专家系统的逻辑基础

从“若、则”表示充分条件关系出发指出:(1)狭谓词演算F系统的局限性,(2)制约式如实地反映了充分条件关系。探讨专家系统的逻辑基础。     

平分术剖析

平分术是《九章算术》的运算法则之一,是推求分数的算术平均的方法.本文对平分术进行了研究论证,对刘徽的注释文字作了校勘,并纠正了一些误解.     

浅水方程大规模并行计算模拟城市洪水演进

基于有限体积法建立求解溃坝水流运动的数学模型,利用Riemann问题求解Godunov格式计算通量,通过空间分块划分的大规模并行计算来加速运算,实现了城市洪水演进的精细数值模拟.数值模拟结果表明,建筑物在溃坝波波前到达初期所受水流荷载最大;受上游建筑物消波、蔽护作用,溃口下游建筑物所受荷载随至溃口的距离的增大而减小,建筑物的存在使得溃坝波在城区传播速度减慢.并行测试表明,缓冲模式比非缓冲模式更适用于浅水方程大规模并行求解.目前大规模并行计算能够实现对面积达400,km2的城区洪水演进进行实时仿真模拟,为滨河、滨海城市在受到溃坝、海啸等洪水威胁时的快速决策和应急疏散提供科学依据.     

Three-dimensional FEM analysis of stress distribution in dynamic maxillary canine movement

An alteration in stress/strain distribution within periodontal ligament (PDL) occurs when the tooth is mechanical stimulated in orthodontic treatment. The majority of previous finite element studies were confined to a static evaluation on initial loading status, and a dynamic long-term analysis was rarely performed in orthodontics. The present study sought to analyze the stress distribution patterns within tooth root, PDL, and alveolar bone during dynamic canine tipping and bodily movement with three-dimensional finite element method in four consecutive therapeutic weeks. We observed that the highest stress was on root surface, secondly alveolar bone, and finally, PDL for either tipping or bodily movement. Throughout the PDL and root surface, the highest stress was always around the cervical area in both patterns of movement through four phases. Moreover, a lower and more uniform stress distribution was produced during bodily movement compared with tipping movement. These results indicated that canine translation might be healthier for periodontal tissue than tipping movement; the cervical region bore a greater load and might also be a susceptible area for tissue damage (except for the apex) regardless of movement pattern.     

Adaptive dynamic surface control for air-breathing hypersonic vehicle

This paper describes an adaptive control approach for an air-breathing hypersonic vehicle.The control objective is to provide robust altitudes and velocity tracking in the presence of model uncertainties and varying disturbances.A fuzzy-neural disturbance observer is developed to estimate uncertainties and disturbances,and the adaptive controller is synthesized by the dynamic surface approach combing with the observer.The tracking error at the steady state can be guaranteed to converge to inside of a small residue set which the size of the set can be an arbitrary small value.Simulation results demonstrate the effectiveness of the presented approach.     

带有扩散的两种群时滞生态模型的振动性

对用偏泛函微分方程组所描述的密度分布非均匀的两种群相互作用生态模型进行了讨论 .通过利用时滞泛函微分不等式 ,研究了时滞生态模型的振动性 ,得到了其解关于正平衡态振动的简捷的充分判据 .     

维吾尔族青少年的友谊特点

采用整群抽样法从新疆地区抽取5、7、10年级维吾尔族青少年621人.通过朋友提名问卷和修订版友谊质量问卷(Modified Friendship Quality Questionmaire)考察维吾尔族青少年的友谊特点.结果发现:1.绝大多数维族青少年都拥有互选朋友;拥有互选朋友及同件朋友的青少年数量存在年级和性别差异;拥有异性朋友的青少年数量存在年级差异,而不存在性别差异.2.在友谊质量上,除陪伴维度外,年级在其它6个维度上的主效应均显著;性别在所有友谊质量维度上的主效应均不显著.并进一步讨论了维族青少年的友谊特点与其文化特征的联系.     

化工专业实验报告撰写改革探索

实验报告是实验操作过程总结以及对获得实验结果分析讨论的书面表达形成。针对传统实验报告存在形式固定和缺乏个性等弊端,在化工专业实验教学中,探索以小论文代替传统实验报告形式的教学改革。实验教学表明,小论文形式的实验报告有助于提供教学质量,对提高学生查阅文献资料和撰写科技论文的能力以及培养学生实事求是的科研态度都起到了积极作用,为大四的毕业论文以及后续的继续学习或科研奠定良好的基础。     

七辊卧式轧机液压系统技术改进

七辊卧式轧机是1995年引进的加拿大二手设备,在国内至今已使用近10年,在这10年期间对机械方面作了大量的修理和更换,但作为轧机重要的控制部分液压控制系统并未改动,频繁出现问题,为了提高轧机运行的稳定性和产品产出,对其系统作了全面改进.