不同镍含量钨基碳化态催化剂对十氢萘加氢开环的影响

采用共浸渍法制备不同镍含量的Ni-W/ USY-Al2O3碳化态催化剂。通过N2吸附-脱附、元素分析、CO滴定、X射线衍射（XRD）、程序升温还原等技术对催化剂进行表征。以十氢萘为模型化合物考察了不同Ni含量钨基碳化态催化剂对十氢萘加氢开环反应性能的影响。结果表明，适当的镍钨原子比能够提高催化剂的金属活性位，进而提高催化剂的加氢开环性能。     

印尼BAYAH电厂一次风机故障原因分析与处理

本文针对印尼BAYAH电厂一次风机设备故障，详细的分析了故障产生的原因，介绍了三点法找转子动平衡和工装车削式在线修复电机滑环工法，阐述了两种工法的原理以及实施步骤。     

A theoretically-based novel protocol for the analytic treatment of the glass failure stresses associated with coaxial double ring test method

With the aim of validating a new standardized Coaxial Double Ring testing procedure, without overpressure and with fixed geometry, an ad hoc theoretical approach has been proposed here to rearrange the laboratory outcomes accounting for the effects of the geometric non-linearities associated with such a testing configuration. By borrowing this idea, once the experimental values of the failure load have been determined, it has been possible to obtain an expression in closed form (fully defined by only two coefficients) of the maximum tensile stress (σ_max) in the core of the specimen. Following this, in order to make the laboratory outcomes comparable and homogeneous, the σ_max-values have been then re-scaled to a common reference condition (equibiaxial stress on a reference area, σ_eqbx), by means of the use of a correction coefficient (K) able to determine, under a condition of equal probability of failure, the effective area (A_eff) of the tested specimens. After being corrected to account for the effects of the stress corrosion cracking (static fatigue effect), all re-scaled data have been finally interpreted using a Weibull-type statistical distribution to determine the main fractile values of the glass strength. Doing so, despite some unavoidable approximations, this procedure furnished a highly effective means of determining the bending strength of float glass. Unlike the pure numerical approach proposed in codes and literature, which requires to correct the experimental data via FEM simulation, the rationale behind the proposed approach is in fact to elaborate the experimental data through an analytic treatment of the problem, which would greatly facilitate the interpretation of the data as well as the standardization of the testing procedure.     

Electrocatalytic hydrogen evolution of highly dispersed Pt/NC nanoparticles derived from porphyrin MOFs under acidic and alkaline medium

Platinum (Pt)-based electrocatalysts often exhibit an excellent electrocatalytic activity for hydrogen evolution due to their best hydrogen bonding energy, but materials with high Pt content can easily cause aggregation and reduce their efficiency. In this article, Pt-based electrocatalysts with uniform dispersion and high efficiency were fabricated by a successive hydrothermal and calcination method, and the uniformly distributed Pt nanoparticle was mainly due to the anchoring effect of porphyrin ring in porphyrin MOFs, which made the minimized agglomerations as much as possible in the process of high temperature calcination. The results showed that the optimal Pt/NC-850 could reach current density of 10, 50 and 100 mA cm^?2 with only 17, 82 and 152 mV overpotentials, while the Pt/NC-850 also exhibited a superior stability and durability under acidic medium. Impressively, the Pt/NC-850 also had an excellent activity, good stability and durability under alkaline medium.     

Dynamic analysis of spinning triangle geometry part 2: spinning triangle geometry and yarn quality

This paper examines empirical relationships between the geometrical parameters of the spinning triangle and the quality parameters of ring spun yarns. For this purpose, controlled variations in the geometry of the spinning triangle were induced using two existing modifications in the ring spinning process and by varying the yarn twist level. The geometrical parameters of the spinning triangle were measured using the clear rubber roller combined with digital image processing techniques as described in the first part of this study. The yarn quality parameters measured included yarn hairiness, strength, elongation and evenness. Yarn hairiness showed more noticeable sensitivity towards the physical shape of the spinning triangle than yarn tenacity, while yarn evenness and elongation were not significantly influenced by changes in spinning triangle geometry.     

综合传动装置胀圈密封轴槽间隙设计方法

研究一种基于理论计算与CFD仿真的胀圈密封环轴槽间隙尺寸设计方法。基于流体力学的基本方程,建立胀圈密封流场的数学模型;结合实际工况与使用要求,确定胀圈密封环与轴槽径向间隙、轴向间隙及配流衬套与旋转轴之间的间隙尺寸的约束范围;建立流场的计算流体力学模型,通过正交试验设计,分析影响胀圈密封性能的高灵敏度因素;以密封泄漏量最小为目标函数,选取最佳的轴槽间隙设计参数。结果表明,研究的3种间隙中,相比于胀圈密封环与轴槽的径向间隙、轴向间隙,配流衬套与旋转轴之间的间隙对密封环的泄漏量影响更为显著,当配流衬套与旋转轴之间的间隙增大,泄漏量也随之增大。     

Advances in analysis of total uncertainties in a semi‐invasive residual stress measurement method

The ability to characterise residual stress distribution accurately and over different length scales, particularly deep into an engineering part, plays a significant role in assessing structural integrity. Two most commonly used techniques to measure residual stress fields deep into engineering components include neutron diffraction (ND) and deep‐hole drilling (DHD). As the measurements depend on several physical quantities, they are susceptible to error. The error or uncertainties may turn substantial and compromise the suitability of the results. Although noninvasive, the neutron diffraction technique is neither readily available nor portable and is limited to approximately 60‐mm‐thick specimen; errors associated with results become unacceptable at greater flight paths. Moreover, a mock‐up representing the engineering component is normally used in the ND technique. In contrast, the DHD technique is portable and measures residual stresses with high spatial resolution. An error propagation technique was applied to develop an error analysis procedure taking into consideration various stages of the DHD method and successfully applied to different DHD measurements. An essential feature comprising the effect of plasticity due to the creation of reference hole in the DHD procedure has not yet been taken into account in the error analysis procedure. This paper briefly describes how the uncertainties due to the creation of the initial reference hole can be determined. The effect of plasticity in the drilling procedure is quantified in this study. This error is combined with other sources of error and formulated to determine the total error. An incremental DHD technique was used to measure the complex triaxial residual stress field in an as‐welded circular disc, and the measured data were used to illustrate the total error using the error analysis method developed in the study.     

Influence of aliphatic polycarbonate middle block on mechanical and microstructural behaviour of triblock copolymers based on poly(l‐lactide) and polycarbonate

Three different ABA‐type triblock copolymers each containing biodegradable aliphatic polycarbonate as the middle block and poly(l ‐lactide) as the outer blocks were synthesized and the influence of the methylene chain length of the aliphatic polycarbonate middle block on various properties of the triblock copolymers was evaluated. Differential scanning calorimetry and wide‐angle X‐ray diffraction studies revealed that the incorporation of the outer blocks reduced the crystallinity of the middle aliphatic polycarbonate block. Variation of methylene chain length of the middle block led to a change in morphology from spherical to cylindrical as evidenced from atomic force microscopy studies. In addition, the mechanical properties of the block copolymers showed semi‐ductile to quasi‐brittle behaviour depending upon the composition of the middle block which was also confirmed using scanning electron microscopy. Dynamic mechanical analysis of the triblock copolymers indicated that storage modulus increased with a decrease in methylene chain length. © 2018 Society of Chemical Industry