于都县黄麟地区绿色富硒土壤分布选区评价

通过于都县黄麟地区1:5万土地质量地球化学调查,基本査明该地区农作物中硒元素及其他元素的地球化学特征,综合分析岀绿色富硒土壤分布,并优选出绿色富硒地块,为特色农产品基地建设的开发与利用提供理论依据。     

超高性能混凝土国内外研究与应用进展*

介绍了超高性能混凝土（UHPC）的制备原理和性能特点，对UHPC国内外研究和应用情况进行了综述，指出了我国UHPC研究和应用中存在的问题。结果表明：UHPC是一种具有优异的力学性能、耐久性能和环保效益的新型水泥基复合材料。国外在UHPC理论研究和应用研究方面都取得了大量成果，在实际工程中已经获得了广泛的应用；近年来我国在理论研究和应用方面也得到了快速发展；如何简化UHPC制备工艺、降低生产成本、补偿自收缩是今后的主要研究方向，完善相关规范标准以更好地指导UHPC现浇工程应用是目前首要解决的问题。随着环保和可持续发展理念的日益重视，UHPC这种低碳环保材料将有广阔的发展前景。     

基于数据驱动理念的电力日负荷曲线预测方法研究

针对短期日负荷预测的精度问题,本文提出一种基于数据驱动理念的电力负荷预测方法。在建立预测模型前对所给数据采取一定的预处理:首先提取所收集的海量数据的负荷特征,对负荷特征进行分析,然后进行负荷数据与影响负荷值的因素之间的相关性分析,以此确定对负荷影响较密切的因素,随后建立分类器得到各主要影响因素与各负荷类别之间的关系为后续预测模型奠定基础。对预处理后得到的不同类型的负荷数据采用最小二乘支持向量机方法建立不同的负荷预测模型。以南方某发达城市2008年的负荷数据作为算例验证数据,将本文所提负荷预测方法所得结果与未经数据预处理的负荷预测方法所得结果进行比较,结果表明本文提出的方法得到的预测结果精度较传统方法提高约6%。     

双季戊四醇在3种混合溶剂中的固-液相平衡

采用动态平衡法，在293.15～332.80 K、常压下，测定了双季戊四醇(DPE)在水+(甲醇、乙醇、异丙醇)三种混合溶剂中的溶解度数据。结果表明：DPE在不同质量分数的水+(甲醇、乙醇、异丙醇)混合溶剂中的溶解度随体系温度升高而增大；同一温度下，其在所选取溶剂体系中的溶解度随着甲醇、乙醇或异丙醇质量分数的增大而先增大后减小。λh方程、两参数方程与Apelblat方程均能够对所测定的溶解度数据进行较好的关联；通过修正的van’t Hoff方程计算得到DPE在所选取溶剂体系中Δ_sol H ⁰、Δ_sol S ⁰和Δ_sol G ⁰均大于零，表明DPE在所选取溶剂体系中的溶解过程为吸热、熵增的非自发过程。     

Analysis and control of micro-stepping characteristics of ultrasonic motor

Frontiers of Mechanical Engineering - Micro-stepping motion of ultrasonic motors satisfies biomedical applications, such as cell operation and nuclear magnetic resonance, which require a precise...     

Physicochemical characteristics,antioxidant capacity and thermodynamic properties of purple-fleshed potatos dried by radio frequency energy

Abstract

The impacts of using radio frequency (RF) energy to dry purple-fleshed potatoes were investigated and compared to infrared radiation (IR) and microwave (MW) drying techniques. The gelatinization rate, color, flavor, morphological, and structural characteristics, thermodynamic properties, as well as antioxidant capacity were examined. The results indicated that the drying time of RF (70?min) and MW (21?min) were shorter than IR (105?min). The gelatinization ratio of MW, RF, and IR were 94.4?±?2.0, 88.3?±?1.4, and 64.5?±?1.1%, respectively. The degree of crystallization of purple-fleshed potato powder decreased with all three drying methods. RF-dried potatoes were able to retain higher polyphenols (loss rate: 4.3%), total anthocyanin (3.7%), and total flavonoid content (35.1%), whereas IR showed the lowest retention. The content of polyphenols also decreased significantly. Furthermore, after RF heating, the scavenging of free radicals was higher compared to MW and IR.     

CNG-电混动公交车道路行驶工况与排放特性研究

CNG-电公交车以天然气作为发动机燃料,辅以电机共同驱动的混合动力车辆,车辆行驶速度低、启动频繁等特性,发动机实际运行工况与型式检验工况具有较大差异。为研究其实际行驶工况与排放特性,选取4辆国V排放标准的CNG-电混合动力公交车,往返于市区与城郊,使用PEMS(portable emission measurement system)实时收集车辆行驶及NO_X排放数据。结果表明,发动机运行工况集中于中低功率段,与型式检验工况差异较大,污染物排放集中于发动机切入车辆传动系统的临界车速附近。     

An observational study of driving distractions on urban roads in Spain

The present research investigated the prevalence of driver engagement in secondary tasks and whether there were any differences by age and gender, as well as day of the week and time of the day. Two independent researchers observed 6578 drivers at nine randomly selected urban locations in Girona, Spain. Nearly 20% of the drivers observed were engaged in some type of secondary task, with the most common being: conversing with a passenger (11.1%), smoking (3.7%) and talking on a handheld mobile phone (1.3%). Surprisingly there were no differences by gender, but there were age-related differences with younger drivers being more frequently observed engaged in a number of different types of secondary tasks while driving (i.e. drinking, talking on a handheld mobile phone, and texting or keying numbers). Logistic regression showed that younger drivers, and to a lesser extent middle-age drivers, were significantly more likely to be observed engaged in a technological distraction than older drivers. Conversely, non-technological distractions were significantly predicted by day of the week, time of the day and location. A substantial number of the drivers observed in this study were putting themselves at an increased risk of becoming involved in a crash by engaging in non-driving related tasks at the same time as driving. Furthermore, the higher crash rate among young drivers may be partially accounted for by their more frequent engagement in some types of secondary tasks while driving.     

Structural,microstructural, and thermal characterizations of a chalcopyrite concentrate from the Singhbhum shear zone,India

The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron mi...