Displaying publications 361 - 380 of 761 in total

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  1. Fulltext The Gut-Brain-Axis on the Manifestation of Depressive Symptoms in Epilepsy: An Evidence-Driven Hypothesis
    Shaikh MF, Lee CY, Chen WN, Shaikh FA
    Front Pharmacol, 2020;11:465.
    PMID: 32322213 DOI: 10.3389/fphar.2020.00465
    Epilepsy is a severe neurological disorder involving 70 million people around the globe. Epilepsy-related neuropsychiatric comorbidities such as depression, which is the most common, is an additional factor that negatively impacts the living quality of epilepsy patients. There are many theories and complexities associated with both epilepsy and associated comorbidities, one of which is the gut-brain-axis influence. The gut microbiome is hypothesized to be linked with many neurological disorders; however, little conclusive evidence is available in this area. Thus, highlighting the role will create interest in researchers to conduct detailed research in comprehending the influence of gut-brain-axis in the manifestation of depressive symptoms in epilepsy. The hypothesis which is explored in this review is that the gut-brain-axis do play an important role in the genesis of epilepsy and associated depression. The correction of this dysbiosis might be beneficial in treating both epilepsy and related depression. This hypothesis is illustrated through extensive literature discussion, proposed experimental models, and its applicability in the field. There is indirect evidence which revealed some specific bacterial strains that might cause depression in epilepsy.
    Matched MeSH terms: Models, Theoretical
  2. Fulltext Multi-Agent Systems in Fog-Cloud Computing for Critical Healthcare Task Management Model (CHTM) Used for ECG Monitoring
    Mutlag AA, Ghani MKA, Mohammed MA, Lakhan A, Mohd O, Abdulkareem KH, et al.
    Sensors (Basel), 2021 Oct 19;21(20).
    PMID: 34696135 DOI: 10.3390/s21206923
    In the last decade, the developments in healthcare technologies have been increasing progressively in practice. Healthcare applications such as ECG monitoring, heartbeat analysis, and blood pressure control connect with external servers in a manner called cloud computing. The emerging cloud paradigm offers different models, such as fog computing and edge computing, to enhance the performances of healthcare applications with minimum end-to-end delay in the network. However, many research challenges exist in the fog-cloud enabled network for healthcare applications. Therefore, in this paper, a Critical Healthcare Task Management (CHTM) model is proposed and implemented using an ECG dataset. We design a resource scheduling model among fog nodes at the fog level. A multi-agent system is proposed to provide the complete management of the network from the edge to the cloud. The proposed model overcomes the limitations of providing interoperability, resource sharing, scheduling, and dynamic task allocation to manage critical tasks significantly. The simulation results show that our model, in comparison with the cloud, significantly reduces the network usage by 79%, the response time by 90%, the network delay by 65%, the energy consumption by 81%, and the instance cost by 80%.
    Matched MeSH terms: Models, Theoretical
  3. Fulltext Asymmetric impact of temperature on COVID-19 spread in India: Evidence from quantile-on-quantile regression approach
    Irfan M, Razzaq A, Suksatan W, Sharif A, Madurai Elavarasan R, Yang C, et al.
    J Therm Biol, 2022 Feb;104:103101.
    PMID: 35180949 DOI: 10.1016/j.jtherbio.2021.103101
    The emergence of new coronavirus (SARS-CoV-2) has become a significant public health issue worldwide. Some researchers have identified a positive link between temperature and COVID-19 cases. However, no detailed research has highlighted the impact of temperature on COVID-19 spread in India. This study aims to fill this research gap by investigating the impact of temperature on COVID-19 spread in the five most affected Indian states. Quantile-on-Quantile regression (QQR) approach is employed to examine in what manner the quantiles of temperature influence the quantiles of COVID-19 cases. Empirical results confirm an asymmetric and heterogenous impact of temperature on COVID-19 spread across lower and higher quantiles of both variables. The results indicate a significant positive impact of temperature on COVID-19 spread in the three Indian states (Maharashtra, Andhra Pradesh, and Karnataka), predominantly in both low and high quantiles. Whereas, the other two states (Tamil Nadu and Uttar Pradesh) exhibit a mixed trend, as the lower quantiles in both states have a negative effect. However, this negative effect becomes weak at middle and higher quantiles. These research findings offer valuable policy recommendations.
    Matched MeSH terms: Models, Theoretical
  4. Prediction of outcomes in traumatic brain injury: The IMPACT and CRASH prognostic models in a single neurosurgical center, Malaysia
    Abdullah JM, Idris Z, Ghani AR, Lim MS
    J Neurosurg Sci, 2023 Jun;67(3):367-373.
    PMID: 33709663 DOI: 10.23736/S0390-5616.21.05249-8
    BACKGROUND: Traumatic brain injury (TBI) has recently become a major concern for public health care and a socioeconomic burden internationally. Prognostic models are mathematical models developed from specific populations which are used to predict the mortality and unfavorable outcomes especially in trauma centers. Hence, we formulate a study to perform an external validation of the IMPACT and CRASH prognostic models; the CRASH model to predict 14-day mortality and 6-month unfavorable outcome and the IMPACT model to estimate 6-month mortality and unfavorable outcome in a single center cohort of TBI patients in Malaysia.

    METHODS: All patients with traumatic brain injury (mild, moderate, and severe) who were admitted to Queen Elizabeth Hospital from November 1, 2017, to January 31, 2019, were prospectively analyzed through a data collection sheet. The discriminatory power of the models was assessed as area under the receiver operating characteristic curve and calibration was assessed using the Hosmer-Lemeshow (H-L) goodness-of-fit test and Cox calibration regression analysis.

    RESULTS: We analyzed 281 patients with significant TBI treated in a single neurosurgical center in Malaysia over a 2-year period. The overall observed 14-day mortality was 9.6%, a 6-month unfavorable outcome of 23.5%, and a 6-month mortality of 13.2%. Overall, both the CRASH and IMPACT models showed good discrimination with AUCs ranging from 0.88 to 0.94 and both models calibrating satisfactorily H-L GoF P>0.05 and calibration slopes >1.0 although IMPACT seemed to be slightly more superior compared to the CRASH model.

    CONCLUSIONS: The CRASH and IMPACT prognostic models displayed satisfactory overall performance in our cohort of TBI patients, but further investigations on factors contributing to TBI outcomes and continuous updating on both models remain crucial.

    Matched MeSH terms: Models, Theoretical
  5. Fulltext Image-based 3D canopy reconstruction to determine potential productivity in complex multi-species crop systems
    Burgess AJ, Retkute R, Pound MP, Mayes S, Murchie EH
    Ann Bot, 2017 Mar 01;119(4):517-532.
    PMID: 28065926 DOI: 10.1093/aob/mcw242
    BACKGROUND AND AIMS: Intercropping systems contain two or more species simultaneously in close proximity. Due to contrasting features of the component crops, quantification of the light environment and photosynthetic productivity is extremely difficult. However it is an essential component of productivity. Here, a low-tech but high-resolution method is presented that can be applied to single- and multi-species cropping systems to facilitate characterization of the light environment. Different row layouts of an intercrop consisting of Bambara groundnut ( Vigna subterranea ) and proso millet ( Panicum miliaceum ) have been used as an example and the new opportunities presented by this approach have been analysed.

    METHODS: Three-dimensional plant reconstruction, based on stereo cameras, combined with ray tracing was implemented to explore the light environment within the Bambara groundnut-proso millet intercropping system and associated monocrops. Gas exchange data were used to predict the total carbon gain of each component crop.

    KEY RESULTS: The shading influence of the tall proso millet on the shorter Bambara groundnut results in a reduction in total canopy light interception and carbon gain. However, the increased leaf area index (LAI) of proso millet, higher photosynthetic potential due to the C4 pathway and sub-optimal photosynthetic acclimation of Bambara groundnut to shade means that increasing the number of rows of millet will lead to greater light interception and carbon gain per unit ground area, despite Bambara groundnut intercepting more light per unit leaf area.

    CONCLUSIONS: Three-dimensional reconstruction combined with ray tracing provides a novel, accurate method of exploring the light environment within an intercrop that does not require difficult measurements of light interception and data-intensive manual reconstruction, especially for such systems with inherently high spatial possibilities. It provides new opportunities for calculating potential productivity within multi-species cropping systems, enables the quantification of dynamic physiological differences between crops grown as monoculture and those within intercrops, and enables the prediction of new productive combinations of previously untested crops.

    Matched MeSH terms: Models, Theoretical
  6. Anthropogenic climate change exacerbates the risk of successive flood-heat extremes: Multi-model global projections based on the Inter-Sectoral Impact Model Intercomparison Project
    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. Mathematical Model of COVID-19 Pandemic with Double Dose Vaccination
    Peter OJ, Panigoro HS, Abidemi A, Ojo MM, Oguntolu FA
    Acta Biotheor, 2023 Mar 06;71(2):9.
    PMID: 36877326 DOI: 10.1007/s10441-023-09460-y
    This paper is concerned with the formulation and analysis of an epidemic model of COVID-19 governed by an eight-dimensional system of ordinary differential equations, by taking into account the first dose and the second dose of vaccinated individuals in the population. The developed model is analyzed and the threshold quantity known as the control reproduction number [Formula: see text] is obtained. We investigate the equilibrium stability of the system, and the COVID-free equilibrium is said to be locally asymptotically stable when the control reproduction number is less than unity, and unstable otherwise. Using the least-squares method, the model is calibrated based on the cumulative number of COVID-19 reported cases and available information about the mass vaccine administration in Malaysia between the 24th of February 2021 and February 2022. Following the model fitting and estimation of the parameter values, a global sensitivity analysis was performed by using the Partial Rank Correlation Coefficient (PRCC) to determine the most influential parameters on the threshold quantities. The result shows that the effective transmission rate [Formula: see text], the rate of first vaccine dose [Formula: see text], the second dose vaccination rate [Formula: see text] and the recovery rate due to the second dose of vaccination [Formula: see text] are the most influential of all the model parameters. We further investigate the impact of these parameters by performing a numerical simulation on the developed COVID-19 model. The result of the study shows that adhering to the preventive measures has a huge impact on reducing the spread of the disease in the population. Particularly, an increase in both the first and second dose vaccination rates reduces the number of infected individuals, thus reducing the disease burden in the population.
    Matched MeSH terms: Models, Theoretical
  8. An intrusion detection model to detect zero-day attacks in unseen data using machine learning
    Dai Z, Por LY, Chen YL, Yang J, Ku CS, Alizadehsani R, et al.
    PLoS One, 2024;19(9):e0308469.
    PMID: 39259729 DOI: 10.1371/journal.pone.0308469
    In an era marked by pervasive digital connectivity, cybersecurity concerns have escalated. The rapid evolution of technology has led to a spectrum of cyber threats, including sophisticated zero-day attacks. This research addresses the challenge of existing intrusion detection systems in identifying zero-day attacks using the CIC-MalMem-2022 dataset and autoencoders for anomaly detection. The trained autoencoder is integrated with XGBoost and Random Forest, resulting in the models XGBoost-AE and Random Forest-AE. The study demonstrates that incorporating an anomaly detector into traditional models significantly enhances performance. The Random Forest-AE model achieved 100% accuracy, precision, recall, F1 score, and Matthews Correlation Coefficient (MCC), outperforming the methods proposed by Balasubramanian et al., Khan, Mezina et al., Smith et al., and Dener et al. When tested on unseen data, the Random Forest-AE model achieved an accuracy of 99.9892%, precision of 100%, recall of 99.9803%, F1 score of 99.9901%, and MCC of 99.8313%. This research highlights the effectiveness of the proposed model in maintaining high accuracy even with previously unseen data.
    Matched MeSH terms: Models, Theoretical
  9. Fulltext Prediction of Poisson's ratio for a petroleum engineering application: Machine learning methods
    Alakbari FS, Mahmood SM, Ayoub MA, Khan MJ, Afolabi F, Mohyaldinn ME, et al.
    PLoS One, 2025;20(2):e0317754.
    PMID: 39982951 DOI: 10.1371/journal.pone.0317754
    Static Poisson's ratio (νs) is an essential property used in petroleum calculations, namely fracture pressure (FP). The νs is often determined in the laboratory; however, due to time and cost constraints, quicker and cheaper alternatives are sought, such as data-driven models. However, existing methods lack the accuracy needed for critical applications, necessitating the need to explore more accurate methods. In addition, the previous studies used limited datasets and they do not show the relationships between the inputs and output. Therefore, this study developed a reliable model to predict the νs accurately using the nineteen most common learning methods. The proposed models were created based on a large data of 1691 datasets from different countries. The best-performing model of the nineteen models was selected and further enhanced using various approaches such as trend analysis to improve the model's performance and robustness as some models show high accuracy but show incorrect relationships between the inputs and output because the machine learning model only built based on the data and do not consider the physical behavior of the model. The proposed Gaussian process regression (GPR) model was also compared with published models. After the proposed GPR model was developed, the FP was determined based on the proposed GPR νs model and the previous νs models to evaluate their accuracy on the FP determinations. The best approach out of the published and proposed methods was GPR with a coefficient of determination (R2) and average-absolute-percentage-relative-error (AAPRE) of 0.95 and 2.73%. The GPR model showed proper trends for all inputs. The cross-plotting and group error analyses also confirmed that the proposed GPR approach had high precision and surpassed other methods within all practical ranges. The GPR model decreased the residual error of FP from 87% to 26%. It is believed that such a significant improvement in the accuracy of the GPR model will have a significant effect on realistic FP determination.
    Matched MeSH terms: Models, Theoretical
  10. Fulltext Livelihoods and Fisheries Governance in a Contemporary Pacific Island Setting
    Sulu RJ, Eriksson H, Schwarz AM, Andrew NL, Orirana G, Sukulu M, et al.
    PLoS One, 2015;10(11):e0143516.
    PMID: 26599412 DOI: 10.1371/journal.pone.0143516
    Inshore marine resources play an important role in the livelihoods of Pacific Island coastal communities. However, such reliance can be detrimental to inshore marine ecosystems. Understanding the livelihoods of coastal communities is important for devising relevant and effective fisheries management strategies. Semi-structured household interviews were conducted with householders in Langalanga Lagoon, Solomon Islands, to understand household livelihoods and resource governance in fishing-dependent communities. Households were engaged in a diverse range of livelihoods. Fishing, shell money production and gardening were the most important livelihoods. Proximity to an urban centre influenced how households accessed some livelihoods. Perceptions of management rules varied and different reasons were cited for why rules were broken, the most common reason being to meet livelihood needs. Current models of inshore small-scale fisheries management that are based on the notion of community-based resource management may not work in locations where customary management systems are weak and livelihoods are heavily reliant on marine resources. An important step for fisheries management in such locations should include elucidating community priorities through participatory development planning, taking into consideration livelihoods as well as governance and development aspirations.
    Matched MeSH terms: Models, Theoretical
  11. Fulltext Chronology of DIC technique based on the fundamental mathematical modeling and dehydration impact
    Alias N, Saipol HF, Ghani AC
    J Food Sci Technol, 2014 Dec;51(12):3647-57.
    PMID: 25477631 DOI: 10.1007/s13197-012-0913-7
    A chronology of mathematical models for heat and mass transfer equation is proposed for the prediction of moisture and temperature behavior during drying using DIC (Détente Instantanée Contrôlée) or instant controlled pressure drop technique. DIC technique has the potential as most commonly used dehydration method for high impact food value including the nutrition maintenance and the best possible quality for food storage. The model is governed by the regression model, followed by 2D Fick's and Fourier's parabolic equation and 2D elliptic-parabolic equation in a rectangular slice. The models neglect the effect of shrinkage and radiation effects. The simulations of heat and mass transfer equations with parabolic and elliptic-parabolic types through some numerical methods based on finite difference method (FDM) have been illustrated. Intel®Core™2Duo processors with Linux operating system and C programming language have been considered as a computational platform for the simulation. Qualitative and quantitative differences between DIC technique and the conventional drying methods have been shown as a comparative.
    Matched MeSH terms: Models, Theoretical
  12. Fulltext Simultaneous time-temperature-thickness superposition theoretical and statistical modelling of convective drying of guava
    Kek SP, Chin NL, Yusof YA
    J Food Sci Technol, 2014 Dec;51(12):3609-22.
    PMID: 25477628 DOI: 10.1007/s13197-013-0923-0
    Modelling studies of guava drying and quality are presented using theoretical and statistical models by varying temperature from 55 to 75 °C and slice thickness from 3 to 9 mm. The quality of dried fruit was measured for its water activity, colour, vitamin C, and texture. The superposition technique with Midilli-Kucuk model showed efficiency in modelling the drying process with R (2)  = 0.9991. The second-order polynomial equations adequately described the quality of dried guava with regression coefficient, R (2)  > 0.7. Drying time was a good function of temperature and thickness (P 
    Matched MeSH terms: Models, Theoretical
  13. A global strategy for road building
    Laurance WF, Clements GR, Sloan S, O'Connell CS, Mueller ND, Goosem M, et al.
    Nature, 2014 Sep 11;513(7517):229-32.
    PMID: 25162528 DOI: 10.1038/nature13717
    The number and extent of roads will expand dramatically this century. Globally, at least 25 million kilometres of new roads are anticipated by 2050; a 60% increase in the total length of roads over that in 2010. Nine-tenths of all road construction is expected to occur in developing nations, including many regions that sustain exceptional biodiversity and vital ecosystem services. Roads penetrating into wilderness or frontier areas are a major proximate driver of habitat loss and fragmentation, wildfires, overhunting and other environmental degradation, often with irreversible impacts on ecosystems. Unfortunately, much road proliferation is chaotic or poorly planned, and the rate of expansion is so great that it often overwhelms the capacity of environmental planners and managers. Here we present a global scheme for prioritizing road building. This large-scale zoning plan seeks to limit the environmental costs of road expansion while maximizing its benefits for human development, by helping to increase agricultural production, which is an urgent priority given that global food demand could double by mid-century. Our analysis identifies areas with high environmental values where future road building should be avoided if possible, areas where strategic road improvements could promote agricultural development with relatively modest environmental costs, and 'conflict areas' where road building could have sizeable benefits for agriculture but with serious environmental damage. Our plan provides a template for proactively zoning and prioritizing roads during the most explosive era of road expansion in human history.
    Matched MeSH terms: Models, Theoretical
  14. Fulltext Circularly polarized S band dual frequency square patch antenna using glass microfiber reinforced PTFE composite
    Samsuzzaman M, Islam MT, Arshad H, Mandeep JS, Misran N
    ScientificWorldJournal, 2014;2014:345190.
    PMID: 24982943 DOI: 10.1155/2014/345190
    Circularly polarized (CP) dual frequency cross-shaped slotted patch antenna on 1.575 mm thick glass microfiber reinforced polytetrafluoroethylene (PTFE) composite material substrate is designed and fabricated for satellite applications. Asymmetric cross-shaped slots are embedded in the middle of the square patch for CP radiation and four hexagonal slots are etched on the four sides of the square patch for desired dual frequency. Different substrate materials have been analysed to achieve the desired operating band. The experimental results show that the impedance bandwidth is approximately 30 MHz (2.16 GHz to 2.19 GHz) for lower band and 40 MHz (3.29 GHz to 3.33 GHz) for higher band with an average peak gain of 6.59 dBiC and 5.52 dBiC, respectively. Several optimizations are performed to obtain the values of the antenna physical parameters. Moreover, the proposed antenna possesses compactness, light weight, simplicity, low cost, and circularly polarized. It is an attractive candidate for dual band satellite antennas where lower band can be used for uplink and upper band can be used for downlink.
    Matched MeSH terms: Models, Theoretical
  15. Fulltext Seluge++: a secure over-the-air programming scheme in wireless sensor networks
    Doroodgar F, Abdur Razzaque M, Isnin IF
    Sensors (Basel), 2014;14(3):5004-40.
    PMID: 24618781 DOI: 10.3390/s140305004
    Over-the-air dissemination of code updates in wireless sensor networks have been researchers' point of interest in the last few years, and, more importantly, security challenges toward the remote propagation of code updating have occupied the majority of efforts in this context. Many security models have been proposed to establish a balance between the energy consumption and security strength, having their concentration on the constrained nature of wireless sensor network (WSN) nodes. For authentication purposes, most of them have used a Merkle hash tree to avoid using multiple public cryptography operations. These models mostly have assumed an environment in which security has to be at a standard level. Therefore, they have not investigated the tree structure for mission-critical situations in which security has to be at the maximum possible level (e.g., military applications, healthcare). Considering this, we investigate existing security models used in over-the-air dissemination of code updates for possible vulnerabilities, and then, we provide a set of countermeasures, correspondingly named Security Model Requirements. Based on the investigation, we concentrate on Seluge, one of the existing over-the-air programming schemes, and we propose an improved version of it, named Seluge++, which complies with the Security Model Requirements and replaces the use of the inefficient Merkle tree with a novel method. Analytical and simulation results show the improvements in Seluge++ compared to Seluge.
    Matched MeSH terms: Models, Theoretical
  16. Fulltext Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber
    Shaddad RQ, Mohammad AB, Al-Gailani SA, Al-Hetar AM
    ScientificWorldJournal, 2014;2014:170471.
    PMID: 24772009 DOI: 10.1155/2014/170471
    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.
    Matched MeSH terms: Models, Theoretical
  17. Fulltext Determination of acceptor concentration, depletion width, donor level movement and sensitivity factor of ZnO on diamond heterojunction under UV illumination
    Saw KG, Tneh SS, Yam FK, Ng SS, Hassan Z
    PLoS One, 2014;9(2):e89348.
    PMID: 24586707 DOI: 10.1371/journal.pone.0089348
    The concentration of acceptor carriers, depletion width, magnitude of donor level movement as well as the sensitivity factor are determined from the UV response of a heterojunction consisting of ZnO on type IIb diamond. From the comparison of the I-V measurements in dark condition and under UV illumination we show that the acceptor concentration (∼10(17) cm(-3)) can be estimated from p-n junction properties. The depletion width of the heterojunction is calculated and is shown to extend farther into the ZnO region in dark condition. Under UV illumination, the depletion width shrinks but penetrates both materials equally. The ultraviolet illumination causes the donor level to move closer to the conduction band by about 50 meV suggesting that band bending is reduced to allow more electrons to flow from the intrinsically n-type ZnO. The sensitivity factor of the device calculated from the change of threshold voltages, the ratio of dark and photocurrents and identity factor is consistent with experimental data.
    Matched MeSH terms: Models, Theoretical
  18. Estimating the demand for drop-off recycling sites: a random utility travel cost approach
    Sidique SF, Lupi F, Joshi SV
    J Environ Manage, 2013 Sep 30;127:339-46.
    PMID: 23810167 DOI: 10.1016/j.jenvman.2013.05.001
    Drop-off recycling is one of the most widely adopted recycling programs in the United States. Despite its wide implementation, relatively little literature addresses the demand for drop-off recycling. This study examines the demand for drop-off recycling sites as a function of travel costs and various site characteristics using the random utility model (RUM). The findings of this study indicate that increased travel costs significantly reduce the frequency of visits to drop-off sites implying that the usage pattern of a site is influenced by its location relative to where people live. This study also demonstrates that site specific characteristics such as hours of operation, the number of recyclables accepted, acceptance of commingled recyclables, and acceptance of yard-waste affect the frequency of visits to drop-off sites.
    Matched MeSH terms: Models, Theoretical
  19. Fulltext Conjugate effects of heat and mass transfer on MHD free convection flow over an inclined plate embedded in a porous medium
    Ali F, Khan I, Samiulhaq, Shafie S
    PLoS One, 2013;8(6):e65223.
    PMID: 23840321 DOI: 10.1371/journal.pone.0065223
    The aim of this study is to present an exact analysis of combined effects of radiation and chemical reaction on the magnetohydrodynamic (MHD) free convection flow of an electrically conducting incompressible viscous fluid over an inclined plate embedded in a porous medium. The impulsively started plate with variable temperature and mass diffusion is considered. The dimensionless momentum equation coupled with the energy and mass diffusion equations are analytically solved using the Laplace transform method. Expressions for velocity, temperature and concentration fields are obtained. They satisfy all imposed initial and boundary conditions and can be reduced, as special cases, to some known solutions from the literature. Expressions for skin friction, Nusselt number and Sherwood number are also obtained. Finally, the effects of pertinent parameters on velocity, temperature and concentration profiles are graphically displayed whereas the variations in skin friction, Nusselt number and Sherwood number are shown through tables.
    Matched MeSH terms: Models, Theoretical
  20. Sustaining the environment through recycling: an empirical study
    Ramayah T, Lee JW, Lim S
    J Environ Manage, 2012 Jul 15;102:141-7.
    PMID: 22446140 DOI: 10.1016/j.jenvman.2012.02.025
    This paper examines the determinants of recycling behaviour among 200 university students from the perspective of the theory of planned behaviour (TPB). Data was analysed using Structural Equation Modelling technique. Findings indicate that environmental awareness was significantly related to attitude towards recycling, whilst attitude and social norms had significant impact on recycling behaviour. However, convenience and cost of recycling were not significant reasons for recycling. The study has enhanced the understanding of the determinants of recycling behaviour and has implications for schools and governmental agencies in educating and encouraging positive recycling behaviour. It also confirms the appropriateness of the TPB in examining studies of this nature. Further suggestions for future research are offered.
    Matched MeSH terms: Models, Theoretical
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