叶片式脉动发生器的设计与实验

设计了一种叶片式脉动发生器,并进行了实验.实验结果表明:通过周期性开、闭管路的方法,叶片式脉动发生器可以实现对流体的脉动作用,获得脉动流.该脉动发生器具有沿程脉动效果损失低,所产生脉动作用具有传递性的特点.形成脉动流的脉动振幅随脉动频率的变化而有所改变.引入叶片式脉动发生器会对管路流速产生一定的影响,脉动频率与流速间呈现非线性关系.     

A new technique to measure soil CO2 efflux at constant CO2 concentration

A new principle for measuring soil CO₂ efflux at constant ambient concentration is introduced. The measuring principle relies on the continuous absorption of CO₂ within the system to achieve a constant CO₂ concentration inside the soil chamber at ambient level, thus balancing the amount of CO₂ entering the soil chamber by diffusion from the soil. We report results that show reliable soil CO₂ efflux measurements with the new system. The novel measuring principle does not disturb the natural gradient of CO₂ within the soil, while allowing for continuous capture of the CO₂ released from the soil. It therefore holds great potential for application in simultaneous measurements of soil CO₂ efflux and its δ¹³C, since both variables show sensitivity to a distortion of the soil CO₂ profile commonly found in conventional chamber techniques.     

六要素自动气象站资料的二次开发和应用

通过对逐时六要素自动气象站资料的二次开发,利用逐时六要素气象资料,对一些物理量公式进行计算机编程计算,自动生成逐时的水汽压、相对湿度、本站气压、位温及14：00浮力共5个物理量产品,并把它保存为能被M icaps系统调阅的第三类数据格式文件。通过对2009年发生在南平市的一次强对流天气过程分析表明,应用这些新增加的物理量产品,将提高对中小尺度系统,特别是强对流天气的短时监测、预报和预警能力。     

射水减弱混流式水轮机尾水管内压力脉动的数值模拟

选用RNGk-ε湍流模型,对一台混流式模型水轮机在部分负荷工况下的流动进行了全流道三维瞬态湍流数值模拟.数值计算结果与模型试验结果进行了比较,成功预测了水轮机尾水管内压力脉动的幅值与频率特性.从混流式水轮机泄水锥处向尾水管内射水可减弱尾水管内低频压力脉动,对射水后水轮机内的流动进行了数值模拟.计算结果表明,通过射水可以有效减弱尾水管内的压力脉动,减小压力脉动幅值.随着射水量的增加,压力脉动幅值减小更加明显,但是同时会导致水轮机效率的下降.为了尽可能大的减小压力脉动幅值,并兼顾水轮机效率,建议选择0.03～0.05倍该工况流量的射水量.此时,水轮机压力脉动幅值降低明显,而水轮机效率下降不大.     

武汉城市圈边缘区域耕地压力与耕地红线研究——以赤壁市为例

耕地红线是国家粮食安全和生态安全的重要保障,然而科学合理的划定耕地红线仍是目前研究领域的一个难点.该研究运用“耕地最低保有量”和“耕地压力指数”法,探讨区域耕地红线的划定方法并分析当前赤壁市各乡镇耕地红线状况.结果表明：2003 ～2012年赤壁市耕地面积总体上呈先减少后增加的趋势,实际人均耕地面积和标准人均耕地面积均有降低趋势,粮食总产和单产在波动中有所增加,耕地压力指数先减后增.2010年后赤壁市耕地压力增大,主要原因是新增耕地利用效率较低.赤壁市各乡镇间耕地压力状况差异较大,耕地压力最小的柳山镇只有0.38,而压力最大的陆水湖办事处高达22.59.目前陆水湖办事处、蒲圻办事处、赵李桥镇和官塘驿林场已经越过区域内部的耕地红线,建立区际之间的占补平衡和实施有效的土地流转制度是减缓区域耕地压力的有效措施.     

环境温度对拖拉机压敏胶标签剥离强度的影响

考察了温度变化对拖拉机用压敏胶平面标签180°剥离强度的影响,并模拟季节变化及现场粘贴情况,对压敏胶标签的剥离强度进行分析。结果表明,不同品种的压敏胶标签由于压敏胶粘剂自身特性的不同,达到最佳剥离性能的粘贴环境温度也不同。拖拉机压敏胶标签粘贴时,可根据环境温度的不同,选择合适的压敏胶标签,或适当控制被粘贴面温度,以达到理想的粘贴效果。     

山区滴灌工程灌溉参数与减压阀位置设计

滴灌具有高效节水、省工节地、增加产量等优点。山地滴灌工程设计、灌溉参数的设计与压力控制是保证工程正常运行的关键,为了充分发挥滴灌工程效益,结合实际工程,对微灌工程的耗水强度、补水强度、土壤湿润比、灌水均匀度等参数做了计算,对管道布置、毛管长度、轮灌组做了设计并对支管入口压力与减压阀位置做了分析,得出了滴灌耗水强度和补水强度均为6mm·d-1,湿润带宽75cm,灌溉湿润比值48%,在计算水压为3~4kg范围内安放减压阀的结论,可为类似的工程设计提供参考。     

Radial pressures generated by the earthworm Aporrectodea rosea

Summary The radial pressures generated by the earthworm Aporrectodea rosea were measured in a study of the conditions under which the worms were able to crack soil discs into which they were encouraged to tunnel. The tensile strength of replicate discs was determined by indirect tension tests and by expansion of rubber membranes in soil discs. Simple engineering theory was used to relate the stress required to fracture a disc with the applied internal stress. Mean values for the radial stress applied by the earthworms in tunnelling through the discs was 230 kPa. With some assumptions about the distribution of muscles across the worm diameter, it was estimated that the mean maximum force generated by all the longitudinal muscles in any segment was 3.2 N.     

Rice yield reduction by chamber enclosure: a possible effect on enhancing methane production

Major rice growth characteristics and grain yield were compared between inside and outside of a chamber coverage area after a seasonal CH₄ and N₂O flux measurement using a closed chamber technique. Results show that only grain yield was significantly (P<0.01) reduced by chamber enclosure. There was no significant difference (P>0.05) in plant height, total straw weight, spike length, and average grain weight. Temperature increase during the gas flux measurement was likely the major cause for the observed grain yield decrease by sterilizing rice reproductive organs. Methane flux rates from rice fields were likely overestimated by using closed chamber technique because decreasing grain yield by chamber enclosure may result in more plant photosynthesis products released into soils to enhance CH₄ production. Analyzing CH₄ and CO₂ emission ratio from the rice field, after cutting the above-water part of rice plants, indicated that CH₄–C emission accounted for approximately 13% of the total CO₂ and CH₄–C emission during the major rice growing season.     

超高压处理对绵羊肉嫩化机理的研究

实验研究了超高压处理条件下绵羊肌肉感官特性、显微结构、钙激活酶(Calpains)粗酶活性和剪切力值的变化，并探讨了超高压处理对绵羊肌肉的嫩化机理。超高压处理后绵羊肌肉的感官特性发生变化，随处理压力升高，绵羊肌肉颜色变淡，出现轻微的类似蒸煮的成熟风味。在压力为400 MPa，保压时间为10 min的处理条件下，绵羊肌肉显微组织结构变化明显：肌节收缩，肌原纤维的Z线断裂，M线降解，I带变白。当压力水平在100～400 MPa范围变动时，随压力升高，Calpains粗酶活性显著下降(P＜0.01)；当压力达到400 MPa时，Calpains粗酶活性几乎失活。超高压处理后绵羊肉的剪切力值显著下降(P＜0.05)。实验结果表明，超高压处理促进了绵羊肉的嫩化。