Effects of the chemical foaming agents,injection parameters,and melt‐flow index on the microstructure and mechanical properties of microcellular injection‐molded wood‐fiber/polypropylene composites

Wood‐fiber‐reinforced plastic profiles are growing rapidly in nonstructural wood‐replacement applications. Most manufacturers are evaluating new alternative foamed composites, which are lighter and more like wood. Foamed wood composites accept screws and nails better than their nonfoamed counterparts, and they have other advantages as well. For example, internal pressures created by foaming give better surface definition and sharper contours and corners than nonfoamed profiles have. In this study, the microfoaming of polypropylene (PP) containing hardwood fiber was performed with an injection‐molding process. The effects of different chemical foaming agents (endothermic, exothermic, and endothermic/exothermic), injection parameters (the mold temperature, front flow speed, and filling quantity), and different types of PP (different melt‐flow indices) on the density, microvoid content, physicomechanical properties, surface roughness, and microcell classification of microfoamed PP/wood‐fiber composites were studied. A maleic anhydride/polypropylene copolymer (MAH‐PP) compatibilizer was used with the intention of improving the mechanical properties of microfoamed composites. The microcell classification (from light microscopy) and scanning electron micrographs showed that an exothermic chemical foaming agent produced the best performance with respect to the cell size, diameter, and distance. The polymer melt‐flow index and the variation of the injection parameters affected the properties and microstructure of the microfoamed composites. The density of the microfoamed hardwood‐fiber/PP (with a high melt‐flow index) composites was reduced by approximately 30% and decreased to 0.718 g/cm³ with an exothermic chemical foaming agent. Tensile and flexural tests were performed on the foamed composites to determine the dependence of the mechanical properties on the density and microvoid content of the foamed specimens, and these properties were compared with those of nonfoamed composites. MAH‐PP improved the physicomechanical properties up to 80%. With an increase in the mold temperature (80–110°C), the surface roughness was reduced by nearly 70% for the foamed composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1090–1096, 2005     

Development of flame retardancy properties of new halogen‐free phosphorous doped SiO2 thin films on fabrics

In this study, flame retardancy properties of fabrics treated with phosphorous (P) doped and undoped SiO₂ thin films were developed by sol–gel technique. As to this aim, P‐doped and undoped SiO₂ film were coated on cotton fabric from the solutions prepared from P, Si‐based precursors, solvent, and chelating agent at low temperature in air using sol–gel technique. To determine solution characteristics, which affect thin film structure, turbidity, pH values, and rheological properties of the prepared solutions were measured using a turbidimeter, a pH meter, and a rheometer machines before coating process. The thermal, structural, and microstructural characterization of the coating were done using differential thermal analysis/thermograviometry, fourier transform infrared spectroscopy, X‐ray diffractometry, and scanning electron microscopy. In addition, tensile strength, wash fastness, flame retandancy, and lightness properties of the coated fabrics were determined. To compensate the slight loss of tensile strength of samples, which occurred at the treated fabrics with P‐doped Si‐based solutions, the cotton fabrics were coated with polyurethane films during second step. In conclusion, the flame retardant cotton fabric with durability of washing as halogen‐free without requiring after treatment with formaldehyde was fabricated using sol–gel processing for the first time. Moreover the cotton fabrics, which were treated with P‐doped Si‐based solutions and then coated with polyurethane at second step, still has got nonflammable property. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Forced vibration of composite cylindrical helical rods

The dynamic behavior of composite cylindrical helical rods subjected to time-dependent loads is theoretically investigated in the Laplace domain. The governing equations for naturally twisted and curved spatial laminated rods obtained using Timoshenko beam theory are rewritten for cylindrical helical rods. The curvature of the rod axis, the anisotropy of the rod material, effect of the rotary inertia, axial and shear deformations are considered in the formulations. The material of the rod is assumed to be homogeneous, linear elastic and anisotropic. Ordinary differential equations in scalar form obtained in the Laplace domain are solved numerically using the complementary functions method to calculate the dynamic stiffness matrix of the problem accurately. The solutions obtained are transformed to the time domain using an appropriate numerical inverse Laplace transform method. The free vibration is then taken into account as a special case of forced vibration. The results obtained in this study are found to be in a good agreement with those available in the literature.     

Effect of the Inclined Edge Notches on the Fatigue-Fracture Behavior of Soft Annealed and Quenched AISI O2 Tool Steel

In this research, the effects of edge notches with inclined angles on the fatigue-fracture behavior and fatigue life between soft annealed and hardened AISI O2 tool steel (DIN 1.2842) were investigated. Hardening was provided by the quenching and cooling by oil. A rotating bending fatigue machine was used to determine the fatigue strength. It was found that edge notches caused a reduction in the fatigue strength and fatigue life for soft annealed AISI O2 steel, but this reduction transformed to an increase for quenched AISI O2 steel. In addition to this, kink occurred on the all inclined edge notches for both materials. After fatigue tests, the fracture surfaces, specimen surface microstructures and specimen center microstructures were observed by scanning electron microscopy.     

Immigration and location choices of native‐born workers in Canada

This paper investigates a possible crowding‐out effect of immigration in Canadian labour markets and explores how location choices of native‐born workers can be influenced by industry and occupation specific immigration clustering in both the potential destinations and the departure regions. We apply choice‐specific, clustered fixed‐effect response models. The results show that industry‐specific immigration clustering indices have strong and negative effects on the location choices of the native born. When the scaled immigration measures are used, the results confirm the ‘substitution’ hypothesis: native‐born workers who choose lower immigration in their destinations also move from the origins with higher immigration in their industry.     

Combined Cu‐CeO2 /YSZ and Ni/YSZ dual layer anode structures for direct methane solid oxide fuel cells

In this study, a conventional Ni/yttria‐stabilized zirconia (YSZ) anode and a new Cu‐CeO₂‐YSZ anode structure were assembled in an attempt to combine the advantages of both structures for use in direct methane solid oxide fuel cells. For this purpose, only a limited region (≤20 μm) of NiO/YSZ was deposited at the boundary of the electrolyte to benefit from the superior catalytic activity of Ni in the cells, while the rest of the cell benefited from the Cu‐CeO₂‐YSZ anode structure, which does not cause cracking reactions. First, the effects of different pore formers on the anode skeleton, as well as the interactions of the Ni‐Cu species in the anode skeleton, are discussed. Then, the NiO/YSZ‐interlayer‐containing button cells with different thicknesses (≤20) and different ratios of NiO (40 wt%, 50 wt%, and 60 wt%) were studied. After the examination of the cells, 2 model cells with outstanding performance and 2 additional internal reference cells, conventional Ni/YSZ and Cu‐CeO₂‐YSZ, were scaled up, and performance analysis and long‐term stability studies were carried out. As a result, for solid oxide fuel cells with increased carbonization resistance (around 6% performance loss due to carbonization after 100‐hour stability testing) and 86.1% of the initial performance of the conventional Ni/YSZ anode structure, a 15‐μm‐thick 40 wt% NiO/60 wt% YSZ interlayer with a dual layer anode structure is proposed.     

Operational strategies for seru production system: a bi-objective optimisation model and solution methods

In recent years, the interest in seru production system (SPS) has increased to enhance the flexibility of production systems. Because the worker resource in an SPS is critical for adapting to changes in demand, this study focuses on workforce-related operational strategies rarely considered for SPS. To this end, for the first time in the literature, a bi-objective workforce scheduling problem is addressed by considering the interseru worker transfer in SPS. A novel optimisation model is proposed to achieve two objectives, that of minimising makespan and reducing workload imbalance among workers. Because it is proved that the problem falls within a non-deterministic polynomial-time hardness (NP-hard) class, non-dominated sorting genetic algorithm-II (NSGA-II) is employed to solve large-sized problems. For small-sized problems, the second version of the augmented ε-constrained (AUGMECON2) method is implemented and Pareto-optimal solutions are obtained. A set of evaluation metrics is considered to compare two different operational strategies in terms of the desired objectives. The computational results indicate that allowing worker transfer leads to better results for all metrics. The main contribution of the present study is to provide a novel optimisation model for the addressed problem to compare two operational strategies by considering the heterogeneity inherent of workers.     

The use of pure methanol as fuel at high compression ratio in a single cylinder gasoline engine

The methanol has greater resistance to knock and it emits lower emissions than neat gasoline. As single cylinder small engines have low compression ratio (CR), and they run with slightly rich mixture, their power are low and emission values are high. The performance can be increased at high CR if these engines are run with fuels which have high octane number. In this study, methanol was used at high CR to increase performance and decrease emissions of a single-cylinder engine. Initially, the engine whose CR was 6/1 was tested with gasoline and methanol at full load and various speeds. Then, the CR was raised from 6/1 to 8/1and 10/1, gradually. The knock was not observed at the CRs of 8/1 and 10/1 when using methanol while the knock was observed at the CR of 8/1 when using gasoline. The knock was determined from the cylinder pressure-time curves. The results showed that some decreases were obtained in CO, CO₂ and NO_x emissions without any noticeable power loss when using methanol at the CR of 6/1. By increasing the CR from 6/1 to 10/1 with methanol, the engine power and brake thermal efficiency increased by up to 14% and 36%, respectively. Moreover, CO, CO₂ and NO_x emissions were reduced by about 37%, 30% and 22%, respectively.     

Energy efficiency in pumps

In this paper, “energy efficiency” studies, done in a big industrial facility’s pumps, are reported. For this purpose; the flow rate, pressure and temperature have been measured for each pump in different operating conditions and at maximum load. In addition, the electrical power drawn by the electric motor has been measured. The efficiencies of the existing pumps and electric motor have been calculated by using the measured data.

Potential energy saving opportunities have been studied by taking into account the results of the calculations for each pump and electric motor. As a conclusion, improvements should be made each system. The required investment costs for these improvements have been determined, and simple payback periods have been calculated.

The main energy saving opportunities result from: replacements of the existing low efficiency pumps, maintenance of the pumps whose efficiencies start to decline at certain range, replacements of high power electric motors with electric motors that have suitable power, usage of high efficiency electric motors and elimination of cavitation problems.