应用决策集选播模式的SIP测控网络负载均衡策略

针对目前单优化目标选播模式容易导致负载发生新的不均衡问题,建立了SIP测控网络平台并分析其选播机理。采用网络层选播和应用层选播综合的方式,提出了最优决策集选播的负载均衡策略。选播目标为一个集合,包含多个满足要求的服务器,以避免蜂拥抢占服务器资源的情况发生;建立SIP测控网络最优决策集选播数学模型,采用证据理论决策选播目标权重,从而产生最优决策集。在OPNET仿真环境下,搭建SIP测控网络平台进行实验,结果表明最优决策集选播模式比单优化目标选播模式的服务器占用资源不均衡率降低了31%,能够很好地将负载均衡到各个服务器中,并减少了单个服务器处理多进程需要的额外资源开销。     

SIP的VoWLAN通信平台设计与实现

如何将会话初始化协议（SIP）与现有的通信网络有机结合,提供安全可靠的数据及通信服务已成为当今的热点问题。VoIP应用也受到业界的持续关注。安全问题一直都是企业实施VoIP的一个阻碍。提出了一个基于SIP的VoWLAN通信平台,将各种语音服务构建于无线局域网之上。利用虚拟专用网(VPN)、数据加密技术、VLAN和防火墙等必要安全技术和策略,应对在系统中的安全威胁,实现了通话质量可靠、安全性高的企业级VoIP无线网络架构。描述了该系统的设计和实现过程,讨论了其中的关键技术。     

Mode I and mode II initiation fracture toughness and resistance curve of medium density fiberboard measured by double cantilever beam and three-point bend end-notched flexure tests

Using specimens of medium density fiberboard, double cantilever beam and three-point bend end-notched flexure tests were conducted to obtain the mode I and mode II initiation fracture toughness and resistance curve for in-plane and through-the-thickness systems. The mode I initiation fracture toughness was smaller than that of mode II for the in-plane crack systems, but this tendency was inverse for the through-the-thickness systems. The fracture toughness increased during the crack propagation because of the significant fiber bridgings induced between the crack surfaces, but the increase of the mode I propagation fracture toughness was moderated after the crack reached a certain length. In contrast, the mode II propagation fracture toughness continuously increased during the crack propagation.     

房颤患者华法林初始剂量及出血危险因素的调查分析

目的: 比较两种华法林初始剂量在房颤患者中应用的安全性及有效性,并探讨其出血相关危险因素。方法: 采用回顾性调查方法,将某医院服用华法林的住院房颤患者按初始剂量分为超低剂量组(1.25~1.875 mg)和低剂量组(2.5~3.0 mg),比较两组患者抗凝的安全性和有效性指标。同时采用Logistic回归分析主要的出血危险因素。结果: 超低剂量患者各项安全性指标与低剂量组均无统计学差异(P>0.05);但前者首次达到目标国际标准化比值(INR)的时间较后者显著延长(P＜0.05),同时INR低于目标范围的比例显著增加且INR的控制率显著降低(P＜0.001)。年龄>65岁,肝功能不全,出血体质,卒中史,联用胺碘酮会显著增加华法林的出血风险(OR>1且P<0.05)。结论: 房颤患者应用超低初始剂量华法林抗凝的出血风险与低初始剂量相当但血栓风险增加;对于联用胺碘酮的患者,应加强出血风险的监护。     

Initiation Pressure Thresholds from Three Sources

Pressure thresholds are minimum pressures needed to start explosive initiation that ends in detonation. We obtain pressure thresholds from three sources. Run‐to‐detonation times are the poorest source but the fitting of a function gives rough results. Flyer‐induced initiation gives the best results because the initial conditions are the best known. However, very thick flyers are needed to give the lowest, asymptotic pressure thresholds used in modern models and this kind of data is rarely available. Gap test data are in much larger supply but the various test sizes and materials are confusing. We find that explosive pressures are almost the same if the distance in the gap test spacers are in units of donor explosive radius. Calculated half‐width time pulses in the spacers may be used to create a pressure‐time curve similar to that of the flyers. The very‐large Eglin gap tests give asymptotic thresholds comparable to extrapolated flyer results. The three sources are assembled into a much‐expanded set of near‐asymptotic pressure thresholds. These thresholds vary greatly with density: for TATB/LX‐17/PBX 9502, we find values of 4.9 and 8.7 GPa at 1.80 and 1.90 g/cm³, respectively.     

On the Initiation of High Explosives by Laser Radiation

The problem of laser initiation of high explosives in munitions is considered. In this situation, the laser illuminates a small spot on the casing, and lateral thermal transport affects the initiation temperature. We use a variational method to calculate the critical temperature for explosives' initiation as a function of the laser spot size for common high explosives. The effect of the dwelling time of the irradiation is then evaluated. We demonstrate that in typical situations the critical temperature is determined by the dwelling time rather than by the laser spot size.     

Laser Ignition of DAAF,DHT and DAATO3.5

CO₂ laser ignition experimental results are reported for the high‐nitrogen materials 3,6‐dihydrazino‐1,2,4,5‐tetrazine (DHT), 3,3′‐diamino‐4,4′‐azoxyfurazan (DAAF), and mixed N‐oxides of 3,3′‐azo‐bis(6‐amino‐1,2,4,5‐tetrazine) (DAATO_3.5, where the “3.5” indicates the average oxide content) at a maximum irradiance level of approximately 140 W/cm². Diagnostics include a photodiode, indium antimonide (InSb) IR detector, high speed (HS) video and a CO₂ photodetector. “First light” is measured for DAATO_3.5 and DAAF, however, due to the low visible light emission of the gas phase, thermal runaway, as measured by the InSb, is used as the ignition criterion for DHT. Ignition in the gas phase is captured by the high speed camera. It is observed that an increase in laser irradiance results in an increase in ignition and flame stand‐off distance for DAATO_3.5. The high‐nitrogen material laser ignition results are compared to the common nitramine explosive, octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX). Laser ignition delays for the different high‐nitrogen materials are also compared in the context of Differential Scanning Calorimetry (DSC) data. It is determined that DSC onset temperature, while a rough indicator of ignition delay trends, is not the equivalent of a direct measure of ignition temperature.     

Applying web-enabled self-regulated learning and problem-based learning with initiation to involve low-achieving students in learning

Vocational degree earners represent a major portion of the work force in Taiwan. However, vocational education in Taiwan is highly competitive in that it must attract sufficient student enrollment in an environment with a rapidly increasing number of schools. In this context, many vocational students tend to have lower levels of academic achievement. Under such constraints but moving toward more practical orientation, the authors conducted a quasi-experiment to examine the effects of applying web-based self-regulated learning (SRL), web-based problem-based learning (PBL) with initiation, and their combination to help these low-achieving students be involved positively in their learning. Four classes in successive years, with a total of 177 third-year students, were divided into 2 (SRL vs. non-SRL) × 2 (PBL with initiation vs. PBL without initiation) experimental groups. Results were generally positive. The authors further discuss the implications for schools, particularly vocational schools, and for scholars and teachers concerned about e-learning.     

聚能效应在深水井壁钢管上射孔的应用

利用聚装药理论，采用普通爆破器材，成功地在深水井井壁钢管上射孔而达到注浆堵水的目的。文中论述了聚能装药各参数的选择普通爆破器材的防水处理及可靠起爆等问题。     

基于SIP-MIP移动性管理的研究

随着无线通信技术的发展,越来越多的终端用户希望在移动环境下也能够接入互联网,得到互联网所提供的各种服务。移动管理是制约未来无线网络发展的一个关键问题。本文深入分析了基于SIP-MIP的双层移动管理方案的优点。分析表明,与现有单层移动管理相比,SIP-MIP具有较低的信令开销,可以更好的支持节点的移动。