Asymmetric Coefficients Research Articles

Thermoelectric effects in quantum Hall systems beyond linear response

We consider a quantum Hall system with an antidot acting as a energy dependent scatterer. In the purely charge case, we find deviations from the Wiedemann-Franz law that take place in the nonlinear regime of transport. We also discuss Peltier effects beyond linear response and describe both effects using magnetic-field asymmetric transport coefficients. For the spin case such as that arising along the helical edge states of a two-dimensional topological insulator, we investigate the generation of spin currents as a result of applied voltage and temperature differences in samples attached to ferromagnetic leads. We find that in the parallel configuration the spin current can be tuned with the leads' polarization even in the linear regime of transport. In contrast, for antiparallel magnetizations the spin currents has a strict nonlinear dependence on the the applied fields.

Infestation of weed species in monocrop coffee or intercropped with banana, under agroecological system

We aimed with this study to compare weed infestation in coffee under two different cropping managements: conventional coffee grown alone, or intercropped with banana plantation in a year-round basis (late spring, late summer, late fall and late winter). The experiment was installed in 2009 under field conditions at the Escola Municipal Rural Benedita Figueiró de Oliveira, in the city of Ivinhema in the state of Mato Grosso do Sul, Brazil. Assessments of weed occurrence were made three years after employment, on both cropping systems, and density, frequency, dominance and the importance value for each plant species in each system and season were quantified. Plant diversity within each system was estimated by Simpson and Shannon-Weiner indexes. Similarity between cropping systems were also assessed by the binary asymmetric similarity coefficient of Jaccard. Absolute infestation and spontaneous species differed between the two cropping systems in all seasons. Overall species diversity is higher in the monocrop compared with the intercrop, and it is associated in this study with the higher incidence of troublesome species. Areas were similar in terms of weed composition only in the Fall. Shading provided by the banana trees shows to be an efficient culture management aiming to suppress weeds in agro-ecological planting systems.

A Fifth-Order Low-Dissipative Conservative Upwind Compact Scheme Using Centered Stencil

AbstractIn this paper, a conservative fifth-order upwind compact scheme using centered stencil is introduced. This scheme uses asymmetric coefficients to achieve the upwind property since the stencil is symmetric. Theoretical analysis shows that the proposed scheme is low-dissipative and has a relatively large stability range. To maintain the convergence rate of the whole spatial discretization, a proper non-periodic boundary scheme is also proposed. A detailed analysis shows that the spatial discretization implemented with the boundary scheme proposed by Pirozzoli [J. Comput. Phys., 178 (2001), pp. 81–117] is approximately fourth-order. Furthermore, a hybrid methodology, coupling the compact scheme with WENO scheme, is adopted for problems with discontinuities. Numerical results demonstrate the effectiveness of the proposed scheme.

A Fifth-Order Low-Dissipative Conservative Upwind Compact Scheme Using Centered Stencil

In this paper, a conservative fifth-order upwind compact scheme using centered stencil is introduced. This scheme uses asymmetric coefficients to achieve the upwind property since the stencil is symmetric. Theoretical analysis shows that the proposed scheme is low-dissipative and has a relatively large stability range. To maintain the convergence rate of the whole spatial discretization, a proper non-periodic boundary scheme is also proposed. A detailed analysis shows that the spatial discretization implemented with the boundary scheme proposed by Pirozzoli [J. Comput. Phys., 178 (2001), pp. 81–117] is approximately fourth-order. Furthermore, a hybrid methodology, coupling the compact scheme with WENO scheme, is adopted for problems with discontinuities. Numerical results demonstrate the effectiveness of the proposed scheme.

Co-Movements of US and Asian Equity Markets: Evidence from Asymmetric and Time-Varying Coefficients

We examine co-movements of nine Asian equity markets with both the US and Japan with special interest in distinguishing co-movements during periods of positive returns from those during periods of negative returns. A discrete asymmetric piecewise linear conditional mean returns specification is adopted to generate asymmetric co-movement parameters for periods of positive and negative returns. Conditional heteroskedasticity is modeled using GARCH and EGARCH specifications. Predicted conditional volatilities are used to generate alternative estimates of asymmetric and time-varying co-movement parameters. Conditional mean returns from asymmetric and symmetric conditional mean return models along with GARCH and EGARCH volatilities are used to generate estimates of asymmetric and symmetric conditional (ex-ante) Sharpe ratios. Asian markets returns and volatilities show a clear tendency to move more with the US than with Japan; and their co-movements with negative US returns far exceed their co-movements with positive US returns, thereby suggesting that any diversification benefits into Asian equities are likely to manifest themselves more during periods of positive than negative US returns. Conditional asymmetric Sharpe ratios exceed conditional symmetric Sharpe ratios; however, and more importantly, performance-ranking differs depending on whether asymmetric versus symmetric conditional Sharpe ratios are used. Asymmetric conditional Sharpe ratios suggest that India (followed by Malaysia) offers the best return/risk tradeoff, with the least favorable market is South Korea (using GARCH) and Philippines (using EGARCH).

Effects of Asymmetric Coupling on Winding AC Resistance in Medium-Frequency High-Power Transformer

Medium-frequency high-power (MFHP) isolated dc/dc converter has been extensively employed in various applications, including the high-voltage dc, distributed generation, high-speed railway, more electric ship, and more electric aircraft. The MFHP transformer is one of the most important components of the dc/dc converter. In MFHP application, the circulating current often occurs in the parallel secondary windings for transformer with foil-wound winding, together with primary-series secondary-parallel (PSSP) structure. It is because of the existence of asymmetric mutual inductance, described as asymmetric coupling between the primary and the secondary winding, that the absolutely symmetry cannot be achieved. Thus, a knee frequency exists, which in turn leads to significantly increased ac resistance if the working frequency of transformer is set above it. To predict the knee frequency caused by asymmetric coupling in windings, an analytical model together with a scaled-down experimental transformer to obtain the asymmetrical coupling coefficients is developed to predict the knee frequency for real-scaled transformer. The accuracy of developed analytical model is validated by the measured result. Then, a prototype 980 kVA megawatt-level MFHP transformer having PSSP structure is been built based on the analytical and experimental optimized knee frequency.

수산물 거래량의 변동성이 가격변동성에 미치는 영향분석

Abstract This paper presents the GJR GARCH model (Glosten et. al, 1993) to analyze the influences of volumevolatilities on price volatilities in the fishery market. For the analysis, this study used the monthly price and volume data of aquacultural flatfish in Jeju. As a result, empirical analysis suggested volatility clustering. The persistency parameter( ) was estimated to be approximately 1 in aquacultural flatfish. The results showed that there is a significant negative relationship between the conditional variance of supply and that of price for aquacultural flatfish.This means that the general law of supply is valid. Finally, the empirical analysis was that an asymmetric coefficient ( ) of GJR GARCH model was negative (-). This means that the higher volatility of volume leads to lower pricevolatility. That is, it is useful to make government policies that can adjust the volume (stockpiling, stabilizing supply and demand). Key Words : GJR GARCH, Price Volatilities, Volume Volatilities, Fishery Market, Aquacultural Flatfish, Volatility Clustering

Symmetrization Method for the Generalized Plasticity Model with Nonassociated Plastic Flow Rule

AbstractWhen the generalized plasticity model with nonassociated flow rule is utilized to simulate the mechanical behaviors of sands, the asymmetric elastoplastic matrices or coefficient matrix has to be encountered in finite-element (FE) computations, posing a great challenge to the solution of large-scale asymmetric linear systems of equations. In this study, a simple symmetrization method for the asymmetric stiffness matrix attributable to the generalized plasticity model is presented and then verified by simulating a series of triaxial tests involving the asymmetric stiffness matrices. Furthermore, the symmetric and asymmetric preconditioned iterative methods are employed to solve the asymmetric and symmetrized FE linear systems of equations, respectively, arising from a three-dimensional earth dam example. Finite-element elastoplastic dynamic analyses of the dam show that compared with the solution method based on the asymmetric FE equation, the symmetrization method can produce accurate results, but...

Study of multiwavelength DFB semiconductor laser array with asymmetric structures based on sampling technique

Multiwavelength distributed feedback (DFB) semiconductor laser arrays (MLA) with asymmetric structures are studied in this paper. Thanks to the sampling technique, the asymmetric structures, including asymmetric phase shift and asymmetric coupling coefficient, can be achieved by common holographic exposure. Therefore, the cost of fabrication is remarkably reduced. In addition, due to the large scale of the sampling pattern, the wavelength precision of these kinds of MLA can be simultaneously improved. As an example, we designed and fabricated an asymmetrically phase-shifted MLA with 10 wavelengths for the first time. Compared with the common phase-shifted DFB laser, slope efficiency is significantly improved and single longitudinal mode is still guaranteed. Besides, relatively high wavelength precision is also obtained. The proposed MLA configurations may significantly benefit multiwavelength emitters for future photonic integration.

Azimuthal Transmission Lines for Inductive Voltage Adders With Four PFLs Driving Simultaneously or Separately

In this paper, an inductive cell driven by four pulse forming lines (PFLs), capable of operating at two modes to create a single pulse or four separate pulses, is proposed. A single hardware configuration of azimuthal lines must meet the different requirements of the two operating modes. The optimizations and tradeoffs of azimuthal lines for these two modes are presented. Four candidate azimuthal line configurations that are compatible with either mode are proposed. The cell output voltage and azimuthal uniformity of feed currents are simulated, respectively. The simulation results indicate that the cylinder azimuthal line with four equidistant tabs connected to the cathode palates is the most suitable configuration. As the input pulses are 1000 kV and 25-ns rise time, at the mode with four PFLs driving simultaneously, the cell would produce a pulse with a peak of 865 kV and a rise time of 46 ns into 1.5-Ω load. Meanwhile, it could create four separate pulses of 980 kV and 32-ns rise time into 5-Ω load with each PFL driving separately. In this case, the azimuthally asymmetric coefficient is calculated to be 25.6%. In addition, the voltage of undriven ports, i.e., the voltage applied across the separating switches, is estimated to be about 1150 kV.

Effects of surface asymmetry on neuronal growth.

Detailed knowledge of how the surface physical properties, such as mechanics, topography and texture influence axonal outgrowth and guidance is essential for understanding the processes that control neuron development, the formation of functional neuronal connections and nerve regeneration. Here we synthesize asymmetric surfaces with well-controlled topography and texture and perform a systematic experimental and theoretical investigation of axonal outgrowth on these substrates. We demonstrate unidirectional axonal bias imparted by the surface ratchet-based topography and quantify the topographical guidance cues that control neuronal growth. We describe the growth cone dynamics using a general stochastic model (Fokker-Planck formalism) and use this model to extract two key dynamical parameters: diffusion (cell motility) coefficient and asymmetric drift coefficient. The drift coefficient is identified with the torque caused by the asymmetric ratchet topography. We relate the observed directional bias in axonal outgrowth to cellular contact guidance behavior, which results in an increase in the cell-surface coupling with increased surface anisotropy. We also demonstrate that the disruption of cytoskeletal dynamics through application of Taxol (stabilizer of microtubules) and Blebbistatin (inhibitor of myosin II activity) greatly reduces the directional bias imparted by these asymmetric surfaces. These results provide new insight into the role played by topographical cues in neuronal growth and could lead to new methods for stimulating neuronal regeneration and the engineering of artificial neuronal tissue.

Stability Analysis of Symbiotic Bioenergy Parks

In this work, a novel stability analysis for symbiotic bioenergy park is introduced. The concept of incremental investment return (IIR) analysis is adapted to determine the distribution of the savings associated with the additional investment required for implementation of industrial symbiosis (IS) scheme. Deviation from the ideal status of IS system can be obtained by determining the asymmetric distribution coefficient of each processing plant. An IS system is stable for as long as no partner bears a disproportionate share of additional investment costs relative to benefits gained from cooperation. To ensure a stable IS system, the asymmetric distribution coefficient must be bounded within maximum and minimum limits that can be determined based on the individual plants’ requirements or company policies. In case where the asymmetric distribution coefficient of one of the processing plants falls outside of the predefined limits, the symbiotic bioenergy park is not stable, and the proposed IS scheme cannot be implemented. A palm-based symbiotic bioenergy park case study is solved to illustrate the proposed approach.

Investigation on the Wind Pressure Asymmetric Coefficient of Transmission Line

The wind pressure asymmetric coefficient is used to express the variation of wind distribution along the transmission line. In this paper, the value of the wind pressure asymmetric coefficient in some international codes is discussed and compared. It’s shown that the coefficient has no relationship with the span length of transmission only in Chinese code. When the span of the checked transmission line is small, the wind pressure calculated based on Chinese code will be smaller than that based on others.

Application of a Cavity Resonator Model for Characterization and Estimation of Radiation From a PCB–Chassis System

The electric far-field radiated from a printed circuit board (PCB)-chassis system is characterized using a cavity resonator model employing the far field calculated using an equivalent magnetic current loop. The inductive network method with measured current flowing through screws as a stimulus is used to calculate the frequency spectra of the electric field strength along the edge of the PCB with various locations of screws that connect the PCB ground to the chassis. Electric far fields from the equivalent magnetic current loop were derived using correction coefficients that incorporate the asymmetric dimensions of a parallel pair of PCB planes and the chassis. The calculation results reveal that the horizontal far field exceeds the vertical far field due to the asymmetric size coefficients and exhibit good agreement with the measurement results.

Redox cycling in nanoporous electrochemical devices

Nanoscale redox cycling is a powerful technique for detecting electrochemically active molecules, based on fast repetitive oxidation and reduction reactions. An ideal implementation of redox cycling sensors can be realized by nanoporous dual-electrode systems in easily accessible and scalable geometries. Here, we introduce a multi-electrode array device with highly efficient nanoporous redox cycling sensors. Each of the sensors holds up to 209,000 well defined nanopores with minimal pore radii of less than 40 nm and an electrode separation of ~100 nm. We demonstrate the efficiency of the nanopore array by screening a large concentration range over three orders of magnitude with area-specific sensitivities of up to 81.0 mA (cm(-2) mM(-1)) for the redox-active probe ferrocene dimethanol. Furthermore, due to the specific geometry of the material, reaction kinetics has a unique potential-dependent impact on the signal characteristics. As a result, redox cycling experiments in the nanoporous structure allow studies on heterogeneous electron transfer reactions revealing a surprisingly asymmetric transfer coefficient.

Experimental verification of substrate-induced bianisotropy in optical metamaterials

This paper reports on substrate-induced bianisotropy in an impedance-matched near-zero-index metallodielectric fishnet nanostructure with vertical sidewalls and a supporting substrate. The effect of bianisotropy on the metamaterial optical properties is confirmed through spectral holography measurements and full-wave electromagnetic simulations, showing asymmetric reflection coefficients from opposite sides of the structure at normal incidence. The non-zero magnetoelectric coupling parameter causes a 0.03 μm shift in the near-infrared zero-index band centered at 1.5 μm and a 38% reduction in transmitted power. The substrate-induced bianisotropy is due to the excitation of an anti-symmetric plasmonic resonance mode identified by comparing simulations of the current distributions on free-standing and substrate-mounted fishnet structures. This experimental demonstration of substrate-induced bianisotropy verifies the previously proposed theory and provides valuable guidance for future plasmonic and metamaterial nanostructures that include substrates.

Econometrics of the Basu Asymmetric Timeliness Coefficient and Accounting Conservatism

ABSTRACTA substantial literature investigates conditional conservatism, defined as asymmetric accounting recognition of economic shocks (“news”), and how it depends on various market, political, and institutional variables. Studies typically assume the Basu [1997] asymmetric timeliness coefficient (the incremental slope on negative returns in a piecewise‐linear regression of accounting income on stock returns) is a valid conditional conservatism measure. We analyze the measure's validity, in the context of a model with accounting income incorporating different types of information with different lags, and with noise. We demonstrate that the asymmetric timeliness coefficient varies with firm characteristics affecting their information environments, such as the length of the firm's operating and investment cycles, and its degree of diversification. We particularly examine one characteristic, the extent to which “unbooked” information (such as revised expectations about rents and growth options) is independent of other information, and discuss the conditions under which a proxy for this characteristic is the market‐to‐book ratio. We also conclude that much criticism of the Basu regression misconstrues researchers’ objectives.

Optimized Design of Azimuthal Transmission Lines for the Cell Driven by Two PFLs in Induction Voltage Adders

In this paper, a full-size 3-D electromagnetic model (without electrons) and an equivalent circuit model of a single cell in magnetically insulated induction voltage adders has been established. The simulation results of these two models agree well with each other. On the basis of these two models, azimuthal transmission lines for a cell driven by two pulse forming lines (PFLs) have been optimized. The optimization process aims at matching the impedance to the feed PFLs, ensuring uniform potential distribution along the insulator-stack, maximizing the symmetric current flow around the bore, and minimizing the waveform distortion of the injected pulse. A formula is presented to estimate the azimuthal impedance and an asymmetric coefficient is also defined to quantify the asymmetric extent of the feed pulses. The profiles of the total four candidate azimuthal lines have been simulated and analyzed. The simulation results indicate a relatively low feed asymmetry for all the four profiles. However, considering the waveform quality of the cell output voltage, the azimuthal line profiles with four points connected or wholly connected to the cathode plate are the most suitable for induction cells with two PFL feeding. And the corresponding coefficients $\delta$ are 3.1% and 7.6%, respectively. It is concluded that, when optimizing azimuthal lines for cells with two PFL feeding, the principal consideration should be matching the impedance instead of symmetrizing the current flow.

Proposal and Analysis of Distributed Reflector-Laser Diode Integrated with an Electroabsorption Modulator

A novel integrated laser, that is, a distributed reflector laser diode integrated with an electroabsorption modulator, is proposed to improve the output efficiency, single-mode stability, and chirp. The proposed laser can be realized using the selective metalorganic vapor phase epitaxy technique (that is, control of the width of the insulating mask), and its fabrication process is almost the same as the conventional electroabsorption modulated laser (EML) process except for the asymmetric coupling coefficient structure along the cavity. For our analysis, an accurate time-domain transfer-matrix-based laser model is developed. Based on this model, we perform steady-state and large-signal analyses. The performances of the proposed laser, such as the output power, extinction ratio, and chirp, are compared with those of the EML. Under 10-Gbps NRZ modulation, we can obtain a 30% higher output power and about 50% lower chirp than the conventional EML. In particular, the simulation results show that the chirp provided by the proposed laser can appear to have a longer wavelength side at the leading edge of the pulse and a shorter wavelength side at the falling edge.

Optical Sensing Properties Optimization of a Slot-Waveguide-Based Silicon Ring Resonator Biosensor

An optical biosensor with a slot-waveguide-based micro-ring resonator on silicon-on-insulator (SOI) is reported. By numerical analyzing, a small-sized sensor of 25×15μm2 with a sensitivity of 594nm/RIU can be achieved for NaCl solution, which is about eight times of that of the conventional micro-ring sensor. The free spectral range of 25.6nm and a quality factor Q of 430 are also observed. If SNR is more important, an asymmetric coefficient of 0.7 can be introduced to enhance Q factor. Our analysis also shows that the sensor has good sensing characteristics to other organic solutions.