关于电感线圈的联接问题

探讨了电感线圈的几种联接,得到了两线圈顺接并联时完全耦合的必要条件,以及n个线圈串联或并联时的电感计算公式．     

在任意控制点测设缓圆曲线

缓圆曲线在线路测量中经常使用 ,测量员应了解如何正确计算曲线上任意点的坐标 ,在实地快速计算点位坐标并进行精确 ,能提高测量工作的效率     

整体最优双圆弧拟合

提出了用整体最优双圆弧样条拟合离散数据点的算法．首先分析了双圆弧逼近的误差分布,并且根据这个误差分布调整端点、切向和双圆弧插值时的惟一自由变量,使得数据点的误差分布均匀、圆弧的段数尽可能少,由此得到G^1连续的整体最优双圆弧样条．这个方法在数值控制刀具的运动路线的设计和机器人的移动路线设计上非常有用。     

关于需求价格弹性的探讨

需求价格弹性是管理经济学中的一个重要概念,是指导市场行为的重要指标,如何理解需求价格弹性概念,掌握弹性的计算方法就显得格外重要.本文探讨需求价格弹性的概念及计算方法.     

风琴管空化清洗喷嘴结构改进及数值分析

空化水射流是一种运用水机械"汽蚀"的原理来增强射流冲蚀效果的高效水射流技术,风琴管喷嘴由于具有良好的空化初生和空化打击效果而在该领域广泛使用。该喷嘴流场中收缩段入口壁面附近会由于压力的降低而产生较强空化现象,如果将喷嘴收缩段壁面边界向外部扩展,增大低压产生区域的作用范围,设计了圆弧段扩张口径的空化喷嘴,同时引入脉冲结构进行改进。采用CFD软件对相同参数下普通风琴管喷嘴和新型喷嘴进行流场分析。结果表明,新型喷嘴圆弧段内部的大漩涡流场更有利于空化产生,具有脉冲结构的新型喷嘴中漩涡区域的空化气泡能够较容易地随脉动水体喷出,且水射流具有较强的瞬时冲击力,因而喷嘴的空化清洗效果将会更显著提升。     

Developing electrodeposition techniques for preconcentration of ultra-traces of Ni, Cr and Pb prior to arc-atomic emission spectrometry determination

Electrodeposition is known to be proper for separation and preconcentration of extremely low concentrations of analytes from the bulk sample which is instrumentally very simple. In the present research, a combination of electrodeposition with arc atomic emission spectrometry (ED-AAES) method has been developed in order to improve the analytical performance of this spectrometry technique. The results show that sensitivity and detection limits by using ED-AAES were improved 1000–2000 folds over those of normal arc atomic emission spectrometry in determination of the selected elements. The detection limits for measurement of Ni, Cr and Pb were 2.56, 3.05 and 2.11 µg L^{− 1} for monodeposition and 3.31, 3.72 and 3.25 µg L^{− 1} for simultaneously deposition, respectively. The precision of determination was in the range of 2–4% RSD. Typical calibration graphs for these elements were linear up to 100 µg L^{− 1}, depending on the element and matrix.Application of this technique was also tested on determination of the studied elements in an electroplating plant's waste water. The accuracy of technique was verified by comparing the results of the waste water analysis with those of electrothermal atomic absorption spectroscopy as a reference standard method.The obtained results show that the combined technique (ED-AAES) has been progressed substantially toward the ultimate goal of direct interference-free determination of trace analysis in complex samples by AAES.     

Simultaneous determination of Cr,Ga, In and V in soil and water samples by tungsten coil atomic emission spectrometry

Tungsten coil atomic emission spectrometry is employed for the simultaneous determination of Cr, Ga, In, and V. Both V and In are detected by this technique for the first time. The atomizer is a simple, inexpensive tungsten filament extracted from a mass-produced, commercially-available 150 W, 15 V microscope bulb. A 25 µl sample aliquot is placed directly on the coil and a small constant-current power source is used to carefully dry, ash and atomize the sample. Analytical signals are detected with a Czerny-Turner spectrograph and a charge coupled device detector. Multiple emission lines from all 4 elements are monitored simultaneously in a 54 nm spectral window. Concentration limits of detection are in the µg l^− 1 range for all elements, and the absolute limits of detection are 0.2, 2, 0.5, and 10 ng for Cr, Ga, In, and V, respectively. Even lower values may be obtained by combining the signals for the multiple emission lines of a single element. The method precision is typically better than 5.0% relative standard deviation, and sometimes as good as 0.95% (Ga). Standard reference materials of soil and water are used to check the method accuracy. After a simple acid extraction, the values determined by the method presented no significant difference from the reported values at the 95% confidence level.     

双脉冲MIG/MAG焊全数字控制策略

对于双脉冲MIG/MAG焊,在基于变速送丝的基础上,为实现等弧长控制与过程稳定,提出了包括弧长稳定、电压和电流瞬时值反馈计算的三闭环控制模型.在每个熔滴过渡周期内,该模型能够检测弧长变化并做出调整,对于干伸长的变化也能进行实时补偿.采用DSP进行了全数字实现,样机实验表明,所提出的控制策略可行,焊接过程稳定,焊缝成型美观.     

Synthesis and micellization behavior of stimuli-responsive polypeptide hybrid triblock copolymer

Polypeptide hybrid triblock copolymer, poly（L-glutamic acid）-b-poly（propylene oxide）-b-poly （L-glutamic acid） （PLGA-b-PPO-b-PLGA）, was synthesized by the ring-opening polymerization of benzyI-L- glutamic N-carboxyanhydride （BLG-NCA） using poly（propylene glycol） bis（2-aminopropyl ether） as initiator, followed by the subsequent deprotection step. The obtained double hydrophilic triblock co- polymer exhibits ＂schizophrenic＂ micellization behavior in aqueous solution upon dually playing with solution pH and temperature. The multi-responsive micellization behavior of this polypeptide hybrid triblock copolymer has been thoroughly investigated by 1H NMR, laser light scattering （LLS）, tempera- ture-dependent optical transmittance, and circular dichroism spectroscopy （CD）.     

电弧离子镀制备Cr-O-N涂层及生长机理探讨

为了弄清O2和N2的流量变化和基体负偏压对涂层微观结构的影响,利用电弧离子镀技术制备了Cr-O-N涂层,对涂层样品进行了X射线衍射分析,扫描电镜和原子力显微镜观察,电子探针成分分析,结果表明Cr-O-N涂层含CrN和Cr2O3相,衍射峰的择优取向、涂层的表面粗糙度、相含量和化学成分与制备过程中的气体流量、基体负偏压等因素密切相关:随着氧流量的增加,涂层的表面粗糙度上升,涂层中氧元素含量和Cr2O3相含量增多;基体负偏压的升高有利于涂层沿CrN(220),Cr2O3(300)面择优生长和涂层的致密性提高.