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Publication

A review on the potential of polylactic acid based thermoplastic elastomer as filament material for fused deposition modelling

( 2022)

Luqman Musa

;

Nitiyah Krishna Kumar

;

Shayfull Zamree Abd. Rahim

;

Mohamad Syahmie Mohamad Rasidi

;

Allan Edward Watson Rennie

;

Rozyanty Rahman

;

Armin Yousefi Kanani

;

Ahmad Azrem Azmi

Currently, a range of sectors are implementing three-dimensional (3D) printing, which is a part of additive manufacturing (AM) technology via the fused deposition modelling (FDM) approach. As of now, various filament materials are available in the market and have their limitations. Thermoplastic elastomer (TPE) blend as a filament material in 3D printing should be implemented to overcome the weakness of available filaments. TPE blend stands out due to its flexibility, thermoplastic-like processability, and renewability. Based on the findings, TPE blend filament can be made with polylactic acid (PLA) thermoplastic and elastomers such as natural rubber (NR) and epoxidized natural rubber (ENR). The TPE printed components will be flexible; tough with excellent thermal and mechanical properties. In this paper, the characteristics of TPE are being reviewed to show the potential of TPE material as filament.

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Publication

A study on the effect of fin pitch variation on the thermal performance of a bus duct conductor

(Elsevier, 2023)

Mark Selvan

;

Mohd Sharizal Abdul Aziz

;

Kok Hwa Yu

;

Mohd Sharif Nurulakmal

;

Heng Pin Ong

;

Khor Chu Yee

The numerical results of this work provide an optimum design for a three-dimensional natural convection heat sink on the bus duct conductor's casing. The size of the fin pitch is regarded as a design variable. Using ANSYS FLUENT, a numerical model that closely resembles the experimental setup was created. The experimental data were compared to the IEC 60439-1 and IEC 60439-2 standards as a benchmark. Five potential fin pitch sizes (s1 = 1.0 mm, s2 = 1.5 mm, s3 = 2.0 mm, s4 = 3.0 mm, and s5 = 4.0 mm) were taken into consideration. It was shown that as the fin pitch gap size is reduced, the average surface temperature falls. According to the investigation, conduction resistance increased while convective resistance reduced as the fin pitch gap size grew. The overall heat resistance did, however, rise. The optimal fin pitch size, s1 = 1 mm, outperformed the other fin pitches in terms of thermal performance. The current numerical analysis expects an improved knowledge of the influence of fin pitch on a bus duct conductor's thermal performance.

Publication

A UDP-TRIZ method as a universal design approach for product design

(The Society of Systematic Innovation, 2023)

Mohamad Suhaimi Shahrin

;

Khairul Aidil Adlin Abdul Rahman

;

Khairul Manami Kamarudin

;

Rosalam Che Me

To encourage the participation of individuals with diverse abilities in the community, universal design has been adopted as the foundation for creating user-friendly designs that include people of all ages, the disabled, and the elderly. However, the approach to universal design lacks a systematic and directed strategy for designers to ensure that their designs fit universal design requirements. Most manuals and guidelines focus on the built environment, and there is no specific guidance for product design. This situation is seen as an opportunity to introduce an approach for designers to approach universal designs effectively. Therefore, this research proposes an intervention tool for universal design. Universal design principles and TRIZ 40 creative principles are synergised and used in the design process to benefit one another mutually. A UDP - TRIZ methodology framework is introduced to a group of designers engaged in a series of design activities to create a product with a universal design for visually impaired persons in mind. This study demonstrates that this strategy can assist designers in understanding user-related problems, identifying innovations, justifying designs in terms of universal design requirements, and fostering the creative process.

Publication

Acoustic characteristic of Bio-Composite Micro-Perforated Panel (BC-MPP) backed with natural fiber

(The Korean Society of Mechanical Engineers and Springer-Verlag, 2023)

Faridah Wahab

;

Tan Wei Hong

;

Mohamad Haziman Mohamad Azhar

;

Nor Hafizul Hilni Abdul Rahman

We investigated the sound absorption properties of a bio-composite microperforated panel (BC-MPP) with a combination of backed-structure and several types of natural fibers such as loofah, kapok, and coconut coir. The sound absorption coefficient (SAC) of different combinations of natural fibers samples was obtained by using a two-microphone impedance tube. In addition, three models, including Delany-Bazley model, Maa theory, and electroacoustical analogy, were employed to estimate the SAC value of natural fiber, BC-MPP, and BC-MPP with a backed structure, respectively. The experimental results demonstrate that the SAC value was increased to almost 0.99 as compared to BC-MPP alone when natural fiber was introduced at the back of BC-MPP either by insertion in the hole of backed structure or attached directly at the back of BC-MPP. The SAC peak also shifted to a lower frequency bandwidth with the highest peak obtained at 930 Hz, 800 Hz and 640 Hz for MPP with coconut husk, BC-MPP with kapok and BC-MPP with loofah, respectively. The absorption frequency was also observed slightly wider than BC-MPP without natural fiber. In comparison of BC-MPP with loofah and BC-MPP with others natural fibers, the insertion of kapok and coconut coir in the hole of backed structure provides a wider effective sound absorption coefficient. The comparison of experimental result with the theoretical calculation shows that the SAC obtained from experiment provides higher SAC value over the theoretical model for both BC-MPP and BC-MPP backed structure.

Publication

Adoption of improved rice varieties in the global south: a review

(Elsevier, 2023)

Julia Checco

;

Fathin Ayuni Azizan

;

Jaquie Mitchell

;

Ammar Abdul Aziz Abdullah Kallaroth

Improved rice varieties (IRVs) play a significant role in establishing food security and improving livelihood in the Global South since its introduction in the 1960s. However, the adoption of new IRVs has remained relatively low. This low adoption poses a challenge to rice-producing and consuming countries as they are increasingly threatened by production shortages, malnutrition, and poor rice quality. Many empirical studies have attempted to identify the determinants influencing the adoption of IRVs by distinguishing the characteristics between adopters and non-adopters. This review showed a consensus on the important determinants influencing the adoption of IRVs in the Global South. Findings synthesized from 99 studies suggested that variables (farm size, education, information access and farm location) examined extensively are not necessarily the most important determinants of adoption when undertaking a weighted analysis. Terrain, source of seed and technology-related attributes (perceived yield, maturity, ease of use, marketability and technical efficiency) are more important determinants of adoption, with determinants changing according to adoption type (probability or intensity of adoption), variety type and region. The recommendations for future adoption studies include: incorporating more technology-specific variables, increasing research for overlooked regions and variety types, shifting away from predominant static analysis by capturing the dynamics of the adoption process, and considering the potential biases in analyses. This review will facilitate the development of targeted interventions and policies that promote IRV adoption in the Global South.

Publication

Advanced value stream mapping: development of a conceptual model considering variability in production processes

(SAE International, 2023)

Alaa Salahuddin Araibi

;

Mohamad Shaiful Ashrul Ishak

;

Muhanad Hatem Shadhar

Recently, lean manufacturing (LM) practices are being combined with tools and techniques that belong to other areas of knowledge such as risk management (RM). Value stream mapping (VSM) is a well-known tool in showing the value, the value stream, and the flow, which represents the three lean principles. VSM and RM, when used in tandem with one another, are more advantageous in covering VSM issues such as the variability of production processes. In this article, a conceptual model that integrates the two is shown and explained. The model helps to generate scenarios of current state map (CSM) and future state map (FSM) in a dynamic way by identifying current and potential risks. These risks might happen in the future, bringing with it negative ramifications including not reaching the main objectives within the defined time. The model has been tested in a coffee production company belonging to health and food sector. The proposed model specified the ranges of variability through the drawing of CSM and FSM. This is quite a milestone because one of the challenges of VSM is that it is a static tool, and, as such, process variability cannot be captured appropriately. This new model is expected to overcome this drawback.

Publication

An investigation of the processability of natural fibre reinforced polymer composites on shallow and flat thin-walled parts by injection moulding process

( 2013)

Mohd Azaman Md Deros

;

S.M. Sapuan

;

S. Sulaiman

;

E.S. Zainudin

;

K. Abdan

Currently, many industries are trending towards producing products exhibit such properties as small thickness, lightweight, small dimensions, and environmental friendliness. In this project, flat or shallow thin-walled parts were designed to compare the advantages and disadvantages of lignocellulosic polymer composites (PP + 50 wt% wood) in terms of processability. This study focused on the filling, in-cavity residual stresses and warpage parameters associated with both types of thin-walled moulded parts. Thin-walled parts 0.7 mm in thickness were suitably moulded using lignocellulosic composite materials to determine the effects of filling. The analysis showed, the shallow thin-walled part is preferable in moulding lignocellulosic polymer composite material due to the low residual stress and warpage measured. The results also indicate that the shallow thin-walled part is structurally rigid, such that it can be used in applications involving small shell parts, and can be processed more economically using less material than the flat thin-walled part.

Publication

Analysis of accent-sensitive words in multi-resolution mel-frequency cepstral coefficients for classification of accents in Malaysian English

( 2013-06)

M.A. Yusnita

;

M.P. Paulraj

;

Sazali Yaacob

;

R. Yusuf

;

Shahriman Abu Bakar

This paper investigates the most accent-sensitive words for Malaysian English (MalE) speakers in multi-resolution 13 Mel-frequency cepstral coefficients. A text-independent accent system was implemented using different numbers of Mel-filters to determine the optimal settings for this database. Then, text-dependent accent systems were developed to rank the most accent-sensitive words for MalE speakers according to the classification rates. Prior work has also been conducted to test the significance of the wordlist for both gender and accent factors, and to investigate any interaction between these two factors. Experimental results show that male speakers have a higher intensity of accent effects compared with female speakers by 3.91% on text-independent and 3.47% on text-dependent tasks. Another finding has proven that by selecting appropriate words that carry severe accent markers could improve the task of speaker accent classification. An improvement of at most 8.45% and 8.91% was achieved on the male and female datasets, respectively, following vocabulary selection.

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Publication

Antioxidant capacity and total phenolic content of fresh, oven-dried and stir-fried tamarind leaves

( 2017)

Lee Yit Leng

;

Mohd Nadzrin Mohammad Radzi

;

Abd Razak Shaari

;

Norawanis Abdul Razak

;

Khor Chu Yee

The aim of this study was to compare the antioxidant capacity and total phenolic content as well as the chemical groups of fresh, oven-dried and stir-fried tamarind (Tamarindus indica L.) leaves. Methanol was used for extraction of fresh, oven-dried and stir-fried tamarind leaves. The stir-fried leaves were prepared using medium heat for 10 minutes prior to extraction and chemical analysis while dried leaves were obtained by oven drying at 60°C for 3 hours. The stir-fried leaves had significantly highest total phenolic content (TPC) (139.87 mg/g) and percentage DPPH radical-scavenging inhibition (69.92%) while the fresh leaves had the lowest TPC (39.31 mg/g) and antioxidant capacity (16.46%). The FTIR spectral data suggest that the heat treatment increased the amine groups as well as the antioxidant capacity of the tamarind leaves. To increase the antioxidant capacity, the tamarind leaves should be prepared in a stir-frying process.

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Publication

Biodegradability of bioplastic film using different regions of Pennisetum purpureum incorporated with gelatine and chitosan

(Springer, 2022)

T. N. Tuan Rohadi

;

Mohd Ridzuan Mohd Jamir

;

Mohd Shukry Abdul Majid

;

Mohd Hafis Sulaiman

The accumulation of plastic waste and rapid reduction of fossil reserves have pushed the development of packaging towards eco-friendly materials, such as bioplastics. However, most bioplastics are manufactured with chemical additives that are inorganic and entirely nondegradable. Therefore, bioplastics from renewable and biodegradable sources have been developed by incorporating cellulose, gelatine, and chitosan. This paper presents the optical properties, moisture content, swelling behaviour, assessment as packaging materials, and biodegradability tests of bioplastics. The considered bioplastics consisted of raw and cellulose from the whole, fibre, and bark of Pennisetum purpureum, with gelatine and chitosan fabricated using the solution-casting method. Cellulose was isolated using 8 wt% concentration of sodium hydroxide followed by 1.7 wt% concentration of sodium chlorite. The compatibility of fibre-matrix adhesion was improved by including cellulose from WPP, FPP, and BPP into the incorporation of chitosan and gelatine in bioplastics. Nevertheless, improving their optical properties, moisture content, and swelling behaviour had caused bioplastics to be more resistant to microbial activity and have the slower degradation rate.

Publication

Biodegradable natural fiber polymer composite as future 3D printing feedstock

(CRC Press, 2023)

Sanusi Hamat

;

Mohamad Ridzwan Ishak

;

Mohd Sapuan Salit

;

Noorfaizal Yidris

The key advantages of 3D printing are its capability to produce complex structures and rapid prototyping. This has contributed to the development of modern material processing methods over the past years for industrial tasks and needs. However, the development of biodegradable feedstock for 3D printing filament and enhanced natural fiber as reinforcement filler to improve mechanical properties and biodegradation is still not fully explored. Also, there have been alarming concerns around the world about the use of non-biodegradable resources during 3D printing that could threaten the sustainable environment. This review discusses the types of biodegradable polymers, natural fibers with their properties and applications, the development method for non-biodegradable and biodegradable polymer composites obtained through fused filament fabrication (FFF). Finally, the challenges and future opportunities associated with 3D printing feedstock of biodegradable polymer composites are reviewed and analyzed.

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Publication

Biomass fuel characteristics of Malaysian Khaya Senegalensis wood-derived energy pellets: effects of densification at varied processing temperatures

( 2024)

Ras Izzati Ismail

;

Khor Chu Yee

;

Alina Rahayu Mohamed

This study addresses the effects of densification at varied pelletization temperatures on the novel Malaysian Khaya senegalensis wood-derived pellets biomass fuel characteristics. The lack of comprehensive understanding regarding the biomass fuel characteristics of this species prompted the research. By addressing this knowledge gap, this study explores the impact of temperature variations on key fuel properties, contributing to the optimization of sustainable biomass fuel production in manufacturing and materials processing. Khaya senegalensis wood, grown and harvested in Malaysia, was pelletized at different temperatures to analyze the calorific value, volatile matter content, ash content, fixed carbon, bulk density, and moisture contents of the pellets. The experimental data revealed a significant relationship between temperature and these fuel properties. Pelletizing at 75 °C produced the highest calorific value of 19.47 MJ/kg and the maximum fixed carbon content of 10.04%. A low ash level of 4.26% was achieved via pelletizing at 75 °C. According to the results, 75 °C produced the best thermophysical properties. These findings provide valuable understanding of how pelletization temperature influences fuel pellet thermophysical properties, a critical aspect in optimizing fuel pellet production, storage, advancing renewable energy resource utilization, and, finally, promoting a cleaner and more sustainable energy future.

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Publication

CFD Simulation on an Improvised Ice Cream Container

(Semarak Ilmu Publishing, 2023)

Mohd Tasyrif Abdul Rahman

;

Nursyazwani Abdul Aziz

;

Nasrul Amri Mohd Amin

;

Mohd Ijmal Kamil Patriot

;

Mohd Sofwan Mohd Resali

;

Azizul Mohamad

;

Muhammad Izham Ismail

;

Mohd Asrul Md Saad

A temperature-sensitive product such as ice-cream may cause the industry to face several challenges throughout the production, storage, packaging, and distribution processes. With the purpose to improve the performance of an ice cream container that acts as cold storage during the delivery process, the integration of a tube-type phase change material (PCM) thermal storage system was studied. In this work, a Computational Fluid Dynamic (CFD) method was used to model and analysed eight designs of phase change thermal storage systems incorporated within the ice-cream container. The tube type PCM was modeled, with and without the conducting pins, aiming to maximise the heat exchange within the system. To obtain a proper design, parametric studies on the number of pins and its diameter were further analysed. For all simulations, the initial time for freezing simulation was set to 2℃, assuming the PCM was fully in a liquid state with the ice mass fraction was set to 0. With that, the PCM average temperature and the total mass fraction was observed and analysed. From the results, the ice mass fraction percentage of the systems was observed to increase with the increasing number of pins. Model with (the maximum) 40 pins has improved ice mass fraction for at least 67.58% when compared to the configuration without pin. Also, the average temperature of PCM for model with maximum pins, was observed to be 37.14% lower when compared to the configuration without pins and less pin numbers. Nevertheless, although the presence of pins has proven to enhance the heat exchange within the system, the percentage of ice formation was considered to be low and the average temperature was still as high as 0.66℃ after 12 hrs of freezing process. This indicating that a proper design of TES is inevitably needed, in order to maximise both heat exchanges and PCM storage ability within the system. © 2023, Semarak Ilmu Publishing. All rights reserved.

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Publication

Characteristics of the surface topography and tribological properties of reinforced aluminum matrix composite

( 2022)

Magdalena Niemczewska-Wójcik

;

Manickaraj Pethuraj

;

Marimuthu Uthayakumar

;

Mohd Shukry Abdul Majid

Due to their excellent synergistic properties, Aluminum Matrix Composites (AMC) have achieved a high degree of prominence in different industries. In addition to strength, the wear resistance of materials is also an important criterion for numerous applications. The wear resistance depends on the surface topography as well as the working conditions of the interacting parts. Therefore, extensive experiments are being conducted to improve the suitability of engineering materials (including AMC) for different applications. This paper presents research on manufactured aluminum metal matrix composites reinforced with 10 wt.% of Al2SiO5 (aluminum sillimanite). The manufactured and prepared samples were subjected to surface topography measurements and to tribological studies both with and without lubricant using a block-on-ring tester. Based on the results, analyses of the surface topography (i.e., surface roughness parameters, Abbott–Firestone curve, and surface defects) as well as of the tribological characteristics (i.a. friction coefficient, linear wear, and wear intensity) were performed. Differences in the surface topography of the manufactured elements were shown. The surface topography had a significant impact on tribological characteristics of the sliding joints in the tests where lubrication was and was not used. Better tribological characteristics were obtained for the surfaces characterized by greater roughness (determined on the basis of both the profile and surface texture parameters). In the case of tribological tests with lubrication, the friction coefficient as well as the wear intensity was significantly lower compared to tribological tests without lubrication. However, lower values of the friction coefficient and wear intensity were still recorded for the surfaces that were characterized by greater roughness. The obtained results showed that it is important to analyze the surface topography because surface characteristics influence tribological properties.

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Publication

Charging strategy in electric vehicle chargers by utilizing demand side management scheme

(Elsevier B.V., 2023)

Aziah Khamis

;

M.H. Aiman

;

Wan Mohd Faizal Wan Ab Rahim

;

Khor Chu Yee

Electric vehicles (EVs) have received significant attention recently, given their potential technical, environmental, and economic benefits. However, given the fact that EV charging could happen at peak demand. This situation may deteriorate the distribution network's overall performance, particularly in terms of voltage stability. The novelty of this paper is to evaluate the impacts of the integration of EV chargers in the distribution network and to propose a charging strategy in EV chargers. The proposed charging strategy manages the power in the distribution network during the EV charger connection by utilizing demand side management. The IEEE 9-bus radial distribution system was used as the test network. Four scenarios were conducted by relevant assessments using the deterministic and probabilistic approaches. The result showed the influence of charging strategy on EV charging systems where it can reduce the impact of integration EV chargers by shifting the load of EV charging from the on-peak period to the off-peak period. As a result of using EV charging strategy, peak active power losses were reduced by 2.2 to 3.2 percent. The proposed method contributes the idea to the engineer and researcher in designing the EV charging strategy. However, the charging EV strategy could be further improved by optimizing the value of the relay setting of both the UVLS relay and the power demand relay in future research.

4 14

Publication

Chip morphology and surface integrity in turning AZ31 magnesium alloy under dry machining and submerged convective cooling

( 2023)

Muhammad Syamil Zakaria

;

Mazli Mustapha

;

Azwan Iskandar bin Azmi

;

Khor Chu Yee

Magnesium alloys have broad applications, including medical implants and the aerospace sector owing to their great density and high strength-to-weight ratio. Dry cutting is a frequent technique for machining this material. However, it always leads to an excessive rise in temperature due to the absence of cooling at the cutting zone, which affects the machined surface integrity and chip morphology. In this study, chip morphology and surface integrity of the AZ31 magnesium alloy were investigated in the turning process using an internal cooling method called submerged convective cooling (SCC) to overcome the absence of cooling in dry cutting. This method can exploit the advantage of the high specific heat capacity of water as a cooling fluid without any reaction between water and magnesium to create a cooling element in the cutting zone. The chip morphologies and surface integrity were analyzed experimentally with varying cutting speeds under SCC and dry cutting. The experimental results revealed that SCC and dry cutting produced saw-tooth or serrated chip formation. The chips produced in dry cutting were continuous, while SCC was short and discontinuous as a result of a severe crack on the back surface of the chip. It was discovered that the grain refinement layer on the machined samples was thinner under SCC turning. SCC machining increased the microhardness of the AZ31 magnesium alloy by 60.5% from 55 HV to 88.3 HV, while dry turning exhibited a 49% increase in microhardness. The result revealed that surface roughness improved by 10.8%, 9.4% and 4.7% for cutting speeds (V) of 120, 180, and 240 m/min, respectively, under the SCC internal cooling. Based on the result obtained, SCC cutting outperformed dry cutting in terms of chip breakability, grain refinement, microhardness, and surface roughness.

Publication

Chip morphology and surface integrity in turning AZ31 Magnesium alloy under dry machining and submerged convective cooling

(MDPI, 2023)

Muhammad Syamil Zakaria

;

Mazli Mustapha

;

Azwan Iskandar Azmi

;

Khor Chu Yee

Magnesium alloys have broad applications, including medical implants and the aerospace sector owing to their great density and high strength-to-weight ratio. Dry cutting is a frequent technique for machining this material. However, it always leads to an excessive rise in temperature due to the absence of cooling at the cutting zone, which affects the machined surface integrity and chip morphology. In this study, chip morphology and surface integrity of the AZ31 magnesium alloy were investigated in the turning process using an internal cooling method called submerged convective cooling (SCC) to overcome the absence of cooling in dry cutting. This method can exploit the advantage of the high specific heat capacity of water as a cooling fluid without any reaction between water and magnesium to create a cooling element in the cutting zone. The chip morphologies and surface integrity were analyzed experimentally with varying cutting speeds under SCC and dry cutting. The experimental results revealed that SCC and dry cutting produced saw-tooth or serrated chip formation. The chips produced in dry cutting were continuous, while SCC was short and discontinuous as a result of a severe crack on the back surface of the chip. It was discovered that the grain refinement layer on the machined samples was thinner under SCC turning. SCC machining increased the microhardness of the AZ31 magnesium alloy by 60.5% from 55 HV to 88.3 HV, while dry turning exhibited a 49% increase in microhardness. The result revealed that surface roughness improved by 10.8%, 9.4% and 4.7% for cutting speeds (V) of 120, 180, and 240 m/min, respectively, under the SCC internal cooling. Based on the result obtained, SCC cutting outperformed dry cutting in terms of chip breakability, grain refinement, microhardness, and surface roughness.

Publication

Color detection using non‐target reflectivity plastic optical fiber displacement sensor

(Wiley, 2020)

Muhammad Fadhli Muhammad Azri

;

Mohd Zamani Zulkifli

;

Farah Diana Muhammad

;

Muhammad Khudori Yusof

;

Muhammad Syahril Bahari

;

Sani Amril Samsudin

;

Moh Yasin

A simple plastic optical fiber displacement sensor has been demonstrated as a non-contact color detection device. The sensitivity of the sensor is 0.0228, 0.1718, 0.1122, 0.106, and 0.1267 mW/mm for black, blue, green, red, and white, respectively. The experimental results prove that as the color changes from dark to bright, the peak output power increases proportionally. The proposed sensor is highly stable and persistent, with additional advantages of practicality of design, high efficiency, comprehensive depth of field, and low cost of production, which could be beneficial for applications in the sensing field.

Publication

Complex impedance and modulus analysis on porous and non-porous scaffold composites due to effect of Hydroxyapatite/starch proportion

( 2023)

Chong You Beh

;

Cheng Ee Meng

;

Xiao Jian Tan

;

Nashrul Fazli Mohd Nasir

;

Mohd Shukry Abdul Majid

;

Mohd Ridzuan Mohd Jamir

;

Khor Shing Fhan

;

Kim Yee Lee

;

Che Wan Sharifah Robiah Mohamad

This study aims to investigate the electric responses (complex modulus and complex impedance analysis) of hydroxyapatite/starch bone scaffold as a function of hydroxyapatite/starch proportion and the microstructural features. Hence, the non-porous and porous hydroxyapatite/starch composites were fabricated with various hydroxyapatite/starch proportions (70/30, 60/40, 50/50, 40/60, 30/70, 20/80, and 10/90 wt/wt%). Microstructural analysis of the porous hydroxyapatite/starch composites was carried out by using scanning electron microscopy. It shows that the formation of hierarchical porous microstructures with high porosity is more significant at a high starch proportion. The complex modulus and complex impedance analysis were conducted to investigate the electrical conduction mechanism of the hydroxyapatite/starch composites via dielectric spectroscopy within a frequency range from 5 MHz to 12 GHz. The electrical responses of the hydroxyapatite/starch composites are highly dependent on the frequency, material proportion, and microstructures. High starch proportion and highly porous hierarchical microstructures enhance the electrical responses of the hydroxyapatite/starch composite. The material proportion and microstructure features of the hydroxyapatite/starch composites can be indirectly reflected by the simulated electrical parameters of the equivalent electrical circuit models.

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Publication

Computational fluid dynamics analysis on overweight sleep APNEA patient under various breathing flow patterns

(Penerbit UTM Press, 2023)

Muhammad Nooramin Che Yaakob

;

Wan Mohd Faizal Wan Ab Rahim

;

Khor Chu Yee

Obstructive Sleep Apnea (OSA) is a breathing disorder that occurs during sleep. This syndrome affects numerous people, especially those with abnormal body fat composition parameters such as body mass index (BMI) of more than 25 kg/m2 (overweight & obesity). OSA ensues when the tongue and soft palate muscles in a relaxed condition move towards gravity when the patient is in a supine position; this causes narrowing and blockage on the upper airway affecting breathing. There are several treatments for OSA, including upper airway surgery. A better understanding of airflow characteristics will assist ENT surgeons in identifying the blockage area. This paper examines airflow characteristics of the upper airway for overweight sleep apnea patients. The narrow and blockage area on the respiratory tract causes turbulence formation that is evaluated using Computational Fluid Dynamic (CFD) based on an actual parameter of the 3D model obtained by CT scan image result. Reynold’s averaged Navier-Stoke (RANS) equation and turbulent model, k-ω shear stress transport (SST), were applied. Airflow fluctuation was characterized by crucial parameters such as velocity, pressure, and turbulent kinetic energy (TKE). The result shows that the narrow cross-sectional area of the airway causes accretion of the velocity and pressure in the pharyngeal airway. The increasing airflow parameter results in high turbulent kinetic energy (TKE) that will determine the severity level of OSA patients. Investigating airflow characteristics in overweight OSA patients will help the medical practitioner validate the narrow and blockage area for the surgery.

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