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PERFORMANCE OF HIGH STRENGTH LIGHTWEIGHT CONCRETE USING PALM WASTES
Get PDFThe performance of high strength structural lightweight concrete (LWC) using the palm wastes, oil palm shell (OPS) as well as palm oil clinker (POC) has been reported. Existing literatures used either OPS or POC individually for production of LWC. Each concept has their own advantages-disadvantages. In this study, both OPS and POC have been put together as coarse aggregate on the way to see the improvement of mechanical properties of waste based LWC. To achieve this purpose, regular coarse aggregate has been fully replaced by OPS and POC in the concrete. This structural grade lightweight concrete is named as palm shell and clinker concrete (PSCC). Attempts have been made with the series of OPS and POC mixture aimed at identifying for better performance. The quantity of OPS and POC mix has been varied as 30%, 40%, 50%, 60% and 70%. Mechanical properties of PSCC like density, workability, compressive strength at different ages, flexural strength, splitting tensile strength as well as modulus of elasticity have been evaluated. It is revealed that the proposed PSCC has extensive potential in terms of high compressive strength and good material behavior to perform as a better LWC. The study could offer structural lightweight concrete of compressive strength up to 46 MPa that is 31% higher than the control mix. The usage of 50% OPS to 50% POC coarse aggregate by vol. in the concrete mix is found to be the optimum mix. Furthermore, simple correlations have been developed which can easily predict compressive strength, splitting tensile strength, flexural strength, modulus of elasticity and ultrasonic pulse velocity of lightweight concrete
ON THE CONTROL OF THE HEAT CONDUCTION
No full textMathematical models of thermo control processes in a rectangular plate are considered. In the model under consideration, the temperature inside a plate is controlled by heat exchange through one boundary while the other three are insulated. The control parameter is a function that satisfies certain integral equations. Sufficient conditions for achieving the given projection of the temperature at a fixed point on the plate and given average temperature are studied. ABSTRAK: Model matematik bagi proses kawalan suhu dalam bekas segi empat tepat telah dipilih. Melalui model ini, suhu bekas dikawal dengan menukar haba melalui salah satu sisi bekas, manakala tiga sisi lain telah ditebat. Parameter kawalan ini ialah fungsi, di mana ia sesuai dengan persamaan sesetengah integral. Keadaan sesuai bagi mencapai suhu tetap bekas seperti cadangan dan suhu purata yang diberikan turut dikaji
AMORPHOUS STRUCTURE IN CU-ZN-V-AL OXIDE COMPOSITE CATALYST FOR METHANOL REFORMING
Get PDFCu-Zn-V-Al oxide composite catalysts were prepared using a co-precipitation method to investigate hydrogen and carbon monoxide yield of a methanol reforming reaction. The mass compositions of metals were initially determined on the Simplex Centroid statistical design. The effects of various metal compositions on the physicochemical properties of the catalyst were studied via X-ray diffractogram (XRD), temperature-programmed reduction (TPR) analyses, and reaction. XRD revealed crystals in the samples. Crystalline CuO in Cu30V30Al40 formed with the addition of zinc oxide at the metal loading below 30 wt%. A combination of zinc oxide and vanadia, however, had no Zn-V complex crystal but its scanning electron microscopy image showed the formation of string structures (AS). The catalyst that contained the AS exhibited a broad hydrogen reduction peak in the TPR analysis. Vanadium at a loading below 40 wt% with various zinc and cuprum compositions also formed small ASs and exhibited single TPR peaks. A reaction yield study revealed the optimum compositions of metal oxides when the data was fitted by response surface plots. The catalysts with high content of AS were not at the peaks however. Cu-Zn based catalysts showed the highest hydrogen yield for the reaction temperature of between 150 oC to 225 oC and vanadia-promoted catalyst with AS only appeared to be the optimum catalyst at the higher temperature. ABSTRAK: Mangkin komposit oksida Cu-Zn-V-Al disediakan menggunakan kaedah pemendakan bersama untuk mengkaji hasil hidrogen dan karbon monoksida daripada tindak balas pembentukan semula metanol. Komposisi jisim logam-logam dikenal pasti terlebih dahulu menggunakan reka bentuk statistik Simplex Centroid. Pelbagai kesan komposisi logam terhadap sifat-sifat mangkin kimia-fizikal dikaji menerusi analisis-analisis pembelauan sinar-X (XRD) dan program penurunan suhu teratur (TPR), dan tindak balas kimia. Hasil analisis XRD menzahirkan kristal pada sampel-sampel. Hablur CuO terbentuk dalam Cu30V30Al40 dengan penambahan zink oksida pada muatan logam kurang daripada 30% berat. Gabungan zink oksida dan vanadia walau bagaimanapun tidak menghasilkan hablur kompleks Zn-V, namun imbasan imej mikroskop elektron menunjukkan pembentukan struktur tetali (AS). Mangkin yang mengandungi AS menunjukkan penurunan puncak hidrogen yang lebar dalam analisis TPR. Vanadium pada muatan berat logam kurang daripada 40% berbanding komposisi zink dan kuprum juga membentuk AS kecil dan menghasilkan puncak-puncak TPR tunggal. Hasil tindak balas kajian menunjukkan komposisi optimum oksida logam apabila data ujikaji dipadankan dengan menggunakan plot permukaan respon. Mangkin yang mempunyai kandungan AS tertinggi bagaimanapun tidak berada pada puncak. Mangkin berasaskan Cu-Zn menunjukkan hasil hidrogen tertinggi bagi suhu tindak balas antara 150 oC hingga 225 oC dan mangkin yang ditambah vanadia bersama AS pula muncul sebagai mangkin optimum pada suhu lebih tinggi
COMBINING FUSED DEPOSITION MODELLING WITH ABRASIVE MILLING TO ATTAIN HIGHER DIMENSIONAL ACCURACY AND BETTER SURFACE FINISH ON THE FINISHED PRODUCT
No full textABSTRACT: Currently, two manufacturing methods, namely CNC (Computer Numerical Control) machining and rapid prototyping (RP), are widely used to produce final products and prototypes. Both the processes have their own advantages. CNC machining such as milling and grinding (subtractive method) can fabricate parts with higher precision and accuracy. On the other hand, RP (additive method), can manufacture parts with complicated 3-D (three dimensional) features, which ensures effective material usage. However, RP produced parts lack accuracy and smooth surface finish. In this research, we are aiming to achieve on-machine mechanical post-processing of 3-D printed (using Fused Deposition Modelling, a kind of RP process) parts to achieve higher dimensional accuracy and better surface roughness. To achieve the goal, we developed a new hybrid system to assimilate both of these processes. There are, however, two vital considerations needed to be taken into account for integrating the two processes. The first concern is the integration of dissimilar control systems for two processes and the second aspect is maintaining the tools’ (milling spindle and the heat extruder) setup accuracy during the changeover step. The developed hybrid machine has been tested with experimentations and the result showed that the dimensional accuracy was improved by 71% to 99% when the FDM part was compared with the final part after abrasive milling operation. At the same time, average surface roughness (Ra) was improved up to 91.3%. Further, we found that low layer thickness improves the product quality. The proposed system could push the conventional FDM system to the next level to attain better quality of final products.
ABSTRAK: Dua kaedah terkini proses pembuatan, dinamakan mesin Kawalan Komputer Bernombor (CNC) dan prototaip langsung (RP) telah digunakan secara meluas bagi menghasilkan produk dan prototaip. Kedua-dua proses mempunyai keistimewaan tersendiri. Mesin CNC seperti mesin penghasil permukaan dan mesin penebuk lubang (melalui kaedah pengurangan) dapat menghasilkan sesuatu bahagian dengan ketepatan tinggi. Pada sudut lain, RP (melalui kaedah penambahan), dapat menghasilkan bahagian dengan kaedah 3D (tiga dimensi) yang rumit tetapi berkesan dalam memaksimakan penggunaan material. Walau bagaimanapun, penghasilan bahagian melalui kaedah RP mempunyai kekurangan pada ketepatan dan kekurangan pada kekemasan permukaan akhir. Kajian ini bertujuan meraih ketepatan dimensi yang lebih tinggi dan kekemasan permukaan yang lebih bagus pada proses terakhir pada bahagian cetakan mesin mekanikal 3D (menggunakan Model Deposit Fuse iaitu salah satu proses RP). Bagi mencapai tujuan ini, kami menghasilkan sistem hibrid terbaru untuk mengasimulasi kedua-dua proses. Walau bagaimanapun, terdapat dua perkara penting perlu diambil kira untuk diintegrasi bersama kedua-dua proses. Penilaian pertama adalah pada sistem kawalan tidak serupa, dan kedua pada aspek pengekalan alat (gelendung pemutar dan kepanasan pembentuk) ketepatan penyediaan semasa peringkat perubahan. Mesin hibrid yang dicipta telah diuji melalui eksperimentasi dan keputusan menunjukkan ketepatan dimensi telah bertambah daripada 71% kepada 99% semasa bahagian FDM dibandingkan dengan bahagian akhir selepas operasi putaran kasar. Pada masa sama, purata permukaan kasar (Ra) telah bertambah kepada 91.3%. Kami juga mendapati ketebalan lapisan bawah telah menambah baik kualiti produk. Sistem yang dicadangkan dapat mengubah sistem FDM konvensional kepada peringkat lebih tinggi bagi memperolehi kualiti terbaik pada produk akhir
WIDE RANGE MODULATION INDEXES FEATURED CARRIER-BASED PWM STEPPED WAVEFORM FOR HALF-BRIDGE MODULAR MULTILEVEL CONVERTERS
Get PDFABSTRACT: This paper presents simulation results of the influence of wide range modulation index values ( ) in carrier-based PWM strategy for application in generating the stepped waveform. The waveform is tested for application in single-phase half-bridge modular multilevel converters (MMCs) topology. The results presented in this paper include a variation of the fundamental component (50 Hz) in the voltage output. It also studies total harmonic distortion of the output voltage (THDv) and the output current (THDi) when the modulation index is changed over the linear-modulation region, 0 < < 1. It also explores the effect of a modulation index greater than 1. Moreover, different output voltage shapes, as a consequence of varied on MMCs, are also illustrated for showing the effect of varying the value of on sub-module of MMCs.
ABSTRAK: Kajian ini berkenaan tentang pengaruh simulasi terhadap pelbagai nilai indeks ( ) berasaskan strategi PWM bagi menghasilkan bentuk gelombang bertingkat. Bentuk gelombang ini diuji untuk aplikasi topologi MMCs. Keputusan menunjukkan variasi pada komponen asas (50Hz) pada voltan akhir. Keputusan menunjukkan jumlah penyelarasan harmonik voltan akhir (THDv) dan arus (THDv) apabila indeks modulasi telah ditukar pada had modulasi linear, 0 < < 1. Ia juga membincangkan tentang kesan indeks modulasi lebih daripada 1. Selain itu, bentuk voltan akhir yang berbeza mengikut perubahan nilai pada MMCs juga dilampirkan bagi menunjukkan kesan perbezaan nilai pada sub-modul MMCs
EFFECT OF ALKALINE TREATMENT ON PROPERTIES OF RATTAN WASTE AND FABRICATED BINDERLESS PARTICLEBOARD
Get PDFBinderless particleboard (BPB) has become an alternative to avoiding the usage of synthetic resin, possessing excellent properties but having low dimensional stability characteristics. Hence, this study aims to investigate the effects of alkaline treatment on properties of rattan furniture waste (RFW) and fabricated BPB. The RFW was fully immersed in a 1% sodium hydroxide (NaOH) solution for 10 minutes and dried in an oven at 35°C for two days. Then, the treated RFW was used to fabricate the BPB via a hot-pressing process at pressing parameters of 180°C and 5 minutes. The colour of the RFW changed to dark yellowish and chemical analysis showed some reduction in hemicellulose, lignin and ash content after the alkaline treatment, which have been confirmed through peak decline in Fourier Transform Infrared Spectroscopy (FTIR). Only cellulose content increased after treatment due to a disruption of hydrogen bonding on the fibre surface. The treated BPB panels had improved mechanical and dimensional stability compared to untreated BPB panels, and achieved the minimum requirement of board standards. Removal of the fibres’ impurities, led to tremendous physical consolidation among fibres. The nature of the panels changed from hydrophilic to hydrophobic as water molecules were released from the fibres during the treatment process. These results were supported by Scanning Electron Microscopy (SEM) analysis that displayed cleaner RFW fibres and rougher surfaces on the treated BPB panels. ABSTRAK: Papan partikel tanpa pelekat (papan BPB) menjadi salah satu alternatif bagi menggelak penggunaan pelekat sintetik, ianya mempunyai sifat-sifat terbaik walaupun keseimbangan dimensi papan masih berada pada tahap rendah. Oleh itu, tujuan kajian ini dijalankan adalah bagi menyelidik kesan rawatan alkali ke atas sifat sisa perabot rotan dan papan BPB yang dihasilkan. Sisa perabot rotan direndam penuh ke dalam cecair alkali Natrium Hidroksida (NaOH) berkepekatan 1%, selama 10 minit dan sesudah itu dikeringkan di dalam ketuhar pada suhu 35°C selama dua hari. Kemudian, sisa perabot rotan yang telah dirawat ini digunakan bagi menghasilkan papan BPB melalui kaedah tekanan haba pada suhu tekanan 180°C selama 5 minit. Warna sisa perabot rotan telah berubah kepada kuning gelap, dan hasil analisa kimia menunjukkan pengurangan pada hemi-selulosa, lignin dan komposisi abu dalam serat rotan selepas rawatan alkali dan terbukti melalui pengurangan nilai puncak pada analisa Fourier Transform Infrared Spectroscopy (FTIR). Hanya kandungan selulosa meningkat selepas rawatan alkali, disebabkan gangguan pada ikatan hidrogen pada permukaan serat. Papan BPB yang terhasil menggunakan serat dirawat telah menunjukkan peningkatan pada sifat mekanikal dan keseimbangan dimensi papan, serta mencapai piawaian minima papan, berbanding dengan papan BPB yang terhasil menggunakan serat tidak dirawat. Hal ini disebabkan pembuangan kotoran serat menghasilkan penyatuan fizikal yang sangat baik antara serat. Sifat semulajadi pada papan BPB juga telah bertukar dari hidrofilik kepada hidrofobik, kerana molekul-molekul air dilepaskan dari serat semasa rawatan alkali. Keputusan ini disokong melalui analisa Mikroskop Pengimbas Elektron (SEM) yang menunjukkan permukaan serat rotan RFW lebih jelas dan permukaan papan BPB yang lebih kasar
An analytical technique to obtain higher-order approximate periods for nonlinear oscillator
Get PDFABSTRACT: This paper presents simulation results of the influence of wide range modulation index values ( ) in carrier-based PWM strategy for application in generating the stepped waveform. The waveform is tested for application in single-phase half-bridge modular multilevel converters (MMCs) topology. The results presented in this paper include a variation of the fundamental component (50 Hz) in the voltage output. It also studies total harmonic distortion of the output voltage (THDv) and the output current (THDi) when the modulation index is changed over the linear-modulation region, 0 < < 1. It also explores the effect of a modulation index greater than 1. Moreover, different output voltage shapes, as a consequence of varied on MMCs, are also illustrated for showing the effect of varying the value of on sub-module of MMCs.
ABSTRAK: Penulisan ini berkenan simulasi pengaruh pelbagai nilai indeks modulasi ( ) dalam strategi PWM berasaskan aplikasi dalam menghasilkan bentuk gelombang yang bertingkat. Bentuk gelombang ini diuji untuk aplikasi dalam topologi MMCs. Penilaian dan hasil dari artikle ini termasuk variasi komponen asas (50 Hz) dalam voltan keluar. Ia juga meneliti jumlah penyelarasan harmonik voltan keluar (THDv) dan arus keluaran (THDi) apabila indeks modulasi ditukar dalam rantau modulasi linear, 0 < <1. Ia juga meneroka kesan indeks modulasi lebih daripada 1. Selain itu, bentuk voltan keluar yang berbeza sebagai akibat dari pelbagai pada MMCs juga digambarkan untuk menunjukkan kesan berbeza-beza nilai pada sub-modul MMCs
INVESTIGATION ON NEED FOR SPECIFIC PROPAGATION MODEL FOR SPECIFIC ENVIRONMENT BASED ON DIFFERENT TERRAIN CHARACTERISTICS
Get PDFABSTRACT: Owing to their speed of excution as well as their limited reliance on detailed knowledge of the terrain characteristics of the service environments, empirical propagation models have enjoyed general acceptability in the wireless communication research community. However, recent industrial observations show that no single propagation model can best fit all the radio service environments, which led to the hypothesis of specific models for specific environments. In order to scientifically verify this hypothesis, the study presented in this paper investigated the performance of the free space propagation loss (FSPL) model in two different radio environments characterised with different types of obstructions. The investigation was conducted through field strength distribution measurement of two broadcasting radio stations transmitting at 96.5 MHz and 102.3 MHz. The field strength measurement data obtained were analysed. The result of the analysis shows gross disparity between the measured path losses and calculated path losses using FSPL model. The disparity thus necessitates the modification of the FSPL model in order to develop each propagation model for each of the two radio stations employed and their environment. The developed models were then evaluated to ascertain their performances relative to the FSPL model. The performance evaluation results show that the predictions of the developed propagation models vary for each of the two environments. Furthermore, the comparative performance evaluation result of the developed models with similar studies in the literature shows that the developed models perform favourably. The overall result from the developed models confirms the hypothesis that each location requires a specific propagation model for proper radio wave design and quality of signal transmission and reception.
ABSTRAK: Kelebihan yang ada pada kelajuan perlaksanaannya dan juga kurang pergantungannya pada butiran terperinci ciri-ciri khusus bentuk rupa bumi di persekitaran servisnya, model penyebaran empirik telah diterima umum dalam komuniti kajian komunikasi tanpa wayar. Walau bagaimanapun, pemerhatian industri terkini menunjukkan tidak ada sebarang model penyebaran yang sesuai bagi semua keadaan servis radio, ini menghala kepada hipotesis keperluan model tertentu pada keadaan servis tertentu. Bagi menentusahkan secara saintifik hipotesis ini, kajian yang dibentangkan dalam kertas ini mengkaji tentang prestasi model kehilangan penyebaran pada ruang bebas (FSPL) dalam dua persekitaran radio berlainan melalui beberapa jenis halangan berbeza. Kajian telah dijalankan ke atas dua stesen radio penyiaran pada frekuensi 96.5 MHz dan 102.3 MHz melalui ukuran sebaran ruang keupayaan. Data ukuran ruang keupayaan telah diperoleh dan dianalisa. Keputusan analisis menunjukkan keputusan tidak seragam yang melampau antara ukuran kehilangan laluan dan pada kiraan model FSPL. Ketidaksamaan ini memungkinkan keperluan mengubah model FSPL bagi membangunkan model penyebaran pada setiap dua radio stesen yang digunakan dan persekitarannya. Model yang dibangunkan ini kemudiannya dinilai bagi mengesahkan prestasinya dengan model FSPL. Keputusan penilaian menunjukkan perbezaan pada jangkaan model penyebaran bagi setiap dua keadaan. Tambahan, keputusan perbandingan model yang dibangunkan dalam karya ini adalah serupa seperti kajian lain yang berkaitan. Secara keseluruhannya model yang dibangunkan ini mengesahkan hipotesis bahawa setiap lokasi memerlukan model penyebaran bagi rekaan gelombang radio yang sesuai dan juga kualiti signal penyebaran dan penerimaan
A PARAMETRIC STUDY ON CONTROL OF FLOW SEPARATION OVER AN AIRFOIL IN INCOMPRESSIBLE REGIME
Get PDFThis paper presents the effects of airfoil geometry on flow separation behavior and obtains the transition patterns at a specific angle of attack. A strong adverse pressure gradient field is observed at the leading edge of the airfoil, and it results in a flow detachment. Leading edge flow separation is studied along with the variation of skin friction coefficient over the airfoil. Novelty in the approach is the development of a hybrid control scheme to delay the flow separation with blowing/suction of air (termed active control) over the airfoil together with the tapping of flow from the pressure side as in a classical passive control procedure. The active controller delays the flow separation, while the passive controller is used to reduce the drag coefficient significantly and increases the total performance of an airfoil. The effectiveness of these controls is examined by varying the control parameters including blowing/suction velocity, the position of the slot in terms of percentage of chord and size of the slot. All the numerical simulations are carried out using ANSYS-Fluent software. A surrogate model is also developed to predict the aerodynamic characteristics conveniently without much computational effort. The outcome of this study reveals that the blowing/suction velocity has a higher influence in delaying the flow separation. ABSTRAK: Kertas ini membentangkan tentang kesan geometri aerofoil pada perubahan pemisah aliran udara dan memperoleh bentuk peralihan pada darjah yang tepat. Terdapat tekanan kuat yang tidak sesuai pada kawasan kecerunan di hujung hadapan permukaan aerofoil, dan ini menyebabkan aliran udara terpisah. Pemisah aliran udara pada hujung hadapan ini dikaji bersama koefisien geseran pada permukaan aerofoil. Pendekatan baru pada kaedah ini adalah berkaitan pembangunan skim kawalan hibrid bagi melengahkan aliran pemisah udara melalui tiupan/sedutan udara (kawalan aktif) ke atas aerofoil bersama ketukan pada aliran dari tepi tekanan seperti mana prosedur klasik kawalan pasif. Kawalan aktif ini melengahkan aliran pemisah udara, sebaliknya kawalan pasif telah digunakan bagi mengurangkan koefisien penangguhan dengan ketara dan menambahkan jumlah prestasi aerofoil. Keberhasilan kawalan-kawalan ini dikaji dengan mengubah parameter kawalan termasuk kelajuan tiupan/sedutan udara, posisi slot berdasarkan peratusan garis temu dan saiz slot. Semua simulasi-simulasi numerikal ini dijalankan menggunakan perisian Ansys-Fluent. Model pengganti turut dibangunkan untuk menjangka ciri-ciri aero-dinamik dengan mudah tanpa usaha pengiraan yang banyak. Keputusan kajian ini mendedahkan tentang kelajuan tiupan/sedutan udara berpengaruh besar dalam melambatkan pemisahan aliran udara
GREEN SYNTHESIS OF SILVER NANOPARTICLES USING SAGO (METROXYLON SAGU) VIA AUTOCLAVING METHOD
Get PDFSago (metroxylon sagu) is a polysaccharide bio resource, which is biodegradable and low in toxicity that can be found in large scale in Mukah, Sarawak. A simple green method of synthesizing silver nanoparticles (AgNPs) has been developed using sago dissolved in water as the reducing agent. The mixture of dissolved sago and silver nitrate (AgNO3) were autoclaved at 121 °C for 20 minutes. The size, morphology and structures of the AgNPs formed in the sago solution were investigated through UV-Vis spectrophotemeter, XRD and FESEM analysis. The synthesized AgNPs were spherical in shape and well distributed with average particle sizes of 19.3 ± 2.7 nm.ABSTRAK: Sago (Pokok Rumbia) adalah sumber bio polisakarida yang bioterurai dan rendah ketoksikan yang boleh didapati dalam skala yang besar di Mukah, Sarawak. Satu kaedah hijau yang mudah untuk mensintesis nanopartikel perak telah dihasilkan dengan menggunakan sagu yang larut dalam air sebagai ejen penurunan. Campuran sagu yang dilarutkan dan perak nitrat (AgNO3) telah autoklaf pada suhu 121°C selama 20 minit. Saiz, morfologi dan struktur nanopartikel perak yang terhasil di dalam larutan sago telah disiasat melalui analisis spektrofotometer UV-Vis, XRD dan FESEM. Nanopartikel perak yang dihasilkan adalah berbentuk bulat dengan purata saiz partikel 19.3 ± 2.7 nm