一种基于 CDMA 自组网的通信网络 MAC 准同步协议

为了提高无线自组网通信网络吞吐量和数据包发送成功率,提出一种基于准同步 CDMA 的自组网MAC 协议,并对其收发电路进行设计。在采用零相关区序列的准同步 CDMA 系统中,到达接收端的各用户信号存在一定的相对时延,如果用户信号相对时延控制在零相关窗口范围之内,可以达到近似于同步的效果,同时零相关序列的相关性能大大提高了系统抗多址干扰和多径干扰能力。仿真结果表明,该协议的系统吞吐量是未采用零相关序列系统的 5 倍,在数据包发送数为 50 时仍有 30%的发送成功率。     

Assessment of the power performance of racing cyclists

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.     

Physiological variables and performance markers of serving soldiers from two “elite” units of the British Army

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.     

VoIP中SIP呼叫在三网合一交换机中的实现

详细地描述了VoIP(Voice over Internet Protocol)的SIP呼叫在三网合一交换机中实现过程,讨论了SIP呼叫的处理流程,用开源的oSIP协议栈实现SIP呼叫。包括注册,电话号码处理,以及接通和挂断处理。从原理上描述了SIP呼叫在三网合一交换机中的具体实现。分析了SIP协议栈的运行机制,设计了将SIP协议栈移植到三网合一交换机,并以此为基础开发基于SIP呼叫的实现方案。     

基于最优多属性约束的IPV6动态路由协议优化

提出一种基于最优多属性约束的IPV6动态路由协议优化方法。根据IPV6动态路由协议中数据属性的约束条件,建立最优多属性约束模型,用来描述不同属性约束条件需要符合的要求。详细描述了IPV6动态路由协议的设计方式,从而实现大范围网络通信。实验结果表明,利用这种方法进行网络通信,能够避免传统算法的缺陷,提高了通信效率,取得了令人满意的结果。     

有关口语报告法效度的几个争议问题

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。     

VLAN技术浅议

介绍了VLAN的概念、VLAN的优势、实现VLAN的方式、VLAN的配置方法、VLAN的测试和管理。     

The classroom observation protocol for socioscientific issue-based instruction: development and implementation of a new research tool

Background: For the past decade, science educators have been exploring the use of Socio-scientific Issues (SSI) as contexts for science teaching and learning, and research indicates that doing so can support significant learning gains. However, research related to how teachers take up the practice of SSI-based instruction is far more limited, due in part to a lack of tools for use in this kind of research.

Purpose: The focus of this research is development and testing of a new classroom observation protocol specifically designed for SSI-based instructional contexts.

Design and methods: Development of this SSI-Observation Protocol (SSI-OP) took place in four distinct phases: review of existing protocols and SSI-based instruction frameworks, writing and revision of protocol items, initial testing of the draft protocol, and soliciting feedback from SSI experts.

Sample: Following the four stages of SSI-OP development, we progressed to a series of field tests. The field tests were conducted with three different samples. The first sample was an experienced (10 + years) high school biology teacher and one of her honors biology classes. The second sample consisted of seven Turkish Pre-service Science Teachers (PST) participating in a science methods course. The third sample included two Thai PST from a field experience course embedded within a teacher education program.

Results: The final version of the protocol addressed five dimensions of SSI-based instructional activities: focus of instruction, teaching moves, role of teacher, role of students, and classroom environment.

Conclusions: The SSI-OP could be used in a variety of ways for research including documentation of current practices, impacts of professional development and/or curricula on teaching practices, and changes in teaching over time. We offer the SSI-OP as a new tool with the potential to contribute to science teacher education and research that may advance the teaching and learning of science through SSI.     

基于消息传递的远程桌面控制协议实现

简要分析了现有消息传递工作模式.针对现有远程控制协议消息传递低效,根据实际的需要设计出一种新颖的远程控制协议.这种协议改变原有的工作模式,利用现有的技术,弥补了这个不足.     

基于分布式数据库的两阶段提交协议在UNIX下的实现

详细阐述了分布式数据库的两阶段提交协议在UNIX下的实现,并模拟了一个实际的航空售票系统来阐明两阶段提交技术在实际中的应用.