基于遗传算法的轴向柱塞泵配流盘密封环结构多目标优化

为改善微小型轴向柱塞泵配流副润滑特性,对缸体进行受力分析,建立了配流副油膜润滑模型,以泄漏量、缸体倾覆角、粘性摩擦力矩为优化目标,采用多目标遗传算法(Non-dominated sorting genetic algorithm,NSGA-Ⅱ)对配流盘密封环结构参数进行了优化,包括配流盘密封环径向尺寸R1、R2、R3、...     

Effect of lacrimal punctal occlusion on tear production and tear fluorescein dilution in normal dogs

OBJECTIVE: To evaluate effects of lacrimal punctal plugs positioned in either the upper, lower, or combination of upper and lower lacrimal canaliculi on plug retention and tolerance; tear production, as measured by the Schirmer tear test; and the dilution of fluorescein within the tear film in normal dogs. MATERIAL AND METHODS: Lacrimal punctal plugs were positioned in the lower, upper, or combination of lower and upper plugs in six laboratory-quality Beagles under topical anesthesia. Retention of plugs was evaluated daily from 8 to 23 days by visual inspection and slit-lamp biomicroscopy. Schirmer tear tests (STT 1 without topical anesthesia) were performed at 48-h intervals. Dilution of fluorescein was determined at 5- and 45-min post-fluorescein instillations once weekly. RESULTS: Lacrimal punctal plugs of 0.4 and 0.6 mm in diameter were retained for 14 (lower plugs: 100%) and 23 days (75%), and for the upper plugs at 8 days less often (75%), and were infrequently locally nonirritating. Combination of lower and upper plugs seemed to adversely affect retention of either plug. When loss of the plugs occurred, a next larger size plug was necessary suggesting some stretching of the lacrimal canaliculi occurred. Pre- and postplug placement STT results indicated no change with lower and combination lacrimal punctal plugs, but decreased levels following upper lacrimal punctal plugs. Tear fluorescein levels at 5 and 45 min in control eye (no punctum plugs) were 3.39% and 0.14%, respectively. With lower, upper, and the combination of lower and upper lacrimal puncta plugs, tear fluorescein levels at 45 min were higher than the controls (lower: 0.76%; upper: 0.45%, and combination 0.56%). CONCLUSION: Lacrimal punctal silicone plugs are retained for 8-23 days in the lower, upper, and combined lower and upper canaliculi at high rates. Effects on STT levels appear limited. Fluorescein within the tear film persists longer with all different positioned lacrimal punctum plugs than in the control eyes.     

Effects of fenoldopam mesylate on systemic hemodynamics and indices of renal function in normotensive neonatal foals

BACKGROUND: Fenoldopam mesylate, a dopamine-1 receptor agonist, has dose- and species-dependent effects on hemodynamics and renal function. The effects of this drug in normotensive neonatal foals have not been reported. HYPOTHESIS: Two doses of fenoldopam would result in distinct changes in the systemic circulation, urine output, and creatinine clearance of neonatal foals. ANIMALS: Six Thoroughbred foals. METHODS: Each foal received 2 dosages of fenoldopam (low dose, 0.04 microg/kg/min; high dose, 0.4 microg/kg/min) and a control administration of saline, in a masked, placebo-controlled study. RESULTS: High-dosage fenoldopam had no effect on renal function but caused a significant increase in heart rate and decrease in mean, systolic and diastolic arterial blood pressure compared with saline. Low-dosage fenoldopam had no effects on systemic hemodynamics, significantly increased urine output, and had no significant effect on creatinine clearance or the fractional excretions of sodium, potassium, or chloride compared with saline. CONCLUSIONS AND CLINICAL IMPORTANCE: These data suggest that high-dosage fenoldopam increases heart rate, decreases arterial blood pressure, and has no significant effects on renal function, whereas low-dosage fenoldopam has no significant effects on systemic hemodynamics while increasing urine output. This contrast is unique to this species and warrants further investigation.     

切纵流双滚筒联合收获机脱粒分离装置

提出了一种喂入量为4~5 kg/s的履带式切纵流双滚筒联合收获机的总体配置方案,论述了切纵流双滚筒脱粒分离装置切流脱粒滚筒、切流凹板、过渡口、纵轴流滚筒和纵轴流凹板等结构与运动参数的设计。田间试验与性能测试表明:该机收获水稻时喂入量达到4.86 kg/s时,整机损失率为1.47%,破碎率为0.2%,各项技术指标达到了设计要求。     

Improvement of bacterial clearance and relief of clinical signs of Salmonella enterica serovar Typhimurium infection in pigs through upregulation of Th 1-specific responses by administration of a combination of two silicate minerals,biotite and bentonite

Biotite and bentonite are phyllosilicate minerals that were originally used inindustrial applications. Several beneficial activities of them have recently beenreported, especially regulation of the immune system and antimicrobial effects. Therefore,we investigated the immune-enhancing and bacterial clearance effects of a biotite andbentonite mixture (BBM) on experimental infection of Salmonella entericaserovar Typhimurium (S. Typhimurium) to determine whether the BBM couldbe used as an alternative antibiotic. We administered 1% or 2% BBM as a feed supplement.We then evaluated the bacterial clearance effects of the BBM against S.Typhimurium. We also evaluated the immune-enhancing effect of the BBM through severalimmunological experiments that included examination of the lysozyme activity,CD4⁺/CD8⁺ T lymphocyte ratio and the T-helper type 1 (Th 1)cytokine profile. The clinical signs of S. Typhimurium and the number ofviable bacteria in feces and tissues were significantly decreased in both BBM groups,especially in the 2% BBM group. The BBM also markedly enhanced the lysozyme activity,CD4⁺/CD8⁺ T lymphocyte ratio and expression levels of IFN-γ andIL-12 in S. Typhimurium-challenged pigs. Therefore, the BBM could be agood candidate as an alternative antibiotic that improves Th 1-specific immune responsesand the bacterial clearance effect.     

切纵流双滚筒脱粒分离性能试验

在切纵流双滚筒脱粒分离性能试验装置上,进行喂入量为6kg／s的水稻脱粒分离性能试验,研究其最佳脱粒分离的结构参数和运动参数。试验结果表明,切纵流双滚筒联合收割机收获水稻的最佳组合方式为：切流滚筒间隙27mm,纵轴流滚筒间隙14mm,切流滚筒线速度为25．9 5m/s,纵轴流滚筒线速度为28．23m/s,纵轴流滚筒齿杆间距为140mm。并对切流滚筒脱粒分离籽粒的轴向分布、纵轴流滚筒脱粒分离籽粒的轴向和径向分布进行了研究,为后续清选装置的研究提供了设计依据。     

冷弯卷边槽钢轴压屈曲机理试验与数值研究

对6根冷弯卷边槽钢进行了轴力加载试验.其中4根试件用以研究截面高宽比和长细比对试件屈曲行为、承载力等参数的影响;另2根组合试件用以对比分析组合作用以及组合形式对试件静力性能的改善.试验结果表明：截面高宽比、长细比以及偏心是影响板组效应与承载力的重要因素,能很大程度上影响试件的屈曲形式;组合作用能大大改善试件承载力,不同的组合形式还影响试件的屈曲形式.同时,建立了有限元数值模型,考虑几何和材料非线性,并考虑初始缺陷,将计算结果与试验进行了对比分析,分析结果显示试验与数值模拟吻合良好.     

轴伸贯流泵压力脉动特性及其改善方法

为研究轴伸贯流泵压力脉动特性及其改善方法,应用计算流体动力学数值方法,采用在出水流道内增设导流板的方式进行贯流泵优化设计,并结合真机试验验证了数值计算方法的正确性.研究结果表明:在小流量工况下,原模型与优化模型泵的压力脉动时域特性和频域特性较额定工况下要差,但不同流量工况下叶轮进口处压力脉动特性均受到旋转叶轮显著影响;小流量工况下压力脉动变化强烈,原模型在叶轮出口及后导出口处的压力脉动低频成分明显,增设导流板可有效降低这2处的压力脉动变化幅值及其低频成分;在额定工况下,贯流泵压力脉动周期性规律显著,导流板则能有效降低前导进口及叶轮进口处的压力脉动变化幅值及其低频成分;在不同流量工况下,出水流道内导流板消涡效果均十分显著.     

不同工况下轴流泵转子径向力及其压力脉动分析

【目的】研究轴流泵转子所受径向力及内部压力脉动。【方法】采用试验以及ANSYS CFX定常计算的方法,研究了轴流泵的外特性;采用ANSYS CFX软件对轴流泵内部流场进行了非定常计算,研究了不同流量工况下轴流泵内部转子径向力的分布情况及内部不同监测点压力脉动的时域和频域特性。【结果】(1)数值计算的外特性结果与试验结果的趋势基本吻合,数值计算具有较高准确度;(2)转子运动时,内部流场关于转动中心呈现不对称性;(3)3种流量工况下径向力的分布均呈现一定的周期性,小流量工况下瞬态径向力最不稳定,波动较大,设计流量工况下瞬态径向力较小,大流量工况呈现较好的平衡状态;(4)不同流量工况下压力脉动受叶片数影响,主要以叶频为主,且随着频率的增加,压力脉动逐渐减小,说明低频信号是引起压力脉动的主要原因,从整体来看,各监测点压力系数随着流量幅值的增大而逐渐减小,但轮缘进口处变化较快,说明轮缘进口压力脉动受流量变化影响最大。【结论】轴流泵内部转子径向力随流量的增大趋于稳定,不同流量下内部不同点的压力脉动存在明显差异。     

小型拖拉机气门间隙及其调整

详细讲解了气门间隙及其功用,气门间隙过大、过小对柴油机工作的影响和气门间隙的检查调整及调整方法。