Displaying publications 81 - 100 of 735 in total

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  1. Low-gradient magnetic separation of magnetic nanoparticles under continuous flow: Experimental study, transport mechanism and mathematical modelling
    Tan YW, Leong SS, Lim J, Yeoh WM, Toh PY
    Electrophoresis, 2022 Nov;43(21-22):2234-2249.
    PMID: 35921231 DOI: 10.1002/elps.202200078
    Low-gradient magnetic separation (LGMS) of magnetic nanoparticles (MNPs) has been proven as one of the techniques with great potential for biomedical and environmental applications. Recently, the underlying principle of particle capture by LGMS, through a process known as magnetophoresis, under the influence of hydrodynamic effect has been widely studied and illustrated. Even though the hydrodynamic effect is very substantial for batch processes, its impact on LGMS operated at continuous flow (CF) condition remained largely unknown. Hence, in this study, the dynamical behaviour of LGMS process operated under CF was being studied. First, the LGMS experiments using poly(sodium 4-styrenesulfonate)-functionalized-MNP as modelled particle system were performed through batchwise (BW) and CF modes at different operating conditions. Here BW operation was used as a comparative study to elucidate the transport mechanism of MNP under the similar environment of CF-LGMS process, and it was found out that the convection induced by magnetophoresis (timescale effective is ∼1200 s) is only significant at far-from-magnet region. Hence, it can be deduced that forced convection is more dominant on influencing the transport behaviour of CF-LGMS (with resident time ≤240 s). Moreover, we found that the separation efficiency of CF-LGMS process can be boosted by the higher number of magnets, the higher MNP concentration and the lower flowrate of MNP solution. To better illustrate the underlying dynamical behaviour of LGMS process, a mathematical model was developed to predict its kinetic profile and separation efficiency (with average error of ∼2.6% compared to the experimental results).
    Matched MeSH terms: Models, Theoretical
  2. Fulltext Recruitment constraints in Singapore's fluted giant clam (Tridacna squamosa) population--a dispersal model approach
    Neo ML, Erftemeijer PL, van Beek JK, van Maren DS, Teo SL, Todd PA
    PLoS One, 2013;8(3):e58819.
    PMID: 23555597 DOI: 10.1371/journal.pone.0058819
    Recruitment constraints on Singapore's dwindling fluted giant clam, Tridacna squamosa, population were studied by modelling fertilisation, larval transport, and settlement using real-time hydrodynamic forcing combined with knowledge of spawning characteristics, larval development, behaviour, and settlement cues. Larval transport was simulated using a finite-volume advection-diffusion model coupled to a three-dimensional hydrodynamic model. Three recruitment constraint hypotheses were tested: 1) there is limited connectivity between Singapore's reefs and other reefs in the region, 2) there is limited exchange within Singapore's Southern Islands, and 3) there exist low-density constraints to fertilisation efficacy (component Allee effects). Results showed that connectivity among giant clam populations was primarily determined by residual hydrodynamic flows and spawning time, with greatest chances of successful settlement occurring when spawning and subsequent larval dispersal coincided with the period of lowest residual flow. Simulations suggested poor larval transport from reefs located along the Peninsular Malaysia to Singapore, probably due to strong surface currents between the Andaman Sea and South China Sea combined with a major land barrier disrupting larval movement among reefs. The model, however, predicted offshore coral reefs to the southeast of Singapore (Bintan and Batam) may represent a significant source of larvae. Larval exchange within Singapore's Southern Islands varied substantially depending on the locations of source and sink reefs as well as spawning time; but all simulations resulted in low settler densities (2.1-68.6 settled individuals per 10,000 m(2)). Poor fertilisation rates predicted by the model indicate that the low density and scattered distribution of the remaining T. squamosa in Singapore are likely to significantly inhibit any natural recovery of local stocks.
    Matched MeSH terms: Models, Theoretical*
  3. Fulltext A multiscale mathematical model describing the growth and development of bambara groundnut
    Dodd J, Sweby PK, Mayes S, Murchie EH, Karunaratne AS, Massawe F, et al.
    J Theor Biol, 2023 Mar 07;560:111373.
    PMID: 36509139 DOI: 10.1016/j.jtbi.2022.111373
    A principal objective in agriculture is to maximise food production; this is particularly relevant with the added demands of an ever increasing population, coupled with the unpredictability that climate change brings. Further improvements in productivity can only be achieved with an increased understanding of plant and crop processes. In this respect, mathematical modelling of plants and crops plays an important role. In this paper we present a two-scale mathematical model of crop yield that accounts for plant growth and canopy interactions. A system of nonlinear ordinary differential equations (ODEs) is formulated to describe the growth of each individual plant, where equations are coupled via a term that describes plant competition via canopy-canopy interactions. A crop of greenhouse plants is then modelled via an agent based modelling approach in which the growth of each plant is described via our system of ODEs. The model is formulated for the African drought tolerant legume bambara groundnut (Vigna subterranea), which is currently being investigated as a food source in light of climate change and food insecurity challenges. Our model allows us to account for plant diversity and also investigate the effect of individual plant traits (e.g. plant canopy size and planting distance) on the yield of the overall crop. Informed with greenhouse data, model results show that plant positioning relative to other plants has a large impact on individual plant yield. Variation in physiological plant traits from genetic diversity and the environmental effects lead to experimentally observed variations in crop yield. These traits include plant height, plant carrying capacity, leaf accumulation rate and canopy spread. Of these traits plant height and ground cover growth rates are found to have the greatest impact on crop yield. We also consider a range of different planting arrangements (uniform grid, staggered grid, circular rings and random allocation) and find that the staggered grid leads to the greatest crop yield (6% more compared to uniform grid). Whilst formulated specifically for bambara groundnut, the generic formulation of our model means that with changes to certain parameter's, it may be extended to other crop species that form a canopy.
    Matched MeSH terms: Models, Theoretical
  4. The determinants of fertility: a theoretical forecasting model
    Fish M, Thompson AA
    Behav Sci, 1970 Jul;15(4):318-28.
    PMID: 5424500
    Matched MeSH terms: Models, Theoretical*
  5. Fulltext Modelling of precast concrete composite slab using finite and interface elements
    Jaafar, M.S., Wong, N.J., Noorzaei, J., Thanoon, W.A.
    Pertanika Journal of Science & Technology, 2009;17(2):-.
    MyJurnal
    This study presents an efficient finite element analysis technique which shows great versatility in
    modelling of precast composite flooring system subjected to static loadings. The method incorporates sliding and opening in the analysis of composite structures using the interface element which was specifically designed to simulate the actual behaviour at the interfaces between contacting materials. A three-dimensional finite element model of the precast composite slab which exhibits discontinuous behaviour was performed to demonstrate the potential and applicability of the proposed method of analysis. The results of the analysis demonstrate that the overall response of a discontinuous system to external loading is significantly affected by the bonding condition at the interfaces between the contacting materials.
    Matched MeSH terms: Models, Theoretical
  6. Fulltext Heuristics for multiobjective optimization of two-sided assembly line systems
    Jawahar N, Ponnambalam SG, Sivakumar K, Thangadurai V
    ScientificWorldJournal, 2014;2014:458959.
    PMID: 24790568 DOI: 10.1155/2014/458959
    Products such as cars, trucks, and heavy machinery are assembled by two-sided assembly line. Assembly line balancing has significant impacts on the performance and productivity of flow line manufacturing systems and is an active research area for several decades. This paper addresses the line balancing problem of a two-sided assembly line in which the tasks are to be assigned at L side or R side or any one side (addressed as E). Two objectives, minimum number of workstations and minimum unbalance time among workstations, have been considered for balancing the assembly line. There are two approaches to solve multiobjective optimization problem: first approach combines all the objectives into a single composite function or moves all but one objective to the constraint set; second approach determines the Pareto optimal solution set. This paper proposes two heuristics to evolve optimal Pareto front for the TALBP under consideration: Enumerative Heuristic Algorithm (EHA) to handle problems of small and medium size and Simulated Annealing Algorithm (SAA) for large-sized problems. The proposed approaches are illustrated with example problems and their performances are compared with a set of test problems.
    Matched MeSH terms: Models, Theoretical
  7. Analysis of coupling efficiency on hemispherical fiber lens by method of lines
    Lambak Z, Abdul Rahman F, Mokhtar MR, Tengku IA
    Opt Express, 2009 Feb 16;17(4):2926-37.
    PMID: 19219196
    The method of lines (MoL) has been developed to study coupling efficiency on hemispherical lens. In this paper, the physical shape of the lens is approximated by cascading a number of straight waveguide segments. The perfectly matched layer (PML) is applied as an absorber for the MoL to reduce numerical reflection in the simulation region. Analysis is done by calculating coupling efficiency at the plane of integration where the coupling efficiency is an overlap integral between laser diode field and fiber field. The result of coupling efficiency in this analysis is compared to the experiment and ABCD matrix. It is found that MoL gives good result accuracy.
    Matched MeSH terms: Models, Theoretical*
  8. Fulltext A review of subsequence time series clustering
    Zolhavarieh S, Aghabozorgi S, Teh YW
    ScientificWorldJournal, 2014;2014:312521.
    PMID: 25140332 DOI: 10.1155/2014/312521
    Clustering of subsequence time series remains an open issue in time series clustering. Subsequence time series clustering is used in different fields, such as e-commerce, outlier detection, speech recognition, biological systems, DNA recognition, and text mining. One of the useful fields in the domain of subsequence time series clustering is pattern recognition. To improve this field, a sequence of time series data is used. This paper reviews some definitions and backgrounds related to subsequence time series clustering. The categorization of the literature reviews is divided into three groups: preproof, interproof, and postproof period. Moreover, various state-of-the-art approaches in performing subsequence time series clustering are discussed under each of the following categories. The strengths and weaknesses of the employed methods are evaluated as potential issues for future studies.
    Matched MeSH terms: Models, Theoretical
  9. Fulltext Simulation of spray drying on Piper betle Linn extracts using computational fluid dynamics
    Cher Pin, S., Rashmi, W., Khalid, M., Chong, C.H., Woo, M.W., Tee, L.H.
    International Food Research Journal, 2014;21(3):1089-1096.
    MyJurnal
    The drying of Piper betle Linn (betel) leaf extract using a lab scale spray dryer was simulated using Computational Fluid Dynamics (CFD). Three different turbulent models (standard k-ε, RNG k-ε and realizable k-ε) were used in the present study to determine the most suitable model for predicting the flow profile. Parametric studies were also conducted to evaluate the effect of process variables on the final moisture content. Four different initial droplet sizes (36, 79, 123 and 166 μm) were tested with four sets of combination of hot air temperature (140 and 160°C) and feed rate (4, 9.5 and 15 ml/min). It was found that standard k-ε is the most suitable turbulent model to predict the flow behaviour Moreover, the lowest final moisture content present in samples was obtained at 140°C and a feed rate of 15.0 ml/min.
    Matched MeSH terms: Models, Theoretical
  10. Are Pyrodinium blooms in the Southeast Asian region recurring and spreading? A view at the end of the millennium
    Azanza RV, Taylor FJ
    Ambio, 2001 Sep;30(6):356-64.
    PMID: 11757284
    Pyrodinium bahamense (var. compressum) has been the only dinoflagellate species that has caused major public health and economic problems in the Southeast Asian region for more than 2 decades now. It produces saxitoxin, a suite of toxins that cause Paralytic Shellfish Poisoning (PSP). A serious toxicological problem affecting many countries of the world, mild cases of this poisoning can occur within 30 minutes while in extreme cases, death through respiratory paralysis may occur within 2-24 hrs of ingestion of intoxicated shellfish. Blooms of the organism have been reported in Malaysia, Brunei Darussalam, the Philippines and Indonesia. The ASEAN-Canada Red Tide Network has recorded 31 blooms of the organism in 26 areas since 1976 when it first occurred in Sabah, Malaysia. As of 1999, the most hard hit country has been the Philippines which has the greatest number of areas affected (18) and highest number of Paralytic Shellfish Poisoning (PSP) cases (about 1995). Malaysia has reported a total of 609 PSP cases and 44 deaths while Brunei has recorded 14 PSP cases and no fatalities. Indonesia, on the other hand has a record of 427 PSP cases and 17 deaths. Studies on ecological/environmental impacts of these blooms have not been done in the region. Estimates of economic impacts have shown that the loss could be up to USD 300,000 day-1. Most of the data and information useful for understanding Pyrodinium bloom dynamics have come from harmful/toxic algal monitoring and research that have developed to different degrees in the various countries in the region affected by the organism's bloom. Regional collaborative research and monitoring efforts can help harmonize local data sets and ensure their quality and availability for comparative analysis and modeling. Temporal patterns of the blooms at local and regional scales and possible signals and trends in the occurrence/recurrence and spread of Pyrodinium blooms could be investigated. Existing descriptive and simple predictive models of Pyrodinium blooms can be improved and refined to help in the management of the wild harvest and aquaculture of shellfish in a region where the people are dependent on these resources for their daily food sustainance and livelihood.
    Matched MeSH terms: Models, Theoretical*
  11. Fulltext Theoretical analysis and optimization of chromatic dispersion measurement using the technique of relative power of two beating frequencies
    Abdul-Rashid, H.A., Al-Qdah, M.T., Chuah, H.T., Tayahi, M.
    ASM Science Journal, 2008;2(2):129-132.
    MyJurnal
    The operating principle and the performance of chromatic dispersion (CD) measurement technique are discussed through developed numerical models. The performance of the CD measurement technique was studied in terms of the measurement range and sensitivity as the wavelength separation was varied. Based on the numerical model, the technique sensitivity increased with wavelength separation. However, this increase in sensitivity was traded off with a narrower measurement range. The measurement technique was optimized at 5.0 GHz wavelength separation with a sensitivity of 0.009 (dB/ps/nm) and measurement range of 2500 ps/nm.
    Matched MeSH terms: Models, Theoretical
  12. The fate of sotalol in aqueous chlorination: Kinetics, mechanisms and ecotoxicity assessment
    Khalit WNAW, Tay KS
    Ecotoxicol Environ Saf, 2017 Nov;145:214-220.
    PMID: 28738204 DOI: 10.1016/j.ecoenv.2017.07.020
    Unmetabolized pharmaceuticals often enter the water treatment plants and exposed to various treatment processes. Among these water treatment processes, disinfection is a process which involves the application of chemical oxidation to remove pathogen. Untreated pharmaceuticals from primary and secondary treatment have the potential to be exposed to the chemical oxidation process during disinfection. This study investigated the kinetics and mechanism of the degradation of sotalol during chlorination process. Chlorination with hypochlorous acid (HOCl) as main reactive oxidant has been known as one of the most commonly used disinfection methods. The second order rate constant for the reaction between sotalol and free available chlorine (FAC) was found to decrease from 60.1 to 39.1M-1min-1 when the pH was increased from 6 to 8. This result was mainly attributed by the decreased of HOCl concentration with increasing pH. In the real water samples, the presence of the higher amount of organic content was found to reduce the efficiency of chlorination in the removal of sotalol. This result showed that sotalol competes with natural organic matter to react with HOCl during chlorination. After 24h of FAC exposure, sotalol was found to produce three stable transformation by-products. These by-products are mainly chlorinated compounds. According to the acute and chronic toxicity calculated using ECOSAR computer program, the transformation by-products are more harmful than sotalol.
    Matched MeSH terms: Models, Theoretical
  13. Attenuation of excitation decay rate due to collective effect
    Tay BA
    Phys Rev E Stat Nonlin Soft Matter Phys, 2014 Aug;90(2):022142.
    PMID: 25215723
    We study a series of N oscillators, each coupled to its nearest neighbors, and linearly to a phonon field through the oscillator's number operator. We show that the Hamiltonian of a pair of adjacent oscillators, or a dimer, within the series of oscillators can be transformed into a form in which they are collectively coupled to the phonon field as a composite unit. In the weak coupling and rotating-wave approximation, the system behaves effectively as the trilinear boson model in the one excitation subspace of the dimer subsystem. The reduced dynamics of the one excitation subspace of the dimer subsystem coupled weakly to a phonon bath is similar to that of a two-level system, with a metastable state against the vacuum. The decay constant of the subsystem is proportional to the dephasing rate of the individual oscillator in a phonon bath, attenuated by a factor that depends on site asymmetry, intersite coupling, and the resonance frequency between the transformed oscillator modes, or excitons. As a result of the collective effect, the excitation relaxation lifetime is prolonged over the dephasing lifetime of an individual oscillator coupled to the same bath.
    Matched MeSH terms: Models, Theoretical*
  14. Unravelling proximate cues of mass flowering in the tropical forests of South-East Asia from gene expression analyses
    Yeoh SH, Satake A, Numata S, Ichie T, Lee SL, Basherudin N, et al.
    Mol Ecol, 2017 Oct;26(19):5074-5085.
    PMID: 28749031 DOI: 10.1111/mec.14257
    Elucidating the physiological mechanisms of the irregular yet concerted flowering rhythm of mass flowering tree species in the tropics requires long-term monitoring of flowering phenology, exogenous and endogenous environmental factors, as well as identifying interactions and dependencies among these factors. To investigate the proximate factors for floral initiation of mast seeding trees in the tropics, we monitored the expression dynamics of two key flowering genes, meteorological conditions and endogenous resources over two flowering events of Shorea curtisii and Shorea leprosula in the Malay Peninsula. Comparisons of expression dynamics of genes studied indicated functional conservation of FLOWERING LOCUS T (FT) and LEAFY (LFY) in Shorea. The genes were highly expressed at least 1 month before anthesis for both species. A mathematical model considering the synergistic effect of cool temperature and drought on activation of the flowering gene was successful in predicting the observed gene expression patterns. Requirement of both cool temperature and drought for floral transition suggested by the model implies that flowering phenologies of these species are sensitive to climate change. Our molecular phenology approach in the tropics sheds light on the conserved role of flowering genes in plants inhabiting different climate zones and can be widely applied to dissect the flowering processes in other plant species.
    Matched MeSH terms: Models, Theoretical
  15. Fulltext Controlled Release Fertilizers: A Review on Coating Materials and Mechanism of Release
    Lawrencia D, Wong SK, Low DYS, Goh BH, Goh JK, Ruktanonchai UR, et al.
    Plants (Basel), 2021 Jan 26;10(2).
    PMID: 33530608 DOI: 10.3390/plants10020238
    Rising world population is expected to increase the demand for nitrogen fertilizers to improve crop yield and ensure food security. With existing challenges on low nutrient use efficiency (NUE) of urea and its environmental concerns, controlled release fertilizers (CRFs) have become a potential solution by formulating them to synchronize nutrient release according to the requirement of plants. However, the most significant challenge that persists is the "tailing" effect, which reduces the economic benefits in terms of maximum fertilizer utilization. High materials cost is also a significant obstacle restraining the widespread application of CRF in agriculture. The first part of this review covers issues related to the application of conventional fertilizer and CRFs in general. In the subsequent sections, different raw materials utilized to form CRFs, focusing on inorganic and organic materials and synthetic and natural polymers alongside their physical and chemical preparation methods, are compared. Important factors affecting rate of release, mechanism of release and mathematical modelling approaches to predict nutrient release are also discussed. This review aims to provide a better overview of the developments regarding CRFs in the past ten years, and trends are identified and analyzed to provide an insight for future works in the field of agriculture.
    Matched MeSH terms: Models, Theoretical
  16. A clonal selection algorithm model for daily rainfall data prediction
    Noor Rodi NS, Malek MA, Ismail AR, Ting SC, Tang CW
    Water Sci Technol, 2014;70(10):1641-7.
    PMID: 25429452 DOI: 10.2166/wst.2014.420
    This study applies the clonal selection algorithm (CSA) in an artificial immune system (AIS) as an alternative method to predicting future rainfall data. The stochastic and the artificial neural network techniques are commonly used in hydrology. However, in this study a novel technique for forecasting rainfall was established. Results from this study have proven that the theory of biological immune systems could be technically applied to time series data. Biological immune systems are nonlinear and chaotic in nature similar to the daily rainfall data. This study discovered that the proposed CSA was able to predict the daily rainfall data with an accuracy of 90% during the model training stage. In the testing stage, the results showed that an accuracy between the actual and the generated data was within the range of 75 to 92%. Thus, the CSA approach shows a new method in rainfall data prediction.
    Matched MeSH terms: Models, Theoretical*
  17. Statistical factorial analysis approach for parameter calibration on material nonlinearity of intervertebral disc finite element model
    Masni-Azian, Tanaka M
    Comput Methods Biomech Biomed Engin, 2017 Aug;20(10):1066-1076.
    PMID: 28532164 DOI: 10.1080/10255842.2017.1331345
    In the biomechanics field, material parameters calibration is significant for finite element (FE) model to ensure a legit estimation of biomechanical response. Determining an appropriate combination of calibration factors is challenging as each constitutive component responds differently. This study proposes a statistical factorial analysis approach using L16(4(5)) orthogonal array to evaluate material nonlinearity and applicable calibration factor of the intervertebral disc FE model in pure moment. The calibrated model exhibits improved agreement to the experimental findings for all directions. Appropriate combination of calibration parameter reduces the estimation gap to the experimental findings, ensuring agreeable biomechanical responses.
    Matched MeSH terms: Models, Theoretical
  18. A causal eco-industrial park hierarchical transition model with qualitative information: Policy and regulatory framework leads to collaboration among firms
    Tseng ML, Negash YT, Nagypál NC, Iranmanesh M, Tan RR
    J Environ Manage, 2021 Aug 15;292:112735.
    PMID: 33992872 DOI: 10.1016/j.jenvman.2021.112735
    Eco-industrial parks promise to reduce environmental and social impacts and improve the economic performance of industrial parks. However, the transition from industrial parks to eco-industrial parks is still not well understood. This study contributes to developing valid hierarchical eco-industrial park transition attribute sets with qualitative information, as prior studies lack an exploration of the attributes in the transition of eco-industrial parks in Hungary. In nature, eco-industrial park transition attributes have causal and hierarchical interrelationships and are described with qualitative information. The assessment involves an analysis of the industrial symbiosis principles by using linguistic preferences. However, multiple attributes are involved in the assessment; therefore, this study proposes the Delphi method to develop a valid attribute set and applies fuzzy set theory to translate qualitative information into crisp values. The fuzzy decision-making trial evaluation laboratory method is used to visualize the attributes' causal interrelationships under uncertainties. The results indicate that the policy and regulatory framework leads to collaboration among firms in the eco-industrial park transition model. In practice, price reforms, management commitment, strategic planning, cognitive barriers and the integration of external information are the practical criteria for improvement. Theoretical and practical implications are also discussed.
    Matched MeSH terms: Models, Theoretical
  19. An External Independent Validation of APACHE IV in a Malaysian Intensive Care Unit
    Wong RS, Ismail NA, Tan CC
    Ann Acad Med Singap, 2015 Apr;44(4):127-32.
    PMID: 26041636
    INTRODUCTION: Intensive care unit (ICU) prognostic models are predominantly used in more developed nations such as the United States, Europe and Australia. These are not that popular in Southeast Asian countries due to costs and technology considerations. The purpose of this study is to evaluate the suitability of the acute physiology and chronic health evaluation (APACHE) IV model in a single centre Malaysian ICU.

    MATERIALS AND METHODS: A prospective study was conducted at the single centre ICU in Hospital Sultanah Aminah (HSA) Malaysia. External validation of APACHE IV involved a cohort of 916 patients who were admitted in 2009. Model performance was assessed through its calibration and discrimination abilities. A first-level customisation using logistic regression approach was also applied to improve model calibration.

    RESULTS: APACHE IV exhibited good discrimination, with an area under receiver operating characteristic (ROC) curve of 0.78. However, the model's overall fit was observed to be poor, as indicated by the Hosmer-Lemeshow goodness-of-fit test (Ĉ = 113, P <0.001). Predicted in-ICU mortality rate (28.1%) was significantly higher than the actual in-ICU mortality rate (18.8%). Model calibration was improved after applying first-level customisation (Ĉ = 6.39, P = 0.78) although discrimination was not affected.

    CONCLUSION: APACHE IV is not suitable for application in HSA ICU, without further customisation. The model's lack of fit in the Malaysian study is attributed to differences in the baseline characteristics between HSA ICU and APACHE IV datasets. Other possible factors could be due to differences in clinical practice, quality and services of health care systems between Malaysia and the United States.

    Matched MeSH terms: Models, Theoretical*
  20. Fulltext Linear-Nonlinear Stiffness Responses of Carbon Fiber-Reinforced Polymer Composite Materials and Structures: A Numerical Study
    R Koloor SS, Karimzadeh A, Abdullah MR, Petrů M, Yidris N, Sapuan SM, et al.
    Polymers (Basel), 2021 Jan 22;13(3).
    PMID: 33498984 DOI: 10.3390/polym13030344
    The stiffness response or load-deformation/displacement behavior is the most important mechanical behavior that frequently being utilized for validation of the mathematical-physical models representing the mechanical behavior of solid objects in numerical method, compared to actual experimental data. This numerical study aims to investigate the linear-nonlinear stiffness behavior of carbon fiber-reinforced polymer (CFRP) composites at material and structural levels, and its dependency to the sets of individual/group elastic and damage model parameters. In this regard, a validated constitutive damage model, elastic-damage properties as reference data, and simulation process, that account for elastic, yielding, and damage evolution, are considered in the finite element model development process. The linear-nonlinear stiffness responses of four cases are examined, including a unidirectional CFRP composite laminate (material level) under tensile load, and also three multidirectional composite structures under flexural loads. The result indicated a direct dependency of the stiffness response at the material level to the elastic properties. However, the stiffness behavior of the composite structures depends both on the structural configuration, geometry, lay-ups as well as the mechanical properties of the CFRP composite. The value of maximum reaction force and displacement of the composite structures, as well as the nonlinear response of the structures are highly dependent not only to the mechanical properties, but also to the geometry and the configuration of the structures.
    Matched MeSH terms: Models, Theoretical
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