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     

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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.     

Statistical analysis of electrostatic spark ignition of lean H2/O2/Ar mixtures

The concept of minimum ignition energy (MIE) has traditionally formed the basis for studying ignition hazards of fuels. However, the viewpoint of ignition as a statistical phenomenon appears to be more consistent with the inherent variability in engineering test data. We have developed a very low-energy capacitive spark ignition system to produce short sparks with fixed lengths of 1-2 mm, and the ignition system is used to perform spark ignition tests using a range of spark energies in lean hydrogen-oxygen-argon test mixtures used in aviation safety testing. The test results are analyzed using statistical tools to obtain probability distributions for ignition versus spark energy. A second low-energy spark ignition system was also developed to generate longer sparks with varying lengths up to 10 mm. A second set of ignition tests is performed in one of the test mixtures using a range of spark energies and spark lengths. The results are analyzed to obtain a probability distribution for ignition versus the spark energy per unit spark length. Preliminary results show that a single threshold MIE value does not exist, but rather that ignition is statistical in nature and highly dependent on mixture composition and spark length.     

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.     

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.     

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。     

Congenital mesoblastic nephroma: an immunohistochemical and lectin study

Eight cases of congenital mesoblastic nephroma (CMN) were examined. Three CMNs were of the classical (typical) variant, two were cellular (atypical), and three showed a mixed pattern. A panel of nephron segment-specific tubular epithelial markers (the lectins Tetragonolobus purpureas, Phaseolus vulgaris erythroagglutinin, and Arachis hypogaea and antibodies to epithelial membrane antigen, cytokeratin, and Tamm-Horsfall protein) were used to differentiate epithelial structures within the tumor. Antibodies against vimentin, desmin, and muscle-specific actin were used as mesenchymal markers. A monoclonal antibody to the long (embryonic) form of polysialic acid (PSA) on the neural cell adhesion molecule was used as a putative renal oncodevelopmental marker. An antibody to proliferating cell nuclear antigen also was applied, which revealed increased proliferative rate in cellular CMNs. In addition to clearly entrapped native renal tubules, CMNs contain tubular structures with immature, dysplastic epithelium and occasional epithelial cell clusters embedded deep within the tumor. These immature tubules and clusters express distal nephron, including collecting duct markers and, occasionally, vimentin and PSA. We propose that these primitive tubules and epithelial structures may originate from the ureteric bud. An epithelial differentiation of the tumor cells also is possible. In one pure cellular CMN and two mixed CMNs the cellular component showed diffuse staining for PSA. The PSA (neural cell adhesion molecule) expression of the cellular component suggests that CMN may originate from the uninduced nephrogenic mesenchyme.     

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.     

The mechanism of tubulin-colchicine recognition--a kinetic study of the binding of a bicyclic colchicine analogue with a minor modification of the A ring

2-Methoxy-5-(2',3',4'-trimethoxy)-2,4,6-cycloheptatrien-1-one (MTC) is a colchicine analogue that lacks the B ring. 2-Methoxy-5-(2',4'-dimethoxyphenyl)-2,4,6-cycloheptatrien-1-one (MD) is an A-ring analogue of MTC, in which one methoxy group is replaced by a hydrogen atom. This paper describes the kinetic features of MDC binding to tubulin, and compares its behaviour with MTC to analyse the effect of the A-ring modification on the recognition process by tubulin. Binding is accompanied by a strong enhancement of MDC fluorescence and quenching of protein fluorescence. The kinetic and thermodynamic parameters were obtained from fluorescence stopped-flow measurements. The kinetics are described by a single exponential, indicating that this drug does not discriminate between the different tubulin isotypes. The observed pseudo-first-order rate constant of the fluorescence increase upon binding increases in a non-linear way, indicating that this ligand binds with a similar overall mechanism as colchicine and MTC, consisting of a fast initial binding of low affinity followed by a slower isomerisation step leading to full affinity. The K1 and k2 values for MDC at 25 degrees C were 540 +/- 65 M(-1) and 70 +/- 6 s(-1) respectively. From the temperature dependence, a reaction enthalpy change (deltaH(o)1) of the initial binding of 49 +/- 11 kJ/mol(-1) and an activation energy for the second step of 28 +/- 9 kJ/mol(-1) were calculated. Displacement experiments of bound MDC by MTC allowed the determination of a rate constant of reverse isomerisation of 0.60 +/- 0.07 s(-1) at 25 degrees C and the activation energy of 81 +/- 6 kJ/mol(-1). The overall binding constant was (6.3 +/- 0.2) x 10(4) M(-1) at 25 degrees C. Combination of these results with the kinetic parameters for association gives a full characterisation of the enthalpy pathway for the binding of MDC. The pathway of MDC is shown to differ considerably from that of MTC binding. Since its structural difference is located in ring A, this result indicates the use of ring A in the first step. The kinetics of the binding of MDC in the presence of some A-ring colchicine analogues (podophyllotoxin, 3',4',5'-trimethoxyacetophenone and N-acetylmescaline) and a C-ring analogue (tropolone methyl ether) suggest that the A and C rings are involved in the binding of MDC.