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Influence of overhanging tool length and vibrator material on electromechanical impedance and amplitude prediction in ultrasonic spindle vibrator

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journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第4期25卷 292-310页

作者： Rendi KURNIAWAN Moran XU Min Ki CHOO Shuo CHEN Yein KWAK' Jielin CHEN Saood ALI Hanwei TENG Pil Wan HAN Gi Soo KIM tae jo ko Precision Machining Laboratory Department of Mechanical Engineering Yeungnam UniversityGyeongsansiGyeongbuk-doRepublic of Korea korea Electrotechnology Research Institute(KERI) ChangwonsiGyeongsangnam-doRepublic of Korea KASWIN Co. LtdChangwon-siGyeongsangnamdoRepublic of Korea

This study presents the development of an ultrasonic transducer with a radius horn for an ultrasonic milling spindle(UMS)*** ultrasonic transducer was intended to have a working frequency of approximately 30 *** different materials were considered in the study:stainless steel(SS 316L)and titanium alloy(Ti-6Al-4V).Titanium alloy gave a higher resonance frequency(33 kHz)than stainless steel(30 kHz)under the same preload compression *** electromechanical impedance simulation was carried out to predict the impedance resonance frequency for both materials,and the effect of the overhanging toolbar was *** to the electromechanical impedance simulation,the overhanging toolbar length affected the resonance frequency,and the error was less than 3%.Harmonic analysis confirmed that the damping ratio helps determine the resonance ***,damping ratios of 0.015-0.020 and 0.005-0.020 were selected for stainless steel and titanium alloy,respectively,with an error of less than 1.5%.Experimental machining was also performed to assess the feasibility of ultrasonic-assisted milling;the result was a lesser cutting force and better surface topography of Al 6061.

关键词： Ultrasonic spindle Ultrasonic vibration assisted-milling(UVAM) 1-degree of freedom(DOF) Frequency Amplitude Milling

Development of a hybrid scaffold and a bioreactor for cartilage regeneration

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Chinese Science Bulletin 2009年第19期54卷 3608-3612页

作者： LEE Seung-Jae LEE In Hwan PARK Jeong Hun GWAK So-Jung RHIE jong-Won CHO Dong-Woo ko tae jo KIM Dong Sung BK21 Mechatronics Group at Chungnam National University School of Mechanical Engineering Chungbuk National University DDS Research Lab. CKD Research Institute CKD Pharmaceutical Corp. Department of Plastic Surgery College of Medicine The Catholic University of Korea Department of Mechanical Engineering Pohang University of Science and Technology School of Mechanical Engineering Yeungnam University School of Mechanical Engineering Chung-Ang University

We developed a hybrid scaffold and a bioreactor for cartilage regeneration. The hybrid scaffold was developed as combination of two components: a biodegradable framework and hydrogel-containing chondrocytes. We performed the MTT cell proliferation assay to compare the proliferation and viability of chondrocytes on three types of scaffolds: an alginate gel, the hybrid scaffold, and an alginate sponge. Cells were encapsulated in 2% agarose gel. The bioreactor consisted of a circulation system and a compression system. We performed dynamic cell culture on these agarose gels in the bioreactor for 3 days.

关键词： MTT 生物分解凝解胶研究

Anode surface engineering of zinc-ion batteries using tellurium nanobelt as a protective layer for enhancing energy storage performance

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journal of Energy Chemistry 2024年第5期92卷 113-123页

作者： Soobeom Lee Yeonjin Je Boeun Seok Hyun tae Kim Yong-Ryun jo Soong Ju Oh Byoungyong Im Dae Guen Kim Sang-Soo Chee Geon-Hyoung An Department of Energy System Engineering Gyeongsang National UniversityJinju 52725Republic of Korea Nano Convergence Materials Center Korea Institute of Ceramic Engineering and Technology(KICET)Jinju 52851Republic of Korea Department of Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea School of Materials Science and Engineering Gyeongsang National UniversityJinju 52828Republic of Korea GIST Advanced Insitute of Instrumental Analysis(GAIA) Electron Microscopy LaboratoryGwangju Institute of Science and TechnologyGwangju 61005Republic of Korea Center for Advanced Materials and Processing Institute for Advanced EngineeringYongin 17180Republic of Korea Department of Energy Engineering Gyeongsang National UniversityJinju 52725Republic of Korea

Over the years,zinc-ion batteries(ZIBs)have attracted attention as a promising next-generation energy storage technology because of their excellent safety,long cycling performance,eco-friendliness,and high-power ***,issues,such as the corrosion and dissolution of the Zn anode,limited wet-tability,and lack of sufficient nucleation sites for Zn plating,have limited their practical *** introduction of a protective layer comprising of tellurium(Te)nanobelts onto the surface of Zn anode has emerged as a promising approach to overcome these limitations and improve the electrochemical behav-ior by enhancing the safety and wettability of ZIBs,as well as providing numerous nucleation sites for Zn *** the presence of a Te-based protective layer,the energy power density of the surface-engineered Zn anode improved significantly(ranging from 310 to 144 W h kg^(-1),over a power density range of 270 to 1,800 W kg^(-1)),and the lifespan capability was *** results demonstrate that the proposed strategy of employing Te nanobelts as a protective layer holds great promise for enhancing the energy storage performance of zIBs,making them even more attractive as a viable energy storage solution forthefuture.

关键词： Zn ion battery Anode Protective layer Tellurium Nanobelt

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Cr12MoV钢电火花辅助铣削实验研究

宇航材料工艺 2022年第6期52卷 44-51页

作者：李常平黄磊李树健李鹏南高泰祖湖南科技大学机电工程学院湘潭411201 韩国岭南大学机械工程学院大邱38541

以典型难切削金属材料Cr12MoV模具钢为研究对象,使用ABAQUS对其在电火花放电条件下温度场进行数值模拟,在不同进给率下对其进行传统铣削和电火花辅助铣削对比试验。借助高速摄像机、扫描电镜和测力计等设备,对其切削力特征、表面形貌和... 详细信息

以典型难切削金属材料Cr12MoV模具钢为研究对象,使用ABAQUS对其在电火花放电条件下温度场进行数值模拟,在不同进给率下对其进行传统铣削和电火花辅助铣削对比试验。借助高速摄像机、扫描电镜和测力计等设备,对其切削力特征、表面形貌和刀具磨损进行了对比分析研究。结果表明,电火花辅助铣削的切削力比传统铣削降低28.57%~51.47%,表面粗糙度降低2/3。与传统铣削相比,电火花辅助铣削在降低切削力、提高表面质量和减少刀具磨损方面具有显著优势。

关键词： Cr12MoV钢电火花辅助铣削温度场切削力表面形貌刀具磨损

Tribological properties of hierarchical micro-dimples produced on a cylindrical surface by dual-frequency texturing

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Friction 2023年第2期11卷 246-258页

作者： Saood ALI Rendi KURNIAWAN Park Gun CHUL tae jo ko School of Mechanical Engineering Yeungnam UniversityGyeongsan-si 712749Republic of Korea

An experimental investigation was performed for investigating the tribological performance of micro-dimple surface texture patterns on a cylindrical surface in a realistic operating environment of starved lubrication. Micro-dimples were generated by a dual-frequency surface texturing method, in which a high-frequency (16.3 kHz) three-dimensional (3D) vibration and a low-frequency (230 Hz) one-dimensional (1D) vibration were applied at the tool tip simultaneously, resulting in the generation of the hierarchical micro-dimples in a single step. Rotating cylinder-on-pin tribological tests were conducted to compare the tribological performance of the non-textured reference specimen and micro-dimple samples. The effect of surface textures generated with various shape parameters (long drop and short drop), dimension parameters (length and surface texture density), and operation parameters (load and sliding velocity) on the tribological performance was evaluated. Stribeck curves indicate that the hierarchical micro-dimples exhibit a lower coefficient of friction than the reference specimen in the high contact-pressure regions. It is also observed that variation in the length of a micro-dimple, the shape effect, is the major factor affecting the friction response of the textured surfaces. The generation of additional hydrodynamic pressure and lift effect by hierarchical structures is the main reason for the improved performance of hierarchical micro-dimple surfaces.

关键词： dual-frequency surface texturing hierarchical surfaces tribology starved lubrication three-dimensional elliptical vibration transducer

Prediction of characteristic blast-induced vibration frequency during underground excavation by using wavelet transform

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Frontiers of Structural and Civil Engineering 2022年第8期16卷 1029-1039页

作者： tae Un PAK Guk Rae jo Un Chol HAN Faculty of Mining Engineering Kim Chaek University of TechnologyPyongyang 999093Democratic People’s Republic of Korea School of Science and Engineering Kim Chaek University of TechnologyPyongyang 999093Democratic People’s Republic of Korea

Blast-induced vibration produces a very complex signal,and it is very important to work out environmental problems induced by *** this study,blasting vibration signals were measured during underground excavation in carbonaceous shale by using vibration pickup CB-30 and FFT analyzer ***,wavelet analysis on the measured results was carried out to identify frequency bands reflecting changes of blasting vibration parameters such as vibration velocity and energy in different frequency *** characteristics are then discussed in view of blast source distance and charge weight per *** analysis of results,it can be found that peak velocity and energy of blasting vibration in frequency band of 62.5–125 Hz were larger than ones in other bands,indicating the similarity to characteristics in the distribution band(31–130 Hz)of main vibration *** frequency bands were affected by blasting source distance,and the frequency band of 0–62.5 Hz reflected the change of charge weight per *** presenting a simplified method to predict main vibration frequency,this research may provide significant reference for future blasting engineering.

关键词： wavelet analysis blast-induced vibration frequency characteristics underground excavation

Bimetallic Ni-Co MOF@PAN modified electrospun separator enhances high-performance lithium-sulfur batteries

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journal of Energy Chemistry 2023年第7期82卷 484-496,I0010页

作者： Xiaolong Leng Jie Zeng Mingdai Yang Changping Li S.V.Prabhakar Vattikuti Jielin Chen Shuang Li Jaesool Shim Tong Guo tae jo ko School of Mechanical Engineering Yeungnam UniversityGyeongsangbuk-do 38541Republic of Korea College of Mechanical and Electrical Engineering Hunan University of Science and TechnologyXiangtan 411201HunanChina Key Laboratory for Soft Chemistry and Functional Materials of Ministry of Education Nanjing University of Science and TechnologyNanjing 210094JiangsuChina

Lithium-sulfur(Li-S)batteries with high energy density are considered promising energy storage devices for the next ***,the shuttle effect and the passive layer between the separator and the electrodes still seriously affect the cycle stability and ***,a bimetallic Ni-Co metal-organic framework(MOF)with adsorption and catalytic synergism for polysulfides was successfully synthesized as an electrospinning separator sandwich for Li-S *** porous Ni-Co MOF coatings into the separator provides more adsorption catalytic sites for polysulfides,prevents their diffusion to the anode,and enhances sulfur ***,the improved Li-S batteries with a Ni-Co MOF@PAN(NCMP)electrospun separator delivered excellent rate performance and outstanding cycle stability,yielding an ultra-high initial capacity of 1560 mA h g^(-1)at 0.1 ***,remarkable Li-S battery performance with a discharge capacity of 794 mA h g^(-1)(84.1%capacity retention)was obtained after500 cycles,while delivering a low capacity decay rate of 0.032%during long-term cycling(up to 500cycles)at 1 ***,even at the current density of 2 C,the capacity attenuation rate of 2000 cycles is only 0.034%per *** addition,compared with the Celgard separator,the NCMP separator also had high thermal stability(keeping the separator outline at 200℃)that ensured battery safety and excellent electrolyte wettability(73%porosity and 535%electrolyte absorption)and significantly enhanced the ionic conductivity and Li^(+) transfer number,and protected the surface integrity of the anode.

关键词： Li-S batteries Ni-Co MOF Adsorption catalysis Synergistic effect

Advanced heterolytic H_(2) adsorption of K-added Ru/MgO catalysts for accelerating hydrogen storage into aromatic benzyltoluenes

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journal of Energy Chemistry 2022年第8期31卷 333-343,I0009页

作者： tae Wan Kim Hwiram Jeong Yeongin jo Dongun Kim Ji Hoon Park Seok Ki Kim Young-Woong Suh Department of Chemical Engineering Hanyang UniversitySeoul 04763Republic of Korea Environmental&Sustainable Resources Research Center Korea Research Institute of Chemical TechnologyDaejeon 34114Republic of Korea Department of Chemical Engineering Ajou UniversitySuwon 16499Republic of Korea

Herein,we report a highly active K-added Ru/MgO catalyst for hydrogen storage into aromatic benzyltoluenes at low temperatures to advance liquid organic hydrogen carrier *** hydrogenation activity of Ru/K/MgO catalysts exhibits a volcano-shaped dependence on the K content at the maximum with 0.02 wt%.This is in good agreement with the strength and capacity of H_(2) adsorption derived from basicity,despite a gradual decrease in the textural property and the corresponding increase in the Ru particle size with increasing the K *** functional theory calculations show that heterolytic hydrogen adsorption properties(strength and polarization)are facilitated up to a specific density of K on the Ru–MgO interface and excessive K suppresses heterolytic H_(2) adsorption by direct interaction between K and hydrogen,assuring the hydrogenation activity and H_(2) adsorption capability of Ru/K/MgO ***,the Ru/K/MgO catalyst,when K is added in an optimal amount,is highly effective to accelerate hydrogen storage kinetics at low temperatures owing to the enhanced heterolytic H_(2) adsorption.

关键词： Chemical hydrogen storage Supported Ru catalysts Ru–MgO interface Heterolytic H_(2)adsorption Charge transfer Potassium promotion

Fibrillary gelation and dedoping of PEDOT:PSS fibers for interdigitated organic electrochemical transistors and circuits

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npj Flexible Electronics 2022年第1期6卷 330-340页

作者： Young Jin jo Soo Young Kim Jeong Hun Hyun Byeonghak Park Seunghwan Choy Gyan Raj koirala tae-il Kim School of Chemical Engineering Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Biomedical Institute for Convergence(BICS) Sungkyunkwan University(SKKU)Suwon 16419Korea

As one of conducting polymers,PEDOT:PSS,is commonly used in organic electronics,especially for bioelectronics due to its advantages such as high electrical and ionic conductivity,solution-processability and *** bioelectronics with the PEDOT:PSS requires advanced techniques to obtain physical/chemical modification of the PEDOT:PSS for improved performance and various *** satisfy these demands,fibrillary gelation of PEDOT:PSS by injection to choline acetate,an ionic liquid,with a constant flow rate was used in this study to make a conductive fiber and improve characteristics of PEDOT:*** fibers by fibrillary gelation showed enhanced electrical conductivity of about 400 S cm^(-1) and volumetric capacitance of about 154 F cm^(−3) which would be strongly beneficial to be utilized for organic electrochemical transistors(OECTs),resulting in a high transconductance of 19 mS in a ***,dedoping of the conductive fibers by PEI(polyethyleneimine)enabled the creation of enhancement-mode *** inverters were then fabricated by connecting depletion and enhancement-mode *** results demonstrate that these conductive fibers and electronic-textiles are suitable candidates for applications in bio-integrated electronics.

关键词： fibers doping digit