• Journal of Korean Foot and Ankle Society
• /
• v.23 no.4
• /
• pp.183-188
• /
• 2019

Purpose: Bone contusion is usually treated with conservative therapy for 3 months. Bone contusion around knee and hip joints has been extensively reported on, but there are scant reports on this condition in foot and ankle joints. This study evaluated the nature, characteristics and location of bone contusion around foot and ankle joints to enlighten clinicians on how to better treat this disease entity. Materials and Methods: We classified bone contusion of the 76 patients into three types (102 sites; 47 ankle sprains, 18 traffic accidents, 11 falls) according to the Costa-Paz system with employing magnetic resonance imaging (MRI), and the study then analyzed the common sites and areas of occurrence according to the mechanism of injury and duration of pain after first conducting conservative therapy. Results: Of the 76 patients (102 sites) on the MRI, 43 case (42.2%) for talus, 19 cases for distal tibia, and 12 cases for calcaneus were involved. The classification, according to the Costa-Paz system, was Type I, 51 cases; Type II, 32 cases; and Type III, 19 cases. The duration of pain after conservative treatment was 12.15±2.17 weeks for Type I, 14.5±2.15 weeks for Type II, and 21.0±3.8 weeks for Type III. Conclusion: The most common location of post-traumatic bone contusion around both the foot and ankle is the talus, distal tibia, and calcaneus. The most common type of injury noted on MRI is a diffuse signal with change of the medullary component (Type I), In cases of bone contusion extending to a subjacent articular surface or disruption or depression of the normal contour of the cortical surface (Types II, III), the patients' pain appears to last longer. Thus, it is necessary to consider a longer period of conservative treatment in cases of Types II and III bone contusion because the patients' pain may last longer than 3 months.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.34 no.6
• /
• pp.480-486
• /
• 2021

Magnetoelectric (ME) composite is composed of a piezoelectric material and a magnetostrictive material. Among various ME structures, 2-2 type layered ME composites are anticipated to be used as high-sensitivity magnetic field sensors and energy harvesting devices especially operating at its resonance modes. Rosen type piezoelectric transducer using piezoelectric material is known to amplify a small electrical input voltage to a large electrical output voltage. The output voltage of these Rosen type piezoelectric transducers can be further enhanced by modifying them into ME composite structures. Herein, we fabricated Rosen type ME composites by sandwiching Rosen type PMN-PZT single crystal between two Ni layers and studied their ME coupling. However, the voltage step-up ratio at the resonance frequency was found to be smaller than the value calculated with α_ME value. The ATILA FEA (Finite Elements Analysis) simulation results showed that the position of the nodal point was changed with the presence of a magnetostrictive layer. Thus, while designing a Rosen type ME composite with high performance in a resonant driving situation, it is necessary to optimize the position of the nodal point by optimizing the thickness or length of the magnetostrictive layer.

• Journal of the Society of Naval Architects of Korea
• /
• v.55 no.4
• /
• pp.321-329
• /
• 2018

Resonance phenomena occurs at large vertical pump which is operating to cool down the hot steam using sea water in the power plant. To avoid the resonance, the natural frequency needs to be isolated about 20% from motor operating speed. Yet, excessive vibration occurs especially at low tide. At first, natural frequency of the whole pump system and each part is calculated using ANSYS. As it is revealed in the previous journal papers that only circular pipe part is related to resonance, the FSI technique is applied for free vibration analysis. The natural frequency is reduced to 60% (compared to that) of the frequency measured in air as it is similar to other published results. And the frequency obtained by finite element analysis is almost same to that obtained from modal test. Based on the accurate finite element model and analysis, design change is tried to avoid the resonance by changing the thickness of pipe and base supporting plate. In stead of doing optimization process, design sensitivity is computed and used to find such designs to avoid resonance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.964-968
• /
• 2007

A helmholtz resonator has been widely used for the purpose of suppressing low frequency noises propagated from various heat and fluid machineries. However, the resonator has demerits that the absorption bandwidth at resonance frequency is very small and a large cavity is necessary. In order to overcome these problems, in this paper, a resonator with perforated panels at the neck and/or in the cavity is proposed. The absorption performances of resonators are measured by two-microphone method and are estimated by transfer matrix method. The experimentally measured values of normal absorption coefficients are agreed well with the corresponding values from the transfer matrix method. By introducing perforated panels at the neck of a resonator, it is shown that the absorption performances and bandwidth have a significant improvement.

• Journal of Sensor Science and Technology
• /
• v.13 no.5
• /
• pp.342-349
• /
• 2004

SK (SPR Kinds) index, which can categorize the complicated measurement methods of surface plasmon resonance by simple method, has been proposed and verified. SK index is composed of three digits, where each digit presents the type of immobilized ligand, the type of illumination and the kinds of varying parameter, sequentially. The measurement method of (33#) series among SK indices shows the possibility of the multi-sensing capability, by which the response of 2-dimensional array of immobilized ligands can be detected simultaneously. The proposed possibility of multi-sensing capability has been verified by the modeling that is based on Fresnel reflection model.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.10
• /
• pp.530-535
• /
• 2001

Resonant-type electronic ballast for a metal halide discharge(MHD) lamp is proposed and implemented for 400W MHD lamp. HID lamps have good color rendition, long life and good focusing capability but they have flickers by acoustic resonance when driven at high frequency. A new control method is employed to remove acoustic resonance related instability in HID lamp. By using the amplitude modulation, a spread spectrum effect is employed on the ballast. The control loop of resonant inverter is analyzed and a current is designed. The ballast consists of a power factor controller, an half-bridge resonant inverter, a simple ignitor and an integrator with OP-amps. The experimental results show the good performance as PF 0.93, ballast loss 22W at output 400W and the conducted EMI level is below 60dBuV.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.7
• /
• pp.111-120
• /
• 1996

In this paper, we proposed an inductance loaded small type open-loop travelling wave antenna model for the suitable VHF/UHF frequency bands moisture measurement systems and analyzed its operating characteristics by galerkin's solution method. This antenna model enables to change the oeprating rsonance frequency from the frequency range 150 Mhz to 1.0 Ghz without changing the antenna design dimensions by only varing the load inductance values and it showed the similar operating charcteristics and narrowband resonance characteristics at each resonance frequencies. Also this model showed the uniformly distriubte dpower radiation characteristics above the loop axis and it can effectively suppress the spurious radiations from its narrowband resonance characteristics.

• Journal of the Korean Ceramic Society
• /
• v.31 no.10
• /
• pp.1133-1140
• /
• 1994

Nonlinear resonance characteristics of transverse type-PZT ceramic resonator were investigated, and their nonlinear coefficients were calculated using the nonlinear theory proposed by Duffing. Resonance characteristics of sample showed nonlinearity by the thermal effects due to driving current. Nonlinear coefficients greatly affected by sample dimension, however comparing with respect to current density, it was almost constant. Nonlinear coefficients were not changed as driving current increased upto 40 mA/$\textrm{cm}^2$, when $\alpha$ and $\beta$ was 920 and -10.6, respectively, while nonlinear coefficients exponentially increased beyond the current density of 40 mA/$\textrm{cm}^2$. Nonlinear coefficients were slightly increased as temperature increased.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.04a
• /
• pp.212-217
• /
• 2008

Acoustic noises generated during motor operation in mechanical system are from electromagnetic, mechanical, aerodynamic, and electrical sources. For identification of mechanical noise origins, misalignment, unbalance, fan shape, resonance, and vibration modes have been extensively considered to describe noise behavior. An experiment-based approach as well as a mathematical approach needs to be adopted for a realistic study into noise and vibration of the motor, because motor noise characteristics differ from type to type due to various noise sources. In this paper, a brushless DC motor for air-conditioner fan is analyzed by finite element method to identify noise source, and the analysis results are verified by experiments, and sensitivity analysis is performed by design of experiments.

• Journal of the Korea Society of Computer and Information
• /
• v.9 no.4 s.32
• /
• pp.93-97
• /
• 2004

This paper proposed that a small type conductor surface open-loop antenna model for the moisture sensor and its operating characteristics were analysed numerically by using the moment methods. The numerical analysis results from this antenna model showed that this antenna could match the input impedance to $50[{\Omega}]$ by changing parameters of the antenna in the frequency range from 300[MHz] to 500[MHz]. This model also showed that the open-loop radius. height and wire width give a tremendous influence on the antenna resonance variation. while the loaded inductance values affects the variation or the input impedance at the resonance frequencies.