Search results

The purpose of this paper is to develop a generalized model of the nonlinear conductivity of varistor ceramic suitable for solving problems of prediction and control of ceramic nonlinearity, stability of varistor properties.

The modeling of current-voltage characteristic of the intergranular barrier in metal oxide varistor ceramics is based on the development of the algorithm. It includes all the known mechanisms of electrotransfer in a wide range of voltages and currents of the current-voltage characteristics, and also takes into account the deviation of the barrier form the Schottky barrier.

The models of double Schottky barrier and double barrier of arbitrary form, as well as the algorithms for calculating the current-voltage characteristics of a single intergranular potential barrier and a separate “microvaristor” with the use of the most well-established understanding of the main mechanisms of electrical are developed. The results of current-voltage characteristics modeling correspond to the existing understanding of the nonlinear electrical conductivity varistor ceramics are based on zinc oxide. The model of double barrier of arbitrary form takes into account the deviation of the barrier form the Schottky barrier which is important in predicting the deformation of the current-voltage characteristics of the varistor products in the process of degradation.

The relation between the form of the current-voltage characteristic and the distribution profile of the donor concentration in the surface regions of the semiconductor crystallites constituting the intergranular potential barrier is established. The accumulation of donors in the space charge region leads to the increase in the current on the prebreakdown region of the current-voltage characteristic and the reduction of voltage corresponding to the breakdown region beginning of the current-voltage characteristic. The significant role of the interlayer in the formation of current-voltage characteristic of the intergranular potential barrier is shown.

The border control becomes challenging when a protected region is large and there is a limited number of border patrols. This research paper proposes a novel heuristic-based patrol path planning scheme in order to efficiently patrol with resource scarcity.

The trespasser influencing score, which is determined from the environmental characteristics and trespassing statistic of the region, is used as a heuristic for measuring a chance of approaching a trespasser. The patrol plan is occasionally updated with a new trespassing statistic during a border operation. The performance of the proposed patrol path planning scheme was evaluated and compared with other patrol path planning schemes by the empirical experiment under different scenarios.

The result from the experiment indicates that the proposed patrol planning outperforms other patrol path planning schemes in terms of the trespasser detection rate, when more environment-aware trespassers are in the region.

The experiment was conducted through simulated agents in simulated environment, which were assumed to mimic real behavior and environment.

This research paper contributes a heuristic-based patrol path planning scheme that applies the environmental characteristics and dynamic statistic of the region, as well as a border surveillance problem model that would be useful for mobile sensor planning in a border surveillance application.

This research applies a static hedging portfolio method derived from Derman, Ergener, and Kani (1995) (henceforth Derman's SHP method) and a new SHP method with European cash-or-nothing binary options developed by Chung, Shih, and Tsai (2013) to price European continuous double barrier (ECDB) options and the rebates of the ECDB options. Our numerical results indicate that the new SHP method outperforms Derman's SHP method in terms of efficiency and effectiveness under all circumstances.

This paper aims to estimate the relationship between defect structure with gas concentration for use as a gas sensor. The change in defect concentration caused a shift in the Fermi level, which in turn changed the surface potential, which is manifested as the potentiometric response of the sensing element.

A new theoretical concept based on defect chemistry and band structure was used to explain the experimental gas response of a sensor. The theoretically simulated response was compared with experimental results.

Understanding the origin of potentiometric response, through the generation of defects and a corresponding shift in Fermi level of sensing surface, by the adsorption of gas. Through this understanding, the design of a sensor with improved selectivity and stability to a gas can be achieved by the study of defect structure and subsequent band analysis.

This paper provides information about various types of surface defects and numerical simulation of material with defect structure. The Fermi energy of the simulated value is correlated with the potentiometric sensor response.

Gas sensors are an integral part of vehicular and industrial pollution control. The theory developed shows the origin of response which can help in identifying the best sensing material and its optimum temperature of operation.

Low-cost, reliable and highly sensitive gas sensors are highly demanded which is fulfilled by potentiometric sensors.

The operating principle of potentiometric sensors is analyzed through electron band structure analysis. With the change in measured gas concentration, the oxygen partial pressure changes. This results in a change in defect concentration in the sensing surface. Band structure analysis shows that change in defect concentration is associated with a shift in Fermi level. This is the origin of the potentiometric response.

The purpose of this paper is to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of synchronous reluctance machine with emphasis on output torque capability and torque ripple.

AC synchronous reluctance machine (SynRM) or permanent magnet assisted SynRM presently receives a great deal of interest, since there is less or even no rare-earth permanent magnet in the rotor. Most of SynRM machines employ a stator that is originally designed for a standard squirrel cage induction motor for a similar output rating and application, or the SynRM machine with 24-slot, four-pole are often directly chosen for investigation in most of the available literature. Therefore, it is necessary to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of SynRM machine with emphasis on output torque capability and torque ripple.

The average torque decreases with the increase of the pole numbers but remain almost constant when employing different stator slot numbers but with the same pole number. In addition, the torque ripple decreases significantly with the increase of the stator slot number. The machine with double-layer flux-barrier in the rotor has the biggest average torque, while the machines with three- and four-layer flux-barrier in the rotor have almost the same average torque but their value is slightly smaller than that of machine with double-layer flux-barrier. However, the machine with three-layer flux-barrier has the lowest torque ripple but the highest torque ripple exists in the machine with double-layer flux-barrier.

The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple are not considered in this application.

This paper has analyzed the torque ripple and average torque of SynRMs with considering slot/pole number combinations together with the flux-barrier number.

Compares the two strands of women and management to the DNA molecule which consists of a double helix. Explores this relationship through the eyes of women managers in Iceland. Discusses the results of four seminars focusing on women′s efforts to be successful in management. Compares priorities between the groups with regard to barriers and potential remedies.

Applying theories of entrepreneurship, the paper aims to identify the factors – with theoretical explanations – that act as barriers to migrant women entrepreneurs (MWEs), particularly women from developing countries starting businesses in developed economies. The paper further seeks to explore which barriers also have the potential to act as enablers.

The relationship between immigration, ethnicity, gender and entrepreneurship has received little theoretical attention. Linking these discourses, the paper theoretically develops a framework of the possible barriers or enablers faced by MWEs.

The paper reinforces earlier research that MWEs are not a homogeneous group; the problems they face are multifaceted, and MWEs from developing countries are the most disadvantaged of entrepreneurs. It identifies multiple factors – human capital, culture, family, institutional factors, gender and social capital – as possible barriers for MWEs. Findings further indicate that among those barriers, culture, family, social capital and gender have the potential to play a dual role for MWEs, by acting either as a barrier or an enabler. Findings also highlight the overarching and predominant influence of culture – as explained by cultural theory – acting as a barrier for MWEs from developing countries.

This is a theoretical paper. Empirical research is needed to test the framework and its different dimensions. Given the diversity of MWEs and the factors that shape their entrepreneurial endeavours, it is difficult to develop a single framework to encompass the complexity of the situation. Nevertheless, the proposed framework provides useful insights into the barriers or enablers that MWEs face, along with theoretical explanations and, thus, acts as a springboard for future research.

Given the increasing potential of MWEs, the paper provides implications for not only addressing the barriers but also viewing the barriers as ways to promote entrepreneurship among such minority groups. It further stresses a needs‐based approach to customizing policies to benefit the diverse group of MWEs.

By providing a theory‐based framework of the barriers or enablers faced by MWEs, along with policy implications, the paper contributes to a better understanding of the phenomenon of migrant women entrepreneurship.

This paper presents a self‐consistent I‐V simulation technique for an RTD with defect wells placed inside the barriers. The motivation of this paper was to model the excess valley current by a defect‐assisted tunneling mechanism. We have calculated the transmission coefficients and I‐V characteristics self consistently with Poisson's equation coupled to quantum mechanical tunneling through the barrier. The shape of transmission coefficient was broadened and greatly enhanced in the off‐resonance region when the defect well was introduced in the barriers. Our results gave a good qualitative estimation of the valley current and the peak to valley current ratio (PVCR).

The purpose of this paper is to report the empirical findings of a survey aimed to investigate the need to improve cross‐phase learning between design and construction. Through exploring the need to introduce a design‐construction feedback loop, combined with the barriers against its development, an expansion of knowledge surrounding the deficiencies of current practice is provided.

The paper reports the results from an online survey conducted in spring 2011 targeted at experienced personnel in the planning, design, construction and facilities management phases of healthcare infrastructure projects.

The current approach of detecting and correcting errors is significantly hindering the extent to which learning from previous experiences is taking place. It is shown that improved integration between design and construction is required in the form of improved feedback if continuous improvement in the areas of efficiency, quality, value and general learning from previous experiences/projects is to be achieved.

The focused population of this study limits the extent to which the findings can be generalised. However, it is viewed that this context is potentially one of the most complex and unique project participant arrangements to overcome. Therefore if the need and ability to share learning outcomes across such a complex arrangement can be achieved, then it may be easier within traditional arrangements.

The practical implications of moving away from single‐loop learning towards a double‐loop learning approach are provided.

This paper identifies that there is a distinct need for further efforts to be applied in the area of improving feedback between the phases of design and construction.

Theoretical calculations of tunneling characteristics of the Gated Resonant Tunneling Diode (GRTD) aie obtained in low dimensionality using a scattering transfer matrix approach. In the bias conditions whereby the GRTD reaches zero‐dimension in the well region, we consider attractive and repulsive perturbation potential (Vsc) of impurity or defect scattering in emitter and well regions. We describe the scattering matrices using the presence of evanescent, or nonpropagating, modes in different lateral confinement structure. Numerical solutions to the two‐dimensional Poisson equation and the continuity equation are used to calculate the lateral depletion region and carrier concentrations by the finite difference method. Electron transport in double‐barrier structure is calculated by a self‐consistent approach.