19672 research outputs found
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Solubility of CO 2 in aqueous solutions of glycerol and monoethanolamine
No full textFor decades, carbon dioxide emissions have been an environmental and health issue. Amines like Monoethanolamine (MEA) have long been favoured in strategies based on chemical absorption aimed at CO2 capture and thus reduction of its harmful environmental impacts. However, some drawbacks, such as toxicity, low stability and high cost limit widespread adoption of this technology. New and green solvents are a possible solution to this issue. As a part of the present study, CO2 solubility in aqueous solutions of different molar ratios of MEA and glycerol as a green solvent was studied. The CO2 absorption was performed at three different temperatures (303, 318, and 333 K) at normal atmospheric pressure, while CO2 partial pressure was varied from 1 to 15 kPa, and the gas flow rate in the mixture was changed from 350 to 700 ml/min. The response surface methodology (RSM) based on central composite design (CCD) was used to design the experiment and explore the effects of four independent parameters (molar concentration of MEA, molar concentration of glycerol, temperature, and gas flow rate) on the solubility of CO2 in solution. Analysis of variance (ANOVA) results showed a good agreement between the experimental data and the statistical model. The maximum solubility occurred for 4 M MEA + 2 M glycerol at 333 K and 350 ml/min CO2 flow rate. The CO2 solubility values pertaining to different pressures and concentrations were in good agreement with the general absorption trend. However, as the temperature increased, so did the loading. The findings further revealed that the optimum CO2 solubility was obtained at low glycerol to MEA ratio, as this ensured the solubility at elevated temperatures. As glycerol is a viscous fluid, it can be confirmed that it is a suitable solvent at low pressures and high temperatures. Therefore, it can be a viable alternative solution for post-combustion CO2 capture. In addition, an artificial neural network (ANN) model and correlations of CO2 solubility with CO2 partial pressure for all the studied solvent mixtures were developed in this study. Both the ANN model and the correlations fit the experimental CO2 solubility data reasonably well
Waste level detection and HMM based collection scheduling of multiple bins
No full textIn this paper, an image-based waste collection scheduling involving a node with three waste bins is considered. First, the system locates the three bins and determines the waste level of each bin using four Laws Masks and a set of Support Vector Machine (SVM) classifiers. Next, a Hidden Markov Model (HMM) is used to decide on the number of days remaining before waste is collected from the node. This decision is based on the HMM’s previous state and current observations. The HMM waste collection scheduling seeks to maximize the number of days between collection visits while preventing waste contamination due to late collection. The proposed system was trained using 100 training images and then tested on 100 test images. Each test image contains three bins that might be shifted, rotated, occluded or toppled over. The upright bins could be empty, partially full or full of garbage of various shapes and sizes. The method achieves bin detection, waste level classification and collection day scheduling rates of 100%, 99.8% and 100% respectively
An analysis of Malaysian retracted papers: Misconduct or mistakes?
No full textRetracted publications are a crucial, yet overlooked, issue in the scientific community. The purpose of this study was to analyze the prevalence, characteristics and reasons of Malaysian retracted papers. The Web of Science and Scopus databases were queried to identify Malaysian retracted publications. Available versions of original articles and publication notices were accessed from journal websites. The publications were assessed for various characteristics, including reason for retraction, based on the Committee on Publication Ethics guidelines, and the authority calling for the retractions. From 2009 to June 2017, 125 Malaysian publications comprising (33 journal articles and 92 conference papers) were retracted. There was a spike in the prevalence of retracted articles in 2010 and 2012 with 42 articles (33.6%) and 41 articles (32.8%) respectively from the 125 retracted articles. The mean time from electronic publication to retraction was 1 year. There is no significant relationship between a journal quartile and the mean number of months to retraction (P = 0.842). The reason for retraction for conference papers was specified as “violation of publication principle”. Journal articles were retracted mainly for duplicate publication, plagiarism, compromised peer review process, and self-plagiarism. Most retracted articles do not contain flawed data; and only 2 retracted articles have been accused of scientific mistakes. The study concludes that retractions were mostly due to the authors misconduct. Despite the increases, the proportion of published scholarly literature affected by retraction remains very small, indicating that retraction represents an uncommon, yet potentially increasing and incipient, issue within Malaysian papers, which publishers as well as editors may have consistently and sufficiently addressed
Effect of hesperidin on the temporal regulation of redox homeostasis in clock mutant (Cryb) of Drosophila melanogaster
No full textDisorganized redox homeostasis is a main factor causing a number of diseases and it is imperative to comprehend the orchestration of circadian clock under oxidative stress in the organism, Drosophila melanogaster. This investigation analyses the influence of hesperidin on the circadian rhythms of lipid peroxidation products and antioxidants during rotenone-stimulated oxidative stress in fruit fly. The characteristics of rhythms of thiobarbituric acid reactive substances (TBARS), antioxidants (superoxide dismutase (SOD) and catalase (CAT)) were noticeably decreased in rotenone administered flies. Supplementation of hesperidin to rotenone-treated flies increased the mesor and modulated the amplitudes of antioxidants and conspicuously decreased the mesor values of TBARS. In addition, delays in acrophase in rotenone-induced flies were reversed by hesperidin treatment. Thus, treatment of hesperidin caused normalization of the altered rhythms. Disorganization of 24 h rhythms in markers of redox homeostasis was observed during rotenone treatment and the impairment is severe in circadian clock mutant (Cryb) flies. Reversibility of rhythms was prominent subsequent to hesperidin treatment in wild-type flies than (Cryb) flies. These observations denote a role of circadian clock in redox homeostasis and the use of Drosophila model in screening putative antioxidative phytomedicines prior to their usage in mammalian systems
Analysing the accuracy of machine learning techniques to develop an integrated influent time series model: case study of a sewage treatment plant, Malaysia
No full textThe function of a sewage treatment plant is to treat the sewage to acceptable standards before being discharged into the receiving waters. To design and operate such plants, it is necessary to measure and predict the influent flow rate. In this research, the influent flow rate of a sewage treatment plant (STP) was modelled and predicted by autoregressive integrated moving average (ARIMA), nonlinear autoregressive network (NAR) and support vector machine (SVM) regression time series algorithms. To evaluate the models’ accuracy, the root mean square error (RMSE) and coefficient of determination (R2) were calculated as initial assessment measures, while relative error (RE), peak flow criterion (PFC) and low flow criterion (LFC) were calculated as final evaluation measures to demonstrate the detailed accuracy of the selected models. An integrated model was developed based on the individual models’ prediction ability for low, average and peak flow. An initial assessment of the results showed that the ARIMA model was the least accurate and the NAR model was the most accurate. The RE results also prove that the SVM model’s frequency of errors above 10% or below − 10% was greater than the NAR model’s. The influent was also forecasted up to 44 weeks ahead by both models. The graphical results indicate that the NAR model made better predictions than the SVM model. The final evaluation of NAR and SVM demonstrated that SVM made better predictions at peak flow and NAR fit well for low and average inflow ranges. The integrated model developed includes the NAR model for low and average influent and the SVM model for peak inflow
β-Cyclodextrin conjugated bifunctional isocyanate linker polymer for enhanced removal of 2,4-dinitrophenol from environmental waters
No full textIn this work, we reported the synthesis, characterization and adsorption study of two b-cyclodextrin (bCD) cross-linked polymers using aromatic linker 2,4-toluene diisocyanate (2,4-TDI) and aliphatic linker 1,6-hexamethylene diisocyanate (1,6-HDI) to form insoluble bCD-TDI and bCD-HDI. The adsorption of 2,4-dinitrophenol (DNP) on both polymers as an adsorbent was studied in batch adsorption experiments. Both polymers were well characterized using various tools that include Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer-Emmett-Teller analysis and scanning electron microscopy, and the results obtained were compared with the native bCD. The adsorption isotherm of 2,4-DNP onto polymers was studied. It showed that the Freundlich isotherm is a better fit for bCD-TDI, while the Langmuir isotherm is a better fit for bCD-HMDI. The pseudo-second-order kinetic model represented the adsorption process for both of the polymers. The thermodynamic study showed that bCD-TDI polymer was more favourable towards 2,4-DNP when compared with bCD-HDI polymer. Under optimized conditions, both bCD polymers were successfully applied on various environmental water samples for the removal of 2,4-DNP. bCD-TDI polymer showed enhanced sorption capacity and higher removal efficiency (greater than 80%) than bCD-HDI (greater than 70%) towards 2,4-DNP. The mechanism involved was discussed, and the effects of cross-linkers on bCD open up new perspectives for the removal of toxic contaminants from a body of water
Application of modified classical numerical methods for DMPPT on Buck and Boost converters
No full textApplication of Classical Numerical Methods (CNM) for Digital maximum power point tracking (DMPPT) confronts many issues. The issues highlighted in this paper include limited range of operation, PV array dependence and accuracy of the initial guess. In order to address such shortcomings of CNM for DMPPT, Hybrid Techniques (HT) have been proposed. The HT are a combination of the modified incremental conductance method (MINC) and various modified CNM. An overview of the considered MCNM, which are applied to the photovoltaic (PV) application, has also been provided. The HT not only address the issues confronted by the CNM, but also improve the transient response time and remove the steady state oscillations for the conventional MPPT technique. In addition, for DMPPT the DC-DC converter topology under consideration cannot be treated as a black box, by ignoring the effects of the converter topology and control dynamics. Here, a theoretical analysis has been provided to ascertain the optimum performance of DMPPT applications on various DC-DC converter designs. To measure the effectiveness of the proposed HT, Boost, 2-Stage Switch Capacitor Based (2-SSC) Boost, and Optimum Buck Converters (OBC) have been employed. Simulation and experimental results are provided to validate the effectiveness of the proposed HT
Generation of flood map using infoworks for Sungai Johor
No full textFlood has become regular disaster in Malaysia which it is happens every year in different states especially during northeast monsoon. Johor State, the most southern part of Peninsular Malaysia experienced numerous flooding from 1926 to 2013. However, Sungai Johor catchment had the most devastating impact during December 2006 and January 2007 flood events. The objectives of this study are to perform river modeling and generate a flood map fpr Sungai Johor. The river modeling of Sungai Johor has been done using InfoWorks RS software. Necessary data were collected and transferred into the required modelling procedures. The results indicated that the model was able to simulate the flood depth to a reasonable agreement and generate the flood map. The generated flood map can serve as a beneficial planning and design tools for the local authority and community in minimizing the flood effects and damage as well as in preparing the evaluation plan
Food Addiction Does Not Explain Weight Gain in Smoking Cessation
No full textIntroduction: Weight gain during smoking cessation is a major concern. The relationship between smoking and weight is complex and not well understood. There is interest in substitution of nicotine with food. Aims: This study investigates whether the development of food addiction explains weight gain following a quit smoking attempt. Methods: This study was a subset of a larger study investigating smoking cessation in New Zealand. Participants were assessed on five visits over a 1-year period. Using validated instruments, measurements for smoking, weight, food intake, craving and food addiction were taken. Results: Among the 256 participants, 54.7% attended at least one follow-up. Food addiction prevalence at baseline was 0.8%. 14.5% were quit at early follow-up and 14.8% at late follow-up. Weight gain was found in abstainers compared to those still smoking. No increase in food addiction was detected. Conclusion: The development of food addiction does not play a prominent role in post quit weight gain. Further research is needed to elucidate the underlying weight gain mechanisms
Minimizing the Principle Stresses of Powerhoused Rock-Fill Dams Using Control Turbine Running Units: Application of Finite Element Method
No full textThis study focuses on improving the safety of embankment dams by considering the effects of vibration due to powerhouse operation on the dam body. The study contains two main parts. In the first part, ANSYS-CFX is used to create the three-dimensional (3D) Finite Volume (FV) model of one vertical Francis turbine unit. The 3D model is run by considering various reservoir conditions and the dimensions of units. The Re-Normalization Group (RNG) k-ε turbulence model is employed, and the physical properties of water and the flow characteristics are defined in the turbine model. In the second phases, a 3D finite element (FE) numerical model for a rock-fill dam is created by using ANSYS®, considering the dam connection with its powerhouse represented by four vertical Francis turbines, foundation, and the upstream reservoir. Changing the upstream water table minimum and maximum water levels, standers earth gravity, fluid-solid interface, hydrostatic pressure, and the soil properties are considered. The dam model runs to cover all possibilities for turbines operating in accordance with the reservoir discharge ranges. In order to minimize stresses in the dam body and increase dam safety, this study optimizes the turbine operating system by integrating turbine and dam models