1,721,870 research outputs found
Experimental and numerical study of surface texturing for low power combustion engines
No full textThe proliferation of small off-grid internal combustion (IC) engines in mobile power equipment has led to an alarming rise in smog-forming emissions and greenhouse gas levels, surpassing those emitted by passenger vehicles with an anticipated doubling by 2031. To address this concerning trajectory and meet stricter regulations, there is a global push to enhance the fuel efficiency of these engines. One promising approach involves integrating surface texturing with low viscosity lubricants to enhance engine liner tribological performance. However, establishing empirical design rules remains unclear due to its dependence on engine operating conditions. Small-size engines have lower operating pressures and higher speeds than large-size engines, necessitating different criteria for surface texturing compared to current solutions established on large engines. This research endeavours to advance the efficiency of small-scale IC engines by introducing surface texturing on engine liners through an electrochemical jet processing (EJP) texturing technique. A methodology has been devised to design and optimise surface texturing patterns using full-scale engine measurements, numerical RINGPAK engine modelling and computational fluid dynamics (CFD) simulations. Desired uniform and variable texture patterns (as a function of crank angle) were fabricated on engine liner materials, and their tribological performances was evaluated using laboratory reciprocating TE77 tribometer. An experimentally validated numerical engine model based on a Honda GX200 generator engine was utilised to underpin the engine load and temperature conditions for designing 2D multiphase hydrodynamic CFD numerical simulations and tribological testing. The CFD simulations suggested features with depths ranging from 5 to 15 µm and widths between 500 and 700 µm can increase lift forces up to 58.7 %, further suggesting a shallow angle design criteria that the inlet angle (IA) should be between 0.82° and 3.34° to improve performances. Desired texture patterns were fabricated using the EJP on three cylinder liner materials: hardened ASP 2023 steel, EN-GJS 400-15 spheroidal graphite cast iron and a hyper-eutectic Al-Si A390 alloy, revealing significant material microstructural influence on surface finishing. Tribological testing was conducted against two counter surface materials (AISI 52100 and cast iron) materials in PAO4 with a stroke length of 25 mm under different loads (11, 50 and 60 N) and two temperatures (30 and 100 ᵒC). The testing results highlighted tribological performance sensitivity to geometric parameters, testing conditions and surface topography. Under recentgular contact configuration at 11 N, the cast iron surface exhibited a maximum decrease of 21.8 %, whilst at 50 and 60 N, this increased to 36.4 and 23.8%, respectively. At 50 N, ASP 2023 surface exhibited a 22.0 % decrease, while the A390 surface decreased up to 10.6 %. Under a liner contact configuration at 50 N and 30 ᵒC, the ASP 2023 surface exhibited up to a 50.9 % reduction in the COF. However, there is no apparent improvement on the textured cast iron surface at 100 ᵒC due to low viscosity of PAO4. The CFD friction predictions exhibited an error up to 36.05 %, 143.21 % and 36.57 % when compared to experimental results for ASP 2023, cast iron and A390 surfaces, suggesting that a lower surface roughness exhibited less impact on predictions. Results also indicated cavitation's adverse effects on tribological performances in specific lubrication regimes, along with surface roughness. Surface analysis revealed chemical etching initiating two-body abrasion, while texture features could capture wear-off debris
Six new species of Zaischnopsis Ashmead (Hymenoptera: Chalcidoidea: Eupelmidae) from China based on morphological and molecular data
No full textSix new species of Zaischnopsis Ashmead (Hymenoptera: Eupelmidae) from China are described, Zaischnopsis covid Jiang & Peng sp. nov., Zaischnopsis fuscolivida Tang & Peng sp. nov., Zaischnopsis lii Jiang & Peng sp. nov., Zaischnopsis pacis Jiang & Peng sp. nov., Zaischnopsis campaniformis Tang & Peng sp. nov., and Zaischnopsis zhongi Jiang & Peng sp. nov. All the new species are described and illustrated based on females, and partial mitochondrial cytochrome oxidase subunit I (COI) sequences are provided for the six new species as well as for the previously described Z. fumosa Peng & Xiang. Females of all the species of Zaischnopsis recorded from China are differentiated in a key
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
Variable pressure scuffing of a flake graphite cast iron diesel cylinder liner
No full textA novel scuffing methodology was developed utilising variable specimen geometry to replicate numerically modelled top compression ring contact pressures (4-62 MPa) from a 12.8-litre heavy duty diesel engine as a function of stroke position. Scuffing of grade 250 cast iron was induced by reciprocating sliding (TE77) against a drip lubricated (PAO4) 52100 rectangular contact operating at 15 Hz and 311 N normal load by incrementing the temperature at 4˚C per minute until a sharp rise in friction coefficient was observed. Scuffing initiation temperature was insensitive to dynamic contact pressure. Formation of an oxide ‘glaze’ layer resulted in friction coefficients as low as 0.03 prior to severe scuffing
Dataset in support of the thesis 'Experimental and Numerical Study of Surface Texturing for Low Power Combustion Engines'
No full textThe dataset comprises a comprehensive array of information for PhD research entitled ‘Experimental and Numerical Study of Surface Texturing for Low Power Combustion Engines’. The data encompasses:
1) Basic 2D CFD models utilised for simulating ring/liner contact in the ANSYS FLUENT.
2) Cylinder pressure data from full scale engine testing and surface topography data from engine interfaces, used for numerical engine RINGPAK modelling.
3) CAD models developed in the SolidWorks for designing texture patterns on coupon.
4) Low speed and high speed data from TE77 testing, conducted on both ASP2023 and Cast Iron samples.
5) Surface analysis data from Alicona and SEM for samples under pre/post testing.
This dataset serves as a valuable resource, incorporating various experimental and numerical data points essential for studying surface texturing's impact on low-power combustion engines.
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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
Adaptive fault tolerant control against actuator faults
No full textAbstract not availableQikun Shen, Bin Jiang, Peng Sh
Observer based fault-tolerant control for a class of nonlinear networked control systems
No full textNo abstract available.Zehui Mao, Bin Jiang, Peng Sh
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