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Microstructure,mechanical properties and corrosion resistance of as-cast and as-extruded Mg-4Zn-1La magnesium alloy

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Rare Metals 2020年第8期39卷 909-917页

作者： Huseyin Zengin yunus Turen Hayrettin Ahlatci Yavuz Sun Department of Metallurgy and Materials Engineering Karabuk University78050 KarabukTurkey Iron and Steel Institute Karabuk University78050 KarabukTurkey

Microstructure,mechanical properties and corrosion resistance of as-cast and as-extruded Mg-4 wt%Zn-1 wt%La magnesium alloys were *** alloys were produced by low-pressure die casting method and extruded at 350℃after homogenization at 400℃for 24 *** results show that the as-cast alloy mainly consists of primaryα-Mg matrix and Mg-Zn-La ternary second phases(also called T-Phase)along grain boundaries and isolated spherical particles inside the *** extrusion at350℃,the average grain size decreases by 81%due to dynamic recrystallization mechanism and T-phase particles are distributed along the extrusion *** elongation,yield strength and tensile strength of the as-cast Mg-4Zn-1La alloy increase by 179%,90%and 40%,respectively,as a result of the extrusion *** as-extruded Mg-4Zn-1La alloy shows better corrosion resistance than the as-cast alloy due to increased grain boundaries and decreased content of T-phase.

关键词： Magnesium alloys La modification Extrusion Microstructure Mechanical properties Corrosion

Multi-output optimization of tribological characteristics control factors of thermally sprayed industrial ceramic coatings using hybrid Taguchi-grey relation analysis

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Friction 2016年第3期4卷 208-216页

作者： Mohammed yunus Mohammad S.ALSOUFI Mechanical Engineering Department College of Engineering and Islamic Architecture Umm Al-Qura University Makkah 21514 Kingdom of Saudi Arabia

Lasma-sprayed thermal barrier coatings (TBCs) are gaining wide popularity and becoming more attractive for many industrial applications due to their high strength, thermal barrier/fatigue characteristics at elevated temperatures, resistance to chemical degradation, wear resistance, and environmental corrosion protection provided when coated on the surface of engineering components. To characterize the tribological properties of TBCs, a better understanding of their failure mechanisms and a thorough investigation of their performance are required. In this research, we used Taguchi-based grey relational analysis (GRA) to optimize the process parameters of various tribological characteristics of ceramic coatings applied via an atmospheric plasma spray process. Using Taguchi L16 factorial mixed-level experimental design, we also evaluated tribological characteristics such as wear loss and the coefficient of friction. Using GRA, we successfully performed a multiple output optimization and ranking of the control factors. Based on ANOVA results, we evaluated the significance of each process parameter and validated our findings in tests using the obtained optimum set of process parameters. Our study results will help to minimize wear loss and the coefficient of friction and to maximize TBC life.

关键词： tribological characteristics wear loss coefficient of friction hybrid Taguchi-grey relational analysis analysis of variance (ANOVA) thermal barrier coatings (TBCs)

EFFECTS OF SEASONALITY ON STREAMFLOW AND WATER QUALITY OF THE PINANG RIVER IN PENANG ISLAND,MALAYSIA

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Chinese Geographical Science 2004年第2期14卷 153-161页

作者： Ahmad Jailani Muhamed yunus Nobukazu NAKAGOSHI Graduate School for International Development and Cooperation Hiroshima University. 1-5-1 Kagamiyama Higashi-Hiroshima City. 739-8529 JapanGraduate School for International Development and Cooperation Hiroshima University. 1-5-1 Kagamiyama Higashi-Hiroshima City. 739-8529 Japan

For the Pinang River, originating in the western highlands of Penang Island, the nature, sources and extent of pollution were studied. The river water samples collected at five selected sites were analyzed for various physical and chemical parameters, namely temperature, DO, BOD, COD, SS, pH, ammoniac nitrogen (AN), and conductance, Long-term data of rainfall and temperature were analyzed to determine the seasonal variations of the streamflow. The streamflow during the dry season is extremely low compared to the wet season, thus concentrations of contaminants derived from point pollution source increase due to lack of rainfall and runoff events. On the contrary, in the predominantly urban and agricultural catchments, non-point pollution source increases during rainy season through seepage and runoff. Effects of seasonal variations consequently determine the quantity and quality of the water parameters. The Jelutong River, the Dondang River and the Air Itam River carry the seepage from widely urban and residential areas to the main Pinang River systems. Water quality of the Pinang River at different points assessed by the water quality indices was compared. According to the quality indices during the study period, water quality in the upper reaches of the river is medium to good. It dwindled in the plains, due to the seepage from urban areas and discharges from the industrial and agricultural lands.

关键词： hydrology landscape ccology seasonal variations water quality index watershed

Grobner-Shirshov Basis of Quantum Groups

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Algebra Colloquium 2015年第3期22卷 495-516页

作者： Gulshadam yunus Zhenzhen Gao Abdukadir Obul College of Mathematics and System Sciences Xinjiang University Urumqi Xinjiang 830046 China

In this paper, by using the Ringel-Hall algebra method, we prove that the set of the skew-commutator relations of quantum root vectors forms a minimal GrSbner- Shirshov basis for the quantum groups of Dynkin type. As ... 详细信息

关键词： Ringel-Hall algebra indecomposable modules Gr6bner-Shirshov basis skew-commutator relations

Application of ultrasonic waves in measurement of hardness of welded carbon steels

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Defence Technology（防务技术） 2015年第3期11卷 255-261页

作者： Fatih uzun Ali Nezihi BILGE Department of Chemical Engineering Yeditepe University Department of Energy Systems Engineering Bilgi University

The ultrasonic contact impedance technique and ultrasonic wave velocities have been widely used for non-destructive hardness *** wave velocity shift provides through the thickness average hardness, however, the correlations are performed according to surface hardness. In order to accept this technique as a particular non-destructive method for determination of hardness, it is necessary to test it with industrial applications. A widely used joining(welding) technique is selected for this purpose. Samples of carbon steels with three different carbon contents, but similar composition, are annealed in order to obtain the softened samples with different hardness values. Rockwell B scale hardness of heat treated samples, which are assumed to be isotropic, are determined and correlated with ultrasonic wave velocity shifts. Effect of welding process on hardness is investigated using ultrasonic wave velocity shifts, and the results are verified with destructive hardness measurements.

关键词：超声波速度硬度测量焊接工艺工业应用碳钢非破坏性硬度测试接触阻抗

The effects of drainage basin geomorphometry on minimum low flow discharge: the study of small watershed in Kelang River Valley in Peninsular Malaysia

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Journal of Environmental Sciences 2003年第2期15卷 249-262页

作者： Ahmad Jailani Muhamed yunus Nobukazu Nakagoshi Khairulmaini Osman Salleh Graduate School for International Development Cooperation Hiroshima UniversityGraduate School for International Development Cooperation Hiroshima UniversityFaculty of Arts and Social Sciences University of Malaya 1-5-1 Kagamiyama Higashi-Hiroshima City 739-8529 Japan1-5-1 Kagamiyama Higashi-Hiroshima City 739-8529 Japan50603 Wilayah Persekutuan Kuala Lumpur Malaysia

This study investigate the relationships between geomorphometric properties and the minimum low flow discharge of undisturbed drainage basins in the Taman Bukit Cahaya Seri Alam Forest Reserve, Peninsular Malaysia. The drainage basins selected were third-order basins so as to facilitate a common base for sampling and performing an unbiased statistical analyses. Three levels of relationships were observed in the study. Significant relationships existed between the geomorphometric properties as shown by the correlation network analysis; secondly, individual geomorphometric properties were observed to influence minimum flow discharge; and finally, the multiple regression model set up showed that minimum flow discharge(Q min) was dependent of basin area(AU), stream length(LS), maximum relief(Hmax), average relief(HAV) and stream frequency(SF). These findings further enforced other studies of this nature that drainage basins were dynamic and functional entities whose operations were governed by complex interrelationships occurring within the basins. Changes to any of the geomorphometric properties would influence their role as basin regulators thus influencing a change in basin response. In the case of the basin's minimum low flow, a change in any of the properties considered in the regression model influenced the “time to peak' of flow. A shorter time period would mean higher discharge, which is generally considered the prerequisite to flooding. This research also conclude that the role of geomorphometric properties to control the water supply within the stream through out the year even though during the drought and less precipitations months. Drainage basins are sensitive entities and any deteriorations involve will generate reciprocals and response to the water supply as well as the habitat within the areas.

关键词： geomorphometric minimum low flow discharge regression model third-order drainage basins

Improving mechanical and antibacterial properties of PMMA via polyblend electrospinning with silk fibroin and polyethyleneimine towards dental applications

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Bioactive Materials 2020年第3期5卷 510-515页

作者： Ugur yunus Karatepe Tugba Ozdemir Molecular Biology and Genetics Department Tokat Gaziosmanpasa UniversityTasliciftlikTokatTurkey

Poly(methylmethacrylate)(PMMA)is a widely used material in dental applications,particularly as denture *** to thermally unstable and wet oral cavity,the implanted PMMA based resins occasionally deform and grow bacterial biofilms at the interface between oral cavity and the *** strategies attempted earlier to improve the bacterial resistance and mechanical performance of ***(ethyleneimine)(PEI)is a hyperbranched cationic polymer shown earlier to improve antibacterial activity of resins but do not improve mechanical properties of the resins alone,while silk fibroin(SF)is a natural biopolymer with unique material *** this study,we combined SF and PEI towards development of antibacterial and mechanically superior PMMA based materials towards overcoming its *** polyblend electrospinning to combine SF,PEI and PMMA,we successfully developed intrinsically antibacterial and mechanically reinforced nanofiber *** propose that the resulting nanofiber mats have the potential to be incorporated into PMMA based denture resin materials to overcome the problems of patients and improve their quality of life.

关键词： Dental biomaterials Reinforced Bacterial resistance PEI SF

Tor topography in Giresun mountains,Türkiye

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Journal of Mountain Science 2023年第11期20卷 3121-3137页

作者： uzun Ali AYLAR Faruk ZEYBEK Halilİbrahim ALEMDAĞSelçuk Ondokuz Mayis University Faculty of Art and ScienceGeography DepartmentSamsun 55200Türkiye Gümüşhane University Faculty of Engineering and Natural Sciences Department of Geological EngineeringGümüşhane 29100Türkiye

Tors are mound-like rock landforms,resistant to erosion,that may sometimes reach the size of several storeys of house by *** may develop in different climate regions and different rock types,led by granitic *** this study,tors developed in granitic rocks around Yaylal?village linked to Kürtün county in Gümü?hane were *** study area is located in the eastern part of the Giresun mountain range in northeastern Turkey,2000-2300 m above sea *** aim of the study is to determine the natural environmental characteristics in tor formation and to reveal the effect of bedrock on tor *** field studies,18 tors were selected by noting location,size and structural features,and dimensions were *** sections were first made from the rock samples taken from the tors and then the mineralogical composition was investigated by modal analysis *** a result of this analysis,it was determined that the bedrock forming the tors is *** the field observations,it was determined that the intersecting vertical joints supported the formation of castle-like tors,while the horizontal joints supported the formation of pita pileshaped *** are also pseudokarstic shapes resembling kamenitza and karst *** conclusion,joint sets causing local resistance differences directed the formation of tors,while excess slope affected surface erosion and suitability of climate conditions-controlled weathering rate.

关键词： Joint sets Granite Northern Anatolian Mountains Gümü?hane Türkiye

Comparative performance of different urea coating materials for slow release

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Particuology 2014年第6期12卷 165-172页

作者： Khairul Ridzwan Mohd Ibrahim Farahnaz Eghbali Babadi Robiah yunus Department of Chemical and Environmental Engineering Faculty of EngineeringUniversiti Putra Malaysia Institute of Advanced Technology Universiti Putra Malaysia

Approximately 70%of the applied urea fertilizer may be lost into the *** loss is due to leaching,decomposition and ammonium volatilization in soil,water and *** coating,the slow release technology can be used to reduce losses and to increase the fertilizer *** has been used as a coating material,but the coating cracks easily because of its friability,sometimes being peeled off from the urea *** this study,four types of materials,namely,gypsum,cement,sulfur and zeolite,were mixed and used as coating materials to search for the most effective and cheap coating *** primary reasons for selecting these materials were improving fruit quality and preventing plant diseases,providing a plant nutrient,increasing soil fertility and water *** materials were also selected based on their availability,processiblity and *** effects of the coating materials,thickness,drying time,sieving and sealant on the crushing strength and dissolution rate of urea were *** urea with the same proportion of gypsum-sulfur exhibited high crushing strength and lower dissolution ***,the performance was further enhanced by applying molten paraffin wax on the hot urea *** images demonstrated that the micro-structure of gypsum-sulfur coated urea after sieving resulted in a smoother coated *** efficiency of the coated urea was improved by26%using gypsum-sulfur（20%total coating）,3%paraffin wax and sieving the coating materials before application.

关键词： Coating Urea Gypsum Sulfur Slow release Crushing strength