Search results

Currently, the existing similar simulation is still limited in the following aspects: un-rotatable laboratory devices, the difficulty in the pavement on steep seams and great error of the experimental data.

To address above-mentioned problems, this study combined theoretical analysis and numerical simulation and developed a rotatable experimental system for similar simulation on steep coal seam mining on the premise of ensuring experimental safety.

The present experimental system mainly consists of the model support, the rotation system and the bearing system. By taking into account the experimental requirements and actual laboratory space, the sizes of the model support and the bearing system were determined. Considering the requirements in space limit and rotation stability, the rotation mode of vertical sliding on the left side and the horizontal sliding on the lower side was designed.

Using programmable logic controller automatic angle control technology, the rotation angle, velocity and displacement of the model can be automatically adjusted and controlled so as to achieve safe rotation and precise control. Finally, the calculation method of the mass of the required similar materials for paving the coal strata at different inclination angles and in different horizons was analyzed, and the related mass proportion calculation software was developed.

1. Introduction Victorian librarians saw the public library as a place where citizens could find material relating to their contemporary community — its health, finance, welfare and educational organisations; it would also be a depository for items relating to its past. By 1901 the Cambridge Free Library had taken so much care in this regard that “the historian of the future will find here all that he will need and that is as it should be”. But priorities changed within the library service. Within 50 years 60 per cent of that material had been dispersed and the remainder moved out of public view where it lay largely unused and unremembered. It had no place in the post‐war priorities of the public library service which had turned instead to “current information”, lists of societies, tourist information and the development of a general reference service concentrating on areas of comprehensiveness such as bus and train timetables from across the country. Today, community information and computer databases are the current information priorities, and although the unique, comprehensive local collection has been revived, invigorated and republicised, it remains an oddity, non‐conforming to the pre‐ordained management structure, an “albatross inheritance”.

Anecdotal evidence indicates that one of the more difficult issues faced by accounting students is the understanding and preparation of the statement of cash flows (SCF). This study investigates the impact of different instruction methods for covering the statement on student learning outcomes. Currently, two prominent intermediate-level financial accounting texts cover the SCF primarily in one end-of-text chapter, a massed presentation. The current study argues that the SCF is a topic that is cross-sectional in nature, and is applicable to the textbook material on the accounting transactions that are spread throughout the texts. In accordance with the spacing effect (Dempster, 1988), instruction of SCF material across the major recognition and measurement topic chapters, a spaced presentation format, potentially yields enhanced learning outcomes in comparison to the massed presentation.

Across three semesters of an intermediate-level financial accounting course, the SCF delivery format and coverage were varied in a 1 × 3 between-subjects experiment. The subjects completed an indirect-method SCF preparation task, which I analyzed across the three conditions.

Students learning the SCF presentation of intermediate-level transactions in a spaced presentation earned higher scores on the task compared to those learning the material in a massed format. Furthermore, the students exposed to the massed presentation performed no better than those not instructed on the material.

I base my findings on the results of one assessment of the SCF in one course. Future research should consider various tasks related to the SCF at different course levels and across a variety of instructional techniques.

The results imply that changes to the delivery of SCF material could potentially produce benefits to student learning.

This study highlights the demand for low-cost and high accuracy products through the design and development of new 3D printing technologies. Besides, significant progress has been made in this field. A comparative study helps to understand the latest development in materials and future prospect of this technology.

Nevertheless, a large amount of progress still remains to be made. While some of the works have focused on the performances of the materials, the rest have focused on the development of new methods and techniques in additive manufacturing.

This paper critically evaluates the current 3D printing technologies, including the development and optimizations made to the printing methods, as well as the printed objects. Meanwhile, previous developments in this area and contributions to the modern trend in manufacturing technology are summarized briefly.

The paper can be summarized in three sections. Firstly, the existing printing methods along with the frequently used printing materials, as well as the processing parameters, and the factors which influence the quality and mechanical performances of the printed objects are discussed. Secondly, the optimization techniques, such as topology, shape, structure and mechanical property, are described. Thirdly, the latest development and applications of additive manufacturing are depicted, and the scope of future research in the relevant area is put forward.

April 8, 1970 Building — Construction regulations — Applicability — Goggles to be provided where any specified process carried on — “Breaking, cutting,…of stone, concrete, slag or similar materials” — Whether bricks “similar materials” — Plaintiff demolishing brickwork with hammer and chisel — Injury to eye caused by falling dust — Whether engaged on “process” within the regulation — Failure of employer to provide goggles — Whether in breach of regulation — Whether negligent — Regulation requiring employer to provide protection from falling material — Whether applicable — Construction (General Provisions) Regulations, 1961 (S.I. 1961 No. 1580), regs. 46(1), 52, Sch.(2).

Functionally graded materials are a special class of composites in which material are graded either continuously or layered wise depending upon its applications. With such variations of materials, the properties of structure vary either lengthwise or thickness wise. This paper aims to investigate models for effective estimation of material properties, as it is necessary for industries to identify the properties of composites or functionally graded materials (FGM’s) before manufacturing and also to develop novel material combinations.

Available models were compared for different material combinations and tested with experimental data for properties such as Young’s modulus, density, coefficient of thermal expansion (CTE) and thermal conductivity. Combinations of metal–ceramic and metal–metal were selected such that their ratios cover a wide range of materials.

This study reveals different models will be required depending on the material used and properties to be identified.

The results of the present work will help researchers in the effective modeling of composites or FGM’s for any analysis.

This paper presents a comparison and review of various analytical methods with experimental data graphically to find out the best suitable method. For the first time, the Halpin-Tsai model was extended in the analysis of the CTE which shows good approximations.

Dissimilar materials found applications in the structural fields to withstand the different types of loads and provide multi-facet properties to the final structure. Aluminum alloy materials are mostly used in aerospace and marine industries to provide better strength and safeguard the material from severe environmental conditions. The purpose of this study is to develop new material with superior strength to challenge the severe environmental conditions.

In the present investigation, friction stir welding (FSW) dissimilar joints were prepared from AA6061 and AA5083 aluminum alloys, and the weld nugget (WN) was reinforced with hard reinforcement particles such as La₂O₃ and CeO₂. The tribological and mechanical properties of the prepared materials were tested to analyze the suitability of material in the aerospace and marine environmental conditions.

The results showed that the AA6061–AA5083/La₂O₃ material exhibited better mechanical and tribological characteristics. The FSW dissimilar AA6061–AA5083/La₂O₃ material exhibited lower wear rate of 7.37 × 10⁻³ mm3/m and minimum friction coefficient of 0.31 compared to all other materials owing to the reinforcing effect of La₂O₃ particles and the fine grains formed by FSW process at WN region. Further, FSW dissimilar AA6061–AA5083/La₂O₃ material displayed a maximum tensile strength and hardness of 378 MPa and 118 HV, respectively, among all the other materials tested.

This work is original and novel in the field of materials science engineering focusing on tribological characteristics of friction stir welded dissimilar aluminum alloys by the reinforcing effect of hard particles such as La₂O₃ and CeO₂.

IN the March 1951 issue of AIRCRAFT ENGINEERING an article was presented by D. L. McElhinney entitled ‘The Effects of Grain Direction on the Mechanical Properties of Light Alloy Extrusions’.

This study aims to propose and demonstrate a practical application of a new three-part holistic sensory evaluation (HSE) method for textiles and apparel based on the senses of sight, touch, hearing and smell. HSE method development was carefully documented, described and successfully applied to evaluate sensory characteristics and consumer perceptions and acceptance of bacterial cellulose (BC), a novel sustainable material for apparel.

In Part One of the HSE method, research participants described the material in their own words based on the senses of sight, touch, hearing and smell. In Part Two, they rated the intensities and their linking for 25 predetermined attributes describing BC. Part Three measured participants’ overall liking of BC and its perceived suitability for apparel and accessories.

Application of the HSE method resulted in an in-depth understanding of BC material. Areas for material improvements and positive characteristics were identified, providing direction for further development. Consumers found BC suitable for accessories and outer-layer garments but not for apparel.

Sensory evaluation of textiles and apparel has traditionally focused on the senses of touch and sight. The new HSE method allows evaluating the full range of sensory characteristics of materials/products and holistically assessing consumer perceptions. The method is especially useful for novel materials and wearable technology. BC has gained increased interests as a novel sustainable material, yet consumer studies have been lacking. This study reports a comprehensive evaluation of BC material from consumer perspective.

This paper aims to show critical processing issues observed for the newer restriction of the use of hazardous substances compliant laminate materials.

Several samples of the popular lead‐free and halogen‐free laminate materials were tested under laboratory conditions to ascertain their desmear characteristics in comparison to the standard FR4 and high T_g laminate materials available on the market. Literature searches and experiences in the field were used to give a supplier's point of view of the newer laminate materials.

The new directives forcing the exclusion of solder and restricting the use of halogens means that newer laminate materials have significantly different chemical and physical properties to laminates previously considered standard. These differences have a drastic effect on the desmearing process in general, making it more difficult to get high weight losses and, for almost all lead‐free materials, reducing the roughness that can be generated. This affects the copper/laminate bonding strength and so increases risks of blistering and hole wall pull away. Alternative approaches are required to improve this adhesion and one of these is to use a specifically designed low stress electroless copper with good adhesion properties.

Most of the work was performed under laboratory conditions and, although mainly substantiated in production lines, can only be used as a guide. Owing to the large amount of different laminate materials, applications and processing techniques it is difficult to predict the full effect for every PCB manufacturer. In‐house testing should be performed by individual PCB manufacturers on each laminate material considered suitable for their technical requirements.

The paper details the main areas to concentrate on when desmearing and metallising newer laminate materials and suggests alternative approaches to improve the processing of these materials.