工作压力对滴灌管迷宫流道灌水器水力性能的影响   总被引：1，自引：8，他引：1  

杜少卿  曾文杰  施泽  刘耀泽  李云开  高福栋 《农业工程学报》2011,27(14):55-60

降低滴灌系统灌水器工作压力有望成为减少滴灌系统能耗以及运行费用的一种有效途径,但目前低压灌水器还十分少见。基于此,选取了国内应用较为广泛的5种典型迷宫流道灌水器,分析了不同工作压力区间对灌水器水力性能及消能特征的影响。结果表明：5种灌水器在低压条件下运行对于灌水器流量系数Kd和流态指数x具有一定影响,但对于流态指数x的影响未达显著水平。同一流道类型的灌水器流量系数Kd与无量纲数A/L2呈显著的线性相关关系,不同流道类型之间差异显著。5种灌水器流道内流态为紊流,未发生流态转捩行为,采用常规管道流态转捩雷诺数2200去判断流道内流态是不合适的。  相似文献   

Characterization of geosmin as source of earthy odor in different aroma type Chinese liquors     

Du H  Fan W  Xu Y 《Journal of agricultural and food chemistry》2011,59(15):8331-8337

Earthy odor is one of the most frequent and serious causes for the aroma deterioration in Chinese liquor, which causes a dirty and dusty impression. The odor in Chinese liquor is similar to that of rice husk, one kind of auxiliary material widely used as a filler in the distillation process. So it is experientially hypothesized that such odor may derive from rice husk. In this paper, the gas chromatography-olfactometry (GC-O) technique and gas chromatography-mass spectrometry (GC-MS) were used to discover and identify the characteristic odoriferous zone of Chinese liquor marked by earthy odor. Geosmin was found to be responsible for this odor. The levels of the compound in ten bottled liquors and thirty liquors aging for different years belonging to four different aroma types were determined by the optimized headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method. Quantitative analysis of bottled liquor revealed the presence of geosmin in all aroma type liquors with concentrations ranging from 1.10 μg/L to 9.90 μg/L, except for strong-aroma type liquor. Meanwhile in the aged liquors belonging to the same aroma type, geosmin was detected with significant concentrations and high odor activity values (OAVs) during different years of aging. However, geosmin was not detected in steamed rice husk nor in nonsteamed rice husk, which suggests that rice husk is not the origin of earthy odor in Chinese liquor, and there may be another origin of it during the brewing process.  相似文献   

Screening of danofloxacin residue in bovine tissue by terbium-sensitized luminescence on c18 sorbent strips     

Chen G  Du Y 《Journal of agricultural and food chemistry》2011,59(4):1058-1062

Danofloxacin (DANO) residue in bovine muscle was screened at 200 ng/g by terbium-sensitized luminescence (TSL) directly measured on 10 × 6 mm C18 sorbent strips. The analyte was first adsorbed on sorbent surface by immersion in defatted homogenates. After reagent application and desiccation, TSL was directly measured on sorbent surfaces at λ(ex) = 273 nm and λ(em) = 546 nm. The luminescence intensity was linearly dependent on DANO concentration in the 0-1000 ng/g range (R(2) = 0.9967). A threshold was established at x(200) - 3σ(200), where x(200) and σ(200) are the mean and standard deviation, respectively, of the DANO signals at 200 ng/g. Among 48 blind samples randomly fortified at 0-1000 ng/g, 45 were screened correctly and 3 negative samples were presumed positive. This simple screening protocol has the potential to significantly reduce sample numbers and hence improve sample throughput and save assay costs.  相似文献   

Identification of new strawberry sulfur volatiles and changes during maturation     

Du X  Song M  Rouseff R 《Journal of agricultural and food chemistry》2011,59(4):1293-1300

Two Florida strawberry cultivars, 'Strawberry Festival' and 'Florida Radiance', were harvested at five fruit developmental stages (white, half red, three-quarter red, full ripe, and overripe) at four harvest dates. A static headspace solid-phase microextraction (SPME) sampling technique coupled with gas chromatography (GC) using pulsed flame photometric detection (PFPD) was employed to measure 16 sulfur volatiles in these strawberries. A total of 7 sulfur volatiles have been previously reported, and 9 are reported for the first time in strawberries. Newly identified sulfur volatiles include methyl thiopropionate, ethyl thiobutanoate, methyl thiohexanoate, methyl (methylthio)acetate, ethyl (methylthio)acetate, methyl 2-(methylthio)butyrate, methyl 3-(methylthio)propionate, ethyl 3-(methylthio)propionate, and methyl thiooctanoate. Identifications were based on matching sulfur peak linear retention indexes (LRIs) of unknowns with authentic standards and gas chromatography-mass spectrometry (GC-MS) data. Concentrations were determined using both internal and external standards. Most sulfur volatiles increased with increasing maturity, with only concentrations of hydrogen sulfide and methanethiol remaining relatively consistent at all five stages. At the white and half red stages, most sulfur volatiles consisted of various alkyl sulfides. At three-quarter red (commercial ripe), full ripe, and overripe stages, the majority of sulfur volatiles consisted of sulfur esters. Most sulfur volatiles increased dramatically between the commercial ripe, full ripe, and overripe stages, increasing as much as 100% between full ripe and overripe. Principal component analysis indicated that sulfur volatiles could be used to distinguish overripe from full ripe and commercial ripe berries.  相似文献   

磷在潮土肥际微域中的迁移和转化   总被引：3，自引：0，他引：3  

杜振宇  王清华  周健民  王火焰 《土壤学报》2012,49(4):725-730

采用室内土柱实验研究了磷在潮土肥际微域中的迁移和形态转化。结果表明,磷在潮土中的移动距离很短,经过7 d和28 d的迁移,磷的迁移距离仅为8～14 mm。施入的磷主要固定在紧靠施肥点2 mm土体范围内,随距施肥点距离的增加,土壤水溶性磷、酸溶性磷和有效磷的含量呈指数曲线迅速降低。磷在施肥后7 d内的迁移量较大,迁移进入土壤的磷绝大部分被吸附固定。施肥量对不同形态磷在肥际微域中的迁移量产生显著影响;但培养时间只明显影响了水溶性磷的迁移量。  相似文献   

基于多源遥感数据的综合干旱监测模型构建   总被引：1，自引：7，他引：1  

杜灵通  田庆久  王磊  黄彦  南岭 《农业工程学报》2014,30(9):126-132

在全球气候变化越来越复杂的大背景下,准确监测华北粮食主产区的旱情对区域农业生产有重要的指导意义。以往的遥感干旱监测方法多侧重于监测土壤或植被等单一干旱响应因子,反映综合信息的能力较差,为此该研究使用中分辨率成像光谱仪(moderate-resolution imaging spectroradiometer,MODIS)、热带降水测量计划(tropical rainfall measuring mission,TRMM)卫星等多源遥感数据,在综合考虑干旱发生发展过程中的土壤水分胁迫、植被生长状态和气象降水盈亏等因素的基础上,利用空间数据挖掘技术,构建综合干旱监测模型,并以山东省为例进行了试验验证。结果表明,模型监测出山东省近年来所经历的重大干旱过程与实际旱情一致,模型输出的旱情指标-综合干旱指数(synthesized drought index,SDI)与小麦的标准化作物单产变量的相关系数均大于0.7(P0.05);在小麦和玉米的生长期,综合干旱指数与作物受灾面积的相关系数在-0.67～-0.85之间,与标准化降水指数(standardized precipitation index,SPI)的相关系数在0.44～0.67之间,且通过了P0.01的极显著检验(3月份除外)。研究结果为综合评估区域干旱提供了一种新的方法。  相似文献   

高速插秧机钵体毯状苗纵向送秧装置的设计与试验     

杜立恒  俞高红  张国凤  李革  刘大庆 《农业工程学报》2014,30(14):17-25

基于现有高速插秧机平台,改进设计适用于钵体毯状苗的纵向送秧装置。对钵体毯状苗的插秧特点进行分析。针对钵体毯状苗对纵向送秧装置的要求,对纵向送秧装置进行了详细的理论分析和设计。通过Solidworks建模并对装置的工作状态进行虚拟仿真。设计加工样机进行试验分析,试验结果表明,多次纵向送秧误差均在2 mm以内,且不存在累积误差,故满足设计要求。保证了机器在高速工作状况下,纵向送秧的精度和非送秧过程时秧苗的纵向位置固定。该文设计的纵向送秧装置使得钵体毯状苗在插秧机平台上的纵向送秧:精准、稳定、可靠。为钵体毯状苗实现高速机械插秧提供了可靠的设计方案和理论依据。  相似文献   

蜡样芽孢杆菌及其生物被膜对有机酸及乙醇的抗性比较     

李南薇  杜冰  杨公明  余铭 《农业工程学报》2013,29(21):295-300

为比较蜡样芽孢杆菌及其生物被膜对环境压力的抗性,该文主要研究了4种有机酸（乙酸、柠檬酸、乳酸和苹果酸）和乙醇对蜡样芽孢杆菌及其生物被膜存活率的影响。结果表明：生物被膜态蜡样芽孢杆菌对乙酸的抗性高于浮游态菌。扫描电镜结果显示,经乙酸处理后,浮游态蜡样芽孢杆菌的细胞表面严重受损,而生物被膜态菌的表面形态未发生明显变化。在柠檬酸、乳酸、苹果酸和乙醇存在的条件下,生物被膜态蜡样芽孢杆菌比浮游态菌表现出更强的压力抗性,特别是在高浓度（有机酸16%～20%,乙醇50%～60%）的情况下,该现象尤为显著。因此,在食品工业中控制被膜态蜡样芽孢杆菌对预防和阻止食品腐败非常重要。该研究结果为实际生产中有效控制蜡样芽孢杆菌及其生物被膜的形成提供参考。  相似文献   

激光平地改善土壤水盐分布并提高春小麦产量   总被引：7，自引：6，他引：7  

白岗栓  杜社妮  于健  张沛琪 《农业工程学报》2013,29(8):125-134

为了促进激光平地技术的应用与推广,在河套灌区以普通畦田为对照,分期、分段测定了激光平地畦田0～80 cm土层土壤水分、土壤盐分及春小麦生长状况。结果表明,从渠口到畦尾,激光平地畦田不同地段的土壤水分在春小麦生长的不同时期无显著差异,但从拔节期开始,上层土壤盐分逐渐升高;普通畦田从三叶期开始,上层土壤水分、盐分逐渐提高,且显著或极显著高于激光平地。普通畦田从三叶期开始,激光平地从拔节期开始,从渠口到畦尾,春小麦的生长状况逐渐变差,千粒质量、产量均逐渐降低,但激光平地的春小麦千粒质量、产量高于普通畦田。激光平地改善了畦田的土壤水分、盐分分布,促进了畦田中后段的春小麦生长,提高了畦田中后段的水分利用率及产出率。  相似文献   

生产建设项目用地土壤风蚀量监测方法与预报模型分析     

杜鹏飞  刘孝盈  宁堆虎 《中国水土保持科学》2013,11(1):117-122

准确掌握生产建设项目用地土壤风蚀量是合理编制水土流失治理方案的必要前提和有效防控人为水土流失的重要基础;但目前对监测方法和预报模型的研究比较薄弱,一些研究中监测方法的适用性和模型参数的准确性还有待商榷。文章系统总结土壤风蚀的观测方法和预报模型,根据这些方法和模型的各自特点,分析它们在生产建设项目中的适用性。认为测扦法、调查法、扫描法、风蚀盘法、集沙仪法、核素示踪法以及Pasak模型和风蚀流失量公式都可以根据不同项目的实际情况和地区特征应用到生产实践中。在此基础上,讨论相关研究的发展方向。本文结果可为生产建设项目土壤风蚀量测算模型的构建提供参考。  相似文献