• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1225-1229
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• 2018

The Drosophila auditory system consists of four large basal segments: the arista, the funiculus, the pedicel, and the scape. When an acoustic stimulus is applied to the arista and the funiculus their mechanical vibrations are transmitted to chordotonal neurons in Johnston's organ where mechanoelectric transduction arises. We study the mechanotransduction mechanism in the Drosophila auditory system by using a laser Doppler vibrometer (LDV) and extracellular electrophysiology. We find that large and small peaks appear alternatively and that the antenna vibration is asymmetric depending on whether the pedicel and the scape are fixed. Interestingly, we find that this asymmetric vibration accompanies the alternating neural peak structure. Here, we propose a mathematical model to explain the alternating peak structure by using a model consisting of two opposing neurons that are modeled as strings. Generally, strings have tension only when they are elongated. This property allows the alternating neural peaks for asymmetric antenna motion.

• Archives of Plastic Surgery
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• v.32 no.4
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• pp.503-510
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• 2005

If we could predict the necrosis of the flap caused by reperfusion injury, we can minimize the necrosis of the flap by taking appropriate action before necrosis begins. In this study, we examined whether we can predict the survival of flap under reperfusion injury or not, by measuring laser doppler flow meter values. We divided the group into the control and experimental groups corresponding to 6, 8, 9, 10, and 12hours after reperfusion(hours after ligation of auricular central artery). In each group, we examined necrotic change, perfusion unit (PU), serum superoxide dismutase (SOD), glutathione peroxidase, angiography and pathologic findings. No necrosis was observed in the 6 and 8 hours group but 8, 18, 20 hours after ligation, necrosis was observed, Also in each of 9, 10 and 12 hours group (each group consisted of 20 flaps), necrosis were noted. According to the above data, the critical time of necrosis in the auricular skin flap model lies between about 8 to 9 hours. Comparing the PU between the necrosis and non-necrosis groups, the former group showed a mean 39.57 PU increase after 60 min of reperfusion, and the latter group showed a mean increase of 21.21 PU. We can conclude that better flow can dilute oxygen free radical into systemic circulation, and this means less injuries are caused on vessels. Our study implies that if blood flow increase is less than 30 PU, intensive care is needed to save the flap. Additionally, we found significant decrease of serum SOD and glutathione peroxidase in the necrotic group. Therefore, monitoring these serum markers will be helpful in predicting reperfusion injury and supplementing these enzymes could be helpful to save the flap. The laser doppler flow meter is thought to be helpful in clinical circumstances for evaluating the circulation of the flap after the operation. However, more accumulation of clinical studies should be necessary establishing useful clinical data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.607-611
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• 2006

There are several methods to obtain structural vibration for analysis of vibro-acoustic noise. First of all, vibration data can be obtained through the structural analysis using finite element method. Although this method has no need to experiment, the analysis result is unreliable when the structure and the vibration source is complex to model exactly. The second method is to measure vibration using a number of sensors. The analyzed vibro-acoustic noise with directly measured data is setting morereliable when the number of data acquisition points is getting larger. However, it requires large amount of time and effort to measure all vibration data on every node especially when the size of vibrating structure is large. The Modal Expansion Method(MEM), which uses mode information and measurement data, has been introduced to compensate their limits. With a relatively small number of measurement data, the reliable structural vibration for vibro-acoustic noise can be obtained using this semi-analysis method. Although MEM gives reliable result, it is restricted by the number of modes and measurement points. In this paper, structural analysis, direct vibration measurement method and MEM are compared using the simple aluminum box model. Furthermore, the washing machine case is also provided as a comparative example. The Laser Doppler Vibrometer(LDV) was used instead of contact type accelerometer to get vibration data.

• Archives of Plastic Surgery
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• v.47 no.3
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• pp.209-216
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• 2020

Background Perforator flaps have led to a revolution in reconstructive surgery by reducing donor site morbidity. However, many surgeons have witnessed partial flap necrosis. Experimental methods to increase inflow have relied on adding a separate pedicle to the flap. The aim of our study was to experimentally determine whether increasing blood flow in the perforator pedicle itself could benefit flap survival. Methods In 30 male Lewis rats, an extended posterior thigh perforator flap was elevated and the pedicle was dissected to its origin from the femoral vessels. The rats were assigned to three groups: control (group I), acute inflow (group II) and arterial preconditioning (group III) depending on the timing of ligation of the femoral artery distal to the site of pedicle emergence. Digital planimetry was performed on postoperative day (POD) 7 and all flaps were monitored using laser Doppler flowmetry perioperatively and postoperatively in three regions (P1-proximal flap, P2-middle of the flap, P3-distal flap). Results Digital planimetry showed the highest area of survival in group II (78.12%±8.38%), followed by groups III and I. The laser Doppler results showed statistically significant higher values in group II on POD 7 for P2 and P3. At P3, only group II recorded an increase in the flow on POD 7 in comparison to POD 1. Conclusions Optimization of arterial inflow, regardless if performed acutely or as preconditioning, led to increased flap survival in a rat perforator flap model.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.141-148
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• 2003

This paper presents a rotating ann test for assessment of an underwater hybrid navigation system for a semi-autonomous underwater vehicle. The navigation system consists of an inertial measurement unit (IMU), an ultra-short baseline (USBL) acoustic navigation sensor and a doppler velocity log (DVL) accompanying a magnetic compass. The errors of inertial measurement units increase with time due to the bias errors of gyros and accelerometers. A navigational system model is derived to include the error model of the USBL acoustic navigation sensor and the scale effect and bias errors of the DVL, of which the state equation composed of the navigation states and sensor parameters is 25 in the order. The conventional extended Kalman filter was used to propagate the error covariance, update the measurement errors and correct the state equation when the measurements are available. The rotating ann tests are conducted in the Ocean Engineering Basin of KRISO, KORDI to generate circular motion in laboratory, where the USBL system was absent in the basin. The hybrid underwater navigation system shows good tracking performance against the circular planar motion. Additionally this paper checked the effects of the sampling ratio of the navigation system and the possibility of the dead reckoning with the DVL and the magnetic compass to estimate the position of the vehicle.

• Journal of Ocean Engineering and Technology
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• v.31 no.4
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• pp.315-323
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• 2017

This paper presents an integrated navigation system that combines ultra-short baseline (USBL), Doppler velocity log (DVL), and heading measurements for a deep-sea remotely operated vehicle, Hemire. A navigation model is introduced based on the kinematic relation of the position and velocity. The system states are predicted using the navigation model and corrected with the USBL, DVL, and heading measurements using the Kalman filter. The performance of the navigation system was confirmed through re-navigation simulations with the measured data at the Southern Mariana Arc submarine volcanoes. Based on the characteristics of the measurements, the design process for the parameters of the system modeling error covariance, measurement error covariance, and initial error covariance are presented. This paper reviews the influence of the outliers and blackout of the USBL and DVL measurements, and proposes an outlier rejection algorithm that is robust to USBL blackout. The effectiveness of the method is demonstrated with re-navigation for the data that includes USBL blackouts.

• Smart Structures and Systems
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• v.25 no.3
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• pp.369-384
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• 2020

A wavefield sparse reconstruction technique based on compressed sensing is developed in this work to dramatically reduce the number of measurements. Firstly, a severely underdetermined representation of guided wavefield at a snapshot is established in the spatial domain. Secondly, an optimal compressed sensing model of guided wavefield sparse reconstruction is established based on l₁-norm penalty, where a suite of discrete cosine functions is selected as the dictionary to promote the sparsity. The regular, random and jittered undersampling schemes are compared and selected as the undersampling matrix of compressed sensing. Thirdly, a gradient projection method is employed to solve the compressed sensing model of wavefield sparse reconstruction from highly incomplete measurements. Finally, experiments with different excitation frequencies are conducted on an aluminum plate to verify the effectiveness of the proposed sparse reconstruction method, where a scanning laser Doppler vibrometer as the true benchmark is used to measure the original wavefield in a given inspection region. Experiments demonstrate that the missing wavefield data can be accurately reconstructed from less than 12% of the original measurements; The reconstruction accuracy of the jittered undersampling scheme is slightly higher than that of the random undersampling scheme in high probability, but the regular undersampling scheme fails to reconstruct the wavefield image; A quantified mapping relationship between the sparsity ratio and the recovery error over a special interval is established with respect to statistical modeling and analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.458-467
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• 2019

The purpose of this study is the suggestion of optimized parameters in OI (Optimal Interpolation) by experimental study. The observation of applying optimal interpolation is ADCP (Acoustic Doppler Current Profiler) data at the southwestern sea of Korea. FVCOM (Finite Volume Coastal Ocean Model) is used for the barotropic model. OI is to the estimation of the gain matrix by a minimum value between the background error covariance and the observation error covariance using the least square method. The scaling factor and correlation radius are very important parameters for OI. It is used to calculate the weight between observation data and model data in the model domain. The optimized parameters from the experiments were found by the Taylor diagram. Constantly each observation point requires optimizing each parameter for the best assimilation. Also, a high accuracy of numerical model means background error covariance is low and then it can decrease all of the parameters in OI. In conclusion, it is expected to have prepared the foundation for research for the selection of ocean observation points and the construction of ocean prediction systems in the future.

• Ocean and Polar Research
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• v.35 no.2
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• pp.135-146
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• 2013

This study investigates the characteristic of the Tsushima Warm Current from an assimilated high resolution global ocean prediction model, $1/12^{\circ}$ Global HYbrid Coordiate Ocean Model (HYCOM). The model results were verified through a comparison with current measurements obtained by acoustic Doppler current profiler (ADCP) mounted on the passenger ferryboat between Busan, Korea, and Hakata, Japan. The annual mean transport of the Tsushima Warm Current was 2.56 Sverdrup (Sv) (1 Sv = $10^6m^3s^{-1}$), which is similar to those from previous studies (Takikawa et al. 1999; Teague et al. 2002). The volume transport time series of the Tsushima Warm Current from HYCOM correlates to a high degree with that from the ADCP observation (the correlation coefficient between the two is 0.82). The spatiotemporal structures of the currents as well as temperature and salinity from HYCOM are comparable to the observed ones.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.650-659
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• 2016

As a type of accident-tolerant fuel, fully ceramic microencapsulated (FCM) fuel was proposed after the Fukushima accident in Japan. The FCM fuel consists of tristructural isotropic particles randomly dispersed in a silicon carbide (SiC) matrix. For a fuel element with such high heterogeneity, we have proposed a two-temperature homogenized model using the particle transport Monte Carlo method for the heat conduction problem. This model distinguishes between fuel-kernel and SiC matrix temperatures. Moreover, the obtained temperature profiles are more realistic than those of other models. In Part I of the paper, homogenized parameters for the FCM fuel in which tristructural isotropic particles are randomly dispersed in the fine lattice stochastic structure are obtained by (1) matching steady-state analytic solutions of the model with the results of particle transport Monte Carlo method for heat conduction problems, and (2) preserving total enthalpies in fuel kernels and SiC matrix. The homogenized parameters have two desirable properties: (1) they are insensitive to boundary conditions such as coolant bulk temperatures and thickness of cladding, and (2) they are independent of operating power density. By performing the Monte Carlo calculations with the temperature-dependent thermal properties of the constituent materials of the FCM fuel, temperature-dependent homogenized parameters are obtained.