“燃烧热测定”教学实验的改进

本文介绍了在燃烧热的测定实验中采用双孔带槽模底,单、双股燃烧丝相结合的挂样片法,代替单孔或无孔模底,单股燃烧丝接触样片法,以及压片操作技法。四年的实践表明,这种实验方法大大提高了实验的成功率,缩短了实验操作时间。     

Groin injuries in professional rugby league players: a prospective study

Altogether, 100 uninjured professional rugby league players were evaluated over a 2-year period. Their height, body mass, sum of skinfolds, girths and bone diameters were recorded. A Cybex 340 isokinetic dynamometer was used to determine peak torque, work, power, endurance ratios and peak torque ratios of the hip abductors and adductors (5 repetitions at 0.52 and 2.08 rad?·?s^??1; 20 repetitions at 3.66 rad?·?s^??1) and knee flexors and extensors (4 repetitions at 1.04 and 3.14 rad?·?s^??1; 30 repetitions at 5.22 rad?·?s^??1). Hip abduction and adduction were also assessed with the hip in external rotation. Discriminant function analysis was conducted on all predictor variables to develop a multivariate predictive model capable of classifying players with a high degree of accuracy into groups with and without a groin injury. The model consisted of eight variables and correctly classified 91.7% of the non-injured players and 90.5% of the injured players. The correct classification for the model as a whole was 91.4%. The aetiological factors identified as being related to injury of the groin musculotendinous unit included abduction and adduction-with-rotation peak torque, angle of adduction and abduction-with-rotation peak torque, strength ratio of hip muscle groups, bilateral difference in extension peak torque, femur diameter and body mass.     

Hip adductor activations during run-to-cut manoeuvres in compression shorts: implications for return to sport after groin injury

Abstract

Athletes at high risk of groin strains in sports such as hockey and soccer often choose to wear shorts with directional compression to aid in prevention of or recovery from hip adductor strains. Large, eccentric contractions are known to result in or exacerbate strain injuries, but it is unknown if these shorts have a beneficial effect on hip adductor muscle activity. In this study, surface electromyography (EMG) of the adductor longus and ground reaction force (GRF) data were obtained simultaneously on 29 healthy individuals without previous history of serious injury while performing unanticipated 45° run-to-cut manoeuvres in a laboratory setting wearing shorts with non-directional compression (control, HeatGear, Under Armour, USA) or shorts with directional compression (directional, CoreShort PRO, Under Armour, USA), in random order. Average adductor activity in the stance leg was significantly lower in the directional condition than in the control condition during all parts of stance phase (all P < 0.042). From this preliminary analysis, wearing directional compression shorts appears to be associated with reduced stance limb hip adductor activity. Athletes seeking to reduce demand on the hip adductors as they approach full return to activities may benefit from the use of directional compression shorts.     

极限迫敛性的推广及其应用

从一道极限题的错解谈起,对极限迫敛性进行了推广,用推广结论,较好的解决了一些极限问题,并由此强调教学研究的重要性.     

个性化需求预测面临的挑战及解决方法研究

本文首先运用计划行为理论和信息交换理论分析得出,个性化需求预测在获取预测所用信息阶段的主要挑战是“如何帮助顾客将其拥有的与需求相关的隐性信息转换成显性信息”,并提出了应对该挑战的方法“开发需求相关隐性信息转换系统”;然后运用“自我推理”和“错误一致性效应”等理论分析得出,在理解需求相关信息阶段的主要挑战是“制造商在理解顾客需求相关信息时,如何避免自我推理和错误一致性效应”,基于认知图作用的分析,提出了应对该挑战的方法“充分运用描述顾客价值系统的认知图理解顾客需求相关信息”;将顾客需求相关信息转换成预测信息阶段的主要挑战是“如何提高预测精度”,运用锚定一调整过程理论、信念更新范式理论、状态依赖性理论和记忆可接近性优势理论分析得出,制造商采取以顾客前一次购买订单所含信息为起始点的净变预测方式实现基于属性的预测,将有助于提高个性化需求预测的预测精度。     

魏强斜井围岩变形监测与分析

为保证斜井施工的安全、可靠、经济,对魏强斜井施工过程中的拱顶下沉和周边收敛进行监控量测,应用回归分析法对所量测的数据进行处理,结果表明运用指数函数进行回归拟合是合理的,较好地反映了围岩位移和时间之间的线形关系,从而简单直观地反映出了围岩的变形稳定状态。     

20世纪20-40年代五邑侨眷的生活状况——以开平、台山为例

江门五邑是侨眷比较集中的地区,侨汇在当地经济生活中具有重要地位。侨汇将五邑经济与世界经济联系起来,世界经济变化必然引起五邑经济的波动。19世纪末至20世纪二三十年代,欧美经济经历了从繁荣到萧条的过程,侨乡经济也受到明显影响,侨眷生活相应地经历了富足、拮据和困窘三个阶段。     

社会学视野中的安徽省出生性别比异常现象

通过对安徽省出生性别比状况的描述，从婚姻家庭和城乡二元差异角度对出生性别比偏高进行了分析。最后从个人、家庭及社会三个方面对出生性别比持续偏高将会产生的婚姻挤压、异质性婚姻增加等现象进行了论述。     

活塞挤压铸造用高性能铝合金材料的制备研究

针对现有铝合金材料不能满足动力机械用的薄壁高强韧铝合金零件的要求,通过改进材料配方和制备方法,得到符合铝合金挤压铸造工艺要求的高强韧新材料。实验结果表明,利用该材料生产的铸件平均抗拉强度达到300MPa,高温抗拉强度268MPa,伸长率超过1.73％,硬度超过HB95,微观组织晶粒致密,基本无缩松缩孔等缺陷,达到了高性能要求。     

涌潮冲击丁坝时涌潮压力初步研究

钱塘江涌潮压力的作用性状及大小一直是困扰工程界的一个难题。本文采用VOF方法．对涌潮冲击丁坝过程中的涌潮压力进行了计算,并与原位测试结果进行对比。从而揭示了涌潮压力的部分规律：(1)涌潮对丁坝的破坏力最大的时刻是在涌潮冲击丁坝的瞬间;(2)涌潮压力随时间的变化规律;(3)涌潮压力在垂线方向上的分布。为排桩式丁坝的设计提出了新型的受力模式。