PES News

This letter proposes a model reference adaptive system (MRAS)-based algorithm for simultaneous stator resistance (R/sub s/) and rotor speed (/spl omega/) identification of position sensorless induction motor to accurately estimate /spl omega/ at low speeds without affecting drive performance. The R/sub s/ has to be estimated concurrently with the /spl omega/ estimation to compensate for the fluctuation in R/sub s/. The reference model and adjustable model are interchangeable for concurrent /spl omega/ and R/sub s/ estimation. For stator resistance identification, the two models switch roles. Extensive computer simulation and experimental investigation prove the effectiveness of the proposed solution.     

Generalized low-density parity-check codes for optical communication systems

This paper is concerned with investigating the performance of regular and irregular, randomlike and structured generalized low-density parity-check (GLDPC) codes for long-haul transmission. The proposed GLDPC codes outperform currently known turbo and low-density parity-check (LDPC) coding schemes with comparable parameters utilized in optical communication systems. For a GLDPC coding scheme with 23.6% redundancy, the largest so far reported coding gain of at least 11dB (at 40 Gb/s) is demonstrated.     

交流调速电梯中的电能质量

因为人们越来越多地使用非线性负载，电网中就存在电源质量问题。在交流传动系统中广泛使用功率变换器，由于其非线性的工作运行状态，导致电压发生畸变，从而影响敏感设备的性能。本文试图分析由功率变换器供电的电梯交流传动系统对电源质量的影响。敏感电气设备和电梯交流传动系统都连接到0．4kV输电线路上。因功率逆变器导致的电压畸变能够导致系统故障甚至电气设备中部分元件的损坏。     

Procedure for setting up the drying regime that is consistent with the nature and properties of the clay raw material

Over the past three decades, traditional ceramic facilities, such as chamber and tunnel dryers, are improved. Better thermotechnical equipment, operational strategies, and reliable scale-up methodologies have lead to higher quality of the dried clay roofing tiles. Although there has been a progress, up to this study, there is no universally or even widely applicable criterion, which could be used to precisely define the change of drying air parameters (humidity, temperature, and velocity) during the drying process. The objective of this study was to specify the variable air parameters that should be used during the drying process to approach as much as possible to the theoretically defined optimal drying process.     

Aging of the over-voltage protection elements caused by over-voltages

The aim of this work is examining the influence of the number of the activation––over-voltage pulses to the aging of over-voltage protection elements. Both non-linear (gas-filled surge arresters (GFSA), varistors, over-voltage diodes) and linear (capacitors––constituents of filters) over-voltage protection elements were tested. The instruments employed allow reliable measurements, 1000 consecutive activation were tested. The double-exponential current pulse (amplitude I₁^max=13 A, I₂^max=16 A, rise time T₁=8 μs, fall time T₂=20 μs) for non-linear elements and a double-exponential over-voltage pulse (rise time T₁=1.2 μs, fall time T₂=50 μs) of the amplitude U₁^max=320 V, U₂^max=480 V and U₃^max=640 V for capacitors were used. The experimental results show that the over-voltage diodes are the most reliable elements in view of characteristic modifications that are consequence of aging. However, it was observed that varistors, GFSA and capacitors undergo noticeable changes in characteristics.     

An Improved Technique for Suppression of Intrachannel Four-Wave Mixing in 40-Gb/s Optical Transmission Systems

This letter presents an efficient method for testing the efficiency of modulation techniques for countering the effects of intrachannel four-wave mixing by calculating the sum of all the contributors at a given resonance position (the position affected by the surrounding pulses). In addition to this method, we are proposing a modulation technique that shows a significant Q-factor improvement of up to 7.5 dB (depending on the number of spans and the phase sequence implemented) over the uncoded return-to-zero on-off keying. Although the implementation of this phase modulation technique is simple, it is still very efficient in extending the nonlinearity tolerance and enhancing the performance of a high-speed optical transmission system     

Atomically thin layers of MoS2 via a two step thermal evaporation-exfoliation method

Two dimensional molybdenum disulfide (MoS(2)) has recently become of interest to semiconductor and optic industries. However, the current methods for its synthesis require harsh environments that are not compatible with standard fabrication processes. We report on a facile synthesis method of layered MoS(2) using a thermal evaporation technique, which requires modest conditions. In this process, a mixture of MoS(2) and molybdenum dioxide (MoO(2)) is produced by evaporating sulfur powder and molybdenum trioxide (MoO(3)) nano-particles simultaneously. Further annealing in a sulfur-rich environment transforms majority of the excess MoO(2) into layered MoS(2). The deposited MoS(2) is then mechanically exfoliated into minimum resolvable atomically thin layers, which are characterized using micro-Raman spectroscopy and atomic force microscopy. Furthermore Raman spectroscopy is employed to determine the effect of electrochemical lithium ion exposure on atomically thin layers of MoS(2).     

LDPC-Coded MIMO Optical Communication Over the Atmospheric Turbulence Channel

In this paper, coded multiple-input-multiple-output (MIMO) communication schemes for data transmission over the optical atmospheric turbulence channels are studied. Two strategies are proposed and compared. The first is based on repetition coding, and the second on space-time (ST) coding. Both approaches employ low-density parity-check (LDPC) codes. The LDPC codes are designed using the concept of pairwise balanced design (PBD), balanced incomplete block design (BIBBD), and block-circulant (array) codes. To improve the spectral efficiency, we employ a bit-interleaved (BI) LDPC-coded modulation based on the pulse amplitude modulation (PAM). A better bit error rate (BER) performance is achieved by the iteration of extrinsic information between a demapper and LDPC decoder. The simulations show that the LDPC-coded MIMO schemes can operate under a strong atmospheric turbulence and at the same time provide excellent coding gains compared with the transmission of uncoded data. To verify the efficiency of the proposed coding schemes, achievable information rates are computed when the turbulence is modeled by a gamma-gamma distribution.     

A digital tachometer for high-temperature telemetry utilizing thermally uprated commercial electronic components

The high-temperature environment of an oil well requires reliable downhole instrumentation, typically based on simple and robust circuits, low power consumption, and smart measurement algorithms. In this paper, we present an electronic design and measurement methodology for a simple microcontroller-based digital tachometer, optimized for downhole spinner-flowmeter applications and multichannel telemetry. We have developed and experimentally evaluated an effective algorithm for direction-sensitive rotational speed measurement, which combines quadrature pulse decoding with the method of dependent count. The algorithm employs a temperature compensation technique, making it suitable for the high-temperature application of commercial-grade electronic parts. Our results confirm the functionality and reliable operation of the tachometer, targeted at high-temperature short-term oil-well logging applications.     

Calculation of Achievable Information Rates of Long-Haul Optical Transmission Systems Using Instanton Approach

A method for estimation of achievable information rates of high-speed optical transmission systems is proposed. This method consists of two steps: 1) approximating probability density functions for energy of pulses, which is done by the instanton approach, and 2) estimating achievable information rates by applying a method originally proposed by Arnold and Pfitser. Numerical results for a specific optical transmission system (submarine system at transmission rate 40 Gb/s) are reported