Maryam Mohd Isa

Development of a Hydrogen Gas Sensor Using a Double Saw Resonator System at Room Temperature

A double SAW resonator system was developed as a novel method for gas sensing applications. The proposed system was investigated for hydrogen sensing. Commercial Surface Acoustic Wave (SAW) resonators with resonance frequencies of 433.92 MHz and 433.42 MHz were employed in the double SAW resonator system configuration. The advantages of using this configuration include its ability for remote measurements, and insensitivity to vibrations and other external disturbances. The sensitive layer is composed of functionalized multiwalled carbon nanotubes and polyaniline nanofibers which were deposited on pre-patterned platinum metal electrodes fabricated on a piezoelectric substrate. This was mounted into the DSAWR circuit and connected in parallel. The sensor response was measured as the difference between the resonance frequencies of the SAW resonators, which is a measure of the gas concentration. The sensor showed good response towards hydrogen with a minimum detection limit of 1%.

Application of a sensor array based on capillary-attached conductive gas sensors for odor identification

An electronic nose based on an array of capillary-attached conductive gas sensors was fabricated. The identification ability of the developed structure was investigated by employing different categories of simple and complex odor databases. Feature data sets were generated from the dynamic and steady state responses of the sensor array to the applied odor databases. Combinations of different feature extraction and classification methods were used to detect target gases. Validation of each technique was evaluated. Achievements of the study proved high classification rates of the fabricated e-nose in odor identification. It was indicated that gas identification is possible by applying the early selected portion of transient responses of the developed sensor array. The ability of the mentioned structure in analyzing gas mixtures was also investigated. The results presented high accuracy in the classification of gas mixtures.

Disturbance Rejection for a 2-DOF Nonlinear Helicopter Model by Using MIMO Fuzzy Sliding Mode Control with Boundary Layer

In this paper, one helicopter model with two degrees of freedom (2-DOF) is controlled by fuzzy sliding mode control with boundary layer (FSMC-BL) while exposed to disturbance. The model is a nonlinear and multi-input multi-output (MIMO) system that requires a MIMO, robust, stable, and nonlinear control to reject the disturbance. These requirements have been satisfied by SMC. In this paper, boundary layer removes the chattering phenomenon and fuzzy logic tunes the switching gains of SMC control law online. The simulation results which are achieved for step and sinusoidal disturbances applied to both pitch and yaw angles, are compared with those of PID control based on linear quadratic regulator algorithm (LQR-PID). Considerable improvement in control signal and yaw angle is observed by using FSMC-BL.

Real-time gas identification by analyzing the transient response of capillary-attached conductive gas sensor.

In this study, the ability of the Capillary-attached conductive gas sensor (CGS) in real-time gas identification was investigated. The structure of the prototype fabricated CGS is presented. Portions were selected from the beginning of the CGS transient response including the first 11 samples to the first 100 samples. Different feature extraction and classification methods were applied on the selected portions. Validation of methods was evaluated to study the ability of an early portion of the CGS transient response in target gas (TG) identification. Experimental results proved that applying extracted features from an early part of the CGS transient response along with a classifier can distinguish short-chain alcohols from each other perfectly. Decreasing time of exposition in the interaction between target gas and sensing element improved the reliability of the sensor. Classification rate was also improved and time of identification was decreased. Moreover, the results indicated the optimum interval of the early transient response of the CGS for selecting portions to achieve the best classification rates.

Evaluation of dimension effects on a capillary-attached gas sensor

The analysis and useful gas sensing properties of a capillary-attached gas sensor (CGS) have been recently investigated. The aim of the present work was the assessment of dimension effects on the CGS sensing properties both diameterwise and lengthwise. CGS samples in different dimensions were fabricated and tested by exposure to different target gases in different concentration ranges. Dimension effects on CGS properties such as selectivity, sensitivity, rise time and input range were investigated. It was observed that the CGS with smaller diameter and longer lengths generated more selective information. However, decreasing sensitivity and increasing minimum input range were some disadvantages of smaller diameters. Longer length also made longer rise time and slower sensor. Finally, the optimum ranges for the CGS in length and diameter were suggested.

Sugar content in watermelon juice based on dielectric properties at 10.45GHz

Determination of sugar content in 10 matured red seedless watermelons by measuring the dielectric properties is described in this paper. The determination is made based on the comparison of watermelon juice and water with sugar mixture. The dielectric properties of both the extracted watermelon juice and water with sugar mixture are measured over the frequency range from 200 MHz to 20 GHz and permittivity data at frequency 10.45 GHz is highlighted using an open-ended coaxial-line probe and network analyzer. Measurements are made at room temperature ± 27 °C; 70–80% RH. The sugar content was the most significant factor affecting the maturity of watermelon. Dielectric properties of watermelon juice and water with sugar mixture were measured and the dielectric properties of both liquids were compared. In this study, data obtained suggests that dielectric properties shows strong relation with sugar content. The dielectric constant is inversely proportional with increment of sugar content. From the dielectric properties measured, the sugar content in the watermelon is predicted. In additional, the standard sugar content measurement, HPLC method is also measured and result of the study is reported in this paper. Dielectric measurement of watermelon juice and water with sugar mixture are presented graphically to show their relationships.

Single selective gas sensor for detecting flammable gases

The analysis and useful gas sensing properties of capillary-attached gas sensor (CGS) have recently been investigated. The aim of the present work was to investigate the possibility of applying CGS as single selective sensor in detecting organic gases. A CGS samples were fabricated and tested by exposure to five different flammable target gases, hydrogen, methanol, ethanol, acetone and 1-butanol. Classic feature extraction and classifiers were employed to analyze the transient response of CGS. Extracted features of fabricated CGS could differentiate between the pure target gases (TG) perfectly. Results indicated this fact that CGS can be applied as a smart single sensor to diagnose TGs.

Design of ultra-low voltage and low-power CMOS current bleeding mixer

This paper presents an ultra-low voltage and low power current bleeding CMOS double balanced mixer targeted for ZigBee application in 2.4GHz operating frequency band. The proposed mixer uses a modified CMOS current bleeding mixer topology adapting the forward body bias design technique integrated with a NMOS based current bleeding transistor, PMOS based local oscillator (LO) switching stage and on-chip inductors to achieve ultra-low voltage headroom operation down to 0.35V. The conversion gain is further enhanced by integrating an inductor at the gate of the bleeding transistor to reduce RF current leakage. The proposed architecture is simulated and verified in 0.13μm standard CMOS technology. The RC extracted simulation result shows a high conversion gain (CG) of 16dB, 1dB compression point (P1dB) at -17.65dBm, third-order intercept point (IIP3) of -7.45dBm and a noise figure (NF) of 18dB is achieved with a power consumption of 526μW.

Centered-gap and aligned-gap multiple split ring resonator for bio-sensing application

In general, a classical Split Ring Resonator (SRR) structure exhibits high Q-factor based on deeper and sharper transmission dips at resonance as well as produce high electric field density at the gaps. It is believed, by introducing more gaps, a strong and localized E-field will be obtained in the area between the split gaps. Based on these features, three types of rectangular multiple Split Ring Resonators (SRRs) were proposed to resonate in the frequency range of 3-7 GHz and simulated using Computer Simulation Technology (CST) Microwave Studio to determine the transmission characteristics and the resonance frequency. A Nicolson-Ross-Weir (NRW) technique is used to retrieve the effective parameters from the resultant S-parameter. It is shown that the resonance frequency of investigated structures falls in a frequency region in which the real part of permeability is negative. Later, the simulated results were investigated and the performances as well as the size of each unit cell itself were compared. Simulation for three different type of dielectric samples were also presented to demonstrate that the proposed structure may be well suited for bio-sensing.

Measurement technique for bidirectional four sensor rotary encoder

Measurement and monitoring of fluid flow are considered as crucial issues in industry and domestic applications especially for the water measurement. Numerous approach based on different physical principles have been proposed such as ultrasonic, electromagnetic, and differential pressure systems which each one of them requires its own particular measurement technique and algorithm to compute the necessary information such as flow speed, consumption and flow direction. However, there are some weaknesses in their measurement techniques including complexity and power consumption in their implementation. Therefore, in this paper, a measurement technique based on four sensor rotary encoder is presented. The measurement technique is simple and able to measure the speed, number of rotation and recognize the direction of the rotation. Furthermore, in the proposed measurement technique the error of the system is detectable in which debugging the system is required expensive equipment and long time for the conventional rotary encoder system. The functionality and performance of the measurement technique have been evaluated and found that the proposed technique is able to accurately measure the flow speed, the number of rotation, identify the direction of rotation and recognize the error occurred.