Ce、Nb对Al_(66)Mn_9Ti_(25)金属间化合物形变和断裂行为的影响

本工作研究了微量Ｃｅ、Ｎｂ对Ａｌ６６Ｍｎ９Ｔｉ２５金属间化合物显微组织、微裂纹生成及扩展倾向、维氏硬度、压缩性能、断裂特征、变形亚结构的影响。结果表明，添加微量Ｃｅ有显著的促进晶粒枝晶化和第二相弥散化作用，从而使微裂纹生成和扩展以及沿晶开裂受到一定程度的抑制，因而，压缩强度明显提高，压缩塑性也有改善。微量Ｎｂ的加入，显微组织仍保持等轴状晶粒和粗大第二相，压缩性能未能改善。     

纺丝级尼龙6的反应挤出研究

利用阴离子开环聚合反应在双螺杆上快速制得了相对分子质量适当 ,相对分子质量分布较低(小于 3) ,单体含量低 (质量分数为 2 .5%～ 2 .8% ) ,流变性能好 ,易于纺丝的纺丝级尼龙 6。介绍了双螺杆反应挤出机的设计原理 ,讨论了催化剂、活化剂、助剂和挤出条件等因素对纺丝级尼龙 6的相对分子质量及其分布、残留单体量等的影响。实验发现 ,催化剂主要起引发反应的作用 ,活化剂则可大大加快反应速度 ,而助剂的加入可有效地提高聚合物的可纺性。     

Automatic deletion of obsolete information

Information generated in a programming environment is often allowed to grow indefinitely. Designer and user alike are counting on standard backup and disc clearing procedures for archiving old data. In this paper we take the view that one should distinguish between relevant old data that is purposely archived and obsolete information that should automatically be deleted. The two main topics of the paper are the strategies and mechanisms for deleting information and the facilities available to designers of programming environments to specify deletion strategies. Information can be deleted applying a passive or an active strategy. With the passive strategy, information will not actually be deleted until it is certain that there is no interest in it any longer. With the active strategy, an object is immediately deleted when it becomes obsolete, while users of the object are notified of the deletion event. The paper discusses various implementations for these two strategies and shows when they apply. Taking the view that it must be easy to modify and fine tune programming environments, much attention must be given to the designer's support environment for generating programming environments. The paper discusses in particular the facilities for expressing the semantics of names in an environment. Various naming modes are useful for a designer to specify the deletion strategies for his target programming environment. Details are illustrated by applying the ideas to an environment for software development and maintenance.     

基于双核NiosⅡ系统的数字预失真器设计

设计了一种基于双核Nios Ⅱ系统的数字预失真器(DPD)。在FPGA中构建多查找表结构,实现了基于记忆多项式模型的DPD;采用双核处理器完成并行RLS算法处理,保证了DPD模型参数提取过程的执行效率。实验结果证明,该系统能够对功放的非线性进行较好补偿。     

Three ∑ P 2 -complete problems in computational learning theory

The consistency problem associated with a concept classC is to determine, given two setsA andB of examples, whether there exists a conceptc inC such that eachx inA is a positive example ofc and eachy inB is a negative example ofc. We explore in this paper the following intuition: for a concept classC, if the membership problem of determining whether a given example is positive for a concept isNP-complete, then the corresponding consistency problem is likely to be _P ² -complete. To support this intuition, we prove that the following three consistency problems for concept classes of patterns, graphs and generalized Boolean formulas, whose membership problems are known to beNP-complete, are _P ² -complete: (a) given two setsA andB of strings, determine whether there exists a patternp such that every string inA is in the languageL(p) and every string inB is not in the languageL(p); (b) given two setsA andB of graphs, determine whether there exists a graphG such that every graph inA is isomorphic to a subgraph ofG and every graph inB is not isomorphic to any subgraph ofG; and (c) given two setsA andB of Boolean formulas, determine whether there exists a 3-CNF Boolean formula such that for every A, is satisfiable and for every B, is not satisfiable. These results suggest that consistendy problems in machine learning are natural candidates for _P ² -complete problems if the corresponding membership problems are known to beNP-complete.In addition, we prove that the corresponding prediction problems for concept classes of polynomial-time nondeterministic Turing machines, nondeterministic Boolean circuits, generalized Boolean formulas, patterns and graphs are prediction-complete for the classR _NP of all concept classes whose membership problems are inNP.     

OOram与面向对象方法

OOram（Object Oriented Role Analysis and Modeling）是挪威工业研究中心和奥斯陆大学提出的一种新一代面向对象软件工程方法,与众多其它面向对象方法相比较,其鲜明的特点是引入了角色模型的概念,将传统面向对象方法中的对象模型和类模型统一为单一的角色模型。文章提出了理想的面向对象开发方法所应具备的特性,简要介绍了OOram方法,并与其他面向对象方法作了比较。     

一种复杂BIU的设计及其CPLD实现

文章分析了可配置成多机系统的嵌入式微处理器中的总线接口单元的结构。文章首先详细分析了这种情况下总线接口单元的控制通路。然后从采用格雷方式FSM编码、FSM有效描述和接口信号的正确描述三个方面讨论该部件的高效实现。     

计算机通信中的一个组播路由算法

在计算机通信的实际应用中,组播（multicasting）技术日益重要,但由于网络节点处理信息的能力不同,有些节点并不具备组播能力,为此该文用节点的度约束来表示每个节点所具备的组播能力,研究在网络节点具有不同组播能力的路由问题,提出了一种新的解决此问题的利用局部信息的组播路由算法。     

基于SimBiology洋葱伯克霍尔德菌CF-66发酵过程的模拟

过度使用化学农药所引起的一系列环境问题,使人们对安全的生物农药的需求不断增长。本实验室从堆肥中筛选出一株对若干植物病原霉菌和病原真菌具有强烈抑制作用、并显示广谱抗菌活性的洋葱伯克霍尔德菌CF-66,发酵液通过分离纯化后得到一种新型抗菌物质,有望作为新型生物农药来开发利用。为了检测洋葱伯克霍尔德菌CF-66的发酵能力,预测其发酵过程中菌体、底物及代谢产物的浓度变化,通过在3.7L发酵罐内对洋葱伯克霍尔德菌CF-66进行分批培养,在MATLAB的SimBiology图形用户界面下,建立了基于分批培养实验的发酵动力学模型,通过改进的Monod和Gaden方程,对发酵参数进行了估计,实现了对发酵过程的模拟。结果表明:模型预测与实测值拟合良好,参数估计值μ_(max)、Y_(x/s)及β分别为(0.3220±0.0075)h~(-1),(0.0278±0.0072)和(0.1244±0.0025)h~(-1)。用SimBiology建立分批培养可视化动力学模型,方法简单,并可用于各种生物途径。     

基于QR-RLS算法的预失真模型

讨论一种基于正交递归最小二乘法(QR-RLS)的功率放大器行为模型。该模型采用Gives旋转提高QR-RLS算法的运算效率,能够提升数字预失真模型的系数更新速度,更快地实现数字预失真模型的收敛。测试一个44 dBm的两载波WIMAX功率放大器,并基于测试数据建立动态数字预失真模型。分析结果表明,该模型能校正宽带功率放大器的非线性特性,并快速实时地获得模型参数。