纺织结构复合材料的纺织几何学模型

提出一种分析纺织结构复合材料力学性能的模型——纺织几何学模型。该模型由分析单细胞的纤维束几何特征入手 ,考虑纤维束的曲率、非圆形截面形状、纤维纱之间相互纽结等因素 ,建立本构模型。以三维编织结构复合材料为例 ,进行了理论预测并与实验结果进行了比较 ,结果比较满意。

龙门山褶皱冲断带南北分段性与汶川地震的关系

龙门山褶皱冲断带位于青藏高原东缘与四川盆地之间,中生代以来主要经历了晚三叠世和新生代两期重要的地壳缩短变形,形成了典型的逆冲推覆构造带。龙门山的形成和演化与青藏高原隆升以及地震活动有着密切的关系,因此龙门山褶皱冲断带南北两段的差异性被众多学者所关注。文章在前人工作的基础之上从3个角度来阐述龙门山南北两段的差异性:1)地质调查和地震反射剖面解释表明,晚三叠世龙门山北段变形强烈而南段变形不明显,南北分段格局就此形成;2)汶川地震同震地表破裂的差异,北段以右旋斜向逆冲为主,南段则主要以逆冲为主,兼有少量的走滑分量;3)同震断裂的三维构造建模揭示出,同震断层的三维几何形态同样存在南北差异,北段同震断层只有一条且不能向下延伸至深部的主滑脱层,而南段同震断层有两条分支,二者在大约10km的深度合并成一条,并向下延伸至约17km深度与主滑脱层相连。因此,认为汶川地震同震破裂的南北分段性是由于晚三叠世龙门山先存的南北构造差异性所引发的。

甘肃金塔南山河流阶地褶皱变形分析

金塔南山的抬升变形主要受到青藏高原向北推挤的影响,其构造活动的几何学和运动学特征包含了高原北缘扩展的重要信息.金塔南山山顶普遍覆盖一层砾石,砾石层胶结弱,砾石磨圆度、分选性均较好,岩性组成以砂岩、石英砂岩和硅质砂岩为主.砾石层顶面连续,区域上与黑河第二级阶地（T2）对应.根据其组成和展布特征,笔者认为金塔南山地貌面与黑河第二级阶地为同一时期的产物.笔者对展布于金塔南山上及其周边的阶地高程进行了差分GPS测量,并对基岩地层产状进行了测量,结果显示阶地面发生了明显的褶皱变形.通过阶地面变形特征和下伏岩层产状分析,得到金塔南山褶皱主要以翼旋转的方式活动,形成了前翼陡倾而后翼宽缓且核部平坦的几何特征.依据T2阶地面的变形特征,初步建立了金塔南山下伏铲式逆冲断裂相关褶皱的几何学模型.根据几何学关系计算得到断裂上升盘自黑河第二级阶地形成以来产生了约200 m的垂直抬升量和143～190 m的水平缩短量,中更新世以来断裂的平均滑动速率为1.18±0.16 mm/a.由于深部断裂的逆冲作用,金塔南山主要以背斜方式发生抬升变形,断裂可延伸到地表16 km以下.通过对比分析金塔南山地区的构造,笔者认为褶皱的形成为阿拉善地块与柴达木-祁连块体相互挤压下金塔南山北缘断裂活动的结果.金塔南山在中更新世开始的抬升反映了青藏高原东北部扩展的最新过程.

Oxidation of formic acid on stepped Au(997) surface

The adsorption and reaction of formic acid （HCOOH） on clean and atomic oxygen‐covered Au（997） surfaces were studied by temperature‐programmed desorption/reaction spectroscopy （TPRS） and X‐ray photoelectron spectroscopy （XPS）. At 105 K, HCOOH molecularly adsorbs on clean Au（997） and interacts more strongly with low‐coordinated Au atoms at （111） step sites than with those at （111） terrace sites. On an atomic oxygen‐covered Au（997） surface, HCOOH reacts with oxygen at‐oms to form HCOO and OH at 105 K. Upon subsequent heating, surface reactions occur among ad‐sorbed HCOO, OH, and atomic oxygen and produce CO2, H2O, and HCOOH between 250 and 400 K. The Au（111） steps bind surface adsorbates more strongly than the Au（111） terraces and exhibit larger barriers for HCOO（a） oxidation reactions. The surface reactions also depend on the relative coverages of co‐existing surface species. Our results elucidate the elementary surface reactions between formic acid and oxygen adatoms on Au surfaces and highlight the effects of the coordina‐tion number of the Au atoms on the Au catalysis.

A Geometry-Based Non-Stationary MIMO Channel Model for Vehicular Communications

This paper derives a non-stationary multiple-input multiple-output(MIMO) from the one-ring scattering model. The proposed channel model characterizes vehicular radio propagation channels with considerations of moving base and mobile stations, which makes the angle of arrivals(AOAs) along with the angle of departures(AODs) time-variant. We introduce the methodology of including the time-variant impacts when characterizing non-stationary radio propagation channels through the geometrical channel modelling approach. We analyze the statistical properties of the proposed channel model including the local time-variant autocorrelation function(ACF) and the space cross-correlation functions(CCFs). We show that the model developed in this paper for non-stationary scenarios includes the existing one-ring wide-sense stationary channel model as its special case.

ALTERNATING METHOD STUDY ON STRESS ANALYSIS OF SURROUNDING ROCK FOR TWO RANDOM GEOMETRY TUNNELS

The stress analysis of surrounding rock for two random geometry tunnels is studied in this paper by using Schwarz’s alternating method. The simple and effective alternating algorithm is found, in which the surplus surface force is approximated by Fourier series, thus the iteration derivation can be conducted according to the precision required, finally, the stress results with high precision are obtained.

Study on the Grey Polynomial Geometric Programming

In the model of geometric programming, values of parameters cannot be gotten owing to data fluctuation and incompletion. But reasonable bounds of these parameters can be attained. This is to say, parameters of this model can be regarded as interval grey numbers. When the model contains grey numbers, it is hard for common programming method to solve them. By combining the common programming model with the grey system theory, and using some analysis strategies, a model of grey polynomial geometric programming, a model of θ positioned geometric programming and their quasi-optimum solution or optimum solution are put forward. At the same time, we also developed an algorithm for the problem. This approach brings a new way for the application research of geometric programming. An example at the end of this paper shows the rationality and feasibility of the algorithm.

Dirac Neutrino Masses in NCG

Several models in noncommutative geometry (NCG) with mild changes to the standard model are introduced to discuss the neutrino mass problem. We use two constraints, Poincaré duality and gauge anomaly free, to discuss the possibility of containing right-handed neutrinos in them. Our work shows that no model in this paper, with each generation containing a right-handed neutrino, can satisfy these two constraints at the same time. So, to consist with neutrino oscillation experiment results, maybe fundamental changes to the present version of NCG are usually needed to include Dirac massive neutrinos.

Geometric Approximation Technique for Minimum Zone Sphericity Error

The mathematical modeling for evaluation of the sphericity error is proposed with minimum radial separation center. To obtain the minimum sphericity error from the form data, a geometric approximation technique was devised. The technique regarded the least square sphere center as the initial center of the concentric spheres containing all measurement points, and then the center was moved gradually to reduce the radial separation till the minimum radial separation center was got where the constructed concentric spheres conformed to the minimum zone condition. The method was modeled firstly, then the geometric approximation process was analyzed, and finally,the software for data processing was programmed. As evaluation example, five steel balls were measured and the measurement data were processed with the developed program. The average iteration times of the approximation technique is 4.2, and on average the obtained sphericity error is 0. 529μm smaller than the least square solution,with accuracy increased by 7. 696%.

Integrity of grinding face-gear with worm wheel

Aiming at the issue of the grinding integrity of face-gear with worm wheel, the envelope mathematical model of shaper, worm wheel and face-gear is established based on theories of differential geometry and gear mesh. The judgment of completely grinding the face-gear with the avoidance of singularities is established, and the mathematical expression to show the reason why singularities appear is derived, through the research on the surface contact area and singularity rules of the worm thread surface. The disadvantage of current face-gear grinding method that only part of the working surface of the face-gear can be covered is analyzed and the influence of coefficient of judgment is studied through changing the design parameters.

An XML-based information model for archaeological pottery

An information model is defined to support sharing scientific information on Web for archaeological pottery. Apart from non-shape information, such as age, material, etc., the model also consists of shape information and shape feature information. Shape information is collected by Lasers Scanner and geometric modelling techniques. Feature information is generated from shape information via feature extracting techniques. The model is used in an integrated storage, archival, and sketch-based query and retrieval system for 3D objects, native American ceramic vessels. A novel aspect of the information model is that it is totally implemented with XML, and is designed for Web-based visual query and storage application.

Entropy Error Model of Planar Geometry Features in GIS

Positional error of line segments is usually described by using "g-band", however, its band width is in relation to the confidence level choice. In fact, given different confidence levels, a series of concentric bands can be obtained. To overcome the effect of confidence level on the error indicator, by introducing the union entropy theory, we propose an entropy error ellipse index of point, then extend it to line segment and polygon, and establish an entropy error band of line segment and an entropy error donut of polygon. The research shows that the entropy error index can be determined uniquely and is not influenced by confidence level, and that they are suitable for positional uncertainty of planar geometry features.

Cutting edge curve models for equal pitch cutters and their applications

A mathematic model is established using infinitesimal geometry for the cutting edge design of special milling cutters which use equal lead helix as cutting edges; equations are given for front-end and proclitic surface of revolution of ball pillar milling cutters, ball taper milling cutters and angularly conical milling cutters; and corresponding models are established for the continuity cutting edge curves of milling cutters. Typical examples are given to illustrate the applications of mathematic models, which prove the correctness and applicability of these geometric models.

Geometry effect on mechanical properties of woven fabric composites

The effects of geometry on mechanical properties in woven fabric composites were explored. Two types of composites, including one-layered and two-layered composites, were designed and studied. For one-layered composites, inter-strand gap effects on the mechanical properties were studied, while three cases of geometries with inter-strand gaps in two-layered composites were evaluated. A woven fiber micromechanics analytical model called MESOTEX was employed for theoretical simulation. The predicted results show that the inter-strand gap and simple variation of the strand positions in a repeating unit cell significantly affect the mechanical properties of woven fabric composites.

RESEARCH AND IMPROVEMENT OF SPIRAL BUNKER

A great attention has been paid to slowing the degradation of coal nowadays. The spiral bunker is the main measure to lower the degradation. In this paper the application and research of spiral bunker are introduced. And two non-normal spiral chutes are discussed. One is in the tangential direction of the inner wall of the bunker, another is in the direction of the diameter of the bunker. Mathematical models of the non-normal spiral chutes are set up to optimize the geometrical parameters of the spiral curved surface, which would ensure that coal travels smoothly to the bottom of the bunker. The results would be useful for designing and retrofitting the spiral bunker.

Geometric Properties of AR(q) Nonlinear Regression Models

This paper is devoted to a study of geometric properties of AR(q) nonlinear regression models. We present geometric frameworks for regression parameter space and autoregression parameter space respectively based on the weighted inner product by fisher information matrix. Several geometric properties related to statistical curvatures are given for the models. The results of this paper extended the work of Bates & Watts(1980,1988)[1.2] and Seber & Wild (1989)[3].

CT-based Individualized Medical Implant Design

Most implantation cases are implemented using implants selected from the available standard set, but in some cases, only those implants conforming to individual patient's skeletal morphology can serve the purpose. This paper proposes a new approach to design and fabricate custom-made exact-fit medical implants. With a real surgical case as the example,technical design details are presented; and three algorithms are given respectively for segmentation based on object features, triangular mesh defragmentation and mesh cutting.

秦岭造山带的结构构造

综合研究厘定秦岭造山带有二类造山带基底,主造山作用时期有3个板块沿2个缝合带斜向俯冲碰撞,同期发育有深部背景的垂向加积增生构造。秦岭造山带现今三维构造几何学模型呈现为一种“立交桥”式结构。深部地球物理场为近南北向异常与状态,而上部地壳则以近东西向构造为主导,其间的中、下地壳呈水平流变状态。上部地壳结构由主造山期构造所奠定,包含先期残存构造,并强烈迭加晚近陆内造山构造,形成统一而又包容多期不同动力学体制与成因的多种构造组合模型。