A modeling study on lateral compressive behavior of structured needle - punched nonwovens

The aim of this work is to study the compression behavior of cord-structured needled fabrics. In order to achieve the objectives of this research, melt-spun polypropylene fibres of various linear densities have been produced by varying the spinning pump speed. The effect of linear density of melt-spun polypropylene fibres on compressive behavior of the fabrics has been investigated. A Zwick tester set in compressive mode is used to obtain variation of compressive force versus compression thickness. Van Wyk law is adapted to model the lateral compressive behavior of cord-structured needled fabrics. The experimental results are compared with the theoretical curves calculated using Van Wyk law. Results show that the increase in linear density of fibres tends to reduce the compressive force required to compress the samples to a pre-defined thickness. An acceptable conformity between Van Wyk’s equation and compressive behavior of cord-structured needled fabrics is also observed

High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes

High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes has been developed. This technique allows injection of the hypochlorite solution into the channel of the fibres at a high pressure. The effect of this treatment on water flux of the membranes is studied. The results are compared with the water flux of identical membranes subjected to traditional hypochlorite treatment. Concentrated polymer solution containing polysulfone (PSf) /poly-vinyl pyrrolidone (PVP-K90)/N-Methyl-2-pyrrolidone (NMP) in weight ratio of 15/5/80 together with two types of bore fluids have been used for the production of two types of hollow fibre membranes via dry-wet-spinning process. Distilled water and mixture of NMP/ distilled water are used as bore fluids. Atomic force microscopic analysis and image processing technique (SEM microphotographs) have been employed to investigate performance of PSf hollow fibres treated with the traditional and high pressure injection techniques in relation to the composition of bore fluid. It is observed that in general both treatment methods result in the increase in water flux of the hollow fibres due to elimination of PVP (poly-vinyl pyrrolidone) swelling and alteration in pore size and pore distribution. The rate of increase in water flux in the membranes treated by high pressure injection technique is found to be higher in comparison to traditionally treated membranes. It is also found that the membranes produced using a mixture of NMP/ distilled water as bore fluid exhibit a higher rate of flux increase than those produced using distilled water. High pressure injection technique yields to production of highly permeable membranes. In addition, it is found that the composition of bore fluid controls the performance of the membranes subjected to hypochlorite treatment

Prediction of heat transfer and air permeability properties of light weight nonwovens using artificial intelligence

Effects of pore sizes and distribution of pore sizes of light weight spunlace nonwovens on the heat transfer and air permeability of these fabrics have been studied. Image analysis has been applied to extract the geometrical features of the cross-section of spunlace samples (pore sizes and distribution of pore sizes) at the different layers in the thickness direction. A neural network model is also developed for the prediction of heat transfer and air permeability with respects to structural properties of light weight nonwovens. Results show that the increase in pore sizes and distribution factor of pore sizes increases the air flow rate and heat transfer properties of the nonwoven fabrics respectively. The neural network model also predicts the air permeability and heat transfer of nonwovens in terms of the measured geometrical properties

A modeling study on lateral compressive behavior of structured needle - punched nonwovens

31-35The aim of this work is to study the compression behavior of cord-structured needled fabrics. In order to achieve the objectives of this research, melt-spun polypropylene fibres of various linear densities have been produced by varying the spinning pump speed. The effect of linear density of melt-spun polypropylene fibres on compressive behavior of the fabrics has been investigated. A Zwick tester set in compressive mode is used to obtain variation of compressive force versus compression thickness. Van Wyk law is adapted to model the lateral compressive behavior of cord-structured needled fabrics. The experimental results are compared with the theoretical curves calculated using Van Wyk law. Results show that the increase in linear density of fibres tends to reduce the compressive force required to compress the samples to a pre-defined thickness. An acceptable conformity between Van Wyk’s equation and compressive behavior of cord-structured needled fabrics is also observed

A power-efficient coverage scheme for cell-edge users using cognitive beamforming

This paper addresses the problem of strong intercell interference on cell-edge users in conventional cellular networks by deploying cognitive cells within the vicinity of primary cell borders. The cognitive base stations serve primary cell-edge users within the cognitive cells. In return, the cognitive base stations are rewarded by the same spectrum allocated to the primary base stations to serve secondary users. We propose a strategy that is formulated as an optimization problem for the cognitive cell to minimize the total transmit power of the cognitive base station. This optimization problem is subjected to maintain a controlled level of interference at the primary outer-cell users falling outside of the cognitive cell and to assure required levels of signal-to-noise-plus-interference-ratio (SINR) at all primary cell-edge and secondary users within the cognitive cell. Simulation results confirm that the beamforming scheme in conjunction with the proposed cognitive structure lead to a significant reduction in overall power transmitted in the network

Prediction of heat transfer and air permeability properties of light weight nonwovens using artificial intelligence

373-379Effects of pore sizes and distribution of pore sizes of light weight spunlace nonwovens on the heat transfer and air permeability of these fabrics have been studied. Image analysis has been applied to extract the geometrical features of the cross-section of spunlace samples (pore sizes and distribution of pore sizes) at the different layers in the thickness direction. A neural network model is also developed for the prediction of heat transfer and air permeability with respects to structural properties of light weight nonwovens. Results show that the increase in pore sizes and distribution factor of pore sizes increases the air flow rate and heat transfer properties of the nonwoven fabrics respectively. The neural network model also predicts the air permeability and heat transfer of nonwovens in terms of the measured geometrical properties. </span

An investigation into sound transmission loss by polypropylene needle-punched nonwovens

In this work, the effects of variables such as initial carded web mass, needle penetration depth, punch density, and the frequency of incident sound wave on transmission of sound through polypropylene needle-punched nonwovens were investigated. Fibrous carded webs using commercially available 17 dtex, 90 mm staple length polypropylene fibers were prepared with different mass per unit area using carding machine. Samples were needled at various punch-densities and needle penetration depths were produced. Design points of experiments were set up using Taguchi experimental design method. Sound transmission loss (STL) of needled samples was measured using an impedance tube equipped with four microphones. Minitab software was used to analyze the sound transmission ability of the samples. Results indicated that all of the considered controllable factor have significant effects on STL values determined for the needled nonwovens. Also, initial carded web mass was found to be the most influential factor affecting sound transmission through the samples. It was concluded that an increase in thickness of the samples as well as mass per unit area of nonwovens results in higher sound transmission loss by the samples

High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes

405-413High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes has been developed. This technique allows injection of the hypochlorite solution into the channel of the fibres at a high pressure. The effect of this treatment on water flux of the membranes is studied. The results are compared with the water flux of identical membranes subjected to traditional hypochlorite treatment. Concentrated polymer solution containing polysulfone (PSf) /poly-vinyl pyrrolidone (PVP-K90)/N-Methyl-2-pyrrolidone (NMP) in weight ratio of 15/5/80 together with two types of bore fluids have been used for the production of two types of hollow fibre membranes via dry-wet-spinning process. Distilled water and mixture of NMP/ distilled water are used as bore fluids. Atomic force microscopic analysis and image processing technique (SEM microphotographs) have been employed to investigate performance of PSf hollow fibres treated with the traditional and high pressure injection techniques in relation to the composition of bore fluid. It is observed that in general both treatment methods result in the increase in water flux of the hollow fibres due to elimination of PVP (poly-vinyl pyrrolidone) swelling and alteration in pore size and pore distribution. The rate of increase in water flux in the membranes treated by high pressure injection technique is found to be higher in comparison to traditionally treated membranes. It is also found that the membranes produced using a mixture of NMP/ distilled water as bore fluid exhibit a higher rate of flux increase than those produced using distilled water. High pressure injection technique yields to production of highly permeable membranes. In addition, it is found that the composition of bore fluid controls the performance of the membranes subjected to hypochlorite treatment

Power-efficient downlink transmission in multicell networks with limited wireless backhaul

This article shows that division of a cell into tiers of smaller cells reduces power consumption. However, using the same frequency-time resources within multiple divided cells causes strong intercell interference. Given this circumstance, three beamforming techniques for multicell networks are presented to tackle the resultant challenging intercell interference environment. The schemes minimize the total transmit power across the coordinating base stations while simultaneously considering the quality of service of each user so that the latter is not unduly affected. Since the beamforming approaches require the circulation of information, an energy-efficient backhaul protocol is demonstrated