Aslina Abu Bakar

Investigation on Simulation of Train Loading on Prestressed Concrete Sleepers

Railway concrete sleepers have been developed and utilized in railway industry for over 50 years. Cyclic loading because of vibration on sleepers due to the train loading and the velocity of train itself and also a small percentage of bad wheels, can eventually lead to a crack network and failure of component. The objective of this study is to investigate the load carrying capacity of the selected prestressed concrete sleepers – prepared for Keretapi Tanah Melayu Berhad, KTMB, under static and dynamic loading conditions. In order to determine the behavior of the railway concrete sleepers under repeated low-velocity impact load and to study the fatigue performance of railway concrete sleepers, the research efforts are required to perform comprehensive studies on the behaviors and dynamic response of these prestressed concrete sleepers. The fatigue performance of railway sleepers was investigated under constant amplitude load and compared with the actual train loading on site. For the laboratory work, the concrete sleepers were subjected to repeated low-velocity sinusoidal loads typical to loading from commuter trains only and attaining the fatigue toughness, energy absorption, and crack formations of the concrete sleepers.

Crack Behaviour of Retrofitted Pre-Tensioned Concrete Beam

Crack is a common cause of the degradation of concrete and may affect its structural durability. In order to ensure the bridge is safe utilized in anticipated period of their future service, a proper maintenance process and procedure should be taken. Therefore in this study, static load test were performed on a pre-tensioned (PRT) concrete beam to investigate crack behaviour before and after retrofitting process as well as to determine the effectiveness of the retrofitting method. A control beam named PRTB1 will fully loaded until fail to determine its maximum load capacity and critical load of the beam. Hence another beam named PRTB-FRP will be loaded until it reached it critical load capacity before retrofitted using Fiber Reinforced Polymer (FRP) plates located beneath the centre of the beam. After the retrofitting process PRTB-FRP will be put again under the static load. The load capacity of PRTB-FRP increased compared to PRTB1 with some improvement in crack propagation behaviour after retrofitted.

Bending Effects on Wearable Antenna with Silver Nanowires and Polydimethylsiloxane

This paper presents an investigation of an inset-fed microstrip patch antenna designed with silver nanowires (AgNWs) radiating patch and polydimethylsiloxane (PDMS) substrate. Highly conductive and stretchable radiating element AgNWs is embedded in flexible and durable PDMS elastomer. The antenna is designed to be wearable and flexible for body-centric wireless communications (BCWCs) applications, specifically in the 2.45 GHz Industrial, Scientific and Medical (ISM) band. The radiation characteristics are simulated and analyzed when the antenna is under flat and bent conditions. The proposed antenna demonstrates good performance for H-plane and E-plane bending orientations. The antenna offers great mechanical flexibility and robustness, which indicates its good potential for BCWCs applications.

Ultra Wideband Fat Tissue Fabrication Using Different Cross Linking Agent for Microwave Imaging

The paper discusses the fabrication of fat tissue using glyoxal and glutaraldehyde as a cross linking agent to be used in breast phantom for microwave imaging application. The fabricated fat tissue’s dielectric constant is measured in the ultra-wideband frequency range of 3.1–10.6 GHz. In brief this paper addresses the two issues of breast phantom fabrication; first to simulate the wide range of permittivity of the breast fat tissue and secondly using different cross linking agent such as glyoxal and glutaraldehyde to replace formaldehyde. The previously reported fat tissue fabrication using formaldehyde as a cross linking agent was not safe for handling and hazardous for health. The fabricated fat tissue using the proposed material has shown that it has a close proximity of dielectric constant when compared with the real fat tissue fitted by using a Debye model.

Wideband Monopole Antenna for WWAN Services

An approach to design a compact monopole antenna for use in portable RF transceivers that feature wideband performance and miniaturized dimension is presented. The antenna structure is initially designed as a microstrip-fed planar monopole quarter elliptical shape supported by a 60 × 90 mm2 ground plane bolstered on FR-4 substrate. A parasitic microstrip stub and a ground plane cut are introduced to achieve wideband characteristic. The proposed approach modifies the antenna’s structure by introducing two miniaturization steps on both the radiator and ground plane. The modification that partially removes the radiator and ground plane to enact a slot is the first step in the proposed miniaturization. In the second step, the main radiator is carefully corrugated near the tapered end of the elliptical radiator to further reduce antenna’s size without undermining the wideband performance. The simulation and experimental results are compared and discussed. The designed antenna operates at all wireless wide area network (WWAN) services from 850 MHz to 3 GHz at 6 dB return loss reference.

Design of Folded Planar Inverted-F Antennas with Stair-Shaped Radiator for LTE700

A miniaturized Planar Inverted Antenna F-Antenna for LTE700M service band is presented. The main radiator of PIFA antenna is been folded into three radiating arm which provide optimized dimensions. Then, stair-shaped geometry have been used in order enhance impedance bandwidth for both lower band and higher band. Finally, the size of the finite ground is gradually reduced to achieve optimum size reductions. In the experimental results, the antenna achieves lower band impedance bandwidth between 725 MHz and 1.18 GHz at 6 dB return loss. At upper band, the antenna covers bandwidth between 2.33 and 3.82 GHz at 10 dB return loss. The final antenna #2 achieved reduction in overall dimension by 46.6 % in length, 33.7 % in width, and 5.19 % in height as compared to its reference antenna. Hence, this miniaturized size of proposed PIFA antenna is a promising candidate for several wireless services such as LTE700, GSM850/900, WLAN2.45G and WiMAX3.5G.

Bandwidth enhancement technique using ground slot for ultra-wideband Coplanar Inverted-F Antenna

This paper presents an ultra-wideband Coplanar Inverted-F Antenna (CIFA) proposed for WiMAX and WLAN band applications. This paper also introduces an ultra-wideband CIFA based on two techniques which are bandwidth enhancement and radiator miniaturization. As a result, this modification increases the antenna resonant bandwidth to cover almost all UWB range covering the WiMAX and WLAN services. The 10dB return loss bandwidth cover two frequency ranges. The first bandwidth is from 3.6 to 6.4 GHz and the second bandwidth is from 6.9 to 9.5 GHz. From the analysis, the antenna radiation patterns are nearly omnidirectional with low antenna gain. The design of antenna configuration, return loss, far field radiation pattern and gain results are presented and discussed. The performance of this antenna can lead to a promising candidate to be considered by mobile communication designers for application in compact multiband mobile phone and other UWB applications.