CO2气体保护焊与焊条电弧焊工艺及成本分析

在焊接实验实训中,采用CO2气体保护焊与焊条电弧焊两种焊接方法在同等的条件下现场施焊,进行工艺及成本分析。     

基于信息融合理论的刀具切削状态智能监测

运用多传感器信息融合技术,提出了基于信息融合理论的智能刀具状态监测系统的基本结构框架,该模式将小波变换和人工神经网络的优点结合起来,用小波变换实现特征提取,对刀具的状态进行预报。     

Average of trial peaks versus peak of average profile: impact on change of direction biomechanics

ABSTRACT

The aims of this study were twofold: firstly, to compare lower limb kinematic and kinetic variables during a sprint and 90° cutting task between two averaging methods of obtaining discrete data (peak of average profile vs. average of individual trial peaks); secondly, to determine the effect of averaging methods on participant ranking of each variable within a group. Twenty-two participants, from multiple sports, performed a 90° cut, whereby lower limb kinematics and kinetics were assessed via 3D motion and ground reaction force (GRF) analysis. Six of the eight dependent variables (vertical and horizontal GRF; hip flexor, knee flexor, and knee abduction moments, and knee abduction angle) were significantly greater (p ≤ 0.001, g = 0.10–0.37, 2.74–10.40%) when expressed as an average of trial peaks compared to peak of average profiles. Trivial (g ≤ 0.04) and minimal differences (≤ 0.94%) were observed in peak hip and knee flexion angle between averaging methods. Very strong correlations (ρ ≥ 0.901, p < 0.001) were observed for rankings of participants between averaging methods for all variables. Practitioners and researchers should obtain discrete data based on the average of trial peaks because it is not influenced by misalignments and variations in trial peak locations, in contrast to the peak from average profile.     

Metal hydride work pair development and its application on automobile air conditioning systems

INTRODUCTION Metal hydrides are special alloys which absorb and desorb hydrogen reversibly. At room temperature, metal hydrides could absorb as much hydrogen as liquid hydrogen of the same volume under much lower pressure and much higher temperature (Güther and Otto, 1999). Massive reaction heat is generated accompanying this reaction, which could be used for waste heat recovery, solar energy utilization and re-frigeration with no side effect to environment (Izhvanov et al., 1996). Con…     

Lead soaps in paintings: Friends or foes?

The origin(s) and role(s) of metal soaps in paints are a worldwide concern today. These hybrid compounds, containing both fatty acid chains and metals associated with a carboxylate function, are increasingly identified in paints. As reviewed in the first part of this work, the presence of metal soaps in paints is differently interpreted in scientific publications: metal soaps are sometimes considered to play a positive role as anchor points, during paint drying processes; they can also be considered as responsible for many degradation processes (protrusions, efflorescences, darkening, etc.). Their origins are also interpreted in various ways. In some paintings (in particular from the twentieth century), they have sometimes introduced on purpose, as additives, to modify the physical properties of the painting materials. In older paintings, metal soaps are usually thought to result from an uncontrolled reaction of oil with lead-based pigments, in particular lead white, red lead, and lead tin yellow. In the second part of this work, the review of historical recipes of lead-based paint shows an important number of recipes based on controlled mixing of oil with lead driers. In the third part, the experimental reproduction of such traditional recipes using walnut oil and litharge (PbO) shows that lead soaps can be formed, both in about one hour at ～100°C, or in about one month at room temperature. It shows as well that after a few years, litharge is no longer detected in the paint medium, while different lead carbonates are. Finally, the micro-infrared spectroscopy and micro-X-ray diffraction re-analysis of protrusions from a nine-year model painting shows together with lead soaps, the presence of Pb₅(CO₃)₃(OH)₂O (‘synthetic plumbonacrite’), an unusual phase recently observed in a protrusion from a painting by Vincent Van Gogh. This work highlights (i) the multiple origins and roles of metal soaps in paints and (ii) the importance of combining the analysis of fragments from historical paintings with the analysis and reproduction of historical recipes. In particular, we show that the components detected today in historical paintings may severely differ from those originally used or prepared by the painter, complicating the assessment of the painter's intentions. More than the presence of metal soaps, the key questions to be tackled should be about their origins and (re)mobilization.     

下料问题最优化方法研究

在生产实践中通常要求解决用料最省、浪费最少等问题.下料问题即是其一,属最优化研究范畴.给出了解决适当规模下料问题的求解方法.该方法既可手工演算又可通过计算机求解,在实践中可以借鉴使用.     

《齐风·南山》新解

《齐风.南山》一诗,后人大都认为是一首讽刺齐襄公淫乱无耻的诗。然此说是对“雄狐绥绥”兴义的误解。本文对“齐子”的身份进行了探讨,又从挖掘“南山”、“雄狐绥绥”、“葛屦五两,冠纟委双止”、“艺麻和析薪”的深层含义入手,从而证明这首诗与婚姻有关,是一位齐国诸侯亲自到鲁国定亲回家后,听说别人仍在追求自己的未婚妻而发感慨所作的诗。     

湖南花垣和苏仙矿区重金属污染评价及优势植物富集研究

通过湖南花垣和苏仙两矿区野外踏查,数据检测Pb、Zn、Cu、Cd在两矿区相应植物土壤及植物中的含量及相关分析。结果表明：两矿区均受到Pb、Zn、Cd的污染。Pb元素在苏仙矿区是重污染,Zn对花垣矿区为中度污染,Cd对两矿区污染均为重污染,综合污染指数表明两矿区均为重污染。通过富集系数、转移系数、滞留率分析,发现14种优势植物表现出不同的吸收和富集特征,其中箬竹(Indocalamus tessella?tus)、油茶(Camellia oleifera)为富集型植物,菖蒲(Acorus calamus)、灯心草(Juncus effusus)、节节草(Equisetum ramosissimum)、毛萼莓(Rubus chroosepalus)、茅草(Imperata cylindrica)为根部囤积型植物,飞龙掌血(Todda?lia asiatica)为规避型植物。     

基于VB的平面回转车削轨迹仿真

针对一种车削加工异型截面的新型车床,该车床对传统的车床进行了改进,除了与传统车床一样车床主轴有旋转运动以外,给刀具的轴线也增加了旋转运动,并且通过机械传动系统或者采用伺服电机使它们之间按照所需的传动比关系转动。使用VB语言编写了程序对该回转车床的刀具相对于工件的运动轨迹进行了仿真,通过仿真得出的轨迹可以为该机床在异型截面车削时提供技术上的支持,可以将该程序嵌套在数控机床的加工程序中实现异型截面的数控车削。     

浅谈刀具和切削用量的合理选择对数控加工的影响

数控机床加工工件时,刀具直接担负着对工件的切削加工,刀具的合理选择和切削用量的合理选择是数控加工工艺中的重要内容,它不仅影响数控机床的加工效率,而且直接影响工件的加工质量。