射流通风增压技术的研究

目前，公路、铁路隧道普遍采用纵向式射流通风，虽然射流通风系统具有很多优点，但射流通风效率较低，一般仅为15％左右．本文采用在射流风机出口设置收缩管以提高射流速度的方法。通过射流增压和隧道通风效率的理论分析及实例计算，表明该方法可使射流增压有显著的提高，最高达到54．8％。从而提高了隧道射流通风的通风效率，大约能提高10个百分点。     

Reaction synthesis of TiC–TiB<Subscript>2</Subscript>/Al composites from an Al–Ti–B<Subscript>4</Subscript>C system

The TiC–TiB₂/Al composites were fabricated by self-propagating high-temperature synthesis (SHS) from Al–Ti–B₄C compacts. The addition of Al to the Ti–B₄C reactants facilitates the ignition occurrence, lowers the reaction exothermicity, and modifies the resultant microstructure. The maximum combustion temperature and combustion wave velocity decrease with the increase in the Al amount. The B₄C particle size exerts a significant effect on the combustion wave velocity and the extent of the reaction, while that of Ti has only a limited influence. The reaction products are primarily dependent on the B₄C particle size and the Al content in the reactants. Desired products consisting of only the TiC, TiB₂, and Al phases could be obtained by a cooperative control of the B₄C particle size and the Al content.     

液态渣显热回收技术现状及前景分析

阐述了国内外冶金液态渣显热回收技术状况以及发展趋势，分析了其基本原理，提出了液态渣显热回收技术的发展前景与开发方向，对铁合金行业进一步研究该技术具有促进作用。     

Preparation of Mesostructured Lamellar Zirconia

Mesostructured lamellar zirconia was synthesized in the hydrothermal systems using Cetyltrimethyl Ammonium Bromide (CTAB) as a template and zirconyl chloride as zirconium precursor. The as-prepared composites were characterized by X-ray diffraction (XRD), TG-DTA, and DR-UV techniques. The influences of hydrothermal aging time, total concentration of solution, different mole ratio of zirconyl chloride/surfactant, and post treatment on the structure of mesostructured lamellar zirconia were discussed in this article.     

Toward using confidence intervals to compare correlations.

Confidence intervals are widely accepted as a preferred way to present study results. They encompass significance tests and provide an estimate of the magnitude of the effect. However, comparisons of correlations still rely heavily on significance testing. The persistence of this practice is caused primarily by the lack of simple yet accurate procedures that can maintain coverage at the nominal level in a nonlopsided manner. The purpose of this article is to present a general approach to constructing approximate confidence intervals for differences between (a) 2 independent correlations, (b) 2 overlapping correlations, (c) 2 nonoverlapping correlations, and (d) 2 independent R2s. The distinctive feature of this approach is its acknowledgment of the asymmetry of sampling distributions for single correlations. This approach requires only the availability of confidence limits for the separate correlations and, for correlated correlations, a method for taking into account the dependency between correlations. These closed-form procedures are shown by simulation studies to provide very satisfactory results in small to moderate sample sizes. The proposed approach is illustrated with worked examples. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physical modeling of hole mobility in silicon inversion layers under uniaxial stress

A physical model for hole mobility under either biaxial or uniaxial stress has been developed. The six-band k ? p theory is used to obtain the bandstructure through stress-dependent Hamiltonian. The hole mobility in the silicon inversion layer is studied in details using Monte Carlo method. A numerically robust method has been applied to achieve self-consistent solution of Poisson’s and Schrödinger equations.     

Sintering and dielectric properties of Al2O3 ceramics doped by TiO2 and CuO

The effects of CuO and TiO₂ additives on the microstructure and microwave dielectric properties of Al₂O₃ ceramics were investigated. Al₂O₃ ceramics with CuO and TiO₂ additions can be well sintered to achieve 93∼98% theoretical densities below 1,360 °C due to Ti₄Cu₂O liquid phase sintering effect. The Qf values decreased with increasing CuO and TiO₂ content, due to the formation of the second phase Ti₄Cu₂O. However, the varying behaviors of the dielectric constant (ɛ _r ) and temperature coefficients (τ _f ) were associated with phase constitutions, as a result of the change of CuO and TiO₂content. The τ _f can be shifted close to 0 ppm/°C by controlling the content of CuO and TiO₂. The specimens with 0.5 wt.% CuO and 7 wt.% TiO₂ sintered at 1,360 °C for 4 h showed ɛ _r of 11.8, Qf value of 30,000 GHz, and τ _f of −7 ppm/°C.     

T - Vmin addressing mode and an improved equivalent circuit model for ferroelectric liquid crystal displays

The authors describe an improved model for modelling the electro-optical response of a ferroelectric liquid crystal display and discuss its applicability. The model includes the direct coupling of applied electric fields to dielectric permittivity, an effect not accounted for in previous equivalent circuits. Compared with previous models, the new model has more capability in optical response prediction and device setup optimisation when the dielectric biaxiality of ferroelectric liquid crystals is of a relatively high value. In the improved model, different trends of switching time are observed as drive voltage rises in cases of positive anisotropy and negative anisotropy. The bend in tau-V_min mode, that is, the minimum pulse area for switching directors, is measured and the mechanism of optical contrast enhancement and switching process complemented by high-frequency ac pulses is clearly explained. Results obtained from the improved model compare favourably with that obtained from numerical models and from testing of a real cell     

Large third-order optical nonlinearity of SrBi2Nb2O9 thin films fabricated by pulsed laser deposition

SrBi₂Nb₂O₉ (SBN) thin films with a single phase of layered perovskite structure have been fabricated on fused quartz substrates at room temperature by pulsed laser deposition. The XRD and AFM analysis indicated that the films had better crystallinity, less rough surface morphology, and larger grain size with increasing oxygen pressure. The nonlinear optical properties of the samples were determined using a single beam Z-scan technique at a laser wavelength of 532 nm with laser duration of 25 ps. The real and imaginary parts of the third-order nonlinear optical susceptibility χ⁽³⁾ of the films were measured to be 3.18 × 10^− 8 esu and 5.94 × 10^− 9 esu, respectively.     

石油钻机井架载荷谱的编制

载荷谱是进行机械结构强度试验和疲劳损伤研究的重要依据,而井架本身承受随时间变化的动载荷作用,加之各钻井工况承载变化不一,建立符合钻井实际的载荷时间历程成为进行瞬态分析和疲劳损伤研究的需要。通过实测钻机井架在钻探过程的大钩载荷,运用极值统计分析方法,建立最大载荷概率分布模型,运用疲劳载荷谱的编制方法,完成了井架正常钻探时的载荷时间历程的编制,并获得了可用于试验加载的程序载荷谱。编制的程序载荷谱包含了所有钻探作业工况,反映了井架真实承载环境,可用于钻机井架的瞬态分析和疲劳损伤研究,并大大简化了计算过程,提高了井架动力分析的可靠性。