Physics, Engineering and Material Science

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Mechanical performance of carbon fibre reinforced vinyl ester composite plate bonded concrete exposed to tropical climate
(Universiti Teknologi Malaysia, 2007) Abu Hassan, Shukur
Most of the past and recent short-term and long-term experimental studies on Fibre Reinforced Polymer (FRP) plate or laminate system bonded to reinforced concrete members have shown an improvement in terms of mechanical performances but the findings on the bond durability characteristics are still in doubt. This study programme focused on the mechanical performances of Carbon Fibre Reinforced Polymer (i.e. CFRP with vinyl ester matrix) composite plate bonded to concrete exposed to tropical climate conditions. In this programme the test samples were divided into three groups, namely; CFRP plate, epoxy adhesive and CFRP plate bonded to concrete (stressed and unstressed). The specimens were experimented to designated exposure conditions for six months, namely; laboratory (LB), outdoor (OD), plain water (PW-wet/dry cycles) and salt water (SW wet/dry cycles). After exposure, the groups of CFRP plate and epoxy adhesive were loaded in tensile and shear while the group of CFRP plate bonded to concrete was loaded to failure under tension-compression loads. The performance of the exposed specimens was then compared with that of similar control specimens in terms of strength and modulus for CFRP plate and epoxy, respectively. In addition, the load carrying capacity, bond slips, local force and bond stress distribution for CFRP plate bonded to concrete were studied. The results of the study had indicated that exposure to tropical climate had reduced the strength properties of CFRP plate by nearly 10% for those exposed to plain and salt water, while in contrast to that, those specimens exposed to outdoor showed an increment of strength of up to 5% compared to the control group. Meanwhile, the elasticity of CFRP plate was significantly affected by exposure to salt water, i.e. 15% reduction compared to the control ones. It was also found that all the exposure conditions had reduced the epoxy shear strength by nearly 32%, with the exposure to plain water being the most aggressive. On the other hand, the exposure conditions had also affected the epoxy shear modulus by up to 25%, where the most reduction was shown by specimens exposed to plain water. Finally, it can be said that the tropical climate conditions had significantly influenced the mechanical bond performances of the bonded specimens. This could be seen for those specimens that had been exposed to outdoor condition which experienced debonding at load level about 30% of the ultimate load compared to about 50 to 60% load level for those exposed to the other three exposure conditions. It was also found, that all exposure conditions produced non-linear bond slips at specimens’ most stressed end which could be related to the influences of moisture ingression on bond interfaces that weaken the bond performances
Dynamic Time Warping fixed - frame coefficient with pitch feature for speech recognition system with neural network
(University Technology Malaysia, 2007) Sudirman, Rubita
Automatic Speech Recognition products are already available in the market since many years ago. Intensive research and development still continue for further improvement of speech technology. Among typical methods that have been applied to speech technology are Hidden Markov Model (HMM), Dynamic Time Warping (DTW), and Neural Network (NN). However previous research relied heavily on the HMM without paying much attention to Neural Network (NN). In this research, NN with back-propagation algorithm is used to perform the recognition, with inputs derived from Linear Predictive Coefficient (LPC) and pitch feature. It is known that back-propagation NN is capable of handling large learning problems and is a very promising method due to its ability to train data and classify them. NN has not been fully employed as a successful speech recognition engine since it requires a normalized input length. The nonlinear time normalization based on DTW is identified as the suitable tool to overcome time variation problem by expanding or compressing the speech to a desired number of data. The proposed DTW frame fixing (DTW-FF) algorithm is an extended DTW algorithm to reduce the number of inputs into the NN. This method had reduced the amount of computation and network complexity by reducing the number of inputs by 90%. Therefore a faster recognition is achieved. Recognition using DTW showed the same results when LPC or DTW-FF feature were used. This indicates no loss of information occurred during data manipulation. Pitch estimate is another feature introduced to the NN that has helped to increase recognition accuracy. An average of 10.32% improvement is recorded when pitch is added to DTW-FF feature as input to back-propagation NN using Malay digits samples. The back-propagation algorithm was then designed with both the Quasi Newton and Conjugate Gradient methods. This is to compare which method is able to achieve optimal global minimum. Results showed that Conjugate Gradient performed better.
Development of aerobic granular sludge technology for domestic wastewater treatment in hot climates
(Universiti Teknologi Malaysia, 2008) Nor Anuar, Aznah
Conventional domestic wastewater treatment plants based on activated sludge technology require large footprint (big settling tank) due to the relatively slow settling characteristics of sludge flocs. Aerobic Granular Sludge (AGS) technology offers a possibility to design a compact system based on simultaneous organic and nutrient removal and because of the good settling characteristics of the AGS, the use of a big settling tank is not necessary. Therefore, the installation can be more compact, at a cheaper cost. The aim of this study was to develop AGS system for domestic wastewater treatment applications in hot climate conditions. Special emphasis is given to the settling characteristics and physical strength of the AGS. Therefore, a 3-litre laboratory-scale reactor known as Cyclic Aerobic Granular Sludge Bioreactor (CAgSBio) was designed and used. The operation of the reactor was based on the Sequencing Batch Reactor (SBR) system with a complete cycle operation of three (3) hours and specifically designed to be operated for twenty-four (24) hours continuously at temperature of 30°C. A 3-litre laboratory-scale reactor in Delft University of Technology (TU Delft), the Netherlands operated at 20°C was also used to compare the results on AGS granulation and performance. AGS developed at this low temperature and from a 1.4 m3-pilot plant at Ede Wastewater Treatment Plant, the Netherlands (fed with pre-treated domestic wastewater) were also used for a physical strength study, to compare with AGS at 30°C. All analytical measurements performed in this study were conducted according to Standard Methods for the Examination of Water and Wastewater (APHA, 2005). The study shows that after ninety (90) days of operation, stable AGS (fed with synthetic wastewater) with average size of 1.1 mm were formed at 30°C. To demonstrate the simultaneous organic and nutrient removal by AGS, a removal study was also conducted. CAgSBio system showed stable removal performance. Average removal efficiencies during steady state cycles at 30°C of organic carbon, total inorganic nitrogen and phosphorus reached 100%, 94% and almost 98% respectively. A study with actual wastewater (pre-treated domestic wastewater) at 30°C indicates that the granulation process does occur but at a slower rate (125 days is essential to develop mature granules) compared to synthetic influent (90 days). Meanwhile, AGS settling behaviour study shows that AGS settled relatively fast (velocities >12 mh-1 for size > 0.2 mm) compared to other conventional sludge flocs. The study also indicates that excessive mixing is not favourable for AGS reactors. Thus, the mixing criteria for AGS reactors was developed based on results obtained through experiments under mechanical and aerated-mixing conditions. Finally, a procedure was developed to evaluate the AGS strength based on the stability of AGS against shear stress. Determination of a stability coefficient (S) was introduced as an indicator of AGS strength. The results shows that AGS at 20°C and 30°C, fed with synthetic wastewater are very stable. For AGS fed with pre-treated domestic wastewater, the AGS at 30°C (produced using the laboratory-scale reactor) is more stable than the AGS at 20°C (produced using the pilot plant). As a conclusion, stable and compact AGS can be developed and performed effectively in hot climate conditions for domestic wastewater treatment applications, particularly as an alternative technology which is compact, high speed operation process (≈3 hours complete cycle) and more efficient
The effectiveness of various structural system in reducing tall building response due to wind
(Universiti Teknologi Malaysia, 2008) Abd. Samat, Roslida
Recently, many tall building structural systems have been innovated in order to reduce the building responses due to wind loading. However, there are no systematic study conducted on the effectiveness of the different tall building systems in minimizing the responses of the building due to wind load. The objective of this research is to study the effectiveness of five tall building structural systems: core wall, outrigger, belt wall, tube-in-tube and megacolumns in minimizing the building responses due to wind. Reinforced concrete buildings with 64 stories and the ratio of height to the breadth of 6:1 were analysed for their responses to wind load. The buildings that were analysed have five different structural systems. The natural frequencies and eigenvectors of the buildings in the along-wind, across-wind and torsional mode are computed by a structural engineering software. The along-wind responses are determined by employing the procedures from the ASCE 7-02 while the across-wind and torsional responses of the buildings are calculated based on the procedures and wind tunnel data available in a data base of aerodynamic load. The database is comprised of high-frequency base balance measurements on a host of isolated tall building models. It is found that increasing the size of the core wall is more effective to reduce the building responses than increasing the thickness of the core wall. As for the outriggers, the most optimum position to construct the outriggers is between one quarter to two third of the height of the building. However, outrigger system is effective to reduce only the along-wind and acrosswind responses. The torsional responses cannot be reduced by the addition of the outriggers. Interestingly, the addition of the belt walls will reduce the torsional response of the buildings which otherwise cannot be lessened by the outriggers. The belt walls also further reduce the building responses in the along-wind and acrosswind directions. Moreover, the most optimal tube-in-tube structure is achieved when the spacing of the exterior columns is 4 metre, while the addition of megacolumns to the structural systems reduces the building responses drastically in all the three directions
Influence of rainfall pattern on suction distribution and slope stability
(Universiti Teknologi Malaysia, 2008) Lee, Min Lee
Rainfall-induced slope failure is one of the most severe disasters in tropical regions causing major loss of life and property. This study was carried out to investigate the effect of various rainfall patterns on the suction distribution, hence on slope stability. A series of numerical analyses were conducted via Seep/W on an infinite slope model to simulate the responses of the slope consisting of typical soil types to the extreme rainfalls of five selected locations in the Malaysian Peninsular. One-dimensional infiltration tests were also performed by using a soil column model, instrumented with tensiometers and gypsum blocks, to provide laboratory evidences for the findings of numerical study. The study shows that the combination of antecedent rainfall and major rainfall is the critical rainfall pattern for shallow failure, while the prolonged antecedent rainfall contributes to the deep-seated failure for most types of soil. The critical combined duration of antecedent rainfall and major rainfall varies from 11 hours to 13 days. The duration can be estimated from an equation proposed in this study. The critical duration of antecedent rainfall varies from 1 day to 30 days, depending on the soil type, slip plane depth and geographical location. Soil permeability could significantly affect the pattern and the duration of critical rainfall. A computer software (PERISI) was developed to perform the preliminary evaluation of rainfall-induced slope instability. The critical suction distribution and factor of safety computed by PERISI software show good agreement with the results of numerical simulation and field monitoring
Design and operating parameters of a fluidized bed for the combustion of municipal solid waste using standpipes air distributors
(Universiti Teknologi Malaysia, 2009) Johari, Anwar
Hydrodynamic studies and combustion of simulated and actual municipal solid waste were carried out in a fluidized bed system. A wide range of parameters was investigated in hydrodynamic study after which the optimum parameters were implemented in the combustion studies. A newly fabricated standpipes air distributor (primary air inlet) was designed based on findings of the optimum orifice diameter, orifice distance and distance between pipes. Orifice diameter, orifice distance and distance between pipes of 3 mm, 10 mm and 70 mm were used in the hydrodynamic studies of circular and rectangular columns (CHS and RHS). The operating parameters investigated in the CHS and RHS included the effect of sand sizes and aspect ratios on the fluidization profile. Standpipes air distributors having the same orifice diameter and distance but with a wider pipe distance of 200 mm were used in the hydrodynamic studies of a bigger rectangular (big scale) column. Different air flow strategies were implemented to ensure good mixing between sand and samples and to investigate the penetration of the incombustibles into the sand bed. Parameters studied in the combustion of municipal solid waste included the effect of fluidizing velocity and air factor on the combustion profile in the bed as well as the freeboard region with standpipe air distributor design and dimension established from the hydrodynamic studies of a bigger scale rectangular column. Findings from the CHS and RHS showed that sand particles with mean size of 0.34 mm performed good fluidization profile compared to other coarser sand sizes. The ratio of the bed height over diameter of column (Dc) for good fluidization was determined at H = Dc for the circular column whereas the ratio of the bed height (H) over the length of column was observed at H
The performance of membrane bioreactor in treating high temperature municipal wastewater
(Universiti Teknologi Malaysia, 2010) Al Amri, Abdullah Ali
Membrane bioreactor (MBR) is a promising technology which has been applied to treat a wide range of municipal wastewater in different regions around the world. However, it has not yet been employed in arid and semi arid areas such as Arabic Gulf Cooperation Council States (AGCCS). The application of MBR process in treating high temperature municipal wastewater (HTMW) has not been documented and could pose as an obstacle. Therefore, the aim of this study was to investigate the effect of high temperature on MBR process in treating municipal wastewater. The objectives were to study the biomass properties, the membrane fouling tendency and the biological and final removal efficiencies (Bio and Fin R E) of COD, NH3-N and turbidity. In this study, a 3.6 L lab-scale aerobic MBR was seeded with 1.5 L activated sludge inoculum from Oman and was fed with a real municipal wastewater from Taman Pulai Utama sewage treatment plant in Johor. The system was then run under four main experimental stages. For the first three stages, it was run at three various temperatures (25, 35 and 45°C) and two different fluxes (10 and 15 LMH). In the fourth stage, it was run at drastic temperature changes with constant flux (10 LMH). The study demonstrated that the increase in temperature caused biomass shock. This resulted in the biomass reduction, lowered sludge settling properties and higher supernatant’s turbidity. Due to biomass reduction (low richness and diversity), DO and ML pH increased. The temperature increase led to increase in SMP carbohydrate and protein, and decrease in EPS protein. Biomass reduction, high pH, SMP concentration increase and EPS decrease were the factors that caused relatively high membrane fouling. TMP and BWP ascended critically with temperature and flux increase. The highest TMP values scored were 348 mbar at 10 LMH flux and 429 mbar at 15 LMH flux, and both of them were at 45°C. Membrane openings widen with temperature increase, thus membrane fouling tended to be internal rather than external at higher temperatures. As a result of biomass shock the removal efficiencies dropped temporarily and then improved gradually with the acclimatization despite the flux increase. COD Bio R E was 90%, 84% and 62%, while Fin R E was 95%, 91% and 79% at 25°C, 35°C and 45°C respectively. Both NH3-N removal efficiencies were very high up to 100% at 25 and 35°C, while at 45°C they were 52% Bio R E and 56% Fin R E as high nitrification has not yet been achieved at high temperatures. Despite the higher biomass shock at drastic temperature changes stage, COD and turbidity Fin R E were very high up to 90% and 100% respectively, while NH3-N Fin R E was nearly 50%. The viscosity decreased with the increased in temperature and SVI. In spite of the critical operating conditions, the use of hollow fiber membrane module was able to achieve comparatively good removal efficiencies, however at the highest temperature i,e (45°C) the membrane fouling was the highes
Parameter optimization methods for calibrating tank model and neural network for rainfall-runoff modelling
(Universiti Teknologi Malaysia, 2010) Kuok, King Kuok
The transformation of rainfall into runoff involves many highly complex hydrological components that require various hydrological data and topographical information. These data are hard to obtain and not consistent. Therefore, hydrologic tank and artificial neural networks models that require only rainfall and runoff data were proposed. The selected study area is Bedup Basin, Sarawak, Malaysia, a rural catchment in humid region. A new global optimization method named as particle swarm optimization (PSO) was proposed, and compared with shuffle complex evolution and genetic algorithm techniques for calibrating the tank models’ parameters automatically. PSO is also hybrid with neural network to form particle swarm optimization feedforward neural network (PSONN) to overcome the slow convergence rate and trapping at local minima problems. PSONN performance is then compared with multilayer perceptron and recurrent networks, that used backpropagation algorithm. Models performances are measured using coefficient of correlation (R) and Nash-Sutcliffe coefficient (E2). Generally, artificial neural networks performance is slightly better than tank model. Results of tank model calibration indicate that PSO method appeared to be the best based on its robustness, reliability, efficiency, accuracy and smallest variability in boxplots. Shuffle complex evolution follows as the second best and the third best is genetic algorithm for both daily and hourly runoff simulation. Among multilayer perceptron, recurrent and PSONN investigated, recurrent network forecasts daily and hourly runoff most accurately, followed second best by multilayer perceptron and lastly PSONN. PSONN has proven its remarkable capability to simulate daily and hourly runoff with an acceptable accuracy. This study revealed that artificial intelligence methods especially PSO, have offered a real prospect for an efficient, simple, cheaper, more flexible, and well suited to model flood processes
Evaluation of sustainable construction understanding among AEC professionals
(Mendeley Data, 2010-12-22) Muhammad-Jamil Abubakar
The questionnaire and responses of the evaluation of sustainable construction understanding among AEC professionals in Nigeria's AEC industry
Bitumen modification using oil palm fruit ash for stone mastic asphalt
(Universiti Teknologi Malaysia, 2011) Rusbintardjo, Gatot
The objective of this study was to investigate the feasibility of using oil palm fruit ash (OPFA) as a bitumen modifier, to formulate the mix between OPFA and bitumen as a new binder with better physical and mechanical properties, and to evaluate the use of OPFA-modified bitumen (OPFA-MB) as a binder of stone mastic asphalt (SMA). In this study two sources of bitumen, bitumen B-1 and bitumen B-2 each had penetration grade 80/100 were modified by using OPFA. The bitumen was mixed with 2.5%, 5%, 7.5%, 10%, 12.5%, and 15% OPFA by weight of the bitumen at mixing temperature 160°C, mixing time 60 minutes, and mixing stirring speed 800 revolution per minute. There were two types of OPFA, Fine and Coarse-OPFA. FineOPFA was OPFA which had uniform particle size 75µm, and Coarse-OPFA was OPFA which had graded particle with maximum grains size 600µm. The bitumen mixed with OPFA was called OPFA-modified bitumen (OPFA-MB). There were four types of OPFA-MB namely Fine-OPFA-MB1, Coarse-OPFA-MB1, FineOPFA-MB2, and Coarse-OPFA-MB2. Each type of OPFA-MB had six OPFA content. For all of OPFA-MB penetration test at 25°C, softening point test, and viscosity test at 60°C and 135°C were conducted to determine penetration index (PI) and penetration-viscosity number (PVN). The results show that all OPFA-MB were not susceptible to the changes of temperature. Rheology test using dynamic shear rheometer (DSR), bending beam rheometer (BBR), and direct tension tester (DTT) show that OPFA-MB with the content of fine-OPFA 5%, 2, 5%, and 10% can withstand rutting at a temperature of 70°C, withstand fatigue cracking at a temperature of 20°C, and resist to thermal cracking at a temperature of -15°C. Using in stone mastic asphalt (SMA-14) mixtures resulted in higher Marshall stability than the minimum specification requirements. Resilient modulus, creep, and wheel tracking rutting tests show that OPFA-MB can strengthen SMA-14 mixtures. Static immersion test, boiling water and drain-down test show that OPFA-MB has good adhesion to bind aggregate. Based on penetration value and the results of rheology testing, OPFA-MB can be categorized as binder penetration grade 60/700 and Superpave bitumen grade PG 70 – 16. Overall test results suggest that OPFA is feasible to be used as modifier of the bitumen, and as a binder for stone mastic asphalt.
Tree-induced deformation in unsaturated soils
(Universiti Teknologi Malaysia, 2011) Mohammed Abdullahi, Mu’azu
Settlements of lightly loaded structures are frequently caused by changes in matric suction causing shrinkage or swelling of soils. These structures are often not designed to deal with influences of these changes. This study explores issues related to ground displacement due to changes in matric suctions induced by root wateruptake by tree. Numerical simulations of moisture migration patterns in the unsaturated zone and in the vicinity of established tree were performed. The moisture flow model used is based on Richard’s equation with incorporated sink term and integrated with appropriate water-uptake models in 2D and 2D axi-symmetric form. The numerical solution was derived from a finite element approach for spatial discretisation along with a finite difference time-marching scheme. A series of numerical simulations have been performed by the model to assess functionality of stress-deformation analysis partially coupled to flow equation. The model is capable of estimating matric suction changes and accompanying volume change profiles due to water-uptake over a full-annual cycle. Time dependent boundary conditions based on rainfall data effects have also been explored. Results of sensitivity and parametric analyses shows that the predicted ground displacements are sensitive to all the parameters tested. On the other hand, all initial time step sizes used for testing the convergence criterion on the simulation works was found to converge and the simulated results shows difference of not more than ±5 %, which is considered satisfactory. The research also provides an assessment of the significance of trees induced suction changes on unsaturated soil slopes. The model is capable of estimating ground displacements due to matric suction changes on sloping ground. The magnitude of the ground displacement on the sloping surface depends on the relative position of trees on the slope. A relatively straight forward simple approach to model the matric suction changes and accompanying volume change profiles beneath tree as a result of water-uptake has been developed. The resulting model is potentially valuable for a range of geotechnical engineering problems situated on the vadose zones containing trees.
Dynamic behavior of fuel cell motorcycle power train
(Universiti Teknologi Malaysia, 2011) Inayati
An accurate and reliable fuel cell power train simulation model is needed to design a fuel cell powered motorcycle having the required maximum speed, cruising speed, acceleration and efficiency. In this study a fuel cell power train simulation model was developed to investigate the performance of the 8.5 kW fuel cell motorcycle power train under variable dynamic loads. The power train of the fuel cell motorcycle consists of fuel cell system, battery, ultra capacitor, main traction motor, booster motor, and power conditioner. Mathematical models have been developed for each power train subsystem to study their characteristics. The fuel cell stack performance was modeled using empirical polarization curve and the parameters of the polarization curve namely Tafel slope, iloss, i0, and area specific resistance of the fuel cell stack were determined using experimental data. Parameters of the main traction motor namely torque constant and armature resistance were also determined experimentally using acceleration test on the dynamometer. The performance of lithium ion battery was found to behave according to Peukert law. Peukert coefficient (kp) was determined from the battery discharging data for different discharge currents. Each subsystem in the power train was modeled individually and validated using experimental data. A master computer program for the fuel cell motorcycle power train simulator was developed to integrate the sub-components models using Labview platform to study their interactions under variable dynamic loads. The model was validated using experimental data obtained by running the fuel cell power train on the dynamometer using drive cycle from Worldwide Harmonized Motorcycle Test Cycle (WMTC) . The results showed that the fuel cell power train simulator model was able to present the dynamic behavior of each component in the fuel cell power train in terms of power, voltage, current, regenerative braking, speed and efficiency. The simulator was then used to predict the performance of a fuel cell motorcycle which runs on the Highway Fuel Economy Driving drive cycle (HWYCOL). In conclusion, the model based simulator developed in this work is capable to present and to predict the fuel cell motorcycle power train behavior under dynamic condition.
Influence of forest plantation establishment on the hydrological characteristics of small catchments in Selangor
(Universiti Teknologi Malaysia, 2011) Shamsuddin, Siti Aisah
The interception, evapotranspiration and stormflow characteristics in a young plantation of Hopea odorata were studied. The forest plantation was established within the Bukit Tarek Tambahan Forest Reserve in Kerling, Selangor. Experimental catchment (C3) with an area of 14.4 hectare was set up in year 1993. The H.odorata stands were two years old when this study commenced in year 2006 and the data collection was carried out for two years. Establishment of forest plantation usually involved clear felling of natural forest change the hydrological properties of the natural forest ecosystem. C3 was clear-cut during the preparation of the forest plantation. The evapotranspiration and stormflow characteristics of a forested catchment, namely C1, which covers 32.8 hectare, were also determined. Throughfall (Tf) and stemflow (Sf) were measured in two plots in C3 and the interception was determined from both values. Tf and Sf showed positive relationships with gross rainfall. The Tf in plot 1 was not affected by the tree characteristics viz. tree height (TH), stem diameter, canopy depth (CD), canopy area and canopy volume. However, CD influenced the Tf in plot 2. Similarly, the Sf in plot 1 was not influenced by the TH, stem diameter, CD and canopy area but positive relationships with these parameters were found for larger trees in plot 2. The canopy storage capacity was small (maximum 1.49 mm) while the trunk storage capacity was negligible. The average Tf under young H.odorata was between 77.4% and 83.2% of the rainfall while the Sf was between 3.1% and 4.1% of the rainfall. This gave an interception loss between 12.7% and 19.5% of the rainfall. The forest clearing resulted in reduced evapotranspiration. Based on the catchment water balance and short-time period water budget analyses, the evapotranspiration from C3 was 5.6% lower than in C1. In the rainfall-runoff response study using hydrograph analyses, strong relationships between gross rainfall and stormflow were found in both C1 and C3. The plantation catchment is more responsive to storm with higher total water yield than in the forested catchment. The C3 also showed steeper rising and falling limbs; shorter durations of stormflow, time to peak, and time of concentration; higher minimum contributing area and lower ratios of stormflow/total discharge and stormflow/rainfall for single-peak hydrographs. The patterns of stormflow response to rainfall can reflect three conditions; wet, transition from wet to dry, and dry. During wet conditions, the threshold rainfalls for generating stormflow were 34.5 mm for C1 and 22.1 mm for C3. These thresholds increase during dry conditions to 53.1 mm for C1 and 45.8 mm for C3. A long term study to evaluate the evapotranspiration rate and water yield from matured H.odorata plantations is necessary to avoid possible conflict between forestry and water resources management objectives
Modeling of vacuum gas oil hydrocracking process using lumping approach
(Universiti Teknologi Malaysia, 2012) Sadighi, Sepehr
Conversion of heavy feedstock into lighter products in a hydrocracking process has a strong influence on the profitability of petroleum refining. To facilitate initiatives toward improving the process efficiency, a good process model is required. This thesis discusses the development and application of lump modeling strategies in a pilot plant and industrial scale hydrocracking processes. For the pilot plant, two different four-lump models are considered, i.e., combined bed and dual bed models. Unlike the simpler combined bed model, the dual bed model includes hydrogen consumption and hydrotreating reactions, and the reactor is subdivided into two different layers so that the effect of hydrotreating reactions can be integrated. To extend the application to a commercial refinery, a full-lump model is configured to predict the product yields of a commercial hydrocracking unit known as Isomax. Using bed temperatures, flow rate of fresh vacuum gas oil (VGO), recycle rate and catalyst life as process variables, the model is proven capable of predicting the yield of all products. The model also provides improvement to previous works by considering liquefied petroleum gas (LPG), light gases, fresh VGO and recycle feed as separate lumps. This model is then used in optimizing the reactor operation where the bed temperature, flow rate of fresh VGO and combined feed ratio are adjusted to increase the plant profitability whilst maintaining all process limitations and operating constraints. To extend the model for dynamic applications, a modified space-time conservation element and solution element method (CE-SE) is introduced. The results obtained from simulation of the pilot plant based on fourlump model using CE-SE method are comparable to those obtained using finite difference method, thus providing opportunities for further works involving dynamic behavior of the process. Although the study is focussed on hydrocracking, this thesis has proved the practicality of using lumped modeling technique to address model development requirement for complex industrial processes.
Assessment of building performance under ground movement due to tunnel construction
(Universiti Teknologi Malaysia, 2012) Namazi, Eshagh
The construction of tunnel in urban area can induce ground displacement which distort and, in severe cases, damage overlying buildings and services. The earlier methods to predict building damage assumed the building as two-dimensional elastic deep beam with building cracking is associated with the current state of tensile strain in the wall. However, when the structures are subjected to threedimensional displacements such as twist, the building cannot be analysed using the simple deep-beam approach. The aim of this research is to obtain new damage criteria for buildings undergoing twist including the effect of tilt movement. This study improves the previous assessment methods by idealising building as thick elastic plate that enables analysis of three-dimensional building distortion using simplified closed-form solutions. A number of case studies of damaged building were used to assess the ability of this method to predict the damage. Furthermore, the relative stiffness of structure to soil in modifying the distribution surface settlement from tunnel excavation was investigated through parametric study of threedimensional finite element model using ABAQUS. The tunnels were excavated in London clay with validation of ground settlement being made to the previous Jubilee Line Extension project. An isotropic non-linear elastic-perfectly plastic soil model, using Mohr-Coulomb failure criterion was adopted in this study. The results show that the presence of the building affects the twist deformation and in the most of the cases reduce settlement in comparison to those in the greenfield condition. However in the case of low building stiffness, and when the tunnel is excavated with skew angle less than 30° relative to the existing buildings, the twist displacement can be greater than those when no structure is at present. A new set of design curves is established based on these results to estimate the building twist from the greenfield condition. These investigations have lead to an improved understanding of the threedimensional tunnel-soil-building interaction problem
Constructability database knowledge model and guidelines of industrial plant at construction stage
(Universiti Teknologi Malaysia, 2012) Bakti, Erman Surya
Constructability is a common issue faced by the construction industry which is defined as the ability to construct effectively. The separation of design from procurement and construction in the traditional contracting system has led to a certain degree of isolation of the construction knowledge from design in construction projects. This contracting system has resulted in poor constructability implementation, thus exceeding time and cost of construction projects. This study aimed to provide a constructability database knowledge model and guideline for implementation of industrial plant at construction stage. The objective includes to identify the constructability problems, innovations, best practices and develop the constructability guidelines and database knowledge model. An extensive study was performed in five distinct phases including literature review, interviews, two stages of questionnaire surveys, and four case studies. The first questionnaire was distributed among headquarter of an organization and the second questionnaire was distributed among key personnel of four construction sites. Then four case studies were performed to provide a basis of constructability innovation, best practices, and method statement. Finally, a constructability guidelines and database knowledge model were developed for construction stage. The constructability model was developed based on the consideration both of United States of America and Australia Construction Industry Institute (CII) model. The guidelines developed for this research has referred to the American College of Cardiology tools and methods. Frequency, average index analysis and Wilcoxon rank test statistical techniques were used in this research to analyse the quantitative data. Two organization were selected to validate the findings. The results indicated that the lack of understanding on the overall constructability concept, the availability of lesson learned, and qualified personnel has prevented them from being more committed in implementing the constructability. Despite the above results, current constructability practices have had some benefits on projects’ performance. Not only design-construction interface and early contractor’s involvement were the main factors in improving project performance, but there are also possibilities for significant improvement at the construction stage. The application of this constructability guidelines and database knowledge model were implemented at the organization. It is recommended to improve constructability by adapting constructability concepts which have been developed in other countries but it is necessary to include the following considerations: appropriate construction methods, available resources and, optimum use of lessons learned and best practices. This research is limited on constructability problems, improvement and contracting using the traditional system of industrial plant at construction stage.
In-situ melting assessment of AZ91D magnesium alloy investment casting
(Universiti Teknologi Malaysia, 2012) Jafari, Hassan
In this research, a new technique in casting of magnesium alloy using ceramic shell investment casting process was explored. AZ91D granules were charged into shell investment mould and heated at different temperatures (650-800°C) and times (30 and 60 min) in air as well as argon gas with and without flux comprising MgCl2, KCl and CaF2. Field emission scanning electron microscopy, energy dispersive Xray spectroscopy and X-ray diffraction analysis were used to characterise the products. The results showed that with increasing heating temperature and time, significant increase in oxide/metal ratio with no development of molten pool was observed when no protected atmosphere was used. However, thermal analysis proved that the granules melted but remained in isolation due to being encapsulated by oxides, which prevented the melted granules from merging into a pool of molten metal. Even though heating in argon atmosphere prevented oxidation, prolonged heating did not produce complete melting due to the high surface tension between the liquid droplets. Further experiments were conducted using flux-argon combination in different amounts of flux (0.5, 1.0, 1.5 and 2.0 wt.%) and application conditions: on top of the granules, bottom of the mould, inner surface of the mould and mixed with the granules. The results revealed that applying 1.5 and 1.0 wt.% flux on the top of and mixed with the granules, respectively, produced comparatively best results. Thermal analysis showed that 30 min heating time is sufficient to melt the granules completely. Black residue with nodular morphology of the mould-metal reaction product formed on casting surface was found to be of the same alloy. Mg2Si, Mg3N2 and AlN in black oxide proved the reaction occurred between the alloy and shell material and air during cooling, while their absence and the presence of K6MgO4 and MgF2 in the white residue confirmed less reaction occurred due to the formation of a protective barrier at the mould-metal interface. Investigation on the effect of heating temperature (650-775°C) and shell thickness on the reaction revealed that heating of the granules mixed with flux in argon atmosphere at 650°C in thin mould suppressed the mould-metal reaction and produced casting with good surface quality. Thermal analysis showed that use of thinner moulds increased melting temperature arrests by enhancing the heating rate and providing higher solidification rates that were favourable for in-situ melting of magnesium alloy. Results also showed that shell mould permeability was found ineffective in suppressing the reaction at 650ºC. Castings produced using this technique possessed large grain size but very low level of casting defects as well as high homogeneity of microstructure
Carbon dioxide reduction to fuels using modified titanium nanocatalysts in monolith photoreactor
(Universiti Teknologi Malaysia, 2013) Tahir, Muhammad
Carbon dioxide (CO2) is the largest contributor to global warming and its conversion to renewable fuels has stirred interest for greenhouse gas mitigation and energy crises alleviations. The photocatalytic CO2 reduction to fuels is promising, yet existing technologies registered low CO2 reduction efficiency. The main objective of this study was to develop a microchannel system for selective CO2 reduction to fuels. Initially, nanocatalysts were investigated using cell type reactor with methane (CH4) and carbon monoxide (CO) as the main products during CO2 reduction with water vapour (H2O) over indium (In)/TiO2 and montmorillonite (MMT)/TiO2 catalysts. Yield of CH4 over TiO2 was 31.25, enhanced to 244 µmole g-catal.-1 h-1 using 10% In-doped TiO2. Loading MMT evidently enhanced TiO2 performance with CH4 yield rate 441.5 µmole g-catal.-1 h-1. Next, microchannel monolith photoreactor was explored for selective CO2 reduction using H2O and hydrogen (H2) as reducing agents. Yield rate of CO attained was 962 µmole g-catal.-1 h-1 and selectivity 95%. Performance comparison revealed 183 fold higher yield rate in monolith compared to cell type reactor. Significantly higher monolith reactor performance reached using H2 reducing agent and co-metal-doped TiO2 nanocatalysts. Yield rate of CO over nickel (Ni) and In-co-doped TiO2 reached to 12028 µmole g-catal.-1 h-1, higher in order of 1.8 times than copper (Cu)- In/TiO2, 5.93 times than In/TiO2, 207.4 times than TiO2 with performance 902 fold higher than the cell type reactor. Besides, monolith geometry, reaction temperature, feed ratios, metals-content and irradiation time contributed significantly to enhance reactor performances. Quantum efficiency of CO production was 1.04 %, 87 fold higher than reported in literature. Finally, Langmuir-Hinshelwood and kinetic model were developed to investigate adsorption behaviors and photocatalytic oxidation and reduction process, fitted well with experimental data, and assured efficient adsorption-desorption inside microchannels. In conclusion, microchannel monolith photoreactor with modified TiO2 nanocatalysts could make possible markedly higher CO2 reduction to fuels with higher selectivity
Stress-strain behaviour of high-strength concrete with lateral pre-tensioning confinement
(Universiti Teknologi Malaysia, 2013) Awang, Abdullah Zawawi
High-strength concrete is currently being used in columns of multi-storey building all over the world. Although, it offers superior properties, it is relatively a brittle material. This study intends to improve the ductility of the concrete using a pre-tensioning lateral confinement technique. It investigates the effects of the technique on strength and ductility of the concrete and develops model equations to predict the stress-strain behaviour of confined concrete. The basis of the technique is to apply a pre-tensioning force to relatively low cost steel straps wrapped around the cylindrical concrete specimens. The experimental work was carried out using cylindrical specimens with a dimension of 100mm in diameter and 200mm in height and concrete compressive strength were fixed at 50, 60 and 80 MPa. The parameters studied including different properties of steel straps, various spacing between straps, number of layers of straps and different levels of pre-tensioning stress in the steel straps. The confined specimens were tested in compression until failure under monotonic and cyclic loading conditions. Data collected from the test included mode of failure, loads at peak and ultimate condition, and longitudinal and lateral strains in both concrete and straps. The data were analysed based on volumetric ratio of confinement which is a function of strength of steel straps, compressive strength of concrete, spacing and number of layers of straps. The experimental results show that the pre-tensioning technique using steel straps enhanced the ductility as well as strength of the concrete as the volumetric ratio increases. The results also depicted the ability of the technique to improve the ductility and strength of the concrete, especially for concrete with higher compressive strength by effectively utilising the confinement material. Moreover, the layers of straps had also delayed the onset of volumetric expansion and, undoubtedly, the concrete failure. Based on the analysis, new equations of strength and strain enhancement with confinement coefficients of 2.62 and 11.6 respectively, using pre-tensioning technique had been developed to predict the stress-strain behaviour of confined high-strength concrete
Uplift response of symmetrical anchor plates in non-reinforced and reinforced sand using geogrid and grid fixed reinforced
(Universiti Teknologi Malaysia, 2013) Niroumand, Hamed
Anchors with symmetrical plates are typically fixed to the structure and embedded in the ground to effective depth so that they can resist uplift load. This research is focused to improve the existing symmetrical anchor plate system by introducing Geogrid and Grid Fixed Reinforced (GFR) as a new system for ground anchor. The symmetrical anchor plates consist of three different shapes that represent the square, circular and the rectangular. For each shape, three series of anchor system were tested. The first series was the symmetrical anchor plates with sand as backfill. The second series included the Geogrid that was placed in several layers in the backfill. The third series introduced the GFR to tie up the Geogrid thus providing extra reinforcement to the backfill. GFR is a new tied up system with innovative design, made from fiber reinforcement polymer (FRP) which anchor the Geogrid into the soil. A series of numerical analyses using PLAXIS as finite element method software was carried out and the results were compared with the findings from the experimental model tests. The failure mechanism and the associated rupture surface were observed and discussed. It was found that inclusion of one layer of Geogrid on the symmetrical anchor plate improved the uplift capacity by 20% as compared to the same symmetrical anchor plate embedded without reinforcement. However with the inclusion of GFR the uplift respond improved further to 30%. The single layer Geogrid was also more effective in enhancing the uplift capacity compared to the multilayer Geogrid reinforcement although the single layer GFR gives higher uplift capacity as compared to single layer Geogrid.

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