Rates in Approximations to Ruin Probabilities for Heavy-Tailed Distributions

A well known result by Embrechts and Veraverbeke [3] says that, for subexponential distribution functions F(x), the tail of the compound sum distribution function is approximated by as x . We show that the rate of convergence in this result can be arbitrarily slow. On the other hand, if F satisfies some smoothness condition (for example if F is an integrated tail distribution function) then the rate cannot be worse than O(x^-1).     

加氢处理催化剂的制备和表征 Ⅰ.MoNiP/Al2O3催化剂的制备及助剂的作用

 采用专利方法制备出一种新型的γ－Al2O3,并以其为载体,制备出加氢处理催化剂MoNiP／Al2O3．用PAS－CA,XPS,DRS,TPR和微型反应色谱等技术对γ－Al2O3和催化剂进行了表征,考察了Ni和P两种助剂的作用．结果表明,γ－Al2O3具有较大的孔径,集中的孔分布和较高的机械强度;活性金属Mo在γ－Al2O3表面上的化学分散量（分散阈值）可达5．04～5．82μmol／m2．因而特别适合用作高活性加氢处理催化剂的载体．引入的Ni主要是同Mo／Al2O3催化剂表面上较稳定的金属－载体相互作用复合物反应,并生成类NiMoO4化合物;在MoNi／Al2O3催化剂中引入P,有利于抑制四面体配位结构的物种Mo［T］,增加八面体配位结构的物种Mo［O］,改善催化剂的还原性能,从而提高催化剂的加氢处理活性．助剂Ni和P的最佳含量分别为w（Ni）＝4．0％和w（P）＝2．6％．     

压气机无级间冷燃气轮机性能的理论研究

本文针对压气机入口喷水方式,探讨了利用水的显热及蒸发潜热对压缩空气进行连续冷却的效果,建立了连续冷却（无级间冷）数学模型,在理论上研究了最大注水量、最佳注水量、以及注水最小压比,分析了相应循环的性能特点。     

利用国产全色银盐干版制作真彩色反射全息图

本文介绍了利用国产KL型全色银盐干版制作真彩色反射全息图的技术,其中包括干版的化学处理方法、拍摄光路和三基色的选取,提出通过确定全息干版的曝光常量,拍摄具有预期衍射效率全息图的方法,解决曝光量的计算和色平衡的问题.     

Differences in oxygen-18 and deuterium content of throughfall and rainfall during different flood events in a small headwater watershed

Inter-storm stable isotopic values of rainfall and throughfall for three flooding events were measured during the period of July to August 2011 to estimate their differences in a first-order chestnut watershed, Meilin, within the Taihu Lake basin. Comparison of δ²H and δ¹⁸O was conducted from four aspects: (1) sampling methods, (2) calculation methods, (3) stable isotopes and (4) flood events. Arithmetic and weighted incremental values of throughfall were generally lighter than those of rainfall. Isotopic composition of both incremental rainfall and throughfall exhibits marked temporal variation, particularly during large storm events; the former shows a higher variation than the latter. Differences of averaged precipitation and throughfall between storms were small, but individual storm variations were larger. Isotopic differences using different calculation methods are not significant; however, the differences resulting from sampling methods are of greater importance.     

超声速射流装置的流场特性研究

超声速射流装置能很好地模拟榴弹引信发电机飞行时大气环境的工况,已成为地面考核和验收必不可少的设备。本文结合双曝光全息干涉技术和数值模拟方法,对超声速射流装置有无模型的流场进行了研究,将实验干涉图与数值模拟结果进行了比较,从而辨识出实验干涉图中的条纹级数并计算了条纹位移量,由此得出实验干涉图的密度场,经适当的修正就可应用到实物飞行中,解决了过去引信电机选取当地参考密度难的问题。另外由实验结果也验证了数值模拟结果的可靠性。     

Research on abrasion of debris flow to high-speed drainage structure

As one weak topic in research of debris flow, abrasion of debris flow shortens obviously application life of control structure composed of concrete. High-speed drainage structure, one of the most effective techniques to control giant debris flow disaster, has shortened one-third application life due to abrasion by debris flow. Based on velocity calculation method founded by two-phase theory, research of abrasion mechanism of debris flow to high-speed drainage structure was mode. The mechanism includes both abrasion mechanism of homogeneous sizing and shearing mechanism of particle of debris flow to high- speed drainage trough structure. Further abrasion equations of both sizing and particle were established by Newton movement theory of debris flow. And abrasion amount formula of the high-speed drainage trough structure is set up by dimensional analysis. Amount to calculating in the formula is consistent with testing data in-situ, which is valuable in design of high-speed drainage structure.     

Analysis of the relationship between total and effective rainfall by means of streamflow shot noise and rainfall stochastic models

Linking the results of two research topics on rainfall and streamflow stochastic models, the relationship between total and effective rainfall is studied here. The short time streamflow process is examined concerning the climatic and hydrogeological characters of the watershed, identifying four distinct components giving rise to runoff. In this way the watershed can be regarded as a four-component linear system, whose input is the effective rainfall. Finally, the streamflow model is used as an effective rainfall inverse estimator, allowing the analysis of the links between total and effective rainfall assuming a simple transformation law. The determination of this law is performed by applying a stochastic model, whose parameters are estimated on the companion series of recorded total rainfall and reconstructed effective rainfall. An application to a case study shows the effectiveness of the proposed approach.

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Sommario Raccordando i risultati di due ricerche sui modelli stocastici di pioggia e dei deflussi, vengono qui studiate le relazioni fra la pioggia totale e la pioggia efficace. I deflussi aggregati a breve scala temporale sono esaminati alla luce delle caratteristiche climatiche e idrogeologiche del bacino idrografico, identificando quanttro distinte componenti che danno origine al deflusso. II bacino idrografico viene così rappresentato da un sistema lineare a quattro componenti, il cui input è la pioggia efficace. Pertanto, il modello dei deflussi viene usato per effettuare la stima inversa delle piogge efficaci, consentendo lo studio delle relazioni fra le piogge totali ed efficaci ipotizzando una semplice legge di trasformazione. La determinazione di questa legge è effettuata applicando un modello stocastico, i cui parametri sono stimati sulle serie corrispondenti di pioggia totale registrata e di pioggia efficace ricostruita. Un'applicazione a un caso reale mostra l'efficacia dell'approccio proposto.

     

销售量预测的REM-GM(1,1)模型及群预测方法研究

库存管理是商业企业经营管理的重要组成部分,其管理应以销售出库量为主要依据,而客户需求的不确定性一直是困扰管理者的首要难题.提出在灰色GM(1,1)模型的基础上,结合残差时刻的灰灾变预测,建立了REM-GM(1,1)模型,并采用群预测的方法,对商业企业中的销售出库量进行了预测.经实证结果检验,表明该模型对商业企业的销售出库量的预测不论是单步预测还是多步远期预测,其预测精度与传统GM模型相比均有较大提高,且误差的波动较为稳定,其预测的结果是令人满意的.     

浙江省东阳市紫色土坡面土壤侵蚀和降雨因子关系的初步研究

紫色土分布区是我国南方水土流失区的重要组成部分。本文通过对东阳市紫色土坡面土壤侵蚀和降雨因子之间的相关分析,建立了利用降雨量和平均降雨强度对土壤流失量进行预测预报的回归方程,为紫色土地区土壤过度侵蚀的治理提供了定量方法,并为紫色土的综合开发利用提供了科学根据.