紫外激光辐照非纯7-DHC研究

本文报道用KrF准分子激光和N_2分子激光分别辐照含杂质的7-去氢胆留醇合成维生素D_3的实验研究。维主素D_3的前身P_3的转化率～63％。     

Dependence uniformization: a loop parallelization technique

Data dependence uniformization, a method for overcoming the difficulties in parallelizing a doubly nested loop with irregular dependence constraints is proposed. This approach is based on the concept of vector decomposition. A simple set of basic dependences is developed from which all dependence constraints can be composed. The set of basic dependences is added to every iteration to replace all original dependences so that the dependence constraints become uniform. An efficient synchronization method is presented to obey the uniform dependence constraints in every iteration     

水压爆破拆除钢筋混凝土隐蔽部

水压爆破是一种控制爆破技术，它可在不动用机械设备情况下，用水作为介质，把炸药的爆炸能传递给待拆构筑物，达到破碎的目的。本文介绍采用水压爆破拆除钢筋混凝土工事的设计与实施，爆破取得圆满成功。     

混凝土爆破孔壁动态初始参量的数值模拟

在考虑爆轰波与孔壁相互作用及孔壁的可压缩性等主要因素情况下，根据爆轰理论和流体动力学原理，建立了计算偶合装药点起爆时孔壁动态初始参量的物理模型，给出了计算公式。计算了中等威力炸药（如２＃岩石炸药、乳化炸药和水胶炸药）在混凝土中爆炸时孔壁动态初始参量（如初始冲击波压力、速度等值），得到了自起爆点开始沿炮孔长度方向各参量的变化规律、并得出了一些有意义的结论。     

Diagnosis of involutometric issues in flat rolling of external helical gears through the use of finite-element models

High-volume production of precision external-involute helical gears using flat-rolling is impeded by a number of quality issues. Experimental resolution of these issues is expensive and time consuming. The present study utilizes finite-element models (FEM) to diagnose three of these quality issues and to explore possible solutions. Two- and three-dimensional (2D and 3D) ABAQUS models were developed for a specific gear-manufacturing process and resulting geometries were not satisfactory. Subsequently, 3D DEFORM simulations were developed for the same process. Numerically predicted geometries were benchmarked against actual results obtained through designed experiments. Finite-element modeling and experimental results were correlated and the models were validated. Possible solutions were simulated and analyzed through additional modeling. Results obtained from the initial pass of the 3D models have been promising although progress has been limited by the excessive computational time needed. Frequency of re-meshing, high number of elements due to fine mesh, and changing re-mesh criteria contribute to the computational difficulties.     

Comments on "H/sub /spl infin// fuzzy control design for nonlinear singularly perturbed systems with pole placement constraints: an LMI Approach"

In this correspondence, we point out some lethal errors in the proof of the theorems given in the aforementioned paper.     

利用系统试井资料求取异常高压油藏储层渗透率变化系数的方法

在异常高压油藏储层中,储集层渗透率随地层压力下降而急剧降低,渗透率变化系数是重要的特性参数。本文研究了异常高压油藏稳定渗流规律,建立了利用系统试井资料求取渗透率变化系数的方法。     

Trimble 5700常见故障及排除方法

Timble 5700已成为工程测量市场上的主力军，本文介绍了Trimble 5700在RTK作业中常见的三例故障的故障现象，并给出了故障的排除方法。     

液晶投影电视技术的研究

本文介绍了国外液晶投影电视的发展动态,结合对典型液晶彩色投影机特性的介绍,剖析了液晶投影电视机的结构和原理,并进一步探讨了研究液晶投影电视技术的有关技术要点,阐述了在我国进行这项技术研究的有关问题。     

A direct digital frequency synthesizer with fourth-order phase domain /spl Delta//spl Sigma/ noise shaper and 12-bit current-steering DAC

This paper presents a direct digital frequency synthesizer (DDFS) with a 16-bit accumulator, a fourth-order phase domain single-stage /spl Delta//spl Sigma/ interpolator, and a 300-MS/s 12-bit current-steering DAC based on the Q/sup 2/ Random Walk switching scheme. The /spl Delta//spl Sigma/ interpolator is used to reduce the phase truncation error and the ROM size. The implemented fourth-order single-stage /spl Delta//spl Sigma/ noise shaper reduces the effective phase bits by four and reduces the ROM size by 16 times. The DDFS prototype is fabricated in a 0.35-/spl mu/m CMOS technology with active area of 1.11mm/sup 2/ including a 12-bit DAC. The measured DDFS spurious-free dynamic range (SFDR) is greater than 78 dB using a reduced ROM with 8-bit phase, 12-bit amplitude resolution and a size of 0.09 mm/sup 2/. The total power consumption of the DDFS is 200mW with a 3.3-V power supply.