渠道非恒定流过渡时间影响研究

采用特征线法,模拟了不同渠道长度、闸门调控时间、流量变化率及运行方式下渠道水流过渡过程,并分析了其对水流过渡时间的影响。结果表明,渠道运行方式对水流过渡时间影响较小。渠长、调控时间、流量变化率为影响过渡时间的敏感因素。渠道越长,闸门调控时间越长,流量变化率越小,水流过渡时间就越短,水位流量波动越小,水流过渡越平缓。     

杜仲种质资源雄花主要数量性状变异及概率分级

为更好地对杜仲种质资源雄花进行评价和利用,对193份不同种质杜仲雄花14个主要数量性状进行变异分析和概率分级。结果表明:杜仲雄花数量性状存在丰富的变异,14个性状变异系数均在12%以上,京尼平苷含量(112.00%)变异系数最大,其次为紫云英苷含量(89.56%)、京尼平苷酸含量(88.60%),氨基酸含量(12.52%)变异系数最小。经K-S检验,花高、雄蕊长度、雄蕊数、桃叶珊瑚苷含量、绿原酸含量、异槲皮苷含量、总黄酮含量、氨基酸含量等8个数量性状Sig值大于0.05,均符合正态分布;花径、鲜质量、干质量均呈偏态分布,去除拖尾部分,也近似看作正态分布;京尼平苷酸含量、京尼平苷含量、紫云英苷含量均不符合正态分布。对符合正态分布的数量性状统一用(X-1.281 8S)、(X-0.524 6S)、(X+0.524 6S)、(X+1.281 8S)4个点分为5级,对不符合正态分布的性状按实际分布情况分级,使1~5级出现的概率分别为10%、20%、40%、20%和10%。      

Effect of shade regime on flower development,yield and quality in lisianthus

The effects of shading on lisianthus (Eustoma grandiflorum) floral transition, plant development, flower yield and quality, and content of starch and soluble sugars were assessed in three cultivars, over two consecutive years. Shading nets affording 67% or 88% reduction in light intensity, were fitted at planting in the greenhouse for periods ranging from 3 to 8 weeks. Meristem morphology at floral transition was characterized by apical meristem widening and the appearance of two bract primordia. Floral transition time was affected by cultivars, but in general, longer and heavier shade treatments delayed floral transition; the longest delay (6 weeks) being recorded in Mariachi White under 88% shade for 7 weeks or under a combined shade treatment of 88% for 3 weeks followed by 67% for 5 weeks. Despite interactions between cultivar and shade treatment, consistent trends were discerned: the heaviest and most prolonged shading reduced yield (up to 40%), cut stem length (up to 15%), and number of flower buds/stem (up to 26%), within cultivar. Total carbohydrates levels were very low, and it is questionable whether changes observed in carbohydrate quantity following shade treatments had any effect on plant growth or flower yield. Rather, it appears that lisianthus is very dependent on current photosynthesis, so that even a brief shading interlude could reduce branching and flower quality. It may be concluded that the intensive shading usually applied is detrimental for lisianthus.     

河西走廊绿洲—荒漠过渡带生态恢复治理研究

绿洲—荒漠过渡带不仅影响着绿洲的物质循环和能量流动,同时还影响绿洲的稳定性和沙区群众的生存质量。结合遥感技术,对河西走廊绿洲—荒漠过渡带现状的研究结果显示:绿洲—荒漠过渡带地貌主要以流沙、固定沙地、半固定沙地为主;景观的破碎化程度高,各景观要素内部生境面积小,边缘长度短。采用由封沙育林育草带、植物活体沙障阻沙带、固沙林带和前沿防风阻沙带组成的"四带一体"综合模式治理后,在春季,绿洲—荒漠过渡区过境风速下降;生长季植物多样性增加,盖度提高,土壤含水量的变化不明显,治理区的生态环境得到了改善。     

基于CAE的汽车结构件有限寿命设计

针对我国汽车结构件目前还很难做到有限寿命设计的现状,结合机械概率疲劳分析理论和汽车振动理论,采用CAD/CAE手段,通过建立汽车结构件正确的有限元振动分析模型,确定其分析载荷,并基于有限元的疲劳分析结果,提出对汽车结构件进行有限寿命设计的设计流程和设计方法,并以路面不平引起满载汽车振动的随机动载荷和汽车满载时的静态载荷两部分作为分析载荷来验算汽车结构件的有限寿命,在缺少汽车实际行驶工作载荷的情况下,具有一定的可信性和实用性。     

能量平衡对围产期奶牛泌乳和干物质摄入量及机体代谢的影响

为了阐明不同能量平衡状况的围产期奶牛泌乳量、干物质摄入的变化及其机体代谢调节作用。在某一集约化牛场选取胎次、年龄相近的奶牛,分为高血糖组(H)和低血糖组(L),每组各15头。在产前21、14、7d和分娩当天,产后7、14、21d,分别记录奶牛围产期干物质摄入量(DMI)、泌乳量(MY),并测定血浆血糖(Glu)、游离脂肪酸(NEFA)、β-羟丁酸(BHBA)、胰岛素(Ins)、胰高血糖素(Gn)、瘦蛋白(Lp)、皮质醇(Cor)的浓度。结果显示,试验奶牛产后泌乳量和干物质摄入量均增加,但是产后能量负平衡发生率高于产前,产后21d达最高;两组产后血浆Glu水平均降低,血浆NEFA和BHBA升高,L组血浆NEFA和BH-BA水平高于H组(P0.05);H组血浆Ins与Lp水平高于L组(P0.05),血浆Gn与Cor水平低于L组(P0.05)。围产期不同能量平衡状态的奶牛机体能量代谢发生了各自适应性的变化。血浆低水平Ins、Lp和高水平Cor在缓解能量负平衡方面发挥了重要作用。     

Effect of fat supplementation during transition period on plasma leptin and non‐esterified fatty acid concentrations in Holstein cows

The objective of this experiment was to investigate the effect of fat supplementation during the transition period on pre and postpartum body weight (BW), body condition score (BCS), non‐esterified fatty acids (NEFA), glucose and leptin concentrations in Holstein cows. Holstein cows (n = 15) received a low fat diet (LF; 1.61 Mcal net energy for lactation (NEL)/kg of dry matter [DM]), moderate fat diet (MF; 1.68 Mcal NEL/kg DM) or a high fat diet (HF; 1.74 Mcal NEL/kg DM) for 4 weeks prior to calving. All cows were fed similar lactation diets ad libitum (1.74 Mcal NEL/kg DM) for 30 days after calving. Increasing diet energy density during transition period had no effect on prepartum DMI, BCS, BW, glucose and NEFA concentrations (P > 0.05); but leptin concentrations and energy balance (EB) were affected by treatments (P < 0.05). Animals fed HF had less plasma leptin prepartum. After parturition, BW, milk production, milk fat, protein, urea nitrogen and plasma glucose concentrations were affected by prepartum diets (P < 0.05). Fat supplementation prepartum did not affect postpartum NEFA. In conclusion, prepartum fat supplementation decreased leptin concentration prepartum.     

新疆经济转型与产业结构转移互动研究

利用产业结构变动系数及相关评价模式分析新疆经济转型与产业结构转移的互动关系。结果表明,新疆产业结构调整的专业化、合理化、高级化趋向日渐明朗,但其转移的动力和方向仍然高度依赖资源密集型、劳动密集型产业,技术密集型加工制造业、知识密集型新兴第三产业转型滞后,经济增长粗放、二元结构明显、创新资本匮乏使新疆产业结构升级和经济增长转型面临严峻挑战。     

基于CA的土地利用动态演变预测研究

基于元胞自动机的原理,提出了一种从历史地图数据中挖掘状态转换规则,并根据蒙特-卡罗法预测未来时刻单元状态的方法。实例应用表明,利用空间数据挖掘状态转换规则的方法,在模拟土地利用动态演变中具有简单、准确、实时性强等优点,实现了从地图到地图的空间动态预测,其结果与实际大致相符,可以为土地利用规划提供参考。     

基于环境源项法的SSTγ-Reθt转捩模型修正

边界层转捩的准确预测对于提高轴流泵内部流动计算精度具有重要意义。以轴流泵叶片的简化模型——水翼为研究对象,探索了SST γ-Re_θt转捩模型在不同雷诺数下的适用性。研究发现,在低雷诺数条件(Re_L小于1.6×10⁶)下,SST γ-Re_θt转捩模型的预测精度与试验值较为接近;在高雷诺数条件下,随着雷诺数的增大,SST γ-Re_θt转捩模型预测的边界层转捩位置相较试验值逐渐靠前,说明SST γ-Re_θt转捩模型对高雷诺数水翼边界层转捩发生的判断效果不佳。基于此,针对SST γ-Re_θt模型中输运方程采用环境源项法进行修正,引入环境湍动能和环境湍流比耗散率参数,建立了湍流比耗散率与雷诺数的关系,得到SST γ-Re_θt转捩修正模型。在Donaldson修型尾缘水翼和NACA0016水翼高雷诺数流动中验证表明,修正模型提高了水翼边界层转捩位置及其它流场参数预测的准确性。