氮掺杂碳纤维负载镍钴硒化物的制备及其电催化析氢性能

以静电纺丝制备的纤维为前驱体,通过煅烧、硒化处理等工艺合成了负载双金属硒化物纳米粒子的氮掺杂碳纤维(NCF)材料((Ni,Co)Se2/NCF),并对其进行了一系列相关的表征,研究了其在酸性和碱性条件下的析氢性能.(Ni,Co)Se2纳米粒子被锚定于NCF中,有效地阻止了纳米粒子的聚集,提供了更多的催化活性位点.电催化...     

Routes to halogen‐free flame‐retardant polypropylene wood plastic composites

Developing halogen‐free flame retardants with reasonably high efficiency, which thus function at limited loadings in polypropylene‐based wood/plastic composites (WPC), is still a challenge. Cost‐effective flame‐retarded WPC have been identified as a way to open the door to an interesting, broader spectrum of application in the building and transportation sectors. This work imparts a systematic comprehensive understanding and assessment of different basic routes to halogen‐free flame‐retarded WPC, taking into account economic and environmental considerations. Cheap, halogen‐free single‐component flame retardants and their multicomponent systems are investigated at reasonable filling grades of 20 wt%. The basic routes of promising synergistic multicomponent systems are discussed, and their potential and limits assessed. Optimizing the consistency of fire residue; closing the surface of inorganic‐organic residual layers; the thermal stabilization and design of the residue, eg, synergistic combination of ammonium polyphosphate and expandable graphite; and the combination of different flame‐retardant mechanisms, eg, intumescence and flame inhibition, are proposed as promising routes to boost the flame‐retardant efficiency.     

基于Kolmogorov熵的系统协同效应度量方法及实证

度量协同度是协同学研究的核心和难点。通过分析现有协同度模型及其使用条件,发现基于协调发展思想的协同度模型在实际应用时有严格的限制条件,极大限制了其适用范围。基于协同效应思想,验证了Kolmogorov熵与系统协同度的关系,并构建了基于k熵的复杂系统协同度模型及量化方法。该方法考虑了序参量在系统某一时刻的发展趋势,能够在更大程度上反映系统的有序程度,弥补了现有研究的不足。最后,以中国2004~2015年各省份的科技金融系统为评价对象,对新的协同度模型与评价方法的应用范围进行了实证研究。分析发现,本模型不仅能够有效找到子系统的序参量,而且可以方便的计算系统协同度并以此描述系统发展对重大事件的反映。     

湿磨工况下冲击功对高锰钢腐蚀磨损交互作用的影响

采用自制的冲击腐蚀磨损试验机模拟湿磨工况,通过电化学等方法研究了冲击工况条件下高锰钢在锡矿浆料中的腐蚀磨损行为,定量分析了腐蚀磨损中交互作用各个分量的相对比例.结果表明,虽然弱酸性的矿浆对高锰钢的腐蚀性较小,但腐蚀增量是静态腐蚀率的15.76～26.54倍,腐蚀磨损交互作用的比例为12.08%～26.70%,表明磨损与腐蚀有一定的协同促进作用.在低冲击功1 J时,交互作用是以磨损促进腐蚀为主;在冲击功为2、3、4 J时,交互作用是以腐蚀促进磨损为主.最后探讨了冲击载荷下磨损与腐蚀的交互作用机理,以及冲击功对交互作用机理的影响.     

Three-dimensional numerical study and field synergy principle analysis of wavy fin heat exchangers with elliptic tubes

Three dimensional numerical studies were performed for laminar heat transfer and fluid flow characteristics of wavy fin heat exchangers with elliptic/circular tubes by body-fitted coordinates system. The simulation results of circular tube were compared with the experiment data, then circular and elliptic (e = b/a = 0.6) arrangements with the same minimum flow cross-sectional area were compared. A max relative heat transfer gain of up to 30% is observed in the elliptic arrangement, and corresponding friction factor only increased by about 10%. The effects of five factors on wavy fin and elliptic tube heat exchangers were examined: Reynolds number (based on the smaller ellipse axis, 500  4000), eccentricity (b/a, 0.6  1.0), fin pitch (F_p/2b, 0.05  0.4), fin thickness (F_t/2b, 0.006  0.04) and tube spanwise pitch (S₁/2b, 1.0  2.0). The results show that with the increasing of Reynolds number and fin thickness, decreasing of the eccentricity and spanwise tube pitch, the heat transfer of the finned tube bank are enhanced with some penalty in pressure drop. There is an optimum fin pitch (F_p/2b = 0.1) for heat transfer, but friction factor always decreases with increase of fin pitch. And when F_p/2b is larger than 0.25, it has little effects on heat transfer and pressure drop. The results were also analyzed from the view point of field synergy principle. It was found that the effects of the five factors on the heat transfer performance can be well described by the field synergy principle.     

Defining synergy thermodynamically using quantitative measurements of entropy and free energy

Synergy is often defined as the creation of a whole that is greater than the sum of its parts. It is found at all levels of organization in physics, chemistry, biology, social sciences, and the arts. Synergy occurs in open irreversible thermodynamic systems making it difficult to quantify. Negative entropy or negentropy ( ) has been related to order and complexity, and so has work efficiency, information content, Gibbs Free Energy in equilibrium thermodynamics, and useful work efficiency in general ( ). To define synergy in thermodynamic terms, we use the quantitative estimates of changes in and in seven different systems that suffer process described as synergistic. The results show that synergistic processes are characterized by an increase in coupled to an increase in . Processes not associated to synergy show a different pattern. The opposite of synergy are dissipative processes such as combustion where both and decrease. The synergistic processes studied showed a relatively greater increase in compared to opening ways to quantify energy—or information—dissipation due to the second law of thermodynamics in open irreversible systems. As a result, we propose a precise thermodynamic definition of synergy and show the potential of thermodynamic measurements in identifying, classifying and analysing in detail synergistic processes. © 2016 Wiley Periodicals, Inc. Complexity 21: 235–242, 2016     

Current problems in insurance economics

This paper presents a survey of the lectures held within the B.V.V.O.-chair for insurance economics, 1990–1991. Within this context, a ‘company mission’ for the Center for Insurance Studies is formulated. Future topics to be tackled are given and some results to questions raised during the lectures are presented. In this respect, the corporate strategist will be interested in Sections 2 (positioning of the industry vis-à-vis the competitive forces) and 4 (potential competition from 1992 and synergy with banks). The economist will find some reflections on the nature of insurance from both partial (industrial organisation) and general equilibrium analyses.     

Cellulases and their interaction with cellulose

Most effective cellulolytic enzymes are made of at least two constitutive domains, a catalytic domain and a non-catalytic cellulose-binding domain linked by a flexible peptide. There are several families of catalytic domains and of cellulose-binding domains resulting in a large number of their possible combinations. Removal of the cellulose-binding domain drastically reduces the binding capacity of cellulases to insoluble cellulose while the catalytic efficiency on soluble substrates is usually maintained. Isolated cellulose-binding domains bear most of the binding properties of cellulases (quasi-irreversibility and dispersive effect) but do not hydrolyse cellulose. The multiple types of synergy that cellulases display when acting in combination on cellulose appear to result from their different activities and selectivity, from the substrate microheterogeneity, and sometimes from both.To the memory of Prof. Elwyn T. Reese.     

近红外光谱结合特征变量筛选方法用于农药乳油中毒死蜱含量的测定

为提高毒死蜱农药乳油中有效成分近红外光谱定量分析模型的精度和稳定性。采用联合区间偏最小二乘法(siPLS)结合遗传算法(GA)筛选特征变量,由交互验证法确定最佳主成分因子数及筛选的变量数。结果表明,从全光谱区优选出81个变量,主成分因子数为11时,能建立性能最优的模型,模型预测集的决定系数R_p~2为0.972,预测均方根误差(RMSEP)为0.353%。研究表明,利用siPLS结合GA方法优选特征变量,能大幅度地消除农药乳油光谱变量间的冗余信息和无关信息,降低模型的复杂度,提高农药有效成分预测模型的精度及稳定性。     

场协同理论在交变流动缝隙式回热器中的数值验证

本文对缝隙式回热器在非稳态交交流动下的流动和换热问题做了二维的数值模拟,并重点对其在交交流动下的场协同问题做了计算与分析。数值计算表明,场协同原理作为指导强化对流换热的原则,同样可以指导交交流动下的换热强化。