窑车轮水玻璃砂型铸造工艺改进

窑车轮是窑车中一个重要部件,工业生产中以砂型铸造为主.根据铸钢合金铸造的特点和工艺要求,采用开放—封闭式浇注系统以及设置冒口,成功地试制生产出了窑车轮零件.同时,也确定了合理实用的铸钢砂型铸造工艺.     

lordif: An R Package for Detecting Differential Item Functioning Using Iterative Hybrid Ordinal Logistic Regression/Item Response Theory and Monte Carlo Simulations

Logistic regression provides a flexible framework for detecting various types of differential item functioning (DIF). Previous efforts extended the framework by using item response theory (IRT) based trait scores, and by employing an iterative process using group-specific item parameters to account for DIF in the trait scores, analogous to purification approaches used in other DIF detection frameworks. The current investigation advances the technique by developing a computational platform integrating both statistical and IRT procedures into a single program. Furthermore, a Monte Carlo simulation approach was incorporated to derive empirical criteria for various DIF statistics and effect size measures. For purposes of illustration, the procedure was applied to data from a questionnaire of anxiety symptoms for detecting DIF associated with age from the Patient-Reported Outcomes Measurement Information System.     

钢中贝氏体转变的开始温度Bs与转变驱动力

贝氏体转变开始的模式可表示为γ→γ′+γ_1→α′+γ_1,由此提出了计算贝氏体转变开始温度 B_s 的公式,B_s(x)=M_s(x′),x′=Ax+B(相似文献   

Competing risks as a multi-state model

This paper deals with the competing risks model as a special case of a multi-state model. The properties of the model are reviewed and contrasted to the so-called latent failure time approach. The relation between the competing risks model and right-censoring is discussed and regression analysis of the cumulative incidence function briefly reviewed. Two real data examples are presented and a guide to the practitioner is given.     

节约为本谈打造

网游中的顶级装备、稀世物品是可遇而不可求的。除了爆率问题外．能打到稀世物品的地方长期被某些玩家所霸占也是一个原因。何况在等级低的情况下，要去打一套高级装备．也存在着很大的风险。不过在《天骄2》中．这个问题却不存在。     

Light-scattering studies of packed stationary phases for capillary electrochromatography

Multiply scattered light through turbid media, packed particles, or compressed powders will inherently have a significantly longer optical path length than that of light which is not scattered. The concept of using the multiply scattered light potentially generated in the packed stationary phase of a capillary electrochromatography (CEC) column for enhanced detection as a result of its increased optical path length was examined. Ultraviolet (UV) light at 365 nm or laser light at 635 nm was focused to a small spot onto the packed section of a 3 microns spherisorb ODS1 CEC column (100 microns i.d.). The light was transported inside the capillary, and an image of the multiply scattered light several millimeters along the capillary was collected using a charged-couple device detector. Even if the spot size was less than 100 microns in diameter, evidence of light scattering was observed at a detection spatial off-set distance of 1-2 mm from the illumination point. When the calcium channel blocking drug felodipine was flushed through the column, the light intensity value dropped (increase in absorbance) to a greater degree at a spatial off-set (1.5 mm) than at the illumination point. The greater absorbance values at the spatial off-set were examined experimentally when felodipine was eluted from the column in the CEC mode in 6 min using MeCN/50 mM TRIS (pH 8.0) (80:20, v/v) at an applied voltage of 300 V/cm and an injection time of 2 s at 10 kV. A factor of 8.5 increase in absorbance was observed at a spatial off-set of 1 mm compared to the value obtained at the illumination point. An efficiency value of approximately 234,000 plates m-1 was obtained for this higher felodipine peak. Higher noise values, however, were also observed with this increase in absorbance. Using a spectrophotometer or an open capillary to obtain reference values for optical length, it was possible to estimate the average optical path length of light traveled through the packed stationary phase when transmitted at a spatial off-set. It was concluded that, although an increase in absorbance of 8.5 was observed at a spatial off-set, this most likely arises from the light being "redirected" and scattered in a straightforward fashion along the capillary. It was expected that if substantial multiple scattering did occur inside the packed stationary phase, a significantly larger absorbance increase would be attained. A number of proposals are thus given to explain the relatively low degree of multiple scattering in this stationary phase and suggestions offered on means to attain even higher absorbance increases at a spatial off-set. Additional potential applications are also discussed.     

几种重金属对紫背萍的过氧化氢酶（CAT）活性的影响

通过测定试验植物的过氧化氢酶分解过氧化氢后所放出氧气的量，确定紫背萍的过氧化氢酶的活性。结果表明，紫背萍在暴露到镉，锌，铜和铁的不同浓度时，其ＣＡＴ活性明显升高这表明４种重金属对紫背萍的ＣＡＴ活性均有刺激作用。结果不表明，此 萍在有铁存在的两种金属的复合作用下，其ＣＡＴ活性明显降低。     

残余奥氏体及其机械稳定性与钢强韧性关系的研究

钢中残余奥氏体发生应变诱发马氏体相变的百分量与拉伸应变量的对数呈线性关系,用直线斜率的倒数Ks值可表示残余奥氏体机械稳定性的大小。提高钢中残余奥氏体量及其机械稳定性是改善钢强韧性的有效途径之一。残余奥氏体发生应变诱发马氏体相变吸收能量是提高钢韧性的主要原因。在低碳贝氏体钢中,以M—A岛形式存在的残余奥氏体因受岛中马氏体的强化作用使屈服强度保持较高水平,而残余奥氏体在拉伸的均匀塑性变形阶段因应变诱发相变形成的马氏体使钢的抗拉强度提高。     

低,中碳合金钢中的马氏体与贝氏体形态

本文主要介绍低、中碳合金钢中的马氏体除局部区域因成份偏析呈孪晶亚结构外,主要是位错亚结构的板条马氏体。低碳合金钢的中温转变组织主要有三类,即粒状组织、上贝氏体和下贝氏体。其中上贝氏体又分为粒状贝氏体、准上贝氏体和典型下贝氏体;下贝氏体又有准下贝氏体、变态下贝氏体和典型下贝氏体。中碳合金钢的中温转变组织只有上、下贝氏体,其中上贝氏体又分为准上贝氏体和典型上贝氏体,而下贝体则包括准下贝氏体、变态下贝氏体和典型下贝氏体。