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Sample records for nonuniform current distribution

  1. A poloidal non-uniformity of the collisionless parallel current in a tokamak plasma

    Energy Technology Data Exchange (ETDEWEB)

    Romannikov, A.; Fenzi-Bonizec, C

    2005-07-01

    The collisionless distortion of the ion (electron) distribution function at certain points on a magnetic surface is studied in the framework of a simple model of a large aspect ratio tokamak plasma. The flow velocity driven by this distortion is calculated. The possibility of an additional non-uniform collisionless parallel current density on a magnetic surface, other than the known neo-classical non-uniformity is shown. The difference between the parallel current density on the low and high field side of a magnetic surface is close to the neoclassical bootstrap current density. The first Tore-Supra experimental test indicates the possibility of the poloidal non-uniformity of the parallel current density. (authors)

  2. Mechanical Effects of the Non-Uniform Current Distribution on HTS Coils for Accelerators Wound with REBCO Roebel Cable

    CERN Document Server

    Murtomaeki, Jaako; Kirby, Glen; Rossi, Lucio; Ruuskanen, Janne; Stenvall, Antti; Murtomaeki, Jaako

    2017-01-01

    Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 WP10 Future Magnets collaboration is aiming at testing HTS-based Roebel cables in an accelerator magnet. The demonstrator should produce around 17 T, when inserted into the 100 mm aperture of Feather-M2 13 T outsert magnet. HTS Roebel cables are assembled from meander shaped REBCO coated conductor tapes. In comparison with fair level of uniformity of current distribution in cables made out of round Nb-Ti or Nb$_{3}$Sn strands, current distribution within the coils wound from Roebel cables is highly non-homogeneous. It results in nonuniform electromagnetic force distribution over the cable that could damage the very thin REBCO superconducting layer. This paper focuses on the numerical models to describe the effect of the non-homogenous current distribution on stress distribution in the demonstrator magnet designed for the EuCARD-2 project. Preliminary results indicate that the impregnation bonding betweenthe...

  3. Non-uniform current distribution in a force-cooled superconductor under changing magnetic field

    International Nuclear Information System (INIS)

    Koizumi, Norikiyo

    2000-02-01

    Strands in a large current force-cooled superconductor, referred to a CICC (cable-in-conduit conductor) hereafter, are coated with formvar (insulated layer) or chrome plating (high resistive layer) to reduce coupling current loss due to magnetic field variation. The author first carried out an experiment of the large superconducting coil consisting of such CICCs for demonstration of their applicability to a large superconducting coil. These CICCs exhibited instability, i.e. the normal zone propagation with thermal runaway (quench), at 1/20 and 1/5 of the expected conductor critical currents, respectively. The author constructed the database of this instability and studies its reason through experimental and theoretical investigations and then finds such instability is caused as a result of non-uniform current distribution in the conductor. Joule heating loss at electrical connections at the ends of the conductor should be small. Therefore, the strands in the CICC are electrically connected from each other with low resistance there. Circulation current is induced in the loop composed of the strands electrically connected at the ends of the conductor if its leakage magnetic flux is not completely vanished. The non-uniform current distribution is caused as a result of superimposition of the circulation and transport currents. The strand carrying large current becomes the normal state when it reaches or approaches to its critical current. Thus, the strands are twisted in order to vanish the leakage magnetic flux. The instability due to the current imbalance was not observed in the middle-scale coil (an element coil, such as a single double-pancake, of a large superconducting coil) consisting of the conductor in which the formvar-coated strands were twisted as above-mentioned. Consequently, it was believed that the leakage magnetic flux could be vanished by the normal twisting. However, the magnetic field increases in a large coil as a result of piling element coils

  4. The Consequence of Self-field and Non-uniform Current Distribution on Short Sample Tests of Superconducting Cables

    CERN Document Server

    Verweij, A P

    1998-01-01

    Electrical measurements on samples of superconducting cables are usually performed in order to determine the critical current $I_c$ and the n-value, assuming that the voltage U at the transition from the superconducting to the normal state follows the power law, U\\sim($I/I_c$)$^n$. An accurate measurement of $I_c$ and n demands, first of all, good control of temperature and field, and precise measurement of current and voltage. The critical current and n-value of a cable are influenced by the self-field of the cable, an effect that has to be known in order to compare the electrical characteristics of the cable with those of the strands from which it is made. The effect of the self-field is dealt with taking into account the orientation and magnitude of the applied field and the n-value of the strands. An important source of inaccuracy is related to the distribution of the currents among the strands. Non-uniform distributions, mainly caused by non-equal resistances of the connections between the strands of the...

  5. Analysis of the Elastic Large Deflection Behavior for Metal Plates under Nonuniformly Distributed Lateral Pressure with In-Plane Loads

    Directory of Open Access Journals (Sweden)

    Jeom Kee Paik

    2012-01-01

    Full Text Available The Galerkin method is applied to analyze the elastic large deflection behavior of metal plates subject to a combination of in-plane loads such as biaxial loads, edge shear and biaxial inplane bending moments, and uniformly or nonuniformly distributed lateral pressure loads. The motive of the present study was initiated by the fact that metal plates of ships and ship-shaped offshore structures at sea are often subjected to non-uniformly distributed lateral pressure loads arising from cargo or water pressure, together with inplane axial loads or inplane bending moments, but the current practice of the maritime industry usually applies some simplified design methods assuming that the non-uniform pressure distribution in the plates can be replaced by an equivalence of uniform pressure distribution. Applied examples are presented, demonstrating that the current plate design methods of the maritime industry may be inappropriate when the non-uniformity of lateral pressure loads becomes more significant.

  6. Effect of non-uniform current distribution on the stability in Nb-Ti cable-in-conduit superconducting conductor

    International Nuclear Information System (INIS)

    Wadayama, Y.; Koizumi, N.; Takahashi, Y.; Matsui, K.; Tsuji, H.; Shimamoto, S.

    1996-01-01

    30kA-NbTi Demo Poloidal Coil (DPC-U) exhibited instability such as the conductor quenches at 40% of the rated current which is still much smaller than the expected conductor critical current. It was found that this instability was caused by the non-uniform current distribution in the DPC-U conductor whose strands were insulated from each other. To investigate the instability of the DPC-U conductor, a stability experiment of a subsize conductor consisting of 27 strands was performed and the effect of the current imbalance on the stability was investigated. The current imbalance was forcibly established in the conductor using two current sources in this experiment. The experimental results indicate that the stability margin decreases as the current imbalance becomes larger and that the stability margin of the conductor is governed by the stability of the strand with the highest current in the conductor. Also, it is confirmed from the experimental results that the instability of DPC-U has to be attributed to the current imbalance in the conductor

  7. Measurement of fuel importance distribution in non-uniformly distributed fuel systems

    International Nuclear Information System (INIS)

    Yamane, Yoshihiro; Hirano, Yasushi; Yasui, Hazime; Izima, Kazunori; Shiroya, Seiji; Kobayashi, Keiji.

    1995-01-01

    A reactivity effect due to a spatial variation of nuclear fuel concentration is an important problem for nuclear criticality safety in a reprocessing plant. As a theory estimating this reactivity effect, the Goertzel and fuel importance theories are well known. It has been shown that the Goertzel's theory is valid in the range of our experiments based on measurements of reactivity effect and thermal neutron flux in non-uniformly distributed fuel systems. On the other hand, there have been no reports concerning systematic experimental studies on the flatness of fuel importance which is a more general index than the Goertzel's theory. It is derived from the perturbation theory that the fuel importance is proportional to the reactivity change resulting from a change of small amount of fuel mass. Using a uniform and three kinds of nonuniform fuel systems consisting of 93.2% enriched uranium plates and polyethylene plates, the fuel importance distributions were measured. As a result, it was found experimentally that the fuel importance distribution became flat, as its reactivity effect became large. Therefore it was concluded that the flatness of fuel importance distribution is the useful index for estimating reactivity effect of non-uniformly distributed fuel system. (author)

  8. Current Density Distribution on the Perimeter of Waveguide Exciter Cylindrical Vibrator Conductor

    OpenAIRE

    Zakharia, Yosyp

    2010-01-01

    On ground of electrodynamic analysis the surface current distribution nonuniformity on the perimeter of waveguide-exciter cylindrical conductor is found. Considerable influence of current distribution nonuniformity on exciter input reactance is established. It is also showed, that the current distribution on the vibrator perimeter, for conductor radius no greater then 0,07 of waveguide cross section breadth, approximately uniform is.

  9. Investigation of Non-Uniform Rust Distribution and Its Effects on Corrosion Induced Cracking in Reinforced Concrete

    Directory of Open Access Journals (Sweden)

    Sutrisno Wahyuniarsih

    2017-01-01

    Full Text Available Uniform corrosion still widely used by a lot of researchers and engineers to analyze the corrosion induced cracking. However, in practice, corrosion process occurred non-uniformly. The part nearest to the exposed surface is more likely to have faster corrosion initiation compared with other regions. This research is mainly focused on investigating the effect of non-uniform rust distribution to cover cracking in reinforced concrete. An experimental test performed using accelerated corrosion test by using 5% NaCl solution and applied a constant electric current to the concrete samples. The rust distribution and measurement were observed by using a digital microscope. Based on the experimental result, it was found that the rust was distributed in a non-uniform pattern. As a result, the cracks also formed non-uniformly along the perimeter of steel bar. At the last part of this paper, a simulation result of concrete cracking induced by non-uniform corrosion is presented. The result compared with a simulation using uniform corrosion assumption to investigate the damage pattern of each model. The simulation result reveals stress evolution due to rust expansion which leads to concrete cracking. Furthermore, a comparison of stresses induced by non-uniform corrosion and uniform corrosion indicates that non-uniform corrosion could lead to earlier damage to the structure which is specified by the formation and propagation of the crack.

  10. Radio-frequency properties of stacked long Josephson junctions with nonuniform bias current distribution

    DEFF Research Database (Denmark)

    Filatrella, G; Pedersen, Niels Falsig

    1999-01-01

    We have numerically investigated the behavior of stacks of long Josephson junctions considering a nonuniform bias profile. In the presence of a microwave field the nonuniform bias, which favors the formation of fluxons, can give rise to a change of the sequence of radio-frequency induced steps...

  11. Emittance growth caused by nonuniform charge distribution of bunched beam in linac

    International Nuclear Information System (INIS)

    Chen Yinbao; Zhang Zhenhai

    1993-09-01

    The nonlinear space charge effect of bunched beam in linac is one of the important reasons that induces the emittance growth because of the conversion of the field energy to kinetic energy. The authors have worked out the internal field energies associated with some nonuniform space change distributions of a bunched beam, such as Gaussian distribution, waterbag distribution and parabolic distribution. And the emittance growths caused by these nonuniformities are obtained

  12. Estimation of current density distribution under electrodes for external defibrillation

    Directory of Open Access Journals (Sweden)

    Papazov Sava P

    2002-12-01

    Full Text Available Abstract Background Transthoracic defibrillation is the most common life-saving technique for the restoration of the heart rhythm of cardiac arrest victims. The procedure requires adequate application of large electrodes on the patient chest, to ensure low-resistance electrical contact. The current density distribution under the electrodes is non-uniform, leading to muscle contraction and pain, or risks of burning. The recent introduction of automatic external defibrillators and even wearable defibrillators, presents new demanding requirements for the structure of electrodes. Method and Results Using the pseudo-elliptic differential equation of Laplace type with appropriate boundary conditions and applying finite element method modeling, electrodes of various shapes and structure were studied. The non-uniformity of the current density distribution was shown to be moderately improved by adding a low resistivity layer between the metal and tissue and by a ring around the electrode perimeter. The inclusion of openings in long-term wearable electrodes additionally disturbs the current density profile. However, a number of small-size perforations may result in acceptable current density distribution. Conclusion The current density distribution non-uniformity of circular electrodes is about 30% less than that of square-shaped electrodes. The use of an interface layer of intermediate resistivity, comparable to that of the underlying tissues, and a high-resistivity perimeter ring, can further improve the distribution. The inclusion of skin aeration openings disturbs the current paths, but an appropriate selection of number and size provides a reasonable compromise.

  13. Modeling of parallel-plate regenerators with non-uniform plate distributions

    DEFF Research Database (Denmark)

    Jensen, Jesper Buch; Engelbrecht, Kurt; Bahl, Christian Robert Haffenden

    2010-01-01

    plate spacing distributions are presented in order to understand the impact of spacing non-uniformity. Simulations of more realistic distributions where the plate spacings follow normal distributions are then discussed in order to describe the deviation of the performance of a regenerator relative...

  14. Measurement of reactivity effect caused by nonuniform fuel distribution

    International Nuclear Information System (INIS)

    Yamane, Yoshihiro; Hirano, Yasushi; Yasui, Hazime; Nishina, Kojiro; Shiroya, Seiji

    1991-01-01

    A reactivity effect due to a spatial variation of nuclear fuel concentration is an important problem in a reprocessing plant. To estimate this reactivity effect theoretically, the ''Goertzel's necessary condition, and th Fuel Importance'' theory have been proposed. In order to verify these theories, we have performed systematic measurements of reactivity effect due to the nonuniformity in the fuel distribution within the Kyoto University Critical Assembly. Neutron flux distribution and Fuel Importance distribution were also determined. A nonuniform assembly whose fuel concentration in the center region was 40% higher than the uniform one was found to have an excess reactivity of 0.3%Δk/k, with the same total uranium mass for which the uniform assembly was just critical. Moreover, its spatial distribution of thermal neutron flux and of Fuel Importance were more flat than those of the uniform assembly, as expected by the Goertzel's condition and the Fuel Importance theory. (Author)

  15. Impact of uniform electrode current distribution on ETF

    Science.gov (United States)

    Bents, D. J.

    1982-01-01

    The design impacts on the ETF electrode consolidation network associated with uniform channel electrode current distribution are examined and the alternate consolidation design which occur are presented compared to the baseline (non-uniform current) design with respect to performance, and hardware requirements. A rational basis is given for comparing the requirements for the different designs and the savings that result from uniform current distribution. Performance and cost impacts upon the combined cycle plant are discussed.

  16. Impact of uniform electrode current distribution on ETF. [Engineering Test Facility MHD generator

    Science.gov (United States)

    Bents, D. J.

    1982-01-01

    A basic reason for the complexity and sheer volume of electrode consolidation hardware in the MHD ETF Powertrain system is the channel electrode current distribution, which is non-uniform. If the channel design is altered to provide uniform electrode current distribution, the amount of hardware required decreases considerably, but at the possible expense of degraded channel performance. This paper explains the design impacts on the ETF electrode consolidation network associated with uniform channel electrode current distribution, and presents the alternate consolidation designs which occur. They are compared to the baseline (non-uniform current) design with respect to performance, and hardware requirements. A rational basis is presented for comparing the requirements for the different designs and the savings that result from uniform current distribution. Performance and cost impacts upon the combined cycle plant are discussed.

  17. Light extraction in planar light-emitting diode with nonuniform current injection: model and simulation.

    Science.gov (United States)

    Khmyrova, Irina; Watanabe, Norikazu; Kholopova, Julia; Kovalchuk, Anatoly; Shapoval, Sergei

    2014-07-20

    We develop an analytical and numerical model for performing simulation of light extraction through the planar output interface of the light-emitting diodes (LEDs) with nonuniform current injection. Spatial nonuniformity of injected current is a peculiar feature of the LEDs in which top metal electrode is patterned as a mesh in order to enhance the output power of light extracted through the top surface. Basic features of the model are the bi-plane computation domain, related to other areas of numerical grid (NG) cells in these two planes, representation of light-generating layer by an ensemble of point light sources, numerical "collection" of light photons from the area limited by acceptance circle and adjustment of NG-cell areas in the computation procedure by the angle-tuned aperture function. The developed model and procedure are used to simulate spatial distributions of the output optical power as well as the total output power at different mesh pitches. The proposed model and simulation strategy can be very efficient in evaluation of the output optical performance of LEDs with periodical or symmetrical configuration of the electrodes.

  18. Modeling of a Pouch Lithium Ion Battery Using a Distributed Parameter Equivalent Circuit for Internal Non-Uniformity Analysis

    Directory of Open Access Journals (Sweden)

    Dafen Chen

    2016-10-01

    Full Text Available A battery model that has the capability of analyzing the internal non-uniformity of local state variables, including the state of charge (SOC, temperature and current density, is proposed in this paper. The model is built using a set of distributed parameter equivalent circuits. In order to validate the accuracy of the model, a customized battery with embedded T-type thermocouple sensors inside the battery is tested. The simulated temperature conforms well with the measured temperature at each test point, and the maximum difference is less than 1 °C. Then, the model is applied to analyze the evolution processes of local state variables’ distribution inside the battery during the discharge process. The simulation results demonstrate drastic distribution changes of the local state variables inside the battery during the discharge process. The internal non-uniformity is originally caused by the resistance of positive and negative foils, while also influenced by the change rate of open circuit voltage and the total resistance of the battery. Hence, the factors that affect the distribution of the local state variables are addressed.

  19. Transient current distributions in porous zinc electrodes in KOH electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Liu, M.B.; Yamazaki, Y.; Cook, G.M.; Yao, N.P.

    1981-02-01

    A zero-resistance ammeter circuit with a 10-channel operational amplifier was used to measure the current distribution during a discharge of 10 to 100 mA with simulated zinc porous electrodes in 7.24 M KOH saturated with ZnO. The reaction distribution was found to be highly nonuniform, with 70 to 78% of the charge transfer reaction completed in a depth of 0.01 cm. The high nonuniformity of the initial reaction profile was believed to be due to low conductivity of the electrolyte in the electrode pores. The current distribution changes during passivation of the electrode were experimentally obtained. A mathematical model based upon a macroscope averaging technique was used to predict the time dependence of charge transfer reaction profiles. With mathematical model, current distributions and overpotentials were predicted as a function of time for the segmented zinc electrode discharged at a current of 10 to 100 mA; for these predictions, assumed values of both precipitation rate constants for porous ZnO and diffusion coefficients for hydroxide and zincate ions were used. A gradual decrease in the specific conductivity of the pore electrolyte to 20% of the initial value during discharge yields predictions of current distributions and overpotentials in good agreement with the experimental data. The extent of reduction in the specific conductivity of the pore electrolyte implies a supersaturation of zincate of four times chemical saturation, which was been observed experimentally.At high discharge current (25 to 100 mA), the passivation behavior of the electrode has been simulated. The results of the experiments and mathematical model show that the effective reaction penetration depth is less than 0.02 cm.

  20. Analysis of effect on microdose of 10B nonuniform distribution in cellular

    International Nuclear Information System (INIS)

    Xie Qin; Geng Changran; Tang Xiaobin; Chen Da

    2012-01-01

    Boron neutron capture therapy (BNCT) is one of the effective way to treat malignant melanoma and head-neck cancer. The intercellular nonuniform distributions of 10 B in tumor cell impact the estimates of inactivation dose. The α-Li Version l.0 code was developed based on Monte-Carlo method to calculate the S values of cell induced by α and 7 Li particle which are the products of 10 B (n,a) 7 Li. The calculation included two types of cell size, eight kinds of energy of a particle and three kinds of source distributions. Differences between results of this code and an analytical algorithm of MIRD committee were within 1%. On this basis, a total of 3420 cases were calculated and analyzed with different kinds of nucleus radius, cell radius, and source launch position combination. Finally, cellular S values of 10 B (n,a) 7 Li calculated in this paper can be used to compute the excellent precision dose under 10 B compound nonuniform distribution in intercellular scale. (authors)

  1. A two-dimensional finite element model of front surface current flow in cells under non-uniform, concentrated illumination

    Energy Technology Data Exchange (ETDEWEB)

    Mellor, A.; Domenech-Garret, J.L.; Chemisana, D.; Rosell, J.I. [Departament de Medi Ambient i C.S., University of Lleida, Av. Alcalde Rovira Roure 191, E25198 (Spain)

    2009-09-15

    A two-dimensional finite element model of current flow in the front surface of a PV cell is presented. In order to validate this model we perform an experimental test. Later, particular attention is paid to the effects of non-uniform illumination in the finger direction which is typical in a linear concentrator system. Fill factor, open circuit voltage and efficiency are shown to decrease with increasing degree of non-uniform illumination. It is shown that these detrimental effects can be mitigated significantly by reoptimization of the number of front surface metallization fingers to suit the degree of non-uniformity. The behavior of current flow in the front surface of a cell operating at open circuit voltage under non-uniform illumination is discussed in detail. (author)

  2. Modelling non-uniform strain distributions in aerospace composites using fibre Bragg gratings

    NARCIS (Netherlands)

    Rajabzadehdizaji, Aydin; Groves, R.M.; Hendriks, R.C.; Heusdens, R.; Chung, Y.; Jin, W.; Lee, B.; Canning, J.; Nakamura, K.; Yuan, L.

    2017-01-01

    In this paper the behaviour of fibre Bragg grating (FBG) sensors under non-uniform strain distributions was analysed. Using the fundamental matrix approach, the length of the FBG sensor was discretised, with each segment undergoing different strain values. FBG sensors that are embedded inside

  3. The influence of nonuniform micro-distribution of alpha emitter on microdosimetry in cells

    International Nuclear Information System (INIS)

    Tian Yuan; Zhang Liang'an; Dai Guangfu

    2007-01-01

    Objective: To study the influence of nonuniform micro-distribution of alpha emitter on cellular S values(in the radioimmunotherapy). Methods: Emission of alpha particles is randomly simulated by Monte Carlo method; the incident energy and exit energy are calculated with interpolation technique based on the relationship between range and energy of alpha particle and the analytical Continuous Slowing Down Approximation (CSDA) model. So energy deposited in the target area can be obtained. To take 213 Po as an example, cellular S values with various cell dimensions and possible micro-distributions of radioactivity are calculated, such as linear increase, linear decrease, exponential increase and exponential decrease. Results: S values from cell to cell of uniform distribution showed no difference with the Hamacher's results. S values of different micro-distributions are distinguishing with each other. It is indicated that different micro-distributions of radioactivity will result in significant change of average chord length of alpha particles traveling in the target area, as well as the change of average stopping power over the chord, which is primary reason for differences of S values. Conclusions: The nonuniform micro-distributions show remarkable influence on cellular S values and hence should be taken consideration in cellular absorbed dose estimation, especially in microdosimetry. (authors)

  4. Tumour control probability (TCP) for non-uniform activity distribution in radionuclide therapy

    International Nuclear Information System (INIS)

    Uusijaervi, Helena; Bernhardt, Peter; Forssell-Aronsson, Eva

    2008-01-01

    Non-uniform radionuclide distribution in tumours will lead to a non-uniform absorbed dose. The aim of this study was to investigate how tumour control probability (TCP) depends on the radionuclide distribution in the tumour, both macroscopically and at the subcellular level. The absorbed dose in the cell nuclei of tumours was calculated for 90 Y, 177 Lu, 103m Rh and 211 At. The radionuclides were uniformly distributed within the subcellular compartment and they were uniformly, normally or log-normally distributed among the cells in the tumour. When all cells contain the same amount of activity, the cumulated activities required for TCP = 0.99 (A-tilde TCP=0.99 ) were 1.5-2 and 2-3 times higher when the activity was distributed on the cell membrane compared to in the cell nucleus for 103m Rh and 211 At, respectively. TCP for 90 Y was not affected by different radionuclide distributions, whereas for 177 Lu, it was slightly affected when the radionuclide was in the nucleus. TCP for 103m Rh and 211 At were affected by different radionuclide distributions to a great extent when the radionuclides were in the cell nucleus and to lesser extents when the radionuclides were distributed on the cell membrane or in the cytoplasm. When the activity was distributed in the nucleus, A-tilde TCP=0.99 increased when the activity distribution became more heterogeneous for 103m Rh and 211 At, and the increase was large when the activity was normally distributed compared to log-normally distributed. When the activity was distributed on the cell membrane, A-tilde TCP=0.99 was not affected for 103m Rh and 211 At when the activity distribution became more heterogeneous. A-tilde TCP=0.99 for 90 Y and 177 Lu were not affected by different activity distributions, neither macroscopic nor subcellular

  5. On the burnout in annular channels at non-uniform heat release distribution in length

    International Nuclear Information System (INIS)

    Ornatskij, A.P.; Chernobaj, V.A.; Vasil'ev, A.F.; Struts, G.V.

    1982-01-01

    The effect of axial heat release non-uniformity on the conditions of the burnout in annular channels is investigated. The investigation is carried out in annular channels with different laws of heat flux density distribution by channel length. The heat release non-uniformity coefficient was varied from 4.4 to 10, the pressure from 9.8 to 17.6 MPa, mass rate from 500 to 1700 kg (m 2 xS), liquid temperature (chemically desalted water) at the channel inlet constituted 30-300 deg C. The experiments have been performed at the test bench with a closed circulation circuit. The data obtained testify to the fact that under non-uniform heat release the influence of main operating parameters on the value of critical power is of the same character as under uniform heat release. The character of wall temperature variation by channel length before the burnout is determined by the form of heat supply temperature profile. The temperature maximum is observed in the region lying behind the cross section with maximum heat flux. The conclusion is drawn that the dominant influence on the position of the cross section in which the burnout arises is exerted by the form of heat flux density distribution by length. Independently of this distribution form the burnout developes when the vapour content near the wall reaches a limiting value

  6. γ-irradiation effect on the electrical properties on n-Ge with nonuniform distribution of impurity

    International Nuclear Information System (INIS)

    Antonenko, R.S.; Shakhovtsov, V.I.; Shakhovtsova, S.I.

    1975-01-01

    There has been experimentally investigated the effect of γ-irradiation on the electrical properties of germanium alloyed with antimony, when the alloying element is non-uniformly distributed. It is shown that in response to γ-irradiation the mobility of the current carriers is reduced, whereas the temperature dependence is changed. At the radiation doses providing for a high degree of compensation the temperature dependence of the current carrier mobility changes abnormaly the volt-ampere characteristics of the samples within the 'non-heating' electric field range are linear up to the radiation doses corresponding to the conductivity conversion. The experimental results are discussed from the point of view of the conceptions pertaining to current-carrying ability of a heterogeneous material. There has been drawn up a conclusion that the degree of compensation substantially affects the electrical properties of a semiconductor

  7. The Influence of nonuniform activity distribution on cellular dosimetry

    International Nuclear Information System (INIS)

    Naling, Song; Yuan, Tian; Liangan, Zhang; Guangfu, Dai

    2008-01-01

    S value is an important parameter in determination of absorbed dose in nuclear medicine and radiobiology. The distribution of radioactivity shows significant influence on the S value especially in microdosimetry. In present work, a semi Monte Carlo Model is developed to calculate the microdosimetric cellular S value for different micro-distributions of radioactivity, i.e. uniform, linear increase, linear decrease, exponential increase, exponential decrease and centroid distribution. Emission of alpha particles is simulated by Monte Carlo model and the energy imparted to the target volume is calculated by the analytical Continuous Slowing Down Approximation (CSDA) model and the spline interpolation of range-energy relationship. We calculate tables of S values for 213 Po and 210 Po with various dimensions and most important with various possible micro-distributions of radioactivity, such as linear increase, linear decrease, exponential increase and exponential decrease. Then we compare the S values from cell to cell of uniform distribution with the Hamacher's results to test the feasibility of our model. S values of some nonuniform micro-distributions are compared to the corresponding data of the uniform distribution. The possible sources of these differences are theoretical analyzed. (author)

  8. Distributed ISAR Subimage Fusion of Nonuniform Rotating Target Based on Matching Fourier Transform.

    Science.gov (United States)

    Li, Yuanyuan; Fu, Yaowen; Zhang, Wenpeng

    2018-06-04

    In real applications, the image quality of the conventional monostatic Inverse Synthetic Aperture Radar (ISAR) for the maneuvering target is subject to the strong fluctuation of Radar Cross Section (RCS), as the target aspect varies enormously. Meanwhile, the maneuvering target introduces nonuniform rotation after translation motion compensation which degrades the imaging performance of the conventional Fourier Transform (FT)-based method in the cross-range dimension. In this paper, a method which combines the distributed ISAR technique and the Matching Fourier Transform (MFT) is proposed to overcome these problems. Firstly, according to the characteristics of the distributed ISAR, the multiple channel echoes of the nonuniform rotation target from different observation angles can be acquired. Then, by applying the MFT to the echo of each channel, the defocused problem of nonuniform rotation target which is inevitable by using the FT-based imaging method can be avoided. Finally, after preprocessing, scaling and rotation of all subimages, the noncoherent fusion image containing all the RCS information in all channels can be obtained. The accumulation coefficients of all subimages are calculated adaptively according to the their image qualities. Simulation and experimental data are used to validate the effectiveness of the proposed approach, and fusion image with improved recognizability can be obtained. Therefore, by using the distributed ISAR technique and MFT, subimages of high-maneuvering target from different observation angles can be obtained. Meanwhile, by employing the adaptive subimage fusion method, the RCS fluctuation can be alleviated and more recognizable final image can be obtained.

  9. Current distribution in parallel paths of the coils of a 50 Hz prototype dipole magnet

    International Nuclear Information System (INIS)

    Otter, A.J.

    1995-06-01

    The prototype dipole made for TRIUMF's Kaon Factory proposal used coils with 12 parallel paths to reduce eddy current losses in the conductors. The ac current distribution in these paths was non-uniform due to different self and mutual inductances. Small differences in inductance can cause large circulating currents in the parallel windings. This paper describes the measurement of the inductances and shows an attempt to predict the current distribution for two alternative connection schemes. (author). 4 refs., 8 figs

  10. Nonuniform distribution of gas-liquid system in gas-distributing collector

    Energy Technology Data Exchange (ETDEWEB)

    Kasimov, R.Sh.; Abdullayev, E.A.; Eyubov, A.A.; Khudobakhshiyev, M.R.

    1979-01-01

    In the example of studying GS-1 of the field Shatlyk, the effect of nonuniform distribution of the liquid phase is examined (hydrocarbon condensate, water) on production lines of the unit of low temperature separation on the process of field preparation of gas. In particular, the unequal efficiency of single-type equipment operating under comparable conditions is noted: differences in the magnitude of under recuperation of coal of the recuperation heat exchangers, in the values of the integrated effect of Joule-Thomson, the coefficients of removal of low-temperature separators, etc. A consequence of this situation is deterioration in the quality of gas fed to the main pipe line. It is suggested that efforts be concentrated on developing technical designs which guarantee uniform supply of liquid from the field collector to the production lines of the unit for low temperature separation.

  11. Current-induced nonuniform enhancement of sheet resistance in A r+ -irradiated SrTi O3

    Science.gov (United States)

    Roy, Debangsu; Frenkel, Yiftach; Davidovitch, Sagi; Persky, Eylon; Haham, Noam; Gabay, Marc; Kalisky, Beena; Klein, Lior

    2017-06-01

    The sheet resistance Rs of A r+ irradiated SrTi O3 in patterns with a length scale of several microns increases significantly below ˜40 K in connection with driving currents exceeding a certain threshold. The initial lower Rs is recovered upon warming with accelerated recovery around 70 and 160 K. Scanning superconducting quantum interference device microscopy shows local irreversible changes in the spatial distribution of the current with a length scale of several microns. We attribute the observed nonuniform enhancement of Rs to the attraction of the charged single-oxygen and dioxygen vacancies by the crystallographic domain boundaries in SrTi O3 . The boundaries, which are nearly ferroelectric below 40 K, are polarized by the local electrical field associated with the driven current and the clustered vacancies which suppress conductivity in their vicinity and yield a noticeable enhancement in the device resistance when the current path width is on the order of the boundary extension. The temperatures of accelerated conductivity recovery are associated with the energy barriers for the diffusion of the two types of vacancies.

  12. Computer Simulation of Nonuniform MTLs via Implicit Wendroff and State-Variable Methods

    Directory of Open Access Journals (Sweden)

    L. Brancik

    2011-04-01

    Full Text Available The paper deals with techniques for a computer simulation of nonuniform multiconductor transmission lines (MTLs based on the implicit Wendroff and the statevariable methods. The techniques fall into a class of finitedifference time-domain (FDTD methods useful to solve various electromagnetic systems. Their basic variants are extended and modified to enable solving both voltage and current distributions along nonuniform MTL’s wires and their sensitivities with respect to lumped and distributed parameters. An experimental error analysis is performed based on the Thomson cable whose analytical solutions are known, and some examples of simulation of both uniform and nonuniform MTLs are presented. Based on the Matlab language programme, CPU times are analyzed to compare efficiency of the methods. Some results for nonlinear MTLs simulation are presented as well.

  13. The importance of non-uniform dose-distribution in an organ

    International Nuclear Information System (INIS)

    Richmond, C.R.

    1975-01-01

    The recent revival of interest in the 'hot particle' problem, especially as regards particulate plutonium and other actinide elements in the lung, stimulated the preparation of this paper. Non-uniformity of dose-distribution has been of concern to standards-setting bodies and other groups such as the National Academy of Sciences and to health protectionists for many years. This paper reviews data from animal experiments that are used by some to implicate particulate plutonium as being especially hazardous to man. Other relevant biological data are also discussed. (author)

  14. Generation of zonal magnetic fields by drift waves in a current carrying nonuniform magnetoplasma

    International Nuclear Information System (INIS)

    Shukla, Nitin; Shukla, P.K.

    2010-01-01

    It is shown that zonal magnetic fields (ZMFs) can be nonlinearly excited by incoherent drift waves (DWs) in a current carrying nonuniform magnetoplasma. The dynamics of incoherent DWs in the presence of ZMFs is governed by a wave-kinetic equation. The governing equation for ZMFs in the presence of nonlinear advection force of the DWs is obtained from the parallel component of the electron momentum equation and the Faraday law. Standard techniques are used to derive a nonlinear dispersion relation, which depicts instability via which ZMFs are excited in plasmas. ZMFs may inhibit the turbulent cross-field particle and energy transport in a nonuniform magnetoplasma.

  15. Fluxon dynamics in long Josephson junctions in the presence of a temperature gradient or spatial nonuniformity

    DEFF Research Database (Denmark)

    Krasnov, V.M.; Oboznov, V.A.; Pedersen, Niels Falsig

    1997-01-01

    Fluxon dynamics in nonuniform Josephson junctions was studied both experimentally and theoretically. Two types of nonuniform junctions were considered: the first type had a nonuniform spatial distribution of critical and bias currents and the second had a temperature gradient applied along...... the junction. An analytical expression for the I-V curve in the presence of a temperature gradient or spatial nonuniformity was derived. It was shown that there is no static thermomagnetic Nernst effect due to Josephson fluxon motion despite the existence of a force pushing fluxons in the direction of smaller...

  16. Critical current of the nonuniform Josephson transition at intergranular boundary with random dislocation distribution

    International Nuclear Information System (INIS)

    Mejlikhov, E.Z.; Farzetdinova, R.M.

    1997-01-01

    Critical current of inhomogeneous intergranular Josephson transition is calculated in the assumption concerning superconductivity suppression by local strains of boundary dislocations with random distribution

  17. Experimental results of current distribution in Rutherford-type LHC cables

    CERN Document Server

    Verweij, A P

    2000-01-01

    Current distribution among the wires of multi-strand superconducting cables is an important item for accelerator magnets. A non-uniform distribution could cause additional field distortions in the magnet bore and can as well be one of the reasons of premature quenching. Since two years electrical measurements on superconducting Rutherford-type cables are performed at CERN as part of the reception tests for the Large Hadron Collider (LHC). Cable samples of 2.4 m length are tested at currents up to 32 kA, temperatures around 1.9 and 4.3 K, and fields up to 10 T, applied perpendicularly as well as parallel to the broad face of the cable. Last year, an array of 24 Hall probes was installed in the test set-up in order to measure the self-field of the cable samples along one cable pitch. Each of the probes measures the local field generated by the current in the strands close by, and the results of the all probes reflect therefore the distribution of the strand currents. Experiments are done varying the applied fie...

  18. Reactivity effect of non-uniformly distributed fuel in fuel solution systems

    International Nuclear Information System (INIS)

    Hirano, Yasushi; Yamane, Yoshihiro; Nishina, Kojiro; Mitsuhashi, Ishi.

    1991-01-01

    A numerical method to determine the optimal fuel distribution for minimum critical mass, or maximum k-effective, is developed using the Maximum Principle in order to evaluate the maximum effect of non-uniformly distributed fuel on reactivity. This algorithm maximizes the Hamiltonian directly by an iterative method under a certain constraint-the maintenance of criticality or total fuel mass. It ultimately reaches the same optimal state of a flattened fuel importance distribution as another algorithm by Dam based on perturbation theory. This method was applied to two kinds of spherical cores with water reflector in the simulating reprocessing facility. In the slightly-enriched uranyl nitrate solution core, the minimum critical mass decreased by less than 1% at the optimal moderation state. In the plutonium nitrate solution core, the k-effective increment amounted up to 4.3% Δk within the range of present study. (author)

  19. A comparison on the heat load of HTS current leads with respect to uniform and non-uniform cross-sectional areas

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seung Hak; Nam, Seok Ho; Lee, Je Yull; Song, Seung Hyun; Jeon, Hae Ryong; Baek, Geon Woo; Ko, Tae Kuk [Yonsei University, Seoul (Korea, Republic of); Kang, Hyoung Ku [Korea National University of Transportation, Chungju (Korea, Republic of)

    2017-09-15

    Current lead is a device that connects the power supply and superconducting magnets. High temperature superconductor (HTS) has lower thermal conductivity and higher current density than normal metal. For these reasons, the heat load can be reduced by replacing the normal metal of the current lead with the HTS. Conventional HTS current lead has same cross-sectional area in the axial direction. However, this is over-designed at the cold-end (4.2 K) in terms of current. The heat load can be reduced by reducing this part because the heat load is proportional to the cross-sectional area. Therefore, in this paper, heat load was calculated from the heat diffusion equation of HTS current leads with uniform and non-uniform cross-sectional areas. The cross-sectional area of the warm-end (65K) is designed considering burnout time when cooling system failure occurs. In cold-end, Joule heat and heat load due to current conduction occurs at the same time, so the cross-sectional area where the sum of the two heat is minimum is obtained. As a result of simulation, current leads for KSTAR TF coils with uniform and non-uniform cross-sectional areas were designed, and it was confirmed that the non-uniform cross-sectional areas could further reduce the heat load.

  20. Modeling radar backscattering from melting snowflakes using spheroids with nonuniform distribution of water

    International Nuclear Information System (INIS)

    Tyynelä, Jani; Leinonen, Jussi; Moisseev, Dmitri; Nousiainen, Timo; Lerber, Annakaisa von

    2014-01-01

    In a number of studies it is reported that at the early stages, melting of aggregate snowflakes is enhanced at lower parts. In this paper, the manifestation of the resulting nonuniform distribution of water is studied for radar backscattering cross sections at C, Ku, Ka and W bands. The melting particles are described as spheroids with a mixture of water and air at the bottom part of the particle and a mixture of ice and air at the upper part. The radar backscattering is modeled using the discrete-dipole approximation in a horizontally pointing geometry. The results are compared to the T-matrix method, Mie theory, and the Rayleigh approximation using the Maxwell Garnett mixing formula. We find that the differential reflectivity and the linear depolarization ratio show systematic differences between the discrete-dipole approximation and the T-matrix method, but that the differences are relatively small. The horizontal cross sections show only small differences between the methods with the aspect ratio and the presence of resonance peaks having a larger effect on it than the nonuniform distribution of water. Overall, the effect of anisotropic distribution of water, reported for early stages of melting, is not significant for radar observations at the studied frequencies. -- Highlights: • We model backscattering from spheroidal melting snowflakes at C, Ku, Ka, and W bands. • We study the effect of anisotropic distribution of meltwater in the snow particles. • We find systematic, but relatively small differences for the backscattering properties. • We find that the aspect ratio and resonance peaks have a bigger effect than anisotropic distribution of water. • Anisotropic distribution of water is not significant for radar observations at early stages of melting

  1. Hydrodynamic characteristics of steady magnetic fluid flow in a straight tube by taking into account the non-uniform distribution of mass concentration

    International Nuclear Information System (INIS)

    Shuchi, S.; Shimada, K.; Kamiyama, S.; Yamaguchi, H.

    2002-01-01

    We clarify numerically the wall friction coefficient, the distributions of velocity and shear rate, and the number of aggregated particles on steady magnetic fluid flow in a straight tube by taking into account the non-uniform distribution of mass concentration (DMC). Also the effect of DMC is clarified under the uniform and non-uniform transverse steady magnetic field. In comparison with the published data, the numerical results show good agreement with the experimental data

  2. Numerical research on natural convection in molten salt reactor with non-uniformly distributed volumetric heat generation

    International Nuclear Information System (INIS)

    Qian Libo; Qiu Suizheng; Zhang Dalin; Su Guanghui; Tian Wenxi

    2010-01-01

    Molten salt reactor is one of the six Generation IV systems capable of breeding and transmutation of actinides and long-lived fission products, which uses the liquid molten salt as the fuel solvent, coolant and heat generation simultaneously. The present work presents a numerical investigation on natural convection with non-uniform heat generation through which the heat generated by the fluid fuel is removed out of the core region when the reactor is under post-accident condition or zero-power condition. The two-group neutron diffusion equation is applied to calculated neutron flux distribution, which leads to non-uniform heat generation. The SIMPLER algorithm is used to calculate natural convective heat transfer rate with isothermal or adiabatic rigid walls. These two models are coupled through the temperature field and heat sources. The peculiarities of natural convection with non-uniform heat generation are investigated in a range of Ra numbers (10 3 ∼ 10 7 ) for the laminar regime of fluid motion. In addition, the numerical results are also compared with those containing uniform heat generation.

  3. Advanced characterization techniques of nonuniform indium distribution within InGaN/GaN heterostructures grown by MOCVD

    International Nuclear Information System (INIS)

    Lu, D.; Florescu, D.I.; Lee, D.S.; Ramer, J.C.; Parekh, A.; Merai, V.; Li, S.; Begarney, M.J.; Armour, E.A.; Gardner, J.J.

    2005-01-01

    Nonuniform indium distribution within InGaN/GaN single quantum well (SQW) structures with nanoscale islands grown by metalorganic chemical vapor deposition (MOCVD) have been characterized by advanced characterization techniques. Robinson backscattered electron (BSE) measurements show cluster-like BSE contrast of high brightness regions, which are not centered at small dark pits in a SQW structure of spiral growth mode. By comparing with the secondary electron (SE) images, the bright cluster areas from the BSE images were found to have higher indium content compared to the surrounding dark areas. Temperature dependant photoluminescence (PL) measurement shows typical ''S-shape'' curve, which shows good correlation with nonuniform indium distribution from BSE measurement. Optical evaluation of the samples show increased PL slope efficiency of the spiral mode SQW, which can be attributed to the presence of Indium inhomogeneities. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Modelling of the reactive sputtering process with non-uniform discharge current density and different temperature conditions

    International Nuclear Information System (INIS)

    Vasina, P; Hytkova, T; Elias, M

    2009-01-01

    The majority of current models of the reactive magnetron sputtering assume a uniform shape of the discharge current density and the same temperature near the target and the substrate. However, in the real experimental set-up, the presence of the magnetic field causes high density plasma to form in front of the cathode in the shape of a toroid. Consequently, the discharge current density is laterally non-uniform. In addition to this, the heating of the background gas by sputtered particles, which is usually referred to as the gas rarefaction, plays an important role. This paper presents an extended model of the reactive magnetron sputtering that assumes the non-uniform discharge current density and which accommodates the gas rarefaction effect. It is devoted mainly to the study of the behaviour of the reactive sputtering rather that to the prediction of the coating properties. Outputs of this model are compared with those that assume uniform discharge current density and uniform temperature profile in the deposition chamber. Particular attention is paid to the modelling of the radial variation of the target composition near transitions from the metallic to the compound mode and vice versa. A study of the target utilization in the metallic and compound mode is performed for two different discharge current density profiles corresponding to typical two pole and multipole magnetics available on the market now. Different shapes of the discharge current density were tested. Finally, hysteresis curves are plotted for various temperature conditions in the reactor.

  5. Prediction of the Velocity Contours in Triangular Channel with Non-uniform Roughness Distributions by Adaptive Neuro-Fuzzy Inference System

    Directory of Open Access Journals (Sweden)

    Sara Bardestani

    2017-09-01

    Full Text Available Triangular channels have different applications in many water and wastewater engineering problems. For this purpose investigating hydraulic characteristics of flow in these sections has great importance. Researchers have presented different prediction methods for the velocity contours in prismatic sections. Most proposed methods are not able to consider the effect of walls roughness, the roughness distribution and secondary flows. However, due to complexity and nonlinearity of velocity contours in open channel flow, there is no simple relationship that can be fully able to exactly draw the velocity contours. In this paper an efficient approach for modeling velocity contours in triangular open channels with non-uniform roughness distributions by Adaptive Neuro-Fuzzy Inference System (ANFIS has been suggested. For training and testing model, the experimental data including 1703 data in triangular channels with geometric symmetry and non-uniform roughness distributions have been used. Comparing experimental results with predicted values by model indicates that ANFIS model is capable to be used in simulation of local velocity and determining velocity contours and the independent evaluation showed that the calculated values of discharge and depth-averaged velocity from model information are precisely in conformity with experimental values.

  6. Current limitation and formation of plasma double layers in a non-uniform magnetic field

    International Nuclear Information System (INIS)

    Plamondon, R.; Teichmann, J.; Torven, S.

    1986-07-01

    Formation of strong double layers has been observed experimentally in a magnetised plasma column maintained by a plasma source. The magnetic field is approximately axially homogenous except in a region at the anode where the electric current flows into a magnetic mirror. The double layer has a stationary position only in the region of non-uniform magnetic field or at the aperture separating the source and the plasma column. It is characterized by a negative differential resistance in the current-voltage characteristic of the device. The parameter space,where the double layer exists, has been studied as well as the corresponding potential profiles and fluctuation spectra. The electric current and the axial electric field are oppositely directed between the plasma source and a potential minimum which is formed in the region of inhomogeneous magnetic field. Electron reflection by the resulting potential barrier is found to be an important current limitation mechanism. (authors)

  7. Analysis of Causes of Non-Uniform Flow Distribution in Manifold Systems with Variable Flow Rate along Length

    Science.gov (United States)

    Zemlyanaya, N. V.; Gulyakin, A. V.

    2017-11-01

    The uniformity of flow distribution in perforated manifolds is a relevant task. The efficiency of water supply, sewerage and perflation systems is determined by hydraulics of the flow with a variable mass. The extensive study of versatile available information showed that achieving a uniform flow distribution through all of the outlets is almost impossible. The analysis of the studies conducted by other authors and our numerical experiments performed with the help of the software package ANSYS 16.1 were made in this work. The results allowed us to formulate the main causes of non-uniform flow distribution. We decided to suggest a hypothesis to explain the static pressure rise problem at the end of a perforated manifold.

  8. Assessment of 12 CHF prediction methods, for an axially non-uniform heat flux distribution, with the RELAP5 computer code

    Energy Technology Data Exchange (ETDEWEB)

    Ferrouk, M. [Laboratoire du Genie Physique des Hydrocarbures, University of Boumerdes, Boumerdes 35000 (Algeria)], E-mail: m_ferrouk@yahoo.fr; Aissani, S. [Laboratoire du Genie Physique des Hydrocarbures, University of Boumerdes, Boumerdes 35000 (Algeria); D' Auria, F.; DelNevo, A.; Salah, A. Bousbia [Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, Universita di Pisa (Italy)

    2008-10-15

    The present article covers the evaluation of the performance of twelve critical heat flux methods/correlations published in the open literature. The study concerns the simulation of an axially non-uniform heat flux distribution with the RELAP5 computer code in a single boiling water reactor channel benchmark problem. The nodalization scheme employed for the considered particular geometry, as modelled in RELAP5 code, is described. For this purpose a review of critical heat flux models/correlations applicable to non-uniform axial heat profile is provided. Simulation results using the RELAP5 code and those obtained from our computer program, based on three type predictions methods such as local conditions, F-factor and boiling length average approaches were compared.

  9. Modelling of HVDC wall bushing flashover in nonuniform rain

    International Nuclear Information System (INIS)

    Rizk, F.A.M.; Kamel, S.I.

    1991-01-01

    This paper presents the first mathematical model to provide necessary and sufficient conditions for flashover of an HVDC wall bushing under nonuniform rain. The suggested mechanism is initiated by streamer bridging of the dry zone enhanced by nonuniform voltage distribution along the bushing and within the dry zone. Fast voltage collapse across the dry zone die to energy stored in the bushing stray capacitance to ground leads to impulsive stressing of the wet part of the bushing. The nonuniform distribution of the impulse stress and the process of streamer bridging, fast voltage collapse as well as subsequent recharging of the bushing capacitances can lead to continued discharge propagation and flashover of the complete bushing. The findings of the model have been satisfactorily compared with previous experiments and field observations and can, for the first time, account for the following aspects of the flashover mechanism: critical dry zone length, polarity effect, specific leakage path, wet layer conductance per unit leakage length as well as the DC system voltage

  10. Monte Carlo simulation of scatter in non-uniform symmetrical attenuating media for point and distributed sources

    International Nuclear Information System (INIS)

    Henry, L.J.; Rosenthal, M.S.

    1992-01-01

    We report results of scatter simulations for both point and distributed sources of 99m Tc in symmetrical non-uniform attenuating media. The simulations utilized Monte Carlo techniques and were tested against experimental phantoms. Both point and ring sources were used inside a 10.5 cm radius acrylic phantom. Attenuating media consisted of combinations of water, ground beef (to simulate muscle mass), air and bone meal (to simulate bone mass). We estimated/measured energy spectra, detector efficiencies and peak height ratios for all cases. In all cases, the simulated spectra agree with the experimentally measured spectra within 2 SD. Detector efficiencies and peak height ratios also are in agreement. The Monte Carlo code is able to properly model the non-uniform attenuating media used in this project. With verification of the simulations, it is possible to perform initial evaluation studies of scatter correction algorithms by evaluating the mechanisms of action of the correction algorithm on the simulated spectra where the magnitude and sources of scatter are known. (author)

  11. Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents

    Science.gov (United States)

    Sharma, Sanchar; Muralidharan, Bhaskaran; Tulapurkar, Ashwin

    2015-09-01

    We propose a new mechanism and a related device concept for a robust, magnetic field tunable radio-frequency (rf) oscillator using the self oscillation of a magnetic domain wall subject to a uniform static magnetic field and a spatially non-uniform vertical dc spin current. The self oscillation of the domain wall is created as it translates periodically between two unstable positions, one being in the region where both the dc spin current and the magnetic field are present, and the other, being where only the magnetic field is present. The vertical dc spin current pushes it away from one unstable position while the magnetic field pushes it away from the other. We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000. A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples. Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.

  12. Weighted backprojection implemented with a non-uniform attenuation map for improved SPECT quantitation

    International Nuclear Information System (INIS)

    Manglos, S.H.; Jaszczak, R.J.; Floyd, C.E.

    1988-01-01

    A method is developed to improve quantitation in SPECT imaging by using an attenuation compensation method which includes the correct non-uniform attenuation spatial distribution (''map''). The method is based on the technique of weighted back projection, previously developed for uniform attenuation. The method is tested by imaging a non-uniform phantom, reconstructing with the known attenuation map, and quantitatively comparing the resultant image with the known activity distribution. Reconstructed image profiles are dramatically improved in comparison to reconstructions without compensation or with an assumed uniform attenuation map. Contrast measurements further quantify the improvement. Line spread function distortions seen previously in non-uniform geometries are essentially eliminated by the method. Therefore, the method appears to be appropriate for these geometries, if the non-uniform map can be determined. Some additional image distortions introduced by the compensation method are noted and will require further study

  13. Nonuniform Illumination Correction Algorithm for Underwater Images Using Maximum Likelihood Estimation Method

    Directory of Open Access Journals (Sweden)

    Sonali Sachin Sankpal

    2016-01-01

    Full Text Available Scattering and absorption of light is main reason for limited visibility in water. The suspended particles and dissolved chemical compounds in water are also responsible for scattering and absorption of light in water. The limited visibility in water results in degradation of underwater images. The visibility can be increased by using artificial light source in underwater imaging system. But the artificial light illuminates the scene in a nonuniform fashion. It produces bright spot at the center with the dark region at surroundings. In some cases imaging system itself creates dark region in the image by producing shadow on the objects. The problem of nonuniform illumination is neglected by the researchers in most of the image enhancement techniques of underwater images. Also very few methods are discussed showing the results on color images. This paper suggests a method for nonuniform illumination correction for underwater images. The method assumes that natural underwater images are Rayleigh distributed. This paper used maximum likelihood estimation of scale parameter to map distribution of image to Rayleigh distribution. The method is compared with traditional methods for nonuniform illumination correction using no-reference image quality metrics like average luminance, average information entropy, normalized neighborhood function, average contrast, and comprehensive assessment function.

  14. Nonlinear Dynamics of Non-uniform Current-Vortex Sheets in Magnetohydrodynamic Flows

    Science.gov (United States)

    Matsuoka, C.; Nishihara, K.; Sano, T.

    2017-04-01

    A theoretical model is proposed to describe fully nonlinear dynamics of interfaces in two-dimensional MHD flows based on an idea of non-uniform current-vortex sheet. Application of vortex sheet model to MHD flows has a crucial difficulty because of non-conservative nature of magnetic tension. However, it is shown that when a magnetic field is initially parallel to an interface, the concept of vortex sheet can be extended to MHD flows (current-vortex sheet). Two-dimensional MHD flows are then described only by a one-dimensional Lagrange parameter on the sheet. It is also shown that bulk magnetic field and velocity can be calculated from their values on the sheet. The model is tested by MHD Richtmyer-Meshkov instability with sinusoidal vortex sheet strength. Two-dimensional ideal MHD simulations show that the nonlinear dynamics of a shocked interface with density stratification agrees fairly well with that for its corresponding potential flow. Numerical solutions of the model reproduce properly the results of the ideal MHD simulations, such as the roll-up of spike, exponential growth of magnetic field, and its saturation and oscillation. Nonlinear evolution of the interface is found to be determined by the Alfvén and Atwood numbers. Some of their dependence on the sheet dynamics and magnetic field amplification are discussed. It is shown by the model that the magnetic field amplification occurs locally associated with the nonlinear dynamics of the current-vortex sheet. We expect that our model can be applicable to a wide variety of MHD shear flows.

  15. The magnetostriction in a superconductor-magnet system under non-uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xueyi; Jiang, Lang; Wu, Hao [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, Lanzhou University, Lanzhou, Gansu 730000 (China); Gao, Zhiwen, E-mail: gaozhw@lzu.edu.cn [Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2017-03-15

    Highlights: • We studied firstly magnetostriction in HTS under non-uniform magnetic field. • The superconductors may be homogeneous and nonhomogeneous. • The magnetostrictions response of the HTS is sensitive to the critical current density and amplitude of the applied magnetic field. • The magnetostriction of nonhomogeneous HTS is larger than that of homogeneous HTS. - Abstract: This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.

  16. Optimal threshold of error decision related to non-uniform phase distribution QAM signals generated from MZM based on OCS

    Science.gov (United States)

    Han, Xifeng; Zhou, Wen

    2018-03-01

    Optical vector radio-frequency (RF) signal generation based on optical carrier suppression (OCS) in one Mach-Zehnder modulator (MZM) can realize frequency-doubling. In order to match the phase or amplitude of the recovered quadrature amplitude modulation (QAM) signal, phase or amplitude pre-coding is necessary in the transmitter side. The detected QAM signals usually have one non-uniform phase distribution after square-law detection at the photodiode because of the imperfect characteristics of the optical and electrical devices. We propose to use optimal threshold of error decision for non-uniform phase contribution to reduce the bit error rate (BER). By employing this scheme, the BER of 16 Gbaud (32 Gbit/s) quadrature-phase-shift-keying (QPSK) millimeter wave signal at 36 GHz is improved from 1 × 10-3 to 1 × 10-4 at - 4 . 6 dBm input power into the photodiode.

  17. Magneto-acoustic resonance in a non-uniform current carrying plasma column

    OpenAIRE

    Vaclavik, J.

    2017-01-01

    The forced radial magneto-acoustic oscillations in a plasma column with nonuniform mass density and temperature are investigated. It turns out that the oscillations have a resonant character similar to that of the magneto-acoustic oscillations in a uniform plasma column. The properties of the axial and azimuthal components of the oscillating magnetic field are discussed in detail

  18. Electron Beam Dose Distribution in the Presence of Non-Uniform Magnetic Field

    Directory of Open Access Journals (Sweden)

    Mohamad Javad Tahmasebi-Birgani

    2014-04-01

    Full Text Available Introduction Magnetic fields are capable of altering the trajectory of electron beams andcan be used in radiation therapy.Theaim of this study was to produce regions with dose enhancement and reduction in the medium. Materials and Methods The NdFeB permanent magnets were arranged on the electron applicator in several configurations. Then, after the passage of the electron beams (9 and 15 MeV Varian 2100C/D through the non-uniform magnetic field, the Percentage Depth Dose(PDDs on central axis and dose profiles in three depths for each energy were measured in a 3D water phantom. Results For all magnet arrangements and for two different energies, the surface dose increment and shift in depth of maximum dose (dmax were observed. In addition, the pattern of dose distribution in buildup region was changed. Measurement of dose profile showed dose localization and spreading in some other regions. Conclusion The results of this study confirms that using magnetic field can alter the dose deposition patterns and as a result can produce dose enhancement as well as dose reduction in the medium using high-energy electron beams. These effects provide dose distribution with arbitrary shapes for use in radiation therapy.

  19. Distributions of the ion temperature, ion pressure, and electron density over the current sheet surface

    International Nuclear Information System (INIS)

    Kyrie, N. P.; Markov, V. S.; Frank, A. G.; Vasilkov, D. G.; Voronova, E. V.

    2016-01-01

    The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampère force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampère force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampère force is counterbalanced by the pressure gradient.

  20. Distributions of the ion temperature, ion pressure, and electron density over the current sheet surface

    Energy Technology Data Exchange (ETDEWEB)

    Kyrie, N. P., E-mail: kyrie@fpl.gpi.ru; Markov, V. S., E-mail: natalya.kyrie@yandex.ru; Frank, A. G.; Vasilkov, D. G.; Voronova, E. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

    2016-06-15

    The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampère force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampère force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampère force is counterbalanced by the pressure gradient.

  1. Jet array impingement flow distributions and heat transfer characteristics. Effects of initial crossflow and nonuniform array geometry. [gas turbine engine component cooling

    Science.gov (United States)

    Florschuetz, L. W.; Metzger, D. E.; Su, C. C.; Isoda, Y.; Tseng, H. H.

    1982-01-01

    Two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered. The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface. The configurations considered are intended to model those of interest in current and contemplated gas turbine airfoil midchord cooling applications. The effects of an initial crossflow which approaches the array through an upstream extension of the channel are considered. Flow distributions as well as heat transfer coefficients and adiabatic wall temperatures resolved to one streamwise hole spacing were measured as a function of the initial crossflow rate and temperature relative to the jet flow rate and temperature. Both Nusselt number profiles and dimensionless adiabatic wall temperature (effectiveness) profiles are presented and discussed. Special test results which show a significant reduction of jet orifice discharge coefficients owing to the effect of a confined crossflow are also presented, along with a flow distribution model which incorporates those effects. A nonuniform array flow distribution model is developed and validated.

  2. Linear q-nonuniform difference equations

    International Nuclear Information System (INIS)

    Bangerezako, Gaspard

    2010-01-01

    We introduce basic concepts of q-nonuniform differentiation and integration and study linear q-nonuniform difference equations and systems, as well as their application in q-nonuniform difference linear control systems. (author)

  3. Suppression of Specular Reflections by Metasurface with Engineered Nonuniform Distribution of Reflection Phase

    Directory of Open Access Journals (Sweden)

    Xin Mi Yang

    2015-01-01

    Full Text Available We make preliminary investigations on a new approach to reducing radar cross section (RCS of conducting objects. This approach employs novel planar metasurfaces characterizing nonuniform distribution of reflection phase. The operation principle of this approach and the design rule of the associated metasurfaces are explained using a simplified theoretical model. We then present a design example of such metasurfaces, in which three-layer stacked square patches with variable sizes are utilized as the reflecting elements. The proposed RCS-reduction approach is verified by both numerical simulations and measurements on the example, under the assumption of normal plane wave incidence. It is observed that, in a fairly wide frequency band (from 3.6 to 5.5 GHz, the presented example is capable of suppressing the specular reflections of conducting plates significantly (by more than 7 dB for two orthogonal incident polarizations.

  4. Effect of nonuniform radial density distribution on the space charge dominated beam bunching

    International Nuclear Information System (INIS)

    Sing Babu, P.; Goswami, A.; Pandit, V. S.

    2011-01-01

    Beam dynamics of a space charge dominated beam during the bunch compression is studied self consistently for the case of fixed shape non-uniform bell shape and hollow shape density distributions in the transverse direction. We have used thick slices at different parts of the beam to account for variation in the beam radius in the study of the transverse dynamics. The longitudinal dynamics has been studied using the disc model. The axial variation of the radius of the slices and emittance growth arising from the phase dependence of the transverse rf forces are also included in the simulation. We have modified the beam envelope equation to take into account the longitudinal space charge effect on the transverse motion which arises due to the finite bunch size. To demonstrate the application of the theoretical formulations developed, we have studied a sinusoidal beam bunching system and presented detailed numerical results.

  5. Degradation nonuniformity in the solar diffuser bidirectional reflectance distribution function.

    Science.gov (United States)

    Sun, Junqiang; Chu, Mike; Wang, Menghua

    2016-08-01

    The assumption of angular dependence stability of the solar diffuser (SD) throughout degradation is critical to the on-orbit calibration of the reflective solar bands (RSBs) in many satellite sensors. Recent evidence has pointed to the contrary, and in this work, we present a thorough investigative effort into the angular dependence of the SD degradation for the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite and for the twin Moderate-resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua spacecrafts. One common key step in the RSB calibration is the use of the SD degradation performance measured by an accompanying solar diffuser stability monitor (SDSM) as a valid substitute for the SD degradation factor in the direction of the RSB view. If SD degradations between these two respective directions do not maintain the same relative relationship over time, then the unmitigated use of the SDSM-measured SD degradation factor in the RSB calibration calculation will generate bias, and consequently, long-term drift in derived science products. We exploit the available history of the on-orbit calibration events to examine the response of the SDSM and the RSB detectors to the incident illumination reflecting off SD versus solar declination angle and show that the angular dependency, particularly at short wavelengths, evolves with respect to time. The generalized and the decisive conclusion is that the bidirectional reflectance distribution function (BRDF) of the SD degrades nonuniformly with respect to both incident and outgoing directions. Thus, the SDSM-based measurements provide SD degradation factors that are biased relative to the RSB view direction with respect to the SD. The analysis also reveals additional interesting phenomena, for example, the sharp behavioral change in the evolving angular dependence observed in Terra MODIS and SNPP VIIRS. For SNPP VIIRS the mitigation for this

  6. Design of Chebychev’s Low Pass Filters Using Nonuniform Transmission Lines

    Directory of Open Access Journals (Sweden)

    Said Attamimi

    2016-03-01

    Full Text Available Transmission lines are utilized in many applications to convey energy as well as information. Nonuniform transmission lines (NTLs are obtained through variation of the characteristic quantities along the axial direction. Such NTLs can be used to design network elements, like matching circuits, delay equalizers, filters, VLSI interconnections, etc. In this work, NTLs were analyzed with a numerical method based on the implementation of method of moment. In order to approximate the voltage and current distribution along the transmission line, a sum of basis functions with unknown amplitudes was introduced. As basis function, a constant function was used. In this work, we observed several cases such as lossless and lossy uniform transmission lines with matching and arbitrary load. These cases verified the algorithm developed in this work. The second example consists of nonuniform transmission lines in the form of abruptly changing transmission lines. This structure was used to design a Chebychev’s low pass filter. The calculated reflection and transmission factors of the filters showed some coincidences with the measurements.

  7. Modelling refrigerant distribution in minichannel evaporators

    DEFF Research Database (Denmark)

    Brix, Wiebke

    of the liquid and vapour in the inlet manifold. Combining non-uniform airflow and non-uniform liquid and vapour distribution shows that a non-uniform airflow distribution to some degree can be compensated by a suitable liquid and vapour distribution. Controlling the superheat out of the individual channels...... to be equal, results in a cooling capacity very close to the optimum. A sensitivity study considering parameter changes shows that the course of the pressure gradient in the channel is significant, considering the magnitude of the capacity reductions due to non-uniform liquid and vapour distribution and non......This thesis is concerned with numerical modelling of flow distribution in a minichannel evaporator for air-conditioning. The study investigates the impact of non-uniform airflow and non-uniform distribution of the liquid and vapour phases in the inlet manifold on the refrigerant mass flow...

  8. Current distribution tomography for determination of internal current density distributions

    International Nuclear Information System (INIS)

    Gailey, P.C.

    1993-01-01

    A method is presented for determination of current densities inside a cylindrical object using measurements of the magnetic fields outside the object. The cross section of the object is discretized with the current assumed constant over each defined region. Magnetic fields outside the object are related to the internal current densities through a geometry matrix which can be inverted to yield a solution for the current densities in terms of the measured fields. The primary limitation of this technique results from singularities in the geometry matrix that arise due to cylindrical symmetry of the problem. Methods for circumventing the singularities to obtain information about the distribution of current densities are discussed. This process of current distribution tomography is designed to determine internal body current densities using measurements of the external magnetic field distribution. It is non-invasive, and relatively simple to implement. Although related to a more general study of magnetic imaging which has been used to investigate endogenous currents in the brain and other parts of the body, it is restricted to currents either applied directly or induced by exposure to an external field. The research is related to public concern about the possibility of health effects resulting from exposure to power frequency electric and magnetic fields

  9. Simulation of Non-Uniform Electron Beams in the Gyrotron Electron-Optical System

    Science.gov (United States)

    Louksha, O. I.; Trofimov, P. A.

    2018-04-01

    New calculated data on the effect of emission inhomogeneities on the quality of the electron beam, which is formed in an electron-optical system of a gyrotron, have been obtained. The calculations were based on emission current density distributions, which were measured for the different cathodes in the gyrotron of Peter the Great St. Petersburg Polytechnic University. A satisfactory agreement between the experimental and calculated data on the influence of emission nonuniformities on the velocity spread of electrons has been shown. The necessity of considering the real distribution of the emission current density over the cathode surface to determine the main parameters of the electron beam—the velocity and energy spreads of the electrons, spatial structure of the beam, and coefficient of reflection of electrons from the magnetic mirror—has been demonstrated. The maximum level of emission inhomogeneities, which are permissible for effective work of gyrotrons, has been discussed.

  10. Effect of non-uniform surface resistance on the quality factor of superconducting niobium cavity

    Science.gov (United States)

    Tan, Weiwei; Lu, Xiangyang; Yang, Ziqin; Zhao, Jifei; Yang, Deyu; Yang, Yujia

    2016-08-01

    The formula Rs = G /Q0 is commonly used in the calculation of the surface resistance of radio frequency niobium superconducting cavities. The applying of such equation is under the assumption that surface resistance is consistent over the cavity. However, the distribution of the magnetic field varies over the cavity. The magnetic field in the equator is much higher than that in the iris. According to Thermal Feedback Theory, it leads non-uniform distribution of the density of heat flux, which results in a different temperature distribution along the cavity inter surface. The BCS surface resistance, which depends largely on the temperature, is different in each local inner surface. In this paper, the effect of surface non-uniform resistance on the quality factor has been studied, through the calculation of Q0 in the original definition of it. The results show that it is necessary to consider the non-uniform distribution of magnetic field when the accelerating field is above 20 MV/m for TESLA cavities. Also, the effect of inhomogeneity of residual resistance on the quality factor is discussed. Its distribution barely affects the quality factor.

  11. Thermal freeze-out and longitudinally non-uniform collective expansion flow in relativistic heavy ion collisions

    CERN Document Server

    Feng Sheng Qin; LianShouLiu

    2002-01-01

    The non-uniform longitudinal flow model (NUFM) proposed recently is extended to include also the transverse flow. The resulting longitudinally non-uniform collective expansion model (NUCEM) is applied to the calculation of rapidity distribution of kaons, lambdas and protons in relativistic heavy ion collisions at CERN-SPS energies. The model results are compared with the 200 A GeV/c S-S and 158 A GeV/c Pb-Pb collision data. The central dips observed in experiments are reproduced in a natural way. It is found that the depth of the central dip depends on the magnitude of the parameter e and the mass of produced particles, i.e. the non-uniformity of the longitudinal flow which is described by the parameter e determines the depth of the central dip for produced particles. Comparing with one-dimensional non-uniform longitudinal flow model, the rapidity distribution of lighter strange particle kaon also shows a dip due to the effect of transverse flow

  12. Downsampling Non-Uniformly Sampled Data

    Directory of Open Access Journals (Sweden)

    Fredrik Gustafsson

    2007-10-01

    Full Text Available Decimating a uniformly sampled signal a factor D involves low-pass antialias filtering with normalized cutoff frequency 1/D followed by picking out every Dth sample. Alternatively, decimation can be done in the frequency domain using the fast Fourier transform (FFT algorithm, after zero-padding the signal and truncating the FFT. We outline three approaches to decimate non-uniformly sampled signals, which are all based on interpolation. The interpolation is done in different domains, and the inter-sample behavior does not need to be known. The first one interpolates the signal to a uniformly sampling, after which standard decimation can be applied. The second one interpolates a continuous-time convolution integral, that implements the antialias filter, after which every Dth sample can be picked out. The third frequency domain approach computes an approximate Fourier transform, after which truncation and IFFT give the desired result. Simulations indicate that the second approach is particularly useful. A thorough analysis is therefore performed for this case, using the assumption that the non-uniformly distributed sampling instants are generated by a stochastic process.

  13. The Effects of Nonuniform Illumination on the Electrical Performance of a Single Conventional Photovoltaic Cell

    Directory of Open Access Journals (Sweden)

    Damasen Ikwaba Paul

    2015-01-01

    Full Text Available Photovoltaic (PV concentrators are a promising approach for lowering PV electricity costs in the near future. However, most of the concentrators that are currently used for PV applications yield nonuniform flux profiles on the surface of a PV module which in turn reduces its electrical performance if the cells are serially connected. One way of overcoming this effect is the use of PV modules with isolated cells so that each cell generates current that is proportional to the energy flux absorbed. However, there are some cases where nonuniform illumination also exists in a single cell in an isolated cells PV module. This paper systematically studied the effect of nonuniform illumination on various cell performance parameters of a single monocrystalline standard PV cell at low and medium energy concentration ratios. Furthermore, the effect of orientation, size, and geometrical shapes of nonuniform illumination was also investigated. It was found that the effect of nonuniform illumination on various PV cell performance parameters of a single standard PV cell becomes noticeable at medium energy flux concentration whilst the location, size, and geometrical shape of nonuniform illumination have no effect on the performance parameters of the cell.

  14. Skin carcinogenesis following uniform and non-uniform β irradiation

    International Nuclear Information System (INIS)

    Charles, M.W.; Williams, J.P.; Coggle, J.E.

    1989-01-01

    Where workers or the general public may be exposed to ionising radiation, the irradiation is rarely uniform. The risk figures and dose limits recommended by the International Commission on Radiological Protection (ICRP) are based largely on clinical and epidemiological studies of reasonably uniform irradiated organs. The paucity of clinical or experimental data for highly non-uniform exposures has prevented the ICRP from providing adequate recommendations. This weakness has led on a number of occasions to the postulate that highly non-uniform exposures of organs could be 100,000 times more carcinogenic than ICRP risk figures would predict. This so-called ''hot-particle hypothesis'' found little support among reputable radiobiologists, but could not be clearly and definitively refuted on the basis of experiment. An experiment, based on skin tumour induction in mouse skin, is described which was developed to test the hypothesis. The skin of 1200 SAS/4 male mice has been exposed to a range of uniform and non-uniform sources of the β emitter 170 Tm (E max ∼ 1 MeV). Non-uniform exposures were produced using arrays of 32 or 8 2-mm diameter sources distributed over the same 8-cm 2 area as a uniform control source. Average skin doses varied from 2-100 Gy. The results for the non-uniform sources show a 30% reduction in tumour incidence by the 32-point array at the lower mean doses compared with the response from uniform sources. The eight-point array showed an order-of-magnitude reduction in tumour incidence compared to uniform irradiation at low doses. These results, in direct contradiction to the ''hot particle hypothesis'', indicate that non-uniform exposures produce significantly fewer tumours than uniform exposures. (author)

  15. Laterally excited flexible tanks with nonuniform density liquid

    International Nuclear Information System (INIS)

    Tang, Yu

    1996-01-01

    A study of the dynamic responses of flexible tanks containing nonuniform liquid under horizontal base excitations is presented. The system considered is an upright, circular cylindrical tank filled with an incompressible and inviscid liquid in which the density increases with the liquid depth. Only the impulsive components of response are considered in this study since the convective components can be computed by considering the tank to be rigid. It is shown in this study that for tanks with height-to-radius ratios between 0.3 and 1.2, the response quantities may be estimated utilizing the rigid tank solutions. Also, it is found that the pressure distribution along the tank wall is not sensitive to the detailed distribution function of the liquid density, and that the base shear and moments for the tank with nonuniform liquid can be estimated conservatively by assuming that the tank is filled with an equivalent uniform liquid density that preserves the total liquid weight. Finally, a simple equation for evaluating the fundamental natural frequency of the system is proposed

  16. Derivation of nonlinear wave equations for ultrasound beam in nonuniform bubbly liquids

    Science.gov (United States)

    Kanagawa, Tetsuya; Yano, Takeru; Kawahara, Junya; Kobayashi, Kazumichi; Watanabe, Masao; Fujikawa, Shigeo

    2012-09-01

    Weakly nonlinear propagation of diffracted ultrasound beams in a nonuniform bubbly liquid is theoretically studied based on the method of multiple scales with the set of scaling relations of some physical parameters. It is assumed that the spatial distribution of the number density of bubbles in an initial state at rest is a slowly varying function of space coordinates and the amplitude of its variation is small compared with a mean number density. As a result, a Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation with dispersion and nonuniform effects for a low frequency case and a nonlinear Schrödinger (NLS) equation with dissipation, diffraction, and nonuniform effects for a high frequency case, are derived from the basic equations of bubbly flows.

  17. Effects of non-uniformities on electrical conduction in weakly ionized plasmas

    International Nuclear Information System (INIS)

    Numano, M.; Murakami, Y.; Nitta, T.

    1989-01-01

    The effect of non-uniformities on the flow of electric current in weakly ionized plasmas is investigated by taking into account the ion slip as well as the Hall current. An Ohm's law for a non-uniform plasma is derived, from which the formula previously obtained by Numano, i.e. an extension of Rosa's equation, is obtainable as a special case. Making use of this new Ohm's law, the effective electrical conductivity and the effective Hall parameter are determined for isotropically turbulent plasmas. It is found that when the ion-slip effect is absent they are in good agreement with the results obtained previously. (author)

  18. Elimination of macrostep-induced current flow nonuniformity in vertical GaN PN diode using carbon-free drift layer grown by hydride vapor phase epitaxy

    Science.gov (United States)

    Fujikura, Hajime; Hayashi, Kentaro; Horikiri, Fumimasa; Narita, Yoshinobu; Konno, Taichiro; Yoshida, Takehiro; Ohta, Hiroshi; Mishima, Tomoyoshi

    2018-04-01

    In vertical GaN PN diodes (PNDs) grown entirely by metal–organic chemical vapor deposition (MOCVD), large current nonuniformity was observed. This nonuniformity was induced by macrosteps on the GaN surface through modulation of carbon incorporation into the n-GaN crystal. It was eliminated in a hybrid PND consisting of a carbon-free n-GaN layer grown by hydride vapor phase epitaxy (HVPE) and an MOCVD-regrown p-GaN layer. The hybrid PND showed a fairly low on-resistance (2 mΩ cm2) and high breakdown voltage (2 kV) even without a field plate electrode. These results clearly indicated the strong advantages of the HVPE-grown drift layer for improving power device performance, uniformity, and yield.

  19. Impulsive response of nonuniform density liquid in a laterally excited tank

    International Nuclear Information System (INIS)

    Tang, Y.; Chang, Y.W.

    1994-04-01

    A study on the impulsive component of the dynamic response of a liquid of nonuniform density in a tank undergoing lateral base excitations is presented. The system considered is a circular cylindrical tank containing an incompressible and inviscid liquid whose density increases with the liquid depth. The density distribution along the depth can be of any arbitrary continuous or discontinuous function. In the analysis, the liquid field is divided into n layers. The thickness of the liquid layers can be different, but the density of each liquid layer is considered to be uniform and is equal to the value of the original liquid density at the mid-height of that layer. The problem is solved by the eigenfunction expansion in conjunction with the transfer matrix technique. The effect of the nonuniform liquid density on the impulsive component of the dynamic response is illustrated in a numerical example in which the linear and cosine distributions of the liquid density are assumed. The response quantities examined include the impulsive pressure, base shear and moments. The results are presented in tabular and graphical forms. It is found that the impulsive pressure distribution along the tank wall is not sensitive to the detailed distribution function of the density, and the base shear and moments for the nonuniform liquid can be estimated by assuming an equivalent uniform liquid density that preserves the total liquid weight. The effect of tank flexibility is assessed by a simple approach in which the response quantities for flexible tanks are evaluated by simplified equations

  20. High-order nonuniformly correlated beams

    Science.gov (United States)

    Wu, Dan; Wang, Fei; Cai, Yangjian

    2018-02-01

    We have introduced a class of partially coherent beams with spatially varying correlations named high-order nonuniformly correlated (HNUC) beams, as an extension of conventional nonuniformly correlated (NUC) beams. Such beams bring a new parameter (mode order) which is used to tailor the spatial coherence properties. The behavior of the spectral density of the HNUC beams on propagation has been investigated through numerical examples with the help of discrete model decomposition and fast Fourier transform (FFT) algorithm. Our results reveal that by selecting the mode order appropriately, the more sharpened intensity maxima can be achieved at a certain propagation distance compared to that of the NUC beams, and the lateral shift of the intensity maxima on propagation is closed related to the mode order. Furthermore, analytical expressions for the r.m.s width and the propagation factor of the HNUC beams on free-space propagation are derived by means of Wigner distribution function. The influence of initial beam parameters on the evolution of the r.m.s width and the propagation factor, and the relation between the r.m.s width and the occurring of the sharpened intensity maxima on propagation have been studied and discussed in detail.

  1. Circumferential nonuniformity of cladding radiation swelling of fast reactor peripheral fuel elements

    International Nuclear Information System (INIS)

    Reutov, V.F.; Farkhutdinov, K.G.

    1977-01-01

    The results are presented of the investigation into the perimeter radiation swelling of Kh18N10T stainless steel cladding in different cross sections of a peripheral fuel element of the BR-5 reactor. The fluence on the cladding is 1.8-2.9 x 10 22 fast neutr/cm 2 , the operating temperatures in different parts of the fuel element being 430 deg to 585 deg C. There has been observed circumferential non-uniformity of the distribution, concentration, and of the total volume of radiation cavities, which is due to temperature non-uniformity along the cladding perimeter. It is shown that such non-uniformity of radiation swelling of the cladding material may result in bending of the peripheral fuel element with regard to the fuel assembly sheath walls

  2. Methanol and ethanol vapor conversion in gas discharge with strongly non-uniform distribution of electric field on atmospheric pressure

    International Nuclear Information System (INIS)

    Golota, V.I.; Zavada, L.M.; Kotyukov, O.V.; Kudin, D.V.; Rodionov, S.V.; Pis'menetskoj, A.S.; Dotsenko, Yu.V.

    2010-01-01

    The barrierless gas discharge of negative polarity with strongly non-uniform distribution of electrical field in the methanol and ethanol vapour was studied. It is shown that level of methanol and ethanol conversion depended from power consumed by the discharge and exposition time for gas mixture in discharge zone. The condition for deep conversion of the methanol and ethanol vapours were determined. The water and carbon dioxide are the end products for the methanol and ethanol conversion. Formaldehyde and formic acid are the intermediates products in the conversion of methanol. And ethanol has a number of different compounds, including acetic acid, acetaldehyde, etc.

  3. Effect of nonuniform fuel distribution

    International Nuclear Information System (INIS)

    Katakura, Jun-ichi

    1987-01-01

    In order to ensure the subcriticality of nuclear fuel, the method of controlling the mass, form or dimensions below the limit values and the method of confirming subcriticality by calculation are taken, but at this time, it is often assumed that the concentration of fuel is constant in a fuel region, or fuel rods are arranged at constant intervals. However, in the extraction process in fuel reprocessing or in fuel storage vessels, the concentration distribution may arise in fuel regions even though temporarily. Even if subcriticality is expected in a uniform system, when concentration distribution arises, and an uneven system results in, criticality may occur. Therefore, it is important to grasp the effect of uneven fuel distribution for ensuring the safety against criticality. In this paper, the effect of uneven fuel distribution is discussed, centering around the critical mass. The examples in literatures and the examples of calculation of uneven fuel distribution are shown. As the result of calculation in Japan Atomic Energy Research Institute, in a high enrichment U-235-water system, the critical mass decreased by about 7 % due to uneven distribution, which nearly agreed with the result of Clark of about 6 %. As for a low enrichment system, the conspicuous decrease of the critical mass was not observed. (Kako, I.)

  4. Effects of a nonuniform open magnetic field on the plasma presheath

    International Nuclear Information System (INIS)

    Sato, Kunihiro; Miyawaki, Fujio

    1991-01-01

    Effects of a nonuniform magnetic field on the plasma presheath is numerically investigated using the plasma equation for a collisionless plasma with a finite-temperature particle source. The present calculation confirms that analytical solutions previously published by the authors are available over a wide range of mirror ratio. Potential drop in the presheath, which considerably depends on both the magnetic strength profile and the spatial distribution of the particle source, is remarkably increased by applying an expanding magnetic field when plasma particles are generated in the inner part of the plasma. An effect of a nonuniform magnetic field on sheath formation is also discussed by using the calculated ion distribution function. If the plasma equation has no singularity at the sheath edge, its solution satisfies the generalized Bohm criterion with the inequality sign in the expanding magnetic field. (author)

  5. Electrostatic ion-cyclotron waves in a nonuniform magnetic field

    International Nuclear Information System (INIS)

    Cartier, S.L.; D'Angelo, N.; Merlino, R.L.

    1985-01-01

    The properties of electrostatic ion-cyclotron waves excited in a single-ended cesium Q machine with a nonuniform magnetic field are described. The electrostatic ion-cyclotron waves are generated in the usual manner by drawing an electron current to a small exciter disk immersed in the plasma column. The parallel and perpendicular (to B) wavelengths and phase velocities are determined by mapping out two-dimensional wave phase contours. The wave frequency f depends on the location of the exciter disk in the nonuniform magnetic field, and propagating waves are only observed in the region where f> or approx. =f/sub c/i, where f/sub c/i is the local ion-cyclotron frequency. The parallel phase velocity is in the direction of the electron drift. From measurements of the plasma properties along the axis, it is inferred that the electron drift velocity is not uniform along the entire current channel. The evidence suggests that the waves begin being excited at that axial position where the critical drift velocity is first exceeded, consistent with a current-driven excitation mechanism

  6. Instruction sequence based non-uniform complexity classes

    NARCIS (Netherlands)

    Bergstra, J.A.; Middelburg, C.A.

    2013-01-01

    We present an approach to non-uniform complexity in which single-pass instruction sequences play a key part, and answer various questions that arise from this approach. We introduce several kinds of non-uniform complexity classes. One kind includes a counterpart of the well-known non-uniform

  7. Non-uniformly sampled grids in double pole coordinate system for freeform reflector construction

    Science.gov (United States)

    Ma, Donglin; Pacheco, Shaun; Feng, Zexin; Liang, Rongguang

    2015-08-01

    We propose a new method to design freeform reflectors by nonuniformly sampling the source intensity distribution in double pole coordinate system. In double pole coordinate system, there is no pole for the whole hemisphere because both poles of the spherical coordinate system are moved to southernmost point of the sphere and overlapped together. With symmetric definition of both angular coordinates in the modified double pole coordinate system, a better match between the source intensity distribution and target irradiance distribution can be achieved for reflectors with large acceptance solid angle, leading to higher light efficiency and better uniformity on the target surface. With non-uniform sampling of the source intensity, we can design circular freeform reflector to obtain uniform rectangular illumination pattern. Aided by the feedback optimization, the freeform reflector can achieve the collection efficiency for ideal point source over 0.7 and relative standard deviation (RSD) less than 0.1.

  8. Improving the quality factor of an RF spiral inductor with non-uniform metal width and non-uniform coil spacing

    International Nuclear Information System (INIS)

    Shen Pei; Zhang Wanrong; Huang Lu; Jin Dongyue; Xie Hongyun

    2011-01-01

    An improved inductor layout with non-uniform metal width and non-uniform spacing is proposed to increase the quality factor (Q factor). For this inductor layout, from outer coil to inner coil, the metal width is reduced by an arithmetic-progression step, while the metal spacing is increased by a geometric-progression step. An improved layout with variable width and changed spacing is of benefit to the Q factor of RF spiral inductor improvement (approximately 42.86%), mainly due to the suppression of eddy-current loss by weakening the current crowding effect in the center of the spiral inductor. In order to increase the Q factor further, for the novel inductor, a patterned ground shield is used with optimized layout together. The results indicate that, in the range of 0.5 to 16 GHz, the Q factor of the novel inductor is at an optimum, which improves by 67% more than conventional inductors with uniform geometry dimensions (equal width and equal spacing), is enhanced by nearly 23% more than a PGS inductor with uniform geometry dimensions, and improves by almost 20% more than an inductor with an improved layout. (semiconductor devices)

  9. Clinical implications of alternative TCP models for nonuniform dose distributions

    International Nuclear Information System (INIS)

    Deasy, J. O.

    1995-01-01

    Several tumor control probability (TCP) models for nonuniform dose distributions were compared, including: (a) a logistic/inter-patient-heterogeneity model, (b) a probit/inter-patient-heterogeneity model, (c) a Poisson/radioresistant-strain/identical-patients model, (d) a Poisson/inter-patient-heterogeneity model and (e) a Poisson/intra-tumor- and inter-patient-heterogeneity model. The models were analyzed in terms of the probability of controlling a single tumor voxel (the voxel control probability, or VCP), as a function of voxel volume and dose. Alternatively, the VCP surface can be thought of as the effect of a small cold spot. The models based on the Poisson equation which include inter-patient heterogeneity ((d) and (e)) have VCP surfaces (VCP as a function of dose and volume) which have a threshold 'waterfall' shape: below the waterfall (in dose), VCP is nearly zero. The threshold dose decreases with decreasing voxel volume. However, models (a), (b), and (c) all show a high probability of controlling a voxel (VCP>50%) with very low dose (e.g., 1 Gy) if the voxel is small (smaller than about 10 -3 of the tumor volume). Model (c) does not have the waterfall shape at low volumes due to the assumption of patient uniformity and a neglect of the effect of the clonogens which are more radiosensitive (and more numerous). Models (a) and (b) deviate from the waterfall shape at low volumes due to numerical differences between the functions used and the Poisson function. Hence, the Possion models which include inter-patient heterogeneities ((d) and (e)) are more sensitive to the effects of small cold spots than the other models considered

  10. Analysis of single blow effectiveness in non-uniform parallel plate regenerators

    DEFF Research Database (Denmark)

    Jensen, Jesper Buch; Bahl, Christian Robert Haffenden; Engelbrecht, Kurt

    2011-01-01

    Non-uniform distributions of plate spacings in parallel plate regenerators have been found to induce loss of performance. In this paper, it has been investigated how variations of three geometric parameters (the aspect ratio, the porosity, and the standard deviation of the plate spacing) affects...

  11. Additive non-uniform random sampling in superimposed fiber Bragg grating strain gauge

    Science.gov (United States)

    Ma, Y. C.; Liu, H. Y.; Yan, S. B.; Yang, Y. H.; Yang, M. W.; Li, J. M.; Tang, J.

    2013-05-01

    This paper demonstrates an additive non-uniform random sampling and interrogation method for dynamic and/or static strain gauge using a reflection spectrum from two superimposed fiber Bragg gratings (FBGs). The superimposed FBGs are designed to generate non-equidistant space of a sensing pulse train in the time domain during dynamic strain gauge. By combining centroid finding with smooth filtering methods, both the interrogation speed and accuracy are improved. A 1.9 kHz dynamic strain is measured by generating an additive non-uniform randomly distributed 2 kHz optical sensing pulse train from a mean 500 Hz triangular periodically changing scanning frequency.

  12. Characterization and Processing of Non-Uniformities in Back-Illuminated CCDs

    Science.gov (United States)

    Lemm, Alia D.; Della-Rose, Devin J.; Maddocks, Sally

    2018-01-01

    In astronomical photometry, Charged Coupled Device (CCD) detectors are used to achieve high precision photometry and must be properly calibrated to correct for noise and pixel non-uniformities. Uncalibrated images may contain bias offset, dark current, bias structure and uneven illumination. In addition, standard data reduction is often not sufficient to “normalize” imagery to single-digit millimagnitude (mmag) precision. We are investigating an apparent non-uniformity, or interference pattern, in a back-illuminated sensor, the Alta U-47, attached to a DFM Engineering 41-cm Ritchey-Chrétien f/8 telescope. Based on the amplitude of this effect, we estimate that instrument magnitude peak-to-valley deviations of 50 mmag or more may result. Our initial testing strongly suggests that reflected skylight from high pressure sodium city lights may be the cause of this interference pattern. Our research goals are twofold: to fully characterize this non-uniformity and to determine the best method to remove this interference pattern from our reduced CCD images.

  13. Errors due to non-uniform distribution of fat in dual X-ray absorptiometry of the lumbar spine

    International Nuclear Information System (INIS)

    Tothill, P.; Pye, D.W.

    1992-01-01

    Errors in spinal dual X-ray absorptiometry (DXA) were studied by analysing X-ray CT scans taken for diagnostic purposes on 20 patients representing a wide range of fat content. The mean difference between the fat thickness over the vertebral bodies and that over a background area in antero-posterior (AP) scanning was 6.7 ± 8.1 mm for men and 13.4 ± 4.7 mm for women. For AP scanning a non-uniform fat distribution leads to a mean overestimate of 0.029 g/cm 2 for men and 0.057 g/cm 2 for women. The error exceeded 0.1 g/cm 2 in 10% of slices. For lateral scanning the error exceeded 0.1 g/cm 2 (about 15% of normal) in a quarter of slices. (author)

  14. Experimental Investigation of Electron Cloud Containment in a Nonuniform Magnetic Field

    Science.gov (United States)

    Eninger, J. E.

    1974-01-01

    Dense clouds of electrons were generated and studied in an axisymmetric, nonuniform magnetic field created by a short solenoid. The operation of the experiment was similar to that of a low-pressure (approximately 0.000001 Torr) magnetron discharge. Discharge current characteristics are presented as a function of pressure, magnetic field strength, voltage, and cathode end-plate location. The rotation of the electron cloud is determined from the frequency of diocotron waves. In the space charge saturated regime of operation, the cloud is found to rotate as a solid body with frequency close to V sub a/phi sub a where V sub a is the anode voltage and phi suba is the total magnetic flux. This result indicates that, in regions where electrons are present, the magnetic field lines are electrostatic equipotentials (E bar, B bar = 0). Equilibrium electron density distributions suggested by this conditions are integrated with respect to total ionizing power and are found consistent with measured discharge currents.

  15. Experimental investigation of electron cloud containment in a nonuniform magnetic field

    International Nuclear Information System (INIS)

    Eninger, J.E.

    1974-05-01

    Dense clouds of electrons were generated and studied in an axisymmetric, nonuniform magnetic field created by a short solenoid. The operation of the experiment was similar to that of a low-pressure (approximately 0.000001 torr) magnetron discharge. Discharge current characteristics are presented as a function of pressure, magnetic field strength, voltage, and cathode end-plate location. The rotation of the electron cloud is determined from the frequency of diocotron waves. In the space charge saturated regime of operation, the cloud is found to rotate as a solid body with frequency close to V/sub a/phi/sub a/ where V/sub a/ is the anode voltage and phi/sub a/ is the total magnetic flux. This result indicates that, in regions where electrons are present, the magnetic field lines are electrostatic equipotentials (E bar, B bar = 0). Equilibrium electron density distributions suggested by this condition are integrated with respect to total ionizing power and are found consistent with measured discharge currents. (U.S.)

  16. Nonquasineutral electron vortices in nonuniform plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Angus, J. R.; Richardson, A. S.; Swanekamp, S. B.; Schumer, J. W. [Plasma Physics Division, Naval Research Laboratory, Washington, District of Columbia 20375 (United States); Ottinger, P. F. [Engility Corporation, Chantilly, Virginia 20151 (United States)

    2014-11-15

    Electron vortices are observed in the numerical simulation of current carrying plasmas on fast time scales where the ion motion can be ignored. In plasmas with nonuniform density n, vortices drift in the B × ∇n direction with a speed that is on the order of the Hall speed. This provides a mechanism for magnetic field penetration into a plasma. Here, we consider strong vortices with rotation speeds V{sub ϕ} close to the speed of light c where the vortex size δ is on the order of the magnetic Debye length λ{sub B}=|B|/4πen and the vortex is thus nonquasineutral. Drifting vortices are typically studied using the electron magnetohydrodynamic model (EMHD), which ignores the displacement current and assumes quasineutrality. However, these assumptions are not strictly valid for drifting vortices when δ ≈ λ{sub B}. In this paper, 2D electron vortices in nonuniform plasmas are studied for the first time using a fully electromagnetic, collisionless fluid code. Relatively large amplitude oscillations with periods that correspond to high frequency extraordinary modes are observed in the average drift speed. The drift speed W is calculated by averaging the electron velocity field over the vorticity. Interestingly, the time-averaged W from these simulations matches very well with W from the much simpler EMHD simulations even for strong vortices with order unity charge density separation.

  17. Magnetic reconnection through the current sheets as the universal process for plasma dynamics in nonuniform magnetic fields

    International Nuclear Information System (INIS)

    Frank, A.G.; Bogdanov, S.Yu.; Burilina, V.B.; Kyrie, N.P.

    1997-01-01

    Laboratory experiments are reported, in which we studied the possibilities of the formation of current sheets (CS) in different magnetic configurations, as well as the magnetic reconnection phenomena. In 2D magnetic fields with null-lines the CS formation was shown to be a typical process in both linear and nonlinear regimes. The problem of CS formation is of a fundamental importance in the general case of 3D magnetic configurations. We have revealed experimentally, that the formation of CS occurs in the various 3D configurations, both containing magnetic null-points and without them. At the same time, the CS parameters essentially depend on the local characteristics of the configuration. We may conclude therefore, that the self-organization of CS represents the universal process for the plasma dynamics in the nonuniform magnetic fields. (author)

  18. Taylor dispersion in wind-driven current

    Science.gov (United States)

    Li, Gang; Wang, Ping; Jiang, Wei-Quan; Zeng, Li; Li, Zhi; Chen, G. Q.

    2017-12-01

    Taylor dispersion associated with wind-driven currents in channels, shallow lakes and estuaries is essential to hydrological environmental management. For solute dispersion in a wind-driven current, presented in this paper is an analytical study of the evolution of concentration distribution. The concentration moments are intensively derived for an accurate presentation of the mean concentration distribution, up to the effect of kurtosis. The vertical divergence of concentration is then deduced by Gill's method of series expansion up to the fourth order. Based on the temporal evolution of the vertical concentration distribution, the dispersion process in the wind-driven current is concretely characterized. The uniform shear leads to a special symmetrical distribution of mean concentration free of skewness. The non-uniformity of vertical concentration is caused by convection and smeared out gradually by the effect of diffusion, but fails to disappear even at large times.

  19. A parametric transfer function methodology for analyzing reactive transport in nonuniform flow.

    Science.gov (United States)

    Luo, Jian; Cirpka, Olaf A; Fienen, Michael N; Wu, Wei-min; Mehlhorn, Tonia L; Carley, Jack; Jardine, Philip M; Criddle, Craig S; Kitanidis, Peter K

    2006-02-01

    We analyze reactive transport during in-situ bioremediation in a nonuniform flow field, involving multiple extraction and injection wells, by the method of transfer functions. Gamma distributions are used as parametric models of the transfer functions. Apparent parameters of classical transport models may be estimated from those of the gamma distributions by matching temporal moments. We demonstrate the method by application to measured data taken at a field experiment on bioremediation conducted in a multiple-well system in Oak Ridge, TN. Breakthrough curves (BTCs) of a conservative tracer (bromide) and a reactive compound (ethanol) are measured at multi-level sampling (MLS) wells and in extraction wells. The BTCs of both compounds are jointly analyzed to estimate the first-order degradation rate of ethanol. To quantify the tracer loss, we compare the approaches of using a scaling factor and a first-order decay term. Results show that by including a scaling factor both gamma distributions and inverse-Gaussian distributions (transfer functions according to the advection-dispersion equation) are suitable to approximate the transfer functions and estimate the reactive rate coefficients for both MLS and extraction wells. However, using a first-order decay term for tracer loss fails to describe the BTCs at the extraction well, which is affected by the nonuniform distribution of travel paths.

  20. Effects of Nonuniform Incident Illumination on the Thermal Performance of a Concentrating Triple Junction Solar Cell

    Directory of Open Access Journals (Sweden)

    Fahad Al-Amri

    2014-01-01

    Full Text Available A numerical heat transfer model was developed to investigate the temperature of a triple junction solar cell and the thermal characteristics of the airflow in a channel behind the solar cell assembly using nonuniform incident illumination. The effects of nonuniformity parameters, emissivity of the two channel walls, and Reynolds number were studied. The maximum solar cell temperature sharply increased in the presence of nonuniform light profiles, causing a drastic reduction in overall efficiency. This resulted in two possible solutions for solar cells to operate in optimum efficiency level: (i adding new receiver plate with higher surface area or (ii using forced cooling techniques to reduce the solar cell temperature. Thus, surface radiation exchanges inside the duct and Re significantly reduced the maximum solar cell temperature, but a conventional plain channel cooling system was inefficient for cooling the solar cell at medium concentrations when the system was subjected to a nonuniform light distribution. Nonuniformity of the incident light and surface radiation in the duct had negligible effects on the collected thermal energy.

  1. Additive non-uniform random sampling in superimposed fiber Bragg grating strain gauge

    International Nuclear Information System (INIS)

    Ma, Y C; Liu, H Y; Yan, S B; Li, J M; Tang, J; Yang, Y H; Yang, M W

    2013-01-01

    This paper demonstrates an additive non-uniform random sampling and interrogation method for dynamic and/or static strain gauge using a reflection spectrum from two superimposed fiber Bragg gratings (FBGs). The superimposed FBGs are designed to generate non-equidistant space of a sensing pulse train in the time domain during dynamic strain gauge. By combining centroid finding with smooth filtering methods, both the interrogation speed and accuracy are improved. A 1.9 kHz dynamic strain is measured by generating an additive non-uniform randomly distributed 2 kHz optical sensing pulse train from a mean 500 Hz triangular periodically changing scanning frequency. (paper)

  2. GEPOIS: a two dimensional nonuniform mesh Poisson solver

    International Nuclear Information System (INIS)

    Quintenz, J.P.; Freeman, J.R.

    1979-06-01

    A computer code is described which solves Poisson's equation for the electric potential over a two dimensional cylindrical (r,z) nonuniform mesh which can contain internal electrodes. Poisson's equation is solved over a given region subject to a specified charge distribution with either Neumann or Dirichlet perimeter boundary conditions and with Dirichlet boundary conditions on internal surfaces. The static electric field is also computed over the region with special care given to normal electric field components at boundary surfaces

  3. Many-junction photovoltaic device performance under non-uniform high-concentration illumination

    Science.gov (United States)

    Valdivia, Christopher E.; Wilkins, Matthew M.; Chahal, Sanmeet S.; Proulx, Francine; Provost, Philippe-Olivier; Masson, Denis P.; Fafard, Simon; Hinzer, Karin

    2017-09-01

    A parameterized 3D distributed circuit model was developed to calculate the performance of III-V solar cells and photonic power converters (PPC) with a variable number of epitaxial vertically-stacked pn junctions. PPC devices are designed with many pn junctions to realize higher voltages and to operate under non-uniform illumination profiles from a laser or LED. Performance impacts of non-uniform illumination were greatly reduced with increasing number of junctions, with simulations comparing PPC devices with 3 to 20 junctions. Experimental results using Azastra Opto's 12- and 20-junction PPC illuminated by an 845 nm diode laser show high performance even with a small gap between the PPC and optical fiber output, until the local tunnel junction limit is reached.

  4. Direct numerical simulation of turbulent pipe flow with nonuniform surface heat flux

    International Nuclear Information System (INIS)

    Satake, Shin-ichi; Kunugi, Tomoaki

    1998-01-01

    Turbulent transport computations of a scalar quantity for fully-developed turbulent pipe flow were carried out by means of a direct numerical simulation (DNS) procedure. In this paper, three wall-heating boundary conditions were considered as follows: Case-1) a uniform heat-flux condition along the wall, Case-2) a nonuniform wall-heating condition, that is, a cosine heat-flux distribution along the wall and Case-3) a nonuniform wall-heating condition with a constant temperature over a half of the pipe wall. The number of computational grids used in this paper is 256 x 128 x 128. Prandtl number of the working fluid is 0.71. The Nusselt number in case of Case-1 is in good agreement with the empirical correlation. In case of Case-3, the distributions of the turbulent quantity and the Nusselt number seem to be reasonable. However, as for Case-2, the distributions of the turbulent quantity and the Nusselt number seem to be unrealistic. Two numerical treatments of thermal boundary condition on the wall were applied and their results were discussed from the viewpoint of the turbulent transport feature. (author)

  5. Non-uniform approximations for sums of discrete m-dependent random variables

    OpenAIRE

    Vellaisamy, P.; Cekanavicius, V.

    2013-01-01

    Non-uniform estimates are obtained for Poisson, compound Poisson, translated Poisson, negative binomial and binomial approximations to sums of of m-dependent integer-valued random variables. Estimates for Wasserstein metric also follow easily from our results. The results are then exemplified by the approximation of Poisson binomial distribution, 2-runs and $m$-dependent $(k_1,k_2)$-events.

  6. Current distribution in conducting nanowire networks

    Science.gov (United States)

    Kumar, Ankush; Vidhyadhiraja, N. S.; Kulkarni, Giridhar U.

    2017-07-01

    Conducting nanowire networks find diverse applications in solar cells, touch-screens, transparent heaters, sensors, and various related transparent conducting electrode (TCE) devices. The performances of these devices depend on effective resistance, transmittance, and local current distribution in these networks. Although, there have been rigorous studies addressing resistance and transmittance in TCE, not much attention is paid on studying the distribution of current. Present work addresses this compelling issue of understanding current distribution in TCE networks using analytical as well as Monte-Carlo approaches. We quantified the current carrying backbone region against isolated and dangling regions as a function of wire density (ranging from percolation threshold to many multiples of threshold) and compared the wired connectivity with those obtained from template-based methods. Further, the current distribution in the obtained backbone is studied using Kirchhoff's law, which reveals that a significant fraction of the backbone (which is believed to be an active current component) may not be active for end-to-end current transport due to the formation of intervening circular loops. The study shows that conducting wire based networks possess hot spots (extremely high current carrying regions) which can be potential sources of failure. The fraction of these hot spots is found to decrease with increase in wire density, while they are completely absent in template based networks. Thus, the present work discusses unexplored issues related to current distribution in conducting networks, which are necessary to choose the optimum network for best TCE applications.

  7. Compensation for nonuniform attenuation in SPECT brain imaging

    International Nuclear Information System (INIS)

    Glick, S.J.; King, M.A.; Pan, T.S.; Soares, E.J.

    1996-01-01

    Accurate compensation for photon attenuation is needed to perform quantitative brain single-photon-emission computed tomographic (SPECT) imaging. Bellini's attenuation-compensation method has been used with a nonuniform attenuation map to account for the nonuniform attenuation properties of the head. Simulation studies using a three-dimensional (3-D) digitized anthropomorphic brain phantom were conducted to compare quantitative accuracy of reconstructions obtained with the nonuniform Bellini method to that obtained with the Chang method and to iterative reconstruction using maximum-likelihood expectation maximization (ML-EM). Using the Chang method and assuming the head to be a uniform attenuator gave reconstructions with an average bias of approximately 6-8%, whereas using the Bellini or the iterative ML-EM method with a nonuniform attenuation map gave an average bias of approximately 1%. The computation time required to implement nonuniform attenuation compensation with the Bellini algorithm is approximately equivalent to the time required to perform one iteration of ML-EM. Thus, using the Bellini method with a nonuniform attenuation map provides accurate compensation for photon attenuation within the head, and the method can be implemented in computation times suitable for routine clinical use

  8. Non-uniform sampling of NMR relaxation data

    DEFF Research Database (Denmark)

    Schwarz-Linnet, Troels; Teilum, Kaare

    2016-01-01

    The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors...... in the extracted dynamic parameters. By systematic reducing the coverage of the Nyquist grid of (15)N Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion datasets for four different proteins and performing a full data analysis of the resulting non-uniform sampled datasets, we have compared the performance...... of the multi-dimensional decomposition and iterative re-weighted least-squares algorithms in reconstructing spectra with accurate peak intensities. As long as a single fully sampled spectrum is included in a series of otherwise non-uniform sampled two-dimensional spectra, multi-dimensional decomposition...

  9. Nonuniformity correction of infrared cameras by reading radiance temperatures with a spatially nonhomogeneous radiation source

    International Nuclear Information System (INIS)

    Gutschwager, Berndt; Hollandt, Jörg

    2017-01-01

    We present a novel method of nonuniformity correction (NUC) of infrared cameras and focal plane arrays (FPA) in a wide optical spectral range by reading radiance temperatures and by applying a radiation source with an unknown and spatially nonhomogeneous radiance temperature distribution. The benefit of this novel method is that it works with the display and the calculation of radiance temperatures, it can be applied to radiation sources of arbitrary spatial radiance temperature distribution, and it only requires sufficient temporal stability of this distribution during the measurement process. In contrast to this method, an initially presented method described the calculation of NUC correction with the reading of monitored radiance values. Both methods are based on the recording of several (at least three) images of a radiation source and a purposeful row- and line-shift of these sequent images in relation to the first primary image. The mathematical procedure is explained in detail. Its numerical verification with a source of a predefined nonhomogeneous radiance temperature distribution and a thermal imager of a predefined nonuniform FPA responsivity is presented. (paper)

  10. Nonuniform Changes in the Distribution of Visual Attention from Visual Complexity and Action: A Driving Simulation Study.

    Science.gov (United States)

    Park, George D; Reed, Catherine L

    2015-02-01

    Researchers acknowledge the interplay between action and attention, but typically consider action as a response to successful attentional selection or the correlation of performance on separate action and attention tasks. We investigated how concurrent action with spatial monitoring affects the distribution of attention across the visual field. We embedded a functional field of view (FFOV) paradigm with concurrent central object recognition and peripheral target localization tasks in a simulated driving environment. Peripheral targets varied across 20-60 deg eccentricity at 11 radial spokes. Three conditions assessed the effects of visual complexity and concurrent action on the size and shape of the FFOV: (1) with no background, (2) with driving background, and (3) with driving background and vehicle steering. The addition of visual complexity slowed task performance and reduced the FFOV size but did not change the baseline shape. In contrast, the addition of steering produced not only shrinkage of the FFOV, but also changes in the FFOV shape. Nonuniform performance decrements occurred in proximal regions used for the central task and for steering, independent of interference from context elements. Multifocal attention models should consider the role of action and account for nonhomogeneities in the distribution of attention. © 2015 SAGE Publications.

  11. Properties of multilayer nonuniform holographic structures

    International Nuclear Information System (INIS)

    Pen, E F; Rodionov, Mikhail Yu

    2010-01-01

    Experimental results and analysis of properties of multilayer nonuniform holographic structures formed in photopolymer materials are presented. The theoretical hypotheses is proved that the characteristics of angular selectivity for the considered structures have a set of local maxima, whose number and width are determined by the thicknesses of intermediate layers and deep holograms and that the envelope of the maxima coincides with the selectivity contour of a single holographic array. It is also experimentally shown that hologram nonuniformities substantially distort shapes of selectivity characteristics: they become asymmetric, the local maxima differ in size and the depths of local minima reduce. The modelling results are made similar to experimental data by appropriately choosing the nonuniformity parameters. (imaging and image processing. holography)

  12. Stable and efficient retrospective 4D-MRI using non-uniformly distributed quasi-random numbers

    Science.gov (United States)

    Breuer, Kathrin; Meyer, Cord B.; Breuer, Felix A.; Richter, Anne; Exner, Florian; Weng, Andreas M.; Ströhle, Serge; Polat, Bülent; Jakob, Peter M.; Sauer, Otto A.; Flentje, Michael; Weick, Stefan

    2018-04-01

    The purpose of this work is the development of a robust and reliable three-dimensional (3D) Cartesian imaging technique for fast and flexible retrospective 4D abdominal MRI during free breathing. To this end, a non-uniform quasi random (NU-QR) reordering of the phase encoding (k y –k z ) lines was incorporated into 3D Cartesian acquisition. The proposed sampling scheme allocates more phase encoding points near the k-space origin while reducing the sampling density in the outer part of the k-space. Respiratory self-gating in combination with SPIRiT-reconstruction is used for the reconstruction of abdominal data sets in different respiratory phases (4D-MRI). Six volunteers and three patients were examined at 1.5 T during free breathing. Additionally, data sets with conventional two-dimensional (2D) linear and 2D quasi random phase encoding order were acquired for the volunteers for comparison. A quantitative evaluation of image quality versus scan times (from 70 s to 626 s) for the given sampling schemes was obtained by calculating the normalized mutual information (NMI) for all volunteers. Motion estimation was accomplished by calculating the maximum derivative of a signal intensity profile of a transition (e.g. tumor or diaphragm). The 2D non-uniform quasi-random distribution of phase encoding lines in Cartesian 3D MRI yields more efficient undersampling patterns for parallel imaging compared to conventional uniform quasi-random and linear sampling. Median NMI values of NU-QR sampling are the highest for all scan times. Therefore, within the same scan time 4D imaging could be performed with improved image quality. The proposed method allows for the reconstruction of motion artifact reduced 4D data sets with isotropic spatial resolution of 2.1  ×  2.1  ×  2.1 mm3 in a short scan time, e.g. 10 respiratory phases in only 3 min. Cranio-caudal tumor displacements between 23 and 46 mm could be observed. NU-QR sampling enables for stable 4D

  13. Current Distribution Characteristics of CFRP Panels

    Science.gov (United States)

    Yamamoto, Kazuo

    CFRP (Carbon Fiber Reinforced Plastic) is widely used in the structures of aircrafts, automobiles, wing turbines, and rockets because of its qualities of high mechanical strength, low weight, fatigue resistance, and dimensional stability. However, these structures are often at risk of being struck by lightning. When lightning strikes such structures and lightning current flows through the CFRP, it may be structurally damaged because of the impact of the lightning strike or ignitions between layers. If there are electronic systems near the CFRP, they may break down or malfunction because of the resulting electromagnetic disturbance. In fact, the generation mechanisms of these breakdowns and malfunctions depend on the current distribution in the CFRP. Hence, it is critical to clarify the current distribution in various kinds of CFRPs. In this study, two kinds of CFRP panels—one composed of quasi-isotropic lamination layers and the other composed of 0°/90° lamination layers of unidirectional CFRP prepregs—are used to investigate the dependence of current distribution on the nature of the lamination layers. The current distribution measurements and simulations for CFRP panels are compared with those for a same-sized aluminum plate. The knowledge of these current distribution characteristics would be very useful for designing the CFRP structures of aircrafts, automobiles, wing turbines, rockets, etc. in the future.

  14. Calculation of the fuel temperature coefficient of reactivity considering non-uniform radial temperature distribution in the fuel rod

    Energy Technology Data Exchange (ETDEWEB)

    Pazirandeh, Ali [Islamic Azad Univ., Tehran (Iran, Islamic Republic of). Science and Research Branch; Hooshyar Mobaraki, Almas

    2017-07-15

    The safe operation of a reactor is based on feedback models. In this paper we attempted to discuss the influence of a non-uniform radial temperature distribution on the fuel rod temperature coefficient of reactivity. The paper demonstrates that the neutron properties of a reactor core is based on effective temperature of the fuel to obtain the correct fuel temperature feedback. The value of volume-averaged temperature being used in the calculations of neutron physics with feedbacks would result in underestimating the probable event. In the calculation it is necessary to use the effective temperature of the fuel in order to provide correct accounting of the fuel temperature feedback. Fuel temperature changes in different zones of the core and consequently reactivity coefficient change are an important parameter for analysis of transient conditions. The restricting factor that compensates the inserted reactivity is the temperature reactivity coefficient and effective delayed neutron fraction.

  15. Effects of transverse temperature field nonuniformity on stress in silicon sheet growth

    Science.gov (United States)

    Mataga, P. A.; Hutchinson, J. W.; Chalmers, B.; Bell, R. O.; Kalejs, J. P.

    1987-01-01

    Stress and strain rate distributions are calculated using finite element analysis for steady-state growth of thin silicon sheet temperature nonuniformities imposed in the transverse (sheet width) dimension. Significant reductions in residual stress are predicted to occur for the case where the sheet edge is cooled relative to its center provided plastic deformation with high creep rates is present.

  16. Bridge density functional approximation for non-uniform hard core repulsive Yukawa fluid

    International Nuclear Information System (INIS)

    Zhou Shiqi

    2008-01-01

    In this work, a bridge density functional approximation (BDFA) (J. Chem. Phys. 112, 8079 (2000)) for a non-uniform hard-sphere fluid is extended to a non-uniform hard-core repulsive Yukawa (HCRY) fluid. It is found that the choice of a bulk bridge functional approximation is crucial for both a uniform HCRY fluid and a non-uniform HCRY fluid. A new bridge functional approximation is proposed, which can accurately predict the radial distribution function of the bulk HCRY fluid. With the new bridge functional approximation and its associated bulk second order direct correlation function as input, the BDFA can be used to well calculate the density profile of the HCRY fluid subjected to the influence of varying external fields, and the theoretical predictions are in good agreement with the corresponding simulation data. The calculated results indicate that the present BDFA captures quantitatively the phenomena such as the coexistence of solid-like high density phase and low density gas phase, and the adsorption properties of the HCRY fluid, which qualitatively differ from those of the fluids combining both hard-core repulsion and an attractive tail. (condensed matter: structure, thermal and mechanical properties)

  17. A stability criterion for HNFDE with non-uniform delays

    International Nuclear Information System (INIS)

    Liu Xingwen; Zhong Shouming; Zhang Fengli

    2005-01-01

    Stability of functional differential equations (FDE) is an increasingly important problem in both science and engineering. Delays, whether uniform or non-uniform, play an important role in the dynamics of a system. Since non-uniform delay is more general and less focused than uniform delay, this paper concentrates on the stability of high-order neutral functional differential equations (HNFDE) with non-uniform delay, and proposes a sufficient condition for it. This result may be widely helpful, thanks to the frequent emergence of a HNFDE with non-uniform delay in various fields. Its effectiveness is illustrated by some examples

  18. A tuning method for nonuniform traveling-wave accelerating structures

    International Nuclear Information System (INIS)

    Gong Cunkui; Zheng Shuxin; Shao Jiahang; Jia Xiaoyu; Chen Huaibi

    2013-01-01

    The tuning method of uniform traveling-wave structures based on non-resonant perturbation field distribution measurement has been widely used in tuning both constant-impedance and constant-gradient structures. In this paper, the method of tuning nonuniform structures is proposed on the basis of the above theory. The internal reflection coefficient of each cell is obtained from analyzing the normalized voltage distribution. A numerical simulation of tuning process according to the coupled cavity chain theory has been done and the result shows each cell is in right phase advance after tuning. The method will be used in the tuning of a disk-loaded traveling-wave structure being developed at the Accelerator Laboratory, Tsinghua University. (authors)

  19. Non-uniform temperature field measurement and simulation of a radio telescope’s main reflector under solar radiation

    International Nuclear Information System (INIS)

    Chen, Deshen; Qian, Hongliang; Wang, Huajie; Zhang, Gang; Fan, Feng; Shen, Shizhao

    2017-01-01

    Highlights: • Solar non-uniform temperature field test of a telescope’s reflector is conducted initially. • Time-varying distribution regularities are analyzed contrastively. • Simulation methods are proposed involving environmental factors and self-shadowing. • Refined discrimination method for the shadow distribution is put forward. • Validity of simulation methods is evaluated with the experimental data. - Abstract: To improve the ability of deep-space exploration, many astronomers around the world are actively engaged in the construction of large-aperture and high-precision radio telescopes. The temperature effect is one of three main factors affecting the reflector accuracy of radio telescopes. To study the daily non-uniform temperature field of the main reflector, experimental studies are first carried out with a 3-m-aperture radio telescope model. According to the test results for 16 working conditions, the distribution rule and time-varying regularity of the daily temperature field are summarized initially. Next, theoretical methods for the temperature field of the main reflector are studied considering multiple environmental parameters and self-shadows. Finally, the validity of the theoretical methods is evaluated with test results. The experimental study demonstrates that the non-uniform temperature distribution of the main reflector truly exists and should not be overlooked, and that the theoretical methods for the reflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision radio telescopes.

  20. Quasiparticles in non-uniformly magnetized plasma

    International Nuclear Information System (INIS)

    Sosenko, P.P.

    1994-01-01

    A quasiparticle concept is generalized for the case of non-uniformly magnetized plasma. Exact and reduced continuity equations for the microscopic density in the quasiparticle phase space are derived, and the nature of quasiparticles is analyzed. The theory is developed for the general case of relativistic particles in electromagnetic fields, besides non-uniform but stationary magnetic fields. Effects of non-stationary magnetic fields are briefly investigated also. 26 refs

  1. Statistical evaluation of unobserved nonuniform corrosion in A216 steel

    International Nuclear Information System (INIS)

    Pulsipher, B.A.

    1988-07-01

    Tests designed to promote nonuniform corrosion have been conducted at PNL on A216 steel. In all of the tests performed to date, there have been no manifestations of significant nonuniform corrosion. Although this may suggest that nonuniform corrosion in A216 steel may not be a significant problem in the nuclear waste repository, a question arises as to whether enough tests have been conducted for a sufficient length of time to rule out nonuniform corrosion of A216 steel. In this report, a method for determining the required number of tests is examined for two of the mechanisms of nonuniform corrosion: pitting and crevice corrosion

  2. Tunable pinning effects produced by non-uniform antidot arrays in YBCO thin films

    Energy Technology Data Exchange (ETDEWEB)

    George, J.; Jones, A.; Al-Qurainy, M. [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW (Australia); Fedoseev, S.A. [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW (Australia); Centre for Medical Radiation Physics, University of Wollongong, NSW (Australia); Rosenfeld, A. [Centre for Medical Radiation Physics, University of Wollongong, NSW (Australia); Pan, A.V. [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW (Australia); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2017-04-15

    Uniform, graded and spaced arrays of 3 μm triangular antidots in pulsed laser deposited YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) superconducting thin films are compared by examining the improvements in the critical current density J{sub c} they produced. The comparison is made to establish the role of their lithographically defined (non-)uniformity and the effectiveness to control and/or enhance the critical current density. It is found that almost all types of non-uniform arrays, including graded ones enhance J{sub c} over the broad applied magnetic field and temperature range due to the modified critical state. Whereas uniform arrays of antidots either reduce or produce no effect on J{sub c} compared to the original (as-deposited) thin films. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Strain distributions in nano-onions with uniform and non-uniform compositions

    International Nuclear Information System (INIS)

    Duan, H L; Karihaloo, B L; Wang, J; Yi, X

    2006-01-01

    Nano-onions are ellipsoidal or spherical particles consisting of a core surrounded by concentric shells of nanometre size. Nano-onions produced by self-assembly and colloidal techniques have different structures and compositions, and thus differ in the state of strains. The mismatch of the thermal expansion coefficients and lattice constants between neighbouring shells induces stress/strain fields in the core and shells, which in turn affect their physical/mechanical properties and/or the properties of the composites containing them. In this paper, the strains in embedded and free-standing nano-onions with uniform and non-uniform compositions are studied in detail. It is found that the strains in the nano-onions can be modified by adjusting their compositions and structures. The results are useful for the band structure engineering of semiconductor nano-onions

  4. Effective electrodiffusion equation for non-uniform nanochannels.

    Science.gov (United States)

    Marini Bettolo Marconi, Umberto; Melchionna, Simone; Pagonabarraga, Ignacio

    2013-06-28

    We derive a one-dimensional formulation of the Planck-Nernst-Poisson equation to describe the dynamics of a symmetric binary electrolyte in channels whose section is nanometric and varies along the axial direction. The approach is in the spirit of the Fick-Jacobs diffusion equation and leads to a system of coupled equations for the partial densities which depends on the charge sitting at the walls in a non-trivial fashion. We consider two kinds of non-uniformities, those due to the spatial variation of charge distribution and those due to the shape variation of the pore and report one- and three-dimensional solutions of the electrokinetic equations.

  5. R.f.-induced steps in mutually coupled, two-dimensional distributed Josephson tunnel junctions

    International Nuclear Information System (INIS)

    Klein, U.; Dammschneider, P.

    1991-01-01

    This paper reports on the amplitudes of the current steps in the I-V characteristics of mutually coupled two-dimensional distributed Josephson tunnel junctions driven by microwaves. For this purpose we use a numerical computation algorithm based on a planar resonator model for the individual Josephson tunnel junctions to calculate the d.c. current density distribution. In addition to the fundamental microwave frequency, harmonic contents of the tunneling current are also considered. The lateral dimensions of the individual junctions are small compared to the microwave wavelength and the Josephson penetration depth, giving an almost constant current density distribution. Therefore, the coupled junctions can give much greater step amplitudes than a single junction with an equal tunneling area, because of their nonuniform current density distribution

  6. Nonuniformity mitigation of beam illumination in heavy ion inertial fusion

    International Nuclear Information System (INIS)

    Kawata, S; Noguchi, K; Suzuki, T; Kurosaki, T; Barada, D; Ogoyski, A I; Zhang, W; Xie, J; Zhang, H; Dai, D

    2014-01-01

    In inertial fusion, a target DT fuel should be compressed to typically 1000 times the solid density. The target implosion nonuniformity is introduced by a driver beam’s illumination nonuniformity, for example. The target implosion should be robust against the implosion nonuniformities. In this paper, the requirement for implosion uniformity is first discussed. The implosion non-uniformity should be less than a few percent. The implosion dynamics is also briefly reviewed in heavy ion inertial fusion (HIF). Heavy ions deposit their energy inside the target energy absorber, and the energy deposition layer is rather thick, depending on the ion particle energy. Then nonuniformity mitigation mechanisms of the heavy ion beam (HIB) illumination in HIF are discussed. A density valley appears in the energy absorber, and the large-scale density valley also works as a radiation energy confinement layer, which contributes to a radiation energy smoothing. In HIF, wobbling heavy ion beam illumination was also introduced to realize a uniform implosion. The wobbling HIB axis oscillation is precisely controlled. In the wobbling HIBs’ illumination, the illumination nonuniformity oscillates in time and space on an HIF target. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs’ illumination nonuniformity by its smoothing effect on the HIB illumination nonuniformity and also by a growth mitigation effect on the Rayleigh–Taylor instability. (invited comment)

  7. Analyte preconcentration in nanofluidic channels with nonuniform zeta potential

    Science.gov (United States)

    Eden, A.; McCallum, C.; Storey, B. D.; Pennathur, S.; Meinhart, C. D.

    2017-12-01

    It is well known that charged analytes in the presence of nonuniform electric fields concentrate at locations where the relevant driving forces balance, and a wide range of ionic stacking and focusing methods are commonly employed to leverage these physical mechanisms in order to improve signal levels in biosensing applications. In particular, nanofluidic channels with spatially varying conductivity distributions have been shown to provide increased preconcentration of charged analytes due to the existence of a finite electric double layer (EDL), in which electrostatic attraction and repulsion from charged surfaces produce nonuniform transverse ion distributions. In this work, we use numerical simulations to show that one can achieve greater levels of sample accumulation by using field-effect control via wall-embedded electrodes to tailor the surface potential heterogeneity in a nanochannel with overlapped EDLs. In addition to previously demonstrated stacking and focusing mechanisms, we find that the coupling between two-dimensional ion distributions and the axial electric field under overlapped EDL conditions can generate an ion concentration polarization interface in the middle of the channel. Under an applied electric field, this interface can be used to concentrate sample ions between two stationary regions of different surface potential and charge density. Our numerical model uses the Poisson-Nernst-Planck system of equations coupled with the Stokes equation to demonstrate the phenomenon, and we discuss in detail the driving forces behind the predicted sample enhancement. The numerical velocity and salt concentration profiles exhibit good agreement with analytical results from a simplified one-dimensional area-averaged model for several limiting cases, and we show predicted amplification ratios of up to 105.

  8. Spatial model of the gecko foot hair: functional significance of highly specialized non-uniform geometry.

    Science.gov (United States)

    Filippov, Alexander E; Gorb, Stanislav N

    2015-02-06

    One of the important problems appearing in experimental realizations of artificial adhesives inspired by gecko foot hair is so-called clusterization. If an artificially produced structure is flexible enough to allow efficient contact with natural rough surfaces, after a few attachment-detachment cycles, the fibres of the structure tend to adhere one to another and form clusters. Normally, such clusters are much larger than original fibres and, because they are less flexible, form much worse adhesive contacts especially with the rough surfaces. Main problem here is that the forces responsible for the clusterization are the same intermolecular forces which attract fibres to fractal surface of the substrate. However, arrays of real gecko setae are much less susceptible to this problem. One of the possible reasons for this is that ends of the seta have more sophisticated non-uniformly distributed three-dimensional structure than that of existing artificial systems. In this paper, we simulated three-dimensional spatial geometry of non-uniformly distributed branches of nanofibres of the setal tip numerically, studied its attachment-detachment dynamics and discussed its advantages versus uniformly distributed geometry.

  9. Potential distribution of a nonuniformly charged ellipsoid

    International Nuclear Information System (INIS)

    Kiwamoto, Y.; Aoki, J.; Soga, Y.

    2004-01-01

    A convenient formula is obtained for fast calculation of the three-dimensional potential distribution associated with a spatially varying charge-density distribution by reconstructing it as a superposed set of nested spheroidal shells. It is useful for experimental analyses of near-equilibrium states of non-neutral plasmas and for quick evaluation of the gravity field associated with stellar mass distributions

  10. Deformation of Two-Dimensional Nonuniform-Membrane Red Blood Cells Simulated by a Lattice Boltzmann Model

    International Nuclear Information System (INIS)

    Hua-Bing, Li; Li, Jin; Bing, Qiu

    2008-01-01

    To study two-dimensional red blood cells deforming in a shear Bow with the membrane nonuniform on the rigidity and mass, the membrane is discretized into equilength segments. The fluid inside and outside the red blood cell is simulated by the D2Q9 lattice Boltzmann model and the hydrodynamic forces exerted on the membrane from the inner and outer of the red blood cell are calculated by a stress-integration method. Through the global deviation from the curvature of uniform-membrane, we find that when the membrane is nonuniform on the rigidity, the deviation first decreases with the time increases and implies that the terminal profile of the red blood cell is static. To a red blood cell with the mass nonuniform on the membrane, the deviation becomes more large, and the mass distribution affects the profile of the two sides of the flattened red blood cell in a shear flow. (fundamental areas of phenomenology(including applications))

  11. Nonuniform sampling by quantiles

    Science.gov (United States)

    Craft, D. Levi; Sonstrom, Reilly E.; Rovnyak, Virginia G.; Rovnyak, David

    2018-03-01

    A flexible strategy for choosing samples nonuniformly from a Nyquist grid using the concept of statistical quantiles is presented for broad classes of NMR experimentation. Quantile-directed scheduling is intuitive and flexible for any weighting function, promotes reproducibility and seed independence, and is generalizable to multiple dimensions. In brief, weighting functions are divided into regions of equal probability, which define the samples to be acquired. Quantile scheduling therefore achieves close adherence to a probability distribution function, thereby minimizing gaps for any given degree of subsampling of the Nyquist grid. A characteristic of quantile scheduling is that one-dimensional, weighted NUS schedules are deterministic, however higher dimensional schedules are similar within a user-specified jittering parameter. To develop unweighted sampling, we investigated the minimum jitter needed to disrupt subharmonic tracts, and show that this criterion can be met in many cases by jittering within 25-50% of the subharmonic gap. For nD-NUS, three supplemental components to choosing samples by quantiles are proposed in this work: (i) forcing the corner samples to ensure sampling to specified maximum values in indirect evolution times, (ii) providing an option to triangular backfill sampling schedules to promote dense/uniform tracts at the beginning of signal evolution periods, and (iii) providing an option to force the edges of nD-NUS schedules to be identical to the 1D quantiles. Quantile-directed scheduling meets the diverse needs of current NUS experimentation, but can also be used for future NUS implementations such as off-grid NUS and more. A computer program implementing these principles (a.k.a. QSched) in 1D- and 2D-NUS is available under the general public license.

  12. A non-uniform expansion mechanical safety model of the stent.

    Science.gov (United States)

    Yang, J; Huang, N; Du, Q

    2009-01-01

    Stents have a serial unstable structure that readily leads to non-uniform expansion. Non-uniform expansion in turn creates a stent safety problem. We explain how a stent may be simplified to a serial unstable structure, and present a method to calculate the non-uniform expansion of the stent on the basis of the serial unstable structure. We propose a safety criterion based on the expansion displacement instead of the strain, and explain that the parameter Rd, the ratio of the maximum displacement of the elements to normal displacement, is meaningful to assess the safety level of the stent. We also examine how laser cutting influences non-uniform expansion. The examples illustrate how to calculate the parameter Rd to assess non-uniform expansion of the stent, and demonstrate how the laser cutting offset and strengthening coefficient of the material influence the stent expansion behaviour. The methods are valuable for assessing stent safety due to non-uniform expansion.

  13. Planned studies of charge collection in non-uniformly irradiated Si and GaAs detectors

    International Nuclear Information System (INIS)

    Rosenfeld, A.; Reinhard, M.; Carolan, M.; Kaplan, G.; Lerch, M.; Alexiev, D.

    1995-01-01

    The aim of this project is to study the time and amplitude characteristics of silicon ion-implanted detectors non-uniformly irradiated with fast neutrons in order to predict their radiation behaviour in the LHC and space. It is expected in such detectors increases of the charge deficit due to trapping by large scale traps and transient time increases due to the reduction of the mobility. The theoretical model will be modified to describe the charge kinetics in the electrical field of the detector created by a non uniform space charge distribution. Experimental confirmation techniques are needed to develop non uniform predictable damage of silicon detectors using fast neutron sources (accelerators, reactors) and to study peculiarities of the charge transport in different parts of the detector. In parallel to experimental research will be started the theoretical development of the charge transport model for non-uniform distribution of space charge in the depletion layer (Neff). The model will include the linear distribution of Neff(y) along the detector as well as the change of sign of Neff (conversion from n to p type of silicon) inside the detector

  14. Current distribution characteristics of superconducting parallel circuits

    International Nuclear Information System (INIS)

    Mori, K.; Suzuki, Y.; Hara, N.; Kitamura, M.; Tominaka, T.

    1994-01-01

    In order to increase the current carrying capacity of the current path of the superconducting magnet system, the portion of parallel circuits such as insulated multi-strand cables or parallel persistent current switches (PCS) are made. In superconducting parallel circuits of an insulated multi-strand cable or a parallel persistent current switch (PCS), the current distribution during the current sweep, the persistent mode, and the quench process were investigated. In order to measure the current distribution, two methods were used. (1) Each strand was surrounded with a pure iron core with the air gap. In the air gap, a Hall probe was located. The accuracy of this method was deteriorated by the magnetic hysteresis of iron. (2) The Rogowski coil without iron was used for the current measurement of each path in a 4-parallel PCS. As a result, it was shown that the current distribution characteristics of a parallel PCS is very similar to that of an insulated multi-strand cable for the quench process

  15. Alternative methods for evaluation of non-uniformity in nuclear medicine images

    International Nuclear Information System (INIS)

    Rasaneh, S.; Rajabi, H.; Hajizadeh, E.

    2005-01-01

    Non-uniformity test is the most essential in daily quality control procedures of nuclear medicine equipment's. However, the calculation of non-uniformity is hindered due to high level of noise in nuclear medicine data. Non-uniformity may be considered as a type of systematic error while noise is certainly a random error. The present methods of uniformity evaluation are not able to distinguish between systematic and random error and therefore produce incorrect results when noise is significant. In the present study, two hypothetical methods have been tested for evaluation of non-uniformity in nuclear medicine images. Materials and Methods: Using the Monte Carlo method, uniform and non-uniform flood images of different matrix sizes and different counts were generated. The uniformity of the images was calculated using the conventional method and proposed methods. The results were compared with the known non-uniformity data of simulated images. Results: It was observed that the value of integral uniformity never went below the recommended values except in small matrix size of high counts (more than 80 millions counts). The differential uniformity was quite insensitive to the degree of non-uniformity in large matrix size. Matrix size of 64*64 was only found to be suitable for the calculation of differential uniformity. It was observed that in uniform images, a small amount of non-uniformity changes the p-value of Kolmogorov-Smirnov test and noise amplitude of fast fourier transformation test significantly while the conventional methods failed to detect the nonuniformity. Conclusion: The conventional methods do not distinguish noise, which is always present in the data and occasional non-uniformity at low count density. In a uniform intact flood image, the difference between maximum and minimum pixel count (the value of integral uniformity) is much more than the recommended values for non-uniformity. After filtration of image, this difference decreases, but remains high

  16. Non-Uniformity Correction Using Nonlinear Characteristic Performance Curves for Calibration

    Science.gov (United States)

    Lovejoy, McKenna Roberts

    Infrared imaging is an expansive field with many applications. Advances in infrared technology have lead to a greater demand from both commercial and military sectors. However, a known problem with infrared imaging is its non-uniformity. This non-uniformity stems from the fact that each pixel in an infrared focal plane array has its own photoresponse. Many factors such as exposure time, temperature, and amplifier choice affect how the pixels respond to incoming illumination and thus impact image uniformity. To improve performance non-uniformity correction (NUC) techniques are applied. Standard calibration based techniques commonly use a linear model to approximate the nonlinear response. This often leaves unacceptable levels of residual non-uniformity. Calibration techniques often have to be repeated during use to continually correct the image. In this dissertation alternates to linear NUC algorithms are investigated. The goal of this dissertation is to determine and compare nonlinear non-uniformity correction algorithms. Ideally the results will provide better NUC performance resulting in less residual non-uniformity as well as reduce the need for recalibration. This dissertation will consider new approaches to nonlinear NUC such as higher order polynomials and exponentials. More specifically, a new gain equalization algorithm has been developed. The various nonlinear non-uniformity correction algorithms will be compared with common linear non-uniformity correction algorithms. Performance will be compared based on RMS errors, residual non-uniformity, and the impact quantization has on correction. Performance will be improved by identifying and replacing bad pixels prior to correction. Two bad pixel identification and replacement techniques will be investigated and compared. Performance will be presented in the form of simulation results as well as before and after images taken with short wave infrared cameras. The initial results show, using a third order

  17. Spatial and temporal distribution of ionospheric currents-4: altitude ...

    African Journals Online (AJOL)

    (a) The continuous distribution of current density model reproduces the altitude distribution parameters of EEJ current density very well, (b) the altitude distribution parameters of EEJ current density in India and Peru are not significantly different and (c) The altitude distribution parameters of EEJ current density from rockets ...

  18. Subrandom methods for multidimensional nonuniform sampling.

    Science.gov (United States)

    Worley, Bradley

    2016-08-01

    Methods of nonuniform sampling that utilize pseudorandom number sequences to select points from a weighted Nyquist grid are commonplace in biomolecular NMR studies, due to the beneficial incoherence introduced by pseudorandom sampling. However, these methods require the specification of a non-arbitrary seed number in order to initialize a pseudorandom number generator. Because the performance of pseudorandom sampling schedules can substantially vary based on seed number, this can complicate the task of routine data collection. Approaches such as jittered sampling and stochastic gap sampling are effective at reducing random seed dependence of nonuniform sampling schedules, but still require the specification of a seed number. This work formalizes the use of subrandom number sequences in nonuniform sampling as a means of seed-independent sampling, and compares the performance of three subrandom methods to their pseudorandom counterparts using commonly applied schedule performance metrics. Reconstruction results using experimental datasets are also provided to validate claims made using these performance metrics. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. A Method of Sky Ripple Residual Nonuniformity Reduction for a Cooled Infrared Imager and Hardware Implementation.

    Science.gov (United States)

    Li, Yiyang; Jin, Weiqi; Li, Shuo; Zhang, Xu; Zhu, Jin

    2017-05-08

    Cooled infrared detector arrays always suffer from undesired ripple residual nonuniformity (RNU) in sky scene observations. The ripple residual nonuniformity seriously affects the imaging quality, especially for small target detection. It is difficult to eliminate it using the calibration-based techniques and the current scene-based nonuniformity algorithms. In this paper, we present a modified temporal high-pass nonuniformity correction algorithm using fuzzy scene classification. The fuzzy scene classification is designed to control the correction threshold so that the algorithm can remove ripple RNU without degrading the scene details. We test the algorithm on a real infrared sequence by comparing it to several well-established methods. The result shows that the algorithm has obvious advantages compared with the tested methods in terms of detail conservation and convergence speed for ripple RNU correction. Furthermore, we display our architecture with a prototype built on a Xilinx Virtex-5 XC5VLX50T field-programmable gate array (FPGA), which has two advantages: (1) low resources consumption; and (2) small hardware delay (less than 10 image rows). It has been successfully applied in an actual system.

  20. Nonuniform Sparse Data Clustering Cascade Algorithm Based on Dynamic Cumulative Entropy

    Directory of Open Access Journals (Sweden)

    Ning Li

    2016-01-01

    Full Text Available A small amount of prior knowledge and randomly chosen initial cluster centers have a direct impact on the accuracy of the performance of iterative clustering algorithm. In this paper we propose a new algorithm to compute initial cluster centers for k-means clustering and the best number of the clusters with little prior knowledge and optimize clustering result. It constructs the Euclidean distance control factor based on aggregation density sparse degree to select the initial cluster center of nonuniform sparse data and obtains initial data clusters by multidimensional diffusion density distribution. Multiobjective clustering approach based on dynamic cumulative entropy is adopted to optimize the initial data clusters and the best number of the clusters. The experimental results show that the newly proposed algorithm has good performance to obtain the initial cluster centers for the k-means algorithm and it effectively improves the clustering accuracy of nonuniform sparse data by about 5%.

  1. Pattern of diffusion-limited aggregation on nonuniform substrate

    CERN Document Server

    Ouyang Wen Ze; Zou Xian Wu; Jin Zhun Zhi

    2003-01-01

    Pattern of diffusion-limited aggregation (DLA) on nonuniform substrate was investigated by computer simulations. The nonuniform substrates are represented by Leath percolations with the probability p. p stands for the degree of nonuniformity and takes values in the range p sub c<=p<=1, where p sub c is the threshold of percolation. The DLA cluster grows up on the Leath percolation substrate. The patterns of the DLA clusters appear asymmetrical and nonuniform, and the branches are relative few for the case p is close to p sub c. In addition, the pattern depends on the shape of substrate. As p increases from p sub c to 1, cluster changes to pure DLA gradually. Correspondingly, the fractal dimension increases from 1.46 to 1.68. Also, the random walks on Leath percolations through the range p sub c<=p<=1 were examined. Our simulations show the Honda-Toyoki-Matsushita relation is still reasonable for fractional dimensional systems.

  2. Axial mercury segregation in direct current operated low-pressure argon-mercury gas discharge: Part I. Experimental

    NARCIS (Netherlands)

    Gielen, J.W.A.M.; de Groot, S.; Dijk, van J.; Mullen, van der J.J.A.M.

    2004-01-01

    Due to cataphoresis, axial segregation of mercury will occur when the gas discharge of a fluorescent lamp is operated by means of a direct current. A consequence of this is a non-uniform axial luminance distribution along the lamp. To determine the degree of axial mercury segregation experimentally,

  3. Non-Uniform Cathode Emission Studies of a MIG Gun

    Science.gov (United States)

    Marchewka, C. D.; Shapiro, M. A.; Sirigiri, J. R.; Temkin, R. J.

    2004-11-01

    We present the initial results of the modeling of the effect of emission non-uniformity in 96 kV, 40 A Magnetron Injection Gun (MIG) of a 1.5 MW 110 GHz gyrotron using a 3D gun simulation code. The azimuthal emission nonuniformity can lead to increased mode competition and an overall decreased efficiency of the device [1]. The electron beam is modeled from the cathode to a downstream position where the velocity spread saturates using the AMAZE 3D suite of codes. After bench marking the results of the 3D code with 2D codes such as TRAK2D and EGUN, the emitter was modified to simulate asymmetric emission from the cathode to gain an understanding into the effects of inhomogeneous beam current density on the velocity spread and pitch factor of the electron beam. [1] G. S. Nusinovich, A.N. Vlasov, M. Botton, T. M. Antonsen, Jr., S. Cauffman, K. Felch, ``Effect of the azimuthal inhomogeneity of electron emission on gyrotron operation,'' Phys. Plasmas, vol. 8, no. 7, pp. 3473-3479, 2001

  4. The use of non-uniform drowning terminology: a follow-up study.

    Science.gov (United States)

    Schmidt, Andrew C; Sempsrott, Justin R; Szpilman, David; Queiroga, Ana Catarina; Davison, Matt S; Zeigler, Ryan J; McAlister, Sean J

    2017-07-17

    In 2002, the World Congress on Drowning developed a uniform definition for drowning. The aim of this study is to determine the prevalence of "non-uniform drowning terminology" (NUDT) and "non-uniform drowning definitions" (NUDD) in peer-reviewed scientific literature from 2010 to 2016, and compare these findings with those from our unpublished study performing a similar analysis on literature from 2003 to 2010. A systematic review was performed using drowning-specific search terms in Pubmed and Web of Science. Titles and abstracts published between July 2010 and January 2016 were screened for relevance to the study focus. Articles meeting screening criteria were reviewed for exclusion criteria to produce the final group of studies. These articles were reviewed by four reviewers for NUDT and NUDD. The Fisher exact test was used to determine any statistically significant changes. The final group of studies included 167 articles. A total of 53 articles (32%) utilized NUDT, with 100% of these including the term "near drowning". The proportion of articles utilizing NUDT was significantly less than reported by our previous study (p drowning (uniform or non-uniform), with 15% of these utilizing NUDD. Our study reveals a statistically significant improvement over the past thirteen years in the use of uniform drowning terminology in peer-reviewed scientific literature, although year-to-year variability over the current study period does not yield an obvious trend. Of the articles reviewed during the 2010-2016 study period, 32% included outdated and non-uniform drowning terminology and definitions. While this reveals an absolute decrease of 11% as compared with the previous study period (2003-2010), there is still significant room for improvement.

  5. Non-uniform distribution pattern for differentially expressed genes of transgenic rice Huahui 1 at different developmental stages and environments.

    Directory of Open Access Journals (Sweden)

    Zhi Liu

    Full Text Available DNA microarray analysis is an effective method to detect unintended effects by detecting differentially expressed genes (DEG in safety assessment of genetically modified (GM crops. With the aim to reveal the distribution of DEG of GM crops under different conditions, we performed DNA microarray analysis using transgenic rice Huahui 1 (HH1 and its non-transgenic parent Minghui 63 (MH63 at different developmental stages and environmental conditions. Considerable DEG were selected in each group of HH1 under different conditions. For each group of HH1, the number of DEG was different; however, considerable common DEG were shared between different groups of HH1. These findings suggested that both DEG and common DEG were adequate for investigation of unintended effects. Furthermore, a number of significantly changed pathways were found in all groups of HH1, indicating genetic modification caused everlasting changes to plants. To our knowledge, our study for the first time provided the non-uniformly distributed pattern for DEG of GM crops at different developmental stages and environments. Our result also suggested that DEG selected in GM plants at specific developmental stage and environment could act as useful clues for further evaluation of unintended effects of GM plants.

  6. A Test of Thick-Target Nonuniform Ionization as an Explanation for Breaks in Solar Flare Hard X-Ray Spectra

    Science.gov (United States)

    Holman, gordon; Dennis Brian R.; Tolbert, Anne K.; Schwartz, Richard

    2010-01-01

    Solar nonthermal hard X-ray (HXR) flare spectra often cannot be fitted by a single power law, but rather require a downward break in the photon spectrum. A possible explanation for this spectral break is nonuniform ionization in the emission region. We have developed a computer code to calculate the photon spectrum from electrons with a power-law distribution injected into a thick-target in which the ionization decreases linearly from 100% to zero. We use the bremsstrahlung cross-section from Haug (1997), which closely approximates the full relativistic Bethe-Heitler cross-section, and compare photon spectra computed from this model with those obtained by Kontar, Brown and McArthur (2002), who used a step-function ionization model and the Kramers approximation to the cross-section. We find that for HXR spectra from a target with nonuniform ionization, the difference (Delta-gamma) between the power-law indexes above and below the break has an upper limit between approx.0.2 and 0.7 that depends on the power-law index delta of the injected electron distribution. A broken power-law spectrum with a. higher value of Delta-gamma cannot result from nonuniform ionization alone. The model is applied to spectra obtained around the peak times of 20 flares observed by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI from 2002 to 2004 to determine whether thick-target nonuniform ionization can explain the measured spectral breaks. A Monte Carlo method is used to determine the uncertainties of the best-fit parameters, especially on Delta-gamma. We find that 15 of the 20 flare spectra require a downward spectral break and that at least 6 of these could not be explained by nonuniform ionization alone because they had values of Delta-gamma with less than a 2.5% probability of being consistent with the computed upper limits from the model. The remaining 9 flare spectra, based on this criterion, are consistent with the nonuniform ionization model.

  7. Free vibration analysis of a robotic fish based on a continuous and non-uniform flexible backbone with distributed masses

    Science.gov (United States)

    Coral, W.; Rossi, C.; Curet, O. M.

    2015-12-01

    This paper presents a Differential Quadrature Element Method for free transverse vibration of a robotic fish based on a continuous and non-uniform flexible backbone with distributed masses (fish ribs). The proposed method is based on the theory of a Timoshenko cantilever beam. The effects of the masses (number, magnitude and position) on the value of natural frequencies are investigated. Governing equations, compatibility and boundary conditions are formulated according to the Differential Quadrature rules. The convergence, efficiency and accuracy are compared to other analytical solution proposed in the literature. Moreover, the proposed method has been validate against the physical prototype of a flexible fish backbone. The main advantages of this method, compared to the exact solutions available in the literature are twofold: first, smaller computational cost and second, it allows analysing the free vibration in beams whose section is an arbitrary function, which is normally difficult or even impossible with other analytical methods.

  8. The effects of non-uniform flow velocity on vibrations of single-walled carbon nanotube conveying fluid

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi-Goughari, Moslem [Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Hosseini, Mohammad [Sirjan University of Technology, Sirjan (Iran, Islamic Republic of)

    2015-02-15

    The vibrational behavior of a viscous nanoflow-conveying single-walled carbon nanotube (SWCNT) was investigated. The nonuniformity of the flow velocity distribution caused by the viscosity of fluid and the small-size effects on the flow field was considered. Euler-Bernoulli beam model was used to investigate flow-induced vibration of the nanotube, while the non-uniformity of the flow velocity and the small-size effects of the flow field were formulated through Knudsen number (Kn), as a discriminant parameter. For laminar flow in a circular nanotube, the momentum correction factor was developed as a function of Kn. For Kn = 0 (continuum flow), the momentum correction factor was found to be 1.33, which decreases by the increase in Kn may even reach near 1 for the transition flow regime. We observed that for passage of viscous flow through a nanotube with the non-uniform flow velocity, the critical continuum flow velocity for divergence decreased considerably as opposed to those for the uniform flow velocity, while by increasing Kn, the difference between the uniform and non-uniform flow models may be reduced. In the solution part, the differential transformation method (DTM) was used to solve the governing differential equations of motion.

  9. The effects of non-uniform flow velocity on vibrations of single-walled carbon nanotube conveying fluid

    International Nuclear Information System (INIS)

    Sadeghi-Goughari, Moslem; Hosseini, Mohammad

    2015-01-01

    The vibrational behavior of a viscous nanoflow-conveying single-walled carbon nanotube (SWCNT) was investigated. The nonuniformity of the flow velocity distribution caused by the viscosity of fluid and the small-size effects on the flow field was considered. Euler-Bernoulli beam model was used to investigate flow-induced vibration of the nanotube, while the non-uniformity of the flow velocity and the small-size effects of the flow field were formulated through Knudsen number (Kn), as a discriminant parameter. For laminar flow in a circular nanotube, the momentum correction factor was developed as a function of Kn. For Kn = 0 (continuum flow), the momentum correction factor was found to be 1.33, which decreases by the increase in Kn may even reach near 1 for the transition flow regime. We observed that for passage of viscous flow through a nanotube with the non-uniform flow velocity, the critical continuum flow velocity for divergence decreased considerably as opposed to those for the uniform flow velocity, while by increasing Kn, the difference between the uniform and non-uniform flow models may be reduced. In the solution part, the differential transformation method (DTM) was used to solve the governing differential equations of motion.

  10. An Improved Rate-Transient Analysis Model of Multi-Fractured Horizontal Wells with Non-Uniform Hydraulic Fracture Properties

    Directory of Open Access Journals (Sweden)

    Youwei He

    2018-02-01

    Full Text Available Although technical advances in hydraulically fracturing and drilling enable commercial production from tight reservoirs, oil/gas recovery remains at a low level. Due to the technical and economic limitations of well-testing operations in tight reservoirs, rate-transient analysis (RTA has become a more attractive option. However, current RTA models hardly consider the effect of the non-uniform production on rate decline behaviors. In fact, PLT results demonstrate that production profile is non-uniform. To fill this gap, this paper presents an improved RTA model of multi-fractured horizontal wells (MFHWs to investigate the effects of non-uniform properties of hydraulic fractures (production of fractures, fracture half-length, number of fractures, fracture conductivity, and vertical permeability on rate transient behaviors through the diagnostic type curves. Results indicate obvious differences on the rate decline curves among the type curves of uniform properties of fractures (UPF and non-uniform properties of fractures (NPF. The use of dimensionless production integral derivative curve magnifies the differences so that we can diagnose the phenomenon of non-uniform production. Therefore, it’s significant to incorporate the effects of NPF into the RDA models of MFHWs, and the model proposed in this paper enables us to better evaluate well performance based on long-term production data.

  11. THE BEHAVIOR OF TRANSVERSE WAVES IN NONUNIFORM SOLAR FLUX TUBES. I. COMPARISON OF IDEAL AND RESISTIVE RESULTS

    International Nuclear Information System (INIS)

    Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Goossens, Marcel

    2013-01-01

    Magnetohydrodynamic (MHD) waves are ubiquitously observed in the solar atmosphere. Kink waves are a type of transverse MHD waves in magnetic flux tubes that are damped due to resonant absorption. The theoretical study of kink MHD waves in solar flux tubes is usually based on the simplification that the transverse variation of density is confined to a nonuniform layer much thinner than the radius of the tube, i.e., the so-called thin boundary approximation. Here, we develop a general analytic method to compute the dispersion relation and the eigenfunctions of ideal MHD waves in pressureless flux tubes with transversely nonuniform layers of arbitrary thickness. Results for kink waves are produced and compared with fully numerical resistive MHD eigenvalue computations in the limit of small resistivity. We find that the frequency and resonant damping rate are the same in both ideal and resistive cases. The actual results for thick nonuniform layers deviate from the behavior predicted in the thin boundary approximation and strongly depend on the shape of the nonuniform layer. The eigenfunctions in ideal MHD are very different from those in resistive MHD. The ideal eigenfunctions display a global character regardless of the thickness of the nonuniform layer, while the resistive eigenfunctions are localized around the resonance and are indistinguishable from those of ordinary resistive Alfvén modes. Consequently, the spatial distribution of wave energy in the ideal and resistive cases is dramatically different. This poses a fundamental theoretical problem with clear observational consequences

  12. Selective catalytic reduction converter design: The effect of ammonia nonuniformity at inlet

    International Nuclear Information System (INIS)

    Paramadayalan, Thiyagarajan; Pant, Atul

    2013-01-01

    A three-dimensional CFD model of SCR converter with detailed chemistry is developed. The model is used to study the effects of radial variation in inlet ammonia profile on SCR emission performance at different temperatures. The model shows that radial variation in inlet ammonia concentration affects the SCR performance in the operating range of 200-400 .deg. C. In automotive SCR systems, ammonia is non-uniformly distributed due to evaporation/reaction of injected urea, and using a 1D model or a 3D model with flat ammonia profile at inlet for these conditions can result in erroneous emission prediction. The 3D SCR model is also used to study the effect of converter design parameters like inlet cone angle and monolith cell density on the SCR performance for a non-uniform ammonia concentration profile at the inlet. The performance of SCR is evaluated using DeNO x efficiency and ammonia slip

  13. Whole-body voxel-based personalized dosimetry: Multiple voxel S-value approach for heterogeneous media with non-uniform activity distributions.

    Science.gov (United States)

    Lee, Min Sun; Kim, Joong Hyun; Paeng, Jin Chul; Kang, Keon Wook; Jeong, Jae Min; Lee, Dong Soo; Lee, Jae Sung

    2017-12-14

    Personalized dosimetry with high accuracy is becoming more important because of the growing interests in personalized medicine and targeted radionuclide therapy. Voxel-based dosimetry using dose point kernel or voxel S-value (VSV) convolution is available. However, these approaches do not consider medium heterogeneity. Here, we propose a new method for whole-body voxel-based personalized dosimetry for heterogeneous media with non-uniform activity distributions, which is referred to as the multiple VSV approach. Methods: The multiple numbers (N) of VSVs for media with different densities covering the whole-body density ranges were used instead of using only a single VSV for water. The VSVs were pre-calculated using GATE Monte Carlo simulation; those were convoluted with the time-integrated activity to generate density-specific dose maps. Computed tomography-based segmentation was conducted to generate binary maps for each density region. The final dose map was acquired by the summation of N segmented density-specific dose maps. We tested several sets of VSVs with different densities: N = 1 (single water VSV), 4, 6, 8, 10, and 20. To validate the proposed method, phantom and patient studies were conducted and compared with direct Monte Carlo, which was considered the ground truth. Finally, patient dosimetry (10 subjects) was conducted using the multiple VSV approach and compared with the single VSV and organ-based dosimetry approaches. Errors at the voxel- and organ-levels were reported for eight organs. Results: In the phantom and patient studies, the multiple VSV approach showed significant improvements regarding voxel-level errors, especially for the lung and bone regions. As N increased, voxel-level errors decreased, although some overestimations were observed at lung boundaries. In the case of multiple VSVs ( N = 8), we achieved voxel-level errors of 2.06%. In the dosimetry study, our proposed method showed much improved results compared to the single VSV and

  14. Experience in treatment of the radiation syndrome in accident victims exposed with non-uniform distribution of the dose within a body

    International Nuclear Information System (INIS)

    Guskova, A.; Barabanova, A

    1996-01-01

    Experience in diagnosis and treatment of radiation accident victims undergone to radiation expose with non-uniform distribution of the dose within a body is presented and the most significant features of medical management of such patients are discussed. The term 'compound radiation injure' is proposed to use for this form of radiation disease. Treatment of compound radiation injure demands a participation of very qualified specialists. The first medical aid and management should include careful body surface monitoring. Beside daily haematological observation and cytogenetic study with corresponding treatment, careful observation and registration of skin reaction are necessary. Some features of treatment are the following: more early administration of anti infection means, including isolation in sterile room, timely surgical intervention, prophylacsis and treatment of endorganic intoxication improving of microcirculation, long time follow up study with pathogenic therapy. (author)

  15. Thermal stability improvement of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations using non-uniform finger spacing

    International Nuclear Information System (INIS)

    Chen Liang; Zhang Wan-Rong; Jin Dong-Yue; Shen Pei; Xie Hong-Yun; Ding Chun-Bao; Xiao Ying; Sun Bo-Tao; Wang Ren-Qing

    2011-01-01

    A method of non-uniform finger spacing is proposed to enhance thermal stability of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations. Temperature distribution on the emitter fingers of a multi-finger SiGe heterojunction bipolar transistor is studied using a numerical electro-thermal model. The results show that the SiGe heterojunction bipolar transistor with non-uniform finger spacing has a small temperature difference between fingers compared with a traditional uniform finger spacing heterojunction bipolar transistor at the same power dissipation. What is most important is that the ability to improve temperature non-uniformity is not weakened as power dissipation increases. So the method of non-uniform finger spacing is very effective in enhancing the thermal stability and the power handing capability of power device. Experimental results verify our conclusions. (interdisciplinary physics and related areas of science and technology)

  16. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Wenjie; Guan, Xiaotong; Yan, Yang [THz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2016-01-15

    The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper.

  17. One-step fabrication of nanostructure-covered microstructures using selective aluminum anodization based on non-uniform electric field

    Science.gov (United States)

    Park, Yong Min; Kim, Byeong Hee; Seo, Young Ho

    2016-06-01

    This paper presents a selective aluminum anodization technique for the fabrication of microstructures covered by nanoscale dome structures. It is possible to fabricate bulging microstructures, utilizing the different growth rates of anodic aluminum oxide in non-uniform electric fields, because the growth rate of anodic aluminum oxide depends on the intensity of electric field, or current density. After anodizing under a non-uniform electric field, bulging microstructures covered by nanostructures were fabricated by removing the residual aluminum layer. The non-uniform electric field induced by insulative micropatterns was estimated by computational simulations and verified experimentally. Utilizing computational simulations, the intensity profile of the electric field was calculated according to the ratio of height and width of the insulative micropatterns. To compare computational simulation results and experimental results, insulative micropatterns were fabricated using SU-8 photoresist. The results verified that the shape of the bottom topology of anodic alumina was strongly dependent on the intensity profile of the applied electric field, or current density. The one-step fabrication of nanostructure-covered microstructures can be applied to various fields, such as nano-biochip and nano-optics, owing to its simplicity and cost effectiveness.

  18. Theoretical Analysis of Unit Friction Force Working on the Metal Contact Surface with the Roll Change during Feedstock with Non-Uniform Temperature Distribution Rolling Process

    Directory of Open Access Journals (Sweden)

    Sygut P.

    2016-06-01

    Full Text Available The paper presents the results of theoretical studies influence of non-uniform temperature distribution along the feedstock length to the unit friction force working on the metal contact surface with the roll change during the round bars 70 mm in diameter continuous rolling process. This value is one of the major factors affecting the grooves wear during the rolling process. The studies were carried out based on the actual engineering data for 160 × 160 mm square cross-section feedstock of steel S355J0. Numerical modelling of the rolling process was performed using Forge2008®, a finite-element based computer program.

  19. Determination of corrosion rate of reinforcement with a modulated guard ring electrode; analysis of errors due to lateral current distribution

    International Nuclear Information System (INIS)

    Wojtas, H.

    2004-01-01

    The main source of errors in measuring the corrosion rate of rebars on site is a non-uniform current distribution between the small counter electrode (CE) on the concrete surface and the large rebar network. Guard ring electrodes (GEs) are used in an attempt to confine the excitation current within a defined area. In order to better understand the functioning of modulated guard ring electrode and to assess its effectiveness in eliminating errors due to lateral spread of current signal from the small CE, measurements of the polarisation resistance performed on a concrete beam have been numerically simulated. Effect of parameters such as rebar corrosion activity, concrete resistivity, concrete cover depth and size of the corroding area on errors in the estimation of polarisation resistance of a single rebar has been examined. The results indicate that modulated GE arrangement fails to confine the lateral spread of the CE current within a constant area. Using the constant diameter of confinement for the calculation of corrosion rate may lead to serious errors when test conditions change. When high corrosion activity of rebar and/or local corrosion occur, the use of the modulated GE confinement may lead to significant underestimation of the corrosion rate

  20. Two types of nonlinear wave equations for diffractive beams in bubbly liquids with nonuniform bubble number density.

    Science.gov (United States)

    Kanagawa, Tetsuya

    2015-05-01

    This paper theoretically treats the weakly nonlinear propagation of diffracted sound beams in nonuniform bubbly liquids. The spatial distribution of the number density of the bubbles, initially in a quiescent state, is assumed to be a slowly varying function of the spatial coordinates; the amplitude of variation is assumed to be small compared to the mean number density. A previous derivation method of nonlinear wave equations for plane progressive waves in uniform bubbly liquids [Kanagawa, Yano, Watanabe, and Fujikawa (2010). J. Fluid Sci. Technol. 5(3), 351-369] is extended to handle quasi-plane beams in weakly nonuniform bubbly liquids. The diffraction effect is incorporated by adding a relation that scales the circular sound source diameter to the wavelength into the original set of scaling relations composed of nondimensional physical parameters. A set of basic equations for bubbly flows is composed of the averaged equations of mass and momentum, the Keller equation for bubble wall, and supplementary equations. As a result, two types of evolution equations, a nonlinear Schrödinger equation including dissipation, diffraction, and nonuniform effects for high-frequency short-wavelength case, and a Khokhlov-Zabolotskaya-Kuznetsov equation including dispersion and nonuniform effects for low-frequency long-wavelength case, are derived from the basic set.

  1. Desynchronization boost by non-uniform coordinated reset stimulation in ensembles of pulse-coupled neurons

    Science.gov (United States)

    Lücken, Leonhard; Yanchuk, Serhiy; Popovych, Oleksandr V.; Tass, Peter A.

    2013-01-01

    Several brain diseases are characterized by abnormal neuronal synchronization. Desynchronization of abnormal neural synchrony is theoretically compelling because of the complex dynamical mechanisms involved. We here present a novel type of coordinated reset (CR) stimulation. CR means to deliver phase resetting stimuli at different neuronal sub-populations sequentially, i.e., at times equidistantly distributed in a stimulation cycle. This uniform timing pattern seems to be intuitive and actually applies to the neural network models used for the study of CR so far. CR resets the population to an unstable cluster state from where it passes through a desynchronized transient, eventually resynchronizing if left unperturbed. In contrast, we show that the optimal stimulation times are non-uniform. Using the model of weakly pulse-coupled neurons with phase response curves, we provide an approach that enables to determine optimal stimulation timing patterns that substantially maximize the desynchronized transient time following the application of CR stimulation. This approach includes an optimization search for clusters in a low-dimensional pulse coupled map. As a consequence, model-specific non-uniformly spaced cluster states cause considerably longer desynchronization transients. Intriguingly, such a desynchronization boost with non-uniform CR stimulation can already be achieved by only slight modifications of the uniform CR timing pattern. Our results suggest that the non-uniformness of the stimulation times can be a medically valuable parameter in the calibration procedure for CR stimulation, where the latter has successfully been used in clinical and pre-clinical studies for the treatment of Parkinson's disease and tinnitus. PMID:23750134

  2. Nonuniformities in organic liquid ionization calorimeters

    International Nuclear Information System (INIS)

    Wenzel, W.A.

    1989-06-01

    Hermeticity and uniformity in SSC calorimeter designs are compromised by structure and modularity. Some of the consequences of the cryogenic needs of liquid argon calorimetry are relatively well known. If the active medium is an organic liquid (TMP, TMS, etc.), a large number of independent liquid volumes is needed for safety and for rapid liquid exchange to eliminate local contamination. Modular construction ordinarily simplifies fabrication, assembly, handling and preliminary testing at the price of additional walls, other dead regions and many nonuniformities. Here we examine ways of minimizing the impact of some generic nonuniformities on the quality of calorimeter performance. 6 refs., 7 figs

  3. Integer channels in nonuniform non-equilibrium 2D systems

    Science.gov (United States)

    Shikin, V.

    2018-01-01

    We discuss the non-equilibrium properties of integer channels in nonuniform 2D electron (hole) systems in the presence of a strong magnetic field. The results are applied to a qualitative explanation of the Corbino disk current-voltage characteristics (IVC) in the quantum Hall effect (QHE) regime. Special consideration is paid to the so-called "QHE breakdown" effect, which is readily observed in both the Hall bar and Corbino geometries of the tested cells. The QHE breakdown is especially evident in the Corbino samples, allowing for a more in-depth study of these effects.

  4. Physical Limitations To Nonuniformity Correction In IR Focal Plane Arrays

    Science.gov (United States)

    Scribner, D. A.; Kruer, M. R.; Gridley, J. C.; Sarkady, K.

    1988-05-01

    Simple nonuniformity correction algorithms currently in use can be severely limited by nonlinear response characteristics of the individual pixels in an IR focal plane array. Although more complicated multi-point algorithms improve the correction process they too can be limited by nonlinearities. Furthermore, analysis of single pixel noise power spectrums usually show some level of 1 /f noise. This in turn causes pixel outputs to drift independent of each other thus causing the spatial noise (often called fixed pattern noise) of the array to increase as a function of time since the last calibration. Measurements are presented for two arrays (a HgCdTe hybrid and a Pt:Si CCD) describing pixel nonlinearities, 1/f noise, and residual spatial noise (after nonuniforming correction). Of particular emphasis is spatial noise as a function of the lapsed time since the last calibration and the calibration process selected. The resulting spatial noise is examined in terms of its effect on the NEAT performance of each array tested and comparisons are made. Finally, a discussion of implications for array developers is given.

  5. Non-uniformity Correction of Infrared Images by Midway Equalization

    Directory of Open Access Journals (Sweden)

    Yohann Tendero

    2012-07-01

    Full Text Available The non-uniformity is a time-dependent noise caused by the lack of sensor equalization. We present here the detailed algorithm and on line demo of the non-uniformity correction method by midway infrared equalization. This method was designed to suit infrared images. Nevertheless, it can be applied to images produced for example by scanners, or by push-broom satellites. The obtained single image method works on static images, is fully automatic, having no user parameter, and requires no registration. It needs no camera motion compensation, no closed aperture sensor equalization and is able to correct for a fully non-linear non-uniformity.

  6. Efficient SPECT scatter calculation in non-uniform media using correlated Monte Carlo simulation

    International Nuclear Information System (INIS)

    Beekman, F.J.

    1999-01-01

    Accurate simulation of scatter in projection data of single photon emission computed tomography (SPECT) is computationally extremely demanding for activity distribution in non-uniform dense media. This paper suggests how the computation time and memory requirements can be significantly reduced. First the scatter projection of a uniform dense object (P SDSE ) is calculated using a previously developed accurate and fast method which includes all orders of scatter (slab-derived scatter estimation), and then P SDSE is transformed towards the desired projection P which is based on the non-uniform object. The transform of P SDSE is based on two first-order Compton scatter Monte Carlo (MC) simulated projections. One is based on the uniform object (P u ) and the other on the object with non-uniformities (P ν ). P is estimated by P-tilde=P SDSE P ν /P u . A tremendous decrease in noise in P-tilde is achieved by tracking photon paths for P ν identical to those which were tracked for the calculation of P u and by using analytical rather than stochastic modelling of the collimator. The method was validated by comparing the results with standard MC-simulated scatter projections (P) of 99m Tc and 201 Tl point sources in a digital thorax phantom. After correction, excellent agreement was obtained between P-tilde and P. The total computation time required to calculate an accurate scatter projection of an extended distribution in a thorax phantom on a PC is a only few tens of seconds per projection, which makes the method attractive for application in accurate scatter correction in clinical SPECT. Furthermore, the method removes the need of excessive computer memory involved with previously proposed 3D model-based scatter correction methods. (author)

  7. Temporal high-pass non-uniformity correction algorithm based on grayscale mapping and hardware implementation

    Science.gov (United States)

    Jin, Minglei; Jin, Weiqi; Li, Yiyang; Li, Shuo

    2015-08-01

    In this paper, we propose a novel scene-based non-uniformity correction algorithm for infrared image processing-temporal high-pass non-uniformity correction algorithm based on grayscale mapping (THP and GM). The main sources of non-uniformity are: (1) detector fabrication inaccuracies; (2) non-linearity and variations in the read-out electronics and (3) optical path effects. The non-uniformity will be reduced by non-uniformity correction (NUC) algorithms. The NUC algorithms are often divided into calibration-based non-uniformity correction (CBNUC) algorithms and scene-based non-uniformity correction (SBNUC) algorithms. As non-uniformity drifts temporally, CBNUC algorithms must be repeated by inserting a uniform radiation source which SBNUC algorithms do not need into the view, so the SBNUC algorithm becomes an essential part of infrared imaging system. The SBNUC algorithms' poor robustness often leads two defects: artifacts and over-correction, meanwhile due to complicated calculation process and large storage consumption, hardware implementation of the SBNUC algorithms is difficult, especially in Field Programmable Gate Array (FPGA) platform. The THP and GM algorithm proposed in this paper can eliminate the non-uniformity without causing defects. The hardware implementation of the algorithm only based on FPGA has two advantages: (1) low resources consumption, and (2) small hardware delay: less than 20 lines, it can be transplanted to a variety of infrared detectors equipped with FPGA image processing module, it can reduce the stripe non-uniformity and the ripple non-uniformity.

  8. Optical property of few-mode fiber with non-uniform refractive index for cylindrical vector beam generation

    Science.gov (United States)

    Li, Hongye; Wan, Hongdan; Zhang, Zuxing; Sun, Bing; Zhang, Lin

    2016-10-01

    This paper investigates optical properties of few-mode fiber with non-uniform refractive index, namely: the few mode fiber with U-shape refractive index and the two-mode and four-mode few-mode fiber with bent radius. Finite element method is used to analyze the mode distributions based on their non-uniform refractive index. Effective mode control can be achieved through these few mode fibers to achieve vector beam generation. Finally, reflection spectra of a few-mode fiber Bragg grating are calculated theoretically and then measured under different bending conditions. Experimental results are in good accordance with the theoretical ones. These few mode fibers show potential applications in generation of cylindrical vector beam both for optical lasing and sensing systems.

  9. A Heuristic Probabilistic Approach to Estimating Size-Dependent Mobility of Nonuniform Sediment

    Science.gov (United States)

    Woldegiorgis, B. T.; Wu, F. C.; van Griensven, A.; Bauwens, W.

    2017-12-01

    Simulating the mechanism of bed sediment mobility is essential for modelling sediment dynamics. Despite the fact that many studies are carried out on this subject, they use complex mathematical formulations that are computationally expensive, and are often not easy for implementation. In order to present a simple and computationally efficient complement to detailed sediment mobility models, we developed a heuristic probabilistic approach to estimating the size-dependent mobilities of nonuniform sediment based on the pre- and post-entrainment particle size distributions (PSDs), assuming that the PSDs are lognormally distributed. The approach fits a lognormal probability density function (PDF) to the pre-entrainment PSD of bed sediment and uses the threshold particle size of incipient motion and the concept of sediment mixture to estimate the PSDs of the entrained sediment and post-entrainment bed sediment. The new approach is simple in physical sense and significantly reduces the complexity and computation time and resource required by detailed sediment mobility models. It is calibrated and validated with laboratory and field data by comparing to the size-dependent mobilities predicted with the existing empirical lognormal cumulative distribution function (CDF) approach. The novel features of the current approach are: (1) separating the entrained and non-entrained sediments by a threshold particle size, which is a modified critical particle size of incipient motion by accounting for the mixed-size effects, and (2) using the mixture-based pre- and post-entrainment PSDs to provide a continuous estimate of the size-dependent sediment mobility.

  10. Liquid jets injected into non-uniform crossflow

    Science.gov (United States)

    Tambe, Samir

    An experimental study has been conducted with liquid jets injected transversely into a crossflow to study the effect of non-uniformities in the crossflow velocity distribution to the jet behavior. Two different non-uniform crossflows were created during this work, a shear-laden crossflow and a swirling crossflow. The shear-laden crossflow was generated by merging two independent, co-directional, parallel airstreams creating a shear mixing layer at the interface between them. The crossflow exhibited a quasi-linear velocity gradient across the height of the test chamber. By varying the velocities of the two airstreams, the sense and the slope of the crossflow velocity gradient could be changed. Particle Image Velocimetry (PIV) studies were conducted to characterize the crossflow. The parameter, UR, is defined as the ratio of the velocities of the two streams and governs the velocity gradient. A positive velocity gradient was observed for UR > 1 and a negative velocity gradient for UR Phase Doppler Particle Anemometry (PDPA) studies were conducted to study the penetration and atomization of 0.5 mm diameter water jets injected into this crossflow. The crossflow velocity gradient was observed to have a significant effect on jet penetration as well as the post breakup spray. For high UR (> 1), jet penetration increased and the Sauter Mean Diameter (SMD) distribution became more uniform. For low UR (Doppler Velocimetry (LDV) was used to study the crossflow velocities. The axial (Ux) and the tangential (Utheta) components of the crossflow velocity were observed to decrease with increasing radial distance away from the centerbody. The flow angle of the crossflow was smaller than the vane exit angle, with the difference increasing with the vane exit angle. Water jets were injected from a 0.5 mm diameter orifice located on a cylindrical centerbody. Multi-plane PIV measurements were conducted to study the penetration and droplet velocity distribution of the jets. The jets were

  11. Vortices in nonuniform upper-hybrid field

    International Nuclear Information System (INIS)

    Davydova, T.A.; Vranjes, J.

    1992-01-01

    The equations describing the interaction of an upper-hybrid pump wave with small low-frequency density perturbations are discussed under assumption that the pump is spatially nonuniform. The conditions for the modulational instability are investigated. Instead of a dispersion relation, describing the growth of perturbations in the case of an uniform pump, in our case of nonuniform pump a differential equation is obtained and from its eigenvalues are found the instability criteria. Taking into account the slow-frequency self-interaction terms some localized solutions similar to dipole vortices are found, but described by analytic functions in all space. It is shown that their characteristic size and speed are determined by the pump intensity and its spatial structure. (au)

  12. Below-threshold harmonic generation from strong non-uniform fields

    Science.gov (United States)

    Yavuz, I.

    2017-10-01

    Strong-field photoemission below the ionization threshold is a rich/complex region where atomic emission and harmonic generation may coexist. We studied the mechanism of below-threshold harmonics (BTH) from spatially non-uniform local fields near the metallic nanostructures. Discrete harmonics are generated due to the broken inversion symmetry, suggesting enriched coherent emission in the vuv frequency range. Through the numerical solution of the time-dependent Schrödinger equation, we investigate wavelength and intensity dependence of BTH. Wavelength dependence identifies counter-regular resonances; individual contributions from the multi-photon emission and channel-closing effects due to quantum path interferences. In order to understand the underlying mechanism of BTH, we devised a generalized semi-classical model, including the influence of Coulomb and non-uniform field interactions. As in uniform fields, Coulomb potential in non-uniform fields is the determinant of BTH; we observed that the generation of BTH are due to returning trajectories with negative energies. Due to large distance effectiveness of the non-uniformity, only long trajectories are noticeably affected.

  13. A method to measure the mean thickness and non-uniformity of non-uniform thin film by alpha-ray thickness gauge

    International Nuclear Information System (INIS)

    Miyahara, Hiroshi; Yoshida, Makoto; Watanabe, Tamaki

    1977-01-01

    The α-ray thickness gauge is used to measure non-destructively the thicknesses of thin films, and up to the present day, a thin film with uniform thickness is only taken up as the object of α-ray thickness gauge. When the thickness is determined from the displacement between the absorption curves in the presence and absence of thin film, the absorption curve must be displaced in parallel. When many uniform particles were dispersed as sample, the shape of the absorption curve was calculated as the sum of many absorption curves corresponding to the thin films with different thicknesses. By the comparison of the calculated and measured absorption curves, the number of particles, or the mean superficial density can be determined. This means the extension of thickness measurement from uniform to non-uniform films. Furthermore, these particle models being applied to non-uniform thin film, the possibility of measuring the mean thickness and non-uniformity was discussed. As the result, if the maximum difference of the thickness was more than 0.2 mg/cm 2 , the nonuniformity was considered to distinguish by the usual equipment. In this paper, an α-ray thickness gauge using the absorption curve method was treated, but one can apply this easily to an α-ray thickness gauge using α-ray energy spectra before and after the penetration of thin film. (auth.)

  14. Heat transfer improvement due to the imposition of non-uniform wall heating for in-tube laminar forced convection

    International Nuclear Information System (INIS)

    Hajmohammadi, M.R.; Poozesh, S.; Rahmani, M.; Campo, A.

    2013-01-01

    This paper explores the bearing that a non-uniform distribution of heat flux used as a wall boundary condition exerts on the heat transfer improvement in a round pipe. Because the overall heat load is considered fixed, the heat transfer improvement is viewed through a reduction in the maximum temperature (‘hot spot’) by imposing optimal distribution of heat flux. Two cases are studied in detail 1) fully developed and 2) developing flow. Peak temperatures in the heated pipe wall are calculated via an analytical approach for the fully developed case, while a numerical simulation based on CFD is employed for the developing case. By relaxing the heat flux distribution on the pipe wall, the numerical results imply that the optimum distribution of heat flux, which minimizes the peak temperatures corresponds with the ‘descending’ distribution. Given that the foregoing approach is quite different from the ‘ascending’ heat flux distribution recommended in the literature by means of the entropy generation minimization (EGM) method, it is inferred that the optimization of heat transfer and fluid flow, in comparison with the thermodynamic optimization, may bring forth quite different guidelines for the designs of thermal systems under the same constraints and circumstances. -- Highlights: • Considered the bearing of non-uniform distribution of heat flux on the hot spots. • Determined the optimal distribution of heat flux that minimizes the hot spots. • Results are compared with those obtained by EGM method

  15. A new correlation of non-uniformly heated round tube burnout data

    International Nuclear Information System (INIS)

    Kirby, G.J.

    1966-07-01

    A new correlation of non-uniformly heated round tube burnout data is presented. This fits the available data better than any previously published correlation - the root-mean-square deviation being 5.7% for all data at 1000 p.s.i.a. and the worst fit being to data at 2000 p.s.i.a. where the r.m.s. error is 6.6%. The correlation is used to investigate the effect of flux profile changes and no significant increase in burnout power is obtained by modifying the present chopped cosine distribution. (author)

  16. Design of Nonuniform Filter Bank Transceivers for Frequency Selective Channels

    Directory of Open Access Journals (Sweden)

    Yuan-Pei Lin

    2007-01-01

    Full Text Available In recent years, there has been considerable interest in the theory and design of filter bank transceivers due to their superior frequency response. In many applications, it is desired to have transceivers that can support multiple services with different incoming data rates and different quality-of-service requirements. To meet these requirements, we can either do resource allocation or design transceivers with a nonuniform bandwidth partition. In this paper, we propose a method for the design of nonuniform filter bank transceivers for frequency selective channels. Both frequency response and signal-to-interference ratio (SIR can be incorporated in the transceiver design. Moreover, the technique can be extended to the case of nonuniform filter bank transceivers with rational sampling factors. Simulation results show that nonuniform filter bank transceivers with good filter responses as well as high SIR can be obtained by the proposed design method.

  17. Viscoelastic Fluid over a Stretching Sheet with Electromagnetic Effects and Nonuniform Heat Source/Sink

    Directory of Open Access Journals (Sweden)

    Kai-Long Hsiao

    2010-01-01

    Full Text Available A magnetic hydrodynamic (MHD of an incompressible viscoelastic fluid over a stretching sheet with electric and magnetic dissipation and nonuniform heat source/sink has been studied. The buoyant effect and the electric number E1 couple with magnetic parameter M to represent the dominance of the electric and magnetic effects, and adding the specific item of nonuniform heat source/sink is presented in governing equations which are the main contribution of this study. The similarity transformation, the finite-difference method, Newton method, and Gauss elimination method have been used to analyze the present problem. The numerical solutions of the flow velocity distributions, temperature profiles, and the important wall unknown values of f''(0 and θ'(0 have been carried out. The parameter Pr, E1, or Ec can increase the heat transfer effects, but the parameter M or A* may decrease the heat transfer effects.

  18. Illumination non-uniformity of spirally wobbling beam in heavy ion fusion

    International Nuclear Information System (INIS)

    Suzuki, T.; Noguchi, K.; Kurosaki, T.; Barada, D.; Kawata, S.; Ma, Y. Y.; Ogoyski, A.I.

    2016-01-01

    In inertial confinement fusion, the driver beam illumination non-uniformity leads a degradation of fusion energy output. The illumination non-uniformity allowed is less than a few percent in inertial fusion target implosion. Heavy ion beam (HIB) accelerator provides a capability to oscillate a beam axis with a high frequency. The wobbling beams may provide a new method to reduce or smooth the beam illumination non-uniformity. In this paper the HIBs wobbling illumination scheme was optimized. (paper)

  19. Non-uniform Mutation Rates for Problems with Unknown Solution Lengths

    DEFF Research Database (Denmark)

    Cathabard, Stephan; Lehre, Per Kristian; Yao, Xin

    2011-01-01

    Many practical optimisation problems allow candidate solu- tions of varying lengths, and where the length of the opti- mal solution is thereby a priori unknown. We suggest that non-uniform mutation rates can be beneficial when solving such problems. In particular, we consider a mutation oper- ator...... that flips each bit with a probability that is inversely proportional to the bit position, rather than the bitstring length. The runtime of the (1+1) EA using this mutation operator is analysed rigorously on standard example func- tions. Furthermore, the behaviour of the new mutation op- erator...... distribution, and show that the new operator can yield exponentially faster runtimes for some parameters of this distribution. The experimental results show that the new mutation operator leads to dramatically shorter runtimes on a class of instances of the software engi- neering problem that is conjectured...

  20. Non-uniformity calibration for MWIR polarization imagery obtained with integrated microgrid polarimeters

    Science.gov (United States)

    Liu, Hai-Zheng; Shi, Ze-Lin; Feng, Bin; Hui, Bin; Zhao, Yao-Hong

    2016-03-01

    Integrating microgrid polarimeters on focal plane array (FPA) of an infrared detector causes non-uniformity of polarization response. In order to reduce the effect of polarization non-uniformity, this paper constructs an experimental setup for capturing raw flat-field images and proposes a procedure for acquiring non-uniform calibration (NUC) matrix and calibrating raw polarization images. The proposed procedure takes the incident radiation as a polarization vector and offers a calibration matrix for each pixel. Both our matrix calibration and two-point calibration are applied to our mid-wavelength infrared (MWIR) polarization imaging system with integrated microgrid polarimeters. Compared with two point calibration, our matrix calibration reduces non-uniformity by 30 40% under condition of flat-field data test with polarization. The ourdoor scene observation experiment indicates that our calibration can effectively reduce polarization non-uniformity and improve the image quality of our MWIR polarization imaging system.

  1. The evaluation of the degree of impairment of pulmonary perfusion in lung cancer patients treated by radiotherapy by the quantification of nonuniform distribution of lung perfusion scintigraphy SPECT

    International Nuclear Information System (INIS)

    Mitomo, Osamu; Tsunoda, Takashi; Kuwabara, Hidemasa

    2004-01-01

    By means of quantifying the nonuniform distribution of pulmonary perfusion in Lung Perfusion Scintigraphy SPECT (single photon emission tomography), which is called ''SPECT'' for short, we evaluated the degree of functional impairment of pulmonary perfusion in non-operated lung cancer patients treated by the radiotherapy. Sixty-eight patients with non-operated lung cancer treated with radiotherapy, and who either received or did not receive chemotherapy, from February, 1996 to August, 2002, were examined using SPECT within 6 weeks prior to, or within 2 weeks following radiotherapy. This group was called ''irradiated lung cancer patients''. Twenty-six patients, who were called ''follow-up irradiated lung cancer patients'', were reexamined within four weeks after radiotherapy. On the other hand, 323 patients without lung cancer, who were subdivided into four groups; pulmonary, cardiac, cardio-pulmonary, and non-cardiopulmonary. The SPECT was examined in the supine position after infusing Tc-99m-MAA, 185 MBq in a bolus, mainly into an antecubital vein with the patient's arm elevated. From reconstructed SPECT images, the volume of lung as a whole calculated at 10% of thresholds was assumed to be the ''Baseline Lung Perfusion Volume'' (BPV), and the functional volume rates were calculated in 10% threshold widths from 10% to 100% of the threshold. Assuming the total absolute differences in functional volume rate between each subject and the control to be the distribution index of the lung as a whole (D index), we quantified the degree of nonuniform distribution of the lung as a whole in each subject. In the same way, the distribution index of the left or right lung respectively was calculated as D l or D r index assuming the volume of left or right lung were calculated at 10% of the threshold as left or right BPV and calculating the functional volume rates of each lung in 10% threshold widths from 10% to 100% of the threshold. The D index of irradiated lung cancer

  2. LDPC Code Design for Nonuniform Power-Line Channels

    Directory of Open Access Journals (Sweden)

    Sanaei Ali

    2007-01-01

    Full Text Available We investigate low-density parity-check code design for discrete multitone channels over power lines. Discrete multitone channels are well modeled as nonuniform channels, that is, different bits experience various channel parameters. We propose a coding system for discrete multitone channels that allows for using a single code over a nonuniform channel. The number of code parameters for the proposed system is much greater than the number of code parameters in conventional channel. Therefore, search-based optimization methods are impractical. We first formulate the problem of optimizing the rate of an irregular low-density parity-check code, with guaranteed convergence over a general nonuniform channel, as an iterative linear programming which is significantly more efficient than search-based methods. Then we use this technique for a typical power-line channel. The methodology of this paper is directly applicable to all decoding algorithms for which a density evolution analysis is possible.

  3. Electric current distribution of a multiwall carbon nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Li-Ying; Chang, Chia-Seng, E-mail: jasonc@phys.sinica.edu.tw [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Nano Science and Technology Program, Taiwan International Graduate Program, Academia Sinica and National Taiwan University, Taiwan (China); Chen, Yu-Jyun [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China)

    2016-07-15

    The electric current distribution in a multiwall carbon nanotube (MWCNT) was studied by in situ measuring the electric potential along an individual MWCNT in the ultra-high vacuum transmission electron microscope (TEM). The current induced voltage drop along each section of a side-bonded MWCNT was measured by a potentiometric probe in TEM. We have quantitatively derived that the current on the outermost shell depends on the applied current and the shell diameter. More proportion of the total electronic carriers hop into the inner shells when the applied current is increased. The larger a MWCNT’s diameter is, the easier the electronic carriers can hop into the inner shells. We observed that, for an 8 nm MWCNT with 10 μA current applied, 99% of the total current was distributed on the outer two shells.

  4. Non-uniform tube representation of proteins

    DEFF Research Database (Denmark)

    Hansen, Mikael Sonne

    Treating the full protein structure is often neither computationally nor physically possible. Instead one is forced to consider various reduced models capturing the properties of interest. Previous work have used tubular neighborhoods of the C-alpha backbone. However, assigning a unique radius...... might not correctly capture volume exclusion - of crucial importance when trying to understand a proteins $3$d-structure. We propose a new reduced model treating the protein as a non-uniform tube with a radius reflecting the positions of atoms. The tube representation is well suited considering X......-ray crystallographic resolution ~ 3Å while a varying radius accounts for the different sizes of side chains. Such a non-uniform tube better capture the protein geometry and has numerous applications in structural/computational biology from the classification of protein structures to sequence-structure prediction....

  5. Hydrodynamic and thermal mechanisms of filtration combustion inclinational instability based on non-uniform distribution of initial preheating temperature

    Science.gov (United States)

    Xia, Yongfang; Shi, Junrui; Xu, Youning; Ma, Rui

    2018-03-01

    Filtration combustion (FC) is one style of porous media combustion with inert matrix, in which the combustion wave front propagates, only downstream or reciprocally. In this paper, we investigate the FC flame front inclinational instability of lean methane/air mixtures flowing through a packed bed as a combustion wave front perturbation of the initial preheating temperature non-uniformity is assumed. The predicted results show that the growth rate of the flame front inclinational angle is proportional to the magnitude of the initial preheating temperature difference. Additionally, depending on gas inlet gas velocity and equivalence ratio, it is demonstrated that increase of gas inlet gas velocity accelerates the FC wave front deformation, and the inclinational instability evolves faster at lower equivalence ratio. The development of the flame front inclinational angle may be regarded as a two-staged evolution, which includes rapid increase, and approaching maximum value of inclinational angle due to the quasi-steady condition of the combustion system. The hydrodynamic and thermal mechanisms of the FC inclinational instability are analyzed. Consequently, the local propagation velocity of the FC wave front is non-uniform to result in the development of inclinational angle at the first stage of rapid increase.

  6. Field nonuniformity correction for quantitative analysis of digitized mammograms

    International Nuclear Information System (INIS)

    Pawluczyk, Olga; Yaffe, Martin J.

    2001-01-01

    Several factors, including the heel effect, variation in distance from the x-ray source to points in the image and path obliquity contribute to the signal nonuniformity of mammograms. To best use digitized mammograms for quantitative image analysis, these field non-uniformities must be corrected. An empirically based correction method, which uses a bowl-shaped calibration phantom, has been developed. Due to the annular spherical shape of the phantom, its attenuation is constant over the entire image. Remaining nonuniformities are due only to the heel and inverse square effects as well as the variable path through the beam filter, compression plate and image receptor. In logarithmic space, a normalized image of the phantom can be added to mammograms to correct for these effects. Then, an analytical correction for path obliquity in the breast can be applied to the images. It was found that the correction causes the errors associated with field nonuniformity to be reduced from 14% to 2% for a 4 cm block of material corresponding to a combination of 50% fibroglandular and 50% fatty breast tissue. A repeatability study has been conducted to show that in regions as far as 20 cm away from the chest wall, variations due to imaging conditions and phantom alignment contribute to <2% of overall corrected signal

  7. Study on the dynamic behavior of a current in cable-in-conduit conductors by using self magnetic field measurements

    Energy Technology Data Exchange (ETDEWEB)

    Obana, Tetsuhiro, E-mail: obana.tetsuhiro@LHD.nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi, Toki 509-5292, Gifu (Japan); Takahata, Kazuya; Hamaguchi, Shinji; Imagawa, Shinsaku; Mito, Toshiyuki [National Institute for Fusion Science, 322-6 Oroshi, Toki 509-5292, Gifu (Japan); Kizu, Kaname; Murakami, Haruyuki; Yoshida, Kiyoshi [Japan Atomic Energy Agency, Ibaraki (Japan)

    2011-10-15

    In order to understand the current behavior inside a cable-in-conduit conductor (CICC), self magnetic field measurements on the CICC were conducted. A prototype NbTi CICC, the configuration of which is a racket shape, for JT-60SA EF coil was used as a short conductor sample. By using Hall sensors arranged around the short conductor sample, the variation in the self magnetic field was measured. Taking into account the measurements, the current behavior inside the CICC was analyzed by using analytical models consisting of line currents. The analytical results indicate that the current distribution in the cross-section of the CICC would be non-uniform before a normal propagation, and the current distribution would be improved after the normal propagation.

  8. Heat transfer in boundary layer stagnation-point flow towards a shrinking sheet with non-uniform heat flux

    International Nuclear Information System (INIS)

    Bhattacharyya Krishnendu

    2013-01-01

    In this paper, the effect of non-uniform heat flux on heat transfer in boundary layer stagnation-point flow over a shrinking sheet is studied. The variable boundary heat fluxes are considered of two types: direct power-law variation with the distance along the sheet and inverse power-law variation with the distance. The governing partial differential equations (PDEs) are transformed into non linear self-similar ordinary differential equations (ODEs) by similarity transformations, and then those are solved using very efficient shooting method. The direct variation and inverse variation of heat flux along the sheet have completely different effects on the temperature distribution. Moreover, the heat transfer characteristics in the presence of non-uniform heat flux for several values of physical parameters are also found to be interesting

  9. Going from microscopic to macroscopic on nonuniform growing domains.

    Science.gov (United States)

    Yates, Christian A; Baker, Ruth E; Erban, Radek; Maini, Philip K

    2012-08-01

    Throughout development, chemical cues are employed to guide the functional specification of underlying tissues while the spatiotemporal distributions of such chemicals can be influenced by the growth of the tissue itself. These chemicals, termed morphogens, are often modeled using partial differential equations (PDEs). The connection between discrete stochastic and deterministic continuum models of particle migration on growing domains was elucidated by Baker, Yates, and Erban [Bull. Math. Biol. 72, 719 (2010)] in which the migration of individual particles was modeled as an on-lattice position-jump process. We build on this work by incorporating a more physically reasonable description of domain growth. Instead of allowing underlying lattice elements to instantaneously double in size and divide, we allow incremental element growth and splitting upon reaching a predefined threshold size. Such a description of domain growth necessitates a nonuniform partition of the domain. We first demonstrate that an individual-based stochastic model for particle diffusion on such a nonuniform domain partition is equivalent to a PDE model of the same phenomenon on a nongrowing domain, providing the transition rates (which we derive) are chosen correctly and we partition the domain in the correct manner. We extend this analysis to the case where the domain is allowed to change in size, altering the transition rates as necessary. Through application of the master equation formalism we derive a PDE for particle density on this growing domain and corroborate our findings with numerical simulations.

  10. Nonimaging optics for nonuniform brightness distributions

    Science.gov (United States)

    Jenkins, David G.; Winston, Roland

    1995-08-01

    We present a general design method of nonimaging optics that obtains the highest possible concentration for a given absorber shape. This technique, which uses a complimentary edge ray to simplify the geometrical formulism, recovers familiar designs for flat phase space distributions, such as trumpets, and (theta) 1-(theta) 2 concentrators. This method is easy to use and handles diverse boundary conditions, such as reflection, satisfying total internal reflection or design within a material of graded index. Presented is a novel two-stage 2D solar collector with a fixed circular primary mirror and nonimaging secondary. This newly developed secondary gives a 25% improvement over conventional nonimaging concentrators.

  11. Parallel processing and non-uniform grids in global air quality modeling

    NARCIS (Netherlands)

    Berkvens, P.J.F.; Bochev, Mikhail A.

    2002-01-01

    A large-scale global air quality model, running efficiently on a single vector processor, is enhanced to make more realistic and more long-term simulations feasible. Two strategies are combined: non-uniform grids and parallel processing. The communication through the hierarchy of non-uniform grids

  12. Space cutter compensation method for five-axis nonuniform rational basis spline machining

    Directory of Open Access Journals (Sweden)

    Yanyu Ding

    2015-07-01

    Full Text Available In view of the good machining performance of traditional three-axis nonuniform rational basis spline interpolation and the space cutter compensation issue in multi-axis machining, this article presents a triple nonuniform rational basis spline five-axis interpolation method, which uses three nonuniform rational basis spline curves to describe cutter center location, cutter axis vector, and cutter contact point trajectory, respectively. The relative position of the cutter and workpiece is calculated under the workpiece coordinate system, and the cutter machining trajectory can be described precisely and smoothly using this method. The three nonuniform rational basis spline curves are transformed into a 12-dimentional Bézier curve to carry out discretization during the discrete process. With the cutter contact point trajectory as the precision control condition, the discretization is fast. As for different cutters and corners, the complete description method of space cutter compensation vector is presented in this article. Finally, the five-axis nonuniform rational basis spline machining method is further verified in a two-turntable five-axis machine.

  13. Microscopic image processing system for measuring nonuniform film thickness profiles: Image scanning ellipsometry

    International Nuclear Information System (INIS)

    Liu, A.H.; Plawsky, J.L.; Wayner, P.C. Jr.

    1993-01-01

    The long-term objective of this research program is to determine the stability and heat transfer characteristics of evaporating thin films. The current objective is to develop and use a microscopic image-processing system (IPS) which has two parts: an image analyzing interferometer (IAI) and an image scanning ellipsometer (ISE). The primary purpose of this paper is to present the basic concept of ISE, which is a novel technique to measure the two dimensional thickness profile of a non-uniform, thin film, from several nm up to several μm, in a steady state as well as in a transient state. It is a full-field imaging technique which can study every point on the surface simultaneously with high spatial resolution and thickness sensitivity, i.e., it can measure and map the 2-D film thickness profile. The ISE was tested by measuring the thickness profile and the refractive index of a nonuniform solid film

  14. Assessment of a non-uniform heat flux correction model to predicting CHF in PWR rod bundles

    International Nuclear Information System (INIS)

    Dae-Hyun, Hwang; Sung-Quun, Zee

    2001-01-01

    The full text follows. The prediction of CHF (critical heat flux) has been, in most cases, based on the empirical correlation. For PWR fuel assemblies the local parameter correlation requires the local thermal-hydraulic conditions usually calculated by a subchannel analysis code. The cross-sectional averaged fluid conditions of the subchannel, however, are not sufficient for determining CHF, especially for the cases of non-uniform axial heat flux distributions. Many investigators have studied the effect of the upstream heat flux on the CHF. In terms of the upstream memory effect, two different approaches have been considered as the limiting cases. The 'local conditions' hypothesis assumes that there is a unique relationship between the CHF and the local thermal-hydraulic conditions, and consequently there is no memory effect. In the 'overall power' hypothesis, on the other hand, it is assumed that the total power which can be fed into the tube with nonuniform heating will be the same as that for a uniformly heated tube of the same heated length with the same inlet conditions. Thus the CHF is totally influenced by the upstream heat flux distribution. In view of some experimental investigations such as the DeBortoli's test, it revealed that the two approaches are inadequate in general. It means that the local critical heat flux may be affected to some extent by the heat flux distribution upstream of the CHF location. Some correction-factor models have been suggested to take into account the upstream memory effect. Typically, Tong devised a correction factor on the basis of the heat balance of the superheated liquid layer that is spread underneath a highly viscous bubbly layer along the heated surface. His physical model suggested that the fluid enthalpy obtained from an energy balance of the superheated liquid layer is a representative quantity for the onset of DNB (departure nucleate boiling). A theoretically based correction factor model has been proposed by the

  15. TDM/FM/FDMA - A modulation technique for multiple-beam satellites which precludes cochannel interference and allows non-uniform geographic distribution of user channels

    Science.gov (United States)

    Springett, J. C.

    1982-01-01

    The technique outlined in this paper is intended to eliminate the problems of cochannel interference and uniform geographic distribution of user channels which arise in conventional designs for a multiple spot beam communication satellite to serve mobile telephony users across the CONUS. By time multiplexing FM/FDMA signal ensembles so that only those beams operating on distinct frequency subbands are allowed to transmit concurrently, cochannel interference arising from simultaneous frequency subband reuse is precluded. Thus, time disjoint frequency reuse is accomplished over a repetitive sequence of fixed time slots. By assigning different size subbands to each time slot, a market of nonuniform users can be accommodated. The technique results in a greatly simplified antenna feed system design for the satellite, at a cost of imposing the need for time slot synchronization on the mobile FM receivers whose ability for rejecting adjacent channel interference is somewhat diminished.

  16. TDM/FM/FDMA - A modulation technique for multiple-beam satellites which precludes cochannel interference and allows non-uniform geographic distribution of user channels

    Science.gov (United States)

    Springett, J. C.

    The technique outlined in this paper is intended to eliminate the problems of cochannel interference and uniform geographic distribution of user channels which arise in conventional designs for a multiple spot beam communication satellite to serve mobile telephony users across the CONUS. By time multiplexing FM/FDMA signal ensembles so that only those beams operating on distinct frequency subbands are allowed to transmit concurrently, cochannel interference arising from simultaneous frequency subband reuse is precluded. Thus, time disjoint frequency reuse is accomplished over a repetitive sequence of fixed time slots. By assigning different size subbands to each time slot, a market of nonuniform users can be accommodated. The technique results in a greatly simplified antenna feed system design for the satellite, at a cost of imposing the need for time slot synchronization on the mobile FM receivers whose ability for rejecting adjacent channel interference is somewhat diminished.

  17. Further Development of Ko Displacement Theory for Deformed Shape Predictions of Nonuniform Aerospace Structures

    Science.gov (United States)

    Ko, William L.; Fleischer, Van Tran

    2009-01-01

    The Ko displacement theory previously formulated for deformed shape predictions of nonuniform beam structures is further developed mathematically. The further-developed displacement equations are expressed explicitly in terms of geometrical parameters of the beam and bending strains at equally spaced strain-sensing stations along the multiplexed fiber-optic sensor line installed on the bottom surface of the beam. The bending strain data can then be input into the displacement equations for calculations of local slopes, deflections, and cross-sectional twist angles for generating the overall deformed shapes of the nonuniform beam. The further-developed displacement theory can also be applied to the deformed shape predictions of nonuniform two-point supported beams, nonuniform panels, nonuniform aircraft wings and fuselages, and so forth. The high degree of accuracy of the further-developed displacement theory for nonuniform beams is validated by finite-element analysis of various nonuniform beam structures. Such structures include tapered tubular beams, depth-tapered unswept and swept wing boxes, width-tapered wing boxes, and double-tapered wing boxes, all under combined bending and torsional loads. The Ko displacement theory, combined with the fiber-optic strain-sensing system, provide a powerful tool for in-flight deformed shape monitoring of unmanned aerospace vehicles by ground-based pilots to maintain safe flights.

  18. The prediction of burnout in non-uniformly heated rod clusters from burnout data for uniformly heated round tubes

    International Nuclear Information System (INIS)

    Barnett, P.G.

    1964-11-01

    The practice of using burnout data for uniformly heated round tubes to predict burnout in non-uniformly heated reactor channels having complex cross sections is examined. At least two hypotheses are involved: (i) a relationship exists between uniform and non-uniform heat flux distributions and (ii) a relationship exists between simple and complex channel cross sections. Use of two such hypotheses each accurate to ± 15% and a correlation of uniformly heated round tube data having an R.M.S. error of 5%, could yield errors of ± 40% in any predicted value; this figure of ± 40% is regarded as a realistic upper limit for design purposes. It is shown that no method can exist for relating different channel cross sections to within ± 15% and existing methods for relating different heat flux distributions incur some errors exceeding 20%. Furthermore, any suggested method for relating different heat flux distributions can be adequately checked only when a sufficiently large number of results are available and then the preferable alternative of correlating the data is possible. It is concluded that no reliable method can exist for predicting burnout in rod bundles from uniformly heated round tube data with sufficient accuracy for design purposes. (author)

  19. Wetting layer and void fraction nonuniformity in a liquid-metal MHD generator

    International Nuclear Information System (INIS)

    Branover, H.; Yakhot, A.

    1981-01-01

    The quetion of the effect of a liquid layer on the walls of an MHD channel in the case of uniform void fraction distribution in the flow core was first considered several years ago. More recently an analytic solution for high Hartmann numbers was obtained, which led to the conclusion that this layer does not have a significant effect on the efficiency of large generators. This paper postulates an analytic model which makes it possible to estimate the effect of a void fraction nonuniformity, in the presence of the wetting layer on the walls, on the generator performance. 3 refs

  20. Initial particle loadings for a nonuniform simulation plasma in a magnetic field

    International Nuclear Information System (INIS)

    Naitou, Hiroshi; Kamimura, Tetsuo; Tokuda, Sinji.

    1978-09-01

    Improved methods for initially loading particles in a magnetized simulation plasma with nonuniform density and temperature distributions are proposed. In the usual guiding center loading (GCL), a charge separation coming from finite Larmor radius effects remains due to the difference between the guiding center density and the actual density. The modified guiding center loading (MGCL) presented here eliminates the electric field so generated and can be used for arbitrary density and temperature profiles. Some applications of these methods to actual simulations are given for comparison. The significance of these methods of initial particle loadings is also discussed. (author)

  1. Laser investigation of the non-uniformity of fluorescent species in dental enamel

    Science.gov (United States)

    Tran, Stephanie U.; Ridge, Jeremy S.; Nelson, Leonard Y.; Seibel, Eric J.

    In the present study, artificial type I and type II erosions were created on dental specimen using acetic acid and EDTA respectively. Specimens were prepared by etching extracted teeth samples in acid to varying degrees, after which the absolute fluorescence intensity ratio of the etched enamel relative to sound enamel was recorded for each specimen using 405 and 532 nm laser excitation. Results showed differences in the fluorescence ratio of etched to sound enamel for type I and II erosions. These findings suggest a non-uniform distribution of fluorescent species in the interprismatic region as compared to the prismatic region.

  2. Stone Stability in Non-uniform Flow

    NARCIS (Netherlands)

    Hoan, N.T.; Stive, M.J.F.; Booij, R.; Hofland, B.; Verhagen, H.J.

    2011-01-01

    This paper presents the results of an experimental study on stone stability under nonuniform turbulent flow, in particular expanding flow. Detailed measurements of both flow and turbulence and the bed stability are described. Than various manners of quantifying the hydraulic loads exerted on the

  3. Stone Stability under Stationary Nonuniform Flows

    NARCIS (Netherlands)

    Steenstra, Remco; Hofland, B.; Paarlberg, Andries; Smale, Alfons; Huthoff, Fredrik; Uijttewaal, W.S.J.

    2016-01-01

    A stability parameter for rock in bed protections under nonuniform stationary flow is derived. The influence of the mean flow velocity, turbulence, and mean acceleration of the flow are included explicitly in the parameter. The relatively new notion of explicitly incorporating the mean acceleration

  4. Comparison of Measured Dark Current Distributions with Calculated Damage Energy Distributions in HgCdTe

    Science.gov (United States)

    Marshall, C. J.; Marshall, P. W.; Howe, C. L.; Reed, R. A.; Weller, R. A.; Mendenhall, M.; Waczynski, A.; Ladbury, R.; Jordan, T. M.

    2007-01-01

    This paper presents a combined Monte Carlo and analytic approach to the calculation of the pixel-to-pixel distribution of proton-induced damage in a HgCdTe sensor array and compares the results to measured dark current distributions after damage by 63 MeV protons. The moments of the Coulombic, nuclear elastic and nuclear inelastic damage distributions were extracted from Monte Carlo simulations and combined to form a damage distribution using the analytic techniques first described in [1]. The calculations show that the high energy recoils from the nuclear inelastic reactions (calculated using the Monte Carlo code MCNPX [2]) produce a pronounced skewing of the damage energy distribution. While the nuclear elastic component (also calculated using the MCNPX) contributes only a small fraction of the total nonionizing damage energy, its inclusion in the shape of the damage across the array is significant. The Coulombic contribution was calculated using MRED [3-5], a Geant4 [4,6] application. The comparison with the dark current distribution strongly suggests that mechanisms which are not linearly correlated with nonionizing damage produced according to collision kinematics are responsible for the observed dark current increases. This has important implications for the process of predicting the on-orbit dark current response of the HgCdTe sensor array.

  5. An improved non-uniformity correction algorithm and its GPU parallel implementation

    Science.gov (United States)

    Cheng, Kuanhong; Zhou, Huixin; Qin, Hanlin; Zhao, Dong; Qian, Kun; Rong, Shenghui

    2018-05-01

    The performance of SLP-THP based non-uniformity correction algorithm is seriously affected by the result of SLP filter, which always leads to image blurring and ghosting artifacts. To address this problem, an improved SLP-THP based non-uniformity correction method with curvature constraint was proposed. Here we put forward a new way to estimate spatial low frequency component. First, the details and contours of input image were obtained respectively by minimizing local Gaussian curvature and mean curvature of image surface. Then, the guided filter was utilized to combine these two parts together to get the estimate of spatial low frequency component. Finally, we brought this SLP component into SLP-THP method to achieve non-uniformity correction. The performance of proposed algorithm was verified by several real and simulated infrared image sequences. The experimental results indicated that the proposed algorithm can reduce the non-uniformity without detail losing. After that, a GPU based parallel implementation that runs 150 times faster than CPU was presented, which showed the proposed algorithm has great potential for real time application.

  6. Assessment indices for uniform and non-uniform thermal environments

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Different assessment indices for thermal environments were compared and selected for proper assessment of indoor thermal environments.30 subjects reported their overall thermal sensation,thermal comfort,and thermal acceptability in uniform and non-uniform conditions.The results show that these three assessment indices provide equivalent evaluations in uniform environments.However,overall thermal sensation differs from the other two indices and cannot be used as a proper index for the evaluation of non-uniform environments.The relationship between the percentage and the mean vote for each index is established.

  7. Concentration polarization effects on the macromolecular transport in the presence of non-uniform magnetic field: A numerical study using a lumen-wall model

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadpourfard, M., E-mail: Mohammadpour@azaruniv.edu [Department of Mechanical Engineering, Azarbaijan Shahid Madani University, Tabriz 53751-71379 (Iran, Islamic Republic of); Aminfar, H., E-mail: hh_aminfar@tabrizu.ac.ir [Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of); Khajeh, K., E-mail: khajeh.k.2005@gmail.com [Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2014-04-01

    In this paper, the concentration polarization phenomena in a two dimensional tube under steady state conditions containing ferrofluid (blood and 4 vol% Fe{sub 3}O{sub 4}) is reported in the presence of non-uniform magnetic field. Lumen-wall model has been used for solving the mass transport equation. Hemodynamics parameters such as flow rate, viscosity, wall shear stress (WSS) and the macromolecules surface concentration which accumulate on the blood vessel wall, influenced the formation and progression of atherosclerosis disease. Effective parameters on the low density lipoprotein (LDL) surface concentration (LSC) such as: the wall filtration velocity, inlet Reynolds number and WSS under applied non-uniform magnetic field have been examined. Numerical solution of governing equations of the flow field have been obtained by using the single-phase model and the control volume technique. Magnetic field is generated by an electric current going through a thin and straight wire oriented perpendicular to the tube. Results show WSS in the vicinity of magnetic field source increased and LSC decreased along the wall. - Highlights: • In this paper the concentration polarization phenomena of blood flow is reported in the presence of non-uniform magnetic field. • In presence of non-uniform magnetic field LSC will decrease along the wall due to the increasing the velocity gradients near the magnetic source. • When non-uniform magnetic field intensity increases, LSC along the wall becomes lower. • Non-uniform magnetic field can affects the flow more in low Reynolds numbers.

  8. Systematic studies of the gas humidification effects on spatial PEMFC performance distributions

    International Nuclear Information System (INIS)

    Reshetenko, Tatyana V.; Bender, Guido; Bethune, Keith; Rocheleau, Richard

    2012-01-01

    Highlights: ► We investigated impacts of gases humidification on a local PEMFC performance. ► The spatial performance and EIS were studied by a segmented cell system. ► The data were analyzed in the terms of voltage losses. ► A reduction in anode/cathode gases humidification decreased a PEMFC performance. ► A decrease of humidification led to non-uniform performances and voltage losses distributions. - Abstract: The overall current density that is measured in a proton exchange membrane fuel cell (PEMFC) represents the average of the local reaction rates. The overall and local PEMFC performances are determined by several primary loss mechanisms, namely activation, ohmic, and mass transfer. Spatial performance and loss variabilities are significant and depend on the cell design and operating conditions. A segmented cell system was used to quantify different loss distributions along the gas channel to understand the effects of gas humidification. A reduction in the reactant stream humidification decreased cell performance and resulted in non-uniform distributions of overpotentials and performance along the flow field. Activation and ohmic overpotentials increased with a relative humidity decrease due to insufficient membrane and catalyst layer hydration. The relative humidity of the cathode had a strong impact on the mass transfer overpotential due to a lower oxygen permeability through the dry Nafion film covering the catalyst surface. The mass transfer loss distribution was non-uniform, and the mass transfer overpotential increased for the outlet segments due to the oxygen consumption at the inlet segments, which reduced the oxygen concentration downstream, and a progressive water accumulation from upstream segments. Electrochemical impedance spectroscopy (EIS) and an equivalent electric circuit (EEC) facilitated the analysis and interpretation of the segmented cell data.

  9. On natural frequencies of non-uniform beams modulated by finite periodic cells

    International Nuclear Information System (INIS)

    Xu, Yanlong; Zhou, Xiaoling; Wang, Wei; Wang, Longqi; Peng, Fujun; Li, Bin

    2016-01-01

    It is well known that an infinite periodic beam can support flexural wave band gaps. However, in real applications, the number of the periodic cells is always limited. If a uniform beam is replaced by a non-uniform beam with finite periodicity, the vibration changes are vital by mysterious. This paper employs the transfer matrix method (TMM) to study the natural frequencies of the non-uniform beams with modulation by finite periodic cells. The effects of the amounts, cross section ratios, and arrangement forms of the periodic cells on the natural frequencies are explored. The relationship between the natural frequencies of the non-uniform beams with finite periodicity and the band gap boundaries of the corresponding infinite periodic beam is also investigated. Numerical results and conclusions obtained here are favorable for designing beams with good vibration control ability. - Highlights: • The transfer matrix method to study the natural frequencies of the finite periodic non-uniform beams is derived. • The transfer matrix method to study the band gaps of the infinite periodic non-uniform beams is derived. • The effects of the periodic cells on the natural frequencies are explored. • The relationships of the natural frequencies and band gap boundaries are investigated.

  10. On natural frequencies of non-uniform beams modulated by finite periodic cells

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yanlong, E-mail: xuyanlong@nwpu.edu.cn [School of Aeronautics, Northwestern Polytechnical University, Xi' an 710072, Shaanxi (China); Zhou, Xiaoling [Shanghai Institute of Aerospace System Engineering, Shanghai 201109 (China); Wang, Wei [School of Aeronautics, Northwestern Polytechnical University, Xi' an 710072, Shaanxi (China); Wang, Longqi [School of Civil & Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Peng, Fujun [Shanghai Institute of Aerospace System Engineering, Shanghai 201109 (China); Li, Bin [School of Aeronautics, Northwestern Polytechnical University, Xi' an 710072, Shaanxi (China)

    2016-09-23

    It is well known that an infinite periodic beam can support flexural wave band gaps. However, in real applications, the number of the periodic cells is always limited. If a uniform beam is replaced by a non-uniform beam with finite periodicity, the vibration changes are vital by mysterious. This paper employs the transfer matrix method (TMM) to study the natural frequencies of the non-uniform beams with modulation by finite periodic cells. The effects of the amounts, cross section ratios, and arrangement forms of the periodic cells on the natural frequencies are explored. The relationship between the natural frequencies of the non-uniform beams with finite periodicity and the band gap boundaries of the corresponding infinite periodic beam is also investigated. Numerical results and conclusions obtained here are favorable for designing beams with good vibration control ability. - Highlights: • The transfer matrix method to study the natural frequencies of the finite periodic non-uniform beams is derived. • The transfer matrix method to study the band gaps of the infinite periodic non-uniform beams is derived. • The effects of the periodic cells on the natural frequencies are explored. • The relationships of the natural frequencies and band gap boundaries are investigated.

  11. Influence of inclined Lorentz force on micropolar fluids in a square cavity with uniform and nonuniform heated thin plate

    Energy Technology Data Exchange (ETDEWEB)

    Periyadurai, K. [Department of Mathematics, Bharathiar University, Coimbatore 641046, Tamil Nadu (India); Muthtamilselvan, M., E-mail: muthtamill@yahoo.co.in [Department of Mathematics, Bharathiar University, Coimbatore 641046, Tamil Nadu (India); Doh, Deog-Hee [Division of Mechanical Engineering, College of Engineering,Korea Maritime Ocean University, Busan 606781 (Korea, Republic of)

    2016-12-15

    In the present study, the effect of inclined magnetic field on natural convection of micro-polar fluid in a square cavity with uniform and nonuniform heated thin plate built in centrally is investigated numerically. The vertical walls are cooled while the top and bottom walls are insulated. The thin plate is assumed to be isothermal with a linearly varying temperature. The governing equations were solved by finite volume method using second order central difference scheme and upwind differencing scheme. The numerical investigation is carried out for different governing parameters namely, the Hartmann number, inclination angle of magnetic field, Rayleigh number, vortex viscosity and source non-uniformity parameters. The result shows that the heat transfer rate is decreased when increasing Hartmann number, inclination angle of magnetic field and vortex viscosity parameter. It is found that the non-uniformity parameter affects the fluid flow and temperature distribution especially for the high Rayleigh numbers. Finally, the overall heat transfer rate of micro-polar fluids is found to be smaller than that of Newtonian fluid. - Highlights: • We investigate the effect of inclined magnetic field on micropolar fluid in a cavity. • The effects of uniform and non-uniform heated plate are studied. • The present numerical results are compared with the experimental results. • The addition of vortex viscosity parameter declines the heat transfer performance. • The high heat transfer rate occurs in the vertical plate compared to the horizontal one.

  12. Capacitated Vehicle Routing with Nonuniform Speeds

    DEFF Research Database (Denmark)

    Gørtz, Inge Li; Molinaro, Marco; Nagarajan, Viswanath

    2016-01-01

    is the distance traveled divided by its speed.Our algorithm relies on a new approximate minimum spanning tree construction called Level-Prim, which is related to but different from Light Approximate Shortest-path Trees. We also extend the widely used tour-splitting technique to nonuniform speeds, using ideas from...

  13. Nonequilibrium Microscopic Distribution of Thermal Current in Particle Systems

    KAUST Repository

    Yukawa, Satoshi

    2009-02-15

    A nonequilibrium distribution function of microscopic thermal current is studied by a direct numerical simulation in a thermal conducting steady state of particle systems. Two characteristic temperatures of the thermal current are investigated on the basis of the distribution. It is confirmed that the temperature depends on the current direction; Parallel temperature to the heat-flux is higher than antiparallel one. The difference between the parallel temperature and the antiparallel one is proportional to a macroscopic temperature gradient. ©2009 The Physical Society of Japan.

  14. Nonequilibrium Microscopic Distribution of Thermal Current in Particle Systems

    KAUST Repository

    Yukawa, Satoshi; Shimada, Takashi; Ogushi, Fumiko; Ito, Nobuyasu

    2009-01-01

    A nonequilibrium distribution function of microscopic thermal current is studied by a direct numerical simulation in a thermal conducting steady state of particle systems. Two characteristic temperatures of the thermal current are investigated on the basis of the distribution. It is confirmed that the temperature depends on the current direction; Parallel temperature to the heat-flux is higher than antiparallel one. The difference between the parallel temperature and the antiparallel one is proportional to a macroscopic temperature gradient. ©2009 The Physical Society of Japan.

  15. Experimental study on the CHF in uniformly and non-uniformly heated vertical annuli

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Se Young; Moon, Sang Ki; Chung, Heung June; Park, Jong Kuk; Kim, Bok Deuk; Youn, Young Jung; Chung, Moon Ki

    2001-09-01

    Up to now, KAERI has performed critical heat flux experiments in water under zero-flow and low-flow conditions using a RCS CHF loop facility with uniformly and non-uniformly heated vertical annulus. Since the existing CHF experiments were mainly performed under low-pressure conditions, we performed the CHF experiment to investigate the pressure effect on the CHF under zero-flow and low-flow conditions for a wide range of system pressures. Also, two vertical annuli with the same geometry have been used to investigate the axial heat flux distributions on the CHF. This report summarizes the experimental results and provides the CHF data that can be used for the development for CHF correlation and a thermal hydraulic analysis code. The CHF data have been collected for system pressures ranging from 0.57 to 15.15 MPa, mass flux 0 and from 200 to 650 kg/m2s, inlet subcooling from 75 to 360 kJ/kg and exit quality from 0.07 to 0.57. At low-flow conditions, the total number of data are 242 and 290 with uniformly heated- and non-uniformly heated test sections, respectively. 41 and 94 CHF data are generated with uniformly heated- and non-uniformly heated test sections, respectively, in zero-flow CHF experiments that are performed by blocking test section bottoms. The CHF experiment result shows that the effects of system pressure, mass flux and inlet subcooling are consistent with conventional understandings and similar to those for round tubes. The behavior of the CHF is relatively complex at low pressures. Also, the effects of axial heat flux profile are large at low-pressure conditions.

  16. Experimental study on the CHF in uniformly and non-uniformly heated vertical annuli

    International Nuclear Information System (INIS)

    Chun, Se Young; Moon, Sang Ki; Chung, Heung June; Park, Jong Kuk; Kim, Bok Deuk; Youn, Young Jung; Chung, Moon Ki

    2001-09-01

    Up to now, KAERI has performed critical heat flux experiments in water under zero-flow and low-flow conditions using a RCS CHF loop facility with uniformly and non-uniformly heated vertical annulus. Since the existing CHF experiments were mainly performed under low-pressure conditions, we performed the CHF experiment to investigate the pressure effect on the CHF under zero-flow and low-flow conditions for a wide range of system pressures. Also, two vertical annuli with the same geometry have been used to investigate the axial heat flux distributions on the CHF. This report summarizes the experimental results and provides the CHF data that can be used for the development for CHF correlation and a thermal hydraulic analysis code. The CHF data have been collected for system pressures ranging from 0.57 to 15.15 MPa, mass flux 0 and from 200 to 650 kg/m2s, inlet subcooling from 75 to 360 kJ/kg and exit quality from 0.07 to 0.57. At low-flow conditions, the total number of data are 242 and 290 with uniformly heated- and non-uniformly heated test sections, respectively. 41 and 94 CHF data are generated with uniformly heated- and non-uniformly heated test sections, respectively, in zero-flow CHF experiments that are performed by blocking test section bottoms. The CHF experiment result shows that the effects of system pressure, mass flux and inlet subcooling are consistent with conventional understandings and similar to those for round tubes. The behavior of the CHF is relatively complex at low pressures. Also, the effects of axial heat flux profile are large at low-pressure conditions

  17. Test stand for non-uniformity correction of microbolometer focal plane arrays used in thermal cameras

    Science.gov (United States)

    Krupiński, Michał; Bareła, Jaroslaw; Firmanty, Krzysztof; Kastek, Mariusz

    2013-10-01

    Uneven response of particular detectors (pixels) to the same incident power of infrared radiation is an inherent feature of microbolometer focal plane arrays. As a result an image degradation occurs, known as Fixed Pattern Noise (FPN), which distorts the thermal representation of an observed scene and impairs the parameters of a thermal camera. In order to compensate such non-uniformity, several NUC correction methods are applied in digital data processing modules implemented in thermal cameras. Coefficients required to perform the non-uniformity correction procedure (NUC coefficients) are determined by calibrating the camera against uniform radiation sources (blackbodies). Non-uniformity correction is performed in a digital processing unit in order to remove FPN pattern in the registered thermal images. Relevant correction coefficients are calculated on the basis of recorded detector responses to several values of radiant flux emitted from reference IR radiation sources (blackbodies). The measurement of correction coefficients requires specialized setup, in which uniform, extended radiation sources with high temperature stability are one of key elements. Measurement stand for NUC correction developed in Institute of Optoelectronics, MUT, comprises two integrated extended blackbodies with the following specifications: area 200×200 mm, stabilized absolute temperature range +15 °C÷100 °C, and uniformity of temperature distribution across entire surface +/-0.014 °C. Test stand, method used for the measurement of NUC coefficients and the results obtained during the measurements conducted on a prototype thermal camera will be presented in the paper.

  18. Nonuniform charging effects on ion drag force in drifting dusty plasmas

    International Nuclear Information System (INIS)

    Chang, Dong-Man; Chang, Won-Seok; Jung, Young-Dae

    2006-01-01

    The nonuniform polarization charging effects on the ion drag force are investigated in drifting dusty plasmas. The ion drag force due to the ion-dust grain interaction is obtained as a function of the dust charge, ion charge, plasma temperature, Mach number, Debye length, and collision energy. The result shows that the nonuniform charging effects enhance the momentum transfer cross section as well as the ion drag force. It is found that the momentum transfer cross section and the ion drag force including nonuniform polarization charging effects increase with increasing the Mach number and also the ion drag force increases with increasing the temperature. In addition, it is found that the ion drag force is slightly decreasing with an increase of the Debye length

  19. Zero bias thermally stimulated currents in synthetic diamond

    Science.gov (United States)

    Mori, R.; Miglio, S.; Bruzzi, M.; Bogani, F.; De Sio, A.; Pace, E.

    2009-06-01

    Zero bias thermally stimulated currents (ZBTSCs) have been observed in single crystal high pressure high temperature (HPHT) and polycrystalline chemical vapor deposited (pCVD) diamond films. The ZBTSC technique is characterized by an increased sensitivity with respect to a standard TSC analysis. Due to the absence of the thermally activated background current, new TSC peaks have been observed in both HPHT and pCVD diamond films, related to shallow activation energies usually obscured by the emission of the dominant impurities. The ZBTSC peaks are explained in terms of defect discharge in the nonequilibrium potential distribution created by a nonuniform traps filling at the metal-diamond junctions. The electric field due to the charged defects has been estimated in a quasizero bias TSC experiment by applying an external bias.

  20. Shape and fission instabilities of ferrofluids in non-uniform magnetic fields

    Science.gov (United States)

    Vieu, Thibault; Walter, Clément

    2018-04-01

    We study static distributions of ferrofluid submitted to non-uniform magnetic fields. We show how the normal-field instability is modified in the presence of a weak magnetic field gradient. Then we consider a ferrofluid droplet and show how the gradient affects its shape. A rich phase transitions phenomenology is found. We also investigate the creation of droplets by successive splits when a magnet is vertically approached from below and derive theoretical expressions which are solved numerically to obtain the number of droplets and their aspect ratio as function of the field configuration. A quantitative comparison is performed with previous experimental results, as well as with our own experiments, and yields good agreement with the theoretical modeling.

  1. A DSP-based neural network non-uniformity correction algorithm for IRFPA

    Science.gov (United States)

    Liu, Chong-liang; Jin, Wei-qi; Cao, Yang; Liu, Xiu

    2009-07-01

    An effective neural network non-uniformity correction (NUC) algorithm based on DSP is proposed in this paper. The non-uniform response in infrared focal plane array (IRFPA) detectors produces corrupted images with a fixed-pattern noise(FPN).We introduced and analyzed the artificial neural network scene-based non-uniformity correction (SBNUC) algorithm. A design of DSP-based NUC development platform for IRFPA is described. The DSP hardware platform designed is of low power consumption, with 32-bit fixed point DSP TMS320DM643 as the kernel processor. The dependability and expansibility of the software have been improved by DSP/BIOS real-time operating system and Reference Framework 5. In order to realize real-time performance, the calibration parameters update is set at a lower task priority then video input and output in DSP/BIOS. In this way, calibration parameters updating will not affect video streams. The work flow of the system and the strategy of real-time realization are introduced. Experiments on real infrared imaging sequences demonstrate that this algorithm requires only a few frames to obtain high quality corrections. It is computationally efficient and suitable for all kinds of non-uniformity.

  2. Allowance for influence of gravity field nonuniformity

    Science.gov (United States)

    Tsysar, A. P.

    1987-03-01

    The constants of a quartz-metal pendulum used in higher-order gravimetric networks have been determined and a formula has been derived for the total correction for gravity field nonuniformity measurements made with the pendulum. Nomograms were constructed on the basis of these formulas and are used in introducing corrections into pendulum measurements. A table was prepared giving the components of the correction for some values of the derivatives of gravity potential from surrounding masses. Errors can be caused by building walls, the pedestal on which the instrument sits and other factors, and these must be taken into account since they increase the normal gravity gradient. After introducing these correction components for the nonuniform gravity field, the gravity field at the measurement point is related to the instrument point coinciding with the middle of the pendulum knife blade.

  3. Initial magnetic field decay of the superconducting magnet in persistent current mode

    International Nuclear Information System (INIS)

    Yamamoto, S.; Yanada, T.

    1988-01-01

    The initial magnetic field decay in the persistent current mode of a magnetic resonance imaging magnet has been studied experimentally. The field decay is greater than the steady field decay due to joint resistances of conductors. Imaging experiments cannot be carried out during the periods, which last ten or more hours. The current distribution in the multifilamentory conductor is non-uniform just after the energization. It is suggested that the change of the current distribution causes the initial magnetic field decay. A 6th order superconducting magnet was prepared for experiments (central field = 0.35 T, inner diameters = 1 m, length = 1.86 m). The steady state magnetic field decay was 7*10/sup -8//hr. The initial magnetic field decay was 3*10/sup -6//hr. Overshoot currents (101 and 105 percent of the rated current) were applied to the magnet and the current reduced to the rated current to improve the initial decay. The energizing and de-energizing rate of the field was 1.8 gauss/second. No initial decay was observed when 105 percent current pattern was applied to the magnet

  4. Variational theory of cyclotron emission from nonuniformly magnetized plasmas

    International Nuclear Information System (INIS)

    Shvets, V.F.; Swanson, D.G.

    1992-01-01

    Whereas direct calculations of emission from a source model in both homogeneous and weakly inhomogeneous media have been previously executed, there are no previous theories of the source distribution function from nonuniformly magnetized plasmas where mode conversion phenomena must be taken into account. Whenever the emitting layer is localized due to gradients of the external magnetic field, mode conversion leads to the Generalized Kirchhoff's Law (GKL) E 1 /A 1 = E 2 /A 2 = E 3 /A 3 , where A j represents the absorbed fraction on the j-th wave branch and E j is the corresponding emitted energy along j-th branch. Recently integral expressions for A j and E j in terms of arbitrary localized sink and source distributions have been obtained. The GKL relating absorption to emission along each branch of coexisting in the inhomogeneous mode conversion layer affects the shape of source distribution through a functional of the emissivity. Moreover, E j /A j ≡ I bb , where I bb is a black body radiated power. Accordingly, the distributed emission source function should be an extremal of the emissivity functional. The authors have developed the corresponding variational analysis with nontrivial GKL constraints. As a result they have discovered the correct representation of the ratio of source and sink distributions in the form of an expansion in linearly independent adjoint wave solutions of the absorption problem. Finally, unknown coefficients have been found numerically by further maximization taking account of both source boundedness and the GKL constraints. Calculations performed for a broad variety of plasma parameters will be presented

  5. Testing for Nonuniform Differential Item Functioning with Multiple Indicator Multiple Cause Models

    Science.gov (United States)

    Woods, Carol M.; Grimm, Kevin J.

    2011-01-01

    In extant literature, multiple indicator multiple cause (MIMIC) models have been presented for identifying items that display uniform differential item functioning (DIF) only, not nonuniform DIF. This article addresses, for apparently the first time, the use of MIMIC models for testing both uniform and nonuniform DIF with categorical indicators. A…

  6. Gas dynamic improvement of the axial compressor design for reduction of the flow non-uniformity level

    Science.gov (United States)

    Matveev, V. N.; Baturin, O. V.; Kolmakova, D. A.; Popov, G. M.

    2017-01-01

    Circumferential nonuniformity of gas flow is one of the main problems in the gas turbine engine. Usually, the flow circumferential nonuniformity appears near the annular frame located in the flow passage of the engine. The presence of circumferential nonuniformity leads to the increased dynamic stresses in the blade rows and the blade damage. The goal of this research was to find the ways of the flow non-uniformity reduction, which would not require a fundamental changing of the engine design. A new method for reducing the circumferential nonuniformity of the gas flow was proposed that allows the prediction of the pressure peak values of the rotor blades without computationally expensive CFD calculations.

  7. Control of phase transition dynamics in media with nanoscale nonuniformities by coherence loss spectroscopy

    International Nuclear Information System (INIS)

    Brodsky, Anatol M

    2010-01-01

    The optical nondestructive characterization of chemical transformation dynamics and diffusion kinetics, including phase transitions, in heterogeneous media with a random distribution of nanoparticles (nano-nonuniformities), is of great theoretical and practical importance. Such characterization, with the help of coherence loss spectroscopy, considered in this paper can be applied for the control of a number of industrial processes dynamics, environmental monitoring, and medical diagnostics and therapy. As a specific example, the growth of crystal nuclei (embrions) as a result of the diffusion to them of a substance from the surrounding supersaturated solution is considered

  8. Microwave interaction with nonuniform hydrogen gas in carbon nanotubes

    International Nuclear Information System (INIS)

    Babaei, S.; Babaei, Sh.

    2009-01-01

    In this paper we study the reflection, absorption, and transmission of microwave from nonuniform hydrogen gas in carbon nanotubes, grown by iron-catalyzed high-pressure carbon monoxide disproportionate (HiPco) process. A discussion on the effect of various hydrogen gas parameters on the reflected power, absorbed power, and transmitted power is presented. The nonuniform hydrogen gas slab is modeled by a series of subslabs. The overall number density profile across the whole slab follows a parabolic function. The total reflected, absorbed, and transmitted powers are then deduced and their functional dependence on the number density, collision frequency, and angle of propagation is studied

  9. Current and field distribution in high temperature superconductors

    International Nuclear Information System (INIS)

    Johnston, M.D.

    1998-01-01

    The manufacture of wires from HTS materials containing copper-oxide planes is difficult because their physical and electrical properties are highly anisotropic. The electrical connectivity depends on the nearest-neighbour grain alignment and although a high degree of grain texture is achieved through processing, the tape microstructure is generally far from uniform, with weak links and porosity also complicating the picture. In order to optimise the processing, the microstructural features common to good tapes must be identified, requiring knowledge of the local properties. The preferential path taken by transport current is determined by the properties of the local microstructure and as such can be used to measure the variation in quality across the tape cross-section. By measuring the self-field profile generated by a current-carrying tape, it is possible to extract the associated current distribution. I have designed and built a Scanning Hall Probe Microscope to measure the normal field distribution above superconductor tapes carrying DC currents, operating at liquid nitrogen temperature and zero applied magnetic field. It has a spatial resolution of 50*50 μm and a field sensitivity of 5 μT, and can scan over a distance of 6 mm. The current extraction is performed by means of a deconvolution procedure based on Legendre functions. This allows a nondestructive, non-invasive method of evaluating the effects of the processing on the tapes - especially when correlated with transport and magnetisation measurement data. Conductors fabricated from Bi 2 Sr 2 Ca 2 Cu 3 O 10 , Bi 2 Sr 2 CaCu 2 O 8 and (Tl 0.78 Bi 0.22 )(Sr 0.8 Ba 0.2 ) 2 Ca 2 Cu 3 O x , have been investigated. I have confirmed the reports that in Bi-2223/Ag mono-core conductors produced by the oxide-powder-in-tube (OPIT) technique, the current flows predominantly at the edges of the tape, where the grains are long and well-aligned. This is in contrast to Bi-2212 ribbons, where the better microstructure

  10. Synchronization in a non-uniform network of excitatory spiking neurons

    Science.gov (United States)

    Echeveste, Rodrigo; Gros, Claudius

    Spontaneous synchronization of pulse coupled elements is ubiquitous in nature and seems to be of vital importance for life. Networks of pacemaker cells in the heart, extended populations of southeast asian fireflies, and neuronal oscillations in cortical networks, are examples of this. In the present work, a rich repertoire of dynamical states with different degrees of synchronization are found in a network of excitatory-only spiking neurons connected in a non-uniform fashion. In particular, uncorrelated and partially correlated states are found without the need for inhibitory neurons or external currents. The phase transitions between these states, as well the robustness, stability, and response of the network to external stimulus are studied.

  11. distribution of euphausiid crustaceans from the agulhas current

    African Journals Online (AJOL)

    may set up a northeasterly counter-current close to the coast and cause local upwelling (aowes. 1950; Darbyshire 1964). The Agulhas Current shows considerable seasonal variation in its rate of flow (Darbyshire. 1964) and ...... detailed study of the biology and distribution of this interesting species in eastern Cape coastal.

  12. Radar Doppler Processing with Nonuniform Sampling.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-07-01

    Conventional signal processing to estimate radar Doppler frequency often assumes uniform pulse/sample spacing. This is for the convenience of t he processing. More recent performance enhancements in processor capability allow optimally processing nonuniform pulse/sample spacing, thereby overcoming some of the baggage that attends uniform sampling, such as Doppler ambiguity and SNR losses due to sidelobe control measures.

  13. Experimental and theoretical studies of the effects of nonuniformities in equilibrium MHD generators

    International Nuclear Information System (INIS)

    Rosenbaum, M.; Shamma, S.E.; Louis, J.F.

    1980-01-01

    An experimental study of the effects of thermal and velocity nonuniformities is performed in an equilibrium plasma for a range of Hall parameters. An electrodeless MHD disk generator with radial flow is chosen as the ideal geometry for these experiments. By introducing equally spaced cold blades in the flow, it is possible to create well defined two-dimensional wake nonuniformities with strong variations of the plasma properties in the direction normal to the magnetic field and the flow. This type of nonuniformity is predicted to provide the strongest reduction of Hall coefficient and effective conductivity for high values of Hall parameter. This degradation is controlled by both the level of nonuniformities and the value of the ideal Hall parameter. The former is dependent upon the number of blades (root mean square deviation of the conductivity), and the latter is dependent upon the values of the magnetic field intensities. The results provide basic quantitative information about the effects of conductivity and velocity nonuniformities on the performance of equilibrium MHD generators over a wide range of Hall coefficients, between 2 and 7. Reduction formulae are established between the effective and ideal Hall parameters for different levels of nonuniformities intensities. Theoretical predictions are derived from a detailed two-dimensional electrodynamic analysis and a simplified engineering model based on a generalization of Rosa's layer model. These experiments validate the analytical studies and support the use of the theoretical layer models in describing the effect of boundary layers on the performance of linear generators

  14. Current distribution in a plasma erosion opening switch

    International Nuclear Information System (INIS)

    Weber, B.V.; Commisso, R.J.; Meger, R.A.; Neri, J.M.; Oliphant, W.F.; Ottinger, P.F.

    1984-01-01

    The current distribution in a plasma erosion opening switch is determined from magnetic field probe data. During the closed state of the switch the current channel broadens rapidly. The width of the current channel is consistent with a bipolar current density limit imposed by the ion flux to the cathode. The effective resistivity of the current channel is anomalously large. Current is diverted to the load when a gap opens near the cathode side of the switch. The observed gap opening can be explained by erosion of the plasma. Magnetic pressure is insufficient to open the gap

  15. Current distribution in a plasma erosion opening switch

    International Nuclear Information System (INIS)

    Weber, B.V.; Commisso, R.J.; Meger, R.A.; Neri, J.M.; Oliphant, W.F.; Ottinger, P.F.

    1985-01-01

    The current distribution in a plasma erosion opening switch is determined from magnetic field probe data. During the closed state of the switch the current channel broadens rapidly. The width of the current channel is consistent with a bipolar current density limit imposed by the ion flux to the cathode. The effective resistivity of the current channel is anomalously large. Current is diverted to the load when a gap opens near the cathode side of the switch. The observed gap opening can be explained by erosion of the plasma. Magnetic pressure is insufficient to open the gap

  16. Nonuniformities of electrical resistivity in undoped 6H-SiC wafers

    International Nuclear Information System (INIS)

    Li, Q.; Polyakov, A.Y.; Skowronski, M.; Sanchez, E.K.; Loboda, M.J.; Fanton, M.A.; Bogart, T.; Gamble, R.D.

    2005-01-01

    Chemical elemental analysis, temperature-dependent Hall measurements, deep-level transient spectroscopy, and contactless resistivity mapping were performed on undoped semi-insulating (SI) and lightly nitrogen-doped conducting 6H-SiC crystals grown by physical vapor transport (PVT). Resistivity maps of commercial semi-insulating SiC wafers revealed resistivity variations across the wafers between one and two orders of magnitude. Two major types of variations were identified. First is the U-shape distribution with low resistivity in the center and high in the periphery of the wafer. The second type had an inverted U-shape distribution. Secondary-ion-mass spectrometry measurements of the distribution of nitrogen concentration along the growth axis and across the wafers sliced from different locations of lightly nitrogen-doped 6H-SiC boules were conducted. The measured nitrogen concentration gradually decreased along the growth direction and from the center to the periphery of the wafers. This change gives rise to the U-like distribution of resistivity in wafers of undoped SI-SiC. The concentrations of deep electron traps exhibited similar dependence. Compensation of nitrogen donors by these traps can result in the inverted U-like distribution of resistivity. Possible reasons for the observed nonuniformities include formation of a (0001) facet in PVT growth coupled with orientation-dependent nitrogen incorporation, systematic changes of the gas phase composition, and increase of the deposition temperature during boule growth

  17. Imaging of current distributions in superconducting thin film structures

    International Nuclear Information System (INIS)

    Doenitz, D.

    2006-01-01

    Local analysis plays an important role in many fields of scientific research. However, imaging methods are not very common in the investigation of superconductors. For more than 20 years, Low Temperature Scanning Electron Microscopy (LTSEM) has been successfully used at the University of Tuebingen for studying of condensed matter phenomena, especially of superconductivity. In this thesis LTSEM was used for imaging current distributions in different superconducting thin film structures: - Imaging of current distributions in Josephson junctions with ferromagnetic interlayer, also known as SIFS junctions, showed inhomogeneous current transport over the junctions which directly led to an improvement in the fabrication process. An investigation of improved samples showed a very homogeneous current distribution without any trace of magnetic domains. Either such domains were not present or too small for imaging with the LTSEM. - An investigation of Nb/YBCO zigzag Josephson junctions yielded important information on signal formation in the LTSEM both for Josephson junctions in the short and in the long limit. Using a reference junction our signal formation model could be verified, thus confirming earlier results on short zigzag junctions. These results, which could be reproduced in this work, support the theory of d-wave symmetry in the superconducting order parameter of YBCO. Furthermore, investigations of the quasiparticle tunneling in the zigzag junctions showed the existence of Andreev bound states, which is another indication of the d-wave symmetry in YBCO. - The LTSEM study of Hot Electron Bolometers (HEB) allowed the first successful imaging of a stable 'Hot Spot', a self-heating region in HEB structures. Moreover, the electron beam was used to induce an - otherwise unstable - hot spot. Both investigations yielded information on the homogeneity of the samples. - An entirely new method of imaging the current distribution in superconducting interference devices

  18. Prevention of Bridge Scour with Non-uniform Circular Piers Plane under Steady Flows

    Science.gov (United States)

    Chen, Hsing-Ting; Wang, Chuan-Yi

    2017-04-01

    River bed scour and deposit variation extremely severe because of most of rivers are steep and rapid flows, and river discharge extremely unstable and highly unsteady during different seasons in Taiwan. In addition to the obstruction of piers foundation, it causes local scour and threatens the safety of bridges. In the past, riprap, wire gabion or wrap pier works were adopted as the protections of piers foundation, but there were no effectual outcomes. The events of break off piers still happen sometimes. For example, typhoon Kalmaegi (2008) and Morakot (2009) caused heavy damages on Ho-Fon bridge in the Da-jia river and Shuang-Yuan bridge in the Kao-Ping river, respectively. Accordingly, to understand the piers scour system and propose an appropriate protection of piers foundation becomes an important topic for this study currently. This research improves the protection works of the existing uniform bridge pier (diameter D) to ensure the safety of the bridge. The non-uniform plane of circular piers (diameter D*) are placed on the top of a bridge pier foundation to reduce the down flow impacting energy and scour by its' surface roughness characteristics. This study utilize hydraulic models to simulate local scour depth and scour depth change with time for non-uniform pier diameter ratio D/D* of 0.3,0.4,0.5,0.6,0.7 and 0.8, and different type pier and initial bed level (Y) relative under the foundation top elevation under steady flows of V/Vc=0.95,0.80 and 0.65. The research results show that the scour depth increases with an increase of flow intensity (V/Vc) under different types of steady flow hydrographs. The scour depth decreases with increase of initial bed level (Y=+0.2D*,0D*and -0.2D*) relative under the foundation top elevation of the different type pier. The maximum scour depth occurred in the front of the pier for all conditions. Because of the scouring retardation by the non-uniform plane of foundation, the scour depth is reduced for the un-exposed bridge

  19. Consideration of the 'Burp' phenomenon in solid methane accounting for nonuniform distribution of irradiation defects

    International Nuclear Information System (INIS)

    Shabalin, E. P.

    1997-09-01

    This paper focuses on an optional model of radical recombination in solid methane, apart from conventional theory. It shares the common property of two-order reactions, but accounts for local nonuniformitites of the objects involved (such as radical concentration, the track nature of energy deposition, and others). Accounting for local nonuniformity provides absolutely different results for the time dependence of the space-averaged concentration of radicals, both for the processes of their storage and 'burping', compared to the common approach; it also brings new conditions for the thermal instability of the methane slug under irradiation and gives a better understanding of most of the strange features of burp performances.

  20. From conventional averages to individual dose painting in radiotherapy for human tumors: challenge to non-uniformity

    International Nuclear Information System (INIS)

    Maciejewski, B.; Rodney Withers, H.

    2004-01-01

    The exploitation of a number of current clinical trials and reports on outcomes after radiation therapy (i.e. breast, head and neck, prostate) in clinical practice reflects many limitations for conventional techniques and dose-fractionation schedules and for 'average' conclusions. Even after decades of evolution of radiation therapy we still do not know how to optimize treatment for the individual patient and only have 'averages' and ill-defined 'probabilities' to guide treatment prescription. Wide clinical and biological heterogeneity within the groups of patients recruited into clinical trials with a few-fold variation in tumour volume within one stage of disease is obvious. Basic radiobiological guidelines concerning average cell killing of uniformly distributed and equally radiosensitive tumour cells arose from elegant but idealistic in vitro experiments and seem to be of uncertain validity. Therefore, we are confronted with more dilemmas than dogmas. Nonlinearity and in homogeneity of human tumour pattern and response to irradiation are discussed. The purpose of this paper is to present and discuss various aspects of non-uniform tumour cell targeted radiotherapy using conformal and dose intensity modulated techniques. (author)

  1. Instruction sequences and non-uniform complexity theory

    NARCIS (Netherlands)

    Bergstra, J.A.; Middelburg, C.A.

    2008-01-01

    We develop theory concerning non-uniform complexity in a setting in which the notion of single-pass instruction sequence considered in program algebra is the central notion. We define counterparts of the complexity classes P/poly and NP/poly and formulate a counterpart of the complexity theoretic

  2. Casimir energy of a nonuniform string

    Science.gov (United States)

    Hadasz, L.; Lambiase, G.; Nesterenko, V. V.

    2000-07-01

    The Casimir energy of a nonuniform string built up from two pieces with different speeds of sound is calculated. A standard procedure of subtracting the energy of an infinite uniform string is applied, the subtraction being interpreted as the renormalization of the string tension. It is shown that in the case of a homogeneous string this method is completely equivalent to zeta renormalization.

  3. [Nonuniform distribution and contribution of the P- and P/Q-type calcium channels to short-term inhibitory synaptic transmission in cultured hippocampal neurons].

    Science.gov (United States)

    Mizerna, O P; Fedulova, S A; Veselovs'kyĭ, M S

    2010-01-01

    In the present study, we investigated the sensitivity of GABAergic short-term plasticity to the selective P- and P/Q-type calcium channels blocker omega-agatoxin-IVA. To block the P-type channels we used 30 nM of this toxin and 200 nM of the toxin was used to block the P/Q channel types. The evoked inhibitory postsynaptic currents (eIPSC) were studied using patch-clamp technique in whole-cell configuration in postsynaptic neuron and local extracellular stimulation of single presynaptic axon by rectangular pulse. The present data show that the contribution of P- and P/Q-types channels to GABAergic synaptic transmission in cultured hippocampal neurons are 30% and 45%, respectively. It was shown that the mediate contribution of the P- and P/Q-types channels to the amplitudes of eIPSC is different to every discovered neuron. It means that distribution of these channels is non-uniform. To study the short-term plasticity of inhibitory synaptic transmission, axons of presynaptic neurons were paired-pulse stimulated with the interpulse interval of 150 ms. Neurons demonstrated both the depression and facilitation. The application of 30 nM and 200 nM of the blocker decreased the depression and increased facilitation to 8% and 11%, respectively. In addition, we found that the mediate contribution of the P- and P/Q-types channels to realization of synaptic transmission after the second stimuli is 4% less compared to that after the first one. Therefore, blocking of both P- and P/Q-types calcium channels can change the efficiency of synaptic transmission. In this instance it facilitates realization of the transmission via decreased depression or increased facilitation. These results confirm that the P- and P/Q-types calcium channels are involved in regulation of the short-term inhibitory synaptic plasticity in cultured hippocampal neurons.

  4. Outer region scaling using the freestream velocity for nonuniform open channel flow over gravel

    Science.gov (United States)

    Stewart, Robert L.; Fox, James F.

    2017-06-01

    The theoretical basis for outer region scaling using the freestream velocity for nonuniform open channel flows over gravel is derived and tested for the first time. Owing to the gradual expansion of the flow within the nonuniform case presented, it is hypothesized that the flow can be defined as an equilibrium turbulent boundary layer using the asymptotic invariance principle. The hypothesis is supported using similarity analysis to derive a solution, followed by further testing with experimental datasets. For the latter, 38 newly collected experimental velocity profiles across three nonuniform flows over gravel in a hydraulic flume are tested as are 43 velocity profiles previously published in seven peer-reviewed journal papers that focused on fluid mechanics of nonuniform open channel over gravel. The findings support the nonuniform flows as equilibrium defined by the asymptotic invariance principle, which is reflective of the consistency of the turbulent structure's form and function within the expanding flow. However, roughness impacts the flow structure when comparing across the published experimental datasets. As a secondary objective, we show how previously published mixed scales can be used to assist with freestream velocity scaling of the velocity deficit and thus empirically account for the roughness effects that extend into the outer region of the flow. One broader finding of this study is providing the theoretical context to relax the use of the elusive friction velocity when scaling nonuniform flows in gravel bed rivers; and instead to apply the freestream velocity. A second broader finding highlighted by our results is that scaling of nonuniform flow in gravel bed rivers is still not fully resolved theoretically since mixed scaling relies to some degree on empiricism. As researchers resolve the form and function of macroturbulence in the outer region, we hope to see the closing of this research gap.

  5. Effect of a superconducting coil as a fault current limiter on current density distribution in BSCCO tape after an over-current pulse

    International Nuclear Information System (INIS)

    Tallouli, M; Yamaguchi, S.; Shyshkin, O.

    2017-01-01

    The development of power transmission lines based on long-length high temperature superconducting (HTS) tapes is complicated and technically challenging task. A serious problem for transmission line operation could become HTS power cable damage due to over-current pulse conditions. To avoid the cable damage in any urgent case the superconducting coil technology, i.e. superconductor fault current limiter (SFCL) is required. Comprehensive understanding of the current density characteristics of HTS tapes in both cases, either after pure over-current pulse or after over-current pulse limited by SFCL, is needed to restart or to continue the operation of the power transmission line. Moreover, current density distribution along and across the HTS tape provides us with the sufficient information about the quality of the tape performance in different current feeding regimes. In present paper we examine BSCCO HTS tape under two current feeding regimes. The first one is 100A feeding preceded by 900A over-current pulse. In this case none of tape protection was used. The second scenario is similar to the fist one but SFCL is used to limit an over-current value. For both scenarios after the pulse is gone and the current feeding is set up at 100A we scan magnetic field above the tape by means of Hall probe sensor. Then the feeding is turned of and the magnetic field scanning is repeated. Using the inverse problem numerical solver we calculate the corresponding direct and permanent current density distributions during the feeding and after switch off. It is demonstrated that in the absence of SFCL the current distribution is highly peaked at the tape center. At the same time the current distribution in the experiment with SFCL is similar to that observed under normal current feeding condition. The current peaking in the first case is explained by the effect of an opposite electric field induced at the tape edges during the overcurrent pulse decay, and by degradation of

  6. Joint de-blurring and nonuniformity correction method for infrared microscopy imaging

    Science.gov (United States)

    Jara, Anselmo; Torres, Sergio; Machuca, Guillermo; Ramírez, Wagner; Gutiérrez, Pablo A.; Viafora, Laura A.; Godoy, Sebastián E.; Vera, Esteban

    2018-05-01

    In this work, we present a new technique to simultaneously reduce two major degradation artifacts found in mid-wavelength infrared microscopy imagery, namely the inherent focal-plane array nonuniformity noise and the scene defocus presented due to the point spread function of the infrared microscope. We correct both nuisances using a novel, recursive method that combines the constant range nonuniformity correction algorithm with a frame-by-frame deconvolution approach. The ability of the method to jointly compensate for both nonuniformity noise and blur is demonstrated using two different real mid-wavelength infrared microscopic video sequences, which were captured from two microscopic living organisms using a Janos-Sofradir mid-wavelength infrared microscopy setup. The performance of the proposed method is assessed on real and simulated infrared data by computing the root mean-square error and the roughness-laplacian pattern index, which was specifically developed for the present work.

  7. A non-uniform three-gap buncher cavity with suppression of transverse-electromagnetic mode leakage in the triaxial klystron amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Zumin; Zhang, Jun, E-mail: zhangjun-nudt@126.com; Zhong, Huihuang; Zhu, Danni; Qiu, Yongfeng [College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China)

    2014-01-15

    The triaxial klystron amplifier is an efficient high power relativistic klystron amplifier operating at high frequencies due to its coaxial structure with large radius. However, the coaxial structures result in coupling problems among the cavities as the TEM mode is not cut-off in the coaxial tube. Therefore, the suppression of the TEM mode leakage, especially the leakage from the buncher cavity to the input cavity, is crucial in the design of a triaxial klystron amplifier. In this paper, a non-uniform three-gap buncher cavity is proposed to suppress the TEM mode leakage. The cold cavity analysis shows that the non-uniform three-gap buncher cavity can significantly suppress the TEM mode generation compared to a uniform three-gap buncher cavity. Particle-in-cell simulation shows that the power leakage to the input cavity is less than 1.5‰ of the negative power in the buncher cavity and the buncher cavity can efficiently modulate an intense relativistic electron beam free of self-oscillations. A fundamental current modulation depth of 117% is achieved by employing the proposed non-uniform buncher cavity into an X-band triaxial amplifier, which results in the high efficiency generation of high power microwave.

  8. Nonequilibrium Distribution of the Microscopic Thermal Current in Steady Thermal Transport Systems

    KAUST Repository

    Yukawa, Satoshi; Ogushi, Fumiko; Shimada, Takashi; Ito, Nobuyasu

    2010-01-01

    Nonequilibrium distribution of the microscopic thermal current is investigated by direct molecular dynamics simulations. The microscopic thermal current in this study is defined by a flow of kinetic energy carried by a single particle. Asymptotic parallel and antiparallel tails of the nonequilibrium distribution to an average thermal current are identical to ones of equilibrium distribution with different temperatures. These temperatures characterizing the tails are dependent on a characteristic length in which a memory of dynamics is completely erased by several particle collisions. This property of the tails of nonequilibrium distribution is confirmed in other thermal transport systems. In addition, statistical properties of a particle trapped by a harmonic potential in a steady thermal conducting state are also studied. This particle feels a finite force parallel to the average thermal current as a consequence of the skewness of the distribution of the current. This force is interpreted as the microscopic origin of thermophoresis.

  9. POSSOL, 2-D Poisson Equation Solver for Nonuniform Grid

    International Nuclear Information System (INIS)

    Orvis, W.J.

    1988-01-01

    1 - Description of program or function: POSSOL is a two-dimensional Poisson equation solver for problems with arbitrary non-uniform gridding in Cartesian coordinates. It is an adaptation of the uniform grid PWSCRT routine developed by Schwarztrauber and Sweet at the National Center for Atmospheric Research (NCAR). 2 - Method of solution: POSSOL will solve the Helmholtz equation on an arbitrary, non-uniform grid on a rectangular domain allowing only one type of boundary condition on any one side. It can also be used to handle more than one type of boundary condition on a side by means of a capacitance matrix technique. There are three types of boundary conditions that can be applied: fixed, derivative, or periodic

  10. 3D Nondestructive Visualization and Evaluation of TRISO Particles Distribution in HTGR Fuel Pebbles Using Cone-Beam Computed Tomography

    Directory of Open Access Journals (Sweden)

    Gongyi Yu

    2017-01-01

    Full Text Available A nonuniform distribution of tristructural isotropic (TRISO particles within a high-temperature gas-cooled reactor (HTGR pebble may lead to excessive thermal gradients and nonuniform thermal expansion during operation. If the particles are closely clustered, local hotspots may form, leading to excessive stresses on particle layers and an increased probability of particle failure. Although X-ray digital radiography (DR is currently used to evaluate the TRISO distributions in pebbles, X-ray DR projection images are two-dimensional in nature, which would potentially miss some details for 3D evaluation. This paper proposes a method of 3D visualization and evaluation of the TRISO distribution in HTGR pebbles using cone-beam computed tomography (CBCT: first, a pebble is scanned on our high-resolution CBCT, and 2D cross-sectional images are reconstructed; secondly, all cross-sectional images are restructured to form the 3D model of the pebble; then, volume rendering is applied to segment and display the TRISO particles in 3D for visualization and distribution evaluation. For method validation, several pebbles were scanned and the 3D distributions of the TRISO particles within the pebbles were produced. Experiment results show that the proposed method provides more 3D than DR, which will facilitate pebble fabrication research and production quality control.

  11. Crack problem in superconducting cylinder with exponential distribution of critical-current density

    Science.gov (United States)

    Zhao, Yufeng; Xu, Chi; Shi, Liang

    2018-04-01

    The general problem of a center crack in a long cylindrical superconductor with inhomogeneous critical-current distribution is studied based on the extended Bean model for zero-field cooling (ZFC) and field cooling (FC) magnetization processes, in which the inhomogeneous parameter η is introduced for characterizing the critical-current density distribution in inhomogeneous superconductor. The effect of the inhomogeneous parameter η on both the magnetic field distribution and the variations of the normalized stress intensity factors is also obtained based on the plane strain approach and J-integral theory. The numerical results indicate that the exponential distribution of critical-current density will lead a larger trapped field inside the inhomogeneous superconductor and cause the center of the cylinder to fracture more easily. In addition, it is worth pointing out that the nonlinear field distribution is unique to the Bean model by comparing the curve shapes of the magnetization loop with homogeneous and inhomogeneous critical-current distribution.

  12. Photocathode non-uniformity contribution to the energy resolution of scintillators

    International Nuclear Information System (INIS)

    Mottaghian, M.; Koohi-Fayegh, R.; Ghal-Eh, N.; Etaati, G. R.

    2010-01-01

    This paper introduces the basics of the light transport simulation in scintillators and the wavelength-dependencies in the process. The non-uniformity measurement of the photocathode surface is undertaken, showing that for the photocathode used in this study the quantum efficiency falls to about 4% of its maximum value, especially in areas far from the centre. The wavelength-and position-dependent quantum efficiency is implemented in the Monte Carlo light transport code, showing that, the contribution of the photocathode non-uniformity to the energy resolution is estimated to be around 18%, when all position-and wavelength-dependencies are included. (authors)

  13. ELECTRONIC CIRCUIT BOARDS NON-UNIFORM COOLING SYSTEM MODEL

    Directory of Open Access Journals (Sweden)

    D. V. Yevdulov

    2016-01-01

    Full Text Available Abstract. The paper considers a mathematical model of non-uniform cooling of electronic circuit boards. The block diagram of the system implementing this approach, the method of calculation of the electronic board temperature field, as well as the principle of its thermal performance optimizing are presented. In the considered scheme the main heat elimination from electronic board is produced by the radiator system, and additional cooling of the most temperature-sensitive components is produced by thermoelectric batteries. Are given the two-dimensional temperature fields of the electronic board during its uniform and non-uniform cooling, is carried out their comparison. As follows from the calculations results, when using a uniform overall cooling of electronic unit there is a waste of energy for the cooling 0f electronic board parts which temperature is within acceptable temperature range without the cooling system. This approach leads to the increase in the cooling capacity of used thermoelectric batteries in comparison with the desired values. This largely reduces the efficiency of heat elimination system. The use for electronic boards cooling of non-uniform local heat elimination removes this disadvantage. The obtained dependences show that in this case, the energy required to create a given temperature is smaller than when using a common uniform cooling. In this approach the temperature field of the electronic board is more uniform and the cooling is more efficient. 

  14. Effects of transient and non-uniform distribution of heat flux on intensity of heat transfer and burnout conditions in the channels of nuclear reactors

    Energy Technology Data Exchange (ETDEWEB)

    Vitaly Osmachkin [Russian Research Center ' Kurchatov Institute' 1, Kurchatov sq, Moscow 123182 (Russian Federation)

    2005-07-01

    Full text of publication follows: The influence of power transient, changes of flow rate, inlet temperatures or pressure in cores of nuclear reactors on heat transfer and burnout conditions in channels depend on rate of such violations. Non-uniform distribution of the heat flux is also important factor for heat transfer and development of crisis phenomenon. Such effects may be significant for NPPs safety. But they have not yet generally accepted interpretation. Steady state approach is often recommended for use in calculations. In the paper a review of experimental observed so-called non-equilibrium effects is presented. The effects of space and time factors are displaying due delay in reformation turbulence intensity, velocity, temperatures or void fraction profiles, water film flow on the surface of heated channels. For estimation of such effect different methods are used. Modern computer codes based on two or three fluids approaches are considered as most effective. But simple and clear correlations may light up the mechanics of effects on heat transfer and improve general understanding of scale and significance of the transient events. In the paper the simplified methods for assessment the influence of lags in the development of distributions of parameters of flow, the relaxation of temporal or space violations are considered. They are compared with more sophisticated approaches. Velocities of disturbance fronts moving along the channels are discussed also. (author)

  15. Modeling the current distribution in HTS tapes with transport current and applied magnetic field

    NARCIS (Netherlands)

    Yazawa, T.; Yazawa, Takashi; Rabbers, J.J.; Chevtchenko, O.A.; ten Haken, Bernard; ten Kate, Herman H.J.; Maeda, Hideaki

    1999-01-01

    A numerical model is developed for the current distribution in a high temperature superconducting (HTS) tape, (Bi,Pb)2Sr2 Ca2Cu3Ox-Ag, subjected to a combination of a transport current and an applied magnetic field. This analysis is based on a two-dimensional formulation of Maxwell's equations in

  16. Non-uniformity measurements of PbWO4 crystals

    International Nuclear Information System (INIS)

    Depasse, P.; Ernenwein, J.P.; Ille, B.; Martin, F.; Rosset, C.; Zach, F.

    1998-11-01

    Two independent methods have been used to measure the longitudinal non-uniformity scintillation response of 3 different (23-cm long) PbWO 4 crystals. The first one is the classical 60 Co source method. The source is collimated along the crystal, each 1,5-cm, and the scintillation signal is measured with a photomultiplier (a hybrid photomultiplier in our case). The second one is the use of cosmic particles (Minimum Ionizing Particles). A cosmic bench allows reconstructing the track of the MIP's and thus the energy deposit with the help of a full GEANT simulation of the setup. Variations of E along the crystal artificially cut in 1,5-cm divisions, leads to determine the non-uniformity. The conclusion is that both methods agree quite well. Furthermore, a good estimation of crystal light yield can be obtained. (author)

  17. Welding Current Distribution in the Work-piece and Pool in Arc Welding

    Directory of Open Access Journals (Sweden)

    A. M. Rybachuk

    2015-01-01

    Full Text Available In order to select the optimal configuration of controlling magnetic fields and build rational construction of magnetic systems, we need to know the distribution of welding current in the molten metal of the weld pool. So the objective of the work is to establish the calculated methods for determining current density in the weld pool during arc welding. The distribution of welding current in the pool depends on the field of the electrical resistance, which is determined by the deformed temperature field while arc moves with the welding speed. The previous works have shown experimentally and by simulation on the conductive paper that deformation of temperature field defines deformation of electric field. On the basis thereof, under certain boundary conditions the problem has been solved to give a general solution of differential equation, which relates the potential distribution to the temperature in the product during arc welding. This solution is obtained under the following boundary conditions: 1 metal is homogeneous; 2 input and output surfaces of heat flux and electric current coincide; 3 input and output surfaces of heat flux and electric current are insulated and equipotential; 4 other (lateral surfaces are adiabatic boundaries. Therefore, this paper pays basic attention to obtaining the analytical solution of a general differential equation, which relates distribution of potential to the temperature in the product. It considers the temperature field of the heat source, which moves at a welding speed with normal-circular distribution of the heat flow at a certain concentration factor. The distribution of current density is calculated on the assumption that the welding current is introduced through the same surface as the heat flux and the distribution of current density corresponds to the normally circular at a certain concentration factor. As a result, we get an expression that allows us to calculate the current density from the known

  18. Bone-Marrow Stem-Cell Survival in the Non-Uniformly Exposed Mammal

    Energy Technology Data Exchange (ETDEWEB)

    Bond, V. P.; Robinson, C. V. [Brookhaven National Laboratory, Medical Research Center, Upton, Long Island, NY (United States)

    1967-07-15

    For comparison of the effectiveness of non-uniform versus uniform irradiations in causing haematological death in mammals, a model of the irradiated haemopoietic system has been proposed. The essential features of this model are: (1) that different parts of the haemopoietic system have numbers of stem cells which are proportioned to the amounts of active marrow in those parts as measured by {sup 59}Fe uptake, (2) that stem cells in the different parts are subject to the, same dose-survival relationship, and (3) that survival of the animal depends on survival of a critical fraction of the total number of stem cells independent of their distribution among the parts of the total marrow mass. To apply this model one needs to know: (a) the relative {sup 59}Fe uptakes of the different parts of the haemopoietic system, (b) the doses delivered to those parts by each of the exposures to be compared, and (c) the dose-survival curve applicable to the stem cells. From these one can calculate the fraction of stem cells surviving each exposure. In a preliminary communication the applicability of the model was investigated using data obtained entirely from the literature. Additional data, particularly on bone-marrow distribution, have since been obtained and are included here. The primary object of the present paper is to test further the validity of the above 'stem-cell survival model'. Data on bilateral (essentially uniform) versus unilateral and non-uniform rotational exposures in mammals are examined with respect to the surviving fraction of stem cells at the LD{sub 50/30} day dose level. Although an adequate test is not possible at present for lack of a full set of data in any one species, a partial test indicates compatibility with data for dogs and rats. Other possible mortality determinants such as doses or exposures at entrance, midline or exit, or the gram-rads or average dose to the marrow, appear to be less useful than the critical stem-cell survival fraction.

  19. Effects of non-uniform core flow on peak cladding temperature: MOXY/SCORE sensitivity calculations

    Energy Technology Data Exchange (ETDEWEB)

    Chang, S.C.

    1979-08-15

    The MOXY/SCORE computer program is used to evaluate the potential effect on peak cladding temperature of selective cooling that may result from a nonuniform mass flux at the core boundaries during the blowdown phase of the LOFT L2-4 test. The results of this study indicate that the effect of the flow nonuniformity at the core boundaries will be neutralized by a strong radial flow redistribution in the neighborhood of core boundaries. The implication is that the flow nonuniformity at the core boundaries has no significant effect on the thermal-hydraulic behavior and cladding temperature at the hot plane.

  20. Effects of non-uniform core flow on peak cladding temperature: MOXY/SCORE sensitivity calculations

    International Nuclear Information System (INIS)

    Chang, S.C.

    1979-01-01

    The MOXY/SCORE computer program is used to evaluate the potential effect on peak cladding temperature of selective cooling that may result from a nonuniform mass flux at the core boundaries during the blowdown phase of the LOFT L2-4 test. The results of this study indicate that the effect of the flow nonuniformity at the core boundaries will be neutralized by a strong radial flow redistribution in the neighborhood of core boundaries. The implication is that the flow nonuniformity at the core boundaries has no significant effect on the thermal-hydraulic behavior and cladding temperature at the hot plane

  1. Modelling refrigerant distribution in microchannel evaporators

    DEFF Research Database (Denmark)

    Brix, Wiebke; Kærn, Martin Ryhl; Elmegaard, Brian

    2009-01-01

    of the refrigerant distribution is carried out for two channels in parallel and for two different cases. In the first case maldistribution of the inlet quality into the channels is considered, and in the second case a non-uniform airflow on the secondary side is considered. In both cases the total mixed superheat...... out of the evaporator is kept constant. It is shown that the cooling capacity of the evaporator is reduced significantly, both in the case of unevenly distributed inlet quality and for the case of non-uniform airflow on the outside of the channels.......The effects of refrigerant maldistribution in parallel evaporator channels on the heat exchanger performance are investigated numerically. For this purpose a 1D steady state model of refrigerant R134a evaporating in a microchannel tube is built and validated against other evaporator models. A study...

  2. Reduction of gas flow nonuniformity in gas turbine engines by means of gas-dynamic methods

    Science.gov (United States)

    Matveev, V.; Baturin, O.; Kolmakova, D.; Popov, G.

    2017-08-01

    Gas flow nonuniformity is one of the main sources of rotor blade vibrations in the gas turbine engines. Usually, the flow circumferential nonuniformity occurs near the annular frames, located in the flow channel of the engine. This leads to the increased dynamic stresses in blades and as a consequence to the blade damage. The goal of the research was to find an acceptable method of reducing the level of gas flow nonuniformity as the source of dynamic stresses in the rotor blades. Two different methods were investigated during this research. Thus, this study gives the ideas about methods of improving the flow structure in gas turbine engine. On the basis of existing conditions (under development or existing engine) it allows the selection of the most suitable method for reducing gas flow nonuniformity.

  3. Advanced GF(32) nonbinary LDPC coded modulation with non-uniform 9-QAM outperforming star 8-QAM.

    Science.gov (United States)

    Liu, Tao; Lin, Changyu; Djordjevic, Ivan B

    2016-06-27

    In this paper, we first describe a 9-symbol non-uniform signaling scheme based on Huffman code, in which different symbols are transmitted with different probabilities. By using the Huffman procedure, prefix code is designed to approach the optimal performance. Then, we introduce an algorithm to determine the optimal signal constellation sets for our proposed non-uniform scheme with the criterion of maximizing constellation figure of merit (CFM). The proposed nonuniform polarization multiplexed signaling 9-QAM scheme has the same spectral efficiency as the conventional 8-QAM. Additionally, we propose a specially designed GF(32) nonbinary quasi-cyclic LDPC code for the coded modulation system based on the 9-QAM non-uniform scheme. Further, we study the efficiency of our proposed non-uniform 9-QAM, combined with nonbinary LDPC coding, and demonstrate by Monte Carlo simulation that the proposed GF(23) nonbinary LDPC coded 9-QAM scheme outperforms nonbinary LDPC coded uniform 8-QAM by at least 0.8dB.

  4. Wastewater diffusive dilution and sedimentation of the fine contaminated particles for nonuniform flow in open channels

    Directory of Open Access Journals (Sweden)

    Lyapin Anton

    2018-01-01

    Full Text Available The influence of non-uniformity on mass transfer processes in open channels have been investigated under the action of urbanization factors. The study is related to the urgent problem of environmental degradation of water objects in urbanized areas. It is known that the water quality in the water objects depends on the manner in which the contaminants spread how they mix with the river water and diluted by it. The main results of the study consist of recommendations to incorporate non-uniformity factor to the calculation of diffusion dilution of wastewater and prediction of river processes. So the effect of the flow non-uniformity on the diffusion model of pollutants dilution and diffusion coefficient have been investigated. Formulas for the concentration profiles calculating and the average concentration of fine particulate matter in nonuniform gradually varied flow were presented. The deposition length of suspended contaminants were received, based on the hydraulic resistance laws of nonuniform gradually varied flow.

  5. The Pierce diode with an external circuit: II, Non-uniform equilibria

    International Nuclear Information System (INIS)

    Lawson, W.S.

    1987-01-01

    The non-uniform (non-linear) equilibria of the classical (short circuit) Pierce diode and the extended (series RLC external circuit) Pierce diode are described theoretically, and explored via computer simulation. It is found that most equilibria are correctly predicted by theory, but that the continuous set of equilibria of the classical Pierce diode at α = 2π are not observed. The stability characteristics of the non-uniform equilibria are also worked out, and are consistent with the simulations. 8 refs., 22 figs., 3 tabs

  6. Monte carlo simulation of vesicular release, spatiotemporal distribution of glutamate in synaptic cleft and generation of postsynaptic currents.

    Science.gov (United States)

    Glavinovíc, M I

    1999-02-01

    The release of vesicular glutamate, spatiotemporal changes in glutamate concentration in the synaptic cleft and the subsequent generation of fast excitatory postsynaptic currents at a hippocampal synapse were modeled using the Monte Carlo method. It is assumed that glutamate is released from a spherical vesicle through a cylindrical fusion pore into the synaptic cleft and that S-alpha-amino-3-hydroxy -5-methyl-4-isoxazolepropionic acid (AMPA) receptors are uniformly distributed postsynaptically. The time course of change in vesicular concentration can be described by a single exponential, but a slow tail is also observed though only following the release of most of the glutamate. The time constant of decay increases with vesicular size and a lower diffusion constant, and is independent of the initial concentration, becoming markedly shorter for wider fusion pores. The cleft concentration at the fusion pore mouth is not negligible compared to vesicular concentration, especially for wider fusion pores. Lateral equilibration of glutamate is rapid, and within approximately 50 micros all AMPA receptors on average see the same concentration of glutamate. Nevertheless the single-channel current and the number of channels estimated from mean-variance plots are unreliable and different when estimated from rise- and decay-current segments. Greater saturation of AMPA receptor channels provides higher but not more accurate estimates. Two factors contribute to the variability of postsynaptic currents and render the mean-variance nonstationary analysis unreliable, even when all receptors see on average the same glutamate concentration. Firstly, the variability of the instantaneous cleft concentration of glutamate, unlike the mean concentration, first rapidly decreases before slowly increasing; the variability is greater for fewer molecules in the cleft and is spatially nonuniform. Secondly, the efficacy with which glutamate produces a response changes with time. Understanding

  7. Non-uniform Solar Temperature Field on Large Aperture, Fully-Steerable Telescope Structure

    Science.gov (United States)

    Liu, Yan

    2016-09-01

    In this study, a 110-m fully steerable radio telescope was used as an analysis platform and the integral parametric finite element model of the antenna structure was built in the ANSYS thermal analysis module. The boundary conditions of periodic air temperature, solar radiation, long-wave radiation shadows of the surrounding environment, etc. were computed at 30 min intervals under a cloudless sky on a summer day, i.e., worstcase climate conditions. The transient structural temperatures were then analyzed under a period of several days of sunshine with a rational initial structural temperature distribution until the whole set of structural temperatures converged to the results obtained the day before. The non-uniform temperature field distribution of the entire structure and the main reflector surface RMS were acquired according to changes in pitch and azimuth angle over the observation period. Variations in the solar cooker effect over time and spatial distributions in the secondary reflector were observed to elucidate the mechanism of the effect. The results presented here not only provide valuable realtime data for the design, construction, sensor arrangement and thermal deformation control of actuators but also provide a troubleshooting reference for existing actuators.

  8. Computation of nonuniform transmission lines using the FDTD method

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, G.C.; Paulino, J.O.S. [Universidade Federal de Minas Gerais, Belo Horizonte, MG (Brazil). School of Engineering

    1997-12-31

    Calculation of lightning overvoltages on transmission lines has been described. Lightning induced overvoltages are of great significance under certain conditions because of the main characteristics of the phenomena. The lightning channel model is one of the most important parameters essential to obtaining the generated electromagnetic fields. In this study, nonuniform transmission line equations were solved using the finite difference method and the leap-frog scheme, the Finite Difference Time Domain (FDTD) method. The subroutine was interfaced with the Electromagnetic Transients Program (EMTP). Two models were used to represent the characteristic impedance of the nonuniform lines used to model the transmission line towers and the lightning main channel. The advantages of the FDTD method was the much smaller code and faster processing time. 35 refs., 5 figs.

  9. Gas-Dynamic Methods to Reduce Gas Flow Nonuniformity from the Annular Frames of Gas Turbine Engines

    Science.gov (United States)

    Kolmakova, D.; Popov, G.

    2018-01-01

    Gas flow nonuniformity is one of the main sources of rotor blade vibrations in the gas turbine engines. Usually, the flow circumferential nonuniformity occurs near the annular frames, located in the flow channel of the engine. This leads to the increased dynamic stresses in blades and consequently to the blade damage. The goal of the research was to find an acceptable method of reducing the level of gas flow nonuniformity. Two different methods were investigated during this research. Thus, this study gives the ideas about methods of improving the flow structure in gas turbine engine. Based on existing conditions (under development or existing engine) it allows the selection of the most suitable method for reducing gas flow nonuniformity.

  10. Nonuniform quantum turbulence in superfluids

    Science.gov (United States)

    Nemirovskii, Sergey K.

    2018-04-01

    The problem of quantum turbulence in a channel with an inhomogeneous counterflow of superfluid turbulent helium is studied. The counterflow velocity Vns x(y ) along the channel is supposed to have a parabolic profile in the transverse direction y . Such statement corresponds to the recent numerical simulation by Khomenko et al. [Phys. Rev. B 91, 180504 (2015), 10.1103/PhysRevB.91.180504]. The authors reported about a sophisticated behavior of the vortex-line density (VLD) L (r ,t ) , different from L ∝Vns x(y) 2 , which follows from the straightforward application of the conventional Vinen theory. It is clear that Vinen theory should be refined by taking into account transverse effects, and the way it ought to be done is the subject of active discussion in the literature. In this work, we discuss several possible mechanisms of the transverse flux of VLD L (r ,t ) which should be incorporated in the standard Vinen equation to describe adequately the inhomogeneous quantum turbulence. It is shown that the most effective among these mechanisms is the one that is related to the phase-slippage phenomenon. The use of this flux in the modernized Vinen equation corrects the situation with an unusual distribution of the vortex-line density, and satisfactorily describes the behavior L (r ,t ) both in stationary and nonstationary situations. The general problem of the phenomenological Vinen theory in the case of nonuniform and nonstationary quantum turbulence is thoroughly discussed.

  11. Nonlinear evolution of broad-bandwidth, laser-imprinted nonuniformities in planar targets accelerated by 351-nm laser light

    International Nuclear Information System (INIS)

    Smalyuk, V.A.; Boehly, T.R.; Bradley, D.K.; Goncharov, V.N.; Delettrez, J.A.; Knauer, J.P.; Meyerhofer, D.D.; Oron, D.; Shvarts, D.; Srebro, Y.; Town, R.P.

    1999-01-01

    Planar, 20 and 40 μm thick CH targets have been accelerated by 351 nm laser beams of the OMEGA laser system [Opt. Commun. 133, 495 (1997)]. Different beam-smoothing techniques were employed including distributed phase plates, smoothing by spectral dispersion, and distributed polarization rotators. The Rayleigh - Taylor evolution of three-dimensional (3D) broadband planar-target perturbations seeded by laser nonuniformities was measured using x-ray radiography at ∼1.3 keV. Fourier analysis shows that the perturbations evolve to longer wavelengths and the shorter wavelengths saturate. The saturation amplitudes and rates of growth of these features are consistent with the predictions of Haan [Phys. Rev. A 39, 5812 (1989)]. copyright 1999 American Institute of Physics

  12. Inducted circulation current in a conductor consisting of strands coated with a high resistive layer

    International Nuclear Information System (INIS)

    Koizumi, Norikiyo; Takahashi, Yoshikazu; Kato, Takashi; Tsuji, Hiroshi; Shimamoto, Susumu

    2000-01-01

    Nonuniform current distribution is generated in a conductor consisting of strands coated by a high resistive layer, such as chromium plating, as a result of superimposition of transport and induce circulation currents. The characteristics of the induced circulation current are analytically studied by using a distributed model circuit. The parameters mostly used in this calculation are those of US-DPC coil, which at first exhibited instability and so-called ramp rate limitation (RRL) because of current imbalance in the conductor consisting of chrome-plated strands. Thus the conductance along strands and the inductance of unit length loop and length of the conductor are mostly assumed to be 10 kS/m, 0.5 μH/m and 150 m, respectively. The analysis results indicate that the induced circulation current can be classified into the boundary and interstrand-induce circulation currents hereafter referred to as BICC an IICC. BICC is induced only across the joint at the ends of the conductor, resulting in a constant along the conductor axis, when the total leakage magnetic flux of the loop is not zero. Its decay time constant is quite long, more than a few hours. In contrast, when the leakage magnetic flux distributes along the conductor axis, IICC is induced among strands in the conductor to eliminate this flux. Since the leakage magnetic flux normally becomes largest where the magnetic field is highest, it becomes larger where the time variation of the magnetic field is larger. Its decay time contrast is much less than that of BICC. If the leakage magnetic flux linearly changes along the US-DPC conductor, it is evaluated to be about 10 s. This IICC therefore becomes dominate in a pulse charge, whose ramping tine is less than 10 s. Moreover, it is found that the variation of the leakage a magnetic flux with the relatively long cycle, such as more than a few 10-meter lengths, causes IICC with a decay-time constant of more than several hundred milliseconds. Such and IICC can

  13. Nonuniform grid implicit spatial finite difference method for acoustic wave modeling in tilted transversely isotropic media

    KAUST Repository

    Chu, Chunlei

    2012-01-01

    Discrete earth models are commonly represented by uniform structured grids. In order to ensure accurate numerical description of all wave components propagating through these uniform grids, the grid size must be determined by the slowest velocity of the entire model. Consequently, high velocity areas are always oversampled, which inevitably increases the computational cost. A practical solution to this problem is to use nonuniform grids. We propose a nonuniform grid implicit spatial finite difference method which utilizes nonuniform grids to obtain high efficiency and relies on implicit operators to achieve high accuracy. We present a simple way of deriving implicit finite difference operators of arbitrary stencil widths on general nonuniform grids for the first and second derivatives and, as a demonstration example, apply these operators to the pseudo-acoustic wave equation in tilted transversely isotropic (TTI) media. We propose an efficient gridding algorithm that can be used to convert uniformly sampled models onto vertically nonuniform grids. We use a 2D TTI salt model to demonstrate its effectiveness and show that the nonuniform grid implicit spatial finite difference method can produce highly accurate seismic modeling results with enhanced efficiency, compared to uniform grid explicit finite difference implementations. © 2011 Elsevier B.V.

  14. Adding muscle where you need it: non-uniform hypertrophy patterns in elite sprinters.

    Science.gov (United States)

    Handsfield, G G; Knaus, K R; Fiorentino, N M; Meyer, C H; Hart, J M; Blemker, S S

    2017-10-01

    Sprint runners achieve much higher gait velocities and accelerations than average humans, due in part to large forces generated by their lower limb muscles. Various factors have been explored in the past to understand sprint biomechanics, but the distribution of muscle volumes in the lower limb has not been investigated in elite sprinters. In this study, we used non-Cartesian MRI to determine muscle sizes in vivo in a group of 15 NCAA Division I sprinters. Normalizing muscle sizes by body size, we compared sprinter muscles to non-sprinter muscles, calculated Z-scores to determine non-uniformly large muscles in sprinters, assessed bilateral symmetry, and assessed gender differences in sprinters' muscles. While limb musculature per height-mass was 22% greater in sprinters than in non-sprinters, individual muscles were not all uniformly larger. Hip- and knee-crossing muscles were significantly larger among sprinters (mean difference: 30%, range: 19-54%) but only one ankle-crossing muscle was significantly larger (tibialis posterior, 28%). Population-wide asymmetry was not significant in the sprint population but individual muscle asymmetries exceeded 15%. Gender differences in normalized muscle sizes were not significant. The results of this study suggest that non-uniform hypertrophy patterns, particularly large hip and knee flexors and extensors, are advantageous for fast sprinting. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  15. Modeling of nonuniform corrosion in salt brines: Salt Repository Project

    International Nuclear Information System (INIS)

    Reimus, P.W.

    1988-03-01

    A mechanistic approach to modeling nonuniform corrosion in brines is presented in this report. Equations are derived for completely describing the electrochemical environment within a localized corrosion cavity, and appropriate initial and boundary conditions are invoked to obtain a solvable system of equations. The initial and boundary conditions can be adjusted to simulate pitting, crevice corrosion, or stress corrosion cracking. Although no numerical results are presented, a numerical strategy for solving the equations is presented. The report focuses on the nonuniform corrosion behavior of mild steel; however, the modeling approach presented is expected to apply to a broad range of metallic materials. 34 refs., 5 figs., 2 tabs

  16. Vibration of nonuniform carbon nanotube with attached mass via nonlocal Timoshenko beam theory

    International Nuclear Information System (INIS)

    Tang, Hai Li; Shen, Zhi Bin; Li, Dao Kui

    2014-01-01

    This paper studies the vibrational behavior of nonuniform single-walled carbon nanotube (SWCNT) carrying a nanoparticle. A nonuniform cantilever beam with a concentrated mass at the free end is analyzed according to the nonlocal Timoshenko beam theory. A governing equation of a nonuniform SWCNT with attached mass is established. The transfer function method incorporating with the perturbation method is utilized to obtain the resonant frequencies of a vibrating nonlocal cantilever-mass system. The effects of the nonlocal parameter, taper ratio and attached mass on the natural frequencies and frequency shifts are discussed. Obtained results indicate that the sensitivity of the frequency shifts on the attached mass increases when the length-to-diameter ratio decreases. Tapered SWCNT possesses higher fundamental frequencies if the taper ratio becomes larger.

  17. The effect of the volumetric heat source distribution of the fuel pellet on the minimum DNBR ratio

    International Nuclear Information System (INIS)

    Hordosy, G.; Kereszturi, A.; Maroti, L.; Trosztel, I.

    1995-01-01

    The radial power distribution in a VVER-440 type fuel assembly is strongly non-uniform as a result of the water-gap between the shrouds and the moderator filled central tube. Consequently, it can be expected that the power density inside a single fuel rod is inhomogeneous, as well. In the paper the methodology and the results of coupled thermohydraulic and neutronic calculations are presented. The objective of the analysis was the investigation of the heat source distribution and the determination of the possible extent of the power non-uniformity in a corner rod which has always the highest peaking factor in a VVER-440 type assembly. The results of the analysis revealed that there can be a strong non-uniformity of power distribution inside a fuel pellet, and the effect depends first of all on the general assembly conditions, while the local subchannel parameters have only a slight influence on the pellet heat source distribution. (author)

  18. An Investigation into Conversion from Non-Uniform Rational B-Spline Boundary Representation Geometry to Constructive Solid Geometry

    Science.gov (United States)

    2015-12-01

    ARL-SR-0347 ● DEC 2015 US Army Research Laboratory An Investigation into Conversion from Non-Uniform Rational B-Spline Boundary...US Army Research Laboratory An Investigation into Conversion from Non-Uniform Rational B-Spline Boundary Representation Geometry to...from Non-Uniform Rational B-Spline Boundary Representation Geometry to Constructive Solid Geometry 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  19. A New Approach on Output Current Calculation for Thimble-type Ionization Chamber with Variation of Gamma-ray Irradiation Angle

    International Nuclear Information System (INIS)

    Kim, Jae Cheon; Kim, Soon Young; Kim, Yong Kyun; Kim, Jong Kyung

    2006-01-01

    The output current of an ionization chamber is directly connected with the size of the active volume and ion-pair distribution in air volume. Their accurate assessments are significantly important in order to analyze the design characteristics of an ionization chamber and interpret the measurements with it. It has been generally assumed that ion-pairs are generated uniformly in air volume for simplicity although they are not uniformly distributed due to various source and geometry conditions. Ion-pair distribution is mainly dependent on the irradiation source conditions, while active volume is deeply related to the ionization chamber design. Therefore, such assumption should be examined if the ion-pair distribution affects real output current of the active volume defined by electric field. A new analytical approach considering both electric field and ion-pair nonuniformity has been proposed to analyze accurately the design characteristics of an ionization chamber and interpretation of measurements with it. The angular dependence analysis was carried out to validate the new concept for calculation of output current

  20. The magneto-optical properties of non-uniform graphene nanoribbons

    Science.gov (United States)

    Chung, Hsien-Ching; Lin, Ming-Fa

    2015-03-01

    When synthesizing few-layer graphene nanoribbons (GNRs), non-uniform GNRs would be made simultaneously. Recently, the non-uniform GNRs, which is a stack of two GNRs with unequal widths, have been fabricated by mechanically exfoliated from bulk graphite. Some theoretical predictions have been reported, such as gap opening and transport properties. Under the influence of magnetic fields, magnetic quantization takes place and drastically changes the electronic properties. By tuning the geometric configuration, four categories of magneto-electronic spectra are exhibited. (1) The spectrum is mostly contributed by quasi-Landau levels (QLLs) of monolayer GNRs. (2) The spectrum displays two groups of QLLs, and the non-uniform GNR behaves like a bilayer one. (3) An intermediate category, the spectrum is composite disordered. (4) The spectrum presents the coexistence of monolayer and bilayer spectra. In this work, the magneto-electronic and optical properties for different geometric configurations are given, such as energy dispersions, density of states, wave functions, and magneto-absorption spectra are presented. Furthermore, the transformation between monolayer and bilayer spectra as well as the coexistence of monolayer and bilayer spectra are discussed in detail. One of us (Hsien-Ching Chung) thanks Ming-Hui Chung and Su-Ming Chen for financial support. This work was supported in part by the National Science Council of Taiwan under Grant Number 98-2112-M-006-013-MY4.

  1. Study of entropy generation in a slab with non-uniform internal heat generation

    Directory of Open Access Journals (Sweden)

    El Haj Assad Mamdouh

    2013-01-01

    Full Text Available Analysis of entropy generation in a rectangular slab with a nonuniform internal heat generation is presented. Dimensionless local and total entropy generation during steady state heat conduction through the slab are obtained. Two different boundary conditions have been considered in the analysis, the first with asymmetric convection and the second with constant slab surface temperature. Temperature distribution within the slab is obtained analytically. The study investigates the effect of some relevant dimensionless heat transfer parameters on entropy generation. The results show that there exists a minimum local entropy generation but there does not exist a minimum total entropy generation for certain combinations of the heat transfer parameters. The results of calculations are presented graphically.

  2. Progress in American Superconductor’s HTS wire and optimization for fault current limiting systems

    Energy Technology Data Exchange (ETDEWEB)

    Malozemoff, Alexis P., E-mail: amalozemoff@amsc.com

    2016-11-15

    Highlights: • AMSC HTS wire critical current needed for rotating machinery is doubled by 16 MeV Au irradiation. • Nonuniformity of HTS wires in power devices causes hot spot formation during power system faults. • Lower normal-state resistivity and critical current lower HTS wire hot spot heating during faults. • HTS wire hot spot heating in HTS cables during faults must stay below lN{sub 2} bubble nucleation point. • HTS wire can be designed to meet hot spot heating limits in fault current limiting cables. - Abstract: American Superconductor has developed composite coated conductor tape-shaped wires using high temperature superconductor (HTS) on a flexible substrate with laminated metal stabilizer. Such wires enable many applications, each requiring specific optimization. For example, coils for HTS rotating machinery require increased current density J at 25–50 K. A collaboration with Argonne, Brookhaven and Los Alamos National Laboratories and several universities has increased J using an optimized combination of precipitates and ion irradiation defects in the HTS. Major commercial opportunities also exist to enhance electric power grid resiliency by linking substations with distribution-voltage HTS power cables [10]. Such links provide alternative power sources if one substation's transmission-voltage power is compromised. But they must also limit fault currents which would otherwise be increased by such distribution-level links. This can be done in an HTS cable, exploiting the superconductor-to-resistive transition when current exceeds the wires’ critical J. A key insight is that such transitions are usually nonuniform; so the wire must be designed to prevent localized hot spots from damaging the wire or even generating gas bubbles in the cable causing dielectric breakdown. Analysis shows that local heating can be minimized by increasing the composite tape's total thickness, decreasing its total resistance in the normal state and

  3. Real-time definition of non-randomness in the distribution of genomic events.

    Directory of Open Access Journals (Sweden)

    Ulrich Abel

    Full Text Available Features such as mutations or structural characteristics can be non-randomly or non-uniformly distributed within a genome. So far, computer simulations were required for statistical inferences on the distribution of sequence motifs. Here, we show that these analyses are possible using an analytical, mathematical approach. For the assessment of non-randomness, our calculations only require information including genome size, number of (sampled sequence motifs and distance parameters. We have developed computer programs evaluating our analytical formulas for the real-time determination of expected values and p-values. This approach permits a flexible cluster definition that can be applied to most effectively identify non-random or non-uniform sequence motif distribution. As an example, we show the effectivity and reliability of our mathematical approach in clinical retroviral vector integration site distribution.

  4. Current and voltage distribution in the diffuse vacuum arc

    NARCIS (Netherlands)

    Schellekens, H.; Schram, D.C.

    1985-01-01

    On the basis of extensive measurements, a model is developed for the diffuse plasma of the high-current vacuum arc. The model shows that the current constriction and the voltage distribution in the diffuse vacuum arc prior to anode-spot formation are caused by the pressure source to which the

  5. Synergistic nonuniform shortening of atrial refractory period induced by autonomic stimulation.

    Science.gov (United States)

    Takei, M; Furukawa, Y; Narita, M; Ren, L M; Karasawa, Y; Murakami, M; Chiba, S

    1991-12-01

    We investigated the nonuniform effects of autonomic nerve stimulation of the effective refractory period (ERP) of the right atrium in the anesthetized dog. Stimulation of the discrete intracardiac sympathetic nerves to the sinoatrial (SA) nodal region uniformly shortened ERPs at three sites in the right atrium after administration of atropine. Right ansa subclavia (RS) stimulation similarly shortened ERPs in the absence of atropine. Stimulation of the discrete intracardiac parasympathetic nerves to the SA nodal region (SAP stimulation) shortened ERPs of the right atrium in a nonuniform manner. Simultaneous RS and SAP stimulation additively shortened ERPs at each site and decreased sinus rate much more than SAP stimulation alone. Shortening of ERP induced by SAP stimulation was greater than that induced by RS stimulation at similar absolute changes in heart rate. These results suggest that simultaneous activation of sympathetic and parasympathetic nerves nonuniformly shortens the ERP in the right atrium as the algebraic sum of the individual responses to each stimulation. However, parasympathetics exert the principal neural control over atrial ERP.

  6. Inverse analysis of non-uniform temperature distributions using multispectral pyrometry

    Science.gov (United States)

    Fu, Tairan; Duan, Minghao; Tian, Jibin; Shi, Congling

    2016-05-01

    Optical diagnostics can be used to obtain sub-pixel temperature information in remote sensing. A multispectral pyrometry method was developed using multiple spectral radiation intensities to deduce the temperature area distribution in the measurement region. The method transforms a spot multispectral pyrometer with a fixed field of view into a pyrometer with enhanced spatial resolution that can give sub-pixel temperature information from a "one pixel" measurement region. A temperature area fraction function was defined to represent the spatial temperature distribution in the measurement region. The method is illustrated by simulations of a multispectral pyrometer with a spectral range of 8.0-13.0 μm measuring a non-isothermal region with a temperature range of 500-800 K in the spot pyrometer field of view. The inverse algorithm for the sub-pixel temperature distribution (temperature area fractions) in the "one pixel" verifies this multispectral pyrometry method. The results show that an improved Levenberg-Marquardt algorithm is effective for this ill-posed inverse problem with relative errors in the temperature area fractions of (-3%, 3%) for most of the temperatures. The analysis provides a valuable reference for the use of spot multispectral pyrometers for sub-pixel temperature distributions in remote sensing measurements.

  7. Magnetoacoustic waves in current-carrying plasmas

    International Nuclear Information System (INIS)

    Brennan, M.H.

    1980-04-01

    The results of theoretical and experimental investigations of the characteristics of magnetoacoustic waves in non-uniform, current-carrying plasmas are reviewed. Dissipative MHD and collisionless theories are considered. Also discussed is the use of magnetoacoustic waves in plasma diagnostics and plasma heating

  8. Magnetic Field Dependence of the Critical Current in S-N Bilayer Thin Films

    Science.gov (United States)

    Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen James; Bandler, Simon; Chervenak, James; Kilbourne, Caroline A.; Finkbeiner, Fred M.; Porter, Frederick S.; Kelley, Richard L.; Adams, Joseph S.; hide

    2013-01-01

    Here we investigate the effects a non-uniform applied magnetic field has on superconducting transition-edge sensors (TESs) critical current. This has implications on TES optimization. It has been shown that TESs resistive transition can be altered by magnetic fields. We have observed critical current rectification effects and explained these effects in terms of a magnetic self-field arising from asymmetric current injection into the sensor. Our TES physical model shows that this magnetic self-field can result in significantly degraded or improved TES performance. In order for this magnetically tuned TES strategy to reach its full potential we are investigating the effect a non-uniform applied magnetic field has on the critical current.

  9. A nonuniform-polarization high-energy ultra-broadband laser with a long erbium-doped fiber

    International Nuclear Information System (INIS)

    Mao, Dong

    2013-01-01

    We have experimentally investigated nonuniformly polarized broadband high-energy pulses delivered from a mode-locked laser with an ultra-long erbium-doped fiber (EDF). The pulses exhibit a broadband spectrum of ∼73 nm and can avoid optical wave breaking at high-pump regimes. The polarization states of the pulses evolve from uniform to nonuniform at each round trip in the oscillator, which is distinct from other pulses. Remarkably, the output pulses broaden in anomalous- or normal-dispersion regimes while they can be shortened with an EDF amplifier external to the cavity. Our results suggest that the long EDF results in a nonuniform-polarization state and plays a decisive role in the formation of high-energy pulses. (paper)

  10. Some Analytical Properties of the Model for Stochastic Evolutionary Games in Finite Populations with Non-uniform Interaction Rate

    International Nuclear Information System (INIS)

    Quan Ji; Wang Xianjia

    2013-01-01

    Traditional evolutionary games assume uniform interaction rate, which means that the rate at which individuals meet and interact is independent of their strategies. But in some systems, especially biological systems, the players interact with each other discriminately. Taylor and Nowak (2006) were the first to establish the corresponding non-uniform interaction rate model by allowing the interaction rates to depend on strategies. Their model is based on replicator dynamics which assumes an infinite size population. But in reality, the number of individuals in the population is always finite, and there will be some random interference in the individuals' strategy selection process. Therefore, it is more practical to establish the corresponding stochastic evolutionary model in finite populations. In fact, the analysis of evolutionary games in a finite size population is more difficult. Just as Taylor and Nowak said in the outlook section of their paper, ''The analysis of non-uniform interaction rates should be extended to stochastic game dynamics of finite populations''. In this paper, we are exactly doing this work. We extend Taylor and Nowak's model from infinite to finite case, especially focusing on the infiuence of non-uniform connection characteristics on the evolutionary stable state of the system. We model the strategy evolutionary process of the population by a continuous ergodic Markov process. Based on the limit distribution of the process, we can give the evolutionary stable state of the system. We make a complete classification of the symmetric 2 × 2 games. For each case game, the corresponding limit distribution of the Markov-based process is given when noise intensity is small enough. In contrast with most literatures in evolutionary games using the simulation method, all our results obtained are analytical. Especially, in the dominant-case game, coexistence of the two strategies may become evolutionary stable states in our model. This result can be

  11. Shape Preserving Interpolatory Subdivision Schemes for Nonuniform Data

    NARCIS (Netherlands)

    Kuijt, F.; van Damme, Rudolf M.J.

    2002-01-01

    This article is concerned with a class of shape preserving four-point subdivision schemes which are stationary and which interpolate nonuniform univariate data {(xi, fi)}. These data are functional data, i.e., xi≠xj if i≠j. Subdivision for the strictly monotone x-values is performed by a subdivision

  12. Josephson flux-flow oscillators in nonuniform microwave fields

    DEFF Research Database (Denmark)

    Salerno, Mario; Samuelsen, Mogens Rugholm

    2000-01-01

    We present a simple theory for Josephson flux-flow oscillators in the presence of nonuniform microwave fields. In particular we derive an analytical expression for the I-V characteristic of the oscillator from which we show that satellite steps are spaced around the main flux-flow resonance by only...

  13. Absolute parametric instability in a nonuniform plane plasma

    Indian Academy of Sciences (India)

    The paper reports an analysis of the effect of spatial plasma nonuniformity on absolute parametric instability (API) of electrostatic waves in magnetized plane waveguides subjected to an intense high-frequency (HF) electric field using the separation method. In this case the effect of strong static magnetic field is considered.

  14. Distribution of ionospheric currents induced by the solar wind interaction with Venus

    International Nuclear Information System (INIS)

    Daniell, R.E. Jr.; Cloutier, P.A.

    1977-01-01

    The electric currents induced in the atmosphere of a non-magnetic planet such as Venus by the interaction of the solar wind satisfy a generalized Ohm's Law relationship with tensor conductivity. The distribution of these currents within the planetary ionosphere may be calculated by a variational technique which minimizes the Joule heating over the ionospheric volume. In this paper, we present the development of the variational technique, and apply it to a model of the solar wind interaction with Venus. Potential and current distributions are shown, and the use of these distributions in determining convective transport patterns of planetary ions is discussed. (author)

  15. On the Inverse EEG Problem for a 1D Current Distribution

    Directory of Open Access Journals (Sweden)

    George Dassios

    2014-01-01

    Full Text Available Albanese and Monk (2006 have shown that, it is impossible to recover the support of a three-dimensional current distribution within a conducting medium from the knowledge of the electric potential outside the conductor. On the other hand, it is possible to obtain the support of a current which lives in a subspace of dimension lower than three. In the present work, we actually demonstrate this possibility by assuming a one-dimensional current distribution supported on a small line segment having arbitrary location and orientation within a uniform spherical conductor. The immediate representation of this problem refers to the inverse problem of electroencephalography (EEG with a linear current distribution and the spherical model of the brain-head system. It is shown that the support is identified through the solution of a nonlinear algebraic system which is investigated thoroughly. Numerical tests show that this system has exactly one real solution. Exact solutions are analytically obtained for a couple of special cases.

  16. Non-uniform Pressure Distribution in Draw-Bend Friction Test and its Influence on Friction Measurement

    International Nuclear Information System (INIS)

    Kim, Young Suk; Jain, Mukesh K.; Metzger, Don R.

    2005-01-01

    From various draw-bend friction tests with sheet metals at lubricated conditions, it has been unanimously reported that the friction coefficient increases as the pin diameter decreases. However, a proper explanation for this phenomenon has not been given yet. In those experiments, tests were performed for different pin diameters while keeping the same average contact pressure by adjusting applied tension forces. In this paper, pressure profiles at pin/strip contacts and the changes in the pressure profiles depending on pin diameters are investigated using finite element simulations. To study the effect of the pressure profile changes on friction measurements, a non-constant friction model (Stribeck friction model), which is more realistic for the lubricated sheet metal contacts, is implemented into the finite element code and applied to the simulations. The study shows that the non-uniformity of the pressure profile increases and the pin/strip contact angle decreases as the pin diameter decreases, and these phenomena increase the friction coefficient, which is calculated from the strip tension forces using a conventional rope-pulley equation

  17. Analysis of current distribution in a large superconductor; Chodendo dotai nai no denryu bunpu kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Hamajima, K.; Alamgir, A.K.M.; Harada, N.; Tsuda, M. [Yamaguchi Univ., Yamaguchi (Japan); Ono, M.; Takano, H. [Toshiba Corp., Tokyo (Japan)

    2000-04-25

    An imbalanced current distribution is often observed in cable-in-conduit (CIC) superconductors, which are composed of multistaged, triplet type sub-cables, and deteriorates the performance of the coils. Therefore, it is very important to analyze the current distribution in a superconductor and find out methods to obtain a homogeneous current distribution in the conductor. We apply a magnetic flux conservation in a loop contoured by electric center lines of filaments in two arbitrary strands located on adjacent layers in a coaxial multilayer superconductor, and then analyze the current distribution in the conductor. A generalized formula governing the current distribution can be described as explicit functions of the superconductor construction parameters, such as twist pitch, twist direction and radius of each layer. It is shown that we can obtain a homogeneous current distribution using this fundamental formula, which is a function of the twist pitches of layers. Moreover, it is demonstrated that we can control current distribution in the coaxial superconductor. (author)

  18. Polarized parton distributions from charged-current deep-inelastic scattering and future neutrino factories

    CERN Document Server

    Forte, Stefano; Ridolfi, G; Forte, Stefano; Mangano, Michelangelo L.; Ridolfi, Giovanni

    2001-01-01

    We discuss the determination of polarized parton distributions from charged-current deep-inelastic scattering experiments. We summarize the next-to-leading order treatment of charged-current polarized structure functions, their relation to polarized parton distributions and scale dependence, and discuss their description by means of a next-to-leading order evolution code. We discuss current theoretical expectations and positivity constraints on the unmeasured C-odd combinations Delta q-Delta qbar of polarized quark distributions, and their determination in charged-current deep-inelastic scattering experiments. We give estimates of the expected errors on charged-current structure functions at a future neutrino factory, and perform a study of the accuracy in the determination of polarized parton distributions that would be possible at such a facility. We show that these measurements have the potential to distinguish between different theoretical scenarios for the proton spin structure.

  19. Polarized parton distributions from charged-current deep-inelastic scattering and future neutrino factories

    International Nuclear Information System (INIS)

    Forte, Stefano; Mangano, Michelangelo L.; Ridolfi, Giovanni

    2001-01-01

    We discuss the determination of polarized parton distributions from charged-current deep-inelastic scattering experiments. We summarize the next-to-leading-order treatment of charged-current polarized structure functions, their relation to polarized parton distributions and scale dependence, and discuss their description by means of a next-to-leading-order evolution code. We discuss current theoretical expectations and positivity constraints on the unmeasured C-odd combinations Δq-Δq-bar of polarized quark distributions, and their determination in charged-current deep-inelastic scattering experiments. We give estimates of the expected errors on charged-current structure functions at a future neutrino factory, and perform a study of the accuracy in the determination of polarized parton distributions that would be possible at such a facility. We show that these measurements have the potential to distinguish between different theoretical scenarios for the proton spin structure

  20. Modelling of temperature distribution and pulsations in fast reactor units

    International Nuclear Information System (INIS)

    Ushakov, P.A.; Sorokin, A.P.

    1994-01-01

    Reasons for the occurrence of thermal stresses in reactor units have been analyzed. The main reasons for this analysis are: temperature non-uniformity at the output of reactor core and breeder and the ensuing temperature pulsation; temperature pulsations due to mixing of sodium jets of a different temperature; temperature nonuniformity and pulsations resulting from the part of loops (circuits) un-plug; temperature nonuniformity and fluctuations in transient and accidental shut down of reactor or transfer to cooling by natural circulation. The results of investigating the thermal hydraulic characteristics are obtained by modelling the processes mentioned above. Analysis carried out allows the main lines of investigation to be defined and conclusions can be drawn regarding the problem of temperature distribution and fluctuation in fast reactor units

  1. Study on the flow nonuniformity in a high capacity Stirling pulse tube cryocooler

    Science.gov (United States)

    You, X.; Zhi, X.; Duan, C.; Jiang, X.; Qiu, L.; Li, J.

    2017-12-01

    High capacity Stirling-type pulse tube cryocoolers (SPTC) have promising applications in high temperature superconductive motor and gas liquefaction. However, with the increase of cooling capacity, its performance deviates from well-accepted one-dimensional model simulation, such as Sage and Regen, mainly due to the strong field nonuniformity. In this study, several flow straighteners placed at both ends of the pulse tube are investigated to improve the flow distribution. A two-dimensional model of the pulse tube based on the computational fluid dynamics (CFD) method has been built to study the flow distribution of the pulse tube with different flow straighteners including copper screens, copper slots, taper transition and taper stainless slot. A SPTC set-up which has more than one hundred Watts cooling power at 80 K has been built and tested. The flow straighteners mentioned above have been applied and tested. The results show that with the best flow straightener the cooling performance of the SPTC can be significantly improved. Both CFD simulation and experiment show that the straighteners have impacts on the flow distribution and the performance of the high capacity SPTC.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kato, S.; Seya, A. [Fuji Electric Co., Ltd., Ichihara-shi (Japan); Asano, A. [Fuji Electric Corporate, Ltd., Yokosuka-shi (Japan)

    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.

  3. Statistical analysis of the distribution of critical current and the correlation of n value to the critical current of bent Bi2223 composite tape

    International Nuclear Information System (INIS)

    Ochiai, S; Matsubayashi, H; Okuda, H; Osamura, K; Otto, A; Malozemoff, A

    2009-01-01

    Distributions of local and overall critical currents and correlation of n value to the critical current of bent Bi2223 composite tape were studied from the statistical viewpoint. The data of the local and overall transport critical currents and n values of the Bi2223 composite tape specimens were collected experimentally for a wide range of bending strain (0-1.1%) by using the specimens, designed so as to characterize the local and overall critical currents and n values. The measured local and overall critical currents were analyzed with various types of Weibull distribution function. Which of the Weibull distribution functions is suitable for the description of the distribution of local and overall critical currents at each bending strain, and also how much the Weibull parameter values characterizing the distribution vary with bending strain, were revealed. Then we attempted to reproduce the overall critical current distribution and correlation of the overall n value to the overall critical current from the distribution of local critical currents and the correlation of the local n value to the local critical current by a Monte Carlo simulation. The measured average values of critical current and n value at each bending strain and the correlation of n value to critical current were reproduced well by the present simulation, while the distribution of critical current values was reproduced fairly well but not fully. The reason for this is discussed.

  4. Research on Creep Relaxation Non-uniformity and Effect on Performance of Combined Rotor

    Science.gov (United States)

    Liu, Qingya; He, Jingfei; Zhao, Lijia

    2017-11-01

    The combined rotor of gas turbine is connected by a certain number of rod bolts. It works in the high temperature environment for a long time, and the rod bolts will creep and relax. Under the influence of elastic interaction, the loss of pretightening force of rod bolts at different positions is non-uniform, which will cause the connection of the combined rotor to be out of tune. In this paper, the creep relaxation non-uniformity model for a class F heavy duty gas turbine is established. On the basis of this, the performance degradation and structural strength change of combined rotor resulting from creep relaxation non-uniformity of rod bolts are studied. The results show that the ratio of preload mistuning increases with time and then converges, and there is a threshold inflection point in about seven thousand hours.

  5. Absolute parametric instability in a nonuniform plane plasma ...

    Indian Academy of Sciences (India)

    Abstract. The paper reports an analysis of the effect of spatial plasma nonuniformity on absolute parametric instability (API) of electrostatic waves in magnetized plane waveguides subjected to an intense high-frequency (HF) electric field using the separation method. In this case the effect of strong static magnetic field is ...

  6. Nonuniform grid implicit spatial finite difference method for acoustic wave modeling in tilted transversely isotropic media

    KAUST Repository

    Chu, Chunlei; Stoffa, Paul L.

    2012-01-01

    sampled models onto vertically nonuniform grids. We use a 2D TTI salt model to demonstrate its effectiveness and show that the nonuniform grid implicit spatial finite difference method can produce highly accurate seismic modeling results with enhanced

  7. Determination of non-uniformity correction factors for cylindrical ionization chambers close to 192Ir brachytherapy sources

    International Nuclear Information System (INIS)

    Toelli, H.; Bielajew, A. F.; Mattsson, O.; Sernbo, G.

    1995-01-01

    When ionization chambers are used in brachytherapy dosimetry, the measurements must be corrected for the non-uniformity of the incident photon fluence. The theory for determination of non-uniformity correction factors, developed by Kondo and Randolph (Rad. Res. 1960) assumes that the electron fluence within the air cavity is isotropic and does not take into account material differences in the chamber wall. The theory was extended by Bielajew (PMB 1990) using an anisotropic electron angular fluence in the cavity. In contrast to the theory by Kondo and Randolph, the anisotropic theory predicts a wall material dependence in the non-uniformity correction factors. This work presents experimental determination of non-uniformity correction factors at distances between 10 and 140 mm from an Ir-192 source. The experimental work makes use of a PTW23331-chamber and Farmer-type chambers (NE2571 and NE2581) with different materials in the walls. The results of the experiments agree well with the anisotropic theory. Due to the geometrical shape of the NE-type chambers, it is shown that the full length of the these chambers, 24.1mm, is not an appropriate input parameter when theoretical non-uniformity correction factors are evaluated

  8. Study of eddy current power loss from outer-winding coils of a magnetic position sensor

    International Nuclear Information System (INIS)

    Liu, C.-P.; Lin, T.-K.; Chang, Y.-H.; Yu, C.-S.; Wu, K.-T.; Wang, S.-J.; Ying, T.-F.; Huang, D.-R.

    2000-01-01

    The present analysis is concerned with eddy current power loss of a magnetic position sensor, which arises from a non-uniform flux linkage distribution between magnetic material and position sensor. In the paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar, and developed a numerical model to compute the electrical characteristics by an excited current source. According to the simulated and measured data in this proposed model from 2.52 to 11.37 Oes, eddy current power losses of conducting material have a variation of 6.1% and 9.77%, respectively. Finally, the phases of waveform of the induced output voltage will also be obtained in the conducting material, and have a variation of 3.68% obtained by using the current source in the proposed model

  9. Study of eddy current power loss from outer-winding coils of a magnetic position sensor

    CERN Document Server

    Liu, C P; Chang, Y H; Yu, C S; Wu, K T; Wang, S J; Ying, T F; Huang, D R

    2000-01-01

    The present analysis is concerned with eddy current power loss of a magnetic position sensor, which arises from a non-uniform flux linkage distribution between magnetic material and position sensor. In the paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar, and developed a numerical model to compute the electrical characteristics by an excited current source. According to the simulated and measured data in this proposed model from 2.52 to 11.37 Oes, eddy current power losses of conducting material have a variation of 6.1% and 9.77%, respectively. Finally, the phases of waveform of the induced output voltage will also be obtained in the conducting material, and have a variation of 3.68% obtained by using the current source in the proposed model.

  10. Parametric Evaluation of SiC/SiC Composite Cladding with UO2 Fuel for LWR Applications: Fuel Rod Interactions and Impact of Nonuniform Power Profile in Fuel Rod

    Science.gov (United States)

    Singh, G.; Sweet, R.; Brown, N. R.; Wirth, B. D.; Katoh, Y.; Terrani, K.

    2018-02-01

    SiC/SiC composites are candidates for accident tolerant fuel cladding in light water reactors. In the extreme nuclear reactor environment, SiC-based fuel cladding will be exposed to neutron damage, significant heat flux, and a corrosive environment. To ensure reliable and safe operation of accident tolerant fuel cladding concepts such as SiC-based materials, it is important to assess thermo-mechanical performance under in-reactor conditions including irradiation and realistic temperature distributions. The effect of non-uniform dimensional changes caused by neutron irradiation with spatially varying temperatures, along with the closing of the fuel-cladding gap, on the stress development in the cladding over the course of irradiation were evaluated. The effect of non-uniform circumferential power profile in the fuel rod on the mechanical performance of the cladding is also evaluated. These analyses have been performed using the BISON fuel performance modeling code and the commercial finite element analysis code Abaqus. A constitutive model is constructed and solved numerically to predict the stress distribution in the cladding under normal operating conditions. The dependence of dimensions and thermophysical properties on irradiation dose and temperature has been incorporated into the models. Initial scoping results from parametric analyses provide time varying stress distributions in the cladding as well as the interaction of fuel rod with the cladding under different conditions of initial fuel rod-cladding gap and linear heat rate. It is found that a non-uniform circumferential power profile in the fuel rod may cause significant lateral bowing in the cladding, and motivates further analysis and evaluation.

  11. Thermoelastic analysis of non-uniform pressurized functionally graded cylinder with variable thickness using first order shear deformation theory(FSDT) and perturbation method

    Science.gov (United States)

    Khoshgoftar, M. J.; Mirzaali, M. J.; Rahimi, G. H.

    2015-11-01

    Recently application of functionally graded materials(FGMs) have attracted a great deal of interest. These materials are composed of various materials with different micro-structures which can vary spatially in FGMs. Such composites with varying thickness and non-uniform pressure can be used in the aerospace engineering. Therefore, analysis of such composite is of high importance in engineering problems. Thermoelastic analysis of functionally graded cylinder with variable thickness under non-uniform pressure is considered. First order shear deformation theory and total potential energy approach is applied to obtain the governing equations of non-homogeneous cylinder. Considering the inner and outer solutions, perturbation series are applied to solve the governing equations. Outer solution for out of boundaries and more sensitive variable in inner solution at the boundaries are considered. Combining of inner and outer solution for near and far points from boundaries leads to high accurate displacement field distribution. The main aim of this paper is to show the capability of matched asymptotic solution for different non-homogeneous cylinders with different shapes and different non-uniform pressures. The results can be used to design the optimum thickness of the cylinder and also some properties such as high temperature residence by applying non-homogeneous material.

  12. A Non-Uniformly Under-Sampled Blade Tip-Timing Signal Reconstruction Method for Blade Vibration Monitoring

    Directory of Open Access Journals (Sweden)

    Zheng Hu

    2015-01-01

    Full Text Available High-speed blades are often prone to fatigue due to severe blade vibrations. In particular, synchronous vibrations can cause irreversible damages to the blade. Blade tip-timing methods (BTT have become a promising way to monitor blade vibrations. However, synchronous vibrations are unsuitably monitored by uniform BTT sampling. Therefore, non-equally mounted probes have been used, which will result in the non-uniformity of the sampling signal. Since under-sampling is an intrinsic drawback of BTT methods, how to analyze non-uniformly under-sampled BTT signals is a big challenge. In this paper, a novel reconstruction method for non-uniformly under-sampled BTT data is presented. The method is based on the periodically non-uniform sampling theorem. Firstly, a mathematical model of a non-uniform BTT sampling process is built. It can be treated as the sum of certain uniform sample streams. For each stream, an interpolating function is required to prevent aliasing in the reconstructed signal. Secondly, simultaneous equations of all interpolating functions in each sub-band are built and corresponding solutions are ultimately derived to remove unwanted replicas of the original signal caused by the sampling, which may overlay the original signal. In the end, numerical simulations and experiments are carried out to validate the feasibility of the proposed method. The results demonstrate the accuracy of the reconstructed signal depends on the sampling frequency, the blade vibration frequency, the blade vibration bandwidth, the probe static offset and the number of samples. In practice, both types of blade vibration signals can be particularly reconstructed by non-uniform BTT data acquired from only two probes.

  13. Photoionization microscopy of Rydberg hydrogen atom in a non-uniform electrical field

    International Nuclear Information System (INIS)

    Cheng Shao-Hao; Wang De-Hua; Chen Zhao-Hang; Chen Qiang

    2016-01-01

    In this paper, we investigate the photoionization microscopy of the Rydberg hydrogen atom in a gradient electric field for the first time. The observed oscillatory patterns in the photoionization microscopy are explained within the framework of the semiclassical theory, which can be considered as a manifestation of interference between various electron trajectories arriving at a given point on the detector plane. In contrast with the photoionization microscopy in the uniform electric field, the trajectories of the ionized electron in the gradient electric field will become chaotic. An infinite set of different electron trajectories can arrive at a given point on the detector plane, which makes the interference pattern of the electron probability density distribution extremely complicated. Our calculation results suggest that the oscillatory pattern in the electron probability density distribution depends sensitively on the electric field gradient, the scaled energy and the position of the detector plane. Through our research, we predict that the interference pattern in the electron probability density distribution can be observed in an actual photoionization microscopy experiment once the external electric field strength and the position of the electron detector plane are reasonable. This study provides some references for the future experimental research on the photoionization microscopy of the Rydberg atom in the non-uniform external fields. (paper)

  14. Surface magnetic canting in a nonuniform film

    International Nuclear Information System (INIS)

    Pini, M.G.; Rettori, A.; Pappas, D.P.; Anisimov, A.V.; Popov, A.P.

    2004-01-01

    The zero temperature equilibrium configuration of a nonuniform system made of a ferromagnetic (FM) monolayer on top of a semi-infinite FM film is calculated using a nonlinear mapping formulation of mean-field theory, where the surface is taken into account via an appropriate boundary condition. The analytical criterion for the existence of surface magnetic canting, previously obtained by Popov and Pappas, is also recovered

  15. Evaluation of Current Controllers for Distributed Power Generation Systems

    DEFF Research Database (Denmark)

    Timbus, Adrian; Liserre, Marco; Teodorescu, Remus

    2009-01-01

    This paper discusses the evaluation of different current controllers employed for grid-connected distributed power generation systems having variable input power, such as wind turbines and photovoltaic systems. The focus is mainly set on linear controllers such as proportional-integral, proportio......This paper discusses the evaluation of different current controllers employed for grid-connected distributed power generation systems having variable input power, such as wind turbines and photovoltaic systems. The focus is mainly set on linear controllers such as proportional......-integral, proportional-resonant, and deadbeat (DB) controllers. Additionally, an improved DB controller robust against grid impedance variation is also presented. Since the paper discusses the implementation of these controllers for grid-connected applications, their evaluation is made in three operating conditions....... First, in steady-state conditions, the contribution of controllers to the total harmonic distortion of the grid current is pursued. Further on, the behavior of controllers in the case of transient conditions like input power variations and grid voltage faults is also examined. Experimental results...

  16. A generic Approach for Reliability Predictions considering non-uniformly Deterioration Behaviour

    International Nuclear Information System (INIS)

    Krause, Jakob; Kabitzsch, Klaus

    2012-01-01

    Predictive maintenance offers the possibility to prognosticate the remaining time until a maintenance action of a machine has to be scheduled. Unfortunately, current predictive maintenance solutions are only suitable for very specific use cases like reliability predictions based on vibration monitoring. Furthermore, they do not consider the fact that machines may deteriorate non-uniformly, depending on external influences (e.g., the work piece material in a milling machine or the changing fruit acid concentration in a bottling plant). In this paper two concepts for a generic predictive maintenance solution which also considers non-uniformly aging behaviour are introduced. The first concept is based on system models representing the health state of a technical system. As these models are usually statically (viz. without a timely dimension) their coefficients are determined periodically and the resulting time series is used as aging indicator. The second concept focuses on external influences (contexts) which change the behaviour of the previous mentioned aging indicators in order to increase the accuracy of reliability predictions. Therefore, context-depended time series models are determined and used to predict machine reliability. Both concepts were evaluated on data of an air ventilation system. Thereby, it could be shown that they are suitable to determine aging indicators in a generic way and to incorporate external influences in the reliability prediction. Through this, the quality of reliability predictions can be significantly increased. In reality this leads to a more accurate scheduling of maintenance actions. Furthermore, the generic character of the solutions makes the concepts suitable for a wide range of aging processes.

  17. Analysis of Quantum Effects in Non-Uniformly Doped MOS Structures

    National Research Council Canada - National Science Library

    Fiegna, Claudio

    1997-01-01

    This paper presents results from the self-consistent solution of Schrodinger and Poisson equations obtained in one-dimensional non-uniformly doped MOS structures suitable for the fabrication of very short transistors...

  18. A dynamic model of gas flow in a non-uniform pipe

    International Nuclear Information System (INIS)

    Mensah, S.; Lepp, R.M.

    1979-08-01

    A gas-line model, based on the analysis of compressible flow with friction, has been developed to describe the dynamics of gas flow in a non-uniform line, i.e. one comprising segments of different lengths and diameters. Acoustic wave analysis was used in a novel way, by considering the line as a cascaded connection of uniform pipes separated by discontinuities. The transmission matrix representing this non-uniform line is the product of the matrices for each element in the system. To facilitate implementation of the theoretical model on a hybrid computer, modal approximatons to its transfer functions were derived. Both models were validated against experimental data. (author)

  19. To the problem of spatial focusing of ultracold neutrons by nonuniform magnetic field. Eikonal approximation

    CERN Document Server

    Chen, T

    2002-01-01

    Motion of the ultracold neutrons in the nonuniform magnetic field with a square nonuniformity by two coordinates is considered. The Schroedinger equation is solved with application of the quasi-classical (eikonal) approach. The theoretical possibility of the neutrons spatial focusing with formation of the point focus and also the neutrons bunches is shown

  20. Spatial linear flows of finite length with nonuniform intensity distribution

    Directory of Open Access Journals (Sweden)

    Mikhaylov Ivan Evgrafovich

    2014-02-01

    Full Text Available Irrotational flows produced by spatial linear flows of finite length with different uneven lows of discharge over the flow length are represented in cylindrical coordinate system. Flows with the length 2a are placed in infinite space filled with ideal (inviscid fluid. In “А” variant discharge is fading linearly downward along the length of the flow. In “B” variant in upper half of the flow (length a discharge is fading linearly downward, in lower half of the flow discharge is fading linearly from the middle point to lower end. In “C” variant discharge of the flow is growing linearly from upper and lower ends to middle point.Equations for discharge distribution along the length of the flow are provided for each variant. Equations consist of two terms and include two dimensional parameters and current coordinate that allows integrating on flow length. Analytical expressions are derived for speed potential functions and flow speed components for flow speeds produced by analyzed flows. These analytical expressions consist of dimensional parameters of discharge distribution patterns along the length of the flow. Flow lines equation (meridional sections of flow surfaces for variants “A”, “B”, “C” is unsolvable in quadratures. Flow lines plotting is proposed to be made by finite difference method. Equations for flow line plotting are provided for each variant. Calculations of these equations show that the analyzed flows have the following flow lines: “A” has confocal hyperbolical curves, “B” and “C” have confocal hyperboles. Flow surfaces are confocal hyperboloids produced by rotation of these hyperboles about the axis passing through the flows. In “A” variant the space filled with fluid is separated by vividly horizontal flow surface in two parts. In upper part that includes the smaller part of the flow length flow lines are oriented downward, in lower part – upward. The equation defining coordinate of

  1. Influence of Non-Uniform Magnetic Field on Quantum Teleportation in Heisenberg XY Model

    Institute of Scientific and Technical Information of China (English)

    SHAO Bin; YANG Tie-jian; ZHAO Yue-hong; ZOU Jian

    2007-01-01

    By considering the intrinsic decoherence, the validity of quantum teleportation of a two-qubit 1D Heisenberg XY chain in a non-uniform external magnetic field is studied. The fidelity as the measurement of a possible quantum teleportation is calculated and the effects of the non-uniform magnetic field and the intrinsic decoherence are discussed. It is found that anti-parallel magnetic field is more favorable for teleportation and the fidelity is suppressed by the intrinsic decoherence.

  2. Nonuniform transformation field analysis of multiphase elasto viscoplastic materials: application to MOX fuels

    International Nuclear Information System (INIS)

    Roussette, S.

    2005-05-01

    The description of the overall behavior of nonlinear materials with nonlinear dissipative phases requires an infinity of internal variables. An approximate model involving only a finite number of internal variables, Nonuniform Transformation Field Analysis, is obtained by considering a decomposition of these variables on a finite set of nonuniform transformation fields, called plastic modes. The method is initially developed for incompressible elasto viscoplastic materials. Karhunen-Loeve expansion is proposed to optimize the plastic modes. Then the method is extended to porous elasto viscoplastic materials. Finally the transformation field analysis, developed by Dvorak, is applied to nuclear fuels MOX. This method enables to make sensitivity studies to determine the role of some microstructural parameters on the fuel behaviour. Moreover the adequacy of the nonuniform method for fuels MOX is shown, the final objective being to be able to apply the model to the MOX in 3D. (author)

  3. Finite element analysis of heating a non-mixed liquid with non-uniform solar flux through semi-transparent medium

    International Nuclear Information System (INIS)

    Safdari, Y.B.; Sirivatch Shimpalee

    2000-01-01

    It has been shown in an application [1-3), in a solar flux heating of a liquid through a semi-transparent medium, that the far side of the medium receiving solar radiation achieves a higher temperature than the side receiving radiation. In this work, a two-dimensional transient finite element analysis of concentrated solo flux heating of a non-mixed liquid through a semi-transparent medium (such as glass) is carried out. The radiation heat flux is provided by a paraboloidal concentrator which focuses a non-uniform flux on the receiver. Realistic boundary conditions are considered to analyse the heat transfer problem to study the transient temperature distribution in the medium. The effects of a non-mixed liquid and a non-uniform flux show dramatic differences between the present work and the previous works [1-31. A non-mixed liquid causes greater temperature difference in the glass in both radial and axial direction than a mixed liquid used in the previous analysis. Therminol-55 is used as heated liquid for lower flux case, and sodium is used for high flux. The effect of the conductivity difference between the two liquids is studied. Results show that in the case of Therminol-55, the temperature of the liquid-side glass is much higher than that of the sodium case. The temperature distribution will be used to analyse the thermal stresses in the glass to see if fracture will occurs [4) in the glass. (Author)

  4. Identification of the material properties in nonuniform nanostructures

    International Nuclear Information System (INIS)

    Bao, Gang; Xu, Xiang

    2015-01-01

    This paper is concerned with addressing two significant challenges arising from quantifying mechanical properties of nanomaterials, namely nonuniformity of the nanomaterial and the high noise level of measurements. For nonuniformity, an explicit solution is derived for the general Euler–Bernoulli equation in terms of the Green function for the Poisson equation. Then, by examining a stochastic source, the systematic error may be removed from measurements, which leads to more accurate estimation of mechanical properties. Based on Itô integral properties, three deterministic Fredholm integral equations can be deduced to extract the stiffness and the structure of the random source from measured data. To overcome ill-posedness and high nonlinearity in solving the Fredholm equations, a Tikhonov regularization method is developed with an a priori strategy of choosing the regularization parameter. Moreover, under a regularity assumption for the stiffness coefficient and structures of the random source, the convergence rate can be obtained in the sense of probability. Numerical examples are presented to illustrate the validity and effectiveness of the novel model and regularization method. (paper)

  5. Potential coherent structures in nonuniform streaming dusty magnetoplasma

    Energy Technology Data Exchange (ETDEWEB)

    Vranjes, Jovo [Inst. of Physics, Belgrade (Yugoslavia); Shukla, Padma Kant [Ruhr-Universitaet Bochum, Institut fuer Theoretische Physik IV, Bochum (Germany)

    2001-07-01

    In this paper we study linear and nonlinear behaviour of modified convective cells and vortices in nonuniform dusty magnetoplasmas with perpendicular and parallel to the magnetic field plasma flows, and in basically two different physical systems, with stationary (corresponding to the case of ShuklaVarma mode) and nonstationary (i.e. taking part in perturbations) dust particles. For the case of stationary dust, by choosing some specific profiles for the sheared plasma flow and the dust density, we analyze the eigenvalue equation in order to deduce the growth rate. A threshold is also obtained for the wavenumber separating spatially damped and convective modes (growing in space) due to its interaction with the sheared plasma flow. In the nonlinear regime, for both stationary and nonstationary dust particles, and in the presence of various plasma flows perpendicular and parallel to the magnetic field lines, a variety of possible nonlinear solutions, driven by the nonuniform shear flow and dust density is presented, i.e., single and double vortex chains accompanied with zonal flows, and tripolar and global vortices. (author)

  6. New ecological mechanism of formation of spatial distribution of radionuclides in river ecosystem

    International Nuclear Information System (INIS)

    Degermendzhy, A.G.; Shevyrnogov, A.P.; Kosolapova, L.G.; Levin, L.A.; Chernousov, A.V.; Vlasik, P.V.

    1996-01-01

    Radioecological expeditions on the Yenissei river revealed 'spotty' distribution of radioisotopes in bottom sediments and along the coastline of the river. This work presents results of theoretical analysis of the formation mechanism of stable spatial non-uniformities of river ecosystem components by population interactions of 'predator-prey' type between the phytoplukton and zooplankton. 'Patchiness contrast' (i.e. the amplitude of the radionuclide spatial propagation wave in the water) for the large oscillations control by increasing or decreasing current velocity depends both on the boundary concentrations of phytoplankton and zooplankton and on the established nature of their interpopulation interactions (or coefficients of interactions). Variation of the below given interaction parameters within the 'phytoplanbon-zooplankton' system makes increase the amplitude of spatial distribution wave: decrease of algal growth rate; increase of algal death rate; decrease of zooplankton death rate; increase of interaction coefficients. It was shown for small oscillations that the period of component distribution waves is in proportion to the current velocity and the amplitude of 'small' waves does not depend on the water current velocity. Theoretically it has been also found that with deep limitation of phytoplankton growth by biogenous elements the 'standing wave' is observed to deteriorate and monotonous distribution of radionuclide concentration fields is found to form. (author)

  7. Scaled nonuniform Fourier transform for image reconstruction in swept source optical coherence tomography

    Science.gov (United States)

    Mezgebo, Biniyam; Nagib, Karim; Fernando, Namal; Kordi, Behzad; Sherif, Sherif

    2018-02-01

    Swept Source optical coherence tomography (SS-OCT) is an important imaging modality for both medical and industrial diagnostic applications. A cross-sectional SS-OCT image is obtained by applying an inverse discrete Fourier transform (DFT) to axial interferograms measured in the frequency domain (k-space). This inverse DFT is typically implemented as a fast Fourier transform (FFT) that requires the data samples to be equidistant in k-space. As the frequency of light produced by a typical wavelength-swept laser is nonlinear in time, the recorded interferogram samples will not be uniformly spaced in k-space. Many image reconstruction methods have been proposed to overcome this problem. Most such methods rely on oversampling the measured interferogram then use either hardware, e.g., Mach-Zhender interferometer as a frequency clock module, or software, e.g., interpolation in k-space, to obtain equally spaced samples that are suitable for the FFT. To overcome the problem of nonuniform sampling in k-space without any need for interferogram oversampling, an earlier method demonstrated the use of the nonuniform discrete Fourier transform (NDFT) for image reconstruction in SS-OCT. In this paper, we present a more accurate method for SS-OCT image reconstruction from nonuniform samples in k-space using a scaled nonuniform Fourier transform. The result is demonstrated using SS-OCT images of Axolotl salamander eggs.

  8. Effects of active conductance distribution over dendrites on the synaptic integration in an identified nonspiking interneuron.

    Directory of Open Access Journals (Sweden)

    Akira Takashima

    Full Text Available The synaptic integration in individual central neuron is critically affected by how active conductances are distributed over dendrites. It has been well known that the dendrites of central neurons are richly endowed with voltage- and ligand-regulated ion conductances. Nonspiking interneurons (NSIs, almost exclusively characteristic to arthropod central nervous systems, do not generate action potentials and hence lack voltage-regulated sodium channels, yet having a variety of voltage-regulated potassium conductances on their dendritic membrane including the one similar to the delayed-rectifier type potassium conductance. It remains unknown, however, how the active conductances are distributed over dendrites and how the synaptic integration is affected by those conductances in NSIs and other invertebrate neurons where the cell body is not included in the signal pathway from input synapses to output sites. In the present study, we quantitatively investigated the functional significance of active conductance distribution pattern in the spatio-temporal spread of synaptic potentials over dendrites of an identified NSI in the crayfish central nervous system by computer simulation. We systematically changed the distribution pattern of active conductances in the neuron's multicompartment model and examined how the synaptic potential waveform was affected by each distribution pattern. It was revealed that specific patterns of nonuniform distribution of potassium conductances were consistent, while other patterns were not, with the waveform of compound synaptic potentials recorded physiologically in the major input-output pathway of the cell, suggesting that the possibility of nonuniform distribution of potassium conductances over the dendrite cannot be excluded as well as the possibility of uniform distribution. Local synaptic circuits involving input and output synapses on the same branch or on the same side were found to be potentially affected under

  9. Long GRBs sources population non-uniformity

    Science.gov (United States)

    Arkhangelskaja, Irene

    Long GRBs observed in the very wide energy band. It is possible to separate two subsets of GRBs with high energy component (E > 500 MeV) presence. First type events energy spectra in low and high energy intervals are similar (as for GRB 021008) and described by Band, power law or broken power law models look like to usual bursts without emission in tens MeV region. For example, Band spectrum of GRB080916C covering 6 orders of magnitude. Second ones contain new additional high energy spectral component (for example, GRB 050525B and GRB 090902B). Both types of GRBs observed since CGRO mission beginning. The low energy precursors existence are typical for all types bursts. Both types of bursts temporal profiles can be similar in the various energy regions during some events or different in other cases. The absence of hard to soft evolution in low energy band and (or) presence of high energy precursors for some events are the special features of second class of GRBs by the results of preliminary data analysis and this facts gives opportunities to suppose differences between these two GRBs subsets sources. Also the results of long GRB redshifts distribution analysis have shown its shape contradiction to uniform population objects one for our Metagalaxy to both total and various redshifts definition methods GRBs sources samples. These evidences allow making preliminary conclusion about non-uniformity of long GRBs sources population.

  10. 6‐GHz‐to‐18‐GHz AlGaN/GaN Cascaded Nonuniform Distributed Power Amplifier MMIC Using Load Modulation of Increased Series Gate Capacitance

    Directory of Open Access Journals (Sweden)

    Dong‐Hwan Shin

    2017-10-01

    Full Text Available A 6‐GHz‐to‐18‐GHz monolithic nonuniform distributed power amplifier has been designed using the load modulation of increased series gate capacitance. This amplifier was implemented using a 0.25‐μm AlGaN/GaN HEMT process on a SiC substrate. With the proposed load modulation, we enhanced the amplifier's simulated performance by 4.8 dB in output power, and by 13.1% in power‐added efficiency (PAE at the upper limit of the bandwidth, compared with an amplifier with uniform gate coupling capacitors. Under the pulse‐mode condition of a 100‐μs pulse period and a 10% duty cycle, the fabricated power amplifier showed a saturated output power of 39.5 dBm (9 W to 40.4 dBm (11 W with an associated PAE of 17% to 22%, and input/output return losses of more than 10 dB within 6 GHz to 18 GHz.

  11. The current distribution in Bi-2223/Ag HTS conductors: comparing Hall probe and magnetic knife

    NARCIS (Netherlands)

    Demencik, E.; Dhalle, Marc M.J.; ten Kate, Herman H.J.; Polak, M.

    2006-01-01

    We analyzed the current distribution in three Bi-2223/Ag tapes with different filament lay-out, comparing the results of magnetic knife and Hall probe experiments. Detailed knowledge of the current distribution can be useful for the diagnostics of HTS conductors. The lateral current distribution was

  12. Current distribution in Cable-In-Conduit Conductors

    International Nuclear Information System (INIS)

    Ferri, M.A.

    1994-05-01

    A numerical study of the current distribution in Cable-In-Conduit Conductors (CICC's) experiencing linearly ramping transport currents and transverse magnetic fields was conducted for both infinitely long, periodic cables and finite length cables terminated in low resistance joints. The goal of the study was to gain insight into the phenomenon known as Ramp Rate Limitation, an as yet unexplained correspondence between maximum attainable current and the ramp time taken to reach that current in CICC superconducting magnets. A discrete geometric model of a 27 strand multiply twisted CICC was developed to effectively represent the flux linkages, mutual inductances, and resistive contact points between the strands of an experimentally tested cable. The results of the numerical study showed that for fully periodic cables, the current imbalances due to ramping magnetic fields and ramping transport currents are negligible in the range of experimentally explored operating conditions. For finite length, joint terminated cables, however, significant imbalances can exist. Unfortunately, quantitative results are limited by a lack of knowledge of the transverse resistance between strands in the joints. Nonetheless, general results are presented showing the dependency of the imbalance on cable length, ramp time, and joint resistance for both ramping transverse magnet fields and ramping transport currents. At the conclusion of the study, it is suggested that calculated current imbalances in a finite length cable could cause certain strands to prematurely ''quench'' -- become non-superconducting --thus leading to an instability for the entire cable. This numerically predicted ''current imbalance instability'' is compared to the experimentally observed Ramp Rate Limitation for the 27 strand CICC sample

  13. Effect of heated length on the Critical Heat Flux of subcooled flow boiling. 2. Effective heated length under axially nonuniform heating condition

    International Nuclear Information System (INIS)

    Kinoshita, Hidetaka; Yoshida, Takuya; Nariai, Hideki; Inasaka, Fujio

    1998-01-01

    Effect of heated length on the Critical Heat Flux (CHF) of subcooled flow boiling with water was experimentally investigated by using direct current heated tube made of stainless steel a part of whose wall thickness was axially cut for realizing nonuniform heat flux condition. The higher enhancement of the CHF was derived for shorter tube length. The effective heated length was determined for the tube under axially nonuniform heat flux condition. When the lower heat flux part below the Net Vapor Generation (NVG) heat flux exists at the middle of tube length, then the effective heated length becomes the tube length downstream the lower heat flux parts. However, when the lower heat flux part is above the NVG, then the effective heated length is full tube length. (author)

  14. Creep to inertia dominated stick-slip behavior in sliding friction modulated by tilted non-uniform loading

    Science.gov (United States)

    Tian, Pengyi; Tao, Dashuai; Yin, Wei; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu

    2016-09-01

    Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors.

  15. Protostellar formation in rotating interstellar clouds. VI. Nonuniform initial conditions

    International Nuclear Information System (INIS)

    Boss, A.P.

    1987-01-01

    The collapse and fragmentation of rotating protostellar clouds is explored, starting from nonuniform density and nonuniform rotation initial conditions. Whether binary fragmentation occurs during the first dynamic collapse phase depends strongly on the initial density profile. Exponential clouds are only somewhat more resistant to fragmentation than uniform-density clouds, but power-law clouds do not undergo fragmentation for likely values of a relevant parameter. Because binary fragments start from profiles intermediate between uniform density and exponential clouds, minimum protostellar mass for population I stars should be increased to approximately 0.02 solar mass. The axisymmetric Terey et al. (1984) model should be stable with respect to nonaxisymmetric perturbations. Considering the observed binary frequency, collapse from power-law initial conditions appears to be less common than collapse from more uniform initial conditions. 34 references

  16. Study of submelt laser induced junction nonuniformities using Therma-Probe

    DEFF Research Database (Denmark)

    Rosseel, E.; Bogdanowicz, J; Clarysse, T.

    2010-01-01

    to standard and micro-four-point probe sheet resistance data, secondary ion mass spectrometry, and Hall measurements obtained during earlier studies. Besides the impact of the nonuniformities on the “conventional” thermal wave signal, they found a strong correlation to the dc reflectance of the probe laser...... both at macroscopic and microscopic levels. In this work, the authors present high resolution Therma-Probe® measurements to assess the junction nonuniformity on 0.5 keV boron junctions and zoom in on the effect of temperature variations and multiple subsequent laser scans. The results are compared...... (lambda = 675 nm). The dc probe reflectance is dominated by free carriers and is highly correlated to the sheet resistance both on blanket wafers and on real device wafers. ©2010 American Vacuum Society...

  17. Enceladus's crust as a non-uniform thin shell: I tidal deformations

    Science.gov (United States)

    Beuthe, Mikael

    2018-03-01

    The geologic activity at Enceladus's south pole remains unexplained, though tidal deformations are probably the ultimate cause. Recent gravity and libration data indicate that Enceladus's icy crust floats on a global ocean, is rather thin, and has a strongly non-uniform thickness. Tidal effects are enhanced by crustal thinning at the south pole, so that realistic models of tidal tectonics and dissipation should take into account the lateral variations of shell structure. I construct here the theory of non-uniform viscoelastic thin shells, allowing for depth-dependent rheology and large lateral variations of shell thickness and rheology. Coupling to tides yields two 2D linear partial differential equations of the fourth order on the sphere which take into account self-gravity, density stratification below the shell, and core viscoelasticity. If the shell is laterally uniform, the solution agrees with analytical formulas for tidal Love numbers; errors on displacements and stresses are less than 5% and 15%, respectively, if the thickness is less than 10% of the radius. If the shell is non-uniform, the tidal thin shell equations are solved as a system of coupled linear equations in a spherical harmonic basis. Compared to finite element models, thin shell predictions are similar for the deformations due to Enceladus's pressurized ocean, but differ for the tides of Ganymede. If Enceladus's shell is conductive with isostatic thickness variations, surface stresses are approximately inversely proportional to the local shell thickness. The radial tide is only moderately enhanced at the south pole. The combination of crustal thinning and convection below the poles can amplify south polar stresses by a factor of 10, but it cannot explain the apparent time lag between the maximum plume brightness and the opening of tiger stripes. In a second paper, I will study the impact of a non-uniform crust on tidal dissipation.

  18. Field-emission from parabolic tips: Current distributions, the net current, and effective emission area

    Science.gov (United States)

    Biswas, Debabrata

    2018-04-01

    Field emission from nano-structured emitters primarily takes place from the tips. Using recent results on the variation of the enhancement factor around the apex [Biswas et al., Ultramicroscopy 185, 1-4 (2018)], analytical expressions for the surface distribution of net emitted electrons, as well as the total and normal energy distributions are derived in terms of the apex radius Ra and the local electric field at the apex Ea. Formulae for the net emitted current and effective emission area in terms of these quantities are also obtained.

  19. An efficient shutter-less non-uniformity correction method for infrared focal plane arrays

    Science.gov (United States)

    Huang, Xiyan; Sui, Xiubao; Zhao, Yao

    2017-02-01

    The non-uniformity response in infrared focal plane array (IRFPA) detectors has a bad effect on images with fixed pattern noise. At present, it is common to use shutter to prevent from radiation of target and to update the parameters of non-uniformity correction in the infrared imaging system. The use of shutter causes "freezing" image. And inevitably, there exists the problems of the instability and reliability of system, power consumption, and concealment of infrared detection. In this paper, we present an efficient shutter-less non-uniformity correction (NUC) method for infrared focal plane arrays. The infrared imaging system can use the data gaining in thermostat to calculate the incident infrared radiation by shell real-timely. And the primary output of detector except the shell radiation can be corrected by the gain coefficient. This method has been tested in real infrared imaging system, reaching high correction level, reducing fixed pattern noise, adapting wide temperature range.

  20. Non-Uniform Dose Mapping Controlled by Modulated Vertical and Horizontal Scans

    International Nuclear Information System (INIS)

    Ninomiya, S.; Kimura, Y.; Kudo, T.; Ochi, A.; Toda, R.; Tsukihara, M.; Sato, F.; Fuse, G.; Ueno, K.; Sugitani, M.

    2008-01-01

    Since geometries of semi-conductor devices continue to shrink, the requirement for each process becomes severer to keep uniformity of electrical parameters of the semi-conductor devices. A larger wafer also causes larger variations. Thus it has been strongly required for ion implantation process to compensate for the variations from other processes because of its good dose controllability. A newly developed mapping of intentional non-uniform dosage system, which is named 'MIND system', is implemented in SEN's single-wafer-type implanters. The MIND system controls both horizontal and vertical scan speed simultaneously. Intentional two-dimensional non-uniform profiles of sheet resistance, such as concentric and eccentric profiles, are obtained only by single-step ion implantation.

  1. Effect of transverse power distribution on the ONB location in the subcooled boiling flow

    International Nuclear Information System (INIS)

    Al-Yahia, Omar S.; Lee, Yong Joong; Jo, Daeseong

    2017-01-01

    Highlights: • Effect of transverse power distribution on ONB incipient. • Uniform and non-uniform heat distribution is simulated in a narrow rectangular channel. • Simulations are performed using CFX and TMAP codes. • For uniform heating, ONB incipient by CFX occurs between predictions by TMAP analyses. • For non-uniform heating, ONB incipient by CFX occurs at a higher power than that by TMAP analysis. - Abstract: This study investigates the effect of transverse power distribution on the ONB (Onset of Nucleate Boiling) incipient. For this purpose, a subcooled boiling model with uniform and non-uniform heat flux distribution is simulated in a narrow vertical rectangular channel heated from both sides by applying a wide range of thermal power (8–16 kW). The simulations are performed using the CFX and TMAP codes. The CFX code incorporates both a two-fluid model and RPI wall boiling model to investigate coolant and wall temperature distributions along the heated channel. The TMAP code implements two different sets of heat transfer correlations to evaluate the wall temperature. The results obtained from the TMAP analyses show that the wall temperatures predicted by the Jo et al. heat transfer correlation are higher than the ones predicted by the Dittus and Boelter heat transfer correlation. The wall temperatures predicted by the CFX analyses lie between the predicted wall temperatures obtained by the TMAP analyses. Based on the superheated temperature on the heated surface, the ONB incipient is determined. The axial locations of the ONB incipient are predicted differently by the CFX and TMAP analyses. For uniform heating, the ONB incipient predicted by the CFX analysis occurs between the predictions made by the TMAP analyses. For non-uniform heating, the ONB incipient by the CFX analysis occurs at a higher power than the power required by the TMAP analyses.

  2. Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE MRI.

    Directory of Open Access Journals (Sweden)

    Noam Shemesh

    Full Text Available Objects making up complex porous systems in Nature usually span a range of sizes. These size distributions play fundamental roles in defining the physicochemical, biophysical and physiological properties of a wide variety of systems - ranging from advanced catalytic materials to Central Nervous System diseases. Accurate and noninvasive measurements of size distributions in opaque, three-dimensional objects, have thus remained long-standing and important challenges. Herein we describe how a recently introduced diffusion-based magnetic resonance methodology, Non-Uniform-Oscillating-Gradient-Spin-Echo (NOGSE, can determine such distributions noninvasively. The method relies on its ability to probe confining lengths with a (length6 parametric sensitivity, in a constant-time, constant-number-of-gradients fashion; combined, these attributes provide sufficient sensitivity for characterizing the underlying distributions in μm-scaled cellular systems. Theoretical derivations and simulations are presented to verify NOGSE's ability to faithfully reconstruct size distributions through suitable modeling of their distribution parameters. Experiments in yeast cell suspensions - where the ground truth can be determined from ancillary microscopy - corroborate these trends experimentally. Finally, by appending to the NOGSE protocol an imaging acquisition, novel MRI maps of cellular size distributions were collected from a mouse brain. The ensuing micro-architectural contrasts successfully delineated distinctive hallmark anatomical sub-structures, in both white matter and gray matter tissues, in a non-invasive manner. Such findings highlight NOGSE's potential for characterizing aberrations in cellular size distributions upon disease, or during normal processes such as development.

  3. Low-frequency electrostatic dust-modes in a non-uniform

    Indian Academy of Sciences (India)

    A self-consistent and general description of obliquely propagating low-frequency electrostatic dust-modes in a non-uniform magnetized dusty plasma system has been presented. A number of different situations, which correspond to different low-frequency electrostatic dust-modes, namely, dust-acoustic mode, dust-drift ...

  4. Hot deformation behavior and microstructure evolution of TA15 titanium alloy with nonuniform microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Pengfei; Zhan, Mei, E-mail: zhanmei@nwpu.edu.cn; Fan, Xiaoguang; Lei, Zhenni; Cai, Yang

    2017-03-24

    The flow behavior and microstructure evolution of a near α titanium alloy with nonuniform microstructure during hot deformation were studied by isothermal compression test and electron backscatter diffraction technique. It is found that the nonuniform microstructure prior to deformation consists of equiaxed α, lamellar α in the colony form and β phase, and the α colony keeps the Burgers orientation relationship with β phase. The flow stress of nonuniform microstructure exhibits significant flow softening after reaching the peak stress at a low strain, which is similar to the lamellar microstructure. Nevertheless, the existence of equiaxed α in nonuniform microstructure makes its flow stress and softening rate be lower than the lamellar microstructure. During deformation, the lamellar α undertakes most of the deformation and turns to be rotated, bended and globularized. Moreover, these phenomena exhibit significant heterogeneity due to the orientation dependence of the deformation of lamellar α. The continuous dynamic recrystallization and bending of lamellar α lead to the “fragmentation” during globularization of lamellar α. The bending of lamellar α is speculated as a form of plastic buckling, because the bending of lamellar α almost proceed in the manner of “rigid rotation” and presents opposite bending directions for the adjacent colonies.

  5. CHF multiplier of subcooled flow boiling for non-uniform heating conditions in swirl tube

    International Nuclear Information System (INIS)

    Inasaka, F.; Nariai, H.

    1994-01-01

    The high heat flux components of fusion reactors, such as divertor plates and beam dumps of neutral beam injectors, are estimated to be subjected to very high heat loads more than 10 MW/m 2 . Critical heat flux (CHF), which determines the upper limit of heat removal, is one of the most important problems in designing cooling systems. For practical applications in cooling systems, subcooled flow boiling in water combined with swirl-flow in tubes with internal twisted tape is thought to be the most superior for CHF characteristics in fusion reactor components, heat by irradiation comes in from one side of the wall, and cooling channel is then under circumferentially non-uniform heating condition. Authors have conducted the experiments on the CHF with internal twisted tapes under circumferentially non-uniform heating conditions and showed that when the intensity of non-uniformity increased, q cH (peak heat flux at burnout under nonuniform heating condition) in tube with internal twisted tape increased above the q c,unif (CHF under uniform heating condition), though the average qualities were the same for both cases. They also showed that this CHF enhancement was not seen in smooth tubes without tape under the same average qualities

  6. Influence Of Nonuniformity On Infrared Focal Plane Array Performance

    Science.gov (United States)

    Milton, A. F.; Barone, F. R.; Kruer, M. R.

    1985-08-01

    It is well known that detector response nonuniformity results in pattern noise with staring sensors that is a severe problem in the infrared due to the low intrinsic contrast of IR imagery. The pattern noise can be corrected by electronic processing; however, the ability to correct for pattern noise is limited by the interaction of interscene and intrascene variability with the dynamic range of the processor (number of bits) and, depending upon the algorithm used, by nonlinearities in the detector response. This paper quantifies these limitations and describes the interaction of detector gain nonuniformity and detector nonlinearities. Probabilistic models are developed to determine the maximum sensitivity that can be obtained using a two-point algorithm to correct a nonlinear response curve over a wide temperature range. Curves that permit a prediction of the noise equivalent differential temperature (NEAT) under varying circumstances are presented. A piecewise linear approach to dealing with severe detector response nonlinearities is presented and analyzed for its effectiveness.

  7. Nonuniform code concatenation for universal fault-tolerant quantum computing

    Science.gov (United States)

    Nikahd, Eesa; Sedighi, Mehdi; Saheb Zamani, Morteza

    2017-09-01

    Using transversal gates is a straightforward and efficient technique for fault-tolerant quantum computing. Since transversal gates alone cannot be computationally universal, they must be combined with other approaches such as magic state distillation, code switching, or code concatenation to achieve universality. In this paper we propose an alternative approach for universal fault-tolerant quantum computing, mainly based on the code concatenation approach proposed in [T. Jochym-O'Connor and R. Laflamme, Phys. Rev. Lett. 112, 010505 (2014), 10.1103/PhysRevLett.112.010505], but in a nonuniform fashion. The proposed approach is described based on nonuniform concatenation of the 7-qubit Steane code with the 15-qubit Reed-Muller code, as well as the 5-qubit code with the 15-qubit Reed-Muller code, which lead to two 49-qubit and 47-qubit codes, respectively. These codes can correct any arbitrary single physical error with the ability to perform a universal set of fault-tolerant gates, without using magic state distillation.

  8. Couple of biomimetic surfaces with different morphologies for remanufacturing nonuniform wear rail surface

    Science.gov (United States)

    Sui, Qi; Zhou, Hong; Yang, Lin; Zhang, Haifeng; Feng, Li; Zhang, Peng

    2018-02-01

    In this work, biomimetic laser treatment was performed on repairing and remanufacturing the nonuniform worn rail surface. The wearing depth distribution of three work regions of a failure rail surface was discussed, and different thickness hardening layers with different microstructure, microhardness and wear resistances were detected from the worm surfaces. Varying wear resistances of the surfaces with different biomimetic morphologies were obtained by biomimetic laser treatments, and the corresponding effect on the lubrication sliding wear of treated and untreated surfaces were studied for comparative study. In addition, the relationship between wear resistance and the spacing of units was also provided, which can lay the important theoretical foundation for avoiding the wear resistance of the serious worn surface is less than that of the slight worn surface in the future practical applications.

  9. Experimental observation of nonlinear behaviour in a helium plasma discharge in the presence of a nonuniform magnetic field

    International Nuclear Information System (INIS)

    Toma, M.; Sanduloviciu, M.

    1994-01-01

    The nonlinear behaviour in an electrical discharge plasma due to the action of an external nonuniform magnetic field is presented. The discharge geometry and the magnetic field configuration ('inverse' cylindrical magnetron discharge) were so chosen that there is a possibility to control the net electron flux in a certain region of a positive electrode. The plasma discharge nonlinearity manifested in the profile of the current-voltage, current-magnetic field and current-gas pressure characteristics by the appearance of the anomalous negative resistance, in the bistability and hysteresis and also in the periodical and chaotic variation of the discharge current. The profile of the current variation vs control discharge parameters was related to the appearance of a space charge structure in the shape of nearly spherical bulges, delimited from the surrounding plasma by a double layer. (Author)

  10. The effects of off-center pellets on the temperature distribution and the heat flux distribution of fuel rods in nuclear reactors

    International Nuclear Information System (INIS)

    Peng Muzhang; Xing Jianhua

    1986-01-01

    This paper analyzes the effects of off-center pellets on the steady state temperature distribution and heat flux distribution of fuel rods in the nuclear reactors, and derives the dimensionless temperature distribution relationships and the dimensionless heat flux distribution relationship from the fuel rods with off-center pellets. The calculated results show that the effects of off-center will result in not only deviations of the highest temperature placement in the fuel pellets, but also the circumferentially nonuniform distributions of the temperatures and heat fluxes of the fuel rod surfaces

  11. Current distribution between petals in PF-FSJS sample

    International Nuclear Information System (INIS)

    Zani, L.

    2003-01-01

    6 Rogowski coils have been installed on each leg of each of the 12 petals in the PF-FSJS sample (poloidal field - full size joint sample) in order to diagnostic current. It appears that Rogowski signal seem reliable for current distribution analysis (Ampere's law is checked and reproducibility is assured) but there is some limitations for qualitative diagnostics. In the series of transparencies results are detailed for the PU1 position, for both leg and right legs and for various unique-angle shift (Δθ) configurations but only results for 0 < Δθ < -5 are consistent

  12. 1RXS J180834.7+101041 is a new cataclysmic variable with non-uniform disc

    Science.gov (United States)

    Yakin, D. G.; Suleimanov, V. F.; Shimansky, V. V.; Borisov, N. V.; Bikmaev, I. F.; Sakhibullin, N. A.

    2010-11-01

    Results of photometric and spectroscopic investigations of the recently discovered disc cataclysmic variable star 1RXS J180834.7+101041 are presented. Emission spectra of the system show broad double peaked hydrogen and helium emission lines. Doppler maps for the hydrogen lines demonstrate strongly non-uniform emissivity distribution in the disc, similar to that found in IP Peg. It means that the system is a new cataclysmic variable with a spiral density wave in the disc. Masses of the components (MWD = 0.8+/-0.22 Msolar and MRD = 0.14+/-0.02 Msolar), and the orbit inclination (i = 78°+/- 1.°5) were estimated using the various well-known relations for cataclysmic variables.

  13. Geomagnetic storms, the Dst ring-current myth and lognormal distributions

    Science.gov (United States)

    Campbell, W.H.

    1996-01-01

    The definition of geomagnetic storms dates back to the turn of the century when researchers recognized the unique shape of the H-component field change upon averaging storms recorded at low latitude observatories. A generally accepted modeling of the storm field sources as a magnetospheric ring current was settled about 30 years ago at the start of space exploration and the discovery of the Van Allen belt of particles encircling the Earth. The Dst global 'ring-current' index of geomagnetic disturbances, formulated in that period, is still taken to be the definitive representation for geomagnetic storms. Dst indices, or data from many world observatories processed in a fashion paralleling the index, are used widely by researchers relying on the assumption of such a magnetospheric current-ring depiction. Recent in situ measurements by satellites passing through the ring-current region and computations with disturbed magnetosphere models show that the Dst storm is not solely a main-phase to decay-phase, growth to disintegration, of a massive current encircling the Earth. Although a ring current certainly exists during a storm, there are many other field contributions at the middle-and low-latitude observatories that are summed to show the 'storm' characteristic behavior in Dst at these observatories. One characteristic of the storm field form at middle and low latitudes is that Dst exhibits a lognormal distribution shape when plotted as the hourly value amplitude in each time range. Such distributions, common in nature, arise when there are many contributors to a measurement or when the measurement is a result of a connected series of statistical processes. The amplitude-time displays of Dst are thought to occur because the many time-series processes that are added to form Dst all have their own characteristic distribution in time. By transforming the Dst time display into the equivalent normal distribution, it is shown that a storm recovery can be predicted with

  14. The effect of electrodeposition process parameters on the current density distribution in an electrochemical cell

    Directory of Open Access Journals (Sweden)

    R. M. STEVANOVIC

    2001-02-01

    Full Text Available Cell voltage – current density dependences for a model electrochemical cell of fixed geometry were calculated for different electrolyte conductivities, Tafel slopes and cathodic exchange current densities. The ratio between the current density at the part of the cathode nearest to the anode and the one furthest away were taken as a measure for the estimation of the current density distribution. The calculations reveal that increasing the conductivity of the electrolyte, as well as increasing the cathodic Tafel slope should both improve the current density distribution. Also, the distribution should be better under total activation control or total diffusion control rather than at mixed activation-diffusion-Ohmic control of the deposition process. On the contrary, changes in the exchange current density should not affect it. These results, being in agreement with common knowledge about the influence of different parameters on the current distribution in an electrochemical cell, demonstrate that a quick estimation of the current distribution can be performed by a simple comparison of the current density at the point of the cathode closest to anode with that at furthest point.

  15. Maximum Likelihood DOA Estimation of Multiple Wideband Sources in the Presence of Nonuniform Sensor Noise

    Directory of Open Access Journals (Sweden)

    K. Yao

    2007-12-01

    Full Text Available We investigate the maximum likelihood (ML direction-of-arrival (DOA estimation of multiple wideband sources in the presence of unknown nonuniform sensor noise. New closed-form expression for the direction estimation Cramér-Rao-Bound (CRB has been derived. The performance of the conventional wideband uniform ML estimator under nonuniform noise has been studied. In order to mitigate the performance degradation caused by the nonuniformity of the noise, a new deterministic wideband nonuniform ML DOA estimator is derived and two associated processing algorithms are proposed. The first algorithm is based on an iterative procedure which stepwise concentrates the log-likelihood function with respect to the DOAs and the noise nuisance parameters, while the second is a noniterative algorithm that maximizes the derived approximately concentrated log-likelihood function. The performance of the proposed algorithms is tested through extensive computer simulations. Simulation results show the stepwise-concentrated ML algorithm (SC-ML requires only a few iterations to converge and both the SC-ML and the approximately-concentrated ML algorithm (AC-ML attain a solution close to the derived CRB at high signal-to-noise ratio.

  16. Numerical simulation of effect of laser nonuniformity in interior interface

    International Nuclear Information System (INIS)

    Yu Xiaojin; Wu Junfeng; Ye Wenhua

    2007-01-01

    Using the LARED-S code and referring to the NIF direct-drive DT ignition target, the effect of laser nonuniformity on the interior interface in direct-drive spherical implosion with high convergence ratio was numerically studied. The two-dimensional results show that the implosion with high convergence ratio is sensitive to the nonuniformity of driving laser, and the growth of hydrodynamic instability on interior interface destroys the symmetric-drive and reduces the volume of central hot spot observably. Taking the limit that perturbation amplitude is equal to 1/3 radius of central hot spot, the simulation also gives that the requirements for the laser uniformity for different mode number(less than 12) on simple physical model are between 2.5% -0.25%, and the modes between 8-10 have the most rigorous requirement which is about 0.25%. (authors)

  17. Streaming current magnetic fields in a charged nanopore

    Science.gov (United States)

    Mansouri, Abraham; Taheri, Peyman; Kostiuk, Larry W.

    2016-01-01

    Magnetic fields induced by currents created in pressure driven flows inside a solid-state charged nanopore were modeled by numerically solving a system of steady state continuum partial differential equations, i.e., Poisson, Nernst-Planck, Ampere and Navier-Stokes equations (PNPANS). This analysis was based on non-dimensional transport governing equations that were scaled using Debye length as the characteristic length scale, and applied to a finite length cylindrical nano-channel. The comparison of numerical and analytical studies shows an excellent agreement and verified the magnetic fields density both inside and outside the nanopore. The radially non-uniform currents resulted in highly non-uniform magnetic fields within the nanopore that decay as 1/r outside the nanopore. It is worth noting that for either streaming currents or streaming potential cases, the maximum magnetic field occurred inside the pore in the vicinity of nanopore wall, as opposed to a cylindrical conductor that carries a steady electric current where the maximum magnetic fields occur at the perimeter of conductor. Based on these results, it is suggested and envisaged that non-invasive external magnetic fields readouts generated by streaming/ionic currents may be viewed as secondary electronic signatures of biomolecules to complement and enhance current DNA nanopore sequencing techniques. PMID:27833119

  18. The non-uniformity correction factor for the cylindrical ionization chambers in dosimetry of an HDR 192Ir brachytherapy source

    International Nuclear Information System (INIS)

    Majumdar, Bishnu; Patel, Narayan Prasad; Vijayan, V.

    2006-01-01

    The aim of this study is to derive the non-uniformity correction factor for the two therapy ionization chambers for the dose measurement near the brachytherapy source. The two ionization chambers of 0.6 cc and 0.1 cc volume were used. The measurement in air was performed for distances between 0.8 cm and 20 cm from the source in specially designed measurement jig. The non-uniformity correction factors were derived from the measured values. The experimentally derived factors were compared with the theoretically calculated non-uniformity correction factors and a close agreement was found between these two studies. The experimentally derived non-uniformity correction factor supports the anisotropic theory. (author)

  19. Experimental study on occupant's thermal responses under the non-uniform conditions in vehicle cabin during the heating period

    Science.gov (United States)

    Zhang, Wencan; Chen, Jiqing; Lan, Fengchong

    2014-03-01

    The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant's thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant's local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc(ASHRAE) Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant's thermal responses, including the skin temperature and the thermal sensation. The skin temperature and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in

  20. Modelling of the toroidal asymmetry of poloidal halo currents in conducting structures

    International Nuclear Information System (INIS)

    Pomphrey, N.; Bialek, J.M.; Part, W.

    1998-01-01

    During plasma disruptions, substantial toroidal and poloidal eddy currents are generated in the vacuum vessel and other plasma facing conducting structures. Eddy currents that conduct charge through paths which close through the plasma periphery are called halo currents, and these can be of substantial magnitude. Of particular concern for tokamak design and operation is the observed toroidal asymmetry of the halo current distribution: such an asymmetric distribution leads to problematic non-uniform forces on the conducting structures. The premise is adopted that the source of toroidal asymmetry is the plasma deformation resulting from the non-linear external kink instability that develops during the current quench phase of a disruption. A simple model is presented of the kinked plasma that allows an analytic calculation of the dependence of the toroidal peaking factor (TPF) on the ratio of the halo current to the total toroidal plasma current, I h /I p . Expressions for the TPF as a function of I h /I p are derived for m/n=2/1 and m/n=1/1 helical instabilities. The expressions depend on a single parameter, which measures the amplitude of the saturated state of the kink instability. A comparison with disruption data from experiments shows good agreement. Numerical experiments that simulate non-linear external kinks provide guidance on the values expected for the saturated amplitude. It is proposed that a simple plasma halo model is adequate for assessing the engineering impact of asymmetric halo currents, since the force distribution on the conducting structures depends mainly on the 'resistive distribution' of the eddy currents. A brief description is given of an electromagnetics code that calculates the time development of eddy currents in conducting structures, and the code is applied to two halo current disruption scenarios. These are used to emphasize the importance of having an accurate eddy current calculation to correctly estimate the engineering impact of

  1. Dynamic behaviour of non-uniform Bernoulli-Euler beams subjected ...

    African Journals Online (AJOL)

    This paper investigates the dynamics behaviour of non-uniform Bernoulli-Euler beams subjected to concentrated loads ravelling at variable velocities. The solution technique is based on the Generalized Galerkin Method and the use of the generating function of the Bessel function type. The results show that, for all the ...

  2. Electrical characteristics of schottky barriers on 4H-SiC: The effects of barrier height nonuniformity

    Science.gov (United States)

    Skromme, B. J.; Luckowski, E.; Moore, K.; Bhatnagar, M.; Weitzel, C. E.; Gehoski, T.; Ganser, D.

    2000-03-01

    Electrical properties, including current-voltage (I-V) and capacitance-voltage (C-V) characteristics, have been measured on a large number of Ti, Ni, and Pt-based Schottky barrier diodes on 4H-SiC epilayers. Various nonideal behaviors are frequently observed, including ideality factors greater than one, anomalously low I-V barrier heights, and excess leakage currents at low forward bias and in reverse bias. The nonidealities are highly nonuniform across individual wafers and from wafer to wafer. We find a pronounced linear correlation between I-V barrier height and ideality factor for each metal, while C-V barrier heights remain constant. Electron beam induced current (EBIC) imaging strongly suggests that the nonidealities result from localized low barrier height patches. These patches are related to discrete crystal defects, which become visible as recombination centers in the EBIC images. Alternative explanations involving generation-recombination current, uniform interfacial layers, and effects related to the periphery are ruled out.

  3. Experimental observation of the inductive electric field and related plasma nonuniformity in high frequency capacitive discharge

    International Nuclear Information System (INIS)

    Ahn, S. K.; Chang, H. Y.

    2008-01-01

    To elucidate plasma nonuniformity in high frequency capacitive discharges, Langmuir probe and B-dot probe measurements were carried out in the radial direction in a cylindrical capacitive discharge driven at 90 MHz with argon pressures of 50 and 400 mTorr. Through the measurements, a significant inductive electric field (i.e., time-varying magnetic field) was observed at the radial edge, and it was found that the inductive electric field creates strong plasma nonuniformity at high pressure operation. The plasma nonuniformity at high pressure operation is physically similar to the E-H mode transition typically observed in inductive discharges. This result agrees well with the theories of electromagnetic effects in large area and/or high frequency capacitive discharges

  4. Divergent and nonuniform gene expression patterns in mouse brain

    Science.gov (United States)

    Morris, John A.; Royall, Joshua J.; Bertagnolli, Darren; Boe, Andrew F.; Burnell, Josh J.; Byrnes, Emi J.; Copeland, Cathy; Desta, Tsega; Fischer, Shanna R.; Goldy, Jeff; Glattfelder, Katie J.; Kidney, Jolene M.; Lemon, Tracy; Orta, Geralyn J.; Parry, Sheana E.; Pathak, Sayan D.; Pearson, Owen C.; Reding, Melissa; Shapouri, Sheila; Smith, Kimberly A.; Soden, Chad; Solan, Beth M.; Weller, John; Takahashi, Joseph S.; Overly, Caroline C.; Lein, Ed S.; Hawrylycz, Michael J.; Hohmann, John G.; Jones, Allan R.

    2010-01-01

    Considerable progress has been made in understanding variations in gene sequence and expression level associated with phenotype, yet how genetic diversity translates into complex phenotypic differences remains poorly understood. Here, we examine the relationship between genetic background and spatial patterns of gene expression across seven strains of mice, providing the most extensive cellular-resolution comparative analysis of gene expression in the mammalian brain to date. Using comprehensive brainwide anatomic coverage (more than 200 brain regions), we applied in situ hybridization to analyze the spatial expression patterns of 49 genes encoding well-known pharmaceutical drug targets. Remarkably, over 50% of the genes examined showed interstrain expression variation. In addition, the variability was nonuniformly distributed across strain and neuroanatomic region, suggesting certain organizing principles. First, the degree of expression variance among strains mirrors genealogic relationships. Second, expression pattern differences were concentrated in higher-order brain regions such as the cortex and hippocampus. Divergence in gene expression patterns across the brain could contribute significantly to variations in behavior and responses to neuroactive drugs in laboratory mouse strains and may help to explain individual differences in human responsiveness to neuroactive drugs. PMID:20956311

  5. A Single Image Deblurring Algorithm for Nonuniform Motion Blur Using Uniform Defocus Map Estimation

    Directory of Open Access Journals (Sweden)

    Chia-Feng Chang

    2017-01-01

    Full Text Available One of the most common artifacts in digital photography is motion blur. When capturing an image under dim light by using a handheld camera, the tendency of the photographer’s hand to shake causes the image to blur. In response to this problem, image deblurring has become an active topic in computational photography and image processing in recent years. From the view of signal processing, image deblurring can be reduced to a deconvolution problem if the kernel function of the motion blur is assumed to be shift invariant. However, the kernel function is not always shift invariant in real cases; for example, in-plane rotation of a camera or a moving object can blur different parts of an image according to different kernel functions. An image that is degraded by multiple blur kernels is called a nonuniform blur image. In this paper, we propose a novel single image deblurring algorithm for nonuniform motion blur images that is blurred by moving object. First, a proposed uniform defocus map method is presented for measurement of the amounts and directions of motion blur. These blurred regions are then used to estimate point spread functions simultaneously. Finally, a fast deconvolution algorithm is used to restore the nonuniform blur image. We expect that the proposed method can achieve satisfactory deblurring of a single nonuniform blur image.

  6. The current duration design for estimating the time to pregnancy distribution

    DEFF Research Database (Denmark)

    Gasbarra, Dario; Arjas, Elja; Vehtari, Aki

    2015-01-01

    This paper was inspired by the studies of Niels Keiding and co-authors on estimating the waiting time-to-pregnancy (TTP) distribution, and in particular on using the current duration design in that context. In this design, a cross-sectional sample of women is collected from those who are currently...... attempting to become pregnant, and then by recording from each the time she has been attempting. Our aim here is to study the identifiability and the estimation of the waiting time distribution on the basis of current duration data. The main difficulty in this stems from the fact that very short waiting...... times are only rarely selected into the sample of current durations, and this renders their estimation unstable. We introduce here a Bayesian method for this estimation problem, prove its asymptotic consistency, and compare the method to some variants of the non-parametric maximum likelihood estimators...

  7. On the Electromagnetic Momentum of Static Charge and Steady Current Distributions

    Science.gov (United States)

    Gsponer, Andre

    2007-01-01

    Faraday's and Furry's formulae for the electromagnetic momentum of static charge distributions combined with steady electric current distributions are generalized in order to obtain full agreement with Poynting's formula in the case where all fields are of class C[superscript 1], i.e., continuous and continuously differentiable, and the…

  8. Beam pattern improvement by compensating array nonuniformities in a guided wave phased array

    International Nuclear Information System (INIS)

    Kwon, Hyu-Sang; Lee, Seung-Seok; Kim, Jin-Yeon

    2013-01-01

    This paper presents a simple data processing algorithm which can improve the performance of a uniform circular array based on guided wave transducers. The algorithm, being intended to be used with the delay-and-sum beamformer, effectively eliminates the effects of nonuniformities that can significantly degrade the beam pattern. Nonuniformities can arise intrinsically from the array geometry when the circular array is transformed to a linear array for beam steering and extrinsically from unequal conditions of transducers such as element-to-element variations of sensitivity and directivity. The effects of nonuniformities are compensated by appropriately imposing weight factors on the elements in the projected linear array. Different cases are simulated, where the improvements of the beam pattern, especially the level of the highest sidelobe, are clearly seen, and related issues are discussed. An experiment is performed which uses A0 mode Lamb waves in a steel plate, to demonstrate the usefulness of the proposed method. The discrepancy between theoretical and experimental beam patterns is explained by accounting for near-field effects. (paper)

  9. Non-uniform cosine modulated filter banks using meta-heuristic algorithms in CSD space

    Directory of Open Access Journals (Sweden)

    Shaeen Kalathil

    2015-11-01

    Full Text Available This paper presents an efficient design of non-uniform cosine modulated filter banks (CMFB using canonic signed digit (CSD coefficients. CMFB has got an easy and efficient design approach. Non-uniform decomposition can be easily obtained by merging the appropriate filters of a uniform filter bank. Only the prototype filter needs to be designed and optimized. In this paper, the prototype filter is designed using window method, weighted Chebyshev approximation and weighted constrained least square approximation. The coefficients are quantized into CSD, using a look-up-table. The finite precision CSD rounding, deteriorates the filter bank performances. The performances of the filter bank are improved using suitably modified meta-heuristic algorithms. The different meta-heuristic algorithms which are modified and used in this paper are Artificial Bee Colony algorithm, Gravitational Search algorithm, Harmony Search algorithm and Genetic algorithm and they result in filter banks with less implementation complexity, power consumption and area requirements when compared with those of the conventional continuous coefficient non-uniform CMFB.

  10. Nanosecond laser texturing of uniformly and non-uniformly wettable micro structured metal surfaces for enhanced boiling heat transfer

    Energy Technology Data Exchange (ETDEWEB)

    Zupančič, Matevž, E-mail: matevz.zupancic@fs.uni-lj.si; Može, Matic; Gregorčič, Peter; Golobič, Iztok

    2017-03-31

    Highlights: • Surfaces with periodically changed wettability were produced by a ns marking laser. • Heat transfer was investigated on uniformly and non-uniformly wettable surfaces. • Microporous surfaces with non-uniform wettability enhance boiling heat transfer. • The most bubble nucleations were observed in the vicinity of the microcavities. • Results agree with the predictions of the nucleation criteria. - Abstract: Microstructured uniformly and non-uniformly wettable surfaces were created on 25-μm-thin stainless steel foils by laser texturing using a marking nanosecond Nd:YAG laser (λ = 1064 nm) and utilizing various laser fluences and scan line separations. High-speed photography and high-speed IR thermography were used to investigate nucleate boiling heat transfer on the microstructured surfaces. The most pronounced results were obtained on a surface with non-uniform microstructure and non-uniform wettability. The obtained results show up to a 110% higher heat transfer coefficients and 20–40 times higher nucleation site densities compared to the untextured surface. We show that the number of active nucleation sites is significantly increased in the vicinity of microcavities that appeared in areas with the smallest (10 μm) scan line separation. Furthermore, this confirms the predictions of nucleation criteria and proves that straightforward, cost-effective nanosecond laser texturing allows the production of cavities with diameters of up to a few micrometers and surfaces with non-uniform wettability. Additionally, this opens up important possibilities for a more deterministic control over the complex boiling process.

  11. Improvement of quantitation in SPECT: Attenuation and scatter correction using non-uniform attenuation data

    International Nuclear Information System (INIS)

    Mukai, T.; Torizuka, K.; Douglass, K.H.; Wagner, H.N.

    1985-01-01

    Quantitative assessment of tracer distribution with single photon emission computed tomography (SPECT) is difficult because of attenuation and scattering of gamma rays within the object. A method considering the source geometry was developed, and effects of attenuation and scatter on SPECT quantitation were studied using phantoms with non-uniform attenuation. The distribution of attenuation coefficients (μ) within the source were obtained by transmission CT. The attenuation correction was performed by an iterative reprojection technique. The scatter correction was done by convolution of the attenuation corrected image and an appropriate filter made by line source studies. The filter characteristics depended on μ and SPEC measurement at each pixel. The SPECT obtained by this method showed the most reasonable results than the images reconstructed by other methods. The scatter correction could compensate completely for a 28% scatter components from a long line source, and a 61% component for thick and extended source. Consideration of source geometries was necessary for effective corrections. The present method is expected to be valuable for the quantitative assessment of regional tracer activity

  12. PHEMT Distributed Power Amplifier Adopting Broadband Impedance Transformer

    DEFF Research Database (Denmark)

    Narendra, K.; Limiti, E.; Paoloni, C.

    2013-01-01

    A non-uniform drain line distributed power amplifier (DPA) employing a broadband impedance transformer is presented. The DPA is based on GaAs PHEMT technology. The impedance transformer employs asymmetric coupled lines and transforms a low output impedance of the amplifier to a standard 50 Ω...

  13. A novel scene-based non-uniformity correction method for SWIR push-broom hyperspectral sensors

    Science.gov (United States)

    Hu, Bin-Lin; Hao, Shi-Jing; Sun, De-Xin; Liu, Yin-Nian

    2017-09-01

    A novel scene-based non-uniformity correction (NUC) method for short-wavelength infrared (SWIR) push-broom hyperspectral sensors is proposed and evaluated. This method relies on the assumption that for each band there will be ground objects with similar reflectance to form uniform regions when a sufficient number of scanning lines are acquired. The uniform regions are extracted automatically through a sorting algorithm, and are used to compute the corresponding NUC coefficients. SWIR hyperspectral data from airborne experiment are used to verify and evaluate the proposed method, and results show that stripes in the scenes have been well corrected without any significant information loss, and the non-uniformity is less than 0.5%. In addition, the proposed method is compared to two other regular methods, and they are evaluated based on their adaptability to the various scenes, non-uniformity, roughness and spectral fidelity. It turns out that the proposed method shows strong adaptability, high accuracy and efficiency.

  14. Modelling distribution of evaporating CO2 in parallel minichannels

    DEFF Research Database (Denmark)

    Brix, Wiebke; Kærn, Martin Ryhl; Elmegaard, Brian

    2010-01-01

    The effects of airflow non-uniformity and uneven inlet qualities on the performance of a minichannel evaporator with parallel channels, using CO2 as refrigerant, are investigated numerically. For this purpose a one-dimensional discretised steady-state model was developed, applying well-known empi......The effects of airflow non-uniformity and uneven inlet qualities on the performance of a minichannel evaporator with parallel channels, using CO2 as refrigerant, are investigated numerically. For this purpose a one-dimensional discretised steady-state model was developed, applying well...... to maldistribution of the refrigerant and considerable capacity reduction of the evaporator. Uneven inlet ualities to the different channels show only minor effects on the refrigerant distribution and evaporator capacity as long as the channels are vertically oriented with CO2 flowing upwards. For horizontal...... channels capacity reductions are found for both non-uniform airflow and uneven inlet qualities. For horizontal minichannels the results are very similar to those obtained using R134a as refrigerant....

  15. Deep convolutional neural networks for dense non-uniform motion deblurring

    CSIR Research Space (South Africa)

    Cronje, J

    2015-11-01

    Full Text Available to form a dense non-uniform motion estimation map. Furthermore, a second CNN is trained to perform deblurring given a blurry image patch and the estimated motion vector. Combining the two trained networks result in a deep learning approach that can enhance...

  16. Effects of polar field-aligned currents on the distribution of the electric field and current in the middle and low latitudes ionosphere

    International Nuclear Information System (INIS)

    Maekawa, Koichiro

    1978-01-01

    According to the analysis of the magnetic records from the Triad satellite, it has been found that there are two regions of the field-aligned current of magnetospheric origin along the auroral oval; Region 1 in higher latitude and Region 2 in lower latitude. These currents seem to have important effect on the distribution of electric field and current in the ionosphere, in addition to the Sq electric field and current of ionospheric origin. The global current systems generated by the field-aligned current were calculated, using some simplified ionospheric models. The effect of the field-aligned current on the distribution of electric field and current of the ionosphere at middle and low latitudes was investigated. (Yoshimori, M.)

  17. Numerical study on coolant flow distribution at the core inlet for an integral pressurized water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Lin; Peng, Min Jun; Xia, Genglei; Lv, Xing; Li, Ren [Fundamental Science on Nuclear Safety and Simulation Technology Laboratory, Harbin Engineering University, Harbin (China)

    2017-02-15

    When an integral pressurized water reactor is operated under low power conditions, once-through steam generator group operation strategy is applied. However, group operation strategy will cause nonuniform coolant flow distribution at the core inlet and lower plenum. To help coolant flow mix more uniformly, a flow mixing chamber (FMC) has been designed. In this paper, computational fluid dynamics methods have been used to investigate the coolant distribution by the effect of FMC. Velocity and temperature characteristics under different low power conditions and optimized FMC configuration have been analyzed. The results illustrate that the FMC can help improve the nonuniform coolant temperature distribution at the core inlet effectively; at the same time, the FMC will induce more resistance in the downcomer and lower plenum.

  18. Factorization method for difference equations of hypergeometric type on nonuniform lattices

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez-Nodarse, R. [Departamento de Analisis Matematico, Universidad de Sevilla, Sevilla (Spain); Instituto Carlos I de Fisica Teorica y Computacional, Universidad de Granada, Granada (Spain); Costas-Santos, R.S. [Departamento de Analisis Matematico, Universidad de Sevilla, Sevilla (Spain)

    2001-07-13

    We study the factorization of the hypergeometric-type difference equation of Nikiforov and Uvarov on nonuniform lattices. An explicit form of the raising and lowering operators is derived and some relevant examples are given. (author)

  19. Postbuckling of magneto-electro-elastic CNT-MT composite nanotubes resting on a nonlinear elastic medium in a non-uniform thermal environment

    Science.gov (United States)

    Kamali, M.; Shamsi, M.; Saidi, A. R.

    2018-03-01

    As a first endeavor, the effect of nonlinear elastic foundation on the postbuckling behavior of smart magneto-electro-elastic (MEE) composite nanotubes is investigated. The composite nanotube is affected by a non-uniform thermal environment. A typical MEE composite nanotube consists of microtubules (MTs) and carbon nanotubes (CNTs) with a MEE cylindrical nanoshell for smart control. It is assumed that the nanoscale layers of the system are coupled by a polymer matrix or filament network depending on the application. In addition to thermal loads, magneto-electro-mechanical loads are applied to the composite nanostructure. Length scale effects are taken into account using the nonlocal elasticity theory. The principle of virtual work and von Karman's relations are used to derive the nonlinear governing differential equations of MEE CNT-MT nanotubes. Using Galerkin's method, nonlinear critical buckling loads are determined. Various types of non-uniform temperature distribution in the radial direction are considered. Finally, the effects of various parameters such as the nonlinear constant of elastic medium, thermal loading factor and small scale coefficient on the postbuckling of MEE CNT-MT nanotubes are studied.

  20. Influence of carbon black distribution on performance of oxide cathodes for Li ion batteries

    International Nuclear Information System (INIS)

    Dominko, Robert; Gaberscek, Miran; Drofenik, Jernej; Bele, Marjan; Jamnik, Janez

    2003-01-01

    The influence of carbon black content and carbon black distribution on performance of oxide-based cathodes, such as LiCoO 2 and LiMn 2 O 4 , is investigated. The electronic conductivity of oxide material/carbon black composites is compared with electrochemical characteristics of the same composites. Uniformity of carbon black distribution in cathode composites is achieved using novel coating technology in cathode preparation. In this technology, the active particles are first pretreated in a gelatin solution. The adsorbed gelatin then controls the deposition of carbon black so that carbon black particles are uniformly distributed in the final composite. The influence of various parameters, such as pH of gelatin, amount of gelatin and concentration of carbon black on the uniformity of carbon black distribution is investigated. It is shown that the conventional technology of cathode preparation yields quite non-uniform distribution of carbon black in cathode material. At the end, we demonstrate that uniformity of carbon black distribution has a crucial impact on reversible capacity, especially at high current densities

  1. Non-uniformity of phase structure in immiscible polymer blends

    Czech Academy of Sciences Publication Activity Database

    Fortelný, Ivan; Lapčíková, Monika; Lednický, František; Starý, Zdeněk; Kruliš, Zdeněk

    2008-01-01

    Roč. 48, č. 3 (2008), s. 564-571 ISSN 0032-3888 R&D Projects: GA ČR GA106/06/0729; GA ČR GA106/06/0761 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer blends * melt mixing * non-uniform morphology Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.245, year: 2008

  2. Calculation of the self-consistent current distribution and coupling of an RF antenna array

    International Nuclear Information System (INIS)

    Ballico, M.; Puri, S.

    1993-10-01

    A self-consistent calculation of the antenna current distribution and fields in an axisymmetric cylindrical geometry for the ICRH antenna-plasma coupling problem is presented. Several features distinguish this calculation from other codes presently available. 1. Variational form: The formulation of the self consistent antenna current problem in a variational form allows good convergence and stability of the algorithm. 2. Multiple straps: Allows modelling of (a) the current distribution across the width of the strap (by dividing it up into sub straps) (b) side limiters and septum (c) antenna cross-coupling. 3. Analytic calculation of the antenna field and calculation of the antenna self-consistent current distribution, (given the surface impedance matrix) gives rapid calculation. 4. Framed for parallel computation on several different parallel architectures (as well as serial) gives a large speed improvement to the user. Results are presented for both Alfven wave heating and current drive antenna arrays, showing the optimal coupling to be achieved for toroidal mode numbers 8< n<10 for typical ASDEX upgrade plasmas. Simulations of the ASDEX upgrade antenna show the importance of the current distribution across the antenna and of image currents flowing in the side limiters, and an analysis of a proposed asymmetric ITER antenna is presented. (orig.)

  3. Axial mercury segregation in direct current operated low-pressure argon-mercury gas discharges: Part I. Experimental

    International Nuclear Information System (INIS)

    Gielen, John W A M; Groot, Simon de; Mullen, Joost J A M van der

    2004-01-01

    Due to cataphoresis, axial segregation of mercury will occur when the gas discharge of a fluorescent lamp is operated by means of a direct current. A consequence of this is a non-uniform axial luminance distribution along the lamp. To determine the degree of axial mercury segregation experimentally, axial luminance distributions have been measured which are converted into axial mercury vapour pressure distributions by an appropriate calibration method. The mercury segregation has been investigated for variations in lamp tube radius (3.6-4.8 mm), argon buffer gas pressure (200-600 Pa) and lamp current (100-250 mA) at mercury vapour pressures set at the anode in the range from 0.2 to 9.0 Pa. From the experiments it has been concluded that the mercury vapour pressure gradient at any axial position for a certain lamp tube diameter, argon pressure and lamp current depends on the local mercury vapour pressure. This observation is in contrast to assumptions made in earlier modelling publications in which one mercury vapour pressure gradient is used for all axial positions. By applying a full factorial design, an empirical relation of the mercury segregation is found for any set of parameters inside the investigated parameter ranges

  4. 3D-2D Deformable Image Registration Using Feature-Based Nonuniform Meshes.

    Science.gov (United States)

    Zhong, Zichun; Guo, Xiaohu; Cai, Yiqi; Yang, Yin; Wang, Jing; Jia, Xun; Mao, Weihua

    2016-01-01

    By using prior information of planning CT images and feature-based nonuniform meshes, this paper demonstrates that volumetric images can be efficiently registered with a very small portion of 2D projection images of a Cone-Beam Computed Tomography (CBCT) scan. After a density field is computed based on the extracted feature edges from planning CT images, nonuniform tetrahedral meshes will be automatically generated to better characterize the image features according to the density field; that is, finer meshes are generated for features. The displacement vector fields (DVFs) are specified at the mesh vertices to drive the deformation of original CT images. Digitally reconstructed radiographs (DRRs) of the deformed anatomy are generated and compared with corresponding 2D projections. DVFs are optimized to minimize the objective function including differences between DRRs and projections and the regularity. To further accelerate the above 3D-2D registration, a procedure to obtain good initial deformations by deforming the volume surface to match 2D body boundary on projections has been developed. This complete method is evaluated quantitatively by using several digital phantoms and data from head and neck cancer patients. The feature-based nonuniform meshing method leads to better results than either uniform orthogonal grid or uniform tetrahedral meshes.

  5. 3D-2D Deformable Image Registration Using Feature-Based Nonuniform Meshes

    Directory of Open Access Journals (Sweden)

    Zichun Zhong

    2016-01-01

    Full Text Available By using prior information of planning CT images and feature-based nonuniform meshes, this paper demonstrates that volumetric images can be efficiently registered with a very small portion of 2D projection images of a Cone-Beam Computed Tomography (CBCT scan. After a density field is computed based on the extracted feature edges from planning CT images, nonuniform tetrahedral meshes will be automatically generated to better characterize the image features according to the density field; that is, finer meshes are generated for features. The displacement vector fields (DVFs are specified at the mesh vertices to drive the deformation of original CT images. Digitally reconstructed radiographs (DRRs of the deformed anatomy are generated and compared with corresponding 2D projections. DVFs are optimized to minimize the objective function including differences between DRRs and projections and the regularity. To further accelerate the above 3D-2D registration, a procedure to obtain good initial deformations by deforming the volume surface to match 2D body boundary on projections has been developed. This complete method is evaluated quantitatively by using several digital phantoms and data from head and neck cancer patients. The feature-based nonuniform meshing method leads to better results than either uniform orthogonal grid or uniform tetrahedral meshes.

  6. Dual-energy digital mammography for calcification imaging: Scatter and nonuniformity corrections

    International Nuclear Information System (INIS)

    Kappadath, S. Cheenu; Shaw, Chris C.

    2005-01-01

    Mammographic images of small calcifications, which are often the earliest signs of breast cancer, can be obscured by overlapping fibroglandular tissue. We have developed and implemented a dual-energy digital mammography (DEDM) technique for calcification imaging under full-field imaging conditions using a commercially available aSi:H/CsI:Tl flat-panel based digital mammography system. The low- and high-energy images were combined using a nonlinear mapping function to cancel the tissue structures and generate the dual-energy (DE) calcification images. The total entrance-skin exposure and mean-glandular dose from the low- and high-energy images were constrained so that they were similar to screening-examination levels. To evaluate the DE calcification image, we designed a phantom using calcium carbonate crystals to simulate calcifications of various sizes (212-425 μm) overlaid with breast-tissue-equivalent material 5 cm thick with a continuously varying glandular-tissue ratio from 0% to 100%. We report on the effects of scatter radiation and nonuniformity in x-ray intensity and detector response on the DE calcification images. The nonuniformity was corrected by normalizing the low- and high-energy images with full-field reference images. Correction of scatter in the low- and high-energy images significantly reduced the background signal in the DE calcification image. Under the current implementation of DEDM, utilizing the mammography system and dose level tested, calcifications in the 300-355 μm size range were clearly visible in DE calcification images. Calcification threshold sizes decreased to the 250-280 μm size range when the visibility criteria were lowered to barely visible. Calcifications smaller than ∼250 μm were usually not visible in most cases. The visibility of calcifications with our DEDM imaging technique was limited by quantum noise, not system noise

  7. Distribution of local critical current along sample length and its relation to overall current in a long Bi2223/Ag superconducting composite tape

    International Nuclear Information System (INIS)

    Ochiai, S; Doko, D; Okuda, H; Oh, S S; Ha, D W

    2006-01-01

    The distribution of the local critical current and the n-value along the sample length and its relation to the overall critical current were studied experimentally and analytically for the bent multifilamentary Bi2223/Ag/Ag-Mg alloy superconducting composite tape. Then, based on the results, it was attempted to simulate on a computer the dependence of the critical current on the sample length. The main results are summarized as follows. The experimentally observed relation of the distributed local critical current and n-value to the overall critical current was described comprehensively with a simple voltage summation model, in which the sample was regarded as a one-dimensional series circuit. The sample length dependence of the critical current was reproduced on the computer by a Monte Carlo simulation incorporating the voltage summation model and the regression analysis results for the local critical current distribution and the relation of the n-value to the critical current

  8. Distributed Secondary Control for DC Microgrid Applications with Enhanced Current Sharing Accuracy

    DEFF Research Database (Denmark)

    Lu, Xiaonan; Guerrero, Josep M.; Sun, Kai

    2013-01-01

    With the consideration of line resistances in a dc microgrid, the current sharing accuracy is lowered down, since the dc output voltage cannot be exactly the same for different interfacing converters. Meanwhile, the dc bus voltage deviation is involved by using droop control. In this paper...... control diagram is accomplished and the requirement of distributed configuration in a microgrid is satisfied. The experimental validation based on a 2×2.2 kW prototype was implemented to demonstrate the proposed approach......., a distributed secondary control method is proposed. Droop control is employed as the primary control method for load current sharing. Meanwhile, the dc output voltage and current in each module is transferred to the others by the low bandwidth communication (LBC) network. Average voltage and current controllers...

  9. Numerical Study of the Inertia Effect on Flow Distribution in Micro-gap Plate Heat Exchanger

    International Nuclear Information System (INIS)

    Park, Jang Min; Yoon, Seok Ho; Lee, Kong Hoon; Song Chan Ho

    2014-01-01

    This paper presents numerical study on flow and heat transfer characteristics in micro-gap plate heat exchanger. In particular, we investigate the effect of flow inertia on the flow distribution from single main channel to multiple parallel micro-gaps. The flow regime of the main channel is varied from laminar regime (Reynolds number of 100) to turbulent regime (Reynolds number of 10000) by changing the flow rate, and non-uniformity of the flow distribution and temperature field is evaluated quantitatively based on the standard deviation. The flow distribution is found to be significantly affected by not only the header design but also the flow rate of the main channel. It is also observed that the non-uniformity of the temperature field has its maximum at the intermediate flow regime

  10. Measurement of Anisotropic Particle Interactions with Nonuniform ac Electric Fields.

    Science.gov (United States)

    Rupp, Bradley; Torres-Díaz, Isaac; Hua, Xiaoqing; Bevan, Michael A

    2018-02-20

    Optical microscopy measurements are reported for single anisotropic polymer particles interacting with nonuniform ac electric fields. The present study is limited to conditions where gravity confines particles with their long axis parallel to the substrate such that particles can be treated using quasi-2D analysis. Field parameters are investigated that result in particles residing at either electric field maxima or minima and with long axes oriented either parallel or perpendicular to the electric field direction. By nonintrusively observing thermally sampled positions and orientations at different field frequencies and amplitudes, a Boltzmann inversion of the time-averaged probability of states yields kT-scale energy landscapes (including dipole-field, particle-substrate, and gravitational potentials). The measured energy landscapes show agreement with theoretical potentials using particle conductivity as the sole adjustable material property. Understanding anisotropic particle-field energy landscapes vs field parameters enables quantitative control of local forces and torques on single anisotropic particles to manipulate their position and orientation within nonuniform fields.

  11. Effects of Long- and Intermediate-Wavelength Nonuniformities on Hot-Spot Energetics of Hydrodynamic Equivalent Targets

    Science.gov (United States)

    Bose, A.; Betti, R.; Woo, K. M.; Christopherson, A. R.; Shvarts, D.

    2015-11-01

    The impact of intermediate- and low-mode nonuniformities on the performance of inertial confinement fusion (ICF) implosions is investigated by a detailed study of hot-spot energetics. It is found that low- (1 ~ 2) and intermediate-mode (1 >= 10) asymmetries affect the hot-spot hydrodynamics in very different ways. It is observed that for low-mode asymmetries, the fusion yield decreases because of a significant reduction in hot-spot pressure while the neutron-averaged hot-spot volume remains comparable to that of unperturbed (clean) simulations. On the other hand, implosions with moderate-amplitude, intermediate-wavelength modes, which are amplified by the Rayleigh-Taylor instability (RTI), exhibit a fusion-yield degradation primarily caused by a reduction in the burn volume without significant degradation of the pressure. For very large amplitudes, the intermediate modes show a ``secondary piston effect,'' where the converging RTI spikes compress a much smaller volume, allowing for a secondary conversion of the shell's kinetic energy to internal energy at a central region. Understanding the effects of nonuniformities on the hot-spot energetics provides valuable insight in determining the causes of performance degradation in current ICF experiments. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center).

  12. Spatial nonuniformity of current flow and its consideration in determination of characteristics of surface illuminated InAsSbP/InAs-based photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Zotova, N V; Karandashev, S A; Matveev, B. A., E-mail: Bmat@iropt3.ioffe.ru; Remennyy, M A; Rybal' chenko, A Yu; Stus' , N M [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)

    2011-04-15

    Current-voltage characteristics of surface-irradiated photodiodes based on the InAsSbP/InAs structures are analyzed using experimental data on the distribution of electroluminescence intensity over the diode surface and taking into account thickening the current streamlines near the contacts. The influence of the potential barrier associated with the N-InAsSbP/n-InAs junction in double heterostructures on the differential resistance of diodes under zero bias, the value of the reverse current, and spreading of the forward current is discussed.

  13. Spatial nonuniformity of current flow and its consideration in determination of characteristics of surface illuminated InAsSbP/InAs-based photodiodes

    International Nuclear Information System (INIS)

    Zotova, N. V.; Karandashev, S. A.; Matveev, B. A.; Remennyy, M. A.; Rybal’chenko, A. Yu.; Stus’, N. M.

    2011-01-01

    Current-voltage characteristics of surface-irradiated photodiodes based on the InAsSbP/InAs structures are analyzed using experimental data on the distribution of electroluminescence intensity over the diode surface and taking into account thickening the current streamlines near the contacts. The influence of the potential barrier associated with the N-InAsSbP/n-InAs junction in double heterostructures on the differential resistance of diodes under zero bias, the value of the reverse current, and spreading of the forward current is discussed.

  14. Characterization of nonuniform chaos in area-preserving nonlinear maps through a continuous archetype

    International Nuclear Information System (INIS)

    Cerbelli, S.; Giona, M.

    2008-01-01

    Numerical investigations conducted over a wealth of nonlinear area-preserving smooth maps (e.g. the Standard Map) showed that these systems possess physically relevant features that are not captured by any continuous archetype of two-dimensional conservative dynamics. Among these properties are the dispersive behavior of stretch factor statistics, the multifractal character of the measure associated with invariant foliations, the sign-alternating property, accounting for the nestedly bent structure of invariant foliations, and the strict inequality between the topological entropy, h top , and the Lyapunov exponent, Λ. We refer to systems possessing all of these properties as nonuniformly chaotic. In this article, we present a globally continuous, piecewise-smooth area-preserving transformation, the toral homeomorphism H, as an archetype of nonuniformly chaotic behavior. The relatively simple structure of point set dynamics and the closed-form knowledge of the pointwise expanding and contracting invariant directions associated with H, permits to derive either analytically, or with arbitrary numerical precision, the standard chaotic properties as well as the dynamics of the physically relevant properties that define nonuniform chaos. Potentialities and limitations of the model proposed in representing geometric and statistical properties of physically relevant smooth systems are discussed in detail

  15. On The Dynamic Analysis of Non-Uniform Beams Under Uniformly ...

    African Journals Online (AJOL)

    ... the non-uniform continuous beam was replaced by a non-continuous (discrete) system made up of beam elements. The modified elemental and overall stiffness, and mass matrices, the elemental and overall centripetal acceleration matrices as well as the load vector were derived. Next, the Newmark's direct integration ...

  16. Polarized parton distributions from charged-current deep-inelastic scattering

    International Nuclear Information System (INIS)

    Ridolfi, G

    2003-01-01

    We investigate the capabilities of a neutrino factory in the determination of polarized parton distributions from charged-current deep-inelastic scattering experiments, with special attention to the accuracy of this kind of measurements. We show that a neutrino factory would allow to distinguish between different theoretical scenarios for the proton spin structure

  17. Current distribution evaluation of dye-sensitized solar cell using HTS-SQUID-based magnetic measurement system

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, Kenji, E-mail: Sakai-k@okayama-u.ac.jp; Tanaka, Kohei; Kiwa, Toshihiko; Tsukada, Keiji

    2016-11-15

    Highlights: • Current distribution and direction of dye-sensitized solar cell (DSSC) was measured. • Electrical current flowing in the indium tin oxide (ITO) glass substrate was uniform. • The distribution of electrical current depended on I–V characteristic. • Current direction changed when the performance of DSSC is low. - Abstract: The current flowing inside a dye-sensitized solar cell (DSSC) was measured using a high-temperature superconductor superconducting quantum interference device (HTS-SQUID)-based magnetic measurement system. Further, a new evaluation method of the DSSC, which is difficult to measure using the conventional method, was investigated to improve the characteristics of the DSSC. The tangential components of the magnetic field generated from the DSSC were measured using two HTS-SQUIDs, and the intensity and direction related to the electrical current were obtained by the measured magnetic field. The DSSCs prepared with different dyes and catalytic substances showed different current-intensity mapping. The current direction was different for the DSSC with low performance. In addition, the current flowing in the ITO layer of the ITO glass substrate was also measured and the results confirmed that it had uniform distribution. These results show that the current mapping and the direction of the electrical current depend on the internal factors of the DSSC, and the detection of the magnetic field distribution generated from it is expected to lead to its new evaluation method.

  18. A new purely growing instability in a strongly magnetized nonuniform pair plasma

    International Nuclear Information System (INIS)

    Shukla, Nitin; Shukla, P.K.

    2007-01-01

    It is shown that a strongly magnetized nonuniform electron-positron (hereafter referred to as e-p or pair) plasma is unstable against low-frequency (in comparison with the electron gyrofrequency) electrostatic oscillations. For this purpose, a dispersion relation is derived by using the Poisson equation as well as the electron and positron continuity equations with the guiding center drifts for the electron and positron fluids. The dispersion relation admits a purely growing instability in the presence of the equilibrium density and magnetic field inhomogeneities. Physically, instability arises because of the inhomogeneous magnetic field induced differential electron and positron density fluctuations, which do not keep in phase with the electrostatic potential arising from the charge separation in our nonuniform pair plasmas

  19. Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode

    OpenAIRE

    Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.

    2010-01-01

    Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma def...

  20. Sharp lower bounds on the extractable randomness from non-uniform sources

    NARCIS (Netherlands)

    Skoric, B.; Obi, C.; Verbitskiy, E.A.; Schoenmakers, B.

    2011-01-01

    Extraction of uniform randomness from (noisy) non-uniform sources is an important primitive in many security applications, e.g. (pseudo-)random number generators, privacy-preserving biometrics, and key storage based on Physical Unclonable Functions. Generic extraction methods exist, using universal

  1. Non-uniform dispersion of the source-sink relationship alters wavefront curvature.

    Directory of Open Access Journals (Sweden)

    Lucia Romero

    Full Text Available The distribution of cellular source-sink relationships plays an important role in cardiac propagation. It can lead to conduction slowing and block as well as wave fractionation. It is of great interest to unravel the mechanisms underlying evolution in wavefront geometry. Our goal is to investigate the role of the source-sink relationship on wavefront geometry using computer simulations. We analyzed the role of variability in the microscopic source-sink relationship in driving changes in wavefront geometry. The electrophysiological activity of a homogeneous isotropic tissue was simulated using the ten Tusscher and Panfilov 2006 action potential model and the source-sink relationship was characterized using an improved version of the Romero et al. safety factor formulation (SFm2. Our simulations reveal that non-uniform dispersion of the cellular source-sink relationship (dispersion along the wavefront leads to alterations in curvature. To better understand the role of the source-sink relationship in the process of wave formation, the electrophysiological activity at the initiation of excitation waves in a 1D strand was examined and the source-sink relationship was characterized using the two recently updated safety factor formulations: the SFm2 and the Boyle-Vigmond (SFVB definitions. The electrophysiological activity at the initiation of excitation waves was intimately related to the SFm2 profiles, while the SFVB led to several counterintuitive observations. Importantly, with the SFm2 characterization, a critical source-sink relationship for initiation of excitation waves was identified, which was independent of the size of the electrode of excitation, membrane excitability, or tissue conductivity. In conclusion, our work suggests that non-uniform dispersion of the source-sink relationship alters wavefront curvature and a critical source-sink relationship profile separates wave expansion from collapse. Our study reinforces the idea that the

  2. Scalable and Fully Distributed Localization in Large-Scale Sensor Networks

    Directory of Open Access Journals (Sweden)

    Miao Jin

    2017-06-01

    Full Text Available This work proposes a novel connectivity-based localization algorithm, well suitable for large-scale sensor networks with complex shapes and a non-uniform nodal distribution. In contrast to current state-of-the-art connectivity-based localization methods, the proposed algorithm is highly scalable with linear computation and communication costs with respect to the size of the network; and fully distributed where each node only needs the information of its neighbors without cumbersome partitioning and merging process. The algorithm is theoretically guaranteed and numerically stable. Moreover, the algorithm can be readily extended to the localization of networks with a one-hop transmission range distance measurement, and the propagation of the measurement error at one sensor node is limited within a small area of the network around the node. Extensive simulations and comparison with other methods under various representative network settings are carried out, showing the superior performance of the proposed algorithm.

  3. Numerical analysis of blood flow in realistic arteries subjected to strong non-uniform magnetic fields

    International Nuclear Information System (INIS)

    Kenjeres, Sasa

    2008-01-01

    The paper reports on a comprehensive mathematical model for simulations of blood flow under the presence of strong non-uniform magnetic fields. The model consists of a set of Navier-Stokes equations accounting for the Lorentz and magnetisation forces, and a simplified set of Maxwell's equations (Biot-Savart/Ampere's law) for treating the imposed magnetic fields. The relevant hydrodynamic and electromagnetic properties of human blood were taken from the literature. The model is then validated for different test cases ranging from a simple cylindrical geometry to real-life right-coronary arteries in humans. The time-dependency of the wall-shear-stress for different stenosis growth rates and the effects of the imposed strong non-uniform magnetic fields on the blood flow pattern are presented and analysed. It is concluded that an imposed non-uniform magnetic field can create significant changes in the secondary flow patterns, thus making it possible to use this technique for optimisations of targeted drug delivery

  4. Effect of current imbalance on stability of a cable-in-conduit conductor consisting of chrome-plated strands

    International Nuclear Information System (INIS)

    Koizumi, Norikiyo; Takahashi, Yoshikazu; Nishi, Masataka; Isono, Takaaki; Tsuji, Hiroshi; Ono, Michitaka; Hamajima, Takataro; Fujioka, Tsutomu.

    1997-02-01

    The effect of an unbalanced current distribution in a conductor consisting of chrome plated strands on stability was investigated using a cable-in-conduit conductor (CICC) consisting of 27 NbTi chrome-plated strands. In addition, the quench behavior when a non-uniform current distribution was produced in the conductor was studied from the experimental results. Moreover, impedance of the chrome-plated strands was measured using the sample conductor. The results show that the stability is determined by the largest strand current when it is sufficiently large otherwise by the transport current when it is not high enough. It was found that it took a long time to make the conductor quench from the onset of the normal transition of the strand carrying the large current. This is explained by the good diffusivity of the coolant temperature in the conductor's cross section. Since the ramp-rate limitation cannot probably take place if the coolant temperature is diffused well in the conductor's cross section, it is expected the ramp-rate limitation can be prevented using this effect. It is also shown that the chrome-plated strands come into contact with one another with uniform transverse conductance on the order of 10 3 S/m. (author)

  5. Current distribution and enhancement of the engineering critical current density in multifilament Bi-2223 tapes

    DEFF Research Database (Denmark)

    Wang, W.G.; Jensen, M.B.; Kindl, B.

    2000-01-01

    The spatial distribution of the critical current density (Jc) and engineering critical current density (Je) along the tape width direction was studied by a cutting technique on Bi-2223 multifilamentary tapes. In general, an increase of Jc towards the centre of the tape was measured. We attribute...... microstructure with a great amount of secondary phases. Local variation of Jc was measured within the centre segment of the tape. This indicates the influence of other factors on Jc, such as filament shape, connectivity of the filaments, and sausaging. Enhancement of Je has been pursued in which average Je of 12...

  6. New fundamental insights into capacitance modeling of laterally nonuniform MOS devices

    NARCIS (Netherlands)

    Aarts, A.C.T.; Hout, van der R.; Paasschens, J.C.J.; Scholten, A.J.; Willemsen, M.B.; Klaassen, D.B.M.

    2006-01-01

    In compact transistor modeling for circuit simulation, the capacitances of conventional MOS devices are commonly determined as the derivatives of terminal charges, which in their turn are obtained from the so-called Ward-Dutton charge partitioning scheme. For devices with a laterally nonuniform

  7. Investigation of assumptions underlying current safety guidelines on EM-induced nerve stimulation

    Science.gov (United States)

    Neufeld, Esra; Vogiatzis Oikonomidis, Ioannis; Iacono, Maria Ida; Angelone, Leonardo M.; Kainz, Wolfgang; Kuster, Niels

    2016-06-01

    An intricate network of a variety of nerves is embedded within the complex anatomy of the human body. Although nerves are shielded from unwanted excitation, they can still be stimulated by external electromagnetic sources that induce strongly non-uniform field distributions. Current exposure safety standards designed to limit unwanted nerve stimulation are based on a series of explicit and implicit assumptions and simplifications. This paper demonstrates the applicability of functionalized anatomical phantoms with integrated coupled electromagnetic and neuronal dynamics solvers for investigating the impact of magnetic resonance exposure on nerve excitation within the full complexity of the human anatomy. The impact of neuronal dynamics models, temperature and local hot-spots, nerve trajectory and potential smoothing, anatomical inhomogeneity, and pulse duration on nerve stimulation was evaluated. As a result, multiple assumptions underlying current safety standards are questioned. It is demonstrated that coupled EM-neuronal dynamics modeling involving realistic anatomies is valuable to establish conservative safety criteria.

  8. Temperature dependence of o-Ps annihilation lifetime in non-uniform cylindrical pores in comparison with ETE model

    Energy Technology Data Exchange (ETDEWEB)

    Khaghani, Morteza, E-mail: m.khaghani@pgs.usb.ac.ir; Mehmandoost-Khajeh-Dad, Ali Akbar, E-mail: mehmandoost@phys.usb.ac.ir

    2017-04-01

    Highlights: • Using the well known multi-physics program COMSOL calculating o-Ps annihilation lifetime in complex geometries. • Investigation of shape non-uniformity of cylindrical pores on o-Ps annihilation lifetime. • Verifying temperature dependency of o-Ps lifetime in non-uniform cylindrical pores. • Suggesting PALS at low temperature as a method to verify pore uniformity in porous material. - Abstract: Ortho-positronium (o-Ps) annihilation lifetime was calculated in non-uniform cylinder-shaped pores by solving Schrodinger equation using a well-known multi-physics program called COMSOL. The o-Ps annihilation lifetime variation in terms of temperature was calculated on the basis of ETE model via a numerical method. The COMSOL simulations indicate that as long as the pore is uniform cylinder-shaped, the results agree with those of two-dimensional ETE model, whereas deformations in the cylinder shape (indentation or protrusion) change the temperature behavior of ETE model and, thereby, higher values are predicted for o-Ps lifetime in the pore at lower temperatures. The geometry of the non-uniform cylinder-shaped pores, which is accompanied by empirical evidence, can be used for the analysis of empirical results obtained from positron lifetime spectroscopy in different temperatures.

  9. AC losses in a type II superconductor strip with inhomogeneous critical current distribution

    International Nuclear Information System (INIS)

    Tsukamoto, Osami

    2005-01-01

    Analytical formulae derived by Brandt and Indenbom (1993 Phys. Rev. B 48 12893-906) and Norris (1970 J. Phys. D: Appl. Phys. 3 489-507) are often used to calculate the magnetization and AC transport current losses in HTS strip conductors, respectively. In these formulae, homogeneous distribution of critical sheet current density σ c in the strip is assumed. However, it is considered that σ c distributions are inhomogeneous in actual HTS strips and that the inhomogeneous σ c distributions cause deviations of the measured AC loss data of actual HTS strips from those formulae. A semi-analytical method to calculate AC transport current and magnetization losses is derived for a type II superconductor strip with inhomogeneous distribution of σ c in the direction of the strip width. The method is derived modifying the analysis of Brandt et al. The validity of the semi-analytical method is shown by comparing the results calculated by this method with those calculated by the Norris and Brandt formulae and by a different method of our previous work and also with experimental data. Moreover, it is shown that the deviation of the measured data from the Norris and Brandt models can be estimated by assuming proper σ c distributions

  10. Current distribution and conductance quantization in the integer quantum Hall regime

    International Nuclear Information System (INIS)

    Cresti, Alessandro; Farchioni, Riccardo; Grosso, Giuseppe; Parravicini, Giuseppe Pastori

    2003-01-01

    Charge transport of a two-dimensional electron gas in the presence of a magnetic field is studied by means of the Keldysh-Green function formalism and the tight-binding method. We evaluate the spatial distributions of persistent (equilibrium) and transport (nonequilibrium) currents, and give a vivid picture of their profiles. In the quantum Hall regime, we find exact conductance quantization both for persistent currents and for transport currents, even in the presence of impurity scattering centres and moderate disorder. (letter to the editor)

  11. Current distribution and conductance quantization in the integer quantum Hall regime

    Energy Technology Data Exchange (ETDEWEB)

    Cresti, Alessandro [NEST-INFM and Dipartimento di Fisica ' E Fermi' , Universita di Pisa, via F Buonarroti 2, I-56127 Pisa (Italy); Farchioni, Riccardo [NEST-INFM and Dipartimento di Fisica ' E Fermi' , Universita di Pisa, via F Buonarroti 2, I-56127 Pisa (Italy); Grosso, Giuseppe [NEST-INFM and Dipartimento di Fisica ' E Fermi' , Universita di Pisa, via F Buonarroti 2, I-56127 Pisa (Italy); Parravicini, Giuseppe Pastori [NEST-INFM and Dipartimento di Fisica ' A Volta' , Universita di Pavia, via A Bassi 6, I-27100 Pavia (Italy)

    2003-06-25

    Charge transport of a two-dimensional electron gas in the presence of a magnetic field is studied by means of the Keldysh-Green function formalism and the tight-binding method. We evaluate the spatial distributions of persistent (equilibrium) and transport (nonequilibrium) currents, and give a vivid picture of their profiles. In the quantum Hall regime, we find exact conductance quantization both for persistent currents and for transport currents, even in the presence of impurity scattering centres and moderate disorder. (letter to the editor)

  12. Critical opalescence of neutrons in nonuniform liquid in the gravitational field

    International Nuclear Information System (INIS)

    Sugakov, V.I.; Chalyj, A.V.; Chernenko, L.M.

    1990-01-01

    The altitude dependence of the refractive index and refractive angle of the neutron beam in a nonuniform liquid near the critical point is investigated. The neutron wave function in a passing beam as well as monochromatic transmission and reflection coefficients of neutrons are found

  13. Electron acoustic vortices in the presence of inhomogeneous current

    Energy Technology Data Exchange (ETDEWEB)

    Haque, Q; Masood, W; Saleem, H [Theoretical Plasma Physics Division, PINSTECH, P O Nilore, Islamabad (Pakistan)], E-mail: qamar@pinstech.org.pk

    2008-03-15

    Linear and nonlinear dynamics of an electron acoustic wave in an inhomogeneous magnetized plasma are studied in the presence of non-uniform background current. The modified Rayleigh instability condition is found due to shear in the magnetic field and the current. A nonlinear stationary solution is also obtained in the form of tripolar vortices. The relevance of the present study to auroral and magnetotail plasmas is pointed out.

  14. Distribution of electric currents in sunspots from photosphere to corona

    Energy Technology Data Exchange (ETDEWEB)

    Gosain, Sanjay [National Solar Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Démoulin, Pascal [Observatoire de Paris, LESIA, UMR 8109 (CNRS), F-92195 Meudon Principal Cedex (France); López Fuentes, Marcelo [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC. 67, Suc. 28 Buenos Aires 1428 (Argentina)

    2014-09-20

    We present a study of two regular sunspots that exhibit nearly uniform twist from the photosphere to the corona. We derive the twist parameter in the corona and in the chromosphere by minimizing the difference between the extrapolated linear force-free field model field lines and the observed intensity structures in the extreme-ultraviolet images of the Sun. The chromospheric structures appear more twisted than the coronal structures by a factor of two. Further, we derive the vertical component of electric current density, j{sub z} , using vector magnetograms from the Hinode Solar Optical Telescope (SOT). The spatial distribution of j{sub z} has a zebra pattern of strong positive and negative values owing to the penumbral fibril structure resolved by Hinode/SOT. This zebra pattern is due to the derivative of the horizontal magnetic field across the thin fibrils; therefore, it is strong and masks weaker currents that might be present, for example, as a result of the twist of the sunspot. We decompose j{sub z} into the contribution due to the derivatives along and across the direction of the horizontal field, which follows the fibril orientation closely. The map of the tangential component has more distributed currents that are coherent with the chromospheric and coronal twisted structures. Moreover, it allows us to map and identify the direct and return currents in the sunspots. Finally, this decomposition of j{sub z} is general and can be applied to any vector magnetogram in order to better identify the weaker large-scale currents that are associated with coronal twisted/sheared structures.

  15. Research for the Influence of Distribution Network Line Reclosing Current on Line Protection

    Directory of Open Access Journals (Sweden)

    Yu Kansheng

    2016-01-01

    Full Text Available According to the distribution network line structure and reclosing control strategy, the system simulation model of distribution network lines has established based on the real-time digital simulation RTDS. Based on this, distribution network switching impulse current characteristic has researched with different capacity, different distribution and different load power factor under the different voltage switching angles. The results of the study provide a scientific basis for distribution network line protection setting, in order to further lay the foundation for improvement the validity and reliability of distribution network line protection action.

  16. A Monte Carlo simulation on critical current distribution of bent-damaged multifilamentary Bi2223 composite tape

    International Nuclear Information System (INIS)

    Ochiai, S.; Okuda, H.; Fujimoto, M.; Shin, J.K.; Oh, S.S.; Ha, D.W.

    2011-01-01

    We simulate critical current distribution of bent-damaged Bi2223 composite tape. We use a Monte Carlo method and a damage evolution model for simulation. With the present simulation approach, experimental results are described well. Critical current distribution stems mainly from difference in damage evolution. It was attempted to reproduce the measured critical current (I c ) distributions of the Bi2223 composite tape bent by 0-0.833% by simulation. Simulation was carried out with a Monte Carlo method in combination with a model that correlates the critical current to damage evolution. Two variables that differ from specimen to specimen were input in the simulation. One was the damage strain parameter, with which the difference in extent of damage among specimens was expressed. Another was the original critical current (I c0 ) values at zero bending strain. With the present simulation approach, the measured distributions of critical current at various bending strains, and the measured variations of average and coefficient of variation of critical current values with increasing bending strain were reproduced well.

  17. Analysis of strain distribution and critical current of superconductors based on a strain-critical current measurement system

    International Nuclear Information System (INIS)

    Liu Fang; Wu Yu; Long Feng

    2010-01-01

    Based on Pacman device which is widely used to investigate the axial strain dependence of the critical current in superconductors, the finite element analysis method is employed to carry out the force analysis of the spring and the superconducting strand, thereby the axial and lateral strain distributions of the superconducting strand are obtained. According to the two extreme assumptions(low inter-filament resistance and high inter-filament resistance), the effects of the strain homogeneity at the cross section of the superconductor on the critical current is analyzed combined with the Nb 3 Sn deviatoric strain-critical current scaling law. (authors)

  18. Processing and properties of pressable ceramic with non-uniform reinforcement for selective-toughening

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Wei [School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia); School of Dentistry, The University of Western Australia, WA 6009 (Australia); Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China); Hu, Xiaozhi, E-mail: xiao.zhi.hu@uwa.edu.au [School of Mechanical and Chemical Engineering, The University of Western Australia, Perth, WA 6009 (Australia); Ichim, Paul [School of Dentistry, The University of Western Australia, WA 6009 (Australia); Sun, Xudong [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China)

    2012-12-15

    Brittle low-strength and low-toughness pressable dental ceramic can be reinforced by ductile elongated gold-particles (GP). A customized crown structure can be adequately strengthened by distributing GP only in critical sections of the crown, where high tensile stresses are experienced. In the present study, a non-uniformly structured ceramic-matrix composite with excellent interfacial bonding, twofold fracture toughness and strength at desired locations, is fabricated using pressable dental ceramic and GP. The layout pattern and sequence of different GP/ceramic powder mixtures, high-temperature flow properties of these mixtures during hot-pressing and the sample mold geometry are used to control the distribution and locations of GP for selective toughening and strengthening. Nano-crystalline structures of the pressable ceramic-matrix and the nano-scaled interfacial region around GP have been revealed by high-magnification field-emission scanning electron microscopy. Toughening and strengthening mechanisms of the elongated GP including residual stresses from composite processing and ductile fracture of GP are discussed together with SEM observations. Bulk flexural strength and local micro-indentation fracture and deformation characteristics of the selective-toughened ceramic/metal composite have been compared to those of the monolithic pressable ceramic to validate the toughening and strengthening mechanisms.

  19. Processing and properties of pressable ceramic with non-uniform reinforcement for selective-toughening

    International Nuclear Information System (INIS)

    Yi, Wei; Hu, Xiaozhi; Ichim, Paul; Sun, Xudong

    2012-01-01

    Brittle low-strength and low-toughness pressable dental ceramic can be reinforced by ductile elongated gold-particles (GP). A customized crown structure can be adequately strengthened by distributing GP only in critical sections of the crown, where high tensile stresses are experienced. In the present study, a non-uniformly structured ceramic–matrix composite with excellent interfacial bonding, twofold fracture toughness and strength at desired locations, is fabricated using pressable dental ceramic and GP. The layout pattern and sequence of different GP/ceramic powder mixtures, high-temperature flow properties of these mixtures during hot-pressing and the sample mold geometry are used to control the distribution and locations of GP for selective toughening and strengthening. Nano-crystalline structures of the pressable ceramic–matrix and the nano-scaled interfacial region around GP have been revealed by high-magnification field-emission scanning electron microscopy. Toughening and strengthening mechanisms of the elongated GP including residual stresses from composite processing and ductile fracture of GP are discussed together with SEM observations. Bulk flexural strength and local micro-indentation fracture and deformation characteristics of the selective-toughened ceramic/metal composite have been compared to those of the monolithic pressable ceramic to validate the toughening and strengthening mechanisms.

  20. A mathematical model of the current density distribution in electrochemical cells - AUTHORS’ REVIEW

    Directory of Open Access Journals (Sweden)

    PREDRAG M. ŽIVKOVIĆ

    2011-06-01

    Full Text Available An approach based on the equations of electrochemical kinetics for the estimation of the current density distribution in electrochemical cells is presented. This approach was employed for a theoretical explanation of the phenomena of the edge and corner effects. The effects of the geometry of the system, the kinetic parameters of the cathode reactions and the resistivity of the solution are also discussed. A procedure for a complete analysis of the current distribution in electrochemical cells is presented.

  1. n value and Jc distribution dependence of AC transport current losses in HTS conductors

    International Nuclear Information System (INIS)

    Ogawa, Jun; Sawai, Yusuke; Nakayama, Haruki; Tsukamoto, Osami; Miyagi, Daisuke

    2004-01-01

    Compared with LTS materials, HTS materials have some peculiarities affecting AC loss characteristics of the conductors. We measured the AC transport current losses in YBCO thin film coated conductors and a Bi2223/Ag sheathed tape. Comparing the measured data with analytical calculations, the dependence of the AC transport current losses on the n value and critical current density distributions are studied. It is shown that, considering the n values and J c distributions, the peculiarities in the HTS materials can be taken into consideration and the transport current losses in HTS conductors can be calculated by the same analytical method used for LTS

  2. Nonadiabatic generation of spin currents in a quantum ring with Rashba and Dresselhaus spin-orbit interactions

    International Nuclear Information System (INIS)

    Niţa, Marian; Ostahie, Bogdan; Marinescu, D C; Manolescu, Andrei; Gudmundsson, Vidar

    2012-01-01

    When subjected to a linearly polarized terahertz pulse, a mesoscopic ring endowed with spin-orbit interaction (SOI) of the Rashba-Dresselhaus type exhibits non-uniform azimuthal charge and spin distributions. Both types of SOI couplings are considered linear in the electron momentum. Our results are obtained within a formalism based on the equation of motion satisfied by the density operator which is solved numerically for different values of the angle φ, the angle determining the polarization direction of the laser pulse. Solutions thus obtained are later employed in determining the time-dependent charge and spin currents, whose values are calculated in the stationary limit. Both these currents exhibit an oscillatory behavior complicated in the case of the spin current by a beating pattern. We explain this occurrence on account of the two spin-orbit interactions which force the electron spin to oscillate between the two spin quantization axes corresponding to Rashba and Dresselhaus interactions. The oscillation frequencies are explained using the single particle spectrum.

  3. Mechanism and scaling for convection of isolated structures in nonuniformly magnetized plasmas

    DEFF Research Database (Denmark)

    Garcia, O.E.; Bian, N.H.; Naulin, V.

    2005-01-01

    Large-scale radial advection of isolated structures in nonuniformly magnetized plasmas is investigated. The underlying mechanism considered is due to the nonlinear evolution of interchange motions, without any presumption of plasma sheaths. Theoretical arguments supported by numerical simulations...

  4. Wastewater diffusive dilution and sedimentation of the fine contaminated particles for nonuniform flow in open channels

    OpenAIRE

    Lyapin Anton; Lyapin Valery

    2018-01-01

    The influence of non-uniformity on mass transfer processes in open channels have been investigated under the action of urbanization factors. The study is related to the urgent problem of environmental degradation of water objects in urbanized areas. It is known that the water quality in the water objects depends on the manner in which the contaminants spread how they mix with the river water and diluted by it. The main results of the study consist of recommendations to incorporate non-uniform...

  5. Electrical current at micro-/macro-scale of undoped and nitrogen-doped MWPECVD diamond films

    Science.gov (United States)

    Cicala, G.; Velardi, L.; Senesi, G. S.; Picca, R. A.; Cioffi, N.

    2017-12-01

    Chemical, structural, morphological and micro-/macro-electrical properties of undoped and nitrogen-(N-)doped diamond films are determined by X-ray photoelectron spectroscopy, Raman and photoluminescence spectroscopies, field emission scanning electron microscopy, atomic force microscopy, scanning capacitance microscopy (SCM) and two points technique for I-V characteristics, respectively. The characterization results are very useful to examine and understand the relationship among these properties. The effect of the nitrogen incorporation in diamond films is investigated through the evolution of the chemical, structural, morphological and topographical features and of the electrical behavior. The distribution of the electrical current is first assessed at millimeter scale on the surface of diamond films and then at micrometer scale on small regions in order to establish the sites where the carriers preferentially move. Specifically, the SCM images indicate a non-uniform distribution of carriers on the morphological structures mainly located along the grain boundaries. A good agreement is found by comparing the electrical currents at the micro- and macro-scale. This work aims to highlight phenomena such as photo- and thermionic emission from N-doped diamond useful for microelectronic engineering.

  6. REGIONAL DEPOSITION OF COARSE PARTICLES AND VENTILATION DISTRIBUTION IN PATIENTS WITH CYSTIC FIBROSIS

    Science.gov (United States)

    The efficacy of inhaled pharmaceuticals depends, in part, on their site of respiratory deposition. Markedly nonuniform ventilation distribution may occur in persons with obstructive airways diseases and may affect particle deposition. We studied the relationship between regional ...

  7. Current density distribution during disruptions and sawteeth in a simple model of plasma current in a tokamak

    International Nuclear Information System (INIS)

    Stefanovskii, A. M.

    2011-01-01

    The processes that are likely to accompany discharge disruptions and sawteeth in a tokamak are considered in a simple plasma current model. The redistribution of the current density in plasma is supposed to be primarily governed by the onset of the MHD-instability-driven turbulent plasma mixing in a finite region of the current column. For different disruption conditions, the variation in the total plasma current (the appearance of a characteristic spike) is also calculated. It is found that the numerical shape and amplitude of the total current spikes during disruptions approximately coincide with those measured in some tokamak experiments. Under the assumptions adopted in the model, the physical mechanism for the formation of the spikes is determined. The mechanism is attributed to the diffusion of the negative current density at the column edge into the zero-conductivity region. The numerical current density distributions in the plasma during the sawteeth differ from the literature data.

  8. Conductance dips and spin precession in a nonuniform waveguide with spin–orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Malyshev, A. I., E-mail: malyshev@phys.unn.ru; Kozulin, A. S. [Lobachevsky Nizhny Novgorod State University (Russian Federation)

    2015-07-15

    An infinite waveguide with a nonuniformity, a segment of finite length with spin–orbit coupling, is considered in the case when the Rashba and Dresselhaus parameters are identical. Analytical expressions have been derived in the single-mode approximation for the conductance of the system for an arbitrary initial spin state. Based on numerical calculations with several size quantization modes, we have detected and described the conductance dips arising when the waves are localized in the nonuniformity due to the formation of an effective potential well in it. We show that allowance for the evanescent modes under carrier spin precession in an effective magnetic field does not lead to a change in the direction of the average spin vector at the output of the system.

  9. Acoustic holography for piston sound radiation with non-uniform velocity profiles

    NARCIS (Netherlands)

    Aarts, R.M.; Janssen, A.J.E.M.

    2010-01-01

    The theory of orthogonal (Zernike) expansions of functions on a disk, as used in the diffraction theory of optical aberrations, is applied to obtain (semi-) analytical results for the radiation of sound due to a non-uniformly moving, baffled, circular piston. For this particular case, a scheme for

  10. Non-Uniformity of Ion Implantation in Direct-Current Plasma Immersion Ion Implantation

    International Nuclear Information System (INIS)

    Cheng-Sen, Liu; Yu-Jia, Fan; Nan, Zhang; Li, Guan; Yuan, Yao; De-Zhen, Wang

    2010-01-01

    A particle-in-cell simulation is developed to study dc plasma immersion ion implantation. Particular attention is paid to the influence of the voltage applied to the target on the ion path, and the ion flux distribution on the target surface. It is found that the potential near the aperture within the plasma region is not the plasma potential, and is impacted by the voltage applied to the implanted target. A curved equipotential contour expands into the plasma region through the aperture and the extent of the expansion depends on the voltage. Ions accelerated by the electric field in the sheath form a beam shape and a flux distribution on the target surface, which are strongly dependent on the applied voltage. The results of the simulations demonstrate the formation mechanism of the grid-shadow effect, which is in agreement with the result observed experimentally. (physics of gases, plasmas, and electric discharges)

  11. Non-similar solutions for unsteady flow over a yawed cylinder with non-uniform mass transfer through a slot

    Directory of Open Access Journals (Sweden)

    G. Revathi

    2014-12-01

    Full Text Available Non-similar solutions are found numerically to a system of coupled non-linear partial differential equations indicating, unsteady laminar water boundary layer flow over yawed cylinder using implicit finite difference scheme along with Quasi-linearization technique. The fluid properties such as viscosity and Prandtl number are considered as an inverse function of temperature. Unsteadiness is caused by upstream velocity in and directions and non-uniform mass transfer (suction/injection which is applied through slot on the surface of the geometry. The effect of yaw angle, variable fluid properties and non-uniform mass transfer on skin friction and heat transfer coefficients is analyzed. It is found that non-uniform slot suction and downstream movement of the slot cause the point of vanishing skin friction moves downstream, but non-uniform slot injection produces the opposite result of that corresponding to the suction case. When the yaw angle increases, both the skin friction coefficient in the – direction and the heat transfer coefficient decrease but the skin friction coefficient in the – direction increases for all times. The effect of the yaw angle is very little on the point of vanishing skin friction.

  12. The effect of nonuniform magnetic targeting of intracoronary-delivering mesenchymal stem cells on coronary embolisation.

    Science.gov (United States)

    Huang, Zheyong; Shen, Yunli; Pei, Ning; Sun, Aijun; Xu, Jianfeng; Song, Yanan; Huang, Gangyong; Sun, Xiaoning; Zhang, Shuning; Qin, Qing; Zhu, Hongming; Yang, Shan; Yang, Xiangdong; Zou, Yunzeng; Qian, Juying; Ge, Junbo

    2013-12-01

    Magnetic targeting has been recently introduced to enhance cell retention in animals with acute myocardial infarction. However, it is unclear whether the magnetic accumulation of intravascular cells increases the risk of coronary embolism. Upon finite element analysis, we found that the permanent magnetic field was nonuniform, manifestated as attenuation along the vertical axis and polarisation along the horizontal axis. In the in vitro experiments, iron-labelled mesenchymal stem cells (MSCs) were accumulated in layers predominantly at the edge of the magnet. In an ischaemic rat model subjected to intracavitary MSCs injection, magnetic targeting induced unfavourable vascular embolisation and an inhomogeneous distribution of the donor cells, which prevented the enhanced cell retention from translating into additional functional benefit. These potential complications of magnetic targeting should be thoroughly investigated and overcome before clinical application. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Multiplicity distributions of charged hadrons produced in (anti)neutrino-deuterium charged- and neutral-current interactions

    International Nuclear Information System (INIS)

    Jongejans, B.; Tenner, A.G.; Apeldoorn, G.W. van

    1989-01-01

    Results are presented on the multiplicity distributions of charged hadrons produced in νn, νp, antiνn and antiνp charged-current interactions for the hadronic energy range 2GeV ≤ W ≤ 14GeV (corresponding approximately to the neutrino energy range 5GeV ≤ E ≤ 150GeV). The experimental distributions are analysed in terms of binomial distributions. With increasing hadronic energy it is found a smooth transition from an ordinary binomial via Poissonian to the negative binomial function. KNO scaling holds approximately for the multiplicity distribution for the whole phase space. Data on the multiplicity distributions for neutral-current interactions are also presented

  14. Using Nonuniform Fiber to Generate Slow Light via SBS

    Directory of Open Access Journals (Sweden)

    Wenhai Li

    2008-01-01

    Full Text Available The data pulse delay based on slow light induced by stimulated Brillouin scattering (SBS in a nonuniform dispersion decreasing fiber (DDF is demonstrated experimentally, and the distortions of data pulses at different beat frequencies are studied. We found that a delay exceeding a pulse width can be achieved at particular beat frequency, and the DDF has larger delay versus gain slope coefficient with much better output pulse quality than single-mode fiber.

  15. Determination of the axial thermal neutron flux non-uniform factor in the MNSR inner irradiation capsule

    International Nuclear Information System (INIS)

    Khattab, K.; Ghazi, N.; Omar, H.

    2007-01-01

    A 3-D neutronic model, using the WIMSD4 and CITATION codes, for the Syrian Miniature Neutron source Reactor (MNSR) is used to calculate the axial thermal neutron flux non-uniform factor in the inner irradiation capsule. The calculated result is 4%. A copper wire is used to measure the axial thermal neutron flux non-uniform factor in the inner irradiation capsule to be compared with the calculated result. The measured result is 5%. Good agreement between the measured and calculated results is obtained. (author)

  16. Determination of the axial thermal neutron flux non-uniform factor in the MNSR inner irradiation capsule

    International Nuclear Information System (INIS)

    Khattab, K.; Ghazi, N.; Omar, H.

    2007-01-01

    A 3-D neutronic model, using the WIMSD4 and CITATION codes, for the Syrian Miniature Neutron Source Reactor (MNSR) is used to calculate the axial thermal neutron flux non-uniform factor in the inner irradiation capsule. The calculated result is 4%. A copper wire is used to measure the axial thermal neutron flux non-uniform factor in the inner irradiation capsule to be compared with the calculated result. The measured result is 5%. Good agreement between the measured and calculated results is obtained

  17. On the Time Variation of Dust Extinction and Gas Absorption for Type Ia Supernovae Observed Through Non-uniform Interstellar Medium

    Science.gov (United States)

    Huang, Xiaosheng; Aldering, Gregory; Biederman, Moriah; Herger, Brendan

    2018-01-01

    For Type Ia supernovae (SNe Ia) observed through a non-uniform interstellar medium (ISM) in its host galaxy, we investigate whether the non-uniformity can cause observable time variations in dust extinction and in gas absorption due to the expansion of the SN photosphere with time. We show that, owing to the steep spectral index of the ISM density power spectrum, sizable density fluctuation amplitudes at the length scale of typical ISM structures (>~ 10 pc) will translate to much smaller fluctuations on the scales of a SN photosphere. Therefore the typical amplitude of time variation due to non-uniform ISM, of absorption equivalent widths and of extinction, would be small. As a result, we conclude that non-uniform ISM density should not impact cosmology measurements based on SNe Ia. We apply our predictions based on the ISM density power law power spectrum to the observations of two highly reddened SNe Ia, SN 2012cu and SN 2014J.

  18. On the Time Variation of Dust Extinction and Gas Absorption for Type Ia Supernovae Observed through a Nonuniform Interstellar Medium

    Science.gov (United States)

    Huang, X.; Aldering, G.; Biederman, M.; Herger, B.

    2017-11-01

    For Type Ia supernovae (SNe Ia) observed through a nonuniform interstellar medium (ISM) in its host galaxy, we investigate whether the nonuniformity can cause observable time variations in dust extinction and in gas absorption due to the expansion of the SN photosphere with time. We show that, owing to the steep spectral index of the ISM density power spectrum, sizable density fluctuation amplitudes at the length scale of typical ISM structures (≳ 10 {pc}) will translate to much smaller fluctuations on the scales of an SN photosphere. Therefore, the typical amplitude of time variation due to a nonuniform ISM, of absorption equivalent widths, and of extinction, would be small. As a result, we conclude that nonuniform ISM density should not impact cosmology measurements based on SNe Ia. We apply our predictions based on the ISM density power-law power spectrum to the observations of two highly reddened SNe Ia, SN 2012cu and SN 2014J.

  19. The influence of printing substrate on macro non-uniformity and line reproduction quality of imprints printed with electrophotographic process

    Directory of Open Access Journals (Sweden)

    Đorđe Vujčić

    2016-12-01

    Full Text Available Print quality is very important for every printing technique. It depends on many different quality attributes. This research included analysis of macro non-uniformities and line reproduction. 16 different paper substrates printed by electrophotographic process were analyzed. They were separated in two groups: coated and uncoated papers. Analysis of macro non-uniformity showed that print mottle has lower values when printed on coated papers than on uncoated papers. Line reproduction analysis showed that the toner spreaded, during melting and fixation, on line edges for both types of paper. According to these results it can be concluded that paper substrate affects the macro non-uniformity and line reproduction, thus overall print quality.

  20. Flexible RF filter using a nonuniform SCISSOR.

    Science.gov (United States)

    Zhuang, Leimeng

    2016-03-15

    This work presents a flexible radiofrequency (RF) filter using an integrated microwave photonic circuit that comprises a nonuniform side-coupled integrated spaced sequence of resonators (N-SCISSOR). The filter passband can be reconfigured by varying the N-SCISSOR parameters. When employing a dual-parallel Mach-Zechnder modulator, the filter is also able to perform frequency down-conversion. In the experiment, various filter response shapes are shown, ranging from a flat-top band-pass filter to a total opposite high-rejection (>40  dB) notch filter, with a frequency coverage of greater than two octaves. The frequency down-conversion function is also demonstrated.

  1. Current distribution in triodes neglecting space charge and initial velocities

    NARCIS (Netherlands)

    Hamaker, H.C.

    1950-01-01

    A theory of the current distribution in triodes with positive grid is developed on the assumption that space charge and the initial velocities of both primary and secondary electrons may be neglected. This theory, which is originally due to De Lussanct de la Sablonière, has been put in a more lucid

  2. Current drive by neutral beams, rotating magnetic fields and helicity injection in compact toroids

    International Nuclear Information System (INIS)

    Farengo, R.

    2002-01-01

    A Monte-Carlo code is used to study neutral beam current drive in Spheromaks. The exact particle trajectories are followed in the self-consistent equilibria calculated including the beam current. Reducing Z(eff) does not increase the current drive efficiency because the reduction of the stopping cross section is compensated by an increase in the electron canceling current. Significant changes in the safety factor profile can be produced with relatively low beam currents. Minimum dissipation states of a flux core spheromak sustained by helicity injection are presented. Helicity balance is used as a constraint and the resistivity is considered to be non-uniform. Two types of relaxed states are found; one has a central core of open flux surrounded by a toroidal region of closed flux surfaces and the other has the open flux wrapped around the closed flux surfaces. Non-uniform resistivity effects can be very important due to the changes they produce in the safety factor profile. A hybrid, fluid electrons particle ions, code is employed to study ion dynamics in FRCs sustained by rotating magnetic fields. (author)

  3. Measurement of current distribution in a proton exchange membrane fuel cell with various flow arrangements – A parametric study

    International Nuclear Information System (INIS)

    Alaefour, Ibrahim; Karimi, G.; Jiao, Kui; Li, X.

    2012-01-01

    Highlights: ► Spatial local current distributions in a single PEMFC are measured. ► Effects of key operating conditions on the local current density are investigated. ► Increasing air and hydrogen stoichiometries improves local current density distributions. ► Operating pressure and temperature have negligible impact on local current distribution. - Abstract: Understanding of current distributions in proton exchange membrane fuel cells (PEMFCs) is crucial for designing cell components such as the flow field plates and the membrane electrode assembly (MEA). In this study, the spatial current density distributions in a single PEMFC with three serpentine flow channels are measured using a segmented bipolar plate and printed circuit board technique. The effects of key operating conditions such as stoichiometry ratios, inlet humidity levels, cell pressure and temperature on the local current density distributions for co-, counter-, and cross-flow arrangements are examined. It is observed that the local current density distribution over the MEA is directly affected by the cell operating conditions along with the configuration of the flow arrangement. It is also found that among the different flow configurations tested under the various operating conditions, the counter flow arrangement provides the optimum average current density and the lowest variations in the local current densities along the flow channels.

  4. Direct observation of the current distribution in thin superconducting strips using magneto-optic imaging

    International Nuclear Information System (INIS)

    Johansen, T.H.; Baziljevich, M.; Bratsberg, H.; Galperin, Y.; Lindelof, P.E.; Shen, Y.; Vase, P.

    1996-01-01

    Magneto-optic imaging was used for a detailed study of the flux and current distribution of a long thin strip of YBa 2 Cu 3 O 7-δ placed in a perpendicular external magnetic field. The inverse magnetic problem, i.e., that of deriving from a field map the underlying current distribution, is formulated and solved for the strip geometry. Applying the inversion to the magneto-optically found field map we find on a model-independent basis the current distribution across the strip to be in remarkable agreement with the profile predicted by the Bean model. The paper also presents results on the behavior of the Bi-doped YIG film with in-plane anisotropy which we use as field indicator, explaining why previous measurements of flux density profiles have displayed surprisingly large deviations from the expected behavior. copyright 1996 The American Physical Society

  5. Human thermal sensation and comfort in a non-uniform environment with personalized heating.

    Science.gov (United States)

    Deng, Qihong; Wang, Runhuai; Li, Yuguo; Miao, Yufeng; Zhao, Jinping

    2017-02-01

    Thermal comfort in traditionally uniform environment is apparent and can be improved by increasing energy expenses. To save energy, non-uniform environment implemented by personalized conditioning system attracts considerable attention, but human response in such environment is unclear. To investigate regional- and whole-body thermal sensation and comfort in a cool environment with personalized heating. In total 36 subjects (17 males and 19 females) including children, adults and the elderly, were involved in our experiment. Each subject was first asked to sit on a seat in an 18°C chamber (uniform environment) for 40min and then sit on a heating seat in a 16°C chamber (non-uniform environment) for another 40min after 10min break. Subjects' regional- and whole-body thermal sensation and comfort were surveyed by questionnaire and their skin temperatures were measured by wireless sensors. We statistically analyzed subjects' thermal sensation and comfort and their skin temperatures in different age and gender groups and compared them between the uniform and non-uniform environments. Overall thermal sensation and comfort votes were respectively neutral and just comfortable in 16°C chamber with personalized heating, which were significantly higher than those in 18°C chamber without heating (pthermal sensation and comfort was consistent in subjects of different age and gender. However, adults and the females were more sensitive to the effect of personalized heating and felt cooler and less comfort than children/elderly and the males respectively. Variations of the regional thermal sensation/comfort across human body were consistent with those of skin temperature. Personalized heating significantly improved human thermal sensation and comfort in non-uniform cooler environment, probably due to the fact that it increased skin temperature. However, the link between thermal sensation/comfort and variations of skin temperature is rather complex and warrant further

  6. A METHOD FOR EVALUATION OF NON-UNIFORM RADIANT-CONVECTIVE LOAD ON HUMAN BODY DURING MENTAL WORK

    Directory of Open Access Journals (Sweden)

    Lenka Prokšová Zuská

    2017-10-01

    Full Text Available The objective of this study was to develop a documentation for the amendment of the microclimatic part of the Czech Government Regulation, particularly in a non-uniform radiant-convective load evaluation. Changes in regulation were made based on experimental data obtained on a group of experimental individuals in a climatic chamber. One of the objectives of the climatic chamber experiments was to evaluate whether there was a possibility to use an alternative method, which utilizes a new value – stereotemperature, for the assessment. A group of 24 women was exposed to a non-uniform radiant-convective load in a climatic chamber for 1 hour during their computer work. Measurements were divided according to the globe temperature into 3 stages. The physical parameters of air were continuously measured: the air temperature, globe temperature, air velocity, radiant temperature, relative humidity, stereotemperature and physiological parameters. Thermal sensations of experimental subjects were expressed in the seven-point scale according to EN ISO 7730. The thermal sensation correlated very well with the difference of stereotemperature and the globe temperature. The stereotemperature correlated very well with the radiant temperature. In this work, the composed equations were used to develop the limit values for the thermal stress evaluation in the uniform and non-uniform thermal environment at workplaces. It is possible to determine how the body of an exposed person perceives the non-uniform climatic conditions in the indoor environment, by adding the stereotemperature to government regulations.

  7. Smoothing and instability with magnetic field in a non-uniformly laser-irradiated planar target

    International Nuclear Information System (INIS)

    Bell, A.R.; Epperlein, E.M.

    1986-01-01

    Calculations are presented of the magneto-hydrodynamic response of a planar target to non-uniformities in energy deposition by a laser. The amplitude of the non-uniformities are assumed small and the equations are linearised in small perturbations about the solution for steady planar ablation driven by uniform laser energy deposition. The grad(n)xgrad(T) magnetic field source is included, along with Nernst convection and the Righi-Leduc heat flow. The magnetic field is shown to give a small increase in smoothing. A source term for magnetic field is included to simulate the effects of the Weibel instability. The instability is not strong enough to overcome the smoothing processes under the present assumptions. (author)

  8. Eddy current distribution and lift force for finite MAGLEV strips

    Energy Technology Data Exchange (ETDEWEB)

    Atherton, D L; Eastham, A R; Fombrun, C; Chong, M

    1974-07-01

    The transverse distribution of induced eddy currents across a flat conducing strip of finite width, due to a rectangular dc magnet moving above it, was modelled experimentally, and was compared with that calculated for an infinite sheet. The electrodynamic suspension was simulated by means of a stationary ac-excited copper magnet suspended above an aluminum strip, and the induced surface current density was measured by a voltage pickup probe connected to a lock-in amplifier. The effect of reducing strip width is examined and shown to produce high current densities close to the edges. These results are related to the variation of lift force with strip width, determined by impedance modelling. A slight enhancement of lift is evident for intermediate strip widths.

  9. Comparison of distributed vortex receptivity coefficients at excitation of 3D TS-waves in presence and absence of surface waviness and pressure gradient

    Science.gov (United States)

    Borodulin, V. I.; Ivanov, A. V.; Kachanov, Y. S.; Mischenko, D. A.; Fedenkova, A. A.

    2016-10-01

    The paper is devoted to quantitative experimental investigation of effective mechanisms of excitation of 3D TS instability waves due to distributed boundary layer receptivity to free-stream vortices. Experiments carried out in a self-similar boundary layer with Hartree parameter βH = -0.115 and concentrated on studying two receptivity mechanisms connected with distributed scattering of 3D unsteady free-stream vortices both on the natural boundary layer nonuniformity (smooth surface) and on 2D surface nonuniformity (waviness). Obtained quantitative characteristics (distributed receptivity coefficients) are compared directly with those obtained in Blasius boundary layer. It is found that the adverse pressure gradient leads to reduction of efficiency of the vortex-roughness receptivity mechanism.

  10. Effects of non-uniform embedments on earthquake responses of nuclear reactor building

    International Nuclear Information System (INIS)

    Koyanagi, Y.; Okamoto, S.; Yoshida, K.; Inove, H.

    1989-01-01

    The nuclear reactor buildings have the portion embedded in soil. In the seismic design of such structures, it is essential to consider the effects of the embedment on the earthquake response. Most studies on these effects, however, assume the uniform embedment, i.e. the depth of the embedment is constant, which is convenient for the design and analysis. The behavior of the earthquake response considering the three-dimensional aspects of non-uniform embedment has not been made clear yet. In this paper, the authors evaluate the effects of the non-uniform embedment in an inclined ground surface on the earthquake response of a nuclear reactor building as illustrated. A typical PWR type reactor building is chosen as an analysis structure model. Four different types of embedment are set up for the comparison study. The three-dimensional analysis is carried out considering the geometry of embedment

  11. Nonuniform Overlapping Method in Designing Microstrip Patch Antennas Using Genetic Algorithm Optimization

    Directory of Open Access Journals (Sweden)

    J. M. Jeevani W. Jayasinghe

    2015-01-01

    Full Text Available Genetic algorithm (GA has been a popular optimization technique used for performance improvement of microstrip patch antennas (MPAs. When using GA, the patch geometry is optimized by dividing the patch area into small rectangular cells. This has an inherent problem of adjacent cells being connected to each other with infinitesimal connections, which may not be achievable in practice due to fabrication tolerances in chemical etching. As a solution, this paper presents a novel method of dividing the patch area into cells with nonuniform overlaps. The optimized design, which is obtained by using fixed overlap sizes, shows a quad-band performance covering GSM1800, GSM1900, LTE2300, and Bluetooth bands. In contrast, use of nonuniform overlap sizes leads to obtaining a pentaband design covering GSM1800, GSM1900, UMTS, LTE2300, and Bluetooth bandswith fractional bands with of 38% due to the extra design flexibility.

  12. Mechanical analysis of non-uniform bi-directional functionally graded intelligent micro-beams using modified couple stress theory

    Science.gov (United States)

    Bakhshi Khaniki, Hossein; Rajasekaran, Sundaramoorthy

    2018-05-01

    This study develops a comprehensive investigation on mechanical behavior of non-uniform bi-directional functionally graded beam sensors in the framework of modified couple stress theory. Material variation is modelled through both length and thickness directions using power-law, sigmoid and exponential functions. Moreover, beam is assumed with linear, exponential and parabolic cross-section variation through the length using power-law and sigmoid varying functions. Using these assumptions, a general model for microbeams is presented and formulated by employing Hamilton’s principle. Governing equations are solved using a mixed finite element method with Lagrangian interpolation technique, Gaussian quadrature method and Wilson’s Lagrangian multiplier method. It is shown that by using bi-directional functionally graded materials in nonuniform microbeams, mechanical behavior of such structures could be affected noticeably and scale parameter has a significant effect in changing the rigidity of nonuniform bi-directional functionally graded beams.

  13. The p - n junction under nonuniform strains: general theory and application to photovoltaics

    Science.gov (United States)

    Guin, L.; Jabbour, M. E.; Triantafyllidis, N.

    2018-01-01

    It is well known that mechanical strains influence the electronic properties of semiconductor devices. Modeling the fully coupled mechanical, electrical, and electronic responses of semiconductors is therefore essential for predicting the effects of mechanical loading on their overall electronic response. In the first part of this paper, we develop a general continuum model that couples the mechanical, electrical, and electronic responses of a finitely deformable semiconductor. The proposed model accounts for the dependence of the band edge energies, densities of states, and electronic mobilities on strain. The governing equations are derived from the basic principles of the thermomechanics of electromagnetic continua undergoing electronic transport. In particular, we find that there exists electronically induced strains that can exceed their electromagnetic (Maxwell) counterparts by an order of magnitude. In the second part, motivated by applications that involve the bending of a photovoltaic cell, we use asymptotic methods to compute the current-voltage characteristic of a p - n junction under nonuniform strains. We find that, for a typical monocrystalline silicon solar cell, the changes in dark current are significant, i.e., of the order of 20% for strains of 0.2%.

  14. Selective exfoliation of single-layer graphene from non-uniform graphene grown on Cu

    International Nuclear Information System (INIS)

    Lim, Jae-Young; Lee, Jae-Hyun; Jang, Hyeon-Sik; Whang, Dongmok; Joo, Won-Jae; Hwang, SungWoo

    2015-01-01

    Graphene growth on a copper surface via metal-catalyzed chemical vapor deposition has several advantages in terms of providing high-quality graphene with the potential for scale-up, but the product is usually inhomogeneous due to the inability to control the graphene layer growth. The non-uniform regions strongly affect the reliability of the graphene in practical electronic applications. Herein, we report a novel graphene transfer method that allows for the selective exfoliation of single-layer graphene from non-uniform graphene grown on a Cu foil. Differences in the interlayer bonding energy are exploited to mechanically separate only the top single-layer graphene and transfer this to an arbitrary substrate. The dry-transferred single-layer graphene showed electrical characteristics that were more uniform than those of graphene transferred using conventional wet-etching transfer steps. (paper)

  15. Orobanche flava (Orobanchaceae in Poland: current distribution, taxonomy, hosts and plant communities

    Directory of Open Access Journals (Sweden)

    Piwowarczyk Renata

    2014-06-01

    Full Text Available Orobanche flava is a species of Central European mountain ranges, mainly the Alps and Carpathian Mts. The paper presents the current distribution of O. flava in Poland based on a critical revision of herbarium and literature data as well as results of field investigations conducted between 1999 and 2014. The distribution of species is centered in southern Poland, mainly in the Carpathian Mts., and, sporadically, in the Sudeten Mts. The distribution of O. flava in Poland is mapped. The taxonomy, biology, and ecology are also discussed.

  16. Effects of warmness and spatial nonuniformity of plasma waveguide on periodic absolute parametric instability

    International Nuclear Information System (INIS)

    Zaki, N.G.; Bekheit, A.H.

    2011-01-01

    The periodic absolute parametric instability (API) of the low-frequency oscillations excited by a monochromatic pumping field of an arbitrary amplitude in a warm 1-D (one-dimensional) nonuniform magnetoactive plasma is investigated. The separation method can be used for solving the two-fluid plasma equations describing the system. By applying this method we were able to determine the frequencies and growth rates of unstable modes and the self-consistent electric field. Plasma electrons are considered to have a thermal velocity. Different solutions for the spatial equation can be obtained the following cases: A) API in a uniform plasma, B) API in a nonuniform plasma. The latter has been studied here for two cases: B.1) the exact harmonic oscillator and B.2) the bounded harmonic oscillator (a bounded plasma). An increment has been found in the build-up of the oscillations, and it has been shown that the spatial nonuniformity of the plasma exerts the stabilizing effect on the parametric instability. A reduced growth rate of API in the warm plasma, in comparison to the cold plasma, is reported. It has also been found that the warmness of the plasma has no effect on the solution of the space part of the problem (only through the separation constant). (authors)

  17. Effects of Warmness and Spatial Nonuniformity of the Plasma Waveguide on Periodic Absolute Parametric Instability

    International Nuclear Information System (INIS)

    Zaki, N.G.; Bekheit, A.H.

    2011-01-01

    The periodic absolute parametric instability (API) of the low-frequency oscillations excited by a monochromatic pumping field of arbitrary amplitude in a warm I-D nonuniform magneto active plasma is investigated. One can use the separation method to solve the two-fluid plasma equations which describe the system. The method used enables us to determine the frequencies and growth rates of unstable modes and the self-consistent electric field. Plasma electrons are considered to have a thermal velocity. One can examine different solutions for the spatial equation in the following cases: A) API in uniform Plasma B) API in nonuniform plasma, we study this case for two variants: B.1) Exact harmonic oscillator and B.2) Bounded harmonic oscillator (bounded plasma). Increment is found in the buildup of the oscillations, and it is shown that the spatial nonuniformity of the plasma exerts a stabilizing effect on the parametric instability. It is shown that the growth rate of API in warm plasma is reduced compared to cold plasma. It is found also that the warmness of the plasma has no effect on the solution of the space part of the problem ( only through the separation constant )

  18. Towards biologically conformal radiation therapy (BCRT): Selective IMRT dose escalation under the guidance of spatial biology distribution

    International Nuclear Information System (INIS)

    Yang Yong; Xing Lei

    2005-01-01

    It is well known that the spatial biology distribution (e.g., clonogen density, radiosensitivity, tumor proliferation rate, functional importance) in most tumors and sensitive structures is heterogeneous. Recent progress in biological imaging is making the mapping of this distribution increasingly possible. The purpose of this work is to establish a theoretical framework to quantitatively incorporate the spatial biology data into intensity modulated radiation therapy (IMRT) inverse planning. In order to implement this, we first derive a general formula for determining the desired dose to each tumor voxel for a known biology distribution of the tumor based on a linear-quadratic model. The desired target dose distribution is then used as the prescription for inverse planning. An objective function with the voxel-dependent prescription is constructed with incorporation of the nonuniform dose prescription. The functional unit density distribution in a sensitive structure is also considered phenomenologically when constructing the objective function. Two cases with different hypothetical biology distributions are used to illustrate the new inverse planning formalism. For comparison, treatments with a few uniform dose prescriptions and a simultaneous integrated boost are also planned. The biological indices, tumor control probability (TCP) and normal tissue complication probability (NTCP), are calculated for both types of plans and the superiority of the proposed technique over the conventional dose escalation scheme is demonstrated. Our calculations revealed that it is technically feasible to produce deliberately nonuniform dose distributions with consideration of biological information. Compared with the conventional dose escalation schemes, the new technique is capable of generating biologically conformal IMRT plans that significantly improve the TCP while reducing or keeping the NTCPs at their current levels. Biologically conformal radiation therapy (BCRT

  19. Gravitational Influences on Flame Propagation through Non-Uniform, Premixed Gas Systems

    Science.gov (United States)

    Miller, Fletcher J.; Easton, John; Ross, Howard D.; Marchese, Anthony; Perry, David; Kulis, Michael

    2001-01-01

    Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized previously, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our progress on furthering the knowledge of layered combustion, in which a fuel concentration gradient exists normal to the direction of flame spread. We present experimental and numerical results for flame spread through propanol-air layers formed near the flash point temperature (25 C) or near the stoichiometric temperature (33 C). Both the model and experimental results show that the removal of gravity results in a faster spreading flame, by as much as 80% depending on conditions. This is exactly the opposite effect as that predicted by an earlier model reported. We also found that having a gallery lid results in faster flame spread, an effect more pronounced at normal gravity, demonstrating the importance of enclosure geometry. Also reported here is the beginning of our spectroscopic measurements of fuel vapor.

  20. Experimental investigation of localized stress-induced leakage current distribution in gate dielectrics using array test circuit

    Science.gov (United States)

    Park, Hyeonwoo; Teramoto, Akinobu; Kuroda, Rihito; Suwa, Tomoyuki; Sugawa, Shigetoshi

    2018-04-01

    Localized stress-induced leakage current (SILC) has become a major problem in the reliability of flash memories. To reduce it, clarifying the SILC mechanism is important, and statistical measurement and analysis have to be carried out. In this study, we applied an array test circuit that can measure the SILC distribution of more than 80,000 nMOSFETs with various gate areas at a high speed (within 80 s) and a high accuracy (on the 10-17 A current order). The results clarified that the distributions of localized SILC in different gate areas follow a universal distribution assuming the same SILC defect density distribution per unit area, and the current of localized SILC defects does not scale down with the gate area. Moreover, the distribution of SILC defect density and its dependence on the oxide field for measurement (E OX-Measure) were experimentally determined for fabricated devices.

  1. The Superconvergence Phenomenon and Proof of the MAC Scheme for the Stokes Equations on Non-uniform Rectangular Meshes

    KAUST Repository

    Li, Jichun

    2014-12-02

    For decades, the widely used finite difference method on staggered grids, also known as the marker and cell (MAC) method, has been one of the simplest and most effective numerical schemes for solving the Stokes equations and Navier–Stokes equations. Its superconvergence on uniform meshes has been observed by Nicolaides (SIAM J Numer Anal 29(6):1579–1591, 1992), but the rigorous proof is never given. Its behavior on non-uniform grids is not well studied, since most publications only consider uniform grids. In this work, we develop the MAC scheme on non-uniform rectangular meshes, and for the first time we theoretically prove that the superconvergence phenomenon (i.e., second order convergence in the (Formula presented.) norm for both velocity and pressure) holds true for the MAC method on non-uniform rectangular meshes. With a careful and accurate analysis of various sources of errors, we observe that even though the local truncation errors are only first order in terms of mesh size, the global errors after summation are second order due to the amazing cancellation of local errors. This observation leads to the elegant superconvergence analysis even with non-uniform meshes. Numerical results are given to verify our theoretical analysis.

  2. Induced charge of spherical dust particle on plasma-facing wall in non-uniform electric field

    International Nuclear Information System (INIS)

    Tomita, Y.; Smirnov, R.; Zhu, S.

    2005-01-01

    Induced charge of a spherical dust particle on a plasma-facing wall is investigated analytically, where non-uniform electric field is applied externally. The one-dimensional non-uniform electrostatic potential is approximated by the polynomial of the normal coordinate toward the wall. The bipolar coordinate is introduced to solve the Laplace equation of the induced electrostatic potential. The boundary condition at the dust surface determines the unknown coefficients of the general solution of the Laplace equation for the induced potential. From the obtained potential the surface induced charge can be calculated. This result allows estimating the effect of the surrounding plasma, which shields the induced charge. (author)

  3. Novel failure mechanism and improvement for split-gate trench MOSFET with large current under unclamped inductive switch stress

    Science.gov (United States)

    Tian, Ye; Yang, Zhuo; Xu, Zhiyuan; Liu, Siyang; Sun, Weifeng; Shi, Longxing; Zhu, Yuanzheng; Ye, Peng; Zhou, Jincheng

    2018-04-01

    In this paper, a novel failure mechanism under unclamped inductive switch (UIS) for Split-Gate Trench Metal Oxide Semiconductor Field Effect Transistor (MOSFET) with large current is investigated. The device sample is tested and analyzed in detail. The simulation results demonstrate that the nonuniform potential distribution of the source poly should be responsible for the failure. Three structures are proposed and verified available to improve the device UIS ruggedness by TCAD simulation. The best one of the structures the device with source metal inserting into source poly through contacts in the field oxide is carried out and measured. The results demonstrate that the optimized structure can balance the trade-off between the UIS ruggedness and the static characteristics.

  4. Environmental Transmission Electron Microscopy Study of the Origins of Anomalous Particle Size Distributions in Supported Metal Catalysts

    DEFF Research Database (Denmark)

    Benavidez, Angelica D.; Kovarik, Libor; Genc, Arda

    2012-01-01

    of the particle size distribution (PSD). The abundance of the larger particles did not fit the log-normal distribution. We can rule out sample nonuniformity as a cause for the growth of these large particles, since images were recorded prior to heat treatments. The anomalous growth of these particles may help...

  5. Unstable Temperature Distribution in Friction Stir Welding

    Directory of Open Access Journals (Sweden)

    Sadiq Aziz Hussein

    2014-01-01

    Full Text Available In the friction stir welding process, a nonuniform and high generated temperature is undesirable. Unstable temperature and distribution affect thermal and residual stresses along the welding line, thus necessitating mitigation. This paper presents a simple method to prevent significant temperature difference along the welding line and also to help nullifying some defect types associated with this welding, such as end-hole, initial unwelded line, and deformed areas. In the experimental investigation, a heat and force thermocouple and dynamometer were utilized while couple-field thermomechanical models were used to evaluate temperature and its distribution, plastic strain, and material displacement. The suggested method generated uniform temperature distributions. Measurement results are discussed, showing a good correlation with predictions.

  6. Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode.

    Science.gov (United States)

    Poehlmann, Flavio R; Cappelli, Mark A; Rieker, Gregory B

    2010-12-01

    Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively.

  7. Linearization of Nonautonomous Impulsive System with Nonuniform Exponential Dichotomy

    Directory of Open Access Journals (Sweden)

    Yongfei Gao

    2014-01-01

    Full Text Available This paper gives a version of Hartman-Grobman theorem for the impulsive differential equations. We assume that the linear impulsive system has a nonuniform exponential dichotomy. Under some suitable conditions, we proved that the nonlinear impulsive system is topologically conjugated to its linear system. Indeed, we do construct the topologically equivalent function (the transformation. Moreover, the method to prove the topological conjugacy is quite different from those in previous works (e.g., see Barreira and Valls, 2006.

  8. CFD analysis of flow distribution at the core inlet of SMART

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Youngmin, E-mail: ybae@kaeri.re.kr [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Kim, Young In; Park, Cheon Tae [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

    2013-05-15

    Highlights: ► Core inlet flow distribution of system-integrated modular advanced reactor (SMART) is numerically investigated. ► Effects of mesh resolution, turbulence model, Reynolds number, and inflow condition are examined. ► Numerical results show that lower core support plate effectively distributes the flow at the core inlet of SMART. -- Abstract: This study numerically investigates the flow distribution at the core inlet region of the system-integrated modular advanced reactor (SMART). The single-phase turbulent flow is computed by the commercial CFD code, Fluent 12.0 on the computational domain consisting of three main parts: fuel assemblies, a lower core support plate, and a flow skirt. Simulations are carried out with different mesh resolutions, turbulence models, and upstream boundary conditions. The CFD results show that the flow distribution at the core inlet is almost identical for the two Reynolds numbers and turbulence models tested here, and the effect of mesh refinement on the flow distribution at the core inlet is negligible. It is also found that under a uniform upstream boundary condition, the maximum difference in mass flow rate between the fuel assemblies is less than 2%, while it slightly increases to 2.3% under a non-uniform condition. These results consequently indicate that the present design of the lower core support plate effectively distributes the flow at the core inlet of SMART, even when the flow discharged from the upstream has a certain degree of non-uniformity.

  9. Electromotive Potential Distribution and Electronic Leak Currents in Working YSZ Based SOCs

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Jacobsen, Torben

    2009-01-01

    The size of electronic leak currents through the YSZ electrolyte of solid oxide cells have been calculated using basic solid state electrochemical relations and literature data. The distribution of the electromotive potential, of Galvani potential, of concentration of electrons, e, and electron...... holes, h, was also calculated as these parameters are the basis for the understanding of the electronic conductivity that causes the electronic leak currents. The results are illustrated with examples. The effects of electrolyte thickness, temperature and cell voltage on the electronic leak current...

  10. Nonuniform nuclear structures and QPOs in giant flares

    International Nuclear Information System (INIS)

    Sotani, Hajime

    2012-01-01

    We show that the shear modes in the neutron star crust are quite sensitive to the existence of nonuniform nuclear structures, the so-called “pasta”. Due to the existence of pasta phase, the frequencies of shear modes are reduced. Since the torsional shear frequencies depend strongly on the structure of pasta phase, through the observations of stellar oscillations, one can probe the pasta structure in the crust. Additionally, considering the effect of pasta phase, we show the possibility to explain all the observed frequencies in the SGR 1806-20 with using only crust torsional oscillations.

  11. Nonuniform nuclear structures and QPOs in giant flares

    Energy Technology Data Exchange (ETDEWEB)

    Sotani, Hajime [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

    2012-11-12

    We show that the shear modes in the neutron star crust are quite sensitive to the existence of nonuniform nuclear structures, the so-called 'pasta'. Due to the existence of pasta phase, the frequencies of shear modes are reduced. Since the torsional shear frequencies depend strongly on the structure of pasta phase, through the observations of stellar oscillations, one can probe the pasta structure in the crust. Additionally, considering the effect of pasta phase, we show the possibility to explain all the observed frequencies in the SGR 1806-20 with using only crust torsional oscillations.

  12. Pressure gradient effect at distributed excitation of 3D TS waves by freestream and wall disturbances

    Directory of Open Access Journals (Sweden)

    Borodulin Vladimir

    2017-01-01

    Full Text Available The present work is a continuation of previous experiments (carried out in the Blasius boundary layer and devoted to quantitative investigation of influence of an adverse pressure gradient on two efficient mechanisms of excitation of 3D TS instability waves due to a distributed boundary layer receptivity to free-stream vortices. These mechanisms are associated with distributed scattering of 3D amplified free-stream vortices both on the natural boundary-layer nonuniformity (on smooth surface and on 2D surface nonuniformities (waviness. The corresponding detailed hotwire measurements were carried out in a self-similar boundary layer with Hartree parameter βH = –0.115 in a wide range of the problem parameters. Complex values of quantitative characteristics of the physical phenomenon under study (the distributed receptivity coefficients are evaluated by based on the obtained experimental data. It is found that the adverse pressure gradient leads to reduction of efficiency of the investigated vortexroughness receptivity mechanism.

  13. A current controller of grid-connected converter for harmonic damping in a distribution network

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

    2011-01-01

    Harmonic resonance caused by the increased use of shunt-connected capacitors in LCL-filters and power factor correction devices may become a serious power quality challenge in electric distribution systems. A voltage-detection method based on current control is developed to damp harmonic resonances....... However, it is susceptible to the mismatch between harmonic conductance and characteristic impedance of distribution feeder. This paper proposes a current controller which allows discrete adjustment of harmonic conductance for both the characteristic harmonic and the non-characteristic harmonic voltages...

  14. On the magnitude and distribution of halo currents during disruptions on MAST

    International Nuclear Information System (INIS)

    Counsell, G F; Martin, R; Pinfold, T; Taylor, D

    2007-01-01

    Recent results from MAST in which all halo current paths are monitored suggest that, during disruptions, the plasma responsible for the generation of halo current acts more as a voltage source than a current source. As a result the resistance of the current path along which the halo current must flow has a profound impact on the magnitude of the current. This may provide opportunities for directing the current away from sensitive components in future devices such as ITER. Analysis of data from over 3800 disruptions shows that the halo currents on MAST are relatively benign, having a peak value less than 25% of the pre-disruption plasma current with a rather symmetric distribution near the centre column (average toroidal peaking factor ∼1.1). The low peaking factor favourably reduces the tilting/bending forces in the region of the centre column, which has limited space for bulky supports

  15. [Ecological affinity and current distribution of primates (Cebidae) in Campeche, Mexico].

    Science.gov (United States)

    Navarro Fernández, Eloísa; Pozo de la Tijera, Carmen; Escobedo Cabrera, Enrique

    2003-06-01

    We carried out surveys realized field work from March to September 2000 to get the current distribution of Cebids in the state of Campeche, Mexico. Based on interviews and direct observations. We defined the distribution of Ateles geoffroyi yucatanensis and Alouatta pigra and we documented the first time localities where Allouata palliata is found in the state. We made distributional maps of each species using vegetation overlays from Inventario Nacional Forestal (Inv For) and each point documented during fieldwork. We presented the distribution of species according to confiability of the verified or expected data. Using the attributes table of Inv For, we calculated the areas of distribution which were 22,735 km2 for Alouatta sp. and 18,501 km2 for A. g. yucatanensis. We also presented the area occupied by each species according to vegetation types and the relative proportion of these vegetation types in the state. We confirmed the ability of Alouatta sp. to survive in disturbed environments produced by habitat fragmentation, and the affinity of A. g. yucatanesis to well preserved habitats.

  16. A distributed current stimulator ASIC for high density neural stimulation.

    Science.gov (United States)

    Jeong Hoan Park; Chaebin Kim; Seung-Hee Ahn; Tae Mok Gwon; Joonsoo Jeong; Sang Beom Jun; Sung June Kim

    2016-08-01

    This paper presents a novel distributed neural stimulator scheme. Instead of a single stimulator ASIC in the package, multiple ASICs are embedded at each electrode site for stimulation with a high density electrode array. This distributed architecture enables the simplification of wiring between electrodes and stimulator ASIC that otherwise could become too complex as the number of electrode increases. The individual ASIC chip is designed to have a shared data bus that independently controls multiple stimulating channels. Therefore, the number of metal lines is determined by the distributed ASICs, not by the channel number. The function of current steering is also implemented within each ASIC in order to increase the effective number of channels via pseudo channel stimulation. Therefore, the chip area can be used more efficiently. The designed chip was fabricated with area of 0.3 mm2 using 0.18 μm BCDMOS process, and the bench-top test was also conducted to validate chip performance.

  17. Electric field distribution and current emission in a miniaturized geometrical diode

    Science.gov (United States)

    Lin, Jinpu; Wong, Patrick Y.; Yang, Penglu; Lau, Y. Y.; Tang, W.; Zhang, Peng

    2017-06-01

    We study the electric field distribution and current emission in a miniaturized geometrical diode. Using Schwarz-Christoffel transformation, we calculate exactly the electric field inside a finite vacuum cathode-anode (A-K) gap with a single trapezoid protrusion on one of the electrode surfaces. It is found that there is a strong field enhancement on both electrodes near the protrusion, when the ratio of the A-K gap distance to the protrusion height d /h spot checked against COMSOL simulations. We calculate the effective field enhancement factor for the field emission current, by integrating the local Fowler-Nordheim current density along the electrode surfaces. We systematically examine the electric field enhancement and the current rectification of the miniaturized geometrical diode for various geometric dimensions and applied electric fields.

  18. Study on classical and excess eddy currents losses of Terfenol-D

    Energy Technology Data Exchange (ETDEWEB)

    Talebian, Soheil; Hojjat, Yousef [Department of Mechanical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Ghodsi, Mojtaba [Department of Mechanical and Industrial Engineering, Sultan Qaboos University, Muscat (Oman); Karafi, Mohammad Reza [Department of Mechanical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of)

    2015-08-15

    In the present paper, classical and excess eddy currents losses of Terfenol-D are studied and effects of magnetic field frequency, peak of magnetic flux density and diameter of Terfenol-D on the eddy currents losses are investigated. To provide reliable data for the purpose of the paper, an experimental laboratory is fabricated and used to obtain major and minor hysteresis loops of Terfenol-D at different frequencies. In theoretical study, initially an analytical model based on uniform distribution of magnetic flux is developed which yields to calculation of classical eddy currents losses. Then, another eddy currents model based on non-uniform distribution of magnetic flux and nonlinear diffusion of electromagnetic fields is presented. The difference between output values of the two models is identified as excess eddy currents losses. Obtained results show that the values of excess losses are generally larger than classical losses and applying just classical model leads to wrong calculation of actual value of eddy currents losses. For the results obtained from two above models, empirical models with respect to the magnetic field frequency and the peak value of magnetic flux density are achieved which can predict the eddy currents losses precisely. To validate the empirical relations, experiments are repeated at a new frequency and values of power losses calculated from analytical equations are compared with the predicted values of the empirical models. The results point towards possibility to use the obtained empirical relations in order to calculate the classical and excess eddy currents losses of Terfenol-D at the frequencies below 200 Hz and different values of magnetic flux density. - Highlights: • Classical eddy currents loss of Terfenol-D is studied using Maxwell's laws. • Excess eddy currents loss of Terfenol-D is studied using Mayergoyz nonlinear model. • Effects of Terfenol-D geometry on the eddy currents losses are investigated. • Power

  19. Non-uniform velocity profile mechanism for flame stabilization in a porous radiant burner

    Energy Technology Data Exchange (ETDEWEB)

    Catapan, R.C.; Costa, M. [Mechanical Engineering Department, Instituto Superior Tecnico, Technical University of Lisbon, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal); Oliveira, A.A.M. [Mechanical Engineering Department, Federal University of Santa Catarina, Campus Universitario Professor Joao David Ferreira Lima, 88040-900 Florianopolis, SC (Brazil)

    2011-01-15

    Industrial processes where the heating of large surfaces is required lead to the possibility of using large surface porous radiant burners. This causes additional temperature uniformity problems, since it is increasingly difficult to evenly distribute the reactant mixture over a large burner surface while retaining its stability and keeping low pollutant emissions. In order to allow for larger surface area burners, a non-uniform velocity profile mechanism for flame stabilization in a porous radiant burner using a single large injection hole is proposed and analyzed for a double-layered burner operating in open and closed hot (laboratory-scale furnace, with temperature-controlled, isothermal walls) environments. In both environments, local mean temperatures within the porous medium have been measured. For lower reactant flow rate and ambient temperature the flame shape is conical and anchored at the rim of the injection hole. As the volumetric flow rate or furnace temperature is raised, the flame undergoes a transition to a plane flame stabilized near the external burner surface. However, the stability range envelope remains the same in both regimes. (author)

  20. Theoretical investigations on two-phase flow instability in parallel channels under axial non-uniform heating

    International Nuclear Information System (INIS)

    Lu, Xiaodong; Wu, Yingwei; Zhou, Linglan; Tian, Wenxi; Su, Guanghui; Qiu, Suizheng; Zhang, Hong

    2014-01-01

    Highlights: • We developed a model based on homogeneous flow model to analyze two-phase flow instability in parallel channels. • The influence of axial non-uniform heating on the system stability has been investigated. • Influences of various factors on system instability under cosine heat flux have been studied. • The system under top-peaked heat flux is the most stable system. - Abstract: Two-phase flow instability in parallel channels heated by axial non-uniform heat flux has been theoretically studied in this paper. The system control equations of parallel channels were established based on the homogeneous flow model in two-phase region. Semi-implicit finite-difference scheme and staggered mesh method were used to discretize the equations, and the difference equations were solved by chasing method. Cosine, bottom-peaked and top-peaked heat fluxes were used to study the influence of non-uniform heating on two-phase flow instability of the parallel channels system. The marginal stability boundaries (MSB) of parallel channels and three-dimensional instability spaces (or instability reefs) under different heat flux conditions have been obtained. Compared with axial uniform heating, axial non-uniform heating will affect the system stability. Cosine and bottom-peaked heat fluxes can destabilize the system stability in high inlet subcooling region, while the opposite effect can be found in low inlet subcooling region. However, top-peaked heat flux can enhance the system stability in the whole region. In addition, for cosine heat flux, increasing the system pressure or inlet resistance coefficient can strengthen the system stability, and increasing the heating power will destabilize the system stability. The influence of inlet subcooling number on the system stability is multi-valued under cosine heat flux

  1. DC current distribution mapping system of the solar panels using a HTS-SQUID gradiometer

    International Nuclear Information System (INIS)

    Miyazaki, Shingo; Kasuya, Syohei; Saari, Mohd Mawardi; Sakai, Kenji; Kiwa, Toshihiko; Tsukada, Keiji; Tsukamoto, Akira; Adachi, Seiji; Tanabe, Keiichi

    2014-01-01

    Solar panels are expected to play a major role as a source of sustainable energy. In order to evaluate solar panels, non-destructive tests, such as defect inspections and response property evaluations, are necessary. We developed a DC current distribution mapping system of the solar panels using a High Critical Temperature Superconductor Superconducting Quantum Interference Device (HTS-SQUID) gradiometer with ramp edge type Josephson junctions. Two independent components of the magnetic fields perpendicular to the panel surface (∂Bz/∂x, ∂Bz/∂y) were detected. The direct current of the solar panel is visualized by calculating the composition of the two signal components, the phase angle, and mapping the DC current vector. The developed system can evaluate the uniformity of DC current distributions precisely and may be applicable for defect detection of solar panels.

  2. Lightning current distribution and hard radiation in aircraft, measured in-flight

    NARCIS (Netherlands)

    van Deursen, A.P.J.; Kochkin, P.; de Boer, A.; Bardet, M.; Allasia, C.; Boissin, J.F.; Flourens, F.

    2017-01-01

    The In-flight Lightning Damage Assessment System ILDAS has been presented in EMC Europe in 2012. ILDAS can determine the lightning current distribution on an aircraft with high resolution in time and amplitude. Later the system was extended and included two x-ray detectors to measure the high-energy

  3. New method for solving inductive electric fields in the non-uniformly conducting ionosphere

    Directory of Open Access Journals (Sweden)

    H. Vanhamäki

    2006-10-01

    Full Text Available We present a new calculation method for solving inductive electric fields in the ionosphere. The time series of the potential part of the ionospheric electric field, together with the Hall and Pedersen conductances serves as the input to this method. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition, no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called the Cartesian Elementary Current Systems (CECS. This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfvén wave reflection from a uniformly conducting ionosphere.

  4. New method for solving inductive electric fields in the non-uniformly conducting ionosphere

    Science.gov (United States)

    Vanhamäki, H.; Amm, O.; Viljanen, A.

    2006-10-01

    We present a new calculation method for solving inductive electric fields in the ionosphere. The time series of the potential part of the ionospheric electric field, together with the Hall and Pedersen conductances serves as the input to this method. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition, no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called the Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfvén wave reflection from a uniformly conducting ionosphere.

  5. Gyrokinetic approach to the propagation of electromagnetic waves in nonuniform bounded plasma slabs

    International Nuclear Information System (INIS)

    Sauter, O.; Vaclavik, J.

    1994-05-01

    A new code, SEMAL, has been developed which solves the linearized Vlasov-Maxwell wave equations to all orders in Larmor radii. Arbitrary density and temperature profiles as well as nonuniform magnetic fields are considered in slab geometry. The vacuum regions adjacent to the plasma slab are limited by perfect conducting walls and contain an antenna as an excitation source. The linear response is obtained by solving the system of one first-order and two second-order integro-differential equations using a non-polluting finite element discretization. The general equations in the Fourier space, derived in a new comprehensive way, and their inverse transform, using k y =0, are described as well as the convergence and non-polluting properties of the method. We present the results concerning the influence of alpha particles on ICRF heating schemes for ITER, where we show that small alphas concentration can alter the steady-state operation envisaged with ICRF fast wave current-drive. (author) 7 figs., 3 tabs., 28 refs

  6. Probing Photocurrent Nonuniformities in the Subcells of Monolithic Perovskite/Silicon Tandem Solar Cells

    KAUST Repository

    Song, Zhaoning

    2016-11-23

    Perovskite/silicon tandem solar cells with high power conversion efficiencies have the potential to become a commercially viable photovoltaic option in the near future. However, device design and optimization is challenging because conventional characterization methods do not give clear feedback on the localized chemical and physical factors that limit performance within individual subcells, especially when stability and degradation is a concern. In this study, we use light beam induced current (LBIC) to probe photocurrent collection nonuniformities in the individual subcells of perovskite/silicon tandems. The choices of lasers and light biasing conditions allow efficiency-limiting effects relating to processing defects, optical interference within the individual cells, and the evolution of water-induced device degradation to be spatially resolved. The results reveal several types of microscopic defects and demonstrate that eliminating these and managing the optical properties within the multilayer structures will be important for future optimization of perovskite/silicon tandem solar cells.

  7. Absolute parametric instability of low frequency waves in a 2-D nonuniform anisotropic warm plasma

    International Nuclear Information System (INIS)

    Zaki, N.G.

    2004-01-01

    Using the separation method, the problem of absolute parametric instability (API) of electrostatic waves in magnetized pumped warm plasma is investigated. In this case the effect of static strong magnetic field is considered. The problem of strong magnetic field is solved in 2-D nonuniform plane plasma. The equations which describe the spatial part of the electric potential are obtained. Also the growth rates and conditions of the parametric instability for periodic cases are obtained. It is found that the spatial nonuniformity of the plasma exerts a stabilizing effect on the API. It is shown that the growth rates of periodic and aperiodic API in warm plasma are reduced in comparison with a cold plasma case

  8. Analysis of cesium-137 vertical distribution in the profile of plowed chernozems at different schemes of their assaying

    International Nuclear Information System (INIS)

    Paramonova, T.A.; Komissarova, O.L.; Belyaev, V.R.; Ivanov, M.M.

    2016-01-01

    In 2011-2015 the assessment of profile cesium-137 distribution in agrocenosis of chernozem zone on the territory of the Plavsk radioactive spot in Tula region formed after the Chernobyl accident has been carried out. It is shown that up until now non-uniformity of cesium-137 vertical distribution over the plowed chernozems profile may be occurred, it should be taken into account at radioecological survey of post-Chernobyl landscapes. For correct evaluation of radioecological state of plowed soils their systematic monitoring on the base of preliminary analysis of cesium-137 distribution and also with the account of agrotechnical peculiarities of various crops cultivation is recommended. On the Plavsk radioactive spot territory the most adequate assessments of cesium-137 stores in plowed chernozems one can obtain on the base of assaying the upper 30-cm soil depth, including not only current topsoil, but also old-arable horizon formed by deep rehabilitation plowing [ru

  9. Modeling Bubble Flow and Current Density Distribution in an Alkaline Electrolysis Cell

    Directory of Open Access Journals (Sweden)

    Ravichandra S. Jupudi

    2009-12-01

    Full Text Available The effect of bubbles on the current density distribution over the electrodes of an alkaline electrolyzer cell is studied using a two-dimensional computational fluid dynamics model. Model includes Eulerian-Eulerian two-phase flow methodology to model the multiphase flow of Hydrogen and Oxygen with water and the behavior of each phase is accounted for using first principle. Hydrogen/Oxygen evolution, flow field and current density distribution are incorporated in the model to account for the complicated physics involved in the process. Fluent 6.2 is used to solve two-phase flow and electrochemistry is incorporated using UDF (User Defined Function feature of Fluent. Model is validated with mesh refinement study and by comparison with experimental measurements. Model is found to replicate the effect of cell voltage and inter-electrode gap (distance between the electrodes on current density accurately. Further, model is found to capture the existence of optimum cell height. The validated model is expected to be a very useful tool in the design and optimization of alkaline electrolyzer cells.

  10. Plasma conditions for non-Maxwellian electron distributions in high current discharges and laser-produced plasmas

    International Nuclear Information System (INIS)

    Whitney, K.G.; Pulsifer, P.E.

    1993-01-01

    Results from the standard quasilinear theory of ion-acoustic and Langmuir plasma microturbulence are incorporated into the kinetic theory of the electron distribution function. The theory is then applied to high current discharges and laser-produced plasmas, where either the current flow or the nonlinear laser-light absorption acts, respectively, as the energy source for the microturbulence. More specifically, the theory is applied to a selenium plasma, whose charge state is determined under conditions of collisional-radiative equilibrium, and plasma conditions are found under which microturbulence strongly influences the electron kinetics. In selenium, we show that this influence extends over a wide range of plasma conditions. For ion-acoustic turbulence, a criterion is derived, analogous to one previously obtained for laser heated plasmas, that predicts when Ohmic heating dominates over electron-electron collisions. This dominance leads to the generation of electron distributions with reduced high-energy tails relative to a Maxwellian distribution of the same temperature. Ion-acoustic turbulence lowers the current requirements needed to generate these distributions. When the laser heating criterion is rederived with ion-acoustic turbulence included in the theory, a similar reduction in the laser intensity needed to produce non-Maxwellian distributions is found. Thus we show that ion-acoustic turbulence uniformly (i.e., by the same numerical factor) reduces the electrical and heat conductivities, as well as the current (squared) and laser intensity levels needed to drive the plasma into non-Maxwellian states

  11. Design of multiplier-less sharp non-uniform cosine modulated filter banks for efficient channelizers in software defined radio

    Directory of Open Access Journals (Sweden)

    Shaeen Kalathil

    2016-03-01

    Full Text Available Forthcoming software defined radios require filter banks which satisfy stringent specifications efficiently with low implementation complexity. Cosine modulated filter banks (CMFB have simple and efficient design procedure. The different wireless standards have different channel spacing or bandwidths and hence demand non-uniform decomposition of subbands. The non-uniform CMFB can be obtained from a uniform CMFB in a simple and efficient approach by merging the adjacent channels of the uniform CMFB. Very narrow transition width filters with low complexity can be achieved using frequency response masking (FRM filter as prototype filter. The complexity is further reduced by the multiplier-less realization of filter banks in which the least number of signed power of two (SPT terms is achieved by representing the filter coefficients using canonic signed digit (CSD representation and then optimizing using suitable modified meta-heuristic algorithms. Hybrid meta-heuristic algorithms are used in this paper. A hybrid algorithm combines the qualities of two meta-heuristic algorithms and results in improved performances with low implementation complexity. Highly frequency selective filter banks characterized by small passband ripple, narrow transition width and high stopband attenuation with non-uniform decomposition of subbands can be designed with least the implementation complexity, using this approach. A digital channelizer can be designed for SDR implementations, using the proposed approach. In this paper, the non-uniform CMFB is designed for various existing wireless standards.

  12. [Measures of occupational exposure to time-varying low frequency magnetic fields of non-uniform spatial distribution in the light of international guidelines and electrodynamic exposure effects in the human body].

    Science.gov (United States)

    Karpowicz, Jolanta; Zradziński, Patryk; Gryz, Krzysztof

    2012-01-01

    The aim of study was to analyze by computer simulations the electrodynamic effects of magnetic field (MF) on workers, to harmonize the principles of occupational hazards assessment with international guidelines. Simulations involved 50 Hz MF of various spatial distributions, representing workers' exposure in enterprises. Homogeneous models of sigma = 0.2 S/m conductivity and dimensions of body parts - palm, head and trunk - were located at 50 cm ("hand-distance") or 5 cm (adjacent) from the source (circle conductor of 20 cm or 200 cm in diameter). Parameters of magnetic flux density (B(i)) affecting the models were the exposure measures, and the induced electric field strength (E(in)) was the measure of MF exposure effects. The ratio E(in)/B(i) in the analyzed cases ranged from 2.59 to 479 (V/m)/T. The strongest correlation (p assessing the effects of non-uniform fields exposure, resulting from a strong dependence of the E(in)/B(i) ratio on the conditions of exposure and its applied measures, requires special caution when defining the permissible MF levels and the principles of exposure assessment at workplace.

  13. Effect of disjoining pressure in a thin film equation with non-uniform forcing

    KAUST Repository

    MOULTON, D. E.; LEGA, J.

    2013-01-01

    We explore the effect of disjoining pressure on a thin film equation in the presence of a non-uniform body force, motivated by a model describing the reverse draining of a magnetic film. To this end, we use a combination of numerical investigations

  14. Core Flow Distribution from Coupled Supercritical Water Reactor Analysis

    Directory of Open Access Journals (Sweden)

    Po Hu

    2014-01-01

    Full Text Available This paper introduces an extended code package PARCS/RELAP5 to analyze steady state of SCWR US reference design. An 8 × 8 quarter core model in PARCS and a reactor core model in RELAP5 are used to study the core flow distribution under various steady state conditions. The possibility of moderator flow reversal is found in some hot moderator channels. Different moderator flow orifice strategies, both uniform across the core and nonuniform based on the power distribution, are explored with the goal of preventing the reversal.

  15. Understanding Breaks in Flare X-Ray Spectra: Evaluation of a Cospatial Collisional Return-current Model

    Science.gov (United States)

    Alaoui, Meriem; Holman, Gordon D.

    2017-12-01

    Hard X-ray (HXR) spectral breaks are explained in terms of a one-dimensional model with a cospatial return current. We study 19 flares observed by the Ramaty High Energy Solar Spectroscopic Imager with strong spectral breaks at energies around a few deka-keV, which cannot be explained by isotropic albedo or non-uniform ionization alone. We identify these breaks at the HXR peak time, but we obtain 8 s cadence spectra of the entire impulsive phase. Electrons with an initially power-law distribution and a sharp low-energy cutoff lose energy through return-current losses until they reach the thick target, where they lose their remaining energy through collisions. Our main results are as follows. (1) The return-current collisional thick-target model provides acceptable fits for spectra with strong breaks. (2) Limits on the plasma resistivity are derived from the fitted potential drop and deduced electron-beam flux density, assuming the return current is a drift current in the ambient plasma. These resistivities are typically 2–3 orders of magnitude higher than the Spitzer resistivity at the fitted temperature, and provide a test for the adequacy of classical resistivity and the stability of the return current. (3) Using the upper limit of the low-energy cutoff, the return current is always stable to the generation of ion-acoustic and electrostatic ion-cyclotron instabilities when the electron temperature is nine times lower than the ion temperature. (4) In most cases, the return current is most likely primarily carried by runaway electrons from the tail of the thermal distribution rather than by the bulk drifting thermal electrons. For these cases, anomalous resistivity is not required.

  16. ROC evaluation of SPECT myocardial lesion detectability with and without single iteration non-uniform Chang attenuation compensation using an anthropomorphic female phantom

    International Nuclear Information System (INIS)

    Jang, S.; Jaszczak, R.J.; Duke Univ. Medical Center, Durham, NC; Gilland, D.R.; Turkington, T.G.; Coleman, R.E.; Tsui, B.M.W.; Metz, C.E.

    1998-01-01

    The purpose of this work was to evaluate lesion detectability with and without nonuniform attenuation compensation (AC) in myocardial perfusion SPECT imaging in women using an anthropomorphic phantom and receiver operating characteristics (ROC) methodology. Breast attenuation causes artifacts in reconstructed images and may increase the difficulty of diagnosis of myocardial perfusion imaging in women. The null hypothesis tested using the ROC study was that nonuniform AC does not change the lesion detectability in myocardial perfusion SPECT imaging in women. The authors used a filtered backprojection (FBP) reconstruction algorithm and Chang's single iteration method for AC. In conclusion, with the proposed myocardial defect model nuclear medicine physicians demonstrated no significant difference for the detection of the anterior wall defect; however, a greater accuracy for the detection of the inferior wall defect was observed without nonuniform AC than with it. Medical physicists did not demonstrate any statistically significant difference in defect detection accuracy with or without nonuniform AC in the female phantom

  17. Investigation of non-uniformity and inclusions in 6LiInSe2 utilizing laser induced breakdown spectroscopy (LIBS)

    Science.gov (United States)

    Wiggins, Brenden; Tupitsyn, Eugene; Bhattacharya, Pijush; Rowe, Emmanuel; Lukosi, Eric; Chvala, Ondrej; Burger, Arnold; Stowe, Ashley

    2013-09-01

    Impurity analysis and compositional distribution studies have been conducted on a crystal of LiInSe2, a compound semiconductor which recently has been shown to respond to ionizing radiation. IR microscopy and laser induced breakdown spectroscopy (LIBS) revealed the presence of inclusions within the crystal lattice. These precipitates were revealed to be alkali and alkaline earth elemental impurities with non-uniform spatial distribution in the crystal. LIBS compositional maps correlate the presence of these impurities with visual color differences in the crystal as well as a significant shift of the band gap. Further, LIBS revealed variation in the ratio of I-III-VI2 elemental constituents throughout the crystal. Analysis of compositional variation and impurities will aid in discerning optimal synthesis and crystal growth parameters to maximize the mobility-lifetime product and charge collection efficiency in the LiInSe2 crystal. Preliminary charge trapping calculations have also been conducted with the Monte Carlo N-particle eXtended (MCNPx) package indicating preferential trapping of holes during irradiation with thermal neutrons.

  18. Distributed Cooperative Current-Sharing Control of Parallel Chargers Using Feedback Linearization

    Directory of Open Access Journals (Sweden)

    Jiangang Liu

    2014-01-01

    Full Text Available We propose a distributed current-sharing scheme to address the output current imbalance problem for the parallel chargers in the energy storage type light rail vehicle system. By treating the parallel chargers as a group of agents with output information sharing through communication network, the current-sharing control problem is recast as the consensus tracking problem of multiagents. To facilitate the design, input-output feedback linearization is first applied to transform the nonidentical nonlinear charging system model into the first-order integrator. Then, a general saturation function is introduced to design the cooperative current-sharing control law which can guarantee the boundedness of the proposed control. The cooperative stability of the closed-loop system under fixed and dynamic communication topologies is rigorously proved with the aid of Lyapunov function and LaSalle invariant principle. Simulation using a multicharging test system further illustrates that the output currents of parallel chargers are balanced using the proposed control.

  19. Determination of High-Frequency Current Distribution Using EMTP-Based Transmission Line Models with Resulting Radiated Electromagnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Mork, B; Nelson, R; Kirkendall, B; Stenvig, N

    2009-11-30

    Application of BPL technologies to existing overhead high-voltage power lines would benefit greatly from improved simulation tools capable of predicting performance - such as the electromagnetic fields radiated from such lines. Existing EMTP-based frequency-dependent line models are attractive since their parameters are derived from physical design dimensions which are easily obtained. However, to calculate the radiated electromagnetic fields, detailed current distributions need to be determined. This paper presents a method of using EMTP line models to determine the current distribution on the lines, as well as a technique for using these current distributions to determine the radiated electromagnetic fields.

  20. Quantum ratchet effect in a time non-uniform double-kicked model

    Science.gov (United States)

    Chen, Lei; Wang, Zhen-Yu; Hui, Wu; Chu, Cheng-Yu; Chai, Ji-Min; Xiao, Jin; Zhao, Yu; Ma, Jin-Xiang

    2017-07-01

    The quantum ratchet effect means that the directed transport emerges in a quantum system without a net force. The delta-kicked model is a quantum Hamiltonian model for the quantum ratchet effect. This paper investigates the quantum ratchet effect based on a time non-uniform double-kicked model, in which two flashing potentials alternately act on a particle with a homogeneous initial state of zero momentum, while the intervals between adjacent actions are not equal. The evolution equation of the state of the particle is derived from its Schrödinger equation, and the numerical method to solve the evolution equation is pointed out. The results show that quantum resonances can induce the ratchet effect in this time non-uniform double-kicked model under certain conditions; some quantum resonances, which cannot induce the ratchet effect in previous models, can induce the ratchet effect in this model, and the strengths of the ratchet effect in this model are stronger than those in previous models under certain conditions. These results enrich people’s understanding of the delta-kicked model, and provides a new optional scheme to control the quantum transport of cold atoms in experiment.