Behavior, Analysis, and Design of an Instrumented Link Slab Bridge

Presented in this paper are the results of a research project on the monitoring and assessment of the first link slab jointless bridge in the state of North Carolina. The structure was instrumented with a remote data acquisition system and monitored for over a year. In addition, a controlled load test was conducted in an effort to determine the demand on the link slab under known loads. A procedure for the limit-states design of a link slab system is also presented. Results indicate that while the crack size in the link slab exceeded the design level, the link slab fulfilled its function. Furthermore, the rotational demand from the large controlled loads as well as the traffic loads was similar in magnitude to the thermal induced rotations due to the difference in temperature between the top and bottom of the bridge.     

Thermal and Irradiation Creep Behavior of a Titanium Aluminide in Advanced Nuclear Plant Environments

Titanium aluminides are well-accepted elevated temperature materials. In conventional applications, their poor oxidation resistance limits the maximum operating temperature. Advanced reactors operate in nonoxidizing environments. This could enlarge the applicability of these materials to higher temperatures. The behavior of a cast gamma-alpha-2 TiAl was investigated under thermal and irradiation conditions. Irradiation creep was studied in beam using helium implantation. Dog-bone samples of dimensions 10 × 2 × 0.2 mm³ were investigated in a temperature range of 300 °C to 500 °C under irradiation, and significant creep strains were detected. At temperatures above 500 °C, thermal creep becomes the predominant mechanism. Thermal creep was investigated at temperatures up to 900 °C without irradiation with samples of the same geometry. The results are compared with other materials considered for advanced fission applications. These are a ferritic oxide-dispersion-strengthened material (PM2000) and the nickel-base superalloy IN617. A better thermal creep behavior than IN617 was found in the entire temperature range. Up to 900 °C, the expected 10⁴ hour stress rupture properties exceeded even those of the ODS alloy. The irradiation creep performance of the titanium aluminide was comparable with the ODS steels. For IN617, no irradiation creep experiments were performed due to the expected low irradiation resistance (swelling, helium embrittlement) of nickel-base alloys.     

容量法测定钴镍试样中锌

提出了在氨-氯化铵介质中用1-(2-吡啶偶氮)-2-萘酚(简称PAN)及丁二酮肟沉淀分离钴、镍,EDTA容量法测定锌的方法。分别对两种沉淀剂的用量、沉淀条件、钴、镍分离情况及分离量进行了试验研究,消除了钴、镍离子对二甲酚橙的封闭干扰作用,锌的回收率:99.90%～100.10%。已成功地应用于含钴、镍试样中EDTA滴定法测定锌含量。     

Comparison of the Microstructure, Tensile, and Creep Behavior for Ti-22Al-26Nb (At. Pct) and Ti-22Al-26Nb-5B (At. Pct)

The effect of the addition of 5 at. pct boron on the microstructure and creep behavior of a nominally Ti-22Al-26Nb (at. pct) alloy was investigated. The boron-modified alloy contained boride needles enriched in titanium and niobium, and because to these borides, this material was considered to be a discontinuously reinforced metal matrix composite. These needle-shaped borides made up to 2 pct of the volume and were up to 158-μm long and 22-μm wide. The effect of boron on the mechanical properties was evaluated through in-situ creep testing and tensile testing at room temperature (RT) and 650 °C. Overall, the addition of 5 at. pct boron proved to be detrimental to the tensile and creep behavior. The composite exhibited a brittle failure and lower elongations-to-failure than the monolithic material. The in-situ tensile and creep experiments revealed that the deformation process initiated in the boride needles, which cracked extensively, and significantly greater primary creep strains and creep rates were exhibited by the composite.

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Design and Dynamic Analysis of an Adjustable Inertia Absorber for Semiactive Structural Vibration Attenuation

A new class of adaptive tuned vibration absorber, a variable effective inertia absorber, is presented to impart optimum vibration absorption. The tuning scheme has two facets: spectral analysis of the excitation and a concurrent in situ tuning of the absorber. The spectral analysis reveals the frequency content of the excitation. The online tuning uses the frequency content of the excitation to reposition a moving mass and change the damping coefficient of a variable rate damper for optimal (broadband) or tonal vibration suppression. The nonlinear differential equations of motion are linearized and then utilized to develop the online tonal and the broadband tuning of the variable effective inertia absorber. A case study is presented to demonstrate the novelty of the concept. The results show that the retuned absorber delivers considerable vibration suppression improvement over the detuned one.     

收尘用高压电源的比较分析与优化设计

为使电场强度满足工况要求,粉尘荷电效果理想,本文在分析不同高压电源技术特性的基础上,设计了由四个电场组成的静电收尘设备,并根据高压电源的使用工况进行了优化设计,其中,第一个电场由高频高压脉冲电源供电,其余电场由适合高比电阻的恒流源供电。设备投运后,工作状况良好,证明本文的相关分析符合实际情况,设计满足使用要求。     

英语专业听力零课时可行性探讨——一项基于学生意见的混合方法研究及课程模式效力的调查

英语专业听力零课时可行性探讨,是一项基于学生意见及对课程模式效力的调查的混合方法研究.通过调查问卷和半结构访谈的方法收集数据,以及从比较分析课程实施主体——学习者的学习效度两点着手,从学习者的角度探讨英语专业实行听力"零课时"模式的可行性.     

Determination and Analysis of Hardenability for Hot-Forging Die Steels with Deep-Hardening

Hardenabilityisanimportantpropertyforlargeandmedium-sizehot-forgingdiesteels.Themainreasonwhythelarge-sizediesmadeofthegeneralhot-forgingdiesteel5CrNiMohaveshortlifeisthelowerhardenabilityofthesteel.Inordertoincreasetheservicelife,aseriesofdeep-hardeningsteels,suchas4Cr2MoVNi,3Cr2WMoVNiand4CrMnSiMoV,weredevelopedinChina.Butthedifferenceofhardenabilityamongthesesteelscan′tbedeterminedbythestandardJominytestbecausetheirJominycurveshavenodrops.Meanwhile,it′sverydifficulttodissectarealqu…     

曲柄连杆机构中十字头与活塞杆连接结构分析与改进设计

分析曲柄连杆机构中十字头与活塞杆原有结构存在的问题,提出新型连接方式设计方案,对连接件进行有限元分析,保证了零件强度要求与连接结构的可靠性,进而提高了机械设备的连续运转率和工作效率。     

Irradiation for bronchial carcinoma: reasons for failure. I. Analysis of local control as a function of dose, time, and fractionation

Radiation therapy is the only potentially curative form of therapy for patients with carcinoma of the lung who are not surgical candidates. Previous studies have evaluated response by evaluating survival. Evaluation of local control of disease is essential if one is to understand and modify therapeutic approaches in an effort to increase survival. Clinical data are presented on 197 patients with primary epithelial tumors of the lung. An analysis of local control data is presented using the concept of nomial standard dose (NSD). If local failure is to occur, it is manifest by 15 months. Survival is affected by the ability or inability to achieve local control. Above a dose of 1450 ret, no correlation between increasing ret dose and increasing local control is observed.     

包钢新系统喷吹低温半焦试验分析

文章介绍了低温半焦的工业分析及其性能,理论上讲低温半焦能满足高炉喷吹用煤的要求,此次新系统喷吹低温半焦工业试验重点考察低温半焦对制粉、喷吹系统和高炉冶炼经济技术指标的影响,对试验中出现的问题进行了分析。     

高铝热镀锌合金中铝锌硅铁铅镉锡的系统分析方法

提出了高铝热镀锌合金中铝锌硅铁铅镉锡的系统分析方法，所拟方法快速简便，效果良好。     

Development of a New Structural Model with Prism and Strip Elements for Pavements on Steel Bridge Decks

A new structural model for pavements on steel bridge decks (SLPE) is developed. In this model, a prism element and a strip element represent the pavement and steel bridge deck, respectively. A newly developed link element models the insulation layer that bonds the pavement to the steel deck plate. The SLPE model is verified by calculations that simulate a simply supported square plate and an actual pavement on a bridge deck. Furthermore, the model is expanded to deal with dynamic problems that consider the viscosity of asphalt materials.     

纽约世贸中心用厚板钢剖析及对宝钢建筑用厚板开发的启示

采集了一组来自纽约世贸中心废墟的不同厚度的废钢样块，分析了该大厦建筑用厚板钢的化学成分、机械性能及金相组织，并结合国内高层用厚板钢市场的调研，探讨了宝钢建筑用宽厚板开发中应注意的相关事宜。     

煤气熔铝炉控制系统的设计与分析

介绍煤气熔铝炉流量比值控制系统的组成、控制原理及系统比值系数的确定，着重分析SLPC可编程调节器功能及其在控制系统中的应用。生产运行表明，整个系统控制精度高，既可以实现煤气熔铝炉的安全运行，又可以降低能源消耗。