Finite Element Analysis for Multi-pass Equal Channel Angular Pressing

Equal channel angular pressing (ECAP) is an attractive process method to produce bulk ultra-fine grained materials. There are many experiment evidences showing that the nature of the microstructural evolution in multi-pass ECAP depends on process routes. Isothermal three dimensional FEM simulations for multi-pass ECAP were performed using DEFORM3D finite element code. The material model of 6061Al-T6 was employed. Flow nets, effective strain distribution in the workpiece and loads during multi-pass ECAP using different routes were analysed respectively. The simulations show process routes influence material flow and effective strain distribution in the workpiece obviously but have few influence on loads.     

An Adaptive Joint Source/Channel Coding Using Error Correcting Arithmetic Codes

An approximately optimal adaptive arithmetic coding (AC) system using a forbidden symbol (FS) over noisy channels was proposed which allows one to jointly and adaptively design the source decoding and channel correcting in a single process, with superior performance compared with traditional separated techniques. The concept of adaptiveness is applied not only to the source model but also to the amount of coding redundancy. In addition, an improved branch metric computing algorithm and a faster sequential searching algorithm compared with the system proposed by Grangetto were proposed. The proposed system is tested in the case of image transmission over the AWGN channel, and compared with traditional separated system in terms of packet error rate and complexity. Both hard and soft decoding were taken into account.     

开敞海域淤泥质深水航道设计年回淤量计算方法及应用

连云港港深水航道是开敞海域淤泥质浅滩深水航道的典型。航道回淤规律和实践表明,连云港淤泥质浅滩深水航道中风天回淤量为航道回淤的主体,占年回淤总量的60%左右。由于中风天频率年际变化较大,导致航道年际回淤水平变幅较大。现有设计回淤量计算模式均未考虑风天分级。提出了“按小、中、大3个概化波浪动力计算回淤强度、再组合各自波浪频率得到设计回淤量”的开敞海域淤泥质浅滩深水航道设计年回淤量计算方法。该方法能够较为合理地体现全年波浪水平和波浪频率年际间差异对年回淤量的影响程度,显著提高了设计年回淤量预报精度,为合理确定开敞海域淤泥质浅滩深水航道的设计年回淤量水平和变化范围、正确评价航道的稳定性和技术可行性提供科学依据。经连云港区25万吨级航道和徐圩港区10万吨级航道工程实践检验,预报回淤量与实际回淤量偏差不超过25%。     

长江南京以下深水航道二期工程碍航水道演变特性及航道治理思路

长江南京以下12.5 m深水航道二期工程建设是落实国家"一带一路"战略、打造长江综合立体交通走廊的重大举措。针对二期工程河段4个水道的碍航情况,在分析上游来流来沙特性、各水道分流分沙特性及演化过程的基础上,对碍航特性、河床演变特性及趋势进行分析,提出各水道的整治时机、关键部位和治理思路。成果为航道整治工程设计与建设提供技术支撑,也为感潮河段航道整治积累经验。     

山区弱支流河口段航道整治参数的确定方法

由于受干流的顶托影响,弱支流河口段水流、泥沙运动规律复杂,其整治参数已不能用天然河段的计算方法来确定,而经验方法也往往由于缺乏科学性而导致工程事倍功半.在总结赤水河口淤沙河段航道整治成功经验的基础上,探讨了山区弱支流河口段航道整治参数的确定方法.提出应根据干流顶托水位降落过程,分段采用浅滩由淤积转人冲刷、流速较大、冲刷...     

新形势下长江口南北港分汊口河段河势变化及治理策略*

长江口南北港分汊口河段历史上是长江口水域河势变化最频繁的区域之一。基于该河段历史河势演变规律,在 分析南北港分汊口治理效果的同时,对南北港分汊口工程兴建后新形势下长江口南北港分汊口河段河势变化趋势及治理策 略进行研究和探讨。结果表明：新形势下南北港分汊口河势仍存在不稳定的因素,突出表现在扁担沙沙体未经人工控制和 整治建筑物防冲抗刷压力增大;针对不稳定因素提出的治理方案经数学模型研究验证较为有效、可行。     

农村公路网规划建设的思考

对现有道路投资理论、道路投资主体的变化以及政府职能等影响农村道路网建设的因素进行分析,得出造成农村路网落后的原因。从政治,经济、公平等方面入手,分析农村路网规划建设的必要性以及内在规律性。     

一种基于导频和循环前缀的信道估计方法

提出了利用循环前缀对信道进行估计的方法,即在梳状导频模式时,使用导频获得导频子信道频率响应后,对其在频域方向进行插值得到数据子信道响应,在以后没有导频的序列的数据周期内,使用循环前缀对信道进行估计.仿真结果表明:和两个一维的插值方法相比,在不降低系统性能的情况下,改善了系统的实时性能.     

"叠加均值法"在沈本高速公路施工中的应用

主要介绍了在高速公路建设中,利用叠加均值法来解决路槽平整度这个较为复杂的问题。这种方法不仅简单实用,操作方便,节约大量的测量工作,而且可以加快施工进度,保证路槽的施工质量。     

老铁山水道航行危险度的模糊综合评价

介绍模糊综合评价法的数学原理,建立航道航行危险度评价模型,并对老铁山水道的航行危险度进行综合评价。结果表明,该评价方法是可行的。