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SPH modeling of fluid-structure interaction

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Journal of Hydrodynamics 2018年第1期30卷 62-69页

作者： Luhui Han Xiangyu Hu Department of Mechanical Engineering Technical University of Munich

This work concerns numerical modeling of fluid-structure interaction（FSI） problems in a uniform smoothed particle hydrodynamics（SPH） framework. It combines a transport-velocity SPH scheme, advancing fluid motions, with a total Lagrangian SPH formulation dealing with the structure deformations. Since both fluid and solid governing equations are solved in SPH framework, while coupling becomes straightforward, the momentum conservation of the FSI system is satisfied strictly. A well-known FSI benchmark test case has been performed to validate the modeling and to demonstrate its potential.

关键词： Fluid-structure interaction(FSI) smoothed particle hydrodynamics(SPH) total Lagrangian formulation

Adsorption and photo-catalytic properties of layered lepidocrocite-like quasi-amorphous compounds based on modified potassium polytitanates

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Particuology 2014年第6期12卷 22-28页

作者： E.V.Tretyachenko A.V.Gorokhovsky G.Y.Yurkov F.S.Fedorov M.A.Vikulova D.S.Kovaleva E.E.Orozaliev Department of Chemistry Saratov State Technical University

TiO2 compounds possess relatively high adsorption abilities and exhibit high photocatalytic activities that exhibit potential for the destruction of organic pollutants in natural and waste *** potassium polytitanates modified using transition metals and their oxides/hydroxides generate new nanomaterials that operate in the visible spectral *** study presents the synthesis and investigation of the structure,composition and photocatalytic activity of powdered nanoscale quasi-amorphous potassium polytitanates particles modified with iron,zinc,copper,cobalt and nickel sulfate in aqueous *** of the powders investigated in this work exhibit a high adsorption capacity for methylene blue dye（15-20mg/g） related to the welldeveloped surface of the layered potassium polytitanate *** transition metals and their oxides/hydroxides influences the electronic structure of the obtained systems.A high photocatalytic activity was observed for systems containing iron,zinc,nickel and their oxides/hydroxides in the ultraviolet and visible ranges.

关键词： Layered potassium titanate Chemical modification Heterostructured particles Photocatalytic activity Adsorption

Characterization and modification of waste magnesium chip utilized as an Mg-rich intermetallic composite

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Particuology 2014年第6期12卷 158-164页

作者： Aysel Kantürk Figen Sabriye Piskin Department of Chemical Engineering Yildiz Technical University

In this study,the characterization and modification of waste magnesium chips（WMCs）,which were produced by plastic molding in a gold manufacturing factory and are used as Mg-rich intermetallic composites in storing hydrogen,were discussed in *** were analyzed using X-ray diffraction（XRD）,X-ray fluorescence（XRF） spectroscopy,differential scanning calorimetry（DSC）,scanning electron microscopy（SEM）,and Brunauer-Emmett-Teller（BET） analysis to characterize the materials’ structural *** milling,organic treatment,and inorganic salt addition were carried out to modify the WMCs’ surface to prepare Mg-rich intermetallic composites for storing *** modified samples were analyzed using high-pressure volumetric analyses to calculate their hydrogen storage *** authors conclude that modified WMC was promising as an Mg-rich intermetallic composite that was suitable for use in hydrogen storage with a 4.59 wt%capacity at 320 C under a hydrogen pressure of 60 bar.

关键词： Waste magnesium chip Characterization Modification Hydrogen storage Intermetallic composite

Effect of Porosity on the Mechanical Properties and Wear Performance of 2% Copper Reinforced Sintered Steel Used in Shock Absorber Piston Production

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Journal of Materials Science & Technology 2009年第5期25卷 577-582页

作者： Bekir Yalin technical Education Faculty Suleyman Demirel University

Powder metallurgy （P/M） method has mainly been used to produce automobile parts such as self-lubrication beds, shock absorber parts, and gear wheels. In order to investigate the effect of porosity on the mechanical and tribological properties in sintered steel, specimens with 10%, 15%, and 20% porosity were produced in a 10 mm×10 mm×55 mm prismatic shape by pre-alloying powders of the MPIF Fe-C-0.205 alloy used in the production of shock absorber pistons. Sintering was carried out at 900℃ for 45 min in an argon atmosphere. Tensile, charpy, and microhardness tests were performed on these specimens. In addition, the wear performance of a 2% Cu reinforced sintered steel alloy under dry sliding conditions was determined. Metallographic studies such as pore formation, worn surface, and fractured surface analyses were performed by scanning electron microscopy and optical microscopy. The results indicate that irregular pore formation tendencies increase with an increase in porosity （%）. Furthermore, an increase in porosity was shown to decrease the mechanical properties and increase the wear trace area and the friction coefficient of sintered steel.

关键词： Shock absorber piston Powder metallurgy Porosity Friction coefficient

Numerical simulation of the sticking process of glass-microparticles to a fiat wall to represent pollutant-particles treatment in a multi-channel cyclone

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Particuology 2017年第3期15卷 112-131页

作者： Raimondas Jasevicius Harald Kruggel-Emden Pranas Baltrenas Institute of Mechanical Science Vilnius Gediminas Technical University Lithuania Research Institute of Environmental Protection Vilnius Gediminas Technical University Lithuania Department of Mechanical Process Engineering and Materials Processing Technical University Berlin Germany

Ultrafine particles are dangerous to human health and are usually difficult to separate from airflow because of their low inertia, which helps them to stick easily to surfaces because of adhesive forces. This characteristic provides opportunities for adhesive ultrafine particle separation by designing air-cleaning devices that exploit the sticking ability. To understand governing effects in such air-cleaning devices, which can be designed as multi-channel cyclones, the sticking of adhesive spherical glass particles under oblique impact has been investigated numerically by using the discrete element method. An adhesive dissipative contact model was applied by implementing different interaction forces for various-sized ultraflne pollutant particles. Normal loading is represented by the elastic Hertz contact model, whereas viscous damping is described by the modified nonlinear Tsuji model. The influence of deformation- dependent adhesive forces for a range of ultrafine particle sizes is illustrated during the sticking process. Dissipative oscillations during the sticking process were observed because of the influence of viscous damping forces.

关键词： Adhesion Discrete element method Microparticles Multi-channel cyclone Sticking process Boundary layer

Meteorological Drought Detection and Forecast Using Standardized Precipitation Index and Univariate Distribution Models: Case Study of Bamako, Mali

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Journal of Geoscience and Environment Protection 2023年第7期11卷 30-55页

作者： Alikalifa Sanogo Prince Appiah Owusu Roland Songotu Kabange Bakary Issa Djire Racheal Fosu Donkoh Nasser Dia Department of Civil Engineering Faculty of Engineering and Technology Kumasi Technical University Kumasi Ghana Department of Mathematical Sciences Clark Atlanta University Atlanta USA

As an extended period of unusually dry weather conditions without sufficient rain, drought poses enormous risk on societies. Characterized by the absence of precipitation for long periods of time, often resulting in water scarcity, droughts are increasingly posing significant environmental challenges. Drought is therefore considered an important element in the management of water resources, especially groundwater resources during drought. This study therefore sought to investigate the rainfall variability and the frequency of drought for the period 1991 to 2020 in Bamako based on monthly rainfall data from Bamako-Senou gauge station. The standardized precipitation index (SPI) for 12-month, 6-month and 3-month timescales and the SPI for annual totals were used to characterized drought in the study area (Bamako). Univariate parametric probability distributions such as Normal, Log-normal, Gumbel type I and Pearson type III (P3) distributions were fitted with drought variables (severity and duration) for future planning and management. Non-parametric test such as Mann-Kendall trend test was also used to detect trend in annual rainfall data. The results showed that based on 12-month SPI, Bamako experienced two (02) extreme droughts one in July 2002 (SPI = -2.2165) and another in June 2015 (SPI = -2.0598 QUOTE SPI=-2.0598 ). Drought years represented 46.67% for the overall periods according to the SPI for annual totals. The result further indicated that based on the goodness of fit test, the P3 distribution represents the best fitted distribution to both drought severity and duration over Bamako. Bamako is expected to experience several severe severities with higher and shorter duration in the future. Severities with 1, 2, 6, and 10-month duration had return periods ranged from 2.4 to 3.8 years, while 5, 10, 20, 25, 50, and 100-year return periods had 18.51, 26.08, 33.25, 35.50, 42.38, and 49.14 severities, respectively, and durations associated to these severities were 1

关键词： Standardized Precipitation Index (SPI) Rainfall Variability Univariate Proba-bility Distribution Drought Bamako

Contemplation on some cyclic N_8 isomers-A DFT treatment

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Defence Technology（防务技术） 2018年第1期14卷 19-27页

作者： Lemi Türker Middle East technical university Department of Chemistry

Various cyclic N_8 isomers are considered at the levels of B3 LYP/6-311++G(d,p) and B3 LYP/c PVTZ. Some energies and molecular orbital properties are obtained. The structures are found to be stable in the singlet state but mostly unstable in the triplet. The heats of formation values calculated by means of T1 recipe reveals that they are highly endothermic. NICS(0) values have been calculated and aromaticity/antiaromaticity of the rings are discussed. Additionally, theoretical IR,UV-VIS spectra and the calculated impulse values have been obtained.

关键词： Polynitrogen compounds Cyclic octanitrogen structures NICS Explosives Specific impulse DFT calculations

Investigation into Recent Temperature and Rainfall Trends in Mali Using Mann-Kendall Trend Test: Case Study of Bamako

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Journal of Geoscience and Environment Protection 2023年第3期11卷 155-172页

作者： Alikalifa Sanogo Roland Songotu Kabange Prince Appiah Owusu Bakary Issa Djire Racheal Fosu Donkoh Nasser Dia Department of Civil Engineering Faculty of Engineering and Technology Kumasi Technical University Kumasi Ghana Department of Mathematical Sciences Clark Atlanta University Atlanta USA

Rainfall and temperature variability analysis is important for researchers and policy formulators in making critical decisions on water availability and use in communities. The Western Sahel, which comprises Mali is considered as one of the vulnerable regions to climate change, and also encountered the challenges of climatic shocks such as flood and drought. This research therefore sought to investigate climate change effects on hydrological events and trends in Sahelian rainfall intensity using Bamako (Mali) as a case study from 1991 to 2020, as limited data availability did not allow an extended period of study. Monthly observed data provided by MALI-METEO was used to validate daily rainfalls data from African Rainfall Climatology Version 2 (ARC2) satellite-based rainfall product on monthly basis. The validated model performance used Nash-Sutcliffe Efficiency (NSE) and Percent Bias (PBAIS) and gave results of 0.904 and 1.0506 respectively. Trends in annual maximum temperatures and rainfalls were analyzed using Mann-Kendall trend test. The result indicated that the trend in annual maximum rainfalls was decreasing, while annual total rainfall was increasing but not significant at 5% significance level. The rate of increase in annual total rainfalls was 0.475 mm/year according to the observed annual rainfall series and decreased to 0.68 mm/year in annual maximum. The analysis further found that annual maximum temperatures were increasing at the rate of 0.03°C/year at 5% significance level. To provide more accurate climate predictions, it is recommended that further studies on rainfall and temperature with data sets spanning 60 - 90 years be carried out.

关键词： Sahel Countries Bamako Recent Trends Mann-Kendall Trend Test Climate Change

Managing System Losses to Improve Energy Efficiency within the Electricity Company of Ghana (ECG) Limited

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Smart Grid and Renewable Energy 2022年第6期13卷 121-136页

作者： Vincent Kwame Osei-Appiah Jones Lewis Arthur kumasi technical university Kumasi Ghana Department of General Agriculture Faculty of Applied Science and Technology Sunyani Technical University Sunyani Ghana Institute of Distance Learning Kwame Nkrumah University of Science and Technology Kumai Ghana

The inability to achieve the target of universal access to electricity is influenced by several factors including funding limitations, the use of obsolete equipment, power theft, and system losses confronting the electricity distribution services of the Electricity Company of Ghana Limited (ECG). The study assessed the components of system losses within the ECG by determining and computing the percentage of system losses within ECG, examining the causes of both commercial and technical losses in ECG, and determining ways to improve energy efficiency by reducing system losses in the most cost-efficient manner. The study adopted deductive reasoning and a quantitative approach to guide data collection and analysis of the research output. A sample of 345 technical and non-technical staff of ECG in the Greater Accra Metropolis was selected from a population of 2500. Purposive, simple random, and cluster sampling techniques were used in identifying and accessing respondents for the study. Descriptive statistics were applied to measure central tendency and degrees of dispersion and the Relative Importance Index (RII) to predict criterion and predictor variables. The impact of low voltage network losses can adversely contribute to technical losses (20%) and reduce energy efficiency in power or electricity distribution companies. Non-technical losses are mainly caused by illegal connections, meter problems, and billing problems. Each of the non-technical losses contributes a maximum of 10% to system losses. Contributors to system losses at ECG are ranked first for power theft and least for lack of incentives. System losses at ECG include metering inaccuracies, bad workmanship, unmetered supply, and lengthy distribution lines, each recording a mean value of above 3.5. Measures to improve monitoring of the networks and systems at ECG and discourage power theft should include an extensive quantification, patrolling, and inspection of the entire network to assess the extent of t

关键词： Network Management System Losses Electricity Cost Efficiency Energy Management