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Validation construct items for the measurement model of permit to work using exploratory factor analysis
No full textThe aim of this paper is to demonstrate how the exploratory factor analysis (EFA) is utilised to validate permit to work constructs. The data for the study was obtained from the questionnaire survey distributed to 260 work leaders and workers at Petrochemical Plant Kerteh, Terengganu. The EFA is the method to validate the items at the respective construct of the measured variable. The items of the construct were developed prudently and carefully so that the items are measurable for the purpose of obtaining value of this measurement model. There are five construct under permit to work (PTW), namely work description, worksite inspection, hazardous activity, supporting document and close out, was developed for the purpose of this study. After the EFA has been performed, it was found that all PTW's construct, i.e., work description, worksite inspection, hazardous activity, supporting document and close out construct has satisfied the validity and reliability requirement and applicable for the study
Effects of zinc chloride impregnation states on specific surface and dielectric properties of activated carbons
Full text linkThe present work was aimed at evaluating the roles of zinc chloride impregnation states on specific surface and dielectric properties in microwave-assisted activated carbon preparation. Activated carbons were synthesized using castor shell at dry impregnation ratios of 1 and 2 (material-to-activator), and in suspensions of distilled water and zinc chloride, at power intensity of 800 W and irradiation time of 5 min. The activated carbons exhibit an improvement in dielectric properties and specific surface with increasing impregnation ratio. Palm kernel shell was employed for comparison to verify the effect of power intensity. At 800 W, the magnitudes of surface area are 1684 m2/g and 1150 m2/g for castor shell- and palm kernel shell-based activated carbons, respectively. A high specific surface brings about a greater methylene blue adsorption for possible applications in wastewater treatment
Adaptive memory control charts constructed on generalized likelihood ratio test to monitor process location
No full textAn adaptive cumulative sum (CUSUM) control chart based on the classical exponential weighted moving average (EWMA) statistic and Huber’s function, symbolized as an ACUSUM E control chart, is an enhanced form of the classical CUSUM control chart that can identify different sizes of shift. However, the classical EWMA statistic for the ACUSUM E control chart does not provide explicit rule for parameter choices to diagnose a specific shift. To overcome this issue, this study has proposed two ACUSUM control charts, symbolized as ACUSUM c control charts to monitor a specific and a certain range of shift. The novelty behind the proposed ACUSUM c (ACUSUMc(1) and ACUSUMc(2)) control charts is initially adaptively updating the reference parameter using the classical CUSUM statistic, generalized likelihood ratio test, and score functions to achieve superior performance. An algorithm in MATLAB using the Monte Carlo simulation technique is designed to obtain numerical results. Furthermore, based on numerical results, performance evaluation measures such as average run length, extra quadratic loss, relative average run length, and comparison index are calculated. The proposed ACUSUM C control charts based on performance evaluation measures and visual presentation are compared against other control charts. Findings reveal the superiority of the proposed ACUSUM C control charts. Besides, for practical point of view, the proposed ACUSUMC(1) control chart is implemented with numerical data to show the significance over other control charts
Effect of tool pin profile on friction stir welding of dissimilar materials AA5083 and AA7075 aluminium alloy
Full text linkFriction stir welding (FSW) currently contributes a significant joining process for welding aluminium, magnesium, and other metals in which no molten or liquid state were involved. It is well known that aluminium alloys are more effective, promising for different applications light weight, strength and low cost. This study aims to determine how such tools geometry and tool speed can be related to dissimilar material in the joining process. Specifically, it investigates whether the distribution of the weld zone particularly between tool pin profile to rotational speed. In this context, the influence of tool pin profile and tool rotational speed in relation to the mechanical properties and microstructure of friction stir welded. The aim of this study is also to test the hypothesis that better mixing between dissimilar metals at higher tool rotational speed along the weld path. Three different tool profiles were configured with AA5083 and AA7075. During welding, notable presence of various types of defects such as voids and wormholes in the weld region. The results of this work showed that the tool pin profile and weld parameter are significant in determining mechanical properties at different tool rotational speed. The highest tensile strength achieved was about 263 MPa and the defectfree joint was obtained by using the threaded tapered cylindrical pin tool at a rotational speed of 800 rpm. These findings indicate that different tool profiles influence differently on the formation of defects at welds. On this basis, the tool geometry should be considered when designing experimental friction stir welded joint
Fabricating V2AlC/g-C3N4 nanocomposite with MAX as electron moderator for promoting photocatalytic CO2-CH4 reforming to CO/H2
No full textExfoliated vanadium aluminum carbide (V2AlC) MAX nanosheets coupled with porous graphitic carbon nitride to construct 2D/2D V2AlC MAX/g-C3N4 heterojunction for photocatalytic CO2 reduction through dry reforming of methane has been investigated. Good interfacial interaction was achieved which enabled proficient charge carrier separation with promoted light absorption. The optimized 10 wt%V2AlC MAX/g-C3N4 was more proficient with CO and H2 evolution rates of 118.74 and 89.52 μmole g−1 h-1 at selectivity 57.01 and 42.98%, respectively. This efficiency for CO and H2 evolution rate was 2.21- and 1.99-folds superior to using pure g-C3N4. This improvement is due to good interfacial contact and efficient charge carrier separation by MAX, which increases photo-induced charge carrier lifetime. The performance was further investigated with different reforming systems to manipulate the effective utilization of holes to extend charges recombination rate. Using CO2 reduction with hydrogen, CO2 methanation and the reverse water-gas shift reaction were activated, whereas CO2 with water promoted more methane formation. By investigating CH4/CO2 feed ratios, the highest yield rates attained with the ratio of 1:0, confirming V2AlC based-composite effectively activates both gases as evidenced by their apparent quantum yields. This study provides a promising route for the fabrication of noble-metal-free nanocomposite and will be useful for future energy and environmental applications
Investigating influential effect of methanol-phenol-steam mixture on hydrogen production through thermodynamic analysis with experimental evaluation
No full textThermodynamic analysis for methanol-phenol mixture steam reforming (M-PSR) for H2 production together with experimental evaluation has been carried out in this study. Firstly, a number of possible reactions were evaluated using Gibbs free energy and equilibrium rate constants to determine its feasibility and nature over the temperature of 100 to 1200°C. Then, the Gibbs free energy minimization method was used to carry out the thermodynamic analysis of the M-PSR system. A comprehensive thermodynamic analysis was used to study the effect of different parameters on product distribution. Temperature is an important parameter that significantly affects product distribution. Within the range of 100 to 400°C, a high CH4 production was obtained due to phenol decomposition and methanol methanation reaction. With further increase in temperature in the range of 300 to 600°C the CH4 production was dropped drastically, where in the reforming reactions, reverse methanation reactions gradually produce CO2 gas. However, as the temperature rises beyond 600°C, the predominant reactions for the M-PSR reaction for H2 production include the phenol steam reforming and methanol steam reforming reactions, where there is an obvious increase in H2 evolution. The feed ratio also affects H2 production, where a high steam feed is beneficial for the reforming reaction, and at the same time, it suppresses the formation of carbon species. Low pressure is also favourable for the M-PSR H2 production, which is in accordance with Le-Chatelier's principle. The optimum operating parameters were determined to be; the temperature of 700°C, atmospheric pressure and methanol-phenol-steam feed molar ratio of 0.1:0.9:20, where H2 production is maximized with minimal side products (CO, CO2, CH4) and coke formation. The comparative analysis of thermodynamics with phenol steam reforming and methanol steam reforming experimental studies complement current thermodynamic results. This research elucidates that thermodynamics analysis using the Gibbs free energy minimization method is immensely helpful in providing insight into the complexity of methanol-phenol steam reforming reaction
A brief review of computation techniques for ECG signal analysis
No full textAutomatic detection of life-threatening cardiac arrhythmias has been a subject of interest for many decades. The automatic ECG signal analysis methods are mainly aiming for the interpretation of long-term ECG recordings. In fact, the experienced cardiologists perform the ECG analysis using a strip of ECG graph paper in an event-by-event manner. This manual interpretation becomes more difficult, time-consuming, and more tedious when dealing with long-term ECG recordings. Rather, an automatic computerized ECG analysis system will provide valuable assistance to the cardiologists to deliver fast or remote medical advice and diagnosis to the patient. However, achieving accurate automated arrhythmia diagnosis is a challenging task that has to account for all the ECG characteristics and processing steps. Detecting the P wave, QRS complex, and T wave is crucial to perform automatic analysis of EEG signals. Most of the research in this area uses the QRS complex as it is the easiest symbol to detect in the first stage. The QRS complex represents ventricular depolarization and consists of three consequences waves. However, the main challenge in any algorithm design is the large variation of QRS, P, and T waveform, leading to failure for each method. The QRS complex may only occupy R waves QR (no R), QR (no S), S (no Q), or RSR, depending on the ECG lead. Variations from the normal electrical patterns can indicate damage to the heart, and these variations are manifested as heart attack or heart disease. This paper will discuss the most recent and relevant methods related to each sub-stage, maintaining the related literature to the scope of ECG research
Formulation and characterization of the physicochemical, antioxidant activity and sensory attributes of curcuma-based herbal drink
No full textCurcuma-based drinks consist of temulawak (Curcuma xanthorrhiza, CX) and turmeric (Curcuma longa, CL) rhizome extracts are widely consumed in the Asian community for health maintenance and beauty. However, the physicochemical and antioxidative properties of Curcuma-based drinks has not been reported. Thus, this study aims to develop and obtain the best ratio of CX and CL rhizome mixture and to analyze its physicochemical and antioxidant properties. The physicochemical properties including total soluble solids (TSS), viscosity, pH and colour of the drinks were analyzed while total phenolic content (TPC) was determined using standard method Folin-ciocalteu assay, total flavonoid content (TFC) using colorimetric assay of aluminum chloride and antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Four formulations of CX:CL ratios (F1 = 4:1, F2 = 3:2, F3 = 2:3, F4 = 1:4) were developed while other ingredient was kept constant. Sensory analysis with 21 panelists was done to determine the sensory acceptability. The results of the physicochemical properties for all formulations were obtained and compared. Formulation F4 has the highest total soluble solid (11.83 %). The pH range of the Curcuma-based drink was between 3.37 and 3.46. F1 has the darkest colour with the Lab value of 0.81 ± 0.1, 1.60 ± 0.30 and 8.15 ± 1.57, respectively. F4 obtained the highest mean score (4.81 ± 0.52) for overall sensory acceptability. The antioxidant properties of F3 had the highest total phenolic content (0.4422 ± 0.01 mg GAE / ml) and percentage of DPPH inhibition (56.61 %) and F4 has the highest flavonoids content (0.82 g GAE / ml). Thus, formulations with a higher content of CL have better sensory acceptability and higher antioxidant activity
Bibliometric analysis of accidental oil spills in ice-infested waters
Full text linkOil spills are environmental pollution events that occur due to natural disasters or human activities, resulting in a liquid petroleum hydrocarbon release in the environment, especially into the marine ecosystem. Once oil spills happen, they cause detrimental consequences to the environment, living organisms, and humans. Although there are increasing oil and gas activities in the Arctic region, which is abundant with undiscovered oil and gas resources, the harsh environmental conditions of the region, such as the ice coverage, cold temperatures, long periods of darkness, and its remoteness, pose significant challenges to managing the risk of accidental oil spills in ice-infested waters. In this paper, a bibliometric analysis has been applied to study the global work on oil spill research in ice-infested waters. The paper aims to present an overview of the available oil spill response methods in ice-infested waters, identify the current trends of the research on oil spills in ice-infested waters, and determine the challenges with the future research directions based on the bibliometric analysis. The analysis includes a total number of 77 articles that have been published in this research field which were available in the Scopus database, involving 193 authors from 17 countries dating from 1960 to September 2022. During the bibliometric analysis, the top five most productive authors and countries as well as the most cited publications on oil spills in ice-infested waters have been identified; the authors’ cooperation network and the cooperation network between the countries in oil spills research in ice-infested waters have been created; a co-citation analysis and a terms analysis have been performed to identify the popular terms and topics. For future directions, it is recommended for researchers (1) to study real oil spills as much as possible to obtain a good overview through replication under different situations; (2) to develop a new technique for the careful examination and management of the potential risks; (3) to study oil separation from the recovered oil–ice mixture
Palm fatty acid distillate-based biodiesel with sulfonated chicken and cow bone catalyst
No full textThe depletion of fossil fuel and the distressing environmental condition originated from the massive consumption of nonrenewable energy has urge towards the seeking for a cleaner and renewable energy source. Numerous forms of renewable energy have been developed over the past few decades and biodiesel emerged as one of the prospective candidate. The demand for global biodiesel production has been steadily growing. In line with that, researches around the world are racing towards making biodiesel technology more sustainable and economically viable process. In this investigation, the development of biodiesel from palm fatty acid distillate via the esterification process using sulfonated chicken bone and cow bone catalyst assisted by microwave irradiation was conducted (replacing the conventional oven heating). Subsequently the bones were calcined at 900 °C and then sulfonated. The synthesized catalysts were characterized using X-Ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscope, Brunauer–Emmett–Teller and temperature-programmed desorption. The reaction was prepared with a catalyst loading of 1 % to 6 % and a molar ratio of 2:1 to 25:1 for methanol:PFAD, while the reaction time was conducted for 30–240 mins and the reaction temperature was kept at 70 °C for each experiment set. In addition, a catalyst loading of 5 wt% and molar ratio of 20:1 for methanol:PFAD with the reaction time of 180 mins and reaction temperature of 70 °C were used as optimal condition parameters. For the sulfonated chicken bone catalyst, the percentage yield and conversion of biodiesel were 80.8% and 98.2%, respectively. In contrast, the percentage yield and conversion rate reached to 81.5% and 97.7%, respectively, for the the sulfonated cow bone catalyst. The biodiesel properties obtained were in accordance with ASTM standards. The percentage of FAME content was determined utilizing gas chromatography. The bones have been shown to be appropriate sustainable precursors for the synthesis of a novel, highly effective heterogeneous acid catalyst for biodiesel development