1,720,966 research outputs found
Use of La2O3 with 8YSZ as thermal barrier coating and its effect on thermal cycle behavior, microstructure, mechanical properties and performance of diesel engine operated by hydrogen-algae biodiesel blend
No full textIn this present work, the effect of lanthanum oxides (La2O3) on the thermal cycle behavior of TBC coatings and mechanical properties such as adhesion strength and microhardness of 8% Yttria Stabilized Zirconia (8YSZ) TBCs were investigated. CoNiCrAlY and aluminium alloy (Al–13%Si) were used as bond coat and substrate materials. 8YSZ and different wt % of La2O3 (10, 20, and 30%) top coatings were applied using the atmospheric plasma spray (APS) method. The thermal cycling test for TBC coated samples were conducted at 800 °C in the electric furnace. The XRD pattern shows that the La2O3 doped 8YSZ material transformed to cubic pyrochloric structured La2Zr2O7 during thermal cycling. Further, the Taguchi-based grey relation analysis (GRA) method was applied to optimize the TBC coating parameters to achieve better mechanical properties such as adhesion strength and microhardness. And the optimized La2O3/8YSZ TBC coating was coated on CRDI engine combustion chamber components. The engine was tested with microalgae biodiesel and hydrogen, and the results were promising for the TBC-coated engine. The engine performance increased while using La2O3/8YSZ coated components, and the emissions from engine exhaust gas such as CO, HC, and smoke reduced considerably. It was found that there was no separation crack and spallation of the coating layer in the microstructure. Ultimately, the microstructural analysis of the optimized TBC coated piston sample after 50 h of running in the diesel engine confirmed that the developed coating had a superior thermal insulation effect and longer life
Investigating the effects of injection and induction modes of hydrogen addition in a CRDI pilot diesel-fuel engine with exhaust gas recirculation
No full textThis work compares the outcomes of different flow rates of hydrogen added by induction and injection methods in three different flow rates (3, 9, and 15 LPM) through the intake manifold of a constant speed CRDI diesel engine operated at 1500 rpm. The premixed air and hydrogen mixture was ignited by injecting diesel fuel at 23⁰ bTDC. Hydrogen addition reduced CO, HC, and smoke in both the techniques, but efficiency was decreased at a higher percentage of hydrogen induction, whereas it increased with the injection technique. The higher calorific value and flame velocity helped proper combustion and improved brake thermal efficiency by 7%, and the brake-specific energy consumption was reduced by 10.7%. In addition, CO, UHC, and Smoke were decreased by 15.8, 29.7, and 15% compared with neat diesel at full BMEP. Nitrogen oxides decreased by 5.6% for 15 LPM of hydrogen injection compared to the induction method with the same flow rate but higher than diesel fuel by 35.9%. Three different EGR percentages (5, 7.5, and 10%) were used to reduce the higher NOx emission. Though the injection process was complex compared to the induction method, the injection process can provide promising results even at higher hydrogen flow rates
RSM optimization of ultrasound-assisted melia dubia oil extraction with green solvents and their suitability for diesel engine applications
No full textMelia-dubia, a member of the neem family, is recognized as a promising biodiesel feedstock due to its higher oil content. Hence, this study uses an ultrasound-assisted extraction method to focus on oil extraction from Melia-dubia seeds. Response surface methodology using a 3-factor, 3-level Box-Behnken design (BBD) optimized the oil yield using environmentally friendly solvents such as 2-Methyl tetrahydrofuran, Cyclopentyl methyl ether, and ethanol. They were utilized in the range of 4–8 mL/g. A maximum of 50.5 % yield was achieved using 2-methyl tetrahydrofuran solvent at the solvent-to-solid ratio of 6.98 mL/g at an extraction time of 87.6 min. Furthermore, the GCMS reveals the presence of higher levels of palmitic and linoleic acids in Melia-dubia oil. The obtained biodiesel was tested in a single-cylinder diesel engine at different BMEP values, where the MD20 blend exhibited a 3.75 % increase in brake thermal efficiency compared to diesel at higher BMEP conditions. Additionally, CO and smoke emissions demonstrated significant reductions of 13.08 % and 27.1 % for MD10, as well as 9.83 % and 16.78 % for MD20 blends, respectively, to the baseline diesel fuel. However, it is worth noting that there was a slight increase in NOx emissions for all blends compared to diesel
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Computational and experimental analysis of yttria stabilized zirconia thermal barrier coated pistons: Impact on temperature distribution, microstructure, CRDI engine performance, emissions, and energy balance
No full textThis study investigates the thermal stress distribution, structural performance, and microstructure of 6–8 % Yttria Stabilized Zirconia (8YSZ) thermal barrier-coated (TBC) pistons and their impact on the performance, emissions, combustion, and energy balance of a CRDI engine. Experimental work was conducted on pistons with four different YSZ-based TBC combinations with 20 % of La2O3, TiO2, Al2O3, and CeO2 with coating thicknesses ranging from 0.20 mm to 0.35 mm. Temperature and thermal stress distributions between coated and uncoated pistons were analyzed and compared using finite element analysis. The microstructural analysis identified imperfections such as cracks, delamination, and surface or interface defects in the TBC coatings. The impact of TBC-coated pistons on engine performance, emissions, and combustion characteristics was experimentally evaluated, along with a comparative analysis of energy distribution. Thermal analysis revealed that the increased surface temperature of the piston crown in TBC-coated pistons effectively reduced substrate temperature, confirming the thermal barrier effect. The brake thermal efficiency (BTE) of the LYSZ-coated engine improved by 15.15 % compared to the uncoated engine at full load. Exhaust emissions, including HC, CO, and smoke, were significantly reduced in all TBC-coated engines due to higher combustion temperatures. Specifically, the LYSZ-coated engine demonstrated reductions in HC, CO, and smoke emissions by 15.15 %, 19.69 %, and 27.27 %, respectively, compared to the uncoated engine. The microscopic analysis revealed fewer imperfections, such as cracks, pores, and delamination, in the LYSZ-coated pistons, indicating superior coating integrity and durability compared to other TBC coatings. Additionally, the unaccounted heat loss in the LYSZ-coated engine decreased by 26.4 %, 23.7 %, and 22 % at low, medium, and high loads, respectively, compared to the uncoated engine
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