龙潭拱坝砼上坝运输方案选择

龙潭拱坝坝高９０ｍ，砼上坝运输是砼施工过程中的中间环节，控制进度的关键，必须因时因地制宜地选择适当的运输机械和运输方案，使砼运输能做到保质、保量、及时和经济，通过论证比较，结合本工程现实情况，砼上坝运输不采用缆机而采用门机方案．     

Carrying and spine loading

The advantages and disadvantages of different methods of carrying objects on spine loading are still not fully understood. Previous studies have either examined the effects of carrying using physiological measures or examined isolated spine segments using biomechanical models. Additionally, most studies have been restricted to only a small number of carrying conditions. Very few studies have attempted to examine the various factors influencing spine loading together. To improve understanding of interacting factors on carrying, this study assessed the lumbar spine loads of 16 subjects as they assumed six styles of carrying at two weight levels and two activity levels (walking vs. standing). Concurrent with each trial, a subject-specific biomechanical model was used to assess spine forces over the full lumbar spine. Most carrying methods in the trials resulted in relatively low levels of spine loading. Anterior/posterior (A/P) shear loading was the only spine-loading dimension that reached biomechanically meaningful levels. Two carrying conditions, with bins carried in front of the body, significantly increased A/P shear compared with other carrying styles. This increase appeared to be due to the greater moment arms occurring in these conditions. Many of the other carrying styles produced A/P shears that were similar to those observed when carrying nothing at all. Of all the tasks, the backpack carry characteristically produced especially low spine loads. The findings of the study suggest that to achieve optimal carrying in terms of spine loading, loads should be positioned close to the body, even when carrying relatively light loads.     

并联安装通风机对锅炉供风系统改造

根据蒸汽锅炉通风系统通风机设备老化、送风量不能满足锅炉燃烧需要等存在的问题,分析问题原因,采取措施进行改造。     

宽带接入网

本文根据国际 ITU-T 对宽带接入网规范的研究,首先介绍宽带接入网的基本概念和业务节点接口,然后分别说明宽带接入网的几种主要功能和协议,它们是传送功能、指配功能、实时管理协调功能、宽带运载连接控制功能。     

32位高速浮点乘法器优化设计

设计了一种用于频率为200 MHz的32位浮点数字信号处理器(DSP)中的高速乘法器.采用修正Booth算法与Wallace压缩树结合结构完成Carry Sum形式的部分积压缩,再由超前进位加法器求得乘积.对乘法器中的4-2压缩器进行了优化设计,压缩单元完成部分积压缩的时间仅为1.47 ns,乘法器延迟时间为3.5 ns.     

对称三进制光学加法器的进位直达通道设计

以对称三进制光学半加器为基础,提出了一个对称三进制光学全加器方案。主要介绍了进位直达并行通道在对称三进制光学全加器中的实现方案和工作原理,从而论证了实现对称三进制光学全加器的可行性。     

基于修正ANT逻辑高速树形32 Bit Carry Lookahead加法器

一种用修正全NMOS管逻辑（ANT）实现的树形结构高速32bit carry Lookahead加法器,使用两相时钟动态CMOS逻辑、修正不反向ANT逻辑和二进制树形结构实现。该加法器运用0．25μm工艺,文中给出了修正ANT逻辑中所有晶体管的宽长尺寸和仿真结果,最高工作频率为2GHz。计算结果在3．5个时钟周期后有效。     

一种基于环形振荡器的轻量级高效率的真随机数发生器

真随机数发生器(TRNG)作为芯片中重要的安全组件,在现代加密系统中扮演着越来越重要的角色.对于TRNG的设计,关键是需要熵提取器可以在恶劣的环境变化(如工艺波动、电压和温度(PVT))下稳定地生成熵值.基于Xilinx FPGA平台提出了一种基于环形振荡器的低成本,高效率真随机数发生器.TRNG一方面通过快速进位逻辑...     

一种基于FPGA进位逻辑的RO PUF设计

物理不可克隆函数(PUF)作为一种可有效地应对硬件安全问题的电路结构,在近些年得到了广泛的关注.环形振荡器(RO)PUF由于不需要完全对称的布线方式,因此被认为是最理想的PUF结构之一.现有的ROPUF设计愈加复杂且需要\"硬宏\"来固定电路,这导致PUF的移植性很差.文章利用FPGA中固有的进位逻辑资源实现RO PUF,...     

VANET协助下载策略研究

互联网的普及,使得人们对网络的依赖日益加深,人们希望能够随时随地连接网络,即使是在行驶的汽车里。然而,目前高速公路两旁稀疏的AP分布及有限的通信范围很难满足用户在车联网环境下对网络的需求。针对这一问题,提出了一种基于目标车组的车联网协助下载方法,利用同向车之间相对速度小、连接质量好的特点在局部范围内形成车组,并选择一组合适的对向车辆携带用户所需数据为其提供协助下载。该方法利用同向车组有效延长了对向协助车与目标车的通信时间,从而在减少对向车辆的协助次数的同时保证网络的吞吐量。仿真结果表明该方法可以使下载吞吐量提高30%以上,且降低了盲区通信时延,并能在车流密度较低的情况下保持较好的性能。