An empirical analysis of heuristics for solving the two-machine flow shop problem with job release times

The theoretical analysis of heuristics for solving intractable optimization problems has many well-known drawbacks. Constructed instances demonstrating an exceptionally poor worst-case performance of heuristics are typically too peculiar to occur in practice. Theoretical results on the average-case performance of most heuristics could not be established due to the difficulty with the use of probabilistic analysis. Moreover, the heuristics for which some type of asymptotic optimality has been proven are likely to perform questionably in practice. The purpose of this paper is to confront known theoretical results with our empirical results concerning heuristics for solving the strongly NP-hard problem of minimizing the makespan in a two-machine flow shop with job release times. The heuristics' performance is examined with respect to their average and maximum relative errors, as well as their optimality rate, that is, the probability of being optimal. In particular, this allows us to observe that the asymptotic optimality rate of so called “almost surely asymptotically optimal” heuristic can be zero. We also present a new heuristic with short worst-case running time and statistically prove that it outperforms all heuristics known so far. However, our empirical experiments reveal that the heuristic is on average slower that its competitors with much longer worst-case running times.     

Physiological responses to simulated firefighter exercise protocols in varying environments

For decades, research to quantify the effects of firefighting activities and personal protective equipment on physiology and biomechanics has been conducted in a variety of testing environments. It is unknown if these different environments provide similar information and comparable responses. A novel Firefighting Activities Station, which simulates four common fireground tasks, is presented for use with an environmental chamber in a controlled laboratory setting. Nineteen firefighters completed three different exercise protocols following common research practices. Simulated firefighting activities conducted in an environmental chamber or live-fire structures elicited similar physiological responses (max heart rate: 190.1 vs 188.0 bpm, core temperature response: 0.047°C/min vs 0.043°C/min) and accelerometry counts. However, the response to a treadmill protocol commonly used in laboratory settings resulted in significantly lower heart rate (178.4 vs 188.0 bpm), core temperature response (0.037°C/min vs 0.043°C/min) and physical activity counts compared with firefighting activities in the burn building.

Practitioner Summary: We introduce a new approach for simulating realistic firefighting activities in a controlled laboratory environment for ergonomics assessment of fire service equipment and personnel. Physiological responses to this proposed protocol more closely replicate those from live-fire activities than a traditional treadmill protocol and are simple to replicate and standardise.     

适应新形势的大城市停车需求预测方法

目前我国已探讨出多种停车需求预测方法,这些方法的前提条件和适用范围各有不同,并且我国大城市交通形势又出现了小汽车进入家庭速度加快,交通拥堵日益突出,轨道交通建设进入黄金时代等新的情况。针对这些新形式,提出了宏观和中观停车需求预测方法,宏观层次为考虑车辆出行吸引和车辆使用率的总体停车需求预测,弥补了以往未考虑未出行车辆停车需求的不足;中观层面为考虑公交可达性和多种性质建筑综合开发共享停车需求预测,可减少配建停车泊位,提高停车泊位利用率。进行实例分析,丰富和扩展了交通规划模型技术,为我国大城市开展停车交通研究提供参考。     

机织物折皱变形量值理论计算分析

基于圆形截面纱线的平纹织物模型,依据几何学,推导出平纹织物折皱弯曲变形计算方程,提出表征织物松紧结构的新指标——织物密度放松值γ．通过数值计算表明,织物折皱变形与织物密度放松值γ呈线性递减的关系,且挤紧结构状态的平纹织物的纱线最外层最大变形率达到40．75％．     

基于行业视角的FDI对人民币实际汇率的影响研究

本文选取1997-2008年间的行业数据,运用偏最小二乘法分析各行业外商直接投资FDI流入对人民币实际汇率的影响。实证分析结果认为:FDI的流入是导致人民币升值的原因,大部分行业的FDI都会引起人民币实际汇率升值,但影响程度不同,而农、林、牧、渔业和建筑业FDI则会引起人民币实际汇率贬值。因此需要制定行之有效的政策以改善我国FDI的行业结构。     

利率随机时的跳跃扩散过程的期权定价模型

假定股票价格的跳过程为一般的计数过程,建立了股票价格服从跳扩散过程的行为模型。运用随机分析中的鞅方法,讨论了当利率为随机变量时的期权定价问题,推导出了利率随机时欧式买权与卖权的定价公式以及平价关系,推广了已有的结果。     

碳化硅添加剂对紫色页岩陶粒烧胀性的影响

利用碳化硅为膨胀成份,紫色页岩为主要原料制作陶粒,研究碳化硅掺加量和焙烧温度对紫色页岩烧胀性的影响,探讨碳化硅引起紫色页岩陶粒膨胀的机理。试验结果表明外加碳化硅0.3wt%可使紫色页岩在1 120℃时膨胀;当碳化硅掺加量提高时,紫色页岩起始烧胀温度下降,添加量为1.2wt%时,起始烧胀温度为1 100℃。     

延边大学朝鲜族女大学生身体成分与身体形态现状分析

对延边大学朝鲜族和其他民族女大学生的身体形态（身高、体重、三围）和身体成分（体重指数、体脂率、腰臀比）进行了比较研究.结果表明：朝鲜族女生的超重和高于正常体脂检出率略高于其他民族,而汉族女生的体重偏低比例略高于朝鲜族和其他少数民族,但均无显著性差异;朝鲜族女生的向心性肥胖比例略高于其他民族,但均无显著性差异;汉族女生的未达腰臀比切点比例高于朝鲜族,具有显著性差异;汉族和其他少数民族女生的身高、体重、臀围均值明显高于朝鲜族,具有显著性差异,但朝鲜族女生的腰臀比均值明显高于汉族,具有显著性差异;朝鲜族女生的体重指数（BMI）和体脂率均值虽然略高于其他民族,但无显著性差异;朝鲜族女生的平均身高略低于全国同龄组女生均值,且超重和肥胖检出率均低于全国同龄组女生检出率.     

未拆/已拆电子元器件的废旧印刷线路板浸铜规律对比研究

以未拆和已拆电子元器件的废旧印刷线路板（Waste Printed Circuit Boards,WPCBs）为研究对象,对比研究了其在硝酸中金属铜的浸出规律。研究结果表明：两者铜的浸出率随粒径的增大、时间的延长和固液比的减小而增大,温度对两者的影响都不大。已拆电子元器件的WPCBs的铜浸出率随H2O2和HNO3用量的增大而增大,而后者在实验讨论的范围内,H2O2和HNO3用量对其浸出率无明显影响。对于1 g样品,当未拆电子元器件的WPCBs粒径为0.25～0.5 mm,固液比为1：1,H2O2和HNO3均为2 mL时,50℃浸出2 h,即可浸出几乎全部的铜;当已拆电子元器件的WPCBs粒径为0.1～0.25 mm,固液比为1：1,H2O2和HNO3用量分别为2 mL和6 mL时,室温浸出2 h,铜浸出率达92.03%。     

碱添加量对金属离子的分布和pH变化的影响

提出了一种计算公式,定量地计算了既有氢氧化物沉淀又有氢氧配离子形成的化学反应体系中的金属离子的分布,考察了影响沉淀和配离子形成的各种因素.基于提出的公式,计算了锌、镉、铜、镍、铁（Ⅲ）、铁（Ⅱ）、铝、钙、镁的沉淀率,理论计算与实验结果一致.