``Phantom'' Modes in Ab Initio Tunneling Calculations: Implications for Theoretical Materials Optimization, Tunneling, and Transport

NASA Astrophysics Data System (ADS)

Barabash, Sergey V.; Pramanik, Dipankar

2015-03-01

Development of low-leakage dielectrics for semiconductor industry, together with many other areas of academic and industrial research, increasingly rely upon ab initio tunneling and transport calculations. Complex band structure (CBS) is a powerful formalism to establish the nature of tunneling modes, providing both a deeper understanding and a guided optimization of materials, with practical applications ranging from screening candidate dielectrics for lowest ``ultimate leakage'' to identifying charge-neutrality levels and Fermi level pinning. We demonstrate that CBS is prone to a particular type of spurious ``phantom'' solution, previously deemed true but irrelevant because of a very fast decay. We demonstrate that (i) in complex materials, phantom modes may exhibit very slow decay (appearing as leading tunneling terms implying qualitative and huge quantitative errors), (ii) the phantom modes are spurious, (iii) unlike the pseudopotential ``ghost'' states, phantoms are an apparently unavoidable artifact of large numerical basis sets, (iv) a presumed increase in computational accuracy increases the number of phantoms, effectively corrupting the CBS results despite the higher accuracy achieved in resolving the true CBS modes and the real band structure, and (v) the phantom modes cannot be easily separated from the true CBS modes. We discuss implications for direct transport calculations. The strategy for dealing with the phantom states is discussed in the context of optimizing high-quality high- κ dielectric materials for decreased tunneling leakage.

Optimal concentrations in transport systems

PubMed Central

Jensen, Kaare H.; Kim, Wonjung; Holbrook, N. Michele; Bush, John W. M.

2013-01-01

Many biological and man-made systems rely on transport systems for the distribution of material, for example matter and energy. Material transfer in these systems is determined by the flow rate and the concentration of material. While the most concentrated solutions offer the greatest potential in terms of material transfer, impedance typically increases with concentration, thus making them the most difficult to transport. We develop a general framework for describing systems for which impedance increases with concentration, and consider material flow in four different natural systems: blood flow in vertebrates, sugar transport in vascular plants and two modes of nectar drinking in birds and insects. The model provides a simple method for determining the optimum concentration copt in these systems. The model further suggests that the impedance at the optimum concentration μopt may be expressed in terms of the impedance of the pure (c = 0) carrier medium μ0 as μopt∼2αμ0, where the power α is prescribed by the specific flow constraints, for example constant pressure for blood flow (α = 1) or constant work rate for certain nectar-drinking insects (α = 6). Comparing the model predictions with experimental data from more than 100 animal and plant species, we find that the simple model rationalizes the observed concentrations and impedances. The model provides a universal framework for studying flows impeded by concentration, and yields insight into optimization in engineered systems, such as traffic flow. PMID:23594815

A mixed optimization method for automated design of fuselage structures.

NASA Technical Reports Server (NTRS)

Sobieszczanski, J.; Loendorf, D.

1972-01-01

A procedure for automating the design of transport aircraft fuselage structures has been developed and implemented in the form of an operational program. The structure is designed in two stages. First, an overall distribution of structural material is obtained by means of optimality criteria to meet strength and displacement constraints. Subsequently, the detailed design of selected rings and panels consisting of skin and stringers is performed by mathematical optimization accounting for a set of realistic design constraints. The practicality and computer efficiency of the procedure is demonstrated on cylindrical and area-ruled large transport fuselages.

Phase 2 - GASB Statement 34 compliance : development of a fixed asset (infrastructure) for the Alabama Department of Transportation

DOT National Transportation Integrated Search

2003-05-01

The Alabama Department of Transportation (ALDOT) Bureau of Materials and Tests has been working with the University of Alabama's Management Information Systems Department to provide a tool for road maintenance and optimization associated funding. Spe...

Extraterrestrial materials processing and construction

NASA Technical Reports Server (NTRS)

Criswell, D. R.

1978-01-01

Applications of available terrestrial skills to the gathering of lunar materials and the processing of raw lunar materials into industrial feed stock were investigated. The literature on lunar soils and rocks was reviewed and the chemical processes by which major oxides and chemical elements can be extracted were identified. The gathering of lunar soil by means of excavation equipment was studied in terms of terrestrial experience with strip mining operations on earth. The application of electrostatic benefication techniques was examined for use on the moon to minimize the quantity of materials requiring surface transport and to optimize the stream of raw materials to be transported off the moon for subsequent industrial use.

Hole-transport material variation in fully vacuum deposited perovskite solar cells

NASA Astrophysics Data System (ADS)

Polander, Lauren E.; Pahner, Paul; Schwarze, Martin; Saalfrank, Matthias; Koerner, Christian; Leo, Karl

2014-08-01

This work addresses the effect of energy level alignment between the hole-transporting material and the active layer in vacuum deposited, planar-heterojunction CH3NH3PbIx-3Clx perovskite solar cells. Through a series of hole-transport materials, with conductivity values set using controlled p-doping of the layer, we correlate their ionization potentials with the open-circuit voltage of the device. With ionization potentials beyond 5.3 eV, a substantial decrease in both current density and voltage is observed, which highlights the delicate energetic balance between driving force for hole-extraction and maximizing the photovoltage. In contrast, when an optimal ionization potential match is found, the open-circuit voltage can be maximized, leading to power conversion efficiencies of up to 10.9%. These values are obtained with hole-transport materials that differ from the commonly used Spiro-MeO-TAD and correspond to a 40% performance increase versus this reference.

A Study to Improve the Brazilian Air Force’s Material Management System

DTIC Science & Technology

1991-12-01

of Technology, in June 1990. Permanent Address: Base A6rea de Sio Paulo Instituto de Logistica da Aerongutica 07181 Guarulhos Sio Paulo Brazil 160 Vita...orders instead of more frequent smaller ones, and transportation from vendor to depot, which includes international fees in most cases, would be...optimized by the same reason. The transportation from depots to final users would not be affected, since only changes of depots and changes of material

High Efficiency Inverted Planar Perovskite Solar Cells with Solution-Processed NiOx Hole Contact.

PubMed

Yin, Xuewen; Yao, Zhibo; Luo, Qiang; Dai, Xuezeng; Zhou, Yu; Zhang, Ye; Zhou, Yangying; Luo, Songping; Li, Jianbao; Wang, Ning; Lin, Hong

2017-01-25

NiO x is a promising hole-transporting material for perovskite solar cells due to its high hole mobility, good stability, and easy processability. In this work, we employed a simple solution-processed NiO x film as the hole-transporting layer in perovskite solar cells. When the thickness of the perovskite layer increased from 270 to 380 nm, the light absorption and photogenerated carrier density were enhanced and the transporting distance of electron and hole would also increase at the same time, resulting in a large charge transfer resistance and a long hole-extracted process in the device, characterized by the UV-vis, photoluminescence, and electrochemical impedance spectroscopy spectra. Combining both of these factors, an optimal thickness of 334.2 nm was prepared with the perovskite precursor concentration of 1.35 M. Moreover, the optimal device fabrication conditions were further achieved by optimizing the thickness of NiO x hole-transporting layer and PCBM electron selective layer. As a result, the best power conversion efficiency of 15.71% was obtained with a J sc of 20.51 mA·cm -2 , a V oc of 988 mV, and a FF of 77.51% with almost no hysteresis. A stable efficiency of 15.10% was caught at the maximum power point. This work provides a promising route to achieve higher efficiency perovskite solar cells based on NiO or other inorganic hole-transporting materials.

Fabrication of Semi-quasi Solid DSSC using Spiro Material as Hole Transport Material

NASA Astrophysics Data System (ADS)

Safriani, L.; Primawati, W. P.; Mulyana, C.; Susilawati, T.; Aprilia, A.

2017-05-01

Dye Sensitized Solar Cells (DSSC) has been emerging a promising development in recent years. DSSC is a low-cost solar cell belonging to the third generation of solar cells. However, the conversion efficiency of DSSC is still far behind compared to silicon based solar cells. To produce long stability of DSSC, the used of solid state electrolyte is recommended instead of liquid electrolyte, though solid state DSSC also has problem relating to a lack of pore-filling hole transport material into mesoporous TiO2. In this work an attempt to improve performance of DSSC has been done by adding hole transport material into mesoporous TiO2 layer and optimizing fabrication method. In the first part of the work, we used low Tg material spiro-TAD and spiro-TPD as hole transport material with mosalyte and hybrid polymer as gel electrolyte to obtain a semi-quasi solid DSSC. In the second part, we modified fabrication method by annealing process before spin-coated spiro material into dye-coated TiO2 substrate. Current-voltage measurement of semi-quasi solid DSSC was performed using halogen lamp. We found that the used of spiro-TPD as hole transport give the best power conversion efficiency η = 2.03% of semi-quasi solid DSSC.

Optimal Cytoplasmic Transport in Viral Infections

PubMed Central

D'Orsogna, Maria R.; Chou, Tom

2009-01-01

For many viruses, the ability to infect eukaryotic cells depends on their transport through the cytoplasm and across the nuclear membrane of the host cell. During this journey, viral contents are biochemically processed into complexes capable of both nuclear penetration and genomic integration. We develop a stochastic model of viral entry that incorporates all relevant aspects of transport, including convection along microtubules, biochemical conversion, degradation, and nuclear entry. Analysis of the nuclear infection probabilities in terms of the transport velocity, degradation, and biochemical conversion rates shows how certain values of key parameters can maximize the nuclear entry probability of the viral material. The existence of such “optimal” infection scenarios depends on the details of the biochemical conversion process and implies potentially counterintuitive effects in viral infection, suggesting new avenues for antiviral treatment. Such optimal parameter values provide a plausible transport-based explanation of the action of restriction factors and of experimentally observed optimal capsid stability. Finally, we propose a new interpretation of how genetic mutations unrelated to the mechanism of drug action may nonetheless confer novel types of overall drug resistance. PMID:20046829

Interdisciplinary optimum design. [of aerospace structures

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, Jaroslaw; Haftka, Raphael T.

1986-01-01

Problems related to interdisciplinary interactions in the design of a complex engineering systems are examined with reference to aerospace applications. The interdisciplinary optimization problems examined include those dealing with controls and structures, materials and structures, control and stability, structure and aerodynamics, and structure and thermodynamics. The discussion is illustrated by the following specific applications: integrated aerodynamic/structural optimization of glider wing; optimization of an antenna parabolic dish structure for minimum weight and prescribed emitted signal gain; and a multilevel optimization study of a transport aircraft.

Optimizing Railroad Tank Car Safety Design to Reduce Hazardous Materials Transportation Risk

ERIC Educational Resources Information Center

Saat, Mohd Rapik

2009-01-01

The design of railroad tank cars is subject to structural and performance requirements and constrained by weight. They can be made safer by increasing tank thickness and adding various protective features, but these increase the weight and cost of the car and reduce its capacity and consequent transportation efficiency. Aircraft, automobiles and…

Optimal Bandwidth for High Efficiency Thermoelectrics

NASA Astrophysics Data System (ADS)

Zhou, Jun; Yang, Ronggui; Chen, Gang; Dresselhaus, Mildred S.

2011-11-01

The thermoelectric figure of merit (ZT) in narrow conduction bands of different material dimensionalities is investigated for different carrier scattering models. When the bandwidth is zero, the transport distribution function (TDF) is finite, not infinite as previously speculated by Mahan and Sofo [Proc. Natl. Acad. Sci. U.S.A. 93, 7436 (1996)PNASA60027-842410.1073/pnas.93.15.7436], even though the carrier density of states goes to infinity. Such a finite TDF results in a zero electrical conductivity and thus a zero ZT. We point out that the optimal ZT cannot be found in an extremely narrow conduction band. The existence of an optimal bandwidth for a maximal ZT depends strongly on the scattering models and the dimensionality of the material. A nonzero optimal bandwidth for maximizing ZT also depends on the lattice thermal conductivity. A larger maximum ZT can be obtained for materials with a smaller lattice thermal conductivity.

Lunar Habitat Optimization Using Genetic Algorithms

NASA Technical Reports Server (NTRS)

SanScoucie, M. P.; Hull, P. V.; Tinker, M. L.; Dozier, G. V.

2007-01-01

Long-duration surface missions to the Moon and Mars will require bases to accommodate habitats for the astronauts. Transporting the materials and equipment required to build the necessary habitats is costly and difficult. The materials chosen for the habitat walls play a direct role in protection against each of the mentioned hazards. Choosing the best materials, their configuration, and the amount required is extremely difficult due to the immense size of the design region. Clearly, an optimization method is warranted for habitat wall design. Standard optimization techniques are not suitable for problems with such large search spaces; therefore, a habitat wall design tool utilizing genetic algorithms (GAs) has been developed. GAs use a "survival of the fittest" philosophy where the most fit individuals are more likely to survive and reproduce. This habitat design optimization tool is a multiobjective formulation of up-mass, heat loss, structural analysis, meteoroid impact protection, and radiation protection. This Technical Publication presents the research and development of this tool as well as a technique for finding the optimal GA search parameters.

Trim and Structural Optimization of Subsonic Transport Wings Using Nonconventional Aeroelastic Tailoring

NASA Technical Reports Server (NTRS)

Stanford, Bret K.; Jutte, Christine V.

2014-01-01

Several minimum-mass aeroelastic optimization problems are solved to evaluate the effectiveness of a variety of novel tailoring schemes for subsonic transport wings. Aeroelastic strength and panel buckling constraints are imposed across a variety of trimmed maneuver loads. Tailoring with metallic thickness variations, functionally graded materials, composite laminates, tow steering, and distributed trailing edge control effectors are all found to provide reductions in structural wing mass with varying degrees of success. The question as to whether this wing mass reduction will offset the increased manufacturing cost is left unresolved for each case.

Thermoelectric transport properties of BaBiTe{sub 3}-based materials

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

Zhou, Yiming; Zhao, Li-Dong, E-mail: zhaolidong@buaa.edu.cn

BaBiTe{sub 3}, a material with low thermal conductivity, is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. We choose two types of dopants, K and La, trying to optimize its electrical transport properties. The minority carriers, which harm the Seebeck coefficient in this system, are suppressed by La doping. With the increase of both electrical conductivity and Seebeck coefficient, the power factor of 3% La doped BaBiTe{sub 3} reaches 3.7 μW cm{sup −1} K{sup −2} which increased by 40% from undoped BaBiTe{sub 3}. Besides high power factor, the thermal conductivity is alsomore » reduced in it. Eventually, a high ZT value, 0.25 at 473 K, for n-type BaBiTe{sub 3} is achieved in 3% La doped BaBiTe{sub 3}. - Graphical abstract: BaBiTe{sub 3} possesses a low thermal conductivity. However, it is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. A high ZT value of 0.25 at 473 K for n-type BaBiTe{sub 3} can be achieved through optimizing electrical transport properties via La doping. - Highlights: • BaBiTe{sub 3} is an analogue of these promising thermoelectric materials: such as CsBi{sub 4}Te{sub 6} and K{sub 2}Bi{sub 8}Se{sub 13}, etc. • BaBiTe{sub 3} possesses a low thermal conductivity. • La is an effective dopant to enhance electrical transport properties. • A high ZT value of 0.25 at 473 K can be achieved in n-type La-doped BaBiTe{sub 3}.« less

The effect of shallow vs. deep level doping on the performance of thermoelectric materials

NASA Astrophysics Data System (ADS)

Song, Qichen; Zhou, Jiawei; Meroueh, Laureen; Broido, David; Ren, Zhifeng; Chen, Gang

2016-12-01

It is well known that the efficiency of a good thermoelectric material should be optimized with respect to doping concentration. However, much less attention has been paid to the optimization of the dopant's energy level. Thermoelectric materials doped with shallow levels may experience a dramatic reduction in their figures of merit at high temperatures due to the excitation of minority carriers that reduces the Seebeck coefficient and increases bipolar heat conduction. Doping with deep level impurities can delay the excitation of minority carriers as it requires a higher temperature to ionize all dopants. We find through modeling that, depending on the material type and temperature range of operation, different impurity levels (shallow or deep) will be desired to optimize the efficiency of a thermoelectric material. For different materials, we further clarify where the most preferable position of the impurity level within the bandgap falls. Our research provides insight on why different dopants often affect thermoelectric transport properties differently and directions in searching for the most appropriate dopants for a thermoelectric material in order to maximize the device efficiency.

Investigate plow blade optimization : executive summary.

DOT National Transportation Integrated Search

2015-08-01

Snow and ice management is the single largest expenditure in the maintenance budget for the Ohio : Department of Transportation (ODOT), with an annual cost including labor, equipment, and materials : reaching approximately $86 million. Given the curr...

Strategies for discovery and optimization of thermoelectric materials: Role of real objects and local fields

NASA Astrophysics Data System (ADS)

Zhu, Hao; Xiao, Chong

2018-06-01

Thermoelectric materials provide a renewable and eco-friendly solution to mitigate energy shortages and to reduce environmental pollution via direct heat-to-electricity conversion. Discovery of the novel thermoelectric materials and optimization of the state-of-the-art material systems lie at the core of the thermoelectric society, the basic concept behind these being comprehension and manipulation of the physical principles and transport properties regarding thermoelectric materials. In this mini-review, certain examples for designing high-performance bulk thermoelectric materials are presented from the perspectives of both real objects and local fields. The highlights of this topic involve the Rashba effect, Peierls distortion, local magnetic field, and local stress field, which cover several aspects in the field of thermoelectric research. We conclude with an overview of future developments in thermoelectricity.

Development of Optimized Welding Solutions for X100 Linepipe Steel

DOT National Transportation Integrated Search

2011-09-01

This investigation is part of a major consolidated program of research sponsored by the US Department of Transportation (DOT) Pipeline Hazardous Materials Safety Administration (PHMSA) and the Pipeline Research Council International (PRCI) to advance...

Multicriteria optimization approach to design and operation of district heating supply system over its life cycle

NASA Astrophysics Data System (ADS)

Hirsch, Piotr; Duzinkiewicz, Kazimierz; Grochowski, Michał

2017-11-01

District Heating (DH) systems are commonly supplied using local heat sources. Nowadays, modern insulation materials allow for effective and economically viable heat transportation over long distances (over 20 km). In the paper a method for optimized selection of design and operating parameters of long distance Heat Transportation System (HTS) is proposed. The method allows for evaluation of feasibility and effectivity of heat transportation from the considered heat sources. The optimized selection is formulated as multicriteria decision-making problem. The constraints for this problem include a static HTS model, allowing considerations of system life cycle, time variability and spatial topology. Thereby, variation of heat demand and ground temperature within the DH area, insulation and pipe aging and/or terrain elevation profile are taken into account in the decision-making process. The HTS construction costs, pumping power, and heat losses are considered as objective functions. Inner pipe diameter, insulation thickness, temperatures and pumping stations locations are optimized during the decision-making process. Moreover, the variants of pipe-laying e.g. one pipeline with the larger diameter or two with the smaller might be considered during the optimization. The analyzed optimization problem is multicriteria, hybrid and nonlinear. Because of such problem properties, the genetic solver was applied.

Chemical vapor deposition modeling for high temperature materials

NASA Technical Reports Server (NTRS)

Gokoglu, Suleyman A.

1992-01-01

The formalism for the accurate modeling of chemical vapor deposition (CVD) processes has matured based on the well established principles of transport phenomena and chemical kinetics in the gas phase and on surfaces. The utility and limitations of such models are discussed in practical applications for high temperature structural materials. Attention is drawn to the complexities and uncertainties in chemical kinetics. Traditional approaches based on only equilibrium thermochemistry and/or transport phenomena are defended as useful tools, within their validity, for engineering purposes. The role of modeling is discussed within the context of establishing the link between CVD process parameters and material microstructures/properties. It is argued that CVD modeling is an essential part of designing CVD equipment and controlling/optimizing CVD processes for the production and/or coating of high performance structural materials.

Evaluation of Spacecraft Shielding Effectiveness for Radiation Protection

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Wilson, John W.

1999-01-01

The potential for serious health risks from solar particle events (SPE) and galactic cosmic rays (GCR) is a critical issue in the NASA strategic plan for the Human Exploration and Development of Space (HEDS). The excess cost to protect against the GCR and SPE due to current uncertainties in radiation transmission properties and cancer biology could be exceedingly large based on the excess launch costs to shield against uncertainties. The development of advanced shielding concepts is an important risk mitigation area with the potential to significantly reduce risk below conventional mission designs. A key issue in spacecraft material selection is the understanding of nuclear reactions on the transmission properties of materials. High-energy nuclear particles undergo nuclear reactions in passing through materials and tissue altering their composition and producing new radiation types. Spacecraft and planetary habitat designers can utilize radiation transport codes to identify optimal materials for lowering exposures and to optimize spacecraft design to reduce astronaut exposures. To reach these objectives will require providing design engineers with accurate data bases and computationally efficient software for describing the transmission properties of space radiation in materials. Our program will reduce the uncertainty in the transmission properties of space radiation by improving the theoretical description of nuclear reactions and radiation transport, and provide accurate physical descriptions of the track structure of microscopic energy deposition.

Standardized Transportation of Human Islets: An Islet Cell Resource Center Study of More Than 2,000 Shipments

PubMed Central

Kaddis, John S.; Hanson, Matthew S.; Cravens, James; Qian, Dajun; Olack, Barbara; Antler, Martha; Papas, Klearchos K.; Iglesias, Itzia; Barbaro, Barbara; Fernandez, Luis; Powers, Alvin C.; Niland, Joyce C.

2013-01-01

Preservation of cell quality during shipment of human pancreatic islets for use in laboratory research is a crucial, but neglected, topic. Mammalian cells, including islets, have been shown to be adversely affected by temperature changes in vitro and in vivo, yet protocols that control for thermal fluctuations during cell transport are lacking. To evaluate an optimal method of shipping human islets, an initial assessment of transportation conditions was conducted using standardized materials and operating procedures in 48 shipments sent to a central location by 8 pancreas-processing laboratories using a single commercial airline transporter. Optimization of preliminary conditions was conducted, and human islet quality was then evaluated in 2,338 shipments pre- and post-implementation of a finalized transportation container and standard operating procedures. The initial assessment revealed that the outside temperature ranged from a mean of −4.6±10.3°C to 20.9±4.8°C. Within-container temperature drops to or below 15°C occurred in 16 shipments (36%), while the temperature was found to be stabilized between 15–29°C in 29 shipments (64%). Implementation of an optimized transportation container and operating procedure reduced the number of within-container temperature drops (≤15°C) to 13% (n=37 of 289 winter shipments), improved the number desirably maintained between 15–29°C to 86% (n=250), but also increased the number reaching or exceeding 29°C to 1% (n=2; overall p<0.0001). Additionally, post-receipt quality ratings of excellent to good improved pre- vs. post- implementation of the standardized protocol, adjusting for pre-shipment purity/viability levels (p<0.0001). Our results show that extreme temperature fluctuations during transport of human islets, occurring when using a commercial airline transporter for long distance shipping, can be controlled using standardized containers, materials, and operating procedures. This cost-effective and pragmatic standardized protocol for the transportation of human islets can potentially be adapted for use with other mammalian cell systems, and is available online at: http://iidp.coh.org/sops.aspx. PMID:22889479

NASA technology program for future civil air transports

NASA Technical Reports Server (NTRS)

Wright, H. T.

1983-01-01

An assessment is undertaken of the development status of technology, applicable to future civil air transport design, which is currently undergoing conceptual study or testing at NASA facilities. The NASA civil air transport effort emphasizes advanced aerodynamic computational capabilities, fuel-efficient engines, advanced turboprops, composite primary structure materials, advanced aerodynamic concepts in boundary layer laminarization and aircraft configuration, refined control, guidance and flight management systems, and the integration of all these design elements into optimal systems. Attention is given to such novel transport aircraft design concepts as forward swept wings, twin fuselages, sandwich composite structures, and swept blade propfans.

First-Principles Calculations of Electronic, Optical, and Transport Properties of Materials for Energy Applications

NASA Astrophysics Data System (ADS)

Shi, Guangsha

Solar electricity is a reliable and environmentally friendly method of sustainable energy production and a realistic alternative to conventional fossil fuels. Moreover, thermoelectric energy conversion is a promising technology for solid-state refrigeration and efficient waste-heat recovery. Predicting and optimizing new photovoltaic and thermoelectric materials composed of Earth-abundant elements that exceed the current state of the art, and understanding how nanoscale structuring and ordering improves their energy conversion efficiency pose a challenge for materials scientists. I approach this challenge by developing and applying predictive high-performance computing methods to guide research and development of new materials for energy-conversion applications. Advances in computer-simulation algorithms and high-performance computing resources promise to speed up the development of new compounds with desirable properties and significantly shorten the time delay between the discovery of new materials and their commercial deployment. I present my calculated results on the extraordinary properties of nanostructured semiconductor materials, including strong visible-light absorbance in nanoporous silicon and few-layer SnSe and GeSe. These findings highlight the capability of nanoscale structuring and ordering to improve the performance of Earth-abundant materials compared to their bulk counterparts for solar-cell applications. I also successfully identified the dominant mechanisms contributing to free-carrier absorption in n-type silicon. My findings help evaluate the impact of the energy loss from this absorption mechanism in doped silicon and are thus important for the design of silicon solar cells. In addition, I calculated the thermoelectric transport properties of p-type SnSe, a bulk material with a record thermoelectric figure of merit. I predicted the optimal temperatures and free-carrier concentrations for thermoelectric energy conversion, as well the theoretical upper limit of the figure of merit. I also determined the electronic structures and thermoelectric properties of Mg2Si, Mg2Ge, and Mg2Sn, a family of Earth-abundant thermoelectric compounds. I uncovered the importance of quasiparticle corrections and the proper treatment of pseudopotentials in the determination of the band gaps and the thermoelectric transport properties at high temperatures. The methods and codes I developed in my research form a general predictive toolbox for the design and optimization of the functional properties of materials for energy applications.

Concepts for the material development of phosphorescent organic materials processable from solution and their application in OLEDs

NASA Astrophysics Data System (ADS)

Janietz, S.; Krueger, H.; Thesen, M.; Salert, B.; Wedel, A.

2014-10-01

One example of organic electronics is the application of polymer based light emitting devices (PLEDs). PLEDs are very attractive for large area and fine-pixel displays, lighting and signage. The polymers are more amenable to solution processing by printing techniques which are favourable for low cost production in large areas. With phosphorescent emitters like Ir-complexes higher quantum efficiencies were obtained than with fluorescent systems, especially if multilayer stack systems with separated charge transport and emitting layers were applied in the case of small molecules. Polymers exhibit the ability to integrate all the active components like the hole-, electron-transport and phosphorescent molecules in only one layer. Here, the active components of a phosphorescent system - triplet emitter, hole- and electron transport molecules - can be linked as a side group to a polystyrene main chain. By varying the molecular structures of the side groups as well as the composition of the side chains with respect to the triplet emitter, hole- and electron transport structure, and by blending with suitable glass-forming, so-called small molecules, brightness, efficiency and lifetime of the produced OLEDs can be optimized. By choosing the triplet emitter, such as iridium complexes, different emission colors can be specially set. Different substituted triazine molecules were introduced as side chain into a polystyrene backbone and applied as electron transport material in PLED blend systems. The influence of alkyl chain lengths of the performance will be discussed. For an optimized blend system with a green emitting phosphorescent Ir-complex efficiencies of 60 cd/A and an lifetime improvement of 66.000 h @ 1000 cd/m2 were achieved.

Oxasmaragdyrins as New and Efficient Hole-Transporting Materials for High-Performance Perovskite Solar Cells.

PubMed

Mane, Sandeep B; Sutanto, Albertus Adrian; Cheng, Chih-Fu; Xie, Meng-Yu; Chen, Chieh-I; Leonardus, Mario; Yeh, Shih-Chieh; Beyene, Belete Bedemo; Diau, Eric Wei-Guang; Chen, Chin-Ti; Hung, Chen-Hsiung

2017-09-20

The high performance of the perovskite solar cells (PSCs) cannot be achieved without a layer of efficient hole-transporting materials (HTMs) to retard the charge recombination and transport the photogenerated hole to the counterelectrode. Herein, we report the use of boryl oxasmaragdyrins (SM01, SM09, and SM13), a family of aromatic core-modified expanded porphyrins, as efficient hole-transporting materials (HTMs) for perovskite solar cells (PSCs). These oxasmaragdyrins demonstrated complementary absorption spectra in the low-energy region, good redox reversibility, good thermal stability, suitable energy levels with CH 3 NH 3 PbI 3 perovskite, and high hole mobility. A remarkable power conversion efficiency of 16.5% (V oc = 1.09 V, J sc = 20.9 mA cm -2 , fill factor (FF) = 72%) is achieved using SM09 on the optimized PSCs device employing a planar structure, which is close to that of the state-of-the-art hole-transporting materials (HTMs), spiro-OMeTAD of 18.2% (V oc = 1.07 V, J sc = 22.9 mA cm -2 , FF = 74%). In contrast, a poor photovoltaic performance of PSCs using SM01 is observed due to the interactions of terminal carboxylic acid functional group with CH 3 NH 3 PbI 3 .

Microstructure investigations of Yb- and Bi-doped Mg{sub 2}Si prepared from metal hydrides for thermoelectric applications

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

Janka, Oliver; Zaikina, Julia V.; Bux, Sabah K.

2017-01-15

Within the field of thermoelectric materials for energy conversion magnesium silicide, Mg{sub 2}Si, is an outstanding candidate due to its low density, abundant constituents and low toxicity. However electronic and thermal tuning of the material is a required necessity to improve its Figure of Merit, zT. Doping of Yb via reactive YbH{sub 2} into the structure is performed with the goal of reducing the thermal conductivity. Hydrogen is released as a by-product at high temperatures allowing for facile incorporation of Yb into the structure. We report on the properties of Yb- and Bi-doped Mg{sub 2}Si prepared with MgH{sub 2} andmore » YbH{sub 2} with the focus on the synthetic conditions, and samples’ microstructure, investigated by various electron microscopy techniques. Yb is found in the form of both Yb{sub 3}Si{sub 5} inclusions and Yb dopant segregated at the grain boundary substituting for Mg. The addition of 1 at% Yb concentration reduced the thermal conductivity, providing a value of 30 mW/cm K at 800 K. In order to adjust carrier concentration, the sample is additionally doped with Bi. The impact of the microstructure on the transport properties of the obtained material is studied. Idealy, the reduction of the thermal conductivity is achieved by doping with Yb and the electronic transport is adjusted by doping with Bi. Large grain microstructure facilitates the electronic transport. However, the synthetic conditions that provide the optimized microstructure for electrical transport do not facilitate the additional Yb dopant incorporation. Therefore, the Yb and Bi containing sample with the optimized microstructure provides a zT=0.46 at 800 K. - Graphical abstract: 1% or less addition of YbH{sub 2} to Mg{sub 2}Si significantly reduces the thermal conductivity of the material. Yb replaces some Mg in Mg{sub 2}Si and the remainder is distributed as Yb{sub 3}Sb{sub 5} in the Yb-doped Mg{sub 2}Si matrix. Correlation between the observed grain size and transport show the difficulty in simultaneously reducing the thermal conductivity with optimal electronic properties.« less

Structural analysis for preliminary design of High Speed Civil Transport (HSCT)

NASA Technical Reports Server (NTRS)

Bhatia, Kumar G.

1992-01-01

In the preliminary design environment, there is a need for quick evaluation of configuration and material concepts. The simplified beam representations used in the subsonic, high aspect ratio wing platform are not applicable for low aspect ratio configurations typical of supersonic transports. There is a requirement to develop methods for efficient generation of structural arrangement and finite element representation to support multidisciplinary analysis and optimization. In addition, empirical data bases required to validate prediction methods need to be improved for high speed civil transport (HSCT) type configurations.

Apparatus for the measurement of electrical resistivity, Seebeck coefficient, and thermal conductivity of thermoelectric materials between 300 K and 12 K

NASA Astrophysics Data System (ADS)

Martin, Joshua; Nolas, George S.

2016-01-01

We have developed a custom apparatus for the consecutive measurement of the electrical resistivity, the Seebeck coefficient, and the thermal conductivity of materials between 300 K and 12 K. These three transport properties provide for a basic understanding of the thermal and electrical properties of materials. They are of fundamental importance in identifying and optimizing new materials for thermoelectric applications. Thermoelectric applications include waste heat recovery for automobile engines and industrial power generators, solid-state refrigeration, and remote power generation for sensors and space probes. The electrical resistivity is measured using a four-probe bipolar technique, the Seebeck coefficient is measured using the quasi-steady-state condition of the differential method in a 2-probe arrangement, and the thermal conductivity is measured using a longitudinal, multiple gradient steady-state technique. We describe the instrumentation and the measurement uncertainty associated with each transport property, each of which is presented with representative measurement comparisons using round robin samples and/or certified reference materials. Transport properties data from this apparatus have supported the identification, development, and phenomenological understanding of novel thermoelectric materials.

Interhospital paediatric intensive care transport: a novel transport unit based on a standard ambulance trolley.

PubMed

Vos, Gijs D; Buurman, Wim A; van Waardenburg, Dick A; Visser, Timo P L; Ramsay, Graham; Donckerwolcke, Raymond A M G

2003-09-01

A recent development in providing intensive care for children is that it is more and more centralized in tertiary centres. The centralization of intensive care facilities for children in tertiary centres demands a safe and well-organized transport system. The transfer of critically ill children from a referring general hospital to a tertiary paediatric intensive care centre should be performed by a specially trained and fully equipped transport team. During the transfer of these children continuous intensive care facilities should be provided. The minimal requirements of equipment and materials for transport that allow such care have been determined. The equipment consists of a monitor allowing continuous measurement of vital signs, a defibrillator, tools for airway and ventilatory management, an oxygen source, suction unit, fluid and electrolyte management, medication, resuscitation chart and a communication system. A mobile paediatric intensive care unit was constructed in order to store this equipment, including easily accessible ventilator and materials optimized for close patient observation and ventilator control.

Link between hopping models and percolation scaling laws for charge transport in mixtures of small molecules

DOE PAGES

Ha, Dong -Gwang; Kim, Jang -Joo; Baldo, Marc A.

2016-04-29

Mixed host compositions that combine charge transport materials with luminescent dyes offer superior control over exciton formation and charge transport in organic light emitting devices (OLEDs). Two approaches are typically used to optimize the fraction of charge transport materials in a mixed host composition: either an empirical percolative model, or a hopping transport model. We show that these two commonly-employed models are linked by an analytic expression which relates the localization length to the percolation threshold and critical exponent. The relation is confirmed both numerically and experimentally through measurements of the relative conductivity of Tris(4-carbazoyl-9-ylphenyl) amine (TCTA) :1,3-bis(3,5-dipyrid-3-yl-phenyl) benzene (BmPyPb)more » mixtures with different concentrations, where the TCTA plays a role as hole conductor and the BmPyPb as hole insulator. Furthermore, the analytic relation may allow the rational design of mixed layers of small molecules for high-performance OLEDs.« less

Link between hopping models and percolation scaling laws for charge transport in mixtures of small molecules

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

Ha, Dong-Gwang; Kim, Jang-Joo; Baldo, Marc A.

2016-04-01

Mixed host compositions that combine charge transport materials with luminescent dyes offer superior control over exciton formation and charge transport in organic light emitting devices (OLEDs). Two approaches are typically used to optimize the fraction of charge transport materials in a mixed host composition: either an empirical percolative model, or a hopping transport model. We show that these two commonly-employed models are linked by an analytic expression which relates the localization length to the percolation threshold and critical exponent. The relation is confirmed both numerically and experimentally through measurements of the relative conductivity of Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) :1,3-bis(3,5-dipyrid-3-yl-phenyl)benzene (BmPyPb) mixtures withmore » different concentrations, where the TCTA plays a role as hole conductor and the BmPyPb as hole insulator. The analytic relation may allow the rational design of mixed layers of small molecules for high-performance OLEDs.« less

Superlattice structure modeling and simulation of High Electron Mobility Transistor for improved performance

NASA Astrophysics Data System (ADS)

Munusami, Ravindiran; Yakkala, Bhaskar Rao; Prabhakar, Shankar

2013-12-01

Magnetic tunnel junction were made by inserting the magnetic materials between the source, channel and the drain of the High Electron Mobility Transistor (HEMT) to enhance the performance. Material studio software package was used to design the superlattice layers. Different cases were analyzed to optimize the performance of the device by placing the magnetic material at different positions of the device. Simulation results based on conductivity reveals that the device has a very good electron transport due to the magnetic materials and will amplify very low frequency signals.

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

Janka, Oliver; Zaikina, Julia V.; Bux, Sabah K.

Within the field of thermoelectric materials for energy conversion magnesium silicide, Mg2Si, is an outstanding candidate due to its low density, abundant constituents and low toxicity. However electronic and thermal tuning of the material is a required necessity to improve its Figure of Merit, zT. Doping of Yb via reactive YbH2 into the structure is performed with the goal of reducing the thermal conductivity. Hydrogen is released as a by-product at high temperatures allowing for facile incorporation of Yb into the structure. We report on the properties of Yb-and Bi-doped Mg2Si prepared with MgH2 and YbH2 with the focus onmore » the synthetic conditions, and samples' microstructure, investigated by various electron microscopy techniques. Yb is found in the form of both Yb3Si5 inclusions and Yb dopant segregated at the grain boundary substituting for Mg. The addition of 1 at% Yb concentration reduced the thermal conductivity, providing a value of 30 mW/cm K at 800 K. In order to adjust carrier concentration, the sample is additionally doped with Bi. The impact of the microstructure on the transport properties of the obtained material is studied. Idealy, the reduction of the thermal conductivity is achieved by doping with Yb and the electronic transport is adjusted by doping with Bi. Large grain microstructure facilitates the electronic transport. However, the synthetic conditions that provide the optimized microstructure for electrical transport do not facilitate the additional Yb dopant incorporation. Therefore, the Yb and Bi containing sample with the optimized microstructure provides a zT=0.46 at 800 K.« less

Evaluating and optimizing recycled concrete fines in PCC mixtures containing supplementary cementitious materials.

DOT National Transportation Integrated Search

2010-08-01

Portland cement concrete (PCC) is used throughout transportation infrastructure, for roads as well as bridges : and other structures. One of the most effective ways of making PCC more green is to replace a portion of the : portland cement (the ...

Determination of Optimal Subsidy for Materials Saving Investment through Recycle/Recovery at Industrial Level

NASA Astrophysics Data System (ADS)

Batzias, Dimitris F.

2009-08-01

This work deals with a methodological framework under the form of a simple/short algorithmic procedure (including 11 activity steps and 3 decision nodes) designed/developed for the determination of optimal subsidy for materials saving investment through recycle/recovery (RR) at industrial level. Two case examples are presented, covering both aspects, without and with recycling. The expected Relative Cost Decrease (RCD) because of recycling, which forms a critical index for decision making on subsidizing, is estimated. The developed procedure can be extended outside the industrial unit to include collection/transportation/processing of recyclable wasted products. Since, in such a case, transportation cost and processing cost are conflict depended variables (when the quantity collected/processed Q is the independent/explanatory variable), the determination of Qopt is examined under energy crises conditions, when corresponding subsidies might be granted to re-set the original equilibrium and avoid putting the recycling enterprise in jeopardize due to dangerous lowering of the first break-even point.

Design optimization of beta- and photovoltaic conversion devices

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

Wichner, R.; Blum, A.; Fischer-Colbrie, E.

1976-01-08

This report presents the theoretical and experimental results of an LLL Electronics Engineering research program aimed at optimizing the design and electronic-material parameters of beta- and photovoltaic p-n junction conversion devices. To meet this objective, a comprehensive computer code has been developed that can handle a broad range of practical conditions. The physical model upon which the code is based is described first. Then, an example is given of a set of optimization calculations along with the resulting optimized efficiencies for silicon (Si) and gallium-arsenide (GaAs) devices. The model we have developed, however, is not limited to these materials. Itmore » can handle any appropriate material--single or polycrystalline-- provided energy absorption and electron-transport data are available. To check code validity, the performance of experimental silicon p-n junction devices (produced in-house) were measured under various light intensities and spectra as well as under tritium beta irradiation. The results of these tests were then compared with predicted results based on the known or best estimated device parameters. The comparison showed very good agreement between the calculated and the measured results.« less

Shield Optimization in Simple Geometry for the Gateway Concept

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Simonsen, L. C.; Nealy, J. E.; Troutman, P. A.; Wilson, J. W.

2002-01-01

The great cost of added radiation shielding is a potential limiting factor in many deep space missions. For this enabling technology, we are developing tools for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of various space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. Preliminary studies of deep space missions indicate that for long duration space missions, improved shield materials will be required. The details of this new method and its impact on space missions and other technologies will be discussed. This study will provide a vital tool for evaluating Gateway designs in their usage context. Providing protection against the hazards of space radiation is one of the challenges to the Gateway infrastructure designs. We will use the mission optimization software to scope the impact of Gateway operations on human exposures and the effectiveness of alternate shielding materials on Gateway infrastructure designs. This study will provide a guide to the effectiveness of multifunctional materials in preparation to more detailed geometry studies in progress.

Analytical transport network theory to guide the design of 3-D microstructural networks in energy materials: Part 1. Flow without reactions

NASA Astrophysics Data System (ADS)

Cocco, Alex P.; Nakajo, Arata; Chiu, Wilson K. S.

2017-12-01

We present a fully analytical, heuristic model - the "Analytical Transport Network Model" - for steady-state, diffusive, potential flow through a 3-D network. Employing a combination of graph theory, linear algebra, and geometry, the model explicitly relates a microstructural network's topology and the morphology of its channels to an effective material transport coefficient (a general term meant to encompass, e.g., conductivity or diffusion coefficient). The model's transport coefficient predictions agree well with those from electrochemical fin (ECF) theory and finite element analysis (FEA), but are computed 0.5-1.5 and 5-6 orders of magnitude faster, respectively. In addition, the theory explicitly relates a number of morphological and topological parameters directly to the transport coefficient, whereby the distributions that characterize the structure are readily available for further analysis. Furthermore, ATN's explicit development provides insight into the nature of the tortuosity factor and offers the potential to apply theory from network science and to consider the optimization of a network's effective resistance in a mathematically rigorous manner. The ATN model's speed and relative ease-of-use offer the potential to aid in accelerating the design (with respect to transport), and thus reducing the cost, of energy materials.

Automated predesign of aircraft

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.; Kruse, G. S.; Tanner, C. J.; Wilson, P. J.

1978-01-01

Program uses multistation structural-synthesis to size and design box-beam structures for transport aircraft. Program optimizes static strength and scales up to satisfy fatigue and fracture criteria. It has multimaterial capability and library of materials properties, including advanced composites. Program can be used to evaluate impact on weight of variables such as materials, types of construction, structural configurations, minimum gage limits, applied loads, fatigue lives, crack-growth lives, initial crack sizes, and residual strengths.

a Multi Objective Model for Optimization of a Green Supply Chain Network

NASA Astrophysics Data System (ADS)

Paksoy, Turan; Özceylan, Eren; Weber, Gerhard-Wilhelm

2010-06-01

This study develops a model of a closed-loop supply chain (CLSC) network which starts with the suppliers and recycles with the decomposition centers. As a traditional network design, we consider minimizing the all transportation costs and the raw material purchasing costs. To pay attention for the green impacts, different transportation choices are presented between echelons according to their CO2 emissions. The plants can purchase different raw materials in respect of their recyclable ratios. The focuses of this paper are conducting the minimizing total CO2 emissions. Also we try to encourage the customers to use recyclable materials as an environmental performance viewpoint besides minimizing total costs. A multi objective linear programming model is developed via presenting a numerical example. We close the paper with recommendations for future researches.

Coupled porohyperelastic mass transport (PHEXPT) finite element models for soft tissues using ABAQUS.

PubMed

Vande Geest, Jonathan P; Simon, B R; Rigby, Paul H; Newberg, Tyler P

2011-04-01

Finite element models (FEMs) including characteristic large deformations in highly nonlinear materials (hyperelasticity and coupled diffusive/convective transport of neutral mobile species) will allow quantitative study of in vivo tissues. Such FEMs will provide basic understanding of normal and pathological tissue responses and lead to optimization of local drug delivery strategies. We present a coupled porohyperelastic mass transport (PHEXPT) finite element approach developed using a commercially available ABAQUS finite element software. The PHEXPT transient simulations are based on sequential solution of the porohyperelastic (PHE) and mass transport (XPT) problems where an Eulerian PHE FEM is coupled to a Lagrangian XPT FEM using a custom-written FORTRAN program. The PHEXPT theoretical background is derived in the context of porous media transport theory and extended to ABAQUS finite element formulations. The essential assumptions needed in order to use ABAQUS are clearly identified in the derivation. Representative benchmark finite element simulations are provided along with analytical solutions (when appropriate). These simulations demonstrate the differences in transient and steady state responses including finite deformations, total stress, fluid pressure, relative fluid, and mobile species flux. A detailed description of important model considerations (e.g., material property functions and jump discontinuities at material interfaces) is also presented in the context of finite deformations. The ABAQUS-based PHEXPT approach enables the use of the available ABAQUS capabilities (interactive FEM mesh generation, finite element libraries, nonlinear material laws, pre- and postprocessing, etc.). PHEXPT FEMs can be used to simulate the transport of a relatively large neutral species (negligible osmotic fluid flux) in highly deformable hydrated soft tissues and tissue-engineered materials.

Analysis of Optimal Transport Route Determination of Oil Palm Fresh Fruit Bunches from Plantation to Processing Factory

NASA Astrophysics Data System (ADS)

Tarigan, U.; Sidabutar, R. F.; Tarigan, U. P. P.; Chen, A.

2018-04-01

Manufacturers engaged in the business, producing CPO and kernels whose raw materials are oil palm fresh fruit bunches taken from their own plantation, generally face problems of transporting from plantation to factory where there is often a change of distance traveled by the truck the carrier of FFB is due to non-specific transport instructions. The research was conducted to determine the optimal transportation route in terms of distance, time and route number. The determination of this transportation route is solved using Nearest Neighbours and Clarke & Wright Savings methods. Based on the calculations performed then found in area I with method Nearest Neighbours has a distance of 200.78 Km while Clarke & Wright Savings as with a result of 214.09 Km. As for the harvest area, II obtained results with Nearest Neighbours method of 264.37 Km and Clarke & Wright Savings method with a total distance of 264.33 Km. Based on the calculation of the time to do all the activities of transporting FFB juxtaposed with the work time of the driver got the reduction of conveyance from 8 units to 5 units. There is also improvement of fuel efficiency by 0.8%.

Optimizing location of manufacturing industries in the context of economic globalization: A bi-level model based approach

NASA Astrophysics Data System (ADS)

Wu, Shanhua; Yang, Zhongzhen

2018-07-01

This paper aims to optimize the locations of manufacturing industries in the context of economic globalization by proposing a bi-level programming model which integrates the location optimization model with the traffic assignment model. In the model, the transport network is divided into the subnetworks of raw materials and products respectively. The upper-level model is used to determine the location of industries and the OD matrices of raw materials and products. The lower-level model is used to calculate the attributes of traffic flow under given OD matrices. To solve the model, the genetic algorithm is designed. The proposed method is tested using the Chinese steel industry as an example. The result indicates that the proposed method could help the decision-makers to implement the location decisions for the manufacturing industries effectively.

Pinning down high-performance Cu-chalcogenides as thin-film solar cell absorbers: A successive screening approach

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

Zhang, Yubo; Zhang, Wenqing, E-mail: wqzhang@mail.sic.ac.cn, E-mail: pzhang3@buffalo.edu; State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050

2016-05-21

Photovoltaic performances of Cu-chalcogenides solar cells are strongly correlated with the absorber fundamental properties such as optimal bandgap, desired band alignment with window material, and high photon absorption ability. According to these criteria, we carry out a successive screening for 90 Cu-chalcogenides using efficient theoretical approaches. Besides the well-recognized CuInSe{sub 2} and Cu{sub 2}ZnSnSe{sub 4} materials, several novel candidates are identified to have optimal bandgaps of around 1.0–1.5 eV, spike-like band alignments with CdS window layer, sharp photon absorption edges, and high absorption coefficients. These new systems have great potential to be superior absorbers for photovolatic applications if their carrriermore » transport and defect properties are properly optimized.« less

An efficient strategy for designing ambipolar organic semiconductor material: Introducing dehydrogenated phosphorus atoms into pentacene core

NASA Astrophysics Data System (ADS)

Tang, Xiao-Dan

2017-09-01

The charge transport properties of phosphapentacene (P-PEN) derivatives were systematically explored by theoretical calculation. The dehydrogenated P-PENs have reasonable frontier molecular orbital energy levels to facilitate both electron and hole injection. The reduced reorganization energies of dehydrogenated P-PENs could be intimately connected to the bonding nature of phosphorus atoms. From the idea of homology modeling, the crystal structure of TIPSE-4P-2p is constructed and fully optimized. Fascinatingly, TIPSE-4P-2p shows the intrinsic property of ambipolar transport in both hopping and band models. Thus, introducing dehydrogenated phosphorus atoms into pentacene core could be an efficient strategy for designing ambipolar material.

Optimization of the Laser Properties of Polymer Films Doped with N,N´-Bis(3-methylphenyl)-N,N´-diphenylbenzidine

PubMed Central

Calzado, Eva M.; Boj, Pedro G.; Díaz-García, María A.

2009-01-01

This review compiles the work performed in the field of organic solid-state lasers with the hole-transporting organic molecule N,N´-bis(3-methylphenyl)-N,N´-diphenyl-benzidine system (TPD), in view of improving active laser material properties. The optimization of the amplified spontaneous emission characteristics, i.e., threshold, linewidth, emission wavelength and photostability, of polystyrene films doped with TPD in waveguide configuration has been achieved by investigating the influence of several materials parameters such as film thickness and TPD concentration. In addition, the influence in the emission properties of the inclusion of a second-order distributed feedback grating in the substrate is discussed.

Ultrafast Microscopy of Energy and Charge Transport

NASA Astrophysics Data System (ADS)

Huang, Libai

The frontier in solar energy research now lies in learning how to integrate functional entities across multiple length scales to create optimal devices. Advancing the field requires transformative experimental tools that probe energy transfer processes from the nano to the meso lengthscales. To address this challenge, we aim to understand multi-scale energy transport across both multiple length and time scales, coupling simultaneous high spatial, structural, and temporal resolution. In my talk, I will focus on our recent progress on visualization of exciton and charge transport in solar energy harvesting materials from the nano to mesoscale employing ultrafast optical nanoscopy. With approaches that combine spatial and temporal resolutions, we have recently revealed a new singlet-mediated triplet transport mechanism in certain singlet fission materials. This work demonstrates a new triplet exciton transport mechanism leading to favorable long-range triplet exciton diffusion on the picosecond and nanosecond timescales for solar cell applications. We have also performed a direct measurement of carrier transport in space and in time by mapping carrier density with simultaneous ultrafast time resolution and 50 nm spatial precision in perovskite thin films using transient absorption microscopy. These results directly visualize long-range carrier transport of 220nm in 2 ns for solution-processed polycrystalline CH3NH3PbI3 thin films. The spatially and temporally resolved measurements reported here underscore the importance of the local morphology and establish an important first step towards discerning the underlying transport properties of perovskite materials.

Multi-length scale tomography for the determination and optimization of the effective microstructural properties in novel hierarchical solid oxide fuel cell anodes

NASA Astrophysics Data System (ADS)

Lu, Xuekun; Taiwo, Oluwadamilola O.; Bertei, Antonio; Li, Tao; Li, Kang; Brett, Dan J. L.; Shearing, Paul R.

2017-11-01

Effective microstructural properties are critical in determining the electrochemical performance of solid oxide fuel cells (SOFCs), particularly when operating at high current densities. A novel tubular SOFC anode with a hierarchical microstructure, composed of self-organized micro-channels and sponge-like regions, has been fabricated by a phase inversion technique to mitigate concentration losses. However, since pore sizes span over two orders of magnitude, the determination of the effective transport parameters using image-based techniques remains challenging. Pioneering steps are made in this study to characterize and optimize the microstructure by coupling multi-length scale 3D tomography and modeling. The results conclusively show that embedding finger-like micro-channels into the tubular anode can improve the mass transport by 250% and the permeability by 2-3 orders of magnitude. Our parametric study shows that increasing the porosity in the spongy layer beyond 10% enhances the effective transport parameters of the spongy layer at an exponential rate, but linearly for the full anode. For the first time, local and global mass transport properties are correlated to the microstructure, which is of wide interest for rationalizing the design optimization of SOFC electrodes and more generally for hierarchical materials in batteries and membranes.

PENGEOM-A general-purpose geometry package for Monte Carlo simulation of radiation transport in material systems defined by quadric surfaces

NASA Astrophysics Data System (ADS)

Almansa, Julio; Salvat-Pujol, Francesc; Díaz-Londoño, Gloria; Carnicer, Artur; Lallena, Antonio M.; Salvat, Francesc

2016-02-01

The Fortran subroutine package PENGEOM provides a complete set of tools to handle quadric geometries in Monte Carlo simulations of radiation transport. The material structure where radiation propagates is assumed to consist of homogeneous bodies limited by quadric surfaces. The PENGEOM subroutines (a subset of the PENELOPE code) track particles through the material structure, independently of the details of the physics models adopted to describe the interactions. Although these subroutines are designed for detailed simulations of photon and electron transport, where all individual interactions are simulated sequentially, they can also be used in mixed (class II) schemes for simulating the transport of high-energy charged particles, where the effect of soft interactions is described by the random-hinge method. The definition of the geometry and the details of the tracking algorithm are tailored to optimize simulation speed. The use of fuzzy quadric surfaces minimizes the impact of round-off errors. The provided software includes a Java graphical user interface for editing and debugging the geometry definition file and for visualizing the material structure. Images of the structure are generated by using the tracking subroutines and, hence, they describe the geometry actually passed to the simulation code.

PCR detection of groundwater bacteria associated with colloidal transport

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

Cruz-Perez, P.; Stetzenbach, L.D.; Alvarez, A.J.

1996-02-29

Colloidal transport may increase the amount of contaminant material than that which could be transported by water flow alone. The role of colloids in groundwater contaminant transport is complicated and may involve many different processes, including sorption of elements onto colloidal particles, coagulation/dissolution, adsorption onto solid surfaces, filtration, and migration. Bacteria are known to concentrate minerals and influence the transport of compounds in aqueous environments and may also serve as organic colloids, thereby influencing subsurface transport of radionuclides and other contaminants. The initial phase of the project consisted of assembling a list of bacteria capable of sequestering or facilitating mineralmore » transport. The development and optimization of the PCR amplification assay for the detection of the organisms of interest, and the examination of regional groundwaters for those organisms, are presented for subsequent research.« less

Optimization Shield Materials Trade Study for Lunar/Gateway Mission

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.; Anderson, B. M.; Simonsen, L. C.

2002-01-01

The great cost of added radiation shielding is a potential limiting factor in many deep space missions. For this enabling technology, we are developing tools for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of various space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. Preliminary studies of deep space missions indicate that for long duration space missions, improved shield materials will be required. The details of this new method and its impact on space missions and other technologies will be discussed. This study will provide a vital tool for evaluating Gateway designs in their usage context. Providing protection against the hazards of space radiation is one of the challenges to the Gateway infrastructure designs. We will use the mission optimization software to scope the impact of Gateway operations on human exposures and the effectiveness of alternate shielding materials on Gateway infrastructure designs. It is being proposed to use Moon and the Lagrange points as the hub for deep space missions. This study will provide a guide to the effectiveness of multifunctional materials in preparation to more detailed geometry studies in progress.

Hole-Transport Materials for Perovskite Solar Cells.

PubMed

Calió, Laura; Kazim, Samrana; Grätzel, Michael; Ahmad, Shahzada

2016-11-14

The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cellular water distribution, transport, and its investigation methods for plant-based food material.

PubMed

Khan, Md Imran H; Karim, M A

2017-09-01

Heterogeneous and hygroscopic characteristics of plant-based food material make it complex in structure, and therefore water distribution in its different cellular environments is very complex. There are three different cellular environments, namely the intercellular environment, the intracellular environment, and the cell wall environment inside the food structure. According to the bonding strength, intracellular water is defined as loosely bound water, cell wall water is categorized as strongly bound water, and intercellular water is known as free water (FW). During food drying, optimization of the heat and mass transfer process is crucial for the energy efficiency of the process and the quality of the product. For optimizing heat and mass transfer during food processing, understanding these three types of waters (strongly bound, loosely bound, and free water) in plant-based food material is essential. However, there are few studies that investigate cellular level water distribution and transport. As there is no direct method for determining the cellular level water distributions, various indirect methods have been applied to investigate the cellular level water distribution, and there is, as yet, no consensus on the appropriate method for measuring cellular level water in plant-based food material. Therefore, the main aim of this paper is to present a comprehensive review on the available methods to investigate the cellular level water, the characteristics of water at different cellular levels and its transport mechanism during drying. The effect of bound water transport on quality of food product is also discussed. This review article presents a comparative study of different methods that can be applied to investigate cellular water such as nuclear magnetic resonance (NMR), bioelectric impedance analysis (BIA), differential scanning calorimetry (DSC), and dilatometry. The article closes with a discussion of current challenges to investigating cellular water. Copyright © 2017 Elsevier Ltd. All rights reserved.

Achieving Optimal Self-Adaptivity for Dynamic Tuning of Organic Semiconductors through Resonance Engineering.

PubMed

Tao, Ye; Xu, Lijia; Zhang, Zhen; Chen, Runfeng; Li, Huanhuan; Xu, Hui; Zheng, Chao; Huang, Wei

2016-08-03

Current static-state explorations of organic semiconductors for optimal material properties and device performance are hindered by limited insights into the dynamically changed molecular states and charge transport and energy transfer processes upon device operation. Here, we propose a simple yet successful strategy, resonance variation-based dynamic adaptation (RVDA), to realize optimized self-adaptive properties in donor-resonance-acceptor molecules by engineering the resonance variation for dynamic tuning of organic semiconductors. Organic light-emitting diodes hosted by these RVDA materials exhibit remarkably high performance, with external quantum efficiencies up to 21.7% and favorable device stability. Our approach, which supports simultaneous realization of dynamically adapted and selectively enhanced properties via resonance engineering, illustrates a feasible design map for the preparation of smart organic semiconductors capable of dynamic structure and property modulations, promoting the studies of organic electronics from static to dynamic.

Bayesian Lagrangian Data Assimilation and Drifter Deployment Strategies

NASA Astrophysics Data System (ADS)

Dutt, A.; Lermusiaux, P. F. J.

2017-12-01

Ocean currents transport a variety of natural (e.g. water masses, phytoplankton, zooplankton, sediments, etc.) and man-made materials and other objects (e.g. pollutants, floating debris, search and rescue, etc.). Lagrangian Coherent Structures (LCSs) or the most influential/persistent material lines in a flow, provide a robust approach to characterize such Lagrangian transports and organize classic trajectories. Using the flow-map stochastic advection and a dynamically-orthogonal decomposition, we develop uncertainty prediction schemes for both Eulerian and Lagrangian variables. We then extend our Bayesian Gaussian Mixture Model (GMM)-DO filter to a joint Eulerian-Lagrangian Bayesian data assimilation scheme. The resulting nonlinear filter allows the simultaneous non-Gaussian estimation of Eulerian variables (e.g. velocity, temperature, salinity, etc.) and Lagrangian variables (e.g. drifter/float positions, trajectories, LCSs, etc.). Its results are showcased using a double-gyre flow with a random frequency, a stochastic flow past a cylinder, and realistic ocean examples. We further show how our Bayesian mutual information and adaptive sampling equations provide a rigorous efficient methodology to plan optimal drifter deployment strategies and predict the optimal times, locations, and types of measurements to be collected.

Optimizing the Dopant and Carrier Concentration of Ca5Al2Sb6 for High Thermoelectric Efficiency

PubMed Central

Yan, Yuli; Zhang, Guangbiao; Wang, Chao; Peng, Chengxiao; Zhang, Peihong; Wang, Yuanxu; Ren, Wei

2016-01-01

The effects of doping on the transport properties of Ca5Al2Sb6 are investigated using first-principles electronic structure methods and Boltzmann transport theory. The calculated results show that a maximum ZT value of 1.45 is achieved with an optimum carrier concentration at 1000 K. However, experimental studies have shown that the maximum ZT value is no more than 1 at 1000 K. By comparing the calculated Seebeck coefficient with experimental values, we find that the low dopant solubility in this material is not conductive to achieve the optimum carrier concentration, leading a smaller experimental value of the maximum ZT. Interestingly, the calculated dopant formation energies suggest that optimum carrier concentrations can be achieved when the dopants and Sb atoms have similar electronic configurations. Therefore, it might be possible to achieve a maximum ZT value of 1.45 at 1000 K with suitable dopants. These results provide a valuable theoretical guidance for the synthesis of high-performance bulk thermoelectric materials through dopants optimization. PMID:27406178

Passivated p-type silicon: Hole injection tunable anode material for organic light emission

NASA Astrophysics Data System (ADS)

Zhao, W. Q.; Ran, G. Z.; Xu, W. J.; Qin, G. G.

2008-02-01

We find that hole injection can be enhanced simply by selecting a lower-resistivity p-Si anode to match an electron injection enhancement for organic light emitting diodes with ultrathin-SiO2-layer-passivated p-Si anode (Si-OLED). For a Si-OLED with ordinary AlQ electron transport layer, the optimized resistivity of the p-Si anode is 40Ωcm; for that with n-doped Bphen electron transport layer, it decreases to 5Ωcm. Correspondingly, the maximum power efficiency increases from 0.3to1.9lm /W, even higher than that of an indium tin oxide control device (1.4lm/W). This passivated p-type silicon is a hole injection tunable anode material for OLED.

Efficient hybrid white organic light-emitting diodes for application of triplet harvesting with simple structure

NASA Astrophysics Data System (ADS)

Hwang, Kyo Min; Lee, Song Eun; Lee, Sungkyu; Yoo, Han Kyu; Baek, Hyun Jung; Kim, Young Kwan; Kim, Jwajin; Yoon, Seung Soo

2016-08-01

In this study, we fabricated hybrid white organic light-emitting diodes (WOLEDs) based on triplet harvesting with a simple structure. All the hole transporting material and host in the emitting layer (EML) of devices utilized the same material N,N'-di-1-naphthalenyl-N,N'-diphenyl [1,1':4',1″:4″,1‴-quaterphenyl]-4,4‴-diamine (4P-NPD), which is known to be blue fluorescent material. Simple hybrid WOLEDs were fabricated with blue fluorescent, green and red phosphorescent materials. We investigated the effect of triplet harvesting (TH) by an exciton generation zone on simple hybrid WOLEDs. The simple hybrid WOLEDs characteristically had a dominant hole mobility, so an exciton generation zone was expected in the EML. Additionally, the optimal the thickness of the hole transporting layer and electron transporting layer was fabricated a simple hybrid WOLEDs. The simple hybrid WOLED exhibits a maximum luminous efficiency of 29.3 cd/A and a maximum external quantum efficiency of 11.2%. The Commission Internationale de l'Éclairage (International Commission on Illumination) coordinates were (0.45, 0.43) at about 10,000 cd/m2.

Mass transport in morphogenetic processes: A second gradient theory for volumetric growth and material remodeling

NASA Astrophysics Data System (ADS)

Ciarletta, P.; Ambrosi, D.; Maugin, G. A.

2012-03-01

In this work, we derive a novel thermo-mechanical theory for growth and remodeling of biological materials in morphogenetic processes. This second gradient hyperelastic theory is the first attempt to describe both volumetric growth and mass transport phenomena in a single-phase continuum model, where both stress- and shape-dependent growth regulations can be investigated. The diffusion of biochemical species (e.g. morphogens, growth factors, migration signals) inside the material is driven by configurational forces, enforced in the balance equations and in the set of constitutive relations. Mass transport is found to depend both on first- and on second-order material connections, possibly withstanding a chemotactic behavior with respect to diffusing molecules. We find that the driving forces of mass diffusion can be written in terms of covariant material derivatives reflecting, in a purely geometrical manner, the presence of a (first-order) torsion and a (second-order) curvature. Thermodynamical arguments show that the Eshelby stress and hyperstress tensors drive the rearrangement of the first- and second-order material inhomogeneities, respectively. In particular, an evolution law is proposed for the first-order transplant, extending a well-known result for inelastic materials. Moreover, we define the first stress-driven evolution law of the second-order transplant in function of the completely material Eshelby hyperstress. The theory is applied to two biomechanical examples, showing how an Eshelbian coupling can coordinate volumetric growth, mass transport and internal stress state, both in physiological and pathological conditions. Finally, possible applications of the proposed model are discussed for studying the unknown regulation mechanisms in morphogenetic processes, as well as for optimizing scaffold architecture in regenerative medicine and tissue engineering.

Taking the Pulse of Plants

NASA Astrophysics Data System (ADS)

Jensen, Kaare H.; Beecher, Sierra; Holbrook, N. Michele; Knoblauch, Michael

2014-11-01

Many biological systems use complex networks of vascular conduits to distribute energy over great distances. Examples include sugar transport in the phloem tissue of vascular plants and cytoplasmic streaming in some slime molds. Detailed knowledge of transport patterns in these systems is important for our fundamental understanding of energy distribution during development and for engineering of more efficient crops. Current techniques for quantifying transport in these microfluidic systems, however, only allow for the determination of either the flow speed or the concentration of material. Here we demonstrate a new method, based on confocal microscopy, which allows us to simultaneously determine velocity and solute concentration by tracking the dispersion of a tracer dye. We attempt to rationalize the observed transport patterns through consideration of constrained optimization problems.

Aerothermodynamic testing requirements for future space transportation systems

NASA Technical Reports Server (NTRS)

Paulson, John W., Jr.; Miller, Charles G., III

1995-01-01

Aerothermodynamics, encompassing aerodynamics, aeroheating, and fluid dynamic and physical processes, is the genesis for the design and development of advanced space transportation vehicles. It provides crucial information to other disciplines involved in the development process such as structures, materials, propulsion, and avionics. Sources of aerothermodynamic information include ground-based facilities, computational fluid dynamic (CFD) and engineering computer codes, and flight experiments. Utilization of this triad is required to provide the optimum requirements while reducing undue design conservatism, risk, and cost. This paper discusses the role of ground-based facilities in the design of future space transportation system concepts. Testing methodology is addressed, including the iterative approach often required for the assessment and optimization of configurations from an aerothermodynamic perspective. The influence of vehicle shape and the transition from parametric studies for optimization to benchmark studies for final design and establishment of the flight data book is discussed. Future aerothermodynamic testing requirements including the need for new facilities are also presented.

Slide Conveying of Granular Materials-Thinking Out of the Glovebox

NASA Technical Reports Server (NTRS)

Goddard, J. D.; Didwania, A. K.; Nott, P. R.

2000-01-01

The vibratory conveyor, routinely employed for normal-gravity transport of granular materials, usually consists of a continuous open trough vibrated sinusoidally to induce axial movement of a granular material. Motivated in part by a hypothetical application in zero gravity, we propose a novel modification of the vibratory conveyor based on a closed 2d trough operating in a "slide-conveying" mode, with the granular mass remaining permanently in contact with the trough walls. We present a detailed analysis of the mechanics of transport, based on a rigid-slab model for the granular mass with frictional (Coulomb) slip at the upper and lower walls. The form of the vibration cycle plays a crucial role, and the optimal conveying cycle is not the commonly assumed rectilinear sinusoidal motion. The conveying efficiency for the novel slide conveyor will be presented for several simple vibration cycles, including one believed to represent the theoretical optimum.

Building mud castles: a perspective from brick-laying termites.

PubMed

Zachariah, Nikita; Das, Aritra; Murthy, Tejas G; Borges, Renee M

2017-07-05

Animal constructions such as termite mounds have received scrutiny by architects, structural engineers, soil scientists and behavioural ecologists but their basic building blocks remain uncharacterized and the criteria used for material selection unexplored. By conducting controlled experiments on Odontotermes obesus termites, we characterize the building blocks of termite mounds and determine the key elements defining material choice and usage by these accomplished engineers. Using biocement and a self-organized process, termites fabricate, transport and assemble spherical unitary structures called boluses that have a bimodal size distribution, achieving an optimal packing solution for mound construction. Granular, hydrophilic, osmotically inactive, non-hygroscopic materials with surface roughness, rigidity and containing organic matter are the easiest to handle and are crucial determinants of mass transfer during mound construction. We suggest that these properties, along with optimal moisture availability, are important predictors of the global geographic distribution of termites.

Integrated aerodynamic-structural design of a forward-swept transport wing

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.; Grossman, Bernard; Kao, Pi-Jen; Polen, David M.; Sobieszczanski-Sobieski, Jaroslaw

1989-01-01

The introduction of composite materials is having a profound effect on aircraft design. Since these materials permit the designer to tailor material properties to improve structural, aerodynamic and acoustic performance, they require an integrated multidisciplinary design process. Futhermore, because of the complexity of the design process, numerical optimization methods are required. The utilization of integrated multidisciplinary design procedures for improving aircraft design is not currently feasible because of software coordination problems and the enormous computational burden. Even with the expected rapid growth of supercomputers and parallel architectures, these tasks will not be practical without the development of efficient methods for cross-disciplinary sensitivities and efficient optimization procedures. The present research is part of an on-going effort which is focused on the processes of simultaneous aerodynamic and structural wing design as a prototype for design integration. A sequence of integrated wing design procedures has been developed in order to investigate various aspects of the design process.

High-efficiency hybrid solar cells based on polymer/PbSx Se1-x nanocrystals benefiting from vertical phase segregation.

PubMed

Liu, Zeke; Sun, Yaxiang; Yuan, Jianyu; Wei, Huaixin; Huang, Xiaodong; Han, Lu; Wang, Weiwei; Wang, Haiqiao; Ma, Wanli

2013-10-25

Solution-processed hybrid solar cells employing a low band-gap polymer and PbSx Se1-x alloy nanocrystals, achieving a record high PCE of 5.50% and an optimal FF of 67% are presented. The remarkable device efficiency can be attributed to the high-performance active materials, the optimal polymer/NCs ratio and, more importantly, the vertical donor/(donor:acceptor)/acceptor structure which benefits charge dissociation and transport. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic materials and devices for the 21st century: stronger, lighter, and more energy efficient.

PubMed

Gutfleisch, Oliver; Willard, Matthew A; Brück, Ekkes; Chen, Christina H; Sankar, S G; Liu, J Ping

2011-02-15

A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy efficiency in the total energy lifecycle, has accelerated research into energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the efficiency and performance of devices in electric power generation, conditioning, conversion, transportation, and other energy-use sectors of the economy. This review focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials, with an emphasis on their optimization for energy applications. Specifically, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, are discussed. The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure-property relationships, are discussed in the context of their respective markets, as well as their potential impact on energy efficiency. Finally, considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Semiconductor apparatus utilizing gradient freeze and liquid-solid techniques

NASA Technical Reports Server (NTRS)

Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

1998-01-01

Transition metals of Group VIII (Co, Rh and Ir) have been prepared as semiconductor compounds with the general formula TSb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using vertical gradient freezing techniques and/or liquid phase sintering techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities (up to 1200 cm.sup.2.V.sup.-1.s.sup.-1) and good Seebeck coefficients (up to 150 .mu.VK.sup.-1 between 300.degree. C. and 700.degree. C.). Optimizing the transport properties of semiconductor materials prepared from elemental mixtures Co, Rh, Ir and Sb resulted in a substantial increase in the thermoelectric figure of merit (ZT) at temperatures as high as 400.degree. C. for thermoelectric elements fabricated from such semiconductor materials.

Materials Genome in Action: Identifying the Performance Limits of Physical Hydrogen Storage

PubMed Central

2017-01-01

The Materials Genome is in action: the molecular codes for millions of materials have been sequenced, predictive models have been developed, and now the challenge of hydrogen storage is targeted. Renewably generated hydrogen is an attractive transportation fuel with zero carbon emissions, but its storage remains a significant challenge. Nanoporous adsorbents have shown promising physical adsorption of hydrogen approaching targeted capacities, but the scope of studies has remained limited. Here the Nanoporous Materials Genome, containing over 850 000 materials, is analyzed with a variety of computational tools to explore the limits of hydrogen storage. Optimal features that maximize net capacity at room temperature include pore sizes of around 6 Å and void fractions of 0.1, while at cryogenic temperatures pore sizes of 10 Å and void fractions of 0.5 are optimal. Our top candidates are found to be commercially attractive as “cryo-adsorbents”, with promising storage capacities at 77 K and 100 bar with 30% enhancement to 40 g/L, a promising alternative to liquefaction at 20 K and compression at 700 bar. PMID:28413259

Materials genome in action: Identifying the performance limits of physical hydrogen storage

DOE PAGES

Thornton, Aaron W.; Simon, Cory M.; Kim, Jihan; ...

2017-03-08

The Materials Genome is in action: the molecular codes for millions of materials have been sequenced, predictive models have been developed, and now the challenge of hydrogen storage is targeted. Renewably generated hydrogen is an attractive transportation fuel with zero carbon emissions, but its storage remains a significant challenge. Nanoporous adsorbents have shown promising physical adsorption of hydrogen approaching targeted capacities, but the scope of studies has remained limited. Here the Nanoporous Materials Genome, containing over 850 000 materials, is analyzed with a variety of computational tools to explore the limits of hydrogen storage. Optimal features that maximize net capacitymore » at room temperature include pore sizes of around 6 Å and void fractions of 0.1, while at cryogenic temperatures pore sizes of 10 Å and void fractions of 0.5 are optimal. Finally, our top candidates are found to be commercially attractive as “cryo-adsorbents”, with promising storage capacities at 77 K and 100 bar with 30% enhancement to 40 g/L, a promising alternative to liquefaction at 20 K and compression at 700 bar.« less

Materials genome in action: Identifying the performance limits of physical hydrogen storage

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

Thornton, Aaron W.; Simon, Cory M.; Kim, Jihan

The Materials Genome is in action: the molecular codes for millions of materials have been sequenced, predictive models have been developed, and now the challenge of hydrogen storage is targeted. Renewably generated hydrogen is an attractive transportation fuel with zero carbon emissions, but its storage remains a significant challenge. Nanoporous adsorbents have shown promising physical adsorption of hydrogen approaching targeted capacities, but the scope of studies has remained limited. Here the Nanoporous Materials Genome, containing over 850 000 materials, is analyzed with a variety of computational tools to explore the limits of hydrogen storage. Optimal features that maximize net capacitymore » at room temperature include pore sizes of around 6 Å and void fractions of 0.1, while at cryogenic temperatures pore sizes of 10 Å and void fractions of 0.5 are optimal. Finally, our top candidates are found to be commercially attractive as “cryo-adsorbents”, with promising storage capacities at 77 K and 100 bar with 30% enhancement to 40 g/L, a promising alternative to liquefaction at 20 K and compression at 700 bar.« less

Optimal perturbations for nonlinear systems using graph-based optimal transport

NASA Astrophysics Data System (ADS)

Grover, Piyush; Elamvazhuthi, Karthik

2018-06-01

We formulate and solve a class of finite-time transport and mixing problems in the set-oriented framework. The aim is to obtain optimal discrete-time perturbations in nonlinear dynamical systems to transport a specified initial measure on the phase space to a final measure in finite time. The measure is propagated under system dynamics in between the perturbations via the associated transfer operator. Each perturbation is described by a deterministic map in the measure space that implements a version of Monge-Kantorovich optimal transport with quadratic cost. Hence, the optimal solution minimizes a sum of quadratic costs on phase space transport due to the perturbations applied at specified times. The action of the transport map is approximated by a continuous pseudo-time flow on a graph, resulting in a tractable convex optimization problem. This problem is solved via state-of-the-art solvers to global optimality. We apply this algorithm to a problem of transport between measures supported on two disjoint almost-invariant sets in a chaotic fluid system, and to a finite-time optimal mixing problem by choosing the final measure to be uniform. In both cases, the optimal perturbations are found to exploit the phase space structures, such as lobe dynamics, leading to efficient global transport. As the time-horizon of the problem is increased, the optimal perturbations become increasingly localized. Hence, by combining the transfer operator approach with ideas from the theory of optimal mass transportation, we obtain a discrete-time graph-based algorithm for optimal transport and mixing in nonlinear systems.

Detecting Shielded Special Nuclear Materials Using Multi-Dimensional Neutron Source and Detector Geometries

NASA Astrophysics Data System (ADS)

Santarius, John; Navarro, Marcos; Michalak, Matthew; Fancher, Aaron; Kulcinski, Gerald; Bonomo, Richard

2016-10-01

A newly initiated research project will be described that investigates methods for detecting shielded special nuclear materials by combining multi-dimensional neutron sources, forward/adjoint calculations modeling neutron and gamma transport, and sparse data analysis of detector signals. The key tasks for this project are: (1) developing a radiation transport capability for use in optimizing adaptive-geometry, inertial-electrostatic confinement (IEC) neutron source/detector configurations for neutron pulses distributed in space and/or phased in time; (2) creating distributed-geometry, gas-target, IEC fusion neutron sources; (3) applying sparse data and noise reduction algorithms, such as principal component analysis (PCA) and wavelet transform analysis, to enhance detection fidelity; and (4) educating graduate and undergraduate students. Funded by DHS DNDO Project 2015-DN-077-ARI095.

Optimization of metallic microheaters for high-speed reconfigurable silicon photonics.

PubMed

Atabaki, A H; Shah Hosseini, E; Eftekhar, A A; Yegnanarayanan, S; Adibi, A

2010-08-16

The strong thermooptic effect in silicon enables low-power and low-loss reconfiguration of large-scale silicon photonics. Thermal reconfiguration through the integration of metallic microheaters has been one of the more widely used reconfiguration techniques in silicon photonics. In this paper, structural and material optimizations are carried out through heat transport modeling to improve the reconfiguration speed of such devices, and the results are experimentally verified. Around 4 micros reconfiguration time are shown for the optimized structures. Moreover, sub-microsecond reconfiguration time is experimentally demonstrated through the pulsed excitation of the microheaters. The limitation of this pulsed excitation scheme is also discussed through an accurate system-level model developed for the microheater response.

Functionalized graphene and other two-dimensional materials for photovoltaic devices: device design and processing.

PubMed

Liu, Zhike; Lau, Shu Ping; Yan, Feng

2015-08-07

Graphene is the thinnest two-dimensional (2D) carbon material and has many advantages including high carrier mobilities and conductivity, high optical transparency, excellent mechanical flexibility and chemical stability, which make graphene an ideal material for various optoelectronic devices. The major applications of graphene in photovoltaic devices are for transparent electrodes and charge transport layers. Several other 2D materials have also shown advantages in charge transport and light absorption over traditional semiconductor materials used in photovoltaic devices. Great achievements in the applications of 2D materials in photovoltaic devices have been reported, yet numerous challenges still remain. For practical applications, the device performance should be further improved by optimizing the 2D material synthesis, film transfer, surface functionalization and chemical/physical doping processes. In this review, we will focus on the recent advances in the applications of graphene and other 2D materials in various photovoltaic devices, including organic solar cells, Schottky junction solar cells, dye-sensitized solar cells, quantum dot-sensitized solar cells, other inorganic solar cells, and perovskite solar cells, in terms of the functionalization techniques of the materials, the device design and the device performance. Finally, conclusions and an outlook for the future development of this field will be addressed.

Review of electronic transport models for thermoelectric materials

NASA Astrophysics Data System (ADS)

Bulusu, A.; Walker, D. G.

2008-07-01

Thermoelectric devices have gained importance in recent years as viable solutions for applications such as spot cooling of electronic components, remote power generation in space stations and satellites etc. These solid-state devices have long been known for their reliability rather than their efficiency; they contain no moving parts, and their performance relies primarily on material selection, which has not generated many excellent candidates. Research in recent years has been focused on developing both thermoelectric structures and materials that have high efficiency. In general, thermoelectric research is two-pronged with (1) experiments focused on finding new materials and structures with enhanced thermoelectric performance and (2) analytical models that predict thermoelectric behavior to enable better design and optimization of materials and structures. While numerous reviews have discussed the importance of and dependence on materials for thermoelectric performance, an overview of how to predict the performance of various materials and structures based on fundamental quantities is lacking. In this paper we present a review of the theoretical models that were developed since thermoelectricity was first observed in 1821 by Seebeck and how these models have guided experimental material search for improved thermoelectric devices. A new quantum model is also presented, which provides opportunities for the optimization of nanoscale materials to enhance thermoelectric performance.

The intrinsic disorder related alloy scattering in ZrNiSn half-Heusler thermoelectric materials

PubMed Central

Xie, Hanhui; Wang, Heng; Fu, Chenguang; Liu, Yintu; Snyder, G. Jeffrey; Zhao, Xinbing; Zhu, Tiejun

2014-01-01

The intrinsic structural disorder dramatically affects the thermal and electronic transport in semiconductors. Although normally considered an ordered compound, the half-Heusler ZrNiSn displays many transport characteristics of a disordered alloy. Similar to the (Zr,Hf)NiSn based solid solutions, the unsubstituted ZrNiSn compound also exhibits charge transport dominated by alloy scattering, as demonstrated in this work. The unexpected charge transport, even in ZrNiSn which is normally considered fully ordered, can be explained by the Ni partially filling interstitial sites in this half-Heusler system. The influence of the disordering and defects in crystal structure on the electron transport process has also been quantitatively analyzed in ZrNiSn1-xSbx with carrier concentration nH ranging from 5.0×1019 to 2.3×1021 cm−3 by changing Sb dopant content. The optimized carrier concentration nH ≈ 3–4×1020 cm−2 results in ZT ≈ 0.8 at 875K. This work suggests that MNiSn (M = Hf, Zr, Ti) and perhaps most other half-Heusler thermoelectric materials should be considered highly disordered especially when trying to understand the electronic and phonon structure and transport features. PMID:25363573

Numerical convergence and validation of the DIMP inverse particle transport model

DOE PAGES

Nelson, Noel; Azmy, Yousry

2017-09-01

The data integration with modeled predictions (DIMP) model is a promising inverse radiation transport method for solving the special nuclear material (SNM) holdup problem. Unlike previous methods, DIMP is a completely passive nondestructive assay technique that requires no initial assumptions regarding the source distribution or active measurement time. DIMP predicts the most probable source location and distribution through Bayesian inference and quasi-Newtonian optimization of predicted detector re-sponses (using the adjoint transport solution) with measured responses. DIMP performs well with for-ward hemispherical collimation and unshielded measurements, but several considerations are required when using narrow-view collimated detectors. DIMP converged well to themore » correct source distribution as the number of synthetic responses increased. DIMP also performed well for the first experimental validation exercise after applying a collimation factor, and sufficiently reducing the source search vol-ume's extent to prevent the optimizer from getting stuck in local minima. DIMP's simple point detector response function (DRF) is being improved to address coplanar false positive/negative responses, and an angular DRF is being considered for integration with the next version of DIMP to account for highly collimated responses. Overall, DIMP shows promise for solving the SNM holdup inverse problem, especially once an improved optimization algorithm is implemented.« less

Optimization and evaluation of gastroretentive ranitidine HCl microspheres by using design expert software.

PubMed

Hooda, Aashima; Nanda, Arun; Jain, Manish; Kumar, Vikash; Rathee, Permender

2012-12-01

The current study involves the development and optimization of their drug entrapment and ex vivo bioadhesion of multiunit chitosan based floating system containing Ranitidine HCl by ionotropic gelation method for gastroretentive delivery. Chitosan being cationic, non-toxic, biocompatible, biodegradable and bioadhesive is frequently used as a material for drug delivery systems and used to transport a drug to an acidic environment where it enhances the transport of polar drugs across epithelial surfaces. The effect of various process variables like drug polymer ratio, concentration of sodium tripolyphosphate and stirring speed on various physiochemical properties like drug entrapment efficiency, particle size and bioadhesion was optimized using central composite design and analyzed using response surface methodology. The observed responses were coincided well with the predicted values given by the optimization technique. The optimized microspheres showed drug entrapment efficiency of 74.73%, particle size 707.26 μm and bioadhesion 71.68% in simulated gastric fluid (pH 1.2) after 8 h with floating lag time 40s. The average size of all the dried microspheres ranged from 608.24 to 720.80 μm. The drug entrapment efficiency of microspheres ranged from 41.67% to 87.58% and bioadhesion ranged from 62% to 86%. Accelerated stability study was performed on optimized formulation as per ICH guidelines and no significant change was found in drug content on storage. Copyright © 2012 Elsevier B.V. All rights reserved.

Development of large area nanostructured silicon-hydrogen alloy material with improved stability for solar cell application by argon dilution method

NASA Astrophysics Data System (ADS)

Dey, Arka; Das, Mrinmay; Datta, Joydeep; Jana, Rajkumar; Dhar, Joydeep; Sil, Sayantan; Biswas, Debasish; Banerjee, Chandan; Ray, Partha Pratim

2016-07-01

Here we have presented the results of large area (30 × 30 cm2) silicon-hydrogen alloy material and solar cell by argon dilution method. As an alternative to hydrogen dilution, argon dilution method has been applied to develop single junction solar cell with appreciable stability. Optimization of deposition conditions revealed that 95% argon dilution gives a nanostructured material with improved transport property and less light induced degradation. The minority carrier diffusion length (L d ) and mobility-lifetime (μτ) product of the material with 95% argon dilution degrades least after light soaking. Also the density of states (DOS) below conduction level reveals that this material is less defective. Solar cell with this argon diluted material has been fabricated with all the layers deposited by argon dilution method. Finally we have compared the argon diluted solar cell results with the optimized hydrogen diluted solar cell. Light soaking study proves that it is possible to develop stable solar cell on large area by argon dilution method and that the degradation of argon diluted solar cell is less than that of hydrogen diluted one. [Figure not available: see fulltext.

Optimizing Transportation of Disaster Relief Material to Support U.S. Pacific Command Foreign Humanitarian Assistance Operations

DTIC Science & Technology

2013-03-01

Approved by: W. Matthew Carlyle, Professor Thesis Advisor Walter DeGrange, CDR, SC, USN Second Reader Robert F. Dell Chair...x THIS PAGE INTENTIONALLY LEFT BLANK xi LIST OF TABLES Table 1.  Disaster Relief Airlift Planner results for Malaysia cyclone scenario with...Planner results for Malaysia cyclone scenario with aircraft allocation varying

Current-limiting challenges for all-spin logic devices

PubMed Central

Su, Li; Zhang, Youguang; Klein, Jacques-Olivier; Zhang, Yue; Bournel, Arnaud; Fert, Albert; Zhao, Weisheng

2015-01-01

All-spin logic device (ASLD) has attracted increasing interests as one of the most promising post-CMOS device candidates, thanks to its low power, non-volatility and logic-in-memory structure. Here we investigate the key current-limiting factors and develop a physics-based model of ASLD through nano-magnet switching, the spin transport properties and the breakdown characteristic of channel. First, ASLD with perpendicular magnetic anisotropy (PMA) nano-magnet is proposed to reduce the critical current (Ic0). Most important, the spin transport efficiency can be enhanced by analyzing the device structure, dimension, contact resistance as well as material parameters. Furthermore, breakdown current density (JBR) of spin channel is studied for the upper current limitation. As a result, we can deduce current-limiting conditions and estimate energy dissipation. Based on the model, we demonstrate ASLD with different structures and channel materials (graphene and copper). Asymmetric structure is found to be the optimal option for current limitations. Copper channel outperforms graphene in term of energy but seriously suffers from breakdown current limit. By exploring the current limit and performance tradeoffs, the optimization of ASLD is also discussed. This benchmarking model of ASLD opens up new prospects for design and implementation of future spintronics applications. PMID:26449410

System-wide organization of actin cytoskeleton determines organelle transport in hypocotyl plant cells

PubMed Central

Nowak, Jacqueline; Ivakov, Alexander; Somssich, Marc; Persson, Staffan; Nikoloski, Zoran

2017-01-01

The actin cytoskeleton is an essential intracellular filamentous structure that underpins cellular transport and cytoplasmic streaming in plant cells. However, the system-level properties of actin-based cellular trafficking remain tenuous, largely due to the inability to quantify key features of the actin cytoskeleton. Here, we developed an automated image-based, network-driven framework to accurately segment and quantify actin cytoskeletal structures and Golgi transport. We show that the actin cytoskeleton in both growing and elongated hypocotyl cells has structural properties facilitating efficient transport. Our findings suggest that the erratic movement of Golgi is a stable cellular phenomenon that might optimize distribution efficiency of cell material. Moreover, we demonstrate that Golgi transport in hypocotyl cells can be accurately predicted from the actin network topology alone. Thus, our framework provides quantitative evidence for system-wide coordination of cellular transport in plant cells and can be readily applied to investigate cytoskeletal organization and transport in other organisms. PMID:28655850

Design issues for optimum solar cell configuration

NASA Astrophysics Data System (ADS)

Kumar, Atul; Thakur, Ajay D.

2018-05-01

A computer based simulation of solar cell structure is performed to study the optimization of pn junction configuration for photovoltaic action. The fundamental aspects of photovoltaic action viz, absorption, separation collection, and their dependence on material properties and deatails of device structures is discussed. Using SCAPS 1D we have simulated the ideal pn junction and shown the effect of band offset and carrier densities on solar cell performance. The optimum configuration can be achieved by optimizing transport of carriers in pn junction under effect of field dependent recombination (tunneling) and density dependent recombination (SRH, Auger) mechanisms.

Optimal thickness of silicon membranes to achieve maximum thermoelectric efficiency: A first principles study

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

Mangold, Claudia; Neogi, Sanghamitra; Max Planck Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz

2016-08-01

Silicon nanostructures with reduced dimensionality, such as nanowires, membranes, and thin films, are promising thermoelectric materials, as they exhibit considerably reduced thermal conductivity. Here, we utilize density functional theory and Boltzmann transport equation to compute the electronic properties of ultra-thin crystalline silicon membranes with thickness between 1 and 12 nm. We predict that an optimal thickness of ∼7 nm maximizes the thermoelectric figure of merit of membranes with native oxide surface layers. Further thinning of the membranes, although attainable in experiments, reduces the electrical conductivity and worsens the thermoelectric efficiency.

Molecular dynamics simulations of Li transport between cathode crystals

NASA Astrophysics Data System (ADS)

Garofalini, S. H.

The molecular dynamics (MD) computer simulation technique has been used to study the effect of an amorphous intergranular film (IGF) present in a polycrystalline cathode on Li transport. The solid electrolyte is a model lithium silicate glass while the cathode is a nanocrystalline vanadia with an amorphous V 2O 5 IGF separating the crystals. Thin (˜1 to a few nanometer thick) IGFs are known to be present in most polycrystalline oxide materials. However, the role of such a film on Li transport in oxide cathodes has not been addressed. Current scanning probe microscopy (SPM) studies have shown that the orientation of the layered nanocrystalline vanadia crystals near the cathode/solid electrolyte interface is not optimized for Li ion transport. While the precise structure of the material between the crystals has not been identified, initially it can be initially considered as likely to be a thin non-crystalline (amorphous) film. This is based on the ubiquitous presence of such a structure in other polycrystalline oxides. Also, and with more relevance to the materials used in thin film batteries, an amorphous film can be expected to form between nanocrystals that crystallized from an amorphous matrix, as would be the case in a deposited thin film cathode. Consistent with simulations of Li transport in amorphous vanadia, the current simulations show that Li ions diffuse more rapidly into the amorphous intergranular thin film than into the layered vanadia with the (0 0 1) planes parallel to the cathode/electrolyte interface.

Regulators of Slc4 bicarbonate transporter activity

PubMed Central

Thornell, Ian M.; Bevensee, Mark O.

2015-01-01

The Slc4 family of transporters is comprised of anion exchangers (AE1-4), Na+-coupled bicarbonate transporters (NCBTs) including electrogenic Na/bicarbonate cotransporters (NBCe1 and NBCe2), electroneutral Na/bicarbonate cotransporters (NBCn1 and NBCn2), and the electroneutral Na-driven Cl-bicarbonate exchanger (NDCBE), as well as a borate transporter (BTR1). These transporters regulate intracellular pH (pHi) and contribute to steady-state pHi, but are also involved in other physiological processes including CO2 carriage by red blood cells and solute secretion/reabsorption across epithelia. Acid-base transporters function as either acid extruders or acid loaders, with the Slc4 proteins moving HCO−3 either into or out of cells. According to results from both molecular and functional studies, multiple Slc4 proteins and/or associated splice variants with similar expected effects on pHi are often found in the same tissue or cell. Such apparent redundancy is likely to be physiologically important. In addition to regulating pHi, a HCO−3 transporter contributes to a cell's ability to fine tune the intracellular regulation of the cotransported/exchanged ion(s) (e.g., Na+ or Cl−). In addition, functionally similar transporters or splice variants with different regulatory profiles will optimize pH physiology and solute transport under various conditions or within subcellular domains. Such optimization will depend on activated signaling pathways and transporter expression profiles. In this review, we will summarize and discuss both well-known and more recently identified regulators of the Slc4 proteins. Some of these regulators include traditional second messengers, lipids, binding proteins, autoregulatory domains, and less conventional regulators. The material presented will provide insight into the diversity and physiological significance of multiple members within the Slc4 gene family. PMID:26124722

Regulators of Slc4 bicarbonate transporter activity.

PubMed

Thornell, Ian M; Bevensee, Mark O

2015-01-01

The Slc4 family of transporters is comprised of anion exchangers (AE1-4), Na(+)-coupled bicarbonate transporters (NCBTs) including electrogenic Na/bicarbonate cotransporters (NBCe1 and NBCe2), electroneutral Na/bicarbonate cotransporters (NBCn1 and NBCn2), and the electroneutral Na-driven Cl-bicarbonate exchanger (NDCBE), as well as a borate transporter (BTR1). These transporters regulate intracellular pH (pHi) and contribute to steady-state pHi, but are also involved in other physiological processes including CO2 carriage by red blood cells and solute secretion/reabsorption across epithelia. Acid-base transporters function as either acid extruders or acid loaders, with the Slc4 proteins moving HCO(-) 3 either into or out of cells. According to results from both molecular and functional studies, multiple Slc4 proteins and/or associated splice variants with similar expected effects on pHi are often found in the same tissue or cell. Such apparent redundancy is likely to be physiologically important. In addition to regulating pHi, a HCO(-) 3 transporter contributes to a cell's ability to fine tune the intracellular regulation of the cotransported/exchanged ion(s) (e.g., Na(+) or Cl(-)). In addition, functionally similar transporters or splice variants with different regulatory profiles will optimize pH physiology and solute transport under various conditions or within subcellular domains. Such optimization will depend on activated signaling pathways and transporter expression profiles. In this review, we will summarize and discuss both well-known and more recently identified regulators of the Slc4 proteins. Some of these regulators include traditional second messengers, lipids, binding proteins, autoregulatory domains, and less conventional regulators. The material presented will provide insight into the diversity and physiological significance of multiple members within the Slc4 gene family.

Hole-Transporting Materials for Printable Perovskite Solar Cells

PubMed Central

Salunke, Jagadish K.; Priimagi, Arri

2017-01-01

Perovskite solar cells (PSCs) represent undoubtedly the most significant breakthrough in photovoltaic technology since the 1970s, with an increase in their power conversion efficiency from less than 5% to over 22% in just a few years. Hole-transporting materials (HTMs) are an essential building block of PSC architectures. Currently, 2,2’,7,7’-tetrakis-(N,N’-di-p-methoxyphenylamine)-9,9’-spirobifluorene), better known as spiro-OMeTAD, is the most widely-used HTM to obtain high-efficiency devices. However, it is a tremendously expensive material with mediocre hole carrier mobility. To ensure wide-scale application of PSC-based technologies, alternative HTMs are being proposed. Solution-processable HTMs are crucial to develop inexpensive, high-throughput and printable large-area PSCs. In this review, we present the most recent advances in the design and development of different types of HTMs, with a particular focus on mesoscopic PSCs. Finally, we outline possible future research directions for further optimization of the HTMs to achieve low-cost, stable and large-area PSCs. PMID:28914823

Decision support for environmental management of industrial non-hazardous secondary materials: New analytical methods combined with simulation and optimization modeling.

PubMed

Little, Keith W; Koralegedara, Nadeesha H; Northeim, Coleen M; Al-Abed, Souhail R

2017-07-01

Non-hazardous solid materials from industrial processes, once regarded as waste and disposed in landfills, offer numerous environmental and economic advantages when put to beneficial uses (BUs). Proper management of these industrial non-hazardous secondary materials (INSM) requires estimates of their probable environmental impacts among disposal as well as BU options. The U.S. Environmental Protection Agency (EPA) has recently approved new analytical methods (EPA Methods 1313-1316) to assess leachability of constituents of potential concern in these materials. These new methods are more realistic for many disposal and BU options than historical methods, such as the toxicity characteristic leaching protocol. Experimental data from these new methods are used to parameterize a chemical fate and transport (F&T) model to simulate long-term environmental releases from flue gas desulfurization gypsum (FGDG) when disposed of in an industrial landfill or beneficially used as an agricultural soil amendment. The F&T model is also coupled with optimization algorithms, the Beneficial Use Decision Support System (BUDSS), under development by EPA to enhance INSM management. Published by Elsevier Ltd.

Integrating aerodynamics and structures in the minimum weight design of a supersonic transport wing

NASA Technical Reports Server (NTRS)

Barthelemy, Jean-Francois M.; Wrenn, Gregory A.; Dovi, Augustine R.; Coen, Peter G.; Hall, Laura E.

1992-01-01

An approach is presented for determining the minimum weight design of aircraft wing models which takes into consideration aerodynamics-structure coupling when calculating both zeroth order information needed for analysis and first order information needed for optimization. When performing sensitivity analysis, coupling is accounted for by using a generalized sensitivity formulation. The results presented show that the aeroelastic effects are calculated properly and noticeably reduce constraint approximation errors. However, for the particular example selected, the error introduced by ignoring aeroelastic effects are not sufficient to significantly affect the convergence of the optimization process. Trade studies are reported that consider different structural materials, internal spar layouts, and panel buckling lengths. For the formulation, model and materials used in this study, an advanced aluminum material produced the lightest design while satisfying the problem constraints. Also, shorter panel buckling lengths resulted in lower weights by permitting smaller panel thicknesses and generally, by unloading the wing skins and loading the spar caps. Finally, straight spars required slightly lower wing weights than angled spars.

Preparation and Enhanced Thermoelectric Performance of Cu2Se-SnSe Composite Materials

NASA Astrophysics Data System (ADS)

Peng, Zhi; He, Danqi; Mu, Xin; Zhou, Hongyu; Li, Cuncheng; Ma, Shifang; Ji, Pengxia; Hou, Weikang; Wei, Ping; Zhu, Wanting; Nie, Xiaolei; Zhao, Wenyu

2018-03-01

A series of p-type xCu2Se-SnSe (x = 0%, 0.10%, 0.15%, 0.20%, and 0.25%) composite thermoelectric materials have been prepared by the combination of ultrasonic dispersion and spark plasma sintering methods. The effects of secondary phase Cu2Se on the phase composition, microstructure, and thermoelectric properties of the composites were investigated. Microstructure characterization and elemental maps indicated Cu2Se grains uniformly distributed on the boundaries of the matrix. Transport measurements demonstrated that enhancement of the power factor and reduction of the thermal conductivity can be realized simultaneously by optimizing the adding content of Cu2Se. The highest ZT value of 0.51 at 773 K was achieved for the sample with x = 0.15%, increased by 24% compared with that of the SnSe matrix. These results demonstrate that optimizing the Cu2Se content can improve the thermoelectric performance of p-type SnSe polycrystalline materials.

Preparation and Enhanced Thermoelectric Performance of Cu2Se-SnSe Composite Materials

NASA Astrophysics Data System (ADS)

Peng, Zhi; He, Danqi; Mu, Xin; Zhou, Hongyu; Li, Cuncheng; Ma, Shifang; Ji, Pengxia; Hou, Weikang; Wei, Ping; Zhu, Wanting; Nie, Xiaolei; Zhao, Wenyu

2018-06-01

A series of p-type xCu2Se-SnSe ( x = 0%, 0.10%, 0.15%, 0.20%, and 0.25%) composite thermoelectric materials have been prepared by the combination of ultrasonic dispersion and spark plasma sintering methods. The effects of secondary phase Cu2Se on the phase composition, microstructure, and thermoelectric properties of the composites were investigated. Microstructure characterization and elemental maps indicated Cu2Se grains uniformly distributed on the boundaries of the matrix. Transport measurements demonstrated that enhancement of the power factor and reduction of the thermal conductivity can be realized simultaneously by optimizing the adding content of Cu2Se. The highest ZT value of 0.51 at 773 K was achieved for the sample with x = 0.15%, increased by 24% compared with that of the SnSe matrix. These results demonstrate that optimizing the Cu2Se content can improve the thermoelectric performance of p-type SnSe polycrystalline materials.

A multi-resolution approach for optimal mass transport

NASA Astrophysics Data System (ADS)

Dominitz, Ayelet; Angenent, Sigurd; Tannenbaum, Allen

2007-09-01

Optimal mass transport is an important technique with numerous applications in econometrics, fluid dynamics, automatic control, statistical physics, shape optimization, expert systems, and meteorology. Motivated by certain problems in image registration and medical image visualization, in this note, we describe a simple gradient descent methodology for computing the optimal L2 transport mapping which may be easily implemented using a multiresolution scheme. We also indicate how the optimal transport map may be computed on the sphere. A numerical example is presented illustrating our ideas.

Mitigating the Effects of the Space Radiation Environment: A Novel Approach of Using Graded-Z Materials

NASA Technical Reports Server (NTRS)

Atwell, William; Rojdev, Kristina; Aghara, Sukesh; Sriprisan, Sirikul

2013-01-01

In this paper we present a novel space radiation shielding approach using various material lay-ups, called "Graded-Z" shielding, which could optimize cost, weight, and safety while mitigating the radiation exposures from the trapped radiation and solar proton environments, as well as the galactic cosmic radiation (GCR) environment, to humans and electronics. In addition, a validation and verification (V&V) was performed using two different high energy particle transport/dose codes (MCNPX & HZETRN). Inherently, we know that materials having high-hydrogen content are very good space radiation shielding materials. Graded-Z material lay-ups are very good trapped electron mitigators for medium earth orbit (MEO) and geostationary earth orbit (GEO). In addition, secondary particles, namely neutrons, are produced as the primary particles penetrate a spacecraft, which can have deleterious effects to both humans and electronics. The use of "dopants," such as beryllium, boron, and lithium, impregnated in other shielding materials provides a means of absorbing the secondary neutrons. Several examples of optimized Graded-Z shielding layups that include the use of composite materials are presented and discussed in detail. This parametric shielding study is an extension of some earlier pioneering work we (William Atwell and Kristina Rojdev) performed in 20041 and 20092.

An analysis of travel costs on transport of load and nest building in golden hamster.

PubMed

Guerra, Rogerio F.; Ades, Cesar

2002-03-28

We investigated the effects of travel costs on transporting nest material and nest-building activity in golden hamsters. Nest-deprived animals were submitted to run alleys 30, 90 and 180 cm long to access a source containing paper strips as nest material (Experiment 1) or were submitted to the same travel costs in 24-h experimental sessions (Experiment 2). We noted that increased travel costs were related to a decreased number of trips to the source, larger amounts (cm(2)) of nest material transported per trip (although total loads also decreased in longer alleys), longer intervals between trips, and increased time spent at the source and in nest building activity. Foraging efficiency (i.e. size of load divided by the time spent at the source) decreased as a function of travel costs, and animals transported their loads in two fundamental ways: in 30-cm alleys, they simply used their mouth to pull the paper strips, but in 90- or 180-cm alleys they transported the loads in their cheek pouches. The animals were faster when returning to the home-cage and their running speed (cm/s) increased as a function of the length of the alley, showing that animals are under different environmental pressures when searching for resources and subsequently running back with the load to the nest. Both male and female subjects were sensitive to travel costs, but males engaged in nest building activity more promptly and exhibited higher mean performances in most measures. We conclude that nest material is a good reinforcer, and our major results are in accordance with the predictions of microeconomic and optimal foraging theories.

Nanoscale Transport Optimization

DTIC Science & Technology

2008-12-04

could be argued that the advantage of using ABAQUS for this modeling construct has more to do with its ability to impose a user-defined subroutine that...finite element analysis. This is accomplished by employing a user defined subroutine for fluid properties at the interface within the finite element...package ABAQUS . Model Components: As noted above the governing equation for the material system is given as, ( ) ( ) 4484476444 8444 76

Organic thermoelectric materials for energy harvesting and temperature control

NASA Astrophysics Data System (ADS)

Russ, Boris; Glaudell, Anne; Urban, Jeffrey J.; Chabinyc, Michael L.; Segalman, Rachel A.

2016-10-01

Conjugated polymers and related processing techniques have been developed for organic electronic devices ranging from lightweight photovoltaics to flexible displays. These breakthroughs have recently been used to create organic thermoelectric materials, which have potential for wearable heating and cooling devices, and near-room-temperature energy generation. So far, the best thermoelectric materials have been inorganic compounds (such as Bi2Te3) that have relatively low Earth abundance and are fabricated through highly complex vacuum processing routes. Molecular materials and hybrid organic-inorganic materials now demonstrate figures of merit approaching those of these inorganic materials, while also exhibiting unique transport behaviours that are suggestive of optimization pathways and device geometries that were not previously possible. In this Review, we discuss recent breakthroughs for organic materials with high thermoelectric figures of merit and indicate how these materials may be incorporated into new module designs that take advantage of their mechanical and thermoelectric properties.

Coherent transport and energy flow patterns in photosynthesis under incoherent excitation.

PubMed

Pelzer, Kenley M; Can, Tankut; Gray, Stephen K; Morr, Dirk K; Engel, Gregory S

2014-03-13

Long-lived coherences have been observed in photosynthetic complexes after laser excitation, inspiring new theories regarding the extreme quantum efficiency of photosynthetic energy transfer. Whether coherent (ballistic) transport occurs in nature and whether it improves photosynthetic efficiency remain topics of debate. Here, we use a nonequilibrium Green's function analysis to model exciton transport after excitation from an incoherent source (as opposed to coherent laser excitation). We find that even with an incoherent source, the rate of environmental dephasing strongly affects exciton transport efficiency, suggesting that the relationship between dephasing and efficiency is not an artifact of coherent excitation. The Green's function analysis provides a clear view of both the pattern of excitonic fluxes among chromophores and the multidirectionality of energy transfer that is a feature of coherent transport. We see that even in the presence of an incoherent source, transport occurs by qualitatively different mechanisms as dephasing increases. Our approach can be generalized to complex synthetic systems and may provide a new tool for optimizing synthetic light harvesting materials.

High-Performance Fluorescent Organic Light-Emitting Diodes Utilizing an Asymmetric Anthracene Derivative as an Electron-Transporting Material.

PubMed

Zhang, Dongdong; Song, Xiaozeng; Li, Haoyuan; Cai, Minghan; Bin, Zhengyang; Huang, Tianyu; Duan, Lian

2018-05-17

Fluorescent organic light-emitting diodes with thermally activated delayed fluorescent sensitizers (TSF-OLEDs) have aroused wide attention, the power efficiencies of which, however, are limited by the mutual exclusion of high electron-transport mobility and large triplet energy of electron-transporting materials (ETMs). Here, an asymmetric anthracene derivative with electronic properties manipulated by different side groups is developed as an ETM to promote TSF-OLED performances. Multiple intermolecular interactions are observed, leading to a kind of "cable-like packing" in the crystal and favoring the simultaneous realization of high electron-transporting mobility and good exciton-confinement ability, albeit the low triplet energy of the ETM. The optimized TSF-OLEDs exhibit a record-high maximum external quantum efficiency/power efficiency of 24.6%/76.0 lm W -1 , which remain 23.8%/69.0 lm W -1 at a high luminance of even 5000 cd m -2 with an extremely low operation voltage of 3.14 V. This work opens a new paradigm for designing ETMs and also paves the way toward practical application of TSF-OLEDs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Research on crude oil storage and transportation based on optimization algorithm

NASA Astrophysics Data System (ADS)

Yuan, Xuhua

2018-04-01

At present, the optimization theory and method have been widely used in the optimization scheduling and optimal operation scheme of complex production systems. Based on C++Builder 6 program development platform, the theoretical research results are implemented by computer. The simulation and intelligent decision system of crude oil storage and transportation inventory scheduling are designed. The system includes modules of project management, data management, graphics processing, simulation of oil depot operation scheme. It can realize the optimization of the scheduling scheme of crude oil storage and transportation system. A multi-point temperature measuring system for monitoring the temperature field of floating roof oil storage tank is developed. The results show that by optimizing operating parameters such as tank operating mode and temperature, the total transportation scheduling costs of the storage and transportation system can be reduced by 9.1%. Therefore, this method can realize safe and stable operation of crude oil storage and transportation system.

Optimization of municipal solid waste collection and transportation routes

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

Das, Swapan, E-mail: swapan2009sajal@gmail.com; Bhattacharyya, Bidyut Kr., E-mail: bidyut53@yahoo.co.in

2015-09-15

Graphical abstract: Display Omitted - Highlights: • Profitable integrated solid waste management system. • Optimal municipal waste collection scheme between the sources and waste collection centres. • Optimal path calculation between waste collection centres and transfer stations. • Optimal waste routing between the transfer stations and processing plants. - Abstract: Optimization of municipal solid waste (MSW) collection and transportation through source separation becomes one of the major concerns in the MSW management system design, due to the fact that the existing MSW management systems suffer by the high collection and transportation cost. Generally, in a city different waste sources scattermore » throughout the city in heterogeneous way that increase waste collection and transportation cost in the waste management system. Therefore, a shortest waste collection and transportation strategy can effectively reduce waste collection and transportation cost. In this paper, we propose an optimal MSW collection and transportation scheme that focus on the problem of minimizing the length of each waste collection and transportation route. We first formulize the MSW collection and transportation problem into a mixed integer program. Moreover, we propose a heuristic solution for the waste collection and transportation problem that can provide an optimal way for waste collection and transportation. Extensive simulations and real testbed results show that the proposed solution can significantly improve the MSW performance. Results show that the proposed scheme is able to reduce more than 30% of the total waste collection path length.« less

Multi-Scale Microstructural Thermoelectric Materials: Transport Behavior, Non-Equilibrium Preparation, and Applications.

PubMed

Su, Xianli; Wei, Ping; Li, Han; Liu, Wei; Yan, Yonggao; Li, Peng; Su, Chuqi; Xie, Changjun; Zhao, Wenyu; Zhai, Pengcheng; Zhang, Qingjie; Tang, Xinfeng; Uher, Ctirad

2017-05-01

Considering only about one third of the world's energy consumption is effectively utilized for functional uses, and the remaining is dissipated as waste heat, thermoelectric (TE) materials, which offer a direct and clean thermal-to-electric conversion pathway, have generated a tremendous worldwide interest. The last two decades have witnessed a remarkable development in TE materials. This Review summarizes the efforts devoted to the study of non-equilibrium synthesis of TE materials with multi-scale structures, their transport behavior, and areas of applications. Studies that work towards the ultimate goal of developing highly efficient TE materials possessing multi-scale architectures are highlighted, encompassing the optimization of TE performance via engineering the structures with different dimensional aspects spanning from the atomic and molecular scales, to nanometer sizes, and to the mesoscale. In consideration of the practical applications of high-performance TE materials, the non-equilibrium approaches offer a fast and controllable fabrication of multi-scale microstructures, and their scale up to industrial-size manufacturing is emphasized here. Finally, the design of two integrated power generating TE systems are described-a solar thermoelectric-photovoltaic hybrid system and a vehicle waste heat harvesting system-that represent perhaps the most important applications of thermoelectricity in the energy conversion area. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of transmission function and electronic transport in one dimensional silver nanowire: Ab-initio method using density functional theory (DFT)

NASA Astrophysics Data System (ADS)

Thakur, Anil; Kashyap, Rajinder

2018-05-01

Single nanowire electrode devices have their application in variety of fields which vary from information technology to solar energy. Silver nanowires, made in an aqueous chemical reduction process, can be reacted with gold salt to create bimetallic nanowires. Silver nanowire can be used as electrodes in batteries and have many other applications. In this paper we investigated structural and electronic transport properties of Ag nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Ag nanowire have been studied theoretically. First of all an optimized geometry for Ag nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations respectively. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Bulk properties of Ag are in agreement with experimental values which make the study of electronic and transport properties in silver nanowires interesting because they are promising materials as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Ag nano wire reveals that silver nanowire can be used as an electrode device.

Breaking the barriers of all-polymer solar cells: Solving electron transporter and morphology problems

NASA Astrophysics Data System (ADS)

Gavvalapalli, Nagarjuna

All-polymer solar cells (APSC) are a class of organic solar cells in which hole and electron transporting phases are made of conjugated polymers. Unlike polymer/fullerene solar cell, photoactive material of APSC can be designed to have hole and electron transporting polymers with complementary absorption range and proper frontier energy level offset. However, the highest reported PCE of APSC is 5 times less than that of polymer/fullerene solar cell. The low PCE of APSC is mainly due to: i) low charge separation efficiency; and ii) lack of optimal morphology to facilitate charge transfer and transport; and iii) lack of control over the exciton and charge transport in each phase. My research work is focused towards addressing these issues. The charge separation efficiency of APSC can be enhanced by designing novel electron transporting polymers with: i) broad absorption range; ii) high electron mobility; and iii) high dielectric constant. In addition to with the above parameters chemical and electronic structure of the repeating unit of conjugated polymer also plays a role in charge separation efficiency. So far only three classes of electron transporting polymers, CN substituted PPV, 2,1,3-benzothiadiazole derived polymers and rylene diimide derived polymers, are used in APSC. Thus to enhance the charge separation efficiency new classes of electron transporting polymers with the above characteristics need to be synthesized. I have developed a new straightforward synthetic strategy to rapidly generate new classes of electron transporting polymers with different chemical and electronic structure, broad absorption range, and high electron mobility from readily available electron deficient monomers. In APSCs due to low entropy of mixing, polymers tend to micro-phase segregate rather than forming the more useful nano-phase segregation. Optimizing the polymer blend morphology to obtain nano-phase segregation is specific to the system under study, time consuming, and not trivial. Thus to avoid micro-phase segregation, nanoparticles of hole and electron transporters are synthesized and blended. But the PCE of nanoparticle blends are far less than those of polymer blends. This is mainly due to the: i) lack of optimal assembly of nanoparticles to facilitate charge transfer and transport processes; and ii) lack of control over the exciton and charge transport properties within the nanoparticles. Polymer packing within the nanoparticle controls the optoelectronic and charge transport properties of the nanoparticle. In this work I have shown that the solvent used to synthesize nanoparticles plays a crucial role in determining the assembly of polymer chains inside the nanoparticle there by affecting its exciton and charge transport processes. To obtain the optimal morphology for better charge transfer and transport, we have also synthesized nanoparticles of different radius with surfactants of opposite charge. We propose that depending on the radius and/or Coulombic interactions these nanoparticles can be assembled into mineral structure-types that are useful for photovoltaic devices.

Aeroelastic Tailoring of Transport Wings Including Transonic Flutter Constraints

NASA Technical Reports Server (NTRS)

Stanford, Bret K.; Wieseman, Carol D.; Jutte, Christine V.

2015-01-01

Several minimum-mass optimization problems are solved to evaluate the effectiveness of a variety of novel tailoring schemes for subsonic transport wings. Aeroelastic stress and panel buckling constraints are imposed across several trimmed static maneuver loads, in addition to a transonic flutter margin constraint, captured with aerodynamic influence coefficient-based tools. Tailoring with metallic thickness variations, functionally graded materials, balanced or unbalanced composite laminates, curvilinear tow steering, and distributed trailing edge control effectors are all found to provide reductions in structural wing mass with varying degrees of success. The question as to whether this wing mass reduction will offset the increased manufacturing cost is left unresolved for each case.

Neutron powder diffraction study on the iron-based nitride superconductor ThFeAsN

NASA Astrophysics Data System (ADS)

Mao, Huican; Wang, Cao; Maynard-Casely, Helen E.; Huang, Qingzhen; Wang, Zhicheng; Cao, Guanghan; Li, Shiliang; Luo, Huiqian

2017-03-01

We report neutron diffraction and transport results on the newly discovered superconducting nitride ThFeAsN with T_c= 30 \\text{K} . No magnetic transition, but a weak structural distortion around 160 K, is observed by cooling from 300 K to 6 K. Analysis on the resistivity, Hall transport and crystal structure suggests that this material behaves as an electron optimally doped pnictide superconductor due to extra electrons from nitrogen deficiency or oxygen occupancy at the nitrogen site, which, together with the low arsenic height, may enhance the electron itinerancy and reduce the electron correlations, thus suppressing the static magnetic order.

High thermoelectric properties of (Sb, Bi)2Te3 nanowire arrays by tilt-structure engineering

NASA Astrophysics Data System (ADS)

Tan, Ming; Hao, Yanming; Deng, Yuan; Chen, Jingyi

2018-06-01

In this paper, we present an innovative tilt-structure design concept for (Sb, Bi)2Te3 nanowire array assembled by high-quality nanowires with well oriented growth, utilizing a simple vacuum thermal evaporation technique. The unusual tilt-structure (Sb, Bi)2Te3 nanowire array with a tilted angle of 45° exhibits a high thermoelectric dimensionless figure-of-merit ZT = 1.72 at room temperature. The relatively high ZT value in contrast to that of previously reported (Sb, Bi)2Te3 materials and the vertical (Sb, Bi)2Te3 nanowire arrays evidently reveals the crucial role of the unique tilt-structure in favorably influencing carrier and phonon transport properties, resulting in a significantly improved ZT value. The transport mechanism of such tilt-structure is proposed and investigated. This method opens a new approach to optimize nano-structure in thin films for next-generation thermoelectric materials and devices.

"Genetically Engineered" Nanoelectronics

NASA Technical Reports Server (NTRS)

Klimeck, Gerhard; Salazar-Lazaro, Carlos H.; Stoica, Adrian; Cwik, Thomas

2000-01-01

The quantum mechanical functionality of nanoelectronic devices such as resonant tunneling diodes (RTDs), quantum well infrared-photodetectors (QWIPs), quantum well lasers, and heterostructure field effect transistors (HFETs) is enabled by material variations on an atomic scale. The design and optimization of such devices requires a fundamental understanding of electron transport in such dimensions. The Nanoelectronic Modeling Tool (NEMO) is a general-purpose quantum device design and analysis tool based on a fundamental non-equilibrium electron transport theory. NEW was combined with a parallelized genetic algorithm package (PGAPACK) to evolve structural and material parameters to match a desired set of experimental data. A numerical experiment that evolves structural variations such as layer widths and doping concentrations is performed to analyze an experimental current voltage characteristic. The genetic algorithm is found to drive the NEMO simulation parameters close to the experimentally prescribed layer thicknesses and doping profiles. With such a quantitative agreement between theory and experiment design synthesis can be performed.

High performance small molecule photodetector with broad spectral response range from 200 to 900 nm

NASA Astrophysics Data System (ADS)

Wu, Shuang-hong; Li, Wen-lian; Chu, Bei; Su, Zi-sheng; Zhang, Feng; Lee, C. S.

2011-07-01

We demonstrate a photodetector (PD) with broad spectral response by taking the advantages of more flexible device design in using small molecule materials. The optimized device shows an external quantum efficiency of over 20% from 200 to 900 nm. The high performance is achieved by jointing two donor (D)/acceptor (A) hetero-junctions [m-MTDATA(D)/TiOPc(A) and TiOPc(D)/F16CuPc: PTCDI-C8(A)] such that photoresponses over the deep-ultraviolet (UV) and visible-near infrared regions can be independently optimized. By choosing D- and A-materials with matched energy level alignment, high carrier mobility, and balanced carrier transporting properties, the present PD shows a fast response of 56 ns. The high speed and deep-UV sensitivity might lead to potential military applications such as missile tracking in addition to optical communications, chemical/biological sensing etc.

Aspects of metallic low-temperature transport in Mott-insulator/band-insulator superlattices: Optical conductivity and thermoelectricity

NASA Astrophysics Data System (ADS)

Rüegg, Andreas; Pilgram, Sebastian; Sigrist, Manfred

2008-06-01

We investigate the low-temperature electrical and thermal transport properties in atomically precise metallic heterostructures involving strongly correlated electron systems. The model of the Mott-insulator/band-insulator superlattice was discussed in the framework of the slave-boson mean-field approximation and transport quantities were derived by use of the Boltzmann transport equation in the relaxation-time approximation. The results for the optical conductivity are in good agreement with recently published experimental data on (LaTiO3)N/(SrTiO3)M superlattices and allow us to estimate the values of key parameters of the model. Furthermore, predictions for the thermoelectric response were made and the dependence of the Seebeck coefficient on model parameters was studied in detail. The width of the Mott-insulating material was identified as the most relevant parameter, in particular, this parameter provides a way to optimize the thermoelectric power factor at low temperatures.

Golden Rays - July 2017 | Solar Research | Solar Research | NREL

Science.gov Websites

Operator, First Solar, and NREL tested a 300-MW PV plant to demonstrate that, with proper controls, PV can technique to measure charge-carrier transport in PV materials. Solar Plus: A Holistic Approach to Distribution Solar PV By optimizing how PV interacts with other electricity loads at the household- and grid

Transport Mechanisms in Organic Thin-Film Transistors

NASA Astrophysics Data System (ADS)

Fung, A. W. P.

1996-03-01

Recent success in fabricating field-effect transistors with polycrystalline α-sexithiophene (α-6T) has allowed us to study charge transport in this organic semiconductor. The appealing structural property that the oligomer chains are seated almost perpendicular to the substrate provides a model π-conjugated system which we find exhibits band transport at low temperatures. We observe a behavioral transition around 50K which is consistent with the metal-insulator transition in Holstein's small-polaron theory. The fact that we can observe intrinsic behavior means that the ambient-temperature mobility obtained in these transistors is optimal for α-6T. Agreement with the Holstein theory provides us with a prescription for rational design of materials for organic transistor applications. Work done in collaboration with L. Torsi, A. Dodabalapur, L. J. Rothberg and H. E. Katz.

Transporting particulate material

DOEpatents

Aldred, Derek Leslie [North Hollywood, CA; Rader, Jeffrey A [North Hollywood, CA; Saunders, Timothy W [North Hollywood, CA

2011-08-30

A material transporting system comprises a material transporting apparatus (100) including a material transporting apparatus hopper structure (200, 202), which comprises at least one rotary transporting apparatus; a stationary hub structure (900) constraining and assisting the at least one rotary transporting apparatus; an outlet duct configuration (700) configured to permit material to exit therefrom and comprising at least one diverging portion (702, 702'); an outlet abutment configuration (800) configured to direct material to the outlet duct configuration; an outlet valve assembly from the material transporting system venting the material transporting system; and a moving wall configuration in the material transporting apparatus capable of assisting the material transporting apparatus in transporting material in the material transporting system. Material can be moved from the material transporting apparatus hopper structure to the outlet duct configuration through the at least one rotary transporting apparatus, the outlet abutment configuration, and the outlet valve assembly.

Development of methodologies for the estimation of thermal properties associated with aerospace vehicles

NASA Technical Reports Server (NTRS)

Scott, Elaine P.

1993-01-01

Thermal stress analyses are an important aspect in the development of aerospace vehicles such as the National Aero-Space Plane (NASP) and the High-Speed Civil Transport (HSCT) at NASA-LaRC. These analyses require knowledge of the temperature within the structures which consequently necessitates the need for thermal property data. The initial goal of this research effort was to develop a methodology for the estimation of thermal properties of aerospace structural materials at room temperature and to develop a procedure to optimize the estimation process. The estimation procedure was implemented utilizing a general purpose finite element code. In addition, an optimization procedure was developed and implemented to determine critical experimental parameters to optimize the estimation procedure. Finally, preliminary experiments were conducted at the Aircraft Structures Branch (ASB) laboratory.

Development of methodologies for the estimation of thermal properties associated with aerospace vehicles

NASA Astrophysics Data System (ADS)

Scott, Elaine P.

1993-12-01

Thermal stress analyses are an important aspect in the development of aerospace vehicles such as the National Aero-Space Plane (NASP) and the High-Speed Civil Transport (HSCT) at NASA-LaRC. These analyses require knowledge of the temperature within the structures which consequently necessitates the need for thermal property data. The initial goal of this research effort was to develop a methodology for the estimation of thermal properties of aerospace structural materials at room temperature and to develop a procedure to optimize the estimation process. The estimation procedure was implemented utilizing a general purpose finite element code. In addition, an optimization procedure was developed and implemented to determine critical experimental parameters to optimize the estimation procedure. Finally, preliminary experiments were conducted at the Aircraft Structures Branch (ASB) laboratory.

Neutron optics concept for the materials engineering diffractometer at the ESS

NASA Astrophysics Data System (ADS)

Šaroun, J.; Fenske, J.; Rouijaa, M.; Beran, P.; Navrátil, J.; Lukáš, P.; Schreyer, A.; Strobl, M.

2016-09-01

The Beamline for European Materials Engineering Research (BEER) has been recently proposed to be built at the European Spallation Source (ESS). The presented concept of neutron delivery optics for this instrument addresses the problems of bi-spectral beam extraction from a small moderator, optimization of neutron guides profile for long-range neutron transport and focusing at the sample under various constraints. They include free space before and after the guides, a narrow guide section with gaps for choppers, closing of direct line of sight and cost reduction by optimization of the guides cross-section and coating. A system of slits and exchangeable focusing optics is proposed in order to match various wavelength resolution options provided by the pulse shaping and modulation choppers, which permits to efficiently trade resolution for intensity in a wide range. Simulated performance characteristics such as brilliance transfer ratio are complemented by the analysis of the histories of “useful” neutrons obtained by back tracing neutrons hitting the sample, which helps to optimize some of the neutron guide parameters such as supermirror coating.

Reliability Methods for Shield Design Process

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Wilson, J. W.

2002-01-01

Providing protection against the hazards of space radiation is a major challenge to the exploration and development of space. The great cost of added radiation shielding is a potential limiting factor in deep space operations. In this enabling technology, we have developed methods for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. An important component of this technology is the estimation of two most commonly identified uncertainties in radiation shield design, the shielding properties of materials used and the understanding of the biological response of the astronaut to the radiation leaking through the materials into the living space. The largest uncertainty, of course, is in the biological response to especially high charge and energy (HZE) ions of the galactic cosmic rays. These uncertainties are blended with the optimization design procedure to formulate reliability-based methods for shield design processes. The details of the methods will be discussed.

Electron beam transport in heterogeneous slab media from MeV down to eV.

PubMed

Yousfi, M; Leger, J; Loiseau, J F; Held, B; Eichwald, O; Defoort, B; Dupillier, J M

2006-01-01

An optimized Monte Carlo method based on the null collision technique and on the treatment of individual interactions is used for the simulation of the electron transport in multilayer materials from high energies (MeV or several hundred of keV) down to low cutoff energies (between 1 and 10 eV). In order to better understand the electron transport and the energy deposition at the interface in the composite application framework, two layer materials are considered (carbon and polystyrene with densities of 1.7 g cm(-3) and 1.06 g cm(-3), respectively) under two slab or three slab configurations as, e.g. a thin layer of carbon sandwiched between two polystyrene layers. The electron-matter cross-sections (electron-carbon and electron-polystyrene) used in the case of pure material (carbon and polystyrene) as well as our Monte-Carlo code have been first validated. The boundary interface layer is considered without any mean free path truncation and with a rigorous treatment of the backscattered and also the forward scattered electrons from one layer to another. The large effect of the choice of a low cutoff energy and the dissociation process consideration are also clearly shown in the heterogeneous multi-layer media more particularly on the secondary electron emission, inelastic collision number and energy spectra.

Innovative forming and fabrication technologies : new opportunities.

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

Davis, B.; Hryn, J.; Energy Systems

2008-01-31

The advent of light metal alloys and advanced materials (polymer, composites, etc.) have brought the possibility of achieving important energy reductions into the full life cycle of these materials, especially in transportation applications. 1 These materials have gained acceptance in the aerospace industry but use of light metal alloys needs to gain wider acceptance in other commercial transportation areas. Among the main reasons for the relatively low use of these materials are the lack of manufacturability, insufficient mechanical properties, and increased material costs due to processing inefficiencies. Considering the enormous potential energy savings associated with the use of light metalmore » alloys and advanced materials in transportation, there is a need to identify R&D opportunities in the fields of materials fabrication and forming aimed at developing materials with high specific mechanical properties combined with energy efficient processes and good manufacturability. This report presents a literature review of the most recent developments in the areas of fabrication and metal forming focusing principally on aluminum alloys. In the first section of the document, the different sheet manufacturing technologies including direct chill (DC) casting and rolling, spray forming, spray rolling, thin slab, and strip casting are reviewed. The second section of the document presents recent research on advanced forming processes. The various forming processes reviewed are: superplastic forming, electromagnetic forming, age forming, warm forming, hydroforming, and incremental forming. Optimization of conventional forming processes is also discussed. Potentially interesting light metal alloys for high structural efficiency including aluminum-scandium, aluminum-lithium, magnesium, titanium, and amorphous metal alloys are also reviewed. This section concludes with a discussion on alloy development for manufacturability. The third section of the document reviews the latest developments in fiber-reinforced composite materials. Emerging curing processes are presented along with a discussion on the possible developments in biocomposite materials. The fourth section presents recent developments in the fabrication of bulk nanomaterials and nanoparticles reinforced materials. Advanced joining technologies are presented in the fifth section. Future research is proposed in the last section.« less

Poster — Thur Eve — 61: A new framework for MPERT plan optimization using MC-DAO

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

Baker, M; Lloyd, S AM; Townson, R

2014-08-15

This work combines the inverse planning technique known as Direct Aperture Optimization (DAO) with Intensity Modulated Radiation Therapy (IMRT) and combined electron and photon therapy plans. In particular, determining conditions under which Modulated Photon/Electron Radiation Therapy (MPERT) produces better dose conformality and sparing of organs at risk than traditional IMRT plans is central to the project. Presented here are the materials and methods used to generate and manipulate the DAO procedure. Included is the introduction of a powerful Java-based toolkit, the Aperture-based Monte Carlo (MC) MPERT Optimizer (AMMO), that serves as a framework for optimization and provides streamlined access tomore » underlying particle transport packages. Comparison of the toolkit's dose calculations to those produced by the Eclipse TPS and the demonstration of a preliminary optimization are presented as first benchmarks. Excellent agreement is illustrated between the Eclipse TPS and AMMO for a 6MV photon field. The results of a simple optimization shows the functioning of the optimization framework, while significant research remains to characterize appropriate constraints.« less

Resealable, optically accessible, PDMS-free fluidic platform for ex vivo interrogation of pancreatic islets.

PubMed

Lenguito, Giovanni; Chaimov, Deborah; Weitz, Jonathan R; Rodriguez-Diaz, Rayner; Rawal, Siddarth A K; Tamayo-Garcia, Alejandro; Caicedo, Alejandro; Stabler, Cherie L; Buchwald, Peter; Agarwal, Ashutosh

2017-02-28

We report the design and fabrication of a robust fluidic platform built out of inert plastic materials and micromachined features that promote optimized convective fluid transport. The platform is tested for perfusion interrogation of rodent and human pancreatic islets, dynamic secretion of hormones, concomitant live-cell imaging, and optogenetic stimulation of genetically engineered islets. A coupled quantitative fluid dynamics computational model of glucose stimulated insulin secretion and fluid dynamics was first utilized to design device geometries that are optimal for complete perfusion of three-dimensional islets, effective collection of secreted insulin, and minimization of system volumes and associated delays. Fluidic devices were then fabricated through rapid prototyping techniques, such as micromilling and laser engraving, as two interlocking parts from materials that are non-absorbent and inert. Finally, the assembly was tested for performance using both rodent and human islets with multiple assays conducted in parallel, such as dynamic perfusion, staining and optogenetics on standard microscopes, as well as for integration with commercial perfusion machines. The optimized design of convective fluid flows, use of bio-inert and non-absorbent materials, reversible assembly, manual access for loading and unloading of islets, and straightforward integration with commercial imaging and fluid handling systems proved to be critical for perfusion assay, and particularly suited for time-resolved optogenetics studies.

Optimal partial mass transportation and obstacle Monge-Kantorovich equation

NASA Astrophysics Data System (ADS)

Igbida, Noureddine; Nguyen, Van Thanh

2018-05-01

Optimal partial mass transport, which is a variant of the optimal transport problem, consists in transporting effectively a prescribed amount of mass from a source to a target. The problem was first studied by Caffarelli and McCann (2010) [6] and Figalli (2010) [12] with a particular attention to the quadratic cost. Our aim here is to study the optimal partial mass transport problem with Finsler distance costs including the Monge cost given by the Euclidian distance. Our approach is different and our results do not follow from previous works. Among our results, we introduce a PDE of Monge-Kantorovich type with a double obstacle to characterize active submeasures, Kantorovich potential and optimal flow for the optimal partial transport problem. This new PDE enables us to study the uniqueness and monotonicity results for the active submeasures. Another interesting issue of our approach is its convenience for numerical analysis and computations that we develop in a separate paper [14] (Igbida and Nguyen, 2018).

Impact of Tortuosity on Charge-Carrier Transport in Organic Bulk Heterojunction Blends

NASA Astrophysics Data System (ADS)

Heiber, Michael C.; Kister, Klaus; Baumann, Andreas; Dyakonov, Vladimir; Deibel, Carsten; Nguyen, Thuc-Quyen

2017-11-01

The impact of the tortuosity of the charge-transport pathways through a bulk heterojunction film on the charge-carrier mobility is theoretically investigated using model morphologies and kinetic Monte Carlo simulations. The tortuosity descriptor provides a quantitative metric to characterize the quality of the charge-transport pathways, and model morphologies with controlled domain size and tortuosity are created using an anisotropic domain growth procedure. The tortuosity is found to be dependent on the anisotropy of the domain structure and is highly tunable. Time-of-flight charge-transport simulations on morphologies with a range of tortuosity values reveal that tortuosity can significantly reduce the magnitude of the mobility and the electric-field dependence relative to a neat material. These reductions are found to be further controlled by the energetic disorder and temperature. Most significantly, the sensitivity of the electric-field dependence to the tortuosity can explain the different experimental relationships previously reported, and exploiting this sensitivity could lead to simpler methods for characterizing and optimizing charge transport in organic solar cells.

The Study on the Optimization of Container Multimodal Transport Business Process in Shandong

NASA Astrophysics Data System (ADS)

Wang, Fengmei; Gong, Xiaoyi; Ni, Yingying; Zhan, Jun; Che, Huiping

2018-06-01

Shandong is a coastal city with good location advantages. As a hub port for international trade goods and a port of transhipment, shandong's demand for multimodal transport is more urgent. By selecting the suitable non-water port and the multimodal transport carrier to improve the efficiency of multimodal transport, the purpose of saving the time of logistics is achieved, thus reducing the logistics cost.It branch out through Shandongt, and it can reach the central region of China, can reach the Western remote area ,too. This paper puts forward the optimization scheme of the business process of container multimodal transport. The optimization of freight forwarding business process is analyzed. The multimodal transport model in Shandong was designed. Finally, the optimal approach of multimodal transport in Shandong is put forward.

Designing high-performance layered thermoelectric materials through orbital engineering

PubMed Central

Zhang, Jiawei; Song, Lirong; Madsen, Georg K. H.; Fischer, Karl F. F.; Zhang, Wenqing; Shi, Xun; Iversen, Bo B.

2016-01-01

Thermoelectric technology, which possesses potential application in recycling industrial waste heat as energy, calls for novel high-performance materials. The systematic exploration of novel thermoelectric materials with excellent electronic transport properties is severely hindered by limited insight into the underlying bonding orbitals of atomic structures. Here we propose a simple yet successful strategy to discover and design high-performance layered thermoelectric materials through minimizing the crystal field splitting energy of orbitals to realize high orbital degeneracy. The approach naturally leads to design maps for optimizing the thermoelectric power factor through forming solid solutions and biaxial strain. Using this approach, we predict a series of potential thermoelectric candidates from layered CaAl2Si2-type Zintl compounds. Several of them contain nontoxic, low-cost and earth-abundant elements. Moreover, the approach can be extended to several other non-cubic materials, thereby substantially accelerating the screening and design of new thermoelectric materials. PMID:26948043

Alternative Fuel Transportation Optimization Tool : Description, Methodology, and Demonstration Scenarios.

DOT National Transportation Integrated Search

2015-09-01

This report describes an Alternative Fuel Transportation Optimization Tool (AFTOT), developed by the U.S. Department of Transportation (DOT) Volpe National Transportation Systems Center (Volpe) in support of the Federal Aviation Administration (FAA)....

Potential application of CuSbS2 as the hole transport material in perovskite solar cell: A simulation study

NASA Astrophysics Data System (ADS)

Teimouri, R.; Mohammadpour, R.

2018-06-01

CH3 NH3 PbI3 (MAPbI3) thin film solar cells, which are reported at laboratory efficiency scale of nearly 22%, are the subject of much attention by energy researchers due to their low cost buildup, acceptable efficiency, high absorption coefficient and diffusion length. The main purpose of this research is to simulate the structure of thin film perovskite solar cells through numerical simulation of SCAPS based on the empirical data for different hole transport layers. After simulating the initial structure of FTO/TiO2/CH3NH3PbI3/Spiro-OMeTAD solar cell, the hole transport layer Spiro-OMeTAD thickness was optimized on a small scale using modeling. The researchers also sought to reduce the amount of this material and the cost of construction. Ultimately, an optimum thickness of 140 nm was obtained for this cell with efficiency of 22.88%. The effect of employing alternative inorganic hole transport layer was investigated as a substitute for Spiro-OMeTAD; Copper antimony sulphide (CuSbS2) was selected due to abundant and available material and high open circuit voltage of about 988 mV. Thickness variations were also performed on a MAPbI3/CuSbS2 solar cell. Finally, It has obtained that perovskite solar cell with 120 nm-thick of CuSbS2 has 23.14% conversion efficiency with acceptable VOC and JSC values.

Multi-Scale Modeling, Surrogate-Based Analysis, and Optimization of Lithium-Ion Batteries for Vehicle Applications

NASA Astrophysics Data System (ADS)

Du, Wenbo

A common attribute of electric-powered aerospace vehicles and systems such as unmanned aerial vehicles, hybrid- and fully-electric aircraft, and satellites is that their performance is usually limited by the energy density of their batteries. Although lithium-ion batteries offer distinct advantages such as high voltage and low weight over other battery technologies, they are a relatively new development, and thus significant gaps in the understanding of the physical phenomena that govern battery performance remain. As a result of this limited understanding, batteries must often undergo a cumbersome design process involving many manual iterations based on rules of thumb and ad-hoc design principles. A systematic study of the relationship between operational, geometric, morphological, and material-dependent properties and performance metrics such as energy and power density is non-trivial due to the multiphysics, multiphase, and multiscale nature of the battery system. To address these challenges, two numerical frameworks are established in this dissertation: a process for analyzing and optimizing several key design variables using surrogate modeling tools and gradient-based optimizers, and a multi-scale model that incorporates more detailed microstructural information into the computationally efficient but limited macro-homogeneous model. In the surrogate modeling process, multi-dimensional maps for the cell energy density with respect to design variables such as the particle size, ion diffusivity, and electron conductivity of the porous cathode material are created. A combined surrogate- and gradient-based approach is employed to identify optimal values for cathode thickness and porosity under various operating conditions, and quantify the uncertainty in the surrogate model. The performance of multiple cathode materials is also compared by defining dimensionless transport parameters. The multi-scale model makes use of detailed 3-D FEM simulations conducted at the particle-level. A monodisperse system of ellipsoidal particles is used to simulate the effective transport coefficients and interfacial reaction current density within the porous microstructure. Microscopic simulation results are shown to match well with experimental measurements, while differing significantly from homogenization approximations used in the macroscopic model. Global sensitivity analysis and surrogate modeling tools are applied to couple the two length scales and complete the multi-scale model.

Enhanced water transport and salt rejection through hydrophobic zeolite pores.

PubMed

Humplik, Thomas; Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N

2017-12-15

The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

Enhanced water transport and salt rejection through hydrophobic zeolite pores

NASA Astrophysics Data System (ADS)

Humplik, Thomas; Lee, Jongho; O'Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N.

2017-12-01

The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

Nanoscale Interfaces in Colloidal Quantum Dot Solar Cells: Physical Insights and Materials Engineering Strategies

NASA Astrophysics Data System (ADS)

Kemp, Kyle Wayne

With growing global energy demand there will be an increased need for sources of renewable energy such as solar cells. To make these photovoltaic technologies more competitive with conventional energy sources such as coal and natural gas requires further reduction in manufacturing costs that can be realized by solution processing and roll-to-roll printing. Colloidal quantum dots are a bandgap tunable, solution processible, semiconductor material which may offer a path forward to efficient, inexpensive photovoltaics. Despite impressive progress in performance with these materials, there remain limitations in photocarrier collection that must be overcome. This dissertation focuses on the characterization of charge recombination and transport in colloidal quantum dot photovoltaics, and the application of this knowledge to the development of new and better materials. Core-shell, PbS-CdS, quantum dots were investigated in an attempt to achieve better surface passivation and reduce electronic defects which can limit performance. Optimization of this material led to improved open circuit voltage, exceeding 0.6 V for the first time, and record published performance of 6% efficiency. Using temperature-dependent and transient photovoltage measurements we explored the significance of interface recombination on the operation of these devices. Careful engineering of the electrode using atomic layer deposition of ZnO helped lead to better TiO2 substrate materials and allowed us to realize a nearly two-fold reduction in recombination rate and an enhancement upwards of 50 mV in open circuit voltage. Carrier extraction efficiency was studied in these devices using intensity dependent current-voltage data of an operational solar cell. By developing an analytical model to describe recombination loss within the active layer of the device we were able to accurately determine transport lengths ranging up to 90 nm. Transient absorption and photoconductivity techniques were used to study charge dynamics by identifying states in these quantum dot materials which facilitate carrier transport. Thermal activation energies for transport of 60 meV or lower were measured for different PbS quantum dot bandgaps, representing a relatively small barrier for carrier transport. From these measurements a dark, quantum confined energy level was attributed to the electronic bandedge of these materials which serves to govern their optoelectronic behavior.

Thickness-controlled electronic structure and thermoelectric performance of ultrathin SnS2 nanosheets.

PubMed

Li, Jun; Shen, Jinni; Ma, Zuju; Wu, Kechen

2017-08-21

The thermoelectric conversion efficiency of a material relies on a dimensionless parameter (ZT = S 2 σT/κ). It is a great challenge in enhancing the ZT value basically due to that the related transport factors of most of the bulk materials are inter-conditioned to each other, making it very difficult to simultaneously optimize these parameters. In this report, the negative correlation between power factor and thermal conductivity of nano-scaled SnS 2 multilayers is predicted by high-level first-principle computations combined with Boltzmann transport theory. By diminishing the thickness of SnS 2 nanosheet to about 3 L, the S and σ along a direction simultaneously increase whereas κ decreases, achieving a high ZT value of 1.87 at 800 K. The microscopic mechanisms for this unusual negative correlation in nano-scaled two dimensional (2D) material are elucidated and attributed to the quantum confinement effect. The results may open a way to explore the high ZT thermoelectric nano-devices for the practical thermoelectric applications.

Ordered materials for organic electronics and photonics.

PubMed

O'Neill, Mary; Kelly, Stephen M

2011-02-01

We present a critical review of semiconducting/light emitting, liquid crystalline materials and their use in electronic and photonic devices such as transistors, photovoltaics, OLEDs and lasers. We report that annealing from the mesophase improves the order and packing of organic semiconductors to produce state-of-the-art transistors. We discuss theoretical models which predict how charge transport and light emission is affected by the liquid crystalline phase. Organic photovoltaics and OLEDs require optimization of both charge transport and optical properties and we identify the various trade-offs involved for ordered materials. We report the crosslinking of reactive mesogens to give pixellated full-colour OLEDs and distributed bi-layer photovoltaics. We show how the molecular organization inherent to the mesophase can control the polarization of light-emitting devices and the gain in organic, thin-film lasers and can also provide distributed feedback in chiral nematic mirrorless lasers. We update progress on the surface alignment of liquid crystalline semiconductors to obtain monodomain devices without defects or devices with spatially varying properties. Finally the significance of all of these developments is assessed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High performance thermoelectric materials and methods of preparation

NASA Technical Reports Server (NTRS)

Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

1997-01-01

Transition metals (T) of Group VIII (Co, Rh and Ir) have been prepared as semiconductor alloys with Sb having the general formula TSb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor alloys and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor alloys having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using vertical gradient freeze techniques, liquid-solid phase sintering techniques, low temperature powder sintering and/or hot-pressing. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities (up to 8000 cm.sup.2.V.sup.-1.s.sup.-1), good Seebeck coefficients (up to 400 .mu.VK.sup.-1 between 300.degree. C. and 700.degree. C.), and low thermal conductivities (as low as 15 mW/cmK). Optimizing the transport properties of semiconductor materials prepared from elemental mixtures Co, Rh, Ir and Sb resulted in a two fold increase in the thermoelectric figure of merit (ZT) at temperatures as high as 400.degree. C. for thermoelectric elements fabricated from such semiconductor materials.

Thermal conductivity measurements via time-domain thermoreflectance for the characterization of radiation induced damage

DOE PAGES

Cheaito, Ramez; Gorham, Caroline S.; Carnegie Mellon Univ., Pittsburgh, PA; ...

2015-05-01

The progressive build up of displacement damage and fission products inside different systems and components of a nuclear reactor can lead to significant defect formation, degradation, and damage of the constituent materials. This structural modification can highly influence the thermal transport mechanisms and various mechanical properties of solids. In this paper we demonstrate the use of time-domain thermoreflectance (TDTR), a non-destructive method capable of measuring the thermal transport in material systems from nano to bulk scales, to study the effect of radiation damage and the subsequent changes in the thermal properties of materials. We use TDTR to show that displacementmore » damage from ion irradiation can significantly reduce the thermal conductivity of Optimized ZIRLO, a material used as fuel cladding in several current nuclear reactors. We find that the thermal conductivity of copper-niobium nanostructured multilayers does not change with helium ion irradiation doses of up to 10 15 cm -2 and ion energy of 200 keV suggesting that these structures can be used and radiation tolerant materials in nuclear reactors. We compare the effect of ion doses and ion beam energies on the measured thermal conductivity of bulk silicon. Results demonstrate that TDTR thermal measurements can be used to quantify depth dependent damage.« less

Optimization of space manufacturing systems

NASA Technical Reports Server (NTRS)

Akin, D. L.

1979-01-01

Four separate analyses are detailed: transportation to low earth orbit, orbit-to-orbit optimization, parametric analysis of SPS logistics based on earth and lunar source locations, and an overall program option optimization implemented with linear programming. It is found that smaller vehicles are favored for earth launch, with the current Space Shuttle being right at optimum payload size. Fully reusable launch vehicles represent a savings of 50% over the Space Shuttle; increased reliability with less maintenance could further double the savings. An optimization of orbit-to-orbit propulsion systems using lunar oxygen for propellants shows that ion propulsion is preferable by a 3:1 cost margin over a mass driver reaction engine at optimum values; however, ion engines cannot yet operate in the lower exhaust velocity range where the optimum lies, and total program costs between the two systems are ambiguous. Heavier payloads favor the use of a MDRE. A parametric model of a space manufacturing facility is proposed, and used to analyze recurring costs, total costs, and net present value discounted cash flows. Parameters studied include productivity, effects of discounting, materials source tradeoffs, economic viability of closed-cycle habitats, and effects of varying degrees of nonterrestrial SPS materials needed from earth. Finally, candidate optimal scenarios are chosen, and implemented in a linear program with external constraints in order to arrive at an optimum blend of SPS production strategies in order to maximize returns.

Particle swarm optimization - Genetic algorithm (PSOGA) on linear transportation problem

NASA Astrophysics Data System (ADS)

Rahmalia, Dinita

2017-08-01

Linear Transportation Problem (LTP) is the case of constrained optimization where we want to minimize cost subject to the balance of the number of supply and the number of demand. The exact method such as northwest corner, vogel, russel, minimal cost have been applied at approaching optimal solution. In this paper, we use heurisitic like Particle Swarm Optimization (PSO) for solving linear transportation problem at any size of decision variable. In addition, we combine mutation operator of Genetic Algorithm (GA) at PSO to improve optimal solution. This method is called Particle Swarm Optimization - Genetic Algorithm (PSOGA). The simulations show that PSOGA can improve optimal solution resulted by PSO.

Two-dimensional metal-organic frameworks with high thermoelectric efficiency through metal ion selection.

PubMed

He, Yuping; Spataru, Catalin D; Léonard, Francois; Jones, Reese E; Foster, Michael E; Allendorf, Mark D; Alec Talin, A

2017-07-26

Two-dimensional (2D) materials have attracted much attention due to their novel properties. An exciting new class of 2D materials based on metal-organic frameworks (MOFs) has recently emerged, displaying high electrical conductivity, a rarity among organic nanoporous materials. The emergence of these materials raises intriguing questions about their fundamental electronic, optical, and thermal properties, but few studies exist in this regard. Here we present an atomistic study of the thermoelectric properties of crystalline 2D MOFs X 3 (HITP) 2 with X = Ni, Pd or Pt, and HITP = 2,3,6,7,10,11-hexaiminotriphenylene, using both ab initio transport models and classical molecular dynamics simulations. We find that these materials have a high Seebeck coefficient and low thermal conductivity, making them promising for thermoelectric applications. Furthermore, we explore the dependence of thermoelectric transport properties on the atomic structure by comparing the calculated band structure, band alignment, and electronic density of states of the three 2D MOFs, and find that the thermoelectric transport properties strongly depend on both the interaction between the ligands and the metal ions, and the d orbital splitting of the metal ions induced by the ligands. This demonstrates that selection of the metal ion is a powerful approach to control and enhance the thermoelectric properties. Interestingly we reveal an unexpected effect where, unlike for electrons, the thermal and electrical current may not be equally carried by the holes, leading to a significant deviation from the Wiedemann-Franz law. The results of this work provide fundamental guidance to optimize the existing 2D MOFs, and to design and discover new families of MOF-like materials for thermoelectric applications.

Materials for Low-Energy Neutron Radiation Shielding

NASA Technical Reports Server (NTRS)

Singleterry, Robert C., Jr.; Thibeault, Sheila A.

2000-01-01

Various candidate aircraft and spacecraft materials were analyzed and compared in a low-energy neutron environment using the Monte Carlo N-Particle (MCNP) transport code with an energy range up to 20 MeV. Some candidate materials have been tested in particle beams, and others seemed reasonable to analyze in this manner before deciding to test them. The two metal alloys analyzed are actual materials being designed into or used in aircraft and spacecraft today. This analysis shows that hydrogen-bearing materials have the best shielding characteristics over the metal alloys. It also shows that neutrons above 1 MeV are reflected out of the face of the slab better by larger quantities of carbon in the material. If a low-energy absorber is added to the material, fewer neutrons are transmitted through the material. Future analyses should focus on combinations of scatterers and absorbers to optimize these reaction channels and on the higher energy neutron component (above 50 MeV).

Weight optimization of plane truss using genetic algorithm

NASA Astrophysics Data System (ADS)

Neeraja, D.; Kamireddy, Thejesh; Santosh Kumar, Potnuru; Simha Reddy, Vijay

2017-11-01

Optimization of structure on basis of weight has many practical benefits in every engineering field. The efficiency is proportionally related to its weight and hence weight optimization gains prime importance. Considering the field of civil engineering, weight optimized structural elements are economical and easier to transport to the site. In this study, genetic optimization algorithm for weight optimization of steel truss considering its shape, size and topology aspects has been developed in MATLAB. Material strength and Buckling stability have been adopted from IS 800-2007 code of construction steel. The constraints considered in the present study are fabrication, basic nodes, displacements, and compatibility. Genetic programming is a natural selection search technique intended to combine good solutions to a problem from many generations to improve the results. All solutions are generated randomly and represented individually by a binary string with similarities of natural chromosomes, and hence it is termed as genetic programming. The outcome of the study is a MATLAB program, which can optimise a steel truss and display the optimised topology along with element shapes, deflections, and stress results.

Review of Hybrid (Deterministic/Monte Carlo) Radiation Transport Methods, Codes, and Applications at Oak Ridge National Laboratory

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

Wagner, John C; Peplow, Douglas E.; Mosher, Scott W

2011-01-01

This paper provides a review of the hybrid (Monte Carlo/deterministic) radiation transport methods and codes used at the Oak Ridge National Laboratory and examples of their application for increasing the efficiency of real-world, fixed-source Monte Carlo analyses. The two principal hybrid methods are (1) Consistent Adjoint Driven Importance Sampling (CADIS) for optimization of a localized detector (tally) region (e.g., flux, dose, or reaction rate at a particular location) and (2) Forward Weighted CADIS (FW-CADIS) for optimizing distributions (e.g., mesh tallies over all or part of the problem space) or multiple localized detector regions (e.g., simultaneous optimization of two or moremore » localized tally regions). The two methods have been implemented and automated in both the MAVRIC sequence of SCALE 6 and ADVANTG, a code that works with the MCNP code. As implemented, the methods utilize the results of approximate, fast-running 3-D discrete ordinates transport calculations (with the Denovo code) to generate consistent space- and energy-dependent source and transport (weight windows) biasing parameters. These methods and codes have been applied to many relevant and challenging problems, including calculations of PWR ex-core thermal detector response, dose rates throughout an entire PWR facility, site boundary dose from arrays of commercial spent fuel storage casks, radiation fields for criticality accident alarm system placement, and detector response for special nuclear material detection scenarios and nuclear well-logging tools. Substantial computational speed-ups, generally O(102-4), have been realized for all applications to date. This paper provides a brief review of the methods, their implementation, results of their application, and current development activities, as well as a considerable list of references for readers seeking more information about the methods and/or their applications.« less

Exploration of perpendicular magnetic anisotropy material system for application in spin transfer torque - Random access memory

NASA Astrophysics Data System (ADS)

Natarajarathinam, Anusha

Perpendicular magnetic anisotropy (PMA) materials have unique advantages when used in magnetic tunnel junctions (MTJ) which are the most critical part of spin-torque transfer random access memory devices (STT-RAMs) that are being researched intensively as future non-volatile memory technology. They have high magnetoresistance which improves their sensitivity. The STT-RAM has several advantages over competing technologies, for instance, low power consumption, non-volatility, ultra-fast read and write speed and high endurance. In personal computers, it can replace SRAM for high-speed applications, Flash for non-volatility, and PSRAM and DRAM for high-speed program execution. The main aim of this research is to identify and optimize the best perpendicular magnetic anisotropy (PMA) material system for application to STT-RAM technology. Preliminary search for perpendicular magnetic anisotropy (PMA) materials for pinned layer for MTJs started with the exploration and optimization of crystalline alloys such as Co50Pd50 alloy, Mn50Al50 and amorphous alloys such as Tb21Fe72Co7 and are first presented in this work. Further optimization includes the study of Co/[Pd/Pt]x multilayers (ML), and the development of perpendicular synthetic antiferromagnets (SAF) utilizing these multilayers. Focused work on capping and seed layers to evaluate interfacial perpendicular anisotropy in free layers for pMTJs is then discussed. Optimization of the full perpendicular magnetic tunnel junction (pMTJ) includes the CoFeB/MgO/CoFeB trilayer coupled to a pinned/pinning layer with perpendicular Co/[Pd/Pt]x SAF and a thin Ta seeded CoFeB free layer. Magnetometry, simulations, annealing studies, transport measurements and TEM analysis on these samples will then be presented.

Reducing Weight for Transportation Applications: Technology Challenges and Opportunities

NASA Astrophysics Data System (ADS)

Taub, Alan I.

Today's land, sea and air transportation industries — as a business necessity — are focused on technology solutions that will make vehicles more sustainable in terms of energy, the environment, safety and affordability. Reducing vehicle weight is a key enabler for meeting these challenges as well as increasing payload and improving performance. The potential weight reductions from substituting lightweight metals (advanced high-strength steels, aluminum, magnesium and titanium alloys) are well established. For magnesium castings, weight savings of 60% have been reported [1]. The value of weight reduction depends on the transportation sector and ranges from about 5/kg saved for automobiles to over 500/kg saved for aircraft [2]. The challenge is to optimize the material properties and develop robust, high volume, manufacturing technologies and the associated supply chain to fabricate components and subsystems at the appropriate cost for each application.

An interdisciplinary computational/experimental approach to evaluate drug-loaded gold nanoparticle tumor cytotoxicity

PubMed Central

Curtis, Louis T; England, Christopher G; Wu, Min; Lowengrub, John; Frieboes, Hermann B

2016-01-01

Aim: Clinical translation of cancer nanotherapy has largely failed due to the infeasibility of optimizing the complex interaction of nano/drug/tumor/patient parameters. We develop an interdisciplinary approach modeling diffusive transport of drug-loaded gold nanoparticles in heterogeneously-vascularized tumors. Materials & methods: Evaluated lung cancer cytotoxicity to paclitaxel/cisplatin using novel two-layer (hexadecanethiol/phosphatidylcholine) and three-layer (with high-density-lipoprotein) nanoparticles. Computer simulations calibrated to in-vitro data simulated nanotherapy of heterogeneously-vascularized tumors. Results: Evaluation of free-drug cytotoxicity between monolayer/spheroid cultures demonstrates a substantial differential, with increased resistance conferred by diffusive transport. Nanoparticles had significantly higher efficacy than free-drug. Simulations of nanotherapy demonstrate 9.5% (cisplatin) and 41.3% (paclitaxel) tumor radius decrease. Conclusion: Interdisciplinary approach evaluating gold nanoparticle cytotoxicity and diffusive transport may provide insight into cancer nanotherapy. PMID:26829163

Evaluation of Laminar Flow Control System Concepts for Subsonic Commercial Transport Aircraft

NASA Technical Reports Server (NTRS)

Sturgeon, R. F.

1980-01-01

Alternatives in the design of laminar flow control (LFC) subsonic commerical transport aircraft for opeation in the 1980's period were studied. Analyses were conducted to select mission parameters and define optimum aircraft configurational parameters for the selected mission, defined by a passenger payload of 400 and a design range of 12, 038 km (6500 n mi). The baseline aircraft developed for this mission was used as a vehicle for the evaluation and development of alternative LFC system concepts. Alternatices in the areas of aerodynamics, structures and materials, LFC systems, leading-edge region cleaning, and integration of auxiliary systems were studied. Relative to a similarly-optimized advanced technology turbulent transport, the final LFC configuration is approximately equal in DOC but provides descreases of 8.2% in gross weight and 21.7% in fuel consumption.

Energy Dissipation and Transport in Carbon Nanotube Devices

NASA Astrophysics Data System (ADS)

Pop, Eric

2011-03-01

Power consumption is a significant challenge in electronics, often limiting the performance of integrated circuits from mobile devices to massive data centers. Carbon nanotubes have emerged as potentially energy-efficient future devices and interconnects, with both large mobility and thermal conductivity. This talk will focus on understanding and controlling energy dissipation [1-3] and transport [4-6] in carbon nanotubes, with applications to low-energy devices, interconnects, heat sinks, and memory elements. Experiments have been used to gain new insight into the fundamental behavior of such devices, and to better inform practical device models. The results suggest much room for energy optimization in nanoelectronics through the design of geometry, interfaces, and materials..

In Silico Modeling of Indigo and Tyrian Purple Single-Electron Nano-Transistors Using Density Functional Theory Approach

NASA Astrophysics Data System (ADS)

Shityakov, Sergey; Roewer, Norbert; Förster, Carola; Broscheit, Jens-Albert

2017-07-01

The purpose of this study was to develop and implement an in silico model of indigoid-based single-electron transistor (SET) nanodevices, which consist of indigoid molecules from natural dye weakly coupled to gold electrodes that function in a Coulomb blockade regime. The electronic properties of the indigoid molecules were investigated using the optimized density-functional theory (DFT) with a continuum model. Higher electron transport characteristics were determined for Tyrian purple, consistent with experimentally derived data. Overall, these results can be used to correctly predict and emphasize the electron transport functions of organic SETs, demonstrating their potential for sustainable nanoelectronics comprising the biodegradable and biocompatible materials.

Algorithms for optimization of the transport system in living and artificial cells.

PubMed

Melkikh, A V; Sutormina, M I

2011-06-01

An optimization of the transport system in a cell has been considered from the viewpoint of the operations research. Algorithms for an optimization of the transport system of a cell in terms of both the efficiency and a weak sensitivity of a cell to environmental changes have been proposed. The switching of various systems of transport is considered as the mechanism of weak sensitivity of a cell to changes in environment. The use of the algorithms for an optimization of a cardiac cell has been considered by way of example. We received theoretically for a cell of a cardiac muscle that at the increase of potassium concentration in the environment switching of transport systems for this ion takes place. This conclusion qualitatively coincides with experiments. The problem of synthesizing an optimal system in an artificial cell has been stated.

The Optimal Location of GEODSS Sensors in Canada

DTIC Science & Technology

1991-02-01

nteractive procedures for solving multiobjective transportation problems. A transportation problem is a classical linear programming problem where a...product must be transported from each of m sources to any of n destinations such that one or more objectives are optimized (36:96). The first algorithm...0, k - 1,...,L where z, is the fth element of zk The function z’(x) can now be optimized using any efficient, single-objectivc transportation

Short-pulse laser interactions with disordered materials and liquids

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

Phinney, L.M.; Goldman, C.H.; Longtin, J.P.

High-power, short-pulse lasers in the picosecond and subpicosecond range are utilized in an increasing number of technologies, including materials processing and diagnostics, micro-electronics and devices, and medicine. In these applications, the short-pulse radiation interacts with a wide range of media encompassing disordered materials and liquids. Examples of disordered materials include porous media, polymers, organic tissues, and amorphous forms of silicon, silicon nitride, and silicon dioxide. In order to accurately model, efficiently control, and optimize short-pulse, laser-material interactions, a thorough understanding of the energy transport mechanisms is necessary. Thus, fractals and percolation theory are used to analyze the anomalous diffusion regimemore » in random media. In liquids, the thermal aspects of saturable and multiphoton absorption are examined. Finally, a novel application of short-pulse laser radiation to reduce surface adhesion forces in microstructures through short-pulse laser-induced water desorption is presented.« less

Development of Spray on Bag for manufacturing of large composites parts: Diffusivity analysis

NASA Astrophysics Data System (ADS)

Dempah, Maxime Joseph

Bagging materials are utilized in many composites manufacturing processes. The selection is mainly driven by cost, temperature requirements, chemical compatibility and tear properties of the bag. The air barrier properties of the bag are assumed to be adequate or in many cases are not considered at all. However, the gas barrier property of a bag is the most critical parameter, as it can negatively affect the quality of the final laminate. The barrier property is a function of the bag material, uniformity, thickness and temperature. Improved barrier properties are needed for large parts, high pressure consolidated components and structures where air stays entrapped on the part surface. The air resistance property of the film is defined as permeability and is investigated in this thesis. A model was developed to evaluate the gas transport through the film and an experimental cell was implemented to characterize various commercial films. Understanding and characterizing the transport phenomena through the film allows optimization of the bagging material for various manufacturing processes. Spray-on-Bag is a scalable alternative bagging method compared to standard films. The approach allows in-situ fabrication of the bag on large and complex geometry structures where optimization of the bag properties can be varied on a local level. An experimental setup was developed and implemented using a six axis robot and an automated spraying system. Experiments were performed on a flat surface and specimens were characterized and compared to conventional films. Air barrier properties were within range of standard film approaches showing the potential to fabricate net shape bagging structures in an automated process.

Manganese oxide-based materials as electrochemical supercapacitor electrodes.

PubMed

Wei, Weifeng; Cui, Xinwei; Chen, Weixing; Ivey, Douglas G

2011-03-01

Electrochemical supercapacitors (ECs), characteristic of high power and reasonably high energy densities, have become a versatile solution to various emerging energy applications. This critical review describes some materials science aspects on manganese oxide-based materials for these applications, primarily including the strategic design and fabrication of these electrode materials. Nanostructurization, chemical modification and incorporation with high surface area, conductive nanoarchitectures are the three major strategies in the development of high-performance manganese oxide-based electrodes for EC applications. Numerous works reviewed herein have shown enhanced electrochemical performance in the manganese oxide-based electrode materials. However, many fundamental questions remain unanswered, particularly with respect to characterization and understanding of electron transfer and atomic transport of the electrochemical interface processes within the manganese oxide-based electrodes. In order to fully exploit the potential of manganese oxide-based electrode materials, an unambiguous appreciation of these basic questions and optimization of synthesis parameters and material properties are critical for the further development of EC devices (233 references).

Study on transfer optimization of urban rail transit and conventional public transport

NASA Astrophysics Data System (ADS)

Wang, Jie; Sun, Quan Xin; Mao, Bao Hua

2018-04-01

This paper mainly studies the time optimization of feeder connection between rail transit and conventional bus in a shopping center. In order to achieve the goal of connecting rail transportation effectively and optimizing the convergence between the two transportations, the things had to be done are optimizing the departure intervals, shorting the passenger transfer time and improving the service level of public transit. Based on the goal that has the minimum of total waiting time of passengers and the number of start of classes, establish the optimizing model of bus connecting of departure time. This model has some constrains such as transfer time, load factor, and the convergence of public transportation grid spacing. It solves the problems by using genetic algorithms.

Optimization of municipal solid waste collection and transportation routes.

PubMed

Das, Swapan; Bhattacharyya, Bidyut Kr

2015-09-01

Optimization of municipal solid waste (MSW) collection and transportation through source separation becomes one of the major concerns in the MSW management system design, due to the fact that the existing MSW management systems suffer by the high collection and transportation cost. Generally, in a city different waste sources scatter throughout the city in heterogeneous way that increase waste collection and transportation cost in the waste management system. Therefore, a shortest waste collection and transportation strategy can effectively reduce waste collection and transportation cost. In this paper, we propose an optimal MSW collection and transportation scheme that focus on the problem of minimizing the length of each waste collection and transportation route. We first formulize the MSW collection and transportation problem into a mixed integer program. Moreover, we propose a heuristic solution for the waste collection and transportation problem that can provide an optimal way for waste collection and transportation. Extensive simulations and real testbed results show that the proposed solution can significantly improve the MSW performance. Results show that the proposed scheme is able to reduce more than 30% of the total waste collection path length. Copyright © 2015 Elsevier Ltd. All rights reserved.

Pore-scale study of effects of macroscopic pores and their distributions on reactive transport in hierarchical porous media

DOE PAGES

Chen, Li; Zhang, Ruiyuan; Min, Ting; ...

2018-05-19

For applications of reactive transport in porous media, optimal porous structures should possess both high surface area for reactive sites loading and low mass transport resistance. Hierarchical porous media with a combination of pores at different scales are designed for this purpose. In this paper, using the lattice Boltzmann method, pore-scale numerical studies are conducted to investigate diffusion-reaction processes in 2D hierarchical porous media generated by self-developed reconstruction scheme. Complex interactions between porous structures and reactive transport are revealed under different conditions. Simulation results show that adding macropores can greatly enhance the mass transport, but at the same time reducemore » the reactive surface, leading to complex change trend of the total reaction rate. Effects of gradient distribution of macropores within the porous medium are also investigated. It is found that a front-loose, back-tight (FLBT) hierarchical structure is desirable for enhancing mass transport, increasing total reaction rate, and improving catalyst utilization. Finally, on the whole, from the viewpoint of reducing cost and improving material performance, hierarchical porous structures, especially gradient structures with the size of macropores gradually decreasing along the transport direction, are desirable for catalyst application.« less

Pore-scale study of effects of macroscopic pores and their distributions on reactive transport in hierarchical porous media

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

Chen, Li; Zhang, Ruiyuan; Min, Ting

For applications of reactive transport in porous media, optimal porous structures should possess both high surface area for reactive sites loading and low mass transport resistance. Hierarchical porous media with a combination of pores at different scales are designed for this purpose. In this paper, using the lattice Boltzmann method, pore-scale numerical studies are conducted to investigate diffusion-reaction processes in 2D hierarchical porous media generated by self-developed reconstruction scheme. Complex interactions between porous structures and reactive transport are revealed under different conditions. Simulation results show that adding macropores can greatly enhance the mass transport, but at the same time reducemore » the reactive surface, leading to complex change trend of the total reaction rate. Effects of gradient distribution of macropores within the porous medium are also investigated. It is found that a front-loose, back-tight (FLBT) hierarchical structure is desirable for enhancing mass transport, increasing total reaction rate, and improving catalyst utilization. Finally, on the whole, from the viewpoint of reducing cost and improving material performance, hierarchical porous structures, especially gradient structures with the size of macropores gradually decreasing along the transport direction, are desirable for catalyst application.« less

Automated sizing of large structures by mixed optimization methods

NASA Technical Reports Server (NTRS)

Sobieszczanski, J.; Loendorf, D.

1973-01-01

A procedure for automating the sizing of wing-fuselage airframes was developed and implemented in the form of an operational program. The program combines fully stressed design to determine an overall material distribution with mass-strength and mathematical programming methods to design structural details accounting for realistic design constraints. The practicality and efficiency of the procedure is demonstrated for transport aircraft configurations. The methodology is sufficiently general to be applicable to other large and complex structures.

Gibbs-Curie-Wulff Theorem in Organic Materials: A Case Study on the Relationship between Surface Energy and Crystal Growth.

PubMed

Li, Rongjin; Zhang, Xiaotao; Dong, Huanli; Li, Qikai; Shuai, Zhigang; Hu, Wenping

2016-02-24

The equilibrium crystal shape and shape evolution of organic crystals are found to follow the Gibbs-Curie-Wulff theorem. Organic crystals are grown by the physical vapor transport technique and exhibit exactly the same shape as predicted by the Gibbs-Curie-Wulff theorem under optimal conditions. This accordance provides concrete proof for the theorem. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dual Vacancies: An Effective Strategy Realizing Synergistic Optimization of Thermoelectric Property in BiCuSeO.

PubMed

Li, Zhou; Xiao, Chong; Fan, Shaojuan; Deng, Yu; Zhang, Wenshuai; Ye, Bangjiao; Xie, Yi

2015-05-27

Vacancy is a very important class of phonon scattering center to reduce thermal conductivity for the development of high efficient thermoelectric materials. However, conventional monovacancy may also act as an electron or hole acceptor, thereby modifying the electrical transport properties and even worsening the thermoelectric performance. This issue urges us to create new types of vacancies that scatter phonons effectively while not deteriorating the electrical transport. Herein, taking BiCuSeO as an example, we first reported the successful synergistic optimization of electrical and thermal parameters through Bi/Cu dual vacancies. As expected, as compared to its pristine and monovacancy samples, these dual vacancies further increase the phonon scattering, which results in an ultra low thermal conductivity of 0.37 W m(-1) K(-1) at 750 K. Most importantly, the clear-cut evidence in positron annihilation unambiguously confirms the interlayer charge transfer between these Bi/Cu dual vacancies, which results in the significant increase of electrical conductivity with relatively high Seebeck coefficient. As a result, BiCuSeO with Bi/Cu dual vacancies shows a high ZT value of 0.84 at 750 K, which is superior to that of its native sample and monovacancies-dominant counterparts. These findings undoubtedly elucidate a new strategy and direction for rational design of high performance thermoelectric materials.

Analysis of Advanced Thermoelectric Materials and Their Functional Limits

NASA Technical Reports Server (NTRS)

Kim, Hyun Jung

2015-01-01

The world's demand for energy is increasing dramatically, but the best energy conversion systems operate at approximately 30% efficiency. One way to decrease energy loss is in the recovery of waste heat using thermoelectric (TE) generators. A TE generator is device that generates electricity by exploiting heat flow across a thermal gradient. The efficiency of a TE material for power generation and cooling is determined by the dimensionless Figure of Merit (ZT): ZT = S(exp. 2)sigmaT/?: where S is the Seebeck coefficient, sigma is the electrical conductivity, T is the absolute temperature, and ? is the thermal conductivity. The parameters are not physically independent, but intrinsically coupled since they are a function of the transport properties of electrons. Traditional research on TE materials has focused on synthesizing bulk semiconductor-type materials that have low thermal conductivity and high electrical conductivity affording ZT values of 1. The optimization of the s/? ratio is difficult to achieve using current material formats, as these material constants are complementary. Recent areas of research are focusing on using nanostructural artifacts that introduce specific dislocations and boundary conditions that scatter the phonons. This disrupts the physical link between thermal (phonon) and electrical (electron) transport. The result is that ? is decreased without decreasing s. These material formats give ZT values of up to 2 which represent approximately 18% energy gain from waste heat recovery. The next challenge in developing the next generation of TE materials with superior performance is to tailor the interconnected thermoelectric physical parameters of the material system. In order to approach this problem, the fundamental physics of each parameter S, sigma, and ? need to be physically understood in their context of electron/phonon interaction for the construction of new high ZT thermoelectric devices. Is it possible to overcome the physical limit imposed by of the effect of phonon lattice oscillation and energetic electrons towards thermal conductivity? Is the Seebeck coefficient, based on the difference in voltage over temperature gradient ( deltaV/deltaT), an intrinsic parameter of each material? All these parameters were manipulated using nano-bridge and twin-lattice structural concepts at the NASA Langley Research Center. This talk will review the current trend of TE research to optimize the ZT and discuss about new approaches on increasing ZT within functional limits of each parameter.

A model to minimize joint total costs for industrial waste producers and waste management companies.

PubMed

Tietze-Stöckinger, Ingela; Fichtner, Wolf; Rentz, Otto

2004-12-01

The model LINKopt is a mixed-integer, linear programming model for mid- and long-term planning of waste management options on an inter-company level. There has been a large increase in the transportation of waste material in Germany, which has been attributed to the implementation of the European Directive 75/442/EEC on waste. Similar situations are expected to emerge in other European countries. The model LINKopt has been developed to determine a waste management system with minimal decision-relevant costs considering transportation, handling, storage and treatment of waste materials. The model can serve as a tool to evaluate various waste management strategies and to obtain the optimal combination of investment options. In addition to costs, ecological aspects are considered by determining the total mileage associated with the waste management system. The model has been applied to a German case study evaluating different investment options for a co-operation between Daimler-Chrysler AG at Rastatt, its suppliers, and the waste management company SITA P+R GmbH. The results show that the installation of waste management facilities at the premises of the waste producer would lead to significant reductions in costs and transportation.

Searching for the best thermoelectrics through the optimization of transport distribution function

NASA Astrophysics Data System (ADS)

Fan, Zheyong; Wang, Hui-Qiong; Zheng, Jin-Cheng

2011-04-01

The thermoelectric performance of materials is dependent on the interplay or competition among three key components, the electrical conductivity, thermopower, and thermal conductivity, which can be written as integrals of a single function, the transport distribution function (TDF). Mahan and Sofo [Proc. Natl. Acad. Sci. USA 93, 7436 (1996)] found that, mathematically, the thermoelectric properties could be maximized by a delta-shaped transport distribution, which was associated with a narrow distribution of the energy of the electrons participating in the transport process. In this work, we revisited the shape effect of TDF on thermoelectric figure of merit. It is confirmed both heuristically and numerically that among all the normalized TDF the Dirac delta function leads to the largest thermoelectric figure of merit. Whereas, for the case of TDF being bounded, a rectangular-shape distribution is instead found to be the most favorable one, which could be achieved through nanoroute. Our results also indicate that high thermoelectric figure of merit is associated with appropriate violations of the Wiedemann-Franz law.

Charge splitters and charge transport junctions based on guanine quadruplexes

NASA Astrophysics Data System (ADS)

Sha, Ruojie; Xiang, Limin; Liu, Chaoren; Balaeff, Alexander; Zhang, Yuqi; Zhang, Peng; Li, Yueqi; Beratan, David N.; Tao, Nongjian; Seeman, Nadrian C.

2018-04-01

Self-assembling circuit elements, such as current splitters or combiners at the molecular scale, require the design of building blocks with three or more terminals. A promising material for such building blocks is DNA, wherein multiple strands can self-assemble into multi-ended junctions, and nucleobase stacks can transport charge over long distances. However, nucleobase stacking is often disrupted at junction points, hindering electric charge transport between the two terminals of the junction. Here, we show that a guanine-quadruplex (G4) motif can be used as a connector element for a multi-ended DNA junction. By attaching specific terminal groups to the motif, we demonstrate that charges can enter the structure from one terminal at one end of a three-way G4 motif, and can exit from one of two terminals at the other end with minimal carrier transport attenuation. Moreover, we study four-way G4 junction structures by performing theoretical calculations to assist in the design and optimization of these connectors.

Role of solute-transport models in the analysis of groundwater salinity problems in agricultural areas

USGS Publications Warehouse

Konikow, Leonard F.

1981-01-01

Undesirable salinity increases occur in both groundwater and surface water and are commonly related to agricultural practices. Groundwater recharge from precipitation or irrigation will transport and disperse residual salts concentrated by evapotranspiration, salts leached from soil and aquifer materials, as well as some dissolved fertilizers and pesticides. Where stream salinity is affected by agricultural practices, the increases in salt load usually are attributable mostly to a groundwater component of flow. Thus, efforts to predict, manage, or control stream salinity increases should consider the role of groundwater in salt transport. Two examples of groundwater salinity problems in Colorado, U.S.A., illustrate that a model which simulates accurately the transport and dispersion of solutes in flowing groundwater can be (1) a valuable investigative tool to help understand the processes and parameters controlling the movement and fate of the salt, and (2) a valuable management tool for predicting responses and optimizing the development and use of the total water resource. ?? 1981.

Lead iodide perovskite light-emitting field-effect transistor

PubMed Central

Chin, Xin Yu; Cortecchia, Daniele; Yin, Jun; Bruno, Annalisa; Soci, Cesare

2015-01-01

Despite the widespread use of solution-processable hybrid organic–inorganic perovskites in photovoltaic and light-emitting applications, determination of their intrinsic charge transport parameters has been elusive due to the variability of film preparation and history-dependent device performance. Here we show that screening effects associated to ionic transport can be effectively eliminated by lowering the operating temperature of methylammonium lead iodide perovskite (CH3NH3PbI3) field-effect transistors. Field-effect carrier mobility is found to increase by almost two orders of magnitude below 200 K, consistent with phonon scattering-limited transport. Under balanced ambipolar carrier injection, gate-dependent electroluminescence is also observed from the transistor channel, with spectra revealing the tetragonal to orthorhombic phase transition. This demonstration of CH3NH3PbI3 light-emitting field-effect transistors provides intrinsic transport parameters to guide materials and solar cell optimization, and will drive the development of new electro-optic device concepts, such as gated light-emitting diodes and lasers operating at room temperature. PMID:26108967

Heuristic Optimization Approach to Selecting a Transport Connection in City Public Transport

NASA Astrophysics Data System (ADS)

Kul'ka, Jozef; Mantič, Martin; Kopas, Melichar; Faltinová, Eva; Kachman, Daniel

2017-02-01

The article presents a heuristic optimization approach to select a suitable transport connection in the framework of a city public transport. This methodology was applied on a part of the public transport in Košice, because it is the second largest city in the Slovak Republic and its network of the public transport creates a complex transport system, which consists of three different transport modes, namely from the bus transport, tram transport and trolley-bus transport. This solution focused on examining the individual transport services and their interconnection in relevant interchange points.

Dopant-Free Tetrakis-Triphenylamine Hole Transporting Material for Efficient Tin-Based Perovskite Solar Cells.

PubMed

Ke, Weijun; Priyanka, Pragya; Vegiraju, Sureshraju; Stoumpos, Constantinos C; Spanopoulos, Ioannis; Soe, Chan Myae Myae; Marks, Tobin J; Chen, Ming-Chou; Kanatzidis, Mercouri G

2018-01-10

Developing dopant-free hole transporting layers (HTLs) is critical in achieving high-performance and robust state-of-the-art perovskite photovoltaics, especially for the air-sensitive tin-based perovskite systems. The commonly used HTLs require hygroscopic dopants and additives for optimal performance, which adds extra cost to manufacturing and limits long-term device stability. Here we demonstrate the use of a novel tetrakis-triphenylamine (TPE) small molecule prepared by a facile synthetic route as a superior dopant-free HTL for lead-free tin-based perovskite solar cells. The best-performing tin iodide perovskite cells employing the novel mixed-cation ethylenediammonium/formamidinium with the dopant-free TPE HTL achieve a power conversion efficiency as high as 7.23%, ascribed to the HTL's suitable band alignment and excellent hole extraction/collection properties. This efficiency is one of the highest reported so far for tin halide perovskite systems, highlighting potential application of TPE HTL material in low-cost high-performance tin-based perovskite solar cells.

Barriers and opportunities for passive removal of indoor ozone

NASA Astrophysics Data System (ADS)

Gall, Elliott T.; Corsi, Richard L.; Siegel, Jeffrey A.

2011-06-01

This paper presents a Monte Carlo simulation to assess passive removal materials (PRMs) that remove ozone with no additional energy input and minimal byproduct formation. Distributions for air exchange rate in a subset of homes in Houston, Texas, were taken from the literature and combined with background ozone removal rates in typical houses and previous experimentally determined ozone deposition velocities to activated carbon cloth and gypsum wallboard PRMs. The median ratio of indoor to outdoor ozone was predicted to be 0.16 for homes with no PRMs installed and ranged from 0.047 to 0.12 for homes with PRMs. Median values of ozone removal effectiveness in these homes ranged from 22% to 68% for the conditions investigated. Achieving an ozone removal effectiveness above 50% in half of the homes would require installing a large area of PRMs and providing enhanced air speed to transport pollutants to PRM surfaces. Challenges associated with achieving this removal include optimizing indoor transport and aesthetic implications of large surface areas of PRM materials.

Modeling of the Thermoelectric Properties of p-Type IrSb(sub 3)

NASA Technical Reports Server (NTRS)

Fleurial, J.

1994-01-01

IrSb(sub 3) is a compound of the skutterudite family of materials now being investigated at JPL. A combination of experimental and theoretical approaches has been recently applied at JPL to evaluate the potential of several thermoelectric materials such as n-type and p-type Si(sub 80) Ge(sub 20) alloys, n-type and p-type Bi(sub 2) Te(sub 3)-based alloys and p-type Ru(sub 2) Ge(sub 3) compound. The use of a comprehensive model for the thermal and electrical transport properties of a given material over its full temperature range of usefulness is a powerful tool for guiding experimental optimization of the composition, temperature and doping level as well as for predicting the maximum ZT value likely to be achieved.

Tuning transport properties of graphene three-terminal structures by mechanical deformation

NASA Astrophysics Data System (ADS)

Torres, V.; Faria, D.; Latgé, A.

2018-04-01

Straintronic devices made of carbon-based materials have been pushed up due to the graphene high mechanical flexibility and the possibility of interesting changes in transport properties. Properly designed strained systems have been proposed to allow optimized transport responses that can be explored in experimental realizations. In multiterminal systems, comparisons between schemes with different geometries are important to characterize the modifications introduced by mechanical deformations, especially if the deformations are localized at a central part of the system or extended in a large region. Then, in the present analysis, we study the strain effects on the transport properties of triangular and hexagonal graphene flakes, with zigzag and armchair edges, connected to three electronic terminals, formed by semi-infinite graphene nanoribbons. Using the Green's function formalism with circular renormalization schemes, and a single band tight-binding approximation, we find that resonant tunneling transport becomes relevant and is more affected by localized deformations in the hexagonal graphene flakes. Moreover, triangular systems with deformation extended to the leads, like longitudinal three-folded type, are shown as an interesting scenario for building nanoscale waveguides for electronic current.

Heterojunction PbS nanocrystal solar cells with oxide charge-transport layers.

PubMed

Hyun, Byung-Ryool; Choi, Joshua J; Seyler, Kyle L; Hanrath, Tobias; Wise, Frank W

2013-12-23

Oxides are commonly employed as electron-transport layers in optoelectronic devices based on semiconductor nanocrystals, but are relatively rare as hole-transport layers. We report studies of NiO hole-transport layers in PbS nanocrystal photovoltaic structures. Transient fluorescence experiments are used to verify the relevant energy levels for hole transfer. On the basis of these results, planar heterojunction devices with ZnO as the photoanode and NiO as the photocathode were fabricated and characterized. Solution-processed devices were used to systematically study the dependence on nanocrystal size and achieve conversion efficiency as high as 2.5%. Optical modeling indicates that optimum performance should be obtained with thinner oxide layers than can be produced reliably by solution casting. Room-temperature sputtering allows deposition of oxide layers as thin as 10 nm, which enables optimization of device performance with respect to the thickness of the charge-transport layers. The best devices achieve an open-circuit voltage of 0.72 V and efficiency of 5.3% while eliminating most organic material from the structure and being compatible with tandem structures.

Electrowetting on plasma-deposited fluorocarbon hydrophobic films for biofluid transport in microfluidics

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

Bayiati, P.; Tserepi, A.; Petrou, P. S.

2007-05-15

The present work focuses on the plasma deposition of fluorocarbon (FC) films on surfaces and the electrostatic control of their wettability (electrowetting). Such films can be employed for actuation of fluid transport in microfluidic devices, when deposited over patterned electrodes. Here, the deposition was performed using C{sub 4}F{sub 8} and the plasma parameters that permit the creation of films with optimized properties desirable for electrowetting were established. The wettability of the plasma-deposited surfaces was characterized by means of contact angle measurements (in the static and dynamic mode). The thickness of the deposited films was probed in situ by means ofmore » spectroscopic ellipsometry, while the surface roughness was provided by atomic force microscopy. These plasma-deposited FC films in combination with silicon nitride, a material of high dielectric constant, were used to create a dielectric structure that requires reduced voltages for successful electrowetting. Electrowetting experiments using protein solutions were conducted on such optimized dielectric structures and were compared with similar structures bearing commercial spin-coated Teflon registered amorphous fluoropolymer (AF) film as the hydrophobic top layer. Our results show that plasma-deposited FC films have desirable electrowetting behavior and minimal protein adsorption, a requirement for successful transport of biological solutions in 'digital' microfluidics.« less

Texture mapping via optimal mass transport.

PubMed

Dominitz, Ayelet; Tannenbaum, Allen

2010-01-01

In this paper, we present a novel method for texture mapping of closed surfaces. Our method is based on the technique of optimal mass transport (also known as the "earth-mover's metric"). This is a classical problem that concerns determining the optimal way, in the sense of minimal transportation cost, of moving a pile of soil from one site to another. In our context, the resulting mapping is area preserving and minimizes angle distortion in the optimal mass sense. Indeed, we first begin with an angle-preserving mapping (which may greatly distort area) and then correct it using the mass transport procedure derived via a certain gradient flow. In order to obtain fast convergence to the optimal mapping, we incorporate a multiresolution scheme into our flow. We also use ideas from discrete exterior calculus in our computations.

Electrochemical impedance spectroscopy for study of electronic structure in disordered organic semiconductors—Possibilities and limitations

NASA Astrophysics Data System (ADS)

Schauer, F.; Nádaždy, V.; Gmucová, K.

2018-04-01

There is potential in applying conjugated polymers in novel organic optoelectronic devices, where a comprehensive understanding of the fundamental processes and energetics involved during transport and recombination is still lacking, limiting further device optimization. The electronic transport modeling and its optimization need the energy distribution of transport and defect states, expressed by the energy distribution of the Density of States (DOS) function, as input/comparative parameters. We present the Energy Resolved-Electrochemical Impedance Spectroscopy (ER-EIS) method for the study of transport and defect electronic states in organic materials. The method allows mapping over unprecedentedly wide energy and DOS ranges. The ER-EIS spectroscopic method is based on the small signal interaction between the surface of the organic film and the liquid electrolyte containing reduction-oxidation (redox) species, which is similar to the extraction of an electron by an acceptor and capture of an electron by a donor at a semiconductor surface. The desired DOS of electronic transport and defect states can be derived directly from the measured redox response signal to the small voltage perturbation at the instantaneous position of the Fermi energy, given by the externally applied voltage. The theory of the ER-EIS method and conditions for its validity for solid polymers are presented in detail. We choose four case studies on poly(3-hexylthiophene-2,5-diyl) and poly[methyl(phenyl)silane] to show the possibilities of the method to investigate the electronic structure expressed by DOS of polymers with a high resolution of about 6 orders of magnitude and in a wide energy range of 6 eV.

Estimated Benefits of Variable-Geometry Wing Camber Control for Transport Aircraft

NASA Technical Reports Server (NTRS)

Bolonkin, Alexander; Gilyard, Glenn B.

1999-01-01

Analytical benefits of variable-camber capability on subsonic transport aircraft are explored. Using aerodynamic performance models, including drag as a function of deflection angle for control surfaces of interest, optimal performance benefits of variable camber are calculated. Results demonstrate that if all wing trailing-edge surfaces are available for optimization, drag can be significantly reduced at most points within the flight envelope. The optimization approach developed and illustrated for flight uses variable camber for optimization of aerodynamic efficiency (maximizing the lift-to-drag ratio). Most transport aircraft have significant latent capability in this area. Wing camber control that can affect performance optimization for transport aircraft includes symmetric use of ailerons and flaps. In this paper, drag characteristics for aileron and flap deflections are computed based on analytical and wind-tunnel data. All calculations based on predictions for the subject aircraft and the optimal surface deflection are obtained by simple interpolation for given conditions. An algorithm is also presented for computation of optimal surface deflection for given conditions. Benefits of variable camber for a transport configuration using a simple trailing-edge control surface system can approach more than 10 percent, especially for nonstandard flight conditions. In the cruise regime, the benefit is 1-3 percent.

Development of a reliable estimation procedure of radioactivity inventory in a BWR plant due to neutron irradiation for decommissioning

NASA Astrophysics Data System (ADS)

Tanaka, Ken-ichi; Ueno, Jun

2017-09-01

Reliable information of radioactivity inventory resulted from the radiological characterization is important in order to plan decommissioning planning and is also crucial in order to promote decommissioning in effectiveness and in safe. The information is referred to by planning of decommissioning strategy and by an application to regulator. Reliable information of radioactivity inventory can be used to optimize the decommissioning processes. In order to perform the radiological characterization reliably, we improved a procedure of an evaluation of neutron-activated materials for a Boiling Water Reactor (BWR). Neutron-activated materials are calculated with calculation codes and their validity should be verified with measurements. The evaluation of neutron-activated materials can be divided into two processes. One is a distribution calculation of neutron-flux. Another is an activation calculation of materials. The distribution calculation of neutron-flux is performed with neutron transport calculation codes with appropriate cross section library to simulate neutron transport phenomena well. Using the distribution of neutron-flux, we perform distribution calculations of radioactivity concentration. We also estimate a time dependent distribution of radioactivity classification and a radioactive-waste classification. The information obtained from the evaluation is utilized by other tasks in the preparatory tasks to make the decommissioning plan and the activity safe and rational.

Synthesis and study of photovoltaic performance on various photoelectrode materials for DSSCs: Optimization of compact layer on nanometer thickness

NASA Astrophysics Data System (ADS)

Surya, Subramanian; Thangamuthu, Rangasamy; Senthil Kumar, Sakkarapalayam Murugesan; Murugadoss, Govindhasamy

2017-02-01

Dye-sensitized solar cells (DSSCs) have gained widespread attention in recent years because of their low production costs, ease of fabrication process and tuneable optical properties, such as colour and transparency. In this work, we explored a strategy wherein nanoparticles of pure TiO2, TiO2sbnd SnO2 nanocomposite, Sn (10%) doped TiO2 and SnO2 synthesized by the simple chemical precipitation method were employed as photoelectrodes to enhance the photovoltaic conversion efficiency of solar cells. The nanoparticles were characterized by different characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM with EDX), transmission electron microscopy (TEM), high resolution electron microscopy (HR-TEM), UV-Visible absorbance (UV-vis), photoluminescence (PL), thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) measurements. Moreover, we also demonstrated the effect of thin compact layer in DSSCs by architecture with various precursor materials of different concentrations. We found that the optimized compact layer material TDIP (titanium diisopropoxide) with a concentration of 0.3 M % is produced the highest efficiency of 2.25% for Sn (10%) doped TiO2 electron transport material (ETM) and 4.38% was achieved for pure TiO2 ETM using SnCl2 compact layer with 0.1 M concentrations.

3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance

NASA Astrophysics Data System (ADS)

Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

2016-02-01

A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g-1 is realized for the optimised case of binary doping over the entire range of 1 A g-1 to 40 A g-1 with stability of 500 cycles at 40 A g-1. Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system.

3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance.

PubMed

Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

2016-02-12

A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g(-1) is realized for the optimised case of binary doping over the entire range of 1 A g(-1) to 40 A g(-1) with stability of 500 cycles at 40 A g(-1). Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system.

Multi objective genetic algorithm to optimize the local heat treatment of a hardenable aluminum alloy

NASA Astrophysics Data System (ADS)

Piccininni, A.; Palumbo, G.; Franco, A. Lo; Sorgente, D.; Tricarico, L.; Russello, G.

2018-05-01

The continuous research for lightweight components for transport applications to reduce the harmful emissions drives the attention to the light alloys as in the case of Aluminium (Al) alloys, capable to combine low density with high values of the strength-to-weight ratio. Such advantages are partially counterbalanced by the poor formability at room temperature. A viable solution is to adopt a localized heat treatment by laser of the blank before the forming process to obtain a tailored distribution of material properties so that the blank can be formed at room temperature by means of conventional press machines. Such an approach has been extensively investigated for age hardenable alloys, but in the present work the attention is focused on the 5000 series; in particular, the optimization of the deep drawing process of the alloy AA5754 H32 is proposed through a numerical/experimental approach. A preliminary investigation was necessary to correctly tune the laser parameters (focus length, spot dimension) to effectively obtain the annealed state. Optimal process parameters were then obtained coupling a 2D FE model with an optimization platform managed by a multi-objective genetic algorithm. The optimal solution (i.e. able to maximize the LDR) in terms of blankholder force and extent of the annealed region was thus evaluated and validated through experimental trials. A good matching between experimental and numerical results was found. The optimal solution allowed to obtain an LDR of the locally heat treated blank larger than the one of the material either in the wrought condition (H32) either in the annealed condition (H111).

Optimized interface and recrystallized grains by CsBr treatment for enhanced photovoltaic performance of perovskite solar cells

NASA Astrophysics Data System (ADS)

Liu, Li; Su, Pengyu; Yao, Huizhen; Wang, Jun; Fu, Wuyou; Liu, Xizhe; Yang, Haibin

2018-06-01

Doping, interface optimization and recrystallization are effective approaches for fabricating high performance perovskite solar cells (PSCs). In our work, simple CsBr treatment is introduced to improve the performance of TiO2 nanorods-based PSCs. Both Cs+ and Br- are doped into CH3NH3PbI3 simultaneously, as well as optimizes the interface between perovskite and hole-transporting material (HTM). In addition, the perovskite grains are recrystallized through this method. Finally, a power conversion efficiency (PCE) of 16.02% with 0.72 in fill factor (FF) and 1.08 in open circuit voltage (VOC) is obtained through CsBr treatment, which is 19.91% higher than that of untreated devices (13.36% with 0.65 in FF and 1.02 in VOC). Furthermore, the power output maintains ∼14% after 3500 h under the humidity within 15% at room temperature.

3D simulation of friction stir welding based on movable cellular automaton method

NASA Astrophysics Data System (ADS)

Eremina, Galina M.

2017-12-01

The paper is devoted to a 3D computer simulation of the peculiarities of material flow taking place in friction stir welding (FSW). The simulation was performed by the movable cellular automaton (MCA) method, which is a representative of particle methods in mechanics. Commonly, the flow of material in FSW is simulated based on computational fluid mechanics, assuming the material as continuum and ignoring its structure. The MCA method considers a material as an ensemble of bonded particles. The rupture of interparticle bonds and the formation of new bonds enable simulations of crack nucleation and healing as well as mas mixing and microwelding. The simulation results showed that using pins of simple shape (cylinder, cone, and pyramid) without a shoulder results in small displacements of plasticized material in workpiece thickness directions. Nevertheless, the optimal ratio of longitudinal velocity to rotational speed makes it possible to transport the welded material around the pin several times and to produce a joint of good quality.

The intelligence of dual simplex method to solve linear fractional fuzzy transportation problem.

PubMed

Narayanamoorthy, S; Kalyani, S

2015-01-01

An approach is presented to solve a fuzzy transportation problem with linear fractional fuzzy objective function. In this proposed approach the fractional fuzzy transportation problem is decomposed into two linear fuzzy transportation problems. The optimal solution of the two linear fuzzy transportations is solved by dual simplex method and the optimal solution of the fractional fuzzy transportation problem is obtained. The proposed method is explained in detail with an example.

Generic Superconducting Inhomogeneity in Single Crystal Fe(Te1-xSex) Probed by Nanostructure-transport

NASA Astrophysics Data System (ADS)

Yue, Chunlei; Hu, Jin; Liu, Xue; Mao, Zhiqiang; Wei, Jiang

2015-03-01

We have investigated the nano-scale electronic properties of the iron-based unconventional superconductor Fe(Te1-xSex) with optimal Se content x = 0.5. Using the microexfoliation method and ion milling thinning, we successfully produced Fe(Te1-xSex) devices with thickness varying from 90nm down to 12nm. Our transport measurements revealed a suppression of superconductivity coinciding with the loss of normal state metallicity. Through the simulation of the formation of superconducting region in nano-scale thin flakes, we show that our observation is in line with the nano-scale inhomogeneity proposed for this material; therefore it provides a more direct evidence for the nano-scale inhomogeneous superconductivity in Fe(Te1-xSex) .

Effect of Li 2O on the microstructure, magnetic and transport properties of Tl-2223 superconductor

DOE PAGES

Shipra, R.; Sefat, Athena Safa

2015-10-08

Here, the present study gives an account of the effect of addition of Li 2O on the ease of phase formation and superconducting properties of Tl 2Ba 2Ca 2Cu 3O 10 + δ (Tl-2223) material. Li 2O slightly decreases the superconducting transition temperature, while an optimal concentration of 20% Li 2O improves the critical current density (J c) by about two fold. We also found substantial effects on the synthesis temperature, microstructure and normal state transport properties of Tl-2223 with Li 2O addition. Short-time annealing under flowing Ar + 4%H 2 (1 h) further improves the superconducting volume fractions, asmore » well as J c.« less

Multi-paradigm simulation at nanoscale: Methodology and application to functional carbon material

NASA Astrophysics Data System (ADS)

Su, Haibin

2012-12-01

Multiparadigm methods to span the scales from quantum mechanics to practical issues of functional nanoassembly and nanofabrication are enabling first principles predictions to guide and complement the experimental developments by designing and optimizing computationally the materials compositions and structures to assemble nanoscale systems with the requisite properties. In this talk, we employ multi-paradigm approaches to investigate functional carbon materials with versatile character, including fullerene, carbon nanotube (CNT), graphene, and related hybrid structures, which have already created an enormous impact on next generation nano devices. The topics will cover the reaction dynamics of C60 dimerization and the more challenging complex tubular fullerene formation process in the peapod structures; the computational design of a new generation of peapod nano-oscillators, the predicted magnetic state in Nano Buds; opto-electronic properties of graphene nanoribbons; and disorder / vibronic effects on transport in carbonrich materials.

Porous Biodegradable Metals for Hard Tissue Scaffolds: A Review

PubMed Central

Yusop, A. H.; Bakir, A. A.; Shaharom, N. A.; Abdul Kadir, M. R.; Hermawan, H.

2012-01-01

Scaffolds have been utilized in tissue regeneration to facilitate the formation and maturation of new tissues or organs where a balance between temporary mechanical support and mass transport (degradation and cell growth) is ideally achieved. Polymers have been widely chosen as tissue scaffolding material having a good combination of biodegradability, biocompatibility, and porous structure. Metals that can degrade in physiological environment, namely, biodegradable metals, are proposed as potential materials for hard tissue scaffolding where biodegradable polymers are often considered as having poor mechanical properties. Biodegradable metal scaffolds have showed interesting mechanical property that was close to that of human bone with tailored degradation behaviour. The current promising fabrication technique for making scaffolds, such as computation-aided solid free-form method, can be easily applied to metals. With further optimization in topologically ordered porosity design exploiting material property and fabrication technique, porous biodegradable metals could be the potential materials for making hard tissue scaffolds. PMID:22919393

Transferable Reactive Force Fields: Extensions of ReaxFF-lg to Nitromethane.

PubMed

Larentzos, James P; Rice, Betsy M

2017-03-09

Transferable ReaxFF-lg models of nitromethane that predict a variety of material properties over a wide range of thermodynamic states are obtained by screening a library of ∼6600 potentials that were previously optimized through the Multiple Objective Evolutionary Strategies (MOES) approach using a training set that included information for other energetic materials composed of carbon, hydrogen, nitrogen, and oxygen. Models that best match experimental nitromethane lattice constants at 4.2 K and 1 atm are evaluated for transferability to high-pressure states at room temperature and are shown to better predict various liquid- and solid-phase structural, thermodynamic, and transport properties as compared to the existing ReaxFF and ReaxFF-lg parametrizations. Although demonstrated for an energetic material, the library of ReaxFF-lg models is supplied to the scientific community to enable new research explorations of complex reactive phenomena in a variety of materials research applications.

Heterogeneous Monolithic Integration of Single-Crystal Organic Materials.

PubMed

Park, Kyung Sun; Baek, Jangmi; Park, Yoonkyung; Lee, Lynn; Hyon, Jinho; Koo Lee, Yong-Eun; Shrestha, Nabeen K; Kang, Youngjong; Sung, Myung Mo

2017-02-01

Manufacturing high-performance organic electronic circuits requires the effective heterogeneous integration of different nanoscale organic materials with uniform morphology and high crystallinity in a desired arrangement. In particular, the development of high-performance organic electronic and optoelectronic devices relies on high-quality single crystals that show optimal intrinsic charge-transport properties and electrical performance. Moreover, the heterogeneous integration of organic materials on a single substrate in a monolithic way is highly demanded for the production of fundamental organic electronic components as well as complex integrated circuits. Many of the various methods that have been designed to pattern multiple heterogeneous organic materials on a substrate and the heterogeneous integration of organic single crystals with their crystal growth are described here. Critical issues that have been encountered in the development of high-performance organic integrated electronics are also addressed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Proton transport in functionalised additives for PEM fuel cells: contributions from atomistic simulations.

PubMed

Tölle, Pia; Köhler, Christof; Marschall, Roland; Sharifi, Monir; Wark, Michael; Frauenheim, Thomas

2012-08-07

The conventional polymer electrolyte membrane (PEM) materials for fuel cell applications strongly rely on temperature and pressure conditions for optimal performance. In order to expand the range of operating conditions of these conventional PEM materials, mesoporous functionalised SiO(2) additives are developed. It has been demonstrated that these additives themselves achieve proton conductivities approaching those of conventional materials. However, the proton conduction mechanisms and especially factors influencing charge carrier mobility under different hydration conditions are not well known and difficult to separate from concentration effects in experiments. This tutorial review highlights contributions of atomistic computer simulations to the basic understanding and eventual design of these materials. Some basic introduction to the theoretical and computational framework is provided to introduce the reader to the field, the techniques are in principle applicable to a wide range of other situations as well. Simulation results are directly compared to experimental data as far as possible.

Solving an emergency rescue materials problem under the joint reserves mode of government and framework agreement suppliers

PubMed Central

Sun, Xiao-Qing; Zhu, Rui; Li, Ming; Miao, Wang

2017-01-01

Emergency rescue material reserves are vital for the success of emergency rescue activities. In this study, we consider a situation where a government owned distribution center and framework agreement suppliers jointly store emergency rescue materials. Using a scenario-based approach to represent demand uncertainty, we propose a comprehensive transportation pattern for the following supply chain: “suppliers—government distribution center—disaster area.” Using a joint reserves model that includes the government and framework agreement suppliers, we develop a non-linear mathematic model that determines the choices of the framework suppliers, the corresponding optimal commitment quantities, and the quantity of materials that are stored at a government distribution center. Finally, we use IBM ILOG CPLEX to solve the numerical examples to verify the effectiveness of the mode and perform sensitivity analyses on the relevant parameters. PMID:29077722

Bio-inspired Murray materials for mass transfer and activity

NASA Astrophysics Data System (ADS)

Zheng, Xianfeng; Shen, Guofang; Wang, Chao; Li, Yu; Dunphy, Darren; Hasan, Tawfique; Brinker, C. Jeffrey; Su, Bao-Lian

2017-04-01

Both plants and animals possess analogous tissues containing hierarchical networks of pores, with pore size ratios that have evolved to maximize mass transport and rates of reactions. The underlying physical principles of this optimized hierarchical design are embodied in Murray's law. However, we are yet to realize the benefit of mimicking nature's Murray networks in synthetic materials due to the challenges in fabricating vascularized structures. Here we emulate optimum natural systems following Murray's law using a bottom-up approach. Such bio-inspired materials, whose pore sizes decrease across multiple scales and finally terminate in size-invariant units like plant stems, leaf veins and vascular and respiratory systems provide hierarchical branching and precise diameter ratios for connecting multi-scale pores from macro to micro levels. Our Murray material mimics enable highly enhanced mass exchange and transfer in liquid-solid, gas-solid and electrochemical reactions and exhibit enhanced performance in photocatalysis, gas sensing and as Li-ion battery electrodes.

Improvement and analysis of the hydrogen-cerium redox flow cell

NASA Astrophysics Data System (ADS)

Tucker, Michael C.; Weiss, Alexandra; Weber, Adam Z.

2016-09-01

The H2-Ce redox flow cell is optimized using commercially-available cell materials. Cell performance is found to be sensitive to the upper charge cutoff voltage, membrane boiling pretreatment, methanesulfonic-acid concentration, (+) electrode surface area and flow pattern, and operating temperature. Performance is relatively insensitive to membrane thickness, Cerium concentration, and all features of the (-) electrode including hydrogen flow. Cell performance appears to be limited by mass transport and kinetics in the cerium (+) electrode. Maximum discharge power of 895 mW cm-2 was observed at 60 °C; an energy efficiency of 90% was achieved at 50 °C. The H2-Ce cell is promising for energy storage assuming one can optimize Ce reaction kinetics and electrolyte.

David Adler Lectureship Award: n-point Correlation Functions in Heterogeneous Materials.

NASA Astrophysics Data System (ADS)

Torquato, Salvatore

2009-03-01

The determination of the bulk transport, electromagnetic, mechanical, and optical properties of heterogeneous materials has a long and venerable history, attracting the attention of some of the luminaries of science, including Maxwell, Lord Rayleigh, and Einstein. The bulk properties can be shown to depend rigorously upon infinite sets of various n-point correlation functions. Many different types of correlation functions arise, depending on the physics of the problem. A unified approach to characterize the microstructure and bulk properties of a large class of disordered materials is developed [S. Torquato, Random Heterogeneous Materials: Microstructure and Macroscopic Properties (Springer-Verlag, New York, 2002)]. This is accomplished via a canonical n-point function Hn from which one can derive exact analytical expressions for any microstructural function of interest. This microstructural information can then be used to estimate accurately the bulk properties of the material. Unlike homogeneous materials, seemingly different bulk properties (e.g., transport and mechanical properties) of a heterogeneous material can be linked to one another because of the common microstructure that they share. Such cross-property relations can be used to estimate one property given a measurement of another. A recently identified decorrelation principle, roughly speaking, refers to the phenomenon that unconstrained correlations that exist in low-dimensional disordered materials vanish as the space dimension becomes large. Among other results, this implies that in sufficiently high dimensions the densest spheres packings may be disordered (rather than ordered) [S. Torquato and F. H. Stillinger, ``New Conjectural Lower Bounds on the Optimal Density of Sphere Packings," Experimental Mathematics, 15, 307 (2006)].

Panthere V2: Multipurpose Simulation Software for 3D Dose Rate Calculations

NASA Astrophysics Data System (ADS)

Penessot, Gaël; Bavoil, Éléonore; Wertz, Laurent; Malouch, Fadhel; Visonneau, Thierry; Dubost, Julien

2017-09-01

PANTHERE is a multipurpose radiation protection software developed by EDF to calculate gamma dose rates in complex 3D environments. PANTHERE takes a key role in the EDF ALARA process, enabling to predict dose rates and to organize and optimize operations in high radiation environments. PANTHERE is also used for nuclear waste characterization, transport of nuclear materials, etc. It is used in most of the EDF engineering units and their design service providers and industrial partners.

On the effects of assembly compression on the performance of liquid-feed DMFCs under methanol-limiting conditions: A 2D numerical study

NASA Astrophysics Data System (ADS)

García-Salaberri, P. A.; Vera, M.

2015-07-01

The influence of assembly compression on the performance of liquid-feed DMFCs under methanol-limiting conditions is explored by means of a 2D/1D multiphysics across-the-channel model. The numerical formulation incorporates a comprehensive 2D description of the anode GDL, including two-phase phenomena, non-uniform anisotropic transport properties, and electrical contact resistances at the GDL/BPP interface. GDL effective properties are evaluated using empirical data corresponding to Toray® carbon paper. A simplified but physically sound 1D description, locally coupled to the 2D anode GDL model, is adopted to describe transport processes in the MPLs, membrane and cathode GDL, whereas the catalyst layers are treated as infinitely thin surfaces. Good agreement is found between the numerical results and previous experimental data. The interplay between assembly compression, bipolar plate material, and channel configuration is also investigated. The results show that there is an optimum GDL compression ratio in terms of overall power density, the optimal compression level being strongly dependent on bipolar plate material. Beyond the optimum, the detrimental effect of compression is larger in non-parallel flow fields due to the additional reduction of methanol transported by under-rib convection. The results suggest that, under certain conditions, this transport mechanism could be more important than diffusion in the anode of liquid-feed DMFCs.

Recent developments in fast pyrolysis of ligno-cellulosic materials.

PubMed

Kersten, Sascha; Garcia-Perez, Manuel

2013-06-01

Pyrolysis is a thermochemical process to convert ligno-cellulosic materials into bio-char and pyrolysis oil. This oil can be further upgraded or refined for electricity, transportation fuels and chemicals production. At the time of writing, several demonstration factories are considered worldwide aiming at maturing the technology. Research is focusing on understanding the underlying processes at all relevant scales, ranging from the chemistry of cell wall deconstruction to optimization of pyrolysis factories, in order to produce better quality oils for targeted uses. Among the several bio-oil applications that are currently investigated the production and fermentation of pyrolytic sugars explores the promising interface between thermochemistry and biotechnology. Copyright © 2013 Elsevier Ltd. All rights reserved.

Optimal III-nitride HEMTs: from materials and device design to compact model of the 2DEG charge density

NASA Astrophysics Data System (ADS)

Li, Kexin; Rakheja, Shaloo

2017-02-01

In this paper, we develop a physically motivated compact model of the charge-voltage (Q-V) characteristics in various III-nitride high-electron mobility transistors (HEMTs) operating under highly non-equilibrium transport conditions, i.e. high drain-source current. By solving the coupled Schrödinger-Poisson equation and incorporating the two-dimensional electrostatics in the channel, we obtain the charge at the top-of-the-barrier for various applied terminal voltages. The Q-V model accounts for cutting off of the negative momenta states from the drain terminal under high drain-source bias and when the transmission in the channel is quasi-ballistic. We specifically focus on AlGaN and AlInN as barrier materials and InGaN and GaN as the channel material in the heterostructure. The Q-V model is verified and calibrated against numerical results using the commercial TCAD simulator Sentaurus from Synopsys for a 20-nm channel length III-nitride HEMT. With 10 fitting parameters, most of which have a physical origin and can easily be obtained from numerical or experimental calibration, the compact Q-V model allows us to study the limits and opportunities of III-nitride technology. We also identify optimal material and geometrical parameters of the device that maximize the carrier concentration in the HEMT channel in order to achieve superior RF performance. Additionally, the compact charge model can be easily integrated in a hierarchical circuit simulator, such as Keysight ADS and CADENCE, to facilitate circuit design and optimization of various technology parameters.

A white organic light emitting diode based on anthracene-triphenylamine derivatives

NASA Astrophysics Data System (ADS)

Jiang, Quan; Qu, Jianjun; Yu, Junsheng; Tao, Silu; Gan, Yuanyuan; Jiang, Yadong

2010-10-01

White organic lighting-diode (WOLED) can be used as flat light sources, backlights for liquid crystal displays and full color displays. Recently, a research mainstream of white OLED is to develop the novel materials and optimize the structure of devices. In this work a WOLED with a structure of ITO/NPB/PAA/Alq3: x% rubrene/Alq3/Mg: Ag, was fabricated. The device has two light-emitting layers. NPB is used as a hole transport layer, PAA as a blue emitting layer, Alq3: rubrene host-guest system as a yellow emitting layer, and Alq3 close to the cathode as an electron transport layer. In the experiment, the doping concentration of rubrene was optimized. WOLED 1 with 4% rubrene achieved a maximum luminous efficiency of 1.80 lm/W, a maximum luminance of 3926 cd/m2 and CIE coordinates of (0.374, 0.341) .WOLED 2 with 2% rubrene achieved a maximum luminous efficiency of 0.65 lm/W, a maximum luminance of 7495cd/m2 and CIE coordinates of (0.365,0.365).

Designing new classes of high-power, high-brightness VECSELs

NASA Astrophysics Data System (ADS)

Moloney, J. V.; Zakharian, A. R.; Hader, J.; Koch, Stephan W.

2005-10-01

Optically-pumped vertical external cavity semiconductor lasers offer the exciting possibility of designing kW-class solid state lasers that provide significant advantages over their doped YAG, thin-disk YAG and fiber counterparts. The basic VECSEL/OPSL (optically-pumped semiconductor laser) structure consists of a very thin (approximately 6 micron thick) active mirror consisting of a DBR high-reflectivity stack followed by a multiple quantum well resonant periodic (RPG) structure. An external mirror (reflectivity typically between 94%-98%) provides conventional optical feedback to the active semiconductor mirror chip. The "cold" cavity needs to be designed to take into account the semiconductor sub-cavity resonance shift with temperature and, importantly, the more rapid shift of the semiconductor material gain peak with temperature. Thermal management proves critical in optimizing the device for serious power scaling. We will describe a closed-loop procedure that begins with a design of the semiconductor active epi structure. This feeds into the sub-cavity optimization, optical and thermal transport within the active structure and thermal transport though the various heat sinking elements. Novel schemes for power scaling beyond current record performances will be discussed.

Decision Support for Environmental Management of Industrial ...

EPA Pesticide Factsheets

Non-hazardous solid materials from industrial processes, once regarded as waste and disposed in landfills, offer numerous environmental and economic advantages when put to beneficial uses (BUs). Proper management of these industrial non-hazardous secondary materials (INSM) requires estimates of their probable environmental impacts among disposal as well as BU options. The U.S. Environmental Protection Agency (EPA) has recently approved new analytical methods (EPA Methods 1313–1316) to assess leachability of constituents of potential concern in these materials. These new methods are more realistic for many disposal and BU options than historical methods, such as the toxicity characteristic leaching protocol. Experimental data from these new methods are used to parameterize a chemical fate and transport (F&T) model to simulate long-term environmental releases from flue gas desulfurization gypsum (FGDG) when disposed of in an industrial landfill or beneficially used as an agricultural soil amendment. The F&T model is also coupled with optimization algorithms, the Beneficial Use Decision Support System (BUDSS), under development by EPA to enhance INSM management. The objective of this paper is to demonstrate the methodologies and encourage similar applications to improve environmental management and BUs of INSM through F&T simulation coupled with optimization, using realistic model parameterization.

Multiphase porous media modelling: A novel approach to predicting food processing performance.

PubMed

Khan, Md Imran H; Joardder, M U H; Kumar, Chandan; Karim, M A

2018-03-04

The development of a physics-based model of food processing is essential to improve the quality of processed food and optimize energy consumption. Food materials, particularly plant-based food materials, are complex in nature as they are porous and have hygroscopic properties. A multiphase porous media model for simultaneous heat and mass transfer can provide a realistic understanding of transport processes and thus can help to optimize energy consumption and improve food quality. Although the development of a multiphase porous media model for food processing is a challenging task because of its complexity, many researchers have attempted it. The primary aim of this paper is to present a comprehensive review of the multiphase models available in the literature for different methods of food processing, such as drying, frying, cooking, baking, heating, and roasting. A critical review of the parameters that should be considered for multiphase modelling is presented which includes input parameters, material properties, simulation techniques and the hypotheses. A discussion on the general trends in outcomes, such as moisture saturation, temperature profile, pressure variation, and evaporation patterns, is also presented. The paper concludes by considering key issues in the existing multiphase models and future directions for development of multiphase models.

The Intelligence of Dual Simplex Method to Solve Linear Fractional Fuzzy Transportation Problem

PubMed Central

Narayanamoorthy, S.; Kalyani, S.

2015-01-01

An approach is presented to solve a fuzzy transportation problem with linear fractional fuzzy objective function. In this proposed approach the fractional fuzzy transportation problem is decomposed into two linear fuzzy transportation problems. The optimal solution of the two linear fuzzy transportations is solved by dual simplex method and the optimal solution of the fractional fuzzy transportation problem is obtained. The proposed method is explained in detail with an example. PMID:25810713

Optimal Protocols and Optimal Transport in Stochastic Thermodynamics

NASA Astrophysics Data System (ADS)

Aurell, Erik; Mejía-Monasterio, Carlos; Muratore-Ginanneschi, Paolo

2011-06-01

Thermodynamics of small systems has become an important field of statistical physics. Such systems are driven out of equilibrium by a control, and the question is naturally posed how such a control can be optimized. We show that optimization problems in small system thermodynamics are solved by (deterministic) optimal transport, for which very efficient numerical methods have been developed, and of which there are applications in cosmology, fluid mechanics, logistics, and many other fields. We show, in particular, that minimizing expected heat released or work done during a nonequilibrium transition in finite time is solved by the Burgers equation and mass transport by the Burgers velocity field. Our contribution hence considerably extends the range of solvable optimization problems in small system thermodynamics.

Optimal protocols and optimal transport in stochastic thermodynamics.

PubMed

Aurell, Erik; Mejía-Monasterio, Carlos; Muratore-Ginanneschi, Paolo

2011-06-24

Thermodynamics of small systems has become an important field of statistical physics. Such systems are driven out of equilibrium by a control, and the question is naturally posed how such a control can be optimized. We show that optimization problems in small system thermodynamics are solved by (deterministic) optimal transport, for which very efficient numerical methods have been developed, and of which there are applications in cosmology, fluid mechanics, logistics, and many other fields. We show, in particular, that minimizing expected heat released or work done during a nonequilibrium transition in finite time is solved by the Burgers equation and mass transport by the Burgers velocity field. Our contribution hence considerably extends the range of solvable optimization problems in small system thermodynamics.

Optimizing pneumatic conveying of biomass materials

NASA Astrophysics Data System (ADS)

DiCianni, Matthew Edward Michael

2011-12-01

Biomass is a readily available but underutilized energy resource. One of the main challenges is the inability of biomass feed stocks like corn stover or wood chips to flow freely without intermittent jamming. This research integrated an automated pneumatic conveying system to efficiently transport biomass into a biomass reactor. Material was held in a storage container until an end effector attached to a 3-axis controller engaged the material to flow through pneumatic vacuum in the carrier fluid of air. The material was disengaged from the carrier fluid through centripetal forces induced by a cyclone separator. As the air was pulled out of the cyclone, the biomass drops out the bottom due to gravitational forces and fell into a secondary storage hopper. The second storage container was for testing purposes only, where the actual apparatus would use a vertically oriented lock hopper to feed material into the biomass reactor. In the experimental test apparatus, sensors measured the storage hopper weight (mass-flow rate), pressure drop from the blower, and input power consumption of the motor. Parameters that were adjusted during testing include pipe diameter, material type, and motor speed. Testing indicated that decreasing the motor speed below its maximum still allows for conveyance of the material without blockage forming in the piping. The data shows that the power consumption of the system can be reduced based on the size and weight of the material introduced to the conveying pipe. Also, conveying certain materials proved to be problematic with particular duct diameters. Ultimately, an optimal duct diameter that can perform efficiently for a broad range of materials was chosen for the given system. Through these improvements, the energy return on investment will be improved for biomass feed stocks, which is taking a step in the right direction to secure the nation's energy independence.

Interfacial Engineering and Charge Carrier Dynamics in Extremely Thin Absorber Solar Cells

NASA Astrophysics Data System (ADS)

Edley, Michael

Photovoltaic energy is a clean and renewable source of electricity; however, it faces resistance to widespread use due to cost. Nanostructuring decouples constraints related to light absorption and charge separation, potentially reducing cost by allowing a wider variety of processing techniques and materials to be used. However, the large interfacial areas also cause an increased dark current which negatively affects cell efficiency. This work focuses on extremely thin absorber (ETA) solar cells that used a ZnO nanowire array as a scaffold for an extremely thin CdSe absorber layer. Photoexcited electrons generated in the CdSe absorber are transferred to the ZnO layer, while photogenerated holes are transferred to the liquid electrolyte. The transfer of photoexcited carriers to their transport layer competes with bulk recombination in the absorber layer. After charge separation, transport of charge carriers to their respective contacts must occur faster than interfacial recombination for efficient collection. Charge separation and collection depend sensitively on the dimensions of the materials as well as their interfaces. We demonstrated that an optimal absorber thickness can balance light absorption and charge separation. By treating the ZnO/CdSe interface with a CdS buffer layer, we were able to improve the Voc and fill factor, increasing the ETA cell's efficiency from 0.53% to 1.34%, which is higher than that achievable using planar films of the same material. We have gained additional insight into designing ETA cells through the use of dynamic measurements. Ultrafast transient absorption spectroscopy revealed that characteristic times for electron injection from CdSe to ZnO are less than 1 ps. Electron injection is rapid compared to the 2 ns bulk lifetime in CdSe. Optoelectronic measurements such as transient photocurrent/photovoltage and electrochemical impedance spectroscopy were applied to study the processes of charge transport and interfacial recombination. With these techniques, the extension of the depletion layer from CdSe into ZnO was determined to be vital to suppression of interfacial recombination. However, depletion of the ZnO also restricted the effective diffusion core for electrons and slowed their transport. Thus, materials and geometries should be chosen to allow for a depletion layer that suppresses interfacial recombination without impeding electron transport to the point that it is detrimental to cell performance. Thin film solar cells are another promising technology that can reduce costs by relaxing material processing requirements. CuInxGa (1-x)Se (CIGS) is a well studied thin film solar cell material that has achieved good efficiencies of 22.6%. However, use of rare elements raise concerns over the use of CIGS for global power production. CuSbS2 shares chemistry with CuInSe2 and also presents desirable properties for thin film absorbers such as optimal band gap (1.5 eV), high absorption coefficient, and Earth-abundant and non-toxic elements. Despite the promise of CuSbS2, direct characterization of the material for solar cell application is scarce in the literature. CuSbS2 nanoplates were synthesized by a colloidal hot-injection method at 220 °C in oleylamine. The CuSbS2 platelets synthesized for 30 minutes had dimensions of 300 nm by 400 nm with a thickness of 50 nm and were capped with the insulating oleylamine synthesis ligand. The oleylamine synthesis ligand provides control over nanocrystal growth but is detrimental to intercrystal charge transport that is necessary for optoelectronic device applications. Solid-state and solution phase ligand exchange of oleylamine with S2- were used to fabricate mesoporous films of CuSbS2 nanoplates for application in solar cells. Exchange of the synthesis ligand with S2- resulted in a two order of magnitude increase in 4-point probe conductivity. Photoexcited carrier lifetimes of 1.4 ns were measured by time-resolved terahertz spectroscopy, indicating potential for CuSbS2 as a solar cell absorber material.

Minimizing stellarator turbulent transport by geometric optimization

NASA Astrophysics Data System (ADS)

Mynick, H. E.

2010-11-01

Up to now, a transport optimized stellarator has meant one optimized to minimize neoclassical transport,ootnotetextH.E. Mynick, Phys. Plasmas 13, 058102 (2006). while the task of also mitigating turbulent transport, usually the dominant transport channel in such designs, has not been addressed, due to the complexity of plasma turbulence in stellarators. However, with the advent of gyrokinetic codes valid for 3D geometries such as GENE,ootnotetextF. Jenko, W. Dorland, M. Kotschenreuther, B.N. Rogers, Phys. Plasmas 7, 1904 (2000). and stellarator optimization codes such as STELLOPT,ootnotetextA. Reiman, G. Fu, S. Hirshman, L. Ku, et al, Plasma Phys. Control. Fusion 41 B273 (1999). designing stellarators to also reduce turbulent transport has become a realistic possibility. We have been using GENE to characterize the dependence of turbulent transport on stellarator geometry,ootnotetextH.E Mynick, P.A. Xanthopoulos, A.H. Boozer, Phys.Plasmas 16 110702 (2009). and to identify key geometric quantities which control the transport level. From the information obtained from these GENE studies, we are developing proxy functions which approximate the level of turbulent transport one may expect in a machine of a given geometry, and have extended STELLOPT to use these in its cost function, obtaining stellarator configurations with turbulent transport levels substantially lower than those in the original designs.

49 CFR 107.117 - Emergency processing.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS... than the hazardous material to be transported) that could not be prevented if the application were...

49 CFR 107.117 - Emergency processing.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS... than the hazardous material to be transported) that could not be prevented if the application were...

49 CFR 176.168 - Transport of Class 1 (explosive) materials in vehicle spaces.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Transport of Class 1 (explosive) materials in vehicle spaces. 176.168 Section 176.168 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS CARRIAGE BY VESSEL Detailed...

Parametric study of a canard-configured transport using conceptual design optimization

NASA Technical Reports Server (NTRS)

Arbuckle, P. D.; Sliwa, S. M.

1985-01-01

Constrained-parameter optimization is used to perform optimal conceptual design of both canard and conventional configurations of a medium-range transport. A number of design constants and design constraints are systematically varied to compare the sensitivities of canard and conventional configurations to a variety of technology assumptions. Main-landing-gear location and canard surface high-lift performance are identified as critical design parameters for a statically stable, subsonic, canard-configured transport.

Mathematical model of highways network optimization

NASA Astrophysics Data System (ADS)

Sakhapov, R. L.; Nikolaeva, R. V.; Gatiyatullin, M. H.; Makhmutov, M. M.

2017-12-01

The article deals with the issue of highways network design. Studies show that the main requirement from road transport for the road network is to ensure the realization of all the transport links served by it, with the least possible cost. The goal of optimizing the network of highways is to increase the efficiency of transport. It is necessary to take into account a large number of factors that make it difficult to quantify and qualify their impact on the road network. In this paper, we propose building an optimal variant for locating the road network on the basis of a mathematical model. The article defines the criteria for optimality and objective functions that reflect the requirements for the road network. The most fully satisfying condition for optimality is the minimization of road and transport costs. We adopted this indicator as a criterion of optimality in the economic-mathematical model of a network of highways. Studies have shown that each offset point in the optimal binding road network is associated with all other corresponding points in the directions providing the least financial costs necessary to move passengers and cargo from this point to the other corresponding points. The article presents general principles for constructing an optimal network of roads.

Computational Modeling of Radiation Phenomenon in SiC for Nuclear Applications

NASA Astrophysics Data System (ADS)

Ko, Hyunseok

Silicon carbide (SiC) material has been investigated for promising nuclear materials owing to its superior thermo-mechanical properties, and low neutron cross-section. While the interest in SiC has been increasing, the lack of fundamental understanding in many radiation phenomena is an important issue. More specifically, these phenomena in SiC include the fission gas transport, radiation induced defects and its evolution, radiation effects on the mechanical stability, matrix brittleness of SiC composites, and low thermal conductivities of SiC composites. To better design SiC and SiC composite materials for various nuclear applications, understanding each phenomenon and its significance under specific reactor conditions is important. In this thesis, we used various modeling approaches to understand the fundamental radiation phenomena in SiC for nuclear applications in three aspects: (a) fission product diffusion through SiC, (b) optimization of thermodynamic stable self-interstitial atom clusters, (c) interface effect in SiC composite and their change upon radiation. In (a) fission product transport work, we proposed that Ag/Cs diffusion in high energy grain boundaries may be the upper boundary in unirradiated SiC at relevant temperature, and radiation enhanced diffusion is responsible for fast diffusion measured in post-irradiated fuel particles. For (b) the self-interstitial cluster work, thermodynamically stable clusters are identified as a function of cluster size, shape, and compositions using a genetic algorithm. We found that there are compositional and configurational transitions for stable clusters as the cluster size increases. For (c) the interface effect in SiC composite, we investigated recently proposed interface, which is CNT reinforced SiC composite. The analytical model suggests that CNT/SiC composites have attractive mechanical and thermal properties, and these fortify the argument that SiC composites are good candidate materials for the cladding. We used grand canonical monte carlo to optimize the interface, as a part of the stepping stone for further study using the interface.

Optimal control of thermally coupled Navier Stokes equations

NASA Technical Reports Server (NTRS)

Ito, Kazufumi; Scroggs, Jeffrey S.; Tran, Hien T.

1994-01-01

The optimal boundary temperature control of the stationary thermally coupled incompressible Navier-Stokes equation is considered. Well-posedness and existence of the optimal control and a necessary optimality condition are obtained. Optimization algorithms based on the augmented Lagrangian method with second order update are discussed. A test example motivated by control of transport process in the high pressure vapor transport (HVPT) reactor is presented to demonstrate the applicability of our theoretical results and proposed algorithm.

High performance p-type half-Heusler thermoelectric materials

NASA Astrophysics Data System (ADS)

Yu, Junjie; Xia, Kaiyang; Zhao, Xinbing; Zhu, Tiejun

2018-03-01

Half-Heusler compounds, which possess robust mechanical strength, good high temperature thermal stability and multifaceted physical properties, have been verified as a class of promising thermoelectric materials. During the last two decades, great progress has been made in half-Heusler thermoelectrics. In this review, we summarize some representative work of p-type half-Heusler materials, the thermoelectric performance of which has been remarkably enhanced in recent years. We introduce the features of the crystal and electronic structures of half-Heusler compounds, and successful strategies for optimizing electrical and thermal transport in the p-type RFeSb (R  =  V, Nb, Ta) and MCoSb (M  =  Ti, Zr, Hf) based systems, including band engineering, the formation of solid solutions and hierarchical phonon scattering. The outlook for future research directions of half-Heusler thermoelectrics is also presented.

The growth of zinc selenide single crystals by physical vapor transport in microgravity

NASA Technical Reports Server (NTRS)

Anderson, Elmer E.; Rosenberger, Franz E.; Cheng, Hai-Yuin

1990-01-01

Growth and characterization studies will be performed on zinc selenide single crystals. The high temperature outgassing behavior of the silica ampoule material will be studied in order to develop a cleaning and bake-out procedure that will minimize the amount of impurities introduced into the vapor from the ampoule materials and in particular during the seal-off procedure. The outgassing behavior of the ZnSe starting material will be studied during high vacuum refinement at elevated temperatures in order to develop a temperature pressure program that will optimize the removal of impurities while minimizing a shift in stoichiometry due to preferred evaporation of the higher fugacity component. The mass spectrometer system was completed, and after calibration, will be used to perform the above tasks. The system and its operation is described in detail.

Synthesis of carbon core–shell pore structures and their performance as supercapacitors

DOE PAGES

Ariyanto, Teguh; Dyatkin, Boris; Zhang, Gui-Rong; ...

2015-07-15

High-power supercapacitors require excellent electrolyte mobility within the pore network and high electrical conductivity for maximum capacitance and efficiency. Achieving high power typically requires sacrificing energy densities, as the latter demands a high specific surface area and narrow porosity that impedes ion transport. Here, we present a novel solution for this optimization problem: a nanostructured core–shell carbonaceous material that exhibits a microporous carbon core surrounded by a mesoporous, graphitic shell. The tunable synthesis parameters yielded a structure that features either a sharp or a gradual transition between the core and shell sections. Electrochemical supercapacitor testing using organic electrolyte revealed thatmore » these novel core–shell materials outperform carbons with homogeneous pore structures. The hybrid core–shell materials showed a combination of good capacitance retention, typical for the carbon present in the shell and high specific capacitance, typical for the core material. These materials achieved power densities in excess of 40 kW kg -1 at energy densities reaching 27 Wh kg -1.« less

Optimizing Nutrient Uptake in Biological Transport Networks

NASA Astrophysics Data System (ADS)

Ronellenfitsch, Henrik; Katifori, Eleni

2013-03-01

Many biological systems employ complex networks of vascular tubes to facilitate transport of solute nutrients, examples include the vascular system of plants (phloem), some fungi, and the slime-mold Physarum. It is believed that such networks are optimized through evolution for carrying out their designated task. We propose a set of hydrodynamic governing equations for solute transport in a complex network, and obtain the optimal network architecture for various classes of optimizing functionals. We finally discuss the topological properties and statistical mechanics of the resulting complex networks, and examine correspondence of the obtained networks to those found in actual biological systems.

10 CFR 71.5 - Transportation of licensed material.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 2 2010-01-01 2010-01-01 false Transportation of licensed material. 71.5 Section 71.5 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) PACKAGING AND TRANSPORTATION OF RADIOACTIVE MATERIAL General Provisions § 71.5 Transportation of licensed material. (a) Each licensee who transports licensed...

10 CFR 71.5 - Transportation of licensed material.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 2 2013-01-01 2013-01-01 false Transportation of licensed material. 71.5 Section 71.5 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) PACKAGING AND TRANSPORTATION OF RADIOACTIVE MATERIAL General Provisions § 71.5 Transportation of licensed material. (a) Each licensee who transports licensed...

10 CFR 71.5 - Transportation of licensed material.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 2 2012-01-01 2012-01-01 false Transportation of licensed material. 71.5 Section 71.5 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) PACKAGING AND TRANSPORTATION OF RADIOACTIVE MATERIAL General Provisions § 71.5 Transportation of licensed material. (a) Each licensee who transports licensed...

10 CFR 71.5 - Transportation of licensed material.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 2 2014-01-01 2014-01-01 false Transportation of licensed material. 71.5 Section 71.5 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) PACKAGING AND TRANSPORTATION OF RADIOACTIVE MATERIAL General Provisions § 71.5 Transportation of licensed material. (a) Each licensee who transports licensed...

10 CFR 71.5 - Transportation of licensed material.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 2 2011-01-01 2011-01-01 false Transportation of licensed material. 71.5 Section 71.5 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) PACKAGING AND TRANSPORTATION OF RADIOACTIVE MATERIAL General Provisions § 71.5 Transportation of licensed material. (a) Each licensee who transports licensed...

A Problem on Optimal Transportation

ERIC Educational Resources Information Center

Cechlarova, Katarina

2005-01-01

Mathematical optimization problems are not typical in the classical curriculum of mathematics. In this paper we show how several generalizations of an easy problem on optimal transportation were solved by gifted secondary school pupils in a correspondence mathematical seminar, how they can be used in university courses of linear programming and…

Disorder-assisted quantum transport in suboptimal decoherence regimes

PubMed Central

Novo, Leonardo; Mohseni, Masoud; Omar, Yasser

2016-01-01

We investigate quantum transport in binary tree structures and in hypercubes for the disordered Frenkel-exciton Hamiltonian under pure dephasing noise. We compute the energy transport efficiency as a function of disorder and dephasing rates. We demonstrate that dephasing improves transport efficiency not only in the disordered case, but also in the ordered one. The maximal transport efficiency is obtained when the dephasing timescale matches the hopping timescale, which represent new examples of the Goldilocks principle at the quantum scale. Remarkably, we find that in weak dephasing regimes, away from optimal levels of environmental fluctuations, the average effect of increasing disorder is to improve the transport efficiency until an optimal value for disorder is reached. Our results suggest that rational design of the site energies statistical distributions could lead to better performances in transport systems at nanoscale when their natural environments are far from the optimal dephasing regime. PMID:26726133

Hybrid UV-Ozone-Treated rGO-PEDOT:PSS as an Efficient Hole Transport Material in Inverted Planar Perovskite Solar Cells

NASA Astrophysics Data System (ADS)

Wang, Shuying; Huang, Xiaona; Sun, Haoxuan; Wu, Chunyang

2017-12-01

Inverted planar perovskite solar cells (PSCs), which are regarded as promising devices for new generation of photovoltaic systems, show many advantages, such as low-temperature film formation, low-cost fabrication, and smaller hysteresis compared with those of traditional n-i-p PSCs. As an important carrier transport layer in PSCs, the hole transport layer (HTL) considerably affects the device performance. Therefore, HTL modification becomes one of the most critical issues in improving the performance of PSCs. In this paper, we report an effective and environmentally friendly UV-ozone treatment method to enhance the hydrophilia of reduced graphene oxide (rGO) with its excellent electrical performance. The treated rGO was applied to doped poly(3,4-ethylenedioxythiophene) poly(styrene-sulfonate) (PEDOT:PSS) as HTL material of PSCs. Consequently, the performance of rGO/PEDOT:PSS-doped PSCs was improved significantly, with power conversion efficiency (PCE) of 10.7%, Jsc of 16.75 mA/cm2, Voc of 0.87 V, and FF of 75%. The PCE of this doped PSCs was 27% higher than that of the PSCs with pristine PEDOT:PSS as HTL. This performance was attributed to the excellent surface morphology and optimized hole mobility of the solution-processable rGO-modified PEDOT:PSS.

Simulations of Fuel Assembly and Fast-Electron Transport in Integrated Fast-Ignition Experiments on OMEGA

NASA Astrophysics Data System (ADS)

Solodov, A. A.; Theobald, W.; Anderson, K. S.; Shvydky, A.; Epstein, R.; Betti, R.; Myatt, J. F.; Stoeckl, C.; Jarrott, L. C.; McGuffey, C.; Qiao, B.; Beg, F. N.; Wei, M. S.; Stephens, R. B.

2013-10-01

Integrated fast-ignition experiments on OMEGA benefit from improved performance of the OMEGA EP laser, including higher contrast, higher energy, and a smaller focus. Recent 8-keV, Cu-Kα flash radiography of cone-in-shell implosions and cone-tip breakout measurements showed good agreement with the 2-D radiation-hydrodynamic simulations using the code DRACO. DRACO simulations show that the fuel assembly can be further improved by optimizing the compression laser pulse, evacuating air from the shell, and by adjusting the material of the cone tip. This is found to delay the cone-tip breakout by ~220 ps and increase the core areal density from ~80 mg/cm2 in the current experiments to ~500 mg/cm2 at the time of the OMEGA EP beam arrival before the cone-tip breakout. Simulations using the code LSP of fast-electron transport in the recent integrated OMEGA experiments with Cu-doped shells will be presented. Cu-doping is added to probe the transport of fast electrons via their induced Cu K-shell fluorescent emission. This material is based upon work supported by the Department of Energy National Nuclear Security Administration DE-NA0001944 and the Office of Science under DE-FC02-04ER54789.

49 CFR 178.338-2 - Material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Material. 178.338-2 Section 178.338-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers for Motor Vehicle Transportation § 178.338-2 Material. (a) All material used in the construction...

49 CFR 178.338-2 - Material.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Material. 178.338-2 Section 178.338-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers for Motor Vehicle Transportation § 178.338-2 Material. (a) All material used in the construction...

49 CFR 178.338-2 - Material.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Material. 178.338-2 Section 178.338-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers for Motor Vehicle Transportation § 178.338-2 Material. (a) All material used in the construction...

49 CFR 178.338-2 - Material.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Material. 178.338-2 Section 178.338-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers for Motor Vehicle Transportation § 178.338-2 Material. (a) All material used in the construction...

Electrical characterization of organic thin film transistors and alternative device architectures

NASA Astrophysics Data System (ADS)

Newman, Christopher R.

In the last 10--15 years, organic semiconductors have evolved from experimental curiosities into viable alternatives for practical applications involving large-area and low-cost electronics such as display backplanes, electronic paper, radio frequency identification (RFID) tags, and solar cells. Many of the initially-stated goals in this field have been achieved; organic semconductors have demonstrated performance comparable to or greater than amorphous silicon (a-Si), the entrenched technology for most of the applications listed above. At present, the major obstacles remaining to commercialization of devices based on organic semiconductors involve material stability, processing considerations and optimization of the other device components (e.g. metal contacts and dielectric materials). Despite these technical achievements, significant gaps remain in our understanding of the underlying transport physics in these devices. This thesis summarizes experiments performed on organic field-effect transistors (OFETs) in an attempt to address some of these knowledge gaps. The FET, in addition to being a very useful device for practical applications (such as the driving elements in pixel backplanes), is also a very flexible architecture from an experimental standpoint. The presence of a capacitively-coupled gate electrode allows the investigation of transport physics as a function of carrier concentration. For devices in which non-idealities (i.e. carrier traps) largely dictate the observed characteristics, this is a very useful feature. Although practical OFETs are fabricated as conventional single-gate structures on an organic thin film (OTFTs), more exotic structures can often provide insights that standard OTFTs cannot. Specifically, single-crystal OFETs allow the investigation of carrier transport in the absence of grain boundaries, and double-gated OTFTs facilitate the investigation and comparison of properties across two discrete interfaces. One of the remaining challenges in terms of achieving stability inorganic semiconductors involves understanding, and hopefully minimizing, the bias stress effect of operating OTFTs. Largely ignored during the years in which research groups sought to optimize the standard device metrics of field-effect mobility, current on/off ratio, and threshold voltage, operational stability is emerging as a dominant consideration in these materials. Experiments performed with the goal of quantifying and understanding the bias-stress effect in organic semiconductors are described at the end of this thesis.

49 CFR 109.17 - Emergency Orders.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS... an Administrator determines that a violation of a provision of the Federal hazardous material...

Modeling & processing of ceramic and polymer precursor ceramic matrix composite materials

NASA Astrophysics Data System (ADS)

Wang, Xiaolin

Synthesis and processing of novel materials with various advanced approaches have attracted much attention of engineers and scientists for the past thirty years. Many advanced materials display a number of exceptional properties and can be produced with different novel processing techniques. For example, AlN is a promising candidate for electronic, optical and opto-electronic applications due to its high thermal conductivity, high electrical resistivity, high acoustic wave velocity and large band gap. Large bulk AlN crystal can be produced by sublimation of AlN powder. Novel nonostructured multicomponent refractory metal-based ceramics (carbides, borides and nitrides) show a lot of exceptional mechanical, thermal and chemical properties, and can be easily produced by pyrolysis of suitable preceramic precursors mixed with metal particles. The objective of this work is to study sublimation and synthesis of AlN powder, and synthesis of SiC-based metal ceramics. For AlN sublimation crystal growth, we will focus on modeling the processes in the powder source that affect significantly the sublimation growth as a whole. To understand the powder porosity evolution and vapor transport during powder sublimation, the interplay between vapor transport and powder sublimation will be studied. A physics-based computational model will be developed considering powder sublimation and porosity evolution. Based on the proposed model, the effect of a central hole in the powder on the sublimation rate is studied and the result is compared to the case of powder without a hole. The effect of hole size on the sublimation rate will be studied. The effects of initial porosity, particle size and driving force on the sublimation rate are also studied. Moreover, the optimal growth condition for large diameter crystal quality and high growth rate will be determined. For synthesis of SiC-based metal ceramics, we will focus on developing a multi-scale process model to describe the dynamic behavior of filler particle reaction, microstructure evolution, at the microscale as well as transient fluid flow, heat transfer, and species transport at the macroscale. The model comprises of (i) a microscale model and (ii) a macroscale transport model, and aims to provide optimal conditions for the fabrication process of the ceramics. The porous media macroscale model for SiC-based metal-ceramic materials processing will be developed to understand the thermal polymer pyrolysis, chemical reaction of active fillers and transport phenomena in the porous media. The macroscale model will include heat and mass transfer, curing, pyrolysis, chemical reaction and crystallization in a mixture of preceramic polymers and submicron/nano-sized metal particles of uranium, zirconium, niobium, or hafnium. The effects of heating rate, sample size, size and volume ratio of the metal particles on the reaction rate and product uniformity will be studied. The microscale model will be developed for modeling the synthesis of SiC matrix and metal particles. The macroscale model provides thermal boundary conditions to the microscale model. The microscale model applies to repetitive units in the porous structure and describes mass transport, composition changes and motion of metal particles. The unit-cell is the representation unit of the source material, and it consists of several metal particles, SiC matrix and other components produced from the synthesis process. The reactions between different components, the microstructure evolution of the product will be considered. The effects of heating rate and metal particle size on species uniformity and microstructure are investigated.

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

PubMed

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

2014-12-23

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

Review of Hybrid (Deterministic/Monte Carlo) Radiation Transport Methods, Codes, and Applications at Oak Ridge National Laboratory

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

Wagner, John C; Peplow, Douglas E.; Mosher, Scott W

2010-01-01

This paper provides a review of the hybrid (Monte Carlo/deterministic) radiation transport methods and codes used at the Oak Ridge National Laboratory and examples of their application for increasing the efficiency of real-world, fixed-source Monte Carlo analyses. The two principal hybrid methods are (1) Consistent Adjoint Driven Importance Sampling (CADIS) for optimization of a localized detector (tally) region (e.g., flux, dose, or reaction rate at a particular location) and (2) Forward Weighted CADIS (FW-CADIS) for optimizing distributions (e.g., mesh tallies over all or part of the problem space) or multiple localized detector regions (e.g., simultaneous optimization of two or moremore » localized tally regions). The two methods have been implemented and automated in both the MAVRIC sequence of SCALE 6 and ADVANTG, a code that works with the MCNP code. As implemented, the methods utilize the results of approximate, fast-running 3-D discrete ordinates transport calculations (with the Denovo code) to generate consistent space- and energy-dependent source and transport (weight windows) biasing parameters. These methods and codes have been applied to many relevant and challenging problems, including calculations of PWR ex-core thermal detector response, dose rates throughout an entire PWR facility, site boundary dose from arrays of commercial spent fuel storage casks, radiation fields for criticality accident alarm system placement, and detector response for special nuclear material detection scenarios and nuclear well-logging tools. Substantial computational speed-ups, generally O(10{sup 2-4}), have been realized for all applications to date. This paper provides a brief review of the methods, their implementation, results of their application, and current development activities, as well as a considerable list of references for readers seeking more information about the methods and/or their applications.« less

Ultra-high density aligned Carbon-nanotube with controled nano-morphology for supercapacitors

NASA Astrophysics Data System (ADS)

Ghaffari, Mehdi; Zhao, Ran; Liu, Yang; Zhou, Yue; Cheng, Jiping; Guzman de Villoria, Roberto; Wardle, B. L.; Zhang, Q. M.

2012-02-01

Recent advances in fabricating controlled-morphology vertically aligned carbon nanotubes (VA-CNTs) with ultrahigh volume fractioncreate unique opportunities for developing unconventional supercapacitors with ultra-high energy density, power density, and long charge/discharge cycle life.Continuous paths through inter-VA-CNT channels allow fast ion transport, and high electrical conduction of the aligned CNTs in the composite electrodes lead to fast discharge speed. We investigate the charge-discharge characteristics of VA-CNTs with >20 vol% of CNT and ionic liquids as electrolytes. By employing both the electric and electromechanical spectroscopes, as well as nanostructured materials characterization, the ion transport and storage behaviors in porous electrodes are studied. The results suggest pathways for optimizing the electrode morphology in supercapacitorsusing ultra-high volume fraction VA-CNTs to further enhance performance.

49 CFR 109.17 - Emergency Orders.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS PROCEDURAL REGULATIONS FOR OPENING OF PACKAGES, EMERGENCY ORDERS, AND...

49 CFR 109.17 - Emergency Orders.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS PROCEDURAL REGULATIONS FOR OPENING OF PACKAGES, EMERGENCY ORDERS, AND...

49 CFR 109.17 - Emergency Orders.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS PROCEDURAL REGULATIONS FOR OPENING OF PACKAGES, EMERGENCY ORDERS, AND...

49 CFR 109.3 - Inspections and Investigations.

Code of Federal Regulations, 2011 CFR

2011-10-01

....3 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS PROCEDURAL REGULATIONS FOR OPENING OF PACKAGES, EMERGENCY...

41 CFR 101-42.405 - Transportation of hazardous materials.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 41 Public Contracts and Property Management 2 2010-07-01 2010-07-01 true Transportation of... Destruction of Surplus Hazardous Materials and Certain Categories of Property § 101-42.405 Transportation of hazardous materials. The transportation of hazardous materials is governed by the hazardous materials...

41 CFR 101-42.405 - Transportation of hazardous materials.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 41 Public Contracts and Property Management 2 2014-07-01 2012-07-01 true Transportation of... Destruction of Surplus Hazardous Materials and Certain Categories of Property § 101-42.405 Transportation of hazardous materials. The transportation of hazardous materials is governed by the hazardous materials...

41 CFR 101-42.405 - Transportation of hazardous materials.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 41 Public Contracts and Property Management 2 2011-07-01 2007-07-01 true Transportation of... Destruction of Surplus Hazardous Materials and Certain Categories of Property § 101-42.405 Transportation of hazardous materials. The transportation of hazardous materials is governed by the hazardous materials...

Improvement and analysis of the hydrogen-cerium redox flow cell

DOE PAGES

Tucker, Michael C.; Weiss, Alexandra; Weber, Adam Z.

2016-08-03

In this paper, the H 2-Ce redox flow cell is optimized using commercially-available cell materials. Cell performance is found to be sensitive to the upper charge cutoff voltage, membrane boiling pretreatment, methanesulfonic-acid concentration, (+) electrode surface area and flow pattern, and operating temperature. Performance is relatively insensitive to membrane thickness, Cerium concentration, and all features of the (-) electrode including hydrogen flow. Cell performance appears to be limited by mass transport and kinetics in the cerium (+) electrode. Maximum discharge power of 895 mW cm -2 was observed at 60 °C; an energy efficiency of 90% was achieved at 50more » °C. Finally, the H 2-Ce cell is promising for energy storage assuming one can optimize Ce reaction kinetics and electrolyte.« less

Mathematical Analysis and Optimization of Infiltration Processes

NASA Technical Reports Server (NTRS)

Chang, H.-C.; Gottlieb, D.; Marion, M.; Sheldon, B. W.

1997-01-01

A variety of infiltration techniques can be used to fabricate solid materials, particularly composites. In general these processes can be described with at least one time dependent partial differential equation describing the evolution of the solid phase, coupled to one or more partial differential equations describing mass transport through a porous structure. This paper presents a detailed mathematical analysis of a relatively simple set of equations which is used to describe chemical vapor infiltration. The results demonstrate that the process is controlled by only two parameters, alpha and beta. The optimization problem associated with minimizing the infiltration time is also considered. Allowing alpha and beta to vary with time leads to significant reductions in the infiltration time, compared with the conventional case where alpha and beta are treated as constants.

Optimal transport and the placenta

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

Morgan, Simon; Xia, Qinglan; Salafia, Carolym

2010-01-01

The goal of this paper is to investigate the expected effects of (i) placental size, (ii) placental shape and (iii) the position of insertion of the umbilical cord on the work done by the foetus heart in pumping blood across the placenta. We use optimal transport theory and modeling to quantify the expected effects of these factors . Total transport cost and the shape factor contribution to cost are given by the optimal transport model. Total placental transport cost is highly correlated with birth weight, placenta weight, FPR and the metabolic scaling factor beta. The shape factor is also highlymore » correlated with birth weight, and after adjustment for placental weight, is highly correlated with the metabolic scaling factor beta.« less

49 CFR 178.338-2 - Material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Material. 178.338-2 Section 178.338-2 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SPECIFICATIONS FOR PACKAGINGS...

49 CFR 178.255-2 - Material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Material. 178.255-2 Section 178.255-2 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SPECIFICATIONS FOR PACKAGINGS...

Structural control of mixed ionic and electronic transport in conducting polymers

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

Rivnay, Jonathan; Inal, Sahika; Collins, Brian A.

Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate), PEDOT:PSS, has been utilized for over two decades as a stable, solution-processable hole conductor. While its hole transport properties have been the subject of intense investigation, recent work has turned to PEDOT:PSS as a mixed ionic/electronic conductor in applications including bioelectronics, energy storage and management, and soft robotics. Conducting polymers can efficiently transport both holes and ions when sufficiently hydrated, however, little is known about the role of morphology on mixed conduction. Here, we show that bulk ionic and electronic mobilities are simultaneously affected by processing-induced changes in nano- and meso-scale structure in PEDOT:PSS films. Wemore » quantify domain composition, and find that domain purification on addition of dispersion co-solvents limits ion mobility, even while electronic conductivity improves. We show that an optimal morphology allows for the balanced ionic and electronic transport that is critical for prototypical mixed conductor devices. As a result, these findings may pave the way for the rational design of polymeric materials and processing routes to enhance devices reliant on mixed conduction.« less

Structural control of mixed ionic and electronic transport in conducting polymers

DOE PAGES

Rivnay, Jonathan; Inal, Sahika; Collins, Brian A.; ...

2016-04-19

Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate), PEDOT:PSS, has been utilized for over two decades as a stable, solution-processable hole conductor. While its hole transport properties have been the subject of intense investigation, recent work has turned to PEDOT:PSS as a mixed ionic/electronic conductor in applications including bioelectronics, energy storage and management, and soft robotics. Conducting polymers can efficiently transport both holes and ions when sufficiently hydrated, however, little is known about the role of morphology on mixed conduction. Here, we show that bulk ionic and electronic mobilities are simultaneously affected by processing-induced changes in nano- and meso-scale structure in PEDOT:PSS films. Wemore » quantify domain composition, and find that domain purification on addition of dispersion co-solvents limits ion mobility, even while electronic conductivity improves. We show that an optimal morphology allows for the balanced ionic and electronic transport that is critical for prototypical mixed conductor devices. As a result, these findings may pave the way for the rational design of polymeric materials and processing routes to enhance devices reliant on mixed conduction.« less

Characterization of Primary Carrier Transport Properties of the Light-Harvesting Chalcopyrite Semiconductors CuIn(S 1–xSe x) 2

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

Frick, Jessica J.; Kushwaha, Satya K.; Cava, Robert J.

We report the carrier transport properties of CuIn(S 1-xSe x) 2 (0 ≤ x ≤ 1), a promising chalcopyrite semiconductor series for solar water splitting. A low concentration Mg dopant is used to decrease the carrier resistivity through facilitating bulk p-type transport at ambient temperature. Temperature-dependent resistivity measurements reveal a four-order magnitude decrease in bulk electrical resistivity (from 10 3 to 10 –1 Ohm cm) for 1% Mg-doped CuIn(S 1–xSe x) 2 as x increases from 0 to 1. Hall effect measurements at room temperature reveal p-type majority carrier concentrations that vary from 10 15 to 10 18 cm –3more » and mobilities of approximately 1–10 cm 2 V –1 s –1. These results provide insights into the fundamental carrier transport properties of CuIn(S 1–xSe x) 2 and will be of value in optimizing these materials further for photoelectrochemistry applications.« less

Characterization of Primary Carrier Transport Properties of the Light-Harvesting Chalcopyrite Semiconductors CuIn(S 1–xSe x) 2

DOE PAGES

Frick, Jessica J.; Kushwaha, Satya K.; Cava, Robert J.; ...

2017-07-27

We report the carrier transport properties of CuIn(S 1-xSe x) 2 (0 ≤ x ≤ 1), a promising chalcopyrite semiconductor series for solar water splitting. A low concentration Mg dopant is used to decrease the carrier resistivity through facilitating bulk p-type transport at ambient temperature. Temperature-dependent resistivity measurements reveal a four-order magnitude decrease in bulk electrical resistivity (from 10 3 to 10 –1 Ohm cm) for 1% Mg-doped CuIn(S 1–xSe x) 2 as x increases from 0 to 1. Hall effect measurements at room temperature reveal p-type majority carrier concentrations that vary from 10 15 to 10 18 cm –3more » and mobilities of approximately 1–10 cm 2 V –1 s –1. These results provide insights into the fundamental carrier transport properties of CuIn(S 1–xSe x) 2 and will be of value in optimizing these materials further for photoelectrochemistry applications.« less

78 FR 42998 - Hazardous Materials: Improving the Safety of Railroad Transportation of Hazardous Materials

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-18

... Materials: Improving the Safety of Railroad Transportation of Hazardous Materials AGENCY: Pipeline and... that affect the safety of the transportation of hazardous materials by rail and are seeking input from... authority to FRA. 49 CFR 1.89(a) through (q). The Federal hazardous materials transportation laws, 49 U.S.C...

Electric measurements of PV heterojunction structures a-SiC/c-Si

NASA Astrophysics Data System (ADS)

Perný, Milan; Šály, Vladimír; Janíček, František; Mikolášek, Miroslav; Váry, Michal; Huran, Jozef

2018-01-01

Due to the particular advantages of amorphous silicon or its alloys with carbon in comparison to conventional crystalline materials makes such a material still interesting for study. The amorphous silicon carbide may be used in a number of micro-mechanical and micro-electronics applications and also for photovoltaic energy conversion devices. Boron doped thin layers of amorphous silicon carbide, presented in this paper, were prepared due to the optimization process for preparation of heterojunction solar cell structure. DC and AC measurement and subsequent evaluation were carried out in order to comprehensively assess the electrical transport processes in the prepared a-SiC/c-Si structures. We have investigated the influence of methane content in deposition gas mixture and different electrode configuration.

A study of gamma-ray and neutron radiation in the interaction of a 2 MeV proton beam with various materials.

PubMed

Kasatov, D; Makarov, A; Shchudlo, I; Taskaev, S

2015-12-01

Epithermal neutron source based on a tandem accelerator with vacuum insulation and lithium target has been proposed, developed and operated in Budker Institute of Nuclear Physics. The source is regarded as a prototype of a future compact device suitable for carrying out BNCT in oncology centers. In this work the measurements of gamma-ray and neutron radiation are presented for the interaction of a 2 MeV proton beam with various materials (Li, C, F, Al, V, Ti, Cu, Mo, stainless steel, and Ta). The obtained results enabled the optimization of the neutron-generating target and the high energy beam transportation path. Copyright © 2015 Elsevier Ltd. All rights reserved.

Edge remap for solids

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

Kamm, James R.; Love, Edward; Robinson, Allen C.

We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approachmore » is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.« less

Predictive framework for shape-selective separations in three-dimensional zeolites and metal-organic frameworks.

PubMed

First, Eric L; Gounaris, Chrysanthos E; Floudas, Christodoulos A

2013-05-07

With the growing number of zeolites and metal-organic frameworks (MOFs) available, computational methods are needed to screen databases of structures to identify those most suitable for applications of interest. We have developed novel methods based on mathematical optimization to predict the shape selectivity of zeolites and MOFs in three dimensions by considering the energy costs of transport through possible pathways. Our approach is applied to databases of over 1800 microporous materials including zeolites, MOFs, zeolitic imidazolate frameworks, and hypothetical MOFs. New materials are identified for applications in gas separations (CO2/N2, CO2/CH4, and CO2/H2), air separation (O2/N2), and chemicals (propane/propylene, ethane/ethylene, styrene/ethylbenzene, and xylenes).

49 CFR 172.101 - Purpose and use of hazardous materials table.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Purpose and use of hazardous materials table. 172.101 Section 172.101 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS HAZARDOUS MATERIALS TABLE, SPECIAL PROVISIONS,...

49 CFR 172.101 - Purpose and use of hazardous materials table.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Purpose and use of hazardous materials table. 172.101 Section 172.101 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS HAZARDOUS MATERIALS TABLE, SPECIAL PROVISIONS,...

49 CFR 172.101 - Purpose and use of hazardous materials table.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Purpose and use of hazardous materials table. 172.101 Section 172.101 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS HAZARDOUS MATERIALS TABLE, SPECIAL PROVISIONS,...

3D Polyaniline Architecture by Concurrent Inorganic and Organic Acid Doping for Superior and Robust High Rate Supercapacitor Performance

PubMed Central

Gawli, Yogesh; Banerjee, Abhik; Dhakras, Dipti; Deo, Meenal; Bulani, Dinesh; Wadgaonkar, Prakash; Shelke, Manjusha; Ogale, Satishchandra

2016-01-01

A good high rate supercapacitor performance requires a fine control of morphological (surface area and pore size distribution) and electrical properties of the electrode materials. Polyaniline (PANI) is an interesting material in supercapacitor context because it stores energy Faradaically. However in conventional inorganic (e.g. HCl) acid doping, the conductivity is high but the morphological features are undesirable. On the other hand, in weak organic acid (e.g. phytic acid) doping, interesting and desirable 3D connected morphological features are attained but the conductivity is poorer. Here the synergy of the positive quality factors of these two acid doping approaches is realized by concurrent and optimized strong-inorganic (HCl) and weak-organic (phytic) acid doping, resulting in a molecular composite material that renders impressive and robust supercapacitor performance. Thus, a nearly constant high specific capacitance of 350 F g−1 is realized for the optimised case of binary doping over the entire range of 1 A g−1 to 40 A g−1 with stability of 500 cycles at 40 A g−1. Frequency dependant conductivity measurements show that the optimized co-doped case is more metallic than separately doped materials. This transport property emanates from the unique 3D single molecular character of such system. PMID:26867570

Nanocarbon networks for advanced rechargeable lithium batteries.

PubMed

Xin, Sen; Guo, Yu-Guo; Wan, Li-Jun

2012-10-16

Carbon is one of the essential elements in energy storage. In rechargeable lithium batteries, researchers have considered many types of nanostructured carbons, such as carbon nanoparticles, carbon nanotubes, graphene, and nanoporous carbon, as anode materials and, especially, as key components for building advanced composite electrode materials. Nanocarbons can form efficient three-dimensional conducting networks that improve the performance of electrode materials suffering from the limited kinetics of lithium storage. Although the porous structure guarantees a fast migration of Li ions, the nanocarbon network can serve as an effective matrix for dispersing the active materials to prevent them from agglomerating. The nanocarbon network also affords an efficient electron pathway to provide better electrical contacts. Because of their structural stability and flexibility, nanocarbon networks can alleviate the stress and volume changes that occur in active materials during the Li insertion/extraction process. Through the elegant design of hierarchical electrode materials with nanocarbon networks, researchers can improve both the kinetic performance and the structural stability of the electrode material, which leads to optimal battery capacity, cycling stability, and rate capability. This Account summarizes recent progress in the structural design, chemical synthesis, and characterization of the electrochemical properties of nanocarbon networks for Li-ion batteries. In such systems, storage occurs primarily in the non-carbon components, while carbon acts as the conductor and as the structural buffer. We emphasize representative nanocarbon networks including those that use carbon nanotubes and graphene. We discuss the role of carbon in enhancing the performance of various electrode materials in areas such as Li storage, Li ion and electron transport, and structural stability during cycling. We especially highlight the use of graphene to construct the carbon conducting network for alloy anodes, such as Si and Ge, to accelerate electron transport, alleviate volume change, and prevent the agglomeration of active nanoparticles. Finally, we describe the power of nanocarbon networks for the next generation rechargeable lithium batteries, including Li-S, Li-O(2), and Li-organic batteries, and provide insights into the design of ideal nanocarbon networks for these devices. In addition, we address the ways in which nanocarbon networks can expand the applications of rechargeable lithium batteries into the emerging fields of stationary energy storage and transportation.

Development of GEM detector for plasma diagnostics application: simulations addressing optimization of its performance

NASA Astrophysics Data System (ADS)

Chernyshova, M.; Malinowski, K.; Kowalska-Strzęciwilk, E.; Czarski, T.; Linczuk, P.; Wojeński, A.; Krawczyk, R. D.

2017-12-01

The advanced Soft X-ray (SXR) diagnostics setup devoted to studies of the SXR plasma emissivity is at the moment a highly relevant and important for ITER/DEMO application. Especially focusing on the energy range of tungsten emission lines, as plasma contamination by W and its transport in the plasma must be understood and monitored for W plasma-facing material. The Gas Electron Multiplier, with a spatial and energy-resolved photon detecting chamber, based SXR radiation detection system under development by our group may become such a diagnostic setup considering and solving many physical, technical and technological aspects. This work presents the results of simulations aimed to optimize a design of the detector's internal chamber and its performance. The study of the effect of electrodes alignment allowed choosing the gap distances which maximizes electron transmission and choosing the optimal magnitudes of the applied electric fields. Finally, the optimal readout structure design was identified suitable to collect a total formed charge effectively, basing on the range of the simulated electron cloud at the readout plane which was in the order of ~ 2 mm.

49 CFR 178.33-5 - Material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Material. 178.33-5 Section 178.33-5 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SPECIFICATIONS FOR PACKAGINGS Specifications for...

49 CFR 176.166 - Transport of Class 1 (explosive) materials on passenger vessels.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Transport of Class 1 (explosive) materials on....166 Transport of Class 1 (explosive) materials on passenger vessels. (a) Only the following Class 1 (explosive) materials may be transported as cargo on passenger vessels: (1) Division 1.4 (explosive...

49 CFR 176.168 - Transport of Class 1 (explosive) materials in vehicle spaces.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Transport of Class 1 (explosive) materials in... REGULATIONS CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Cargo Transport Units and Shipborne Barges § 176.168 Transport of Class 1 (explosive) materials in vehicle spaces. (a) All...

49 CFR 176.170 - Transport of Class 1 (explosive) materials in freight containers.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Transport of Class 1 (explosive) materials in... REGULATIONS CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Cargo Transport Units and Shipborne Barges § 176.170 Transport of Class 1 (explosive) materials in freight containers. (a...

49 CFR 176.166 - Transport of Class 1 (explosive) materials on passenger vessels.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Transport of Class 1 (explosive) materials on....166 Transport of Class 1 (explosive) materials on passenger vessels. (a) Only the following Class 1 (explosive) materials may be transported as cargo on passenger vessels: (1) Division 1.4 (explosive...

49 CFR 176.174 - Transport of Class 1 (explosive) materials in shipborne barges.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Transport of Class 1 (explosive) materials in... REGULATIONS CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Cargo Transport Units and Shipborne Barges § 176.174 Transport of Class 1 (explosive) materials in shipborne barges. (a...

49 CFR 176.174 - Transport of Class 1 (explosive) materials in shipborne barges.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Transport of Class 1 (explosive) materials in... REGULATIONS CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Cargo Transport Units and Shipborne Barges § 176.174 Transport of Class 1 (explosive) materials in shipborne barges. (a...

49 CFR 176.170 - Transport of Class 1 (explosive) materials in freight containers.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Transport of Class 1 (explosive) materials in... REGULATIONS CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Cargo Transport Units and Shipborne Barges § 176.170 Transport of Class 1 (explosive) materials in freight containers. (a...

49 CFR 176.168 - Transport of Class 1 (explosive) materials in vehicle spaces.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Transport of Class 1 (explosive) materials in... REGULATIONS CARRIAGE BY VESSEL Detailed Requirements for Class 1 (Explosive) Materials Cargo Transport Units and Shipborne Barges § 176.168 Transport of Class 1 (explosive) materials in vehicle spaces. (a) All...

Cost and fuel consumption per nautical mile for two engine jet transports using OPTIM and TRAGEN

NASA Technical Reports Server (NTRS)

Wiggs, J. F.

1982-01-01

The cost and fuel consumption per nautical mile for two engine jet transports are computed using OPTIM and TRAGEN. The savings in fuel and direct operating costs per nautical mile for each of the different types of optimal trajectories over a standard profile are shown.

Variable neighborhood search to solve the vehicle routing problem for hazardous materials transportation.

PubMed

Bula, Gustavo Alfredo; Prodhon, Caroline; Gonzalez, Fabio Augusto; Afsar, H Murat; Velasco, Nubia

2017-02-15

This work focuses on the Heterogeneous Fleet Vehicle Routing problem (HFVRP) in the context of hazardous materials (HazMat) transportation. The objective is to determine a set of routes that minimizes the total expected routing risk. This is a nonlinear function, and it depends on the vehicle load and the population exposed when an incident occurs. Thus, a piecewise linear approximation is used to estimate it. For solving the problem, a variant of the Variable Neighborhood Search (VNS) algorithm is employed. To improve its performance, a post-optimization procedure is implemented via a Set Partitioning (SP) problem. The SP is solved on a pool of routes obtained from executions of the local search procedure embedded on the VNS. The algorithm is tested on two sets of HFVRP instances based on literature with up to 100 nodes, these instances are modified to include vehicle and arc risk parameters. The results are competitive in terms of computational efficiency and quality attested by a comparison with Mixed Integer Linear Programming (MILP) previously proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

Application of Mobility Spectrum Analysis to Modern Multi-layered IR Device Material

NASA Astrophysics Data System (ADS)

Brown, Alexander Earl

Modern detector materials used for infrared (IR) imaging purposes contain complex multi-layered architectures, making more robust characterization techniques necessary. In order to determine mutli-carrier transport properties in the presence of mixed conduction, variable-field Hall characterization can be performed and then analyzed using mobility spectrum analysis to extract parameters of interest. Transport parameters are expected to aid in modeling and simulation of materials and can be used in optimization of particular problem areas. The performances of infrared devices ultimately depend on transport mechanisms, so an accurate determination becomes paramount. This work focuses on the characterization of two materials at the forefront of IR detectors; incumbent, tried and true, HgCdTe technologies and emergent III-V based superlattice structures holding much promise for future detector purposes. Ex-situ doped long-wave planar devices and in-situ doped mid-wave dual-layer heterojunctions (P+/n architecture) HgCdTe structures are explored with regards to substrate choice, namely lattice-matched CdZnTe and lattice-mismatched Si or GaAs. A detailed study of scattering mechanisms reveal that growth on lattice-mismatched substrates leads to dislocation scattering limited mobility at low temperature, correlating with extrinsically limited minority carrier lifetime and excesses diode tunneling current, resulting in overall lower performance. Mobility spectrum analysis proves to be an effective diagnostic on performance as well as providing insight in surface, substrate-interface, and minority carrier transport. Two main issues limiting performance of III-V based superlattices are addressed; high residual doping backgrounds and surface passivation. Mobility spectrum analysis proves to be a reliable method of determining background doping levels. Modest improvements are obtained via post-growth thermal annealing, but results suggest future efforts should be placed upon growth improvements. Passivation efforts using charged electret dielectric show promise but further refinements would be needed. Thiol passivation is identified as a successful passivant of Be-doped p-type InAs/GaSb long-wave absorbers using mobility spectrum analysis, correlating with fabricated device dark current. Mobility spectrum analysis demonstrates it will be indispensable in future development of III-V material.

49 CFR 110.80 - Procurement.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Procurement. 110.80 Section 110.80 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS PUBLIC SECTOR...

49 CFR 110.130 - Disputes.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Disputes. 110.130 Section 110.130 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS PUBLIC SECTOR...

49 CFR 110.10 - Eligibility.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Eligibility. 110.10 Section 110.10 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS PUBLIC SECTOR...

Optimization of a superconducting linear levitation system using a soft ferromagnet

NASA Astrophysics Data System (ADS)

Agramunt-Puig, Sebastia; Del-Valle, Nuria; Navau, Carles; Sanchez, Alvaro

2013-04-01

The use of guideways that combine permanent magnets and soft ferromagnetic materials is a common practice in magnetic levitation transport systems (maglevs) with bulk high-temperature superconductors. Theoretical tools to simulate in a realistic way both the behavior of all elements (permanent magnets, soft ferromagnet and superconductor) and their mutual effects are helpful to optimize the designs of real systems. Here we present a systematic study of the levitation of a maglev with translational symmetry consisting of a superconducting bar and a guideway with two identic permanent magnets and a soft ferromagnetic material between them. The system is simulated with a numerical model based on the energy minimization method that allows to analyze the mutual interaction of the superconductor, assumed to be in the critical state, and a soft ferromagnet with infinite susceptibility. Results indicate that introducing a soft ferromagnet within the permanent magnets not only increases the levitation force but also improves the stability. Besides, an estimation of the relative sizes and shapes of the soft ferromagnet, permanent magnets and the superconductor in order to obtain large levitation force with full stability is provided.

Energy-cascade organic photovoltaic devices incorporating a host-guest architecture.

PubMed

Menke, S Matthew; Holmes, Russell J

2015-02-04

In planar heterojunction organic photovoltaic devices (OPVs), broad spectral coverage can be realized by incorporating multiple molecular absorbers in an energy-cascade architecture. Here, this approach is combined with a host-guest donor layer architecture previously shown to optimize exciton transport for the fluorescent organic semiconductor boron subphthalocyanine chloride (SubPc) when diluted in an optically transparent host. In order to maximize the absorption efficiency, energy-cascade OPVs that utilize both photoactive host and guest donor materials are examined using the pairing of SubPc and boron subnaphthalocyanine chloride (SubNc), respectively. In a planar heterojunction architecture, excitons generated on the SubPc host rapidly energy transfer to the SubNc guest, where they may migrate toward the dissociating, donor-acceptor interface. Overall, the incorporation of a photoactive host leads to a 13% enhancement in the short-circuit current density and a 20% enhancement in the power conversion efficiency relative to an optimized host-guest OPV combining SubNc with a nonabsorbing host. This work underscores the potential for further design refinements in planar heterojunction OPVs and demonstrates progress toward the effective separation of functionality between constituent OPV materials.

49 CFR 178.33a-5 - Material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Material. 178.33a-5 Section 178.33a-5 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SPECIFICATIONS FOR PACKAGINGS...

49 CFR 192.63 - Marking of materials.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.63 Marking of materials. (a) Except as...

Proceedings of the 2013 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering - M and C 2013

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

NONE

2013-07-01

The Mathematics and Computation Division of the American Nuclear (ANS) and the Idaho Section of the ANS hosted the 2013 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M and C 2013). This proceedings contains over 250 full papers with topics ranging from reactor physics; radiation transport; materials science; nuclear fuels; core performance and optimization; reactor systems and safety; fluid dynamics; medical applications; analytical and numerical methods; algorithms for advanced architectures; and validation verification, and uncertainty quantification.

Magic Trees in Mammalians Respiration or when Evolution Selected Clever Physical Systems

NASA Astrophysics Data System (ADS)

Sapoval, B.; Filoche, M.

2013-01-01

The respiratory system of mammalians is made of two successive branched structures with different physiological functions. The upper structure, or bronchial tree, is a fluid transportation system made of approximately 15 generations of bifurcations leading to the order of 215 = 30,000 bronchioles with a diameter of order 0.5 mm in the human lung.1 The branching pattern continues up to generation 23 but the structure and function of each of the subsequent structures, called the acini, is different. Each acinus is made of a branched system of ducts surrounded by alveolae and play the role of a diffusion cell where oxygen and carbon dioxide are exchanged with blood across the alveolar membrane.2 We show in this paper that the bronchial tree presents simultaneously several optimal properties of totally different nature. It is first energy efficient;3-6 second, it is space filling;7 and third it is "rapid" as discussed here. It is this multi-optimality that is qualified here as magic. The multi-optimality physical characteristic suggests that, in the course of evolution, an organ selected against one criterion could have been later used for a totally different reason. For example, once energetic efficiency for the transport of a viscous fluid like blood has been selected, the same genetic material could have been used for its optimized rapidity. This would have allowed the emergence of mammalian respiration made of inspiration-expiration cycles. For this phenomenon to exist, the rapid character is essential, as fresh air has to reach the gas exchange organs, the pulmonary acini, before the start of expiration.

49 CFR 178.345-2 - Material and material thickness.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Material and material thickness. 178.345-2 Section... HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation § 178.345-2 Material and material...

49 CFR 178.345-2 - Material and material thickness.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Material and material thickness. 178.345-2 Section... HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation § 178.345-2 Material and material...

49 CFR 178.345-2 - Material and material thickness.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Material and material thickness. 178.345-2 Section... HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation § 178.345-2 Material and material...

49 CFR 178.345-2 - Material and material thickness.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Material and material thickness. 178.345-2 Section... HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) SPECIFICATIONS FOR PACKAGINGS Specifications for Containers for Motor Vehicle Transportation § 178.345-2 Material and material...

Thermoelectric transport coefficients in mono-layer MoS{sub 2} and WSe{sub 2}: Role of substrate, interface phonons, plasmon, and dynamic screening

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

Ghosh, Krishnendu, E-mail: kghosh3@buffalo.edu; Singisetti, Uttam, E-mail: uttamsin@buffalo.edu

2015-10-07

The thermoelectric transport coefficients of electrons in two recently emerged transition metal di-chalcogenides (TMD), MoS{sub 2} and WSe{sub 2}, are calculated by solving Boltzmann transport equation using Rode's iterative technique in the diffusive transport regime and the coupled current (electrical and heat) equations. Scattering from remote phonons along with the hybridization of TMD plasmon with remote phonon modes and dynamic screening under linear polarization response are investigated in TMDs sitting on a dielectric environment. The transport coefficients are obtained for a varying range of temperature and doping density for three different types of substrates—SiO{sub 2}, Al{sub 2}O{sub 3}, and HfO{submore » 2}. The Seebeck co-efficient for MoS{sub 2} and WSe{sub 2} is found to be higher than 3D semiconductors even with diffusive transport. The electronic thermal conductivity is found to be low, however, the thermoelectric figure of merit is limited by the high phonon thermal conductivity. It is found that judicious selection of a dielectric environment based on temperature of operation and carrier density is crucial to optimize the thermoelectric performance of TMD materials.« less

49 CFR 172.205 - Hazardous waste manifest.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Hazardous waste manifest. 172.205 Section 172.205 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS HAZARDOUS MATERIALS TABLE, SPECIAL PROVISIONS, HAZARDOUS MATERIALS...

Covalent organic nanosheets for effective charge transport layers in planar-type perovskite solar cells.

PubMed

Park, Soyun; Kim, Min-Sung; Jang, Woongsik; Park, Jin Kuen; Wang, Dong Hwan

2018-03-08

Herein, solvent-treated bandgap-tunable covalent organic nanosheets (CONs) were prepared via the Stille cross-coupling reaction. These materials are considered useful as interlayers in photovoltaic devices upon the alignment of energy levels between other components. Among various types of solar cells, according to the organic-interlayer study, inverted planar perovskite solar cells (PSCs) are mostly demanded to effectively transport and collect charge carriers due to their high performance. At first, the C-V analysis proved the energy levels of the frontier orbitals for CON-10 and CON-16 nanosheets; this verified the suitability of these nanosheets as hole transport layers (HTLs) with the PEDOT:PSS upon casting both films from DMSO. It became evident, however, that the hole transport property of the PEDOT:PSS on the CON-16 layer was unfavorable with the increasing UPS-proven hole injection barrier. In addition, both CONs induced a rough surface morphology; however, CON-10 showed a relatively smooth surface as compared to CON-16 based on the Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) profiles; furthermore, their surface properties influenced both the PEDOT:PSS layers and the perovskite layers. Especially, the XRD profiles presented an enhanced crystallinity of the perovskite layers with CON-10. All these aspects indicate that CON-10 is a more effective HTL material, and several versions of perovskite solar cells (PSCs) have been fabricated with/without CON-10 and CON-16 together with the PEDOT:PSS to determine the more-HTL-suitable CON. As a result, the power conversion efficiencies (PCEs) of the optimized devices with CON-10 exhibited a value of 10.2%, which represented a 1% increase over those of the reference devices without the CONs and was 4% higher than that of the CON-16 devices. Moreover, the devices with CON-10 were further optimized with TiO x using Al electrodes, leading to a PCE increase of these devices that became slightly higher than the PCEs of the device with CON-10 and without TiO x . This tendency was supported by photoluminescence (PL) spectroscopy, photocurrent density (J ph ), and space-charge-limited current (SCLC) mobility results.

Evaluation of laminar flow control system concepts for subsonic commercial transport aircraft

NASA Technical Reports Server (NTRS)

1980-01-01

A study was conducted to evaluate alternatives in the design of laminar flow control (LFC) subsonic commercial transport aircraft for operation in the 1980's period. Analyses were conducted to select mission parameters and define optimum aircraft configurational parameters for the selected mission, defined by a passenger payload of 400 and a design range of 12,038 km (6500 n mi). The baseline aircraft developed for this mission was used as a vehicle for the evaluation and development of alternative LFC system concepts. Alternatives were evaluated in the areas of aerodynamics structures, materials, LFC systems, leading-edge region cleaning and integration of auxiliary systems. Based on these evaluations, concept in each area were selected for further development and testing and ultimate incorporation in the final study aircraft. Relative to a similarly-optimized advanced technology turbulent transport, the final LFC configuration is approximately equal in direct operating cost but provides decreases of 8.2% in gross weight and 21.7% in fuel consumption.

Efficient Transport Networks in a Dual Electron/Lithium-Conducting Polymeric Composite for Electrochemical Applications.

PubMed

McDonald, Michael B; Hammond, Paula T

2018-05-09

In this work, an all-functional polymer material composed of the electrically conductive poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS) and lithium-conducting poly(ethylene oxide) (PEO) was developed to form a dual conductor for three-dimensional electrodes in electrochemical applications. The composite exhibits enhanced ionic conductivity (∼10 -4 S cm -1 ) and, counterintuitively, electronic conductivity (∼45 S cm -1 ) with increasing PEO proportion, optimal at a monomer ratio of 20:1 PEO:PEDOT. Microscopy reveals a unique morphology, where PSS interacts favorably with PEO, destabilizing PEDOT to associate into highly branched, interconnected networks that allow for more efficient electronic transport despite relatively low concentrations. Thermal and X-ray techniques affirm that the PSS-PEO domain suppresses crystallinity, explaining the high ionic conductivity. Electrochemical experiments in lithium cell environments indicate stability as a function of cycling and improved overpotential due to dual transport characteristics despite known issues with both individual components.

Multilayer organic based structures with enhanced hole transport

NASA Astrophysics Data System (ADS)

Mladenova, D.; Sinigersky, V.; Budurova, D.; Dobreva, T.; Karashanova, D.; Dimov, D.; Zhivkov, I.

2010-11-01

Multilayer Organic Based Devices (OBDs) were constructed by subsequent casting of organic films (from polymers, soluble in the same organic solvent). The problem with dissolution of the underlying layer was avoided by using electrophoretic deposition technique. Optimized conditions for electrophoretic deposition (EPD) of thin films with homogeneous and smooth surfaces, as confirmed by SEM, were found. The EPD, carried out at constant current, requires continuous increase of the voltage between the electrodes. In this way the decreased deposition rate caused by the decreased concentration of the material in the suspension and the increased thickness of the film deposited is compensated. The SEM images and the current voltage characteristics recorded, show that the hole transport polyvinylcarbazole (PVK) underlayer survive the treatment with the suspension used for the electrophoretic deposition of the active poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene vinylene] electroluminescent layer. The PVK hole transport layer increases the device current, as confirmed by the current-voltage measurements. The results obtained demonstrate the possibility of OBDs preparation for electroluminescent and photovoltaic applications.

Roles of Chemical Functionality and Pore Curvature in the Design of Nanoporous Proton Conductors

DOE PAGES

Jackson, Grayson L.; Perroni, Dominic V.; Mahanthappa, Mahesh K.

2017-10-03

Nanoporous proton-transporting media are critical components in fuel cells and other electrochemical devices, yet general molecular design criteria for new materials with enhanced performance remain obscure. Aqueous lyotropic liquid crystals (LLCs) comprise a platform for detailed studies of the molecular-level features governing proton transport in monodisperse, water-filled nanopores lined with well-defined chemical functionalities. Here, we report new alkylsulfonic acid LLCs that exhibit H+ conductivities as high as σ = 380 mS/cm at 80°C, which rival those of more acidic, perfluorinated polymers, thus demonstrating that the acidity of the pore functionality is not the sole determinant of proton transport. Direct experimentalmore » comparisons of LLCs with convex and concave nanopores of similar dimensions indicate that H+ conductivities therein sensitively depend on the hydration state of the acid functionalities and the pore curvature. These experiments suggest that judicious manipulation of pore curvature provides a new means for optimizing the activities of proton-exchange membranes and nanoporous solid acid catalysts.« less

Efficient Carbon-Based CsPbBr3 Inorganic Perovskite Solar Cells by Using Cu-Phthalocyanine as Hole Transport Material

NASA Astrophysics Data System (ADS)

Liu, Zhiyong; Sun, Bo; Liu, Xingyue; Han, Jinghui; Ye, Haibo; Shi, Tielin; Tang, Zirong; Liao, Guanglan

2018-06-01

Metal halide perovskite solar cells (PSCs) have attracted extensive research interest for next-generation solution-processed photovoltaic devices because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication cost. Although the world's best PSC successfully achieves a considerable PCE of over 20% within a very limited timeframe after intensive efforts, the stability, high cost, and up-scaling of PSCs still remain issues. Recently, inorganic perovskite material, CsPbBr3, is emerging as a promising photo-sensitizer with excellent durability and thermal stability, but the efficiency is still embarrassing. In this work, we intend to address these issues by exploiting CsPbBr3 as light absorber, accompanied by using Cu-phthalocyanine (CuPc) as hole transport material (HTM) and carbon as counter electrode. The optimal device acquires a decent PCE of 6.21%, over 60% higher than those of the HTM-free devices. The systematic characterization and analysis reveal a more effective charge transfer process and a suppressed charge recombination in PSCs after introducing CuPc as hole transfer layer. More importantly, our devices exhibit an outstanding durability and a promising thermal stability, making it rather meaningful in future fabrication and application of PSCs.[Figure not available: see fulltext.

Screening of inorganic wide-bandgap p-type semiconductors for high performance hole transport layers in organic photovoltaic devices

NASA Astrophysics Data System (ADS)

Ginley, David; Zakutayev, Andriy; Garcia, Andreas; Widjonarko, Nicodemus; Ndione, Paul; Sigdel, Ajaya; Parilla, Phillip; Olson, Dana; Perkins, John; Berry, Joseph

2011-03-01

We will report on the development of novel inorganic hole transport layers (HTL) for organic photovoltaics (OPV). All the studied materials belong to the general class of wide-bandgap p-type oxide semiconductors. Potential candidates suitable for HTL applications include SnO, NiO, Cu2O (and related CuAlO2, CuCrO2, SrCu2O4 etc) and Co3O4 (and related ZnCo2O4, NiCo2O4, MgCo2O4 etc.). Materials have been optimized by high-throughput combinatorial approaches. The thin films were deposited by RF sputtering and pulsed laser deposition at ambient and elevated temperatures. Performance of the inorganic HTLs and that of the reference organic PEDOT:PSS HTL were compared by measuring the power conversion efficiencies and spectral responses of the P3HT/PCBM- and PCDTBT/PCBM-based OPV devices. Preliminary results indicate that Co3O4-based HTLs have performance comparable to that of our previously reported NiOs and PEDOT:PSS HTLs, leading to a power conversion efficiency of about 4 percent. The effect of composition and work function of the ternary materials on their performance in OPV devices is under investigation.

Optimal solution of full fuzzy transportation problems using total integral ranking

NASA Astrophysics Data System (ADS)

Sam’an, M.; Farikhin; Hariyanto, S.; Surarso, B.

2018-03-01

Full fuzzy transportation problem (FFTP) is a transportation problem where transport costs, demand, supply and decision variables are expressed in form of fuzzy numbers. To solve fuzzy transportation problem, fuzzy number parameter must be converted to a crisp number called defuzzyfication method. In this new total integral ranking method with fuzzy numbers from conversion of trapezoidal fuzzy numbers to hexagonal fuzzy numbers obtained result of consistency defuzzyfication on symmetrical fuzzy hexagonal and non symmetrical type 2 numbers with fuzzy triangular numbers. To calculate of optimum solution FTP used fuzzy transportation algorithm with least cost method. From this optimum solution, it is found that use of fuzzy number form total integral ranking with index of optimism gives different optimum value. In addition, total integral ranking value using hexagonal fuzzy numbers has an optimal value better than the total integral ranking value using trapezoidal fuzzy numbers.

The fundamental downscaling limit of field effect transistors

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

Mamaluy, Denis, E-mail: mamaluy@sandia.gov; Gao, Xujiao

2015-05-11

We predict that within next 15 years a fundamental down-scaling limit for CMOS technology and other Field-Effect Transistors (FETs) will be reached. Specifically, we show that at room temperatures all FETs, irrespective of their channel material, will start experiencing unacceptable level of thermally induced errors around 5-nm gate lengths. These findings were confirmed by performing quantum mechanical transport simulations for a variety of 6-, 5-, and 4-nm gate length Si devices, optimized to satisfy high-performance logic specifications by ITRS. Different channel materials and wafer/channel orientations have also been studied; it is found that altering channel-source-drain materials achieves only insignificant increasemore » in switching energy, which overall cannot sufficiently delay the approaching downscaling limit. Alternative possibilities are discussed to continue the increase of logic element densities for room temperature operation below the said limit.« less

The fundamental downscaling limit of field effect transistors

DOE PAGES

Mamaluy, Denis; Gao, Xujiao

2015-05-12

We predict that within next 15 years a fundamental down-scaling limit for CMOS technology and other Field-Effect Transistors (FETs) will be reached. Specifically, we show that at room temperatures all FETs, irrespective of their channel material, will start experiencing unacceptable level of thermally induced errors around 5-nm gate lengths. These findings were confirmed by performing quantum mechanical transport simulations for a variety of 6-, 5-, and 4-nm gate length Si devices, optimized to satisfy high-performance logic specifications by ITRS. Different channel materials and wafer/channel orientations have also been studied; it is found that altering channel-source-drain materials achieves only insignificant increasemore » in switching energy, which overall cannot sufficiently delay the approaching downscaling limit. Alternative possibilities are discussed to continue the increase of logic element densities for room temperature operation below the said limit.« less

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

Kang, Dongseok; Young, James L.; Lim, Haneol

Despite their excellent photophysical properties and record-high solar-to-hydrogen conversion efficiency, the high cost and limited stability of III-V compound semiconductors prohibit their practical application in solar-driven photoelectrochemical water splitting. Here in this paper we present a strategy for III-V photocatalysis that can circumvent these difficulties via printed assemblies of epitaxially grown compound semiconductors. A thin film stack of GaAs-based epitaxial materials is released from the growth wafer and printed onto a non-native transparent substrate to form an integrated photocatalytic electrode for solar hydrogen generation. The heterogeneously integrated electrode configuration together with specialized epitaxial design serve to decouple the material interfacesmore » for illumination and electrocatalysis. Subsequently, this allows independent control and optimization of light absorption, carrier transport, charge transfer, and material stability. Using this approach, we construct a series-connected wireless tandem system of GaAs photoelectrodes and demonstrate 13.1% solar-to-hydrogen conversion efficiency of unassisted-mode water splitting.« less

75 FR 5258 - Hazardous Materials Transportation; Registration and Fee Assessment Program

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-02

... DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration 49 CFR Part 107 [Docket No. PHMSA-2009-0201 (HM-208H)] RIN 2137-AE47 Hazardous Materials Transportation... transportation, certain categories and quantities of hazardous materials. PHMSA's proposal would provide that...

Non-aqueous Electrode Processing and Construction of Lithium-ion Coin Cells.

PubMed

Stein, Malcolm; Chen, Chien-Fan; Robles, Daniel J; Rhodes, Christopher; Mukherjee, Partha P

2016-02-01

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational analysis. Testing of lithium-ion batteries in an academic setting has taken on several forms, but at the most basic level lies the coin cell construction. In traditional LIB electrode preparation, a multi-phase slurry composed of active material, binder, and conductive additive is cast out onto a substrate. An electrode disc can then be punched from the dried sheet and used in the construction of a coin cell for electrochemical evaluation. Utilization of the potential of the active material in a battery is critically dependent on the microstructure of the electrode, as an appropriate distribution of the primary components are crucial to ensuring optimal electrical conductivity, porosity, and tortuosity, such that electrochemical and transport interaction is optimized. Processing steps ranging from the combination of dry powder, wet mixing, and drying can all critically affect multi-phase interactions that influence the microstructure formation. Electrochemical probing necessitates the construction of electrodes and coin cells with the utmost care and precision. This paper aims at providing a step-by-step guide of non-aqueous electrode processing and coin cell construction for lithium-ion batteries within an academic setting and with emphasis on deciphering the influence of drying and calendaring.

Non-aqueous Electrode Processing and Construction of Lithium-ion Coin Cells

PubMed Central

Stein, Malcolm; Chen, Chien-Fan; Robles, Daniel J.; Rhodes, Christopher; Mukherjee, Partha P.

2016-01-01

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational analysis. Testing of lithium-ion batteries in an academic setting has taken on several forms, but at the most basic level lies the coin cell construction. In traditional LIB electrode preparation, a multi-phase slurry composed of active material, binder, and conductive additive is cast out onto a substrate. An electrode disc can then be punched from the dried sheet and used in the construction of a coin cell for electrochemical evaluation. Utilization of the potential of the active material in a battery is critically dependent on the microstructure of the electrode, as an appropriate distribution of the primary components are crucial to ensuring optimal electrical conductivity, porosity, and tortuosity, such that electrochemical and transport interaction is optimized. Processing steps ranging from the combination of dry powder, wet mixing, and drying can all critically affect multi-phase interactions that influence the microstructure formation. Electrochemical probing necessitates the construction of electrodes and coin cells with the utmost care and precision. This paper aims at providing a step-by-step guide of non-aqueous electrode processing and coin cell construction for lithium-ion batteries within an academic setting and with emphasis on deciphering the influence of drying and calendaring. PMID:26863503

High-Z plasma facing components in fusion devices: boundary conditions and operational experiences

NASA Astrophysics Data System (ADS)

Neu, R.

2006-04-01

In present day fusion devices optimization of the performance and experimental freedom motivates the use of low-Z plasma facing materials (PFMs). However, in a future fusion reactor, for economic reasons, a sufficient lifetime of the first wall components is essential. Additionally, tritium retention has to be small to meet safety requirements. Tungsten appears to be the most realistic material choice for reactor plasma facing components (PFCs) because it exhibits the lowest erosion. But besides this there are a lot of criteria which have to be fulfilled simultaneously in a reactor. Results from present day devices and from laboratory experiments confirm the advantages of high-Z PFMs but also point to operational restrictions, when using them as PFCs. These are associated with the central impurity concentration, which is determined by the sputtering yield, the penetration of the impurities and their transport within the confined plasma. The restrictions could exclude successful operation of a reactor, but concomitantly there exist remedies to ameliorate their impact. Obviously some price has to be paid in terms of reduced performance but lacking of materials or concepts which could substitute high-Z PFCs, emphasis has to be put on the development and optimization of reactor-relevant scenarios which incorporate the experiences and measures.

Influence of architecture and material properties on vanadium redox flow battery performance

NASA Astrophysics Data System (ADS)

Houser, Jacob; Clement, Jason; Pezeshki, Alan; Mench, Matthew M.

2016-01-01

This publication reports a design optimization study of all-vanadium redox flow batteries (VRBs), including performance testing, distributed current measurements, and flow visualization. Additionally, a computational flow simulation is used to support the conclusions made from the experimental results. This study demonstrates that optimal flow field design is not simply related to the best architecture, but is instead a more complex interplay between architecture, electrode properties, electrolyte properties, and operating conditions which combine to affect electrode convective transport. For example, an interdigitated design outperforms a serpentine design at low flow rates and with a thin electrode, accessing up to an additional 30% of discharge capacity; but a serpentine design can match the available discharge capacity of the interdigitated design by increasing the flow rate or the electrode thickness due to differing responses between the two flow fields. The results of this study should be useful to design engineers seeking to optimize VRB systems through enhanced performance and reduced pressure drop.

Comprehensive investigation of noble metal nanoparticles shape, size and material on the optical response of optimal plasmonic Y-splitter waveguides

NASA Astrophysics Data System (ADS)

Ahmadivand, Arash; Golmohammadi, Saeed

2014-01-01

With the purpose of guiding and splitting of optical power at C-band spectrum, we studied Y-shape splitters based on various shapes of nanoparticles as a plasmon waveguide. We applied different configurations of Gold (Au) and Silver (Ag) nanoparticles including spheres, rods and rings, to optimize the efficiency and losses of two and four-branch splitters. The best performance in light transportation specifically at telecom wavelength (λ≈1550 nm) is achieved by nanorings, due to an extra degree of freedom in their geometrical components. In addition, comparisons of several values for offset distance (doffset) of examined structures shows that Au nanoring splitters with feasible lower doffset have high quality in guiding and splitting of light through the structure. Finally, we studied four-branch Y-splitters based on Au and Ag nanorings with least possible offset distances to optimize the splitter performance. The power transmission as a key element is calculated for examined structures.

Supersonic transport grid generation, validation, and optimization

NASA Technical Reports Server (NTRS)

Aaronson, Philip G.

1995-01-01

The ever present demand for reduced flight times has renewed interest in High Speed Civil Transports (HSCT). The need for an HSCT becomes especially apparent when the long distance, over-sea, high growth Pacific rim routes are considered. Crucial to any successful HSCT design are minimal environmental impact and economic viability. Vital is the transport's aerodynamic efficiency, ultimately effecting both the environmental impact and the operating cost. Optimization, including numerical optimization, coupled with the use of computational fluid dynamics (CFD) technology, has and will offer a significant improvement beyond traditional methods.

Multiple Choice Knapsack Problem: example of planning choice in transportation.

PubMed

Zhong, Tao; Young, Rhonda

2010-05-01

Transportation programming, a process of selecting projects for funding given budget and other constraints, is becoming more complex as a result of new federal laws, local planning regulations, and increased public involvement. This article describes the use of an integer programming tool, Multiple Choice Knapsack Problem (MCKP), to provide optimal solutions to transportation programming problems in cases where alternative versions of projects are under consideration. In this paper, optimization methods for use in the transportation programming process are compared and then the process of building and solving the optimization problems is discussed. The concepts about the use of MCKP are presented and a real-world transportation programming example at various budget levels is provided. This article illustrates how the use of MCKP addresses the modern complexities and provides timely solutions in transportation programming practice. While the article uses transportation programming as a case study, MCKP can be useful in other fields where a similar decision among a subset of the alternatives is required. Copyright 2009 Elsevier Ltd. All rights reserved.

75 FR 15613 - Hazardous Materials Transportation; Registration and Fee Assessment Program

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-30

... DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration 49 CFR Part 107 [Docket No. PHMSA-2009-0201 (HM-208H)] RIN 2137-AE47 Hazardous Materials Transportation... registration program are to gather information about the transportation of hazardous materials, and to fund the...

Improved explosive collection and detection with rationally assembled surface sampling materials

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

Chouyyok, Wilaiwan; Bays, J. Timothy; Gerasimenko, Aleksandr A.

Sampling and detection of trace explosives is a key analytical process in modern transportation safety. In this work we have explored some of the fundamental analytical processes for collection and detection of trace level explosive on surfaces with the most widely utilized system, thermal desorption IMS. The performance of the standard muslin swipe material was compared with chemically modified fiberglass cloth. The fiberglass surface was modified to include phenyl functional groups. When compared to standard muslin, the phenyl functionalized fiberglass sampling material showed better analyte release from the sampling material as well as improved response and repeatability from multiple usesmore » of the same swipe. The improved sample release of the functionalized fiberglass swipes resulted in a significant increase in sensitivity. Various physical and chemical properties were systematically explored to determine optimal performance. The results herein have relevance to improving the detection of other explosive compounds and potentially to a wide range of other chemical sampling and field detection challenges.« less

ON THE DEGREE OF CONVERSION AND COEFFICIENT OF THERMAL EXPANSION OF A SINGLE FIBER COMPOSITE USING A FBG SENSOR

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

Lai, M.; Botsis, J.; Coric, D.

2008-08-28

The increasing needs of extending the lifetime in high-technology fields, such as space and aerospace, rail transport and naval systems, require quality enhancing of the composite materials either from a processing standing point or in the sense of resistance to service conditions. It is well accepted that the final quality of composite materials and structures is strongly influenced by processing parameters like curing and post-curing temperatures, rate of heating and cooling, applied vacuum, etc. To optimize manufacturing cycles, residual strains evolution due to chemical shrinkage and other physical parameters of the constituent materials must be characterized in situ. Such knowledgemore » can lead to a sensible reduction in defects and to improved physical and mechanical properties of final products. In this context continuous monitoring of strains distribution developed during processing is important in understanding and retrieving components' and materials' characteristics such as local strains gradients, degree of curing, coefficient of thermal expansion, moisture absorption, etc.« less

Solar energy conversion with photon-enhanced thermionic emission

NASA Astrophysics Data System (ADS)

Kribus, Abraham; Segev, Gideon

2016-07-01

Photon-enhanced thermionic emission (PETE) converts sunlight to electricity with the combined photonic and thermal excitation of charge carriers in a semiconductor, leading to electron emission over a vacuum gap. Theoretical analyses predict conversion efficiency that can match, or even exceed, the efficiency of traditional solar thermal and photovoltaic converters. Several materials have been examined as candidates for radiation absorbers and electron emitters, with no conclusion yet on the best set of materials to achieve high efficiency. Analyses have shown the complexity of the energy conversion and transport processes, and the significance of several loss mechanisms, requiring careful control of material properties and optimization of the device structure. Here we survey current research on PETE modeling, materials, and device configurations, outline the advances made, and stress the open issues and future research needed. Based on the substantial progress already made in this young topic, and the potential of high conversion efficiency based on theoretical performance limits, continued research in this direction is very promising and may yield a competitive technology for solar electricity generation.

Bio-inspired Murray materials for mass transfer and activity

PubMed Central

Zheng, Xianfeng; Shen, Guofang; Wang, Chao; Li, Yu; Dunphy, Darren; Hasan, Tawfique; Brinker, C. Jeffrey; Su, Bao-Lian

2017-01-01

Both plants and animals possess analogous tissues containing hierarchical networks of pores, with pore size ratios that have evolved to maximize mass transport and rates of reactions. The underlying physical principles of this optimized hierarchical design are embodied in Murray's law. However, we are yet to realize the benefit of mimicking nature's Murray networks in synthetic materials due to the challenges in fabricating vascularized structures. Here we emulate optimum natural systems following Murray's law using a bottom-up approach. Such bio-inspired materials, whose pore sizes decrease across multiple scales and finally terminate in size-invariant units like plant stems, leaf veins and vascular and respiratory systems provide hierarchical branching and precise diameter ratios for connecting multi-scale pores from macro to micro levels. Our Murray material mimics enable highly enhanced mass exchange and transfer in liquid–solid, gas–solid and electrochemical reactions and exhibit enhanced performance in photocatalysis, gas sensing and as Li-ion battery electrodes. PMID:28382972

An approach to improving transporting velocity in the long-range ultrasonic transportation of micro-particles

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

Meng, Jianxin; Mei, Deqing, E-mail: meidq-127@zju.edu.cn; Yang, Keji

2014-08-14

In existing ultrasonic transportation methods, the long-range transportation of micro-particles is always realized in step-by-step way. Due to the substantial decrease of the driving force in each step, the transportation is lower-speed and stair-stepping. To improve the transporting velocity, a non-stepping ultrasonic transportation approach is proposed. By quantitatively analyzing the acoustic potential well, an optimal region is defined as the position, where the largest driving force is provided under the condition that the driving force is simultaneously the major component of an acoustic radiation force. To keep the micro-particle trapped in the optimal region during the whole transportation process, anmore » approach of optimizing the phase-shifting velocity and phase-shifting step is adopted. Due to the stable and large driving force, the displacement of the micro-particle is an approximately linear function of time, instead of a stair-stepping function of time as in the existing step-by-step methods. An experimental setup is also developed to validate this approach. Long-range ultrasonic transportations of zirconium beads with high transporting velocity were realized. The experimental results demonstrated that this approach is an effective way to improve transporting velocity in the long-range ultrasonic transportation of micro-particles.« less

30 CFR 57.6201 - Separation of transported explosive material.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Separation of transported explosive material... MINES Explosives Transportation-Surface and Underground § 57.6201 Separation of transported explosive material. Detonators shall not be transported on the same vehicle or conveyance with other explosives...

30 CFR 57.6201 - Separation of transported explosive material.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Separation of transported explosive material... MINES Explosives Transportation-Surface and Underground § 57.6201 Separation of transported explosive material. Detonators shall not be transported on the same vehicle or conveyance with other explosives...

Enhancement of thermal transport in Gel Polymer Electrolytes with embedded BN/Al2O3 nano- and micro-particles

NASA Astrophysics Data System (ADS)

Vishwakarma, Vivek; Jain, Ankur

2017-09-01

While Gel Polymer Electrolytes (GPEs) have been widely investigated for use in next-generation Li-ion cells due to the potential for improved thermal safety, thermal transport within a GPE is still poorly understood. Among all materials in a Li-ion cell, the GPE has the lowest thermal conductivity, and hence determines the overall rate of heat flow in a Li-ion cell. This makes it critical to measure and understand thermal transport in a GPE and investigate trade-offs between thermal and ionic transport. This paper presents measurements of thermal and ionic conductivities in a PVdF-based GPE. The effect of incorporating BN/Al2O3 ceramic nano/microparticles in the GPE on thermal and ionic transport is characterized. Measurements indicate up to 2.5X improvement in thermal conductivity of activated GPE membranes, with relatively minor effect on electrochemical performance of GPE-based single-layer cells. The measured enhancement in thermal conductivity is in very good agreement with theoretical calculations based on the effective medium theory that accounts for thermal transport in a dispersed, two-phase medium such as a GPE. The fundamental insights gained in this work on thermal transport in a GPE and the role of nano/microparticle inclusions may facilitate thermal-electrochemical optimization and design of GPEs for safe, high-performance Li-ion cells.

49 CFR 173.468 - Test for LSA-III material.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Test for LSA-III material. 173.468 Section 173.468 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Class 7 ...

49 CFR 173.468 - Test for LSA-III material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Test for LSA-III material. 173.468 Section 173.468 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS Class 7 ...

Development of a large-scale transportation optimization course.

DOT National Transportation Integrated Search

2011-11-01

"In this project, a course was developed to introduce transportation and logistics applications of large-scale optimization to graduate students. This report details what : similar courses exist in other universities, and the methodology used to gath...

A comprehensive device modelling of perovskite solar cell with inorganic copper iodide as hole transport material

NASA Astrophysics Data System (ADS)

Zulqarnain Haider, Syed; Anwar, Hafeez; Wang, Mingqing

2018-03-01

Hole transport material (HTM) plays an important role in the efficiency and stability of perovskite solar cells (PSCs). Spiro-MeOTAD, the commonly used HTM, is costly and can be easily degraded by heat and moisture, thus offering hindrance to commercialize PSCs. There is dire need to find an alternate inorganic and stable HTM to exploit PSCs with their maximum capability. In this paper, a comprehensive device simulation is used to study various possible parameters that can influence the performance of perovskite solar cell with CuI as HTM. These include the effect of doping density, defect density and thickness of absorber layer, along with the influence of diffusion length of carriers as well as electron affinity of electron transport layer (ETM) and HTM on the performance of PSCs. In addition, hole mobility and doping density of HTM is also investigated. CuI is a p-type inorganic material with low cost and relatively high stability. It is found that concentration of dopant in absorber layer and HTM, the electron affinity of HTM and ETM affect the performance of solar cell minutely, while cell performance improves greatly with the reduction of defect density. Upon optimization of parameters, power conversion efficiency for this device is found to be 21.32%. The result shows that lead-based PSC with CuI as HTM is an efficient system. Enhancing the stability and reduction of defect density are critical factors for future research. These factors can be improved by better fabrication process and proper encapsulation of solar cell.

On the use of controls for subsonic transport performance improvement: Overview and future directions

NASA Technical Reports Server (NTRS)

Gilyard, Glenn; Espana, Martin

1994-01-01

Increasing competition among airline manufacturers and operators has highlighted the issue of aircraft efficiency. Fewer aircraft orders have led to an all-out efficiency improvement effort among the manufacturers to maintain if not increase their share of the shrinking number of aircraft sales. Aircraft efficiency is important in airline profitability and is key if fuel prices increase from their current low. In a continuing effort to improve aircraft efficiency and develop an optimal performance technology base, NASA Dryden Flight Research Center developed and flight tested an adaptive performance seeking control system to optimize the quasi-steady-state performance of the F-15 aircraft. The demonstrated technology is equally applicable to transport aircraft although with less improvement. NASA Dryden, in transitioning this technology to transport aircraft, is specifically exploring the feasibility of applying adaptive optimal control techniques to performance optimization of redundant control effectors. A simulation evaluation of a preliminary control law optimizes wing-aileron camber for minimum net aircraft drag. Two submodes are evaluated: one to minimize fuel and the other to maximize velocity. This paper covers the status of performance optimization of the current fleet of subsonic transports. Available integrated controls technologies are reviewed to define approaches using active controls. A candidate control law for adaptive performance optimization is presented along with examples of algorithm operation.

49 CFR 173.61 - Mixed packaging requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

....61 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL... material that could, under normal conditions of transportation, adversely affect the explosive or its...

49 CFR 173.61 - Mixed packaging requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

....61 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL... material that could, under normal conditions of transportation, adversely affect the explosive or its...

49 CFR 173.61 - Mixed packaging requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

....61 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL... material that could, under normal conditions of transportation, adversely affect the explosive or its...

49 CFR 173.61 - Mixed packaging requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

....61 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL... material that could, under normal conditions of transportation, adversely affect the explosive or its...

49 CFR 173.61 - Mixed packaging requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

....61 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL... material that could, under normal conditions of transportation, adversely affect the explosive or its...

49 CFR 109.3 - Inspections and Investigations.

Code of Federal Regulations, 2014 CFR

2014-10-01

....3 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS PROGRAM PROCEDURES Inspections and Investigations § 109.3 Inspections and Investigations. (a...

49 CFR 107.315 - Admission of violations.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS... transfer may be obtained from the Financial Operations Division (AMZ-120), Federal Aviation Administration...

49 CFR 107.315 - Admission of violations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS... transfer may be obtained from the Financial Operations Division (AMZ-120), Federal Aviation Administration...

30 CFR 56.6201 - Separation of transported explosive material.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Separation of transported explosive material... Explosives Transportation § 56.6201 Separation of transported explosive material. Detonators shall not be transported on the same vehicle or conveyance with other explosives except as follows: (a) Detonators in...

30 CFR 56.6201 - Separation of transported explosive material.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Separation of transported explosive material... Explosives Transportation § 56.6201 Separation of transported explosive material. Detonators shall not be transported on the same vehicle or conveyance with other explosives except as follows: (a) Detonators in...

Summary report on transportation of nuclear fuel materials in Japan : transportation infrastructure, threats identified in open literature, and physical protection regulations.

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

Cochran, John Russell; Ouchi, Yuichiro; Furaus, James Phillip

2008-03-01

This report summarizes the results of three detailed studies of the physical protection systems for the protection of nuclear materials transport in Japan, with an emphasis on the transportation of mixed oxide fuel materials1. The Japanese infrastructure for transporting nuclear fuel materials is addressed in the first section. The second section of this report presents a summary of baseline data from the open literature on the threats of sabotage and theft during the transport of nuclear fuel materials in Japan. The third section summarizes a review of current International Atomic Energy Agency, Japanese and United States guidelines and regulations concerningmore » the physical protection for the transportation of nuclear fuel materials.« less

Optimization of the gypsum-based materials by the sequential simplex method

NASA Astrophysics Data System (ADS)

Doleželová, Magdalena; Vimmrová, Alena

2017-11-01

The application of the sequential simplex optimization method for the design of gypsum based materials is described. The principles of simplex method are explained and several examples of the method usage for the optimization of lightweight gypsum and ternary gypsum based materials are given. By this method lightweight gypsum based materials with desired properties and ternary gypsum based material with higher strength (16 MPa) were successfully developed. Simplex method is a useful tool for optimizing of gypsum based materials, but the objective of the optimization has to be formulated appropriately.

Food preferences and mound-building behaviour of the mound-building mice Mus spicilegus

NASA Astrophysics Data System (ADS)

Hölzl, Michaela; Krištofík, Ján; Darolová, Alžbeta; Hoi, Herbert

2011-10-01

Optimal foraging strategies and food choice are influenced by various factors, e.g. availability, size and caloric content of the food type and predation risk. However, food choice criteria may change when food is not eaten immediately but has to be carried to a storage site for later use. For example, handling time in terms of harvesting and transport time should be optimized, particularly when the risk of predation is high. Thus, it is not clear whether food selected by hoarding animals reflects their food preference due to intrinsic features of the food type, e.g. size, caloric or lipid content, or whether the food type selected is a compromise that also considers the handling time required for harvesting and transport. We investigate this question in relation to food hoarding behaviour in mound-building mice. In autumn, mound-building mice Mus spicilegus collect seeds and other plant material and cover it with soil. Such above-ground storage is quite unusual for rodents. Here, we investigated whether there is a relationship between the seed species preferred as building materials and those preferred for food. We conducted a seed preference test using three most collected weed species for mound building. Controlling factors like food availability or predation risk, mice prefer Setaria spp. as food, although Amaranthus spp. and Chenopodium spp. were preferentially harvested and stored. By including the availability of the three species, our experimental results were confirmed, namely, a clear preference for Setaria spp. Also, handling time and seed size revealed to influence plant choice.

Investigation of nitrogen transport in active screen plasma nitriding processes - Uphill diffusion effect

NASA Astrophysics Data System (ADS)

Jasinski, J. J.; Fraczek, T.; Kurpaska, L.; Lubas, M.; Sitarz, M.

2018-07-01

The paper presents a structure of a nitrided layer formed with active screen plasma nitriding (ASPN) technique, which is a modification of plasma nitriding. The model investigated material was Fe Armco. The nitriding processes were carried out at 773 K for 6 h and 150 Pa. The main objective of this study was to confirm nitrogen migration effect and its influence on the nitride layer formation in different area of the layer interfaces (ε/ε+γ‧/γ‧). The results of the tests were evaluated using scanning electron microscopy (SEM, SEM/EBSD), transmission electron microscopy - electron energy loss spectroscopy (TEM-EFTEM), secondary ion mass spectroscopy (SIMS) and Wavelength Dispersive X-Ray Spectrometry (WDS). The analysis of the results suggests that the structures of the nitrided layers and nitrides morphology differ for various parameters and are dependent on the surface layer saturation mechanism for each of the temperatures and process parameters. New approaches in diffusion of nitrogen and carbon atoms and optimizing process were also analyzed. Nitrogen and also carbon transport in the sublayer was observed by several effects i.e. uphill diffusion effect which confirmed migration of the atoms in diffusive layer towards top surface (ε/ε+γ‧ interface) and stress change effect in the nitrogen saturation area of the (Fe(C,N)+γ‧) layer. Results showed in the paper might be used both for optimization of ASPN processes, modeling of nitrided layers formation mechanism and for controlling the nitrided layers morphology when nitriding different Fe based materials.

Design and analysis of an electromagnetic turnout for the superconducting Maglev system

NASA Astrophysics Data System (ADS)

Li, Y. J.; Dai, Q.; Zhang, Y.; Wang, H.; Chen, Z.; Sun, R. X.; Zheng, J.; Deng, C. Y.; Deng, Z. G.

2016-09-01

Turnout is a crucial track junction device of the ground rail transportation system. For high temperature superconducting (HTS) Maglev system, the permanent magnet guideway (PMG) makes the strong magnetic force existing between rail segments, which may cause moving difficulties and increase the operation cost when switching a PMG. In this paper, a non-mechanical 'Y' shaped Halbach-type electromagnetic turnout was proposed. By replacing the PMs with electromagnets, the turnout can guide the maglev vehicle running into another PMG by simply controlling the current direction of electromagnets. The material and structure parameters of the electromagnets were optimized by simulation. The results show that the optimized electromagnet can keep the magnetic field above it as strong as the PMs', meanwhile feasible for design and manufacture. This work provides valuable references for the future design in non-mechanical PMG turnout.

49 CFR 107.807 - Approval of non-domestic chemical analyses and tests.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Approval of non-domestic chemical analyses and tests. 107.807 Section 107.807 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS AND OIL TRANSPORTATION HAZARDOUS MATERIALS PROGRAM...

49 CFR 193.2607 - Foreign material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Foreign material. 193.2607 Section 193.2607 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY...: FEDERAL SAFETY STANDARDS Maintenance § 193.2607 Foreign material. (a) The presence of foreign material...

49 CFR 193.2607 - Foreign material.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Foreign material. 193.2607 Section 193.2607 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY...: FEDERAL SAFETY STANDARDS Maintenance § 193.2607 Foreign material. (a) The presence of foreign material...

49 CFR 176.108 - Supervision of Class 1 (explosive) materials during loading, unloading, handling and stowage.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Supervision of Class 1 (explosive) materials during loading, unloading, handling and stowage. 176.108 Section 176.108 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS...

78 FR 29016 - Establishing Quality Assurance Programs for Packaging Used in Transport of Radioactive Material

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-16

... Establishing Quality Assurance Programs for Packaging Used in Transport of Radioactive Material AGENCY: Nuclear..., ``Establishing Quality Assurance Programs for Packaging Used in Transport of Radioactive Material.'' This draft... regulations for the packaging and transportation of radioactive material in Part 71 of Title 10 of the Code of...

Designing a system for measuring the flow of material transported on belts using ultrasonic sensors

NASA Astrophysics Data System (ADS)

Mihuţ, N. M.

2015-11-01

Excavation tailings (scraping) and extracting the useful (lignite) in surface mine pits in Mining Basin Oltenia is achieved with technological lines of excavation - transport - dump of high productivity. A correlation of working capacity of the main components of technological lines (motor rotor, high capacity transport, car dumps) is necessary for economic reasons on electricity consumption. To achieve experience in the process was chosen excavator SRS 1400 from South Jilt career in the CET Turceni. The question of coal excavated volume has a great importance in the mine pits. At the excavation is desired a density estimate for each machine production tracking, cost estimation and tracking product unit profitability of each band on various sections zones. Permanent display size excavated volume snapshots in the excavator's cabin permits to track tape loading, eliminating unproductive times and information management to determine profitability. Another important requirement is closing the loop of the machine drive system of an excavator for a uniform deposition of carbon on the strip, thus achieving automatic control of the loading belt. Such equipment is important for the system dispatching in surface mine pits. Through a system of three ultrasound transducers to determine the smart instant of coal excavated section which, coupled with the tape speed, integrated over time will determine the amount of excavated coal. The basis of the system developed is a device for determining the volume and quantity of coal excavated acting on the march and optimize the system speed excavator working order. The device is designed primarily following the careers of lignite production: rotor excavators, rubber conveyor belts and dump facilities. Newly developed system aims to achieve the following determines: the optimum energy excavation depending on the nature of excavated material - lignite, shale, clay, etc., economic times to use the excavator bucket teeth rotor, energy optical regime to rubber belt conveyors, eliminate damage to the plant by conveyor belt breakage detection or tread and eliminating time and energy losses by limiting reproductive idle, monitoring the amount of coal excavated, control power consumption. Systems in general and particularly automated systems cannot be designed without taking into account their degree of effectiveness, compliance with minimum consumption of time, energy and materials, insofar as they are requested and used all the resources it has, at minimum cost production, etc. For this reason any matter of calculation, design, analysis and operation of transport systems continuously subordinate requirements optimality.

Scalable Routes to Efficient Thermoelectric Materials

NASA Astrophysics Data System (ADS)

Feser, Joseph Patrick

Thermoelectrics are solid-state materials with the ability to directly convert heat to electricity and visa versa. Despite their advantages in power density and reliability, state-of-the-art bulk alloy materials have not been efficient enough or inexpensive enough to be deployed widely. Newer nanostructured materials show significantly improved efficiencies and could overcome these long-standing problems. This dissertation studies the conditions that govern efficiency improvements in nanostructured materials with particular attention paid to lattice thermal conductivity reductions as well as methods to make such materials inexpensively using solution processing. Measurements of a new p-type material system, In1-xGa xSb doped with epitaxially embedded metallic ErSb nanocrystals show that lattice thermal conductivity is reduced significantly below the alloy limit with as little as 1% nanocrystal loading by volume. Theoretical modeling based on the Boltzmann transport equation (BTE) is able to explain the reductions on the basis of an increased scattering cross section for long wavelength phonons which are scattered much less effectively by phonon-phonon and alloy impurity interactions. The optimal conditions for nanoparticle size, concentration, alloy composition are explored and the existence of an optimal nanocrystal size which depends on the alloy composition and temperature is predicted. A variety of colloidal nanocrystals are explored as inexpensive building blocks for nanostructured thermoelectric materials with tunable electronic and thermal properties. First, the electronic properties of superlattices of PbSe nanocrystals are studied in the limit of strong quantum confinement (d<10nm). PbSe quantum dot superlattices show size-dependent Seebeck coefficient which exceed that of the bulk material at equivalent carrier concentrations. Reversible control of the carrier concentration is shown by surface exposure of the superlattices to oxidizing and reducing agents and in-situ monitoring of the thermopower. Next, phonon transport in ultra-fine grained nanocomposites with tunable grain size are studied using colloidal nanocrystals. Particles of CdSe are coated with a hydrazine-based metal chalcogenide ligand which serves as a functional "glue." Composites with grain size between 3nm-6nm display ultra-low thermal conductivity approaching the theoretical limit for a crystalline solid, nearly 30 times lower than the bulk compound. Modeling shows that boundary scattering in the framework of BTE cannot adequately explain the measured properties and alternative mechanisms are discussed. Finally, a solution processable route to Bi2Te3-xSex thermoelectrics is developed by reacting Bi2S3 in hydrazine to form a universal precursor. The precursor is spin-coated in the presence of excess Se and Te and annealed to form a thermoelectrics material with a maximum ZT˜0.4 at room temperature, which is the highest for any spin-coated material currently reported.

Non-Fullerene Electron Acceptors for Use in Organic Solar Cells

PubMed Central

2015-01-01

Conspectus The active layer in a solution processed organic photovoltaic device comprises a light absorbing electron donor semiconductor, typically a polymer, and an electron accepting fullerene acceptor. Although there has been huge effort targeted to optimize the absorbing, energetic, and transport properties of the donor material, fullerenes remain as the exclusive electron acceptor in all high performance devices. Very recently, some new non-fullerene acceptors have been demonstrated to outperform fullerenes in comparative devices. This Account describes this progress, discussing molecular design considerations and the structure–property relationships that are emerging. The motivation to replace fullerene acceptors stems from their synthetic inflexibility, leading to constraints in manipulating frontier energy levels, as well as poor absorption in the solar spectrum range, and an inherent tendency to undergo postfabrication crystallization, resulting in device instability. New acceptors have to address these limitations, providing tunable absorption with high extinction coefficients, thus contributing to device photocurrent. The ability to vary and optimize the lowest unoccupied molecular orbital (LUMO) energy level for a specific donor polymer is also an important requirement, ensuring minimal energy loss on electron transfer and as high an internal voltage as possible. Initially perylene diimide acceptors were evaluated as promising acceptor materials. These electron deficient aromatic molecules can exhibit good electron transport, facilitated by close packed herringbone crystal motifs, and their energy levels can be synthetically tuned. The principal drawback of this class of materials, their tendency to crystallize on too large a length scale for an optimal heterojunction nanostructure, has been shown to be overcome through introduction of conformation twisting through steric effects. This has been primarily achieved by coupling two units together, forming dimers with a large intramolecular twist, which suppresses both nucleation and crystal growth. The generic design concept of rotationally symmetrical aromatic small molecules with extended π orbital delocalization, including polyaromatic hydrocarbons, phthalocyanines, etc., has also provided some excellent small molecule acceptors. In most cases, additional electron withdrawing functionality, such as imide or ester groups, can be incorporated to stabilize the LUMO and improve properties. New calamitic acceptors have been developed, where molecular orbital hybridization of electron rich and poor segments can be judiciously employed to precisely control energy levels. Conformation and intermolecular associations can be controlled by peripheral functionalization leading to optimization of crystallization length scales. In particular, the use of rhodanine end groups, coupled electronically through short bridged aromatic chains, has been a successful strategy, with promising device efficiencies attributed to high lying LUMO energy levels and subsequently large open circuit voltages. PMID:26505279

Synthetic building materials for transport buildings and structures

NASA Astrophysics Data System (ADS)

Gerasimova, Vera

2017-10-01

The most effective building materials account for the highest growth not only in construction of residential and public buildings, but also other capital projects including roadways, bridges, drainage, communications and other engineering projects. Advancement in the technology of more efficient and ecologically responsible insulation materials have been a priority for safety, minimal maintenance and longevity of finished construction projects. The practical use of modern building materials such as insulation, sound reduction and low energy consumption are a benefit in cost and application compared to the use of outdated heavier and labor-intensive materials. The most efficient way for maximizing insolation and sound proofing should be done during the design stages of the project according to existing codes and regulations that are required by Western Government. All methods and materials that are used need to be optimized in order to reach a high durability and low operational and maintenance cost exceeding more than 50 years of the life of the building, whether it is for public, industrial or residential use. Western construction techniques and technologies need to be applied and adapted by the Russian Federation to insure the most productive successful methods are being implemented. The issues of efficient insulation materials are outlined in this article.

Municipal solid waste transportation optimisation with vehicle routing approach: case study of Pontianak City, West Kalimantan

NASA Astrophysics Data System (ADS)

Kamal, M. A.; Youlla, D.

2018-03-01

Municipal solid waste (MSW) transportation in Pontianak City becomes an issue that need to be tackled by the relevant agencies. The MSW transportation service in Pontianak City currently requires very high resources especially in vehicle usage. Increasing the number of fleets has not been able to increase service levels while garbage volume is growing every year along with population growth. In this research, vehicle routing optimization approach was used to find optimal and efficient routes of vehicle cost in transporting garbage from several Temporary Garbage Dump (TGD) to Final Garbage Dump (FGD). One of the problems of MSW transportation is that there is a TGD which exceed the the vehicle capacity and must be visited more than once. The optimal computation results suggest that the municipal authorities only use 3 vehicles from 5 vehicles provided with the total minimum cost of IDR. 778,870. The computation time to search optimal route and minimal cost is very time consuming. This problem is influenced by the number of constraints and decision variables that have are integer value.

A genetic fuzzy analytical hierarchy process based projection pursuit method for selecting schemes of water transportation projects

NASA Astrophysics Data System (ADS)

Jin, Juliang; Li, Lei; Wang, Wensheng; Zhang, Ming

2006-10-01

The optimal selection of schemes of water transportation projects is a process of choosing a relatively optimal scheme from a number of schemes of water transportation programming and management projects, which is of importance in both theory and practice in water resource systems engineering. In order to achieve consistency and eliminate the dimensions of fuzzy qualitative and fuzzy quantitative evaluation indexes, to determine the weights of the indexes objectively, and to increase the differences among the comprehensive evaluation index values of water transportation project schemes, a projection pursuit method, named FPRM-PP for short, was developed in this work for selecting the optimal water transportation project scheme based on the fuzzy preference relation matrix. The research results show that FPRM-PP is intuitive and practical, the correction range of the fuzzy preference relation matrix A it produces is relatively small, and the result obtained is both stable and accurate; therefore FPRM-PP can be widely used in the optimal selection of different multi-factor decision-making schemes.

49 CFR 193.2607 - Foreign material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Foreign material. 193.2607 Section 193.2607 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY LIQUEFIED NATURAL GAS FACILITIES...

Recent Advances in Interface Engineering for Planar Heterojunction Perovskite Solar Cells.

PubMed

Yin, Wei; Pan, Lijia; Yang, Tingbin; Liang, Yongye

2016-06-25

Organic-inorganic hybrid perovskite solar cells are considered as one of the most promising next-generation solar cells due to their advantages of low-cost precursors, high power conversion efficiency (PCE) and easy of processing. In the past few years, the PCEs have climbed from a few to over 20% for perovskite solar cells. Recent developments demonstrate that perovskite exhibits ambipolar semiconducting characteristics, which allows for the construction of planar heterojunction (PHJ) perovskite solar cells. PHJ perovskite solar cells can avoid the use of high-temperature sintered mesoporous metal oxides, enabling simple processing and the fabrication of flexible and tandem perovskite solar cells. In planar heterojunction materials, hole/electron transport layers are introduced between a perovskite film and the anode/cathode. The hole and electron transporting layers are expected to enhance exciton separation, charge transportation and collection. Further, the supporting layer for the perovskite film not only plays an important role in energy-level alignment, but also affects perovskite film morphology, which have a great effect on device performance. In addition, interfacial layers also affect device stability. In this review, recent progress in interfacial engineering for PHJ perovskite solar cells will be reviewed, especially with the molecular interfacial materials. The supporting interfacial layers for the optimization of perovskite films will be systematically reviewed. Finally, the challenges remaining in perovskite solar cells research will be discussed.

Constrained Optimal Transport

NASA Astrophysics Data System (ADS)

Ekren, Ibrahim; Soner, H. Mete

2018-03-01

The classical duality theory of Kantorovich (C R (Doklady) Acad Sci URSS (NS) 37:199-201, 1942) and Kellerer (Z Wahrsch Verw Gebiete 67(4):399-432, 1984) for classical optimal transport is generalized to an abstract framework and a characterization of the dual elements is provided. This abstract generalization is set in a Banach lattice X with an order unit. The problem is given as the supremum over a convex subset of the positive unit sphere of the topological dual of X and the dual problem is defined on the bi-dual of X. These results are then applied to several extensions of the classical optimal transport.

Prospects of low-dimensional and nanostructured silicon-based thermoelectric materials: findings from theory and simulation

NASA Astrophysics Data System (ADS)

Neophytou, Neophytos

2015-04-01

Silicon based low-dimensional materials receive significant attention as new generation thermoelectric materials after they have demonstrated record low thermal conductivities. Very few works to-date, however, report significant advances with regards to the power factor. In this review we examine possibilities of power factor enhancement in: (i) low-dimensional Si channels and (ii) nanocrystalline Si materials. For low-dimensional channels we use atomistic simulations and consider ultra-narrow Si nanowires and ultra-thin Si layers of feature sizes below 15 nm. Room temperature is exclusively considered. We show that, in general, low-dimensionality does not offer possibilities for power factor improvement, because although the Seebeck coefficient could slightly increase, the conductivity inevitably degrades at a much larger extend. The power factor in these channels, however, can be optimized by proper choice of geometrical parameters such as the transport orientation, confinement orientation, and confinement length scale. Our simulations show that in the case where room temperature thermal conductivities as low as κ l = 2 W/mK are achieved, the ZT figure of merit of an optimized Si low-dimensional channel could reach values around unity. For the second case of materials, we show that by making effective use of energy filtering, and taking advantage of the inhomogeneity within the nanocrystalline geometry, the underlying potential profile and dopant distribution large improvements in the thermoelectric power factor can be achieved. The paper is intended to be a review of the main findings with regards to the thermoelectric performance of nanoscale Si through our simulation work as well as through recent experimental observations.

Effects of growth temperature on the properties of InGaN channel heterostructures grown by pulsed metal organic chemical vapor deposition

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

Zhang, Yachao; Zhou, Xiaowei; Xu, Shengrui

Pulsed metal organic chemical vapor deposition (P-MOCVD) is introduced into the growth of high quality InGaN channel heterostructures. The effects of InGaN channel growth temperature on the structural and transport properties of the heterostructures are investigated in detail. High resolution x-ray diffraction (HRXRD) and Photoluminescence (PL) spectra indicate that the quality of InGaN channel strongly depends on the growth temperature. Meanwhile, the atomic force microscopy (AFM) results show that the interface morphology between the InGaN channel and the barrier layer also relies on the growth temperature. Since the variation of material properties of InGaN channel has a significant influence onmore » the electrical properties of InAlN/InGaN heterostructures, the optimal transport properties can be achieved by adjusting the growth temperature. A very high two dimension electron gas (2DEG) density of 1.92 × 10{sup 13} cm{sup −2} and Hall electron mobility of 1025 cm{sup 2}/(V⋅s) at room temperature are obtained at the optimal growth temperature around 740 °C. The excellent transport properties in our work indicate that the heterostructure with InGaN channel is a promising candidate for the microwave power devices, and the results in this paper will be instructive for further study of the InGaN channel heterostructures.« less

An energy-optimal solution for transportation control of cranes with double pendulum dynamics: Design and experiments

NASA Astrophysics Data System (ADS)

Sun, Ning; Wu, Yiming; Chen, He; Fang, Yongchun

2018-03-01

Underactuated cranes play an important role in modern industry. Specifically, in most situations of practical applications, crane systems exhibit significant double pendulum characteristics, which makes the control problem quite challenging. Moreover, most existing planners/controllers obtained with standard methods/techniques for double pendulum cranes cannot minimize the energy consumption when fulfilling the transportation tasks. Therefore, from a practical perspective, this paper proposes an energy-optimal solution for transportation control of double pendulum cranes. By applying the presented approach, the transportation objective, including fast trolley positioning and swing elimination, is achieved with minimized energy consumption, and the residual oscillations are suppressed effectively with all the state constrains being satisfied during the entire transportation process. As far as we know, this is the first energy-optimal solution for transportation control of underactuated double pendulum cranes with various state and control constraints. Hardware experimental results are included to verify the effectiveness of the proposed approach, whose superior performance is reflected by being experimentally compared with some comparative controllers.

Use of constrained optimization in the conceptual design of a medium-range subsonic transport

NASA Technical Reports Server (NTRS)

Sliwa, S. M.

1980-01-01

Constrained parameter optimization was used to perform the optimal conceptual design of a medium range transport configuration. The impact of choosing a given performance index was studied, and the required income for a 15 percent return on investment was proposed as a figure of merit. A number of design constants and constraint functions were systematically varied to document the sensitivities of the optimal design to a variety of economic and technological assumptions. A comparison was made for each of the parameter variations between the baseline configuration and the optimally redesigned configuration.

Concurrent Monte Carlo transport and fluence optimization with fluence adjusting scalable transport Monte Carlo

PubMed Central

Svatos, M.; Zankowski, C.; Bednarz, B.

2016-01-01

Purpose: The future of radiation therapy will require advanced inverse planning solutions to support single-arc, multiple-arc, and “4π” delivery modes, which present unique challenges in finding an optimal treatment plan over a vast search space, while still preserving dosimetric accuracy. The successful clinical implementation of such methods would benefit from Monte Carlo (MC) based dose calculation methods, which can offer improvements in dosimetric accuracy when compared to deterministic methods. The standard method for MC based treatment planning optimization leverages the accuracy of the MC dose calculation and efficiency of well-developed optimization methods, by precalculating the fluence to dose relationship within a patient with MC methods and subsequently optimizing the fluence weights. However, the sequential nature of this implementation is computationally time consuming and memory intensive. Methods to reduce the overhead of the MC precalculation have been explored in the past, demonstrating promising reductions of computational time overhead, but with limited impact on the memory overhead due to the sequential nature of the dose calculation and fluence optimization. The authors propose an entirely new form of “concurrent” Monte Carlo treat plan optimization: a platform which optimizes the fluence during the dose calculation, reduces wasted computation time being spent on beamlets that weakly contribute to the final dose distribution, and requires only a low memory footprint to function. In this initial investigation, the authors explore the key theoretical and practical considerations of optimizing fluence in such a manner. Methods: The authors present a novel derivation and implementation of a gradient descent algorithm that allows for optimization during MC particle transport, based on highly stochastic information generated through particle transport of very few histories. A gradient rescaling and renormalization algorithm, and the concept of momentum from stochastic gradient descent were used to address obstacles unique to performing gradient descent fluence optimization during MC particle transport. The authors have applied their method to two simple geometrical phantoms, and one clinical patient geometry to examine the capability of this platform to generate conformal plans as well as assess its computational scaling and efficiency, respectively. Results: The authors obtain a reduction of at least 50% in total histories transported in their investigation compared to a theoretical unweighted beamlet calculation and subsequent fluence optimization method, and observe a roughly fixed optimization time overhead consisting of ∼10% of the total computation time in all cases. Finally, the authors demonstrate a negligible increase in memory overhead of ∼7–8 MB to allow for optimization of a clinical patient geometry surrounded by 36 beams using their platform. Conclusions: This study demonstrates a fluence optimization approach, which could significantly improve the development of next generation radiation therapy solutions while incurring minimal additional computational overhead. PMID:27277051

An ab initio electronic transport database for inorganic materials.

PubMed

Ricci, Francesco; Chen, Wei; Aydemir, Umut; Snyder, G Jeffrey; Rignanese, Gian-Marco; Jain, Anubhav; Hautier, Geoffroy

2017-07-04

Electronic transport in materials is governed by a series of tensorial properties such as conductivity, Seebeck coefficient, and effective mass. These quantities are paramount to the understanding of materials in many fields from thermoelectrics to electronics and photovoltaics. Transport properties can be calculated from a material's band structure using the Boltzmann transport theory framework. We present here the largest computational database of electronic transport properties based on a large set of 48,000 materials originating from the Materials Project database. Our results were obtained through the interpolation approach developed in the BoltzTraP software, assuming a constant relaxation time. We present the workflow to generate the data, the data validation procedure, and the database structure. Our aim is to target the large community of scientists developing materials selection strategies and performing studies involving transport properties.

75 FR 53593 - Hazardous Materials: Minor Editorial Corrections and Clarifications

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-01

... transportation, Packaging and containers, Radioactive materials, Reporting and recordkeeping requirements... section specifies general requirements for packaging hazardous materials for transportation by aircraft... contamination on motor vehicles used to transport Class 7 radioactive materials under exclusive use conditions...

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

H.E. Mynick, N. Pomphrey and P. Xanthopoulos

Recent progress in reducing turbulent transport in stellarators and tokamaks by 3D shaping using a stellarator optimization code in conjunction with a gyrokinetic code is presented. The original applications of the method focussed on ion temperature gradient transport in a quasi-axisymmetric stellarator design. Here, an examination of both other turbulence channels and other starting configurations is initiated. It is found that the designs evolved for transport from ion temperature gradient turbulence also display reduced transport from other transport channels whose modes are also stabilized by improved curvature, such as electron temperature gradient and ballooning modes. The optimizer is also appliedmore » to evolving from a tokamak, finding appreciable turbulence reduction for these devices as well. From these studies, improved understanding is obtained of why the deformations found by the optimizer are beneficial, and these deformations are related to earlier theoretical work in both stellarators and tokamaks.« less

78 FR 69745 - Safety and Security Plans for Class 3 Hazardous Materials Transported by Rail

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-20

... DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration [Docket No... Security Plans for Class 3 Hazardous Materials Transported by Rail AGENCY: Pipeline and Hazardous Materials... characterization, classification, and selection of a packing group for Class 3 materials, and the corresponding...

49 CFR 178.255-2 - Material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Material. 178.255-2 Section 178.255-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-2 Material. (a) Material used in the tank must be steel of good weldable quality...

49 CFR 178.255-2 - Material.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Material. 178.255-2 Section 178.255-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-2 Material. (a) Material used in the tank must be steel of good weldable quality...

49 CFR 178.255-2 - Material.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Material. 178.255-2 Section 178.255-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-2 Material. (a) Material used in the tank must be steel of good weldable quality...

49 CFR 178.255-2 - Material.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Material. 178.255-2 Section 178.255-2 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-2 Material. (a) Material used in the tank must be steel of good weldable quality...

Geologic and physiographic controls on bed-material yield, transport, and channel morphology for alluvial and bedrock rivers, western Oregon

USGS Publications Warehouse

O'Connor, James E.; Mangano, Joseph F.; Anderson, Scott A.; Wallick, J. Rose; Jones, Krista L.; Keith, Mackenzie K.

2014-01-01

The rivers of western Oregon have diverse forms and characteristics, with channel substrates ranging from continuous alluvial gravel to bare bedrock. Analysis of several measurable morphologic attributes of 24 valley reaches on 17 rivers provides a basis for comparing nonalluvial and alluvial channels. Key differences are that alluvial reaches have greater bar area, greater migration rates, and show systematic correlation among variables relating grain size to bed-material transport capacity. We relate these differences between channel types to bed-material transport rates as derived from a coupled regional analysis of empirical sediment yield measurements and physical experiments of clast attrition during transport. This sediment supply analysis shows that overall bed-material transport rates for western Oregon are chiefly controlled by (1) lithology and basin slope, which are the key factors for bed-material supply into the stream network, and (2) lithologic control of bed-material attrition from in-transport abrasion and disintegration. This bed-material comminution strongly affects bed-material transport in the study area, reducing transport rates by 50%–90% along the length of the larger rivers in the study area. A comparison of the bed-material transport estimates with the morphologic analyses shows that alluvial gravel-bed channels have systematic and bounding relations between bed-material transport rate and attributes such as bar area and local transport capacity. By contrast, few such relations are evident for nonalluvial rivers with bedrock or mixed-bed substrates, which are apparently more influenced by local controls on channel geometry and sediment supply. At the scale of western Oregon, the physiographic and lithologic controls on the balance between bed-material supply and transport capacity exert far-reaching influence on the distribution of alluvial and nonalluvial channels and their consequently distinctive morphologies and behaviors—differences germane for understanding river response to tectonics and environmental perturbations, as well as for implementing effective restoration and monitoring strategies.

Optimal one-way and roundtrip journeys design by mixed-integer programming

NASA Astrophysics Data System (ADS)

Ribeiro, Isabel M.; Vale, Cecília

2017-12-01

The introduction of multimodal/intermodal networks in transportation problems, especially when considering roundtrips, adds complexity to the models. This article presents two models for the optimization of intermodal trips as a contribution to the integration of transport modes in networks. The first model is devoted to one-way trips while the second one is dedicated to roundtrips. The original contribution of this research to transportation is mainly the consideration of roundtrips in the optimization process of intermodal transport, especially because the transport mode between two nodes on the return trip should be the same as the one on the outward trip if both nodes are visited on the return trip, which is a valuable aspect for transport companies. The mathematical formulations of both models leads to mixed binary linear programs, which is not a common approach for this type of problem. In this article, as well as the model description, computational experience is included to highlight the importance and efficiency of the proposed models, which may provide a valuable tool for transport managers.

Gold in the hills: patterns of placer gold accumulation under dynamic tectonic and climatic conditions

NASA Astrophysics Data System (ADS)

Roy, Sam; Upton, Phaedra; Craw, Dave

2018-01-01

Formation of placer accumulations in fluvial environments requires 103-106 or even greater times concentration of heavy minerals. For this to occur, regular sediment supply from erosion of adjacent topography is required, the river should remain within a single course for an extended period of time and the material must be reworked such that a high proportion of the sediment is removed while a high proportion of the heavy minerals remains. We use numerical modeling, constrained by observations of circum-Pacific placer gold deposits, to explore processes occurring in evolving river systems in dynamic tectonic environments. A fluvial erosion/transport model is used to determine the mobility of placer gold under variable uplift rate, storm intensity, and rock mass strength conditions. Gold concentration is calculated from hydraulic and bedload grain size conditions. Model results suggest that optimal gold concentration occurs in river channels that frequently approach a threshold between detachment-limited and transport-limited hydraulic conditions. Such a condition enables the accumulation of gold particles within the framework of a residual gravel lag. An increase in transport capacity, which can be triggered by faster uplift rates, more resistant bedrock, or higher intensity storm events, will strip all bedload from the channel. Conversely, a reduction in transport capacity, triggered by a reduction in uplift rate, bedrock resistance, or storm intensity, will lead to a greater accumulation of a majority of sediments and a net decrease in gold concentration. For our model parameter range, the optimal conditions for placer gold concentration are met by 103 times difference in strength between bedrock and fault, uplift rates between 1 and 5 mm a-1, and moderate storm intensities. Fault damage networks are shown to be a critical factor for high Au concentrations and should be a target for exploration.

Experimental models for Murray’s law

NASA Astrophysics Data System (ADS)

Akita, Dai; Kunita, Itsuki; Fricker, Mark D.; Kuroda, Shigeru; Sato, Katsuhiko; Nakagaki, Toshiyuki

2017-01-01

Transport networks are ubiquitous in multicellular organisms and include leaf veins, fungal mycelia and blood vessels. While transport of materials and signals through the network plays a crucial role in maintaining the living system, the transport capacity of the network can best be understood in terms of hydrodynamics. We report here that plasmodium from the large, single-celled amoeboid Physarum was able to construct a hydrodynamically optimized vein-network when evacuating biomass from confined arenas of various shapes through a narrow exit. Increasingly thick veins developed towards the exit, and the network spanned the arena via repetitive bifurcations to give a branching tree. The Hausdorff distance from all parts of the plasmodium to the vein network was kept low, whilst the hydrodynamic conductivity from distal parts of the network to the exit was equivalent, irrespective of the arena shape. This combination of spatial patterning and differential vein thickening served to evacuate biomass at an equivalent rate across the entire arena. The scaling relationship at the vein branches was determined experimentally to be 2.53-3.29, consistent with predictions from Murray’s law. Furthermore, we show that mathematical models for self-organised, adaptive transport in Physarum simulate the experimental network organisation well if the scaling coefficient of the current-reinforcement rule is set to 3. In simulations, this resulted in rapid development of an optimal network that minimised the combined volume and frictional energy in comparison with other scaling coefficients. This would predict that the boundary shear forces within each vein are constant throughout the network, and would be consistent with a feedback mechanism based on a sensing a threshold shear at the vein wall.

Electrical and thermal transport properties of layered Bi2YO4Cu2Se2

NASA Astrophysics Data System (ADS)

Xiao, Yu; Pei, Yanling; Chang, Cheng; Zhang, Xiao; Tan, Xing; Ye, Xinxin; Gong, Shengkai; Lin, Yuanhua; He, Jiaqing; Zhao, Li-Dong

2016-07-01

Bi2YO4Cu2Se2 possesses a low thermal conductivity and high electrical conductivity at room temperature, which was considered as a potential thermoelectric material. In this work, we have investigated the electrical and thermal transport properties of Bi2YO4Cu2Se2 system in the temperature range from 300 K to 873 K. We found that the total thermal conductivity decreases from 1.8 W m-1 K-1 to 0.9 W m-1 K-1, and the electrical conductivity decreases from 850 S/cm to 163 S/cm in the measured temperature range. To investigate how potential of Bi2YO4Cu2Se2 system, we prepared the heavily Iodine doped samples to counter-dope intrinsically high carrier concentration and improve the electrical transport properties. Interestingly, the Seebeck coefficient could be enhanced to +80 μV/K at 873 K, meanwhile, we found that a low thermal conductivity of 0.7 W m-1 K-1 could be achieved. The intrinsically low thermal conductivity in this system is related to the low elastic properties, such as Young's modulus of 70-72 GPa, and Grüneisen parameters of 1.55-1.71. The low thermal conductivity makes Bi2YO4Cu2Se2 system to be a potential thermoelectric material, the ZT value 0.06 at 873 K was obtained, a higher performance is expected by optimizing electrical transport properties through selecting suitable dopants, modifying band structures or by further reducing thermal conductivity through nanostructuring etc.

AN OPTIMAL ADAPTIVE LOCAL GRID REFINEMENT APPROACH TO MODELING CONTAMINANT TRANSPORT

EPA Science Inventory

A Lagrangian-Eulerian method with an optimal adaptive local grid refinement is used to model contaminant transport equations. pplication of this approach to two bench-mark problems indicates that it completely resolves difficulties of peak clipping, numerical diffusion, and spuri...

49 CFR 173.448 - General transportation requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false General transportation requirements. 173.448 Section 173.448 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS...

49 CFR 173.448 - General transportation requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false General transportation requirements. 173.448 Section 173.448 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS...

49 CFR 173.448 - General transportation requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false General transportation requirements. 173.448 Section 173.448 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS...

Optimal routing for efficient municipal solid waste transportation by using ArcGIS application in Chennai, India.

PubMed

Sanjeevi, V; Shahabudeen, P

2016-01-01

Worldwide, about US$410 billion is spent every year to manage four billion tonnes of municipal solid wastes (MSW). Transport cost alone constitutes more than 50% of the total expenditure on solid waste management (SWM) in major cities of the developed world and the collection and transport cost is about 85% in the developing world. There is a need to improve the ability of the city administrators to manage the municipal solid wastes with least cost. Since 2000, new technologies such as geographical information system (GIS) and related optimization software have been used to optimize the haul route distances. The city limits of Chennai were extended from 175 to 426 km(2) in 2011, leading to sub-optimum levels in solid waste transportation of 4840 tonnes per day. After developing a spatial database for the whole of Chennai with 200 wards, the route optimization procedures have been run for the transport of solid wastes from 13 wards (generating nodes) to one transfer station (intermediary before landfill), using ArcGIS. The optimization process reduced the distances travelled by 9.93%. The annual total cost incurred for this segment alone is Indian Rupees (INR) 226.1 million. Savings in terms of time taken for both the current and shortest paths have also been computed, considering traffic conditions. The overall savings are thus very meaningful and call for optimization of the haul routes for the entire Chennai. © The Author(s) 2015.

Criticism of generally accepted fundamentals and methodologies of traffic and transportation theory

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

Kerner, Boris S.

It is explained why the set of the fundamental empirical features of traffic breakdown (a transition from free flow to congested traffic) should be the empirical basis for any traffic and transportation theory that can be reliable used for control and optimization in traffic networks. It is shown that generally accepted fundamentals and methodologies of traffic and transportation theory are not consistent with the set of the fundamental empirical features of traffic breakdown at a highway bottleneck. To these fundamentals and methodologies of traffic and transportation theory belong (i) Lighthill-Whitham-Richards (LWR) theory, (ii) the General Motors (GM) model class (formore » example, Herman, Gazis et al. GM model, Gipps’s model, Payne’s model, Newell’s optimal velocity (OV) model, Wiedemann’s model, Bando et al. OV model, Treiber’s IDM, Krauß’s model), (iii) the understanding of highway capacity as a particular stochastic value, and (iv) principles for traffic and transportation network optimization and control (for example, Wardrop’s user equilibrium (UE) and system optimum (SO) principles). Alternatively to these generally accepted fundamentals and methodologies of traffic and transportation theory, we discuss three-phase traffic theory as the basis for traffic flow modeling as well as briefly consider the network breakdown minimization (BM) principle for the optimization of traffic and transportation networks with road bottlenecks.« less

Convergent evolution of vascular optimization in kelp (Laminariales).

PubMed

Drobnitch, Sarah Tepler; Jensen, Kaare H; Prentice, Paige; Pittermann, Jarmila

2015-10-07

Terrestrial plants and mammals, although separated by a great evolutionary distance, have each arrived at a highly conserved body plan in which universal allometric scaling relationships govern the anatomy of vascular networks and key functional metabolic traits. The universality of allometric scaling suggests that these phyla have each evolved an 'optimal' transport strategy that has been overwhelmingly adopted by extant species. To truly evaluate the dominance and universality of vascular optimization, however, it is critical to examine other, lesser-known, vascularized phyla. The brown algae (Phaeophyceae) are one such group--as distantly related to plants as mammals, they have convergently evolved a plant-like body plan and a specialized phloem-like transport network. To evaluate possible scaling and optimization in the kelp vascular system, we developed a model of optimized transport anatomy and tested it with measurements of the giant kelp, Macrocystis pyrifera, which is among the largest and most successful of macroalgae. We also evaluated three classical allometric relationships pertaining to plant vascular tissues with a diverse sampling of kelp species. Macrocystis pyrifera displays strong scaling relationships between all tested vascular parameters and agrees with our model; other species within the Laminariales display weak or inconsistent vascular allometries. The lack of universal scaling in the kelps and the presence of optimized transport anatomy in M. pyrifera raises important questions about the evolution of optimization and the possible competitive advantage conferred by optimized vascular systems to multicellular phyla. © 2015 The Author(s).

49 CFR 173.467 - Tests for demonstrating the ability of Type B and fissile materials packagings to withstand...

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Tests for demonstrating the ability of Type B and fissile materials packagings to withstand accident conditions in transportation. 173.467 Section 173.467 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION...

49 CFR 173.467 - Tests for demonstrating the ability of Type B and fissile materials packagings to withstand...

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Tests for demonstrating the ability of Type B and fissile materials packagings to withstand accident conditions in transportation. 173.467 Section 173.467 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION...

49 CFR 179.201-4 - Material.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SPECIFICATIONS FOR TANK CARS Specifications for Non-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.201-4 Material. All fittings...

Parallel-Batch Scheduling and Transportation Coordination with Waiting Time Constraint

PubMed Central

Gong, Hua; Chen, Daheng; Xu, Ke

2014-01-01

This paper addresses a parallel-batch scheduling problem that incorporates transportation of raw materials or semifinished products before processing with waiting time constraint. The orders located at the different suppliers are transported by some vehicles to a manufacturing facility for further processing. One vehicle can load only one order in one shipment. Each order arriving at the facility must be processed in the limited waiting time. The orders are processed in batches on a parallel-batch machine, where a batch contains several orders and the processing time of the batch is the largest processing time of the orders in it. The goal is to find a schedule to minimize the sum of the total flow time and the production cost. We prove that the general problem is NP-hard in the strong sense. We also demonstrate that the problem with equal processing times on the machine is NP-hard. Furthermore, a dynamic programming algorithm in pseudopolynomial time is provided to prove its ordinarily NP-hardness. An optimal algorithm in polynomial time is presented to solve a special case with equal processing times and equal transportation times for each order. PMID:24883385

Measuring the misfit between seismograms using an optimal transport distance: application to full waveform inversion

NASA Astrophysics Data System (ADS)

Métivier, L.; Brossier, R.; Mérigot, Q.; Oudet, E.; Virieux, J.

2016-04-01

Full waveform inversion using the conventional L2 distance to measure the misfit between seismograms is known to suffer from cycle skipping. An alternative strategy is proposed in this study, based on a measure of the misfit computed with an optimal transport distance. This measure allows to account for the lateral coherency of events within the seismograms, instead of considering each seismic trace independently, as is done generally in full waveform inversion. The computation of this optimal transport distance relies on a particular mathematical formulation allowing for the non-conservation of the total energy between seismograms. The numerical solution of the optimal transport problem is performed using proximal splitting techniques. Three synthetic case studies are investigated using this strategy: the Marmousi 2 model, the BP 2004 salt model, and the Chevron 2014 benchmark data. The results emphasize interesting properties of the optimal transport distance. The associated misfit function is less prone to cycle skipping. A workflow is designed to reconstruct accurately the salt structures in the BP 2004 model, starting from an initial model containing no information about these structures. A high-resolution P-wave velocity estimation is built from the Chevron 2014 benchmark data, following a frequency continuation strategy. This estimation explains accurately the data. Using the same workflow, full waveform inversion based on the L2 distance converges towards a local minimum. These results yield encouraging perspectives regarding the use of the optimal transport distance for full waveform inversion: the sensitivity to the accuracy of the initial model is reduced, the reconstruction of complex salt structure is made possible, the method is robust to noise, and the interpretation of seismic data dominated by reflections is enhanced.

Optimal Mass Transport for Shape Matching and Comparison

PubMed Central

Su, Zhengyu; Wang, Yalin; Shi, Rui; Zeng, Wei; Sun, Jian; Luo, Feng; Gu, Xianfeng

2015-01-01

Surface based 3D shape analysis plays a fundamental role in computer vision and medical imaging. This work proposes to use optimal mass transport map for shape matching and comparison, focusing on two important applications including surface registration and shape space. The computation of the optimal mass transport map is based on Monge-Brenier theory, in comparison to the conventional method based on Monge-Kantorovich theory, this method significantly improves the efficiency by reducing computational complexity from O(n2) to O(n). For surface registration problem, one commonly used approach is to use conformal map to convert the shapes into some canonical space. Although conformal mappings have small angle distortions, they may introduce large area distortions which are likely to cause numerical instability thus resulting failures of shape analysis. This work proposes to compose the conformal map with the optimal mass transport map to get the unique area-preserving map, which is intrinsic to the Riemannian metric, unique, and diffeomorphic. For shape space study, this work introduces a novel Riemannian framework, Conformal Wasserstein Shape Space, by combing conformal geometry and optimal mass transport theory. In our work, all metric surfaces with the disk topology are mapped to the unit planar disk by a conformal mapping, which pushes the area element on the surface to a probability measure on the disk. The optimal mass transport provides a map from the shape space of all topological disks with metrics to the Wasserstein space of the disk and the pullback Wasserstein metric equips the shape space with a Riemannian metric. We validate our work by numerous experiments and comparisons with prior approaches and the experimental results demonstrate the efficiency and efficacy of our proposed approach. PMID:26440265

Materials with engineered mesoporosity for programmed mass transport

NASA Astrophysics Data System (ADS)

Gough, Dara V.

Transport in nanostructured materials is of great interest for scientists in various fields, including molecular sequestration, catalysis, artificial photosynthesis and energy storage. This thesis will present work on the transport of molecular and ionic species in mesoporous materials (materials with pore sizes between 2 and 50 nm). Initially, discussion will focus on the synthesis of mesoporous ZnS nanorattles and the size selected mass transport of small molecules through the mesopores. Discussion will then shift of exploration of cation exchange and electroless plating of metals to alter the mesoporous hollow sphere (MHS) materials and properties. The focus of discussion will then shift to the transport of ions into and out of a hierarchically structured gold electrode. Finally, a model gamma-bactiophage was developed to study the electromigration of charged molecules into and out of a confined geometry. A catalytically active biomolecular species was encapsulated within the central cavity of ZnS MHS. Both the activity of the encapsulated enzyme and the size-selective transport through the wall of the MHS were verified through the use of a common fluorogen, hydrogen peroxide, and sodium azide. Additionally, the protection of the enzyme was shown through size-selected blocking of a protease. The mesoporous hollow sphere system introduces size-selectivity to catalyzed chemical reactions; future work may include variations in pore sizes, and pore wall chemical functionalization. The pore size in ZnS mesoporous hollow spheres is controlled between 2.5 and 4.1 nm through swelling of the lyotropic liquid crystal template. The incorporation of a swelling agent is shown to linearly vary the hexagonal lyotropic liquid crystalline phase, which templates the mesopores, while allowing the high fidelity synthesis of mesoporous hollow spheres. Fluorescnently labeled ssDNA was utilized as a probe to explore the change in mesopore permeability afforded by the swollen template relative to the unswollen template. Electroless plating and cation exchange were explored as methods to vary the shell material of MHS. Mesoporous Ni MHS were obtained by the reduction of Ni2+ with dimethylamine borane onto a CML latex core. However, the resultant MHS were damaged due to core swelling during etch. To successfully obtain undeformed MHS, a silica core must be utilized; one possible route to explore, in order to reach this goal, is the surface chemistry/ligand effects on Ni2+. Cation exchange was performed in order to obtain CuS MHS; however, it proved an unsuccessful route to PbS, S and HgS. CdS-ZnS, Bi2S3 and Ag2S MHS were obtained only with significant defects. A novel hierarchically structured material, porous opal, was prepared using a colloidal crystal template and the dealloying of silver from gold and possed porosity on length scales range from 10s of nanometers (due to the colloidal crystal template) down to ca. 10 nm (due to dealloying). The transport properties of the material were studied using cyclic voltammetry and electrochemical impedance spectroscopy. The porous opal was found to posses enhanced charge transport properties relative to a unimodal porous gold film and a higher surface area than a gold opal. An equivalent circuit model was presented to explain the enhanced charge transport properties. A biomimetic system for studying the translocation of polymers through a channel and into a spherical cavity was developed based on inspiration from the gamma-bacteriophage. The nanocavity system was synthesized using two template length scales: 250 nm and 1.2 mum. Fabrication challenges that arose when using 1.2 mum colloidal templates were addressed, and the system was optimized for confinement studies of plasmid dsDNA.

Nanometer-Scale Electrical Potential Profiling Across Perovskite Solar Cells

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

Xiao, Chuanxiao; Jiang, Chun-Sheng; Ke, Weijun

2016-11-21

We used Kelvin probe force microscopy to study the potential distribution on cross-section of perovskite solar cells with different types of electron-transporting layers (ETLs). Our results explain the low open-circuit voltage and fill factor in ETL-free cells, and support the fact that intrinsic SnO2 as an alternative ETL material can make high-performance devices. Furthermore, the potential-profiling results indicate a reduction in junction-interface recombination by the optimized SnO2 layer and adding a fullerene layer, which is consistent with the improved device performance and current-voltage hysteresis.

Superstructures and multijunction cells for high efficiency energy conversion

NASA Technical Reports Server (NTRS)

Wagner, M.; Leburton, J. P.

1985-01-01

Potential applications of superlattices to photovoltaic structures are discussed. A single-bandgap, multijunction cell with selective electrodes for lateral transport of collected carriers is proposed. The concept is based on similar doping superlattice (NIPI) structures. Computer simulations show that by reducing bulk recombination losses, the spectral response of such cells is enhanced, particularly for poor quality materials with short diffusion lengths. Dark current contributions of additional junctions result in a trade-off between short-circuit current and open-circuit voltage as the number of layers is increased. One or two extra junctions appear to be optimal.

49 CFR 192.65 - Transportation of pipe.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.65 Transportation of pipe. (a) Railroad...

Impact of longitudinal flying qualities upon the design of a transport with active controls

NASA Technical Reports Server (NTRS)

Sliwa, S. M.

1980-01-01

Direct constrained parameter optimization was used to optimally size a medium range transport for minimum direct operating cost. Several stability and control constraints were varied to study the sensitivity of the configuration to specifying the unaugmented flying qualities of transports designed with relaxed static stability. Additionally, a number of handling quality related design constants were studied with respect to their impact to the design.

Parametric investigations of plasma characteristics in a remote inductively coupled plasma system

NASA Astrophysics Data System (ADS)

Shukla, Prasoon; Roy, Abhra; Jain, Kunal; Bhoj, Ananth

2016-09-01

Designing a remote plasma system involves source chamber sizing, selection of coils and/or electrodes to power the plasma, designing the downstream tubes, selection of materials used in the source and downstream regions, locations of inlets and outlets and finally optimizing the process parameter space of pressure, gas flow rates and power delivery. Simulations can aid in spatial and temporal plasma characterization in what are often inaccessible locations for experimental probes in the source chamber. In this paper, we report on simulations of a remote inductively coupled Argon plasma system using the modeling platform CFD-ACE +. The coupled multiphysics model description successfully address flow, chemistry, electromagnetics, heat transfer and plasma transport in the remote plasma system. The SimManager tool enables easy setup of parametric simulations to investigate the effect of varying the pressure, power, frequency, flow rates and downstream tube lengths. It can also enable the automatic solution of the varied parameters to optimize a user-defined objective function, which may be the integral ion and radical fluxes at the wafer. The fast run time coupled with the parametric and optimization capabilities can add significant insight and value in design and optimization.

Advanced Aerogel Technology

NASA Technical Reports Server (NTRS)

Jones, Steven

2013-01-01

The JPL Aerogel Laboratory has made aerogels for NASA flight missions, e.g., Stardust, 2003 Mars Exploration Rovers and the 2011 Mars Science Laboratory, as well as NASA research projects for the past 14 years. During that time it has produced aerogels of a range of shapes, sizes, densities and compositions. Research is ongoing in the development of aerogels for future sample capture and return missions and for thermal insulation for both spacecraft and scientific instruments. For the past several years, the JPL Aerogel Laboratory has been developing, producing and testing a new composite material for use as the high temperature thermal insulation in the Advanced Sterling Radioisotope Generator (ASRG) being developed by Lockheed Martin and NASA. The composite is made up of a glass fiber felt, silica aerogel, Titania powder, and silica powder. The oxide powders are included to reduce irradiative heat transport at elevated temperatures. These materials have thermal conductivity values that are the same as the best commercially produced high temperature insulation materials, and yet are 40% lighter. By greatly reducing the amount of oxide powder in the composite, the density, and therefore for the value of the thermal conductivity, would be reduced. The JPL Aerogel Laboratory has experimented with using glass fiber felt, expanded glass fiber felt and loose fibers to add structural integrity to silica aerogels. However, this work has been directed toward high temperature applications. By conducting a brief investigation of the optimal combination of fiber reinforcement and aerogel density, a durable, extremely efficient thermal insulation material for ambient temperature applications would be produced. If a transparent thermal insulation is desired, then aerogel is an excellent candidate material. At typical ambient temperatures, silica aerogel prevents the transport of heat via convection and conduction due to its highly porous nature. To prevent irradiative thermal transport, silica aerogel can be used in conjunction with a transparent polymeric material that blocks infrared radiation. The transparency of silica aerogel is typically greater than 90% for visible wavelengths from 500 nm to 900 nm for a 5 mm long path length.

49 CFR 179.300-7 - Materials.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) SPECIFICATIONS FOR TANK CARS Specifications for Multi-Unit Tank Car Tanks (Classes DOT-106A and 110AW) § 179.300-7 Materials. (a) Steel plate material used...

49 CFR 179.300-7 - Materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) SPECIFICATIONS FOR TANK CARS Specifications for Multi-Unit Tank Car Tanks (Classes DOT-106A and 110AW) § 179.300-7 Materials. (a) Steel plate material used...

49 CFR 178.55 - Specification 4B240ET welded or brazed cylinders.

Code of Federal Regulations, 2010 CFR

2010-10-01

.... 178.55 Section 178.55 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS... material. Material must be identified by any suitable method. (d) Manufacture. Cylinders must be...

49 CFR 172.312 - Liquid hazardous materials in non-bulk packagings.

Code of Federal Regulations, 2014 CFR

2014-10-01

... offered or intended for transportation by aircraft, packages containing flammable liquids in inner... 49 Transportation 2 2014-10-01 2014-10-01 false Liquid hazardous materials in non-bulk packagings... HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS...

49 CFR 172.312 - Liquid hazardous materials in non-bulk packagings.

Code of Federal Regulations, 2013 CFR

2013-10-01

... offered or intended for transportation by aircraft, packages containing flammable liquids in inner... 49 Transportation 2 2013-10-01 2013-10-01 false Liquid hazardous materials in non-bulk packagings... HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS...

Advanced Nanostructured Anode Materials for Sodium-Ion Batteries.

PubMed

Wang, Qidi; Zhao, Chenglong; Lu, Yaxiang; Li, Yunming; Zheng, Yuheng; Qi, Yuruo; Rong, Xiaohui; Jiang, Liwei; Qi, Xinguo; Shao, Yuanjun; Pan, Du; Li, Baohua; Hu, Yong-Sheng; Chen, Liquan

2017-11-01

Sodium-ion batteries (NIBs), due to the advantages of low cost and relatively high safety, have attracted widespread attention all over the world, making them a promising candidate for large-scale energy storage systems. However, the inherent lower energy density to lithium-ion batteries is the issue that should be further investigated and optimized. Toward the grid-level energy storage applications, designing and discovering appropriate anode materials for NIBs are of great concern. Although many efforts on the improvements and innovations are achieved, several challenges still limit the current requirements of the large-scale application, including low energy/power densities, moderate cycle performance, and the low initial Coulombic efficiency. Advanced nanostructured strategies for anode materials can significantly improve ion or electron transport kinetic performance enhancing the electrochemical properties of battery systems. Herein, this Review intends to provide a comprehensive summary on the progress of nanostructured anode materials for NIBs, where representative examples and corresponding storage mechanisms are discussed. Meanwhile, the potential directions to obtain high-performance anode materials of NIBs are also proposed, which provide references for the further development of advanced anode materials for NIBs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Entropy as a Gene-Like Performance Indicator Promoting Thermoelectric Materials.

PubMed

Liu, Ruiheng; Chen, Hongyi; Zhao, Kunpeng; Qin, Yuting; Jiang, Binbin; Zhang, Tiansong; Sha, Gang; Shi, Xun; Uher, Ctirad; Zhang, Wenqing; Chen, Lidong

2017-10-01

High-throughput explorations of novel thermoelectric materials based on the Materials Genome Initiative paradigm only focus on digging into the structure-property space using nonglobal indicators to design materials with tunable electrical and thermal transport properties. As the genomic units, following the biogene tradition, such indicators include localized crystal structural blocks in real space or band degeneracy at certain points in reciprocal space. However, this nonglobal approach does not consider how real materials differentiate from others. Here, this study successfully develops a strategy of using entropy as the global gene-like performance indicator that shows how multicomponent thermoelectric materials with high entropy can be designed via a high-throughput screening method. Optimizing entropy works as an effective guide to greatly improve the thermoelectric performance through either a significantly depressed lattice thermal conductivity down to its theoretical minimum value and/or via enhancing the crystal structure symmetry to yield large Seebeck coefficients. The entropy engineering using multicomponent crystal structures or other possible techniques provides a new avenue for an improvement of the thermoelectric performance beyond the current methods and approaches. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tailored material properties using textile composites

NASA Astrophysics Data System (ADS)

Pastore, C. M.

2017-10-01

Lightweighting is essential for the reduction of energy consumption in transportation. The most common approach is through the application of high specific strength and stiffness materials, such as composites and high performance aluminum alloys. One of the challenges associated with the use of advanced materials is the high cost. This paper explores the opportunities of using hybrid composites (glass and carbon, for example) with selective fiber placement to optimize the weight subject to price constraints for given components. Considering the example of a hat-section for hood reinforcement, different material configurations were modeled and developed. The required thickness of the hat section to meet the same bending stiffness as an all carbon composite beam was calculated. It was shown that selective placement of fiber around the highest moments results in a weight savings of around 14% compared to a uniformly blended hybrid with the same total material configuration. From this it is possible to estimate the materials cost of the configurations as well as the weight of the component. To determine which is best it is necessary to find an exchange constant that converts weight into cost - the penalty of carrying the extra weight. The value of this exchange constant will depend on the particular application.

A critical review on the carrier dynamics in 2D layered materials investigated using THz spectroscopy

NASA Astrophysics Data System (ADS)

Lu, Junpeng; Liu, Hongwei

2018-01-01

Accurately illustrating the photocarrier dynamics and photoelectrical properties of two dimensional (2D) materials is crucial in the development of 2D material-based optoelectronic devices. Considering this requirement, terahertz (THz) spectroscopy has emerged as a befitting characterization tool to provide deep insights into the carrier dynamics and measurements of the electrical/photoelectrical conductivity of 2D materials. THz spectroscopic measurements would provide information of transient behaviors of carriers with high accuracy in a nondestructive and noncontact manner. In this article, we present a comprehensive review on recent research efforts on investigations of 2D materials of graphene and transition metal dichalcogenides (TMDs) using THz spectroscopy. A brief introduction of THz time-domain spectroscopy (THz-TDS) and optical pump-THz probe spectroscopy (OPTP) is provided. The characterization of the electron transport of graphene at equilibrium state and transient behavior at non-equilibrium state is reviewed. We also review the characterizations of TMDs including MoS2 and WSe2. Finally, we conclude the recent reports and give a prospect on how THz characterizations would guide the design and optimization of 2D material-based optoelectronic devices.

Reduced-Order Direct Numerical Simulation of Solute Transport in Porous Media

NASA Astrophysics Data System (ADS)

Mehmani, Yashar; Tchelepi, Hamdi

2017-11-01

Pore-scale models are an important tool for analyzing fluid dynamics in porous materials (e.g., rocks, soils, fuel cells). Current direct numerical simulation (DNS) techniques, while very accurate, are computationally prohibitive for sample sizes that are statistically representative of the porous structure. Reduced-order approaches such as pore-network models (PNM) aim to approximate the pore-space geometry and physics to remedy this problem. Predictions from current techniques, however, have not always been successful. This work focuses on single-phase transport of a passive solute under advection-dominated regimes and delineates the minimum set of approximations that consistently produce accurate PNM predictions. Novel network extraction (discretization) and particle simulation techniques are developed and compared to high-fidelity DNS simulations for a wide range of micromodel heterogeneities and a single sphere pack. Moreover, common modeling assumptions in the literature are analyzed and shown that they can lead to first-order errors under advection-dominated regimes. This work has implications for optimizing material design and operations in manufactured (electrodes) and natural (rocks) porous media pertaining to energy systems. This work was supported by the Stanford University Petroleum Research Institute for Reservoir Simulation (SUPRI-B).

49 CFR 178.44 - Specification 3HT seamless steel cylinders for aircraft use.

Code of Federal Regulations, 2010 CFR

2010-10-01

... to check analysis for phosphorus. (c) Identification of material. Material must be identified by any... aircraft use. 178.44 Section 178.44 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS...

49 CFR 195.206 - Material inspection.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Material inspection. 195.206 Section 195.206 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.206 Material inspection. No pipe or other component may be installed in a...

49 CFR 195.206 - Material inspection.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 3 2010-10-01 2010-10-01 false Material inspection. 195.206 Section 195.206 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.206 Material inspection. No pipe or other component may be installed in a...

Hazardous Materials Routing Study Phase I: Establishing Hazardous Materials Truck Routes for Shipments Through the Dallas-Fort Worth Area

DOT National Transportation Integrated Search

1985-10-01

The transportation of hazardous materials over streets and highways in the Dallas-Fort Worth area has become a significant transportation safety concern. Recent accidents involving vehicles transporting hazardous materials have resulted in extensive ...

49 CFR 195.206 - Material inspection.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Material inspection. 195.206 Section 195.206 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.206 Material inspection. No pipe or other component may be installed in a...

Methods of increasing efficiency and maintainability of pipeline systems

NASA Astrophysics Data System (ADS)

Ivanov, V. A.; Sokolov, S. M.; Ogudova, E. V.

2018-05-01

This study is dedicated to the issue of pipeline transportation system maintenance. The article identifies two classes of technical-and-economic indices, which are used to select an optimal pipeline transportation system structure. Further, the article determines various system maintenance strategies and strategy selection criteria. Meanwhile, the maintenance strategies turn out to be not sufficiently effective due to non-optimal values of maintenance intervals. This problem could be solved by running the adaptive maintenance system, which includes a pipeline transportation system reliability improvement algorithm, especially an equipment degradation computer model. In conclusion, three model building approaches for determining optimal technical systems verification inspections duration were considered.

Dijkstra Methode for Optimalize Recommendation System of Garbage Transportation Time in Surakarta City

NASA Astrophysics Data System (ADS)

Hartatik; Purbayu, A.; Triyono, L.

2018-03-01

Major problem that often occurs in waste transportation in each region is the route of garbage transportation. Determination of this route should become a major concern because it affects fuel consumption and also the working time from the employee. Therefore, in this research we will develop an application to optimize with pigeonhole and dijsktra algorithm. Pigeonhole algorithm is used to determine which garbage trucks should be taken in a particular TPS. Time optimization is done by determining the shortest path that can be skipped for each garbage truck. Data generated from Pigeonhole then used to determine the shortest path by using Dijkstra algorithm.

Optimizing Mars Sphere of Influence Maneuvers for NASA's Evolvable Mars Campaign

NASA Technical Reports Server (NTRS)

Merrill, Raymond G.; Komar, D. R.; Chai, Patrick; Qu, Min

2016-01-01

NASA's Human Spaceflight Architecture Team is refining human exploration architectures that will extend human presence to the Martian surface. For both Mars orbital and surface missions, NASA's Evolvable Mars Campaign assumes that cargo and crew can be delivered repeatedly to the same destination. Up to this point, interplanetary trajectories have been optimized to minimize the total propulsive requirements of the in-space transportation systems, while the pre-deployed assets and surface systems are optimized to minimize their respective propulsive requirements separate from the in-space transportation system. There is a need to investigate the coupled problem of optimizing the interplanetary trajectory and optimizing the maneuvers within Mars's sphere of influence. This paper provides a description of the ongoing method development, analysis and initial results of the effort to resolve the discontinuity between the interplanetary trajectory and the Mars sphere of influence trajectories. Assessment of Phobos and Deimos orbital missions shows the in-space transportation and crew taxi allocations are adequate for missions in the 2030s. Because the surface site has yet to be selected, the transportation elements must be sized to provide enough capability to provide surface access to all landing sites under consideration. Analysis shows access to sites from elliptical parking orbits with a lander that is designed for sub-periapsis landing location is either infeasible or requires expensive orbital maneuvers for many latitude ranges. In this case the locus of potential arrival perigee vectors identifies the potential maximum north or south latitudes accessible. Higher arrival velocities can decrease reorientation costs and increase landing site availability. Utilizing hyperbolic arrival and departure vectors in the optimization scheme will increase transportation site accessibility and provide more optimal solutions.

30 CFR 75.1403-2 - Criteria-Hoists transporting materials; brakes.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Criteria-Hoists transporting materials; brakes. 75.1403-2 Section 75.1403-2 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF... Mantrips § 75.1403-2 Criteria—Hoists transporting materials; brakes. Hoists and elevators used to transport...

30 CFR 75.1403-2 - Criteria-Hoists transporting materials; brakes.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Criteria-Hoists transporting materials; brakes. 75.1403-2 Section 75.1403-2 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF... Mantrips § 75.1403-2 Criteria—Hoists transporting materials; brakes. Hoists and elevators used to transport...

30 CFR 57.9261 - Transporting tools and materials on locomotives.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Transporting tools and materials on locomotives. 57.9261 Section 57.9261 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... MINES Loading, Hauling, and Dumping Transportation of Persons and Materials § 57.9261 Transporting tools...

30 CFR 57.9261 - Transporting tools and materials on locomotives.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Transporting tools and materials on locomotives. 57.9261 Section 57.9261 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR... MINES Loading, Hauling, and Dumping Transportation of Persons and Materials § 57.9261 Transporting tools...

49 CFR 176.170 - Transport of Class 1 (explosive) materials in freight containers.

Code of Federal Regulations, 2012 CFR

2012-10-01

... ships, freight containers containing Class 1 (explosive) materials must be stowed only in the lowest... freight containers. 176.170 Section 176.170 Transportation Other Regulations Relating to Transportation... and Shipborne Barges § 176.170 Transport of Class 1 (explosive) materials in freight containers. (a...

49 CFR 176.170 - Transport of Class 1 (explosive) materials in freight containers.

Code of Federal Regulations, 2013 CFR

2013-10-01

... ships, freight containers containing Class 1 (explosive) materials must be stowed only in the lowest... freight containers. 176.170 Section 176.170 Transportation Other Regulations Relating to Transportation... and Shipborne Barges § 176.170 Transport of Class 1 (explosive) materials in freight containers. (a...

49 CFR 176.170 - Transport of Class 1 (explosive) materials in freight containers.

Code of Federal Regulations, 2014 CFR

2014-10-01

... ships, freight containers containing Class 1 (explosive) materials must be stowed only in the lowest... freight containers. 176.170 Section 176.170 Transportation Other Regulations Relating to Transportation... and Shipborne Barges § 176.170 Transport of Class 1 (explosive) materials in freight containers. (a...

Nb doped TiO2 as a Cathode Catalyst Support Material for Polymer Electrolyte Membrane Fuel Cells

NASA Astrophysics Data System (ADS)

O'Toole, Alexander W.

In order to reduce the emissions of greenhouse gases and reduce dependence on the use of fossil fuels, it is necessary to pursue alternative sources of energy. Transportation is a major contributor to the emission of greenhouse gases due to the use of fossil fuels in the internal combustion engine. To reduce emission of these pollutants into the atmosphere, research is needed to produce alternative solutions for vehicle transportation. Low temperature polymer electrolyte membrane fuel cells are energy conversion devices that provide an alternative to the internal combustion engine, however, they still have obstacles to overcome to achieve large scale implementation. T he following work presents original research with regards to the development of Nb doped TiO2 as a cathode catalyst support material for low temperature polymer electrolyte membrane fuel cells. The development of a new process to synthesize nanoparticles of Nb doped TiO2 with controlled compositions is presented as well as methods to scale up the process and optimize the synthesis for the aforementioned application. In addition to this, comparison of both electrochemical activity and durability with current state of the art Pt on high surface area carbon black (Vulcan XC-72) is investigated. Effects of the strong metal-support interaction on the electrochemical behavior of these materials is also observed and discussed.

Global or local construction materials for post-disaster reconstruction? Sustainability assessment of 20 post-disaster shelter designs

PubMed Central

Zea Escamilla, E.; Habert, G.

2015-01-01

This data article presents the life cycle inventories of 20 transitional shelter solutions. The data was gathered from the reports 8 shelter designs [1]; 10 post-disaster shelter designs [2]; the environmental impact of brick production outside of Europe [3]; and the optimization of bamboo-based post-disaster housing units for tropical and subtropical regions using LCA methodologies [4]. These reports include bill of quantities, plans, performance analysis, and lifespan of the studied shelters. The data from these reports was used to develop the Life Cycle Inventories (LCI). All the amounts were converted from their original units (length, volume and amount) into mass (kg) units and the transport distance into ton×km. These LCIs represent the production phases of each shelter and the transportation distances for the construction materials. Two types of distances were included, local (road) and international (freight ship), which were estimated based on the area of the country of study. Furthermore, the digital visualization of the shelters is presented for each of the 20 designs. Moreover, this data article presents a summary of the results for the categories Environment, Cost and Risk and the contribution to the environmental impact from the different building components of each shelter. These results are related to the article “Global or local construction materials for post-disaster reconstruction? Sustainability assessment of 20 post-disaster shelter designs”[5] PMID:26217807

Global or local construction materials for post-disaster reconstruction? Sustainability assessment of 20 post-disaster shelter designs.

PubMed

Zea Escamilla, E; Habert, G

2015-09-01

This data article presents the life cycle inventories of 20 transitional shelter solutions. The data was gathered from the reports 8 shelter designs [1]; 10 post-disaster shelter designs [2]; the environmental impact of brick production outside of Europe [3]; and the optimization of bamboo-based post-disaster housing units for tropical and subtropical regions using LCA methodologies [4]. These reports include bill of quantities, plans, performance analysis, and lifespan of the studied shelters. The data from these reports was used to develop the Life Cycle Inventories (LCI). All the amounts were converted from their original units (length, volume and amount) into mass (kg) units and the transport distance into ton×km. These LCIs represent the production phases of each shelter and the transportation distances for the construction materials. Two types of distances were included, local (road) and international (freight ship), which were estimated based on the area of the country of study. Furthermore, the digital visualization of the shelters is presented for each of the 20 designs. Moreover, this data article presents a summary of the results for the categories Environment, Cost and Risk and the contribution to the environmental impact from the different building components of each shelter. These results are related to the article "Global or local construction materials for post-disaster reconstruction? Sustainability assessment of 20 post-disaster shelter designs"[5].

49 CFR 176.89 - Control of transport vehicles.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Control of transport vehicles. 176.89 Section 176... Special Requirements for Transport Vehicles Loaded With Hazardous Materials and Transported on Board Ferry Vessels § 176.89 Control of transport vehicles. (a) A transport vehicle containing hazardous materials may...

49 CFR 176.89 - Control of transport vehicles.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Control of transport vehicles. 176.89 Section 176... Special Requirements for Transport Vehicles Loaded With Hazardous Materials and Transported on Board Ferry Vessels § 176.89 Control of transport vehicles. (a) A transport vehicle containing hazardous materials may...

49 CFR 176.89 - Control of transport vehicles.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Control of transport vehicles. 176.89 Section 176... Special Requirements for Transport Vehicles Loaded With Hazardous Materials and Transported on Board Ferry Vessels § 176.89 Control of transport vehicles. (a) A transport vehicle containing hazardous materials may...

49 CFR 176.89 - Control of transport vehicles.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Control of transport vehicles. 176.89 Section 176... Special Requirements for Transport Vehicles Loaded With Hazardous Materials and Transported on Board Ferry Vessels § 176.89 Control of transport vehicles. (a) A transport vehicle containing hazardous materials may...

49 CFR 176.89 - Control of transport vehicles.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Control of transport vehicles. 176.89 Section 176... Special Requirements for Transport Vehicles Loaded With Hazardous Materials and Transported on Board Ferry Vessels § 176.89 Control of transport vehicles. (a) A transport vehicle containing hazardous materials may...

Impact of the electron-transport layer on the performance of solution-processed small-molecule organic solar cells.

PubMed

Long, Guankui; Wan, Xiangjian; Kan, Bin; Hu, Zhicheng; Yang, Xuan; Zhang, Yi; Zhang, Mingtao; Wu, Hongbing; Huang, Fei; Su, Shijian; Cao, Yong; Chen, Yongsheng

2014-08-01

Although the performance of polymer solar cells has been improved significantly recently through careful optimization with different interlayers for the same materials, more improvement is needed in this respect for small-molecule-based solar cells, particularly for the electron-transport layers (ETLs). In this work, three different solution-processed ETLs, PFN, ZnO nanoparticles, and LiF, were investigated and compared in the performance of small-molecule-based devices, and power conversion efficiencies (PCEs) of 8.32, 7.30, and 7.38% were achieved, respectively. The mechanism for the ETL-induced enhancement has been studied, and different ETLs have a significantly different impact on the device performance. The clearly improved performance of PFN is attributed to the combination of reduced bimolecular recombination and increased effective photon absorption in the active layer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generalized two-temperature model for coupled phonon-magnon diffusion.

PubMed

Liao, Bolin; Zhou, Jiawei; Chen, Gang

2014-07-11

We generalize the two-temperature model [Sanders and Walton, Phys. Rev. B 15, 1489 (1977)] for coupled phonon-magnon diffusion to include the effect of the concurrent magnetization flow, with a particular emphasis on the thermal consequence of the magnon flow driven by a nonuniform magnetic field. Working within the framework of the Boltzmann transport equation, we derive the constitutive equations for coupled phonon-magnon transport driven by gradients of both temperature and external magnetic fields, and the corresponding conservation laws. Our equations reduce to the original Sanders-Walton two-temperature model under a uniform external field, but predict a new magnon cooling effect driven by a nonuniform magnetic field in a homogeneous single-domain ferromagnet. We estimate the magnitude of the cooling effect in an yttrium iron garnet, and show it is within current experimental reach. With properly optimized materials, the predicted cooling effect can potentially supplement the conventional magnetocaloric effect in cryogenic applications in the future.

Enhanced vapor transport in membrane distillation via functionalized carbon nanotubes anchored into electrospun nanofibres

PubMed Central

Kyoungjin An, Alicia; Lee, Eui-Jong; Guo, Jiaxin; Jeong, Sanghyun; Lee, Jung-Gil; Ghaffour, Noreddine

2017-01-01

To ascertain membrane distillation (MD) as an emerging desalination technology to meet the global water challenge, development of membranes with ideal material properties is crucial. Functionalized carbon nanotubes (CNTs) were anchored to nanofibres of electrospun membranes. Covalent modification and fluorination of CNTs improved their dispersibility and interfacial interaction with the polymer membrane, resulting in well-aligned CNTs inside crystalline fibres with superhydrophobicity. Consideration for the chemical/physical properties of the CNT composite membranes and calculation of their theoretical fluxes revealed the mechanism of MD: CNTs facilitated the repulsive force for Knudsen and molecular diffusions, reduced the boundary-layer effect in viscous flow, and assisted surface diffusion, allowing for fast vapor transport with anti-wetting. This study shows that the role of CNTs and an optimal composite ratio can be used to reduce the gap between theoretical and experimental approaches to desalination. PMID:28134288

Rocking-Chair Configuration in Ultrathin Lithium Vanadate-Graphene Hybrid Nanosheets for Electrical Modulation

PubMed Central

Zhu, Haiou; Qin, Xinming; Sun, Xu; Yan, Wensheng; Yang, Jinlong; Xie, Yi

2013-01-01

The ability to control electronic property of a material by externally applied voltage is greatly anticipated in modern electronics, and graphene provide potential application foreground for this issue on account of its exotic ambipolar transport property. In this study, we proposed that inorganic-graphene intercalated nanosheet is an effective solution to optimize the transport property of graphene. As an example, lithium vanadate-graphene (LiVO-graphene) alternately intercalated nanosheets were designed and successfully synthesized. Theoretical calculation implied that its rocking chair configuration may provide a new pathway to switch the carrier in graphene layer between p-type and n-type while the position of embedded Li ions is controlled by an external field. Thus, a demo transistor was fabricated with layer-by-layer overlapping of LiVO-graphene nanosheets which proved that this inorganic-graphene structure could be used for electrical modulation in electronic devices. PMID:23409237

In Situ Synthesis of Vertical Standing Nanosized NiO Encapsulated in Graphene as Electrodes for High-Performance Supercapacitors.

PubMed

Lin, Jinghuang; Jia, Henan; Liang, Haoyan; Chen, Shulin; Cai, Yifei; Qi, Junlei; Qu, Chaoqun; Cao, Jian; Fei, Weidong; Feng, Jicai

2018-03-01

NiO is a promising electrode material for supercapacitors. Herein, the novel vertically standing nanosized NiO encapsulated in graphene layers (G@NiO) are rationally designed and synthesized as nanosheet arrays. This unique vertical standing structure of G@NiO nanosheet arrays can enlarge the accessible surface area with electrolytes, and has the benefits of short ion diffusion path and good charge transport. Further, an interconnected graphene conductive network acts as binder to encapsulate the nanosized NiO particles as core-shell structure, which can promote the charge transport and maintain the structural stability. Consequently, the optimized G@NiO hybrid electrodes exhibit a remarkably enhanced specific capacity up to 1073 C g -1 and excellent cycling stability. This study provides a facial strategy to design and construct high-performance metal oxides for energy storage.

Unified modelling of the thermoelectric properties in SrTiO3

NASA Astrophysics Data System (ADS)

Bouzerar, G.; Thébaud, S.; Adessi, Ch.; Debord, R.; Apreutesei, M.; Bachelet, R.; Pailhès, S.

2017-06-01

Thermoelectric materials are opening a promising pathway to address energy conversion issues governed by a competition between thermal and electronic transport. Improving the efficiency is a difficult task, a challenge that requires new strategies to unearth optimized compounds. We present a theory of thermoelectric transport in electron-doped SrTiO3, based on a realistic tight-binding model that includes relevant scattering processes. We compare our calculations against a wide panel of experimental data, both bulk and thin films. We find a qualitative and quantitative agreement over both a wide range of temperatures and carrier concentrations, from light to heavily doped. Moreover, the results appear insensitive to the nature of the dopant La, B, Gd and Nb. Thus, the quantitative success found in the case of SrTiO3, reveals an efficient procedure to explore new routes to improve the thermoelectric properties in oxides.

Conflicting effect of chemical doping on the thermoelectric response of ordered PEDOT aggregates.

PubMed

Cigarini, Luigi; Ruini, Alice; Catellani, Alessandra; Calzolari, Arrigo

2018-02-14

Poly(3,4-ethylenedioxythiophene) (PEDOT) semiconductor plays a relevant role in the development of organic thermoelectric (TE) devices for low-power generation. While dopant counterions are usually needed to provide electrical conductivity, their overall effects on the thermoelectric response of the systems are unknown and uncontrolled. Here, we present a first principles study of the electronic and thermal transport of PEDOT crystalline assemblies, specifically analysing the role played by tosylate dopants on the thermoelectric figure of merit of the doped system. Our results demonstrate that, beside the desired charging effect, the presence of dopants impacts the bulk configuration by inflating the packing structure and worsening the intrinsic transport properties of the PEDOT host. This provides a rationale for the necessity of controlling the optimal amount and the structural incorporation of dopant in order to maximize the thermoelectric response of organic materials.

Active matter logic for autonomous microfluidics

NASA Astrophysics Data System (ADS)

Woodhouse, Francis G.; Dunkel, Jörn

2017-04-01

Chemically or optically powered active matter plays an increasingly important role in materials design, but its computational potential has yet to be explored systematically. The competition between energy consumption and dissipation imposes stringent physical constraints on the information transport in active flow networks, facilitating global optimization strategies that are not well understood. Here, we combine insights from recent microbial experiments with concepts from lattice-field theory and non-equilibrium statistical mechanics to introduce a generic theoretical framework for active matter logic. Highlighting conceptual differences with classical and quantum computation, we demonstrate how the inherent non-locality of incompressible active flow networks can be utilized to construct universal logical operations, Fredkin gates and memory storage in set-reset latches through the synchronized self-organization of many individual network components. Our work lays the conceptual foundation for developing autonomous microfluidic transport devices driven by bacterial fluids, active liquid crystals or chemically engineered motile colloids.

Enhanced vapor transport in membrane distillation via functionalized carbon nanotubes anchored into electrospun nanofibres

NASA Astrophysics Data System (ADS)

Kyoungjin An, Alicia; Lee, Eui-Jong; Guo, Jiaxin; Jeong, Sanghyun; Lee, Jung-Gil; Ghaffour, Noreddine

2017-01-01

To ascertain membrane distillation (MD) as an emerging desalination technology to meet the global water challenge, development of membranes with ideal material properties is crucial. Functionalized carbon nanotubes (CNTs) were anchored to nanofibres of electrospun membranes. Covalent modification and fluorination of CNTs improved their dispersibility and interfacial interaction with the polymer membrane, resulting in well-aligned CNTs inside crystalline fibres with superhydrophobicity. Consideration for the chemical/physical properties of the CNT composite membranes and calculation of their theoretical fluxes revealed the mechanism of MD: CNTs facilitated the repulsive force for Knudsen and molecular diffusions, reduced the boundary-layer effect in viscous flow, and assisted surface diffusion, allowing for fast vapor transport with anti-wetting. This study shows that the role of CNTs and an optimal composite ratio can be used to reduce the gap between theoretical and experimental approaches to desalination.

Increased xylose affinity of Hxt2 through gene shuffling of hexose transporters in Saccharomyces cerevisiae.

PubMed

Nijland, J G; Shin, H Y; de Waal, P P; Klaassen, P; Driessen, A J M

2018-02-01

Optimizing D-xylose transport in Saccharomyces cerevisiae is essential for efficient bioethanol production from cellulosic materials. We have used a gene shuffling approach of hexose (Hxt) transporters in order to increase the affinity for D-xylose. Various libraries were transformed to a hexose transporter deletion strain, and shuffled genes were selected via growth on low concentrations of D-xylose. This screening yielded two homologous fusion proteins (fusions 9,4 and 9,6), both consisting of the major central part of Hxt2 and various smaller parts of other Hxt proteins. Both chimeric proteins showed the same increase in D-xylose affinity (8·1 ± 3·0 mmol l -1 ) compared with Hxt2 (23·7 ± 2·1 mmol l -1 ). The increased D-xylose affinity could be related to the C terminus, more specifically to a cysteine to proline mutation at position 505 in Hxt2. The Hxt2 C505P mutation increased the affinity for D-xylose for Hxt2, thus providing a way to increase D-xylose transport flux at low D-xylose concentration. The gene shuffling protocol using the highly homologues hexose transporters family provides a powerful tool to enhance the D-xylose affinity of Hxt transporters in S. cerevisiae, thus providing a means to increase the D-xylose uptake flux at low D-xylose concentrations. © 2017 The Society for Applied Microbiology.

Optimizing velocities and transports for complex coastal regions and archipelagos

NASA Astrophysics Data System (ADS)

Haley, Patrick J.; Agarwal, Arpit; Lermusiaux, Pierre F. J.

2015-05-01

We derive and apply a methodology for the initialization of velocity and transport fields in complex multiply-connected regions with multiscale dynamics. The result is initial fields that are consistent with observations, complex geometry and dynamics, and that can simulate the evolution of ocean processes without large spurious initial transients. A class of constrained weighted least squares optimizations is defined to best fit first-guess velocities while satisfying the complex bathymetry, coastline and divergence strong constraints. A weak constraint towards the minimum inter-island transports that are in accord with the first-guess velocities provides important velocity corrections in complex archipelagos. In the optimization weights, the minimum distance and vertical area between pairs of coasts are computed using a Fast Marching Method. Additional information on velocity and transports are included as strong or weak constraints. We apply our methodology around the Hawaiian islands of Kauai/Niihau, in the Taiwan/Kuroshio region and in the Philippines Archipelago. Comparisons with other common initialization strategies, among hindcasts from these initial conditions (ICs), and with independent in situ observations show that our optimization corrects transports, satisfies boundary conditions and redirects currents. Differences between the hindcasts from these different ICs are found to grow for at least 2-3 weeks. When compared to independent in situ observations, simulations from our optimized ICs are shown to have the smallest errors.

Multidimensional MnO2 nanohair-decorated hybrid multichannel carbon nanofiber as an electrode material for high-performance supercapacitors.

PubMed

Jun, Jaemoon; Lee, Jun Seop; Shin, Dong Hoon; Kim, Sung Gun; Jang, Jyongsik

2015-10-14

One-dimensional (1D)-structured nanomaterials represent one of the most attractive candidates for energy-storage systems due to their contribution to design simplicity, fast charge-transportation network, and their allowance for more accessible ion diffusion. In particular, 1D-structured nanomaterials with a highly complex inner-pore configuration enhance functionality by taking advantage of both the hollow and 1D structures. In this study, we report a MnO2 nanohair-decorated, hybrid multichannel carbon nanofiber (Mn_MCNF) fabricated via single-nozzle co-electrospinning of two immiscible polymer solutions, followed by carbonization and redox reactions. With improved ion accessibility, the optimized Mn_MCNF sample (Mn_MCNF_60 corresponding to a reaction duration time of 60 min for optimal MnO2 nanohair growth) exhibited a high specific capacitance of 855 F g(-1) and excellent cycling performance with ∼87.3% capacitance retention over 5000 cycles.

Structural, magnetic, and electronic properties of GdTiO{sub 3} Mott insulator thin films grown by pulsed laser deposition

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

Grisolia, M. N.; Bruno, F. Y.; Sando, D.

2014-10-27

We report on the optimization process to synthesize epitaxial thin films of GdTiO{sub 3} on SrLaGaO{sub 4} substrates by pulsed laser deposition. Optimized films are free of impurity phases and are fully strained. They possess a magnetic Curie temperature T{sub C} = 31.8 K with a saturation magnetization of 4.2 μ{sub B} per formula unit at 10 K. Transport measurements reveal an insulating response, as expected. Optical spectroscopy indicates a band gap of ∼0.7 eV, comparable to the bulk value. Our work adds ferrimagnetic orthotitanates to the palette of perovskite materials for the design of emergent strongly correlated states at oxide interfaces using a versatile growthmore » technique such as pulsed laser deposition.« less

Unequal-area, fixed-shape facility layout problems using the firefly algorithm

NASA Astrophysics Data System (ADS)

Ingole, Supriya; Singh, Dinesh

2017-07-01

In manufacturing industries, the facility layout design is a very important task, as it is concerned with the overall manufacturing cost and profit of the industry. The facility layout problem (FLP) is solved by arranging the departments or facilities of known dimensions on the available floor space. The objective of this article is to implement the firefly algorithm (FA) for solving unequal-area, fixed-shape FLPs and optimizing the costs of total material handling and transportation between the facilities. The FA is a nature-inspired algorithm and can be used for combinatorial optimization problems. Benchmark problems from the previous literature are solved using the FA. To check its effectiveness, it is implemented to solve large-sized FLPs. Computational results obtained using the FA show that the algorithm is less time consuming and the total layout costs for FLPs are better than the best results achieved so far.

In-situ measurement of temperature during rapid thermite deflagrations

NASA Astrophysics Data System (ADS)

Densmore, John; Sullivan, Kyle

Thermites are composite materials that consist of a fuel (metal) and oxidizer (metal oxide), that upon reaction can release a large amount of energy (20.8 kJ/cc for Al:CuO). The time scale for a thermite to release energy (ms) is much longer than a typical detonation (us). In-situ temperature and/or thermal flux measurements can provide fundamental insight into the reaction mechanisms. This information can inform the design and optimization of energy transport during a deflagration, to optimize the energy release rate. To measure the temperature we use a burn tube apparatus and various pyrometry techniques to measure the spatial temperature field as a reaction proceeds towards completion. We show that system properties can be adjusted to achieve custom thermal properties. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

Investigating enhanced thermoelectric performance of graphene-based nano-structures.

PubMed

Hossain, Md Sharafat; Huynh, Duc Hau; Jiang, Liming; Rahman, Sharmin; Nguyen, Phuong Duc; Al-Dirini, Feras; Hossain, Faruque; Bahk, Je-Hyeong; Skafidas, Efstratios

2018-03-08

Recently, it has been demonstrated that graphene nano-ribbons (GNRs) exhibit superior thermoelectric performance compared to graphene sheets. However, the underlying mechanism behind this enhancement has not been systematically investigated and significant opportunity remains for further enhancement of the thermoelectric performance of GNRs by optimizing their charge carrier concentration. In this work, we modulate the carrier concentration of graphene-based nano-structures using a gate voltage and investigate the resulting carrier-concentration-dependent thermoelectric parameters using the Boltzmann transport equations. We investigate the effect of energy dependent scattering time and the role of substrate-induced charge carrier fluctuation in optimizing the Seebeck coefficient and power factor. Our approach predicts the scattering mechanism and the extent of the charge carrier fluctuation in different samples and explains the enhancement of thermoelectric performance of GNR samples. Subsequently, we propose a route towards the enhancement of thermoelectric performance of graphene-based devices which can also be applied to other two-dimensional materials.

Optimal Observations for Variational Data Assimilation

NASA Technical Reports Server (NTRS)

Koehl, Armin; Stammer, Detlef

2003-01-01

An important aspect of Ocean state estimation is the design of an observing system that allows the efficient study of climate aspects in the ocean. A solution of the design problem is presented here in terms of optimal observations that emerge as nondimensionalized singular vectors of the modified data resolution matrix. The actual computation is feasible only for scalar quantities in the limit of large observational errors. In the framework of a lo resolution North Atlantic primitive equation model it is demonstrated that such optimal observations when applied to determining the strength of the volume and heat transport across the Greenland-Scotland ridge, perform significantly better than traditional section data. On seasonal to inter-annual time-scales optimal observations are located primarily along the continental shelf and information about heat-transport, wind stress and stratification is being communicated via boundary waves and advective processes. On time-scales of about a month, sea surface height observations appear to be more efficient in reconstructing the cross-ridge heat transport than hydrographic observations. Optimal observations also provide a tool for understanding how the ocean state is effected by anomalies of integral quantities such as meridional heat transport.

The Interface of Safety and Security in Transport: A Regional Perspective

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

Welch, Tim; Duhamel, David A; Nandakumar, A. N.

Security of nuclear and other radioactive material in transport continues to be a challenge for States that are working on strengthening their nuclear security regime. One reason for this is that State regulatory agencies and other organizations lack the resources and trained personnel to dedicate to this field. For over 50 years safety has been a major focus in the use, storage and transport of radioactive material. Only recently, since the late 1990s, has dedicated focus been given to the field of security. One way to assist States to advance nuclear security is to reach out to safety workers (regulators,more » inspectors, and safety compliance personnel) and showcase the need to better integrate safety and security practices. A recent IAEA regional workshop in Bangkok, Thailand (June 2015) yielded profound results when subject matter experts lectured on both the safety and the security of radioactive material in transport. These experts presented and discussed experiences and best practices for: 1) developing and implementing safety requirements and security recommendations for radioactive material in transport; 2) national and international cooperation; and 3) preventing shipment delays/denials of radioactive material. The workshop participants, who were predominantly from safety organizations, shared that they received the following from this event: 1. A clear understanding of the objectives of the IAEA safety requirements and security recommendations for radioactive material in transport. 2. A general understanding of and appreciation for the similarities and differences between safety requirements and security recommendations for radioactive material in transport. 3. A greater appreciation of the interface between transport safety and security and potential impacts of this interface on the efforts to strengthen the compliance assurance regime for the safe transport of radioactive material. 4. A general understanding of assessing the transport security scenarios and developing transport security plans. Many participants also reported their appreciation of the workshop exercises that specifically focused on practical aspects of safety and security of transport of radioactive material. These workshop outcomes highlight the important role professionals can offer when they receive additional safety training and education for radioactive material in transport. Moreover, these professionals can help to increase capacity in countries with developing nuclear security regimes. This paper explores workshop outcomes and transportation regulations and guidelines for radioactive material.« less

76 FR 37283 - Hazardous Materials: Revision to the List of Hazardous Substances and Reportable Quantities

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-27

... DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration 49 CFR Part... under the Federal hazardous materials transportation law (49 U.S.C. 5101-5128). PHMSA carries out the rulemaking responsibilities of the Secretary of Transportation under the Federal hazardous materials...

76 FR 65779 - Office of Hazardous Materials Safety; Notice of Applications for Modification of Special Permit

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration Office of... processing of, special permits from the Department of Transportation's Hazardous Material Regulations (49 CFR... special permit is published in accordance with Part 107 of the Federal hazardous materials transportation...

49 CFR 178.33a-5 - Material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Material. 178.33a-5 Section 178.33a-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33a-5 Material. (a) Uniform quality steel plate such as black plate, electrotin...

49 CFR 179.201-4 - Material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Material. 179.201-4 Section 179.201-4 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY...-Pressure Tank Car Tanks (Classes DOT-111AW and 115AW) § 179.201-4 Material. All fittings, tubes, and...

49 CFR 178.33b-5 - Material.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 3 2011-10-01 2011-10-01 false Material. 178.33b-5 Section 178.33b-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33b-5 Material. (a) The receptacles must be constructed of polyethylene...

49 CFR 178.33a-5 - Material.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Material. 178.33a-5 Section 178.33a-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33a-5 Material. (a) Uniform quality steel plate such as black plate, electrotin...

49 CFR 178.33b-5 - Material.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Material. 178.33b-5 Section 178.33b-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33b-5 Material. (a) The receptacles must be constructed of polyethylene...

49 CFR 178.33b-5 - Material.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Material. 178.33b-5 Section 178.33b-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33b-5 Material. (a) The receptacles must be constructed of polyethylene...

49 CFR 178.33a-5 - Material.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 3 2014-10-01 2014-10-01 false Material. 178.33a-5 Section 178.33a-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33a-5 Material. (a) Uniform quality steel plate such as black plate, electrotin...

49 CFR 178.33a-5 - Material.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 3 2013-10-01 2013-10-01 false Material. 178.33a-5 Section 178.33a-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33a-5 Material. (a) Uniform quality steel plate such as black plate, electrotin...

49 CFR 178.33b-5 - Material.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 3 2012-10-01 2012-10-01 false Material. 178.33b-5 Section 178.33b-5 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Containers, and Linings § 178.33b-5 Material. (a) The receptacles must be constructed of polyethylene...

Micro-porous layer stochastic reconstruction and transport parameter determination

NASA Astrophysics Data System (ADS)

El Hannach, Mohamed; Singh, Randhir; Djilali, Ned; Kjeang, Erik

2015-05-01

The Micro-Porous Layer (MPL) is a porous, thin layer commonly used in fuel cells at the interfaces between the catalyst layers and gas diffusion media. It is generally made from spherical carbon nanoparticles and PTFE acting as hydrophobic agent. The scale and brittle nature of the MPL structure makes it challenging to study experimentally. In the present work, a 3D stochastic model is developed to virtually reconstruct the MPL structure. The carbon nanoparticle and PTFE phases are fully distinguished by the algorithm. The model is shown to capture the actual structural morphology of the MPL and is validated by comparing the results to available experimental data. The model shows a good capability in generating a realistic MPL successfully using a set of parameters introduced to capture specific morphological features of the MPL. A numerical model that resolves diffusive transport at the pore scale is used to compute the effective transport properties of the reconstructed MPLs. A parametric study is conducted to illustrate the capability of the model as an MPL design tool that can be used to guide and optimize the functionality of the material.

Electron and phonon transport in Co-doped FeV0.6Nb0.4Sb half-Heusler thermoelectric materials

NASA Astrophysics Data System (ADS)

Fu, Chenguang; Liu, Yintu; Xie, Hanhui; Liu, Xiaohua; Zhao, Xinbing; Jeffrey Snyder, G.; Xie, Jian; Zhu, Tiejun

2013-10-01

The electron and phonon transport characteristics of n-type Fe1-xCoxV0.6Nb0.4Sb half-Heusler thermoelectric compounds is analyzed. The acoustic phonon scattering is dominant in the carrier transport. The deformation potential of Edef = 14.1 eV and the density of state effective mass m* ≈ 2.0 me are derived under a single parabolic band assumption. The band gap is calculated to be ˜0.3 eV. Electron and phonon mean free paths are estimated based on the low and high temperature measurements. The electron mean free path is higher than the phonon one above room temperature, which is consistent with the experimental result that the electron mobility decreases more than the lattice thermal conductivity by grain refinement to enhance boundary scattering. A maximum ZT value of ˜0.33 is obtained at 650 K for x = 0.015, an increase by ˜60% compared with FeVSb. The optimal doping level is found to be ˜3.0 × 1020 cm-3 at 600 K.

Development of Advanced Methods of Structural and Trajectory Analysis for Transport Aircraft

NASA Technical Reports Server (NTRS)

Ardema, Mark D.

1996-01-01

In this report the author describes: (1) development of advanced methods of structural weight estimation, and (2) development of advanced methods of flight path optimization. A method of estimating the load-bearing fuselage weight and wing weight of transport aircraft based on fundamental structural principles has been developed. This method of weight estimation represents a compromise between the rapid assessment of component weight using empirical methods based on actual weights of existing aircraft and detailed, but time-consuming, analysis using the finite element method. The method was applied to eight existing subsonic transports for validation and correlation. Integration of the resulting computer program, PDCYL, has been made into the weights-calculating module of the AirCraft SYNThesis (ACSYNT) computer program. ACSYNT bas traditionally used only empirical weight estimation methods; PDCYL adds to ACSYNT a rapid, accurate means of assessing the fuselage and wing weights of unconventional aircraft. PDCYL also allows flexibility in the choice of structural concept, as well as a direct means of determining the impact of advanced materials on structural weight.

Highly Oriented Atomically Thin Ambipolar MoSe2 Grown by Molecular Beam Epitaxy

PubMed Central

2017-01-01

Transition metal dichalcogenides (TMDCs), together with other two-dimensional (2D) materials, have attracted great interest due to the unique optical and electrical properties of atomically thin layers. In order to fulfill their potential, developing large-area growth and understanding the properties of TMDCs have become crucial. Here, we have used molecular beam epitaxy (MBE) to grow atomically thin MoSe2 on GaAs(111)B. No intermediate compounds were detected at the interface of as-grown films. Careful optimization of the growth temperature can result in the growth of highly aligned films with only two possible crystalline orientations due to broken inversion symmetry. As-grown films can be transferred onto insulating substrates, allowing their optical and electrical properties to be probed. By using polymer electrolyte gating, we have achieved ambipolar transport in MBE-grown MoSe2. The temperature-dependent transport characteristics can be explained by the 2D variable-range hopping (2D-VRH) model, indicating that the transport is strongly limited by the disorder in the film. PMID:28530829

Tomographic Reconstruction from a Few Views: A Multi-Marginal Optimal Transport Approach

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

Abraham, I., E-mail: isabelle.abraham@cea.fr; Abraham, R., E-mail: romain.abraham@univ-orleans.fr; Bergounioux, M., E-mail: maitine.bergounioux@univ-orleans.fr

2017-02-15

In this article, we focus on tomographic reconstruction. The problem is to determine the shape of the interior interface using a tomographic approach while very few X-ray radiographs are performed. We use a multi-marginal optimal transport approach. Preliminary numerical results are presented.

Synthesis and thermoelectric properties of Rashba semiconductor BiTeBr with intensive texture.

PubMed

Xin, Jia-Zhan; Fu, Chen-Guang; Shi, Wu-Jun; Li, Guo-Wei; Auffermann, Gudrun; Qi, Yan-Peng; Zhu, Tie-Jun; Zhao, Xin-Bing; Felser, Claudia

2018-01-01

Bismuth tellurohalides with Rashba-type spin splitting exhibit unique Fermi surface topology and are developed as promising thermoelectric materials. However, BiTeBr, which belongs to this class of materials, is rarely investigated in terms of the thermoelectric transport properties. In the study, polycrystalline bulk BiTeBr with intensive texture was synthesized via spark plasma sintering (SPS). Additionally, its thermoelectric properties above room temperature were investigated along both the in-plane and out-plane directions, and they exhibit strong anisotropy. Low sound velocity along two directions is found and contributes to its low lattice thermal conductivity. Polycrystalline BiTeBr exhibits relatively good thermoelectric performance along the in-plane direction, with a maximum dimensionless figure of merit (ZT) of 0.35 at 560 K. Further enhancements of ZT are expected by utilizing systematic optimization strategies.

49 CFR 176.172 - Structural serviceability of freight containers and vehicles carrying Class 1 (explosive...

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Structural serviceability of freight containers and vehicles carrying Class 1 (explosive) materials on ships. 176.172 Section 176.172 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS...

49 CFR 173.30 - Loading and unloading of transport vehicles.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Loading and unloading of transport vehicles. 173.30 Section 173.30 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND...

49 CFR 173.30 - Loading and unloading of transport vehicles.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Loading and unloading of transport vehicles. 173.30 Section 173.30 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND...

A New Model for Optimal Mechanical and Thermal Performance of Cement-Based Partition Wall

PubMed Central

Huang, Shiping; Hu, Mengyu; Cui, Nannan; Wang, Weifeng

2018-01-01

The prefabricated cement-based partition wall has been widely used in assembled buildings because of its high manufacturing efficiency, high-quality surface, and simple and convenient construction process. In this paper, a general porous partition wall that is made from cement-based materials was proposed to meet the optimal mechanical and thermal performance during transportation, construction and its service life. The porosity of the proposed partition wall is formed by elliptic-cylinder-type cavities. The finite element method was used to investigate the mechanical and thermal behaviour, which shows that the proposed model has distinct advantages over the current partition wall that is used in the building industry. It is found that, by controlling the eccentricity of the elliptic-cylinder cavities, the proposed wall stiffness can be adjusted to respond to the imposed loads and to improve the thermal performance, which can be used for the optimum design. Finally, design guidance is provided to obtain the optimal mechanical and thermal performance. The proposed model could be used as a promising candidate for partition wall in the building industry. PMID:29673176

The watershed-scale optimized and rearranged landscape design (WORLD) model and local biomass processing depots for sustainable biofuel production: Integrated life cycle assessments

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

Eranki, Pragnya L.; Manowitz, David H.; Bals, Bryan D.

An array of feedstock is being evaluated as potential raw material for cellulosic biofuel production. Thorough assessments are required in regional landscape settings before these feedstocks can be cultivated and sustainable management practices can be implemented. On the processing side, a potential solution to the logistical challenges of large biorefi neries is provided by a network of distributed processing facilities called local biomass processing depots. A large-scale cellulosic ethanol industry is likely to emerge soon in the United States. We have the opportunity to influence the sustainability of this emerging industry. The watershed-scale optimized and rearranged landscape design (WORLD) modelmore » estimates land allocations for different cellulosic feedstocks at biorefinery scale without displacing current animal nutrition requirements. This model also incorporates a network of the aforementioned depots. An integrated life cycle assessment is then conducted over the unified system of optimized feedstock production, processing, and associated transport operations to evaluate net energy yields (NEYs) and environmental impacts.« less

A New Model for Optimal Mechanical and Thermal Performance of Cement-Based Partition Wall.

PubMed

Huang, Shiping; Hu, Mengyu; Huang, Yonghui; Cui, Nannan; Wang, Weifeng

2018-04-17

The prefabricated cement-based partition wall has been widely used in assembled buildings because of its high manufacturing efficiency, high-quality surface, and simple and convenient construction process. In this paper, a general porous partition wall that is made from cement-based materials was proposed to meet the optimal mechanical and thermal performance during transportation, construction and its service life. The porosity of the proposed partition wall is formed by elliptic-cylinder-type cavities. The finite element method was used to investigate the mechanical and thermal behaviour, which shows that the proposed model has distinct advantages over the current partition wall that is used in the building industry. It is found that, by controlling the eccentricity of the elliptic-cylinder cavities, the proposed wall stiffness can be adjusted to respond to the imposed loads and to improve the thermal performance, which can be used for the optimum design. Finally, design guidance is provided to obtain the optimal mechanical and thermal performance. The proposed model could be used as a promising candidate for partition wall in the building industry.

Targeting blood–brain barrier changes during inflammatory pain: an opportunity for optimizing CNS drug delivery

PubMed Central

Ronaldson, Patrick T; Davis, Thomas P

2012-01-01

The blood–brain barrier (BBB) is the most significant obstacle to effective CNS drug delivery. It possesses structural and biochemical features (i.e., tight-junction protein complexes and, influx and efflux transporters) that restrict xenobiotic permeation. Pathophysiological stressors (i.e., peripheral inflammatory pain) can alter BBB tight junctions and transporters, which leads to drug-permeation changes. This is especially critical for opioids, which require precise CNS concentrations to be safe and effective analgesics. Recent studies have identified molecular targets (i.e., endogenous transporters and intracellular signaling systems) that can be exploited for optimization of CNS drug delivery. This article summarizes current knowledge in this area and emphasizes those targets that present the greatest opportunity for controlling drug permeation and/or drug transport across the BBB in an effort to achieve optimal CNS opioid delivery. PMID:22468221

Mechanisms of Carrier Transport Induced by a Microswimmer Bath

DOE PAGES

Kaiser, Andreas; Sokolov, Andrey; Aranson, Igor S.; ...

2014-10-20

Recently, it was found that a wedgelike microparticle (referred to as ”carrier”) which is only allowed to translate but not to rotate exhibits a directed translational motion along the wedge cusp if it is exposed to a bath of microswimmers. Here we model this effect in detail by resolving the microswimmers explicitly using interaction models with different degrees of mutual alignment. Using computer simulations we study the impact of these interactions on the transport efficiency of V-shaped carrier. We show that the transport mechanisms itself strongly depends on the degree of alignment embodied in the modelling of the individual swimmermore » dynamics. For weak alignment, optimal carrier transport occurs in the turbulent microswimmer state and is induced by swirl depletion inside the carrier. For strong aligning interactions, optimal transport occurs already in the dilute regime and is mediated by a polar cloud of swimmers in the carrier wake pushing the wedge-particle forward. Finally, we also demonstrate that the optimal shape of the carrier leading to maximal transport speed depends on the kind of interaction model used.« less

3D nonrigid registration via optimal mass transport on the GPU.

PubMed

Ur Rehman, Tauseef; Haber, Eldad; Pryor, Gallagher; Melonakos, John; Tannenbaum, Allen

2009-12-01

In this paper, we present a new computationally efficient numerical scheme for the minimizing flow approach for optimal mass transport (OMT) with applications to non-rigid 3D image registration. The approach utilizes all of the gray-scale data in both images, and the optimal mapping from image A to image B is the inverse of the optimal mapping from B to A. Further, no landmarks need to be specified, and the minimizer of the distance functional involved is unique. Our implementation also employs multigrid, and parallel methodologies on a consumer graphics processing unit (GPU) for fast computation. Although computing the optimal map has been shown to be computationally expensive in the past, we show that our approach is orders of magnitude faster then previous work and is capable of finding transport maps with optimality measures (mean curl) previously unattainable by other works (which directly influences the accuracy of registration). We give results where the algorithm was used to compute non-rigid registrations of 3D synthetic data as well as intra-patient pre-operative and post-operative 3D brain MRI datasets.

49 CFR 385.415 - What operational requirements apply to the transportation of a hazardous material for which a...

Code of Federal Regulations, 2011 CFR

2011-10-01

... permitted material is in transportation including storage incidental to transportation. Answering machines... Records Administration (NARA). For information on the availability of this material at NARA, call (202...

49 CFR 192.53 - General.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY TRANSPORTATION OF NATURAL AND OTHER GAS BY PIPELINE: MINIMUM FEDERAL SAFETY STANDARDS Materials § 192.53 General. Materials for pipe and...

An ab initio electronic transport database for inorganic materials

DOE PAGES

Ricci, Francesco; Chen, Wei; Aydemir, Umut; ...

2017-07-04

Electronic transport in materials is governed by a series of tensorial properties such as conductivity, Seebeck coefficient, and effective mass. These quantities are paramount to the understanding of materials in many fields from thermoelectrics to electronics and photovoltaics. Transport properties can be calculated from a material’s band structure using the Boltzmann transport theory framework. We present here the largest computational database of electronic transport properties based on a large set of 48,000 materials originating from the Materials Project database. Our results were obtained through the interpolation approach developed in the BoltzTraP software, assuming a constant relaxation time. We present themore » workflow to generate the data, the data validation procedure, and the database structure. In conclusion, our aim is to target the large community of scientists developing materials selection strategies and performing studies involving transport properties.« less

An ab initio electronic transport database for inorganic materials

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

Ricci, Francesco; Chen, Wei; Aydemir, Umut

Electronic transport in materials is governed by a series of tensorial properties such as conductivity, Seebeck coefficient, and effective mass. These quantities are paramount to the understanding of materials in many fields from thermoelectrics to electronics and photovoltaics. Transport properties can be calculated from a material’s band structure using the Boltzmann transport theory framework. We present here the largest computational database of electronic transport properties based on a large set of 48,000 materials originating from the Materials Project database. Our results were obtained through the interpolation approach developed in the BoltzTraP software, assuming a constant relaxation time. We present themore » workflow to generate the data, the data validation procedure, and the database structure. In conclusion, our aim is to target the large community of scientists developing materials selection strategies and performing studies involving transport properties.« less

Flexible Composite-Material Pressure Vessel

NASA Technical Reports Server (NTRS)

Brown, Glen; Haggard, Roy; Harris, Paul A.

2003-01-01

A proposed lightweight pressure vessel would be made of a composite of high-tenacity continuous fibers and a flexible matrix material. The flexibility of this pressure vessel would render it (1) compactly stowable for transport and (2) more able to withstand impacts, relative to lightweight pressure vessels made of rigid composite materials. The vessel would be designed as a structural shell wherein the fibers would be predominantly bias-oriented, the orientations being optimized to make the fibers bear the tensile loads in the structure. Such efficient use of tension-bearing fibers would minimize or eliminate the need for stitching and fill (weft) fibers for strength. The vessel could be fabricated by techniques adapted from filament winding of prior composite-material vessels, perhaps in conjunction with the use of dry film adhesives. In addition to the high-bias main-body substructure described above, the vessel would include a low-bias end substructure to complete coverage and react peak loads. Axial elements would be overlaid to contain damage and to control fiber orientation around side openings. Fiber ring structures would be used as interfaces for connection to ancillary hardware.

Evidence for Itinerant Carriers in an Anisotropic Narrow-Gap Semiconductor by Angle-Resolved Photoemission Spectroscopy.

PubMed

Ju, Sailong; Bai, Wei; Wu, Liming; Lin, Hua; Xiao, Chong; Cui, Shengtao; Li, Zhou; Kong, Shuai; Liu, Yi; Liu, Dayong; Zhang, Guobin; Sun, Zhe; Xie, Yi

2018-01-01

The ability to accurately determine the electronic structure of solids has become a key prerequisite for modern functional materials. For example, the precise determination of the electronic structure helps to balance the three thermoelectric parameters, which is the biggest challenge to design high-performance thermoelectric materials. Herein, by high-resolution, angle-resolved photoemission spectroscopy (ARPES), the itinerant carriers in CsBi 4 Te 6 (CBT) are revealed for the first time. CBT is a typical anisotropic, narrow-gap semiconductor used as a practical candidate for low-temperature thermoelectric applications, and p-doped CBT series show superconductivity at relatively low carrier concentrations. The ARPES results show a significantly larger bandwidth near the Fermi surface than calculations, which means the carriers transport anisotropically and itinerantly in CBT. It is reasonable to believe that these newly discovered features of carriers in narrow-gap semiconductors are promising for designing optimal thermoelectric materials and superconductors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Printed assemblies of GaAs photoelectrodes with decoupled optical and reactive interfaces for unassisted solar water splitting

DOE PAGES

Kang, Dongseok; Young, James L.; Lim, Haneol; ...

2017-03-27

Despite their excellent photophysical properties and record-high solar-to-hydrogen conversion efficiency, the high cost and limited stability of III-V compound semiconductors prohibit their practical application in solar-driven photoelectrochemical water splitting. Here in this paper we present a strategy for III-V photocatalysis that can circumvent these difficulties via printed assemblies of epitaxially grown compound semiconductors. A thin film stack of GaAs-based epitaxial materials is released from the growth wafer and printed onto a non-native transparent substrate to form an integrated photocatalytic electrode for solar hydrogen generation. The heterogeneously integrated electrode configuration together with specialized epitaxial design serve to decouple the material interfacesmore » for illumination and electrocatalysis. Subsequently, this allows independent control and optimization of light absorption, carrier transport, charge transfer, and material stability. Using this approach, we construct a series-connected wireless tandem system of GaAs photoelectrodes and demonstrate 13.1% solar-to-hydrogen conversion efficiency of unassisted-mode water splitting.« less

Computational Modeling in Structural Materials Processing

NASA Technical Reports Server (NTRS)

Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

1997-01-01

High temperature materials such as silicon carbide, a variety of nitrides, and ceramic matrix composites find use in aerospace, automotive, machine tool industries and in high speed civil transport applications. Chemical vapor deposition (CVD) is widely used in processing such structural materials. Variations of CVD include deposition on substrates, coating of fibers, inside cavities and on complex objects, and infiltration within preforms called chemical vapor infiltration (CVI). Our current knowledge of the process mechanisms, ability to optimize processes, and scale-up for large scale manufacturing is limited. In this regard, computational modeling of the processes is valuable since a validated model can be used as a design tool. The effort is similar to traditional chemically reacting flow modeling with emphasis on multicomponent diffusion, thermal diffusion, large sets of homogeneous reactions, and surface chemistry. In the case of CVI, models for pore infiltration are needed. In the present talk, examples of SiC nitride, and Boron deposition from the author's past work will be used to illustrate the utility of computational process modeling.