A fully soft-switched extended-period quasi-resonantpower-factor-correction circuit

This paper presents the design criteria, procedure, and implementation of a soft-switched power-factor-correction (PFC) circuit based on the extended-period quasi-resonant (EPQR) principles. All power electronic devices including switches and diodes in the circuit are fully soft switched. The design method is demonstrated in a prototype circuit. The operating principles are confirmed with computer simulation and experimental results. A comparison of the EP-QR operation and zero-voltage-transition (ZVT) pulse-width modulation (PWM) method     

On the corrosion fatigue crack initiation model and expression of metallic notched elements

In the present study, attempts are made to extend the application of the mechanical model for the fatigue crack initiation (FCI) and the FCI life formula of metallic notched elements in laboratory air to those in the corrosive environment. The test results and analysis of the corrosion FCI (CFCI) life of aluminum alloys and Ti---6A1---4V show that the expression of the CFCI life obtained by modifying the FCI life formula in laboratory air can give a good fit to the test results of the CFCI life. The salt water (3.5% NaCl) environment has no effects on the CFCI resistant coefficient compared with the FCI resistant coefficient in laboratory air. However, 3.5% NaCl environment greatly decreases the CFCI threshold of aluminum alloy, but has little effect on the CFCI threshold of Ti---6A1---4V. The loading frequency ranging from 1 Hz to 10 Hz has no appreciable effect on the CFCI life, and thus, the CFCI threshold of aluminum alloys investigated. Hence, the expression for the CFCI life of metallic notched elements proposed in this study is a better one, which reveals a correlation between the CFCI life and the governing parameters, such as, the geometry of the notched elements, the nominal stress range, the stress ratio, the tensile properties and the CFCI threshold. However, this new expression of the CFCI life needs to be verified by more test results.     

Digitally tunable optical filters using arrayed-waveguide grating(AWG) multiplexers and optical switches

Two novel configurations for digitally tunable optical filters based on arrayed-waveguide grating (AWG) multiplexers are described in detail with emphasis on the connection of the AWG multiplexer and optical switches. Performance comparisons show that conventional configurations are disadvantaged by the switch size required and loss imbalance among the optical frequency-division-multiplexed (FDM) channels; the proposed configurations require only O(√(N)) switch elements to select one of N FDM channels, and the loss imbalance is lower by up to 75% in decibel     

Reduction of sodium-accelerated oxidation of silicon nitride ceramics by aluminium implantation

Norton NBD 200 silicon nitride ceramics were implanted with sodium to a dose of 7.0×10¹⁵cm^-2 at 72 keV (1 at% peak sodium content at 100 nm). The sodium-implanted samples were further implanted with aluminium to 7.3×10¹⁵cm^-2 at 87 keV (1 at% peak aluminium content at 100 nm). The implanted and unimplanted samples were oxidized in 1 atm dry oxygen at 1100 and 1300°C for 2–6 h. Profilometry and scanning electron microscopy measurements indicated that sodium implantation led to up to a two-fold increase in the oxidation rate of silicon nitride. The sodium effect was effectively neutralized when aluminium was co-implanted. The opposite effects of sodium and aluminium on the oxidation resistance of silicon nitride can be attributed to their different roles in modifying the structure and properties of the oxide formed. This revised version was published online in November 2006 with corrections to the Cover Date.     

The lattice dynamics of the Fe(tpa) (NCS)2 complex : light-induced excited spin state trapping effect

A light-induced excited spin state trapping (LIESST) experiment for a thermal gradual spin crossover complex, Fetris (2-pyridylmethyl) amine(NCS)2 or Fe(tpa) (NCS)2, was attempted for the first time. The high spin (HS) state after light inducement stayed metastable over a period of days without relaxation at 10 K. Intersystem relaxation from a high to a low spin (LS) complex occurred at 50 K after bleaching at 10 K. Investigation of the Mossbauer spectra of the LIESST and relaxation experiment indicated that the Debye–Waller factor was a correlation parameter of the HS fraction and that the co-operative effect played a role in the relaxation process for such a solid compound. This revised version was published online in November 2006 with corrections to the Cover Date.     

Quick estimation of rare events in stochastic networks

This paper presents a method for fast estimation of probabilities of rare events in stochastic networks, with a particular emphasis on coherent reliability systems. The method is based on the concepts of likelihood-ratios (LR), change of probability measure and the bottleneck-cut in the network. Both polynomial and exponential-time Monte Carlo estimators are defined, and conditions under which the time complexity of the proposed LR estimators is bounded by a polynomial are discussed. The accuracy of the method depends only on the size (cardinality) of the bottleneck-cut, not on the topology and actual size of the network. Supporting numerical results are presented, with the cardinality of the bottleneck-cut ⩽20     

Influence of quantum capture and tunneling mechanisms on the dark current of bound-to-continuum quantum-well infrared photodetectors

We present a theoretical model for the dark current of bound-to-continuum quantum-well infrared photodetectors (QWIPs), by considering the field-induced mixing effect, tunneling rate and phonon scattering rate between bound and continuum states. Using this model, we can see clearly how these mechanisms significantly influence the Fermi levels of bound and continuum electrons, and thus, the dark current. Nonlinear temperature dependence of the dark current at low temperature is predicted and discussed in detail. The simulated dark currents exhibit good agreement with the experimental results, without use of parameter fitting techniques.     

STRESS INTENSITY FACTORS AND WEIGHT FUNCTIONS FOR SEMI-ELLIPTICAL SURFACE CRACKS IN FINITE-THICKNESS PLATES UNDER TWO-DIMENSIONAL STRESS DISTRIBUTION

Abstract— A Fourier series approach is proposed to calculate stress intensity factors using weight functions for semi-elliptical surface cracks in flat plates subjected to two-dimensional stress distributions. The weight functions were derived from reference stress intensity factors obtained by three-dimensional finite element analyses. The close form weight functions derived are suitable for the calculation of stress intensity factors for semi-elliptical surface cracks in flat plates under two-dimensional stress distributions with the crack aspect ratio in the range of 0.1 ≤ a/c ≤ 1 and relative depth in the range of 0 ≤ a/t ≤ 0.8. Solutions were verified using several two-dimensional non-linear stress distributions; the maximum difference being 6%.     

Wortmannin enhances CPP32-like activity during neuronal differentiation of P19 embryonal carcinoma cells induced by retinoic acid

P19 EC cells undergoes apoptosis during neuronal differentiation induced by retinoic acid. Two CPP32-like proteases, CPP32 and Mch-3, are expressed in untreated and retinoic acid-treated P19 EC cells. CPP32-like activity is remarkably increased in apoptosis during neuronal differentiation of P19 EC cells. Inhibition of CPP32-like proteases prevents apoptosis, suggesting that activation of CPP32-like proteases play central roles in the apoptosis during neuronal differentiation of P19 EC cells. Wortmannin, PI-3K inhibitor, enhances the CPP32-like activity of the retinoic acid-treated P19 EC cells. PI-3K may be involved in the apoptosis during neuronal differentiation as negative regulator.