Access control system is an important component to protect patients’ information from abuse in a health care system. It is a major concern in the management, design, and development of healthcare systems. Designing access control policies for healthcare systems is complicated due to the dynamic and inherent complexity of the tasks performed by the healthcare personnel. Permissions in access control systems are usually granted on the basis of static policies. However, static policies are not enough to cope with various situations such as emergencies. Most often, the Break-the-glass mechanism is used to bypass static policies to handle emergency situations. Since healthcare systems are critical systems, where errors can be very costly in terms of lives, quality of life, and/or dollars, it is crucial to identify discrepancies between policy specifications and their intended function to implement correctly a flexible access control system. Formal verifications are necessary for exhaustive verification and validation of policy specifications to ensure that the policy specifications truly encapsulate the desires of the policy authors. We present a verifiable framework to enact a dynamic access control model by integrating the ANSI/INCTIS RBAC Reference Model in a workflow and an approach for property verifications of the access control model. Access control policies are expressed by the formal semantics of a model checker and properties are verified by the DiVinE model checker.

Keywords: Model Checking; Formal Verifications; Access Control.

Typhoid fever (TyF), caused by salmonella typhoid bacteria, represents one of the main public health challenge in various parts of the world. It is often treatable when diagnosed early, but if left untreated could lead to other medical complications. This study proposed an artificial intelligence means (arim) for diagnosis of TyF. The objectives are to find out the leading risk factors for TyF, develop fuzzy logic base-expert system, called Typhoid Responsive Expert System (TyRes), that can predict the ailment from symptoms and use TyRes to predict TyF in patients. Two sets of questionnaires were used for data collection. 325 copies were administered to the patients in 25 hospitals in Lagos, Abeokuta and Ifo, South-west Nigeria. Another set of 200 copies were administered to human medical experts (hme), 70 doctors and 140 qualified nurses, to capture hme knowledge about TyF and its symptoms. The data was analysed using Chi-Square to identify the main symptoms spotted by most of the hme. TyRes was implemented in Matlab 2015a using the main factors as input variables. Vomiting, high-temperature, weakness, abdominal-pains and loss-of-appetite were the input variables used to develop TyRes. When tested to predict TyF in 25 patients, 76% accuracy was derived when comparing hme predictions with TyRes results. It can be concluded that TyRes can mimic hme by 76% of all TyF predictions. The arim is considered reliable and can be used at home, school and health centres where hme are scarce.

Keywords: Typhoid fever; expert system; symptoms; patients

Recently, computer-aided design and computer aided manufacturing (CAD/CAM) is largely applied in universal machinery due to the accelerated development of computer technologies. Owing to the technical application of CAD/CAM tool in the manufacturing industry, enterprises have progressively changed their traditional approaches to design and manufacture of products. The CAD module provides product designers with capabilities of designing product model by feature-based design and obtaining product data. The product model is displayed on a screen in the CAD environment before transferring it downstream to the CAM module. This paper presents the application of CAD/CAM in solid modelling, design of machining process, fixture design and virtual manufacture of a flanged tube. Pro/Engineer (Pro/E) Wildfire 4.0 was used to create the three dimensional (3D) model of the flange tube based on its two-dimensional drawing (2D) blank drawing and the mould was designed and created using the same software. The mould creation was based on the clamping and positioning devices of the flange tube being manufactured. The technical schedule of the flange tube was worked out including the choice of machining method, machine tool, cutting tool and selection and computation of machining parameters based on finished drawing the flange tube. Two dedicated fixtures for holding the flange tube in the machine tool were designed and finally Master CAM 9.0 software was applied to the virtual machining of the mould. It is concluded that CAD/CAM tool is important in manufacturing technology as it automates the manufacturing process thereby saving time, energy, cost, and making production highly flexible.

Keywords: CAD/CAM; Machining process; Pro/Engineer; Fixture; Tooling devices

In this study, flow stress behavior of AISI 4340 steel in thermomechanical process was investigated under temperature and strain rate ranges of 1173 to 1373 K and 0.01 to 1 s-1, respectively. In flow curves, mechanisms such as work hardening (WH), dynamic recovery (DRV) and dynamic recrystallization (DRX) occurred. It was also discovered that the flow stress decreases with the increase of deformation temperature and the decrease of strain rate. Flow stress curves declared that in low-strain rate and high temperature, dynamic recrystallization overcome work hardening. Also, decreasing temperature led to dynamic recovery and incomplete dynamic recrystallization. Work hardening rate-stress curves depicted that the presence of a turning point expresses dynamic recrystallization mechanism and sub-boundaries are formed at the beginning of where a turning point occurs. In partial dynamic recrystallization, the microstructure was consisted of long grains reshaped because of deformation and some recrystallized grains that nucleated around those reshaped long grains. The results also indicated that at temperature of 1373 K, stress value of σsf, for strain rate of 0.01 s-1 was increased from 27.8 MPa to 96.5 MPa and also for strain rate of 1 s-1 and stress of σc was increased from 32.3 MPa to 105 MPa. The significance of the approach used in this work was any increase in strain rate leads to accelerating dislocation movements. Therefore, dislocations will hit the barriers sooner and will be stopped and also, as a result of delayed dynamic recovery due to dislocations movements, dynamic recrystallization is also delayed.

Keywords: Flow stress; thermomechanical process; AISI 4340 steel, restoration mechanism, work hardening

Industry 4.0 (I4.0) presents a unique challenge of efficiently transforming traditional manufacturing to smart and autonomous systems.Integrating manufacturing systems, materials, machinery, operators, products and consumers, improve interconnectivity and traceability across the entire product life cycle in order to ensure the horizontal and vertical integration of networked Smart Manufacturing (SM) systems. Manufacturing functions of Material Handling (MH)-control, storage, protection and transport of raw materials, work in process (WIP) and finished products- throughout a manufacturing and distribution process will need a revamp in ways they are currently being carried in order to transition them into the SM era. Radio Frequency Identification (RFID), an Automated Identification Data Capture (AIDC) technology increasingly being used to enhance MH functions in the (SM) industry, due to opportunities it presents for item tracking, out of sight data capturing, navigation and space mapping abilities. The technology readiness level of RFID has presented many implementation challenges as progress is being made to fully integrate the technology into the preexisting MH functions. Recently, many researchers in academia and industry have described various methods of using RFID for improving and efficiently carrying out MH functions as a gradual transition is being made into I4.0 era. This paper reviews and categorize research finding regarding RFID application developments according to various MH functions in SM, tabulates how various I4.0 enablers are needed to transform various traditional manufacturing functions into SM. It aims to let more experts know the current research status of RFID technology and provide some guidance for future research.

Keywords: Industry 4.0; radio frequency identification; smart manufacturing; material handling

This paper proposes a Microwave Imaging System (MIS) for brain stroke detection. In the MIS, the primary challenge is to improve in terms of cost, size, and stroke image quality. Thus, the main contribution of this work is the economy and the compact rotation platform integrated with an array of nine antipodal Vivaldi antenna in circular arrangement and single computer board, Raspberry Pi Module (RPM) as microcontroller developed. The design and fabrication of wideband antenna based on Computer Simulation Technology (CST) software and Rogers RO4350B substrate, which operated from 2.06 GHz to 2.61 GHz. In the RPM, the Python programming language used for regulating the angle of rotation and antenna switching process. The process of receiving reflection signals from the head phantom for each antenna supervised by Single-Pole 8-Throw (SP8T) Radio Frequency (RF) switch. The fabricated head phantom based on the primary tissues of the brain, white matter using inexpensive materials, and located in the middle of the platform. Platform rotation is a combination of wood-based platform with the size 0.36m2 and material Perspex. Then, through an interfacing process between Python script and Vector Network Analyzer (VNA), the raw data in S-Parameters transferred to the MATLAB software for analysis. The fabricated antenna able to realize high directivity, 86.92% efficiency, and 2.45 dBi gain. Overall, the proposed system offers the cost-effective, compact, and able to collect the data effectively around the head phantom that consist of a target clot and without a target clot at 50 different positions. It successfully tracked the presence of stroke clots through color differences in color plots.

Keywords: Microwave Imaging System; brain stroke; antipodal vivaldi antenna; Raspberry Pi

Usage of graphite electrode in a microbial fuel cell (MFC) is favored due to their electron conductivity and stability as a base material for the electrode. Also, graphite is favored as it allows the growth of biofilm, which can enhance the cell’s performance. The efficiency is reported improved through modification. Aryl diazonium modification has been reported to induce biofilm formation on the electrode faster. The modification can be done spontaneously or through electrografting of aryl diazonium salt onto the electrode surface. Control over the quantity of grafted aryl diazonium is essential. A thick layer will cause the performance of the system to drop, which may impede the electron transfer from biofilm to the electrode. Aryl diazonium is preferred as it allows a robust biofilm formation when used as a surface modification on the graphite electrode. Modification using aryl diazonium allows the electrode to be more accommodative for biofilm growth, which will increase the performance of the system. However, it does not act as a redox mediator for the system. It has been reported that power density obtained using aryl diazonium modified electrode is 250 mW.m-2, higher than unmodified graphite electrode of 125 mW.m-2. However, not all bacterial species is compatible with aryl diazonium modification. The unmodified graphite biocathode allows a higher power density compared to aryl diazonium modified biocathode. Hence, depending on the quality of aryl diazonium modification and the types of inoculum used, MFC performance can be further maximized.

Keywords: Aryl diazonium; graphite electrode; microbial fuel cell; electrode modification

Cobalt oxide (CoO) has been widely studied for photocatalyst of water splitting and displaying a high-efficiency material. This paper reports a Density Functional Theory (DFT) study on the electronic properties of rock-salt CoO and analyzes effects of cations (Ni and Fe) and anions (N and F) dopants on the electronic properties. For this purpose, CASTEP software used for first principles plane-wave pseudo-potential calculations at different functional, i.e: GGA-PW91 and LDA. The electronic calculations of the CoO optimized structure showed a metallic structure if without considering spin-orbital interactions. After considering the spin-orbital interaction calculation, the CoO band structure possessed indirect and direct band gaps. The direct bandgap by GGA-PW91 calculation is 2.10 eV, it was agreed to the experimentally reported value of approximately 1.9-2.6 eV. Meanwhile, Ni, Fe, and F-doped CoO, demonstrating decreased CoO direct band gaps to 1.70 eV, 1.80 eV, and 1.73 eV, respectively. While N-doped CoO increased the CoO direct bandgap to 3.05 eV. All dopants shifted the conduction and valence bands position, where Ni-doped CoO band edges keep straddle to the redox potential of water splitting. Among other elements in this study, Ni is a more desirable dopant of CoO to enhance photoelectrochemical hydrogen production.

Keywords: Density Functional Theory; Cobalt oxide; photoelectrochemical; hydrogen production; bandgap

Suhu iklim yang semakin meningkat kini telah membawa perhatian untuk mengurangkan tenaga haba solar masuk ke dalam bangunan. Usaha mengurangkan kebergantungan kepada penyaman udara untuk penyejukan dalaman telah membawa kepada pelaksanaan strategi penyejukan pasif dalam bangunan. Makalah ini membentangkan penyiasatan pelaksanaan teknologi reflektif dalam bentuk sistem penebat reflektif dan sistem penghalang bersinar dalam bumbung “gable.” Prestasi terma sistem penebat reflektif dan sistem penghalang bersinar telah disiasat dengan menggunakan simulasi Computational Fluid Dynamics (CFD). Prestasi terma teknologi reflektif dibentangkan dari segi ketahanan haba, nilai RSI. Kajian ini dijalankan untuk beberapa konfigurasi bumbung di mana ketebalan ruang udara reflektif, sudut bumbung dan jenis bumbung diubah. Hasil yang diperoleh daripada simulasi CFD telah disahkan dengan data empirik untuk memastikan simulasi memberikan ramalan yang berketepatan yang tinggi. Analisis parametrik menunjukkan ruang udara reflektif yang lebih tebal akan memberikan pengudaraan udara yang lebih baik di kawasan ruang udara dan ini membawa kepada daya tahan haba yang lebih tinggi. Selain itu, sudut bumbung yang lebih curam akan meningkatkan kesan keapungan dan meningkatkan penyingkiran haba melalui rabung yang juga menghasilkan daya tahan haba yang lebih tinggi. Dari segi jenis bumbung, hanya perbezaan kecil diperhatikan dari segi kerintangan haba apabila menukar jenis bumbung antara jubin tanah liat dan jubin konkrit. Kajian ini berjaya menggunakan simulasi CFD dalam menyiasat teknologi penebat haba di bangunan dan kaedah ini harus diterokai lebih lanjut pada masa akan datang.

Kata kunci: Penebat reflektif; penghalang radiasi; CFD; penebat bumbung; penebatan haba

Abstract English

The ever-increasing temperature of current climate has brought the attention on reducing the incoming solar heat energy into buildings. The efforts on reducing the dependency on air-conditioning for indoor cooling has led to the implementation of passive cooling strategies in buildings. This paper investigates the implementation of reflective technologies in the form of reflective insulation and radiant barrier systems in a gable roof assembly. The thermal performance of reflective insulation and radiant barrier systems was investigated by using Computational Fluid Dynamics (CFD) simulation. The thermal performance of the reflective technologies was presented in terms of thermal resistivity, RSI value. The study was conducted for several roof configurations where the thickness of reflective air space, roof pitch and the roof material were varied. The results obtained from the CFD simulation was validated against empirical measurements to ensure the simulation gives high accuracy prediction. From the parametric analysis, it was found that thicker reflective air space would provide better air ventilation in the air space area which led to higher thermal resistivity. Besides that, steeper roof pitch would enhance the buoyancy effect and increases the heat exhaustion through the ridge which also results in higher thermal resistivity. In terms of roof tiles material, only small difference was observed in terms of thermal resistivity when switching the roof tiles material between clay tiles and concrete tiles. This research was able to demonstrate the use of CFD simulation in investigating thermal insulation technologies in buildings and this method should be explored further in the future.

Keywords: Reflective insulation; radiant barrier; CFD; roof insulation; thermal resistance

Sistem suntikan menjadi nadi utama di dalam proses Pengacuan Suntikan, di mana ia merangkumi pelbagai faktor yang perlu dikawal dan diselaraskan. Sistem kawalan ini merangkumi parameter yang dikategorikan sebagai empat parameter utama: tekanan, suhu, masa, dan jarak. Tekanan Suntikan adalah tekanan yang diperlukan untuk menggerakan bahan leburan polimer ke dalam acuan. Tekanan Pegangan adalah fasa selepas fasa tekanan suntikan. Suhu Barel mengandungi empat zon suhu pada unit suntikan yang terdiri daripada zon belakang, zon tengah, zon depan, dan zon muncung. Suhu Acuan biasanya digunakan ketika proses penyejukkan bahan plastik selepas ia disuntik ke dalam acuan yang mempunyai saluran air penyejuk. Sejumlah 40 kertas penyelidikan telah dikaji dan diringkaskan berdasarkan kepada parameter yang digunakan di dalam penganalisaan. Kebanyakan penyelidik mengamalkan kaedah Taguchi dalam kaedah penyelidikan mereka. Dari analisa, terdapat empat parameter yang kerap digunakan iaitu Suhu Barel, Suhu Acuan, Tekanan Suntikan dan Tekanan Pegangan dalam usaha untuk menghasilkan produk, menambahbaikan produk agar lebih berkualiti atau menaikkan kadar kekuatan maksimum produk. Kertas kerja ini adalah ulasan ilmiah semua parameter utama yang terlibat dalam proses pengacuan suntikan tersebut.

Kata kunci: Pengacuan suntikan; parameter pemprosesan; tekanan suntikan; Kaedah Taguchi

Abstract English

An injection system is a heart of an Injection Moulding process and it includes a variety of factors that need to be coordinated and adjusted. This control system covers parameter that are classified as four main parameters: pressure, temperature, time, and distance. Injection Pressure is the pressure needed to move melted polymer material into the mould. Holding Pressure is the phase which come after the injection pressure stage. Barrel Temperature which can be divided into four operated temperature zones in the injection unit consisted of the rear zone, the middle zone, the front zone, and the nozzle zone. Mould Temperature is typically used for cooling the polymer material once it is injected into a mould that has a cooling water channel. A total of 40 research papers have been studied and summarized based on their related parameters that has been used in the analysis. Most researchers includes the Taguchi method in their research methodology. From the analysis, there are four frequently used parameters which are Barrel Temperature, Mould Temperature. Injection Pressure and Holding Pressure in order to produce a product, to improve product with better quality or products with maximum strength. This paper is a review of all the main processing parameters that are involves in plastic injection molding process.

Keywords: Injection moulding; processing parameter; injection pressure; Taguchi method

Remote sensing is a potential source of information of land covers on the surface of the Earth. Different types of remote sensing images offer different spatial resolution quality. High resolution images contain rich information, but they are expensive, while low resolution image are less detail but they are cheap. Super-resolution mapping (SRM) technique is used to enhance the spatial resolution of the low resolution image in order to produce land cover mapping with high accuracy. The mapping technique is crucial to differentiate land cover classes. Hopfield neural network (HNN) is a popular approach in SRM. Currently, numerical implementation of HNN uses ordinary differential equation (ODE) calculated with traditional Euler method. Although producing satisfactory accuracy, Euler method is considered slow especially when dealing with large data like remote sensing image. Therefore, in this paper several advanced numerical methods are applied to the formulation of the ODE in SRM in order to speed up the iterative procedure of SRM. These methods are an improved Euler, Runge-Kutta, and Adams-Moulton. Four classes of land covers such as vegetation, water bodies, roads, and buildings are used in this work. Results of traditional Euler produces mapping accuracy of 85.18% computed in 1000 iterations within 220-1020 seconds. Improved Euler method produces accuracy of 86.63% computed in a range of 60-620 iterations within 20-500 seconds. Runge-Kutta method produces accuracy of 86.63% computed in a range of 70-600 iterations within 20-400 seconds. Adams-Moulton method produces accuracy of 86.64% in a range of 40-320 iterations within 10-150 seconds.

Keywords: Euler; optimization; ordinary differential equation; remote sensing; super-resolution mapping

Gallium nitride (GaN) is an excellent choice of semiconductor material due to its optoelectronic, mechanical and wide bandgap properties which are highly demanded by high-power and radio-frequency (RF) electronics but also widely employed for the fabrication of Light Emitting Diode (LED). In this paper, we explored the advantage of GaN as an electromechanical material to be used in microelectromechanical systems (MEMS) microphone as a thin film membrane through a theoretical study performed using the finite element method. We consider also the anisotropy and symmetry structural of GaN to be employed as microphone membrane. In addition, we compared also its performance in terms of sensitivity, C-V measurement and pull-in voltage with several conventional membrane materials such as silicon, nickel, and silicon nitride. The result shows that GaN-based MEMS capacitive microphone has sensitivity -57 dBV/Pa which is 4% higher than silicon nitride-based microphone and resonance frequency of 19 kHz which is higher 11.3% than nickel-based microphone. Hence, this theoretical study could pave a way for GaN to be developed especially for MEMS microphone applications and boasted also by the recent advancement of GaN related fabrication. The advantages of GaN compared to other conventional semiconductor material could be useful for the development of ultrasonic MEMS microphone for utilize detection of sound beyond audible frequency range.

Keywords: Gallium nitride; MEMS capacitive microphone; sensitivity; ultrasonic

Cities are increasingly turning into megacities due to their enlarged and intense population. There has been a global attempt by designers to spread the view that cities can be potential areas for producing loads of food required by communities and fitted for specific ecologies. A similar trend has been spread to developing countries where it is essential to provide food for local consumption, and serious attempts are made to distribute food materials to protect particular urban communities. Therefore, recent attempts of food security have aimed not only to guarantee availability but also the provision of sustainable, locally-fitted and food production that is not industrialized to sustain the potential for production. The solution seems to be Vertical Farming (VF). Producing food can be brought into cities through VF and this significant step, if taken, can make life in cities more viable. The present research aims to review the VF plays in the future of food production in high-density cities. The present research reviews the body of related literature, both online and printed publications on the issue. VF is a turning point of the millennium in urban designing but not limited to that. It further presents a new type of architecture as both a local and global remedy for the 21st crisis.

Keywords: Vertical Farming (VF); Food Security; Urban Farming; Urban High-density; Urban Planning

This paper presents the results of an experimental study on wetting and spreading of Al-Si-Zn filler metal on AR500 steel and AA7075 aluminium alloy surface. Wetting and spreading conditions of filler metal onto the surface of the metal were analysed by contact angle and spread ratio with different surface conditions. The contact angle is the measured angle between the tangent to the liquid-vapour interface and the surface of the solid. While, spread ratio measured according to the change in diameter of spread shape geometry of filler metal. The use of the low melting temperature of filler metal is increasingly popular since they are able to reduce the effect of heat on metals. However, the low spreading and de-wetting condition have limited the application of filler metal due to the adverse effect of these conditions on the joint ability. However, overall, this study with different surface conditions of these metals is to identify the wetting and spreading behaviour of filler metal. In this work, Al-Si-Zn filler metal heated by torch brazing was applied to AR500 steel and AA7075 aluminium alloy surface with the different type of surface conditions. Experimental results showed that the higher spreading area of filler metal occurred on a smooth surface compared to the rough surface of metals.

Keywords: Filler metal; brazing; wetting; spreading; contact angle

Aktiviti penyelidikan dan pembangunan (R&D) dalam sektor tenaga boleh diperbaharui merupakan salah satu elemen penting dalam Dasar dan Pelan Tindakan Tenaga Boleh Diperbaharui (NREPAP). Walau bagaimanapun, aktiviti R&D tenaga boleh diperbaharui tidak dikategorikan sebagai salah satu kelompok utama dalam program R&D negara dan ia perlu bersaing dengan bidang lain untuk mendapatkan dana penyelidikan. Walaupun dana R&D tenaga boleh diperbaharui yang diterima agak rendah, hasil daripada aktiviti R&D tenaga boleh diperbaharui di Malaysia dilihat sangat menggalakkan terutamanya dari segi penerbitan, penghasilan paten dan juga pembangunan modal insan. Ini bermakna aktiviti R&D yang dijalankan memberi sumbangan secara tidak langsung kepada pembangunan tenaga boleh diperbaharui di Malaysia. Tujuan kajian ini adalah untuk menilai prestasi aktiviti R&D di Malaysia berasaskan lima sumber tenaga boleh diperbaharui, iaitu suria, angin, biojisim, biogas dan hidro mini menggunakan pendekatan analisis penyampulan data (DEA) dari tahun 2012 hingga 2017. Kajian ini menggunakan model Charnes, Cooper, Rhodes (CCR)–DEA berorientasikan output dengan nisbah satu output dan empat input. Hasil kajian ini menunjukkan bahawa biojisim merupakan sumber tenaga boleh diperbaharui yang paling cekap manakala angin merupakan sumber tenaga boleh diperbaharui yang paling tidak cekap dari perspektif aktiviti R&D di Malaysia. Prestasi keseluruhan kecekapan aktiviti R&D tenaga boleh diperbaharui di Malaysia berada pada tahap baik iaitu mencapai 69.2% dalam tempoh 2012-2017. Hasil kajian ini selari dengan hasrat Kerajaan Malaysia untuk membangunkan sumber tenaga biojisim selaras dengan inisiatif Strategi Biojisim Kebangsaan 2020. Hasil kajian ini boleh dijadikan sebagai asas untuk mewujudkan dasar atau strategi khusus untuk memperkukuhkan lagi aktiviti R&D bagi menyokong pembangunan tenaga boleh diperbaharui di Malaysia.

Kata kunci: Tenaga boleh diperbaharui; Penyelidikan dan pembangunan; analisis penyampulan data; kecekapan

Abstract English

Research and development (R&D) activities in the renewable energy sector are one of the key elements under the National Renewable Energy Action Plan (NREPAP). However, renewable energy R&D activities are not considered as one of the key components of the country’s R&D program and it needs to compete with other fields to get the research funding. Although the renewable energy R&D fund received is relatively low, the output from the renewable energy R&D activities in Malaysia is seen as encouraging especially on the research publication, patent, and development of human capital. This means that the R&D activities undertaken contribute indirectly to the development of renewable energy in Malaysia. The purpose of this study was to evaluate the performance of R&D activities in Malaysia based on five renewable energy sources, namely solar, wind, biomass, biogas, and mini hydro using the data envelopment analysis (DEA) approach from 2012 to 2017. This study used an output-oriented Charnes, Cooper, Rhodes (CCR)–DEA model with the ratio of one output and four inputs. The result of this study indicates that biomass is the most efficient renewable energy resource, while the wind is the least efficient renewable energy source from the perspective of R&D activities in Malaysia. The overall performance of renewable energy R&D activities in Malaysia is good with a score of 69.2% in 2012-2017. The results of this study are in line with the Malaysia Government’s desire to develop biomass energy resources, as stated in the National Biomass Strategy 2020 initiative. The results of this study can serve as the basis for developing specific policies or strategies to strengthen R&Dactivities further to support the development of renewable energy in Malaysia.

Keywords: Renewable energy; research and development; data envelopment analysis; efficiency

The manual operation of an ON/OFF controller that is being widely used in the air-cooled chiller of the air conditioning system is found to have resulted in a significant daily variation of electricity usage. As such, this study had aimed to investigate the effect from the application of a pre-programmed auto timer control system (ADTCS ON/OFF) on the performance of an air-cooled chiller and its main components in the Penang State Mosque. The ADTCS ON/OFF that had been developed for both the indoor and outdoor usage was installed to an existing air conditioning electrical distribution board (DB) via an external control panel, which had consisted of a selector switch with a timer operation, a power supply, an ON/OFF push button for the AHU, a lamp indicator as well as that of a digital timer (brand Honeywell HWTHC711A). Apart from demonstrating the implementation of the ADTCS ON/OFF control system as contributing to a more consistent operation time, this study had also shown the manual operation of the air-cooled chiller as contributing to an impactful loss of approximately 9.6 hours or 3182 kWh on a normal day when being compared to that of the ADTCS ON/OFF control system. Since the findings from this research had shown the use of an ADTCS ON/OFF control system in the air-cooled chiller system as providing a positive implication of the monthly electricity cost to the Penang State Mosque and the mosque institutions as a whole, this therefore suggests that a big savings of expenditure can also be achieved from the implementation of such a system.

Keywords: Energy consumption; auto timer controller; air conditioning; mosque

Tenaga angin merupakan salah satu sumber tenaga keterbaharuan yang berpotensi sebagai alternatif kepada penjanaan tenaga secara konvensional melalui pembakaran arang batu dan bahan api fosil yang menjadi penyumbang utama kepada perubahan iklim. Sejak kebelakangan ini, kajian tentang turbin angin lebih tertumpu kepada turbin angin paksi menegak jenis Darrieus berskala kecil yang lebih sesuai untuk digunakan di kawasan angin berkelajuan rendah. Justeru, kajian ini dijalankan bertujuan untuk menganalisa kesan kepaduan dengan mengubah diameter turbin, terhadap prestasi kuasa VAWT menggunakan teknologi perkomputeran dinamik bendalir (CFD) secara berangka. Satu siri simulasi CFD dua dimensi telah dijalankan ke atas VAWT 3-bilah yang diperlengkap dengan bilah jenis NACA0018. Penilaian prestasi kuasa terhadap 3 konfigurasi turbin dengan diameter yang berbeza, iaitu 1.0 m, 0.6 m dan 0.43 m telah dijalankan pada julat operasi kelajuan yang besar dengan kelajuan pengaliran masuk angin ditetapkan pada 8.0 m/s. Hasil simulasi jelas memperlihatkan bahawa turbin angin berdiameter besar menunjukkan prestasi yang baik pada nilai λ yang tinggi dan mempunyai julat operasi yang besar manakala turbin angin berdiameter kecil menjana kuasa lebih banyak pada nilai λ yang rendah dan mempunyai keupayaan mula diri yang lebih baik. Hasil kajian ini dapat membantu para penyelidik memahami dengan lebih mendalam kesan kepaduan turbin terhadap prestasi VAWT seterusnya menghasilkan rekaan ideal VAWT yang boleh beroperasi dalam keadaan angin yang kompleks.

Kata kunci: Kepaduan; perkomputeran dinamik bendalir; turbin angin paksi menegak; tenaga angin

Abstract English

Wind energy is one of the potential renewable energy sources and a great alternative to replace conventional power generation using coal and fossil fuel that heavily contribute to climate change. Recently, small scale vertical axis wind turbine (VAWT) has received growing interest as wind energy converter due to its suitability to be used in low wind speed area. Hence, this paper is intended to evaluate numerically the effect of solidity, by varying turbine diameter, on power performance of VAWT using computational fluid dynamic (CFD) technology. A series of two-dimensional CFD simulations was performed on a three-bladed H-type Darrieus rotor equipped with symmetrical NACA0018 blades. Performance evaluation on 3 turbine configurations with different diameter; i.e. 1.0 m, 0.6 m and 0.43 m were performed over a range of tip speed ratio, λ with an incoming velocity of 8.0 m/s. The simulation results clearly show that low solidity turbine performed better at high values of λ and has wider operating range while turbine with low solidity performed better at low λ and has better self-starting capability. The results lend substantially to our understanding of solidity effect on performance of VAWT in order to develop an ideal design of VAWT that can operate optimally in complex wind condition.

Keywords: Solidity; computational fluid dynamic; vertical axis wind turbine; wind energy

Solid oxide fuel cell (SOFC) has significant advantages of clean and quiet operation while providing a relatively high efficiency owing to enhanced reaction kinetics at high operating temperature. The high operating temperature of SOFC, typically around 800 – 1000°C helps to enable internal reforming of hydrocarbons and negate effects of impurities in small quantities in the fuel. However, this limits the application of SOFC only to stationary applications due to the long period needed to reach this temperature range. A high temperature operation is also not ideal in terms of cost reduction and long-term stability of the cell components. Hence, lowering the operating temperature of SOFC is crucial for reduction of cost production and commercialization, which enables SOFC to have a wider range of application areas inclusive of portable and mobile ones. Building a high-performance SOFC with small volume is essential as the underlying criteria for these small-scale portable applications. Therefore, careful design and fabrication methods of SOFC operating on intermediate temperatures with high power outputs need to be considered. The intermediate temperature operation of the fuel cell not only increases the overall lifespan of cell but also allows for longer operation with a lower degradation rate compared to high temperature operation. Furthermore, a modified intermediate temperature stack design can accommodate a wider range of applications compared to the tubular and planar stack designs. This paper reviews the development of SOFC stack designs aimed at intermediate temperature operation towards achieving high performance and the benefits of each design.

Keywords: Solid oxide fuel cell; stack design; intermediate temperature

Direct methanol fuel cell (DMFC) performance tests were carried out in different modes of operation, namely, passive, active (air as oxidant) and active (oxygen as oxidant). Few parameters including methanol concentration (2 M, 4 M, 6 M, and 8 M) and methanol flow rate (1-4 mL min-1) were considered to investigate their effects on the DMFC performance. Fuel consumption was indicated by refractive index tests. Results showed that the performance of DMFC increased with the increase of methanol concentration and flow rate, until they reach certain values, i.e., 4-6 M and 2 mL min-1. Furthermore, for all parameters, the active mode with oxygen yielded the highest power density, followed by the active mode with air and passive DMFC system. The active mode with oxygen yielded the power density which peaks at 10.41 mW cm-2 during 6 M of methanol concentration and 2 mL min-1 rate of flowing methanol, followed by active mode with air at the cathode with 8.39 mW cm-2 and passive mode with 5.39 mW cm-2 respectively. It also records a better fuel consumption efficiency among all modes. These results indicate that investigating the level of fuel concentration and flow rate can lead to enhancement of mass transport and diffusion thus generating better performance of DMFC system.

Keywords: Modes operation; direct methanol fuel cell; methanol flow rate

Solid electrolyte based on cerate-zirconates have been widely investigated world-wide as proton conductor for potential applications in electrochemical devices such as fuel cells, electrochemical sensors, reactors, and devices. The most conventional physical method to prepare these ceramic electrolytes is via solid-state reaction (SSR). However, chemical method or known as wet chemical method (WCM) such as a sol-gel process has become a reliable route in terms of producing high purity and homogenous ultrafine powders. Tailoring the microstructure of the ceramics electrolyte can be achieved as sol gel process produces single perovskite phase of cerate-zirconates at lower processing temperature. This lower heat treatment produces the ceramics with improved quality for instance ultra-fine and agglomerate free powders with narrow size distributions. Subsequently, the innovative procedures generates high relative density of the electrolyte with improved quality and performance. Within the scope, in this paper we summarize our recent results on the synthesis of doped Ba(Ce,Zr)O3 nanopowders by a modified sol-gel routes using metal nitrate salts as precursor.

Keywords: Modified sol-gel; nano particle; cerate-zirconate; chemical agent