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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.

18 1

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

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.

1 22

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.

1 12

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.

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.

1 11

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.

1 14

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.

8 7

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.

1 7

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

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.

2 8

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.

1 4

Publication

Conceptual design and simulation validation based finite element optimisation for tubercle leading edge composite wing of an unmanned aerial vehicle

( 2019)

Ernnie Illyani Basri

;

Faizal Mustapha

;

Mohamed Thariq Hameed Sultan

;

Adi Azriff Basri

;

Mohd Firdaus Abas

;

Mohd Shukry Abdul Majid

A finite element model is developed to determine deformation and stresses on a composite wing of unmanned aerial vehicle (UAV) with a tubercle design at the leading edge of the wing. Tubercles, commonly known as protuberances found on the leading edge of a whale pectoral flipper, offering great performance from an aerodynamic perspective. This paper deals with a first order shear deformation theory (FSDT) approach to discover the UAV laminates composite wing model of tubercle leading edge (TLE) with rib-reinforced so that the equivalent stiffness and material properties are obtained from the simulation of finite element analysis using ANSYS. Another structural configuration of design replicating the idea of monocoque concept, whereby foam is used at the leading and trailing edges of the wing. Styrene acrylonitrile (SAN) core foam is used representing high strength-to-weight ratio with its superiority in the mechanical properties of polymeric sandwich composites. The updated static structural analysis from rib-reinforced can be applied to update the wing stiffness distribution of monocoque-foam. The optimum design is concluded from the tabulated deformation and stresses of both wings, where monocoque-foam showed better performance with a reduction in 50.72% of deformation and 35.88% of stress, compared to rib-reinforced design.

1 9

Publication

Contribution of interfacial bonding towards geopolymers properties in geopolymers reinforced fibers: a review

( 2022)

Muhd Hafizuddin Yazid

;

Meor Ahmad Faris bin Meor Ahmad Tajudin

;

Mohd. Mustafa Al Bakri Abdullah

;

Marcin Nabiałek

;

Shayfull Zamree Abd. Rahim

;

Mohd Arif Anuar Mohd Salleh

;

Marwan Kheimi

;

Andrei Victor Sandu

;

Adam Rylski

;

Bartłomiej Jeż

There is a burgeoning interest in the development of geopolymers as sustainable construction materials and incombustible inorganic polymers. However, geopolymers show quasi-brittle behavior. To overcome this weakness, hundreds of researchers have focused on the development, characterization, and implementation of geopolymer-reinforced fibers for a wide range of applications for light geopolymers concrete. This paper discusses the rapidly developing geopolymer-reinforced fibers, focusing on material and geometrical properties, numerical simulation, and the effect of fibers on the geopolymers. In the section on the effect of fibers on the geopolymers, a comparison between single and hybrid fibers will show the compressive strength and toughness of each type of fiber. It is proposed that interfacial bonding between matrix and fibers is important to obtain better results, and interfacial bonding between matrix and fiber depends on the type of material surface contact area, such as being hydrophobic or hydrophilic, as well as the softness or roughness of the surface.

13 1

Publication

Control of flows around bluff bodies mediated by porous materials

( 2020-06-01)

Sadeghipour, Sakineh

;

Syamir Alihan Showkat Ali

;

Liu, Xiao

;

Azarpeyvand, Mahdi

;

Thorpe, Graham R.

There is evidence that the application of porous media to the surfaces of bluff bodies immersed in turbulent fluid flows has a profound effect on the associated aerodynamic phenomena. This idea is explored by performing a series of experiments on cylinders that have circular, square and rectangular cross sections. The flow fields were established around circular cylinders that had been encased in porous media, and which retained the same dimensions of the bare cylinder. The square and rectangular bluff bodies were modified so that their upstream and downstream halves consisted of solid and porous materials respectively. It is found that the porous media applied to the circular cylinder had the most effect on the wake, and the largest effect was observed in the wake generated by the most permeable material. The principal effect of the porous media was to cause the eyes of the recirculation region to be located further downstream. The effect of the permeability is increasingly diminished in the square and rectangular geometries. The presence of the porous media also had a significant effect on the Reynolds stresses. The effect of the porous media applied is to damp the normal stresses further downstream of the bluff bodies.

2 2

Publication

Correlation between postural stability and lower extremity joint reaction forces in young adults during incline and decline walking

(MDPI, 2023)

Noor Arifah Azwani Abdul Yamin

;

Khairul Salleh Basaruddin

;

Muhammad Farzik Ijaz

;

Hiroshi Takemura

;

Mohd Hanafi Mat Som

;

Muhammad Nazrin Shah Shahrol Aman

Postural stability may be affected during slope walking, as there are different body kinetics and kinematic responses compared with level walking. Understanding body adaptations toward different inclinations is essential to prevent the risk of injury from falls or slips. This study was conducted to determine the correlations between stability parameters and loading response in terms of joint reaction force at the lower-extremity joints during inclined and declined walking. Twenty male subjects walked in the level, incline, and decline directions on a custom-built platform at three different slope angles (i.e., 5°, 7.5°, and 10°). To determine the ground reaction force (GRF), joint reaction force (JRF), center of pressure (COP), and center of mass (COM), a motion capture system was used to read the data of the ten reflective markers and transfer them to visual three-dimensional (3D) software. Pearson’s correlation test was performed with statistical significance set at p < 0.05 to evaluate the correlation of the required coefficient of friction (RCOF), postural stability index (PSI), and COP-COM distance with the JRF. This study has identified that the JRF changes in opposition to the changes in the RCOF during the initial strike during incline and decline walking, as JRF increases, the RCOF decreases with different strengths of correlation. There is also a strong positive correlation between the PSI and JRF in the proximal–distal direction, where the JRFs change in accordance with the change in the PSI, and the JRF increases with the increment of PSI. In addition, the JRF of the lower extremity also changed in a manner similar to the COP-COM distance in the medial–lateral direction. Overall, each stability parameter was correlated with the JRF of the lower-extremity joints in different directions and strengths. This study demonstrated that slope walking is particularly affected by surface inclination in terms of stability and loading. Therefore, this research can serve as a basis for future studies on slopes, as there is no specific basis for a maximum degree of inclination that is safe and suitable for all applications.

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