割草压扁机变速箱斜交锥齿轮设计与强度分析

为解决割草压扁机工作过程中传动轴转动角度过大引起的失效问题,设计一对斜交锥齿轮传动,计算锥齿轮的几何参数,校核锥齿轮的弯曲和接触疲劳强度。结果表明,设计的斜交锥齿轮强度满足使用需要,为后续斜交锥齿轮传动的设计与应用提供了重要的理论依据。     

基于流热固耦合的高温熔盐泵转动系统结构应力分析

基于ANSYS Workbench平台开展高温熔盐泵转动系统的结构应力分析,采用计算流体动力学软件CFX对泵内部全流场进行多工况定常数值计算,并通过试验对计算结果进行验证.综合考虑了高温熔盐泵的水动力载荷、离心力载荷、温度载荷等因素,建立了流、热、固耦合作用下动力学模型,研究不同温度下不同材料属性变化对高温熔盐泵结构性能的影响,并对高温熔盐泵转子部件进行应力分析.结果表明:在同一流量工况下,不同材料的叶轮叶片最大变形量均呈随温度的升高呈先增大后减小的趋势;同时,不同材料的叶轮形变程度基本趋于稳定,受流量影响不大;叶片工作面应力值大于叶片背面应力值,且不同温度工况下不同材料的叶轮背面应力值呈线性递减的趋势;叶轮等效应力最大位置主要集中在叶轮出口处叶片和前、后盖板接触的区域;经过变形及强度综合分析,表明3种不同的不锈钢材料中316L材质的叶轮力学性能最好.研究结果可为高温熔盐泵的结构设计提供一定参考.     

The effect of training on equine metacarpal bone breaking strength

Right third metacarpal bones (n=24) from Thoroughbreds, 24 to 48 months old and in race training, were tested to failure in 3 point bending. The neutral load axis was estimated and the distance from the axis to the outer dorsal cortical surface measured. Mid-diaphyseal dorsopalmar and lateromedial outer cortical and medullary diameters were measured. Breaking strength, cortical area and area moment of inertia were also calculated. Significant correlations were demonstrated between months in training and dorsopalmar bone diameter, cortical area and area moment of inertia. Significant linear models were illustrated between the same 3 variables and number of months in training. It was concluded that increased duration of training significantly enlarges dorsopalmar bone diameter, cortical area and area moment of inertia. Training did not affect metacarpal bone breaking strength as determined by 3 point bending.     

Quality of Ethiopian Durum Wheat Lines in Two Diverse Environments

In Ethiopia, durum wheat is largely used for production of local fermented and flat bread. Two diverse environments (Motta and Adet) were used to evaluate 15 durum wheat genotypes for grain yield and quality traits. The mean flour protein content of genotypes ranged from 10.1 % to 12.5 % and 6.7 % to 8.1 % at Motta and Adet respectively. The mean mixograph development time was 4 min at Motta and 2.8 min at Adet and SDS (Sodium dodecyl sulphate) sedimentation ranged between 10.7 and 32.3 ml across locations. Flour protein content was correlated negatively with mixograph development time and positively with vitreous kernels and single‐kernel hardness at both environments. Mixograph development time was selected to predict the gluten strength. Flour protein content, SDS sedimentation and seed weight were included in a stepwise regression. A prediction model was compiled that explained 69 % of the variation for mixograph development time.     

我国文化产业发展环境研究

在当前我国产业结构调整和优化过程中 ,文化产业异军突起。但文化产业发展还必须有适宜环境。因此 ,必须采取有效措施和通过规范化的途径 ,搞好我国自然环境保护 ,维系好自然界生态平衡 ,倡导民主自由 ,创立宽松健康政治氛围 ,抓好精神文明建设 ,提高国民现代化素质 ,保障文化产业健康发展。     

Therapeutic exercise

Therapeutic exercise is a key component of any rehabilitation program and should be included as part of the concurrent care of any patient whether that patient has two or four legs. Physical therapists have been utilizing therapeutic exercises with great success since the conception of the profession in the beginning of the twentieth century and it has been demonstrated to be fundamental in improving function, performance and disability. Therapeutic exercise can consist of a variety of exercises inclusive of balance, strengthening, range of motion, endurance, and plyometric activities. The goals of therapeutic exercises include the restoration of movement, improvement of function and strength, improvement in gait and balance, and the prevention and the promotion of health, wellness, and fitness. Specific exercises are aimed at restoring strength, power and work, or endurance, or a combination. Therapeutic exercises are also utilized to increase range of motion, decrease pain, improve balance and proprioception, and restore function.     

Wind erosion from crusted playa surfaces by no saltation and with saltation: A comparison through laboratory wind tunnel experiments

Playas are common in many arid regions and recognized as a major source of hypersaline particles. A better understanding of wind erosion on crusted playas has significant implications for land management and pollution control practices. We hypothesized that wind erosion rates of crusted playas were complicated and controlled by the interactions between playa crust and wind-induced saltation conditions. However, comparisons regarding the effects of different playa crusts on wind erosion under no saltation (NS) and with saltation (WS) conditions were lacking. In this study, laboratory wind tunnel experiments were carried out to simulate both NS and WS conditions, to investigate the erosion rates of different crust types (Salt, Takyr, and Puffic crust) at different wind speeds. Results showed that: 1) Salt crust had greater crust strengths than did Takyr crust and Puffic crust; 2) wind erosion rates under the WS condition were up to 60 times greater than those under the NS condition, suggesting that sand bombardment was the dominant mechanism responsible for removal of fine material from crusted playa surfaces; 3) both sand bombardment rate and wind erosion rate of the playa crusts increased with increasing wind speed under the WS conditions; 4) Puffic crust exhibited a greater rate of wind erosion compared to both the Takyr and Salt crusts under the NS condition, yet tended to have a lower rate of wind erosion compared to both the Takyr and Salt crusts under the WS condition. This difference can be attributed to the fact that soft Puffic crusts are pliable and can dissipate the force of impacting grains under the WS conditions. Our results indicated that wind erosion processes on crusted playas are complicated and are affected by wind-induced saltation and crust type, specifically crust strength and elasticity of the surface.     

The effect of cellulase treatment on hydrolysis of linen

In this paper, the effect of cellulase treatment was evaluated by means of phenol-sulphuric acid method. This method was performed by determining sugar liberation in the treatment bath with the amount expressed in glucose equivalent. As compared with conventional method, the measurement of amount of sugar liberated gave a more reliable and accurate result than the weight loss method. It was found that although the weight loss of cellulose became negligible when the treatment was done under agitation-free condition, the amount of sugar liberated was still readily measurable.     

Wind transport of sand surfaces crusted with photoautotrophic microorganisms

Wind tunnel experiments show that while surfaces inoculated with photoautotrophic organisms are stable in winds up to 19 m s⁻¹, only filamentous cyanobacteria, especially Nostoc commune, afford considerable protection against abrasion from windborne particles. Crusts formed by the polysaccharide secreting alga Chlamydomonas acidophila break down easily under impact, the entrainment of large, low density aggregates possibly contributing to higher transport rates than would otherwise be expected for untreated sediment. Surface disintegration encompasses a suite of complex, scale dependent processes which vary with the structure, thickness and strength of the crust. Independent measurements of crust strength based on flexure testing are in good agreement with wind tunnel evaluation of crust stability. The accommodation of a relatively large amount of deformation without rupture is an important property of fibrous, photoautotrophic mats, perhaps outweighing consideration of their peak strength.