An Algebraic Algorithm for Microcomputer-Based (Direct) Inverter Pulsewidth Modulation

A new method of direct inverter pulsewidth modulation (PWM) is described. In this technique the pulsewidths are determined by equating the incremental areas of the reference signal with the output pulse areas. This PWM method is compared to conventional methods, such as the natural PWM and the regular PWM, which are based on geometrical constructions. Harmonic analysis shows that the direct PWM method has less harmonic distortion that the other methods. Moreover, this technique is particularly suitable for microprocessor-based implementation since the pulsewidths are computable in real time from simple analytic expressions. It is shown that the output pulsewidths are directly proportional to the reference amplitude and inversely proportional to frequency. Therefore, constant volts/hertz operations and other modes of operation can be implemented very simply with a minimal storage requirement.     

Comparison of antireflection surfaces based on two-dimensional binary gratings and thin-film coatings

A comparison of antireflection surfaces based on the two-dimensional binary gratings and thin-film coatings is presented. First, a two-dimensional hybrid binary grating is proposed and analyzed by use of a vector-based implementation of the rigorous coupled-wave analysis method. The optimum parameters of the structure are determined and the effects that changing them have on spectral characteristics of the structure are studied. Then this structure is compared with multilayer thin-film antireflection filters. These filters are designed by genetic algorithm and needle methods, which are powerful methods for multilayer filter design. The comparison results show that the sensitivity of the grating to changes in the incident wavelength is high. However, a reflectance of the order of 10(-3)% at the design wavelength can be achieved. The sensitivity of designed antireflection thin-film filters to wavelength changes is lower, however, and the minimum achievable reflectance is higher.     

The Fast Evaluation Strategy for Evolvable Hardware

An evolutionary algorithm implemented in hardware is expected to operate much faster than the equivalent software implementation. However, this may not be true for slow fitness evaluation applications. This paper introduces a fast evolutionary algorithm (FEA) that does not evaluate all new individuals, thus operating faster for slow fitness evaluation applications. Results of a hardware implementation of this algorithm are presented that show the real time advantages of such systems for slow fitness evaluation applications. Results are presented for six optimisation functions and for image compression hardware.     

Untertagevergasung tiefliegender Steinkohle

Bisherige Entwicklungen zur Untertagevergasung von Kohle. Neuere Überlegungen zur Untertagevergasung in Anlehnung an die Methoden bei der Gewinnung von Erdöl und Erdgas. Erörterung über die Verfahren des Bohrlochbergbaus im Durchdringungsverfahren, Kanalverfahren und Blockumströmungsverfahren. Beurteilung der Möglichkeiten der Untertagevergasung bei tiefliegenden Steinkohlelagerstätten. Bericht über die Aktivitäten einer Arbeitsgruppe des Instituts für Eisenhüttenkunde der Technischen Hochschule Aachen mit Angaben über Versuche im Autoklaven zur Simulation der Untertagevergasung und zur Ermittlung grundlegender Stoffdaten. Beurteilung der Zukunftsaussichten der Untertagevergasung.     

A novel low-power full-adder cell for low voltage

This paper presents a novel low-power majority function-based 1-bit full adder that uses MOS capacitors (MOSCAP) in its structure. It can work reliably at low supply voltage. In this design, the time-consuming XOR gates are eliminated. The circuits being studied are optimized for energy efficiency at 0.18-μm CMOS process technology. The adder cell is compared with seven widely used adders based on power consumption, speed, power-delay product (PDP) and area efficiency. Intensive simulation runs on a Cadence environment and HSPICE show that the new adder has more than 11% in power savings over a conventional 28-transistor CMOS adder. In addition, it consumes 30% less power than transmission function adder (TFA) and is 1.11 times faster.     

Sol–gel preparation of titania multilayer membrane for photocatalytic applications

The main goal of the present study is to prepare a titania membrane with high permeability and photocatalytic activity for environmental applications. In this investigation a mesoporous titania multilayer membrane on alumina substrate is successfully fabricated via the sol–gel processing method. The prepared titania polymeric sol for the membrane top layer has an average particle size of 11.7 nm with a narrow distribution. The resulting TiO₂ multilayer membrane exhibits homogeneity with no cracks or pinholes, small pore size (4 nm), large specific surface area (83 m²/g), and small crystallite size (10.3 nm).The permeability and photocatalytic properties of the titania membrane were measured. The photoactivity of the titania membrane was examined to be 41.9% after 9 h UV irradiation based on methyl orange degradation. This measurement indicates high photocatalytic activity per unit mass of the catalyst. Through multilayer coating procedure, the photocatalytic activity of the membrane improved by 60% without sacrificing the membrane permeation. The prepared TiO₂ photocatalytic membrane has a great potential in developing high efficient water treatment and reuse systems due to its multifunctional capability such as decomposition of organic pollutants and physical separation of contaminants.     

Erbium-Ion-Doped Tellurite Glass Fibers and Waveguides—Devices and Future Prospective: Part II

Following on from Part I of this review article that focuses on the suitability of Er³⁺-doped tellurium oxide glass for optical amplification in fiber, this Part II article describes how the fiber gain data were then employed to engineer amplification in waveguides, which can be integrated with semiconductor pump sources. The gain characteristics and bandwidth of a phosphate modified tellurite waveguide formed on a GaAs substrate are discussed. The limiting structural compatibility of Er³⁺-doped tellurite glass with polydimethylsiloxane polymer for active–passive integration is overcome by adopting a nanoscale super-lattice approach for waveguide engineering.     

Development of electrically conductive hybrid nanofibers based on CNT‐polyurethane nanocomposite for cardiac tissue engineering

Conductive nanofibers have been considered as one of the most interesting and promising candidate scaffolds for cardiac patch applications with capability to improve cell–cell communication. Here, we successfully fabricated electroconductive nanofibrous patches by simultaneous electrospray of multiwalled carbon nanotubes (MWCNTs) on polyurethane nanofibers. A series of CNT/PU nanocomposites with different weight ratios (2:10, 3:10, and 6:10wt%) were obtained. Scanning electron microscopy, conductivity analysis, water contact angle measurements, and tensile tests were used to characterize the scaffolds. FESEM showed that CNTs were adhered on PU nanofibers and created an interconnected web‐like structures. The SEM images also revealed that the diameters of nanofibers were decreased by increasing CNTs. The electrical conductivity, tensile strength, Young's modulus, and hydrophilicity of CNT/PU nanocomposites also enhanced after adding CNTs. The scaffolds revealed suitable cytocompatibility for H9c2 cells and human umbilical vein endothelial cells (HUVECs). This study indicated that simultaneous electrospinning and electrospray can be used to fabricate conductive CNT/PUnanofibers, resulting in better cytocompatibility and improved interactions between the scaffold and cardiomyoblasts.     

Effiziente Wasserabtrennung aus Dieselkraftstoff mittels Membrantechnik und Online‐Monitoring

The separation of water from diesel fuel is very important for safety, ecological, and economic reasons, as otherwise it can lead to lower combustion efficiency and engine problems. In addition, the free water from ultra‐low‐sulfur diesel (ULSD) can only be insufficiently separated with the classic separation systems. To solve this problem, a membrane process with different organic/inorganic membranes for the selective separation of water droplets from ULSD and an innovative water‐in‐oil online sensor were developed.