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  1. Zomorodian M, Lai SH, Homayounfar M, Ibrahim S, Fatemi SE, El-Shafie A
    J Environ Manage, 2018 Dec 01;227:294-304.
    PMID: 30199725 DOI: 10.1016/j.jenvman.2018.08.097
    In recent years, water resources management has become more complicated and controversial due to the impacts of various factors affecting hydrological systems. System Dynamics (SD) has in turn become increasingly popular due to its advantages as a tool for dealing with such complex systems. However, SD also has some limitations. This review contains a comprehensive survey of the existing literature on SD as a potential method to deal with the complexity of system integrated modeling, with a particular focus on the application of SD to the integrated modeling of water resources systems. It discusses the limitations of SD in these contexts, and highlights a number of studies which have applied a combination of SD and other methods to overcome these limitations. Finally, our study makes a number of recommendations for future modifications in the application of SD methods in order to enhance their performance.
    Matched MeSH terms: Models, Theoretical*
  2. Zomorodian M, Lai SH, Homayounfar M, Ibrahim S, Pender G
    PLoS One, 2017;12(12):e0188489.
    PMID: 29216200 DOI: 10.1371/journal.pone.0188489
    Conflicts over water resources can be highly dynamic and complex due to the various factors which can affect such systems, including economic, engineering, social, hydrologic, environmental and even political, as well as the inherent uncertainty involved in many of these factors. Furthermore, the conflicting behavior, preferences and goals of stakeholders can often make such conflicts even more challenging. While many game models, both cooperative and non-cooperative, have been suggested to deal with problems over utilizing and sharing water resources, most of these are based on a static viewpoint of demand points during optimization procedures. Moreover, such models are usually developed for a single reservoir system, and so are not really suitable for application to an integrated decision support system involving more than one reservoir. This paper outlines a coupled simulation-optimization modeling method based on a combination of system dynamics (SD) and game theory (GT). The method harnesses SD to capture the dynamic behavior of the water system, utilizing feedback loops between the system components in the course of the simulation. In addition, it uses GT concepts, including pure-strategy and mixed-strategy games as well as the Nash Bargaining Solution (NBS) method, to find the optimum allocation decisions over available water in the system. To test the capability of the proposed method to resolve multi-reservoir and multi-objective conflicts, two different deterministic simulation-optimization models with increasing levels of complexity were developed for the Langat River basin in Malaysia. The later is a strategic water catchment that has a range of different stakeholders and managerial bodies, which are however willing to cooperate in order to avoid unmet demand. In our first model, all water users play a dynamic pure-strategy game. The second model then adds in dynamic behaviors to reservoirs to factor in inflow uncertainty and adjust the strategies for the reservoirs using the mixed-strategy game and Markov chain methods. The two models were then evaluated against three performance indices: Reliability, Resilience and Vulnerability (R-R-V). The results showed that, while both models were well capable of dealing with conflict resolution over water resources in the Langat River basin, the second model achieved a substantially improved performance through its ability to deal with dynamicity, complexity and uncertainty in the river system.
    Matched MeSH terms: Models, Theoretical*
  3. 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
  4. Zinatizadeh AA, Mohamed AR, Abdullah AZ, Mashitah MD, Hasnain Isa M, Najafpour GD
    Water Res, 2006 Oct;40(17):3193-208.
    PMID: 16949124
    In this study, the interactive effects of feed flow rate (QF) and up-flow velocity (V up) on the performance of an up-flow anaerobic sludge fixed film (UASFF) reactor treating palm oil mill effluent (POME) were investigated. Long-term performance of the UASFF reactor was first examined with raw POME at a hydraulic loading rate (HRT) of 3 d and an influent COD concentration of 44300 mg/l. Extreme reactor instability was observed after 25 d. Raw POME was then chemically pretreated and used as feed. Anaerobic digestion of pretreated POME was modeled and analyzed with two operating variables, i.e. feed flow rate and up-flow velocity. Experiments were conducted based on a central composite face-centered design (CCFD) and analyzed using response surface methodology (RSM). The region of exploration for digestion of the pretreated POME was taken as the area enclosed by the feed flow rate (1.01, 7.63 l/d) and up-flow velocity (0.2, 3 m/h) boundaries. Twelve dependent parameters were either directly measured or calculated as response. These parameters were total COD (TCOD) removal, soluble COD (SCOD) removal, effluent pH, effluent total volatile fatty acid (TVFA), effluent bicarbonate alkalinity (BA), effluent total suspended solids (TSS), CH4 percentage in biogas, methane yield (Y M), specific methanogenic activity (SMA), food-to-sludge ratio (F/M), sludge height in the UASB portion and solid retention time (SRT). The optimum conditions for POME treatment were found to be 2.45 l/d and 0.75 m/h for QF and V up, respectively (corresponding to HRT of 1.5 d and recycle ratio of 23.4:1). The present study provides valuable information about interrelations of quality and process parameters at different values of the operating variables.
    Matched MeSH terms: Models, Theoretical*
  5. Zhu C, Li Y, Zhang L, Wang Y
    PLoS One, 2020;15(11):e0241618.
    PMID: 33156886 DOI: 10.1371/journal.pone.0241618
    To provide a theoretical basis for sustainable land resource utilization and a reference for areas with similar natural conditions, an evaluation index for land-based ecological security was constructed based on the Driving force-Pressure-State-Impact-Response (DPSIR) model and the improved analytic hierarchy process (IAHP) and entropy methods, and the land-based ecological security status of Xingtai city from 2006 to 2017 was evaluated. Then, the obstacles to land-based ecological security were diagnosed. The results show that the values of the comprehensive evaluation index of land-based ecological security were 0.28-0.66 in the period from 2006 to 2017. The value of the index of land-based ecological security was low in the first seven years and gradually improved in the last five years of the study period. However, the overall situation was grave, and the ecological security conditions were poor. The main obstacles to land-based ecological security were the usage of pesticides, investment in environmental pollution treatments, the degree of machine cultivation, the rate of cultivation and the usage of fertilizer in Xingtai city. Based on the results of the land-based ecological security evaluation and the main obstacles identified in Xingtai city, this paper proposes management strategies and suggestions for improving land-based ecological security in Xingtai city. The specific proposals are as follows: vigorously develop green agriculture, increase investment in environmental pollution control, increase input in science and technology, and strengthen supervision and management of land use.
    Matched MeSH terms: Models, Theoretical
  6. Zhou J, Wu C, Yeh PJ, Ju J, Zhong L, Wang S, et al.
    Sci Total Environ, 2023 Sep 01;889:164274.
    PMID: 37209749 DOI: 10.1016/j.scitotenv.2023.164274
    The successive flood-heat extreme (SFHE) event, which threatens the securities of human health, economy, and building environment, has attracted extensive research attention recently. However, the potential changes in SFHE characteristics and the global population exposure to SFHE under anthropogenic warming remain unclear. Here, we present a global-scale evaluation of the projected changes and uncertainties in SFHE characteristics (frequency, intensity, duration, land exposure) and population exposure under the Representative Concentration Pathway (RCP) 2.6 and 6.0 scenarios, based on the multi-model ensembles (five global water models forced by four global climate models) within the Inter-Sectoral Impact Model Intercomparison Project 2b framework. The results reveal that, relative to the 1970-1999 baseline period, the SFHE frequency is projected to increase nearly globally by the end of this century, especially in the Qinghai-Tibet Plateau (>20 events/30-year) and the tropical regions (e.g., northern South America, central Africa, and southeastern Asia, >15 events/30-year). The projected higher SFHE frequency is generally accompanied by a larger model uncertainty. By the end of this century, the SFHE land exposure is expected to increase by 12 % (20 %) under RCP2.6 (RCP6.0), and the intervals between flood and heatwave in SFHE tend to decrease by up to 3 days under both RCPs, implying the more intermittent SFHE occurrence under future warming. The SFHE events will lead to the higher population exposure in the Indian Peninsula and central Africa (<10 million person-days) and eastern Asia (<5 million person-days) due to the higher population density and the longer SFHE duration. Partial correlation analysis indicates that the contribution of flood to the SFHE frequency is greater than that of heatwave for most global regions, but the SFHE frequency is dominated by the heatwave in northern North America and northern Asia.
    Matched MeSH terms: Models, Theoretical
  7. Zentou H, Zainal Abidin Z, Yunus R, Awang Biak DR, Abdullah Issa M, Yahaya Pudza M
    ACS Omega, 2021 Feb 16;6(6):4137-4146.
    PMID: 33644536 DOI: 10.1021/acsomega.0c04025
    Despite the advantages of continuous fermentation whereby ethanol is selectively removed from the fermenting broth to reduce the end-product inhibition, this process can concentrate minor secondary products to the point where they become toxic to the yeast. This study aims to develop a new mathematical model do describe the inhibitory effect of byproducts on alcoholic fermentation including glycerol, lactic acid, acetic acid, and succinic acid, which were reported as major byproducts during batch alcoholic fermentation. The accumulation of these byproducts during the different stages of batch fermentation has been quantified. The yields of total byproducts, glycerol, acetic acid, and succinic acid per gram of glucose were 0.0442, 0.023, 0.0155, and 0.0054, respectively. It was found that the concentration of these byproducts linearly increases with the increase in glucose concentration in the range of 25-250 g/L. The results have also showed that byproduct concentration has a significant inhibitory effect on specific growth coefficient (μ) whereas no effect was observed on the half-velocity constant (Ks). A new mathematical model of alcoholic fermentation was developed considering the byproduct inhibitory effect, which showed a good performance and more accuracy compared to the classical Monod model.
    Matched MeSH terms: Models, Theoretical
  8. Zeng W, Halasa-Rappel YA, Baurin N, Coudeville L, Shepard DS
    Vaccine, 2018 01 08;36(3):413-420.
    PMID: 29229427 DOI: 10.1016/j.vaccine.2017.11.064
    Following publication of results from two phase-3 clinical trials in 10 countries or territories, endemic countries began licensing the first dengue vaccine in 2015. Using a published mathematical model, we evaluated the cost-effectiveness of dengue vaccination in populations similar to those at the trial sites in those same Latin American and Asian countries. Our main scenarios (30-year horizon, 80% coverage) entailed 3-dose routine vaccinations costing US$20/dose beginning at age 9, potentially supplemented by catch-up programs of 4- or 8-year cohorts. We obtained illness costs per case, dengue mortality, vaccine wastage, and vaccine administration costs from the literature. We estimated that routine vaccination would reduce yearly direct and indirect illness cost per capita by 22% (from US$10.51 to US$8.17) in the Latin American countries and by 23% (from US$5.78 to US$4.44) in the Asian countries. Using a health system perspective, the incremental cost-effectiveness ratio (ICER) averaged US$4,216/disability-adjusted life year (DALY) averted in the five Latin American countries (range: US$666/DALY in Puerto Rico to US$5,865/DALY in Mexico). In the five Asian countries, the ICER averaged US$3,751/DALY (range: US$1,935/DALY in Malaysia to US$5,101/DALY in the Philippines). From a health system perspective, the vaccine proved to be highly cost effective (ICER under one times the per capita GDP) in seven countries and cost effective (ICER 1-3 times the per capita GDP) in the remaining three countries. From a societal perspective, routine vaccination proved cost-saving in three countries. Including catch-up campaigns gave similar ICERs. Thus, this vaccine could have a favorable economic value in sites similar to those in the trials.
    Matched MeSH terms: Models, Theoretical
  9. Zelenev A, Long E, Bazazi AR, Kamarulzaman A, Altice FL
    Int J Drug Policy, 2016 11;37:98-106.
    PMID: 27639995 DOI: 10.1016/j.drugpo.2016.08.008
    BACKGROUND: HIV is primarily concentrated among people who inject drugs (PWID) in Malaysia, where currently HIV prevention and treatment coverage is inadequate. To improve the targeting of interventions, we examined HIV clustering and the role that social networks and geographical distance play in influencing HIV transmission among PWID.

    METHODS: Data were derived from a respondent-driven survey sample (RDS) collected during 2010 of 460 PWID in greater Kuala Lumpur. Analysis focused on socio-demographic, clinical, behavioural, and network information. Spatial probit models were developed based on a distinction between the influence of peers (individuals nominated through a recruitment network) and neighbours (residing a close distance to the individual). The models were expanded to account for the potential influence of the network formation.

    RESULTS: Recruitment patterns of HIV-infected PWID clustered both spatially and across the recruitment networks. In addition, HIV-infected PWID were more likely to have peers and neighbours who inject with clean needles were HIV-infected and lived nearby (<5km), more likely to have been previously incarcerated, less likely to use clean needles (26.8% vs 53.0% of the reported injections, p<0.01), and have fewer recent injection partners (2.4 vs 5.4, p<0.01). The association between the HIV status of peers and neighbours remained significantly correlated even after controlling for unobserved variation related to network formation and sero-sorting.

    CONCLUSION: The relationship between HIV status across networks and space in Kuala Lumpur underscores the importance of these factors for surveillance and prevention strategies, and this needs to be more closely integrated. RDS can be applied to identify injection network structures, and this provides an important mechanism for improving public health surveillance, accessing high-risk populations, and implementing risk-reduction interventions to slow HIV transmission.

    Matched MeSH terms: Models, Theoretical
  10. Zaroog, Omar Suliman, Aidy Ali, Sahari, B.B., Rizal Zahari
    MyJurnal
    Compressive residual stress, induced by mechanical surface treatment, may relax during component
    operation life, due to thermal or mechanical mechanism. Fatigue life prediction for the components which have residual stress will be misled and inaccurately predicted the phenomenon of residual stress relaxation is not considered. Despite putting an effort on incorporating the residual stress relaxation, the issues remain concerned with the technical challenge of measuring and quantifying
    the magnitude of residual stress relaxation as well as redistribution during the loading cycling itself.
    In this paper, the residual stress relaxation and its models were reviewed and discussed to picture
    the best knowledge related to this topic, i.e. whether relaxation is a cause or an effect.
    Matched MeSH terms: Models, Theoretical
  11. Zaman MR, Islam MT, Misran N, Yatim B
    ScientificWorldJournal, 2014;2014:831435.
    PMID: 24977230 DOI: 10.1155/2014/831435
    A radio frequency (RF) resonator using glass-reinforced epoxy material for C and X band is proposed in this paper. Microstrip line technology for RF over glass-reinforced epoxy material is analyzed. Coupling mechanism over RF material and parasitic coupling performance is explained utilizing even and odd mode impedance with relevant equivalent circuit. Babinet's principle is deployed to explicate the circular slot ground plane of the proposed resonator. The resonator is designed over four materials from different backgrounds which are glass-reinforced epoxy, polyester, gallium arsenide (GaAs), and rogers RO 4350B. Parametric studies and optimization algorithm are applied over the geometry of the microstrip resonator to achieve dual band response for C and X band. Resonator behaviors for different materials are concluded and compared for the same structure. The final design is fabricated over glass-reinforced epoxy material. The fabricated resonator shows a maximum directivity of 5.65 dBi and 6.62 dBi at 5.84 GHz and 8.16 GHz, respectively. The lowest resonance response is less than -20 dB for C band and -34 dB for X band. The resonator is prototyped using LPKF (S63) drilling machine to study the material behavior.
    Matched MeSH terms: Models, Theoretical*
  12. Zainuddin Z, Wan Daud WR, Pauline O, Shafie A
    Bioresour Technol, 2011 Dec;102(23):10978-86.
    PMID: 21996481 DOI: 10.1016/j.biortech.2011.09.080
    In the organosolv pulping of the oil palm fronds, the influence of the operational variables of the pulping reactor (viz. cooking temperature and time, ethanol and NaOH concentration) on the properties of the resulting pulp (yield and kappa number) and paper sheets (tensile index and tear index) was investigated using a wavelet neural network model. The experimental results with error less than 0.0965 (in terms of MSE) were produced, and were then compared with those obtained from the response surface methodology. Performance assessment indicated that the neural network model possessed superior predictive ability than the polynomial model, since a very close agreement between the experimental and the predicted values was obtained.
    Matched MeSH terms: Models, Theoretical
  13. Zainuddin A, Makpol S, Chua KH, Abdul Rahim N, Yusof YA, Ngah WZ
    Med J Malaysia, 2008 Jul;63 Suppl A:73-4.
    PMID: 19024990
    Validation of housekeeping gene is important for accurate quantitation of RNA in real time RT-PCR technique. The purpose of this study was to determine the validity of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as a housekeeping gene for quantitative real time RT-PCR assessment in human skin fibroblast senescent model. The cells were divided into different treatment groups; young (passage 4), senescent (passage 30), treatment with H2O2 and treatment with A-tocotrienol prior to H2O2 treatment. Our results showed that the expression level of GAPDH was constant with different treatment groups. Therefore, we concluded that GAPDH was suitable to be used as housekeeping gene in human skin fibroblast senescent model.
    Matched MeSH terms: Models, Theoretical
  14. 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*
  15. Zahed MA, Aziz HA, Isa MH, Mohajeri L, Mohajeri S, Kutty SR
    J Hazard Mater, 2011 Jan 30;185(2-3):1027-31.
    PMID: 21041026 DOI: 10.1016/j.jhazmat.2010.10.009
    Hydrocarbon pollution in marine ecosystems occurs mainly by accidental oil spills, deliberate discharge of ballast waters from oil tankers and bilge waste discharges; causing site pollution and serious adverse effects on aquatic environments as well as human health. A large number of petroleum hydrocarbons are biodegradable, thus bioremediation has become an important method for the restoration of oil polluted areas. In this research, a series of natural attenuation, crude oil (CO) and dispersed crude oil (DCO) bioremediation experiments of artificially crude oil contaminated seawater was carried out. Bacterial consortiums were identified as Acinetobacter, Alcaligenes, Bacillus, Pseudomonas and Vibrio. First order kinetics described the biodegradation of crude oil. Under abiotic conditions, oil removal was 19.9% while a maximum of 31.8% total petroleum hydrocarbons (TPH) removal was obtained in natural attenuation experiment. All DCO bioreactors demonstrated higher and faster removal than CO bioreactors. Half life times were 28, 32, 38 and 58 days for DCO and 31, 40, 50 and 75 days for CO with oil concentrations of 100, 500, 1000 and 2000 mg/L, respectively. The effectiveness of Corexit 9500 dispersant was monitored in the 45 day study; the results indicated that it improved the crude oil biodegradation rate.
    Matched MeSH terms: Models, Theoretical
  16. Yusop Z, Chan CH, Katimon A
    Water Sci Technol, 2007;56(8):41-8.
    PMID: 17978431
    Rainfall-runoff processes in a small oil palm catchment (8.2 ha) in Johor, Malaysia were examined. Storm hydrographs show rapid responses to rainfall with a short time to peak. The estimated initial hydrologic loss for the oil palm catchment is 5 mm. Despite the low initial loss, the catchment exhibits a high proportion of baseflow, approximately 54% of the total runoff. On an event basis, the stormflow response factor and runoff coefficient ranges from 0.003 to 0.21, and 0.02 to 0.44, respectively. Peakflow and stormflow volume were moderately correlated with rainfall. The hydrographs were satisfactorily modelled using the Hydrologic Engineering Centre-Hydrologic Modelling System (HEC-HMS). The efficiency indexes of the calibration and validation exercises are 0.81 and 0.82, respectively. Based on these preliminary findings, it could be suggested that an oil palm plantation would be able to serve reasonably well in regulating basic hydrological functions.
    Matched MeSH terms: Models, Theoretical*
  17. Yusof F, Md. Ismai l, Ali N
    Hantaviruses are infectious agents that can cause diseases resulting in deaths in humans and are hosted by rodents without affecting the hosts themselves. A simple mathematical model describing the spread of the Hantavirus infection in rodents has been proposed and developed by Abramson and Kenkre where the model takes into account the temporal and spatial characteristics of this infection. In this paper, we extended this model to include the process of harvesting and study the impact of different harvesting strategies in the spread of the Hantavirus infection in rodents. Several numerical simulations were carried out and the results are discussed.
    Matched MeSH terms: Models, Theoretical
  18. Yusof F, Md Ismail A.I.B., Ali N
    Sains Malaysiana, 2014;43:1045-1051.
    Hantavirus is a serious disease caused by rodents which can lead to mortality. Many efforts have been carried out by researchers to develop and analyze mathematical models of Hantavirus infection. In this paper, the Peixoto and Abramson (2006) biodiversity model is modified to include the effect of predators and study the prediction of the modified model. When rodent and predator populations are in competition, the predator populations have the effect of reducing the prevalence of infection. Predators may be used for control and reduces the number of competing species to stabilize the populations at a persistent equilibrium.
    Matched MeSH terms: Models, Theoretical
  19. Yuan B, Nishiura H
    PLoS One, 2018;13(6):e0198734.
    PMID: 29924819 DOI: 10.1371/journal.pone.0198734
    BACKGROUND: Frequent international travel facilitates the global spread of dengue fever. Japan has experienced an increasing number of imported case notifications of dengue virus (DENV) infection, mostly arising from Japanese travelers visiting South and Southeast Asian countries. This has led an autochthonous dengue outbreak in 2014 in Japan. The present study aimed to infer the risk of DENV infection among Japanese travelers to Asian countries, thereby obtaining an actual estimate of the number of DENV infections among travelers.

    METHODOLOGY/PRINCIPAL FINDINGS: For eight destination countries (Indonesia, Philippines, Thailand, India, Malaysia, Vietnam, Sri Lanka, and Singapore), we collected age-dependent seroepidemiological data. We also retrieved the number of imported cases, who were notified to the Japanese government, as well as the total number of travelers to each destination. Using a mathematical model, we estimated the force of infection in each destination country with seroepidemiological data while jointly inferring the reporting coverage of DENV infections among Japanese travelers from datasets of imported cases and travelers. Assuming that travelers had a risk of infection that was identical to that of the local population during travel, the reporting coverage of dengue appeared to range from 0.6% to 4.3%. The risk of infection per journey ranged from 0.02% to 0.44%.

    CONCLUSIONS/SIGNIFICANCE: We found that the actual number of imported cases of DENV infection among Japanese travelers could be more than 20 times the notified number of imported cases. This finding may be attributed to the substantial proportion of asymptomatic and under-ascertained infections.

    Matched MeSH terms: Models, Theoretical
  20. Yu CP, Whynes DK, Sach TH
    Health Policy, 2011 May;100(2-3):256-63.
    PMID: 21129808 DOI: 10.1016/j.healthpol.2010.10.018
    This paper assesses the potential equity impact of Malaysia's projected reform of its current tax financed system towards National Health Insurance (NHI).
    Matched MeSH terms: Models, Theoretical
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