Vol 1, Issue 2 (2018)

International Journal of Defence Science, Engineering & Technology

Nonparametric Robust Estimator for Slope Parameter in Linear Structural Relationship Model

Amel Saad Alshargawi, Abdul Ghapor Hussin, Ummul Fahri binti Abd Rauf

 

Abstract

In this study, the slope parameter of linear structural relationship model is determined by using the proposed robust nonparametric method based on trimmed mean. This method is an upgrade to the nonparametric method that was introduced by Al-Nasser et al. (2005) by employing trimmed mean for all likely paired slopes rather than median slopes. Simulation study and real data were used to compare the proposed method’s performance versus the traditional maximum likelihood method. In the simulation study, based on both methods’ mean square error, it was inferred that the MLE method break down due to the presence of outliers even though its elaborate was not affected when there was no outlier in the data set. Based on the real life examples, it can be concluded that the performance of our proposed method was better in determining the slope parameter and thus provides a good alternative to MLE method when outliers are present.

 

 

Low Cost and Room Temperature Methane Detection using Multi Walled-Carbon Nanotubes Functionalized with Octadecanol

Nurjahirah Janudin, Norli Abdullah, Faizah Md Yasin, Mohd Hanif Yaacob, Muhammad Zamharir Ahmad, Luqman Chuah Abdullah, Raja Nor Izawati Raja Othman, Noor Aisyah Ahmad Syah, Shafreeza Sobri, Noor Azilah Mohd Kasim

 

Abstract

Multi walled-carbon nanotubes (CNT) functionalized with ester was used for detecting methane, CH4 gas at room temperature. Quartz substrate with interdigitated prepatterned gold electrodes was employed as transducers and drop casting method was used to deposit the CNT samples. The electrical properties of the functionalized CNT samples in the presence of CH4 gas were studied and the changes of resistance were recorded using digital multimeter. Concentration of CH4 gas was varied from 0.125 % to 1.0 %. The resistance variation of functionalized CNT increased with the concentration of tested gas. Sensor response of functionalized CNT was improved more than 10 % as compared to pristine CNT. CNT-Ester gives the higher sensitivity due to the presence of ester functional group which act as active site to react with CH4 gas. The fast response of functionalized CNT towards CH4 gas suggested that the functional group enhanced the rate of gas adsorption on sensing layer.

 

 

Carbon Nanotubes-based Gas Sensor in Detection of Methane Gas at Room Temperature

Nurjahirah Janudin, Norli Abdullah, Faizah Md Yasin, Mohd Hanif Yaacob, Muhammad Zamharir Ahmad, Luqman Chuah Abdullah, Raja Nor Izawati Raja Othman, Noor Aisyah Ahmad Syah, Shafreeza Sobri, Noor Azilah Mohd Kasim

 

Abstract

Room temperature carbon nanotubes (CNT)-based gas sensor was utilised in detection of methane, CH4 gas. The CNT was functionalized with amide group via Fischer esterification process and labelled as CNT-Amide. Silicon dioxide, SiO2 substrate with interdigitated prepatterned gold electrodes were employed as transducers and drop casting technique was used to deposit the multi walled-CNT samples. The electrical properties of the functionalized CNT samples in the exposure of CH4 gas are studied by recorded the changes of resistance using digital multimeter. Concentration of CH4 gas was varied from 1250 ppm to 10 000 ppm. The changes of electrical resistance of CNT-Amide increases with the concentration of tested gas. Sensor response of functionalized CNT are improved more than 10% as compared to pristine CNT. The sensitivity of CNT-Amide also better than CNT-Carboxyl due to the presence of nitrogen element in amide functional group which chemically active to react with CH4 gas. Additionally, fast response of CNT-Amide towards CH4 gas suggested that the functional group enhanced the rate of gas adsorption on sensing layer.

 

 

A Short Review of Polylactic Acid Blends Properties for Improvement and Innovation

Mohd Junaedy Osman, Wan Md Zin Wan Yunus, Nabiilah Faris

 

Abstract

Advanced technology in petrochemical-based polymer has brought many benefits to mankind. However, the use of nonbiodegradable plastics materials for disposable application such as food packaging and house whole appliances are significantly disturbing and damaging the earth ecosystem. Polylactic acid (PLA) is a biodegradable plastic that is brittle. Because of this nature, PLA has a limitation in its usage. The common way to improve the toughness of PLA is via adding plasticizer. This review will provide brief account on recent developments in the synthesis of lactic acid (monomer of PLA) through biological route, PLA synthesis, unique material properties of PLA and modification of those by making copolymers and composites PLA absorption and degradation.

 

 

Synthesis of Epoxidized Fatty Hydrazides from Palm Olein: A Preliminary Study

Zakiah Jamingan, Wan Md Zin Wan Yunus, Norli Abdullah, Ong Keat Khim

 

Abstract

Epoxidized fatty hydrazides (EFHs) which have amine, amide and epoxide functional groups in their molecules are a versatile starting material for synthesizing of many industrially important compounds. In this report we describe the results of our preliminary study of synthesizing these compounds using a chemical reaction of epoxidized palm olein (EPO) and hydrazine monohydrate. The products were characterized by using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) technique and CHN elemental analyser. The optimum reaction conditions for the hydrazide preparation were investigated by studying effect of each important reaction parameters on the product yields. The study shows that the optimum conditions to produce EFHs were using EPO to hydrazine monohydrate (mol ratio of 1 to 12), n-hexane as the solvent and at the temperature of 69 ̊C.