高密度聚乙烯/铅硼复合材料屏蔽性能和力学性能研究

研究了高密度聚乙烯/铅硼复合材料的屏蔽性能和力学性能，通过屏蔽仿真比较了密度及碳化硼（B4C）含量对屏蔽性能的影响，通过试验比较了B4C含量对屏蔽性能、弯曲强度及冲击强度的影响。仿真结果表明,随聚乙烯/铅硼复合材料密度升高，快中子屏蔽性能下降，热中子屏蔽性能和γ屏蔽性能提高；保持聚乙烯/铅硼复合材料密度不变，随B4C含量的提高，中子屏蔽性能提高而γ屏蔽性能下降;实验数据表明,随B4C含量的升高，高密度聚乙烯/铅硼材料的快中子屏蔽性能、热中子屏蔽性能升高，γ屏蔽系数下降，冲击强度和弯曲强度下降明显，屏蔽性能测试结果和仿真结果规律性相符；综合仿真结果和实验数据表明，含B4C 2 %左右的高密度聚乙烯/铅硼复合材料同时具有较好的屏蔽性能和力学性能。     

猪场沼气工程改造技术研究

一、概况南平市种猪场位于延平区浆甲村 ,距市区 13km ,地处 316国道旁 ,面临沙溪口库湾边。年存栏猪760 0头 ,其中母猪 60 0头 ,后备种猪 2 5 0 0头 ,商品猪 4 5 0 0头 ,是闽北集种猪、商品猪生产及科研繁育于一体的副食品基地之一。该场日排猪粪便污水约140t,未建沼气工程前 ,直接排入水库 ,严重污染水体。1999年 ,种猪场采用厌氧发酵技术 ,处理猪粪便污水 ,兴建 4× 2 0 0m3沼气工程 ,技术落后 ,基本属于农村户用水压式沼气池的简单放大 ,猪粪便污水直接进入厌氧发酵池 ,出水直接排入水库。工程设计的主要问题是 :1 不设前处理装置 ,冲洗…     

CHARACTERISTICS OF INTERNAL FRICTION AND MODULUS ASSOCIATED WITH NON-EQUILIBRIUM DIFFUSION-TYPE PHASE TRANSFORMATION IN EUTECTOID Al-Zn ALLOY

The characteristics of the low frequency internal friction and the modulus effect associatedwith the non-equilibrium spinodal pretransformation and the following discontinuous trans-formation was investigated in an as-quenched eutectiod Al-Zn alloy.It was observed that theloss of the stability in the lattice,which corresponded to the large-amplitude long-wavelengthstatic concentration wave in the non-equilibrium spinodal pretransformation,did not induceany effect of localized soft modulus.Although there are two aging internal friction peaks inphase transformation which correspond to the appearance and disappearance of the coherencyin spinodal pretransformation and the maximum of the interface area in the discontinuoustransformation respectively,the effect of localized soft modulus did not take place yet.     

Skeleton-based canonical forms for non-rigid 3D shape retrieval

Computational Visual Media - The retrieval of non-rigid 3D shapes is an important task. A common technique is to simplify this problem to a rigid shape retrieval task by producing a...     

Fitting superellipses

In the literature, methods for fitting superellipses to data tend to be computationally expensive due to the nonlinear nature of the problem. This paper describes and tests several fitting techniques which provide different trade-offs between efficiency and accuracy. In addition, we describe various alternative error of fit measures that can be applied by most superellipse fitting methods     

Fast and effective feature-preserving mesh denoising

We present a simple and fast mesh denoising method, which can remove noise effectively, while preserving mesh features such as sharp edges and corners. The method consists of two stages. Firstly, noisy face normals are filtered iteratively by weighted averaging of neighboring face normals. Secondly, vertex positions are iteratively updated to agree with the denoised face normals. The weight function used during normal filtering is much simpler than that used in previous similar approaches, being simply a trimmed quadratic. This makes the algorithm both fast and simple to implement. Vertex position updating is based on the integration of surface normals using a least-squares error criterion. Like previous algorithms, we solve the least-squares problem by gradient descent, but whereas previous methods needed user input to determine the iteration step size, we determine it automatically. In addition, we prove the convergence of the vertex position updating approach. Analysis and experiments show the advantages of our proposed method over various earlier surface denoising methods.     

离心泵蜗壳内压力脉动特性数值分析

为揭示离心泵蜗壳流道内的压力脉动变化规律,采用雷诺时均方法(RANS),对3种工况下的离心泵内部三维非定常湍流流场进行数值计算,分析同一蜗壳断面不同位置以及沿蜗壳周向不同点的压力脉动特性。结果表明:蜗壳流道内具有非常明显的压力脉动,在各种工况下压力脉动的主频均是叶片通过频率;同一蜗壳断面上的压力脉动从蜗壳底部到蜗壳背面先减小后增大,蜗壳底部监测点的高频脉动成分较多;沿蜗壳周向,随着圆周角的增大,压力脉动减弱,隔舌附近压力脉动幅度最大,且高频脉动成分明显增加。