共查询到16条相似文献,搜索用时 67 毫秒
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建立考虑剪切影响时等截面直杆内时的本构方程.将杆端位移、杆变形、截面内力分为不考虑剪切变形和只考虑剪切变形两部分,采用有限元方法并利用虚位移原理和截面内时本构关系,得到杆单元本构关系的初步形式.通过引入杆平衡条件以及两部分挠度之和等于全挠度的几何条件,将杆单元本构关系原始形式中剪力行和弯矩行的两部分加以合并,导出了按增量初内力法表达的杆内时本构方程.结果表明,剪切变形将影响杆单元初始刚度矩阵、杆端等效剪力和等效弯矩、杆端塑性剪力增量和塑性弯矩增量;当剪切系数为零时,本模型退化为既有研究中不考虑剪切变形的杆内时模型.本模型适用于按增量初内力法进行的考虑杆剪切变形的结构弹塑性分析. 相似文献
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为研究预制装配式地铁车站在地铁交通方面的安全使用,从而分析装配式结构的受力和变形,是研究装配式分块方案合理性的前提。针对青岛市某地铁线路预制装配式地铁车站,建立该车站单环结构实体单元模型,研究分析该单环结构的应力及变形情况。计算结果表明,采用该文的有限元模拟方法能够实现装配式车站单环结构受力变形的有效分析。在正常使用工况下,装配式结构的应力和变形都能满足要求。研究结果可为装配式地铁车站安全使用提供参考。 相似文献
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比较4种不同配方芦荟银杏复合制剂对乙醇氧化损伤模型小鼠的抗氧化作用。将小鼠随机分为正常对照组、模型对照组、2A组、1A组、2B组和1B组,除正常对照组外,其余5组在灌胃给药30d后一次性灌胃给予50%乙醇建立氧化损伤动物模型,取材测定指标。选用血清和肝组织GSH含量、SOD活力、GSH-Px活力、MDA含量,肝组织蛋白质羰基含量为指标,比较4种不同配方制剂对乙醇氧化损伤模型小鼠抗氧化能力的影响。不同配方的芦荟银杏复合制剂均能够使乙醇氧化损伤模型小鼠血清和肝组织GSH含量增加,SOD和GSH-Px活力升高,MDA含量和蛋白质羰基含量降低。其抗氧化能力顺序为:2A2B1A1B。 相似文献
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Statistical analysis of wheat under different seed treatments: development of a discriminative model based on physicochemical and rheological properties 下载免费PDF全文
Luiz Antonio Molotto Daniele Scheres Firak Priscila Lagner da Silveira Estevão Beatriz Boger Noemi Nagata Patricio Peralta‐Zamora Daiane Garabeli Trojan 《Journal of the science of food and agriculture》2018,98(8):3084-3088
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Paul R. Shorten Anita M. Ledgard Martyn Donnison Peter L. Pfeffer Robin M. McDonald Debra K. Berg 《Journal of dairy science》2018,101(1):736-751
A complex interaction between the developing bovine embryo and the growth potential of the uterine milieu it inhabits results in an embryo capable of developing past the maternal recognition stage and on to a successful pregnancy. Previously, we observed variation in the lengths of embryos recovered 8 d after bulk transfer of Day 7 in vitro-produced (IVP) blastocysts into the same uterus. Potential causes of the differential embryonic growth were examined and modeled using 2 rounds of bulk (n = 4–6) IVP transfers and recovery of these embryos 8 d later. Morphological and gene expression measurements of the embryos were determined and the progesterone concentration of the cows was measured throughout the reproductive cycle as a reflection of the status of the uterine environment. These data were used to develop and evaluate a model that describes the interaction between the uterine environment and the growth rate of the developing embryo. Expression of 6 trophectoderm genes (IFNT, TKDP1, PAG11, PTGS2, DKK1, and PDPN) was correlated with conceptus length. The model determined that if the embryo develops to blastocyst stage, the uterine environment, driven by progesterone, is a more important component than blastocyst size in the stimulation of embryonic growth rate to ensure adequate interferon tau (IFNT) for pregnancy recognition. We detected an effect of Day 7 progesterone on the expression of all 6 genes, embryonic disc size, and trophectoderm length on Day 15. We also found effects of embryo transfer size on trophectoderm length and expression of IFNT and PAG11 on Day 15. Lower energy balance over the period from transfer to recovery was associated with reduced embryo growth to Day 15, and this effect was independent of progesterone. Energy balance also affected expression of PDPN and TKDP1 on Day 15. We observed an effect of energy balance from transfer to recovery on embryo survival in cows with partial embryo losses, where embryo factors dominate embryo survival, with cows with greater energy balance having lower embryo losses. This effect was independent of energy balance 40 d before transfer and suggests that energy balance has direct, immediate effects on the embryo and maternal environment during this period. Furthermore, energy balance effects on embryo survival in cows with partial embryo losses were largely mediated by expression of TKDP1, PAG11, and PDPN. These results provide candidate signaling pathways for the effect of progesterone and energy balance on embryo growth and survival. 相似文献
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本文采用了荧光光谱、同步荧光光谱和紫外可见光谱的方法,研究了牛血清白蛋白与花青素在不同温度(25、30、35℃)水体系中相互作用的光谱学特征,按照Stern-Volmer和Tachiya模型分析荧光光谱数据,获得了二者反应的热力学参数和结合参数(结合常数Ka、结合位点数n),进一步分析所得结合参数的差异。结果表明,花青素对牛血清白蛋白内源荧光有猝灭作用且属于静态猝灭。根据热力学参数ΔH、ΔS的数值确定它们之间的作用力主要是静电引力。同步荧光光谱显示花青素的加入引起色氨酸荧光峰波长发生蓝移,表明二者结合位点更接近于色氨酸残基。根据Stern-Volmer得出的Ka随温度的升高而降低、n却不受温度的影响,由Tachiya得出的Ka、n均会随温度的升高而增大。由此可知,Stern-Volmer获得的结合位点数几乎不随着温度变化而变化,但由Tachiya得到的实际结合位点数随温度的升高而增大,Tachiya模型得到的结果更符合小分子与生物大分子相互作用的实际情况。 相似文献
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目的 了解公众对食品安全监督抽检的认知、信任与负性情绪的情况以及三者之间的关系。方法 采用配额抽样的方法,在全国七大区域对公众进行自填式问卷调查,运用结构方程模型探讨公众对食品安全监督抽检的认知、信任度和负性情绪三者之间的关系。结果 结构方程模型表明,食品安全监督抽检能力信任对食品安全监督抽检认知产生直接正向影响(标准化β=0.253),其对负性情绪产生直接负向影响,为-0.115;食品安全监督抽检动机信任对食品安全监督抽检认知产生直接正向影响,为0.732,其对负性情绪产生直接负向影响,为-0.503;食品安全监督抽检认知对负性情绪产生直接负向影响,为-0.335。结论 通过提高公众对食品安全监督抽检的信任,尤其是动机信任,可以提升公众对食品安全监督抽检认知,进而改善公众的负性情绪。 相似文献
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目的 研究一种新型复合多糖的提取工艺、降血脂活性及其胆固醇结合力预测模型.方法 以药食同源物质山楂、荷叶、苦荞麦、决明子、枸杞以及茯苓为原料,依照质量比4:2:2:1.5:1:1进行混合,提取复合多糖.运用L9(34)正交试验设计和数量化理论,优化复合多糖提取方法,测定复合多糖的脂肪、胆固醇、胆酸盐结合力,并构建胆固醇... 相似文献
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A ‘near-real’ in vitro stomach model should not only resemble of the biochemical and physiological conditions found in the real stomachs, but also possess their geometrical and morphological details. In this work, quantitative evidences regarding the physiological relevant morphology including wrinkles on the inner-surface of a new rat model stomach, which assisted the compression and digestion behavior of the dynamics in vitro rat stomach (DIVRS), have been presented. A good repeatability in the tests on the DIVRS is shown, compared with the in vivo experiments of the living rats. However the digestion efficiency and the buffering capacity in the DIVRS were lower than the in vivo systems, most likely due to the limited motility mechanism of the movement of the model stomach system. Further improvements are needed to make the DIVRS more attractive for practical applications. 相似文献