Cr12型模具钢锻造内部裂纹产生的原因及预防

基于Cr12型钢种的特点，归纳了Cr12钢锻造时内部裂纹的类型，分析了内部裂纹产生的原因并提出了相应的预防措施。     

光谱法快速测定土壤中的多个微量元素

本法采用碳酸钡、氟化锂、石墨粉作缓冲剂，用锑做铅锌的标．用铪作铌的内标，用钯作铍、铬、镧、锶、铜的内标。采用小孔电极，交流电弧做为激发光源，同时测定铅、锡、锌、铍、铬、镧、铌、铜、锶等九个元素。分析数据基本稳定．能达到土壤样品的检出限要求。     

日毛绒狗信息重组价值增

一只毛绒狗的故事 “大红狗”是正流行在日本京都白领女性圈子里的一款玩具。它选用毛巾布料，因此手感良好，据宣传称它的红色能够刺激脑细胞，使人充满活力，所以兼具一定的医疗保健作用。很多白领女性都喜欢将它摆放在办公室的写字台上，而现在东京都三鹰市内各大商店正以2100日元（含税）的价格热销中。     

浅谈变频器供电条件下电动机的温升与对策

随着变频调速技术的蓬勃发展，变频器供电电机的温升问题已引起人们的广泛关注。本文首先讨论了电动机的温升限度；然后结合感应电机温升实验的相关数据分析了变频器供电对电动机温升的影响及其原因；最后从降低发热量和提高散热能力两方面提出缓解电机温升的措施，并指出了实际应用中应注意的问题。     

彩泥玩出夏日魅力

产品特点 主题新潮健康：每套产品都配合儿童的特点以某一主题来设计，如“恐龙世界”通过不同种类和形状的恐龙，启发孩子去探索人类的起源；“快餐中心”让家长与孩子同乐，一齐制作不同的“美食”等等。这使得孩子在玩的过程中增长了见识。[编者按]     

Drying Equipments for Pharmaceutical Industry

此文为李桢教授在2004年11月时寄予本刊。我们在“干燥刊中刊”发表此文以纪念为中国干燥行业作出巨大贡献的李桢教授。下附李桢教授写给本刊编辑的亲笔信：     

DSP技术在液压混合动力汽车能源控制方面的应用

文章分析了液压混合动力汽车的发展趋势,简述数字信号处理器(DSP)作为控制器的优势和DSP作为控制器对并联式混合动力液压车的能源控制的工作原理,给出了能源控制系统DSP信号流程图和主程序流程图。测试结果表明,DSP能源控制系统能够比较精确的对液压混合动力车的能量消耗与分配进行控制,具有很好的应用前景。     

朔州桑干河流域灌区的改革实践

在社会主义市场经济条件下,朔州市桑干河流域原有的分市县管辖的8处大中型灌区的管理体制和运行机制已不适应水管单位生存发展的需求.从解决长期以来水管单位面临的诸多实际问题出发,按照程序报请各级政府批准后,原分散管理的8处灌区统一划归桑干河水利管理局管理.该改革以理顺关系、设置机构为突破口,建立起了以流域为建制的新型水管体制,在运行过程中不断探索和解决改革中出现的新情况和新问题,有利于维护水资源的可持续利用和生态与环境的协调发展.     

Swelling behavior induced by alteration in granite and its implications on underground excavation

Granite is commonly recognized as an ideal medium for underground construction. However, in the site investigation for Heimifeng Pumped Storage Power Station project, it was found that there are swelling behaviors induced by alteration in granite and eventually causing slaking and disintegration of rock blocks. The study shows that hydrothermal alteration in granite is primarily due to the intrusion of multi-phase igneous magma. The clay minerals, such as montmorillonite, chlorite, kaolinite, are the main causes for the swelling behavior of granite. In the exploratory adits, alteration was observed to occur mainly along faults or fractures in the rock masses and resulted in roof caving if water is present. Some of the highly altered borehole cores swell and crack within 24 h in water and eventually disintegrate completely. From the testing results on the samples, the maximum axial free swelling strain is about 1.2%, while the maximum axial confined swelling strain is around 0.1% with swelling stress less than 25 kPa. Under free swelling tests, 80% of swelling is completed within 24 hours. Under confined swelling condition, swelling process is completed within 1 h for some samples, with 80% of maximum swelling strain finished within around 22 h for most of the samples. Contraction of samples occurs after swelling completed. The strength of granite, reflected by deformation and elastic moduli, shear strength, decreases due to alteration. The deformation and elastic moduli are even lower compared to highly weathered rock. The shear strength is between that for highly weathered and slightly weathered rocks. The swelling characteristics of the altered rock present great challenges for support or lining during construction and operation stages. Support or lining shall be in place immediately after excavation. Since the rock may swell when encountering water, the shotcrete shall be designed accordingly. During the construction of access tunnel and caverns, water shall be drained in time. Drainage directly from surface shall be avoided so as to prevent floor heave.     

Growth and morphology of nanometer LiMn2O4 powder

The growth of Li_1+xMn₂O₄ via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Powder X-ray diffraction and transmission electron microscopy were used to characterize the products. Li_1+xMn₂O₄ with 1-2 μm spherical morphology and more uniform secondary particles, but with smaller primary particles of diameters from 20 to 60 nm and a variety of morphologies were found. The oxides produced by this cheap method affirmed the validity of detonation synthesis of nano-size powders.