Applied Mechanics and Materials Vol. 735

Abstract: This paper investigates the performance of design of experiment (DOE) in response surface methodology (RSM) for vibration-based damage detection. The ability of three major types of DOE, namely central composite design (CCD), Box-Behnken (BBD) and D-optimal (Dopt) for damage detection based on modal frequency are investigated and compared. A procedure comprising three main stages—sampling, response surface (RS) modelling and model updating—are employed for damage localisation and quantification. By considering Young’s modulus and modal frequency as respective input and output, a set of samples is generated from each DOE. Full quadratic functions are considered in RS modelling while model updating is performed for damage detection. The performances of DOE are compared based on damage detectability. A numerical simply supported beam is used as case study by considering several single damage cases. The results show that CCD provides better prediction compared to other DOEs.

Abstract: The magnetic nanoparticles of manganese-doped magnetite (Mn-Fe₂O₄) were synthesized by the simple co-precipitation method. The stable Mn²⁺ and Fe³⁺ salts in the ratio of 1:2 in aqueous solution, were added into the sodium hydroxide solution to form the Mn-Fe₂O₄ precipitate at temperature of 95°C. The synthesized nanoparticles were then characterized by Fourier Transform-Infrared Spectroscopy (FT-IR) and X-ray diffraction spectroscopy (XRD). It was then entrapped in the PVA-alginate matrix to form the nanophotoadsorbent in beads form. The synthesized nanoparticles embedded bead was characterized by Scanning Electron Microscopy (SEM). The effects of various parameters, such as contact time, pH, nanoparticles dosage were investigated. The control study was also performed to reveal the performance of photo-adsorbent towards the Cu (II) removal under the light and dark conditions. It was found that the removal efficiency of the Cu (II) achieved 97.07% (1.46ppm) which complied to the WHO drinking water standard of less than 1.5ppm after 180 min treatment.

Abstract: Agriculture biomasses have been successfully converted into value-added products such as biocomposite plastics, furniture, papers and textiles. However, only the cellulose parts of these lignocellulosic materials are being used while other components such as lignin and wax are discarded. For a tropical country like Malaysia, banana stem is one of the sources of biomasses. Like other biomasses-based products, only cellulose part of banana stem is used while the lignin portion is discarded due to overly hydrophilic character. This water-loving property of lignin can be manipulated into specific application such as water absorbent for waste treatment. This research is aimed to synthesis water absorbent-based lignin from banana stem. The lignin had been extracted from banana stem using Kraft process prior to grafted with acrylic acid monomer (AA) in order to increase its water absorbency. The reaction was carried out via free radical polymerization in the presence of hydrogen peroxide (H₂O₂) as initiator and ammonium iron (II) sulfate hexahydrate as catalyst. The reaction temperature was set at 60°C. Grafting efficiency of polyacrylic acid (PAA) onto lignin backbone was determined by varying the amounts of AA monomer, lignin and initiator. The highest grafting percentage was acquired at 60% with the amount of 6ml acrylic acid, 2ml initiator and 0.2g lignin respectively.

Abstract: The Objective of the Present Study is to Characterize Extreme Droughts during Monsoon (June to September) when Rain-Fed Crops are Grown in Bangladesh. Fifty Years (1963-2012) Rainfall Data Recorded at Twenty-Nine Stations in Bangladesh is Analysed Using Standardized Precipitation Index (SPI) to Reconstruct the Historical Droughts during Monsoon with Various Severities. the Extreme Droughts Events are Identified from the Reconstructed SPI Time Series and their Distribution in Time is Recognized by Fitting Various Frequency Distribution Curves. Finally, the Best Fitted Distribution is Used to Calculate the Return Periods of Extreme Droughts. the Results Show that Extreme Droughts during Monsoon Occur once in Every 18 Years in Northwest Bangladesh. it is Expected that the Study will Help in Planning Adaptation Strategies to Mitigate the Impacts of the Droughts.

Abstract: Downscaling Global Circulation Model (GCM) output is important in order to understand the present climate as well as future climate changes at local scale. In this study, Radial basis function (RBF) neural network was used to downscale the mean monthly rainfall in an arid coastal region located in Baluchistan province of Pakistan. The RBF model was used to downscale monthly rainfall from National Center for environmental prediction (NCEP) reanalysis dataset at four observation stations in the area. The potential predictors were selected using principal component analysis of NCEP variables at grid points located around the study area. Power transformation method was used to remove the bias in the prediction. The results showed that the RBF model was able to establish a good relation between NCEP predictors and local rainfall. The power transformation method was also found to perform well to correct errors in prediction. It can be concluded that RBF and power transformation methods are reliable and effective methods for downscaling rainfall in an arid coastal region.

Abstract: Computational intelligence (CI) tools have been successfully applied in different fields with superior performances. Neuro-fuzzy system (NFS) is one the approach which combines the benefits of two powerful CI tools known as artificial neural networks (ANN) and fuzzy logic. Although NFS has attracted researchers in many areas of study, few of its applications have been undertaken in hydrological modeling. Adaptive Network-based Fuzzy Inference System (ANFIS) is so far the most established NFS technique and this study is an application of ANFIS in river stage prediction by using rainfall and stage antecedents as inputs in the tropical catchment of Bekok River in Malaysia. To evaluate the performance of the ANFIS model, it was compared with a traditional modeling technique known as autoregressive model with exogenous inputs (ARX). The results of this study were evaluated based on several statistical measures such as coefficient of efficiency (CE), coefficient of determination (r²), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE). The results showed that ANFIS can successfully predict the river stage and it outperforms ARX model significantly. ANFIS was also found better in estimating peak river stages comparing to ARX model. This study demonstrates the auspicious potential of ANFIS in river stage modeling.

Abstract: There is a rising demand for energy crops and animal manures in biogas production.This research focused at anaerobic co-digestion of oil palm mesocarp fibre (OPMF) and cattle manure (CM) for biogas production.OPMF is considered as lignocellulosic biomass and acting as the main substrate of the digestion.CM contains high nutrient which could lead to higher biogas production.A batch scale experiment was carried out in mesophilic condition at 37°C.Main parameters involved are pH, soluble chemical oxygen demand (COD) and volume biogas production.The obtained pH values of the samples are between 6.5 and 7.5.This anaerobic co-digestion gave 76% of COD removal on day 30.The observed volume of biogas that produced was between 90 to 130mL.The system was run for two different hydraulic retention time (HRT).The HRTs are 15 and 30 days.Co-digestion of two different organic matters gave good biogas production in comparison to normal single digestion.

Abstract: The aim of this research is to investigate addition of iron (ferric chloride) to control of sulphate reduction in order to enhance the methane production under laboratory scale. The bioreactor Upflow Anaerobic Sludge Blanket (UASB) undergoes continuous operation under anaerobic condition treating synthetic sulphate enriched wastewater. The wastewater used as influent wastewater with a total COD 8000 mg.L^-1. The experiment was conducted for about 64 days and was operated at constant OLR of 2.0(±0.1) kgCOD.m^-3.d^-1 by maintaining a hydraulic retention time (HRT) of 4 days. The UASB then were feed with sulphate and give the COD/SO₄ ratio 5.3, 2.5 and 1.5. Then amount of ferric chloride at 10.4, 22.2 and 44.5 mM was introduce just after methane producing bacteria (MPB) were completely inhibited by sulphate reducing bacteria (SRB) due to decreasing of methane composition (CH₄) and high level production of hydrogen sulphide (H₂S). The obtained results showed that the FeCl₃ negatively impacted the anaerobic digestion process since with each of COD/SO₄^2- ratio, and the amount addition of ferric chloride to feed regime, gives promotion on methane production, with 67, 70 and 69% after approximately 10 to 15 days operating at critical conditions.

Abstract: The removal of Bisphenol A in river water can be accomplished with the application of ozone. Ozone is widely used to disinfect drinking water due to its strong oxidizing properties. This study was conducted to investigate the removal of Bisphenol A in different areas of Skudai River. Batch experiments were conducted at initial Bisphenol A concentration of 0.5 mg L^-1. The concentrations of Bisphenol A and dissolved ozone were measured using Ultra High Performance Liquid Chromatography (UHPLC) and UV-Visible spectrophotometer respectively. Based on the results obtained the stability of ozone in the water were very fast. Ozone was quickly decomposed in water samples. The results indicated that the depletion of ozone varied from different dissolved organic carbon (DOC) value of water samples. Concentration of dissolved ozone was reducing rapidly after spiked into high DOC value (9.17 mg L^-1) of river water. The results of the study have shown that ozonation could be used to effectively remove the Bisphenol A from water. The ozone depletions in river water at 120 seconds were about 87%-99%.

Abstract: Understanding quality of stormwater is important for effective urban rainwater treatment planning and management. In this study, the quality of stormwater runoff from an arid urban residential catchment located in the Karbala city of Iraq, draining through stormwater sewers was investigated. The Storm Water Management Model (SWMM) was used to estimate the concentrations of pollutants in stormwater and wastewater in the sewer networks. The results showed that the concentrations of the Biological Oxygen Demand (BOD₅) and Total Suspended Solids (TSS) increased significantly after rain in the study area. The increase of TSS was very high compared to the BOD₅. It is expected that the long-term simulations of stormwater pollution loading will help to compare the benefits of different scenarios of the sewage treatment plan for the reduction of the pollution in the storm discharge area.