一种新型图解法在无压流圆形断面水力计算中的应用

通过对圆形断面无压流水力计算公式进行适当变换,建立了在一定流量备件下求解其正常水深与临界水深的数学模型,并针对实例采用Matlab语言进行了编程计算,其过程简单,结果精确。     

基于能坡线法的微灌双向异径毛管设计

根据最佳支管位置是位于使两侧毛管灌水器平均工作压力相等处的定义,基于能坡线法推导了微灌双向异径毛管的最佳支管位置、进口工作压力、水力流量偏差系数及极限管长的计算公式,并给出了最佳支管位置参数的数值表。以此为基础,提出了3种常见设计情况下的微灌双向异径毛管设计步骤。通过3个设计实例表明:该方法准确可靠,可以简便快速地设计各种均匀坡条件下的微灌系统双向异径毛管,提高微灌工程设计效率。     

液压脉动衰减器的动态品质

用集中参数法根据液压系统中流量脉动与压力脉动的关系提出了能够准确反映液压脉动衰减器动态品质的概念——液压脉动衰减函数,由此得出关于液压脉动衰减器的一般设计原则,据此对涡流型液压脉动衰减器进行了理论分析和实验研究。     

模型铲刀表面的法向压力及其土壤粘附

采用模型试验法，利用模型铲刀和小型压力传感器对模型铲刀表面的法向压力分布规律及土壤流动、粘附情况进行了试验研究，拟合出模型铲刀表面法向压力的回归方程。研究结果表明，法向压力在模型铲刀表面呈二次曲面分布，在模型铲刀的中部取得最大值。法向压力的变化引起土壤变形区域的含水量发生改变，导致土壤粘附主要发生在模型铲刀的上部和下部。     

Purple spot in loquat (Eriobotrya japonica Lindl.) is associated to changes in flesh-rind water relations during fruit development

Experiments were conducted to assess the link between purple spot in loquat fruit (Eriobotrya japonica Lindl.) and changes in the water relations of the flesh and the rind. Panicles were thinned to 1, 3 or 5 fruit or left unthinned (control), fruit wrapped in foil or exposed to the sun, or trees grown under plastic (night temperature >15 °C) or in the open (night temperature 5–3 °C) to induce different levels of the disorder. Typically, spotting increased with thinning (R² = 0.95), and was higher in exposed fruit (26.3% of fruit affected) than in wrapped fruit (nil), and higher with cool nights (16.2%) than with warm nights (2.7%). Mean tissue water potential (Ψ_w) was similar in the flesh and rind, whereas osmotic potential (π) was higher (less negative) in the flesh, and pressure potential (Ψ_p) lower in the flesh. There were no consistent effects of thinning on Ψ_w, whereas π of the rind decreased (more negative) with thinning during fruit color break. This response was associated with an increase in Ψ_p (more positive) in the rind at the same time. The external rind of exposed fruit had lower π than the external rind of warped fruit, and higher Ψ_p. Similarly, the fruit from trees grown under cool nights had lower rind π and higher rind Ψ_p than fruit under warm nights. These results suggest that low rind π and high rind Ψ_p are associated with purple spotting in loquat, and possibly reflect relatively high sugar concentrations in the flesh that increases the gradient of solute concentration between the flesh and the rind, making easy a dehydration process in the rind, which is responsible for purple spot.     

Influences of ultra‐violet (UV)‐blue light radiation on the growth of cotton. II. Photosynthesis,leaf anatomy,and iron reduction

Cotton (Gossypium hirsutum L.) plants grown under low pressure sodium lamps (LPS) developed chlorosis which was similar in appearance to iron‐stress induced chlorosis, while plants under cool white fluorescent lamps (CWF) at the same level of photosynthetically active radiation (PAR) developed normally. These illumination sources differ in spectral irradiance; CWF lamps emit ultra violet (UV), whereas LPS lamps do not. Ultraviolet radiation is capable of reducing Fe³⁺ to Fe²⁺ through a chlorotic leaf which may be important in establishing an active iron fraction in the leaf. Root reduction of Fe³⁺ to Fe²⁺ was lacking in Fe‐stressed cotton under LPS light, but was present under CWF light. Net photosynthesis, photosynthetic electron transport, and leaf chlorophyll content were lower under LPS than CWF light in most of the growing media studies (soil or solutions with nitrate‐ or ammonium‐nitrogen supplied). Chloroplast ultrastructure and leaf thickness were also altered by LPS irradiance. Electron microscopic studies with plants grown in nutrient solutions for 4 weeks suggested that chioroplastic granal disorganization was more directly associated with diminished iron supplies than with light source. However, plants grown in soil for 6 weeks under LPS light had granal disorganization similar to that found in iron‐stressed plants. These studies suggest an important role for UV radiation in influencing the activity of iron in plants.     

Treatment of shoulder ulcers in sows – rubber mats and zinc ointment compared to chlortetracycline spray

Background

Shoulder ulcers can have a significant impact on the welfare of sows. In Denmark, rubber mats are used for treatment of shoulder ulcers. The objective of the study was to compare a treatment consisting of a combination of rubber mats and zinc ointment with the effect of local antibiotic spray (chlortetracycline) on shoulder ulcers.

Methods

A total of 304 sows with shoulder ulcers were observed shortly after farrowing (day 1) and on days 14 and 21 after the first observation. The sows were paired according to the grade of the shoulder ulcer using the official Danish scoring system. From each pair of sows, one sow was allocated to mat group (M) and the other to an antibiotic group (A) in a random way. In the M group, rubber mats were placed on the floor, and the ulcers were treated with zinc ointment once a day. In the A group, sows were treated with antibiotic spray daily. The size of the shoulder ulcer was measured manually on a continuous scale on days 1, 14 and 21. The data were analysed by use of two multivariable models where the response was the area of the shoulder ulcer on day 14 and day 21, respectively. Explanatory variables were treatment, herd, parity, body condition and size of ulcer on day 1. If a sow had an ulcer on both shoulders, the shoulder with the largest ulcer was selected.

Results

The treatment consisting of mats and zinc ointment had a statistical significant effect on the size of the shoulder ulcer on day 14 and day 21 compared to daily treatment with antibiotic spray. For lean sows that were kept on rubber mats and zinc ointment, the average shoulder ulcer was significantly smaller on day 14 (3.8 cm² versus 9.5 cm² when antibiotic spray was used) and day 21 (3.4 cm² versus 6.6 cm²) compared to lean sows that were only treated with antibiotic spray. For fat sows this was also the case when using the lesion on day 21 as the response (2.0 cm² versus 5.7 cm²) but not on day 14. Moreover, the size of the lesion on day 1 was statistically associated with the size of the lesion on day 14 and on day 21. The treatment was equally effective in the three herds.

Conclusions

Rubber mats and daily smearing with zinc ointment slow progression and contribute to the healing of shoulder ulcers compared with housing on slats and daily spraying with antibiotics. It is recommended to place a rubber mat in the farrowing crate at the first sign of shoulder ulcers.     

挡墙设计中土压力计算的几个问题的探讨

本文从挡土墙设计计算内容来说明土压力计算在挡土墙设计中的重要性 ,重点分析了影响土压力大小的因素 ,探讨了土压力计算误差的根由 ,并指出概念设计在挡土墙设计施工过程中的指导作用     

歧管压力计在汽车空调故障诊断中的应用分析

空调歧管压力计是对汽车空调系统整体工作性能进行分析的一种常用且有效的工具,它不仅应用于制冷剂的加注,而且也是一种故障诊断工具。文中就歧管压力计在空调系统中不同压力显示时的故障原因进行分析,为技术人员用歧管压力计对空调系统的运行状况及其故障进行诊断与排除提供相应的理论与实践借鉴,以保证或维持空调系统正常运行。     

Expression of VEGF and bFGF in rat model of pressure ulcer

AIM:To study the effects of vascular endothelial growth factor(VEGF) and basic fibroblast growth factor(bFGF) on the molecular pathogenesis of pressure ulcer.METHODS:SD rats were randomly divided into control group and experiment group. The pressure ulcer model was established by magnetic disk circulating compression method. HE staining was used to observe the pathological changes of the skin in the rats. The expression of VEGF and bFGF in the tissues was detected by immunohistochemical method. RESULTS:The expression of VEGF and bFGF in the tissues of rat Ⅲ-degree pressure ulcer was lower than that in the surrounding tissues and normal skin(P<0.01). The changes of VEGF and bFGF were consistent(κ=0.58). CONCLUSION:The expression levels of VEGF and bFGF are decreased in the tissues of rat pressure ulcer, suggesting that they may be the potential key factors in the difficult healing of pressure ulcer.