Publications by authors named "Kyung-Chun Kim"

Article Synopsis
  • The study investigates a 3D simulation of magnetorheological (MR) conical bearings, focusing on viscous dissipation and using a conjugated heat transfer approach.
  • The behavior of MR fluids is modeled using the Bingham-Papanastasiou equation, considering how viscosity and yield stress change with magnetic field intensity and temperature.
  • The research employs a multidisciplinary approach with fluid dynamics, magnetism, and heat transfer, using finite element methods to solve governing equations, and highlights the significant impact of temperature on the performance of MR conical bearings.
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This paper presents an analytical solution for fluid flow and heat transfer inside arbitrarily-shaped triangular ducts for the first time. The former analytical solutions are limited to the special case of isosceles triangular ducts. The literature has no report about the analytical solution for the general case of arbitrarily-shaped triangular ducts.

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  • This paper introduces a new analytical solution for understanding how viscoelastic lubrication works in journal bearings using the perturbation method.
  • It utilizes the nonlinear Giesekus model to analyze factors like fluid elasticity, shear-thinning behavior, and strain-hardening effects on lubrication performance.
  • The findings reveal that increased fluid elasticity significantly boosts load capacity in bearings, showing different behaviors in linear and exponential regions related to characteristic parameters like mobility factor and Weissenberg number.
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This study investigates the effect of fluid elasticity on axisymmetric droplets colliding with pre-existing liquid films, using both numerical and experimental approaches. The numerical simulations involve solving the incompressible flow momentum equations with viscoelastic constitutive laws using the finite volume method and the volume of fluid (VOF) technique to track the liquid's free surface. Here, the Oldroyd-B model is used as the constitutive equation for the viscoelastic phase.

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A liquid droplet oscillating between two plane electrodes was visualized, and the electrical power generation based on the reverse-electrowetting-on-dielectric (REWOD) phenomenon was measured. For the upper plate, a hydrophobic surface treated by PTFE was used, and the lower plate was tested using the hydrophilic surface properties of ITO glass. To analyze the dynamic behavior of an oscillating liquid bridge, a modeling study was carried out using the phase field method based on the finite element method.

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  • Heat transfer is more effective in rectangular channels with open-cell metal foam than in empty channels, but the latter faces issues with high pressure drop.
  • Different configurations of metal foam were tested to balance high heat transfer with reduced pressure drop during boiling of R245fa.
  • The study showed that while fully filled metal foam channels had the best thermal performance, the streamwise pattern model achieved lower pressure drops and performed comparably at high mass fluxes.
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In a new therapeutic technique, called magnetic drug targeting (MDT), magnetic particles carrying therapeutic agents are directed to the target tissue by applying an external magnetic field. Meanwhile, this magnetic field also affects the blood as a biomagnetic fluid. Therefore, it is necessary to select a magnetic field with an acceptable range of influence on the blood flow.

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Open-cell metal foams are porous medium for thermo-fluidic systems. However, their complex geometry makes it difficult to perform time-resolved (TR) measurements inside them. In this study, a TR particle image velocimetry (PIV) method is introduced for use inside open-cell metal foam structures.

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This paper proposes a data augmentation method based on artificial intelligence (AI) to obtain sound level spectrum as predicting the spatial and temporal data of time-resolved three-dimensional Particle Tracking Velocimetry (4D PTV) data. A 4D PTV has used to measure flow characteristics of three side mirror models adopting the Shake-The-Box (STB) algorithm with four high-speed cameras on a robotic arm for measuring industrial scale. Helium filled soap bubbles are used as tracers in the wind tunnel experiment to characterize flow structures around automobile side mirror models.

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Background: Electrical socket outlets are used continuously until a failure occurs because they have no indication of manufacturing date or exchange specifications. For this reason, 659 electrical fires related to electrical socket outlets broke out in the Republic of Korea at 2018 only, an increase year on year. To reduce electrical fires from electrical socket outlets, it is necessary to perform an accelerated test and analyze the thermal, insulation resistance, and material properties of electrical socket outlets by installation years.

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A self-seeding particle method is proposed for particle image velocimetry measurements in closed cycles such as Organic Rankine Cycles. Condensed droplets of vapor are used as tracers in a closed cycle for both subsonic and supersonic regimes. A free jet of R245fa in the vapor phase is examined in a case study with two different nozzle pressure ratios of 5.

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Spatial and temporal variations of the hemodynamic features occur under pulsatile conditions in complex vessel geometry. Wall shear stress affected by the disturbed flow can result in endothelial cell dysfunction, which leads to atherogenesis and thrombosis. Therefore, detailed understanding of the hemodynamic characteristics in a curved stenosed channel is highly important when examining the pathological effects of hemodynamic phenomena on the progression of atherosclerosis.

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  • This paper introduces a mathematical model for laser-induced rapid electro-kinetic patterning (REP) that aims to clarify how particles can be concentrated in a microchannel without damaging them.
  • The model is created using COMSOL(®) software and incorporates various equations, such as AC electrothermal flow and dielectrophoresis, to analyze how different factors affect particle focusing.
  • The findings demonstrate that laser illumination creates a toroidal microvortex, aided by ACET and DEP forces, which effectively concentrates particles depending on specific parameters like AC frequency, particle size, and DEP velocity.
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Technologies that can enable concentration of low-abundance biomarkers are essential for early diagnosis of diseases. In this study, an optoelectrokinetic technique, termed Rapid Electrokinetic Patterning (REP), was used to enable dynamic particle manipulation in bead-based bioassays. Various manipulation capabilities, such as micro/nanoparticle aggregation, translation, sorting and patterning, were developed.

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Background: Although there has been continuous evolution in the management of fracture fixation, treatment for osteoporotic proximal humerus fractures is still challenging to trauma surgeons. The purpose of this study was to report early failure of the locking compression plate (LCP) in the treatment of osteoporotic proximal humerus fracture and characterize the mode of failure.

Methods: Nine patients, older than 65 years, underwent internal fixation with the use of a locking compression plate and had early failure within 4 weeks postoperatively.

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  • An amperometric immunosensor was developed for detecting osteoproteogerin (OPG) by attaching a monoclonal antibody to gold nanoparticles on a conductive polymer.
  • The size of the gold nanoparticles was controlled during the electrochemical deposition and characterized using advanced imaging techniques, confirming the successful attachment of the antibody.
  • The immunosensor operates on a competitive immunoassay principle with a detection range of 2.5 to 25 pg/ml and a lower detection limit of 2 pg/ml, effectively identifying OPG in real human samples.
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A new concept using a near-field thermometry sensor is presented, employing atipless microcantilever experimentally validated for an aqueous medium within approximatelyone cantilever width from the solid interface. By correlating the thermal Brownian vibratingmotion of the microcantilever with the surrounding liquid temperature, the near-fieldmicroscale temperature distributions at the probing site are determined at separation distancesof z = 5, 10, 20, and 40 μm while the microheater temperature is maintained at 50°C, 70°C, or90°C. In addition, the near-field correction of the correlation is discussed to account for thequenched cantilever vibration frequencies, which are quenched due to the no-slip solid-wallinterference.

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  • Osteoporosis is a bone disease that needs early detection, and biomarkers play a crucial role in identifying it through clinical proteomics.
  • Various testing techniques, including BMD testing and optical/electrochemical methods, have been compared for effectiveness.
  • Recent findings show new peaks in UV-visible spectroscopy and high sensitivity in electrochemical techniques, making them ideal for creating a new bioMEMS chip for bone marker detection.
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  • The article discusses a new method for creating spherical polymer microcapsules using microfluidic technology and atom transfer radical polymerization (ATRP).
  • The process involves forming spherical droplets of an organic polymer solution in a water phase within a T-junction microchannel, with flow conditions tailored to optimize droplet generation.
  • The study also evaluates the microcapsules' effectiveness for molecule storage and controlled release by encapsulating them with Congo-red dye and measuring release performance through temperature-controlled UV-VIS spectroscopy.
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