快速、高效、独立型NiMH/NiCd电池充电

引言尽管近期人们普遍关注的杰点是锉离子电池,但不应忘却其他化学电池,例如镍锡(NiCd)和镍氢(NiMH)电池在可再充电电源系统中拥有自己的优势。基于镍的电池很坚固、能够承受商放电速率、具有上佳的使用寿命、不需要特殊的保护电路、而且也比铿离子电池便宜。在这两种电池中。由于电池容量(NiMH电池的容量比NiCd电池高4%-50%)和环保方面的原因(NiCd电池含有有毒的镉元素),NiMH电池正在迅速取代NiCd电池。快速、高效、独立型NiMH/NiCd电池充电@Fran Hoffart     

涨价潮之下,家电市场变天

自2020年下半年以来,涨价就成为家电市场的热点话题,进入2021年,多个家电品牌向经销商接连发布涨价通知。TCL自1月15日起,白电产品全面涨价,涨幅为5%-15%;海尔自1月下旬起,统一提高热水器售价5%-20%;美的冰箱产品价格体系自3月1日起上调10%至15%。     

国内LED产业结构及发展趋势分析

LED整体产业链的门槛被连年降低。上游为单体芯片和晶体,中游为LED芯片处理,下游为封装测试和应用。产业上游和中游的具有国际竞争激烈、极具商业风险、极具科技含量和需巨大资金支持等特点。在整个链条中,上游LED芯片及其芯片外延产业占有整个产业70%的利润,封装占有10%-20%,LED应用占10%-20%。全球LED工业在日本、中国台湾、欧洲、美洲、韩国、中国大陆都有不同程度的渗透。日本享有50%的份额,执全球LED工业之牛耳。     

一种弱凝胶调剖剂的合成与性能评价

用聚丙烯酰胺、调节剂、苯酚和交联剂、地层水配制了一种弱凝胶调剖剂,并对合成条件进行了筛选。测定了成胶时间、成胶强度和堵剂的封堵率。结果表明:最佳配方为聚丙烯酰胺浓度为0.4%,苯酚和交联剂的浓度为0.6%-1.2%,调节剂含量为0.5%-0.7%,堵剂封堵率均在97%以上。通过控制各组分的含量和比例,成胶时间可控,成胶强度可调,完全满足现场施工需要,是一种性能优良的调剖剂。     

博士考考你

一、单项选择题1.最先提出全面质量管理概念的学者是()A.朱兰B.菲根堡姆C.戴明D.泰罗2.一般来讲,预防成本占全部质量成本的()A.25%-40%B.20%-40%C.10%-50%D.0.5%-5%3.在正态分布情况下,工序加工产品的质量特性值落在6σ范围内的概率或可能性约为()A.99.73%B.95.45%C.68.27%D.80     

基于气相色谱仪的顶空气相色谱法研究

建立一种气相色谱法测定液碱中异丙胺残留量的方法。采用顶空自动进样气相色谱法,在极性毛细管柱上进行分离,方法重现性好,便于操作,定量结果准确。该方法避免了强碱性物质直接进样的缺点,并且前处理简单,灵敏度好,精确度高,在所考察的浓度范围内呈良好的线性关系,R为0.9996,测得的回收率在94.7%-103.4%之间,相对标准偏差为3.25%-6.78%。     

变频节能技术在矿山风机、水泵上的应用

变频器在矿山除尘离心风机,取水离心水泵,浮选机组上的应用,利用负载转矩与转速的平方成正比,轴功率与转速的立方成正比的原理,通过变速而节能高达26%-28%,功率因数可提高到0.9以上,且具有过流、短路、过压、欠压、缺相、温升等多项保护功能。     

土壤中Pb、Cr元素激光诱导击穿光谱技术定量分析

采用激光诱导击穿光谱技术(Laser-induced b reakdown spectroscopy,LIBS)对土 壤样品中的Pb和Cr元素进行了分析,以PbI280.17 nm和CrI425.43 nm作为分析线,优化了透 镜到样品的距离(Lens to sample distance,LTSD)、延迟时间对光谱信号强度及信噪比 SNR 的影响。在最佳实验条件下,对两种元素的谱峰强度和元素浓度进行分析,针对外标法 和内标法分别建立了谱线峰值强度、谱线峰值积分面积与对应元素浓度的定标曲线。采用谱 线峰值积分面积法对土壤中重金属Pb和Cr元素的检测,相比于外标法,内标法将Pb和Cr元素 最大相对误差分别从13.56%和12.68%降低到了 6.7%;Pb和Cr元素定标曲线的拟合相关 系数R²分别从0.978和0.975提高到了0.996和0.991。实 验结果表明:采用LIBS技术对土 壤中Pb、Cr元素检测具有可行性,采用谱线峰值积分面积的内标法,可以降低最大相对误差 并提高测量精度。     

P元素对Sn-0.3Ag-0.7Cu钎料抗氧化性、润湿性以及显微组织的影响

为改善Sn-0.3Ag-0.7Cu钎料抗氧化性和润湿性差的问题,在钎料中添加了P元素,研究了微量P元素对Sn-0.3Ag-0.7Cu钎料抗氧化性、润湿性以及显微组织的影响。制备了含不同质量分数P元素的Sn-0.3Ag-0.7Cu-xP (x=0%, 0.005%, 0.010%, 0.015%, 0.020%)钎料。以实验的方式测试了钎料的抗氧化性以及润湿性,并使用扫描电镜(SEM)和能谱仪(EDS)观察了显微组织。结果表明：随着P含量的增加,钎料的抗氧化性和润湿性显著提高。当P含量达到0.020%时,与不添加P元素的钎料相比,在250℃保温30 min后的氧化渣质量由2.25 g减少到0.79 g。此时,钎料的铺展面积和润湿力也达到最大,分别为65.74 mm²和5.04 mN,润湿时间为0.96 s。添加微量P元素未改变钎料的相组成,其显微组织主要由β-Sn、Ag₃Sn与Cu₆Sn₅三种相构成。随着P含量的增加,Ag₃Sn的形态由粒状向片状转变。     

不同金属黏附层对无铅焊料SAC305剪切强度的影响

<正>无铅焊料是不含铅或含铅量极少的一种焊料的统称,以Sn为主要的组成成分,向其中加入Ag,Cu等金属元素。在无铅材料中,Sn-Ag-Cu无铅焊料是公认的最优秀的无铅焊料,无铅焊料中铅元素的质量分数极低,基本在0.02%-0.1%之间共晶Sn-Ag-Cu系无铅焊料在凝固过程中产生粗大的Ag_3Sn、Cu_6Sn_5金属间化合物(IMC)。由于在金属间化合物生长的过程中,界面附近的原子会发生穿过界面的互扩散,而不同原子扩散速度不同,     

GEMNET: a generalized, shuffle-exchange-based, regular, scalable,modular, multihop, WDM lightwave network

GEMNET is a generalization of shuffle-exchange networks and it can represent a family of network structures (including ShuffleNet and de Bruijn graph) for an arbitrary number of nodes. GEMNET employs a regular interconnection graph with highly desirable properties such as small nodal degree, simple routing, small diameter, and growth capability (viz. scalability). GEMNET can serve as a logical (virtual), packet-switched, multihop topology which can be employed for constructing the next generation of lightwave networks using wavelength-division multiplexing (WDM). Various properties of GEMNET are studied     

Thermodynamics of copper matte converting: Part III. Steady-state volatilization of Au,Ag, Pb,Zn, Ni,Se, Te,Bi, Sb,and As from slag,matte, and metallic copper

A comprehensive compilation of various thermodynamic data required for a complete analysis of copper matte converting reactions is presented. The data comprise estimated free energies of formation for such gases as SeO, SeS, TeO, TeS, BiO, BiS, SbO, SbS, AsO, and AsS, as well as activity coefficients in dilute copper alloys and vapor pressures of various elements and compounds. The volatilization of minor elements in steady-state reactors comprising gas and several condensed phases is mathematically formulated, and a parameter which governs the volatilization in such reactors is defined and named volatilization constant. The vapor pressures of various volatile species are calculated thermodynamically for the Noranda Process reactor by assuming equilibrium conditions. The volatilization constants of various minor elements are expressed explicitly as functions of oxygen and sulfur activities. Formerly Associate Professor, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT     

PBX技术.市态.营销.选购

本文介绍了ＰＢＸ交换机的技术及市场需求态势。并提出ＰＢＸ产品的营销要素及其用户在选购时应遵循的原则。     

Bits, symbols, bauds, and bandwidth

The use of clear, concise, and unambiguous language in telecommunications engineering is vital to communicate a desired meaning and understanding. Terminology should be based on rigorous engineering principles and traceable to well known and dependable sources. This article deals with four everyday terms commonly encountered in the popular semi-technical press as well as in serious engineering periodicals. The misuse of these and other terms can lead to low-balled cost proposals, court litigation, and patent infringement cases. Imagine how an engineering student can be confused when she/he typically encounters bandwidth measured in bits per second     

Novel planar, square-shaped, dielectric-waveguide, single-, and dual-mode filters

This paper presents a novel concept of a square-shaped dielectric-waveguide resonator, which can easily realize a dielectric-waveguide cross-coupled filter or a dielectric-waveguide dual-mode filter, using the conventional printed circuit board (PCB) process. This planar dielectric-waveguide resonator has a higher Q value than a microstrip resonator. The physical mechanisms of both single- and dual-mode filters are elucidated. Some new coupling structures are developed for undergoing the PCB process. Filter design procedures are detailed. Design curves for the coupling coefficients of internal- and external-coupling structures are determined by full-wave finite-element-method electromagnetic calculations. Measurement results are highly consistent with theory for all trial filters. This study offers an effective means of producing low-cost high-performance planar circuit filters.     

人工智能时代“微机原理与接口技术”教学探讨

本文简述了在人工智能时代，我们的“微机原理与接口技术”课程教学团队基于线下线上混合教学模式，开展微机原理与接口技术的关键知识单元讲解的同时，实时课程思政，讲好微机原理的新故事；如何培养学生自主探索式学习技能，在课程基本知识单元学习的基础上扩展延伸相关深度学习、GPU技术、Python语言、FPGA技术等人工智能方面的知识单元的探究与学习，使得课程学习与人工智能的前沿发展相结合，理论联系实际，吸引和培养学生对该课程学习的兴趣和整体知识面扩展，这对于我们培养具有自主创新的科学探索精神的高素质专业人才具有重要的现实意义。