Thermoelectric Properties of the Perovskite-Type Oxide SrTi1-xNbxO3 Synthesized by Solid-State Reaction Method

NASA Astrophysics Data System (ADS)

Khan, Tamal Tahsin; Ur, Soon-Chul

2018-05-01

The perovskite-type oxide materials SrTi1-xNbxO3 (X = .02, 0.03, 0.04, 0.05 and 0.06) were synthesized by the conventional solid-state reaction method and the thermoelectric properties in terms of Nb doping at the B-site in the oxides were investigated in this study. The formation of single phase cubic perovskite structure was confirmed by the powder X-ray diffraction analysis. Negative conduction is shown in this materials system. The absolute value of Seebeck coefficient increased with increasing temperature over the measured temperature. The electrical conductivity decreased monotonically with increasing temperature, showing degenerating conduction behavior. The thermal conductivity, k, generally decreased with increasing temperature. The power factor increased with increasing Nb-doping level up to 5.0 mol% and hence the dimensionless figure of merit ZT, increased up to 5.0 mol%. The maximum ZT value was observed for SrTi0.95Nb0.05O3 at 873 K.

Estimating Energy Conversion Efficiency of Thermoelectric Materials: Constant Property Versus Average Property Models

NASA Astrophysics Data System (ADS)

Armstrong, Hannah; Boese, Matthew; Carmichael, Cody; Dimich, Hannah; Seay, Dylan; Sheppard, Nathan; Beekman, Matt

2017-01-01

Maximum thermoelectric energy conversion efficiencies are calculated using the conventional "constant property" model and the recently proposed "cumulative/average property" model (Kim et al. in Proc Natl Acad Sci USA 112:8205, 2015) for 18 high-performance thermoelectric materials. We find that the constant property model generally predicts higher energy conversion efficiency for nearly all materials and temperature differences studied. Although significant deviations are observed in some cases, on average the constant property model predicts an efficiency that is a factor of 1.16 larger than that predicted by the average property model, with even lower deviations for temperature differences typical of energy harvesting applications. Based on our analysis, we conclude that the conventional dimensionless figure of merit ZT obtained from the constant property model, while not applicable for some materials with strongly temperature-dependent thermoelectric properties, remains a simple yet useful metric for initial evaluation and/or comparison of thermoelectric materials, provided the ZT at the average temperature of projected operation, not the peak ZT, is used.

Dimensionless Analysis Applied to Bacterial Chemotaxis towards NAPL Contaminants

NASA Astrophysics Data System (ADS)

Wang, X.; GAO, B.; Zhong, W.; Kihaule, K. S.; Ford, R.

2017-12-01

The use of chemotactic bacteria in bioremediation may improve the efficiency and decrease the cost of restoration, which means it has the potential to address environmental problems caused by oil spills. However, most previous studies were focused at the laboratory-scale and there lacks a formalism that can use these laboratory-scale results as input to evaluate the relative importance of chemotaxis at the field scale. In this study, a dimensionless equation is formulated to solve this problem. First, the main influential factors were extracted based on previous researches in environmental bioremediation and then five sets of dimensionless numbers were obtained according to Buckingham theory. After collecting basic parameter values and supplementary calculations to determine the concentration gradient of the chemoattractant, all dimensionless numbers were calculated and categorized into two types, those that were sensitive to chemotaxis or those to groundwater velocity. The bacteria ratio (BR), defined as the ratio of maximum bacteria concentration to its original value, was correlated with a combination of dimensionless numbers to yield, BR=cP1-0.085P20.329P30.1P4-0.098. For a bacterial ratio greater than one, the bioremediation strategy based on chemotaxis is expected to be effective, and chemotactic bacteria are expected to accumulate around NAPL contaminant sources efficiently.

Optimization of self-acting step thrust bearings for load capacity and stiffness.

NASA Technical Reports Server (NTRS)

Hamrock, B. J.

1972-01-01

Linearized analysis of a finite-width rectangular step thrust bearing. Dimensionless load capacity and stiffness are expressed in terms of a Fourier cosine series. The dimensionless load capacity and stiffness were found to be a function of the dimensionless bearing number, the pad length-to-width ratio, the film thickness ratio, the step location parameter, and the feed groove parameter. The equations obtained in the analysis were verified. The assumptions imposed were substantiated by comparing the results with an existing exact solution for the infinite width bearing. A digital computer program was developed which determines optimal bearing configuration for maximum load capacity or stiffness. Simple design curves are presented. Results are shown for both compressible and incompressible lubrication. Through a parameter transformation the results are directly usable in designing optimal step sector thrust bearings.

Flow Transition in Gas Turbine Airfoil Boundary Layers: Fundamentals and Empiricisms.

DTIC Science & Technology

1985-09-01

another perspective in Figure 18, which is plotted for three selected dimensionless wavenumbers. Kahawita and Meroney [95] utilized a linearized...the results indicate stabilization for 0. less than about 0.3 (long wavelengths) and destabilization for higher values of a0. Kahawita and Meroney...are fairly large and buoyancy effects are negligible. However, if the boundary layer is unstably stratified, the results of Kahawita and Meroney [95

Enhancing figure-of-merit of n-type Bi2Te3-xSex

NASA Astrophysics Data System (ADS)

Yan, Xiao; Yang, Jian; Ma, Yi; Poudel, Bed; Lan, Yucheng; Wang, Dezhi; Ren, Zhifeng; Hao, Qing; Chen, Gang

2008-03-01

Themoelectric materials with high dimensionless figure-of-merit (ZT) are greatly demanded in energy industry, among which bismuth telluride (Bi2Te3) exhibits decent ZT around room temperature. However, thermal conductivity of Bi2Te3 is still high which limits its wider use for low temperature cooling devices. Here we investigate nanostructured bulk n-type Bi2Te3-xSex by reducing the thermal conductivity via increased phonon scattering of the significantly increased grain boundaries due to nano size grains. We first make alloyed nanopowders by mechanical alloying a mixture of elements with the right ratio and then 100% nanostructured samples by hot press.

Thermoelectric and transport properties of sintered n-type K{sub 8}Ba{sub 16}Ga{sub 40}Sn{sub 96} with type-II clathrate structure

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

Koda, Shota; Kishimoto, Kengo, E-mail: kkishi@yamaguchi-u.ac.jp; Asada, Hironori

This clathrate had a maximum dimensionless figure-of-merit, ZT, of 0.93 at 637 K, which was slightly higher than that of 0.83 for the sintered type-VIII clathrate Ba{sub 8}Ga{sub 16}Sn{sub 30}. We investigated the high-temperature thermoelectric properties, transport properties, electronic structures, and thermal stabilities of the clathrates. The type-II clathrate was found to be superior to the type-VIII clathrate as a thermoelectric material; it had a high thermal stability and melting point, 859 K, high mobility, 141 cm{sup 2}V{sup −1}s{sup −1} at 300 K, because of its low inertial mass, and low high-temperature lattice thermal conductivity, approximately 4 mW cm{sup −1}K{sup −1}, resulting frommore » a larger unit cell and weaker bipolar thermal conduction. We discuss these properties in terms of the electronic structure and the differences between the two types of clathrate.« less

Evaluation of Ultra High Pressure (UHP) Firefighting in a Room-and-Contents Fire

DTIC Science & Technology

2017-03-15

Burn Room and Hangar Temperature Prior to Ignition ............................................... 18 Figure 12. Effect of Temperature on Normalized...Figure 20. Maximum Average Temperature and Heat Flux ......................................................... 22 Figure 21. Effect of Maximum Average...Aspirated Ceiling Temperature .................................... 23 Figure 22. Effect of Maximum Average Floor Heat Flux on Extinguishment Quantity

Design Model for the Heat Transfer in a Short Straight Tube Boiler.

DTIC Science & Technology

1981-06-01

Equilibrium Quality XT - True Quality XTT - Martinelli Parameter Dimensionless Groups Nu - Nusselt Number Pr - Prandtl Number Re - Reynolds Number...fill a cylinder in which a piston was mounted. When the steam was suddenly condensed by a spray of water, a partial vacuum was created, and the piston...BOILER - 1725 SFET YAL OOS _ FIGURE 6: JAMES WATTS WAGON-TYPE BOILER - 1785 25 water-inlet, a condensate return, a steam outlet, a gauge glass for

The magnetic, electrical transport and thermal transport properties of Fe-based antipervoskite compounds ZnCxFe3

NASA Astrophysics Data System (ADS)

Lin, S.; Wang, B. S.; Lin, J. C.; Huang, Y. N.; Hu, X. B.; Lu, W. J.; Zhao, B. C.; Tong, P.; Song, W. H.; Sun, Y. P.

2011-10-01

The effects of carbon concentration on the crystal structure, magnetic, and electrical/thermal transport properties of ZnCxFe3 (1.0 ≤ x ≤ 1.5) have been investigated systematically. Both the Curie temperature and the saturated magnetization decrease firstly and then reach saturation with increasing x. The investigations of heat capacity and resistivity indicate that ZnC1.2Fe3 displays a strongly correlated Fermi liquid behavior considering its Kadowaki-Woods ratio (˜0.64 a0). Around the ferromagnetic-paramagnetic phase transition (˜358 K), a reversible room-temperature magnetocaloric effect is observed. The relative cooling power (RCP) is ˜164 J/kg (˜385 J/kg) with the magnetic field change ΔH = 20 kOe (45 kOe). Considering the considerable large RCP, inexpensive and innoxious raw materials, ZnC1.2Fe3 is suggested to be a promising candidate for room-temperature magnetic refrigeration. Furthermore, the studies of thermal transport properties indicate that ZnC1.2Fe3 can also be a potential thermoelectric material with the dimensionless figure of merit (ZT = α2T/ρk) reaching its maximum of 0.0112 around 170 K.

Thermoelectric Properties of n-type SnSe Single Crystal

NASA Astrophysics Data System (ADS)

Nguyen, Phuong; Duong, Anh Tuan; Rhim, S. H.; Nguyen, Van Quang; Duong, Van Thiet; Shin, Yooleemi; Cho, Sunglae; Kwon, Suyong; Song, Jae Yong; Park, Hyun Min

Although thermoelectric materials are well known for their reliability and have been used for many years, even in the field of space engineering, their performance is quite small due to low energy conversion efficiency. Dimensionless figure of merit, ZT = S2. σ.T.κ-1 (where S, σ, T, κ are Seebeck coefficient, electrical conductivity, absolute temperature and thermal conductivity, respectively) is conveniently used to evaluate the conversion efficiency of a thermoelectric materials. Recently, the highest value of ZT to date has been reported for single crystal SnSe, ZT = 2.6 along the b axis of unit cell at 923 K. This temperature is rather high and the range of temperature for high reported ZT is quite narrow. Here we report an attempt to modify the thermoelectric properties of SnSe by using group V and VII as n-type dopant. A negative value of Seebeck coefficient was observed and the power factor reached a peak of 10 μW.K-2.cm-1 at around 600 K. The maximum n-type ZT was 0.57 at 650 K. We will discuss on dopant dependent thermoelectric properties of n-type SnSe single crystals.

Collateral Damage to Satellites from an EMP Attack

DTIC Science & Technology

2010-08-01

peak dose is computed in an infinite half plane of silicon. The resulting in- plane stresses in silicon are shown in Figure VI.23. In- plane refers to...achieved by the SLAR coating 81 Figure VIII.6. Ratio of the peak in- plane compressive stress to the maximum compressive stress for the SLAR coating...82 Figure VIII.7. Maximum in- plane compressive stress in a SLAR coating on DMSP/NOAA subjected to the threat events 83 Figure VIII.8. Maximum in

High-Throughput Screening of Sulfide Thermoelectric Materials Using Electron Transport Calculations with OpenMX and BoltzTraP

NASA Astrophysics Data System (ADS)

Miyata, Masanobu; Ozaki, Taisuke; Takeuchi, Tsunehiro; Nishino, Shunsuke; Inukai, Manabu; Koyano, Mikio

2018-06-01

The electron transport properties of 809 sulfides have been investigated using density functional theory (DFT) calculations in the relaxation time approximation, and a material design rule established for high-performance sulfide thermoelectric (TE) materials. Benchmark electron transport calculations were performed for Cu12Sb4S13 and Cu26V2Ge6S32, revealing that the ratio of the scattering probability of electrons and phonons ( κ lat τ el -1 ) was constant at about 2 × 1014 W K-1 m-1 s-1. The calculated thermopower S dependence of the theoretical dimensionless figure of merit ZT DFT of the 809 sulfides showed a maximum at 140 μV K-1 to 170 μV K-1. Under the assumption of constant κ lat τ el -1 of 2 × 1014 W K-1 m-1 s-1 and constant group velocity v of electrons, a slope of the density of states of 8.6 states eV-2 to 10 states eV-2 is suitable for high- ZT sulfide TE materials. The Lorenz number L dependence of ZT DFT for the 809 sulfides showed a maximum at L of approximately 2.45 × 10-8 V2 K-2. This result demonstrates that the potential of high- ZT sulfide materials is highest when the electron thermal conductivity κ el of the symmetric band is equal to that of the asymmetric band.

Spherical Harmonic-based Random Fields Based on Real Particle 3D Data: Improved Numerical Algorithm and Quantitative Comparison to Real Particles

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

X Liu; E Garboczi; m Grigoriu

Many parameters affect the cyclone efficiency, and these parameters can have different effects in different flow regimes. Therefore the maximum-efficiency cyclone length is a function of the specific geometry and operating conditions in use. In this study, we obtained a relationship describing the minimum particle diameter or maximum cyclone efficiency by using a theoretical approach based on cyclone geometry and fluid properties. We have compared the empirical predictions with corresponding literature data and observed good agreement. The results address the importance of fluid properties. Inlet and vortex finder cross-sections, cone-apex diameter, inlet Reynolds number and surface roughness are found tomore » be the other important parameters affecting cyclone height. The surface friction coefficient, on the other hand, is difficult to employ in the calculations.We developed a theoretical approach to find the maximum-efficiency heights for cyclones with tangential inlet and we suggested a relation for this height as a function of cyclone geometry and operating parameters. In order to generalize use of the relation, two dimensionless parameters, namely for geometric and operational variables, we defined and results were presented in graphical form such that one can calculate and enter the values of these dimensionless parameters and then can find the maximum efficiency height of his own specific cyclone.« less

Modeling thermoelectric transport in organic materials.

PubMed

Wang, Dong; Shi, Wen; Chen, Jianming; Xi, Jinyang; Shuai, Zhigang

2012-12-28

Thermoelectric energy converters can directly convert heat to electricity using semiconducting materials via the Seebeck effect and electricity to heat via the Peltier effect. Their efficiency depends on the dimensionless thermoelectric figure of merit of the material, which is defined as zT = S(2)σT/κ with S, σ, κ, and T being the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature respectively. Organic materials for thermoelectric applications have attracted great attention. In this review, we present our recent progress made in developing theories and computational schemes to predict the thermoelectric figure of merit at the first-principles level. The methods have been applied to model thermoelectric transport in closely-packed molecular crystals and one-dimensional conducting polymer chains. The physical insight gained in these studies will help in the design of efficient organic thermoelectric materials.

Filamentation instability in a quantum plasma

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

Bret, A.

2007-08-15

The growth rate of the filamentation instability triggered when a diluted cold electron beam passes through a cold plasma is evaluated using the quantum hydrodynamic equations. Compared with a cold fluid model, quantum effects reduce both the unstable wave vector domain and the maximum growth rate. Stabilization of large wave vector modes is always achieved, but significant reduction of the maximum growth rate depends on a dimensionless parameter that is provided. Although calculations are extended to the relativistic regime, they are mostly relevant to the nonrelativistic one.

Interacting Effects Induced by Two Neighboring Pits Considering Relative Position Parameters and Pit Depth

PubMed Central

Huang, Yongfang; Gang, Tieqiang; Chen, Lijie

2017-01-01

For pre-corroded aluminum alloy 7075-T6, the interacting effects of two neighboring pits on the stress concentration are comprehensively analyzed by considering various relative position parameters (inclination angle θ and dimensionless spacing parameter λ) and pit depth (d) with the finite element method. According to the severity of the stress concentration, the critical corrosion regions, bearing high susceptibility to fatigue damage, are determined for intersecting and adjacent pits, respectively. A straightforward approach is accordingly proposed to conservatively estimate the combined stress concentration factor induced by two neighboring pits, and a concrete application example is presented. It is found that for intersecting pits, the normalized stress concentration factor Ktnor increases with the increase of θ and λ and always reaches its maximum at θ = 90°, yet for adjacent pits, Ktnor decreases with the increase of λ and the maximum value appears at a slight asymmetric location. The simulations reveal that Ktnor follows a linear and an exponential relationship with the dimensionless depth parameter Rd for intersecting and adjacent cases, respectively. PMID:28772758

Systems and methods for the synthesis of high thermoelectric performance doped-SnTe materials

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

Ren, Zhifeng; Zhang, Qian; Chen, Gang

A thermoelectric composition comprising tin (Sn), tellurium (Te) and at least one dopant that comprises a peak dimensionless figure of merit (ZT) of 1.1 and a Seebeck coefficient of at least 50 .mu.V/K and a method of manufacturing the thermoelectric composition. A plurality of components are disposed in a ball-milling vessel, wherein the plurality of components comprise tin (Sn), tellurium (Te), and at least one dopant such as indium (In). The components are subsequently mechanically and thermally processed, for example, by hot-pressing. In response to the mechanical-thermally processing, a thermoelectric composition is formed, wherein the thermoelectric composition comprises a dimensionlessmore » figure of merit (ZT) of the thermoelectric composition is at least 0.8, and wherein a Seebeck coefficient of the thermoelectric composition is at least 50 .mu.V/K at any temperature.« less

Enhancement of thermoelectric performance in strontium titanate by praseodymium substitution

NASA Astrophysics Data System (ADS)

Kovalevsky, A. V.; Yaremchenko, A. A.; Populoh, S.; Weidenkaff, A.; Frade, J. R.

2013-02-01

In order to identify the effects of Pr additions on thermoelectric properties of strontium titanate, crystal structure, electrical and thermal conductivity, and Seebeck coefficient of Sr1-xPrxTiO3 (x = 0.02-0.30) materials were studied at 400 < T < 1180 K under highly reducing atmosphere. The mechanism of electronic transport was found to be similar up to 10% of praseodymium content, where generation of the charge carriers upon substitution resulted in significant increase of the electrical conductivity, moderate decrease in Seebeck coefficient, and general improvement of the power factor. Formation of point defects in the course of substitution led to suppression of the lattice thermal conductivity, whilst the contribution from electronic component was increasing with carrier concentration. Possible formation of layered structures and growing distortion of the perovskite lattice resulted in relatively low thermoelectric performance for Sr0.80Pr0.20TiO3 and Sr0.70Pr0.30TiO3. The maximum dimensionless figure of merit was observed for Sr0.90Pr0.10TiO3 and amounted to ˜0.23 at 670 K and ˜0.34 at 1170 K, close to the values, obtained in similar conditions for the best bulk thermoelectrics, based on rare-earth substituted SrTiO3.

Influences of spark plasma sintering temperature on the microstructures and thermoelectric properties of (Sr0.95Gd0.05)TiO3 ceramics

NASA Astrophysics Data System (ADS)

Li, Liang-Liang; Qin, Xiao-Ying; Liu, Yong-Fei; Liu, Quan-Zhen

2015-06-01

(Sr0.95Gd0.05)TiO3 (SGTO) ceramics are successfully prepared via spark plasma sintering (SPS) respectively at 1548, 1648, and 1748 K by using submicron-sized SGTO powders synthesized from a sol-gel method. The densities, microstructures, and thermoelectric properties of the SGTO ceramics are studied. Though the Seebeck coefficient shows no obvious difference in the case that SPS temperatures range from 1548 K to 1648 K, the electrical conductivity and the thermal conductivity increase remarkably due to the increase in grain size and density. The sample has a density higher than 98% theoretical density as the sintering temperature increases up to 1648 K and shows average grain sizes increasing from ˜ 0.7 μm to 7 μm until 1748 K. As a result, the maximum of the dimensionless figure of merit of ˜ 0.24 is achieved at ˜ 1000 K for the samples sintered at 1648 K and 1748 K, which was ˜ 71% larger than that (0.14 at ˜ 1000 K) for the sample sintered at 1548 K due to the enhancement of the power factor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174292, 51101150, and 11374306).

Cosmological horizons, uncertainty principle, and maximum length quantum mechanics

NASA Astrophysics Data System (ADS)

Perivolaropoulos, L.

2017-05-01

The cosmological particle horizon is the maximum measurable length in the Universe. The existence of such a maximum observable length scale implies a modification of the quantum uncertainty principle. Thus due to nonlocality of quantum mechanics, the global properties of the Universe could produce a signature on the behavior of local quantum systems. A generalized uncertainty principle (GUP) that is consistent with the existence of such a maximum observable length scale lmax is Δ x Δ p ≥ℏ2/1/1 -α Δ x2 where α =lmax-2≃(H0/c )2 (H0 is the Hubble parameter and c is the speed of light). In addition to the existence of a maximum measurable length lmax=1/√{α }, this form of GUP implies also the existence of a minimum measurable momentum pmin=3/√{3 } 4 ℏ√{α }. Using appropriate representation of the position and momentum quantum operators we show that the spectrum of the one-dimensional harmonic oscillator becomes E¯n=2 n +1 +λnα ¯ where E¯n≡2 En/ℏω is the dimensionless properly normalized n th energy level, α ¯ is a dimensionless parameter with α ¯≡α ℏ/m ω and λn˜n2 for n ≫1 (we show the full form of λn in the text). For a typical vibrating diatomic molecule and lmax=c /H0 we find α ¯˜10-77 and therefore for such a system, this effect is beyond the reach of current experiments. However, this effect could be more important in the early Universe and could produce signatures in the primordial perturbation spectrum induced by quantum fluctuations of the inflaton field.

A figure of merit for AMTEC electrodes

NASA Technical Reports Server (NTRS)

Underwood, M. L.; Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.

1991-01-01

As a method to compare the results of alkali metal thermoelectric converter (AMTEC) electrode performance measured under different conditions, an AMTEC figure of merit called ZA is proposed. This figure of merit is the ratio of the experimental maximum power for an electrode to a calculated maximum power density as determined from a recently published electrode performance model. The calculation of a maximum power density assumes that certain loss terms in the electrode can be reduced to essentially zero by improved cell design and construction, and that the electrochemical exchange current is determined from a standard value. Other losses in the electrode are considered inherent to the electrode performance. Thus, these terms remain in the determination of the calculated maximum power. A value of ZA near one, then, indicates an electrode performance near the maximum possible performance. The primary limitation of this calculation is that the small electrode effect cannot be included. This effect leads to anomalously high values of ZA. Thus, the electrode area should be reported along with the figure of merit.

Dimensional Analysis on Forest Fuel Bed Fire Spread.

PubMed

Yang, Jiann C

2018-01-01

A dimensional analysis was performed to correlate the fuel bed fire rate of spread data previously reported in the literature. Under wind condition, six pertinent dimensionless groups were identified, namely dimensionless fire spread rate, dimensionless fuel particle size, fuel moisture content, dimensionless fuel bed depth or dimensionless fuel loading density, dimensionless wind speed, and angle of inclination of fuel bed. Under no-wind condition, five similar dimensionless groups resulted. Given the uncertainties associated with some of the parameters used to estimate the dimensionless groups, the dimensionless correlations using the resulting dimensionless groups correlate the fire rates of spread reasonably well under wind and no-wind conditions.

Thermoelectric properties and figure of merit of perovskite-type Ba1-xLaxSnO3 with x=0.002-0.008

NASA Astrophysics Data System (ADS)

Yasukawa, Masahiro; Kono, Toshio; Ueda, Kazushige; Yanagi, Hiroshi; Wng Kim, Sung; Hosono, Hideo

2013-10-01

Thermoelectric properties and figure of merit were evaluated from the Seebeck coefficient S, electrical conductivity σ, and thermal conductivity κ measured at high temperatures for perovskite-type ceramics of Ba1-xLaxSnO3 with x=0.002, 0.005, and 0.008, which were prepared by a polymerized complex method and a subsequent spark plasma sintering technique. All the polycrystalline dense ceramics showed n-type degenerate semiconducting behavior in the temperature range of 373-1073 K. The La content dependence of the S values revealed successful increase in the electron carriers with the La doping in this x range. The κ values remained almost unchanged with x showing ~9.6 Wm-1 K-1 at room temperature and decreased with increasing temperature. The electronic thermal conductivities calculated by the Wiedemann-Franz law as well as the T-1 dependence of the κ values indicate that the phonon thermal conductivity was dominant. The dimensionless figure of merit ZT increased with increasing temperature for all the ceramics and showed ~0.1 at 1073 K for the ceramics with x=0.002 and 0.005.

Preparation and Thermoelectric Properties of Cu2Se Hot-Pressed from Hydrothermal Synthesis Nanopowders

NASA Astrophysics Data System (ADS)

Gao, F.; Leng, S. L.; Zhu, Z.; Li, X. J.; Hu, X.; Song, H. Z.

2018-04-01

The nanopowders of Cu2Se were synthesized by the hydrothermal method, and then were hot-pressed into bulk pellets. The effects of different preparation conditions on the structure and thermoelectric properties of Cu2Se nanocrystalline bulk alloys were investigated. The resistivity and Seebeck coefficients increase with the increment of hot-pressing temperatures, while they decrease with the increment of hot-pressing time, except for the Seebeck coefficients of the sample hot-pressed for 30 min. Based on the power factors and dimensionless thermoelectric figure-of-merit ( ZT) values, the optimum hot-pressing parameters are 700°C and 30 min.

Relations between the efficiency, power and dissipation for linear irreversible heat engine at maximum trade-off figure of merit

NASA Astrophysics Data System (ADS)

Iyyappan, I.; Ponmurugan, M.

2018-03-01

A trade of figure of merit (\\dotΩ ) criterion accounts the best compromise between the useful input energy and the lost input energy of the heat devices. When the heat engine is working at maximum \\dotΩ criterion its efficiency increases significantly from the efficiency at maximum power. We derive the general relations between the power, efficiency at maximum \\dotΩ criterion and minimum dissipation for the linear irreversible heat engine. The efficiency at maximum \\dotΩ criterion has the lower bound \

Dynamic Stiffness and Damping Characteristics of a High-Temperature Air Foil Journal Bearing

NASA Technical Reports Server (NTRS)

Howard, Samuel A.; DellaCorte, Christopher; Valco, Mark J.; Prahl, Joseph M.; Heshmat, Hooshang

2001-01-01

Using a high-temperature optically based displacement measurement system, a foil air bearing's stiffness and damping characteristics were experimentally determined. Results were obtained over a range of modified Sommerfeld Number from 1.5E6 to 1.5E7, and at temperatures from 25 to 538 C. An Experimental procedure was developed comparing the error in two curve fitting functions to reveal different modes of physical behavior throughout the operating domain. The maximum change in dimensionless stiffness was 3.0E-2 to 6.5E-2 over the Sommerfeld Number range tested. Stiffness decreased with temperature by as much as a factor of two from 25 to 538 C. Dimensionless damping was a stronger function of Sommerfeld Number ranging from 20 to 300. The temperature effect on damping being more qualitative, showed the damping mechanism shifted from viscous type damping to frictional type as temperature increased.

Determination of Thermal State of Charge in Solar Heat Receivers

NASA Technical Reports Server (NTRS)

Glakpe, E. K.; Cannon, J. N.; Hall, C. A., III; Grimmett, I. W.

1996-01-01

The research project at Howard University seeks to develop analytical and numerical capabilities to study heat transfer and fluid flow characteristics, and the prediction of the performance of solar heat receivers for space applications. Specifically, the study seeks to elucidate the effects of internal and external thermal radiation, geometrical and applicable dimensionless parameters on the overall heat transfer in space solar heat receivers. Over the last year, a procedure for the characterization of the state-of-charge (SOC) in solar heat receivers for space applications has been developed. By identifying the various factors that affect the SOC, a dimensional analysis is performed resulting in a number of dimensionless groups of parameters. Although not accomplished during the first phase of the research, data generated from a thermal simulation program can be used to determine values of the dimensionless parameters and the state-of-charge and thereby obtain a correlation for the SOC. The simulation program selected for the purpose is HOTTube, a thermal numerical computer code based on a transient time-explicit, axisymmetric model of the total solar heat receiver. Simulation results obtained with the computer program are presented the minimum and maximum insolation orbits. In the absence of any validation of the code with experimental data, results from HOTTube appear reasonable qualitatively in representing the physical situations modeled.

Analysis of microfluidic flow driven by electrokinetic and pressure forces

NASA Astrophysics Data System (ADS)

Chen, Chien-Hsin

2011-12-01

This work presents an analysis of microfluidic flow introduced by mixed electrokinetic force and pressure gradient. Analytical solutions are presented for the case of constant surface heat flux, taking the Joule heating effect into account. The present problem is governed by two scale ratios and the dimensionless source term. The two important ratios are the length scale ratio e (the ratio of Debye length to the tube radius R) and the velocity scale ratio Γ (the ratio of the pressuredriven velocity scale for Poiseuille flow to Helmholtz-Smoluchowski velocity for electroosmotic flow). For mixed electroosmotic and pressure-driven flow, the resulting velocity profile is the superimposed effect of both electroosmotic and Poiseuille flow phenomena. It is found that the velocity profile decreases as e increases and the normalized temperature profiles across the tube increases monotonously form the core to the wall. The maximum dimensionless temperature is observed at the wall and the wall temperature increases with increasing Joule heating. Also, the temperature is increased with increasing the value of ɛ . The fully developed Nusselt number takes the maximum value at the limiting case of ɛ --> 0 , and then decreases with increasing ɛ . Moreover, the Nusselt number decreases with Γ and then goes asymptotically to the limit of Poiseuille flow as Γ --> ∞ , where the flow is dominated by the pressure force.

Synthesis and Thermoelectric Properties of Partially Double-Filled (Ce1- z Pr z ) y Fe4- x Co x Sb12 Skutterudites

NASA Astrophysics Data System (ADS)

Cha, Ye-Eun; Shin, Dong-Kil; Kim, Il-Ho

2018-06-01

Partially double-filled p-type (Ce1- z Pr z ) y Fe4- x Co x Sb12 ( z = 0.25, 0.75; y = 0.8; x = 0, 0.5, 1.0) skutterudites were synthesized by encapsulated melting and consolidated by hot pressing. The microstructure, phase, charge transport characteristics, and thermoelectric properties of the hot-pressed specimens were analyzed. Detailed measurements indicated that the skutterudite phase was successfully synthesized, but a small amount of a secondary phase (FeSb2) was also identified. However, the amount of the FeSb2 phase decreased with an increase in the Co substitution. Unlike for the filled Ce1- z Pr z Fe4- x Co x Sb12 skutterudites with y = 1, the (Ce,Pr)Sb2 phases were not formed by partial filling with Ce/Pr. The electrical conductivity decreased with increasing temperature, similar to the behavior shown by degenerate semiconductors. The Hall coefficient and the Seebeck coefficients were positive, indicating that all specimens exhibited p-type characteristics. The electrical conductivity and the electronic thermal conductivity decreased with increasing Pr filling and Co substitution because of the decreased carrier concentration caused by charge compensation. A maximum dimensionless figure of merit, ZTmax = 0.84, was obtained at 623 K for (Ce0.75Pr0.25)0.8Fe3CoSb12.

Conditional maximum-entropy method for selecting prior distributions in Bayesian statistics

NASA Astrophysics Data System (ADS)

Abe, Sumiyoshi

2014-11-01

The conditional maximum-entropy method (abbreviated here as C-MaxEnt) is formulated for selecting prior probability distributions in Bayesian statistics for parameter estimation. This method is inspired by a statistical-mechanical approach to systems governed by dynamics with largely separated time scales and is based on three key concepts: conjugate pairs of variables, dimensionless integration measures with coarse-graining factors and partial maximization of the joint entropy. The method enables one to calculate a prior purely from a likelihood in a simple way. It is shown, in particular, how it not only yields Jeffreys's rules but also reveals new structures hidden behind them.

Morganza to the Gulf of Mexico Floodgate Study

DTIC Science & Technology

2011-10-01

133  Figure B61 . Humble Canal maximum velocity (base). ........................................................................ 134...exceedance velocity (base). Figure B60. Bayou Terrebonne 50th percentile exceedance velocity (Plan 6). ERDC/CHL TR-11-6 134 Figure B61 . Humble

A Cross-Shore Model of Barrier Island Migration over a Compressible Substrate

DTIC Science & Technology

2010-01-01

possibly become submerged (e.g., Penland and Boyd, 1981; Leather - man et al., 1982; McBride et al., 1995). Penland and Boyd (1981) defined three stages of...tð Þ + d tð Þð Þ2 " #1=2 for 1 30 ≤ tan β tð Þ≤ 1 5 ð11Þ in which ρ is the density of water, and the maximum dimensionless depth-integrated wave

Temperature dependent thermoelectric property of reduced graphene oxide-polyaniline composite

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

Mitra, Mousumi, E-mail: mousumimitrabesu@gmail.com; Banerjee, Dipali, E-mail: dipalibanerjeebesu@gmail.com; Kargupta, Kajari, E-mail: karguptakajari2010@gmail.com

2016-05-06

A composite material of reduced graphene oxide (rG) nanosheets with polyaniline (PANI) protonated by 5-sulfosalicylic acid has been synthesized via in situ oxidative polymerization method. The morphological and spectral characterizations have been done using FESEM and XRD measurements. The thermoelectric (TE) properties of the reduced graphene oxide-polyaniline composite (rG-P) has been studied in the temperature range from 300-400 K. The electrical conductivity and the Seebeck coefficient of rG-P is higher than the of pure PANI, while the thermal conductivity of the composite still keeps much low value ensuing an increase in the dimensionless figure of merit (ZT) in the wholemore » temperature range.« less

50 CFR Figures 14a and 14b to Part... - Maximum Angle of Deflector Bars With Straight Bars Attached to the Bottom of the Frame and...

Code of Federal Regulations, 2010 CFR

2010-10-01

... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Maximum Angle of Deflector Bars With Straight Bars Attached to the Bottom of the Frame and Maximum Angle of Deflector Bars With Bent Bars Attached to the Bottom of the Frame 14a Figures 14a and 14b to Part 223 Wildlife and Fisheries NATIONAL...

50 CFR Figures 14a and 14b to Part... - Maximum Angle of Deflector Bars With Straight Bars Attached to the Bottom of the Frame and...

Code of Federal Regulations, 2011 CFR

2011-10-01

... 50 Wildlife and Fisheries 9 2011-10-01 2011-10-01 false Maximum Angle of Deflector Bars With Straight Bars Attached to the Bottom of the Frame and Maximum Angle of Deflector Bars With Bent Bars Attached to the Bottom of the Frame 14a Figures 14a and 14b to Part 223 Wildlife and Fisheries NATIONAL...

A dimensionless ordered pull-through model of the mammalian lens epithelium evidences scaling across species and explains the age-dependent changes in cell density in the human lens

PubMed Central

Wu, Jun Jie; Wu, Weiju; Tholozan, Frederique M.; Saunter, Christopher D.; Girkin, John M.; Quinlan, Roy A.

2015-01-01

We present a mathematical (ordered pull-through; OPT) model of the cell-density profile for the mammalian lens epithelium together with new experimental data. The model is based upon dimensionless parameters, an important criterion for inter-species comparisons where lens sizes can vary greatly (e.g. bovine (approx. 18 mm); mouse (approx. 2 mm)) and confirms that mammalian lenses scale with size. The validated model includes two parameters: β/α, which is the ratio of the proliferation rate in the peripheral and in the central region of the lens; and γGZ, a dimensionless pull-through parameter that accounts for the cell transition and exit from the epithelium into the lens body. Best-fit values were determined for mouse, rat, rabbit, bovine and human lens epithelia. The OPT model accounts for the peak in cell density at the periphery of the lens epithelium, a region where cell proliferation is concentrated and reaches a maximum coincident with the germinative zone. The β/α ratio correlates with the measured FGF-2 gradient, a morphogen critical to lens cell survival, proliferation and differentiation. As proliferation declines with age, the OPT model predicted age-dependent changes in cell-density profiles, which we observed in mouse and human lenses. PMID:26236824

Green-Naghdi dynamics of surface wind waves in finite depth

NASA Astrophysics Data System (ADS)

Manna, M. A.; Latifi, A.; Kraenkel, R. A.

2018-04-01

The Miles’ quasi laminar theory of waves generation by wind in finite depth h is presented. In this context, the fully nonlinear Green-Naghdi model equation is derived for the first time. This model equation is obtained by the non perturbative Green-Naghdi approach, coupling a nonlinear evolution of water waves with the atmospheric dynamics which works as in the classic Miles’ theory. A depth-dependent and wind-dependent wave growth γ is drawn from the dispersion relation of the coupled Green-Naghdi model with the atmospheric dynamics. Different values of the dimensionless water depth parameter δ = gh/U 1, with g the gravity and U 1 a characteristic wind velocity, produce two families of growth rate γ in function of the dimensionless theoretical wave-age c 0: a family of γ with h constant and U 1 variable and another family of γ with U 1 constant and h variable. The allowed minimum and maximum values of γ in this model are exhibited.

A mesoscopic simulation of static and dynamic wetting using many-body dissipative particle dynamics

NASA Astrophysics Data System (ADS)

Ghorbani, Najmeh; Pishevar, Ahmadreza

2018-01-01

A many-body dissipative particle dynamics simulation is applied here to pave the way for investigating the behavior of mesoscale droplets after impact on horizontal solid substrates. First, hydrophobic and hydrophilic substrates are simulated through tuning the solid-liquid interfacial interaction parameters of an innovative conservative force model. The static contact angles are calculated on homogeneous and several patterned surfaces and compared with the predicted values by the Cassie's law in order to verify the model. The results properly evaluate the amount of increase in surface superhydrophobicity as a result of surface patterning. Then drop impact phenomenon is studied by calculating the spreading factor and dimensionless height versus dimensionless time and the comparisons made between the results and the experimental values for three different static contact angles. The results show the capability of the procedure in calculating the amount of maximum spreading factor, which is a significant concept in ink-jet printing and coating process.

Investigation and optimization of performance of nano-scale Stirling refrigerator using working fluid as Maxwell-Boltzmann gases

NASA Astrophysics Data System (ADS)

Ahmadi, Mohammad H.; Amin Nabakhteh, Mohammad; Ahmadi, Mohammad-Ali; Pourfayaz, Fathollah; Bidi, Mokhtar

2017-10-01

The motivation behind this work is to explore a nanoscale irreversible Stirling refrigerator with respect to size impacts and shows two novel thermo-ecological criteria. Two distinct strategies were suggested in the optimization process and the consequences of every strategy were examined independently. In the primary strategy, with the purpose of maximizing the energetic sustainability index and modified the ecological coefficient of performance (MECOP) and minimizing the dimensionless Ecological function, a multi-objective optimization algorithm (MOEA) was used. In the second strategy, with the purpose of maximizing the ECOP and MECOP and minimizing the dimensionless Ecological function, a MOEA was used. To conclude the final solution from each strategy, three proficient decision makers were utilized. Additionally, to quantify the deviation of the results gained from each decision makers, two different statistical error indexes were employed. Finally, based on the comparison between the results achieved from proposed scenarios reveals that by maximizing the MECOP the maximum values of ESI, ECOP, and a minimum of ecfare achieved.

Brick Paving Systems in Expeditionary Environments: Field Testing

DTIC Science & Technology

2012-07-01

specific gravity of 2.7, optimum moisture content of 2.6 percent, and a maximum dry density of 114.2 pcf. Figure 5 shows the Proctor curve developed by...4  Figure 3. Dry density versus moisture content for CH material...6  Figure 5. Dry density versus moisture content for blended GM base course. ..................................... 7  Figure 6

Receptor-mediated binding of IgE-sensitized rat basophilic leukemia cells to antigen-coated substrates under hydrodynamic flow.

PubMed Central

Tempelman, L A; Hammer, D A

1994-01-01

The physiological function of many cells is dependent on their ability to adhere via receptors to ligand-coated surfaces under fluid flow. We have developed a model experimental system to measure cell adhesion as a function of cell and surface chemistry and fluid flow. Using a parallel-plate flow chamber, we measured the binding of rat basophilic leukemia cells preincubated with anti-dinitrophenol IgE antibody to polyacrylamide gels covalently derivatized with 2,4-dinitrophenol. The rat basophilic leukemia cells' binding behavior is binary: cells are either adherent or continue to travel at their hydrodynamic velocity, and the transition between these two states is abrupt. The spatial location of adherent cells shows cells can adhere many cell diameters down the length of the gel, suggesting that adhesion is a probabilistic process. The majority of experiments were performed in the excess ligand limit in which adhesion depends strongly on the number of receptors but weakly on ligand density. Only 5-fold changes in IgE surface density or in shear rate were necessary to change adhesion from complete to indistinguishable from negative control. Adhesion showed a hyperbolic dependence on shear rate. By performing experiments with two IgE-antigen configurations in which the kinetic rates of receptor-ligand binding are different, we demonstrate that the forward rate of reaction of the receptor-ligand pair is more important than its thermodynamic affinity in the regulation of binding under hydrodynamic flow. In fact, adhesion increases with increasing receptor-ligand reaction rate or decreasing shear rate, and scales with a single dimensionless parameter which compares the relative rates of reaction to fluid shear. Images FIGURE 2 FIGURE 3 FIGURE 6 FIGURE 8 FIGURE 10 PMID:8038394

Numerical Calculation of the Peaking Factor of a Water-Cooled W/Cu Monoblock for a Divertor

NASA Astrophysics Data System (ADS)

Han, Le; Chang, Haiping; Zhang, Jingyang; Xu, Tiejun

2015-09-01

In order to accurately predict the incident critical heat flux (ICHF, the heat flux at the heated surface when CHF occurs) of a water-cooled W/Cu monoblock for a divertor, the exact knowledge of its peaking factors (fp) under one-sided heating conditions with different design parameters is a key issue. In this paper, the heat conduction in the solid domain of a water-cooled W/Cu monoblock is calculated numerically by assuming the local heat transfer coefficients (HTC) of the cooling wall to be functions of the local wall temperature, so as to obtain fp. The reliability of the calculation method is validated by an experimental example result, with the maximum error of 2.1% only. The effects of geometric and flow parameters on the fp of a water-cooled W/Cu monoblock are investigated. Within the scope of this study, it is shown that the fp increases with increasing dimensionless W/Cu monoblock width and armour thickness (the shortest distance between the heated surface and Cu layer), and the maximum increases are 43.8% and 22.4% respectively. The dimensionless W/Cu monoblock height and Cu thickness have little effect on fp. The increase of Reynolds number and Jakob number causes the increase of fp, and the maximum increases are 6.8% and 9.6% respectively. Based on the calculated results, an empirical correlation on peaking factor is obtained via regression. These results provide a valuable reference for the thermal-hydraulic design of water-cooled divertors. supported by National Magnetic Confinement Fusion Science Program of China (No. 2010GB104005) and Funding of Jiangsu Innovation Program for Graduate Education, China (CXLX12_0170), the Fundamental Research Funds for the Central Universities of China

Effects of Ge and Sn substitution on the metal-semiconductor transition and thermoelectric properties of Cu12Sb4S13 tetrahedrite.

PubMed

Kosaka, Yasufumi; Suekuni, Koichiro; Hashikuni, Katsuaki; Bouyrie, Yohan; Ohta, Michihiro; Takabatake, Toshiro

2017-03-29

The synthetic tetrahedrites Cu 12-y Tr y Sb 4 S 13 (Tr: Mn, Fe, Co, Ni, Zn) have been extensively studied due to interest in metal-semiconductor transition as well as in superior thermoelectric performance. We have prepared Ge- and Sn-bearing tetrahedrites, Cu 12-x M x Sb 4 S 13 (M = Ge, Sn; x ≤ 0.6), and investigated the effects of the substitutions on the phase transition and the thermoelectric properties. The substitutions of Ge and Sn for Cu suppress the metal-semiconductor transition and increase the electrical resistivity ρ and the positive thermopower S. This finding suggests that the phase transition is prevented by electron doping into the unoccupied states of the valence band. The variations of ρ, S, and magnetic susceptibility for the present systems correspond well with those for the system with Tr = Zn 2+ , confirming the tetravalent states for Ge and Sn. The substitution of M 4+ for Cu 1+ decreases the power factor S 2 /ρ but enhances the dimensionless thermoelectric figure of merit ZT, due to reductions in both the charge carrier contribution and lattice contribution to the thermal conductivity. As a result, ZT has a maximum value of ∼0.65 at 665 K for x = 0.3-0.5 in Cu 12-x M x Sb 4 S 13 with M = Ge and Sn.

On the tin impurity in the thermoelectric compound ZnSb: Charge-carrier generation and compensation

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

Prokofieva, L. V., E-mail: lprokofieva496@gmail.com; Konstantinov, P. P.; Shabaldin, A. A.

2016-06-15

The technique for measuring the Hall coefficient and electrical conductivity in the thermal cycling mode is used to study the effect of the Sn impurity on the microstructure and properties of pressed ZnSb samples. Tin was introduced as an excess component (0.1 and 0.2 at %) and as a substitutional impurity for Zn and Sb atoms in a concentration of (2–2.5) at % The temperature dependences of the parameters of lightly doped samples are fundamentally like similar curves for ZnSb with 0.1 at % of Cu. The highest Hall concentration, 1.4 × 10{sup 19} cm{sup –3} at 300 K, ismore » obtained upon the introduction of 0.1 at % of Sn; the dimensionless thermoelectric figure of merit attains its maximum value of 0.85 at 660 K. The experimental data are discussed under the assumption of two doping mechanisms, which are effective in different temperature ranges, with zinc vacancies playing the decisive role of acceptor centers. In two ZnSb samples with SnSb and ZnSn additives, the charge-carrier compensation effect is observed; this effect depends on temperature and markedly changes with doping type. As in p-type A{sup IV}–B{sup VI} materials with a low Sn content, hole compensation can be attributed to atomic recharging Sn{sup 2+} → Sn{sup 4+}. Types of compensating complexes are considered.« less

Giant Pressure-Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

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

Baker, Jason; Kumar, Ravhi; Park, Changyong

The thermoelectric properties of polycrystalline SnTe have been measured up to 4.5 GPa at 330 K. SnTe shows an enormous enhancement in Seebeck coefficient, greater than 200 % after 3 GPa, which correlates to a known pressure-induced structural phase transition that is observed through simultaneous in situ X-ray diffraction measurement. We also measured electrical resistance and relative changes to the thermal conductivity, enabling the determination of relative changes in the dimensionless figure of merit (ZT), which increases dramatically after 3 GPa, reaching 350 % of the lowest pressure ZT value. Our results demonstrate a fundamental relationship between structure and thermoelectricmore » behaviours and suggest that pressure is an effective tool to control them.« less

Giant Pressure-Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

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

Baker, Jason; Kumar, Ravhi; Park, Changyong

The thermoelectric properties of polycrystalline SnTe have been measured up to 4.5 GPa at 330 K. SnTe shows an enormous enhancement in Seebeck coefficient, greater than 200 % after 3 GPa, which correlates to a known pressure-induced structural phase transition that is observed through simultaneous in situ X-ray diffraction measurement. Electrical resistance and relative changes to the thermal conductivity were also measured, enabling the determination of relative changes in the dimensionless figure of merit (ZT), which increases dramatically after 3 GPa, reaching 350 % of the lowest pressure ZT value. The results demonstrate a fundamental relationship between structure and thermoelectricmore » behaviours and suggest that pressure is an effective tool to control them.« less

Giant Pressure-Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

DOE PAGES

Baker, Jason; Kumar, Ravhi; Park, Changyong; ...

2017-10-30

The thermoelectric properties of polycrystalline SnTe have been measured up to 4.5 GPa at 330 K. SnTe shows an enormous enhancement in Seebeck coefficient, greater than 200 % after 3 GPa, which correlates to a known pressure-induced structural phase transition that is observed through simultaneous in situ X-ray diffraction measurement. We also measured electrical resistance and relative changes to the thermal conductivity, enabling the determination of relative changes in the dimensionless figure of merit (ZT), which increases dramatically after 3 GPa, reaching 350 % of the lowest pressure ZT value. Our results demonstrate a fundamental relationship between structure and thermoelectricmore » behaviours and suggest that pressure is an effective tool to control them.« less

Effects of Mn Substitution on the Thermoelectric Properties and Thermal Excitations of the Electron-doped Perovskite Sr1-xLaxTiO3

NASA Astrophysics Data System (ADS)

Okuda, Tetsuji; Hata, Hiroto; Eto, Takahiro; Sobaru, Shogo; Oda, Ryosuke; Kaji, Hiroki; Nishina, Kousuke; Kuwahara, Hideki; Nakamura, Mitsutaka; Kajimoto, Ryoichi

2016-09-01

We studied how Mn substitution affects the thermoelectric properties and thermal excitations of the electron-doped perovskite Sr1-xLaxTiO3 by measuring its electrical and thermal transport properties, magnetization, specific heat, and inelastic neutron scattering. Slight Mn substitution with the lattice defects enhanced the Seebeck coefficient, perhaps because of coupling between itinerant electrons and localized spins or between itinerant electrons and local lattice distortion around Mn3+ ions, while it enhanced anharmonic lattice vibrations, which effectively suppressed thermal conductivity in a state of high electrical conductivity. Consequently, slight Mn substitution increased the dimensionless thermoelectric figure of merit for Sr1-xLaxTiO3 near room temperature.

Modeling Gas Exchange in a Closed Plant Growth Chamber

NASA Technical Reports Server (NTRS)

Cornett, J. D.; Hendrix, J. E.; Wheeler, R. M.; Ross, C. W.; Sadeh, W. Z.

1994-01-01

Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant a growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.

Modeling gas exchange in a closed plant growth chamber

NASA Technical Reports Server (NTRS)

Cornett, J. D.; Hendrix, J. E.; Wheeler, R. M.; Ross, C. W.; Sadeh, W. Z.

1994-01-01

Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.

Measurement of laser spot quality

NASA Technical Reports Server (NTRS)

Milster, T. D.; Treptau, J. P.

1991-01-01

Several ways of measuring spot quality are compared. We examine in detail various figures of merit such as full width at half maximum (FWHM), full width at 1/(e exp 2) maximum, Strehl ratio, and encircled energy. Our application is optical data storage, but results can be applied to other areas like space communications and high energy lasers. We found that the optimum figure of merit in many cases is Strehl ratio.

Quadruple Cone Coil with improved focality than Figure-8 coil in Transcranial Magnetic Stimulation

NASA Astrophysics Data System (ADS)

Rastogi, Priyam; Lee, Erik G.; Hadimani, Ravi L.; Jiles, David C.

Transcranial Magnetic Stimulation (TMS) is a non-invasive therapy which uses a time varying magnetic field to induce an electric field in the brain and to cause neuron depolarization. Magnetic coils play an important role in the TMS therapy since their coil geometry determines the focality and penetration's depth of the induced electric field in the brain. Quadruple Cone Coil (QCC) is a novel coil with an improved focality when compared to commercial Figure-8 coil. The results of this newly designed QCC coil are compared with the Figure-8 coil at two different positions of the head - vertex and dorsolateral prefrontal cortex, over the 50 anatomically realistic MRI derived head models. Parameters such as volume of stimulation, maximum electric, area of stimulation and location of maximum electric field are determined with the help of computer modelling of both coils. There is a decrease in volume of brain stimulated by 11.6 % and a modest improvement of 8 % in the location of maximum electric field due to QCC in comparison to the Figure-8 coil. The Carver Charitable Trust and The Galloway Foundation.

Astronomical reach of fundamental physics.

PubMed

Burrows, Adam S; Ostriker, Jeremiah P

2014-02-18

Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.

Rewetting of hot vertical rod during jet impingement surface cooling

NASA Astrophysics Data System (ADS)

Agrawal, Chitranjan; Kumar, Ravi; Gupta, Akhilesh; Chatterjee, Barun

2016-06-01

A stainless steel (SS-316) vertical rod of 12 mm diameter at 800 ± 10 °C initial temperature was cooled by normal impinging round water jet. The surface rewetting phenomenon was investigated for a range of jet diameter 2.5-4.8 mm and jet Reynolds number 5000-24,000 using a straight tube type nozzle. The investigation were made from the stagnation point to maximum 40 mm downstream locations, simultaneously for both upside and downside directions. The cooling performance of the vertical rod was evaluated on the basis of rewetting parameters i.e. rewetting temperature, wetting delay, rewetting velocity and the maximum surface heat flux. Two separate Correlations have been proposed for the dimensionless rewetting velocity in terms of rewetting number and the maximum surface heat flux that predicts the experimental data within an error band of ±20 and ±15 % respectively.

Astronomical reach of fundamental physics

PubMed Central

Burrows, Adam S.; Ostriker, Jeremiah P.

2014-01-01

Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law. PMID:24477692

Effect of Element Substitution at V site on Thermoelectric Properties of Aurivillius Phase Bi2VO5.5

NASA Astrophysics Data System (ADS)

Kohri, Hitoshi; Yagasaki, Takayoshi

2016-10-01

Thermoelectric oxides are suitable at the high temperature range because of chemical stability. Aurivillius compounds are bismuth layered oxides, and known as oxygen ion conductors. The Aurivillius compounds consist of Perovskite layers and Bi-O layers. It is expected that nano-layered structure shows high Seebeck coefficients due to the quantum confinement of carriers in Perovskite layers. It was reported that the Seebeck coefficient of hot pressed specimens for Aurivillius phase Bi2VO5.5 was a high value of -28.3 mVK-1 at 1010 K, and the electrical resistivity of one was also a high value of 0.033 Ωm at 1010 K. In this paper, the effect of element substitution at the V site on thermoelectric properties of Aurivillius phase Bi2VO5.5 was investigated. Bi2V1- x M x O5.5 (M = Cr, Mo, W x = 0, 0.05, 0.1, 0.2) were prepared by solid-state reaction. The electrical resistivity of Cr-substituted specimens were indicated at larger values than the ones for unsubstituted specimens over the measurement temperature range. The resistivity above 800 K was reduced by substitution of W or Mo. W as a substituted element was effective for reducing the thermal conductivity of Bi2VO5.5. The maximum value of the dimensionless figure of merit ZT was 0.05 at 799 K for Bi2V0.8Mo0.2O5.5 and at 902 K for Bi2V0.8W0.1O5.5. The maximum ZT of an unsubstituted sample was 0.02 at 993 K. From these results, it was found that tungsten or molybdenum substitution was effective to improve ZT for Aurivillius phase Bi2VO5.5.

Weak scale from the maximum entropy principle

NASA Astrophysics Data System (ADS)

Hamada, Yuta; Kawai, Hikaru; Kawana, Kiyoharu

2015-03-01

The theory of the multiverse and wormholes suggests that the parameters of the Standard Model (SM) are fixed in such a way that the radiation of the S3 universe at the final stage S_rad becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the SM, we can check whether S_rad actually becomes maximum at the observed values. In this paper, we regard S_rad at the final stage as a function of the weak scale (the Higgs expectation value) vh, and show that it becomes maximum around vh = {{O}} (300 GeV) when the dimensionless couplings in the SM, i.e., the Higgs self-coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by vh ˜ T_{BBN}2 / (M_{pl}ye5), where ye is the Yukawa coupling of electron, T_BBN is the temperature at which the Big Bang nucleosynthesis starts, and M_pl is the Planck mass.

Techniques for simulating flood hydrographs and estimating flood volumes for ungaged basins in east and west Tennessee

USGS Publications Warehouse

Gamble, C.R.

1989-01-01

A dimensionless hydrograph developed for a variety of basin conditions in Georgia was tested for its applicability to streams in East and West Tennessee by comparing it to a similar dimensionless hydrograph developed for streams in East and West Tennessee. Hydrographs of observed discharge at 83 streams in East Tennessee and 38 in West Tennessee were used in the study. Statistical analyses were performed by comparing simulated (or computed) hydrographs, derived by application of the Georgia dimensionless hydrograph, and dimensionless hydrographs developed from Tennessee data, with the observed hydrographs at 50 and 75% of their peak-flow widths. Results of the tests indicate that the Georgia dimensionless hydrography is virtually the same as the one developed for streams in East Tennessee, but that it is different from the dimensionless hydrograph developed for streams in West Tennessee. Because of the extensive testing of the Georgia dimensionless hydrograph, it was determined to be applicable for East Tennessee, whereas the dimensionless hydrograph developed from data on streams in West Tennessee was determined to be applicable in West Tennessee. As part of the dimensionless hydrograph development, an average lagtime in hours for each study basin, and the volume in inches of flood runoff for each flood event were computed. By use of multiple-regression analysis, equations were developed that relate basin lagtime to drainage area size, basin length, and percent impervious area. Similarly, flood volumes were related to drainage area size, peak discharge, and basin lagtime. These equations, along with the appropriate dimensionless hydrograph, can be used to estimate a typical (average) flood hydrograph and volume for recurrence-intervals up to 100 years at any ungaged site draining less than 50 sq mi in East and West Tennessee. (USGS)

Observational constraints on disc galaxy formation

NASA Astrophysics Data System (ADS)

Syer, D.; Mao, Shude; Mo, H. J.

1999-04-01

We use data from the literature to constrain theoretical models of galaxy formation. We show how to calculate the dimensionless spin parameter lambda of the haloes of disc galaxies, and we compare the distribution of lambda with that observed in cosmological N-body simulations. The agreement is excellent, which provides strong support for the hierarchical picture of galaxy formation. Assuming only that the radial surface density distribution of discs is exponential, we estimate crudely the maximum-disc mass-to-light ratio in the I band, and obtain < Upsilon_I> <~ 3.56 h, for a Hubble constant of 100 h km s^-1 Mpc^-1. We discuss this result and its limitations in relation to other independent determinations of Upsilon_I. We also define a dimensionless form of the Tully-Fisher relation, and use it to derive a value of the baryon fraction in disc galaxies; the median value is m_d = 0.084 (Upsilon_I3.56 h). Assuming that the gas fraction in galactic haloes is at most as large as that in clusters, we also conclude that < Upsilon_I> <~ 2.56 h^-1/2.

Determination of Dimensionless Attenuation Coefficient in Shaped Resonators

NASA Technical Reports Server (NTRS)

Daniels, C.; Steinetz, B.; Finkbeiner, J.; Raman, G.; Li, X.

2003-01-01

The value of dimensionless attenuation coefficient is an important factor when numerically predicting high-amplitude acoustic waves in shaped resonators. Both the magnitude of the pressure waveform and the quality factor rely heavily on this dimensionless parameter. Previous authors have stated the values used, but have not completely explained their methods. This work fully describes the methodology used to determine this important parameter. Over a range of frequencies encompassing the fundamental resonance, the pressure waves were experimentally measured at each end of the shaped resonators. At the corresponding dimensionless acceleration, the numerical code modeled the acoustic waveforms generated in the resonator using various dimensionless attenuation coefficients. The dimensionless attenuation coefficient that most closely matched the pressure amplitudes and quality factors of the experimental and numerical results was determined to be the value to be used in subsequent studies.

Summary of dimensionless Texas hyetographs and distribution of storm depth developed for Texas Department of Transportation research project 0–4194

USGS Publications Warehouse

Asquith, William H.; Roussel, Meghan C.; Thompson, David B.; Cleveland, Theodore G.; Fang, Xing

2005-01-01

Hyetographs and storm depth distributions are important elements of hydraulic design by Texas Department of Transportation engineers. Design hyetographs are used in conjunction with unit hydrographs to obtain peak discharge and hydrograph shape for hydraulic design. Storm-depth distributions can be used to assess the probability of a total rainfall depth for a storm. A research project from 2000–2004 has been conducted to (1) determine if existing Natural Resources Conservation Service (NRCS) dimensionless hyetographs are representative of storms in Texas, (2) provide new procedures for dimensionless hyetograph estimation if the NRCS hyetographs are not representative, and (3) provide a procedure to estimate the distribution of storm depth for Texas. This report summarizes the research activities and results of the research project. The report documents several functional models of dimensionless hyetographs and provides curves and tabulated ordinates of empirical (nonfunctional) dimensionless hyetographs for a database of runoff-producing storms in Texas. The dimensionless hyetographs are compared to the NRCS dimensionless hyetographs. The distribution of storm depth is documented for seven values of minimum interevent time through dimensionless frequency curves and tables of mean storm depth for each county in Texas. Conclusions regarding application of the research results are included in the report.

High-performance thermoelectric mineral Cu12-xNixSb4S13 tetrahedrite

NASA Astrophysics Data System (ADS)

Suekuni, Koichiro; Tsuruta, Kojiro; Kunii, Masaru; Nishiate, Hirotaka; Nishibori, Eiji; Maki, Sachiko; Ohta, Michihiro; Yamamoto, Atsushi; Koyano, Mikio

2013-01-01

X-ray structural analysis and high-temperature thermoelectric properties measurements are performed on polycrystalline samples of artificial mineral Cu12-xNixSb4S13 tetrahedrite. Analysis of the atomic displacement parameter manifests low-energy vibration of Cu(2) out of CuS3 triangle plane. The vibration results in low lattice thermal conductivity of less than 0.5 W K-1 m-1. By tuning of the Ni composition x and decrease of electronic thermal conductivity, dimensionless thermoelectric figure of merit for x = 1.5 achieves 0.7 at 665 K, which is a considerably high value among p-type Pb-free sulfides. Because the tetrahedrite is an environmentally friendly material, it constitutes a good thermoelectric material for use in support of a sustainable society.

Analytic Couple Modeling Introducing Device Design Factor, Fin Factor, Thermal Diffusivity Factor, and Inductance Factor

NASA Technical Reports Server (NTRS)

Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

2014-01-01

A set of convenient thermoelectric device solutions have been derived in order to capture a number of factors which are previously only resolved with numerical techniques. The concise conversion efficiency equations derived from governing equations provide intuitive and straight-forward design guidelines. These guidelines allow for better device design without requiring detailed numerical modeling. The analytical modeling accounts for factors such as i) variable temperature boundary conditions, ii) lateral heat transfer, iii) temperature variable material properties, and iv) transient operation. New dimensionless parameters, similar to the figure of merit, are introduced including the device design factor, fin factor, thermal diffusivity factor, and inductance factor. These new device factors allow for the straight-forward description of phenomenon generally only captured with numerical work otherwise. As an example a device design factor of 0.38, which accounts for thermal resistance of the hot and cold shoes, can be used to calculate a conversion efficiency of 2.28 while the ideal conversion efficiency based on figure of merit alone would be 6.15. Likewise an ideal couple with efficiency of 6.15 will be reduced to 5.33 when lateral heat is accounted for with a fin factor of 1.0.

47 CFR 73.509 - Prohibited overlap.

Code of Federal Regulations, 2011 CFR

2011-10-01

... by Figure 1a, curves in Figure 1 must be used. (3) The effective radiated power (ERP) that is the maximum ERP for any elevation plane on any bearing will be used. (d) An application for a change (other...

47 CFR 73.509 - Prohibited overlap.

Code of Federal Regulations, 2010 CFR

2010-10-01

... by Figure 1a, curves in Figure 1 must be used. (3) The effective radiated power (ERP) that is the maximum ERP for any elevation plane on any bearing will be used. (d) An application for a change (other...

Relativistic thermal plasmas - Effects of magnetic fields

NASA Technical Reports Server (NTRS)

Araki, S.; Lightman, A. P.

1983-01-01

Processes and equilibria in finite, relativistic, thermal plasmas are investigated, taking into account electron-positron creation and annihilation, photon production by internal processes, and photon production by a magnetic field. Inclusion of the latter extends previous work on such plasmas. The basic relations for thermal, Comptonized synchrotron emission are analyzed, including emission and absorption without Comptonization, Comptonized thermal synchrotron emission, and the Comptonized synchrotron and bremsstrahlung luminosities. Pair equilibria are calculated, including approximations and dimensionless parameters, the pair balance equation, maximum temperatures and field strengths, and individual models and cooling curves.

Optimal multiple-pass aeroassisted plane change

NASA Technical Reports Server (NTRS)

Vinh, Nguyen X.; Ma, Der-Ming

1990-01-01

This paper presents the exact dimensionless equation of motion and the necessary conditions for the computation of the optimal trajectories of a hypervelocity vehicle flying through a non-rotating spherical planetary atmosphere. Numerical solution is then presented for the case when the vehicle makes several passages through the atmosphere near the perigee of its orbit. While the orbit is slowly contracting, aerodynamic maneuver is performed to obtain the maximum plane change. Several plots were presented to show the optimal variations of the lift coefficient and the bank angle and the various elements of the orbit.

On the Debye-Hückel effect of electric screening

NASA Astrophysics Data System (ADS)

Campos, L. M. B. C.; Lau, F. J. P.

2014-07-01

The paper considers non-linear self-consistent electric potential equation (Sec. I), due to a cloud made of a single species of electric charges, satisfying a Boltzmann distribution law (Sec. II). Exact solutions are obtained in a simple logarithmic form, in three cases: (Sec. III) spherical radial symmetry; (Sec. IV) plane parallel symmetry; (Sec. V) a special case of azimuthal-cylindrical symmetry. All these solutions, and their transformations (Sec. VI), involve the Debye-Hückel radius; the latter was originally defined from a solution of the linearized self-consistent potential equation. Using an exact solution of the self-consistent potential equation, the distance at which the potential vanishes differs from the Debye-Hückel radius by a factor of √2 . The preceding (Secs. II-VI) simple logarithmic exact solutions of the self-consistent potential equations involve no arbitrary constants, and thus are special or singular integrals not the general integral. The general solution of the self-consistent potential equation is obtained in the plane parallel case (Sec. VII), and it involves two arbitrary constants that can be reduced to one via a translation (Sec. VIII). The plots of dimensionless potential (Figure 1), electric field (Figure 2), charge density (Figure 3), and total charge between ζ and infinity (Figure 4), versus distance normalized to Debye-Hückel radius ζ ≡ z/a, show that (Sec. IX) there is a continuum of solutions, ranging from a charge distribution concentrated inside the Debye-Hückel radius to one spread-out beyond it. The latter case leads to the limiting case of logarithmic potential, and stronger electric field; the former case, of very concentrated charge distribution, leads to a fratricide effect and weaker electric field.

On the Debye–Hückel effect of electric screening

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

Campos, L. M. B. C.; Lau, F. J. P.

2014-07-15

The paper considers non-linear self-consistent electric potential equation (Sec. I), due to a cloud made of a single species of electric charges, satisfying a Boltzmann distribution law (Sec. II). Exact solutions are obtained in a simple logarithmic form, in three cases: (Sec. III) spherical radial symmetry; (Sec. IV) plane parallel symmetry; (Sec. V) a special case of azimuthal-cylindrical symmetry. All these solutions, and their transformations (Sec. VI), involve the Debye-Hückel radius; the latter was originally defined from a solution of the linearized self-consistent potential equation. Using an exact solution of the self-consistent potential equation, the distance at which the potentialmore » vanishes differs from the Debye-Hückel radius by a factor of √(2). The preceding (Secs. II–VI) simple logarithmic exact solutions of the self-consistent potential equations involve no arbitrary constants, and thus are special or singular integrals not the general integral. The general solution of the self-consistent potential equation is obtained in the plane parallel case (Sec. VII), and it involves two arbitrary constants that can be reduced to one via a translation (Sec. VIII). The plots of dimensionless potential (Figure 1), electric field (Figure 2), charge density (Figure 3), and total charge between ζ and infinity (Figure 4), versus distance normalized to Debye-Hückel radius ζ ≡ z/a, show that (Sec. IX) there is a continuum of solutions, ranging from a charge distribution concentrated inside the Debye-Hückel radius to one spread-out beyond it. The latter case leads to the limiting case of logarithmic potential, and stronger electric field; the former case, of very concentrated charge distribution, leads to a fratricide effect and weaker electric field.« less

Regionalization of precipitation characteristics in Montana using L-moments

USGS Publications Warehouse

Parrett, C.

1998-01-01

Dimensionless precipitation-frequency curves for estimating precipitation depths having small exceedance probabilities were developed for 2-, 6-, and 24-hour storm durations for three homogeneous regions in Montana. L-moment statistics were used to help define the homogeneous regions. The generalized extreme value distribution was used to construct the frequency curves for each duration within each region. The effective record length for each duration in each region was estimated using a graphical method and was found to range from 500 years for 6-hour duration data in Region 2 to 5,100 years for 24-hour duration data in Region 3. The temporal characteristics of storms were analyzed, and methods for estimating synthetic storm hyetographs were developed. Dimensionless depth-duration data were grouped by independent duration (2,6, and 24 hours) and by region, and the beta distribution was fit to dimensionless depth data for various incremental time intervals. Ordinary least-squares regression was used to develop relations between dimensionless depths for a key, short duration - termed the kernel duration - and dimensionless depths for other durations. The regression relations were used, together with the probabilistic dimensionless depth data for the kernel duration, to calculate dimensionless depth-duration curves for exceedance probabilities from .1 to .9. Dimensionless storm hyetographs for each independent duration in each region were constructed for median value conditions based on an exceedance probability of .5.

Loss of efficiency in a coaxial arrangement of a pair of wind rotors

NASA Astrophysics Data System (ADS)

Okulov, V. L.; Naumov, I. V.; Tsoy, M. A.; Mikkelsen, R. F.

2017-07-01

The efficiency of a pair of wind turbines is experimentally investigated for the case when the model of the second rotor is coaxially located in the wake of the first one. This configuration implies the maximum level of losses in wind farms, as in the rotor wakes, the deceleration of the freestream is maximum. As a result of strain gauge measurements, the dependences of dimensionless power characteristics of both rotors on the distances between them were determined for different modes at different tip speed ratios. The obtained results are of interest for further development of aerodynamics of wind turbines, for optimizing the work of existing wind farms and reducing their power losses due to interactions with wakes of other wind turbines during design and calculation.

Fire Resistant Fuel for Military Compression Ignition Engines

DTIC Science & Technology

2013-12-04

Turbo Diesel Maximum Power Output Figure 5. 6.5L Turbo Diesel Maximum Torque Output 40 60 80 100 120 140 160 180 1000 1200 1400 1600 1800 2000 2200...H2O & 250ppm) JP8-FRF AMA (5% H2O & 250ppm) UNCLASSIFIED 9 UNCLASSIFIED Figure 6. 6.5L Turbo Diesel Brake Specific Fuel Consumption From...mid-1980s, fire-resistant diesel fuel that self extinguished when ignited by an explosive projectile was developed. Chemically, this fire resistant

Experimental Verification of the Streamline Curvature Numerical Analysis Method Applied to the Flow through an Axial Flow Fan.

DTIC Science & Technology

1980-05-28

Total Deviation Angles and Measured Inlet Axial Velocity . . . . 55 ix LIST OF FIGURES (Continued) Figure Page 19 Points Defining Blade Sections of...distance from leading edge to point of maximum camber along chord line ar tip vortex core radius AVR axial velocity ratio (Vx /V x c chord length CL tip...yaw ceoefficient d longitudinal distance from leading edge to tip vortex calculation point G distance from chord line to maximum camber point K cascade

Stress Analysis of Composites.

DTIC Science & Technology

1981-01-01

agree well at the midsurface , where the maximum positive value of a occurs. The maximum negative value occurs at the 45/-45 interface, where the TFE...results for the E45/-45/0/90Js case. The distribu- tion of a, along the 0/90 interface and along the midsurface are plotted in Figures lla and llb...interface, and z along the midsurface are shown in z Figures 12a and 12b for the .90/0/-45/451s laminate. Again the three analysis agree well up the

Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals.

PubMed

Zhao, Li-Dong; Lo, Shih-Han; Zhang, Yongsheng; Sun, Hui; Tan, Gangjian; Uher, Ctirad; Wolverton, C; Dravid, Vinayak P; Kanatzidis, Mercouri G

2014-04-17

The thermoelectric effect enables direct and reversible conversion between thermal and electrical energy, and provides a viable route for power generation from waste heat. The efficiency of thermoelectric materials is dictated by the dimensionless figure of merit, ZT (where Z is the figure of merit and T is absolute temperature), which governs the Carnot efficiency for heat conversion. Enhancements above the generally high threshold value of 2.5 have important implications for commercial deployment, especially for compounds free of Pb and Te. Here we report an unprecedented ZT of 2.6 ± 0.3 at 923 K, realized in SnSe single crystals measured along the b axis of the room-temperature orthorhombic unit cell. This material also shows a high ZT of 2.3 ± 0.3 along the c axis but a significantly reduced ZT of 0.8 ± 0.2 along the a axis. We attribute the remarkably high ZT along the b axis to the intrinsically ultralow lattice thermal conductivity in SnSe. The layered structure of SnSe derives from a distorted rock-salt structure, and features anomalously high Grüneisen parameters, which reflect the anharmonic and anisotropic bonding. We attribute the exceptionally low lattice thermal conductivity (0.23 ± 0.03 W m(-1) K(-1) at 973 K) in SnSe to the anharmonicity. These findings highlight alternative strategies to nanostructuring for achieving high thermoelectric performance.

Magnetic field line random walk in two-dimensional dynamical turbulence

NASA Astrophysics Data System (ADS)

Wang, J. F.; Qin, G.; Ma, Q. M.; Song, T.; Yuan, S. B.

2017-08-01

The field line random walk (FLRW) of magnetic turbulence is one of the important topics in plasma physics and astrophysics. In this article, by using the field line tracing method, the mean square displacement (MSD) of FLRW is calculated on all possible length scales for pure two-dimensional turbulence with the damping dynamical model. We demonstrate that in order to describe FLRW with the damping dynamical model, a new dimensionless quantity R is needed to be introduced. On different length scales, dimensionless MSD shows different relationships with the dimensionless quantity R. Although the temporal effect affects the MSD of FLRW and even changes regimes of FLRW, it does not affect the relationship between the dimensionless MSD and dimensionless quantity R on all possible length scales.

A brief compendium of correlations and analytical formulae for the thermal field generated by a heat source embedded in porous and purely-conductive media

NASA Astrophysics Data System (ADS)

Conti, P.; Testi, D.; Grassi, W.

2017-11-01

This work reviews and compares suitable models for the thermal analysis of forced convection over a heat source in a porous medium. The set of available models refers to an infinite medium in which a fluid moves over different three heat source geometries: i.e. the moving infinite line source, the moving finite line source, and the moving infinite cylindrical source. In this perspective, the present work presents a plain and handy compendium of the above-mentioned models for forced external convection in porous media; besides, we propose a dimensionless analysis to figure out the reciprocal deviation among available models, helping the selection of the most suitable one in the specific case of interest. Under specific conditions, the advection term becomes ineffective in terms of heat transfer performances, allowing the use of purely-conductive models. For that reason, available analytical and numerical solutions for purely-conductive media are also reviewed and compared, again, by dimensionless criteria. Therefore, one can choose the simplest solution, with significant benefits in terms of computational effort and interpretation of the results. The main outcomes presented in the paper are: the conditions under which the system can be considered subject to a Darcy flow, the minimal distance beyond which the finite dimension of the heat source does not affect the thermal field, and the critical fluid velocity needed to have a significant contribution of the advection term in the overall heat transfer process.

29 CFR 1910.27 - Fixed ladders.

Code of Federal Regulations, 2014 CFR

2014-07-01

... unbroken length of 30 feet. EC27OC91.005 Figure D-5—Deflector Plates for Head Hazards EC27OC91.006 Figure D.... Vertical bars shall be located at a maximum spacing of 40 degrees around the circumference of the cage...

29 CFR 1910.27 - Fixed ladders.

Code of Federal Regulations, 2011 CFR

2011-07-01

... unbroken length of 30 feet. EC27OC91.005 Figure D-5—Deflector Plates for Head Hazards EC27OC91.006 Figure D.... Vertical bars shall be located at a maximum spacing of 40 degrees around the circumference of the cage...

29 CFR 1910.27 - Fixed ladders.

Code of Federal Regulations, 2013 CFR

2013-07-01

... unbroken length of 30 feet. EC27OC91.005 Figure D-5—Deflector Plates for Head Hazards EC27OC91.006 Figure D.... Vertical bars shall be located at a maximum spacing of 40 degrees around the circumference of the cage...

Application of genetic algorithms in nonlinear heat conduction problems.

PubMed

Kadri, Muhammad Bilal; Khan, Waqar A

2014-01-01

Genetic algorithms are employed to optimize dimensionless temperature in nonlinear heat conduction problems. Three common geometries are selected for the analysis and the concept of minimum entropy generation is used to determine the optimum temperatures under the same constraints. The thermal conductivity is assumed to vary linearly with temperature while internal heat generation is assumed to be uniform. The dimensionless governing equations are obtained for each selected geometry and the dimensionless temperature distributions are obtained using MATLAB. It is observed that GA gives the minimum dimensionless temperature in each selected geometry.

Bedload and Total Load Sediment Transport Equations for Rough Open-Channel Flow

NASA Astrophysics Data System (ADS)

Abrahams, A. D.; Gao, P.

2001-12-01

The total sediment load transported by an open-channel flow may be divided into bedload and suspended load. Bedload transport occurs by saltation at low shear stress and by sheetflow at high shear stress. Dimensional analysis is used to identify the dimensionless variables that control the transport rate of noncohesive sediments over a plane bed, and regression analysis is employed to isolate the significant variables and determine the values of the coefficients. In the general bedload transport equation (i.e. for saltation and sheetflow) the dimensionless bedload transport rate is a function of the dimensionless shear stress, the friction factor, and an efficiency coefficient. For sheetflow the last term approaches 1, so that the bedload transport rate becomes a function of just the dimensionless shear stress and the friction factor. The dimensional analysis indicates that the dimensionless total load transport rate is a function of the dimensionless bedload transport rate and the dimensionless settling velocity of the sediment. Predicted values of the transport rates are graphed against the computed values of these variables for 505 flume experiments reported in the literature. These graphs indicate that the equations developed in this study give good unbiased predictions of both the bedload transport rate and total load transport rate over a wide range of conditions.

Thermoelectric energy converters under a trade-off figure of merit with broken time-reversal symmetry

NASA Astrophysics Data System (ADS)

Iyyappan, I.; Ponmurugan, M.

2017-09-01

We study the performance of a three-terminal thermoelectric device such as heat engine and refrigerator with broken time-reversal symmetry by applying the unified trade-off figure of merit (\\dotΩ criterion) which accounts for both useful energy and losses. For the heat engine, we find that a thermoelectric device working under the maximum \\dotΩ criterion gives a significantly better performance than a device working at maximum power output. Within the framework of linear irreversible thermodynamics such a direct comparison is not possible for refrigerators, however, our study indicates that, for refrigerator, the maximum cooling load gives a better performance than the maximum \\dotΩ criterion for a larger asymmetry. Our results can be useful to choose a suitable optimization criterion for operating a real thermoelectric device with broken time-reversal symmetry.

Synthesis and Evaluation of Single Layer, Bilayer, and Multilayer Thermoelectric Thin Films

DOE R&D Accomplishments Database

Farmer, J. C.; Barbee, T. W. Jr.; Chapline, G. C. Jr.; Olsen, M. L.; Foreman, R. J.; Summers, L. J.; Dresselhaus, M. S.; Hicks, L. D.

1995-01-20

The relative efficiency of a thermoelectric material is measured in terms of a dimensionless figure of merit, ZT. Though all known thermoelectric materials are believed to have ZT{le}1, recent theoretical results predict that thermoelectric devices fabricated as two-dimensional quantum wells (2D QWs) or one-dimensional (ID) quantum wires could have ZT{ge}3. Multilayers with the dimensions of 2D QWs have been synthesized by alternately sputtering thermoelectric and barrier materials onto a moving single-crystal sapphire substrate from dual magnetrons. These materials have been used to test the thermoelectric quantum well concept and gain insight into relevant transport mechanisms. If successful, research could lead to thermoelectric devices that have efficiencies close to that of an ideal Carnot engine. Ultimately, such devices could be used to replace conventional heat engines and mechanical refrigeration systems.

Carrier concentration tuning in thermoelectric thiospinel Cu2CoTi3S8 by oxidative extraction of copper

NASA Astrophysics Data System (ADS)

Hashikuni, Katsuaki; Suekuni, Koichiro; Watanabe, Kosuke; Bouyrie, Yohan; Ohta, Michihiro; Ohtaki, Michitaka; Takabatake, Toshiro

2018-03-01

We report a method for carrier concentration tuning in the thermoelectric thiospinel Cu2CoTi3S8, which exhibits an n-type metallic character and a high power factor. An oxidative Cu extraction treatment produced Cu defects, resulting in Cu2-xCoTi3S8 up to x = 0.62. The electron carrier concentration was effectively reduced by this treatment, leading to the decrease in power factor, whereas the electronic contribution to the thermal conductivity was suppressed. As a result, the dimensionless figure of merit ZT remained unchanged as 0.2 at 670 K in the whole range of x ≤ 0.62. The oxidative Cu extraction described in this paper offers an opportunity to tune the electron carrier concentration for Cu-containing thermoelectric materials.

Effects of Mn substitution on the thermoelectric properties of the electron-doped perovskite Sr1-xLaxTiO3

NASA Astrophysics Data System (ADS)

Okuda, T.; Hata, H.; Eto, T.; Nishina, K.; Kuwahara, H.; Nakamura, M.; Kajimoto, R.

2014-12-01

We have tried to improve the n-type thermoelectric properties of the electron- doped Perovskite Sr1-xLaxTiO3 by a Mn substitution. The 1 ~ 2 % Mn substitution enhances the Seebeck coefficient (S) and reduces the thermal conductivity (κ) by about 50 % at room temperature (RT) without largely increasing the resistivity for the 5 % electron-doped SrTiO3. Consequently, the power factor at RT keeps a large value comparable to that of Bi2Te3 and the dimensionless figure-of-merits at RT increases twofold by the slight Mn substitution. Such a large reduction of κ at RT is perhaps due to the effect of Jahn-Teller active Mn3+ ions, around which dynamical local lattice distortion may occur.

Optimal energy-utilization ratio for long-distance cruising of a model fish

NASA Astrophysics Data System (ADS)

Liu, Geng; Yu, Yong-Liang; Tong, Bing-Gang

2012-07-01

The efficiency of total energy utilization and its optimization for long-distance migration of fish have attracted much attention in the past. This paper presents theoretical and computational research, clarifying the above well-known classic questions. Here, we specify the energy-utilization ratio (fη) as a scale of cruising efficiency, which consists of the swimming speed over the sum of the standard metabolic rate and the energy consumption rate of muscle activities per unit mass. Theoretical formulation of the function fη is made and it is shown that based on a basic dimensional analysis, the main dimensionless parameters for our simplified model are the Reynolds number (Re) and the dimensionless quantity of the standard metabolic rate per unit mass (Rpm). The swimming speed and the hydrodynamic power output in various conditions can be computed by solving the coupled Navier-Stokes equations and the fish locomotion dynamic equations. Again, the energy consumption rate of muscle activities can be estimated by the quotient of dividing the hydrodynamic power by the muscle efficiency studied by previous researchers. The present results show the following: (1) When the value of fη attains a maximum, the dimensionless parameter Rpm keeps almost constant for the same fish species in different sizes. (2) In the above cases, the tail beat period is an exponential function of the fish body length when cruising is optimal, e.g., the optimal tail beat period of Sockeye salmon is approximately proportional to the body length to the power of 0.78. Again, the larger fish's ability of long-distance cruising is more excellent than that of smaller fish. (3) The optimal swimming speed we obtained is consistent with previous researchers’ estimations.

Revisiting the Fundamental Analytical Solutions of Heat and Mass Transfer: The Kernel of Multirate and Multidimensional Diffusion

NASA Astrophysics Data System (ADS)

Zhou, Quanlin; Oldenburg, Curtis M.; Rutqvist, Jonny; Birkholzer, Jens T.

2017-11-01

There are two types of analytical solutions of temperature/concentration in and heat/mass transfer through boundaries of regularly shaped 1-D, 2-D, and 3-D blocks. These infinite-series solutions with either error functions or exponentials exhibit highly irregular but complementary convergence at different dimensionless times, td. In this paper, approximate solutions were developed by combining the error-function-series solutions for early times and the exponential-series solutions for late times and by using time partitioning at the switchover time, td0. The combined solutions contain either the leading term of both series for normal-accuracy approximations (with less than 0.003 relative error) or the first two terms for high-accuracy approximations (with less than 10-7 relative error) for 1-D isotropic (spheres, cylinders, slabs) and 2-D/3-D rectangular blocks (squares, cubes, rectangles, and rectangular parallelepipeds). This rapid and uniform convergence for rectangular blocks was achieved by employing the same time partitioning with individual dimensionless times for different directions and the product of their combined 1-D slab solutions. The switchover dimensionless time was determined to minimize the maximum approximation errors. Furthermore, the analytical solutions of first-order heat/mass flux for 2-D/3-D rectangular blocks were derived for normal-accuracy approximations. These flux equations contain the early-time solution with a three-term polynomial in √td and the late-time solution with the limited-term exponentials for rectangular blocks. The heat/mass flux equations and the combined temperature/concentration solutions form the ultimate kernel for fast simulations of multirate and multidimensional heat/mass transfer in porous/fractured media with millions of low-permeability blocks of varying shapes and sizes.

Revisiting the Fundamental Analytical Solutions of Heat and Mass Transfer: The Kernel of Multirate and Multidimensional Diffusion

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

Zhou, Quanlin; Oldenburg, Curtis M.; Rutqvist, Jonny

There are two types of analytical solutions of temperature/concentration in and heat/mass transfer through boundaries of regularly shaped 1D, 2D, and 3D blocks. These infinite-series solutions with either error functions or exponentials exhibit highly irregular but complementary convergence at different dimensionless times, t d0. In this paper, approximate solutions were developed by combining the error-function-series solutions for early times and the exponential-series solutions for late times and by using time partitioning at the switchover time, t d0. The combined solutions contain either the leading term of both series for normal-accuracy approximations (with less than 0.003 relative error) or the firstmore » two terms for high-accuracy approximations (with less than 10-7 relative error) for 1D isotropic (spheres, cylinders, slabs) and 2D/3D rectangular blocks (squares, cubes, rectangles, and rectangular parallelepipeds). This rapid and uniform convergence for rectangular blocks was achieved by employing the same time partitioning with individual dimensionless times for different directions and the product of their combined 1D slab solutions. The switchover dimensionless time was determined to minimize the maximum approximation errors. Furthermore, the analytical solutions of first-order heat/mass flux for 2D/3D rectangular blocks were derived for normal-accuracy approximations. These flux equations contain the early-time solution with a three-term polynomial in √td and the late-time solution with the limited-term exponentials for rectangular blocks. The heat/mass flux equations and the combined temperature/concentration solutions form the ultimate kernel for fast simulations of multirate and multidimensional heat/mass transfer in porous/fractured media with millions of low-permeability blocks of varying shapes and sizes.« less

Revisiting the Fundamental Analytical Solutions of Heat and Mass Transfer: The Kernel of Multirate and Multidimensional Diffusion

DOE PAGES

Zhou, Quanlin; Oldenburg, Curtis M.; Rutqvist, Jonny; ...

2017-10-24

There are two types of analytical solutions of temperature/concentration in and heat/mass transfer through boundaries of regularly shaped 1D, 2D, and 3D blocks. These infinite-series solutions with either error functions or exponentials exhibit highly irregular but complementary convergence at different dimensionless times, t d0. In this paper, approximate solutions were developed by combining the error-function-series solutions for early times and the exponential-series solutions for late times and by using time partitioning at the switchover time, t d0. The combined solutions contain either the leading term of both series for normal-accuracy approximations (with less than 0.003 relative error) or the firstmore » two terms for high-accuracy approximations (with less than 10-7 relative error) for 1D isotropic (spheres, cylinders, slabs) and 2D/3D rectangular blocks (squares, cubes, rectangles, and rectangular parallelepipeds). This rapid and uniform convergence for rectangular blocks was achieved by employing the same time partitioning with individual dimensionless times for different directions and the product of their combined 1D slab solutions. The switchover dimensionless time was determined to minimize the maximum approximation errors. Furthermore, the analytical solutions of first-order heat/mass flux for 2D/3D rectangular blocks were derived for normal-accuracy approximations. These flux equations contain the early-time solution with a three-term polynomial in √td and the late-time solution with the limited-term exponentials for rectangular blocks. The heat/mass flux equations and the combined temperature/concentration solutions form the ultimate kernel for fast simulations of multirate and multidimensional heat/mass transfer in porous/fractured media with millions of low-permeability blocks of varying shapes and sizes.« less

Neurobehavioral Effects of Carbon Monoxide (CO) Exposure in Humans: Elevated Carboxyhemoglobin (COHb) and Cerebrovascular Responses

DTIC Science & Technology

1989-05-19

were (a) the dicrotic notch (see Figure 1) had to be present (b) no truncation or clipping could be present (c) the falling portion after the dichrotic... dicrotic notch or closing of the aortic valve (see Figure 1). The analog signal is fed to a delta z rebalancing circuit which has a maximum D.C. limit in... notch had to be relatively linear and (d) there could be only moderate baseline drift (maximum of approximately 30 degree baseline angle with respect

Double emulsion formation through hierarchical flow-focusing microchannel

NASA Astrophysics Data System (ADS)

Azarmanesh, Milad; Farhadi, Mousa; Azizian, Pooya

2016-03-01

A microfluidic device is presented for creating double emulsions, controlling their sizes and also manipulating encapsulation processes. As a result of three immiscible liquids' interaction using dripping instability, double emulsions can be produced elegantly. Effects of dimensionless numbers are investigated which are Weber number of the inner phase (Wein), Capillary number of the inner droplet (Cain), and Capillary number of the outer droplet (Caout). They affect the formation process, inner and outer droplet size, and separation frequency. Direct numerical simulation of governing equations was done using volume of fluid method and adaptive mesh refinement technique. Two kinds of double emulsion formation, the two-step and the one-step, were simulated in which the thickness of the sheath of double emulsions can be adjusted. Altering each dimensionless number will change detachment location, outer droplet size and droplet formation period. Moreover, the decussate regime of the double-emulsion/empty-droplet is observed in low Wein. This phenomenon can be obtained by adjusting the Wein in which the maximum size of the sheath is discovered. Also, the results show that Cain has significant influence on the outer droplet size in the two-step process, while Caout affects the sheath in the one-step formation considerably.

Reynolds analogy for the Rayleigh problem at various flow modes.

PubMed

Abramov, A A; Butkovskii, A V

2016-07-01

The Reynolds analogy and the extended Reynolds analogy for the Rayleigh problem are considered. For a viscous incompressible fluid we derive the Reynolds analogy as a function of the Prandtl number and the Eckert number. We show that for any positive Eckert number, the Reynolds analogy as a function of the Prandtl number has a maximum. For a monatomic gas in the transitional flow regime, using the direct simulation Monte Carlo method, we investigate the extended Reynolds analogy, i.e., the relation between the shear stress and the energy flux transferred to the boundary surface, at different velocities and temperatures. We find that the extended Reynolds analogy for a rarefied monatomic gas flow with the temperature of the undisturbed gas equal to the surface temperature depends weakly on time and is close to 0.5. We show that at any fixed dimensionless time the extended Reynolds analogy depends on the plate velocity and temperature and undisturbed gas temperature mainly via the Eckert number. For Eckert numbers of the order of unity or less we generalize an extended Reynolds analogy. The generalized Reynolds analogy depends mainly only on dimensionless time for all considered Eckert numbers of the order of unity or less.

Towards a universal description of cohesive-particle flows

NASA Astrophysics Data System (ADS)

Lamarche, Casey; Liu, Peiyuan; Kellogg, Kevin; Lattanzi, Aaron; Hrenya, Christine

2017-11-01

A universal framework for describing cohesive granular flows seems unattainable based on prior works, making a fundamental continuum theory to predict such flows appear unachievable. For the first time, universal behavior of cohesive-grain flows is demonstrated by linking the macroscopic (many-grain) behavior to grain-grain interactions via two dimensionless groups: a generalized Bond number BoG - ratio of maximum cohesive force to the force driving flow - and a new Agglomerate number Ag - ratio of critical cohesive energy to the granular energy. Cohesive-grain flow is investigated in several systems, and universal behavior is determined via collapse of a cohesion-dependent output variable from each system with the appropriate dimensionless group. Universal behavior is observed using BoG for dense (enduring-contact-dominated) flows and Ag for dilute (collision-dominated) flows, as BoG accounts for the cohesive contact force and Ag for increased collisional dissipation due to cohesion. Hence, a new physical picture is presented, namely, BoG dominates in dense flows, where force chains drive momentum transfer, and Ag dominates in dilute systems, where the dissipative collisions dominate momentum transfer. Apparent discrepancies with past treatments are resolved. Dow Corning Corporation.

Effect of Quenching Medium on Mechanical Properties of Alloy Al7049-T6 and Lowering of its After-Machining Warpage

NASA Astrophysics Data System (ADS)

Sani, Saeed Aliakbari; Feizabadi, Javad; Pourgharibshahi, Mohammad; Hashemi, Seyed Hamidreza

2017-07-01

Aluminum alloy Al 7049 is studied in state T6. Heat treatment of the specimens is performed in different quenching media (cold water, boiling water, aqueous polymer solutions). The mechanical properties and the Brinell hardness of the alloy are determined after different modes of heat treatment. Comparative analysis is used to find the maximum residual stresses responsible for warpage of the alloy after machining. The relation between the warpage and the dimensionless Biot number is obtained. Quenching modes removing the warpage in billets of Al7049 are determined.

Characteristics of heat exchange in the region of injection into a supersonic high-temperature flow

NASA Technical Reports Server (NTRS)

Bakirov, F. G.; Shaykhutdinov, Z. G.

1985-01-01

An experimental investigation of the local heat transfer coefficient distribution during gas injection into the supersonic-flow portion of a Laval nozzle is discussed. The controlling dimensionless parameters of the investigated process are presented in terms of a generalized relation for the maximum value of the heat transfer coefficient in the nozzle cross section behind the injection hole. Data on the heat transfer coefficient variation along the nozzle length as a function of gas injection rate are also presented, along with the heat transfer coefficient distribution over a cross section of the nozzle.

Sinking a Granular Raft

NASA Astrophysics Data System (ADS)

Protière, Suzie; Josserand, Christophe; Aristoff, Jeffrey M.; Stone, Howard A.; Abkarian, Manouk

2017-03-01

We report experiments that yield new insights on the behavior of granular rafts at an oil-water interface. We show that these particle aggregates can float or sink depending on dimensionless parameters taking into account the particle densities and size and the densities of the two fluids. We characterize the raft shape and stability and propose a model to predict its shape and maximum length to remain afloat. Finally we find that wrinkles and folds appear along the raft due to compression by its own weight, which can trigger destabilization. These features are characteristics of an elastic instability, which we discuss, including the limitations of our model.

Network Routing Using the Network Tasking Order, a Chron Approach

DTIC Science & Technology

2015-03-26

57  Figure 4.6: Maximum bandwidth possible. ..................................................................... 58  Figure 4.7: MikroTik Router...iv xii RouterOS MikroTik Router Operating System...traffic through the network. Within the ESXi platform, four MikroTik Router Operating Systems (RouterOS) are installed. Within ESXi, the network

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

Prokofieva, L. V., E-mail: lprokofieva496@gmail.com; Pshenay-Severin, D. A.; Konstantinov, P. P.

The reliability of determination of model parameters for the Bi{sub 2}Te{sub 3-x}Se{sub x} alloys is improved by extending the concentration and temperature ranges in experimental studies and, correspondingly, in calculations of kinetic coefficients based on the two-band model of the electronic spectrum. The obtained results served as a motivation for a study of the thermoelectric figure of merit for the above-mentioned alloys with x = 0.3, 0.45, and 0.6 and with the electron concentration varied in the range (1-50) x 10{sup 18} cm{sup -3} at temperatures 300-550 K. Comparison of the results showed that the highest efficiency is exhibited bymore » the Bi{sub 2}Te{sub 2.7}Se{sub 0.3} alloy with the absolute value of the thermoelectric power of about 165 {mu}VK{sup -1} at 300 K, and the dimensionless efficiency is equal to 1.2 at 410 K. An appreciable decrease in thermal conductivity in alloys with x = 0.6 at 410 K is related to a larger band gap and could beneficially affect the figure of merit. However, the magnitude of this effect is found to be too small to compensate a decrease in electrical conductivity due to a large fraction of heavy electrons in the concentration and to a high content of selenium.« less

Small-Scale Surf Zone Geometric Roughness

DTIC Science & Technology

2017-12-01

and an image of the tie points can be seen (Figure 6). 23 Figure 6. Screen Shot of Alignment Process On the left side is the workspace which...rest of the points, producing the 3D surface. 24 Figure 7. Screen Shot of Dense Cloud Process On the left side is the workspace which...maximum 200 words) Measurements of small-scale (O(mm)) geometric roughness (kf) associated with breaking wave foam were obtained within the surf zone on

A benchmark study for the crown-type splashing dynamics of one- and two-component droplet wall-film interactions

NASA Astrophysics Data System (ADS)

Geppert, A.; Terzis, A.; Lamanna, G.; Marengo, M.; Weigand, B.

2017-12-01

The present paper investigates experimentally the impact dynamics of crown-type splashing for miscible two- and one-component droplet wall-film interactions over a range of Weber numbers and dimensionless film thicknesses. The splashing outcome is parametrised in terms of a set of quantifiable parameters, such as crown height, top and base diameter, wall inclination, number of fingers, and secondary droplet properties. The results show that the outcome of a splashing event is not affected by the choice of similar or dissimilar fluids, provided the dimensionless film thickness is larger than 0.1. Below this threshold, distinctive features of two-component interactions appear, such as hole formation and crown bottom breakdown. The observation of different crown shapes (e.g. V-shaped, cylindrical, and truncated-cone) confirms that vorticity production induces changes in the crown wall inclination, thus affecting the evolution of the crown height and top diameter. The evolution of the crown base diameter, instead, is mainly dependent on the relative importance of liquid inertia and viscous losses in the wall-film. The maximum number of liquid fingers decreases with increasing wall, film thickness, due to the enhanced attenuation of the effect of surface properties on the fingering process. The formation of secondary droplets is also affected by changes in the crown wall inclination. In particular, for truncated-cone shapes the occurrence of crown rim contraction induces a large scatter in the secondary droplet properties. Consequently, empirical models for the maximum number and mean diameter of the secondary droplets are derived for V-shaped crowns, as observed for the hexadecane-Hyspin interactions.

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.

Thermoelectric properties of Ge 1-xSn xTe crystals grown by vertical Bridgman method

NASA Astrophysics Data System (ADS)

Wu, C. C.; Ferng, N. J.; Gau, H. J.

2007-06-01

Single crystals of Ge 1-xSn xTe compounds with x=0, 0.8, 0.9 and 1.0 were grown by vertical Bridgman method. The crystalline phase and stochiometry for these crystals were investigated by X-ray diffraction, metallographic microscope as well as electron-probe microanalysis (EPMA). Electrical property of the as-grown samples was characterized using room temperature resistivity and Hall measurements. The thermoelectric behaviors for the Ge 1-xSn xTe crystals were studied by means of thermal and carrier transport measurements. Temperature dependences of resistivity, Seebeck coefficient and thermal conductivity for the various compositions of Ge 1-xSn xTe were analyzed. A two-valence band model was proposed to describe the temperature dependence of thermoelectric property of the Ge 1-xSn xTe crystals. The dimensionless thermoelectric figure of merit ZT for the alloys was evaluated and discussed.

Influence of phonon-assisted tunneling on the linear thermoelectric transport through molecular quantum dots

NASA Astrophysics Data System (ADS)

Khedri, A.; Meden, V.; Costi, T. A.

2017-11-01

We investigate the effect of vibrational degrees of freedom on the linear thermoelectric transport through a single-level quantum dot described by the spinless Anderson-Holstein impurity model. To study the effects of strong electron-phonon coupling, we use the nonperturbative numerical renormalization group approach. We also compare our results, at weak to intermediate coupling, with those obtained by employing the functional renormalization group method, finding good agreement in this parameter regime. When applying a gate voltage at finite temperatures, the inelastic scattering processes, induced by phonon-assisted tunneling, result in an interesting interplay between electrical and thermal transport. We explore different parameter regimes and identify situations for which the thermoelectric power as well as the dimensionless figure of merit are significantly enhanced via a Mahan-Sofo type of mechanism. We show, in particular, that this occurs at strong electron-phonon coupling and in the antiadiabatic regime.

High thermopower of mechanically stretched single-molecule junctions

PubMed Central

Tsutsui, Makusu; Morikawa, Takanori; He, Yuhui; Arima, Akihide

2015-01-01

Metal-molecule-metal junction is a promising candidate for thermoelectric applications that utilizes quantum confinement effects in the chemically defined zero-dimensional atomic structure to achieve enhanced dimensionless figure of merit ZT. A key issue in this new class of thermoelectric nanomaterials is to clarify the sensitivity of thermoelectricity on the molecular junction configurations. Here we report simultaneous measurements of the thermoelectric voltage and conductance on Au-1,4-benzenedithiol (BDT)-Au junctions mechanically-stretched in-situ at sub-nanoscale. We obtained the average single-molecule conductance and thermopower of 0.01 G0 and 15 μV/K, respectively, suggesting charge transport through the highest occupied molecular orbital. Meanwhile, we found the single-molecule thermoelectric transport properties extremely-sensitive to the BDT bridge configurations, whereby manifesting the importance to design the electrode-molecule contact motifs for optimizing the thermoelectric performance of molecular junctions. PMID:26112999

High-performance thermoelectric minerals: Colusites Cu26V2M6S32 (M = Ge, Sn)

NASA Astrophysics Data System (ADS)

Suekuni, Koichiro; Kim, Fiseong S.; Nishiate, Hirotaka; Ohta, Michihiro; Tanaka, Hiromi I.; Takabatake, Toshiro

2014-09-01

We report thermoelectric (TE) properties of dense samples of colusites Cu26V2M6S32 (M = Ge, Sn), most of which are composed of earth-abundant elements; Cu and S. The combination of p-type metallic conduction and large thermopowers greater than 200 μV/K leads to high TE power factors of 0.61 and 0.48 mW/K2 m at 663 K for M = Ge and Sn samples, respectively. Furthermore, the lattice thermal conductivity is smaller than 0.6 W/Km over the temperature range from 350 K to 663 K due to the structural complexity. As a consequence, the values of dimensionless TE figure of merit ZT for M = Ge and Sn reach 0.73 and 0.56 at 663 K, respectively. Thus, the colusites are promising candidates for environmental friendly TE materials usable in the range of 500-700 K.

Low-temperature thermoelectric properties of the electron-doped perovskites SrTi1-xNbxO3

NASA Astrophysics Data System (ADS)

Okuda, Tetsuji; Fukuyado, Junichi; Narikiyo, Kuraihito; Akaki, Mitsuru; Kuwahara, Hideki

2014-03-01

Electron-doped perovskite SrTiO3 is one of the candidates of the n-type oxide thermoelectric materials. In this study, we have investigated thermoelectric (TE) properties for single crystals of SrTi1-xNbxO3 for 0 <= x <= 0.03 below room temperature. We found that SrTi0.99Nb0.01O3 shows a large power factor at low temperature (PF = 50 μW/K2 cm at 100 K - 90 μW/K2 cm at 50 K) and the largest dimensionless TE figure-of-merit below 40 K (ZT ~ 0.07) among the reported materials. Such a large low-temperature TE response around a carrier concentration of 1020 cm-3 is due to a distinct phonon drag effect, i.e., a distinct electron-phonon interaction, which could relate to the superconducting state.

Thermoelectric properties and chlorine doping effect of In4Pb0.01Sn0.03Se2.9Clx polycrystalline compounds.

PubMed

Hee Kim, Jin; Jae Kim, Min; Oh, Suekyung; Rhyee, Jong-Soo; Park, Su-Dong; Ahn, Docheon

2015-02-21

We investigated the thermoelectric properties of Cl-doped polycrystalline compounds In4Pb0.01Sn0.03Se2.9Clx (x = 0.02, 0.04, and 0.06). X-ray diffraction measurement shows a gradual change in lattice volume for x ≤ 0.04 without any impurity phases indicating a systemic change in Cl doping. The Cl doping in the compounds has the effect of increasing carrier concentration and the effective mass of carriers, resulting in an increase in power factor at a high temperature (∼700 K). Because of the increased electrical conductivity at a high temperature, the dimensionless thermoelectric figure of merit ZT reaches 1.25 at 723 K for the x = 0.04 Cl-doped compound, which is a relatively high value for n-type polycrystalline materials.

Effect of selenium deficiency on the thermoelectric properties of n -type In 4 Se 3 - x compounds

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

Zhu, G. H.; Lan, Y. C.; Wang, H.

2011-03-01

Thermoelectric properties of dense bulk polycrystalline In 4 Se 3 - x ( x = 0, 0.25, 0.5, 0.65, and 0.8) compounds are investigated. A peak dimensionless thermoelectric figure of merit ( ZT ) of about 1 is achieved for x = 0.65 and 0.8. The peak ZT is about 50% higher than the previously reported highest value for polycrystalline In 4 Se 3 - x compounds. Our In 4 Se 3 - x samples were prepared by ball milling and hot pressing. We show that it is possible to effectively control the electrical conductivity and thermal conductivity by controllingmore » selenium (Se) deficiency x . The ZT enhancement is mainly attributed to the thermal conductivity reduction due to the increased phonon scattering by Se deficiency, defects, and nanoscale inclusions in the ball-milled and hot-pressed dense bulk In 4 Se 3 - x samples.« less

Effect of selenium deficiency on the thermoelectric properties of n-type In 4Se 3-x compounds

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

Zhu, G H; Lan, Y C; Wang, H

2011-03-04

Thermoelectric properties of dense bulk polycrystalline In 4Se 3-x (x = 0, 0.25, 0.5, 0.65, and 0.8) compounds are investigated. A peak dimensionless thermoelectric figure of merit (ZT) of about 1 is achieved for x = 0.65 and 0.8. The peak ZT is about 50% higher than the previously reported highest value for polycrystalline In 4Se 3-x} compounds. Our In 4Se 3-x samples were prepared by ball milling and hot pressing. We show that it is possible to effectively control the electrical conductivity and thermal conductivity by controlling selenium (Se) deficiency x. The ZT enhancement is mainly attributed to themore » thermal conductivity reduction due to the increased phonon scattering by Se deficiency, defects, and nanoscale inclusions in the ball-milled and hot-pressed dense bulk In 4Se 3-x samples.« less

Assessing the Thermal Conductivity of Cu2-xSe Alloys Undergoing a Phase Transition via the Simultaneous Measurement of Thermoelectric Parameters by a Harman-Based Setup

NASA Astrophysics Data System (ADS)

Vasilevskiy, D.; Keshavarz, M. K.; Simard, J.-M.; Masut, R. A.; Turenne, S.; Snyder, G. J.

2018-06-01

Some materials such as Cu2-xSe, Cu1.97Ag0.03Se, and SnSe have attracted attention by demonstrating a significant enhancement of their thermoelectric performance, which is associated with a phase transition. This phenomenon, observed in a limited temperature ( T) interval, results in sharp changes of the Seebeck coefficient ( S), the electrical resistivity ( ρ), and the thermal conductivity ( κ), which may render the correct evaluation of the dimensionless figure of merit (ZT) difficult. We report the thermoelectric properties of a polycrystalline Cu2-xSe sample which is known to undergo a phase transition near 410 K, containing a mixture of α- and β-phases at room temperature, as determined by x-ray diffraction measurements. We have used a Harman-based setup (TEMTE Inc.), which assures the direct measurement of ZT at all temperatures, including the phase transition region. This approach ensures that κ( T) is determined under steady-state conditions at any given temperature, including points arbitrarily close to the transition temperature which cannot be guaranteed by previously used techniques such as laser flash. We have observed a sharp maximum for κ( T) near 410 K, similar to the reported specific heat variation, with a ZT peak value of 0.2 at 400 K. The expected gain in ZT related to the phase transition is reduced because the increase in S is counterbalanced by the increase in κ( T). Thus, our detailed assessment of the temperature variation of the individual thermoelectric properties accurately evaluates the performance enhancement associated to a structural phase transition and helps to elucidate this complex phenomenon.

Coefficient of performance at maximum figure of merit and its bounds for low-dissipation Carnot-like refrigerators.

PubMed

Wang, Yang; Li, Mingxing; Tu, Z C; Hernández, A Calvo; Roco, J M M

2012-07-01

The figure of merit for refrigerators performing finite-time Carnot-like cycles between two reservoirs at temperature T(h) and T(c) (

Compliance calibration of the short rod chevron-notch specimen for fracture toughness testing of brittle materials

NASA Technical Reports Server (NTRS)

Bubsey, R. T.; Pierce, W. S.; Shannon, J. L., Jr.; Munz, D.

1982-01-01

The short rod chevron-notch specimen has the advantages of (1) crack development at the chevron tip during the early stage of test loading, and (2) convenient calculation of plane-strain fracture toughness from the maximum test load and from a calibration factor which depends only on the specimen geometry and manner of loading. For generalized application, calibration of the specimen over a range of specimen proportions and chevron-notch configurations is necessary. Such was the objective of this investigation, wherein calibration of the short rod specimen was made by means of experimental compliance measurements converted into dimensionless stress intensity factor coefficients.

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

Friar, James Lewis; Goldman, Terrance J.; Pérez-Mercader, J.

In this paper, we apply the Law of Total Probability to the construction of scale-invariant probability distribution functions (pdf's), and require that probability measures be dimensionless and unitless under a continuous change of scales. If the scale-change distribution function is scale invariant then the constructed distribution will also be scale invariant. Repeated application of this construction on an arbitrary set of (normalizable) pdf's results again in scale-invariant distributions. The invariant function of this procedure is given uniquely by the reciprocal distribution, suggesting a kind of universality. Finally, we separately demonstrate that the reciprocal distribution results uniquely from requiring maximum entropymore » for size-class distributions with uniform bin sizes.« less

Neural Modeling of Fuzzy Controllers for Maximum Power Point Tracking in Photovoltaic Energy Systems

NASA Astrophysics Data System (ADS)

Lopez-Guede, Jose Manuel; Ramos-Hernanz, Josean; Altın, Necmi; Ozdemir, Saban; Kurt, Erol; Azkune, Gorka

2018-06-01

One field in which electronic materials have an important role is energy generation, especially within the scope of photovoltaic energy. This paper deals with one of the most relevant enabling technologies within that scope, i.e, the algorithms for maximum power point tracking implemented in the direct current to direct current converters and its modeling through artificial neural networks (ANNs). More specifically, as a proof of concept, we have addressed the problem of modeling a fuzzy logic controller that has shown its performance in previous works, and more specifically the dimensionless duty cycle signal that controls a quadratic boost converter. We achieved a very accurate model since the obtained medium squared error is 3.47 × 10-6, the maximum error is 16.32 × 10-3 and the regression coefficient R is 0.99992, all for the test dataset. This neural implementation has obvious advantages such as a higher fault tolerance and a simpler implementation, dispensing with all the complex elements needed to run a fuzzy controller (fuzzifier, defuzzifier, inference engine and knowledge base) because, ultimately, ANNs are sums and products.

Boys who pee the farthest have a large hollow head, a thin skin, and medium-size manhood

NASA Astrophysics Data System (ADS)

Attinger, Daniel; Lee, Vincent

2016-11-01

Following a recent trend of scientific studies on artwork, we study here the thermodynamics of a jetting thermometer made of ceramic, related to the Chinese tea culture. The thermometer represents a boy who "urinates" shortly after hot water is poured onto his head. Long jetting distance indicates if the water temperature is hot enough to brew tea. Here, a thermofluid model describes the jetting phenomenon of that pee-pee boy. The study demonstrates how thermal expansion of an interior air pocket causes jetting. The validity of assumptions underlying the Hagen-Poiseuille flow is discussed for urethra of finite length. A thermodynamic potential is shown to define maximum jetting velocity. Seven optimization criteria to maximize jetting distance are provided, including two dimensionless numbers. The dimensionless numbers are obtained by comparing the time scales of the internal pressure buildup due to heating, with that of pressure relief due to jetting. Optimization results show that longer jets are produced by large individuals, with low body mass index, with a boyhood of medium size inclined at an angle π/4. Analogies are drawn with pissing contests among humans and lobsters. The study ends by noting similitudes of working principle between that politically incorrect thermometer and Galileo Galilei's thermoscope.

76 FR 53633 - Airworthiness Directives; Viking Air Limited (Type Certificate No. A-815 Formerly Held by...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-29

... Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590. FOR FURTHER... form required in paragraph (f)(1) of airplanes: Within (figure 1 of this this AD, the total maximum...) 329-4090; e-mail: [email protected] . Figure 1 (g) Paperwork Reduction Act Burden Statement A...

Terrain Classification Using Multi-Wavelength Lidar Data

DTIC Science & Technology

2015-09-01

Figure 9. Pseudo- NDVI of three layers within the vertical structure of the forest. (Top) First return from the LiDAR instrument, including the ground...in NDVI throughout the vertical canopy. ........................................................17 Figure 10. Optech Titan operating wavelengths...and Ranging LMS LiDAR Mapping Suite ML Maximum Likelihood NIR Near Infrared N-D VIS n-Dimensional Visualizer NDVI Normalized Difference

The relationship between the thermoelectric generator efficiency and the device engineering figure of merit Zd,eng. The maximum efficiency 𝜼max

NASA Astrophysics Data System (ADS)

Hapenciuc, C. L.; Borca-Tasciuc, T.; Mihailescu, I. N.

2017-04-01

Thermoelectric materials are used today in thermoelectric devices for heat to electricity(thermoelectric generators-TEG) or electricity to heat(heat pumps) conversion in a large range of applications. In the case of TEGs the final measure of their performance is given by a quantity named the maximum efficiency which shows how much from the heat input is converted into electrical power. Therefore it is of great interest to know correctly how much is the efficiency of a device to can make commercial assessments. The concept of engineering figure of merit, Zeng, and engineering power factor, Peng, were already introduced in the field to quantify the efficiency of a single material under temperature dependent thermoelectric properties, with the mention that the formulas derivation was limited to one leg of the thermoelectric generator. In this paper we propose to extend the concept of engineering figure of merit to a thermoelectric generator by introducing a more general concept of device engineering thermoelectric figure of merit, Zd,eng, which depends on the both TEG materials properties and which shall be the right quantity to be used when we are interested in the evaluation of the efficiency. Also, this work takes into account the electrical contact resistance between the electrodes and thermoelement legs in an attempt to quantify its influence upon the performance of a TEG. Finally, a new formula is proposed for the maximum efficiency of a TEG.

Short-term gas dispersion in idealised urban canopy in street parallel with flow direction

NASA Astrophysics Data System (ADS)

Chaloupecká, Hana; Jaňour, Zbyněk; Nosek, Štěpán

2016-03-01

Chemical attacks (e.g. Syria 2014-15 chlorine, 2013 sarine or Iraq 2006-7 chlorine) as well as chemical plant disasters (e.g. Spain 2015 nitric oxide, ferric chloride; Texas 2014 methyl mercaptan) threaten mankind. In these crisis situations, gas clouds are released. Dispersion of gas clouds is the issue of interest investigated in this paper. The paper describes wind tunnel experiments of dispersion from ground level point gas source. The source is situated in a model of an idealised urban canopy. The short duration releases of passive contaminant ethane are created by an electromagnetic valve. The gas cloud concentrations are measured in individual places at the height of the human breathing zone within a street parallel with flow direction by Fast-response Ionisation Detector. The simulations of the gas release for each measurement position are repeated many times under the same experimental set up to obtain representative datasets. These datasets are analysed to compute puff characteristics (arrival, leaving time and duration). The results indicate that the mean value of the dimensionless arrival time can be described as a growing linear function of the dimensionless coordinate in the street parallel with flow direction where the gas source is situated. The same might be stated about the dimensionless leaving time as well as the dimensionless duration, however these fits are worse. Utilising a linear function, we might also estimate some other statistical characteristics from datasets than the datasets means (medians, trimeans). The datasets of the dimensionless arrival time, the dimensionless leaving time and the dimensionless duration can be fitted by the generalized extreme value distribution (GEV) in all sampling positions except one.

MeV Si ion modifications on the thermoelectric generators from Si/Si + Ge superlattice nano-layered films

NASA Astrophysics Data System (ADS)

Budak, S.; Heidary, K.; Johnson, R. B.; Colon, T.; Muntele, C.; Ila, D.

2014-08-01

The performance of thermoelectric materials and devices is characterized by a dimensionless figure of merit, ZT = S2σT/K, where, S and σ denote, respectively, the Seebeck coefficient and electrical conductivity, T is the absolute temperature in Kelvin and K represents the thermal conductivity. The figure of merit may be improved by means of raising either S or σ or by lowering K. In our laboratory, we have fabricated and characterized the performance of a large variety of thermoelectric generators (TEG). Two TEG groups comprised of 50 and 100 alternating layers of Si/Si + Ge multi-nanolayered superlattice films have been fabricated and thoroughly characterized. Ion beam assisted deposition (IBAD) was utilized to assemble the alternating sandwiched layers, resulting in total thickness of 300 nm and 317 nm for 50 and 100 layer devices, respectively. Rutherford Backscattering Spectroscopy (RBS) was employed in order to monitor the precise quantity of Si and Ge utilized in the construction of specific multilayer thin films. The material layers were subsequently impregnated with quantum dots and/or quantum clusters, in order to concurrently reduce the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and raise the cross plane electrical conductivity. The quantum dots/clusters were implanted via the 5 MeV Si ion bombardment which was performed using a Pelletron high energy ion beam accelerator. We have achieved remarkable results for the thermoelectric and optical properties of the Si/Si + Ge multilayer thin film TEG systems. We have demonstrated that with optimal setting of the 5 MeV Si ion beam bombardment fluences, one can fabricate TEG systems with figures of merits substantially higher than the values previously reported.

Clarifying atomic weights: A 2016 four-figure table of standard and conventional atomic weights

USGS Publications Warehouse

Coplen, Tyler B.; Meyers, Fabienne; Holden, Norman E.

2017-01-01

To indicate that atomic weights of many elements are not constants of nature, in 2009 and 2011 the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) replaced single-value standard atomic weight values with atomic weight intervals for 12 elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, bromine, and thallium); for example, the standard atomic weight of nitrogen became the interval [14.00643, 14.00728]. CIAAW recognized that some users of atomic weight data only need representative values for these 12 elements, such as for trade and commerce. For this purpose, CIAAW provided conventional atomic weight values, such as 14.007 for nitrogen, and these values can serve in education when a single representative value is needed, such as for molecular weight calculations. Because atomic weight values abridged to four figures are preferred by many educational users and are no longer provided by CIAAW as of 2015, we provide a table containing both standard atomic weight values and conventional atomic weight values abridged to four figures for the chemical elements. A retrospective review of changes in four-digit atomic weights since 1961 indicates that changes in these values are due to more accurate measurements over time or to the recognition of the impact of natural isotopic fractionation in normal terrestrial materials upon atomic weight values of many elements. Use of the unit “u” (unified atomic mass unit on the carbon mass scale) with atomic weight is incorrect because the quantity atomic weight is dimensionless, and the unit “amu” (atomic mass unit on the oxygen scale) is an obsolete term: Both should be avoided.

9 CFR 310.1 - Extent and time of post-mortem inspection; post-mortem inspection staffing standards.

Code of Federal Regulations, 2010 CFR

2010-01-01

... inspector performs the viscera and upper carcass inspection. 1 1 The “Maximum Slaughter Rates” figures... accompanying rules. (i) Inspection Using the Viscera Truck. Steers and Heifers Maximum slaughter rates (head... 1 1 1 85 to 86 1 2 1 87 to 143 2 2 1 Cows and Bulls Maximum slaughter rates (head per hour) Number...

9 CFR 310.1 - Extent and time of post-mortem inspection; post-mortem inspection staffing standards.

Code of Federal Regulations, 2013 CFR

2013-01-01

... inspector performs the viscera and upper carcass inspection. 1 1 The “Maximum Slaughter Rates” figures... accompanying rules. (i) Inspection Using the Viscera Truck. Steers and Heifers Maximum slaughter rates (head... 1 1 1 85 to 86 1 2 1 87 to 143 2 2 1 Cows and Bulls Maximum slaughter rates (head per hour) Number...

9 CFR 310.1 - Extent and time of post-mortem inspection; post-mortem inspection staffing standards.

Code of Federal Regulations, 2012 CFR

2012-01-01

... inspector performs the viscera and upper carcass inspection. 1 1 The “Maximum Slaughter Rates” figures... accompanying rules. (i) Inspection Using the Viscera Truck. Steers and Heifers Maximum slaughter rates (head... 1 1 1 85 to 86 1 2 1 87 to 143 2 2 1 Cows and Bulls Maximum slaughter rates (head per hour) Number...

9 CFR 310.1 - Extent and time of post-mortem inspection; post-mortem inspection staffing standards.

Code of Federal Regulations, 2011 CFR

2011-01-01

... inspector performs the viscera and upper carcass inspection. 1 1 The “Maximum Slaughter Rates” figures... accompanying rules. (i) Inspection Using the Viscera Truck. Steers and Heifers Maximum slaughter rates (head... 1 1 1 85 to 86 1 2 1 87 to 143 2 2 1 Cows and Bulls Maximum slaughter rates (head per hour) Number...

9 CFR 310.1 - Extent and time of post-mortem inspection; post-mortem inspection staffing standards.

Code of Federal Regulations, 2014 CFR

2014-01-01

... inspector performs the viscera and upper carcass inspection. 1 1 The “Maximum Slaughter Rates” figures... accompanying rules. (i) Inspection Using the Viscera Truck. Steers and Heifers Maximum slaughter rates (head... 1 1 1 85 to 86 1 2 1 87 to 143 2 2 1 Cows and Bulls Maximum slaughter rates (head per hour) Number...

Ideal strength of bcc molybdenum and niobium

NASA Astrophysics Data System (ADS)

Luo, Weidong; Roundy, D.; Cohen, Marvin L.; Morris, J. W.

2002-09-01

The behavior of bcc Mo and Nb under large strain was investigated using the ab initio pseudopotential density-functional method. We calculated the ideal shear strength for the {211}<111> and {011}<111> slip systems and the ideal tensile strength in the <100> direction, which are believed to provide the minimum shear and tensile strengths. As either material is sheared in either of the two systems, it evolves toward a stress-free tetragonal structure that defines a saddle point in the strain-energy surface. The inflection point on the path to this tetragonal ``saddle-point'' structure sets the ideal shear strength. When either material is strained in tension along <100>, it initially follows the tetragonal, ``Bain,'' path toward a stress-free fcc structure. However, before the strained crystal reaches fcc, its symmetry changes from tetragonal to orthorhombic; on continued strain it evolves toward the same tetragonal saddle point that is reached in shear. In Mo, the symmetry break occurs after the point of maximum tensile stress has been passed, so the ideal strength is associated with the fcc extremum as in W. However, a Nb crystal strained in <100> becomes orthorhombic at tensile stress below the ideal strength. The ideal tensile strength of Nb is associated with the tetragonal saddle point and is caused by failure in shear rather than tension. In dimensionless form, the ideal shear and tensile strengths of Mo (τ*=τm/G111=0.12, σ*=σm/E100=0.078) are essentially identical to those previously calculated for W. Nb is anomalous. Its dimensionless shear strength is unusually high, τ*=0.15, even though the saddle-point structure that causes it is similar to that in Mo and W, while its dimensionless tensile strength, σ*=0.079, is almost the same as that of Mo and W, even though the saddle-point structure is quite different.

Study of ATES thermal behavior using a steady flow model

NASA Astrophysics Data System (ADS)

Doughty, C.; Hellstroem, G.; Tsang, C. F.; Claesson, J.

1981-01-01

The thermal behavior of a single well aquifer thermal energy storage system in which buoyancy flow is neglected is studied. A dimensionless formulation of the energy transport equations for the aquifer system is presented, and the key dimensionless parameters are discussed. A simple numerical model is used to generate graphs showing the thermal behavior of the system as a function of these parameters. Some comparisons with field experiments are given to illustrate the use of the dimensionless groups and graphs.

Study of the influence of the parameters of an experiment on the simulation of pole figures of polycrystalline materials using electron microscopy

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

Antonova, A. O., E-mail: aoantonova@mail.ru; Savyolova, T. I.

2016-05-15

A two-dimensional mathematical model of a polycrystalline sample and an experiment on electron backscattering diffraction (EBSD) is considered. The measurement parameters are taken to be the scanning step and threshold grain-boundary angle. Discrete pole figures for materials with hexagonal symmetry have been calculated based on the results of the model experiment. Discrete and smoothed (by the kernel method) pole figures of the model sample and the samples in the model experiment are compared using homogeneity criterion χ{sup 2}, an estimate of the pole figure maximum and its coordinate, a deviation of the pole figures of the model in the experimentmore » from the sample in the space of L{sub 1} measurable functions, and the RP-criterion for estimating the pole figure errors. Is is shown that the problem of calculating pole figures is ill-posed and their determination with respect to measurement parameters is not reliable.« less

Theoretical Evaluation of the Maximum Work of Free-Piston Engine Generators

NASA Astrophysics Data System (ADS)

Kojima, Shinji

2017-01-01

Utilizing the adjoint equations that originate from the calculus of variations, we have calculated the maximum thermal efficiency that is theoretically attainable by free-piston engine generators considering the work loss due to friction and Joule heat. Based on the adjoint equations with seven dimensionless parameters, the trajectory of the piston, the histories of the electric current, the work done, and the two kinds of losses have been derived in analytic forms. Using these we have conducted parametric studies for the optimized Otto and Brayton cycles. The smallness of the pressure ratio of the Brayton cycle makes the net work done negative even when the duration of heat addition is optimized to give the maximum amount of heat addition. For the Otto cycle, the net work done is positive, and both types of losses relative to the gross work done become smaller with the larger compression ratio. Another remarkable feature of the optimized Brayton cycle is that the piston trajectory of the heat addition/disposal process is expressed by the same equation as that of an adiabatic process. The maximum thermal efficiency of any combination of isochoric and isobaric heat addition/disposal processes, such as the Sabathe cycle, may be deduced by applying the methods described here.

Performance analysis for minimally nonlinear irreversible refrigerators at finite cooling power

NASA Astrophysics Data System (ADS)

Long, Rui; Liu, Zhichun; Liu, Wei

2018-04-01

The coefficient of performance (COP) for general refrigerators at finite cooling power have been systematically researched through the minimally nonlinear irreversible model, and its lower and upper bounds in different operating regions have been proposed. Under the tight coupling conditions, we have calculated the universal COP bounds under the χ figure of merit in different operating regions. When the refrigerator operates in the region with lower external flux, we obtained the general bounds (0 < ε <(√{ 9 + 8εC } - 3) / 2) under the χ figure of merit. We have also calculated the universal bounds for maximum gain in COP under different operating regions to give a further insight into the COP gain with the cooling power away from the maximum one. When the refrigerator operates in the region located between maximum cooling power and maximum COP with lower external flux, the upper bound for COP and the lower bound for relative gain in COP present large values, compared to a relative small loss from the maximum cooling power. If the cooling power is the main objective, it is desirable to operate the refrigerator at a slightly lower cooling power than at the maximum one, where a small loss in the cooling power induces a much larger COP enhancement.

Quadrotor Intercept Trajectory Planning and Simulation

DTIC Science & Technology

2017-06-01

Figure 41. Results are grouped by geometry type and colored based on trajectory planner. Figure 41. Summary of Experimental Data Intercept Time...DISTRIBUTION CODE 13. ABSTRACT (maximum 200 words) Quadrotor drones pose a safety hazard when operated in or near controlled airspace. A hazardous...quadrotor could be intercepted and removed by another quadrotor. In this thesis, we seek to determine if optimal control methods outperform missile

F-76 Lubricity Improver Additive Evaluation

DTIC Science & Technology

2013-09-16

Figure 4. NCT differential water readings of 2x maximum dosage of Additive A .............................. 8 Figure 5. NCT differential water ...to compensate for the decrease in lubricity as ultra low sulfur fuels shift into focus while still retaining the fuel’s water separability traits...specification and fit-for-purpose testing, and several of these tests focused on the effects of the additives to the fuel’s water separation

Magnetic Stimulation and Epilepsy

DTIC Science & Technology

2013-10-14

the seizure-induced groups exhibited varying degrees of EEG activity reduction. Figure 2. The effects of TMS on penicillin-induced seizures...the EEG recording including (a) baseline (pre-penicillin injection), (b) 30-min post-penicillin injection (30min-PI), (c) 10-min post- TMS stimulation...stable conditions 55% faster, and the 5 pps TMS -treated group 78% faster. Figure 3. Maximum frequency relationships in EEG activity among the

Stress Intensity Factors of Semi-Circular Bend Specimens with Straight-Through and Chevron Notches

NASA Astrophysics Data System (ADS)

Ayatollahi, M. R.; Mahdavi, E.; Alborzi, M. J.; Obara, Y.

2016-04-01

Semi-circular bend specimen is one of the useful test specimens for determining fracture toughness of rock and geo-materials. Generally, in rock test specimens, initial cracks are produced in two shapes: straight-edge cracks and chevron notches. In this study, the minimum dimensionless stress intensity factors of semi-circular bend specimen (SCB) with straight-through and chevron notches are calculated. First, using finite element analysis, a suitable relation for the dimensionless stress intensity factor of SCB with straight-through crack is presented based on the normalized crack length and half-distance between supports. For evaluating the validity and accuracy of this relation, the obtained results are then compared with numerical and experimental results reported in the literature. Subsequently, by performing some experiments and also finite element analysis of the SCB specimen with chevron notch, the minimum dimensionless stress intensity factor of this specimen is obtained. Using the new equation for the dimensionless stress intensity factor of SCB with straight-through crack and an analytical method, i.e., Bluhm's slice synthesis method, the minimum (critical) dimensionless stress intensity factor of chevron notched semi-circular bend specimens is calculated. Good agreement is observed between the results of two mentioned methods.

Development and evaluation of a dimensionless mechanistic pan coating model for the prediction of coated tablet appearance.

PubMed

Niblett, Daniel; Porter, Stuart; Reynolds, Gavin; Morgan, Tomos; Greenamoyer, Jennifer; Hach, Ronald; Sido, Stephanie; Karan, Kapish; Gabbott, Ian

2017-08-07

A mathematical, mechanistic tablet film-coating model has been developed for pharmaceutical pan coating systems based on the mechanisms of atomisation, tablet bed movement and droplet drying with the main purpose of predicting tablet appearance quality. Two dimensionless quantities were used to characterise the product properties and operating parameters: the dimensionless Spray Flux (relating to area coverage of the spray droplets) and the Niblett Number (relating to the time available for drying of coating droplets). The Niblett Number is the ratio between the time a droplet needs to dry under given thermodynamic conditions and the time available for the droplet while on the surface of the tablet bed. The time available for drying on the tablet bed surface is critical for appearance quality. These two dimensionless quantities were used to select process parameters for a set of 22 coating experiments, performed over a wide range of multivariate process parameters. The dimensionless Regime Map created can be used to visualise the effect of interacting process parameters on overall tablet appearance quality and defects such as picking and logo bridging. Copyright © 2017 Elsevier B.V. All rights reserved.

Deformation of ferrofluid marbles in the presence of a permanent magnet.

PubMed

Nguyen, Nam-Trung

2013-11-12

This paper investigates the deformation of ferrofluid marbles in the presence of a permanent magnet. Ferrofluid marbles are formed using a water-based ferrofluid and 1 μm hydrophobic polytetrafluoride particles. A marble placed on a Teflon coated glass plate deforms under gravity. In the presence of a permanent magnet, the marble is further deformed with a larger contact area. The geometric parameters are normalized by the radius of an undistorted spherical marble. The paper first discusses a scaling relationship between the dimensionless radius of the contact area as well as the dimensionless height and the magnetic Bond number. The dimensionless contact radius is proportional to the fourth root of the magnetic bond number. The dimensionless height scales with the inverse square root of the magnetic Bond number. In the case of a moving marble dragged by a permanent magnet, the deformation is evaluated as the difference between advancing and receding curvatures of the top view. The dimensionless height and the contact diameter of the marble do not significantly depend on the speed or the capillary number. The scaling analysis and experimental data show that the deformation is proportional to the capillary number.

Gaussian beam profile shaping apparatus, method therefor and evaluation thereof

DOEpatents

Dickey, Fred M.; Holswade, Scott C.; Romero, Louis A.

1999-01-01

A method and apparatus maps a Gaussian beam into a beam with a uniform irradiance profile by exploiting the Fourier transform properties of lenses. A phase element imparts a design phase onto an input beam and the output optical field from a lens is then the Fourier transform of the input beam and the phase function from the phase element. The phase element is selected in accordance with a dimensionless parameter which is dependent upon the radius of the incoming beam, the desired spot shape, the focal length of the lens and the wavelength of the input beam. This dimensionless parameter can also be used to evaluate the quality of a system. In order to control the radius of the incoming beam, optics such as a telescope can be employed. The size of the target spot and the focal length can be altered by exchanging the transform lens, but the dimensionless parameter will remain the same. The quality of the system, and hence the value of the dimensionless parameter, can be altered by exchanging the phase element. The dimensionless parameter provides design guidance, system evaluation, and indication as to how to improve a given system.

Gaussian beam profile shaping apparatus, method therefore and evaluation thereof

DOEpatents

Dickey, F.M.; Holswade, S.C.; Romero, L.A.

1999-01-26

A method and apparatus maps a Gaussian beam into a beam with a uniform irradiance profile by exploiting the Fourier transform properties of lenses. A phase element imparts a design phase onto an input beam and the output optical field from a lens is then the Fourier transform of the input beam and the phase function from the phase element. The phase element is selected in accordance with a dimensionless parameter which is dependent upon the radius of the incoming beam, the desired spot shape, the focal length of the lens and the wavelength of the input beam. This dimensionless parameter can also be used to evaluate the quality of a system. In order to control the radius of the incoming beam, optics such as a telescope can be employed. The size of the target spot and the focal length can be altered by exchanging the transform lens, but the dimensionless parameter will remain the same. The quality of the system, and hence the value of the dimensionless parameter, can be altered by exchanging the phase element. The dimensionless parameter provides design guidance, system evaluation, and indication as to how to improve a given system. 27 figs.

Focusing of a dark hollow Gaussian electromagnetic beam in a magnetoplasma

NASA Astrophysics Data System (ADS)

Sodha, Mahendra Singh; Mishra, S. K.; Misra, Shikha

2009-12-01

This paper presents an analysis and subsequent discussion of the self focusing of a dark hollow Gaussian electromagnetic beam (HGB) in a magnetoplasma, considering ponderomotive and collisional nonlinearities. A paraxial-like approach, in which the relevant parameters are expanded in terms of radial distance from the maximum of the irradiance rather than that from the axis, has been adopted to analyze the propagation of the HGB. The nature of self focusing is highlighted through the critical curves as a plot of dimensionless radius versus power of the beam. The effect of the magnetic field and the nature of the nonlinearity on self focusing of various order HGBs has also been explored.

Natural convection in symmetrically heated vertical parallel plates with discrete heat sources

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

Manca, O.; Nardini, S.; Naso, V.

Laminar air natural convection in a symmetrically heated vertical channel with uniform flush-mounted discrete heat sources has been experimentally investigated. The effects of heated strips location and of their number are pointed out in terms of the maximum wall temperatures. A flow visualization in the entrance region of the channel was carried out and air temperatures and velocities in two cross sections have been measured. Dimensionless local heat transfer coefficients have been evaluated and monomial correlations among relevant parameters have bee derived in the local Rayleigh number range 10--10{sup 6}. Channel Nusselt number has been correlated in a polynomial formmore » in terms of channel Rayleigh number.« less

Ubiquity of Benford's law and emergence of the reciprocal distribution

DOE PAGES

Friar, James Lewis; Goldman, Terrance J.; Pérez-Mercader, J.

2016-04-07

In this paper, we apply the Law of Total Probability to the construction of scale-invariant probability distribution functions (pdf's), and require that probability measures be dimensionless and unitless under a continuous change of scales. If the scale-change distribution function is scale invariant then the constructed distribution will also be scale invariant. Repeated application of this construction on an arbitrary set of (normalizable) pdf's results again in scale-invariant distributions. The invariant function of this procedure is given uniquely by the reciprocal distribution, suggesting a kind of universality. Finally, we separately demonstrate that the reciprocal distribution results uniquely from requiring maximum entropymore » for size-class distributions with uniform bin sizes.« less

Department of Defense Weapon System Acquisition Policy: A System Dynamics Model and Analysis.

DTIC Science & Technology

1982-09-01

dimensionless) PRPRD = Perceived Pressure for R&D (dimensionless) PU - Programs in Progress (programs) RPRD - Raw Pressure for R&D (dimensionless) TDPP - Time...ECAP) TH9 Pressure Ra Pressure_.- for Acquisition ( TDPP ) TH25 4for Acquisition (DPFAO) TH22D (DPPFAO) TH21 US Intelligence \\ - 7 Delay Time / efense...DIBP, DPPFAQ. K) TH22 A CPPFAG.K=DLINF3(RPFAG.KTCPP) TH23 A CPFAQ.K=MAX (DIBPCPPFAQ.K) TH24 C TDPP =12 TH25 C TCPP-24 TH26 CPFAQ Congressional Pressure

Dimensionless Analysis and Mathematical Modeling of Electromagnetic Levitation (EML) of Metals

NASA Astrophysics Data System (ADS)

Gao, Lei; Shi, Zhe; Li, Donghui; Yang, Yindong; Zhang, Guifang; McLean, Alexander; Chattopadhyay, Kinnor

2016-02-01

Electromagnetic levitation (EML), a contactless metal melting method, can be used to produce ultra-pure metals and alloys. In the EML process, the levitation force exerted on the droplet is of paramount importance and is affected by many parameters. In this paper, the relationship between levitation force and parameters affecting the levitation process were investigated by dimensionless analysis. The general formula developed by dimensionless analysis was tested and evaluated by numerical modeling. This technique can be employed to design levitation systems for a variety of materials.

Design Manual for Microgravity Two-Phase Flow and Heat Transfer

DTIC Science & Technology

1989-10-01

simultaneous solution of two equations. One equation is a dimensionless two-.nhase momentum equation for a separated flow and the other is a dimensionless...created by the flow of the gas over a wave (the Bernoulli effect) is sufficient to lift the waves in a stratified flow to the top of the pipe. A... momentum equation to determine a dimensionless parameter related to the liquid flow rate: 14 [(Ug*Dg*)1(1J*) 2[ [ [ + - 4Y X 2 =9 k (1-16) [U *D1*] -n

14 CFR 23.841 - Pressurized cabins.

Code of Federal Regulations, 2012 CFR

2012-01-01

... descent is made by an approved emergency procedure. A 17-second flight crew recognition and reaction time... altitude-time history shown in Figure 1 of this section. (ii) Maximum cabin altitude is limited to 30,000 feet. If cabin altitude exceeds 25,000 feet, the maximum time the cabin altitude may exceed 25,000 feet...

40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

Code of Federal Regulations, 2011 CFR

2011-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE... procedures of 40 CFR part 1065, based on the manufacturer's design and production specifications for the... swept volume from the design specifications for the cylinders using enough significant figures to allow...

40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

Code of Federal Regulations, 2010 CFR

2010-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE... procedures of 40 CFR part 1065, based on the manufacturer's design and production specifications for the... swept volume from the design specifications for the cylinders using enough significant figures to allow...

40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

Code of Federal Regulations, 2014 CFR

2014-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE... procedures of 40 CFR part 1065, based on the manufacturer's design and production specifications for the... swept volume from the design specifications for the cylinders using enough significant figures to allow...

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

DTIC Science & Technology

2014-06-01

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

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

Brown, C. S.; Zhang, Hongbin

Uncertainty quantification and sensitivity analysis are important for nuclear reactor safety design and analysis. A 2x2 fuel assembly core design was developed and simulated by the Virtual Environment for Reactor Applications, Core Simulator (VERA-CS) coupled neutronics and thermal-hydraulics code under development by the Consortium for Advanced Simulation of Light Water Reactors (CASL). An approach to uncertainty quantification and sensitivity analysis with VERA-CS was developed and a new toolkit was created to perform uncertainty quantification and sensitivity analysis with fourteen uncertain input parameters. Furthermore, the minimum departure from nucleate boiling ratio (MDNBR), maximum fuel center-line temperature, and maximum outer clad surfacemore » temperature were chosen as the selected figures of merit. Pearson, Spearman, and partial correlation coefficients were considered for all of the figures of merit in sensitivity analysis and coolant inlet temperature was consistently the most influential parameter. We used parameters as inputs to the critical heat flux calculation with the W-3 correlation were shown to be the most influential on the MDNBR, maximum fuel center-line temperature, and maximum outer clad surface temperature.« less

Uncertainty quantification and sensitivity analysis with CASL Core Simulator VERA-CS

DOE PAGES

Brown, C. S.; Zhang, Hongbin

2016-05-24

Uncertainty quantification and sensitivity analysis are important for nuclear reactor safety design and analysis. A 2x2 fuel assembly core design was developed and simulated by the Virtual Environment for Reactor Applications, Core Simulator (VERA-CS) coupled neutronics and thermal-hydraulics code under development by the Consortium for Advanced Simulation of Light Water Reactors (CASL). An approach to uncertainty quantification and sensitivity analysis with VERA-CS was developed and a new toolkit was created to perform uncertainty quantification and sensitivity analysis with fourteen uncertain input parameters. Furthermore, the minimum departure from nucleate boiling ratio (MDNBR), maximum fuel center-line temperature, and maximum outer clad surfacemore » temperature were chosen as the selected figures of merit. Pearson, Spearman, and partial correlation coefficients were considered for all of the figures of merit in sensitivity analysis and coolant inlet temperature was consistently the most influential parameter. We used parameters as inputs to the critical heat flux calculation with the W-3 correlation were shown to be the most influential on the MDNBR, maximum fuel center-line temperature, and maximum outer clad surface temperature.« less

Speedometer app videos to provide real-world velocity-time graph data 1: rail travel

NASA Astrophysics Data System (ADS)

King, Julien

2018-03-01

The use of modern rail travel as a source of real-life velocity-time data to aid in the teaching of velocity and acceleration is discussed. A technique for using GPS speedometer apps to produce videos of velocity and time figures during a rail journey is described. The technique is applied to a UK rail journey, demonstrating how students can use its results to produce a velocity-time graph from which acceleration and deceleration figures can be calculated. These are compared with theoretical maximum figures, calculated from the train’s technical specification.

A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe-Mn-C system exhibiting multicomposition sets.

PubMed

Nakano, Jinichiro

2013-02-01

The thermodynamic properties of the Fe-Mn-C system were investigated by using an analytical model constructed by a CALPHAD approach. The stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T 0 , independent of the composition and temperature when other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T 0 . The driving force for the fcc to hcp transition, defined as a dimensionless value -d G m /( RT ), was determined in the presence of Fe-rich and Mn-rich composition sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the compositions studied. The results obtained revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed.

Spontaneous pituitary tumors in the Wistar/Furth/Ico rat strain. An animal model of human prolactin adenoma.

PubMed Central

Trouillas, J.; Girod, C.; Claustrat, B.; Curé, M.; Dubois, M. P.

1982-01-01

Twenty-three spontaneous pituitary tumors in 58 rats of Wistar/Furth/Ico strain were studied. The incidence is 38% in rats older than 10 months; it rises with age, with a maximum at 28-32 months (68.7%) and is higher in females (71.4%) than in males (35%) over 17 months. Light-microscopic and immunocytochemical studies revealed 20 prolactinomas in 19 rats (19/58, 32.7%) and 3 spongiocytic nonimmunostaining adenomas (3/58, 5.2%). The prolactinoma is often hemorrhagic. The cells, often arranged in sheets and agranular, are mostly positive with anti-rat prolactin (rPRL) serum. They have few polymorph granules and a well-developed rough endoplasmic reticulum. In the spongiocytic adenoma, the cells are arranged in cords. Their cytoplasm is slightly vacuolated. In prolactinoma-bearing rats, the mean plasma PRL value was 213 +/- 72.5 microgram/1 (SEM) (N = 15 +/- 1.8 microgram/1 [SEM]). A linear correlation was found between the logarithm of the tumoral pituitary weight or of the tumor size and the logarithm of the prolactinemia. Because of the analogies between these rat prolactinomas and 57 human prolactinomas, the Wistar/Furth/Ico rat strain is considered as a good animal model. Images Figure 14 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 12 Figure 13 PMID:7124908

Searching fundamental information in ordinary differential equations. Nondimensionalization technique.

PubMed

Sánchez Pérez, J F; Conesa, M; Alhama, I; Alhama, F; Cánovas, M

2017-01-01

Classical dimensional analysis and nondimensionalization are assumed to be two similar approaches in the search for dimensionless groups. Both techniques, simplify the study of many problems. The first approach does not need to know the mathematical model, being sufficient a deep understanding of the physical phenomenon involved, while the second one begins with the governing equations and reduces them to their dimensionless form by simple mathematical manipulations. In this work, a formal protocol is proposed for applying the nondimensionalization process to ordinary differential equations, linear or not, leading to dimensionless normalized equations from which the resulting dimensionless groups have two inherent properties: In one hand, they are physically interpreted as balances between counteracting quantities in the problem, and on the other hand, they are of the order of magnitude unity. The solutions provided by nondimensionalization are more precise in every case than those from dimensional analysis, as it is illustrated by the applications studied in this work.

Detecting binary neutron star systems with spin in advanced gravitational-wave detectors

NASA Astrophysics Data System (ADS)

Brown, Duncan A.; Harry, Ian; Lundgren, Andrew; Nitz, Alexander H.

2012-10-01

The detection of gravitational waves from binary neutron stars is a major goal of the gravitational-wave observatories Advanced LIGO and Advanced Virgo. Previous searches for binary neutron stars with LIGO and Virgo neglected the component stars’ angular momentum (spin). We demonstrate that neglecting spin in matched-filter searches causes advanced detectors to lose more than 3% of the possible signal-to-noise ratio for 59% (6%) of sources, assuming that neutron star dimensionless spins, cJ/GM2, are uniformly distributed with magnitudes between 0 and 0.4 (0.05) and that the neutron stars have isotropically distributed spin orientations. We present a new method for constructing template banks for gravitational-wave searches for systems with spin. We present a new metric in a parameter space in which the template placement metric is globally flat. This new method can create template banks of signals with nonzero spins that are (anti-)aligned with the orbital angular momentum. We show that this search loses more than 3% of the maximum signal-to-noise for only 9% (0.2%) of binary neutron star sources with dimensionless spins between 0 and 0.4 (0.05) and isotropic spin orientations. Use of this template bank will prevent selection bias in gravitational-wave searches and allow a more accurate exploration of the distribution of spins in binary neutron stars.

Design of a Slowed-Rotor Compound Helicopter for Future Joint Service Missions

DTIC Science & Technology

2010-01-01

achieves a 208kt top speed at engine MCP and 11,000ft/ISA while having 216hp/ton installed power, based on engine MRP and MTOW. Figure 33...Intermediate rated power ISA International Standard Atmosphere MCP Maximum continuous power MRP Maximum rated power MTOW Maximum Takeoff Weight NDARC...NASA Design and Analysis of Rotorcraft SFC Specific fuel consumption SRC Slowed-Rotor Compound Symbols σ Rotor solidity (geometric) CD Drag

Ripening-Related Gene from Avocado Fruit 1

PubMed Central

McGarvey, Douglas J.; Sirevåg, Reidun; Christoffersen, Rolf E.

1992-01-01

Fruit ripening involves a series of changes in gene expression regulated by the phytohormone ethylene. AVOe3, a ripening-related gene in avocado fruit (Persea americana Mill. cv Hass), was characterized with regard to its ethylene-regulated expression. The AVOe3 mRNA and immunopositive protein were induced in mature fruit within 12 hours of propylene treatment. The AVOe3 mRNA levels reached a maximum 1 to 2 days before the ethylene climacteric, whereas the immunopositive protein continued to accumulate. RNA selected by the pAVOe3 cDNA clone encoded a polypeptide with molecular mass of 34 kilodaltons, corresponding to the molecular mass of the AVOe3 protein determined by immunoblots. The protein was soluble, remaining in solution at 100,000 gravity and eluted as a monomer on gel filtration. Because of its pattern of induction and relationship to an ethylene-related gene of tomato, the possible involvement of AVOe3 in ethylene biosynthesis is discussed. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6 PMID:16668676

High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell

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

Baker, Jason; Kumar, Ravhi S.; Park, Changyong

2016-01-01

A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid–solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric materialmore » PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. Furthermore, this new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.« less

3D printing of shape-conformable thermoelectric materials using all-inorganic Bi2Te3-based inks

NASA Astrophysics Data System (ADS)

Kim, Fredrick; Kwon, Beomjin; Eom, Youngho; Lee, Ji Eun; Park, Sangmin; Jo, Seungki; Park, Sung Hoon; Kim, Bong-Seo; Im, Hye Jin; Lee, Min Ho; Min, Tae Sik; Kim, Kyung Tae; Chae, Han Gi; King, William P.; Son, Jae Sung

2018-04-01

Thermoelectric energy conversion offers a unique solution for generating electricity from waste heat. However, despite recent improvements in the efficiency of thermoelectric materials, the widespread application of thermoelectric generators has been hampered by challenges in fabricating thermoelectric materials with appropriate dimensions to perfectly fit heat sources. Herein, we report an extrusion-based three-dimensional printing method to produce thermoelectric materials with geometries suitable for heat sources. All-inorganic viscoelastic inks were synthesized using Sb2Te3 chalcogenidometallate ions as inorganic binders for Bi2Te3-based particles. Three-dimensional printed materials with various geometries showed homogenous thermoelectric properties, and their dimensionless figure-of-merit values of 0.9 (p-type) and 0.6 (n-type) were comparable to the bulk values. Conformal cylindrical thermoelectric generators made of 3D-printed half rings mounted on an alumina pipe were studied both experimentally and computationally. Simulations show that the power output of the conformal, shape-optimized generator is higher than that of conventional planar generators.

High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell.

PubMed

Baker, Jason; Kumar, Ravhi; Park, Changyong; Kenney-Benson, Curtis; Cornelius, Andrew; Velisavljevic, Nenad

2016-11-01

A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid-solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric material PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. This new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.

FP-LAPW calculations of the elastic, electronic and thermoelectric properties of the filled skutterudite CeRu{sub 4}Sb{sub 12}

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

Shankar, A., E-mail: amitshan2009@gmail.com; Rai, D.P.; Chettri, Sandeep

2016-08-15

We have investigated the electronic structure, elastic and thermoelectric properties of the filled skutterudite CeRu{sub 4}Sb{sub 12} using the density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) approach is used to perform the calculations presented here. The electronic structure calculation suggests an indirect band gap semiconducting nature of the material with energy band gap of 0.08 eV. The analysis of the elastic constants at relaxed positions reveals the ductile nature of the sample material with covalent contribution in the inter-atomic bonding. The narrow band gap semiconductingmore » nature with high value of Seebeck coefficient suggests the possibility of the thermoelectric application of the material. The analysis of the thermal transport properties confirms the result obtained from the energy band structure of the material with high thermopower and dimensionless figure of merit 0.19 at room temperature.« less

Early-Time Solution of the Horizontal Unconfined Aquifer in the Buildup Phase

NASA Astrophysics Data System (ADS)

Gravanis, Elias; Akylas, Evangelos

2017-10-01

We derive the early-time solution of the Boussinesq equation for the horizontal unconfined aquifer in the buildup phase under constant recharge and zero inflow. The solution is expressed as a power series of a suitable similarity variable, which is constructed so that to satisfy the boundary conditions at both ends of the aquifer, that is, it is a polynomial approximation of the exact solution. The series turns out to be asymptotic and it is regularized by resummation techniques that are used to define divergent series. The outflow rate in this regime is linear in time, and the (dimensionless) coefficient is calculated to eight significant figures. The local error of the series is quantified by its deviation from satisfying the self-similar Boussinesq equation at every point. The local error turns out to be everywhere positive, hence, so is the integrated error, which in turn quantifies the degree of convergence of the series to the exact solution.

Contrastive thermoelectric properties of strained SnSe crystals from the first-principles calculations

NASA Astrophysics Data System (ADS)

Tang, Yu; Cheng, Feng; Li, Decong; Deng, Shuping; Chen, Zhong; Sun, Luqi; Liu, Wenting; Shen, Lanxian; Deng, Shukang

2018-06-01

SnSe is a promising thermoelectric material with a record high dimensionless figure of merit ZT at high temperature ∼923 K. However, the ZT values for low-Temperature Pnma phase SnSe are just 0.1-0.9. Here, we use First-principle combine with Boltzmann transport theory methods to study the effect of tensile and compressible strain on the thermoelectric transport properties. The power factor of SnSe with -4% strain have a large boost along b and c directions of 7.7 and 3.9 μW cm-1 K-2, respectively, which are 2.5 and 2 times as large as those pristine SnSe. The charge density distributions reveal that the overlap of wave function has significant change due to the changed bond lengths and bond angles under different strain, which lead to the change of band gap and band dispersion. Our work provides a new effective strategy to enhance the thermoelectric properties of materials.

Thermoelectric Properties of Ca1−xGdxMnO3−δ (0.00, 0.02, and 0.05) Systems

PubMed Central

Bhaskar, Ankam; Liu, Chia-Jyi; Yuan, J. J.

2012-01-01

Polycrystalline samples of Ca1−xGdxMnO3−δ (x = 0.00, 0.02, and 0.05) have been studied by X-ray diffraction (XRD), electrical resistivity (ρ), thermoelectric power (S), and thermal conductivity (κ). All the samples were single phase with an orthorhombic structure. The Seebeck coefficient of all the samples was negative, indicating that the predominant carriers are electrons over the entire temperature range. The iodometric titration measurements indicate that the electrical resistivity of Ca1−xGdxMnO3−δ correlated well with the average valence of Mnv+ and oxygen deficiency. Among the doped samples, Ca0.98Gd0.02MnO3−δ had the highest dimensionless figure of merit 0.018 at 300 K, representing an improvement of about 125% with respect to the undoped GaMnO3−δ sample at the same temperature. PMID:22997488

Control of p-type and n-type thermoelectric properties of bismuth telluride thin films by combinatorial sputter coating technology

NASA Astrophysics Data System (ADS)

Goto, Masahiro; Sasaki, Michiko; Xu, Yibin; Zhan, Tianzhuo; Isoda, Yukihiro; Shinohara, Yoshikazu

2017-06-01

p- and n-type bismuth telluride thin films have been synthesized by using a combinatorial sputter coating system (COSCOS). The crystal structure and crystal preferred orientation of the thin films were changed by controlling the coating condition of the radio frequency (RF) power during the sputter coating. As a result, the p- and n-type films and their dimensionless figure of merit (ZT) were optimized by the technique. The properties of the thin films such as the crystal structure, crystal preferred orientation, material composition and surface morphology were analyzed by X-ray diffraction, energy-dispersive X-ray spectroscopy and atomic force microscopy. Also, the thermoelectric properties of the Seebeck coefficient, electrical conductivity and thermal conductivity were measured. ZT for n- and p-type bismuth telluride thin films was found to be 0.27 and 0.40 at RF powers of 90 and 120 W, respectively. The proposed technology can be used to fabricate thermoelectric p-n modules of bismuth telluride without any doping process.

Multiscale microstructures and improved thermoelectric performance of Mg2(Si0.4Sn0.6)Sbx solid solutions

NASA Astrophysics Data System (ADS)

Zhang, Xin; Liu, Hongliang; Li, Songhao; Zhang, Feipeng; Lu, Qingmei; Li, Jingfeng

2014-03-01

A series of Sb-doped Mg2(Si0.4Sn0.6)Sbx (0 ≤ x ≤ 0.025) solid solutions were prepared by an induction melting, Melt Spinning (MS) and Spark Plasma Sintering (SPS) method, namely the non-equilibrium technique MS-SPS, using bulks of Magnesium, Silicon, Tin, and Antimony as raw materials. The non-equilibrium technique generates the unique multiscale microstructures of samples containing micronscale grains and nanoscale precipitates, the multiscale microstructures remarkably make the lattice thermal conductivities decreased, particularly for samples with the nanoscale precipitates having the size of 10-20 nm. Meanwhile, Sb-doping greatly increased the electrical performance of samples. Consequently, the Sb-doping combined with the multiscale microstructures strategy remarkably improves the overall thermoelectric (TE) performance of Sb doped samples, and a high dimensionless figure of merit (ZT) value of up to 1.25 at 723 K is obtained with Mg2(Si0.4Sn0.6)Sb0.02 sample in a relatively wide temperature range.

Missile Defense in the 21st Century Acquisition Environment: Exploring a BMD-Capable LCS Mission Package

DTIC Science & Technology

2013-09-01

75 Figure 25: Swing Weight Analysis....................................................................................76 Figure 26...AN/SPY-1D radar “can track golf ball-sized targets at ranges in excess of 165 kilometers” (Robinson, 2004). Given the radar cross section (RCS) of a... golf ball (calculated as a simple metallic sphere), it was determined that this would correspond to a maximum detection range beyond the Launch

I-Love relations for irrotational stars

NASA Astrophysics Data System (ADS)

Delsate, Térence

2015-12-01

In this short paper, we investigate the existence of universal relations between the gravimagnetic Love number of irrotational stars and the dimensionless moment of inertia. These Love numbers take into account the internal motion of the fluid, while the star is globally irrotational. The goal is to extend the so-called I-Love-Q relations—providing a strong correlation between the gravitoelectric Love number, the dimensionless moment of inertia and the dimensionless rotation-induced quadrupole—to the gravitomagnetic sector, where internal motion is taken into account. As a byproduct, we present for the first time this new gravitomagnetic Love number for realistic equations of state.

Critical capillary channel flow

NASA Astrophysics Data System (ADS)

Grah, Aleksander; Klatte, Jörg; Dreyer, Michael E.

The main subject are numerical studies on capillary channel flow, based on results of the sounding rocket experiments TEXUS 41/42. The flow through a capillary channel is established by a gear pump at the outlet. The channel, consists of two parallel glass plates with a width of 25 mm, a gap of 10 mm and a length of 12 mm. The meniscus of a compensation tube maintains a constant system pressure. Steady and dynamic pressure effects in the system force the surfaces to bend inwards. A maximum flow rate is achieved when the free surface collapses and gas ingestion occurs at the outlet. This critical flow rate depends on the channel geometry, the flow regime and the liquid properties. The aim of the experiments is the determination of the free surface shape and to find the maximum flow rate. In order to study the unsteady liquid loop behaviour, a dimensionless transient model was developed. It is based on the unsteady Bernoulli equation, the unsteady continuity equation and geometrical conditions for the surface curvature and the flow cross-section. The pressure is related to the curvature of the free liquid surface by the dimensionless Gauss-Laplace equation with two principal radii. The experimental and evaluated contour data shows good agreement for a sequence of transient flow rate perturbations. The surface oscillation frequencies and amplitudes can be predicted with quite high accuracy. The dynamic of the pump is defined by the increase of the flow rate in a time period. To study the unsteady system behavior in the "worst case", we use a perturbations related to the natural frequency of the oscillating liquid. In the case of steady flow at maximum flow rate, when the "choking" effect occurs, the surfaces collapse and cause gas ingestion into the channel. This effect is related to the Speed Index. At the critical flow rate the Speed Index reaches the value Sca = 1, in analogy to the Mach Number. Unsteady choking does not necessarily cause surface collapse. We show, that temporarily Speed Index values exceeding One may be achieved for a perfectly stable supercritical dynamic flow. As a supercritical criterion for the dynamic free surface stability we define a Dynamic Index D considering the local capillary pressure and the convective pressure, which is a function of the local velocity. The Dynamic Index is below One for stable flow while D = 1 indicates surface collapse. This studies result in a stability diagram, which defines the limits of flow dynamics and the maximum unsteady flow rate. It may serve as a road map for open capillary channel flow control.

Prediction of Hot Tearing Using a Dimensionless Niyama Criterion

NASA Astrophysics Data System (ADS)

Monroe, Charles; Beckermann, Christoph

2014-08-01

The dimensionless form of the well-known Niyama criterion is extended to include the effect of applied strain. Under applied tensile strain, the pressure drop in the mushy zone is enhanced and pores grow beyond typical shrinkage porosity without deformation. This porosity growth can be expected to align perpendicular to the applied strain and to contribute to hot tearing. A model to capture this coupled effect of solidification shrinkage and applied strain on the mushy zone is derived. The dimensionless Niyama criterion can be used to determine the critical liquid fraction value below which porosity forms. This critical value is a function of alloy properties, solidification conditions, and strain rate. Once a dimensionless Niyama criterion value is obtained from thermal and mechanical simulation results, the corresponding shrinkage and deformation pore volume fractions can be calculated. The novelty of the proposed method lies in using the critical liquid fraction at the critical pressure drop within the mushy zone to determine the onset of hot tearing. The magnitude of pore growth due to shrinkage and deformation is plotted as a function of the dimensionless Niyama criterion for an Al-Cu alloy as an example. Furthermore, a typical hot tear "lambda"-shaped curve showing deformation pore volume as a function of alloy content is produced for two Niyama criterion values.

Theoretical investigation of the upper and lower bounds of a generalized dimensionless bearing health indicator

NASA Astrophysics Data System (ADS)

Wang, Dong; Tsui, Kwok-Leung

2018-01-01

Bearing-supported shafts are widely used in various machines. Due to harsh working environments, bearing performance degrades over time. To prevent unexpected bearing failures and accidents, bearing performance degradation assessment becomes an emerging topic in recent years. Bearing performance degradation assessment aims to evaluate the current health condition of a bearing through a bearing health indicator. In the past years, many signal processing and data mining based methods were proposed to construct bearing health indicators. However, the upper and lower bounds of these bearing health indicators were not theoretically calculated and they strongly depended on historical bearing data including normal and failure data. Besides, most health indicators are dimensional, which connotes that these health indicators are prone to be affected by varying operating conditions, such as varying speeds and loads. In this paper, based on the principle of squared envelope analysis, we focus on theoretical investigation of bearing performance degradation assessment in the case of additive Gaussian noises, including distribution establishment of squared envelope, construction of a generalized dimensionless bearing health indicator, and mathematical calculation of the upper and lower bounds of the generalized dimensionless bearing health indicator. Then, analyses of simulated and real bearing run to failure data are used as two case studies to illustrate how the generalized dimensionless health indicator works and demonstrate its effectiveness in bearing performance degradation assessment. Results show that squared envelope follows a noncentral chi-square distribution and the upper and lower bounds of the generalized dimensionless health indicator can be mathematically established. Moreover, the generalized dimensionless health indicator is sensitive to an incipient bearing defect in the process of bearing performance degradation.

Revealing a quantum feature of dimensionless uncertainty in linear and quadratic potentials by changing potential intervals

NASA Astrophysics Data System (ADS)

Kheiri, R.

2016-09-01

As an undergraduate exercise, in an article (2012 Am. J. Phys. 80 780-14), quantum and classical uncertainties for dimensionless variables of position and momentum were evaluated in three potentials: infinite well, bouncing ball, and harmonic oscillator. While original quantum uncertainty products depend on {{\\hslash }} and the number of states (n), a dimensionless approach makes the comparison between quantum uncertainty and classical dispersion possible by excluding {{\\hslash }}. But the question is whether the uncertainty still remains dependent on quantum number n. In the above-mentioned article, there lies this contrast; on the one hand, the dimensionless quantum uncertainty of the potential box approaches classical dispersion only in the limit of large quantum numbers (n\\to ∞ )—consistent with the correspondence principle. On the other hand, similar evaluations for bouncing ball and harmonic oscillator potentials are equal to their classical counterparts independent of n. This equality may hide the quantum feature of low energy levels. In the current study, we change the potential intervals in order to make them symmetric for the linear potential and non-symmetric for the quadratic potential. As a result, it is shown in this paper that the dimensionless quantum uncertainty of these potentials in the new potential intervals is expressed in terms of quantum number n. In other words, the uncertainty requires the correspondence principle in order to approach the classical limit. Therefore, it can be concluded that the dimensionless analysis, as a useful pedagogical method, does not take away the quantum feature of the n-dependence of quantum uncertainty in general. Moreover, our numerical calculations include the higher powers of the position for the potentials.

Extreme Wave Statistics within the Mouth of the Columbia River

DTIC Science & Technology

2014-12-01

nearshore coastal environment. Because of his guidance, I was able to make the most of this challenging learning experience. I spent countless hours...the current field induces a refractive caustic along the principal current axis. Caustic focusing causes an increase of wave height to its maximum...the largest waves are found upstream of the caustic area (around x/Lo=25 in Figure 6). 10 Figure 6. Transformation of 0.1-Hz swell

Integrating Experimentation, Modeling, and Visualization Through Full-Field Methods (Preprint)

DTIC Science & Technology

2009-04-01

including fatigue, fatigue-crack growth, tribology , fracture toughness, Figure 1. Full-field, in-plane, maximum principal stress in a fully lamellar...studied, and 3) the correlation between 1) and 2). The emphases in this paper will be on the first and second areas, but the need for work in the third ...problems, concentrating on displacements rather than strains is appropriate for this work. The top figure shows the overall displacements, after rigid- body

CT Demonstration of Caput Medusae

ERIC Educational Resources Information Center

Weber, Edward C.; Vilensky, Joel A.

2009-01-01

Maximum intensity and volume rendered CT displays of caput medusae are provided to demonstrate both the anatomy and physiology of this portosystemic shunt associated with portal hypertension. (Contains 2 figures.)

The Shubnikov-de Haas effect and thermoelectric properties of Tl-doped Sb{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3}

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

Kulbachinskii, V. A., E-mail: kulb@mig.phys.msu.ru; Kudryashov, A. A.; Kytin, V. G.

2015-06-15

The influence of doping with Tl on the Shubnikov-de Haas effect at T = 4.2 K in magnetic fields up to 38 T in p-Sb{sub 2−x}Tl{sub x}Te{sub 3} (x = 0, 0.005, 0.015, and 0.05) and n-Bi{sub 2−x}Tl{sub x}Se{sub 3} (x = 0, 0.01, 0.02, 0.04, and 0.06) single crystals is investigated. Extreme cross-sections of the Fermi surface in both materials decrease upon doping with Tl: the hole concentration decreases in Sb{sub 2−x}Tl{sub x}Te{sub 3} due to the donor effect of Tl and the electron concentration in n-Bi{sub 2−x}Tl{sub x}Se{sub 3} decreases due to the acceptor effect of Tl. Themore » temperature dependences of the Seebeck coefficient, electrical conductivity, thermal conductivity, and dimensionless thermoelectric figure of merit in a temperature range of 77–300 K are measured. The thermal conductivity and electrical conductivity decrease upon doping with Tl both in p-Sb{sub 2−x}Tl{sub x}Te{sub 3} and in n-Bi{sub 2−x}Tl{sub x}Se{sub 3}. The Seebeck coefficient increases in all compositions upon an increase in doping over the entire measured temperature range. The thermoelectric figure of merit increases upon doping with Tl.« less

Estimating flood hydrographs for urban basins in North Carolina

USGS Publications Warehouse

Mason, R.R.; Bales, J.D.

1996-01-01

A dimensionless hydrograph for North Carolina was developed from data collected in 29 urban and urbanizing basins in the State. The dimen- sionless hydrograph can be used with an estimate of peak flow and basin lagtime to synthesize a design flood hydrograph for urban basins in North Carolina. Peak flows can be estimated from a number of avail- able techniques; a procedure for estimating basin lagtime from main channel length, stream slope, and percentage of impervious area was developed from data collected at 50 sites and is presented in this report. The North Carolina dimensionless hydrograph provides satis- factory predictions of flood hydrographs in all regions of the State except for basins in or near Asheville where the method overestimated 11 of 12 measured hydrographs. A previously developed dimensionless hydrograph for urban basins in the Piedmont and upper Coastal Plain of South Carolina provides better flood-hydrograph predictions for the Asheville basins and has a standard error of 21 percent as compared to 41 percent for the North Carolina dimensionless hydrograph.

Stoichiometric network analysis and associated dimensionless kinetic equations. Application to a model of the Bray-Liebhafsky reaction.

PubMed

Schmitz, Guy; Kolar-Anić, Ljiljana Z; Anić, Slobodan R; Cupić, Zeljko D

2008-12-25

The stoichiometric network analysis (SNA) introduced by B. L. Clarke is applied to a simplified model of the complex oscillating Bray-Liebhafsky reaction under batch conditions, which was not examined by this method earlier. This powerful method for the analysis of steady-states stability is also used to transform the classical differential equations into dimensionless equations. This transformation is easy and leads to a form of the equations combining the advantages of classical dimensionless equations with the advantages of the SNA. The used dimensionless parameters have orders of magnitude given by the experimental information about concentrations and currents. This simplifies greatly the study of the slow manifold and shows which parameters are essential for controlling its shape and consequently have an important influence on the trajectories. The effectiveness of these equations is illustrated on two examples: the study of the bifurcations points and a simple sensitivity analysis, different from the classical one, more based on the chemistry of the studied system.

Specimen size and geometry effects on fracture toughness of Al2O3 measured with short rod and short bar chevron-notch specimens

NASA Technical Reports Server (NTRS)

Shannon, J. L., Jr.; Munz, D. G.

1983-01-01

Plane strain fracture toughness measurements were made on Al2O3 using short rod and short bar chevron notch specimens previously calibrated by the authors for their dimensionless stress intensity factor coefficients. The measured toughness varied systematically with variations in specimen size, proportions, and chevron notch angle apparently due to their influence on the amount of crack extension to maximum load (the measurement point). The toughness variations are explained in terms of a suspected rising R curve for the material tested, along with a discussion of an unavoidable imprecision in the calculation of K sub Ic for materials with rising R curves when tested with chevron notch specimens.

Analytical model of ground-state lasing phenomenon in broadband semiconductor quantum dot lasers

NASA Astrophysics Data System (ADS)

Korenev, Vladimir V.; Savelyev, Artem V.; Zhukov, Alexey E.; Omelchenko, Alexander V.; Maximov, Mikhail V.

2013-05-01

We introduce an analytical approach to the description of broadband lasing spectra of semiconductor quantum dot lasers emitting via ground-state optical transitions of quantum dots. The explicit analytical expressions describing the shape and the width of lasing spectra as well as their temperature and injection current dependences are obtained in the case of low homogeneous broadening. It is shown that in this case these dependences are determined by only two dimensionless parameters, which are the dispersion of the distribution of QDs over the energy normalized to the temperature and loss-to-maximum gain ratio. The possibility of optimization of laser's active region size and structure by using the intentionally introduced disorder is also carefully considered.

Experimental investigation of the wake behind a rotating sphere

NASA Astrophysics Data System (ADS)

Skarysz, M.; Rokicki, J.; Goujon-Durand, S.; Wesfreid, J. E.

2018-01-01

The wake behind a sphere, rotating about an axis aligned with the streamwise direction, has been experimentally investigated in a low-velocity water tunnel using laser-induced fluorescence visualizations and particle image velocimetry measurements. The measurements focused on the evolution of the flow regimes that appear depending on two control parameters: the Reynolds number Re and the dimensionless rotation or swirl rate Ω , which is the ratio of the maximum azimuthal velocity of the body to the free-stream velocity. In the present investigation, we cover the range of Re smaller than 400 and Ω from 0 and 4. Different wakes regimes such as an axisymmetric flow, a low helical state, and a high helical mode are represented in the (Re, Ω ) parameter plane.

Final Report One-Twelfth-Scale Mixing Experiments to Characterize Double-Shell Tank Slurry Uniformity

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

Bamberger, Judith A.; Liljegren, Lucia M.; Enderlin, Carl W.

The objectives of these 1/12-scale scoping experiments were to: Determine which of the dimensionless parameters discussed in Bamberger and Liljegren (1994) affect the maximum concentration that can be suspended during jet mixer pump operation in the full-scale double-shell tanks; Develop empirical correlations to predict the nozzle velocity required for jet mixer pumps to suspend the contents of full-scale double-shell tanks; Apply the models to predict the nozzle velocity required to suspend the contents of Tank 241 AZ-101; Obtain experimental concentration data to compare with the TEMPEST( )(Trent and Eyler 1989) computational modeling predictions to guide further code development; Analyze themore » effects of changing nozzle diameter on exit velocity (U0) and U0D0 (the product of the exit velocity and nozzle diameter) required to suspend the contents of a tank. The scoping study experimentally evaluated uniformity in a 1/12-scale experiment varying the Reynolds number, Froude number, and gravitational settling parameter space. The initial matrix specified only tests at 100% U0D0 and 25% U0D0. After initial tests were conducted with small diameter, low viscosity simulant this matrix was revised to allow evaluation of a broader range of U0D0s. The revised matrix included full factorial test between 100% and 50% U0D0 and two half-factorial tests at 75% and 25% U0D0. Adding points at 75% U0D0 and 50% U0D0 allowed evaluation curvature. Eliminating points at 25% U0D0 decreased the testing time by several weeks. Test conditions were achieved by varying the simulant viscosity, the mean particle size, and the jet nozzle exit velocity. Concentration measurements at sampling locations throughout the tank were used to assess the degree of uniformity achieved during each test. Concentration data was obtained using a real time ultrasonic attenuation probe and discrete batch samples. The undissolved solids concentration at these locations was analyzed to determine whether the tank contents were uniform (< ±10% variation about mean) or nonuniform (> ±10% variation about mean) in concentration. Concentration inhomogeneity was modeled as a function of dimensionless groups. The two parameters that best describe the maximum solids volume fraction that can be suspended in a double-shell tank were found to be 1) the Froude number (Fr) based on nozzle velocity (U0) and tank contents level (H) and 2) the dimensionless particle size (dp/D0). The dependence on the Reynolds number (Re) does not appear to be statistically significant.« less

Promising thermoelectric properties of phosphorenes.

PubMed

Sevik, Cem; Sevinçli, Hâldun

2016-09-02

Electronic, phononic, and thermoelectric transport properties of single layer black- and blue-phosphorene structures are investigated with first-principles based ballistic electron and phonon transport calculations employing hybrid functionals. The maximum values of room temperature thermoelectric figure of merit, ZT corresponding to armchair and zigzag directions of black-phosphorene, ∼0.5 and ∼0.25, are calculated as rather smaller than those obtained with first-principles based semiclassical Boltzmann transport theory calculations. On the other hand, the maximum value of room temperature ZT of blue-phosphorene is predicted to be substantially high and remarkable values as high as 2.5 are obtained for elevated temperatures. Besides the fact that these figures are obtained at the ballistic limit, our findings mark the strong possibility of high thermoelectric performance of blue-phosphorene in new generation thermoelectric applications.

Tsunamis generated by subaerial mass flows

USGS Publications Warehouse

Walder, S.J.; Watts, P.; Sorensen, O.E.; Janssen, K.

2003-01-01

Tsunamis generated in lakes and reservoirs by subaerial mass flows pose distinctive problems for hazards assessment because the domain of interest is commonly the "near field," beyond the zone of complex splashing but close enough to the source that wave propagation effects are not predominant. Scaling analysis of the equations governing water wave propagation shows that near-field wave amplitude and wavelength should depend on certain measures of mass flow dynamics and volume. The scaling analysis motivates a successful collapse (in dimensionless space) of data from two distinct sets of experiments with solid block "wave makers." To first order, wave amplitude/water depth is a simple function of the ratio of dimensionless wave maker travel time to dimensionless wave maker volume per unit width. Wave amplitude data from previous laboratory investigations with both rigid and deformable wave makers follow the same trend in dimensionless parameter space as our own data. The characteristic wavelength/water depth for all our experiments is simply proportional to dimensionless wave maker travel time, which is itself given approximately by a simple function of wave maker length/water depth. Wave maker shape and rigidity do not otherwise influence wave features. Application of the amplitude scaling relation to several historical events yields "predicted" near-field wave amplitudes in reasonable agreement with measurements and observations. Together, the scaling relations for near-field amplitude, wavelength, and submerged travel time provide key inputs necessary for computational wave propagation and hazards assessment.

MXLKID: a maximum likelihood parameter identifier. [In LRLTRAN for CDC 7600

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

Gavel, D.T.

MXLKID (MaXimum LiKelihood IDentifier) is a computer program designed to identify unknown parameters in a nonlinear dynamic system. Using noisy measurement data from the system, the maximum likelihood identifier computes a likelihood function (LF). Identification of system parameters is accomplished by maximizing the LF with respect to the parameters. The main body of this report briefly summarizes the maximum likelihood technique and gives instructions and examples for running the MXLKID program. MXLKID is implemented LRLTRAN on the CDC7600 computer at LLNL. A detailed mathematical description of the algorithm is given in the appendices. 24 figures, 6 tables.

Electronics Reliability Fracture Mechanics, Volume 1. Causes of Failures of Shop Replaceable Units and Hybrid Microcircuits

DTIC Science & Technology

1992-05-01

Plate Figure H-1. Temperature Coefficient Test Circuit The forward voltage was measured at 3 different termperatures. The average TC was calculated to be...AT, rather than the average figure given by the large area Isolation diffusion. The peak temperature , rather than the average temperature , is the...components would cause the temperatures of the components to be nearer the average , particularly those near the minimum and maximum. X-I The largest

Radial Distribution of Stars, Gas, and Dust in SINGS Galaxies. III. Modeling the Evolution of the Stellar Component in Galaxy Disks

NASA Astrophysics Data System (ADS)

Muñoz-Mateos, J. C.; Boissier, S.; Gil de Paz, A.; Zamorano, J.; Kennicutt, R. C., Jr.; Moustakas, J.; Prantzos, N.; Gallego, J.

2011-04-01

We analyze the evolution of 42 spiral galaxies in the Spitzer Infrared Nearby Galaxies Survey. We make use of ultraviolet (UV), optical, and near-infrared radial profiles, corrected for internal extinction using the total-infrared to UV ratio, to probe the emission of stellar populations of different ages as a function of galactocentric distance. We fit these radial profiles with models that describe the chemical and spectro-photometric evolution of spiral disks within a self-consistent framework. These backward evolutionary models successfully reproduce the multi-wavelength profiles of our galaxies, except for the UV profiles of some early-type disks for which the models seem to retain too much gas. From the model fitting we infer the maximum circular velocity of the rotation curve V C and the dimensionless spin parameter λ. The values of V C are in good agreement with the velocities measured in H I rotation curves. Even though our sample is not volume limited, the resulting distribution of λ is close to the lognormal function obtained in cosmological N-body simulations, peaking at λ ~ 0.03 regardless of the total halo mass. We do not find any evident trend between λ and Hubble type, besides an increase in the scatter for the latest types. According to the model, galaxies evolve along a roughly constant mass-size relation, increasing their scale lengths as they become more massive. The radial scale length of most disks in our sample seems to have increased at a rate of 0.05-0.06 kpc Gyr-1, although the same cannot be said of a volume-limited sample. In relative terms, the scale length has grown by 20%-25% since z = 1 and, unlike the former figure, we argue that this relative growth rate can be indeed representative of a complete galaxy sample.

Precipitation records and flood-producing storms in Cheyenne, Wyoming

USGS Publications Warehouse

Lindner-Lunsford, J. B.

1988-01-01

Annual maximum precipitation data for Cheyenne, Wyoming, are presented for the years 1871-1986 for durations of 5, 10, 15, and 30 minutes and 1, 2, and 24 hours. Precipitation-frequency curves are developed on the basis of data collected before 1985; a second set of curves are developed on the basis of data collected through 1986. The data are plotted and analyzed three times, assuming: (1) The data are described by a Gumbel distribution; (2) the logarithms of the data are described by a Gumbel distribution; and (3) the logarithms of the data are described by a Pearson Type III distribution. The inclusion of data for the large storm of August 1, 1985, had the most noticeable effect on the prediction of the magnitude of storms of long average recurrence intervals for the 1-, 2-, and 24-hour durations. Seven intensity-duration curves were calculated for the August 1, 1985 storm. For durations greater than 30 minutes, the observed curve indicates greater intensity than do five of the seven calculated curves. Dimensionless hyetographs were developed for 10 flood-producing storms that have occurred in the Cheyenne area since 1903. The pattern index (integral of the dimensionless hyetograph curve) for the storm of August 1, 1985, is 3 standard deviations lower than the mean of the pattern indices for the remaining 9 storms, indicating that the distribution of precipitation with time for the August 1, 1985, storm was outside the normal range for Cheyenne. (USGS)

Effect of particle polydispersity on the irreversible adsorption of fine particles on patterned substrates

NASA Astrophysics Data System (ADS)

Marques, J. F.; Lima, A. B.; Araújo, N. A. M.; Cadilhe, A.

2012-06-01

We performed extensive Monte Carlo simulations of the irreversible adsorption of polydispersed disks inside the cells of a patterned substrate. The model captures relevant features of the irreversible adsorption of spherical colloidal particles on patterned substrates. The pattern consists of (equal) square cells, where adsorption can take place, centered at the vertices of a square lattice. Two independent, dimensionless parameters are required to control the geometry of the pattern, namely, the cell size and cell-cell distance, measured in terms of the average particle diameter. However, to describe the phase diagram, two additional dimensionless parameters, i.e., the minimum and maximum particle radii, are also required. We find that the transition between any two adjacent regions of the phase diagram solely depends on the largest and smallest particle sizes, but not on the shape of the distribution function of the radii. We consider size dispersions up to 20% of the average radius using a physically motivated, truncated, Gaussian-size distribution, and focus on the regime where adsorbing particles do not interact with those previously adsorbed on neighboring cells to characterize the jammed state structure. The study generalizes previous exact relations on monodisperse particles to account for size dispersion. Due to the presence of the pattern, the coverage shows a nonmonotonic dependence on the cell size. The pattern also affects the radius of adsorbed particles, where one observes preferential adsorption of smaller radii, particularly at high polydispersity.

Scaling for Dynamical Systems in Biology.

PubMed

Ledder, Glenn

2017-11-01

Asymptotic methods can greatly simplify the analysis of all but the simplest mathematical models and should therefore be commonplace in such biological areas as ecology and epidemiology. One essential difficulty that limits their use is that they can only be applied to a suitably scaled dimensionless version of the original dimensional model. Many books discuss nondimensionalization, but with little attention given to the problem of choosing the right scales and dimensionless parameters. In this paper, we illustrate the value of using asymptotics on a properly scaled dimensionless model, develop a set of guidelines that can be used to make good scaling choices, and offer advice for teaching these topics in differential equations or mathematical biology courses.

Exact closed-form solutions of a fully nonlinear asymptotic two-fluid model

NASA Astrophysics Data System (ADS)

Cheviakov, Alexei F.

2018-05-01

A fully nonlinear model of Choi and Camassa (1999) describing one-dimensional incompressible dynamics of two non-mixing fluids in a horizontal channel, under a shallow water approximation, is considered. An equivalence transformation is presented, leading to a special dimensionless form of the system, involving a single dimensionless constant physical parameter, as opposed to five parameters present in the original model. A first-order dimensionless ordinary differential equation describing traveling wave solutions is analyzed. Several multi-parameter families of physically meaningful exact closed-form solutions of the two-fluid model are derived, corresponding to periodic, solitary, and kink-type bidirectional traveling waves; specific examples are given, and properties of the exact solutions are analyzed.

40 CFR 1042.350 - Recordkeeping.

Code of Federal Regulations, 2010 CFR

2010-07-01

... additional records: (1) A description of all test equipment for each test cell that you can use to test... may ask you to divide your production figures by maximum engine power, displacement, fuel type, or...

How fundamental are fundamental constants?

NASA Astrophysics Data System (ADS)

Duff, M. J.

2015-01-01

I argue that the laws of physics should be independent of one's choice of units or measuring apparatus. This is the case if they are framed in terms of dimensionless numbers such as the fine structure constant, ?. For example, the standard model of particle physics has 19 such dimensionless parameters whose values all observers can agree on, irrespective of what clock, rulers or scales? they use to measure them. Dimensional constants, on the other hand, such as ?, c, G, e and k ?, are merely human constructs whose number and values differ from one choice of units to the next. In this sense, only dimensionless constants are 'fundamental'. Similarly, the possible time variation of dimensionless fundamental 'constants' of nature is operationally well defined and a legitimate subject of physical enquiry. By contrast, the time variation of dimensional constants such as ? or ? on which a good many (in my opinion, confusing) papers have been written, is a unit-dependent phenomenon on which different observers might disagree depending on their apparatus. All these confusions disappear if one asks only unit-independent questions. We provide a selection of opposing opinions in the literature and respond accordingly.

The European Office of Aerospace Research and Development’s Small Satellite Propulsion System Research Program

DTIC Science & Technology

2000-04-12

Investigation S..showed that the pressure reading saturated at 13 bar (maximum limit) compared to 10 bar which the pressure switch should have...controlled to. It was concluded that the commercial grade pressure switch had failed and that the pressure Figure 5: Nitrous Oxide feed system control valve...firing on 11 th April 2000. The performance using a pressure switch to control a solenoid results of this firing are shown in Figure 7. valve giving

Performance Testing of Twist Drills on AISI 4140 Alloy Steel

DTIC Science & Technology

1979-07-01

AISI 4140 Annealed, RPM: 110, Feed Rate: 0.005 Ipr 2^ vi 1 LIST OF FIGURES (cont.) Figure Page 20. Maximum Height of Built-up Edge at Various...period. This investigation was conducted using only one kind of work material, AISI 4140 steel, annealed. The drill used for this investigation was a...HSS (M7), 0.5 inch diameter regular point, taper shank. AISI 4140 steel, annealed, belongs to a group of high strength materials relatively hard to

Chena River Lakes Project, Fairbanks, Alaska. Overview of Tanana River Monitoring Research Studies Near Fairbanks, Alaska.

DTIC Science & Technology

1984-01-01

concentration-depth profiles for suspended sand sizes at Fairbanks gauge . 5.1 Apparent downstream migration of main channel loops upstream of Goose Island, 1938...at the Fairbanks gauging station is plotted in Figure 3.1. Table 3.1 shows year-by-year and period-of-record statistics for mean, minimum and maximum...Associated Relationships Figure 3.3 shows a plot of stage vs. discharge data for the Fairbanks gauging station.* There has been considerable scatter

Maximum Power Point Tracking Control of Hydrokinetic Turbine and Low-speed High-Thrust Permanent Magnet Generator Design

DTIC Science & Technology

2012-01-01

Schematic of the generator and power converters built in PLECS ............. 26 Figure 3.12. Block diagram of the MPPT control built in Matlab/Simulink...validated by simulation results done in Matlab/Simulink R2010a and PLECS . Figure 3.9 shows the block diagram of the hydrokinetic system built in Matlab...rectifier, boost converter and battery model built in PLECS . The battery bank on the load side is simulated by a constant dc voltage source. 25

Fracture and Plasticity Characterization of DH-36 Navy Steel

DTIC Science & Technology

2012-06-01

32 Figure 30: Butterfly shear test showing front and back views and highlighting the unwanted edge buckling and fracture...maximum point of equivalent plastic strain in the edge section not the gage section. The face shown is the middle of the specimen...0 100 200 300 400 500 600 700 800 900 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 T ru e S tr e ss Plastic Strain Experiment Power Law 19 Figure 12

Laboratory Studies and Preliminary Evaluation of Destructive Technologies for the Removal of RDX from the Water Waste Stream of Holston Army Ammunition Plan

DTIC Science & Technology

2010-05-01

with electrode plates . ERDC/EL TR-10-4 29 Total Electrode Surface Area = 0.4311 m² Cathodic Surface Area = 0.2156 m² Reactor Volume = 1632 mL 35...27 Figure 15. Continuous flow electrochemical reactor packed with electrode plates . .......................... 28 Figure...Environmental Compliance (TDEC) is in the process of establishing a total maximum daily load (TMDL) that will regulate the mass of hexahydro- 1,3,5

Effect of Protective Devices on Brain Trauma Mechanics Under Idealized Shock Wave Loading

DTIC Science & Technology

2015-03-29

shots was taken 1.5” from the open end. Although the incident pressure measured for both D1 and D2 are similar, the pressure experienced by the head...of the free field shock wave pushing up and underneath the helmet brim , as indicated in the Figure 12. Figure 11 comparisons of (a) maximum...head form and potential shockwave interactions. Blue square indicates location of sensor 1 with respect to the brim of the helmet. The shock fronts

Navigation, Guidance and Control For the CICADA Expendable Micro Air Vehicle

DTIC Science & Technology

2015-01-01

aircraft, as shown in Figure 5a. A Tempest UAV mothership was used as the host platform for the CICADA vehicles. Figure 5b shows how two CICADAs were...mounted on wing pylon drop mechanisms located on each wing of the Tempest . The Tempest was needed to carry the CICADAs back within range of the recovery...carried the Tempest and CICADA combination to a maximum altitude of 57,000 feet above sea-level. At that point, Tempest was released from the balloon and

The mirrors for the Extreme Ultraviolet Explorer

NASA Technical Reports Server (NTRS)

Finley, David S.; Green, James C.; Bowyer, Stuart; Malina, Roger F.

1986-01-01

Flight mirrors for the Extreme Ultraviolet Explorer satellite are currently under fabrication. The grazing incidence metal mirrors are Wolter-Schwarzschild Type I and II and are figured by diamond turning. Imaging performance is excellent, with the figure after polishing for the best mirror being such that the full width-half maximum is 1.0 arc seconds and the half energy width is 8 arc seconds measured at visible wavelengths. Surface finish, as determined from scattering measurements in the extreme ultraviolet, is about 20 A rms.

Experimental Research on Thermocapillary-Buoyancy Migration Interaction of Axisymmetric Two Drops by Using Digital Holographic Interferometry

NASA Astrophysics Data System (ADS)

Zhang, Shuoting; Duan, Li; Kang, Qi

2018-05-01

The migration and interaction of axisymmetric two drops in a vertical temperature gradient is investigated experimentally on the ground. A silicon oil is used as the continuous phase, and a water-ethanol mixture is used as the drop phase, respectively. The migration and interaction of two drops, under the combined effects of buoyancy and thermocapillary, is recorded by a digital holographic interferometry measurement in the experiment to analyse the velocities and temperature distribution of the drops. As a result, when two drops migrate together, the drop affects the other drop by perturbing the temperature field around itself. For the leading drop, the velocity is faster than the one of the isolated drop, and the maximum of the interfacial temperature distribution is larger than the one of the isolated drop. For the trailing drop, the velocity is slower than the one of the isolated drop, and the maximum of the interfacial temperature distribution is less than the one of the isolated drop. The influence of the dimensionless initial distance between the drop centres to the drop migration is discussed in detail in this study.

A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe–Mn–C system exhibiting multicomposition sets

PubMed Central

Nakano, Jinichiro

2013-01-01

The thermodynamic properties of the Fe–Mn–C system were investigated by using an analytical model constructed by a CALPHAD approach. The stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T0, independent of the composition and temperature when other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T0. The driving force for the fcc to hcp transition, defined as a dimensionless value –dGm/(RT), was determined in the presence of Fe-rich and Mn-rich composition sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the compositions studied. The results obtained revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed. PMID:27877555

A thermo-mechanical correlation with driving forces for hcp martensite and twin formations in the Fe–Mn–C system exhibiting multicomposition sets

DOE PAGES

Nakano, Jinichiro

2013-03-15

Thermodynamic properties of the Fe-Mn-C system were investigated by using an analytical model constructed by a CALPHAD approach. Stacking fault energy (SFE) of the fcc structure with respect to the hcp phase was always constant at T 0, independent of composition and temperature when the other related parameters were assumed to be constant. Experimental limits for the thermal hcp formation and the mechanical (deformation-induced) hcp formation were separated by the SFE at T 0. The driving force for the fcc to hcp transition, defined as a dimensionless value –dG m/(RT), was determined in the presence of Fe-rich and Mn-rich compositionmore » sets in each phase. Carbon tended to partition to the Mn-rich phase rather than to the Fe-rich phase for the studied compositions. The obtained results revealed a thermo-mechanical correlation with empirical yield strength, maximum true stress and maximum true strain. The proportionality between thermodynamics and mechanical properties is discussed.« less

Regional analysis of annual precipitation maxima in Montana

USGS Publications Warehouse

Parrett, Charles

1997-01-01

Dimensionless precipitation-frequency curves for estimating precipitation depths having large recurrence intervals were developed for 2-, 6-, and 24-hour storm durations for three homogeneous regions in Montana. Within each homogeneous region, at-site annual precipitation maxima were made dimensionless by dividing by the at-site mean and grouped so that a single frequency curve would be applicable for each duration. L-moment statistics were used to help define the homogeneous regions and to develop the dimensionless precipitation- frequency curves. Data from 459 precipitation stations were used after application of statistical tests to ensure that the data were not serially correlated and were stationary over the general period of data collection (1900-92). The data were found to have a small, but significant, degree of interstation correlation. The GEV distribution was used to construct dimensionless frequency curves of annual precipitation maxima for each duration within each region. Each dimensionless frequency curve was considered to be reliable for recurrence intervals up to the effective record length. Because of significant, though small, interstation correlation in all regions for all durations, and because the selected regions exhibited some heterogeneity, the effective record length was considered to be less than the total number of station-years of data. The effective record length for each duration in each region was estimated using a graphical method and found to range from 500 years for 6-hour duration data in Region 2 to 5,100 years for 24-hour duration data in Region 3.

Dimensionless numbers and correlating equations for the analysis of the membrane-gas diffusion electrode assembly in polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Gyenge, E. L.

The Quraishi-Fahidy method [Can. J. Chem. Eng. 59 (1981) 563] was employed to derive characteristic dimensionless numbers for the membrane-electrolyte, cathode catalyst layer and gas diffuser, respectively, based on the model presented by Bernardi and Verbrugge for polymer electrolyte fuel cells [AIChE J. 37 (1991) 1151]. Monomial correlations among dimensionless numbers were developed and tested against experimental and mathematical modeling results. Dimensionless numbers comparing the bulk and surface-convective ionic conductivities, the electric and viscous forces and the current density and the fixed surface charges, were employed to describe the membrane ohmic drop and its non-linear dependence on current density due to membrane dehydration. The analysis of the catalyst layer yielded electrode kinetic equivalents of the second Damköhler number and Thiele modulus, influencing the penetration depth of the oxygen reduction front based on the pseudohomogeneous film model. The correlating equations for the catalyst layer could describe in a general analytical form, all the possible electrode polarization scenarios such as electrode kinetic control coupled or not with ionic and/or oxygen mass transport limitation. For the gas diffusion-backing layer correlations are presented in terms of the Nusselt number for mass transfer in electrochemical systems. The dimensionless number-based correlating equations for the membrane electrode assembly (MEA) could provide a practical approach to quantify single-cell polarization results obtained under a variety of experimental conditions and to implement them in models of the fuel cell stack.

On Instability of Geostrophic Current with Linear Vertical Shear at Length Scales of Interleaving

NASA Astrophysics Data System (ADS)

Kuzmina, N. P.; Skorokhodov, S. L.; Zhurbas, N. V.; Lyzhkov, D. A.

2018-01-01

The instability of long-wave disturbances of a geostrophic current with linear velocity shear is studied with allowance for the diffusion of buoyancy. A detailed derivation of the model problem in dimensionless variables is presented, which is used for analyzing the dynamics of disturbances in a vertically bounded layer and for describing the formation of large-scale intrusions in the Arctic basin. The problem is solved numerically based on a high-precision method developed for solving fourth-order differential equations. It is established that there is an eigenvalue in the spectrum of eigenvalues that corresponds to unstable (growing with time) disturbances, which are characterized by a phase velocity exceeding the maximum velocity of the geostrophic flow. A discussion is presented to explain some features of the instability.

40 CFR 1048.350 - What records must I keep?

Code of Federal Regulations, 2010 CFR

2010-07-01

... additional records: (1) A description of all test equipment for each test cell that you can use to test... production figures by maximum engine power, displacement, fuel type, or assembly plant (if you produce...

An Alternative Assessment of Second-Order Closure Models in Turbulent Shear Flows

DTIC Science & Technology

1994-03-01

Here, the dimensionless turbulent kinetic energy and dimensionless time are given by K* -- K/ Ko and t* = St, 4 respectively. These results exhibit the...function F 1 + 911 + 27111 in homogeneous shear flow: SKo /eo = 15, (bl)0 -= -0.32 and (b22)0 = (b53)o = 0.16. 16 fiublic reporting burden for this

Unsteady MHD blood flow through porous medium in a parallel plate channel

NASA Astrophysics Data System (ADS)

Latha, R.; Rushi Kumar, B.

2017-11-01

In this study, we have analyzed heat and mass transfer effects on unsteady blood flow through parallel plate channel in a saturated porous medium in the presence of a transverse magnetic field with thermal radiation. The governing higher order nonlinear PDE’S are converted to dimensionless equations using dimensionless variables. The dimensionless equations are then solved analytically using boundary conditions by choosing the axial flow transport and the fields of concentration and temperature apart from the normal velocity as a function of y and t. The effects of different pertinent parameters appeared in this model viz thermal radiation, Prandtl number, Heat source parameter, Hartmann number, Permeability parameter, Decay parameter on axial flow transport and the normal velocity are analyzed in detail.

An Interpretation of the Laminar-Turbulent Transition Startup against the Consideration of the Transverse Viscosity Factor

NASA Astrophysics Data System (ADS)

Kolodezhnov, V. N.

2018-03-01

This paper proposes a rheological model of a fluid having the Newtonian model applicability limit and a potential for further “addition” of the transverse viscosity factor. The dynamic equations for a fluid that has such rheological model are discussed, the analysis of which demonstrates the possibility of “generating” the cross stream velocity components. The transition to the dimensionless notation introduces four dimensionless complexes of local characterization for the transition conditions in the neighborhood of the flow region point in question. Based on such dimensionless complexes and using the known experimental data, the empiric conditions of “generating” the cross stream velocity components and starting the laminar-turbulent transition are proposed.

Drilling the near cortex with elongated figure-of-8 holes to reduce the stiffness of a locking compression plate construct.

PubMed

Chen, Jerry Yongqiang; Zhou, Zhihong; Ang, Benjamin Fu Hong; Yew, Andy Khye Soon; Chou, Siaw Meng; Chia, Shi-Lu; Koh, Joyce Suang Bee; Howe, Tet Sen

2015-12-01

To compare the stiffness of locking compression plate (LCP) constructs with or without drilling the near cortex with elongated figure-of-8 holes. 24 synthetic bones were sawn to create a 10-mm gap and were fixed with a 9-hole 4.5-mm narrow LCP. In 12 bones, the near cortex of the adjacent holes to the LCP holes was drilled to create elongated figure-of-8 holes before screw insertion. The stiffness of LCP constructs under axial loading or 4-point bending was assessed by (1) dynamic quasi-physiological testing for fatigue strength, (2) quasi-static testing for stiffness, and (3) testing for absolute strength to failure. None of the 24 constructs had subcatastrophic or catastrophic failure after 10 000 cycles of fatigue loading (p=1.000). The axial stiffness reduced by 16% from 613±62 to 517±44 N/mm (p=0.012) in the case group, whereas the bending stiffness was 16±1 Nm2 in both groups (p=1.000). The maximum axial load to catastrophic failure was 1596±84 N for the control group and 1627±48 N for the case group (p=0.486), whereas the maximum bending moment to catastrophic failure was 79±12 and 80±10 Nm, respectively (p=0.919). Drilling the near cortex with elongated figure-of-8 holes reduces the axial stiffness of the LCP construct, without compromising its bending stiffness or strength.

An experimental approach of decoupling Seebeck coefficient and electrical resistivity

NASA Astrophysics Data System (ADS)

Muhammed Sabeer N., A.; Paulson, Anju; Pradyumnan, P. P.

2018-04-01

The Thermoelectrics (TE) has drawn increased attention among renewable energy technologies. The performance of a thermoelectric material is quantified by a dimensionless thermoelectric figure of merit, ZT=S2σT/κ, where S and σ vary inversely each other. Thus, improvement in ZT is not an easy task. So, researchers have been trying different parameter variations during thin film processing to improve TE properties. In this work, tin nitride (Sn3N4) thin films were deposited on glass substrates by reactive RF magnetron sputtering and investigated its thermoelectric response. To decouple the covariance nature of Seebeck coefficient and electrical resistivity for the enhancement of power factor (S2σ), the nitrogen gas pressure during sputtering was reduced. Reduction in nitrogen gas pressure reduced both sputtering pressure and amount of nitrogen available for reaction during sputtering. This experimental approach of combined effect introduced preferred orientation and stoichiometric variations simultaneously in the sputtered Sn3N4 thin films. The scattering mechanism associated with these variations enhanced TE properties by independently drive the Seebeck coefficient and electrical resistivity parameters.

The Next Generation Thermoelectric Materials

NASA Astrophysics Data System (ADS)

Tritt, Terry M.

1999-11-01

Recently there been renewed interest in materials for thermoelectric refrigeration and power generation applications.^1, 2 Many new materials and new classes of materials are being investigated for potential thermoelectric applications. An introduction to thermoelectric refrigeration and power generation, the advantages and disadvantages and potential applications will be discussed. An overview of some of the current thermoelectric materials under investigation and the criteria for selection of new materials will be given. To be promising as a thermoelectric material, a material must have a high Seebeck coefficient, α, high electrical conductivity, σ, and a low thermal conductivity, λ. These parameters go into the material's dimensionless figure of merit ZT = α ^2σT/λ. Our research at Clemson is focused on a number of new materials, quasicrystals and pentatelluride materials, which show promise for thermoelectrics and these systems will be briefly discussed. Demonstrations of thermoelectric devices will be shown and discussed. 1.) Thermoelectric Materials: New Directions and Approaches, MRS Volumes 478 and 545, edited by Terry M. Tritt et. al. 2.) G. Mahan, B. Sales and J. Sharp, Physics Today, March 50, 42, 1997

Transport properties of undoped and Br-doped PbTe sintered at high temperature and pressure> 4.0 GPa

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

Yongkwan, Dong; McGuire, Michael A; Malik, Abds-Sami

2009-01-01

The thermoelectric properties of nominally undoped PbTe and Br doped PbTe materials sintered at high-pressure and high-temperature (HPHT) have been studied. All samples show n-type semiconducting behavior with negative thermopower. For undoped PbTe, four different HPHT treatments were performed at pressures between 4.0 and 6.5 GPa. PbTe doped with Br at 0.5, 1.0, 2.0, 3.0 x 10{sup 19} cm{sup -3} was HPHT treated at 4.0 GPa and 1045 C. As the dopant concentration increases, the absolute thermopower decreases, thermal conductivity increases, and electrical resistivity decreases. At a nominal dopant concentration of 1.0 x 10{sup 19} cm{sup -3}, carrier mobility ofmore » 1165 cm{sup 2}/V s and dimensionless thermoelectric figure-of-merit, ZT, of around 0.27 at 300 K were obtained. These results demonstrate that HPHT post-processing is a viable and controllable way of tuning the thermoelectric properties of PbTe-based materials.« less

Thermoelectric Properties of Nanograined Si-Ge-Au Thin Films Grown by Molecular Beam Deposition

NASA Astrophysics Data System (ADS)

Nishino, Shunsuke; Ekino, Satoshi; Inukai, Manabu; Omprakash, Muthusamy; Adachi, Masahiro; Kiyama, Makoto; Yamamoto, Yoshiyuki; Takeuchi, Tsunehiro

2018-06-01

Conditions to achieve extremely large Seebeck coefficient and extremely small thermal conductivity in Si-Ge-Au thin films formed of nanosized grains precipitated in amorphous matrix have been investigated. We employed molecular beam deposition to prepare Si1- x Ge x Au y thin films on sapphire substrate. The deposited films were annealed under nitrogen gas atmosphere at 300°C to 500°C for 15 min to 30 min. Nanocrystals dispersed in amorphous matrix were clearly observed by transmission electron microscopy. We did not observe anomalously large Seebeck coefficient, but very low thermal conductivity of nearly 1.0 W K-1 m-1 was found at around 0.2 < x < 0.6. The compositional dependence of the thermal conductivity was well accounted for by the compositional dependence of the mixing entropy. Some of these values agree exactly with the amorphous limit predicted by theoretical calculations. The smallest lattice thermal conductivity found for the present samples is lower than that of nanostructured Si-Ge bulk material for which dimensionless figure of merit of ZT ≈ 1 was reported at high temperature.

Selection Criteria for New Materials For Thermoelectric Applications

NASA Astrophysics Data System (ADS)

Tritt, T. M.

1997-11-01

Recently there has been renewed interest in materials for thermoelectric refrigeration and power generation applications.(Terry M. Tritt, Science, 272, 1276, 1996),(G. Mahan, B. Sales and J. Sharp, Physics Today, March 50, 42, 1997) We have established a multidisciplinary program within the Physics Department and in collaboration with the Chemistry Department at Clemson University. The focus of our research utilizes a broad understanding of solid state physics coupled with solid state chemistry to synthesize and fully characterize promising materials for their potential as the "next generation" thermoelectric materials. An introduction to thermoelectric materials and the criteria for their selection and potential for applications will be given. To be promising as a thermoelectric material, a material must have a high Seebeck coefficient, α, high electrical conductivity, σ, and a low thermal conductivity, λ. These parameters go into the materials dimensionless figure of merit ZT = α^2σT/λ. We will discuss these parameters in relation to this materials performance as a potential thermoelectric material. We will also discuss some of the materials that are currently being investigated in the program at Clemson University.

40 CFR 1054.350 - What records must I keep?

Code of Federal Regulations, 2010 CFR

2010-07-01

... additional records: (1) A description of all test equipment for each test cell that you can use to test... may ask you to divide your production figures by maximum engine power, displacement, fuel type, or...

49 CFR 572.186 - Abdomen assembly.

Code of Federal Regulations, 2014 CFR

2014-10-01

... longitudinal axis of the probe's impact face as shown in Figure U5-A in appendix A to this subpart; (4) The... the three load cell forces must be concurrent in time. (2) Maximum impactor force (impact probe...

Dimensional analysis of MINMOD leads to definition of the disposition index of glucose regulation and improved simulation algorithm.

PubMed

Nittala, Aparna; Ghosh, Soumitra; Stefanovski, Darko; Bergman, Richard; Wang, Xujing

2006-07-14

Frequently Sampled Intravenous Glucose Tolerance Test (FSIVGTT) together with its mathematical model, the minimal model (MINMOD), have become important clinical tools to evaluate the metabolic control of glucose in humans. Dimensional analysis of the model is up to now not available. A formal dimensional analysis of MINMOD was carried out and the degree of freedom of MINMOD was examined. Through re-expressing all state variable and parameters in terms of their reference scales, MINMOD was transformed into a dimensionless format. Previously defined physiological indices including insulin sensitivity, glucose effectiveness, and first and second phase insulin responses were re-examined in this new formulation. Further, the parameter estimation from FSIVGTT was implemented using both the dimensional and the dimensionless formulations of MINMOD, and the performances were compared utilizing Monte Carlo simulation as well as real human FSIVGTT data. The degree of freedom (DOF) of MINMOD was found to be 7. The model was maximally simplified in the dimensionless formulation that normalizes the variation in glucose and insulin during FSIVGTT. In the new formulation, the disposition index (Dl), a composite parameter known to be important in diabetes pathology, was naturally defined as one of the dimensionless parameters in the system. The numerical simulation using the dimensionless formulation led to a 1.5-5 fold gain in speed, and significantly improved accuracy and robustness in parameter estimation compared to the dimensional implementation. Dimensional analysis of MINMOD led to simplification of the model, direct identification of the important composite factors in the dynamics of glucose metabolic control, and better simulations algorithms.

Piezoviscous effects in nonconformal contacts lubricated hydrodynamically

NASA Technical Reports Server (NTRS)

Jeng, Y. R.; Hamrock, B. J.; Brewe, D. E.

1985-01-01

The analysis is concerned with the piezoviscous-rigid regime of lubrication for the general case of elliptical contacts. In this regime several formulas of the lubricant film thickness have been proposed by Hamrock and Dowson, by Dowson et al., and more recently by Houpert. However, either they do not include the load parameter W, which has a strong effect on film thickness, or they overestimate the film thickness by using the Barus formula for pressure-viscosity characteristics. The Roelands formula was used for the pressure-viscosity relationship. The effects of the dimensionless load, speed, and materials parameters, the radius ratio, and the lubricant entrainment direction were investigated. The dimensionless load parameter was varied over a range of one order of magnitude. The dimensionless speed parameter was varied by 5.6 times the lowest value. Conditions corresponding to the use of solid materials of steel, bronze, and silicon nitride and lubricants of paraffinic and naphthenic mineral oil were considered in obtaining the exponent in the dimensionless materials parameter. The radius ratio was varied from 0.2 to 64 (a configuration approaching a line contact). Forty-one cases were used in obtaining a minimum film thickness formula. Contour plots indicate in detail the pressure developed between the contacting solids.

Dimensionless numbers in additive manufacturing

NASA Astrophysics Data System (ADS)

Mukherjee, T.; Manvatkar, V.; De, A.; DebRoy, T.

2017-02-01

The effects of many process variables and alloy properties on the structure and properties of additively manufactured parts are examined using four dimensionless numbers. The structure and properties of components made from 316 Stainless steel, Ti-6Al-4V, and Inconel 718 powders for various dimensionless heat inputs, Peclet numbers, Marangoni numbers, and Fourier numbers are studied. Temperature fields, cooling rates, solidification parameters, lack of fusion defects, and thermal strains are examined using a well-tested three-dimensional transient heat transfer and fluid flow model. The results show that lack of fusion defects in the fabricated parts can be minimized by strengthening interlayer bonding using high values of dimensionless heat input. The formation of harmful intermetallics such as laves phases in Inconel 718 can be suppressed using low heat input that results in a small molten pool, a steep temperature gradient, and a fast cooling rate. Improved interlayer bonding can be achieved at high Marangoni numbers, which results in vigorous circulation of liquid metal, larger pool dimensions, and greater depth of penetration. A high Fourier number ensures rapid cooling, low thermal distortion, and a high ratio of temperature gradient to the solidification growth rate with a greater tendency of plane front solidification.

Piezoviscous effects in nonconformal contacts lubricated hydrodynamically

NASA Technical Reports Server (NTRS)

Jeng, Yeau-Ren; Hamrock, Bernard J.; Brewe, David E.

1987-01-01

The analysis is concerned with the piezoviscous-rigid regime of lubrication for the general case of elliptical contacts. In this regime several formulas of the lubricant film thickness have been proposed by Hamrock and Dowson, by Dowson et al., and more recently by Houpert. However, either they do not include the load parameter W, which has a strong effect on film thickness, or they overestimate the film thickness by using the Barus formula for pressure-viscosity characteristics. The Roelands formula was used for the pressure-viscosity relationship. The effects of the dimensionless load, speed, and materials parameters, the radius ratio, and the lubricant entrainment direction were investigated. The dimensionless load parameter was varied over a range of one order of magnitude. The dimensionless speed parameter was varied by 5.6 times the lowest value. Conditions corresponding to the use of solid materials of steel, bronze, and silicon nitride and lubricants of paraffinic and naphthenic mineral oil were considered in obtaining the exponent in the dimensionless materials parameter. The radius ratio was varied from 0.2 to 64 (a configuration approaching a line contact). Forty-one cases were used in obtaining a minimum film thickness formula. Contour plots indicate in detail the pressure developed between the contacting solids.

Performance assessment and optimization of an irreversible nano-scale Stirling engine cycle operating with Maxwell-Boltzmann gas

NASA Astrophysics Data System (ADS)

Ahmadi, Mohammad H.; Ahmadi, Mohammad-Ali; Pourfayaz, Fathollah

2015-09-01

Developing new technologies like nano-technology improves the performance of the energy industries. Consequently, emerging new groups of thermal cycles in nano-scale can revolutionize the energy systems' future. This paper presents a thermo-dynamical study of a nano-scale irreversible Stirling engine cycle with the aim of optimizing the performance of the Stirling engine cycle. In the Stirling engine cycle the working fluid is an Ideal Maxwell-Boltzmann gas. Moreover, two different strategies are proposed for a multi-objective optimization issue, and the outcomes of each strategy are evaluated separately. The first strategy is proposed to maximize the ecological coefficient of performance (ECOP), the dimensionless ecological function (ecf) and the dimensionless thermo-economic objective function ( F . Furthermore, the second strategy is suggested to maximize the thermal efficiency ( η), the dimensionless ecological function (ecf) and the dimensionless thermo-economic objective function ( F). All the strategies in the present work are executed via a multi-objective evolutionary algorithms based on NSGA∥ method. Finally, to achieve the final answer in each strategy, three well-known decision makers are executed. Lastly, deviations of the outcomes gained in each strategy and each decision maker are evaluated separately.

The best thermoelectric.

PubMed Central

Mahan, G D; Sofo, J O

1996-01-01

What electronic structure provides the largest figure of merit for thermoelectric materials? To answer that question, we write the electrical conductivity, thermopower, and thermal conductivity as integrals of a single function, the transport distribution. Then we derive the mathematical function for the transport distribution, which gives the largest figure of merit. A delta-shaped transport distribution is found to maximize the thermoelectric properties. This result indicates that a narrow distribution of the energy of the electrons participating in the transport process is needed for maximum thermoelectric efficiency. Some possible realizations of this idea are discussed. PMID:11607692

The Designs of Fins Air-Cooled Cylinders

DTIC Science & Technology

1939-06-28

4 (a). EMer part of figure 4 clearly shows that, for one pnir of values of s and t, the heat transfer is a maximum. The peak values of the curves of...specified s” curves. Similarly, the peak values of the curves of constant values of t shown in &ure 4 (b) and of similar cwwes plotted for othm values of... picking the values of optimum g and t from these curves: PIots of tk type shown in figure 4 were obtained for - other \\ralues of M and Aplpa,/m by means

Influence of Compensating Defect Formation on the Doping Efficiency and Thermoelectric Properties of Cu2ySe1xBrx

DTIC Science & Technology

2015-09-24

level spectra (Figure S3b). The relative contents of Cu to Se were determined using a Thermo- Finnigan ELEMENT2 single collector sector field...has a wide range of stoichiometric deviation (Cu2−δSe). 17,22,23 Above 410 K, the compound has an average cubic structure with Se ions forming a face...extrinsically, and a single parabolic band model can be applied to analyze the transport and predict the optimum carrier densities for a maximum figure of

Development of High-k Dielectric for Antimonides and a sub 350 degree Celsius III-V pMOSFET Outperforming Germanium

DTIC Science & Technology

2010-12-01

due to BTBT was observed in the surface channel device (Figure 23). Buried channel device moves the maximum E-field due to VGD in the WB cap (Figure...23(inset)) suppressing BTBT which might be the dominant component of IOFF in scaled devices [10]. Lastly, a 4.3% increase in ID was observed when...inset : SS with T). Fig. 21 : Temp Dependence of mobility. Fig. 23 :GIDL due to BTBT seen in surface channel device at 80K. Use of wide bandgap (WB

Crack Growth Modeling in an Advanced Powder Metallurgy Alloy

DTIC Science & Technology

1980-07-01

Figure ~ ~ ~ ~ ~ 1 90. SpcmnCniuain CorMtra ulfcto Experiments. .= is5.9 mm__ C ,, . 625 inch) , so t’ 0 1 ".6 12.7 mm (0.50 inch) Figure 5. Configuration...best simple correlation of hold time and stress ratio (R = 0.05 through 0.8) effects on Inconel 718 at 650* C (1200" F) was by the maximum stress...in the work done in another studyt22) on Inconel 718. Based on these room-temperature studies, the interpolative model was ex- pected to have a

Polarimetric SAR Antenna Characterization

DTIC Science & Technology

1989-07-28

an Alpha Industries model A858-12 scalar-horn/lens antenna that scans in azimuth and elevation inside a monolithic spherical radome. Figure 1-1 shows a...ADTS1ADIR. DAT LINEAR XMIT, LINEAR RECEIVE. W/SHARD, W/SHROUD, W/O POLARIZER COPOL 79198-53 Figure 2-4. VV/ power versus azimuth and elevation for 33.6...GHz.. 9 -’ / 8160 7. 𔄁 / (Z Z 󈧄 \\ w ~~~ 0 0 C \\,- -- 23 MAX XPOL (dB) REL TO COPOL AT SAME Az, El MAXIMUM XPOL = -29.52 dB ADTSIADIR.DAT LINEAR XMIT

On the Curvature Function: Where Does a Curve Bend the Fastest?

ERIC Educational Resources Information Center

Chrysafi, Loucas; Gordon, Sheldon

2006-01-01

We examine the behavior of the curvature function associated with most common families of functions and curves, with the focus on establishing where maximum curvature occurs. Many examples are included for student illustrations. (Contains 18 figures.)

Geochemical Weathering in Glacial and Proglacial Environments

NASA Astrophysics Data System (ADS)

Tranter, M.

2003-12-01

It seems counterintuitive that chemical erosion in glaciated regions proceeds at rates comparable to those of temperate catchments with comparable specific runoff (Anderson et al., 1997). All the usual factors that are associated with elevated rates of chemical weathering ( Drever, 1988, 1994), such as water, soil, and vegetation, are either entirely absent or absent for much of the year. For example, glaciated regions are largely frozen for significant periods each year, the residence time of liquid water in the catchment is low ( Knight, 1999), there are thin, skeletal soils at best, and vegetation is either absent or limited ( French, 1997). Other chapters in this volume have highlighted how these factors are important in other, more temperate and tropical environments. Even so, chemical erosion rates in glaciated terrain are usually near to or greater than the continental average ( Sharp et al., 1995; Wadham et al., 1997; Hodson et al., 2000). This is because glaciated catchments usually have high specific runoff, there are high concentrations of freshly comminuted rock flour, which is typically silt sized and coated with microparticles, and adsorbed organic matter or surface precipitates that may hinder water-rock interactions are largely absent ( Tranter, 1982). In short, the rapid flow of water over fine-grained, recently crushed, reactive mineral surfaces maximizes both the potential rates of chemical weathering and chemical erosion.A range of both lab- and field-based studies of glacial chemical weathering have been undertaken, mainly on the smaller glaciers of Continental Europe (e.g., Brown et al., 1993a, b), Svalbard (e.g., Hodson et al., 2002), and North America (e.g., Anderson et al., 2000). The field-based studies typically generate hydrographs of glacier runoff, which show a characteristic diurnal cycle during summer in low latitudes ( Figure 1), and more subdued diurnal cycles at high latitudes (Figure 2 and Figure 3). The concentration of ions in solution, typically monitored by electrical conductivity, is often inverse with discharge on both a diurnal and a seasonal basis at lower latitudes, but ismore complex at higher latitudes (Figure 1, Figure 2 and Figure 3). Figure 1, Figure 2 and Figure 3 also show that the total flux of glacial solutes is usually dominated by fluxes associated with high discharge, dilute waters. The chemical weathering reactions that are inferred to occur from the field studies have been supported, in part, by controlled laboratory studies (e.g., Brown et al., 1993a). Recent stable-isotope studies have reported the key involvement of microbial processes in certain regions of the glacier bed ( Bottrell and Tranter, 2002), and these processes are yet to be incorporated in lab-based chemical weathering studies. (14K)Figure 1. (a) The temporal variation of discharge and in non-sea-salt calcium (*Ca2+) concentration in runoff from Haut Glacier d'Arolla, a small, warm-based, valley glacier in the Swiss Alps, during 1989 (Brown et al., 1993a). (b) The temporal variation in *Ca2+ flux from Haut Glacier d'Arolla during 1989. Maximum fluxes are associated with higher discharge waters. (9K)Figure 2. (a) The temporal variation of discharge (Q) and non-sea-salt *Ca2+ concentration in runoff from Manitsoq Glacier, a small outlet glacier on the SW margin of the Greenland Ice Sheet, during 1999. The glacier is warm based, but has a cold-based margin during the winter and early ablation season, so displays polythermal-based hydrological features (Skidmore et al., in preparation). (b) The temporal variation in *Ca2+ flux from Manitsoq Glacier during 1999. Maximum flux is associated with an early season "outburst" event, where longer stored subglacial water first exits the glacier. Otherwise, maximum fluxes are associated with higher discharge waters. (10K)Figure 3. (a) The temporal variation of discharge and *Ca2+ concentration in runoff from Scott Turnerbreen, a small, cold-based, valley glacier on Svalbard, during 1994 (after Hodgkins et al., 1997). (b) The temporal variation in *Ca2+ flux from Scott Turnerbreen during 1994. Maximum fluxes are associated with higher discharge waters, although the precise associations are complex. This chapter will expand on these themes, and endeavor to integrate ongoing research into a state-of-the-science review, as well as indicating the areas into which the next generation of studies are likely to proceed. It is first necessary to understand a little basic glaciology and glacier hydrology to appreciate the principal features of the different chemical weathering environments that will be described below. The following sections summarize the types of glacial environments in which water flows, their typical debris content, the relative residence time of water, and the typical reactions that occur within them.

Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field.

PubMed

Forbes, Thomas P; Degertekin, F Levent; Fedorov, Andrei G

2011-01-01

Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

The structure and dynamics of tornado-like vortices

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

Nolan, D.S.; Farrell, B.F.

The structure and dynamics of axisymmetric tornado-like vortices are explored with a numerical model of axisymmetric incompressible flow based on recently developed numerical methods. The model is first shown to compare favorably with previous results and is then used to study the effects of varying the major parameters controlling the vortex: the strength of the convective forcing, the strength of the rotational forcing, and the magnitude of the model eddy viscosity. Dimensional analysis of the model problem indicates that the results must depend on only two dimensionless parameters. The natural choices for these two parameters are a convective Reynolds numbermore » (based on the velocity scale associated with the convective forcing) and a parameter analogous to the swirl ratio in laboratory models. However, by examining sets of simulations with different model parameters it is found that a dimensionless parameter known as the vortex Reynolds number, which is the ratio of the far-field circulation to the eddy viscosity, is more effective than the convention swirl ratio for predicting the structure of the vortex. The parameter space defined by the choices for model parameters is further explored with large sets of numerical simulations. For much of this parameter space it is confirmed that the vortex structure and time-dependent behavior depend strongly on the vortex Reynolds number and only weakly on the convective Reynolds number. The authors also find that for higher convective Reynolds numbers, the maximum possible wind speed increases, and the rotational forcing necessary to achieve that wind speed decreases. Physical reasoning is used to explain this behavior, and implications for tornado dynamics are discussed.« less

Super-spinning compact objects and models of high-frequency quasi-periodic oscillations observed in Galactic microquasars. II. Forced resonances

NASA Astrophysics Data System (ADS)

Kotrlová, A.; Šrámková, E.; Török, G.; Stuchlík, Z.; Goluchová, K.

2017-11-01

In our previous work (Paper I) we applied several models of high-frequency quasi-periodic oscillations (HF QPOs) to estimate the spin of the central compact object in three Galactic microquasars assuming the possibility that the central compact body is a super-spinning object (or a naked singularity) with external spacetime described by Kerr geometry with a dimensionless spin parameter a ≡ cJ/GM2 > 1. Here we extend our consideration, and in a consistent way investigate implications of a set of ten resonance models so far discussed only in the context of a < 1. The same physical arguments as in Paper I are applied to these models, I.e. only a small deviation of the spin estimate from a = 1, a ≳ 1, is assumed for a favoured model. For five of these models that involve Keplerian and radial epicyclic oscillations we find the existence of a unique specific QPO excitation radius. Consequently, there is a simple behaviour of dimensionless frequency M × νU(a) represented by a single continuous function having solely one maximum close to a ≳ 1. Only one of these models is compatible with the expectation of a ≳ 1. The other five models that involve the radial and vertical epicyclic oscillations imply the existence of multiple resonant radii. This signifies a more complicated behaviour of M × νU(a) that cannot be represented by single functions. Each of these five models is compatible with the expectation of a ≳ 1.

Angular circulation speed of tablets in a vibratory tablet coating pan.

PubMed

Kumar, Rahul; Wassgren, Carl

2013-03-01

In this work, a single tablet model and a discrete element method (DEM) computer simulation are developed to obtain the angular circulation speed of tablets in a vibratory tablet coating pan for range of vibration frequencies and amplitudes. The models identify three important dimensionless parameters that influence the speed of the tablets: the dimensionless amplitude ratio (a/R), the Froude number (aω2/g), and the tablet-wall friction coefficient, where a is the peak vibration amplitude at the drum center, ω is the vibration angular frequency, R is the drum radius, and g is the acceleration due to gravity. The models predict that the angular circulation speed of tablets increases with an increase in each of these parameters. The rate of increase in the angular circulation speed is observed to decrease for larger values of a/R. The angular circulation speed reaches an asymptote beyond a tablet-wall friction coefficient value of about 0.4. Furthermore, it is found that the Froude number should be greater than one for the tablets to start circulating. The angular circulation speed increases as Froude number increases but then does not change significantly at larger values of the Froude number. Period doubling, where the motion of the bed is repeated every two cycles, occurs at a Froude number larger than five. The single tablet model, although much simpler than the DEM model, is able to predict the maximum circulation speed (the limiting case for a large value of tablet-wall friction coefficient) as well as the transition to period doubling.

Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

PubMed Central

Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

2011-01-01

Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing. PMID:21301636

Accurate measurement of dispersion data through short and narrow tubes used in very high-pressure liquid chromatography.

PubMed

Gritti, Fabrice; McDonald, Thomas; Gilar, Martin

2015-09-04

An original method is proposed for the accurate and reproducible measurement of the time-based dispersion properties of short L< 50cm and narrow rc< 50μm tubes at mobile phase flow rates typically used in very high-pressure liquid chromatography (vHPLC). Such tubes are used to minimize sample dispersion in vHPLC; however, their dispersion characteristics cannot be accurately measured at such flow rates due to system dispersion contribution of vHPLC injector and detector. It is shown that using longer and wider tubes (>10μL) enables a reliable measurement of the dispersion data. We confirmed that the dimensionless plot of the reduced dispersion coefficient versus the reduced linear velocity (Peclet number) depends on the aspect ratio, L/rc, of the tube, and unexpectedly also on the diffusion coefficient of the analyte. This dimensionless plot could be easily obtained for a large volume tube, which has the same aspect ratio as that of the short and narrow tube, and for the same diffusion coefficient. The dispersion data for the small volume tube are then directly extrapolated from this plot. For instance, it is found that the maximum volume variances of 75μm×30.5cm and 100μm×30.5cm prototype finger-tightened connecting tubes are 0.10 and 0.30μL(2), respectively, with an accuracy of a few percent and a precision smaller than seven percent. Copyright © 2015 Elsevier B.V. All rights reserved.

Optimum parallel step-sector bearing lubricated with an incompressible fluid

NASA Technical Reports Server (NTRS)

Hamrock, B. J.

1983-01-01

The dimensionless parameters normally associated with a step sector thrust bearing are the film thickness ratio, the dimensionless step location, the number of sectors, the radius ratio, and the angular extent of the lubrication feed groove. The optimum number of sectors and the parallel step configuration for a step sector thrust bearing while considering load capacity or stiffness and assuming an incompressible fluid are presented.

47 CFR 90.303 - Availability of frequencies.

Code of Federal Regulations, 2013 CFR

2013-10-01

...)” curve in Figure B in 47 CFR 90.309(b). (ii) For base stations located west of the Hudson River, Kill Van Kull, and Arthur Kill, the maximum ERP and antenna height shall be limited to the entries specified in...

47 CFR 90.303 - Availability of frequencies.

Code of Federal Regulations, 2012 CFR

2012-10-01

...)” curve in Figure B in 47 CFR 90.309(b). (ii) For base stations located west of the Hudson River, Kill Van Kull, and Arthur Kill, the maximum ERP and antenna height shall be limited to the entries specified in...

47 CFR 90.303 - Availability of frequencies.

Code of Federal Regulations, 2014 CFR

2014-10-01

...)” curve in Figure B in 47 CFR 90.309(b). (ii) For base stations located west of the Hudson River, Kill Van Kull, and Arthur Kill, the maximum ERP and antenna height shall be limited to the entries specified in...

Topic Detection in Online Chat

DTIC Science & Technology

2009-09-01

CODE 17. SECURITY CLASSIFICATION OF REPORT Unclassified 18 . SECURITY CLASSIFICATION OF THIS PAGE Unclassified 19. SECURITY CLASSIFICATION...Documents and Author-Author Documents—Radial Kernel. .............. 66 Figure 18 . Classifiers Results: LDA Models Created by Textbook-Author...Trained on Two Classes............................................................................................... 72 Table 18 . Maximum

A minimalist probabilistic description of root zone soil water

USGS Publications Warehouse

Milly, P.C.D.

2001-01-01

The probabilistic response of depth‐integrated soil water to given climatic forcing can be described readily using an existing supply‐demand‐storage model. An apparently complex interaction of numerous soil, climate, and plant controls can be reduced to a relatively simple expression for the equilibrium probability density function of soil water as a function of only two dimensionless parameters. These are the index of dryness (ratio of mean potential evaporation to mean precipitation) and a dimensionless storage capacity (active root zone soil water capacity divided by mean storm depth). The first parameter is mainly controlled by climate, with surface albedo playing a subsidiary role in determining net radiation. The second is a composite of soil (through moisture retention characteristics), vegetation (through rooting characteristics), and climate (mean storm depth). This minimalist analysis captures many essential features of a more general probabilistic analysis, but with a considerable reduction in complexity and consequent elucidation of the critical controls on soil water variability. In particular, it is shown that (1) the dependence of mean soil water on the index of dryness approaches a step function in the limit of large soil water capacity; (2) soil water variance is usually maximized when the index of dryness equals 1, and the width of the peak varies inversely with dimensionless storage capacity; (3) soil water has a uniform probability density function when the index of dryness is 1 and the dimensionless storage capacity is large; and (4) the soil water probability density function is bimodal if and only if the index of dryness is <1, but this bimodality is pronounced only for artificially small values of the dimensionless storage capacity.

Impact of droplet on superheated surfaces

NASA Astrophysics Data System (ADS)

Lohse, Detlef; Staat, Hendrik J. J.; Tran, Tuan; Prosperetti, Andrea; Sun, Chao

2012-11-01

At impact of a liquid droplet on a smooth surface heated way above the liquid's boiling point, the droplet spreads without any surface contact, floating on its own (Leidenfrost-type) vapor layer, and then bounces back. We show that the dimensionless maximum spreading factor Γ, defined by the ratio of the maximal spreading diameter and the droplet diameter, shows a universal scaling Γ ~ Weγ with the Weber number We - regardless of surface temperature and of liquid properties - which is much steeper than that for the impact on non-heated (hydrophilic or hydrophobic) surfaces, for which γ = 1 / 4 . Based on the idea that the vapor shooting out of the gap between the droplet and the superheated surface drags the liquid outwards, we derive scaling laws for the spreading factor Γ, the vapor layer thickness, and the vapor flow velocity.

Mechanical and Physical Properties of ASTM C33 Sand

DTIC Science & Technology

2008-02-01

ERDC/GSL TR-08-2 7 Grain-size Distribution (1) (ASTM D 422) 1 test run on total sand sample Proctor Density Curves (2) (ASTM D 698 and D... Proctor (Figure 4). Because of the noncohesive nature of the SP material, a series of relative density tests measuring both minimum and maximum... density tests were conducted with moisture added to the sand. A summary of the minimum and maximum densities is given in Table 2. During Proctor

Mass Efficiency Considerations for Thermally Insulated Structural Skin of an Aerospace Vehicle

NASA Technical Reports Server (NTRS)

Blosser, Max L.

2012-01-01

An approximate equation was derived to predict the mass of insulation required to limit the maximum temperature reached by an insulated structure subjected to a transient heating pulse. In the course of the derivation two figures of merit were identified. One figure of merit correlates to the effectiveness of the heat capacity of the underlying structural material in reducing the amount of required insulation. The second figure of merit provides an indicator of the mass efficiency of the insulator material. An iterative, one dimensional finite element analysis was used to size the external insulation required to protect the structure at a single location on the Space Shuttle Orbiter and a reusable launch vehicle. Required insulation masses were calculated for a range of different materials for both structure and insulator. The required insulation masses calculated using the approximate equation were shown to typically agree with finite element results within 10 to 20 percent over the range of parameters studied. Finite element results closely followed the trends indicated by both figures of merit.

Comparative Application of Dimensionless Bankfull Hydraulic Relations for Earth and Titan

NASA Astrophysics Data System (ADS)

Parker, G.

2005-12-01

Recent evidence from the Huygens Probe of the Cassini Mission suggests that Titan, a satellite of Saturn, has rivers of flowing liquid methane which transport disaggregated crustal sediment in the form of ice. Surface images from the Huygens Probe show gravel-sized ice clasts that appear to be well-rounded by fluvial processes. If river morphodynamics on Earth is truly understood at a physical level, then relations that provide reasonable results on Earth ought to provide similarly reasonable results on Titan. These basic relations should be expressed in terms of dimensionless variabes. At least three dimensioned parameters that would be used to form the relevant dimensionless variables can be expected to vary notably between Earth and Titan. These are a) the acceleration of gravity, the kinematic viscosity of the flowing fluid and the submerged specific gravity of the sediment. Dimensionless relations for the threshold of motion, the threshold of significant suspension and bankfull hydraulic geometry that are known to work on Earth are used to predict features of rivers on Titan. Wildcards that make the predictions tentative include the formation of hydrocarbons on Titan that might add a kind of cohesivity not encountered on Earth and a freeze-thaw process of methane that might not be analogous to freeze-thaw processes in high-latitude rivers on Earth.

Thinking Outside the Box...Inside the Box

ERIC Educational Resources Information Center

Winkel, Brian

2012-01-01

We consider an oblique approach to cutting regions out of a flat rectangular sheet and folding to make a maximum volume container. We compare our approach to the traditional approach of cutting out squares at each vertex of the sheet. (Contains 4 figures.)

A Core Curriculum in Geometry.

ERIC Educational Resources Information Center

Tietze, Martha

1992-01-01

Presents four hands-on activities to teach geometric concepts to both honors and non-college-bound students. The activities are adaptable to various levels and use manipulatives and technology to explore the concepts of enlargement, area, maximum volume, and figure duplication in a cooperative setting. (MDH)

The shape and dynamics of the generation of the splash forms in single-phase systems after drop hitting

NASA Astrophysics Data System (ADS)

Sochan, Agata; Beczek, Michał; Mazur, Rafał; RyŻak, Magdalena; Bieganowski, Andrzej

2018-02-01

The splash phenomenon is being increasingly explored with the use of modern measurement tools, including the high-speed cameras. Recording images at a rate of several thousand frames per second facilitates parameterization and description of the dynamics of splash phases. This paper describes the impact of a single drop of a liquid falling on the surface of the same liquid. Three single-phase liquid systems, i.e., water, petrol, and diesel fuel, were examined. The falling drops were characterized by different kinetic energy values depending on the height of the fall, which ranged from 0.1 to 7.0 m. Four forms, i.e., waves, crowns, semi-closed domes, and domes, were distinguished depending on the drop energy. The analysis of the recorded images facilitated determination of the static and dynamic parameters of each form, e.g., the maximum height of each splash form, the width of the splash form at its maximum height, and the rate of growth of the splash form. We, Re, Fr, and K numbers were determined for all analyzed liquid systems. On the basis of the obtained values of dimensionless numbers, the areas of occurrence of characteristic splash forms were separated.

Wave Propagation and Localization via Quasi-Normal Modes and Transmission Eigenchannels

NASA Astrophysics Data System (ADS)

Wang, Jing; Shi, Zhou; Davy, Matthieu; Genack, Azriel Z.

2013-10-01

Field transmission coefficients for microwave radiation between arrays of points on the incident and output surfaces of random samples are analyzed to yield the underlying quasi-normal modes and transmission eigenchannels of each realization of the sample. The linewidths, central frequencies, and transmitted speckle patterns associated with each of the modes of the medium are found. Modal speckle patterns are found to be strongly correlated leading to destructive interference between modes. This explains distinctive features of transmission spectra and pulsed transmission. An alternate description of wave transport is obtained from the eigenchannels and eigenvalues of the transmission matrix. The maximum transmission eigenvalue, τ1 is near unity for diffusive waves even in turbid samples. For localized waves, τ1 is nearly equal to the dimensionless conductance, which is the sum of all transmission eigenvalues, g = Στn. The spacings between the ensemble averages of successive values of lnτn are constant and equal to the inverse of the bare conductance in accord with predictions by Dorokhov. The effective number of transmission eigenvalues Neff determines the contrast between the peak and background of radiation focused for maximum peak intensity. The connection between the mode and channel approaches is discussed.

Wave Propagation and Localization via Quasi-Normal Modes and Transmission Eigenchannels

NASA Astrophysics Data System (ADS)

Wang, Jing; Shi, Zhou; Davy, Matthieu; Genack, Azriel Z.

Field transmission coefficients for microwave radiation between arrays of points on the incident and output surfaces of random samples are analyzed to yield the underlying quasi-normal modes and transmission eigenchannels of each realization of the sample. The linewidths, central frequencies, and transmitted speckle patterns associated with each of the modes of the medium are found. Modal speckle patterns are found to be strongly correlated leading to destructive interference between modes. This explains distinctive features of transmission spectra and pulsed transmission. An alternate description of wave transport is obtained from the eigenchannels and eigenvalues of the transmission matrix. The maximum transmission eigenvalue, τ1 is near unity for diffusive waves even in turbid samples. For localized waves, τ1 is nearly equal to the dimensionless conductance, which is the sum of all transmission eigenvalues, g = Στn. The spacings between the ensemble averages of successive values of lnτn are constant and equal to the inverse of the bare conductance in accord with predictions by Dorokhov. The effective number of transmission eigenvalues Neff determines the contrast between the peak and background of radiation focused for maximum peak intensity. The connection between the mode and channel approaches is discussed.

Transition Experiments on Large Bluntness Cones with Distributed Roughness in Hypersonic Flight

NASA Technical Reports Server (NTRS)

Reda, Daniel. C.; Wilder, Michael C.; Prabhu, Dinesh K.

2012-01-01

Large bluntness cones with smooth nosetips and roughened frusta were flown in the NASA Ames hypersonic ballistic range at a Mach number of 10 through quiescent air environments. Global surface intensity (temperature) distributions were optically measured and analyzed to determine transition onset and progression over the roughened surface. Real-gas Navier-Stokes calculations of model flowfields, including laminar boundary layer development in these flowfields, were conducted to predict values of key dimensionless parameters used to correlate transition on such configurations in hypersonic flow. For these large bluntness cases, predicted axial distributions of the roughness Reynolds number showed (for each specified freestream pressure) that this parameter was a maximum at the physical beginning of the roughened zone and decreased with increasing run length along the roughened surface. Roughness-induced transition occurred downstream of this maximum roughness Reynolds number location, and progressed upstream towards the beginning of the roughened zone as freestream pressure was systematically increased. Roughness elements encountered at the upstream edge of the roughened frusta thus acted like a finite-extent trip array, consistent with published results concerning the tripping effectiveness of roughness bands placed on otherwise smooth surfaces.

Whistler turbulence heating of electrons and ions: Three-dimensional particle-in-cell simuations

DOE PAGES

Gary, S. Peter; Hughes, R. Scott; Wang, Joseph

2016-01-14

In this study, the decay of whistler turbulence in a collisionless, homogeneous, magnetized plasma is studied using three-dimensional particle-in-cell simulations. The simulations are initialized with a narrowband, relatively isotropic distribution of long wavelength whistler modes. A first ensemble of simulations at electron betamore » $${\\beta }_{{\\rm{e}}}$$ = 0.25 and ion-to-electron mass ratio $${m}_{{\\rm{i}}}$$/$${m}_{{\\rm{e}}}$$ = 400 is carried out on a domain cube of dimension $$L{\\omega }_{\\mathrm{pi}}$$/c = 5.12 where $${\\omega }_{\\mathrm{pi}}$$ is the ion plasma frequency. The simulations begin with a range of dimensionless fluctuating field energy densities, $${\\epsilon }_{{\\rm{o}}}$$, and follow the fluctuations as they cascade to broadband, anisotropic turbulence which dissipates at shorter wavelengths, heating both electrons and ions. The electron heating is stronger and preferentially parallel/antiparallel to the background magnetic field $${{\\boldsymbol{B}}}_{{\\rm{o}}};$$ the ion energy gain is weaker and is preferentially in directions perpendicular to $${{\\boldsymbol{B}}}_{{\\rm{o}}}$$. The important new results here are that, over 0.01 < $${\\epsilon }_{{\\rm{o}}}$$ < 0.25, the maximum rate of electron heating scales approximately as $${\\epsilon }_{{\\rm{o}}}$$, and the maximum rate of ion heating scales approximately as $${\\epsilon }_{{\\rm{o}}}^{1.5}$$. A second ensemble of simulations at $${\\epsilon }_{{\\rm{o}}}$$ = 0.10 and $${\\beta }_{{\\rm{e}}}$$ = 0.25 shows that, over 25 < $${m}_{{\\rm{i}}}$$/$${m}_{{\\rm{e}}}\\;$$< 1836, the ratio of the maximum ion heating rate to the maximum electron heating rate scales approximately as $${m}_{{\\rm{e}}}$$/$${m}_{{\\rm{i}}}$$.« less

Scale Properties of Anisotropic and Isotropic Turbulence in the Urban Surface Layer

NASA Astrophysics Data System (ADS)

Liu, Hao; Yuan, Renmin; Mei, Jie; Sun, Jianning; Liu, Qi; Wang, Yu

2017-11-01

The scale properties of anisotropic and isotropic turbulence in the urban surface layer are investigated. A dimensionless anisotropic tensor is introduced and the turbulent tensor anisotropic coefficient, defined as C, where C = 3d3 + 1 (d3 is the minimum eigenvalue of the tensor) is used to characterize the turbulence anisotropy or isotropy. Turbulence is isotropic when C ≈ 1, and anisotropic when C ≪ 1. Three-dimensional velocity data collected using a sonic anemometer are analyzed to obtain the anisotropic characteristics of atmospheric turbulence in the urban surface layer, and the tensor anisotropic coefficient of turbulent eddies at different spatial scales calculated. The analysis shows that C is strongly dependent on atmospheric stability ξ = (z-zd)/L_{{it{MO}}}, where z is the measurement height, zd is the displacement height, and L_{{it{MO}}} is the Obukhov length. The turbulence at a specific scale in unstable conditions (i.e., ξ < 0) is closer to isotropic than that at the same scale under stable conditions. The maximum isotropic scale of turbulence is determined based on the characteristics of the power spectrum in three directions. Turbulence does not behave isotropically when the eddy scale is greater than the maximum isotropic scale, whereas it is horizontally isotropic at relatively large scales. The maximum isotropic scale of turbulence is compared to the outer scale of temperature, which is obtained by fitting the temperature fluctuation spectrum using the von Karman turbulent model. The results show that the outer scale of temperature is greater than the maximum isotropic scale of turbulence.

Figures of merit for laser beam quality

NASA Technical Reports Server (NTRS)

Milster, T. D.; Walker, E. P.

1993-01-01

It was shown how full-width at half maximum (FWHM), full-width at 1/e(sup 2) (FW1/e(sup 2)), Strehl ratio, and encircled energy figures of merit vary with different types of aberration and measurement methods. The array sampling method and the slit-scan method are examined in detail. Our irradiance in the exit pupil of the optical system is a simple gaussian. It was found that in general the slit-scan method and the array method do not yield the same result. The width measurements for the central lobe of the diffraction pattern are very insensitive to aberration.

Providing a complete online multimedia patient record.

PubMed Central

Dayhoff, R. E.; Kuzmak, P. M.; Kirin, G.; Frank, S.

1999-01-01

Seamless integration of all types of patient data is a critical feature for clinical workstation software. The Dept. of Veterans Affairs has developed a multimedia online patient record that includes traditional medical chart information as well as a wide variety of medical images from specialties such as cardiology, pulmonary and gastrointestinal medicine, pathology, radiology, hematology, and nuclear medicine. This online patient record can present data in ways not possible with a paper chart or other physical media. Obtaining a critical mass of information online is essential to achieve the maximum benefits from an integrated patient record system. Images Figure 1 Figure 2 PMID:10566357

The Modification of HOMER Software Application to Provide the United States Marine Corps with an Energy Planning Tool

DTIC Science & Technology

2012-12-01

circuit used to discharge LiFePO4 batteries. .................84  Figure 33.  The PSPICE model of our constant current circuit...Ion Battery LiFePO4 Lithium Iron Phosphate xviii MEP Mobile Electric Power MP Maximum Power MPPT Maximum Power Point Tracker NASA National...GREENS). GREENS has eight large 200-W solar panels, four Lithium Iron Phosphate ( LiFePO4 ) batteries, and an integrated controller. GREENS is not

Analysis of a Van de Graaff Generator for EMP Direct Current Survivability Testing

DTIC Science & Technology

2013-03-01

voltage source, VS , equals the voltage load, VL, as shown in the schematic of Figure 12. When impedance is matched, maximum power is transferred...maximum power is 42 transmitted, and VS =VL. The voltage drops shown in Table 7 are from the skin effect at frequencies above 1 MHz, as well... voltage . 46 3.1.6 Response to CVR Location The purpose of these experiments was to find the best cable and connector attachment that would

Ad-Hoc Sensor Networks for Maritime Interdiction Operations and Regional Security

DTIC Science & Technology

2012-09-01

as resistant to rough sea conditions as the SHARC, since its maximum operation limit is sea state 3. Its maximum speed approaches three knots and...which renders it corrosion resistant and lightweight. Its length is 3.2 meters with a rotor diameter at 3.3 meters. It flies at speeds of 50 knots...NMIOTC main building and to a moored training ship (see Figure 50), (2) GSM/GPRS was networked with swimmers , (3) security patrol and target vessels

Substrate mass transfer: analytical approach for immobilized enzyme reactions

NASA Astrophysics Data System (ADS)

Senthamarai, R.; Saibavani, T. N.

2018-04-01

In this paper, the boundary value problem in immobilized enzyme reactions is formulated and approximate expression for substrate concentration without external mass transfer resistance is presented. He’s variational iteration method is used to give approximate and analytical solutions of non-linear differential equation containing a non linear term related to enzymatic reaction. The relevant analytical solution for the dimensionless substrate concentration profile is discussed in terms of dimensionless reaction parameters α and β.

Characterization of rarefaction waves in van der Waals fluids

NASA Astrophysics Data System (ADS)

Yuen, Albert; Barnard, John J.

2015-12-01

We calculate the isentropic evolution of an instantaneously heated foil, assuming a van der Waals equation of state with the Maxwell construction. The analysis by Yuen and Barnard [Phys. Rev. E 92, 033019 (2015), 10.1103/PhysRevE.92.033019] is extended for the particular case of three degrees of freedom. We assume heating to temperatures in the vicinity of the critical point. The self-similar profiles of the rarefaction waves describing the evolution of the foil display plateaus in density and temperature due to a phase transition from the single-phase to the two-phase regime. The hydrodynamic equations are expressed in a dimensionless form and the solutions form a set of universal curves, depending on a single parameter: the dimensionless initial entropy. We characterize the rarefaction waves by calculating how the plateau length, density, pressure, temperature, velocity, internal energy, and sound speed vary with dimensionless initial entropy.

Fast Magnetic Micropropellers with Random Shapes

PubMed Central

2015-01-01

Studying propulsion mechanisms in low Reynolds number fluid has implications for many fields, ranging from the biology of motile microorganisms and the physics of active matter to micromixing in catalysis and micro- and nanorobotics. The propulsion of magnetic micropropellers can be characterized by a dimensionless speed, which solely depends on the propeller geometry for a given axis of rotation. However, this dependence has so far been only investigated for helical propeller shapes, which were assumed to be optimal. In order to explore a larger variety of shapes, we experimentally studied the propulsion properties of randomly shaped magnetic micropropellers. Surprisingly, we found that their dimensionless speeds are high on average, comparable to previously reported nanofabricated helical micropropellers. The highest dimensionless speed we observed is higher than that of any previously reported propeller moving in a low Reynolds number fluid, proving that physical random shape generation can be a viable optimization strategy. PMID:26383225

Estimating Mass of Inflatable Aerodynamic Decelerators Using Dimensionless Parameters

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.

2011-01-01

This paper describes a technique for estimating mass for inflatable aerodynamic decelerators. The technique uses dimensional analysis to identify a set of dimensionless parameters for inflation pressure, mass of inflation gas, and mass of flexible material. The dimensionless parameters enable scaling of an inflatable concept with geometry parameters (e.g., diameter), environmental conditions (e.g., dynamic pressure), inflation gas properties (e.g., molecular mass), and mass growth allowance. This technique is applicable for attached (e.g., tension cone, hypercone, and stacked toroid) and trailing inflatable aerodynamic decelerators. The technique uses simple engineering approximations that were developed by NASA in the 1960s and 1970s, as well as some recent important developments. The NASA Mars Entry and Descent Landing System Analysis (EDL-SA) project used this technique to estimate the masses of the inflatable concepts that were used in the analysis. The EDL-SA results compared well with two independent sets of high-fidelity finite element analyses.

Coefficient of performance and its bounds with the figure of merit for a general refrigerator

NASA Astrophysics Data System (ADS)

Long, Rui; Liu, Wei

2015-02-01

A general refrigerator model with non-isothermal processes is studied. The coefficient of performance (COP) and its bounds at maximum χ figure of merit are obtained and analyzed. This model accounts for different heat capacities during the heat transfer processes. So, different kinds of refrigerator cycles can be considered. Under the constant heat capacity condition, the upper bound of the COP is the Curzon-Ahlborn (CA) coefficient of performance and is independent of the time durations of the heat exchanging processes. With the maximum χ criterion, in the refrigerator cycles, such as the reversed Brayton refrigerator cycle, the reversed Otto refrigerator cycle and the reversed Atkinson refrigerator cycle, where the heat capacity in the heat absorbing process is not less than that in the heat releasing process, their COPs are bounded by the CA coefficient of performance; otherwise, such as for the reversed Diesel refrigerator cycle, its COP can exceed the CA coefficient of performance. Furthermore, the general refined upper and lower bounds have been proposed.

An autostratigraphic view of the long-term dynamics of delta distributary channels: A new step forward with the grade index model

NASA Astrophysics Data System (ADS)

Naruse, H.; Muto, T.

2017-12-01

Autostratigraphy is the stratigraphy that is generated by large-scale, deterministic autogenic processes of depositional systems, based on the full recognition of non-equilibrium behavior in response to steady external forcing. Recent experimental studies to explore the effects of basin water depth on the dynamics of distributary channels have brought a new geometrical scheme, here referred to as the grade index model, which is expected to make a significant step forward for development of the autostratigraphy of river deltas. Grade index (0 ≤ Gindex ≤1) is a dimensionless number that describes how close the alluvial river is to a graded state and is given as the ratio of subaerial allocation of the supplied sediment to both subaerial and subaqueous allocation of the sediment, in the form of a function of dimensionless basin water depth (h*). The grade index model for a particular geometrical setting suggests that as h* increase toward +∞, all of dimensionless magnitudes of delta progradation rate (Rpro*), alluvial aggradation rate (Ragg*), channel migration rate (Rmig*), avulsion frequency decrease toward 0, and all of dimensionless timescales of channel shifting (τs*), recurrence of channels (τr*), channel avulsion (τA*) increase toward +∞, and also that Rpro* = Ragg* = Rmig* = fA* = (τs*)-1 = (τr*)-1 = (τA* )-1 = Gindex. This grade index model, despite its simple structure, offers deep insight into the rationale of shoreline autoretreat, a typical large-scale, deterministic autogenic process that is realized by non-equilibrium response to steady base level rise. A simple geometrical modeling leads to a finding that Ppro* = (1 - Ab*) Gindex, where Ab* is a dimensionless form of the bottom surface of the deltaic deposit (Ab) given by dividing Ab with the square of autostratigraphic length scale (Λ). As the delta grows with base level rise, Ab progressively increases and then inevitably meets an event that Ab* exceeds 1 (i.e. Ab exceeds Λ2). We also find that Pagg* = A* + (1 - Ab*) Gindex, where A* is a dimensionless horizontal area of the deltaplain (A* = A/Λ2). At the moment of autodrowning, A* becomes 0, Ab* takes a positive value larger than one, h* is infinitely large, and thus and Gindex takes a value close to zero. Thus, shoreline autoretreat and autodrowning of the delta are closely related to grade index.

A physically-based method for predicting peak discharge of floods caused by failure of natural and constructed earthen dams

USGS Publications Warehouse

Walder, J.S.; O'Connor, J. E.; Costa, J.E.; ,

1997-01-01

We analyse a simple, physically-based model of breach formation in natural and constructed earthen dams to elucidate the principal factors controlling the flood hydrograph at the breach. Formation of the breach, which is assumed trapezoidal in cross-section, is parameterized by the mean rate of downcutting, k, the value of which is constrained by observations. A dimensionless formulation of the model leads to the prediction that the breach hydrograph depends upon lake shape, the ratio r of breach width to depth, the side slope ?? of the breach, and the parameter ?? = (V.D3)(k/???gD), where V = lake volume, D = lake depth, and g is the acceleration due to gravity. Calculations show that peak discharge Qp depends weakly on lake shape r and ??, but strongly on ??, which is the product of a dimensionless lake volume and a dimensionless erosion rate. Qp(??) takes asymptotically distinct forms depending on whether < ??? 1 or < ??? 1. Theoretical predictions agree well with data from dam failures for which k could be reasonably estimated. The analysis provides a rapid and in many cases graphical way to estimate plausible values of Qp at the breach.We analyze a simple, physically-based model of breach formation in natural and constructed earthen dams to elucidate the principal factors controlling the flood hydrograph at the breach. Formation of the breach, which is assumed trapezoidal in cross-section, is parameterized by the mean rate of downcutting, k, the value of which is constrained by observations. A dimensionless formulation of the model leads to the prediction that the breach hydrograph depends upon lake shape, the ratio r of breach width to depth, the side slope ?? of the breach, and the parameter ?? = (V/D3)(k/???gD), where V = lake volume, D = lake depth, and g is the acceleration due to gravity. Calculations show that peak discharge Qp depends weakly on lake shape r and ??, but strongly on ??, which is the product of a dimensionless lake volume and a dimensionless erosion rate. Qp(??) takes asymptotically distinct forms depending on whether ?????1 or ?????1. Theoretical predictions agree well with data from dam failures for which k could be reasonably estimated. The analysis provides a rapid and in many cases graphical way to estimate plausible values of Qp at the breach.

Association between ozone and asthma emergency department visits in Saint John, New Brunswick, Canada.

PubMed Central

Stieb, D M; Burnett, R T; Beveridge, R C; Brook, J R

1996-01-01

This study examines the relationship of asthma emergency department (ED) visits to daily concentrations of ozone and other air pollutants in Saint John, New Brunswick, Canada. Data on ED visits with a presenting complaint of asthma (n = 1987) were abstracted for the period 1984-1992 (May-September). Air pollution variables included ozone, sulfur dioxide, nitrogen dioxide, sulfate, and total suspended particulate (TSP); weather variables included temperature, humidex, dewpoint, and relative humidity. Daily ED visit frequencies were filtered to remove day of the week and long wave trends, and filtered values were regressed on air pollution and weather variables for the same day and the 3 previous days. The mean daily 1-hr maximum ozone concentration during the study period was 41.6 ppb. A positive, statistically significant (p < 0.05) association was observed between ozone and asthma ED visits 2 days later, and the strength of the association was greater in nonlinear models. The frequency of asthma ED visits was 33% higher (95% CI, 10-56%) when the daily 1-hr maximum ozone concentration exceeded 75 ppb (the 95th percentile). The ozone effect was not significantly influenced by the addition of weather or other pollutant variables into the model or by the exclusion of repeat ED visits. However, given the limited number of sampling days for sulfate and TSP, a particulate effect could not be ruled out. We detected a significant association between ozone and asthma ED visits, despite the vast majority of sampling days being below current U.S. and Canadian standards. Images Figure 1. A Figure 1. B Figure 2. Figure 3. PMID:9118879

Energy-Efficient Underwater Surveillance by Means of Hybrid Aquacopters

DTIC Science & Technology

2014-12-01

life-cycle analysis, photovoltaic device maximum power point tracking (MPPT), and surface treatments for antifouling of the solar cells can be...108 3. Power Conversion and Storage...15 Figure 10. Shallow Water Analysis and Forecast System product, displaying regional ocean current vectors overlaying a sea surface

Ecotoxicity in the Reconquista River, province of Buenos Aires, Argentina: a preliminary study.

PubMed Central

Herkovits, J; Perez-Coll, C S; Herkovits, F D

1996-01-01

The Reconquista River in Argentina is considered a "supercritical" river basin due to environmental degradation. Within its valley of 1.547 km2, there are more than 3 million inhabitants and 12,000 industries. Using early-life-stage toxicity tests with Bufo arenarum embryos (the most sensitive of three native species), we determined the water quality at six sampling stations of the river valley and expressed the results as acute and chronic toxicity units. Along most of the river, the toxicity was higher than the allowable level of whole industrial effluent toxicity recommended by U.S. EPA. In a tributary stream, Arroyo Moron, the water was about 10 times more toxic than the criteria maximum concentration (CMC) recommended by U.S. EPA for industrial effluents. Similar degradation of the water quality was found taking as a reference value an upstream sampling station. In all places where the water quality was worse than the CMC, no macroorganisms were found, and in one of these places, a large number of dead fishes was observed. Our study points out that amphibian early-life-stage toxicity tests could be appropriate for assessing water contamination and water quality, which is essential for diagnosis, protection of environmental services, monitoring, and restoration purposes. Images Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. PMID:8820587

Assessment of capabilities of lidar systems in day-and night-time under different atmospheric and internal-noise conditions

NASA Astrophysics Data System (ADS)

Agishev, Ravil; Comerón, Adolfo

2018-04-01

As an application of the dimensionless parameterization concept proposed earlier for the characterization of lidar systems, the universal assessment of lidar capabilities in day and night conditions is considered. The dimensionless parameters encapsulate the atmospheric conditions, the lidar optical and optoelectronic characteristics, including the photodetector internal noise, and the sky background radiation. Approaches to ensure immunity of the lidar system to external background radiation are discussed.

Stretching a Curved Surface in a Viscous Fluid

NASA Astrophysics Data System (ADS)

Sajid, M.; N., Ali; T., Javed; Z., Abbas

2010-02-01

This work is concerned with the viscous flow due to a curved stretching sheet. The similarity solution of the problem is obtained numerically by a shooting method using the Runge-Kutta algorithm. The physical quantities of interest like the fluid velocity and skin friction coefficient are obtained and discussed under the influence of dimensionless curvature. It is evident from the results that dimensionless curvature causes an increase in boundary layer thickness and a decrease in the skin friction coefficient.

Modeling of spray droplets deformation and breakup

NASA Technical Reports Server (NTRS)

Ibrahim, E. A.; Yang, H. Q.; Przekwas, A. J.

1993-01-01

A droplet deformation and breakup (DDB) model is proposed to study shear-type mechanism of spray droplets in pure extentional flows. A numerical solution of the DDB model equation is obtained using a fourth-order Runge-Kutta initial-value solver. The predictions of the DDB model as well as semianalytical and the Taylor analogy models are compared with the experimental data (Krzeczkowski, 1980) for shear breakup, which depict the dimensionless deformation of the drop vs dimensionless time.

Various methods of determining the natural frequencies and damping of composite cantilever plates. 2. Approximate solution by Galerkin's method for the trinomial model of damping

NASA Astrophysics Data System (ADS)

Ekel'chik, V. S.; Ryabov, V. M.

1997-01-01

The application of Kantorovich's method to a trinomial model of deformation taking into account transverse bending of a plate leads to a connected system of three ordinary differential equations of fourth order with respect to three unknown functions of the longitudinal coordinate and to the coresponding boundary conditions for them at the fixed end and on the free edge. For the approximate calculation of the frequencies and forms of natural vibrations Galerkin's method is used, and as coordinate functions we chose orthogonal Jacobi polynomials with weight function. The dimensionless frequencies depend on the magnitude of the four dimensionless complexes, three of which characterize the anisotropy of the elastic properties of the composite. For the fibrous composites used at present we determined the possible range of change of the dimensionless complexes d16 and d26 attained by oblique placement. The article examines the influence of the angle of reinforcement on some first dimensionless frequencies of a plate made of unidirectional carbon reinforced plastic. It also analyzes the asymptotics of the frequencies when the length of the plate is increased, and it shows that for strongly anisotropic material with the structure [ϕ]T the frequencies of the flexural as well as of the torsional vibrations may be substantially lower when flexural-torsional interaction is taken into account.

Thermochemically evolved nanoplatelets of bismuth selenide with enhanced thermoelectric figure of merit

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

Ali, Zulfiqar; Cao, Chuanbao, E-mail: cbcao@bit.edu.cn; Butt, Faheem K.

We firstly present a simple thermochemical method to fabricate high-quality Bi{sub 2}Se{sub 3} nanoplatelets with enhanced figure of merit using elemental bismuth and selenium powders as precursors. The crystal structure of as synthesized products is characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) measurements. Morphological and chemical synthetic parameters are investigated through a series of experiments; thickness and composition of the platelets are well controlled in large scale production. Subsequently spark plasma sintering (SPS) is performed to fabricate n-type nanostructured bulk thermoelectric materials. Raman Spectroscopy of the two selected samples with approximatelymore » of 50 and 100 nm thicknesses shows three vibrational modes. The lower thickness sample exhibits the maximum red shift of about 2.17 cm{sup -1} and maximum broadening of about 10 cm{sup -1} by in-plane vibrational mode E{sup 2}{sub g}. The enhanced value of figure of merit ∼0.41 is obtained for pure phase bismuth selenide to the best of our knowledge. We observe metallic conduction behavior while semiconducting behavior for nanostructured bismuth selenide is reported elsewhere which could be due to different synthetic techniques adopted. These results clearly suggest that our adopted synthetic technique has profound effect on the electronic and thermoelectric transport properties of this material.« less

Advanced dielectric continuum model of preferential solvation

NASA Astrophysics Data System (ADS)

Basilevsky, Mikhail; Odinokov, Alexey; Nikitina, Ekaterina; Grigoriev, Fedor; Petrov, Nikolai; Alfimov, Mikhail

2009-01-01

A continuum model for solvation effects in binary solvent mixtures is formulated in terms of the density functional theory. The presence of two variables, namely, the dimensionless solvent composition y and the dimensionless total solvent density z, is an essential feature of binary systems. Their coupling, hidden in the structure of the local dielectric permittivity function, is postulated at the phenomenological level. Local equilibrium conditions are derived by a variation in the free energy functional expressed in terms of the composition and density variables. They appear as a pair of coupled equations defining y and z as spatial distributions. We consider the simplest spherically symmetric case of the Born-type ion immersed in the benzene/dimethylsulfoxide (DMSO) solvent mixture. The profiles of y(R ) and z(R ) along the radius R, which measures the distance from the ion center, are found in molecular dynamics (MD) simulations. It is shown that for a given solute ion z(R ) does not depend significantly on the composition variable y. A simplified solution is then obtained by inserting z(R ), found in the MD simulation for the pure DMSO, in the single equation which defines y(R ). In this way composition dependences of the main solvation effects are investigated. The local density augmentation appears as a peak of z(R ) at the ion boundary. It is responsible for the fine solvation effects missing when the ordinary solvation theories, in which z =1, are applied. These phenomena, studied for negative ions, reproduce consistently the simulation results. For positive ions the simulation shows that z ≫1 (z =5-6 at the maximum of the z peak), which means that an extremely dense solvation shell is formed. In such a situation the continuum description fails to be valid within a consistent parametrization.

Fluid-driven cracks in an elastic matrix in the toughness-dominated limit

PubMed Central

Lai, Ching-Yao; Zheng, Zhong; Dressaire, Emilie

2016-01-01

The dynamics of fluid-driven cracks in an elastic matrix is studied experimentally. We report the crack radius R(t) as a function of time, as well as the crack shapes w(r,t) as a function of space and time. A dimensionless parameter, the pressure ratio Δpf/Δpv, is identified to gauge the relative importance between the toughness (Δpf) and viscous (Δpv) effects. In our previous paper (Lai et al. 2015 Proc. R. Soc. A 471, 20150255. (doi:10.1098/rspa.2015.0255)), we investigated the viscous limit experimentally when the toughness-related stresses are negligible for the crack propagation. In this paper, the experimental parameters, i.e. Young’s modulus E of the gelatin, viscosity μ of the fracturing liquid and the injection flow rate Q, were chosen so that the viscous effects in the flow are negligible compared with the toughness effects, i.e. Δpf/Δpv≫1. In this limit, the crack dynamics can be described by the toughness-dominated scaling laws, which give the crack radius R(t)∝t2/5 and the half maximum crack thickness W(t)∝t1/5. The experimental results are in good agreement with the predictions of the toughness scaling laws: the experimental data for crack radius R(t) for a wide range of parameters (E,μ,Q) collapse after being rescaled by the toughness scaling laws, and the rescaled crack shapes w(r,t) also collapse to a dimensionless shape, which demonstrates the self-similarity of the crack shape. The appropriate choice of the viscous or toughness scaling laws is important to accurately describe the crack dynamics. This article is part of the themed issue ‘Energy and the subsurface’. PMID:27597782

DOES MAGNETIC-FIELD-ROTATION MISALIGNMENT SOLVE THE MAGNETIC BRAKING CATASTROPHE IN PROTOSTELLAR DISK FORMATION?

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

Li Zhiyun; Krasnopolsky, Ruben; Shang, Hsien

2013-09-01

Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. In the simplest case of a laminar (non-turbulent) core with the magnetic field aligned with the rotation axis, both analytic considerations and numerical simulations have shown that the formation of a large, 10{sup 2} AU scale, rotationally supported protostellar disk is suppressed by magnetic braking in the ideal MHD limit for a realistic level of core magnetization. This theoretical difficulty in forming protostellar disks is termed the ''magnetic braking catastrophe''. A possible resolution to this problem, proposed by Hennebelle and Ciardi and Joos et al.,more » is that misalignment between the magnetic field and rotation axis may weaken the magnetic braking enough to enable disk formation. We evaluate this possibility quantitatively through numerical simulations. We confirm the basic result of Joos et al. that the misalignment is indeed conducive to disk formation. In relatively weakly magnetized cores with dimensionless mass-to-flux ratio {approx}> 4, it enabled the formation of rotationally supported disks that would otherwise be suppressed if the magnetic field and rotation axis are aligned. For more strongly magnetized cores, disk formation remains suppressed, however, even for the maximum tilt angle of 90 Degree-Sign . If dense cores are as strongly magnetized as indicated by OH Zeeman observations (with a mean dimensionless mass-to-flux ratio {approx}2), it would be difficult for the misalignment alone to enable disk formation in the majority of them. We conclude that, while beneficial to disk formation, especially for the relatively weak field case, misalignment does not completely solve the problem of catastrophic magnetic braking in general.« less

Traction contact performance evaluation at high speeds

NASA Technical Reports Server (NTRS)

Tevaarwerk, J. L.

1981-01-01

The results of traction tests performed on two fluids are presented. These tests covered a pressure range of 1.0 to 2.5 GPa, an inlet temperature range of 30 'C to 70 'C, a speed range of 10 to 80 m/sec, aspect ratios of .5 to 5 and spin from 0 to 2.1 percent. The test results are presented in the form of two dimensionless parameters, the initial traction slope and the maximum traction peak. With the use of a suitable rheological fluid model the actual traction curves measured can now be reconstituted from the two fluid parameters. More importantly, the knowledge of these parameters together with the fluid rheological model, allow the prediction of traction under conditions of spin, slip and any combination thereof. Comparison between theoretically predicted traction under these conditions and those measured in actual traction tests shows that this method gives good results.

Experimental study of the oscillating flow characteristics for a regenerator in a pulse tube cryocooler

NASA Astrophysics Data System (ADS)

Ju, Yonglin; Jiang, Yan; Zhou, Yuan

A dynamic experimental apparatus was designed and constructed to investigate oscillating flow characteristics in a regenerator subjected to a periodically reversing flow established by means of a self-made linear compressor. Detailed experimental data of oscillating pressure drops and phase shift characteristics for regenerators in a high frequency pulse tube cryocooler with an operating frequency of 50 Hz were given. The correlation equations for the maximum and cycle-averaged friction factors in terms of Reynolds numbers and dimensionless distance X were obtained. It was found that the value of the cycle-averaged pressure drop in the oscillating flow across the regenerator is two to three times higher than that of a steady flow at the same Reynolds numbers based on the cross-sectional mean velocity. In addition, the relationship of the phase shifts between the velocity and pressure wave is also discussed.

Drop Impact on Superheated Surfaces

NASA Astrophysics Data System (ADS)

Tran, Tuan; Staat, Hendrik J. J.; Prosperetti, Andrea; Sun, Chao; Lohse, Detlef

2012-01-01

At the impact of a liquid droplet on a smooth surface heated above the liquid’s boiling point, the droplet either immediately boils when it contacts the surface (“contact boiling”), or without any surface contact forms a Leidenfrost vapor layer towards the hot surface and bounces back (“gentle film boiling”), or both forms the Leidenfrost layer and ejects tiny droplets upward (“spraying film boiling”). We experimentally determine conditions under which impact behaviors in each regime can be realized. We show that the dimensionless maximum spreading γ of impacting droplets on the heated surfaces in both gentle and spraying film boiling regimes shows a universal scaling with the Weber number We (γ˜We2/5), which is much steeper than for the impact on nonheated (hydrophilic or hydrophobic) surfaces (γ˜We1/4). We also interferometrically measure the vapor thickness under the droplet.

Thermal elastohydrodynamic lubrication of spur gears

NASA Technical Reports Server (NTRS)

Wang, K. L.; Cheng, H. S.

1980-01-01

An analysis and computer program called TELSGE were developed to predict the variations of dynamic load, surface temperature, and lubricant film thickness along the contacting path during the engagement of a pair of involute spur gears. The analysis of dynamic load includes the effect of gear inertia, the effect of load sharing of adjacent teeth, and the effect of variable tooth stiffness which are obtained by a finite-element method. Results obtained from TELSGE for the dynamic load distributions along the contacting path for various speeds of a pair of test gears show patterns similar to that observed experimentally. Effects of damping ratio, contact ratio, tip relief, and tooth error on the dynamic load were examined. In addition, two dimensionless charts are included for predicting the maximum equilibrium surface temperature, which can be used to estimate directly the lubricant film thickness based on well established EHD analysis.

Modeling texture kinetics during thermal processing of potato products.

PubMed

Moyano, P C; Troncoso, E; Pedreschi, F

2007-03-01

A kinetic model based on 2 irreversible serial chemical reactions has been proposed to fit experimental data of texture changes during thermal processing of potato products. The model links dimensionless maximum force F*(MAX) with processing time. Experimental texture changes were obtained during frying of French fries and potato chips at different temperatures, while literature data for blanching/cooking of potato cubes have been considered. A satisfactory agreement between experimental and predicted values was observed, with root mean square values (RMSs) in the range of 4.7% to 16.4% for French fries and 16.7% to 29.3% for potato chips. In the case of blanching/cooking, the proposed model gave RMSs in the range of 1.2% to 17.6%, much better than the 6.2% to 44.0% obtained with the traditional 1st-order kinetics. The model is able to predict likewise the transition from softening to hardening of the tissue during frying.

Comparison of predicted and measured elastohydrodynamic film thickness in a 20-millimeter-bore ball bearing

NASA Technical Reports Server (NTRS)

Coy, J. J.; Gorla, R. S. R.; Townsend, D. P.

1979-01-01

Elastohydrodynamic film thicknesses were measured for a 20-mm bore ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 445, and 778 N (20, 100, and 175 lb). The corresponding maximum contact stress on the inner race was 1.28, 2.09, and 2.45 GPa (185 000, 303,000, and 356, 000 psi). Test speeds ranged from 400 to 15,000 rpm. Measurements were taken with four different lubricants: (1) synthetic paraffinic; (2) synthetic paraffinic with additives; (3) synthetic type II aircraft oil; and (4) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 27, 65, and 121 C (80, 150, and 250 F). The measured results for the various test parameters were compared to theoretical predictions from computer programs. Also the data were plotted on dimensionless coordinates and compared to several classical isothermal theories.

Design of a Millimeter-Wave Concentrator for Beam Reception in High-Power Wireless Power Transfer

NASA Astrophysics Data System (ADS)

Fukunari, Masafumi; Wongsuryrat, Nat; Yamaguchi, Toshikazu; Nakamura, Yusuke; Komurasaki, Kimiya; Koizumi, Hiroyuki

2017-02-01

This study examined the performance of a developed taper-tube concentrator for 94-GHz millimeter-wave beam reception during wireless power transfer. The received energy is converted into kinetic energy of a working gas in the tube to drive an engine or thruster. The concentrator, which is assumed to have mirror reflection of millimeter waves in it, is designed to be shorter than conventional tapered waveguides of millimeter waves. A dimensionless design law of a concentrator is proposed based on geometric optics theory. Because the applicability of geometric optics theory is unclear, the ratio of its bore diameter to its wavelength was set as small compared to those in other possible applications. Then, the discrepancy between the designed and measured power reception was examined. Results show that the maximum discrepancy was as low as 7 % for the bore-to-wavelength ratio of 20 at the narrow end of the concentrator.

Incorporation of MoS2 nanosheets in CoSb3 matrix as an efficient novel strategy to enhance its thermoelectric performance

NASA Astrophysics Data System (ADS)

Yadav, Suchitra; Chaudhary, Sujeet; Pandya, Dinesh K.

2018-03-01

The nanocomposite approach is considered as an effective way to improve the thermoelectric properties of bulk materials and we have exploited it by simultaneous though independent tackling of the electron and phonon transports. In the present study, through the strategy of anchoring the CoSb3 nanoparticles on the 2-dimensional nanosheets of MoS2, we demonstrate a controlled interplay of the newly created CoSb3/MoS2 interfaces in nanocomposites of varying concentration of MoS2 via significant enhancement of the phonon scattering without deterioration of electron transport. A concurrent occurrence of low energy carrier filtering on account of the interfacial potential barrier helps in beneficial manipulation of grain to grain carrier transport. The dimensionless figure of merit ZT maximizes to 0.53 at 600 K for the CoSb3/MoS2 nanocomposite containing 3 wt% of MoS2, 4-fold increase over the pristine CoSb3 in the 300-600 K range. This study paves the way towards improvement of the thermoelectric performance of p-type CoSb3 using 2D MoS2 as an interfacial additive.

Synthesis and characterization of novel nanostructured thermoelectric materials

NASA Astrophysics Data System (ADS)

Qiu, Xiaofeng; Burda, Clemens

2005-08-01

Having been hibernated for almost 50 years, research in thermoelectric materials is beginning to regain activity because of the recent advances in nanoscience and nanotechnology. Thermoelectric is an old topic, which was discovered as early as 1821 by Thomas Johann Seebeck. During the following 120 years, great advances in both the theories and experiments were achieved. Since the 1950s, studies in thermoelectric have developed very little, because of the painful difficulties in elevating the efficiency of these kinds of materials. The efficiency of thermoelectric materials is determined by a dimensionless parameter--figure of merit (ZT), given by ZT = S2σT/κ where T is the temperature, S is the thermoelectric power (or Seebeck coefficient), σ is the electrical conductivity, and κ is the thermal conductivity. The best commercially available thermoelectric materials nowadays have a ZT around 1.0, which can be only used in some special cases. To be competitive to the kitchen refrigerators or air-conditioners, a ZT >= 3 at room temperature is required. Recently, some exciting results indicated that higher ZT values can be realized by nanoengineering of these materials. Both theoretical calculations and experimental modulations have shown the promising potentials in the elevation of the efficiency of thermoelectric materials.

Bulk Thermoelectric Materials Reinforced with SiC Whiskers

NASA Astrophysics Data System (ADS)

Akao, Takahiro; Fujiwara, Yuya; Tarui, Yuki; Onda, Tetsuhiko; Chen, Zhong-Chun

2014-06-01

SiC whiskers have been incorporated into Zn4Sb3 compound as reinforcements to overcome its extremely brittle nature. The bulk samples were prepared by either hot-extrusion or hot-pressing techniques. The obtained products containing 1 vol.% to 5 vol.% SiC whiskers were confirmed to exhibit sound appearance, high density, and fine-grained microstructure. Mechanical properties such as the hardness and fracture resistance were improved by the addition of SiC whiskers, as a result of dispersion strengthening and microstructural refinement induced by a pinning effect. Furthermore, crack deflection and/or bridging/pullout mechanisms are invoked by the whiskers. Regarding the thermoelectric properties, the Seebeck coefficient and electrical resistivity values comparable to those of the pure compound are retained over the entire range of added whisker amount. However, the thermal conductivity becomes large with increasing amount of SiC whiskers because of the much higher conductivity of SiC relative to the Zn4Sb3 matrix. This results in a remarkable degradation of the dimensionless figure of merit in the samples with addition of SiC whiskers. Therefore, the optimum amount of SiC whiskers in the Zn4Sb3 matrix should be determined by balancing the mechanical properties and thermoelectric performance.

Elastohydrodynamics of elliptical contacts for materials of low elastic modulus

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1983-01-01

The influence of the ellipticity parameter k and the dimensionless speed U, load W, and materials G parameters on minimum film thickness for materials of low elastic modulus was investigated. The ellipticity parameter was varied from 1 (a ball-on-plane configuration) to 12 (a configuration approaching a line contact); U and W were each varied by one order of magnitude. Seventeen cases were used to generate the minimum- and central-film-thickness relations. The influence of lubricant starvation on minimum film thickness in starved elliptical, elastohydrodynamic configurations was also investigated for materials of low elastic modulus. Lubricant starvation was studied simply by moving the inlet boundary closer to the center of the conjunction in the numerical solutions. Contour plots of pressure and film thickness in and around the contact were presented for both fully flooded and starved lubrication conditions. It is evident from these figures that the inlet pressure contours become less circular and closer to the edge of the Hertzian contact zone and that the film thickness decreases substantially as the serverity of starvation increases. The results presented reveal the essential features of both fully flooded and starved, elliptical, elastohydrodynamic conjunctions for materials of low elastic modulus.

Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

DOE PAGES

Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; ...

2014-12-21

In this study, silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K -1 m -1 at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constantsmore » were measured, which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K -1 m -1, which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT ≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators.« less

Cosubstitution effect on the magnetic, transport, and thermoelectric properties of the electron-doped perovskite manganite CaMnO3

NASA Astrophysics Data System (ADS)

Okuda, T.; Fujii, Y.

2010-11-01

We have investigated magnetic, transport, and thermoelecric properties of polycrystalline Ca1-xSrxMn1-yMoyO3, and have tried to optimize the n-type thermoelectric response below room temperature. The Sr substitution enlarges a Mn-O-Mn bond angle and increases a crystal symmetry, which enhances one electron transfer of the electrons doped by the Mo substitution. This effect promotes the competition between correlations of a G-type antiferromagnetic (AF) order and a C-type AF order accompanying a 3d3z2-r2 orbital order, leading to the more complicated magnetic phase diagram of Ca0.75Sr0.25Mn1-yMoyO3 than that of CaMn1-yMoyO3. A subtle balance between the effects of the enhanced one electron transfer and the introduced disorder into the A(Ca)-site upon the transport properties enhances a dimensionless thermoelectric figure-of-merit ZT up to 0.03 at room temperature. However, a correlation of the 3d3z2-r2 orbital order is also promoted by the Sr substitution, which bounds a further enhancement of ZT.

Thermoelectric properties of the electron-doped perovskites Sr1-xCaxTi1-yNbyO3

NASA Astrophysics Data System (ADS)

Fukuyado, J.; Narikiyo, K.; Akaki, M.; Kuwahara, H.; Okuda, T.

2012-02-01

We have investigated thermoelectric (TE) properties for single crystals of perovskites Sr1-xCaxTi1-yNbyO3 for 0 ⩽ x ⩽ 0.4 and 0 ⩽ y ⩽ 0.03 below room temperature (RT). We found that SrTi0.99Nb0.01O3 shows a large power factor at low temperature (PF=50 μW/K2 cm at 100 K ˜ 90 μW/K2 cm at 50 K) and the largest dimensionless TE figure-of-merit below 40 K (ZT ˜ 0.07) among the ever-reported materials. Such a large low-temperature TE response around a carrier concentration of 1020 cm-3 is due to a distinct electron-phonon interaction, which could relate to the superconducting state. We also found that the Ca2+ substitution for Sr2+ increases ZT at 300 K for Sr1-xCaxTi0.97Nb0.03O3 from 0.08 to 0.105. The enhancement of ZT around RT originates both in a large reduction of a thermal conductivity due to an introduced randomness into the crystal structure and in an unexpected enhancement of a Seebeck coefficient.

On the Long-Term "Hesitation Waltz" Between the Earth's Figure and Rotation Axes

NASA Astrophysics Data System (ADS)

Couhert, A.; Mercier, F.; Bizouard, C.

2017-12-01

The principal figure axis of the Earth refers to its axis of maximum inertia. In the absence of external torques, the latter should closely coincide with the rotation pole, when averaged over many years. However, because of tidal and non-tidal mass redistributions within the Earth system, the rotational axis executes a circular motion around the figure axis essentially at seasonal time scales. In between, it is not clear what happens at decadal time spans and how well the two axes are aligned. The long record of accurate Satellite Laser Ranging (SLR) observations to Lageos makes possible to directly measure the long time displacement of the figure axis with respect to the crust, through the determination of the degree 2 order 1 geopotential coefficients for the 34-year period 1983-2017. On the other hand, the pole coordinate time series (mainly from GNSS and VLBI data) yield the motion of the rotation pole with even a greater accuracy. This study is focused on the analysis of the long-term behavior of the two time series, as well as the derivation of possible explanations for their discrepancies.

CARNELIAN containment data report

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

Stubbs, T

The CARNELIAN event was detonated in hole U4af of the Nevada Test Site as indicated in figure 1 .l. The CARNELIAN device had a depth-of-burial (DOB) of 208 m in the alluvium of Area 4 , about 70 m above the Paleozoic formation and 330 m above the standing water level, as shown in the geologic cross-sections of figure 1.2 (l) Figure 1 3 displays the local surface area showing nearby events Stemming of the 2 44 m diameter emplacement hole followed the plan shown in figure 1 4. A log of the stemming operations was maintained by Holmes &more » Narver (2) Detonation time was about 07 00 PDT on July 28,1977, and collapse progressed to the surface at about 19 minutes after the detonation resulting in a crater having a "cookie-cutter" geometry (steep walls with a relatively flat bottom) with a mean radius of 32 2 m and a maximum depth of 10 5 m No radiation arrivals were detected above ground and the CARNELIAN containment was considered successful« less

Morphological and physiological studies on Indian national kabaddi players.

PubMed Central

Dey, S K; Khanna, G L; Batra, M

1993-01-01

Twenty-five national kabaddi players (Asiad gold medalists 1990), mean age 27.91 years, who attended a national camp at the Sports Authority of India, Bangalore before the Beijing Asian Games in 1990, were investigated for their physical characteristics, body fat, lean body mass (LBM) and somatotype. The physiological characteristics assessed included back strength, maximum oxygen uptake capacity and anaerobic capacity (oxygen debt) and related cardiorespiratory parameters (oxygen pulse, breathing equivalent, maximum pulmonary ventilation, maximum heart rate). Body fat was calculated from skinfold thicknesses taken at four different sites, using Harpenden skinfold calipers. An exercise test (graded protocol) was performed on a bicycle ergometer (ER-900) using a computerized EOS Sprint (Jaeger, West Germany). The mean(s.d.) percentage body fat (17.56(3.48)) of kabaddi players was found to be higher than normal sedentary people. Their physique was found to be endomorphic mesomorph (3.8-5.2-1.7). Mean(s.d.) back strength, maximum oxygen uptake capacity (VO2max) and oxygen debt were found to be 162.6(18.08) kg, 42.6(4.91) ml kg-1 min-1 and 5.02(1.29) litre respectively. Physical characteristics, percentage body fat, somatotype, maximum oxygen uptake capacity and anaerobic capacity (oxygen debt) and other cardiorespiratory parameters were compared with other national counterparts. Present data are comparable with data for judo, wrestling and weightlifting. Since no such study has been conducted on international counterparts, these data could not be compared. These data may act as a guideline in the selection of future kabaddi players and to attain the physiological status comparable to the present gold medalists. Images Figure 4 Figure 5 p242-a PMID:8130960

Modes of Power in Technical and Professional Visuals.

ERIC Educational Resources Information Center

Barton, Ben F.; Barton, Marthalee S.

1993-01-01

Treats visuals as sites of power inscription. Advances a Foucauldian design model based on the Panoptican--Jeremy Bentham's architectural figure for empowerment based on bimodal surveillance. Notes that numerous examples serve in demonstrating that maximum effectiveness results when visuals foster simultaneous viewing in the two panoptic modes,…

49 CFR 179.400-25 - Stenciling.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Specification for Cryogenic Liquid Tank Car Tanks and Seamless Steel Tanks (Classes DOT-113 and 107A) § 179.400... design service temperature and maximum lading weight, in letters and figures at least 11/2 inches high... at its coldest operating temperature, after deduction for the volume above the inlet to the pressure...

Visualizing Mixed Variable-Type Multidimensional Data Using Tree Distances

DTIC Science & Technology

2015-09-01

24 1. The Regression Method .................................................. 25 2. Maximum Deviance Ratio Method... Deviance Change as a Factor of the Amount of Correlation? ................................................... 50 B. A PROPOSED SOLUTION...Splice mapping using d1 ...................... 36 Figure 18. Reduction in 2R analog ( deviance ratio-DevRat) per variable for the Splice data

Correlations by the entrainment theory of thermodynamic effects for developed cavitation in venturis and comparisons with ogive data

NASA Technical Reports Server (NTRS)

Billet, M. L.; Holl, J. W.; Weir, D. S.

1975-01-01

A semi-empirical entrainment theory was employed to correlate the measured temperature depression, Delta T, in a developed cavity for a venturi. This theory correlates Delta t in terms of the dimensionless numbers of Nusselt, Reynolds, Froude, Weber and Peclet, and dimensionless cavity length, L/D. These correlations are then compared with similar correlations for zero and quarter caliber ogives. In addition, cavitation number data for both limited and developed cavitation in venturis are presented.

Analysis of the Performance of Heat Pipes and Phase-Change Materials with Multiple Localized Heat Sources for Space Applications

DTIC Science & Technology

1989-05-01

NUMERICAL ANALYSIS OF STEFAN PROBLEMS FOR GENERALIZED MULTI- DIMENSIONAL PHASE-CHANGE STRUCTURES USING THE ENTHALPY TRANSFORMING MODEL 4.1 Summary...equation St Stefan number, cs(Tm-Tw)/H or cs(Tm-Ti)/H s circumferential distance coordinate, m, Section III s dimensionless interface position along...fluid, kg/m 3 0 viscous dissipation term in the energy eqn. (1.4), Section I; dummy variable, Section IV r dimensionless time, ta/L 2 a Stefan -Boltzmann

Self-similar Theory of Wind-driven Sea

NASA Astrophysics Data System (ADS)

Zakharov, V. E.

2015-12-01

More than two dozens field experiments performed in the ocean and on the lakes show that the fetch-limited growth of dimensionless energy and dimensionless peak frequency is described by powerlike functions of the dimensionless fetch. Moreover, the exponents of these two functions are connected with a proper accuracy by the standard "magic relation", 10q-2p=1. Recent massive numerical experiments as far as experiments in wave tanks also confirm this magic relation. All these experimental facts can be interpreted in a framework of the following simple theory. The wind-driven sea is described by the "conservative" Hasselmann kinetic equation. The source terms, wind input and white-capping dissipation, play a secondary role in comparison with the nonlinear term Snl that is responsible for the four-wave resonant interaction. This equation has four-parameter family of self-similar solutions. The magic relation holds for all numbers of this family. This fact gives strong hope that development of self-consistent analytic theory of wind-driven sea is quite realizable task.

Hovering efficiency comparison of rotary and flapping flight for rigid rectangular wings via dimensionless multi-objective optimization.

PubMed

Bayiz, Yagiz; Ghanaatpishe, Mohammad; Fathy, Hosam; Cheng, Bo

2018-05-08

In this work, a multi-objective optimization framework is developed for optimizing low Reynolds number ([Formula: see text]) hovering flight. This framework is then applied to compare the efficiency of rigid revolving and flapping wings with rectangular shape under varying [Formula: see text] and Rossby number ([Formula: see text], or aspect ratio). The proposed framework is capable of generating sets of optimal solutions and Pareto fronts for maximizing the lift coefficient and minimizing the power coefficient in dimensionless space, explicitly revealing the trade-off between lift generation and power consumption. The results indicate that revolving wings are more efficient when the required average lift coefficient [Formula: see text] is low (<1 for [Formula: see text] and  <1.6 for [Formula: see text]), while flapping wings are more efficient in achieving higher [Formula: see text]. With the dimensionless power loading as the single-objective performance measure to be maximized, rotary flight is more efficient than flapping wings for [Formula: see text] regardless of the amount of energy storage assumed in the flapping wing actuation mechanism, while flapping flight is more efficient for [Formula: see text]. It is observed that wings with low [Formula: see text] perform better when higher [Formula: see text] is needed, whereas higher [Formula: see text] cases are more efficient at [Formula: see text] regions. However, for the selected geometry and [Formula: see text], the efficiency is weakly dependent on [Formula: see text] when the dimensionless power loading is maximized.

Development of Dimensionless Index Assessing Low Impact Development in Urban Areas

NASA Astrophysics Data System (ADS)

Jun, S. H.; Lee, E. H.; Kim, J. H.

2017-12-01

Because the rapid urbanization and industrialization have increased the impervious area of watersheds, inundation in urban area and water pollution of river by non-point pollutants have caused serious problems for a long time. Low Impact Development (LID) techniques have been implemented for the solution of these problems due to its cost effectiveness for mitigating the water quality and quantity impact on urban areas. There have been many studies about the effectiveness of LID, but there is a lack of research on developing an index for the assessment of LID performance. In this study, the dimensionless reliability index of LID is proposed. The index is developed using Distance Measure Method (DMM). DMM is used to consider the parameters that have different units. The parameters for reliability of LID are the amount of pollutant at the outfall and the flooding volume. Both parameters become dimensionless index by DMM. Weighted factors in dimensionless index are considered to realize the behavior of reliability for the variation of importance to the parameters. LID is applied to an actual area called Gasan city in Seoul, South Korea where inundation is frequently occurred. The reliability is estimated for 16 different rainfall events. For each rainfall event, the parameters with LID installation are compared with those of no LID installation. Depending on which parameter is considered more important, the results showed difference. In conclusion, the optimal locations of LID are suggested as the weighted factors change.

Effects of a temperature-dependent rheology on large scale continental extension

NASA Technical Reports Server (NTRS)

Sonder, Leslie J.; England, Philip C.

1988-01-01

The effects of a temperature-dependent rheology on large-scale continental extension are investigated using a thin viscous sheet model. A vertically-averaged rheology is used that is consistent with laboratory experiments on power-law creep of olivine and that depends exponentially on temperature. Results of the calculations depend principally on two parameters: the Peclet number, which describes the relative rates of advection and diffusion of heat, and a dimensionless activation energy, which controls the temperature dependence of the rheology. At short times following the beginning of extension, deformation occurs with negligible change in temperature, so that only small changes in lithospheric strength occur due to attenuation of the lithosphere. However, after a certain critical time interval, thermal diffusion lowers temperatures in the lithosphere, strongly increasing lithospheric strength and slowing the rate of extension. This critical time depends principally on the Peclet number and is short compared with the thermal time constant of the lithosphere. The strength changes cause the locus of high extensional strain rates to shift with time from regions of high strain to regions of low strain. Results of the calculations are compared with observations from the Aegean, where maximum extensional strains are found in the south, near Crete, but maximum present-day strain rates are largest about 300 km further north.

Vortex formation with a snapping shrimp claw.

PubMed

Hess, David; Brücker, Christoph; Hegner, Franziska; Balmert, Alexander; Bleckmann, Horst

2013-01-01

Snapping shrimp use one oversized claw to generate a cavitating high speed water jet for hunting, defence and communication. This work is an experimental investigation about the jet generation. Snapping shrimp (Alpheus-bellulus) were investigated by using an enlarged transparent model reproducing the closure of the snapper claw. Flow inside the model was studied using both High-Speed Particle Image Velocimetry (HS-PIV) and flow visualization. During claw closure a channel-like cavity was formed between the plunger and the socket featuring a nozzle-type contour at the orifice. Closing the mechanism led to the formation of a leading vortex ring with a dimensionless formation number of approximate ΔT*≈4. This indicates that the claw might work at maximum efficiency, i.e. maximum vortex strength was achieved by a minimum of fluid volume ejected. The subsequent vortex cavitation with the formation of an axial reentrant jet is a reasonable explanation for the large penetration depth of the water jet. That snapping shrimp can reach with their claw-induced flow. Within such a cavitation process, an axial reentrant jet is generated in the hollow cylindrical core of the cavitated vortex that pushes the front further downstream and whose length can exceed the initial jet penetration depth by several times.

Tropical Cyclone Genesis Efficiency: Mid-Level Versus Bottom Vortex

DTIC Science & Technology

2011-12-16

storm strength). Figure 4b shows the time evolutions of the corresponding maximum surface wind speed from the four experiments. Based on the definition...Pacific during summer. Mon. Wea. Rev., 124, 2245–2266. Chen, S. S. and W. M. Frank, 1993: A numerical study of the genesis of extratropical convective

Self-Reported Well-Being of Women and Men with Intellectual Disabilities in England

ERIC Educational Resources Information Center

Emerson, Eric; Hatton, Chris

2008-01-01

We investigated the association between indicators of subjective well-being and the personal characteristics, socioeconomic position, and social relationships of a sample of 1,273 English adults with intellectual disabilities. Mean overall happiness with life was 71% of the scale maximum, a figure only marginally lower than typically reported…

14 CFR 25.485 - Side load conditions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... accordance with figure 5 of appendix A. (b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with one-half of the maximum vertical ground reactions obtained in the level landing conditions. These loads are...

14 CFR 25.485 - Side load conditions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... accordance with figure 5 of appendix A. (b) Side loads of 0.8 of the vertical reaction (on one side) acting inward and 0.6 of the vertical reaction (on the other side) acting outward must be combined with one-half of the maximum vertical ground reactions obtained in the level landing conditions. These loads are...

Design and Implementation of High Performance Content-Addressable Memories.

DTIC Science & Technology

1985-12-01

content addressability and two basic implementations of content addressing. The need and application of hardware CAM is presented to motivate the " topic...3r Pass 4th Ps4 Pass Figure 2.15 Maximum SearchUsing All-Parallel CAM - left-most position (the most significant bit) and the other IF bits are zeros

Recent Advances in the Development of Ferroelectric Generators

DTIC Science & Technology

2013-06-01

multi FEG- VIG oscillator operating at only 20% maximum voltage (Fig. 4) can generate 10s of kV/m fields at 3 m. The waveform in Fig. 5 was produced...Figure 5. Waveforms produced by a Radiance multi-FEG array driving a VIG (Courtesy of Zachary Roberts, Radiance). This requires large antennas to

Laboratory Characterization of Gray Masonry Concrete

DTIC Science & Technology

2007-08-01

Based on the appropriate values of posttest water content, wet density, and an assumed grain density of 2.61 Mg/m3, values of dry density, porosity...velocity measurements were performed on each specimen. The TXC tests exhibited a continuous increase in maximum principal stress difference with...14 Figure 3. Spring-arm lateral deformeter mounted on test

Evaluation of Effects of Fire on the I-465 Mainline Bridges : Volume I, APPENDIX D Maximum Stress Ranges Figures--Triggered Data Files

DOT National Transportation Integrated Search

2012-06-01

On October 22, 2009, in Indianapolis, Indiana, a semi tanker carrying liquefied propane lost control on the underpass from I69 southbound to I465 eastbound, crashing beneath the east and westbound bridges carrying mainline I465 traffic. The ...

76 FR 4550 - Income Level for Individuals Eligible for Assistance

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-26

... Poverty Guidelines as issued by the Department of Health and Human Services. DATES: Effective Date: This... maximum income level equivalent to one hundred and twenty-five percent (125%) of the Federal Poverty... issuing the Federal Poverty Guidelines. The figures for 2010 set out below are equivalent to 125% of the...

Climate change mitigation effect of harvested wood products in regions of Japan.

PubMed

Kayo, Chihiro; Tsunetsugu, Yuko; Tonosaki, Mario

2015-12-01

Harvested wood products (HWPs) mitigate climate change through carbon storage, material substitution, and energy substitution. We construct a model to assess the overall climate change mitigation effect (comprising the carbon storage, material substitution, and energy substitution effects) resulting from HWPs in regions of Japan. The model allows for projections to 2050 based on future scenarios relating to the domestic forestry industry, HWP use, and energy use. Using the production approach, a nationwide maximum figure of 2.9 MtC year -1 for the HWP carbon storage effect is determined for 2030. The maximum nationwide material substitution effect is 2.9 MtC year -1 in 2050. For the energy substitution effect, a nationwide maximum projection of 4.3 MtC year -1 in 2050 is established, with at least 50 % of this figure derived from east and west Japan, where a large volume of logging residue is generated. For the overall climate change mitigation effect, a nationwide maximum projection of 8.4 MtC year -1 in 2050 is established, equivalent to 2.4 % of Japan's current carbon dioxide emissions. When domestic roundwood production and HWP usage is promoted, an overall climate change mitigation effect is consistently expected to be attributable to HWPs until 2050. A significant factor in obtaining the material substitution effect will be substituting non-wooden buildings with wooden ones. The policy of promoting the use of logging residue will have a significant impact on the energy substitution effect. An important future study is an integrated investigation of the climate change mitigation effect for both HWPs and forests.

Analytic theory of the selection mechanism in the Saffman-Taylor problem. [concerning shape of fingers in Hele-Shaw cell

NASA Technical Reports Server (NTRS)

Hong, D. C.; Langer, J. S.

1986-01-01

An analytic approach to the problem of predicting the widths of fingers in a Hele-Shaw cell is presented. The analysis is based on the WKB technique developed recently for dealing with the effects of surface tension in the problem of dendritic solidification. It is found that the relation between the dimensionless width lambda and the dimensionless group of parameters containing the surface tension, nu, has the form lambda - 1/2 = nu exp 2/3 in the limit of small nu.

Wire perturbations in the Staffman-Taylor problem

NASA Technical Reports Server (NTRS)

Hong, D. C.

1988-01-01

Zocchi et al. (1987) discovered that when two wires are symmetrically placed along the center of a Hele-Shaw cell, symmetric but narrow fingers of dimensionless width lambda less than 0.5 develop. The value of lambda decreases as the pushing velocity increases, but at a certain critical finger width the finger suddenly undergoes a transition to the asymmetrical state. A simple theory to predict this critical finger width as a function of D, the dimensionless distance between two wires is developed by assuming that the finger opens up a negative angle at the contact point.

A strategy to optimize the thermoelectric performance in a spark plasma sintering process

PubMed Central

Chiu, Wan-Ting; Chen, Cheng-Lung; Chen, Yang-Yuan

2016-01-01

Spark plasma sintering (SPS) is currently widely applied to existing alloys as a means of further enhancing the alloys’ figure of merit. However, the determination of the optimal sintering condition is challenging in the SPS process. This report demonstrates a systematic way to independently optimize the Seebeck coefficient S and the ratio of electrical to thermal conductivity (σ/κ) and thus achieve the maximum figure of merit zT = S2(σ/κ)T. Sb2−xInxTe3 (x = 0–0.2) were chosen as examples to validate the method. Although high sintering temperature and pressure are helpful in enhancing the compactness and electrical conductivity of pressed samples, the resultant deteriorated Seebeck coefficient and increasing thermal conductivity eventually offset the benefit. We found that the optimal sintering temperature coincides with temperatures at which the maximum Seebeck coefficient begins to degrade, whereas the optimal sintering pressure coincided with the pressure at which the σ/κ ratio reaches a maximum. Based on this principle, the optimized sintering conditions were determined, and the zT of Sb1.9In0.1Te3 is raised to 0.92 at 600 K, showing an approximately 84% enhancement. This work develops a facile strategy for selecting the optimal SPS sintering condition to further enhance the zT of bulk specimens. PMID:26975209

SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator

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

Anderson, J; Bernard, D; Liao, Y

2014-06-01

Purpose: Craniospinal irradiation (CSI) of systemic disease requires a high level of beam intensity modulation to reduce dose to bone marrow and other critical structures. Current helical delivery machines can take 30 minutes or more of beam-on time to complete these treatments. This pilot study aims to test the feasibility of performing helical treatments with a conventional linear accelerator using longitudinal couch travel during multiple gantry revolutions. Methods: The VMAT optimization package of the Eclipse 10.0 treatment planning system was used to optimize pseudo-helical CSI plans of 5 clinical patient scans. Each gantry revolution was divided into three 120° arcsmore » with each isocenter shifted longitudinally. Treatments requiring more than the maximum 10 arcs used multiple plans with each plan after the first being optimized including the dose of the others (Figure 1). The beam pitch was varied between 0.2 and 0.9 (couch speed 5- 20cm/revolution and field width of 22cm) and dose-volume histograms of critical organs were compared to tomotherapy plans. Results: Viable pseudo-helical plans were achieved using Eclipse. Decreasing the pitch from 0.9 to 0.2 lowered the maximum lens dose by 40%, the mean bone marrow dose by 2.1% and the maximum esophagus dose by 17.5%. (Figure 2). Linac-based helical plans showed dose results comparable to tomotherapy delivery for both target coverage and critical organ sparing, with the D50 of bone marrow and esophagus respectively 12% and 31% lower in the helical linear accelerator plan (Figure 3). Total mean beam-on time for the linear accelerator plan was 8.3 minutes, 54% faster than the tomotherapy average for the same plans. Conclusions: This pilot study has demonstrated the feasibility of planning pseudo-helical treatments for CSI targets using a conventional linac and dynamic couch movement, and supports the ongoing development of true helical optimization and delivery.« less

Thermomechanical conditions and stresses on the friction stir welding tool

NASA Astrophysics Data System (ADS)

Atthipalli, Gowtam

Friction stir welding has been commercially used as a joining process for aluminum and other soft materials. However, the use of this process in joining of hard alloys is still developing primarily because of the lack of cost effective, long lasting tools. Here I have developed numerical models to understand the thermo mechanical conditions experienced by the FSW tool and to improve its reusability. A heat transfer and visco-plastic flow model is used to calculate the torque, and traverse force on the tool during FSW. The computed values of torque and traverse force are validated using the experimental results for FSW of AA7075, AA2524, AA6061 and Ti-6Al-4V alloys. The computed torque components are used to determine the optimum tool shoulder diameter based on the maximum use of torque and maximum grip of the tool on the plasticized workpiece material. The estimation of the optimum tool shoulder diameter for FSW of AA6061 and AA7075 was verified with experimental results. The computed values of traverse force and torque are used to calculate the maximum shear stress on the tool pin to determine the load bearing ability of the tool pin. The load bearing ability calculations are used to explain the failure of H13 steel tool during welding of AA7075 and commercially pure tungsten during welding of L80 steel. Artificial neural network (ANN) models are developed to predict the important FSW output parameters as function of selected input parameters. These ANN consider tool shoulder radius, pin radius, pin length, welding velocity, tool rotational speed and axial pressure as input parameters. The total torque, sliding torque, sticking torque, peak temperature, traverse force, maximum shear stress and bending stress are considered as the output for ANN models. These output parameters are selected since they define the thermomechanical conditions around the tool during FSW. The developed ANN models are used to understand the effect of various input parameters on the total torque and traverse force during FSW of AA7075 and 1018 mild steel. The ANN models are also used to determine tool safety factor for wide range of input parameters. A numerical model is developed to calculate the strain and strain rates along the streamlines during FSW. The strain and strain rate values are calculated for FSW of AA2524. Three simplified models are also developed for quick estimation of output parameters such as material velocity field, torque and peak temperature. The material velocity fields are computed by adopting an analytical method of calculating velocities for flow of non-compressible fluid between two discs where one is rotating and other is stationary. The peak temperature is estimated based on a non-dimensional correlation with dimensionless heat input. The dimensionless heat input is computed using known welding parameters and material properties. The torque is computed using an analytical function based on shear strength of the workpiece material. These simplified models are shown to be able to predict these output parameters successfully.

Seasonal and spatial variation of the bacterial mutagenicity of fine organic aerosol in southern california.

PubMed Central

Hannigan, M P; Cass, G R; Lafleur, A L; Busby, W F; Thilly, W G

1996-01-01

The bacterial mutagenicity of a set of 1993 urban particulate air pollution samples is examined using the Salmonella typhimurium TM677 forward mutation assay. Amibent fine particulate samples were collected for 24 hr every sixth day throughout 1993 at four urban sites, including Long Beach, central Los Angeles, Azusa, and Rubidoux, California, and at an upwind background site on San Nicolas Island. Long Beach and central Los Angeles are congested urban areas where air quality is dominated by fresh emissions from air pollution sources; Azuasa and Rubidoux are located farther downwind and receive transported air pollutants plus increased quantities of the products of atmospheric chemical reactions. Fine aerosol samples from Long Beach and Los Angeles show a pronounced seasonal variation in bacterial mutagenicity per cubic meter of- ambient air, with maximum in the winter and a minimum in the summer. The down-wind smog receptor site at Rubidoux shows peak mutagenicity (with postmitochondrial supernatant but no peak without postmitochondrial supernatant) during the September-October periods when direct transport from upwind sources can be expected. At most sites the mutagenicity per microgram of organic carbon from the aerosol is not obviously higher during the summer photochemical smog period than during the colder months. Significant spatial variation in bacterial mutagenicity is observed: mutagenicity per cubic meter of ambient air, on average, is more than an order of magnitude lower at San Nicolas Island than within the urban area. The highest mutagenicity values per microgram of organics supplied to the assay are found at the most congested urban sites at central Los Angeles and Long Beach. The highest annual average values of mutagenicity per cubic meter of air sampled occur at central Los Angeles. These findings stress the importance of proximity to sources of direct emissions of bacterial mutagens and imply that if important mutagen-forming atmospheric reactions occur, they likely occur in the winter and spring seasons as well as the photochemically more active summer and early fall periods. Images Figure 1. Figure 2. Figure 2. Figure 2. Figure 2. Figure 3. Figure 3. Figure 4. Figure 5. Figure 6. PMID:8732954

Enhancing thermoelectric properties through a three-terminal benzene molecule

NASA Astrophysics Data System (ADS)

Sartipi, Z.; Vahedi, J.

2018-05-01

The thermoelectric transport through a benzene molecule with three metallic terminals is discussed. Using general local and non-local transport coefficients, we investigated different conductance and thermopower coefficients within the linear response regime. Based on the Onsager coefficients which depend on the number of terminal efficiencies, efficiency at maximum power is also studied. In the three-terminal setup with tuning temperature differences, a great enhancement of the figure of merit is observed. Results also show that the third terminal model can be useful in improving the efficiency at maximum output power compared to the two-terminal model.

The Effect of the Ionosphere on Radiowave Signals and Systems Performance Based on Ionospheric Effects Symposium Held on 1-3 May 1990

DTIC Science & Technology

1990-05-03

winter and a minimum in summer ; in contrast, at sunspot maximum the seasonal peaks tend to occur around the equinoxes and the minima in summer . ’riis is...more clearly seen in Figures 4(b) ahnd 4(c). Note that around sunspot maximum the summer noon value may be less than the summer midnight value. (3) The...seasonal variation of the midnight values show summer peaks and winter minima with high values near the peaks of the sunspot cycles and low values

Condensation heat transfer and flow friction in silicon microchannels

NASA Astrophysics Data System (ADS)

Wu, Huiying; Wu, Xinyu; Qu, Jian; Yu, Mengmeng

2008-11-01

An experimental investigation was performed on heat transfer and flow friction characteristics during steam condensation flow in silicon microchannels. Three sets of trapezoidal silicon microchannels, with hydraulic diameters of 77.5 µm, 93.0 µm and 128.5 µm respectively, were tested under different flow and cooling conditions. It was found that both the condensation heat transfer Nusselt number (Nu) and the condensation two-phase frictional multiplier (phi2Lo) were dependent on the steam Reynolds number (Rev), condensation number (Co) and dimensionless hydraulic diameter (Dh/L). With the increase in the steam Reynolds number, condensation number and dimensionless hydraulic diameter, the condensation Nusselt number increased. However, different variations were observed for the condensation two-phase frictional multiplier. With the increase in the steam Reynolds number and dimensionless hydraulic diameter, the condensation two-phase frictional multiplier decreased, while with the increase in the condensation number, the condensation two-phase frictional multiplier increased. Based on the experimental results, dimensionless correlations for condensation heat transfer and flow friction in silicon microchannels were proposed for the first time. These correlations can be used to determine the condensation heat transfer coefficient and pressure drop in silicon microchannels if the steam mass flow rate, cooling rate and geometric parameters are fixed. It was also found that the condensation heat transfer and flow friction have relations to the injection flow (a transition flow pattern from the annular flow to the slug/bubbly flow), and with injection flow moving toward the outlet, both the condensation heat transfer coefficient and the condensation two-phase frictional multiplier increased.

49 CFR 571.126 - Standard No. 126; Electronic stability control systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... counterclockwise steering, and the other series uses clockwise steering. The maximum time permitted between each... or side slip derivative with respect to time; (4) That has a means to monitor driver steering inputs... dwell steering input (time T0 + 1 in Figure 1) must not exceed 35 percent of the first peak value of yaw...

49 CFR 571.126 - Standard No. 126; Electronic stability control systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... series uses counterclockwise steering, and the other series uses clockwise steering. The maximum time... rate and to estimate its side slip or side slip derivative with respect to time; (4) That has a means... after completion of the sine with dwell steering input (time T0 + 1 in Figure 1) must not exceed 35...

49 CFR 571.126 - Standard No. 126; Electronic stability control systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... counterclockwise steering, and the other series uses clockwise steering. The maximum time permitted between each... or side slip derivative with respect to time; (4) That has a means to monitor driver steering inputs... dwell steering input (time T0 + 1 in Figure 1) must not exceed 35 percent of the first peak value of yaw...

Method of making segmented pyrolytic graphite sputtering targets

DOEpatents

McKernan, M.A.; Alford, C.S.; Makowiecki, D.M.; Chen, C.W.

1994-02-08

Anisotropic pyrolytic graphite wafers are oriented and bonded together such that the graphite's high thermal conductivity planes are maximized along the back surface of the segmented pyrolytic graphite target to allow for optimum heat conduction away from the sputter target's sputtering surface and to allow for maximum energy transmission from the target's sputtering surface. 2 figures.

5 CFR 734.503 - Allocation and reimbursement of costs associated with political activities.

Code of Federal Regulations, 2011 CFR

2011-01-01

... the type represented by the substantial figure. The balance should be treated as de minimis and need... employee that is required in the performance of his or her duties to accompany or assist the person... should be applied to any Government maximum for that type of expenditure. (5) The determination of the...

A Rapid Soils Analysis Kit

DTIC Science & Technology

2008-03-01

behavior of moisture content-dry density Proctor curves......................................... 16 Figure 8. Moisture- density data scatter for an... density . Built-in higher order regression equations allow the user to visua- lize complete curves for Proctor density , as-built California Bearing Ratio...requirements involving soil are optimum moisture content (OMC) and maximum dry density (MDD) as determined from a laboratory compaction or Proctor test

Performance and Analysis of Vortex Oxidizer Injection in a Hybrid Rocket

DTIC Science & Technology

2009-05-05

Braid for Gas Service SS Fem Fittings, SS Hose , 2’L, 1/4" ID McMaster Number: 5665K32 Maximum Pressure: 4250 psi @ 72° F Operating Temperature...Figure J. 9 Type T (328 to 700 F) Thermocouple Probe J.7 Flexible Hydraulic Tubing Extreme Temperature Stainless Steel Hose with Stainless Steel Wire

Does Citrulline Malate Enhance Physical Performance

DTIC Science & Technology

2010-10-01

Jakeman, P.M. (2010). Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. Journal of Strength and Conditioning...returned for their third and final VO2 max test. VO2max, lactate threshold , maximum watts reached, ratings of perceived exertion and pre- and post...7 Figure 7. Lactate threshold (as % of VO2max) for all three conditions

Anthropometric Survey of U.S. Army Personnel: Summary Statistics, Interim Report for 1988

DTIC Science & Technology

1989-03-01

measurement is taken at the maximum point of quiet respiration. Note: Breast tissue and latissimus dorsi muscle tissue are NOT included in this measurement...sides of the body; as opposed to medial (see Figure A-l). latissimus dorsi — the large muscle covering the lower half of the back above the waist and

Temperature thresholds related to flight of Dendroctonus frontalis Zimm. (Col.: Scolytidae)

Treesearch

John C. Moser; William A. Thompson

1986-01-01

We have plotted the complete range of flight temperatures for the southern pine beele, the first such figures for any bark beetle.The optimum flight temperature was about 27oC.Observed minimum and maximum flight temperatures for southern pine beetle were 6.7oC and 36.7oC, respectively. Projected...

Combined electroosmotically and pressure driven flow in soft nanofluidics.

PubMed

Matin, Meisam Habibi; Ohshima, Hiroyuki

2015-12-15

The present study is devoted to the analysis of mixed electroosmotic and pressure driven flows through a soft charged nanochannel considering boundary slip and constant charge density on the walls of the slit channel. The sources of the fluid flow are the pressure gradient along the channel axis and the electrokinetic effects that trigger an electroosmotic flow under the influence of a uniformly applied electric field. The polyelectrolyte layer (PEL) is denoted as a fixed charge layer (FCL) and the electrolyte ions can be present both inside and outside the PEL i.e., the PEL-electrolyte interface acts as a semi-penetrable membrane. The Poisson-Boltzmann equation is solved assuming the Debye-Hückel linearization for the low electric potential to provide us with analytical closed form solutions for the conservation equations. The conservation equations are solved to obtain the electric potential and velocity distributions in terms of governing dimensionless parameters. The results for the dimensionless electric potential, the dimensionless velocity and Poiseuille number are presented graphically and discussed in detail. Copyright © 2015 Elsevier Inc. All rights reserved.

Reynolds-number dependence of the dimensionless dissipation rate in homogeneous magnetohydrodynamic turbulence.

PubMed

Linkmann, Moritz; Berera, Arjun; Goldstraw, Erin E

2017-01-01

This paper examines the behavior of the dimensionless dissipation rate C_{ɛ} for stationary and nonstationary magnetohydrodynamic (MHD) turbulence in the presence of external forces. By combining with previous studies for freely decaying MHD turbulence, we obtain here both the most general model equation for C_{ɛ} applicable to homogeneous MHD turbulence and a comprehensive numerical study of the Reynolds number dependence of the dimensionless total energy dissipation rate at unity magnetic Prandtl number. We carry out a series of medium to high resolution direct numerical simulations of mechanically forced stationary MHD turbulence in order to verify the predictions of the model equation for the stationary case. Furthermore, questions of nonuniversality are discussed in terms of the effect of external forces as well as the level of cross- and magnetic helicity. The measured values of the asymptote C_{ɛ,∞} lie between 0.193≤C_{ɛ,∞}≤0.268 for free decay, where the value depends on the initial level of cross- and magnetic helicities. In the stationary case we measure C_{ɛ,∞}=0.223.

Analysis of activation energy in Couette-Poiseuille flow of nanofluid in the presence of chemical reaction and convective boundary conditions

NASA Astrophysics Data System (ADS)

Zeeshan, A.; Shehzad, N.; Ellahi, R.

2018-03-01

The motivation of the current article is to explore the energy activation in MHD radiative Couette-Poiseuille flow nanofluid in horizontal channel with convective boundary conditions. The mathematical model of Buongiorno [1] effectively describes the current flow analysis. Additionally, the impact of chemical reaction is also taken in account. The governing flow equations are simplified with the help of boundary layer approximations. Non-linear coupled equations for momentum, energy and mass transfer are tackled with analytical (HAM) technique. The influence of dimensionless convergence parameter like Brownian motion parameter, radiation parameter, buoyancy ratio parameter, dimensionless activation energy, thermophoresis parameter, temperature difference parameter, dimensionless reaction rate, Schmidt number, Brinkman number, Biot number and convection diffusion parameter on velocity, temperature and concentration profiles are discussed graphically and in tabular form. From the results, it is elaborate that the nanoparticle concentration is directly proportional to the chemical reaction with activation energy and the performance of Brownian motion on nanoparticle concentration gives reverse pattern to that of thermophoresis parameter.

Numerical investigation of potential stratification caused by a cryogenic helium spill inside a tunnel

NASA Astrophysics Data System (ADS)

Sinclair, Cameron; Malecha, Ziemowit; Jedrusyna, Artur

2018-04-01

The sudden release of cryogenic fluid into an accelerator tunnel can pose a significant health and safety risk. For this reason, it is important to evaluate the consequences of such a spill. Previous publications concentrated on either Oxygen Deficiency Hazard or the evaluation of mathematical models using experimental data. No studies to date have focussed on the influence of cryogen inlet conditions on flow development. In this paper, the stratification behaviour of low-temperature helium released into an air-filled accelerator tunnel is investigated for varying helium inlet diameters. A numerical model was constructed using the OpenFOAM Toolbox of a generalised 3D geometry, with similar hydraulic characteristics to the CERN and SLAC tunnels. This model has been validated against published experimental and numerical data. A dimensionless parameter, based on Bakke number, was then determined for the onset of stratification, taking into account the helium inlet diameter; a dimensionless parameter for the degree of stratification was also employed. The simulated flow behaviour is described in terms of these dimensionless parameters, as well as the temperature and oxygen concentration at various heights throughout the tunnel.

Nonlinear Dynamics in Viscoelastic Jets

NASA Astrophysics Data System (ADS)

Majmudar, Trushant; Varagnat, Matthieu; McKinley, Gareth

2008-11-01

Instabilities in free surface continuous jets of non-Newtonian fluids, although relevant for many industrial processes, remain poorly understood in terms of fundamental fluid dynamics. Inviscid, and viscous Newtonian jets have been studied in considerable detail, both theoretically and experimentally. Instability in viscous jets leads to regular periodic coiling of the jet, which exhibits a non-trivial frequency dependence with the height of the fall. Here we present a systematic study of the effect of viscoelasticity on the dynamics of continuous jets of worm-like micellar surfactant solutions of varying viscosities and elasticities. We observe complex nonlinear spatio-temporal dynamics of the jet, and uncover a transition from periodic to quasi-periodic to a multi-frequency, broad-spectrum dynamics. Beyond this regime, the jet dynamics smoothly crosses over to exhibit the ``leaping shampoo'' or the Kaye effect. We examine different dynamical regimes in terms of scaling variables, which depend on the geometry (dimensionless height), kinematics (dimensionless flow rate), and the fluid properties (elasto-gravity number) and present a regime map of the dynamics of the jet in terms of these dimensionless variables.

Nonlinear Dynamics in Viscoelastic Jets

NASA Astrophysics Data System (ADS)

Majmudar, Trushant; Varagnat, Matthieu; McKinley, Gareth

2009-03-01

Instabilities in free surface continuous jets of non-Newtonian fluids, although relevant for many industrial processes, remain poorly understood in terms of fundamental fluid dynamics. Inviscid, and viscous Newtonian jets have been studied in considerable detail, both theoretically and experimentally. Instability in viscous jets leads to regular periodic coiling of the jet, which exhibits a non-trivial frequency dependence with the height of the fall. Here we present a systematic study of the effect of viscoelasticity on the dynamics of continuous jets of worm-like micellar surfactant solutions of varying viscosities and elasticities. We observe complex nonlinear spatio-temporal dynamics of the jet, and uncover a transition from periodic to quasi-periodic to a multi-frequency, broad-spectrum dynamics. Beyond this regime, the jet dynamics smoothly crosses over to exhibit the ``leaping shampoo'' or the Kaye effect. We examine different dynamical regimes in terms of scaling variables, which depend on the geometry (dimensionless height), kinematics (dimensionless flow rate), and the fluid properties (elasto-gravity number) and present a regime map of the dynamics of the jet in terms of these dimensionless variables.

Depicting mass flow rate of R134a /LPG refrigerant through straight and helical coiled adiabatic capillary tubes of vapor compression refrigeration system using artificial neural network approach

NASA Astrophysics Data System (ADS)

Gill, Jatinder; Singh, Jagdev

2018-07-01

In this work, an experimental investigation is carried out with R134a and LPG refrigerant mixture for depicting mass flow rate through straight and helical coil adiabatic capillary tubes in a vapor compression refrigeration system. Various experiments were conducted under steady-state conditions, by changing capillary tube length, inner diameter, coil diameter and degree of subcooling. The results showed that mass flow rate through helical coil capillary tube was found lower than straight capillary tube by about 5-16%. Dimensionless correlation and Artificial Neural Network (ANN) models were developed to predict mass flow rate. It was found that dimensionless correlation and ANN model predictions agreed well with experimental results and brought out an absolute fraction of variance of 0.961 and 0.988, root mean square error of 0.489 and 0.275 and mean absolute percentage error of 4.75% and 2.31% respectively. The results suggested that ANN model shows better statistical prediction than dimensionless correlation model.

Development of thermal stratification and destratification scaling concepts. Volume 1: Definition of thermal stratification scaling parameters and experimental investigations

NASA Technical Reports Server (NTRS)

Lovrich, T. N.; Schwartz, S. H.

1975-01-01

The dimensionless parameters associated with the thermal stratification and pressure history of a heated container of liquid and its vapor were examined. The Modified Grashof number, the Fourier number, and an Interface number were parameterized using a single test liquid, Freon 113. Cylindrical test tanks with spherical dome end caps were built. Blanket heaters covered the tanks and thermocouples monitored the temperatures of the liquid, the ullage, the tank walls, and the foam insulation encapsulating the tank. A centrifuge was used for the 6 inch tank to preserve the same scaling parameter values between it and the larger tanks. Tests were conducted over a range of Gr* values and the degree of scaling was checked by comparing the dimensionless pressures and temperatures for each scaled pair of tests. Results indicate that the bulk liquid temperature, the surface temperature of the liquid, and the tank pressure can be scaled with the three dimensionless parameters. Some deviation was, however, found in the detailed temperature profiles between the scaled pairs of tests.

The Whole Elephant: A Synoptic View of Liquid Rope Coiling

NASA Astrophysics Data System (ADS)

Ribe, Neil

2016-11-01

Liquid rope coiling is the instability that occurs when e.g. a thin stream of honey is poured onto toast. While we now have a fine-grained understanding of each of the four principal coiling modes (viscous, gravitational, inertio-gravitational and inertial), we still lack a global view of how the modes cohere to form a larger whole. Using a numerical continuation procedure, I determine how the dimensionless coiling frequency depends on the dimensionless fall height and flow rate, for several values of the dimensionless nozzle diameter. Starting with the onset of coiling, I propose a purely geometrical definition of the critical surface between coiling and no coiling as the locus of points where the radius a1 of the rope at the contact point is just equal to the coil radius R. Coiling with a1 > R is impossible because the rope would intersect itself. I characterize the asymptotic limits of the critical surface as well as the structure of the supercritical volume inside that surface. The procedure reveals a new mode of coiling onset that has not yet been identified.

ION BEAM POLARIZATION DYNAMICS IN THE 8 GEV BOOSTER OF THE JLEIC PROJECT AT JLAB

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

Kondratenko, A. M.; Kondratenko, M. A.; Morozov, Vasiliy

2016-05-01

In the Jefferson Lab’s Electron-Ion Collider (JLEIC) project, an injector of polarized ions into the collider ring is a superconducting 8 GeV booster. Both figure-8 and racetrack booster versions were considered. Our analysis showed that the figure-8 ring configuration allows one to preserve the polarization of any ion species during beam acceleration using only small longitudinal field with an integral less than 0.5 Tm. In the racetrack booster, to pre-serve the polarization of ions with the exception of deu-terons, it suffices to use a solenoidal Siberian snake with a maximum field integral of 30 Tm. To preserve deuteron polarization, wemore » propose to use arc magnets for the race-track booster structure with a field ramp rate of the order of 1 T/s. We calculate deuteron and proton beam polari-zations in both the figure-8 and racetrack boosters includ-ing alignment errors of their magnetic elements using the Zgoubi code.« less

Au-Graphene Hybrid Plasmonic Nanostructure Sensor Based on Intensity Shift

PubMed Central

Alharbi, Raed; Irannejad, Mehrdad; Yavuz, Mustafa

2017-01-01

Integrating plasmonic materials, like gold with a two-dimensional material (e.g., graphene) enhances the light-material interaction and, hence, plasmonic properties of the metallic nanostructure. A localized surface plasmon resonance sensor is an effective platform for biomarker detection. They offer a better bulk surface (local) sensitivity than a regular surface plasmon resonance (SPR) sensor; however, they suffer from a lower figure of merit compared to that one in a propagating surface plasmon resonance sensors. In this work, a decorated multilayer graphene film with an Au nanostructures was proposed as a liquid sensor. The results showed a significant improvement in the figure of merit compared with other reported localized surface plasmon resonance sensors. The maximum figure of merit and intensity sensitivity of 240 and 55 RIU−1 (refractive index unit) at refractive index change of 0.001 were achieved which indicate the capability of the proposed sensor to detect a small change in concentration of liquids in the ng/mL level which is essential in early-stage cancer disease detection. PMID:28106850

Electromagnetic characteristics of eccentric figure-eight coils for transcranial magnetic stimulation: A numerical study

NASA Astrophysics Data System (ADS)

Kato, Takuya; Sekino, Masaki; Matsuzaki, Taiga; Nishikawa, Atsushi; Saitoh, Youichi; Ohsaki, Hiroyuki

2012-04-01

Repetitive transcranial magnetic stimulation (rTMS) is effective for treatment of several neurological and psychiatric diseases. We proposed an eccentric figure-eight coil, which induces strong eddy currents in the target brain tissue. In this study, numerical analyses were carried out to obtain magnetic field distribution of the eccentric figure-eight coil and eddy current in the brain. The analyses were performed with various coil design parameters, such as the outer and inner diameters and number of turns, to investigate the influence of these parameters on the coil characteristics. Increases in the inner diameter, outer diameter, and number of turns caused increases in the maximum eddy current densities. Coil inductance, working voltage, and heat generation also became higher with the increases in these design parameters. In order to develop a compact stimulator system for use at home, we need to obtain strong eddy current density, keeping the working voltage as low as possible. Our results show that it is effective to enlarge the outer diameter.

High-temperature thermoelectric properties of Ca0.92La0.04RE0.04MnO3 (RE = Sm, Dy and Yb) prepared by coprecipitation

NASA Astrophysics Data System (ADS)

Li, Cuiqin; Chen, Qianlin; Yan, Yunan; Li, Yanan; Zhao, Ying

2018-02-01

A series of Ca0.92La0.04RE0.04MnO3 (RE = Sm, Dy and Yb) compounds are synthesized via a coprecipitation technique. The influence of La/RE dual doping on the phase structure, microstructure and thermoelectric properties of the CaMnO3 system is investigated. Increased material density with grain sizes of 1-2 μm and a homogeneous microstructure is realized. Dual doping decreases the electrical resistivity due to an increase in the carrier concentration and also decreases the thermal conductivity due to increased grain scattering, damping of local vibrations by heavier La/RE ions compared to Ca and lattice distortion. The Ca0.92La0.04Yb0.04MnO3 shows the highest power factor of 3.49 × 10-4 W m-1 K-2 and the highest dimensionless figure of merit ZT of 0.25 at 770 K, which is approximately 3 times larger than that obtained for the undoped CaMnO3 and significantly larger than that of single-doped CaMnO3 prepared by solid-state reaction. This work provides a basic foundation for the industrial application of this thermoelectric material.

Charging and Transport Dynamics of a Flow-Through Electrode Capacitive Deionization System.

PubMed

Qu, Yatian; Campbell, Patrick G; Hemmatifar, Ali; Knipe, Jennifer M; Loeb, Colin K; Reidy, John J; Hubert, Mckenzie A; Stadermann, Michael; Santiago, Juan G

2018-01-11

We present a study of the interplay among electric charging rate, capacitance, salt removal, and mass transport in "flow-through electrode" capacitive deionization (CDI) systems. We develop two models describing coupled transport and electro-adsorption/desorption which capture salt removal dynamics. The first model is a simplified, unsteady zero-dimensional volume-averaged model which identifies dimensionless parameters and figures of merits associated with cell performance. The second model is a higher fidelity area-averaged model which captures both spatial and temporal responses of charging. We further conducted an experimental study of these dynamics and considered two salt transport regimes: (1) advection-limited regime and (2) dispersion-limited regime. We use these data to validate models. The study shows that, in the advection-limited regime, differential charge efficiency determines the salt adsorption at the early stage of the deionization process. Subsequently, charging transitions to a quasi-steady state where salt removal rate is proportional to applied current scaled by the inlet flow rate. In the dispersion-dominated regime, differential charge efficiency, cell volume, and diffusion rates govern adsorption dynamics and flow rate has little effect. In both regimes, the interplay among mass transport rate, differential charge efficiency, cell capacitance, and (electric) charging current governs salt removal in flow-through electrode CDI.

Transport properties of undoped and Br-doped PbTe sintered at high-temperature and pressure >=4.0 GPa

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

Dong, Yongkwan; McGuire, Michael A.; Malik, Abds-Sami, E-mail: abds-sami.malik@diamondinnovations.co

2009-10-15

The thermoelectric properties of nominally undoped PbTe and Br doped PbTe materials sintered at high-pressure and high-temperature (HPHT) have been studied. All samples show n-type semiconducting behavior with negative thermopower. For undoped PbTe, four different HPHT treatments were performed at pressures between 4.0 and 6.5 GPa. PbTe doped with Br at 0.5, 1.0, 2.0, 3.0x10{sup 19} cm{sup -3} was HPHT treated at 4.0 GPa and 1045 deg. C. As the dopant concentration increases, the absolute thermopower decreases, thermal conductivity increases, and electrical resistivity decreases. At a nominal dopant concentration of 1.0x10{sup 19} cm{sup -3}, carrier mobility of 1165 cm{sup 2}/Vmore » s and dimensionless thermoelectric figure-of-merit, ZT, of around 0.27 at 300 K were obtained. These results demonstrate that HPHT post-processing is a viable and controllable way of tuning the thermoelectric properties of PbTe-based materials. - Abstract: The effect, on thermoelectric properties, of sintering undoped and Br doped PbTe at pressures >=4.0 GPa and 1045 deg. C are reported and compared with conventionally sintered materials. Display Omitted« less

Effect of Te substitution on crystal structure and transport properties of AgBiSe2 thermoelectric material.

PubMed

Goto, Y; Nishida, A; Nishiate, H; Murata, M; Lee, C H; Miura, A; Moriyoshi, C; Kuroiwa, Y; Mizuguchi, Y

2018-02-20

Silver bismuth diselenide (AgBiSe 2 ) has attracted much attention as an efficient thermoelectric material, owing to its intrinsically low lattice thermal conductivity. While samples synthesized using a solid-state reaction showed n-type conductivity and their dimensionless figure of merit (ZT) reached ∼1 by electron doping, theoretical calculations predicted that a remarkably high thermoelectric performance can be achieved in p-type AgBiSe 2 . In this paper, we present the effect of Te substitution on the crystal structure and thermoelectric properties of AgBiSe 2 , expecting p-type conductivity due to the shallowing of the energy potential of the valence band. We found that all AgBiSe 2-x Te x (x = 0-0.8) prepared using a solid-state reaction exhibits n-type conductivity from 300 to 750 K. The room-temperature lattice thermal conductivity decreased to as low as 0.3 W m -1 K -1 by Te substitution, which was qualitatively described using the point defect scattering model for the solid solution. We show that ZT reaches ∼0.6 for x = 0.8 at a broad range of temperatures, from 550 to 750 K, due to the increased power factor, although the carrier concentration has not been optimized yet.

Transport Properties of Bulk Thermoelectrics—An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity

NASA Astrophysics Data System (ADS)

Wang, Hsin; Porter, Wallace D.; Böttner, Harald; König, Jan; Chen, Lidong; Bai, Shengqiang; Tritt, Terry M.; Mayolet, Alex; Senawiratne, Jayantha; Smith, Charlene; Harris, Fred; Gilbert, Patricia; Sharp, Jeff W.; Lo, Jason; Kleinke, Holger; Kiss, Laszlo

2013-04-01

Recent research and development of high-temperature thermoelectric materials has demonstrated great potential for converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air-conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The dimensionless figure of merit, ZT, still needs to be improved from the current value of 1.0 to 1.5 to above 2.0 to be competitive with other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods, and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as a key component for improving energy efficiency. The International Energy Agency (IEA) group under the Implementing Agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main foci in part I are the measurement of two electronic transport properties: Seebeck coefficient and electrical resistivity.

Thermoelectric and Magnetic Properties of Ca0.98RE0.02MnO3- δ (RE = Sm, Gd, and Dy)

NASA Astrophysics Data System (ADS)

Bhaskar, Ankam; Liu, Chia-Jyi; Yuan, J. J.

2012-09-01

Polycrystalline samples of Ca0.98RE0.02MnO3- δ (RE = Sm, Gd, and Dy) have been prepared by conventional solid-state reactions and their properties measured at 300 K to 700 K. All samples were single phase with orthorhombic structure. The average valence and oxygen content of Ca0.98RE0.02MnO3- δ were determined by iodometric titration. Doping at the Ca site by rare-earth metals causes a strong decrease of electrical resistivity due to the creation of charge carrier content by Mn3+ in the Mn4+ matrix, as evidenced by iodometric titration results. The Seebeck coefficient of all the samples was negative, indicating that the predominant carriers are electrons over the entire temperature range. Among the doped samples, Ca0.98Dy0.02MnO3- δ had the highest dimensionless figure of merit of 0.073 at 612 K, representing an improvement of about 115% with respect to the undoped CaMnO3- δ sample at the same temperature. All the samples exhibited an antiferromagnetic transition with Néel temperature of around 120 K. Magnetization measurements indicated that Ca0.98RE0.02 MnO3- δ samples exhibited a high-spin state of Mn3+.

Low-temperature thermoelectric properties of the electron-doped perovskites Sr1- x Ca x Ti1- y Nb y O3

NASA Astrophysics Data System (ADS)

Okuda, Tetsuji; Fukuyado, Junichi; Narikiyo, Kurahito; Akaki, Mitsuru; Kuwahara, Hideki

2013-08-01

We have investigated the thermoelectric (TE) properties for single crystals of the perovskites Sr1- x Ca x Ti1- y Nb y O3 for 0 ≤ x ≤ 0.4 and 0 ≤ y ≤ 0.03 at temperatures below room temperature (RT). We found that SrTi0.99Nb0.01O3 showed a large power factor at low temperatures ( PF = 50 µW/K2cm at 100 K ˜ 90 µW/K2cm at 50 K) and the largest dimensionless TE figure-ofmerit at temperatures below 40 K ( ZT ˜ 0.07) among the reported materials. Such a large low-temperature TE response around a carrier concentration of 1020 cm-3 is due to a distinct phonon drag effect. We also found that the Ca2+ substitution for Sr2+ increased the ZT at 300 K for Sr1- x Ca x Ti0.97Nb0.03O3 from 0.08 to 0.105. The enhancement of the ZT around RT originates both from a large reduction of a thermal conductivity due to a randomness introduced into the crystal structure and from an unexpected enhancement of a Seebeck coefficient.

Enhanced thermoelectric efficiency via orthogonal electrical and thermal conductances in phosphorene.

PubMed

Fei, Ruixiang; Faghaninia, Alireza; Soklaski, Ryan; Yan, Jia-An; Lo, Cynthia; Yang, Li

2014-11-12

Thermoelectric devices that utilize the Seebeck effect convert heat flow into electrical energy and are highly desirable for the development of portable, solid state, passively powered electronic systems. The conversion efficiencies of such devices are quantified by the dimensionless thermoelectric figure of merit (ZT), which is proportional to the ratio of a device's electrical conductance to its thermal conductance. In this paper, a recently fabricated two-dimensional (2D) semiconductor called phosphorene (monolayer black phosphorus) is assessed for its thermoelectric capabilities. First-principles and model calculations reveal not only that phosphorene possesses a spatially anisotropic electrical conductance, but that its lattice thermal conductance exhibits a pronounced spatial-anisotropy as well. The prominent electrical and thermal conducting directions are orthogonal to one another, enhancing the ratio of these conductances. As a result, ZT may reach the criterion for commercial deployment along the armchair direction of phosphorene at T = 500 K and is close to 1 even at room temperature given moderate doping (∼2 × 10(16) m(-2) or 2 × 10(12) cm(-2)). Ultimately, phosphorene hopefully stands out as an environmentally sound thermoelectric material with unprecedented qualities. Intrinsically, it is a mechanically flexible material that converts heat energy with high efficiency at low temperatures (∼300 K), one whose performance does not require any sophisticated engineering techniques.

Enhanced Thermoelectric Performance of n-type Bi2O2Se Ceramics Induced by Ge Doping

NASA Astrophysics Data System (ADS)

Ruleova, P.; Plechacek, T.; Kasparova, J.; Vlcek, M.; Benes, L.; Lostak, P.; Drasar, C.

2018-02-01

Ceramic samples with the composition Bi2- x Ge x O2Se1.01 ( x = 0, 0.05, 0.075, and 0.1) were synthesized by solid-state reaction and compacted using a hot-pressing technique. The prepared materials were characterized by x-ray diffraction analysis, electron microscopy, and measurements of electrical conductivity σ, Seebeck coefficient S, and thermal conductivity in the temperature range 300-780 K. Ge in the Bi2O2Se host structure led to an increase of the free electron concentration compared to pristine Bi2O2Se1.01. The donor effect is attributed to point substitutional defects in the Bi sublattice— {Ge}_{{Bi}}^{ + }, and oxygen vacancies {V}_{{O}}^{ + 2} producing free electrons. As a result, we observe an increase in the electrical conductivity and decrease in Seebeck coefficient while thermal conductivity κ changes slightly. The highest value of the dimensionless figure of merit ZT = σS 2 T/ κ reaches 0.25 for the composition Bi1.95Ge0.05O2Se1.01 at T = 723 K, which is, to date, the highest ZT value reported for Bi2O2Se ceramics. Our results suggest that Bi2O2Se is still worth exploring.

ZT Optimization: An Application Focus

PubMed Central

Tuley, Richard; Simpson, Kevin

2017-01-01

Significant research has been performed on the challenge of improving thermoelectric materials, with maximum peak figure of merit, ZT, the most common target. We use an approximate thermoelectric material model, matched to real materials, to demonstrate that when an application is known, average ZT is a significantly better optimization target. We quantify this difference with some examples, with one scenario showing that changing the doping to increase peak ZT by 19% can lead to a performance drop of 16%. The importance of average ZT means that the temperature at which the ZT peak occurs should be given similar weight to the value of the peak. An ideal material for an application operates across the maximum peak ZT, otherwise maximum performance occurs when the peak value is reduced in order to improve the peak position. PMID:28772668

Minimization of a free-energy-like potential for non-equilibrium flow systems at steady state

PubMed Central

Niven, Robert K.

2010-01-01

This study examines a new formulation of non-equilibrium thermodynamics, which gives a conditional derivation of the ‘maximum entropy production’ (MEP) principle for flow and/or chemical reaction systems at steady state. The analysis uses a dimensionless potential function ϕst for non-equilibrium systems, analogous to the free energy concept of equilibrium thermodynamics. Spontaneous reductions in ϕst arise from increases in the ‘flux entropy’ of the system—a measure of the variability of the fluxes—or in the local entropy production; conditionally, depending on the behaviour of the flux entropy, the formulation reduces to the MEP principle. The inferred steady state is also shown to exhibit high variability in its instantaneous fluxes and rates, consistent with the observed behaviour of turbulent fluid flow, heat convection and biological systems; one consequence is the coexistence of energy producers and consumers in ecological systems. The different paths for attaining steady state are also classified. PMID:20368250

On the role of disks in the formation of stellar systems: A numerical parameter study of rapid accretion

DOE PAGES

Kratter, Kaitlin M.; Matzner, Christopher D.; Krumholz, Mark R.; ...

2009-12-23

We study rapidly accreting, gravitationally unstable disks with a series of idealized global, numerical experiments using the code ORION. Our numerical parameter study focuses on protostellar disks, showing that one can predict disk behavior and the multiplicity of the accreting star system as a function of two dimensionless parameters which compare the infall rate to the disk sound speed and orbital period. Although gravitational instabilities become strong, we find that fragmentation into binary or multiple systems occurs only when material falls in several times more rapidly than the canonical isothermal limit. The disk-to-star accretion rate is proportional to the infallmore » rate and governed by gravitational torques generated by low-m spiral modes. Furthermore, we also confirm the existence of a maximum stable disk mass: disks that exceed ~50% of the total system mass are subject to fragmentation and the subsequent formation of binary companions.« less

Non-steady state simulation of BOM removal in drinking water biofilters: model development.

PubMed

Hozalski, R M; Bouwer, E J

2001-01-01

A numerical model was developed to simulate the non-steady-state behavior of biologically-active filters used for drinking water treatment. The biofilter simulation model called "BIOFILT" simulates the substrate (biodegradable organic matter or BOM) and biomass (both attached and suspended) profiles in a biofilter as a function of time. One of the innovative features of BIOFILT compared to previous biofilm models is the ability to simulate the effects of a sudden loss in attached biomass or biofilm due to filter backwash on substrate removal performance. A sensitivity analysis of the model input parameters indicated that the model simulations were most sensitive to the values of parameters that controlled substrate degradation and biofilm growth and accumulation including the substrate diffusion coefficient, the maximum rate of substrate degradation, the microbial yield coefficient, and a dimensionless shear loss coefficient. Variation of the hydraulic loading rate or other parameters that controlled the deposition of biomass via filtration did not significantly impact the simulation results.

Topography associated with crustal flow in continental collisions, with application to Tibet

NASA Astrophysics Data System (ADS)

Bendick, R.; McKenzie, D.; Etienne, J.

2008-10-01

Collision between an undeformable indenter and a viscous region generates isostatically compensated topography by solid-state flow. We model this process numerically, using a finite element scheme. The slope, amplitude and symmetry of the topographic signal depend on the indenter size and the Argand number of the viscous region, a dimensionless ratio of gravitational body forces to viscous forces. When applied to convergent continental settings, these scaling rules provide estimates of the position of an indenter at depth and the mechanical properties of the viscous region, especially effective viscosity. In Tibet, forward modelling suggests that some elevated, low relief topography within the northern plateau may be attributed to lower crustal flow, stimulated by a crustal indenter, possibly Indian lithosphere. The best-fit model constrains the northernmost limit of this indenter to 33.7°N and the maximum effective viscosity of Eurasian middle and lower crust to 1 × 1020 +/- 0.3 × 1020 Pa s.

Experimental study of laminar forced convective heat transfer of deionized water based copper (I) oxide nanofluids in a tube with constant wall heat flux

NASA Astrophysics Data System (ADS)

Umer, Asim; Naveed, Shahid; Ramzan, Naveed

2016-10-01

Nanofluids, having 1-100 nm size particles in any base fluid are promising fluid for heat transfer intensification due to their enhanced thermal conductivity as compared with the base fluid. The forced convection of nanofluids is the major practical application in heat transfer equipments. In this study, heat transfer enhancements at constant wall heat flux under laminar flow conditions were investigated. Nanofluids of different volume fractions (1, 2 and 4 %) of copper (I) oxide nanoparticles in deionized water were prepared using two step technique under mechanical mixing and ultrasonication. The results were investigated by increasing the Reynolds number of the nanofluids at constant heat flux. The trends of Nusselt number variation with dimensionless length (X/D) and Reynolds numbers were studied. It was observed that heat transfer coefficient increases with increases particles volume concentration and Reynolds number. The maximum enhancement in heat transfer coefficient of 61 % was observed with 4 % particle volume concentration at Reynolds number (Re ~ 605).

Epitaxial Relationships between Calcium Carbonate and Inorganic Substrates

PubMed Central

Yang, Taewook; Jho, Jae Young; Kim, Il Won

2014-01-01

The polymorph-selective crystallization of calcium carbonate has been studied in terms of epitaxial relationship between the inorganic substrates and the aragonite/calcite polymorphs with implication in bioinspired mineralization. EpiCalc software was employed to assess the previously published experimental results on two different groups of inorganic substrates: aragonitic carbonate crystals (SrCO3, PbCO3, and BaCO3) and a hexagonal crystal family (α-Al2O3, α-SiO2, and LiNbO3). The maximum size of the overlayer (aragonite or calcite) was calculated for each substrate based on a threshold value of the dimensionless potential to estimate the relative nucleation preference of the polymorphs of calcium carbonate. The results were in good agreement with previous experimental observations, although stereochemical effects between the overlayer and substrate should be separately considered when existed. In assessing the polymorph-selective nucleation, the current method appeared to provide a better tool than the oversimplified mismatch parameters without invoking time-consuming molecular simulation\\. PMID:25226539

Analysis of Heat Transfers inside Counterflow Plate Heat Exchanger Augmented by an Auxiliary Fluid Flow

PubMed Central

Khaled, A.-R. A.

2014-01-01

Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost. PMID:24719572

Analysis of heat transfers inside counterflow plate heat exchanger augmented by an auxiliary fluid flow.

PubMed

Khaled, A-R A

2014-01-01

Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost.

Thermal analysis of insulated north-wall greenhouse with solar collector under passive mode

NASA Astrophysics Data System (ADS)

Chauhan, Prashant Singh; Kumar, Anil

2018-04-01

An insulated north wall greenhouse dryer has been fabricated and tested for no-load condition under passive mode. Testing has been conducted in two different cases. Case-I is considered for solar collector kept inside the dryer and Case-II is dryer without solar collector. Convective heat transfer coefficient and various heat transfer dimensionless numbers with have been calculated for thermal analysis. The maximum convective heat transfer coefficient is found 52.18 W/m2°C at 14 h during the first day for Case-I. The difference of the highest convective heat transfer coefficient of both cases was 8.34 W/m2°C. Net heat gain inside room curves are uniform and smooth for Case-I, which shows the steady heat generation process due to presence of solar collector inside the dryer. Above results depicts the effectiveness of solar collector and insulated north wall. The selection of suitable crop for drying can be done by analysing article's result.

Role of turbulence fluctuations on uncertainties of acoutic Doppler current profiler discharge measurements

USGS Publications Warehouse

Tarrab, Leticia; Garcia, Carlos M.; Cantero, Mariano I.; Oberg, Kevin

2012-01-01

This work presents a systematic analysis quantifying the role of the presence of turbulence fluctuations on uncertainties (random errors) of acoustic Doppler current profiler (ADCP) discharge measurements from moving platforms. Data sets of three-dimensional flow velocities with high temporal and spatial resolution were generated from direct numerical simulation (DNS) of turbulent open channel flow. Dimensionless functions relating parameters quantifying the uncertainty in discharge measurements due to flow turbulence (relative variance and relative maximum random error) to sampling configuration were developed from the DNS simulations and then validated with field-scale discharge measurements. The validated functions were used to evaluate the role of the presence of flow turbulence fluctuations on uncertainties in ADCP discharge measurements. The results of this work indicate that random errors due to the flow turbulence are significant when: (a) a low number of transects is used for a discharge measurement, and (b) measurements are made in shallow rivers using high boat velocity (short time for the boat to cross a flow turbulence structure).

On the propulsive efficiency of rotating elastica.

NASA Astrophysics Data System (ADS)

Fermigier, Marc; Champagne, Nicolas; Laik, Eric; Marthelot, Joel; Du Roure, Olivia

2007-11-01

A majority of microorganisms propel themselves with long flexible cilia or flagella. Understanding in detail the hydrodynamics of such propulsion mechanisms is important both from biological and engineering point of views, in particular to design artificial microswimmers. We report an experimental investigation of the propulsive force delivered by a rotating elastic filament. Macroscopic filaments made of an elastomer (Young's modulus E) loaded with solid particles to match the density of the suspending liquid are rotated at constant velocity φ in a bath of glycerin. Their three dimensional shape is time independent but varies with φ and aspect ratio L/a. The force on the filament is computed from the experimental shape using a slender body approximation (ratio of perpendicular and parallel friction coefficients : ζ= 2 ζ). The evolution of axial force is captured by a single dimensionless parameter comparing viscous and elastic stresses: Sp = (ηφ/E) (L/a)^4. As for a planar oscillating flexible tail a maximum force is found at Sp 1.

Cyclic voltammetry of fast conducting electrocatalytic films.

PubMed

Costentin, Cyrille; Savéant, Jean-Michel

2015-07-15

In the framework of contemporary energy challenges, cyclic voltammetry is a particularly useful tool for deciphering the kinetics of catalytic films. The case of fast conducting films is analyzed, whether conduction is of the ohmic type or proceeds through rapid electron hopping. The rate-limiting factors are then the diffusion of the substrate in solution and through the film as well as the catalytic reaction itself. The dimensionless combination of the characteristics of these factors allows reducing the number of actual parameters to a maximum of two. The kinetics of the system may then be fully analyzed with the help of a kinetic zone diagram. Observing the variations of the current-potential responses with operational parameters such as film thickness, the potential scan rate and substrate concentration allows a precise assessment of the interplay between these factors and of the values of the rate controlling factors. A series of thought experiments is described in order to render the kinetic analysis more palpable.

Experimental investigation for cavity dimensions of highly porous small bodies

NASA Astrophysics Data System (ADS)

Okamoto, T.; Nakamura, A.; Hasegawa, S.

2014-07-01

Small bodies were probably very porous during the formation of the solar system. In order to understand the surface evolution of highly porous bodies, it is necessary to investigate the impact process for targets with such high porosity. In this study, impact experiments with sintered glass-bead targets of 87 and 94 % porosities were conducted. Growth of cavities with time and the final cavity dimensions were analyzed and compared with previous studies of porous targets. Impact experiments were conducted using a two-stage light-gas gun at ISAS, Japan. The projectiles of a few millimeters were composed of titanium, aluminum, nylon, and basalt. The impact velocities ranged from 1.8 to 7.2 km s^{-1}. In order to observe the inside of the targets, we used a flash X-ray system and a micro-X-ray tomography instrument. The track shape was found to be divided into two types, elongated 'carrot' shape and short 'bulb' shape [1]. The figures on the left and right present a transmission image of the bulb shape track and a sketch of a cross section of the cavity, respectively. The results of the final maximum diameter, D_max and the final entrance-hole diameter, D_ent show that both dimensions tend to increase with impact velocity and decrease with target porosity. We adopted the scaling law of crater diameter [2] for our analysis of D_max and D_ent. The following empirical relations are obtained for targets with porosity ≥ 87 %: {D_max}/{d_p}(ρ_t/ρ_p)^{0.4} =10^{-1.52±0.27} ({Y}/ρ_t{v_0^2})^{-0.49 ± 0.07}, {D_ent}/{d_p}(ρ_t/ρ_p)^{0.4} =10^{-2.12±0.39} ({Y}/ρ_t{v_0^2})^{-0.53 ± 0.11}, where d_p, ρ_t, ρ_p, Y, and v_0 are the projectile diameter, target density, projectile density, target compressive strength, and the impact velocity, respectively. The results of the depth from the entrance hole to the maximum diameter of the cavity, L_max, shows that L_max decreases with impact velocity and increases with target porosity. If we assume that a projectile decelerates by inertial drag [1], the characteristic length L_0, which is the depth from the surface where the kinetic energy of the projectile becomes 1/e of the initial energy, is described as follows: L_0={2ρ_p}/{3C_dρ_t}d_p, where C_d is the drag coefficient that increases with dynamic pressure normalized by tensile strength of the projectile [1]. We found that L_max/d_p increases with L_0/d_p. It indicates that L_max depends on the degree of projectile deformation or disruption through the drag coefficient and also depends on the projectile-target density ratio. We will also discuss the growth of the cavity volume, maximum diameter, and depth of the cavity with time using dimensionless parameters of crater scaling [3].

Variation in the reference Shields stress for bed load transport in gravel‐bed streams and rivers

USGS Publications Warehouse

Mueller, Erich R.; Pitlick, John; Nelson, Jonathan M.

2005-01-01

The present study examines variations in the reference shear stress for bed load transport (τr) using coupled measurements of flow and bed load transport in 45 gravel‐bed streams and rivers. The study streams encompass a wide range in bank‐full discharge (1–2600 m3/s), average channel gradient (0.0003–0.05), and median surface grain size (0.027–0.21 m). A bed load transport relation was formed for each site by plotting individual values of the dimensionless transport rate W* versus the reach‐average dimensionless shear stress τ*. The reference dimensionless shear stress τ*r was then estimated by selecting the value of τ* corresponding to a reference transport rate of W* = 0.002. The results indicate that the discharge corresponding to τ*r averages 67% of the bank‐full discharge, with the variation independent of reach‐scale morphologic and sediment properties. However, values of τ*r increase systematically with average channel gradient, ranging from 0.025–0.035 at sites with slopes of 0.001–0.006 to values greater than 0.10 at sites with slopes greater than 0.02. A corresponding relation for the bank‐full dimensionless shear stress τ*bf, formulated with data from 159 sites in North America and England, mirrors the relation between τ*r and channel gradient, suggesting that the bank‐full channel geometry of gravel‐ and cobble‐bedded streams is adjusted to a relatively constant excess shear stress, τ*bf − τ*r, across a wide range of slopes.

An empirical/theoretical model with dimensionless numbers to predict the performance of electrodialysis systems on the basis of operating conditions.

PubMed

Karimi, Leila; Ghassemi, Abbas

2016-07-01

Among the different technologies developed for desalination, the electrodialysis/electrodialysis reversal (ED/EDR) process is one of the most promising for treating brackish water with low salinity when there is high risk of scaling. Multiple researchers have investigated ED/EDR to optimize the process, determine the effects of operating parameters, and develop theoretical/empirical models. Previously published empirical/theoretical models have evaluated the effect of the hydraulic conditions of the ED/EDR on the limiting current density using dimensionless numbers. The reason for previous studies' emphasis on limiting current density is twofold: 1) to maximize ion removal, most ED/EDR systems are operated close to limiting current conditions if there is not a scaling potential in the concentrate chamber due to a high concentration of less-soluble salts; and 2) for modeling the ED/EDR system with dimensionless numbers, it is more accurate and convenient to use limiting current density, where the boundary layer's characteristics are known at constant electrical conditions. To improve knowledge of ED/EDR systems, ED/EDR models should be also developed for the Ohmic region, where operation reduces energy consumption, facilitates targeted ion removal, and prolongs membrane life compared to limiting current conditions. In this paper, theoretical/empirical models were developed for ED/EDR performance in a wide range of operating conditions. The presented ion removal and selectivity models were developed for the removal of monovalent ions and divalent ions utilizing the dominant dimensionless numbers obtained from laboratory scale electrodialysis experiments. At any system scale, these models can predict ED/EDR performance in terms of monovalent and divalent ion removal. Copyright © 2016 Elsevier Ltd. All rights reserved.

Response of the Water Level in a Well to Earth Tides and Atmospheric Loading Under Unconfined Conditions

NASA Astrophysics Data System (ADS)

Rojstaczer, Stuart; Riley, Francis S.

1990-08-01

The response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions can be explained if the water level is controlled by the aquifer response averaged over the saturated depth of the well. Because vertical averaging tends to diminish the influence of the water table, the response is qualitatively similar to the response of a well under partially confined conditions. When the influence of well bore storage can be ignored, the response to Earth tides is strongly governed by a dimensionless aquifer frequency Q'u. The response to atmospheric loading is strongly governed by two dimensionless vertical fluid flow parameters: a dimensionless unsaturated zone frequency, R, and a dimensionless aquifer frequency Qu. The differences between Q'u and Qu are generally small for aquifers which are highly sensitive to Earth tides. When Q'u and Qu are large, the response of the well to Earth tides and atmospheric loading approaches the static response of the aquifer under confined conditions. At small values of Q'u and Qu, well response to Earth tides and atmospheric loading is strongly influenced by water table drainage. When R is large relative to Qu, the response to atmospheric loading is strongly influenced by attenuation and phase shift of the pneumatic pressure signal in the unsaturated zone. The presence of partial penetration retards phase advance in well response to Earth tides and atmospheric loading. When the theoretical response of a phreatic well to Earth tides and atmospheric loading is fit to the well response inferred from cross-spectral estimation, it is possible to obtain estimates of the pneumatic diffusivity of the unsaturated zone and the vertical hydraulic conductivity of the aquifer.

Typhoon Impacts

DTIC Science & Technology

2014-09-30

and Rmax is the radius of maximum winds . Figure 1 compares two properties of the cold wake, its location and its strength , from 6 storms. The...dimensional response of the underlying ocean including strong surface currents, upwelling of the thermocline, intense mixing across the thermocline, the...mixing determining the rate and character of wake dissipation. The wake is also expected to modify the atmospheric boundary layer and the biology

Geolocation of LTE Subscriber Stations Based on the Timing Advance Ranging Parameter

DTIC Science & Technology

2010-12-01

provides the maximum achievable data rates. The specifications for LTE include FDD and TDD in all of its descriptions since there is little to no...parameters used during LTE network entry are examined as they relate to calculating these distances. Computer simulation is used to demonstrate...11 Figure 4. Principles of TDD and FDD modes of

The Shock and Vibration Bulletin. Part 2. Ship Shock, Shock and Blast and Ground Shock

DTIC Science & Technology

1984-06-01

followee As built, structures have a maximumSsomu of Inelastic respose whic they can ::• Governina Failure Mode Approximate Failure itai fielsi epne ih...inside surface of window "panes. Typical films are about 0.002 to Charts are presented in Figures 2 to 16 for 0.004 inch thick polyester with a self

Augmentation of the Differentiation Response to Antitumor Antimalarials

DTIC Science & Technology

2004-07-01

Release; Distribution Unlimited 13. ABSTRACT (Maximum 200 Words) We have shown that the quinoline antimalarials chloroquine (CQ) and hydroxychloroquine (HCQ...Introduction: Preliminary studies showed that two of the quinoline antimalarials, chloroquine (CQ) and hydroxychloroquine (HCQ), displayed selective... hydroxychloroquine upon pretreatment with ATRA or Aza on tumor cell survival (Figures 1 and 2, respectively). Clonogenic survival of MDA-MB-231 cells exposed to

[Biaggi law, transformation of the labor market, protection of health at the workplace].

PubMed

Menegozzo, M; Diglio, G; Canfora, M L; Menegozzo, S; Quagliuolo, R

2003-01-01

The new legislation on the labor market (Biagi Law, Ministerial Decree approved by the Council of Ministers on 06.06.2003) introduces new contractual profiles imprinted to the criterion of maximum mobility and flexibility. This new legislation does not appear equipped from a parallel legislation that guarantees occupational safety and the protection of the new professional figures.

MH-53J/M Pave Low III/IV Systems Engineering. Case Study

DTIC Science & Technology

2010-01-01

53H Black Knight ............................................................................................. 15 Figure 10. General Dynamics YF-16...boundary was defined; • they used disciplined methodologies for complex systems ; • human systems integration was accomplished; • problem solving ...wartime) • Power plant: 2× General Electric T64-GE-100 turboshaft, 4,330 shaft horsepower ( shp ) each Performance • Maximum speed: 170 knots (196

Effect of microstructure on the thermoelectric performance of La{sub 1−x}Sr{sub x}CoO{sub 3}

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

Viskadourakis, Z.; Department of Mechanical and Manufacturing Engineering, University of Cypruss, 75 Kallipoleos Avenue, P.O. Box 20537, 1678 Nicosia; Athanasopoulos, G.I.

We present a case where the microstructure has a profound effect on the thermoelectric properties of oxide compounds. Specifically, we have investigated the effect of different sintering treatments on La{sub 1−x}Sr{sub x}CoO{sub 3} samples synthesized using the Pechini method. We found that the samples, which are dense and consist of inhomogeneously-mixed grains of different size, exhibit both higher Seebeck coefficient and thermoelectric figure of merit than the samples, which are porous and consist of grains with almost identical size. The enhancement of Seebeck coefficient in the dense samples is attributed to the so-called “energy-filtering” mechanism that is related to themore » energy barrier of the grain boundary. On the other hand, the thermal conductivity for the porous compounds is significantly reduced in comparison to the dense compounds. It is suggested that a fine-manipulation of grain size ratio combined with a fine-tuning of porosity could considerably enhance the thermoelectric performance of oxides. - Graphical abstract: The enhancement of the dimensionless thermoelectric figure ZT of merit is presented for two equally Sr-doped LaCoO3 compounds, possessing different microstructure, indicating the effect of the latter to the thermoelectric performance of the La{sub 1−x}Sr{sub x}CoO{sub 3} solid solution. - Highlights: • Electrical and thermal transport properties are affected by the microstructure in La{sub 1−x}Sr{sub x}CoO{sub 3} polycrystalline materials. • Coarse/fine grain size distribution enhances the Seebeck coefficient. • Porosity reduces the thermal conductivity in La{sub 1−x}Sr{sub x}CoO{sub 3} polycrystalline samples. • The combination of large/small grain ratio distribution with the high porosity may result to the enhancement of the thermoelectric performance of the material.« less

Analysis of Nanoprecipitates in a Na-Doped PbTe-SrTe Thermoelectric Material with a High Figure of Merit.

PubMed

Kim, Yoon-Jun; Zhao, Li-Dong; Kanatzidis, Mercouri G; Seidman, David N

2017-07-05

The dimensionless figure of merit, ZT, of bulk thermoelectric materials depends mainly on the transport properties of charge carriers and heat-carrying phonons. PbTe-4 mol % SrTe doped with 2 mol % Na (Pb 0.94 Na 0.02 Sr 0.04 Te) is a nanostructured material system that exhibits a ZT higher than 2. The precipitate size distribution of SrTe precipitates is believed to play a key role. This raises the question of whether its performance is limited by precipitate coarsening (Ostwald ripening) at elevated temperatures. Herein, we utilize an atom-probe tomography (APT) to study the number density and mean radii of precipitates in concert with partial radial distribution functions (RDFs) of individual atoms. We find that the SrTe precipitates actually contain oxygen: SrTe 1-x O x . We correlate this information with the overall ZT performance, specifically focusing on the electrical and lattice thermal conductivities after isothermal heat treatments at 300 and 400 °C for 7 days, followed by furnace cooling. Comparison of the samples annealed at 400 and 300 °C demonstrates significant coarsening of SrTe 1-x O x precipitates as well as strong segregation of oxygen impurities in the SrTe 1-x O x precipitates. Additionally, on the basis of the partial RDFs, the Na dopant atoms cluster with other Na atoms as well as with Pb, Te, and Sr atoms; clustering depends strongly on the annealing temperature and concomitantly affects the overall ZT values. We found that the coarsening slightly increases the lattice thermal conductivity and also increases the electrical conductivity, thereby having little or even a beneficial effect on the ZT values. Importantly, these findings demonstrate that APT enables quantitative analyses in three dimensions of the PbTe-4 mol % SrTe samples in addition to correlation of their properties with the thermoelectric performance.

Transcranial Magnetic Stimulation-coil design with improved focality

NASA Astrophysics Data System (ADS)

Rastogi, P.; Lee, E. G.; Hadimani, R. L.; Jiles, D. C.

2017-05-01

Transcranial Magnetic Stimulation (TMS) is a technique for neuromodulation that can be used as a non-invasive therapy for various neurological disorders. In TMS, a time varying magnetic field generated from an electromagnetic coil placed on the scalp is used to induce an electric field inside the brain. TMS coil geometry plays an important role in determining the focality and depth of penetration of the induced electric field responsible for stimulation. Clinicians and basic scientists are interested in stimulating a localized area of the brain, while minimizing the stimulation of surrounding neural networks. In this paper, a novel coil has been proposed, namely Quadruple Butterfly Coil (QBC) with an improved focality over the commercial Figure-8 coil. Finite element simulations were conducted with both the QBC and the conventional Figure-8 coil. The two coil's stimulation profiles were assessed with 50 anatomically realistic MRI derived head models. The coils were positioned on the vertex and the scalp over the dorsolateral prefrontal cortex to stimulate the brain. Computer modeling of the coils has been done to determine the parameters of interest-volume of stimulation, maximum electric field, location of maximum electric field and area of stimulation across all 50 head models for both coils.

Adjustments of the Pesticide Risk Index Used in Environmental Policy in Flanders

PubMed Central

Fevery, Davina; Peeters, Bob; Lenders, Sonia; Spanoghe, Pieter

2015-01-01

Indicators are used to quantify the pressure of pesticides on the environment. Pesticide risk indicators typically require weighting environmental exposure by a no effect concentration. An indicator based on spread equivalents (ΣSeq) is used in environmental policy in Flanders (Belgium). The pesticide risk for aquatic life is estimated by weighting active ingredient usage by the ratio of their maximum allowable concentration and their soil halflife. Accurate estimates of total pesticide usage in the region are essential in such calculations. Up to 2012, the environmental impact of pesticides was estimated on sales figures provided by the Federal Government. Since 2013, pesticide use is calculated based on results from the Farm Accountancy Data Network (FADN). The estimation of pesticide use was supplemented with data for non-agricultural use based on sales figures of amateur use provided by industry and data obtained from public services. The Seq-indicator was modified to better reflect reality. This method was applied for the period 2009-2012 and showed differences between estimated use and sales figures of pesticides. The estimated use of pesticides based on accountancy data is more accurate compared to sales figures. This approach resulted in a better view on pesticide use and its respective environmental impact in Flanders. PMID:26046655

Adjustments of the Pesticide Risk Index Used in Environmental Policy in Flanders.

PubMed

Fevery, Davina; Peeters, Bob; Lenders, Sonia; Spanoghe, Pieter

2015-01-01

Indicators are used to quantify the pressure of pesticides on the environment. Pesticide risk indicators typically require weighting environmental exposure by a no effect concentration. An indicator based on spread equivalents (ΣSeq) is used in environmental policy in Flanders (Belgium). The pesticide risk for aquatic life is estimated by weighting active ingredient usage by the ratio of their maximum allowable concentration and their soil halflife. Accurate estimates of total pesticide usage in the region are essential in such calculations. Up to 2012, the environmental impact of pesticides was estimated on sales figures provided by the Federal Government. Since 2013, pesticide use is calculated based on results from the Farm Accountancy Data Network (FADN). The estimation of pesticide use was supplemented with data for non-agricultural use based on sales figures of amateur use provided by industry and data obtained from public services. The Seq-indicator was modified to better reflect reality. This method was applied for the period 2009-2012 and showed differences between estimated use and sales figures of pesticides. The estimated use of pesticides based on accountancy data is more accurate compared to sales figures. This approach resulted in a better view on pesticide use and its respective environmental impact in Flanders.

Figure-Ground Segmentation Using Factor Graphs

PubMed Central

Shen, Huiying; Coughlan, James; Ivanchenko, Volodymyr

2009-01-01

Foreground-background segmentation has recently been applied [26,12] to the detection and segmentation of specific objects or structures of interest from the background as an efficient alternative to techniques such as deformable templates [27]. We introduce a graphical model (i.e. Markov random field)-based formulation of structure-specific figure-ground segmentation based on simple geometric features extracted from an image, such as local configurations of linear features, that are characteristic of the desired figure structure. Our formulation is novel in that it is based on factor graphs, which are graphical models that encode interactions among arbitrary numbers of random variables. The ability of factor graphs to express interactions higher than pairwise order (the highest order encountered in most graphical models used in computer vision) is useful for modeling a variety of pattern recognition problems. In particular, we show how this property makes factor graphs a natural framework for performing grouping and segmentation, and demonstrate that the factor graph framework emerges naturally from a simple maximum entropy model of figure-ground segmentation. We cast our approach in a learning framework, in which the contributions of multiple grouping cues are learned from training data, and apply our framework to the problem of finding printed text in natural scenes. Experimental results are described, including a performance analysis that demonstrates the feasibility of the approach. PMID:20160994

Luminescence from cavitation bubbles deformed in uniform pressure gradients

NASA Astrophysics Data System (ADS)

Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed

2017-09-01

Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single-collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelength range, 300-900 nm) from the individual collapses of laser-induced bubbles in water. By varying the bubble size, driving pressure, and perceived gravity level aboard parabolic flights, we probed the limit from aspherical to highly spherical bubble collapses. Luminescence was detected for bubbles of maximum radii within the previously uncovered range, R0=1.5 -6 mm, for laser-induced bubbles. The relative luminescence energy was found to rapidly decrease as a function of the bubble asymmetry quantified by the anisotropy parameter ζ , which is the dimensionless equivalent of the Kelvin impulse. As established previously, ζ also dictates the characteristic parameters of bubble-driven microjets. The threshold of ζ beyond which no luminescence is observed in our experiment closely coincides with the threshold where the microjets visibly pierce the bubble and drive a vapor jet during the rebound. The individual fitted blackbody temperatures range between Tlum=7000 and Tlum=11 500 K but do not show any clear trend as a function of ζ . Time-resolved measurements using a high-speed photodetector disclose multiple luminescence events at each bubble collapse. The averaged full width at half-maximum of the pulse is found to scale with R0 and to range between 10 and 20 ns.

ADRC for spacecraft attitude and position synchronization in libration point orbits

NASA Astrophysics Data System (ADS)

Gao, Chen; Yuan, Jianping; Zhao, Yakun

2018-04-01

This paper addresses the problem of spacecraft attitude and position synchronization in libration point orbits between a leader and a follower. Using dual quaternion, the dimensionless relative coupled dynamical model is derived considering computation efficiency and accuracy. Then a model-independent dimensionless cascade pose-feedback active disturbance rejection controller is designed to spacecraft attitude and position tracking control problems considering parameter uncertainties and external disturbances. Numerical simulations for the final approach phase in spacecraft rendezvous and docking and formation flying are done, and the results show high-precision tracking errors and satisfactory convergent rates under bounded control torque and force which validate the proposed approach.

Fluid/Solid Boundary Conditions in Non-Isothermal Systems

NASA Technical Reports Server (NTRS)

Rosner, Daniel E.

1999-01-01

The existing theoretical research concerned with thermal creep at fluid/solid interfaces is briefly reviewed, and the importance of microgravity-based experimental data is then discussed. It is noted that the ultimate goal of this research is a rational molecular level theory that predicts the dependence of a dimensionless thermal creep coefficient, Ctc, on relevant dimensionless parameters describing the way fluid molecules interact with the solid surface and how they interact among themselves. The discussion covers thermophoresis of isolated solid spheres and aggregates in gases; solid sphere thermophoresis in liquids and dense vapors; thermophoresis of small immiscible liquid droplets; and applications of the direct simulation Monte Carlo method.

Dosage-based parameters for characterization of puff dispersion results.

PubMed

Berbekar, Eva; Harms, Frank; Leitl, Bernd

2015-01-01

A set of parameters is introduced to characterize the dispersion of puff releases based on the measured dosage. These parameters are the dosage, peak concentration, arrival time, peak time, leaving time, ascent time, descent time and duration. Dimensionless numbers for the scaling of the parameters are derived from dimensional analysis. The dimensionless numbers are tested and confirmed based on a statistically representative wind tunnel dataset. The measurements were carried out in a 1:300 scale model of the Central Business District in Oklahoma City. Additionally, the effect of the release duration on the puff parameters is investigated. Copyright © 2014 Elsevier B.V. All rights reserved.

Physical scales in the Wigner-Boltzmann equation

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

Nedjalkov, M., E-mail: mixi@iue.tuwien.ac.at; Selberherr, S.; Ferry, D.K.

2013-01-15

The Wigner-Boltzmann equation provides the Wigner single particle theory with interactions with bosonic degrees of freedom associated with harmonic oscillators, such as phonons in solids. Quantum evolution is an interplay of two transport modes, corresponding to the common coherent particle-potential processes, or to the decoherence causing scattering due to the oscillators. Which evolution mode will dominate depends on the scales of the involved physical quantities. A dimensionless formulation of the Wigner-Boltzmann equation is obtained, where these scales appear as dimensionless strength parameters. A notion called scaling theorem is derived, linking the strength parameters to the coupling with the oscillators. Itmore » is shown that an increase of this coupling is equivalent to a reduction of both the strength of the electric potential, and the coherence length. Secondly, the existence of classes of physically different, but mathematically equivalent setups of the Wigner-Boltzmann evolution is demonstrated. - Highlights: Black-Right-Pointing-Pointer Dimensionless parameters determine the ratio of quantum or classical WB evolution. Black-Right-Pointing-Pointer The scaling theorem evaluates the decoherence effect due to scattering. Black-Right-Pointing-Pointer Evolution processes are grouped into classes of equivalence.« less

Ultimate Lateral Capacity of Rigid Pile in c- φ Soil

NASA Astrophysics Data System (ADS)

Zhang, Wei-min

2018-03-01

To date no analytical solution of the pile ultimate lateral capacity for the general c- φ soil has been obtained. In the present study, a new dimensionless embedded ratio was proposed and the analytical solutions of ultimate lateral capacity and rotation center of rigid pile in c- φ soils were obtained. The results showed that both the dimensionless ultimate lateral capacity and dimensionless rotation center were the univariate functions of the embedded ratio. Also, the ultimate lateral capacity in the c- φ soil was the combination of the ultimate lateral capacity ( f c ) in the clay, and the ultimate lateral capacity ( f φ ) in the sand. Therefore, the Broms chart for clay, solution for clay ( φ=0) put forward by Poulos and Davis, solution for sand ( c=0) obtained by Petrasovits and Awad, and Kondner's ultimate bending moment were all proven to be the special cases of the general solution in the present study. A comparison of the field and laboratory tests in 93 cases showed that the average ratios of the theoretical values to the experimental value ranged from 0.85 to 1.15. Also, the theoretical values displayed a good agreement with the test values.

On the effect of velocity gradients on the depth of correlation in μPIV

NASA Astrophysics Data System (ADS)

Mustin, B.; Stoeber, B.

2016-03-01

The present work revisits the effect of velocity gradients on the depth of the measurement volume (depth of correlation) in microscopic particle image velocimetry (μPIV). General relations between the μPIV weighting functions and the local correlation function are derived from the original definition of the weighting functions. These relations are used to investigate under which circumstances the weighting functions are related to the curvature of the local correlation function. Furthermore, this work proposes a modified definition of the depth of correlation that leads to more realistic results than previous definitions for the case when flow gradients are taken into account. Dimensionless parameters suitable to describe the effect of velocity gradients on μPIV cross correlation are derived and visual interpretations of these parameters are proposed. We then investigate the effect of the dimensionless parameters on the weighting functions and the depth of correlation for different flow fields with spatially constant flow gradients and with spatially varying gradients. Finally this work demonstrates that the results and dimensionless parameters are not strictly bound to a certain model for particle image intensity distributions but are also meaningful when other models for particle images are used.

Theoretical results for fully flooded, elliptical hydrodynamic contacts

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1982-01-01

The influence of the ellipticity parameter and the dimensionless speed, load, and materials parameters on minimum film thickness was investigated. The ellipticity parameter was varied from 1 (a ball-on-plate configuration) to 8 (a configuration approaching a line contact). The dimensionless speed parameter was varied over a range of nearly two orders of magnitude. Conditions corresponding to the use of solid materials of bronze, steel, and silicon nitride and lubricants of praffinic and naphthemic mineral oils were considered in obtaining the exponent in the dimensionless materials parameter. Thirty-four different cases were used in obtaining the minimum film thickness formula H min = 3.63U to the 0.68 power G to the 0.49 power W to the -0.073 power 1-e to the 0.68K power). A simplified expression for the ellipticity parameter was found where k = 1.03 (r(y)/r(x)) to the 0.64 power. Contour plots were also shown which indicate in detail the pressure spike and two side lobes in which the minimum film thickness occurs. These theoretical solutions of film thickness have all the essential features of the previously reported experimental observations based upon optical interferometry.

Dimensionless number is central to stress relaxation and expansive growth of the cell wall.

PubMed

Ortega, Joseph K E

2017-06-07

Experiments demonstrate that both plastic and elastic deformation of the cell wall are necessary for wall stress relaxation and expansive growth of walled cells. A biophysical equation (Augmented Growth Equation) was previously shown to accurately model the experimentally observed wall stress relaxation and expansive growth rate. Here, dimensional analysis is used to obtain a dimensionless Augmented Growth Equation with dimensionless coefficients (groups of variables, or Π parameters). It is shown that a single Π parameter controls the wall stress relaxation rate. The Π parameter represents the ratio of plastic and elastic deformation rates, and provides an explicit relationship between expansive growth rate and the wall's mechanical properties. Values for Π are calculated for plant, algal, and fungal cells from previously reported experimental results. It is found that the Π values for each cell species are large and very different from each other. Expansive growth rates are calculated using the calculated Π values and are compared to those measured for plant and fungal cells during different growth conditions, after treatment with IAA, and in different developmental stages. The comparison shows good agreement and supports the claim that the Π parameter is central to expansive growth rate of walled cells.

Stagnation region gas film cooling: Effects of dimensionless coolant temperature

NASA Technical Reports Server (NTRS)

Bonnice, M. A.; Lecuyer, M. R.

1983-01-01

An experimental investigation was conducted to mode the film cooling performance for a turbine vane leading edge using the stagnation region of a cylinder in cross flow. Experiments were conducted with a single row of spanwise angled (25 deg) coolant holes for a range of the coolant blowing ratio and dimensionless coolant temperature with free stream-to-wall temperature ratio approximately 1.7 and Re sub D = 90000. the cylindrical test surface was instrumented with miniature heat flux gages and wall thermocouples to determine the percentage reduction in the Stanton number as a function of the distance downstream from injection (x/d sub 0) and the location between adjacent holes (z/S). Data from local heat flux measurements are presented for injection from a single row located at 5 deg, 22.9 deg, 40.8 deg, from stagnation using a hole spacing ratio of S/d = 5. The film coolant was injected with T sub c T sub w with a dimensionless coolant temperature in the range 1.18 or equal to theta sub c or equal to 1.56. The data for local Stanton Number Reduction (SNR) showed a significant increase in SNR as theta sub c was increased above 1.0.

Dimensionless factors for an alternating-current non-thermal arc plasma

NASA Astrophysics Data System (ADS)

Zhang, Si-Yuan; Li, Xiao-Song; Liu, Jin-Bao; Liu, Jing-Lin; Li, He-Ping; Zhu, Ai-Min

2016-12-01

A gliding arc discharge, as a source of warm plasma combining advantages of both thermal and cold plasmas, would have promising application prospects in the fields of fuel conversion, combustion enhancement, material synthesis, surface modifications, pollution control, etc. In order to gain insight into the features of an alternating-current gliding arc discharge plasma, three dimensionless factors, i.e., the extinction span (ψ), current lag (δ), and heating lag (χ) factors are proposed in this letter based on the measured waveforms of the discharge voltage and current in an AC gliding arc discharge plasma. The influences of the driving frequency of the power supply (f) on these three dimensionless parameters are investigated experimentally with the explanations on the physical meanings of these factors. The experimental results show that a higher value of f would lead to the lower values of ψ and δ, as well as a higher value of χ. These experimental phenomena indicate a lower threshold ignition voltage of the discharges, a lower current-growth inertia of the gliding arcs and a larger relative thermal inertia of the plasmas with increase the driving frequency of the power supply in the operating parameter range studied in this letter.

Dimensionless parameterization of lidar for laser remote sensing of the atmosphere and its application to systems with SiPM and PMT detectors.

PubMed

Agishev, Ravil; Comerón, Adolfo; Rodriguez, Alejandro; Sicard, Michaël

2014-05-20

In this paper, we show a renewed approach to the generalized methodology for atmospheric lidar assessment, which uses the dimensionless parameterization as a core component. It is based on a series of our previous works where the problem of universal parameterization over many lidar technologies were described and analyzed from different points of view. The modernized dimensionless parameterization concept applied to relatively new silicon photomultiplier detectors (SiPMs) and traditional photomultiplier (PMT) detectors for remote-sensing instruments allowed predicting the lidar receiver performance with sky background available. The renewed approach can be widely used to evaluate a broad range of lidar system capabilities for a variety of lidar remote-sensing applications as well as to serve as a basis for selection of appropriate lidar system parameters for a specific application. Such a modernized methodology provides a generalized, uniform, and objective approach for evaluation of a broad range of lidar types and systems (aerosol, Raman, DIAL) operating on different targets (backscatter or topographic) and under intense sky background conditions. It can be used within the lidar community to compare different lidar instruments.

Self-focusing and defocusing of Gaussian laser beams in collisional underdense magnetized plasmas with considering the nonlinear ohmic heating and ponderomotive force effects

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

Ettehadi Abari, Mehdi; Sedaghat, Mahsa; Shokri, Babak, E-mail: b-shokri@sbu.ac.ir

2015-10-15

The propagation characteristics of a Gaussian laser beam in collisional magnetized plasma are investigated by considering the ponderomotive and ohmic heating nonlinearities. Here, by taking into account the effect of the external magnetic field, the second order differential equation of the dimensionless beam width parameter is solved numerically. Furthermore, the nonlinear dielectric permittivity of the mentioned plasma medium in the paraxial approximation and its dependence on the propagation characteristics of the Gaussian laser pulse is obtained, and its variation in terms of the dimensionless plasma length is analyzed at different initial normalized plasma and cyclotron frequencies. The results show thatmore » the dimensionless beam width parameter is strongly affected by the initial plasma frequency, magnetic strength, and laser pulse intensity. Furthermore, it is found that there exists a certain intensity value below which the laser pulse tends to self focus, while the beam diverges above of this value. In addition, the results confirm that, by increasing the plasma and cyclotron frequencies (plasma density and magnetic strength), the self-focusing effect can occur intensively.« less

Lagtime relations for urban streams in Georgia

USGS Publications Warehouse

Inman, Ernest J.

2000-01-01

Urban flood hydrographs are needed for the design of many highway drainage structures, embankments, and entrances to detention ponds. The three components that are needed to simulate urban flood hydrographs at ungaged sites are the design flood, the dimensionless hydrograph, and lagtime. The design flood and the dimensionless hydrograph have been presented in earlier studies for urban streams in Georgia. The objective of this study was to develop equations for estimating lagtime for urban streams in Georgia. Lagtimes were computed for 329 floods at 69 urban gaging stations in 11 cities in Georgia. These data were used to compute an average lagtime for each gaging station. Multiple regression analysis was then used to define relations between lagtime and certain physical basin characteristics, of which drainage area, slope, and impervious area were found to be significant. A qualitative variable was used to account for a geographical bias in flood-frequency region 4, a small area of southwestern Georgia. Information from this report can be used to simulate a flood hydrograph using a dimensionless hydrograph, the design flood, and the lagtime obtained from regression equations for any urban site with less than a 25-square-mile drainage area in Georgia.

A physically-based method for predicting peak discharge of floods caused by failure of natural and constructed earthen dams

USGS Publications Warehouse

Walder, J.S.

1997-01-01

We analyse a simple, physically-based model of breach formation in natural and constructed earthen dams to elucidate the principal factors controlling the flood hydrograph at the breach. Formation of the breach, which is assumed trapezoidal in cross-section, is parameterized by the mean rate of downcutting, k, the value of which is constrained by observations. A dimensionless formulation of the model leads to the prediction that the breach hydrograph depends upon lake shape, the ratio r of breach width to depth, the side slope ?? of the breach, and the parameter ?? = (V/ D3)(k/???gD), where V = lake volume, D = lake depth, and g is the acceleration due to gravity. Calculations show that peak discharge Qp depends weakly on lake shape r and ??, but strongly on ??, which is the product of a dimensionless lake volume and a dimensionless erosion rate. Qp(??) takes asymptotically distinct forms depending on whether ?? > 1. Theoretical predictions agree well with data from dam failures for which k could be reasonably estimated. The analysis provides a rapid and in many cases graphical way to estimate plausible values of Qp at the breach.

Linear instability of compound liquid threads in the presence of surfactant

NASA Astrophysics Data System (ADS)

Ye, Han-yu; Yang, Li-jun; Fu, Qing-fei

2017-08-01

This paper investigates the linear instability of compound liquid threads in the presence of surfactant. The limitation of the one-dimensional approximation in previous work [Craster, Matar, and Papageorgiou, Phys. Fluids 15, 3409 (2003), 10.1063/1.1611879] is removed; hence the radial dependence of the axial velocity can be taken into account. Therefore both the stretching and the squeezing modes can be investigated. The disturbance growth rate is reduced with an increase of the dimensionless surface-tension gradient (whether in the stretching or squeezing mode). For the parameter range investigated, it is found that the squeezing mode is much more sensitive to the Marangoni effect than the stretching mode. The disturbance axial velocity and disturbance surfactant concentration for a typical case is investigated. It is found that the disturbance axial velocity is close to uniform in the stretching mode when the dimensionless surface-tension gradient and the wave number are small. In contrast, for wave numbers close to cutoff, or a large dimensionless surface-tension gradient, or in the squeezing mode, the disturbance axial velocity is not uniform. Analytical relations between growth rate and wave number valid in the long-wave limit are derived. In the stretching mode, the flow moves from an extension-dominated regime to a shear-dominated regime when β1+R σ β2 increases through 1 +R σ , where β1 and β2 are the dimensionless surface-tension gradient of the inner and outer interface, respectively, R is the radius ratio, and σ is the surface tension ratio. In the squeezing mode, whatever the values of β1 and β2, the flow is always in the shear-dominated regime. The expressions of the leading-order axial perturbation velocity in the long-wave limit are derived and they explain the applicability of one-dimensional models. It is found that the leading-order axial velocity in the extension-dominated regime is always uniform and one-dimensional models work well in this regime. For the shear-dominated regime, the leading-order axial velocity can be either nonuniform or close to uniform, depending on the ratio between the dimensionless surfactant diffusivity d1 and the Laplace number La : when d1≫La the velocity profile is close to uniform and one-dimensional models work well; otherwise the velocity profile is nonuniform and one-dimensional models fail.

A 500 megabyte/second disk array

NASA Technical Reports Server (NTRS)

Ruwart, Thomas M.; Okeefe, Matthew T.

1994-01-01

Applications at the Army High Performance Computing Research Center's (AHPCRC) Graphic and Visualization Laboratory (GVL) at the University of Minnesota require a tremendous amount of I/O bandwidth and this appetite for data is growing. Silicon Graphics workstations are used to perform the post-processing, visualization, and animation of multi-terabyte size datasets produced by scientific simulations performed of AHPCRC supercomputers. The M.A.X. (Maximum Achievable Xfer) was designed to find the maximum achievable I/O performance of the Silicon Graphics CHALLENGE/Onyx-class machines that run these applications. Running a fully configured Onyx machine with 12-150MHz R4400 processors, 512MB of 8-way interleaved memory, 31 fast/wide SCSI-2 channel each with a Ciprico disk array controller we were able to achieve a maximum sustained transfer rate of 509.8 megabytes per second. However, after analyzing the results it became clear that the true maximum transfer rate is somewhat beyond this figure and we will need to do further testing with more disk array controllers in order to find the true maximum.

Portable Chemical Agent Detection System: Differential Reflectometer and Light Scattering Approaches

DTIC Science & Technology

2005-02-15

possible to conduct elemental analysis on modified capillaries because of the polymer coating. Instead, measurements of electroosmotic flow were used...design There are several essential requirements for a sensitive chemiluminescence cell (Figure 1); good reagent/analyte mixing for maximum photon yield...Cutaway of Chemiluminescence cell the cooled pint housing. In our design, the concentric inlets will increase photon collection due to better mixing of

An Experimental Investigation of the Process of Isotope Exchange that Takes Place when Heavy Water Is Exposed to the Atmosphere

ERIC Educational Resources Information Center

Deeney, F. A.; O'Leary, J. P.

2009-01-01

We have used the recently developed method for rapid measurement of maximum density temperature to determine the rate at which hydrogen and deuterium isotope exchange takes place when a sample of heavy water is exposed to the atmosphere. We also provide a simple explanation for the observed linear rate of transition. (Contains 2 figures.)

Optimized Granularity Analysis of Maximum Power Point Trackers in Low Power Applications

DTIC Science & Technology

2017-06-01

Second Reader: Robert Ashton THIS PAGE INTENTIONALLY LEFT BLANK i REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704–0188 Public reporting...Unclassified 19. SECURITY CLASSIFICATION OF ABSTRACT Unclassified 20. LIMITATION OF ABSTRACT UU NSN 7540–01-280-5500 Standard Form 298 (Rev...5  Figure 2.  Germanium Atoms Sharing Outermost Shell Electrons That Form Covalent Bonds. Source: [6

Innovative Processing of Composites for Ultra-High Temperature Applications. Book 3

DTIC Science & Technology

1993-11-01

SiC Samples Prepared with Four Preceramic Polymer Infiltration / Pyrolysis (at 15750C) Cycles Figure 21 Scanning Electron...Micrograph of Large Pores near the Surface of Siliconized SIC Sample with Four Preceramic Polymer Infiltration / Pyrolysis (at 1575*C) Cycles II...In order to achieve dense, bulk composites with maximum SiC /Si ratio, two infiltration / pyrolysis cycles were used. S (4) After siliconization,

Fatigue 󈨛. Volume 2,

DTIC Science & Technology

1987-06-01

non -propagating cracks should be considered and maximum principal strain amplitude Is the controlling parameter. FATIGUE DAMAGE MAPS The preceding...fatigue is strain- controlled and not stress- controlled . The small effect of R-ratio suggested by Figure 2 may simply reflect the high experimental ...present a model (and its experimental verification) describing non -damaging notches in fatigue. &FFECT OF GRAIN SIZE AND TEMPERATURE In this part we shall

Thermoelectric transport properties in graphene connected molecular junctions

NASA Astrophysics Data System (ADS)

Rodriguez, S. T.; Grosu, I.; Crisan, M.; Ţifrea, I.

2018-02-01

We study the electronic contribution to the main thermoelectric properties of a molecular junction consisting of a single quantum dot coupled to graphene external leads. The system electrical conductivity (G), Seebeck coefficient (S), and the thermal conductivity (κ), are numerically calculated based on a Green's function formalism that includes contributions up to the Hartree-Fock level. We consider the system leads to be made either of pure or gapped-graphene. To describe the free electrons in the gapped-graphene electrodes we used two possible scenarios, the massive gap scenario, and the massless gap scenario, respectively. In all cases, the Fano effect is responsible for a strong violation of the Wiedemann-Franz law and we found a substantial increase of the system figure of merit ZT due to a drastic reduction of the system thermal coefficient. In the case of gapped-graphene electrodes, the system figure of merit presents a maximum at an optimal value of the energy gap of the order of Δ / D ∼ 0.002 (massive gap scenario) and Δ / D ∼ 0.0026 (massless gap scenario). Additionally, for all cases, the system figure of merit is temperature dependent.

Jet formation and shock wave emission during collapse of ultrasound-induced cavitation bubbles and their role in the therapeutic applications of high-intensity focused ultrasound.

PubMed

Brujan, E A; Ikeda, T; Matsumoto, Y

2005-10-21

The dynamics of inertial cavitation bubbles produced by short pulses of high-intensity focused ultrasound near a rigid boundary are studied to get a better understanding of the role of jet formation and shock wave emission during bubble collapse in the therapeutic applications of ultrasound. The bubble dynamics are investigated by high-speed photography with up to 2 million frames/s and acoustic measurements, as well as by numerical calculations. The significant parameter of this study is the dimensionless stand-off, gamma, which is defined as the distance of the bubble centre at its maximum expansion scaled by the maximum bubble radius. High-speed photography is applied to observe the bubble motion and the velocity of the liquid jet formed during bubble collapse. Hydrophone measurements are used to determine the pressure and the duration of the shock wave emitted during bubble rebound. Calculations yield the variation with time of the bubble wall, the maximum velocity and the kinetic energy of the re-entrant jet. The comparisons between experimental and numerical data are favourable with regard to both shape history and translational motion of the bubble. The acoustic energy constitutes the largest individual amount in the energy balance of bubble collapse. The ratio of the shock wave energy, measured at 10 mm from the emission centre, to the cavitation bubble energy was 1:2.4 at gamma = 1.55 and 1:3.5 at gamma = 1. At this distance, the shock wave pressure ranges from 0.122 MPa, at gamma = 1, to 0.162 MPa, at gamma = 1.55, and the temporal duration at the half maximum level is 87 ns. The maximum jet velocity ranges from 27 m s(-1), at gamma = 1, to 36 m s(-1), at gamma = 1.55. For gamma < 1.2, the re-entrant jet can generate an impact pressure on the nearby boundary larger than 50 MPa. We discuss the implications of the results for the therapeutic applications of high-intensity focused ultrasound.

Numerical heat transfer study in a scattering, absorbing and emitting semi-transparent porous medium in a cylindrical enclosure

NASA Astrophysics Data System (ADS)

Timoumi, M.; Chérif, B.; Sifaoui, M. S.

2005-12-01

In this paper, heat transfer problem through a semi-transparent porous medium in a cylindrical enclosure is investigated. The governing equations for this problem and the boundary conditions are non-linear differential equations depending on the dimensionless radial coordinate, Planck number N, scattering albedo ω, walls emissivity and thermal conductivity ratio kr. The set of differential equations are solved by a numerical technique taken from the IMSL MATH/LIBRARY. Various results are obtained for the dimensionless temperature profiles in the solid and fluid phases and the radiative heat flux. The effects of some radiative properties of the medium on the heat transfer rate are examined.

Energy-density field approach for low- and medium-frequency vibroacoustic analysis of complex structures using a statistical computational model

NASA Astrophysics Data System (ADS)

Kassem, M.; Soize, C.; Gagliardini, L.

2009-06-01

In this paper, an energy-density field approach applied to the vibroacoustic analysis of complex industrial structures in the low- and medium-frequency ranges is presented. This approach uses a statistical computational model. The analyzed system consists of an automotive vehicle structure coupled with its internal acoustic cavity. The objective of this paper is to make use of the statistical properties of the frequency response functions of the vibroacoustic system observed from previous experimental and numerical work. The frequency response functions are expressed in terms of a dimensionless matrix which is estimated using the proposed energy approach. Using this dimensionless matrix, a simplified vibroacoustic model is proposed.

Dimensionless Numbers Expressed in Terms of Common CVD Process Parameters

NASA Technical Reports Server (NTRS)

Kuczmarski, Maria A.

1999-01-01

A variety of dimensionless numbers related to momentum and heat transfer are useful in Chemical Vapor Deposition (CVD) analysis. These numbers are not traditionally calculated by directly using reactor operating parameters, such as temperature and pressure. In this paper, these numbers have been expressed in a form that explicitly shows their dependence upon the carrier gas, reactor geometry, and reactor operation conditions. These expressions were derived for both monatomic and diatomic gases using estimation techniques for viscosity, thermal conductivity, and heat capacity. Values calculated from these expressions compared well to previously published values. These expressions provide a relatively quick method for predicting changes in the flow patterns resulting from changes in the reactor operating conditions.

Theoretical results for starved elliptical contacts

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1983-01-01

Eighteen cases were used in the theoretical study of the influence of lubricant starvation on film thickness and pressure in elliptical elastohydrodynamic conjunctions. From the results a simple and important critical dimensionless inlet boundary distance at which lubricant starvation becomes significant was specified. This inlet boundary distance defines whether a fully flooded or a starved condition exists in the contact. Furthermore, it was found that the film thickness for a starved condition is written in dimensionless terms as a function of the inlet distance parameter and the film thickness for a fully flooded condition. Contour plots of pressure and film thickness in and around the contact are shown for fully flooded and starved conditions.

Effects of End Conditions of Cross-Ply Laminated Composite Beams on Their Dimensionless Natural Frequencies

NASA Astrophysics Data System (ADS)

Algarray, A. F. A.; Jun, H.; Mahdi, I.-E. M.

2017-11-01

The effects of the end conditions of cross-ply laminated composite beams on their dimensionless natural frequencies of free vibration is investigated. The problem is analyzed and solved by using the energy approach, which is formulated by a finite element model. Various end conditions of beams are used. Each beam has either movable ends or immovable ends. Numerical results are verified by comparisons with other relevant works. It is found that more constrained beams have higher values of natural frequencies of transverse vibration. The values of the natural frequencies of longitudinal modes are found to be the same for all beams with movable ends because they are generated by longitudinal movements only.

Maximum Likelihood Detection of Electro-Optic Moving Targets

DTIC Science & Technology

1992-01-16

indicates intensity. The Infrared Measurements Sensor (IRMS) is a scanning sensor that collects both long wave- length infrared ( LWIR , 8 to 12 fim...moving clutter. Nonstationary spatial statistics correspond to the nonuniform intensity of the background scene. An equivalent viewpoint is to...Figure 6 compares theory and experiment for 10 frames of the Longjump LWIR data obtained from the IRMS scanning sensor, which is looking at a background

Long-Range Forecasting of Surface Air Temperature and Precipitation for the Korean Peninsula

DTIC Science & Technology

2013-03-01

tropics and extratropics and tend to produce their maximum extratropical impacts in the winter hemisphere. For example, ENLN have been shown to...convection anomalies during the summer that can extend across large portions of the extratropics (Figure 3). This tropical convection is significantly...anomalously frequent (less frequent) and strong (weak) extratropical cyclones tracking in a more northerly (southerly) path across the North Atlantic

Wind Power Generation Design Considerations.

DTIC Science & Technology

1984-12-01

DISTRIBUTION 4 I o ....................................... . . . e . * * TABLES Number Page I Wind Turbine Characteristics II 0- 2 Maximum Economic Life II 3...Ratio of Blade Tip Speed to Wind Speed 10 4 Interference with Microwave and TV Reception by Wind Turbines 13 5 Typical Flow Patterns Over Two...18 * 12 Annual Mean Wind Power Density 21 5 FIGURES (Cont’d) Number Page 13 Wind - Turbine /Generator Types Currently Being Tested on Utility Sites 22 14

USSR and Eastern Europe Scientific Abstracts, Biomedical and Behavioral Sciences, Number 84

DTIC Science & Technology

1977-12-28

36 Molecular Biology 4° Pharmacology ^2 Physiology • 46 Plant Biochemistry • 5^ Public Health. 56 Radiobiology ->9 Therapy 60...Tyagunenko) USSR UDC 615.332 (Oxycarminomycinum) SYNTHESIS OF II+-OXYCARMINOMYCIN AND STUDY OF ITS ANTINEOPLASTIC ACTIVITY Moscow ANTIBIOTIKI in...antineoplastic activity and toxicity as carminomycin. It suppressed tumor growth by 90% in doses that did not exceed the maximum tolerable (LD10). Figure 1

Innovative Control Effectors (ICE)

DTIC Science & Technology

1996-01-01

Figure 4-1 shows the ICE high AOA roll performance goals compared to several current fighter aircraft. For this comparison, the 1-DOF roll equation ...9 ]Body The first bracketed term in equation (1) is recognizable as the expression for Cnpdyn. The second term represents control power for controls...deflected to provide Cn’MAX, trimmed in pitch and roll. The user selects the maximum sideslip to augment by specifying f. Equation (1) can be

Improvement, Verification, and Refinement of Spatially-Explicit Exposure Models in Risk Assessment - SEEM

DTIC Science & Technology

2015-06-01

hazard quotient HSI Habitat Suitability Index LOAEL lowest observed adverse effect level mg/kg milligrams per kilogram NOAEL no observed adverse... effect level NPL National Priorities List PRR Patuxent Research Refuge QA quality assurance QC quality control ACRONYMS AND...mean and maximum) for each individual for the exposure period; EHQs are then compiled to arrive at a modeled population— effects curve. Figure 1

Improvement, Verification, and Refinement of Spatially Explicit Exposure Models in Risk Assessment - SEEM Demonstration

DTIC Science & Technology

2015-06-01

hazard quotient HSI Habitat Suitability Index LOAEL lowest observed adverse effect level mg/kg milligrams per kilogram NOAEL no observed adverse... effect level NPL National Priorities List PRR Patuxent Research Refuge QA quality assurance QC quality control ACRONYMS AND...mean and maximum) for each individual for the exposure period; EHQs are then compiled to arrive at a modeled population— effects curve. Figure 1

Coupling of electromagnetics and structural/fluid dynamics - application to the dual coolant blanket subjected to plasma disruptions

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

Jordan, T.

Some aspects concerning the coupling of quasi-stationary electromagnetics and the dynamics of structure and fluid are investigated. The necessary equations are given in a dimensionless form. The dimensionless parameters in these equations are used to evaluate the importance of the different coupling effects. A finite element formulation of the eddy-current damping in solid structures is developed. With this formulation, an existing finite element method (FEM) structural dynamics code is extended and coupled to an FEM eddy-current code. With this program system, the influence of the eddy-current damping on the dynamic loading of the dual coolant blanket during a centered plasmamore » disruption is determined. The analysis proves that only in loosely fixed or soft structures will eddy-current damping considerably reduce the resulting stresses. Additionally, the dynamic behavior of the liquid metal in the blankets` poloidal channels is described with a simple two-dimensional magnetohydrodynamic approach. The analysis of the dimensionless parameters shows that for small-scale experiments, which are designed to model the coupled electromagnetic and structural/fluid dynamic effects in such a blanket, the same magnetic fields must be applied as in the real fusion device. This will be the easiest way to design experiments that produce transferable results. 10 refs., 7 figs.« less

New Bedform Phase Diagrams and Discriminant Functions for Formative Conditions of Bedforms in Open-Channel Flows

NASA Astrophysics Data System (ADS)

Ohata, Koji; Naruse, Hajime; Yokokawa, Miwa; Viparelli, Enrica

2017-11-01

Understanding of the formative conditions of fluvial bedforms is significant for both river management and geological studies. Diagrams showing bedform stability conditions have been widely used for the analyses of sedimentary structures. However, the use of discriminants to determine the boundaries of different bedforms regimes has not yet been explored. In this study, we use discriminant functions to describe formative conditions for a range of fluvial bedforms in a 3-D dimensionless parametric space. We do this by means of discriminant analysis using the Mahalanobis distance. We analyzed 3,793 available laboratory and field data and used these to produce new bedform phase diagrams. These diagrams employ three dimensionless parameters representing properties of flow hydraulics and sediment particles as their axes. The discriminant functions for bedform regimes proposed herein are quadratic functions of three dimensionless parameters and are expressed as curved surfaces in 3-D space. These empirical functions can be used to estimate paleoflow velocities from sedimentary structures. As an example of the reconstruction of hydraulic conditions, we calculated the paleoflow velocity of the 2011 Tohoku-Oki tsunami backwash flow from the sedimentary structures of the tsunami deposit. In so doing, we successfully reconstructed reasonable values of the paleoflow velocities.

Composite recovery type curves in normalized time from Theis' exact solution

USGS Publications Warehouse

Goode, Daniel J.

1997-01-01

Type curves derived from Theis’ exact nonequilibrium well function solution are proposed for graphical estimation of aquifer hydraulic properties, transmissivity (T), and storage coefficient (S), from water-level recovery data after cessation of a constant-rate discharge test. Drawdown (on log scale) is plotted versus the ratio of time since pumping stopped to duration of pumping, a normalized time. Under Theis conditions, individual type curves depend on only the dimensionless pumping duration, which depends in turn on S and radial distance from the pumping well. Type curve matching, in contrast to the Theis procedure for pumping data, is performed by shifting only the drawdown axis; the time axis is fixed because it is a relative or normalized time. The match-point for the drawdown axis is used to compute T, and S is determined from matching the curve shape, which depends on early dimensionless-time data. Multiple well data can be plotted and matched simultaneously (a composite plot), with drawdown at different radial distances matching different curves. The ratio of dimensionless pumping durations for any two matched curves is equal to one over the squared ratio of radial distances. Application to two recovery datasets from the literature confirm the utility of these type curves in normalized time for composite estimation of T and S.

Analysis of heat transfer for unsteady MHD free convection flow of rotating Jeffrey nanofluid saturated in a porous medium

NASA Astrophysics Data System (ADS)

Mohd Zin, Nor Athirah; Khan, Ilyas; Shafie, Sharidan; Alshomrani, Ali Saleh

In this article, the influence of thermal radiation on unsteady magnetohydrodynamics (MHD) free convection flow of rotating Jeffrey nanofluid passing through a porous medium is studied. The silver nanoparticles (AgNPs) are dispersed in the Kerosene Oil (KO) which is chosen as conventional base fluid. Appropriate dimensionless variables are used and the system of equations is transformed into dimensionless form. The resulting problem is solved using the Laplace transform technique. The impact of pertinent parameters including volume fraction φ , material parameters of Jeffrey fluid λ1 , λ , rotation parameter r , Hartmann number Ha , permeability parameter K , Grashof number Gr , Prandtl number Pr , radiation parameter Rd and dimensionless time t on velocity and temperature profiles are presented graphically with comprehensive discussions. It is observed that, the rotation parameter, due to the Coriolis force, tends to decrease the primary velocity but reverse effect is observed in the secondary velocity. It is also observed that, the Lorentz force retards the fluid flow for both primary and secondary velocities. The expressions for skin friction and Nusselt number are also evaluated for different values of emerging parameters. A comparative study with the existing published work is provided in order to verify the present results. An excellent agreement is found.

Multi-objective optimization and design for free piston Stirling engines based on the dimensionless power

NASA Astrophysics Data System (ADS)

Mou, Jian; Hong, Guotong

2017-02-01

In this paper, the dimensionless power is used to optimize the free piston Stirling engines (FPSE). The dimensionless power is defined as a ratio of the heat power loss and the output work. The heat power losses include the losses of expansion space, heater, regenerator, cooler and the compression space and every kind of the heat loss calculated by empirical formula. The output work is calculated by the adiabatic model. The results show that 82.66% of the losses come from the expansion space and 54.59% heat losses of expansion space come from the shuttle loss. At different pressure the optimum bore-stroke ratio, heat source temperature, phase angle and the frequency have different values, the optimum phase angles increase with the increase of pressure, but optimum frequencies drop with the increase of pressure. However, no matter what the heat source temperature, initial pressure and frequency are, the optimum ratios of piston stroke and displacer stroke all about 0.8. The three-dimensional diagram is used to analyse Stirling engine. From the three-dimensional diagram the optimum phase angle, frequency and heat source temperature can be acquired at the same time. This study offers some guides for the design and optimization of FPSEs.

Relationships between PEMFC Cathode Kinetic Losses and Contaminants’ Dipole Moment and Adsorption Energy on Pt

DOE PAGES

St-Pierre, Jean; Zhai, Yunfeng; Ge, Junjie

2016-01-05

A database summarizing the effects of 21 contaminants on the performance of proton exchange membrane fuel cells (PEMFCs) was used to examine relationships between cathode kinetic losses and contaminant physicochemical parameters. Impedance spectroscopy data were employed to obtain oxygen reduction kinetic resistances by fitting data in the 10-158 Hz range to a simplified equivalent circuit. The contaminant dipole moment and the adsorption energy of the contaminant on a Pt surface were chosen as parameters. Dipole moments did not correlate with dimensionless cathode kinetic resistances. In contrast, adsorption energies were quantitatively and linearly correlated with minimum dimensionless cathode kinetic resistances. Contaminantsmore » influence the oxygen reduction for contaminant adsorption energies smaller than -24.5 kJ mol -1, a value near the high limit of the adsorption energy of O 2 on Pt. Dimensionless cathode kinetic resistances linearly increase with decreasing O 2 adsorption energies below -24.5 kJ mol -1. Measured total cell voltage losses are mostly larger than the cathode kinetic losses calculated from kinetic resistance changes, which indicates the existence of other sources of performance degradation. Modifications to the experimental procedure are proposed to ensure that data are comparable on a similar basis and improve the correlation between contaminant adsorption energy and kinetic cell voltage losses.« less

Relationships between PEMFC Cathode Kinetic Losses and Contaminants’ Dipole Moment and Adsorption Energy on Pt

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

St-Pierre, Jean; Zhai, Yunfeng; Ge, Junjie

A database summarizing the effects of 21 contaminants on the performance of proton exchange membrane fuel cells (PEMFCs) was used to examine relationships between cathode kinetic losses and contaminant physicochemical parameters. Impedance spectroscopy data were employed to obtain oxygen reduction kinetic resistances by fitting data in the 10-158 Hz range to a simplified equivalent circuit. The contaminant dipole moment and the adsorption energy of the contaminant on a Pt surface were chosen as parameters. Dipole moments did not correlate with dimensionless cathode kinetic resistances. In contrast, adsorption energies were quantitatively and linearly correlated with minimum dimensionless cathode kinetic resistances. Contaminantsmore » influence the oxygen reduction for contaminant adsorption energies smaller than -24.5 kJ mol -1, a value near the high limit of the adsorption energy of O 2 on Pt. Dimensionless cathode kinetic resistances linearly increase with decreasing O 2 adsorption energies below -24.5 kJ mol -1. Measured total cell voltage losses are mostly larger than the cathode kinetic losses calculated from kinetic resistance changes, which indicates the existence of other sources of performance degradation. Modifications to the experimental procedure are proposed to ensure that data are comparable on a similar basis and improve the correlation between contaminant adsorption energy and kinetic cell voltage losses.« less

Technical characterization of dialysis fluid flow and mass transfer rate in dialyzers with various filtration coefficients using dimensionless correlation equation.

PubMed

Fukuda, Makoto; Yoshimura, Kengo; Namekawa, Koki; Sakai, Kiyotaka

2017-06-01

The objective of the present study is to evaluate the effect of filtration coefficient and internal filtration on dialysis fluid flow and mass transfer coefficient in dialyzers using dimensionless mass transfer correlation equations. Aqueous solution of vitamin B 12 clearances were obtained for REXEED-15L as a low flux dialyzer, and APS-15EA and APS-15UA as high flux dialyzers. All the other design specifications were identical for these dialyzers except for filtration coefficient. The overall mass transfer coefficient was calculated, moreover, the exponents of Reynolds number (Re) and film mass transfer coefficient of the dialysis-side fluid (k D ) for each flow rate were derived from the Wilson plot and dimensionless correlation equation. The exponents of Re were 0.4 for the low flux dialyzer whereas 0.5 for the high flux dialyzers. Dialysis fluid of the low flux dialyzer was close to laminar flow because of its low filtration coefficient. On the other hand, dialysis fluid of the high flux dialyzers was assumed to be orthogonal flow. Higher filtration coefficient was associated with higher k D influenced by mass transfer rate through diffusion and internal filtration. Higher filtration coefficient of dialyzers and internal filtration affect orthogonal flow of dialysis fluid.

Thermoelectric Performance Enhancement by Surrounding Crystalline Semiconductors with Metallic Nanoparticles

NASA Technical Reports Server (NTRS)

Kim, Hyun-Jung; King, Glen C.; Park, Yeonjoon; Lee, Kunik; Choi, Sang H.

2011-01-01

Direct conversion of thermal energy to electricity by thermoelectric (TE) devices may play a key role in future energy production and utilization. However, relatively poor performance of current TE materials has slowed development of new energy conversion applications. Recent reports have shown that the dimensionless Figure of Merit, ZT, for TE devices can be increased beyond the state-of-the-art level by nanoscale structuring of materials to reduce their thermal conductivity. New morphologically designed TE materials have been fabricated at the NASA Langley Research Center, and their characterization is underway. These newly designed materials are based on semiconductor crystal grains whose surfaces are surrounded by metallic nanoparticles. The nanoscale particles are used to tailor the thermal and electrical conduction properties for TE applications by altering the phonon and electron transport pathways. A sample of bismuth telluride decorated with metallic nanoparticles showed less thermal conductivity and twice the electrical conductivity at room temperature as compared to pure Bi2Te3. Apparently, electrons cross easily between semiconductor crystal grains via the intervening metallic nanoparticle bridges, but phonons are scattered at the interfacing gaps. Hence, if the interfacing gap is larger than the mean free path of the phonon, thermal energy transmission from one grain to others is reduced. Here we describe the design and analysis of these new materials that offer substantial improvements in thermoelectric performance.

Response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions

USGS Publications Warehouse

Rojstaczer, Stuart; Riley, Francis S.

1990-01-01

The response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions can be explained if the water level is controlled by the aquifer response averaged over the saturated depth of the well. Because vertical averaging tends to diminish the influence of the water table, the response is qualitatively similar to the response of a well under partially confined conditions. When the influence of well bore storage can be ignored, the response to Earth tides is strongly governed by a dimensionless aquifer frequency Q′u. The response to atmospheric loading is strongly governed by two dimensionless vertical fluid flow parameters: a dimensionless unsaturated zone frequency, R, and a dimensionless aquifer frequency Qu. The differences between Q′u and Qu are generally small for aquifers which are highly sensitive to Earth tides. When Q′u and Qu are large, the response of the well to Earth tides and atmospheric loading approaches the static response of the aquifer under confined conditions. At small values of Q′u and Qu, well response to Earth tides and atmospheric loading is strongly influenced by water table drainage. When R is large relative to Qu, the response to atmospheric loading is strongly influenced by attenuation and phase shift of the pneumatic pressure signal in the unsaturated zone. The presence of partial penetration retards phase advance in well response to Earth tides and atmospheric loading. When the theoretical response of a phreatic well to Earth tides and atmospheric loading is fit to the well response inferred from cross-spectral estimation, it is possible to obtain estimates of the pneumatic diffusivity of the unsaturated zone and the vertical hydraulic conductivity of the aquifer.

Hydraulic shock waves in an inclined chute contraction

NASA Astrophysics Data System (ADS)

Jan, C.-D.; Chang, C.-J.

2009-04-01

A chute contraction is a common structure used in hydraulic engineering for typical reasons such as increase of bottom slope, transition from side channel intakes to tunnel spillways, reduction of chute width due to bridges, transition structures in flood diversion works, among others. One of the significant chute contractions in Taiwan is that used in the Yuanshantzu Flood Diversion Project of Keelung River. The diversion project is designed to divert flood water from upper Keelung River into East Sea with a capasity of 1,310 cubic meters per second for mitigating the flood damage of lower part of Keelung River basin in Northern Taiwan. An inclined chute contraction is used to connect Keelung River and a diversion turnel. The inlet and outlet works of the diversion project is located at Ruifang in the Taipei County of north Taiwan. The diameter of diversion tunnel is 12 meters and the total length of tunnel is 2,484 meters. The diversion project has been completed and successfully executed many times since 2004 to lower the water level of Keelung River in typhoon seasons for avioding flooding problems in the lower part of Keelung River basin. Flow in a chute contraction has complicated flow pattern due to the existence of shock waves in it. A simple and useful calculation procedure for the maximum height and its position of shock waves is essentially needed for the preliminary design stage of a chute contraction. Hydraulic shock waves in an inclined chute contraction were experimentally and numerically investigated in this study with the consideration of the effects of sidewall deflection angle, bottom inclination angle and Froude number of approaching flow. The flow pattern of hydraulic shock waves in a chute contraction was observed. The main issue of designing chute contraction is to estimate the height and position of maximum shock wave for the consideration of freeboards. Achieving this aim, the experimental data are adopted and analyzed for the shock angle, the height of maximum shock wave and the corresponding position of maximum shock wave. The dimensionless relations for the shock angle, the height of maximum shock wave and the corresponding position of maximum shock wave are obtained by regression analysis. These empirical regression relations, basically relating to the sidewall deflection angle, bottom angle and approach Froude number, are very useful for further practical engineering applications in chute contraction design for avoiding flow overtopping.

Synthesis and thermoelectric properties of the (GeTe) 1-x(PbTe) x alloys

NASA Astrophysics Data System (ADS)

Li, S. P.; Li, J. Q.; Wang, Q. B.; Wang, L.; Liu, F. S.; Ao, W. Q.

2011-02-01

The Ge-rich (GeTe) 1-x(PbTe) x alloys with x = 0.10, 0.14, 0.18 and 0.22 were prepared by induction melting, ball milling and spark plasma sintering techniques. The thermoelectric properties of the samples were investigated. The experimental results show that all samples consist of the solid solutions of the two phases GeTe and PbTe. The samples are of p-type semiconductors. The existence of PbTe solution in GeTe increases its resistivity and Seebeck coefficient slightly, but reduces its thermal conductivity significantly. As result, the figures of merit for the materials can be enhanced. The maximum figure of merit ZT value of 0.81 was obtained in the sample (GeTe) 0.82(PbTe) 0.18 at 673K.

Compact all-fiber figure-9 dissipative soliton resonance mode-locked double-clad Er:Yb laser.

PubMed

Krzempek, Karol; Sotor, Jaroslaw; Abramski, Krzysztof

2016-11-01

The first demonstration of a compact all-fiber figure-9 double-clad erbium-ytterbium laser working in the dissipative soliton resonance (DSR) regime is presented. Mode-locking was achieved using a nonlinear amplifying loop (NALM) resonator configuration. The laser was assembled with an additional 475 m long spool of SMF28 fiber in the NALM loop in order to obtain large net-anomalous cavity dispersion (-10.4  ps²), and therefore ensure that DSR would be the dominant mode-locking mechanism. At maximum pump power (4.78 W) the laser generated rectangular-shaped pulses with 455 ns duration and an average power of 950 mW, which at a repetition frequency of 412 kHz corresponds to a record energy of 2.3 μJ per pulse.

Maximum likelihood estimation in calibrating a stereo camera setup.

PubMed

Muijtjens, A M; Roos, J M; Arts, T; Hasman, A

1999-02-01

Motion and deformation of the cardiac wall may be measured by following the positions of implanted radiopaque markers in three dimensions, using two x-ray cameras simultaneously. Regularly, calibration of the position measurement system is obtained by registration of the images of a calibration object, containing 10-20 radiopaque markers at known positions. Unfortunately, an accidental change of the position of a camera after calibration requires complete recalibration. Alternatively, redundant information in the measured image positions of stereo pairs can be used for calibration. Thus, a separate calibration procedure can be avoided. In the current study a model is developed that describes the geometry of the camera setup by five dimensionless parameters. Maximum Likelihood (ML) estimates of these parameters were obtained in an error analysis. It is shown that the ML estimates can be found by application of a nonlinear least squares procedure. Compared to the standard unweighted least squares procedure, the ML method resulted in more accurate estimates without noticeable bias. The accuracy of the ML method was investigated in relation to the object aperture. The reconstruction problem appeared well conditioned as long as the object aperture is larger than 0.1 rad. The angle between the two viewing directions appeared to be the parameter that was most likely to cause major inaccuracies in the reconstruction of the 3-D positions of the markers. Hence, attempts to improve the robustness of the method should primarily focus on reduction of the error in this parameter.

Size limits for rounding of volcanic ash particles heated by lightning

PubMed Central

Vasseur, Jérémie; Llewellin, Edward W.; Genareau, Kimberly; Cimarelli, Corrado; Dingwell, Donald B.

2017-01-01

Abstract Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high‐temperature conditions of volcanic lightning discharges, which are hard to measure directly. We use a 1‐D numerical solution to the heat equation to determine the timescales of heating and cooling of volcanic particles during and after rapid heating and compare these with the capillary timescale for rounding an angular particle. We define dimensionless parameters—capillary, Fourier, Stark, Biot, and Peclet numbers—to characterize the competition between heat transfer within the particle, heat transfer at the particle rim, and capillary motion, for particles of different sizes. We apply this framework to the lightning case and constrain a maximum size for ash particles susceptible to surface tension‐driven rounding, as a function of lightning temperature and duration, and ash properties. The size limit agrees well with maximum sizes of glass spheres found in volcanic ash that has been subjected to lightning or experimental discharges, demonstrating that the approach that we develop can be used to obtain a first‐order estimate of lightning conditions in volcanic plumes. PMID:28781929

Size limits for rounding of volcanic ash particles heated by lightning.

PubMed

Wadsworth, Fabian B; Vasseur, Jérémie; Llewellin, Edward W; Genareau, Kimberly; Cimarelli, Corrado; Dingwell, Donald B

2017-03-01

Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high-temperature conditions of volcanic lightning discharges, which are hard to measure directly. We use a 1-D numerical solution to the heat equation to determine the timescales of heating and cooling of volcanic particles during and after rapid heating and compare these with the capillary timescale for rounding an angular particle. We define dimensionless parameters-capillary, Fourier, Stark, Biot, and Peclet numbers-to characterize the competition between heat transfer within the particle, heat transfer at the particle rim, and capillary motion, for particles of different sizes. We apply this framework to the lightning case and constrain a maximum size for ash particles susceptible to surface tension-driven rounding, as a function of lightning temperature and duration, and ash properties. The size limit agrees well with maximum sizes of glass spheres found in volcanic ash that has been subjected to lightning or experimental discharges, demonstrating that the approach that we develop can be used to obtain a first-order estimate of lightning conditions in volcanic plumes.

Size limits for rounding of volcanic ash particles heated by lightning

NASA Astrophysics Data System (ADS)

Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Genareau, Kimberly; Cimarelli, Corrado; Dingwell, Donald B.

2017-03-01

Volcanic ash particles can be remelted by the high temperatures induced in volcanic lightning discharges. The molten particles can round under surface tension then quench to produce glass spheres. Melting and rounding timescales for volcanic materials are strongly dependent on heating duration and peak temperature and are shorter for small particles than for large particles. Therefore, the size distribution of glass spheres recovered from ash deposits potentially record the short duration, high-temperature conditions of volcanic lightning discharges, which are hard to measure directly. We use a 1-D numerical solution to the heat equation to determine the timescales of heating and cooling of volcanic particles during and after rapid heating and compare these with the capillary timescale for rounding an angular particle. We define dimensionless parameters—capillary, Fourier, Stark, Biot, and Peclet numbers—to characterize the competition between heat transfer within the particle, heat transfer at the particle rim, and capillary motion, for particles of different sizes. We apply this framework to the lightning case and constrain a maximum size for ash particles susceptible to surface tension-driven rounding, as a function of lightning temperature and duration, and ash properties. The size limit agrees well with maximum sizes of glass spheres found in volcanic ash that has been subjected to lightning or experimental discharges, demonstrating that the approach that we develop can be used to obtain a first-order estimate of lightning conditions in volcanic plumes.

Experimental and numerical study on bubble-sphere interaction near a rigid wall

NASA Astrophysics Data System (ADS)

Li, S.; Zhang, A. M.; Han, R.; Liu, Y. Q.

2017-09-01

This study is concerned with the interaction between a violently oscillating bubble and a movable sphere with comparable size near a rigid wall, which is an essential physical phenomenon in many applications such as cavitation, underwater explosion, ultrasonic cleaning, and biomedical treatment. Experiments are performed in a cubic water tank, and the underwater electric discharge technique (580 V DC) is employed to generate a bubble that is initiated between a rigid wall and a sphere in an axisymmetric configuration. The bubble-sphere interactions are captured using a high-speed camera operating at 52 000 frames/s. A classification of the bubble-sphere interaction is proposed, i.e., "weak," "intermediate," and "strong" interactions, identified with three distinct bubble shapes at the maximum volume moment. In the numerical simulations, the boundary integral method and the auxiliary function method are combined to establish a full coupling model that decouples the mutual dependence between the force and the sphere motion. The main features of bubble dynamics in different experiments are well reproduced by our numerical model. Meanwhile, the pressure and velocity fields are also provided for clarifying the associated mechanisms. The effects of two dimensionless standoff parameters, namely, γs (defined as ds/Rm, where ds is the minimum distance between the initial bubble center and the sphere surface and Rm is the maximum bubble radius) and γw (defined as dw/Rm, where dw is the distance between the initial bubble center and the rigid wall), are also discussed.

Critical Concentration Ratio for Solar Thermoelectric Generators

NASA Astrophysics Data System (ADS)

ur Rehman, Naveed; Siddiqui, Mubashir Ali

2016-10-01

A correlation for determining the critical concentration ratio (CCR) of solar concentrated thermoelectric generators (SCTEGs) has been established, and the significance of the contributing parameters is discussed in detail. For any SCTEG, higher concentration ratio leads to higher temperatures at the hot side of modules. However, the maximum value of this temperature for safe operation is limited by the material properties of the modules and should be considered as an important design constraint. Taking into account this limitation, the CCR can be defined as the maximum concentration ratio usable for a particular SCTEG. The established correlation is based on factors associated with the material and geometric properties of modules, thermal characteristics of the receiver, installation site attributes, and thermal and electrical operating conditions. To reduce the number of terms in the correlation, these factors are combined to form dimensionless groups by applying the Buckingham Pi theorem. A correlation model containing these groups is proposed and fit to a dataset obtained by simulating a thermodynamic (physical) model over sampled values acquired by applying the Latin hypercube sampling (LHS) technique over a realistic distribution of factors. The coefficient of determination and relative error are found to be 97% and ±20%, respectively. The correlation is validated by comparing the predicted results with literature values. In addition, the significance and effects of the Pi groups on the CCR are evaluated and thoroughly discussed. This study will lead to a wide range of opportunities regarding design and optimization of SCTEGs.

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

Ko, Sung Moon; Park, Jeong-Hyuck; Suh, Minwoo, E-mail: sinsmk2003@sogang.ac.kr, E-mail: park@sogang.ac.kr, E-mail: minsuh@usc.edu

Double Field Theory suggests to view the whole massless sector of closed strings as the gravitational unity. The fundamental symmetries therein, including the O( D , D ) covariance, can determine unambiguously how the Standard Model as well as a relativistic point particle should couple to the closed string massless sector. The theory also refines the notion of singularity. We consider the most general, spherically symmetric, asymptotically flat, static vacuum solution to D =4 Double Field Theory, which contains three free parameters and consequently generalizes the Schwarzschild geometry. Analyzing the circular geodesic of a point particle in string frame, wemore » obtain the orbital velocity as a function of R /( M {sub ∞} G ) which is the dimensionless radial variable normalized by mass. The rotation curve generically features a maximum and thus non-Keplerian over a finite range, while becoming asymptotically Keplerian at infinity, R /( M {sub ∞} G )→ ∞. The adoption of the string frame rather than Einstein frame is the consequence of the fundamental symmetry principle. Our result opens up a new scheme to solve the dark matter/energy problems by modifying General Relativity at 'short' range of R /( M {sub ∞} G ).« less

A viscometric approach of pH effect on hydrodynamic properties of human serum albumin in the normal form.

PubMed

Monkos, Karol

2013-03-01

The paper presents the results of viscosity determinations on aqueous solutions of human serum albumin (HSA) at isoelectric point over a wide range of concentrations and at temperatures ranging from 5°C to 45°C. On the basis of a modified Arrhenius equation and Mooney's formula some hydrodynamic parameters were obtained. They are compared with those previously obtained for HSA in solutions at neutral pH. The activation energy and entropy of viscous flow and the intrinsic viscosity reach a maximum value, and the effective specific volume, the self-crowding factor and the Huggins coefficient a minimum value in solutions at isoelectric point. Using the dimensionless parameter [η]c, the existence of three ranges of concentrations: diluted, semi-diluted and concentrated, was shown. By applying Lefebvre's relation for the relative viscosity in the semi-dilute regime, the Mark-Houvink-Kuhn-Sakurada (MHKS) exponent was established. The analysis of the results obtained from the three ranges of concentrations showed that both conformation and stiffness of HSA molecules in solutions at isoelectric point and at neutral pH are the same.

Rocket noise - A review

NASA Astrophysics Data System (ADS)

McInerny, S. A.

1990-10-01

This paper reviews what is known about far-field rocket noise from the controlled studies of the late 1950s and 1960s and from launch data. The peak dimensionless frequency, the dependence of overall sound power on exhaust parameters, and the directivity of the overall sound power of rockets are compared to those of subsonic jets and turbo-jets. The location of the dominant sound source in the rocket exhaust plume and the mean flow velocity in this region are discussed and shown to provide a qualitative explanation for the low peak Strouhal number, fD(e)/V(e), and large angle of maximum directivity. Lastly, two empirical prediction methods are compared with data from launches of a Titan family vehicle (two, solid rocket motors of 5.7 x 10 to the 6th N thrust each) and the Saturn V (five, liquid oxygen/rocket propellant engines of 6.7 x 10 to the 6th N thrust, each). The agreement is favorable. In contrast, these methods appear to overpredict the far-field sound pressure levels generated by the Space Shuttle.

Modeling viscous dissipation during vocal fold contact: the influence of tissue viscosity and thickness with implications for hydration.

PubMed

Erath, Byron D; Zañartu, Matías; Peterson, Sean D

2017-06-01

The mechanics of vocal fold contact during phonation is known to play a crucial role in both normal and pathological speech production, though the underlying physics is not well understood. Herein, a viscoelastic model of the stresses during vocal fold contact is developed. This model assumes the cover to be a poroelastic structure wherein interstitial fluid translocates in response to mechanical squeezing. The maximum interstitial fluid pressure is found to generally increase with decreasing viscous dissipation and/or decreasing tissue elasticity. A global minimum in the total contact stress, comprising interstitial fluid pressure and elastic stress in the tissue, is observed over the studied dimensionless parameter range. Interestingly, physiologically reasonable estimates for the governing parameters fall within this global minimum region. The model is validated against prior experimental and computational work, wherein the predicted contact stress magnitude and impact duration agree well with published results. Lastly, observations of the potential relationship between vocal fold hydration and increased risk of tissue damage are discussed based upon model predictions of stress as functions of cover layer thickness and viscosity.

Density stratification effects in sand-bed rivers

USGS Publications Warehouse

Wright, S.; Parker, G.

2004-01-01

In this paper the effects of density stratification in sand-bed rivers are studied by the application of a model of vertical velocity and concentration profiles, coupled through the use of a turbulence closure that retains the buoyancy terms. By making the governing equations dimensionless, it is revealed that the slope is the additional dimensionless parameter introduced by inclusion of the buoyancy terms. The primary new finding is that in general density stratification effects tend to be greater in large, low-slope rivers than in their smaller, steeper brethren. Under high flow conditions the total suspended load and size distribution of suspended sediment can be significantly affected by density stratification, and should be accounted for in any general theory of suspended transport. ?? ASCE.

Determination of constant-volume balloon capabilities for aeronautical research. [specifically measurement of atmospheric phenomena

NASA Technical Reports Server (NTRS)

Tatom, F. B.; King, R. L.

1977-01-01

The proper application of constant-volume balloons (CVB) for measurement of atmospheric phenomena was determined. And with the proper interpretation of the resulting data. A literature survey covering 176 references is included. the governing equations describing the three-dimensional motion of a CVB immersed in a flow field are developed. The flowfield model is periodic, three-dimensional, and nonhomogeneous, with mean translational motion. The balloon motion and flow field equations are cast into dimensionless form for greater generality, and certain significant dimensionless groups are identified. An alternate treatment of the balloon motion, based on first-order perturbation analysis, is also presented. A description of the digital computer program, BALLOON, used for numerically integrating the governing equations is provided.

Dimensionless Analysis and Numerical Modeling of Rebalancing Phenomena During Levitation

NASA Astrophysics Data System (ADS)

Gao, Lei; Shi, Zhe; Li, Donghui; McLean, Alexander; Chattopadhyay, Kinnor

2016-06-01

Electromagnetic levitation (EML) has proved to be a powerful tool for research activities in areas pertaining to materials physics and engineering. The customized EML setups in various fields, ranging from solidification to nanomaterial manufacturing, require the designing of stable levitation systems. Since the elevated droplet is opaque, the most effective way to research on EML is mathematical modeling. In the present study, a 3D model was built to investigate the rebalancing phenomenon causing instabilities during droplet melting. A mathematical model modified based on Hooke's law (spring) was proposed to describe the levitation system. This was combined with dimensionless analysis to investigate the generation of levitation forces as it will significantly affect the behavior of the spring model.

The superradiant instability regime of the spinning Kerr black hole

NASA Astrophysics Data System (ADS)

Hod, Shahar

2016-07-01

Spinning Kerr black holes are known to be superradiantly unstable to massive scalar perturbations. We here prove that the instability regime of the composed Kerr-black-hole-massive-scalar-field system is bounded from above by the dimensionless inequality Mμ < m ṡ√{2(1 + γ) (1 -√ 1 -γ2) / -γ2 4γ2, where { μ , m } are respectively the proper mass and azimuthal harmonic index of the scalar field and γ ≡r- /r+ is the dimensionless ratio between the horizon radii of the black hole. It is further shown that this analytically derived upper bound on the superradiant instability regime of the spinning Kerr black hole agrees with recent numerical computations of the instability resonance spectrum.

Beneath Our Feet: Strategies for Locomotion in Granular Media

NASA Astrophysics Data System (ADS)

Hosoi, A. E.; Goldman, Daniel I.

2015-01-01

“If you find yourself in a hole, stop digging.” Although Denis Healey's famous adage ( Metcalfe 2007 ) may offer sound advice for politicians, it is less relevant to worms, clams, and other higher organisms that rely on their digging ability for survival. In this article, we review recent work on the development of simple models that elucidate the fundamental principles underlying digging and burrowing strategies employed by biological systems. Four digging regimes are identified based on dimensionless digger size and the dimensionless inertial number. We select biological organisms to represent three of the four regimes: razor clams, sandfish, and nematodes. Models for all three diggers are derived and discussed, and analogies are drawn to low-Reynolds number swimmers.

Thermal radiation and mass transfer effects on unsteady MHD free convection flow past a vertical oscillating plate

NASA Astrophysics Data System (ADS)

Rana, B. M. Jewel; Ahmed, Rubel; Ahmmed, S. F.

2017-06-01

Unsteady MHD free convection flow past a vertical porous plate in porous medium with radiation, diffusion thermo, thermal diffusion and heat source are analyzed. The governing non-linear, partial differential equations are transformed into dimensionless by using non-dimensional quantities. Then the resultant dimensionless equations are solved numerically by applying an efficient, accurate and conditionally stable finite difference scheme of explicit type with the help of a computer programming language Compaq Visual Fortran. The stability and convergence analysis has been carried out to establish the effect of velocity, temperature, concentration, skin friction, Nusselt number, Sherwood number, stream lines and isotherms line. Finally, the effects of various parameters are presented graphically and discussed qualitatively.

Rebuttal to "On the distribution of the modulus of Gabor wavelet coefficients and the upper bound of the dimensionless smoothness index in the case of additive Gaussian noises: Revisited" by Dong Wang, Qiang Zhou, and Kwok-Leung Tsui

NASA Astrophysics Data System (ADS)

Soltani Bozchalooi, Iman; Liang, Ming

2018-04-01

A discussion paper entitled "On the distribution of the modulus of Gabor wavelet coefficients and the upper bound of the dimensionless smoothness index in the case of additive Gaussian noises: revisited" by Dong Wang, Qiang Zhou, Kwok-Leung Tsui has been brought to our attention recently. This discussion paper (hereafter called Wang et al. paper) is based on arguments that are fundamentally incorrect and which we rebut within this commentary. However, as the flaws in the arguments proposed by Wang et al. are clear, we will keep this rebuttal as brief as possible.

Band structure analysis of a thin plate with periodic arrangements of slender beams

NASA Astrophysics Data System (ADS)

Serrano, Ó.; Zaera, R.; Fernández-Sáez, J.

2018-04-01

This work analyzes the wave propagation in structures composed of a periodic arrangement of vertical beams rigidly joined to a plate substrate. Three different configurations for the distribution of the beams have been analyzed: square, triangular, and hexagonal. A dimensional analysis of the problem indicates the presence of three dimensionless groups of parameters controlling the response of the system. The main features of the wave propagation have been found using numerical procedures based on the Finite Element Method, through the application of the Bloch's theorem for the corresponding primitive unit cells. Illustrative examples of the effect of the different dimensionless parameters on the dynamic behavior of the system are presented, providing information relevant for design.

Study of the zinc-silver oxide battery system

NASA Technical Reports Server (NTRS)

Nanis, L.

1973-01-01

Theoretical and experimental models for the evaluation of current distribution in flooded, porous electrodes are discussed. An approximation for the local current distribution function was derived for conditions of a linear overpotential, a uniform concentration, and a very conductive matrix. By considering the porous electrode to be an analog of chemical catalyst structures, a dimensionless performance parameter was derived from the approximated current distribution function. In this manner the electrode behavior was characterized in terms of an electrochemical Thiele parameter and an effectiveness factor. It was shown that the electrochemical engineering approach makes possible the organizations of theoretical descriptions and of practical experience in the form of dimensionless parameters, such as the electrochemical Thiele parameters, and hence provides useful information for the design of new electrochemical systems.

Overcoming the Practical Barriers to Spinal Cord Cell Transplantation for ALS

DTIC Science & Technology

2012-10-01

ABSTRACT: This grant will provide critical data on tolerance and toxicity of cell dosing and numbers of permissible spinal cord injections. Rigorous...Surgical Technique) will provide critical data on tolerance and toxicity of cell dosing and numbers of permissible spinal cord injections. Aim 2 (Graft...connected to a rigid needle of the same gauge as the floating cannula one – Figure 7) using the maximum volume/number of injections could result in

An Assessment Tool of Performance Based Logistics Appropriateness

DTIC Science & Technology

2012-03-01

weighted tool score. The reason might be the willing to use PBL as an acquisition method . There is an 8.51% positive difference is present. Figure 20 shows...performance-based acquisition methods to the maximum extent practicable when acquiring services with little exclusion’ is mandated. Although PBL...determines the factors affecting the success in selecting PBL as an acquisition method . Each factor is examined in detail and built into a spreadsheet tool

Power Aware Signal Processing Environment (PASPE) for PAC/C

DTIC Science & Technology

2003-02-01

vs. FFT Size For our implementation , the Annapolis FFT core was radix-256, and therefore the smallest PN code length that could be processed was the...PN-64. A C- code version of correlate was compared to the FPGA 61 implementation . The results in Figure 68 show that for a PN-1024, the...12a. DISTRIBUTION / AVAILABILITY STATEMENT APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. 12b. DISTRIBUTION CODE 13. ABSTRACT (Maximum

Understanding the Microphysical Properties of Developing Cloud Clusters during TCS-08

DTIC Science & Technology

2011-09-30

resolution (1.67-km) sensitivity simulations have been performed using Typhoon Mawar (2005) from the western North Pacific to demonstrate considerable...cloud-resolving) scheme is used in the model. Initial calculations of some basic cloud properties from infrared imagery for Typhoon Mawar indicate that...Figure 4: Intensity traces of simulated Typhoon Mawar (2005) showing sea-level pressure on the left axis and maximum wind speed on the right axis

Increasing Reliability of a Small 2-Stroke Internal Combustion Engine for Dynamically Changing Altitudes

DTIC Science & Technology

2012-03-01

63 Figure 20: New 3 inch stainless pipe used as an intake manifold...speed range of 1,000 RPM to 4,000 RPM. Six electric heaters with a total capacity of 900 W were used to heat the inlet air allowing a maximum...of the engine volume and had a gummy diaphragm attached to reduce pressure and flow pulsations to allow for more accurate air flow measurements

Fundamentals of Electrical Propulsion Plant Design,

DTIC Science & Technology

1982-04-06

through connection of resonant filters or through use of multiphase conversion power circuits. Figure 9.25. Block Diagram of a Frequency Converter Control...first harmonic, active power Pa’ consumed by the converter at the point of application of this emf, is determined from expression P. = 3EM i cos i...armature shunting contactor K3 KDD diesel starting contactor K.U KZ protection contactor K3 KMM maximum power contactor KM KO compensating winding KO

Screening Adhesively Bonded Single-Lap-Joint Testing Results Using Nonlinear Calculation Parameters

DTIC Science & Technology

2012-03-01

versus displacement response for single-lap-joints bonded with damage-tolerant adhe- sives, such the polyurea adhesive plotted in Figure 2, is much...displacement response for a single-lap-joint bonded with a polyurea adhesive. Complex x-y plots are commonly fitted using the Levenberg-Marquardt...expected decrease in maximum strength for the polyurea in compar- ison to the epoxy, which could have been obtained using a traditional analysis approach

2002 Controls Design Challenge

NASA Technical Reports Server (NTRS)

Hess, Ronald A.; Vetter, T. K.; Wells, S. R.

2002-01-01

This document is intended to provide the specifications and requirements for a flight control system design challenge. The response to the challenge will involve documenting whether the particular design has met the stated requirements through analysis and computer simulation. The response should be written in the general format of a technical publication with corresponding length limits, e.g., an approximate maximum length of 45 units, with each full-size figure and double-spaced typewritten page constituting one unit.

The Chena River Watershed Hydrology Model

DTIC Science & Technology

2012-04-01

Moose Creek Dam Pro- ject and determine the Probable Maximum Flood (PMF) hydrograph. The Chena River water- shed covers 2115 mi2 . It is characterized...Tanana River in Fairbanks, AK (Figure 1). The watershed has a total area of 2115 mi2 , and elevations range from 420 ft at the outlet to 5280 ft at...physical characteristics. Sub- basin Description Area ( mi2 ) Longest flow path (mi) Elevation at divide (ft) Elevation at outlet (ft

Modelling and Simulation in the Design Process of Armored Vehicles

DTIC Science & Technology

2003-03-01

trackway conditions is a demanding optimization task. Basically, a high level of ride comfort requires soft suspension tuning, whereas driving safety relies...The maximum off-road speed is generally limited by traction, input torque, driving safety and ride comfort. When obstacles are to be negotiated, the...wheel travel was defined during the mobility simulation runs. Figure 14: Ramp 1.5m at 40 kph; virtual and physical prototype Driving safety and ride

Electrically Tunable Mid-Infrared Single-Mode High-Speed Semiconductor Laser

DTIC Science & Technology

2010-11-01

effective and the net tunnel rate may decrease in spite of progressing carrier density buildup in the accumulation well. Enforcing the bias current at...In te ns ity , a .u . E, eV Regular ICL Figure 4 The dependence of the electroluminescence (EL) quantum energy on the bias voltage for a...spectral maximum energy increases linearly with the bias voltage. Since the dependence is measured in the sub-threshold pumping region, the linear

Study of Magnetospheric Currents and Resultant Surface Magnetic Variations.

DTIC Science & Technology

1980-04-17

compressed as indicated by solar -wind data, automatically injected a ring current with a strength consistent with the observed Dst. The computed inner...Fig!ire 2?; bottoim panal of Figure 5_. Agreement is very acceptahle. The model overestimated the maximum depression of RX, but by a factor that is well...Contributed Papers Presented at the Solar -Terrestrial Physics Symposium, Innsbruck, 1978. Harel, M., R. A. Wolf, P. H. Reiff and M. Siiddy, Computer

High-Performance Liquid Chromatography (HPLC) Measurements of Phytoplankton Pigment Distributions of Ocean Waters

DTIC Science & Technology

1988-11-01

coccolithophorids 19. ABSTRACT (CanMyw on rviosfe Inhcesway aM den*t byblock nmber) Until the application of high-performance liquid chromatography (HPLC) to... phycocyanin , has a maximum 0 01 absorption peak. The spectra for the 008 chlorophyll degradation products (chlo- 0.06 rophyllides, phaeophorbides and...phaeo- phytins) which are not shown in Figure z I have similar absorption maxima as their associated chlorophylls, 002 , Until the application of high

Safety Parameter Considerations of Anodal Transcranial Direct Current Stimulation in Rats

DTIC Science & Technology

2017-10-01

under standard laboratory conditions, including a 12 hour light/ dark cycle with food and water available ad libitum. Following a ten day quarantine...values greater than 7.04619 A/m2 are presented in dark red. The maximum threshold was determined by preliminary analysis corresponding the first...increased. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.). 11

TCAD Analysis of Heating and Maximum Current Density in Carbon Nanofiber Interconnects

DTIC Science & Technology

2011-09-01

a metallic MWCNT interconnect. From [20]. ....20  Figure 11.  Simple equivalent circuit model of a metallic MWCNT interconnect. From [20...Carbon Nanotube MWCNT Multi-Walled Carbon Nanotube SCU Santa Clara University Si Silicon SiO2 Silicon Dioxide SiC Silicon Carbide Au Gold...proven, multi-walled carbon nanotube ( MWCNT ) [2]. He later discovered single-walled carbon nanotubes (SWCNT) in 1993 [13]. Since Iijima’s discovery

Installation Restoration Program. Phase 2. Confirmation, Edwards AFB, California

DTIC Science & Technology

1982-09-01

aquifer boundaries has created unique hydrological conditions, with fluctuating water levels and continuously changing regimes of confinement...wells, resulting in changes in the regional gradien,ý from north to south. Figure 2.3 shows the groundwater table contours as of 1979 (U.S.G.S., 1980...of 11 inches. The maximum mean monthly rainfall occurs in February with about 0.5 inch in one day (Envirodyne Engineers, Inc., 1981). In arid climates

Erratum to. Energy calibration of gamma spectra in plastic scintillators using Compton kinematics [Nucl. Instr. and Meth. A 594 (2008) 232–243

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

Siciliano, Edward R.; Ely, James H.; Kouzes, Richard T.

2009-11-01

In recent work at our laboratory, we were re-examining our data and found an inconsistency between the values listed for 137Cs in Table 2 (Siciliano et al. 2008) and results plotted for that source in Figures 11 and 12. In the course of fitting the parabolic function (Equation 4) to the Compton maxima, two ranges of channels were used when determining the parameters for 137Cs. The parabolic fit curve shown in Figure 11 resulted from fitting channels 50 to 70. The parameters for that fit are: are: A = 0.972(12), B = 1.42(24) x 10 -3, and C NO =more » 60.2(5). The parameters for 137Cs listed in Table 2 (and also used to determine the calibration relations in Figure 12—the main result of this paper) came from fitting the 137Cs data in channels 40 to 80. Although the curves plotted from these two different sets of parameters would be visually distinguishable in Figure 11, when incorporated with the other isotope values shown in Figure 12 to obtain the linear energy-channel fit, the 50-70 channel parameter set plus the correction from the Compton maximum to the Compton edge gives a negligible change in the slope [6.470(41) as opposed to the reported 6.454(15) keV/channel] and a small change in the intercept [41(8) as opposed to 47(3) keV] for the dashed line. The conclusions of the article therefore do not change as a result of this inconsistency.« less

Wells syndrome and its relationship to Churg-Strauss syndrome.

PubMed

Ratzinger, Gudrun; Zankl, Julia; Zelger, Bernhard

2013-08-01

  Wells syndrome has been described as an inflammatory disorder based on typical clinical appearance combined with the histopathological presence of eosinophilic infiltrates and flame figures in the absence of vasculitis. Churg-Strauss syndrome, on the other hand, is primarily a diffuse, necrotizing vasculitis but is also typically displaying eosinophils and flame figures. Despite several parallels, the present understanding of these two diseases excludes any pathogenetic relationship.   We describe the clinical course and histopathological appearance of three patients who had initially been diagnosed with Wells syndrome that developed into Churg-Strauss syndrome during the course of their disease.   The clinical presentation of all three patients led to the diagnosis of Wells syndrome by independent specialists. Histopathology showed an eosinophilic infiltrate and flame figures next to features of leukocytoclastic vasculitis. Detailed examination revealed asthma bronchiale and additional symptoms indicating Churg-Strauss syndrome. The initial diagnosis of Wells syndrome had to be revised to Churg-Strauss syndrome.   We conclude that Wells syndrome could be the starting point of a pathogenetic process that might reach its maximum in Churg-Strauss syndrome. As a clinical consequence, patients with Wells syndrome should be evaluated and followed for Churg-Strauss syndrome. © 2013 The International Society of Dermatology.

SLS complementary logic devices with increase carrier mobility

DOEpatents

Chaffin, R.J.; Osbourn, G.C.; Zipperian, T.E.

1991-07-09

In an electronic device comprising a semiconductor material and having at least one performance characteristic which is limited by the mobility of holes in the semiconductor material, said mobility being limited because of a valence band degeneracy among high-mobility and low-mobility energy levels accessible to said holes at the energy-momentum space maximum, an improvement is provided wherein the semiconductor material is a strained layer superlattice (SLS) whose layer compositions and layer thicknesses are selected so that the strain on the layers predominantly containing said at least one carrier type splits said degeneracy and modifies said energy levels around said energy-momentum space maximum in a manner whereby said limitation on the mobility of said holes is alleviated. 5 figures.

Hydrodynamics of pedestrians' instability in floodwaters

NASA Astrophysics Data System (ADS)

Arrighi, Chiara; Oumeraci, Hocine; Castelli, Fabio

2017-01-01

People's safety is the first objective to be fulfilled by flood risk mitigation measures, and according to existing reports on the causes of casualties, most of the fatalities are due to inappropriate behaviour such as walking or driving in floodwaters. Currently available experimental data on people instability in floodwaters suffer from a large dispersion primarily depending on the large variability of the physical characteristics of the subjects. This paper introduces a dimensionless mobility parameter θP for people partly immersed in flood flows, which accounts for both flood and subject characteristics. The parameter θP is capable of identifying a unique threshold of instability depending on a Froude number, thus reducing the scatter of existing experimental data. Moreover, a three-dimensional (3-D) numerical model describing the detailed geometry of a human body and reproducing a selection of critical pairs of water depth and velocity is presented. The numerical results in terms of hydrodynamic forces and force coefficients are analysed and discussed. Both the mobility parameter θP and the numerical results hint at the crucial role of the Froude number and relative submergence as the most relevant dimensionless numbers to interpret the loss of stability. Finally, the mobility parameter θP is compared with an analogous dimensionless parameter for vehicles' instability in floodwaters, providing a new contribution to support flood risk management and educating people.

MHD Free Convective Boundary Layer Flow of a Nanofluid past a Flat Vertical Plate with Newtonian Heating Boundary Condition

PubMed Central

Uddin, Mohammed J.; Khan, Waqar A.; Ismail, Ahmed I.

2012-01-01

Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

Theory of linear sweep voltammetry with diffuse charge: Unsupported electrolytes, thin films, and leaky membranes

NASA Astrophysics Data System (ADS)

Yan, David; Bazant, Martin Z.; Biesheuvel, P. M.; Pugh, Mary C.; Dawson, Francis P.

2017-03-01

Linear sweep and cyclic voltammetry techniques are important tools for electrochemists and have a variety of applications in engineering. Voltammetry has classically been treated with the Randles-Sevcik equation, which assumes an electroneutral supported electrolyte. In this paper, we provide a comprehensive mathematical theory of voltammetry in electrochemical cells with unsupported electrolytes and for other situations where diffuse charge effects play a role, and present analytical and simulated solutions of the time-dependent Poisson-Nernst-Planck equations with generalized Frumkin-Butler-Volmer boundary conditions for a 1:1 electrolyte and a simple reaction. Using these solutions, we construct theoretical and simulated current-voltage curves for liquid and solid thin films, membranes with fixed background charge, and cells with blocking electrodes. The full range of dimensionless parameters is considered, including the dimensionless Debye screening length (scaled to the electrode separation), Damkohler number (ratio of characteristic diffusion and reaction times), and dimensionless sweep rate (scaled to the thermal voltage per diffusion time). The analysis focuses on the coupling of Faradaic reactions and diffuse charge dynamics, although capacitive charging of the electrical double layers is also studied, for early time transients at reactive electrodes and for nonreactive blocking electrodes. Our work highlights cases where diffuse charge effects are important in the context of voltammetry, and illustrates which regimes can be approximated using simple analytical expressions and which require more careful consideration.