This manuscript contains the development stages of a multi-purpose wind tunnel built at the Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia. The fully automated wind tunnel is named Pangkor after an island in Perak, Malaysia. The development of the wind tunnel consists of three stages namely the design, fabrication and testing & commissioning. The computational fluids dynamic (CFD) approach was employed to ascertain the main geometries to optimize space utilization. Calculations are made based on typical wind tunnel design guidelines. Pitot tubes-pressure transducer, hotwire anemometry, temperature, room humidity and barometric sensors were used to verify actual flow of our construction. A traverse installed at the wind tunnel is capable of a two dimensional movements. The 15 kW axial fan used is especially selected because of space limitation. A variable frequency drive (VFD) connected to fan’s motor allows velocity control from a computer. All devices are connected a computer with one single controlling software; Scilab – ensuring ease of operation. The project shows that, with a limited budget, a wind tunnel with full functionalities could be constructed

The aims of this research is to look into the percentage drag reduction on a NACA 0026 airfoil with V-Groove riblets installed around at some locations around its surface. NACA 0026 is a symmetrical airfoil mostly used as turbine blade and aircraft wing. Research on drag reduction by using riblets on the surface was introduced by NASA Langley Research Centre in 1970s. There are many types of riblet designed in this research area such as V groove, segmented blade and continuous saw tooth. This research used NACA 0026 with external geometry 500 mm spans, 615 mm chord and 156 mm thickness. V-groove riblets with 1 mm pitch and 1 mm high and 30 mm width are attached at peak points of the airfoil profile. The CFD simulation used ANSYS Fluent to analyze the velocity, pressure gradient, turbulent kinetic energy and vortex development. The result shows the percentage in drag reduction compared to clean surface for the zero angle of attack is 11.8% and 30 0 angle of attack is 1.64%. By this condition the airfoil will have better motion performance in their applications.

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The design and modelling of a 1×4 asymmetric waveguide couplers based on optical glue Epoxy OG142 is presented. The 1×4 asymmetric coupler is based on a cascaded design of a 1×2 Y-branch with two 1×2 asymmetric couplers. The design of the asymmetric coupler is based on asymmetric Y-junction splitter using tap-off ratio (TOFR) technique. This asymmetric design was achieved by varying the size of the tap line while the bus line was fixed at 1 mm size. A Y-branch and the 1×2 asymmetric couplers with different taper sizes have been designed using CAD tool and ray traced using non-sequential ray tracing. The designed TOFR for the 1×2 asymmetric coupler varies from 23% to 50% for tap line width of 300 µm to 1000 µm. Ray tracing models of various coupler design showed a linear relationship between the tap-off ratio (TOFR) and the waveguide tap width. The simulated ray tracing result shows TOFR values for the 1×4 asymmetric waveguide coupler varies from 23.1 to 50% for tap width of 300 µm to 1000 µm.

A three-step molding softlithographic process has been developed for the construction of a sharp Y-junction structure formation in a 1 × 2 Y-branch plastic optical fiber (POF) coupler design. The 1 × 2 Y-branch POF coupler is based on a Y-junction splitter which requires that the splitting part is constructed with sharp infinitesimal junction. The softlithographic process enables a PDMS mold to be constructed which then allows mass replication of the polymer-based POF coupler. A standard master mold based on PMMA material is fabricated using CNC milling. A secondary or auxiliarymold process step is then introduced in order to produce a sharp Y-junction structure which is then transferred to the final PDMS stamp prior to device replication. This step utilizes a free flowing, low viscosity casting-based resin, which after curing and hardening provide the auxiliary mold for PDMS mold fabrication. The result shows that a very fine and sharp Y-junction structure can be produced easily which cannot be produced via standard two step molding softlithographic process. Models for the Y-branch POF coupler produced with and without an auxiliary mold process are constructed which show that a 16% increased in optical performance with the device replicated with the auxiliary mold process. 1. INTRODUCTION Plastic Optical Fiber (POF) is a widely recognized optical medium for short distance optical data communication due to its favorably large-core size, multimode characteristics, low cost and robust features. Many applications for multimode fibers are well known. Nevertheless, waveguide-based POF devices development is limited because multimode devices have a smaller market especially for data communication application due to the high attenuation of POF devices compared to that of glass-based optical devices [1]. POF devices are produced with variety of new and economical materials for vast application which not only are for optical communications, but also include the entertainment, sensor, lighting and decoration system fields [2]. POF devices can be categorized in two parts: active and passive components. Active component are devices such as transmitter and receiver whereas passive component are devices such as filters, connectors, attenuators, and coupler or splitter, and other related passive devices [3]. Coupler or splitter as a passive device has great interest in applications in such as short length networks, optical sensors, and security system. These applications sometimes require that optical signals need to be split or divided. Standard fiber-based Y-branch couplers are normally made by polishing two fibers and gluing them together. These Y-branch couplers are vastly used in applications where incoming light signals need to be split. Nevertheless, this technique will be very impractical for producing asymmetrical-type couplers