压塑工艺及模具设计——上篇 塑料压制成型 第七讲 压制塑料质量控制及缺陷分析

压塑与注塑采用不同类型的塑料,前者采用热固性塑料,后者采用热塑性塑料。压塑成型工艺及模具设计是一门不断发展的综合科学,不仅随着高分子材料合成技术的提高,压塑成型设备的更新,成型工艺的成熟而改进,而且随着计算机技术,快速造型技术,数值模拟技术,数字化应用技术,智能技术等在压塑成型加工领域渗透而发展。本讲座内容主要包括:压制成型工艺及分类,压制件设计,压制模结构设计及其零件设计,压制成型设备,压制塑件质量控制及缺陷分析,压制成型模应用举例;压注成型原理及工艺过程,压注成型模具结构设计,压注成型压力的计算,压注成型设备的选择,压注塑件质量及缺陷分析,压注成型模应用举例。     

轮胎成型机旋转密封技术研究

在经济全球化的背景下,随着我国轮胎生产技术的提高,轮胎企业和世界汽车工业的迅猛发展,我国轮胎的生产量不断增加。近年来,随着轮胎生产技术不断提高,轮胎成型机科技成果不断涌现,消费者对于轮胎的耐用性、安全性、舒适度和环保方面更加优质的产品的需求不断增加。本文对轮胎成型机旋转密封的结构、系统稳定性以及使用寿命进行简单介绍,讨论了机械结构的工艺性和稳定性。     

一种雪地轮胎的结构设计

本文介绍了265/70R17115S规格雪地轮胎的设计,外轮廓方面,轮胎的设计外直径797 mm,充气断面宽282 mm,轮胎的行驶面宽207 mm,设计行驶面弧高度8.5 mm,胎圈着合直径取值430 mm,轮胎的胎圈着合宽度237.8 mm,轮胎的断面水平轴位置取值0.96746;轮胎的胎面花纹设计分为长型花纹(M型、L型)与短型花纹(S型),3种花纹为交替变节距呈现,花纹深度10.4 mm,花纹饱和度68.16%。轮胎的施工设计方面:胎面挤出部件为全分层设计,可更好的区分胶种,功能性更强,胎侧挤出部件为双复合设计,冠带层的1#、2#带束层材料使用3×0.30HT钢丝帘线,胎圈部位的钢丝圈为斜六角形结构,更好的保证了成品断面钢丝圈部位,切割后呈近圆形;胎胚成型使用的设备是萨驰一次法成型机,胎胚硫化使用的设备是韩国东和液压硫化机,硫化工艺为氮气硫化。生产的成品轮胎的外缘尺寸、强度性能和耐久性能等均满足国家标准要求。     

Rational Design of CYP3A4 Inhibitors: A One-Atom Linker Elongation in Ritonavir-Like Compounds Leads to a Marked Improvement in the Binding Strength

Inhibition of the major human drug-metabolizing cytochrome P450 3A4 (CYP3A4) by pharmaceuticals and other xenobiotics could lead to toxicity, drug–drug interactions and other adverse effects, as well as pharmacoenhancement. Despite serious clinical implications, the structural basis and attributes required for the potent inhibition of CYP3A4 remain to be established. We utilized a rational inhibitor design to investigate the structure–activity relationships in the analogues of ritonavir, the most potent CYP3A4 inhibitor in clinical use. This study elucidated the optimal length of the head-group spacer using eleven (series V) analogues with the R₁/R₂ side-groups as phenyls or R₁–phenyl/R₂–indole/naphthalene in various stereo configurations. Spectral, functional and structural characterization of the inhibitory complexes showed that a one-atom head-group linker elongation, from pyridyl–ethyl to pyridyl–propyl, was beneficial and markedly improved K_s, IC₅₀ and thermostability of CYP3A4. In contrast, a two-atom linker extension led to a multi-fold decrease in the binding and inhibitory strength, possibly due to spatial and/or conformational constraints. The lead compound, 3h, was among the best inhibitors designed so far and overall, the strongest binder (K_s and IC₅₀ of 0.007 and 0.090 µM, respectively). 3h was the fourth structurally simpler inhibitor superior to ritonavir, which further demonstrates the power of our approach.     

A Holistic Evolutionary and 3D Pharmacophore Modelling Study Provides Insights into the Metabolism,Function, and Substrate Selectivity of the Human Monocarboxylate Transporter 4 (hMCT4)

Monocarboxylate transporters (MCTs) are of great research interest for their role in cancer cell metabolism and their potential ability to transport pharmacologically relevant compounds across the membrane. Each member of the MCT family could potentially provide novel therapeutic approaches to various diseases. The major differences among MCTs are related to each of their specific metabolic roles, their relative substrate and inhibitor affinities, the regulation of their expression, their intracellular localization, and their tissue distribution. MCT4 is the main mediator for the efflux of L-lactate produced in the cell. Thus, MCT4 maintains the glycolytic phenotype of the cancer cell by supplying the molecular resources for tumor cell proliferation and promotes the acidification of the extracellular microenvironment from the co-transport of protons. A promising therapeutic strategy in anti-cancer drug design is the selective inhibition of MCT4 for the glycolytic suppression of solid tumors. A small number of studies indicate molecules for dual inhibition of MCT1 and MCT4; however, no selective inhibitor with high-affinity for MCT4 has been identified. In this study, we attempt to approach the structural characteristics of MCT4 through an in silico pipeline for molecular modelling and pharmacophore elucidation towards the identification of specific inhibitors as a novel anti-cancer strategy.     

A Web Server for Designing Molecular Switches Composed of Two Interacting RNAs

The programmability of RNA–RNA interactions through intermolecular base-pairing has been successfully exploited to design a variety of RNA devices that artificially regulate gene expression. An in silico design for interacting structured RNA sequences that satisfies multiple design criteria becomes a complex multi-objective problem. Although multi-objective optimization is a powerful technique that explores a vast solution space without empirical weights between design objectives, to date, no web service for multi-objective design of RNA switches that utilizes RNA–RNA interaction has been proposed. We developed a web server, which is based on a multi-objective design algorithm called MODENA, to design two interacting RNAs that form a complex in silico. By predicting the secondary structures with RactIP during the design process, we can design RNAs that form a joint secondary structure with an external pseudoknot. The energy barrier upon the complex formation is modeled by an interaction seed that is optimized in the design algorithm. We benchmarked the RNA switch design approaches (MODENA+RactIP and MODENA+RNAcofold) for the target structures based on natural RNA-RNA interactions. As a result, MODENA+RactIP showed high design performance for the benchmark datasets.     

非共沸混合工质有机朗肯循环系统变工况特性研究

鉴于分布式能源系统中燃气轮机负荷波动较大,而目前对有机朗肯循环（Organic Rankine Cycle,ORC）研究更注重相同吸热量及其热力性能随初始参数变化的对比,很少考虑燃气轮机负荷降低时导致烟气温度和质量流量均下降对系统性能的影响。通过HYSYS平台构建特性模型,以换热器内窄点温差为约束条件,研究变工况特性ORC工质优选方案。在燃气电厂变负荷工况下,寻求对应系统最大净输出功的最佳运行参数,从热耗率、质量流量和AP值等特性比较,采用不同组分工质的循环性能,经对比发现R152a系统净输出功、热耗率、质量流量在所选工况区间内相比混合工质具有明显优势,而冷凝器AP值及系统热回收率却相反。研究结果为ORC系统二元非共沸混合工质优选提供参考。     

地方高校转型背景下生物工程专业课程设计教学改革与探索

以地方本科高校转型发展为背景,以提高生物工程专业应用技术人才培养质量为目标,针对地方高校生物工程专业课程设计教学的特点和存在的问题,以生物工程专业的本科教学为例,探讨课程设计教学改革的有效措施,为探索课程设计教学环节的改革措施提供了参考。     

基于热电联产的汽轮机组油膜振荡故障诊断系统设计

常规振荡故障诊断系统,采集振荡信号噪声较大,导致诊断的故障类别信任度较低。针对这一问题,提出基于热电联产的汽轮机组油膜振荡故障诊断系统。耦合热电联产生产方式,循环汽轮机组多余排汽,通过排汽热量增加系统发电量完成硬件设计;采用小波包降噪算法,消除采集振荡信号噪声,分解信号各个时刻和频带,排序频带内时域子信号能量值,构成故障信号特征向量,输入神经网络,训练后输出振荡故障诊断模式完成软件设计。采集满负荷、最小负荷、噪声条件下的油膜振荡信号,设置对比实验,结果表明,所设计系统提高了故障诊断信任度,故障诊断结果更为准确可靠。     

《单片机原理及应用》课程思政的实践探索——以“单片机的存储器结构”知识点讲解为例

针对《单片机原理及应用》及其相关课程在课程思政建设中存在的问题,提出一种课程思政设计思路,即选取合适的授课内容与思政素材,从教学目标和教学设计出发,将思政素材自然融入到授课内容中。并以“单片机的存储器结构”知识点讲解为例,详细介绍了以上课程思政设计思路的具体设计与实施过程,具有较强的创新性与可操作性,对单片机类课程线上及线下教学的课程思政建设有一定的借鉴意义。