Experimental Analysis of Local Pressure Losses for Microirrigation Laterals

The accurate design of drip irrigation laterals needs to consider the variation of hydraulic head due to pipe elevation changes, head losses along the lines, and also, at a given operating pressure, emitter discharge variations related to manufacturing variability, clogging, and water temperature. Hydraulic head variations are consequent to both the friction losses and local losses due to the in-line or on-line emitters along the pipe, which determine the contraction and subsequent enlargement of the flow streamlines. Moreover, in-line emitters usually have a smaller diameter than the pipe, and therefore an additional friction loss must be considered. Evaluation of energy losses and consequently the design of drip irrigation lines is usually carried out by assuming the hypothesis that local losses can be neglected, even if previous experimental researches showed that local losses can become a significant percentage of total head losses as a consequence of the high number of emitters installed along the lines. This paper reports the results of an experimental investigation to evaluate local losses in integrated laterals in which coextruded emitters are installed inside the pipe. Local losses were measured for 10 different types of commercially available integrated laterals and for different Reynolds numbers. A practical power relationship was deduced between the α coefficient, expressing the amount of local losses as a fraction of the kinetic head, and a simple geometric parameter characterizing the geometry of the emitter and the pipe. Local losses obtained for integrated laterals were then compared with those due to the on-line emitters, previously determined as a function of the pipe-emitter geometry. The proposed criterion for calculating the local losses was finally verified by using a step-by-step procedure.     

浅谈双支管滴灌系统在果棉间作套种中的应用

发展间作套种经济是促进农民增收的有效途径。在水资源严重短缺的情况下,对间作套种的作物如何实施高新节水灌溉问题进行研究具有非常重要的现实意义。为此,引入双支管滴灌系统技术,并以新疆皮山县为例,对红枣套种棉花进行了双支管滴灌的设计。实施和运行结果表明,双支管滴灌系统有效地解决了间作套种情况下的作物灌溉问题,为今后在立体种植模式条件下的滴灌设计提供了重要的技术依据和宝贵的实践经验。     

短流程工艺铸造金属颗粒的研究

研究了一种短流程工艺铸造金属颗粒设备,包括预热室、加热炉、金属熔液输送陶瓷管、保温炉、定量器滴嘴和冷却箱等。该设备可以实现铸锭的预热、熔化、保温和造粒过程一次完成。其中铸锭预热温度为100～120℃。铸锭熔化后,采用陶瓷管将金属液输送到保温炉内,保温炉金属液温度控制在金属熔点以上25～28℃。在保温炉底部,安装多个定量器滴嘴,保温炉内的金属液流经定量器滴嘴后,滴入保温炉下方的冷却箱内,金属颗粒在冷却水中停留10～18s。最后通过斗式提升机直接输送到包装箱内。采用短流程工艺制备金属颗粒,具有能耗低、效率高等优点,比普通流程降低能耗15％～20％,制备的金属颗粒固整、致密,表面光洁、无裂纹、无夹渣,且尺寸均匀稳定。     

相容剂改性PE/PP共混物在滴灌带中的应用

介绍了相容剂改性聚乙烯/聚丙(烯PE/PP)共混物在生产滴灌带中的应用,探讨了相容剂改性PE/PP共混体系的相容机理,通过大量的实验找到了最佳配比方案。结果表明:以相容剂改性PE/PP共混物生产的滴灌带与普通滴灌带对比界面黏结性强;改善和提高了PE/PP共混物的相容性和力学性能。     

Changes in water holding capacity and drip loss of Atlantic salmon (Salmo salar) muscle during superchilled storage

Changes in water holding capacity and drip loss of Atlantic salmon (Salmo salar) fillets during superchilled storage were studied. Due to the significant differences in ice crystal sizes observed in our previous study, the liquid loss (LL) was analysed separately, at the surface and centre of the superchilled samples. No significant differences were found in LL between surface and centre parts of the superchilled samples. No significant difference in the LL was observed from surface samples between 1 and 14 days of storage. There was a significant difference in the LL at day 1 of the centre samples, but no significant differences were observed between 3 and 14 days of storage. In contrast, the LL was significantly decreased at day 21 both at the centre and the surface of the superchilled samples. No significant difference (p < 0.05) was found in drip loss between 1 and 14 days of storage for the superchilled samples. A significant increase in drip loss for the superchilled samples was observed at day 21. These findings are significant for the industry because it provides valuable information on the quality of food in relation to ice crystallisation/recrystallisation during superchilled storage.     

新型单回程烟管0.7～14MW与1～20t/h系列卧式燃油(气)锅炉的开发

文章介绍了卧式燃油(气)锅炉应用螺纹烟管后，烟管由双回程改为单回程的必然趋势与明显优越性；提出了防止锅炉尾部滴水、高温管板开裂与降低局部水位升高的可行措施。     

温室滴灌施肥条件下水肥耦合对番茄产量影响的研究

在滴灌施肥条件下,采用311A—D最优饱和设计,通过温室小区试验,研究了水肥耦合效应对番茄产量的影响。通过主因素、单因素效应分析,定量地评价了灌水下限、氮肥用量和钾肥用量与番茄产量的关系,提出了目标产量的最优水肥组合方案。     

Phospholipase A2 and antioxidant enzyme activities in normal and PSE pork

In order to reveal the relationship between phospholipase A₂ and antioxidant enzymes and drip loss in pork, the study was designed to examine the effects of phospholipase A₂ and antioxidant enzymes on the water-holding capacity of pork during postmortem chilling. Six PSE and RFN samples (longissimus muscle) were used to determine the activities of phospholipase A₂ (tPLA_2, cPLA₂ + sPLA₂ and iPLA₂), superoxide dismutase (SOD) and GSH-Px, and acid phospholipase. The results showed that pH_1 h and pH_24 h from PSE pork were lower (p < 0.01) than for normal pork (RFN), but the L* value at 1 h and 24 h postmortem, TBARS content, drip loss at 48 h and 96 h, cooking loss, tPLA₂ activity and iPLA₂ were higher (p < 0.01) than of normal pork. Correlation analysis indicated that drip loss at 48 h was negatively related to pH_1 h (p < 0.01) and pH_24 h (p < 0.01) but positively to T_1 h (p < 0.01) and the activities of total phospholipase A₂ (p < 0.05) and calcium-independent phospholipases A₂ (p < 0.01). The tPLA₂ and GSH-Px play important roles in drip loss.     

长期滴灌棉田耕层土壤盐分累积特征研究

针对长期膜下滴灌棉田灌区土壤次生盐渍化问题,研究了膜下滴灌条件下土壤盐分随种植年限的变化特征,结果表明:在实施膜下滴灌的最初1―5年,土壤盐分整体呈现随种植年限的推后而降低的趋势,表层5cm及深层100cm始终处于积盐趋势;实施膜下滴灌技术6年以上的地块,其盐分值基本保持在0.2%左右,处于完全脱盐状态,土壤盐分恢复新的平衡。本研究可以为试验区膜下滴灌技术的应用提供理论参考,对水土资源的可持续利用有着重要的意义。