再生混凝土结构性能研究现状分析

混凝土作为最大宗的人造建筑材料,其废弃混凝土碎块的产生量也继续增多,对自然资源的占用及其对环境造成负面影响巨大。如何处理废弃混凝土碎块的问题将更趋严峻,因此提出了再生混凝土的概念。本文对再生混凝土结构性能在国内外研究现状进行论述,指出再生混凝土结构具有广阔的应用前景。     

混凝土的耐久性研究

混凝土的耐久性是指混凝土在实际使用条件下抵抗各种破坏因素的作用,长期保持强度和外观完整性的能力,影响结构耐久性的因素很多,混凝土质量及其保护层是内在因素,环境与载荷作用则是外在因素,不同的原因会造成不同的后果。本文从混凝土耐久性的概念入手,分析了混凝土冻融作用破坏机理分析,混凝土缺陷检测,提出了提高混凝土耐久性的措施。     

混凝土结构的耐久性评估和未确知模型研究

混凝土结构长期在物理和化学作用下会发生各种老化病害,影响其耐久性使用,对混凝土耐久性评估有助于,加强结构的使用效果,给以后的建设提供参考作用.本文以未确定理论为基础,对影响耐久性的因素进行分析归类,介绍了评估的层次分析方法.     

高性能混凝土技术发展与应用初探

高性能混凝土具有优良的高强度、高耐久性能、高体积性能、高工艺性、力学性能和施工性能,并能长期保持其强度,有降低工程造价、方便施工、美化城市建设空间等诸多优点,其社会、经济性能益显著,是适应城市化、现代化基本建设的一项重大的技术举措,具有积极、深远的现实意义和实用价值。     

沥青路面就地热再生机组在路面养护工程中的应用

本文依托某省道复拌就地热再生工程,系统的阐述了整个再生过程的施工工艺。通过试验分析了旧路面级配及旧沥青老化程度,试验表明原路面已经不能满足行车要求;确定了5%的再生剂的添加量以恢复原路面老化沥青路用性能及15%的新料添加量以改善原路面级配;现场施工时通过现场技术人员实时监控的方法严格控制作业温度,保障各工艺环节的最佳施工效果。     

混凝土工程裂缝的形成、预防与处理

随着人们对工程质量要求的提高,工程施工质量管理日趋严格,混凝土的裂缝问题也被越来越多的人所重视。本文根据夏热冬寒、大风干燥的特殊气候环境以及特殊的地质水文条件,从混凝土的收缩、温差、活性碱骨料化学反应和不均匀沉陷等四个方面阐述了混凝土裂缝形成的原因、特点以及根据工程实际,列举了一些常用的预防措施。     

外加剂和掺合料对混凝土强度和耐久性的影响

外加剂和掺合料是现代混凝土不可缺少的组成部分,但外加剂和掺合料的种类较多,性能各异,若使用不当,会影响混凝土强度和耐久性。本文阐述了常用外加剂和掺合料的性能及对混凝土强度、耐久性的影响,以期对相关技术人员提供参考。     

高性能混凝土研制的技术途径探析

我国社会主义经济建设正处在大发展时期,城市的建设发展迅速,高层或超高层建筑不断涌现,同时大跨和超大跨桥梁的兴建与日俱增,这些建筑物均对结构构件提出了高强、轻质的要求,要获得良好的经济效益,就要求设法增加建筑物的使用周期,而这要求结构的主要材料混凝土具有良好的耐久性,高性能混凝土的产生使得这一切成为可能.     

高储水生态混凝土储水性能研究及其应用推广

高储水生态混凝土是一种新型的建筑材料,在国内高储水生态混凝土研究还处于起步阶段.本试验通过正交设计,改变原材料及其配比,从而改变混凝土的性能,找到了适合不同道路情况的配比组合.     

混凝土结构与砌体结构工程事故分析及处理

近年来,我国一直在进行大规模的工程建设,建筑工程事故及重大事故时有发生,已成为人们关注的焦点。对于量大面广的混凝土结构和砌体结构的质量事故的分析和处理等方面作进一步的研究十分有必要。本文就对混凝土和砌体结构工程施工中易发生的质量缺陷进行了分析,从质量缺陷的种类、产生原因和预防措施等方面进行了详细的论述,并提出了在实际工作中发生质量事故的处理方法,以减少事故的发生,保证工程质量。     

试论高原训练法的基本原理及其应用

系统实施高原训练足当前竞技体育高水平运动项目提高竞技能力妁重要途径之一。科学掌握高原训练法妁基本原理与应用方式足提高高原训练效益妁关键。详细讨论了高原训练法应用妁基本原理和分类、高原训练法妁主要功能和特点、高原训练法妁基本结构和要素、高原训练法的应用方式与要求等问题，旨在为教练员提供高原训练妁科学依据。     

Magnesium status and the physical performance of volleyball players: effects of magnesium supplementation

Abstract

The aim of this study was to test the hypothesis that magnesium supplementation influences the physical performance of volleyball players, as the efficacy of this approach remains questionable. Twenty-five professional male volleyball players were assigned randomly to experimental (350 mg Mg · d^–1, 4 weeks) and control groups (500 mg maltodextrin · d^–1, 4 weeks) maintaining inter-group homogeneity of urinary magnesium. Erythrocyte, plasma and urinary magnesium levels, plasma creatine kinase activity, lactate production, maximal oxygen uptake (VO₂ max) and plyometric (squat jump, countermovement jump, countermovement jump with arm swing) and isokinetic (peak torque, potency and total work) performances were evaluated before (T₀) and after (T₁) supplementation. Levels of erythrocyte and urinary magnesium and creatine kinase activity and VO₂ max remained within normal ranges in both groups. Plasma magnesium decreased significantly only within the experimental group. Significant decreases in lactate production and significant increases (of up to 3 cm) in countermovement jump and countermovement jump with arm swing values were detected in the experimental group following magnesium supplementation, but not in the control group at T₁. It is concluded that magnesium supplementation improved alactic anaerobic metabolism, even though the players were not magnesium-deficient.     

Advances in the application of information technology to sport performance

This paper overviews the diverse information technologies that are used to provide athletes with relevant feedback. Examples taken from various sports are used to illustrate selected applications of technology-based feedback. Several feedback systems are discussed, including vision, audition and proprioception. Each technology described here is based on the assumption that feedback would eventually enhance skill acquisition and sport performance and, as such, its usefulness to athletes and coaches in training is critically evaluated.     

手纹特征的研究现状及其在体育运动选材上的应用

手纹包括指纹和掌纹两部分,是皮纹学的主要研究对象.皮纹具有较强的稳定性、特异性、遗传性,被科学家形象地称为"暴露在体表的遗传因子".随着组织学、遗传学等诸多学科的发展以及基因技术的逐渐成熟,对手纹这一个古老而现代的人体特征的研究不断取得新的进展,而且其应用领域越来越广.对手纹特征的基础理论的现状及其应用领域进行综述.     

辽宁省基层乒乓球教练员人才资源开发现状与对策分析

运用文献资料、专家访谈、问卷调查、数理统计等方法,从选聘机制、用人机制、培养机制、留人机制和流动机制五个方面对辽宁省基层乒乓球教练员人才资源开发现状进行分析,结果表明：选聘机制效果一般;用人机制不合理;培养机制不完善;留人机制有待提高;流动机制急需改革。建议：改革乒乓球教练员选聘机制;改善乒乓球教练员用人机制;加强乒乓球教练员培养机制;提高乒乓球教练员留人机制;建立合理的乒乓球教练员流动机制。     

新升本科高校应用技术型人才培养方法

现代企业对应用型人才的需求越来越多,高校在应用型人才培养中还存在诸多问题。以应用型技术人才所具有的特征为出发点,提出加强校企合作,加大双师型人才培养力度,提高学生参与企业实际生产研发的机会,强化学生动手实践能力培养。通过多条路径建设,摸索应用型人才培养模式。     

The effect of pre-exercise ingestion of corinthian currant on endurance performance and blood redox status

The present study investigated the effect of Corinthian currant pre-exercise supplementation on metabolism, performance and blood redox status during, and after prolonged exercise. Eleven healthy participants (21-45y) performed a 90-min constant-intensity (60–70% VO_2max) submaximal-trial, plus a time-trial (TT) to exhaustion (95% VO_2max) after consuming an isocaloric (1.5g CHO/kg BM) amount of randomly assigned Corinthian currant or glucose-drink, or water (control). Blood was drawn at baseline, pre-exercise, 30min, 60min, 90min of submaximal-trial, post-TT, and 1h post-TT. Post-ingestion blood glucose (GLU) under Corinthian currant was higher compared with water, and similar compared with glucose-drink throughout the study. Respiratory quotient under Corinthian currant was similar with glucose-drink and higher than water throughout the submaximal trial. Accordingly, higher CHO and lower fat oxidation were observed under Corinthian currant compared with water. The TT performance was similar between Corinthian currant, glucose-drink and water. Redox status were similar under all three conditions. Reduced glutathione (GSH) declined while total antioxidant capacity (TAC) and uric acid increased during exercise. GSH and TAC returned to baseline, while uric acid remained increased the following 1h. Corinthian currant, although did not alter exercise-mediated redox status changes and performance, was equally effective to a glucose-drink in maintaining GLU levels during prolonged cycling.     

The effect of inspiratory muscle fatigue on acid-base status and performance during race-paced middle-distance swimming

The aim of this study was to investigate the effect of pre-induced inspiratory muscle fatigue (IMF) on race-paced swimming and acid-base status. Twenty-one collegiate swimmers performed two discontinuous 400-m race-paced swims on separate days, with (IMF trial) and without (control trial) pre-induced IMF. Swimming characteristics, inspiratory and expiratory mouth pressures, and blood parameters were recorded. IMF and expiratory muscle fatigue (P < 0.05) were evident after both trials and swimming time was slower (P < 0.05) from 150-m following IMF inducement. Pre-induced IMF increased pH before the swim (P < 0.01) and reduced bicarbonate (P < 0.05) and the pressure of carbon dioxide (PCO₂) (P < 0.05). pH (P < 0.05), bicarbonate (P < 0.01) and PCO₂ (P < 0.05) were lower during swimming in the IMF trial. Blood lactate was similar before both trials (P > 0.05) but was higher (P < 0.01) in the IMF trial after swimming. Pre-induced IMF induced respiratory alkalosis, reduced bicarbonate buffering capacity and slowed swimming speed. Pre-induced and propulsion-induced IMF reflected metabolic acidosis arising from dual role breathing and propulsion muscle fatigue.     

传动机构的设计与计算

机械传动机构,可以将动力所提供的运动方式、方向或速度加以改变,被人们有目的地利用。机械传动分为很多种,例如丝杠传动、齿轮传动、链传动、带轮传动、蜗轮蜗杆传动等。本文将以同步带传动为例,设计一个传动机构。