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排序方式: 共有636条查询结果,搜索用时 31 毫秒
71.
本文介绍了VoIP的实现原理及标准协议,分析了VoIP网络所面临的安全威胁,提出了一种VoIP安全防护方案,并对其中的相关技术和方法作了简要的介绍和分析。最后对VoIP网络安全问题作了总结,并指出下一步研究VoIP网络安全性问题的研究方向。 相似文献
72.
基于TCP/IP协议的常见攻击方法 总被引:1,自引:0,他引:1
陈派樟 《宁德师专学报(自然科学版)》2010,22(1):56-58
TCP/IP协议是目前世界上应用最为广泛的协议.但现在使用的TCP/IP协议存在很多漏洞,对联网主机的安全构成了严重威胁.TCP/IP协议从开始设计时候并没有考虑到现在网络上如此多的威胁,由此导致了许多形形色色的攻击方法.现在就网络中使用的基本通信协议TCP/IP的攻击方法进行探讨. 相似文献
73.
研究了定向扩散(Directed Diffusion)路由协议的工作原理和传播机制,并使用NS2对其进行了仿真分析.采用平均消耗能量、平均网络延迟和平均分组接收率这三个参数作为性能评价的技术指标,在分别改变网络节点数目、源节点数目、汇聚节点数目的情况下,对定向扩散协议进行了一系列的模拟实验.实验结果显示,定向扩散虽然表现出了较好的性能,但仍然有待提高. 相似文献
74.
刘慧琳 《四川教育学院学报》2010,26(11):114-116
在当今这个网络信息系统高度发达的时代,对于一个组织的网络管理员来说,要想知晓试图接入企业网络的设备的真实身份是一件十分困难的事情。面对手段高明、资金雄厚的黑客,用户设备很可能在不知不觉间感染致命的恶意软件。当前可信网络连接(TNC)技术就为解决这一难题提供一个网络接入控制解决方案,它能保护系统免受有病毒、蠕虫和其它恶意应用的PC和设备的侵害。文章分析了EAP-TNC协议[1]及其应用。 相似文献
75.
Yang Bai Paul Hibbing Constantine Mantis Gregory J. Welk 《Journal of sports sciences》2018,36(15):1734-1741
The purpose of this investigation was to examine the validity of energy expenditure (EE), steps, and heart rate measured with the Apple Watch 1 and Fitbit Charge HR. Thirty-nine healthy adults wore the two monitors while completing a semi-structured activity protocol consisting of 20 minutes of sedentary activity, 25 minutes of aerobic exercise, and 25 minutes of light intensity physical activity. Criterion measures were obtained from an Oxycon Mobile for EE, a pedometer for steps, and a Polar heart rate strap worn on the chest for heart rate. For estimating whole-trial EE, the mean absolute percent error (MAPE) from Fitbit Charge HR (32.9%) was more than twice that of Apple Watch 1 (15.2%). This trend was consistent for the individual conditions. Both monitors accurately assessed steps during aerobic activity (MAPEApple: 6.2%; MAPEFitbit: 9.4%) but overestimated steps in light physical activity. For heart rate, Fitbit Charge HR produced its smallest MAPE in sedentary behaviors (7.2%), followed by aerobic exercise (8.4%), and light activity (10.1%). The Apple Watch 1 had stronger validity than the Fitbit Charge HR for assessing overall EE and steps during aerobic exercise. The Fitbit Charge HR provided heart rate estimates that were statistically equivalent to Polar monitor. 相似文献
76.
包琴 《福建工程学院学报》2018,(1):61-65
针对节能监管系统数据采集网关对现场设备控制能力有限的问题,设计基于MDT单片机的Modbus远程控制器,实现了采集网关对现场设备的协作控制,以提高节能监管系统的监控效果。远程控制器以MDT单片机为核心,整合了Modbus通信协议,并通过RS485总线与数据采集网关的下行RS485主机接口互联,实现对现场控制量的监测和控制。通过实践验证,远程控制器能够可靠地实现状态量的采集和切换控制,工作稳定可靠。 相似文献
77.
A 30‐s ‘all‐out’ power protocol was studied in four groups of racing cyclists including internationals (n = 8), Category 1 (n = 10), Category 2 (n = 15) and Category 3 (n = 11). Following warm‐up each subject completed five trials interspersed by 3 min of low intensity exercise on an ergowheel racing cycle ergometry system at a power output of 15 W kg–1 body weight, generated at 130 rev min–1. Temporal indices of performance included delay time (DT) to achieve the power criterion, total time (TT) of the maintenance of the power criterion and the ratio of TT/DT. ‘Explosive’ leg strength was assessed from a vertical jump. The results indicated that international and Category 1 cyclists had lower DT (2.2 ± 0.1s and 2.1 +0.0s, respectively; P<0.05), higher TT (28.1 ±0.7s and 27.0+0.7s, respectively; P<0.05) and elevated TT/DT (12.8 and 12.9, respectively; P<0.01). ‘Explosive’ leg strength was also higher (P<0.05) in the internationals than in the other groups of cyclists. The protocol provides a sport‐related method for the assessment of short term endurance performance ability in racing cyclists which may be of value in identifying the anaerobic capability of individual cyclists. 相似文献
78.
Abstract The aim of this study was to compare selected physiological variables and performance markers of soldiers from two “elite” units of the British Army. Ten soldiers from each of the two units were recruited for this study (n = 20). All participants completed three tests while carrying a 20 kg backpack load: (1) a maximal treadmill test using the Bruce protocol; (2) a 2 mile backpack run test specific to Unit A on a consistently flat tarmac road; and (3) a 29 km time-trial over hilly terrain typical of a mountainous area used by Unit B for performance assessment. Heart rate, maximal blood lactate concentration and performance (run time) were assessed during all three tests, with peak oxygen uptake also being measured during the maximal treadmill test. Measurements of anthropometry, isokinetic strength and mental toughness (MT48) were also recorded. There were no significant differences in terms of performance markers between the units (P > 0.05). Performance on the maximal treadmill test correlated with performance on the 2 mile backpack run test (r = ?0.57) and 29 km time-trial (r = ?0.66). Performance on the 2 mile backpack run test in turn correlated with 29 km time-trial performance (r = ?0.77), accounting for 59% of the variance. In conclusion, the maximal treadmill test and the 2 mile backpack run test are useful indicators of performance on the arduous hill march and could be employed in the screening and selection of potential recruits. 相似文献
79.
有关口语报告法效度的几个争议问题 总被引:1,自引:0,他引:1
张裕鼎 《宁波大学学报(教育科学版)》2007,29(6):25-28
尽管口语报告法在当前心理学、教育学以及认知科学的研究中被广泛使用,但关于其效度的争议依然存在。这些争议主要包括:第一,口语报告的准确性,即口语报告能否准确地反映我们的思维内容?第二,口语报告的完整性,即搜集到的口语报告能否为我们了解被试的认知过程提供足够的信息?第三,口语报告的反应性,即口语报告是否会影响思维的正常进程?文章对这些问题进行了较为深入的分析和思考,并指出了对口语报告法进行研究的几个新趋势。 相似文献
80.