Influence of the Metal–Semiconductor Interface Model on Power Conservation Principle in a Simulation of Bipolar Devices

The purpose of the study is to present a proper approach that ensures the energy conservation principle during electrothermal simulations of bipolar devices. The simulations are done using Sentaurus TCAD software from Synopsys. We focus on the drift-diffusion model that is still widely used for power device simulations. We show that without a properly designed contact(metal)–semiconductor interface, the energy conservation is not obeyed when bipolar devices are considered. This should not be accepted for power semiconductor structures, where thermal design issues are the most important. The correct model of the interface is achieved by proper doping and mesh of the contact-semiconductor region or by applying a dedicated model. The discussion is illustrated by simulation results obtained for the GaN p–n structure; additionally, Si and SiC structures are also presented. The results are also supported by a theoretical analysis of interface physics.

A General Outflow Theory Based on Momentum Balance

One of the oldest problems in the history of hydraulics is the outflow from a vessel through an orifice. In 1644 it was described by the Torricelli principle stating that the outflow velocity is the fall velocity from the filling level. From a theoretical point of view the Torricelli principle is valid because it follows from Bernoulli's energy conservation principle. In this paper the outflowproblem will be described by Newton's momentum balance principle. Here the Torricelli formula is obtained when the rounded orifice is treated as a contraction. For the sharp edged orifice the bulk outflow velocity is the fall velocity from half the filling height. In this momentum balance theory no artificial outflow coefficients are needed to distinguish between the cases of sharp edged and rounded orifices.

Effort investment in uncontrollable situations: The moderating role of motivation toward closure

According to the principle of energy-conservation principle, effort investment is usually reduced in situations that are perceived as uncontrollable. This is because when success is recognized as impossible, any effortful actions are no longer justified. However, we predicted that individual differences in uncertainty tolerance, i.e., the need for closure (NFC), may moderate effort investment in uncontrollable situations. We tested this prediction in two experimental studies in which we exposed participants with differing levels of NFC to uncontrollable events, and indexed effort through the assessment of systolic blood pressure (SBP) responses. As predicted, in the uncontrollability (vs. controllability) condition, effort investment decreased significantly among low- but not high-NFC participants. Since gaining certainty and achieving closure is not a critical epistemic goal for low-NFC individuals, exerting extra effort to gain certainty is therefore no longer justified. On the other hand, high-NFC participants do not withhold their efforts, as they are highly motivated to obtain certainty. These results may help to account for contradictory findings in effort-investment behaviour and add substantively to the literature concerning motivation toward closure.

Direct Derivation of Liénard–Wiechert Potentials, Maxwell’s Equations and Lorentz Force from Coulomb’s Law

In this paper, the solution to long standing problem of deriving Maxwell’s equations and Lorentz force from first principles, i.e., from Coulomb’s law, is presented. This problem was studied by many authors throughout history but it was never satisfactorily solved, and it was never solved for charges in arbitrary motion. In this paper, relativistically correct Liénard–Wiechert potentials for charges in arbitrary motion and Maxwell equations are both derived directly from Coulomb’s law by careful mathematical analysis of the moment just before the charge in motion stops. In the second part of this paper, the electrodynamic energy conservation principle is derived directly from Coulomb’s law by using similar approach. From this energy conservation principle the Lorentz force is derived. To make these derivations possible, the generalized Helmholtz theorem was derived along with two novel vector identities. The special relativity was not used in our derivations, and the results show that electromagnetism as a whole is not the consequence of special relativity, but it is rather the consequence of time retardation.

A Simple Energy-based Approach of Stent Elastic Properties

Simple closed-form expressions were derived for the elastic moduli of lozenge grid structure based on the convenient beam theory and energy conservation principle. Finite element analysis was employed to validate the analytical estimates of the Young’s modulus. The theoretic results were also compared with the numerical data in the literature. The results show that the calculation method of Young’s modulus obtained by energy conservation is feasible, which provides a new way for stress analysis of sandwich structures. At the same time, the cell structure proposed in this paper provides a new scheme for the design of vascular stent.

Research on the computing method for the forming velocity of circumferential multiple explosive formed projectiles

To evaluate the damage capability of circumferential multiple explosive formed projectiles (MEFPs), it is required to predict the EFP forming velocity accurately and quickly. According to the circumferential MEFP liner characteristics of uniform circumferential distribution and layered axial structure, a simplified physical model of circumferential MEFPs is put forward innovatively. The Lagrange and Euler coupling algorithm is selected to simulate the simulation model, which is verified as equivalent to the circumferential MEFPs. Based on the energy conservation principle and the simplified equivalent physical model, the calculating model of the circumferential MEFP forming velocity is derived. The correctness and accuracy of the calculation model are verified by using the numerical simulation software and the test device of the round-shaped charge model.

A physical theory of accounting: particular study issues

The subject matter of the paper is related to theoretical and methodological basics of accounting as a field of study. Over many centuries, the laws of economics have been examined dialectically by scholars. In the course of establishing a study of economics, there have been a number of orthodox scholarly traditions, united by a common idea of †development and patterns of performance. For a long time, economists from different countries worked hard in order to understand the essence of economic and social processes, derive and explain economic laws using knowledge and experience acquired by people. The aim of the article is to explore in what way the research methods which are generally applied in natural sciences can be deployed for economic studies, and in particular for describing the nature of accounting. The key objectives of the paper are to develop a methodology for applying methods of physics to the study of economics, and to identify the link between conceptual framework of accounting and physics. In the paper, the following general and specific research methods are used: modeling, algorithmization, formalization, generalization, comparison, analogy, system approach. It is justified that the laws of physics can be prospectively applied for explaining economic phenomena and processes, particularly in accounting, which is viewed as an important source of information. Hence, the correlation between accounting and the field of physics and mathematics is determined through: the use of formal description of accounting items; the consideration in terms of seeing accounting as a specific knowledge field; the interpretation of accounting methods (in particular, the balance method) through algorithmization and parallelism with the laws of physics (for example, the energy conservation principle); the establishment of an information hierarchy of the current state and behavior of assets, capital and liabilities of the enterprise; the examination of balances by means of appropriate algorithmization and justification of advisability of developing a physical nature of accounting theory. It is pointed out, that there is a difference between the balance method and the energy conservation principle (the energy in an enclosed system is constant, which makes it impossible to observe the process of arrival or creation of new energy in enclosed space). The conclusion is based on the positive influence of econophysics on the economy’s performance, and the advisability of its application for a more accurate study of economic processes, and a more qualitative economic analysis of enterprise performance.

Ice Multiplication by Breakup in Ice–Ice Collisions. Part I: Theoretical Formulation

For decades, enhancement of ice concentrations above those of active ice nucleus aerosols was observed in deep clouds with tops too warm for homogeneous freezing, indicating fragmentation of ice (multiplication). Several possible mechanisms of fragmentation have been suggested from laboratory studies, and one of these involves fragmentation in ice–ice collisions. In this two-part paper, the role of breakup in ice–ice collisions in a convective storm consisting of many cloud types is assessed with a modeling approach. The colliding ice particles can belong to any microphysical species, such as crystals, snow, graupel, hail, or freezing drops. In the present study (Part I), a full physical formulation of initiation of cloud ice by mechanical breakup in collisions involving snow, graupel, and/or hail is developed based on an energy conservation principle. Theoretically uncertain parameters are estimated by simulating laboratory and field experiments already published in the literature. Here, collision kinetic energy (CKE) is the fundamental governing variable of fragmentation in any collision, because it measures the energy available for breakage by work done to create the new surface of fragments. The developed formulation is general in the sense that it includes all the types of fragmentation observed in previous published studies and encompasses collisions of either snow or crystals with graupel/hail, collisions among only graupel/hail, and collisions among only snow/crystals. It explains the observed dependencies on CKE, size, temperature, and degree of prior riming.