Ee Meng Cheng

RUBBER TIRE DUST-RICE HUSK PYRAMIDAL MICROWAVE ABSORBER

Rubber tire dust-rice husk is an innovation in improving the design of pyramidal microwave absorbers to be used in radio frequency (RF) anechoic chambers. An RF anechoic chamber is a shielded room covered with absorbers to eliminate unwanted re∞ection signals. To design the pyramidal microwave absorber, rice husk will be added to rubber tire dust since the study shows that both have high percentages of carbon. This innovative material combination will be investigated to determine the best re∞ectivity or re∞ection loss performance of pyramidal microwave absorbers. Carbon is the most important element that must be in the absorber in order to help the absorption of unwanted microwave signals. In the commercial

Experimental determination of the performance of rice husk-carbon nanotube composites for absorbing microwave signals in the frequency range of 12.4-18 GHz

Composites of rice husks and carbon nanotubes (RHC- NTs) are an innovation in improving the absorption of microwave sig- nals. Rice husks, which are an agricultural waste material, have been found to possess a signiflcant propensity for absorbing microwave sig- nals. Studies have shown that both rice husks and carbon nanotubes (CNTs) have high percentages of carbon. Thus, in this paper, we present the results of our experimental study in which we varied the ratios of rice husks and CNTs in the composite materials and deter- mined the dielectric properties of the composites and measured their abilities to absorb microwave signals. The experimental microwave

Designing Asian-Sized Hand Model for SAR Determination at Gsm900/1800: Simulation Part

A simple geometrical Asian-hand model with human tissue properties posed at two common talk-mode positions is proposed for comparative study. The newly designed hand is formed by measuring an adult female hand at open-hand position before being posed into the presented styles. Four human hand tissues are included: skin, bone, muscle, and tendon, and also three homogeneous sets of hands using speciflc anthropomorphic mannequin (SAM) hand phantom dielectric properties. A candy-bar type mobile phone with Planar Inverted-F Antenna (PIFA) is used to radiate dual-band frequency of GSM900/1800 in the vicinity of the SAM head phantom. The mobile phone casing is made out of plastic, and only two components are considered: the FR-4 ground plane and PIFA. The speciflc absorption rate (SAR) averaged over a mass of 10gram and 1gram is calculated after obtaining the power loss density and electric fleld value from simulation in CST Studio Suite 2011. The SAR and return loss results of six hand structures, including the SAM hand phantom are compared. The antenna performance with the inclusion of hand does not decrease as much as 1800MHz in 900MHz range, but absorbs energy more in the hands for 1800MHz than 900MHz SAR values.

Precise Moisture Monitoring for Various Soil Types Using Handheld Microwave-Sensor Meter

A handheld microwave reflectometer-sensor system is developed to operate from 1.35 to 1.95 GHz and used to measure volumetric and gravimetric moisture content in various types of soils from 0% to 45%. A small monopole driver from coaxial line is buried into the soil, and its reflected voltage is measured and correlated with corresponding soil moisture content obtained from oven dying method. The measured reflected voltage is dependent on the nonlinear change of dielectric properties of the soil with the moisture content.

Amplitude-only measurements of a dual open ended coaxial sensor system for determination of complex permittivity of materials

This paper describes a novel permittivity measurement technique using dual open ended coaxial sensors. The magnitudes of the re∞ection coe-cient from two open ended coaxial sensors were used to determine complex re∞ection coe-cients and permittivity of a sample under test.

Tissue engineering scaffold based on starch: A review

An ideal scaffold should has a good porosity, acceptable mechanical strength, and biocompatible. One of the way to achieved these criteria is to incorporate polymers in the scaffold fabrication. Starch is one of the most common natural polymers that have been used to fabricate tissue engineering scaffold. Previously, starch as a biomedical material has found wider application such as hydrogel and drug delivery system. Hence, by blending starch with other materials such as Hydroxyapatite (HA) might improve scaffolds properties. This paper reviews how the incorporation of starch is significant to the improvement of scaffold fabrication.

Non-destructive dielectric measurements and calibration for thin materials using waveguide-coaxial adaptors

Abstract This paper focuses on the calibration of apertures for rectangular waveguides using open-short-load (OSL) standards and transmission-line (TL) approaches. The reflection coefficients that were measured using both calibration techniques were compared with the coefficients acquired using the thru-reflect-line (TRL) method. In this study, analogous relationships between the results of OSL calibration and TL calibration were identified. In the OSL calibration method, the theoretical, open-standard values are calculated from quasi-static integral models. The proposed TL calibration procedure is a simple, rapid, broadband approach, and its results were validated by using the OSL calibration method and by comparing the results with the calculated integral admittance. The quasi-static integral models were used to convert the measured reflection coefficients to relative permittivities for the infinite samples and the thin, finite samples

A comparative study on the effect of quasi-block hand model specific absorption rate measurement

A candy bar mobile phone with Planar Inverted-F Antenna (PIFA) operating at 900 MHz and 1800 MHz is simulated with two models of quasi-block hand — homogeneous and inhomogeneous. Maximum Specific Absorption Rate (SAR) is investigated by using Standard Anthropomorphic Model (SAM) hand phantom properties in comparison with the properties of human skin and bone towards the models. Dimension of the quasi-block hand is based on a typical Malaysian hand, while the solid hand properties is as approved by CTIA standards. The simulation results of peak SAR for two conditions are observed and compared between both hands.

Composites Based on Rice Husk Ash/Polyester for Use as Microwave Absorber

This paper is to study the dielectric properties and microwave absorption of rice husk ash/polyester (RHAP) composites. The RHAP composites prepared with different weight ratio (40–80 wt. %) of rice husk ash (RHA) loading into polyester was fabricated. A rectangular waveguide transmission line method was used to measure the dielectric properties of the RHAP composites. The RHAP samples were designed and simulated with different thickness and percentage of RHA loading by using Computer Simulation Technology Microwave Studio (CST-MWS) software. The materials, their dielectrics properties measurement and microwave absorption result over 12.4–18 GHz (Ku-Band) frequency range are discussed. The dielectric properties of composites increase with increasing loading the RA wt%. The RHAP sample with different thickness was investigated in Ku-Band. The microwave absorption was up to 99.84 %, using 80 % loading of RHA with thickness 15 mm at 13.81 GHz, and showing the RHAP composites is applicable as microwave absorber.

Study of Dual Open Ended Coaxial Sensor System for Calculation of Phase Using Two Magnitudes

A dual open ended coaxial sensor system to determine complex permittivity was studied in detail. This paper focuses on determination of a reflection coefficient phase from two magnitudes using modified capacitance model from 300 kHz to 8 GHz. The phase information can then be used for calculation of the samples complex permittivity. Factors such as range and limitation of the model, samples permittivity, operating frequency, and size of sensor were investigated. Sensitivity of calculated phase with respect to small changes in measured magnitude was carried out.