research programs. The Electronics Materials program continued its work on the growth and characterization of gallium arsenide crystals, and the development of theories to understand the nature and distribution of defects in the crystals. The High Tc Superconductivity Program continued to make significant contributions to the field in theoretical and experimental work on both bulk materials and thin films and devices. The Ceramic Processing group developed a new technique for cladding YBCO superconductors for high current applications in work with the Electric Power Research Institute. The Polymers and Composites program published a number of important studies involving atomistic simulations of polymer surfaces with excellent correlations to experimental results. The new Enzymatic Synthesis of Materials project produced its first fluorinated polymers and successfully began engineering enzymes designed for materials synthesis. The structural Materials Program continued work on novel alloys, development of processing methods for advanced ceramics, and characterization of mechanical properties of these materials, including the newly documented characterization of cyclic fatigue crack propagation behavior in toughened ceramics. Finally, the Surface Science and Catalysis program made significant contributions to the understanding of microporous catalysts and the nature of surface structures and interface compounds.

30 CFR 77.805 - Cable couplers and connection boxes; minimum design requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Cable couplers and connection boxes; minimum... WORK AREAS OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.805 Cable couplers and connection boxes; minimum design requirements. (a)(1) Couplers that are used in medium- or high-voltage power...

30 CFR 77.805 - Cable couplers and connection boxes; minimum design requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Cable couplers and connection boxes; minimum... WORK AREAS OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.805 Cable couplers and connection boxes; minimum design requirements. (a)(1) Couplers that are used in medium- or high-voltage power...

30 CFR 77.805 - Cable couplers and connection boxes; minimum design requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Cable couplers and connection boxes; minimum... WORK AREAS OF UNDERGROUND COAL MINES Surface High-Voltage Distribution § 77.805 Cable couplers and connection boxes; minimum design requirements. (a)(1) Couplers that are used in medium- or high-voltage power...

30 CFR 75.705-1 - Work on high-voltage lines.

Code of Federal Regulations, 2012 CFR

2012-07-01

... power system, either the steel armor or conduit enclosing the system or a surface grounding field is a... supported by any pole or structure which also supports other high-voltage lines until: (1) All lines supported on the pole or structure are deenergized and grounded in accordance with all of the provisions of...

30 CFR 75.705-1 - Work on high-voltage lines.

Code of Federal Regulations, 2014 CFR

2014-07-01

... power system, either the steel armor or conduit enclosing the system or a surface grounding field is a... supported by any pole or structure which also supports other high-voltage lines until: (1) All lines supported on the pole or structure are deenergized and grounded in accordance with all of the provisions of...

30 CFR 75.705-1 - Work on high-voltage lines.

Code of Federal Regulations, 2013 CFR

2013-07-01

... power system, either the steel armor or conduit enclosing the system or a surface grounding field is a... supported by any pole or structure which also supports other high-voltage lines until: (1) All lines supported on the pole or structure are deenergized and grounded in accordance with all of the provisions of...

30 CFR 77.704-1 - Work on high-voltage lines.

Code of Federal Regulations, 2012 CFR

2012-07-01

... ungrounded power system, either the steel armor or conduit enclosing the system or a surface grounding field... supported by any pole or structure which also supports other high-voltage lines until: (1) All lines supported on the pole or structure are deenergized and grounded in accordance with all of the provisions of...

30 CFR 77.704-1 - Work on high-voltage lines.

Code of Federal Regulations, 2013 CFR

2013-07-01

... ungrounded power system, either the steel armor or conduit enclosing the system or a surface grounding field... supported by any pole or structure which also supports other high-voltage lines until: (1) All lines supported on the pole or structure are deenergized and grounded in accordance with all of the provisions of...

30 CFR 77.704-1 - Work on high-voltage lines.

Code of Federal Regulations, 2014 CFR

2014-07-01

... ungrounded power system, either the steel armor or conduit enclosing the system or a surface grounding field... supported by any pole or structure which also supports other high-voltage lines until: (1) All lines supported on the pole or structure are deenergized and grounded in accordance with all of the provisions of...

Optical design and fabrication of palm/fingerprint uniform illumination system with a high-power near-infrared light-emitting diode.

PubMed

Jing, Lei; Wang, Yao; Zhao, Huifu; Ke, Hongliang; Wang, Xiaoxun; Gao, Qun

2017-06-10

In order to meet the requirements of uniform illumination for optical palm/fingerprint instruments and overcome the shortcomings of the poor uniform illumination on the working plane of the optical palm/fingerprint prism, a novel secondary optical lens with a free-form surface, compact structure, and high uniformity is presented in this paper. The design of the secondary optical lens is based on emission properties of the near-infrared light-emitting diode (LED) and basic principles of non-imaging optics, especially considering the impact of the thickness of the prism in the design. Through the numerical solution of Snell's law in geometric optics, we obtain the profile of the free-form surface of the lens. Using the optical software TracePro, we trace and simulate the illumination system. The results show that the uniformity is 89.8% on the working plane of the prism, and the test results show that the actual uniformity reaches 85.7% in the experiment, which provides an effective way for realizing a highly uniform illumination system with high-power near-infrared LED.

Experimental Investigation of Shrouding on Meshed Spur Gear Windage Power Loss

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.; Hurrell, Michael J.

2017-01-01

Windage power loss in high-speed gearboxes results in efficiency losses and increased heating due to drag on the gear teeth. Test results for meshed spur gear windage power loss are presented at ambient oil inlet temperatures, both with and without shrouding. The rate of windage power loss is observed to increase above a gear surface speed of 10,000 feet per minute (51 meters per second), similar to results presented in the literature. Shrouding is observed to become more effective above 15,000 feet per minute (76 meters per second), decreasing power loss by 10 percent at 25,000 feet per minute (127 meters per second). The need for gearbox oil drain slots limits the effectiveness of shrouding in reducing windage power loss. Windage power loss is observed to decrease with increasing gearbox temperatures and to increase with oil flow. Windage power losses for unshrouded meshed spur gears are 7 times greater than losses determined from unshrouded single spur gear tests. A 6- to 12-times increase in windage power loss is observed in the shrouded meshed spur gear data compared with shrouded single spur gear data. Based on this preliminary study, additional research is suggested to determine the effect of oil drain slot configurations, axial and radial shroud clearances, and higher gear surface speeds on windage power loss. Additional work is also suggested to determine the sensitivity of windage power loss to oil temperature and oil flow. Windage power loss for meshed spur gears tested in both the shrouded and unshrouded configurations is shown to be more than double versus windage power loss for the same spur gears run individually in the same shroud configurations. Further study of the physical processes behind these results is needed to optimize gearbox shrouds for minimum windage power loss.

Output of skeletal muscle contractions. a study of isokinetic plantar flexion in athletes.

PubMed

Fugl-Meyer, A R; Mild, K H; Hörnsten, J

1982-06-01

Maximum torques, total work and mean power of isokinetic plantar flexions were measured with simultaneous registrations. The integrated electromyograms (iEMG) were obtained by surface electrodes from all three heads of the m. triceps surae. The method applied offers possibilities for adequate description of dynamic muscular work which in the case of plantar flexion in trained man declines as a negative exponential function of angular motion velocity. The decline is parallel to that of maximum torques. The summed triceps surae iEMG was inversely proportional to the velocity and direct proportional to time suggesting that structural rather than neural factors determine the relationships between velocity of angular motion and maximum torque/total work of single Mmaneuvers. Moreover, the fact that maximum mean power as well as maximum electrical efficiency were reached at the functional velocity of toe-off during gait suggests an influence of pragmatic demands on plantar flexion mechanical output.

The lithium vapor box divertor

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

Goldston, R. J.; Myers, R.; Schwartz, J.

It has long been recognized that volumetric dissipation of the plasma heat flux from a fusion power system is preferable to its localized impingement on a material surface. Volumetric dissipation mitigates both the anticipated very high heat flux and intense particle-induced damage due to sputtering. Our recent projections to a tokamak demonstration power plant suggest an immense upstream parallel heat flux, of order 20 GW m -2, implying that fully detached operation may be a requirement for the success of fusion power. Building on pioneering work on the use of lithium by Nagayama et al and by Ono et almore » as well as earlier work on the gas box divertor by Watkins and Rebut, we present here a concept for a lithium vapor box divertor, in which lithium vapor extracts momentum and energy from a fusion-power-plant divertor plasma, using fully volumetric processes. Furthermore, at the high powers and pressures that are projected this requires a high density of lithium vapor, which must be isolated from the main plasma in order to avoid lithium build-up on the chamber walls or in the plasma. Isolation is achieved through a powerful multi-box differential pumping scheme available only for condensable vapors. The preliminary box-wise calculations are encouraging, but much more work is required in order to demonstrate the practical viability of this scheme, taking into account at least 2D plasma and vapor flows within and between the vapor boxes and out of the vapor boxes to the main plasma.« less

The lithium vapor box divertor

NASA Astrophysics Data System (ADS)

Goldston, R. J.; Myers, R.; Schwartz, J.

2016-02-01

It has long been recognized that volumetric dissipation of the plasma heat flux from a fusion power system is preferable to its localized impingement on a material surface. Volumetric dissipation mitigates both the anticipated very high heat flux and intense particle-induced damage due to sputtering. Recent projections to a tokamak demonstration power plant suggest an immense upstream parallel heat flux, of order 20 GW m-2, implying that fully detached operation may be a requirement for the success of fusion power. Building on pioneering work on the use of lithium by Nagayama et al and by Ono et al as well as earlier work on the gas box divertor by Watkins and Rebut, we present here a concept for a lithium vapor box divertor, in which lithium vapor extracts momentum and energy from a fusion-power-plant divertor plasma, using fully volumetric processes. At the high powers and pressures that are projected this requires a high density of lithium vapor, which must be isolated from the main plasma in order to avoid lithium build-up on the chamber walls or in the plasma. Isolation is achieved through a powerful multi-box differential pumping scheme available only for condensable vapors. The preliminary box-wise calculations are encouraging, but much more work is required to demonstrate the practical viability of this scheme, taking into account at least 2D plasma and vapor flows within and between the vapor boxes and out of the vapor boxes to the main plasma.

The lithium vapor box divertor

DOE PAGES

Goldston, R. J.; Myers, R.; Schwartz, J.

2016-01-13

It has long been recognized that volumetric dissipation of the plasma heat flux from a fusion power system is preferable to its localized impingement on a material surface. Volumetric dissipation mitigates both the anticipated very high heat flux and intense particle-induced damage due to sputtering. Our recent projections to a tokamak demonstration power plant suggest an immense upstream parallel heat flux, of order 20 GW m -2, implying that fully detached operation may be a requirement for the success of fusion power. Building on pioneering work on the use of lithium by Nagayama et al and by Ono et almore » as well as earlier work on the gas box divertor by Watkins and Rebut, we present here a concept for a lithium vapor box divertor, in which lithium vapor extracts momentum and energy from a fusion-power-plant divertor plasma, using fully volumetric processes. Furthermore, at the high powers and pressures that are projected this requires a high density of lithium vapor, which must be isolated from the main plasma in order to avoid lithium build-up on the chamber walls or in the plasma. Isolation is achieved through a powerful multi-box differential pumping scheme available only for condensable vapors. The preliminary box-wise calculations are encouraging, but much more work is required in order to demonstrate the practical viability of this scheme, taking into account at least 2D plasma and vapor flows within and between the vapor boxes and out of the vapor boxes to the main plasma.« less

Assessing the potential of surface-immobilized molecular logic machines for integration with solid state technology.

PubMed

Dunn, Katherine E; Trefzer, Martin A; Johnson, Steven; Tyrrell, Andy M

2016-08-01

Molecular computation with DNA has great potential for low power, highly parallel information processing in a biological or biochemical context. However, significant challenges remain for the field of DNA computation. New technology is needed to allow multiplexed label-free readout and to enable regulation of molecular state without addition of new DNA strands. These capabilities could be provided by hybrid bioelectronic systems in which biomolecular computing is integrated with conventional electronics through immobilization of DNA machines on the surface of electronic circuitry. Here we present a quantitative experimental analysis of a surface-immobilized OR gate made from DNA and driven by strand displacement. The purpose of our work is to examine the performance of a simple representative surface-immobilized DNA logic machine, to provide valuable information for future work on hybrid bioelectronic systems involving DNA devices. We used a quartz crystal microbalance to examine a DNA monolayer containing approximately 5×10(11)gatescm(-2), with an inter-gate separation of approximately 14nm, and we found that the ensemble of gates took approximately 6min to switch. The gates could be switched repeatedly, but the switching efficiency was significantly degraded on the second and subsequent cycles when the binding site for the input was near to the surface. Otherwise, the switching efficiency could be 80% or better, and the power dissipated by the ensemble of gates during switching was approximately 0.1nWcm(-2), which is orders of magnitude less than the power dissipated during switching of an equivalent array of transistors. We propose an architecture for hybrid DNA-electronic systems in which information can be stored and processed, either in series or in parallel, by a combination of molecular machines and conventional electronics. In this architecture, information can flow freely and in both directions between the solution-phase and the underlying electronics via surface-immobilized DNA machines that provide the interface between the molecular and electronic domains. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

A Screen Space GPGPU Surface LIC Algorithm for Distributed Memory Data Parallel Sort Last Rendering Infrastructures

NASA Astrophysics Data System (ADS)

Loring, B.; Karimabadi, H.; Rortershteyn, V.

2015-10-01

The surface line integral convolution(LIC) visualization technique produces dense visualization of vector fields on arbitrary surfaces. We present a screen space surface LIC algorithm for use in distributed memory data parallel sort last rendering infrastructures. The motivations for our work are to support analysis of datasets that are too large to fit in the main memory of a single computer and compatibility with prevalent parallel scientific visualization tools such as ParaView and VisIt. By working in screen space using OpenGL we can leverage the computational power of GPUs when they are available and run without them when they are not. We address efficiency and performance issues that arise from the transformation of data from physical to screen space by selecting an alternate screen space domain decomposition. We analyze the algorithm's scaling behavior with and without GPUs on two high performance computing systems using data from turbulent plasma simulations.

Removal of Microbial Contamination from Surface by Plasma

NASA Astrophysics Data System (ADS)

Feng, Xinxin; Liu, Hongxia; Shen, Zhenxing; Wang, Taobo

2018-01-01

Microbial contamination is closely associated with human and environmental health, they can be tested on food surfaces, medical devices, packing material and so on. In this paper the removal of the microbial contamination from surface using plasma treatment is investigated. The Escherichia coli (E. coli) has been chosen as a bio-indicator enabling to evaluate the effect of plasma assisted microbial inactivation. Oxygen gas was as the working gas. The plasma RF power, plasma exposition time, gas flow and the concentration of organic pollutant were varied in order to see the effect of the plasma treatment on the Gram-negative germ removal. After the treatment, the microbial abatement was evaluated by the standard plate count method. This proved a positive effect of the plasma treatment on Gram-negative germ removal. The kinetics and mathematical model of removal were studied after plasma treatment, and then the removing course of E. coli was analyzed. This work is meaningful for deepening our understanding of the fundamental scientific principles regarding microbial contamination from surface by plasma.

A Screen Space GPGPU Surface LIC Algorithm for Distributed Memory Data Parallel Sort Last Rendering Infrastructures

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

Loring, Burlen; Karimabadi, Homa; Rortershteyn, Vadim

2014-07-01

The surface line integral convolution(LIC) visualization technique produces dense visualization of vector fields on arbitrary surfaces. We present a screen space surface LIC algorithm for use in distributed memory data parallel sort last rendering infrastructures. The motivations for our work are to support analysis of datasets that are too large to fit in the main memory of a single computer and compatibility with prevalent parallel scientific visualization tools such as ParaView and VisIt. By working in screen space using OpenGL we can leverage the computational power of GPUs when they are available and run without them when they are not.more » We address efficiency and performance issues that arise from the transformation of data from physical to screen space by selecting an alternate screen space domain decomposition. We analyze the algorithm's scaling behavior with and without GPUs on two high performance computing systems using data from turbulent plasma simulations.« less

Thermoelectric Power Generation System for Future Hybrid Vehicles Using Hot Exhaust Gas

NASA Astrophysics Data System (ADS)

Kim, Sun-Kook; Won, Byeong-Cheol; Rhi, Seok-Ho; Kim, Shi-Ho; Yoo, Jeong-Ho; Jang, Ju-Chan

2011-05-01

The present experimental and computational study investigates a new exhaust gas waste heat recovery system for hybrid vehicles, using a thermoelectric module (TEM) and heat pipes to produce electric power. It proposes a new thermoelectric generation (TEG) system, working with heat pipes to produce electricity from a limited hot surface area. The current TEG system is directly connected to the exhaust pipe, and the amount of electricity generated by the TEMs is directly proportional to their heated area. Current exhaust pipes fail to offer a sufficiently large hot surface area for the high-efficiency waste heat recovery required. To overcome this, a new TEG system has been designed to have an enlarged hot surface area by the addition of ten heat pipes, which act as highly efficient heat transfer devices and can transmit the heat to many TEMs. As designed, this new waste heat recovery system produces a maximum 350 W when the hot exhaust gas heats the evaporator surface of the heat pipe to 170°C; this promises great possibilities for application of this technology in future energy-efficient hybrid vehicles.

Potential for natural evaporation as a reliable renewable energy resource

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

Cavusoglu, Ahmet-Hamdi; Chen, Xi; Gentine, Pierre

About 50% of the solar energy absorbed at the Earth’s surface drives evaporation, fueling the water cycle that affects various renewable energy resources, such as wind and hydropower. Recent advances demonstrate our nascent ability to convert evaporation energy into work, yet there is little understanding about the potential of this resource. Here in this paper we study the energy available from natural evaporation to predict the potential of this ubiquitous resource. We find that natural evaporation from open water surfaces could provide power densities comparable to current wind and solar technologies while cutting evaporative water losses by nearly half. Wemore » estimate up to 325 GW of power is potentially available in the United States. Strikingly, water’s large heat capacity is sufficient to control power output by storing excess energy when demand is low, thus reducing intermittency and improving reliability. Our findings motivate the improvement of materials and devices that convert energy from evaporation.« less

Potential for natural evaporation as a reliable renewable energy resource

DOE PAGES

Cavusoglu, Ahmet-Hamdi; Chen, Xi; Gentine, Pierre; ...

2017-09-26

About 50% of the solar energy absorbed at the Earth’s surface drives evaporation, fueling the water cycle that affects various renewable energy resources, such as wind and hydropower. Recent advances demonstrate our nascent ability to convert evaporation energy into work, yet there is little understanding about the potential of this resource. Here in this paper we study the energy available from natural evaporation to predict the potential of this ubiquitous resource. We find that natural evaporation from open water surfaces could provide power densities comparable to current wind and solar technologies while cutting evaporative water losses by nearly half. Wemore » estimate up to 325 GW of power is potentially available in the United States. Strikingly, water’s large heat capacity is sufficient to control power output by storing excess energy when demand is low, thus reducing intermittency and improving reliability. Our findings motivate the improvement of materials and devices that convert energy from evaporation.« less

Consideration of the use of origami-style solar panels for use on a terrestrial/orbital wireless power generation and transmission spacecraft

NASA Astrophysics Data System (ADS)

Holland, Alexander F.; Pearson, Jens; Lysford, Wilson; Straub, Jeremy

2016-05-01

This paper presents work on the development of Origami-style solar panels and their adaption and efficacy for use in Earth orbit. It focuses on the enabling capability of this technology for the generation and transmission of power. The proposed approach provides increased collection (solar panel) and transmission (microwave radiation) surface area, as compared to other systems with similar mass and volume. An overview of the system is presented, including its pre-deployment configuration, the deployment process and its final configuration. Its utility for wireless power transmission mission is then considered. An economic discussion is then presented to consider how the mass and volume efficiencies provided enable the system to approach target willingness-to-pay values that were presented and considered in prior work. A key consideration regarding the use of wireless power transfer in Earth orbit is the reliability of the technology. This has several different areas of consideration. It must reliably supply power to its customers (or they would have to have local generation capabilities sufficient for their needs, defeating the benefit of this system). It must also be shown to reliably supply power only to designated locations (and not inadvertently or otherwise beam power at other locations). The effect of the system design (including the Origami structure and deployment / rigidity mechanisms) is considered to assess whether the use of this technology may impair either of these key mission/safety-critical goals. This analysis is presented and a discussion of mitigation techniques to several prospective problems is presented, before concluding with a discussion of future work.

Laser surface processing with controlled nitrogen-argon concentration levels for regulated surface life time

NASA Astrophysics Data System (ADS)

Obeidi, M. Ahmed; McCarthy, E.; Brabazon, D.

2018-03-01

Laser surface modification can be used to enhance the mechanical properties of a material, such as hardness, toughness, fatigue strength, and corrosion resistance. Surface nitriding is a widely used thermochemical method of surface modification, in which nitrogen is introduced into a metal or other material at an elevated temperature within a furnace. It is used on parts where there is a need for increased wear resistance, corrosion resistance, fatigue life, and hardness. Laser nitriding is a novel method of nitriding where the surface is heated locally by a laser, either in an atmosphere of nitrogen or with a jet of nitrogen delivered to the laser heated site. It combines the benefits of laser modification with those of nitriding. Recent work on high toughness tool steel samples has shown promising results due to the increased nitrogen gas impingement onto the laser heated region. Increased surface activity and nitrogen adsorption was achieved which resulted in a deeper and harder surface compared to conventional hardening methods. In this work, the effects of the laser power, pulse repetition frequency, and overlap percentage on laser surface treatment of 316 L SST steel samples with an argon-nitrogen jet will be presented. Resulting microstructure, phase type, microhardness, and wear resistance are presented.

Carbon-Carbon Recuperators in Closed-Brayton-Cycle Nuclear Space Power Systems: A Feasibility Assessment

NASA Technical Reports Server (NTRS)

Barrett, Michael J.; Johnson, Paul K.

2004-01-01

The feasibility of using carbon-carbon recuperators in closed-Brayton-cycle (CBC) nuclear space power conversion systems (PCS) was assessed. Recuperator performance expectations were forecast based on projected thermodynamic cycle state values for a planetary mission. Resulting thermal performance, mass and volume for a plate-fin carbon-carbon recuperator were estimated and quantitatively compared with values for a conventional offset-strip-fin metallic design. Material compatibility issues regarding carbon-carbon surfaces exposed to the working fluid in the CBC PCS were also discussed.

Design considerations for a Mars solar energy system

NASA Technical Reports Server (NTRS)

Atkinson, David H.; Gwynne, Owen

1992-01-01

The supply, collection and demand for solar power needed for a ten person base on Mars are examined. A detailed discussion is presented for the estimation of the amount of usable solar energy than can reach the surface of Mars. The irradiance is determined for high, middle and low latitudes. In general it was found that the variation of dust in the Martian atmosphere affected the optimal choice for solar power collection mechanisms. Sun tracking systems worked best under clearer conditions and basic horizontal collectors performed best under cloud/hazy conditions.

Experimental Investigation of Shrouding on Meshed Spur Gear Windage Power Loss

NASA Technical Reports Server (NTRS)

Delgado, Irebert; Hurrell, Michael

2017-01-01

Windage power loss in high-speed gearboxes result in efficiency losses and increased heating due to drag on the gear teeth. Meshed spur gear windage power loss test results are presented at ambient oil inlet temperatures both with and without shrouding. The rate of windage power loss is observed to increase above 10,000 ft.min., gear surface speed, similar to results presented in the literature. Shrouding is observed to become more effective above 15,000 ft.min., decreasing power loss by 10 at 25,000 ft.min. The need for gearbox oil drain slots limits the effectiveness of shrouding on reducing windage power loss. Also, windage power loss is observed to decrease with increasing gearbox temperatures and to increase with oil flow. Windage power losses for the unshrouded meshed spur gears are 7x more than losses determined from unshrouded single spur gear tests. A 6x to 12x increase in windage power is observed comparing shrouded single spur gear data with shrouded meshed spur gear data. Based on this preliminary study additional research is suggested to determine the effect of oil drain slot configurations, axial and radial shroud clearances, and higher gear surface speeds on windage power loss. Additional work is also suggested to determine the sensitivity of windage power loss to oil temperature and oil flow. Windage power loss of meshed spur gears tested in both the shrouded and unshrouded configurations is shown to be more than double versus the same spur gears run individually in the same shroud configurations. Further study of the physical processes behind these results is needed for optimizing gearbox shrouds for minimum windage power loss.

Empirical Requirements Analysis for Mars Surface Operations Using the Flashline Mars Arctic Research Station

NASA Technical Reports Server (NTRS)

Clancey, William J.; Lee, Pascal; Sierhuis, Maarten; Norvig, Peter (Technical Monitor)

2001-01-01

Living and working on Mars will require model-based computer systems for maintaining and controlling complex life support, communication, transportation, and power systems. This technology must work properly on the first three-year mission, augmenting human autonomy, without adding-yet more complexity to be diagnosed and repaired. One design method is to work with scientists in analog (mars-like) setting to understand how they prefer to work, what constrains will be imposed by the Mars environment, and how to ameliorate difficulties. We describe how we are using empirical requirements analysis to prototype model-based tools at a research station in the High Canadian Arctic.

Thiol-Capped Gold Nanoparticles Swell-Encapsulated into Polyurethane as Powerful Antibacterial Surfaces Under Dark and Light Conditions

PubMed Central

Macdonald, Thomas J.; Wu, Ke; Sehmi, Sandeep K.; Noimark, Sacha; Peveler, William J.; du Toit, Hendrik; Voelcker, Nicolas H.; Allan, Elaine; MacRobert, Alexander J.; Gavriilidis, Asterios; Parkin, Ivan P.

2016-01-01

A simple procedure to develop antibacterial surfaces using thiol-capped gold nanoparticles (AuNPs) is shown, which effectively kill bacteria under dark and light conditions. The effect of AuNP size and concentration on photo-activated antibacterial surfaces is reported and we show significant size effects, as well as bactericidal activity with crystal violet (CV) coated polyurethane. These materials have been proven to be powerful antibacterial surfaces against both Gram-positive and Gram-negative bacteria. AuNPs of 2, 3 or 5 nm diameter were swell-encapsulated into PU before a coating of CV was applied (known as PU-AuNPs-CV). The antibacterial activity of PU-AuNPs-CV samples was tested against Staphylococcus aureus and Escherichia coli as representative Gram-positive and Gram-negative bacteria under dark and light conditions. All light conditions in this study simulated a typical white-light hospital environment. This work demonstrates that the antibacterial activity of PU-AuNPs-CV samples and the synergistic enhancement of photoactivity of triarylmethane type dyes is highly dependent on nanoparticle size and concentration. The most powerful PU-AuNPs-CV antibacterial surfaces were achieved using 1.0 mg mL−1 swell encapsulation concentrations of 2 nm AuNPs. After two hours, Gram-positive and Gram-negative bacteria were reduced to below the detection limit (>4 log) under dark and light conditions. PMID:27982122

Influence of hydrogen on the thermoelectric voltage signal in a Pt/WO x /6 H-SiC/Ni/Pt layered structure

NASA Astrophysics Data System (ADS)

Zuev, V. V.; Grigoriev, S. N.; Fominski, V. Yu.; Volosova, M. A.; Soloviev, A. A.

2017-09-01

The possibility of detecting H2 by registering the thermal electromotive force signal, which arises between the surfaces of 6 H-SiC plates with a thickness of 400 μm, is established. The working surface of the plates is modified by deposition of a WO x film and catalytic Pt. An ohmic contact (Ni/Pt) is created on the rear surface of the plate, and this surface is maintained at a stabilized temperature of 350°C. The temperature gradient through the plate thickness arises due to the cooling of the working surface with the air medium. The delivery of H2 into this medium up to a concentration of 2% gives rise to a 15-fold increase in the electric signal, which considerably exceeds the Pt/WO x /SiC/Ni/Pt system's response registered in the usual way by measuring the current-voltage dependence. In this case, an additional power source for the registration of the thermal electromotive force is not required.

Modeling of efficient light extraction in light-pipes through specular surfaces with elliptical and lineal front shapes

NASA Astrophysics Data System (ADS)

Sánchez-Guerrero, Guillermo E.; Viera-González, Perla M.; Ceballos-Herrera, Daniel E.; Martínez-Guerra, Edgar

2016-09-01

Extraction light in light-pipes with different specular surfaces was analyzed. In the analysis, the impact of the surface shape in all properties of the extracted light in order to obtain an efficient extraction and a uniform illumination using a LED as light source. Also, several parameters of the specular surface to obtain spatial uniformity inside the light-pipe are considered. In this case, the simulation was made for a rectangular light­pipe. One objective of this work is to compare how the front face shape of the specular surface can affect the extraction of light in the lateral face of the light-pipe, only straight and elliptical front faces were used in this work and the comparison between them at different tilts and lengths were made. The main purpose of the front face was extract the light uniformly at the lateral face and this was done by studying simulations on OpticStudio Zemax. The results show how the extraction length is lower in the elliptical front but its total power performs better than the line front.

The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids.

PubMed

Hu, Bin; Kieweg, Sarah L

2012-07-15

Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability.

Thermosyphon Flooding Limits in Reduced Gravity Environments

NASA Technical Reports Server (NTRS)

Gibson, Marc A.; Jaworske, Donald A.; Sanzi, James L.; Ljubanovic, Damir

2012-01-01

Fission Power Systems have long been recognized as potential multi-kilowatt power solutions for lunar, Martian, and extended planetary surface missions. Current heat rejection technology associated with fission surface power systems has focused on titanium water thermosyphons embedded in carbon composite radiator panels. The thermosyphons, or wickless heat pipes, are used as a redundant and efficient way to spread the waste heat from the power conversion unit(s) over the radiator surface area where it can be rejected to space. It is well known that thermosyphon performance is reliant on gravitational forces to keep the evaporator wetted with the working fluid. One of the performance limits that can be encountered, if not understood, is the phenomenon of condenser flooding, otherwise known as evaporator dry out. This occurs when the gravity forces acting on the condensed fluid cannot overcome the shear forces created by the vapor escaping the evaporator throat. When this occurs, the heat transfer process is stalled and may not re-stabilize to effective levels without corrective control actions. The flooding limit in earth's gravity environment is well understood as experimentation is readily accessible, but when the environment and gravity change relative to other planetary bodies, experimentation becomes difficult. An innovative experiment was designed and flown on a parabolic flight campaign to achieve the Reduced Gravity Environments (RGE) needed to obtain empirical data for analysis. The test data is compared to current correlation models for validation and accuracy.

On thermophysical effects on the surface of functional nanostructured materials obtained with the application of femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Babenko, D. D.; Dmitriev, A. S.; Makarov, P. G.; Mikhailova, I. A.

2017-11-01

In recent years, a great scientific and practical interest is caused by functional energy surfaces, modified for certain technological problems. The urgency of the work is to develop promising technologies for thermal and nuclear power engineering, methods for converting solar energy, cooling low-current and high-current electronics devices, energy storage and transport systems on the basis of studying and developing new ways of creating and modifying the functional surfaces of heat exchange and other devices. Modified functional surfaces must have a number of new mechanical and thermophysical properties, including mechanical strength, a new surface morphology for controlling the processes of wetting and spreading working fluids on them, and have high efficiency from the viewpoint of thermohydrodynamic processes of flow and heat and mass transfer of working fluids to them. Among the various ways of modifying surfaces, recently, the method of surface exposure to femtosecond laser pulses (FLI) has become widespread. The technology of femtosecond laser surface treatment (FLPO) of solid materials has shown high efficiency, reliability, high productivity and a huge variety of modification methods. The paper presents new results on the study of thermophysical phenomena - the wetting and spreading of drops of various liquids, the study of the hysteresis of the contact angle, the study of evaporation and boiling processes on functional energy surfaces modified by femtosecond laser pulses. It is shown that in the majority of cases the presence of regular or stochastic nanostructures on the surface leads to a very strong change in the basic properties of the surface, which makes it possible to use such a technology to quickly and efficiently modify and obtain functional energy surfaces for certain predetermined purposes.

Surface Treatment on Physical Properties and Biocompatibility of Orthodontic Power Chains

PubMed Central

Cheng, H. C.; Chen, M. S.; Peng, B. Y.; Lin, W. T.; Wang, Y. H.

2017-01-01

The conventional orthodontic power chain, often composed of polymer materials, has drawbacks such as a reduction of elasticity owing to water absorption as well as surface discoloration and staining resulting from food or beverages consumed by the patient. The goal of this study was to develop a surface treatment (nanoimprinting) for orthodontic power chains and to alleviate their shortcomings. A concave template (anodic alumina) was manufactured by anodization process using pure aluminum substrate by employing the nanoimprinting process. Convex nanopillars were fabricated on the surface of orthodontic power chains, resulting in surface treatment. Distinct parameters of the nanoimprinting process (e.g., imprinting temperature, imprinting pressure, imprinting time, and demolding temperature) were used to fabricate nanopillars on the surface of orthodontic power chains. The results of this study showed that the contact angle of the power chains became larger after surface treatment. In addition, the power chains changed from hydrophilic to hydrophobic. The power chain before surface treatment without water absorption had a water absorption rate of approximately 4%, whereas a modified chain had a water absorption rate of approximately 2%–4%. Furthermore, the color adhesion of the orthodontic power chains after surface modification was less than that before surface modification. PMID:28540299

Decreased Charge Transport Barrier and Recombination of Organic Solar Cells by Constructing Interfacial Nanojunction with Annealing-Free ZnO and Al Layers.

PubMed

Liu, Chunyu; Zhang, Dezhong; Li, Zhiqi; Zhang, Xinyuan; Guo, Wenbin; Zhang, Liu; Ruan, Shengping; Long, Yongbing

2017-07-05

To overcome drawbacks of the electron transport layer, such as complex surface defects and unmatched energy levels, we successfully employed a smart semiconductor-metal interfacial nanojunciton in organic solar cells by evaporating an ultrathin Al interlayer onto annealing-free ZnO electron transport layer, resulting in a high fill factor of 73.68% and power conversion efficiency of 9.81%. The construction of ZnO-Al nanojunction could effectively fill the surface defects of ZnO and reduce its work function because of the electron transfer from Al to ZnO by Fermi level equilibrium. The filling of surface defects decreased the interfacial carrier recombination in midgap trap states. The reduced surface work function of ZnO-Al remodulated the interfacial characteristics between ZnO and [6,6]-phenyl C71-butyric acid methyl ester (PC 71 BM), decreasing or even eliminating the interfacial barrier against the electron transport, which is beneficial to improve the electron extraction capacity. The filled surface defects and reduced interfacial barrier were realistically observed by photoluminescence measurements of ZnO film and the performance of electron injection devices, respectively. This work provides a simple and effective method to simultaneously solve the problems of surface defects and unmatched energy level for the annealing-free ZnO or other metal oxide semiconductors, paving a way for the future popularization in photovoltaic devices.

Glucose Fuel Cells with a MicroChannel Fabricated on Flexible Polyimide Film

NASA Astrophysics Data System (ADS)

Sano, Ryohei; Fukushi, Yudai; Sasaki, Tsubasa; Mogi, Hiroshi; Koide, Syohei; Ikoma, Ryuta; Akatsuka, Wataru; Tsujimura, Seiya; Nishioka, Yasushiro

2013-12-01

In this work, a glucose fuel cell was fabricated using microfabrication processes assigned for microelectromechanical systems. The fuel cell was equipped with a microchannel to flow an aqueous solution of glucose. The cell was fabricated on a flexible polyimide substrate, and its porous carbon-coated aluminum (Al) electrodes of 2.8 mm in width and 11 mm in length were formed using photolithography and screen printing techniques. Porous carbon was deposited by screen printing of carbon black ink on the Al electrode surfaces in order to increase the effective electrode surface area and to absorb more enzymes on the electrode surfaces. The microchannel with a depth of 200 μm was fabricated using a hot embossing technique. A maximum power of 0.45 μW at 0.5 V that corresponds to a power density of 1.45 μW/cm2 was realized by introducing a 200 mM concentrated glucose solution at room temperature.

Model of thermal fatigue of a copper surface under the action of high-power microwaves

NASA Astrophysics Data System (ADS)

Kuzikov, S. V.; Plotkin, M. E.

2007-10-01

The accelerating structures of modern supercolliders, as well as the components of high-power microwave electron devices operated in strong cyclic electromagnetic fields should have long lifetimes. Along with the electric breakdown, the surfaces of these microwave components deteriorate and their lifetimes decrease due to thermal strains and subsequent mechanical loads on the surface metal layer. The elementary theory of thermal fatigue was developed in the 1970s. In particular, a model of metal as a continuous medium was considered. Within the framework of this model, thermal fatigue is caused by the strains arising between the hot surface layer and the cold internal layer of the metal. However, this theory does not describe all the currently available experimental data. In particular, the notion of “safe temperature” of the heating, i.e., temperature at which the surface is not destroyed during an arbitrarily long series of pulses, which was proposed in the theoretical model, is in poor agreement with the experiment performed in the Stanford Linear Accelerator Center (SLAC, USA). In this work, the thermal-fatigue theory is developed on the basis of consideration of the copper polycrystalline structure. The necessity to take it into account was demonstrated by the results of the SLAC experiment, in which a change in the mutual orientation of copper grains and the formation of cracks at their boundaries was recorded for the first time. The developed theory makes it possible to use the experimental data to refine the coefficients in the obtained formulas for the lifetime of the metal surface and to predict the number of microwave pulses before its destruction as a function of the radiation power, the surface-temperature increase at the pulse peak, and the pulse duration.

Electric Motor Thermal Management Research: Annual Progress Report

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

Bennion, Kevin S.

Past work in the area of active convective cooling provided data on the average convective heat transfer coefficients of circular orifice automatic transmission fluid (ATF) jets impinging on stationary targets intended to represent the wire bundle surface of the motor end-winding. Work during FY16 focused on the impact of alternative jet geometries that could lead to improved cooling over a larger surface of the motor winding. Results show that the planar jet heat transfer coefficients over a small (12.7-mm-diameter) target surface are not too much lower than for the circular orifice jet in which all of the ATF from themore » jet impinges on the target surface. The planar jet has the potential to achieve higher heat transfer over a larger area of the motor end winding. A new test apparatus was constructed to measure the spatial dependence of the heat transfer relative to the jet nozzle over a larger area representative of a motor end-winding. The tested planar flow geometry has the potential to provide more uniform cooling over the full end-winding surface versus the conventional jet configuration. The data will be used by motor designers to develop thermal management strategies to improve motor power density. Work on passive thermal design in collaboration with Oak Ridge National Laboratory to measure the thermal conductivity of wire bundle samples representative of end-winding and slot-winding materials was completed. Multiple measurement techniques were compared to determine which was most suitable for measuring composite wire bundle samples. NREL used a steady-state thermal resistance technique to measure the direction-dependent thermal conductivity. The work supported new interactions with industry to test new materials and reduce passive-stack thermal resistance in motors, leading to motors with increased power density. NREL collaborated with Ames Laboratory in the area of material characterization. The work focused on measuring the transverse rupture strength of new magnet materials developed at Ames. The impact of the improved transverse rupture strength is a mechanically stronger magnet that is easier for manufacturers to implement into motor designs. The thermal conductivity of the new magnet materials was also measured in comparison to two commercially available AlNiCo magnet materials. The impact of the thermal conductivity of the magnet material will need to be analyzed in the context of a motor application.« less

Surface phenomena revealed by in situ imaging: studies from adhesion, wear and cutting

NASA Astrophysics Data System (ADS)

Viswanathan, Koushik; Mahato, Anirban; Yeung, Ho; Chandrasekar, Srinivasan

2017-03-01

Surface deformation and flow phenomena are ubiquitous in mechanical processes. In this work we present an in situ imaging framework for studying a range of surface mechanical phenomena at high spatial resolution and across a range of time scales. The in situ framework is capable of resolving deformation and flow fields quantitatively in terms of surface displacements, velocities, strains and strain rates. Three case studies are presented demonstrating the power of this framework for studying surface deformation. In the first, the origin of stick-slip motion in adhesive polymer interfaces is investigated, revealing a intimate link between stick-slip and surface wave propagation. Second, the role of flow in mediating formation of surface defects and wear particles in metals is analyzed using a prototypical sliding process. It is shown that conventional post-mortem observation and inference can lead to erroneous conclusions with regard to formation of surface cracks and wear particles. The in situ framework is shown to unambiguously capture delamination wear in sliding. Third, material flow and surface deformation in a typical cutting process is analyzed. It is shown that a long-standing problem in the cutting of annealed metals is resolved by the imaging, with other benefits such as estimation of energy dissipation and power from the flow fields. In closure, guidelines are provided for profitably exploiting in situ observations to study large-strain deformation, flow and friction phenomena at surfaces that display a variety of time-scales.

Effect of plasma-induced surface charging on catalytic processes: application to CO2 activation

NASA Astrophysics Data System (ADS)

Bal, Kristof M.; Huygh, Stijn; Bogaerts, Annemie; Neyts, Erik C.

2018-02-01

Understanding the nature and effect of the multitude of plasma-surface interactions in plasma catalysis is a crucial requirement for further process development and improvement. A particularly intriguing and rather unique property of a plasma-catalytic setup is the ability of the plasma to modify the electronic structure, and hence chemical properties, of the catalyst through charging, i.e. the absorption of excess electrons. In this work, we develop a quantum chemical model based on density functional theory to study excess negative surface charges in a heterogeneous catalyst exposed to a plasma. This method is specifically applied to investigate plasma-catalytic CO2 activation on supported M/Al2O3 (M = Ti, Ni, Cu) single atom catalysts. We find that (1) the presence of a negative surface charge dramatically improves the reductive power of the catalyst, strongly promoting the splitting of CO2 to CO and oxygen, and (2) the relative activity of the investigated transition metals is also changed upon charging, suggesting that controlled surface charging is a powerful additional parameter to tune catalyst activity and selectivity. These results strongly point to plasma-induced surface charging of the catalyst as an important factor contributing to the plasma-catalyst synergistic effects frequently reported for plasma catalysis.

Fractal analysis as a potential tool for surface morphology of thin films

NASA Astrophysics Data System (ADS)

Soumya, S.; Swapna, M. S.; Raj, Vimal; Mahadevan Pillai, V. P.; Sankararaman, S.

2017-12-01

Fractal geometry developed by Mandelbrot has emerged as a potential tool for analyzing complex systems in the diversified fields of science, social science, and technology. Self-similar objects having the same details in different scales are referred to as fractals and are analyzed using the mathematics of non-Euclidean geometry. The present work is an attempt to correlate fractal dimension for surface characterization by Atomic Force Microscopy (AFM). Taking the AFM images of zinc sulphide (ZnS) thin films prepared by pulsed laser deposition (PLD) technique, under different annealing temperatures, the effect of annealing temperature and surface roughness on fractal dimension is studied. The annealing temperature and surface roughness show a strong correlation with fractal dimension. From the regression equation set, the surface roughness at a given annealing temperature can be calculated from the fractal dimension. The AFM images are processed using Photoshop and fractal dimension is calculated by box-counting method. The fractal dimension decreases from 1.986 to 1.633 while the surface roughness increases from 1.110 to 3.427, for a change of annealing temperature 30 ° C to 600 ° C. The images are also analyzed by power spectrum method to find the fractal dimension. The study reveals that the box-counting method gives better results compared to the power spectrum method.

A comparative study on performance of CBN inserts when turning steel under dry and wet conditions

NASA Astrophysics Data System (ADS)

Abdullah Bagaber, Salem; Razlan Yusoff, Ahmad

2017-10-01

Cutting fluids is the most unsustainable components of machining processes, it is negatively impacting on the environmental and additional energy required. Due to its high strength and corrosion resistance, the machinability of stainless steel has attracted considerable interest. This study aims to evaluate performance of cubic boron nitride (CBN) inserts for the machining parameters includes the power consumption and surface roughness. Due to the high single cutting-edge cost of CBN, the performance of significant is importance for hard finish turning. The present work also deals with a comparative study on power consumption and surface roughness under dry and flood conditions. Turning process of the stainless steel 316 was performed. A response surface methodology based box-behnken design (BBD) was utilized for statistical analysis. The optimum process parameters are determined as the overall performance index. The comparison study has been done between dry and wet stainless-steel cut in terms of minimum value of energy and surface roughness. The result shows the stainless still can be machined under dry condition with 18.57% improvement of power consumption and acceptable quality compare to the wet cutting. The CBN tools under dry cutting stainless steel can be used to reduce the environment impacts in terms of no cutting fluid use and less energy required which is effected in machining productivity and profit.

Reticulated vitreous carbon as a scaffold for enzymatic fuel cell designing.

PubMed

Kizling, Michal; Dzwonek, Maciej; Olszewski, Bartłomiej; Bącal, Paweł; Tymecki, Łukasz; Więckowska, Agnieszka; Stolarczyk, Krzysztof; Bilewicz, Renata

2017-09-15

Three - dimensional (3D) electrodes are successfully used to overcome the limitations of the low space - time yield and low normalized space velocity obtained in electrochemical processes with two - dimensional electrodes. In this study, we developed a three - dimensional reticulated vitreous carbon - gold (RVC-Au) sponge as a scaffold for enzymatic fuel cells (EFC). The structure of gold and the real electrode surface area can be controlled by the parameters of metal electrodeposition. In particular, a 3D RVC-Au sponge provides a large accessible surface area for immobilization of enzyme and electron mediators, moreover, effective mass diffusion can also take place through the uniform macro - porous scaffold. To efficiently bind the enzyme to the electrode and enhance electron transfer parameters the gold surface was modified with ultrasmall gold nanoparticles stabilized with glutathione. These quantum sized nanoparticles exhibit specific electronic properties and also expand the working surface of the electrode. Significantly, at the steady state of power generation, the EFC device with RVC-Au electrodes provided high volumetric power density of 1.18±0.14mWcm -3 (41.3±3.8µWcm -2 ) calculated based on the volume of electrode material with OCV 0.741±0.021V. These new 3D RVC-Au electrodes showed great promise for improving the power generation of EFC devices. Copyright © 2017 Elsevier B.V. All rights reserved.

Fission Surface Power Technology Development Status

NASA Technical Reports Server (NTRS)

Palac, Donald T.; Mason, Lee S.; Harlow, Scott

2009-01-01

With the potential future deployment of a lunar outpost there is expected to be a clear need for a high-power, lunar surface power source to support lunar surface operations independent of the day-night cycle, and Fission Surface Power (FSP) is a very effective solution for power levels above a couple 10 s of kWe. FSP is similarly enabling for the poorly illuminated surface of Mars. The power levels/requirements for a lunar outpost option are currently being studied, but it is known that cost is clearly a predominant concern to decision makers. This paper describes the plans of NASA and the DOE to execute an affordable fission surface power system technology development project to demonstrate sufficient technology readiness of an affordable FSP system so viable and cost-effective FSP system options will be available when high power lunar surface system choices are expected to be made in the early 2010s.

Fission Surface Power Technology Development Status

NASA Technical Reports Server (NTRS)

Palac, Donald T.; Mason, Lee S.; Houts, Michael G.; Harlow, Scott

2010-01-01

Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and beyond. Nuclear power is an important option, especially for locations in the solar system where sunlight is limited in availability or intensity. NASA is maintaining the option for fission surface power for the Moon and Mars by developing and demonstrating technology for an affordable fission surface power system. Because affordability drove the determination of the system concept that this technology will make possible, low development and recurring costs result, while required safety standards are maintained. However, an affordable approach to fission surface power also provides the benefits of simplicity, robustness, and conservatism in design. This paper will illuminate the multiplicity of benefits to an affordable approach to fission surface power, and will describe how the foundation for these benefits is being developed and demonstrated in the Exploration Technology Development Program s Fission Surface Power Project.

Surface charge method for molecular surfaces with curved areal elements I. Spherical triangles

NASA Astrophysics Data System (ADS)

Yu, Yi-Kuo

2018-03-01

Parametrizing a curved surface with flat triangles in electrostatics problems creates a diverging electric field. One way to avoid this is to have curved areal elements. However, charge density integration over curved patches appears difficult. This paper, dealing with spherical triangles, is the first in a series aiming to solve this problem. Here, we lay the ground work for employing curved patches for applying the surface charge method to electrostatics. We show analytically how one may control the accuracy by expanding in powers of the the arc length (multiplied by the curvature). To accommodate not extremely small curved areal elements, we have provided enough details to include higher order corrections that are needed for better accuracy when slightly larger surface elements are used.

Radiation curing progress in Hungary

NASA Astrophysics Data System (ADS)

Czvikovszky, T.

Radiation chemistry and radiation processing is an actively cultivated field of chemical technology and of applied research in several Central/Eastern European countries. Hungary, with his synthetic polymer production over 50 kg/capita/year, with his strong commitment in nuclear power production /almost 40 % of total electric power/, with his pioneering activity in food irradiation, radiation sterilization as well as EB processing of polymer — performs an iniciating role in this region. Actually four industrial EB machines are working in Hungary on plastics converting. Two of these accelerators, manufactured in SU are producing heat-shrinkable products. Two other, low-energy EB machines from FRG are working on industrial-scale surface-coating. An ELECTROCURTAIN /USA/ is serving R/D. Some actual problems of the applied radiation chemistry of EB-curing will be discussed.

First-Principles Studies of Structure-Property Relationships: Enabling Design of Functional Materials

NASA Astrophysics Data System (ADS)

Zhou, Qunfei

First-principles calculations based on quantum mechanics have been proved to be powerful for accurately regenerating experimental results, uncovering underlying myths of experimental phenomena, and accelerating the design of innovative materials. This work has been motivated by the demand to design next-generation thermionic emitting cathodes and techniques to allow for synthesis of photo-responsive polymers on complex surfaces with controlled thickness and patterns. For Os-coated tungsten thermionic dispenser cathodes, we used first-principles methods to explore the bulk and surface properties of W-Os alloys in order to explain the previously observed experimental phenomena that thermionic emission varies significantly with W-Os alloy composition. Meanwhile, we have developed a new quantum mechanical approach to quantitatively predict the thermionic emission current density from materials perspective without any semi-empirical approximations or complicated analytical models, which leads to better understanding of thermionic emission mechanism. The methods from this work could be used to accelerate the design of next-generation thermionic cathodes. For photoresponsive materials, we designed a novel type of azobenzene-containing monomer for light-mediated ring-opening metathesis polymerization (ROMP) toward the fabrication of patterned, photo-responsive polymers by controlling ring strain energy (RSE) of the monomer that drives ROMP. This allows for unprecedented remote, noninvasive, instantaneous spatial and temporal control of photo-responsive polymer deposition on complex surfaces.This work on the above two different materials systems showed the power of quantum mechanical calculations on predicting, understanding and discovering the structures and properties of both known and unknown materials in a fast, efficient and reliable way.

The simulation of thermal characteristics of 980 nm vertical cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Fang, Tianxiao; Cui, Bifeng; Hao, Shuai; Wang, Yang

2018-02-01

In order to design a single mode 980 nm vertical cavity surface emitting laser (VCSEL), a 2 μm output aperture is designed to guarantee the single mode output. The effects of different mesa sizes on the lattice temperature, the output power and the voltage are simulated under the condition of continuous working at room temperature, to obtain the optimum process parameters of mesa. It is obtained by results of the crosslight simulation software that the sizes of mesa radius are between 9.5 to 12.5 μm, which cannot only obtain the maximum output power, but also improve the heat dissipation of the device. Project supported by the Beijing Municipal Eduaction Commission (No. PXM2016_014204_500018) and the Construction of Scientific and Technological Innovation Service Ability in 2017 (No. PXM2017_014204_500034).

Evaluation of Environmentally Acceptable Lubricants (EALS) for Dams Managed by the U.S. Army Corps of Engineers

DTIC Science & Technology

2015-08-01

power, and seal against dirt, dust, and water. Lubricants work by serving as a lower viscosity material between moving surfaces. The wearing surfaces...aluminum, clay , polyurea, sodium, and calcium are most common. Complex thickeners can be composed of metal soaps mixed with low-molecular-weight organic...Polyalkyl DAE N Polyest Rape Seed Viscosity Temperature Behavior (VI) 4 2 2 2 2 2 Low Temperature Behavior (Pourpoint) 5 1 3 1 2 3 Liquid Range 4 2 3 1 2 3

Design of a CO2 laser power control system for a Spacelab microgravity experiment

NASA Technical Reports Server (NTRS)

Wenzler, Carl J.; Eichenberg, Dennis J.

1990-01-01

The surface tension driven convection experiment (STDCE) is a Space Transportation System flight experiment manifested to fly aboard the USML-1 Spacelab mission. A CO2 laser is used to heat a spot on the surface of silicone oil contained inside a test chamber. Several CO2 laser control systems were evaluated and the selected system will be interfaced with the balance of the experimental hardware to constitute a working engineering model. Descriptions and a discussion of these various design approaches are presented.

Electrode architectures for efficient electronic and ionic transport pathways in high power lithium ion batteries

NASA Astrophysics Data System (ADS)

Faulkner, Ankita Shah

As the demand for clean energy sources increases, large investments have supported R&D programs aimed at developing high power lithium ion batteries for electric vehicles, military, grid storage and space applications. State of the art lithium ion technology cannot meet power demands for these applications due to high internal resistances in the cell. These resistances are mainly comprised of ionic and electronic resistance in the electrode and electrolyte. Recently, much attention has been focused on the use of nanoscale lithium ion active materials on the premise that these materials shorten the diffusion length of lithium ions and increase the surface area for electrochemical charge transfer. While, nanomaterials have allowed significant improvements in the power density of the cell, they are not a complete solution for commercial batteries. Due to their large surface area, they introduce new challenges such as a poor electrode packing densities, high electrolyte reactivity, and expensive synthesis procedures. Since greater than 70% of the cost of the electric vehicle is due to the cost of the battery, a cost-efficient battery design is most critical. To address the limitations of nanomaterials, efficient transport pathways must be engineered in the bulk electrode. As a part of nanomanufacturing research being conducted the Center for High-rate Nanomanufacturing at Northeastern University, the first aim of the proposed work is to develop electrode architectures that enhance electronic and ionic transport pathways in large and small area lithium ion electrodes. These architectures will utilize the unique electronic and mechanical properties of carbon nanotubes to create robust electrode scaffolding that improves electrochemical charge transfer. Using extensive physical and electrochemical characterization, the second aim is to investigate the effect of electrode parameters on electrochemical performance and evaluate the performance against standard commercial electrodes. These parameters include surface morphology, electrode composition, electrode density, and operating temperature. Finally, the third aim is to investigate commercial viability of the electrode architecture. This will be accomplished by developing pouch cell prototypes using a high-rate and low cost scale-up process. Through this work, we aim to realize a commercially viable high-power electrode technology.

Low contact resistance of the MWCNTs ohmic contact to p-GaN and its application for high power LED

NASA Astrophysics Data System (ADS)

Yokogawa, Toshiya; Miyake, Syota

2017-08-01

A low contact resistance electrode for p-GaN was obtained using the metallic multi-wall carbon nanotubes (MWCNTs) as the electrode material. The work function of the metallic MWCNTs was confirmed to be 4.84 eV as large as that of Au, Pd and Ni which are generally used for the p-GaN electrode material. Consequently the specific contact resistance was obtained to be as low as 2×10-3 Ωcm2 by optimizing the GaN surface treatment using hydrochloric acid because of the large work function of the MWCNTs. We also characterized the properties of LEDs using the MWCNTs ohmic contact for p-GaN. Low operation voltage and high optical output power was successfully obtained. Threshold voltage was about 2.7 V, and optical output power was about 0.8 W for the 1×1 mm2 size LED chip.

Industrial applications of high-average power high-peak power nanosecond pulse duration Nd:YAG lasers

NASA Astrophysics Data System (ADS)

Harrison, Paul M.; Ellwi, Samir

2009-02-01

Within the vast range of laser materials processing applications, every type of successful commercial laser has been driven by a major industrial process. For high average power, high peak power, nanosecond pulse duration Nd:YAG DPSS lasers, the enabling process is high speed surface engineering. This includes applications such as thin film patterning and selective coating removal in markets such as the flat panel displays (FPD), solar and automotive industries. Applications such as these tend to require working spots that have uniform intensity distribution using specific shapes and dimensions, so a range of innovative beam delivery systems have been developed that convert the gaussian beam shape produced by the laser into a range of rectangular and/or shaped spots, as required by demands of each project. In this paper the authors will discuss the key parameters of this type of laser and examine why they are important for high speed surface engineering projects, and how they affect the underlying laser-material interaction and the removal mechanism. Several case studies will be considered in the FPD and solar markets, exploring the close link between the application, the key laser characteristics and the beam delivery system that link these together.

An analysis of power beaming for the Moon and Mars

NASA Technical Reports Server (NTRS)

Stavnes, Mark W.

1992-01-01

Operations on the surface of the Moon and Mars will depend on a reliable source of electrical power. At NASA Lewis Research Center, the feasibility of powering lunar and Martian surface sites by power beaming was studied. Constellations of nuclear or solar powered satellites using microwave or laser transmitters were designed to power an equatorial surface base. Additional surface assets, such as rovers, can also be powered from the same orbiting satellites, requiring only the additional mass of a receiver. However, the actual mass and power capabilities of the system are dependent on the location of the surface receiver. The masses of the beam power systems can be reduced by up to 50 percent, by using the power source of an electric propulsion vehicle to power the beam system. The important analyses results and any additional issues that remain unresolved are discussed.

Baseline Experimental Results on the Effect of Oil Temperature on Shrouded Meshed Spur Gear Windage Power Loss

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.; Hurrell, Michael

2017-01-01

Rotorcraft gearbox efficiencies are reduced at increased surface speeds due to viscous and impingement drag on the gear teeth. This windage power loss can affect overall mission range, payload, and frequency of transmission maintenance. Experimental and analytical studies on shrouding for single gears have shown it to be potentially effective in mitigating windage power loss. Efficiency studies on unshrouded meshed gears have shown the effect of speed, oil viscosity, temperature, load, lubrication scheme, etc. on gear windage power loss. The open literature does not contain experimental test data on shrouded meshed spur gears. Gear windage power loss test results are presented on shrouded meshed spur gears at elevated oil inlet temperatures and constant oil pressure both with and without shrouding. Shroud effectiveness is compared at four oil inlet temperatures. The results are compared to the available literature and follow-up work is outlined.

Baseline Experimental Results on the Effect of Oil Temperature on Shrouded Meshed Spur Gear Windage Power Loss

NASA Technical Reports Server (NTRS)

Delgado, Irebert R.; Hurrell, Michael James

2017-01-01

Rotorcraft gearbox efficiencies are reduced at increased surface speeds due to viscous and impingement drag on the gear teeth. This windage power loss can affect overall mission range, payload, and frequency of transmission maintenance. Experimental and analytical studies on shrouding for single gears have shown it be potentially effective in mitigating windage power loss. Efficiency studies on unshrouded meshed gears have shown the effect of speed, oil viscosity, temperature, load, lubrication scheme, etc. on gear windage power loss. The open literature does not cite data on shrouded meshed spur gears. Gear windage power loss test results are presented on shrouded meshed spur gears at elevated oil inlet temperatures and constant oil pressure both with and without shrouding. Shroud effectiveness is compared at four oil inlet temperatures. The results are compared to the available literature and follow-up work is outlined.

Technologies for Lunar Surface Power Systems Power Beaming and Transfer

NASA Astrophysics Data System (ADS)

Marzwell, Neville; Pogorzelski, Ronald J.; Chang, Kai; Little, Frank

2008-01-01

Wireless power transmission within a given working area is required or enabling for many NASA Exploration Systems. Fields of application include robotics, habitats, autonomous rendezvous and docking, life support, EVA, and many others. In robotics applications, for example, the robots must move in the working area without being hampered by power cables and, meanwhile, obtain a continuous and constant power from a power transmitter. The development of modern technology for transmitting electric power over free space has been studied for several decades, but its use in a system has been mainly limited to low power, 1-2 Vdc output voltage at a transmission distance of few meters for which relatively less than 0.5 mW/cm2 is required (e.g., Radio frequency identification RFID). Most of the rectenna conversion efficiency research to date has concentrated in low GHz frequency range of 2.45 to 10 GHz, with some work at 35 GHz. However, for space application, atmospheric adsorbtion is irrelevant and higher frequency systems with smaller transmit and receive apertures may be appropriate. For high power, most of the work on rectennas has concentrated on optimizing the conversion efficiency of the microwave rectifier element; the highest power demonstrated was 35 kW of power over a distance of 1.5 km. The objective of this paper is to establish the manner in which a very large number of very low power microwave devices can be synchronized to provide a beam of microwaves that can be used to efficiently and safely transport a significant amount of power to a remote location where it can be converted to dc (or ac) power by a ``rectenna.'' The proposed system is based on spatial power combining of the outputs of a large number of devices synchronized by mutual injection locking. We have demonstrated at JPL that such power could be achieved by combining 25 sources in a configuration that allows for convenient steering of the resulting beam of microwaves. Retrodirective beam steering for microwave power transmission (the ability to accurately track a moving receiver) has been demonstrated at Texas A&M. It is proposed that the next step in development of this concept is a modest scale up from 25 elements to 435 followed by a further scale up using such 435 element arrays as subarrays for a still larger retrodirective system. Ultimately, transmit antenna sizes on the order of 100 meters are envisioned permitting transfer levels on the order of 30 kW to aerial vehicles up to 20 km.

Superhydrophobic surfaces for applications in seawater.

PubMed

Ferrari, Michele; Benedetti, Alessandro

2015-08-01

Technological fields in which seawater is implied are numerorus, working in seawater (shipping, oil industry, marine aquaculture,..), and exploiting seawater in plants (cooling heat-exchange, desalination, power plants,..). All suffer from detrimental effects induced by biofouling mainly enhancing material failures and limiting energetic efficiencies. Among the remediation solutions, technologies coniugating economical, green and efficiency criteria should represent the direction. With the aim to meet these criteria, superhydrophobic (SH) technology attracted many researches for the protection of materials operating in contact with seawater. In this work, the literature focusing on such technology for the protection of surfaces in contact with seawater has been reviewed, mainly focusing on boat and ship hull protection. Despite the growing interest around SH technology in seawater for fouling control and friction drag reduction of hulls, to date literature shows that superhydrophobicity in seawater is still limited if compared with a time window compatible with technological needs (set on years). An evaluation of the causes of early superhydrophobicity loss under operative conditions clearly indicates that, to the best of present knowledge, a SH surface cannot preserve this feature by itself alone (especially in real seawater). Hence, we have considered to highlight the behaviour of SH surfaces in seawater in relation to early stages of biocolonization (conditioning film and pioneering bioslime formation). Considering the annual costs sustained for the biofouling impact control, advantages coming from SH surfaces, in terms of foul control and friction drag reduction, would allow economical savings allowing to cover both the appliance of longevity keeping strategies of the SH surfaces and investments in green technologies of SH coating life cycle (production, storing). In addition a brief outlook is provided on technological fields exploiting seawater in pipelines (power and desalination plants), where the SH surface finishing finds potentially interesting application for fouling and corrosion prevention applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Surface chemical analysis and ab initio investigations of CsI coated C fiber cathodes for high power microwave sources

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Morgan, Dane; LaCour, Matthew; Golby, Ken; Shiffler, Don; Booske, John H.

2010-02-01

CsI coated C fiber cathodes are promising electron emitters utilized in field emission applications. Ab initio calculations, in conjunction with experimental investigations on CsI-spray coated C fiber cathodes, were performed in order to better understand the origin of the low turn-on E-field obtained, as compared to uncoated C fibers. One possible mechanism for lowering the turn-on E-field is surface dipole layers reducing the work function. Ab initio modeling revealed that surface monolayers of Cs, CsI, Cs2O, and CsO are all capable of producing low work function C fiber cathodes (1 eV<Φ<1.5 eV), yielding a reduction in the turn-on E-field by as much as ten times, when compared to the bare fiber. Although a CsI-containing aqueous solution is spray deposited on the C fiber surface, energy dispersive x-ray spectroscopy and scanning auger microscopy measurements show coabsorption of Cs and I into the fiber interior and Cs and O on the fiber surface, with no surface I. It is therefore proposed that a cesium oxide (CsxOy) surface coating is responsible, at least in part, for the low turn E-field and superior emission characteristics of this type of fiber cathode. This CsxOy layer could be formed during preconditioning heating. CsxOy surface layers cannot only lower the fiber work function by the formation of surface dipoles (if they are thin enough) but may also enhance surface emission through their ability to emit secondary electrons due to a process of grazing electron impact. These multiple electron emission processes may explain the reported 10-100 fold reduction in the turn-on E-field of coated C fibers.

Simulation of the evolution of fused silica's surface defect during wet chemical etching

NASA Astrophysics Data System (ADS)

Liu, Taixiang; Yang, Ke; Li, Heyang; Yan, Lianghong; Yuan, Xiaodong; Yan, Hongwei

2017-08-01

Large high-power-laser facility is the basis for achieving inertial confinement fusion, one of whose missions is to make fusion energy usable in the near future. In the facility, fused silica optics plays an irreplaceable role to conduct extremely high-intensity laser to fusion capsule. But the surface defect of fused silica is a major obstacle limiting the output power of the large laser facility and likely resulting in the failure of ignition. To mitigate, or event to remove the surface defect, wet chemical etching has been developed as a practical way. However, how the surface defect evolves during wet chemical etching is still not clearly known so far. To address this problem, in this work, the three-dimensional model of surface defect is built and finite difference time domain (FDTD) method is developed to simulate the evolution of surface defect during etching. From the simulation, it is found that the surface defect will get smooth and result in the improvement of surface quality of fused silica after etching. Comparatively, surface defects (e.g. micro-crack, scratch, series of pinholes, etc.) of a typical fused silica at different etching time are experimentally measured. It can be seen that the simulation result agrees well with the result of experiment, indicating the FDTD method is valid for investigating the evolution of surface defect during etching. With the finding of FDTD simulation, one can optimize the treatment process of fused silica in practical etching or even to make the initial characterization of surface defect traceable.

Alpha power gates relevant information during working memory updating.

PubMed

Manza, Peter; Hau, Chui Luen Vera; Leung, Hoi-Chung

2014-04-23

Human working memory (WM) is inherently limited, so we must filter out irrelevant information in our environment or our mind while retaining limited important relevant contents. Previous work suggests that neural oscillations in the alpha band (8-14 Hz) play an important role in inhibiting incoming distracting information during attention and selective encoding tasks. However, whether alpha power is involved in inhibiting no-longer-relevant content or in representing relevant WM content is still debated. To clarify this issue, we manipulated the amount of relevant/irrelevant information using a task requiring spatial WM updating while measuring neural oscillatory activity via EEG and localized current sources across the scalp using a surface Laplacian transform. An initial memory set of two, four, or six spatial locations was to be memorized over a delay until an updating cue was presented indicating that only one or three locations remained relevant for a subsequent recognition test. Alpha amplitude varied with memory maintenance and updating demands among a cluster of left frontocentral electrodes. Greater postcue alpha power was associated with the high relevant load conditions (six and four dots cued to reduce to three relevant) relative to the lower load conditions (four and two dots reduced to one). Across subjects, this difference in alpha power was correlated with condition differences in performance accuracy. In contrast, no significant effects of irrelevant load were observed. These findings demonstrate that, during WM updating, alpha power reflects maintenance of relevant memory contents rather than suppression of no-longer-relevant memory traces.

Low power arcjet system spacecraft impacts

NASA Technical Reports Server (NTRS)

Pencil, Eric J.; Sarmiento, Charles J.; Lichtin, D. A.; Palchefsky, J. W.; Bogorad, A. L.

1993-01-01

Application of electrothermal arcjets on communications satellites requires assessment of integration concerns identified by the user community. Perceived risks include plume contamination of spacecraft materials, induced arcing or electrostatic discharges between differentially charged spacecraft surfaces, and conducted and radiated electromagnetic interference (EMI) for both steady state and transient conditions. A Space Act agreement between Martin Marietta Astro Space, the Rocket Research Company, and NASA's Lewis Research Center was established to experimentally examine these issues. Spacecraft materials were exposed to an arcjet plume for 40 hours, representing 40 weeks of actual spacecraft life, and contamination was characterized by changes in surface properties. With the exception of the change in emittance of one sample, all measurable changes in surface properties resulted in acceptable end of life characteristics. Charged spacecraft samples were benignly and consistently reduced to ground potential during exposure to the powered arcjet plume, suggesting that the arcjet could act as a charge control device on spacecraft. Steady state EMI signatures obtained using two different power processing units were similar to emissions measured in a previous test. Emissions measured in UHF, S, C, Ku and Ka bands obtained a null result which verified previous work in the UHF, S, and C bands. Characteristics of conducted and radiated transient emissions appear within standard spacecraft susceptibility criteria.

Design of Servo Scheme and Drive Electronics for the Integrated Electrohydraulic Actuation System of RLV-TD

NASA Astrophysics Data System (ADS)

Kurian, Priya C.; Gopinath, Anish; Shinoy, K. S.; Santhi, P.; Sundaramoorthy, K.; Sebastian, Baby; Jaya, B.; Namboodiripad, M. N.; Mookiah, T.

2017-12-01

Reusable Launch Vehicle-Technology Demonstrator (RLV-TD) is a system which has the ability to carry a payload from the earth's surface to the outer space more than once. The control actuation forms the major component of the control system and it actuates the control surfaces of the RLV-TD based on the control commands. Eight electro hydraulic actuators were used in RLV-TD for vectoring the control surfaces about their axes. A centralised Hydraulic Power Generating Unit (HPU) was used for powering the eight actuators located in two stages. The actuation system had to work for the longest ever duration of about 850 s for an Indian launch vehicle. High bandwidth requirement from autopilot was met by the servo design using the nonlinear mathematical model. Single Control Electronics which drive four electrohydraulic actuators was developed for each stage. High power electronics with soft start scheme was realized for driving the BLDC motor which is the prime mover for hydraulic pump. Many challenges arose due to single HPU for two stages, uncertainty of aero load, higher bandwidth requirements etc. and provisions were incorporated in the design to successfully overcome them. This paper describes the servo design and control electronics architecture of control actuation system.

Effects of Iris Surface Curvature on Iris Recognition

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

Thompson, Joseph T; Flynn, Patrick J; Bowyer, Kevin W

To focus on objects at various distances, the lens of the eye must change shape to adjust its refractive power. This change in lens shape causes a change in the shape of the iris surface which can be measured by examining the curvature of the iris. This work isolates the variable of iris curvature in the recognition process and shows that differences in iris curvature degrade matching ability. To our knowledge, no other work has examined the effects of varying iris curvature on matching ability. To examine this degradation, we conduct a matching experiment across pairs of images with varyingmore » degrees of iris curvature differences. The results show a statistically signi cant degradation in matching ability. Finally, the real world impact of these ndings is discussed« less

Growth of porous anodized alumina on the sputtered aluminum films with 2D-3D morphology for high specific surface area

NASA Astrophysics Data System (ADS)

Liao, M. W.; Chung, C. K.

2014-08-01

The porous anodic aluminum oxide (AAO) with high-aspect-ratio pore channels is widely used as a template for fabricating nanowires or other one-dimensional (1D) nanostructures. The high specific surface area of AAO can also be applied to the super capacitor and the supporting substrate for catalysis. The rough surface could be helpful to enhance specific surface area but it generally results in electrical field concentration even to ruin AAO. In this article, the aluminum (Al) films with the varied 2D-3D morphology on Si substrates were prepared using magnetron sputtering at a power of 50 W-185 W for 1 h at a working pressure of 2.5 × 10-1 Pa. Then, AAO was fabricated from the different Al films by means of one-step hybrid pulse anodizing (HPA) between the positive 40 V and the negative -2 V (1 s:1 s) for 3 min in 0.3 M oxalic acid at a room temperature. The microstructure and morphology of Al films were characterized by X-ray diffraction, scanning electron microscope and atomic force microscope, respectively. Some hillocks formed at the high target power could be attributed to the grain texture growth in the normal orientation of Al(1 1 1). The 3D porous AAO structure which is different from the conventional 2D planar one has been successfully demonstrated using HPA on the film with greatly rough hillock-surface formed at the highest power of 185 W. It offers a potential application of the new 3D AAO to high specific surface area devices.

Improvement of the overall performances of LiMn{sub 2}O{sub 4} via surface-modification by polypyrrole

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

Wang, Ting; Wang, Wan; Zhu, Ding

2015-11-15

Graphical abstract: Polypyrrole(PPy) film has improved the rate performance of LiMn{sub 2}O{sub 4} efficiently due to its excellent conductivity. PPy@LiMn{sub 2}O{sub 4} could provide more energy under the higher power than pristine LMO. - Highlights: • The PPy layer on the surface of LMO particles hasn’t been studied in LiMn{sub 2}O{sub 4} so far. • The solvent in the synthesis process of PPy@LMO is absolute ethyl alcohol. • The differences of surface-modification between the PPy and PI for LMO. • The analyses of rate performances are through specific power. - Abstract: Polypyrrole (PPy) is an excellent conductive polymer and themore » study on its utilization in the surface modification of the LiMn{sub 2}O{sub 4} (LMO) is few. In this work, the structure, morphology and electrochemical performance of surface-modified LiMn{sub 2}O{sub 4} composites with PPy and polyimides (PI) were discussed. The crystal structure, chemical bonds and morphology were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Moreover, the specific power and cycling performance were tested at room and high (55 °C) temperature. The PPy@LMO (surface-modified LMO composites with PPy) shows better performances than the pristine LMO. The addition of PPy not only weakens the corrosion caused by electrolyte, but also improves the discharge capacity at higher rates. The charge transfer resistance of the PPy@LMO is much lower than that of the pristine LMO after cycling.« less

Simplified correction of B1 inhomogeneity for chemical exchange saturation transfer (CEST) MRI measurement with surface transceiver coil

NASA Astrophysics Data System (ADS)

Sun, Phillip Z.; Zhou, Iris Y.; Igarashi, Takahiro; Guo, Yingkun; Xiao, Gang; Wu, Renhua

2015-03-01

Chemical exchange saturation transfer (CEST) MRI is sensitive to dilute exchangeable protons and local properties such as pH and temperate, yet its susceptibility to field inhomogeneity limits its in vivo applications. Particularly, CEST measurement varies with RF irradiation power, the dependence of which is complex due to concomitant direct RF saturation (RF spillover) effect. Because the volume transmitters provide relatively homogeneous RF field, they have been conventionally used for CEST imaging despite of their elevated specific absorption rate (SAR) and relatively low sensitivity than surface coils. To address this limitation, we developed an efficient B1 inhomogeneity correction algorithm that enables CEST MRI using surface transceiver coils. This is built on recent work that showed the inverse CEST asymmetry analysis (CESTRind) is not susceptible to confounding RF spillover effect. We here postulated that the linear relationship between RF power level and CESTRind can be extended for correcting B1 inhomogeneity induced CEST MRI artifacts. Briefly, we prepared a tissue-like Creatine gel pH phantom and collected multiparametric MRI including relaxation, field map and CEST MRI under multiple RF power levels, using a conventional surface transceiver coil. The raw CEST images showed substantial heterogeneity due to B1 inhomogeneity, with pH contrast to noise ratio (CNR) being 8.8. In comparison, pH MRI CNR of the fieldinhomogeneity corrected CEST MRI was found to be 17.2, substantially higher than that without correction. To summarize, our study validated an efficient field inhomogeneity correction that enables sensitive CEST MRI with surface transceiver, promising for in vivo translation.

A two-stage ceramic tile grout sealing process using a high power diode laser—Grout development and materials characteristics

NASA Astrophysics Data System (ADS)

Lawrence, J.; Li, L.; Spencer, J. T.

1998-04-01

Work has been conducted using a 60 Wcw high power diode laser (HPDL) in order to determine the feasibility and characteristics of sealing the void between adjoining ceramic tiles with a specially developed grout material having an impermeable enamel surface glaze. A two-stage process has been developed using a new grout material which consists of two distinct components: an amalgamated compound substrate and a glazed enamel surface; the amalgamated compound seal providing a tough, heat resistant bulk substrate, whilst the enamel provides an impervious surface. HPDL processing has resulted in crack free seals produced in normal atmospheric conditions. The basic process phenomena are investigated and the laser effects in terms of seal morphology, composition and microstructure are presented. Also, the resultant heat affects are analysed and described, as well as the effects of the shield gases, O 2 and Ar, during laser processing. Tiles were successfully sealed with power densities as low as 500 W/cm 2 and at rates up to 600 mm/min. Contact angle measurements revealed that due to the wettability characteristics of the amalgamated oxide compound grout (AOCG), laser surface treatment was necessary in order to alter the surface from a polycrystalline to a semi-amorphous structure, thus allowing the enamel to adhere. Bonding of the enamel to the AOCG and the ceramic tiles was identified as being principally due to van der Waals forces, and on a very small scale, some of the base AOCG material dissolving into the glaze.

Experimental validation of a sub-surface model of solar power for distributed marine sensor systems

NASA Astrophysics Data System (ADS)

Hahn, Gregory G.; Cantin, Heather P.; Shafer, Michael W.

2016-04-01

The capabilities of distributed sensor systems such as marine wildlife telemetry tags could be significantly enhanced through the integration of photovoltaic modules. Photovoltaic cells could be used to supplement the primary batteries for wildlife telemetry tags to allow for extended tag deployments, wherein larger amounts of data could be collected and transmitted in near real time. In this article, we present experimental results used to validate and improve key aspects of our original model for sub-surface solar power. We discuss the test methods and results, comparing analytic predictions to experimental results. In a previous work, we introduced a model for sub-surface solar power that used analytic models and empirical data to predict the solar irradiance available for harvest at any depth under the ocean's surface over the course of a year. This model presented underwater photovoltaic transduction as a viable means of supplementing energy for marine wildlife telemetry tags. The additional data provided by improvements in daily energy budgets would enhance the temporal and spatial comprehension of the host's activities and/or environments. Photovoltaic transduction is one method that has not been widely deployed in the sub-surface marine environments despite widespread use on terrestrial and avian species wildlife tag systems. Until now, the use of photovoltaic cells for underwater energy harvesting has generally been disregarded as a viable energy source in this arena. In addition to marine telemetry systems, photovoltaic energy harvesting systems could also serve as a means of energy supply for autonomous underwater vehicles (AUVs), as well as submersible buoys for oceanographic data collection.

Design of Simple Landslide Monitoring System

NASA Astrophysics Data System (ADS)

Meng, Qingjia; Cai, Lingling

2018-01-01

The simple landslide monitoring system is mainly designed for slope, collapse body and surface crack. In the harsh environment, the dynamic displacement data of the disaster body is transmitted to the terminal acquisition system in real time. The main body of the system adopt is PIC32MX795F512. This chip is to realize low power design, wakes the system up through the clock chip, and turns on the switching power supply at set time, which makes the wireless transmission module running during the interval to ensure the maximum battery consumption, so that the system can be stable long term work.

Summary of NASA landing-gear research

NASA Technical Reports Server (NTRS)

Fisher, B. D.; Sleeper, R. K.; Stubbs, S. M.

1978-01-01

This paper presents a brief summary of the airplane landing gear research underway at NASA. The technology areas include: ground handling simulator, antiskid braking systems, space shuttle nose-gear shimmy, active control landing gear, wire brush skid landing gear, air cushion landing systems, tire/surface friction characteristics, tire mechanical properties, tire-tread materials, powered wheels for taxiing, and crosswind landing gear. This paper deals mainly with the programs on tire-tread materials, powered wheel taxiing, air cushion landing systems, and crosswind landing gear research with particular emphasis on previously unreported results of recently completed flight tests. Work in the remaining areas is only mentioned.

Experimental study of radiation dose rate at different strategic points of the BAEC TRIGA Research Reactor.

PubMed

Ajijul Hoq, M; Malek Soner, M A; Salam, M A; Haque, M M; Khanom, Salma; Fahad, S M

2017-12-01

The 3MW TRIGA Mark-II Research Reactor of Bangladesh Atomic Energy Commission (BAEC) has been under operation for about thirty years since its commissioning at 1986. In accordance with the demand of fundamental nuclear research works, the reactor has to operate at different power levels by utilizing a number of experimental facilities. Regarding the enquiry for safety of reactor operating personnel and radiation workers, it is necessary to know the radiation level at different strategic points of the reactor where they are often worked. In the present study, neutron, beta and gamma radiation dose rate at different strategic points of the reactor facility with reactor power level of 2.4MW was measured to estimate the rising level of radiation due to its operational activities. From the obtained results high radiation dose is observed at the measurement position of the piercing beam port which is caused by neutron leakage and accordingly, dose rate at the stated position with different reactor power levels was measured. This study also deals with the gamma dose rate measurements at a fixed position of the reactor pool top surface for different reactor power levels under both Natural Convection Cooling Mode (NCCM) and Forced Convection Cooling Mode (FCCM). Results show that, radiation dose rate is higher for NCCM in compared with FCCM and increasing with the increase of reactor power. Thus, concerning the radiological safety issues for working personnel and the general public, the radiation dose level monitoring and the experimental analysis performed within this paper is so much effective and the result of this work can be utilized for base line data and code verification of the nuclear reactor. Copyright © 2017 Elsevier Ltd. All rights reserved.

Superhydrophobic Ceramic Coatings by Solution Precursor Plasma Spray

PubMed Central

Cai, Yuxuan; Coyle, Thomas W.; Azimi, Gisele; Mostaghimi, Javad

2016-01-01

This work presents a novel coating technique to manufacture ceramic superhydrophobic coatings rapidly and economically. A rare earth oxide (REO) was selected as the coating material due to its hydrophobic nature, chemical inertness, high temperature stability, and good mechanical properties, and deposited on stainless steel substrates by solution precursor plasma spray (SPPS). The effects of various spraying conditions including standoff distance, torch power, number of torch passes, types of solvent and plasma velocity were investigated. The as-sprayed coating demonstrated a hierarchically structured surface topography, which closely resembles superhydrophobic surfaces found in nature. The water contact angle on the SPPS superhydrophobic coating was up to 65% higher than on smooth REO surfaces. PMID:27091306

Experimental demonstration of Martian soil simulant removal from a surface using a pulsed plasma jet.

PubMed

Ticoş, C M; Scurtu, A; Toader, D; Banu, N

2015-03-01

A plasma jet produced in a small coaxial plasma gun operated at voltages up to 2 kV and working in pure carbon dioxide (CO2) at a few Torr is used to remove Martian soil simulant from a surface. A capacitor with 0.5 mF is charged up from a high voltage source and supplies the power to the coaxial electrodes. The muzzle of the coaxial plasma gun is placed at a few millimeters near the dusty surface and the jet is fired parallel with the surface. Removal of dust is imaged in real time with a high speed camera. Mars regolith simulant JSC-Mars-1A with particle sizes up to 5 mm is used on different types of surfaces made of aluminium, cotton fabric, polyethylene, cardboard, and phenolic.

Experimental demonstration of Martian soil simulant removal from a surface using a pulsed plasma jet

NASA Astrophysics Data System (ADS)

Ticoş, C. M.; Scurtu, A.; Toader, D.; Banu, N.

2015-03-01

A plasma jet produced in a small coaxial plasma gun operated at voltages up to 2 kV and working in pure carbon dioxide (CO2) at a few Torr is used to remove Martian soil simulant from a surface. A capacitor with 0.5 mF is charged up from a high voltage source and supplies the power to the coaxial electrodes. The muzzle of the coaxial plasma gun is placed at a few millimeters near the dusty surface and the jet is fired parallel with the surface. Removal of dust is imaged in real time with a high speed camera. Mars regolith simulant JSC-Mars-1A with particle sizes up to 5 mm is used on different types of surfaces made of aluminium, cotton fabric, polyethylene, cardboard, and phenolic.

Probing and controlling terahertz-driven structural dynamics with surface sensitivity

DOE PAGES

Bowlan, Pamela Renee; Bowlan, J.; Trugman, S. A.; ...

2017-03-17

Intense, single-cycle terahertz (THz) pulses are powerful tools to understand and control material properties through low-energy resonances, such as phonons. Combining this with optical second harmonic generation (SHG) makes it possible to observe the resulting ultrafast structural changes with surface sensitivity. This makes SHG an ideal method to probe phonon dynamics in topological insulators (TI), materials with unique surface transport properties. Here, we resonantly excite a phonon mode in the TI Bi 2Se 3with THz pulses and use SHG to separate the resulting symmetry changes at the surface from the bulk. Furthermore, we coherently control the lattice vibrations with amore » pair of THz pulses. Lastly, our work demonstrates a versatile, table-top tool to probe and control phonon dynamics in a range of systems, particularly at surfaces and interfaces.« less

High-powered CO2 -lasers and noise control

NASA Astrophysics Data System (ADS)

Honkasalo, Antero; Kuronen, Juhani

High-power CO2 -lasers are being more and more widely used for welding, drilling and cutting in machine shops. In the near future, different kinds of surface treatments will also become routine practice with laser units. The industries benefitting most from high power lasers will be: the automotive industry, shipbuilding, the offshore industry, the aerospace industry, the nuclear and the chemical processing industries. Metal processing lasers are interesting from the point of view of noise control because the working tool is a laser beam. It is reasonable to suppose that the use of such laser beams will lead to lower noise levels than those connected with traditional metal processing methods and equipment. In the following presentation, the noise levels and possible noise-control problems attached to the use of high-powered CO2 -lasers are studied.

Nanocrystalline mesoporous SMO thin films prepared by sol gel process for MEMS-based hydrogen sensor

NASA Astrophysics Data System (ADS)

Gong, Jianwei; Fei, Weifeng; Seal, Sudipta; Chen, Quanfang

2004-01-01

MEMS based SnO2 gas sensor with sol gel synthesized mesoporous nanocrystalline (<10 nm) semiconductor thin (100~150 nm) film has been recently developed. The SnO2 nano film is fabricated with the combination of polymeric sol gel chemistry with block copolymers used for structure directing agents. The novel hydrogen sensor has a fast response time (1s) and quick recovery time (3s), as well as good sensitivity (about 90%), comparing to other hydrogen sensors developed. The improved capabilities are credited to the large surface to volume ratio of gas sensing thin film with nano sized porous surface topology, which can greatly increase the sensitivity even at relatively low working temperature. The gas sensing film is deposited onto a thin dielectric membrane of low thermal conductivity, which provides good thermal isolation between substrate and the gas-sensitive heated area on the membrane. In this way the power consumption can be kept very low. Since the fabrication process is completely compatible with IC industry, it makes mass production possible and greatly reduces the cost. The working temperature of the new sensor can be reduced as low as 100°C. The low working temperature posse advantages such as lower power consumption, lower thermal induced signal shift as well as safe detection in certain environments where temperature is strictly limited.

Space Technology Plasma Issues in 2001

NASA Technical Reports Server (NTRS)

Garrett, Henry (Editor); Feynman, Joan (Editor); Gabriel, Stephen (Editor)

1986-01-01

The purpose of the workshop was to identify and discuss plasma issues that need to be resolved during the next 10 to 20 years (circa 2001) to facilitate the development of the advanced space technology that will be required 20 or 30 years into the future. The workshop consisted of 2 days of invited papers and 2 sessions of contributed poster papers. During the third day the meeting broke into 5 working groups, each of which held discussions and then reported back to the conference as a whole. The five panels were: Measurements Technology and Active Experiments Working Group; Advanced High-Voltage, High-Power and Energy-Storage Space Systems Working Group; Large Structures and Tethers Working Group; Plasma Interactions and Surface/Materials Effects Working Group; and Beam Plasmas, Electronic Propulsion and Active Experiments Using Beams Working Group.

Solar panel cleaning robot

NASA Astrophysics Data System (ADS)

Nalladhimmu, Pavan Kumar Reddy; Priyadarshini, S.

2018-04-01

As the demand of electricity is increasing, there is need to using the renewable sources to produce the energy at present of power shortage, the use of solar energy could be beneficial to great extent and easy to get the maximum efficiency. There is an urgent in improving the efficiency of solar power generation. Current solar panels setups take a major power loss when unwanted obstructions cover the surface of the panels. To make solar energy more efficiency of solar array systems must be maximized efficiency evaluation of PV panels, that has been discussed with particular attention to the presence of dust on the efficiency of the PV panels have been highlighted. This paper gives the how the solar panel cleaning system works and designing of the cleaning system.

Solar vs. Fission Surface Power for Mars

NASA Technical Reports Server (NTRS)

Rucker, Michelle A.; Oleson, Steve; George, Pat; Landis, Geoffrey A.; Fincannon, James; Bogner, Amee; Jones, Robert E.; Turnbull, Elizabeth; Martini, Michael C.; Gyekenyesi, John Z.;

A solar engine using the thermal expansion of metals.

NASA Technical Reports Server (NTRS)

Beam, R.; Jedlicka, J.

1973-01-01

A thermal engine which uses solid metal as the single-phase working substance to convert solar energy into small amounts of mechanical energy is described. Test data are given for an engine whose working substance was annealed 304-type steel welded into a thin-walled tube that was mounted in a bearing at each end (making it free to rotate about its axis) with a flywheel mass at its midpoint. When heated on its upper surface, the tube rotates producing steady power. The theory of the engine is outlined.

Analytical and experimental investigation of the feasibility of accelerated lifetime testing of materials exposed to an atomic oxygen beam

NASA Technical Reports Server (NTRS)

Albridge, Royal; Barnes, Alan; Tolk, Norman

1993-01-01

The interaction of atomic particles with surfaces is of both scientific and technological interest. Past work emphasizes the measurement of high-energy sputtering yields. Very little work utilized low-energy beams for which chemical and electronic effects can be important. Even less work has been carried out using well-defined low-energy projectiles. The use of low-energy, reactive projectiles permits one to investigate surface processes that have not been well characterized. As the energy of the projectile decreases, the collisional cascades and spikes, that are common for high-energy projectiles, become less important, and chemical and electronic effects can play a significant role. Aspects of particle-surface interactions are of concern in several areas of technology. For example, the erosion, desorption, and glow of surfaces of spacecraft in orbit are important in the arena of space technology. The materials studied under this contract are of possible use on the exterior portions of the power generation system of Space Station Freedom. Under the original designs, Space Station Freedom's power generation system would generate potential differences on the surface as high as 200 volts. Ions in the plasma that often surround orbiting vehicles would be accelerated by these potentials leading to bombardment and erosion of the exposed surfaces. The major constituent of the atmosphere, approximately 90 percent, in the low earth orbit region is atomic oxygen. Since atomic oxygen is extremely reactive with most materials, chemical effects can arise in addition to the physical sputtering caused by the acceleration of the oxygen ions. Furthermore, the incident oxygen ions can remain embedded in the exposed surfaces, altering the chemical composition of the surfaces. Since the effective binding energy of a chemically altered surface can be quite different from that of the pure substrate, the sputtering yield of a chemically altered surface is usually different also. The low-energy O+ sputtering yield measurements, reported here, will help quantify the erosion rates for materials exposed to the low-earth orbit environment. These measurements are of technological importance in another respect. In most surface analysis techniques, a surface is bombarded with ions, electrons or photons. Information concerning the structure of the surface and near-surface bulk, abundance of impurities and defects, as well as other surface properties are obtained either from the desorbed species or from the scattered projectiles. Because of their low penetration depth, low-energy ions provide an advantage over other techniques because they provide information that is more indicative of conditions on the surface rather than integrated effects arising from deeper in the bulk. A better understanding of the microscopic processes involved in these interactions is not only of basic scientific interest, but will also aid the scientific community by increasing the accuracy and usefulness of these surface analysis techniques.

Theoretical modeling and experimental validation of a torsional piezoelectric vibration energy harvesting system

NASA Astrophysics Data System (ADS)

Qian, Feng; Zhou, Wanlu; Kaluvan, Suresh; Zhang, Haifeng; Zuo, Lei

2018-04-01

Vibration energy harvesting has been extensively studied in recent years to explore a continuous power source for sensor networks and low-power electronics. Torsional vibration widely exists in mechanical engineering; however, it has not yet been well exploited for energy harvesting. This paper presents a theoretical model and an experimental validation of a torsional vibration energy harvesting system comprised of a shaft and a shear mode piezoelectric transducer. The piezoelectric transducer position on the surface of the shaft is parameterized by two variables that are optimized to obtain the maximum power output. The piezoelectric transducer can work in d 15 mode (pure shear mode), coupled mode of d 31 and d 33, and coupled mode of d 33, d 31 and d 15, respectively, when attached at different angles. Approximate expressions of voltage and power are derived from the theoretical model, which gave predictions in good agreement with analytical solutions. Physical interpretations on the implicit relationship between the power output and the position parameters of the piezoelectric transducer is given based on the derived approximate expression. The optimal position and angle of the piezoelectric transducer is determined, in which case, the transducer works in the coupled mode of d 15, d 31 and d 33.

Multiphysics Modeling of an Annular Linear Induction Pump With Applications to Space Nuclear Power Systems

NASA Technical Reports Server (NTRS)

Kilbane, J.; Polzin, K. A.

2014-01-01

An annular linear induction pump (ALIP) that could be used for circulating liquid-metal coolant in a fission surface power reactor system is modeled in the present work using the computational COMSOL Multiphysics package. The pump is modeled using a two-dimensional, axisymmetric geometry and solved under conditions similar to those used during experimental pump testing. Real, nonlinear, temperature-dependent material properties can be incorporated into the model for both the electrically-conducting working fluid in the pump (NaK-78) and structural components of the pump. The intricate three-phase coil configuration of the pump is implemented in the model to produce an axially-traveling magnetic wave that is qualitatively similar to the measured magnetic wave. The model qualitatively captures the expected feature of a peak in efficiency as a function of flow rate.

[Michel Foucault and the persistence of psychiatric power].

PubMed

Caponi, Sandra

2009-01-01

This article aims studying the course held by Michel Foucault at the Collège de France in 1973-1974. The records of this course were published in 2003 under the name ' Psychiatric power' . The objective was to compare the different ways in which Foucault analyzes the question of madness in ' Psychiatric power' and in ' History of Madness in the Classical Age' (1961). It is a comparative study about the different ways of analyzing madness developed by Michel Foucault during the archeological and genealogic periods of his work. The absence of the body; binary diagnosis; the description of the surface of symptoms; the classification of diseases more similar to the botanical classification than to pathology; the process of cure directly linked to restitution of behaviors and moral values; as well as the over-power of the psychiatrist, seem to speak about the persistence of an old model of power, a pre-modern and pre-capitalist model, a residue of the old sovereign power.

Lightweight Solar Power for Small Satellites

NASA Technical Reports Server (NTRS)

Nabors, Sammy A.

2015-01-01

The innovation targets small satellites or CubeSats for which conventional deployable arrays are not feasible due to their size, weight and complexity. This novel solar cell array includes a thin and flexible photovoltaic cell applied to an inflatable structure to create a high surface area array for collecting solar energy in a lightweight, simple and deployable structure. The inflatable array, with its high functional surface area, eliminates the need and the mechanisms required to point the system toward the sun. The power density achievable in these small arrays is similar to that of conventional high-power deployable/pointable arrays used on large satellites or space vehicles. Although inflatable solar arrays have been previously considered by others, the arrays involved the use of traditional rigid solar cells. Researchers are currently working with thin film photovoltaics from various suppliers so that the NASA innovation is not limited to any particular solar cell technology. NASA has built prototypes and tested functionality before and after inflation. As shown in the current-voltage currents below, deployment does not damage the cell performance.

Solar Power Grid Unfurled

NASA Technical Reports Server (NTRS)

2008-01-01

Shown here is one of the first images taken by NASA's Phoenix Mars Lander of one of the octagonal solar panels, which opened like two handheld, collapsible fans on either side of the spacecraft. Beyond this view is a small slice of the north polar terrain of Mars.

The successfully deployed solar panels are critical to the success of the 90-day mission, as they are the spacecraft's only means of replenishing its power. Even before these images reached Earth, power readings from the spacecraft indicated to engineers that the solar panels were already at work recharging the spacecraft's batteries.

Before deploying the Surface Stereo Imager to take these images, the lander waited about 15 minutes for the dust to settle.

This image was taken by the spacecraft's Surface Stereo Imager on Sol, or Martian day, 0 (May 25, 2008).

This image has been geometrically corrected.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

Solar Power Grid

NASA Technical Reports Server (NTRS)

2008-01-01

Shown here is one of the first images taken by NASA's Phoenix Mars Lander of one of the octagonal solar panels, which opened like two handheld, collapsible fans on either side of the spacecraft. Beyond this view is a small slice of the north polar terrain of Mars.

The successfully deployed solar panels are critical to the success of the 90-day mission, as they are the spacecraft's only means of replenishing its power. Even before these images reached Earth, power readings from the spacecraft indicated to engineers that the solar panels were already at work recharging the spacecraft's batteries.

Before deploying the Surface Stereo Imager to take these images, the lander waited about 15 minutes for the dust to settle.

This image was taken by the spacecraft's Surface Stereo Imager on Sol, or Martian day, 0 (May 25, 2008).

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

Effectiveness of the Wavelet Transform on the Surface EMG to Understand the Muscle Fatigue During Walk

NASA Astrophysics Data System (ADS)

Hussain, M. S.; Mamun, Md.

2012-01-01

Muscle fatigue is the decline in ability of a muscle to create force. Electromyography (EMG) is a medical technique for measuring muscle response to nervous stimulation. During a sustained muscle contraction, the power spectrum of the EMG shifts towards lower frequencies. These effects are due to muscle fatigue. Muscle fatigue is often a result of unhealthy work practice. In this research, the effectiveness of the wavelet transform applied to the surface EMG (SEMG) signal as a means of understanding muscle fatigue during walk is presented. Power spectrum and bispectrum analysis on the EMG signal getting from right rectus femoris muscle is executed utilizing various wavelet functions (WFs). It is possible to recognize muscle fatigue appreciably with the proper choice of the WF. The outcome proves that the most momentous changes in the EMG power spectrum are symbolized by WF Daubechies45. Moreover, this research has compared bispectrum properties to the other WFs. To determine muscle fatigue during gait, Daubechies45 is used in this research to analyze the SEMG signal.

Microstructure and corrosion behavior of laser processed NiTi alloy.

PubMed

Marattukalam, Jithin J; Singh, Amit Kumar; Datta, Susmit; Das, Mitun; Balla, Vamsi Krishna; Bontha, Srikanth; Kalpathy, Sreeram K

2015-12-01

Laser Engineered Net Shaping (LENS™), a commercially available additive manufacturing technology, has been used to fabricate dense equiatomic NiTi alloy components. The primary aim of this work is to study the effect of laser power and scan speed on microstructure, phase constituents, hardness and corrosion behavior of laser processed NiTi alloy. The results showed retention of large amount of high-temperature austenite phase at room temperature due to high cooling rates associated with laser processing. The high amount of austenite in these samples increased the hardness. The grain size and corrosion resistance were found to increase with laser power. The surface energy of NiTi alloy, calculated using contact angles, decreased from 61 mN/m to 56 mN/m with increase in laser energy density from 20 J/mm(2) to 80 J/mm(2). The decrease in surface energy shifted the corrosion potentials to nobler direction and decreased the corrosion current. Under present experimental conditions the laser power found to have strong influence on microstructure, phase constituents and corrosion resistance of NiTi alloy. Copyright © 2015 Elsevier B.V. All rights reserved.

Pulsed voltage electrospray ion source and method for preventing analyte electrolysis

DOEpatents

Kertesz, Vilmos [Knoxville, TN; Van Berkel, Gary [Clinton, TN

2011-12-27

An electrospray ion source and method of operation includes the application of pulsed voltage to prevent electrolysis of analytes with a low electrochemical potential. The electrospray ion source can include an emitter, a counter electrode, and a power supply. The emitter can include a liquid conduit, a primary working electrode having a liquid contacting surface, and a spray tip, where the liquid conduit and the working electrode are in liquid communication. The counter electrode can be proximate to, but separated from, the spray tip. The power system can supply voltage to the working electrode in the form of a pulse wave, where the pulse wave oscillates between at least an energized voltage and a relaxation voltage. The relaxation duration of the relaxation voltage can range from 1 millisecond to 35 milliseconds. The pulse duration of the energized voltage can be less than 1 millisecond and the frequency of the pulse wave can range from 30 to 800 Hz.

Overview of Multi-Kilowatt Free-Piston Stirling Power Conversion Research at Glenn Research Center

NASA Technical Reports Server (NTRS)

Geng, Steven M.; Mason, Lee S.; Dyson, Rodger W.; Penswick, L. Barry

2008-01-01

As a step towards development of Stirling power conversion for potential use in Fission Surface Power (FSP) systems, a pair of commercially available 1 kW class free-piston Stirling convertors and a pair of commercially available pressure wave generators (which will be plumbed together to create a high power Stirling linear alternator test rig) have been procured for in-house testing at Glenn Research Center (GRC). Delivery of both the Stirling convertors and the linear alternator test rig is expected by October 2007. The 1 kW class free-piston Stirling convertors will be tested at GRC to map and verify performance. The convertors will later be modified to operate with a NaK liquid metal pumped loop for thermal energy input. The high power linear alternator test rig will be used to map and verify high power Stirling linear alternator performance and to develop power management and distribution (PMAD) methods and techniques. This paper provides an overview of the multi-kilowatt free-piston Stirling power conversion work being performed at GRC.

Overview of Multi-kilowatt Free-Piston Stirling Power Conversion Research at GRC

NASA Technical Reports Server (NTRS)

Geng, Steven M.; Mason, Lee S.; Dyson, Rodger W.; Penswick, L. Barry

2008-01-01

As a step towards development of Stirling power conversion for potential use in Fission Surface Power (FSP) systems, a pair of commercially available 1 kW class free-piston Stirling convertors and a pair of commercially available pressure wave generators (which will be plumbed together to create a high power Stirling linear alternator test rig) have been procured for in-house testing at Glenn Research Center. Delivery of both the Stirling convertors and the linear alternator test rig is expected by October, 2007. The 1 kW class free-piston Stirling convertors will be tested at GRC to map and verify performance. The convertors will later be modified to operate with a NaK liquid metal pumped loop for thermal energy input. The high power linear alternator test rig will be used to map and verify high power Stirling linear alternator performance and to develop power management and distribution (PMAD) methods and techniques. This paper provides an overview of the multi-kilowatt free-piston Stirling power conversion work being performed at GRC.

Overview of Multi-Kilowatt Free-Piston Stirling Power Conversion Research at GRC

NASA Astrophysics Data System (ADS)

Geng, Steven M.; Mason, Lee S.; Dyson, Rodger W.; Penswick, L. Barry

2008-01-01

As a step towards development of Stirling power conversion for potential use in Fission Surface Power (FSP) systems, a pair of commercially available 1 kW class free-piston Stirling convertors and a pair of commercially available pressure wave generators (which will be plumbed together to create a high power Stirling linear alternator test rig) have been procured for in-house testing at Glenn Research Center. Delivery of both the Stirling convertors and the linear alternator test rig is expected by October, 2007. The 1 kW class free-piston Stirling convertors will be tested at GRC to map and verify performance. The convertors will later be modified to operate with a NaK liquid metal pumped loop for thermal energy input. The high power linear alternator test rig will be used to map and verify high power Stirling linear alternator performance and to develop power management and distribution (PMAD) methods and techniques. This paper provides an overview of the multi-kilowatt free-piston Stirling power conversion work being performed at GRC.

Ab initio investigation of barium-scandium-oxygen coatings on tungsten for electron emitting cathodes

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Booske, John H.; Morgan, Dane

2010-02-01

Microwave, x-ray, and radio-frequency radiation sources require a cathode emitting electrons into vacuum. Thermionic B-type dispenser cathodes consist of BaxOz coatings on tungsten (W), where the surface coatings lower the W work function and enhance electron emission. The new and promising class of scandate cathodes modifies the B-type surface through inclusion of Sc, and their superior emissive properties are also believed to stem from the formation of a low work function surface alloy. In order to better understand these cathode systems, density-functional theory (DFT)-based ab initio modeling is used to explore the stability and work function of BaxScyOz on W(001) monolayer-type surface structures. It is demonstrated how surface depolarization effects can be calculated easily using ab initio calculations and fitted to an analytic depolarization equation. This approach enables the rapid extraction of the complete depolarization curve (work function versus coverage relation) from relatively few DFT calculations, useful for understanding and characterizing the emitting properties of novel cathode materials. It is generally believed that the B-type cathode has some concentration of Ba-O dimers on the W surface, although their structure is not known. Calculations suggest that tilted Ba-O dimers are the stable dimer surface configuration and can explain the observed work function reduction corresponding to various dimer coverages. Tilted Ba-O dimers represent a new surface coating structure not previously proposed for the activated B-type cathode. The thermodynamically stable phase of Ba and O on the W surface was identified to be the Ba0.25O configuration, possessing a significantly lower Φ value than any of the Ba-O dimer configurations investigated. The identification of a more stable Ba0.25O phase implies that if Ba-O dimers cover the surface of emitting B-type cathodes, then a nonequilibrium steady state must dominate the emitting surface. The identification of a stable and low work function Ba0.25Sc0.25O structure suggests that addition of Sc to the B-type cathode surface could form this alloy structure under operating conditions, leading to improved cathode performance and stability. Detailed comparison to previous experimental results of BaxScyOz on W surface coatings are made to both validate the modeling and aid in interpretation of experimental data. The studies presented here demonstrate that ab initio methods are powerful for understanding the fundamental physics of electron emitting materials systems and can potentially aid in the development of improved cathodes.

Development and use of culture systems to modulate specific cell responses

NASA Astrophysics Data System (ADS)

Martin, Yves

Culture surfaces that induce specific localized cell responses are required to achieve tissue-like cell growth in three-dimensional (3D) environments, as well as to develop more efficient cell-based diagnostic techniques, noticeably when working with fragile cells such as stem cells or platelets. As such, Chapter 1 of this thesis work is devoted to the review of 3D cell-material interactions in vitro and the corresponding existing culture systems available to achieve in vivo-like cell responses. More adequate 3D culture systems will need to be developed to mimic several characteristics of in vivo environments, including lowered non-specific cell-material interactions and localized biochemical signaling. The experimental work in this thesis is based on the hypothesis that well-studied and optimized surface treatments will be able to lower non-specific cell-material interactions and allow local chemical modification in order to achieve specific localized cell-material interactions for different applications. As such, in Chapter 2 and Chapter 3 of this thesis, surface treatments were developed using plasma polymerization and covalent immobilization of a low-fouling polymer (i.e., poly(ethylene glycol)) and characterized and optimized using a large number of techniques including atomic force microscopy, quartz crystal microbalance, surface plasmon resonance, x-ray photoelectron spectroscopy and fluorescence-based techniques. The main plasma polymerization parameter important for surface chemical content, specifically nitrogen to carbon content, was identified as being glow discharge power, while reaction time and power determined plasma film thickness. Moreover, plasma films were shown to be stable in aqueous environments. Covalently-bound poly(ethylene glycol) (PEG) layers physicochemical and mechanical properties are dependent on fabrication methods. Polymer concentration in solution is an important indicator of final layer properties, and use of a theta solvent induces complex aggregation phenomena in solution yielding layers with widely different properties. Chemically available primary amine groups are also shown to be present, paving the way for the immobilization of bio-active molecules. An application of low-fouling locally modified surfaces is given in Chapter 4 by the development of a novel diagnostic surface to evaluate platelet activation which is until now very difficult as platelets are readily activated by in vitro manipulations. Significant results from volunteer donors indicate that this diagnostic instrument has the potential to allow the rapid estimation of platelet activation levels in whole blood.

Performance of Inductors Attached to a Galvanizing Bath

NASA Astrophysics Data System (ADS)

Zhou, Xinping; Yuan, Shuo; Liu, Chi; Yang, Peng; Qian, Chaoqun; Song, Bao

2013-12-01

By taking a galvanizing bath with inductors from an Iron and Steel Co., Ltd as an example, the distributions of Lorentz force and generated heat in the inductor are simulated. As a result, the zinc flow and the temperature distribution driven by the Lorentz force and the generated heat in the inductor of a galvanizing bath are simulated numerically, and their characteristics are analyzed. The relationship of the surface-weighted average velocity at the outlet and the temperature difference between the inlet and the outlet and the effective power for the inductor is studied. Results show that with an increase in effective power for the inductor, the surface-weighted average velocity at the outlet and the temperature difference between the inlet and the outlet increase gradually. We envisage this work to lay a foundation for the study of the performance of the galvanizing bath in future.

A post-processing method to simulate the generalized RF sheath boundary condition

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

Myra, James R.; Kohno, Haruhiko

For applications of ICRF power in fusion devices, control of RF sheath interactions is of great importance. A sheath boundary condition (SBC) was previously developed to provide an effective surface impedance for the interaction of the RF sheath with the waves. The SBC enables the surface power flux and rectified potential energy available for sputtering to be calculated. For legacy codes which cannot easily implement the SBC, or to speed convergence in codes which do implement it, we consider here an approximate method to simulate SBCs by post-processing results obtained using other, e.g. conducting wall, boundary conditions. The basic approximationmore » is that the modifications resulting from the generalized SBC are driven by a fixed incoming wave which could be either a fast wave or a slow wave. Finally, the method is illustrated in slab geometry and compared with exact numerical solutions; it is shown to work very well.« less

A post-processing method to simulate the generalized RF sheath boundary condition

DOE PAGES

Myra, James R.; Kohno, Haruhiko

2017-10-23

For applications of ICRF power in fusion devices, control of RF sheath interactions is of great importance. A sheath boundary condition (SBC) was previously developed to provide an effective surface impedance for the interaction of the RF sheath with the waves. The SBC enables the surface power flux and rectified potential energy available for sputtering to be calculated. For legacy codes which cannot easily implement the SBC, or to speed convergence in codes which do implement it, we consider here an approximate method to simulate SBCs by post-processing results obtained using other, e.g. conducting wall, boundary conditions. The basic approximationmore » is that the modifications resulting from the generalized SBC are driven by a fixed incoming wave which could be either a fast wave or a slow wave. Finally, the method is illustrated in slab geometry and compared with exact numerical solutions; it is shown to work very well.« less

Origin and Reduction of 1 / f Magnetic Flux Noise in Superconducting Devices

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

Kumar, P.; Sendelbach, S.; Beck, M. A.

2016-10-01

Magnetic flux noise is a dominant source of dephasing and energy relaxation in superconducting qubits. The noise power spectral density varies with frequency as 1=fα, with α ≲ 1, and spans 13 orders of magnitude. Recent work indicates that the noise is from unpaired magnetic defects on the surfaces of the superconducting devices. Here, we demonstrate that adsorbed molecular O2 is the dominant contributor to magnetism in superconducting thin films. We show that this magnetism can be reduced by appropriate surface treatment or improvement in the sample vacuum environment. We observe a suppression of static spin susceptibility by more thanmore » an order of magnitude and a suppression of 1=f magnetic flux noise power spectral density of up to a factor of 5. These advances open the door to the realization of superconducting qubits with improved quantum coherence.« less

Field tests of 2- and 40-tube condensers at the East Mesa Geothermal Test Site

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

Murphy, R.W.; Domingo, N.

1982-05-01

Two water-cooled isobutane condensers, one with 2 tubes and one with 40 tubes, were subjected to field tests at the East Mesa Geothermal Test Site to assess relative heat transfer performance in both surface evaporator and direct-contact evaporator modes. The five groups of tests established that field performance was below earlier laboratory-determined levels and that direct-contact evaporator mode performance was poorer than that for the surface evaporator mode. In all test situations, fluted condenser tubes performed better than smooth condenser tubes. Cooling water quality had no significant effect on performance, but brine preflash in the direct-contact mode did promote somemore » relative performance improvement. Important implications of these results for binary geothermal power plants are that (1) working-fluid-side impurities can significantly degrade heat transfer performance of the power plant condensers and (2) provisions for minimizing such impurities may be required.« less

Performance of Surface-Mount Ceramic and Solid Tantalum Capacitors for Cryogenic Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; MacDonald, Thomas L.; Hammoud, Ahmad; Gerber, Scott

1998-01-01

Low temperature electronics are of great interest for space exploration programs. These include missions to the outer planets, earth-orbiting and deep-space probes, remote-sensing and communication satellites. Terrestrial applications would also benefit from the availability of low temperature electronics. Power components capable of low temperature operation would, thus, enhance the technologies needed for the development of advanced power systems suitable for use in harsh environments. In this work, ceramic and solid tantalum capacitors were evaluated in terms of their dielectric properties as a function of temperature and at various frequencies. The surface-mount devices were characterized in terms of their capacitance stability and dissipation factor in the frequency range of 50 Hz to 100 kHz at temperatures ranging from room temperature (20 deg. C) to about liquid nitrogen temperature (-190 deg. C). The results are discussed and conclusions made concerning the suitability of the capacitors investigated for low temperature applications.

Origin and Reduction of 1 /f Magnetic Flux Noise in Superconducting Devices

NASA Astrophysics Data System (ADS)

Kumar, P.; Sendelbach, S.; Beck, M. A.; Freeland, J. W.; Wang, Zhe; Wang, Hui; Yu, Clare C.; Wu, R. Q.; Pappas, D. P.; McDermott, R.

2016-10-01

Magnetic flux noise is a dominant source of dephasing and energy relaxation in superconducting qubits. The noise power spectral density varies with frequency as 1 /fα, with α ≲1 , and spans 13 orders of magnitude. Recent work indicates that the noise is from unpaired magnetic defects on the surfaces of the superconducting devices. Here, we demonstrate that adsorbed molecular O2 is the dominant contributor to magnetism in superconducting thin films. We show that this magnetism can be reduced by appropriate surface treatment or improvement in the sample vacuum environment. We observe a suppression of static spin susceptibility by more than an order of magnitude and a suppression of 1 /f magnetic flux noise power spectral density of up to a factor of 5. These advances open the door to the realization of superconducting qubits with improved quantum coherence.

Low-power, high-uniform, and forming-free resistive memory based on Mg-deficient amorphous MgO film with rough surface

NASA Astrophysics Data System (ADS)

Guo, Jiajun; Ren, Shuxia; Wu, Liqian; Kang, Xin; Chen, Wei; Zhao, Xu

2018-03-01

Saving energy and reducing operation parameter fluctuations remain crucial for enabling resistive random access memory (RRAM) to emerge as a universal memory. In this work, we report a resistive memory device based on an amorphous MgO (a-MgO) film that not only exhibits ultralow programming voltage (just 0.22 V) and low power consumption (less than 176.7 μW) but also shows excellent operative uniformity (the coefficient of variation is only 1.7% and 2.2% for SET and RESET voltage, respectively). Moreover, it also shows a forming-free characteristic. Further analysis indicates that these distinctive properties can be attributed to the unstable local structures and the rough surface of the Mg-deficient a-MgO film. These findings show the potential of using a-MgO in high-performance nonvolatile memory applications.

Analysis and experimental investigation of ceramic powder coating on aluminium piston

NASA Astrophysics Data System (ADS)

Pal, S.; Deore, A.; Choudhary, A.; Madhwani, V.; Vijapuri, D.

2017-11-01

Energy conservation and efficiency have always been the quest of engineers concerned with internal combustion engines. The diesel engine generally offers better fuel economy than its counterpart petrol engine. Even the diesel engine rejects about two thirds of the heat energy of the fuel, one-third to the coolant, and one third to the exhaust, leaving only about one-third as useful power output. Theoretically if the heat rejected could be reduced, then the thermal efficiency would be improved, at least up to the limit set by the second law of thermodynamics. Low Heat Rejection engines aim to do this by reducing the heat lost to the coolant. Thermal Barrier Coatings (TBCs) in diesel engines lead to advantages including higher power density, fuel efficiency, and multifuel capacity due to higher combustion chamber temperature. Using TBC can increase engine power by 8%, decrease the specific fuel consumption by 15-20% and increase the exhaust gas temperature by 200K. Although several systems have been used as TBC for different purposes, yttria stabilized zirconia with 7-8 wt.% yttria has received the most attention. Several factors playing important role in TBC life include thermal conductivity, thermo chemical stability at the service temperature, high thermo mechanical stability to the maximum service temperature and thermal expansion coefficient (TEC). This work mainly concentrates on the behaviour of three TBC powders under the same diesel engine conditions. This work finds out the best powder among yttria, alumina and zirconia to be used as a piston coating material i.e., the one resulting in lowest heat flux and low side skirt and bottom temperature has been chosen for the coating purpose. This work then analyses the coated sample for its surface properties such as hardness, roughness, corrosion resistance and microstructural study. This work aims at making it easier for the manufacturers choose the coating material for engine coating purposes and surface properties for operating them in their service period.

Tilt optimized flip uniformity (TOFU) RF pulse for uniform image contrast at low specific absorption rate levels in combination with a surface breast coil at 7 Tesla.

PubMed

van Kalleveen, Irene M L; Boer, Vincent O; Luijten, Peter R; Klomp, Dennis W J

2015-08-01

Going to ultrahigh field MRI (e.g., 7 Tesla [T]), the nonuniformity of the B1+ field and the increased radiofrequency (RF) power deposition become challenging. While surface coils improve the power efficiency in B1+, its field remains nonuniform. In this work, an RF pulse was designed that uses the slab selection to compensate the inhomogeneous B1+ field of a surface coil without a substantial increase in specific absorption rate (SAR). A breast surface coil was used with a decaying B1+ field in the anterior-posterior direction of the human breast. Slab selective RF pulses were designed and compared with adiabatic and spokes RF pulses. Proof of principle was demonstrated with FFE and B1+ maps of the human breast. In vivo measurements obtained with the breast surface coil show that the tilt optimized flip uniformity (TOFU) RF pulses can improve the flip angle homogeneity by 31%, while the SAR will be lower compared with BIR-4 and spokes RF pulses. By applying TOFU RF pulses to the breast surface coil, we are able to compensate the inhomogeneous B1+ field, while keeping the SAR low. Therefore stronger T1 -weighting in FFE sequences can be obtained, while pulse durations can remain short, as shown in the human breast at 7T. © 2014 Wiley Periodicals, Inc.

Detection and monitoring of surface micro-cracks by PPP-BOTDA.

PubMed

Meng, Dewei; Ansari, Farhad; Feng, Xin

2015-06-01

Appearance of micrometer size surface cracks is common in structural elements such as welded connections, beams, and gusset plates in bridges. Brillouin scattering-based sensors are capable of making distributed strain measurements. Pre-pump-pulse Brillouin optical time domain analysis (PPP-BOTDA) provides a centimeter-level spatial resolution, which facilitates detection and monitoring of the cracks. In the work described here, in addition to the shift in Brillouin frequency (distributed strains), change in the Brillouin gain spectrum (BGS) width is investigated for the detection and monitoring of surface micro-cracks. A theoretical analysis was undertaken in order to verify the rationality of the proposed method. The theoretical approach involved simulation of strain within a segment of the optical fiber traversing a crack and use of the simulated strain distribution in the opto-mechanical relations in order to numerically obtain the change in the BGS. Simulations revealed that the increase in crack opening displacements is associated with increase in BGS width and decrease in its peak power. Experimental results also indicated that the increases in crack opening displacements are accompanied with increases in BGS widths. However, it will be difficult to use the decrease in BGS power peak as another indicator due to practical difficulties in establishing generalized power amplitude in all the experiments. The study indicated that, in combination with the shift in Brillouin frequency, the increase in BGS width will provide a strong tool for detection and monitoring of surface micro-crack growths.

Options for Affordable Fission Surface Power Systems

NASA Technical Reports Server (NTRS)

Houts, Mike; Gaddis, Steve; Porter, Ron; VanDyke, Melissa; Martin Jim; Godfroy, Tom; Bragg-Sitton, Shannon; Garber, Anne; Pearson, Boise

2006-01-01

Fission surface power systems could provide abundant power anywhere on free surface of the moon or Mars. Locations could include permanently shaded regions on the moon and high latitudes on Mars. To be fully utilized; however, fission surface power systems must be safe, have adequate performance, and be affordable. This paper discusses options for the design and development of such systems.

Modelling of multi-vortex convection of fine alloying components in the molten pool under the laser radiation

NASA Astrophysics Data System (ADS)

Gurin, A. M.; Kovalev, O. B.

2013-06-01

The work is devoted to the mathematical modelling and numerical solution of the problems of conjugate micro-convection, which arises under the laser radiation action in the metal melt with surface-active refractory disperse components added for the modification, hardening, and doping of the treated surface. A multi-vortex structure of the melt flow has been obtained, the number of vortices in which depends on the surface tension variation, on the temperature and power of laser radiation. Special attention is paid to the numerical modelling of the behavior in the melt of the substrate of disperse admixture consisting of the tungsten carbide particles. The role of microconvection in the distribution of powder particles in the surface layer of the substrate after its cooling is shown.

High-performance finite-difference time-domain simulations of C-Mod and ITER RF antennas

NASA Astrophysics Data System (ADS)

Jenkins, Thomas G.; Smithe, David N.

2015-12-01

Finite-difference time-domain methods have, in recent years, developed powerful capabilities for modeling realistic ICRF behavior in fusion plasmas [1, 2, 3, 4]. When coupled with the power of modern high-performance computing platforms, such techniques allow the behavior of antenna near and far fields, and the flow of RF power, to be studied in realistic experimental scenarios at previously inaccessible levels of resolution. In this talk, we present results and 3D animations from high-performance FDTD simulations on the Titan Cray XK7 supercomputer, modeling both Alcator C-Mod's field-aligned ICRF antenna and the ITER antenna module. Much of this work focuses on scans over edge density, and tailored edge density profiles, to study dispersion and the physics of slow wave excitation in the immediate vicinity of the antenna hardware and SOL. An understanding of the role of the lower-hybrid resonance in low-density scenarios is emerging, and possible implications of this for the NSTX launcher and power balance are also discussed. In addition, we discuss ongoing work centered on using these simulations to estimate sputtering and impurity production, as driven by the self-consistent sheath potentials at antenna surfaces.

High-performance finite-difference time-domain simulations of C-Mod and ITER RF antennas

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

Jenkins, Thomas G., E-mail: tgjenkins@txcorp.com; Smithe, David N., E-mail: smithe@txcorp.com

Finite-difference time-domain methods have, in recent years, developed powerful capabilities for modeling realistic ICRF behavior in fusion plasmas [1, 2, 3, 4]. When coupled with the power of modern high-performance computing platforms, such techniques allow the behavior of antenna near and far fields, and the flow of RF power, to be studied in realistic experimental scenarios at previously inaccessible levels of resolution. In this talk, we present results and 3D animations from high-performance FDTD simulations on the Titan Cray XK7 supercomputer, modeling both Alcator C-Mod’s field-aligned ICRF antenna and the ITER antenna module. Much of this work focuses on scansmore » over edge density, and tailored edge density profiles, to study dispersion and the physics of slow wave excitation in the immediate vicinity of the antenna hardware and SOL. An understanding of the role of the lower-hybrid resonance in low-density scenarios is emerging, and possible implications of this for the NSTX launcher and power balance are also discussed. In addition, we discuss ongoing work centered on using these simulations to estimate sputtering and impurity production, as driven by the self-consistent sheath potentials at antenna surfaces.« less

Complex amine-based reagents

NASA Astrophysics Data System (ADS)

Suslov, S. Yu.; Kirilina, A. V.; Sergeev, I. A.; Zezyulya, T. V.; Sokolova, E. A.; Eremina, E. V.; Timofeev, N. V.

2017-03-01

Amines for a long time have been applied to maintaining water chemistry conditions (WCC) at power plants. However, making use of complex reagents that are the mixture of neutralizing and the filmforming amines, which may also contain other organic components, causes many disputes. This is mainly due to lack of reliable information about these components. The protective properties of any amine with regard to metal surfaces depend on several factors, which are considered in this article. The results of applying complex reagents to the protection of heating surfaces in industrial conditions and estimated behavior forecasts for various reagents under maintaining WCC on heat-recovery boilers with different thermal circuits are presented. The case of a two-drum heat-recovery boiler with in-line drums was used as an example, for which we present the calculated pH values for various brands of reagents under the same conditions. Work with different reagent brands and its analysis enabled us to derive a composition best suitable for the conditions of their practical applications in heat-recovery boilers at different pressures. Testing the new amine reagent performed at a CCPP power unit shows that this reagent is an adequate base for further development of reagents based on amine compounds. An example of testing a complex reagent is shown created with the participation of the authors within the framework the program of import substitution and its possible use is demonstrated for maintaining WCC of power-generating units of combined-cycle power plants (CCPP) and TPP. The compliance of the employed reagents with the standards of water chemistry conditions and protection of heating surfaces were assessed. The application of amine-containing reagents at power-generating units of TPP makes it possible to solve complex problems aimed at ensuring the sparing cleaning of heating surfaces from deposits and the implementation of conservation and management of water chemistry condition on the TPP equipment.

Effect of Bauxite addition on Adhesion Strength and Surface Roughness of Fly ash based Plasma Sprayed Coatings

NASA Astrophysics Data System (ADS)

Bhuyan, S. K.; Samal, S.; Pattnaik, D.; Sahu, A.; Swain, B.; Thiyagarajan, T. K.; Mishra, S. C.

2018-03-01

The environment is being contaminated with advancement of new technology, day by day. One of the primary sources for this contamination is the industrial waste. Industrialization is the prime reason behind the prosperity of any country to meet the materialistic demand. To run the industries, a huge amount of (electric) power is needed and hence need for thermal power plants to serve the purpose. In present scenario, coal fired thermal power plants are set up which generates a huge quantity of Fly ash. Consumption of industrial waste (Fly ash), continually a major concern for human race. In recent years, fly ash is being utilized for various purposes i.e. making bricks, mine reclamation, production of cements etc. The presence of Silica and Alumina in fly ash makes it useful for thermal barrier applications also. The plasma spray technology has the advantage of being able to process any types of metal/ceramic mineral, low-grade-ore minerals etc. to make value-added products and also to deposit ceramics, metals and a combination of these to deposit composite coatings with desired microstructure and required properties on a range of substrate materials. The present work focuses on utilization of fly ash mixing with bauxite (ore mineral) for a high valued application. Fly ash with 10 and 20% bauxite addition is used to deposit plasma spray overlay coatings at different power levels (10-20kW) on aluminum and mild steel substrates. Adhesion strength and surface roughness of the coatings are evaluated. Phase composition analysis of the coatings were done using X-ray diffraction analysis. Surface morphology of the coatings was studied using a scanning electron microscope (SEM). Maximum adhesion strength of 4.924 MPa is obtained for the composition fly ash and bauxite (10%), coated on mild steel at 16kW torch power level. The surface roughness (Ra) of the coatings is found to vary between 10.0102 to 17.2341 micron.

Investigations on Cs-free alternatives for negative ion formation in a low pressure hydrogen discharge at ion source relevant parameters

NASA Astrophysics Data System (ADS)

Kurutz, U.; Friedl, R.; Fantz, U.

2017-07-01

Caesium (Cs) is applied in high power negative hydrogen ion sources to reduce a converter surface’s work function and thus enabling an efficient negative ion surface formation. Inherent drawbacks with the usage of this reactive alkali metal motivate the search for Cs-free alternative materials for neutral beam injection systems in fusion research. In view of a future DEMOnstration power plant, a suitable material should provide a high negative ion formation efficiency and comply with the RAMI issues of the system: reliability, availability, maintainability, inspectability. Promising candidates, like low work function materials (molybdenum doped with lanthanum (MoLa) and LaB6), as well as different non-doped and boron-doped diamond samples were investigated in this context at identical and ion source relevant parameters at the laboratory experiment HOMER. Negative ion densities were measured above the samples by means of laser photodetachment and compared with two reference cases: pure negative ion volume formation with negative ion densities of about 1× {10}15 {{{m}}}-3 and the effect of H- surface production using an in situ caesiated stainless steel sample which yields 2.5 times higher densities. Compared to pure volume production, none of the diamond samples did exhibit a measurable increase in H- densities, while showing clear indications of plasma-induced erosion. In contrast, both MoLa and LaB6 produced systematically higher densities (MoLa: ×1.60 LaB6: ×1.43). The difference to caesiation can be attributed to the higher work functions of MoLa and LaB6 which are expected to be about 3 eV for both compared to 2.1 eV of a caesiated surface.

Effects of laser shock peening with contacting foil on micro laser texturing surface of Ti6Al4V

NASA Astrophysics Data System (ADS)

Dai, Fengze; Zhang, Zidong; Ren, Xudong; Lu, Jinzhong; Huang, Shu

2018-02-01

Ti6Al4V samples with micro-dimple arrays were subjected to laser shock peening in contact with foil (HCLSP). The surface roughness, micro-hardness, the residual stress distribution and the surface morphology of the micro-dimple arrays were studied to evaluate the effects of HCLSP. Moreover, the surface topography of the foils in contact was also analyzed. The gap existence between the foil and the to-be treated surface led the mechanism of HCLSP to be different compared to regular laser shock peening. The surface roughness reduction, the work-hardening effects, the compressive residual stress and the micro crack enclosure were achieved. A simplified ball-hitting-surface model was utilized to analyze the HCLSP impact. The model could well explain the experimental results. When treated by the HCLSP with H62 foil at the laser power density of 4.24 GW/cm2, the Ti6Al4V samples with micro-dimple arrays exhibit well surface topography and mechanical performance.

Enhancing Efficiency of Perovskite Solar Cells via Surface Passivation with Graphene Oxide Interlayer.

PubMed

Li, Hao; Tao, Leiming; Huang, Feihong; Sun, Qiang; Zhao, Xiaojuan; Han, Junbo; Shen, Yan; Wang, Mingkui

2017-11-08

Perovskite solar cells have been demonstrated as promising low-cost and highly efficient next-generation solar cells. Enhancing V OC by minimization the interfacial recombination kinetics can further improve device performance. In this work, we for the first time reported on surface passivation of perovskite layers with chemical modified graphene oxides, which act as efficient interlayer to reduce interfacial recombination and enhance hole extraction as well. Our modeling points out that the passivation effect mainly comes from the interaction between functional group (4-fluorophenyl) and under-coordinated Pb ions. The resulting perovskite solar cells achieved high efficient power conversion efficiency of 18.75% with enhanced high open circuit V OC of 1.11 V. Ultrafast spectroscopy, photovoltage/photocurrent transient decay, and electronic impedance spectroscopy characterizations reveal the effective passivation effect and the energy loss mechanism. This work sheds light on the importance of interfacial engineering on the surface of perovskite layers and provides possible ways to improve device efficiency.

Physical characterization and recovery of corroded fingerprint impressions from postblast copper pipe bomb fragments.

PubMed

Bond, John W; Brady, Thomas F

2013-05-01

Pipe bombs made from 1 mm thick copper pipe were detonated with a low explosive power powder. Analysis of the physical characteristics of fragments revealed that the copper had undergone work hardening with an increased Vickers Hardness of 107HV1 compared with 80HV1 for unexploded copper pipe. Mean plastic strain prior to fracture was calculated at 0.28 showing evidence of both plastic deformation and wall thinning. An examination of the external surface showed microfractures running parallel with the length of the pipe at approximately 100 μm intervals and 1-2 μm in width. Many larger fragments had folded "inside out" making the original outside surface inaccessible and difficult to fold back through work hardening. A visual examination for fingerprint corrosion revealed ridge details on several fragments that were enhanced by selective digital mapping of colors reflected from the surface of the copper. One of these fingerprints was identified partially to the original donor. © 2013 American Academy of Forensic Sciences.

Design and fabrication of non silicon substrate based MEMS energy harvester for arbitrary surface applications

NASA Astrophysics Data System (ADS)

Balpande, Suresh S.; Pande, Rajesh S.

2016-04-01

Internet of Things (IoT) uses MEMS sensor nodes and actuators to sense and control objects through Internet. IOT deploys millions of chemical battery driven sensors at different locations which are not reliable many times because of frequent requirement of charging & battery replacement in case of underground laying, placement at harsh environmental conditions, huge count and difference between demand (24 % per year) and availability (energy density growing rate 8% per year). Energy harvester fabricated on silicon wafers have been widely used in manufacturing MEMS structures. These devices require complex fabrication processes, costly chemicals & clean room. In addition to this silicon wafer based devices are not suitable for curved surfaces like pipes, human bodies, organisms, or other arbitrary surface like clothes, structure surfaces which does not have flat and smooth surface always. Therefore, devices based on rigid silicon wafers are not suitable for these applications. Flexible structures are the key solution for this problems. Energy transduction mechanism generates power from free surrounding vibrations or impact. Sensor nodes application has been purposefully selected due to discrete power requirement at low duty cycle. Such nodes require an average power budget in the range of about 0.1 microwatt to 1 mW over a period of 3-5 seconds. Energy harvester is the best alternate source in contrast with battery for sensor node application. Novel design of Energy Harvester based on cheapest flexible non silicon substrate i.e. cellulose acetate substrate have been modeled, simulated and analyzed on COMSOL multiphysics and fabricated using sol-gel spin coating setup. Single cantilever based harvester generates 60-75 mV peak electric potential at 22Hz frequency and approximately 22 µW power at 1K-Ohm load. Cantilever array can be employed for generating higher voltage by replicating this structure. This work covers design, optimization, fabrication of harvester and schottky diodes based voltage multiplier.

Design and fabrication of non silicon substrate based MEMS energy harvester for arbitrary surface applications

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

Balpande, Suresh S., E-mail: balpandes@rknec.edu; Pande, Rajesh S.

Internet of Things (IoT) uses MEMS sensor nodes and actuators to sense and control objects through Internet. IOT deploys millions of chemical battery driven sensors at different locations which are not reliable many times because of frequent requirement of charging & battery replacement in case of underground laying, placement at harsh environmental conditions, huge count and difference between demand (24 % per year) and availability (energy density growing rate 8% per year). Energy harvester fabricated on silicon wafers have been widely used in manufacturing MEMS structures. These devices require complex fabrication processes, costly chemicals & clean room. In addition tomore » this silicon wafer based devices are not suitable for curved surfaces like pipes, human bodies, organisms, or other arbitrary surface like clothes, structure surfaces which does not have flat and smooth surface always. Therefore, devices based on rigid silicon wafers are not suitable for these applications. Flexible structures are the key solution for this problems. Energy transduction mechanism generates power from free surrounding vibrations or impact. Sensor nodes application has been purposefully selected due to discrete power requirement at low duty cycle. Such nodes require an average power budget in the range of about 0.1 microwatt to 1 mW over a period of 3-5 seconds. Energy harvester is the best alternate source in contrast with battery for sensor node application. Novel design of Energy Harvester based on cheapest flexible non silicon substrate i.e. cellulose acetate substrate have been modeled, simulated and analyzed on COMSOL multiphysics and fabricated using sol-gel spin coating setup. Single cantilever based harvester generates 60-75 mV peak electric potential at 22Hz frequency and approximately 22 µW power at 1K-Ohm load. Cantilever array can be employed for generating higher voltage by replicating this structure. This work covers design, optimization, fabrication of harvester and schottky diodes based voltage multiplier.« less

Dual-purpose self-deliverable lunar surface PV electrical power system

NASA Technical Reports Server (NTRS)

Arnold, Jack H.; Harris, David W.; Cross, Eldon R.; Flood, Dennis J.

1991-01-01

A safe haven and work supported PV power systems on the lunar surface will likely be required by NASA in support of the manned outpost scheduled for the post-2000 lunar/Mars exploration and colonization initiative. Initial system modeling and computer analysis shows that the concept is workable and contains no major high risk technology issues which cannot be resolved in the circa 2000 to 2025 timeframe. A specific selection of the best suited type of electric thruster has not been done; the initial modeling was done using an ion thruster, but Rocketdyne must also evaluate arc and resisto-jets before a final design can be formulated. As a general observation, it appears that such a system can deliver itself to the Moon using many system elements that must be transported as dead payload mass in more conventional delivery modes. It further appears that a larger power system providing a much higher safe haven power level is feasible if this delivery system is implemented, perhaps even sufficient to permit resource prospecting and/or lab experimentation. The concept permits growth and can be expanded to include cargo transport such as habitat and working modules. In short, the combined payload could be manned soon after landing and checkout. NASA has expended substantial resources in the development of electric propulsion concepts and hardware that can be applied to a lunar transport system such as described herein. In short, the paper may represent a viable mission on which previous investments play an invaluable role. A more comprehensive technical paper which embodies second generation analysis and system size will be prepared for near-term presentation.

Effects of microwave heating on porous structure of regenerated powdered activated carbon used in xylose.

PubMed

Li, Wei; Wang, Xinying; Peng, Jinhui

2014-01-01

The regeneration of spent powdered activated carbons used in xylose decolourization by microwave heating was investigated. Effects of microwave power and microwave heating time on the adsorption capacity of regenerated activated carbons were evaluated. The optimum conditions obtained are as follows: microwave power 800W; microwave heating time 30min. Regenerated activated carbon in this work has high adsorption capacities for the amount of methylene blue of 16 cm3/0.1 g and the iodine number of 1000.06mg/g. The specific surface areas of fresh commercial activated carbon, spent carbon and regenerated activated carbon were calculated according to the Brunauer, Emmett and Teller method, and the pore-size distributions of these carbons were characterized by non-local density functional theory (NLDFT). The results show that the specific surface area and the total pore volume of regenerated activated carbon are 1064 m2/g and 1.181 mL/g, respectively, indicating the feasibility of regeneration of spent powdered activated carbon used in xylose decolourization by microwave heating. The results of surface fractal dimensions also confirm the results of isotherms and NLDFT.

Pitting and Bending Fatigue Evaluations of a New Case-Carburized Gear Steel

NASA Technical Reports Server (NTRS)

Krantz, Timothy; Tufts, Brian

2007-01-01

The power density of a gearbox is an important consideration for many applications and is especially important for gearboxes used on aircraft. One approach to improving power density of gearing is to improve the steel properties by design of the alloy. The alloy tested in this work was designed to be case-carburized with surface hardness of Rockwell C66 after hardening. Test gear performance was evaluated using surface fatigue tests and single-tooth bending fatigue tests. The performance of gears made from the new alloy was compared to the performance of gears made from two alloys currently used for aviation gearing. The new alloy exhibited significantly better performance in surface fatigue testing, demonstrating the value of the improved properties in the case layer. However, the alloy exhibited lesser performance in single-tooth bending fatigue testing. The fracture toughness of the tested gears was insufficient for use in aircraft applications as judged by the behavior exhibited during the single tooth bending tests. This study quantified the performance of the new alloy and has provided guidance for the design and development of next generation gear steels.

Pool boiler heat transport system for a 25 kWe advanced Stirling conversion system

NASA Astrophysics Data System (ADS)

Anderson, W. G.; Rosenfeld, J. H.; Saaski, E. L.; Noble, J.; Tower, L.

Experiments to determine alkali metal/enhanced surface combinations that have stable boiling at the temperatures and heat fluxes that occur in the Stirling engine are reported. Two enhanced surfaces and two alkali metal working fluids were evaluated. The enhanced surfaces were an EDM hole covered surface and a sintered-powder-metal porous layer surface. The working fluids tested were potassium and eutectic sodium-potasium alloy (NaK), both with and without undissolved noncondensible gas. Noncondensible gas (He and Xe) was added to the system to provide gas in the nucleation sites, preventing quenching of the sites. The experiments demonstrated the potential of an alkali metal pool boiler heat transport system for use in a solar-powered Stirling engine. The most favorable fluid/surface combination tested was NaK boiling on a -100 +140 mesh 304L stainless steel sintered porous layer with no undissolved noncondensible gas. This combination provided stable, high-performance boiling at the operating temperature of 700 C. Heat fluxes into the system ranged from 10 to 50 W/sq cm. The transition from free convection to nucleate boiling occurred at temperatures near 540 C. Based on these experiments, a pool boiler was designed for a full-scale 25-kWe Stirling system.

Pool boiler heat transport system for a 25 kWe advanced Stirling conversion system

NASA Technical Reports Server (NTRS)

Anderson, W. G.; Rosenfeld, J. H.; Saaski, E. L.; Noble, J.; Tower, L.

1990-01-01

Experiments to determine alkali metal/enhanced surface combinations that have stable boiling at the temperatures and heat fluxes that occur in the Stirling engine are reported. Two enhanced surfaces and two alkali metal working fluids were evaluated. The enhanced surfaces were an EDM hole covered surface and a sintered-powder-metal porous layer surface. The working fluids tested were potassium and eutectic sodium-potasium alloy (NaK), both with and without undissolved noncondensible gas. Noncondensible gas (He and Xe) was added to the system to provide gas in the nucleation sites, preventing quenching of the sites. The experiments demonstrated the potential of an alkali metal pool boiler heat transport system for use in a solar-powered Stirling engine. The most favorable fluid/surface combination tested was NaK boiling on a -100 +140 mesh 304L stainless steel sintered porous layer with no undissolved noncondensible gas. This combination provided stable, high-performance boiling at the operating temperature of 700 C. Heat fluxes into the system ranged from 10 to 50 W/sq cm. The transition from free convection to nucleate boiling occurred at temperatures near 540 C. Based on these experiments, a pool boiler was designed for a full-scale 25-kWe Stirling system.

Local Charge Injection and Extraction on Surface-Modified Al2O3 Nanoparticles in LDPE.

PubMed

Borgani, Riccardo; Pallon, Love K H; Hedenqvist, Mikael S; Gedde, Ulf W; Haviland, David B

2016-09-14

We use a recently developed scanning probe technique to image with high spatial resolution the injection and extraction of charge around individual surface-modified aluminum oxide nanoparticles embedded in a low-density polyethylene (LDPE) matrix. We find that the experimental results are consistent with a simple band structure model where localized electronic states are available in the band gap (trap states) in the vicinity of the nanoparticles. This work offers experimental support to a previously proposed mechanism for enhanced insulating properties of nanocomposite LDPE and provides a powerful experimental tool to further investigate such properties.

Efficiency of Cs-free materials for negative ion production in H2 and D2 plasmas

NASA Astrophysics Data System (ADS)

Friedl, R.; Kurutz, U.; Fantz, U.

2017-08-01

High power negative ion sources use caesium to reduce the work function of the converter surface which significantly increases the negative ion yield. Caesium, however, is a very reactive alkali-metal and shows complex redistribution dynamics in consequence of plasma-surface-interaction. Thus, maintaining a stable and homogenous low work function surface is a demanding task, which is not easily compatible with the RAMI issues (reliability, availability, maintainability, inspectability) for a future DEMO fusion reactor. Hence, Cs-free alternative materials for efficient negative ion formation are desirable. At the laboratory experiment HOMER materials which are referred to as promising are investigated under identical and ion source relevant parameters: the refractory metals Ta and W, non-doped and boron-doped diamond as well as materials with inherent low work function (lanthanum-doped molybdenum, MoLa and lanthanum hexaboride, LaB6). The results are compared to the effect of in-situ caesiation, which at HOMER leads to a maximal increase of the negative ion density by a factor of 2.5. Among the examined samples low work function materials are most efficient. In particular, MoLa leads to an increase of almost 50 % compared to pure volume formation. The difference to a caesiated surface can be attributed to the still higher work function of MoLa, which is expected to be slightly below 3 eV. Using deuterium instead of hydrogen leads to increased atomic and positive ion densities, while comparable negative ion densities are achieved. In contrast to the low work function materials, bulk samples of the refractory metals as well as carbon based materials have no enhancing effect on H-, where the latter materials furthermore show severe erosion due to the hydrogen plasma.

Lunar Surface-to-Surface Power Transfer

NASA Technical Reports Server (NTRS)

Kerslake, Thomas W.

2007-01-01

A human lunar outpost, under NASA study for construction in the 2020's, has potential requirements to transfer electric power up to 50-kW across the lunar surface from 0.1 to 10-km distances. This power would be used to operate surface payloads located remotely from the outpost and/or outpost primary power grid. This paper describes concept designs for state-of-the-art technology power transfer subsystems including AC or DC power via cables, beamed radio frequency power and beamed laser power. Power transfer subsystem mass and performance are calculated and compared for each option. A simplified qualitative assessment of option operations, hazards, costs and technology needs is also described. Based on these concept designs and performance analyses, a DC power cabling subsystem is recommended to minimize subsystem mass and to minimize mission and programmatic costs and risks. Avenues for additional power transfer subsystem studies are recommended.

Transient analysis of a molten salt central receiver (MSCR) in a solar power plant

NASA Astrophysics Data System (ADS)

Joshi, A.; Wang, C.; Akinjiola, O.; Lou, X.; Neuschaefer, C.; Quinn, J.

2016-05-01

Alstom is developing solar power tower plants utilizing molten salt as the working fluid. In solar power tower, the molten salt central receiver (MSCR) atop of the tower is constructed of banks of tubes arranged in panels creating a heat transfer surface exposed to the solar irradiation from the heliostat field. The molten salt heat transfer fluid (HTF), in this case 60/40%wt NaNO3-KNO3, flows in serpentine flow through the surface collecting sensible heat thus raising the HTF temperature from 290°C to 565°C. The hot molten salt is stored and dispatched to produce superheated steam in a steam generator, which in turn produces electricity in the steam turbine generator. The MSCR based power plant with a thermal energy storage system (TESS) is a fully dispatchable renewable power plant with a number of opportunities for operational and economic optimization. This paper presents operation and controls challenges to the MSCR and the overall power plant, and the use of dynamic model computer simulation based transient analyses applied to molten salt based solar thermal power plant. This study presents the evaluation of the current MSCR design, using a dynamic model, with emphasis on severe events affecting critical process response, such as MS temperature deviations, and recommend MSCR control design improvements based on the results. Cloud events are the scope of the transient analysis presented in this paper. The paper presents results from a comparative study to examine impacts or effects on key process variables related to controls and operation of the MSCR plant.

Thinking Through Egyptian Tradition: The Potential of Pre-Colonial Craft Working Methods in Art Education

ERIC Educational Resources Information Center

Shafer, Ann

2013-01-01

The January 25th 2011 Revolution in Egypt brought the eyes of the world to the "cradle of civilization" once more, as existing power structures toppled and hidden voices surfaced to forge a unified vision for the future. In many parts of the Middle East, and indeed all over the world, the visual arts embody cultural values and remain a…

A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems

NASA Technical Reports Server (NTRS)

Mason, Lee S.; Siamidis, John

2006-01-01

This paper describes potential heat rejection design concepts for Brayton power conversion systems. Brayton conversion systems are currently under study by NASA for Nuclear Electric Propulsion (NEP) and surface power applications. The Brayton Heat Rejection Subsystem (HRS) must dissipate waste heat generated by the power conversion system due to inefficiencies in the thermal-to-electric conversion process. Sodium potassium (NaK) and H2O are two coolant working fluids that have been investigated in the design of a pumped loop and heat pipe space HRS. In general NaK systems are high temperature (300 to 1000 K) low pressure systems, and H2O systems are low temperature (300 to 600 K) high pressure systems. NaK is an alkali metal with health and safety hazards that require special handling procedures. On the other hand, H2O is a common fluid, with no health hazards and no special handling procedures. This paper compares NaK and H20 for the HRS pumped loop coolant working fluid. A detailed Microsoft Excel (Microsoft Corporation, Redmond, WA) analytical model, HRS_Opt, was developed to evaluate the various HRS design parameters. It is capable of analyzing NaK or H2O coolant, parallel or series flow configurations, and numerous combinations of other key parameters (heat pipe spacing, diameter and radial flux, radiator facesheet thickness, fluid duct system pressure drop, system rejected power, etc.) of the HRS. This paper compares NaK against water for the HRS coolant working fluid with respect to the relative mass, performance, design and implementation issues between the two fluids.

A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems

NASA Technical Reports Server (NTRS)

Siamidis, John; Mason, Lee S.

2006-01-01

This paper describes potential heat rejection design concepts for Brayton power conversion systems. Brayton conversion systems are currently under study by NASA for Nuclear Electric Propulsion (NEP) and surface power applications. The Brayton Heat Rejection Subsystem (HRS) must dissipate waste heat generated by the power conversion system due to inefficiencies in the thermal-to-electric conversion process. Sodium potassium (NaK) and H2O are two coolant working fluids that have been investigated in the design of a pumped loop and heat pipe space HRS. In general NaK systems are high temperature (300 to 1000 K) low pressure systems, and H2O systems are low temperature (300 to 600 K) high pressure systems. NaK is an alkali metal with health and safety hazards that require special handling procedures. On the other hand, H2O is a common fluid, with no health hazards and no special handling procedures. This paper compares NaK and H2O for the HRS pumped loop coolant working fluid. A detailed Microsoft Excel (Microsoft Corporation, Redmond, WA) analytical model, HRS_Opt, was developed to evaluate the various HRS design parameters. It is capable of analyzing NaK or H2O coolant, parallel or series flow configurations, and numerous combinations of other key parameters (heat pipe spacing, diameter and radial flux, radiator facesheet thickness, fluid duct system pressure drop, system rejected power, etc.) of the HRS. This paper compares NaK against water for the HRS coolant working fluid with respect to the relative mass, performance, design and implementation issues between the two fluids.

A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems

NASA Astrophysics Data System (ADS)

Siamidis, John; Mason, Lee

2006-01-01

This paper describes potential heat rejection design concepts for Brayton power conversion systems. Brayton conversion systems are currently under study by NASA for Nuclear Electric Propulsion (NEP) and surface power applications. The Brayton Heat Rejection Subsystem (HRS) must dissipate waste heat generated by the power conversion system due to inefficiencies in the thermal-to-electric conversion process. Sodium potassium (NaK) and H2O are two coolant working fluids that have been investigated in the design of a pumped loop and heat pipe space HRS. In general NaK systems are high temperature (300 to 1000 K) low pressure systems, and H2O systems are low temperature (300 to 600 K) high pressure systems. NaK is an alkali metal with health and safety hazards that require special handling procedures. On the other hand, H2O is a common fluid, with no health hazards and no special handling procedures. This paper compares NaK and H2O for the HRS pumped loop coolant working fluid. A detailed excel analytical model, HRS_Opt, was developed to evaluate the various HRS design parameters. It is capable of analyzing NaK or H2O coolant, parallel or series flow configurations, and numerous combinations of other key parameters (heat pipe spacing, diameter and radial flux, radiator facesheet thickness, fluid duct system pressure drop, system rejected power, etc.) of the HRS. This paper compares NaK against water for the HRS coolant working fluid with respect to the relative mass, performance, design and implementation issues between the two fluids.

Conceptual design of a self-deployable, high performance parabolic concentrator for advanced solar-dynamic power systems

NASA Astrophysics Data System (ADS)

Dehne, Hans J.

1991-05-01

NASA has initiated technology development programs to develop advanced solar dynamic power systems and components for space applications beyond 2000. Conceptual design work that was performed is described. The main efforts were the: (1) conceptual design of self-deploying, high-performance parabolic concentrator; and (2) materials selection for a lightweight, shape-stable concentrator. The deployment concept utilizes rigid gore-shaped reflective panels. The assembled concentrator takes an annular shape with a void in the center. This deployable concentrator concept is applicable to a range of solar dynamic power systems of 25 kW sub e to in excess of 75 kW sub e. The concept allows for a family of power system sizes all using the same packaging and deployment technique. The primary structural material selected for the concentrator is a polyethyl ethylketone/carbon fiber composite also referred to as APC-2 or Vitrex. This composite has a nearly neutral coefficient of thermal expansion which leads to shape stable characteristics under thermal gradient conditions. Substantial efforts were undertaken to produce a highly specular surface on the composite. The overall coefficient of thermal expansion of the composite laminate is near zero, but thermally induced stresses due to micro-movement of the fibers and matrix in relation to each other cause the surface to become nonspecular.

The fractal nature of vacuum arc cathode spots

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

Anders, Andre

2005-05-27

Cathode spot phenomena show many features of fractals, for example self-similar patterns in the emitted light and arc erosion traces. Although there have been hints on the fractal nature of cathode spots in the literature, the fractal approach to spot interpretation is underutilized. In this work, a brief review of spot properties is given, touching the differences between spot type 1 (on cathodes surfaces with dielectric layers) and spot type 2 (on metallic, clean surfaces) as well as the known spot fragment or cell structure. The basic properties of self-similarity, power laws, random colored noise, and fractals are introduced. Severalmore » points of evidence for the fractal nature of spots are provided. Specifically power laws are identified as signature of fractal properties, such as spectral power of noisy arc parameters (ion current, arc voltage, etc) obtained by fast Fourier transform. It is shown that fractal properties can be observed down to the cutoff by measurement resolution or occurrence of elementary steps in physical processes. Random walk models of cathode spot motion are well established: they go asymptotically to Brownian motion for infinitesimal step width. The power spectrum of the arc voltage noise falls as 1/f {sup 2}, where f is frequency, supporting a fractal spot model associated with Brownian motion.« less

Conceptual design of a self-deployable, high performance parabolic concentrator for advanced solar-dynamic power systems

NASA Technical Reports Server (NTRS)

Dehne, Hans J.

1991-01-01

NASA has initiated technology development programs to develop advanced solar dynamic power systems and components for space applications beyond 2000. Conceptual design work that was performed is described. The main efforts were the: (1) conceptual design of self-deploying, high-performance parabolic concentrator; and (2) materials selection for a lightweight, shape-stable concentrator. The deployment concept utilizes rigid gore-shaped reflective panels. The assembled concentrator takes an annular shape with a void in the center. This deployable concentrator concept is applicable to a range of solar dynamic power systems of 25 kW sub e to in excess of 75 kW sub e. The concept allows for a family of power system sizes all using the same packaging and deployment technique. The primary structural material selected for the concentrator is a polyethyl ethylketone/carbon fiber composite also referred to as APC-2 or Vitrex. This composite has a nearly neutral coefficient of thermal expansion which leads to shape stable characteristics under thermal gradient conditions. Substantial efforts were undertaken to produce a highly specular surface on the composite. The overall coefficient of thermal expansion of the composite laminate is near zero, but thermally induced stresses due to micro-movement of the fibers and matrix in relation to each other cause the surface to become nonspecular.

Development of a nearshore oscillating surge wave energy converter with variable geometry

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

Tom, N. M.; Lawson, M. J.; Yu, Y. H.

This paper presents an analysis of a novel wave energy converter concept that combines an oscillating surge wave energy converter (OSWEC) with control surfaces. The control surfaces allow for a variable device geometry that enables the hydrodynamic properties to be adapted with respect to structural loading, absorption range and power-take-off capability. The device geometry is adjusted on a sea state-to-sea state time scale and combined with wave-to-wave manipulation of the power take-off (PTO) to provide greater control over the capture efficiency, capacity factor, and design loads. This work begins with a sensitivity study of the hydrodynamic coefficients with respect tomore » device width, support structure thickness, and geometry. A linear frequency domain analysis is used to evaluate device performance in terms of absorbed power, foundation loads, and PTO torque. Previous OSWEC studies included nonlinear hydrodynamics, in response a nonlinear model that includes a quadratic viscous damping torque that was linearized via the Lorentz linearization. Inclusion of the quadratic viscous torque led to construction of an optimization problem that incorporated motion and PTO constraints. Results from this study found that, when transitioning from moderate-to-large sea states the novel OSWEC was capable of reducing structural loads while providing a near constant power output.« less

Computer-controlled wall servicing robot

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

Lefkowitz, S.

1995-03-01

After four years of cooperative research, Pentek has unveiled a new robot with the capability to automatically deliver a variety of cleaning, painting, inspection, and surveillance devices to large vertical surfaces. The completely computer-controlled robot can position a working tool on a 50-foot tall by 50-foot wide vertical surface with a repeatability of 1/16 inch. The working end can literally {open_quotes}fly{close_quotes} across the face of a wall at speed of 60 per minute, and can handle working loads of 350 pounds. The robot was originally developed to decontaminate the walls of reactor fueling cavities at commercial nuclear power plants duringmore » fuel outages. If these cavities are left to dry after reactor refueling, contamination present in the residue could later become airborne and move throughout the containment building. Decontaminating the cavity during the refueling outage reduces the need for restrictive personal protective equipment during plant operations to limit the dose rates.« less

A Kolmogorov-Brutsaert structure function model for evaporation into a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Katul, Gabriel; Liu, Heping

2017-05-01

In 1965, Brutsaert proposed a model that predicted mean evaporation rate E¯ from rough surfaces to scale with the 3/4 power law of the friction velocity (u∗) and the square-root of molecular diffusivity (Dm) for water vapor. In arriving at these results, a number of assumptions were made regarding the surface renewal rate describing the contact durations between eddies and the evaporating surface, the diffusional mass process from the surface into eddies, and the cascade of turbulent kinetic energy sustaining the eddy renewal process itself. The working hypothesis explored here is that E¯˜Dmu∗3/4 is a direct outcome of the Kolmogorov scaling for inertial subrange eddies modified to include viscous cutoff thereby bypassing the need for a surface renewal assumption. It is demonstrated that Brutsaert's model for E¯ may be more general than its original derivation implied.

Effect of Novel Quercetin Titanium Dioxide-Decorated Multi-Walled Carbon Nanotubes Nanocomposite on Bacillus subtilis Biofilm Development

PubMed Central

Raie, Diana S.; Mhatre, Eisha; El-Desouki, Doaa S.; Labena, Ahmed; El-Ghannam, Gamal; Farahat, Laila A.; Youssef, Tareq; Fritzsche, Wolfgang; Kovács, Ákos T.

2018-01-01

The present work was targeted to design a surface against cell seeding and adhering of bacteria, Bacillus subtilis. A multi-walled carbon nanotube/titanium dioxide nano-power was produced via simple mixing of carbon nanotube and titanium dioxide nanoparticles during the sol-gel process followed by heat treatment. Successfully, quercetin was immobilized on the nanocomposite via physical adsorption to form a quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite. The adhesion of bacteria on the coated-slides was verified after 24 h using confocal laser-scanning microscopy. Results indicated that the quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite had more negativity and higher recovery by glass surfaces than its counterpart. Moreover, coating surfaces with the quercetin-modified nanocomposite lowered both hydrophilicity and surface-attached bacteria compared to surfaces coated with the multi-walled carbon nanotubes/titanium dioxide nanocomposite. PMID:29346268

MgO Nanoparticle Modified Anode for Highly Efficient SnO2-Based Planar Perovskite Solar Cells.

PubMed

Ma, Junjie; Yang, Guang; Qin, Minchao; Zheng, Xiaolu; Lei, Hongwei; Chen, Cong; Chen, Zhiliang; Guo, Yaxiong; Han, Hongwei; Zhao, Xingzhong; Fang, Guojia

2017-09-01

Reducing the energy loss and retarding the carrier recombination at the interface are crucial to improve the performance of the perovskite solar cell (PSCs). However, little is known about the recombination mechanism at the interface of anode and SnO 2 electron transfer layer (ETL). In this work, an ultrathin wide bandgap dielectric MgO nanolayer is incorporated between SnO 2 :F (FTO) electrode and SnO 2 ETL of planar PSCs, realizing enhanced electron transporting and hole blocking properties. With the use of this electrode modifier, a power conversion efficiency of 18.23% is demonstrated, an 11% increment compared with that without MgO modifier. These improvements are attributed to the better properties of MgO-modified FTO/SnO 2 as compared to FTO/SnO 2 , such as smoother surface, less FTO surface defects due to MgO passivation, and suppressed electron-hole recombinations. Also, MgO nanolayer with lower valance band minimum level played a better role in hole blocking. When FTO is replaced with Sn-doped In 2 O 3 (ITO), a higher power conversion efficiency of 18.82% is demonstrated. As a result, the device with the MgO hole-blocking layer exhibits a remarkable improvement of all J-V parameters. This work presents a new direction to improve the performance of the PSCs based on SnO 2 ETL by transparent conductive electrode surface modification.

Applications of high power lasers. [using reflection holograms for machining and surface treatment

NASA Technical Reports Server (NTRS)

Angus, J. C.

1979-01-01

The use of computer generated, reflection holograms in conjunction with high power lasers for precision machining of metals and ceramics was investigated. The Reflection holograms which were developed and made to work at both optical wavelength (He-Ne, 6328 A) and infrared (CO2, 10.6) meet the primary practical requirement of ruggedness and are relatively economical and simple to fabricate. The technology is sufficiently advanced now so that reflection holography could indeed be used as a practical manufacturing device in certain applications requiring low power densities. However, the present holograms are energy inefficient and much of the laser power is lost in the zero order spot and higher diffraction orders. Improvements of laser machining over conventional methods are discussed and addition applications are listed. Possible uses in the electronics industry include drilling holes in printed circuit boards making soldered connections, and resistor trimming.

A high-power ultrasonic microreactor and its application in gas-liquid mass transfer intensification.

PubMed

Dong, Zhengya; Yao, Chaoqun; Zhang, Xiaoli; Xu, Jie; Chen, Guangwen; Zhao, Yuchao; Yuan, Quan

2015-02-21

The combination of ultrasound and microreactor is an emerging and promising area, but the report of designing high-power ultrasonic microreactor (USMR) is still limited. This work presents a robust, high-power and highly efficient USMR by directly coupling a microreactor plate with a Langevin-type transducer. The USMR is designed as a longitudinal half wavelength resonator, for which the antinode plane of the highest sound intensity is located at the microreactor. According to one dimension design theory, numerical simulation and impedance analysis, a USMR with a maximum power of 100 W and a resonance frequency of 20 kHz was built. The strong and uniform sound field in the USMR was then applied to intensify gas-liquid mass transfer of slug flow in a microfluidic channel. Non-inertial cavitation with multiple surface wave oscillation was excited on the slug bubbles, enhancing the overall mass transfer coefficient by 3.3-5.7 times.

Characterization of Novel Materials with Very Low Secondary Electron Emission Yield for Use in High-Power Microwave Devices

NASA Astrophysics Data System (ADS)

Svimonishvili, Tengiz; Zameroski, Nathan; Gilmore, Mark; Schamiloglu, Edl; Gaudet, John; Yan, Lincan

2004-11-01

Secondary Electron Emission (SEE) results from bombarding materials with electrons, atoms, or ions. The amount of secondary emission depends on factors such as bulk and surface properties of materials, energy of incident particles, and their angle of incidence. Total secondary electron emission yield, defined as the number of secondary electrons ejected per primary electron, is an important material parameter. Materials with high yield find use, for instance, in photomultiplier tubes, whereas materials with low yield, such as graphite, are used for SEE suppression in high-power microwave devices. The lower the SEE yield, the better the performance of high-power microwave devices (for example, gyrotrons). Employing a low-energy electron gun (energy range from 5 eV to 2000 eV), our work aims at characterizing and eventually identifying novel materials (with the lowest possible SEE yield) that will enhance operation and efficiency of high-power microwave devices.

Plasma power recycling at the divertor surface

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

Tang, Xian -Zhu; Guo, Zehua

With a divertor made of solid materials like carbon and tungsten, plasma ions are expected to be recycled at the divertor surface with a time-averaged particle recycling coefficient very close to unity in steady-state operation. This means that almost every plasma ion (hydrogen and helium) will be returned to the plasma, mostly as neutrals. The power flux deposited by the plasma on the divertor surface, on the other hand, can have varying recycling characteristics depending on the material choice of the divertor; the run-time atomic composition of the surface, which can be modified by material mix due to impurity migrationmore » in the chamber; and the surface morphology change over time. In general, a high-Z–material (such as tungsten) surface tends to reflect light ions and produce stronger power recycling, while a low-Z–material (such as carbon) surface tends to have a larger sticking coefficient for light ions and hence lower power recycling. Here, an explicit constraint on target plasma density and temperature is derived from the truncated bi-Maxwellian sheath model, in relation to the absorbed power load and power recycling coefficient at the divertor surface. Lastly, it is shown that because of the surface recombination energy flux, the attached plasma has a sharper response to power recycling in comparison to a detached plasma.« less

Plasma power recycling at the divertor surface

DOE PAGES

Tang, Xian -Zhu; Guo, Zehua

2016-12-03

With a divertor made of solid materials like carbon and tungsten, plasma ions are expected to be recycled at the divertor surface with a time-averaged particle recycling coefficient very close to unity in steady-state operation. This means that almost every plasma ion (hydrogen and helium) will be returned to the plasma, mostly as neutrals. The power flux deposited by the plasma on the divertor surface, on the other hand, can have varying recycling characteristics depending on the material choice of the divertor; the run-time atomic composition of the surface, which can be modified by material mix due to impurity migrationmore » in the chamber; and the surface morphology change over time. In general, a high-Z–material (such as tungsten) surface tends to reflect light ions and produce stronger power recycling, while a low-Z–material (such as carbon) surface tends to have a larger sticking coefficient for light ions and hence lower power recycling. Here, an explicit constraint on target plasma density and temperature is derived from the truncated bi-Maxwellian sheath model, in relation to the absorbed power load and power recycling coefficient at the divertor surface. Lastly, it is shown that because of the surface recombination energy flux, the attached plasma has a sharper response to power recycling in comparison to a detached plasma.« less

Analysis of tuning methods in semiconductor frequency-selective surfaces

NASA Astrophysics Data System (ADS)

Shemelya, Corey; Palm, Dominic; Fip, Tassilo; Rahm, Marco

2017-02-01

Advanced technology, such as sensing and communication equipment, has recently begun to combine optically sensitive nano-scale structures with customizable semiconductor material systems. Included within this broad field of study is the aptly named frequency-selective surface; which is unique in that it can be artificially designed to produce a specific electromagnetic or optical response. With the inherent utility of a frequency-selective surface, there has been an increased interest in the area of dynamic frequency-selective surfaces, which can be altered through optical or electrical tuning. This area has had exciting break throughs as tuning methods have evolved; however, these methods are typically energy intensive (optical tuning) or have met with limited success (electrical tuning). As such, this work investigates multiple structures and processes which implement semiconductor electrical biasing and/or optical tuning. Within this study are surfaces ranging from transmission meta-structures to metamaterial surface-waves and the associated coupling schemes. This work shows the utility of each design, while highlighting potential methods for optimizing dynamic meta-surfaces. As an added constraint, the structures were also designed to operate in unison with a state-of-the-art Ti:Sapphire Spitfire Ace and Spitfire Ace PA dual system (12 Watt) with pulse front matching THz generation and an EOS detection system. Additionally, the Ti:Sapphire laser system would provide the means for optical tunablity, while electrical tuning can be obtained through external power supplies.

Femtosecond laser microstructured Alumina toughened Zirconia: A new strategy to improve osteogenic differentiation of hMSCs

NASA Astrophysics Data System (ADS)

Carvalho, Angela; Cangueiro, Liliana; Oliveira, Vítor; Vilar, Rui; Fernandes, Maria H.; Monteiro, Fernando J.

2018-03-01

The use of topographic patterns has been a continuously growing area of research for tissue engineering and it is widely accepted that the surface topography of biomaterials can influence and modulate the initial biological response. Ultrafast lasers are extremely powerful tools to machine and pattern the surface of a wide range of biomaterials, however, only few work has been performed on ceramics with the intent of biomedical applications, and the biological characterization of these structured materials is scarce. In this work, relevance is given to the biological performance of such materials. A femtosecond laser ablation technique was used to modify Alumina toughened Zirconia (ATZ) surface topography, developing surfaces structured at the micro and nanoscale levels (μATZ), in a controlled and reproducible manner. Materials characterization was performed before and after laser treatment, and both materials were compared in terms of osteogenic response of human bone marrow derived mesenchymal stem cells cultured under basal conditions, expecting that the micro/nanofeatures will improve the biological response of cells. Cells metabolic activity and proliferation increased with the culture time and surface microtopography modulated cells alignment and guided proliferation. The modified surface, displayed significantly higher expression of osteogenic transcription factors and genes and, additionally, the formation of a mineralized extracellular matrix, when compared to the control surface, i.e. unmodified ATZ.

New solutions for steady bubbles in a Hele-Shaw cell

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

Tanveer, S.

1987-03-01

Exact solutions are presented for steadily moving bubbles in a Hele--Shaw cell when the effect of surface tension is neglected. These solutions form a three-parameter family. For specified area, both the speed of the bubble and the distance of its centroid from the channel centerline remain arbitrary when surface tension is ignored. However, numerical evidence suggests that this twofold arbitrariness is removed by the effect of surface tension, i.e., for given bubble area and surface tension, solutions exist only when the bubble velocity and the centroid distance from the channel centerline attain one or more isolated values. From a limitedmore » numerical search, no nonsymmetric solutions could be found; however, a branch of symmetric bubble solutions that was not found in earlier work was found. This branch corresponds to one of the Romero-Vanden-Broeck branch of finger solutions when the bubble size is large. A new procedure for numerical calculations of bubble solutions in the presence of surface tension is presented and is found to work very well for reasonably large bubbles, unlike the previous method of Tanveer (Phys. Fluids 29, 3537 (1986)). The precise power law dependence of bubble velocity on surface tension for small surface tension is explored for bubbles of different area. Agreement is noted with recent analytical results for a finger.« less

Laser-Ultrasonic Testing and its Applications to Nuclear Reactor Internals

NASA Astrophysics Data System (ADS)

Ochiai, M.; Miura, T.; Yamamoto, S.

2008-02-01

A new nondestructive testing technique for surface-breaking microcracks in nuclear reactor components based on laser-ultrasonics is developed. Surface acoustic wave generated by Q-switched Nd:YAG laser and detected by frequency-stabilized long pulse laser coupled with confocal Fabry-Perot interferometer is used to detect and size the cracks. A frequency-domain signal processing is developed to realize accurate sizing capability. The laser-ultrasonic testing allows the detection of surface-breaking microcrack having a depth of less than 0.1 mm, and the measurement of their depth with an accuracy of 0.2 mm when the depth exceeds 0.5 mm including stress corrosion cracking. The laser-ultrasonic testing system combined with laser peening system, which is another laser-based maintenance technology to improve surface stress, for inner surface of small diameter tube is developed. The generation laser in the laser-ultrasonic testing system can be identical to the laser source of the laser peening. As an example operation of the system, the system firstly works as the laser-ultrasonic testing mode and tests the inner surface of the tube. If no cracks are detected, the system then changes its work mode to the laser peening and improves surface stress to prevent crack initiation. The first nuclear industrial application of the laser-ultrasonic testing system combined with the laser peening was completed in Japanese nuclear power plant in December 2004.

Experimental study of surface integrity and fatigue life in the face milling of inconel 718

NASA Astrophysics Data System (ADS)

Wang, Xiangyu; Huang, Chuanzhen; Zou, Bin; Liu, Guoliang; Zhu, Hongtao; Wang, Jun

2018-06-01

The Inconel 718 alloy is widely used in the aerospace and power industries. The machining-induced surface integrity and fatigue life of this material are important factors for consideration due to high reliability and safety requirements. In this work, the milling of Inconel 718 was conducted at different cutting speeds and feed rates. Surface integrity and fatigue life were measured directly. The effects of cutting speed and feed rate on surface integrity and their further influences on fatigue life were analyzed. Within the chosen parameter range, the cutting speed barely affected the surface roughness, whereas the feed rate increased the surface roughness through the ideal residual height. The surface hardness increased as the cutting speed and feed rate increased. Tensile residual stress was observed on the machined surface, which showed improvement with the increasing feed rate. The cutting speed was not an influencing factor on fatigue life, but the feed rate affected fatigue life through the surface roughness. The high surface roughness resulting from the high feed rate could result in a high stress concentration factor and lead to a low fatigue life.

Smoothing Polymer Surfaces by Solvent-Vapor Exposure

NASA Astrophysics Data System (ADS)

Anthamatten, Mitchell

2003-03-01

Ultra-smooth polymer surfaces are of great importance in a large body of technical applications such as optical coatings, supermirrors, waveguides, paints, and fusion targets. We are investigating a simple approach to controlling surface roughness: by temporarily swelling the polymer with solvent molecules. As the solvent penetrates into the polymer, its viscosity is lowered, and surface tension forces drive surface flattening. To investigate sorption kinetics and surface-smoothing phenomena, a series of vapor-deposited poly(amic acid) films were exposed to dimethyl sulfoxide vapors. During solvent exposure, the surface topology was continuously monitored using light interference microscopy. The resulting power spectra indicate that high-frequency defects smooth faster than low-frequency defects. This frequency dependence was studied by depositing polymer films onto a series of 2D sinusoidal surfaces and performing smoothing experiments. Results show that the amplitudes of the sinusoidal surfaces decay exponentially with solvent exposure time, and the exponential decay constants are proportional to surface frequency. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Solar-based navigation for robotic explorers

NASA Astrophysics Data System (ADS)

Shillcutt, Kimberly Jo

2000-12-01

This thesis introduces the application of solar position and shadowing information to robotic exploration. Power is a critical resource for robots with remote, long-term missions, so this research focuses on the power generation capabilities of robotic explorers during navigational tasks, in addition to power consumption. Solar power is primarily considered, with the possibility of wind power also contemplated. Information about the environment, including the solar ephemeris, terrain features, time of day, and surface location, is incorporated into a planning structure, allowing robots to accurately predict shadowing and thus potential costs and gains during navigational tasks. By evaluating its potential to generate and expend power, a robot can extend its lifetime and accomplishments. The primary tasks studied are coverage patterns, with a variety of plans developed for this research. The use of sun, terrain and temporal information also enables new capabilities of identifying and following sun-synchronous and sun-seeking paths. Digital elevation maps are combined with an ephemeris algorithm to calculate the altitude and azimuth of the sun from surface locations, and to identify and map shadows. Solar navigation path simulators use this information to perform searches through two-dimensional space, while considering temporal changes. Step by step simulations of coverage patterns also incorporate time in addition to location. Evaluations of solar and wind power generation, power consumption, area coverage, area overlap, and time are generated for sets of coverage patterns, with on-board environmental information linked to the simulations. This research is implemented on the Nomad robot for the Robotic Antarctic Meteorite Search. Simulators have been developed for coverage pattern tests, as well as for sun-synchronous and sun-seeking path searches. Results of field work and simulations are reported and analyzed, with demonstrated improvements in efficiency, productivity and lifetime of robotic explorers, along with new solar navigation abilities.

Radiative energy transfer from MoS2 excitons to surface plasmons

NASA Astrophysics Data System (ADS)

Kang, Yimin; Li, Bowen; Fang, Zheyu

2017-12-01

In this work, we demonstrated the energy transfer process from few-layer MoS2 to gold dimer arrays via ultrafast pump-probe spectroscopy. With the overlap between the MoS2 exciton and the designed plasmon dipolar modes in the frequency domain, the exciton energy can be radiatively transferred to plasmonic structures, excited the localized surface plasmon resonance, and then enhanced the oscillation of coherent acoustic phonons. Power-dependent differential reflection signals and an analytical model based on the rate equation of exciton density were carried out to quantitatively study the energy transfer process. Our finding explores the energy flow between MoS2 excitons and surface plasmons, and can be contributed to the design of exciton-plasmon structures utilizing ultrathin materials.

Advanced Electrodes for High Power Li-ion Batteries.

PubMed

Zaghib, Karim; Mauger, Alain; Groult, Henri; Goodenough, John B; Julien, Christian M

2013-03-15

While little success has been obtained over the past few years in attempts to increase the capacity of Li-ion batteries, significant improvement in the power density has been achieved, opening the route to new applications, from hybrid electric vehicles to high-power electronics and regulation of the intermittency problem of electric energy supply on smart grids. This success has been achieved not only by decreasing the size of the active particles of the electrodes to few tens of nanometers, but also by surface modification and the synthesis of new multi-composite particles. It is the aim of this work to review the different approaches that have been successful to obtain Li-ion batteries with improved high-rate performance and to discuss how these results prefigure further improvement in the near future.

Advanced Solar Power Systems

NASA Technical Reports Server (NTRS)

Atkinson, J. H.; Hobgood, J. M.

1984-01-01

The Advanced Solar Power System (ASPS) concentrator uses a technically sophisticated design and extensive tooling to produce very efficient (80 to 90%) and versatile energy supply equipment which is inexpensive to manufacture and requires little maintenance. The advanced optical design has two 10th order, generalized aspheric surfaces in a Cassegrainian configuration which gives outstanding performance and is relatively insensitive to temperature changes and wind loading. Manufacturing tolerances also have been achieved. The key to the ASPS is the direct absorption of concentrated sunlight in the working fluid by radiative transfers in a black body cavity. The basic ASPS design concepts, efficiency, optical system, and tracking and focusing controls are described.

Development of a single-axis ultrasonic levitator and the study of the radial particle oscillations

NASA Astrophysics Data System (ADS)

Baer, Sebastian; Andrade, Marco A. B.; Esen, Cemal; Adamowski, Julio Cezar; Ostendorf, Andreas

2012-05-01

This work describes the development and analysis of a new single-axis acoustic levitator, which consists of a 38 kHz Langevin-type piezoelectric transducer with a concave radiating surface and a concave reflector. The new levitator design allows to significantly reducing the electric power necessary to levitate particles and to stabilize the levitated sample in both radial and axial directions. In this investigation the lateral oscillations of a levitated particle were measured with a single point Laser Doppler Vibrometer (LDV) and an image evaluation technique. The lateral oscillations were measured for different values of particle diameter, particle density and applied electrical power.

Decontamination work in the area surrounding Fukushima Dai-ichi Nuclear Power Plant: another occupational health challenge of the nuclear disaster.

PubMed

Wada, Koji; Yoshikawa, Toru; Murata, Masaru

2012-01-01

This article describes occupational health measures for workers involved in decontamination of radioactive material discharged around Fukushima Dai-ichi Nuclear Power Plant after the explosions in 2011. Decontamination is performed by removing radioactive particles (mainly cesium) from surfaces of soil, grass and trees, and buildings. Measurement of radiation doses is necessary to reduce exposure, and to determine whether workers can work below dose limits. Protective equipment for decontamination is determined based on the concentration of radiation in contaminated soil and the exposure to dust. Health examinations by physicians are mandated for decontamination workers upon hiring and every 6 months. While there is no possibility of acute radiation injury from decontamination, workers may be anxious about the unclear effects of chronic low level radiation exposure on health. Measures to protect the decontamination workers are the top priority.

Exploring the effect of diffuse reflection on indoor localization systems based on RSSI-VLC.

PubMed

Mohammed, Nazmi A; Elkarim, Mohammed Abd

2015-08-10

This work explores and evaluates the effect of diffuse light reflection on the accuracy of indoor localization systems based on visible light communication (VLC) in a high reflectivity environment using a received signal strength indication (RSSI) technique. The effect of the essential receiver (Rx) and transmitter (Tx) parameters on the localization error with different transmitted LED power and wall reflectivity factors is investigated at the worst Rx coordinates for a directed/overall link. Since this work assumes harsh operating conditions (i.e., a multipath model, high reflectivity surfaces, worst Rx position), an error of ≥ 1.46 m is found. To achieve a localization error in the range of 30 cm under these conditions with moderate LED power (i.e., P = 0.45 W), low reflectivity walls (i.e., ρ = 0.1) should be used, which would enable a localization error of approximately 7 mm at the room's center.

Understanding the bond-energy, hardness, and adhesive force from the phase diagram via the electron work function

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

Lu, Hao; Huang, Xiaochen; Li, Dongyang, E-mail: dongyang.li@ualberta.ca

2014-11-07

Properties of metallic materials are intrinsically determined by their electron behavior. However, relevant theoretical treatment involving quantum mechanics is complicated and difficult to be applied in materials design. Electron work function (EWF) has been demonstrated to be a simple but fundamental parameter which well correlates properties of materials with their electron behavior and could thus be used to predict material properties from the aspect of electron activities in a relatively easy manner. In this article, we propose a method to extract the electron work functions of binary solid solutions or alloys from their phase diagrams and use this simple approachmore » to predict their mechanical strength and surface properties, such as adhesion. Two alloys, Fe-Ni and Cu-Zn, are used as samples for the study. EWFs extracted from phase diagrams show same trends as experimentally observed ones, based on which hardness and surface adhesive force of the alloys are predicted. This new methodology provides an alternative approach to predict material properties based on the work function, which is extractable from the phase diagram. This work may also help maximize the power of phase diagram for materials design and development.« less

Increasing the efficiency of the condensing boiler

NASA Astrophysics Data System (ADS)

Zaytsev, O. N.; Lapina, E. A.

2017-11-01

Analysis of existing designs of boilers with low power consumption showed that the low efficiency of the latter is due to the fact that they work in most cases when the heating period in the power range is significantly less than the nominal power. At the same time, condensing boilers do not work in the most optimal mode (in condensing mode) in the central part of Russia, a significant part of their total operating time during the heating season. This is due to existing methods of equipment selection and joint operation with heating systems with quantitative control of the coolant. It was also revealed that for the efficient operation of the heating system, it is necessary to reduce the inertia of the heat generating equipment. Theoretical patterns of thermal processes in the furnace during combustion gas at different radiating surfaces location schemes considering the influence of the very furnace configuration, characterized in that to reduce the work condensing boiler in conventional gas boiler operation is necessary to maintain a higher temperature in the furnace (in the part where spiral heat exchangers are disposed), which is possible when redistributing heat flow - increase the proportion of radiant heat from the secondary burner emitter allow Perey For the operation of the condensing boiler in the design (condensation) mode practically the entire heating period.

Energy transmission through a double-wall curved stiffened panel using Green's theorem

NASA Astrophysics Data System (ADS)

Ghosh, Subha; Bhattacharya, Partha

2015-04-01

It is a common practice in aerospace and automobile industries to use double wall panels as fuselage skins or in window panels to improve acoustic insulation. However, the scientific community is yet to develop a reliable prediction method for a suitable vibro-acoustic model for sound transmission through a curved double-wall panel. In this quest, the present work tries to delve into the modeling of energy transmission through a double-wall curved panel. Subsequently the radiation of sound power into the free field from the curved panel in the low to mid frequency range is also studied. In the developed model to simulate a stiffened aircraft fuselage configuration, the outer wall is provided with longitudinal stiffeners. A modal expansion theory based on Green's theorem is implemented to model the energy transmission through an acoustically coupled double-wall curved panel. An elemental radiator approach is implemented to calculate the radiated energy from the curved surface in to the free field. The developed model is first validated with various numerical models available. It has been observed in the present study that the radius of curvature of the surface has a prominent effect on the behavior of radiated sound power into the free field. Effect of the thickness of the air gap between the two curved surfaces on the sound power radiation has also been noted.

Development of an Empirical Model for Optimization of Machining Parameters to Minimize Power Consumption

NASA Astrophysics Data System (ADS)

Kant Garg, Girish; Garg, Suman; Sangwan, K. S.

2018-04-01

The manufacturing sector consumes huge energy demand and the machine tools used in this sector have very less energy efficiency. Selection of the optimum machining parameters for machine tools is significant for energy saving and for reduction of environmental emission. In this work an empirical model is developed to minimize the power consumption using response surface methodology. The experiments are performed on a lathe machine tool during the turning of AISI 6061 Aluminum with coated tungsten inserts. The relationship between the power consumption and machining parameters is adequately modeled. This model is used for formulation of minimum power consumption criterion as a function of optimal machining parameters using desirability function approach. The influence of machining parameters on the energy consumption has been found using the analysis of variance. The validation of the developed empirical model is proved using the confirmation experiments. The results indicate that the developed model is effective and has potential to be adopted by the industry for minimum power consumption of machine tools.

Integrated Surface Power Strategy for Mars

NASA Technical Reports Server (NTRS)

Rucker, Michelle

2015-01-01

A National Aeronautics and Space Administration (NASA) study team evaluated surface power needs for a conceptual crewed 500-day Mars mission. This study had four goals: 1. Determine estimated surface power needed to support the reference mission; 2. Explore alternatives to minimize landed power system mass; 3. Explore alternatives to minimize Mars Lander power self-sufficiency burden; and 4. Explore alternatives to minimize power system handling and surface transportation mass. The study team concluded that Mars Ascent Vehicle (MAV) oxygen propellant production drives the overall surface power needed for the reference mission. Switching to multiple, small Kilopower fission systems can potentially save four to eight metric tons of landed mass, as compared to a single, large Fission Surface Power (FSP) concept. Breaking the power system up into modular packages creates new operational opportunities, with benefits ranging from reduced lander self-sufficiency for power, to extending the exploration distance from a single landing site. Although a large FSP trades well for operational complexity, a modular approach potentially allows Program Managers more flexibility to absorb late mission changes with less schedule or mass risk, better supports small precursor missions, and allows a program to slowly build up mission capability over time. A number of Kilopower disadvantages-and mitigation strategies-were also explored.

Dry etching of copper phthalocyanine thin films: effects on morphology and surface stoichiometry.

PubMed

Van Dijken, Jaron G; Brett, Michael J

2012-08-24

We investigate the evolution of copper phthalocyanine thin films as they are etched with argon plasma. Significant morphological changes occur as a result of the ion bombardment; a planar surface quickly becomes an array of nanopillars which are less than 20 nm in diameter. The changes in morphology are independent of plasma power, which controls the etch rate only. Analysis by X-ray photoelectron spectroscopy shows that surface concentrations of copper and oxygen increase with etch time, while carbon and nitrogen are depleted. Despite these changes in surface stoichiometry, we observe no effect on the work function. The absorbance and X-ray diffraction spectra show no changes other than the peaks diminishing with etch time. These findings have important implications for organic photovoltaic devices which seek nanopillar thin films of metal phthalocyanine materials as an optimal structure.

Contribution to the beam plasma material interactions during material processing with TEA CO2 laser radiation

NASA Astrophysics Data System (ADS)

Jaschek, Rainer; Konrad, Peter E.; Mayerhofer, Roland; Bergmann, Hans W.; Bickel, Peter G.; Kowalewicz, Roland; Kuttenberger, Alfred; Christiansen, Jens

1995-03-01

The TEA-CO2-laser (transversely excited atmospheric pressure) is a tool for the pulsed processing of materials with peak power densities up to 1010 W/cm2 and a FWHM of 70 ns. The interaction between the laser beam, the surface of the work piece and the surrounding atmosphere as well as gas pressure and the formation of an induced plasma influences the response of the target. It was found that depending on the power density and the atmosphere the response can take two forms. (1) No target modification due to optical break through of the atmosphere and therefore shielding of the target (air pressure above 10 mbar, depending on the material). (2) Processing of materials (air pressure below 10 mbar, depending on the material) with melting of metallic surfaces (power density above 0.5 109 W/cm2), hole formation (power density of 5 109 W/cm2) and shock hardening (power density of 3.5 1010 W/cm2). All those phenomena are usually linked with the occurrence of laser supported combustion waves and laser supported detonation waves, respectively for which the mechanism is still not completely understood. The present paper shows how short time photography and spatial and temporal resolved spectroscopy can be used to better understand the various processes that occur during laser beam interaction. The spectra of titanium and aluminum are observed and correlated with the modification of the target. If the power density is high enough and the gas pressure above a material and gas composition specific threshold, the plasma radiation shows only spectral lines of the background atmosphere. If the gas pressure is below this threshold, a modification of the target surface (melting, evaporation and solid state transformation) with TEA-CO2- laser pulses is possible and the material specific spectra is observed. In some cases spatial and temporal resolved spectroscopy of a plasma allows the calculation of electron temperatures by comparison of two spectral lines.

Investigation of Liquid Metal Heat Exchanger Designs for Fission Surface Power

NASA Technical Reports Server (NTRS)

Dyson, Rodger W.; Penswick, Barry; Robbie, Malcolm; Geng, Steven M.

2009-01-01

Fission surface power is an option for future Moon and Mars surface missions. High power nuclear reactor heated Stirling convertors are an option to provide reliable power for long duration outpost operations. This report investigates various design approaches for the liquid metal to acceptor heat exchange and clarifies the details used in the analysis.

La and Al co-doped CaMnO3 perovskite oxides: From interplay of surface properties to anion exchange membrane fuel cell performance

NASA Astrophysics Data System (ADS)

Dzara, Michael J.; Christ, Jason M.; Joghee, Prabhuram; Ngo, Chilan; Cadigan, Christopher A.; Bender, Guido; Richards, Ryan M.; O'Hayre, Ryan; Pylypenko, Svitlana

2018-01-01

This work reports the first account of perovskite oxide and carbon composite oxygen reduction reaction (ORR) catalysts integrated into anion exchange membrane fuel cells (AEMFCs). Perovskite oxides with a theoretical stoichiometry of Ca0.9La0.1Al0.1Mn0.9O3-δ are synthesized by an aerogel method and calcined at various temperatures, resulting in a set of materials with varied surface chemistry and surface area. Material composition is evaluated by X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The perovskite oxide calcined at 800 °C shows the importance of balance between surface area, purity of the perovskite phase, and surface composition, resulting in the highest ORR mass activity when evaluated in rotating disk electrodes. Integration of this catalyst into AEMFCs reveals that the best AEMFC performance is obtained when using composites with 30:70 perovskite oxide:carbon composition. Doubling the loading leads to an increase in the power density from 30 to 76 mW cm-2. The AEMFC prepared with a composite based on perovskite oxide and N-carbon achieves a power density of 44 mW cm-2, demonstrating an ∼50% increase when compared to the highest performing composite with undoped carbon at the same loading.

An Investigation Into: I) Active Flow Control for Cold-Start Performance Enhancement of a Pump-Assisted, Capillary-Driven, Two-Phase Cooling Loop II) Surface Tension of n-Pentanol + Water, a Self-Rewetting Working Fluid, From 25 °C to 85 °C

NASA Astrophysics Data System (ADS)

Bejarano, Roberto Villa

Cold-start performance enhancement of a pump-assisted, capillary-driven, two-phase cooling loop was attained using proportional integral and fuzzy logic controls to manage the boiling condition inside the evaporator. The surface tension of aqueous solutions of n-Pentanol, a self-rewetting fluid, was also investigated for enhancing heat transfer performance of capillary driven (passive) thermal devices was also studied. A proportional-integral control algorithm was used to regulate the boiling condition (from pool boiling to thin-film boiling) and backpressure in the evaporator during cold-start and low heat input conditions. Active flow control improved the thermal resistance at low heat inputs by 50% compared to the baseline (constant flow rate) case, while realizing a total pumping power savings of 56%. Temperature overshoot at start-up was mitigated combining fuzzy-logic with a proportional-integral controller. A constant evaporator surface temperature of 60°C with a variation of +/-8°C during start-up was attained with evaporator thermal resistances as low as 0.10 cm2--K/W. The surface tension of aqueous solutions of n-Pentanol, a self-rewetting working fluid, as a function of concentration and temperature were also investigated. Self-rewetting working fluids are promising in two-phase heat transfer applications because they have the ability to passively drive additional working fluid towards the heated surface; thereby increasing the dryout limitations of the thermal device. Very little data is available in literature regarding the surface tension of these fluids due to the complexity involved in fluid handling, heating, and experimentation. Careful experiments were performed to investigate the surface tension of n-Pentanol + water. The concentration and temperature range investigated were from 0.25%wt. to1.8%wt and 25°C to 85°C, respectively.

Design of a secondary lens using gaussian function

NASA Astrophysics Data System (ADS)

Anh, Nguyen Doan Quoc; Long, Nguyen Ngoc; Van Phuoc, Nguyen; Voznak, Miroslav; Zdralek, Jaroslav

2018-04-01

In the article, it is recognized that the high-intensity discharge (HID) fishing lamp becomes obsolete, so we designed a free secondary lens for an LED fishing/working lamp (LFWL) to serve the lighting needs of fishing and the on-board activities on fishing boats through gaussian decomposition for taking the place it. The results proved that it is really useful to the board, sea-surface, and underwater. Moreover, the lighting efficiency of 91 % with the power consumption reducing more than 3 times could be achieved when the proposed LED fishing/working lamps are used instead of the HID fishing lamps.

Emergence of flagellar beating from the collective behavior of individual ATP-powered dyneins

NASA Astrophysics Data System (ADS)

Namdeo, S.; Onck, P. R.

2016-10-01

Flagella are hair-like projections from the surface of eukaryotic cells, and they play an important role in many cellular functions, such as cell-motility. The beating of flagella is enabled by their internal architecture, the axoneme, and is powered by a dense distribution of motor proteins, dyneins. The dyneins deliver the required mechanical work through the hydrolysis of ATP. Although the dynein-ATP cycle, the axoneme microstructure, and the flagellar-beating kinematics are well studied, their integration into a coherent picture of ATP-powered flagellar beating is still lacking. Here we show that a time-delayed negative-work-based switching mechanism is able to convert the individual sliding action of hundreds of dyneins into a regular overall beating pattern leading to propulsion. We developed a computational model based on a minimal representation of the axoneme consisting of two representative doublet microtubules connected by nexin links. The relative sliding of the microtubules is incorporated by modeling two groups of ATP-powered dyneins, each responsible for sliding in opposite directions. A time-delayed switching mechanism is postulated, which is key in converting the local individual sliding action of multiple dyneins into global beating. Our results demonstrate that an overall nonreciprocal beating pattern can emerge with time due to the spatial and temporal coordination of the individual dyneins. These findings provide insights in the fundamental working mechanism of axonemal dyneins and could possibly open new research directions in the field of flagellar motility.

Emergence of flagellar beating from the collective behavior of individual ATP-powered dyneins.

PubMed

Namdeo, S; Onck, P R

2016-10-01

Flagella are hair-like projections from the surface of eukaryotic cells, and they play an important role in many cellular functions, such as cell-motility. The beating of flagella is enabled by their internal architecture, the axoneme, and is powered by a dense distribution of motor proteins, dyneins. The dyneins deliver the required mechanical work through the hydrolysis of ATP. Although the dynein-ATP cycle, the axoneme microstructure, and the flagellar-beating kinematics are well studied, their integration into a coherent picture of ATP-powered flagellar beating is still lacking. Here we show that a time-delayed negative-work-based switching mechanism is able to convert the individual sliding action of hundreds of dyneins into a regular overall beating pattern leading to propulsion. We developed a computational model based on a minimal representation of the axoneme consisting of two representative doublet microtubules connected by nexin links. The relative sliding of the microtubules is incorporated by modeling two groups of ATP-powered dyneins, each responsible for sliding in opposite directions. A time-delayed switching mechanism is postulated, which is key in converting the local individual sliding action of multiple dyneins into global beating. Our results demonstrate that an overall nonreciprocal beating pattern can emerge with time due to the spatial and temporal coordination of the individual dyneins. These findings provide insights in the fundamental working mechanism of axonemal dyneins and could possibly open new research directions in the field of flagellar motility.

Feasibility of Self Powered Actuation for Flow, Separation and Vibration Control

NASA Technical Reports Server (NTRS)

Shyam, Vikram; Bak, Dillon; Izadnegahdar, Alain

2015-01-01

A gas turbine engine is anywhere from 40-50% efficient. A large amount of energy is wasted as heat. Some of this heat is recoverable through the use of energy harvesting and can be used for powering on-board systems or for storing energy in batteries to replace auxiliary power units (APUs). As hybrid electric aircraft become more common, the use of energy harvesting will see increasingly more benefit and become commonplace in gas turbine engines. For electric aircraft with motors, TEGs would be beneficial for reclaiming waste heat from electric motors. The primary focus of this work was to evaluate the feasibility of harvesting energy from the hot section of a gas turbine engine (for a single aisle Boeing 737 thrust class) using thermoelectric generators (TEGs). The resulting heat could be used to power on-board actuation mechanisms such as plasma actuators and piezoelectric actuators. The work is a result of a two year NASA Center Innovation Fund from 2009 to 2011. The trade-off between thermoelectric harvesting and blade surface temperature were studied to ensure that blade durability is not adversely impacted by embedding a low thermal conductivity TEG. Calculations show that.5-10 Watts can be harvested per blade depending on flow conditions and on the thermoelectric material chosen. BiTe and SiGe were used for this analysis and future thermoelectric generators or multiferroic alloys could considerably improve power output.

Polymer-based wireless implantable sensor and platform for systems biology study

NASA Astrophysics Data System (ADS)

Xue, Ning

Wireless implantable MEMS (microelectromechanical systems) devices have been developed over the past decade based on the combination of bio-MEMS and Radio frequency (RF) MEMS technology. These devices require the components of wireless telemetric antenna and the corresponding circuit. In the meanwhile, biocompatible material needs to be involved in the devices design. To supply maximum power upon the implantable device at given power supply from the external coil circuit, this dissertation theoretically analyzed the mutual inductance under the positions of variety of vertical distances, lateral displacements and angular misalignments between two coils in certain surgical coils misalignment situations. A planar spiral coil has been developed as the receiver coil of the coupling system. To get maximum induced voltage over the receiver circuit, different geometries of the power coil, system operation frequencies were investigated. An intraocular pressure (IOP) sensor has been developed consisting of only biocompatible matierials-SU-8 and gold. Its size is sufficiently small to be implanted in the eye. The measurement results showed that it has relatively linear pressure response, high resolution and relatively long working stability in saline environment. Finally, a simple and low cost micro-wells bio-chip has been developed with sole polydimethylsiloxane (PDMS) to be used for single cell or small group cells isolation. By performing atomic force microscopy (AFM), contact angle and x-ray photoelectron spectroscopy (XPS) measurements on the PDMS surfaces under various surface treatment conditions, the physical and chemical surface natures were thoroughly analyzed as the basis of study of cells attachment and isolation to the surfaces.

Laser surface processing on sintered PM alloys

NASA Astrophysics Data System (ADS)

Reiter, Wilfred; Daurelio, Giuseppe; Ludovico, Antonio D.

1997-08-01

Usually the P.M. alloys are heat treated like case hardening, gas nitriding or plasma nitriding for a better wear resistance of the product surface. There is an additional method for gaining better tribological properties and this is the surface hardening (or remelting or alloying) of the P.M. alloy by laser treatment on a localized part of the product without heating the whole sample. This work gives a cured experimentation about the proper sintering powder alloys for laser surface processing from the point of view of wear, fatigue life and surface quality. As concerns the materials three different basic alloy groups with graduated carbon contents were prepared. Regarding these sintered powder alloys one group holds Fe, Mo and C and other group holds Fe, Ni, Mo and C and the last one holds Fe, Ni, Cu, Mo and C contents. Obviously each group has a different surface hardness, different porosity distribution, different density and diverse metallurgical structures (pearlite or ferrite-pearlite, etc.). ON the sample surfaces a colloidal graphite coating, in different thicknesses, has been sprayed to increase laser energy surface absorption. On some other samples a Mo coating, in different thicknesses, has been produced (on the bulk alloy) by diverse deposition techniques (D.C. Sputtering, P.V.D. and Flame Spraying). Only a few samples have a Mo coating and also an absorber coating, that is a bulk material- Mo and a colloidal graphite coating. All these sintered alloys have been tested by laser technology; so that, many laser working parameters (covering gas, work-speed, focussed and defocussed spot, rastered and integrated beam spots, square and rectangular beam shapes and so on) have been experimented for two different processes at constant laser power and at constant surface temperature (by using a temperature surface sensor and a closed controlled link). For all experiments a transverse fast axial flow CO2 2.5 kW c.w. laser source has been employed.

Reference Reactor Module for the Affordable Fission Surface Power System

NASA Astrophysics Data System (ADS)

Poston, David I.; Kapernick, Richard J.; Dixon, David D.; Amiri, Benjamin W.; Marcille, Thomas F.

2008-01-01

Surface fission power systems on the Moon and Mars may provide the first US application of fission reactor technology in space since 1965. The requirements of many surface power applications allow the consideration of systems with much less development risk than most other space reactor applications, because of modest power (10s of kWe) and no driving need for minimal mass (allowing temperatures <1000 K). The Affordable Fission Surface Power System (AFSPS) study was completed by NASA/DOE to determine the cost of a modest performance, low-technical risk surface power system. This paper describes the reference AFSPS reactor module concept, which is designed to provide a net power of 40 kWe for 8 years on the lunar surface; note, the system has been designed with technologies that are fully compatible with a Martian surface application. The reactor concept uses stainless-steel based, UO2-fueled, liquid metal-cooled fission reactor coupled to free-piston Stirling converters. The reactor shielding approach utilizes both in-situ and launched shielding to keep the dose to astronauts much lower than the natural background radiation on the lunar surface. One of the important ``affordability'' attributes is that the concept has been designed to minimize both the technical and programmatic safety risk.

Piezoelectric Nanogenerators for Self-Powered Nanosystems and Nanosensors

DTIC Science & Technology

2013-05-15

mechanical triggering applied onto the nanogenerator. The structure and general working principle of the spring-substrated nanogenerator ( SNG ) are...schematically shown in Fig. 3a–c. Compressive springs with variable sizes were selected as the skeletons of the SNG devices. The helix-shaped spring surface...In the measurement for the output performance of the SNG , one end of the spring was fixed onto a three-dimensional stage; meanwhile a mechanical

Innovative Exploration Techniques for Geothermal Assessment at Jemez Pueblo, New Mexico

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

Albrecht, Michael

2015-06-28

Surface exploration methods like geological mapping, mineralogical analysis, hydrogeochemistry, magnetotelluric as well as seismic, have been used to analyze the study area and identify a location for a production size exploration well. After that location has been identified in a blind resource scenario, a 5,657 feet deep deviated production size exploration well has been drilled. The surface casing is 13 3/8 inch with open hole starting at 4,136 feet. The well has been designed to be deepened up to 8,000 feet if needed. The first 4,180 feet have been sufficiently analyzed and were considered only of direct use interest priormore » to drilling. That has been confirmed. The remaining depth couldn't be logged by the time the report has been submitted because the well had an obstruction at 4,180 feet. Currently the power production potential for the drilling location cannot be determined without additional work-over of the well. The seismic conducted prior to drilling was a 100% success, providing a clear image of the subsurface and allowing for geosteering to be fact based and on target. Once the obstruction has been removed, work can continue to determine the power generation potential at that location.« less

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is secure after transfer to the work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is secure after transfer to the work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is lifted off the pallet for transfer to a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is lifted off the pallet for transfer to a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, workers check the placement of NASA’s MESSENGER spacecraft on a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, workers check the placement of NASA’s MESSENGER spacecraft on a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane moves NASA’s MESSENGER spacecraft toward a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane moves NASA’s MESSENGER spacecraft toward a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane lowers NASA’s MESSENGER spacecraft onto a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane lowers NASA’s MESSENGER spacecraft onto a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

Optimized mirror shape tuning using beam weightings based on distance, angle of incidence, reflectivity, and power.

PubMed

Goldberg, Kenneth A; Yashchuk, Valeriy V

2016-05-01

For glancing-incidence optical systems, such as short-wavelength optics used for nano-focusing, incorporating physical factors in the calculations used for shape optimization can improve performance. Wavefront metrology, including the measurement of a mirror's shape or slope, is routinely used as input for mirror figure optimization on mirrors that can be bent, actuated, positioned, or aligned. Modeling shows that when the incident power distribution, distance from focus, angle of incidence, and the spatially varying reflectivity are included in the optimization, higher Strehl ratios can be achieved. Following the works of Maréchal and Mahajan, optimization of the Strehl ratio (for peak intensity with a coherently illuminated system) occurs when the expectation value of the phase error's variance is minimized. We describe an optimization procedure based on regression analysis that incorporates these physical parameters. This approach is suitable for coherently illuminated systems of nearly diffraction-limited quality. Mathematically, this work is an enhancement of the methods commonly applied for ex situ alignment based on uniform weighting of all points on the surface (or a sub-region of the surface). It follows a similar approach to the optimization of apodized and non-uniformly illuminated optical systems. Significantly, it reaches a different conclusion than a more recent approach based on minimization of focal plane ray errors.

Robust Thermal Control of Propulsion Lines for Space Missions

NASA Technical Reports Server (NTRS)

Bhandari, Pradeep

2011-01-01

A document discusses an approach to insulating propulsion lines for spacecraft. In spacecraft that have propulsion lines that are located externally with open bus architecture, the lines are typically insulated by Multi Layer Insulation (MLI) blankets. MLI on propulsion lines tends to have large and somewhat random variances in its heat loss properties (effective emittance) from one location to the next, which makes it an un-robust approach to control propulsion line temperatures. The approach described here consists of a clamshell design in which the inner surface of the shell is coated with low-emissivity aluminized Kapton tape, and the outer surface is covered with black tape. This clamshell completely encloses the propulsion line. The line itself is covered with its heater, which in turn, is covered completely with black tape. This approach would be low in heater power needs because even though the outer surface of the prop line (and its heater) is covered with black tape as well as the outer surface of the clamshell, the inner surface of the clamshell is covered with low-emissivity aluminized Kapton tape. Hence, the heat loss from the line will be small and comparable to the MLI based one. In terms of contamination changing the radiative properties of surfaces, since the clamshell s inner surface is always protected during handling and is only installed after all the work on the prop line has been completed, the controlling surface, which is the clamshell s inner surface, is always in pristine condition. This proposed design allows for a much more deterministic and predictable design using a very simple and implementable approach for thermal control. It also uses low heater power and is robust to handling and contamination during and after implementation.

Surfactant adsorption and aggregate structure of silica nanoparticles: a versatile stratagem for the regulation of particle size and surface modification

NASA Astrophysics Data System (ADS)

Chaudhary, Savita; Rohilla, Deepak; Mehta, S. K.

2014-03-01

The area of silica nanoparticles is incredibly polygonal. Silica particles have aroused exceptional deliberation in bio-analysis due to great progress in particular arenas, for instance, biocompatibility, unique properties of modifiable pore size and organization, huge facade areas and pore volumes, manageable morphology and amendable surfaces, elevated chemical and thermal stability. Currently, silica nanoparticles participate in crucial utilities in daily trade rationales such as power storage, chemical and genetic sensors, groceries dispensation and catalysis. Herein, the size-dependent interfacial relation of anionic silica nanoparticles with twelve altered categories of cationic surfactants has been carried out in terms of the physical chemical facets of colloid and interface science. The current analysis endeavours to investigate the virtual consequences of different surfactants through the development of the objective composite materials. The nanoparticle size controls, the surface-to-volume ratio and surface bend relating to its interaction with surfactant will also be addressed in this work. More importantly, the simulated stratagem developed in this work can be lengthened to formulate core-shell nanostructures with functional nanoparticles encapsulated in silica particles, making this approach valuable and extensively pertinent for employing sophisticated materials for catalysis and drug delivery.

In situ plasma removal of surface contaminants from ion trap electrodes

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

Haltli, Raymond A.

2015-05-01

In this thesis, the construction and implementation of an in situ plasma discharge designed to remove surface contaminants from electrodes in an ion trapping experimental system is presented with results. In recent years, many advances have been made in using ion traps for quantum information processing. All of the criteria defined by DiVincenzo for using ion traps for implementing a quantum computer have been individually demonstrated, and in particular surface traps provide a scalable platform for ions. In order to be used for quantum algorithms, trapped ions need to be cooled to their motional (quantum mechanical) ground state. One ofmore » the hurdles in integrating surface ion traps for a quantum computer is minimizing electric field noise, which causes the ion to heat out of its motional ground state and which increases with smaller ion-to-electrode distances realized with surface traps. Surface contamination of trap electrodes is speculated to be the primary source of electric field noise. The main goal achieved by this work was to implement an in situ surface cleaning solution for surface electrode ion traps, which would not modify the ion trap electrode surface metal. Care was taken in applying the RF power in order to localize a plasma near the trap electrodes. A method for characterizing the energy of the plasma ions arriving at the ion trap surface is presented and results for plasma ion energies are shown. Finally, a method for quantifying the effectiveness of plasma cleaning of trap electrodes, using the surface analysis technique of X-ray photoelectron spectroscopy for measuring the amount and kind of surface contaminants, is described. A significant advantage of the trap electrode surface cleaning method presented here is the minimal changes necessary for implementation on a working ion trap experimental system.« less

Testing a high-power LED based light source for hyperspectral imaging microscopy

NASA Astrophysics Data System (ADS)

Klomkaew, Phiwat; Mayes, Sam A.; Rich, Thomas C.; Leavesley, Silas J.

2017-02-01

Our lab has worked to develop high-speed hyperspectral imaging systems that scan the fluorescence excitation spectrum for biomedical imaging applications. Hyperspectral imaging can be used in remote sensing, medical imaging, reaction analysis, and other applications. Here, we describe the development of a hyperspectral imaging system that comprised an inverted Nikon Eclipse microscope, sCMOS camera, and a custom light source that utilized a series of high-power LEDs. LED selection was performed to achieve wavelengths of 350-590 nm. To reduce scattering, LEDs with low viewing angles were selected. LEDs were surface-mount soldered and powered by an RCD. We utilized 3D printed mounting brackets to assemble all circuit components. Spectraradiometric calibration was performed using a spectrometer (QE65000, Ocean Optics) and integrating sphere (FOIS-1, Ocean Optics). Optical output and LED driving current were measured over a range of illumination intensities. A normalization algorithm was used to calibrate and optimize the intensity of the light source. The highest illumination power was at 375 nm (3300 mW/cm2), while the lowest illumination power was at 515, 525, and 590 nm (5200 mW/cm2). Comparing the intensities supplied by each LED to the intensities measured at the microscope stage, we found there was a great loss in power output. Future work will focus on using two of the same LEDs to double the power and finding more LED and/or laser diodes and chips around the range. This custom hyperspectral imaging system could be used for the detection of cancer and the identification of biomolecules.

Laser Surface Alloying of Copper, Manganese, and Magnesium with Pure Aluminum Substrate

NASA Astrophysics Data System (ADS)

Jiru, Woldetinsay G.; Sankar, M. Ravi; Dixit, Uday S.

2016-03-01

Laser surface alloying is one of the recent technologies used in the manufacturing sector for improving the surface properties of the metals. Light weight materials like aluminum alloys, titanium alloys, and magnesium alloys are used in the locomotive, aerospace, and structural applications. In the present work, an experimental study was conducted to improve the surface hardness of commercially pure aluminum plate. CO2 laser is used to melt pre-placed powders of pure copper, manganese, and magnesium. Microstructure of alloyed surface was analyzed using optical microscope. The best surface alloying was obtained at the optimum values of laser parameters, viz., laser power, scan speed, and laser beam diameter. In the alloyed region, microhardness increased from 30 HV0.5 to 430 HV0.5, while it was 60 HV0.5 in the heat-affected region. Tensile tests revealed some reduction in the strength and total elongation due to alloying. On the other hand, corrosion resistance improved.

Surface energy effect on nonlinear buckling and postbuckling behavior of functionally graded piezoelectric cylindrical nanoshells under lateral pressure

NASA Astrophysics Data System (ADS)

Fang, Xue-Qian; Zhu, Chang-Song; Liu, Jin-Xi; Zhao, Jing

2018-04-01

In this paper, the surface energy effect on the nonlinear buckling and postbuckling behavior of functionally graded piezoelectric (FGP) cylindrical nanoshells subjected to lateral pressure is studied based on the electro-elastic surface/interface theory together with von-Kármán-Donnell-type kinematics of nonlinearity. The total strain energy of the FGP nanoshell, including surface energy, is derived by considering the constitutive formulations of surface phase. The principle of minimum potential energy is utilized to establish the nonlinear governing differential equations, and the singular perturbation technique is employed to obtain the asymptotic solutions. Then, two sets of comparison are conducted to validate the present work, and some numerical examples are given to study the effects of surface parameters, power law index and aspect ratio on the buckling and postbuckling behavior of FGP nanoshells. The results show that the critical buckling load and postbuckling path of FGP nanoshell are significantly size-dependent.

ITER Baseline Scenario with ECCD Applied to Neoclassical Tearing Modes in DIII-D

NASA Astrophysics Data System (ADS)

Welander, A. G.; La Haye, R. J.; Lohr, J. M.; Humphreys, D. A.; Prater, R.; Paz-Soldan, C.; Kolemen, E.; Turco, F.; Olofsson, E.

2015-11-01

The neoclassical tearing mode (NTM) is a magnetic island that can occur on flux surfaces where the safety factor q is a rational number. Both m/n=3/2 and 2/1 NTM's degrade confinement, and the 2/1 mode often locks to the wall and disrupts the plasma. An NTM can be suppressed by depositing electron cyclotron current drive (ECCD) on the q-surface by injecting microwave beams into the plasma from gyrotrons. Recent DIII-D experiments have studied the application of ECCD/ECRH in the ITER Baseline Scenario. The power required from the gyrotrons can be significant enough to impact the fusion gain, Q in ITER. However, if gyrotron power could be minimized or turned off in ITER when not needed, this impact would be small. In fact, tearing-stable operation at low torque has been achieved previously in DIII-D without EC power. A vision for NTM control in ITER will be described together with results obtained from simulations and experiments in DIII-D under ITER like conditions. Work supported by the US DOE under DE-FC02-04ER54698, DE-AC02-09CH11466, DE-FG02-04ER54761.

Laser Brazing Characteristics of Al to Brass with Zn-Based Filler

NASA Astrophysics Data System (ADS)

Tan, Caiwang; Liu, Fuyun; Sun, Yiming; Chen, Bo; Song, Xiaoguo; Li, Liqun; Zhao, Hongyun; Feng, Jicai

2018-05-01

Laser brazing of Al to brass in lap configuration with Zn-based filler was performed in this work. The process parameters including laser power, defocused distance were found to have a significant influence on appearance, microstructure and mechanical properties. The process parameters were optimized to be laser power of 2700 W and defocusing distance of + 40 mm from brass surface. In addition, preheating exerted great influence on wetting and spreading ability of Zn filler on brass surface. The microstructure observation showed the thickness of reaction layer (CuZn phase) at the interface of the brass side would grow with the increase in laser power and the decrease in the laser defocusing distance. Moreover, preheating could increase the spreading area of the filler metal and induced the growth of the reaction layer. The highest tensile-shear load of the joint could reach 2100 N, which was 80% of that of Al alloy base metal. All the joints fractured along the CuZn reaction layer and brass interface. The fracture morphology displayed the characteristics of the cleavage fracture when without preheating before welding, while it displayed the characteristics of the quasi-cleavage fracture with preheating before welding.

Wind farm density and harvested power in very large wind farms: A low-order model

NASA Astrophysics Data System (ADS)

Cortina, G.; Sharma, V.; Calaf, M.

2017-07-01

In this work we create new understanding of wind turbine wakes recovery process as a function of wind farm density using large-eddy simulations of an atmospheric boundary layer diurnal cycle. Simulations are forced with a constant geostrophic wind and a time varying surface temperature extracted from a selected period of the Cooperative Atmospheric Surface Exchange Study field experiment. Wind turbines are represented using the actuator disk model with rotation and yaw alignment. A control volume analysis around each turbine has been used to evaluate wind turbine wake recovery and corresponding harvested power. Results confirm the existence of two dominant recovery mechanisms, advection and flux of mean kinetic energy, which are modulated by the background thermal stratification. For the low-density arrangements advection dominates, while for the highly loaded wind farms the mean kinetic energy recovers through fluxes of mean kinetic energy. For those cases in between, a smooth balance of both mechanisms exists. From the results, a low-order model for the wind farms' harvested power as a function of thermal stratification and wind farm density has been developed, which has the potential to be used as an order-of-magnitude assessment tool.

A Compendium of Brazed Microstructures For Fission Power Systems Applications

NASA Technical Reports Server (NTRS)

Locci, Ivan E.; Bowman, Cheryl L.

2012-01-01

NASA has been supporting design studies and technology development for fission-based power systems that could provide power to an outpost on the Moon, Mars, or an asteroid. Technology development efforts have included fabrication and evaluation of components used in a Stirling engine power conversion system. This investigation is part of the development of several braze joints crucial for the heat exchanger transfer path from a hot-side heat exchanger to a Stirling engine heat acceptor. Dissimilar metal joints are required to impart both mechanical strength and thermal path integrity for a heater head of interest. Preliminary design work for the heat exchanger involved joints between low carbon stainless steel to Inconel 718, where the 316L stainless steel would contain flowing liquid metal NaK while Inconel 718, a stronger alloy, would be used as structural reinforcement. This paper addressed the long-term microstructural stability of various braze alloys used to join 316L stainless steel heater head to the high conductivity oxygen-free copper acceptor to ensure the endurance of the critical metallic components of this sophisticated heat exchanger. The bonding of the 316L stainless steel heater head material to a copper heat acceptor is required to increase the heat-transfer surface area in contact with flowing He, which is the Stirling engine working fluid.

Evaluation of modulating field of photoreflectance of surface-intrinsic-n+ type doped GaAs by using photoinduced voltage

NASA Astrophysics Data System (ADS)

Lee, W. Y.; Chien, J. Y.; Wang, D. P.; Huang, K. F.; Huang, T. C.

2002-04-01

Photoreflectance (PR) of surface-intrinsic-n+ type doped GaAs has been measured for various power densities of pump laser. The spectra exhibited many Franz-Keldysh oscillations, whereby the strength of electric field F in the undoped layer can be determined. The thus obtained Fs are subject to photovoltaic effect and are less than built-in field Fbi. In the previous work we have obtained the relation F≈Fbi-δF/2 when δF≪Fbi by using electroreflectance to simulate PR, where δF is the modulating field of the pump beam. In this work a method was devised to evaluate δF by using photoinduced voltages Vs and, hence, the relation can be verified by PR itself. The δFs obtained by Vs are also consistent with those of using imaginary part of fast Fourier transform of PR spectra.

Fluid film force control in lubricated journal bearings by means of a travelling wave generated with a piezoelectric actuators' system

NASA Astrophysics Data System (ADS)

Iula, Antonio; Lamberti, Nicola; Savoia, Alessandro; Caliano, Giosue

2012-05-01

In this work an experimental evaluation of the possiblity to influence and control the fluid film forces in the gap of a lubricated journal bearing by means of a rotating travelling wave is carried out. The travellig wave is generated by two power actuators opportunely positioned on the outer surface of the bearing and electrically driven with a phase shift of 90°. Each transducer is designed to work at the natural frequency of the radial nonaxisymmetrical mode 0-5 (23.6 kHz). Experimental results show that the travelling wave is capable to control the motion of an oil drop on the inner surface of the bearing and that it is capable to put in rotation a rotor layed on the drop oil via the viscous forces in the oil drop itself.

Cavitation-based hydro-fracturing technique for geothermal reservoir stimulation

DOEpatents

Wang, Jy-An John; Wang, Hong; Ren, Fei; Cox, Thomas S.

2017-02-21

A rotary shutter valve 500 is used for geothermal reservoir stimulation. The valve 500 includes a pressure chamber 520 for holding a working fluid (F) under pressure. A rotatable shutter 532 is turned with a powering device 544 to periodically align one or more windows 534 with one or more apertures 526 in a bulkhead 524. When aligned, the pressurized working fluid (F) flows through the bulkhead 524 and enters a pulse cavity 522, where it is discharged from the pulse cavity 522 as pressure waves 200. The pressure wave propagation 200 and eventual collapse of the bubbles 202 can be transmitted to a target rock surface 204 either in the form of a shock wave 206, or by micro jets 208, depending on the bubble-surface distance. Once cavitation at the rock face begins, fractures are initiated in the rock to create a network of micro-fissures for enhanced heat transfer.

Power electronics substrate for direct substrate cooling

DOEpatents

Le, Khiet [Mission Viejo, CA; Ward, Terence G [Redondo Beach, CA; Mann, Brooks S [Redondo Beach, CA; Yankoski, Edward P [Corona, CA; Smith, Gregory S [Woodland Hills, CA

2012-05-01

Systems and apparatus are provided for power electronics substrates adapted for direct substrate cooling. A power electronics substrate comprises a first surface configured to have electrical circuitry disposed thereon, a second surface, and a plurality of physical features on the second surface. The physical features are configured to promote a turbulent boundary layer in a coolant impinged upon the second surface.

Surface Power Radiative Cooling Tests

NASA Astrophysics Data System (ADS)

Vaughn, Jason; Schneider, Todd

2006-01-01

Terrestrial nuclear power plants typically maintain their temperature through convective cooling, such as water and forced air. However, the space environment is a vacuum environment, typically 10-8 Torr pressure, therefore in proposed missions to the lunar surface, power plants would have to rely on radiative cooling to remove waste heat. Also, the Martian surface has a very tenuous atmosphere (e.g. ~5 Torr CO2), therefore, the main heat transfer method on the Martian surface is also radiative. Because of the lack of atmosphere on the Moon and the tenuous atmosphere on Mars, surface power systems on both the Lunar and Martian surface must rely heavily on radiative heat transfer. Because of the large temperature swings on both the lunar and the Martian surfaces, trying to radiate heat is inefficient. In order to increase power system efficiency, an effort is underway to test various combinations of materials with high emissivities to demonstrate their ability to survive these degrading atmospheres to maintain a constant radiator temperature improving surface power plant efficiency. An important part of this effort is the development of a unique capability that would allow the determination of a materials emissivity at high temperatures. A description of the test capability as well as initial data is presented.

Flexible carbon micro-supercapacitors prepared by direct cw-laser writing

NASA Astrophysics Data System (ADS)

Cai, Jinguang; Watanabe, Akira

2016-03-01

Micro-/nano-scale power supply units with high energy and high power densities are critical components for the development of compact miniaturized portable electronic devices. Supercapacitors have attracted many research attentions due to their high power density, robust cycle performance, pollution-free operation, and maintenance-free features. Besides, the properties of small size, light weight, and flexibility are also required. On-chip microsupercapacitors (MSCs) have the potential acting as power supply units in portable devices, due to their simplified packaging processes and compatibility to the integrated circuits. However, the fabrication methods and materials should be cost-effective, scalable, and compatible to current electronic industry. Carbon materials own high specific surface areas, electrochemical stability, and high electrical conductivity, which are critical parameters for high-power supercapacitors. Moreover, the high mechanical tolerance makes them good candidates for flexible wearable devices. Therefore, MSCs based on carbon materials would satisfy the requirements of portable electronics. In this work, we demonstrated the fabrication of carbon MSCs by laser direct writing on commercial polyimide sheets in Ar with lowcost semiconductor cw-laser with a wavelength of 405nm. The obtained structures are macro-nanostructures comprising graphitized and amorphous carbon with relatively smooth surfaces and low resistance, in compared with the structures obtained by laser writing in air. As-prepared micro-supercapacitors show a high capacitance of about 14.9 mF/cm2 at a scanning rate of 10 mV/s, which is comparable to the reported highest capacitance of carbon-based supercapacitors fabricated by pulse-laser writing.

A Novel Device for Total Acoustic Output Measurement of High Power Transducers

NASA Astrophysics Data System (ADS)

Howard, S.; Twomey, R.; Morris, H.; Zanelli, C. I.

2010-03-01

The objective of this work was to develop a device for ultrasound power measurement applicable over a broad range of medical transducer types, orientations and powers, and which supports automatic measurements to simplify use and minimize errors. Considering all the recommendations from standards such as IEC 61161, an accurate electromagnetic null-balance has been designed for ultrasound power measurements. The sensing element is placed in the water to eliminate errors due to surface tension and water evaporation, and the motion and detection of force is constrained to one axis, to increase immunity to vibration from the floor, water sloshing and water surface waves. A transparent tank was designed so it could easily be submerged in a larger tank to accommodate large transducers or side-firing geometries, and can also be turned upside-down for upward-firing transducers. A vacuum lid allows degassing the water and target in situ. An external control module was designed to operate the sensing/driving loop and to communicate to a local computer for data logging. The sensing algorithm, which incorporates temperature compensation, compares the feedback force needed to cancel the motion for sources in the "on" and "off" states. These two states can be controlled by the control unit or manually by the user, under guidance by a graphical user interface (the system presents measured power live during collection). Software allows calibration to standard weights, or to independently calibrated acoustic sources. The design accommodates a variety of targets, including cone, rubber, brush targets and an oil-filled target for power measurement via buoyancy changes. Measurement examples are presented, including HIFU sources operating at powers from 1 to 100.

Design and optimization of G-band extended interaction klystron with high output power

NASA Astrophysics Data System (ADS)

Li, Renjie; Ruan, Cunjun; Zhang, Huafeng

2018-03-01

A ladder-type Extended Interaction Klystron (EIK) with unequal-length slots in the G-band is proposed and designed. The key parameters of resonance cavities working in the π mode are obtained based on the theoretical analysis and 3D simulation. The influence of the device fabrication tolerance on the high-frequency performance is analyzed in detail, and it is found that at least 5 μm of machining precision is required. Thus, the dynamic tuning is required to compensate for the frequency shift and increase the bandwidth. The input and output coupling hole dimensions are carefully designed to achieve high output power along with a broad bandwidth. The effect of surface roughness of the metallic material on the output power has been investigated, and it is proposed that lower surface roughness leads to higher output power. The focusing magnetic field is also optimized to 0.75 T in order to maintain the beam transportation and achieve high output power. With 16.5 kV operating voltage and 0.30 A beam current, the output power of 360 W, the efficiency of 7.27%, the gain of 38.6 dB, and the 3 dB bandwidth of 500 MHz are predicted. The output properties of the EIK show great stability with the effective suppression of oscillation and mode competition. Moreover, small-signal theory analysis and 1D code AJDISK calculations are carried out to verify the results of 3D PIC simulations. A close agreement among the three methods proves the relative validity and the reliability of the designed EIK. Thus, it is indicated that the EIK with unequal-length slots has potential for power improvement and bandwidth extension.

Surface Texture-Induced Enhancement of Optical and Photoelectrochemical Activity of Cu2ZnSnS4 Photocathodes

NASA Astrophysics Data System (ADS)

Sarswat, Prashant K.; Deka, Nipon; Jagan Mohan Rao, S.; Free, Michael L.; Kumar, Gagan

2017-08-01

The objective of this work is to understand and improve the photocatalytic activity of Cu2ZnSnS4 (CZTS) through postgrowth modification techniques to create surface textures. This objective can be achieved using a combination of solvents, etching agents, and anodization techniques. One of the most effective surface treatments for enhancing the surface properties of photovoltaic materials is formation of nanoscale flakes, although other surface modifications were also evaluated. The superior performance of textured films can be attributed to enhanced surface area of absorber material exposed to electrolyte, ZnS deficiency, and high catalytic activity due to reduced charge-transfer resistance. Fine-tuning of ion flux and electrolyte stoichiometry can be used to create a controlled growth algorithm for CZTS thin films. The resulting information can be utilized to optimize film properties. The utility of nanostructured or engineered surfaces was evaluated using photoelectrochemical measurements. Finite-difference time-domain (FDTD)-assisted simulations were conducted for selected texturing, revealing enhanced surface area of absorbing medium that ultimately resulted in greater power loss of light in the medium.

Surface roughness analysis after laser assisted machining of hard to cut materials

NASA Astrophysics Data System (ADS)

Przestacki, D.; Jankowiak, M.

2014-03-01

Metal matrix composites and Si3N4 ceramics are very attractive materials for various industry applications due to extremely high hardness and abrasive wear resistance. However because of these features they are problematic for the conventional turning process. The machining on a classic lathe still requires special polycrystalline diamond (PCD) or cubic boron nitride (CBN) cutting inserts which are very expensive. In the paper an experimental surface roughness analysis of laser assisted machining (LAM) for two tapes of hard-to-cut materials was presented. In LAM, the surface of work piece is heated directly by a laser beam in order to facilitate, the decohesion of material. Surface analysis concentrates on the influence of laser assisted machining on the surface quality of the silicon nitride ceramic Si3N4 and metal matrix composite (MMC). The effect of the laser assisted machining was compared to the conventional machining. The machining parameters influence on surface roughness parameters was also investigated. The 3D surface topographies were measured using optical surface profiler. The analysis of power spectrum density (PSD) roughness profile were analyzed.

Size effects and charge transport in metals: Quantum theory of the resistivity of nanometric metallic structures arising from electron scattering by grain boundaries and by rough surfaces

NASA Astrophysics Data System (ADS)

Munoz, Raul C.; Arenas, Claudio

2017-03-01

We discuss recent progress regarding size effects and their incidence upon the coefficients describing charge transport (resistivity, magnetoresistance, and Hall effect) induced by electron scattering from disordered grain boundaries and from rough surfaces on metallic nanostructures; we review recent measurements of the magneto transport coefficients that elucidate the electron scattering mechanisms at work. We review as well theoretical developments regarding quantum transport theories that allow calculating the increase in resistivity induced by electron-rough surface scattering (in the absence of grain boundaries) from first principles—from the parameters that describe the surface roughness that can be measured with a Scanning Tunnelling Microscope (STM). We evaluate the predicting power of the quantum version of the Fuchs-Sondheimer theory and of the model proposed by Calecki, abandoning the method of parameter fitting used for decades, but comparing instead theoretical predictions with resistivity measured in thin films where surface roughness has also been measured with a STM, and where electron-grain boundary scattering can be neglected. We also review the theory of Mayadas and Shatzkes (MS) [Phys. Rev. B 1, 1382 (1970)] used for decades, and discuss its severe conceptual difficulties that arise out of the fact that: (i) MS employed plane waves to describe the electronic states within the metal sample having periodic grain boundaries, rather than the Bloch states known since the thirties to be the solutions of the Schrödinger equation describing electrons propagating through a Krönig-Penney [Proc. R. Soc. London Ser. A 130, 499 (1931)] periodic potential; (ii) MS ignored the fact that the wave functions describing electrons propagating through a 1-D disordered potential are expected to decay exponentially with increasing distance, a fact known since the work of Anderson [Phys. Rev. 109, 1492 (1958)] in 1958 for which he was awarded the Nobel Prize in 1977; (iii) The current in the sample should be proportional to TN, the probability that an electron traverses N consecutive (disordered) grains found along a mean free path; MS assumed that TN = 1. We review unpublished details of a quantum transport theory based upon a model of diffusive transport and Kubo's linear response formalism recently published [Arenas et al., Appl. Surf. Sci. 329, 184 (2015)], which permits estimating the increase in resistivity of a metallic specimen (over the bulk resistivity) under the combined effects of electron scattering by phonons, impurities, disordered grain boundaries, and rough surfaces limiting the sample. We evaluate the predicting power of both the MS theory and of the new quantum model on samples where the temperature dependence of the resistivity has been measured between 4 K and 300 K, and where surface roughness and grain size distribution has been measured on each sample via independent experiments. We find that the quantum theory does exhibit a predicting power, whereas the predicting power of the MS model as well as the significance and reliability of its fitting parameters seems questionable. We explore the power of the new theory by comparing, for the first time, the resistivity predicted and measured on nanometric Cu wires of (approximately) rectangular cross section employed in building integrated circuits, based upon a quantum description of electron motion.

Thermal power systems point-focusing distributed receiver technology project. Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

Lucas, J.

1979-01-01

Thermal or electrical power from the sun's radiated energy through Point-Focusing Distributed Receiver Technology is the goal of this project. The energy thus produced must be technically, as well as economically, competitive with other energy sources. This project is to support the industrial development of the required technology to achieve the above stated goal. Solar energy is concentrated by either a reflecting surface or a lense to a receiver where it is transferred to a working liquid or gas. Receiver temperatures are in the 1000 - 2000 F range. Conceptual design studies are expected to identify power conversion units with a viable place in the solar energy future. Rankine and Brayton cycle engines are under investigation. This report details the Jet Propulsion Laboratory's accomplishments with point-focusing technology in Fy 1978.

Crouch gait can be an effective form of forced-use/no constraint exercise for the paretic lower limb in stroke.

PubMed

Tesio, Luigi; Rota, Viviana; Malloggi, Chiara; Brugliera, Luigia; Catino, Luigi

2017-09-01

In hemiplegic gait the paretic lower limb provides less muscle power and shows a briefer stance compared with the unaffected limb. Yet, a longer stance and a higher power can be obtained from the paretic lower limb if gait speed is increased. This supports the existence of a 'learned non-use' phenomenon, similar to that underlying some asymmetric impairments of the motion of the eyes and of the upper limbs. Crouch gait (CG) (bent-hip bent-knee, about 30° minimum knee flexion) might be an effective form of 'forced-use' treatment of the paretic lower limb. It is not known whether it also stimulates a more symmetric muscle power output. Gait analysis on a force treadmill was carried out in 12 healthy adults and seven hemiplegic patients (1-127 months after stroke, median: 1.6). Speed was imposed at 0.3 m/s. Step length and single and double stance times, sagittal joint rotations, peak positive power, and work in extension of the hip, knee, and ankle (plantar flexion), and surface electromyography (sEMG) area from extensor muscles during the generation of power were measured on either side during both erect and crouch walking. Significance was set at P less than 0.05; corrections for multiplicity were applied. Patients, compared with healthy controls, adopted in both gait modalities and on both sides a shorter step length (61-84%) as well as a shorter stance (76-90%) and swing (63-83%) time. As a rule, they also provided a higher muscular work (median: 137%, range: 77-250%) paralleled by a greater sEMG area (median: 174%, range: 75-185%). In erect gait, the generation of peak extensor power across hip, knee, and ankle joints was in general lower (83-90%) from the paretic limb and higher (98-165%) from the unaffected limb compared with control values. In CG, peak power generation across the three lower limb joints was invariably higher in hemiparetic patients: 107-177% from the paretic limb and 114-231% from the unaffected limb. When gait shifted from erect to crouch, only for hemiplegic patients, at the hip, the paretic/unaffected ratio increased significantly. For peak power, work, sEMG area, and joint rotation, the paretic/unaffected ratio increased from 55 to 85%, 56 to 72%, 68 to 91%, and 67 to 93%, respectively. CG appears to be an effective form of forced-use exercise eliciting more power and work from the paretic lower limb muscles sustained by a greater neural drive. It also seems effective in forcing a more symmetric power and work from the hip extensor muscles, but neither from the knee nor the ankle.

Optimization of palm fruit sterilization by microwave irradiation using response surface methodology

NASA Astrophysics Data System (ADS)

Sarah, M.; Madinah, I.; Salamah, S.

2018-02-01

This study reported optimization of palm fruit sterilization process by microwave irradiation. The results of fractional factorial experiments showed no significant external factors affecting temperature of microwave sterilization (MS). Response surface methodology (RSM) was employed and model equation of MS of palm fruit was built. Response surface plots and their corresponding contour plots were analyzed as well as solving model equation. The optimum process parameters for lipase reduction were obtained from MS of 1 kg palm fruit at microwave power of 486 Watt and heating time of 14 minutes. The experimental results showed reduction of lipase activity in the present work under MS treatment. The adequacy of the model equation for predicting the optimum response value was verified by validation data (P>0.15).

Mechanisms for the adhesion of silver to glow discharge sensitized perfluorinated ethylene propylene (PEP)

NASA Technical Reports Server (NTRS)

Schutt, J. B.; Gilchrist, W. H.; Paczkowski, F. N.

1972-01-01

Details are given for the deposition of silver onto FEP for a batch coater capable of handling 864 square inches at a time. The effectiveness of the glow discharge is shown to be optimum when the FEP faces the anode. Using solid state theory based upon the work function difference, and the heuristic assumption that the surface of FEP is populated with fluoride ions, it is argued that an anode sensitized surface develops states receptive to electron transfer from silver, whereas a cathode sensitized surface is polarized only, and as a result cannot permanently trap charge. Thermodynamic arguments given show that an order of magnitude of 10 to the 9th power electrons are transferred into states to a depth of 10 nm.

Three-dimensional strutted graphene grown by substrate-free sugar blowing for high-power-density supercapacitors

PubMed Central

Wang, Xuebin; Zhang, Yuanjian; Zhi, Chunyi; Wang, Xi; Tang, Daiming; Xu, Yibin; Weng, Qunhong; Jiang, Xiangfen; Mitome, Masanori; Golberg, Dmitri; Bando, Yoshio

2013-01-01

Three-dimensional graphene architectures in the macroworld can in principle maintain all the extraordinary nanoscale properties of individual graphene flakes. However, current 3D graphene products suffer from poor electrical conductivity, low surface area and insufficient mechanical strength/elasticity; the interconnected self-supported reproducible 3D graphenes remain unavailable. Here we report a sugar-blowing approach based on a polymeric predecessor to synthesize a 3D graphene bubble network. The bubble network consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts. Such a topological configuration provides intimate structural interconnectivities, freeway for electron/phonon transports, huge accessible surface area, as well as robust mechanical properties. The graphene network thus overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for diverse practical usages, for example, high-power high-energy electrochemical capacitors, as highlighted in this work. PMID:24336225

Three-dimensional strutted graphene grown by substrate-free sugar blowing for high-power-density supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Xuebin; Zhang, Yuanjian; Zhi, Chunyi; Wang, Xi; Tang, Daiming; Xu, Yibin; Weng, Qunhong; Jiang, Xiangfen; Mitome, Masanori; Golberg, Dmitri; Bando, Yoshio

2013-12-01

Three-dimensional graphene architectures in the macroworld can in principle maintain all the extraordinary nanoscale properties of individual graphene flakes. However, current 3D graphene products suffer from poor electrical conductivity, low surface area and insufficient mechanical strength/elasticity; the interconnected self-supported reproducible 3D graphenes remain unavailable. Here we report a sugar-blowing approach based on a polymeric predecessor to synthesize a 3D graphene bubble network. The bubble network consists of mono- or few-layered graphitic membranes that are tightly glued, rigidly fixed and spatially scaffolded by micrometre-scale graphitic struts. Such a topological configuration provides intimate structural interconnectivities, freeway for electron/phonon transports, huge accessible surface area, as well as robust mechanical properties. The graphene network thus overcomes the drawbacks of presently available 3D graphene products and opens up a wide horizon for diverse practical usages, for example, high-power high-energy electrochemical capacitors, as highlighted in this work.

CPV performance versus soiling effects: Cleaning policies

NASA Astrophysics Data System (ADS)

Sanchez, D.; Trujillo, P.; Martinez, M.; Ferrer, J. P.; Rubio, F.

2012-10-01

In order to improve the performance of the CPV Plants in a cost effective way it is important to define the best cleaning policies, analyzing the effect of soiling in the surface of CPV modules. The energy generation of a CPV technology based in Fresnel Lens improves up to 7% when the surface of the module is cleaned. Some experimental measurements have been carried out over CPV modules and a model has been defined to analyze what is the best cleaning policy for that Technology in Puertollano. The power losses because of soiling and the critical time until the power losses stabilizes are obtained from the measurements; they are used as an input for the simulation. Using an established cleaning cost and the feeding tariff from Spain in 2007 it has been obtained that cleaning only reports a profit during the summer. The conclusion of the work is that the cleaning tasks have to be carefully planned together with the meteorological forecast in order to maximize the investment made in the cleaning.

OAST Space Theme Workshop. Volume 3: Working group summary. 3: Sensors (E-3). A. Statement. B. Technology needs (form 1). C. Priority assessment (form 2). D. Additional assessment

NASA Technical Reports Server (NTRS)

1976-01-01

Developments required to support the space power, SETI, solar system exploration and global services programs are identified. Instrumentation and calibration sensors (rather than scientific) are needed for the space power system. Highly sophisticated receivers for narrowband detection of microwave sensors and sensors for automated stellar cataloging to provide a mapping data base for SETI are needed. Various phases of solar system exploration require large area solid state imaging arrays from UV to IR; a long focal plane telescope; high energy particle detectors; advanced spectrometers; a gravitometer; and atmospheric distanalyzer; sensors for penetrometers; in-situ sensors for surface chemical analysis, life detection, spectroscopic and microscopic analyses of surface soils, and for meteorological measurements. Active and passive multiapplication sensors, advanced multispectral scanners with improved resolution in the UV and IR ranges, and laser techniques for advanced probing and oceanographic characterization will enhance for global services.

Plasma-treated Langmuir-Blodgett reduced graphene oxide thin film for applications in biophotovoltaics

NASA Astrophysics Data System (ADS)

Ibrahim, Siti Aisyah; Jaafar, Muhammad Musoddiq; Ng, Fong-Lee; Phang, Siew-Moi; Kumar, G. Ghana; Majid, Wan Haliza Abd; Periasamy, Vengadesh

2018-01-01

The surface optimization and structural characteristics of Langmuir-Blodgett (LB) reduced graphene oxide thin (rGO) film treated by argon plasma treatment were studied. In this work, six times deposition of rGO was deposited on a clean glass substrate using the LB method. Plasma technique involving a variation of plasma power, i.e., 20, 60, 100 and 140 W was exposed to the LB-rGO thin films under argon ambience. The plasma treatment generally improves the wettability or hydrophilicity of the film surface compared to without treatment. Maximum wettability was observed at a plasma power of 20 W, while also increasing the adhesion of the rGO film with the glass substrate. The multilayer films fabricated were characterized by means of spectroscopic, structural and electrical studies. The treatment of rGO with argon plasma was found to have improved its biocompatibility, and thus its performance as an electrode for biophotovoltaic devices has been shown to be enhanced considerably.

Study on the high-power semi-insulating GaAs PCSS with quantum well structure

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

Luan, Chongbiao; Wang, Bo; Huang, Yupeng

A high-power semi-insulating GaAs photoconductive semiconductor switch (PCSS) with quantum well structure was fabricated. The AlGaAs layer was deposited on the surface of the GaAs material, and the reflecting film and the antireflection film have been made on the surface of the GaAs and AlGaAs, respectively. When the prepared PCSS worked at a bias voltage of 9.8 kV and triggered by a laser pulse with an incident optical energy of 5.4 mJ, a wavelength of 1064 nm and an optical pulse width of 25 ns, the on-state resistance of the AlGaAs/GaAs PCSS was only 0.45 Ω, and the longevity ofmore » the AlGaAs/GaAs PCSS was larger than 10{sup 6} shots. The results show that this structure reduces the on-state resistance and extends the longevity of the GaAs PCSS.« less

Shield Design for Lunar Surface Applications

NASA Astrophysics Data System (ADS)

Johnson, Gregory A.

2006-01-01

A shielding concept for lunar surface applications of nuclear power is presented herein. The reactor, primary shield, reactor equipment and power generation module are placed in a cavity in the lunar surface. Support structure and heat rejection radiator panels are on the surface, outside the cavity. The reactor power of 1,320 kWt was sized to deliver 50 kWe from a thermoelectric power conversion subsystem. The dose rate on the surface is less than 0.6 mRem/hr at 100 meters from the reactor. Unoptimized shield mass is 1,020 kg which is much lighter than a comparable 4π shield weighing in at 17,000 kg.

Chemical etching mechanism and properties of microstructures in sapphire modified by femtosecond laser

NASA Astrophysics Data System (ADS)

Liu, Manyu; Hu, Youwang; Sun, Xiaoyan; Wang, Cong; Zhou, Jianying; Dong, Xinran; Yin, Kai; Chu, Dongkai; Duan, Ji'an

2017-01-01

Sapphire, with extremely high hardness, high-temperature stability and wear resistance, often corroded in molten KOH at 300 °C after processing. The fabrication of microstructures on sapphire substrate performed by femtosecond laser irradiation combined with KOH solution chemical etching at room temperature is presented. It is found that this method reduces the harsh requirements of sapphire corrosion. After femtosecond irradiation, the sapphire has a high corrosion speed at room temperature. Through the analysis of Raman spectrum and XRD spectrum, a novel insight of femtosecond laser interaction with sapphire (α-Al2O3) is proposed. Results indicated that grooves on sapphire surface were formed by the lasers ablation removal, and the groove surface was modified in a certain depth. The modified area of the groove surface was changed from α-Al2O3 to γ-Al2O3. In addition, the impacts of three experimental parameters, laser power, scanning velocities and etching time, on the width and depth of microstructures are investigated, respectively. The modified area dimension is about 2 μm within limits power and speed. This work could fabricate high-quality arbitrary microstructures and enhance the performance of sapphire processing.

High power transcranial beam steering for ultrasonic brain therapy

PubMed Central

Pernot, Mathieu; Aubry, Jean-François; Tanter, Mickaël; Thomas, Jean-Louis; Fink, Mathias

2003-01-01

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single-elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5cm2 and works at 0.9 MHz central frequency with a maximum 20W.cm−2 intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducers distributions on a spherical surface are simulated: hexagonal, annular, and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/− 15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system. PMID:12974575

High power transcranial beam steering for ultrasonic brain therapy

NASA Astrophysics Data System (ADS)

Pernot, M.; Aubry, J.-F.; Tanter, M.; Thomas, J.-L.; Fink, M.

2003-08-01

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5 cm2 and works at 0.9 MHz central frequency with a maximum 20 W cm-2 intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducer distributions on a spherical surface are simulated: hexagonal, annular and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/-15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system.

Advanced Energy Conversion Technologies and Architectures for Earth and Beyond

NASA Technical Reports Server (NTRS)

Howell, Joe T.; Fikes, John C.; Phillips, Dane J.; Laycock, Rustin L.; ONeill, Mark; Henley, Mark W.; Fork, Richard L.

2006-01-01

Research, development and studies of novel space-based solar power systems, technologies and architectures for Earth and beyond are needed to reduce the cost of clean electrical power for terrestrial use and to provide a stepping stone for providing an abundance of power in space, i.e., manufacturing facilities, tourist facilities, delivery of power between objects in space, and between space and surface sites. The architectures, technologies and systems needed for space to Earth applications may also be used for in-space applications. Advances in key technologies, i.e., power generation, power management and distribution, power beaming and conversion of beamed power are needed to achieve the objectives of both terrestrial and extraterrestrial applications. There is a need to produce "proof-ofconcept" validation of critical WPT technologies for both the near-term, as well as far-term applications. Investments may be harvested in near-term beam safe demonstrations of commercial WPT applications. Receiving sites (users) include ground-based stations for terrestrial electrical power, orbital sites to provide power for satellites and other platforms, future space elevator systems, space vehicle propulsion, and space surface sites. Space surface receiving sites of particular interest include the areas of permanent shadow near the moon s North and South poles, where WPT technologies could enable access to ice and other useful resources for human exploration. This paper discusses work addressing a promising approach to solar power generation and beamed power conversion. The approach is based on a unique high-power solar concentrator array called Stretched Lens Array (SLA) applied to both solar power generation and beamed power conversion. Since both versions (solar and laser) of SLA use many identical components (only the photovoltaic cells need to be different), economies of manufacturing and scale may be realized by using SLA on both ends of the laser power beaming system in a space solar power application. Near-term uses of this SLA-laser-SLA system may include terrestrial and space exploration in near Earth space. Later uses may include beamed power for bases or vehicles on Mars. Strategies for developing energy infrastructures in space which utilize this technology are presented. This dual use system produces electrical energy efficiently from either coherent light, such as from a highly coherent laser, or from conventional solar illumination. This allows, for example, supplementing solar energy with energy provided by highly coherent laser illumination during periods of low solar illumination or no illumination. This reduces the need for batteries and alternate sources of power. The capability of using laser illumination in a lowest order Gaussian laser mode provides means for transmitting power optically with maximum efficiency and precision over the long distances characteristic of space. A preliminary receiving system similar to that described here, has been produced and tested under solar and laser illumination. A summary of results is given.

Modeling guided wave excitation in plates with surface mounted piezoelectric elements: coupled physics and normal mode expansion

NASA Astrophysics Data System (ADS)

Ren, Baiyang; Lissenden, Cliff J.

2018-04-01

Guided waves have been extensively studied and widely used for structural health monitoring because of their large volumetric coverage and good sensitivity to defects. Effectively and preferentially exciting a desired wave mode having good sensitivity to a certain defect is of great practical importance. Piezoelectric discs and plates are the most common types of surface-mounted transducers for guided wave excitation and reception. Their geometry strongly influences the proportioning between excited modes as well as the total power of the excited modes. It is highly desirable to predominantly excite the selected mode while the total transduction power is maximized. In this work, a fully coupled multi-physics finite element analysis, which incorporates the driving circuit, the piezoelectric element and the wave guide, is combined with the normal mode expansion method to study both the mode tuning and total wave power. The excitation of circular crested waves in an aluminum plate with circular piezoelectric discs is numerically studied for different disc and adhesive thicknesses. Additionally, the excitation of plane waves in an aluminum plate, using a stripe piezoelectric element is studied both numerically and experimentally. It is difficult to achieve predominant single mode excitation as well as maximum power transmission simultaneously, especially for higher order modes. However, guidelines for designing the geometry of piezoelectric elements for optimal mode excitation are recommended.

The Development of a Control System for a 5 Kilowatt Free Piston Stirling Space Convertor

NASA Technical Reports Server (NTRS)

Kirby, Raymond L.; Vitale, Nicholas

2008-01-01

The new NASA Vision for Exploration, announced by President Bush in January 2004, proposes an ambitious program that plans to return astronauts to the moon by the 2018 time frame. A recent NASA study entitled "Affordable Fission Surface Power Study" recommended a 40 kWe, 900 K, NaK-cooled, Stirling conversion for 2020 launch. Use of two of the nominal 5 kW converters allows the system to be dynamically balanced. A group of four dual-converter combinations that would yield 40 kWe can be tested to validate the viability of Stirling technology for space fission surface power systems. The work described in this paper deals specifically with the control system for the 5 kW convertor described in the preceding paragraph. This control system is responsible for maintaining piston stroke to a setpoint in the presence of various disturbances including electrical load variations. Pulse starting of the FSPE convertor is also an inherent part of such a control system. Finally, the ability to throttle the engine to match the required output power is discussed in terms of setpoint control. Several novel ideas have been incorporated into the piston stroke control strategy that will engender a stable response to disturbances in the presence of midpoint drift while providing useful data regarding the position of both the power piston and displacer.

The Development of a Control System for a 5 Kilowatt Free Piston Stirling Engine Convertor

NASA Technical Reports Server (NTRS)

Kirby, Raymond L.; Vitale, Nick

2008-01-01

The new NASA Vision for Exploration, announced by President Bush in January 2004, proposes an ambitious program that plans to return astronauts to the moon by the 2018 time frame. A recent NASA study entitled "Affordable Fission Surface Power Study" recommended a 40 kWe, 900 K, NaK-cooled, Stirling convertors for 2020 launch. Use of two of the nominal 5 kW convertors allows the system to be dynamically balanced. A group of four dual-convertor combinations that would yield 40 kWe can be tested to validate the viability of Stirling technology for space fission surface power systems. The work described in this paper deals specifically with the control system for the 5 kW convertor described in the preceding paragraph. This control system is responsible for maintaining piston stroke to a setpoint in the presence of various disturbances including electrical load variations. Pulse starting of the Free Piston Stirling Engine (FPSE) convertor is also an inherent part of such a control system. Finally, the ability to throttle the engine to match the required output power is discussed in terms of setpoint control. Several novel ideas have been incorporated into the piston stroke control strategy that will engender a stable response to disturbances in the presence of midpoint drift while providing useful data regarding the position of both the power piston and displacer.

Statistical modeling of an integrated boiler for coal fired thermal power plant.

PubMed

Chandrasekharan, Sreepradha; Panda, Rames Chandra; Swaminathan, Bhuvaneswari Natrajan

2017-06-01

The coal fired thermal power plants plays major role in the power production in the world as they are available in abundance. Many of the existing power plants are based on the subcritical technology which can produce power with the efficiency of around 33%. But the newer plants are built on either supercritical or ultra-supercritical technology whose efficiency can be up to 50%. Main objective of the work is to enhance the efficiency of the existing subcritical power plants to compensate for the increasing demand. For achieving the objective, the statistical modeling of the boiler units such as economizer, drum and the superheater are initially carried out. The effectiveness of the developed models is tested using analysis methods like R 2 analysis and ANOVA (Analysis of Variance). The dependability of the process variable (temperature) on different manipulated variables is analyzed in the paper. Validations of the model are provided with their error analysis. Response surface methodology (RSM) supported by DOE (design of experiments) are implemented to optimize the operating parameters. Individual models along with the integrated model are used to study and design the predictive control of the coal-fired thermal power plant.

New Earth-abundant Materials for Large-scale Solar Fuels Generation.

PubMed

Prabhakar, Rajiv Ramanujam; Cui, Wei; Tilley, S David

2018-05-30

The solar resource is immense, but the power density of light striking the Earth's surface is relatively dilute, necessitating large area solar conversion devices in order to harvest substantial amounts of power for renewable energy applications. In addition, energy storage is a key challenge for intermittent renewable resources such as solar and wind, which adds significant cost to these energies. As the majority of humanity's present-day energy consumption is based on fuels, an ideal solution is to generate renewable fuels from abundant resources such as sunlight and water. In this account, we detail our recent work towards generating highly efficient and stable Earth-abundant semiconducting materials for solar water splitting to generate renewable hydrogen fuel.

Supporting Energy-Related Societal Applications Using NASA's Satellite and Modeling Data

NASA Technical Reports Server (NTRS)

Stackhouse, Paul W., Jr.; Whitlock, C. H.; Chandler, W. S.; Hoell, J. M.; Zhang, T.; Mikovitz, J. C.; Leng, G. S.; Lilienthal, P.

2006-01-01

Improvements to NASA Surface Meteorology and Solar Energy (SSE) web site are now being made through the Prediction of Worldwide Energy Resource (POWER) project under NASA Science Mission Directorate Applied Science Energy Management Program. The purpose of this project is to tailor NASA Science Mission results for energy sector applications and decision support systems. The current status of SSE and research towards upgrading estimates of total, direct and diffuse solar irradiance from NASA satellite measurements and analysis are discussed. Part of this work involves collaborating with partners such as the National Renewable Energy Laboratory (NREL) and the Natural Resources Canada (NRCan). Energy Management and POWER plans including historic, near-term and forecast datasets are also overviewed.

Unstable behaviour of normally-off GaN E-HEMT under short-circuit

NASA Astrophysics Data System (ADS)

Martínez, P. J.; Maset, E.; Sanchis-Kilders, E.; Esteve, V.; Jordán, J.; Bta Ejea, J.; Ferreres, A.

2018-04-01

The short-circuit capability of power switching devices plays an important role in fault detection and the protection of power circuits. In this work, an experimental study on the short-circuit (SC) capability of commercial 600 V Gallium Nitride enhancement-mode high-electron-mobility transistors (E-HEMT) is presented. A different failure mechanism has been identified for commercial p-doped GaN gate (p-GaN) HEMT and metal-insulator-semiconductor (MIS) HEMT. In addition to the well known thermal breakdown, a premature breakdown is shown on both GaN HEMTs, triggered by hot electron trapping at the surface, which demonstrates that current commercial GaN HEMTs has requirements for improving their SC ruggedness.

Free-Piston Stirling Power Conversion Unit for Fission Surface Power, Phase I Final Report

NASA Technical Reports Server (NTRS)

Wood, J. Gary; Buffalino, Andrew; Holliday, Ezekiel; Penswick, Barry; Gedeon, David

2010-01-01

This report summarizes the design of a 12 kW dual opposed free-piston Stirling convertor and controller for potential future use in space missions. The convertor is heated via a pumped NaK loop and cooling is provided by a pumped water circuit. Convertor efficiency is projected at 27 percent (AC electrical out/heat in). The controller converts the AC electrical output to 120 Vdc and is projected at 91 percent efficiency. A mechanically simple arrangement, based on proven technology, was selected in which the piston is resonated almost entirely by the working space pressure swing, while the displacer is resonated by planar mechanical springs in the bounce space.

Adaptable piezoelectric hemispherical composite strips using a scalable groove technique for a self-powered muscle monitoring system.

PubMed

Alluri, Nagamalleswara Rao; Vivekananthan, Venkateswaran; Chandrasekhar, Arunkumar; Kim, Sang-Jae

2018-01-18

Contrary to traditional planar flexible piezoelectric nanogenerators (PNGs), highly adaptable hemispherical shape-flexible piezoelectric composite strip (HS-FPCS) based PNGs are required to harness/measure non-linear surface motions. Therefore, a feasible, cost-effective and less-time consuming groove technique was developed to fabricate adaptable HS-FPCSs with multiple lengths. A single HS-CSPNG generates 130 V/0.8 μA and can also work as a self-powered muscle monitoring system (SP-MMS) to measure maximum human body part movements, i.e., spinal cord, throat, jaw, elbow, knee, foot stress, palm hand/finger force and inhale/exhale breath conditions at a time or at variable time intervals.

Plasmonic computing of spatial differentiation

NASA Astrophysics Data System (ADS)

Zhu, Tengfeng; Zhou, Yihan; Lou, Yijie; Ye, Hui; Qiu, Min; Ruan, Zhichao; Fan, Shanhui

2017-05-01

Optical analog computing offers high-throughput low-power-consumption operation for specialized computational tasks. Traditionally, optical analog computing in the spatial domain uses a bulky system of lenses and filters. Recent developments in metamaterials enable the miniaturization of such computing elements down to a subwavelength scale. However, the required metamaterial consists of a complex array of meta-atoms, and direct demonstration of image processing is challenging. Here, we show that the interference effects associated with surface plasmon excitations at a single metal-dielectric interface can perform spatial differentiation. And we experimentally demonstrate edge detection of an image without any Fourier lens. This work points to a simple yet powerful mechanism for optical analog computing at the nanoscale.

Destruction of monocrystalline silicon with nanosecond pulsed fiber laser accompanied by the oxidation of ablation microparticles

NASA Astrophysics Data System (ADS)

Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

2013-11-01

In this work, we report an observation of process of local destruction monocrystalline silicon with a scanning beam irradiation of pulse ytterbium fiber laser with a wavelength λ= 1062 nm, accompanied by the oxidation of ablation microparticles. It is shown that depending on the power density of irradiation was observed a large scatter size of the microparticles. From a certain average power density is observed beginning oxidation particulate emitted from the surface of the irradiated area. By varying the parameters of the laser beam such as scanning speed, pulse repetition rate, overlap of laser spot, radiation dose can be achieved almost complete oxidation of all formed during the ablation of microparticles.

Alfven's critical ionization velocity observed in high power impulse magnetron sputtering discharges

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

Brenning, N.; Lundin, D.

2012-09-15

Azimuthally rotating dense plasma structures, spokes, have recently been detected in several high power impulse magnetron sputtering (HiPIMS) devices used for thin film deposition and surface treatment, and are thought to be important for plasma buildup, energizing of electrons, as well as cross-B transport of charged particles. In this work, the drift velocities of these spokes are shown to be strongly correlated with the critical ionization velocity, CIV, proposed by Alfven. It is proposed as the most promising approach in combining the CIV and HiPIMS research fields is to focus on the role of spokes in the process of electronmore » energization.« less

Recent work on use of lunar materials for SPS construction

NASA Technical Reports Server (NTRS)

Oneill, G. K.

1980-01-01

The feasibility of mounting a small operation on the Moon to productively use lunar materials in support of programs such as the solar power satellite is addressed. A cost effective scenario of a small chemical process plant on the surface of the Moon and a small machine shop located in orbit is presented. The mass of the space installation is compared to the projected outputs in 90 days. It is indicated that the system would have the capability of replicating about 90% of its own components and would provide the metals, glasses, and silicon needed for the contruction of 90% to 96% of the mass of one solar power satellite per year.

JPRS Report, Science & Technology: China.

DTIC Science & Technology

1989-01-31

et al.; GUANGXUE XUEBAO, No 8, Aug 88] 130 Hardening Treatment for the Surface of 50 SiMnP Steel for High Power Laser [Yu Hongtao , Cao Tianshun...and Qian Bin [6929 2430]; helped with the technical work; the tool enzyme unit provided the enzymes; and the Shanghai Biological Products Institute...154 [Article by Yu Hongtao ]0060 3163 3447] and Cao Tianshun [2580 1131 7311] of Angang College of Technology] [Abstract] The article proposes a

Investigation of Material Problems for High Temperature, High Power Space Energy-Conversion Systems.

DTIC Science & Technology

1986-07-01

Microplastic Deformation in Molybdenum with Grain-Boundary Segregations of Nickel, Phys. Met. Metall. 54, 180, 1982. 76. C. Lea, B. Muddle and D...8217-- *. ~a.-. ~ ~ ~ .. . ~ . ~ . .*.. -- ~ .. 25 93. T. Noda, T. Kainuma and M. Okada: Oxygen Desorption from Grain Boundaries of Molybdenum During Vacuu...behavior of this work function climb was explained by the desorption of atoms adsorbed or, the surface. The test result of the present W-Re samples showed

Development of Low Cost, High Energy-Per-Unit-Area Solar Cell Modules

NASA Technical Reports Server (NTRS)

Jones, G. T.; Chitre, S.

1977-01-01

Work on the development of low cost, high energy per unit area solar cell modules was conducted. Hexagonal solar cell and module efficiencies, module packing ratio, and solar cell design calculations were made. The cell grid structure and interconnection pattern was designed and the module substrates were fabricated for the three modules to be used. It was demonstrated that surface macrostructures significantly improve cell power output and photovoltaic energy conversion efficiency.

Environmental dust effects on aluminum surfaces in humid air ambient.

PubMed

Yilbas, Bekir Sami; Hassan, Ghassan; Ali, Haider; Al-Aqeeli, Nasser

2017-04-05

Environmental dusts settle on surfaces and influence the performance of concentrated solar energy harvesting devices, such as aluminum troughs. The characteristics of environmental dust and the effects of mud formed from the dust particles as a result of water condensing in humid air conditions on an aluminum wafer surface are examined. The dissolution of alkaline and alkaline earth compounds in water condensate form a chemically active mud liquid with pH 8.2. Due to gravity, the mud liquid settles at the interface of the mud and the aluminum surface while forming locally scattered patches of liquid films. Once the mud liquid dries, adhesion work to remove the dry mud increases significantly. The mud liquid gives rise to the formation of pinholes and local pit sites on the aluminum surface. Morphological changes due to pit sites and residues of the dry mud on the aluminum surface lower the surface reflection after the removal of the dry mud from the surface. The characteristics of the aluminum surface can address the dust/mud-related limitations of reflective surfaces and may have implications for the reductions in the efficiencies of solar concentrated power systems.

Environmental dust effects on aluminum surfaces in humid air ambient

PubMed Central

Yilbas, Bekir Sami; Hassan, Ghassan; Ali, Haider; Al-Aqeeli, Nasser

2017-01-01

Environmental dusts settle on surfaces and influence the performance of concentrated solar energy harvesting devices, such as aluminum troughs. The characteristics of environmental dust and the effects of mud formed from the dust particles as a result of water condensing in humid air conditions on an aluminum wafer surface are examined. The dissolution of alkaline and alkaline earth compounds in water condensate form a chemically active mud liquid with pH 8.2. Due to gravity, the mud liquid settles at the interface of the mud and the aluminum surface while forming locally scattered patches of liquid films. Once the mud liquid dries, adhesion work to remove the dry mud increases significantly. The mud liquid gives rise to the formation of pinholes and local pit sites on the aluminum surface. Morphological changes due to pit sites and residues of the dry mud on the aluminum surface lower the surface reflection after the removal of the dry mud from the surface. The characteristics of the aluminum surface can address the dust/mud-related limitations of reflective surfaces and may have implications for the reductions in the efficiencies of solar concentrated power systems. PMID:28378798

Defects and Small Polarons on Oxide Surfaces

NASA Astrophysics Data System (ADS)

Janotti, Anderson

The presence and behavior of defects on the surface of oxides are central in many research areas, including catalysis, photochemistry, solar cells, and surface science in general. Experimental characterization of individual defects and their activities are challenging and often requires special preparations of the surface. First-principles calculations based on density functional theory are a powerful tool to study surfaces and defects, often providing information on properties that are difficult to access experimentally. Here we discuss the behavior of defects on oxide surfaces from the perspective on first-principles calculations. We use the oxygen vacancy on TiO2 surface as example, a system that has been extensively reported in the literature. Using DFT with a hybrid function, we discuss surface states induced by the defect and localization of the excess charge in the form of small polarons. We then discuss the effects of hydrogen and compare the behavior of these defects on the surface with that in the bulk. We also compare our recent results with previous theoretical studies and experiments. Finally, we generalize the findings on TiO2 to the surfaces of other oxides. This work was supported by the NSF.

Role of organic cations on hybrid halide perovskite CH3NH3PbI3 surfaces

NASA Astrophysics Data System (ADS)

Teng, Qiang; Shi, Ting-Ting; Tian, Ren-Yu; Yang, Xiao-Bao; Zhao, Yu-Jun

2018-02-01

Organic-inorganic hybrid halide perovskite CH3NH3PbI3 (MAPbI3) has received rapid progress in power conversion efficiency as promising photovoltaic materials, yet the surface structures and the role of MA cations are not well understood. In this work, we investigated the structural stability and electronic properties of (001) surface of cubic, (001) and (110) surfaces of tetragonal and orthorhombic phases of MAPbI3 with considering the orientation of MA cations, by density functional theory calculations. We demonstrate that the orientation of MA cations has profound consequences on the structural stability and the electronic properties of the surfaces, in contrast to the bulk phases. Compared with the MA-I terminated surfaces, the Pb-I2 terminated ones generally have smaller band gaps and the advantage to enable the photo-excited holes to transfer to the hole-transport materials in both tetragonal and orthorhombic phases. Overall, we suggest that the films with Pb-I2 terminated surfaces would prevail in high performance solar energy absorbers.

Patterned self-assembled monolayers for nanoscale lithography and the control of catalytically produced electroosmosis

NASA Astrophysics Data System (ADS)

Subramanian, Shyamala

This thesis explores two applications of self-assembled monolayers (SAMs) (a) for developing novel molecular assembly based nanolithography techniques and (b) for tailoring zeta-potential of surfaces towards achieving directional control of catalytically induced fluid flow. The first half of the thesis develops the process of molecular ruler lithography using sacrificial host structures. This is a novel hybrid nanolithography technique which combines chemical self-assembly with conventional fabrication methods for improving the resolution of existing lithography tools to sub-50 nm. Previous work related to molecular ruler lithography have shown the use of thiol-SAMs, placed one on top of the other like a molecular resist, for scaling down feature sizes. In this thesis various engineering solutions for improving the reproducibility, yield, nanoscale roughness and overall manufacturability of the process are introduced. This is achieved by introducing a sacrificial inert layer underneath the gold parent structure. This bilayer sacrificial host allows for preferential, easy and quick removal of the parent structures, isolates the parent metal from the underlying substrate and improves reproducibility of the lift-off process. Also it opens avenues for fabrication of high aspect ratio features. Also molecular layer vapor deposition method is developed for building the multilayer molecular resist via vapor phase to reduce contaminations and yield issues associated with solution phase deposition. The smallest isolated metal features produced using this process were 40 nm in width. The second half of the thesis describes application of thiol-SAMs to tailor surface properties of gold, specifically the surface charge or zeta potential. Previous work has demonstrated that the direction of movement of fluid in the vicinity of a catalytically active bimetallic junction placed in a solution of dilute hydrogen peroxide depends on the charge of the gold surface. SAMs with different end-group functionality impart different surface zeta potential to the gold surface. Zeta-potential engineering via patterning various end-group functionalized SAMs on gold surface to control direction of catalytically induced electroosmotic fluid flow is demonstrated for the first time. This work also describes the application of catalytic power to produce controlled rotational motion. Gold gears-like structures made using conventional microfabrication techniques and propelled by catalytic power are shown to rotate at speeds of 1 rotation/sec in a dilute solution of hydrogen peroxide. Fabrication of a force sensor for detection and measurement of catalytic forces is also introduced. The force sensor, with sensitivity in the piconewton range, consists of a microcantilever with a catalytically active silver post patterned on the tip. Changes in cantilever displacement and resonance frequency due to the catalytic force were monitored as a function of concentration of hydrogen peroxide. Overall, this thesis integrates SAM deposition and patterning techniques with conventional fabrication methods to engineer and control nanoscale structures and devices. Possible future device designs are described including CMOS devices having channel width defined using molecular ruler lithography with sacrificial hosts, drug delivery device based on AFM force sensor and channeless pumps powered by catalytic reactions with SAM controlled electroosmotic fluid flow.

Structural, electrical, and optical properties of antimony-doped tin oxide films prepared at room temperature by radio frequency magnetron sputtering for transparent electrodes

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

Lee, Sung Uk; Hong, Byungyou; Choi, Won Seok

2009-07-15

Antimony-doped tin oxide (ATO) films were prepared on 7059 Corning glass substrate by the radio frequency (rf) magnetron sputtering method using SnO{sub 2} target mixed with Sb of 6 wt % at room temperature. The working pressure was varied from 0.67 to 2 Pa in steps of 0.67 Pa, and the rf power was varied from 100 to 175 W in steps of 25 W at room temperature. The thickness of the deposited ATO films was about 150 nm. X-ray diffraction (XRD) measurements showed the ATO films to be crystallized with a strong (101) preferred orientation as the rf powermore » is increased. The spectra revealed that the deposited films were polycrystalline, retaining the tetragonal structure. The grain size was estimated from the XRD spectra using the Scherrer equation and found to decrease with a decrease in the working pressure and an increase in the rf power, while the surface roughness was observed to be smoothened. The ATO film that was deposited at a working pressure of 0.67 Pa with rf power of 175 W showed the lowest resistivity of 8.6x10{sup -3} {Omega} cm, and the optical transmittance was 86.5% in the visible wavelength range from 400 to 800 nm.« less

Atomic force microscopy as a tool to study Xenopus laevis embryo

NASA Astrophysics Data System (ADS)

Pukhlyakova, E. A.; Efremov, Yu M.; Bagrov, D. V.; Luchinskaya, N. N.; Kiryukhin, D. O.; Belousov, L. V.; Shaitan, K. V.

2012-02-01

Atomic force microscopy (AFM) has become a powerful tool for imaging biological structures (from single molecules to living cells) and carrying out measurements of their mechanical properties. AFM provides three-dimensional high-resolution images of the studied biological objects in physiological environment. However there are only few AFM investigations of fresh tissue explants and virtually no such research on a whole organism, since most researchers work with cell cultures. In the current work AFM was used to observe the surface of living and fixed embryos and to measure mechanical properties of naive embryos and embryos with overexpression of guanine nucleotide-binding protein G-alpha-13.

Eccentricity and misalignment effects on the performance of high-pressure annular seals

NASA Technical Reports Server (NTRS)

Chen, W. C.; Jackson, E. D.

1985-01-01

Annular pressure seals act as powerful hydrostatic bearings and influence the dynamic characteristics of rotating machinery. This work, using the existing concentric seal theories, provides a simple approximate method for calculation of both seal leakage and the dynamic coefficients for short seals with large eccentricity and/or misalignment of the shaft. Rotation and surface roughness effects are included for leakage and dynamic force calculation. The leakage calculations for both laminar and turbulent flow are compared with experimental results. The dynamic coefficients are compared with analytical results. Excellent agreement between the present work and published results have been observed up to the eccentricitiy ratio of 0.8.

The impact of surface chemistry on the performance of localized solar-driven evaporation system

PubMed Central

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-01-01

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation. PMID:26337561

The impact of surface chemistry on the performance of localized solar-driven evaporation system.

PubMed

Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

2015-09-04

This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation.

The impact of sea surface currents in wave power potential modeling

NASA Astrophysics Data System (ADS)

Zodiatis, George; Galanis, George; Kallos, George; Nikolaidis, Andreas; Kalogeri, Christina; Liakatas, Aristotelis; Stylianou, Stavros

2015-11-01

The impact of sea surface currents to the estimation and modeling of wave energy potential over an area of increased economic interest, the Eastern Mediterranean Sea, is investigated in this work. High-resolution atmospheric, wave, and circulation models, the latter downscaled from the regional Mediterranean Forecasting System (MFS) of the Copernicus marine service (former MyOcean regional MFS system), are utilized towards this goal. The modeled data are analyzed by means of a variety of statistical tools measuring the potential changes not only in the main wave characteristics, but also in the general distribution of the wave energy and the wave parameters that mainly affect it, when using sea surface currents as a forcing to the wave models. The obtained results prove that the impact of the sea surface currents is quite significant in wave energy-related modeling, as well as temporally and spatially dependent. These facts are revealing the necessity of the utilization of the sea surface currents characteristics in renewable energy studies in conjunction with their meteo-ocean forecasting counterparts.

Heat transfer mechanisms in pulsating heat-pipes with nanofluid

NASA Astrophysics Data System (ADS)

Gonzalez, Miguel; Kelly, Brian; Hayashi, Yoshikazu; Kim, Yoon Jo

2015-01-01

In this study, the effect of silver nanofluid on a pulsating heat-pipe (PHP) thermal performance was experimentally investigated to figure out how nanofluid works with PHP. A closed loop PHP was built with 3 mm diameter tubes. Thermocouples and pressure transducers were installed for fluid and surface temperature and pressure measurements. The operating temperature of the PHP varied from 30-100 °C, with power rates of 61 W and 119 W. The fill ratio of 30%, 50%, and 70% were tested. The results showed that the evaporator heat transfer performance was degraded by the addition of nanoparticles due to increased viscosity at high power rate, while the positive effects of high thermal conductivity and enhanced nucleate boiling worked better at low power rate. In the condenser section, owing to the relatively high liquid content, nanofluid more effectively improved the heat transfer performance. However, since the PHP performance was dominantly affected by evaporator heat transfer performance, the overall benefit of enhanced condenser section performance was greatly limited. It was also observed that the poor heat transfer performance with nanofluid at the evaporator section led to lower operating pressure of PHP.

Sandwich Core Heat-Pipe Radiator for Power and Propulsion Systems

NASA Technical Reports Server (NTRS)

Gibson, Marc; Sanzi, James; Locci, Ivan

2013-01-01

Next-generation heat-pipe radiator technologies are being developed at the NASA Glenn Research Center to provide advancements in heat-rejection systems for space power and propulsion systems. All spacecraft power and propulsion systems require their waste heat to be rejected to space in order to function at their desired design conditions. The thermal efficiency of these heat-rejection systems, balanced with structural requirements, directly affect the total mass of the system. Terrestrially, this technology could be used for thermal control of structural systems. One potential use is radiant heating systems for residential and commercial applications. The thin cross section and efficient heat transportability could easily be applied to flooring and wall structures that could evenly heat large surface areas. Using this heat-pipe technology, the evaporator of the radiators could be heated using any household heat source (electric, gas, etc.), which would vaporize the internal working fluid and carry the heat to the condenser sections (walls and/or floors). The temperature could be easily controlled, providing a comfortable and affordable living environment. Investigating the appropriate materials and working fluids is needed to determine this application's potential success and usage.

Actuation of flexoelectric membranes in viscoelastic fluids with applications to outer hair cells

PubMed Central

Herrera-Valencia, E. E.; Rey, Alejandro D.

2014-01-01

Liquid crystal flexoelectric actuation uses an imposed electric field to create membrane bending, and it is used by the outer hair cells (OHCs) located in the inner ear, whose role is to amplify sound through generation of mechanical power. Oscillations in the OHC membranes create periodic viscoelastic flows in the contacting fluid media. A key objective of this work on flexoelectric actuation relevant to OHCs is to find the relations and impact of the electromechanical properties of the membrane, the rheological properties of the viscoelastic media, and the frequency response of the generated mechanical power output. The model developed and used in this work is based on the integration of: (i) the flexoelectric membrane shape equation applied to a circular membrane attached to the inner surface of a circular capillary and (ii) the coupled capillary flow of contacting viscoelastic phases, such that the membrane flexoelectric oscillations drive periodic viscoelastic capillary flows, as in OHCs. By applying the Fourier transform formalism to the governing equation, analytical expressions for the transfer function associated with the curvature and electrical field and for the power dissipation of elastic storage energy were found. PMID:25332388

Hybrid supercapacitor-battery materials for fast electrochemical charge storage

PubMed Central

Vlad, A.; Singh, N.; Rolland, J.; Melinte, S.; Ajayan, P. M.; Gohy, J.-F.

2014-01-01

High energy and high power electrochemical energy storage devices rely on different fundamental working principles - bulk vs. surface ion diffusion and electron conduction. Meeting both characteristics within a single or a pair of materials has been under intense investigations yet, severely hindered by intrinsic materials limitations. Here, we provide a solution to this issue and present an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a Li-ion battery material (LiFePO4). The PTMA constituent dominates the hybrid battery charge process and postpones the LiFePO4 voltage rise by virtue of its ultra-fast electrochemical response and higher working potential. We detail on a unique sequential charging mechanism in the hybrid electrode: PTMA undergoes oxidation to form high-potential redox species, which subsequently relax and charge the LiFePO4 by an internal charge transfer process. A rate capability equivalent to full battery recharge in less than 5 minutes is demonstrated. As a result of hybrid's components synergy, enhanced power and energy density as well as superior cycling stability are obtained, otherwise difficult to achieve from separate constituents. PMID:24603843

Powerful glow discharge excilamp

DOEpatents

Tarasenko, Victor F.; Panchenko, Aleksey N.; Skakun, Victor S.; Sosnin, Edward A.; Wang, Francis T.; Myers, Booth R.; Adamson, Martyn G.

2002-01-01

A powerful glow discharge lamp comprising two coaxial tubes, the outer tube being optically transparent, with a cathode and anode placed at opposite ends of the tubes, the space between the tubes being filled with working gas. The electrodes are made as cylindrical tumblers placed in line to one other in such a way that one end of the cathode is inserted into the inner tube, one end of the anode coaxially covers the end of the outer tube, the inner tube penetrating and extending through the anode. The increased electrodes' surface area increases glow discharge electron current and, correspondingly, average radiation power of discharge plasma. The inner tube contains at least one cooling liquid tube placed along the axis of the inner tube along the entire lamp length to provide cathode cooling. The anode has a circumferential heat extracting radiator which removes heat from the anode. The invention is related to lighting engineering and can be applied for realization of photostimulated processes under the action of powerful radiation in required spectral range.

Embedding solar cell materials with on-board integrated energy storage for load-leveling and dark power delivery (Presentation Recording)

NASA Astrophysics Data System (ADS)

Pint, Cary L.; Westover, Andrew S.; Cohn, Adam P.; Erwin, William R.; Share, Keith; Metke, Thomas; Bardhan, Rizia

2015-10-01

This work will discuss our recent advances focused on integrating high power energy storage directly into the native materials of both conventional photovoltaics (PV) and dye-sensitized solar cells (DSSCs). In the first case (PV), we demonstrate the ability to etch high surface-area porous silicon charge storage interfaces directly into the backside of a conventional polycrystalline silicon photovoltaic device exhibiting over 14% efficiency. These high surface area materials are then coupled with solid-state ionic liquid-polymer electrolytes to produce solid-state fully integrated devices where the PV device can directly inject charge into an on-board supercapacitor that can be separately discharged under dark conditions with a Coulombic efficiency of 84%. In a similar manner, we further demonstrate that surface engineered silicon materials can be utilized to replace Pt counterelectrodes in conventional DSSC energy conversion devices. As the silicon counterelectrodes rely strictly on surface Faradaic chemical reactions with the electrolyte on one side of the wafer electrode, we demonstrate double-sided processing of electrodes that enables dual-function of the material for simultaneous energy storage and conversion, each on opposing sides. In both of these devices, we demonstrate the ability to produce an all-silicon coupled energy conversion and storage system through the common ability to convert unused silicon in solar cells into high power silicon-based supercapacitors. Beyond the proof-of-concept design and performance of this integrated solar-storage system, this talk will conclude with a brief discussion of the hurdles and challenges that we envision for this emerging area both from a fundamental and technological viewpoint.

LOW-ENGINE-FRICTION TECHNOLOGY FOR ADVANCED NATURAL-GAS RECIPROCATING ENGINES

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

Victor Wong; Tian Tian; Luke Moughon

2005-09-30

This program aims at improving the efficiency of advanced natural-gas reciprocating engines (ANGRE) by reducing piston and piston ring assembly friction without major adverse effects on engine performance, such as increased oil consumption and wear. An iterative process of simulation, experimentation and analysis is being followed towards achieving the goal of demonstrating a complete optimized low-friction engine system. To date, a detailed set of piston and piston-ring dynamic and friction models have been developed and applied that illustrate the fundamental relationships between design parameters and friction losses. Low friction ring designs have already been recommended in a previous phase, withmore » full-scale engine validation partially completed. Current accomplishments include the addition of several additional power cylinder design areas to the overall system analysis. These include analyses of lubricant and cylinder surface finish and a parametric study of piston design. The Waukesha engine was found to be already well optimized in the areas of lubricant, surface skewness and honing cross-hatch angle, where friction reductions of 12% for lubricant, and 5% for surface characteristics, are projected. For the piston, a friction reduction of up to 50% may be possible by controlling waviness alone, while additional friction reductions are expected when other parameters are optimized. A total power cylinder friction reduction of 30-50% is expected, translating to an engine efficiency increase of two percentage points from its current baseline towards the goal of 50% efficiency. Key elements of the continuing work include further analysis and optimization of the engine piston design, in-engine testing of recommended lubricant and surface designs, design iteration and optimization of previously recommended technologies, and full-engine testing of a complete, optimized, low-friction power cylinder system.« less

Bohm criterion and plasma particle/power exhaust to and recycling at the wall

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

Tang, Xianzhu; Guo, Zehua

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview onmore » how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.« less

Bohm criterion and plasma particle/power exhaust to and recycling at the wall

DOE PAGES

Tang, Xianzhu; Guo, Zehua

2017-06-07

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview onmore » how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.« less

A new laboratory-scale experimental facility for detailed aerothermal characterizations of volumetric absorbers

NASA Astrophysics Data System (ADS)

Gomez-Garcia, Fabrisio; Santiago, Sergio; Luque, Salvador; Romero, Manuel; Gonzalez-Aguilar, Jose

2016-05-01

This paper describes a new modular laboratory-scale experimental facility that was designed to conduct detailed aerothermal characterizations of volumetric absorbers for use in concentrating solar power plants. Absorbers are generally considered to be the element with the highest potential for efficiency gains in solar thermal energy systems. The configu-ration of volumetric absorbers enables concentrated solar radiation to penetrate deep into their solid structure, where it is progressively absorbed, prior to being transferred by convection to a working fluid flowing through the structure. Current design trends towards higher absorber outlet temperatures have led to the use of complex intricate geometries in novel ceramic and metallic elements to maximize the temperature deep inside the structure (thus reducing thermal emission losses at the front surface and increasing efficiency). Although numerical models simulate the conjugate heat transfer mechanisms along volumetric absorbers, they lack, in many cases, the accuracy that is required for precise aerothermal validations. The present work aims to aid this objective by the design, development, commissioning and operation of a new experimental facility which consists of a 7 kWe (1.2 kWth) high flux solar simulator, a radiation homogenizer, inlet and outlet collector modules and a working section that can accommodate volumetric absorbers up to 80 mm × 80 mm in cross-sectional area. Experimental measurements conducted in the facility include absorber solid temperature distributions along its depth, inlet and outlet air temperatures, air mass flow rate and pressure drop, incident radiative heat flux, and overall thermal efficiency. In addition, two windows allow for the direct visualization of the front and rear absorber surfaces, thus enabling full-coverage surface temperature measurements by thermal imaging cameras. This paper presents the results from the aerothermal characterization of a siliconized silicon carbide monolithic honeycomb, conducted at realistic conditions of incident radiative power per unit mass flow rate in order to validate its operation.

Novel Thermal Powered Technology for UUV Persistent Surveillance

NASA Technical Reports Server (NTRS)

Jones, Jack A.; Chao, Yi

2006-01-01

Buoyancy Generation: Various technology attempts include melting a wax, which pushes directly against a piston (U.S. Patent 5,291,847) or against a bladder (Webb Research), using ammonia or Freon 21 (U.S. Patent 5,303,552), and using solar heat to expand an oil (www.space.com, April, 10, 2002). All these heat-activated buoyancy control designs have thus far proved impractical and have ultimately failed during repeated cycling in ocean testing. JPL has demonstrated fully reversible 10 C encapsulated wax phase change, which can be used to change buoyancy without electrical hydraulic pumps. This technique has greatly improved heat transfer and much better reversibility than previous designs. Power Generation: Ocean Thermal Energy Conversion (OTEC) systems have been designed that transfer deep, cold sea water to the surface to generate electricity using turbine cycles with ammonia or water as the working fluid. JPL has designed several UUV systems: 1) Using a propeller water turbine to generate power on a gliding submersible; 2) Employing a compact CO2 turbine cycle powered by moving through thermoclines; and 3) Using melted wax to directly produce power through a piston-geared generator.

Advanced Electrical Materials and Components Development: An Update

NASA Technical Reports Server (NTRS)

Schwarze, Gene E.

2005-01-01

The primary means to develop advanced electrical components is to develop new and improved materials for magnetic components (transformers, inductors, etc.), capacitors, and semiconductor switches and diodes. This paper will give an update of the Advanced Power Electronics and Components Technology being developed by the NASA Glenn Research Center for use in future Power Management and Distribution subsystems used in space power systems for spacecraft and lunar and planetary surface power. The initial description and status of this technology program was presented two years ago at the First International Energy Conversion Engineering Conference held at Portsmouth, Virginia, August 2003. The present paper will give a brief background of the previous work reported and a summary of research performed the past several years on soft magnetic materials characterization, dielectric materials and capacitor developments, high quality silicon carbide atomically smooth substrates, and SiC static and dynamic device characterization under elevated temperature conditions. The rationale for and the benefits of developing advanced electrical materials and components for the PMAD subsystem and also for the total power system will also be briefly discussed.

Thin-film Solar Cells for Space Applications

NASA Technical Reports Server (NTRS)

Lush, Gregory B.

2003-01-01

The proposed work supports MURED goals by fostering research and development activities at Fisk and UTEP which contribute substantially to NASA's mission, preparing faculty and students at Fisk and UTEP to successfully participate in the conventional, competitive research and education process, and increasing the number of students to successfully complete degrees in NASA related fields. The project also addresses directly a core need of NASA for space power and is consistent with the Core Responsibilities of the John Glenn Space Center. Current orbital missions are limited by radiation from high energy particles trapped in the Van Allen Belt because that solar radiation degrades cell performance by damaging the crystalline lattice. Some potential orbits have been inaccessible because the radiation is too severe. Thin-film solar cells, if they can be adapted for use in the unfriendly space environment, could open new orbits to satellites by providing a radiation hard source of power. The manned mission to Mars requires photovoltaic devices for both the trip there and as a power supply on the surface. Solar arrays using thin films offer a low power/weight ratio solution that provides reliable photovoltaic power.

System engineering study of electrodynamic tether as a spaceborne generator and radiator of electromagnetic waves in the ULF/ELF frequency band

NASA Technical Reports Server (NTRS)

Estes, Robert D.

1987-01-01

An electrodynamic tether deployed from a satellite in low-Earth orbit can perform, if properly instrumented, as a partially self-powered generator of electromagnetic waves in the ULF/ELF band, potentially at power levels high enough to be of practical use. Two basic problems are examined. The first is that of the level of wave power that the system can be expected to generate in the ULF/ELF radiation band. The second major question is whether an electrodynamic tethered satellite system for transmitting waves can be made partially self-powering so that power requirements for drag compensation can be met within economical constraints of mass, cost, and complexity. The theoretical developments and the system applications study are presented. The basic design criteria, the drag-compensation method, the effects on the propagation paths from orbit to Earth surface of high-altitude nuclear debris patches, and the estimate of masses and sizes are covered. An outline of recommended analytical work, to be performed as a follow-on to the present study, is contained.

Conformal phased surfaces for wireless powering of bioelectronic microdevices

PubMed Central

Agrawal, Devansh R.; Tanabe, Yuji; Weng, Desen; Ma, Andrew; Hsu, Stephanie; Liao, Song-Yan; Zhen, Zhe; Zhu, Zi-Yi; Sun, Chuanbowen; Dong, Zhenya; Yang, Fengyuan; Tse, Hung Fat; Poon, Ada S. Y.; Ho, John S.

2017-01-01

Wireless powering could enable the long-term operation of advanced bioelectronic devices within the human body. Although both enhanced powering depth and device miniaturization can be achieved by shaping the field pattern within the body, existing electromagnetic structures do not provide the spatial phase control required to synthesize such patterns. Here, we describe the design and operation of conformal electromagnetic structures, termed phased surfaces, that interface with non-planar body surfaces and optimally modulate the phase response to enhance the performance of wireless powering. We demonstrate that the phased surfaces can wirelessly transfer energy across anatomically heterogeneous tissues in large animal models, powering miniaturized semiconductor devices (<12 mm3) deep within the body (>4 cm). As an illustration of in vivo operation, we wirelessly regulated cardiac rhythm by powering miniaturized stimulators at multiple endocardial sites in a porcine animal model. PMID:29226018

La and Al co-doped CaMnO 3 perovskite oxides: From interplay of surface properties to anion exchange membrane fuel cell performance

DOE PAGES

Dzara, Michael J.; Christ, Jason M.; Joghee, Prabhuram; ...

2017-09-01

This work reports the first account of perovskite oxide and carbon composite oxygen reduction reaction (ORR) catalysts integrated into anion exchange membrane fuel cells (AEMFCs). Perovskite oxides with a theoretical stoichiometry of Ca 0.9La 0.1Al 0.1Mn 0.9O 3-δ are synthesized by an aerogel method and calcined at various temperatures, resulting in a set of materials with varied surface chemistry and surface area. Material composition is evaluated by X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The perovskite oxide calcined at 800 degrees C shows the importance of balance between surface area, purity of the perovskite phase, and surfacemore » composition, resulting in the highest ORR mass activity when evaluated in rotating disk electrodes. Integration of this catalyst into AEMFCs reveals that the best AEMFC performance is obtained when using composites with 30:70 perovskite oxide:carbon composition. Doubling the loading leads to an increase in the power density from 30 to 76 mW cm -2. The AEMFC prepared with a composite based on perovskite oxide and N-carbon achieves a power density of 44 mW cm -2, demonstrating an ~50% increase when compared to the highest performing composite with undoped carbon at the same loading.« less

Evaluating the predictive power of multivariate tensor-based morphometry in Alzheimer's disease progression via convex fused sparse group Lasso

NASA Astrophysics Data System (ADS)

Tsao, Sinchai; Gajawelli, Niharika; Zhou, Jiayu; Shi, Jie; Ye, Jieping; Wang, Yalin; Lepore, Natasha

2014-03-01

Prediction of Alzheimers disease (AD) progression based on baseline measures allows us to understand disease progression and has implications in decisions concerning treatment strategy. To this end we combine a predictive multi-task machine learning method1 with novel MR-based multivariate morphometric surface map of the hippocampus2 to predict future cognitive scores of patients. Previous work by Zhou et al.1 has shown that a multi-task learning framework that performs prediction of all future time points (or tasks) simultaneously can be used to encode both sparsity as well as temporal smoothness. They showed that this can be used in predicting cognitive outcomes of Alzheimers Disease Neuroimaging Initiative (ADNI) subjects based on FreeSurfer-based baseline MRI features, MMSE score demographic information and ApoE status. Whilst volumetric information may hold generalized information on brain status, we hypothesized that hippocampus specific information may be more useful in predictive modeling of AD. To this end, we applied Shi et al.2s recently developed multivariate tensor-based (mTBM) parametric surface analysis method to extract features from the hippocampal surface. We show that by combining the power of the multi-task framework with the sensitivity of mTBM features of the hippocampus surface, we are able to improve significantly improve predictive performance of ADAS cognitive scores 6, 12, 24, 36 and 48 months from baseline.

A miniaturized microbial fuel cell with three-dimensional graphene macroporous scaffold anode demonstrating a record power density of over 10,000 W m(-3) .

PubMed

Ren, Hao; Tian, He; Gardner, Cameron L; Ren, Tian-Ling; Chae, Junseok

2016-02-14

A microbial fuel cell (MFC) is a bio-inspired renewable energy converter which directly converts biomass into electricity. This is accomplished via the unique extracellular electron transfer (EET) of a specific species of microbe called the exoelectrogen. Many studies have attempted to improve the power density of MFCs, yet the reported power density is still nearly two orders of magnitude lower than other power sources/converters. Such a low performance can primarily be attributed to two bottlenecks: (i) ineffective electron transfer from microbes located far from the anode and (ii) an insufficient buffer supply to the biofilm. This work takes a novel approach to mitigate these two bottlenecks by integrating a three-dimensional (3D) macroporous graphene scaffold anode in a miniaturized MFC. This implementation has delivered the highest power density reported to date in all MFCs of over 10,000 W m(-3). The miniaturized configuration offers a high surface area to volume ratio and improved mass transfer of biomass and buffers. The 3D graphene macroporous scaffold warrants investigation due to its high specific surface area, high porosity, and excellent conductivity and biocompatibility which facilitates EET and alleviates acidification in the biofilm. Consequently, the 3D scaffold houses an extremely thick and dense biofilm from the Geobacter-enriched culture, delivering an areal/volumetric current density of 15.51 A m(-2)/31,040 A m(-3) and a power density of 5.61 W m(-2)/11,220 W m(-3), a 3.3 fold increase when compared to its planar two-dimensional (2D) control counterparts.

Surface Acoustic Wave Vibration Sensors for Measuring Aircraft Flutter

NASA Technical Reports Server (NTRS)

Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

2016-01-01

Under NASA's Advanced Air Vehicles Program the Advanced Air Transport Technology (AATT) Project is investigating flutter effects on aeroelastic wings. To support that work a new method for measuring vibrations due to flutter has been developed. The method employs low power Surface Acoustic Wave (SAW) sensors. To demonstrate the ability of the SAW sensor to detect flutter vibrations the sensors were attached to a Carbon fiber-reinforced polymer (CFRP) composite panel which was vibrated at six frequencies from 1Hz to 50Hz. The SAW data was compared to accelerometer data and was found to resemble sine waves and match each other closely. The SAW module design and results from the tests are presented here.

NUCLEAR REACTOR

DOEpatents

Grebe, J.J.

1959-12-15

A reactor which is particularly adapted tu serve as a heat source for a nuclear powered alrcraft or rocket is described. The core of this reactor consists of a porous refractory modera;or body which is impregnated with fissionable nuclei. The core is designed so that its surface forms tapered inlet and outlet ducts which are separated by the porous moderator body. In operation a gaseous working fluid is circulated through the inlet ducts to the surface of the moderator, enters and passes through the porous body, and is heated therein. The hot gas emerges into the outlet ducts and is available to provide thrust. The principle advantage is that tremendous quantities of gas can be quickly heated without suffering an excessive pressure drop.

High reduction of interfacial charge recombination in colloidal quantum dot solar cells by metal oxide surface passivation.

PubMed

Chang, Jin; Kuga, Yuki; Mora-Seró, Iván; Toyoda, Taro; Ogomi, Yuhei; Hayase, Shuzi; Bisquert, Juan; Shen, Qing

2015-03-12

Bulk heterojunction (BHJ) solar cells based on colloidal QDs and metal oxide nanowires (NWs) possess unique and outstanding advantages in enhancing light harvesting and charge collection in comparison to planar architectures. However, the high surface area of the NW structure often brings about a large amount of recombination (especially interfacial recombination) and limits the open-circuit voltage in BHJ solar cells. This problem is solved here by passivating the surface of the metal oxide component in PbS colloidal quantum dot solar cells (CQDSCs). By coating thin TiO2 layers onto ZnO-NW surfaces, the open-circuit voltage and power conversion efficiency have been improved by over 40% in PbS CQDSCs. Characterization by transient photovoltage decay and impedance spectroscopy indicated that the interfacial recombination was significantly reduced by the surface passivation strategy. An efficiency as high as 6.13% was achieved through the passivation approach and optimization for the length of the ZnO-NW arrays (device active area: 16 mm2). All solar cells were tested in air, and exhibited excellent air storage stability (without any performance decline over more than 130 days). This work highlights the significance of metal oxide passivation in achieving high performance BHJ solar cells. The charge recombination mechanism uncovered in this work could shed light on the further improvement of PbS CQDSCs and/or other types of solar cells.

Chemistry of fast electrons

PubMed Central

Maximoff, Sergey N.; Head-Gordon, Martin P.

2009-01-01

A chemicurrent is a flux of fast (kinetic energy ≳ 0.5−1.3 eV) metal electrons caused by moderately exothermic (1−3 eV) chemical reactions over high work function (4−6 eV) metal surfaces. In this report, the relation between chemicurrent and surface chemistry is elucidated with a combination of top-down phenomenology and bottom-up atomic-scale modeling. Examination of catalytic CO oxidation, an example which exhibits a chemicurrent, reveals 3 constituents of this relation: The localization of some conduction electrons to the surface via a reduction reaction, 0.5 O2 + δe− → Oδ− (Red); the delocalization of some surface electrons into a conduction band in an oxidation reaction, Oδ− + CO → CO2δ− → CO2 + δe− (Ox); and relaxation without charge transfer (Rel). Juxtaposition of Red, Ox, and Rel produces a daunting variety of metal electronic excitations, but only those that originate from CO2 reactive desorption are long-range and fast enough to dominate the chemicurrent. The chemicurrent yield depends on the universality class of the desorption process and the distribution of the desorption thresholds. This analysis implies a power-law relation with exponent 2.66 between the chemicurrent and the heat of adsorption, which is consistent with experimental findings for a range of systems. This picture also applies to other oxidation-reduction reactions over high work function metal surfaces. PMID:19561296

Introduction of low-temperature swirl technology of burning as a way of increase in ecological of low power boilers

NASA Astrophysics Data System (ADS)

Trinchenko, A. A.; Paramonov, A. P.

2017-10-01

Work is devoted to the solution of problems of energy efficiency increase in low power boilers at combustion of solid fuel. The technological method of nitrogen oxides decomposition on a surface of carbon particles with education environmentally friendly carbonic acid and molecular nitrogen is considered during the work of a low-temperature swirl fire chamber. Based on the analysis of physical and chemical processes of a fuel chemically connected energy transition into thermal, using the diffusive and kinetic theory of burning modern approaches the technique, mathematical model and the settlement program for assessment of plant ecological indicators when using a new method are developed. Alternative calculations of furnace process are carried out, quantitative assessment of nitrogen oxides emissions level of the reconstructed boiler is executed. The results of modeling and experimental data have approved that the organization of swirl burning increases overall performance of a fire chamber and considerably reduces emissions of nitrogen oxides.

Development of Ceramic Coating on Metal Substrate using Industrial Waste and Ore Minerals

NASA Astrophysics Data System (ADS)

Bhuyan, S. K.; Thiyagarajan, T. K.; Mishra, S. C.

2017-02-01

The technological advancement in modern era has a boon for enlightening human life; but also is a bane to produce a huge amount of (industrial) wastes, which is of great concern for utilization and not to create environmental threats viz. polution etc. In the present piece of research work, attempts have been made to utilize fly ash (wastes of thermal power plants) and along with alumina bearing ore i.e. bauxite, for developing plasma spray ceramic coatings on metals. Fly ash and with 10 and 20% bauxite addition is used to deposit plasma spray coatings on a metal substrate. The surface morphology of the coatings deposited at different power levels of plasma spraying investigated through SEM and EDS analysis. The coating thickness is measured. The porosity levels of the coatings are evaluated. The coating hardness isalso measured. This piece of research work will be beneficial for future development and use of industrial waste and ore minerals for high-valued applications.

Antenna coupled photonic wire lasers

DOE PAGES

Kao, Tsung-Kao; Cai, Xiaowei; Lee, Alan W. M.; ...

2015-06-22

Slope efficiency (SE) is an important performance metric for lasers. In conventional semiconductor lasers, SE can be optimized by careful designs of the facet (or the modulation for DFB lasers) dimension and surface. However, photonic wire lasers intrinsically suffer low SE due to their deep sub-wavelength emitting facets. Inspired by microwave engineering techniques, we show a novel method to extract power from wire lasers using monolithically integrated antennas. These integrated antennas significantly increase the effective radiation area, and consequently enhance the power extraction efficiency. When applied to wire lasers at THz frequency, we achieved the highest single-side slope efficiency (~450more » mW/A) in pulsed mode for DFB lasers at 4 THz and a ~4x increase in output power at 3 THz compared with a similar structure without antennas. This work demonstrates the versatility of incorporating microwave engineering techniques into laser designs, enabling significant performance enhancements.« less

Power spectral density analysis of the electromyogram from a work task performed in a full pressure suit. Ph.D. Thesis - Houston Univ.; [for determining muscular fatigue

NASA Technical Reports Server (NTRS)

Lafevers, E. V.

1974-01-01

Surface electromyograms (EMG) taken from three upper torso muscles during a push-pull task were analyzed by a power spectral density technique to determine the utility of the spectral analysis for identifying changes in the EMG caused by muscular fatigue. The results confirmed the value of the frequency analysis for identifying fatigue producing muscular performance. Data revealed reliable differences between muscles in fatigue induced responses to various locations in the reach envelope at which the subjects were required to perform the push-pull exercise, and the differential sensitivity of individual muscles to the various reach positions; i.e., certain reach positions imposed more fatigue related shifts in EMG power than did others. It was found that a pressurized space suit changed the pattern of normal shirtsleeve muscle fatigue responses in all three of the muscles.

New dynamic silicon photonic components enabled by MEMS technology

NASA Astrophysics Data System (ADS)

Errando-Herranz, Carlos; Edinger, Pierre; Colangelo, Marco; Björk, Joel; Ahmed, Samy; Stemme, Göran; Niklaus, Frank; Gylfason, Kristinn B.

2018-02-01

Silicon photonics is the study and application of integrated optical systems which use silicon as an optical medium, usually by confining light in optical waveguides etched into the surface of silicon-on-insulator (SOI) wafers. The term microelectromechanical systems (MEMS) refers to the technology of mechanics on the microscale actuated by electrostatic actuators. Due to the low power requirements of electrostatic actuation, MEMS components are very power efficient, making them well suited for dense integration and mobile operation. MEMS components are conventionally also implemented in silicon, and MEMS sensors such as accelerometers, gyros, and microphones are now standard in every smartphone. By combining these two successful technologies, new active photonic components with extremely low power consumption can be made. We discuss our recent experimental work on tunable filters, tunable fiber-to-chip couplers, and dynamic waveguide dispersion tuning, enabled by the marriage of silicon MEMS and silicon photonics.

30 CFR 57.12053 - Circuits powered from trolley wires.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Circuits powered from trolley wires. 57.12053... Electricity Surface and Underground § 57.12053 Circuits powered from trolley wires. Ground wires for lighting circuits powered from trolley wires shall be connected securely to the ground return circuit. Surface Only ...

30 CFR 57.12053 - Circuits powered from trolley wires.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Circuits powered from trolley wires. 57.12053... Electricity Surface and Underground § 57.12053 Circuits powered from trolley wires. Ground wires for lighting circuits powered from trolley wires shall be connected securely to the ground return circuit. Surface Only ...

KENNEDY SPACE CENTER, FLA. - In the high bay clean room at the Astrotech Space Operations processing facilities near KSC, workers prepare NASA’s MESSENGER spacecraft for transfer to a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - In the high bay clean room at the Astrotech Space Operations processing facilities near KSC, workers prepare NASA’s MESSENGER spacecraft for transfer to a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

How important is getting the land surface energy exchange correct in WRF for wind energy forecasting?

NASA Astrophysics Data System (ADS)

Wharton, S.; Simpson, M.; Osuna, J. L.; Newman, J. F.; Biraud, S.

2013-12-01

Wind power forecasting is plagued with difficulties in accurately predicting the occurrence and intensity of atmospheric conditions at the heights spanned by industrial-scale turbines (~ 40 to 200 m above ground level). Better simulation of the relevant physics would enable operational practices such as integration of large fractions of wind power into power grids, scheduling maintenance on wind energy facilities, and deciding design criteria based on complex loads for next-generation turbines and siting. Accurately simulating the surface energy processes in numerical models may be critically important for wind energy forecasting as energy exchange at the surface strongly drives atmospheric mixing (i.e., stability) in the lower layers of the planetary boundary layer (PBL), which in turn largely determines wind shear and turbulence at heights found in the turbine rotor-disk. We hypothesize that simulating accurate a surface-atmosphere energy coupling should lead to more accurate predictions of wind speed and turbulence at heights within the turbine rotor-disk. Here, we tested 10 different land surface model configurations in the Weather Research and Forecasting (WRF) model including Noah, Noah-MP, SSiB, Pleim-Xiu, RUC, and others to evaluate (1) the accuracy of simulated surface energy fluxes to flux tower measurements, (2) the accuracy of forecasted wind speeds to observations at rotor-disk heights, and (3) the sensitivity of forecasting hub-height rotor disk wind speed to the choice of land surface model. WRF was run for four, two-week periods covering both summer and winter periods over the Southern Great Plains ARM site in Oklahoma. Continuous measurements of surface energy fluxes and lidar-based wind speed, direction and turbulence were also available. The SGP ARM site provided an ideal location for this evaluation as it centrally located in the wind-rich Great Plains and multi-MW wind farms are rapidly expanding in the area. We found significant differences in simulated wind speeds at rotor-disk heights from WRF which indicated, in part, the sensitivity of lower PBL winds to surface energy exchange. We also found significant differences in energy partitioning between sensible heat and latent energy depending on choice of land surface model. Overall, the most consistent, accurate model results were produced using Noah-MP. Noah-MP was most accurate at simulating energy fluxes and wind shear. Hub-height wind speed, however, was predicted with most accuracy with Pleim-Xiu. This suggests that simulating wind shear in the surface layer is consistent with accurately simulating surface energy exchange while the exact magnitudes of wind speed may be more strongly influenced by the PBL dynamics. As the nation is working towards a 20% wind energy goal by 2030, increasing the accuracy of wind forecasting at rotor-disk heights becomes more important considering that utilities require wind farms to estimate their power generation 24 to 36 hours ahead and face penalties for inaccuracies in those forecasts.

Effects of decontamination work on riverine radiocaesium activity concentrations in Fukushima affected area

NASA Astrophysics Data System (ADS)

Taniguchi, K.; Onda, Y.; Yoshimura, K.; Smith, H.; Brake, W.; Kubo, T.; Kuramoto, T.; Sato, T.; Onuma, S.

2016-12-01

Radionuclides such as Cs-134 and Cs-137 were widely distributed in the area affected by the accident at Fukushima Daiichi nuclear power plant. The radionuclides were deposited on the surface, absorbed by soil particles, and transported via river systems to Pacific Ocean due to rainfall events. In order to reduce air dose rate surrounding residential area, decontamination works have been conducted between 2013 and 2016 Fiscal Years. In paddy field and farmland contaminated by the fallout, 5 cm of surface soil was stripped, and then clean sands put on the surface. This work could reduce radiocaesium inventory, while the coverage of vegetation was significantly decreased. Therefore, runoff characteristics in the decontaminated area were different before and after the decontamination. Activity concentrations of particulate Cs-137 were measured in Abukuma river system and 8 small catchments located in coastal zone of Fukushima affected area. In all monitoring sites, Cs-137 concentrations have decreased over an entire monitoring period. Kuchibuto river, which is a tributary of Abukuma river showed significant effect of decontamination. In Yamakiya district, in the watershed of the tributary, the decontamination work had conducted from 2013 FY to December 2015. Particulate Cs-137 concentration at two monitoring sites located in the district showed around 30% of decline in the beginning of 2014 FY whereas the decline was not so significant at sites in lower reach of the tributary. Decontaminated paddy field and farmland can be judged as the important source of suspended sediments in the tributary.

Blockage effects on the hydrodynamic performance of a marine cross-flow turbine.

PubMed

Consul, Claudio A; Willden, Richard H J; McIntosh, Simon C

2013-02-28

This paper explores the influence of blockage and free-surface deformation on the hydrodynamic performance of a generic marine cross-flow turbine. Flows through a three-bladed turbine with solidity 0.125 are simulated at field-test blade Reynolds numbers, O(10(5)-10(6)), for three different cross-stream blockages: 12.5, 25 and 50 per cent. Two representations of the free-surface boundary are considered: rigid lid and deformable free surface. Increasing the blockage is observed to lead to substantial increases in the power coefficient; the highest power coefficient computed is 1.23. Only small differences are observed between the two free-surface representations, with the deforming free-surface turbine out-performing the rigid lid turbine by 6.7 per cent in power at the highest blockage considered. This difference is attributed to the increase in effective blockage owing to the deformation of the free surface. Hydrodynamic efficiency, the ratio of useful power generated to overall power removed from the flow, is found to increase with blockage, which is consistent with the presence of a higher flow velocity through the core of the turbine at higher blockage ratios. Froude number is found to have little effect on thrust and power coefficients, but significant influence on surface elevation drop across the turbine.

Functional Carbon Materials for Electrochemical Energy Storage

NASA Astrophysics Data System (ADS)

Zhou, Huihui

The ability to harvest and convert solar energy has been associated with the evolution of human civilization. The increasing consumption of fossil fuels since the industrial revolution, however, has brought to concerns in ecological deterioration and depletion of the fossil fuels. Facing these challenges, humankind is forced to seek for clean, sustainable and renewable energy resources, such as biofuels, hydraulic power, wind power, geothermal energy and other kinds of alternative energies. However, most alternative energy sources, generally in the form of electrical energy, could not be made available on a continuous basis. It is, therefore, essential to store such energy into chemical energy, which are portable and various applications. In this context, electrochemical energy-storage devices hold great promises towards this goal. The most common electrochemical energy-storage devices are electrochemical capacitors (ECs, also called supercapacitors) and batteries. In comparison to batteries, ECs posses high power density, high efficiency, long cycling life and low cost. ECs commonly utilize carbon as both (symmetric) or one of the electrodes (asymmetric), of which their performance is generally limited by the capacitance of the carbon electrodes. Therefore, developing better carbon materials with high energy density has been emerging as one the most essential challenges in the field. The primary objective of this dissertation is to design and synthesize functional carbon materials with high energy density at both aqueous and organic electrolyte systems. The energy density (E) of ECs are governed by E = CV 2/2, where C is the total capacitance and V is the voltage of the devices. Carbon electrodes with high capacitance and high working voltage should lead to high energy density. In the first part of this thesis, a new class of nanoporous carbons were synthesized for symmetric supercapacitors using aqueous Li2SO4 as the electrolyte. A unique precursor was adopted to create uniformly distributed nanopores with large surface area, leading to high-performance electrodes with high capacitance, excellent rate performance and stable cycling, even under a high working voltage of 1.6V. The second part of this dissertation work further improved the capacitance of the carbon electrodes by fluorine doping. This doping process enhances the affinity of the carbon surface with organic electrolytes, leading to further improved capacitance and energy density. In the third part, carbon materials were synthesized with high surface area, capacitance and working voltage of 4V in organic electrolyte, leading to the construction of prototyped devices with energy density comparable to those of the current lead-acid batteries. Besides the abovementioned research, hierarchical graphitic carbons were also explored for lithium ion batteries and supercapacitors. Overall, through rational design of carbons with optimized pore configuration and surface chemistry, carbon electrodes with improved energy density and rate performance were improved significantly. Collectively, this thesis work systematically unveils simple yet effective strategies to achieve high performance carbon-based supercapacitors with high power density and high energy density, including the following aspects: 1) Constructed electrodes with high capacitance through building favorable ion/electron transportation pathways, tuning pore structure and pore size. 2) Improved the capacitance through enhancing the affinity between the carbon electrodes and electrolytes by doping the carbons with heteroatoms. 3) Explored and understand the roles of heteroatom doping in the capacitive behavior by both experimental measurement and computational modeling. 4) Improved energy density of carbon electrodes by enlarging their working voltage in aqueous and organic electrolyte. 5) Scalable and effective production of hierarchically porous graphite particles through aerosol process for use as the anode materials of lithium ion batteries. These strategies can be extended as a general design platform for other high-performance energy storage materials such as fuel cells and lithium-ion batteries.

Heteroepitaxial growth of Pt and Au thin films on MgO single crystals by bias-assisted sputtering

DOE PAGES

Tolstova, Yulia; Omelchenko, Stefan T.; Shing, Amanda M.; ...

2016-03-17

The crystallographic orientation of a metal affects its surface energy and structure, and has profound implications for surface chemical reactions and interface engineering, which are important in areas ranging from optoelectronic device fabrication to catalysis. However, it can be very difficult and expensive to manufacture, orient, and cut single crystal metals along different crystallographic orientations, especially in the case of precious metals. One approach is to grow thin metal films epitaxially on dielectric substrates. In this work, we report on growth of Pt and Au films on MgO single crystal substrates of (100) and (110) surface orientation for use asmore » epitaxial templates for thin film photovoltaic devices. We develop bias-assisted sputtering for deposition of oriented Pt and Au films with sub-nanometer roughness. We show that biasing the substrate decreases the substrate temperature necessary to achieve epitaxial orientation, with temperature reduction from 600 to 350 °C for Au, and from 750 to 550 °C for Pt, without use of transition metal seed layers. Additionally, this temperature can be further reduced by reducing the growth rate. Biased deposition with varying substrate bias power and working pressure also enables control of the film morphology and surface roughness.« less

In Situ Investigation of Electrochemically Mediated Surface-Initiated Atom Transfer Radical Polymerization by Electrochemical Surface Plasmon Resonance.

PubMed

Chen, Daqun; Hu, Weihua

2017-04-18

Electrochemically mediated atom transfer radical polymerization (eATRP) initiates/controls the controlled/living ATRP chain propagation process by electrochemically generating (regenerating) the activator (lower-oxidation-state metal complex) from deactivator (higher-oxidation-state metal complex). Despite successful demonstrations in both of the homogeneous polymerization and heterogeneous systems (namely, surface-initiated ATRP, SI-ATRP), the eATRP process itself has never been in situ investigated, and important information regarding this process remains unrevealed. In this work, we report the first investigation of the electrochemically mediated SI-ATRP (eSI-ATRP) by rationally combining the electrochemical technique with real-time surface plasmon resonance (SPR). In the experiment, the potential of a SPR gold chip modified by the self-assembled monolayer of the ATRP initiator was controlled to electrochemically reduce the deactivator to activator to initiate the SI-ATRP, and the whole process was simultaneously monitored by SPR with a high time resolution of 0.1 s. It is found that it is feasible to electrochemically trigger/control the SI-ATRP and the polymerization rate is correlated to the potential applied to the gold chip. This work reveals important kinetic information for eSI-ATRP and offers a powerful platform for in situ investigation of such complicated processes.

Surface-enhanced Raman spectroscopy applied to food safety.

PubMed

Craig, Ana Paula; Franca, Adriana S; Irudayaraj, Joseph

2013-01-01

Surface-enhanced Raman spectroscopy (SERS) is an advanced Raman technique that enhances the vibrational spectrum of molecules adsorbed on or in the vicinity of metal particles and/or surfaces. Because of its readiness, sensitivity, and minimum sample preparation requirements, SERS is being considered as a powerful technique for food inspection. Key aspects of food-safety assurance, spectroscopy methods, and SERS are briefly discussed in an extended introduction of this review. The recent and potential advances in SERS are highlighted in sections that deal with the (a) detection of food-borne pathogenic microorganisms and (b) the detection of food contaminants and adulteration, concentrated specifically on antibiotics, drugs, hormones, melamine, and pesticides. This review provides an outlook of the work done and a perspective on the future directions of SERS as a reliable tool for food-safety assessment.

Hydrophilic/hydrophobic surface modification impact on colloid lithography: Schottky-like defects, dislocation, and ideal distribution

NASA Astrophysics Data System (ADS)

Burtsev, Vasilii; Marchuk, Valentina; Kugaevskiy, Artem; Guselnikova, Olga; Elashnikov, Roman; Miliutina, Elena; Postnikov, Pavel; Svorcik, Vaclav; Lyutakov, Oleksiy

2018-03-01

Nano-spheres lithography is actually considered as a powerful tool to manufacture various periodic structures with a wide potential in the field of nano- and micro-fabrication. However, during self-assembling of colloid microspheres, various defects and mismatches can appear. In this work the size and quality of single-domains of closed-packed polystyrene (PS), grown up on thin Au layers modified by hydrophilic or hydrophobic functional groups via diazonium chemistry was studied. The effects of the surface modification on the quality and single-domain size of polystyrene (PS) microspheres array were investigated and discussed. Modified surfaces were characterized using the AFM and wettability tests. PS colloidal suspension was deposited using the drop evaporation method. Resulted PS microspheres array was characterized using the SEM, AFM and confocal microscopy technique.

Investigation of the thermal and optical performance of a spatial light modulator with high average power picosecond laser exposure for materials processing applications

NASA Astrophysics Data System (ADS)

Zhu, G.; Whitehead, D.; Perrie, W.; Allegre, O. J.; Olle, V.; Li, Q.; Tang, Y.; Dawson, K.; Jin, Y.; Edwardson, S. P.; Li, L.; Dearden, G.

2018-03-01

Spatial light modulators (SLMs) addressed with computer generated holograms (CGHs) can create structured light fields on demand when an incident laser beam is diffracted by a phase CGH. The power handling limitations of these devices based on a liquid crystal layer has always been of some concern. With careful engineering of chip thermal management, we report the detailed optical phase and temperature response of a liquid cooled SLM exposed to picosecond laser powers up to 〈P〉  =  220 W at 1064 nm. This information is critical for determining device performance at high laser powers. SLM chip temperature rose linearly with incident laser exposure, increasing by only 5 °C at 〈P〉  =  220 W incident power, measured with a thermal imaging camera. Thermal response time with continuous exposure was 1-2 s. The optical phase response with incident power approaches 2π radians with average power up to 〈P〉  =  130 W, hence the operational limit, while above this power, liquid crystal thickness variations limit phase response to just over π radians. Modelling of the thermal and phase response with exposure is also presented, supporting experimental observations well. These remarkable performance characteristics show that liquid crystal based SLM technology is highly robust when efficiently cooled. High speed, multi-beam plasmonic surface micro-structuring at a rate R  =  8 cm2 s-1 is achieved on polished metal surfaces at 〈P〉  =  25 W exposure while diffractive, multi-beam surface ablation with average power 〈P〉  =100 W on stainless steel is demonstrated with ablation rate of ~4 mm3 min-1. However, above 130 W, first order diffraction efficiency drops significantly in accord with the observed operational limit. Continuous exposure for a period of 45 min at a laser power of 〈P〉  =  160 W did not result in any detectable drop in diffraction efficiency, confirmed afterwards by the efficient parallel beam processing at 〈P〉  =  100 W. Hence, no permanent changes in SLM phase response characteristics have been detected. This research work will help to accelerate the use of liquid crystal spatial light modulators for both scientific and ultra high throughput laser-materials micro-structuring applications.

Nonlinear Slewing Spacecraft Control Based on Exergy, Power Flow, and Static and Dynamic Stability

NASA Astrophysics Data System (ADS)

Robinett, Rush D.; Wilson, David G.

2009-10-01

This paper presents a new nonlinear control methodology for slewing spacecraft, which provides both necessary and sufficient conditions for stability by identifying the stability boundaries, rigid body modes, and limit cycles. Conservative Hamiltonian system concepts, which are equivalent to static stability of airplanes, are used to find and deal with the static stability boundaries: rigid body modes. The application of exergy and entropy thermodynamic concepts to the work-rate principle provides a natural partitioning through the second law of thermodynamics of power flows into exergy generator, dissipator, and storage for Hamiltonian systems that is employed to find the dynamic stability boundaries: limit cycles. This partitioning process enables the control system designer to directly evaluate and enhance the stability and performance of the system by balancing the power flowing into versus the power dissipated within the system subject to the Hamiltonian surface (power storage). Relationships are developed between exergy, power flow, static and dynamic stability, and Lyapunov analysis. The methodology is demonstrated with two illustrative examples: (1) a nonlinear oscillator with sinusoidal damping and (2) a multi-input-multi-output three-axis slewing spacecraft that employs proportional-integral-derivative tracking control with numerical simulation results.

Insights into the Streaming Instability in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Youdin, Andrew N.; Lin, Min-Kai; Li, Rixin

2017-10-01

The streaming instability is a leading mechanism to concentrate particles in protoplanetary disks, thereby triggering planetesimal formation. I will present recent analytical and numerical work on the origin of the streaming instability and its robustness. Our recent analytic work examines the origin of, and relationship between, a variety of drag-induced instabilities, including the streaming instability as well as secular gravitational instabilities, a drag instability driven by self-gravity. We show that drag instabilities are powered by a specific phase relationship between gas pressure and particle concentrations, which power the instability via pressure work. This mechanism is analogous to pulsating instabilities in stars. This mechanism differs qualitatively from other leading particle concentration mechanisms in pressure bumps and vortices. Our recent numerical work investigates the numerical robustness of non-linear particle clumping by the streaming instability, especially with regard to the location and boundary condition of vertical boundaries. We find that particle clumping is robust to these choices in boxes that are not too short. However, hydrodynamic activity away from the particle-dominated midplane is significantly affected by vertical boundary conditions. This activity affects the observationally significant lofting of small dust grains. We thus emphasize the need for larger scale simulations which connect disk surface layers, including outflowing winds, to the planet-forming midplane.

Surface and Bulk Characteristics of Cesium Iodide (CsI) coated Carbon (C) Fibers for High Power Microwave (HPM) Field Emission Cathodes

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Morgan, Dane; Booske, John H.; Shiffler, Don

2008-11-01

CsI coated C fibers [1] are promising field emission cathodes for HPM applications. Ab initio computational modeling has shown that atomically-thin CsI coatings reduce the work function of C substrates by a surface dipole mechanism [2]. Characterization measurements of the composition and morphology of the CsI-coated C fibers are underway for determining the properties and characteristics of the following important regions of the fiber: (i) the surface on the tip of the fiber where the majority of electron emission is believed to occur, (ii) the surface covering the body of the fiber and its role on the emission properties of the system, and (iii) the interior volume of the fiber and its effects on the CsI surface re-supply process and rate. The results will be interpreted in terms of surface electronic properties and theoretical electron emission models. [1]D. Shiffler, et al., Phys. Plasmas 11 (2004) 1680. [2]V.Vlahos et al., Appl. Phys. Lett. 91 (2007) 144102.

Single and multiple streamer DBD micro-discharges for testing inactivation of biologically contaminated surfaces

NASA Astrophysics Data System (ADS)

Prukner, Vaclav; Dolezalova, Eva; Simek, Milan

2014-10-01

Highly reactive environment produced by atmospheric-pressure, non-equilibrium plasmas generated by surface dielectric barrier discharges (SDBDs) may be used for inactivation of biologically contaminated surfaces. We investigated decontamination efficiency of reactive environment produced by single/multiple surface streamer micro-discharge driven by amplitude-modulated AC power in coplanar electrode geometry on biologically contaminated surface by Escherichia coli. The discharges were fed by synthetic air with water vapor admixtures at atmospheric pressure, time of treatment was set from 10 second to 10 minutes, diameters of used SDBD electrodes (single and multiple streamer) and homogeneously contaminated disc samples were equal (25 mm), the distance between the electrode and contaminated surface was 2 mm. Both a conventional cultivation and fluorescent method LIVE/DEAD Bacterial Viability kit were applied to estimate counts of bacteria after the plasma treatment. Inactivation was effective and bacteria partly lost ability to grow and became injured and viable/active but non-cultivable (VBNC/ABNC). Work was supported by the MEYS under Project LD13010, VES13 COST CZ (COST Action MP 1101).

Investigating biomolecular recognition at the cell surface using atomic force microscopy.

PubMed

Wang, Congzhou; Yadavalli, Vamsi K

2014-05-01

Probing the interaction forces that drive biomolecular recognition on cell surfaces is essential for understanding diverse biological processes. Force spectroscopy has been a widely used dynamic analytical technique, allowing measurement of such interactions at the molecular and cellular level. The capabilities of working under near physiological environments, combined with excellent force and lateral resolution make atomic force microscopy (AFM)-based force spectroscopy a powerful approach to measure biomolecular interaction forces not only on non-biological substrates, but also on soft, dynamic cell surfaces. Over the last few years, AFM-based force spectroscopy has provided biophysical insight into how biomolecules on cell surfaces interact with each other and induce relevant biological processes. In this review, we focus on describing the technique of force spectroscopy using the AFM, specifically in the context of probing cell surfaces. We summarize recent progress in understanding the recognition and interactions between macromolecules that may be found at cell surfaces from a force spectroscopy perspective. We further discuss the challenges and future prospects of the application of this versatile technique. Copyright © 2014 Elsevier Ltd. All rights reserved.

Recurrent filmwise and dropwise condensation on a beetle mimetic surface.

PubMed

Hou, Youmin; Yu, Miao; Chen, Xuemei; Wang, Zuankai; Yao, Shuhuai

2015-01-27

Vapor condensation plays a key role in a wide range of industrial applications including power generation, thermal management, water harvesting and desalination. Fast droplet nucleation and efficient droplet departure as well as low interfacial thermal resistance are important factors that determine the thermal performances of condensation; however, these properties have conflicting requirements on the structural roughness and surface chemistry of the condensing surface or condensation modes (e.g., filmwise vs dropwise). Despite intensive efforts over the past few decades, almost all studies have focused on the dropwise condensation enabled by superhydrophobic surfaces. In this work, we report the development of a bioinspired hybrid surface with high wetting contrast that allows for seamless integration of filmwise and dropwise condensation modes. We show that the synergistic cooperation in the observed recurrent condensation modes leads to improvements in all aspects of heat transfer properties including droplet nucleation density, growth rate, and self-removal, as well as overall heat transfer coefficient. Moreover, we propose an analytical model to optimize the surface morphological features for dramatic heat transfer enhancement.

Titanium Disulfide Coated Carbon Nanotube Hybrid Electrodes Enable High Energy Density Symmetric Pseudocapacitors.

PubMed

Zang, Xining; Shen, Caiwei; Kao, Emmeline; Warren, Roseanne; Zhang, Ruopeng; Teh, Kwok Siong; Zhong, Junwen; Wei, Minsong; Li, Buxuan; Chu, Yao; Sanghadasa, Mohan; Schwartzberg, Adam; Lin, Liwei

2018-02-01

While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS 2 ) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g -1 in an Li-rich electrolyte. A symmetric cell demonstrates an energy density of 60.9 Wh kg -1 -the highest among symmetric pseudocapacitors using metal oxides, conducting polymers, 2D transition metal carbides (MXene), and other transition metal dichalcogenides. Nanostructures prepared by an atomic layer deposition/sulfurization process facilitate ion transportation and surface reactions to result in a high power density of 1250 W kg -1 with stable operation over 10 000 cycles. A flexible solid-state supercapacitor prepared by transferring the TiS 2 -VACNT composite film onto Kapton tape is demonstrated to power a 2.2 V light emitting diode (LED) for 1 min. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhancing the performance of NaNbO3 triboelectric nanogenerators by dielectric modulation and electronegative modification

NASA Astrophysics Data System (ADS)

Lai, Meihui; Cheng, Lu; Xi, Yi; Wu, Yinghui; Hu, Chengguo; Guo, Hengyu; Du, Bolun; Liu, Guanlin; Liu, Qipeng; Liu, Ruchuan

2018-01-01

Increasing the triboelectric charge density on the friction layer of polydimethylsiloxane (PDMS) is a basic approach towards improving the output performance of a triboelectric nanogenerator (TENG). Most previous work focuses on the surface structure or dielectric properties, nonetheless, a few studies have focused on electronegative modification. NaNbO3-PDMS TENG (N-TENG) devices are fabricated by dispersing cubic NaNbO3, which is a lead-free piezoelectric material with molecular oxygen dangling bonds on the surface of the crystal, into the PDMS at different mass ratios. When the mass ratio is 7 wt%, the maximum output performance of the N-TENG is obtained. The open-circuit voltage is 550 V, the short-circuit current is 16 µA, and the effective power densities reach up to 5.5 W m-2 at a load resistance of ~100 MΩ. The N-TENG has been used to assemble self-powered electronic watches and illuminate commercial light-emitting diodes, respectively. Its fundamental mechanism has also been discussed in detail from the perspective of dielectric modulation and electronegative modification. This N-TENG technology is revealed to be a splendid candidate for application in large-scale device fabrication, flexible sensors and biological devices thanks to its easy fabrication process, low consumption, high output power density and biocompatibility.

Skin friction measurements of mathematically generated roughness in the transitionally- to fully-rough regimes

NASA Astrophysics Data System (ADS)

Barros, Julio; Schultz, Michael; Flack, Karen

2016-11-01

Engineering systems are affected by surface roughness which cause an increase in drag leading to significant performance penalties. One important question is how to predict frictional drag purely based upon surface topography. Although significant progress has been made in recent years, this has proven to be challenging. The present work takes a systematic approach by generating surface roughness in which surfaces parameters, such as rms , skewness, can be controlled. Surfaces were produced using the random Fourier modes method with enforced power-law spectral slopes. The surfaces were manufactured using high resolution 3D-printing. In this study three surfaces with constant amplitude and varying slope, P, were investigated (P = - 0 . 5 , - 1 . 0 , - 1 . 5). Skin-friction measurements were conducted in a high Reynolds number turbulent channel flow facility, covering a wide range of Reynolds numbers, from hydraulic-smooth to fully-rough regimes. Results show that some long wavelength roughness scales do not contribute significantly to the frictional drag, thus highlighting the need for filtering in the calculation of surface statistics. Upon high-pass filtering, it was found that krms is highly correlated with the measured ks.

Hyperspectral imaging with deformable gratings fabricated with metal-elastomer nanocomposites

NASA Astrophysics Data System (ADS)

Potenza, Marco A. C.; Nazzari, Daniele; Cremonesi, Llorenç; Denti, Ilaria; Milani, Paolo

2017-11-01

We report the fabrication and characterization of a simple and compact hyperspectral imaging setup based on a stretchable diffraction grating made with a metal-polymer nanocomposite. The nanocomposite is produced by implanting Ag clusters in a poly(dimethylsiloxane) film by supersonic cluster beam implantation. The deformable grating has curved grooves and is imposed on a concave cylindrical surface, thus obtaining optical power in two orthogonal directions. Both diffractive and optical powers are obtained by reflection, thus realizing a diffractive-catoptric optical device. This makes it easier to minimize aberrations. We prove that, despite the extended spectral range and the simplified optical scheme, it is actually possible to work with a traditional CCD sensor and achieve a good spectral and spatial resolution.

Inductively-Coupled RF Powered O2 Plasma as a Sterilization Source

NASA Technical Reports Server (NTRS)

Sharma, S. P.; Rao, M. V. V. S.; Cruden, B. A.; Meyyappan, M.; Mogul, R.; Khare, B.; Chan, S. L.; Arnold, James O. (Technical Monitor)

2001-01-01

Low-temperature or cold plasmas have been shown to be effective for the sterilization of sensitive medical devices and electronic equipment. Low-temperature plasma sterilization procedures possess certain advantages over other protocols such as ethylene oxide, gamma radiation, and heat due to the use of inexpensive reagents, the insignificant environmental impacts and the low energy requirements. In addition, plasmas may also be more efficacious in the removal of robust microorganisms due to their higher chemical reactivity. Together, these attributes render cold plasma sterilization as ideal for the surface decontamination requirements for NASA Planetary Protection. Hence, the work described in this study involves the construction, characterization, and application of an inductively-coupled, RF powered oxygen (O2) plasma.

Seven Enigmas: The Universe Within and Without

NASA Astrophysics Data System (ADS)

Cogswell, J.

2013-04-01

Seven Enigmas was a multi-media collaborative performance work celebrating the capacity of the human spirit to imaginatively explore the universe outside and within. It was co-created by dancer and choreographer Peter Sparling and the author, a visual artist. Inspired by the spatial movement and gestural power of seven dance miniatures choreographed by Sparling, I mapped out a multimedia sculptural installation for our stage production: objects and surfaces in motion with human bodies, along with film and video projections. The piece was realized through the joint efforts of a team of artists, scientists, dancers, and musicians, and performed at the Power Center for the Performing Arts in Ann Arbor in July and again in September 1997 by the Peter Sparling Dance Company.

PSAW/MicroSWIS [Microminiature Surface Acoustic Wave (SAW) based Wirelesss Instrumentation System

NASA Technical Reports Server (NTRS)

Heermann, Doug; Krug, Eric

2004-01-01

This Final Report for the PSAW/MicroSWIS Program is provided in compliance with contract number NAS3-01118. This report documents the overall progress of the program and presents project objectives, work carried out, and results obtained. Program Conceptual Design Package stated the following objectives: To develop a sensor/transceiver network that can support networking operations within spacecraft with sufficient bandwidth so that (1) flight control data, (2) avionics data, (3) payload/experiment data, and (4) prognostic health monitoring sensory information can flow to appropriate locations at frequencies that contain the maximum amount of information content but require minimum interconnect and power: a very high speed, low power, programmable modulation, spread-spectrum radio sensor/transceiver.

Crouch gait can be an effective form of forced-use/no constraint exercise for the paretic lower limb in stroke

PubMed Central

Rota, Viviana; Malloggi, Chiara; Brugliera, Luigia; Catino, Luigi

2017-01-01

In hemiplegic gait the paretic lower limb provides less muscle power and shows a briefer stance compared with the unaffected limb. Yet, a longer stance and a higher power can be obtained from the paretic lower limb if gait speed is increased. This supports the existence of a ‘learned non-use’ phenomenon, similar to that underlying some asymmetric impairments of the motion of the eyes and of the upper limbs. Crouch gait (CG) (bent-hip bent-knee, about 30° minimum knee flexion) might be an effective form of ‘forced-use’ treatment of the paretic lower limb. It is not known whether it also stimulates a more symmetric muscle power output. Gait analysis on a force treadmill was carried out in 12 healthy adults and seven hemiplegic patients (1–127 months after stroke, median: 1.6). Speed was imposed at 0.3 m/s. Step length and single and double stance times, sagittal joint rotations, peak positive power, and work in extension of the hip, knee, and ankle (plantar flexion), and surface electromyography (sEMG) area from extensor muscles during the generation of power were measured on either side during both erect and crouch walking. Significance was set at P less than 0.05; corrections for multiplicity were applied. Patients, compared with healthy controls, adopted in both gait modalities and on both sides a shorter step length (61–84%) as well as a shorter stance (76–90%) and swing (63–83%) time. As a rule, they also provided a higher muscular work (median: 137%, range: 77–250%) paralleled by a greater sEMG area (median: 174%, range: 75–185%). In erect gait, the generation of peak extensor power across hip, knee, and ankle joints was in general lower (83–90%) from the paretic limb and higher (98–165%) from the unaffected limb compared with control values. In CG, peak power generation across the three lower limb joints was invariably higher in hemiparetic patients: 107–177% from the paretic limb and 114–231% from the unaffected limb. When gait shifted from erect to crouch, only for hemiplegic patients, at the hip, the paretic/unaffected ratio increased significantly. For peak power, work, sEMG area, and joint rotation, the paretic/unaffected ratio increased from 55 to 85%, 56 to 72%, 68 to 91%, and 67 to 93%, respectively. CG appears to be an effective form of forced-use exercise eliciting more power and work from the paretic lower limb muscles sustained by a greater neural drive. It also seems effective in forcing a more symmetric power and work from the hip extensor muscles, but neither from the knee nor the ankle. PMID:28574860

Understanding the role of Si doping on surface charge and optical properties: Photoluminescence study of intrinsic and Si-doped InN nanowires

NASA Astrophysics Data System (ADS)

Zhao, S.; Mi, Z.; Kibria, M. G.; Li, Q.; Wang, G. T.

2012-06-01

In the present work, the photoluminescence (PL) characteristics of intrinsic and Si-doped InN nanowires are studied in detail. For intrinsic InN nanowires, the emission is due to band-to-band carrier recombination with the peak energy at ˜0.64 eV (at 300 K) and may involve free-exciton emission at low temperatures. The PL spectra exhibit a strong dependence on optical excitation power and temperature, which can be well characterized by the presence of very low residual electron density and the absence or a negligible level of surface electron accumulation. In comparison, the emission of Si-doped InN nanowires is characterized by the presence of two distinct peaks located at ˜0.65 and ˜0.73-0.75 eV (at 300 K). Detailed studies further suggest that these low-energy and high-energy peaks can be ascribed to band-to-band carrier recombination in the relatively low-doped nanowire bulk region and Mahan exciton emission in the high-doped nanowire near-surface region, respectively; this is a natural consequence of dopant surface segregation. The resulting surface electron accumulation and Fermi-level pinning, due to the enhanced surface doping, are confirmed by angle-resolved x-ray photoelectron spectroscopy measurements on Si-doped InN nanowires, which is in direct contrast to the absence or a negligible level of surface electron accumulation in intrinsic InN nanowires. This work elucidates the role of charge-carrier concentration and distribution on the optical properties of InN nanowires.

Mechanisms of anode power deposition in a low pressure free burning arc

NASA Technical Reports Server (NTRS)

Soulas, George C.; Myers, Roger M.

1994-01-01

Anode power deposition is a dominant power loss mechanism for arc jets and MPD thrusters. In this study, a free burning arc experiment was operated at pressures and current densities similar to those in arc jets and MPD thrusters in an attempt to identify the physics controlling this loss mechanism. Use of a free burning arc allowed for the isolation of independent variables controlling anode power deposition and provided a convenient and flexible way to cover a broad range of currents, anode surface pressures, and applied magnetic field strengths and orientations using an argon gas. Test results showed that anode power deposition decreased with increasing anode surface pressure up to 6.7 Pa (0.05 torr) and then became insensitive to pressure. Anode power increased with increasing arc current while the electron number density near the anode surface increased linearity. Anode power also increased with increasing applied magnetic field strength due to an increasing anode fall voltage. Applied magnetic field orientation had an effect only at high currents and low anode surface pressures, where anode power decreased when applied field lines intercepted the anode surface. The results demonstrated that anode power deposition was dominated by the current carrying electrons and that the anode fall voltage was the largest contributor. Furthermore, the results showed that anode power deposition can be reduced by operating at increased anode pressures, reduced arc currents, and applied magnetic field strengths and with magnetic field lines intercepting the anode.

Characteristics of ITO films with oxygen plasma treatment for thin film solar cell applications

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

Park, Yong Seob; Kim, Eungkwon; Hong, Byungyou

2013-12-15

Graphical abstract: The effect of O{sub 2} plasma treatment on the surface and the work function of ITO films. - Highlights: • ITO films were prepared on the glass substrate by RF magnetron sputtering method. • Effects of O{sub 2} plasma treatment on the properties of ITO films were investigated. • The work function of ITO film was changed from 4.67 to 5.66 eV by plasma treatment. - Abstract: The influence of oxygen plasma treatment on the electro-optical and structural properties of indium-tin-oxide films deposited by radio frequency magnetron sputtering method were investigated. The films were exposed at different O{submore » 2} plasma powers and for various durations by using the plasma enhanced chemical vapor deposition (PECVD) system. The resistivity of the ITO films was almost constant, regardless of the plasma treatment conditions. Although the optical transmittance of ITO films was little changed by the plasma power, the prolonged treatment slightly increased the transmittance. The work function of ITO film was changed from 4.67 eV to 5.66 eV at the plasma treatment conditions of 300 W and 60 min.« less

Pulsed discharges produced by high-power surface waves

NASA Astrophysics Data System (ADS)

Böhle, A.; Ivanov, O.; Kolisko, A.; Kortshagen, U.; Schlüter, H.; Vikharev, A.

1996-02-01

The mechanisms of the ionization front advance in surface-wave-produced discharges are investigated using two experimental set-ups. The high-power surface waves are excited in a 3 cm wavelength band by a surfaguide and a novel type of launcher (an E-plane junction). The ionization front velocity of the surface wave is measured for a wide range of gas pressures, incident microwave power and initial pre-ionization. The experimental results are compared with theoretical ones based on three different models. The comparison between theory and experiment allows one to suggest a new interpretation of the ionization front's advance. The ionization front velocity is determined by a breakdown wave or an ionization wave in the electric field of a high-power surface wave in the zone near the ionization front.

Battery Power Management in Heavy-duty HEVs based on the Estimated Critical Surface Charge

DTIC Science & Technology

2011-03-01

health prospects without any penalty on fuel efficiency. Keywords: Lithium - ion battery ; power management; critical surface charge; Lithium-ion...fuel efficiency. 15. SUBJECT TERMS Lithium - ion battery ; power management; critical surface charge; Lithium-ion concentration; estimation; extended...Di Domenico, D., Fiengo, G., and Stefanopoulou, A. (2008) ’ Lithium - ion battery state of charge estimation with a kalman filter based on a

Carbon nanofibers grafted on activated carbon as an electrode in high-power supercapacitors.

PubMed

Gryglewicz, Grażyna; Śliwak, Agata; Béguin, François

2013-08-01

A hybrid electrode material for high-power supercapacitors was fabricated by grafting carbon nanofibers (CNFs) onto the surface of powdered activated carbon (AC) through catalytic chemical vapor deposition (CCVD). A uniform thin layer of disentangled CNFs with a herringbone structure was deposited on the carbon surface through the decomposition of propane at 450 °C over an AC-supported nickel catalyst. CNF coating was controlled by the reaction time and the nickel content. The superior CNF/AC composite displays excellent electrochemical performance in a 0.5 mol L(-1) solution of K2 SO4 due to its unique structure. At a high scan rate (100 mV s(-1) ) and current loading (20 A g(-1) ), the capacitance values were three- and fourfold higher than those for classical AC/carbon black composites. Owing to this feature, a high energy of 10 Wh kg(-1) was obtained over a wide power range in neutral medium at a voltage of 0.8 V. The significant enhancement of charge propagation is attributed to the presence of herringbone CNFs, which facilitate the diffusion of ions in the electrode and play the role of electronic bridges between AC particles. An in situ coating of AC with short CNFs (below 200 nm) is a very attractive method for producing the next generation of carbon composite materials with a high power performance in supercapacitors working in neutral medium. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Miller, A.J.

The author concludes that it is probable that unconventional weapons and their associated delivery systems will form a permanent part of future political and strategic calculations in the Middle East. Some possible consequences of this situation can be divided into three classes: intra-regional, inter-regional and extra-regional. There is no doubt that Israel, driven by the need for security,precipitated the proliferation of unconventional weapons and of surface-to-surface missiles in the Middle East. It will now be driven to secure itself from the new threat to its security posed by its regional opponents. The most significant extra-regional consequence of developments in themore » Middle East may be further complication of great power arms control negotiations. To the re-discovery by the United States and the Soviet Union of their obligations under the Non-Proliferation Treaty to reduce the level of their nuclear weapons must now be added the desire to reduce, if not entirely eliminate, their chemical weapons stockpiles in advance of a global ban. It is possible that lesser powers will learn from the evidence of the great powers behavior, although that contradicts much of what we know of the psychology of decision making in international politics. What is necessary, though not necessarily sufficient, is that the U.S. and the USSR as the two external powers with potentially the greatest leverage, work together toward the resolution of the underlying causes of conflict in a region marked by more than a generation of competition between them.« less

Wireless induction coils embedded in diamond for power transfer in medical implants.

PubMed

Sikder, Md Kabir Uddin; Fallon, James; Shivdasani, Mohit N; Ganesan, Kumaravelu; Seligman, Peter; Garrett, David J

2017-08-26

Wireless power and data transfer to medical implants is a research area where improvements in current state-of-the-art technologies are needed owing to the continuing efforts for miniaturization. At present, lithographical patterning of evaporated metals is widely used for miniature coil fabrication. This method produces coils that are limited to low micron or nanometer thicknesses leading to high impedance values and thus limiting their potential quality. In the present work we describe a novel technique, whereby trenches were milled into a diamond substrate and filled with silver active braze alloy, enabling the manufacture of small, high cross-section, low impedance microcoils capable of transferring up to 10 mW of power up to a distance of 6 mm. As a substitute for a metallic braze line used for hermetic sealing, a continuous metal loop when placed parallel and close to the coil surface reduced power transfer efficiency by 43%, but not significantly, when placed perpendicular to the microcoil surface. Encapsulation of the coil by growth of a further layer of diamond reduced the quality factor by an average of 38%, which can be largely avoided by prior oxygen plasma treatment. Furthermore, an accelerated ageing test after encapsulation showed that these coils are long lasting. Our results thus collectively highlight the feasibility of fabricating a high-cross section, biocompatible and long lasting miniaturized microcoil that could be used in either a neural recording or neuromuscular stimulation device.

Safe corrosion inhibitor for treating cooling water on heat power engineering plants

NASA Astrophysics Data System (ADS)

Nikolaeva, L. A.; Khasanova, D. I.; Mukhutdinova, E. R.; Safin, D. Kh.; Sharifullin, I. G.

2017-08-01

Heat power engineering (HPE) consumes significant volumes of water. There are, therefore, problems associated with corrosion, biological fouling, salt deposits, and sludge formation on functional surfaces of heat power equipment. One of the effective ways to solve these problems is the use of inhibitory protection. The development of new Russian import-substituting environmentally friendly inhibitors is very relevant. This work describes experimental results on the OPC-800 inhibitor (TU 2415-092-00206 457-2013), which was produced at Karpov Chemical Plant and designed to remove mineral deposits, scale, and biological fouling from the surfaces of water-rotation node systems on HPE objects. This reagent is successfully used as an effective corrosion inhibitor in the water recycling systems of Tatarstan petrochemical enterprises. To save fresh make-up water, the circulating system is operated in a no-blow mode, which is characterized by high evaporation and salt content coefficients. It was experimentally found that corrosion rate upon treatment of recycled water with the OPC-800 inhibitor is 0.08-0.10 mm/year. HPE mainly uses inhibitors based on oxyethylidene diphosphonic (OEDPA) and nitrilotrimethylphosphonic (NTMPA) acids. The comparative characteristic of inhibition efficiency for OPC-800 and OEDF-Zn-U2 is given. The results obtained indicate that OPC-800 can be used as an inhibitor for treatment of cooling water in HPE plants. In this case, it is necessary to take into account the features of water rotation of a thermal power plant.

Neural Anatomy of Primary Visual Cortex Limits Visual Working Memory.

PubMed

Bergmann, Johanna; Genç, Erhan; Kohler, Axel; Singer, Wolf; Pearson, Joel

2016-01-01

Despite the immense processing power of the human brain, working memory storage is severely limited, and the neuroanatomical basis of these limitations has remained elusive. Here, we show that the stable storage limits of visual working memory for over 9 s are bound by the precise gray matter volume of primary visual cortex (V1), defined by fMRI retinotopic mapping. Individuals with a bigger V1 tended to have greater visual working memory storage. This relationship was present independently for both surface size and thickness of V1 but absent in V2, V3 and for non-visual working memory measures. Additional whole-brain analyses confirmed the specificity of the relationship to V1. Our findings indicate that the size of primary visual cortex plays a critical role in limiting what we can hold in mind, acting like a gatekeeper in constraining the richness of working mental function. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

A highly shape-adaptive, stretchable design based on conductive liquid for energy harvesting and self-powered biomechanical monitoring

PubMed Central

Yi, Fang; Wang, Xiaofeng; Niu, Simiao; Li, Shengming; Yin, Yajiang; Dai, Keren; Zhang, Guangjie; Lin, Long; Wen, Zhen; Guo, Hengyu; Wang, Jie; Yeh, Min-Hsin; Zi, Yunlong; Liao, Qingliang; You, Zheng; Zhang, Yue; Wang, Zhong Lin

2016-01-01

The rapid growth of deformable and stretchable electronics calls for a deformable and stretchable power source. We report a scalable approach for energy harvesters and self-powered sensors that can be highly deformable and stretchable. With conductive liquid contained in a polymer cover, a shape-adaptive triboelectric nanogenerator (saTENG) unit can effectively harvest energy in various working modes. The saTENG can maintain its performance under a strain of as large as 300%. The saTENG is so flexible that it can be conformed to any three-dimensional and curvilinear surface. We demonstrate applications of the saTENG as a wearable power source and self-powered sensor to monitor biomechanical motion. A bracelet-like saTENG worn on the wrist can light up more than 80 light-emitting diodes. Owing to the highly scalable manufacturing process, the saTENG can be easily applied for large-area energy harvesting. In addition, the saTENG can be extended to extract energy from mechanical motion using flowing water as the electrode. This approach provides a new prospect for deformable and stretchable power sources, as well as self-powered sensors, and has potential applications in various areas such as robotics, biomechanics, physiology, kinesiology, and entertainment. PMID:27386560

High power diode lasers for solid-state laser pumps

NASA Technical Reports Server (NTRS)

Linden, Kurt J.; Mcdonnell, Patrick N.

1994-01-01

The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

A highly shape-adaptive, stretchable design based on conductive liquid for energy harvesting and self-powered biomechanical monitoring.

PubMed

Yi, Fang; Wang, Xiaofeng; Niu, Simiao; Li, Shengming; Yin, Yajiang; Dai, Keren; Zhang, Guangjie; Lin, Long; Wen, Zhen; Guo, Hengyu; Wang, Jie; Yeh, Min-Hsin; Zi, Yunlong; Liao, Qingliang; You, Zheng; Zhang, Yue; Wang, Zhong Lin

2016-06-01

The rapid growth of deformable and stretchable electronics calls for a deformable and stretchable power source. We report a scalable approach for energy harvesters and self-powered sensors that can be highly deformable and stretchable. With conductive liquid contained in a polymer cover, a shape-adaptive triboelectric nanogenerator (saTENG) unit can effectively harvest energy in various working modes. The saTENG can maintain its performance under a strain of as large as 300%. The saTENG is so flexible that it can be conformed to any three-dimensional and curvilinear surface. We demonstrate applications of the saTENG as a wearable power source and self-powered sensor to monitor biomechanical motion. A bracelet-like saTENG worn on the wrist can light up more than 80 light-emitting diodes. Owing to the highly scalable manufacturing process, the saTENG can be easily applied for large-area energy harvesting. In addition, the saTENG can be extended to extract energy from mechanical motion using flowing water as the electrode. This approach provides a new prospect for deformable and stretchable power sources, as well as self-powered sensors, and has potential applications in various areas such as robotics, biomechanics, physiology, kinesiology, and entertainment.

Yeast surface display of dehydrogenases in microbial fuel-cells.

PubMed

Gal, Idan; Schlesinger, Orr; Amir, Liron; Alfonta, Lital

2016-12-01

Two dehydrogenases, cellobiose dehydrogenase from Corynascus thermophilus and pyranose dehydrogenase from Agaricus meleagris, were displayed for the first time on the surface of Saccharomyces cerevisiae using the yeast surface display system. Surface displayed dehydrogenases were used in a microbial fuel cell and generated high power outputs. Surface displayed cellobiose dehydrogenase has demonstrated a midpoint potential of -28mV (vs. Ag/AgCl) at pH=6.5 and was used in a mediator-less anode compartment of a microbial fuel cell producing a power output of 3.3μWcm(-2) using lactose as fuel. Surface-displayed pyranose dehydrogenase was used in a microbial fuel cell and generated high power outputs using different substrates, the highest power output that was achieved was 3.9μWcm(-2) using d-xylose. These results demonstrate that surface displayed cellobiose dehydrogenase and pyranose dehydrogenase may successfully be used in microbial bioelectrochemical systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Proton exchange membrane and electrode surface areas as factors that affect power generation in microbial fuel cells.

PubMed

Oh, Sang-Eun; Logan, Bruce E

2006-03-01

Power generation in microbial fuel cells (MFCs) is a function of the surface areas of the proton exchange membrane (PEM) and the cathode relative to that of the anode. To demonstrate this, the sizes of the anode and cathode were varied in two-chambered MFCs having PEMs with three different surface areas (A (PEM)=3.5, 6.2, or 30.6 cm(2)). For a fixed anode and cathode surface area (A (An)=A (Cat)=22.5 cm(2)), the power density normalized to the anode surface area increased with the PEM size in the order 45 mW/m(2) (A (PEM)=3.5 cm(2)), 68 mW/m(2) (A (PEM)=6.2 cm(2)), and 190 mW/m(2) (A (PEM)=30.6 cm(2)). PEM surface area was shown to limit power output when the surface area of the PEM was smaller than that of the electrodes due to an increase in internal resistance. When the relative cross sections of the PEM, anode, and cathode were scaled according to 2A (Cat)=A(PEM)=2A (An), the maximum power densities of the three different MFCs, based on the surface area of the PEM (A (PEM)=3.5, 6.2, or 30.6 cm(2)), were the same (168+/-4.53 mW/m(2)). Increasing the ionic strength and using ferricyanide at the cathode also increased power output.

On the transfer of radiation at asteroidal surfaces in relation to their orbit deflection - II

NASA Astrophysics Data System (ADS)

Yabushita, Shin

1998-08-01

The efficiency of absorption of X-rays generated by a nuclear explosion at the surface of an asteroid, estimated earlier, is used to calculate the explosion yield needed to deflect the orbit of an asteroid. Following the work of Ahrens & Harris, it is shown that a recoil velocity of 1 cm s^-1 is required to deflect an asteroid from a collision course with the Earth, and the necessary yield of explosion energy is estimated. If it is assumed that the scaling law between the energy and the diameter of the resulting crater, obtained from experiments carried out on the Earth, remains valid on the asteroid surface, where gravity is much weaker, an explosion energy of 8 and 800 megaton (Mton) equivalent of TNT would be required for asteroids of diameter 1 and 10 km respectively. If, on the other hand, the crater diameter is proportional to a certain power of the gravity g, the power being determined from a dimension analysis, 130 kton and 12 Mton would be required to endow asteroids of diameters 1 and 10 km with the required velocity, respectively. The result indicates that in order to estimate the required explosion energy, a better understanding of cratering under gravity much weaker than on the Earth would be required.

On the Character of the Zeros of Polynomials Relevant to the Small Curvature Approximation in Asymptotic Diffraction Theory

NASA Technical Reports Server (NTRS)

Pogorzelski, Ronald J.

1995-01-01

In dealing with the problem of estimating the high frequency coupling between two antennas mounted on a non-metallic aircraft skin, one is faced with approximation of the spectral integrals representing the propagation of rays along the geodesics of the surface between the antennas. When the antennas are sufficiently separated, the integrals can be conveniently represented as a rapidly convergent residue series. On the other hand, when the antennas are in close proximity, the residue series fails to converge rapidly and a power series representation proves to be efficacious. [Paknys and Wang, IEEE Trans. AP-35(3), 1987, 293-298]. When the effective surface impedance is not small, an intermediate region of separation appears in which neither the residue series nor the power series is effective. Recently, an asymptotic formalism was presented [Pogorzelski, National Radio Science Meeting, Boulder, CO, January 1995] which extends the earlier work of Bremmer [IRE Trans. AP-6, 1958, 267-272] and Wait curvature approximation' to the case of general (non-azimuthal) ray directions on the surface of a cylinder (excluding only axial propagation). Based on the formulation of Pearson [Radio Sci. 21(4), 1986] this asymptotic formalism provided a means of approximating the spectral integrals in the intermediate region of separation.

Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

NASA Astrophysics Data System (ADS)

Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

2014-09-01

In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

Multichannel Discriminative Detection of Explosive Vapors with an Array of Nanofibrous Membranes Loaded with Quantum Dots.

PubMed

Wu, Zhaofeng; Duan, Haiming; Li, Zhijun; Guo, Jixi; Zhong, Furu; Cao, Yali; Jia, Dianzeng

2017-11-20

The multichannel fluorescent sensor array based on nanofibrous membranes loaded with ZnS quantum dots (QDs) was created and demonstrated for the discriminative detection of explosives. The synergistic effect of the high surface-to-volume ratio of QDs, the good permeability of nanofibrous membranes and the differential response introduced by surface ligands was played by constructing the sensing array using nanofibrous membranes loaded with ZnS QDs featuring several surface ligands. Interestingly, although the fluorescence quenching of the nanofibrous membranes is not linearly related to the exposure time, the fingerprint of each explosive at different times is very similar in shape, and the fingerprints of the three explosives show different shapes. Three saturated vapors of nitroaromatic explosives could be reliably detected and discriminated by the array at room temperature. This work is the first step toward devising a monitoring system for explosives in the field of public security and defense. It could, for example, be coupled with the technology of image recognition and large data analysis for a rapid diagnostic test of explosives. This work further highlights the power of differential, multichannel arrays for the rapid and discriminative detection of a wide range of chemicals.

Multichannel Discriminative Detection of Explosive Vapors with an Array of Nanofibrous Membranes Loaded with Quantum Dots

PubMed Central

Wu, Zhaofeng; Duan, Haiming; Li, Zhijun; Guo, Jixi; Zhong, Furu; Cao, Yali; Jia, Dianzeng

2017-01-01

The multichannel fluorescent sensor array based on nanofibrous membranes loaded with ZnS quantum dots (QDs) was created and demonstrated for the discriminative detection of explosives. The synergistic effect of the high surface-to-volume ratio of QDs, the good permeability of nanofibrous membranes and the differential response introduced by surface ligands was played by constructing the sensing array using nanofibrous membranes loaded with ZnS QDs featuring several surface ligands. Interestingly, although the fluorescence quenching of the nanofibrous membranes is not linearly related to the exposure time, the fingerprint of each explosive at different times is very similar in shape, and the fingerprints of the three explosives show different shapes. Three saturated vapors of nitroaromatic explosives could be reliably detected and discriminated by the array at room temperature. This work is the first step toward devising a monitoring system for explosives in the field of public security and defense. It could, for example, be coupled with the technology of image recognition and large data analysis for a rapid diagnostic test of explosives. This work further highlights the power of differential, multichannel arrays for the rapid and discriminative detection of a wide range of chemicals. PMID:29156627

Interfacial contact stiffness of fractal rough surfaces.

PubMed

Zhang, Dayi; Xia, Ying; Scarpa, Fabrizio; Hong, Jie; Ma, Yanhong

2017-10-09

In this work we describe a theoretical model that predicts the interfacial contact stiffness of fractal rough surfaces by considering the effects of elastic and plastic deformations of the fractal asperities. We also develop an original test rig that simulates dovetail joints for turbo machinery blades, which can fine tune the normal contact load existing between the contacting surfaces of the blade root. The interfacial contact stiffness is obtained through an inverse identification method in which finite element simulations are fitted to the experimental results. Excellent agreement is observed between the contact stiffness predicted by the theoretical model and by the analogous experimental results. We demonstrate that the contact stiffness is a power law function of the normal contact load with an exponent α within the whole range of fractal dimension D(1 < D < 2). We also show that for 1 < D < 1.5 the Pohrt-Popov behavior (α = 1/(3 - D)) is valid, however for 1.5 < D < 2, the exponent α is different and equal to 2(D - 1)/D. The diversity between the model developed in the work and the Pohrt-Popov one is explained in detail.

Terahertz and infrared Smith-Purcell radiation from Babinet metasurfaces: Loss and efficiency

NASA Astrophysics Data System (ADS)

Liu, Liu; Chang, Huiting; Zhang, Chi; Song, Yanan; Hu, Xinhua

2017-10-01

When a charged particle moves close and parallel to the surface of a Babinet metasurface composed of metallic C -aperture resonators, strong electromagnetic radiation arises at resonant frequency. Here we systematically study the Smith-Purcell effects in Babinet metasurfaces with different periods. By tuning the period, the resonant (or working) frequency of the metasurface can vary from GHz to THz and infrared ranges. It is found that for working frequencies lower than 10 GHz, the ratio of absorption loss to input power is about 3.7%. Although the loss ratio increases with increasing working frequency, it remains as low as 11% (29%) at a working frequency of 10 THz (224 THz). Due to the existence of loss, a nonlinear relationship is also found between resonant frequency and the reciprocal of period. Our results suggest that Babinet metasurfaces could be a good candidate for fabricating efficient, compact THz and infrared free-electron light sources.

47 CFR 25.208 - Power flux density limits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... COMMUNICATIONS Technical Standards § 25.208 Power flux density limits. (a) In the band 3650-4200 MHz, the power flux density at the Earth's surface produced by emissions from a space station for all conditions and... and 10.7-11.7 GHz for NGSO FSS space stations, the power flux-density at the Earth's surface produced...

Electromagnetic Control of High Heat-Flux Spray Impingement Boiling Under Microgravity Conditions

DTIC Science & Technology

2007-03-01

impingement boiling ( Mudawar , 2000; Chow et al., 1997; Tilton, 1989). With water as the working fluid, spray cooling has achieved a heat flux on the...Stebbins, C. J., and Mudawar , I., 1996. "Mapping of Impact and Heat Transfer Regimes of Water Drops Impinging on a Polished Surface," Int. J. Heat and Mass...34 Proceedings of SAE 2004 Power Systems Conference, 2004-01-3204, Reno NV, November, pp. 309-317. Mudawar , 1., 2000. "Assessment of High-heat Flux

Survey of Advanced Propulsion Systems for Surface Vehicles

DTIC Science & Technology

1975-01-01

RROGRAM ELEMENT. PROJECT, T AM AREA • WORK UNIT NUMBERS T-102 12 . RERORT OATE January 1975 ’» NUMBER OF RAGES ZoL • S. SECURITY CLASS...wa*a«ilt,l,8>aaw^ •’ ..,-..,, I 1 I I 1 1 I I 0 a e 12 1 5 I 2. MILITARY NEEDS ~ Preceding page blank 21...sfc = endurance weight of fuel gross weight of vehicle power from engine specific fuel consumption 3-7-75- 12 40 60 80 100 120 140 SPECIFIC

High-Temperature Piezoelectric Sensing

PubMed Central

Jiang, Xiaoning; Kim, Kyungrim; Zhang, Shujun; Johnson, Joseph; Salazar, Giovanni

2014-01-01

Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented. PMID:24361928

Martian Surface Boundary Layer Characterization: Enabling Environmental Data for Science, Engineering and Human Exploration

NASA Technical Reports Server (NTRS)

England, C.

2000-01-01

For human or large robotic exploration of Mars, engineering devices such as power sources will be utilized that interact closely with the Martian environment. Heat sources for power production, for example, will use the low ambient temperature for efficient heat rejection. The Martian ambient, however, is highly variable, and will have a first order influence on the efficiency and operation of all large-scale equipment. Diurnal changes in temperature, for example, can vary the theoretical efficiency of power production by 15% and affect the choice of equipment, working fluids, and operating parameters. As part of the Mars Exploration program, missions must acquire the environmental data needed for design, operation and maintenance of engineering equipment including the transportation devices. The information should focus on the variability of the environment, and on the differences among locations including latitudes, altitudes, and seasons. This paper outlines some of the WHY's, WHAT's and WHERE's of the needed data, as well as some examples of how this data will be used. Environmental data for engineering design should be considered a priority in Mars Exploration planning. The Mars Thermal Environment Radiator Characterization (MTERC), and Dust Accumulation and Removal Technology (DART) experiments planned for early Mars landers are examples of information needed for even small robotic missions. Large missions will require proportionately more accurate data that encompass larger samples of the Martian surface conditions. In achieving this goal, the Mars Exploration program will also acquire primary data needed for understanding Martian weather, surface evolution, and ground-atmosphere interrelationships.

Surface EMG and intra-socket force measurement to control a prosthetic device

NASA Astrophysics Data System (ADS)

Sanford, Joe; Patterson, Rita; Popa, Dan

2015-06-01

Surface electromyography (SEMG) has been shown to be a robust and reliable interaction method allowing for basic control of powered prosthetic devices. Research has shown a marked decrease in EMG-classification efficiency throughout activities of daily life due to socket shift and movement and fatigue as well as changes in degree of fit of the socket throughout the subject's lifetime. Users with the most severe levels of amputation require the most complex devices with the greatest number of degrees of freedom. Controlling complex dexterous devices with limited available inputs requires the addition of sensing and interaction modalities. However, the larger the amputation severity, the fewer viable SEMG sites are available as control inputs. Previous work reported the use of intra-socket pressure, as measured during wrist flexion and extension, and has shown that it is possible to control a powered prosthetic device with pressure sensors. In this paper, we present data correlations of SEMG data with intra-socket pressure data. Surface EMG sensors and force sensors were housed within a simulated prosthetic cuff fit to a healthy-limbed subject. EMG and intra-socket force data was collected from inside the cuff as a subject performed pre-defined grip motions with their dominant hand. Data fusion algorithms were explored and allowed a subject to use both intra-socket pressure and SEMG data as control inputs for a powered prosthetic device. This additional input modality allows for an improvement in input classification as well as information regarding socket fit through out activities of daily life.

The influence of surface chemistry and size of nanoscale graphene oxide on photothermal therapy of cancer using ultra-low laser power.

PubMed

Yang, Kai; Wan, Jianmei; Zhang, Shuai; Tian, Bo; Zhang, Youjiu; Liu, Zhuang

2012-03-01

Photothermal therapy as a physical treatment approach to destruct cancer has emerged as an alternative of currently used cancer therapies. Previously we have shown that polyethylene glycol (PEG) functionalized nano-graphene oxide (nGO-PEG) with strong optical absorption in the near-infrared (NIR) region was a powerful photothermal agent for in vivo cancer treatment. In this work, by using ultra-small reduced graphene oxide (nRGO) with non-covalent PEG coating, we study how sizes and surface chemistry affect the in vivo behaviors of graphene, and remarkably improve the performance of graphene-based in vivo photothermal cancer treatment. Owing to the enhanced NIR absorbance and highly efficient tumor passive targeting of nRGO-PEG, excellent in vivo treatment efficacy with 100% of tumor elimination is observed after intravenous injection of nRGO-PEG and the followed 808 nm laser irradiation, the power density (0.15 W/cm(2), 5 min) of which is an order of magnitude lower than that usually applied for in vivo tumor ablation using many other nanomaterials. All mice after treatment survive over a period of 100 days without a single death or any obvious sign of side effect. Our results highlight that both surface chemistry and sizes are critical to the in vivo performance of graphene, and show the promise of using optimized nano-graphene for ultra-effective photothermal treatment, which may potentially be combined with other therapeutic approaches to assist our fight against cancer. Copyright © 2011 Elsevier Ltd. All rights reserved.

Present status of liquid metal research for a fusion reactor

NASA Astrophysics Data System (ADS)

Tabarés, Francisco L.

2016-01-01

Although the use of solid materials as targets of divertor plasmas in magnetic fusion research is accepted as the standard solution for the very challenging issue of power and particle handling in a fusion reactor, a generalized feeling that the present options chosen for ITER will not represent the best choice for a reactor is growing up. The problems found for tungsten, the present selection for the divertor target of ITER, in laboratory tests and in hot plasma fusion devices suggest so. Even in the absence of the strong neutron irradiation expected in a reactor, issues like surface melting, droplet ejection, surface cracking, dust generation, etc., call for alternative solutions in a long pulse, high efficient fusion energy-producing continuous machine. Fortunately enough, decades of research on plasma facing materials based on liquid metals (LMs) have produced a wealth of appealing ideas that could find practical application in the route to the realization of a commercial fusion power plant. The options presently available, although in a different degree of maturity, range from full coverage of the inner wall of the device with liquid metals, so that power and particle exhaust together with neutron shielding could be provided, to more conservative combinations of liquid metal films and conventional solid targets basically representing a sort of high performance, evaporative coating for the alleviation of the surface degradation issues found so far. In this work, an updated review of worldwide activities on LM research is presented, together with some open issues still remaining and some proposals based on simple physical considerations leading to the optimization of the most conservative alternatives.

Optical Structural Health Monitoring Device

NASA Technical Reports Server (NTRS)

Buckner, Benjamin D.; Markov, Vladimir; Earthman, James C.

2010-01-01

This non-destructive, optical fatigue detection and monitoring system relies on a small and unobtrusive light-scattering sensor that is installed on a component at the beginning of its life in order to periodically scan the component in situ. The method involves using a laser beam to scan the surface of the monitored component. The device scans a laser spot over a metal surface to which it is attached. As the laser beam scans the surface, disruptions in the surface cause increases in scattered light intensity. As the disruptions in the surface grow, they will cause the light to scatter more. Over time, the scattering intensities over the scanned line can be compared to detect changes in the metal surface to find cracks, crack precursors, or corrosion. This periodic monitoring of the surface can be used to indicate the degree of fatigue damage on a component and allow one to predict the remaining life and/or incipient mechanical failure of the monitored component. This wireless, compact device can operate for long periods under its own battery power and could one day use harvested power. The prototype device uses the popular open-source TinyOS operating system on an off-the-shelf Mica2 sensor mote, which allows wireless command and control through dynamically reconfigurable multi-node sensor networks. The small size and long life of this device could make it possible for the nodes to be installed and left in place over the course of years, and with wireless communication, data can be extracted from the nodes by operators without physical access to the devices. While a prototype has been demonstrated at the time of this reporting, further work is required in the system s development to take this technology into the field, especially to improve its power management and ruggedness. It should be possible to reduce the size and sensitivity as well. Establishment of better prognostic methods based on these data is also needed. The increase of surface roughness with fatigue is closely connected to the microstructure of the metal, and ongoing research is seeking to connect this observed evidence of the fatigue state with microstructural theories of fatigue evolution to allow more accurate prognosis of remaining component life. Plans are also being discussed for flight testing, perhaps on NASA s SOFIA platform.

Niobium pentoxide: a promising surface-enhanced Raman scattering active semiconductor substrate

NASA Astrophysics Data System (ADS)

Shan, Yufeng; Zheng, Zhihui; Liu, Jianjun; Yang, Yong; Li, Zhiyuan; Huang, Zhengren; Jiang, Dongliang

2017-03-01

Surface-enhanced Raman scattering technique, as a powerful tool to identify the molecular species, has been severely restricted to the noble metals. The surface-enhanced Raman scattering substrates based on semiconductors would overcome the shortcomings of metal substrates and promote development of surface-enhanced Raman scattering technique in surface science, spectroscopy, and biomedicine studies. However, the detection sensitivity and enhancement effects of semiconductor substrates are suffering from their weak activities. In this work, a semiconductor based on Nb2O5 is reported as a new candidate for highly sensitive surface-enhanced Raman scattering detection of dye molecules. The largest enhancement factor value greater than 107 was observed with the laser excitation at 633 and 780 nm for methylene blue detection. As far as literature review shows, this is in the rank of the highest sensitivity among semiconductor materials; even comparable to the metal nanostructure substrates with "hot spots". The impressive surface-enhanced Raman scattering activities can be attributed to the chemical enhancement dominated by the photo-induced charge transfer, as well as the electromagnetic enhancement, which have been supported by the density-functional-theory and finite element method calculation results. The chemisorption of dye on Nb2O5 creates a new highest occupied molecular orbital and lowest unoccupied molecular orbital contributed by both fragments in the molecule-Nb2O5 system, which makes the charge transfer more feasible with longer excitation wavelength. In addition, the electromagnetic enhancement mechanism also accounts for two orders of magnitude enhancement in the overall enhancement factor value. This work has revealed Nb2O5 nanoparticles as a new semiconductor surface-enhanced Raman scattering substrate that is able to replace noble metals and shows great potentials applied in the fields of biology related.

Method of plasma etching GA-based compound semiconductors

DOEpatents

Qiu, Weibin; Goddard, Lynford L.

2013-01-01

A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent thereto. The chamber contains a Ga-based compound semiconductor sample in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. SiCl.sub.4 and Ar gases are flowed into the chamber. RF power is supplied to the platen at a first power level, and RF power is supplied to the source electrode. A plasma is generated. Then, RF power is supplied to the platen at a second power level lower than the first power level and no greater than about 30 W. Regions of a surface of the sample adjacent to one or more masked portions of the surface are etched at a rate of no more than about 25 nm/min to create a substantially smooth etched surface.

Numerical simulations of electric potential field for alternating current potential drop associated with surface cracks in low-alloy steel nuclear material

NASA Astrophysics Data System (ADS)

Yeh, Chun-Ping; Huang, Jiunn-Yuan

2018-04-01

Low-alloy steels used as structural materials in nuclear power plants are subjected to cyclic stresses during power plant operations. As a result, cracks may develop and propagate through the material. The alternating current potential drop technique is used to measure the lengths of cracks in metallic components. The depth of the penetration of the alternating current is assumed to be small compared to the crack length. This assumption allows the adoption of the unfolding technique to simplify the problem to a surface Laplacian field. The numerical modelling of the electric potential and current density distribution prediction model for a compact tension specimen and the unfolded crack model are presented in this paper. The goal of this work is to conduct numerical simulations to reduce deviations occurring in the crack length measurements. Numerical simulations were conducted on AISI 4340 low-alloy steel with different crack lengths to evaluate the electric potential distribution. From the simulated results, an optimised position for voltage measurements in the crack region was proposed.

Effects of O2 plasma post-treatment on ZnO: Ga thin films grown by H2O-thermal ALD

NASA Astrophysics Data System (ADS)

Lee, Yueh-Lin; Chuang, Jia-Hao; Huang, Tzu-Hsuan; Ho, Chong-Long; Wu, Meng-Chyi

2013-03-01

Transparent conducting oxides have been widely employed in optoelectronic devices using the various deposition methods such as sputtering, thermal evaporator, and e-gun evaporator technologies.1-3 In this work, gallium doped zinc oxide (ZnO:Ga) thin films were grown on glass substrates via H2O-thermal atomic layer deposition (ALD) at different deposition temperatures. ALD-GZO thin films were constituted as a layer-by-layer structure by stacking zinc oxides and gallium oxides. Diethylzinc (DEZ), triethylgallium (TEG) and H2O were used as zinc, gallium precursors and oxygen source, respectively. Furthermore, we investigated the influences of O2 plasma post-treatment power on the surface morphology, electrical and optical property of ZnO:Ga films. As the result of O2 plasma post-treatment, the characteristics of ZnO:Ga films exhibit a smooth surface, low resistivity, high carrier concentration, and high optical transmittance in the visible spectrum. However, the transmittance decreases with O2 plasma power in the near- and mid-infrared regions.

Surface-enhanced Raman spectroscopy on litographically constructed microelectrodes

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

Zhelyaskov, V.R.; Milne, E.T.; Weldon, M.K.

1995-12-31

A novel silicon substrate microelectrode array has been demonstrated to function as a surface-enhanced Raman Spectroscopy (SERS) microelectrode. SERS from adenosine and pyridine down to 10 mM concentration on silver coated iridium and gold microelectrode arrays have been observed with excitation at 532 nm and 633 nm correspondingly. Ag/AgCl reference electrode and platinum or integrated on the microelectrode iridium counter electrodes were used. Owing to the small area of the activated sites on the microelectrode (10 mm x 15 mm) the SERS signal exhibited a strong laser power dependence. The optimal laser power on the activated site was shown tomore » be in the order of x 100 mW. Good quality SERS spectra were recorded with exposure times of 10s and less. The small size of the electrodes makes them promising for studies in confined spaces. This includes potential applications as capillary electrophoreses detectors and probes of chemistry of biological organisms. A work on detection of lipids adhered to self-organized monolayers (SAM)s of alkanethiols on the activated microelectrodes is in progress.« less