牵引变电所防雷技术浅析

从过电压的概念入手,简要分析了雷电的形成原因,粗浅提出了目前变电所的主要防雷保护措施。     

改良半固体四硫磺酸钠煌绿培养基用于鸡肉中沙门菌的检测

目的使用改良半固体四硫磺酸钠煌绿(MSTT)培养基对鸡肉样品中的沙门菌进行初筛,作为附加步骤对ISO 6579.2002方法进行改良,以节约人力物力和时间。方法将MSTT培养基经虹吸法装入玻璃毛细管,插入预增菌液或增菌液类液体培养基,使半固体培养基和液体培养基相结合,预增菌或增菌过程同动力增菌过程同步进行。此外对使用MSTT培养基改良ISO 6579.2002方法分为纯菌种组和自然鸡肉样品组分别试验,并对结果进行评估。结果应用改良ISO 6579.2002方法,沙门菌株检出率纯菌种组为98%(126/129),自然污染的沙门菌阳性鸡肉样品检出率为92%(35/38),而原ISO 6579.2002方法对自然污染的沙门菌阳性鸡肉样品检出率为87%(33/38),低于改良法;与原方法相比,72%(264/367)的阴性样品不需要进一步分离和鉴定试验。结论应用MSTT培养基改良后的ISO 6579.2002方法能够应用于鸡肉中沙门菌的检测,且优势明显。     

水电项目总承包成本风险系统动力学识别模型

水电工程的建设一般投资大、周期长,受自然环境、技术手段和市场波动等内外部不确定因素影响较大,所以成本变动可能性很大。总承包商要避免成本风险带来的不利影响就必须了解项目成本变动的影响因素并采取有效措施。系统动力学通过动态分析和反馈来帮助决策者理解复杂系统的结构和特点。本文提出了运用系统动力学进行总承包成本风险识别的基本思路,从风险模型结构要素及作用机理方面进行了论述,运用Vensim PLE软件绘出风险结构图,建立了风险识别模型,揭示了风险因素及其内在联系,对成本风险进行反馈识别,从而降低项目成本中威胁的负面影响,提高总承包商对建设项目的管理水平。     

叔丁基头孢克肟侧链酸的合成

以去甲氨噻肟酸乙酯为起始原料,在相转移催化剂聚乙烯醇400存在下"一锅法"完成水解、醚化反应,精制后得到目标化合物,确定了较优的反应条件,总收率72.8%,纯度98.7%。目标产物的结构均经1HNMR表征。该合成路线原料易得,成本低,操作简单。     

干燥机托轮位置的分析及调整

针对化纤厂干燥机系统运行中出现的转动筒体的位置调整,通过对干燥机托轮和轮带的受力分析以及托轮位置的具体调整方法,从根本上解决了影响干燥机运行中的问题,收到了良好的效果,达到了设备运行要求,提高了设备运行周期,保证了装置平稳运行。     

Analysis of the ionospheric variability based on wavelet decomposition

In this work,the ionospheric variability is analyzed by applying the wavelet decomposition technique to the noontime fo F2,F10.7,interplanetary magnetic field(IMF)Bz,Ap,and lower thermospheric temperature at pressure of 10?4 h Pa in 2002.Results show that the variance of periodic oscillations in the ionosphere is largest in the 2–4-day period and declines with the increase of the period.The maximum variance of the periodic oscillations in solar irradiation is in the 16–32-day period.For geomagnetic activities,most of the variance is about equally distributed on intervals of periods shorter than 32 days.Variance distributions of IMF Bz and lower thermospheric temperature are similar to those of the ionosphere.They show the maximum in the 2–4-day period and decline with the increase of the period.By analyzing the distributions of the variances,the potential connections between the ionosphere and the external sources are discussed.     

In-situ Fabricated TiB2 Particle-whisker Synergistically Toughened Ti（C,N）-based Ceramic Cutting Tool Material

The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers.However,the process of adding whiskers or nanoparticles has the disadvantages of high cost and health hazard as well as the agglomeration;although a new in-situ two-step sintering process can solve the above problems to some extent,yet the problems of low conversion ratio of the raw materials and the abnormal grain growth exist in this process.In this paper,an in-situ one-step synthesis technology is proposed,which means the growth of whiskers or nanoparticles and the sintering of the compact can be accomplished by one time in furnace.A kind of Ti(C,N)-based ceramic cutting tool material synergistically toughened by TiB_2 particles and whiskers is fabricated with this new process.The phase compositions,relationships between microstructure and mechanical properties as well as the toughening mechanisms are analyzed by means of X-ray diffraction(XRD)and scanning electron microscopy(SEM).The composite which is sintered under a pressure of 32 MPa at a temperature of 1700℃in vacuum holding for 60 min can get the optimal mechanical properties.Its flexural strength,fracture toughness and Vickers hardness are 540 MPa,7.81 MPa?m~(1/2)and 20.42 GPa,respectively.The composite has relatively high density,and the in-situ synthesized TiB_2 whiskers have good surface integrity,which is beneficial for the improvement of the fracture toughness.It is concluded that the main toughening mechanisms of the present composite are whiskers pulling-out and crack deflection induced by whiskers,crack bridging by whiskers/particles and multi-scale particles synergistically toughening.This study proposes an in-situ one-step synthesis technology which can be well used for fabricating particles and whiskers synergistically toughened ceramic tool materials.     

基于技术进化趋势的裁剪方法研究

裁剪是TRIZ中一种有效解决问题的方法,其通过删除问题元件,重组系统有用功能进行产品创新设计,达到简化系统与优化产品的目的.为了启发和引导设计者在裁剪过程中有效地利用资源,在使用裁剪规则引导创新设计的基础上,以具有预测性和启发性的技术进化趋势作为知识源,综合分析进化趋势解题与裁剪规则引导功能重组的资源来源,构建了进化趋势与裁剪规则的映射关系,提出了基于裁剪规则的多层次进化趋势选择策略,利用进化趋势辅助功能重组,构建了基于进化趋势的裁剪方法过程模型.最后通过钢带铠装机裁剪实例验证了此方法的合理性.     

高抽巷合理层位相似模拟的研究

为研究煤层开采对覆岩的移动破坏规律,获得覆岩的破坏范围,从而确定高抽巷的布设位置,以淮南刘庄矿151305工作面为研究对象,建立了倾向和走向模型。通过相似模拟的方法在煤层走向及倾向上结合应力场、裂隙场以及瓦斯场,验证对上覆高瓦斯煤层实行"煤与瓦斯共采"这一战略的可行性。通过模拟,得出煤岩体水平变形和竖直位移变化规律并监测岩体内应力变化情况,并以此为依据,确定高抽巷的位置。结果表明:从回风巷开始向采空区沿走向延伸12 cm并以55°角度向上和在回风巷处以114°角度向上的范围内,布置高抽巷时,既有利于巷道完整性的保持,同时与裂隙发育区沟通的离层裂隙也有利于采空区瓦斯的抽采。     

变频节电技术在炼钢厂高压电动机上的应用

中天钢铁集团有限公司第二烧结厂、第二炼铁厂的10台高压电机依靠管道的风门调节风量,致使管道阻力增大,容易使管道积灰堵塞,浪费电能。采用变频节能技术对10台高压电动机进行改造,提高电动机运行效率,节约电能,降低生产成本。