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As multilayer ceramic capacitors (MLCCs) act like piezo-actuators, printed circuit board (PCB) such as solid-state drive (SSD) vibrates and radiates acoustic noise when input AC electric field’s frequency coincides with the resonance frequency of the PCB. To minimize PCB vibration, in this study, the effect of mounting condition of MLCC was analyzed. Finite element (FE) models of PCB and MLCC was constructed to simulate various mounting condition. Each FE model was verified with experiment in previous studies. First, the influence of solder height was analyzed. The vibration amplitude at the center point of PCB was increased as the solder height increased. Second, the influence of mounting direction and position of MLCC was analyzed. As the vibration level varies considerably with frequency, especially for resonant frequencies, three mode shapes were chosen as the reference mode shapes considering the wave propagation direction. Parametric study was performed by changing the mounting direction by 0 and 90 degree and mounting position within a 3 X 3 grid for each reference mode. Low vibration was observed when MLCCs were mounted at nodal point with orthogonal direction to wave propagation direction.
Dongjoon Kim; Wheejae Kim; Joo Young Yoon; Eunho Lee; No-Cheol Park. Analysis of Influence of Multilayer Ceramic Capacitor Mounting Method on Circuit Board Vibration. Vibration Engineering for a Sustainable Future 2021, 137 -140.
AMA StyleDongjoon Kim, Wheejae Kim, Joo Young Yoon, Eunho Lee, No-Cheol Park. Analysis of Influence of Multilayer Ceramic Capacitor Mounting Method on Circuit Board Vibration. Vibration Engineering for a Sustainable Future. 2021; ():137-140.
Chicago/Turabian StyleDongjoon Kim; Wheejae Kim; Joo Young Yoon; Eunho Lee; No-Cheol Park. 2021. "Analysis of Influence of Multilayer Ceramic Capacitor Mounting Method on Circuit Board Vibration." Vibration Engineering for a Sustainable Future , no. : 137-140.
Vibrotactile feedback has been utilized in various electronic devices with interactive touch surfaces to improve the tactile interaction between the user and the touch surface. Recent studies have proposed vibration rendering methods that enable specific vibration patterns to be generated at desired positions on a touch surface. However, the vibration rendering causes the surface to radiate considerable acoustic noise, which can deteriorate the overall quality of the haptic interaction. This paper proposes a vibration rendering method that reduces the sound radiation from vibrating touch surfaces. In the proposed method, a vibroacoustic model of a touch surface system, combined with measured frequency response functions, is utilized to predict the vibration responses and sound radiation generated by actuator driving signals. Subsequently, a constrained optimization problem is formulated to obtain the optimal driving signals that minimize the estimated sound radiation while rendering a target vibration pattern at desired positions. To validate the proposed method, vibration rendering experiments were conducted on an experimental touch surface system. The driving signals obtained through the proposed method accurately rendered a complex target vibration pattern at the desired positions on the touch surface. Compared to an existing vibration rendering method, the proposed method reduced the estimated sound radiation by 5.1 to 12.3 dB, without structural modifications and hardware additions.
Sangwon Park; Wheejae Kim; Dongjoon Kim; Jaebeom Kwon; Hyejin Bae; No-Cheol Park. Vibrotactile rendering on a touch surface with reduced sound radiation. Journal of Sound and Vibration 2021, 497, 115936 .
AMA StyleSangwon Park, Wheejae Kim, Dongjoon Kim, Jaebeom Kwon, Hyejin Bae, No-Cheol Park. Vibrotactile rendering on a touch surface with reduced sound radiation. Journal of Sound and Vibration. 2021; 497 ():115936.
Chicago/Turabian StyleSangwon Park; Wheejae Kim; Dongjoon Kim; Jaebeom Kwon; Hyejin Bae; No-Cheol Park. 2021. "Vibrotactile rendering on a touch surface with reduced sound radiation." Journal of Sound and Vibration 497, no. : 115936.
Existing elastic analysis methods cannot be adhered to in order to assess the structural integrity of a reactor vessel and internals for a beyond design basis earthquake. Elasto-plastic analysis methods are required, and the factors that affect the elasto-plastic behavior of reactor materials should be taken into account. In this study, a material behavior model was developed that considers the irradiation embrittlement effect, which affects the elasto-plastic behavior of the reactor material. This was used to perform the elasto-plastic time history analyses of the reactor vessel and its internals for beyond design basis earthquake. For this investigation, appropriate beyond design basis earthquakes and reliable finite element models were used. Based on the analysis results, consideration was given to the load reduction effect and the margin change. These were transferred to the internals due to the plastic deformation of the reactor vessel.
Sang-Jeong Lee; Eun-Ho Lee; Changkyun Lee; No-Cheol Park; Youngin Choi; Changsik Oh. Investigation of seismic responses of reactor vessel and internals for beyond-design basis earthquake using elasto-plastic time history analysis. Nuclear Engineering and Technology 2020, 53, 988 -1003.
AMA StyleSang-Jeong Lee, Eun-Ho Lee, Changkyun Lee, No-Cheol Park, Youngin Choi, Changsik Oh. Investigation of seismic responses of reactor vessel and internals for beyond-design basis earthquake using elasto-plastic time history analysis. Nuclear Engineering and Technology. 2020; 53 (3):988-1003.
Chicago/Turabian StyleSang-Jeong Lee; Eun-Ho Lee; Changkyun Lee; No-Cheol Park; Youngin Choi; Changsik Oh. 2020. "Investigation of seismic responses of reactor vessel and internals for beyond-design basis earthquake using elasto-plastic time history analysis." Nuclear Engineering and Technology 53, no. 3: 988-1003.
This paper presents a new method to compute the sound radiation emanating from a thin plate structure due to complex inputs that include normal force and in-plane bending moments. A set of new formulas for the sound radiation of baffled and unbaffled plates are derived by substituting the moment components of the plates with the equivalent couples using finite difference analysis. This approach allows to calculate sound power purely by the input location and amplitude of each component. Thus, it enables faster, more accurate calculations than the existing methods such as the average radiation efficiency analysis and the radiation mode analysis. Based on these calculations, the vibroacoustic characteristics of a simply supported rectangular plate are analyzed. The computational results are in good agreement with the finite element analysis results. It is suggested to keep the grid spacing less than 2.5% of the shortest dimension of the target structure to accurately calculate the moment mobility. Accurate sound power can also be obtained by downsampling the grid to satisfy ka<0.2 within the frequency band of interest. Furthermore, a sound reduction method is proposed by analyzing each structural mode's contribution to the sound radiation. Using the proposed methodology, sound power at a specific frequency or multi-frequency range can be reduced or amplified by changing the location and angle of the complex inputs.
Dongjoon Kim; No-Cheol Park. Calculation and reduction of sound radiation from a thin plate structure excited by complex inputs. Journal of Sound and Vibration 2020, 484, 115517 .
AMA StyleDongjoon Kim, No-Cheol Park. Calculation and reduction of sound radiation from a thin plate structure excited by complex inputs. Journal of Sound and Vibration. 2020; 484 ():115517.
Chicago/Turabian StyleDongjoon Kim; No-Cheol Park. 2020. "Calculation and reduction of sound radiation from a thin plate structure excited by complex inputs." Journal of Sound and Vibration 484, no. : 115517.
In this paper, we report an optical system that can effectively enhance the resolution of continuous-wave (CW) stimulated emission depletion (STED) microscopy by applying an amplitude-modulated azimuthally polarized light with vortex phase (AV) as an excitation beam. Based on the vector field diffraction theory, we analyzed electric fields near the focal plane for various polarization states and rotationally symmetric amplitude modulation conditions. From the analysis, it was found that by applying the amplitude modulated AV beam by the ring-shaped blocking aperture, the resolution in the lateral direction can be improved while minimizing the degradation of the resolution in the axial direction. The reported novel excitation method was experimentally verified based on the imaging of gold beads and fluorescent nano-beads. Accordingly, it was confirmed that the lateral resolution was improved by ~20% and the spot elongation in the axial direction was effectively suppressed.
Geon Lim; Wan-Chin Kim; No-Cheol Park. Resolution enhancement in continuous-wave stimulated emission depletion microscopy by excitation beam with modulated vortex-phased azimuthally polarized light. Optics and Lasers in Engineering 2020, 134, 106253 .
AMA StyleGeon Lim, Wan-Chin Kim, No-Cheol Park. Resolution enhancement in continuous-wave stimulated emission depletion microscopy by excitation beam with modulated vortex-phased azimuthally polarized light. Optics and Lasers in Engineering. 2020; 134 ():106253.
Chicago/Turabian StyleGeon Lim; Wan-Chin Kim; No-Cheol Park. 2020. "Resolution enhancement in continuous-wave stimulated emission depletion microscopy by excitation beam with modulated vortex-phased azimuthally polarized light." Optics and Lasers in Engineering 134, no. : 106253.
We developed F-theta raster scanning optics for high-resolution ultraviolet (UV) beam direct micro-patterning, capable of machining on a 300-mm wide image with a confined beam spot of less than 20 μm, a 13.5% spot size. To achieve the imaging performance with resolution, F-theta optics based on synthetic silica glass were designed using a high-power laser light source with a wavelength of 355 nm. In addition, to improve the difficulty of optical alignment in conventional systems and the scan linearity between the scan angle and exposing position, F-theta scanning optics were designed to contain two lenses with a rotationally asymmetric high-order polynomial surface. The designed optical system showed a performance of 20 ± 2 μm at the full width of a 1/e2 maximum intensity value through a 0.8 mm focal depth. The scanning linearity error and root-mean-square (RMS) wavefront error were designed to be less than 0.2% and 0.05 λ, respectively. The design performance was verified using optical characteristic measurements and actual patterning experiments with the optics composed of proto lenses
Jongbok Park; Hyun Choi; Geon Lim; Dong-Kil Lee; No-Cheol Park; Wan-Chin Kim. Development of a wide-width raster scanning optical system for high-resolution ultraviolet laser direct micro-patterning. Optics and Lasers in Engineering 2020, 134, 106179 .
AMA StyleJongbok Park, Hyun Choi, Geon Lim, Dong-Kil Lee, No-Cheol Park, Wan-Chin Kim. Development of a wide-width raster scanning optical system for high-resolution ultraviolet laser direct micro-patterning. Optics and Lasers in Engineering. 2020; 134 ():106179.
Chicago/Turabian StyleJongbok Park; Hyun Choi; Geon Lim; Dong-Kil Lee; No-Cheol Park; Wan-Chin Kim. 2020. "Development of a wide-width raster scanning optical system for high-resolution ultraviolet laser direct micro-patterning." Optics and Lasers in Engineering 134, no. : 106179.
Vibration is a mechanical phenomenon and exists throughout society. The vibrations in daily life would cause emotional discomfort as well as physical fatigue. Vibration even can give a life threat depending on its magnitude. Vibration is one of the significantly important factors to consider for the safety of the overall society, and therefore study of vibration reduction is indispensable. This paper presents a novel tunable electromagnetic vibration absorber based on an elastic metamaterial. The electromagnetic vibration absorber is a lattice structure dynamic model comprising elastic metamaterial unit cells having negative refractive index property and interconnected by springs. To verify the tunability of the elastic-metamaterial-based vibration absorber, the electromagnetic stiffness change in a finite element (FE) model of the electromagnet was analyzed through a parametric study of the air gap size, internal composition of the electromagnet, and amount of current. The conditions under which the electromagnet generates the highest electromagnetic stiffness were also explored. Each different value of electromagnetic stiffness obtained from the parametric studies was used for FE analysis of the dynamic model to investigate the influence on bandgap variations. The results reveal that the variation of electromagnetic stiffness has an effect on the location and bandwidth of bandgap. Moreover, vibration reduction was achieved due to the structural aspects of the dynamic model and the negative refractive index property of the elastic metamaterial. It is demonstrated that the elastic metamaterial vibration absorber is tunable in real time with the change of electromagnetic stiffness and has vibration reduction effect in various frequency ranges.
Junsun Yoo; No-Cheol Park. Bandgap analysis of a tunable elastic-metamaterial-based vibration absorber with electromagnetic stiffness. Microsystem Technologies 2020, 26, 3339 -3348.
AMA StyleJunsun Yoo, No-Cheol Park. Bandgap analysis of a tunable elastic-metamaterial-based vibration absorber with electromagnetic stiffness. Microsystem Technologies. 2020; 26 (11):3339-3348.
Chicago/Turabian StyleJunsun Yoo; No-Cheol Park. 2020. "Bandgap analysis of a tunable elastic-metamaterial-based vibration absorber with electromagnetic stiffness." Microsystem Technologies 26, no. 11: 3339-3348.
We propose a configuration of Fourier ptychographic microscopy (FPM) to modulate the focus to a large extent. FPM is widely used to obtain high-resolution images in a wide field of view. A conjugation mirror with an axially scannable mirror is introduced to conventional FPM to extend the focus range. The proposed FPM provides a wider field of view with higher resolution compared to general microscopy using the same numerical aperture. In addition, it can measure a wider focus range. Therefore, it is expected to be applied to volumetric samples more easily compared to FPM. The proposed technique is validated by measuring resolution while moving the United States Air Force resolution chart up to ± 2 mm in the axial direction and experimentally verified by measuring a volumetric sample with a depth of 4 mm created using bead with 1 μm of diameter.
Jinsang Lim; Guk-Jong Choi; Hyun Choi; No-Cheol Park. Fourier ptychographic microscopy for extended focus range with conjugated optics. Optics and Lasers in Engineering 2020, 129, 106080 .
AMA StyleJinsang Lim, Guk-Jong Choi, Hyun Choi, No-Cheol Park. Fourier ptychographic microscopy for extended focus range with conjugated optics. Optics and Lasers in Engineering. 2020; 129 ():106080.
Chicago/Turabian StyleJinsang Lim; Guk-Jong Choi; Hyun Choi; No-Cheol Park. 2020. "Fourier ptychographic microscopy for extended focus range with conjugated optics." Optics and Lasers in Engineering 129, no. : 106080.
In this paper, a space tether with pendulum-type elastic metamaterials is constructed as a scaled model considering initial tension of a tether cable. A similarity analysis is used to design the scaled model to ensure that it has similar dynamic characteristics as that of a real tether cable. The pendulum-type elastic metamaterials are used to produce a bandgap in the measurable frequency range. To investigate the bandgap of the metamaterials, a ground experiment that can excite the scaled model of the tether cable is proposed. The experiment results of the harmonic responses for the scaled model for external shocks indicate that the bandgap is attributed to beam resonance. The correlation between the natural frequency of the beam and the bandgap is provided, and the deformation shapes of the metamaterial in the bandgap are measured.
Joo Young Yoon; Weon Keun Song; No-Cheol Park. Experiment and analysis of a space tether with pendulum-type elastic metamaterials. International Journal of Mechanical Sciences 2020, 177, 105557 .
AMA StyleJoo Young Yoon, Weon Keun Song, No-Cheol Park. Experiment and analysis of a space tether with pendulum-type elastic metamaterials. International Journal of Mechanical Sciences. 2020; 177 ():105557.
Chicago/Turabian StyleJoo Young Yoon; Weon Keun Song; No-Cheol Park. 2020. "Experiment and analysis of a space tether with pendulum-type elastic metamaterials." International Journal of Mechanical Sciences 177, no. : 105557.
In this Letter, a quantitative measurement method with an extended axial range in low-coherence light digital holography is presented. Based on the characteristics of the light source, the degree of coherence and phase values are obtained. Because the degree of coherence is modulated with respect to the optical path difference, it can be used to remove the 2π ambiguity of the phase, without the use of numerical or dual-wavelength methods. The mathematical procedures from three phase-shifting holograms are numerically described. From experimental results, the accurate measurements of a sample with high step are presented to confirm the effectiveness.
Sungbin Jeon; Janghyun Cho; Liangcai Cao; No-Cheol Park. Digital holography free of 2π ambiguity, using coherence modulation. Optics Letters 2019, 44, 4626 -4629.
AMA StyleSungbin Jeon, Janghyun Cho, Liangcai Cao, No-Cheol Park. Digital holography free of 2π ambiguity, using coherence modulation. Optics Letters. 2019; 44 (19):4626-4629.
Chicago/Turabian StyleSungbin Jeon; Janghyun Cho; Liangcai Cao; No-Cheol Park. 2019. "Digital holography free of 2π ambiguity, using coherence modulation." Optics Letters 44, no. 19: 4626-4629.
CW STED nanoscopy using illumination of continuous wave is considerably easy and less expensive to construct compared with the pulsed STED nanoscopy. In this study, to improve the resolution of CW STED nanoscopy, we analyzed the imaging characteristics of CW STED nanoscopy by amplitude modulation of incident light flux of the excitation beam illumination considering the polarization state and geometry of the pupil mask for amplitude modulation. We analyzed the imaging characteristics of STED nanoscopy by applying the characteristic, which shows an extremely confined electric field in transverse direction when the light waves with high spatial frequencies and with the same polarization direction are diffracted and interfered in the focal region. By applying linearly polarized illumination and the mixed-shaped aperture composed of the bow tie-shaped blocking area and the circular blocking aperture area, we analyzed that imaging resolution can be enhanced above 20% higher than the resolution of the conventional CW STED nanoscopy.
Geon Lim; No-Cheol Park; Wan-Chin Kim. Analysis on improvement in resolution by excitation beam modulation in stimulated emission depletion nanoscopy. Optical Review 2019, 26, 512 -521.
AMA StyleGeon Lim, No-Cheol Park, Wan-Chin Kim. Analysis on improvement in resolution by excitation beam modulation in stimulated emission depletion nanoscopy. Optical Review. 2019; 26 (5):512-521.
Chicago/Turabian StyleGeon Lim; No-Cheol Park; Wan-Chin Kim. 2019. "Analysis on improvement in resolution by excitation beam modulation in stimulated emission depletion nanoscopy." Optical Review 26, no. 5: 512-521.
In this paper, we present a pendulum-type elastic metamaterial that can be used to absorb the shock of a tether system. A tether system comprises a long and thin cable, so the resonant part of the elastic metamaterial should be attached to outside the cable. The unit cell of the elastic metamaterial consists of three strings and one ring, and strings are attached to the tether cable and reduces the shock transmitted to the satellite. We used modal analysis to find mode shapes of the unit cell of the elastic metamaterial that do not deform when in contact with the tether cable. A harmonic analysis on the properties of the strings confirmed the presence of bandgaps for the pendulum-type metamaterial because of the lateral resonance of the strings. The effect of the unit cell design parameters on the bandgaps were also investigated.
Joo Young Yoon; Weon Keun Song; No-Cheol Park. Pendulum-type elastic metamaterial for reducing the vibration of a space tether. Acta Astronautica 2019, 162, 359 -366.
AMA StyleJoo Young Yoon, Weon Keun Song, No-Cheol Park. Pendulum-type elastic metamaterial for reducing the vibration of a space tether. Acta Astronautica. 2019; 162 ():359-366.
Chicago/Turabian StyleJoo Young Yoon; Weon Keun Song; No-Cheol Park. 2019. "Pendulum-type elastic metamaterial for reducing the vibration of a space tether." Acta Astronautica 162, no. : 359-366.
The light detection and ranging (LiDAR) technology is based on irradiating near-infrared light and measuring the time-of-flight of the scattered light in an object. This technology is becoming increasingly important, as the requirement of three-dimensional camera technology for future autonomous vehicles is on the rise. In this study, we propose an ultra-wide field-of-view (FOV) optical system for LiDAR that can sequentially scan a beam emitted from a high power laser through a small beam steering system using a liquid lens and a fisheye lens. The proposed optical system consists of a series of liquid lenses for beam steering, a commercial fisheye lens with a wide FOV, and a relay optics to effectively conjugate the intermediate image planes of the two lens systems. To verify theoretical feasibility, we have designed a practical optical system with an FOV of approximately 170°, which is much higher than the FOVs in any other non-rotating LiDAR systems.
Hyun Choi; No-Cheol Park; Wan-Chin Kim. Optical system design for light detection and ranging with ultra-wide field-of-view using liquid lenses. Microsystem Technologies 2019, 26, 121 -131.
AMA StyleHyun Choi, No-Cheol Park, Wan-Chin Kim. Optical system design for light detection and ranging with ultra-wide field-of-view using liquid lenses. Microsystem Technologies. 2019; 26 (1):121-131.
Chicago/Turabian StyleHyun Choi; No-Cheol Park; Wan-Chin Kim. 2019. "Optical system design for light detection and ranging with ultra-wide field-of-view using liquid lenses." Microsystem Technologies 26, no. 1: 121-131.
The lateral resolution of continuous wave (CW) stimulated emission depletion (STED) microscopy is enhanced about 12% by applying annular‐shaped amplitude modulation to the radially polarized excitation beam. A focused annularly filtered radially polarized excitation beam provides a more condensed point spread function (PSF), which contributes to enhance effective STED resolution of CW STED microscopy. Theoretical analysis shows that the FWHM of the effective PSF on the detection plane is smaller than for conventional CW STED. Simulation shows the donut‐shaped PSF of the depletion beam and confocal optics suppress undesired PSF sidelobes. Imaging experiments agree with the simulated resolution improvement. This article is protected by copyright. All rights reserved.
Geon Lim; Wan‐Chin Kim; Seunghee Oh; Hyungsuk Lee; No‐Cheol Park. Enhanced lateral resolution in continuous wave stimulated emission depletion microscopy using tightly focused annular radially polarized excitation beam. Journal of Biophotonics 2019, 12, e201900060 .
AMA StyleGeon Lim, Wan‐Chin Kim, Seunghee Oh, Hyungsuk Lee, No‐Cheol Park. Enhanced lateral resolution in continuous wave stimulated emission depletion microscopy using tightly focused annular radially polarized excitation beam. Journal of Biophotonics. 2019; 12 (9):e201900060.
Chicago/Turabian StyleGeon Lim; Wan‐Chin Kim; Seunghee Oh; Hyungsuk Lee; No‐Cheol Park. 2019. "Enhanced lateral resolution in continuous wave stimulated emission depletion microscopy using tightly focused annular radially polarized excitation beam." Journal of Biophotonics 12, no. 9: e201900060.
Nuclear power generates a large portion of the energy used today and plays an important role in energy development. To ensure safe nuclear power generation, it is essential to conduct an accurate analysis of reactor structural integrity. Accordingly, in this study, a methodology for obtaining accurate structural responses to the combined seismic and reactor coolant loads existing prior to the shutdown of a nuclear reactor is proposed. By applying the proposed analysis method to the reactor vessel internals, it is possible to derive the seismic responses considering the influence of the hydraulic loads present during operation for the first time. The validity of the proposed methodology is confirmed in this research by using the finite element method to conduct seismic and hydraulic load analyses of the advanced APR1400 1400 MWe power reactor, one of the commercial reactors. The structural responses to the combined applied loads are obtained using displacement-based and stress-based superposition methods. The safety of the subject nuclear reactor is then confirmed by analyzing the design margin according to the American Society for Mechanical Engineers (ASME) evaluation criteria, demonstrating the promise of the proposed analysis method.
Jong-Beom Park; Sang-Jeong Lee; Eun-Ho Lee; No-Cheol Park; Yong-Beom Kim. Seismic responses of nuclear reactor vessel internals considering coolant flow under operating conditions. Nuclear Engineering and Technology 2019, 51, 1658 -1668.
AMA StyleJong-Beom Park, Sang-Jeong Lee, Eun-Ho Lee, No-Cheol Park, Yong-Beom Kim. Seismic responses of nuclear reactor vessel internals considering coolant flow under operating conditions. Nuclear Engineering and Technology. 2019; 51 (6):1658-1668.
Chicago/Turabian StyleJong-Beom Park; Sang-Jeong Lee; Eun-Ho Lee; No-Cheol Park; Yong-Beom Kim. 2019. "Seismic responses of nuclear reactor vessel internals considering coolant flow under operating conditions." Nuclear Engineering and Technology 51, no. 6: 1658-1668.
Worldwide, high-speed rail is becoming an increasingly popular and efficient means of transport. However, increasing the speed of a train leads to major reductions in stability and ride comfort. Here, we develop a tubular permanent magnet actuator to overcome these problems. To increase actuator thrust, the electromagnetic circuit requires a high current and, thus, becomes hot. We use a water cooling system with 12 straight copper channels to reduce the temperature. We calculate heat transfer coefficients using empirical convection correlations between laminar flow in the channels and experimental results. The predicted, tube surface temperatures correlated well with the experimental data. We evaluated the effects of flow rate and initial water temperature on various design parameters. The cooling system allowed application of a current greater than 100 A, developing a thrust force of over 8000 N. Thus, the system was robust under harsh operating conditions. We measured the thrust and cogging forces and the performance of the water cooling system in terms of the maximum acceptable temperature. The thrust was high and the cogging torque was low, greatly reducing lateral vibration; the temperature remained below the acceptable maximum.
Ng-Wook Kim; Jung-Hyun Woo; Kyoung-Su Park. Investigation of the thermal effect of a tubular permanent magnet actuator with a water cooling channel for active lateral suspension of a high-speed train. Advances in Mechanical Engineering 2019, 11, 1 .
AMA StyleNg-Wook Kim, Jung-Hyun Woo, Kyoung-Su Park. Investigation of the thermal effect of a tubular permanent magnet actuator with a water cooling channel for active lateral suspension of a high-speed train. Advances in Mechanical Engineering. 2019; 11 (3):1.
Chicago/Turabian StyleNg-Wook Kim; Jung-Hyun Woo; Kyoung-Su Park. 2019. "Investigation of the thermal effect of a tubular permanent magnet actuator with a water cooling channel for active lateral suspension of a high-speed train." Advances in Mechanical Engineering 11, no. 3: 1.
Purpose: Excessive bulking force during ureteral access sheath placement may induce injury. The sliding friction between surfaces can be reduced with the application of ultrasonic vibration. We investigated the efficacy and safety of an ultrasonic vibration transducing device for reducing the maximal ureteral access sheath insertion force (UASIF). Materials and Methods: A device was developed for transducing ultrasonic longitudinal-axis vibration onto the ureteral access sheath at an adjustable amplitude and frequency while measuring the degree of UASIF. In the pilot study, six porcine models were used to investigate the optimal amplitude and frequency of vibration, and to calculate sample size. Twelve porcine models were utilized in a randomized controlled trial. Resected ureters were pathologically evaluated for ureteral injury. Results: The transduction of ultrasonic vibration at an amplitude of 0.04 g and a frequency of 18,000 Hz resulted in a maximal UASIF reduction of 36.4% (interquartile range 32.7-43.1). Maximal UASIF tended to decrease with increasing vibration frequency. No significant differences in UASIF reductions were observed according to amplitude. In the randomized controlled trial, the maximal UASIF reduction was 37.0% (interquartile range 21.4-44.2). Grade II injury was pathologically diagnosed in 8.3% (1/12) of the ureters in both groups. Conclusions: The transduction of ultrasonic longitudinal-axis vibration onto the ureteral access sheath reduces maximal UASIF and does not harm the ureter. Reducing the velocity of sheath insertion may further reduce maximal UASIF.
Kyo Chul Koo; Kwang Suk Lee; Miss Gyu Rang Min; Hye Sun Lee; Beom Jin Lim; Ji Sup Kim; Dongwook Kim; No-Cheol Park. Efficacy and Safety of Ultrasonic Longitudinal-Axis Vibration for the Reduction of Ureteral Access Sheath Insertion Force: A Randomized Controlled Trial in a Porcine Model. Journal of Endourology 2019, 33, 140 -145.
AMA StyleKyo Chul Koo, Kwang Suk Lee, Miss Gyu Rang Min, Hye Sun Lee, Beom Jin Lim, Ji Sup Kim, Dongwook Kim, No-Cheol Park. Efficacy and Safety of Ultrasonic Longitudinal-Axis Vibration for the Reduction of Ureteral Access Sheath Insertion Force: A Randomized Controlled Trial in a Porcine Model. Journal of Endourology. 2019; 33 (2):140-145.
Chicago/Turabian StyleKyo Chul Koo; Kwang Suk Lee; Miss Gyu Rang Min; Hye Sun Lee; Beom Jin Lim; Ji Sup Kim; Dongwook Kim; No-Cheol Park. 2019. "Efficacy and Safety of Ultrasonic Longitudinal-Axis Vibration for the Reduction of Ureteral Access Sheath Insertion Force: A Randomized Controlled Trial in a Porcine Model." Journal of Endourology 33, no. 2: 140-145.
A multilayer ceramic capacitor (MLCC) contains layers of ceramics as the dielectric materials. It has been known that Class 2 MLCCs, made of ferroelectric ceramics such as barium titanate, tend to suffer from electromechanical coupling hence vibration, which leads to the generation of acoustic humming noise, a source of annoyance in many modern electronic devices. In this article, a repoling method to control the electromechanical properties and the resulting vibration of MLCCs is presented. The repoling protocol hinges on the understanding that two independent mechanisms are responsible for the electromechanical coupling in MLCCs: piezoelectricity and electrostriction of the ceramic layers. The vibration due to piezoelectricity is linearly proportional to the input voltage, whereas the vibration due to electrostriction shows a quadratic dependence. Given the DC bias and the AC input voltage under normal operating conditions, the vibration is composed of the fundamental component at the frequency of the AC input and the second harmonic component spawned by the quadratic nonlinearity of electrostriction. It is demonstrated that by engineering the coefficients of piezoelectricity and electrostriction of the ceramic layers through a carefully designed repoling treatment, vibration reduction can be achieved for both the fundamental and second harmonic components. Especially, the fundamental component of vibration can be reduced significantly, as the piezoelectric effect is made to offset the electrostrictive effect.
Won-Suk Ohm; Dongjoon Kim; Byung-Han Ko; No-Cheol Park. Control of electromechanical properties of multilayer ceramic capacitors for vibration reduction. Journal of the American Ceramic Society 2017, 101, 1982 -1990.
AMA StyleWon-Suk Ohm, Dongjoon Kim, Byung-Han Ko, No-Cheol Park. Control of electromechanical properties of multilayer ceramic capacitors for vibration reduction. Journal of the American Ceramic Society. 2017; 101 (5):1982-1990.
Chicago/Turabian StyleWon-Suk Ohm; Dongjoon Kim; Byung-Han Ko; No-Cheol Park. 2017. "Control of electromechanical properties of multilayer ceramic capacitors for vibration reduction." Journal of the American Ceramic Society 101, no. 5: 1982-1990.
This paper describes the finite element (FE)-based design of a slotted tubular permanent magnet actuator (TPMA) used in railway vehicle active lateral secondary suspension that improves the actuator’s thrust and lowers its cogging force under thermal and geometric constraints. To consider the electromagnetic and thermal fields and the complex interactions among the design variables, design was carried out in an electromagnet and thermal field environment using accurate and time-effective FE analysis. A six-slot prototype model was fabricated to estimate critical thermal parameters, which are difficult to compute without experiments. Three-dimensional FE analysis using the determined thermal parameters was adopted to calculate the precise thermal distribution of the TPMA and verify the forced air-cooling effect. A prototype TPMA with a quasi-Halbach array of permanent magnets and a moving magnet was manufactured through the FE-based design process; the dynamic, electromagnetic, and thermal characteristics of the prototype TPMA were validated experimentally.
Jun-Ho Yoon; Dongwook Kim; No-Cheol Park; Young-Pil Park. Design of a Tubular Permanent Magnet Actuator for Active Lateral Secondary Suspension of a Railway Vehicle. Applied Sciences 2017, 7, 152 .
AMA StyleJun-Ho Yoon, Dongwook Kim, No-Cheol Park, Young-Pil Park. Design of a Tubular Permanent Magnet Actuator for Active Lateral Secondary Suspension of a Railway Vehicle. Applied Sciences. 2017; 7 (2):152.
Chicago/Turabian StyleJun-Ho Yoon; Dongwook Kim; No-Cheol Park; Young-Pil Park. 2017. "Design of a Tubular Permanent Magnet Actuator for Active Lateral Secondary Suspension of a Railway Vehicle." Applied Sciences 7, no. 2: 152.
Radiation therapy system is preferred to surgery for the most cancer because it is noninvasive. In radiotherapy, respiratory motion is an obstacle of high-precision therapy. The patient support system (PSS) is a method to compensate respiratory motion without increasing treatment time. But treatment time could not be decreased dramatically with conventional PSS because it increases duty cycle of linear accelerator (LINAC). To apply multiple LINACs, the conventional PSS is not suitable as the structure of PSS interrupt workspace of LINACs. In this study, we designed a new moving bed to apply multiple LINACs as well under the bed. A force distribution method and dynamics of the bed were identified. Rigid body simulation model was made to verify that the bed can operate well as expected. And a real size model was manufactured on a basis of the simulation model. Experiments were conducted to identify that the bed can move in desired objectives.
Ngwook Kim; Jun-Ho Yoon; No-Cheol Park; Seungho Kim; Yeong-Geol Bae; Kyung-Min Jeong. Design of a moving bed for a radiation therapy system with multiple linear accelerators. Microsystem Technologies 2016, 23, 5239 -5245.
AMA StyleNgwook Kim, Jun-Ho Yoon, No-Cheol Park, Seungho Kim, Yeong-Geol Bae, Kyung-Min Jeong. Design of a moving bed for a radiation therapy system with multiple linear accelerators. Microsystem Technologies. 2016; 23 (11):5239-5245.
Chicago/Turabian StyleNgwook Kim; Jun-Ho Yoon; No-Cheol Park; Seungho Kim; Yeong-Geol Bae; Kyung-Min Jeong. 2016. "Design of a moving bed for a radiation therapy system with multiple linear accelerators." Microsystem Technologies 23, no. 11: 5239-5245.