挤出机螺杆转速对马来酸酐官能化EVA性能的影响及其增韧研究

采用添加引发剂过氧化二异丙苯（DCP）和提高熔融挤出过程中双螺杆挤出机螺杆转速的机械力引发方法研究了马来酸酐（MAH）官能化乙烯一醋酸乙烯酯共聚物（EVA）的熔融挤出反应.研究了引发剂用量和螺杆转速对产物的接枝率和熔体流动速率的影响.结果表明,随着DCP用量的增加,产物接枝率出现峰值,而随着螺杆转速的增加,产物接枝率出现先下降后增大的变化,接枝产物的熔体质量流动速率（MFR）在螺杆转速达到300r/min时出现显著增大,在一定的配方条件下,通过改变螺杆转速,可以抑制EVA在接枝过程中的交联副反应,控制制得具有较高接枝率（0.29%～0.8%）和较好熔体质量流动速率（0.7～1.2g/10 min）的接枝产物（EVA-g-MAH）.力学性能测试表明,此复合引发接枝产物对尼龙66具有较好的增韧效果.     

基于SIP协议非语音信息扩展的应用研究

利用SIP事件通告机制这一扩展,提出了一种基于SIP的VoIP非语音信息扩展的应用方案,描述了该方案的设计原理,讨论了一些方案实现的技术要点.该设计方案结合了XML技术,结构清晰,故具有较强的扩展性.在VoIP系统中,该方案实现的扩展功能使用户了解当前其他用户的通信状态,避免了一些呼叫事故的发生.     

Utilizing bloom filters for detecting flooding attacks against SIP based services

Any application or service utilizing the Internet is exposed to both general Internet attacks and other specific ones. Most of the times the latter are exploiting a vulnerability or misconfiguration in the provided service and/or in the utilized protocol itself. Consequently, the employment of critical services, like Voice over IP (VoIP) services, over the Internet is vulnerable to such attacks and, on top of that, they offer a field for new attacks or variations of existing ones. Among the various threats–attacks that a service provider should consider are the flooding attacks, at the signaling level, which are very similar to those against TCP servers but have emerged at the application level of the Internet architecture. This paper examines flooding attacks against VoIP architectures that employ the Session Initiation Protocol (SIP) as their signaling protocol. The focus is on the design and implementation of the appropriate detection method. Specifically, a bloom filter based monitor is presented and a new metric, named session distance, is introduced in order to provide an effective protection scheme against flooding attacks. The proposed scheme is evaluated through experimental test bed architecture under different scenarios. The results of the evaluation demonstrate that the required time to detect such an attack is negligible and also that the number of false alarms is close to zero.     

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.     

氧化还原引发乳液聚合单体水溶性与动力学之间的关系

本文研究了以过硫酸钾／焦亚硫酸钠为氧化还原引发体系，在苯乙烯、醋酸乙烯酯为具体单体的乳液聚合中，单体水溶性与动力学之间的关系。通过实验考察了聚合温度、搅拌速率、电解质浓度对聚合反应转化率～时间关系的影响，并讨论了单体水溶性、自由基水相反应和聚合速率等之间的内在联系。同时得出该氧化还原引发下苯乙烯和醋酸乙烯酯体系的表观活化能分别为４７．０６ｋｊ／ｍｏｌ和约７０ｋＪ／ｍｏｌ。     

Effects of cricket ball colour and illuminance levels on catching behaviour in professional cricketers

In recent years there have been many alterations to equipment and technology in professional cricket, including the introduction of white balls during day — night matches. In the present study simulated slip-catching performance and movement initiation time were examined in professional cricketers when ball colour and illuminance levels differed. Five male professional cricketers (mean age: 27.3 ± 1.4 years) volunteered to catch a total of 60 cricket balls, 20 (10 red and 10 white) under each of three illuminance levels (571, 1143 and 1714 lux). Balls were projected from a ball machine at 20 m s^?1 (45 mph) over a distance of 8.4 m, to the subject's dominant side. Catching performance was measured using an established catching scale. Movement initiation times for each hand were also calculated for each trial using a motion-analysis system. Data were submitted to separate two-way (ball colour [2] × illuminance level [3]) repeated measures analysis of variance. No significant effects were obtained for ball colour or illuminance levels for either catching performance or movement initiation time. Neither ball colour nor light level (within the range tested) affected slip-catching performance and movement initiation times in professional cricketers. Therefore it was concluded that the changes made to ball colour and light conditions in professional cricket were not detrimental to catching performance.     

On the possible generalizations of the Kitagawa–Takahashi diagram and of the El Haddad equation to finite life

The celebrated Kitagawa–Takahashi (KT) diagram, and the El Haddad (EH) equation, have received great attention since they define quite successfully the region of non-propagation (or the condition of self-arrest) for short to long cracks. The EH equation can be also seen as an “asymptotic matching” between the fatigue limit and the threshold of crack propagation. Above this curve, finite life is expected, since cracks propagate and eventually lead to final failure. In this paper, possible extensions of the EH equation to give the life of a specimen with a given initial crack as a function of the applied stress range, using only “asymptotic matching” equation between known regimes, namely the Wöhler SN curve (or some simplified form, like Basquin law), and the crack propagation rate curve (or just the Paris’ law). This permits an extension of the so-called “intrinsic crack” size concept in the EH equation for infinite life. The generalized El Haddad equation permits to take into account approximately of some of the known deviations from the Paris regimes, for short cracks, near the fatigue threshold or fatigue limit, or to the static failure envelope. The new equations are also plotted as SN curves, showing that power-law regimes seem very limited with many possible deviations and truncations, even when the crack propagation law has a significant power-law regime. The diagram remains partly qualitative (for example, we neglect geometric factors), and can be considered a first attempt towards more realistic maps. Particularly interesting are the cases with the Paris exponent m < 2, in which propagation tends to be very slow until very close to the toughness failure, making the maps qualitatively different.     

1Cr18Ni9Ti管道焊缝金属疲劳短裂纹萌生与早期扩展

复型研究了1Cr8N9Ti管道焊缝金属的疲劳短裂纹萌生与早期扩展特点，结果表明，有效短裂纹萌生于与管道内外表面一致的试样表面局部区域中delta铁素体与基质的界面，早期扩展具有显著微观结构效应特征，最大障碍尺度约为40μm，与焊缝金属特征微观组织结构――柱状晶中富delta铁素体带距离一致，该尺度范围。由于强微观结构约束，短裂纹密度较高并逐渐增加；尺度不规则扩展，直到若干较长短裂纹发生合并形成导致试样失效的主导短裂纹。这一过程通常称为“微观结构短裂纹（MSC）“阶段，主导短裂纹及其发路径上的短裂纹对疲劳损伤做出直接贡献，可分别称为“主导有效短裂纹（DESFC）“和“有效短裂纹（ESFCs）“，为描述该阶段不规则行为，有必要引入尺度等于ESFCs尺度均值的虚裂纹即MSC阶段DESFC的概念，该阶段DESFC尺度恒定增加，扩展率恒减小。     

SIP协议在VoIP中的实现

会议初始化协议(SIP)是一种基于应用层地信令控制协议,由于具有简单、灵活和良好扩展性地体系结构,将其融入Internet数字语音通信技术中,建立基于SIP的VoIP网络,将会成为下一代VoIP技术的发展趋势之一。为此,介绍了一种基于SIP协议的VoIP网络实现模型,详尽阐述了SIP在VoIP网络中的实现原理,以及SIP对整个对话的控制过程。     

IN呼叫方处理能力在VoIP中的实现

文章分析了标准化组织提出的基于分组网络的电话的主要体系结构和协议,提出了智能网中呼叫方处理能力(CPH,callpartyhandling)在VoIP网络中的实现方案,并得出了结论。