室内清扫机器人区域充满拓扑算法

针对室内清扫机器人清扫任务的特点，即要充满房间的可达区域，提出了一种区域充满拓扑算法。文中介绍了机器人工作环境的识别和表示，区域充满采用的运动方式．详细给出拓扑算法，并运用该算法进行了机器人清扫路径规划。     

拓扑及参数优化方法在专用汽车车架结构设计中的应用

提出了将拓扑优化理论和结构参数优化方法综合应用于集装箱半挂车车架结构设计中的设计思想。在结构设计的开始阶段引入拓扑优化理论．先对结构进行布局优化,以获得较合理的初始结构方案,再通过结构参数优化设计,得到满足其强度和刚度及设计工艺要求的最优结构。探讨了拓扑优化设计过程中,基本结构建立、优化过程控制及优化结果分析与应用等问题。在ANSYS软件平台上进行了CAE软件包的二次开发．设计了集装箱半挂车车架优化设计专用软件模块。     

考虑配筋影响的混凝土构件早期收缩量计算方法

为获得普通/预应力混凝土构件收缩量的简化计算方法,在素混凝土收缩量的基础上,考虑钢筋及预应力筋的影响,推导出普通/预应力钢筋混凝土构件收缩值的计算公式。对比分析表明,所建议公式的计算结果合理。为便于工程应用,给出了素混凝土早期收缩的建议值。     

Simplifications for hydronic system models in modelica

Building systems and their heating, ventilation and air conditioning flow networks, are becoming increasingly complex. Some building energy simulation tools simulate these flow networks using pressure drop equations. These flow network models typically generate coupled algebraic nonlinear systems of equations, which become increasingly more difficult to solve as their sizes increase. This leads to longer computation times and can cause the solver to fail. These problems also arise when using the equation-based modelling language Modelica and Annex 60-based libraries. This may limit the applicability of the library to relatively small problems unless problems are restructured. This paper discusses two algebraic loop types and presents an approach that decouples algebraic loops into smaller parts, or removes them completely. The approach is applied to a case study model where an algebraic loop of 86 iteration variables is decoupled into smaller parts with a maximum of five iteration variables.     

碳纤维布加固RC梁后的荷载-挠度全曲线的简化计算

为了得到碳纤维布加固RC梁后的荷载-挠度全曲线,许多文献的分析过程都需要借助计算机程序进行迭代计算,以确定每一个时段的中和轴高度,由此可得到相应的荷载-挠度关系。为了能在实际的工程设计中进行简化计算,本文通过求出各个界限荷载值以及与之对应的位移,利用各个界限点之间线性插值来得到荷载-挠度全曲线关系。给出了钢筋混凝土结构的分阶段平截面弹塑性分析法。计算结果与试验结果、有限元分析结果吻合良好,表明了该方法具有较高的精度,为碳纤维布加固梁提供了参考依据。     

基于网状含拓扑剖面的三维地质多体建模

针对传统的基于剖面建模方法使用平行的共面剖面的不足,提出基于网状含拓扑剖面的三维地质多体建模方法,利用一系列含有"结点–弧段–多边形"拓扑关系的、相互连接成网状的剖面,来进行多个地质体的三维模型构建,并且模型之间没有空隙和交叠。该方法将建模区域划分为若干网格分区,每个分区独立进行模型构建,最后将各分区模型拼合成为全区整体模型。建模过程中提供对模型的整体光滑。运用北京地区的实际数据,成功建立了北京市城市地质调查中的8个地质模型,证明该方法具有快速构建大区域高精度复杂地质模型的能力。     

浅探优化设计与桥梁美学的关系

通过阐述优化设计的发展与桥梁美学的特点,探讨了两者之间相辅相成的关系,并提出了一种把桥梁美感度量化后进行优化设计的全新构思,为建造出更多既经济又符合美学要求的桥梁提供了理论指导。     

民机疲劳试验载荷谱简化研究与验证北大核心

在常规试验技术下,民用飞机全机疲劳试验周期过长,不仅费用高,更影响到适航取证和服役使用,开展载荷谱简化研究可有效加速疲劳试验。结合细节疲劳额定值(DFR)法和线性损伤累积理论,建立以损伤比门限值为折算依据的载荷谱等损伤折算方法。选用螺接和铆接的两种试验件进行试验验证,将原谱分别折算简化为五级谱和三级谱,折算后循环次数减少了约98%,且疲劳寿命结果符合工程要求,证明了该载荷谱折算方法的正确性和有效性。     

Non-keyhole Friction Stir Welding for 6061-T6 Aluminum Alloy

A novel non-keyhole friction stir welding technique was proposed to weld the butt joint of 6061-T6 aluminum alloy with the thickness of 6 mm. A sound joint was obtained by this technique, simultaneously eliminating the flash, shoulder mark and keyhole defects. The sleeve directly affected zone (SDAZ) and the sleeve indirectly affected zone (SIAZ) were divided into the joint according to the plunging position of the hollow sleeve. The lack of root penetration defect was avoided when the plunging depth of the hollow sleeve was only 4.2 mm, because the hollow part inside the sleeve improved the material flow below the sleeve. An S-shaped line was left at the SIAZ, and the height of it had the minimum value of 1.47 mm at 20 mm/min. Whether the failure location of the joint was in SIAZ/SDAZ or the heat-affected zone (HAZ) depended on the height and bonding strength of the S-shaped line. The joint fracture location changed from the SIAZ/SDAZ at 35 mm/min to the HAZ at 20 and 30 mm/min. The maximum tensile strength of 224.3 MPa was obtained at 30 mm/min which was 73.7% of that of the base material. The fracture surface morphology exhibited the typical ductile fracture.     

Full supervised learning for osteoporosis diagnosis using micro‐CT images

Early osteoporosis diagnosis is of important significance for reducing fracture risk. Image analysis provides a new perspective for noninvasive diagnosis in recent years. In this article, we propose a novel method based on machine‐learning method performed on micro‐CT images todiagnose osteoporosis. The aim of this work is to find a way to more effectively and accurately diagnose osteoporosis on which many methods have been proposed and practiced. In this method, in contrast to the previously proposed methods in which features are analyzed individually, several features are combined to build a classifier for distinguishing osteoporosis group and normal group. Twelve features consisting of two groups are involved in our research, including bone volume/total volume (BV/TV), bone surface/bone volume (BS/BV), trabecular number (Tb.N), obtained from the software of micro‐CT, and other four features from volumetric topological analysis (VTA). Support vector machine (SVM) method and k‐nearest neighbor (kNN) method are introduced to create classifiers with these features due to their excellent performances on classification. In the experiment, 200 micro‐CT images are used in which half are from osteoporosis patients and the rest are from normal people. The performance of the obtained classifiers is evaluated by precision, recall, and F‐measure. The best performance with precision of 100%, recall of 100%, and F‐measure of 100% is acquired when all the features are included. The satisfying result demonstrates that SVM and kNN are effective for diagnosing osteoporosis with micro‐CT images. Microsc. Res. Tech. 76:333–341, 2013. © 2013 Wiley Periodicals, Inc.