Displaying publications 101 - 120 of 735 in total

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  1. Zahmatkesh F, Osman MH, Talebi E
    ScientificWorldJournal, 2014;2014:323206.
    PMID: 24587720 DOI: 10.1155/2014/323206
    Research on the steel structures with confining of axial expansion in fixed beams has been quite intensive in the past decade. It is well established that the thermal behaviour has a key influence on steel structural behaviours. This paper describes mechanical behaviour of beams with bolted slant end-plate connection with nonsymmetric gravity load, subjected to temperature increase. Furthermore, the performance of slant connections of beams in steel moment frame structures in the elastic field is investigated. The proposed model proved that this flexible connection system could successfully decrease the extra thermal induced axial force by both of the friction force dissipation among two faces of slant connection and a small upward movement on the slant plane. The applicability of primary assumption is illustrated. The results from the proposed model are examined within various slant angles, thermal and friction factors. It can be concluded that higher thermal conditions are tolerable when slanting connection is used.
    Matched MeSH terms: Models, Theoretical*
  2. Mohamad MH, Sali A, Hashim F, Nordin R, Takyu O
    Sensors (Basel), 2018 Dec 10;18(12).
    PMID: 30544655 DOI: 10.3390/s18124351
    This paper investigated the throughput performance of a secondary user (SU) for a random primary user (PU) activity in a realistic experimental model. This paper proposed a sensing and frame duration of the SU to maximize the SU throughput under the collision probability constraint. The throughput of the SU and the probability of collisions depend on the pattern of PU activities. The pattern of PU activity was obtained and modelled from the experimental data that measure the wireless local area network (WLAN) environment. The WLAN signal has detected the transmission opportunity length (TOL) which was analyzed and clustered into large and small durations in the CTOL model. The performance of the SU is then analyzed and compared with static and dynamic PU models. The results showed that the SU throughput in the CTOL model was higher than the static and dynamic models by almost 45% and 12.2% respectively. Furthermore, the probability of collisions in the network and the SU throughput were influenced by the value of the minimum contention window and the maximum back-off stage. The simulation results revealed that the higher contention window had worsened the SU throughput even though the channel has a higher number of TOLs.
    Matched MeSH terms: Models, Theoretical
  3. Ahmad N, Ramsch R, Llinàs M, Solans C, Hashim R, Tajuddin HA
    Colloids Surf B Biointerfaces, 2014 Mar 1;115:267-74.
    PMID: 24384142 DOI: 10.1016/j.colsurfb.2013.12.013
    The effect of incorporating new nonionic glycolipid surfactants on the properties of a model water/nonionic surfactant/oil nano-emulsion system was investigated using branched-chain alkyl glycosides: 2-hexyldecyl-β(/α)-D-glucoside (2-HDG) and 2-hexyldecyl-β(/α)-D-maltoside (2-HDM), whose structures are closely related to glycero-glycolipids. Both 2-HDG and 2-HDM have an identical hydrophobic chain (C16), but the former consists a monosaccharide glucose head group, in contrast to the latter which has a disaccharide maltose unit. Consequently, their hydrophilic-lipophilic balance (HLB) is different. The results obtained have shown that these branched-chain alkyl glycosides affect differently the stability of the nano-emulsions. Compared to the model nano-emulsion, the presence of 2-HDG reduces the oil droplet size, whereas 2-HDM modify the properties of the model nano-emulsion system in terms of its droplet size and storage time stability at high temperature. These nano-emulsions have been proven capable of encapsulating ketoprofen, showing a fast release of almost 100% in 24h. Thus, both synthetically prepared branched-chain alkyl glycosides with mono- and disaccharide sugar head groups are suitable as nano-emulsion stabilizing agents and as drug delivery systems in the future.
    Matched MeSH terms: Models, Theoretical
  4. Dominic JA, Aris AZ, Sulaiman WN, Tahir WZ
    Environ Monit Assess, 2016 Mar;188(3):191.
    PMID: 26914327 DOI: 10.1007/s10661-016-5192-8
    The approach of this paper is to predict the sand mass distribution in an urban stormwater holding pond at the Stormwater Management And Road Tunnel (SMART) Control Centre, Malaysia, using simulated depth average floodwater velocity diverted into the holding during storm events. Discriminant analysis (DA) was applied to derive the classification function to spatially distinguish areas of relatively high and low sand mass compositions based on the simulated water velocity variations at corresponding locations of gravimetrically measured sand mass composition of surface sediment samples. Three inflow parameter values, 16, 40 and 80 m(3) s(-1), representing diverted floodwater discharge for three storm event conditions were fixed as input parameters of the hydrodynamic model. The sand (grain size > 0.063 mm) mass composition of the surface sediment measured at 29 sampling locations ranges from 3.7 to 45.5%. The sampling locations of the surface sediment were spatially clustered into two groups based on the sand mass composition. The sand mass composition of group 1 is relatively lower (3.69 to 12.20%) compared to group 2 (16.90 to 45.55%). Two Fisher's linear discriminant functions, F 1 and F 2, were generated to predict areas; both consist of relatively higher and lower sand mass compositions based on the relationship between the simulated flow velocity and the measured surface sand composition at corresponding sampling locations. F 1 = -9.405 + 4232.119 × A - 1795.805 × B + 281.224 × C, and F 2 = -2.842 + 2725.137 × A - 1307.688 × B + 231.353 × C. A, B and C represent the simulated flow velocity generated by inflow parameter values of 16, 40 and 80 m(3) s(-1), respectively. The model correctly predicts 88.9 and 100.0% of sampling locations consisting of relatively high and low sand mass percentages, respectively, with the cross-validated classification showing that, overall, 82.8% are correctly classified. The model predicts that 31.4% of the model domain areas consist of high-sand mass composition areas and the remaining 68.6% comprise low-sand mass composition areas.
    Matched MeSH terms: Models, Theoretical
  5. Tahmasbi F, Maleki S, Shariati M, Ramli Sulong NH, Tahir MM
    PLoS One, 2016;11(8):e0156989.
    PMID: 27478894 DOI: 10.1371/journal.pone.0156989
    This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed.
    Matched MeSH terms: Models, Theoretical*
  6. Tahriri F, Dawal SZ, Taha Z
    ScientificWorldJournal, 2014;2014:505207.
    PMID: 24982962 DOI: 10.1155/2014/505207
    A new multiobjective dynamic fuzzy genetic algorithm is applied to solve a fuzzy mixed-model assembly line sequencing problem in which the primary goals are to minimize the total make-span and minimize the setup number simultaneously. Trapezoidal fuzzy numbers are implemented for variables such as operation and travelling time in order to generate results with higher accuracy and representative of real-case data. An improved genetic algorithm called fuzzy adaptive genetic algorithm (FAGA) is proposed in order to solve this optimization model. In establishing the FAGA, five dynamic fuzzy parameter controllers are devised in which fuzzy expert experience controller (FEEC) is integrated with automatic learning dynamic fuzzy controller (ALDFC) technique. The enhanced algorithm dynamically adjusts the population size, number of generations, tournament candidate, crossover rate, and mutation rate compared with using fixed control parameters. The main idea is to improve the performance and effectiveness of existing GAs by dynamic adjustment and control of the five parameters. Verification and validation of the dynamic fuzzy GA are carried out by developing test-beds and testing using a multiobjective fuzzy mixed production assembly line sequencing optimization problem. The simulation results highlight that the performance and efficacy of the proposed novel optimization algorithm are more efficient than the performance of the standard genetic algorithm in mixed assembly line sequencing model.
    Matched MeSH terms: Models, Theoretical
  7. Samrat NH, Ahmad N, Choudhury IA, Taha Z
    PLoS One, 2015;10(6):e0130678.
    PMID: 26121032 DOI: 10.1371/journal.pone.0130678
    Energy is one of the most important factors in the socioeconomic development of a country. In a developing country like Malaysia, the development of islands is mostly related to the availability of electric power. Power generated by renewable energy sources has recently become one of the most promising solutions for the electrification of islands and remote rural areas. But high dependency on weather conditions and the unpredictable nature of these renewable energy sources are the main drawbacks. To overcome this weakness, different green energy sources and power electronic converters need to be integrated with each other. This study presents a battery storage hybrid standalone photovoltaic-wind energy power supply system. In the proposed standalone hybrid system, a DC-DC buck-boost bidirectional converter controller is used to accumulates the surplus hybrid power in the battery bank and supplies this power to the load during the hybrid power shortage by maintaining the constant dc-link voltage. A three-phase voltage source inverter complex vector control scheme is used to control the load side voltage in terms of the voltage amplitude and frequency. Based on the simulation results obtained from MATLAB/Simulink, it has been found that the overall hybrid framework is capable of working under variable weather and load conditions.
    Matched MeSH terms: Models, Theoretical
  8. Matlan SJ, Mukhlisin M, Taha MR
    ScientificWorldJournal, 2014;2014:569851.
    PMID: 24971384 DOI: 10.1155/2014/569851
    Soil-water characteristic curves (SWCCs) are important in terms of groundwater recharge, agriculture, and soil chemistry. These relationships are also of considerable value in geotechnical and geoenvironmental engineering. Their measurement, however, is difficult, expensive, and time-consuming. Many empirical models have been developed to describe the SWCC. Statistical assessment of soil-water characteristic curve models found that exponential-based model equations were the most difficult to fit and generally provided the poorest fit to the soil-water characteristic data. In this paper, an exponential-based model is devised to describe the SWCC. The modified equation is similar to those previously reported by Gardner (1956) but includes exponential variable. Verification was performed with 24 independent data sets for a wide range of soil textures. Prediction results were compared with the most widely used models to assess the model's performance. It was proven that the exponential-based equation of the modified model provided greater flexibility and a better fit to data on various types of soil.
    Matched MeSH terms: Models, Theoretical*
  9. Hooi, M.H., Tiong, W. K., Tay, K. G., Chiew,K. L., Sze, S. N.
    MATEMATIKA, 2018;34(2):333-350.
    MyJurnal
    In this paper, we look at the propagation of internal solitary waves over three
    different types of slowly varying region, i.e. a slowly increasing slope, a smooth bump and
    a parabolic mound in a two-layer fluid flow. The appropriate mathematical model for this
    problem is the variable-coefficient extended Korteweg-de Vries equation. The governing
    equation is then solved numerically using the method of lines. Our numerical simulations
    show that the internal solitary waves deforms adiabatically on the slowly increasing slope.
    At the same time, a trailing shelf is generated as the internal solitary wave propagates
    over the slope, which would then decompose into secondary solitary waves or a wavetrain.
    On the other hand, when internal solitary waves propagate over a smooth bump or a
    parabolic mound, a trailing shelf of negative polarity would be generated as the results of
    the interaction of the internal solitary wave with the decreasing slope of the bump or the
    parabolic mound. The secondary solitary waves is observed to be climbing the negative
    trailing shelf.
    Matched MeSH terms: Models, Theoretical
  10. Siswanto, W.A., Syiddiq, M.
    MyJurnal
    This paper presents a mathematical model of the traditional musical instrument, the kompang. In this study, a mathematical model of the kompang membrane is developed to simulate the vibration of the kompang membrane in polar coordinates by implementing the Fourier-Bessel wave function. The wave equation in polar direction is applied to provide the vibration modes of the membrane with the corresponding natural frequencies of the circular membrane. The initial and boundary conditions are determined to allow the development of numerical equation based on kompang membrane attachment. The mathematical model is coded in Smath for the numerical analysis as well as the plotting tool. Two kompang membrane cases with different membrane materials i.e. goat-skin and x-ray film are tried to test the model. The Finite Element Method (FEM) programme, Mecway, shows that the natural frequencies and the corresponding mode shapes are comparable with those from the developed model.
    Matched MeSH terms: Models, Theoretical
  11. Hidayat R, Zulnaidi H, Syed Zamri SNA
    PLoS One, 2018;13(11):e0206211.
    PMID: 30399170 DOI: 10.1371/journal.pone.0206211
    This study investigates the relationship between metacognition and achievement goals which may influence mathematical modeling competency in students of mathematics education programs. The current study employs 538 students of mathematics education program; 483 (89.8%) of whom are male and 55 (10.2%) are aged from 18 years old to 22 years old. The study follows a correlational research design to investigate and measure the degree of relationship amongst mathematical modeling competencies, achievement goals and metacognition. Results indicate that achievement goals and metacognition positively influence mathematical modeling competency. Moreover, four metacognition dimensions including awareness, planning, cognitive strategy and self-checking are positive partial mediators because they increase the association between achievement goals and mathematical modeling competency. In conclusion, metacognition and achievement goals positively affect students' mathematical modeling competency.
    Matched MeSH terms: Models, Theoretical*
  12. Norzaida Abas, Rafidah Mohd Shamsuddin, Noor Shazwani Osman, Syafrina Abd. Halim
    MyJurnal
    Dengue fever is an endemic disease in many tropical and subtropical regions. In
    Malaysia, it is the leading public health challenge despite the extensive intervention
    programs by the related authorities. Distribution of dengue cases in Malaysia varies
    according to states and districts where cases are more distinct in urban and suburban
    areas. Preparedness strategies of dengue cases could be more successful with some
    comprehensive and technical analysis on disease incidences. Hence, the present study
    analyses dengue cases using mathematical modelling in the state of Penang, one of the
    more urbanised state. In particular, two time series models are fitted to the dengue
    data from the region in order to identify the mathematical model that best describe
    the data. Results show that both proposed models are able to represent the cases
    rather well; however numerical inspection revealed that Double Exponential
    Smoothing method is the better choice. Subsequently, the identified model is used to
    make forecasting on the number of expected cases. Results show that dengue cases in
    Penang are expected to increase gradually.
    Matched MeSH terms: Models, Theoretical
  13. Swarna Nantha Y, Haque S, Swarna Nantha H
    Fam Pract, 2019 10 08;36(5):581-586.
    PMID: 30534941 DOI: 10.1093/fampra/cmy119
    BACKGROUND: There has been a shift in worldwide disease burden from infections to non-communicable diseases, especially type 2 diabetes (T2D). Behavioural change and self-management are key to optimal T2D control. Several universal models of diabetic care have been proposed to help explain the dimensions of T2D self-care such as medication adherence, physical activity, diet and patient-doctor interaction. These models do not allow an objective and quantifiable measurement of the problems faced by patients in terms of medication compliance.

    OBJECTIVE: To create a comprehensive conceptual model of behavioural change related to T2D medication compliance.

    METHODS: A cross-sectional study will be conducted at a regional primary care clinic using a mixed-method technique. First, a Grounded Theory qualitative inquiry will be used to investigate predictors of medication adherence in T2D patients. Consequently, the elements derived from the interview will be incorporated into the Theory of Planned Behaviour framework to generate an integrated behavioural model. This model will then be used to quantify the factors related to compliance with medication amongst T2D patients.

    DISCUSSION: The framework developed here could help in the design of policies to optimize T2D control by identifying lapses in patients' intake of diabetic medications. This can be done by exploring the patients' fundamental and unarticulated belief system via a naturalistic approach adopted in this study. The properties of the framework can be replicated in other settings to serve as a benchmark for quality improvement in T2D patient care.

    Matched MeSH terms: Models, Theoretical*
  14. Mustafa S, Bahar A, Aziz ZA, Suratman S
    J Environ Manage, 2016 Jan 01;165:159-166.
    PMID: 26433356 DOI: 10.1016/j.jenvman.2015.09.026
    Analytical study of the influence of both the pumping well discharge rate and pumping time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both pumping time and travelling time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the pumping time and pumping rate, which control the travelling time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the pumping rate or simulation pumping time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.
    Matched MeSH terms: Models, Theoretical*
  15. Harkness S, Super CM
    Soc Sci Med, 1994 Jan;38(2):217-26.
    PMID: 8140448
    Recent efforts to promote child survival and development internationally have focused new attention on the importance of the household as a mediator of both environmental risks and programmatic interventions to promote better health. In this paper, we introduce a theoretical framework, the 'developmental niche,' derived from studies of children's behavior and development in different cultural contexts, as a tool for analyzing the household production of health. The developmental niche is conceptualized in terms of three basic components: (1) the physical and social settings of the child's everyday life; (2) culturally regulated customs of child care and child rearing; and (3) the psychology of the caretakers. The relevance of each of these components to the household production of health is illustrated through examples from research in several cultures, including Malaysia, Kenya, Bangladesh, India, and the U.S. Further discussion centers on three corollaries of the developmental niche framework that point to the interactive relationships among the three components, between the niche and the larger environment, and between the niche and the child (or any individual seen from a developmental perspective). It is suggested that this approach is useful for identifying and collecting relevant information on household-level factors that affect health outcomes, and thus for organizing more effective interventions. At a theoretical level, the developmental niche framework also facilitates understanding processes of mutual adaptation between the individual and the environment as they are filtered through the constraints of household settings, customs and caretaker psychologies.
    Matched MeSH terms: Models, Theoretical*
  16. S. Bhatia, K. T. Lee, A. R. Mohamed, Sumathi, S.
    MyJurnal
    Simultaneous removal of SO2 and NO from simulated flue gas by cerium oxide supported over palm shell activated carbon (Ce/PSAC) was studied in a fixed bed adsorber. In this study, the adsorption breakthrough of SO2 and NO on Ce/PSAC at different reaction temperatures was manipulated to test their applicability to a model developed by Yoon and Nelson (1984) for breakthrough curves. Yoon and Nelson (1984) developed a relatively simple model addressing the adsorption and breakthrough of adsorbate vapour with respect to activated charcoal. This model was based on the assumption that the rate of decrease in the probability of adsorption for each adsorbate molecule is proportional to the probability of adsorbate adsorption and the probability of adsorbate breakthrough on the adsorbent. A regression analysis (least square method) has been used to give the model parameters of k and t1/2. The results showed that the agreement between the model and the experimental results is satisfactory. From the observation, it is concluded that the simple two-parameter model of Yoon and Nelson’s model can be applied for modelling the breakthrough curves of SO2 and NO gas adsorption over Ce/PSAC.
    Matched MeSH terms: Models, Theoretical
  17. Hasan, Talaat I., Shaharuddin Salleh, Sulaiman, Nejmaddin A.
    MATEMATIKA, 2017;33(2):191-206.
    MyJurnal
    In this paper, we consider the system of Volterra-Fredholm integral equations
    of the second kind (SVFI-2). We proposed fixed point method (FPM) to solve
    SVFI-2 and improved fixed point method (IFPM) for solving the problem. In addition,
    a few theorems and two new algorithms are introduced. They are supported by
    numerical examples and simulations using Matlab. The results are reasonably good
    when compared with the exact solutions.
    Matched MeSH terms: Models, Theoretical
  18. Saini S, Zakaria N, Rambli DR, Sulaiman S
    PLoS One, 2015;10(5):e0127833.
    PMID: 25978493 DOI: 10.1371/journal.pone.0127833
    The high-dimensional search space involved in markerless full-body articulated human motion tracking from multiple-views video sequences has led to a number of solutions based on metaheuristics, the most recent form of which is Particle Swarm Optimization (PSO). However, the classical PSO suffers from premature convergence and it is trapped easily into local optima, significantly affecting the tracking accuracy. To overcome these drawbacks, we have developed a method for the problem based on Hierarchical Multi-Swarm Cooperative Particle Swarm Optimization (H-MCPSO). The tracking problem is formulated as a non-linear 34-dimensional function optimization problem where the fitness function quantifies the difference between the observed image and a projection of the model configuration. Both the silhouette and edge likelihoods are used in the fitness function. Experiments using Brown and HumanEva-II dataset demonstrated that H-MCPSO performance is better than two leading alternative approaches-Annealed Particle Filter (APF) and Hierarchical Particle Swarm Optimization (HPSO). Further, the proposed tracking method is capable of automatic initialization and self-recovery from temporary tracking failures. Comprehensive experimental results are presented to support the claims.
    Matched MeSH terms: Models, Theoretical
  19. Issabayeva G, Aroua MK, Sulaiman NM
    Bioresour Technol, 2006 Dec;97(18):2350-5.
    PMID: 16321520
    The performance of a commercially available palm shell based activated carbon to remove lead ions from aqueous solutions by adsorption was evaluated. The adsorption experiments were carried out at pH 3.0 and 5.0. The effect of malonic and boric acid presence on the adsorption of lead ions was also studied. Palm shell activated carbon showed high adsorption capacity for lead ions, especially at pH 5 with an ultimate uptake of 95.2mg/g. This high uptake showed palm shell activated carbon as amongst the best adsorbents for lead ions. Boric acid presence did not affect significantly lead uptake, whereas malonic acid decreased it. The diffuse layer surface complexation model was applied to predict the extent of adsorption. The model prediction was found to be in concordance with the experimental values.
    Matched MeSH terms: Models, Theoretical
  20. Talib AT, Mokhtar MN, Baharuddin AS, Sulaiman A
    Bioresour Technol, 2014 Oct;169:428-38.
    PMID: 25079208 DOI: 10.1016/j.biortech.2014.07.033
    The effect of different aeration rates on the organic matter (OM) degradation during the active phase of oil palm empty fruit bunch (EFB)-rabbit manure co-composting process under constant forced-aeration system has been studied. Four different aeration rates, 0.13 L min(-1) kg(DM)(-1),0.26 L min(-1) kg(DM)(-1),0.49 L min(-1) kg(DM)(-1) and 0.74 L min(-1) kg(DM)(-1) were applied. 0.26 L min(-1) kg(DM)(-1) provided enough oxygen level (10%) for the rest of composting period, showing 40.5% of OM reduction that is better than other aeration rates. A dynamic mathematical model describing OM degradation, based on the ratio between OM content and initial OM content with correction functions of moisture content, free air space, oxygen and temperature has been proposed.
    Matched MeSH terms: Models, Theoretical*
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