Ω Monograph (FRGS)

Developments of entropy-consistent residual distribution and finite/Prof. Madya Dr. Farzad Ismai

Mon, 21 Dec 2020 15:02:10 +0800

Asymptotic crack tip fields of surface cracked panels under non-hardening bending loads / Rizman Hariz Abdul Latiff and Feizal Yusof

Mon, 21 Dec 2020 13:29:01 +0800

In this paper, the investigation of in-plane constraint loss in a semi-elliptical surface cracked panei(SCP) specimen based on a detailed non-hardening finite element analysis with aspect ratios ale ofO.S and relative depths aft of 0.33 and 0.5 under bending loads. The asymptotic stress field solutions were compared to the fully constrained Prandtl field for the plane-strain case and Sham & Hancock crack tip plane-stress fields. The asymptotic solutions of the semi elliptical shallow and the deep cracked bars were found to be contained within a Prandtl crack tip field at the centre of thespecimen. Loss of constraint was observed at the free surface ofthe semi-elliptical surface cr ck.

Analysis of pedestrian walking characteristics at vertical facilities in underground train station /Nur Sabahiah Abdul Sukor

Mon, 21 Dec 2020 12:48:44 +0800

Kuala Lumpur is the national capital of Malaysia as well as the center of attraction for people looking for jobs. Thus, in the future people will tend to use public transport including the Light Rail Transit (LRT) more often than driving their vehicle. This is especially so due to critical traffic congestion on the road especially during peak hours. The increasing population in Kuala Lumpur could lead the LRT stations to become more crowded form day to day due to excessive demand. Due to this problem, the facilities provided will not be enough and suitable to cater the space demand. Unfortunately, the limited study was done regarding the pedestrian spaces and facilities at underground LRT in Malaysia. Thus, this paper aims to esta blish the fundamental understanding of pedestrian behavior at vertical facilities in underground train station.

An improved method to model semi-elliptical surface cracks using element mismatch in abaqus / R. H. A. Latiff , F. Yusof

Mon, 21 Dec 2020 12:27:14 +0800

The purpose of this paper is to propose and investigate the feasibility of using multiple element types in a single model, termed element mismatch, for a three-dimensional semi-elliptical crack problem. The purpose behind the exploration of this method is to ease the meshing process in complex models. Multiple semi-elliptical surface crack in tension models were created with single element mesh and multi-elementmeshes with different mesh densities. It was found that the element mismatch modelsdeveloped a consistent stress intensity factor for all the applied loading and geometries. When compared to the single element type models, the computation times were found to be significantly lower for the element mismatch models and the results were la rgely independent of mesh density.

A study on the effects of three-dimensionalcrack tip constraint in mixed modes problem Numerical and Experimental analysis / lr. Dr. Feizal Bin Yusof, Prof. Madya Choong

Mon, 21 Dec 2020 12:20:10 +0800

Failure of engineering structures usually manifest from cracks preceded by local plastic deformation. The characterization of three-dimensional crack tip plastic deformation hence is important to assessment of susceptibility of cracks in structures. Three-dimensional elastic plastic techniques are available but application to complex problem are limited. To extend application of assessment of a new approach for three-dimensional crack tip constraint, a three dimensional constraint estimation scheme was examined for surface cracked plates with semi elliptical surface cracks under tensile and bending loads and deep and shallow through cracks. The J-llcr approach was found to be able to estimate the in-plane and out-of-plane crack-tip constraint along the semi-elliptical crack front by characterising the principal stresses over a dimensionless J/zcro parameter.

The study of direct thermal-to-electricity conversion using thermionic heat cell device_Assoc. Prof. Dr. Abdus Samad Mahmud, Assoc. Prof. Dr. Jamaluddin Abdullah, _M4_2015_NI

Fri, 18 Dec 2020 14:59:15 +0800

Thermionic energy conversion (TEC) is the direct conversion of heat into electricity by the mechanism of thermionic emission, the spontaneous ejection of hot electrons from a surface in vacuum environment. There are two major obstacles for achieving highly efficient TECs; the strict need for low emitter and collector work functions, and the mutual repulsion of electron within the inter electrode gap, known as the space charge effect. Despite the aforementioned issues, TEC still remains an attractive approach to power generation. Like other direct energy conversion approaches, it requires no moving parts and thus has the potential for long lifetimes with little-to-no maintenance. In this project, we focuses on two sub-studies which are studying a mechanism of suppressing space charge problem and introducing nanostructures surface topography of low work function on anode/cathode materials for the enhancement of thermionic electrons emission. Based on the simulation work, a new concept for better performance TEC is proposed based on cylindrical configuration. With better heat transfer management, the concept offers approximately 15% better efficiency than the planar configuration. Silicon Carbide nanowires (SiC NWs) are successfully synthesized on the surface of the silicon substrate via a low-temperature (600 oc) synthesis method. . A total of —0.36 ev reduction of the effective work function has been achieved b as-s nthesized SiC NWs' thermionic cathode.

Novel piezoelectric material characterization with hysteresis, creep, vibration and saturation non-linearity effects/Dr. Ahmad Zhafran Ahmad Mazlan, Prof. Dr Zaidi Mohd Ripin

Fri, 18 Dec 2020 14:54:46 +0800

This research aims to investigate the presence of four non-linear characteristics (i.e., hysteresis, saturation, creep and vibration) when a piezoelectric patch material is acted as actuator for the AVC of a beam. The parameters such as frequencies and voltages are taken into account for the piezoelectric patch material characterization and the vibration before and after activation of PID controller in AVC system are measured. From the results, the piezoelectic actuator posed all the four non-linearity effects and increased significantly with the increased of operating frequencies and voltages. In term of controller, PGS shows the best performance by scoring 3/5 of highest vibration attenuation percentages compared to manual and Z-N methods. For the frequency dependent excitation, the effective frequency range for the AVC system is determined between 75 Hz to 245 1-IZ with the highest vibration attenuation of 79.6 % occurred at the second natural frequency of the beam

Pt-based catalytic microcombustor for micropower generation/Muhamad Nazri Murat Muhamad Azman Miskam, Mohd Azmier Ahmad, Zainal Alimuddin Zainal Alauddin, Mohammad Zulfikar Ishak

Fri, 11 Dec 2020 11:09:15 +0800

This paper presents the fabrication and characterization of platinum-based catalytic microcombustor. The platinum catalyst was deposited onto type-304 stainless steel using the wet impregnation method. The stainless steel undergoes controlled conversion coating treatment in sulfuric acid solution to increase the porosity of its surface before the deposition of the platinum catalyst. The scanning electron microscopy result showed that the porosity on the stainless steel surface will depend on the length of treatment time in the sulfuric acid solution. The surface porosity increased as the treatment time increases. The stainless steel surface morphology changed from smooth to 'cracked-mud ' morphology after treatment in sulfuric acid solution. The treatment time also provide significant effect to the amount of platinum deposited on the stainless steel surface. The energy dispersive x-ray analysis showed that the amount of deposited platinum for 10 seconds of treatment time was 0.68 wt%. whereas those for 20 and 30 seconds were 0.87 wt% and 1.10 wt%. respectively. Liquetied petroleum gas-air combustion result showed that the flame completely submerged in side the microcombustor with a catalyst, whereas portions of flame can be observed at the exhaust for the microcombustor without a catalyst. The minimum a ir-to-fuel ratios before the combustion blow-out for I 0, 20, and 30 seconds of treatment time was 0.5, 0.4, and 0.3 respectively.

Characterization of wet impregnation method for catalytic microcombustor by using platinum/Muhamad Nazri Murat, Muhamad Azman Miskam, Mohd Azmier Ahmad, Zainal Alimuddin Zainal Alauddin, Mohammad Zulfikar Ishak

Thu, 10 Dec 2020 09:28:42 +0800

The wet impregnation method for catalytic microcombustor was characterized by using platinum as a catalyst. The main purpose of this stud y i s to increase the surface porosity of the catalyst support. A high surface porosity indicates that a high amount of catalyst was deposited within the surface areas. The performance of the catalytic microcombustor improves with increasing catalytic surface area. The stainless steel catalyst support was treated with sulfuric acid solution containing polyvinyl (3.89 w t%) and propargyl alcohol ( 1.48 w t%). Combustion test was performed using LPG-air to test the performance of the catalyst. The surface support treated with polyvinyl (PYA) showed a higher surface porosity and combustion blow-out limit compared with propargyl alcohol. The combustion mode changes from surface to submerged combustion after the catalyst was deposited in the support surface.

Analysis on the influence of environmental, physical, and socioeconomic (epse) spatial variables as applied in spatial decision model for landfill site selection/Pm Dr. Mohd Sanusi S. Ahamad, Pm Dr. Mohd Suffian Yusoff

Wed, 09 Dec 2020 16:30:25 +0800

New Landfills must comply with the requirements of governmental regulations that put emphasis on minimising the environmental, physical and socio-economic (EPSE) impacts. This research has primarily identified and characterise local spatial EPSE variables for locational suitability decision model for MSW landfill siting problem commonly encountered in the public and private planning sectors in Malaysia. Consequently, the final outcome is set of characterised EPSE variables that are useful and applicable to standard Malaysian landfill location planning scenario. In addition, a prototype spatial decision model was built on GIS platform to support policy makers in searching and solving new sustainable future landfill sites within Malaysia

Understanding of photo-degradafion mechanism in nr latex with the incorporation of surface modified bi-metal oxide/Assoc.Prof. Dr Nadras Othman

Thu, 24 Sep 2020 09:09:51 +0800

The aim of this work is to prepare I-NR using a photodegradation method, hence to characterize its physical and chemical properties. In this study, UV light was used to degrade NR in latex state. Reaction parameters such as UV radiation, temperature, hydrogen peroxide, reaction time, DRC and stabilizers showed synergistic effect and influenced the reaction's efficiency. At an optimum reaction condition, the molecular weight of NR was reduced from 544 x 103 g/mol to about 18 x 103 g/mol with almost negligible amount of gel content. The zeta potential of NR latex was increased during the photodegradation, provided by the negatively charge of fatty acid. Dispersed the Ti02 in latex showed catalytic effect on the photodegradation reaction when the molecular weight of LNR was further reduced to about 7 x 103 g/mol with negligible amount of gel content. The molecular structure of LNRs were similar to that the NR, but with increasing of hydroxyl and carbonyl groups on its chain. These functional groups were formed as a result of chain cleavage and located at the chain end.

The study of direct thermal-to-electricity conversion using thermionic heat cell device/ Assoc Prof. Dr. Khairudin Mohamed

Thu, 24 Sep 2020 09:04:24 +0800

Novel piezoelectric material characterization with hysteresis, creep, vibration and saturation non-linearity effects /Dr. Ahmad Zhafran Ahmad Mazlan

Wed, 23 Sep 2020 17:26:18 +0800

Solid state lighting driver ic modeling using behavioral simulation technique/A. Marzuki, S. R. Abdul Aziz, Tun Zainal Ami Zulkifli

Mon, 09 Mar 2020 12:20:04 +0800

Solid state lighting (SSL) technology has a potential to provide artificial lighting more efficiently, low cost and longlasting alternatives to conventional incandescent and fluorescent lighting sources. As the LED technology evolves, the applications involving LEDs are innumerable and its varieties impose a clear demand on design of controllable SSL drivers. A step down DCDC converter has a great performance as SSL driver that regulates the power to LED by supplying a constant amount of current. This paper introduces an SSL driver model using behavioral simulation technique. Behavioral modeling using Verilog-A language represents the top level models rather than actual transistor implementation of the circuit. The models have predicted the required voltage levels for the ramp signal and the error amplifier gain. The achieved maximum current ripple was less than 5 0/0. This technique has great potential for faster and better system verification.

Investigation of improvement on the sensitivity of low noise low power cmos optical crop sensor/Arjuna Marzuki, Mohd Tafir Mustaffa, Norlaili Mohd. Noh and Basir Saibon

Mon, 09 Mar 2020 12:10:59 +0800

Plant phenotyping studies represent a challenge in agriculture application. The studies normally employ CMOS optical and image sensor. One of the most difficult challenges in designing the CMOS sensor is the need to achieve good sensitivity while achieving low noise and low power simultaneously for the sensor. At low power, the CMOS amplifier in the sensor is normally having a lower gain, and it makes even worse when the frequency of the interest in the vicinity of flicker noise region. Using conventional topology such as folded cascode will result in the CMOS amplifier having high gain, but with the drawback of high power. Hence, there is a need for a new approach that improves the sensitivity of the CMOS sensor while achieving low power.

Environmental monitoring and controlling system for mushroom farm with online interface /Arjuna Marzuki, Soh Yan Ying

Mon, 09 Mar 2020 11:57:57 +0800

Agriculture sensors play an important role in modern agriculture. The use of sensors in various agriculture sectors minimizes the environmental impact on crops, helps in increasing yield and saving cost of operation. Among all agriculture industries in Malaysia, the mushroom industry is a comparatively new and small. As most of the mushroom farms in Malaysia are small-scaled, their production capability is limited by inadequate environmental control system and the lack offinancial resources to upgrade the systems. This paper presents an environmental monitoring and controlling system to monitor and control the environmental conditions in a mushroom farm. It enables user to monitor temperature, humidity, carbon dioxide concentration and light intensity in a mushroom farm on an android device by using ThingSpeak online platform. The control algorithm is able to control devices in a mushroom farm automatically based on feedbackfrom the sensors to maintain the environment in an optimum condition for mushroom growth. The measured percentage error of temperature, humidity, carbon dioxide and the light using the developed system was as low as 0.4%, 1.5%, 2.2% and 1.34% respectively

Application of shotcrete constitutive model to the time dependent behavior of tbm tunnel lining/Heyam H. Shaalan, Mohd Ashraf Mohamad Ismail, Romziah Azit

Mon, 09 Mar 2020 11:38:50 +0800

Shotcrete is ordinary concrete applied to the surface under high pressure. It demonstrates a highly time-dependent behaviour after few hours of application. Traditional approaches assume a simple linear elastic behaviour using a hypothetical young modulus to investigate the time-dependency and creep effects. In this paper, a new constitutive model of shotcrete is applied to evaluate the time-dependent behaviour of a TBM tunnel lining and investigate the parameters that can influence this behaviour. The Shotcrete model is based on the framework of Elasto-plasticity and designed to model shotcrete linings more realistically. The basic data of Pahang-Selangor Raw Water Transfer Project is used for the analysis study. An attempt is made to investigate the influence of some input parameters of the shotcrete model on the time-dependent behaviour ofthe shotcrete lining. These parameters include the time-dependent stiffness/strength parameters, creep and shrinkage parameters and steel fibre parameters. The variation in shotcrete strength classes causes a noticeable influence on the development of shotcrete compressive strength with time, particularly during the first days of application. The creep and shrinkage strain cause a considerable reduction in the development of the shotcrete stress with time. The impact of steel fibre content is determined, and the result indicated that the development of plain shotcrete stresses with time is lower than that of the reinforced shotcrete. In addition, a comparison study is performed to analyse the tunnel lining behaviour using both shotcrete model and an elastic analysis. Significant differences in shotcrete lining stresses are achieved when using the elastic analysis while the shotcrete model results in a reasonable result that can be used for the design requirements.

Analysis of rock burst event in deep tbm excavation of pahang-selangor raw water transfer tunnel /Romziah Azit, Mohd Ashraf Mohamad Ismail

Mon, 09 Mar 2020 11:29:01 +0800

Tunneling under high overburden and high in-situ stress can pose a major threat to the tunnel construction due to the phenomenon of rock burst. Rock burst is a typical phenomenon caused by underground excavation due to stress release and rock explosion where the rock masses broken in large or small pieces. Thus, predicting the occurrence of this phenomenon and its mechanism is important especially in determining suitable tunnel support system. In this study, the event of rock burst phenomenon at the Pahang-Selangor Raw Water Transfer Tunnel which is evaluated between the Chainage of 13 to 27 km beneath the Titiwangsa Main Range. This is the most critical section because of the high overburden up to 1200 m and presence several fault zones. Stress-strength method was used to analyze the tunnel behavior under high overburden stress based on strength factor and tangential stress. Analyzed results show that section with high overburden have high possibility of rock burst. Furthermore, it allows a reasonable prediction of the tunnel behaviors under different rock conditions, support systems and overburden stress which serves as a tool in the observational design and construction method for the deep tunnel excavation.

Time-dependency behavior of steel fiber reinforced shotcrete lining under rock overstressing using shotcrete model / Heyam Shaalan

Mon, 09 Mar 2020 10:51:34 +0800

A numerical analysis is implemented to estimate the time-dependent behavior of the steel fiber reinforced shotcrete lining (SFRS) using the constitutive model of shotcrete. Based on the concept of elasto—plastic strain hardening/softening plasticity, a new model of shotcrete is formulated, in which the time dependent strength, stiffness, creep and shrinkage could be determined. In this study, the steel fiber reinforced shotcrete lining behavior of the critical section of Pahang-SeIangor Raw Water Transfer Tunnel, which is under high overburden, is presented. For the finite element analysis, the high overburden above the tunnel is simulated using the field stresses, and the rock mass surrounding the tunnel is considered as a homogeneous medium. The investigation of the time-dependent behavior is carried out though the development of the steel fiber reinforced shotcrete lining properties, such as the elastic stiffness, compressive strength, and the major stresses with time. For the purposes of the current study, the results reveal the ability the shotcrete model to predict the behavior of the steel fiber reinforced shotcrete lining. In addition, the results indicate the efficiency of the shotcrete lining to resist the disturbances and transfer the loads shortly after application.

Rock overstressing in deep tunnel excavation of pahang-selangor/Romziah Azit, Mohd Ashraf Mohamad lsmail, Sharifah Farah Fariza Syed Zainal

Mon, 09 Mar 2020 10:43:29 +0800

Tunneling under high overburden and in-situ stress may cause tunnel instability because of rock overstressing. Evaluating overstressing in deep hard rocks is crucial to minimize excavation risks. The excavation of the Pahang-Selangor Raw Water Transfer Tunnel is evaluated in this study. A potential overstressing problem is expected at a tunnel depth more than 500 m. Therefore, the possibility of rock overstressing is assessed based on the evaluations of in-situ stress measurement, rock strength, and actual observations during the tunnel excavation. An analytical method is used to analyze the behavior of the tunnel under high overburden stress based on rock strength and tangential stress factors. The empirical assessment approach to the observation of actual overstressing appeared to be valid for the prediction of overstressing. These approaches facilitate the reasonable prediction of tunnel behavior under different rock conditions, support systems, and overburden stresses, which serve as useful tools in the observational design and constftlction method of long and deep tunnels.

Numerical analysis of TBM tunnel lining behavior using shotcrete constitutive model /Prof Madya Dr. Mohd Ashraf Mohd Ismail

Mon, 09 Mar 2020 10:34:13 +0800

Shotcrete is a ftlndamental support element for tunnels and underground constructions. Shortly after application, shotcrete linings undergo a high load while the ordinary concrete is not fully hardened yet. Therefore, the time-dependent behaviour of the shotcrete material must consider. Traditional approaches assume a linear elastic behaviour using a hypothetical young modulus to model this time-dependency and creep effects. In this paper, a new constitutive model of shotcrete is applied to evaluate the time-dependent behaviour ofTBM tunnel lining under high in-situ stress state. The Shotcrete model is based on the framework of Elasto-plasticity and designed to account for non-linear and time-dependent behaviour for concrete material more realistically. A parametric study of the time-dependent behaviour of the shotcrete lining, using the shotcrete model, is performed. To achieve this, the influence of the lining thickness, tunnel diameter and tunnel depth on the development ofthe stresses and displacement ofthe shotcrete lining with time is investigated. The results showed that the development of the lining tensile stress with time at tunnel crown increases by increasing the lining thickness and tunnel depth, whereas it decreases by increasing of the tunnel diameter. At the tunnel sidewall, the lining compression stress with time increases with the increase of the tunnel depth and diameter, while higher lining thickness decreases the lining compressive stresses. However, the œsults showed the ability of the shotcrete model to simulate the structural behaviour of the shotcrete lining with time.

Modeling stress-induced failure for deep tunnel excavation of pahang-selangor raw water transfer project / Romziah Azita, Mohd Ashraf Mohamad Ismail

Mon, 09 Mar 2020 10:22:52 +0800

The stress-induced failure, such as spalling and rock burst are considered as engineering disasters in deep underground excavations in hard rock. A practical predictive technique or a model to evaluate these stress-induced failures and a spalling strength is a concern in the design of support systems and excavations in underground tunnels. In the present study, tunnel excavations subjected to rock spalling failure is investigated in Pahang-Selangor Raw Water Project and the numerical model is conducted. The rock mass properties and spalling depth were recorded and compared with predictions from numerical modeling. The numerical modeling using the finite element analysis program Phase2 provides a visual representation of the stress and deformation situations and their respective locations in the tunnel. The predicted depth of spalling failure in the model was in good agreement with the observed failures. The model provided a reasonable spalling prediction of the maximum depth of failure in a deep hard rock tunnel.

Finite Element Analysis of Tunnelling Induced Deformation Towards/Mohd Ashraf Mohammad Ismail, Lim Siao Phin, Tay Wui Wenn

Mon, 09 Mar 2020 10:06:04 +0800

The demand of surface area increases rapidly in the urban areas due to the increase in populations. This leads to the shortage of surface area for development in the future. Underground development is one of the solutions to solve the problems, such as the tunnel constructed underground, to provide new spaces for the development without claiming valuable spaces on the surface. Since construction of tunnel might influence the integrity of above ground structures, it is important to evaluate the impact of tunneling towards adjacent building foundation. This paper presents the numerical analysis of pile-tunnel interaction under greenfield condition for the optimization of tunnel distance, position and size relative to pile. Parametric study concerning the pile-tunnel interaction was concluded to assess the differential stress around the tunnel, ground settlement bending moment and axial force acting on pile. Pile-tunnel interaction was found directly proportional to the tunnel diameter and inversely proportional to pile-tunnel distance. The maximum surface settlement was observed at the tunnel with diameter of 1.5 times diameter (d). The highest pile bending moment and axial forces was observed at pile-tunnel distance equal to Id.

Evaluation of spalling fallout on excavation disturbed zone under deep hard rock tunnel / Romziah Azit

Thu, 05 Mar 2020 16:34:49 +0800

The prediction of compressive stress-induced failures is of concern when designing and constructing facilities in rock for deep underground excavation. The purpose of this study is to model compressive stress-induced failure and fallouts with appropriate material models and strength parameters for deep hard rock tunnel excavation. Three method of numerical modelling are used, which are Generalised Hoek-Brown; Mohr-Coulomb; and Mohr-Coulomb with Cohesion Softening Friction Hardening (CSFH) material models for capturing the observed rock behaviour. A parametric study was also carried out to verify that the peak friction angle of 100 used in CSFH model. The results show that numerical models used only Generalised Hoek-Brown and Mohr Coulomb strength parameters does not show a good agreement with the observed fallout. The comparison revealed that the numerical models using the Mohr-Coulomb with CSFH provides most realistic to the observation fallout length. This model is valid for prediction of failure and fallouts in hard rock masses with high quality (GSI >65 MPa; intact rock compressive strength >70MPa).

Evaluation of rock overstressing in the excavation of pahang-selangor raw water transfer tunnel project/Mohd Ashraf Mohamad Ismail , Romziah Azita, Norzani Mahmood

Thu, 05 Mar 2020 16:23:51 +0800

Tunneling under high overburden and high in-situ stress may lead to tunnel instability due to rock overstressing in its surrounding. Overstressing of the hard rock tunnel can cause brittle fractures in the form of rock burst or spalling, which may cause safety hazards, damage of equipment and production disturbances. Therefore, the evaluation of overstressing in deep hard rock is crucial prior to tunnel construction to minimize risks during excavation. In this study, the potential of overstressing at the Pahang-Selangor Raw Water Transfer tunnel was evaluated between Chainage of 6.8 to 41.5 beneath the Titiwangsa Main Range, with high overburden of up to 1200 m. In addition, field observations were compared with predictions from empirical and analytical methods. The empirical assessment approach to the observation of actual overstressing appeared to be valid for the prediction of overstressing. The analytical method was used to analyze the tunnel's behavior under high overburden stress based on factors of strength and tangential stress. Analyzed results have shown that certain tunnel sections with high overburden have the possibility of moderate spalling. These approaches allow reasonable predictions of tunnel behavior under different rock conditions, support systems and overburden stress which serves as a useful tool in the observational design and construction method for long and deep tunnels.

Brittle failure simulation of Pahang Selangor raw water transfer tunnel under rock overstressing/Heyam H. Shaalan, Mohd Ashraf Mohamad Ismail, Romziah Azit

Thu, 05 Mar 2020 16:00:23 +0800

Modelling a rock brittle failure around underground openings is used to simulate or contemplate the shape, depth and extent of the failure zone and achieved a suitable ground support system, consequently the underground construction safety increases and the construction cost decreases. This study analyses the critical section of the Pahang Selangor Raw Water Transfer Tunnel under high overburden using the 21) elasto-plastic finite elements stress analysis software. Site observations showed that the high overburden stresses created a failure zone on the tunnel sides, which damaged the steel fiber reinforced shotcrete lining. The observed failure depth is approximately 0.3 m. A numerical analysis is performed to predict the extent, shape and depth of the actual failure. Various approaches are adopted in the numerical modelling, which include the elastic analysis model, elastic-perfectly-plastic model and elastic-brittle-plastic model with (m = 0 and Sr — 0.11) and instantaneous cohesion-softening friction-hardening (CSFH) model. A parametric study on the CSFH model strength parameters is also implemented to describe the influence of the strength parameters on the extent, shape and depth of the failure, as well as investigate which parameters can simulate the actual failure depth. Results are compared with the observed failure to decide which approach can predict the actual failure. The (CSFH) model results predict the observed failure depth and shape correctly.

The effect of space holder content and sintering temperature of magnesium foam on microstructural and properties prepared by sintering dissolution process (sdp) using carbamide space holder/S.F. Aida , H. Zuhailawati , A.S. Anasyida

Thu, 05 Mar 2020 15:07:56 +0800

Magnesium foam has gained a significant interest in structural application due to low density and greater strength than aluminium foam. In this study, magnesium foam was produced by sintering dissolution process (SDP) using spherical carbamide as the space holder. Magnesium foam was prepared using SDP at sintering temperatures (600 'C, 630 0 C, 650 • C) and carbamide composition (30 wt.%, 50 wt.%, and 70 wt.%). The foams produced were characterized for morphology, density, porosity and compressive strength. Porosity of the magnesium foam increased with increasing amount of spacc holder at all the sintcring temperatures while the density showed thc rcverscd trend. Magncsium foam with 50 wt.% carbamidc at all the sintering temperatures showed the acceptable range of density and porosity for energy absorbent which are in the range of 0.57-0.61 g/cm3 and 64.7-67.3%. Magnesium foam with 50 wt.% carbamide at sintering temperature of 630 0 C has density, porosity and compressive strength of 0.61 g/cm3, 64.7% and 5 MPa.

The effect of space holder content and decomposition methods in fabrication of aluminum foams by powder metallurgy method using carbamide space holder/A. H. Amirah, M. S. Nurulakmal, And A. S. Anasyida

Thu, 05 Mar 2020 14:56:17 +0800

The effect of space holder amount and decomposition methods on the morphology, density and porosity and compressive properties of aluminum foams were investigated. Aluminum foam was fabricated by powder metallurgy method using spherical carbamide as space holder using three different decomposition method of carbamide includes; dissolution process, normal sintering process and two step sintering process. Aluminum foam with 60 wt.% carbamide has the lowest density and exhibited the highest porosity for all the decomposition. The results indicated that Al foams produced by dissolution method have the highest compressive properties with acceptable density and porosity value.

Semisolid nucleation mechanism of open cell foam aluminium/Dr. Anasyida Abu Seman @ Hj Ahmad, Dr. Nurulakmal Mohd Sharif , Prof. Ir. Dr. Zuhailawati Hussain

Thu, 05 Mar 2020 14:41:24 +0800

Gravity die casting and squeeze casting are the techniques used for the fabrication of hypoeutectic open-cell Al-Si foams which are characterized and studied for their energy absorbing quality in compression tests. The effect of different amounts of sodium chloride (NaCl) (up to 56 vol.%) as a space holder in the casting of aluminum foam on the morphology, density, porosity, compressive and energy absorption properties of aluminum foam was studied. The hypoeutectic Al-Si alloy with NaCl particles as a space holder was used to fabricate the aluminum foam using gravity die casting and squeeze casting. The hypoeutectic open-cell Al-Si foams produced by squeeze casting showed smaller pore size, better pore distribution, higher porosity, good compressive strength and greater energy absorption energy compared to that of gravity die casting. The hypoeutectic open-cell Al-Si foams with 44 vol.% NaCl using squeeze casting showed the best properties among all foams due to its moderate and well-distributed porosity.

Evaluation of tunnel seismic prediction (tsp) result using the japanese highway rock mass classification system for pahang-selangor raw water transfer tunnel_W. C. Von , M. A. M. Ismail

Thu, 05 Mar 2020 14:29:17 +0800

The knowing of geological profile ahead of tunnel face is significant to minimize the risk in tunnel excavation work and cost control in preventative measure. Due to mountainous area, site investigation with vertical boring is not recommended to obtain the geological profile for Pahang-Selangor Raw Water Transfer project. Hence, tunnel seismic prediction (TSP) method is adopted to predict the geological profile ahead of tunnel face. In order to evaluate the TSP results, IBM SPSS Statistic 22 is used to run artificial neural network (ANN) analysis to back calculate the predicted Rock Grade Points (JH) from actual Rock Grade Points (JH) using Vp, Vs and VpNs from TSP. The results show good correlation between predicted Rock Grade points and actual Rock Grade Points (JH). In other words, TSP can provide geological profile prediction ahead of tunnel face significantly while allowing continuously TBM excavation works. Identifying weak zones or faults ahead of tunnel face is crucial for preventative measures to be carried out in advance for a safer tunnel excavation works.

Fabrication and characterization of hypoeutectic open-cell al-si foams using gravity die casting and squeeze casting /Samsudin Fitri Aida, Mirsad Nur Hijrah, Amirah Ahmad Hamdi, Hussain Zuhailawati, Abu Seman Anasyida

Wed, 04 Mar 2020 16:56:40 +0800

Gravity die casting and squeeze casting are the techniques used for the fabrication of hypoeutectic open-cell Al-Si foams which are characterized and studied for their energy absorbing quality in compression tests. The effect of different amounts of sodium chloride (NaCl) (up to 56 vol.%) as a space holder in the casting of aluminum foam on the morphology, density, porosity, compressive and energy absorption properties of aluminum foam was studied. The hypoeutectic Al-Si alloy with NaCl particles as a space holder was used to fabricate the aluminum foam using gravity die casting and squeeze casting. The hypoeutectic open-cell Al-Si foams produced by squeeze casting showed smaller pore size, better pore distribution, higher porosity, good compressive strength and greater energy absorption enerw compared to that of gravity die casting. The hypoeutectic open-cell Al-Si foams with 44 vol.% NaCl using squeeze casting showed the best properties among all foams due to its moderate and well-distributed porosity.

Effect ofnacl as a space holder in producing open cell A356 aluminium foam by gravity die casting process/ S.F. Aida , M.N. Hijrah, A.H.Amirah, H. Zuhailawati , A.S. Anasyida

Wed, 04 Mar 2020 16:48:28 +0800

Gravity die casting is the technique which enables fabrication of open-cell A356 aluminium foam as a suitable absorber material with good quality performance. A356 aluminium alloy was used with varies amount of sodium chloride (NaCI) particles as a space holder to fabricate the aluminium foam using gravity die casting. Microstructural analysis, porosity and density were investigated in this study. As the addition of the NaCl space holder increases, porosity increases leading to decreasing density of the foam. Aluminium foam with 30 wt.% NaCI showed moderate porosity among the others foam.

Analysis of rock burst behaviour under overstressed rock in deep tunnel excavation across the titiwangsa range, Malaysiatle of research/Prof. Madya Dr Mohd Ashaf Bin Mohamad, Prof. Madya Dr. Fadzli Mohamaed Nazri

Wed, 04 Mar 2020 16:34:48 +0800

In this study a critical section of the Pahang—Selangor raw water transfer tunnel under high overburden stress creates a zone of rock failure along the sides of the tunnel. This zone damages the steel fiber-reinforced shotcrete lining, and the observed failure depth in this zone is approximately 0.3 m. Elastic analysis model, elastic-perfectly plastic and elastic-brittle plastic models (D = O and m = 0.11) and instantaneous cohesion-softening friction-hardening (CSFH) model with parametric study are implemented to describe the influence of strength parameters on the extent, shape and depth of failure and investigate which parameters can simulate actual failure depth. As a result, the CSFH model results show good agreement with the observed depth and shape of the failure.

A single-stage led driver with voltage doubler rectifier/Nurul Asikin, Zawawi , Shahid Iqball, Mohamad Kamarol, Mohd Jamil

Wed, 04 Mar 2020 16:18:12 +0800

In this paper, a configuration of a single-stage AC-DC converter and a high voltage resonant controller IC 1.6598 for LED street light driver is discussed. The converter is obtained by integrating two boost circuits and a half-bridge LLC resonant circuit. A voltage double rectifier circuit is adopted as output to lower the voltage stress on transformer and the associated core. The two boost circuits work in boundary conduction mode (BCM) to achieve the power factor correction (PFC). The converter works in soft-switching mode allowing the power switches to operate in zero-voltage-switching (ZVS) and the output diodes to operate in zero-current-switching (ZCS). This reduces the switching losses and enhances the efficiency. The converter features lower voltage stress on the power switches and the bus voltage is reduced to slightly higher than the peak input voltage. Therefore, the converter can perform well under high-input-voltage. Here, the DC bus and the output filter capacitances are greatly reduced. So, electrolytic capacitor-less converter can be realized for a long lifetime LED driver. Simulation results from PSpice are presented for a 100-W prototype.

Effect of nozzle rotation angles and sizes on thermal characteristic of swirl anti-icing t /Mohd Azmi Ismail , Jian Wang

Tue, 03 Mar 2020 10:28:26 +0800

The Federal Aviation Administration requires all ai rcraft manufacturers to ad here to maximum noise level standards. Thus, a bias acoustic l i ner is introduced. to intensi fy the noise eq u ipment system. as well as preven t ice accumulation on the nacelle 0-chamber. The hotspot phenomenon. by the Piccolo tu be anti-i<.:ing sysh:m. cou ld damage t he bias acoustic liner. Therefore. a swi rl ant i-icing system is fu rther i n vestigated, to reduce t he hotspot t:ffcct on the bi as acoustic l iner. The pr

Mechanics of mineral and oxides based 3D cordierite tempalte_Prof Madya Dr. Hasmaliza Mohamed

Wed, 26 Feb 2020 17:09:15 +0800

In this study, cordierite was prepared by glass-route method using Si02, A1203 and MgO as raw materials. Cordierite powder produced was then used to fabricate 3-D porous cordierite using gel casting method using different amount of GRF (2.5, 4.0 and 6.0g) and dried egg white (DEW) (1.5, 2.5 and 4.0g) as binder to observed their effect on the strength of 3-D porous cordierite produced. Results show that the decreasing of solid loading shows decreasing of density, increasing of porosity and decreasing of strength of 3-d porous cordierite. While, decreasing of dispersant amount shows decreasing of density, increasing of porosity and decreasing of strength. The optimum properties of 3-D porous cordierite obtained with the addition of 4.0 g starch (GRF) , having 0.5 g/cm3 density, 74 % porosity, 9.13 MPa compressive strength and 4.07 MPa MOR. Generally, results obtained shows that 3-D porous cordierite produced from this study was possible to become alternative materials for filter application.

Effect of freezing temperature on the pore formation of beta /Dr. Nurazreena Ahmad

Wed, 26 Feb 2020 15:54:48 +0800

. Beta-tricalcium phosphate (P-TCP) has been widely used for biomedical application due to its excellent mechanical strength, good tissue compatibility and outstanding chemical stability. There are several methods to fabricate porous scaffolds including solvent casting, phase separation, rapid prototyping and electrospinning methods. In the present study, P-TCP scaffolds were fabricated using freeze drying method. P-TCP slurry was frozen and freeze dried for 24 hours followed by sintering process to form P-TCP scaffolds. The porous P-TCP scaffold were fabricated at different percentages of ß-TCP powder used (10 wt. 0/0, 20 wt. % and 30 wt. 0/0) and froze at different freezing temperature (- I OOC, -200C, -400C and -800C) in order to study the effect of these parameters on the pore formation of the scaffolds. Scanning electron microscopy (SEM) analysis for 30 wt. % ß-TCP scaffold frozen at -IOOC revealed acceptable pore size distribution with majority pore size within the range of 102.65 pm to 372.90 pm. Furthermore, this scaffold also possessed highest compressive strength of 0.31 MPa.

Effect of calophyllum inophyllum biodiesel-diesel blends on combustion, performance, exhaust particulate matter and gaseous emissions in a multi-cylinder diesel engine /H.G.How , H.H. Masjuki

Wed, 26 Feb 2020 11:14:00 +0800

In this work, the effects of adding of inedible Calophyllum Inophyllum biodiesel to diesel fuel on performance, gaseous emissions, particulate matter (PM) and combustion characteristics were studied in a medium-duty, highpressure common-rail turbocharged four-cylinder diesel engine under different speed and torque conditions. The key physicochemical properties of neat biodiesel, biodiesel-diesel blends and diesel were characterized and analysed. The test fuels used were a fossil diesel fuel, BIO, B20, 1330, and B50 Of biodiesel-diesel fuels. The results indicated that all blends of biodiesel fuels have physicochemical properties relatively close to those of petroleum diesel. The experimental results also demonstrated that there are some drawbacks in engine brake power, brake specific fuel consumption (BSFC), and nitrogen oxide (NOX) with the blend of biodiesel in the fuel. Besides, refinement in brake thermal efficiency (BTE) and exhaust emissions were recorded across all engine speeds. Moreover, the emission improvement was characterized by lower carbon monoxide (CO) and reduced in both of the smoke and PM emissions. Also, reduction in the magnitude of peak combustion pressure and heat release rate (HRR) were also found with biodiesel blends. Overall, the results indicated that Calophyllum Inophyllum biodiesel can be used satisfactorily in an unmodified multi-cylinder high-pressure common-rail diesel engine.

Developments of entropy-stable residual distribution methods for conservation laws 1 scalar problems /Farzad Ismail , Hossain Chizari

Wed, 26 Feb 2020 10:52:29 +0800

This paper presents preliminary developments of entropy-stable residual distribution methods for scalar problems. Controlling entropy generation is achieved by formulating a entropy conserved signals distribution coupled with an entropy-stable signals distribution.Numerical results of the entropy-stable residual distribution methods are accurate and comparable with the classic residual distribution methods for steady-state problems. High order accurate extensions for the new method on steady-state problems are also demonstrated. Moreover, the new method preserves second order accuracy on unsteady problems using an explicit time integration scheme. The idea of the multi-dimensional entropy-stable residual distribution method is generic enough to be extended to the system of hyperbolic equations, which will be presented in the sequel of this paper.

Advanced workshop on hyperbolic conservation laws _Prof. Ismail Farzad

Wed, 26 Feb 2020 10:41:47 +0800

Allylic and epoxy monomers as reactive plasticizers in polyetherimide /Dr. Arjulizan Rusli

Wed, 26 Feb 2020 10:32:16 +0800

Addition of allylic and epoxy monomers as reactive plasticizers in polyetherimide(PEl) was investigated to improve processibility without reduction of thermo-mechanical properties of the PEI. Blends of various concentrations of PEI and monomers with different initiators/curatives were prepared by solvent and melt blending methods. Miscibility study indicated that unpolymerized blends of PEI with either allylic or epoxy monomers were miscible with PEI at more (than 40%PEl but partially immiscible at low PEI content. Curing characterization showed that peroxides and aromatic amine capable of initiating cure at high temperatures thus considered as suitable initiator/curative. Thermal properties study indicated that all compositions phase separated when polymerized but retaining thermomechanical properties of the PEI with only slight reduction of glass transition temperature.

A grid-insensitive lda method on triangular grids solving the system of euler equations/Hossain Chizari, Farzad Ismail

Wed, 26 Feb 2020 10:16:40 +0800

The performance of the classic upwind-type residual distribution (RD) methods on skewed triangular grids are rigorously investigated in this paper. Based on an improved signals distribution, an improved second order RD method based on the LDA approach is proposed to faithfully replicate the flow physics on skewed triangular grids. It will be mathematically and numerically shown that the improved LDA method is found to have minimal accuracy variations when grids are skewed compared to classic RD and cell vertex finite volume methods on scalar equations and system of Euler equations.

A study on the effects of three-dimensional crack tip constraint in mixed modes problem numerical and experimental analysis / lr. Dr. Feizal Yusof, Prof. Madya Prof.Choong Kok Keong

Thu, 09 Jan 2020 16:37:07 +0800

Asymptotic crack tip fields of surface cracked panels under non-hardening bending loads / Rizman Hariz, Abdul Latiff , Feizal Yusof

Mon, 30 Dec 2019 12:21:38 +0800

In this paper, the investigation of in-plane constraint loss in a semi-elliptical surface cracked panei(SCP) specimen based on a detailed non-hardening finite element analysis with aspect ratios ale ofO.S and relative depths aft of 0.33 and 0.5 under bending loads. The asymptotic stress field solutions were compared to the fully constrained Prandtl field for the plane-strain case and Sham & Hancock crack tip plane-stress fields. The asymptotic solutions of the semi elliptical shallow and the deep cracked bars were found to be contained within a Prandtl crack tip field at the centre of the specimen. Loss of constraint was observed at the free surface ofthe semi-elliptical surface cr ck.

Analysis of pedestrian walking characteristics at vertical facilities in underground train station / Nur Sabahiah Abdul Sukor

Mon, 30 Dec 2019 12:14:42 +0800

Analysis of pedestrian speed flow relationship based on different egress facilities criteria for pedestrian evacuation / Nur Sabahiah Abdul Sukor

Mon, 30 Dec 2019 12:05:36 +0800

The increment of the population in Kuala Lumpur had caused the LRT stations become crowded with excessive demand during the peak hours. This also includes the underground LRT stations especially near the KLCC area. Unfortunately, limited study was done regarding the pedestrian and train passengers at underground spaces in Malaysia. Due to this problem, the facilities provided will not be enough and suitable for the increment of the pedestrian volume in the future. Thus, more studies focusing pedestrian evacuation in underground spaces is required. This project aims to establish the fundamental diagram of pedestrian speed-flow-density relationship at vertical spaces in underground train station for understanding the appropriate emergency response plan (ERP) that suitable for the case of KLCC train station.

An improved method to model semi-elliptical surface cracks using element mismatch in abaqus / R. H. A. Latiff , F. Yusof

Mon, 30 Dec 2019 11:51:58 +0800

Synergistic response of pogostemon cablin (blanco) benth cell suspension cultures to precursor feeding and elicitation / Dr.Derek Chan Juinn Chieh, Fatin Izzatie Mazlan

Mon, 30 Dec 2019 11:28:50 +0800

This research investigates the synergistic effect of precursor feeding and elicitation towards the production of patchouli alcohol (PA) from Pogostemon cab/in callus and cell suspensron cultures rn shake flask systems. Initial study on feeding cis-farnesol as the precursor to activate PA production revelead tho prt sence of 68 mg/ml of PAin the culture system. Screening of abiotic and biotic elicitors was carried out to find the best elicitor that is able to enhance PA production. Out of four different elicitors from both categories, around 984 mg/L ot PA was produced when elicited with methyl jasmonate, MeJA (50 JlM concentration) after 3 days of eliartation, <;hewing that MeJA could stimulate metabolic pathway leading to PA production. Elicitation using yeast extroct has also shown some production of PA at varying concentrations, but the addition of chitosan and Pycnoporus sangumeu, extract did not improve PA production. It was found that the combination of cis-farnesol feeding and MeJA elicitatron drd not further increase PA production, indicating that only the individually elicited cell suspension cultures of P. coblm is c:lpable in improving the PA yield.

Melamine-nitrogenated mesoporous activated carbon derived from rice husk for carbon dioxide adsorption in fixed-bed / A.L. Yaumi, M.Z. Abu Bakar

Mon, 30 Dec 2019 11:07:34 +0800

This work presents the preparation of melamine-nitrogenated mesoporous activated carbon from rice husk via single step chemical activation with phosphoric acid and subsequent modifica tion with mel amine for efficient carbon dioxide adsorption. The nitrogen-containing carbons were characterized for their textural and chemical properties and thereafter tested for carbon dioxide adsorption in fixed-bed adsorption system. Characterization of the prepared adsorbent reveals better textural properties with high basicity, porosity and nitrogen functionalities indicating that nitrogen was successfully incorporated on to the surface of activated carbons. The nitrogen-containing activated carbon exhibited a maximum carbon dioxide capacity of 5.43 mmol{g at 30 •c attributing to well-developed porous structure and high surface basicity. The nitrogen functionalities in addition to textural properties, surface chemistry and nitrogen content played vital roles towards enhanced adsorption capacity of the prepared adsorbent The isotherm and kinetic studies showed that Freundlich isotherm and Avrami model best fit the experi mental data thus, indicating the heterogeneity of the adsorbent su rface. The C02 molecules were completely released during the regeneration process and thus showed good regeneration performance with stable carbon dioxide adsorption capacity after twelve cycles

Chitosan-bleaching earth clay composite as an efficient adsorbent for carbon dioxide adsorption Process optimization_M. Azharul Islam, Y. L. Tan

Mon, 30 Dec 2019 10:58:38 +0800

In this study, chitosan-bleaching earth clay composite (Chi-BE) was prepared in three different ratios (1:0.4, 1:0.6 and 1:0.8) by the alkali gelation method for carbon dioxide (COv adsorption in a fixed-bed adsorption system. Chi-BE (1:0.6) with best adsorption capacity was selected through fractional factorial design and characterised through Brunauer-Emmett-Teller, scanning electron microscope a nd Fourier transform infrared analyses. The C02 adsorption study was carried out via a central composite design and optimised it using de Optimisation sirability function. Results showed significantly positive roles of temperature, adsorbent loading and C02 concentration on C02 adsorption by Chi-BE within the range and individual levels. However, only adsorbent load ing and C02 concentration presented a mutual effect on C02 adsorption. The optimised factor levels of 38.13 'C for temperature, 0.72 g for adsorbent loadi ng and 25% C02 concentration were obtai ned, which resuited in the C02 adsorption capacity of 344.98 mg/g. The regeneration study revealed that the spent Chi-BE was recycled 10 times. This study suggests that Chi-BE is an effective and stable C0 2 adsorbent under moderate environment.