Linear Size Optimal $q$-ary Constant-Weight Codes and Constant-Composition Codes

An optimal constant-composition or constant-weight code of weight w has linear size if and only if its distance d is at least 2w-1. When d ? 2w, the determination of the exact size of such a constant-composition or constant-weight code is trivial, but the case of d=2w-1 has been solved previously only for binary and ternary constant-composition and constant-weight codes, and for some sporadic instances. This paper provides a construction for quasicyclic optimal constant-composition and constant-weight codes of weight w and distance 2w-1 based on a new generalization of difference triangle sets. As a result, the sizes of optimal constant-composition codes and optimal constant-weight codes of weight w and distance 2w-1 are determined for all such codes of sufficiently large lengths. This solves an open problem of Etzion. The sizes of optimal constant-composition codes of weight w and distance 2w-1 are also determined for all w ? 6, except in two cases.     

Composite beam composed of steel and precast concrete (Modularized Hybrid System,MHS). Part I: experimental investigation

An experimental investigation of composite beams composed of wide flange steel and precast concrete is presented. The bottom flange of the steel section is encased in precast concrete. Utilizing the merits of both steel and concrete material, the size of the steel beams can be reduced without sacrificing performance. The bottom flange of the steel beam is reinforced with concrete at a manufacturing plant, eliminating the use of temporary pour forms. The composite beams were tested to investigate how the size of the wide flange steel and how the top and bottom reinforcements influence the behaviour of the beams. Flexural load carrying capacity, load displacement relationships and failure modes were examined. The test specimens were T‐shaped composite beams with slabs, each measuring 10‐m long. The flexural moment strength of all of the composite beams—at both the yield limit state and the maximum load limit state—was measured and compared with the analytical flexural capacity. The stiffness degradation, ductility and dissipating energy capabilities of the composite beams were investigated based on the hysteresis curves. The composite beams tested in this study successfully reduced both the floor height of the building and the size of the steel beams needed to meet code requirements. Copyright © 2008 John Wiley & Sons, Ltd.     

Optimizing natural rubber blends for examination gloves: Vacuum radiation for mechanical strength and solvent barrier

Natural rubber (NR) is emblematic of sustainability compared to synthetic rubber. However, the tradition of adding sulfur as a vulcanization ingredient results in the release of toxic substances and the potential for health issues. In this study, a feasible strategy was proposed to replace sulfur and discover a safe bulk modification process for NR films. The results have shown that the NR particle size was disintegrated to below 10 nm by gamma irradiation. High tension strength up to 24.45 MPa was observed in the vulcanized NR blend film, which could be elongated up to 800% strain after exposure to an optimum dose of 14 kGy. In comparison to commercial NR latex and nitrile gloves, the vulcanized NR/ SIS films exhibited better chemical resistance ability against hexane, methanol, toluene, and acetone, as revealed by the permeation test. The appearance of amorphous regions and highly oriented NR crystallites was observed through transmission electron microscopy. Findings from this study propose the vacuum radiation strategy that can replace conventional vulcanization methods, resulting in NR films with high mechanical and barrier performance. Furthermore, the emission of toxic substances is reduced by this green process, making it practically useful for potential chemical-resistant examination glove applications.     

Formation of novel mesoporous TiC microspheres through a sol–gel and carbothermal reduction process

Novel mesoporous TiC microspheres with uniform size are synthesized via a sol–gel combined carbothermal reduction process. A microfluidic aerosol nozzle was used to produce droplets which were subsequently dried into gel microspheres under different conditions. The influence of drying temperatures and sol aging time on the diameters of obtained gel microspheres was investigated. The spherical morphology of TiC spheres can be maintained after a two-step heat treatment. Moreover, the TiC microspheres exhibit a high surface area of 267 m²/g and consist of 30–50 nm nano TiC grains and 4.5 nm pores. This unique nanostructure is directly formed from the carbothermal reduction of non-porous and template-free titania/carbon spheres.     

Characteristics of Milk Powders Produced by Spray Freeze Drying

Skim and whole milk powders were manufactured at lab scale by spray freeze drying (SFD), using liquid nitrogen as the cryogen. The polydispersity of droplet/particle sizes was limited using an encapsulator nozzle to atomize the feed. Particle morphology was examined using a scanning electron microscope. Samples were compared with equivalent spray-dried powders in tests of wettability and dissolution in water. The spray freeze-dried powders were found to be highly porous, with a uniform structure of pores throughout the entire particles. When tested in water, SFD skim milk powders wetted roughly three times as fast as industrially spray-dried agglomerated skim milk powders and were observed to dissolve rapidly by breaking down into smaller particles.     

Fundamental mechanisms of bonding of glass fiber reinforced polymer reinforcement to concrete

Fundamental mechanisms of bonding between glass fiber reinforced polymer (GFRP) bar and concrete are presented. Contributions from chemical bonding, bearing resistance, and frictional resistance to bond were delineated by measuring the following: the load corresponding to complete debonding of the bar, the load corresponding to onset of sliding and pullout of the bar along the entire embedment length, and the frictional load corresponding to frictional resistance to sliding. Research findings indicate that while chemical bonding was the main contributor to the interfacial bond strength, the other two mechanisms contributed to the pullout strength of the bar. Correlation between the bar’s surface geometry and the contributions from the three mechanisms are discussed.     

The adsorption of chlordane by wheat flour from chlordane-treated shelf paper

Packaged wheat flour stored in direct contact with chlordane-treated shelf paper adsorbed with time appreciable amounts of the pesticide from the paper. Direct contact of the package with the paper was more conducive to flour contamination than it was from exposure of the flour to the vaporized pesticide components from the paper. Sorption effects of the pesticide with flour varied with the mode of exposure and the type of bag used, i.e. when the bags were in direct contact with the shelf paper, the flour packaged in polyethylene bags contained the largest amount of chlordane residue (29 ppm), which decreased about 10 per cent when packaged in single-thickness kraft paper bags and about 35 per cent in double-thickness kraft paper bags. When the bags were separated from direct contact with the shelf paper by means of open glass containers, contamination of the flour was tangibly decreased, whereby the amounts of residue found in the kraft single- and double-thickness paper bags were 0·4 and 0·3 ppm, respectively, compared to only 0·06 ppm in the polyethylene bags.