基于有限元的塑料异型材挤出模头分流段设计

针对由于模具设计不合理导致流动性能较差的塑料异型材挤出模具,通过有限元软件ANSYS模拟计算,根据流动平衡理论,分析了模头分流段流动平衡方面存在的问题,以流动平衡为原则对其设计加以改进,对比改进前后理论分析结果与模头的实际使用情况,提出了提高挤出模头稳定性的模头分流段流道设计准则。

经肝段下腔静脉建立TIPS分流道的初步临床结果

目的 评估经肝段下腔静脉TIPS分流术在肝静脉与门静脉间解剖异常时操作的可行性 ,讨论其临床意义。 方法 6 5例肝硬变门静脉高压患者行经肝段下腔静脉直接穿刺门静脉完成TIPS分流术。 结果 6 5经肝段下腔静脉TIPS分流术均获成功 ,技术成功率 10 0 % ,未出现术中技术相关并发症 ,一年内再狭窄率明显低于常规TIPS ,3例肝性脑病经限流支架置入得以控制。 结论 经肝段下腔静脉TIPS分流术技术用于肝静脉与门静脉间解剖异常病例是安全有效的 ,同时提示由于肝内分流道曲度较小 ,一年内支架开通率明显提高。

跨节段分流术治疗外伤和感染导致的脊髓空洞症

目的本研究结合脑脊液动力学,探讨脊髓空洞跨节段分流术治疗由于外伤和感染导致的脊髓空洞症的临床疗效。方法收集2019年7月至2021年6月就诊于郑州市中心医院脊髓空洞专科的脊髓空洞症患者共17例的临床资料,入组者均行脊髓空洞跨节段分流手术。分析患者手术前后的临床特征、肌电图、影像学特征。使用芝加哥Chiari畸形预后评分(CCOS)、日本骨科协会(JOA)评分改善指数评估患者临床预后。采用Pearson法分析JOA评分改善指数及CCOS评分与脑脊液峰值流速差值的相关性。结果跨节段分流术后,14例临床症状明显改善,3例术后症状未改善。术后JOA评分高于术前(17.65±1.80 vs 8.94±2.36,t=11.609,P<0.01)。手术后肢体麻木、分离性感觉障碍、步态障碍、头晕症状、下肢无力、共济失调、感觉神经传导、运动神经传导、空洞最大径及枕骨大孔区及中脑导水管收缩期、舒张期脑脊液峰值流速较术前改善(P<0.05)。JOA评分改善指数及CCOS评分与脑脊液峰值流速差值显著相关(P<0.05)。结论对于外伤和感染导致的脊髓空洞症患者,脊髓空洞跨节段分流术一定程度上改善患者的脑脊液动力学,促进脊髓空洞缩小,改善临床症状。

Conditions of Ratio Changing Continuously for Multirange-Split-Transmission

According to the flow chart and the characteristics of components, the equation of ratio changing of multirange split transmission (MRST) was established. By mathematical analysis, both the relations among the ratios of the components and the condition for the ratio of MRST changing continuously were obtained. With the help of two examples, the correctness was proved.

UPVC异型材挤出口模设计技巧

本文阐述了UPVC异型材挤出口模定型段、压缩段、分流段和发散段流道设计的一种简易方法。

Top coal flows in an excavation disturbed zone of high section top coal caving of an extremely steep and thick seam

Compared with gentle dip long-wall caving,the length of a working face in fully-mechanized top-coal caving for extremely steep and thick seams is short,while its horizontal section is high with increasing production.But the caving ratio is low,which might result in some disasters,such as roof falls,induced by local and large area collapse of the top coal in a working face and dangers induced by gas accumulation. After the development of cracks and weakening of the coal body,the tall,broken section of the top coal（a granular medium）of an extremely steep seam（over 60°）shows clear characteristics of nonlinear movement.We have thoroughly analyzed the geological environment and mining conditions of an excavation disturbed zone.Based on the results from a physical experiment of large-scale 3D modeling and coupling simulation of top coal-water-gas,we conclude that the weakened top coal can be regarded as a non-continuous medium.We used a particle flow code program to compare and analyze migration processes and the movements of a 30 m high section top coal over time before and after weakening of an extremely steep seam in the Weihuliang coal mine.The results of our simulation, experiment and monitoring show that pre-injection of water and pre-splitting blasting improve caving ability and symmetrical caving,relieve space for large area dynamic collapse of top coal,prolong migration time of noxious gases and release them from the mined out area and so achieve safety in mining.

Modeling and optimization of unbalanced multi-stage logistic system

To decompose an unbalanced multi-stage logistic system to multipleindependent single-stage logistic systems, a new notion of parameterized interface distribution ispresented. For encoding the logistic pattern on each stage, the Pruefer number is used. With theimproved decoding procedure, any Pruefer number produced stochastically can be decoded to a feasiblelogistic pattern, which can match with the capacities of the nodes of the logistic system. Withthese two innovations, a new modeling method based on parameterized interface distribution and thePriifer number coding is put forward. The corresponding genetic algorithm, named as PIP-GA, can findbetter solutions and require less computational time than st-GA. Although requiring a little moreconsumption of memory, PIP-GA is still an efficient and robust method in the modeling andoptimization of unbalanced multi-stage logistic systems.

Effect of Ripening Stages on Basic Deep-Fat Frying Qualities of Plantain Chips

Plantains （Musa paradisiaca L.） are a major food staple in West Africa and are cooked in various forms. The objective of this work was to evaluate the frying characteristics of plantains at different stages of ripening. The plantains used in the study were at the unripe stage through four different ripening stages. The samples were peeled and sliced into 2 mm thickness and blanched in hot water at 70 ℃ for 3 min. The slices were then deep flied in canola oil at 180 ℃. The result showed that ripening stage significantly affected moisture loss and fat absorption profiles of the plantain chips. Fully ripened plantain absorbed up to 34% （db） oil during 4 min frying, much higher than unripe plantain. The oil uptake and moisture loss during frying of the plantain chip samples were modelled using 1st order kinetics. The kinetic parameters including rates of moisture loss and oil uptake varied according to the different stages of ripening. Ripening had a significant effect on the colour lightness （L） of the chips. Similarly, the redness （a）, the yellowness （b） and textural characteristics were significantly affected by ripening stage.

Chronological constraints on multi-staged rapid cooling of the Tianshan Mountains inferred from apatite fission track analysis of modern river sands

The extreme modern elevation of the Tianshan Mountains reflects the Cenozoic deformation. Apatite Fission Track （AFI） chronometry is widely used to study the latest cooling stages caused by tectonic process or by exhumation in the uppermost crust. However, uncertainties remain over timing constraints on thermal history of the Tianshan Mountains since the Cenozoic though a great mount of dating work had been done in this area. To address this issue, modern river sands from the drainage basin on the piedmont of the Tianshan Mountains were sampled to integrate regional information. Single grains were dated with the AFT method, and then different grain-age components were identified to provide thermochronological constraints of their sources. Combined with discussion of previous dataset, our results show the multi-staged rapid cooling cluster at 46-32, 25-24, 19-13, 8-6, and -3 Ma, respectively. We interpreted these cooling events as a result of interplays between the Cenozo- ic tectonic uplift of the mountains and regional climate change.

Developed ‘laminar’ bubbly flow with non-uniform bubble sizes

Bubbles with different sizes have different dynamic and kinetic behavior in a two-phase bubbly flow. A common two-fluid model based on the uniform bubble size assumption is not suitable for a bubbly flow with non-uniform bubble sizes. To deal with non-uniform bubbly flows, a multi-fluid model is established, with which bubbles are divided into several groups according to their sizes and a set of basic equations is derived for each group of bubbles with almost the same size. Through analyzing the bubble-bubble and bubble-pipe wall interactions, two new constitutive laws for the wall-force and pressure difference between the liquid phase and interface are developed to close the averaged basic equations. The respective phase distributions for each group of bubbles measured by a specially designed three-dimensional photographic method are used to check the model. Comparison between model-predicted values and experimental data shows that the model can describe laminar bubbly flow with non-uniform bubble sizes.

Growth of gas bubbles in the biotissues with convective acceleration

This paper presents formulae and explanation about the growth of a convective gas bubble in the blood and other tissues of divers who surface too quickly, concentration distribution around the growing bubble is also presented. The formulae are valid all over the growth stages, i.e. under variable ambient pressure while the diver is ascending, and under constant ambient pressure at diving stops or at sea level. The mathematical model is solved analytically by using the method of combined variables. The growth process is affected by tissue diffusivity, concentration constant and the initial void fraction, which is the dominant parameter. Results show that, the time of the complete growth, in the convective growth model, is shorter than those earlier presented by Mohammadein and Mohamed [Concentration distribution around a growing gas bubble in tissue, Math. Biosci. 225（1） （2010） 11-17] and Srinivasan et al. [Mathematical models of diffusion- limited gas bubble dynamics in tissue, J. Appl. Physiol. 86 （1999） 732-741] for the growth of a stationary gas bubble, this explains the effect of bubble motion on consuming the oversaturated dissolved gas from the tissue into growing bubble which leads to increment in the growth rate to be more than those presented in the previous stationary models.