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Displaying publications 481 - 500 of 761 in total

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Industrial wastewater minimization using water pinch analysis: a case study on an old textile plant

Ujang Z, Wong CL, Manan ZA

Water Sci Technol, 2002;46(11-12):77-84.
PMID: 12523736

Industrial wastewater minimization can be conducted using four main strategies: (i) reuse; (ii) regeneration-reuse; (iii) regeneration-recycling; and (iv) process changes. This study is concerned with (i) and (ii) to investigate the most suitable approach to wastewater minimization for an old textile industry plant. A systematic water networks design using water pinch analysis (WPA) was developed to minimize the water usage and wastewater generation for the textile plant. COD was chosen as the main parameter. An integrated design method has been applied, which brings the engineering insight using WPA that can determine the minimum flowrate of the water usage and then minimize the water consumption and wastewater generation as well. The overall result of this study shows that WPA has been effectively applied using both reuse and regeneration-reuse strategies for the old textile industry plant, and reduced the operating cost by 16% and 50% respectively.

Matched MeSH terms: Models, Theoretical*
Accurate measurement of exposure rate from a 60Co teletherapy source: deviations from the inverse-square law

Samat SB, Evans CJ, Kadni T, Dolah MT

Br J Radiol, 2000 Aug;73(872):867-77.
PMID: 11026863

A cylindrical gamma-ray 60Co source of activity alpha is predicted to produce an exposure rate X at a distance d in vacuum, given by X = gamma(T)(alpha/d2), where gamma(T) is the specific gamma-ray constant. It has been documented that this formula may be used to approximate X with an accuracy of 1% from a source of length l, provided that d/l > or = 5. It is shown that the formula is accurate to 0.1% under these conditions, provided that the distance is measured from the centre of the source. When absorption in the source and scattering in the collimator are considered, the position of the origin d = 0 can shift by a distance of the order of centimetres. Absorption in air between the source and the ionization chamber adds an exponential factor to the formula. It is shown that even when these modifications are included the discrepancy in the results, although generally less than 1%, is still large compared with the measurement errors. Some suggestions are made for the origin of this discrepancy.

Matched MeSH terms: Models, Theoretical*
Will sex selection reduce fertility?

Leung SF

J Popul Econ, 1994;7(4):379-92.
PMID: 12288505
Matched MeSH terms: Models, Theoretical*
Chinese culture and fertility decline

Wu C, Jia S

Chin J Popul Sci, 1992;4(2):95-103.
PMID: 12317926
Matched MeSH terms: Models, Theoretical*
Chinese culture and demographic trends in Thailand and Malaysia

Barbie J

Chin J Popul Sci, 1992;4(2):139-48.
PMID: 12317919
Matched MeSH terms: Models, Theoretical*
Age at marriage in Malaysia: a hazard model of marriage timing

Anderson KH, Hill MA, Butler JS

J Dev Econ, 1987 Aug;26(2):223-34.
PMID: 12280709

"This paper estimates a proportional hazards model for the timing of age at marriage of women in Malaysia. We hypothesize that age at marriage responds significantly to differences in male and female occupations, race, and age. We find considerable empirical support for the relevance of economic variables in determining age at marriage as well as evidence of strong differences in marriage patterns across races."

Matched MeSH terms: Models, Theoretical*
Migration and fertility in Malaysia: a tale of two hypotheses

Bach RL

Int Migr Rev, 1981;15(3):502-21.
PMID: 12337653
Matched MeSH terms: Models, Theoretical*
A model of the demand for medical and health services in Peninsular Malaysia

Heller PS

Soc Sci Med, 1982;16(3):267-84.
PMID: 7100978 DOI: 10.1016/0277-9536(82)90337-9

This paper provides an empirical analysis of the determinants of the demand for medical services in Peninsular Malaysia. After elaborating a theoretical model of household demand for medical care in Section II an econometric model is specified and estimated in Sections III, IV, and V. The results indicate that total medical demand, as measured by the absolute volume of outpatient and inpatient consumption, is highly inelastic to the cash price and to the cost in time of utilization. Total medical demand is also inelastic with respect to income. Yet consumers are clearly responsive to the relative prices of alternative sources of medical care. Consumers are also sensitive to the way in which the time of utilization is spent, with high travel and treatment time causing reduced demand for services.

Matched MeSH terms: Models, Theoretical*
Migration, income and fertility in Malaysia: a simultaneous equations model with limited dependent variables

Lee KS

Appl Econ, 1989;21:1589-610.
PMID: 12342770
Matched MeSH terms: Models, Theoretical*
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*
Fulltext The development of an integrated behavioural model of patient compliance with diabetes medication: a mixed-method study protocol

Swarna Nantha Y, Haque S, Swarna Nantha H

Fam Pract, 2019 10 08;36(5):581-586.
PMID: 30534941 DOI: 10.1093/fampra/cmy119

BACKGROUND: There has been a shift in worldwide disease burden from infections to non-communicable diseases, especially type 2 diabetes (T2D). Behavioural change and self-management are key to optimal T2D control. Several universal models of diabetic care have been proposed to help explain the dimensions of T2D self-care such as medication adherence, physical activity, diet and patient-doctor interaction. These models do not allow an objective and quantifiable measurement of the problems faced by patients in terms of medication compliance.
OBJECTIVE: To create a comprehensive conceptual model of behavioural change related to T2D medication compliance.
METHODS: A cross-sectional study will be conducted at a regional primary care clinic using a mixed-method technique. First, a Grounded Theory qualitative inquiry will be used to investigate predictors of medication adherence in T2D patients. Consequently, the elements derived from the interview will be incorporated into the Theory of Planned Behaviour framework to generate an integrated behavioural model. This model will then be used to quantify the factors related to compliance with medication amongst T2D patients.
DISCUSSION: The framework developed here could help in the design of policies to optimize T2D control by identifying lapses in patients' intake of diabetic medications. This can be done by exploring the patients' fundamental and unarticulated belief system via a naturalistic approach adopted in this study. The properties of the framework can be replicated in other settings to serve as a benchmark for quality improvement in T2D patient care.

Matched MeSH terms: Models, Theoretical*
Fulltext Local Government Competition, Environmental Regulation Intensity and Regional Innovation Performance: An Empirical Investigation of Chinese Provinces

Deng J, Zhang N, Ahmad F, Draz MU

Int J Environ Res Public Health, 2019 06 16;16(12).
PMID: 31208141 DOI: 10.3390/ijerph16122130

：The aim of this paper is to examine the impact of local government competition and environmental regulation intensity on regional innovation performance and its regional heterogeneity. Based on the theoretical mechanism of the aforementioned variables, this study uses the Chinese provincial panel data from 2001 to 2016. We use the super-efficiency data envelopment analysis (SE-DEA) to evaluate regional innovation performance. To systematically examine the impact of local government competition and environmental regulation intensity on regional innovation performance, we build a panel date model using the feasible generalized least squares (FGLS) method. The results indicate that: the regional innovation performance can be significantly improved through technological spillover; local governments compete for foreign direct investment (FDI) to participate in regional innovative production. Moreover, improvements in environmental regulation intensity enhance regional innovation performance through the innovation compensation effect. Our results show that the local governments tend to choose lower environmental regulation intensity to compete for more FDI, which has an inhibitory effect on regional innovation performance. Furthermore, due to regional differences in factor endowments, economic reforms and economic development levels in Chinese provinces, there exists a significant regional consistency in the impact of local government competition and environmental regulation intensity on regional innovation performance. Therefore, institutional arrangements and incentive constraints must be adopted to enhance regional innovation performance as well as to guide and foster the mechanism of green innovation competition among local governments. At the same time, considering the regional heterogeneity of local government competition and environmental regulation intensity affecting regional innovation performance, policy makers should avoid the "one-size-fits-all" strategy of institutional arrangements.

Matched MeSH terms: Models, Theoretical*
Fulltext The Influence of Scleral Flap Thickness, Shape, and Sutures on Intraocular Pressure (IOP) and Aqueous Humor Flow Direction in a Trabeculectomy Model

Samsudin A, Eames I, Brocchini S, Khaw PT

J Glaucoma, 2016 07;25(7):e704-12.
PMID: 26561421 DOI: 10.1097/IJG.0000000000000360

PURPOSE: Intraocular pressure and aqueous humor flow direction determined by the scleral flap immediately after trabeculectomy are critical determinants of the surgical outcome. We used a large-scale model to objectively measure the influence of flap thickness and shape, and suture number and position on pressure difference across the flap and flow of fluid underneath it.
METHODS: The model exploits the principle of dynamic and geometric similarity, so while dimensions were up to 30× greater than actual, the flow had similar properties. Scleral flaps were represented by transparent 0.8- and 1.6-mm-thick silicone sheets on an acrylic plate. Dyed 98% glycerin, representing the aqueous humor was pumped between the sheet and plate, and the equilibrium pressure measured with a pressure transducer. Image analysis based on the principle of dye dilution was performed using MATLAB software.
RESULTS: The pressure drop across the flap was larger with thinner flaps, due to reduced rigidity and resistance. Doubling the surface area of flaps and reducing the number of sutures from 5 to 3 or 2 also resulted in larger pressure drops. Flow direction was affected mainly by suture number and position, it was less toward the sutures and more toward the nearest free edge of the flap. Posterior flow of aqueous humor was promoted by placing sutures along the sides while leaving the posterior edge free.
CONCLUSION: We demonstrate a new physical model which shows how changes in scleral flap thickness and shape, and suture number and position affect pressure and flow in a trabeculectomy.

Matched MeSH terms: Models, Theoretical*
Fulltext An empirical study on asymmetric jump diffusion for option and annuity pricing

Lau KJ, Goh YK, Lai AC

PLoS One, 2019;14(5):e0216529.
PMID: 31063498 DOI: 10.1371/journal.pone.0216529

In this paper, we present a method to estimate the market parameters modelled by an asymmetric jump diffusion process. The method proposed is based on Kou's jump diffusion model while the market parameters refer to the market drift, the market volatility, the jump intensity on market price, and the rate of jump occurrence in a consistent manner throughout the entire paper. The model captures the asymmetric nature of the price fluctuation during up trend markets and down trend markets. The results are compared to conventional options to observe the impact of jump effects. The results from simulation show that the asymmetric jump diffusion model can estimate the fair prices of European call options and annuity better than the Black-Scholes model and the symmetric jump diffusion model proposed by Kou and Merton.

Matched MeSH terms: Models, Theoretical*
Theoretical analyses on enantiospecificity of L-2-haloacid dehalogenase (DehL) from Rhizobium sp. RC1 towards 2-chloropropionic acid

Adamu A, Abdul Wahab R, Aliyu F, Abdul Razak FI, Mienda BS, Shamsir MS, et al.

J Mol Graph Model, 2019 11;92:131-139.
PMID: 31352207 DOI: 10.1016/j.jmgm.2019.07.012

Dehalogenases continue to garner interest of the scientific community due to their potential applications in bioremediation of halogen-contaminated environment and in synthesis of various industrially relevant products. Example of such enzymes is DehL, an L-2-haloacid dehalogenase (EC 3.8.1.2) from Rhizobium sp. RC1 that catalyses the specific cleavage of halide ion from L-2-halocarboxylic acids to produce the corresponding D-2-hydroxycarboxylic acids. Recently, the catalytic residues of DehL have been identified and its catalytic mechanism has been fully elucidated. However, the enantiospecificity determinants of the enzyme remain unclear. This information alongside a well-defined catalytic mechanism are required for rational engineering of DehL for substrate enantiospecificity. Therefore, using quantum mechanics/molecular mechanics and molecular mechanics Poisson-Boltzmann surface area calculations, the current study theoretically investigated the molecular basis of DehL enantiospecificity. The study found that R51L mutation cancelled out the dehalogenation activity of DehL towards it natural substrate, L-2-chloropropionate. The M48R mutation, however introduced a new activity towards D-2-chloropropionate, conveying the possibility of inverting the enantiospecificity of DehL from L-to d-enantiomer with a minimum of two simultaneous mutations. The findings presented here will play important role in the rational design of DehL dehalogenase for improving substrate utility.

Matched MeSH terms: Models, Theoretical*
Fulltext Pneumocephalus and air travel: an experimental investigation on the effects of aircraft cabin pressure on intracranial pressure

Lim E, Lan BL, Ooi EH, Low HL

Sci Rep, 2020 08 12;10(1):13626.
PMID: 32788610 DOI: 10.1038/s41598-020-70614-w

This study investigates the effects of aircraft cabin pressure on intracranial pressure (ICP) elevation of a pneumocephalus patient. We propose an experimental setup that simulates the intracranial hydrodynamics of a pneumocephalus patient during flight. It consists of an acrylic box (skull), air-filled balloon [intracranial air (ICA)], water-filled balloon (cerebrospinal fluid and blood) and agarose gel (brain). The cabin was replicated using a custom-made pressure chamber. The setup can measure the rise in ICP during depressurization to levels similar to that inside the cabin at cruising altitude. ΔICP, i.e. the difference between mean cruising ICP and initial ICP, was found to increase with ICA volume and ROC. However, ΔICP was independent of the initial ICP. The largest ΔICP was 5 mmHg; obtained when ICA volume and ROC were 20 ml and 1,600 ft/min, respectively. The postulated ICA expansion and the subsequent increase in ICP in pneumocephalus patients during flight were successfully quantified in a laboratory setting. Based on the quantitative and qualitative analyses of the results, an ICA volume of 20 ml and initial ICP of 15 mmHg were recommended as conservative thresholds that are required for safe air travel among pneumocephalus patients. This study provides laboratory data that may be used by doctors to advise post-neurosurgical patients if they can safely fly.

Matched MeSH terms: Models, Theoretical*
Formation, modeling and validation of trihalomethanes (THM) in Malaysian drinking water: a case study in the districts of Tampin, Negeri Sembilan and Sabak Bernam, Selangor, Malaysia

Abdullah MP, Yew CH, Ramli MS

Water Res, 2003 Nov;37(19):4637-44.
PMID: 14568050

A modeling procedure that predicts trihalomethane (THM) formation from field sampling at the treatment plant and along its distribution system using Tampin district, Negeri Sembilan and Sabak Bernam district, Selangor as sources of data were studied and developed. Using Pearson method of correlation, the organic matter measured as TOC showed a positive correlation with formation of THM (r=0.380,P=0.0001 for Tampin and r=0.478,P=0.0001 for Sabak Bernam). Similar positive correlation was also obtained for pH in both districts with Tampin (r=0.362,P=0.0010) and Sabak Bernam (r=0.215,P=0.0010). Chlorine dosage was also found to have low correlation with formation of THM for the two districts with Tampin (r=0.233,P=0.0230) and Sabak Bernam (r=0.505,P=0.0001). Distance from treatment plant was found to have correlation with formation of THM for Tampin district with r=0.353 and P=0.0010. Other parameters such as turbidity, ammonia, temperature and residue chlorine were found to have no correlation with formation of THM. Linear and non-linear models were developed for these two districts. The results obtained were validated using three different sets of field data obtained from own source and district of Seremban (Pantai and Sg. Terip), Negeri Sembilan. Validation results indicated that there was significant difference in the predictive and determined values of THM when two sets of data from districts of Seremban were used with an exception of field data of Sg. Terip for non-linear model developed for district of Tampin. It was found that a non-linear model is slightly better than linear model in terms of percentage prediction errors. The models developed were site specific and the predictive capabilities in the distribution systems vary with different environmental conditions.

Matched MeSH terms: Models, Theoretical*
Fulltext Development of Toxicological Risk Assessment Models for Acute and Chronic Exposure to Pollutants

Reichwaldt ES, Stone D, Barrington DJ, Sinang SC, Ghadouani A

Toxins (Basel), 2016 08 31;8(9).
PMID: 27589798 DOI: 10.3390/toxins8090251

Alert level frameworks advise agencies on a sequence of monitoring and management actions, and are implemented so as to reduce the risk of the public coming into contact with hazardous substances. Their effectiveness relies on the detection of the hazard, but with many systems not receiving any regular monitoring, pollution events often go undetected. We developed toxicological risk assessment models for acute and chronic exposure to pollutants that incorporate the probabilities that the public will come into contact with undetected pollution events, to identify the level of risk a system poses in regards to the pollutant. As a proof of concept, we successfully demonstrated that the models could be applied to determine probabilities of acute and chronic illness types related to recreational activities in waterbodies containing cyanotoxins. Using the acute model, we identified lakes that present a 'high' risk to develop Day Away From Work illness, and lakes that present a 'low' or 'medium' risk to develop First Aid Cases when used for swimming. The developed risk models succeeded in categorising lakes according to their risk level to the public in an objective way. Modelling by how much the probability of public exposure has to decrease to lower the risks to acceptable levels will enable authorities to identify suitable control measures and monitoring strategies. We suggest broadening the application of these models to other contaminants.

Matched MeSH terms: Models, Theoretical*
Nutrient fluxes across sediment-water interface in Bohai Bay Coastal Zone, China

Mu D, Yuan D, Feng H, Xing F, Teo FY, Li S

Mar Pollut Bull, 2017 Jan 30;114(2):705-714.
PMID: 27802871 DOI: 10.1016/j.marpolbul.2016.10.056

Sediment cores and overlying water samples were collected at four sites in Tianjin Coastal Zone, Bohai Bay, to investigate nutrient (N, P and Si) exchanges across the sediment-water interface. The exchange fluxes of each nutrient species were estimated based on the porewater profiles and laboratory incubation experiments. The results showed significant differences between the two methods, which implied that molecular diffusion alone was not the dominant process controlling nutrient exchanges at these sites. The impacts of redox conditions and bioturbation on the nutrient fluxes were confirmed by the laboratory incubation experiments. The results from this study showed that the nutrient fluxes measured directly from the incubation experiment were more reliable than that predicted from the porewater profiles. The possible impacts causing variations in the nutrient fluxes include sewage discharge and land reclamation.

Matched MeSH terms: Models, Theoretical*
Optimization of photocatalytic degradation of palm oil mill effluent in UV/ZnO system based on response surface methodology

Ng KH, Cheng YW, Khan MR, Cheng CK

J Environ Manage, 2016 Dec 15;184(Pt 3):487-493.
PMID: 27784576 DOI: 10.1016/j.jenvman.2016.10.034

This paper reports on the optimization of palm oil mill effluent (POME) degradation in a UV-activated-ZnO system based on central composite design (CCD) in response surface methodology (RSM). Three potential factors, viz. O2 flowrate (A), ZnO loading (B) and initial concentration of POME (C) were evaluated for the significance analysis using a 2(3) full factorial design before the optimization process. It is found that all the three main factors were significant, with contributions of 58.27% (A), 15.96% (B) and 13.85% (C), respectively, to the POME degradation. In addition, the interactions between the factors AB, AC and BC also have contributed 4.02%, 3.12% and 1.01% to the POME degradation. Subsequently, all the three factors were subjected to statistical central composite design (CCD) analysis. Quadratic models were developed and rigorously checked. A 3D-response surface was subsequently generated. Two successive validation experiments were carried out and the degradation achieved were 55.25 and 55.33%, contrasted with 52.45% for predicted degradation value.

Matched MeSH terms: Models, Theoretical*

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