电视发射机射频放大模块的分析与故障排除

全固态电视发射机具有智能化管理、平均故障率低、保护功能可靠完善等优点。其功放单元和供电单元采用积木化、冗余化设计,有完善的保护、指示功能,以及热插拔和激励器主备自动切换,这就决定了电视发射机维护观念和维护模式发生改变,使发射机功率放大器模块成为发射机主要的维护对象。本文以泰克诺公司生产的BT03-103S型全固态电视发射机为例,介绍全固态电视发射机功率放大模块AU152及其故障与维护。     

Kinematic analysis of the drag flick in field hockey

Attaining high speed of the stick head and consequently of the ball is essential for successful performance of the drag flick in field hockey, but the coordination pattern used to maximise stick head speed is unknown. The kinematics of the drag flick was studied in ten elite hockey players who performed twenty shots each towards a target located 1.5 m high. A 150 Hz active marker motion analysis system was used, alongside two force plates to detect foot touchdown. Angular velocity and contribution to stick endpoint speed of upper body joints were analysed. Repeated measures ANOVA was used to compare timing of onset and peak angular velocities between joints. Participants used a kinematic pattern that was close to a proximal-to-distal sequence. Trunk axial rotation and lateral rotation towards the target, right wrist flexion and left wrist extension were the main contributors to stick endpoint speed. Coaches should emphasise trunk rotations and wrist flexion and extension movements for maximising stick head speed. Given the high level of the participants in this study, the coordination of joints motions, as reported here, can serve as a guideline for drag flick training.     

Shoe drop reduction influences the lower limb biomechanics of children tennis players during an open stance forehand: A longitudinal study

Compared to traditional tennis shoes, using 0-drop shoes was shown to induce an immediate switch from rear- to forefoot strike pattern to perform an open stance tennis forehand for 30% of children tennis players. The purpose of the study was to examine the long-term effects of a gradual reduction in the shoe drop on the biomechanics of children tennis players performing open stance forehands. Thirty children tennis players participated in 2 laboratory biomechanical test sessions (intermediate: +4 months and final: +8 months) after an inclusion visit where they were randomly assigned to control (CON) or experimental (EXP) group. CON received 12-mm-drop shoes twice, whereas EXP received 8?mm then 4-mm-drop shoes. Strike index indicated that all CON were rearfoot strikers in intermediate and final test sessions. All EXP were rearfoot strikers in intermediate test session, but half the group switched towards a forefoot strike pattern in final test session. This switch resulted in a decreased loading rate of the ground reaction force (?73%, p?=?.005) but increased peak ankle plantarflexors moment (+47%, p?=?.050) and peak ankle power absorption (+107%, p?=?.005) for these participants compared with CON. Biomechanical changes associated with the long-term use of partial minimalist shoes suggest a reduction in heel compressive forces but an increase in Achilles tendon tensile forces.     

The De Kretser case: a note on Sri Lankan writing in English

Abstract

How is the content of a literary canon, or tradition to be configured? What counts as a literary archive? More than 25 years after Edward Said’s Orientalism (1978 Said, W. Edward. 1978. Orientalism, New York: Vintage.  [Google Scholar]), it seems reasonable to assume, that central to such traditions, would be the work of those who live and work in the society that gives rise to it. In this review, such a location of Michele de Kretser’s new novel, The Hamilton Case, is offered, as a caution to metropolitan literary critics who continue to approach Sri Lankan writing in English, as Christopher Columbus approached ‘America’. It is argued that the novel owes much to, and can be read as echoing and elaborating the detective fiction of S.W.R.D. Bandaranaike, who was, also, the fourth Prime Minister of Ceylon (Sri Lanka), 1956–59.     

集中连片特困地区贫困发生率的空间特征*--基于3D框架对武陵山片区的个案分析

扶持集中连片特殊困难地区脱贫致富是中国新一轮减贫的重点,片区扶贫是把片区作为主战场,以片区的形式组织扶贫开发。选取武陵山片区有代表性的41个县为样本,采用中国农村贫困监测报告的相关数据,基于密度、距离和整合的3D框架分析县域贫困发生率的影响因素,结果表明：与经济中心距离越远、基于面积的经济密度越高、扶贫资金越多的县,贫困发生率越高,反映出经济发展与扶贫工作不同步、偏远地区经济增长动力不足以及扶贫资金使用效率和扶贫精准度有待提高等问题。因此,应转变发展方式,实现县域经济密度和减贫绩效“双赢”;加快基础设施建设,缩小偏远地区与中心城市的经济距离;建立和完善精准扶贫、协作扶贫机制,提高扶贫资金使用效率。     

基于虚拟现实技术的救助船对外消防培训仿真系统

针对救助船消防训练中存在的海况复杂,对外消防炮射流受风影响大,往往无法准确控制其射向目标区域的问题,在理想状态下射流理论的基础上探究风对射流轨迹的影响,建立自然风条件下射流轨迹的数学模型,模拟对外消防炮射流的运动情况。应用3ds Max构建船舶模型,用Unity3D构建救助船在面临大风浪、遇险船着火等状况时对外消防系统的工作场景,提出一种精确构建粒子系统轨迹的方法,使射流模型能精确体现在场景中。通过虚拟现实设备能实现救助船对外消防培训仿真系统的立体显示和人机交互,起到更好的虚拟仿真和培训效果。     

文献资源发展政策简论

文献资源发展政策(即馆藏发展政策)研究于20世纪70年代起始于美国,此后20年,文献资源发展政策实践在美国图书馆界得到了大力普及.我国图书馆界虽然从20世纪80年代起就开展这项研究,但时至今日,我国文献资源发展政策实践成果仍寥寥无几.文献资源发展政策可分为"总纲""学科文献资源描述""附件"三个部分,文章从编制实践出发,对撰写"政策"时需要明确的具体内容进行详细阐述,同时提出了文献资源发展政策工作办法.参考文献6.     

从文献课教材内容特点看高校信息素质教育发展新动向

通过对近三年出版的具有代表性的文献课教材的抽样调查,对现行教材内容的特点进行分析和归纳,并从中总结出当前信息素质教育发展的新动向:信息素质教育要强调全面培养学生的信息意识、信息技能和信息道德;只有注重实际教学效果,强化检索实践,关注社会需求,才能不断拓展文献课的作用和影响;教材内容必须及时反映信息资源变化及信息检索技术的最新成果,尤其需要突出信息创新意识、创新技能以及信息道德规范教育。