WAPN: a distributed wormhole attack detection approach for wireless sensor networks

As the applications of wireless sensor networks （WSNs） diversify, providing secure communication is emerging as a critical requirement. In this paper, we investigate the detection of wormhole attack, a serious security issue for WSNs. Wormhole attack is difficult to detect and prevent, as it can work without compromising sensor nodes or breaching the encryption key. We present a wormhole attack detection approach based on the probability distribution of the neighboring-node-number, WAPN, which helps the sensor nodes to judge distributively whether a wormhole attack is taking place and whether they are in the influencing area of the attack. WAPN can be easily implemented in resource-constrained WSNs without any additional requirements such as node localization, tight synchronization, or directional antennas. WAPN uses the neighboring-node-number as the judging criterion, since a wormhole usually results in a significant increase of the neighboring-node-number due to the extra attacking link. Firstly, we model the distribution of the neighboring-node-number in the form of a Bernoulli distribution. Then the model is simplified to meet the sensor nodes＇ constraints in computing and memory capacity. Finally, we propose a simple method to obtain the threshold number, which is used to detect the existence of a wormhole, Simulation results show that WAPN is effective under the conditions of different network topologies and wormhole parameters.     

加强高职院校学生的理想信念教育的途径和方法初探

本文仅就加强高职院校学生的理想信念教育的迫切性以及当前高职院校学生理想信念状况进行了阐释,对加强高职院校学生的理想信念教育的途径和方法进行了探索.     

Microfluidic fabrication of polymeric core-shell microspheres for controlled release applications

We report a facile and robust microfluidic method to fabricate polymeric core-shell microspheres as delivery vehicles for biomedical applications. The characteristics of core-shell microspheres can be precisely and easily tuned by manipulating the microfluidic double emulsion templates. The addition of a shell can significantly improve the versatility as well as functionality of these microspheres as delivery vehicles. We demonstrate that the nature of the shell material plays an important role in the properties of the core-shell delivery vehicles. The release kinetics is significantly influenced by the material of the shell and other characteristics such as the thickness. For example, by adding a poly(lactic-co-glycolic acid) (PLGA) shell to an alginate core, the encapsulation efficiency is enhanced and undesired leakage of hydrophilic actives is prevented. By contrast, adding an alginate shell to PLGA core can lead to a reduction of the initial release rate, thus extending the release period of hydrophobic actives. Microfluidic fabrication enables the generation of precisely controlled core-shell microspheres with a narrow size distribution, which enables the investigation of the relationship between the release kinetics of these microspheres and their characteristics. The approach of using core-shell particles as delivery vehicles creates new opportunities to customize the release kinetics of active ingredients.     

Hip extension during the come-out of multiple forward and inward pike somersaulting dives is controlled by eccentric contraction of the hip flexors

Abstract

A modelling approach was used in the present study to investigate the role of the hip muscles during the come-out of forward and inward multiple somersaulting dives in a pike position. A planar two-segment model was used to simulate the somersault and come-out of three commonly performed dives from a 3-m springboard: forward two-and-one-half somersault pike dive (105B), forward three-and-one-half somersault pike dive (107B), and inward two-and-one-half somersault pike dive (405B). Three simulations were run for each dive: (1) hip angle was constrained to be constant, (2) hip torque was removed after 0.1 s, and (3) hip angle was constrained to a typical come-out time history used by elite divers. Simulation results indicated that hip flexion torque was required both to maintain a rigid pike position during somersault (range = 205.5–282.3 Nm) and to control the hip extension movement during the come-out (peak torque range = 355.8–548.1 Nm) in forward and inward multiple somersaulting dives. Coaches and divers should be aware that dry-land exercise drills producing hip extension movement by concentric actions of the hip extensor muscles do not replicate the neuromuscular control during the come-out of fast rotating dives.     

竞技视域下空手道运动中“控”的探骊

“控”是空手道运动的重要技术特征,对空手道组手比赛获胜起着至关重要的作用。文章运用文献资料法、田野调查法、录像分析法与专家访谈法,对空手道组手比赛中“控”的运用状况进行了分析与阐述,得出在空手道组手比赛中合理有效的对人的因素（自身、对手、裁判员、教练员、观众）与物的因素（场地、规则）控制是获取比赛胜利的核心环节。     

基于课程创生视角的高校信息化教学探讨

随着现代信息技术的发展,高校运用信息化教学手段进行教学已经比较普遍,但是其效果并不明显,原因也是多方面的。为了利于学生的学习自主性、主动性、合作性和创造性的发挥,提高学生学习能力、分析问题和解决问题的能力,笔者从课程创生视角出发,分析了高等教育人才培养的需求与当前课堂传统教学的瓶颈问题,探讨了信息化教学与课程创生教学结合的发展思路,重点从课程实践和操作层面阐述了进行课程创生教学的高校信息化教学设计问题。     

基于课程创生视角的高校信息化教学探讨

随着现代信息技术的发展,高校运用信息化教学手段进行教学已经比较普遍,但是其效果并不明显,原因也是多方面的。为了利于学生的学习自主性、主动性、合作性和创造性的发挥,提高学生学习能力、分析问题和解决问题的能力,笔者从课程创生视角出发,分析了高等教育人才培养的需求与当前课堂传统教学的瓶颈问题,探讨了信息化教学与课程创生教学结合的发展思路,重点从课程实践和操作层面阐述了进行课程创生教学的高校信息化教学设计问题。     

学习化社会中的美国成人大学生教育: 课程的视角

学习化社会意味着寻求教育机会的新群体的不断出现,在学习化社会,高校课程不仅包括学分和非学分课程、工厂实习、研讨会和校园内外提供的多媒体课程,也包括公共服务活动。美国高校成人学生的课程设置的广泛性与实用性和针对特殊成人群体的课程需求作出的灵活调整,启示我国普通高校应满足成人学生入学的需求,满足成人学生课程和课程质量的需求。     

Thermo-mechanical behaviour of floating energy pile groups in sand

This paper presents the experimental results of small-scale model tests of an instrumented floating energy pile group in which the piles were embedded in dry medium-dense sand and subjected to the seasonal temperature pattern of the city of Nanjing in China. The study also included a model test to assess the effect of including nonthermal piles on the thermo-mechanical behaviour of the floating energy pile group. For comparison, a model test of a single floating energy pile embedded in the same soil and subjected to a similar temperature pattern was also conducted. The results show that the thermo-mechanical behaviour of an energy pile group is different from that of a single energy pile in terms of the thermally induced change in axial pile stress and the displacement of the pile top and tip. This difference in behaviour could be explained by the higher lateral confining pressure expected on a single pile than on a pile in a group due to pile interaction effects, which could lead to different end restraint boundary conditions. We conclude that the thermo-mechanical behaviour of an energy pile is controlled mainly by the end restraint boundary conditions.