基于CFD的主轴密封泵板装置结构优化设计

为研究混流式水轮机主轴密封泵板装置内泄漏水流动特性,应用计算流体动力学软件,针对新疆红山嘴一级电站4号水轮机,将不同泵板装置作为研究对象,研究提高其水力效率的可行性以及对主轴密封降压的效果.在模型准确基础上对泵叶角度和泵盖高度分别改进,对两者联合结构共计22种改进模型进行数值模拟.研究结果表明:泵叶斜置45°且泵盖高度比为0.081 5的联合改进结构对主轴密封真空度提高率可达60.9%;泵盖高度比比泵叶角度改变对该装置水力效率提高更有利;泵盖存在“最不利高度比”,泵盖位置的确定需避免最不利高度比0.135 9.该研究结果将模型结构参数化使得结论的普适性有一定提高,为工程实际主轴密封设计改造提供了一定的理论依据.     

黄板诱杀与杀虫剂混剂相配合综合防治温室白粉虱(Trialeurodes vaporariorum(Westwood))的研究

经室内毒力测定证明:虫螨磷与氰戊菊酯(3:1)混用,共毒系数(CTC)达972.1,有显著增效作用。增效磷(SV_1)与氰戊菊酯(5:1)混用有一定增效作用(CTC=274.6)。噻嗪酮的 LC_(50)o值为0.01272ppm,毒力明显高于氰戊菊酯(LC_(50)为475.77ppm),两者混用(5:1)时 CTC 为356.2,倍硫磷与氰戊菊酯(5:1)混用 CTC 为708.4,均有明显增效作用。在农大小温室试验诱杀成虫证明用20×28.5cm~2黄板垂直挂在番茄植株顶部的支架上且黄板底边与植株顶部相平时效果最好。1987～1988两年在四季青温室番茄上对温室白粉虱的综合防治试验证明:在黄板的配合下,氰戊菊酯分别与虫螨磷和 SV_1混用,其防治效果均在84.5%以上,前一种混剂更好在91.6%以上。而喷药次数只需2～3次。单用氰戊菊酯,对成虫和卵、若虫的防治效果1987年分别为95.5%和73.5%,1988年分别为75.3%和35.9%,明显低于混剂的防效。试验还证明,黄板加上噻嗪酮,不仅用药量小(5.685有效成分 g/ha),而且其防治效果在94.8%以上。与综合防治相比,只用农药的常规防治法效...     

退热灵注射液的药效学研究

本文以扑热息痛片剂为对照,对自制的退热灵注射液(含扑热息痛15%)进行了药效学研究。结果表明:退热灵注射液与相应剂量的扑热息痛片剂均具有良好的解热作用,二者的解热效果无显著差异。注射剂起效较片剂迅速,一般给药后15～30min 即呈现明显作用,且体温回升所需时间较长。镇痛试验表明:注射剂对小鼠扭体反应抑制率明显高于相应剂量的扑热息痛混悬液,但注射液只有在高剂量(150mg/kg体重)时才有一定程度的镇痛作用。注射液及混悬液对小鼠热板痛反应时间均无明显影响。退热灵注射液使用方便,解热效果好,在兽医临床上具有实用价值。     

冷藏养殖大黄鱼品质变化特征及细菌相分析

对养殖大黄鱼5℃冷藏过程中品质变化特征及新鲜鱼、货架期终点时细菌相进行了定性和定量分析,用Gompertz方程定量描述了冷藏大黄鱼(Pseudosciaena crocea)细菌生长情况。新鲜大黄鱼菌落总数(TVC)为(5.52±0.41)log10cfu/g,挥发性盐基氮(TVBN)为(10.65±0.41)mg/100g,细菌相比较复杂,革兰氏阴性菌占84.3%,主要包括气单胞菌属(Aeromonasspp.)7.1%,不动杆菌属(Acinetobacterspp.)15.7%,弗氏柠檬酸杆菌(Citrobacter freundii)10.0%,假单胞菌属(Pseudomonasspp.)12.9%,嗜麦芽窄食单胞菌(Stenotrophomonasmaltophilia)18.6%,革兰氏阳性菌玫瑰小球菌(Micrococcus rose)7.1%。货架期终点216~264 h时,菌落总数为(7.63±0.28)log10cfu/g,挥发性盐基氮为(30.35±0.95)mg/100g。冷藏过程中细菌相发生很大变化,腐败希瓦氏菌(Shewanella putrefaciens)增殖比其他细菌快,货架期终点比例为86.0%。     

USE OF FORCE PLATE ANALYSIS TO EVALUATE THE EFFICACY OF EXTERNAL BEAM RADIATION TO ALLEVIATE OSTEOSARCOMA PAIN

A standard of therapy for osteosarcoma includes amputation with or without adjuvant chemotherapy. There is a subset of dogs with osteosarcoma that are unsuitable for amputation. We evaluated kinetic variables in dogs with appendicular osteosarcoma treated with a single 8 Gy dose of radiation. Eighteen pet dogs with appendicular osteosarcoma received one 8 Gy fraction of palliative radiation on day 0. Force plate measurements and clinical assessments were made on days 0, 7, 14, and 21. Peak vertical forces ( F _z) were recorded for each limb and a symmetric index (SI) was calculated. There were no significant changes in kinetic parameters after one 8 Gy dose of radiation therapy. Nine of these 18 dogs exhibited increased limb function at day 21 based on force plate analysis. Significant factors affecting F _z included gender and tumor location. There was a significant correlation between F _z and response to therapy based on SI at day 21. SI seems to be useful to objectively assess response in this mixed population of dogs. One 8 Gy fraction of radiation therapy alone did not reduce lameness associated with appendicular osteosarcoma, but a subset of dogs did have improved limb function after a single dose.     

Worm infections in high and low bodyweight Merino ewes during winter and spring

Objective   To compare infections of gastrointestinal nematodes in 2-year-old ('maiden') spring-lambing Merino ewes in the upper and lower 25% of body weights (BW) at joining.
Design   An observational study over two consecutive years on two farms in western Victoria.
Methods   On each farm, ewes were weighed at the end of mating. Ewes within the upper and lower quartile of BW formed two groups that grazed together for the remainder of the year. On each farm, 20 ewes from each group were also treated with controlled release capsules containing ivermectin to minimise the effects of parasitism. Measures of worm infections were worm egg counts, total worm counts and assessment of breech soiling ('dag score'). Measures of production were BW, numbers of deaths, pregnant ewes and weaned lambs in each group, and response to treatment with a capsule.
Results   No consistent difference was found in mean worm egg counts between ewes in the high and low BW groups and total worm counts of ewes before lambing were not significantly different in either year. Breech soiling of low BW ewes was consistently higher on both farms in both years. Those ewes also reared 7% to 14% fewer lambs. The difference in BW between the low and high groups remained highly significant on both farms throughout both years.
Conclusion   A strategic approach to worm control is appropriate for ewes in both high and low BW categories. Management options for low BW ewes include culling, supplementary feeding to increase BW before mating, or delaying mating for 12 months.     

Fungal N2O production in an arable peat soil in Central Kalimantan,Indonesia

Abstract

To clarify the microbiological factors that explain high N₂O emission in an arable peat soil in Central Kalimantan, Indonesia, a substrate-induced respiration-inhibition experiment was conducted for N₂O production. The N₂O emission rate decreased by 31% with the addition of streptomycin, whereas it decreased by 81% with the addition of cycloheximide, compared with a non-antibiotic-added control. This result revealed a greater contribution of the fungal community than bacterial community to the production of N₂O in the soil. The population density of fungi in the soil, determined using the dilution plate method, was 5.5 log c.f.u. g^?1 soil and 4.9 log c.f.u. g^?1 soil in the non-selective medium (rose bengal) and the selective medium for Fusarium, respectively. The N₂O-producing potential was randomly examined in each of these isolates by inoculation onto Czapek agar medium (pH 4.3) and incubation at 28°C for 14 days. Significant N₂O-producing potential was found in six out of 19 strains and in five out of seven strains isolated from the non-selective and selective media, respectively. Twenty-three out of 26 strains produced more than 20% CO₂ during the 14-day incubation period, suggesting the presence of facultative fungi in the soil. These strains were identified to be Fusarium oxysporum and Neocosmospora vasinfecta based on the sequence of 18S rDNA, irrespective of the N₂O-producing potential and the growth potential in conditions of low O₂ concentration.     

蓄冷板对冷库融霜温度波动影响的模拟及试验研究

为了探究蓄冷板对冷库融霜温度波动的影响,基于计算流体力学(Computational fluid dynam-ics,CFD)对带有蓄冷板冷库的融霜过程进行了数值模拟,并用试验验证了融霜模型的可靠性,得到了冷库在融霜过程中的温度变化云图.同时对采用两台并联冷风机连续融霜的小型冷库,在冷风机结霜时有、无蓄冷板和冷风机不结霜时有、无蓄冷板进行了试验研究,结果表明,在融霜过程中,通过对不同高度截面温度场进行温度测试发现:带蓄冷板的冷库温度均低于无蓄冷板的冷库温度;融霜风机融霜期间,制冷风机有霜时,蓄冷板使冷库温度波动下降了47.20％;制冷风机无霜时,蓄冷板使冷库温度波动下降了58.95％.     

Accuracy of the composite somatic cell count to detect intra-mammary infection in dairy cows using latent class analysis

The somatic cell count (SCC) is considered an important indicator of intra-mammary infection (IMI). The purpose of this study was to determine the accuracy of both SCC and culture to detect IMI and their conditional dependence by means of latent class methods. This study involved 175 dairy cows from 2 herds with different udder infection prevalences. Quarter and composite milk samples were collected for SCC and bacteriological culture. Latent-class models using Bayesian methods were used to estimate test sensitivity (Se) and specificity (Sp) and population prevalence. The models ran involved only major mastitis pathogens and composite SCC (CSCC). Five thresholds between 100,000 and 300,000 cells/mL were evaluated and the receiver operating characteristics (ROC) curve analysis was performed. Fifty-five percent of the cows had CSCC ≥200,000 cells/mL and 95.4% of the cows had at least one infected quarter either with minor or major pathogens. Considering a threshold of 150,000 cells/mL, the estimated Se and Sp for the CSCC were, 0.80 (95% CrI 0.71–0.88) and 0.57 (95% CrI 0.44–0.71), respectively. The estimated culture Se and Sp were 0.83 (95% CrI 0.73–0.93) and 0.89 (95% CrI 0.74–0.98), respectively. There was no evidence of dependence between CSCC and culture. The area under curve for CSCC was 0.72. To the best of our knowledge, this is the first report of the CSCC accuracy to detect IMI for major pathogens considering the effect of culture misclassification. The estimates provided here could help to examine the performance of sampling schemes based on CSCC to manage udder health.