基于一阶谓词和范畴论的形状与形状型

为了对形状的语义分析进行更加深入地研究,在形式系统、一阶谓词演算和范畴论的基础上,给出了形状及形状型的定义,并讨论了形状与形状型在计算机科学中的应用.

7×19构型NiTi形状记忆合金绞线超弹性试验研究

为充分发挥大直径NiTi形状记忆合金(SMA)绞线的超弹性性能,在常温下对单丝直径1.0 mm的7×19构型SMA绞线进行了循环拉伸试验;分析了热处理方案、应变幅值、循环次数、预训练和加载速率等因素对其超弹性的影响,得到了各因素下SMA绞线的残余应变、能量耗散、等效粘滞阻尼比、强度和刚度等力学参数变化规律。结果表明:针对本研究的7×19构型SMA绞线,400℃退火10 min的热处理方案下其相变应力和恢复率最高,热处理时间过长会造成这些特性严重退化;SMA绞线内部单丝变形和应力发展不均匀程度更高,滞回曲线无明显相变平台;恒定幅值拉伸下SMA绞线的初始弹性模量和极限应力变化相对较小,而相变平台高度、恢复率以及等效粘滞阻尼比退化较为明显;通过预训练的方式可以减轻SMA绞线的功能损伤,显著减小残余变形,提高可恢复能力;加载速率对SMA绞线的马氏体应力和屈服平台切线模量的影响较大,当加载速率超过1×10^(-2) s^(-1)后,滞回曲线对加载速率的变化不再敏感。试验结果可为7×19构型SMA绞线的应用提供数据支持。

温敏型形状记忆聚合物及其在雄安新区热储钻进的应用展望

雄安新区地热资源丰富,其深部蓟县系雾迷山组碳酸盐岩热储是目前首要的目标储层。其碳酸盐岩热储高度发育地裂隙网使得钻井中存在钻井液严重漏失与储层伤害问题,导致地热井产能下降。为在实现地热钻井裂隙封堵的同时不伤害热储层,从而最大程度地提高地热井产能,本文提出应用温敏型形状记忆聚合物对温度响应的形状记忆特性以实现雄安新区裂隙型碳酸盐岩热储钻进过程中屏蔽暂堵。温敏型形状记忆聚合物既能够有效地应对雄安新区目标热储由于裂隙发育而造成的钻井液漏失问题,在地热井生产时又能够完全离开储层裂隙从而最大程度实现热储保护,是一种具有发展潜力的裂隙型热储屏蔽暂堵技术,为雄安新区高效地热钻井及热储保护技术提供一种新的技术手段。

安装新型形状记忆合金阻尼器的古塔结构地震反应有限元分析

将设计的拉压型形状记忆合金(SMA)阻尼器,安装在古塔上,可同时减少古塔在水平地震和竖直地震作用下的响应。采用大型通用软件ANSYS对古塔安装和不安装SMA阻尼器结构分别进行有限元仿真,对结构的动力特性、水平地震反应和竖向地震反应进行分析和对比,探讨SMA阻尼器的控制效果,分析结果与振动台试验数据进行比较,验证分析结果的可靠性。

软段对形状记忆型聚氨酯的性能影响

以4,4’-二苯基甲烷二异氰酸酯(MDI)为硬段,1,4-丁二醇(BDO)为扩链剂,分别以分子量1000、2000、3000的聚己内酯(PCL),聚己二酸乙二醇酯(PEAG),聚己二酸丁二醇酯(PBAG)为软段,在硬段含量不变的条件下,合成了一系列的形状记忆型聚氨酯(SMPU)。通过FT-IR,DSC,XRD等测试了其结构,并比较了形状记忆性能,研究表明,分子量2000的PEAG在硬段含量不变的情况下性能最佳,形状恢复率可达到100%。

大型风力机叶片腹板根部形状研究

叶片腹板根部形状不同,造成腹板应力分布也不同,特别是对于薄弱部位还可能因为应力叠加引发叶片破坏。本文主要研究不同腹板根部形状对腹板根部危险区域应力分布的影响,并将腹板根部切除形状的比例系数定义为C型结构形状因子F,然后对C型结构形状因子分为三种情况进行讨论,结合有限元分析结果和现场的挂机结果,确定腹板根部的最优形状。

热致型形状记忆高分子材料研究

热致型形状记忆高分子材料制备方法简便,控制形变的方法较易,应用范围非常广泛,因而成为目前研究与开发领域较活跃的形状记忆高分子。文章阐述了热致型形状记忆高分子材料的研究进展、形状记忆原理、制备技术,并介绍了几种重要的热致型形状记忆聚合物。

集成开关型霍尔传感器在测量物体转动惯量中的应用

介绍集成开关型霍尔传感器的优点、特性测量及其在物理实验和自动化监测中的应用。

改进型PSI算法及其在高空间分辨率遥感影像分割中的应用

本文针对PSI(Pixel Shape Index,PSI)算法存在的弊端,对其加以改进,并提出了一种改进型PSI算法。相比原算法,新算法的改进主要体现在:1在方向线生成阶段,为了充分考虑不同波段光谱特征的同质性存在的差异,每个波段数据层方向线的生成分开独立进行,这提高了方向线生成的合理性;2提出了每一条方向线长度为各波段数据层的方向线长度的加权和,以进一步体现不同波段光谱特征之间同质性上存在的差异,从而提高像元(尤其是边缘处的像元)PSI值的准确性。最后,通过实验证明:影像分割时,联合改进型PSI派生波段,能有效提高外形规则的人工地物的分割精度,"边缘效应"明显减少。

《二刻拍案惊奇》外形特征类名量词研究

量词是汉藏语系语言的一大特色，近代汉语量词的研究有助于整个量词发展史的建立。本文在全面考察《二刻拍案惊奇》名量词的基础上，对其外形特征类名量词进行了语义特征分析，并与魏晋南北朝和现代汉语名量词相比较，举例说明量词在《二刻拍案惊奇》中的用法。

LOCALIZATION OF OBJECT (SPINE) IN MEDICAL IMAGE USING ACTIVE SHAPE MODELS

Active shape models (ASM), consisting of a shape model and a local gray-level appearance model, can be used to locate the objects in images. In original ASM scheme, the model of object′s gray-level variations is based on the assumption of one-dimensional sampling and searching method. In this work a new way to model the gray-level appearance of the objects is explored, using a two-dimensional sampling and searching technique in a rectangular area around each landmark of object shape. The ASM based on this improvement is compared with the original ASM on an identical medical image set for task of spine localization. Experiments demonstrate that the method produces significantly fast, effective, accurate results for spine localization in medical images.

Optimal shape space and searching in the active shape model

A novel idea,called the optimal shape subspace （OSS） is first proposed for optimizing active shape model （ASM） search.It is constructed from the principal shape subspace and the principal shape variance subspace.It allows the reconstructed shape to vary more than that reconstructed in the standard ASM shape space,hence it is more expressive in representing shapes in real life.Then a cost function is developed,based on a study on the search process.An optimal searching method using the feedback information provided by the evaluation cost is proposed to improve the performance of ASM alignment.Experimental results show that the proposed OSS can offer the maximum shape variation with reserving the principal information and a unique local optimal shape is acquired after optimal searching.The combination of OSS and optimal searching can improve the ASM performance greatly.

一种IPSIAST算法及其在遥感影像分割中的应用

针对PSI(Pixel Shape Index)算法存在的弊端,本文对其加以改进,提出一种光谱阈值自适应的改进型像元形状指数(Improved Pixel Shape Index of Adaptive Spectral Threshold,IPSIAST)算法。相比原算法,新算法的改进主要体现在:1)在方向线生成阶段,为了充分考虑不同波段光谱特征的同质性存在的差异,每个波段数据层方向线的生成分开独立进行,提高了方向线生成的合理性;2)将每一条方向线长度定义为各波段数据层在该方向的方向线长度的加权和,以体现不同波段光谱特征之间同质性上存在的差异,从而提高像元PSI值的精确性;3)光谱阈值T1能根据局部区域内光谱特征同质性的大小而自适应地调整,降低了地物边缘处的对比度对像元形状指数计算的影响。最后,结合目视对比和5个定量评价指标,通过影像分割对比实验证明:相比PSI指数,IPSIAST指数能进一步提高影像的分割精度。

Elastic Behaviors of Adsorbed Protein-like Chains

Elastic behaviors of protein-like chains are investigated by Pruned-Enriched-Rosenbluth method and modified orientation-dependent monomer-monomer interactions model. The protein-like chain is pulled away from the attractive surface slowly with elastic force acting on it. Strong adsorption interaction and no adsorption interaction are both considered. We calculate the characteristic ratio and shape factor of protein-like chains in the process of elongation. The conformation change of the protein-like chain is well depicted. The shape of chain changes from “rod” to “sphere” at the beginning of elongation. Then, the shape changes from “sphere” to “rod”. In the end, the shape becomes a “sphere” as the chain leaves away from the surface. In the meantime, we discuss average Helmoholtz free energy per bond, average energy per bond, average adsorbed energy per bond, average α-helical energy per bond, average β-sheet energy per bond and average contact energy per bond. On the other hand, elastic force is also studied. It is found that elastic force has a long plateau during the tensile elongation when there exists adsorption interaction. This result is consistent with SMFS experiment of general polymers. Energy contribution to elastic force and contact energy contribution to elastic force are both discussed. These investigations can provide some insights into the elastic behaviors of adsorbed protein chains.

Warpage prediction of the injection-molded strip-like plastic parts

For most strip-like plastic injection molded parts, whose cross section size is much smaller than their length, the traditional Hele-Shaw model and three-dimensional model do not work well in the prediction of the warpage be- cause of their special shape. A new solution was suggested in this work. The strip-like plastic part was regarded as a little-curved beam macrnscopically, and was divided into a few one-dimensional elements. On the section of each elemental node location, two-dimensional thermal finite element analysis was made to obtain the non- uniform thermal stress caused by the time difference of the solidification of the plastic melt in the mold. The stress relaxation, or equivalently, strain creep was dealt with by using a special computing model. On the bases of in-mold elastic stress, the final bending moment to the beam was obtained and the warpage was predict- ed in good a^reement with practical cases.

Simulation of mold filling and prediction of gas entrapment on practical high pressure die castings

Element parameters including volume filled ratio,surface dimensionless distance,and surface filled ratio for DFDM(direct finite difference method)were proposed to describe shape and location of free surfaces in casting mold filling processes.A mathematical model of the filling process was proposed specially considering the mass,momentum and heat transfer in the vicinity of free surfaces.Furthermore,a method for gas entrapment was established by tracking flow of entrapped gas.The model and method were applied to practical ADC1 high pressure die castings.The gas entrapment prediction was compared with the fraction and maximum size of porosities in the different casting parts.The comparison shows validity of the proposed model and method.The study indicates that final porosities in high pressure die castings are dependent on both gas entrapment during mold filling process and pressure transfer within solidification period.

3D Engineering Model Retrieval Based on Enhanced Shape Distributions

To reuse and share the valuable knowledge embedded in repositories of engineering models for accelerating the design process, improving product quality, and reducing costs, it is crucial to devise search engines capable of matching 3D models efficiently and effectively. In this paper, an enhanced shape distributions-based technique of using geometrical and topological information to search 3D engineering models represented by polygonal meshes was presented. A simplification method of polygonal meshes was used to simplify engineering model as the pretreatment for generation of sample points. The method of sampling points was improved and a pair of functions that was more sensitive to shape was employed to construct a 2D shape distribution. Experiments were conducted to evaluate the proposed algorithm utilizing the Engineering Shape Benchmark (ESB) database. The experiential results suggest that the search effectiveness is significantly improved by enforcing the simplification and enhanced shape distributions to engineering model retrieval.

2-D IMAGE-BASED VOLUMETRIC MODELING FOR PARTICLE OF RANDOM SHAPE

In this paper, an approach to predicting randomly-shaped particle volume based on its two- Dimensional （2-D） digital image is explored. Conversion of gray-scale image of the particles to its binary counterpart is first performed using backlighting technique. The silhouette of particle is thus obtained, and consequently, informative features such as particle area, centroid and shape-related descriptors are collected. Several dimensionless parameters are defined, and used as regressor variables in a multiple linear regression model to predict particle volume. Regressor coefficients are found by fitting to a randomly selected sample of 501 panicles ranging in size from 4.75mm to 25ram. The model testing experiment is conducted against a different aggregate sample of the similar statistical properties, the errors of the model-predicted volume of the batch is within ±2%.

Shape retention of injection molded stainless steel compacts

The effects of the binder composition, the powder loading, the thermal properties of feedstocks, and the injection molding parameters on the compact shape retention for metal injection molding 17-4PH stainless steel were investigated. The high-density polyethylene is more effective than ethylene vinyl acetate as a second component of the wax-based binder to retain compact shape due to its higher pyrolytic temperature and less heat of fusion. The compact distortion decreases with increasing the powder loading, molding pressure and molding temperature. There exists an optimal process combination including the powder loading of 68%, molding pressure of 120MPa and molding temperature of 150℃. Under this process condition, the percentage of distorted compacts is the lowest.

Process of back pressure deep drawing with solid granule medium on sheet metal

The experimental die apparatus of the solid granules medium forming on sheet metal was designed and manufactured.Typical parts,such as conical,parabolic,cylindrical and square-box-shaped components,were successfully trial-produced as well.According to the analysis of the changing trends of the cross-section shape and the wall thickness during the process,it can be found that the shape of the free deformation zone of the sheet metal,which is the most critical thinning area,can be described as an approximately spherical cap.According to this forming feature,back pressure deep drawing technology with solid granules medium on sheet metal was proposed to restrain drastic thinning at the bottom of the part through the joint friction effect of solid granules medium,the back pressure tringle and the sheet metal.Therefore,the deep drawing limit of the sheet metal is significantly improved.In order to fabricate thin-walled rotary parts with great drawing ratio and complex cross-sections,a finite element model based on the material property test of the solid granules medium was established to optimize the scheme of the back pressure deep drawing.The effects on the forming performance of sheet metal from back pressure load and the approach of blank holding control were analyzed through this model.