含双向布复合材料开孔薄板拉伸性能研究

对含有双向布的三种不同铺层厚度的中心开孔复合材料薄板拉伸性能进行研究,分别得到三种复合材料带孔板的孔边应变分布规律以及试件的损伤演化和失效行为,并得到其断裂强度值。试验结果表明,试件的铺层对试件的刚度和强度影响较大,相对于[45/0/45]的铺层,[45/(0)/0/(0)/45]增加了两个0°单向布层,其刚度及强度得到大幅改善;[45/90/0/0/0/90]s增加了多个0°双向布层,使得其刚度最大,强度也有明显提升。用Abaqus软件对三种薄板的拉伸行为进行渐进损伤模拟分析,分析中采用Hashin准则作为材料的失效准则获得薄板的断裂载荷、应力分布及渐进损伤失效过程,得到的模拟结果与试验结果吻合较好。

双向纤维布约束加固钢筋混凝土柱的FRP锚钉设计方法研究

改造工程中既有钢筋混凝土框架结构抗震等级提高,常使柱产生弯剪压复合加固的需求.使用双向纤维布约束钢筋混凝土柱,采用FRP锚钉给予布中纵向纤维较好的锚固,使得布中的两向纤维丝可同时受拉.基于已有相关研究,提出了双向纤维布约束加固钢筋混凝土柱底FRP锚钉设计制作方法,并进行了加固柱的拟静力推覆试验验证.结果表明:使用FRP锚钉后有效避免纤维布在端部破坏,提高了纵向纤维应变水平,使得约束加固柱的变形能力、抗弯和抗剪承载力同时提高.

试论局部均布荷载作用下双向板等效均布荷载的确定方法

建筑结构荷载规范中对民用建筑楼面均布荷载取值有明确的说明,但是楼面局部荷载采用等效均布荷载的方法,随着单向板、双向板、主梁、次梁不同,都略有不同。结合相关工程介绍了对局部楼面荷载进行等效均布处理的方法。

锚固的双向纤维布约束加固钢筋混凝土柱抗震性能

双向纤维增强聚合物(Fiber reinforced polymer,FRP)复合材料布具有良好的两向正交抗拉性能,与传统单向布相比,使用其约束加固柱时能使构件获得抗剪、抗弯承载力和抗震延性的同时提高。开展了基于纤维锚钉锚固的双向布约束加固钢筋混凝土柱低周反复加载试验,参数包含布种类、层数和锚固方式,研究了加固柱的破坏模式、抗震性能和材料应变。结果表明,柱在约束加固前后的破坏形态由剪切转变为弯曲破坏,构件延性大幅度提高;同层数的双向纤维布在环向应变值发挥少于单向布;使用锚钉可显著提升双向布纵向纤维应变,其应变值比未锚固前的提高了约1.5倍;并进一步提高约束柱抗弯承载力,较未加锚固前的约束柱承载力提高了2.9%~7.1%。成果可为双向纤维布在既有结构加固领域的应用提供指导。

谈预应力平板结构铺筋的施工方法

阐述了在无黏结预应力平板结构中简便布置预应力板筋的方法,从而简化施工过程,方便复查调整,并满足结构设计的要求。

A Real-Time Photo-Realistic Rendering Algorithm of Ocean Color Based on Bio-Optical Model

Abstract A real-time photo-realistic rendering algorithm of ocean color is introduced in the paper, which considers the impact of ocean bio-optical model. The ocean bio-optical model mainly involves the phytoplankton, colored dissolved organic material （CDOM）, inorganic suspended particle, etc., which have different contributionsto absorption and scattering of light. We decompose the emergent light of the ocean surface into the reflected light from the sun and the sky, and the subsurface scattering light. We estab- lish an ocean surface transmission model based on ocean bidirectional reflectance distribution function （BRDF） and the Fresnel law, and this model＇s outputs would be the incident light parameters of subsurface scattering. Using ocean subsurface scattering algorithm combined with bio-optical model, we compute the scattering light emergent radiation in different directions. Then, we blend the re- flection of sunlight and sky light to implement the real-time ocean color rendering in graphics processing unit （GPU）. Finally, we use two kinds of radiance reflectance calculated by Hydrolight radiative transfer model and our algorithm to validate the physical reality of our method, and the results show that our algorithm can achieve real-time highly realistic ocean color scenes.

Dielectrophoretic force distribution of growing microwires

The Dielectropheretic assembly of electrically functional microwires from nanopartical suspensions is introduced. Meanwhile growth mechanism of the microwires is discussed. The agglomeration is based on the polarization and mobility of particles caused by alternating electric fields, commonly referred to as dielectrophoresis (DEP). The spatial distributions of the electric potential, field and dieletrophoretic force are analytically calculated in terms of AC electrokinetics. The calculated results show that the electrophoretic force, very strong near the apex of the microwire, drops abruptly with increasing distance. The electrophoretic force near the apex of the microwire agrees well with the fact that the nanoparticles are highly concentrated at the end of the tip and subsequently aggregate to extend the wire in the direction of the field gradient.

Modeling of radiative properties of metallic microscale rough surface

The radiative properties of a gold surface with one-dimensional Gaussian random roughness distribution were obtained with the finite-difference time-domain （FDTD） method and the recursive convolution treatment of the Drude Model. The bi-directional reflection distribution function （BRDF） for both TM mode and TE mode were obtained and compared with the highly accurate experimental data from the earlier work. The incident wavelength varies from 1.152 μm to 3.392 μm and incident angle is at 300-70°, respectively. The results show that, the predicted values and experimental results are in good agreement. The highly specular peak in the BRDF is reproduced in the numerical simulations, and the increase of the TM mode BRDF is found to be attributed to the effect of a variation in the optical constant at the incident wavelength period.

快速铺放预应力板筋的探索

阐述了预应力楼板结构中,采用快速铺放预应力板筋施工、减少施工难度的方法,并结合工程实例,从方案及现场施工着手,进行了一定的探索,针对预应力张拉问题提出了处理措施,以供参考。

Swap of Information between Two-End States in an Open Ferromagnetic Spin Chain

The bidirectional transfer of information can be realized in an open Heisenberg ferromagnetic spin chain.The information is encoded in the probability distributions of the states at two end spins. The relative entropy is used toevaluate the effective transmission of the probability. The evolution of the relative entropy shows a periodical behavior.The period is increased with increasing the length of the chain and the magnetic field while it decreases with increasingthe coupling strength.

Modeling bidirectional reflection distribution function of microscale random rough surfaces

The radiative properties of three different materials surfaces with one-dimensional microscale random roughness were obtained with the finite difference time domain method(FDTD) and near-to-far-field transformation.The surface height conforms to the Gaussian probability density function distribution.Various computational modeling issues that affect the accuracy of the predicted properties were discussed.The results show that,for perfect electric conductor(PEC) surfaces,as the surface roughness increases,the magnitude of the spike reduces and eventually the spike disappears,and also as the ratio of root mean square roughness to the surface correlation distance increases,the retroreflection becomes evident.The predicted values of FDTD solutions are in good agreement with the ray tracing and integral equation solutions.The overall trend of bidirectional reflection distribution function(BRDF) of PEC surfaces and silicon surfaces is the same,but the silicon's is much less than the former's.The BRDF difference from two polarization modes for the gold surfaces is little for smaller wavelength,but it is much larger for the longer wavelength and the FDTD simulation results agree well with the measured data.In terms of PEC surfaces,as the incident angle increases,the reflectivity becomes more specular.

Visible characteristics of space-based targets based on bidirectional reflection distribution function

A precise modeling method of visible characteristics of the space-based target was presented based on bidirectional reflection distribution function (BRDF). The background characteristics of the space-based target were represented to build models of direct solar radiation and reflected radiation of the Earth based on blackbody radiation theory. The geometry characteristics of the target were analyzed to establish a surface equation of each surface based on its body coordinate system. The material characteristics of the target surface were described by introducing a BRDF model which considers the character of surface Gauss statistics and self-shadow and is obtained by measurement and modeling in advance. The relative positions of the space-based target, the background radiation sources and the observation platform were determined based on coordinate con- version to judge contributing surface of the target to observation system. Then a mathematical model on visible characteristics of the space target for the given optical system was built by summing reflection components of all the surfaces. Simulation of visible characteristics of the space-based target in orbit was achieved according to its given geometrical dimensions, physical parameters and orbital parameters. The results show that the method is effective for analysis on visible characteristics of the space-based target when single reflection is considered and its surface is regularly described in a surface equation, which provides a way to real-time calculation of visible characteristics of the space-based target.

A unified canopy bidirectional reflectance (BRDF) model for row ceops

Row sowing is a basic crop sowing method in China,and thus an accurate Bidirectional Reflectance Distribution Function (BRDF) model of row crops is the foundation for describing the canopy bidirectional reflectance characteristics and estimating crop ecological parameters.Because of the macroscopically geometric difference,the row crop is usually regarded as a transition between continuous and discrete vegetation in previous studies.Were row treated as the unit for calculating the four components in the Geometric Optical model (GO model),the formula would be too complex and difficult to retrieve.This study focuses on the microscopic structure of row crops.Regarding the row crop as a result of leaves clumped at canopy scale,we apply clumping index to link continuous vegetation and row crops.Meanwhile,the formula of clumping index is deduced theoretically.Then taking leaf as the basic unit,we calculate the four components of the GO model and develop a BRDF model for continuous vegetation,which is gradually extended to the unified BRDF model for row crops.It is of great importance to introduce clumping index into BRDF model.In order to evaluate the performance of the unified BRDF model,the canopy BRDF data collected in field experiment,"Watershed Allied Telemetry Experiment Research (WATER)",from May 30th to July 1st,2008 are used as the validation dataset for the simulated values.The results show that the unified model proposed in this paper is able to accurately describe the non-isotropic characteristics of canopy reflectance for row crops.In addition,the model is simple and easy to retrieve.In general,there is no irreconcilable conflict between continuous and discrete vegetation,so understanding their common and individual characteristics is advantageous for simulating canopy BRDF.It is proven that the four components of the GO model is the basic motivational factor for bidirectional reflectance of all vegetation types.