高速钢麻花钻的磨损试验研究

麻花钻是实现孔加工的重要工具,然而切削刃口的快速磨损是制约钻孔质量和钻头寿命的重要因素。基于产品抽样钻孔试验与正交试验,本文对高速钢麻花钻的磨损、破损等失效形式进行了综合分析,探讨了以钻孔直径为评价指标时的孔加工数量与孔径的关系,并对麻花钻磨损的关键影响因素进行了正交试验研究。结果表明,麻花钻磨损与破损形式主要有主切削刃前刀面与后刀面磨损、横刃磨损、刃带磨损、外圆转角磨损、崩刃等;切削速度对麻花钻磨损影响最大、进给量次之、孔深影响最小;此外,随着加工孔数量的增加,孔径呈减小趋势。     

Endometrial arteriogenesis: vascular smooth muscle cell proliferation and differentiation during the menstrual cycle and changes associated with endometrial bleeding disorders

The cyclical regrowth of the human endometrial vasculature every 28 days following menstruation provides an excellent opportunity for studying arteriogenesis in a human tissue. Despite this, very little has been published to date about temporal or spatial changes in endometrial arteriolar structure or function. Immunohistochemical studies using vascular smooth muscle cell (VSMC) differentiation markers have identified spatially organised differences in VSMC phenotype. However, these have not significantly increased our understanding of how or when arteriogenesis occurs. Endometrial VSMC proliferation continues at a steady rate throughout the cycle, increasing in the specialised spiral arterioles in the mid and late secretory phases. Although estrogen and progesterone play a dominant role in regulating endometrial growth and regression, their direct involvement in arteriogenesis is less clear. Estrogen and progesterone receptors have been reported in endometrial VSMC, although heterogeneity of expression occurs. The angiopoietin/Tie axis has been investigated in endometrium, although the results of 3 studies published to date are contradictory, making conclusions about a role in arteriogenesis problematic. Abnormalities of arteriogenesis may play a role in disorders such as menorrhagia and breakthrough bleeding in contraceptive and hormone replacement therapy users. There is evidence that VSMC proliferation is reduced in spiral arterioles of women with menorrhagia, along with reduced pulsatility index of the uterine artery as shown by Doppler ultrasound. In women taking progestin-only contraception, endometrial perivascular alpha smooth muscle actin is reduced in those who suffer from breakthrough bleeding compared to those that don't. Considerable work is still required to elucidate when in the cycle, where in the tissue, and what mechanisms regulate endometrial arteriogenesis.     

Nonorthogonal designs: Sample versus population.

Focuses on important issues which have been neglected in recent papers concerning the problem of using analysis of variance with an unbalanced design. The concept of population cell weights is introduced and used to define parameters for various models. Variance components associated with these parameters are also defined. The use of regression analysis is demonstrated, employing population weights to obtain the parameters of the different models. Finally, sample estimates of both parameters and components are introduced. Emphasis is given to the important issue of distinguishing between population parameters and sample statistics. Questions of the relations between population and sample are discussed. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Positive ion spectra in He-CO-O2-laser discharges

The ion spectra of He-CO-laser discharges with and without small addition of O2is presented. It is shown that upon addition of oxygen the dominant positive charge carriers in the discharge are O2⁺ions. It is argued that the oxygen ion O2⁺is populated in stage processes: thea^{3}Pistate of CO relaxes to a metastable state of oxygen, which in turn is ionized by electrons.     

生态高技术建筑设计——法兰克福商业银行大厦建筑设计特点

本文介绍了诺曼·福斯特及其事务所设计的法兰克福商业银行大厦.在设计中,福斯特运用了生态技术,结合高新技术、新材料,充分体现了可持续发展的思想,对生态高技术建筑设计作出了贡献.     

HDP—PVC／ABS合金材料的研究

研究了高聚合度聚氯乙烯（ＨＤＰ－ＰＶＣ）／ＡＢＳ二元体系力学性能以及添加第三组分对合金材料力学性能的影响。结果表明：ＨＤＰ－ＰＶＣ／ＡＢＳ配比为１００／２５时,共混物的综合性能好,体系能形成较完善的海岛结构;ＨＤＰ－ＰＶＣ／ＡＢＳ／ＭＢＳ体系中,ＭＢＳ能改善多元体系的界面性能,提高合金材料的综合性能;ＨＤＰ－ＰＶＣ／ＡＢＳ／ＣＰＥ体系中,ＣＰＥ能使形成网状结构和海岛结构共存的合金体系,提高合金材料     

The role of domain knowledge in requirements elicitation via interviews: an exploratory study

Requirements elicitation is the first activity in the requirements engineering process. It includes learning, surfacing, and discovering the requirements of the stakeholders of the developed system. Various elicitation techniques exist to help analysts elicit the requirements from the different stakeholders; the most commonly used technique is the interview. Analysts may have domain knowledge prior to the elicitation process. Such knowledge is commonly assumed to have positive effects on requirements engineering processes, in that it fosters communication, and a mutual understanding of the needs. However, to a minor extent, some negative effects have also been reported. This paper presents an empirical study in which the perceived and actual effects of prior domain knowledge on requirements elicitation via interviews were examined. The results indicate that domain knowledge affects elicitation via interview in two main aspects: communication with the customers and understanding their needs. The findings provide insights as to both the positive and negative effects of domain knowledge on requirements elicitation via interview, as perceived by participants with and without domain knowledge, and show the existence of an actual effect on the course of the interviews. Furthermore, these insights can be utilized in practice to support analysts in the elicitation process and to form requirements analysis teams. They highlight the different contributions that can be provided by analysts with different levels of domain knowledge in requirements analysis teams and the synergy that can be gained by forming heterogeneous teams of analysts.     

Formulating Portland cement–reactive alumina blend through thermodynamic modeling to prevent the alkali–silica reaction

This study aims to formulate solid and aqueous compositions of hydrated Portland cement incorporated with reactive alumina (RA) via thermodynamic modeling, with the goal to prevent alkali–silica reaction (ASR). Based on SEM/EDS point analysis, the uptake of Al into C–S–H was corrected in the thermodynamic modeling to improve the accuracy. The predicted solid and aqueous compositions were validated by means of XRD, TGA, and ICP. An accelerated mortar bar test was also carried out to confirm the ASR mitigating efficiency, and a preliminary relationship among the ASR expansion, solid assemblage, and aqueous species was established. The critical content for RA is around 5.75% in the studied systems, above which katoite precipitates, resulting in increased Al concentration in the pore solution (∼0.8 mmol/L); hence, ASR can be effectively inhibited.     

Linearization of logical functions defined by a set of orthogonal terms. I. Theoretical aspects

Consideration was given to the linearization of logical functions defined by a set of pairwise orthogonal terms. The linearization is carried out by computing the autocorrelation functions. Proposed was a method consisting of (i) calculation of the autocorrelation function in the space of orthogonal terms, (ii) generation of the corresponding matrix of linear transformation, and (iii) the linear transformation proper of the variables in the space of orthogonal terms. Complexity of the proposed method and its effectiveness were estimated. Effectiveness was verified by a series of experiments with standard benchmarks. The distinctions of the proposed method from other existing methods of linearization were examined.