Science.gov

Sample records for power density distribution

  1. A High Power Density DC-DC Converter for Distributed PV Architectures

    SciTech Connect

    Agamy, Mohammed S; Chi, Song; Elasser, Ahmed; Harfman-Todorovic, Maja; Jiang, Yan; Mueller, Frank; Tao, Fengfeng

    2012-06-01

    In order to maximize solar energy harvesting capabilities, power converters have to be designed for high efficiency and good MPPT and voltage/current performance. When many converters are used in distributed systems, power density also becomes an important factor as it allows for simpler system integration. In this paper a high power density string dc-dc converter suitable for distributed medium to large scale PV installation is presented. A simple partial power processing topology, implemented with all silicon carbide devices provides high efficiency as well as high power density. A 3.5kW, 100kHz converter is designed and tested to verify the proposed methods.

  2. Influence of Mobile Users' Density Distribution on the CDMA Base Station Power

    NASA Astrophysics Data System (ADS)

    Lebl, Aleksandar; Mitić, Dragan; Popović, Miroslav; Markov, Žarko; Mileusnić, Mladen; Matić, Vladimir

    2016-12-01

    In this paper we analyze the influence of users' density distribution in one cell of CDMA mobile network (ie adjusted power control on the forward link) on base station emission power. This influence is analyzed for different circles radii around base station within which same emission power is generated for all mobile users, and for different values of propagation loss coefficient. It is proved that emission power in this cell must be increased comparing to the similar cell, which uses complete power control. The power increase is greater when greater number of users are situated near base station, and for greater values of propagation loss coefficient. The results are presented, illustrated by numerical examples and verified by simulation for three users' density distributions: uniform, decreasing and increasing density from the base station to the cell rim. The simulation process, which is based on random traffic process, is presented briefly.

  3. Linearized image reconstruction method for ultrasound modulated electrical impedance tomography based on power density distribution

    NASA Astrophysics Data System (ADS)

    Song, Xizi; Xu, Yanbin; Dong, Feng

    2017-04-01

    Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results.

  4. User's Guide: An Enhanced Modified Faraday Cup for the Profiling of the Power Density Distribution in Electron Beams

    SciTech Connect

    Elmer, J W; Teruya, A T; Palmer, T A

    2002-06-01

    This handbook describes the assembly and operation of an enhanced Modified Faraday Cup (MFC) diagnostic device for measuring the power density distribution of high power electron beams used for welding. The most recent version of this diagnostic device, [1] Version 2.0, contains modifications to the hardware components of previous MFC designs.[2] These modifications allow for more complete capture of the electrons and better electrical grounding, thus improving the quality of the acquired data and enabling a more accurate computed tomographic (CT) reconstruction [3,4] of the power density distribution of the electron beam to be performed. [ 5-9

  5. Enhanced modified faraday cup for determination of power density distribution of electron beams

    DOEpatents

    Elmer, John W.; Teruya, Alan T.

    2001-01-01

    An improved tomographic technique for determining the power distribution of an electron or ion beam using electron beam profile data acquired by an enhanced modified Faraday cup to create an image of the current density in high and low power ion or electron beams. A refractory metal disk with a number of radially extending slits, one slit being about twice the width of the other slits, is placed above a Faraday cup. The electron or ion beam is swept in a circular pattern so that its path crosses each slit in a perpendicular manner, thus acquiring all the data needed for a reconstruction in one circular sweep. The enlarged slit enables orientation of the beam profile with respect to the coordinates of the welding chamber. A second disk having slits therein is positioned below the first slit disk and inside of the Faraday cup and provides a shield to eliminate the majority of secondary electrons and ions from leaving the Faraday cup. Also, a ring is located below the second slit disk to help minimize the amount of secondary electrons and ions from being produced. In addition, a beam trap is located in the Faraday cup to provide even more containment of the electron or ion beam when full beam current is being examined through the center hole of the modified Faraday cup.

  6. High power density targets

    NASA Astrophysics Data System (ADS)

    Pellemoine, Frederique

    2013-12-01

    In the context of new generation rare isotope beam facilities based on high-power heavy-ion accelerators and in-flight separation of the reaction products, the design of the rare isotope production targets is a major challenge. In order to provide high-purity beams for science, high resolution is required in the rare isotope separation. This demands a small beam spot on the production target which, together with the short range of heavy ions in matter, leads to very high power densities inside the target material. This paper gives an overview of the challenges associated with this high power density, discusses radiation damage issues in targets exposed to heavy ion beams, and presents recent developments to meet some of these challenges through different projects: FAIR, RIBF and FRIB which is the most challenging. Extensive use of Finite Element Analysis (FEA) has been made at all facilities to specify critical target parameters and R&D work at FRIB successfully retired two major risks related to high-power density and heavy-ion induced radiation damage.

  7. Spatial Distribution of Oxygen Chemical Potential under Potential Gradients and Theoretical Maximum Power Density with 8YSZ Electrolyte

    PubMed Central

    Lim, Dae-Kwang; Im, Ha-Ni; Song, Sun-Ju

    2016-01-01

    The maximum power density of SOFC with 8YSZ electrolyte as the function of thickness was calculated by integrating partial conductivities of charge carriers under various DC bias conditions at a fixed oxygen chemical potential gradient at both sides of the electrolyte. The partial conductivities were successfully taken using the Hebb-Wagner polarization method as a function of temperature and oxygen partial pressure, and the spatial distribution of oxygen partial pressure across the electrolyte was calculated based on Choudhury and Patterson’s model by considering zero electrode polarization. At positive voltage conditions corresponding to SOFC and SOEC, the high conductivity region was expanded, but at negative cell voltage condition, the low conductivity region near n-type to p-type transition was expanded. In addition, the maximum power density calculated from the current-voltage characteristic showed approximately 5.76 W/cm2 at 700 oC with 10 μm thick-8YSZ, while the oxygen partial pressure of the cathode and anode sides maintained ≈0.21 and 10−22 atm. PMID:26725369

  8. Spatial Distribution of Oxygen Chemical Potential under Potential Gradients and Theoretical Maximum Power Density with 8YSZ Electrolyte.

    PubMed

    Lim, Dae-Kwang; Im, Ha-Ni; Song, Sun-Ju

    2016-01-04

    The maximum power density of SOFC with 8YSZ electrolyte as the function of thickness was calculated by integrating partial conductivities of charge carriers under various DC bias conditions at a fixed oxygen chemical potential gradient at both sides of the electrolyte. The partial conductivities were successfully taken using the Hebb-Wagner polarization method as a function of temperature and oxygen partial pressure, and the spatial distribution of oxygen partial pressure across the electrolyte was calculated based on Choudhury and Patterson's model by considering zero electrode polarization. At positive voltage conditions corresponding to SOFC and SOEC, the high conductivity region was expanded, but at negative cell voltage condition, the low conductivity region near n-type to p-type transition was expanded. In addition, the maximum power density calculated from the current-voltage characteristic showed approximately 5.76 W/cm(2) at 700 (o)C with 10 μm thick-8YSZ, while the oxygen partial pressure of the cathode and anode sides maintained ≈0.21 and 10(-22) atm.

  9. High Power Density Motors

    NASA Technical Reports Server (NTRS)

    Kascak, Daniel J.

    2004-01-01

    With the growing concerns of global warming, the need for pollution-free vehicles is ever increasing. Pollution-free flight is one of NASA's goals for the 21" Century. , One method of approaching that goal is hydrogen-fueled aircraft that use fuel cells or turbo- generators to develop electric power that can drive electric motors that turn the aircraft's propulsive fans or propellers. Hydrogen fuel would likely be carried as a liquid, stored in tanks at its boiling point of 20.5 K (-422.5 F). Conventional electric motors, however, are far too heavy (for a given horsepower) to use on aircraft. Fortunately the liquid hydrogen fuel can provide essentially free refrigeration that can be used to cool the windings of motors before the hydrogen is used for fuel. Either High Temperature Superconductors (HTS) or high purity metals such as copper or aluminum may be used in the motor windings. Superconductors have essentially zero electrical resistance to steady current. The electrical resistance of high purity aluminum or copper near liquid hydrogen temperature can be l/lOO* or less of the room temperature resistance. These conductors could provide higher motor efficiency than normal room-temperature motors achieve. But much more importantly, these conductors can carry ten to a hundred times more current than copper conductors do in normal motors operating at room temperature. This is a consequence of the low electrical resistance and of good heat transfer coefficients in boiling LH2. Thus the conductors can produce higher magnetic field strengths and consequently higher motor torque and power. Designs, analysis and actual cryogenic motor tests show that such cryogenic motors could produce three or more times as much power per unit weight as turbine engines can, whereas conventional motors produce only 1/5 as much power per weight as turbine engines. This summer work has been done with Litz wire to maximize the current density. The current is limited by the amount of heat it

  10. Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

    SciTech Connect

    Bobrov, A. A.; Glushkov, E. S.; Zimin, A. A.; Kapitonova, A. V.; Kompaniets, G. V.; Nosov, V. I. Petrushenko, R. P.; Smirnov, O. N.

    2012-12-15

    A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.

  11. Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

    NASA Astrophysics Data System (ADS)

    Bobrov, A. A.; Glushkov, E. S.; Zimin, A. A.; Kapitonova, A. V.; Kompaniets, G. V.; Nosov, V. I.; Petrushenko, R. P.; Smirnov, O. N.

    2012-12-01

    A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.

  12. The use of segmented cathodes to determine the spoke current density distribution in high power impulse magnetron sputtering plasmas

    SciTech Connect

    Poolcharuansin, Phitsanu; Estrin, Francis Lockwood; Bradley, James W.

    2015-04-28

    The localized target current density associated with quasi-periodic ionization zones (spokes) has been measured in a high power impulse magnetron sputtering (HiPIMS) discharge using an array of azimuthally separated and electrical isolated probes incorporated into a circular aluminum target. For a particular range of operating conditions (pulse energies up to 2.2 J and argon pressures from 0.2 to 1.9 Pa), strong oscillations in the probe current density are seen with amplitudes up to 52% above a base value. These perturbations, identified as spokes, travel around the discharge above the target in the E×B direction. Using phase information from the angularly separated probes, the spoke drift speeds, angular frequencies, and mode number have been determined. Generally, at low HiPIMS pulse energies E{sub p} < 0.8 J, spokes appear to be chaotic in nature (with random arrival times), however as E{sub p} increases, coherent spokes are observed with velocities between 6.5 and 10 km s{sup −1} and mode numbers m = 3 or above. At E{sub p} > 1.8 J, the plasma becomes spoke-free. The boundaries between chaotic, coherent, and no-spoke regions are weakly dependent on pressure. During each HiPIMS pulse, the spoke velocities increase by about 50%. Such an observation is explained by considering spoke velocities to be determined by the critical ionization velocity, which changes as the plasma composition changes during the pulse. From the shape of individual current density oscillations, it appears that the leading edge of the spoke is associated with a slow increase in local current density to the target and the rear with a more rapid decrease. The measurements show that the discharge current density associated with individual spokes is broadly spread over a wide region of the target.

  13. PWM Converter Power Density Barriers

    NASA Astrophysics Data System (ADS)

    Kolar, Johann W.; Drofenik, Uwe; Biela, Juergen; Heldwein, Marcelo; Ertl, Hans; Friedli, Thomas; Round, Simon

    Power density of power electronic converters has roughly doubled every 10 years since 1970. Behind this trajectory is the continuous advancement of power semiconductor devices, which has increased the converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts and passive components are major barriers for a continuation of this trend. To identify such technological barriers, this paper investigates the volume of the cooling system and passive components as a function of the switching frequency for power electronic converters and determines the switching frequency that minimizes the total volume. A power density limit of 28kW/dm3 at 300kHz is calculated for an isolated DC-DC converter, 44kW/dm3 at 820kHz for a three-phase unity power factor PWM rectifier, and 26kW/dm3 at 21kHz for a sparse matrix converter. For single-phase AC-DC conversion a general limit of 35kW/dm3 results from the DC link capacitor. These power density limits highlight the need to broaden the scope of power electronics research to include cooling systems, high frequency electromagnetics, interconnection and packaging technology, and multi-domain modelling and simulation to ensure further advancement along the power density trajectory.

  14. Exponentiated power Lindley distribution.

    PubMed

    Ashour, Samir K; Eltehiwy, Mahmoud A

    2015-11-01

    A new generalization of the Lindley distribution is recently proposed by Ghitany et al. [1], called as the power Lindley distribution. Another generalization of the Lindley distribution was introduced by Nadarajah et al. [2], named as the generalized Lindley distribution. This paper proposes a more generalization of the Lindley distribution which generalizes the two. We refer to this new generalization as the exponentiated power Lindley distribution. The new distribution is important since it contains as special sub-models some widely well-known distributions in addition to the above two models, such as the Lindley distribution among many others. It also provides more flexibility to analyze complex real data sets. We study some statistical properties for the new distribution. We discuss maximum likelihood estimation of the distribution parameters. Least square estimation is used to evaluate the parameters. Three algorithms are proposed for generating random data from the proposed distribution. An application of the model to a real data set is analyzed using the new distribution, which shows that the exponentiated power Lindley distribution can be used quite effectively in analyzing real lifetime data.

  15. Exponentiated power Lindley distribution

    PubMed Central

    Ashour, Samir K.; Eltehiwy, Mahmoud A.

    2014-01-01

    A new generalization of the Lindley distribution is recently proposed by Ghitany et al. [1], called as the power Lindley distribution. Another generalization of the Lindley distribution was introduced by Nadarajah et al. [2], named as the generalized Lindley distribution. This paper proposes a more generalization of the Lindley distribution which generalizes the two. We refer to this new generalization as the exponentiated power Lindley distribution. The new distribution is important since it contains as special sub-models some widely well-known distributions in addition to the above two models, such as the Lindley distribution among many others. It also provides more flexibility to analyze complex real data sets. We study some statistical properties for the new distribution. We discuss maximum likelihood estimation of the distribution parameters. Least square estimation is used to evaluate the parameters. Three algorithms are proposed for generating random data from the proposed distribution. An application of the model to a real data set is analyzed using the new distribution, which shows that the exponentiated power Lindley distribution can be used quite effectively in analyzing real lifetime data. PMID:26644927

  16. High power density carbonate fuel cell

    SciTech Connect

    Yuh, C.; Johnsen, R.; Doyon, J.; Allen, J.

    1996-12-31

    Carbonate fuel cell is a highly efficient and environmentally clean source of power generation. Many organizations worldwide are actively pursuing the development of the technology. Field demonstration of multi-MW size power plant has been initiated in 1996, a step toward commercialization before the turn of the century, Energy Research Corporation (ERC) is planning to introduce a 2.85MW commercial fuel cell power plant with an efficiency of 58%, which is quite attractive for distributed power generation. However, to further expand competitive edge over alternative systems and to achieve wider market penetration, ERC is exploring advanced carbonate fuel cells having significantly higher power densities. A more compact power plant would also stimulate interest in new markets such as ships and submarines where space limitations exist. The activities focused on reducing cell polarization and internal resistance as well as on advanced thin cell components.

  17. Density Distributions of Cyclotrimethylenetrinitramines (RDX)

    SciTech Connect

    Hoffman, D M

    2002-03-19

    As part of the US Army Foreign Comparative Testing (FCT) program the density distributions of six samples of class 1 RDX were measured using the density gradient technique. This technique was used in an attempt to distinguish between RDX crystallized by a French manufacturer (designated insensitive or IRDX) from RDX manufactured at Holston Army Ammunition Plant (HAAP), the current source of RDX for Department of Defense (DoD). Two samples from different lots of French IRDX had an average density of 1.7958 {+-} 0.0008 g/cc. The theoretical density of a perfect RDX crystal is 1.806 g/cc. This yields 99.43% of the theoretical maximum density (TMD). For two HAAP RDX lots the average density was 1.786 {+-} 0.002 g/cc, only 98.89% TMD. Several other techniques were used for preliminary characterization of one lot of French IRDX and two lot of HAAP RDX. Light scattering, SEM and polarized optical microscopy (POM) showed that SNPE and Holston RDX had the appropriate particle size distribution for Class 1 RDX. High performance liquid chromatography showed quantities of HMX in HAAP RDX. French IRDX also showed a 1.1 C higher melting point compared to HAAP RDX in the differential scanning calorimetry (DSC) consistent with no melting point depression due to the HMX contaminant. A second part of the program involved characterization of Holston RDX recrystallized using the French process. After reprocessing the average density of the Holston RDX was increased to 1.7907 g/cc. Apparently HMX in RDX can act as a nucleating agent in the French RDX recrystallization process. The French IRDX contained no HMX, which is assumed to account for its higher density and narrower density distribution. Reprocessing of RDX from Holston improved the average density compared to the original Holston RDX, but the resulting HIRDX was not as dense as the original French IRDX. Recrystallized Holston IRDX crystals were much larger (3-500 {micro}m or more) then either the original class 1 HAAP RDX or

  18. Industrial power distribution

    SciTech Connect

    Sorrells, M.A.

    1990-01-01

    This paper is a broad overview of industrial power distribution. Primary focus will be on selection of the various low voltage components to achieve the end product. Emphasis will be on the use of national standards to ensure a safe and well designed installation.

  19. Shaping of the axial power density distribution in the core to minimize the vapor volume fraction at the outlet of the VVER-1200 fuel assemblies

    NASA Astrophysics Data System (ADS)

    Savander, V. I.; Shumskiy, B. E.; Pinegin, A. A.

    2016-12-01

    The possibility of decreasing the vapor fraction at the VVER-1200 fuel assembly outlet by shaping the axial power density field is considered. The power density field was shaped by axial redistribution of the concentration of the burnable gadolinium poison in the Gd-containing fuel rods. The mathematical modeling of the VVER-1200 core was performed using the NOSTRA computer code.

  20. The Density Distribution in Turbulent Bistable Flows

    NASA Astrophysics Data System (ADS)

    Gazol, Adriana; Kim, Jongsoo

    2013-03-01

    We numerically study the volume density probability distribution function (n-PDF) and the column density probability distribution function (Σ-PDF) resulting from thermally bistable turbulent flows. We analyze three-dimensional hydrodynamic models in periodic boxes of 100 pc by side, where turbulence is driven in the Fourier space at a wavenumber corresponding to 50 pc. At low densities (n <~ 0.6 cm-3), the n-PDF is well described by a lognormal distribution for an average local Mach number ranging from ~0.2 to ~5.5. As a consequence of the nonlinear development of thermal instability (TI), the logarithmic variance of the distribution of the diffuse gas increases with M faster than in the well-known isothermal case. The average local Mach number for the dense gas (n >~ 7.1 cm-3) goes from ~1.1 to ~16.9 and the shape of the high-density zone of the n-PDF changes from a power law at low Mach numbers to a lognormal at high M values. In the latter case, the width of the distribution is smaller than in the isothermal case and grows slower with M. At high column densities, the Σ-PDF is well described by a lognormal for all of the Mach numbers we consider and, due to the presence of TI, the width of the distribution is systematically larger than in the isothermal case but follows a qualitatively similar behavior as M increases. Although a relationship between the width of the distribution and M can be found for each one of the cases mentioned above, these relations are different from those of the isothermal case.

  1. THE DENSITY DISTRIBUTION IN TURBULENT BISTABLE FLOWS

    SciTech Connect

    Gazol, Adriana; Kim, Jongsoo E-mail: jskim@kasi.re.kr

    2013-03-01

    We numerically study the volume density probability distribution function (n-PDF) and the column density probability distribution function ({Sigma}-PDF) resulting from thermally bistable turbulent flows. We analyze three-dimensional hydrodynamic models in periodic boxes of 100 pc by side, where turbulence is driven in the Fourier space at a wavenumber corresponding to 50 pc. At low densities (n {approx}< 0.6 cm{sup -3}), the n-PDF is well described by a lognormal distribution for an average local Mach number ranging from {approx}0.2 to {approx}5.5. As a consequence of the nonlinear development of thermal instability (TI), the logarithmic variance of the distribution of the diffuse gas increases with M faster than in the well-known isothermal case. The average local Mach number for the dense gas (n {approx}> 7.1 cm{sup -3}) goes from {approx}1.1 to {approx}16.9 and the shape of the high-density zone of the n-PDF changes from a power law at low Mach numbers to a lognormal at high M values. In the latter case, the width of the distribution is smaller than in the isothermal case and grows slower with M. At high column densities, the {Sigma}-PDF is well described by a lognormal for all of the Mach numbers we consider and, due to the presence of TI, the width of the distribution is systematically larger than in the isothermal case but follows a qualitatively similar behavior as M increases. Although a relationship between the width of the distribution and M can be found for each one of the cases mentioned above, these relations are different from those of the isothermal case.

  2. High Density Power Converters for Photovoltaic Power Management

    NASA Astrophysics Data System (ADS)

    Sangwan, Rahul

    In typical photovoltaic systems, PV cells are connected in series to achieve high output voltages, which decreases conduction losses and helps the downstream power electronics operate at higher efficiencies. A series connection means that the current through the string is limited by the worst case cell, substring, or module, which can result in suboptimal operation of the rest of the string. Given how even small shading can have a large effect on performance, there has been growing interest in the use of distributed power management architectures to mitigate losses from variation in PV systems. In particular, partial power processing converters have gained traction as a means to improve the performance of PV arrays with small, distributed converters that configure in parallel with PV cells. These converters can use low voltage components, only process a fraction of the total power allowing them to achieve higher efficiencies and power density and also have higher reliability. This work details the design and operation of a partial power processing converter implemented as a Resonant Switched Capacitor (ReSC) converter. An integrated circuit (IC) is designed in 0.18 mum CMOS process. Operation at high frequencies (20-50 MHz) allows high levels of integration with air core inductors directly attached to the die through a gold bump, solder reflow process. Test results for the IC are presented with power density and efficiency metrics. The IC is then used as a partial power processing converter to implement equalization with a specially constructed PV panel. The converter is shown to mitigate power loss due to mismatch.

  3. Automated Power-Distribution System

    NASA Technical Reports Server (NTRS)

    Ashworth, Barry; Riedesel, Joel; Myers, Chris; Miller, William; Jones, Ellen F.; Freeman, Kenneth; Walsh, Richard; Walls, Bryan K.; Weeks, David J.; Bechtel, Robert T.

    1992-01-01

    Autonomous power-distribution system includes power-control equipment and automation equipment. System automatically schedules connection of power to loads and reconfigures itself when it detects fault. Potential terrestrial applications include optimization of consumption of power in homes, power supplies for autonomous land vehicles and vessels, and power supplies for automated industrial processes.

  4. Simultaneous visualization of oxygen partial pressure, current density, and water droplets in serpentine fuel cell during power generation for understanding reaction distributions

    NASA Astrophysics Data System (ADS)

    Takanohashi, Kazuhiro; Suga, Takeo; Uchida, Makoto; Ueda, Toshihide; Nagumo, Yuzo; Inukai, Junji; Nishide, Hiroyuki; Watanabe, Masahiro

    2017-03-01

    Understanding the reaction distributions inside a polymer electrolyte fuel cell (PEFC) is essential for the higher performance and durability. We have developed a new see-through cell and visualized the distributions of oxygen partial pressure and current density inside a running PEFC at the temperature of 40 and 80 °C and the relative humidity of 53%. The oxygen utilization was changed from 0% to 80% by changing the current density. At higher oxygen utilizations, the current density was higher and therefore the water generation. Generated water droplets in the flow channel were also visualized, allowing for the simultaneous visualization of the distribution of the oxygen partial pressure, current density, and water droplets. By combining the observations of all three parameters, the reactions inside a membrane-electrode assembly were discussed.

  5. SSP Power Management and Distribution

    NASA Technical Reports Server (NTRS)

    Lynch, Thomas H.; Roth, A. (Technical Monitor)

    2000-01-01

    Space Solar Power is a NASA program sponsored by Marshall Space Flight Center. The Paper presented here represents the architectural study of a large power management and distribution (PMAD) system. The PMAD supplies power to a microwave array for power beaming to an earth rectenna (Rectifier Antenna). The power is in the GW level.

  6. RHOCUBE: 3D density distributions modeling code

    NASA Astrophysics Data System (ADS)

    Nikutta, Robert; Agliozzo, Claudia

    2016-11-01

    RHOCUBE models 3D density distributions on a discrete Cartesian grid and their integrated 2D maps. It can be used for a range of applications, including modeling the electron number density in LBV shells and computing the emission measure. The RHOCUBE Python package provides several 3D density distributions, including a powerlaw shell, truncated Gaussian shell, constant-density torus, dual cones, and spiralling helical tubes, and can accept additional distributions. RHOCUBE provides convenient methods for shifts and rotations in 3D, and if necessary, an arbitrary number of density distributions can be combined into the same model cube and the integration ∫ dz performed through the joint density field.

  7. Probability distribution of the vacuum energy density

    SciTech Connect

    Duplancic, Goran; Stefancic, Hrvoje; Glavan, Drazen

    2010-12-15

    As the vacuum state of a quantum field is not an eigenstate of the Hamiltonian density, the vacuum energy density can be represented as a random variable. We present an analytical calculation of the probability distribution of the vacuum energy density for real and complex massless scalar fields in Minkowski space. The obtained probability distributions are broad and the vacuum expectation value of the Hamiltonian density is not fully representative of the vacuum energy density.

  8. Distributed Space Solar Power

    NASA Technical Reports Server (NTRS)

    Fork, Richard L.

    2001-01-01

    The objective was to assess the feasibility of safely collecting solar power at geostationary orbit and delivering it to earth. A strategy which could harness a small fraction of the millions of gigawatts of sunlight passing near earth could adequately supply the power needs of earth and those of space exploration far into the future. Light collected and enhanced both spatially and temporally in space and beamed to earth provides probably the only practical means of safe and efficient delivery of this space solar power to earth. In particular, we analyzed the feasibility of delivering power to sites on earth at a comparable intensity, after conversion to a usable form, to existing power needs. Two major obstacles in the delivery of space solar power to earth are safety and the development of a source suitable for space. We focused our approach on: (1) identifying system requirements and designing a strategy satisfying current eye and skin safety requirements; and (2) identifying a concept for a potential space-based source for producing the enhanced light.

  9. Power management and distribution technology

    NASA Technical Reports Server (NTRS)

    Dickman, John Ellis

    1993-01-01

    Power management and distribution (PMAD) technology is discussed in the context of developing working systems for a piloted Mars nuclear electric propulsion (NEP) vehicle. The discussion is presented in vugraph form. The following topics are covered: applications and systems definitions; high performance components; the Civilian Space Technology Initiative (CSTI) high capacity power program; fiber optic sensors for power diagnostics; high temperature power electronics; 200 C baseplate electronics; high temperature component characterization; a high temperature coaxial transformer; and a silicon carbide mosfet.

  10. Information Theory and the Earth's Density Distribution

    NASA Technical Reports Server (NTRS)

    Rubincam, D. P.

    1979-01-01

    An argument for using the information theory approach as an inference technique in solid earth geophysics. A spherically symmetric density distribution is derived as an example of the method. A simple model of the earth plus knowledge of its mass and moment of inertia lead to a density distribution which was surprisingly close to the optimum distribution. Future directions for the information theory approach in solid earth geophysics as well as its strengths and weaknesses are discussed.

  11. Passive Microwave Power Distribution Systems.

    DTIC Science & Technology

    wavelength by switching a reciprocal latching ferrite phase shifter in the stub, in response to termination of microwave power from one of the feed tubes....A standby microwave transmitter power amplifier tube is switched into a microwave power distribution system for a phased array in microseconds when...after the switching is completed, the switching being accomplished by changing electrical length of a quarter-wavelength waveguide stub to one-half

  12. Density Distribution of Near Earth Asteroids

    NASA Astrophysics Data System (ADS)

    Dotson, Jessie L.; Mathias, Donovan; Ostrowski, Daniel

    2016-10-01

    The density of near earth asteroids is a fundamental property which can illuminate the structure of the asteroid and is key in assessing the risk of an impact of an NEA with Earth. A low density can be indicative of a rubble pile structure whereas a higher density can imply a monolith and/or a higher metal content. Since the damage resulting from an impact of an asteroid with Earth depends on its interior structure and its total mass, density is a key parameter to understanding the risk of asteroid impact. Unfortunately, measuring the density of asteroids is extremely difficult, has only been attempted for a tiny fraction of NEAs and usually results in measurements with large uncertainties. In the absence of density measurements for a specific object, understanding the range and distribution of likely densities can allow for probabilistic assessment of the ensemble risk of an impact of an NEA and permit estimates of the range of reasonable masses for specific object. We have developed a candidate density distribution for near earth asteroids based on measurements of meteorite densities and an assumed range of macroporosities. Bayesian inference and existing near earth asteroid density measurements are used to develop an updated distribution.

  13. Information theory and the earth's density distribution

    NASA Technical Reports Server (NTRS)

    Rubincam, D. P.

    1978-01-01

    The present paper argues for using the information theory approach as an inference technique in solid earth geophysics. A spherically symmetric density distribution is derived as an example of the method. A simple model of the earth plus knowledge of its mass and moment of inertia leads to a density distribution. Future directions for the information theory approach in solid earth geophysics as well as its strengths and weaknesses are discussed.

  14. Power Law Distribution in Education

    NASA Astrophysics Data System (ADS)

    Gupta, Hari M.; Campanha, José R.; Prado, Fernando D.

    We studied the statistical distribution of candidate's performance which is measured through their marks in university entrance examination (Vestibular) of UNESP (Universidade Estadual Paulista) for years 1998, 1999, and 2000. All students are divided in three groups: Physical, Biological and Humanities. We paid special attention to the examination of Portuguese language which is common for all and examinations for the particular area. We observed long ubiquitous power law tails in Physical and Biological sciences. This indicate the presence of strong positive feedback in sciences. We are able to explain completely these statistical distributions through Gradually Truncated Power law distributions which we developed recently to explain statistical behavior of financial market. The statistical distribution in case of Portuguese language and humanities is close to normal distribution. We discuss the possible reason for this peculiar behavior.

  15. High power density solid oxide fuel cells

    DOEpatents

    Pham, Ai Quoc; Glass, Robert S.

    2004-10-12

    A method for producing ultra-high power density solid oxide fuel cells (SOFCs). The method involves the formation of a multilayer structure cells wherein a buffer layer of doped-ceria is deposited intermediate a zirconia electrolyte and a cobalt iron based electrode using a colloidal spray deposition (CSD) technique. For example, a cobalt iron based cathode composed of (La,Sr)(Co,Fe)O (LSCF) may be deposited on a zirconia electrolyte via a buffer layer of doped-ceria deposited by the CSD technique. The thus formed SOFC have a power density of 1400 mW/cm.sup.2 at 600.degree. C. and 900 mW/cm.sup.2 at 700.degree. C. which constitutes a 2-3 times increased in power density over conventionally produced SOFCs.

  16. Complexity Analysis of Peat Soil Density Distribution

    NASA Astrophysics Data System (ADS)

    Sampurno, Joko; Diah Faryuni, Irfana; Dzar Eljabbar Latief, Fourier; Srigutomo, Wahyu

    2016-08-01

    The distributions of peat soil density have been identified using fractal analysis method. The study was conducted on 5 peat soil samples taken from a ground field in Pontianak, West Kalimantan, at the coordinates (0 ° 4 '2:27 "S, 109 ° 18' 48.59" E). In this study, we used micro computerized tomography (pCT Scanner) at 9.41 micro meter per pixel resolution under peat soil samples to provide 2-D high-resolution images L1-L5 (200 200 pixels) that were used to detect the distribution of peat soil density. The method for determining the fractal dimension and intercept was the 2-D Fourier analysis method. The method was used to obtain the log log-plot of magnitude with frequency. Fractal dimension was obtained from the straight regression line that interpolated the points in the interval with the largest coefficient determination. Intercept defined by the point of intersection on the -axis. The conclusion was that the distributions of peat soil density showing the fractal behaviour with the heterogeneity of the samples from the highest to the lowest were L5, L1, L4, L3 and L2. Meanwhile, the range of density values of the samples from the highest to the lowest was L3, L2, L4, L5 and L1. The study also concluded that the behaviour of the distribution of peat soil density was a weakly anisotropic.

  17. Relationship between input power and power density of SMA spring

    NASA Astrophysics Data System (ADS)

    Park, Cheol Hoon; Ham, Sang Yong; Son, Young Su

    2016-04-01

    The important required characteristics of an artificial muscle for a human arm-like manipulator are high strain and high power density. From this viewpoint, an SMA (shape memory alloy) spring is a good candidate for the actuator of a robotic manipulator that utilizes an artificial muscle. In this study, the maximum power density of an SMA spring was evaluated with respect to the input power. The spring samples were fabricated from SMA wires of different diameters ranging between 0.1 and 0.3 mm. For each diameter, two types of wires with different transition temperatures were used. The relationship between the transition temperature and maximum power density was also evaluated. Each SMA spring was stretched downward by an attached weight and the temperature was increased through the application of an electric current. The displacement, velocity, and temperature of the SMA spring were measured by laser displacement sensors and a thermocouple. Based on the experimental data, it was determined that the maximum power densities of the different SMA springs ranged between 1,300 and 5,500 W/kg. This confirmed the applicability of an SMA spring to human arm-like robotic manipulators. The results of this study can be used as reference for design.

  18. Density distributions of outflow-driven turbulence

    NASA Astrophysics Data System (ADS)

    Moraghan, Anthony; Kim, Jongsoo; Yoon, Suk-Jin

    2013-05-01

    Protostellar jets and outflows are signatures of star formation and promising mechanisms for driving supersonic turbulence in molecular clouds. We quantify outflow-driven turbulence through three-dimensional numerical simulations using an isothermal version of the robust total variation diminishing code. We drive turbulence in real space using a simplified spherical outflow model, analyse the data through density probability distribution functions (PDFs), and investigate the core formation rate per free-fall time (CFRff). The real-space turbulence-driving method produces a negatively skewed density PDF possessing an enhanced tail on the low-density side. It deviates from the log-normal distributions typically obtained from Fourier-space turbulence driving at low densities, but can provide a good fit at high densities, particularly in terms of mass-weighted rather than volume-weighted density PDF. Due to this fact, we suggest that the CFRff determined from a Fourier-driven turbulence model could be comparable to that of our particular real-space-driving model, which has a ratio of solenoidal to compressional components from the resulting turbulence velocity fields of ˜0.6.

  19. Cooling Concepts for High Power Density Magnetic Devices

    NASA Astrophysics Data System (ADS)

    Biela, Juergen; Kolar, Johann W.

    In the area or power electronics there is a general trend to higher power densities. In order to increase the power density the systems must be designed optimally concerning topology, semiconductor selection, etc. and the volume of the components must be decreased. The decreasing volume comes along with a reduced surface for cooling. Consequently, new cooling methods are required. In the paper an indirect air cooling system for magnetic devices which combines the transformer with a heat sink and a heat transfer component is presented. Moreover, an analytic approach for calculating the temperature distribution is derived and validated by measurements. Based on these equations a transformer with an indirect air cooling system is designed for a 10kW telecom power supply.

  20. Central depression of nuclear charge density distribution

    SciTech Connect

    Chu Yanyun; Ren Zhongzhou; Wang Zaijun; Dong Tiekuang

    2010-08-15

    The center-depressed nuclear charge distributions are investigated with the parametrized distribution and the relativistic mean-field theory, and their corresponding charge form factors are worked out with the phase shift analysis method. The central depression of nuclear charge distribution of {sup 46}Ar and {sup 44}S is supported by the relativistic mean-field calculation. According to the calculation, the valence protons in {sup 46}Ar and {sup 44}S prefer to occupy the 1d{sub 3/2} state rather than the 2s{sub 1/2} state, which is different from that in the less neutron-rich argon and sulfur isotopes. As a result, the central proton densities of {sup 46}Ar and {sup 44}S are highly depressed, and so are their central charge densities. The charge form factors of some argon and sulfur isotopes are presented, and the minima of the charge form factors shift upward and inward when the central nuclear charge distributions are more depressed. Besides, the effect of the central depression on the charge form factors is studied with a parametrized distribution, when the root-mean-square charge radii remain constant.

  1. Noise analysis in power distribution systems

    NASA Astrophysics Data System (ADS)

    Danisor, Alin

    2016-12-01

    This paper proposes an analysis, especially in time domain, of the electrical noise existent on the power distribution lines. This study is important for the use of powerlines as a channel of information transmissions. This information may refer to analog signals and as well to digital signals. The main problem addressed in this paper consists in the characterization of the background noise and to establish his statistical proprieties. It is very important to know if the noise induced in the transmission channel is a stationary one, or even an ergodic one. The main parameters like the mean value, the mean square value were determined in this paper. The approximation of the probability density function of each statistical parameter was studied. The pulses induced in the transmission channel by the transient phenomena of the power electrical systems were considered deterministic signals and their contributions were not included in this study.

  2. Fabrication Flaw Density and Distribution in Piping Weldments

    SciTech Connect

    Doctor, Steven R.

    2009-09-01

    The U.S. Nuclear Regulatory Commission supported the Pacific Northwest National Laboratory (PNNL) to develop empirical data on the density and distribution of fabrication flaws in nuclear reactor components. These data are needed to support probabilistic fracture mechanics calculations and studies on component structural integrity. PNNL performed nondestructive examination inspections and destructive testing on archived piping welds to determine the fabrication flaw size and distribution characteristics of the flaws in nuclear power plant piping weldments. Eight different processes and product forms in piping weldments were studied including wrought stainless steel and dissimilar metal weldments. Parametric analysis using an exponential fit was performed on the data. Results were created as a function of the through-wall size of the fabrication flaws as well as the length distribution. The results are compared and contrasted with those developed for reactor pressure vessel processes and product forms. The most significant findings were that the density of fabrication flaws versus through-wall size was higher in piping weldments than that for the reactor pressure vessel weldments, and the density of fabrication flaws versus through-wall size in both reactor pressure vessel weld repairs and piping weldments were greater than the density in the original weldments. Curves showing these distributions are presented.

  3. Simultaneous distribution of AC and DC power

    DOEpatents

    Polese, Luigi Gentile

    2015-09-15

    A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

  4. Quantum Quenches and Work Distributions in Ultralow-Density Systems

    NASA Astrophysics Data System (ADS)

    Shchadilova, Yulia E.; Ribeiro, Pedro; Haque, Masudul

    2014-02-01

    We present results on quantum quenches in lattice systems with a fixed number of particles in a much larger number of sites. Both local and global quenches in this limit generically have power-law work distributions ("edge singularities"). We show that this regime allows for large edge singularity exponents beyond that allowed by the constraints of the usual thermodynamic limit. This large-exponent singularity has observable consequences in the time evolution, leading to a distinct intermediate power-law regime in time. We demonstrate these results first using local quantum quenches in a low-density Kondo-like system, and additionally through global and local quenches in Bose-Hubbard, Aubry-Andre, and hard-core boson systems at low densities.

  5. Power spectral density specifications for high-power laser systems

    SciTech Connect

    Lawson, J.K.; Aikens, D.A.; English, R.E. Jr.; Wolfe, C.R.

    1996-04-22

    This paper describes the use of Fourier techniques to characterize the transmitted and reflected wavefront of optical components. Specifically, a power spectral density, (PSD), approach is used. High power solid-state lasers exhibit non-linear amplification of specific spatial frequencies. Thus, specifications that limit the amplitude of these spatial frequencies are necessary in the design of these systems. Further, NIF optical components have square, rectangular or irregularly shaped apertures with major dimensions up-to 800 mm. Components with non-circular apertures can not be analyzed correctly with Zernicke polynomials since these functions are an orthogonal set for circular apertures only. A more complete and powerful representation of the optical wavefront can be obtained by Fourier analysis in 1 or 2 dimensions. The PSD is obtained from the amplitude of frequency components present in the Fourier spectrum. The shape of a resultant wavefront or the focal spot of a complex multicomponent laser system can be calculated and optimized using PSDs of the individual optical components which comprise the system. Surface roughness can be calculated over a range of spatial scale-lengths by integrating the PSD. Finally, since the optical transfer function (OTF) of the instruments used to measure the wavefront degrades at high spatial frequencies, the PSD of an optical component is underestimated. We can correct for this error by modifying the PSD function to restore high spatial frequency information. The strengths of PSD analysis are leading us to develop optical specifications incorporating this function for the planned National Ignition Facility (NIF).

  6. Computation-distributed probability hypothesis density filter

    NASA Astrophysics Data System (ADS)

    Wang, Junjie; Zhao, Lingling; Su, Xiaohong; Shi, Chunmei; Ma, JiQuan

    2016-12-01

    Particle probability hypothesis density filtering has become a promising approach for multi-target tracking due to its capability of handling an unknown and time-varying number of targets in a nonlinear, non-Gaussian system. However, its computational complexity linearly increases with the number of obtained observations and the number of particles, which can be very time consuming, particularly when numerous targets and clutter exist in the surveillance region. To address this issue, we present a distributed computation particle probability hypothesis density(PHD) filter for target tracking. It runs several local decomposed particle PHD filters in parallel while processing elements. Each processing element takes responsibility for a portion of particles but all measurements and provides local estimates. A central unit controls particle exchange among the processing elements and specifies a fusion rule to match and fuse the estimates from different local filters. The proposed framework is suitable for parallel implementation. Simulations verify that the proposed method can significantly accelerate and maintain a comparative accuracy compared to the standard particle PHD filter.

  7. 47 CFR 25.208 - Power flux density limits.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... flux density at the Earth's surface produced by emissions from a space station for all conditions and... and 10.7-11.7 GHz for NGSO FSS space stations, the power flux-density at the Earth's surface produced... frequency bands, the power flux density at the Earth's surface produced by emissions from a space...

  8. Mobile Centers For Secondary Power Distribution

    NASA Technical Reports Server (NTRS)

    Mears, Robert L.

    1990-01-01

    Concept for distribution of 60-Hz ac power in large building devoted to assembly and testing of equipment improves safety, reduces number of outlets and lengthy cables, and readily accommodates frequent changes in operations and configuration. Power from floor recess fed via unobtrusive cable to portable power management center. A cart containing variety of outlets and circuit breakers, wheeled to convenient location near equipment to be assembled or tested. Power distribution system presents larger range of operational configurations than fixed location. Meets tighter standards to feed computers and delicate instruments. Industrial-grade power suitable for power tools and other hardware. Three-phase and single-phase outlets available from each.

  9. Solar power generation and distribution

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The production of electricity from solar energy is discussed. The economics of the proposed generation and distribution systems are analyzed. The use of photovoltaics for converting solar energy to home heating is proposed. The problems of energy distribution are analyzed from the standpoint of equipment costs and complexity.

  10. Nearly degenerate electron distributions and superluminal radiation densities

    NASA Astrophysics Data System (ADS)

    Tomaschitz, Roman

    2010-02-01

    Polylogarithmic fugacity expansions of the partition function, the caloric and thermal equations of state, and the specific heat of fermionic power-law distributions are derived in the nearly degenerate low-temperature/high-density quantum regime. The spectral functions of an ultra-relativistic electron plasma are obtained by averaging the tachyonic radiation densities of inertial electrons with Fermi power-laws, whose entropy is shown to be extensive and stable. The averaged radiation densities are put to test by performing tachyonic cascade fits to the γ-ray spectrum of the TeV blazar Markarian 421 in a low and high emission state. Estimates of the thermal electron plasma in this active galactic nucleus are extracted from the spectral fits, such as temperature, number count, and internal energy. The tachyonic cascades reproduce the quiescent as well as a burst spectrum of the blazar obtained with imaging atmospheric Cherenkov detectors. Double-logarithmic plots of the differential tachyon flux exhibit intrinsic spectral curvature, caused by the Boltzmann factor of the electron gas.

  11. Noise distribution and denoising of current density images.

    PubMed

    Beheshti, Mohammadali; Foomany, Farbod H; Magtibay, Karl; Jaffray, David A; Krishnan, Sridhar; Nanthakumar, Kumaraswamy; Umapathy, Karthikeyan

    2015-04-01

    Current density imaging (CDI) is a magnetic resonance (MR) imaging technique that could be used to study current pathways inside the tissue. The current distribution is measured indirectly as phase changes. The inherent noise in the MR imaging technique degrades the accuracy of phase measurements leading to imprecise current variations. The outcome can be affected significantly, especially at a low signal-to-noise ratio (SNR). We have shown the residual noise distribution of the phase to be Gaussian-like and the noise in CDI images approximated as a Gaussian. This finding matches experimental results. We further investigated this finding by performing comparative analysis with denoising techniques, using two CDI datasets with two different currents (20 and 45 mA). We found that the block-matching and three-dimensional (BM3D) technique outperforms other techniques when applied on current density ([Formula: see text]). The minimum gain in noise power by BM3D applied to [Formula: see text] compared with the next best technique in the analysis was found to be around 2 dB per pixel. We characterize the noise profile in CDI images and provide insights on the performance of different denoising techniques when applied at two different stages of current density reconstruction.

  12. Thermal-To-Electric Converter With Greater Power Density

    NASA Technical Reports Server (NTRS)

    Williams, Roger M.; Suitor, Jerry W.; Jeffries-Nakamura, Barbara; Underwood, Mark L.; Ryan, Margaret A.; O'Connor, Dennis

    1992-01-01

    Proposed design for alkali-metal thermal-to-electric converter (AMTEC) incorporates refinements to increase power density and reduce input temperature below typical prior design. Converter has compact, planar configuration. Cells stacked densely with remote condenser for thermal efficiency and high power density. Either liquid- or vapor-fed cells utilized. Heat fed-in at lower temperature.

  13. High frequency power distribution system

    NASA Technical Reports Server (NTRS)

    Patel, Mikund R.

    1986-01-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  14. Distribution-Agnostic Stochastic Optimal Power Flow for Distribution Grids

    SciTech Connect

    Baker, Kyri; Dall'Anese, Emiliano; Summers, Tyler

    2016-11-21

    This paper outlines a data-driven, distributionally robust approach to solve chance-constrained AC optimal power flow problems in distribution networks. Uncertain forecasts for loads and power generated by photovoltaic (PV) systems are considered, with the goal of minimizing PV curtailment while meeting power flow and voltage regulation constraints. A data- driven approach is utilized to develop a distributionally robust conservative convex approximation of the chance-constraints; particularly, the mean and covariance matrix of the forecast errors are updated online, and leveraged to enforce voltage regulation with predetermined probability via Chebyshev-based bounds. By combining an accurate linear approximation of the AC power flow equations with the distributionally robust chance constraint reformulation, the resulting optimization problem becomes convex and computationally tractable.

  15. Computer Power: Part 1: Distribution of Power (and Communications).

    ERIC Educational Resources Information Center

    Price, Bennett J.

    1988-01-01

    Discussion of the distribution of power to personal computers and computer terminals addresses options such as extension cords, perimeter raceways, and interior raceways. Sidebars explain: (1) the National Electrical Code; (2) volts, amps, and watts; (3) transformers, circuit breakers, and circuits; and (4) power vs. data wiring. (MES)

  16. High density operation for reactor-relevant power exhaust

    NASA Astrophysics Data System (ADS)

    Wischmeier, M.

    2015-08-01

    With increasing size of a tokamak device and associated fusion power gain an increasing power flux density towards the divertor needs to be handled. A solution for handling this power flux is crucial for a safe and economic operation. Using purely geometric arguments in an ITER-like divertor this power flux can be reduced by approximately a factor 100. Based on a conservative extrapolation of current technology for an integrated engineering approach to remove power deposited on plasma facing components a further reduction of the power flux density via volumetric processes in the plasma by up to a factor of 50 is required. Our current ability to interpret existing power exhaust scenarios using numerical transport codes is analyzed and an operational scenario as a potential solution for ITER like divertors under high density and highly radiating reactor-relevant conditions is presented. Alternative concepts for risk mitigation as well as strategies for moving forward are outlined.

  17. A High Power Density Power System Electronics for NASA's Lunar Reconnaissance Orbiter

    NASA Technical Reports Server (NTRS)

    Hernandez-Pellerano, A.; Stone, R.; Travis, J.; Kercheval, B.; Alkire, G.; Ter-Minassian, V.

    2009-01-01

    A high power density, modular and state-of-the-art Power System Electronics (PSE) has been developed for the Lunar Reconnaissance Orbiter (LRO) mission. This paper addresses the hardware architecture and performance, the power handling capabilities, and the fabrication technology. The PSE was developed by NASA s Goddard Space Flight Center (GSFC) and is the central location for power handling and distribution of the LRO spacecraft. The PSE packaging design manages and distributes 2200W of solar array input power in a volume less than a cubic foot. The PSE architecture incorporates reliable standard internal and external communication buses, solid state circuit breakers and LiIon battery charge management. Although a single string design, the PSE achieves high reliability by elegantly implementing functional redundancy and internal fault detection and correction. The PSE has been environmentally tested and delivered to the LRO spacecraft for the flight Integration and Test. This modular design is scheduled to flight in early 2009 on board the LRO and Lunar Crater Observation and Sensing Satellite (LCROSS) spacecrafts and is the baseline architecture for future NASA missions such as Global Precipitation Measurement (GPM) and Magnetospheric MultiScale (MMS).

  18. Millimeter-wave Line Ratios and Sub-beam Volume Density Distributions

    NASA Astrophysics Data System (ADS)

    Leroy, Adam K.; Usero, Antonio; Schruba, Andreas; Bigiel, Frank; Kruijssen, J. M. Diederik; Kepley, Amanda; Blanc, Guillermo A.; Bolatto, Alberto D.; Cormier, Diane; Gallagher, Molly; Hughes, Annie; Jiménez-Donaire, Maria J.; Rosolowsky, Erik; Schinnerer, Eva

    2017-02-01

    We explore the use of mm-wave emission line ratios to trace molecular gas density when observations integrate over a wide range of volume densities within a single telescope beam. For observations targeting external galaxies, this case is unavoidable. Using a framework similar to that of Krumholz & Thompson, we model emission for a set of common extragalactic lines from lognormal and power law density distributions. We consider the median density of gas that produces emission and the ability to predict density variations from observed line ratios. We emphasize line ratio variations because these do not require us to know the absolute abundance of our tracers. Patterns of line ratio variations have the potential to illuminate the high-end shape of the density distribution, and to capture changes in the dense gas fraction and median volume density. Our results with and without a high-density power law tail differ appreciably; we highlight better knowledge of the probability density function (PDF) shape as an important area. We also show the implications of sub-beam density distributions for isotopologue studies targeting dense gas tracers. Differential excitation often implies a significant correction to the naive case. We provide tabulated versions of many of our results, which can be used to interpret changes in mm-wave line ratios in terms of adjustments to the underlying density distributions.

  19. High thermal power density heat transfer. [thermionic converters

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1980-01-01

    Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. The heat pipe is used to cool the nuclear reactor while the heat pipe is connected thermally and electrically to a thermionic converter. If the receiver requires greater thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparatively low thermal power densities through the electrically non-conducting gap between the two heat pipes.

  20. Electron beam machining using rotating and shaped beam power distribution

    DOEpatents

    Elmer, John W.; O'Brien, Dennis W.

    1996-01-01

    An apparatus and method for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: 1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and 2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1000 .mu.m (1 mm or larger), compared to the 250 .mu.m diameter of laser drilling.

  1. Electron beam machining using rotating and shaped beam power distribution

    DOEpatents

    Elmer, J.W.; O`Brien, D.W.

    1996-07-09

    An apparatus and method are disclosed for electron beam (EB) machining (drilling, cutting and welding) that uses conventional EB guns, power supplies, and welding machine technology without the need for fast bias pulsing technology. The invention involves a magnetic lensing (EB optics) system and electronic controls to: (1) concurrently bend, focus, shape, scan, and rotate the beam to protect the EB gun and to create a desired effective power-density distribution, and (2) rotate or scan this shaped beam in a controlled way. The shaped beam power-density distribution can be measured using a tomographic imaging system. For example, the EB apparatus of this invention has the ability to drill holes in metal having a diameter up to 1,000 {micro}m (1 mm or larger), compared to the 250 {micro}m diameter of laser drilling. 5 figs.

  2. Space Solar Power Management and Distribution (PMAD)

    NASA Technical Reports Server (NTRS)

    Lynch, Thomas H.

    2000-01-01

    This paper presents, in viewgraph form, SSP PMAD (Space Solar Power Management and Distribution). The topics include: 1) Architecture; 2) Backside Thermal View; 3) Solar Array Interface; 4) Transformer design and risks; 5) Twelve phase rectifier; 6) Antenna (80V) Converters; 7) Distribution Cables; 8) Weight Analysis; and 9) PMAD Summary.

  3. Cathode power distribution system and method of using the same for power distribution

    DOEpatents

    Williamson, Mark A; Wiedmeyer, Stanley G; Koehl, Eugene R; Bailey, James L; Willit, James L; Barnes, Laurel A; Blaskovitz, Robert J

    2014-11-11

    Embodiments include a cathode power distribution system and/or method of using the same for power distribution. The cathode power distribution system includes a plurality of cathode assemblies. Each cathode assembly of the plurality of cathode assemblies includes a plurality of cathode rods. The system also includes a plurality of bus bars configured to distribute current to each of the plurality of cathode assemblies. The plurality of bus bars include a first bus bar configured to distribute the current to first ends of the plurality of cathode assemblies and a second bus bar configured to distribute the current to second ends of the plurality of cathode assemblies.

  4. Intelligent Systems for Power Management and Distribution

    NASA Technical Reports Server (NTRS)

    Button, Robert M.

    2002-01-01

    The motivation behind an advanced technology program to develop intelligent power management and distribution (PMAD) systems is described. The program concentrates on developing digital control and distributed processing algorithms for PMAD components and systems to improve their size, weight, efficiency, and reliability. Specific areas of research in developing intelligent DC-DC converters and distributed switchgear are described. Results from recent development efforts are presented along with expected future benefits to the overall PMAD system performance.

  5. Hierarchical distributed stabilization of power networks

    NASA Astrophysics Data System (ADS)

    Ishizaki, Takayuki; Sadamoto, Tomonori; Imura, Jun-ichi

    2014-10-01

    Large fluctuation of electric power due to high penetration of renewable energy sources such as photovoltaic and wind power generation increases the risk to make the whole power network system unstable. The conventional frequency control called load frequency control is based on PID (proportional-integral-derivative) control or more advanced centralized and decentralized/distributed control. If we could more effectively use information on the state of the other neighbor generators, we can expect to make the whole system more robust against the large frequency fluctuation. This paper proposes a fundamental framework towards the design of hierarchical distributed stabilizing controllers for a network of power generators and loads. This novel type of distributed controller, composed of a global controller and a set of local controllers, takes into account the effect of the interaction among the generators and loads to improve robustness for the variation of locally stabilizing controllers.

  6. Advanced Electric Distribution, Switching, and Conversion Technology for Power Control

    NASA Technical Reports Server (NTRS)

    Soltis, James V.

    1998-01-01

    The Electrical Power Control Unit currently under development by Sundstrand Aerospace for use on the Fluids Combustion Facility of the International Space Station is the precursor of modular power distribution and conversion concepts for future spacecraft and aircraft applications. This unit combines modular current-limiting flexible remote power controllers and paralleled power converters into one package. Each unit includes three 1-kW, current-limiting power converter modules designed for a variable-ratio load sharing capability. The flexible remote power controllers can be used in parallel to match load requirements and can be programmed for an initial ON or OFF state on powerup. The unit contains an integral cold plate. The modularity and hybridization of the Electrical Power Control Unit sets the course for future spacecraft electrical power systems, both large and small. In such systems, the basic hybridized converter and flexible remote power controller building blocks could be configured to match power distribution and conversion capabilities to load requirements. In addition, the flexible remote power controllers could be configured in assemblies to feed multiple individual loads and could be used in parallel to meet the specific current requirements of each of those loads. Ultimately, the Electrical Power Control Unit design concept could evolve to a common switch module hybrid, or family of hybrids, for both converter and switchgear applications. By assembling hybrids of a common current rating and voltage class in parallel, researchers could readily adapt these units for multiple applications. The Electrical Power Control Unit concept has the potential to be scaled to larger and smaller ratings for both small and large spacecraft and for aircraft where high-power density, remote power controllers or power converters are required and a common replacement part is desired for multiples of a base current rating.

  7. Thin-film power-density meter for millimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Lee, Karen A.; Guo, Yong; Stimson, Philip A.; Potter, Kent A.; Chiao, Jung-Chih

    1991-01-01

    A quasi-optical power density meter for millimeter and submillimeter wavelengths has been developed. The device is a 2-cm2 thin-film bismuth bolometer deposited on a mylar membrane. The resistance responsivity is 150 Ohms/W, and the time constant is 1 min. The meter is calibrated at DC. The bolometer is much thinner than a wavelength, and can thus be modeled as a lumped resistance in a transmission-line equivalent circuit. The absorption coefficient is 0.5 for 189-Ohms/square film. The power-density meter has been used to measure absolute power densities for millimeter-wave antenna efficiency measurements. Absolute power densities of 0.5 mW/sq cm have been measured to an estimated accuracy of 5 percent.

  8. High volumetric power density, non-enzymatic, glucose fuel cells.

    PubMed

    Oncescu, Vlad; Erickson, David

    2013-01-01

    The development of new implantable medical devices has been limited in the past by slow advances in lithium battery technology. Non-enzymatic glucose fuel cells are promising replacement candidates for lithium batteries because of good long-term stability and adequate power density. The devices developed to date however use an "oxygen depletion design" whereby the electrodes are stacked on top of each other leading to low volumetric power density and complicated fabrication protocols. Here we have developed a novel single-layer fuel cell with good performance (2 μW cm⁻²) and stability that can be integrated directly as a coating layer on large implantable devices, or stacked to obtain a high volumetric power density (over 16 μW cm⁻³). This represents the first demonstration of a low volume non-enzymatic fuel cell stack with high power density, greatly increasing the range of applications for non-enzymatic glucose fuel cells.

  9. High-Power-Density Organic Radical Batteries.

    PubMed

    Friebe, Christian; Schubert, Ulrich S

    2017-02-01

    Batteries that are based on organic radical compounds possess superior charging times and discharging power capability in comparison to established electrochemical energy-storage technologies. They do not rely on metals and, hence, feature a favorable environmental impact. They furthermore offer the possibility of roll-to-roll processing through the use of different printing techniques, which enables the cost-efficient fabrication of mechanically flexible devices. In this review, organic radical batteries are presented with the focus on the hitherto developed materials and the key properties thereof, e.g., voltage, capacity, and cycle life. Furthermore, basic information, such as significant characteristics, housing approaches, and applied additives, are presented and discussed in the context of organic radical batteries.

  10. Anode current density distribution in a cusped field thruster

    SciTech Connect

    Wu, Huan Liu, Hui Meng, Yingchao; Zhang, Junyou; Yang, Siyu; Hu, Peng; Chen, Pengbo; Yu, Daren

    2015-12-15

    The cusped field thruster is a new electric propulsion device that is expected to have a non-uniform radial current density at the anode. To further study the anode current density distribution, a multi-annulus anode is designed to directly measure the anode current density for the first time. The anode current density decreases sharply at larger radii; the magnitude of collected current density at the center is far higher compared with the outer annuli. The anode current density non-uniformity does not demonstrate a significant change with varying working conditions.

  11. Anode current density distribution in a cusped field thruster

    NASA Astrophysics Data System (ADS)

    Wu, Huan; Liu, Hui; Meng, Yingchao; Zhang, Junyou; Yang, Siyu; Hu, Peng; Chen, Pengbo; Yu, Daren

    2015-12-01

    The cusped field thruster is a new electric propulsion device that is expected to have a non-uniform radial current density at the anode. To further study the anode current density distribution, a multi-annulus anode is designed to directly measure the anode current density for the first time. The anode current density decreases sharply at larger radii; the magnitude of collected current density at the center is far higher compared with the outer annuli. The anode current density non-uniformity does not demonstrate a significant change with varying working conditions.

  12. Grid-connected distributed solar power systems

    NASA Astrophysics Data System (ADS)

    Moyle, R.; Chernoff, H.; Schweizer, T.

    This paper discusses some important, though often ignored, technical and economic issues of distributed solar power systems: protection of the utility system and nonsolar customers requires suitable interfaced equipment. Purchase criteria must mirror reality; most analyses use life-cycle costing with low discount rates - most buyers use short payback periods. Distributing, installing, and marketing small, distributed solar systems is more costly than most analyses estimate. Results show that certain local conditions and uncommon purchase considerations can combine to make small, distributed solar power attractive, but lower interconnect costs (per kW), lower marketing and product distribution costs, and more favorable purchase criteria make large, centralized solar energy more attractive. Specifically, the value of dispersed solar systems to investors and utilities can be higher than $2000/kw. However, typical residential owners place a value of well under $1000 on the installed system.

  13. Vibration Monitoring of Power Distribution Poles

    SciTech Connect

    Clark Scott; Gail Heath; John Svoboda

    2006-04-01

    Some of the most visible and least monitored elements of our national security infrastructure are the poles and towers used for the distribution of our nation’s electrical power. Issues surrounding these elements within the United States include safety such as unauthorized climbing and access, vandalism such as nut/bolt removal or destructive small arms fire, and major vandalism such as the downing of power poles and towers by the cutting of the poles with a chainsaw or torches. The Idaho National Laboratory (INL) has an ongoing research program working to develop inexpensive and sensitive sensor platforms for the monitoring and characterization of damage to the power distribution infrastructure. This presentation covers the results from the instrumentation of a variety of power poles and wires with geophone assemblies and the recording of vibration data when power poles were subjected to a variety of stimuli. Initial results indicate that, for the majority of attacks against power poles, the resulting signal can be seen not only on the targeted pole but on sensors several poles away in the distribution network and a distributed sensor system can be used to monitor remote and critical structures.

  14. Specification of optical components using the power spectral density function

    SciTech Connect

    Lawson, J.K.; Wolfe, C.R.; Manes, K.R.; Trenholme, J.B.; Aikens, D.M.; English, R.E. Jr.

    1995-06-20

    This paper describes the use of Fourier techniques to characterize the wavefront of optical components, specifically, the use of the power spectral density, (PSD), function. The PSDs of several precision optical components will be shown. Many of the optical components of interest to us have square, rectangular or irregularly shaped apertures with major dimensions up-to 800 mm. The wavefronts of components with non-circular apertures cannot be analyzed with Zernicke polynomials since these functions are an orthogonal set for circular apertures only. Furthermore, Zernicke analysis is limited to treating low frequency wavefront aberrations; mid-spatial scale and high frequency error are expressed only as ``residuals.`` A more complete and powerful representation of the optical wavefront can be obtained by Fourier analysis in 1 or 2 dimensions. The PSD is obtained from the amplitude of frequency components present in the Fourier spectrum. The PSD corresponds to the scattered intensity as a function of scattering angle in the wavefront and can be used to describe the intensity distribution at focus. The shape of a resultant wavefront or the focal spot of a complex multi-component laser system can be calculated and optimized using the PSDs of individual optical components which comprise it.

  15. Improving Power Density of Free-Piston Stirling Engines

    NASA Technical Reports Server (NTRS)

    Briggs, Maxwell H.; Prahl, Joseph; Loparo, Kenneth

    2016-01-01

    Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58 using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

  16. Improving Power Density of Free-Piston Stirling Engines

    NASA Technical Reports Server (NTRS)

    Briggs, Maxwell H.; Prahl, Joseph M.; Loparo, Kenneth A.

    2016-01-01

    Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free-piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58 percent using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a piston power increase of as much as 14 percent. Analytical predictions are compared to experimental data and show close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

  17. Improving Free-Piston Stirling Engine Power Density

    NASA Technical Reports Server (NTRS)

    Briggs, Maxwell H.

    2016-01-01

    Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58% using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14%. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

  18. Density and Macroporosity Distribution of Near Earth Asteroids

    NASA Astrophysics Data System (ADS)

    Dotson, Jessie L.; Mathias, Donovan

    2017-01-01

    The density of near earth asteroids is a fundamental property which can illuminate the structure of the asteroid, provide clues about it’s collisional history and is key in assessing the hazard of an impact of an NEA with Earth. A low density can be indicative of a rubble pile structure whereas a higher density can imply a monolith and/or a higher metal content. Unfortunately, measuring the density of asteroids is extremely difficult, has only been attempted for a tiny fraction of NEAs and usually results in measurements with large uncertainties. In the absence of density measurements for a specific object, understanding the range and distribution of likely densities can allow for probabilistic assessments of the population and facilitate estimates of the range of reasonable masses for a specific object. We have developed a candidate macroporosity distribution for near earth asteroids based on measurements of meteorite densities and asteroid densities. The macroporosity of an asteroid can be used to aid extrapolation from meteorite physical properties to asteroid physical properties. In addition, we discuss estimating an asteroid density distribution from the macroporosity distribution.

  19. High power density alkali metal thermal to electric converter

    NASA Astrophysics Data System (ADS)

    Sievers, R. K.; Wright, R. F.

    A description is given of the alkali metal thermal-to-electric converter (AMTEC), an emerging technology for static power conversion that has the potential of matching dynamic system efficiency. This high efficiency is produced when cells of beta double prime alumina solid electrolyte (BASE) are series connected, packed in a space-efficient manner, and designed to minimize parasitic heat loss. Design studies have shown that power densities of up to 400 W/kg and efficiencies of up to 35 percent are feasible. This is higher than power densities and efficiencies reported for other AMTEC designs, but continued design studies are necessary to assess applications.

  20. Field line distribution of mass density at geostationary orbit

    NASA Astrophysics Data System (ADS)

    Denton, R. E.; Takahashi, Kazue; Lee, Jimyoung; Zeitler, C. K.; Wimer, N. T.; Litscher, L. E.; Singer, H. J.; Min, Kyungguk

    2015-06-01

    The distribution of mass density along the field lines affects the ratios of toroidal (azimuthally oscillating) Alfvén frequencies, and given the ratios of these frequencies, we can get information about that distribution. Here we assume the commonly used power law form for the field line distribution, ρm = ρm,eq(LRE/R)α, where ρm,eq is the value of the mass density ρm at the magnetic equator, L is the L shell, RE is the Earth's radius, R is the geocentric distance to a point on the field line, and α is the power law coefficient. Positive values of α indicate that ρm increases away from the magnetic equator, zero value indicates that ρm is constant along the magnetic field line, and negative α indicates that there is a local peak in ρm at the magnetic equator. Using 12 years of observations of toroidal Alfvén frequencies by the Geostationary Operational Environmental Satellites, we study the typical dependence of inferred values of α on the magnetic local time (MLT), the phase of the solar cycle as specified by the F10.7 extreme ultraviolet solar flux, and geomagnetic activity as specified by the auroral electrojet (AE) index. Over the mostly dayside range of the observations, we find that α decreases with respect to increasing MLT and F10.7, but increases with respect to increasing AE. We develop a formula that depends on all three parameters, α3Dmodel=2.2+1.3·cos(MLT·15°)+0.0026·AE·cos((MLT-0.8)·15°)+2.1·10-5·AE·F10.7-0.010·F10.7, that models the binned values of α within a standard deviation of 0.3. While we do not yet have a complete theoretical understanding of why α should depend on these parameters in such a way, we do make some observations and speculations about the causes. At least part of the dependence is related to that of ρm,eq; higher α, corresponding to steeper variation with respect to magnetic latitude, occurs when ρm,eq is lower.

  1. Statistical link between the structure of molecular clouds and their density distribution

    NASA Astrophysics Data System (ADS)

    Donkov, Sava; Veltchev, Todor V.; Klessen, Ralf S.

    2017-04-01

    We introduce the concept of a class of equivalence of molecular clouds represented by an abstract spherically symmetric, isotropic object. This object is described by use of abstract scales in respect to a given mass-density distribution. Mass and average density are ascribed to each scale and thus are linked to the density distribution: a power-law type and an arbitrary continuous one. In the latter case, we derive a differential relationship between the mean density at a given scale and the structure parameter that defines the mass-density relationship. The two-dimensional (2D) projection of the cloud along the line of sight is also investigated. Scaling relations of mass and mean density are derived in the considered cases of power-law and arbitrary continuous distributions. We obtain relations between scaling exponents in the 2D and 3D cases. The proposed classes of equivalence are representative for the general structure of real clouds with various types of column-density distributions: power law, lognormal or combination of both.

  2. Inverter design for high frequency power distribution

    NASA Technical Reports Server (NTRS)

    King, R. J.

    1985-01-01

    A class of simple resonantly commutated inverters are investigated for use in a high power (100 KW - 1000 KW) high frequency (10 KHz - 20 KHz) AC power distribution system. The Mapham inverter is found to provide a unique combination of large thyristor turn-off angle and good utilization factor, much better than an alternate 'current-fed' inverter. The effects of loading the Mapham inverter entirely with rectifier loads are investigated by simulation and with an experimental 3 KW 20 KHz inverter. This inverter is found to be well suited to a power system with heavy rectifier loading.

  3. Galileo spacecraft power management and distribution system

    NASA Technical Reports Server (NTRS)

    Detwiler, R. C.; Smith, R. L.

    1990-01-01

    The Galileo PMAD (power management and distribution system) is described, and the design drivers that established the final as-built hardware are discussed. The spacecraft is powered by two general-purpose heat-source-radioisotope thermoelectric generators. Power bus regulation is provided by a shunt regulator. Galileo PMAD distributes a 570-W beginning of mission (BOM) power source to a user complement of some 137 load elements. Extensive use of pyrotechnics requires two pyro switching subassemblies. They initiate 148 squibs which operate the 47 pyro devices on the spacecraft. Detection and correction of faults in the Galileo PMAD is an autonomous feature dictated by requirements for long life and reliability in the absence of ground-based support. Volatile computer memories in the spacecraft command and data system and attitude control system require a continuous source of backup power during all anticipated power bus fault scenarios. Power for the Jupiter Probe is conditioned, isolated, and controlled by a Probe interface subassembly. Flight performance of the spacecraft and the PMAD has been successful to date, with no major anomalies.

  4. Power Management and Distribution System Developed for Thermionic Power Converters

    NASA Technical Reports Server (NTRS)

    Baez, Anastacio N.

    1998-01-01

    A spacecraft solar, bimodal system combines propulsion and power generation into a single integrated system. An Integrated Solar Upper Stage (ISUS) provides orbital transfer capabilities, power generation for payloads, and onboard propulsion to the spacecraft. A key benefit of a bimodal system is a greater payload-to-spacecraft mass ratio resulting in lower launch vehicle requirements. Scaling down to smaller launch vehicles increases space access by reducing overall mission cost. NASA has joined efforts with the Air Force Phillips Laboratory to develop enabling technologies for such a system. The NASA/Air Force bimodal concept uses solar concentrators to focus energy into an integrated power plant. This power plant consists of a graphite core that stores thermal energy within a cavity. An array of thermionic converters encircles the graphite cavity and provides electrical energy conversion functions. During the power generation phase of the bimodal system, the thermionic converters are exposed to the heated cavity and convert the thermal energy to electricity. Near-term efforts of the ISUS bimodal program are focused on a ground demonstration of key technologies in order to proceed to a full space flight test. Thermionic power generation is one key technology of the bimodal concept. Thermionic power converters impose unique operating requirements upon a power management and distribution (PMAD) system design. Single thermionic converters supply large currents at very low voltages. Operating voltages can vary over a range of up to 3 to 1 as a function of operating temperature. Most spacecraft loads require regulated 28-volts direct-current (Vdc) power. A combination of series-connected converters and powerprocessing boosters is required to deliver power to the spacecraft's payloads at this level.

  5. Improving power density and efficiency of miniature radioisotopic thermoelectric generators

    NASA Astrophysics Data System (ADS)

    Whalen, Scott A.; Apblett, Christopher A.; Aselage, Terrence L.

    We have built and tested a prototype miniaturized thermoelectric power source that generates 450 μW of electrical power in a system volume of 4.3 cm 3. The measured power density of 104 μW cm -3 exceeds that of any previously reported thermoelectric power system of equivalent size. This improvement was achieved by implementing a novel thermopile design in which wagon wheel-shaped thermoelectric elements contact the entire circumference of the heat source whereas traditional approaches utilize only one heat source surface. The thermopile consists of 22 wagon wheel-shaped elements (11 P-N thermocouples) fabricated from 215-μm thick bismuth-telluride wafers having ZT = 0.97 at 30 °C. The power source operates on a 150 mW thermal input provided by an electrical resistance heater that simulates a capsule containing 0.4 g of 238PuO 2 located at the center of the device. Our primary research objective was to develop and demonstrate a prototype thermopile and radioisotopic thermoelectric generator (RTG) architecture with improved power density at small scales. Output power from this device, while optimized for efficiency, was not optimized for output voltage, and the maximum power was delivered at 41 mV. We also discuss modifications to our prototype design that result in significantly improved voltage and power. Numerical predictions show that a power output of 1.4 mW, power density of 329 μW cm -3, and voltage of 362 mV, is possible in the same package size.

  6. Real time two-dimensional spatial distribution measurement method of electron temperature and plasma density

    NASA Astrophysics Data System (ADS)

    Kim, Young Cheol; Jang, Sung Ho; Kim, Gun Ho; Chung, Chin Wook

    2009-10-01

    Real time two-dimensional spatial distribution measurement method of electron temperature and plasma density was developed. It is based on a floating probe method [1] because the floating probe has high time resolution. Two-dimensional array of sensors on a 300 mm diameter wafer-shaped printed circuit board (PCB) and a high speed multiplexer circuit were used for real time distribution measurement. The method was tested at various powers and pressures, spatial distributions of the electron temperature and the plasma density could be obtained. And in the measurement results, asymmetric plasma density distributions caused by pumping port effect could be observed. This method can measure spatial distribution of plasma parameters on the wafer in real time without plasma perturbation, therefore it will be expected to improve the uniformity of processing plasmas such as etching and deposition. [4pt] [1] M. H. Lee, S. H. Jang, C. W. Chung, J. Appl. Phys. 101, 033305 (2007).

  7. Uncertainty evaluation in BEACON power distribution monitoring

    SciTech Connect

    Morita, T.; Goldstein, N.P. )

    1989-11-01

    BEACON is an advanced operational core support package that has a three-dimensional nodal code as its cornerstone. The three-dimensional calculation includes all necessary pressurized water reactor feedback effects. The generation of the measured power distribution from the core instrumentation is one of the primary functions of the core-monitoring software. The purpose of this paper is to discuss evaluation of the uncertainty in the measured assembly power from the BEACON system. The study covers not only the normal operating conditions, but off-normal situations to demonstrate BEACON's applicability for that condition.

  8. Distributed Wireless Power Transfer With Energy Feedback

    NASA Astrophysics Data System (ADS)

    Lee, Seunghyun; Zhang, Rui

    2017-04-01

    Energy beamforming (EB) is a key technique for achieving efficient radio-frequency (RF) transmission enabled wireless energy transfer (WET). By optimally designing the waveforms from multiple energy transmitters (ETs) over the wireless channels, they can be constructively combined at the energy receiver (ER) to achieve an EB gain that scales with the number of ETs. However, the optimal design of EB waveforms requires accurate channel state information (CSI) at the ETs, which is challenging to obtain practically, especially in a distributed system with ETs at separate locations. In this paper, we study practical and efficient channel training methods to achieve optimal EB in a distributed WET system. We propose two protocols with and without centralized coordination, respectively, where distributed ETs either sequentially or in parallel adapt their transmit phases based on a low-complexity energy feedback from the ER. The energy feedback only depends on the received power level at the ER, where each feedback indicates one particular transmit phase that results in the maximum harvested power over a set of previously used phases. Simulation results show that the two proposed training protocols converge very fast in practical WET systems even with a large number of distributed ETs, while the protocol with sequential ET phase adaptation is also analytically shown to converge to the optimal EB design with perfect CSI by increasing the training time. Numerical results are also provided to evaluate the performance of the proposed distributed EB and training designs as compared to other benchmark schemes.

  9. Relativity, nonextensivity, and extended power law distributions.

    PubMed

    Silva, R; Lima, J A S

    2005-11-01

    A proof of the relativistic theorem by including nonextensive effects is given. As it happens in the nonrelativistic limit, the molecular chaos hypothesis advanced by Boltzmann does not remain valid, and the second law of thermodynamics combined with a duality transformation implies that the parameter lies on the interval [0,2]. It is also proven that the collisional equilibrium states (null entropy source term) are described by the relativistic power law extension of the exponential Juttner distribution which reduces, in the nonrelativistic domain, to the Tsallis power law function. As a simple illustration of the basic approach, we derive the relativistic nonextensive equilibrium distribution for a dilute charged gas under the action of an electromagnetic field . Such results reduce to the standard ones in the extensive limit, thereby showing that the nonextensive entropic framework can be harmonized with the space-time ideas contained in the special relativity theory.

  10. 40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., power density, and maximum in-use engine speed. 1042.140 Section 1042.140 Protection of Environment... Maximum engine power, displacement, power density, and maximum in-use engine speed. This section describes how to determine the maximum engine power, displacement, and power density of an engine for...

  11. Density-noise power fluctuations in vibrated granular media

    NASA Astrophysics Data System (ADS)

    Nowak, E. R.; Grushin, A.; Barnum, A. C.; Weissman, M. B.

    2001-02-01

    The noise power spectra of the fluctuations in density of a vibrated column of granular material are found to be time dependent. Spectral analysis of these noise power fluctuations shows nontrivial frequency dependences. The noise powers at different frequencies are also found to fluctuate in a partially correlated way. In most instances, the slow variations of the noise are strongly correlated over a broad range of frequencies. These results indicate that highly cooperative interactions exist between fluctuators. In contrast, effects of such strongly coupled fluctuators are absent in the one-dimensional parking-lot-model, one of the simplest systems used to provide a model for recent granular compaction experiments.

  12. Density Distributions in TATB Prepared by Various Methods

    SciTech Connect

    Hoffman, D M; Fontes, A T

    2008-05-13

    The density distribution of two legacy types of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) particles were compared with TATB synthesized by new routes and recrystallized in several different solvents using a density gradient technique. Legacy wet (WA) and dry aminated (DA) TATB crystalline aggregates gave average densities of 1.9157 and 1.9163 g/cc, respectively. Since the theoretical maximum density (TMD) for a perfect crystal is 1.937 g/cc, legacy TATB crystals averaged 99% of TMD or about 1% voids. TATB synthesized from phloroglucinol (P) had comparable particle size to legacy TATBs, but significantly lower density, 1.8340 g/cc. TATB synthesized from 3,5 dibromoanisole (BA) was very difficult to measure because it contained extremely fine particles, but had an average density of 1.8043 g/cc over a very broad range. Density distributions of TATB recrystallized from dimethylsulfoxide (DMSO), sulfolane, and an 80/20 mixture of DMSO with the ionic liquid 1-ethyl-3-methyl- imidazolium acetate (EMImOAc), with some exceptions, gave average densities comparable or better than the legacy TATBs.

  13. High volumetric power density, non-enzymatic, glucose fuel cells

    PubMed Central

    Oncescu, Vlad; Erickson, David

    2013-01-01

    The development of new implantable medical devices has been limited in the past by slow advances in lithium battery technology. Non-enzymatic glucose fuel cells are promising replacement candidates for lithium batteries because of good long-term stability and adequate power density. The devices developed to date however use an “oxygen depletion design” whereby the electrodes are stacked on top of each other leading to low volumetric power density and complicated fabrication protocols. Here we have developed a novel single-layer fuel cell with good performance (2 μW cm−2) and stability that can be integrated directly as a coating layer on large implantable devices, or stacked to obtain a high volumetric power density (over 16 μW cm−3). This represents the first demonstration of a low volume non-enzymatic fuel cell stack with high power density, greatly increasing the range of applications for non-enzymatic glucose fuel cells. PMID:23390576

  14. Electroweak charge density distributions with parity-violating electron scattering

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Ren, Zhongzhou; Xu, Chang; Xu, Renli

    2013-11-01

    Parity-violating electron scattering (PVS) is an accurate and model-independent way to investigate the weak-charge density distributions of nuclei. In this paper, we study parity-violating electron scattering with the Helm model where the effects of spin-orbit currents on nuclear weak skins are taken into account. The conditions of two PVS measurements to constrain the surface thickness σW of Helm weak-charge densities are investigated. According to the plane wave Born approximation, Apv is expressed in terms of parameters of the corresponding Helm charge and weak-charge densities. After fitting the results of Apv calculated from the phase-shift analysis method where the Coulomb distortion effects are incorporated, an empirical formula in terms of Helm model parameters for calculating Apv is obtained. If two PVS measurements with different scattering angles are carried out, the modeled weak-charge density distributions with two parameters could be extracted from this empirical formula.

  15. Increased power density from a spiral wound microbial fuel cell.

    PubMed

    Jia, Boyang; Hu, Dawei; Xie, Beizhen; Dong, Kun; Liu, Hong

    2013-03-15

    Using Microbial fuel cell (MFC) to convert organic and inorganic matter into electricity is of great interest for powering portable devices, which is now still limited by the output of MFC. In this study, a spiral wound MFC (SWMFC) with relatively large volume normalized surface area of separator (4.2 cm(2)/ml) was fabricated to enhance power generation. Compared with double-membrane MFC (DMMFC) and conventional double chamber MFC (DCMFC), the power density of SWMFC increased by 42% and 99% resulted from its lower internal resistance. Besides larger separator area, the better performance of SWMFC benefited from its structure sandwiching the cathodes between two separators. This point was proved again by a comparison of another DCMFC and a triple chamber MFC (TCMFC) as well as a simulation using finite element method. Moreover, the feature of SWMFC was more convenient and compact to scale up. Therefore, SWMFC provides a promising configuration for high power output as a portable power source.

  16. Nonparametric Estimation of Distribution and Density Functions with Applications.

    DTIC Science & Technology

    1982-05-01

    have been used: kurtosis, Hogg’s Q statistic, and percentile ratios. Applications of the discriminants in parametric estimation problem can be found...particularly in the sense of parametric estimation (Ref 108). Reiss proposes minimum distance estimators of unimodal densities. He proves consistency and...in distribution and density estimation, and goodness of fit testing. 129 The next chapter will venture into the realm of parametric estimation using

  17. Electrical power systems for distributed generation

    SciTech Connect

    Robertson, T.A.; Huval, S.J.

    1996-12-31

    {open_quotes}Distributed Generation{close_quotes} has become the {open_quotes}buzz{close_quotes} word of an electric utility industry facing deregulation. Many industrial facilities utilize equipment in distributed installations to serve the needs of a thermal host through the capture of exhaust energy in a heat recovery steam generator. The electrical power generated is then sold as a {open_quotes}side benefit{close_quotes} to the cost-effective supply of high quality thermal energy. Distributed generation is desirable for many different reasons, each with unique characteristics of the product. Many years of experience in the distributed generation market has helped Stewart & Stevenson to define a range of product features that are crucial to most any application. The following paper will highlight a few of these applications. The paper will also examine the range of products currently available and in development. Finally, we will survey the additional services offered by Stewart & Stevenson to meet the needs of a rapidly changing power generation industry.

  18. Calculated CIM Power Distributions for Coil Design

    SciTech Connect

    Hardy, B.J.

    1999-02-17

    Excessive bed expansion and material expulsion have occurred during experiments with the 3-inch diameter Cylindrical Induction Melter (CIM). Both events were attributed in part to the high power density in the bottom of the melter and the correspondingly high temperatures there. It is believed that the high temperatures resulted in the generation of gasses at the bottom of the bed which could not escape. The gasses released during heating and the response of the bed to gas evolution depend upon the composition of the bed.

  19. Retrieval of plasmaspheric He+ density distributions from EUV imaging data

    NASA Astrophysics Data System (ADS)

    Keika, K.; Brandt, P. C.; Toigo, A. D.; Demajistre, R.

    2013-12-01

    We retrieve the He+ density distribution in the plasmasphere from EUV imaging data, by using a forward modeling technique. We use a parametric model for the density distribution to simulate line-of-sight integrated He+ densities (i.e., EUV images), and then find parameters that give the best fit to real EUV images. The He+ density (nHe+) distribution is described as a function of radial distance (r) and L: nHe+ = n0 (L0/L)^α_L * (r0L/rL0)^α_f, where n0 and L0 are He+ density and L value at the inner boundary of this model (i.e., the topside ionosphere), and α_L and α_f are parameters that represent L and field-aligned dependence of He+ density, respectively. We evaluated how well our forward model can retrieve the He+ density distribution, by performing the following analysis. (1) EUV emission intensities were simulated through the EUV camera response function, given a vantage point of the IMAGE satellite. (2) EUV images were simulated for a large number of (α_L, α_f) pairs: α_L was chosen from 4.0 to 6.0 with 0.1 increment, and α_f was from 0.0 to 2.0 with 0.1 increment. (3) The EUV image corresponding to the (α_L, α_f)=(5.0, 1.0) pair was chosen as our synthetic EUV image. After noise was added to the synthetic image, the forward modeling was applied to all simulated images made in (2). The reduced chi2 (rchi2) was used to determine how well simulated image data fit to the synthetic image. The results of this analysis confirm that the He+ density distributions can be retrieved with good certainty within |40 deg.| MLAT. However, beyond this magnetic latitude it is difficult to determine the L dependence or field-aligned dependence of plasmaspheric He+ density. For further evaluation and better accuracy, we use density distributions provided by physics-based ionosphere/plasmasphere models as our synthetic data. We also apply our forward simulation model to real EUV image data from the EUV imager onboard IMAGE.

  20. Power distribution for an Am/Cm bushing melter

    SciTech Connect

    Gong, C.; Hardy, B.J.

    1996-12-31

    Decades of nuclear material production at the Savannah River Site (SRS) has resulted in the generation of large quantities of the isotopes Am{sup 243} and Cm{sup 244}. Currently, the Am and Cm isotopes are stored as a nitric acid solution in a tank. The Am and Cm isotopes have great commercial value but must be transferred to ORNL for processing. The nitric acid solution contains other isotopes and is intensely radioactive, which makes storage a problem and precludes shipment in the liquid form. In order to stabilize the material for onsite storage and to permit transport the material from SRS to ORNL, it has been proposed that the Am and Cm be separated from other isotopes in the solution and vitrified. Vitrification will be effected by depositing a liquid feed stream containing the isotopes in solution, together with a stream of glass frit, onto the top of a molten glass pool in a melter. The glass is non-conducting and the melter is a Platinum/Rhodium alloy vessel which is heated by passing an electric current through it. Because most of the power is required to evaporate the liquid feed at the top of the glass pool, power demands differ for the upper and lower parts of the melter. In addition, the melter is batch fed so that the local power requirements vary with time. In order to design a unique split power supply, which ensures adequate local power delivery, an analysis of the melter power distribution was performed with the ABAQUS finite element code. ABAQUS was used to calculate the electric potential and current density distributions in the melter for a variety of current and potential boundary conditions. The results of the calculation were compared with test data and will be used to compute power densities for input to a computational fluid dynamics model for the melter.

  1. Study of nuclear matter density distributions using hadronic probes

    SciTech Connect

    Kohama, Akihisa; Iida, Kei; Oyamatsu, Kazuhiro

    2011-05-06

    We briefly review our formula for a proton-nucleus total reaction cross section, {sigma}{sub R}, constructed in the black-sphere approximation of nuclei, in which a nucleus is viewed as a 'black' sphere of radius 'a'. Some years ago, using the Glauber model, one of the authors (A.K.) and his collaborators performed numerical simulations to examine the possibility to probe the nuclear matter density distributions of neutron-rich unstable nuclei from proton elastic scatterings 'model-independently'. The present study is another attempt to seek a 'model-independent' framework for systematically analyzing scattering data for studying the matter density distributions of atomic nuclei.

  2. Electron density and parallel electric field distribution of the auroral density cavity

    NASA Astrophysics Data System (ADS)

    Alm, L.; Marklund, G. T.; Karlsson, T.

    2015-11-01

    We present an event study in which Cluster satellites C1 and C3 encounters the flux tube of a stable auroral arc in the premidnight sector. C1 observes the midcavity, while C3 enters the flux tube of the auroral arc at an altitude which is below the acceleration region, before crossing into the top half of the acceleration region. This allows us to study the boundary between the ionosphere and the density cavity, as well as large portion of the upper density cavity. The position of the two satellites, in relation to the acceleration region, is described using a pseudo altitude derived from the distribution of the parallel potential drop above and below the satellites. The electron density exhibits an anticorrelation with the pseudo altitude, indicating that the lowest electron densities are found near the top of the density cavity. Over the entire pseudo altitude range, the electron density distribution is similar to a planar sheath, formed out of a plasma sheet dominated electron distribution, in response to the parallel electric field of the acceleration region. This indicates that the parallel electric fields on the ionosphere-cavity boundary, as well as the midcavity parallel electric fields, are part of one unified structure rather than two discrete entities. The results highlight the strong connection between the auroral density cavity and auroral acceleration as well as the necessity of studying them in a unified fashion.

  3. A Piezoelectric Micropump Using Resonance Drive with High Power Density

    NASA Astrophysics Data System (ADS)

    Park, Jung-Ho; Yokota, Shinichi; Yoshida, Kazuhiro

    As fluid power sources mounted on practical and powerful micromachines such as in-pipe working micromachines using fluid power, micropumps having high power density are required. A piezoelectric micropump using resonance drive is proposed and developed. First, a large model of the proposed micropump is fabricated and the effectiveness of resonance drive is confirmed through basic experiments. Second, a micropump having the size of 9mm diameter and 10mm length for practical applications is fabricated. Next, frequency characteristics and load characteristics of the pressure-dependent flow rate are experimentally investigated with various structural parameters for the optimal design. Through those experiments, the optimal amounts of additional mass and valve thickness are experimentally obtained for stable and high performance of the micropump. The maximum flow rate of 80mm3/s, maximum pumping pressure of 0.32MPa and maximum power of 8.7mW are obtained at the driving frequency of 2.0kHz. Finally, the feasibility of developing the piezoelectric micropump using resonance drive is confirmed through comparisons of maximum power density among conventional micropumps.

  4. Longitudinal Differences of Ionospheric Vertical Density Distribution and Equatorial Electrodynamics

    NASA Technical Reports Server (NTRS)

    Yizengaw, E.; Zesta, E.; Moldwin, M. B.; Damtie, B.; Mebrahtu, A.; Valledares, C.E.; Pfaff, R. F.

    2012-01-01

    Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian approx. 37 deg and 290 deg E, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation

  5. High Energy Density Sciences with High Power Lasers at SACLA

    NASA Astrophysics Data System (ADS)

    Kodama, Ryosuke

    2013-10-01

    One of the interesting topics on high energy density sciences with high power lasers is creation of extremely high pressures in material. The pressures of more than 0.1 TPa are the energy density corresponding to the chemical bonding energy, resulting in expectation of dramatic changes in the chemical reactions. At pressures of more than TPa, most of material would be melted on the shock Hugoniot curve. However, if the temperature is less than 1eV or lower than a melting point at pressures of more than TPa, novel solid states of matter must be created through a pressured phase transition. One of the interesting materials must be carbon. At pressures of more than TPa, the diamond structure changes to BC and cubic at more than 3TPa. To create such novel states of matter, several kinds of isentropic-like compression techniques are being developed with high power lasers. To explore the ``Tera-Pascal Science,'' now we have a new tool which is an x-ray free electron laser as well as high power lasers. The XFEL will clear the details of the HED states and also efficiently create hot dense matter. We have started a new project on high energy density sciences using an XFEL (SACLA) in Japan, which is a HERMES (High Energy density Revolution of Matter in Extreme States) project.

  6. Microwave Driven Actuators Power Allocation and Distribution

    NASA Technical Reports Server (NTRS)

    Forbes, Timothy; Song, Kyo D.

    2000-01-01

    Design, fabrication and test of a power allocation and distribution (PAD) network for microwave driven actuators is presented in this paper. Development of a circuit that would collect power from a rectenna array amplify and distribute the power to actuators was designed and fabricated for space application in an actuator array driven by a microwave. A P-SPICE model was constructed initially for data reduction purposes, and was followed by a working real-world model. A voltage up - converter (VUC) is used to amplify the voltage from the individual rectenna. The testing yielded a 26:1 voltage amplification ratio with input voltage at 9 volts and a measured output voltage 230VDC. Future work includes the miniaturization of the circuitry, the use of microwave remote control, and voltage amplification technology for each voltage source. The objective of this work is to develop a model system that will collect DC voltage from an array of rectenna and propagate the voltage to an array of actuators.

  7. Power Requirements Determined for High-Power-Density Electric Motors for Electric Aircraft Propulsion

    NASA Technical Reports Server (NTRS)

    Johnson, Dexter; Brown, Gerald V.

    2005-01-01

    Future advanced aircraft fueled by hydrogen are being developed to use electric drive systems instead of gas turbine engines for propulsion. Current conventional electric motor power densities cannot match those of today s gas turbine aircraft engines. However, if significant technological advances could be made in high-power-density motor development, the benefits of an electric propulsion system, such as the reduction of harmful emissions, could be realized.

  8. Nanostructured thin solid oxide fuel cells with high power density.

    PubMed

    Ignatiev, Alex; Chen, Xin; Wu, Naijuan; Lu, Zigui; Smith, Laverne

    2008-10-28

    Nanostructured thin film solid oxide fuel cells (SOFC) have been developed for reduced temperature operation, with high power density, and to be self reforming. A thin film electrolyte (1-2 microm thickness), e.g., yttria-stabilized zirconia (YSZ), is deposited on a nickel foil substrate. The electrolyte thin film is polycrystalline when deposited on a polycrystalline nickel foil substrate, and is (100) textured when deposited on an atomically textured nickel foil substrate. The Ni foil substrate is then converted into a porous SOFC anode by photolithographic patterning and etching to develop porosity. A composite La(0.5)Sr(0.5)CoO(3) cathode is then deposited on the thin film electrolyte. The resultant thin film hetero structure fuel cells have operated at a significantly reduced temperature: as low as 470 degrees C, with a maximum power density of 140 mW cm(-2) at 575 degrees C, and an efficiency of >50%. This drastic reduction in operating temperature for an SOFC now also allows for the use of hydrocarbon fuels without the need for a separate reformer as the nickel anode effectively dissociates hydrocarbons within this temperature range. These nanostructured fuel cells show excellent potential for high power density, small volume, high efficiency fuel cells for power generation applications.

  9. Thermodynamic, energy efficiency, and power density analysis of reverse electrodialysis power generation with natural salinity gradients.

    PubMed

    Yip, Ngai Yin; Vermaas, David A; Nijmeijer, Kitty; Elimelech, Menachem

    2014-05-06

    Reverse electrodialysis (RED) can harness the Gibbs free energy of mixing when fresh river water flows into the sea for sustainable power generation. In this study, we carry out a thermodynamic and energy efficiency analysis of RED power generation, and assess the membrane power density. First, we present a reversible thermodynamic model for RED and verify that the theoretical maximum extractable work in a reversible RED process is identical to the Gibbs free energy of mixing. Work extraction in an irreversible process with maximized power density using a constant-resistance load is then examined to assess the energy conversion efficiency and power density. With equal volumes of seawater and river water, energy conversion efficiency of ∼ 33-44% can be obtained in RED, while the rest is lost through dissipation in the internal resistance of the ion-exchange membrane stack. We show that imperfections in the selectivity of typical ion exchange membranes (namely, co-ion transport, osmosis, and electro-osmosis) can detrimentally lower efficiency by up to 26%, with co-ion leakage being the dominant effect. Further inspection of the power density profile during RED revealed inherent ineffectiveness toward the end of the process. By judicious early discontinuation of the controlled mixing process, the overall power density performance can be considerably enhanced by up to 7-fold, without significant compromise to the energy efficiency. Additionally, membrane resistance was found to be an important factor in determining the power densities attainable. Lastly, the performance of an RED stack was examined for different membrane conductivities and intermembrane distances simulating high performance membranes and stack design. By thoughtful selection of the operating parameters, an efficiency of ∼ 37% and an overall gross power density of 3.5 W/m(2) represent the maximum performance that can potentially be achieved in a seawater-river water RED system with low

  10. Calculated power distribution of a thermionic, beryllium oxide reflected, fast-spectrum reactor

    NASA Technical Reports Server (NTRS)

    Mayo, W.; Lantz, E.

    1973-01-01

    A procedure is developed and used to calculate the detailed power distribution in the fuel elements next to a beryllium oxide reflector of a fast-spectrum, thermionic reactor. The results of the calculations show that, although the average power density in these outer fuel elements is not far from the core average, the power density at the very edge of the fuel closest to the beryllium oxide is about 1.8 times the core avearge.

  11. Power system operations: State estimation distributed processing

    NASA Astrophysics Data System (ADS)

    Ebrahimian, Mohammad Reza

    We present an application of a robust and fast parallel algorithm to power system state estimation with minimal amount of modifications to existing state estimators presently in place using the Auxiliary Problem Principle. We demonstrate its effectiveness on IEEE test systems, the Electric Reliability Counsel of Texas (ERCOT), and the Southwest Power Pool (SPP) systems. Since state estimation formulation may lead to an ill-conditioned system, we provide analytical explanations of the effects of mixtures of measurements on the condition of the state estimation information matrix. We demonstrate the closeness of the analytical equations to condition of several test case systems including IEEE RTS-96 and IEEE 118 bus systems. The research on the condition of the state estimation problem covers the centralized as well as distributed state estimation.

  12. Nonuniform distribution of collagen density in human knee ligaments.

    PubMed

    Mommersteeg, T J; Blankevoort, L; Kooloos, J G; Hendriks, J C; Kauer, J M; Huiskes, R

    1994-03-01

    It is generally recognized that the mechanical properties of soft connective tissues are affected by their structural components. We documented collagen density distributions in human knee ligaments to quantify differences in density within and between these ligaments. In order to explain the variations in mechanical properties within and between different knee ligaments as described in the literature, the distributions of collagen density were correlated with these biomechanical findings. Human knee ligaments were shown to be nonhomogeneous structures with regard to collagen density. The anterior bundles of all ligaments contained significantly more collagen mass per unit of volume than the posterior bundles did. The percentage differences between the anterior and posterior bundles, in relation to the posterior bundles, were about 25% for the anterior cruciate ligament (ACL) and the collateral ligaments and about 10% for the posterior cruciate ligament (PCL). Along the cruciate ligaments, the central segments had higher collagen densities than did segments adjacent to the ligament insertions (ACL 9%, PCL 24%). The collagen density in the ACL was significantly lower than that in the other ligaments. These variations within and between the ligaments correlate well with the variations in mechanical properties described in the literature; however, other structural differences have to be taken into account to fully explain the variations in mechanical properties from the structural components.

  13. Evolving molecular cloud structure and the column density probability distribution function

    NASA Astrophysics Data System (ADS)

    Ward, Rachel L.; Wadsley, James; Sills, Alison

    2014-12-01

    The structure of molecular clouds can be characterized with the probability distribution function (PDF) of the mass surface density. In particular, the properties of the distribution can reveal the nature of the turbulence and star formation present inside the molecular cloud. In this paper, we explore how these structural characteristics evolve with time and also how they relate to various cloud properties as measured from a sample of synthetic column density maps of molecular clouds. We find that, as a cloud evolves, the peak of its column density PDF will shift to surface densities below the observational threshold for detection, resulting in an underlying lognormal distribution which has been effectively lost at late times. Our results explain why certain observations of actively star-forming, dynamically older clouds, such as the Orion molecular cloud, do not appear to have any evidence of a lognormal distribution in their column density PDFs. We also study the evolution of the slope and deviation point of the power-law tails for our sample of simulated clouds and show that both properties trend towards constant values, thus linking the column density structure of the molecular cloud to the surface density threshold for star formation.

  14. Distributed Power Electronics for PV Systems (Presentation)

    SciTech Connect

    Deline, C.

    2011-12-01

    An overview of the benefits and applications of microinverters and DC power optimizers in residential systems. Some conclusions from this report are: (1) The impact of shade is greater than just the area of shade; (2) Additional mismatch losses include panel orientation, panel distribution, inverter voltage window, soiling; (3) Per-module devices can help increase performance, 4-12% or more depending on the system; (4) Value-added benefits (safety, monitoring, reduced design constraints) are helping their adoption; and (5) The residential market is growing rapidly. Efficiency increases, cost reductions are improving market acceptance. Panel integration will further reduce price and installation cost. Reliability remains an unknown.

  15. Interaction of lightning with power distribution lines

    NASA Astrophysics Data System (ADS)

    Mata, Carlos Tomas

    Triggered-lightning experiments were conducted in 1996, 1999, and 2000 to study the responses of overhead power distribution lines to lightning at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida. The lightning was artificially initiated (triggered) from natural thunderclouds using the rocket-and-wire technique, and its current was directed to a phase conductor at midspan or at a pole near the center of the line. Experimental results and associated EMTP modeling are presented in this dissertation for the following line configurations: (1)a two-conductor, 740-m overhead distribution line with 2 arrester stations in 1996; (2)a four- conductor, 245-m overhead distribution line with 2 arrester stations in 1999; and (3)a four-conductor, 829-m overhead distribution line with 6 arrester stations in 2000. The three-phase lines tested in 1999 and 2000 were standard designs of a major Florida power company. Lightning peak currents injected into the lines ranged from 7 to 57 kA. Voltages and currents were measured at various locations along the line. Video and photographic cameras were used to image lightning channels and detect line flashovers. The significant results of the research are (1)flashovers between conductors were observed, both accompanied and not accompanied by arrester failures, (2)an arrester failed on seven of eight direct lightning strikes to the line in 2000, (3)arcing between conductors may prevent failures of arresters connected to the struck phase, (4)the bulk of the lightning current flows from the struck phase to neutral through the arresters closest to the strike point, (5)the withstand energy of the arresters can be exceeded due to the contribution from multiple strokes and/or relatively low-level, long-lasting current components, (6)the distribution of charge transferred to ground among multiple neutral grounds, which is determined by low-frequency, low-current grounding resistances is different from the

  16. Structure Learning in Power Distribution Networks

    SciTech Connect

    Deka, Deepjyoti; Chertkov, Michael; Backhaus, Scott N.

    2015-01-13

    Traditionally power distribution networks are either not observable or only partially observable. This complicates development and implementation of new smart grid technologies, such as these related to demand response, outage detection and management, and improved load-monitoring. Here, inspired by proliferation of the metering technology, we discuss statistical estimation problems in structurally loopy but operationally radial distribution grids consisting in learning operational layout of the network from measurements, e.g. voltage data, which are either already available or can be made available with a relatively minor investment. Our newly suggested algorithms apply to a wide range of realistic scenarios. The algorithms are also computationally efficient – polynomial in time – which is proven theoretically and illustrated computationally on a number of test cases. The technique developed can be applied to detect line failures in real time as well as to understand the scope of possible adversarial attacks on the grid.

  17. Fuel areal density distributions derived from nuclear scattering signatures

    NASA Astrophysics Data System (ADS)

    Bionta, R. M.; Casey, D. T.; Cerjan, C. J.; Yeamans, C. B.; Gatu Johnson, M. G.

    2016-10-01

    The spatial variation of activities measured in the array of 20 Nuclear Activation Detectors mounted on the flanges around the NIF target chamber (FNADs) are correlated with asymmetries in the underlying fuel areal density of compressed ICF targets. The asymmetric areal density distributions cause variations in the neutron spectra with direction which are seen in the dsr (down scattered ratio) metric, the ratio of the number of 10-12 MeV neutrons to the number of 13-15 MeV neutrons. We show, using a simple physics based simulation of neutron scattering through an idealized non-uniform DT shell with a realistic neutron source, that for most shots an areal distribution can be found which reproduces both the FNAD activity and the dsr measurements. Furthermore, by linking the simulation to a Marquardt minimizer, we fit the areal distribution to a truncated set of spherical harmonics. Prepared by LLNL under Contract DE-AC52-07NA27344.

  18. Super-X divertors and high power density fusion devices

    SciTech Connect

    Valanju, P. M.; Kotschenreuther, M.; Mahajan, S. M.; Canik, J.

    2009-05-15

    The Super-X Divertor (SXD), a robust axisymmetric redesign of the divertor magnetic geometry that can allow a fivefold increase in the core power density of toroidal fusion devices, is presented. With small changes in poloidal coils and currents for standard divertors, the SXD allows the largest divertor plate radius inside toroidal field coils. This increases the plasma-wetted area by 2-3 times over all flux-expansion-only methods (e.g., plate near main X point, plate tilting, X divertor, and snowflake), decreases parallel heat flux and hence plasma temperature at plate, and increases connection length by 2-5 times. Examples of high-power-density fusion devices enabled by SXD are discussed; the most promising near-term device is a 100 MW modular compact fusion neutron source 'battery' small enough to fit inside a conventional fission blanket.

  19. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, J.C.; Swift, G.W.; Migliori, A.

    1985-09-03

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas. 5 figs.

  20. Method of measuring reactive acoustic power density in a fluid

    DOEpatents

    Wheatley, John C.; Swift, Gregory W.; Migliori, Albert

    1985-01-01

    A method for determining reactive acoustic power density level and its direction in a fluid using a single sensor is disclosed. In the preferred embodiment, an apparatus for conducting the method, which is termed a thermoacoustic couple, consists of a stack of thin, spaced apart polymeric plates, selected ones of which include multiple bimetallic thermocouple junctions positioned along opposite end edges thereof. The thermocouple junctions are connected in series in the nature of a thermopile, and are arranged so as to be responsive to small temperature differences between the opposite edges of the plates. The magnitude of the temperature difference, as represented by the magnitude of the electrical potential difference generated by the thermopile, is found to be directly related to the level of acoustic power density in the gas.

  1. Magnetocaloric Materials and the Optimization of Cooling Power Density

    NASA Technical Reports Server (NTRS)

    Wikus, Patrick; Canavan, Edgar; Heine, Sarah Trowbridge; Matsumoto, Koichi; Numazawa, Takenori

    2014-01-01

    The magnetocaloric effect is the thermal response of a material to an external magnetic field. This manuscript focuses on the physics and the properties of materials which are commonly used for magnetic refrigeration at cryogenic temperatures. After a brief overview of the magnetocaloric effect and associated thermodynamics, typical requirements on refrigerants are discussed from a standpoint of cooling power density optimization. Finally, a compilation of the most important properties of several common magnetocaloric materials is presented.

  2. 47 CFR 25.208 - Power flux density limits.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... for angles of arrival between 0 and 5 degrees above the horizontal plane; −152+(δ−5)/2 dB(W/m2) in any 4 kHz band for angles of arrival δ (in degrees) between 5 and 25 degrees above the horizontal plane... horizontal plane These limits relate to the power flux density which would be obtained under assumed...

  3. 47 CFR 25.208 - Power flux density limits.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... for angles of arrival between 0 and 5 degrees above the horizontal plane; −152+(δ−5)/2 dB(W/m2) in any 4 kHz band for angles of arrival δ (in degrees) between 5 and 25 degrees above the horizontal plane... horizontal plane These limits relate to the power flux density which would be obtained under assumed...

  4. 47 CFR 25.208 - Power flux density limits.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... for angles of arrival between 0 and 5 degrees above the horizontal plane; −152+(δ−5)/2 dB(W/m2) in any 4 kHz band for angles of arrival δ (in degrees) between 5 and 25 degrees above the horizontal plane... horizontal plane These limits relate to the power flux density which would be obtained under assumed...

  5. 47 CFR 25.208 - Power flux density limits.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... for angles of arrival between 0 and 5 degrees above the horizontal plane; −152+(δ−5)/2 dB(W/m2) in any 4 kHz band for angles of arrival δ (in degrees) between 5 and 25 degrees above the horizontal plane... horizontal plane These limits relate to the power flux density which would be obtained under assumed...

  6. Probabilistic Density Function Method for Stochastic ODEs of Power Systems with Uncertain Power Input

    SciTech Connect

    Wang, Peng; Barajas-Solano, David A.; Constantinescu, Emil; Abhyankar, S.; Ghosh, Donetta L.; Smith, Barry; Huang, Zhenyu; Tartakovsky, Alexandre M.

    2015-09-22

    Wind and solar power generators are commonly described by a system of stochastic ordinary differential equations (SODEs) where random input parameters represent uncertainty in wind and solar energy. The existing methods for SODEs are mostly limited to delta-correlated random parameters (white noise). Here we use the Probability Density Function (PDF) method for deriving a closed-form deterministic partial differential equation (PDE) for the joint probability density function of the SODEs describing a power generator with time-correlated power input. The resulting PDE is solved numerically. A good agreement with Monte Carlo Simulations shows accuracy of the PDF method.

  7. Robust distribution and use of electric power

    NASA Astrophysics Data System (ADS)

    Catalan Izquierdo, Saturnino

    2001-07-01

    One of the major problems related to the simultaneous operation of electrical converters in a wide open power system is the concordance between the characteristics of the feeder itself and the load. Nowadays we usually call Electric Power Quality or Electromagnetic Compatibility to this Concordance Degree. Currently, the most important non concordance are voltage sag (voltage dip) and short time interruptions, that is: decreasings in voltage RMS value lasting from some tenths of a second to several seconds. Current analysis usually study this problem from the feeder side, by means of morphological or stadistical approaches, or from the load side in order to evaluate immunity, emission or specific solutions. This line of research, undoubtly needed provided we need to know the current state of the power system and to increase the concordance degree, is not enough because of the huge variability between power lines and from one instant to another. Moreover, the legal boundaries that can support business decisions are not developed yet. The proposed new theory is widely contrasted by field and laboratory measurement. Detailed analysis include instant voltage, instant current, power system and load effects from many places inside the power system of Spain. This theory is a novel approach to the determination of Concordance Degree (CG) of a whole system (be it a distribution line or a single machine) and to the corrective steps needed to increase it. In addition, the proposed model allow a quantitative evaluation of corrective actions like the increase of energy system storage (in a mechanical to electrical convertible form) or/and the increase of the supplied reactive power. Profitability of corrective actions is mainly a function of the number of voltage dips (sags) and short time interruptions that happen in a given period of time. To reduce this number we have studied and developed new fault characterization and location algorithms designed specifically for medium

  8. Test report light duty utility arm power distribution system (PDS)

    SciTech Connect

    Clark, D.A.

    1996-03-04

    The Light Duty Utility Arm (LDUA) Power Distribution System has completed vendor and post-delivery acceptance testing. The Power Distribution System has been found to be acceptable and is now ready for integration with the overall LDUA system.

  9. Tidal Densities of Globular Clusters and the Galactic Mass Distribution

    NASA Astrophysics Data System (ADS)

    Lee, Hyung Mok

    1990-12-01

    The tidal radii of globular clusters reflect the tidal field of the Galaxy. The mass distribution of the Galaxy thus may be obtained if the tidal fields of clusters are well known. Although large amounts of uncertainties in the determination of tidal radii have been obstacles in utilizing this method, analysis of tidal density could give independent check for the Galactic mass distribution. Recent theoretical modeling of dynamical evolution including steady Galactic tidal field shows that the observationally determined tidal radii could be systematically larger by about a factor of 1.5 compared to the theoretical values. From the analysis of entire sample of 148 globular clusters and 7 dwarf spheroidal systems compiled by Webbink(1985), we find that such reduction from observed values would make the tidal density(the mean density within the tidal radius) distribution consistent with the flat rotation curve of our Galaxy out to large distances if the velocity distribution of clusters and dwarf spheroidals with respect to the Galactic center is isotropic.

  10. Electron density power spectrum in the local interstellar medium

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.; Rickett, B. J.; Spangler, S. R.

    1995-01-01

    Interstellar scintillation (ISS), fluctuations in the amplitude and phase of radio waves caused by scattering in the interstellar medium, is important as a diagnostic of interstellar plasma turbulence. ISS is also of interest because it is noise for other radio astronomical observations. The unifying concern is the power spectrum of the interstellar electron density. Here we use ISS observations through the nearby (less than or approximately =1 kpc) (ISM) to estimate the spectrum. From measurements of angular broadening of pulsars and extragalactic sources, decorrelation bandwidth of pulsars, refractive steering of features in pulsar dynamic spectra, dispersion measured fluctuations of pulsars, and refractive scintillation index measurements, we construct a composite structure function that is approximately power law over 2 x 10(exp 6) m less than scale less than 10(exp 13) m. The data are consistent with the structure function having a logarithmic slope versus baseline less than 2; thus there is a meaningful connection between scales in the radiowave fluctuation field and the scales in the electron density field causing the scattering. The data give an upper limit to the inner scale, l(sub o) less than or approximately 10(exp 8) m and are consistent with much smaller values. We construct a composite electron density spectrum that is approximately power law over at least the approximately = 5 decade wavenumber range 10(exp -13)/m less than wavenumber less than 10(exp -8)/m and that may extend to higher wavenumbers. The average spectral index of electron density over this wavenumber range is approximately = 3.7, very close to the value expected for a Kolmogorov process. The outer scale size, L(sub o), must be greater than or approximately = 10(exp 13) m (determined from dispersion measure fluctuations). When the ISS data are combined with measurements of differential Faraday rotation angle, and gradients in the average electron density, constraints can be put on the

  11. Electric power processing, distribution, management and energy storage

    NASA Technical Reports Server (NTRS)

    Giudici, R. J.

    1980-01-01

    Power distribution subsystems are required for three elements of the SPS program: (1) orbiting satellite, (2) ground rectenna, and (3) Electric Orbiting Transfer Vehicle (EOTV). Power distribution subsystems receive electrical power from the energy conversion subsystem and provide the power busses rotary power transfer devices, switchgear, power processing, energy storage, and power management required to deliver control, high voltage plasma interactions, electric thruster interactions, and spacecraft charging of the SPS and the EOTV are also included as part of the power distribution subsystem design.

  12. Power density improvement of the power conditioning circuit for combined piezoelectric and electrodynamic generators

    NASA Astrophysics Data System (ADS)

    Zessin, H.; Spies, P.; Mateu, L.

    2016-11-01

    In this study, we report a power management circuit for a combined piezoelectric- electrodynamic generator. A piezoelectric element is bonded to a spring steel cantilever beam and a magnet, used as tip mass, oscillates through a coil. This principle creates the combined generator. A test setup has been created to automate the characterization of the piezoelectric generator and its power management circuit. Three different power management circuits for the piezoelectric part of the combined generator have been analysed: a bridge rectifier, an SSHI circuit with an external inductance and an SSHI circuit which utilizes the coil of the electrodynamic generator as circuit element. The three circuits are compared in terms of their output power, efficiency and power density. The SSHI circuit with an external inductance has the highest output power and efficiency, followed by the SSHI circuit with the electrodynamic generator coil. The power density of the bridge rectifier is the highest but for higher efficiency the power density of the SSHI circuit with the coil of the electromagnetic generator reaches the best results.

  13. Student Difficulties in Learning Density: A Distributed Cognition Perspective

    NASA Astrophysics Data System (ADS)

    Xu, Lihua; Clarke, David

    2012-08-01

    Density has been reported as one of the most difficult concepts for secondary school students (e.g. Smith et al. 1997). Discussion about the difficulties of learning this concept has been largely focused on the complexity of the concept itself or student misconceptions. Few, if any, have investigated how the concept of density was constituted in classroom interactions, and what consequences these interactions have for individual students' conceptual understanding. This paper reports a detailed analysis of two lessons on density in a 7th Grade Australian science classroom, employing the theory of Distributed Cognition (Hollan et al. 1999; Hutchins 1995). The analysis demonstrated that student understanding of density was shaped strongly by the public classroom discussion on the density of two metal blocks. It also revealed the ambiguities associated with the teacher demonstration and the student practical work. These ambiguities contributed to student difficulties with the concept of density identified in this classroom. The results of this study suggest that deliberate effort is needed to establish shared understanding not only about the purpose of the activities, but also about the meaning of scientific language and the utility of tools. It also suggests the importance of appropriate employment of instructional resources in order to facilitate student scientific understanding.

  14. On the Galactic Distributions of Radio Pulsars and Plasma Density

    NASA Astrophysics Data System (ADS)

    Ankay, A.; Yazgan, E.; Kutukcu, P.

    2016-12-01

    A brief review of distance measurement methods for some astronomical sources is presented. Galactic plasma density distribution as related to the distribution of radio pulsars is discussed and a method for constructing relations between dispersion measure and distance for Galactic radio pulsars in small solid angle intervals is described. Dispersion measure - distance relations for radio pulsars based on this approach in the Galactic longitude and latitude intervals of Δ l = 0°±2° and Δ b = 0°±2° are displayed and comparisons are made with the predictions of the two commonly used models.

  15. Probability density function characterization for aggregated large-scale wind power based on Weibull mixtures

    DOE PAGES

    Gomez-Lazaro, Emilio; Bueso, Maria C.; Kessler, Mathieu; ...

    2016-02-02

    Here, the Weibull probability distribution has been widely applied to characterize wind speeds for wind energy resources. Wind power generation modeling is different, however, due in particular to power curve limitations, wind turbine control methods, and transmission system operation requirements. These differences are even greater for aggregated wind power generation in power systems with high wind penetration. Consequently, models based on one-Weibull component can provide poor characterizations for aggregated wind power generation. With this aim, the present paper focuses on discussing Weibull mixtures to characterize the probability density function (PDF) for aggregated wind power generation. PDFs of wind power datamore » are firstly classified attending to hourly and seasonal patterns. The selection of the number of components in the mixture is analyzed through two well-known different criteria: the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). Finally, the optimal number of Weibull components for maximum likelihood is explored for the defined patterns, including the estimated weight, scale, and shape parameters. Results show that multi-Weibull models are more suitable to characterize aggregated wind power data due to the impact of distributed generation, variety of wind speed values and wind power curtailment.« less

  16. Probability density function characterization for aggregated large-scale wind power based on Weibull mixtures

    SciTech Connect

    Gomez-Lazaro, Emilio; Bueso, Maria C.; Kessler, Mathieu; Martin-Martinez, Sergio; Zhang, Jie; Hodge, Bri -Mathias; Molina-Garcia, Angel

    2016-02-02

    Here, the Weibull probability distribution has been widely applied to characterize wind speeds for wind energy resources. Wind power generation modeling is different, however, due in particular to power curve limitations, wind turbine control methods, and transmission system operation requirements. These differences are even greater for aggregated wind power generation in power systems with high wind penetration. Consequently, models based on one-Weibull component can provide poor characterizations for aggregated wind power generation. With this aim, the present paper focuses on discussing Weibull mixtures to characterize the probability density function (PDF) for aggregated wind power generation. PDFs of wind power data are firstly classified attending to hourly and seasonal patterns. The selection of the number of components in the mixture is analyzed through two well-known different criteria: the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). Finally, the optimal number of Weibull components for maximum likelihood is explored for the defined patterns, including the estimated weight, scale, and shape parameters. Results show that multi-Weibull models are more suitable to characterize aggregated wind power data due to the impact of distributed generation, variety of wind speed values and wind power curtailment.

  17. Three-parameter probability distribution density for statistical image analysis

    NASA Astrophysics Data System (ADS)

    Schau, H. C.

    1980-01-01

    Statistical analysis of 2-D image data or data gathered from a scanning radiometer requires that both the non-Gaussian nature and finite sample size of the process be considered. To aid the statistical analysis of this data, a higher moment description density function has been defined, and parameters have been identified with the estimated moments of the data. It is shown that the first two moments may be computed from a knowledge of the Weiner spectrum, whereas all higher moments require the complex spatial frequency spectrum. Parameter identification is carried out for a three-parameter density function and applied to a scene in the IR region, 8-14 microns. Results indicate that a three-parameter distribution density generally provides different probabilities than does a two-parameter Gaussian description if maximum entropy (minimum bias) forms are sought.

  18. Development of An On-Line, Core Power Distribution Monitoring System

    SciTech Connect

    Tunc ALdemir; Don Miller; Peng Wang

    2007-10-02

    The objective of the proposed work was to develop a software package that can construct in three-dimensional core power distributions using the signals from constant temperature power sensors distributed in the reactor core. The software developed uses a mode-based state/parameter estmation technique that is particularly attractive when there are model uncertainties and/or large signal noise. The software yields the expected value of local power at the detector locations and points in between, as well as the probability distribution of the local power density

  19. Tomographic determination of the power distribution in electron beams

    DOEpatents

    Teruya, Alan T.; Elmer, John W.

    1996-01-01

    A tomographic technique for determining the power distribution of an electron beam using electron beam profile data acquired from a modified Faraday cup to create an image of the current density in high and low power beams. A refractory metal disk with a number of radially extending slits is placed above a Faraday cup. The beam is swept in a circular pattern so that its path crosses each slit in a perpendicular manner, thus acquiring all the data needed for a reconstruction in one circular sweep. Also, a single computer is used to generate the signals actuating the sweep, to acquire that data, and to do the reconstruction, thus reducing the time and equipment necessary to complete the process.

  20. Probability distributions and confidence intervals for simulated power law noise.

    PubMed

    Ashby, Neil

    2015-01-01

    A method for simulating power law noise in clocks and oscillators is presented based on modification of the spectrum of white phase noise, then Fourier transforming to the time domain. Symmetric real matrices are introduced whose traces-the sums of their eigenvalues-are equal to the Allan variances, in overlapping or non-overlapping forms, as well as for the corresponding forms of the modified Allan variance. We show that the standard expressions for spectral densities, and their relations to Allan variance, are obtained with this method. The matrix eigenvalues determine probability distributions for observing a variance at an arbitrary value of the sampling interval τ, and hence for estimating confidence in the measurements. Examples are presented for the common power-law noises. Extension to other variances such as the Hadamard variance, and variances with dead time, are discussed.

  1. Tomographic determination of the power distribution in electron beams

    DOEpatents

    Teruya, A.T.; Elmer, J.W.

    1996-12-10

    A tomographic technique for determining the power distribution of an electron beam using electron beam profile data acquired from a modified Faraday cup to create an image of the current density in high and low power beams is disclosed. A refractory metal disk with a number of radially extending slits is placed above a Faraday cup. The beam is swept in a circular pattern so that its path crosses each slit in a perpendicular manner, thus acquiring all the data needed for a reconstruction in one circular sweep. Also, a single computer is used to generate the signals actuating the sweep, to acquire that data, and to do the reconstruction, thus reducing the time and equipment necessary to complete the process. 4 figs.

  2. Satellite control of electric power distribution

    NASA Technical Reports Server (NTRS)

    Bergen, L.

    1981-01-01

    An L-band frequencies satellite link providing the medium for direct control of electrical loads at individual customer sites from remote central locations is described. All loads supplied under interruptible-service contracts are likely condidates for such control, and they can be cycled or switched off to reduce system loads. For every kW of load eliminated or deferred to off-peak hours, the power company reduces its need for additional generating capacity. In addition, the satellite could switch meter registers so that their readings automatically reflected the time of consumption. The system would perform load-shedding operations during emergencies, disconnecting large blocks of load according to predetermined priorities. Among the distribution operations conducted by the satellite in real time would be: load reconfiguration, voltage regulation, fault isolation, and capacitor and feeder load control.

  3. Fabrication Flaw Density and Distribution in Weld Repairs

    SciTech Connect

    Doctor, Steven R.

    2009-09-01

    The Pacific Northwest National Laboratory (PNNL) is developing a generalized flaw distribution for the population of nuclear reactor pressure vessels and for piping welds in the U. S. operating reactors. The purpose of the generalized flaw distribution is to predict component-specific flaw densities. The estimates of fabrication flaws are intended for use in fracture mechanics structural integrity assessments. Structural integrity assessments, such as estimating the frequency of loss-of-coolant accidents, are performed by computer codes that require, as input, accurate estimates of flaw densities. Welds from four different cancelled reactor pressure vessels and a collection of archived pipes have been studied to develop empirical estimates of fabrication flaw densities. This paper describes the fabrication flaw distribution and characterization in the repair weld metal of vessels and piping. This work indicates that large flaws occur in these repairs which are complex in composition and sometimes include cracks on the ends of the repair cavities. Parametric analysis using an exponential fit is performed on the data. Construction records where available were reviewed. It is difficult to make conclusions due to the limited number of construction records reviewed. However, the records reviewed to date show a significant change in repair frequency over the years when the components in this study were fabricated. A description of repair flaw morphology is provided with a discussion of fracture mechanics significance.

  4. Calculation of nanodrop profile from fluid density distribution.

    PubMed

    Berim, Gersh O; Ruckenstein, Eli

    2016-05-01

    Two approaches are examined, which can be used to determine the drop profile from the fluid density distributions (FDDs) obtained on the basis of microscopic theories. For simplicity, only two-dimensional (cylindrical, or axisymmetrical) distributions are examined and it is assumed that the fluid is either in contact with a smooth solid or separated from the smooth solid by a lubricating liquid film. The first approach is based on the sharp-kink interface approximation in which the density of the liquid inside and the density of the vapor outside the drop are constant with the exception of the surface layer of the drop where the density is different from the above ones. In this case, the drop profile was calculated by minimizing the total potential energy of the system. The second approach is based on a nonuniform FDD obtained either by the density functional theory or molecular dynamics simulations. To determine the drop profile from such an FDD, which does not contain sharp interfaces, three procedures can be used. In the first two procedures, P1 and P2, the one-dimensional FDDs along straight lines which are parallel to the surface of the solid are extracted from the two-dimensional FDD. Each of those one-dimensional FDDs has a vapor-liquid interface at which the fluid density changes from vapor-like to liquid-like values. Procedure P1 uses the locations of the equimolar dividing surfaces for the one-dimensional FDDs as points of the drop profile. Procedure P2 is based on the assumption that the fluid density is constant on the surface of the drop, that density being selected either arbitrarily or as a fluid density at the location of the equimolar dividing surface for one of the one-dimensional FDDs employed in procedure P1. In the third procedure, P3, which is suggested for the first time in this paper, the one-dimensional FDDs are taken along the straight lines passing through a selected point inside the drop (radial line). Then, the drop profile is

  5. Device for the distribution of motive power

    SciTech Connect

    Teroka, M.

    1986-12-30

    A device is described for the distribution of motive power comprising: a hollow shaft receiving input power from the drive device; a pinion shaft provided on the output side of the hollow shaft; a pinion gear rotatably supported on the pinion shaft; a pair of side gears meshed with the pinion gear; a front wheel drive shaft integrally coupled to one of the side gears and passing through the center of the hollow shaft; a differential case having an outer shell, a front and a rear end and being integrally formed with the outer side gear and enclosing the pinion shaft, pinion gear and side gears. A rear wheel drive shaft is coupled to the differential case through a drive gear formed on the outer shell of the differential case and an input gear is integrally connected to an end of the rear wheel drive shaft so as to mesh with the drive gear, the rear drive wheel drive shaft being located above the front wheel drive shaft.

  6. An improved AVC strategy applied in distributed wind power system

    NASA Astrophysics Data System (ADS)

    Zhao, Y. N.; Liu, Q. H.; Song, S. Y.; Mao, W.

    2016-08-01

    Traditional AVC strategy is mainly used in wind farm and only concerns about grid connection point, which is not suitable for distributed wind power system. Therefore, this paper comes up with an improved AVC strategy applied in distributed wind power system. The strategy takes all nodes of distribution network into consideration and chooses the node having the most serious voltage deviation as control point to calculate the reactive power reference. In addition, distribution principles can be divided into two conditions: when wind generators access to network on single node, the reactive power reference is distributed according to reactive power capacity; when wind generators access to network on multi-node, the reference is distributed according to sensitivity. Simulation results show the correctness and reliability of the strategy. Compared with traditional control strategy, the strategy described in this paper can make full use of generators reactive power output ability according to the distribution network voltage condition and improve the distribution network voltage level effectively.

  7. Patch Network for Power Allocation and Distribution in Smart Materials

    NASA Technical Reports Server (NTRS)

    Golembiewski, Walter T.

    2000-01-01

    The power allocation and distribution (PAD) circuitry is capable of allocating and distributing a single or multiple sources of power over multi-elements of a power user grid system. The purpose of this invention is to allocate and distribute power that is collected by individual patch rectennas to a region of specific power-user devices, such as actuators. The patch rectenna converts microwave power into DC power. Then this DC power is used to drive actuator devices. However, the power from patch rectennas is not sufficient to drive actuators unless all the collected power is effectively used to drive another group by allocation and distribution. The power allocation and distribution (PAD) circuitry solves the shortfall of power for devices in a large array. The PAD concept is based on the networked power control in which power collected over the whole array of rectennas is allocated to a sub domain where a group of devices is required to be activated for operation. Then the allocated power is distributed to individual element of power-devices in the sub domain according to a selected run-mode.

  8. Spatial Density Distributions and Correlations in a Quasi-one-Dimensional Polydisperse Granular Gas

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-Yuan; Zhang, Duan-Ming

    2009-02-01

    By Monte Carlo simulations, the effect of the dispersion of particle size distribution on the spatial density distributions and correlations of a quasi one-dimensional polydisperse granular gas with fractal size distribution is investigated in the same inelasticity. The dispersive degree of the particle size distribution can be measured by a fractal dimension df, and the smooth particles are constrained to move along a circle of length L, colliding inelastically with each other and thermalized by a viscosity heat bath. When the typical relaxation time τ of the driving Brownian process is longer than the mean collision time τc, the system can reach a nonequilibrium steady state. The average energy of the system decays exponentially with time towards a stable asymptotic value, and the energy relaxation time τB to the steady state becomes shorter with increasing values of df. In the steady state, the spatial density distribution becomes more clusterized as df increases, which can be quantitatively characterized by statistical entropy of the system. Furthermore, the spatial correlation functions of density and velocities are found to be a power-law form for small separation distance of particles, and both of the correlations become stronger with the increase of df. Also, the density clusterization is explained from the correlations.

  9. An automated system for studying the power distribution of electron beams

    SciTech Connect

    Filarowski, C.A.

    1994-12-01

    Precise welds with an electron beam welder are difficult to reproduce because the factors effecting the electron beam current density distribution are not easily controlled. One method for measuring the power density distribution in EB welds uses computer tomography to reconstruct an image of the current density distribution. This technique uses many separate pieces of hardware and software packages to obtain the data and then reconstruct it consequently, transferring this technology between different machines and operators is difficult. Consolidating all of the hardware and software into one machine to execute the same tasks will allow for real-time measurement of the EB power density distribution and will provide a facilitated means for transferring various welding procedure between different machines and operators, thereby enhancing reproducibility of electron beam welds.

  10. Ion flux, ion energy distribution and neutral density in an inductively coupled argon discharge

    NASA Astrophysics Data System (ADS)

    Chevolleau, T.; Fukarek, W.

    2000-11-01

    The dependence of ion flux, ion energy distribution and neutral density of a planar radiofrequency (RF) driven inductively coupled plasma source on pressure and power is analysed using a plasma monitor and a Faraday cup. The ion flux is about 7 mA cm-2 at 5 Pa and 300 W and increases as RF power and argon pressure increase. The ion energy distribution consists of a single peak with a full width at half maximum of 3 eV for a discharge power in the range from 50 to 300 W and for a pressure in the range from 0.5 to 5 Pa. This indicates that inductive coupling mainly drives the discharge while capacitive coupling between coil and plasma is weak. A significant decrease in Ar neutral density is observed when the plasma is ignited. The Ar depletion increases with increasing RF power and increasing Ar base pressure and reaches 30% at 5 Pa and 300 W. The contributions of the different mechanisms resulting in an Ar depletion are estimated and compared. The decrease in neutral density cannot be explained by the ionization of Ar atoms only but is significantly attributed to the heating of Ar atoms by collisions with energetic particles. The increase in neutral gas temperature is estimated and found to be in reasonable agreement with measurements of the gas temperature reported previously by other groups.

  11. Carbon density and distribution of six Chinese temperate forests.

    PubMed

    Zhang, QuanZhi; Wang, ChuanKuan

    2010-07-01

    Quantifying forest carbon (C) storage and distribution is important for forest C cycling studies and terrestrial ecosystem modeling. Forest inventory and allometric approaches were used to measure C density and allocation in six representative temperate forests of similar stand age (42-59 years old) and growing under the same climate in northeastern China. The forests were an aspen-birch forest, a hardwood forest, a Korean pine plantation, a Dahurian larch plantation, a mixed deciduous forest, and a Mongolian oak forest. There were no significant differences in the C densities of ecosystem components (except for detritus) although the six forests had varying vegetation compositions and site conditions. However, the differences were significant when the C pools were normalized against stand basal area. The total ecosystem C density varied from 186.9 tC hm(-2) to 349.2 tC hm(-2) across the forests. The C densities of vegetation, detritus, and soil ranged from 86.3-122.7 tC hm(-2), 6.5-10.5 tC hm(-2), and 93.7-220.1 tC hm(-2), respectively, which accounted for 39.7% +/- 7.1% (mean +/- SD), 3.3% +/- 1.1%, and 57.0% +/- 7.9% of the total C densities, respectively. The overstory C pool accounted for > 99% of the total vegetation C pool. The foliage biomass, small root (diameter < 5mm) biomass, root-shoot ratio, and small root to foliage biomass ratio varied from 2.08-4.72 tC hm(-2), 0.95-3.24 tC hm(-2), 22.0%-28.3%, and 34.5%-122.2%, respectively. The Korean pine plantation had the lowest foliage production efficiency (total biomass/foliage biomass: 22.6 g g(-1)) among the six forests, while the Dahurian larch plantation had the highest small root production efficiency (total biomass/small root biomass: 124.7 g g(-1)). The small root C density decreased with soil depth for all forests except for the Mongolian oak forest, in which the small roots tended to be vertically distributed downwards. The C density of coarse woody debris was significantly less in the two

  12. High power density proton exchange membrane fuel cells

    NASA Technical Reports Server (NTRS)

    Murphy, Oliver J.; Hitchens, G. Duncan; Manko, David J.

    1993-01-01

    Proton exchange membrane (PEM) fuel cells use a perfluorosulfonic acid solid polymer film as an electrolyte which simplifies water and electrolyte management. Their thin electrolyte layers give efficient systems of low weight, and their materials of construction show extremely long laboratory lifetimes. Their high reliability and their suitability for use in a microgravity environment makes them particularly attractive as a substitute for batteries in satellites utilizing high-power, high energy-density electrochemical energy storage systems. In this investigation, the Dow experimental PEM (XUS-13204.10) and unsupported high platinum loading electrodes yielded very high power densities, of the order of 2.5 W cm(exp -2). A platinum black loading of 5 mg per cm(exp 2) was found to be optimum. On extending the three-dimensional reaction zone of fuel cell electrodes by impregnating solid polymer electrolyte into the electrode structures, Nafion was found to give better performance than the Dow experimental PEM. The depth of penetration of the solid polymer electrolyte into electrode structures was 50-70 percent of the thickness of the platinum-catalyzed active layer. However, the degree of platinum utilization was only 16.6 percent and the roughness factor of a typical electrode was 274.

  13. Submicron gate InP power MISFET's with improved output power density at 18 and 20 GHz

    NASA Technical Reports Server (NTRS)

    Biedenbender, Michael D.; Kapoor, Vik J.; Shalkhauser, Kurt A.; Messick, Louis J.; Nguyen, Richard; Schmitz, Dietmar; Jurgensen, Holger

    1991-01-01

    The microwave characteristics are presented at 18 and 20 GHz of submicron gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFETs) for high output power density applications. InP power MISFET's were fabricated and the output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacing of 3 micron. The output power density is 2.7 times greater than was previously measured for InP MISFET's at 18 and 20 GHz, and the power-added efficiency also increased.

  14. Submicron gate InP power MISFET's with improved output power density at 18 and 20 GHz

    NASA Technical Reports Server (NTRS)

    Biedenbender, M. D.; Kapoor, Vik J.; Shalkhauser, K. A.; Messick, L. J.; Nguyen, R.; Schmitz, D.; Juergensen, H.

    1991-01-01

    The microwave characteristics are presented at 18 and 20 GHz of submicron gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFET's) for high output power density applications. InP power MISFET's were fabricated and the output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacing of 3 microns. The output power density is 2.7 times greater than was previously measured for InP MISFET's at 18 and 20 GHz, and the power-added efficiency also increased.

  15. Aneurysm permeability following coil embolization: packing density and coil distribution

    PubMed Central

    Chueh, Ju-Yu; Vedantham, Srinivasan; Wakhloo, Ajay K; Carniato, Sarena L; Puri, Ajit S; Bzura, Conrad; Coffin, Spencer; Bogdanov, Alexei A; Gounis, Matthew J

    2015-01-01

    Background Rates of durable aneurysm occlusion following coil embolization vary widely, and a better understanding of coil mass mechanics is desired. The goal of this study is to evaluate the impact of packing density and coil uniformity on aneurysm permeability. Methods Aneurysm models were coiled using either Guglielmi detachable coils or Target coils. The permeability was assessed by taking the ratio of microspheres passing through the coil mass to those in the working fluid. Aneurysms containing coil masses were sectioned for image analysis to determine surface area fraction and coil uniformity. Results All aneurysms were coiled to a packing density of at least 27%. Packing density, surface area fraction of the dome and neck, and uniformity of the dome were significantly correlated (p<0.05). Hence, multivariate principal components-based partial least squares regression models were used to predict permeability. Similar loading vectors were obtained for packing and uniformity measures. Coil mass permeability was modeled better with the inclusion of packing and uniformity measures of the dome (r2=0.73) than with packing density alone (r2=0.45). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures. Conclusions A densely packed aneurysm with a high degree of coil mass uniformity will reduce permeability. PMID:25031179

  16. Locational Marginal Pricing in the Campus Power System at the Power Distribution Level

    SciTech Connect

    Hao, Jun; Gu, Yi; Zhang, Yingchen; Zhang, Jun Jason; Gao, David Wenzhong

    2016-11-14

    In the development of smart grid at distribution level, the realization of real-time nodal pricing is one of the key challenges. The research work in this paper implements and studies the methodology of locational marginal pricing at distribution level based on a real-world distribution power system. The pricing mechanism utilizes optimal power flow to calculate the corresponding distributional nodal prices. Both Direct Current Optimal Power Flow and Alternate Current Optimal Power Flow are utilized to calculate and analyze the nodal prices. The University of Denver campus power grid is used as the power distribution system test bed to demonstrate the pricing methodology.

  17. Developments in space power components for power management and distribution

    NASA Technical Reports Server (NTRS)

    Renz, D. D.

    1984-01-01

    Advanced power electronic components development for space applications is discussed. The components described include transformers, inductors, semiconductor devices such as transistors and diodes, remote power controllers, and transmission lines.

  18. Numerical Distributions of Parasite Densities During Asymptomatic Malaria

    PubMed Central

    Imwong, Mallika; Stepniewska, Kasia; Tripura, Rupam; Peto, Thomas J.; Lwin, Khin Maung; Vihokhern, Benchawan; Wongsaen, Klanarong; von Seidlein, Lorenz; Dhorda, Mehul; Snounou, Georges; Keereecharoen, Lilly; Singhasivanon, Pratap; Sirithiranont, Pasathorn; Chalk, Jem; Nguon, Chea; Day, Nicholas P. J.; Nosten, Francois; Dondorp, Arjen; White, Nicholas J.

    2016-01-01

    Background. Asymptomatic parasitemia is common even in areas of low seasonal malaria transmission, but the true proportion of the population infected has not been estimated previously because of the limited sensitivity of available detection methods. Methods. Cross-sectional malaria surveys were conducted in areas of low seasonal transmission along the border between eastern Myanmar and northwestern Thailand and in western Cambodia. DNA was quantitated by an ultrasensitive polymerase chain reaction (uPCR) assay (limit of accurate detection, 22 parasites/mL) to characterize parasite density distributions for Plasmodium falciparum and Plasmodium vivax, and the proportions of undetected infections were imputed. Results. The prevalence of asymptomatic malaria as determined by uPCR was 27.5% (1303 of 4740 people tested). Both P. vivax and P. falciparum density distributions were unimodal and log normal, with modal values well within the quantifiable range. The estimated proportions of all parasitemic individuals identified by uPCR were >70% among individuals infected with P. falciparum and >85% among those infected with P. vivax. Overall, 83% of infections were predicted to be P. vivax infections, 13% were predicted to be P. falciparum infections, and 4% were predicted to be mixed infections. Geometric mean parasite densities were similar; 5601 P. vivax parasites/mL and 5158 P. falciparum parasites/mL. Conclusions. This uPCR method identified most infected individuals in malaria-endemic areas. Malaria parasitemia persists in humans at levels that optimize the probability of generating transmissible gametocyte densities without causing illness. PMID:26681777

  19. The invariances of power law size distributions.

    PubMed

    Frank, Steven A

    2016-01-01

    Size varies. Small things are typically more frequent than large things. The logarithm of frequency often declines linearly with the logarithm of size. That power law relation forms one of the common patterns of nature. Why does the complexity of nature reduce to such a simple pattern? Why do things as different as tree size and enzyme rate follow similarly simple patterns? Here I analyze such patterns by their invariant properties. For example, a common pattern should not change when adding a constant value to all observations. That shift is essentially the renumbering of the points on a ruler without changing the metric information provided by the ruler. A ruler is shift invariant only when its scale is properly calibrated to the pattern being measured. Stretch invariance corresponds to the conservation of the total amount of something, such as the total biomass and consequently the average size. Rotational invariance corresponds to pattern that does not depend on the order in which underlying processes occur, for example, a scale that additively combines the component processes leading to observed values. I use tree size as an example to illustrate how the key invariances shape pattern. A simple interpretation of common pattern follows. That simple interpretation connects the normal distribution to a wide variety of other common patterns through the transformations of scale set by the fundamental invariances.

  20. The invariances of power law size distributions

    PubMed Central

    Frank, Steven A.

    2016-01-01

    Size varies. Small things are typically more frequent than large things. The logarithm of frequency often declines linearly with the logarithm of size. That power law relation forms one of the common patterns of nature. Why does the complexity of nature reduce to such a simple pattern? Why do things as different as tree size and enzyme rate follow similarly simple patterns? Here I analyze such patterns by their invariant properties. For example, a common pattern should not change when adding a constant value to all observations. That shift is essentially the renumbering of the points on a ruler without changing the metric information provided by the ruler. A ruler is shift invariant only when its scale is properly calibrated to the pattern being measured. Stretch invariance corresponds to the conservation of the total amount of something, such as the total biomass and consequently the average size. Rotational invariance corresponds to pattern that does not depend on the order in which underlying processes occur, for example, a scale that additively combines the component processes leading to observed values. I use tree size as an example to illustrate how the key invariances shape pattern. A simple interpretation of common pattern follows. That simple interpretation connects the normal distribution to a wide variety of other common patterns through the transformations of scale set by the fundamental invariances. PMID:27928497

  1. Design note about a 75 KVA quiet power distribution system

    SciTech Connect

    Visser, A.T.

    1984-04-05

    This note describes a 75KVA quiet power distribution system for X 653 in neutrino Lab D. It is fed from the regular AC distribution which exists in the building and it has no standby power. Its purpose is to remove electrical disturbances which are present on the regular AC distribution.

  2. Yield QTLome distribution correlates with gene density in maize.

    PubMed

    Martinez, Ana Karine; Soriano, Jose Miguel; Tuberosa, Roberto; Koumproglou, Rachil; Jahrmann, Torben; Salvi, Silvio

    2016-01-01

    The genetic control of yield and related traits in maize has been addressed by many quantitative trait locus (QTL) studies, which have produced a wealth of QTL information, also known as QTLome. In this study, we assembled a yield QTLome database and carried out QTL meta-analysis based on 44 published studies, representing 32 independent mapping populations and 49 parental lines. A total of 808 unique QTLs were condensed to 84 meta-QTLs and were projected on the 10 maize chromosomes. Seventy-four percent of QTLs showed a proportion of phenotypic variance explained (PVE) smaller than 10% confirming the high genetic complexity of grain yield. Yield QTLome projection on the genetic map suggested pericentromeric enrichment of QTLs. Conversely, pericentromeric depletion of QTLs was observed when the physical map was considered, suggesting gene density as the main driver of yield QTL distribution on chromosomes. Dominant and overdominant yield QTLs did not distribute differently from additive effect QTLs.

  3. Power-Law Distributions Based on Exponential Distributions: Latent Scaling, Spurious Zipf's Law, and Fractal Rabbits

    NASA Astrophysics Data System (ADS)

    Chen, Yanguang

    2015-03-01

    The difference between the inverse power function and the negative exponential function is significant. The former suggests a complex distribution, while the latter indicates a simple distribution. However, the association of the power-law distribution with the exponential distribution has been seldom researched. This paper is devoted to exploring the relationships between exponential laws and power laws from the angle of view of urban geography. Using mathematical derivation and numerical experiments, I reveal that a power-law distribution can be created through a semi-moving average process of an exponential distribution. For the distributions defined in a one-dimension space (e.g. Zipf's law), the power exponent is 1; while for those defined in a two-dimension space (e.g. Clark's law), the power exponent is 2. The findings of this study are as follows. First, the exponential distributions suggest a hidden scaling, but the scaling exponents suggest a Euclidean dimension. Second, special power-law distributions can be derived from exponential distributions, but they differ from the typical power-law distributions. Third, it is the real power-law distributions that can be related with fractal dimension. This study discloses an inherent link between simplicity and complexity. In practice, maybe the result presented in this paper can be employed to distinguish the real power laws from spurious power laws (e.g. the fake Zipf distribution).

  4. Fuel Cycle Comparison for Distributed Power Technologies

    SciTech Connect

    Elgowainy, A.; Wang, M. Q.

    2008-11-15

    This report examines backup power and prime power systems and addresses the potential energy and environmental effects of substituting fuel cells for existing combustion technologies based on microturbines and internal combustion engines.

  5. Seagrass species distribution, density and coverage at Panggang Island, Jakarta

    NASA Astrophysics Data System (ADS)

    Wahab, Iswandi; Madduppa, Hawis; Kawaroe, Mujizat

    2017-01-01

    This study aimed to assess species distribution, density and coverage of seagrass in Panggang Island, within Kepulauan Seribu Marine National Park, northern Jakarta. Seagrass sampling was conducted between March to April 2016 at three observation stations in the West, East, and South of Panggang Island. A total of 6 seagrass species was recorded during sampling period, including Cymodocea rotundata, C. serulata, Halodule uninervis, Syiringodium isoetifolium, Enhalus acoroides, and Thalassia hempricii. All species were observed in the South station, while in the West and East station found only three species (C. rotundata, E. acoroides, and T. hemprichii). While, C. rotundata and T. hemprichii were observed at all station. The highest density was observed for C. rotundata (520 ind/m2) and for T. hempricii (619 ind/m2) in the West station and South Station, respectively. The lowest density was observed in South Station for C. serulata (18 ind/m2), Halodule uninervis (20 ind/m2), and Syiringodium isoetifolium (15 ind/m2). Seagrass coverage of Thalassia hempricii was the highest (43.60%) and the lowest observed at Syiringodium isoetifolium (0.40%). This could be basic information for the management of seagrass ecosystem in the Kepulauan Seribu Marine National Park.

  6. Distributed energy store powered railguns for hypervelocity launch

    NASA Astrophysics Data System (ADS)

    Maas, Brian L.; Bauer, David P.; Marshall, Richard A.

    1993-01-01

    Highly distributed power supplies are proposed as a basis for current difficulties with hypervelocity railgun power-supply compactness. This distributed power supply configuration reduces rail-to-rail voltage behind the main armature, thereby reducing the tendency for secondary armature current formation; secondary current elimination is essential for achieving the efficiencies associated with muzzle velocity above 6 km/sec. Attention is given to analytical and experimental results for two distributed energy storage schemes.

  7. PSD computations using Welch's method. [Power Spectral Density (PSD)

    SciTech Connect

    Solomon, Jr, O M

    1991-12-01

    This report describes Welch's method for computing Power Spectral Densities (PSDs). We first describe the bandpass filter method which uses filtering, squaring, and averaging operations to estimate a PSD. Second, we delineate the relationship of Welch's method to the bandpass filter method. Third, the frequency domain signal-to-noise ratio for a sine wave in white noise is derived. This derivation includes the computation of the noise floor due to quantization noise. The signal-to-noise ratio and noise flood depend on the FFT length and window. Fourth, the variance the Welch's PSD is discussed via chi-square random variables and degrees of freedom. This report contains many examples, figures and tables to illustrate the concepts. 26 refs.

  8. Power Spectrum Density of Long-Term MAXI Data

    NASA Astrophysics Data System (ADS)

    Sugimoto, Juri; Mihara, Tatehiro; Sugizaki, Mutsumi; Serino, Motoko; Kitamoto, Shunji; Sato, Ryousuke; Ueda, Yoshihiro; Ueno, Shiro

    Monitor of All-sky X-ray Image (MAXI) on the International Space Station has been observing the X-ray sky since 2009 August 15. It has accumulated the X-ray data for about four years, so far. X-ray objects are usually variable and their variability can be studied by the power spectrum density (PSD) of the X-ray light curves. We applied our method to calculate PSDs of several kinds of objects observed with MAXI. We obtained significant PSDs from 16 Seyfert galaxies. For blackhole binary Cygnus X-1 there was a difference in the shape of PSD between the hard state and the soft state. For high mass X-ray binaries, Cen X-3, SMC X-1, and LMC X-4, there were several peaks in the PSD corresponding to the orbital period and the superorbital period.

  9. More systematic errors in the measurement of power spectral density

    NASA Astrophysics Data System (ADS)

    Mack, Chris A.

    2015-07-01

    Power spectral density (PSD) analysis is an important part of understanding line-edge and linewidth roughness in lithography. But uncertainty in the measured PSD, both random and systematic, complicates interpretation. It is essential to understand and quantify the sources of the measured PSD's uncertainty and to develop mitigation strategies. Both analytical derivations and simulations of rough features are used to evaluate data window functions for reducing spectral leakage and to understand the impact of data detrending on biases in PSD, autocovariance function (ACF), and height-to-height covariance function measurement. A generalized Welch window was found to be best among the windows tested. Linear detrending for line-edge roughness measurement results in underestimation of the low-frequency PSD and errors in the ACF and height-to-height covariance function. Measuring multiple edges per scanning electron microscope image reduces this detrending bias.

  10. CENTER FOR PULSED POWER DRIVEN HIGH ENERGY DENSITY PLASMA STUDIES

    SciTech Connect

    Professor Bruce R. Kusse; Professor David A. Hammer

    2007-04-18

    This annual report summarizes the activities of the Cornell Center for Pulsed-Power-Driven High-Energy-Density Plasma Studies, for the 12-month period October 1, 2005-September 30, 2006. This period corresponds to the first year of the two-year extension (awarded in October, 2005) to the original 3-year NNSA/DOE Cooperative Agreement with Cornell, DE-FC03-02NA00057. As such, the period covered in this report also corresponds to the fourth year of the (now) 5-year term of the Cooperative Agreement. The participants, in addition to Cornell University, include Imperial College, London (IC), the University of Nevada, Reno (UNR), the University of Rochester (UR), the Weizmann Institute of Science (WSI), and the P.N. Lebedev Physical Institute (LPI), Moscow. A listing of all faculty, technical staff and students, both graduate and undergraduate, who participated in Center research activities during the year in question is given in Appendix A.

  11. Concentric Parallel Combining Balun for Millimeter-Wave Power Amplifier in Low-Power CMOS with High-Power Density

    NASA Astrophysics Data System (ADS)

    Han, Jiang-An; Kong, Zhi-Hui; Ma, Kaixue; Yeo, Kiat Seng; Lim, Wei Meng

    2016-11-01

    This paper presents a novel balun for a millimeter-wave power amplifier (PA) design to achieve high-power density in a 65-nm low-power (LP) CMOS process. By using a concentric winding technique, the proposed parallel combining balun with compact size accomplishes power combining and unbalance-balance conversion concurrently. For calculating its power combination efficiency in the condition of various amplitude and phase wave components, a method basing on S-parameters is derived. Based on the proposed parallel combining balun, a fabricated 60-GHz industrial, scientific, and medical (ISM) band PA with single-ended I/O achieves an 18.9-dB gain and an 8.8-dBm output power at 1-dB compression and 14.3-dBm saturated output power ( P sat) at 62 GHz. This PA occupying only a 0.10-mm2 core area has demonstrated a high-power density of 269.15 mW/mm2 in 65 nm LP CMOS.

  12. Maximizing the power density of aqueous electrochemical flow cells with in operando deposition

    NASA Astrophysics Data System (ADS)

    Goulet, Marc-Antoni; Ibrahim, Omar A.; Kim, Will H. J.; Kjeang, Erik

    2017-01-01

    To transition toward sustainable energy systems, next generation power sources must provide high power density at minimum cost. Using inexpensive and environmentally friendly fabrication methods, this work describes a room temperature electrochemical flow cell with a maximum power density of 2.01 W cm-2 or 13.4 W cm-3. In part, this is achieved by minimizing ohmic resistance through decreased electrode spacing, implementation of current collectors and improvement of electrolyte conductivity. The majority of the performance gain is provided by a novel in operando dynamic flowing deposition method for which the cell design has been optimized. Carbon nanotubes (CNTs) are deposited dynamically at the entrance of and within the carbon paper electrodes during operation of the cell. A natural equilibrium is reached between deposition and detachment of CNTs at which the electrochemical surface area and pore size distribution of the flow-through porous electrodes are greatly enhanced. In this way, the novel deposition method more than doubles the power density of the cell and sets a new performance benchmark for what is practically attainable with aqueous electrochemical flow cells. Overall, it is expected that the design and operation methods illustrated here will enable a wide range of electrochemical flow cell technologies to achieve optimal performance.

  13. Electromagnetic potentials basis for energy density and power flux

    NASA Astrophysics Data System (ADS)

    Puthoff, H. E.

    2016-09-01

    In rounding out the education of students in advanced courses in applied electromagnetics it is incumbent on us as mentors to raise issues that encourage appreciation of certain subtle aspects that are often overlooked during first exposure to the field. One of these has to do with the interplay between fields and potentials, with the latter often seen as just a convenient mathematical artifice useful in solving Maxwell’s equations. Nonetheless, to those practiced in application it is well understood that various alternatives in the use of fields and potentials are available within electromagnetic (EM) theory for the definitions of energy density, momentum transfer, EM stress-energy tensor, and so forth. Although the various options are all compatible with the basic equations of electrodynamics (e.g., Maxwell’s equations, Lorentz force law, gauge invariance), nonetheless certain alternative formulations lend themselves to being seen as preferable to others with regard to the transparency of their application to physical problems of interest. Here we argue for the transparency of an energy density/power flux option based on the EM potentials alone.

  14. Particle visualization in high-power impulse magnetron sputtering. I. 2D density mapping

    SciTech Connect

    Britun, Nikolay Palmucci, Maria; Konstantinidis, Stephanos; Snyders, Rony

    2015-04-28

    Time-resolved characterization of an Ar-Ti high-power impulse magnetron sputtering discharge has been performed. This paper deals with two-dimensional density mapping in the discharge volume obtained by laser-induced fluorescence imaging. The time-resolved density evolution of Ti neutrals, singly ionized Ti atoms (Ti{sup +}), and Ar metastable atoms (Ar{sup met}) in the area above the sputtered cathode is mapped for the first time in this type of discharges. The energetic characteristics of the discharge species are additionally studied by Doppler-shift laser-induced fluorescence imaging. The questions related to the propagation of both the neutral and ionized discharge particles, as well as to their spatial density distributions, are discussed.

  15. Kinetics of density striations excited by powerful electromagnetic waves in the ionosphere

    NASA Astrophysics Data System (ADS)

    Istomin, Ya. N.; Leyser, T. B.

    2010-03-01

    One of the most important effects observed when pumping ionospheric plasma by powerful radio waves from the ground is the excitation of filamentary density striations that are stretched along the ambient geomagnetic field. The kinetics of the striations present in the pump electromagnetic field is studied theoretically. The density irregularities cause inhomogeneities in the pump field, which result in a ponderomotive force acting on the striations that makes the density depressions move perpendicular to the geomagnetic field. Striations moving with different velocities can collide, thereby merging to produce larger scale striations. The merging of striations constitutes a cascade process that distributes the energy over the spatial spectrum of the striations. The resulting inhomogeneity spectrum as well as the obtained outward radial drift of a few meters per second is consistent with experimental results.

  16. Planckian Power Spectral Densities from Human Calves during Posture Maintenance and Controlled Isometric Contractions

    PubMed Central

    Lugo, J. E.

    2015-01-01

    Background The relationship between muscle anatomy and physiology and its corresponding electromyography activity (EMGA) is complex and not well understood. EMGA models may be broadly divided in stochastic and motor-unit-based models. For example, these models have successfully described many muscle physiological variables such as the value of the muscle fiber velocity and the linear relationship between median frequency and muscle fiber velocity. However they cannot explain the behavior of many of these variables with changes in intramuscular temperature, or muscle PH acidity, for instance. Here, we propose that the motor unit action potential can be treated as an electromagnetic resonant mode confined at thermal equilibrium inside the muscle. The motor units comprising the muscle form a system of standing waves or modes, where the energy of each mode is proportional to its frequency. Therefore, the power spectral density of the EMGA is well described and fit by Planck’s law and from its distribution we developed theoretical relationships that explain the behavior of known physiological variables with changes in intramuscular temperature or muscle PH acidity, for instance. Methods EMGA of the calf muscle was recorded during posture maintenance in seven participants and during controlled isometric contractions in two participants. The power spectral density of the EMGA was then fit with the Planckian distribution. Then, we inferred nine theoretical relationships from the distribution and compared the theoretically derived values with experimentally obtained values. Results The power spectral density of EMGA was fit by Planckian distributions and all the theoretical relationships were validated by experimental results. Conclusions Only by considering the motor unit action potentials as electromagnetic resonant modes confined at thermal equilibrium inside the muscle suffices to predict known or new theoretical relationships for muscle physiological variables that

  17. Price Based Local Power Distribution Management System (Local Power Distribution Manager) v1.0

    SciTech Connect

    BROWN, RICHARD E.; CZARNECKI, STEPHEN; SPEARS, MICHAEL; NORDMAN, BRUCE; BROUGHTON, ALEX; VON HIPPEL, MICHAEL; LIAO, ANNA

    2016-11-28

    A trans-active energy micro-grid controller is implemented in the VOLTTRON distributed control platform. The system uses the price of electricity as the mechanism for conducting transactions that are used to manage energy use and to balance supply and demand. In order to allow testing and analysis of the control system, the implementation is designed to run completely as a software simulation, while allowing the inclusion of selected hardware that physically manages power. Equipment to be integrated with the micro-grid controller must have an IP (Internet Protocol)-based network connection and a software "driver" must exist to translate data communications between the device and the controller.

  18. Validating MCNP for LEU Fuel Design via Power Distribution Comparisons

    SciTech Connect

    Primm, Trent; Maldonado, G Ivan; Chandler, David

    2008-11-01

    The mission of the Reduced Enrichment for Research and Test Reactors (RERTR) Program is to minimize and, to the extent possible, eliminate the use of highly enriched uranium (HEU) in civilian nuclear applications by working to convert research and test reactors, as well as radioisotope production processes, to low enriched uranium (LEU) fuel and targets. Oak Ridge National Lab (ORNL) is reviewing the design bases and key operating criteria including fuel operating parameters, enrichment-related safety analyses, fuel performance, and fuel fabrication in regard to converting the fuel of the High Flux Isotope Reactor (HFIR) from HEU to LEU. The purpose of this study is to validate Monte Carlo methods currently in use for conversion analyses. The methods have been validated for the prediction of flux values in the reactor target, reflector, and beam tubes, but this study focuses on the prediction of the power density profile in the core. A current 3-D Monte Carlo N-Particle (MCNP) model was modified to replicate the HFIR Critical Experiment 3 (HFIRCE-3) core of 1965. In this experiment, the power profile was determined by counting the gamma activity at selected locations in the core. Foils (chunks of fuel meat and clad) were punched out of the fuel elements in HFIRCE-3 following irradiation and experimental relative power densities were obtained by measuring the activity of these foils and comparing each foil s activity to the activity of a normalizing foil. The current work consisted of calculating corresponding activities by inserting volume tallies into the modified MCNP model to represent the punchings. The average fission density was calculated for each foil location and then normalized to the normalizing foil. Power distributions were obtained for the clean core (no poison in moderator and symmetrical rod position at 17.5 inches) and fully poisoned-moderator (1.35 g B/liter in moderator and rods fully withdrawn) conditions. The observed deviations between the

  19. Distribution of High-Density Lipoprotein Subfractions and Hypertensive Status

    PubMed Central

    Zhang, Yan; Li, Sha; Xu, Rui-Xia; Guo, Yuan-Lin; Wu, Na-Qiong; Zhu, Cheng-Gang; Gao, Ying; Dong, Qian; Liu, Geng; Sun, Jing; Li, Jian-Jun

    2015-01-01

    Abstract The exact mechanisms of hypertension contributing to atherosclerosis have not been fully elucidated. Although multiple studies have clarified the association with low-density lipoprotein (LDL) subfractions, uncertainty remains about its relationship with high-density lipoprotein (HDL) subfractions. Therefore, we aimed to comprehensively determine the relationship between distribution of HDL subfractions and hypertensive status. A total of 953 consecutive subjects without previous lipid-lowering drug treatment were enrolled and were categorized based on hypertension history (with hypertension [n = 550] or without hypertension [n = 403]). Baseline clinical and laboratory data were collected. HDL separation was performed using the Lipoprint System. Plasma large HDL-cholesterol (HDL-C) and large HDL percentage were dramatically lower whereas the small HDL-C and small HDL percentage were higher in patients with hypertension (all P < 0.05). The antihypertensive drug therapy was not associated with large or small HDL subfractions (on treatment vs not on treatment, P > 0.05; combination vs single drug therapy, P > 0.05). However, the blood pressure well-controlled patients have significantly lower small HDL subfraction (P < 0.05). Moreover, large HDL-C and percentage were inversely whereas small HDL percentage was positively associated with incident hypertension after adjusting potential confounders (all P < 0.05). In the multivariate model conducted in patients with and without hypertension separately, the cardio-protective value of large HDL-C was disappeared in patients with hypertension (OR 95%CI: 1.011 [0.974–1.049]). The distribution of HDL subfractions is closely associated with hypertensive status and hypertension may potentially impact the cardio-protective value of large HDL subfraction. PMID:26512616

  20. Exponential and power-law mass distributions in brittle fragmentation

    NASA Astrophysics Data System (ADS)

    Åström, J. A.; Linna, R. P.; Timonen, J.; Møller, Peder Friis; Oddershede, Lene

    2004-08-01

    Generic arguments, a minimal numerical model, and fragmentation experiments with gypsum disk are used to investigate the fragment-size distribution that results from dynamic brittle fragmentation. Fragmentation is initiated by random nucleation of cracks due to material inhomogeneities, and its dynamics are pictured as a process of propagating cracks that are unstable against side-branch formation. The initial cracks and side branches both merge mutually to form fragments. The side branches have a finite penetration depth as a result of inherent damping. Generic arguments imply that close to the minimum strain (or impact energy) required for fragmentation, the number of fragments of size s scales as s-(2D-1)/Df1(-(2/λ)Ds)+f2(-s0-1(λ+s1/D)D) , where D is the Euclidean dimension of the space, λ is the penetration depth, and f1 and f2 can be approximated by exponential functions. Simulation results and experiments can both be described by this theoretical fragment-size distribution. The typical largest fragment size s0 was found to diverge at the minimum strain required for fragmentation as it is inversely related to the density of initially formed cracks. Our results also indicate that scaling of s0 close to this divergence depends on, e.g., loading conditions, and thus is not universal. At the same time, the density of fragment surface vanishes as L-1 , L being the linear dimension of the brittle solid. The results obtained provide an explanation as to why the fragment-size distributions found in nature can have two components, an exponential as well as a power-law component, with varying relative weights.

  1. Pauling bond strength, bond length and electron density distribution

    SciTech Connect

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.; Iversen, Bo B.; Spackman, M. A.

    2014-01-18

    A power law regression equation, = 1.46(<ρ(rc)>/r)-0.19, connecting the average experimental bond lengths, , with the average accumulation of the electron density at the bond critical point, <ρ(rc)>, between bonded metal M and oxygen atoms, determined at ambient conditions for oxide crystals, where r is the row number of the M atom, is similar to the regression equation R(M-O) = 1.39(ρ(rc)/r)-0.21 determined for three perovskite crystals for pressures as high as 80 GPa. The two equations are also comparable with those, = 1.43(/r)-0.21, determined for a large number of oxide crystals at ambient conditions and = 1.39(/r)-0.22, determined for geometry optimized hydroxyacid molecules, that connect the bond lengths to the average Pauling electrostatic bond strength, , for the M-O bonded interactions. On the basis of the correspondence between the two sets of equations connecting ρ(rc) and the Pauling bond strength s with bond length, it appears that Pauling’s simple definition of bond strength closely mimics the accumulation of the electron density between bonded pairs of atoms. The similarity of the expressions for the crystals and molecules is compelling evidence that the M-O bonded interactions for the crystals and molecules 2 containing the same bonded interactions are comparable. Similar expressions, connecting bond lengths and bond strength, have also been found to hold for fluoride, nitride and sulfide molecules and crystals. The Brown-Shannon bond valence, σ, power law expression σ = [R1/(R(M-O)]N that has found wide use in crystal chemistry, is shown to be connected to a more universal expression determined for oxides and the perovskites, <ρ(rc)> = r[(1.41)/]4.76, demonstrating that the bond valence for a bonded interaction is likewise closely connected to the accumulation of the electron density between the bonded atoms. Unlike the Brown-Shannon expression, it is universal in that it holds for the M

  2. High-power-density prime power systems: A literature search and analysis

    SciTech Connect

    Hamby, D.C. . Research Inst.)

    1989-06-01

    The electrical characteristics of the loads to be faced by the power source are given. Two loads are inductive-resistive; one to be brought to a specified flux in the inductor and one to be brought to a specified energy in the inductor within stated time limits which are of the order of milliseconds. The third load is capacitive-resistive and the capacitor is to be brought to a specified voltage in a period of seconds. Charge (a few Coulombs) and energy (about 10{sup 5} Joules) requirements of the loads are modest compared to the capabilities of common automotive batteries; however, the average power demands of the loads are high (25 to 50 MW or higher for the inductive-resistive loads). Source voltages required to drive the specified loads are much larger than those of common batteries. The literature indicates that the way to achieve the required voltages at high power density and specific power is to utilize thin cell bipolar batteries, a bipolar design offers potential advantages of low cell resistance and weight, and uniformity of electrode current density. 123 refs., 31 figs., 3 tabs.

  3. 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... an engine family's power density in kW/L by dividing the unrounded maximum engine power by the...

  4. Study on load forecasting to data centers of high power density based on power usage effectiveness

    NASA Astrophysics Data System (ADS)

    Zhou, C. C.; Zhang, F.; Yuan, Z.; Zhou, L. M.; Wang, F. M.; Li, W.; Yang, J. H.

    2016-08-01

    There is usually considerable energy consumption in data centers. Load forecasting to data centers is in favor of formulating regional load density indexes and of great benefit to getting regional spatial load forecasting more accurately. The building structure and the other influential factors, i.e. equipment, geographic and climatic conditions, are considered for the data centers, and a method to forecast the load of the data centers based on power usage effectiveness is proposed. The cooling capacity of a data center and the index of the power usage effectiveness are used to forecast the power load of the data center in the method. The cooling capacity is obtained by calculating the heat load of the data center. The index is estimated using the group decision-making method of mixed language information. An example is given to prove the applicability and accuracy of this method.

  5. 14 CFR 23.1310 - Power source capacity and distribution.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Power source capacity and distribution. 23.1310 Section 23.1310 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... Equipment General § 23.1310 Power source capacity and distribution. (a) Each installation whose...

  6. 14 CFR 23.1310 - Power source capacity and distribution.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Power source capacity and distribution. 23.1310 Section 23.1310 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... Equipment General § 23.1310 Power source capacity and distribution. (a) Each installation whose...

  7. 14 CFR 23.1310 - Power source capacity and distribution.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Power source capacity and distribution. 23.1310 Section 23.1310 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... Equipment General § 23.1310 Power source capacity and distribution. (a) Each installation whose...

  8. Validity of power functionals for a homogeneous electron gas in reduced-density-matrix-functional theory

    NASA Astrophysics Data System (ADS)

    Putaja, A.; Eich, F. G.; Baldsiefen, T.; Räsänen, E.

    2016-03-01

    Physically valid and numerically efficient approximations for the exchange and correlation energy are critical for reduced-density-matrix-functional theory to become a widely used method in electronic structure calculations. Here we examine the physical limits of power functionals of the form f (n ,n') =(nn')α for the scaling function in the exchange-correlation energy. To this end we obtain numerically the minimizing momentum distributions for the three- and two-dimensional homogeneous electron gas, respectively. In particular, we examine the limiting values for the power α to yield physically sound solutions that satisfy the Lieb-Oxford lower bound for the exchange-correlation energy and exclude pinned states with the condition n (k )<1 for all wave vectors k . The results refine the constraints previously obtained from trial momentum distributions. We also compute the values for α that yield the exact correlation energy and its kinetic part for both the three- and two-dimensional electron gas. In both systems, narrow regimes of validity and accuracy are found at α ≳0.6 and at rs≳10 for the density parameter, corresponding to relatively low densities.

  9. Inverter power module with distributed support for direct substrate cooling

    DOEpatents

    Miller, David Harold [San Pedro, CA; Korich, Mark D [Chino Hills, CA; Ward, Terence G [Redondo Beach, CA; Mann, Brooks S [Redondo Beach, CA

    2012-08-21

    Systems and/or methods are provided for an inverter power module with distributed support for direct substrate cooling. An inverter module comprises a power electronic substrate. A first support frame is adapted to house the power electronic substrate and has a first region adapted to allow direct cooling of the power electronic substrate. A gasket is interposed between the power electronic substrate and the first support frame. The gasket is configured to provide a seal between the first region and the power electronic substrate. A second support frame is adapted to house the power electronic substrate and joined to the first support frame to form the seal.

  10. A Testbed for Deploying Distributed State Estimation in Power Grid

    SciTech Connect

    Jin, Shuangshuang; Chen, Yousu; Rice, Mark J.; Liu, Yan; Gorton, Ian

    2012-07-22

    Abstract—With the increasing demand, scale and data information of power systems, fast distributed applications are becoming more important in power system operation and control. This paper proposes a testbed for evaluating power system distributed applications, considering data exchange among distributed areas. A high-performance computing (HPC) version of distributed state estimation is implemented and used as a distributed application example. The IEEE 118-bus system is used to deploy the parallel distributed state estimation, and the MeDICi middleware is used for data communication. The performance of the testbed demonstrates its capability to evaluate parallel distributed state estimation by leveraging the HPC paradigm. This testbed can also be applied to evaluate other distributed applications.

  11. Improved calibration of mass stopping power in low density tissue for a proton pencil beam algorithm

    NASA Astrophysics Data System (ADS)

    Warren, Daniel R.; Partridge, Mike; Hill, Mark A.; Peach, Ken

    2015-06-01

    Dose distributions for proton therapy treatments are almost exclusively calculated using pencil beam algorithms. An essential input to these algorithms is the patient model, derived from x-ray computed tomography (CT), which is used to estimate proton stopping power along the pencil beam paths. This study highlights a potential inaccuracy in the mapping between mass density and proton stopping power used by a clinical pencil beam algorithm in materials less dense than water. It proposes an alternative physically-motivated function (the mass average, or MA, formula) for use in this region. Comparisons are made between dose-depth curves calculated by the pencil beam method and those calculated by the Monte Carlo particle transport code MCNPX in a one-dimensional lung model. Proton range differences of up to 3% are observed between the methods, reduced to  <1% when using the MA function. The impact of these range errors on clinical dose distributions is demonstrated using treatment plans for a non-small cell lung cancer patient. The change in stopping power calculation methodology results in relatively minor differences in dose when plans use three fields, but differences are observed at the 2%-2 mm level when a single field uniform dose technique is adopted. It is therefore suggested that the MA formula is adopted by users of the pencil beam algorithm for optimal dose calculation in lung, and that a similar approach is considered when beams traverse other low density regions such as the paranasal sinuses and mastoid process.

  12. Improved calibration of mass stopping power in low density tissue for a proton pencil beam algorithm.

    PubMed

    Warren, Daniel R; Partridge, Mike; Hill, Mark A; Peach, Ken

    2015-06-07

    Dose distributions for proton therapy treatments are almost exclusively calculated using pencil beam algorithms. An essential input to these algorithms is the patient model, derived from x-ray computed tomography (CT), which is used to estimate proton stopping power along the pencil beam paths. This study highlights a potential inaccuracy in the mapping between mass density and proton stopping power used by a clinical pencil beam algorithm in materials less dense than water. It proposes an alternative physically-motivated function (the mass average, or MA, formula) for use in this region. Comparisons are made between dose-depth curves calculated by the pencil beam method and those calculated by the Monte Carlo particle transport code MCNPX in a one-dimensional lung model. Proton range differences of up to 3% are observed between the methods, reduced to  <1% when using the MA function. The impact of these range errors on clinical dose distributions is demonstrated using treatment plans for a non-small cell lung cancer patient. The change in stopping power calculation methodology results in relatively minor differences in dose when plans use three fields, but differences are observed at the 2%-2 mm level when a single field uniform dose technique is adopted. It is therefore suggested that the MA formula is adopted by users of the pencil beam algorithm for optimal dose calculation in lung, and that a similar approach is considered when beams traverse other low density regions such as the paranasal sinuses and mastoid process.

  13. Matter density perturbation and power spectrum in running vacuum model

    NASA Astrophysics Data System (ADS)

    Geng, Chao-Qiang; Lee, Chung-Chi

    2017-01-01

    We investigate the matter density perturbation δm and power spectrum P(k) in the running vacuum model, with the cosmological constant being a function of the Hubble parameter, given by Λ = Λ0 + 6σHH0 + 3νH2, in which the linear and quadratic terms of H would originate from the QCD vacuum condensation and cosmological renormalization group, respectively. Taking the dark energy perturbation into consideration, we derive the evolution equation for δm and find a specific scale dcr = 2π/kcr, which divides the evolution of the universe into the sub-interaction and super-interaction regimes, corresponding to k ≪ kcr and k ≫ kcr, respectively. For the former, the evolution of δm has the same behaviour as that in the Λ cold dark model, while for the latter, the growth of δm is frozen (greatly enhanced) when ν + σ > (<)0 due to the couplings between radiation, matter and dark energy. It is clear that the observational data rule out the cases with ν < 0 and ν + σ < 0, while the allowed window for the model parameters is extremely narrow with ν , |σ | ≲ O(10^{-7}).

  14. An overview of power spectral density (PSD) calculations

    NASA Astrophysics Data System (ADS)

    Youngworth, Richard N.; Gallagher, Benjamin B.; Stamper, Brian L.

    2005-09-01

    Specifications for optical surfaces have traditionally been given in terms of low frequency and high frequency components, often with a separate classification for surface slope. Low spatial frequency components are commonly referred to as figure errors and can be described by the standard 37-term Zernike polynomial set. High spatial frequency errors are commonly referred to as finish and are quantified using rms roughness. Specification with the qualitative scratch and dig classification is done usually for cosmetic or aesthetic purposes. Mid-spatial frequency errors such as waviness, ripple, and quilting can be important and are not explicitly covered by such traditional figure and finish specifications. In order to bridge the gap to cover mid-spatial frequencies, in terms of quantifying surface characteristics, Power Spectral Density (PSD) can be utilized. For such usage, it is important for the greater optics community to understand the metric, how to calculate it, and how to use it. The purpose of this paper is to provide an overview of PSD, its application in optics, and an outline of calculations needed to effectively apply it to specify optical surfaces.

  15. Local control of reactive power by distributed photovoltaic generators

    SciTech Connect

    Chertkov, Michael; Turitsyn, Konstantin; Sulc, Petr; Backhaus, Scott

    2010-01-01

    High penetration levels of distributed photovoltaic (PV) generation on an electrical distribution circuit may severely degrade power quality due to voltage sags and swells caused by rapidly varying PV generation during cloud transients coupled with the slow response of existing utility compensation and regulation equipment. Although not permitted under current standards for interconnection of distributed generation, fast-reacting, VAR-capable PV inverters may provide the necessary reactive power injection or consumption to maintain voltage regulation under difficult transient conditions. As side benefit, the control of reactive power injection at each PV inverter provides an opportunity and a new tool for distribution utilities to optimize the performance of distribution circuits, e.g. by minimizing thermal losses. We suggest a local control scheme that dispatches reactive power from each PV inverter based on local instantaneous measurements of the real and reactive components of the consumed power and the real power generated by the PVs. Using one adjustable parameter per circuit, we balance the requirements on power quality and desire to minimize thermal losses. Numerical analysis of two exemplary systems, with comparable total PV generation albeit a different spatial distribution, show how to adjust the optimization parameter depending on the goal. Overall, this local scheme shows excellent performance; it's capable of guaranteeing acceptable power quality and achieving significant saving in thermal losses in various situations even when the renewable generation in excess of the circuit own load, i.e. feeding power back to the higher-level system.

  16. Brief communication: coaxial lines for multiphase power distribution.

    PubMed

    Barnes, F S; Harwick, P; Banerjee, A

    1996-01-01

    A coaxial cable can be used to reduce the magnetic and electric fields that extend into environments in the vicinity of transmission lines and distribution lines and in-house or building wiring for power distribution systems. The use of the coaxial geometry may prove useful in cases where there are environmental concerns with respect to health effects and in cases where there is a need to run high-speed data communications in close proximity to power distribution systems.

  17. The correlation function for density perturbations in an expanding universe. IV - The evolution of the correlation function. [galaxy distribution

    NASA Technical Reports Server (NTRS)

    Mcclelland, J.; Silk, J.

    1979-01-01

    The evolution of the two-point correlation function for the large-scale distribution of galaxies in an expanding universe is studied on the assumption that the perturbation densities lie in a Gaussian distribution centered on any given mass scale. The perturbations are evolved according to the Friedmann equation, and the correlation function for the resulting distribution of perturbations at the present epoch is calculated. It is found that: (1) the computed correlation function gives a satisfactory fit to the observed function in cosmological models with a density parameter (Omega) of approximately unity, provided that a certain free parameter is suitably adjusted; (2) the power-law slope in the nonlinear regime reflects the initial fluctuation spectrum, provided that the density profile of individual perturbations declines more rapidly than the -2.4 power of distance; and (3) both positive and negative contributions to the correlation function are predicted for cosmological models with Omega less than unity.

  18. High-resolution Tangential AXUV Arrays for Radiated Power Density Measurements on NSTX-U

    SciTech Connect

    Delgado-Aparicio, L; Bell, R E; Faust, I; Tritz, K; Diallo, A; Gerhardt, S P; Kozub, T A; LeBlanc, B P; Stratton, B C

    2014-07-01

    Precise measurements of the local radiated power density and total radiated power are a matter of the uttermost importance for understanding the onset of impurity-induced instabilities and the study of particle and heat transport. Accounting of power balance is also needed for the understanding the physics of various divertor con gurations for present and future high-power fusion devices. Poloidal asymmetries in the impurity density can result from high Mach numbers and can impact the assessment of their flux-surface-average and hence vary the estimates of P[sub]rad (r, t) and (Z[sub]eff); the latter is used in the calculation of the neoclassical conductivity and the interpretation of non-inductive and inductive current fractions. To this end, the bolometric diagnostic in NSTX-U will be upgraded, enhancing the midplane coverage and radial resolution with two tangential views, and adding a new set of poloidally-viewing arrays to measure the 2D radiation distribution. These systems are designed to contribute to the near- and long-term highest priority research goals for NSTX-U which will integrate non-inductive operation at reduced collisionality, with high-pressure, long energy-confinement-times and a divertor solution with metal walls.

  19. Quantum quenches and work distributions in ultra-low-density systems

    NASA Astrophysics Data System (ADS)

    Shchadilova, Yulia; Ribeiro, Pedro; Haque, Masudul

    2014-03-01

    In our contribution we present results on quantum quenches in systems with a fixed number of particles in a large volume, the situation accessible in cold atom experiments. We show that the typical differences between local and global quenches present in systems with regular thermodynamic limit are lacking in this low-density limit. In particular, we show that local and global quenches can have power-law work distributions (edge singularities) typically associated with only local quenches for finite-density systems. We show that this regime allows for large edge singularity exponents beyond that allowed by the constraints of the usual thermodynamic limit (e.g., by Anderson's orthogonality catastrophe). This large-exponent singularity has observable consequences in the time evolution, leading to a distinct intermediate power-law regime in time. We demonstrate these results using local quantum quenches in a low-density Kondo-like system, and additionally through global and local quenches in Bose-Hubbard, Aubry-Andre, and hard-core boson systems in the low-density regime. Max Planck Institute for the Physics of Complex Systems, Dresden, Germany; A. M. Prokhorov General Physical Institute, Moscow, Russia.

  20. 1310 nm quantum dot DFB lasers with high dot density and ultra-low linewidth-power product

    NASA Technical Reports Server (NTRS)

    Qiu, Y.; Lester, L. F.; Gray, A. L.; Newell, T. C.; Hains, C.; Gogna, P.; Muller, R.; Maker, P.; Su, H.; Stintz, A.

    2002-01-01

    Laterally coupled distributed feedback lasers using high-density InAs quantum dots-in-a-well (DWELL) active region demonstrate a nominal wavelength of 1310 nm, a linewidth as small as 68 kHz, and a linewidth-power product of 100 kHz-mW.

  1. Technology spin-off from space power automation to terrestrial electrical power distribution control and operation

    NASA Astrophysics Data System (ADS)

    Callis, C. T.; Broadwater, R. P.; Chandrasekaran, A.

    Areas which hold potential for technology spin-off from space power automation into terrestrial electrical power distribution control and automation are investigated. Areas touched upon include load management, loss reduction, trend analysis, energy storage, and fault diagnosis and analysis with expert systems. A brief overview of terrestrial electric power technology and automation in terrestrial distribution is provided. Power handling capabilities, hardware, loads, and goals of terrestrial and space systems are compared.

  2. Thresholded Power law Size Distributions of Instabilities in Astrophysics

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.

    2015-11-01

    Power-law-like size distributions are ubiquitous in astrophysical instabilities. There are at least four natural effects that cause deviations from ideal power law size distributions, which we model here in a generalized way: (1) a physical threshold of an instability; (2) incomplete sampling of the smallest events below a threshold x0; (3) contamination by an event-unrelated background xb; and (4) truncation effects at the largest events due to a finite system size. These effects can be modeled in the simplest terms with a “thresholded power law” distribution function (also called generalized Pareto [type II] or Lomax distribution), N(x){dx}\\propto {(x+{x}0)}-a{dx}, where x0 > 0 is positive for a threshold effect, while x0 < 0 is negative for background contamination. We analytically derive the functional shape of this thresholded power law distribution function from an exponential growth evolution model, which produces avalanches only when a disturbance exceeds a critical threshold x0. We apply the thresholded power law distribution function to terrestrial, solar (HXRBS, BATSE, RHESSI), and stellar flare (Kepler) data sets. We find that the thresholded power law model provides an adequate fit to most of the observed data. Major advantages of this model are the automated choice of the power law fitting range, diagnostics of background contamination, physical instability thresholds, instrumental detection thresholds, and finite system size limits. When testing self-organized criticality models that predict ideal power laws, we suggest including these natural truncation effects.

  3. Electric power processing, distribution and control for advanced aerospace vehicles.

    NASA Technical Reports Server (NTRS)

    Krausz, A.; Felch, J. L.

    1972-01-01

    The results of a current study program to develop a rational basis for selection of power processing, distribution, and control configurations for future aerospace vehicles including the Space Station, Space Shuttle, and high-performance aircraft are presented. Within the constraints imposed by the characteristics of power generation subsystems and the load utilization equipment requirements, the power processing, distribution and control subsystem can be optimized by selection of the proper distribution voltage, frequency, and overload/fault protection method. It is shown that, for large space vehicles which rely on static energy conversion to provide electric power, high-voltage dc distribution (above 100 V dc) is preferable to conventional 28 V dc and 115 V ac distribution per MIL-STD-704A. High-voltage dc also has advantages over conventional constant frequency ac systems in many aircraft applications due to the elimination of speed control, wave shaping, and synchronization equipment.

  4. Statistical analyses support power law distributions found in neuronal avalanches.

    PubMed

    Klaus, Andreas; Yu, Shan; Plenz, Dietmar

    2011-01-01

    The size distribution of neuronal avalanches in cortical networks has been reported to follow a power law distribution with exponent close to -1.5, which is a reflection of long-range spatial correlations in spontaneous neuronal activity. However, identifying power law scaling in empirical data can be difficult and sometimes controversial. In the present study, we tested the power law hypothesis for neuronal avalanches by using more stringent statistical analyses. In particular, we performed the following steps: (i) analysis of finite-size scaling to identify scale-free dynamics in neuronal avalanches, (ii) model parameter estimation to determine the specific exponent of the power law, and (iii) comparison of the power law to alternative model distributions. Consistent with critical state dynamics, avalanche size distributions exhibited robust scaling behavior in which the maximum avalanche size was limited only by the spatial extent of sampling ("finite size" effect). This scale-free dynamics suggests the power law as a model for the distribution of avalanche sizes. Using both the Kolmogorov-Smirnov statistic and a maximum likelihood approach, we found the slope to be close to -1.5, which is in line with previous reports. Finally, the power law model for neuronal avalanches was compared to the exponential and to various heavy-tail distributions based on the Kolmogorov-Smirnov distance and by using a log-likelihood ratio test. Both the power law distribution without and with exponential cut-off provided significantly better fits to the cluster size distributions in neuronal avalanches than the exponential, the lognormal and the gamma distribution. In summary, our findings strongly support the power law scaling in neuronal avalanches, providing further evidence for critical state dynamics in superficial layers of cortex.

  5. A study of power conditioning and power distribution and components

    NASA Technical Reports Server (NTRS)

    Horton, H. M.; Honnell, M. A.

    1973-01-01

    A comprehensive simulation and analysis performed on the operation of the regulator part of the Charger/Battery/Regulator Module (CBRM) are detailed. The CBRM is utilized as an integral component of the Skylab/Apollo Telescope Mount (ATM) electrical power system and contains a switching mode electronic regulator. Implementing circuit analysis techniques, pertinent voltages and currents are calculated; these, in turn, are incorporated into the regulator system study. Investigation of the turn-on and turn-off times associated with the switching circuitry is performed and an examination is made on these calculations. A simulation model computer program is utilized to generate graphs that relate various CBRM parameters to one another.

  6. Probability density distribution of velocity differences at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Praskovsky, Alexander A.

    1993-01-01

    Recent understanding of fine-scale turbulence structure in high Reynolds number flows is mostly based on Kolmogorov's original and revised models. The main finding of these models is that intrinsic characteristics of fine-scale fluctuations are universal ones at high Reynolds numbers, i.e., the functional behavior of any small-scale parameter is the same in all flows if the Reynolds number is high enough. The only large-scale quantity that directly affects small-scale fluctuations is the energy flux through a cascade. In dynamical equilibrium between large- and small-scale motions, this flux is equal to the mean rate of energy dissipation epsilon. The pdd of velocity difference is a very important characteristic for both the basic understanding of fully developed turbulence and engineering problems. Hence, it is important to test the findings: (1) the functional behavior of the tails of the probability density distribution (pdd) represented by P(delta(u)) is proportional to exp(-b(r) absolute value of delta(u)/sigma(sub delta(u))) and (2) the logarithmic decrement b(r) scales as b(r) is proportional to r(sup 0.15) when separation r lies in the inertial subrange in high Reynolds number laboratory shear flows.

  7. Description of a 20 Kilohertz power distribution system

    NASA Technical Reports Server (NTRS)

    Hansen, I. G.

    1986-01-01

    A single phase, 440 VRMS, 20 kHz power distribution system with a regulated sinusoidal wave form is discussed. A single phase power system minimizes the wiring, sensing, and control complexities required in a multi-sourced redundantly distributed power system. The single phase addresses only the distribution link; mulitphase lower frequency inputs and outputs accommodation techniques are described. While the 440 V operating potential was initially selected for aircraft operating below 50,000 ft, this potential also appears suitable for space power systems. This voltage choice recognizes a reasonable upper limit for semiconductor ratings, yet will direct synthesis of 220 V, 3 power. A 20 kHz operating frequency was selected to be above the range of audibility, minimize the weight of reactive components, yet allow the construction of single power stages of 25 to 30 kW. The regulated sinusoidal distribution system has several advantages. With a regulated voltage, most ac/dc conversions involve rather simple transformer rectifier applications. A sinusoidal distribution system, when used in conjunction with zero crossing switching, represents a minimal source of EMI. The present state of 20 kHz power technology includes computer controls of voltage and/or frequency, low inductance cable, current limiting circuit protection, bi-directional power flow, and motor/generator operating using standard induction machines. A status update and description of each of these items and their significance is presented.

  8. Space Station Freedom power management and distribution system design

    NASA Technical Reports Server (NTRS)

    Teren, Fred

    1989-01-01

    The design is described of the Space Station Freedom Power Management and Distribution (PMAD) System. In addition, the significant trade studies which were conducted are described, which led to the current PMAD system configuration.

  9. Power distribution in two-dimensional optical network channels

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Xue; Karim, Mohammad A.

    1996-04-01

    The power distribution in two-dimensional optical network channels is analyzed. The maximum number of allowable channels as determined by the characteristics of optical detector is identified, in particular, for neural-network and wavelet-transform applications.

  10. Energy loss analysis of an integrated space power distribution system

    NASA Technical Reports Server (NTRS)

    Kankam, M. D.; Ribeiro, P. F.

    1992-01-01

    The results of studies related to conceptual topologies of an integrated utility-like space power system are described. The system topologies are comparatively analyzed by considering their transmission energy losses as functions of mainly distribution voltage level and load composition. The analysis is expedited by use of a Distribution System Analysis and Simulation (DSAS) software. This recently developed computer program by the Electric Power Research Institute (EPRI) uses improved load models to solve the power flow within the system. However, present shortcomings of the software with regard to space applications, and incompletely defined characteristics of a space power system make the results applicable to only the fundamental trends of energy losses of the topologies studied. Accountability, such as included, for the effects of the various parameters on the system performance can constitute part of a planning tool for a space power distribution system.

  11. Ion energy distributions and densities in the plume of Enceladus

    NASA Astrophysics Data System (ADS)

    Sakai, Shotaro; Cravens, Thomas E.; Omidi, Nojan; Perry, Mark E.; Waite, J. Hunter

    2016-10-01

    Enceladus has a dynamic plume that is emitting gas, including water vapor, and dust. The gas is ionized by solar EUV radiation, charge exchange, and electron impact and extends throughout the inner magnetosphere of Saturn. The charge exchange collisions alter the plasma composition. Ice grains (dust) escape from the vicinity of Enceladus and form the E ring, including a portion that is negatively charged by the local plasma. The inner magnetosphere within 10 RS (Saturn radii) contains a complex mixture of plasma, neutral gas, and dust that links back to Enceladus. In this paper we investigate the energy distributions, ion species and densities of water group ions in the plume of Enceladus using test particle and Monte Carlo methods that include collisional processes such as charge exchange and ion-neutral chemical reactions. Ion observations from the Cassini Ion and Neutral Mass Spectrometer (INMS) for E07 are presented for the first time. We use the modeling results to interpret observations made by the Cassini Plasma Spectrometer (CAPS) and the INMS. The low energy ions, as observed by CAPS, appear to be affected by a vertical electric field (EZ=-10 μV/m) in the plume. The EZ field may be associated with the charged dust and/or the pressure gradient of plasma. The model results, along with the results of earlier models, show that H3O+ ions created by chemistry are predominant in the plume, which agrees with INMS and CAPS data, but the INMS count rate in the plume for the model is several times greater than the data, which we do not fully understand. This composition and the total ion count found in the plume agree with INMS and CAPS data. On the other hand, the Cassini Langmuir Probe measured a maximum plume ion density more than 30,000 cm-3, which is far larger than the maximum ion density from our model, 900 cm-3. The model results also demonstrate that most of the ions in the plume are from the external magnetospheric flow and are not generated by local

  12. determination of current density distribution in an electron beam

    NASA Astrophysics Data System (ADS)

    Kandel, Yudhishthir Prasad

    Electron beams are useful in many applications because they can be focused down to a spot far exceeding the physical limit of focusing visible light or x-rays. Additionally, electron beams are useful in transferring concentrated amounts of energy to a very small well defined region of a target for a fixed duration. This has led to the development of both scanning electron microscopes (SEMs) and electron beam lithography. The goal of this work was to develop a general method that accurately and easily yields the best estimate of the electron current density distribution of a focused electron beam, known as point spread function (PSF). The method developed is fast, easy to use and accurate. Two specific areas of research have been addressed for PSF determination. The first is concerned with the monotonic response of EUV photoresist as a function of electron beam dose. An external metrology is used for mapping the change in thickness that is smaller than the beam spot size. The method developed in this study simultaneously gives the photo-resist thickness change as a function of electron dose and electron beam PSF. A second thrust of this research has been to develop set of PSF characterization approaches that apply to the SEM. Here a knowledge of the PSF offers many benefits including the ability to monitor and optimize SEM performance such as astigmatism control. Perhaps, even more importantly, a knowledge of the PSF combined with a series of well-defined experimental steps has led to the development of new methods for improving the resolution of SEM images through computational means rather than very costly and complex equipment modification.

  13. Evaluation of ion current density distribution on an extraction electrode of a radio frequency ion thruster

    NASA Astrophysics Data System (ADS)

    Masherov, P.; Riaby, V.; Abgaryan, V.

    2017-01-01

    The radial distributions of ion current density on an ion extracting electrode of a radio frequency (RF) ion thruster (RIT) with an inductive plasma source were obtained using probe diagnostics of the RF xenon plasma. Measurements were carried out using a plane wall probe simulator and the VGPS-12 Probe System of Plasma Sensors Co. At xenon flow rate q  =  2 sccm plasma pressure was 2 · 10-3 Torr, incident RF generator power varied in the range P g  =  50-250 W with RF power absorbed by plasma up to P p  =  220 W. Ion current densities were determined using semi- and double-logarithmic probe characteristics by linear extrapolations of their ion branches to probe floating potentials. The same parameters were also measured in undisturbed plasma by a classic cylindrical probe. They exceeded plane probe data by more than two times, showing the effectiveness of plasma sheath reproduction of the RIT ion extracting electrode by the plane wall probe simulator. Slight non-uniformity of the resulting plasma distributions and simplified RIT model design showed that the studied device with flat antenna coil and ferrite core could be considered as a promising prospect for RITs of new generation.

  14. A comparative study of electric power distribution systems for spacecraft

    NASA Technical Reports Server (NTRS)

    Stuart, Thomas A.; King, Roger J.

    1990-01-01

    The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems.

  15. Power laws in citation distributions: evidence from Scopus.

    PubMed

    Brzezinski, Michal

    Modeling distributions of citations to scientific papers is crucial for understanding how science develops. However, there is a considerable empirical controversy on which statistical model fits the citation distributions best. This paper is concerned with rigorous empirical detection of power-law behaviour in the distribution of citations received by the most highly cited scientific papers. We have used a large, novel data set on citations to scientific papers published between 1998 and 2002 drawn from Scopus. The power-law model is compared with a number of alternative models using a likelihood ratio test. We have found that the power-law hypothesis is rejected for around half of the Scopus fields of science. For these fields of science, the Yule, power-law with exponential cut-off and log-normal distributions seem to fit the data better than the pure power-law model. On the other hand, when the power-law hypothesis is not rejected, it is usually empirically indistinguishable from most of the alternative models. The pure power-law model seems to be the best model only for the most highly cited papers in "Physics and Astronomy". Overall, our results seem to support theories implying that the most highly cited scientific papers follow the Yule, power-law with exponential cut-off or log-normal distribution. Our findings suggest also that power laws in citation distributions, when present, account only for a very small fraction of the published papers (less than 1 % for most of science fields) and that the power-law scaling parameter (exponent) is substantially higher (from around 3.2 to around 4.7) than found in the older literature.

  16. 10 CFR 960.5-2-1 - Population density and distribution.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general...

  17. 10 CFR 960.5-2-1 - Population density and distribution.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general...

  18. 10 CFR 960.5-2-1 - Population density and distribution.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 4 2014-01-01 2014-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general...

  19. 10 CFR 960.5-2-1 - Population density and distribution.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general...

  20. 10 CFR 960.5-2-1 - Population density and distribution.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general...

  1. OXIDATION OF DRY HYDROCARBONS AT HIGH-POWER DENSITY ANODES

    SciTech Connect

    K.Krist; O. Spaldon-Stewart; R. Remick

    2004-03-01

    performance life on dry methane with sulfur compounds was much longer than with dry methane alone. The effect of sulfur compounds in these cases appeared to correlate with inhibition of carbon deposition. Mixed results were obtained for the effect of the sulfur compounds on power density. Progress also was made in understanding the mechanisms involved in direct utilization of dry natural gas. Evidence was developed for three possible mechanisms for dry methane utilization in addition to the usually cited mechanism--direct oxidation of methane by oxygen anions. Further work is required at a fundamental level before the knowledge gained here can be translated into higher levels of performance.

  2. Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices

    DOEpatents

    Chassin, David P.; Donnelly, Matthew K.; Dagle, Jeffery E.

    2006-12-12

    Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices are described. In one aspect, an electrical power distribution control method includes providing electrical energy from an electrical power distribution system, applying the electrical energy to a load, providing a plurality of different values for a threshold at a plurality of moments in time and corresponding to an electrical characteristic of the electrical energy, and adjusting an amount of the electrical energy applied to the load responsive to an electrical characteristic of the electrical energy triggering one of the values of the threshold at the respective moment in time.

  3. Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices

    DOEpatents

    Chassin, David P [Pasco, WA; Donnelly, Matthew K [Kennewick, WA; Dagle, Jeffery E [Richland, WA

    2011-12-06

    Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices are described. In one aspect, an electrical power distribution control method includes providing electrical energy from an electrical power distribution system, applying the electrical energy to a load, providing a plurality of different values for a threshold at a plurality of moments in time and corresponding to an electrical characteristic of the electrical energy, and adjusting an amount of the electrical energy applied to the load responsive to an electrical characteristic of the electrical energy triggering one of the values of the threshold at the respective moment in time.

  4. Effect of power density and pulse repetition on laser shock peening of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Smith, P. R.; Shepard, M. J.; Prevéy, P. S.; Clauer, A. H.

    2000-02-01

    Laser shock peening (LSP) was applied to Ti-6Al-4V (wt. %) simulated airfoil specimens using a Nd:Glass laser. Laser shock peening processing parameters examined in the present study included power density (5.5, 7, and 9 GW/cm2) and number of laser pulses per spot (one and three pulses/spot). The LSP’d Ti-6Al-4V samples were examined using x-ray diffraction techniques to determine the residual stress distribution and percent cold work as a function of depth. It was found that the residual stress state and percent of cold work were relatively independent of LSP power density. However, the number of laser pulses per spot had a significant effect on both residual stress and percent of cold work for a given power density level. In addition, there was a strong correlation between the magnitude of residual compressive stresses generated and the percent cold work measured.

  5. Effect of power density and pulse repetition on laser shock peening of Ti-6Al-4V

    SciTech Connect

    Smith, P.R.; Shepard, M.J.; Prevey, P.S. III; Clauer, A.H.

    2000-02-01

    Laser shock peening (LSP) was applied to Ti-6Al-4V (wt.%) simulated airfoil specimens using a Nd:Glass laser. Laser shock peening processing parameters examined in the present study included power density (5.5, 7, and 9 GW/cm{sup 2}) and number of laser pulses per spot (one and three pulses/spot). The LSP's Ti-6Al-4V samples were examined using x-ray diffraction techniques to determine the residual stress distribution and percent cold work as a function of depth. It was found that the residual stress state and percent of cold work were relatively independent of LSP power density. However, the number of laser pulses per spot had a significant effect on both residual stress and percent of cold work for a given power density level. In addition, there was a strong correlation between the magnitude of residual compressive stresses generated and the percent cold work measured.

  6. 62. View of amplifiermodulator control system with power distribution panel ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    62. View of amplifier-modulator control system with power distribution panel on left, control power supply in middle, and amplifier modulator on right, second floor in transmitter building no. 102. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  7. A generalization of the power law distribution with nonlinear exponent

    NASA Astrophysics Data System (ADS)

    Prieto, Faustino; Sarabia, José María

    2017-01-01

    The power law distribution is usually used to fit data in the upper tail of the distribution. However, commonly it is not valid to model data in all the range. In this paper, we present a new family of distributions, the so-called Generalized Power Law (GPL), which can be useful for modeling data in all the range and possess power law tails. To do that, we model the exponent of the power law using a non-linear function which depends on data and two parameters. Then, we provide some basic properties and some specific models of that new family of distributions. After that, we study a relevant model of the family, with special emphasis on the quantile and hazard functions, and the corresponding estimation and testing methods. Finally, as an empirical evidence, we study how the debt is distributed across municipalities in Spain. We check that power law model is only valid in the upper tail; we show analytically and graphically the competence of the new model with municipal debt data in the whole range; and we compare the new distribution with other well-known distributions including the Lognormal, the Generalized Pareto, the Fisk, the Burr type XII and the Dagum models.

  8. Student Difficulties in Learning Density: A Distributed Cognition Perspective

    ERIC Educational Resources Information Center

    Xu, Lihua; Clarke, David

    2012-01-01

    Density has been reported as one of the most difficult concepts for secondary school students (e.g. Smith et al. 1997). Discussion about the difficulties of learning this concept has been largely focused on the complexity of the concept itself or student misconceptions. Few, if any, have investigated how the concept of density was constituted in…

  9. Space Station Freedom power management and distribution design status

    NASA Technical Reports Server (NTRS)

    Javidi, S.; Gholdston, E.; Stroh, P.

    1989-01-01

    The design status of the power management and distribution electric power system for the Space Station Freedom is presented. The current design is a star architecture, which has been found to be the best approach for meeting the requirement to deliver 120 V dc to the user interface. The architecture minimizes mass and power losses while improving element-to-element isolation and system flexibility. The design is partitioned into three elements: energy collection, storage and conversion, system protection and distribution, and management and control.

  10. Surface Area, Volume, Mass, and Density Distributions for Sized Biomass Particles

    SciTech Connect

    Ramanathan Sampath

    2007-06-30

    This final technical report describes work performed at Morehouse College under DOE Grant No. DE-FC26-04NT42130 during the period July 01, 2004 to June 30, 2007 which covers the entire performance period of the project. 25 individual biomass particles (hardwood sawdust AI14546 in the size range of 100-200 microns) were levitated in an electrodynamic balance (EDB) and their external surface area, volume, and drag coefficient/mass (C{sub d}/m) ratios were characterized applying highly specialized video based and high-speed diode array imaging systems. Analysis methods were employed using shape and drag information to calculate mass and density distributions for these particles. Results of these measurements and analyses were validated by independent mass measurements using a particle weighing and counting technique. Similar information for 28 PSOC 1451D bituminous coal particles was retrieved from a previously published work. Using these two information, density correlations for coal/biomass blends were developed. These correlations can be used to estimate the density of the blend knowing either the volume fraction or the mass fraction of coal in the blend. The density correlations presented here will be useful in predicting the burning rate of coal/biomass blends in cofiring combustors. Finally, a discussion on technological impacts and economic projections of burning biomass with coal in US power plants is presented.

  11. Relationship between the column density distribution and evolutionary class of molecular clouds as viewed by ATLASGAL

    NASA Astrophysics Data System (ADS)

    Abreu-Vicente, J.; Kainulainen, J.; Stutz, A.; Henning, Th.; Beuther, H.

    2015-09-01

    We present the first study of the relationship between the column density distribution of molecular clouds within nearby Galactic spiral arms and their evolutionary status as measured from their stellar content. We analyze a sample of 195 molecular clouds located at distances below 5.5 kpc, identified from the ATLASGAL 870 μm data. We define three evolutionary classes within this sample: starless clumps, star-forming clouds with associated young stellar objects, and clouds associated with H ii regions. We find that the N(H2) probability density functions (N-PDFs) of these three classes of objects are clearly different: the N-PDFs of starless clumps are narrowest and close to log-normal in shape, while star-forming clouds and H ii regions exhibit a power-law shape over a wide range of column densities and log-normal-like components only at low column densities. We use the N-PDFs to estimate the evolutionary time-scales of the three classes of objects based on a simple analytic model from literature. Finally, we show that the integral of the N-PDFs, the dense gas mass fraction, depends on the total mass of the regions as measured by ATLASGAL: more massive clouds contain greater relative amounts of dense gas across all evolutionary classes. Appendices are available in electronic form at http://www.aanda.org

  12. Analytical Limit Distributions from Random Power-Law Interactions

    NASA Astrophysics Data System (ADS)

    Zaid, Irwin; Mizuno, Daisuke

    2016-07-01

    Nature is full of power-law interactions, e.g., gravity, electrostatics, and hydrodynamics. When sources of such fields are randomly distributed in space, the superposed interaction, which is what we observe, is naively expected to follow a Gauss or Lévy distribution. Here, we present an analytic expression for the actual distributions that converge to novel limits that are in between these already-known limit distributions, depending on physical parameters, such as the concentration of field sources and the size of the probe used to measure the interactions. By comparing with numerical simulations, the origin of non-Gauss and non-Lévy distributions are theoretically articulated.

  13. Insights into the crystal chemistry of Earth materials rendered by electron density distributions: Pauling's rules revisited

    SciTech Connect

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.

    2014-05-20

    Pauling's first two rules are examined in terms of the accumulation of the electron density between bonded pairs of atoms for a relatively large number of oxide and silicate crystals and siloxane molecules. The distribution of the electron density shows that the radius of the oxygen atom is not fixed, but that it actually decreases systematically from ~1.40 Å to ~ 0.65 Å as the polarizing power and the electronegativity of the bonded metal atoms increase and the distribution of the O atom is progressively polarized and contracted along the bond vectors by the impact of the bonded interactions. The contractions result in an aspherical oxygen atom that displays as many different bonded “radii” as it has bonded interactions. The bonded radii for the metal atoms match the Shannon and Prewitt ionic radii for the more electropositive atoms like potassium and sodium, but they are systematically larger for the more electronegative atoms like aluminum, silicon and phosphorous. Pauling's first rule is based on the assumption that the radius of the oxide anion is fixed and that the radii of the cations are such that radius sum of the spherical oxide anion and a cation necessarily equals the separation between the cation-anion bonded pair with the coordination number of the cation being determined by the ratio of the radii of the cation and anion. In the case of the bonded radii, the sum of the bonded radii for the metal atoms and the oxide anion necessarily equals the bond lengths by virtue of the way that the bonded radii were determined in the partitioning of the electron density along the bond path into metal and O atom parts. But, the radius ratio for the O and M atoms is an unsatisfactory rule for determining the coordination number of the metal atom inasmuch as a bonded O atom is not, in general, spherical, and its size varies substantially along its bonded directions. But by counting the number of bond paths that radiate from a bonded atom, the coordination

  14. Space station automation of common module power management and distribution

    NASA Technical Reports Server (NTRS)

    Miller, W.; Jones, E.; Ashworth, B.; Riedesel, J.; Myers, C.; Freeman, K.; Steele, D.; Palmer, R.; Walsh, R.; Gohring, J.

    1989-01-01

    The purpose is to automate a breadboard level Power Management and Distribution (PMAD) system which possesses many functional characteristics of a specified Space Station power system. The automation system was built upon 20 kHz ac source with redundancy of the power buses. There are two power distribution control units which furnish power to six load centers which in turn enable load circuits based upon a system generated schedule. The progress in building this specified autonomous system is described. Automation of Space Station Module PMAD was accomplished by segmenting the complete task in the following four independent tasks: (1) develop a detailed approach for PMAD automation; (2) define the software and hardware elements of automation; (3) develop the automation system for the PMAD breadboard; and (4) select an appropriate host processing environment.

  15. Probabilistic Vulnerability Assessment Based on Power Flow and Voltage Distribution

    SciTech Connect

    Ma, Jian; Huang, Zhenyu; Wong, Pak C.; Ferryman, Thomas A.

    2010-04-30

    Risk assessment of large scale power systems has been an important problem in power system reliability study. Probabilistic technique provides a powerful tool to solve the task. In this paper, we present the results of a study on probabilistic vulnerability assessment on WECC system. Cumulant based expansion method is applied to obtain the probabilistic distribution function (PDF) and cumulative distribution function (CDF) of power flows on transmission lines and voltage. Overall risk index based on the system vulnerability analysis is calculated using the WECC system. The simulation results based on WECC system is used to demonstrate the effectiveness of the method. The methodology can be applied to the risk analysis on large scale power systems.

  16. Optimal load distribution between units in a power plant.

    PubMed

    Bortoni, Edson C; Bastos, Guilherme S; Souza, Luiz E

    2007-10-01

    This paper presents a strategy for load distribution between the generating units in hydro power plants. The objective is to reach the maximum energy conversion efficiency for a given dispatched power. The developed tool employs a heuristic-based combinatorial optimization technique in conjunction with a set of system variables measurement allowing real-time load sharing. The developed equipment is used to give online energy conversion efficiency from each unit of the power plant. No specific previous information about the efficiency of system components is required. Simulation results of the proposed optimization technique when applied to typical hydro power plant data are presented.

  17. Optimal Operation of Energy Storage in Power Transmission and Distribution

    NASA Astrophysics Data System (ADS)

    Akhavan Hejazi, Seyed Hossein

    In this thesis, we investigate optimal operation of energy storage units in power transmission and distribution grids. At transmission level, we investigate the problem where an investor-owned independently-operated energy storage system seeks to offer energy and ancillary services in the day-ahead and real-time markets. We specifically consider the case where a significant portion of the power generated in the grid is from renewable energy resources and there exists significant uncertainty in system operation. In this regard, we formulate a stochastic programming framework to choose optimal energy and reserve bids for the storage units that takes into account the fluctuating nature of the market prices due to the randomness in the renewable power generation availability. At distribution level, we develop a comprehensive data set to model various stochastic factors on power distribution networks, with focus on networks that have high penetration of electric vehicle charging load and distributed renewable generation. Furthermore, we develop a data-driven stochastic model for energy storage operation at distribution level, where the distribution of nodal voltage and line power flow are modelled as stochastic functions of the energy storage unit's charge and discharge schedules. In particular, we develop new closed-form stochastic models for such key operational parameters in the system. Our approach is analytical and allows formulating tractable optimization problems. Yet, it does not involve any restricting assumption on the distribution of random parameters, hence, it results in accurate modeling of uncertainties. By considering the specific characteristics of random variables, such as their statistical dependencies and often irregularly-shaped probability distributions, we propose a non-parametric chance-constrained optimization approach to operate and plan energy storage units in power distribution girds. In the proposed stochastic optimization, we consider

  18. The Effects of Transients on Photospheric and Chromospheric Power Distributions

    NASA Astrophysics Data System (ADS)

    Samanta, T.; Henriques, V. M. J.; Banerjee, D.; Krishna Prasad, S.; Mathioudakis, M.; Jess, D.; Pant, V.

    2016-09-01

    We have observed a quiet-Sun region with the Swedish 1 m Solar Telescope equipped with the CRISP Imaging SpectroPolarimeter. High-resolution, high-cadence, Hα line scanning images were taken to observe different layers of the solar atmosphere from the photosphere to upper chromosphere. We study the distribution of power in different period bands at different heights. Power maps of the upper photosphere and the lower chromosphere show suppressed power surrounding the magnetic-network elements, known as “magnetic shadows.” These also show enhanced power close to the photosphere, traditionally referred to as “power halos.” The interaction between acoustic waves and inclined magnetic fields is generally believed to be responsible for these two effects. In this study we explore whether small-scale transients can influence the distribution of power at different heights. We show that the presence of transients, like mottles, Rapid Blueshifted Excursions (RBEs), and Rapid Redshifted Excursions (RREs), can strongly influence the power maps. The short and finite lifetime of these events strongly affects all power maps, potentially influencing the observed power distribution. We show that Doppler-shifted transients like RBEs and RREs that occur ubiquitously can have a dominant effect on the formation of the power halos in the quiet Sun. For magnetic shadows, transients like mottles do not seem to have a significant effect on the power suppression around 3 minutes, and wave interaction may play a key role here. Our high-cadence observations reveal that flows, waves, and shocks manifest in the presence of magnetic fields to form a nonlinear magnetohydrodynamic system.

  19. Comparison of Wind Power and Load Forecasting Error Distributions: Preprint

    SciTech Connect

    Hodge, B. M.; Florita, A.; Orwig, K.; Lew, D.; Milligan, M.

    2012-07-01

    The introduction of large amounts of variable and uncertain power sources, such as wind power, into the electricity grid presents a number of challenges for system operations. One issue involves the uncertainty associated with scheduling power that wind will supply in future timeframes. However, this is not an entirely new challenge; load is also variable and uncertain, and is strongly influenced by weather patterns. In this work we make a comparison between the day-ahead forecasting errors encountered in wind power forecasting and load forecasting. The study examines the distribution of errors from operational forecasting systems in two different Independent System Operator (ISO) regions for both wind power and load forecasts at the day-ahead timeframe. The day-ahead timescale is critical in power system operations because it serves the unit commitment function for slow-starting conventional generators.

  20. Forty-seventh annual power distribution conference, 1994

    SciTech Connect

    Not Available

    1994-01-01

    This is a collection of papers presented at the forty-seventh annual Power Distribution Conference in 1994. The topics of the papers include recent developments in distribution grounding, partial discharge analysis of electrical machinery, insulating fluids analysis as a basis for a complete transformer monitoring program, environmental and regulatory issues regarding the use of silicone transformer fluids, locating and identifying harmonic sources, optimizing distribution operations resources, surface launch directional boring units, electrical supply to Dallas/Fort Worth international airport, a microprocessor-based digital feeder monitor with high-impedance fault detection, a modern review of distribution system protective coordination, and Ski Apache electric service improvements.

  1. Power laws, discontinuities and regional city size distributions

    USGS Publications Warehouse

    Garmestani, A.S.; Allen, C.R.; Gallagher, C.M.

    2008-01-01

    Urban systems are manifestations of human adaptation to the natural environment. City size distributions are the expression of hierarchical processes acting upon urban systems. In this paper, we test the entire city size distributions for the southeastern and southwestern United States (1990), as well as the size classes in these regions for power law behavior. We interpret the differences in the size of the regional city size distributions as the manifestation of variable growth dynamics dependent upon city size. Size classes in the city size distributions are snapshots of stable states within urban systems in flux. ?? 2008.

  2. High power density dc/dc converter: Component selection and design

    NASA Technical Reports Server (NTRS)

    Divan, Deepakraj M.

    1989-01-01

    Further work pertaining to design considerations for the new high power, high frequency dc/dc converters is discussed. The goal of the project is the development of high power, high power density dc/dc converters at power levels in the multi-kilowatt to megawatt range for aerospace applications. The prototype converter is rated for 50 kW at a switching frequency of 50 kHz, with an input voltage of 200 Vdc and an output of 2000 Vdc. The overall power density must be in the vicinity of 0.2 to 0.3 kg/kW.

  3. Comment on "probability distribution of power fluctuations in turbulence".

    PubMed

    Nadarajah, Saralees; Ongodiebi, Zuonaki

    2014-06-01

    Bandi et al. [Phys. Rev. E 79, 016309 (2009)] reported a closed form expression for the probability density function of the product of two correlated normal random variables and proposed an approximation for the distribution of its mean. Here, we question the closed form expression and derive exact expressions for the distribution of the mean. The proposed approximation is shown to be poor.

  4. Systematics of nucleon density distributions and neutron skin of nuclei

    NASA Astrophysics Data System (ADS)

    Seif, W. M.; Mansour, Hesham

    2015-10-01

    Proton and neutron density profiles of 760 nuclei in the mass region of A = 16-304 are analyzed using the Skyrme energy density for the parameter set SLy4. Simple formulae are obtained to fit the resulting radii and diffuseness data. These formulae are useful to estimate the values of the unmeasured radii and especially in extrapolating charge radii values for nuclei which are far from the valley of stability. Also, it provides an easy way to formulate the density profile for nuclear applications and to perform analytic calculations for bound and/or scattering problems. The obtained neutron and proton root-mean-square (rms) radii and the neutron skin thicknesses are in agreement with the available experimental data and previous Hartree-Fock (HF) calculations.

  5. Distributed photovoltaic generation in residential distribution systems: Impacts on power quality and anti-islanding

    NASA Astrophysics Data System (ADS)

    Mitra, Parag

    The past few decades have seen a consistent growth of distributed PV sources. Distributed PV, like other DG sources, can be located at or near load centers and provide benefits which traditional generation may lack. However, distribution systems were not designed to accommodate such power generation sources as these sources might lead to operational as well as power quality issues. A high penetration of distributed PV resources may lead to bi-directional power flow resulting in voltage swells, increased losses and overloading of conductors. Voltage unbalance is a concern in distribution systems and the effect of single-phase residential PV systems on voltage unbalance needs to be explored. Furthermore, the islanding of DGs presents a technical hurdle towards the seamless integration of DG sources with the electricity grid. The work done in this thesis explores two important aspects of grid inte-gration of distributed PV generation, namely, the impact on power quality and anti-islanding. A test distribution system, representing a realistic distribution feeder in Arizona is modeled to study both the aforementioned aspects. The im-pact of distributed PV on voltage profile, voltage unbalance and distribution sys-tem primary losses are studied using CYMDIST. Furthermore, a PSCAD model of the inverter with anti-island controls is developed and the efficacy of the anti-islanding techniques is studied. Based on the simulations, generalized conclusions are drawn and the problems/benefits are elucidated.

  6. Edge effect on the power law distribution of granular avalanches.

    PubMed

    Lorincz, Kinga A; Wijngaarden, Rinke J

    2007-10-01

    Many punctuated phenomena in nature are claimed [e.g., by the theory of self-organized criticality (SOC)] to be power-law distributed. In our experiments on a three-dimensional pile of long-grained rice, we find that by only changing the boundary condition of the system, we switch from such power-law-distributed avalanche sizes to quasiperiodic system-spanning avalanches. Conversely, by removing ledges the incidence of system-spanning avalanches is significantly reduced. This may offer a perspective on new avalanche prevention schemes. In addition, our findings may help to explain why the archetype of SOC, the sandpile, was found to have power-law-distributed avalanches in some experiments, while in other experiments quasiperiodic system-spanning avalanches were found.

  7. Benefits of Power Electronic Interfaces for Distributed Energy Systems

    SciTech Connect

    Kroposki, B.; Pink, C.; DeBlasio, R.; Thomas, H.; Simoes, M.; Sen, P. K.

    2006-01-01

    Optimization of overall electrical system performance is important for the long-term economic viability of distributed energy (DE) systems. With the increasing use of DE systems in industry and its technological advancement, it is becoming more important to understand the integration of these systems with the electric power systems. New markets and benefits for distributed energy applications include the ability to provide ancillary services, improve energy efficiency, enhance power system reliability, and allow customer choice. Advanced power electronic (PE) interfaces will allow DE systems to provide increased functionality through improved power quality and voltage/VAR support, increase electrical system compatibility by reducing the fault contributions, and flexibility in operations with various other DE sources, while reducing overall interconnection costs. This paper examines the system integration and optimization issues associated with DE systems and show the benefits of using PE interfaces for such applications.

  8. Damage detection by a FE model updating method using power spectral density: Numerical and experimental investigation

    NASA Astrophysics Data System (ADS)

    Pedram, Masoud; Esfandiari, Akbar; Khedmati, Mohammad Reza

    2017-06-01

    This paper investigates the viability of damage detection using power spectral density (PSD) of structural response both numerically and experimentally. The paper establishes a sensitivity based damage detection method to use PSD. The advantages of PSD as a model updating metric are explained and its challenges are addressed. An approximate frequency response function of damaged model is used to redeem the method for the effect of incomplete measurement. The robust solution of the developed sensitivity equation is achieved through a least-squares error minimization scheme, and the challenging issues are discussed. The ability of the method in localizing and quantifying the damage and its robustness against measurement and modeling errors is investigated by a numerical example. Experimental vibration test data of a laboratory concrete beam with various level of distributed damage is used to probe the method in practical conditions. The results show that PSD of response can be used to detect damages in lower frequency ranges with acceptable accuracy.

  9. High Energy Density Dielectrics for Pulsed Power Applications

    DTIC Science & Technology

    2008-09-01

    next page). 14. ABSTRACT This report was developed under a SBIR contract. Aluminum oxynitride (AlON) capacitors exhibit several promising...characteristics for high energy density capacitor applications in extreme environments. Dielectric constants in the range of 9 and dielectric strength in...properties remain stable from cryogenic temperatures of -200 °C to temperatures above 400 °C. Stacked capacitor devices have been developed and

  10. Hydroacoustic Estimates of Fish Density Distributions in Cougar Reservoir, 2011

    SciTech Connect

    Ploskey, Gene R.; Zimmerman, Shon A.; Hennen, Matthew J.; Batten, George W.; Mitchell, T. D.

    2012-09-01

    Day and night mobile hydroacoustic surveys were conducted once each month from April through December 2011 to quantify the horizontal and vertical distributions of fish throughout Cougar Reservoir, Lane County, Oregon.

  11. Power optimization of random distributed feedback fiber lasers.

    PubMed

    Vatnik, Ilya D; Churkin, Dmitry V; Babin, Sergey A

    2012-12-17

    We present a comprehensive study of power output characteristics of random distributed feedback Raman fiber lasers. The calculated optimal slope efficiency of the backward wave generation in the one-arm configuration is shown to be as high as ~90% for 1 W threshold. Nevertheless, in real applications a presence of a small reflection at fiber ends can appreciably deteriorate the power performance. The developed numerical model well describes the experimental data.

  12. Electrical Power Distribution and Control Modeling and Analysis

    NASA Technical Reports Server (NTRS)

    Fu, Johnny S.; Liffring, Mark; Mehdi, Ishaque S.

    2001-01-01

    This slide presentation reviews the use of Electrical Power Distribution and Control (EPD&C) Modeling and how modeling can support analysis. The presentation discusses using the EASY5 model to simulate and analyze the Space Shuttle Electric Auxiliary Power Unit. Diagrams of the model schematics are included, as well as graphs of the battery cell impedance, hydraulic load dynamics, and EPD&C response to hydraulic load variations.

  13. System-wide power management control via clock distribution network

    DOEpatents

    Coteus, Paul W.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Reed, Don D.

    2015-05-19

    An apparatus, method and computer program product for automatically controlling power dissipation of a parallel computing system that includes a plurality of processors. A computing device issues a command to the parallel computing system. A clock pulse-width modulator encodes the command in a system clock signal to be distributed to the plurality of processors. The plurality of processors in the parallel computing system receive the system clock signal including the encoded command, and adjusts power dissipation according to the encoded command.

  14. Evaluation of power control concepts using the PMAD systems test bed. [Power Management and Distribution

    NASA Technical Reports Server (NTRS)

    Beach, R. F.; Kimnach, G. L.; Jett, T. A.; Trash, L. M.

    1989-01-01

    The Lewis Research Center's Power Management and Distribution (PMAD) System testbed and its use in the evaluation of control concepts applicable to the NASA Space Station Freedom electric power system (EPS) are described. The facility was constructed to allow testing of control hardware and software in an environment functionally similar to the space station electric power system. Control hardware and software have been developed to allow operation of the testbed power system in a manner similar to a supervisory control and data acquisition (SCADA) system employed by utility power systems for control. The system hardware and software are described.

  15. Distribution-Agnostic Stochastic Optimal Power Flow for Distribution Grids: Preprint

    SciTech Connect

    Baker, Kyri; Dall'Anese, Emiliano; Summers, Tyler

    2016-09-01

    This paper outlines a data-driven, distributionally robust approach to solve chance-constrained AC optimal power flow problems in distribution networks. Uncertain forecasts for loads and power generated by photovoltaic (PV) systems are considered, with the goal of minimizing PV curtailment while meeting power flow and voltage regulation constraints. A data- driven approach is utilized to develop a distributionally robust conservative convex approximation of the chance-constraints; particularly, the mean and covariance matrix of the forecast errors are updated online, and leveraged to enforce voltage regulation with predetermined probability via Chebyshev-based bounds. By combining an accurate linear approximation of the AC power flow equations with the distributionally robust chance constraint reformulation, the resulting optimization problem becomes convex and computationally tractable.

  16. DETERMINATION OF INVENTORIES AND POWER DISTRIBUTIONS FOR THE NSBR.

    SciTech Connect

    HANSON, A.L.; DIAMOND, D.J.

    2005-09-12

    This memo presents the details of the methodology for developing fuel inventories for the NBSR along with power distributions predicted with this set of inventories. Several improvements have been made to the MCNP model of the NBSR since a set of calculations was performed in 2002 in support of the NBSR relicensing and SAR update. One of the most significant changes in the model was to divide the fuel elements into upper and lower halves so the effects of uneven burn between the two halves (due to the shim arms) can be determined. The present set of power distributions are provided for comparison with the previous safety analyses.

  17. Measurement of output power density from mobile phone as a function of input sound frequency.

    PubMed

    Calabrò, Emanuele; Magazù, Salvatore

    2013-01-01

    Measurements of power density emitted by a mobile phone were carried out as a function of the sound frequency transmitted by a sound generator, ranging from 250 to 14000 Hz. Output power density was monitored by means of the selective radiation meter Narda SRM 3000 in spectrum analysis mode, and the octave frequency analysis of each tone used for the experimental design was acquired by the sound level meter Larson Davis LxT Wind. Vodafone providers were used for mobile phone calls with respect to various local base station in Southern-Italy. A relationship between the mobile phone microwaves power density and the sound frequencies transmitted by the sound generator was observed. In particular, microwaves power density level decreases significantly at sound frequency values larger than 4500 Hz. This result can be explained assuming that discontinuous transmission mode of global system for mobile communications is powered not only in silence-mode, but also at frequencies larger than 4500 Hz.

  18. Frequency dependent power and energy flux density equations of the electromagnetic wave

    NASA Astrophysics Data System (ADS)

    Muhibbullah, M.; Haleem, Ashraf M. Abdel; Ikuma, Yasuro

    The calculation of the power and energy of the electromagnetic wave is important for numerous applications. There are some equations to compute the power and energy density of the electromagnetic wave radiation. For instance, the Poynting vector is frequently used to calculate the power density. However those including the Poynting vector are not perfect to represent the actual values because the equations are frequency independent. In the present study we have derived the frequency-dependent equations to calculate the power and energy flux density of the electromagnetic wave by help of the classical electromagnetic theories. It is seems that the Poynting vector with a certain electric and magnetic fields is correct only for a specific frequency. However our equations are perfect to calculate the values of the power and energy flux density for all frequencies of the electromagnetic radiation. The equations may help to develop the applications of the electromagnetic wave radiation.

  19. Lifetime of high-power GaAs photoconductive semiconductor switch triggered by laser of different power density

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Wang, Wei; Shen, Yi; Shi, Jinshui; Zhang, Linwen; Xia, Liansheng

    2015-02-01

    Conduction modes of GaAs photoconductive semiconductor switch (PCSS) and their conditions are expounded. Laser diode and high-power picosecond Nd:YAG lasers are used as triggers for nonlinear mode and quasi-linear mode respectively in high-power conduction experiment. GaAs PCSS`s failure mechanisms and factors influencing lifetime in both modes are analyzed. It is found that the power density of laser at trigger time determines in which mode GaAs PCSS operates. Low-power laser triggers a nonlinear mode conduction in which GaAs PCSS`s lifetime is only 103, while high-power laser triggers a quasi-linear mode conduction in which GaAs PCSS`s lifetime is up to 105. According to the findings, the compact high-power pulsed power system based on mass of GaAs PCSSs demands for miniature high-power laser generators.

  20. High Energy Density Utracapacitors: Low-Cost, High Energy and Power Density, Nanotube-Enhanced Ultracapacitors

    SciTech Connect

    2010-04-01

    Broad Funding Opportunity Announcement Project: FastCAP is improving the performance of an ultracapacitor—a battery-like electronic device that can complement, and possibly even replace, an HEV or EV battery pack. Ultracapacitors have many advantages over conventional batteries, including long lifespans (over 1 million cycles, as compared to 10,000 for conventional batteries) and better durability. Ultracapacitors also charge more quickly than conventional batteries, and they release energy more quickly. However, ultracapacitors have fallen short of batteries in one key metric: energy density—high energy density means more energy storage. FastCAP is redesigning the ultracapacitor’s internal structure to increase its energy density. Ultracapacitors traditionally use electrodes made of irregularly shaped, porous carbon. FastCAP’s ultracapacitors are made of tiny, aligned carbon nanotubes. The nanotubes provide a regular path for ions moving in and out of the ultracapacitor’s electrode, increasing the overall efficiency and energy density of the device.

  1. Power law distribution of dividends in horse races

    NASA Astrophysics Data System (ADS)

    Park, K.; Domany, E.

    2001-02-01

    We discovered that the distribution of dividends in Korean horse races follows a power law. A simple model of betting is proposed, which reproduces the observed distribution. The model provides a mechanism to arrive at the true underlying winning probabilities, which are initially unknown, in a self-organized collective fashion, through the dynamic process of betting. Numerical simulations yield excellent agreement with the empirical data.

  2. Electric power scheduling - A distributed problem-solving approach

    NASA Technical Reports Server (NTRS)

    Mellor, Pamela A.; Dolce, James L.; Krupp, Joseph C.

    1990-01-01

    Space Station Freedom's power system, along with the spacecraft's other subsystems, needs to carefully conserve its resources and yet strive to maximize overall Station productivity. Due to Freedom's distributed design, each subsystem must work cooperatively within the Station community. There is a need for a scheduling tool which will preserve this distributed structure, allow each subsystem the latitude to satisfy its own constraints, and preserve individual value systems while maintaining Station-wide integrity.

  3. On the averaging area for incident power density for human exposure limits at frequencies over 6 GHz.

    PubMed

    Hashimoto, Yota; Hirata, Akimasa; Morimoto, Ryota; Aonuma, Shinta; Laakso, Ilkka; Jokela, Kari; Foster, Kenneth R

    2017-02-08

    Incident power density is used as the dosimetric quantity to specify the restrictions on human exposure to electromagnetic fields at frequencies above 3 or 10 GHz in order to prevent excessive temperature elevation at the body surface. However, international standards and guidelines have different definitions for the size of the area over which the power density should be averaged. This study reports computational evaluation of the relationship between the size of the area over which incident power density is averaged and the local peak temperature elevation in a multi-layer model simulating a human body. Three wave sources are considered in the frequency range from 3 to 300 GHz: an ideal beam, a half-wave dipole antenna, and an antenna array. 1D analysis shows that averaging area of 20 mm  ×  20 mm is a good measure to correlate with the local peak temperature elevation when the field distribution is nearly uniform in that area. The averaging area is different from recommendations in the current international standards/guidelines, and not dependent on the frequency. For a non-uniform field distribution, such as a beam with small diameter, the incident power density should be compensated by multiplying a factor that can be derived from the ratio of the effective beam area to the averaging area. The findings in the present study suggest that the relationship obtained using the 1D approximation is applicable for deriving the relationship between the incident power density and the local temperature elevation.

  4. On the averaging area for incident power density for human exposure limits at frequencies over 6 GHz

    NASA Astrophysics Data System (ADS)

    Hashimoto, Yota; Hirata, Akimasa; Morimoto, Ryota; Aonuma, Shinta; Laakso, Ilkka; Jokela, Kari; Foster, Kenneth R.

    2017-04-01

    Incident power density is used as the dosimetric quantity to specify the restrictions on human exposure to electromagnetic fields at frequencies above 3 or 10 GHz in order to prevent excessive temperature elevation at the body surface. However, international standards and guidelines have different definitions for the size of the area over which the power density should be averaged. This study reports computational evaluation of the relationship between the size of the area over which incident power density is averaged and the local peak temperature elevation in a multi-layer model simulating a human body. Three wave sources are considered in the frequency range from 3 to 300 GHz: an ideal beam, a half-wave dipole antenna, and an antenna array. 1D analysis shows that averaging area of 20 mm  ×  20 mm is a good measure to correlate with the local peak temperature elevation when the field distribution is nearly uniform in that area. The averaging area is different from recommendations in the current international standards/guidelines, and not dependent on the frequency. For a non-uniform field distribution, such as a beam with small diameter, the incident power density should be compensated by multiplying a factor that can be derived from the ratio of the effective beam area to the averaging area. The findings in the present study suggest that the relationship obtained using the 1D approximation is applicable for deriving the relationship between the incident power density and the local temperature elevation.

  5. Wind Power Forecasting Error Distributions: An International Comparison; Preprint

    SciTech Connect

    Hodge, B. M.; Lew, D.; Milligan, M.; Holttinen, H.; Sillanpaa, S.; Gomez-Lazaro, E.; Scharff, R.; Soder, L.; Larsen, X. G.; Giebel, G.; Flynn, D.; Dobschinski, J.

    2012-09-01

    Wind power forecasting is expected to be an important enabler for greater penetration of wind power into electricity systems. Because no wind forecasting system is perfect, a thorough understanding of the errors that do occur can be critical to system operation functions, such as the setting of operating reserve levels. This paper provides an international comparison of the distribution of wind power forecasting errors from operational systems, based on real forecast data. The paper concludes with an assessment of similarities and differences between the errors observed in different locations.

  6. 2240-MW(th) high-temperature reactor core power density study

    SciTech Connect

    Vondy, D.R.

    1984-09-01

    This study was done to estimate the effects of reducing the design power density of a 2240-MW(t) high-temperature gas-cooled reactor. Core history and thermal hydraulics calculations were performed for average power densities of 5.8 and 7.2 W/cm/sup 3/ and the use of highly enriched fuel was considered. The fuel temperature conditions for the higher power density were found to be only moderately elevated at normal operating conditions. Economic considerations associated with changes in core performance, core size, and coolant pumping requirements were assessed.

  7. A Distributed Cooperative Power Allocation Method for Campus Buildings

    SciTech Connect

    Hao, He; Sun, Yannan; Carroll, Thomas E.; Somani, Abhishek

    2015-09-01

    We propose a coordination algorithm for cooperative power allocation among a collection of commercial buildings within a campus. We introduced thermal and power models of a typical commercial building Heating, Ventilation, and Air Conditioning (HVAC) system, and utilize model predictive control to characterize their power flexibility. The power allocation problem is formulated as a cooperative game using the Nash Bargaining Solution (NBS) concept, in which buildings collectively maximize the product of their utilities subject to their local flexibility constraints and a total power limit set by the campus coordinator. To solve the optimal allocation problem, a distributed protocol is designed using dual decomposition of the Nash bargaining problem. Numerical simulations are performed to demonstrate the efficacy of our proposed allocation method

  8. New Data on the Topside Electron Density Distribution

    NASA Technical Reports Server (NTRS)

    Huang, Xue-Qin; Reinisch, Bodo; Bilitza, Dieter; Benson, Robert F.

    2001-01-01

    The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from hmF2 to approx. 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms and most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350,000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis-status.html. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2) down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The automatic topside ionogram scaler with true height algorithm TOPIST software developed for this task is successfully scaling approx.70 % of the ionograms. An 'editing process' is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle. The ISIS data restoration efforts are supported through NASA's Applied Systems and Information Research Program.

  9. Stable formation of ultrahigh power-density 248 nm channels in Xe cluster targets

    SciTech Connect

    Borisov, Alex B.; Racz, Ervin; Khan, Shahab F.; Poopalasingam, Sankar; McCorkindale, John C.; Boguta, John; Longworth, James W.; Rhodes, Charles K.

    2012-07-11

    The optimization of relativistic and ponderomotive self-channeling of ultra-powerful 248 nm laser pulses launched in underdense plasmas with an appropriate longitudinal gradient in the electron density profile located at the initial stage of the self-channeling leads to (1) stable channel formation and (2) highly efficient power compression producing power densities in the 10{sup 19}-10{sup 20} W/cm{sup 3} range. The comparison of theoretical studies with experimental results involving the correlation of (a) Thomson images of the electron density with (b) x-ray images of the channel morphology demonstrates that more than 90% of the incident 248 nm power can be trapped in stable channels and that this stable propagation can be extended to power levels significantly exceeding the critical power of the self-channeling process.

  10. Distribution and density of bird species hazardous to aircraft

    USGS Publications Warehouse

    Robbins, C.S.; Gauthreaux, Sidney A.

    1975-01-01

    Only in the past 5 years has it become feasible to map the relative abundance of North American birds. Two programs presently under way and a third that is in the experimental phase are making possible the up-to-date mapping of abundance as well as distribution. A fourth program that has been used successfully in Europe and on a small scale in parts of North America yields detailed information on breeding distribution. The Breeding Bird Survey, sponsored by the U.S. Bureau of Sport Fisheries and Wildlife and the Canadian Wildlife Service, involves 2,000 randomly distributed roadside counts that are conducted during the height of the breeding season in all U.S. States and Canadian Provinces. Observations of approximately 1.4 million birds per year are entered on magnetic tape and subsequently used both for statistical analysis of population trends and for computer mapping of distribution and abundance. The National Audubon Society's Christmas Bird Count is conducted in about 1,000 circles, each 15 miles (24 km) in diameter, in the latter half of December. Raw data for past years have been published in voluminous reports, but not in a form for ready analysis. Under a contract between the U.S. Air Force and the U. S. Bureau of Sport Fisheries and Wildlife (in cooperation with the National Audubon Society), preliminary maps showing distribution and abundance of selected species that are potential hazards to aircraft are presently being mapped and prepared for publication. The Winter Bird Survey, which is in its fifth season of experimental study in a limited area in Central Maryland, may ultimately replace the Christmas Bird Count source. This Survey consists of a standardized 8-kilometer (5-mile) route covered uniformly once a year during midwinter. Bird Atlas programs, which map distribution but not abundance, are well established in Europe and are gaining interest in America

  11. Assessment of distributed wind-power systems. Final report

    SciTech Connect

    Kaupang, B.M.

    1983-02-01

    A utility-oriented methodology for the purpose of evaluating distributed wind-power systems was developed and tested, utilizing data from three actual utility systems. Conventional utility planning techniques were used, including loss-of-load probability and production-cost-simulation methods in the generation planning area, transmission and distribution (T and D) system expansion models, and loss calculations. Evaluations were based on comparison of total utility-system cost with an without wind-power plants, and wre expressed in terms of wind-power-plant value and cost. Value is measured by the worth of displaced energy and capacity of conventional power plants, of T and D equipmen deferrals, and of T and D loss savings. Cost consists of he capital, and operating and maintenace costs of the wind-power plants. The value of distributed wind-power generation was found to be dominated by the generation energy and capacity value, as opposed to T and D system impacts. The energy value alone did, in two of the three utilities studied, result in a favorable value/cost relationship for the cost assumptions that were used. The problem of voltage fluctuation on distribution feeders from wind turbines due to wind gusts was studied for several sites. In most relaistic applications, the voltage fluctuations would not be a limiting criterion for practical wind-turbine penetration levels. If the wind turbine is connected to the distributionfeeder through a rectifier-inverter, voltage fluctuations become a negligible factor. However, reactive-power compensation of the inverter would most likely be required for this application.

  12. Estimation of current density distribution of PAFC by analysis of cell exhaust gas

    SciTech Connect

    Kato, S.; Seya, A.; Asano, A.

    1996-12-31

    To estimate distributions of Current densities, voltages, gas concentrations, etc., in phosphoric acid fuel cell (PAFC) stacks, is very important for getting fuel cells with higher quality. In this work, we leave developed a numerical simulation tool to map out the distribution in a PAFC stack. And especially to Study Current density distribution in the reaction area of the cell, we analyzed gas composition in several positions inside a gas outlet manifold of the PAFC stack. Comparing these measured data with calculated data, the current density distribution in a cell plane calculated by the simulation, was certified.

  13. Using ultrasound tomography to identify the distributions of density throughout the breast

    NASA Astrophysics Data System (ADS)

    Sak, Mark; Duric, Neb; Littrup, Peter; Sherman, Mark E.; Gierach, Gretchen L.

    2016-04-01

    Women with high breast density are at increased risk of developing breast cancer. Breast density has usually been defined using mammography as the ratio of fibroglandular tissue to total breast area. Ultrasound tomography (UST) is an emerging modality that can also be used to measure breast density. UST creates tomographic sound speed images of the patient's breast which is useful as sound speed is directly proportional to tissue density. Furthermore, the volumetric and quantitative information contained in the sound speed images can be used to describe the distribution of breast density. The work presented here measures the UST sound speed density distributions of 165 women with negative screening mammography. Frequency distributions of the sound speed voxel information were examined for each patient. In a preliminary analysis, the UST sound speed distributions were averaged across patients and grouped by various patient and density-related factors (e.g., age, body mass index, menopausal status, average mammographic breast density). It was found that differences in the distribution of density could be easily visualized for different patient groupings. Furthermore, findings suggest that the shape of the distributions may be used to identify participants with varying amounts of dense and non-dense tissue.

  14. Power-law time distribution of large earthquakes.

    PubMed

    Mega, Mirko S; Allegrini, Paolo; Grigolini, Paolo; Latora, Vito; Palatella, Luigi; Rapisarda, Andrea; Vinciguerra, Sergio

    2003-05-09

    We study the statistical properties of time distribution of seismicity in California by means of a new method of analysis, the diffusion entropy. We find that the distribution of time intervals between a large earthquake (the main shock of a given seismic sequence) and the next one does not obey Poisson statistics, as assumed by the current models. We prove that this distribution is an inverse power law with an exponent mu=2.06+/-0.01. We propose the long-range model, reproducing the main properties of the diffusion entropy and describing the seismic triggering mechanisms induced by large earthquakes.

  15. Numerical analysis of atomic density distribution in arc driven negative ion sources

    SciTech Connect

    Yamamoto, T. Shibata, T.; Hatayama, A.; Kashiwagi, M.; Hanada, M.; Sawada, K.

    2014-02-15

    The purpose of this study is to calculate atomic (H{sup 0}) density distribution in JAEA 10 ampere negative ion source. A collisional radiative model is developed for the calculation of the H{sup 0} density distribution. The non-equilibrium feature of the electron energy distribution function (EEDF), which mainly determines the H{sup 0} production rate, is included by substituting the EEDF calculated from 3D electron transport analysis. In this paper, the H{sup 0} production rate, the ionization rate, and the density distribution in the source chamber are calculated. In the region where high energy electrons exist, the H{sup 0} production and the ionization are enhanced. The calculated H{sup 0} density distribution without the effect of the H{sup 0} transport is relatively small in the upper region. In the next step, the effect should be taken into account to obtain more realistic H{sup 0} distribution.

  16. System for tomographic determination of the power distribution in electron beams

    DOEpatents

    Elmer, John W.; Teruya, Alan T.; O'Brien, Dennis W.

    1995-01-01

    A tomographic technique for measuring the current density distribution in electron beams using electron beam profile data acquired from a modified Faraday cup to create an image of the current density in high and low power beams. The modified Faraday cup includes a narrow slit and is rotated by a stepper motor and can be moved in the x, y and z directions. The beam is swept across the slit perpendicular thereto and controlled by deflection coils, and the slit rotated such that waveforms are taken every few degrees form 0.degree. to 360.degree. and the waveforms are recorded by a digitizing storage oscilloscope. Two-dimensional and three-dimensional images of the current density distribution in the beam can be reconstructed by computer tomography from this information, providing quantitative information about the beam focus and alignment.

  17. System for tomographic determination of the power distribution in electron beams

    DOEpatents

    Elmer, J.W.; Teruya, A.T.; O'Brien, D.W.

    1995-01-17

    A tomographic technique is disclosed for measuring the current density distribution in electron beams using electron beam profile data acquired from a modified Faraday cup to create an image of the current density in high and low power beams. The modified Faraday cup includes a narrow slit and is rotated by a stepper motor and can be moved in the x, y and z directions. The beam is swept across the slit perpendicular thereto and controlled by deflection coils, and the slit rotated such that waveforms are taken every few degrees form 0[degree] to 360[degree] and the waveforms are recorded by a digitizing storage oscilloscope. Two-dimensional and three-dimensional images of the current density distribution in the beam can be reconstructed by computer tomography from this information, providing quantitative information about the beam focus and alignment. 12 figures.

  18. System for tomographic determination of the power distribution in electron beams

    DOEpatents

    Elmer, J.W.; Teruya, A.T.; O`Brien, D.W.

    1995-11-21

    A tomographic technique for measuring the current density distribution in electron beams using electron beam profile data acquired from a modified Faraday cup to create an image of the current density in high and low power beams. The modified Faraday cup includes a narrow slit and is rotated by a stepper motor and can be moved in the x, y and z directions. The beam is swept across the slit perpendicular thereto and controlled by deflection coils, and the slit rotated such that waveforms are taken every few degrees form 0{degree} to 360{degree} and the waveforms are recorded by a digitizing storage oscilloscope. Two-dimensional and three-dimensional images of the current density distribution in the beam can be reconstructed by computer tomography from this information, providing quantitative information about the beam focus and alignment. 12 figs.

  19. High Resolution PV Power Modeling for Distribution Circuit Analysis

    SciTech Connect

    Norris, B. L.; Dise, J. H.

    2013-09-01

    NREL has contracted with Clean Power Research to provide 1-minute simulation datasets of PV systems located at three high penetration distribution feeders in the service territory of Southern California Edison (SCE): Porterville, Palmdale, and Fontana, California. The resulting PV simulations will be used to separately model the electrical circuits to determine the impacts of PV on circuit operations.

  20. Exploring empowerment in settings: mapping distributions of network power.

    PubMed

    Neal, Jennifer Watling

    2014-06-01

    This paper brings together two trends in the empowerment literature-understanding empowerment in settings and understanding empowerment as relational-by examining what makes settings empowering from a social network perspective. Specifically, extending Neal and Neal's (Am J Community Psychol 48(3/4):157-167, 2011) conception of network power, an empowering setting is defined as one in which (1) actors have existing relationships that allow for the exchange of resources and (2) the distribution of network power among actors in the setting is roughly equal. The paper includes a description of how researchers can examine distributions of network power in settings. Next, this process is illustrated in both an abstract example and using empirical data on early adolescents' peer relationships in urban classrooms. Finally, implications for theory, methods, and intervention related to understanding empowering settings are explored.

  1. Distributed Power Flow Control: Distributed Power Flow Control using Smart Wires for Energy Routing

    SciTech Connect

    2012-04-24

    GENI Project: Smart Wire Grid is developing a solution for controlling power flow within the electric grid to better manage unused and overall transmission capacity. The 300,000 miles of high-voltage transmission line in the U.S. today are congested and inefficient, with only around 50% of all transmission capacity utilized at any given time. Increased consumer demand should be met in part with more efficient and an economical power flow. Smart Wire Grid’s devices clamp onto existing transmission lines and control the flow of power within—much like how internet routers help allocate bandwidth throughout the web. Smart wires could support greater use of renewable energy by providing more consistent control over how that energy is routed within the grid on a real-time basis. This would lessen the concerns surrounding the grid’s inability to effectively store intermittent energy from renewables for later use.

  2. HEMP interaction with an electric power distribution circuit. Final report

    SciTech Connect

    Zaininger, H.W.; Jaszewski, G.M.

    1985-08-01

    A high altitude nuclear burst, detonated at a height of 50 km or more, causes two types of electromagnetic pulses, high altitude EMP (HEMP) and magnetohydrodynamic EMP, which will interact with electric power systems. Previous work indicated that millions of miles of electric distribution systems in the United States may be especially vulnerable to HEMP incident simultaneously throughout large portions of the United States. Purpose of this work was to perform an initial assessment of HEMP induced surges on a simplified electric distribution system. This report presents the assumptions, methodology, and resulting induced transient voltages and currents at various points in the distribution circuit in the microsecond timeframe, considering the impacts of HEMP incident simultaneously throughout the distribution system for a range of parametric conditions. Results of this work suggest that EMP could induce voltage transients that far exceed the basic insulation level (BIL) of distribution systems and that a more detailed analysis is warranted.

  3. Intra-plasmaspheric wave power density deduced from long-term DEMETER measurements of terrestrial VLF transmitter wave amplitudes

    NASA Astrophysics Data System (ADS)

    Lauben, D.; Cohen, M.; Inan, U.

    2012-12-01

    We deduce the 3d intra-plasmaspheric distribution of VLF wave power between conjugate regions of strong VLF wave amplitudes as measured by DEMETER for high-power terrestrial VLF transmitters during its ~6-yr lifetime. We employ a mixed WKB/full-wave technique to solve for the primary and secondary electromagnetic and electrostatic waves which are transmitted and reflected from strong cold-plasma density gradients and posited irregularities, in order to match the respective end-point measured amplitude distributions. Energy arriving in the conjugate region and also escaping to other regions of the magnetosphere is note. The resulting 3d distribution allows improved estimates for the long-term average particle scattering induced by terrestrial VLF transmitters.

  4. Power laws from linear neuronal cable theory: power spectral densities of the soma potential, soma membrane current and single-neuron contribution to the EEG.

    PubMed

    Pettersen, Klas H; Lindén, Henrik; Tetzlaff, Tom; Einevoll, Gaute T

    2014-11-01

    Power laws, that is, power spectral densities (PSDs) exhibiting 1/f(α) behavior for large frequencies f, have been observed both in microscopic (neural membrane potentials and currents) and macroscopic (electroencephalography; EEG) recordings. While complex network behavior has been suggested to be at the root of this phenomenon, we here demonstrate a possible origin of such power laws in the biophysical properties of single neurons described by the standard cable equation. Taking advantage of the analytical tractability of the so called ball and stick neuron model, we derive general expressions for the PSD transfer functions for a set of measures of neuronal activity: the soma membrane current, the current-dipole moment (corresponding to the single-neuron EEG contribution), and the soma membrane potential. These PSD transfer functions relate the PSDs of the respective measurements to the PSDs of the noisy input currents. With homogeneously distributed input currents across the neuronal membrane we find that all PSD transfer functions express asymptotic high-frequency 1/f(α) power laws with power-law exponents analytically identified as α∞(I) = 1/2 for the soma membrane current, α∞(p) = 3/2 for the current-dipole moment, and α∞(V) = 2 for the soma membrane potential. Comparison with available data suggests that the apparent power laws observed in the high-frequency end of the PSD spectra may stem from uncorrelated current sources which are homogeneously distributed across the neural membranes and themselves exhibit pink (1/f) noise distributions. While the PSD noise spectra at low frequencies may be dominated by synaptic noise, our findings suggest that the high-frequency power laws may originate in noise from intrinsic ion channels. The significance of this finding goes beyond neuroscience as it demonstrates how 1/f(α) power laws with a wide range of values for the power-law exponent α may arise from a simple, linear partial differential equation.

  5. Power Laws from Linear Neuronal Cable Theory: Power Spectral Densities of the Soma Potential, Soma Membrane Current and Single-Neuron Contribution to the EEG

    PubMed Central

    Pettersen, Klas H.; Lindén, Henrik; Tetzlaff, Tom; Einevoll, Gaute T.

    2014-01-01

    Power laws, that is, power spectral densities (PSDs) exhibiting behavior for large frequencies f, have been observed both in microscopic (neural membrane potentials and currents) and macroscopic (electroencephalography; EEG) recordings. While complex network behavior has been suggested to be at the root of this phenomenon, we here demonstrate a possible origin of such power laws in the biophysical properties of single neurons described by the standard cable equation. Taking advantage of the analytical tractability of the so called ball and stick neuron model, we derive general expressions for the PSD transfer functions for a set of measures of neuronal activity: the soma membrane current, the current-dipole moment (corresponding to the single-neuron EEG contribution), and the soma membrane potential. These PSD transfer functions relate the PSDs of the respective measurements to the PSDs of the noisy input currents. With homogeneously distributed input currents across the neuronal membrane we find that all PSD transfer functions express asymptotic high-frequency power laws with power-law exponents analytically identified as for the soma membrane current, for the current-dipole moment, and for the soma membrane potential. Comparison with available data suggests that the apparent power laws observed in the high-frequency end of the PSD spectra may stem from uncorrelated current sources which are homogeneously distributed across the neural membranes and themselves exhibit pink () noise distributions. While the PSD noise spectra at low frequencies may be dominated by synaptic noise, our findings suggest that the high-frequency power laws may originate in noise from intrinsic ion channels. The significance of this finding goes beyond neuroscience as it demonstrates how power laws with a wide range of values for the power-law exponent α may arise from a simple, linear partial differential equation. PMID:25393030

  6. Multiple Streaming and the Probability Distribution of Density in Redshift Space

    SciTech Connect

    Hui, Lam; Kofman, Lev; Shandarin, Sergei F.

    2000-07-01

    We examine several aspects of redshift distortions by expressing the redshift-space density in terms of the eigenvalues and orientation of the local Lagrangian deformation tensor. We explore the importance of multiple streaming using the Zeldovich approximation (ZA), and compute the average number of streams in both real and redshift space. We find that multiple streaming can be significant in redshift space but negligible in real space, even at moderate values of the linear fluctuation amplitude ({sigma}{sub l}(less-or-similar sign)1). Moreover, unlike their real-space counterparts, redshift-space multiple streams can flow past each other with minimal interactions. Such nonlinear redshift-space effects, which are physically distinct from the fingers-of-God due to small-scale virialized motions, might in part explain the well-known departure of redshift distortions from the classic linear prediction by Kaiser, even at relatively large scales where the corresponding density field in real space is well described by linear perturbation theory. We also compute, using the ZA, the probability distribution function (PDF) of the density, as well as S{sub 3}, in real and redshift space, and compare it with the PDF measured from N-body simulations. The role of caustics in defining the character of the high-density tail is examined. We find that (non-Lagrangian) smoothing, due to both finite resolution or discreteness and small-scale velocity dispersions, is very effective in erasing caustic structures, unless the initial power spectrum is sufficiently truncated. (c) 2000 The American Astronomical Society.

  7. Learning geotemporal nonstationary failure and recovery of power distribution.

    PubMed

    Wei, Yun; Ji, Chuanyi; Galvan, Floyd; Couvillon, Stephen; Orellana, George; Momoh, James

    2014-01-01

    Smart energy grid is an emerging area for new applications of machine learning in a nonstationary environment. Such a nonstationary environment emerges when large-scale failures occur at power networks because of external disruptions such as hurricanes and severe storms. Power distribution networks lie at the edge of the grid, and are especially vulnerable to external disruptions. Quantifiable approaches are lacking and needed to learn nonstationary behaviors of large-scale failure and recovery of power distribution. This paper studies such nonstationary behaviors in three aspects. First, a novel formulation is derived for an entire life cycle of large-scale failure and recovery of power distribution. Second, spatial-temporal models of failure and recovery of power distribution are developed as geolocation-based multivariate nonstationary GI(t)/G(t)/∞ queues. Third, the nonstationary spatial-temporal models identify a small number of parameters to be learned. Learning is applied to two real-life examples of large-scale disruptions. One is from Hurricane Ike, where data from an operational network is exact on failures and recoveries. The other is from Hurricane Sandy, where aggregated data is used for inferring failure and recovery processes at one of the impacted areas. Model parameters are learned using real data. Two findings emerge as results of learning: 1) failure rates behave similarly at the two different provider networks for two different hurricanes but differently at the geographical regions and 2) both the rapid and slow-recovery are present for Hurricane Ike but only slow recovery is shown for a regional distribution network from Hurricane Sandy.

  8. Multi-kw dc power distribution system study program

    NASA Technical Reports Server (NTRS)

    Berkery, E. A.; Krausz, A.

    1974-01-01

    The first phase of the Multi-kw dc Power Distribution Technology Program is reported and involves the test and evaluation of a technology breadboard in a specifically designed test facility according to design concepts developed in a previous study on space vehicle electrical power processing, distribution, and control. The static and dynamic performance, fault isolation, reliability, electromagnetic interference characterisitics, and operability factors of high distribution systems were studied in order to gain a technology base for the use of high voltage dc systems in future aerospace vehicles. Detailed technical descriptions are presented and include data for the following: (1) dynamic interactions due to operation of solid state and electromechanical switchgear; (2) multiplexed and computer controlled supervision and checkout methods; (3) pulse width modulator design; and (4) cable design factors.

  9. Design of Ultra-High-Power-Density Machine Optimized for Future Aircraft

    NASA Technical Reports Server (NTRS)

    Choi, Benjamin B.

    2004-01-01

    The NASA Glenn Research Center's Structural Mechanics and Dynamics Branch is developing a compact, nonpolluting, bearingless electric machine with electric power supplied by fuel cells for future "more-electric" aircraft with specific power in the projected range of 50 hp/lb, whereas conventional electric machines generate usually 0.2 hp/lb. The use of such electric drives for propulsive fans or propellers depends on the successful development of ultra-high-power-density machines. One possible candidate for such ultra-high-power-density machines, a round-rotor synchronous machine with an engineering current density as high as 20,000 A/sq cm, was selected to investigate how much torque and power can be produced.

  10. The power associated with density fluctuations and velocity fluctuations in the solar wind

    NASA Technical Reports Server (NTRS)

    Intriligator, D. S.

    1974-01-01

    Direct observations from Pioneer 6 of solar-wind-proton fluctuations have been used to obtain the power spectra associated with solar-wind-proton number density and velocity fluctuations in the frequency range of 0.001 to 0.01 Hz, extending previous analyses by an order of magnitude at the higher frequencies. The slopes of the power spectra associated with the density fluctuations and the velocity fluctuations are similar and are in agreement with the shape of the power spectra found at the lower frequencies. The power spectra indicate that the power-law density spectrum observed at lower frequencies extends to at least 0.01 Hz. This smooth variation in the spectrum at these frequencies is consistent with previous extrapolations of both spacecraft and interplanetary scintillation observations.

  11. Modeling and Verification of Distributed Generation and Voltage Regulation Equipment for Unbalanced Distribution Power Systems; Annual Subcontract Report, June 2007

    SciTech Connect

    Davis, M. W.; Broadwater, R.; Hambrick, J.

    2007-07-01

    This report summarizes the development of models for distributed generation and distribution circuit voltage regulation equipment for unbalanced power systems and their verification through actual field measurements.

  12. Improving Advanced Inverter Control Convergence in Distribution Power Flow

    SciTech Connect

    Nagarajan, Adarsh; Palmintier, Bryan; Ding, Fei; Mather, Barry; Baggu, Murali

    2016-11-21

    Simulation of modern distribution system powerflow increasingly requires capturing the impact of advanced PV inverter voltage regulation on powerflow. With Volt/var control, the inverter adjusts its reactive power flow as a function of the point of common coupling (PCC) voltage. Similarly, Volt/watt control curtails active power production as a function of PCC voltage. However, with larger systems and higher penetrations of PV, this active/reactive power flow itself can cause significant changes to the PCC voltage potentially introducing oscillations that slow the convergence of system simulations. Improper treatment of these advanced inverter functions could potentially lead to incorrect results. This paper explores a simple approach to speed such convergence by blending in the previous iteration's reactive power estimate to dampen these oscillations. Results with a single large (5MW) PV system and with multiple 500kW advanced inverters show dramatic improvements using this approach.

  13. Chattanooga Electric Power Board Case Study Distribution Automation

    SciTech Connect

    Glass, Jim; Melin, Alexander M.; Starke, Michael R.

    2016-10-01

    In 2009, the U.S. Department of Energy under the American Recovery and Reinvestment Act (ARRA) awarded a grant to the Chattanooga, Tennessee, Electric Power Board (EPB) as part of the Smart Grid Investment Grant Program. The grant had the objective “to accelerate the transformation of the nation’s electric grid by deploying smart grid technologies.” This funding award enabled EPB to expedite the original smart grid implementation schedule from an estimated 10-12 years to 2.5 years. With this funding, EPB invested heavily in distribution automation technologies including installing over 1,200 automated circuit switches and sensors on 171 circuits. For utilities considering a commitment to distribution automation, there are underlying questions such as the following: “What is the value?” and “What are the costs?” This case study attempts to answer these questions. The primary benefit of distribution automation is increased reliability or reduced power outage duration and frequency. Power outages directly impact customer economics by interfering with business functions. In the past, this economic driver has been difficult to effectively evaluate. However, as this case study demonstrates, tools and analysis techniques are now available. In this case study, the impact on customer costs associated with power outages before and after the implementation of distribution automation are compared. Two example evaluations are performed to demonstrate the benefits: 1) a savings baseline for customers under normal operations1 and 2) customer savings for a single severe weather event. Cost calculations for customer power outages are performed using the US Department of Energy (DOE) Interruption Cost Estimate (ICE) calculator2. This tool uses standard metrics associated with outages and the customers to calculate cost impact. The analysis shows that EPB customers have seen significant reliability improvements from the implementation of distribution automation. Under

  14. Enhanced power production from microbial fuel cells with high cell density culture.

    PubMed

    Zhai, Dan-Dan; Li, Bing; Sun, Jian-Zhong; Sun, De-Zhen; Si, Rong-Wei; Yong, Yang-Chun

    2016-01-01

    Improvement of power production in a microbial fuel cell (MFC) with a high cell density culture strategy was developed. By using high cell density culture, the voltage output and power density output of the MFC were enhanced about 0.6 and 1.6 times compared to the control, respectively. Further analysis showed that riboflavin concentration in the MFC was dramatically increased from 0.1 mg/L to 1.2 mg/L by high cell density culture. Moreover, the biofilm formation on the anode surface was significantly enhanced by this new strategy. The increased accumulation of electron shuttle (riboflavin) as well as enhanced biofilm formation contributed to the improvement in anodic electrochemical activity and these factors were the underlying mechanism for MFC performance improvement by high cell density culture. This work demonstrated that high cell density culture would be a simple and practical strategy for MFC manipulation.

  15. Distributed renewable power from biomass and other waste fuels

    NASA Astrophysics Data System (ADS)

    Lyons, Chris

    2012-03-01

    The world population is continually growing and putting a burden on our fossil fuels. These fossil fuels such as coal, oil and natural gas are used for a variety of critical needs such as power production and transportation. While significant environmental improvements have been made, the uses of these fuels are still causing significant ecological impacts. Coal power production efficiency has not improved over the past thirty years and with relatively cheap petroleum cost, transportation mileage has not improved significantly either. With the demand for these fossil fuels increasing, ultimately price will also have to increase. This presentation will evaluate alternative power production methods using localized distributed generation from biomass, municipal solid waste and other waste sources of organic materials. The presentation will review various gasification processes that produce a synthetic gas that can be utilized as a fuel source in combustion turbines for clean and efficient combined heat and power. This fuel source can produce base load renewable power. In addition tail gases from the production of bio-diesel and methanol fuels can be used to produce renewable power. Being localized can reduce the need for long and costly transmission lines making the production of fuels and power from waste a viable alternative energy source for the future.

  16. Theoretical study of pump power distribution on modal instabilities in high power fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Tao, Rumao; Ma, Pengfei; Wang, Xiaolin; Zhou, Pu; Liu, Zejin

    2017-02-01

    Influence of pump power distribution on modal instabilities (MI) is studied numerically, which reveals that the MI threshold is dependent on the pump power distribution in fiber amplifiers and can be increased by optimizing the pump power distribution without any adjustment of other amplifier parameters. It shows that amplifiers with backward or bi-direction pump schemes have a higher threshold than those employing forward pump schemes. For backward pumped amplifiers employing fiber with core/clad diameter being 20/400 µm, the MI threshold yields a 42% increase compared to the forward pumped ones. For bi-direction pumped amplifiers, there exists an optimal power ratio between forward and backward pump power, which results in the highest threshold power. When amplifiers with core/clad diameter being 20/400 µm employ a bi-direction pump scheme at the optimal backward pump power fraction, the threshold can be increased by a factor of approximately 60% with respect to the forward pump configuration. The threshold increment factor reduces as the gain saturation effect weakens. It also shows that the MI threshold can be increased by employing multi-point side pump schemes.

  17. Development of a bionanobattery for distributed power storage systems

    NASA Astrophysics Data System (ADS)

    King, Glen C.; Choi, Sang H.; Chu, Sang-Hyon; Kim, Jae-Woo; Park, Yeonjoon; Lillehei, Peter T.; Watt, Gerald D.; Davis, Robert C.; Harb, John N.

    2004-07-01

    Currently available power storage systems, such as those used to supply power to microelectronic devices, typically consist of a single centralized canister and a series of wires to supply electrical power to where it is needed in a circuit. As the size of electrical circuits and components become smaller, there exists a need for a distributed power system to reduce Joule heating, wiring, and to allow autonomous operation of the various functions performed by the circuit. Our research is being conducted to develop a bio-nanobattery using ferritins reconstituted with both an iron core (Fe-ferritin) and a cobalt core (Co-ferritin). Both Co-ferritin and Fe-ferritin were synthesized and characterized as candidates for the bio-nanobattery. The reducing capability was determined as well as the half-cell electrical potentials, indicating an electrical output of nearly 0.5 V for the battery cell. Ferritins having other metallic cores are also being investigated, in order to increase the overall electrical output. Two dimensional ferritin arrays were also produced on various substrates, demonstrating the necessary building blocks for the bio-nanobattery. The bio-nanobattery will play a key role in moving to a distributed power storage system for electronic applications.

  18. GIS for mapping waterfowl density and distribution from aerial surveys

    USGS Publications Warehouse

    Butler, W.I.; Stehn, R.A.; Balogh, G.R.

    1995-01-01

    We modified standard aerial survey data collection to obtain the geographic location for each waterfowl observation on surveys in Alaska during 1987-1993. Using transect navigation with CPS (global positioning system), data recording on continuously running tapes, and a computer data input program, we located observations with an average deviation along transects of 214 m. The method provided flexibility in survey design and data analysis. Although developed for geese nesting near the coast of the Yukon-Kuskokwim Delta, the methods are widely applicable and were used on other waterfowl surveys in Alaska to map distribution and relative abundance of waterfowl. Accurate location data with GIS analysis and display may improve precision and usefulness of data from any aerial transect survey.

  19. Deviation from power law of the global seismic moment distribution

    NASA Astrophysics Data System (ADS)

    Serra, Isabel; Corral, Álvaro

    2017-01-01

    The distribution of seismic moment is of capital interest to evaluate earthquake hazard, in particular regarding the most extreme events. We make use of likelihood-ratio tests to compare the simple Gutenberg-Richter power-law (PL) distribution with two statistical models that incorporate an exponential tail, the so-called tapered Gutenberg-Richter (Tap) and the truncated gamma, when fitted to the global CMT earthquake catalog. Although the Tap distribution does not introduce any significant improvement of fit respect the PL, the truncated gamma does. Simulated samples of this distribution, with parameters β = 0.68 and mc = 9.15 and reshuffled in order to mimic the time occurrence of the order statistics of the empirical data, are able to explain the temporal heterogeneity of global seismicity both before and after the great Sumatra-Andaman earthquake of 2004.

  20. Deviation from power law of the global seismic moment distribution

    PubMed Central

    Serra, Isabel; Corral, Álvaro

    2017-01-01

    The distribution of seismic moment is of capital interest to evaluate earthquake hazard, in particular regarding the most extreme events. We make use of likelihood-ratio tests to compare the simple Gutenberg-Richter power-law (PL) distribution with two statistical models that incorporate an exponential tail, the so-called tapered Gutenberg-Richter (Tap) and the truncated gamma, when fitted to the global CMT earthquake catalog. Although the Tap distribution does not introduce any significant improvement of fit respect the PL, the truncated gamma does. Simulated samples of this distribution, with parameters β = 0.68 and mc = 9.15 and reshuffled in order to mimic the time occurrence of the order statistics of the empirical data, are able to explain the temporal heterogeneity of global seismicity both before and after the great Sumatra-Andaman earthquake of 2004. PMID:28053311

  1. Method and apparatus for measuring the momentum, energy, power, and power density profile of intense particle beams

    DOEpatents

    Gammel, George M.; Kugel, Henry W.

    1992-10-06

    A method and apparatus for determining the power, momentum, energy, and power density profile of high momentum mass flow. Small probe projectiles of appropriate size, shape and composition are propelled through an intense particle beam at equal intervals along an axis perpendicular to the beam direction. Probe projectiles are deflected by collisions with beam particles. The net beam-induced deflection of each projectile is measured after it passes through the intense particle beam into an array of suitable detectors.

  2. Influence of light energy and power density on the microhardness of two nanohybrid composites.

    PubMed

    Gritsch, Kerstin; Souvannasot, Sourasith; Schembri, Catherine; Farge, Pierre; Grosgogeat, Brigitte

    2008-02-01

    The purpose of this study was to investigate the role of light parameters on nanohybrid composite curing. Two nanohybrid resins were cured by two light-emitting diode (LED) devices and by one quartz-tungsten-halogen (QTH) device using different combinations of energy density and power density (8 J cm(-2) and 400 mW cm(-2); 8 J cm(-2) and 1,000 mW cm(-2); 16 J cm(-2) and 400 mW cm(-2); and 16 J cm(-2)-1,000 mW cm(-2)). The effects of these combinations on polymerization were assessed by measuring the Vickers microhardness. Data differed for the two composites and varied according to the light parameters and the nature of the curing device. For both resins, an energy density of 16 J cm(-2) yielded the best microhardness values at both the top and the bottom of the sample, independently of the power density. When using a lower energy density of 8 J cm(-2), a modulated power density was required to achieve proper curing at the bottom of the sample: 8 J cm(-2) and 400 mW cm(-2) induced greater values at the bottom surface. At an energy density of 16 J cm(-2), the power density was not relevant (no significant differences were found between 400 and 1,000 mW cm(-2)), except when the emission spectra of the light-curing units (LCUs) did not match exactly with the absorption spectra of the photoinitators included in the resins (greatest values with 16 J cm(-2) and 1,000 mW cm(-2)). These results suggest that above a certain energy density threshold, the power density may not significantly influence the polymerization kinetics.

  3. Power management and distribution considerations for a lunar base

    NASA Technical Reports Server (NTRS)

    Kenny, Barbara H.; Coleman, Anthony S.

    1991-01-01

    Design philosophies and technology needs for the power management and distribution (PMAD) portion of a lunar base power system are discussed. A process is described whereby mission planners may proceed from a knowledge of the PMAD functions and mission performance requirements to a definition of design options and technology needs. Current research efforts at the NASA LRC to meet the PMAD system needs for a Lunar base are described. Based on the requirements, the lunar base PMAD is seen as best being accomplished by a utility like system, although with some additional demands including autonomous operation and scheduling and accurate, predictive modeling during the design process.

  4. Structural design and manufacture of high packing density micro-thermoelectric power generators using thermoelectric films

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Jin, Yi-Teng; Zhu, Yan-Bing; Liao, Xia; Xu, Han; Li, Huan; Gao, Jian-Ping

    2011-05-01

    A new micro-thermoelectric power generator module with high packing density of film thermoelectric legs has been proposed, in which a large number of p-type and n-type thin-film thermoelectric legs are electrically connected in series. A theoretical model has been established to simulate the output voltage and power of the proposed module, and the results shows that much higher output voltage and output power can be obtained simply by integrating more film thermoelectric components. Based on the proposed module, a micro-thermoelectric power generator containing 160 film thermocouples is fabricated with a size of 25mm (length) × 4mm (width) × 1mm (thickness). Its open-circuit voltage, maximum output power and corresponding power density at a temperature difference of 20K are 630mV, 35.73μW and 357.3μW·cm-3, respectively.

  5. Information theory lateral density distribution for Earth inferred from global gravity field

    NASA Technical Reports Server (NTRS)

    Rubincam, D. P.

    1981-01-01

    Information Theory Inference, better known as the Maximum Entropy Method, was used to infer the lateral density distribution inside the Earth. The approach assumed that the Earth consists of indistinguishable Maxwell-Boltzmann particles populating infinitesimal volume elements, and followed the standard methods of statistical mechanics (maximizing the entropy function). The GEM 10B spherical harmonic gravity field coefficients, complete to degree and order 36, were used as constraints on the lateral density distribution. The spherically symmetric part of the density distribution was assumed to be known. The lateral density variation was assumed to be small compared to the spherically symmetric part. The resulting information theory density distribution for the cases of no crust removed, 30 km of compensated crust removed, and 30 km of uncompensated crust removed all gave broad density anomalies extending deep into the mantle, but with the density contrasts being the greatest towards the surface (typically + or 0.004 g cm 3 in the first two cases and + or - 0.04 g cm 3 in the third). None of the density distributions resemble classical organized convection cells. The information theory approach may have use in choosing Standard Earth Models, but, the inclusion of seismic data into the approach appears difficult.

  6. Advanced power supply and distribution systems for Columbus

    NASA Astrophysics Data System (ADS)

    Eggers, Gert

    1988-01-01

    The paper describes power supply and distribution systems to be used on unmanned/man-tended Columbus elements, capable of supplying 10 kW to 30 kW to a variety of users in low earth orbits (LEO's). For the definition of the Electrical Power System (EPS) challenging requirements as the provision of high power levels under hard LEO conditions, maintainability, commonality etc. are to be taken into account. These requirements are to be seen in conjunction with the Columbus IOC (initial operational capability) scenario stipulating that EPS hardware shall be used on the Polar Platform, the Pressurized Module attached to the U.S. Space Station and the Man-Tended Free Flier. According to the availability of European technologies, the baseline in the power generation area is a photovoltaic system which provides three regulated main buses (150 V d.c.) to the users. In order to maintain power supply during eclipse phases, nickel hydrogen batteries will be used for energy storage purposes with nickel cadmium as back-up solution. The power distribution system needs special attention. Due to the elevated voltage levels mechanical switch gear cannot be used any longer. It is to be replaced by solid state power controllers (SSPC). Because these devices show a totally different behaviour with regard to conventional relay contacts, new approaches in the area of switching and protection are necessary. In view of the crucial role of this new technology for the realization of medium voltage d.c. systems, it is of great importance for Columbus and, hence will receive adequate consideration in the paper. In order to cater for effective management and control of the power supply and distribution hardware, a so called power system internal data processing assembly (PINDAP) has been introduced in the EPS. PINDAP is the key to reduced dependence on ground stations (alleviated ground support requirements); it keeps crew involvement in the EPS control process to as minimum and provides

  7. Power system distributed oscilation detection based on Synchrophasor data

    NASA Astrophysics Data System (ADS)

    Ning, Jiawei

    Along with increasing demand for electricity, integration of renewable energy and deregulation of power market, power industry is facing unprecedented challenges nowadays. Within the last couple of decades, several serious blackouts have been taking place in United States. As an effective approach to prevent that, power system small signal stability monitoring has been drawing more interests and attentions from researchers. With wide-spread implementation of Synchrophasors around the world in the last decade, power systems real-time online monitoring becomes much more feasible. Comparing with planning study analysis, real-time online monitoring would benefit control room operators immediately and directly. Among all online monitoring methods, Oscillation Modal Analysis (OMA), a modal identification method based on routine measurement data where the input is unmeasured ambient excitation, is a great tool to evaluate and monitor power system small signal stability. Indeed, high sampling Synchrophasor data around power system is fitted perfectly as inputs to OMA. Existing methods in OMA for power systems are all based on centralized algorithms applying at control centers only; however, with rapid growing number of online Synchrophasors the computation burden at control centers is and will be continually exponentially expanded. The increasing computation time at control center compromises the real-time feature of online monitoring. The communication efforts between substation and control center will also be out of reach. Meanwhile, it is difficult or even impossible for centralized algorithms to detect some poorly damped local modes. In order to avert previous shortcomings of centralized OMA methods and embrace the new changes in the power systems, two new distributed oscillation detection methods with two new decentralized structures are presented in this dissertation. Since the new schemes brought substations into the big oscillation detection picture, the proposed

  8. Distributed Optimal Generation Control of Shipboard Power Systems

    DTIC Science & Technology

    2012-05-01

    address the needs of SPSs, a fully-distributed, multi - agent system (MAS)-based solution is proposed to optimize the control references of distributed...Transactions on Power Systems, Vol.27, No.1, pp.233-242, Feb. 2012. [4] J. M. Solanki and N. N. Schulz, “Using intelligent multi - agent systems for shipboard...D 2005/2006, pp. 562-567, May 21-24, 2006. [11] J. A. Momoh, K. Alfred and Y. Xia, “Framework for Multi - Agent System (MAS) Detection and Control

  9. Distributed Optimal Generation Control of Shipboard Power Systems

    DTIC Science & Technology

    2012-05-01

    address the needs of SPSs, a fully-distributed, multi - agent system (MAS)-based solution is proposed to optimize the control references of distributed...Systems, Vol.27, No.1, pp.233-242, Feb. 2012. [4] J. M. Solanki and N. N. Schulz, “Using intelligent multi - agent systems for shipboard power...pp. 562-567, May 21-24, 2006. [11] J. A. Momoh, K. Alfred and Y. Xia, “Framework for Multi - Agent System (MAS) Detection and Control of Arcing of

  10. Electric power scheduling: A distributed problem-solving approach

    NASA Technical Reports Server (NTRS)

    Mellor, Pamela A.; Dolce, James L.; Krupp, Joseph C.

    1990-01-01

    Space Station Freedom's power system, along with the spacecraft's other subsystems, needs to carefully conserve its resources and yet strive to maximize overall Station productivity. Due to Freedom's distributed design, each subsystem must work cooperatively within the Station community. There is a need for a scheduling tool which will preserve this distributed structure, allow each subsystem the latitude to satisfy its own constraints, and preserve individual value systems while maintaining Station-wide integrity. The value-driven free-market economic model is such a tool.

  11. High energy density capacitors for power electronic applications using nano-structure multilayer technology

    SciTech Connect

    Barbee, T.W. Jr.; Johnson, G.W.

    1995-09-01

    Power electronics applications are currently limited by capacitor size and performance. Only incremental improvements are anticipated in existing capacitor technologies, while significant performance advances are required in energy density and overall performance to meet the technical needs of the applications which are important for U.S. economic competitiveness. One application, the Power Electronic Building Block (PEBB), promises a second electronics revolution in power electronic design. High energy density capacitors with excellent electrical thermal and mechanical performance represent an enabling technology in the PEBB concept. We propose a continuing program to research and develop LLNL`s nano-structure multilayer technologies for making high voltage, high energy density capacitors. Our controlled deposition techniques are capable of synthesizing extraordinarily smooth sub-micron thick layers of dielectric and conductor materials. We have demonstrated that, with this technology, high voltage capacitors with an order of magnitude improvement in energy density are achievable.

  12. The effect of illumination power density on carbon defect configuration in silicon doped GaN

    NASA Astrophysics Data System (ADS)

    Kaess, Felix; Reddy, Pramod; Alden, Dorian; Klump, Andrew; Hernandez-Balderrama, Luis H.; Franke, Alexander; Kirste, Ronny; Hoffmann, Axel; Collazo, Ramón; Sitar, Zlatko

    2016-12-01

    A study of efficacy of point defect reduction via Fermi level control during growth of GaN:Si as a function of above bandgap illumination power density and hence excess minority carrier density is presented. Electrical characterization revealed an almost two-fold increase in carrier concentration and a three-fold increase in mobility by increasing the illumination power density from 0 to 1 W cm-2, corroborating a decrease in compensation and ionic impurity scattering. The effect was further supported by the photoluminescence studies, which showed a monotonic decrease in yellow luminescence (attributed to CN) as a function of illumination power density. Secondary ion mass spectroscopy studies showed no effect of illumination on the total incorporation of Si or C. Thus, it is concluded that Fermi level management changed the configuration of the C impurity as the CN-1 configuration became energetically less favorable due to excess minority carriers.

  13. Optimal Power Flow for Distribution Systems under Uncertain Forecasts

    SciTech Connect

    Dall'Anese, Emiliano; Baker, Kyri; Summers, Tyler

    2016-12-29

    The paper focuses on distribution systems featuring renewable energy sources and energy storage devices, and develops an optimal power flow (OPF) approach to optimize the system operation in spite of forecasting errors. The proposed method builds on a chance-constrained multi-period AC OPF formulation, where probabilistic constraints are utilized to enforce voltage regulation with a prescribed probability. To enable a computationally affordable solution approach, a convex reformulation of the OPF task is obtained by resorting to i) pertinent linear approximations of the power flow equations, and ii) convex approximations of the chance constraints. Particularly, the approximate chance constraints provide conservative bounds that hold for arbitrary distributions of the forecasting errors. An adaptive optimization strategy is then obtained by embedding the proposed OPF task into a model predictive control framework.

  14. Power-law distribution in Japanese racetrack betting

    NASA Astrophysics Data System (ADS)

    Ichinomiya, Takashi

    2006-08-01

    Gambling is one of the basic economic activities that humans indulge in. An investigation of gambling activities provides deep insights into the economic actions of people and sheds lights on the study of econophysics. In this paper we present an analysis of the distribution of the final odds of the races organized by the Japan Racing Association. The distribution of the final odds Po(x) indicates a clear power-law Po(x)∝1/x, where x represents the final odds. This power-law can be explained on the basis of the assumption that every bettor bets his money on the horse that appears to be the strongest in a race.

  15. Optimal Power Flow for Distribution Systems under Uncertain Forecasts: Preprint

    SciTech Connect

    Dall'Anese, Emiliano; Baker, Kyri; Summers, Tyler

    2016-12-01

    The paper focuses on distribution systems featuring renewable energy sources and energy storage devices, and develops an optimal power flow (OPF) approach to optimize the system operation in spite of forecasting errors. The proposed method builds on a chance-constrained multi-period AC OPF formulation, where probabilistic constraints are utilized to enforce voltage regulation with a prescribed probability. To enable a computationally affordable solution approach, a convex reformulation of the OPF task is obtained by resorting to i) pertinent linear approximations of the power flow equations, and ii) convex approximations of the chance constraints. Particularly, the approximate chance constraints provide conservative bounds that hold for arbitrary distributions of the forecasting errors. An adaptive optimization strategy is then obtained by embedding the proposed OPF task into a model predictive control framework.

  16. High thermal power density heat transfer apparatus providing electrical isolation at high temperature using heat pipes

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1985-01-01

    This invention is directed to transferring heat from an extremely high temperature source to an electrically isolated lower temperature receiver. The invention is particularly concerned with supplying thermal power to a thermionic converter from a nuclear reactor with electric isolation. Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. If the receiver requires gratr thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparative low thermal power densities through the electrically nonconducting gap between the two heat pipes.

  17. High thermal power density heat transfer apparatus providing electrical isolation at high temperature using heat pipes

    NASA Astrophysics Data System (ADS)

    Morris, J. F.

    1985-03-01

    This invention is directed to transferring heat from an extremely high temperature source to an electrically isolated lower temperature receiver. The invention is particularly concerned with supplying thermal power to a thermionic converter from a nuclear reactor with electric isolation. Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. If the receiver requires gratr thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparative low thermal power densities through the electrically nonconducting gap between the two heat pipes.

  18. E→H mode transition density and power in two types of inductively coupled plasma configuration

    SciTech Connect

    Wang, Jian; Du, Yin-chang; Zhang, Xiao; Zheng, Zhe; Liu, Yu; Xu, Liang; Wang, Pi; Cao, Jin-xiang

    2014-07-15

    E → H transition power and density were investigated at various argon pressures in inductively coupled plasma (ICP) in a cylindrical interlaid chamber. The transition power versus the pressure shows a minimum transition power at 4 Pa (ν/ω=1) for argon. Then the transition density hardly changes at low pressures (ν/ω≪1), but it increases clearly when argon pressure exceeds an appropriate value. In addition, both the transition power and transition density are lower in the re-entrant configuration of ICP compared with that in the cylindrical configuration of ICP. The result may be caused from the decrease of stochastic heating in the re-entrant configuration of ICP. This work is useful to understand E → H mode transition and control the transition points in real plasma processes.

  19. Noise power spectral density of a fibre scattered-light interferometer with a semiconductor laser source

    SciTech Connect

    Alekseev, A E; Potapov, V T

    2013-10-31

    Spectral characteristics of the noise intensity fluctuations at the output of a scattered-light interferometer, caused by phase fluctuations of semiconductor laser radiation are considered. This kind of noise is one of the main factors limiting sensitivity of interferometric sensors. For the first time, to our knowledge, the expression is obtained for the average noise power spectral density at the interferometer output versus the degree of a light source coherence and length of the scattering segment. Also, the approximate expressions are considered which determine the power spectral density in the low-frequency range (up to 200 kHz) and in the limiting case of extended scattering segments. The expression obtained for the noise power spectral density agrees with experimental normalised power spectra with a high accuracy. (interferometry of radiation)

  20. Distributed Electrical Power Generation: Summary of Alternative Available Technologies

    DTIC Science & Technology

    2003-09-01

    Technical Report (TR)-01-18, ADA388687. Borbely, Ann-Marie and Jan F. Kreider. 2001. Dis ributed Genera on: The Power Paradigm for the New...Construction Engineering Research Laboratory PO Box 9005 Champaign, IL 61826-9005 Final Report Approved for public release; distribution is...are provided. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade

  1. Durability of Low Platinum Fuel Cells Operating at High Power Density

    SciTech Connect

    Polevaya, Olga; Blanchet, Scott; Ahluwalia, Rajesh; Borup, Rod; Mukundan, Rangachary

    2014-03-19

    Understanding and improving the durability of cost-competitive fuel cell stacks is imperative to successful deployment of the technology. Stacks will need to operate well beyond today’s state-of-the-art rated power density with very low platinum loading in order to achieve the cost targets set forth by DOE ($15/kW) and ultimately be competitive with incumbent technologies. An accelerated cost-reduction path presented by Nuvera focused on substantially increasing power density to address non-PGM material costs as well as platinum. The study developed a practical understanding of the degradation mechanisms impacting durability of fuel cells with low platinum loading (≤0.2mg/cm2) operating at high power density (≥1.0W/cm2) and worked out approaches for improving the durability of low-loaded, high-power stack designs. Of specific interest is the impact of combining low platinum loading with high power density operation, as this offers the best chance of achieving long-term cost targets. A design-of-experiments approach was utilized to reveal and quantify the sensitivity of durability-critical material properties to high current density at two levels of platinum loading (the more conventional 0.45 mgPt.cm–1 and the much lower 0.2 mgPt.cm–2) across several cell architectures. We studied the relevance of selected component accelerated stress tests (AST) to fuel cell operation in power producing mode. New stress tests (NST) were designed to investigate the sensitivity to the addition of electrical current on the ASTs, along with combined humidity and load cycles and, eventually, relate to the combined city/highway drive cycle. Changes in the cathode electrochemical surface area (ECSA) and average oxygen partial pressure on the catalyst layer with aging under AST and NST protocols were compared based on the number of completed cycles. Studies showed elevated sensitivity of Pt growth to the potential limits and the initial particle size distribution. The ECSA loss

  2. The Razor’s Edge of Collapse: The Transition Point from Lognormal to Power-Law Distributions in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Burkhart, Blakesley; Stalpes, Kye; Collins, David C.

    2017-01-01

    We derive an analytic expression for the transitional column density value ({η }t) between the lognormal and power-law form of the probability distribution function (PDF) in star-forming molecular clouds. Our expression for {η }t depends on the mean column density, the variance of the lognormal portion of the PDF, and the slope of the power-law portion of the PDF. We show that {η }t can be related to physical quantities such as the sonic Mach number of the flow and the power-law index for a self-gravitating isothermal sphere. This implies that the transition point between the lognormal and power-law density/column density PDF represents the critical density where turbulent and thermal pressure balance, the so-called “post-shock density.” We test our analytic prediction for the transition column density using dust PDF observations reported in the literature, as well as numerical MHD simulations of self-gravitating supersonic turbulence with the Enzo code. We find excellent agreement between the analytic {η }t and the measured values from the numerical simulations and observations (to within 1.2 AV). We discuss the utility of our expression for determining the properties of the PDF from unresolved low-density material in dust observations, for estimating the post-shock density, and for determining the H i–H2 transition in clouds.

  3. The force distribution probability function for simple fluids by density functional theory.

    PubMed

    Rickayzen, G; Heyes, D M

    2013-02-28

    Classical density functional theory (DFT) is used to derive a formula for the probability density distribution function, P(F), and probability distribution function, W(F), for simple fluids, where F is the net force on a particle. The final formula for P(F) ∝ exp(-AF(2)), where A depends on the fluid density, the temperature, and the Fourier transform of the pair potential. The form of the DFT theory used is only applicable to bounded potential fluids. When combined with the hypernetted chain closure of the Ornstein-Zernike equation, the DFT theory for W(F) agrees with molecular dynamics computer simulations for the Gaussian and bounded soft sphere at high density. The Gaussian form for P(F) is still accurate at lower densities (but not too low density) for the two potentials, but with a smaller value for the constant, A, than that predicted by the DFT theory.

  4. Distributed Solar Photovoltaic Power Production - Technology and Benefits

    SciTech Connect

    Matos, Al; Stuby, Rick

    2011-11-02

    As part of its nationally recognized Solar 4 All program, PSE&G has partnered with Petra Solar to deploy the world’s first and largest pole attached solar project. The project, based on Petra Solar’s distributed Smart Solar solution, will create a 40 megawatt solar “virtual power plant.” In deployment as 200,000 individual grid-connected solar power producers on utility poles in PSE&G territory, Petra Solar SunWave® solutions leverage Smart Grid communications and high-tech panel-level inverters to implement a robust system with many technical benefits over traditional solar photovoltaic solutions. The program overview, deployment model, smart grid communications and enabling inverter technology and safety features will be presented, as well the future challenges of, and solutions for, solar power intermittency as photovoltaic penetration on the electric grid increases.

  5. Assessment of distributed solar power systems: Issues and impacts

    NASA Astrophysics Data System (ADS)

    Moyle, R. A.; Chernoff, H.; Schweizer, T. C.; Patton, J. B.

    1982-11-01

    The installation of distributed solar-power systems presents electric utilities with a host of questions. Some of the technical and economic impacts of these systems are discussed. Among the technical interconnect issues are isolated operation, power quality, line safety, and metering options. Economic issues include user purchase criteria, structures and installation costs, marketing and product distribution costs, and interconnect costs. An interactive computer program that allows easy calculation of allowable system prices and allowable generation-equipment prices was developed as part of this project. It is concluded that the technical problems raised by distributed solar systems are surmountable, but their resolution may be costly. The stringent purchase criteria likely to be imposed by many potential system users and the economies of large-scale systems make small systems (less than 10 to 20 kW) less attractive than larger systems. Utilities that consider life-cycle costs in making investment decisions and third-party investors who have tax and financial advantages are likely to place the highest value on solar-power systems.

  6. Power Management and Distribution (PMAD) Model Development: Final Report

    NASA Technical Reports Server (NTRS)

    Metcalf, Kenneth J.

    2011-01-01

    Power management and distribution (PMAD) models were developed in the early 1990's to model candidate architectures for various Space Exploration Initiative (SEI) missions. They were used to generate "ballpark" component mass estimates to support conceptual PMAD system design studies. The initial set of models was provided to NASA Lewis Research Center (since renamed Glenn Research Center) in 1992. They were developed to estimate the characteristics of power conditioning components predicted to be available in the 2005 timeframe. Early 90's component and device designs and material technologies were projected forward to the 2005 timeframe, and algorithms reflecting those design and material improvements were incorporated into the models to generate mass, volume, and efficiency estimates for circa 2005 components. The models are about ten years old now and NASA GRC requested a review of them to determine if they should be updated to bring them into agreement with current performance projections or to incorporate unforeseen design or technology advances. This report documents the results of this review and the updated power conditioning models and new transmission line models generated to estimate post 2005 PMAD system masses and sizes. This effort continues the expansion and enhancement of a library of PMAD models developed to allow system designers to assess future power system architectures and distribution techniques quickly and consistently.

  7. Klystron Cluster Scheme for ILC High Power RF Distribution

    SciTech Connect

    Nantista, Christopher; Adolphsen, Chris; /SLAC

    2009-07-06

    We present a concept for powering the main linacs of the International Linear Collider (ILC) by delivering high power RF from the surface via overmoded, low-loss waveguides at widely spaced intervals. The baseline design employs a two-tunnel layout, with klystrons and modulators evenly distributed along a service tunnel running parallel to the accelerator tunnel. This new idea eliminates the need for the service tunnel. It also brings most of the warm heat load to the surface, dramatically reducing the tunnel water cooling and HVAC requirements. In the envisioned configuration, groups of 70 klystrons and modulators are clustered in surface buildings every 2.5 km. Their outputs are combined into two half-meter diameter circular TE{sub 01} mode evacuated waveguides. These are directed via special bends through a deep shaft and along the tunnel, one upstream and one downstream. Each feeds approximately 1.25 km of linac with power tapped off in 10 MW portions at 38 m intervals. The power is extracted through a novel coaxial tap-off (CTO), after which the local distribution is as it would be from a klystron. The tap-off design is also employed in reverse for the initial combining.

  8. Reinvestigation of the charge density distribution in arc discharge fusion system

    SciTech Connect

    Sheng, Lin Horng; Yee, Lee Kim; Nan, Phua Yeong; Thung, Yong Yun; Khok, Yong Thian; Rahman, Faidz Abd

    2015-04-24

    A continual arc discharge system has been setup and the light intensity of arc discharge has been profiled. The mathematical model of local energy density distribution in arc discharge fusion has been simulated which is in good qualitative agreement with light intensity profile of arc discharge in the experiments. Eventually, the local energy density distribution of arc discharge system is able to be precisely manipulated to act as heat source in the fabrication of fused fiber devices.

  9. Design of Instantaneous High Power Supply System with power distribution management for portable military devices

    NASA Astrophysics Data System (ADS)

    Kwak, Kiho; Kwak, Dongmin; Yoon, Joohong

    2015-08-01

    A design of an Instantaneous High Power Supply System (IHPSS) with a power distribution management (PDM) for portable military devices is newly addressed. The system includes a power board and a hybrid battery that can not only supply instantaneous high power but also maintain stable operation at critical low temperature (-30 °C). The power leakage and battery overcharge are effectively prevented by the optimal PDM. The performance of the proposed system under the required pulse loads and the operating conditions of a Korean Advanced Combat Rifle employed in the battlefield is modeled with simulations and verified experimentally. The system with the IHPSS charged the fuse setter with 1.7 times higher voltage (8.6 V) than the one without (5.4 V) under the pulse discharging rate (1 A at 0.5 duty, 1 ms) for 500 ms.

  10. Relation Between Cigarette Smoking, Body Fat Distribution and Density of Lipoprotein Cholesterol in Women.

    DTIC Science & Technology

    1992-08-01

    Cholesterol in Women Linda R. Beson, Major AFIT Student Attending: University of Florida AFIT/CI/CIA-92-085 DTIC Wright-Patterson AFB OH 45433-6583 ELECTE 1...CIGARETTE SMOKING, BODY FAT DISTRIBUTION AND DENSITY OF LIPOPROTEIN CHOLESTEROL IN WOMEN By W: , LINDA R. BESON " Di t A THESIS PRESENTED TO THE GRADUATE...12 Cholesterol and Serum Lipoproteins ......... .. 14 Low Density Lipoprotein (LDL) Cholesterol . . . 18 High Density Lipoprotein (HDL

  11. High power density alkaline fuel cell technology for MMW space burst power

    NASA Astrophysics Data System (ADS)

    Preston, J. Lawrence, Jr.; Trocciola, John C.; Wertheim, Ronald J.

    The use of advanced alkaline regenerative fuel cell energy storage systems to provide 10's to 100's of MWe of sprint (burst) power for 100's of seconds per orbit of SDI weapons platform was studied. Recharge power is supplied by a multimegawatt space based nuclear power system. Regenerative fuel cell energy storage systems offer the potential for significant platform mass reduction by reducing the size and mass of the nuclear power source required. This is because the reactor can be sized for the smaller average power level for the energy storage system, rather than the sprint power level. The regenerative fuel cell is a particularly attractive energy storage device because the fuel cell is essentially a static power conversion device, which results in excellent platform stability for weapon pointing and tracking. Based upon the detailed point design and conceptual layout, the alkaline regenerative fuel cell energy storage system is an attractive choice for integration with a nuclear thermionic system for providing multimegawatt burst power and multi orbit capability.

  12. Non-Gaussian velocity distributions in vibrated granular matter at low densities

    NASA Astrophysics Data System (ADS)

    Kudrolli, Arshad; Henry, J.

    2000-03-01

    Velocity distribution of 100-500 steel and brass spheres rolling inside a rectangular two dimensional flat surface are obtained by high speed imaging. The particles are excited by periodic forcing of one of the confining walls and the surface can be also inclined to introduce gravitation. Rolling leads to an significantly lower effective coefficient of restitution during collisions thus amplifying its effect on the velocity and density distributions. The position and velocity of individual particles are accurately measured, and good statistical information of the distribution of the velocity components is obtained as a function of position by averaging over at least 10^6 data points. Recent experiments and numerical work have shown that clustering of particles are observed due to inelasticity which leads to non-gaussian velocity distributions at high densities. Our data suggests that strongly non-gaussian velocity distributions can occur in excited granular materials even in the absence of significant density correlations or clustering.

  13. Current density and catalyst-coated membrane resistance distribution of hydro-formed metallic bipolar plate fuel cell short stack with 250 cm2 active area

    NASA Astrophysics Data System (ADS)

    Haase, S.; Moser, M.; Hirschfeld, J. A.; Jozwiak, K.

    2016-01-01

    An automotive fuel cell with an active area of 250 cm2 is investigated in a 4-cell short stack with a current and temperature distribution device next to the bipolar plate with 560 current and 140 temperature segments. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this current scan shunt module. The applied fuel cell consists of bipolar plates constructed of 75-μm-thick, welded stainless-steel foils and a graphitic coating. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this module with a 6% deviation in in-plane conductivity. The current density distribution is evaluated up to 2.4 A cm-2. The entire cell's investigated volumetric power density is 4.7 kW l-1, and its gravimetric power density is 4.3 kW kg-1 at an average cell voltage of 0.5 V. The current density distribution is determined without influencing the operating cell. In addition, the current density distribution in the catalyst-coated membrane and its effective resistivity distribution with a finite volume discretisation of Ohm's law are evaluated. The deviation between the current density distributions in the catalyst-coated membrane and the bipolar plate is determined.

  14. Study of variations of radiofrequency power density from mobile phone base stations with distance.

    PubMed

    Ayinmode, B O; Farai, I P

    2013-10-01

    The variations of radiofrequency (RF) radiation power density with distance around some mobile phone base stations (BTSs), in ten randomly selected locations in Ibadan, western Nigeria, were studied. Measurements were made with a calibrated hand-held spectrum analyser. The maximum Global System of Mobile (GSM) communication 1800 signal power density was 323.91 µW m(-2) at 250 m radius of a BTS and that of GSM 900 was 1119.00 µW m(-2) at 200 m radius of another BTS. The estimated total maximum power density was 2972.00 µW m(-2) at 50 m radius of a different BTS. This study shows that the maximum carrier signal power density and the total maximum power density from a BTS may be observed averagely at 200 and 50 m of its radius, respectively. The result of this study demonstrates that exposure of people to RF radiation from phone BTSs in Ibadan city is far less than the recommended limits by International scientific bodies.

  15. Minimizing the instant and accumulative effects of salt permeability to sustain ultrahigh osmotic power density.

    PubMed

    Zhang, Sui; Chung, Tai-Shung

    2013-09-03

    We have investigated the instant and accumulative effects of salt permeability on the sustainability of high power density in the pressure-retarded osmosis (PRO) process experimentally and theoretically. Thin-film composite (TFC) hollow-fiber membranes were prepared. A critical wall thickness was observed to ensure sufficient mechanical stability and hence a low salt permeability, B. The experimental results revealed that a lower B was essential to enhance the maximum power density from 15.3 W/m(2) to as high as 24.3 W/m(2) when 1 M NaCl and deionized water were feeds. Modeling work showed that a large B not only causes an instant drop in the initial water flux but also accelerates the flux decline at high hydraulic pressures, leading to reduced optimal operating pressure and maximal power density. However, the optimal operating pressure to harvest energy can be greater than one-half of the osmotic pressure gradient across the membrane if one can carefully design a PRO membrane with a large water permeability, small B value, and reasonably small structural parameter. It was also found that a high B accumulates salts in the feed, leads to the oversalinization of the feed, and largely lowers both the water flux and power density along the membrane module. Therefore, a low salt permeability is highly desirable to sustain high power density not only locally but also throughout the whole module.

  16. Flexible asymmetric supercapacitors with high energy and high power density in aqueous electrolytes.

    PubMed

    Cheng, Yingwen; Zhang, Hongbo; Lu, Songtao; Varanasi, Chakrapani V; Liu, Jie

    2013-02-07

    Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO(2), activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of the original capacitance retained when the scan rate was increased from 2 mV s(-1) to 500 mV s(-1). Owing to the unique composite structure, these supercapacitors were able to deliver high energy density (24 W h kg(-1)) under high power density (7.8 kW kg(-1)) conditions. These features could enable supercapacitor based energy storage systems to be very attractive for a variety of critical applications, such as the power sources in hybrid electric vehicles and the back-up powers for wind and solar energy, where both high energy density and high power density are required.

  17. Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation

    SciTech Connect

    David Deangelis; Rich Depuy; Debashis Dey; Georgia Karvountzi; Nguyen Minh; Max Peter; Faress Rahman; Pavel Sokolov; Deliang Yang

    2004-09-30

    This report summarizes the work performed by Hybrid Power Generation Systems, LLC (HPGS) during the April to October 2004 reporting period in Task 2.3 (SOFC Scaleup for Hybrid and Fuel Cell Systems) under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL), entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. This study analyzes the performance and economics of power generation systems for central power generation application based on Solid Oxide Fuel Cell (SOFC) technology and fueled by natural gas. The main objective of this task is to develop credible scale up strategies for large solid oxide fuel cell-gas turbine systems. System concepts that integrate a SOFC with a gas turbine were developed and analyzed for plant sizes in excess of 20 MW. A 25 MW plant configuration was selected with projected system efficiency of over 65% and a factory cost of under $400/kW. The plant design is modular and can be scaled to both higher and lower plant power ratings. Technology gaps and required engineering development efforts were identified and evaluated.

  18. Enhanced power quality based single phase photovoltaic distributed generation system

    NASA Astrophysics Data System (ADS)

    Panda, Aurobinda; Pathak, M. K.; Srivastava, S. P.

    2016-08-01

    This article presents a novel control strategy for a 1-ϕ 2-level grid-tie photovoltaic (PV) inverter to enhance the power quality (PQ) of a PV distributed generation (PVDG) system. The objective is to obtain the maximum benefits from the grid-tie PV inverter by introducing current harmonics as well as reactive power compensation schemes in its control strategy, thereby controlling the PV inverter to achieve multiple functions in the PVDG system such as: (1) active power flow control between the PV inverter and the grid, (2) reactive power compensation, and (3) grid current harmonics compensation. A PQ enhancement controller (PQEC) has been designed to achieve the aforementioned objectives. The issue of underutilisation of the PV inverter in nighttime has also been addressed in this article and for the optimal use of the system; the PV inverter is used as a shunt active power filter in nighttime. A prototype model of the proposed system is developed in the laboratory, to validate the effectiveness of the control scheme, and is tested with the help of the dSPACE DS1104 platform.

  19. Progress in High Power Density SOFC Material Development for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Cable, Thomas L.; Sofie, Stephen W.; Setlock, John A.; Misra, Ajay K.

    2004-01-01

    Solid oxide fuel cell (SOFC) systems for aircraft applications require order of magnitude increase in specific power density and long life under aircraft operating conditions. Advanced SOFC materials and fabrication processes are being developed at NASA GRC to increase specific power density and durability of SOFC cell and stack. Initial research efforts for increasing specific power density are directed toward increasing the operating temperature for the SOFC system and reducing the weight of the stack. While significant research is underway to develop anode supported SOFC system operating at temperatures in the range of 650 - 850 C for ground power generation applications, such temperatures may not yield the power densities required for aircraft applications. For electrode-supported cells, SOFC stacks with power densities greater than 1.0 W/sq cm are favorable at temperatures in excess of 900 C. The performance of various commercial and developmental anode supported cells is currently being evaluated in the temperature range of 900 to 1000 C to assess the performance gains and materials reliability. The results from these studies will be presented. Since metal interconnects developed for lower temperature operation are not practical at these high temperatures, advanced perovskite based ceramic interconnects with high electronic conductivity and lower sintering temperatures are being developed. Another option for increasing specific power density of SOFC stacks is to decrease the stack weight. Since the interconnect contributes to a significant portion of the stack weight, considerable weight benefits can be derived by decreasing its thickness. Eliminating the gas channels in the interconnect by engineering the pore structure in both anode and cathode can offer significant reduction in thickness of the ceramic interconnect material. New solid oxide fuel cells are being developed with porous engineered electrode supported structures with a 10 - 20 micron thin

  20. Random sampling of skewed distributions implies Taylor’s power law of fluctuation scaling

    PubMed Central

    Cohen, Joel E.; Xu, Meng

    2015-01-01

    Taylor’s law (TL), a widely verified quantitative pattern in ecology and other sciences, describes the variance in a species’ population density (or other nonnegative quantity) as a power-law function of the mean density (or other nonnegative quantity): Approximately, variance = a(mean)b, a > 0. Multiple mechanisms have been proposed to explain and interpret TL. Here, we show analytically that observations randomly sampled in blocks from any skewed frequency distribution with four finite moments give rise to TL. We do not claim this is the only way TL arises. We give approximate formulae for the TL parameters and their uncertainty. In computer simulations and an empirical example using basal area densities of red oak trees from Black Rock Forest, our formulae agree with the estimates obtained by least-squares regression. Our results show that the correlated sampling variation of the mean and variance of skewed distributions is statistically sufficient to explain TL under random sampling, without the intervention of any biological or behavioral mechanisms. This finding connects TL with the underlying distribution of population density (or other nonnegative quantity) and provides a baseline against which more complex mechanisms of TL can be compared. PMID:25852144

  1. Correlation between ultrasonic power spectrum and bone density on the heel.

    PubMed

    Xu, Yubing; Xu, Yang; Ding, Zenghui; Chen, Yanyan; Su, Benyue; Ma, Zuchang; Sun, Yi-Ning

    2017-01-01

    The purposes of this paper were to evaluate the correlation between ultrasonic power spectrum and bone density and to extract the effectiveness of parameters from power spectrum for evaluating bone density. A total of 50 persons 24-72years of age were recruited. All study participants underwent bone mineral density (BMD) measurements of the lumbar spine (vertebral levels L1-L4). The participants also underwent calcaneal measurements to determine ultrasonic power spectrum with central frequencies of 0.5MHz. Three parameters from normalized power spectrum, called principle frequency (PF), frequency band (FB), and amplitude for principle frequency (APF), were chosen and be evaluated the correlation with the lumbar spine BMD. The correlation coefficient of PF, FB and APF with BMD was r=-0.48 (p<0.001), r=0.48 (p<0.001), and r=-0.71 (p<0.001), respectively. The results showed that the correlation between APF and BMD was better than the correlation among PF, FB and BMD, and APF have a significant correlation with BMD. In conclusion, the correlations among the parameters of ultrasonic power spectrum and BMD are significant, and especially APF performs better than PF and FB in evaluating bone density of participants. These results suggest that ultrasonic power spectrum may contain substantial information not already contained in BUA and SOS. A multiple regression model including all three QUS variables was somewhat more predictive of BMD than a model including only BUA and SOS.

  2. Theoretical discussion for electron-density distribution in multicusp ion source

    SciTech Connect

    Zhan Hualin; Hu Chundong; Xie Yahong; Wu Bin; Wang Jinfang; Liang Lizheng; Wei Jianglong

    2011-03-21

    By introducing some ideas of magnetohydrodynamics (MHD) and kinetic theories, some useful solutions for electron-density distribution in the radial direction in multicusp ion source are obtained. Therefore, some conclusions are made in this perspective: 1, the electron-density distributions in a specific region in the sheath are the same with or without magnetic field; 2, the influence of magnetic field on the electron density obeys exponential law, which should take into account the collision term as well if the magnetic field is strong; 3, the result derived from the Boltzmann equation is qualitatively consistent with some given experimental results.

  3. Quantitation of molecular densities by cryo-electron microscopy. Determination of the radial density distribution of tobacco mosaic virus.

    PubMed

    Smith, M F; Langmore, J P

    1992-08-05

    We have determined the absolute mass and radial scattering density distribution of tobacco mosaic virus in the frozen-hydrated state by energy-filtered low-dose bright-field transmission electron microscopy. The absolute magnitude of electron scattering from tobacco mosaic virus in 150 nm of ice was within 3.0% of that predicted, with inelastic scattering accounting for approximately 80% of the scattering contrast. In order to test the accuracy of the radial reconstruction, a computer model of tobacco mosaic virus was built from the atomic co-ordinates assuming uniform solvent density. The validity of the model was confirmed by comparison of X-ray scattering and predictions of the model (R factor = 0.05). First-order corrections for the microscope contrast transfer function were necessary and sufficient for conversion of the cryo-electron microscopy images into accurate representations of the mass density. At 1.9 nm resolution the compensated reconstruction and model had density peaks of similar magnitude at 2.4, 4.2, 6.0 and 7.8 nm radius and a central hole of 2 nm radius. Equatorial Fourier transforms of the corrected electron images were in excellent agreement with predictions of the model (R factor = 0.12). Thus, the uniform solvent approximation was adequate at 1.9 nm resolution to describe quantitatively X-ray scattering in liquid water and electron imaging in vitreous ice. This is the first demonstration that cryo-electron microscopy images can be used to quantitate the absolute mass, mass per unit length and internal density distributions of proteins and nucleic acids.

  4. Item Response Theory with Estimation of the Latent Population Distribution Using Spline-Based Densities

    ERIC Educational Resources Information Center

    Woods, Carol M.; Thissen, David

    2006-01-01

    The purpose of this paper is to introduce a new method for fitting item response theory models with the latent population distribution estimated from the data using splines. A spline-based density estimation system provides a flexible alternative to existing procedures that use a normal distribution, or a different functional form, for the…

  5. Accuracy of Determination of the Parameters of Exotic Nuclei Nuclear Density Distributions in the Glauber Model

    NASA Astrophysics Data System (ADS)

    Rueter, Keiti; Novikov, Ivan

    2016-09-01

    Parameters of a nuclear density distribution for an exotic nuclei with halo or skin structures can be determined from the experimentally measure interaction cross-section. In the presented work, to extract parameters for a halo and core, we compare experimental data on interaction cross section with reaction cross-sections calculated using expressions obtained in the Glauber Model and its optical approximation. These calculations are performed using Markov Chain Monte Carlo algorithm. In addition, we discuss the accuracy of the Monte Carlo approach to calculating the interaction and reaction cross-sections. The dependence of the accuracy of the density parameters of various exotic nuclei on the ``quality'' of the random numbers chains (here, ``quality'' is defined by lag-1 autocorrelation time of a sequence of random numbers) is obtained for the Gaussian density distribution for a core and the Gaussian density distribution for a halo. KY NSF EPSCoR Research Scholars Program.

  6. Hardness and density distributions of pharmaceutical tablets measured by terahertz pulsed imaging.

    PubMed

    May, Robert K; Su, Ke; Han, Lianghao; Zhong, Shuncong; Elliott, James A; Gladden, Lynn F; Evans, Mike; Shen, Yaochun; Zeitler, J Axel

    2013-07-01

    We present terahertz pulsed imaging (TPI) as a novel tool to quantify the hardness and surface density distribution of pharmaceutical tablets. Good agreement between the surface refractive index (SRI) measured by TPI and the crushing force measured from diametral compression tests was found using a set of tablets that were compacted at various compression forces. We also found a strong correlation between TPI results and tablet bulk density, and how these relate to tablet hardness. Numerical simulations of tablet surface density distribution by finite element analysis exhibit excellent agreement with the TPI measured SRI maps. These results show that TPI has an advantage over traditional diametral compression and is more suitable for nondestructive hardness and density distribution monitoring and control of pharmaceutical manufacturing processes.

  7. Development of Optimized Core Design and Analysis Methods for High Power Density BWRs

    NASA Astrophysics Data System (ADS)

    Shirvan, Koroush

    Increasing the economic competitiveness of nuclear energy is vital to its future. Improving the economics of BWRs is the main goal of this work, focusing on designing cores with higher power density, to reduce the BWR capital cost. Generally, the core power density in BWRs is limited by the thermal Critical Power of its assemblies, below which heat removal can be accomplished with low fuel and cladding temperatures. The present study investigates both increases in the heat transfer area between ~he fuel and coolant and changes in operating parameters to achieve higher power levels while meeting the appropriate thermal as well as materials and neutronic constraints. A scoping study is conducted under the constraints of using fuel with cylindrical geometry, traditional materials and enrichments below 5% to enhance its licensability. The reactor vessel diameter is limited to the largest proposed thus far. The BWR with High power Density (BWR-HD) is found to have a power level of 5000 MWth, equivalent to 26% uprated ABWR, resulting into 20% cheaper O&M and Capital costs. This is achieved by utilizing the same number of assemblies, but with wider 16x16 assemblies and 50% shorter active fuel than that of the ABWR. The fuel rod diameter and pitch are reduced to just over 45% of the ABWR values. Traditional cruciform form control rods are used, which restricts the assembly span to less than 1.2 times the current GE14 design due to limitation on shutdown margin. Thus, it is possible to increase the power density and specific power by 65%, while maintaining the nominal ABWR Minimum Critical Power Ratio (MCPR) margin. The plant systems outside the vessel are assumed to be the same as the ABWR-Il design, utilizing a combination of active and passive safety systems. Safety analyses applied a void reactivity coefficient calculated by SIMULA TE-3 for an equilibrium cycle core that showed a 15% less negative coefficient for the BWR-HD compared to the ABWR. The feedwater

  8. Method of Fabrication of High Power Density Solid Oxide Fuel Cells

    DOEpatents

    Pham, Ai Quoc; Glass, Robert S.

    2008-09-09

    A method for producing ultra-high power density solid oxide fuel cells (SOFCs). The method involves the formation of a multilayer structure cells wherein a buffer layer of doped-ceria is deposited intermediate a zirconia electrolyte and a cobalt iron based electrode using a colloidal spray deposition (CSD) technique. For example, a cobalt iron based cathode composed of (La,Sr)(Co,Fe)O(LSCF) may be deposited on a zirconia electrolyte via a buffer layer of doped-ceria deposited by the CSD technique. The thus formed SOFC have a power density of 1400 mW/cm.sup.2 at 600.degree. C. and 900 mW/cm.sup.2 at 700.degree. C. which constitutes a 2-3 times increased in power density over conventionally produced SOFCs.

  9. Life cycle assessment of overhead and underground primary power distribution.

    PubMed

    Bumby, Sarah; Druzhinina, Ekaterina; Feraldi, Rebe; Werthmann, Danae; Geyer, Roland; Sahl, Jack

    2010-07-15

    Electrical power can be distributed in overhead or underground systems, both of which generate a variety of environmental impacts at all stages of their life cycles. While there is considerable literature discussing the trade-offs between both systems in terms of aesthetics, safety, cost, and reliability, environmental assessments are relatively rare and limited to power cable production and end-of-life management. This paper assesses environmental impacts from overhead and underground medium voltage power distribution systems as they are currently built and managed by Southern California Edison (SCE). It uses process-based life cycle assessment (LCA) according to ISO 14044 (2006) and SCE-specific primary data to the extent possible. Potential environmental impacts have been calculated using a wide range of midpoint indicators, and robustness of the results has been investigated through sensitivity analysis of the most uncertain and potentially significant parameters. The studied underground system has higher environmental impacts in all indicators and for all parameter values, mostly due to its higher material intensity. For both systems and all indicators the majority of impact occurs during cable production. Promising strategies for impact reduction are thus cable failure rate reduction for overhead and cable lifetime extension for underground systems.

  10. Free energies, vacancy concentrations, and density distribution anisotropies in hard-sphere crystals: A combined density functional and simulation study

    NASA Astrophysics Data System (ADS)

    Oettel, M.; Görig, S.; Härtel, A.; Löwen, H.; Radu, M.; Schilling, T.

    2010-11-01

    We perform a comparative study of the free energies and the density distributions in hard-sphere crystals using Monte Carlo simulations and density functional theory (employing Fundamental Measure functionals). Using a recently introduced technique [T. Schilling and F. Schmid, J. Chem. Phys. 131, 231102 (2009)10.1063/1.3274951] we obtain crystal free energies to a high precision. The free energies from fundamental measure theory are in good agreement with the simulation results and demonstrate the applicability of these functionals to the treatment of other problems involving crystallization. The agreement between fundamental measure theory and simulations on the level of the free energies is also reflected in the density distributions around single lattice sites. Overall, the peak widths and anisotropy signs for different lattice directions agree, however, it is found that fundamental measure theory gives slightly narrower peaks with more anisotropy than seen in the simulations. Among the three types of fundamental measure functionals studied, only the White Bear II functional [H. Hansen-Goos and R. Roth, J. Phys.: Condens. Matter 18, 8413 (2006)10.1088/0953-8984/18/37/002] exhibits sensible results for the equilibrium vacancy concentration and a physical behavior of the chemical potential in crystals constrained by a fixed vacancy concentration.

  11. Time series power flow analysis for distribution connected PV generation.

    SciTech Connect

    Broderick, Robert Joseph; Quiroz, Jimmy Edward; Ellis, Abraham; Reno, Matthew J.; Smith, Jeff; Dugan, Roger

    2013-01-01

    Distributed photovoltaic (PV) projects must go through an interconnection study process before connecting to the distribution grid. These studies are intended to identify the likely impacts and mitigation alternatives. In the majority of the cases, system impacts can be ruled out or mitigation can be identified without an involved study, through a screening process or a simple supplemental review study. For some proposed projects, expensive and time-consuming interconnection studies are required. The challenges to performing the studies are twofold. First, every study scenario is potentially unique, as the studies are often highly specific to the amount of PV generation capacity that varies greatly from feeder to feeder and is often unevenly distributed along the same feeder. This can cause location-specific impacts and mitigations. The second challenge is the inherent variability in PV power output which can interact with feeder operation in complex ways, by affecting the operation of voltage regulation and protection devices. The typical simulation tools and methods in use today for distribution system planning are often not adequate to accurately assess these potential impacts. This report demonstrates how quasi-static time series (QSTS) simulation and high time-resolution data can be used to assess the potential impacts in a more comprehensive manner. The QSTS simulations are applied to a set of sample feeders with high PV deployment to illustrate the usefulness of the approach. The report describes methods that can help determine how PV affects distribution system operations. The simulation results are focused on enhancing the understanding of the underlying technical issues. The examples also highlight the steps needed to perform QSTS simulation and describe the data needed to drive the simulations. The goal of this report is to make the methodology of time series power flow analysis readily accessible to utilities and others responsible for evaluating

  12. Neutron density distributions analyzed in terms of relativistic impulse approximation for nickel isotopes

    NASA Astrophysics Data System (ADS)

    Kaki, Kaori

    2015-03-01

    Observables of proton elastic scattering from nickel isotopes (48-82Ni) are calculated based on relativistic impulse approximation (RIA), and nuclear density distributions are provided by relativistic mean-field (RMF) calculations. Contributions of a medium effect and multiple scattering to observables are evaluated and shown to be small at incident proton energies from 200 MeV through 500 MeV so that it is confirmed to perform a model analysis based on the fundamental RIA calculation. For 58,60,62,64Ni isotopes, are considered proton distributions which are obtained by means of unfolding the charge form factor of proton from charge densities determined by the experiments of electron scattering. Through comparisons between results for the different proton densities, contributions of proton form factor to proton distributions and to elastic scattering observables at 300 MeV are discussed. It is shown that the neutron distribution is determined from the restricted observables, reaction cross-section and the first dip of differential cross-section, based on a model analysis of Woods-Saxon distribution in the case of 64Ni target at 300 MeV. Contributions of tensor density and empirical proton density are shown to obtaining the neutron distribution with the model analysis. Compared with the similar studies for 40,60Ca and 208Pb, problems of the model analysis, which arise out of errors in observables, are discussed.

  13. The application of terahertz pulsed imaging in characterising density distribution of roll-compacted ribbons.

    PubMed

    Zhang, Jianyi; Pei, Chunlei; Schiano, Serena; Heaps, David; Wu, Chuan-Yu

    2016-09-01

    Roll compaction is a commonly used dry granulation process in pharmaceutical, fine chemical and agrochemical industries for materials sensitive to heat or moisture. The ribbon density distribution plays an important role in controlling properties of granules (e.g. granule size distribution, porosity and strength). Accurate characterisation of ribbon density distribution is critical in process control and quality assurance. The terahertz imaging system has a great application potential in achieving this as the terahertz radiation has the ability to penetrate most of the pharmaceutical excipients and the refractive index reflects variations in density and chemical compositions. The aim of this study is to explore whether terahertz pulse imaging is a feasible technique for quantifying ribbon density distribution. Ribbons were made of two grades of microcrystalline cellulose (MCC), Avicel PH102 and DG, using a roll compactor at various process conditions and the ribbon density variation was investigated using terahertz imaging and section methods. The density variations obtained from both methods were compared to explore the reliability and accuracy of the terahertz imaging system. An average refractive index is calculated from the refractive index values in the frequency range between 0.5 and 1.5THz. It is shown that the refractive index gradually decreases from the middle of the ribbon towards to the edges. Variations of density distribution across the width of the ribbons are also obtained using both the section method and the terahertz imaging system. It is found that the terahertz imaging results are in excellent agreement with that obtained using the section method, demonstrating that terahertz imaging is a feasible and rapid tool to characterise ribbon density distributions.

  14. A Multi-Agent Design for Power Distribution Systems Automation

    NASA Astrophysics Data System (ADS)

    Ghorbani, M. Jawad

    A new Multi Agent System (MAS) design for fault location, isolation and restoration in power distribution systems is presented. In proposed approach, when there is a fault in the Power Distribution System (PDS), MAS quickly isolates the fault and restores the service to fault-free zones. Hierarchical coordination strategy is introduced to manage the agents which integrate the advantages of both centralized and decentralized coordination strategies. In this framework, Zone Agent (ZA) locate and isolate the fault based on the locally available information and assist the Feeder Agent (FA) for reconfiguration and restoration. FA can solve the restoration problem using the existing algorithms for the 0-1 Knapsack problem. A novel Q-learning mechanism is also introduced to support the FAs in decision making for restoration. Also a distributed MAS-Based Load Shedding (LS) technique has been used to supply as many of higher priority customers as possible, in case there is more demand than generation. The design is illustrated by the use of simulation case studies for fault location, isolation and restoration on West Virginia Super Circuit (WVSC) and hardware implementation for fault location and isolation in a laboratory platform. The results from the case studies indicate the performance of proposed MAS designs.

  15. Power-law distributions from additive preferential redistributions

    NASA Astrophysics Data System (ADS)

    Ree, Suhan

    2006-02-01

    We introduce a nongrowth model that generates the power-law distribution with the Zipf exponent. There are N elements, each of which is characterized by a quantity, and at each time step these quantities are redistributed through binary random interactions with a simple additive preferential rule, while the sum of quantities is conserved. The situation described by this model is similar to those of closed N -particle systems when conservative two-body collisions are only allowed. We obtain stationary distributions of these quantities both analytically and numerically while varying parameters of the model, and find that the model exhibits the scaling behavior for some parameter ranges. Unlike well-known growth models, this alternative mechanism generates the power-law distribution when the growth is not expected and the dynamics of the system is based on interactions between elements. This model can be applied to some examples such as personal wealths, city sizes, and the generation of scale-free networks when only rewiring is allowed.

  16. Patients with Rheumatoid Arthritis and Chronic Pain Display Enhanced Alpha Power Density at Rest

    PubMed Central

    Meneses, Francisco M.; Queirós, Fernanda C.; Montoya, Pedro; Miranda, José G. V.; Dubois-Mendes, Selena M.; Sá, Katia N.; Luz-Santos, Cleber; Baptista, Abrahão F.

    2016-01-01

    Patients with chronic pain due to neuropathy or musculoskeletal injury frequently exhibit reduced alpha and increased theta power densities. However, little is known about electrical brain activity and chronic pain in patients with rheumatoid arthritis (RA). For this purpose, we evaluated power densities of spontaneous electroencephalogram (EEG) band frequencies (delta, theta, alpha, and beta) in females with persistent pain due to RA. This was a cross-sectional study of 21 participants with RA and 21 healthy controls (mean age = 47.20; SD = 10.40). EEG was recorded at rest over 5 min with participant's eyes closed. Twenty electrodes were placed over five brain regions (frontal, central, parietal, temporal, and occipital). Significant differences were observed in depression and anxiety with higher scores in RA participants than healthy controls (p = 0.002). Participants with RA exhibited increased average absolute alpha power density in all brain regions when compared to controls [F(1.39) = 6.39, p = 0.016], as well as increased average relative alpha power density [F(1.39) = 5.82, p = 0.021] in all regions, except the frontal region, controlling for depression/anxiety. Absolute theta power density also increased in the frontal, central, and parietal regions for participants with RA when compared to controls [F(1, 39) = 4.51, p = 0.040], controlling for depression/anxiety. Differences were not exhibited on beta and delta absolute and relative power densities. The diffuse increased alpha may suggest a possible neurogenic mechanism for chronic pain in individuals with RA. PMID:27540360

  17. Patients with Rheumatoid Arthritis and Chronic Pain Display Enhanced Alpha Power Density at Rest.

    PubMed

    Meneses, Francisco M; Queirós, Fernanda C; Montoya, Pedro; Miranda, José G V; Dubois-Mendes, Selena M; Sá, Katia N; Luz-Santos, Cleber; Baptista, Abrahão F

    2016-01-01

    Patients with chronic pain due to neuropathy or musculoskeletal injury frequently exhibit reduced alpha and increased theta power densities. However, little is known about electrical brain activity and chronic pain in patients with rheumatoid arthritis (RA). For this purpose, we evaluated power densities of spontaneous electroencephalogram (EEG) band frequencies (delta, theta, alpha, and beta) in females with persistent pain due to RA. This was a cross-sectional study of 21 participants with RA and 21 healthy controls (mean age = 47.20; SD = 10.40). EEG was recorded at rest over 5 min with participant's eyes closed. Twenty electrodes were placed over five brain regions (frontal, central, parietal, temporal, and occipital). Significant differences were observed in depression and anxiety with higher scores in RA participants than healthy controls (p = 0.002). Participants with RA exhibited increased average absolute alpha power density in all brain regions when compared to controls [F (1.39) = 6.39, p = 0.016], as well as increased average relative alpha power density [F (1.39) = 5.82, p = 0.021] in all regions, except the frontal region, controlling for depression/anxiety. Absolute theta power density also increased in the frontal, central, and parietal regions for participants with RA when compared to controls [F (1, 39) = 4.51, p = 0.040], controlling for depression/anxiety. Differences were not exhibited on beta and delta absolute and relative power densities. The diffuse increased alpha may suggest a possible neurogenic mechanism for chronic pain in individuals with RA.

  18. Exponents in Lifetime and Power Spectral Density Forms in Self-Organized Critical Systems

    DTIC Science & Technology

    1994-08-01

    exponentially cutoff power laws. For example, the behavior of real sandpiles (ref 3) and the Barkhausen effect (ref 4) indicate that the distributions...are cut off, but the ý,est form is not obvious. The distribution of lifetimes in the Barkhausen effect in three ferromagnetic metals (Metglas 2605S

  19. Density distribution of high energy electrons in pulsed corona discharge of NO+N2 mixture.

    PubMed

    Wang, Wenchun; Liu, Feng; Zhang, Jialiang; Wang, Younian

    2003-12-01

    Emission spectroscopy of the high-voltage pulsed positive corona discharge in a line-cylinder reactor is used to investigate the high-energy electron density distribution in the discharge gap. The relative overall emission intensity spatial distribution profile of the A2Sigma+ --> X2Pi transition of NO is successfully recorded against a severe electromagnetic pulse interference coming from the corona discharge at one atmosphere. The spectroscopic investigation shows that the high-energy electron density in the discharge has a nonlinearly decline in the radial distribution. When varying the discharge voltage, the absolute emission intensity of NO is different but the radial distribution profile is similar. If an oxygen flow was introduced into the discharge reactor, the emission intensity of NO decreases tremendously and, therefore, the high-energy electron density decreases reasonably.

  20. Low density, microcellular, dopable, agar/gelatin foams for pulsed power experiments

    SciTech Connect

    McNamara, W.F.; Aubert, J.H.

    1997-04-01

    Low-density, microcellular foams prepared from the natural polymers agar and gelatin have been developed for pulsed-power physics experiments. Numerous experiments were supported with foams having densities at or below 10 mg/cm{sup 3}. For some of the experiments, the agar/gelatin foam was uniformly doped with metallic elements using soluble salts. Depending on the method of preparation, cell sizes were typically below 10 microns and for one process were below 1.0 micron.

  1. NASA Glenn Research Center Program in High Power Density Motors for Aeropropulsion

    NASA Technical Reports Server (NTRS)

    Brown, Gerald V.; Kascak, Albert F.; Ebihara, Ben; Johnson, Dexter; Choi, Benjamin; Siebert, Mark; Buccieri, Carl

    2005-01-01

    Electric drive of transport-sized aircraft propulsors, with electric power generated by fuel cells or turbo-generators, will require electric motors with much higher power density than conventional room-temperature machines. Cryogenic cooling of the motor windings by the liquid hydrogen fuel offers a possible solution, enabling motors with higher power density than turbine engines. Some context on weights of various systems, which is required to assess the problem, is presented. This context includes a survey of turbine engine weights over a considerable size range, a correlation of gear box weights and some examples of conventional and advanced electric motor weights. The NASA Glenn Research Center program for high power density motors is outlined and some technical results to date are presented. These results include current densities of 5,000 A per square centimeter current density achieved in cryogenic coils, finite element predictions compared to measurements of torque production in a switched reluctance motor, and initial tests of a cryogenic switched reluctance motor.

  2. Raising the Bar: Increased Hydraulic Pressure Allows Unprecedented High Power Densities in Pressure-Retarded Osmosis

    SciTech Connect

    Straub, AP; Yip, NY; Elimelech, M

    2014-01-01

    Pressure-retarded osmosis (PRO) has the potential to generate sustainable energy from salinity gradients. PRO is typically considered for operation with river water and seawater, but a far greater energy of mixing can be harnessed from hypersaline solutions. This study investigates the power density that can be obtained in PRO from such concentrated solutions. Thin-film composite membranes with an embedded woven mesh were supported by tricot fabric feed spacers in a specially designed crossflow cell to maximize the operating pressure of the system, reaching a stable applied hydraulic pressure of 48 bar (700 psi) for more than 10 h. Operation at this increased hydraulic pressure allowed unprecedented power densities, up to 60 W/m(2) with a 3 M (180 g/L) NaCl draw solution. Experimental power densities demonstrate reasonable agreement with power densities modeled using measured membrane properties, indicating high-pressure operation does not drastically alter membrane performance. Our findings exhibit the promise of the generation of power from high-pressure PRO with concentrated solutions.

  3. Thermal Diagnosis of Rural Power Grid Distribution Substation Electrical Joints

    NASA Astrophysics Data System (ADS)

    Ge, Le-Yi; Wang, Yue-Xin; Qiao, Yu-Jing

    2016-05-01

    Rural Power Grid Distribution Substation (RPGDS) in long-term operation process, often due to thermal power of the high voltage unit is very big, which leads to serious local heat. In order to ensure the stability, security and reliability, it is necessary to measure and detect for some specific electrical joints of RPGDS. This paper presents a novel diagnosis method based on infrared thermal imaging technology for the specific electrical joints, the method obtains the original infrared thermal image firstly, then carries out following steps as: preprocessing, noise filtering, image enhancement, and extract image edge line, finally, analyzes the results of infrared thermal image data processing. This novel method not only overcomes the shortcomings of traditional contact measurement methods, but can realize fault diagnose more accurately for the electrical joints.

  4. Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation

    SciTech Connect

    Nguyen Minh

    2004-07-04

    This report summarizes the work performed by Hybrid Power Generation Systems, LLC (HPGS) during the January to June 2004 reporting period under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. The main objective of this project is to develop and demonstrate the feasibility of a highly efficient hybrid system integrating a planar Solid Oxide Fuel Cell (SOFC) and a micro-turbine. In addition, an activity included in this program focuses on the development of an integrated coal gasification fuel cell system concept based on planar SOFC technology. Also, another activity included in this program focuses on the development of SOFC scale up strategies.

  5. Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation

    SciTech Connect

    Faress Rahman; Nguyen Minh

    2004-01-04

    This report summarizes the work performed by Hybrid Power Generation Systems, LLC (HPGS) during the July 2003 to December 2003 reporting period under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. The main objective of this project is to develop and demonstrate the feasibility of a highly efficient hybrid system integrating a planar Solid Oxide Fuel Cell (SOFC) and a micro-turbine. In addition, an activity included in this program focuses on the development of an integrated coal gasification fuel cell system concept based on planar SOFC technology. Also, another activity included in this program focuses on the development of SOFC scale up strategies.

  6. Operational maintenance data for power generation distribution and HVAC components

    SciTech Connect

    Hollis, H.D.; Hale, P.S. Jr.; Arno, R.G.; Briggs, S.J.

    1995-12-31

    This paper describes the culmination of a 24,000 man hour effort to collect operational and maintenance data on 239 power generation, power distribution and HVAC items, including gas turbine generators, diesel engine generators, switch gear assemblies, cables, boilers, piping, valves and chillers. This program was designed to determine the effects of new technology equipment, i.e., equipment installed after 1971, on availability. The central hypothesis was that this new equipment would exhibit a significant increase in availability, with corresponding decreases in required maintenance and the occurrence of failures. Information was obtained on a variety of commercial and industrial facility types (including office buildings, hospitals, water treatment facilities, prisons, utilities, manufacturing facilities, school universities and bank computer centers), with varying degrees of maintenance quality.

  7. Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation

    SciTech Connect

    Nguyen Minh; Faress Rahman

    2002-12-31

    This report summarizes the work performed by Hybrid Power Generation Systems, LLC during the October 2002 to December 2002 reporting period under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. The main objective of this project is to develop and demonstrate the feasibility of a highly efficient hybrid system integrating a planar Solid Oxide Fuel Cell (SOFC) and a turbogenerator. The following activities have been carried out during this reporting period: {lg_bullet} Conceptual system design trade studies were performed {lg_bullet} Part-load performance analysis was conducted {lg_bullet} Primary system concept was down-selected {lg_bullet} Dynamic control model has been developed {lg_bullet} Preliminary heat exchanger designs were prepared {lg_bullet} Pressurized SOFC endurance testing was performed

  8. A distributed control approach for power and energy management in a notional shipboard power system

    NASA Astrophysics Data System (ADS)

    Shen, Qunying

    The main goal of this thesis is to present a power control module (PCON) based approach for power and energy management and to examine its control capability in shipboard power system (SPS). The proposed control scheme is implemented in a notional medium voltage direct current (MVDC) integrated power system (IPS) for electric ship. To realize the control functions such as ship mode selection, generator launch schedule, blackout monitoring, and fault ride-through, a PCON based distributed power and energy management system (PEMS) is developed. The control scheme is proposed as two-layer hierarchical architecture with system level on the top as the supervisory control and zonal level on the bottom as the decentralized control, which is based on the zonal distribution characteristic of the notional MVDC IPS that was proposed as one of the approaches for Next Generation Integrated Power System (NGIPS) by Norbert Doerry. Several types of modules with different functionalities are used to derive the control scheme in detail for the notional MVDC IPS. Those modules include the power generation module (PGM) that controls the function of generators, the power conversion module (PCM) that controls the functions of DC/DC or DC/AC converters, etc. Among them, the power control module (PCON) plays a critical role in the PEMS. It is the core of the control process. PCONs in the PEMS interact with all the other modules, such as power propulsion module (PPM), energy storage module (ESM), load shedding module (LSHED), and human machine interface (HMI) to realize the control algorithm in PEMS. The proposed control scheme is implemented in real time using the real time digital simulator (RTDS) to verify its validity. To achieve this, a system level energy storage module (SESM) and a zonal level energy storage module (ZESM) are developed in RTDS to cooperate with PCONs to realize the control functionalities. In addition, a load shedding module which takes into account the reliability

  9. Retinal ganglion cell distribution and spatial resolving power in the Japanese catshark Scyliorhinus torazame.

    PubMed

    Muguruma, Kaori; Takei, Shiro; Yamamoto, Naoyuki

    2013-01-01

    Topographic distribution of retinal ganglion cells (GCs) is linked with the visual capabilities and behavioral ecology of vertebrates. Studies on the distribution of different types of GCs, however, have been conducted in only a few species of elasmobranchs. In the present study, the distribution and peak cell density of GCs, and spatial resolving power (SRP) were examined in the Japanese catshark, Scyliorhinus torazame. Distinct populations of GCs were identified in the ganglion cell layer of S. torazame based on soma size: small and large GCs, which showed different spatial distribution patterns. A horizontal streak of high cell density was recognized in the dorsal retina for small GCs. The highest cell density occurred within the streak, and the peak SRPs of the three fish investigated in the present study were 2.32, 2.64, and 3.01 cycles/deg. In contrast, two spots of high cell density, or areae gigantocellulares, were identified for large GCs, one in the temporal and the other in the nasal retina. The highest cell density occurred in the temporal or nasal area gigantocellularis (SRP: 1.36, 1.55 and 1.83 cycles/deg). This is the first study reporting an elasmobranch species with a horizontal visual streak of small GCs and two areae gigantocellulares. The horizontal streak of small GCs in the dorsal retina, which serves for the inferior visual field, is likely important for food search on the bottom, and the areae gigantocellulares may be important to the detection of prey and/or predators approaching from the front or behind the catshark.

  10. A three-phase soft-switched high-power-density dc/dc converter for high power applications

    SciTech Connect

    DeDoncker, R.W.A.A. ); Divan, D.M.; Kheraluwala, M.H. )

    1991-01-01

    In this paper three dc/dc converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is seen to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode. In contrast to existing single-phase ac-link dc/dc converters, lower turn-off peak currents in the power devices and lower rms current ratings for both the input and output filter capacitors are obtained. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. Furthermore, the use of a three phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable.

  11. Power system voltage stability and agent based distribution automation in smart grid

    NASA Astrophysics Data System (ADS)

    Nguyen, Cuong Phuc

    2011-12-01

    negotiation. Communication latency is modeled using a user-defined probability density function. Failure-tolerant communication strategies are developed for agent communications. Major elements of advanced DA are developed in a completely distributed way and successfully tested for several IEEE standard systems, including: Fault Detection, Location, Isolation, and Service Restoration (FLISR); Coordination of Distributed Energy Storage Systems (DES); Distributed Power Flow (DPF); Volt-VAR Control (VVC); and Loss Reduction (LR).

  12. Densities of some molten fluoride salt mixtures suitable for heat storage in space power applications

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Liquid densities were determined for a number of fluoride salt mixtures suitable for heat storage in space power applications, using a procedure that consisted of measuring the loss of weight of an inert bob in the melt. The density apparatus was calibrated with pure LiF and NaF at different temperatures. Density data for safe binary and ternary fluoride salt eutectics and congruently melting intermediate compounds are presented. In addition, a comparison was made between the volumetric heat storage capacity of different salt mixtures.

  13. Density distribution of a dust cloud in three-dimensional complex plasmas

    NASA Astrophysics Data System (ADS)

    Naumkin, V. N.; Zhukhovitskii, D. I.; Molotkov, V. I.; Lipaev, A. M.; Fortov, V. E.; Thomas, H. M.; Huber, P.; Morfill, G. E.

    2016-09-01

    We propose a method of determination of the dust particle spatial distribution in dust clouds that form in three-dimensional (3D) complex plasmas under microgravity conditions. The method utilizes the data obtained during the 3D scanning of a cloud, and it provides reasonably good accuracy. Based on this method, we investigate the particle density in a dust cloud realized in gas discharge plasma in the PK-3 Plus setup onboard the International Space Station. We find that the treated dust clouds are both anisotropic and inhomogeneous. One can isolate two regimes in which a stationary dust cloud can be observed. At low pressures, the particle density decreases monotonically with the increase of the distance from the discharge center; at higher pressures, the density distribution has a shallow minimum. Regardless of the regime, we detect a cusp of the distribution at the void boundary and a slowly varying density at larger distances (in the foot region). A theoretical interpretation of the obtained results is developed that leads to reasonable estimates of the densities for both the cusp and the foot. The modified ionization equation of state, which allows for violation of the local quasineutrality in the cusp region, predicts the spatial distributions of ion and electron densities to be measured in future experiments.

  14. Density distribution of a dust cloud in three-dimensional complex plasmas.

    PubMed

    Naumkin, V N; Zhukhovitskii, D I; Molotkov, V I; Lipaev, A M; Fortov, V E; Thomas, H M; Huber, P; Morfill, G E

    2016-09-01

    We propose a method of determination of the dust particle spatial distribution in dust clouds that form in three-dimensional (3D) complex plasmas under microgravity conditions. The method utilizes the data obtained during the 3D scanning of a cloud, and it provides reasonably good accuracy. Based on this method, we investigate the particle density in a dust cloud realized in gas discharge plasma in the PK-3 Plus setup onboard the International Space Station. We find that the treated dust clouds are both anisotropic and inhomogeneous. One can isolate two regimes in which a stationary dust cloud can be observed. At low pressures, the particle density decreases monotonically with the increase of the distance from the discharge center; at higher pressures, the density distribution has a shallow minimum. Regardless of the regime, we detect a cusp of the distribution at the void boundary and a slowly varying density at larger distances (in the foot region). A theoretical interpretation of the obtained results is developed that leads to reasonable estimates of the densities for both the cusp and the foot. The modified ionization equation of state, which allows for violation of the local quasineutrality in the cusp region, predicts the spatial distributions of ion and electron densities to be measured in future experiments.

  15. EMC and power quality standards for 20-kHz power distribution

    NASA Technical Reports Server (NTRS)

    Hansen, Irving G.

    1987-01-01

    The Space Station Power Distribution System has been baselined as a sinusoidal single phase, 440 VRMS system. This system has certain unique characteristics directly affecting its application. In particular, existing systematic description and control documents were modified to reflect the high operating frequency. This paper will discuss amendments made on Mil STD 704 (Electrical Power Characteristics), and Mil STD 461-B (Electromagnetic Emission and Susceptibility Requirements for the Control of Electromagnetic Interference). In some cases these amendments reflect changes of several orders of magnitude. Implications and impacts of these changes are discussed.

  16. Single-phase power distribution system power flow and fault analysis

    NASA Technical Reports Server (NTRS)

    Halpin, S. M.; Grigsby, L. L.

    1992-01-01

    Alternative methods for power flow and fault analysis of single-phase distribution systems are presented. The algorithms for both power flow and fault analysis utilize a generalized approach to network modeling. The generalized admittance matrix, formed using elements of linear graph theory, is an accurate network model for all possible single-phase network configurations. Unlike the standard nodal admittance matrix formulation algorithms, the generalized approach uses generalized component models for the transmission line and transformer. The standard assumption of a common node voltage reference point is not required to construct the generalized admittance matrix. Therefore, truly accurate simulation results can be obtained for networks that cannot be modeled using traditional techniques.

  17. Automated fault location and diagnosis on electric power distribution feeders

    SciTech Connect

    Zhu, J.; Lubkeman, D.L.; Girgis, A.A.

    1997-04-01

    This paper presents new techniques for locating and diagnosing faults on electric power distribution feeders. The proposed fault location and diagnosis scheme is capable of accurately identifying the location of a fault upon its occurrence, based on the integration of information available from disturbance recording devices with knowledge contained in a distribution feeder database. The developed fault location and diagnosis system can also be applied to the investigation of temporary faults that may not result in a blown fuse. The proposed fault location algorithm is based on the steady-state analysis of the faulted distribution network. To deal with the uncertainties inherent in the system modeling and the phasor estimation, the fault location algorithm has been adapted to estimate fault regions based on probabilistic modeling and analysis. Since the distribution feeder is a radial network, multiple possibilities of fault locations could be computed with measurements available only at the substation. To identify the actual fault location, a fault diagnosis algorithm has been developed to prune down and rank the possible fault locations by integrating the available pieces of evidence. Testing of the developed fault location and diagnosis system using field data has demonstrated its potential for practical use.

  18. Measurement of the temperature distribution inside the power cable using distributed temperature system

    NASA Astrophysics Data System (ADS)

    Jaros, Jakub; Liner, Andrej; Papes, Martin; Vasinek, Vladimir; Mach, Veleslav; Hruby, David; Kajnar, Tomas; Perecar, Frantisek

    2015-01-01

    Nowadays, the power cables are manufactured to fulfill the following condition - the highest allowable temperature of the cable during normal operation and the maximum allowable temperature at short circuit conditions cannot exceed the condition of the maximum allowable internal temperature. The distribution of the electric current through the conductor leads to the increase of the amplitude of electrons in the crystal lattice of the cables material. The consequence of this phenomenon is the increase of friction and the increase of collisions between particles inside the material, which causes the temperature increase of the carrying elements. The temperature increase is unwanted phenomena, because it is causing losses. In extreme cases, the long-term overload leads to the cable damaging or fire. This paper deals with the temperature distribution measurement inside the power cables using distributed temperature system. With cooperation with Kabex company, the tube containing optical fibers was installed into the center of power cables. These fibers, except telecommunications purposes, can be also used as sensors in measurements carrying out with distributed temperature system. These systems use the optical fiber as a sensor and allow the continual measurement of the temperature along the whole cable in real time with spatial resolution 1 m. DTS systems are successfully deployed in temperature measurement applications in industry areas yet. These areas include construction, drainage, hot water etc. Their advantages are low cost, resistance to electromagnetic radiation and the possibility of real time monitoring at the distance of 8 km. The location of the optical fiber in the center of the power cable allows the measurement of internal distribution of the temperature during overloading the cable. This measurement method can be also used for prediction of short-circuit and its exact location.

  19. Efficient two-level cryogenic power distribution system

    NASA Astrophysics Data System (ADS)

    Mueller, O. M.; Mueller, E. K.

    2002-05-01

    The availability of new technologies such as high-temperature superconducting (HTS) cables, high-voltage, high-speed semiconductor switches, and cryogenic power conversion suggests that one considers how these technologies can be combined and applied effectively to provide a more efficient energy distribution system. The present-day 60 Hz concept is, after all, a century old. Advantages can be obtained by combining DC and high-frequency AC technologies. DC transmission solves the problem of AC losses in HTS cables and high-frequency switching techniques reduce size, weight and cost. This paper proposes and discusses a distribution system based on two DC voltage levels (˜4 kVDC/650 VDC) interconnected with DC/DC converters using high-voltage insulated-gate bipolar transistors (HV-IGBT's), integrated gate-commutated thyristors (IGCT's), or MOS-controlled turn-off thyristors (MTO's) operated at cryogenic temperatures. Cryo-MOSFET DC/AC inverters provide the 60 Hz, 240/120 VAC user voltages. HTS cables supply power as well as the cooling fluid liquid nitrogen (LN2). The load shedding properties of such a system based on the use of LN2 are evaluated. The proposed concept is suitable for city blocks with many high-rise buildings. It provides an increase in efficiency and therefore contributes to the reduction of global warming.

  20. Comparisons of ionospheric electron density distributions reconstructed by GPS computerized tomography, backscatter ionograms, and vertical ionograms

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Lei, Yong; Li, Bofeng; An, Jiachun; Zhu, Peng; Jiang, Chunhua; Zhao, Zhengyu; Zhang, Yuannong; Ni, Binbin; Wang, Zemin; Zhou, Xuhua

    2015-12-01

    Global Positioning System (GPS) computerized ionosphere tomography (CIT) and ionospheric sky wave ground backscatter radar are both capable of measuring the large-scale, two-dimensional (2-D) distributions of ionospheric electron density (IED). Here we report the spatial and temporal electron density results obtained by GPS CIT and backscatter ionogram (BSI) inversion for three individual experiments. Both the GPS CIT and BSI inversion techniques demonstrate the capability and the consistency of reconstructing large-scale IED distributions. To validate the results, electron density profiles obtained from GPS CIT and BSI inversion are quantitatively compared to the vertical ionosonde data, which clearly manifests that both methods output accurate information of ionopsheric electron density and thereby provide reliable approaches to ionospheric soundings. Our study can improve current understanding of the capability and insufficiency of these two methods on the large-scale IED reconstruction.

  1. The reasons for the high power density of fuel cells fabricated with directly deposited membranes

    NASA Astrophysics Data System (ADS)

    Vierrath, Severin; Breitwieser, Matthias; Klingele, Matthias; Britton, Benjamin; Holdcroft, Steven; Zengerle, Roland; Thiele, Simon

    2016-09-01

    In a previous study, we reported that polymer electrolyte fuel cells prepared by direct membrane deposition (DMD) produced power densities in excess of 4 W/cm2. In this study, the underlying origins that give rise to these high power densities are investigated and reported. The membranes of high power, DMD-fabricated fuel cells are relatively thin (12 μm) compared to typical benchmark, commercially available membranes. Electrochemical impedance spectroscopy, at high current densities (2.2 A/cm2) reveals that mass transport resistance was half that of reference, catalyst-coated-membranes (CCM). This is attributed to an improved oxygen supply in the cathode catalyst layer by way of a reduced propensity of flooding, and which is facilitated by an enhancement in the back diffusion of water from cathode to anode through the thin directly deposited membrane. DMD-fabricated membrane-electrode-assemblies possess 50% reduction in ionic resistance (15 mΩcm2) compared to conventional CCMs, with contributions of 9 mΩcm2 for the membrane resistance and 6 mΩcm2 for the contact resistance of the membrane and catalyst layer ionomer. The improved mass transport is responsible for 90% of the increase in power density of the DMD fuel cell, while the reduced ionic resistance accounts for a 10% of the improvement.

  2. Low cobalt content electrical sheets for optimized high power density rotating machines

    NASA Astrophysics Data System (ADS)

    Waeckerlé, T.; Fraisse, H.; Chaput, L.; Leroy, M.

    2000-06-01

    The "high performance soft magnetic material" described in the present paper is a new low cobalt Fe-Co alloy designed as an economic solution to the requirements of high power density rotating machines for applications in relatively non-hostile environments.

  3. Density distribution of a rotating plasma in Tornado magnetic confinement systems

    SciTech Connect

    Kuznetsov, V.M.; Pakhomov, A.B.; Rusakov, A.I.

    1984-12-01

    The density distribution of a rotating plasma in a Tornado magnetic confinement system is calculated under the assumption that the plasma rotates at constant angular velocity throughout the region bounded by the separatrix. The component of the centrifugal inertial force parallel to the magnetic force lines is shown to pinch the plasma toward the equatorial plane of the system. The density distribution depends on the ratio v/T of the plasma drift velocity and temperature. The experimentally measured density distribution can be used to determine v/T and thus to analyze the rotating plasma. If v is known for the rotating plasma then T can be calculated from v, and vice versa.

  4. Distributed optimal power and rate control in wireless sensor networks.

    PubMed

    Tang, Meiqin; Bai, Jianyong; Li, Jing; Xin, Yalin

    2014-01-01

    With the rapid development of wireless sensor networks, reducing energy consumption is becoming one of the important factors to extend node lifetime, and it is necessary to adjust the launching power of each node because of the limited energy available to the sensor nodes in the networks. This paper proposes a power and rate control model based on the network utility maximization (NUM) framework, where a weighting factor is used to reflect the influence degree of the sending power and transmission rate to the utility function. In real networks, nodes interfere with each other in the procedure of transmitting signal, which may lead to signal transmission failure and may negatively have impacts on networks throughput. Using dual decomposition techniques, the NUM problem is decomposed into two distributed subproblems, and then the conjugate gradient method is applied to solve the optimization problem with the calculation of the Hessian matrix and its inverse in order to guarantee fast convergence of the algorithm. The convergence proof is also provided in this paper. Numerical examples show that the proposed solution achieves significant throughput compared with exiting approaches.

  5. Distributed Optimal Power and Rate Control in Wireless Sensor Networks

    PubMed Central

    Tang, Meiqin; Bai, Jianyong; Li, Jing; Xin, Yalin

    2014-01-01

    With the rapid development of wireless sensor networks, reducing energy consumption is becoming one of the important factors to extend node lifetime, and it is necessary to adjust the launching power of each node because of the limited energy available to the sensor nodes in the networks. This paper proposes a power and rate control model based on the network utility maximization (NUM) framework, where a weighting factor is used to reflect the influence degree of the sending power and transmission rate to the utility function. In real networks, nodes interfere with each other in the procedure of transmitting signal, which may lead to signal transmission failure and may negatively have impacts on networks throughput. Using dual decomposition techniques, the NUM problem is decomposed into two distributed subproblems, and then the conjugate gradient method is applied to solve the optimization problem with the calculation of the Hessian matrix and its inverse in order to guarantee fast convergence of the algorithm. The convergence proof is also provided in this paper. Numerical examples show that the proposed solution achieves significant throughput compared with exiting approaches. PMID:24895654

  6. Fuel cycle comparison of distributed power generation technologies.

    SciTech Connect

    Elgowainy, A.; Wang, M. Q.; Energy Systems

    2008-12-08

    The fuel-cycle energy use and greenhouse gas (GHG) emissions associated with the application of fuel cells to distributed power generation were evaluated and compared with the combustion technologies of microturbines and internal combustion engines, as well as the various technologies associated with grid-electricity generation in the United States and California. The results were primarily impacted by the net electrical efficiency of the power generation technologies and the type of employed fuels. The energy use and GHG emissions associated with the electric power generation represented the majority of the total energy use of the fuel cycle and emissions for all generation pathways. Fuel cell technologies exhibited lower GHG emissions than those associated with the U.S. grid electricity and other combustion technologies. The higher-efficiency fuel cells, such as the solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC), exhibited lower energy requirements than those for combustion generators. The dependence of all natural-gas-based technologies on petroleum oil was lower than that of internal combustion engines using petroleum fuels. Most fuel cell technologies approaching or exceeding the DOE target efficiency of 40% offered significant reduction in energy use and GHG emissions.

  7. Spacecraft radio scattering observations of the power spectrum of electron density fluctuations in the solar wind

    NASA Technical Reports Server (NTRS)

    Woo, R.; Armstrong, J. W.

    1979-01-01

    Solar wind electron density power spectra in the solar equatorial region are inferred from observations of phase scintillations and spectral broadening made with the Viking, Helios, and Pioneer spacecraft. The heliocentric distance range covered is 2-215 solar radii and for some observations close to the sun the spectra extend to fluctuation frequencies as high as 100 Hz. For heliocentric distances of about 20 solar radii the equivalent spacecraft-measured one-dimensional density spectrum is well modeled by a single power law in the frequency range 0.0001-0.05 Hz. The flattening of the density spectrum within 20 solar radii is presumably associated with energy deposition in the near-sun region and acceleration of the solar wind.

  8. Biotic and abiotic factors predicting the global distribution and population density of an invasive large mammal

    PubMed Central

    Lewis, Jesse S.; Farnsworth, Matthew L.; Burdett, Chris L.; Theobald, David M.; Gray, Miranda; Miller, Ryan S.

    2017-01-01

    Biotic and abiotic factors are increasingly acknowledged to synergistically shape broad-scale species distributions. However, the relative importance of biotic and abiotic factors in predicting species distributions is unclear. In particular, biotic factors, such as predation and vegetation, including those resulting from anthropogenic land-use change, are underrepresented in species distribution modeling, but could improve model predictions. Using generalized linear models and model selection techniques, we used 129 estimates of population density of wild pigs (Sus scrofa) from 5 continents to evaluate the relative importance, magnitude, and direction of biotic and abiotic factors in predicting population density of an invasive large mammal with a global distribution. Incorporating diverse biotic factors, including agriculture, vegetation cover, and large carnivore richness, into species distribution modeling substantially improved model fit and predictions. Abiotic factors, including precipitation and potential evapotranspiration, were also important predictors. The predictive map of population density revealed wide-ranging potential for an invasive large mammal to expand its distribution globally. This information can be used to proactively create conservation/management plans to control future invasions. Our study demonstrates that the ongoing paradigm shift, which recognizes that both biotic and abiotic factors shape species distributions across broad scales, can be advanced by incorporating diverse biotic factors. PMID:28276519

  9. Investigating the effect of tablet thickness and punch curvature on density distribution using finite elements method.

    PubMed

    Diarra, Harona; Mazel, Vincent; Busignies, Virginie; Tchoreloff, Pierre

    2015-09-30

    Finite elements method was used to study the influence of tablet thickness and punch curvature on the density distribution inside convex faced (CF) tablets. The modeling of the process was conducted on 2 pharmaceutical excipients (anhydrous calcium phosphate and microcrystalline cellulose) by using Drucker-Prager Cap model in Abaqus(®) software. The parameters of the model were obtained from experimental tests. Several punch shapes based on industrial standards were used. A flat-faced (FF) punch and 3 convex faced (CF) punches (8R11, 8R8 and 8R6) with a diameter of 8mm were chosen. Different tablet thicknesses were studied at a constant compression force. The simulation of the compaction of CF tablets with increasing thicknesses showed an important change on the density distribution inside the tablet. For smaller thicknesses, low density zones are located toward the center. The density is not uniform inside CF tablets and the center of the 2 faces appears with low density whereas the distribution inside FF tablets is almost independent of the tablet thickness. These results showed that FF and CF tablets, even obtained at the same compression force, do not have the same density at the center of the compact. As a consequence differences in tensile strength, as measured by diametral compression, are expected. This was confirmed by experimental tests.

  10. Laser and Pulsed Power Electron Density Imaging Through Talbot-Lau X-ray Deflectometry

    NASA Astrophysics Data System (ADS)

    Valdivia Leiva, Maria Pia; Stutman, Dan; Stoeckl, Christian; Mileham, Chad; Begischev, Ildar; Theobald, Wolfgang; Bromage, Jake; Regan, Sean; Klein, Salee; Muñoz-Cordovez, Gonzalo; Vescovi, Milenko; Valenzuela-Villaseca, Vicente; Veloso, Felipe

    2016-10-01

    A Talbot-Lau X-ray Deflectometer was deployed using laser driven and x-pinch x-ray backlighters. The Talbot-Lau X-ray Deflectometer is an ideal electron density diagnostic for High Energy Density plasmas with the potential to simultaneously deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single image with source limited resolution. Grating survival and electron density mapping was demonstrated for 10-29 J, 8-30 ps laser pulses using Cu foil targets at the Multi-TeraWatt facility. An areal electron density of 0.050 g/cm2 was obtained at the center of a fluoro-nylon fiber of 300 mm diameter with a source FWHM of 80 µm and resolution of 50 µm. Grating survival and Moiré pattern formation was demonstrated using a Cu x-pinch plasma of FWHM 27 µm, driven by the 350 kA, 350 ns Llampudken pulsed power generator. These results closely match simulations and laboratory results. It was demonstrated that the technique can detect both sharp and smooth density gradients in the range of 2x1023 to 2x1025 cm-3, thus allowing implementation of the electron density technique as a HED plasma diagnostic in both laser and pulsed power experiments U.S. DoE/NNSA and DE-NA0002955.

  11. Theoretical and measured power density in front of VHF/UHF broadcasting antennas.

    PubMed

    Jokela, K

    1988-05-01

    A simple and easy-to-use model based on more rigorous computations was formulated for the prediction of power density levels in front of dipole array-type VHF (very high frequency) and UHF (ultra high frequency) broadcasting antennas. Measurements on site verified the usefulness of the model. The distance at which the power density begins to exceed 10 W.m-2--the value established by standards as a limit--is roughly 40 m for UHF-TV antennas, 30 m for FM (frequency modulated) radio antennas and 15 m for VHF-TV antennas. Typical average input powers of antennas are 20 kW, 4 kW and 10 kW for FM radio, VHF-TV and UHF transmissions, respectively.

  12. Electron momentum spectroscopy study of amantadine: binding energy spectra and valence orbital electron density distributions

    NASA Astrophysics Data System (ADS)

    Litvinyuk, I. V.; Zheng, Y.; Brion, C. E.

    2000-11-01

    The electron binding energy spectrum and valence orbital electron momentum density distributions of amantadine (1-aminoadamantane), an important anti-viral and anti-Parkinsonian drug, have been measured by electron momentum spectroscopy. Theoretical momentum distributions, calculated at the 6-311++G** and AUG-CC-PVTZ levels within the target Hartree-Fock and also the target Kohn-Sham density functional theory approximations, show good agreement with the experimental results. The results for amantadine are also compared with those for the parent molecule, adamantane, reported earlier (Chem. Phys. 253 (2000) 41). Based on the comparison tentative assignments of the valence region ionization bands of amantadine have been made.

  13. High density, uniformly distributed W/UO2 for use in Nuclear Thermal Propulsion

    NASA Astrophysics Data System (ADS)

    Tucker, Dennis S.; Barnes, Marvin W.; Hone, Lance; Cook, Steven

    2017-04-01

    An inexpensive, quick method has been developed to obtain uniform distributions of UO2 particles in a tungsten matrix utilizing 0.5 wt percent low density polyethylene. Powders were sintered in a Spark Plasma Sintering (SPS) furnace at 1600 °C, 1700 °C, 1750 °C, 1800 °C and 1850 °C using a modified sintering profile. This resulted in a uniform distribution of UO2 particles in a tungsten matrix with high densities, reaching 99.46% of theoretical for the sample sintered at 1850 °C. The powder process is described and the results of this study are given below.

  14. Expansion-free evolving spheres must have inhomogeneous energy density distributions

    SciTech Connect

    Herrera, L.; Le Denmat, G.; Santos, N. O.

    2009-04-15

    In a recent paper a systematic study on shearing expansion-free spherically symmetric distributions was presented. As a particular case of such systems, the Skripkin model was mentioned, which corresponds to a nondissipative perfect fluid with a constant energy density. Here we show that such a model is inconsistent with junction conditions. It is shown that in general for any nondissipative fluid distribution, the expansion-free condition requires the energy density to be inhomogeneous. As an example we consider the case of dust, which allows for a complete integration.

  15. Prediction of reserves using multivariate power-normal mixture distribution

    NASA Astrophysics Data System (ADS)

    Ling, Ang Siew; Hin, Pooi Ah

    2016-10-01

    Recently, in the area on stochastic loss reserving, there are a number of papers which analyze the individual claims data using the Position Dependent Marked Poisson Process. The present paper instead uses a different type of individual data. For the i-th (1≤i≤n) customer, these individual data include the sum insured si together with the amount paid yi j and the amount ai j reported but not yet paid in the j-th (1 ≤ j ≤ 6) development year. A technique based on multivariate power-normal mixture distribution is already available for predicting the future value (yi j + 1, ai j + 1) using the present year value (yi j, ai j) and the sum insured si. Presently the above technique is improved by the transformation of distribution which is defined on the whole real line to one which is non-negative and having approximately the same first four moments as the original distribution. It is found that, for the dataset considered in this paper, the improved method gives a better estimate for the reserve when compared with the chain ladder reserve estimate. Furthermore, the method is expected to provide a fairly reliable value for the Provision of Risk Margin for Adverse Deviation (PRAD).

  16. Power law distributions and dynamic behaviour of stock markets

    NASA Astrophysics Data System (ADS)

    Richmond, P.

    2001-04-01

    A simple agent model is introduced by analogy with the mean field approach to the Ising model for a magnetic system. Our model is characterised by a generalised Langevin equation = F ϕ + G ϕ t where t is the usual Gaussian white noise, i.e.: t t' = 2Dδ t-t' and t = 0. Both the associated Fokker Planck equation and the long time probability distribution function can be obtained analytically. A steady state solution may be expressed as P ϕ = exp{ - Ψ ϕ - ln G(ϕ)} where Ψ ϕ = - F/ G dϕ and Z is a normalization factor. This is explored for the simple case where F ϕ = Jϕ + bϕ2 - cϕ3 and fluctuations characterised by the amplitude G ϕ = ϕ + ɛ when it readily yields for ϕ>>ɛ, a distribution function with power law tails, viz: P ϕ = exp{ 2bϕ-cϕ2 /D}. The parameter c ensures convergence of the distribution function for large values of ϕ. It might be loosely associated with the activity of so-called value traders. The parameter J may be associated with the activity of noise traders. Output for the associated time series show all the characteristics of familiar financial time series providing J < 0 and D | J|.

  17. Power spectral density changes and language lateralization during covert object naming tasks measured with high-density EEG recordings.

    PubMed

    Ramon, C; Holmes, M; Freeman, Walter J; Gratkowski, Maciej; Eriksen, K J; Haueisen, Jens

    2009-01-01

    Our objective was to study changes in EEG time-domain power spectral density (PSDt) and localization of language areas during covert object naming tasks in human subjects with epilepsy. EEG data for subjects with epilepsy were acquired during the covert object naming tasks using a net of 256 electrodes. The trials required each subject to provide the names of common objects presented every 4 seconds on slides. Each trial comprised the 1.0 second before and 3.0 seconds after initial object presentation. PSDt values at baseline and during tasks were calculated in the theta, alpha, beta, low gamma, and high gamma bands. The spatial contour plots reveal that PSDt values during object naming were 10-20% higher than the baseline values for different bands. Language was lateralized to left frontal or temporal areas. In all cases, the Wada test disclosed language lateralization to the left hemisphere as well.

  18. Kink and Sausage Modes in Nonuniform Magnetic Slabs with Continuous Transverse Density Distributions

    NASA Astrophysics Data System (ADS)

    Yu, Hui; Li, Bo; Chen, Shao-Xia; Guo, Ming-Zhe

    2015-11-01

    We examine the influence of a continuous density structuring transverse to coronal slabs on the dispersive properties of fundamental standing kink and sausage modes supported therein. We derive generic dispersion relations (DRs) governing linear fast waves in pressureless straight slabs with general transverse density distributions, and focus on cases where the density inhomogeneity takes place in a layer of arbitrary width and in arbitrary form. The physical relevance of the solutions to the DRs is demonstrated by the corresponding time-dependent computations. For all profiles examined, the lowest order kink modes are trapped regardless of longitudinal wavenumber k. A continuous density distribution introduces a difference to their periods of ≲13% when k is the observed range relative to the case where the density profile takes a step function form. Sausage modes and other branches of kink modes are leaky at small k, and their periods and damping times are heavily influenced by how the transverse density profile is prescribed, in particular the length scale. These modes have sufficiently high quality to be observable only for physical parameters representative of flare loops. We conclude that while the simpler DR pertinent to a step function profile can be used for the lowest order kink modes, the detailed information on the transverse density structuring needs to be incorporated into studies of sausage modes and higher order kink modes.

  19. KINK AND SAUSAGE MODES IN NONUNIFORM MAGNETIC SLABS WITH CONTINUOUS TRANSVERSE DENSITY DISTRIBUTIONS

    SciTech Connect

    Yu, Hui; Li, Bo; Chen, Shao-Xia; Guo, Ming-Zhe

    2015-11-20

    We examine the influence of a continuous density structuring transverse to coronal slabs on the dispersive properties of fundamental standing kink and sausage modes supported therein. We derive generic dispersion relations (DRs) governing linear fast waves in pressureless straight slabs with general transverse density distributions, and focus on cases where the density inhomogeneity takes place in a layer of arbitrary width and in arbitrary form. The physical relevance of the solutions to the DRs is demonstrated by the corresponding time-dependent computations. For all profiles examined, the lowest order kink modes are trapped regardless of longitudinal wavenumber k. A continuous density distribution introduces a difference to their periods of ≲13% when k is the observed range relative to the case where the density profile takes a step function form. Sausage modes and other branches of kink modes are leaky at small k, and their periods and damping times are heavily influenced by how the transverse density profile is prescribed, in particular the length scale. These modes have sufficiently high quality to be observable only for physical parameters representative of flare loops. We conclude that while the simpler DR pertinent to a step function profile can be used for the lowest order kink modes, the detailed information on the transverse density structuring needs to be incorporated into studies of sausage modes and higher order kink modes.

  20. Publication of Proceedings for the 6th Workshop on High Energy Density and High Power RF (RF 2003)

    SciTech Connect

    Victor L. Granatstein

    2004-08-08

    The 6th Workshop on High Energy Density and High Power RF (RF 2003) was held from June 22 to June 26 at the Coolfont Resort and Conference Center in Berkeley Springs, West Virginia. The Workshop was hosted by the Institute for Research in Electronics and Applied Physics (IREAP) of the University of Maryland, College Park and by the Naval Research Laboratory, Washington DC. As its name implies this was the sixth in a series of biennial workshops devoted to exchanging information and ideas on high power microwave sources and components. The applications addressed included particle accelerators, radar, HPM, space exploration, neutron sources and plasma heating and current driven in controlled thermonuclear fusion research. This Final Report includes a brief description of the RF 2003 Workshop and the distribution of the published proceedings.

  1. Particle visualization in high-power impulse magnetron sputtering. II. Absolute density dynamics

    SciTech Connect

    Britun, Nikolay Palmucci, Maria; Konstantinidis, Stephanos; Snyders, Rony

    2015-04-28

    Time-resolved characterization of an Ar-Ti high-power impulse magnetron sputtering discharge has been performed. The present, second, paper of the study is related to the discharge characterization in terms of the absolute density of species using resonant absorption spectroscopy. The results on the time-resolved density evolution of the neutral and singly-ionized Ti ground state atoms as well as the metastable Ti and Ar atoms during the discharge on- and off-time are presented. Among the others, the questions related to the inversion of population of the Ti energy sublevels, as well as to re-normalization of the two-dimensional density maps in terms of the absolute density of species, are stressed.

  2. Sensitivity of cross sections for elastic nucleus-nucleus scattering to halo nucleus density distributions

    SciTech Connect

    Alkhazov, G. D.; Sarantsev, V. V.

    2012-12-15

    In order to clear up the sensitivity of the nucleus-nucleus scattering to the nuclear matter distributions in exotic halo nuclei, we have calculated differential cross sections for elastic scattering of the {sup 6}He and {sup 11}Li nuclei on several nuclear targets at the energy of 0.8 GeV/nucleon with different assumed nuclear density distributions in {sup 6}He and {sup 11}Li.

  3. Study of the longitudinal distribution of power generated in a random distributed feedback Raman fibre laser with unidirectional pumping

    SciTech Connect

    Churkin, D V; El-Taher, A E; Vatnik, I D; Babin, Sergei A

    2012-09-30

    The longitudinal distribution of the Stokes-component power in a Raman fibre laser with a random distributed feedback and unidirectional pumping is measured. The fibre parameters (linear loss and Rayleigh backscattering coefficient) are calculated based on the distributions obtained. A numerical model is developed to describe the lasing power distribution. The simulation results are in good agreement with the experimental data. (optical fibres, lasers and amplifiers. properties and applications)

  4. Photovoltaic Impact Assessment of Smart Inverter Volt-VAR Control on Distribution System Conservation Voltage Reduction and Power Quality

    SciTech Connect

    Ding, Fei; Nagarajan, Adarsh; Chakraborty, Sudipta; Baggu, Murali; Nguyen, Andu; Walinga, Sarah; McCarty, Michael; Bell, Frances

    2016-12-01

    This report presents an impact assessment study of distributed photovoltaic (PV) with smart inverter Volt-VAR control on conservation voltage reduction (CVR) energy savings and distribution system power quality. CVR is a methodology of flattening and lowering a distribution system voltage profile in order to conserve energy. Traditional CVR relies on operating utility voltage regulators and switched capacitors. However, with the increased penetration of distributed PV systems, smart inverters provide the new opportunity to control local voltage and power factor by regulating the reactive power output, leading to a potential increase in CVR energy savings. This report proposes a methodology to implement CVR scheme by operating voltage regulators, capacitors, and autonomous smart inverter Volt-VAR control in order to achieve increased CVR benefit. Power quality is an important consideration when operating a distribution system, especially when implementing CVR. It is easy to measure the individual components that make up power quality, but a comprehensive method to incorporate all of these values into a single score has yet to be undertaken. As a result, this report proposes a power quality scoring mechanism to measure the relative power quality of distribution systems using a single number, which is aptly named the 'power quality score' (PQS). Both the CVR and PQS methodologies were applied to two distribution system models, one obtained from the Hawaiian Electric Company (HECO) and another obtained from Pacific Gas and Electric (PG&E). These two models were converted to the OpenDSS platform using previous model conversion tools that were developed by NREL. Multiple scenarios including various PV penetration levels and smart inverter densities were simulated to analyze the impact of smart inverter Volt-VAR support on CVR energy savings and feeder power quality. In order to analyze the CVR benefit and PQS, an annual simulation was conducted for each scenario.

  5. Design of a power management and distribution system for a thermionic-diode powered spacecraft

    NASA Technical Reports Server (NTRS)

    Kimnach, Greg L.

    1996-01-01

    The Electrical Systems Development Branch of the Power Technology Division at the NASA Lewis Research Center in Cleveland, Ohio is designing a Power Management and Distribution (PMAD) System for the Air Force's Integrated Solar Upper Stage (ISUS) Engine Ground Test Demonstration (EGD). The ISUS program uses solar-thermal propulsion to perform orbit transfers from Low Earth Orbit (LEO) to Geosynchronous Orbit (GEO) and from LEO to Molnya. The ISUS uses the same energy conversion receiver to perform the LEO to High Earth Orbit (HEO) transfer and to generate on-orbit electric power for the payloads. On-orbit power generation is accomplished via two solar concentrators heating a dual-cavity graphite-core which has Thermionic Diodes (TMD's) encircling each cavity. The graphite core and concentrators together are called the Receiver and Concentrator (RAC). The TDM-emitters reach peak temperatures of approximately 2200K, and the TID-collectors are run at approximately 1000K. Because of the high Specific Impulse (I(sup sp)) of solar thermal propulsion relative to chemical propulsion, and because a common bus is used for communications, GN&C, power, etc., a substantial increase in payload weight is possible. This potentially allows for a stepdown in the required launch vehicle size or class for similar payload weight using conventional chemical propulsion and a separate spacecraft bus. The ISUS power system is to provide 1000W(sub e) at 28+/-6V(sub dc) to the payload/spacecraft from a maximum TID generation capability of 1070W(sub e) at 2200K. Producing power with this quality, protecting the spacecraft from electrical faults and accommodating operational constraints of the TID's are the responsibilities of the PMAD system. The design strategy and system options examined along with the proposed designs for the Flight and EGD configurations are discussed herein.

  6. Lattice models, packing density, and Boltzmann-like distribution of cavities in proteins.

    PubMed

    Rashin, Alexander A; Rashin, Abraham H L

    2005-02-15

    A model reproducing the experimental Boltzmann-like distribution of empty cavity sizes in proteins is introduced. Proteins are represented by lattices of different dimensionalities, corresponding to different numbers of nearest neighbor contacts. Small cavities emerge and join into larger ones in a random process that can be related to random mutations. Simulations of cavity creation are performed under the constraint of a limiting total packing density. Cavities sufficiently large (20 A(3) or more), that they might accommodate at least one additional methyl group produced by a mutation, are counted and compared to the distribution of cavities according to their sizes from protein statistics. The distributions calculated with this very simple model within a realistic range of packing densities are in good agreement with the empirical cavity distribution. The results suggest that the Boltzmann-like distribution of cavities in proteins might be affected by a mechanism controlled by limiting packing density and maximum allowed protein destabilization. This supports an earlier suggestion that the agreement between the free energies of cavity formation from the mutational experiments and from the statistics of the empty cavity distribution in X-ray protein structures is nonfortuitous. A possible relation of the suggested model to the Boltzmann hypothesis is discussed.

  7. Impact of Increasing Distributed Wind Power and Wind Turbine Siting on Rural Distribution Feeder Voltage Profiles: Preprint

    SciTech Connect

    Allen, A.; Zhang, Y. C.; Hodge, B. M.

    2013-09-01

    Many favorable wind energy resources in North America are located in remote locations without direct access to the transmission grid. Building transmission lines to connect remotely-located wind power plants to large load centers has become a barrier to increasing wind power penetration in North America. By connecting utility-sized megawatt-scale wind turbines to the distribution system, wind power supplied to consumers could be increased greatly. However, the impact of including megawatt-scale wind turbines on distribution feeders needs to be studied. The work presented here examined the impact that siting and power output of megawatt-scale wind turbines have on distribution feeder voltage. This is the start of work to present a general guide to megawatt-scale wind turbine impact on the distribution feeder and finding the amount of wind power that can be added without adversely impacting the distribution feeder operation, reliability, and power quality.

  8. Scaling of midplane separatrix density with power at divertor detachment onset

    NASA Astrophysics Data System (ADS)

    Leonard, A. W.; Makowski, M. A.; McLean, A. G.; Stangeby, P. C.

    2015-11-01

    The midplane separatrix density at divertor detachment onset is found to increase with higher parallel heat flux, q| |, flowing into the divertor, but at a slower rate than expected from simple scaling models. The separatrix density will be an important parameter in determining the compatibility of divertor heat flux control with robust pedestal operation and high core confinement in future devices. The parallel heat flux is examined by separately varying several parameters, including injected power, plasma current, toroidal field and injected impurities. Several methods are employed to locate the separatrix in this critical region of steep density gradients, including magnetic equilibrium reconstruction, power balance assumptions and spatial fiducials from other diagnostics. All methods exhibit a slower than the q|| 5 / 7 scaling predicted by a simple two point model. The nonlinear dependence of divertor radiation with power and density is one of several factors leading to this difference. Supported in part by the US DOE under DE-FC02-04ER54698 & DE-AC52-07NA27344.

  9. Leadership in Mammalian Societies: Emergence, Distribution, Power, and Payoff.

    PubMed

    Smith, Jennifer E; Gavrilets, Sergey; Mulder, Monique Borgerhoff; Hooper, Paul L; El Mouden, Claire; Nettle, Daniel; Hauert, Christoph; Hill, Kim; Perry, Susan; Pusey, Anne E; van Vugt, Mark; Smith, Eric Alden

    2016-01-01

    Leadership is an active area of research in both the biological and social sciences. This review provides a transdisciplinary synthesis of biological and social-science views of leadership from an evolutionary perspective, and examines patterns of leadership in a set of small-scale human and non-human mammalian societies. We review empirical and theoretical work on leadership in four domains: movement, food acquisition, within-group conflict mediation, and between-group interactions. We categorize patterns of variation in leadership in five dimensions: distribution (across individuals), emergence (achieved versus inherited), power, relative payoff to leadership, and generality (across domains). We find that human leadership exhibits commonalities with and differences from the broader mammalian pattern, raising interesting theoretical and empirical issues.

  10. SOLID OXIDE FUEL CELL HYBRID SYSTEM FOR DISTRIBUTED POWER GENERATION

    SciTech Connect

    Kurt Montgomery; Nguyen Minh

    2003-08-01

    This report summarizes the work performed by Honeywell during the October 2001 to December 2001 reporting period under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. The main objective of this project is to develop and demonstrate the feasibility of a highly efficient hybrid system integrating a planar Solid Oxide Fuel Cell (SOFC) and a turbogenerator. The conceptual and demonstration system designs were proposed and analyzed, and these systems have been modeled in Aspen Plus. Work has also started on the assembly of dynamic component models and the development of the top-level controls requirements for the system. SOFC stacks have been fabricated and performance mapping initiated.

  11. Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation

    SciTech Connect

    Nguyen Minh

    2002-03-31

    This report summarizes the work performed by Honeywell during the January 2002 to March 2002 reporting period under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. The main objective of this project is to develop and demonstrate the feasibility of a highly efficient hybrid system integrating a planar Solid Oxide Fuel Cell (SOFC) and a turbogenerator. For this reporting period the following activities have been carried out: {lg_bullet} Conceptual system design trade studies were performed {lg_bullet} System-level performance model was created {lg_bullet} Dynamic control models are being developed {lg_bullet} Mechanical properties of candidate heat exchanger materials were investigated {lg_bullet} SOFC performance mapping as a function of flow rate and pressure was completed

  12. SOLID OXIDE FUEL CELL HYBRID SYSTEM FOR DISTRIBUTED POWER GENERATION

    SciTech Connect

    Unknown

    2002-03-01

    This report summarizes the work performed by Honeywell during the July 2001 to September 2001 reporting period under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. The main objective of this project is to develop and demonstrate the feasibility of a highly efficient hybrid system integrating a planar Solid Oxide Fuel Cell (SOFC) and a turbogenerator. An internal program kickoff was held at Honeywell in Torrance, CA. The program structure was outlined and the overall technical approach for the program was presented to the team members. Detail program schedules were developed and detailed objectives were defined. Initial work has begun on the system design and pressurized SOFC operation.

  13. Boosting Power Density of Microbial Fuel Cells with 3D Nitrogen-Doped Graphene Aerogel Electrode.

    PubMed

    Yang, Yang; Liu, Tianyu; Zhu, Xun; Zhang, Feng; Ye, Dingding; Liao, Qiang; Li, Yat

    2016-08-01

    A 3D nitrogen-doped graphene aerogel (N-GA) as an anode material for microbial fuel cells (MFCs) is reported. Electron microscopy images reveal that the N-GA possesses hierarchical porous structure that allows efficient diffusion of both bacterial cells and electron mediators in the interior space of 3D electrode, and thus, the colonization of bacterial communities. Electrochemical impedance spectroscopic measurements further show that nitrogen doping considerably reduces the charge transfer resistance and internal resistance of GA, which helps to enhance the MFC power density. Importantly, the dual-chamber milliliter-scale MFC with N-GA anode yields an outstanding volumetric power density of 225 ± 12 W m(-3) normalized to the total volume of the anodic chamber (750 ± 40 W m(-3) normalized to the volume of the anode). These power densities are the highest values report for milliliter-scale MFCs with similar chamber size (25 mL) under the similar measurement conditions. The 3D N-GA electrode shows great promise for improving the power generation of MFC devices.

  14. High-temperature, high-power-density thermionic energy conversion for space

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1977-01-01

    Theoretic converter outputs and efficiencies indicate the need to consider thermionic energy conversion (TEC) with greater power densities and higher temperatures within reasonable limits for space missions. Converter-output power density, voltage, and efficiency as functions of current density were determined for 1400-to-2000 K emitters with 725-to-1000 K collectors. The results encourage utilization of TEC with hotter-than-1650 K emitters and greater-than-6W sq cm outputs to attain better efficiencies, greater voltages, and higher waste-heat-rejection temperatures for multihundred-kilowatt space-power applications. For example, 1800 K, 30 A sq cm TEC operation for NEP compared with the 1650 K, 5 A/sq cm case should allow much lower radiation weights, substantially fewer and/or smaller emitter heat pipes, significantly reduced reactor and shield-related weights, many fewer converters and associated current-collecting bus bars, less power conditioning, and lower transmission losses. Integration of these effects should yield considerably reduced NEP specific weights.

  15. Boosting Power Density of Microbial Fuel Cells with 3D Nitrogen‐Doped Graphene Aerogel Electrode

    PubMed Central

    Yang, Yang; Liu, Tianyu; Zhang, Feng; Ye, Dingding; Liao, Qiang

    2016-01-01

    A 3D nitrogen‐doped graphene aerogel (N‐GA) as an anode material for microbial fuel cells (MFCs) is reported. Electron microscopy images reveal that the N‐GA possesses hierarchical porous structure that allows efficient diffusion of both bacterial cells and electron mediators in the interior space of 3D electrode, and thus, the colonization of bacterial communities. Electrochemical impedance spectroscopic measurements further show that nitrogen doping considerably reduces the charge transfer resistance and internal resistance of GA, which helps to enhance the MFC power density. Importantly, the dual‐chamber milliliter‐scale MFC with N‐GA anode yields an outstanding volumetric power density of 225 ± 12 W m−3 normalized to the total volume of the anodic chamber (750 ± 40 W m−3 normalized to the volume of the anode). These power densities are the highest values report for milliliter‐scale MFCs with similar chamber size (25 mL) under the similar measurement conditions. The 3D N‐GA electrode shows great promise for improving the power generation of MFC devices. PMID:27818911

  16. Extensive Variation in the Density and Distribution of DNA Polymorphism in Sorghum Genomes

    PubMed Central

    Evans, Joseph; McCormick, Ryan F.; Morishige, Daryl; Olson, Sara N.; Weers, Brock; Hilley, Josie; Klein, Patricia; Rooney, William; Mullet, John

    2013-01-01

    Sorghum genotypes currently used for grain production in the United States were developed from African landraces that were imported starting in the mid-to-late 19th century. Farmers and plant breeders selected genotypes for grain production with reduced plant height, early flowering, increased grain yield, adaptation to drought, and improved resistance to lodging, diseases and pests. DNA polymorphisms that distinguish three historically important grain sorghum genotypes, BTx623, BTx642 and Tx7000, were characterized by genome sequencing, genotyping by sequencing, genetic mapping, and pedigree-based haplotype analysis. The distribution and density of DNA polymorphisms in the sequenced genomes varied widely, in part because the lines were derived through breeding and selection from diverse Kafir, Durra, and Caudatum race accessions. Genomic DNA spanning dw1 (SBI-09) and dw3 (SBI-07) had identical haplotypes due to selection for reduced height. Lower SNP density in genes located in pericentromeric regions compared with genes located in euchromatic regions is consistent with background selection in these regions of low recombination. SNP density was higher in euchromatic DNA and varied >100-fold in contiguous intervals that spanned up to 300 Kbp. The localized variation in DNA polymorphism density occurred throughout euchromatic regions where recombination is elevated, however, polymorphism density was not correlated with gene density or DNA methylation. Overall, sorghum chromosomes contain distal euchromatic regions characterized by extensive, localized variation in DNA polymorphism density, and large pericentromeric regions of low gene density, diversity, and recombination. PMID:24265758

  17. Extensive variation in the density and distribution of DNA polymorphism in sorghum genomes.

    PubMed

    Evans, Joseph; McCormick, Ryan F; Morishige, Daryl; Olson, Sara N; Weers, Brock; Hilley, Josie; Klein, Patricia; Rooney, William; Mullet, John

    2013-01-01

    Sorghum genotypes currently used for grain production in the United States were developed from African landraces that were imported starting in the mid-to-late 19(th) century. Farmers and plant breeders selected genotypes for grain production with reduced plant height, early flowering, increased grain yield, adaptation to drought, and improved resistance to lodging, diseases and pests. DNA polymorphisms that distinguish three historically important grain sorghum genotypes, BTx623, BTx642 and Tx7000, were characterized by genome sequencing, genotyping by sequencing, genetic mapping, and pedigree-based haplotype analysis. The distribution and density of DNA polymorphisms in the sequenced genomes varied widely, in part because the lines were derived through breeding and selection from diverse Kafir, Durra, and Caudatum race accessions. Genomic DNA spanning dw1 (SBI-09) and dw3 (SBI-07) had identical haplotypes due to selection for reduced height. Lower SNP density in genes located in pericentromeric regions compared with genes located in euchromatic regions is consistent with background selection in these regions of low recombination. SNP density was higher in euchromatic DNA and varied >100-fold in contiguous intervals that spanned up to 300 Kbp. The localized variation in DNA polymorphism density occurred throughout euchromatic regions where recombination is elevated, however, polymorphism density was not correlated with gene density or DNA methylation. Overall, sorghum chromosomes contain distal euchromatic regions characterized by extensive, localized variation in DNA polymorphism density, and large pericentromeric regions of low gene density, diversity, and recombination.

  18. Nest-density distribution patterns in a yellow-legged gull archipelago colony

    NASA Astrophysics Data System (ADS)

    Vidal, Eric; Roche, Philip; Bonnet, Véronique; Tatoni, Thierry

    2001-12-01

    The nest density distribution of yellow-legged gulls Larus cachinnans was investigated on the large Marseille archipelago colony (south-east France) which houses c. 18 000 breeding pairs. The study was performed at two investigation scales, including both mean nesting density on the nine study islands and density distribution within 171 sampling plots. The mean nesting density on each island was negatively correlated with island surface area and with the distance from the initial colony location (south-east end of the archipelago). No significant correlation was found with the other island parameters analysed (maximum elevation, shape index and distance from continent). A partial least squares regression performed between denstiy data from 171 500 m 2 sampling plots and environmental variables showed that the mostly explaining factors were island isolation and percentage of rocks in the plots (positive correlation), and distance of the island from the south-east end of the archipelago, island area, distance from plot to seaside and percentage of stone in the plots (negative correlation). Thus in our case, vegetation parameters (cover and height) were not influencial factors in nest density distribution.

  19. Distribution, density, and biomass of introduced small mammals in the southern mariana islands

    USGS Publications Warehouse

    Wiewel, A.S.; Adams, A.A.Y.; Rodda, G.H.

    2009-01-01

    Although it is generally accepted that introduced small mammals have detrimental effects on island ecology, our understanding of these effects is frequently limited by incomplete knowledge of small mammal distribution, density, and biomass. Such information is especially critical in the Mariana Islands, where small mammal density is inversely related to effectiveness of Brown Tree Snake (Boiga irregularis) control tools, such as mouse-attractant traps. We used mark-recapture sampling to determine introduced small mammal distribution, density, and biomass in the major habitats of Guam, Rota, Saipan, and Tinian, including grassland, Leucaena forest, and native limestone forest. Of the five species captured, Rattus diardii (sensu Robins et al. 2007) was most common across habitats and islands. In contrast, Mus musculus was rarely captured at forested sites, Suncus murinus was not captured on Rota, and R. exulans and R. norvegicus captures were uncommon. Modeling indicated that neophobia, island, sex, reproductive status, and rain amount influenced R. diardii capture probability, whereas time, island, and capture heterogeneity influenced S. murinus and M. musculus capture probability. Density and biomass were much greater on Rota, Saipan, and Tinian than on Guam, most likely a result of Brown Tree Snake predation pressure on the latter island. Rattus diardii and M. musculus density and biomass were greatest in grassland, whereas S. murinus density and biomass were greatest in Leucaena forest. The high densities documented during this research suggest that introduced small mammals (especially R. diardii) are impacting abundance and diversity of the native fauna and flora of the Mariana Islands. Further, Brown Tree Snake control and management tools that rely on mouse attractants will be less effective on Rota, Saipan, and Tinian than on Guam. If the Brown Tree Snake becomes established on these islands, high-density introduced small mammal populations will likely

  20. Two-dimensional AXUV-based radiated power density diagnostics on NSTX-U

    SciTech Connect

    Faust, I.; Parker, R. R.; Delgado-Aparicio, L.; Bell, R. E.; Diallo, A.; Gerhardt, S. P.; LeBlanc, B.; Kozub, T. A.; Tritz, K.; Stratton, B. C.

    2014-11-15

    A new set of radiated-power-density diagnostics for the National Spherical Torus Experiment Upgrade (NSTX-U) tokamak have been designed to measure the two-dimensional poloidal structure of the total photon emissivity profile in order to perform power balance, impurity transport, and magnetohydrodynamic studies. Multiple AXUV-diode based pinhole cameras will be installed in the same toroidal angle at various poloidal locations. The local emissivity will be obtained from several types of tomographic reconstructions. The layout and response expected for the new radially viewing poloidal arrays will be shown for different impurity concentrations to characterize the diagnostic sensitivity. The radiated power profile inverted from the array data will also be used for estimates of power losses during transitions from various divertor configurations in NSTX-U. The effect of in-out and top/bottom asymmetries in the core radiation from high-Z impurities will be addressed.

  1. Control of ion density distribution by magnetic traps for plasma electrons

    SciTech Connect

    Baranov, Oleg; Romanov, Maxim; Fang Jinghua; Cvelbar, Uros; Ostrikov, Kostya

    2012-10-01

    The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated.

  2. Spin-density distribution in the partially magnetized organic quantum magnet F2PNNNO

    SciTech Connect

    Zheludev, Andrey I; Garlea, Vasile O; Nishihara, S.; Hosokoshi, Y.; Cousson, Alain; Gukasov, Arsen; Inoue, K.

    2007-01-01

    Polarized neutron diffraction experiments on an organic magnetic material reveal a highly skewed distribution of spin density within the magnetic molecular unit. The very large magnitude of the observed effect is due to quantum spin fluctuations. The data are in quantitative agreement with direct diagonalization results for a model spin Hamiltonian, and provide insight on the actual microscopic origin of the relevant exchange interactions.

  3. 1.0 Mm Maps and Radial Density Distributions of Southern Hii/molecular Cloud Complexes

    NASA Technical Reports Server (NTRS)

    Cheung, L. H.; Frogel, J. A.; Gezar, D. Y.; Hauser, M. G.

    1980-01-01

    Several 1.0 continuum mapping observations were made of seven southern hemisphere h12/molecular cloud complexes with 65 arcsec resolution. The radial density distribution of the clouds with central luminosity sources was determined observationally. Strong similarities in morphology and general physical conditions were found to exist among all of the southern clouds in the sample.

  4. Comparison of Energy Efficiency and Power Density in Pressure Retarded Osmosis and Reverse Electrodialysis

    SciTech Connect

    Yip, NY; Elimelech, M

    2014-09-16

    Pressure retarded osmosis (PRO) and reverse electrodialysis (RED) are emerging membrane-based technologies that can convert chemical energy in salinity gradients to useful work. The two processes have intrinsically different working principles: controlled mixing in PRO is achieved by water permeation across salt-rejecting membranes, whereas RED is driven by ion flux across charged membranes. This study compares the energy efficiency and power density performance of PRO and RED with simulated technologically available membranes for natural, anthropogenic, and engineered salinity gradients (seawater-river water, desalination brine-wastewater, and synthetic hypersaline solutions, respectively). The analysis shows that PRO can achieve both greater efficiencies (54-56%) and higher power densities (2.4-38 W/m(2)) than RED (18-38% and 0.77-1.2 W/m(2)). The superior efficiency is attributed to the ability of PRO membranes to more effectively utilize the salinity difference to drive water permeation and better suppress the detrimental leakage of salts. On the other hand, the low conductivity of currently available ion exchange membranes impedes RED ion flux and, thus, constrains the power density. Both technologies exhibit a trade-off between efficiency and power density: employing more permeable but less selective membranes can enhance the power density, but undesired entropy production due to uncontrolled mixing increases and some efficiency is sacrificed. When the concentration difference is increased (i.e., natural -> anthropogenic -> engineered salinity gradients), PRO osmotic pressure difference rises proportionally but not so for RED Nernst potential, which has logarithmic dependence on the solution concentration. Because of this inherently different characteristic, RED is unable to take advantage of larger salinity gradients, whereas PRO power density is considerably enhanced. Additionally, high solution concentrations suppress the Donnan exclusion effect of the

  5. Comparison of energy efficiency and power density in pressure retarded osmosis and reverse electrodialysis.

    PubMed

    Yip, Ngai Yin; Elimelech, Menachem

    2014-09-16

    Pressure retarded osmosis (PRO) and reverse electrodialysis (RED) are emerging membrane-based technologies that can convert chemical energy in salinity gradients to useful work. The two processes have intrinsically different working principles: controlled mixing in PRO is achieved by water permeation across salt-rejecting membranes, whereas RED is driven by ion flux across charged membranes. This study compares the energy efficiency and power density performance of PRO and RED with simulated technologically available membranes for natural, anthropogenic, and engineered salinity gradients (seawater-river water, desalination brine-wastewater, and synthetic hypersaline solutions, respectively). The analysis shows that PRO can achieve both greater efficiencies (54-56%) and higher power densities (2.4-38 W/m(2)) than RED (18-38% and 0.77-1.2 W/m(2)). The superior efficiency is attributed to the ability of PRO membranes to more effectively utilize the salinity difference to drive water permeation and better suppress the detrimental leakage of salts. On the other hand, the low conductivity of currently available ion exchange membranes impedes RED ion flux and, thus, constrains the power density. Both technologies exhibit a trade-off between efficiency and power density: employing more permeable but less selective membranes can enhance the power density, but undesired entropy production due to uncontrolled mixing increases and some efficiency is sacrificed. When the concentration difference is increased (i.e., natural → anthropogenic → engineered salinity gradients), PRO osmotic pressure difference rises proportionally but not so for RED Nernst potential, which has logarithmic dependence on the solution concentration. Because of this inherently different characteristic, RED is unable to take advantage of larger salinity gradients, whereas PRO power density is considerably enhanced. Additionally, high solution concentrations suppress the Donnan exclusion effect of the

  6. C -parameter distribution at N3LL' including power corrections

    NASA Astrophysics Data System (ADS)

    Hoang, André H.; Kolodrubetz, Daniel W.; Mateu, Vicent; Stewart, Iain W.

    2015-05-01

    We compute the e+e- C -parameter distribution using the soft-collinear effective theory with a resummation to next-to-next-to-next-to-leading-log prime accuracy of the most singular partonic terms. This includes the known fixed-order QCD results up to O (αs3), a numerical determination of the two-loop nonlogarithmic term of the soft function, and all logarithmic terms in the jet and soft functions up to three loops. Our result holds for C in the peak, tail, and far tail regions. Additionally, we treat hadronization effects using a field theoretic nonperturbative soft function, with moments Ωn. To eliminate an O (ΛQCD) renormalon ambiguity in the soft function, we switch from the MS ¯ to a short distance "Rgap" scheme to define the leading power correction parameter Ω1. We show how to simultaneously account for running effects in Ω1 due to renormalon subtractions and hadron-mass effects, enabling power correction universality between C -parameter and thrust to be tested in our setup. We discuss in detail the impact of resummation and renormalon subtractions on the convergence. In the relevant fit region for αs(mZ) and Ω1, the perturbative uncertainty in our cross section is ≃ 2.5 % at Q =mZ.

  7. SOLID OXIDE FUEL CELL HYBRID SYSTEM FOR DISTRIBUTED POWER GENERATION

    SciTech Connect

    Faress Rahman; Nguyen Minh

    2003-07-01

    This report summarizes the work performed by Hybrid Power Generation Systems, LLC during the January 2003 to June 2003 reporting period under Cooperative Agreement DE-FC26-01NT40779 for the U. S. Department of Energy, National Energy Technology Laboratory (DOE/NETL) entitled ''Solid Oxide Fuel Cell Hybrid System for Distributed Power Generation''. The main objective of this project is to develop and demonstrate the feasibility of a highly efficient hybrid system integrating a planar Solid Oxide Fuel Cell (SOFC) and a micro-turbine. In addition, an activity included in this program focuses on the development of an integrated coal gasification fuel cell system concept based on planar SOFC technology. This report summarizes the results obtained to date on: System performance analysis and model optimization; Reliability and cost model development; System control including dynamic model development; Heat exchanger material tests and life analysis; Pressurized SOFC evaluation; and Pre-baseline system definition for coal gasification fuel cell system concept.

  8. C -parameter distribution at N 3 LL ' including power corrections

    DOE PAGES

    Hoang, André H.; Kolodrubetz, Daniel W.; Mateu, Vicent; ...

    2015-05-15

    We compute the e⁺e⁻ C-parameter distribution using the soft-collinear effective theory with a resummation to next-to-next-to-next-to-leading-log prime accuracy of the most singular partonic terms. This includes the known fixed-order QCD results up to O(α3s), a numerical determination of the two-loop nonlogarithmic term of the soft function, and all logarithmic terms in the jet and soft functions up to three loops. Our result holds for C in the peak, tail, and far tail regions. Additionally, we treat hadronization effects using a field theoretic nonperturbative soft function, with moments Ωn. To eliminate an O(ΛQCD) renormalon ambiguity in the soft function, we switchmore » from the MS¯ to a short distance “Rgap” scheme to define the leading power correction parameter Ω1. We show how to simultaneously account for running effects in Ω1 due to renormalon subtractions and hadron-mass effects, enabling power correction universality between C-parameter and thrust to be tested in our setup. We discuss in detail the impact of resummation and renormalon subtractions on the convergence. In the relevant fit region for αs(mZ) and Ω1, the perturbative uncertainty in our cross section is ≅ 2.5% at Q=mZ.« less

  9. Electrode material dependence of two-dimensional electron and vapour density distribution over vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Inada, Y.; Matsuoka, S.; Kumada, A.; Ikeda, H.; Hidaka, K.

    2017-03-01

    Electrode material dependence of intense-mode vacuum arc behaviour was systematically investigated by using the Shack-Hartmann method capable of simultaneously visualising two-dimensional electron and metal vapour density distributions from single-shot recordings. The electrode materials studied included Cu, CuCr (Cu75Cr25 wt. %), WC, and AgWC (Ag40WC60 wt. %). A comparison between the Cu and CuCr electrodes showed that the metal vapour densities for the CuCr decreased in an even shorter time scale than for the Cu. In the case of the WC electrodes, the widths of the electron density distributions became narrower as the arc current decreased although the electron densities hardly decreased in the decaying process of the arc current. The density measurements conducted at the late stage of the vacuum arcs demonstrated that the metal vapour densities around the anode were maintained at the highest value for the AgWC among the electrode materials in this study.

  10. Relative electron density distribution in a low nd helium dc discharge

    NASA Astrophysics Data System (ADS)

    Ganguly, Biswa N.; Scofield, James D.

    2016-09-01

    The axial and radial variations of the relative electron density distributions have been measured in an obstructed helium dc discharge by a laser collision induced fluorescence (LCIF) from 4 3D to 2 3P state at 447 nm. For this 1.75 Torr, 6.5 mm gap, 1.6 mA helium obstructed gas discharge, the on-axis LCIF intensity is mostly determined by the neutral atom collision. On the basis of this information, we have plotted the LCIF data to obtain a normalized electron density variation in the inter-electrode volume by plotting the ratio, I/-Io n -a x i s Io n -a x i s , where I is the radial variation of the LCIF intensity and Ion-axis is the on-axis LCIF intensity. The normalized LCIF data show an annular current density distribution in this obstructed discharge with the current peaking near the radial boundary of the electrodes.

  11. Kernel density estimation applied to bond length, bond angle, and torsion angle distributions.

    PubMed

    McCabe, Patrick; Korb, Oliver; Cole, Jason

    2014-05-27

    We describe the method of kernel density estimation (KDE) and apply it to molecular structure data. KDE is a quite general nonparametric statistical method suitable even for multimodal data. The method generates smooth probability density function (PDF) representations and finds application in diverse fields such as signal processing and econometrics. KDE appears to have been under-utilized as a method in molecular geometry analysis, chemo-informatics, and molecular structure optimization. The resulting probability densities have advantages over histograms and, importantly, are also suitable for gradient-based optimization. To illustrate KDE, we describe its application to chemical bond length, bond valence angle, and torsion angle distributions and show the ability of the method to model arbitrary torsion angle distributions.

  12. The Distribution of Mass Surface Densities in a High-mass Protocluster

    NASA Astrophysics Data System (ADS)

    Lim, Wanggi; Tan, Jonathan C.; Kainulainen, Jouni; Ma, Bo; Butler, Michael J.

    2016-09-01

    We study the probability distribution function (PDF) of mass surface densities, Σ, of infrared dark cloud (IRDC) G028.37+00.07 and its surrounding giant molecular cloud. This PDF constrains the physical processes, such as turbulence, magnetic fields, and self-gravity, that are expected to be controlling cloud structure and star formation activity. The chosen IRDC is of particular interest since it has almost 100,000 solar masses within a radius of 8 pc, making it one of the most massive, dense molecular structures known and is thus a potential site for the formation of a “super star cluster.” We study Σ in two ways. First, we use a combination of NIR and MIR extinction maps that are able to probe the bulk of the cloud structure up to Σ ˜ 1 g cm-2(A V ≃ 200 mag). Second, we study the FIR and submillimeter dust continuum emission from the cloud utilizing Herschel-PACS and SPIRE images and paying careful attention to the effects of foreground and background contamination. We find that the PDFs from both methods, applied over a ˜20‧(30 pc)-sized region that contains ≃1.5 × 105 M ⊙ and enclosing a minimum closed contour with Σ ≃ 0.013 g cm-2 (A V ≃ 3 mag), shows a lognormal shape with the peak measured at Σ ≃ 0.021 g cm-2 (A V ≃ 4.7 mag). There is tentative evidence for the presence of a high-Σ power-law tail that contains from ˜3% to 8% of the mass of the cloud material. We discuss the implications of these results for the physical processes occurring in this cloud.

  13. High resolution pulmonary computed tomography scans quantified by analysis of density distribution: application to asbestosis.

    PubMed Central

    Eterović, D; Dujić, Z; Tocilj, J; Capkun, V

    1993-01-01

    A new method for quantitative evaluation for high resolution computed tomography (HRCT) of the lungs was developed by assessment of the distribution of radiological densities within the lung slices. To enable effective reduction of data and improve the sensitivity of detection of abnormalities, the density distributions were analysed by curve fitting through the gamma variate model. The output of two variables proved most representative: the most frequent density (Hoansfield units; HU) and width of distribution (HU). The method was applied to seven patients with early asbestosis (positive histological finding and International Labour Office (ILO) profusion score up to 0/1), 15 patients with advanced stage of asbestosis (positive histological finding and ILO score above 1/2), and 13 normal controls. All patients with early asbestosis had isolated reduction of diffusing lung capacity to carbon monoxide (DLCO), whereas all patients with advanced asbestosis had reduced DLCO and restrictive disease; two of them also had an obstruction pattern. The most frequent densities were significantly greater in the advanced asbestosis group (-567 HU) when compared with both the early asbestosis group (-719 HU; p = 2 x 10(-6)), and controls (-799 HU; p = 0), and they also discriminated significantly between the early asbestosis group and controls (p = 0.0002). Significantly stronger linear correlations were established between DLCO and the most frequent densities (r = 0.86) than between DLCO and HRCT score (r = 0.57) or ILO score (r = 0.34). It is concluded that fitting the curve of the density distribution enables a more objective assessment of HRCT pulmonary scans, especially in the early stage of asbestosis. PMID:8329317

  14. A reformer to generate hydrogen for distributed power applications

    SciTech Connect

    Cole, J.A.; Kumar, R.V.; West, J.; Lyon, R.K.

    1998-07-01

    The generation of power using fuel cells is a promising technology for distributed electric power generation applications. Steam reforming of fossil fuels remains the most thermodynamically efficient means for production of hydrogen. Unfortunately, current steam reforming technology achieves high efficiencies only at very large scales, and remains impractical at the small production rates needed for small- to medium-size distributed power applications. A novel reformer process, called unmixed reforming, or UMR, has been developed for the conversion of hydrocarbon fuels (natural gas, diesel, gasoline) to hydrogen. The reformer promises high thermodynamic efficiency as heat is generated right on the catalytic bed unlike conventional reforming. The controlled combustion on the reforming catalyst using a patented technology called unmixed combustion provides the heat for the endothermic reforming reaction. The reformer generates a high-purity hydrogen product stream, which can then be used by fuel cells with minimal processing. The unmixed reformer is a packed-bed consisting of finely divided nickel supported on a ceramic matrix mixed with a calcium oxide bearing matrix such as dolomite. UMR consists of three process steps. During the first step air is passed over the packed-bed reactor to oxidize the nickel. The heat released during the oxidation reaction raises the temperature of the bed and decomposes the dolomite releasing carbon dioxide into a vent gas stream. In the subsequent step fuel passed over the packed-bed reduces the NiO back to Ni and further increases the temperature. In the final step, fuel and steam react to produce hydrogen through conventional steam reforming chemistry. The calcium oxide captures some of the carbon dioxide formed during the reforming reaction and thus shifts the reforming reactions to higher conversions, hence improving the purity of the hydrogen product stream. Although product hydrogen concentrations may be 75--85%, the CO content

  15. High power density energy harvester with high permeability magnetic material embedded in a rotating wheel

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Zhang, Yi; Sun, Nian X.; McDaniel, J. Gregory; Wang, Ming L.

    2012-04-01

    This work presents an alternative design of a rotating energy harvester, which possesses the capability of powering electronic sensors and wireless sensor networks within vehicle. This energy harvester design is based on magnetostatic coupling between a stationary circular-arc hard magnet array and rotating magnetic solenoids, which consists of a unique core with high permeability (μr>10,000) to significantly increase the output power density. A prototype of this rotating energy harvesting system has been fabricated and demonstrated on a rotating wheel at speeds from 10 to 60 miles/hour (mph). Test of the prototype equipped with energy storage circuit and wireless transmission board on actual vehicle has been carried out. Results of different rotating frequencies show average power densities from 1 to 5 W/cm3. A numerical and experimental study of powering a real-time wireless tire pressure monitoring system (TPMS) reveals that the energy harvester design generates constant and steady power sufficient for continuous operation of the TPMS.

  16. Power law olivine crystal size distributions in lithospheric mantle xenoliths

    NASA Astrophysics Data System (ADS)

    Armienti, P.; Tarquini, S.

    2002-12-01

    Olivine crystal size distributions (CSDs) have been measured in three suites of spinel- and garnet-bearing harzburgites and lherzolites found as xenoliths in alkaline basalts from Canary Islands, Africa; Victoria Land, Antarctica; and Pali Aike, South America. The xenoliths derive from lithospheric mantle, from depths ranging from 80 to 20 km. Their textures vary from coarse to porphyroclastic and mosaic-porphyroclastic up to cataclastic. Data have been collected by processing digital images acquired optically from standard petrographic thin sections. The acquisition method is based on a high-resolution colour scanner that allows image capturing of a whole thin section. Image processing was performed using the VISILOG 5.2 package, resolving crystals larger than about 150 μm and applying stereological corrections based on the Schwartz-Saltykov algorithm. Taking account of truncation effects due to resolution limits and thin section size, all samples show scale invariance of crystal size distributions over almost three orders of magnitude (0.2-25 mm). Power law relations show fractal dimensions varying between 2.4 and 3.8, a range of values observed for distributions of fragment sizes in a variety of other geological contexts. A fragmentation model can reproduce the fractal dimensions around 2.6, which correspond to well-equilibrated granoblastic textures. Fractal dimensions >3 are typical of porphyroclastic and cataclastic samples. Slight bends in some linear arrays suggest selective tectonic crushing of crystals with size larger than 1 mm. The scale invariance shown by lithospheric mantle xenoliths in a variety of tectonic settings forms distant geographic regions, which indicate that this is a common characteristic of the upper mantle and should be taken into account in rheological models and evaluation of metasomatic models.

  17. Advanced Microbial Fuel Cell Development, Miniaturization and Energy and Power Density Enhancement

    DTIC Science & Technology

    2007-04-30

    fuel cell development, miniaturization, and energy and power density enhancement. The anode is very important in the performance of a microbial fuel cell "MFC", and is often the limiting factor for a high power output. In present work, we used the CNT/PANI composite as the anode materials of MFCs for the first time and investigated the electrocatalytic properties of the composite associated with the bacterium biocatalyst. A method was developed to fabricate a nanostructured CNT/PANI composite anode for

  18. Aging Management Guideline for commercial nuclear power plants: Power and distribution transformers

    SciTech Connect

    Toman, G.; Gazdzinski, R.

    1994-05-01

    This Aging Management Guideline (AMG) provides recommended methods for effective detection and mitigation of age-related degradation mechanisms in power and distribution transformers important to license renewal in commercial nuclear power plants. The intent of this AMG to assist plant maintenance and operations personnel in maximizing the safe, useful life of these components. It also supports the documentation of effective aging management programs required under the License Renewal Rule 10 CFR Part 54. This AMG is presented in a manner which allows personnel responsible for performance analysis and maintenance to compare their plant-specific aging mechanisms (expected or already experienced) and aging management program activities to the more generic results and recommendations presented herein.

  19. Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

    PubMed Central

    Carney, Randy P.; Kim, Jin Young; Qian, Huifeng; Jin, Rongchao; Mehenni, Hakim; Stellacci, Francesco; Bakr, Osman M.

    2011-01-01

    Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (ρP) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. PMID:21654635

  20. Inverse Beta: Inverse cumulative density function (CDF) of a Beta distribution

    NASA Astrophysics Data System (ADS)

    Kipping, David

    2014-03-01

    The Beta Inverse code solves the inverse cumulative density function (CDF) of a Beta distribution, allowing one to sample from the Beta prior directly. The Beta distribution is well suited as a prior for the distribution of the orbital eccentricities of extrasolar planets; imposing a Beta prior on orbital eccentricity is valuable for any type of observation of an exoplanet where eccentricity can affect the model parameters (e.g. transits, radial velocities, microlensing, direct imaging). The Beta prior is an excellent description of the current, empirically determined distribution of orbital eccentricities and thus employing it naturally incorporates an observer’s prior experience of what types of orbits are probable or improbable. The default parameters in the code are currently set to the Beta distribution which best describes the entire population of exoplanets with well-constrained orbits.

  1. A High Power-Density, Mediator-Free, Microfluidic Biophotovoltaic Device for Cyanobacterial Cells

    PubMed Central

    Bombelli, Paolo; Müller, Thomas; Herling, Therese W; Howe, Christopher J; Knowles, Tuomas P J

    2015-01-01

    Biophotovoltaics has emerged as a promising technology for generating renewable energy because it relies on living organisms as inexpensive, self-repairing, and readily available catalysts to produce electricity from an abundant resource: sunlight. The efficiency of biophotovoltaic cells, however, has remained significantly lower than that achievable through synthetic materials. Here, a platform is devised to harness the large power densities afforded by miniaturized geometries. To this effect, a soft-lithography approach is developed for the fabrication of microfluidic biophotovoltaic devices that do not require membranes or mediators. Synechocystis sp. PCC 6803 cells are injected and allowed to settle on the anode, permitting the physical proximity between cells and electrode required for mediator-free operation. Power densities of above 100 mW m-2 are demonstrated for a chlorophyll concentration of 100 μM under white light, which is a high value for biophotovoltaic devices without extrinsic supply of additional energy. PMID:26190957

  2. Computed lateral power spectral density response of conventional and STOL airplanes to random atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Lichtenstein, J. H.

    1974-01-01

    A method of computing the power spectral densities of the lateral response of airplanes to random atmospheric turbulence was adapted to an electronic digital computer. By use of this program, the power spectral densities of the lateral roll, yaw, and sideslip angular displacement of several conventional and STOL airplanes were computed. The results show that for the conventional airplanes, the roll response is more prominent than that for yaw or sideslip response. For the STOL airplanes, on the other hand, the yaw and sideslip responses were larger than the roll response. The response frequency of the STOL airplanes generally is higher than that for the conventional airplanes. This combination of greater sensitivity of the STOL airplanes in yaw and sideslip and the frequency at which they occur could be a factor causing the poor riding qualities of this class of airplanes.

  3. High-power density piezoelectric energy harvesting using radially strained ultrathin trigonal tellurium nanowire assembly.

    PubMed

    Lee, Tae Il; Lee, Sangmin; Lee, Eungkyu; Sohn, Sungwoo; Lee, Yean; Lee, Sujeong; Moon, Geondae; Kim, Dohyang; Kim, Youn Sang; Myoung, Jae Min; Wang, Zhong Lin

    2013-06-04

    A high-yield solution-processed ultrathin (<10 nm) trigonal tellurium (t-Te) nanowire (NW) is introduced as a new class of piezoelectric nanomaterial with a six-fold higher piezoelectric constant compared to conventional ZnO NWs for a high-volume power-density nanogenerator (NG). While determining the energy-harvesting principle in a NG consisting of t-Te NW, it is theoretically and experimentally found that t-Te NW is piezoelectrically activated only by creating strain in its radial direction, along which it has an asymmetric crystal structure. Based upon this mechanism, a NG with a monolayer consisting of well-aligned t-Te NWs and a power density of 9 mW/cm(3) is fabricated.

  4. Non-invasive liquid level and density gauge for nuclear power reactor pressure vessels

    SciTech Connect

    Baratta, A.J.; Jester, W.A.; Kenney, E.S.; Mc Master, I.B.; Schultz, M.A.

    1987-01-27

    A method is described of non-invasively determining the liquid coolant level and density in a nuclear power reactor pressure vessel comprising the steps: positioning at least three neutron detector fission chambers externally of the reactor pressure vessel at multiple spaced positions along the side of the fuel core. One of the neutron detectors is positioned at the side near the bottom of the fuel core. The multiple spaced positions along the side remove any ambiguity as to whether the liquid level is decreasing or increasing: shielding the neutron detector fission chamber from thermal neutrons to avoid the noise associated therewith, and eliminating the effects of gamma radiation from the detected signals; monitoring the detected neutron level signals to determine to coolant liquid level and density in the nuclear power reactor pressure vessel.

  5. A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage

    SciTech Connect

    Wang, Ruxi; Wang, Fei; Boroyevich, Dushan; Burgos, Rolando; Lai, Rixin; Ning, Puqi; Rajashekara, Kaushik

    2011-01-01

    It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on theminimum ripple energy requirement, the feasibility of the active capacitor s reduction schemes is verified. Then, we propose a bidirectional buck boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.

  6. Quantum-dot density dependence of power conversion efficiency of intermediate-band solar cells

    NASA Astrophysics Data System (ADS)

    Sakamoto, Katsuyoshi; Kondo, Yasunori; Uchida, Keisuke; Yamaguchi, Koichi

    2012-12-01

    For intermediate-band solar cells containing GaAs/InAs quantum dots (QDs), the QD density dependence of the power conversion efficiency (PCE) was theoretically calculated for various sun concentrations under AM1.5 conditions based on detailed balance principles. A QD density of over 5 × 1013 cm-2 was required to achieve a PCE of more than 50% under 10 000 suns. However, under the photo-filled state and 1 sun, the PCE decreased over a wide total QD density range from about 3 × 1010 to 1 × 1013 cm-2. This reduction was attributed to the negative net carrier generation rate through the intermediate band, which was due to insufficient two-step optical absorption. The short-circuit current density increased as the QD density increased up to about 1 × 1011 cm-2 and it then saturated. In contrast, the open-circuit voltage decreased with increasing QD density. This reduction in the open-circuit voltage was suppressed at high sun concentrations.

  7. Enhanced current and power density of micro-scale microbial fuel cells with ultramicroelectrode anodes

    NASA Astrophysics Data System (ADS)

    Ren, Hao; Rangaswami, Sriram; Lee, Hyung-Sool; Chae, Junseok

    2016-09-01

    We present a micro-scale microbial fuel cell (MFC) with an ultramicroelectrode (UME) anode, with the aim of creating a miniaturized high-current/power-density converter using carbon-neutral and renewable energy sources. Micro-scale MFCs have been studied for more than a decade, yet their current and power densities are still an order of magnitude lower than those of their macro-scale counterparts. In order to enhance the current/power densities, we engineer a concentric ring-shaped UME, with a width of 20 μm, to facilitate the diffusion of ions in the vicinity of the micro-organisms that form biofilm on the UME. The biofilm extends approximately 15 μm from the edge of the UME, suggesting the effective biofilm area increases. Measured current/power densities per the effective area and the original anode area are 7.08  ±  0.01 A m-2 & 3.09  ±  0.04 W m-2 and 17.7  ±  0.03 A m-2 & 7.72  ±  0.09 W m-2, respectively. This is substantially higher than any prior work in micro-scale MFCs, and very close, or even higher, to that of macro-scale MFCs. A Coulombic efficiency, a measure of how efficiently an MFC harvests electrons from donor substrate, of 70%, and an energy conversion efficiency of 17% are marked, highlighting the micro-scale MFC as an attractive alternative within the existing energy conversion portfolio.

  8. An innovative demonstration of high power density in a compact MHD (magnetohydrodynamic) generator

    SciTech Connect

    Schmidt, H.J.; Lineberry, J.T.; Chapman, J.N.

    1990-06-01

    The present program was conducted by the University of Tennessee Space Institute (UTSI). It was by its nature a high risk experimental program to demonstrate the feasibility of high power density operation in a laboratory scale combustion driven MHD generator. Maximization of specific energy was not a consideration for the present program, but the results have implications in this regard by virtue of high energy fuel used. The power density is the ratio of the electrical energy output to the internal volume of the generator channel. The MHD process is a volumetric process and the power density is therefore a direct measure of the compactness of the system. Specific energy, is the ratio of the electrical energy output to consumable energy used for its production. The two parameters are conceptually interrelated. To achieve high power density and implied commensurate low system volume and weight, it was necessary to use an energetic fuel. The high energy fuel of choice was a mixture of powdered aluminum and carbon seeded with potassium carbonate and burned with gaseous oxygen. The solid fuel was burned in a hybrid combustion scheme wherein the fuel was cast within a cylindrical combustor in analogy with a solid propellant rocket motor. Experimental data is limited to gross channel output current and voltage, magnetic field strength, fuel and oxidizer flow rates, flow train external temperatures and combustor pressure. Similarly, while instantaneous oxidizer flow rates were measured, only average fuel consumption based on pre and post test component weights and dimensions was possible. 4 refs., 60 figs., 9 tabs.

  9. Electroencephalography Spectral Power Density in First-Episode Mania: A Comparative Study with Subsequent Remission Period

    PubMed Central

    GÜVEN, Sertaç; KESEBİR, Sermin; DEMİRER, R. Murat; BİLİCİ, Mustafa

    2015-01-01

    Introduction Our aim in this study was to investigate spectral power density (PSD) in first-episode mania and subsequent remission period and to evaluate their difference. Methods Sixty-nine consecutive cases referring to our hospital within the previous 1 year, who were evaluated as bipolar disorder manic episode according to The Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) at the first episode and had the informed consent form signed by first degree relatives, were included in this study. Exclusion criteria included having previous depressive episode, using drugs which could influence electroencephalographic activity before electroencephalography (EEG), and having previous neurological disease, particularly epilepsy, head trauma, and/or loss of consciousness. EEG records were obtained using a digital device in 16 channels; 23 surface electrodes were placed according to the International 10–20 system. Spectral power density (dbμV/Hz) of EEG signal provided information on the power carried out by EEG waves in defined frequancy range per unit frequency in the present study. Results A peak power value detected on the right with FP2P4 and on the left with F7T3 electrodes were found to be higher in the manic episode than in the remission period (p=0.018 and 0.025). In the remission period, in cases with psychotic symptoms during the manic period, F4C4 peak power value was found to be lower than that in cases with no psychotic findings during the manic period (p=0.027). There was no relation was found between YMRS scores and peak power scores. Conclusion Electrophysiological corollary of mood episode is present from the onset of the disease, and it differs between the manic and remission periods of bipolar disorder. In the remission period, peak power values of PSD distinguish cases with psychotic findings from cases without psychotic findings when they were manic.

  10. A high power density miniaturized microbial fuel cell having carbon nanotube anodes

    NASA Astrophysics Data System (ADS)

    Ren, Hao; Pyo, Soonjae; Lee, Jae-Ik; Park, Tae-Jin; Gittleson, Forrest S.; Leung, Frederick C. C.; Kim, Jongbaeg; Taylor, André D.; Lee, Hyung-Sool; Chae, Junseok

    2015-01-01

    Microbial fuel cells (MFCs) are a promising technology capable of directly converting the abundant biomass on the planet into electricity. Prior studies have adopted a variety of nanostructured materials with high surface area to volume ratio (SAV), yet the current and power density of these nanostructured materials do not deliver a significant leap over conventional MFCs. This study presents a novel approach to implement a miniaturized MFC with a high SAV of 4000 m-1 using three different CNT-based electrode materials: Vertically Aligned CNT (VACNT), Randomly Aligned CNT (RACNT), and Spin-Spray Layer-by-Layer (SSLbL) CNT. These CNT-based electrodes show unique biofilm morphology and thickness. The study of performance parameters of miniaturized MFCs with these CNT-electrodes are conducted with respect to a control bare gold electrode. The results show that CNT-based materials attract more exoelectrogens, Geobacter sp., than bare gold, yielding thicker biofilm formation. Among CNT-based electrodes, low sheet resistance electrodes result in thick biofilm generation and high current/power density. The miniaturized MFC having an SSLbL CNT anode exhibits a high volumetric power density of 3320 W m-3. This research may help lay the foundation for future research involving the optimization of MFCS with 2D and 3D nanostructured electrodes.

  11. Pulse Power Capability Of High Energy Density Capacitors Based on a New Dielectric Material

    NASA Technical Reports Server (NTRS)

    Winsor, Paul; Scholz, Tim; Hudis, Martin; Slenes, Kirk M.

    1999-01-01

    A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in high energy density pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cu cm whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its mechanical properties to temperatures above 150 C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test actual capacitors. The results of the testing will focus on pulse power applications specifically those found in electro-magnetic armor and guns, high power microwave sources and defibrillators.

  12. Dynamics of the spatial electron density distribution of EUV-induced plasmas

    NASA Astrophysics Data System (ADS)

    van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Banine, V. Y.

    2015-11-01

    We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure.

  13. A geographical model of radio-frequency power density around mobile phone masts.

    PubMed

    Briggs, David; Beale, Linda; Bennett, James; Toledano, Mireille B; de Hoogh, Kees

    2012-06-01

    Public concern about possible health effects of EMF radiation from mobile phone masts has led to an increase of epidemiological studies and health risk assessments which, in turn, require adequate methods of exposure estimation. Difficulties in exposure modelling are exacerbated both by the complexity of the propagation processes, and the need to obtain estimates for large study populations in order to provide sufficient statistical power to detect or exclude the small relative risks that might exist. Use of geographical information system (GIS) techniques offers the means to make such computations efficiently. This paper describes the development and field validation of a GIS-based exposure model (Geomorf). The model uses a modified Gaussian formulation to represent spatial variations in power densities around mobile phone masts, on the basis of power output, antenna height, tilt and the surrounding propagation environment. Obstruction by topography is allowed for, through use of a visibility function. Model calibration was done using field data from 151 measurement sites (1510 antenna-specific measurements) around a group of masts in a rural location, and 50 measurement sites (658 antenna-specific measurements) in an urban area. Different parameter settings were found to be necessary in urban and rural areas to obtain optimum results. The calibrated models were then validated against independent sets of data gathered from measurement surveys in rural and urban areas, and model performance was compared with that of two commonly used path-loss models (the COST-231 adaptations of the Hata and Walfisch-Ikegami models). Model performance was found to vary somewhat between the rural and urban areas, and at different measurement levels (antenna-specific power density, total power density), but overall gave good estimates (R(2)=0.641 and 0.615, RMSE=10.7 and 6.7 dB m at the antenna and site-level respectively). Performance was considerably better than that of both path

  14. A model for (non-lognormal) density distributions in isothermal turbulence

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.

    2013-04-01

    We propose a new, physically motivated fitting function for density probability distribution functions (PDFs) in turbulent, ideal gas. Although it is generally known that when gas is isothermal, the PDF is approximately lognormal in the core, high-resolution simulations show large deviations from exact lognormality. The proposed function provides an extraordinarily accurate description of the density PDFs in simulations with Mach numbers ˜0.1-15 and dispersion in log (ρ) from ˜0.01 to 4 dex. Compared to a lognormal or lognormal-skew-kurtosis model, the fits are improved by orders of magnitude in the wings of the distribution (with fewer free parameters). This is true in simulations using a variety of distinct numerical methods, including or excluding magnetic fields. Deviations from lognormality are represented by a parameter T that appears to increase systematically with the compressive Mach number of the simulations. The proposed distribution can be derived from intermittent cascade models of the longitudinal (compressive) velocity differences, which should be directly related to density fluctuations, and we also provide a simple interpretation of the density PDF as the product of a continuous-time relaxation process. As such this parameter T is consistent with the same single parameter needed to explain the (intermittent) velocity structure functions; its behaviour is consistent with turbulence becoming more intermittent as it becomes more dominated by strong shocks. It provides a new and unique probe of the role of intermittency in the density (not just velocity) structure of turbulence. We show that this naturally explains some apparent contradictory results in the literature (for example, in the dispersion-Mach number relation) based on use of different moments of the density PDF, as well as differences based on whether volume-weighted or mass-weighted quantities are measured. We show how these are fundamentally related to the fact that mass conservation

  15. A comparative analysis of the density distributions and the structure models of 9Li

    NASA Astrophysics Data System (ADS)

    Aygun, M.

    2017-03-01

    In the present study, we have analysed the elastic scattering cross-section data of 9Li + 12C system at E lab = 540 MeV and 9Li + 208Pb system at E c.m. = 28.3 MeV for some cluster models and various density distributions of the 9Li nucleus. First, we have obtained five different density distributions of the 9Li nucleus to generate real potentials with the help of double-folding model. For these densities, we have calculated the elastic scattering angular distributions. Secondly, using a simple approach, we have investigated some cluster models of the 9Li nucleus consisting of 6He + 3H and 8Li + n systems. We have presented the comparison of elastic scattering angular distributions for each system with each other as well as with the experimental data. Finally, we have given the cross-section values obtained from the theoretical calculations for all the systems studied in this paper.

  16. Realizing both high energy and high power densities by twisting three carbon-nanotube-based hybrid fibers.

    PubMed

    Zhang, Ye; Zhao, Yang; Cheng, Xunliang; Weng, Wei; Ren, Jing; Fang, Xin; Jiang, Yishu; Chen, Peining; Zhang, Zhitao; Wang, Yonggang; Peng, Huisheng

    2015-09-14

    Energy storage devices, such as lithium-ion batteries and supercapacitors, are required for the modern electronics. However, the intrinsic characteristics of low power densities in batteries and low energy densities in supercapacitors have limited their applications. How to simultaneously realize high energy and power densities in one device remains a challenge. Herein a fiber-shaped hybrid energy-storage device (FESD) formed by twisting three carbon nanotube hybrid fibers demonstrates both high energy and power densities. For the FESD, the energy density (50 mWh cm(-3) or 90 Wh kg(-1) ) many times higher than for other forms of supercapacitors and approximately 3 times that of thin-film batteries; the power density (1 W cm(-3) or 5970 W kg(-1) ) is approximately 140 times of thin-film lithium-ion battery. The FESD is flexible, weaveable and wearable, which offers promising advantages in the modern electronics.

  17. Power spectrum of small-scale density irregularities in the interstellar medium

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.; Rickett, B. J.

    1981-01-01

    Observations of the interstellar scintillation of radiation from 17 pulsars are reported which are used to place limits on the power spectrum of small-scale electron density irregularities in the interstellar medium. Measurements made at 340, 408, and 450 MHz in the dispersion measure range 3-57/cu cm pc of the time-dependent radio frequency spectrum of interstellar scintillations were analyzed to determine the scintillation index and a scintillation frequency-correlation scale based on the autocorrelation function in radio frequency of the fluctuations in scintillation. The dispersion-measure dependence of the scintillation frequency correlation scale is found to be consistent with both Gaussian model interstellar medium spectra and power-law spectra with indices between 3.0 and 4, while the radio-frequency scaling of the frequency correlation scale is consistent with power law indices between 2.8 and 3.9. However comparison of the shape of the radio-frequency autocorrelation function with model calculations indicates power law models with indices greater than 3.6 are possible. Data are also consistent with a local three-dimensional density spectrum at a wave number of 10 to the -9th/m of 3 x 10 to the 28th to 3 x 10 to the 29th/cu m.

  18. High power density dc-to-dc converters for aerospace applications

    NASA Technical Reports Server (NTRS)

    Divan, Deepakraj M.

    1990-01-01

    Three dc-to-dc converter topologies aimed at high-power high-frequency applications are introduced. Major system parasitics, namely, the leakage inductance of the transformer and the device output capacitance are efficiently utilized. Of the three circuits, the single-phase and three-phase versions of the dual active bridge topology demonstrate minimal stresses, better utilization of the transformer, bidirectional, and buck-boost modes of operation. All circuits operate at a constant switching frequency, thus simplifying design of the reactive elements. The power transfer characteristics and soft-switching regions on the Vout-Iout plane are identified. Two coaxial transformers with different cross-sections were built for a rating of 50 kVA. Based on the single-phase dual active bridge topology, a 50 kW, 50 kHz converter operating at an input voltage of 200 Vdc and an output voltage of 1600 Vdc was fabricated. Characteristics of current-fed output make the dual active bridge topologies amenable to paralleling and hence extension to megawatt power levels. Projections to a 1 MW system operating from a 500 Vdc input, at an output voltage of 10 kVdc and a switching frequency of 50 kHz, using MOS-controlled thyristors, coaxially wound transformers operating at three times the present current density with cooling, and multilayer ceramic capacitors, suggests an overall power density of 0.075 to 0.08 kg/kW and an overall efficiency of 96 percent.

  19. Evolution of Automotive Chopper Circuits Towards Ultra High Efficiency and Power Density

    NASA Astrophysics Data System (ADS)

    Pavlovsky, Martin; Tsuruta, Yukinori; Kawamura, Atsuo

    Automotive industry is considered to be one of the main contributors to environmental pollution and global warming. Therefore, many car manufacturers are in near future planning to introduce hybrid electric vehicles (HEV), fuel cell electric vehicles (FCEV) and pure electric vehicles (EV) to make our cars more environmentally friendly. These new vehicles require highly efficient and small power converters. In recent years, considerable improvements were made in designing such converters. In this paper, an approach based on so called Snubber Assisted Zero Voltage and Zero Current Switching topology otherwise also known as SAZZ is presented. This topology has evolved to be one of the leaders in the field of highly efficient converters with high power densities. Evolution and main features of this topology are briefly discussed. Capabilities of the topology are demonstrated on two case study prototypes based on different design approaches. The prototypes are designed to be fully bi-directional for peak power output of 30kW. Both designs reached efficiencies close to 99% in wide load range. Power densities over 40kW/litre are attainable in the same time. Combination of MOSFET technology and SAZZ topology is shown to be very beneficial to converters designed for EV applications.

  20. Limit Distribution Theory for Maximum Likelihood Estimation of a Log-Concave Density.

    PubMed

    Balabdaoui, Fadoua; Rufibach, Kaspar; Wellner, Jon A

    2009-06-01

    We find limiting distributions of the nonparametric maximum likelihood estimator (MLE) of a log-concave density, i.e. a density of the form f(0) = exp varphi(0) where varphi(0) is a concave function on R. Existence, form, characterizations and uniform rates of convergence of the MLE are given by Rufibach (2006) and Dümbgen and Rufibach (2007). The characterization of the log-concave MLE in terms of distribution functions is the same (up to sign) as the characterization of the least squares estimator of a convex density on [0, infinity) as studied by Groeneboom, Jongbloed and Wellner (2001b). We use this connection to show that the limiting distributions of the MLE and its derivative are, under comparable smoothness assumptions, the same (up to sign) as in the convex density estimation problem. In particular, changing the smoothness assumptions of Groeneboom, Jongbloed and Wellner (2001b) slightly by allowing some higher derivatives to vanish at the point of interest, we find that the pointwise limiting distributions depend on the second and third derivatives at 0 of H(k), the "lower invelope" of an integrated Brownian motion process minus a drift term depending on the number of vanishing derivatives of varphi(0) = log f(0) at the point of interest. We also establish the limiting distribution of the resulting estimator of the mode M(f(0)) and establish a new local asymptotic minimax lower bound which shows the optimality of our mode estimator in terms of both rate of convergence and dependence of constants on population values.

  1. The spectral energy distribution of compact jets powered by internal shocks

    NASA Astrophysics Data System (ADS)

    Malzac, Julien

    2014-09-01

    Internal shocks caused by fluctuations of the outflow velocity are likely to power the radio-to-IR emission of the compact jets of X-ray binaries. The dynamics of internal shocks and the resulting spectral energy distribution (SED) of the jet are very sensitive to the time-scales and amplitudes of the velocity fluctuations injected at the base of the jet. I present a new code designed to simulate the synchrotron emission of a compact jet powered by internal shocks. I also develop a semi-analytical formalism allowing one to estimate the observed SED of the jet as a function of the Power Spectral Density (PSD) of the assumed fluctuations of the Lorentz factor. I discuss the cases of a sine modulation of the Lorentz factor and Lorentz factor fluctuations with a power-law PSD shape. Independently of the details of the model, the observed nearly flat SEDs are obtained for PSDs of Lorentz factor fluctuations that are close to a flicker noise spectrum (i.e. P(f ) ∝ 1/f ). The model also presents a strong wavelength-dependent variability that is similar to that observed in these sources.

  2. The place of solar power: an economic analysis of concentrated and distributed solar power

    PubMed Central

    2012-01-01

    Background This paper examines the cost and benefits, both financial and environmental, of two leading forms of solar power generation, grid-tied photovoltaic cells and Dish Stirling Systems, using conventional carbon-based fuel as a benchmark. Methods First we define how these solar technologies will be implemented and why. Then we delineate a model city and its characteristics, which will be used to test the two methods of solar-powered electric distribution. Then we set the constraining assumptions for each technology, which serve as parameters for our calculations. Finally, we calculate the present value of the total cost of conventional energy needed to power our model city and use this as a benchmark when analyzing both solar models’ benefits and costs. Results The preeminent form of distributed electricity generation, grid-tied photovoltaic cells under net-metering, allow individual homeowners a degree of electric self-sufficiency while often turning a profit. However, substantial subsidies are required to make the investment sensible. Meanwhile, large dish Stirling engine installations have a significantly higher potential rate of return, but face a number of pragmatic limitations. Conclusions This paper concludes that both technologies are a sensible investment for consumers, but given that the dish Stirling consumer receives 6.37 dollars per watt while the home photovoltaic system consumer receives between 0.9 and 1.70 dollars per watt, the former appears to be a superior option. Despite the large investment, this paper deduces that it is far more feasible to get few strong investors to develop a solar farm of this magnitude, than to get 150,000 households to install photovoltaic arrays in their roofs. Potential implications of the solar farm construction include an environmental impact given the size of land require for this endeavour. However, the positive aspects, which include a large CO2 emission reduction aggregated over the lifespan of the farm

  3. Space vehicle electrical power processing distribution and control study. Volume 1: Summary

    NASA Technical Reports Server (NTRS)

    Krausz, A.

    1972-01-01

    A concept for the processing, distribution, and control of electric power for manned space vehicles and future aircraft is presented. Emphasis is placed on the requirements of the space station and space shuttle configurations. The systems involved are referred to as the processing distribution and control system (PDCS), electrical power system (EPS), and electric power generation system (EPGS).

  4. Cell density in prostate histopathology images as a measure of tumor distribution

    NASA Astrophysics Data System (ADS)

    Reynolds, Hayley M.; Williams, Scott; Zhang, Alan M.; Ong, Cheng Soon; Rawlinson, David; Chakravorty, Rajib; Mitchell, Catherine; Haworth, Annette

    2014-03-01

    We have developed an automatic technique to measure cell density in high resolution histopathology images of the prostate, allowing for quantification of differences between tumour and benign regions of tissue. Haemotoxylin and Eosin (H&E) stained histopathology slides from five patients were scanned at 20x magnification and annotated by an expert pathologist. Colour deconvolution and a radial symmetry transform were used to detect cell nuclei in the images, which were processed as a set of small tiles and combined to produce global maps of cell density. Kolmogorov-Smirnov tests showed a significant difference in cell density distribution between tumour and benign regions of tissue for all images analyzed (p < 0.05), suggesting that cell density may be a useful feature for segmenting tumour in un-annotated histopathology images. ROC curves quantified the potential utility of cell density measurements in terms of specificity and sensitivity and threshold values were investigated for their classification accuracy. Motivation for this work derives from a larger study in which we aim to correlate ground truth histopathology with in-vivo multiparametric MRI (mpMRI) to validate tumour location and tumour characteristics. Specifically, cell density maps will be registered with T2-weighted MRI and ADC maps from diffusion-weighted MRI. The validated mpMRI data will then be used to parameterise a radiobiological model for designing focal radiotherapy treatment plans for prostate cancer patients.

  5. Wind Power Forecasting Error Distributions over Multiple Timescales: Preprint

    SciTech Connect

    Hodge, B. M.; Milligan, M.

    2011-03-01

    In this paper, we examine the shape of the persistence model error distribution for ten different wind plants in the ERCOT system over multiple timescales. Comparisons are made between the experimental distribution shape and that of the normal distribution.

  6. Macular pigment density and distribution: comparison of fundus autofluorescence with minimum motion photometry.

    PubMed

    Robson, Anthony G; Moreland, Jack D; Pauleikhoff, Daniel; Morrissey, Tony; Holder, Graham E; Fitzke, Fred W; Bird, Alan C; van Kuijk, Frederik J G M

    2003-07-01

    Macular pigment (MP) distribution profiles were measured for 18 subjects using a Moreland anomaloscope modified for motion photometry. The total amount of MP within the central 7 degrees was estimated from the distribution profile by numerical integration. Fundus autofluorescence images were obtained for eight of these subjects using a scanning laser ophthalmoscope. Peak optical density of MP increased with the total amount present, but the correlation was weakened by inter-subject differences in MP distribution. The mean MP distribution derived from mean grey-scale profiles of fundus autofluorescence images correlated closely with that obtained psychophysically (r=0.96). Autofluorescence imaging provides a fast non-invasive method for assessing MP in vivo.

  7. Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

    NASA Astrophysics Data System (ADS)

    Zhuravleva, I.; Churazov, E.; Arévalo, P.; Schekochihin, A. A.; Allen, S. W.; Fabian, A. C.; Forman, W. R.; Sanders, J. S.; Simionescu, A.; Sunyaev, R.; Vikhlinin, A.; Werner, N.

    2015-07-01

    X-ray surface brightness fluctuations in the core of the Perseus Cluster are analysed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 7 to 12 per cent on scales of ˜10-30 kpc within radii of 30-220 kpc from the cluster centre. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90-140 km s-1 on ˜20-30 kpc scales and 70-100 km s-1 on smaller scales ˜7-10 kpc. The velocity power spectrum (PS) is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the PS of the density fluctuations is lower than 7-8 per cent for radii ˜30-220 kpc from the centre, leading to a density bias of less than 3-4 per cent in the cluster core. Uncertainties of the analysis are examined and discussed. Future measurements of the gas velocities with the Astro-H, Athena and Smart-X observatories will directly measure the gas density-velocity perturbation relation and further reduce systematic uncertainties in this analysis.

  8. The distribution of absorptive power dissipation in irradiated nanoparticulate system

    NASA Astrophysics Data System (ADS)

    Li, Jiayu; Yang, Jian; Gu, Xiaobing

    2016-10-01

    The knowledge of local radiant absorption is important to the nanostructure optimization, it is beneficial to the applications in energy harvesting, optical heating, photocatalysis, etc. In this paper, FDTD model is constructed for the distribution of absorptive power dissipation in irradiated nanoparticulate system. The theoretical model extended from Mie theory is used to examine the FDTD model, the parameters and conditions set for FDTD simulation are confirmed based on the comparison. Then, the influence of Ag nanoparticle on the absorptive properties of nearby TiO2 nanoparticle is investigated by FDTD simulation at the wavelength of 0.25 μm. It is indicated that suitable distance between TiO2 and Ag particles is beneficial to the spectral radiant absorption of TiO2 particle. Considering the agglomeration of nanoparticles and the oxidation at the TiO2-Ag interface, the Ag core coated with Al2O3 shell is suggested, and the simulated results indicated that the shell thickness and the Ag core size need to be optimized for enhancing the radiant absorption of TiO2 particle.

  9. Level density and level-spacing distributions of random, self-adjoint, non-Hermitian matrices

    NASA Astrophysics Data System (ADS)

    Joglekar, Yogesh N.; Karr, William A.

    2011-03-01

    We investigate the level density σ(x) and the level-spacing distribution p(s) of random matrices M=AF≠M†, where F is a (diagonal) inner product and A is a random, real, symmetric or complex, Hermitian matrix with independent entries drawn from a probability distribution q(x) with zero mean and finite higher moments. Although not Hermitian, the matrix M is self-adjoint with respect to F and thus has purely real eigenvalues. We find that the level density σF(x) is independent of the underlying distribution q(x) and solely characterized by F, and therefore generalizes the Wigner semicircle distribution σW(x). We find that the level-spacing distributions p(s) are independent of q(x), and are dependent upon both the inner product F and whether A is real or complex, and therefore generalize the Wigner surmise for level spacing. Our results suggest F-dependent generalizations of the well-known Gaussian Orthogonal Ensemble and Gaussian Unitary Ensemble classes.

  10. Distributed solid state programmable thermostat/power controller

    NASA Technical Reports Server (NTRS)

    Alexander, Jane C. (Inventor); Howard, David E. (Inventor); Smith, Dennis A. (Inventor)

    2008-01-01

    A self-contained power controller having a power driver switch, programmable controller, communication port, and environmental parameter measuring device coupled to a controllable device. The self-contained power controller needs only a single voltage source to power discrete devices, analog devices, and the controlled device. The programmable controller has a run mode which, when selected, upon the occurrence of a trigger event changes the state of a power driver switch and wherein the power driver switch is maintained by the programmable controller at the same state until the occurrence of a second event.

  11. Inter-annual and seasonal trends in cetacean distribution, density and abundance off southern California

    NASA Astrophysics Data System (ADS)

    Campbell, Gregory S.; Thomas, Len; Whitaker, Katherine; Douglas, Annie B.; Calambokidis, John; Hildebrand, John A.

    2015-02-01

    Trends in cetacean density and distribution off southern California were assessed through visual line-transect surveys during thirty-seven California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises from July 2004-November 2013. From sightings of the six most commonly encountered cetacean species, seasonal, annual and overall density estimates were calculated. Blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) were the most frequently sighted baleen whales with overall densities of 0.91/1000 km2 (CV=0.27), 2.73/1000 km2 (CV=0.19), and 1.17/1000 km2 (CV=0.21) respectively. Species specific density estimates, stratified by cruise, were analyzed using a generalized additive model to estimate long-term trends and correct for seasonal imbalances. Variances were estimated using a non-parametric bootstrap with one day of effort as the sampling unit. Blue whales were primarily observed during summer and fall while fin and humpback whales were observed year-round with peaks in density during summer and spring respectively. Short-beaked common dolphins (Delphinus delphis), Pacific white-sided dolphins (Lagenorhynchus obliquidens) and Dall's porpoise (Phocoenoidesdalli) were the most frequently encountered small cetaceans with overall densities of 705.83/1000 km2 (CV=0.22), 51.98/1000 km2 (CV=0.27), and 21.37/1000 km2 (CV=0.19) respectively. Seasonally, short-beaked common dolphins were most abundant in winter whereas Pacific white-sided dolphins and Dall's porpoise were most abundant during spring. There were no significant long-term changes in blue whale, fin whale, humpback whale, short-beaked common dolphin or Dall's porpoise densities while Pacific white-sided dolphins exhibited a significant decrease in density across the ten-year study. The results from this study were fundamentally consistent with earlier studies, but provide greater temporal and seasonal resolution.

  12. Interaction of a high-power laser pulse with supercritical-density porous materials

    SciTech Connect

    Gus'kov, Sergei Yu; Rozanov, Vladislav B; Caruso, A; Strangio, C

    2000-03-31

    The properties of a nonequilibrium plasma produced by high-power laser pulses with intensities I{sub L} {approx} 10{sup 14}-10{sup 15} W cm{sup -2} irradiating plane targets made of a porous material are investigated. The mean density of matter in targets was substantially higher than the critical plasma density corresponding to a plasma resonance. The density of porous material was {rho}{sub a} {approx} 1 - 20 mg cm{sup -3}, whereas the critical density at the wavelength of incident radiation was {rho}{sub cr} {approx} 3 mg cm{sup -3}. An anomalously high absorption (no less than 80%) of laser radiation inside a target was observed. Within the first 3 - 4 ns of interaction, the plasma flow through the irradiated target surface in the direction opposite of the direction of the laser beam was noticeably suppressed. Only about 5% of absorbed laser energy was transformed into the energy of particles in this flow during the laser pulse. Absorbed energy was stored as the internal plasma energy at this stage (the greenhouse effect). Then, this energy was transformed, similar to a strong explosion, into the energy of a powerful hydrodynamic flow of matter surrounding the absorption region. The specific features of the formation and evolution of a nonequilibrium laser-produced plasma in porous media are theoretically analysed. This study allows the results of experiments to be explained. In particular, we investigated absorption of laser radiation in the bulk of a target, volume evaporation of porous material, the expansion of a laser-produced plasma inside the pores, stochastic collisions of plasma flows, and hydrothermal energy dissipation. These processes give rise to long-lived oscillations of plasma density and lead to the formation of an internal region where laser radiation is absorbed. (invited paper)

  13. High energy and power density asymmetric supercapacitors using electrospun cobalt oxide nanowire anode

    NASA Astrophysics Data System (ADS)

    Vidyadharan, Baiju; Aziz, Radhiyah Abd; Misnon, Izan Izwan; Anil Kumar, Gopinathan M.; Ismail, Jamil; Yusoff, Mashitah M.; Jose, Rajan

    2014-12-01

    Electrochemical materials are under rigorous search for building advanced energy storage devices. Herein, supercapacitive properties of highly crystalline and ultrathin cobalt oxide (Co3O4) nanowires (diameter ∼30-60 nm) synthesized using an aqueous polymeric solution based electrospinning process are reported. These nanowire electrodes show a specific capacitance (CS) of ∼1110 F g-1 in 6 M KOH at a current density of 1 A g-1 with coulombic efficiency ∼100%. Asymmetric supercapacitors (ASCs) (CS ∼175 F g-1 at 2 A g-1 galvanostatic cycling) are fabricated using the Co3O4 as anode and commercial activated carbon (AC) as cathode and compared their performance with symmetric electrochemical double layer capacitors (EDLCs) fabricated using AC (CS ∼31 F g-1 at 2 A g-1 galvanostatic cycling). The Co3O4//AC ASCs deliver specific energy densities (ES) of 47.6, 35.4, 20 and 8 Wh kg-1 at specific power densities (PS) 1392, 3500, 7000 and 7400 W kg-1, respectively. The performance of ASCs is much superior to the control EDLCs, which deliver ES of 9.2, 8.9, 8.4 and 6.8 Wh kg-1 at PS 358, 695, 1400 and 3500 W kg-1, respectively. The ASCs show nearly six times higher energy density (∼47.6 Wh kg-1) than EDLC (8.4 Wh kg-1) without compromising its power density (∼1400 W kg-1) at similar galvanostatic cycling conditions (2 A g-1).

  14. Using Horizontal Cosmic Muons to Investigate the Density Distribution of the Popocatepetl Volcano Lava Dome

    NASA Astrophysics Data System (ADS)

    Grabski, V.; Lemus, V.; Nuñez-Cadena, R.; Aguilar, S.; Menchaca-Rocha, A.; Fucugauchi, J. U.

    2013-05-01

    Study of volcanic inner density distributions using cosmic muons is an innovative method, which is still in stage of development[1]. The method can be used to determine the average density along the muon track, as well as the density distribution of any volume by measuring the attenuation of cosmic muon flux in it[2]. In this study we present an analysis of using the muon radiography, integrating geophysical data to determine the density distribution of the Popocatepetl volcano. Popocatepelt is a large andesitic stratovolcano built in the Trans-Mexican volcanic arc, which has been active over the past years. The recent activity includes emplacement of a lava dome, with vulcanian explosions and frequent scoria and ash emissions. The study is directed to detect any variations in the dome and magmatic conduit system in some interval of time in the volume of Popocatepetl volcano lava dome. The study forms part of a long-term project of volcanic hazard monitoring that includes the Popocatepetl and Colima volcanoes[3]. The volcanoes are being studied by conventional geophysical techniques, including aerogeophysical surveys directed to determine the internal structure and characterize source characteristics and mechanism. The detector design mostly depends on the volume size to be investigated as well as the image-taking frequency to detect dynamic density variations. In this study we present a detector prototype design and suggestions on data taking, transferring and analyzing systems. We also present the approximate cost estimation of the suggested detector and discussion on a proposal about the creation of a national network for a volcanic alarm system. References [1] eg.H. Tanaka, et al., Nucl. Instr. and Meth. A 507 (2003) 657. [2] V. Grabski et al, NIM A 585 (2008) 128-135. [3] G. Conte, J. Urrutia-Fucugauchi, et al., International Geology Review, Vol. 46, 2004, p. 210-225.

  15. Application of reconstructive tomography to the measurement of density distribution in two-phase flow

    SciTech Connect

    Fincke, J.R.; Berggren, M.J.; Johnson, S.A.

    1980-01-01

    The technique of reconstructive tomography has been applied to the measurement of average density and density distribution in multiphase flows. The technique of reconstructive tomography provides a model independent method of obtaining flow field density information. The unique features of interest in application of a practical tomographic densitometer system are the limited number of data values and the correspondingly coarse reconstruction grid (0.5 by 0.5 cm). These features were studied both experimentally, through the use of prototype hardware on a 3-in. pipe, and analytically, through computer generation of simulated data. Prototypical data were taken on phantoms constructed of Plexiglas and laminated Plexiglas, wood, and polyurethane foam. Reconstructions obtained from prototype data were compared with reconstructions from the simulated data.

  16. The effects of pure density evolution on the brightness distribution of cosmological gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Horack, J. M.; Emslie, A. G.; Hartmann, D. H.

    1995-01-01

    In this work, we explore the effects of burst rate density evolution on the observed brightness distribution of cosmological gamma-ray bursts. Although the brightness distribution of gamma-ray bursts observed by the BATSE experiment has been shown to be consistent with a nonevolving source population observed to redshifts of order unity, evolution of some form is likely to be present in the gamma-ray bursts. Additionally, nonevolving models place significant constraints on the range of observed burst luminosities, which are relaxed if evolution of the burst population is present. In this paper, three analytic forms of density evolution are examined. In general, forms of evolution with densities that increase monotonically with redshift require that the BATSE data correspond to bursts at larger redshifts, or to incorporate a wider range of burst luminosities, or both. Independent estimates of the maximum observed redshift in the BATSE data and/or the range of luminosity from which a large fraction of the observed bursts are drawn therefore allow for constraints to be placed on the amount of evolution that may be present in the burst population. Specifically, if recent measurements obtained from analysis of the BATSE duration distribution of the actual limiting redshift in the BATSE data at z(sub lim) = 2 are correct, the BATSE N(P) distribution in a Lambda = 0 universe is inconsistent at a level of approximately 3 alpha with nonevolving gamma-ray bursts and some form of evolution in the population is required. The sense of this required source evolution is to provide a higher density, larger luminosities, or both with increasing redshift.

  17. Bimodal Density Distribution of Cryptodome Dacite from the 1980 Eruption of Mount St. Helens, Washington

    USGS Publications Warehouse

    Hoblitt, R.P.; Harmon, R.S.

    1993-01-01

    The explosion of a cryptodome at Mount St. Helens in 1980 produced two juvenile rock types that are derived from the same source magma. Their differences-color, texture and density-are due only to vesicularity differences. The vesicular gray dacite comprises bout 72% of the juvenile material; the black dacite comprises the other 28%. The density of juvenile dacite is bimodally distributed, with peaks at 1.6 g cm-3 (gray dacite) and 2.3 g cm-3 (black dacite). Water contents, deuterium abundances, and the relationship of petrographic structures to vapor-phase crystals indicate both rock types underwent pre-explosion subsurface vesiculation and degassing. The gray dacite underwent a second vesiculation event, probably during the 18 May explosion. In the subsurface, gases probably escaped through interconnected vesicles into the permeable volcanic edifice. We suggest that nonuniform degassing of an initially homogeneous magma produced volatile gradients in the cryptodome and that these gradients were responsible for the density bimodality. That is, water contents less than about 0.2-0.4 wt% produced vesicle growth rates that were slow in comparison to the pyroclast cooling rates; greater water contents produced vesicle growth rates that were fast in comparison to cooling rates. In this scheme, the dacite densities are bimodally distributed simply because, following decompression on 18 May 1980, one clast population vesiculated while the other did not. For clasts that did vesiculate, vesicle growth continued until it was arrested by fragmentation. ?? 1993 Springer-Verlag.

  18. Marine litter distribution and density in European seas, from the shelves to deep basins.

    PubMed

    Pham, Christopher K; Ramirez-Llodra, Eva; Alt, Claudia H S; Amaro, Teresa; Bergmann, Melanie; Canals, Miquel; Company, Joan B; Davies, Jaime; Duineveld, Gerard; Galgani, François; Howell, Kerry L; Huvenne, Veerle A I; Isidro, Eduardo; Jones, Daniel O B; Lastras, Galderic; Morato, Telmo; Gomes-Pereira, José Nuno; Purser, Autun; Stewart, Heather; Tojeira, Inês; Tubau, Xavier; Van Rooij, David; Tyler, Paul A

    2014-01-01

    Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets) was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments.

  19. Marine Litter Distribution and Density in European Seas, from the Shelves to Deep Basins

    PubMed Central

    Pham, Christopher K.; Ramirez-Llodra, Eva; Alt, Claudia H. S.; Amaro, Teresa; Bergmann, Melanie; Canals, Miquel; Company, Joan B.; Davies, Jaime; Duineveld, Gerard; Galgani, François; Howell, Kerry L.; Huvenne, Veerle A. I.; Isidro, Eduardo; Jones, Daniel O. B.; Lastras, Galderic; Morato, Telmo; Gomes-Pereira, José Nuno; Purser, Autun; Stewart, Heather; Tojeira, Inês; Tubau, Xavier; Van Rooij, David; Tyler, Paul A.

    2014-01-01

    Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets) was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments. PMID:24788771

  20. THE STELLAR NUMBER DENSITY DISTRIBUTION IN THE LOCAL SOLAR NEIGHBORHOOD IS NORTH-SOUTH ASYMMETRIC

    SciTech Connect

    Yanny, Brian; Gardner, Susan

    2013-10-17

    We study the number density distribution of a sample of K and M dwarf stars, matched North and South of the Galactic plane within a distance of 2 kpc from the sun, using observations from the Ninth Data Release of the Sloan Digital Sky Survey. We determine distances using the photometric parallax method, and in this context systematic effects exist which could potentially impact the determination of the number density profile with height from the Galactic plane --- and ultimately affect a number density North-South asymmetry. They include: (i) the calibration of the various photometric parallax relations, (ii) the ability to separate dwarfs from giants in our sample, (iii) the role of stellar population differences such as age and metallicity, (iv) the ability to determine the offset of the sun from the Galactic plane, and (v) the correction for reddening from dust in the Galactic plane, though our stars are at high Galactic latitudes. We find the various analyzed systematic effects to have a negligible impact on our observed asymmetry, and using a new and larger sample of stars we confirm and refine the earlier discovery of Widrow et al. of a significant Galactic North-South asymmetry in the stellar number density distribution.

  1. Density and distribution of cattle lice (Phthiraptera:Haematopinidae, Linognathidae, Trichodectidae) on six steers.

    PubMed

    Watson, D W; Lloyd, J E; Kumar, R

    1997-05-01

    The density and distribution of four species of cattle louse, Bovicola bovis (L.). Haematopinus eurysternus (Nitzsch), Linognathus vituli (L.), and Solenopotes capillatus (Enderlein), were elucidated from the hides of six slaughtered steers. Adult and nymphal lice were first removed from one hide by hand and the location of each specimen mapped. The remaining lice were removed by a detergent wash, and KOH dissolution of hide and hair. Lice from the remaining five hides were removed using KOH dissolution of cattle hair and subsequent filtration of the effluent. Bovicola bovis was most abundant, followed by H. eurysternus, L. vituli and S. capillatus. Significant variation was observed in B. bovis, H. eurysternus and L. vituli population densities. Solenopotes capillatus population densities did not differ significantly. All species were contagiously distributed, i.e. 'clumped', suggesting species dependent predilection sites. Predilection sites were ranked according to louse density to facilitate the development of field sampling strategies. Additional biological data were gathered on sex and life stage ratios for each species.

  2. THE STELLAR NUMBER DENSITY DISTRIBUTION IN THE LOCAL SOLAR NEIGHBORHOOD IS NORTH-SOUTH ASYMMETRIC

    SciTech Connect

    Yanny, Brian; Gardner, Susan

    2013-11-10

    We study the number density distribution of a sample of K and M dwarf stars, matched north and south of the Galactic plane within a distance of 2 kpc from the Sun, using observations from the Ninth Data Release of the Sloan Digital Sky Survey. We determine distances using the photometric parallax method, and in this context systematic effects exist which could potentially impact the determination of the number density profile with height from the Galactic plane—and ultimately affect a number density north-south asymmetry. They include: (1) the calibration of the various photometric parallax relations, (2) the ability to separate dwarfs from giants in our sample, (3) the role of stellar population differences such as age and metallicity, (4) the ability to determine the offset of the Sun from the Galactic plane, and (5) the correction for reddening from dust in the Galactic plane, though our stars are at high Galactic latitudes. We find the various analyzed systematic effects to have a negligible impact on our observed asymmetry, and using a new and larger sample of stars we confirm and refine the earlier discovery of Widrow et al. of a significant Galactic north-south asymmetry in the stellar number density distribution.

  3. Timing A Pulsed Thin Film Pyroelectric Generator For Maximum Power Density

    NASA Astrophysics Data System (ADS)

    Smith, A. N.; Hanrahan, B. M.; Neville, C. J.; Jankowski, N. R.

    2016-11-01

    Pyroelectric thermal-to-electric energy conversion is accomplished by a cyclic process of thermally-inducing polarization changes in the material under an applied electric field. The pyroelectric MEMS device investigated consisted of a thin film PZT capacitor with platinum bottom and iridium oxide top electrodes. Electric fields between 1-20 kV/cm with a 30% duty cycle and frequencies from 0.1 - 100 Hz were tested with a modulated continuous wave IR laser with a duty cycle of 20% creating temperature swings from 0.15 - 26 °C on the pyroelectric receiver. The net output power of the device was highly sensitive to the phase delay between the laser power and the applied electric field. A thermal model was developed to predict and explain the power loss associated with finite charge and discharge times. Excellent agreement was achieved between the theoretical model and the experiment results for the measured power density versus phase delay. Limitations on the charging and discharging rates result in reduced power and lower efficiency due to a reduced net work per cycle.

  4. Fabrication Flaw Density and Distribution In Repairs to Reactor Pressure Vessel and Piping Welds

    SciTech Connect

    GJ Schuster, FA Simonen, SR Doctor

    2008-04-01

    The Pacific Northwest National Laboratory is developing a generalized fabrication flaw distribution for the population of nuclear reactor pressure vessels and for piping welds in U.S. operating reactors. The purpose of the generalized flaw distribution is to predict component-specific flaw densities. The estimates of fabrication flaws are intended for use in fracture mechanics structural integrity assessments. Structural integrity assessments, such as estimating the frequency of loss-of-coolant accidents, are performed by computer codes that require, as input, accurate estimates of flaw densities. Welds from four different reactor pressure vessels and a collection of archived pipes have been studied to develop empirical estimates of fabrication flaw densities. This report describes the fabrication flaw distribution and characterization in the repair weld metal of vessels and piping. This work indicates that large flaws occur in these repairs. These results show that repair flaws are complex in composition and sometimes include cracks on the ends of the repair cavities. Parametric analysis using an exponential fit is performed on the data. The relevance of construction records is established for describing fabrication processes and product forms. An analysis of these records shows there was a significant change in repair frequency over the years when these components were fabricated. A description of repair flaw morphology is provided with a discussion of fracture mechanics significance. Fabrication flaws in repairs are characterized using optimized-access, high-sensitivity nondestructive ultrasonic testing. Flaw characterizations are then validated by other nondestructive evaluation techniques and complemented by destructive testing.

  5. Scalp and Source Power Topography in Sleepwalking and Sleep Terrors: A High-Density EEG Study

    PubMed Central

    Castelnovo, Anna; Riedner, Brady A.; Smith, Richard F.; Tononi, Giulio; Boly, Melanie; Benca, Ruth M.

    2016-01-01

    Study Objectives: To examine scalp and source power topography in sleep arousals disorders (SADs) using high-density EEG (hdEEG). Methods: Fifteen adult subjects with sleep arousal disorders (SADs) and 15 age- and gender-matched good sleeping healthy controls were recorded in a sleep laboratory setting using a 256 channel EEG system. Results: Scalp EEG analysis of all night NREM sleep revealed a localized decrease in slow wave activity (SWA) power (1–4 Hz) over centro-parietal regions relative to the rest of the brain in SADs compared to good sleeping healthy controls. Source modelling analysis of 5-minute segments taken from N3 during the first half of the night revealed that the local decrease in SWA power was prominent at the level of the cingulate, motor, and sensori-motor associative cortices. Similar patterns were also evident during REM sleep and wake. These differences in local sleep were present in the absence of any detectable clinical or electrophysiological sign of arousal. Conclusions: Overall, results suggest the presence of local sleep differences in the brain of SADs patients during nights without clinical episodes. The persistence of similar topographical changes in local EEG power during REM sleep and wakefulness points to trait-like functional changes that cross the boundaries of NREM sleep. The regions identified by source imaging are consistent with the current neurophysiological understanding of SADs as a disorder caused by local arousals in motor and cingulate cortices. Persistent localized changes in neuronal excitability may predispose affected subjects to clinical episodes. Citation: Castelnovo A, Riedner BA, Smith RF, Tononi G, Boly M, Benca RM. Scalp and source power topography in sleepwalking and sleep terrors: a high-density EEG study. SLEEP 2016;39(10):1815–1825. PMID:27568805

  6. High power density microbial fuel cell with flexible 3D graphene-nickel foam as anode.

    PubMed

    Wang, Hanyu; Wang, Gongming; Ling, Yichuan; Qian, Fang; Song, Yang; Lu, Xihong; Chen, Shaowei; Tong, Yexiang; Li, Yat

    2013-11-07

    The structure and electrical conductivity of anode play a significant role in the power generation of microbial fuel cells (MFCs). In this study, we developed a three-dimensional (3D) reduced graphene oxide-nickel (denoted as rGO-Ni) foam as an anode for MFC through controlled deposition of rGO sheets onto the nickel foam substrate. The loading amount of rGO sheets and electrode surface area can be controlled by the number of rGO loading cycles. 3D rGO-Ni foam anode provides not only a large accessible surface area for microbial colonization and electron mediators, but also a uniform macro-porous scaffold for effective mass diffusion of the culture medium. Significantly, at a steady state of the power generation, the MFC device with flexible rGO-Ni electrodes produced an optimal volumetric power density of 661 W m(-3) calculated based on the volume of anode material, or 27 W m(-3) based on the volume of the anode chamber. These values are substantially higher than that of plain nickel foam, and other conventional carbon based electrodes (e.g., carbon cloth, carbon felt, and carbon paper) measured in the same conditions. To our knowledge, this is the highest volumetric power density reported for mL-scale MFC device with a pure strain of Shewanella oneidensis MR-1. We also demonstrated that the MFC device can be operated effectively in a batch-mode at least for a week. These new 3D rGO-Ni electrodes show great promise for improving the power generation of MFC devices.

  7. Iron-based cathode catalyst with enhanced power density in polymer electrolyte membrane fuel cells.

    PubMed

    Proietti, Eric; Jaouen, Frédéric; Lefèvre, Michel; Larouche, Nicholas; Tian, Juan; Herranz, Juan; Dodelet, Jean-Pol

    2011-08-02

    H(2)-air polymer-electrolyte-membrane fuel cells are electrochemical power generators with potential vehicle propulsion applications. To help reduce their cost and encourage widespread use, research has focused on replacing the expensive Pt-based electrocatalysts in polymer-electrolyte-membrane fuel cells with a lower-cost alternative. Fe-based cathode catalysts are promising contenders, but their power density has been low compared with Pt-based cathodes, largely due to poor mass-transport properties. Here we report an iron-acetate/phenanthroline/zeolitic-imidazolate-framework-derived electrocatalyst with increased volumetric activity and enhanced mass-transport properties. The zeolitic-imidazolate-framework serves as a microporous host for phenanthroline and ferrous acetate to form a catalyst precursor that is subsequently heat treated. A cathode made with the best electrocatalyst from this work, tested in H(2)-O(2,) has a power density of 0.75 W cm(-2) at 0.6 V, a meaningful voltage for polymer-electrolyte-membrane fuel cells operation, comparable with that of a commercial Pt-based cathode tested under identical conditions.

  8. The Role of Distributed Generation and Combined Heat and Power (CHP) Systems in Data Centers

    EPA Pesticide Factsheets

    This report reviews how distributed generation (DG) resources such as fuel cells, reciprocating engines, and gas turbines can offer powerful energy efficiency savings in data centers, particularly when configured in combined heat and power (CHP) mode.

  9. An Electrochemical Capacitor with Applicable Energy Density of 7.4 Wh/kg at Average Power Density of 3000 W/kg.

    PubMed

    Zhai, Teng; Lu, Xihong; Wang, Hanyu; Wang, Gongming; Mathis, Tyler; Liu, Tianyu; Li, Cheng; Tong, Yexiang; Li, Yat

    2015-05-13

    Electrochemical capacitors represent a new class of charge storage devices that can simultaneously achieve high energy density and high power density. Previous reports have been primarily focused on the development of high performance capacitor electrodes. Although these electrodes have achieved excellent specific capacitance based on per unit mass of active materials, the gravimetric energy densities calculated based on the weight of entire capacitor device were fairly small. This is mainly due to the large mass ratio between current collector and active material. We aimed to address this issue by a 2-fold approach of minimizing the mass of current collector and increasing the electrode performance. Here we report an electrochemical capacitor using 3D graphene hollow structure as current collector, vanadium sulfide and manganese oxide as anode and cathode materials, respectively. 3D graphene hollow structure provides a lightweight and highly conductive scaffold for deposition of pseudocapacitive materials. The device achieves an excellent active material ratio of 24%. Significantly, it delivers a remarkable energy density of 7.4 Wh/kg (based on the weight of entire device) at the average power density of 3000 W/kg. This is the highest gravimetric energy density reported for asymmetric electrochemical capacitors at such a high power density.

  10. Investigation of the delay time distribution of high power microwave surface flashover

    SciTech Connect

    Foster, J.; Krompholz, H.; Neuber, A.

    2011-01-15

    Characterizing and modeling the statistics associated with the initiation of gas breakdown has proven to be difficult due to a variety of rather unexplored phenomena involved. Experimental conditions for high power microwave window breakdown for pressures on the order of 100 to several 100 torr are complex: there are little to no naturally occurring free electrons in the breakdown region. The initial electron generation rate, from an external source, for example, is time dependent and so is the charge carrier amplification in the increasing radio frequency (RF) field amplitude with a rise time of 50 ns, which can be on the same order as the breakdown delay time. The probability of reaching a critical electron density within a given time period is composed of the statistical waiting time for the appearance of initiating electrons in the high-field region and the build-up of an avalanche with an inherent statistical distribution of the electron number. High power microwave breakdown and its delay time is of critical importance, since it limits the transmission through necessary windows, especially for high power, high altitude, low pressure applications. The delay time distribution of pulsed high power microwave surface flashover has been examined for nitrogen and argon as test gases for pressures ranging from 60 to 400 torr, with and without external UV illumination. A model has been developed for predicting the discharge delay time for these conditions. The results provide indications that field induced electron generation, other than standard field emission, plays a dominant role, which might be valid for other gas discharge types as well.

  11. Investigation of the delay time distribution of high power microwave surface flashover

    NASA Astrophysics Data System (ADS)

    Foster, J.; Krompholz, H.; Neuber, A.

    2011-01-01

    Characterizing and modeling the statistics associated with the initiation of gas breakdown has proven to be difficult due to a variety of rather unexplored phenomena involved. Experimental conditions for high power microwave window breakdown for pressures on the order of 100 to several 100 torr are complex: there are little to no naturally occurring free electrons in the breakdown region. The initial electron generation rate, from an external source, for example, is time dependent and so is the charge carrier amplification in the increasing radio frequency (RF) field amplitude with a rise time of 50 ns, which can be on the same order as the breakdown delay time. The probability of reaching a critical electron density within a given time period is composed of the statistical waiting time for the appearance of initiating electrons in the high-field region and the build-up of an avalanche with an inherent statistical distribution of the electron number. High power microwave breakdown and its delay time is of critical importance, since it limits the transmission through necessary windows, especially for high power, high altitude, low pressure applications. The delay time distribution of pulsed high power microwave surface flashover has been examined for nitrogen and argon as test gases for pressures ranging from 60 to 400 torr, with and without external UV illumination. A model has been developed for predicting the discharge delay time for these conditions. The results provide indications that field induced electron generation, other than standard field emission, plays a dominant role, which might be valid for other gas discharge types as well.

  12. A method for evaluating the expectation value of a power spectrum using the probability density function of phases

    SciTech Connect

    Caliandro, G.A.; Torres, D.F.; Rea, N. E-mail: dtorres@aliga.ieec.uab.es

    2013-07-01

    Here, we present a new method to evaluate the expectation value of the power spectrum of a time series. A statistical approach is adopted to define the method. After its demonstration, it is validated showing that it leads to the known properties of the power spectrum when the time series contains a periodic signal. The approach is also validated in general with numerical simulations. The method puts into evidence the importance that is played by the probability density function of the phases associated to each time stamp for a given frequency, and how this distribution can be perturbed by the uncertainties of the parameters in the pulsar ephemeris. We applied this method to solve the power spectrum in the case the first derivative of the pulsar frequency is unknown and not negligible. We also undertook the study of the most general case of a blind search, in which both the frequency and its first derivative are uncertain. We found the analytical solutions of the above cases invoking the sum of Fresnel's integrals squared.

  13. Spatial distribution of limited resources and local density regulation in juvenile Atlantic salmon.

    PubMed

    Finstad, Anders G; Einum, Sigurd; Ugedal, Ola; Forseth, Torbjørn

    2009-01-01

    1. Spatial heterogeneity of resources may influence competition among individuals and thus have a fundamental role in shaping population dynamics and carrying capacity. In the present study, we identify shelter opportunities as a limiting resource for juvenile Atlantic salmon (Salmo salar L.). Experimental and field studies are combined in order to demonstrate how the spatial distribution of shelters may influence population dynamics on both within and among population scales. 2. In closed experimental streams, fish performance scaled negatively with decreasing shelter availability and increasing densities. In contrast, the fish in open stream channels dispersed according to shelter availability and performance of fish remaining in the streams did not depend on initial density or shelters. 3. The field study confirmed that spatial variation in densities of 1-year-old juveniles was governed both by initial recruit density and shelter availability. Strength of density-dependent population regulation, measured as carrying capacity, increased with decreasing number of shelters. 4. Nine rivers were surveyed for spatial variation in shelter availability and increased shelter heterogeneity tended to decrease maximum observed population size (measured using catch statistics of adult salmon as a proxy). 5. Our studies highlight the importance of small-scale within-population spatial structure in population dynamics and demonstrate that not only the absolute amount of limiting resources but also their spatial arrangement can be an important factor influencing population carrying capacity.

  14. Dynamics and density distributions in a capillary-discharge waveguide with an embedded supersonic jet

    SciTech Connect

    Matlis, N. H. Gonsalves, A. J.; Steinke, S.; Tilborg, J. van; Shaw, B.; Mittelberger, D. E.; Geddes, C. G. R.; Matlis, E. H.; Leemans, W. P.

    2015-11-28

    We present an analysis of the gas dynamics and density distributions within a capillary-discharge waveguide with an embedded supersonic jet. This device provides a target for a laser plasma accelerator which uses longitudinal structuring of the gas-density profile to enable control of electron trapping and acceleration. The functionality of the device depends sensitively on the details of the density profile, which are determined by the interaction between the pulsed gas in the jet and the continuously-flowing gas in the capillary. These dynamics are captured by spatially resolving recombination light from several emission lines of the plasma as a function of the delay between the jet and the discharge. We provide a phenomenological description of the gas dynamics as well as a quantitative evaluation of the density evolution. In particular, we show that the pressure difference between the jet and the capillary defines three regimes of operation with qualitatively different longitudinal density profiles and show that jet timing provides a sensitive method for tuning between these regimes.

  15. Distribution and density of moose in relation to landscape characteristics: Effects of scale

    USGS Publications Warehouse

    Maier, J.A.K.; Ver Hoef, J.M.; McGuire, A.D.; Bowyer, R.T.; Saperstein, L.; Maier, H.A.

    2005-01-01

    We analyzed the relation between early winter distribution and density of female moose (Alces alces L.) and habitat heterogeneity in interior Alaska. We tested for effects of vegetation type, topography, distance to rivers and towns, occurrence and timing of fire, and landscape metrics. A spatial linear model was used to analyze effects of independent variables organized at multiple scales. Because densities of moose vary widely as a result of differences in management and other factors, a spatial response surface of the log of moose density was fit to remove large-scale effects. The analysis revealed that the densest populations of moose occurred closer to towns, at moderate elevations, near rivers, and in areas where fire occurred between 11 and 30 years ago. Furthermore, moose tended to occur in areas with large compact patches of varied habitat and avoided variable terrain and nonvegetated areas. Relationships of most variables with moose density occurred at or below 34 km2, suggesting that moose respond to environmental variables within a few kilometres of their location. The spatial model of density of moose developed in this study represents an important application for effective monitoring and management of moose in the boreal forest. ?? 2005 NRC.

  16. Power distribution in complex environmental negotiations: Does balance matter?

    USGS Publications Warehouse

    Burkardt, N.; Lamb, B.L.; Taylor, J.G.

    1997-01-01

    We studied six interagency negotiations covering Federal Energy Regulatory Commission (FERC) hydroelectric power licenses. Negotiations occurred between state and federal resource agencies and developers over project operations and natural resource mitigation. We postulated that a balance of power among parties was necessary for successful negotiations. We found a complex relationship between balanced power and success and conclude that a balance of power was associated with success in these negotiations. Power played a dynamic role in the bargaining and illuminates important considerations for regulatory design.

  17. Status of 20 kHz space station power distribution technology

    NASA Technical Reports Server (NTRS)

    Hansen, Irving G.

    1988-01-01

    Power Distribution on the NASA Space Station will be accomplished by a 20 kHz sinusoidal, 440 VRMS, single phase system. In order to minimize both system complexity and the total power coversion steps required, high frequency power will be distributed end-to-end in the system. To support the final design of flight power system hardware, advanced development and demonstrations have been made on key system technologies and components. The current status of this program is discussed.

  18. Curve Fitting of the Corporate Recovery Rates: The Comparison of Beta Distribution Estimation and Kernel Density Estimation

    PubMed Central

    Chen, Rongda; Wang, Ze

    2013-01-01

    Recovery rate is essential to the estimation of the portfolio’s loss and economic capital. Neglecting the randomness of the distribution of recovery rate may underestimate the risk. The study introduces two kinds of models of distribution, Beta distribution estimation and kernel density distribution estimation, to simulate the distribution of recovery rates of corporate loans and bonds. As is known, models based on Beta distribution are common in daily usage, such as CreditMetrics by J.P. Morgan, Portfolio Manager by KMV and Losscalc by Moody’s. However, it has a fatal defect that it can’t fit the bimodal or multimodal distributions such as recovery rates of corporate loans and bonds as Moody’s new data show. In order to overcome this flaw, the kernel density estimation is introduced and we compare the simulation results by histogram, Beta distribution estimation and kernel density estimation to reach the conclusion that the Gaussian kernel density distribution really better imitates the distribution of the bimodal or multimodal data samples of corporate loans and bonds. Finally, a Chi-square test of the Gaussian kernel density estimation proves that it can fit the curve of recovery rates of loans and bonds. So using the kernel density distribution to precisely delineate the bimodal recovery rates of bonds is optimal in credit risk management. PMID:23874558

  19. Curve fitting of the corporate recovery rates: the comparison of Beta distribution estimation and kernel density estimation.

    PubMed

    Chen, Rongda; Wang, Ze

    2013-01-01

    Recovery rate is essential to the estimation of the portfolio's loss and economic capital. Neglecting the randomness of the distribution of recovery rate may underestimate the risk. The study introduces two kinds of models of distribution, Beta distribution estimation and kernel density distribution estimation, to simulate the distribution of recovery rates of corporate loans and bonds. As is known, models based on Beta distribution are common in daily usage, such as CreditMetrics by J.P. Morgan, Portfolio Manager by KMV and Losscalc by Moody's. However, it has a fatal defect that it can't fit the bimodal or multimodal distributions such as recovery rates of corporate loans and bonds as Moody's new data show. In order to overcome this flaw, the kernel density estimation is introduced and we compare the simulation results by histogram, Beta distribution estimation and kernel density estimation to reach the conclusion that the Gaussian kernel density distribution really better imitates the distribution of the bimodal or multimodal data samples of corporate loans and bonds. Finally, a Chi-square test of the Gaussian kernel density estimation proves that it can fit the curve of recovery rates of loans and bonds. So using the kernel density distribution to precisely delineate the bimodal recovery rates of bonds is optimal in credit risk management.

  20. Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

    SciTech Connect

    Zhuravleva, I.; Churazov, E.; Arevalo, P.; Schekochihin, A. A.; Allen, S. W.; Fabian, A. C.; Forman, W. R.; Sanders, J. S.; Simionescu, A.; Sunyaev, R.; Vikhlinin, A.; Werner, N.

    2015-05-20

    X-ray surface brightness fluctuations in the core of the Perseus Cluster are analysed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 7 to 12 per cent on scales of ~10–30 kpc within radii of 30–220 kpc from the cluster centre. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90–140 km s-1 on ~20–30 kpc scales and 70–100 km s-1 on smaller scales ~7–10 kpc. The velocity power spectrum (PS) is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the PS of the density fluctuations is lower than 7–8 per cent for radii ~30–220 kpc from the centre, leading to a density bias of less than 3–4 per cent in the cluster core. Uncertainties of the analysis are examined and discussed. Future measurements of the gas velocities with the Astro-H, Athena and Smart-X observatories will directly measure the gas density–velocity perturbation relation and further reduce systematic uncertainties in this analysis.