1,720,971 research outputs found
Speciated hydrocarbon emissions from a gas-fuelled spark-ignition engine with various operating parameters
No full textFor natural gas and liquefied petroleum gas (LPG), measurements of the concentrations of individual exhaust hydrocarbon (HQ species have been made under various engine operating conditions in a 2 litre four-cylinder engine using gas chromatography. Non-methane hydrocarbon (NMHC) in addition to the species of HC and other emissions such as CO2, CO and NOx were examined for natural gas and LPG at 1800 r/min for two compression ratios (8.6 and 10.6), various brake mean effective pressure (b.m.e.p.) values (250-800 kPa), spark timings (before top dead centre 10degrees-55degrees) and exhaust gas recirculation ratios up to 7 per cent. Fuel conversion efficiencies were also investigated together with emissions to study the effect of engine parameters on the combustion performance in gas engines, especially under the lean burn conditions. It was found that CO2 emission decreased with smaller C value of fuel, leaner mixture strength, higher compression ratio, higher b.m.e.p. and the ignition near the maximum brake torque spark timing. HC emissions from the LPG engine consisted primarily of propane (C3H8) (more than 60 per cent), ethylene and propylene (C3H6), while the main emissions from natural gas were methane (more than 60 per cent), ethane, ethylene and propane. Natural gas was shown to have less of a tendency to form ozone than LPG. This was accomplished by reducing the emissions of propylene, which has a relatively high maximum incremental reactivity factor, and propane, which forms a large portion of LPG. In addition, natural gas shows a benefit in the other emissions (i.e. NMHC, NOx and CO2), specific reactivity and brake specific reactivity values except fuel conversion efficiency.The authors would like to acknowledge their appreciation of the support given by The Combustion Engineering Research Centre, Kore
Experience with Autonomous Parenting Styles and College Students’ Decision-Making
No full text2025Different parenting styles allow children varying degrees of autonomy throughout all stages of childhood, influencing their self-esteem, self-actualization, and decision-making skills. Research indicates a positive correlation between autonomous parenting styles and children's well-being, encompassing their overall welfare, academic achievement, social values, and age-appropriate decision-making. However, there is limited research on how autonomous parenting relates to decision-making skills, which are vital for future leaders making sustainable choices in a complex and ever-changing world. The purpose of this study was to investigate the effect of levels of autonomous parenting styles received by undergraduate students on the extent of their decision-making proficiency. This study was guided by the hypothesis that parents who support autonomy enhance their college-aged children's decision-making skills. Specifically, higher perceived levels of autonomous parenting result in improved decision-making proficiency among college students. The study employed a quantitative method using a multivariate linear regression model, involving 380 college students aged 19-25 who were studying in the U.S. The findings indicated a statistically significant relationship between parental autonomy and decision-making abilities. These results remained consistent after controlling for variables such as age, gender, ethnicity, race, household income, GPA, and college year. This increases understanding of how autonomous parenting contributes to the successful completion of tasks and seeks to enhance understanding of how autonomous parenting benefits the development of decision-making skills in college students.
Keywords: autonomous parenting styles, decision-making skills, college students, sustainable developmen
Emulsion polymerization of tetrafluoroethylene: Effects of reaction conditions on the polymerization rate and polymer molecular weight
No full textThe emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles, Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 X 10(-3) and 32.48 X 10(-3) mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. (C) 1999 John Wiley & Sons, Inc
Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on particle formation
No full textThe emulsion polymerization of TFE was carried out with a surfactant (FC-143) and an initiator (ammonium persulfate) under various reaction conditions. Two different shapes of PTFE dispersion particles were produced by the emulsion polymerization, rods and spherical particles. Variables, except for surfactant concentration, do not affect the initial and final particle morphology when no coagulation occurs. Rod-like particles are formed when the surfactant concentration is near or above the critical micelle concentration (CMC) of the surfactant. At below CMC, however, spherical particles are dominant. No hexagon-shaped particles or abrupt changes in the particle morphology are observed during polymerization. When no coagulation occurred, the size and number of polymer particles suddenly increased in the early stages of emulsion polymerization and then steadily increased as time progressed. Most particles are formed in the early stages (within 5 min), and the size of particles formed was in the range 60-80 nm in diameter. The particle sizes ranged from 100 to 230 nm at 250 g/l of a specific TFE uptake concentration (the PTFE dispersion had a solid content of about 20%). It was found that the size and number of polymer particles formed are almost independent of the temperature, pressure, concentration of initiator and stabilizer (anti-coagulant), whereas the surfactant concentration, kinds of stabilizer, and agitation speed are important. The particle size decreased gradually as the dispersion concentration increased, whereas the particle number increased exponentially. When the PTFE dispersion coagulated during polymerization under certain conditions (high temperature and agitation speed, and low concentration of surfactant), the particle size suddenly increased, the particle number suddenly decreased, and the rate of the polymerization decreased, indicating that the polymerization occurred on the surface of the polymer particles. (C) 1999 Elsevier Science S.A. All rights reserved
The embedment of fiber Bragg grating sensors into filament wound pressure tanks considering multiplexing
Full text linkFilament wound pressure tanks are under high internal pressure during the operation and it has the complexity in damage mechanism and failure modes. For this reason, it is necessary to monitor the tank through its operation as well as during the whole fabrication process. A large number of sensors must be embedded into multiple positions of the tank from its fabrication step for monitoring the whole tank. Fiber optic sensors, especially fiber Bragg grating (FBG) sensors are widely used for various applications because of good multiplexing capabilities. However, we need to develop the embedding technique of FBG sensors into harsh inner environment of the tank for the successful embedment. In this paper, we studied the embedding technique of a number of FBG sensors into filament wound pressure tanks considering multiplexing and conducted in situ structural health monitoring of filament wound pressure tanks during water-pressurizing test using embedded FBG sensor arrays. From the experimental results, it was demonstrated that FBG sensors can be successfully adapted to filament wound pressure tanks for their structural health monitoring by embedding
Optimal design of filament wound type 3 tanks under internal pressure using a modified genetic algorithm
Full text linkThis research aims to perform the optimal design of filament wound type 3 tanks under internal pressure. So far, most designs have not been optimized to account for the requirements of filament wound structures, and no design method exists for general filament wound structures under internal pressure, satisfying given design requirements. In this research, a new design algorithm which had been proposed in our previous research was utilized. The optimal design algorithm includes the semi-geodesic path algorithm, progressive failure analysis and genetic algorithms. In addition, a modified sub-string genetic operator that improves the genetic algorithm was newly suggested and verified through a basic design. Finally, the optimal design algorithm was applied to a representative filament wound type 3 tank-high pressure hydrogen storage tank
Optimal design of filament wound structures under internal pressure based on the semi-geodesic path algorithm
Full text linkThis research aims to establish an optimal design method of filament wound structures under internal pressure. So far, most design and manufacturing of filament wound structures have been based on manufacturing experiences, and there is no established design rule. In this research, the semi-geodesic path algorithm was used to calculate possible winding patterns taking into account the windability and slippage between the fiber and the mandrel surface. In addition, finite element analyses using commercial code, ABAQUS, were performed to predict the behavior of filament wound structures. On the basis of the semi-geodesic path algorithm and the finite element analysis method, a filament wound structure was designed using the genetic algorithm
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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