Interfacial Properties of Binary Mixtures of Simple Fluids and their Relation to the Phase Diagram

Interfacial properties of binary fluid mixtures were studied using both molecular dynamics (MD) simulations and density gradient theory (DGT). The focus of the study is on the relation of the interfacial properties to the phase diagram of the mixture. Two binary Lennard-Jones mixtures were investigated in a wide range of states: a highly asymmetric mixture (type III), which exhibits vapour–liquid equilibria (VL1E and VL2E), liquid–liquid equilibria (L1L2E), a three-phase equilibrium (VL1L2E), and supercritical fluid–fluid equilibria (F1F2E), and, as a reference, an ideal mixture (type I). The studied interfacial properties are: the surface tension, the relative adsorption, the width of the interfacial region, and the enrichment of the low-boiling component, on which we set a focus. Enrichment was observed at VL1 interfaces; and, to a small extent, also at L1L2 interfaces; but not at the supercritical F1F2 interfaces. The large enrichment found at VL1 interfaces of the type III mixture can be interpreted as a wetting transition: approaching the VL1L2E three-phase line from the VL1 side, the enrichment gets stronger and can be interpreted as precursor of the second liquid phase L2. However, the actual existence of a three-phase line in the phase diagram is no prerequisite for an enrichment. The enrichment is found to be highly temperature-dependent and increases with decreasing temperature.

Modified Space Vector Modulation for Cascaded H-Bridge Multilevel Inverter with Open-Circuit Power Cells

In this research, a new space vector modulation control algorithm is proposed to increase the reliability of the cascaded H-bridge multilevel inverters in case of faulty situations, where one or several power cells do not function. Methods to detect faults ensure finding open-circuit module exactly, which is fast and easy to program. By giving a detailed analysis of the impact of the faulty power cells, optimal redundant level states are chosen such that highest possible output voltage can be achieved, while the balance of the three-phase line-to-line voltage is maintained and common-mode voltage is reduced. The proposed algorithm is generalized so that it can be applied to H-bridge inverters of any level. The validity of the method is verified by numerical simulations and experiment results with an 11-level cascaded H-bridge inverter.

Arduino-Based Three-Phase Inverter Using Power MOSFET for Application in Microgrid Systems

Rapid depletion of fossil fuel reserves, and concerns over climate change have encouraged power generation from sustainable energy based microgrids. And to address the necessity of three-phase inverters in microgrid systems or sustainable-powered households, an Arduino-based three-phase inverter using MOSFET is designed, which converts DC into three-phase AC power. The designed system generates 223V square signals at each phase from a 12V battery through switching of three stages of power MOSFETs using pulse width modulation (PWM) signals at their gates from an Arduino Uno. Each stage of power MOSFETs consists of six transistors making it eighteen in total, which are used to perform the inversion process separately for each three single-phase connections. The system is programmed using an Arduino Uno to generate PWM signals and to keep 120 degrees phase displacement among each phase. Three step-up transformers are coupled at the outputs of MOSFET stages for amplification. The system generates 386.25V of voltage for the three-phase line delivering 0.58A of current using a 60W incandescent bulb at each phase as a load. The design and simulation of the electronic circuit are done by Proteus, and the programming codes are written using Arduino IDE. The designed system is practically contrasted and verified.

Qualitative Analysis of a Resource Management Model and Its Application to the Past and Future of Endangered Whale Populations

Observed whale dynamics show drastic historical population declines, some of which have not been reversed in spite of restrictions on harvesting. This phenomenon is not explained by traditional predator prey models, but we can do better by using models that incorporate more sophisticated assumptions about consumer-resource interaction. To that end, we derive the Holling type 3 consumption rate model and use it in a one-variable differential equation obtained by treating the predator population in a predator-prey model as a parameter rather than a dynamic variable. The resulting model produces dynamics in which low and high consumption levels lead to single high and low-level stable resource equilibria, respectively, while intermediate consumption levels result in both high and low stable equilibria. The phase line analysis is made more transparent by applying a particular structure to the function that gives the derivative in terms of the state. By positing a consumption level that starts low, gradually increases through technological change and human population growth, and decreases as a result of public policy, we are able to tell a story that explains the unexpectedly rapid decline of some resources, such as whales, followed by limited recovery in response to conservation. The analysis also offers guidelines for how to establish sustainable harvesting for restored populations. We include a bifurcation analysis and suggestions for how to teach the material with three different levels of focus on the modeling aspect of the study.

Analysis of rotor asymmetry fault in three-phase line start permanent magnet synchronous motor

This article proposed a detection scheme for three-phase Line start permanent magnet synchronous motor (LSPMSM) under different levels of static eccentricity fault. Finite element method is used to simulate the healthy and faulty LSPMSM with different percentages of static eccentricity. An accurate laboratory test experiment is performed to evaluate the proposed index. Effects of loading condition on LSPMSM are also investigated. The fault related signatures in the stator current are identified and an effective index for LSPMSM is proposed. The simulation and experimental results indicate that the low frequency components are an effective index for detection of the static eccentricity in LSPMSM.