Modeling the reverse base current phenomenon due to avalancheeffect in advanced bipolar transistors

A model of reverse base current characteristics which is based on device physics is presented. The model requires only physical parameters, thus allowing circuit designers to estimate the device performance under avalanche operation prior to the actual device fabrication. Previously reported experimental data are included in support of the model     

箱式变电站箱内温升及变压器的负载率

箱式组合变电站箱内温的特点跟负载特性及箱壳的散热结构有关，而变电站内的电力变压器的负载率又跟箱内温升及箱壳的散热等级有关，本文给出了变压器负载率的计算公式和参考值。     

Diels-Alder Reaction of [60]Fullerene with Dienes Having an Ester Substituent at 1-Position

Treatment of [60]fullerene with ethyl trans, trans-hexa-2,4-dienoate (1) and methyl trans, trans-octa-2,4-dienoate (2) at 70 ∼ 100 °C afforded products 3 and 4, respectively, which are resulted from Diels-Alder addition of the dienoates to a 6/6 ring junction of [60]fullerene.     

Interferometric method for preventing mode-hopping in tunable external-cavity semiconductor lasers

A problem in frequency-tuning of external-cavity lasers is mode-hopping between neighbouring external-cavity modes. We demonstrate a new interferometric method for monitoring mode-hoping and an automatic control circuit for a 1.3 ?m grating external-cavity laser that maintains single-mode operation when the lasing frequency is tuned.     

稀土配合物Eu(TTA)3Phen掺杂的PMMA树脂的制备及其发光性能研究

用新的合成方法合成了稀土配合物Eu(TTA) 3Phen。研究了该配合物的IR、UV、TGA、元素分析和荧光光谱。该配合物具有良好的发光性能和热稳定性。采用加热方法将Eu(TTA) 3Phen掺入PMMA树脂中 ,制成发光塑料树脂 ,并测定其发光性能。结果表明 ,Eu(TTA) 3Phen掺入PMMA树脂后仍保持该稀土配合物原有的发光特性 ,制成的Eu(TTA) 3Phen -PMMA树脂复合材料具有良好的发光性能 ,其发光强度与Eu(TTA) 3Phen掺入的含量有关。     

Integral-equation representations of flow elastoplasticity derived from rate-equation models

Summary Two integral-equation representations are presented in this paper, based on the exact integrations of the conventional rate-equation model of associativeJ ₂ flow elastoplasticity with combined-isotropic-kinematic hardening-softening. Among them the strain-controlled integral-equation representation has two new naturally defined material functionsY(Z) andU(Z) of the normalized active workZ, which plays the role of intrinsic time. One of the immediate benefits derivable from the new representations is, owing to the explicit unfolding of the highly nonlinear path-dependence between stress and strain without a detour to the evolutions of internal state variables, their adaptability for direct calculations without any iteration. Indeed, it is itself a constructive algorithm. It is shown that at a realistic level of precision, the strain-controlled integral-equation representation saves 99% or more of the CPU time compared with the widely used elastic predictor-radial return algorithm of the rate-equation representation.List of symbols e _ij ,e _ij ^e ,e _ij ^p strain deviator, elastic strain deviator, plastic strain deviator - effective strain - ^p effective plastic strain - e ₁,e ₂,e ₃ principal strain deviator,e ₃=–e ₁–e ₂ - e _tan,e _rad tangential strain increment, radial strain increment - E Young's modulus, assumed to be constant - f yield function in stress space - F yield function in strain space - G shear modulus, assumed to be constant - G(Z ₁,Z ₂) shear relaxation function of elastoplasticity - h( ^p ),k( ^p ) material functions of plasticity for the stress-space rate-equation representation - material functions of plasticity for the strain-space rate-equation representation - I ₂ second invariant of the deviatoric strain tensor - J ₂ second invariant of the deviatoric stress tensor - J(z ₁,z ₂) shear creep function of elastoplasticity - K bulk modulus, assumed to be constant - p dummy variable of integration in place of the effective plastic strain - r _ij active stress - R _ij active strain - effective active-stress, i.e. times Euclidean length of active stress - effective active-strain, i.e. times Euclidean length of active strain - S _ij ,S _ij ^e ,S _ij ^r stress deviator, elastic stress deviator, stress relaxation - effective stress - effective stress relaxation - S ₁,S ₂,S ₃ principal stress deviator,S ₃=–S ₁–S ₂ - t, , , time - t ₀ zero-value time - t _u latest unloading time - y(z), u(z) material functions of plasticity for the stress-controlled integral-equation representation - Y(Z), U(Z) material functions of plasticity for the strain-controlled integral-equation representation - z normalized active complementary-work - material functions defined for use in convertingh( ^p ) andk( ^p ) toy(z) andu(z) - Z normalized active work - material functions defined for use in convertingh( ^p ) andk( ^p ) toY(Z) andU(Z) - _ij back stress - A _ij back strain - _ij , _ij ^e , _ij ^p strain, elastic strain, plastic strain - _y (initial) yield strain, _y =h(0)/2G - Poisson's ratio assumed to be constant - _ij , _ij ^e , _ij ^r stress, elastic stress, stress relaxation - _y (initial) yield stress, yield strength, _y =h(0)     

Bandwidth-expandable erbium-doped fiber amplets

A narrow-band optical amplifier (“amplet”) is proposed and demonstrated that can be constructed into an amplifier-based subsystem to perform nonlinear dispersion compensation and to flatten gain while the input level changes in a dense wavelength-division-multiplexed (DWDM) optical networking system. The amplet is designed to inherently provide two networking features: narrow-band accessibility and bandwidth scalability. For a 100-GHz-spaced DWDM application, each amplet can process four channels. The crosstalk between amplets is better than 58 dB. The capability to flatten gain and improve the transient response is experimentally demonstrated when an amplet array subsystem is formed     

磨矿介质对钼精矿碳含量影响研究

分析研究了低铬合金铸球和复相球墨铸球中碳的赋存状态及其对普通钼精矿、57钼精矿和二硫化钼粉碳含量的影响,指出用浮选法生产低碳57钼精矿,一段磨矿介质不宜使用复相球墨铸球.     

A First-Order Model for Depolarization of Propagating Signals by Narrowband Ricean Fading Channels

We show by simulation that when the fading signals observed on orthogonally polarized diversity branches follow Ricean statistics, the distribution of polarization states on the Poincar′e sphere is well-approximated by a Fisher distribution. Further, we show that the Fisher concentration parameter is: (1) completely determined by the corresponding Ricean Kfactors and the cross-correlation coefficient between the diversity branches, both of which can be estimated from simple measurements of received power vs. time, and (2) a good indicator of the level of cross-polar discrimination (XPD) on the channel. The insights gained are potentially useful to those engaged in the development and validation of schemes that use either polarization re-use or polarized MIMO.     

Validation of bulk-charge effect parameter extraction in MOSFETs

Our recently proposed method to extract the bulk-charge effect parameter in MOSFETs is scrutinized by studying SOI devices, a-Si:H TFTs and short- as well as long-channel bulk MOSFETs. The method requires measuring the drain current as a function of gate voltage at two small values of drain voltage chosen in the linear region of operation.