冷拉螺旋叶片展开的精确算法

提出了一种新的、更趋精确合理的关于冷拉螺旋叶片坯料的展开与放样计算方法 ,并从实践中探索出叶片在展开与放样时其内径的精确修正系数k之值。     

复杂地下空间交通体系连接匝道烟气控制方案研究

复杂地下空间交通体系作为新型地下交通形式,车流量大且存在多个分合流点,气流组织复杂,防灾排烟难度极大。以杭州某复杂地下空间交通体系连接匝道为研究背景,提出匝道通风排烟设计方法,再选取其中二合一式连接匝道结构,采用FLUENT模拟其两种防灾排烟方案的有效性。模拟结果表明：两个连接匝道末端单独设置排烟口的设计方案可有效保证火源下游车辆和火源上游人员的逃生安全;根据分合流流速分配理论模型,在合流处只设置一个排烟口且排烟量提高40 m³/s时,也可达到同样的防灾排烟效果,从土建成本考虑,推荐此方案,为同类型隧道结构提供借鉴。     

车库出入口坡道噪声影响因素及预测

选取城市居住区中典型地下车库,在优化其出入口噪声采样点布置和同步采样点分组基础上,通过对噪声样本的声学分析,研究了车库出入口坡道噪声与坡道结构、坡度、线形、上下坡等相关因素的关系.通过对平直混凝土路面车库出入口噪声影响预测值的修正,建立了车库出入口坡道噪声影响预测模式.     

螺旋侧板对立管水动力影响的数值模拟研究

针对附有三板式螺旋侧板的立管水动力影响问题展开三维数值模拟研究,采用CFD大涡模拟方法,对不同的螺旋侧板高度h和螺距P在雷诺数分别为3 900,10 000和20 000条件下进行模拟分析,得到立管后方阻力系数CD、升力系数CrmsL、斯特劳哈尔数St及其频谱等特性。模拟结果表明:螺旋侧板对立管升力和阻力有明显的抑制效果,升力系数均方根值CrmsL较光滑立管降幅最大达到95.8%,但随着螺旋高度h的增加,会引起立管的阻力增加,螺旋高度h为0.1D～0.2D（D为立管直径）时的抑制效果较好,并且h为0.1D时的抑制效果最为理想;CD值和CrmsL值均随螺距P的增大而增大并保持在较低值范围,两者均在P=12.5D附近出现了随螺距P的增大而减小的现象,侧板螺距P在取值为5D～17.5D范围内的选择对立管的升力和阻力抑制效果较好。     

基于实车驾驶试验的螺旋匝道小客车纵向驾驶行为研究

为明确螺旋匝道(螺旋桥)驾驶操纵行为及车辆状态特征,选取2条桥头立交螺旋匝道和2座螺旋桥,开展小客车实车路试,通过连续采集行驶速度、加速度、踏板力等驾驶数据,分析螺旋匝道(桥)及前后衔接段的纵向驾驶行为特性.结果表明:行驶速度在螺旋匝道范围内基本恒定,并明显高于设计速度,螺旋匝道段的速度分布比主线段更集中,螺旋匝道对驾...     

Interaction Between GSM Handset Helical Antenna and User's Head: Theoretical Analysis and Experimental Results

Summary The performance of a cellular phone commercial helical antenna at 900~MHz band, both in free space and in the presence of a human head phantom was studied. Numerical simulation of the phone model for the latter case has been performed giving 3D radiation diagrams. The effect of the phantom head on radiation diagrams is presented. The relative amount of the EM power absorbed in the head was obtained for several distances of the phone. Measurements were carried out in a RF anechoic chamber using standard horn antennas and a calibrated measuring system. Absolute radiation patterns of the antenna gain were obtained in the three principal planes. Significant reduction of the absorbed power could be achieved just by moving the phone 1 cm away from the head.     

Identifying the crash characteristics on freeway segments based on different ramp influence areas

Objective: This study aimed to explore the relationship between crash types and different freeway segments and identify the factors contributing to crashes on different freeway segments. Unlike most of the previous studies on freeway segments, this study separately investigates basic freeway segments, single ramp influence segments, and multiple ramp influence segments.

Methods: Nonlinear canonical correlation analysis (NLCCA) and proportionality test were used to identify the relationship between crash types and different freeway segments. The data sets for the different freeway segments accumulated for this study consist of 9,867 crash samples with complete information on all 22 chosen variables. A multinomial logit model (MNL) was used to estimate the influence of crash factors on different freeway segments.

Results: The results show that weaving and diverge overlap influence segments (WD) are more likely to have injury or fatal crashes; diverge and diverge overlap influence segments (DD) are more likely to have property damage–only (PDO) crashes; merge and merge overlap influence segments (MM) are more likely to have sideswipe crashes; and WD have non-sideswipe crashes; WD and weaving overlap influence segments (MW) are more likely to have rear end crashes; and MM segments are less likely to have hit object crashes. The contributing factors are identified by MNL and the results show that different traffic variables, environmental variables, vehicle variables, driver variables, and geometric variables significantly affected the likelihood of crashes on different freeway segments.

Conclusions: Investigation of crash types and factors contributing to crashes on different freeway segments is based on multiple ramp influence segments, which can promote a better understanding of the safety performance of various freeway segments.     

Comparative experimental analysis of the effect of convective heat losses on the performance of parabolic dish water heater

This paper reveals comparative experimental analysis of the effect of variation of natural and forced convection heat losses on the performance of prototype parabolic dish water heater with coated and non-coated receivers. With the above-described system, hot water needs in domestic applications can be fulfilled instantly. A parabolic dish collector was used for instant water heating. Design of solar parabolic dish collector consists of truncated cone-shaped helical coiled receiver made up of copper at focal point. Instantaneous efficiency of 63% and 48% has been achieved with coated and non-coated receivers. This prototype has been evaluated for its performance with water flow rate of 0.0076 kg/s during the months of April and May 2010 at Shivaji University, Kolhapur, Maharashtra, India (latitude: 16.42° North, longitude: 74.13° West).     

螺旋状中空纤维膜吸收器脱硫性能的研究

用自组装的膜吸收器试验研究了不同操作条件下的烟气脱硫特性。实验结果表明，脱硫过程传质阻力主要集中在气相和膜上，利用螺旋管技术可以强化气相的传质。     

法向模螺旋天线分析与设计

首先对法向模螺旋天线进行了理论分析,然后针对无线局域网(WLAN)的应用,设计了一种满足移动终端2.4GHz工作频率要求的法向模螺旋天线.为实现展宽频带、阻抗匹配等要求,对该移动终端天线进行了优化设计.并且使用CST MWS电磁场仿真软件对所设计的天线进行仿真计算.仿真结果显示该天线具有50MHz的工作带宽,水平增益在1.54dB左右.