3,030 research outputs found
Studies on the adsorption and corrosion inhibition of substituted benzylidene Schiff bases on mild steel in 1 M HCl / Nor Zakiah Nor Hashim
No full textThe objective of this thesis is to investigate the performance of newly synthesized substituted benzylidene Schiff bases as corrosion inhibitors of mild steel in 1 M HCl at 25°C. To accomplish this intention, a series of (E)-N’-benzylidene-N⁴-phenylbenzene-1,4-diamine Schiff bases that contain different substituent groups at para position of benzylidene were synthesized and characterized via physical and spectroscopic analysis. The azomethine double bond (C=N) infrared spectra found for the Schiff bases are at around 1590-1604 cm⁻¹. From ¹H Nuclear Magnetic Spectroscopy (NMR) spectra, the azomethine proton (singlet) shifted in the range of δ 8.634-8.531 ppm, while the peaks at around δ 157.32-155.82 ppm found in ¹³C NMR spectra are assigned for azomethine carbon. The corrosion inhibition performance of N-phenyl-1,4-phenylenediamine (NPPD), (E)-N¹-benzylidene-N⁴-phenylbenzene-1,4-diamine (K1), N-[(E)-4- chlorobenzylidene]-N’-phenylbenzene-1,4-diamine (K2) and N-[(E)-4- methoxybenzylidene]-N’-phenylbenzene-1,4-diamine (K3) was measured in 1 M HCl using electrochemical methods which are polarization, Linear Polarization (LPR) and Electrochemical Impedance Spectroscopy (EIS). The analysis of substrate’s surface via Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) was employed to determine the Schiff base adsorption behaviour on the surface of mild steel in the acidic solution. The electrochemical results revealed that the corrosion inhibition efficiencies of the Schiff bases are higher and achieved up to 96.0% as found for K2, thus more effective than the other Schiff base in the series, and the parent amine of NPPD. The adsorption of inhibitors at the metal-solution interface are well described based on Langmuir adsorption isotherm because R² and slope values are almost to the value of 1
Responsiveness to change of The Malay-Ecohis following treatment of early childhood caries under general anaesthesia / Nor Azlina Hashim
No full textBackground: Oral health-related quality of life (OHRQoL) measures should be tested for their sensitivity and responsiveness to changes in OHRQoL if they are to be used as outcome measures in clinical interventions. Objectives: (a) To evaluate the sensitivity of the Malay version of Early Childhood Oral Health Impact Scale (Malay-ECOHIS) to dental treatment of early childhood caries (ECC) under General Anesthesia (GA) by: (i) assessing changes in the distribution of Malay-ECOHIS scores before and after treatment under GA, (ii) assessing the association between Malay-ECOHIS change scores and severity of decayed teeth (dt) categorized by the median and percentile score, (iii) assessing the correlation between Malay-ECOHIS change scores and the number of decayed teeth, and (iv) assessing the correlation between Malay-ECOHIS change scores and number of extracted teeth; (b) evaluate the responsiveness of the Malay-ECOHIS to dental treatment of ECC under GA by comparing whether the observed changes in Malay-ECOHIS scores and effect size (ES) took the form of a gradient across the global transition judgement; and (c) establish the Minimal Important Difference (MID) of the Malay-ECOHIS. Methods: A consecutive sample of parents of 158 preschool children (aged 6 and younger) with ECC attending five public hospitals in Selangor for dental treatment under GA was recruited over an 8-month period. Parents self-completed the Malay-ECOHIS prior to and 4 weeks following their child’s dental treatment. In addition, parents answered a global health transition judgement concerning the change in their child’s overall oral health condition compared to before treatment. Data were analyzed using independent and paired samples T-test, ANOVA, Pearson correlation, and standardised scores. Results: Overall, 138 children completed the study with response rate of 87.3%. The final sample comprised parents of 76 male (55.1%) and 62 female (44.9%) preschool children with mean age of 4.54 years (SD=1.01). The ECOHIS mean score after treatment was significantly lower compared to before treatment. This significant reduction in mean score existed for total Malay-ECOHIS, Child Impact Section (CIS), Family Impact Section (FIS), and all the sub-domains, respectively (P<0.001). The magnitude of change (ES) of total Malay-ECOHIS following treatment was +1.0 and among domains ranged from +0.4 to +1.9. There was no significant association between Malay-ECOHIS change scores and severity of decayed teeth (dt) categorized by median or percentile score. However, there was a weak, positive correlation between number of decayed teeth (dt) and Malay-ECOHIS (r=0.165, p=0.05) and CIS change scores (r=0.175, p<0.05), respectively. No significant correlation was found between Malay-ECOHIS change scores and number of extracted teeth. Based on global health transition judgement, 62.3% of parents reported their child’s oral condition “a little improved” while 37.7% reported “much improved” following treatment under GA with ECOHIS mean change score of 6.7 (ES=+1.1) and 9.6 (ES=+1.2), respectively. There was an observed gradient in the changes of Malay-ECOHIS scores and effect sizes in relation to global health transition judgement of oral change following treatment, supporting the responsiveness of the measure. The Malay-ECOHIS MID was found to be 7-point change with large ES of +1.0. Conclusion: The Malay-ECOHIS is empirically proven to be sensitive and responsiveness to dental treatment of ECC under GA
An evaluation of business-to-business electronic commerce marketplaces (e-marketplaces) in Malaysia / Nor Azzyati Hashim, Mardziah Hashim and Rogayah Abdul Majid
No full textThe development of business-to-business electronic commerce marketplaces
(B2B e-marketplaces) has influenced the way businesses are conducted. The
emergence of many types of e-marketplaces together with the increase use of
e-marketplaces allows many organizations to become e-market makers in the
electronic commerce environment. Nonetheless, too many B2B e-marketplaces
could become a challenge with e-marketplaces have shown numerous successes
and failures since early existence. With this background, this pap er discusses
the characteristics and success factors of B2B e-marketplaces offered in
Malaysia. A content analysis ofe-marketplace websites using the integrated
model from the Extended Model of Internet Commerce Adoption (eMICA) and
the Internet-Based B2B Stages of Growth enabled an examination of type,
ownership, B2B features and B2B stages of growth. A few e-marketplaces
were then selected as case studies to identify the success factors based on the
Framework of the Critical Success Factors Analysis fo r E-Marketplaces.
Overall, Malaysia B2B public e-marketplaces have shown positive growth
development stages across time with high adoption of e-commerce website
features. In addition,factors of strategic, functional, technology, build liquidity, create value and others were also essential for t e success of the e-marketplaces.
Indeed, good marketing strategies, multiple income streams,
value added information services and government initiatives are among keys
to success
Shear resistance of rubber-ballast composites in simulated water and acid soaked conditions
No full textBallast is one of the main structures for the railway tracks. It can resist the lateral movement under dynamic loading transferred by the passing trains with repeatedly. Under some circumstances, ballast can suffer degradation or breakdown due to the repeated loading and maintenance. Ballast is easily exposed to the weather because it is laid on the track. Acid rain affects the performance of the railway track near the industrial and urban area. As a result, it starts to foul and the small chips from ballast filled the void, as well as reduce the shear strength of ballast particles. This situation can contribute into the increasing of maintenance frequency and costing. This paper examines the potential of rubber inclusions in increasing the shear resistance of rubber-ballast composites in simulated water and acid soaked conditions with several configuration. This lab-based exploratory work is only static load simulation in conventional shear box setup measuring 60 mm × 60 mm. The aggregates size is 10 times smaller than actual size of ballast. In order to identify the shear resistance deterioration of rubber-aggregates mixture under poor drainage conditions by soaked a batch of aggregates in water and acid solution for 2 weeks to simulate accelerated weathering effects. The shear resistance did not rise dramatically with the rubber reinforcement. This susceptible shear strain plots indicate ductile behaviour on the aggregates-rubber composites. This is evident by the linear rise of shear stress with strain up to approximately 10% for the control samples (CS) until it reaches a constant value. Note that all the specimens including CS are in a loose state during the testing because there were no tamping been applied on the samples. Overall the circular patch (CP) specimen was the most favourable than the other configurations. Both mechanisms contributed to the reduced overall subsistence, accompanied by an increase in the shear resistance. The inclusion of rubber elements apparently prevented the dilation of the granular material when approaching the shear failure and the reducing the settlement
Subsidence of dredged organic sediments in cultivated peatlands
No full textMany low-lying peatlands in delta areas undergo significant subsidence due to drainage for agricultural purposes. Subsidence may be attributed to shrinkage, consolidation or oxidation. At the same time the canals and ditches are regularly dredged to maintain water quality and drainage capacity. Often these dredged sediments are placed on land, which may help to slow down subsidence. In this study subsidence of organic sediments was monitored for a period of three years. The sediments were dredged from lakes and canals in the peatlands of Wormer- en Jisperveld, in the Netherlands and placed in an on-land constructed depot. Samples were collected at regular time intervals to measure water content and organic content. Additionally, laboratory tests were performed to characterize the organic sediments and determine the compression, consolidation, shrinkage and water retention characteristics under various oxidizing conditions. The laboratory tests showed that oxidation can significantly affect the compression, consolidation, water retention and shrinkage characteristics of organic soils. However, monitoring results in the field showed that the major part of the subsidence, which occurred within the three years of this study, could be attributed to shrinkage of the dredged sediments and the remainder to consolidation of the underlying peat layers, while the organic matter content did not change significantly
Enantiospecific analysis and fate of 2-arylpropionic acids during biological wastewater treatment
No full textEnantiomeric fraction (EF) analysis of chiral pharmaceuticals has been proposed as a potential indicator of biological transformations of environmental pollutants. Ibuprofen, naproxen and ketoprofen, which are chiral nonsteroidal anti-inflammatory drugs (NSAIDs), were selected for assessment of their potential to be used as such indicators.
A highly sensitive and reliable method for the enantioselective analysis of these NSAIDs in wastewater and environmental water samples was developed. An indirect method for enantioseparation was achieved by the derivatization of the (R)- and (S)-enantiomers to amide diastereomers using (R)-1-phenylethylamine. Separation and detection of the individual diastereomers was undertaken by gas chromatography–tandem mass spectrometry (GC–MS/MS). The method is sufficiently sensitive for the detection of targeted drugs in a real tertiary treated wastewater sample, revealing measurable concentrations of both (R)- and (S)-enantiomers of the drugs. Isotope dilution using racemic D3-ibuprofen, racemic D3-ketoprofen and racemic D3-naproxen was shown to be an essential aspect of this method for accurate quantification and EF determination.
The microbial degradation of both enantiomers of the NSAIDs was observed over 10 days in a Closed Bottle Test (CBT) under controlled laboratory conditions. (S)-ibuprofen was shown to be degraded faster than (R)-ibuprofen while non-enantioselective degradation was observed for ketoprofen. A very minor change was observed in naproxen EF, with a slight increase in (R)-naproxen concentration indicating the formation of this enantiomer during the experimental process. It is proposed that this formation occurred as the result of chiral inversion of (S)-naproxen.
The enantiospecific fate of the NSAIDs was then monitored before and after treatment by a laboratory-scale membrane bioreactor (MBR) treating synthetic wastewater and a full-scale MBR treating real municipal wastewater. Evidence of enantioselective biodegradation for ibuprofen and naproxen were again observed. Clear evidence for the formation of (R)-naproxen in the laboratory-scale reactor is presented and measurable concentrations of (R)-naproxen were consistently observed in full-scale MBR effluent.
This work has expanded our knowledge of the fate of these compounds during wastewater treatment to an understanding of the specific behaviours of the individual enantiomers. The variability of EF observed in the final effluent therefore may provide a useful indicator of the overall biodegradation performance of the wastewater treatment plant. The observation of chiral inversion during wastewater treatment has not previously been reported and adds a new dimension to the important topic of transformation products during wastewater treatment processes
Design and development of high pressure natural gas injector model for single cylinder four stroke engine using matlab simulink
No full textThe aim of this project is to design and develop the hydraulic model for control oriented injector model for single cylinder four-stroke engine using Matlab Simulink. Injector plays significant role in determining engine performance by controlling the fuel supplied consequently the air to fuel ratio. In order to achieve acceptable accuracy for abroad range of engine speed the control of injection process must be carefully studied. The model consist of hydraulic, electromagnetic and mechanical model. This thesis is carried out with purpose to produces a reliable hydraulic model that can be used to study the control process. Reasonable mass flow rate data need to be determine by the model based on predetermined boundary condition. The fuel injector based on HDEV 5 were design using Matlab Simulink. The are two different Matlab Simulink design the fuel flow rate coresponding to the radius/diameter ratio and the fuel flow rate corresponding to the needle-seat relative displacement. Based on the graph and explanation, comparison between fuel flow rate and r/d ratio and fuel flow rate and needle-seat relative displacement are made. The result show that there is cavitation occur at r/d = 0.02 and effect the flow rate of the fuel injected. While in the injector opening phase, the fuel flow rate is slightly increase before the injector reached the transition value. The model of flow through the control volume feeding and discharge holes was further detailed as it was shown to play an important role in determining the flow regime in the orifice
Breeding activities of Ingerophrynus parvus (Anura: Bufonidae) in Kedah, Malaysia
No full textThe breeding activities of the Dwarf Toad, Ingerophrynus parvus were observed under natural conditions at Sungai Junjong, Kulim, Kedah, Peninsular Malaysia for a period of 12 months. Breeding parameters, such as calling activities, amplecant pairs, eggs deposition and presence of tadpoles were examined every week in each month. Pearson correlation was used to analyse the relationship between rainfall and each breeding parameter. The results showed positive relationships between rainfall and calling activities (r=0.74), between rainfall and amplexus activities (r=0.52), and between rainfall and spawning activities (0.81)
Kraichnan-Leith-Batchelor similarity theory and two-dimensional inverse cascades
No full textWe study the scaling properties and Kraichnan-Leith-Batchelor (KLB) theory of forced inverse cascades in generalized two-dimensional (2D) fluids (-turbulence models) simulated at resolution . We consider (surface quasigeostrophic flow), (2D vorticity dynamics) and . The forcing scale is well-resolved, a direct cascade is present and there is no large-scale dissipation. Coherent vortices spanning a range of sizes, most larger than the forcing scale, are present for both and . The active scalar field for contains comparatively few and small vortices. The energy spectral slopes in the inverse cascade are steeper than the KLB prediction in all three systems. Since we stop the simulations well before the cascades have reached the domain scale, vortex formation and spectral steepening are not due to condensation effects; nor are they caused by large-scale dissipation, which is absent. One- and two-point pdfs, hyperflatness factors and structure functions indicate that the inverse cascades are intermittent and non-Gaussian over much of the inertial range for and , while the inverse cascade is much closer to Gaussian and non-intermittent. For the steep spectrum is close to that associated with enstrophy equipartition. Continuous wavelet analysis shows approximate KLB scaling () and () in the interstitial regions between the coherent vortices. Our results demonstrate that coherent vortex formation ( and ) and non-realizability () cause 2D inverse cascades to deviate from the KLB predictions, but that the flow between the vortices exhibits KLB scaling and non-intermittent statistics for and . The results will appear in \cite{BurgessEA2015}, which has been accepted to the \emph{Journal of Fluid Mechanics}
A study of procurement behaviour in small firms
No full textThe purpose of this paper is to introduce research which analyses buyer-supplier relationships from the perspective of small and medium firms (SMEs). The study to be outlined shows that actors within a supply chain are not homogeneous in terms of their size, resources and business motives, which bring into question the validity and relevance of the purchasing literature when examining small firms. The paper will explain the usefulness and importance of studying purchasing behaviour in SMEs and explain how these relationships might differ depending on the nature of the firm. The methodology for the field research will be explained in the paper. The fieldwork draws principally from a series of interviews undertaken with owner-managers within plastic moulding companies in Lancashire. The empirical data will be explored in some depth with a particular focus on their implications for practice
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