Showing papers by "Universiti Teknologi Petronas published in 2008"

Effect of antecedent rainfall on pore‐water pressure distribution characteristics in residual soil slopes under tropical rainfall

Abstract: Characteristics of changes in pore-water pressure distribution are the main parameters associated with slope stability analysis involving unsaturated soils, which are directly affected by the flux boundary conditions (rainfall infiltration, evaporation and evapo-transpiration) at the soil-atmosphere interface. Four slopes were instrumented in two major geological formations in Singapore to provide real-time measurements of pore-water pressures and rainfall events on the slopes. The field monitoring results were analysed to characterize pore-water pressure distributions under various meteorological conditions and to study the effect of antecedent rainfall on pore-water pressure distributions in typical residual soil slopes under tropical climate. Slope stability analyses were also conducted for the best and worst pore-water pressure distributions recorded in each slope to determine the range of factor of safety for the slopes. Results indicate that, antecedent rainfall, initial pore-water pressures prior to a significant rainfall event as well as the magnitude of the rainfall event play a crucial role in the development of the worst pore-water pressure condition in a slope. The role of antecedent rainfall in the development of the worst pore-water pressure condition was found to be more significant in residual soils with low permeability as compared with that in residual soils with high permeability. Pore-water pressure variation due to rainfall was found to take place over a wide range in residual soils with higher permeability as compared to residual soils with lower permeability. The worst pore-water pressure profiles occurred when the total rainfall including the 5-day antecedent rainfall (in most cases) reached a maximum value during a wet period. The factor of safety of residual soils with low permeability was found to be unaffected by the worst pore-water pressure condition.

Development of an appropriate procedure for estimation of RUSLE EI30 index and preparation of erosivity maps for Pulau Penang in Peninsular Malaysia

Abstract: Pluviographic data at 15 min interval from 6 stations in Pulau Penang of Peninsular Malaysia were used to compute rainfall erosivity factor (R) for the revised universal soil loss equation (RUSLE). Three different modelling procedures were applied for the estimation of monthly rainfall erosivity (EI30) values. While storm rainfall (P) and duration (D) data were used in the first approach, the second approach used monthly rainfall for days with rainfall ≥ 10 mm (rain10) and monthly number of days with rainfall ≥ 10 (days10). The third approach however used the Fournier index as the independent variable. Based on the root mean squared error (RMSE) and the percentage error (PE) criteria, models developed using the Fournier index approach was adjudged the best with an average PE value of 0.92 and an average RMSE value of 164.6. Further, this approach was extended to the development of a regional model. Using data from additional sixteen stations and the Fournier index based regional model, EI30 values were computed for each month. ArcView GIS was used to generate monthly maps of EI30 values and also annual rainfall erosivity (R). The rainfall erosivity factor (R) in the region was estimated to vary from 9000 to 14,000 MJ mm ha− 1 h− 1 year− 1.

Two-stage stochastic programming with fixed recourse via scenario planning with economic and operational risk management for petroleum refinery planning under uncertainty

Abstract: This work proposes a hybrid of stochastic programming (SP) approaches for an optimal midterm refinery planning that addresses three sources of uncertainties: prices of crude oil and saleable products, demands, and yields. An SP technique that utilizes compensating slack variables is employed to explicitly account for constraints’ violations to increase model tractability. Four approaches are considered to ensure solution and model robustness: (1) the Markowitz's mean-variance (MV) model to handle randomness in the objective function coefficients by minimizing the variance (economic risk) of the expected value of the random coefficients; (2): the two-stage SP with fixed recourse approach to deal with randomness in the RHS and LHS coefficients of the constraints by minimizing the expected recourse costs due to constraints’ violations; (3) incorporation of the MV model within the framework developed in (2) to formulate a mean–risk model that minimizes both the expectation and the operational risk measure of variance of the recourse costs; and (4) reformulation of the model in (3) by adopting mean-absolute deviation (MAD) as the measure of operational risk imposed by the recourse costs for a novel refinery planning application. A representative numerical example is illustrated.

CO2 Injection into Saline Carbonate Aquifer Formations II: Comparison of Numerical Simulations to Experiments

Abstract: Sequestration of carbon dioxide in geological formations is an alternative way of managing extra carbon. Although there are a number of mathematical modeling studies related to this subject, experimental studies are limited and most studies focus on injection into sandstone reservoirs as opposed to carbonate ones. This study describes a fully coupled geochemical compositional equation-of-state compositional simulator (STARS) for the simulation of CO2 storage in saline aquifers. STARS models physical phenomena including (1) thermodynamics of sub- and supercritical CO2, and PVT properties of mixtures of CO2 with other fluids, including (saline) water; (2) fluid mechanics of single and multiphase flow when CO2 is injected into aquifers; (3) coupled hydrochemical effects due to interactions between CO2, reservoir fluids, and primary mineral assemblages; and (4) coupled hydromechanical effects, such as porosity and permeability change due to the aforementioned blocking of pores by carbonate particles and increased fluid pressures from CO2 injection. Matching computerized tomography monitored laboratory experiments showed the uses of the simulation model. In the simulations dissolution and deposition of calcite as well as adsorption of CO2 that showed the migration of CO2 and the dissociation of CO2 into HCO3 and its subsequent conversion into carbonate minerals were considered. It was observed that solubility and hydrodynamic storage of CO2 is larger compared to mineral trapping.

Viscosity, Refractive Index, Surface Tension, and Thermal Decomposition of Aqueous N-Methyldiethanolamine Solutions from (298.15 to 338.15) K

Abstract: In this work, physical properties such as dynamic viscosity at (298.15 to 338.15) K, surface tension, and refractive index at temperatures (303.15 to 333.15) K of pure and aqueous N-methyldiethanol...

The effect of alkali treatment and filler size on the properties of sawdust/UPR composites based on recycled PET wastes

Abstract: In this study, natural sawdust fillers from acacia were mixed with unsaturated polyester resin (UPR), which was prepared by recycling of polyethylene terephthalate (PET) waste bottles to prepare sawdust/UPR composite. PET wastes were recycled through glycolysis and depolymerized to produce a formulation for the resin. The effects of alkali treatment, filler content, and filler size on the tensile, flexural, hardness, and water absorption of the composites were investigated. The results show that the modulus of both tensile and flexural increased with increasing filler contents, but the tensile and flexural strength of composites decreased. The size of sawdust also played a significant role in the mechanical properties, with smaller size sawdust producing higher strength and modulus. This is due to the greater surface area for filler–matrix interaction. The results also show that alkali treatment causes a better adhesion between sawdust and UPR matrix and improves the mechanical properties of the composites. Furthermore, surface treatment reduced the water absorption of composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

A fully fuzzified, intelligent theory-of-constraints product-mix decision

Abstract: The present research work outlines a fuzzified approach using fuzzy linear programming (FLP) using a suitably designed smooth logistic membership function (MF) for finding fuzziness patterns at disparate levels of satisfaction for theory of constraints-based (TOC) product-mix decision problems. The objective of the present work is to find fuzziness patterns of product-mix decisions with disparate levels of satisfaction of the decision-maker (DM). Another objective is to provide a robust, quantified monitor of the level of satisfaction among DMs and to calibrate these levels of satisfaction against DM expectations. Product-mix decision should take into account considerations such as the DM's level of satisfaction (sometimes called ‘emotions’) in order to make the decision a robust one. Sensitivity of the decision has been focused on a bottleneck-free, optimal product-mix solution of a TOC problem. The inefficiency of traditional linear programming (LP) in handling multiple-bottleneck problems using TOC is ...

The effect of colour space on tracking robustness

Abstract: This paper studies the effect of colour space on the performance of tracking algorithms. The colour spaces that were investigated were grayscale, RGB, YCbCr and HSV. The performance of a normalised cross correlation tracking algorithm was measured to determine robustness and accuracy in the different colour spaces. Track Detection Rate (TDR) and Object Tracking Standard Deviation (OTStd) were used to provide quantitative measures of tracking performance. The combined results indicate that the colour spaces of YCbCr and HSV give more accurate and more robust tracking results compared to grayscale and RGB images. The results also show that the information stored in the chrominance layers of CbCr in the YCbCr colour space and chromaticity layers HS in the HSV colour space, were sufficient for robust tracking. The TDR results range from 93.7% to 97.1% for grayscale and RGB, and 98% to 100% for the YCbCr and HSV colour spaces respectively. A similar trend in the OTStd was observed with a range of 17.0 pixels to 23.9 pixels for grayscale and RGB, and 7.56 pixels to 20.5 pixels for YCbCr and HSV.

Density and Excess Properties of Aqueous N-Methyldiethanolamine Solutions from (298.15 to 338.15) K

Abstract: Densities (ρ) of pure and aqueous N-methyldiethanolamine (MDEA) solutions (wMDEA = 0.3228 or 4 mol·kg−1 and wMDEA = 0.4880 or 8 mol·kg−1) at (298.15 to 338.15) K were measured at atmospheric pressu...

Development of variable ballast mechanism for depth positioning of spherical URV

Abstract: The variable ballast is used to control the buoyancy of the body in Underwater Robotic Vehicle (URV) system. The variable ballast can also be used as a motion actuator in vertical plane. Many variable ballast mechanisms have been developed by researchers. In this paper, development of a variable ballast mechanism is presented. This variable ballast mechanism is designed to make the water always fulfill space in the variable ballast tank with the varying volume. This variable ballast is utilized for motion actuator in vertical plane of a spherical URV. By using physical laws, a nonlinear dynamic model of the URV and variable ballast is derived. The model is simulated using Simulink in MatLab.

An Empirical Model for the Estimation of Moisture Ratio During Microwave Drying of Plaster of Paris

Abstract: The drying characteristics of plaster of Paris (POP) under microwave irradiation were studied for different shapes of materials through various drying parameters like microwave power, initial moisture content, and drying time. An empirical model for the estimation of moisture ratio was developed using the drying kinetic data of POP. Further, the experimental data on moisture ratio of POP for different operating conditions were fitted with the nine basic drying model equations. Based on the observations, the constants and coefficients of the literature models were rewritten in the form of Arrhenius and logarithmic expressions considering microwave power as input variable. Fifty-eight new model expressions were derived by changing the constants and coefficients and tested using the present experimental data. From the analysis of RMSE, χ2, and EF parameters for the derived models, a suitable empirical model (Model No. 55, RMSE = 0.0874; χ2 = 0.0020; EF = 0.9999) was established to represent the present exper...

Characterization and Process Optimization of Microwave Drying of Plaster of Paris

Abstract: The changes in the characteristics of plaster of Paris (pop) during drying operation under microwave irradiation conditions, namely surface morphology, effective moisture diffusivity, and absorption of microwave, were studied. The drying characteristics and kinetics of the process during microwave drying of plaster were studied for rectangular-faced cuboids (80 × 70 × 15, L × B × H in mm) through various drying parameters like microwave power input, initial moisture content, and drying time. Further, the experimental data on moisture ratio of plaster for different operating conditions were obtained and the optimization of the microwave drying process parameters was performed with response surface methodology (RSM) by considering all the above-said independent variables. Based on the RSM analysis, the optimum values of the process variables were obtained as: initial moisture content (A) 60%; microwave power input (B) 180 W; and drying time (C) 480 S.

A system architecture for water quality monitoring system using wired sensors

Abstract: This research paper proposes an aarchitecture for implementing a water quality monitoring system for the aquaculture industry. The system would enable monitoring of the water quality remotely via GSM. Conventional method used by aqua farms requires technical staff to visit ponds at designated time and perform manual testing on the water quality. Consequently, the technique consumes a lot of time and effort. This research project would focus on developing a prototype that can evaluate data collected through three criteria: Dissolved oxygen level, pH level, and temperature level. The system would also be able to send alert messages upon detecting degradation of water quality in the pond via SMS.

Cell Engineering and Molecular Pharming for Biopharmaceuticals

Abstract: Biopharmaceuticals are often produced by recombinant E. coli or mammalian cell lines. This is usually achieved by the introduction of a gene or cDNA coding for the protein of interest into a well-characterized strain of producer cells. Naturally, each recombinant production system has its own unique advantages and disadvantages. This paper examines the current practices, developments, and future trends in the production of biopharmaceuticals. Platform technologies for rapid screening and analyses of biosystems are reviewed. Strategies to improve productivity via metabolic and integrated engineering are also highlighted.

Sulfonation of phenols extracted from the pyrolysis oil of oil palm shells for enhanced oil recovery.

Abstract: The cost of chemicals prohibits many technically feasible enhanced oil recovery methods to be applied in oil fields. It is shown that by-products from oil palm processing can be a source of valuable chemicals. Analysis of the pyrolysis oil from oil palm shells, a by-product of the palm oil industry, reveals a complex mixture of mainly phenolic compounds, carboxylic acids, and aldehydes. The phenolic compounds were extracted from the pyrolysis oil by liquid-liquid extraction using alkali and an organic solvent and analyzed, indicating the presence of over 93% phenols and phenolic compounds. Simultaneous sulfonation and alkylation of the pyrolysis oil was carried out to produce surfactants for application in oil fields. The lowest measured surface tension and critical micelle concentration was 30.2 mNm-1 and 0.22 wt%, respectively. Displacement tests showed that 7-14% of the original oil in place was recovered by using a combination of surfactants and xanthan (polymer) as additives.

Planejamento fatorial: uma ferramenta estatística valiosa para a definição de parâmetros experimentais empregados na pesquisa científica

Abstract: This paper describes both the value and the role of multivariated methods of experimental procedure in scientific research. It is highlighted the advantages of factorial design systems which let simulate simultaneously several variables concerned a studied system, reducing the number of experiments of the research. The impact of these variables on the photopolymerization system is discussed upon the photocure of oligo(methyl methacrylate) (MMA), commercially called Berkel glue B 20, initiated by an UV light source. As feedback of the system it was measured the quantity of oligomer converted to polymer (in weight), finding the polymerization rate (in percent). Aspects related to the experimental design and the interpretations of results are also presented

New NASICON type oxyanion high capacity anode, Li2Co2(MoO4)3, for lithium-ion batteries: preliminary studies

Abstract: We describe in this paper the lithium insertion/extraction behavior of a new NASICON type Li2Co2(MoO4)3 at a low potential and explored the possibility of considering this new oxyanion material as anode for lithium-ion batteries for the first time. Li2Co2(MoO4)3 was synthesized by a soft-combustion glycine-nitrate low temperature protocol. Test cells were assembled using composite Li2Co2(MoO4)3 as the negative electrode material and a thin lithium foil as the positive electrode material separated by a microporous polypropylene (Celgard® membrane) soaked in aprotic organic electrolyte (1 M LiPF6 in EC/DMC). Electrochemical discharge down to 0.001 V from OCV (∼3.5 V) revealed that about 35 Li+ could possibly be inserted into Li2Co2(MoO4)3 during the first discharge (reduction) corresponding to a specific capacity amounting to 1,500 mAh g−1. This is roughly fourfold higher compared to that of frequently used graphite electrodes. However, about 24 Li+ could be extracted during the first charge. It is interesting to note that the same amount of Li+ could be inserted during the second Li+ insertion process (second cycle discharge) giving rise to a second discharge capacity of 1,070 mAh g−1. It was also observed that a major portion of lithium intake occurs below 1.0 V vs Li/Li+, which is typical of anodes being used in lithium-ion batteries.

Svd-based signature verification technique using data glove

Abstract: Data glove is a new dimension in the field of virtual reality environments, initially designed to satisfy the stringent requirements of modern motion capture and animation professionals. In this paper, we try to shift the implementation of data glove from motion animation towards signature verification problem, making use of the offered multiple degrees of freedom for each finger and for the hand as well. The proposed technique is based on the Singular Value Decomposition (SVD) in finding r singular vectors sensing the maximal energy of glove data matrix A, called principal subspace, and thus account for most of the variation in the original data, so the effective dimensionality of the data can be reduced. Having identified data glove signature through its rth principal subspace, the authenticity can then be obtained by calculating the angles between the different subspaces. The SVD-signature verification technique is tested with large number of authentic and forged signatures, showing remarkable level of accuracy in finding the similarities between genuine samples as well as those differentiated between genuine-forgery trials.

The Role of Al2O3 Buffer Layer in the Growth of Aligned CNTs

Abstract: Carbon nanotube (CNT) can be thought of as a hexagonal network of carbon atoms that has been rolled up to make a seamless cylinder. If they are consisting of one layer, they are termed singled-walled CNTs (SWNTs) while if there are multiple walls, they are called multi-walled CNTs (MWNTs). For most functional devices application, an aligned arrangement of CNTs is desired. Aligned multiwalled carbon nanotubes (MWNTs) have been successfully grown by the inclusion of a buffer layer of oxidized Al. An Al2O3 layer has been proven to be an important contributing factor towards obtaining good quality aligned CNTs. In this work, Al is deposited onto the Si wafer using electron beam evaporation and later oxidized by heating in air. A thin layer of iron catalyst is then deposited on top of the oxidized Al layer and annealed at 400oC. The result shows an improvement in the intensity of the graphitization peak (G-band) in the Raman spectra and aligned MWNTs is observed in these samples compared to the ones that have undergone the same process parameter except the Al2O3 layer.

Objective assessment of psoriasis erythema for PASI scoring

Abstract: Skin colour is vital information in dermatological diagnosis. It reflects pathological condition beneath the skin and commonly being used to indicate the extent of a disease. Psoriasis is a skin disease which is indicated by the appearance of red plaques. Although there is no cure for psoriasis, there are many treatment modalities to help control the disease. To evaluate treatment efficacy, PASI (Psoriasis Area and Severity Index) which is the current gold standard method is used to determine severity of psoriasis lesion. Erythema (redness) is one parameter in PASI. Commonly, the erythema is assessed visually, thus leading to subjective and inconsistent result. In this work, we proposed an objective assessment of psoriasis erythema for PASI scoring. The colour of psoriasis lesion is analyzed by ΔL*, Δhue, and Δchroma of CIELAB colour space. References of lesion with different scores are obtained from the selected lesions by two dermatologists. Results based on 38 lesions from 22 patients with various level of skin pigmentation show that PASI erythema score can be determined objectively and consistent with dermatology scoring.

Chaos based constellation scrambling in OFDM systems: Security & interleaving issues

Abstract: Recently, chaos based cryptography has attracted significant attraction of the researchers due to their simplicity of implementation, complex behavior and extreme sensitivity to initial conditions. In this paper an efficient technique to introduce security at physical (PHY) layer is proposed in 802.11i design to provide security in Medium Access Control. Since it does not emphasize on availability, several denial of service (DoS) attacks are possible. The DoS attacks are easy to mount because management and control frames are unprotected and so are MAC headers. This paper proposes a security scheme at PHY layer by scrambling OFDM constellation symbols to encrypt data transmission to resist against these malicious attacks. In addition, it can also acts as random interleaver. Analysis shows that, it has good random interleaver properties and also memory efficient. The scrambling matrix is based on a key derived from a one dimensional chaotic nonlinear dynamical system using logistic map. The initial condition of the map acting as the derived key is dependent on the external key. The scrambling is completely reversible with the use of appropriate key. However, use of a wrong initial condition even at 4th decimal point produces entirely different sequence resulting in erroneous constellations with equal probability.