Construction Management of a Small-Scale Accelerated Pavement Testing Facility

Research in accelerated pavement testing (APT) facilities has traditionally focused on the pavement performance such as rutting and fatigue cracking, but documentation on construction management and information of the actual pavement construction quality is limited. There are typically four critical factors that need to be considered to achieve the best possible outcome in construction: cost, schedule, construction process, and quality control, and management. With the objective of developing guidelines for planning and executing construction of a small-scale APT facility, this paper presents a case study documenting and evaluating the construction process and construction management efforts of two sensor-instrumented hot mix asphalt pavement test sections built in a small-scale APT facility. The focus of the experiment was to study bottom-up fatigue cracking of the flexible pavement structure. The presented information and lessons learned serve as a template and guide for agencies pursuing this type of research and pavement construction.     

轨钢磨损行为的试验

在实验室条件下用圆盘试样模拟了钢轨的接触条件。研究了滑差和接触应力对珠光体轨钢磨损行为的影响。通过滚磨表面下扫描电镜观察及测试,分析了磨损过程中的磨损形式及其相互作用机理。结果表明,磨损速率随滑差而增大,滑差增至4%时,达到极限摩擦系数。磨损量与滑动摩擦功呈线性关系,与滑动距离成正比。干磨条件下,表层组织发生强烈的塑性形变,使组织沿平行于表面层状分布。粘附磨损和疲劳磨损是轨钢的主要磨损形式。     

共析轨钢的循环应变行为

用增量步进试验方法,研究了珠光体和回火索氏体共析轨钢的循环应力-应变行为。结果表明,在试验选定应变范围内,回火索氏体发生循环软化;珠光体表现为软、硬化同时发生。在同类型组织中,低强材料的循环应变性能优于高强材料,而珠光体优于回火索氏体。定义了珠光体组织的临界应变幅,并对临界应变幅随性能的变化规律进行了研究。同时还探讨了循环应力-应变参数与显微组织参数及应变步进增量的关系。     

Cyclic Filtration Apparatus for Testing Subballast under Rail Track

An apparatus capable of testing subballast-subgrade filtration behavior under cyclic loading is presented. The apparatus can be used to accurately monitor the pressure fluctuations, permeability of the filtration system, and turbidity variations of the effluent with time. The test results show that the frequency of cyclic loading has an influence on the filtration behavior of subballast material used in railway tracks. Further, the effect of cyclic load on the design and selection of subballast materials over a wet subgrade must be considered to avoid filter malfunctioning.     

稀土在BNbRE重轨钢中的作用机制

通过化学分析、金相观察和理论分析,研究了稀土在BNbRE重轨钢中的存在状态和含量的变化规律,以及它对钢的硫化物夹杂、微观组织和性能的影响机制。研究发现,对于BNbRE重轨钢,加入大量的稀土并不能增加钢中固溶稀土的含量,固溶稀土的含量均保持在0．0012％以下。少量的固溶稀土可以细化BNbRE重轨钢的奥氏体晶粒和珠光体片层结构。在本实验条件下,BNbRE重轨钢的最佳稀土加入量约为0．02％,此时BNbRE重轨钢的塑性和冲击韧性得到显著提高。     

Microstructure-Fracture Behavior Relationships of Slot-Welded Rail Steels

Microstructural analyses of the parent pearlitic and bainitic rail steels were performed, and the results were compared with the microstructure of the welded pearlitic and bainitic steels. An increase in the ASTM grain size number of the heat-affected zone (HAZ) for both pearlitic and bainitic slot welds was observed. The microstructural features that were identified in the weldment of both slot-welded steels were very similar. This was expected since the same welding wire was used to weld both rail steels. The weld consisted of mainly ferrite and had similar grain size. The fusion zones of the welded pearlitic and bainitic rail steels were examined after flexural tests to determine if there were any cracks present due to improper or weak fusion. Examination of the entire fusion zone under high optical magnification revealed no cracks, indicating that a perfect fusion was achieved. The three-point flexural behavior of the parent pearlitic and bainitic steels was evaluated and compared with that of the slot-welded steels. It was found that that the welded pearlitic steel has superior fracture resistance properties when compared to the parent pearlitic steel. The average fracture resistance of the parent pearlitic steel was 79 MPa√m compared to 119 MPa√m for the welded pearlitic steel. The slot-welded bainitic steel, however, showed similar fracture resistance properties to the parent bainitic steel with average values of 121 and 128 MPa√m, respectively. The failure mechanism of the welded and parent pearlitic and bainitic steels was also identified. Microvoid coalescence was observed in both welded rail steel samples. This was manifested by dimpled features, which are associated with ductile failure.     

A Meta-Analytic Review of Behavior Modeling Training.

A meta-analysis of 117 studies evaluated the effects of behavior modeling training (BMT) on 6 training outcomes, across characteristics of training design. BMT effects were largest for learning outcomes, smaller for job behavior, and smaller still for results outcomes. Although BMT effects on declarative knowledge decayed over time, training effects on skills and job behavior remained stable or even increased. Skill development was greatest when learning points were used and presented as rule codes and when training time was longest. Transfer was greatest when mixed (negative and positive) models were presented, when practice included trainee-generated scenarios, when trainees were instructed to set goals, when trainees' superiors were also trained, and when rewards and sanctions were instituted in trainees' work environments. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

BVRE重轨钢奥氏体长大行为的动力学研究

以BVRE重轨钢为研究对象,通过真空冶炼、锻造和轧制工艺制备合格的重轨钢试样.在此基础上,系统研究稀土重轨钢奥氏体晶粒的长大动力学.实验结果表明,随着加热温度的提高,稀土重轨钢奥氏体晶粒呈指数关系长大;随着保温时间的延长,稀土重轨钢奥氏体晶粒长大呈抛物线规律.重轨钢中添加微量的稀土,可以明显降低不同加热条件下的奥氏体晶粒尺寸.模型计算结果表明,重轨钢的奥氏体晶粒长大公式分别为:d4.80=d4.800+ 2.82×1028texp(- 556450/RT)(不加稀土)和d5.34=d5.340 +4.52×1032texp(- 646890/RT)(稀土重轨钢).稀土主要通过晶界的偏聚机制使奥氏体晶粒长大激活能由556450J·mol-1增加到646890J·mol-1,从而抑制奥氏体晶粒尺寸的增加.     

LS9000激光测量系统在钢轨检测中心的应用

随着激光技术的发展和不断更新,激光测长已应用于诸多行业。LaserSpeed9000系列激光测长仪将探头、处理器、输出、电源等集成为一体,利用激光多普勒原理进行非接触式测量,避免了与被测体的摩擦损伤,大大提高了测量的精度和可靠性,是一种非常优秀的长度测量系统。本文主要介绍了LS9000激光测长技术在钢轨检测中心的应用。     

铈在重轨钢中行为特性的热力学模型分析

以重轨钢为研究对象,建立可以定量描述稀土在重轨钢中行为特性的热力学模型,并通过实验验证了模型的精确度.利用该热力学模型,研究分析了在不同氧、硫的质量分数条件下,铈加入量对重轨钢液及其凝固过程中铈的赋存状态以及夹杂物组成的影响作用规律,得到以下结论:当钢中氧、硫的质量分数较低时,随着铈加入量的增加,Ce2O2S的析出量略有减少;当钢中氧、硫的质量分数较高时,随着铈加入量的增加,Ce2O2S的析出量有所增加;铈加入量的增加以及温度的下降均有利于Ces的析出;当钢中氧、硫的质量分数较低时,在凝固过程中钢中析出CeN和固溶铈;随着铈加入量的增加,CeN的析出温度和析出量均有所增加,当CeN的析出达到平衡时,固溶铈大量析出.     

汽车悬架弹簧用钢的弹性减退行为的试验评估

对各种弹性减退试验方法的适用范围和局限性进行了比较,得出可以用总塑性应变范围这个参数来定量评估弹簧钢的弹性减退.     

Has Dynamic Testing Lived Up to Its Potential? A Review of Sternberg and Grigorenko's Dynamic Testing.

Reviews the book "Dynamic Testing: The Nature and Measurement of Learning Potential," by R. J. Sternberg and E. L. Grigorenko (see record 2002-01422-000). Unlike "static" tests, dynamic tests emphasize learning potential rather than past learning accomplishments. The book opens with a theoretical framework of abilities as forms of development expertise. It continues with an introduction to dynamic testing and then a capsule history of dynamic testing. The book also reviews other diverse approaches to dynamic testing. The authors present their own three-pronged approach to dynamic testing along with two case studies from their own research in which dynamic testing was utilized. The book is valuable for school psychologists interested in understanding more about dynamic testing of abilities and the progress in the field. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Class A Prediction of the Behavior of Soft Estuarine Soil Foundation Stabilized by Short Vertical Drains beneath a Rail Track

In Australia, very few rail tracks have been constructed directly on deep estuarine deposits. In recent years, Kooragang Island has become a major export terminal and most coal trains need to cross the main lines at Sandgate to enter Kooragang Island. In this study, a rail track built on up to 30 m of thick soft estuarine soil was stabilized with relatively short vertical drains to consolidate the soil just beneath the track, and no additional preloading surcharge was provided, except the weight from the trains. The initial soil compression was caused by the passage of trains with a speed restricted at 40 km/h. From this study, it is shown that prefabricated vertical drains significantly decrease the buildup of excess pore-water pressure during cyclic loading, and also continue to dissipate excess pore-water pressure during the rest period. A preliminary finite-element analysis was employed to examine the performance of vertical drains, and a Class A prediction was obtained in terms of lateral and vertical displacements. The monitored settlement and lateral displacement results are presented and discussed. The study shows that relatively short vertical drains are sufficient for providing stability for rail tracks, without the need for driving deep vertical drains through the entire soft soil depth.     

"Septum and Behavior: A Review": Erratum.

Reports an error in the original article "Septum and Behavior: A Review," by P. A. Fried (Psychological Bulletin) Vol. 78(4) Oct 1972, 292-310. Line 19 of the second column of page 292 should read as follows: . . . separate paper (Fried, 1972). One . . . . (The following abstract of this article originally appeared in record 1973-02623-001.) A review of research and discussion related to the behavioral effects of septal dysfunction supports the conclusion that a unitary conceptualization of the role of the septum is inappropriate and simplistic. Discrete lesion and stimulating techniques indicate that the septum cannot be considered equipotential in either its contribution to various types of behavior or in its anatomical relationships with other subcortical structures. Evidence indicates that various nuclei in the septum are important in at least 4 dissociable behavior patterns: (a) damage to the medial septal nucleus impairs the ability to alter a response on the basis of proprioceptive cues, (b) damage to the lateral and posterior regions of the septum increases the magnitude of negative responses to unpalatable solutions, (c) damage to regions of the septum that are anatomically connected to the hypothalamus increases the intake of water, and (d) damage to a variety of septal nuclei results in overresponding to positively-motivating stimuli. This latter finding is interpreted as implicating the septum in a specific type of response-suppressing mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Accelerated Medical Program and the Liberal Arts at Boston University

Since September 1961, fifteen classes have matriculated in Boston University's Six- Year College of Liberal Arts--Medical Education Combined Degree Program. The applicant pool is approximately three to four times larger now than in the earlier years, with classes averaging 50 students. Academic qualifications (high-school class rank and Scholastic Aptitude Test and College Board Achievement Test results) of the entering classes have been at a consistently high level. Fifty percent or more of the graduates receive the BA degree with honors; 10% or more receive the MD degree with honors. The degree of flexibility in the liberal arts component of the program has increased and currently exceeds that of the traditional four-year premedical curriculum. These data, together with additional information concerning postgraduate professional activities, indicate that the combined accelerated program has been successful.     

A Multipurpose Controlled Atmosphere Facility for Production of Rapidly Solidified Particulate

Abstract

The design and operation of equipment to generate rapidly solidified samples in batches as large as 5 kg, under closely controlled atmosphere conditions, is described. Two modes of operation are possible at present: gas atomization-substrate solidification (GASS) and crucible melt extraction (CME). Both produce particulate, the former with a flake type morphology, the latter as a discontinuous fibre. Several aluminium alloys have been processed via GASS and one of them (Al–9 wt-%Mn) has been compared to the same composition processed in air access equipment. Tin and a lead-antimony alloy have been used to demonstrate the operational characteristics of the crucible melt extraction mode. PM/0319