Investigations for indications of deliberate blasting on the front bulkhead of the ro-ro ferry MV ESTONIA

The roll-on-roll-off passenger ferry MV ESTONIA sank during the night of 28 September 1994 in the Baltic Sea. In October 2000, divers recovered two palm-sized test pieces from the front bulkhead of the wreck. The investigators analysed these specimens to determine whether there were any indications of deliberate blasting. Since the wreck had been submerged for almost six years, it was clear that chemical traces would not be present on the surfaces of the test pieces. Therefore, the investigators performed comparative tests on shipbuilding steel to find a microstructural criterion that exclusively characterises a blast. The shipyard Jos. L. Meyer, Germany, had built the ESTONIA and supplied shipbuilding steel plates similar to that used for building the vessel in 1979/1980. The comparative tests comprised mechanical tests, shot peening tests and blasting tests using different explosives. Testing demonstrated that blasting always formed twinned ferrite grains in the microstructure over the whole cross-section of each of the 8 mm thick comparative plates. Although one of the original test pieces of the ESTONIA showed deformation twins, this was only confined up to 0.4 mm underneath the surfaces and not spread over the whole cross-section. Comparative shot peening tests produced the very same pattern of subsurface deformation twins. Therefore, the twins detected in the microsection of the test pieces of the ESTONIA wreck traced back to the shot peening process performed by the shipyard in 1979/1980 and not to a deliberate blast.     

卷烟中非挥发性有机酸、糖类、某些氨基酸和磷酸的同时测定

以山梨醇作内标,羟胺吡啶和BSTFA 1%TMCS为衍生化剂,采用GC法同时测定了国内外21种牌号卷烟中的木糖、阿拉伯糖、鼠李糖、果糖、甘露糖、半乳糖、葡萄糖、蔗糖、麦芽糖、天门冬氨酸、天门冬酰胺、丙二醇、丙三醇、乳酸、丙二酸、苹果酸、柠檬酸和磷酸。结果显示:①丙二醇和阿拉伯糖的RSD>10%,乳酸、天门冬酰胺、鼠李糖、半乳糖和麦芽糖的RSD>5%,其它成分的RSD<5%;②除丙二酸、半乳糖、鼠李糖、丙三醇和阿拉伯糖的回收率介于70%~75%外,其它组分的回收率>80%;③在所分析的卷烟样品中,进口混合型卷烟中柠檬酸、天门冬氨酸、天门冬酰胺、丙二醇和丙三醇含量较国产烤烟型卷烟的高,而糖类的含量则普遍较低,其它成分差别不大。     

一种吸收塔填料层高度的简明推导方式

在化工原理课程教学过程中,吸收塔填料层高度的计算是吸收传质操作计算中一个重要的内容。传统的教科书中关于填料层高度计算式的推导过程因涉及的公式形式复杂、概念点繁杂,教学中往往不易为学生所接受。本文参照间壁综合传热的推导思路,提出了一种填料层高度计算的简明推导方式。     

变圆弧齿轮的形成原理及特性

提出了一类变圆弧齿轮。利用偏差函数法,给出了齿廓的完整构造过程,证明了它满足齿廓啮合基本定律;推导了齿廓方程等基本公式,讨论了变圆弧齿轮的特性,给出了变圆弧齿廓的实例;这种齿轮具有较高的承载能力,特别便于高速、高精度数控加工,它将在重载传动场合得到应用。     

n－参数Ornstein—Uhlenbeck过程的导出

证明了ＯＵｐｎ在射线上导出的过程为ＯＵｐｎ的充要条件，并求出了ＯＵｐｎ的截口过程的单点转移函数和宽过去转移函数．     

面向系统辨识的离散系统模型类库

本文分析了系统辨识中常用的几种离散系统模型的结构,这些离散系统模型及其预测器模型在形式上都能表示成线性回归模型,并且一个复杂的模型能由几个简单的模型所构成。根据离散系统模型结构的这些特点,我们用面向对象的程序设计思想,用“类”的概念来实现各种离散系统模型,从而形成离散系统模型类库,并可由此派生出其它更具针对性的模型类。此离散系统模型类库和递推辨识算法类库结合在一起,可方便地构成完整的系统辨识程序。本文将介绍这一离散系统模型类库的层次结构及模型类库在系统辨识中的一些应用,给出两个例子。     

Deriving real-time action systems in a sampling logic

Action systems have been shown to be applicable for modelling and constructing systems in both discrete and hybrid domains. We present a novel semantics for action systems using a sampling logic that facilitates reasoning about the truly concurrent behaviour between an action system and its environment. By reasoning over the apparent states, the sampling logic allows one to determine whether a state predicate is definitely or possibly true over an interval. We present a semantics for action systems that allows the time taken to sample inputs and evaluate expressions (and hence guards) into account. We develop a temporal logic based on the sampling logic that facilitates formalisation of safety, progress, timing and transient properties. Then, we incorporate this logic to the method of enforced properties, which facilitates stepwise refinement of action systems.     

Office认证机制中密钥导出函数安全性分析

微软Office2007及其后续版本采用ECMA-376的文件加密格式,其安全性主要通过用户认证和文件加密实现,而密钥导出算法是整个安全机制的核心。为此,研究ECMA-376密钥导出算法的安全性,利用Game-Playing技术计算该密钥导出算法与随机函数的不可区分优势的上限。通过该理论和攻击实例对Office安全性进行分析,结果表明,当用户口令字符长度大于6时,Office具有一定的安全性。     

Relative specification and transformational re-use of functional programs

Arelative specification is a collection of laws relating the behaviour of a required new program to that of one or more existing programs. A two stage method for transforming such relative specifications into effective functional programs is described and illustrated. Theinversion stage re-arranges the specifying laws to obtain a collection ofpartial definitions for each unknown function, typically involving non-deterministic operators. The subsequentfusion stage combines each set of partial definitions into a single complete definition, thereby eliminating non-deterministic operators.Supported by Science and Engineering Research Council, Grant GR/E16571     

上古园林年表

中国造园从上古即始,私有财产和统治者是园林产生的物质和政治基础.上自三皇五帝,下至秦始皇统一六国之前,中国历朝历代都出现过园林,只不过形式不同,有些年代太久,只有记载,而没有考古发掘而已.无论如何,这些园林都是中国园林发展历史上的先声,没有它们,就不可能有现代的园林景观.上古园林的审美主要是观生意①,并非如今的观赏人工景观.后世园林中的景点创作,无论是文学文本,还是实际构筑物,常以上古园林名称为出典,如悬圃、上林、华林等,让时人追忆起古老的园林雏形.