Natural Harmonic Elimination of Square-Wave Inverter for Medium-Voltage Application

In this paper, a low-frequency square-wave inverter with a series-connected pulsewidth modulation (PWM) inverter is investigated for high-power applications. The series compensators produce only the desired harmonic voltages to make the net output voltage sinusoidal with small PWM switching harmonics only. An open-loop control strategy for the series compensator is proposed in this paper. This strategy indirectly sets the compensator DC bus voltage to the desired level. No external DC source or active power at fundamental frequency is required to control this dc bus voltage. Different variations of this basic strategy are presented in this paper for medium-voltage applications. Theoretical analysis of this strategy is presented in this paper with simulation and experimental results.     

Effect of heat capacity and physical behavior on strength and durability of shale, as building material

Increasing use of rock materials like shale in building, roofing, embankment filling, brick manufacturing, and in other civil structure application makes it an important rock to consider in construction engineering. Knowledge of thermal and physical properties of shale as building material is required to predict the rock??s strength and permanence against weathering. Inconsistent heat capacity of anisotropic rock can result in differential heat flow. This tendency can expand the building materials leading to reduction in strength and initiate disintegration. Authors have studied various thermo-physical properties of anisotropic shale from Tennessee, which is commonly used as building stones and bricks. Experiment was designed to measure the basic thermal property, ??heat capacity?? of shale. Series of laboratory tests including durability, strength, specific gravity, moisture content, and porosity were conducted to determine the physical and mechanical behavior of the samples. Results indicated that properties like porosity, strength and heat capacity varied significantly within samples, where as specific gravity and moisture content yielded steady values. Multivariate regression analysis was performed to evaluate possible correlations among the tested properties. Strong positive relationship was evident between heat capacity, and porosity. Heat capacity and Unconfined Compressive Strength of shale were inversely related. This study emphasized that physical and thermal properties of shale are directly linked with strength and durability of the rock mass.     

Design Formula for Sierpinski Gasket Pre-Fractal Planar-Monopole Antennas [Antenna Designer's Notebook]

An improved formula for determination of resonant frequencies in different Sierpinski modes is developed from other existing formulas, using physical and analytical reasoning. The superiority of the proposed formula over other existing formulas is verified by comparing the results with those from experiments and simulations. A design formula for the side length of the generating Sierpinski triangle is also proposed by algebraic rearrangement of the formula for the resonant frequency.     

Using multivariate nested distributions to model semiconductormanufacturing processes

This paper demonstrates the advantages of modeling semiconductor process variability using a multivariate nested distribution. This distribution allows estimation not only of correlation among various model parameters, but also allows each of those variations to he apportioned among the various stages of the process (i.e., wafer-to-wafer, lot-to-lot, etc.). This permits matched devices to be more accurately simulated, without having to develop customized models for each configuration of matching. The technique also provides focus for process improvement efforts into those areas with the maximum potential reward. Test structures have been designed and fabricated to facilitate extraction of the parameters for the multivariate nested distribution. Using data from a sample of these structures, a process model is built and analyzed; Monte Carlo techniques are then employed using SPICE and a probabilistic process model to predict the performance of a multiplying digital-to-analog converter (MDAC), and the results are compared to measured data from fabricated circuits. Simulations performed using a model built using the multivariate nested approach are shown to provide superior results when compared to simulations using currently accepted multivariate normal models     

Encapsulation,Visualization and Expression of Genes with Biomimetically Mineralized Zeolitic Imidazolate Framework‐8 (ZIF‐8)

Recent work in biomolecule‐metal–organic framework (MOF) composites has proven to be an effective strategy for the protection of proteins. However, for other biomacromolecules such as nucleic acids, the encapsulation into nano MOFs and the related characterizations are in their infancy. Herein, encapsulation of a complete gene‐set in zeolitic imidazolate framework‐8 (ZIF‐8) MOFs and cellular expression of the gene delivered by the nano MOF composites are reported. Using a green fluorescent protein (GFP) plasmid (plGFP) as a proof‐of‐concept genetic macromolecule, successful transfection of mammalian cancer cells with plGFP for up to 4 days is shown. Cell transfection assays and soft X‐ray cryo‐tomography (cryo‐SXT) demonstrate the feasibility of DNA@MOF biocomposites as intracellular gene delivery vehicles. Expression occurs over relatively prolonged time points where the cargo nucleic acid is released gradually in order to maintain sustained expression.     

Identification and control of induction motor stator currents usingfast on-line random training of a neural network

Artificial neural networks (ANNs), which have no off-line pretraining, can be trained continually on-line to identify an inverter-fed induction motor and control its stator currents. Due to the small time constants of the motor circuits, the time to complete one training cycle has to be extremely small. This paper proposes and evaluates a new form of the random weight change (RWC) algorithm, which is based on the method of random search for the error surface gradient. Simulation results show that the new form of the RWC, termed continually online trained RWC (COT-RWC), yields performance very much the same as conventional backpropagation with on-line training. Unlike backpropagation, however, the COT-RWC method can be implemented in mixed digital/analog hardware and still have a sufficiently small training cycle time. The paper also proposes a VLSI implementation which completes one training cycle in as little as 8 μs. Such a fast ANN can identify and control the motor currents within a few milliseconds and, thus, provide self-tuning of the drive while the ANN has no prior information whatsoever of the connected inverter and motor