Mohamad Ngasri Dimon

A Stochastic Simulation Framework for the Prediction of Strategic Noise Mapping and Occupational Noise Exposure Using the Random Walk Approach

Strategic noise mapping provides important information for noise impact assessment and noise abatement. However, producing reliable strategic noise mapping in a dynamic, complex working environment is difficult. This study proposes the implementation of the random walk approach as a new stochastic technique to simulate noise mapping and to predict the noise exposure level in a workplace. A stochastic simulation framework and software, namely RW-eNMS, were developed to facilitate the random walk approach in noise mapping prediction. This framework considers the randomness and complexity of machinery operation and noise emission levels. Also, it assesses the impact of noise on the workers and the surrounding environment. For data validation, three case studies were conducted to check the accuracy of the prediction data and to determine the efficiency and effectiveness of this approach. The results showed high accuracy of prediction results together with a majority of absolute differences of less than 2 dBA; also, the predicted noise doses were mostly in the range of measurement. Therefore, the random walk approach was effective in dealing with environmental noises. It could predict strategic noise mapping to facilitate noise monitoring and noise control in the workplaces.

Soil moisture dielectric measurement using microwave sensor system

A microwave sensor system has been developed to operate from 2.2 GHz to 4.4 GHz and used to determine the change of soil dielectric constant with various values of gravimetric moisture content from 0% to 26%. Soil samples are placed on a microstrip ring resonator (MRR) sensor and the respective incident and reflected voltages are measured and converted into magnitude of return loss, |S11|. The calculated return loss, |S11| is then correlated with corresponding soil moisture content obtained from oven drying method and also the soil permittivity obtained from commercial dielectric probe with vector network analyzer.

Compact microstrip S-Band 90° hybrid coupler

A compact microstrip S-Band 90° hybrid coupler is designed and tested. The proposed coupler has a pass-band width of 1.9 GHz and approximately twice wider bandwidth than conventional coupler at the operating center frequency of 2 GHz. The size reduction of 40% is achieved from the conventional design model with the arrangement of open stubs.

Application of in-situ method for measuring sound absorption coefficient of direct piercing carved wood panel with daun sireh motif

An application of In-Situ method of measuring sound absorption coefficient on the surface of direct piercing carved wood panel using the concept of ensemble averaged is discussed. The method offer an easier way to measure the absorption performance for each individual aperture of carved wood panel with floral pattern which was replicated from one of the oldest mosque, namely Masjid Abidin located in Terengganu, Malaysia. Two pieces of 20 mm thick of cengal wood (Neobalanocarpus heimii) with 30% and 40% perforation ratio were respectively measured in a reverberation room in order to determine the value of . At lower frequencies (0.1 kHz-1.5 kHz), the measured values of for both direct piercing carved wood panel with floral pattern (Daun Sireh motif) are shown that the sound absoption for both direct piercing carved wood panel are in perform level. From the measurements, clearly, the installation of the direct piercing carved wood panel with floral pattern (Daun Sireh motif) in the Masjid Abidin can provide better air circulation and additional natural sunlight, as well as better sound intelligibility inside the building.

Correlation between Reflection Coefficient, Dielectric Properties and Brix Level of Malaysian Oranges at Microwave Frequencies

With the rapid growth of communications via the Internet, the need for an effective firewall system which has not badly affect the overall network performances has been increased. In this paper, a Field Programmable Gate Array (FPGA) -based firewall system with high performance has been implemented using Network FPGA (NetFPGA) with Xilinx Kintex-7 XC7K325T FPGA. Based on NetFPGA reference router project, a NetFPGA-based firewall system was implemented. The hardware module performs rule matching operation using content addressable memory (CAM) for higher speed data processing. To evaluate system performance, throughput, latency, and memory utilization were measured for different cases using different tools, also the number of rules that an incoming packet is subjected to was varied to get more readings using both software and hardware features. The results showed that the designed firewall system provides better performance than traditional firewalls. System throughput was doubled times of the one with Linux-Iptables firewalls.

Evaluation of the Equivalent Lumped Element Parameters of Modified Microstrip Ring Resonator

Microstrip ring resonator (MRR) sensor was modeled by simple equivalent lumped element circuits in free space based on simulation data obtained from Microwave Office (AWR) simulator and comparison was made with the measurements using the E5071C Network Analyzer. The calculated reflection coefficient, |G| and complex input impedance Zin using lumped element model were compared with the measurements results. Both results showed well agreement with a little discrepancy, basically due to imperfect soldering. The MRR was designed to have operating frequencies between 0.5 GHz and 4.5 GHz. The maximum surrounding of magnetic field, Hϕ is within 15 A/m in free space.

CST Simulation on Monopole Sensor for Determination of Malaysian Local Oranges Sweetness Quality Non-destructively

This paper presents the application of monopole sensor for determination of sweetness level of local oranges in Malaysia which can be investigated non-destructively. Simulation using Computer Simulation Technology (CST) version 2012 was carried out to observe the effect on reflection coefficient (S11) when the monopole sensors grounding dimension is varied. The unique design of a holder for local oranges that is made of nylon is enclosed in this project contributed to its invention. The experiment test bed was set up based on standard dimension of small monopole sensor available in the market. Actual measurement on Malaysian local oranges was measured and its dielectric permittivity is predicted using CST software.

Broken Rice Detection Based on Transmission Power Measurement Using a Microstrip Wide-Ring Sensor

This paper proposes a microstrip wide-ring sensor for percentage of broken rice determination based on transmission power measurement. The microstrip wide-ring sensor with low insertion loss was designed to operate at frequency range from 1 GHz to 3 GHz. Calibration equations for measurement of percentage of broken rice at 1.93 GHz and 2.50 GHz were obtained and validated with white rice for percentage of broken rice ranging from 0% to 100%. The lowest error in percentage of broken rice prediction was 11.03% at 1.93 GHz.

Sound absorption coefficient of direct piercing carved wood panel with uniform geometric patterns

Direct piercing carved wood panels (DPCWP) have been used as part of the wall panel for mosques in this country. Among the earliest used of DPCWP is as in Masjid Sultan Zainal Abidin in 1700s, Kuala Terengganu, Terengganu. It is envisage, the use of DPCWP is to help in achieving good speech intelligibility inside. This is considering DPCWP allowing sound waves to pass through, hence sound reflection to the main prayer is contain. Minimizing sound reflection toward the mosque main area, ensuring optimization of speech intelligibility. DPCWP has the ability to allow sound waves to pass through the panel. This qualifies DPCWP as sound absorber material. This as Sabine, Kutruff and Maekawa definition of sound absorption coefficient. In this paper the sound absorption coefficient of DPCWP with uniform geometric patterns are discussed. The perforation ratios are 31% and 37%. Numerical experiments were conducted using Boundary Element Method (BEM). The measured results were obtained using sound intensity measurements technique. Comparison of sound absorption coefficient obtained through numerical experiment and measured using sound intensity are discussed in details. Analysis of resonance frequencies due to types and sizes of apertures in relation to sound absorption coefficient also highlighted. The measured and numerical results suggest, DPCWP of uniform geometric patterns indeed able to act as good sound absorber. This finding allows DPCWP to be used as sound absorber more effectively in future mosque construction.

Investigation of the effect of low frequency components of sound to speech intelligibility

Sound attenuation depends on source‐to‐listener distance, the finishes, and the shape of the room. The amount of sound attenuation at different frequencies influences the overall speech intelligibility in a room. The sound at high frequencies, especially at 1 kHz and 2 kHz, contribute the most for the articulation of consonants, and thus affects speech intelligibility. However, it has been found previously that sound attenuation is lower and harder to achieve at lower frequencies. This would lead us to assume that reverberant sound is mostly of low frequency components. Even if the contribution of sound at low frequency is low for speech intelligibility, this paper attempts to gauge the effect of sound pollution at low frequencies to the overall speech intelligibility in the room. With fixed source‐to‐listener distances, the measurements were conducted in classrooms with different sizes and finishes.