The study of possibility of efficient use of mineral grain concentrates as bearing elements in diamond wheel working layer

The authors look into the potentiality of efficiently using natural mineral grain concentrates as bearing elements in the abrasive layer of diamond wheels in order to improve their performance in grinding operations.     

Technological aspects of controlling structural orientation of the working layer in superabrasive wheels

The authors of the paper discuss the importance of taking into account the structural orientation of a working layer in grinding wheels of superhard materials—superabrasive grinding wheels. Some manufacturing methods to be used in pressing and sintering of a wheel working layer are put forward, which permit controlling the layer’s structural orientation.     

The structurally changed layer of superabrasive wheel and workpiece contact surfaces as a factor of improving their wear resistance (film component)

The paper addresses the formation of a structurally changed surface layer of contact surfaces of a superabrasive wheel and a workpiece under the action of electrophysical machining methods. The formation of films on these surfaces is shown to alter their electrophysical properties and tribotechnical characteristics and provide conditions for improving wear resistance of the contact surfaces.     

The structurally changed layer of superabrasive wheel and workpiece contact surfaces as a factor of improving their wear resistance (a Change of Elemental Composition)

The paper addresses the formation of a structurally changed contact surface layer in a superabrasive wheel and workpiece under thermal and plasma actions, which occurs through redistribution of elemental composition in the material subjected to such actions. The change of the elemental composition is shown to have an effect on mechanical characteristics of the contact surfaces and thus makes it possible to find conditions for improving their wear resistance.     

The use of CFD to improve the performance of a chilled multi-deck retail display cabinet

Maintaining food temperatures below critical values is the key to maximising the high quality display life of chilled foods. Studies were carried out to see if computational fluid dynamic (CFD) modelling could be used to rapidly identify the changes that would be required to an existing multi-deck display cabinet so that it would meet a higher test specification. Implementing the changes on a Pastorfrigor MV 200TP display cabinet reduced the average power consumption from 1.37 to 1.29 kW as well as significantly reducing the number of test packs which spent any time above 4 °C, from 12 to 1.     

The use of two reactive elements to optimize oxidation performance of alumina-forming alloys

Abstract

Standard reactive element (RE) studies have characterized the behavior of single RE additions such as Y, La or Hf. However, several commercial alumina-forming alloys are “co-doped” with two or more RE additions which allows the total amount of RE dopant in the alloy to be reduced. The oxidation performance of both commercial and laboratory-made co-doped alloys shows better scale adhesion and/or slower scale growth rates than comparable alloys with one RE addition. Characterization of the alumina scales showed no significant change in the grain structure with co-doping; however, as the total RE addition was reduced in co-doped alloys, a smaller volume of RE-rich oxides was observed within the scale. Quantification of the amount of RE ionic segregation on alumina scale grain boundaries formed on single doped and co-doped alloys showed similar amounts of segregation.     

Composites based on cBN micron powders structured by carbon binder for the application as functional elements in the working layer of diamond-abrasive tools. Part 2. Composites as bearing elements

The authors discuss the application of composites based on finely dispersed cubic boron nitride micron powders as polycrystalline wear-resistant bearing elements in the working layer of diamond abrasive wheels for the purpose of improving the wheel performance in grinding.     

A Study of the influence of plasma treatment on the working surface of superabrasive grinding wheels

The paper addresses the effect of plasma treatment on the working surface of polymer- and metal-bonded superabrasive grinding wheels. The investigation has shown a change in hardness of the wheel surface treated with a plasma jet. The paper provides some data on the performance of plasmatreated grinding tools.     

Abrasive cutting factor as a characteristic reflecting the performance parameters of superabrasive grinding

The paper addresses the physical meaning and tendencies of variation of the abrasive cutting factor f _a = P _z /P _y as applied to the processes of grinding with superabrasive wheels. The author shows in which cases one should try to increase the f _a value. A classification of work materials by this factor is put forward.     

Ways to improve the bending response of finite elements

Four new ways to relieve the excessive bending stiffness of linear elements are described, and incorporated into plane elements. All satisfy the ‘patch test’. The new elements are compared with existing elements in test problems. Application to three-dimensional problems is proposed.     

The use of a mixed coupling agent system to improve the performance of polypropylene-based composites reinforced with short-glass-fibre mat

In order to improve the mechanical properties of composites consisting of polypropylene reinforced with mats of short glass fibres, the fibre surface was treated with a silane coupling agent, N-β(N-vinylbenzylaminoethyl)-γ-aminopropyl trimethoxy silane hydrogen chloride (STS), and a titanate coupling agent, isopropyltriisostearoyl titanate (TTS). The flexural properties and the impact absorption energy of these composites were measured as a function of coupling agent concentration. STS-only treatment of the fibre surface enhanced the flexural strength and the flexural modulus of the composite, while TTS-only treatment decreased the flexural strength and the flexural modulus. The improved flexural properties of the composite brought about by the STS-only treatment were obtained at the cost of its impact absorption energy, whereas TTS-only treatment showed the inverse characteristics. However, in a mixed coupling agent system, the impact absorption energy of the composite was improved without a reduction in the flexural properties. A morphological study of the fracture surfaces of the composite after impact testing, void content measurement and single-fibre fragmentation test were also carried out to understand the interfacial phenomena of the surface treated composites.     

The use of transition elements

Since the introduction of transition elements for crack tip singularity modelling, a number of opinions have been expressed regarding their application and performance. In particular, conflicting proposals concerning optimal transition element size have been suggested. In order to resolve the anomaly, a critical examination of these proposals was made. Consequently, several inconsistencies with regard to the derivation of the mid-node location of these transition elements were revealed. The effects of these inconsistencies were examined numerically and the accuracy of the computed stress intensity factors was compared with the original formulation of Lynn and Ingraffea. The results of the numerical analyses appear to show no discernible optimal transition element size.     

The performance of spheroidal infinite elements

A number of spheroidal and ellipsoidal infinite elements have been proposed for the solution of unbounded wave problems in the frequency domain, i.e solutions of the Helmholtz equation. These elements are widely believed to be more effective than conventional spherical infinite elements in cases where the radiating or scattering object is slender or flat and can therefore be closely enclosed by a spheroidal or an ellipsoidal surface. The validity of this statement is investigated in the current article. The radial order which is required for an accurate solution is shown to depend strongly not only upon the type of element that is used, but also on the aspect ratio of the bounding spheroid and the non‐dimensional wave number. The nature of this dependence can partially be explained by comparing the non‐oscillatory component of simple source solutions to the terms available in the trial solution of spheroidal elements. Numerical studies are also presented to demonstrate the rates at which convergence can be achieved, in practice, by unconjugated‐(‘Burnett’) and conjugated (‘Astley‐Leis’)‐type elements. It will be shown that neither formulation is entirely satisfactory at high frequencies and high aspect ratios. Copyright © 2001 John Wiley & Sons, Ltd.     

The attribute-trend-similarity method to improve learning performance for small datasets

Small data-set learning problems are attracting more attention because of the short product lifecycles caused by the increasing pressure of global competition. Although statistical approaches and machine learning algorithms are widely applied to extract information from such data, these are basically developed on the assumption that training samples can represent the properties of the whole population. However, as the properties that the training samples contain are limited, the knowledge that the learning algorithms extract may also be deficient. Virtual sample generation approaches, used as a kind of data pretreatment, have proved their effectiveness when handling small data-set problems. By considering the relationships among attributes in the value generation procedure, this research proposes a non-parametric process to learn the trend similarities among attributes, and then uses these to estimate the corresponding ranges that attribute values may be located in when other attribute values are given. The ranges of the attribute values of the virtual samples are then stepwise estimated using the triangular membership functions (MFs) built to represent the attribute sample distributions. In the experiment, two real cases are examined with four modelling tools, including the M5′ model tree (M5′), multiple linear regression, support vector regression and back-propagation neural network. The results show that the forecasting accuracies of the four modelling tools are improved when training sets contain virtual samples. In addition, the outcomes of the proposed procedure show significantly smaller predictive errors than those of other approaches.     

IT tools to improve the performance of metalworking SMEs

The small manufacturing enterprise is typically recognized as a company that is heavily reliant on its human constituents, namely the skilled manufacturing operators who accept a high level of responsibility for the parts they produce, and also have a major influence on the existence of the company. The significant reduction in costs of IT technology and software tools over recent years has enabled the SME to use hardware and software systems that were previously only available to larger companies. This paper investigates the use of modern IT tools and their application within a metalworking SME. The work is based on a number of major research areas, namely the holonic manufacturing paradigm, distributed planning and control, and open controllers for CNC control. The major emphasis of the paper is the design of appropriate IT tools tailored for the requirements of 'human-centred manufacturing systems' based on holonic concepts to support an autonomous cooperative working environment.     

提升铁电材料光催化性能的途径

光催化反应在降解有害污染物、转化温室气体、生产氢气、消灭有害菌等领域有重要的应用。近年来,具有自发极化的铁电材料被认为是一种新的候选者,其自发极化能产生内置电场,为光生载流子的传输提供驱动力。这一特性有望解决人们在光催化领域中所遇到的棘手问题：电子-空穴对的复合。也正因为具有这一特性,对铁电材料的光催化性能研究主要集中在了减少空穴和电子的复合。但实际上要提高光催化效率还需要通盘考虑整个催化过程,其中包括光子的吸收、光生电子空穴的分离迁移、终端反应这3个关键阶段。以上述光催化过程的三个阶段为着眼点,整理了近年的典型成果,梳理了在光催化的不同阶段提升铁电材料催化性能的有效手段,希望通过我们的总结能够为后续研究工作提供有益的参考。     

The use of mechanical refrigeration to improve the storage of pesticide treated grain

Cooling a bulk of stored grain greatly increases the persistence of chemical pesticides applied to it. In this work, an established mathematical model of heat and mass transfer and chemical kinetics is used to simulate the effects of blowing mechanically refrigerated air through grain on the subsequent rate of decay of pesticides. It is demonstrated that the hardware suitable for such a task may be based on standard, commercial, air conditioners fitted with an appropriate air handling system capable of forcing cold air through the grain. Although the rates of decay of the two pesticides, methacrifos and malathion, in uncooled grain bulks are very sensitive to initial, grain moisture content and temperature, grain cooling renders their degradation relatively insensitive to these variables. It is shown that when the grain cooling units are operated for a fixed time there is an optimum air flow rate for achieving the maximum preservation of pesticide. This air flow rate is in the typical operating range of the commercial air conditioner studied. The effects of cooling strategy and geographical location on pesticide preservation in cooled grain bulks are investigated. The physico-chemical aetiology of these phenomena is discussed in some detail.