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Wear and mechanical properties of carburized AISI 8620 steel produced by powder metallurgy

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International Journal of Minerals,Metallurgy and Materials 2021年第3期28卷 430-439页

作者： Mehmet akif Erden Fatih Aydın Department of Biomedical Engineering Karabuk UniversityKarabuk 78050Turkey Department of Metallurgical and Materials Engineering Karabuk UniversityKarabuk 78050Turkey

The effect of carburization on the tensile strength and wear resistance of AISI 8620 steel produced via powder metallurgy was *** 1 and 2(with 0.2wt%C and 0.25wt%C,respectively)were first pressed at 700 MPa and then sintered at 1300,1400,or 1500℃for 1 *** ideal sintering temperature of 1400℃was ***,Alloys 1 and 2 sintered at 1400℃were carburized at 925℃for 4 *** microstructure characterization of alloys was performed via optical microscopy and scanning electron *** mechanical and wear behavior of carburized and noncarburized alloys were investigated via hardness,tensile,and wear *** carburization,the ultimate tensile strength of Alloys 1 and 2 increased to 134.4%and 138.1%,***,the elongation rate of Alloys 1 and 2 decreased to 62.6%and 64.7%,*** wear depth values of Alloy 2 under noncarburized and carburized conditions and a load of 30 N were 231.2 and 100.1μm,*** wear changed to abrasive wear when the load transitioned from 15 to 30 N.

关键词： powder metallurgy steels carburization microstructure wear mechanical properties

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Subadventitial resection of the ureterd-new method for surgical corrections of the ureteropelvic junction and ureterovesical junction obstructions

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Asian Journal of Urology 2023年第2期10卷 195-200页

作者： akif Memmedoglu Bagirov Department of Urology Azerbaijan Medical UniversityAzerbaijanBakuAzerbaijan

Objective:The aim of our study was to examine results of pyeloplasty using the new methoddsubadventitial resection of the ureter with preservation of the ureteral artery proposed by us and the possibility of using this method in one-stage surgery with ureteropelvic junction(UPJ)and ureterovesical junction(UVJ)obstructions or vesicoureteral ***:A retrospective analysis of 108 patients with hydronephrosis(including two patients with hydroureteronephrosis)who received treatment from March 1998 to March 2020 was carried out,with an average follow-up period of 36 *** pyeloplasty using a subadventitial technique with preservation of ureteral blood supply was performed in 108 patients(including bilateral in two cases).In one patient with UPJ and UVJ obstructions and in one patient with UPJ obstruction and vesicoureteral reflux subadventitial resection of the ureter were performed in both ***:All patients managed to preserve the integrity of the ureteral artery during dismembered pyeloplasty,and two patients simultaneously underwent ureterocystostomy by subadventitial resection of the *** method of pyeloureteroplasty with subadventitial resection of the ureter makes it possible to improve long-term results in patients with hydronephrosis,including those with lesions of the UPJ and UVJ *** all cases,it was feasible to achieve a decrease in the degree of *** complications were observed in five cases(4.6%),in none of which there were complications associated with the surgical technique,and were eliminated without loss of renal ***:Our 22 years of experience shows that the technique of subadventitial resection of the ureter allows us to preserve the ureteral blood circulation during dismembered pyeloplasty and thus creates conditions for prevention of restenosis of UPJ and for single-stage ureteroplasty on the upper and lower ureteral segments.

关键词： Hydronephrosis Hydroureteronephrosis Ureteropelvic obstruction Dismembered pyeloplasty Ureterovesical obstruction Subadventitial resection of the ureter

Epiretinal membrane related vascular changes in diabetic eyes evaluated with optical coherence tomography angiography

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International Journal of Ophthalmology(English edition) 2023年第9期16卷 1503-1511页

作者： Umay güvenç günerÜney NurtenÜnlü Mehmet akif Acar Dicle Hazırolan Özlem Candan Ankara Training and Research Hospital Ophthalmology Department Ankara 06800Türkiye

AIM:To evaluate the retinochoroidal microvascular circulation and anatomical structure of diabetic and nondiabetic patients with epiretinal membrane(ERM)with the help of optical coherence tomography angiography(OCT-A)and compare them with healthy control ***:In this prospective,cross-sectional study,a total of 165 eyes were evaluated,including 50 eyes of patients with diabetic ERM,54 eyes of idiopathic ERM(iERM)patients,and 61 eyes of healthy *** and disc angiography was performed by *** vessel density(VD)ratio was evaluated by dividing the VD of the foveal region by the VD of the parafoveal *** calculations were evaluated at the 95%confidence ***:Macula superficial VD values of ERM cases were lower than that in the control group,while foveal VD was higher in ERM *** deep VD values of ERM cases were lower in all quadrants,except the *** width of the foveal avascular zone(FAZ)area was significantly lower in the ERM groups,and the FAZ width was lowest in iERM *** superficial VD ratio was significantly higher in the ERM groups,but there was no significant difference between ERM *** deep VD ratio was significantly higher in the iERM group than in the control ***:Diabetic and idiopathic ERMs differ in their mechanism of formation and clinical presentation,as well as their effect on retinal vascular *** the relationship of increase of retinal thickness with vascular integrity can be demonstrated with OCT-A,then,OCT-A can be used as a guide for ERM prognosis.

关键词： diabetic macular edema epiretinal membrane macula vessel density ratio optical coherence tomography angiography

The resource-based Kuznets curve hypothesis:An empirical exploration

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geoscience Frontiers 2024年第5期15卷 162-173页

作者： Mehmet akif Destek Tanaya Saha gamze Destek Avik Sinha Department of Economics Gaziantep UniversityGaziantepTurkey Research Methods Application Center of UNEC Azerbaijan State University of Economics(UNEC)Baku AZ1001Azerbaijan general Management and Economics Goa Institute of ManagementIndia Adnan Kassar School of Business Lebanese American UniversityBeirut 1102-2801Lebanon Management Development Institute gurgaon India

Countries face the risk of natural resource curse because of making their economic growth excessively dependent on natural *** excessive resource dependence causes such a risk,it is inevitable that resource-rich countries will need resource rent up to a certain level of economic *** the other hand,transferring the wealth achieved after this maturity level to productive investment areas also reduces the resource dependency levels of *** this context,countries that capture the possible inverted U-shaped relationship between economic growth and resource dependence can escape the *** on this,the aim of this research is to determine the validity of the Kuznets type relationship between resource dependence and economic growth for the first time in the *** nations that rely heavily on natural resources are used as a sample for *** countries with a share of total resource rent in national revenue greater than 25%are taken into consideration throughout the selection process for these *** novel panel data methodologies,the effects of capital accumulation,public spending,foreign direct investment,and economic growth on the dependence on natural resources is examined from 1993 to *** results reveal that capital accumulation reduces resource dependency while foreign investments and government size increases *** addition,the Resource-Based Kuznets curve concept is supported by empirical data demonstrating an inverted-U-shaped relationship between economic growth and resource dependence for these *** thresholds derived from the parameters show that Saudi Arabia and Kazakhstan are well beyond this *** Democratic Republic of the Congo and the Republic of the Congo,on the other hand,remain a long way from this ***,Iraq,Mongolia,Iran,and Azerbaijan have national incomes that are close at the threshold.

关键词： Resource-based Kuznets curve Economic growth Natural resources Foreign direct investment government size

Molecular and atomic manipulation of metal-organic framework-derived LiCoMnO_(4):An oxygen-deficient strategy for advanced lithium storage

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Journal of Energy Chemistry 2022年第12期75卷 216-228,I0006页

作者： Jian-En Zhou Jiahao Chen Xiaoke Zhang akif Zeb Xiaoming Lin guangzhou Key Laboratory of Materials for Energy Conversion and Storage Key Laboratory of Theoretical Chemistry of EnvironmentMinistry of EducationSchool of ChemistrySouth China Normal UniversityGuangzhou 510006GuangdongChina

As a novel class of high-voltage cathode materials,spinel lithium transition metal oxides have been faced with demerits including pronounced structural instability caused by Jahn-Teller distortion(especially at the lower voltage region)and severe capacity degradation despite their intriguing electrochemical *** extend their functionalities as broad-voltage cathodes,the sacrificial template method has been regarded as a promising way to realize structural and compositional control for desirable electrochemical ***,we report a synthetic protocol to directionally prepare Li Co Mn O_(4)(LCMO)using carboxyl-based metal-organic frameworks(MOFs)as self-sacrificing ***,LCMO derived from Co Mn-BDC(H_(2)BDC=1,4-benzenedicarboxylate)displays superior electrochemical performances with a specific capacity of 151.6 m Ah g^(-1)at 1 C(150 m A g^(-1))after 120 cycles and excellent rate capacity of 91.9 m Ah g^(-1)at 10 C due to the morphology control,microstructural modulation,and atomic manipulation of the MOF *** by the optimized atomic and electronic structure,abundant oxygen vacancies,and the nanostructure retained from MOF precursors,LCMO materials display extraordinary electrochemical properties,which have been extensively verified by both experimental and theoretical *** work not only provides guidelines for the directional design of spinel materials at molecular and atomic levels but also sheds light on the practical use of LIBs with broad range voltage.

关键词： Lithium-ion battery Cathode MOFs LiCoMnO_(4) Controllable synthesis Atomic manipulation

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Interfacial Engineering of Defect-Rich and Multi-Heteroatom-Doped Metal-Organic Framework-Derived Manganese Fluoride Anodes to Boost Lithium Storage

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Energy & Environmental Materials 2023年第5期6卷 449-459页

作者： Xiaohong Tan Jiawei Liu Jiating Huang Yilin Li akif Zeb Xiaoming Lin Nation Land Local Joint Engineering Research Center of MPTES in High Energy and Safety LIBs Engineering Research Center of MTEES(Ministry of Education)Key Laboratory of Theoretical Chemistry of EnvironmentMinistry of EducationSchool of ChemistrySouth China Normal UniversityGuangzhou 510006China

Manganese fluoride(MnF2)is a high-performance lithium-ion battery anode material with an excellent structural stability,low synthesis cost,and better manufacturing ***,its low theoretical capacity(577 mAh g^(-1)),weak conductivity of fluoride,and poor recyclability limit its practical ***,oxygen vacancies(Ov)and heteroatomic doping are among the most promising strategies to modulate the inherent reduced electronic conductivity and kinetic response of electrode materials in order to boost their lithium storage ***,self-templating,self-optimizing,and self-supporting metal-organic framework template approach with the introduction of oxygen vacancies by substitution of exogenous heteroatoms is proposed,where triple heteroatom-doped(N,O,and F)carbon-encapsulated MOF-derived manganese fluoride(Ov-ZMF@NOFs)microstructures are ***,the exogenously introduced triple heteroatomic carbon matrix forms a fluffy three-dimensional mechanical structure,interlaced conducting networks,efficient conducting pathways,and intense electrochemical dynamics at the periphery of the manganese fluoride *** from the above-mentioned features,the Ov-ZMF@NOFs exhibit expected electrochemical properties with ultra-long recyclability(high reversible capacity of 419 mAh g^(-1)at 6 A g^(-1))and good rate performance(capacity of 232 mAh g^(-1)at a current density of 16 A g^(-1)).Theoretical calculations underline the essential contribution of multiple heteroatoms doping in boosting the electrode conductivity and reducing the lithium-ion migration energy *** controllable vacancy engineering and heteroatom doping technology at the nanoscale provides a new philosophy and concept for the design and fabrication of next-generation high-energy lithium-ion battery materials.

关键词： anode lithium-ion batteries metal-organic framework multi-heteroatomic doping oxygen vacancies

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Topology-Optimized 4D Printing of a Soft Actuator

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Acta Mechanica Solida Sinica 2020年第3期33卷 418-430页

作者： Ali Zolfagharian Martin Denk Mahdi Bodaghi Abbas Z.Kouzani akif Kaynak School of Engineering Deakin UniversityGeelong 3216Australia Munich University of Applied Sciences 80335 MunichGermany Department of Engineering School of Science and TechnologyNottingham Trent UniversityNottingham NG 118NSUK

Soft robots and actuators are emerging devices providing more capabilities in the field of *** flexibility and compliance attributing to soft functional materials used in the fabrication of these devices make them ideal for delivering delicate tasks in fragile environments,such as food and biomedical ***,the intuitive nonlinearity of soft functional materials and their anisotropic actuation in compliant mechanisms constitute an existent challenge in improving their *** optimization(TO)along with four-dimensional(4D)printing is a powerful digital tool that can be used to obtain optimal internal architectures for the efficient performance of porous soft *** paper employs TO analysis for achieving high bending deflection of a 3D printed polyelectrolyte actuator,which shows bending deformations in response to electrical stimuli in an electrolyte *** performance of the actuator is studied in terms of maximum bending and actuation rate compared with a solid,uniformly 3D printed and topology-optimized *** experimental results proved the effectiveness of TO on achieving higher bending deformation and actuation rate against a uniformly 3D printed actuator.

关键词： Topology optimization 4D printing 3D printing Soft actuator

Robust adaptive repetitive control for unknown linear systems with odd-harmonic periodic disturbances

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Science China(Information Sciences) 2022年第12期65卷 186-203页

作者： Edi KURNIAWAN Hendra g.HARNO Hai WANg Jalu A.PRAKOSA Bernadus H.SIRENDEN Harry SEPTANTO Hendra ADINANTA akif RAHMATILLAH Research Center for Photonics National Research and Innovation Agency Faculty of Science and Technology Sanata Dharma University Discipline of Engineering and Energy Murdoch University Research Center for Electronics National Research and Innovation Agency 5. Research Center for Smart Mechatronics National Research and Innovation Agency 6. Research Center for Hydrodynamics Technology National Research and Innovation Agency Faculty of Science and Technology Airlangga University

This article presents a novel tracking control strategy for unknown linear systems perturbed by odd-harmonic periodic disturbances that combine adaptive and repetitive control methods. The proposed control strategy results in a robust adaptive odd-harmonic repetitive controller(RA-OHRC). Direct adaptive control with a robust adaptation law is utilized to accurately track the desired trajectory, ensuring the boundedness and convergence of the tracking error. An internal-model-based repetitive controller is added to compensate for periodic disturbances with odd-harmonic components. The boundedness and the convergence of the tracking error are verified through the Lyapunov-based stability analysis. The effectiveness of the proposed RA-OHRC scheme can be demonstrated using the simulation studies involving a servomotor model,which achieves accurate reference tracking, excellent disturbance rejection capability, and robustness against uncertainties.

关键词： repetitive control direct adaptive control odd-harmonic frequencies periodic disturbances unknown linear systems

Antimicrobial susceptibility of bacteria isolated from urine cultures in Southern Turkey

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Current Urology 2022年第3期16卷 180-184页

作者： Caner Baran akif Küçükcan Department of Urology Çukurova State HospitalAdanaTurkey Department of Microbiology Çukurova State HospitalAdanaTurkey

Background:Pathogen spectrum and antibiotic susceptibility patterns vary in different regions and should consider the empirical treatment of urinary tract infections(UTIs).Information on susceptibility is the basis for providing reliable *** study aimed to determine the antibiotic susceptibility of bacteria isolated from urine cultures at Çukurova State Hospital,which is located south of Turkey and east of the Mediterranean *** and methods:Urine culture results were retrospectively evaluated between April 2018 and January ***,such as age,sex,and medical department,were also *** criteria were patients aged at least 18 years with pathogenic bacterial growth in their urine *** susceptibility testing and bacterial identification were performed using the VITEK 2 automated ***:Of 12,288 urine samples,2033(16.5%)had pathogenic *** rates of bacterial and yeast growth were 93.3%and 6.7%,***-negative pathogens constituted 91.6%of the *** most prevalent bacteria were Escherichia coli with a 66%rate,followed by Klebsiella(14.2%).According to our results,ciprofloxacin,trimethoprim-sulfamethoxazole,and ampicillin are not suitable for empirical treatment of UTIs,whereas nitrofurantoin and fosfomycin are rational ***:Uropathogens exhibit an increased resistance rate against ampicillin,trimethoprim-sulfamethoxazole,and ***,fosfomycin,and ceftazidime have better efficacy than other investigated antibiotics in urine culture against common uropathogens and are suitable for empirical treatment of UTI.

关键词： Antibiotics Antimicrobial susceptibility Escherichia coli Urinary tract infections