bluuebunny/crossref_metadata_2025 huggingface dataset:
A Bidirectional UPS Inverter Utilising High Frequency Center–Tapped Transformer
Authors: Salam Zainal , Ramli Zulkifli
Published: January 2013

A new variation of transformer-isolated inverter for UPS application is proposed. It is basically similar to the circuit proposed by Kourtroulis with the following modifications: 1) a modified modulation technique for the HF PWM interver stage and 2) replacing the full bridge active rectifier witha center-tapped active rectifier. With these modifications, the switches count is reduced, and expectedly, the efficiency is increased. Futhermore, the modified PWM technique will ensure that the transformer can be utilised near to its full potential. This is due to be absence of the low frequency component that can result in transformer saturation. The paper will detail the design considerations for the proposed topology. It will primarily focus on the power circuit, modulation method, and the high frequency transformer design. To prove the concept, a 1–kW prototype inverter was built and tested.

Keywords: Inverter, bidirectional, high frequency transformer, pulse width modulation
Application of the Modified HAZOP to an Advisory System Using Rule–Based Approach for Packed Column
Authors: Mohd. Yunus M. Y. , Ali M. W.
Published: January 2013

An advisory system using a rule–based approach has been developed in which the knowledge required to perform hazard identification is divided into process–specific and process–general components. Hazard identification has been carried out using the modified Hazard and Operability Study (HAZOP) method. In the proposed modified HAZOP, the two study nodes are connected in one mode of analysis. The process–specific knowledge, which consists of a conventional HAZOP study result, has been stored in the database. This process–general knowledge consists of rule–based which has been developed from the result of process simulation. The combination of hazard identification technique with process simulation result is important, in order to analyse the causes and consequences of the deviation in the process. For hazard identification, the process deviations selected are flow rate, temperature, and pressure. An inference engine for this advisory system has been developed using Visual Basic programming language, for appropriate interaction between knowledge–based components, in order to identify process–specific of causes and consequences for each process deviation specified. The procedure is based on the proposal HAZOP algorithm modified from a conventional HAZOP. The case study used is a packed column of an oleo chemical plant. The study has contributed to an improvement of hazard identification technique, which proposed a modified HAZOP algorithm by considering the consequences of the operation for each process deviation. The modified HAZOP algorithm has been proposed in a generic manner, however, the advisory system developed in this study is limited to the application for packed column of oleo chemical plant only.

Key words: Hazard identification, advisory system, ruled based, process simulation, packed column
Analysis of Formation Damage Caused by Oil–Based Mud on Berea Sandstone Using SEM
Authors: Ismail Issham , Babu Jagdeve
Published: January 2013

Objektif ujikaji ini adalah untuk mengkaji kerosakan yang dialami oleh batu pasir Berea berikutan penggunaan lumpur dasar minyak, dengan menggunakan Mikroskop Elektron Imbasan (SEM – Scanning Electron Microscope). Ujikaji dilakukan di makmal menggunakan lumpur dasar minyak sintetik (Sarapar 147) yang beroperasi dalam keadaan dinamik dengan tekanan pembezaan yang berbeza. Keputusan ujikaji dibincang berdasarkan nisbah kerosakan dan analisis secara visual imej SEM sampel teras yang terdedah kepada lumpur. Nisbah kerosakan yang dialami oleh sampel teras rosak didapati berkurangan apabila tekanan pembezaan meningkat. Imej SEM juga didapati memberikan keputusan yang sama. Imej SEM dan nisbah kerosakan turut membuktikan bahawa sampel yang dipasang pada sudut 180° (mendatar) mengalami penyumbatan partikel yang lebih ketara berbanding sampel yang dipasang pada sudut 90° (tegak).

Kata kunci: Lumpur dasar minyak, kerosakan formasi, nisbah kerosakan, batu pasir Berea, SEM

The objective of this experiment is to investigate the damage caused by oil–based mud on Berea sanstone using Scanning Electron Microscope (SEM). Laboratory experiment had been carried out using synthetic oil–based mud (Sarapar 147) at various differential pressures exerted on the core under dynamic conditions. The discussion of this research results were based on the damage ratio and visual observation of exposed samples using SEM. The damage ratios of the damaged core samples were found to decrease when the differential pressures were increased. These results were confirmed with SEM images. The SEM images and damage ratios also revealed that when samples were positioned at an angle of 180° (horizontal), they experienced higher particles plugging compared to samples positioned at an angle of 90° (vertical).

Key words: Oil-based mud, formation damage, damage ratio, Berea sandstone, SEM
Pendekatan Kabur untuk Mengenal Pasti Kriteria Mempengaruhi Pelajar Memilih Institusi Pengajian Tinggi Awam (IPTA)
Authors: Mat Yusof Muhammad , Jemain Abdul Aziz
Published: January 2013

Saban tahun, ramai pelajar yang berkelayakan memohon untuk meneruskan pengajian ke institusi pengajian tinggi awam. Lantaran itu, suatu penunjuk perlu dicari bagi membantu pihak berwajib mendapat gambaran tentang kriteria pemilihan ke universiti untuk tujuan perancangan, pemantauan, pemulihan, pemuliharaan atau penaiktarafan selanjutnya. Dalam kajian ini, teori set kabur digunakan. Maklumat kecenderungan pemilihan boleh digambarkan dengan menggunakan vektor tertib, vektor kepuasan, vektor linguistik atau vektor pemilihan subset. Para pelajar sebagai pembuat keputusan akan memberi kecenderungan mereka dalam format yang berbeza-beza mengikut idea, sikap, motivasi dan personaliti masing-masing. Perbezaan format ini kemudiannya diseragamkan dan diagregatkan menggunakan format hubungan kecenderungan kabur. Pemberat setiap kriteria akan diperolehi dengan menggunakan operasi pemurata tertib berpemberat (Ordered Weighting Averaging – OWA). Berdasarkan kajian ini, didapati bahawa pelajar memilih kriteria penawaran kursus, kualiti pengajaran pensyarah dan kemudahan pinjaman/biasiswa sebagai kriteria utama untuk meneruskan pengajian di Institusi Pengajian Tinggi Awam.

Kata kunci: Teori set kabur, vektor tertib, vektor kepuasan, vektor linguistik, operasi pemurata tertib berpemberat (OWA)

Every year, many qualified students apply tu further their study to the public higher learning institution. For that reason, indicators are needed in assisting the proper authority to get the current situation in the country regarding criterias used by students in seeking proper places for them to pursue their higher education. Thus, the selection criteria should be treated with a high level of importance, which will provide information useful for planning, monitoring and upgrading in order to ensure all public higher intuitions are able to satisfy the demand from the society. In this study, a fuzzy set theory was applied when the imprecise information was represented in fuzzy terms. Preference information can be represented by means of preference orderings, utility functions, vector of linguistic terms or a selected subset. In this approach, four different preference formats are provided from students as decision makers to express their individual preferences, taking into consideration the decision makers different attitudes, motivation, and personalities. The different formats of preferences are transformed into uniform fuzzy preference relations and aggregated. Ordered Weighting Averaging (OWA) was used to assess the criteria weights. From this study, it was found that offering courses, teaching qualities and availability of financial aid are the most important criteria considered by the students to further their study in public higher learning institutions.

Key words: Fuzzy set, fuzzy consensus, multi-criteria decision, fuzzy preference
SEM Observations on Wear Mechanism of TiN–Coated HSS Twist Drills When Drilling Mild Steel
Authors: Talib R. J. , Saad S. , M. Toff M. R. , Hashim A. H.
Published: January 2013

Dalam kajian ini, haus mekanikal Keluli Laju Tinggi (KLT) telah dikaji dengan menjalankan ujian prestasi gerudi ke atas bahan kerja diperbuat daripada keluli lembut. Salutan TiN ke atas HSS twist drills diperolehi dengan menggunakan kaedah bertindak balas frekuensi radio pemercitan magnetron yang mana dibangunkan secara dalaman. Ujian prestasi gerudi dijalankan pada kelajuan pusingan 1,600 psm, kadar suapan 20 mm/minit dengan kedalaman penggerudian 25 mm. Perubahan morfologi permukaan haus diperhatikan dengan menggunakan kaedah Kemikroskopan Imbasan Elektron (KEI). Keputusan morfologi menunjukkan mekanisme rekatan dan haba beroperasi semasa proses penggerudian. Kertas kerja ini juga akan membincangkan secara mendalam proses penjanaan mekanisme haus rekatan dan haba semasa penggerudian gerudi piuhan ke atas plat keluli lembut. Keputusan ujian prestasi gerudi menunjukkan salutan TiN terendap ke atas KLT gerudi piuhan telah meningkatkan umur gerudi melebihi dua kali ganda jika dibandingkan dengan gerudi yang tidak bersalut.

Kata kunci: Gerudi KLT, KEI, mekanisme haus, rekatan, haba

In this study, High Speed Steel (HSS) twist drills were investigated for mechanical wear by performing drilling test on the work piece of mild steel plate. TiN coatings onto the HSS twist drills were achieved by employing reactive radio frequency (r.f) magnetron sputtering technique, which was developed in–house. The drilling performance tests were set at a rotation speed of 1,600 rpm, feed rate of 20 mm/min, and depth of cut of 25 mm. The morphological changes of the wear surface were observed using Scanning Electron Microscopy (SEM). Results of morphological examination showed that the failure mechanisms in operation during drilling were found to be adhesive and thermal wear mechanism. This paper will also discuss explicitly the processes of adhesive and thermal wear mechanism generated during drilling of twist drill on mild steel plate. Results of drilling performance test showed that the TiN coating deposited on the HSS twist drill had improved drill life by more than 2 times as compared with uncoated drill.

Key words: HSS drill, SEM, wear mechanism, adhesive, thermal
Keutuhan Permukaan Bahan Keluli Perkakas Setelah Pengisaran Hujung Menggunakan Perkakas Karbida Bersalut
Authors: Che Haron Che Hassan , Muchtar Andanastuti , Nik Kundor Nik Faizu
Published: January 2013

Projek ini dijalankan bertujuan untuk mengkaji kesan proses pengisaran terhadap keutuhan permukaan keluli perkakas D2. Dalam kajian ini, keluli perkakas kerja sejuk AISI D2 yang telah dikeraskan kepada 62 HRC dimesin menggunakan sisip karbida bersalut CVD boleh indeks yang dipegang oleh perkakas pengisaran hujung berdiameter 20 mm. Siri–siri ujian dijalankan dalam keadaan kering. Penilaian ke atas permukaan yang dimesin melibatkan kekasaran permukaan dan analisis mikrostruktur. Keputusan kajian menunjukkan bahawa tiada hubungan yang jelas di antara variasi kelajuan pemotongan dan suapan terhadap kekasaran permukaan. Umumnya, permukaan yang dihasilkan adalah sangat licin dengan nilai Ra berada dalam julat 0.10 μm – 0.43 μm dan analisis permukaan pada sampel–sampel ujikaji juga mendapati hampir tiada perubahan dapat dikesan pada mikrostruktur bahagian bawah permukaan yang dimesin. Walau bagaimanapun, pada kelajuan pemotongan tertinggi (160 m/min) dan suapan yang tinggi (0.02 mm/sisip), terdapat kesan termampat dan terherot pada mikrostruktur pada kedalaman yang sangat cetek iaitu lebih kurang 2.2 μm dari permukaan termesin.

Kata kunci: Keutuhan permukaan, keluli perkakas terkeras, pengisaran hujung, mikrostruktur, perkakas karbida bersalut

The effect of milling process on the surface integrity of newly machined surface of D2 tool steel is presented. The hardened AISI D2 (62 HRC) was machined under dry cutting conditions using a 20 mm diameter end–milling tool with indexable CVD coated carbide insert. Analyses revealed that the variation in cutting speeded and feed did not significantly affect the surface roughness of the machined surface. Generally, the surfaces produced are very smooth with Ra values in the range of 0.1 – 0.43 μm, and studies showed almost no microstructure alteration on the machined surfaces. However, at the highest cutting condition, i.e. a cutting speed of 160 m/min, and feed of 0.02 mm/tooth, some compression and distortion effects were detected on the microstructure at the very shallow depth of approximately 2.2 μm from the machined surface.

Key words: Surface integrity, hardened tool steel, end-milling, microstructure, coated carbide tool
Supersolidus Sintering and Mechanical Properties of Water–Atomised M3/2 High–Speed Steel Powder Sintered Under Nitrogen–Based Atmosphere
Authors: Selamat Mohd. Asri , Mohamad Mazlan
Published: January 2013

Keupayaan untuk menghasilkan keluli laju–tinggi kepada bentuk hampir sebenar menggunakan relau tali–sawat berterusan menawarkan peluang untuk mempertingkatkan sifat–sifat serta mengurangkan kos pemprosesan bahan keluli ini. Sehingga kini, masalah yang timbul bagi mencapai matlamat tersebut adalah keperluan menggunakan suhu persinteran tinggi (1250–1350°C) di dalam atmosfera vakum. Satu kaedah persinteran yang murah terhadap serbuk keluli laju–tinggi pengabusan–air telah dibangunkan menerusi projek ini menggunakan mekanisme Persinteran Fasa Pepejalan–lampau Cecair (PFPC). Serbuk M3/2 keluli laju–tinggi ini boleh tersinter kepada ketumpatan penuh (>95% daripada ketumpatan teori) di dalam atmosfera berasaskan–nitrogen pada suhu persinteran 1150°C. Mikrostruktur dan sifat–sifat mekanik yang baik telah berjaya dihasilkan selepas proses rawatan haba yang sesuai dilakukan.

Kata kunci: Pepejalan-lampau, serbuk pengabusan-air, atmosfera berasaskan-nitrogen

The ability to produce near net shape high–speed steels using a continuous belt furnace offers the opportunity to improve the properties and reduce the processing cost of these materials. So far, the difficulty in making this advancement has been the requirement of high sintering temperatures (1250–1350°C) in vacuum atmosphere. A low cost–sintering route of water–atomised high–speed steel powder has been developed during this project using Supersolidus Liquid Phase Sintering (SLPS) mechanism. This water–atomised M3/2 high–speed steel powder can be sintered to full density (>95% of theoretical density) under nitrogen–based atmosphere at sintering temperature of 1150°C. Acceptable microstructures and mechanical properties have been obtained after appropriate heat treatment.

Key words: Supersolidus, water-atomised powder, nitrogen-based atmosphere
Simulation of Groundwater Flow and Pollutant Transport for Alluvial Aquifer in Kampung Tekek, Tioman Island
Authors: Abd. Rahman Norhan , Kuan Woei–Keong
Published: January 2013

Pulau Tioman terletak di pantai timur Semenanjung Malaysia. Akibat pembangunan yang pesat dalam industri pelancongan, permintaan terhadap bekalan air dijangka akan meningkat di pulau ini. Daripada kajian yang telah dijalankan sebelumnya, didapati airbumi merupakan sumber air yang berpotensi. Satu perisian model 3–dimensi (Visual MODFLOW) telah digunakan untuk menghasilkan model aliran airbumi dan pengangkutan bahan pencemar di Kampung Tekek dengan tujuan meramal simpanan airbumi dan penyebaran bahan pencemar, iaitu nitrat, semasa pengepaman. Daripada keputusan simulasi aliran airbumi yang diperolehi, pengepaman akuifer di Kampung Tekek dapat mencapai pada kadar 4000 m3/hari. Kajian model bahan pencemar menunjukkan kepekatan bahan pencemar nitrat yang tercatat di telaga pam didapati agak rendah dan memenuhi piawaian air minuman World Health Organisation (WHO).

Kata kunci: Aliran airbumi, bahan pencemar, model numerik, Visual MODFLOW, pulau

Tioman Island is situated in the east coast of Peninsular Malaysia. With rapid growth in tourism industry, the demand for water supply is expected to increase in this island. From previous studies, groundwater was found to be a potential source of water. A 3–dimensional numerical modelling software (Visual MODFLOW) is used to simulate the groundwater flow and pollutant transport of the aquifer in Kampung Tekek, for the prediction of available yield of groundwater, and also for studying the migration of potential contaminant source, i.e. nitrate, due to the withdrawal. The groundwater flow simulation results showed that the aquifer is capable of pumping 4000 m3/day. Results of pollutant transport modelling showed that the estimated concentration of nitrate in the pump well is generally low and complies with World Health Organisation (WHO) standard for drinking water.

Key words: Groundwater flow, pollutant transport, numerical model, Visual MODFLOW, island
Comparison of the Filterability of Mineral, Organic and Mixed Suspensions Application to Water Clarification
Authors: Sridang P. Choksuchart , Heran M. , Grasmick A.
Published: January 2013

Filtration operations were conducted on porous membrane to evaluate the specific contribution of the main fractions encountered in raw water (solids in suspension, soluble, or colloidal compounds) on the system permeability evolution during industrial operations. Experiments were conducted in a frontal filtration mode with single or mixed synthetic suspensions (clay, ferric hydroxide, activated carbon, latex, and humic acids). Results showed a wild specific resistance coefficient (α.W) difference between mineral and organic suspensions. The α.W coefficient increased with suspended solids concentrations. On the other hand, no actual differences were observed between the tested mineral suspensions, which also presented no actual differences in particle size distribution. In the same condition, latex suspensions composed by smaller elements induced higher hydraulic resistance, comparatively to mineral suspension, the resistance coefficient values were ten to one hundred times greater than the mineral suspensions. Nevertheless, a latex suspensions conditioning with FeCl3 allowed a notably reducing of the resistance coefficient. Moreover, experiments on humic acid suspension pointed out the membrane fouling during filtration, which could disappear in the presence of activated carbon in the suspension. Since similar results were obtained in an immersed membrane system, it can be considered that this methodology can be developed to characterise the filterability of natural suspensions, and optimise the suspension conditioning.

Key words: Water clarification, cake filtration, porous membrane, hydraulic resistance, synthetic suspensions
Theoretical Analysis on Interacting Effect of Steric and Donnan Factors in Nanofiltration Membrane Separation System
Authors: Ali Nora’aini , Mohammad A. Wahab
Published: January 2013

Prestasi pemisahan sistem membran penuras nano didapati sangat bergantung kepada kesan sterik dan cas. Kajian terdahulu telah menunjukkan bahawa kombinasi yang tepat di antara saiz liang (kesan sterik) dan ketumpatan cas berkesannya (kesan Donnan) akan memberikan prestasi pemisahan yang optimum. Justeru itu, keupayaan menghasilkan membran penuras nano bersifat optimum akan memberikan pembaikan yang signifikan dari aspek prestasi membran dan pengurangan kos pemprosesan. Oleh itu, objektif utama kajian teoritikal ini ialah untuk menyelidik kesan interaktif saiz liang (rp) dan ketumpatan cas membran, (Xd) terhadap prestasi pemisahan. Dua parameter tanpa dimensi telah digunakan iaitu λ (λ = rs/rp) dan ζ(ζ = Xd/Cb). Pengangkutan elektrolit melalui membran penuras nano tersebut ditentukan dengan menggunakan model liang sterik-donnan (DSPM). Pelbagai larutan garam dengan pelbagai saiz liang dan kesan cas diuji dengan menggunakan model tersebut. Kajian menunjukkan bahawa untuk kes membran dengan kapasiti cas berkesan yang tinggi, faktor Donnan didapati lebih penting untuk membran yang longgar strukturnya. Sumbangan faktor Donnan ini berkurangan dengan peningkatan saiz liang membran. Sebaliknya, untuk membran berketumpatan cas yang rendah, kesan faktor Donnan terhadap tolakan ion boleh diabaikan, tanpa bergantung kepada saiz liang.

Kata kunci: Penurasan nano, DSPM, ketumpatan caj berkesan, saiz liang, teoritikal

The separation performance of NF membrane system is found to be significantly dependent on the steric and charge effects. Previous studies have shown that the right combination of membrane pore size (steric effect) and its effective charge density (donnan effect) will lead to an optimum separation performance. Hence, the ability to produce nanofiltration membranes with optimized properties will certainly provide significant improvement in terms of membrane performance and processing cost reduction. Therefore, the main objective of this theoretical study is to investigate the interactive effect of membrane pore size (rp) and membrane charge density, (Xd) towards the separation performance. Two general dimensionless parameters were used namely λ (λ = rs/rp) and ζ(ζ = Xd/Cb). The electrolyte transport through nanofiltration membranes is determined using a model based on the application of the extended Nernst–Planck equation coupled with Donnan–steric pore model (DSPM). A variety of salt solution with various pore size and charge effect was tested using the above–mentioned model. It was found that for the case of membranes with high effective charge density, the Donnan factor is more prominent for loose membranes. The contribution of the factor decreased with the increase of membrane pore size. Vice versa, for the lower charge density membrane, the effect of Donnan factor towards ion rejection could be neglected, regardless of membrane pore sizes.

Key words: Nanofiltration, DSPM, membrane charge density, pore size, theoretical
Small Broadband Antenna Designs for 3G Handset Applications
Authors: Abdul Rashid Zainol Abidin , Hsiao Hui Joan Lee , Jiunn Ng Kok
Published: January 2013

Dua reka bentuk antena set tangan yang diperbaiki, kecil, padat dan berjalur lebar bagi jalur 3G berdasarkan kaedah tompok gandinganâ€“sela dan FSâ€“PIFA dibentangkan. Antena gandinganâ€“sela sesatah tompok tersongsang (IGCC) dan satah bumi terhingga satah tersongsangâ€“F terpintasâ€“penuh (FFSâ€“PIFA) disimulasi dengan menggunakan simulator Zealand IE3D 8.2 em. Hasil simulasi memberikan pecahan lebar jalur sebanyak 28.2% dan 40.1% pada kehilangan balikan 10 dB bagi reka bentuk IGCC dan FFSâ€“PIFA masingâ€“masing. Reka bentuk IGCC difabrikasi kerana ia mudah difabrikasi. Hasil pengukuran bagi IGCC memberikan pecahan lebar jalur sebanyak 31% pada 10 dB pada fc = 1.95 GHz dengan gandaan 4 dBi. Dimensi tompok bagi keduaâ€“dua antena ialah 33 Ã— 32 mm dengan satah bumi bersaiz 40 Ã— 60 mm. Antena ini sesuai bagi aplikasi 3G.

Kata kunci: Antena set tangan, antena tompok microstrip, satah tersongsang F, gandingan sela, IMT- 2000

Two improved, small, compact, and broadband handset antenna designs for 3G band based on gapâ€“coupled patch and FSâ€“PIFA techniques are presented. The antennas, the Inverted Gapâ€“Coupled Coplanar patch antenna (IGCC) and Finite ground plane Fullâ€“Shorted Planar Invertedâ€“F Antenna (FFS PIFA) are simulated using Zealand IE3D 8.2 em simulator. Simulation results give fractional bandwidths of 28.2% and 40.1% at 10 dB Return Loss for IGCC and FFSâ€“PIFA respectively. The IGCC was fabricated due to its simple fabrication. Measured results for IGCC gave a fractional bandwidth of 31% at 10 dB Return Loss at fc = 1.95 GHz and with 4 dBi gain. The patch dimensions for both antennas are 33 Ã— 32 mm with a ground plane size of 40 Ã— 60 mm. These antennas are promising for 3G applications.

Key words: Handset antenna, microstrip patch antenna, inverted-F, gap-coupled, IMT-2000
Enacting the Waterfall Software Development Model Using VRPML
Authors: Zamli Kamal Zuhairi , Mat Isa Nor Ashidi
Published: January 2013

Artikel ini menggariskan penggunaan bahasa visual yang baru, Bahasa Permodelan Proses Realiti Maya (VRPML) untuk spesifikasi proses pembangunan perisian. Secara khususnya, artikel ini membincangkan penggunaan VRPML dalam proses permodelan dan larian model air terjun. Matlamat utama kertas kerja ini adalah untuk mengkaji sama ada VRPML mempunyai notasi yang mencukupi untuk tujuan permodelan dan larian proses pembangunan perisian.

Kata kunci: Proses pembangunan perisian, kejuruteraan perisian, bahasa permodelan Proses, VRPML

This paper describes the use of a new visual language called the Virtual Reality Process Modeling Language (VRPML), in order to specify a software process. In particular, this paper demonstrates the use of VRPML to model and enact (i.e. execute) the waterfall software development model. The main objective of this paper is to investigate whether VRPML provides a sufficiently rich notation to enable the modeling and enacting of software processes.

Key words: Software process, software engineering, process modeling languages, VRPML
Water Quality and Chemical Mass Balance of Tropical Freshwater Wetlands, Beriah Swamp,Perak
Authors: Ismail Wan Ruslan , Siow A. Y. , Ali Ahyaudin
Published: January 2013

Satu kajian imbangan jisim kimia dijalankan di kawasan paya Beriah, iaitu paya air tawar di utara Perak bermula dari bulan Jun hingga Oktober 1998. Kajian ini bertujuan untuk mengkaji peranan dan fungsi tanah bencah dalam menjalankan penurasan endapan dan mengekalkan endapan dan/atau nutrien. Fluks nutrien dan endapan dari dua input sungai (Beriah Kanan dan Beriah Kiri) dibandingkan dengan sebatang sungai output (Beriah) yang keluar dari sistem paya tersebut. Pensampelan dilakukan setiap dua minggu ditambah dengan satu kajian intensif melibatkan pensampelan selama 48 jam semasa musim basah pada 10â€“11 Oktober 1998. Keputusan menunjukkan tiada perbezaan yang signifikan (p>0.05) dalam kepekatan semna parameter kecuali SRP antara keduaâ€“dua input. Namun perbezaan yang siginifikan (p0.05) in concentrations of almost all parameters except for SRP between two input rivers, but were significant different (p
A Study of Formation Damage Caused by Oilâ€“Based Mud in Dynamic Condition
Authors: Ismail Issham , Murugesu Thanapala Singam
Published: January 2013

Daya pengeluaran telaga boleh terjejas dengan teruknya akibat daripada kerosakan yang berlaku berhampiran lubang telaga, berikutan aktiviti penggerudian. Dengan itu, kertas kerja teknikal ini membincangkan tentang kerosakan formasi yang dialami teras batu pasir Berea yang ditempatkan di dalam telaga tegak dan mendatar terselaku, berpunca daripada penggunaan lumpur gerudi. Kajian dilaksanakan dalam keadaan dinamik menggunakan tekanan pembezaan yang berlainan. Lumpur dasar minyak disediakan di makmal, dengan peralatan makmal standard digunakan bagi menentukan sifat reologi lumpur terbabit. Sebelum bermulanya kajian, teras batu pasir Berea ditepukan dengan sarapar selama 24 jam. Keputusan kajian dibuat berdasarkan data kehilangan turasan dan data ketertelapan teras yang diukur sebelum dan selepas sampel teras didedahkan kepada lumpur. Keputusan kajian menunjukkan bahawa kerosakan ketertelapan teras bertambah teruk dengan meningkatnya tekanan pembezaan. Walau bagaimanapun, pada tekanan pembezaan 250 psi (1723.7 kPa), kerosakan yang berlaku lebih rendah berbanding 200 psi (1379.0 kPa) bagi keduaâ€“dua telaga mendatar dan tegak. Imej SEM menunjukkan kewujudan retakan halus pada sampel teras yang didedahkan kepada aliran lumpur dengan tekanan pembezaan dan suhu yang tinggi. Keputusan kajian juga menunjukkan bahawa telaga mendatar mengalami kerosakan yang lebih teruk dan kehilangan turasan yang lebih rendah jika dibandingkan dengan telaga tegak.

Kata kunci: Nisbah kerosakan, aliran dinamik, kerosakan formasi, lumpur dasar minyak, SEM

Well productivity can be significantly affected by damage near to wellbore area caused by drilling. Thus, this technical paper discusses the formation damage caused by oilâ€“based mud on the Berea sandstone cores in simulated vertical and horizontal wells. This study was carried out in a dynamic condition at various differentials pressure. Oilâ€“based mud was prepared in the laboratory and standard equipments were used to determine the mud rheological properties. Berea sandstone cores were saturated with sarapar for 24 hours prior to the tests. The result of this study was based on the measurement of filtrate loss and core permeability measurement before and after exposure to oilâ€“based mud in vertical and horizontal conditions at various differentials pressure. The experimental results revealed that the permeability impairment increased as differential pressure increases. However, at differential pressure of 250 psi (1723.7 kPa), the damage occurred was less severe compared to 200 psi (1379.0 kPa), in both vertical and horizontal conditions. SEM image showed the presence of microfractures in the core when exposed to mud at high pressure and temperature, under dynamic condition. Experimental results also showed that the horizontal condition experienced more severe damage amd lower filtrate loss as compared to vertical condition.

Key words: Damage ratio, dynamic flow, formation damage, oil-based mud, SEM
Improvement Of Engine Performance Using Diethylene Glycol Dimethyl Ether (DGM) As Additive
Authors: Nabi Md. Nurun , Chowdhury Md. Wahid
Published: January 2013

This research work investigates diesel combustion and exhaust emissions with additives addition to conventional diesel fuel in a four-stroke naturally aspirated direct injection (DI) diesel engine. The additives include DGM, and liquid cerium. The results show that with the addition of DGM to diesel fuel, brake specific energy consumption (BSEC) and all diesel emissions are significantly reduced. The volumetric blending ratios of additives to diesel fuel are 0, 25, 50, 75 and 100%. All emissions including smoke emissions decrease with the increase in oxygen content in the fuel and it is noted that smoke emission completely disappeared at an oxygen content of 36 wt–%. The reason for improvement in BSEC with the addition of additives to base diesel fuel is the improvement of degree of constant volume combustion, and the reduction of the cooling loss. Engine noise and odor concentrations are remarkably reduced with diesel-additive blends. Significant improvement in BSEC and exhaust emissions is not only found at medium load condition but also at high load condition.

Key words: Diesel engine, DGM, emissions, BSEC, and cooling loss
Analysis, Design And Simulation Of Piezoelectric Acoustic Microsensor
Authors: Mohd Ihsan Ahmad Kamal Ariffin , Lim Hock Aun , Mohd Nor Mohd Jailani
Published: January 2013

Kertas kerja ini membentangkan reka bentuk analisis dan simulasi mikropenderia akustik piezoelektrik untuk meniru tiang-tiang rerambut dalam telinga manusia. Mikropenderia ini dikaji bagi membangunkan mikrofon baru. Bahan piezoelektrik PZT 5A digunakan sebagai tiangtiang rerambut atau rasuk dalam mikropenderia akustik piezoletrik. Analisis dijalankan menggunakan perisian FEMLAB bagi mengenal pasti panjang rasuk untuk mendapatkan frekuensi jalur oktaf dengan julat 31.5Hz dan 16kHz. Kemudian, perisian SIMULINK pula digunakan bagi menyelaku prestasi mikropenderia akustik. Luas keratan rentas rasuk ditetapkan 9 μm × 9 μm dan panjang pula berubah-ubah bagi mendapatkan pelbagai frekuensi salun. Panjang sesuai lebar jalur kuasa separuh dan faktor kualiti telah berjaya diperolehi menggunakan FEMLAB®. Prosedur penyelakuan telah dijalankan bagi mendapatkan aras kuasa bunyi bagi rasuk. Panjang rasuk, separuh kuasa lebar jalur, faktor kualiti dan kuasa bunyi merupakan parameter penting dalam mereka bentuk mikropenderia akustik.

Kata kunci: Mikropenderia akustik, lebar jalur kuasa separuh, frekuensi jalur oktaf, bahan piezoletrik

This paper presents the design analysis, and simulation of piezoelectric acoustic microsensor to imitate outer hair cells (OHCs) inside the human ear. This acoustic microsensor was utilised to develop a new type of microphone. Piezoelectric material PZT 5A was used as the hair cells or beams for the piezoelectric acoustic microsensor. The analysis was conducted using FEMLAB® software to identify the corresponding length to acquire the octave band frequency ranging from 31.5 Hz to 16 kHz. Furthermore, SIMULINK® software was employed to simulate the performance of the acoustic microsensor. The cross section area of the beams was kept at a constant value of 9 × 9 μm and their length was varied to acquire various resonant frequencies. The suitable lengths, the half power bandwidths and the quality factors of the beams were successfully obtained using FEMLAB®. The simulation procedure was undertaken to obtain sound power level of the beams. The length, half power bandwidth, quality factor and the sound power of the beams are important parameters in designing the acoustic microsensor.

Key words: Acoustic microsensor, half power bandwidth, octave band frequency, piezoelectric material
Line Balancing Improvement In The Welding Section Of A Car Assembling Plant
Authors: Chin Wen Kheong , M. Yusof Sha’Ri
Published: January 2013

Kertas kerja ini membentangkan kajian kes masalah imbangan lini di kilang pemasangan kereta. Kajian ini bertujuan menyediakan alternatif dalam mengurangkan masalah semasa di lini kimpalan H–N bahagian pemasangan badan di loji tersebut. Kajian dilakukan untuk mengenal pasti bottleneck yang mengakibatkan tahap produktiviti rendah dan pembaziran sumber yang tinggi. Dengan menggunakan keputusan dari temubual tidak berstruktur, data kajian masa dan pemerhatian proses, masalah dianalisis dan punca utama yang dikenalpasti adalah ketidak seimbangan lini dan sistem pengendalian bahan yang kurang baik. Untuk mengatasi keadaan ini, beberapa alternatif telah dibentuk melalui teknik imbangan lini. QUEST iaitu perisian simulasi 3 dimensi kilang digital telah digunakan untuk menganalisis alternatif-alternatif tersebut. Proses telah dimodel mengunakan QUEST dan seterusnya simulasi dilakukan untuk keadaan semasa dan beberapa alternatif. Keputusan dari kajian simulasi dianalisis dan dinilai sebelum alternatif terbaik dicadangkan. Kertas kerja ini diakhiri dengan satu cadangan penyelesaian untuk membaiki imbangan lini di operasi kimpalan yang dipilih di syarikat tersebut.

Kata kunci: Imbangan lini, peningkatan produktiviti, simulasi

This paper presents a case study on a line balancing problem in a car assembling plant. This study was aimed at providing alternatives in reducing current problems at the H–N welding line of the body assembling section in the plant. Investigation was conducted to identify causes for bottlenecks that resulted in low productivity level and high resource wastage. Using the results of unstructured interviews, time study data and observations on the process, the problem was analysed and the main causes identified were unbalanced line and poor material handling system. To improve the current situation, alternatives were generated using line balance technique. QUEST, which is a 3D digital factory simulation software, was used in the analysis of the alternatives. The process was modelled using QUEST and simulation was conducted on the current system and also several possible alternatives. The results of the simulation studies were analysed and evaluated before the best alternative is selected and proposed. The paper culminates with a proposed solution to improve line balancing at the selected welding operations in the company.

Key words: Line balancing, productivity improvement, simulation
Vibration–Based Damage Detection Of Slab Structure Using Artificial Neural Network
Authors: Bakhary Norhisham
Published: January 2013

Kertas kerja ini memaparkan kajian berkenaan keberkesanan Artificial Neural Network (ANN) dalam mengenal pasti kerosakan di dalam struktur. Data dari getaran seperti frekuensi semula jadi dan mod bentuk digunakan sebagai data masukan bagi ANN untuk meramalkan lokasi dan tahap kerosakan bagi struktur lantai. Analisis unsur terhingga (Finite Element Analysis) telah digunakan untuk memperoleh ciri–ciri dinamik bagi struktur–struktur rosak dan tidak rosak untuk ‘melatih’ model ‘neural network’. Senario kerosakan yang berbeza disimulasikan dengan mengurangkan kekukuhan elemen pada lokasi yang berbeza sepanjang struktur tersebut. Berbagai kombinasi data masukan bagi mod yang berbeza telah digunakan untuk memperolehi model ANN yang terbaik. Hasil kajian ini menunjukkan ANN mampu memberikan keputusan yang baik dalam meramal kerosakan pada struktur lantai tersebut.

Kata kunci: Ramalan kerosakan struktur, Artificial Neural Network

This paper investigates the effectiveness of artificial neural network (ANN) in identifying damages in structures. Global (natural frequencies) and local (mode shapes) vibration–based data has been used as the input to ANN for location and severity prediction of damages in a slab–like structure. A finite element analysis has been used to obtain the dynamic characteristics of intact and damaged structure to train the neural network model. Different damage scenarios have been introduced by reducing the local stiffness of the selected elements at different locations along the structure. Several combinations of input variables in different modes have been used in order to obtain a reliable ANN model. The trained ANN model is validated using laboratory test data. The results show that ANN is capable of providing acceptable result on damage prediction of tested slab structure.

Key words: Structural damage detection, artificial neural network
In–Plane And Biaxial Performance Of Seismic Precast Hollow Core Wall With Different Types Of Energy Dissipators
Authors: Abdul Hamid Nor Hayati
Published: January 2013

Sebanyak dua buah precast hollow core dinding yang mempunyai geometri yang sama telah dibina berserta dengan tapak asas untuk diuji dengan daya selari mendatar, daya bertentangan dan dwi–daya yang berbentuk dua, empat dan lapan kelopak bunga di atas shaking table. Kedua–dua dinding itu telah dimasukkan ke dalam keluli berbentuk ‘C’ dan diletakkan ke atas kepingan keluli. Model 1 telah direka dengan meletakkan unbonded tendons dan fuse–bar ke dalam tapak asas manakala Model 2 telah direka bentuk dengan menggunakan beberapa jenis energy dissipator berserta dengan unbonded tendon. Empat gabungan antara energy dissipator dan unbonded tendon telah direka, dibina dan diuji di dalam makmal. Keputusan makmal menunjukkan bahawa kedua–dua model tidak mengalami sebarangan kerosakan dan keretakan. Daripada uji kaji ini, 50% daripada initial prestressing unbonded tendons telah dipilih kerana menunjukkan keputusan yang paling terbaik di mana tiada keretakan pada model dan kebengkokan pada fuse–bar.

Kata kunci: Daya mendatar, dwi–daya, kerosakan, daya yang berputar, zon sangga plastik

Two geometrically identical seismic precast hollow core walls with foundation beams were constructed and tested under in–plane, out of plane and biaxial loading on shaking table. Both of the walls were steel–armoured at bottom with steel channel and allowed to rock on steel plate located on top of foundation beams. Wall 1 was designed with fixed location of unbonded tendons and a pair of bonded fuse–bar was inserted into the foundation beam. Wall 2 was designed with some flexibility of locations, cross–sectional areas, initial prestressing of unbonded tendons and fuse–bars. Four different combinations of unbonded tendons, unbonded fuse–bars and mechanical energy dissipators were tested using Wall 2. The experimental results showed that Wall 2 performed better than Wall 1 under different load paths without any damage and residual drift. The stiffness of the wall is significantly influenced by the level of initial prestressing, location and cross–sectional area of energy dissipators and unbonded tendons. Fuse–bar with 50% initial prestressing force is recommended because it works efficiently under reverse cyclic loading whereby buckling and plastic hinge zone can be prevented.

Key words: In–plane loading, biaxial loading, damage, cyclic loading, plastic hinge zone
Catalytic Ozonation Of 2–Hydroxy–1,2,3–Propanetricarboxylic Acid
Authors: Ngadi Norzita , Amin Nor Aishah Saidina , Khew Shih Tak , Lai Siok Lian
Published: January 2013

mole ratio of 80. In overall, VZSM5 catalyst could promote the ozonation process better than CuZSM5 and MnZSM5. The results also show that ozone gas with smaller bubble size gave better performance.
Dielectric Behaviour Of BaTiO3 Prepared By Sol–Gel Technique When Exposed To Different Oxygen Concentrations
Authors: Yeoh Cheow Keat , Sreekantan Srimala , Hutagalung Sabar Derita , Ahmad Zainal Arifin
Published: January 2013

Sifat dielektrik serbuk BaTiO3 yang disediakan melalui kaedah akues pada suhu rendah telah dikaji menggunakan kaedah spektroskopi impedans apabila didedahkan terhadap tahap oksigen yang berbeza. Untuk mengatasi masalah kebolehlarutan Ba dan Ti yang berbeza, nisbah sebatian Ba yang ditambah lebih tinggi daripada nisbah stoikiometri (tambahan 10%) dan nilai pH larutan yang tinggi (pH~13) diperlukan. Ujian XRD dan TGDTA menunjukkan BaTiO3 yang hampir tulen dapat disintesis melalui kaedah ini. Suhu pengkalsinan yang lebih tinggi menghasilkan darjah penghabluran bahan yang lebih tinggi. Kajian dielektrik menunjukkan bahan yang dihasilkan mengandungi lebih daripada satu elemen keelektrikan antaranya teras berkerintangan rendah, sempadan butiran berkapasitan tinggi dan suatu elemen pukal feroelektrik. Setelah didedahkan terhadap tahap oksigen yang lebih tinggi, nilai kerintangan sampel bertambah, yang mungkin disebabkan stoikiometri oksigen pada sampel yang diuji. Peningkatan dalam nilai kapasitan daripada sempadan butiran adalah lebih ketara jika dibandingkan dengan peningkatan unsur feroelektrik pukal.

Kata kunci: Kaedah sol-gel, sintesis kimia, sifat dielektrik, BaTiO3

The dielectric properties of BaTiO3 powders prepared by a low temperature aqueous route when exposed to different oxygen concentrations have been studied by means of impedance spectroscopy. Due to the differences of solubility of Ba and Ti in aqueous solutions, deviations from stoichiometric ratios (a 10% excess) and higher solution pH (pH~13) were necessary. XRD traces and TG-DTA curves show the formation of nearly phase-pure BaTiO3 with higher calcinations temperatures promoting greater crystallinities. Dielectric measurements using impedance spectroscopy show the samples to consist of more than one electrical element including a low resistivity core, a high capacitance grain boundary and a ferroelectric bulk component. Exposing the samples to different oxygen concentrations caused a slight increase in resistivities with increasing oxygen concentration, which was attributed to the oxygen stoichiometry. A greater increase in the capacitance of the grain boundary component was also observed compared to the ferroelectric bulk.

Key words: Sol-gel processes, chemical processes, dielectric properties, BaTiO3
Statistical Approach on Grading the Student Achievement via Normal Mixture Modeling
Authors: Md. Desa Zairul Nor Deana , Mohamad Ismail , Mohd. Khalid Zarina , Md. Zin Hanafiah
Published: January 2013

Kajian dijalankan untuk membanding keputusan yang didapati daripada tiga kaedah penggredan terhadap pencapaian pelajar. Kaedah konvensional yang popular adalah kaedah Skala Tegak. Pendekatan statistik yang menggunakan kaedah Sisihan Piawai dan kaedah Bayesian bersyarat dipertimbangkan untuk memberi gred. Dalam model Bayesian, dianggapkan bahawa data adalah mengikut taburan Normal Tergabung di mana setiap gred adalah dipisahkan secara berasingan oleh parameter; min dan kadar bandingan dari taburan Normal Tergabung. Masalah yang timbul adalah sukar untuk menganggarkan ketumpatan posterior bagi parameter tersebut secara analitik. Satu penyelesaiannya adalah dengan menggunakan pendekatan Markov Chain Monte Carlo iaitu melalui algoritma pensampelan Gibbs. Kaedah Skala Tegak, kaedah Sisihan Piawai dan kaedah Bayesian bersyarat diaplikasikan untuk markah mentah peperiksaan bagi dua kumpulan pelajar. Pencapaian ketiga–tiga kaedah dibandingkan melalui nilai Kehilangan Kelas Neutral, Kehilangan Kelas Tidak Tegas dan Pekali Penentuan. Didapati keputusan dari kaedah Bayesian bersyarat menunjukkan penggredan yang lebih baik berbanding kaedah Skala Tegak dan kaedah Sisihan Piawai.

Kata kunci: Kaedah penggredan, pengukuran pendidikan, Skala Tegak, kaedah Sisihan Piawai, Normal Tergabung, Markov Chain Monte Carlo, pensampelan Gibbs

The purpose of this study is to compare results obtained from three methods of assigning letter grades to students’ achievement. The conventional and the most popular method to assign grades is the Straight Scale method (SS). Statistical approaches which used the Standard Deviation (GC) and conditional Bayesian methods are considered to assign the grades. In the conditional Bayesian model, we assume the data to follow the Normal Mixture distribution where the grades are distinctively separated by the parameters: means and proportions of the Normal Mixture distribution. The problem lies in estimating the posterior density of the parameters which is analytically intractable. A solution to this problem is using the Markov Chain Monte Carlo approach namely Gibbs sampler algorithm. The Straight Scale, Standard Deviation and Conditional Bayesian methods are applied to the examination raw scores of two sets of students. The performances of these methods are measured using the Neutral Class Loss, Lenient Class Loss and Coefficient of Determination. The results showed that Conditional Bayesian outperformed the Conventional Methods of assigning grades.

Key words: Grading methods, educational measurement, Straight Scale, Standard Deviation method, Normal Mixture, Markov Chain Monte Carlo, Gibbs sampling
Adaptive Spatial Mode Of Space–Time And Spacefrequency OFDM System Over Fading Channels
Authors: Noordin Nor K. , Ali Borhanuddin M. , Jamuar S. S. , Rahman Tharek A. , Ismail Mahamod
Published: January 2013

Dalam kertas kerja ini kami membentangkan skema mod ruang (ASM) adaptif 2 menghantar 1 menerima (2 Tx : 1 Rx) menggunakan kaedah ruang–masa (ST) dan ruang frekuensi (SF) multiplekskan pembahagian frekuensi ortogonal (OFDM). Pada nilai nisbah isyarat ke hingar yang rendah kami menggunakan ST–OFDM dan menukar kepada mod SF–OFDM pada nilai ambang yang telah ditentukan. Nilai ini ditentukan berdasarkan titik silang antara lengkuk prestasi kedua–dua mod. Keputusan simulasi menunjukkan gandaan banyak 9 dB (pada kadar ralat bit 10–3) diperolehi dengan menggunakan mod ruang adaptif (ASM) berbanding dengan ST–OFDM tanpa kod, lebih kurang 6 dB berbanding SF–OFDM, 4 dB berbanding ST–OFDM terkod dan gandaan sebanyak 2 dB berbanding SF–OFDM terkod, pada rebak lengah 700 ns.

Kata kunci: OFDM, ruang–masa, ruang–frekuensi, pengekodan saluran dan saluran pemudaran berbilang laluan

In this paper we present a 2 transmit 1 receive (1 Tx : 1 Rx) adaptive spatial mode (ASM) of space–time (ST) and space–frequency (SF) orthogonal frequency division multiplexing (OFDM). At low signal to noise ratio (SNR) we employ ST–OFDM and switch to SF–OFDM at a certain SNR threshold. We determine this threshold from the intersection of individual performance curves. Results show a gain of 9 dB (at a bit error rate of 10–3) is achieved by employing adaptive spatial mode compared to a fixed ST–OFDM, almost 6 dB to fixed SF–OFDM, 4 dB to Coded ST–OFDM and 2 dB to a fixed coded SF–OFDM, at a delay spread of 700 ns.

Key words: OFDM, space–time, space–frequency, channel coding and multipath fading channels