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Production optimization and tribological characteristics of cottonseed oil methyl ester
No full textThis paper presented experimental results to evaluate the optimization of production parameters through response surface methodology. These parameters significantly affected the yield of cottonseed oil methyl ester (COME). The input variables for the production of methyl ester from cottonseed oil were methanol/oil molar ratio, concentration of catalyst, temperature, and stirring speed. The response or output variable was the yield of methyl ester. The fatty acid methyl ester composition of COME (biodiesel) was obtained using a gas chromatography (GC) analyzer. BS EN 14103:2011 was the standard used to analyze the fatty acid methyl ester. The derived mathematical model was statistically accurate to predict the optimum value of COME. The optimized values to obtain a 98.3% yield of methyl ester were as follows: methanol/oil molar ratio of 6:1, catalyst concentration of 0.97% (w/w), temperature of 63.8 °C, and speed of 797 rpm. The physicochemical properties of COME were measured in accordance with ASTM D6751. The friction and wear properties of COME and its blends with petroleum diesel were tested using a four-ball wear testing machine. The tribological characteristics of COME as a new biofuel were assessed. COME displayed good lubricity with a low coefficient of friction and wear scar diameter. The coefficient of friction of pure COME (COME100) was lower than that of pure petroleum diesel (DL100) and COME blends with petrol diesel (COME10, COME20, and COME50). The average coefficient of friction of COME 100 was lower than that of DL100, COME10, COME20, and COME50 by 28.06%, 19.49%, 7.49%, and 3.65%, respectively. The wear scar diameter of COME100 for the tested ball was lower than that of DL100, COME10, COME20, and COME50 by 47.6%, 33.3%, 32.1%, and 21.42%, respectively. The worn surfaces of the tested balls were examined by scanning electron microscopy, and the results were presented in this paper
Safe disposal of coal bottom ash by solidification and stabilization techniques
No full textSolidification and stabilization of coal bottom ash waste (CBA) using CEM1 as the binder have been evaluated in case of leaching as well as the possibility to use this mixture for the construction industry. For this, the CEM1/CBA mass ratio has been varied between 0.5 and 2 and heavy metals leaching of Cu, Cd, Ni and Pb evaluated. Two types of crushed block and whole block leaching tests have been conducted to determine the leaching properties of deionized water, acetic acid and nitric acid leachates. It has been demonstrated that all elements can be immobilized successfully to nearly zero even in the case of a low CEM1 content. Furthermore, it has been shown that more heavy metals leached from the matrix when acetic acid used compared to other leachates. Next to this, the mechanical properties have been tested. After 56 days a compressive strength between 25 and 40 MPa has been measured from 0.5 to 2 CEM1/CBA mass ratios. Based on leaching and compressive strength results, CEM1/CBA mixtures can be considered for the construction industry
Cloud-assisted gamification for education and learning – Recent advances and challenges
No full textGamification has gained considerable interest in education circles due to its capability of enhancing the learning process among students. In the future, it is expected that gamification will overtake the traditional way of learning resulting in issues such as scalability, upgradation of learning modules. To address these issues, merging gamification with cloud computing seems a viable solution. However, the employability of gamification through cloud computing is still in its infant stage. Hence, this article investigates the applicability of gamification through cloud computing and presents a comprehensive survey of state-of-the-art gamification in education and learning. We also identify the subject areas that can be gamified and taught using the cloud service. The critical elements and minimum requirements necessary to gamify education are also identified. Moreover, a specific cloud-assisted gamification architecture is proposed and discussed together with its possible applications. The article is concluded with the research challenges and suggestions for future work
Newly developed chromium-doped fiber as a saturable absorber at 1.55- and 2.0-µm regions for Q-switching pulses generation
No full textWe demonstrate a Q-switching operation laser at 1.55- and 2-µm region using a homemade 10 cm long of Chromium-doped fiber (CrDF) as a passive saturable absorber (SA). Erbium-doped fiber (EDF) and Thulium-doped fiber (TDF) as a gain medium cooperate in the all-fiber ring cavity configuration. CrDF was fabricated by Modified Chemical Vapour Deposition (MCVD) technique in conjunction with conventional solution doping (SD) method. The CrDF has a saturable absorption of 9% at 1.55-µm region with a saturation intensity of 22 MW/cm2. Therefore, a stable pulse train obtainable within 75–173 mW, with a repetition rate increases from 68.12 kHz to 115.9 kHz. At the maximum pump level, a shorter pulse width, maximum output power, and maximum pulse energy are 3.85 µs, 10.86 mW, and 94.1 nJ, respectively. In TDF laser cavity, the laser pulsing generates from 363 mW to 528 mW, where the repetition rate increases from 13.02 kHz to 27.62 kHz. At maximum pump power, a shorter pulse width, maximum output power, and pulse energy are obtained with 4.48 µs, 6.36 mW, and 230.27 nJ, respectively. Both pulse trains at 1.55- and 2-µm region are stable with a signal-to-noise ratio (SNR) of 71 dB and 44 dB, respectively. These findings are important to the discovery of robust passive saturable absorber development in a form of fiber which has a similar melting point to the rest of the silica fiber in the proposed cavities. Thus, it will be a kick-started to alternative form of passive SAs in developing a future high-power fiber lasers
Influence of electrodeposited Cu-Ni layer on interfacial reaction and mechanical properties of laser welded-brazed Mg/Ti lap joints
No full textA fiber laser welding-brazing procedure has been developed for joining AZ31B magnesium alloy to Cu-Ni coated Ti-6Al-4V titanium sheet using AZ92D filler wire. The effect of the interlayer arrangements (AZ31B/Ni-Cu/Ti-6Al-4V and AZ31B/Cu-Ni/Ti-6Al-4V) on appearance, interfacial reaction and mechanical properties were investigated at different heat input. It was found that the feasibility of this process depends strongly on the pre-existing Cu-Ni layer on the Ti surface that promotes wetting of the AZ92 filler. Within the range of 1200–1600 W, defect free joints in both interlayer arrangements. Depending on the interlayer arrangements chosen, different reactions layers formed inside the joint region. Nevertheless, at optimum heat input (1400 W), Ti2Ni mingled with Ti3Al interfacial reaction products was produced along the fusion zone (FZ)-Ti brazed interface in both interlayer arrangements. The tensile-shear fracture load of the joints produced at the optimum laser power reached a maximum value of 2016.5 N for AZ31B/Ni-Cu/Ti-6Al-4V and 2014.6 N for AZ31B/Cu-Ni/Ti-6Al-4V, representing an efficiency of 71% compared to AZ31B alloy. Under suitable heat input, the joints failed at the fusion zone of the AZ31B base metal. In contrast, incomplete brazing or large volume of intermetallics at the brazed interface resulted in interfacial failure at lower/higher heat input
Nanosecond pulsed laser ablation to synthesize GaO colloidal nanoparticles: Optical and structural properties
No full textPulsed laser ablation (PLA) has been employed to prepare GaO colloidal nanoparticles to investigate the optical and structural properties using ultraviolet–visible (UV–vis) absorption spectrophotometer, X-ray diffraction (XRD) and Tunneling Electron Microscopy (TEM) instruments, respectively under different laser fluences. Image processing method of TEM images and XRD scheme is used to examine the nanoparticle's mean size and size distribution. Laser fluence has proved its significant effect on the size of nanoparticles. In addition, nanoparticle's mean size and size distribution have undergone under effect of ablation process. It has been resulted that nanoparticle's larger size distribution and mean size have been produced by higher laser fluences
Improving the air change rate in high-rise buildings through a transom ventilation panel: A case study
No full textPassive ventilation techniques can both improve indoor air quality (IAQ) and reduce energy consumption and costs in buildings. In particular, using wind-driven ventilation as a passive design strategy can increase indoor air velocity in naturally ventilated buildings. In tropical regions, where there are only limited differences between indoor and outdoor air temperatures, wind-driven ventilation through a transom ventilation panel (TVP) can be a positive ventilation technique. In this study, we evaluated through experimental tests the efficiency of single-sided ventilation and cross-ventilation through a TVP in a unit within a high-rise residential (HRR) building. To this end, we carried out a series of numerical simulations to calculate the airflow patterns and the indoor air velocity for various outdoor wind speeds when cross-ventilation was applied. The results show that TVP can increase indoor air velocity by up to four times, depending on the outdoor wind speed and the location within the unit. Also, in windy conditions, the mean air change per hour (ACH) in a unit equipped with a TVP is 27% greater than a unit without a TVP. Moreover, a TVP can improve air change rate even when the outdoor wind speed is less than 0.02 ms−1
Thermal, structural and electrical properties of Li2BaSiO4 ceramic electrolyte
No full textLithium Barium Silicate (Li2BaSiO4) solid electrolyte was prepared by Sol - gel method with citric acid as the chelating agent. Thermal, structural and electrical characterization was done using Thermogravimetric/Differential Scanning Calorimetry, X-ray Diffraction, Fourier Transform Infrared and Impedance Spectroscopy respectively. Pure phase of Li2BaSiO4 sintered at 700 °C and 800 °C showed stability at that temperature. The conductivity of the electrolyte increased linearly with temperature. The bulk conductivity of the samples sintered at 800 °C was found to be 1.45 × 10−4 S cm−1 at 500 °C. The temperature dependence also follows the Arrhenius relation with activation energy of 0.11 eV. The complex impedance analysis of the electrolyte showed a typical negative temperature coefficient of resistance (NTCR) behavior
Exploratory and confirmatory factor analysis of PERMA for Indonesian students in mathematics education programmes (Tiriamoji ir patvirtinamoji indonezijos studentų psichologinės gerovės (PERMA) faktorinė analizė matematikos mokymo programose)
No full textThis study examined the validity and reliability of PERMA instruments to determine the nature of PERMA for Indonesian students in mathematics education programmes. A total of 274 students participated, selected by using cluster random sampling. A survey design was employed to investigate the factor structure of the PERMA. Quantitative data were analysed using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) using SPSS 23 and AMOS 18. EFA revealed similar structures from prior research and the present study. The CFA approach verified the questionnaire of PERMA was satisfactory for Indonesian students’ context. This work concludes the PERMA of Indonesian university students have a five-factor structure. These findings imply the greater importance of validating and confirming the structure of students’ PERMA relative to translating a construct into a different language
Passively Q-switched and mode-locked Erbium-doped fiber laser with topological insulator Bismuth Selenide (Bi2Se3) as saturable absorber at C-band region
No full textWe experimentally demonstrate Q-switched and mode-locked Erbium-doped fiber laser (EDFL) by using topological insulator (TI) Bismuth Selenide (Bi2Se3) as saturable absorber (SA). The fabricated Bi2Se3 SA exhibits modulation depth and saturation intensity at 39.8% and 90.2 MW/cm2, respectively. By incorporating the fabricated Bi2Se3 SA into the laser cavity, Q-switching operation is generated with repetition rate ranging from 23.5 kHz to 68.2 kHz, pulse width ranging from 2.4 μs to 8.6 μs and maximum peak power is calculated at 19.9 mW. Our cavity can also generate soliton mode-locked pulse with repetition rate of 23.3 MHz and pulse width of 0.63 ps by inserting an additional 5 m long single mode fiber (SMF) into the existing laser cavity. Spectral peaks due to Kelly side-bands and four wave mixing (FWM) were observed on the soliton spectrum. Both Q-switching and mode-locking pulses are stable in the laboratory environment, allowing the realization of compact and low cost pulsed fiber laser with Bi2Se3 SA for various photonics applications