OPTIMAL REINSURANCE UNDER EXPECTED VALUE PRINCIPLE

The paper concerns the problem how to purchase the reinsurance in order to make the insurer and the reinsurance company＇s total risk to be least under the expected value principle. When the insurer and reinsurance company take arbitrary risk measures, sufficient con- ditions for optimality of reinsurance contract are given within the restricted class of admissible contracts. Further, the explicit forms of optimal reinsurance contract under several special risk measures are given, and the method to decide parameters as well.     

酚醛树脂热裂解产物的结构研究

导电性高聚物聚乙炔在空气中的化学不稳定性,限制了它在电器元件等方面的应用,由酚醛树脂在非氧气氛下经热处理制成的多并苯导电材料,在空气中不仅十分稳定,而且不经掺杂其电导率可由热处理温度不同随意控制在10~(-10)～10~2S/cm范围内,引起人们的高度重视,本文详细报道了多并苯本征材料的结构特性。     

甲壳素类液晶高分子的研究Ⅵ.邻苯二甲酰化壳聚糖中酰胺酸取代度对液晶性的影响

通过控制不同反应时间和邻苯二甲酸酐 壳聚糖的摩尔比制备不同取代度的邻苯二甲酰化壳聚糖(PHCS) .用FTIR研究了反应机理和产物结构 ,观察到PHCS含两类取代即酰胺酸取代和酰亚胺取代 .反应时间较短时主要为前者 ,取代度表示为DS1 ;反应时间较长时主要为后者 ,取代度表示为DS2 .对PHCS在二氯乙酸 (DCA)中的液晶行为观察 ,结果表明 ,PHCS的临界浓度随DS1 的增加而显著增加 .DS1 对PHCS临界浓度的影响明显大于DS2 的影响 .基本上为酰胺酸取代的PHCS的临界浓度高于溶解度 ,以至于观察不到     

Effects of salt on solute association behavior in nanoconfined aqueous solutions

Using molecular dynamics simulations, we have studied the effects of salt on the association behavior of solute molecules in nanoconfined aqueous solutions. Three types of solute association states – dispersion, reversible and aggregation states – are still observed in nanoconfined aqueous solutions in the presence of salt. With the increase of ion concentration, the tendency toward the formation of larger clusters is enhanced and the solute critical aggregation number decreases. We even found the transformation of solute association state from the dispersion to the reversible state or from the reversible to the aggregation state within an intermediate range of solute number. This phenomenon is similar to the salting out process and is attributed to the decrease of free water molecules induced by the ion polarization.     

高效全固化263nm紫外激光脉冲的产生

运用半导体泵浦的Nd:YLF调Q倍频激光器输出的527nm波长激光和BBO晶体直接进行了外腔谐波倍频的实验研究.采用较小的基波光束尺寸和长聚焦相结合的方法实现了高效全固化263nm紫外激光脉冲的大功率输出.基波功率为6.0W时,紫外263nm激光输出780mW,转换效率达13%,实验中还发现紫外输出光束质量很好.     

爆轰波碰撞的聚能效应

利用两高爆速导爆索对称布置于药卷两侧,起爆后炸药爆轰波在对称线处汇聚碰撞,当碰撞角度达到一定值时,发生马赫反射,使爆轰压力成倍增加,形成高压、高能量密度区域的聚能效应。本文在爆轰波传播碰撞理论的基础上,通过炸药做功能力和猛度试验验证爆轰波碰撞的聚能效果。做功能力试验结果表明爆轰波碰撞能够增加炸药能量利用率;猛度试验结果表明采用对称起爆技术下的爆轰波碰撞能够改变爆轰波在特定方向上的扩散作用。试验结果与爆轰波入射角的几何关系表明,当高爆速起爆药条与主装药爆速比例在1.15倍以上时,爆轰波碰撞能够达到一定的聚能效果。     

Three-dimensional desingularized boundary integral methods for potential problems

The concept of desingularization in three-dimensional boundary integral computations is re-examined. The boundary integral equation is desingularized by moving the singular points away from the boundary and outside the problem domain. We show that the desingularization gives better solutions to several problems. As a result of desingularization, the surface integrals can be evaluated by simpler techniques, speeding up the computation. The effects of the desingularization distance on the solution and the condition of the resulting system of algebraic equations are studied for both direct and indirect versions of the boundary integral method. Computations show that a broad range of desingularization distances gives accurate solutions with significant savings in the computation time. The desingularization distance must be carefully linked to the mesh size to avoid problems with uniqueness and ill-conditioning. As an example, the desingularized indirect approach is tested on unsteady non-linear three-dimensional gravity waves generated by a moving submerged disturbance; minimal computational difficulties are encountered at the truncated boundary.     

气相色谱-质谱法测定聚氯乙烯包装材料和食品模拟物中的46种增塑剂

建立了46种增塑剂在聚氯乙烯(PVC)食品包装材料中的含量及其在水、3%乙酸、10%乙醇和橄榄油4种食品模拟物中迁移量的气相色谱-质谱(GC-MS)测定方法。食品包装材料、水质模拟物和橄榄油中增塑剂分别采用溶解-沉淀法、正己烷液-液萃取和凝胶渗透色谱(GPC)法提取。采用GC-MS法,在选择离子监测模式(SIM)下对46种增塑剂进行定性,采用外标法进行定量测定。各种增塑剂在0.1～2.0 mg/L质量浓度范围内呈线性,相关系数为0.9910～0.9999,各组分检出限均在0.005～0.05 mg/kg之间。在2种食品模拟物中,3个浓度添加水平下46种增塑剂的加标回收率在69.51%～107.21%之间,精密度(RSD, n=6)为3.53%～18.95%。该方法可满足PVC食品接触制品及4种不同性质的食品模拟物中多种类增塑剂的快速筛查和准确定性、定量测定要求。     

Studies on Lyotropic Liquid‐Crystalline N‐Alkyl Chitosans in Formic Acid

A series of derivatives of chitosan – N‐alkyl(methyl, ethyl, propyl and butyl) chitosans – were synthesized from completely deacetylated chitosan. The degree of substitution (from 0.15 to 0.81) of the N‐ethyl chitosan were obtained by controlling the molar ratio of the reactants. All the products showed lyotropic liquid‐crystalline properties regardless of the length of the side chains and the degree of substitution. The critical concentration (C*) of the samples were measured by both microscopy and refractometry. C* seemed not to vary with the degree of substitution (ds) in the case of a given subsitituent chain, but rose dramatically depending on the length of the substituent group as this was varied from methyl to butyl. The results were explained according to Flory's classical theory as well as experimental of X‐ray diffraction measurements.