Synthesis of high molecular weight aromatic polyesters via integrated alternating ring-opening copolymerization and chain extension methods

Due to their good mechanical properties, high molecular weight polyesters (PEs) are highly desirable for a wide range of applications especially in the packaging industry. However, the synthesis of high molecular weight polymers by energy efficient methods is difficult. In this study, a series of semi-aromatic PEs were synthesized via the alternating ring-opening copolymerization (ROCOP) of phthalic anhydride (PA) and cyclohexene oxide (CHO) using a salen chromium(III) complex as a catalyst and 4-(dimethylamino)pyridine as a cocatalyst. By varying the molar ratios between CHO and PA, PEs of different molecular weights were obtained. Hexamethylene diisocyanate was used as a chain extender that further increased the molecular weights of these PEs. These chain extended aromatic polyesters (PE-Xs) showed significant improvement in the glass transition temperature (T_g) values. Thus, integration of ROCOP with the chain extension method can be used as an effective strategy to prepare high molecular weight PEs with improved thermal stabilities and enhanced mechanical properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47200.     

基于三角形试验的引张线卡阻位置定位分析

引张线广泛应用于大坝水平位移监测,但在长期运行过程中会因线体卡阻而影响观测成果的真实性。因引张线的护管为不透明的PVC管或镀锌管,直接观察引张线卡阻部位存在一定难度,更换整根护管也显得不经济。为经济有效地消除卡阻,介绍运用三角形试验来准确判定卡阻位置的方法,并给出了相关计算公式。工程实例验证表明,该方法可准确找到卡阻位置,为以后引张线卡阻问题处理提供了参考。     

旋转采样机粒度偏析机理

本文建立了旋转类采样机包含皮带中部采样机、旋斗采样机、旋转缩分机、旋管缩分机的通用数学模型,推导了截取料流时的轨迹方程、速度方程、最大速度波动公式、最大面积波动公式,从数学分析角度阐述了粒度偏析机理,找到了减少粒度偏析及提高采样精度的有效途径。     

Acoustic emission characterization of steel in H2S solution subjected to tensile load

Abstract

This paper investigates the characteristics of acoustic emission (AE) signals generated from hydrogen induced cracking (HIC) and sulfide stress corrosion cracking (SSCC) for a medium strength steel in hydrogen sulfide (H₂S) solution. The experiments performed in this study include the constant load test (CLT) and the constant extension rate test (CERT).

From the results of the CLT, the AE count rate caused by SSCC was found to be much higher than that resulted from the HIC; and the increase of the AE count rate was observed to be approximately proportional to the increase of the applied loading. In addition, the AE frequency distribution diagrams obtained from these tests were found to contain potential information for distinguishing the mechanisms of HIC and SSCC. From the results of CERT, the AE signals detected from the specimens tested in the H₂S solution were compared with those obtained from the specimens tested in the air. In addition, the AE count rate detected from the tensile specimens was studied according to the different deformation stages of the specimens. From this study, the variation of the AE count rate in each deformation stage was described.     

AN ALTERNATIVE PERSPECTIVE ON FUZZY SET-BASED APPROXIMATE REASONING

Abstract

On the subject of fuzzy set-based approximate reasoning, this paper attempts to present a perspective that is both rigorously stated and different from the standard approach as stated by Mamdani and many others. Functionally speaking, this alternative perspective produces results essentially the same as the standard one, and in fact we intend to prove that subject to certain assumptions the results will be exactly die same. We feel however that the alternative perspective offers advantages in that it makes a more appropriate and more understandable use of such concepts as fuzzy relations, the extension principle, and fuzzy composition. If indeed it can lead to a clearer and more widespread understanding of the approximate reasoning formalism then this could conceivably spark broader interest in fuzzy control and other applications.     

Development of Computer Code SAFFRON for Evaluating Breached Pin Performance in FBR's

In order to evaluate the breached pin behavior in FBR, the breached pin performance analysis code SAFFRON was developed. Based on the results of run-beyond-cladding-breach test in EBR-II as a collaborative program between PNC and U.S. DOE, the following behaviors were taken into cosideration; fuel sodium reaction product (FSRP) formation, resultant fuel expansion, breach extension of cladding and release of delayed neutron precursors into the coolant. Using 3-dimensional elastic analyses by finite element method, breached pin diameter increase is adequately predicted with the reduced Young's modulus of the breached fuel. The delayed neutron signal response in on-line diagnosis was evaluated in relation to the growth of FSRP and breached area enlargement.     

管道正等轴测图的阀门与管件的参数化设计

管道轴测图是管道布置设计的基本图样之一,轴测图采用工程图样中的特定表达方法,有别于三视图表达。工程中常用正等轴测图表达管道布局,其中大量存在的阀门和管件在三个不同坐标轴方位上形状不同,绘制阀门和管件耗时费力。采用参数化设计技术,将阀门和管件进行分类,引入核心参数的概念,对每一个选定的阀门和管件实现成组一次性绘制,有效提高管道轴测图的绘图设计效率。     

Cluster ensembles: A survey of approaches with recent extensions and applications

Cluster ensembles have been shown to be better than any standard clustering algorithm at improving accuracy and robustness across different data collections. This meta-learning formalism also helps users to overcome the dilemma of selecting an appropriate technique and the corresponding parameters, given a set of data to be investigated. Almost two decades after the first publication of a kind, the method has proven effective for many problem domains, especially microarray data analysis and its down-streaming applications. Recently, it has been greatly extended both in terms of theoretical modelling and deployment to problem solving. The survey attempts to match this emerging attention with the provision of fundamental basis and theoretical details of state-of-the-art methods found in the present literature. It yields the ranges of ensemble generation strategies, summarization and representation of ensemble members, as well as the topic of consensus clustering. This review also includes different applications and extensions of cluster ensemble, with several research issues and challenges being highlighted.     

Electrical disintegration and micro-focus X-ray CT observations of cement paste samples with dispersed mineral particles

Electrical disintegration is an effective liberation technique in mineral processing where the liberation ratio depends on the mineralogical properties of the mineral grains. However elucidation of the liberation behavior is difficult since the fragments after the electrical disintegration are fine and complex. This study applies electrical disintegration to cement paste samples with various dispersed mineral particles (calcite, quartz, albite, and pyrite) and the disintegrated products are observed with a micro-focus X-ray CT scanner. Current channels and crack extension behavior from the channels are identified by cross sectional CT and three dimensional reconstructed images. A classification of the crack patterns was carried out and compared with the results of liberation ratio measurements of the products.     

A framework for identifying differences and similarities in the managerial competencies associated with different modes of product life extension

It has been noted in the past that economically sound, environmentally preferable life extension modes such as remanufacturing and recycling have special characteristics that complicate the management of their production, logistics and associated operations. This paper considers these complicating characteristics from the perspective of the nine different modes of product life extension. In doing so, a framework and guide is provided to what issues, resource requirements and management capabilities are required for specific life extension modes. This framework provides guidance to practitioners and academics on commonalities between different product life extension modes, thereby assisting practitioners in leveraging current internal skills and capabilities and researchers in determining the generalizability of research.