学校体育与学生心理健康研究

学校体育对学生心理健康具有较大的促进作用. 学校体育在促进学生心理健康发展中应注意教师观念与时俱进、加强校园体育文化建设、面向全体学生、以发展为主、体育运动适度.     

浅析资产减值准备

资产减值是指在谨慎性原则下,资产可能发生的损失.计提资产减值准备可以提高资产的质量,使资产能够真实地反映企业未来获取经济利益的能力.新<企业合计制度>在资产减值准备的计提时间、资产期末计价的模式和计提减值准备后资产的使用及处理等方面没有作出明确具体的规定.因此,应借鉴国际会计准则,统一计量模式,规范资产计提减值准备后的使用及处置的会计处理方法.     

An investigation into the cause of corrosion on indoor bronze sculpture

Abstract

Corrosion noted on a number of nineteenth and twentieth century indoor bronze sculptures in the collection of the National Gallery of Canada was the cause for a major condition survey of its Canadian, American, and European bronzes. The results led to a comprehensive study, which included material analysis. This article outlines the steps undertaken to determine the extent and type of corrosion, its possible cause(s), and potential remediation. The survey included 136 bronzes, of which 40 were selected for an in-depth study. Indoor air quality tests of the current building, housing the collection since 1988, were carried out. The dossiers and database records of the selected sculptures were reviewed to investigate their condition, treatment, and storage history. The metal, patina, and corrosion products were subjected to analysis. More areas of corrosion were generally associated with predominantly green patinas and chloride-containing compounds identified in either patina or corrosion samples. The most frequently identified compounds in the patina samples were atacamite, a copper(II) chloride hydroxide, and cuprite, a copper(I) oxide. The most frequently identified compounds in the corrosion samples were atacamite and rouaite, a copper(II) hydroxide nitrate. The analysis determined that the current environment is not contributing to the surface alterations of the sculptures; however, past storage conditions, chemical residues from artificial patination, and likely casting residues are the main causes of the current condition.     

Optimal machining conditions for turning Ti-6AI-4V using response surface methodology

Machining titanium is one of ever-increasing magnitude problems due to its characteristics such as low thermal conductivity, modulus of elasticity and work hardening. The efficient titanium alloy machining involves a proper selection of process parameters to minimize the tangential force （Fz） and surface roughness （Ra）. In the present work, the performance of PVD/TiA1N coated carbide inserts was investigated using response surface methodology （RSM） for turning Ti-6A1-4V. The effects of process parameters such as speed （v）, feed （/＇）, depth of cut （d） and back rake angle （Ty） on Fz and Ra were investi- gated. The experimental plan used for four factors and three levels was designed based on face centered, central composite design （CCD）. The experimental results indi- cated that Fz increased with the increase in d, f and decreased with the increase in v and yy, whereas Ra decreased with the increase in v and 7y, and increased with d and v. The goodness of fit of the regression equations and model fits （R2） for Fz and Ra were found to be 0.968 and 0.970, which demonstrated that it was an effective model. A confirmation test was also conducted in order to verify the correctness of the model.     

Kinematic effects of repeated turns while running

Abstract

In team sports, non-contact ACL and MCL injuries occur during abrupt changes of direction, like turns or cutting manoeuvres. Fatigue affects dynamic neuromuscular control and increases knee injury risk. This study analysed how lower limb joints and centre-of-mass kinematics are affected throughout a high-intensity running protocol involving repeated 180°-turns. Twenty young men (18–23 years, BMI: 20.8–24.4?kg?m^?2) completed a 5-m shuttle running trial lasting 5?min at an average speed of 75% of their maximum aerobic speed. During the test, cardio-metabolic parameters were obtained, together with joints and centre-of-mass kinematics, using a motion capture system. Kinematic data were compared between the first and the last minute of exercise. Perceived exercise intensity ranged from “hard” to “maximum exertion” and post-exercise lactate concentration ranged from 5.4 to 15.5?mM. The repetition of 180°-turns induced a substantial reduction of hip (?60%, p?<?.001, large effect) and knee flexion (?40%, p?=?.003, medium-to-large effect), and an increase of hip adduction and internal rotation (+25–30%, p?<?.05, medium-to-large effect). Since such movements are factors increasing the likelihood of non-contact knee injuries, we concluded that the prolonged repetition of turns may expose participants to increased risk of ligament failure. Prevention programmes should include discipline-specific neuromuscular training especially in late practices.     

金属离子水解常数的计算

在改进失屏参数计算方法的基础上,根据失屏参数与许多金属元素化学性质相关联,研究得到只用一个参数计算各类金属离子水解常数的方法。     

起动圈端面V型凹槽工艺改进及车夹具设计

本文充分利用切谢加工中的工艺理论,对起动回端面V型凹槽加工中出现的问题进行了工艺改进,根据改进后的工艺设计了专用车夹具,推广了普通车床的加工工艺范围．有效地解决了生产实践中零件加工的质量问题．     

金属材料组织对电解加工质量的影响

工件材料的金相组织对电解加工过程影响很大，球状珠光体组织有利于电解，加工质量好。     

拱型波纹屋盖在风荷载作用下稳定性研究

以W666型金属拱型波纹屋盖结构为研究对象,对不同矢高比、支座边界条件固支的30m跨波纹拱在风荷裁作用下进行了几何非线性稳定性分析,并得出了一些重要结论,这些结论为波纹拱的设计、研究和应用提供了一定的参考和借鉴。