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Bidirectional rotating direct-current triboelectric nanogenerator with self-adaptive mechanical switching for harvesting reciprocating motion

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International Journal of Extreme manufacturing 2024年第4期6卷 324-335页

作者： Donghan Lee Joonmin Chae Sumin Cho Jong Woo Kim Awais Ahmad Mohammad Rezaul Karim Moonwoo La Sung jea.Park Dongwhi Choi Department of Mechanical Engineering(Integrated Engineering Program) Kyung Hee University1732 Deogyeong-daeroYonginGyeonggi 17104Republic of Korea Department of Chemistry University of LahoreLahorePakistan Department of Mechanical Engineering College of EngineeringKing Saud UniversityRiyadh 11421Saudi Arabia School of Mechanical Engineering Korea University of Technology and Education1600 Chungjeol-roCheonanChungnam 31253Republic of Korea

Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic ***,owing to the working mechanisms of conventional DC TENGs,generating a stable DC output from reciprocating motion remains a ***,we propose a bidirectional rotating DC TENG(BiR-TENG),which can generate DC outputs,regardless of the direction of rotation,from reciprocating *** distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC ***,it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational *** to these tailored design strategies and subsequent optimizations,the BiR-TENG could generate an effective unidirectional DC *** of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this *** study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions,highlighting the suitability of DC outputs as an energy source for electronic devices.

关键词： direct-current triboelectric nanogenerator mechanical rectification self-adaptive mechanical design harvesting reciprocation motion

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Flow Characteristics in Compact Thermal Spray Coating Systems with Minimum Length Nozzle

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Plasma Science and Technology 2009年第5期11卷 550-554页

作者： Seung-Hyun KIM Youn-jea.KIM School of Mechanical Engineering Sungkyunkwan University

In this study, numerical analysis is performed to adopt the equivalence ratio on the high velocity oxygen fuel （HVOF） thermal spray coating systems equipped with a minimum length nozzle. The analysis is applied to investigate the axisymmetric, steady-state, turbulent, and chemically combusting flow both within the torch and in a free jet region between the torch and the substrate to be coated. The combustion is modeled using a single-step and eddy-dissipation model which assumes that the reaction rate is limited by the turbulent mixing rate of the fuel and oxidant. As the diameter of the nozzle throat is increased, the location of the mach shock disc moves backward from the nozzle exit. As the throat diameter and the divergent portion are 6 mm and 8 mm, respectively, the pressure in the HVOF system is the lowest at the chamber and the expanding gas is steadily maintained with both high velocity and high temperature for different equivalence ratios. Thus, relatively minor amendments of the equivalence ratio and the geometry of HVOF can lead to improved control over coating characteristics.

关键词： minimum length nozzle HVOF equivalence ratio

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Nanotopography Impact in Shallow Trench Isolation Chemical Mechanical Polishing-Dependence on Slurry Characteristics

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Journal of Rare Earths 2004年第Z2期22卷 1-4页

作者： jea.Gun Park Takeo Katoh Ungyu Paik Nano-SOI Process Laboratory Hanyang University17 Haengdang-DongSeoungdong-GuSeoul 133-791Korea Nano-SOI Process LaboratoryHanyang University17 Haengdang-DongSeoungdong-GuSeoul 133-791Korea Department of Ceramic EngineeringHanyang University17 Haengdang-DongSeoungdong-GuSeoul 133-791Korea

The nanotopography of the surface of silicon wafers has become an important issue in ULSI device manufacturing since it affects the post-chemical mechanical polishing (post-CMP) uniformity of the thickness deviation of dielectric films. In this study, the nanotopography impact was investigated in terms of its dependence on the characteristics of ceriabased slurries, such as the abrasive size, the grain size of the polycrystalline abrasive and the surfactant added to the slurry. It was found that the magnitude of the post-CMP oxide thickness deviation due to nanotopography increased with the surfactant concentration in the case of smaller abrasives but was almost independent of the concentration in the case of larger abrasives. The grain size of the polycrystalline abrasive did not affect the nanotopography impact.

关键词： CMP slurry ceria abrasive surfactant nanotopography

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Acheivement of Nano-Scale SiGe Layer with Discrete Ge Mole Fraction Profile Using Batch-Type HVCVD

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Journal of Rare Earths 2004年第Z2期22卷 178-182页

作者： Gon-sub Lee Tae-hun Shim jea.gun Park Advanced Semiconductor material and Device Development Center Hanyang UniversitySeoul 133-791Korea Advanced Semiconductor Material and Device Development CenterHanyang UniversitySeoul 133-791Korea Advanced Semiconductor Material and Device Development CenterHanyang UniversitySeoul 133-791Korea

The strained Si grown on the relaxed SiGe-on-insulator C-MOSFET's is a promising device for the future system LSI devices with the design rule of sub-micron. The achievement of the discrete Ge mole fraction in the SiGe layer is a key engineering in low-temperature SiGe epitaxial growth using HVCVD. The pre-flow of GeH4 gas enhanced the Ge mole fraction and SiGe layer thickness. In addition, the Ge mole fraction and SiGe layer thickness increases with the gas ratio of GeH4/SiH4 + GeH4, process temperature, and gas flow time. However, the haze was produced if the Ge mole fraction is above 22wt%. The discrete-like Ge mole fraction with 22 wt% in 10 nm SiGe layer was obtained by the pre-flow of GeH4 for 10 s, the mixture gas ratio of GeH4/SiH4 + GeH4 of 67%, and the gas flow time for 150 s at the process temperature of 550 C.

关键词： strained Si nano scale SiGe layer Ge mole fraction HVCVD gas flow boat-out time

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Numerical study on the heat dissipation characteristics of high-power LED module

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Science China(Technological Sciences) 2013年第9期56卷 2150-2155页

作者： LEE DaeWoo CHO Sung-Wook KIM Youn-jea Graduate School of Mechanical Engineering Sungkyunkwan University School of Mechanical Engineering Sungkyunkwan University

LED lighting has problems such as short life span, power reduction due to the LED chip's heat, and decreased luminance efficiency etc. many studies on the optimization of the thermal performance of LEDs have been conducted actively to solve these problems. The present study changes the fin shape and intervals of various heat sink designs so that LED can effectively produce a thermal effect. The water-cooling heat release system and the heat pipe methods show higher thermal performance results than the existing systems; however, the system is of high cost and requires a large-scale apparatus. This study carried out a numerical analysis of the thermal control system by applying heat flux and heat sink properties as an active heat release system using the commercial code ANSYS ver. 13.0 and verified the validity of the new heat sink design for temperature distribution analysis.

关键词： LED lighting water-cooling heat release system heat loss

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Capturability of 3D RTPN guidance law against true-arbitrarily maneuvering target with maneuverability limitation

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Chinese Journal of Aeronautics 2022年第7期35卷 75-90页

作者： Kebo LI Zhihui BAI Hyo-Sang SHIN Antonios TSOURDOS Min-jea.TAHK Department of Applied Mechanics College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China Institute of Aerospace Sciences SATMCranfield UniversityCranfield MK430ALUK Department of Aerospace Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea

The capturability of the Three-Dimensional(3D)Realistic True Proportional Navigation(RTPN)guidance law is thoroughly *** true-arbitrarily maneuvering target is considered,which maneuvers along an arbitrary direction in 3D space with an arbitrary but upperbounded *** whole nonlinear relative kinematics between the interceptor and target is taken into ***,the upper-bound of commanded acceleration of 3D RTPN is deduced,using a novel Lyapunov-like ***,the reasonable selection range of navigation gain of3D RTPN is analyzed,when the maneuver limitation of interceptor is *** that,a more realistic definition of capture is adopted,i.e.,the relative range is smaller than an acceptable miss-distance while the approaching speed is larger than a required impact *** previous researches which present Two-Dimensional(2D)capture regions,the inequality analysis technique is utilized to obtain the 3D capture region,where the three coordinates are the closing speed,transversal relative speed,and relative *** obtained capture region could be taken as a sufficient-but-unnecessary condition of *** new theoretical findings are all given in explicit expressions and are more general than previous results.

关键词： Capture region Lyapunov-like approach maneuverability Limitation Realistic true proportional navigation True-arbitrarily maneuvering target

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Effect of a distal protection device on epicardial blood flow and myocardial perfusion in primary percutaneous coronary intervention

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2007年第8期8卷 575-579页

作者： ZHOU Bin-quan TAHK Seung-jea Department of Cardiology Sir Run Run Shaw Hospital School of Medicine Zhejiang University Hangzhou 310016 China Department of Cardiology School of Medicine Ajou University Suwon 443749 Korea

Objective: The beneficial effect of percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI) has been well established, but there is the problem of no-reflow phenomenon which is an adverse prognostic factor in primary PCI. In the present study the effect of a distal protection device (PercuSurge GuardWire; GW) on epicardial blood flow and myocardial perfusion was evaluated. Methods and Results: Patients with AMI were randomly divided into 2 groups, the GW and the control groups. The GW group included 52 patients with AMI who underwent primary PCI with GW protection and the control group included 60 patients who underwent primary PCI without GW protection. Epicardial blood flow in the infarct-related artery (IRA) and myocardial perfusion were evaluated according to the thrombolysis in myocardial infarction (TIMI) flow grade and the myocardial blush grade (MBG). We found TIMI score of 3 was obtained significantly more frequently in the GW group (96%) than in the control group (80%). The MBG score of 3 was obtained also significantly greater in the GW group (65%) than in the control group (33%). Conclusion: Primary PCI with GW protection can significantly improve epicardial blood flow and myocardial perfusion.

关键词： Acute myocardial infarction (AMI) Distal protection device Percutaneous coronary intervention (PCI)

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Benchmark Computations of the Phase Field Crystal and Functionalized Cahn-Hilliard Equations via Fully Implicit,Nesterov Accelerated Schemes

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Communications in Computational Physics 2023年第2期33卷 367-398页

作者： jea.Hyun Park Abner J.Salgado Steven M.Wise Department of mathematics University of California Santa BarbaraCA 93106USA Department of mathematics University of Tennessee KnoxvilleTN 37996USA.

We introduce a fast solver for the phase field crystal(PFC)and functionalized Cahn-Hilliard(FCH)equations with periodic boundary conditions on a rectangular domain that features the preconditioned Nesterov’s accelerated gradient descent(PAGD)*** discretize these problems with a Fourier collocation method in space,and employ various second-order schemes in *** observe a significant speedup with this solver when compared to the preconditioned gradient descent(PGD)*** the PAGD solver,fully implicit,second-order-in-time schemes are not only feasible to solve the PFC and FCH equations,but also do so more efficiently than some semi-implicit schemes in some cases where accuracy issues are taken into *** computations of four different schemes for the PFC and FCH equations are conducted and the results indicate that,for the FCH experiments,the fully implicit schemes(midpoint rule and BDF2 equipped with the PAGD as a nonlinear time marching solver)perform better than their IMEX versions in terms of computational cost needed to achieve a certain *** the PFC,the results are not as conclusive as in the FCH experiments,which,we believe,is due to the fact that the nonlinearity in the PFC is milder nature compared to the FCH *** also discuss some practical matters in applying the *** introduce an averaged Newton preconditioner and a sweeping-friction strategy as heuristic ways to choose good preconditioner *** sweeping-friction strategy exhibits almost as good a performance as the case of the best manually tuned parameters.

关键词： Phase field crystal functionalized Cahn-Hilliard preconditioning Nesterov acceleration nonlinear solver.

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Stroke gets in your eyes: stroke-induced retinal ischemia and the potential of stem cell therapy

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Neural Regeneration Research 2020年第6期15卷 1014-1018页

作者： Chase Kingsbury matt Heyck Brooke Bonsack jea.Young Lee Cesar V.Borlongan Center of Excellence for Aging and Brain Repair University of South Florida College of Medicine

Stroke persists as a global health and economic crisis,yet only two interventions to reduce stroke-induced brain injury *** the clinic,many patients who experience an ischemic stroke often further suffer from retinal ischemia,which can inhibit their ability to make a functional recovery and may diminish their overall quality of *** this,no treatments for retinal ischemia have been *** both cases,ischemia-induced mitochondrial dysfunction initiates a cell loss cascade and inhibits endogenous brain *** cells have the ability to transfer healthy and functional mitochondria not only ischemic neurons,but also to similarly endangered retinal cells,replacing their defective mitochondria and thereby reducing cell *** this review,we encapsulate and assess the relationship between cerebral and retinal ischemia,recent preclinical advancements made using in vitro and in vivo retinal ischemia models,the role of mitochondrial dysfunction in retinal ischemia pathology,and the therapeutic potential of stem cell-mediated mitochondrial ***,we discuss the pitfalls in classic rodent functional assessments and the potential advantages of laser Doppler as a metric of stroke *** studies evaluated in this review highlight stem cell-derived mitochondrial transfer as a novel therapeutic approach to both retinal ischemia and ***,we posit the immense correlation between cerebral and retinal ischemia as an underserved area of study,warranting exploration with the aim of these treating injuries together.

关键词： laser Doppler MCAO mesenchymal stem cells mitochondrial network mitochondrial transfer ophthalmic artery optic nerve oxygen-glucose deprivation regenerative medicine retinal ganglion cells visual impairment

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Fast-tracking regenerative medicine for traumatic brain injury

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Neural Regeneration Research 2020年第7期15卷 1179-1190页

作者： Brooke Bonsack matt Heyck Chase Kingsbury Blaise Cozene Nadia Sadanandan jea.Young Lee Cesar V. Borlongan Center of Excellence for Aging and Brain Repair University of South Florida College of Medicine

Traumatic brain injury remains a global health crisis that spans all demographics,yet there exist limited treatment options that may effectively curtail its lingering *** brain injury pathology entails a progression from primary injury to inflammation-mediated secondary cell *** this inflammation as a means of ameliorating the greater symptomology of traumatic brain injury has emerged as an attractive treatment *** this review,we recapitulate and evaluate the important developments relating to regulating traumatic brain injury-induced neuroinflammation,edema,and blood-brain barrier disintegration through pharmacotherapy and stem cell *** these studies of stand-alone treatments have yielded some positive results,more therapeutic outcomes have been documented from the promising area of combined drug and stem cell *** the facilitatory properties of certain pharmaceuticals with the anti-inflammatory and regenerative effects of stem cell transplants creates a synergistic effect greater than the sum of its *** burgeoning evidence in favor of combined drug and stem cell therapies warrants more elaborate preclinical studies on this topic in order to pave the way for later clinical trials.

关键词： clinical trials combined therapy inflammatory cascade neuroinflammation neuroprotection neurotrauma pharmacotherapy preclinical studies secondary cell death stem cells

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