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In the past three years, microvia drilling using laser technology has become the dominant method of producing blind vias smaller than 150μm. The ablation characteristics…
In the past three years, microvia drilling using laser technology has become the dominant method of producing blind vias smaller than 150μm. The ablation characteristics of the materials used in the manufacture of PWBs can be divided into three categories: organics, glass, and metals. Organics are composed of resins and epoxies commercially available from a variety of vendors. Two types of resins that are typically used for microvia formation in the telecommunication applications are resin coated copper foil® (RCC or RCF) for subtractive PCB process, and thermal‐curing resin (TCR) for additive PCB process respectively. This paper details the basics of UV YAG laser capabilities, alignment techniques, plating tests, reliability tests, manufacturable microvia design rules, and production experiences.
The purpose of this paper is to study the effects of Angle of Attack (AOA), Axis Ratio (AR) and Reynolds number (Re) on unsteady laminar flow over a stationary elliptic…
The purpose of this paper is to study the effects of Angle of Attack (AOA), Axis Ratio (AR) and Reynolds number (Re) on unsteady laminar flow over a stationary elliptic cylinder.
The governing equations of fluid flow over the elliptic cylinder are solved numerically on a Cartesian grid using Projection method based Immersed Boundary technique. This numerical method is validated with the results available in open literature. This scheme eliminates the requirement of generating a new computational mesh upon varying any geometrical parameter such as AR or AOA, and thus reduces the computational time and cost.
Different vortex shedding patterns behind the elliptic cylinder are identified and classified using time averaged centerline streamwise velocity profile, instantaneous vorticity contours and instantaneous streamline patterns. A parameter space graph is constructed in order to reveal the dependence of AR, AOA and Re on vortex shedding. Integral parameters of flow such as mean drag, mean lift coefficients and Strouhal number are calculated and the effect of AR, AOA and Re on them is studied using various pressure and streamline contours. Functional relationships of each of integral parameters with respect to AR, AOA and Re are proposed with minimum percentage error.
The results obtained can be used to explain the characteristics of flow patterns behind slender to bluff elliptical cylinders which found applications in insect flight modeling, heat exchangers and energy conservation systems. The proposed functional relationships may be very useful for the practicing engineers in those fields.
The results presented in this paper are important for the researchers in the area of bluff body flow. The dependence of AOA on vortex shedding and flow parameters was never reported in the literature. These results are original, new and important.
Medical textile is one aspect of technical textiles and it is classified according to performance and functional properties for hygienic and healthcare products. Seaweeds…
Medical textile is one aspect of technical textiles and it is classified according to performance and functional properties for hygienic and healthcare products. Seaweeds have curative powers for curing most degenerative diseases. The paper aims to discuss these issues.
The present study focusses on the extraction of dyes from five seaweeds such as Ulva reticulata, Ulva lactuca, Sargassum wightii, Padina tetrastomatica and Acanthophora spicefera. The presence of bioactive compounds, antioxidant and antimicrobial properties of dye extracted from seaweeds was analysed. The dye extracted from green seaweed was applied on cotton fabric to obtain antimicrobial and other properties used to make non- implantable materials.
A maximum antioxidant inhibition percentage of 86.48+2.84 and a maximum antibacterial activity of 27 mm inhibition zone were obtained on the fabric treated with the dye extract from the Ulva lactuca seaweed. The physical properties such as tensile strength and tearing strength did not show much significant difference in untreated and treated fabric. The air permeability, water absorbency and wicking behaviour of treated fabric were reduced compared with untreated fabric. The washing and rubbing properties of treated fabric were very good after repeated washing.
This bioactive fabric has been used for non-implantable materials such as wound healing, face mask, surgical gowns and hygienic textiles in recent years.