基于Pro/E软件的手机壳注塑过程模流分析

利用Pro/E软件建立手机壳的三维模型,优化塑料手机壳的注射位置。仿真结果表明:对比手机壳外侧注射位置,手机壳中心注射位置的注射时间短,注塑效率更高,且注射压力更小,不容易出现应力集中,可有效提高塑料制品的加工质量。同时,双注射位置和三注射位置的注射时间分别为0.45 s和0.34 s,均小于单个注射位置的注射时间,具有更高的注塑效率;双注射位置和三注射位置的最大注射压力为33.42 MPa和25.79 MPa,均小于单个注射位置的注射压力,具有更高的注塑质量。因此,采用三注射位置具有更好的注塑效果。     

等温条件下球形颗粒沉降的轨迹特性

采用粒子图像测速仪研究了球形颗粒在重力作用下沉降的流场特性,研究了同一雷诺数(Re)下不同释放位置、同一释放位置不同Re下的颗粒沉降的规律. 结果表明,Re≤100时,同一Re下不同释放位置,颗粒最终稳定沉降位置均在中心处. 颗粒的释放位置沿中心线对称时,颗粒沉降的轨迹线沿中心位置对称;同一释放位置不同Re下,随Re增加,颗粒最终沉降轨迹由稳定的直线下降变为稳定的周期性摆动下降.颗粒的平衡位置与颗粒的初始释放位置及Re无关,但颗粒沉降的轨迹形状与释放位置及Re有关. 模拟结果与实验结果几乎一致.     

电动车箱盖纤维填充取向与浇口位置关系分析

通过Moldflow软件对玻璃纤维增强聚丙烯（PP）复合材料电动车箱盖注射成型塑件的成型过程进行模拟分析;第一步按照常规方法找到最佳浇口位置,确定对比参数, 得到平均玻璃纤维取向值为0.9956;第二步再通过设置不同的浇口位置,得到玻璃纤维在制品中的最佳取向值,最佳浇口位置的平均玻璃纤维取向值为0.9992;根据此最佳浇口位置所得到的拉伸模量云图和泊松比云图的数值可以进一步验证此浇口位置为最佳浇口位置。结果表明,常规方法所分析的最佳浇口位置,不一定是最佳浇口位置,要通过不同的条件进行验证才能得到最佳的结果。     

塑料注塑成型浇口位置优化

塑料注塑成型可以制作大量具有高精度和复杂型腔形状的制件,其中注塑模浇口位置的设定决定了聚合物流动方向和流动平衡性,产品质量可以通过浇口位置的优化得到显著提高.通过对导致制品翘曲和影响材料性能的主要因素进行定量分析构造了浇口位置优化问题,结合遗传算法和数值模拟技术对优化问题求解,得到最优浇口位置设计.算例证明该方法不仅适用于单浇口位置优化,也适用于多浇口位置优化.     

基于正弦曲线的位置控制的应用

随着制造业的升级,工业现场位置控制的应用越来越多,大部分采用伺服控制系统实现位置控制。由于伺服系统较为昂贵,基于公司精度要求的实际状况,提出了一种基于正弦曲线的位置控制方法,介绍了其优点和关键技术,并介绍了使用PLC+变频器实现位置控制的主要算法和程序结构,现场运用表明该方法可稳定的完成位置控制功能。     

精馏塔进料位置探索

精馏塔进料位置的选择极为重要 ,不正确的进料位置会使全塔效率下降。不能用下移进料口位置来增大塔顶产品浓度。     

量子化学课程中物理量量子化的定义及应用

基于时间、空间、动量、能量存在最小基元的假设,证明了定义域区间内任意态函数均可写成正交归一动量本征态叠加的结论。不同于Dirac位置本征态的定义,基于量子化假设重新定义了位置本征态,讨论了位置本征态和位置叠加态的归一性。基于动量和坐标的定义域依据傅立叶变换给出了动量空间和坐标空间的正交基函数系。据此得出,在某些方面,重新定义的位置本征态优于传统位置本征态。     

浓度和点火位置对氢气-空气预混气爆燃特性影响

开展了氢气-空气预混气在透明方管内的爆燃实验研究,分析在一端开口一端封闭的狭长空间内,浓度和点火位置对氢气-空气预混气爆燃特性的影响。实验结果表明：氢气浓度和点火位置对火焰锋面结构以及发展有重要影响;各当量比条件下,均在距封闭端100 mm位置点火时反应最为迅速;在极贫燃或极富燃条件下,点火位置对火焰发展影响更大。氢气浓度与点火位置共同作用于压力波形,以距封闭端300 mm点火位置为界,分别在管道前后两段点火时,不同当量比条件下超压波形呈现复杂变化。超压峰值对氢气浓度具有极强依赖性,并且浓度对爆燃超压的影响程度远大于点火位置;在各点火位置下,均在Φ = 1.25时获得最大超压;最大超压对应的点火位置取决于当量比。     

基于Moldflow的开关面板支架浇口优化设计

注射模具设计中合理的浇口位置和数量十分重要,以开关面板支架为例,借助Moldflow软件对其浇口的数量和位置进行模拟分析。通过3种方案流动分析的比较,预测可能出现气穴、熔接痕的位置,从而优化浇口数量和位置、缩短模具设计制造和产品研发周期。     

基于Moldflow的面板注射模具浇口的优化设计

浇口位置在注塑成型过程中起关键性作用。本文介绍专业注塑模分析软件moldflow在面板注塑模具浇口位置设计的应用,从产品的浇口最佳位置、填充时间等方面对不同的浇口设计方案进行对比。分析表明。方案2的浇口位置具有填充时间短、熔接痕少、气穴数量少的优点。是较佳的浇口位置方案。     

Positional distribution of fatty acids in the triglycerides of bovine milk fat with elevated levels of linoleic acid

A stereospecific distribution of fatty acids in bovine milk fat containing 15.5% linoleic acid has been compared with the distribution in bovine milk fat containing a normal level (1.8%) of linoleic acid. The positional distribution was obtained by the separate analysis of milk fat triglycerides of high, medium, and low molecular weight. The order of preference for linoleic acid in the high molecular weight triglycerides was position 3>position 2 >position 1. There was an accompanying altered distribution of myristic acid and palmitic acid in favor of position 1 at the expense of position 3. However, the proportions of myristic acid and palmitic acid in position 2, relative to positions 1 and 3 were identifical in the high molecular weight fractions of the two milk fats. The distribution of linoleic acid in the medium molecular weight triglycrides of linoleic-rich milk fat was position 1=position 2>position 3. This resulted in a change in the distribution of 18 carbon monounsaturated fatty acids in favor of position 2 at the expense of position 1, but the distribution of myristic acid and palmitic acid was virtually unaltered. The distribution of linoleic acid in the low molecular weight triglycerides was position 2>position 1>position 3. The amounts of myristic acid and palmitic acid in position 2 and of palmitic acid in position 1 decreased in the low molecular weight triglycerides of the milk fat containing elevated levels of linoleic acid. Changes in the distribution of fatty acids which were observed in the separate analysis of the high, medium, and low molecular weight triglycerides were not apparent when comparing the distribution in the total milk fats. For example, the distribution of myristic acid and palmitic acid appeared to be unchanged, while the distribution of 18 carbon monounsaturated fatty acids was slightly altered in favor of positions 2 and 3. Moreover, linoleic acid showed an almost equal preference for the three positions of the glycerol moiety in milk fat containing elevated levels of this fatty acid with some concentration at position 2.     

点火位置对乳胶泡沫水平火蔓延规律的影响

为研究点火位置对乳胶泡沫材料水平方向火蔓延规律的影响。搭建小尺寸实验平台,在距离材料中心点0（x1）、3.54 cm（x2）、7.08 cm（x3）、10.62 cm（x4）、14.16 cm（x5）、17.70 cm（x6）位置处点火,研究了试样表面温度、质量损失、火焰高度、火蔓延速度等特性参数的变化规律。结果表明,随着点火位置由材料中心点向边缘点移动,平均火蔓延速度分别为0.24、0.23、0.19、0.31、0.42、0.51 cm·s^-1,呈现先减小后增大的规律;x3点火位置时的平均火焰高度较低,燃烧时间较长,平均质量损失速率较低,主要与火蔓延过程中的热量传递方式有关。研究结果显示了乳胶泡沫的火蔓延过程,得到了点火位置对火蔓延的影响规律。     

Regiospecific analysis of fractions of bovine milk fat triacylglycerols with the same partition number

Bovine milk fat was fractionated using preparative reversed-phase high-performance liquid chromatography. The conditions consisted of two successive linear gradients of acetonitrile and tert-butylmethylether, followed by a final isocratic mixture of the two eluants, leading to triacylglycerols grouped by their partition number (PN). Fractions corresponding to partition numbers 32 to 50 were isolated and analyzed for fatty acid distribution between sn-1,3 and sn-2 positions by Grignard degradation. Results showed that the fatty acid distribution in milk fat triacylglycerols is nonrandom. The distribution of short-chain fatty acids, stearic (predominantly at sn-1,3 position) and palmitic (predominantly sn-2 position), did not change with triacylglycerol size. Medium-chain fatty acids were predominantly located at sn-2 position, but their proportion at this position decreased with triacylglycerol size. Oleic acid distribution was also size-dependent in that it was located in high proportions at sn-2 position in smaller triacylglycerols and vice versa. Results also showed that the sn-2 position was more unsaturated than sn-1,3 position in the PN range from 32 to 40, but it was more saturated in triacylglycerols with higher PN.     

层状催化剂颗粒的优化设计——双组分等温平行反应体系

针对双组分等温平行反应体系,分析讨论了以提高催化剂活性和选择性为目标时催化剂活性组分的最优分布形式(为δ-函数分布),并给出了确定这种反应体系的催化剂的最佳活性层位置的计算方法。结果表明:以提高选择性为目标的最佳活性层位置比以提高活性为目标的要更靠近催化剂核心,实用的最优位置应介于二者之间。最后,本文还研究了反应动力学级数、本性选择性以及内扩散模数(Thiele 模数)等因素对最佳活性层位置的影响。     

油罐除水自动控制原理探讨

提出了用电阻法测量油罐内油水界面位置的方法 ,通过仪表将油水界面的过渡段电阻分拣出来 ,并换算成高度 ,从而指示出油水混合界面的上下范围。当混合界面的上界达到警戒位置时 ,仪表指令排水阀开 ;当混合界面的下界达到警戒位置时 ,仪表指令排水阀关。此方法为油罐除水操作的自动化控制设计提供了新的思路     

Lipase-catalyzed transesterification of phosphatidylcholine at controlled water activity

The incorporation of a free fatty acid into thesn-1 position of phosphatidylcholine by lipase-catalyzed transesterification was investigated. The thermodynamic water activity of both the enzyme preparation and the substrate solution was adjusted to the same value prior to the reaction. The reaction rate increased with increasing water activity but the yield of modified phosphatidylcholine decreased due to hydrolysis. By using a large excess of the free fatty acid (heptadecanoic acid), the hydrolysis reaction was slowed down, so a higher yield was obtained at a given degree of incorporation. The best results were obtained withRhizopus arrhizus lipase immobilized by adsorption on a polypropylene support. With this preparation, a yield of 60% and nearly 50% incorporation of heptadecanoic acid (100% incorporation in thesn-1 position) was obtained at a water activity of 0.064. The enzyme preparation had good operational stability and position specificity. Little incorporation (<1%) was observed in thesn-2 position, when almost all the fatty acid in thesn-1 position was exchanged.     

外循环撞击流反应器混和时间实验研究

在容积为160L的冷模装置上,以水为介质、KCl水溶液为示踪剂,测定了外循环撞击流反应器（ECISR）的混和时间,采用正交试验法和单因素试验法考察了撞击段结构、进料位置、循环位置、循环流量对ECISR混和时间的影响。结果表明：实验范围内,循环位置对混和时间影响最大,进料位置次之,循环流量越大混和时间越短,撞击段结构Ⅰ的混和时间略低于结构Ⅱ。     

点火位置对氢气/甲烷/空气预混气体爆燃特性的影响

为研究不同点火位置下氢气/甲烷/空气预混气体的爆燃特性，改变点火位置IP和氢气添加比例φ，在100 mm×100 mm×1000 mm方形透明管道实验平台上开展爆燃实验。实验结果表明：火焰结构向泄爆端和封闭端传播时受点火位置和氢气添加比例的控制，当火焰向泄爆端传播时，郁金香火焰的形成因素由IP主导，当火焰向封闭端传播时，IP及φ共同作用于郁金香火焰的形成；IP和φ对火焰前锋演化的作用模式可以分为3类；当混合气体中φ小于0.25时，氢气添加对火焰传播速度的影响不明显；当φ不超过0.75时，仅当IP位于管道中后部时，超压出现周期性振荡，且点火位置距泄爆端越近，振荡时间越长；当为纯氢爆炸时，不同点火位置下压力振荡消失且到达最大压力峰值的时间基本一致；当φ不同时，最大压力峰值随点火位置的变化规律不同。     

Discernment of relative retention values of triglyceride α,β isomers on reverse phase high performance liquid chromatography

Discernment of α,β isomers of triglyceride on reverse phase high performance liquid chromatography (HPLC) was investigated by the use of a multiple regression analysis. The retention effect of triglyceride molecular species was considered to be dependent principally on the addition theorem of chemical potential of both position α and position β (acyl carbon numbers and numbers of double bonds in the acyl group), though it was observed that the retention effect of position α is somewhat larger than that of position β on HPLC when it has the same acyl group combination.