The accuracy of preliminary cost estimates in Public Works Department (PWD) of Peninsular Malaysia

This paper presents the accuracy of preliminary cost estimates prepared by Public Works Department (PWD), which is the largest public construction management in Malaysia. It attempts to understand the Quantity Surveyors' (QS) estimation accuracy in relation to public projects. This study analyses 83 projects of estimates and tender bids. The analysis includes three (3) estimating targets i.e. lowest bid, accepted bid and mean of the bids. To broaden the study, 344 QS involved in the procurement answered the questionnaires. Linear multiple regression analysis on project characteristics shows that project size, number of bidders, location and type of schools affect the bias. Contract period affects the consistency. The use of mean of the bids is the best-fit target to explain the bias in terms of adjusted R². The accuracy may improve if sufficient design information is available, proper cost planning and improving the application of historical cost data. As an alternative, the phenomenon of overestimation is resulted from government directive instruction, which could challenge the rational of accurate estimate.     

Enhanced ductility and tensile properties of hybrid montmorillonite/cellulose nanowhiskers reinforced polylactic acid nanocomposites

Montmorillonite (MMT)/cellulose nanowhiskers (CNW) reinforced polylactic acid (PLA) hybrid nanocomposites were prepared by solution casting. CNW were isolated from microcrystalline cellulose using a chemical swelling method. An initial study showed that the optimum MMT content, for mechanical properties, in a PLA/MMT nanocomposite is five parts per hundred parts of polymer (phr). Various amounts of CNW were added to the optimum formulation of PLA/MMT to produce PLA/MMT/CNW hybrid nanocomposites. FT-IR analysis indicated the formation of some polar interactions, resulting in enhanced tensile properties of the hybrid nanocomposites. The highest tensile strength for the hybrid nanocomposites was obtained for a 1 phr CNW content. Young’s modulus was also found to increase with an increasing CNW content. Interestingly, the strain to failure (or ductility) of the hybrid nanocomposites increased significantly from ~10 to ~90 % with the addition of 1 phr CNW. This increase in ductility was proposed to be due to the nucleation of crazes and the formation of shear bands in the PLA.     

Polymerization of polyaniline under various concentrations of ammonium peroxydisulfate and hydrochloric acid by ultrasonic irradiation

Effects of various molar ratios of monomer (aniline), oxidant (ammonium peroxydisulfate), and dopant (hydrochloric acid) on the polymerization of polyaniline (PANI) were investigated using direct ultrasonic irradiation technique. The effects of varying molar ratio of dopant and oxidant on the structural stability, morphology, and electrical conductivity of the prepared PANI were studied. Firstly, a scheme derived from electrical conductivity point of view, by varying the molar ratio of ammonium peroxydisulfate (APS). As the molar ratio of APS to aniline (ANI) varied from 0.1 to 1.25, the conductivity of PANI reached a maximum of 0.24 S/cm at a ratio of 1. Thereafter, by fixing the optimized molar ratio of APS and aniline the molar ratio of hydrochloric acid (HCl) was varied. The conductivity of PANI increased with an increase of HCl concentration and reached a maximum of 0.5 S/cm at an HCl concentration of 2 M. Finally, the formation mechanism for polymerization of PANI were discussed using Fourier transform infrared spectra, ultraviolet–visible spectra, nuclear magnetic resonance spectroscopy, and X-ray diffraction spectroscopy. The final product is in protonated form, possessing structural stability and electrically conductive.     

Morphology,thermal and mechanical behavior of polypropylene nanocomposites toughened with poly(ethylene‐co‐octene)

Rubber‐toughened polypropylene (PP) nanocomposites containing organophilic layered silicates were prepared by means of melt extrusion at 230 °C using a co‐rotating twin‐screw extruder in order to examine the influence of the organoclay and the addition of PP grafted with maleic anhydride (PPgMAH) as a compatibilizer on the morphological, mechanical and thermal properties. The mechanical properties of rubber‐toughened polypropylene nanocomposites (RTPPNCs) were studied through tensile, flexural and impact tests. Scanning electron microscopy (SEM) was used for investigation of the phase morphology and rubber particles size. X‐ray diffraction (XRD) was employed to characterize the formation of nanocomposites. The thermal properties were investigated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The dynamic mechanical properties were examined by using dynamic mechanical analysis (DMA). From the tensile and flexural tests, the optimum loading of organoclay in RTPP was found to be 6 wt%. The optimum loading of PPgMAH, based on the tensile and flexural properties, was also 6 wt%. The increase in the organoclay and PPgMAH content resulted in a severe embrittlement, manifested by a drop in the impact strength and tensile elongation at break. XRD studies revealed that intercalated RTPPNCs had been successfully prepared where the macromolecular PP segments were intercalated into the interlayer space of the organoclay. In addition, the organoclay was dispersed more evenly in the RTPPNC as the PPgMAH content increased. TGA results revealed that the thermal stability of the RTPPNC improved significantly with the addition of a small amount of organoclay. Copyright © 2006 Society of Chemical Industry     

Realistic Smile Expression Recognition Approach Using Ensemble Classifier with Enhanced Bagging

A robust smile recognition system could be widely used for many real-world applications. Classification of a facial smile in an unconstrained setting is difficult due to the invertible and wide variety in face images. In this paper, an adaptive model for smile expression classification is suggested that integrates a fast features extraction algorithm and cascade classifiers. Our model takes advantage of the intrinsic association between face detection, smile, and other face features to alleviate the over-fitting issue on the limited training set and increase classification results. The features are extracted taking into account to exclude any unnecessary coefficients in the feature vector; thereby enhancing the discriminatory capacity of the extracted features and reducing the computational process. Still, the main causes of error in learning are due to noise, bias, and variance. Ensemble helps to minimize these factors. Combinations of multiple classifiers decrease variance, especially in the case of unstable classifiers, and may produce a more reliable classification than a single classifier. However, a shortcoming of bagging as the best ensemble classifier is its random selection, where the classification performance relies on the chance to pick an appropriate subset of training items. The suggested model employs a modified form of bagging while creating training sets to deal with this challenge (error-based bootstrapping). The experimental results for smile classification on the JAFFE, CK+, and CK+48 benchmark datasets show the feasibility of our proposed model.     

A novel rectifying circuit for microwave power harvesting system

Many researchers continue to look for novel means to harvest energy and generate power using existing sources thus eradicating the need of batteries and power supplies which only add up to the cost of the system. A rectifier is the main component in energy harvesting circuits as it converts RF energy from available sources to DC power. This article aimed at developing a novel rectifying circuit to be used in harvesting applications at a frequency of 900 MHz. Besides, it is also aimed to enhance the output voltage of Cockcroft Walton rectifier circuit and Dickson rectifier. The design is built by integrating the Cockcroft Walton rectifier, arranged in series, with the Dickson rectifier, arranged in parallel. A Schottky diode HSMS 285C is selected for designing the rectifiers circuit. A simulation of the circuit was optimized utilizing ADS 2009. The rectifiers had been fabricated on an RT/Duroid 5880 (RO5880) printed circuit board (PCB) substrate with a dielectric constant and loss tangent of 2.2 and 0.0009, respectively. Simulation and experimental results show great output thresholds for the three models. The novel rectifier had the highest efficiency and output voltage.     

Heat sealability of laminated films with LLDPE and LDPE as the sealant materials in bar sealing application

The heat sealability of laminated films with linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) as the sealant materials was investigated. A laboratory heat sealer was used to study the response of laminated films to temperature, time, and pressure. Platen temperature was confirmed as primary factor in controlling heat‐seal strength. Dwell time must be sufficiently long to bring the interfacial temperature to a desired level. When the desired heat‐seal strength has been achieved, further increase of dwell time did not improved heat‐seal strength. Platen pressure had little effect above the level required to flatten the materials for good contact. Bar sealing process window for each sample were developed. The optimum combination of platen temperature and dwell time for each laminated film can be obtained in the respective process windows. Strength of heat‐seal and its failure modes are closely related. Plateau initiation temperature closely corresponds to the final melting point of sealant materials. Relatively higher platen temperature was required to seal laminated films with lower thermal conductance. Required dwell time corresponds closely to the heat flow rate of bar sealing process. Laminated films made from extrusion lamination process provided lower level of achievable heat seal strength when compared with the laminated films made from dry‐bond lamination process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3736–3745, 2007     

The Effect of the Structure of Clay and Clay Modifier on Polystyrene-Clay Nanocomposite Morphology: A Review

Nanocomposites formation brings about an enhancement of many properties for polymers. They have attracted interests since they attain significant properties with far less clay content. It is generally assumed that exfoliation nanocomposites are preferred for the greatest increases in properties, but that is not correct in flame retardency properties. In this paper the effects of different types of clays and clay modifiers on final morphology of PS/clay nanocomposites were reviewed. Clay charge density and length, bulk, polarity, functional groups and polymerizability of the clay modifier are very significant in their efficiency and final morphology of PS/Clay nanocomposite.     

Electron beam irradiation of low-density polyethylene filled with metal hydroxides for wire and cable applications

The effects of electron beam irradiation for crosslinking of polymers used for wire and cable insulations are still being researched. In this research, the influence of electron beam irradiation on the different blends of low-density polyethylene (LDPE) filled with aluminum trihydrate and magnesium hydroxide (ATH, MH) were studied. It was revealed by melt flow index, tensile strength, and elongation at break tests that addition of MH to LDPE increases the adhesion forces inside polymer matrices more efficient than similar ATH/LDPE compounds. Field emission scanning electron microscopy test showed that MH is platy in structure and more homogenous mixed than ATH with LDPE. The results on thermogravimetric analysis and limiting oxygen index tests revealed that the thermal stability and incombustibility properties of MH blends are more efficient than similar ATH blends. Meanwhile, it was observed by smoke density test that MH blends produce the lowest smoke density compared with virgin LDPE and similar ATH blends. It was also observed that increasing irradiation by electron beam had impressive affections on the density, gel content, and mechanical properties for all the polymeric samples in this study.     

Analysis of Linear Scaling Method in Downscaling Precipitation and Temperature

Climate change is one of the greatest challenges in the 21^st century that may influence the long haul and the momentary changeability of water resources. The vacillations of precipitation and temperature will influence the runoff and water accessibility where it tends to be a major issue when the interest for consumable water will increase. Statistical downscaling model (SDSM) was utilized in the weather parameters forecasting process in every 30 years range (2011-2040, 2041-2070, and 2071-2100) by considering Representative Concentration Pathways (RCP2.6, RCP4.5, and RCP8.5). The Linear Scaling (LS) method was carried out to treat the gaps between ground/ observed data and raw/ simulated results after SDSM. After the LS method was executed to raw/ simulated data after SDSM, the error decrease reaches over 13% for rainfall data. The Concordance Correlation Coefficient (CCC) value clarifies the correlation of rainfall amount among observed and corrected data for all three (3) RCPs categories. There are very enormous contrasts in rainfall amount during the wet season where CCC-values recorded are 0.22 and beneath (low correlation). The findings demonstrated that the rainfall amount during the dry season will contrast for all RCPs with the CCC-values are between 0.44-0.53 (moderate correlation). RCP8.5 is the pathway with the the most elevated ozone-depleting substance emanations and demonstrated that the climate change impact is going on and turn out to be more awful step by step.