• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.26.2-26.2
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• 2011

Flyby anomaly (unexpected energy increase during Earth Gravity Assists) indicates existence of an unknown non-conservative perturbation which affects hyperbolic trajectories. This presentation focuses on first order position and velocity perturbation formulas derived in terms of classical orbital element variations for hyperbolic orbit. By using both the perturbation formulas and numerical approach, we analyze effects of hypothetical acceleration models proposed by Hasse (2009), Lewis (2009), Gerrad and Sumner (2008), and Busack (2007). Based on analysis of perturbation effect on low earth orbit, we find that typical position perturbation is about 10m which is much larger than current orbit determination accuracy. From this, we deduce that anomalous acceleration only affects hyperbolic orbit or behaves differently in bound orbit. On the other hand, based on analysis of perturbation effects on hyperbolic trajectories, we find that position and velocity perturbations are highly different from acceleration models, and all of proposed models fail to explain observed range and Doppler data. Thus, it can be concluded that not only energy variations but also kinematics gives us crucial clues on the flyby anomaly, and kinematical characteristic should be considered in modeling flyby anomaly.

• Archives of Plastic Surgery
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• v.45 no.4
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• pp.375-378
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• 2018

In this report, we present a case of successful treatment of a bowel fistula in the open abdomen by perforator flaps and an aponeurosis plug. A 70-year-old man underwent total gastrectomy and developed anastomotic leakage and dehiscence of the abdominal wound a week later. He was dependent upon extracorporeal membrane oxygenation, continuous hemodiafiltration, and a respirator. Bowel fluids contaminated the open abdomen. Two months after the gastric operation, a plastic surgery team, in consultation with general surgeons, performed perforator flaps on both sides and constructed, as it were, a bridge of skin sealing the orifice of the fistula. The aponeurosis of the external oblique muscle was elevated with the flap to be used as a plug. The perforators of the flaps were identified on preoperative and intraoperative ultrasonography. This modality allowed us to locate the perforators precisely and to evaluate the perforators by assessing their diameters and performing a waveform analysis. The contamination decreased dramatically afterwards. The bare areas were gradually covered by skin grafts. The fistula was closed completely 18 days after the perforator flap. An ultrasound-guided perforator flap with an aponeurosis plug can be an option for patients suffering from an open abdomen with a bowel fistula.

• ETRI Journal
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• v.38 no.1
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• pp.90-99
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• 2016

In this work, we investigate differentially encoded blind transceiver design in low signal-to-noise ratio (SNR) regimes for orthogonal frequency-division multiplexing (OFDM) signaling. Owing to the fact that acquisition of channel state information is not viable for short coherence times or in low SNR regimes, we propose a time-spread frequency-encoded method under OFDM modulation. The repetition (spreading) of differentially encoded symbols allows us to achieve a target energy per bit to noise ratio and higher diversity. Based on the channel order, we optimize subcarrier assignment for spreading (along time) to achieve frequency diversity of an OFDM modulated signal. We present the performance of our proposed transceiver design and investigate the impact of Doppler frequency on the performance of the proposed differentially encoded transceiver design. To further improve reliability of the decoded data, we employ capacity-achieving low-density parity-check forward error correction encoding to the information bits.

• Journal of the Korean Society of Physical Medicine
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• v.5 no.2
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• pp.255-264
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• 2010

Purpose : The purpose of this study is to analysis effects of resistive exercise on cardiopulmonary fitness and cerebral artery blood flow velocity. Methods : Ten healthy university students had done resistive exercise without aerobic exercise over one year participated resistive exercise group and ten general university students, then were calculated oxygen consumption ($VO_2$) and respiratory exchange rate($VO_2/VCO_2$). After a week, they were measured Transcranial Doppler Ultrasonography(TCD) at moderate exercise(HRmax 50%), maximal exercise (HRmax 100%) for taking cerebral blood flow velocity. Results : In the comparison between groups, resistive exercise group showed significant higher oxygen consumption and lower respiratory exchange than controls(p<0.05). In resistive exercise group, oxygen consumption was significant negative correlation with cerebral artery pulsatory index(p<0.05). but, oxygen consumption was significant positive correlation with systolic blood flow velocity in controls(p<0.05). Conclusions : After considering all the factors, important value in resistive exercise is regular participation and help us increasing contingency response ability.

• Childhood Kidney Diseases
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• v.14 no.1
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• pp.84-88
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• 2010

Posterior nutcracker phenomenon (PNP) was found to be the cause of significant proteinuria in a 10-year-old female. PNP was documented by Doppler ultrasonography and abdominal 3D CT as a cause of her proteinuria. Despite treatment with ACE inhibitor for several months, her persistent and progressive proteinuria lead us to perform a left renal biopsy, which revealed no significant finding except for focal effacement of foot processes. We speculate that nutcracker phenomenon can induce not only orthostatic proteinuria but also significant proteinuria by focal effacement of foot processes.

• Archives of Reconstructive Microsurgery
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• v.16 no.1
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• pp.39-47
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• 2007

With the advent of microsurgery, perforator free flap is nowadays considered the first choice for reconstruction of the extensive defect of the extremities because of their moderate thickness. Among them, anterior (anterolateral and anteromedial) thigh perforator free flaps provide the first choice for reconstruction of various soft tissue defects of the extremities with many advantage such as its large, uniform thickness, long vascular pedicle with proper vessel size and minimal donor site morbidity. But, it has still some criticism of unreliable perforators which makes us very careful in elevating the flap. Between March of 2006 and February of 2007, we treated 7 patients of soft tissue defects in the hand and lower extremities with anterior thigh perforator free flap at Hallym and DongGuk University Hospital. We performed 6 anterolateral thigh perforator free flaps based on the descending branch of lateral circumflex femoral artery (LCFA) and 1 anteromedial thigh perforator free flap based on the innominate branch of the LCFA. While approaching for the anterolateral thigh free flap, we happen to meet the cases which we should change into the anteromedial thigh free flap uneventfully on the operating field. In contrast to the original design of anterolateral thigh free flap, we had to harvest the anteromedial thigh perforator free flap in 1 case. All the anterior thigh perforator free flaps survived completely except 1 case of partial necrosis due to venous congestion. Donor sites were closed primarily and healed uneventfully within 2 weeks. Patients were satisfied with the functionally and aesthetically acceptable results. Although doppler sonography is strongly recommended preoperatively in planning the anterior thigh perforator free flaps, we should always remember the variation in vascular anatomy and be ready to change the flap choice from the anterolateral to anteromedial intraoperatively. we provide a review of the literature and present our series of anterior thigh perforator free flaps for reconstruction of the extremities.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.11
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• pp.1868-1878
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• 2016

This paper proposes a novel velocity estimator for long-term underwater navigation of autonomous underwater vehicles(AUVs). Provided that an external position fix is not given, a viable goal in designing a underwater navigation algorithm is to reduce the divergence rate of position error only using the sporadic velocity information obtained from Doppler velocity log(DVL). For such case, the performance of underwater navigation eventually depends on accuracy and reliability of external velocity information. This motivates us to devise a velocity estimator which can drastically enhance the navigation performance even when the DVL measurement is unavailable. Incorporating the Gertler-Hagen hydrodynamics model of an AUV with the measurement models of velocity and depth sensors, the velocity estimator design problem is resolved using the extended Kalman filter. Different from the existing methods in which an AUV simulator is regarded as a virtual sensor, our approach is less sensitive to the model uncertainty often encountered in practice. This is because our velocity filter estimates the simulator errors with sensor aids and furthermore compensates these errors based on the indirect feedforward manner. Through the simulations for typical AUV navigation scenarios, the effectiveness of the proposed scheme is demonstrated.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.49.1-49.1
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• 2010

The study of pores, small penumbraless sunspots, can give us a chance to understand how strong magnetic fields interact with convective motions in the photosphere. For a better understanding of this interaction, we investigate the temporal variation of several tiny pores smaller than 2". These pores were observed by the Solar Optical Telescope (SOT) onboard Hinode on 2006 December 29. We have analyzed the high resolution spectropolarimetric (SP) data and the G-band filtergrams taken during the observation. Magnetic flux density and Doppler velocities of the pores are estimated by applying the center of gravity (COG) method to the SP data. The horizontal motions in and around the pores are tracked by adopting the Nonlinear Affine Velocity Estimator (NAVE) method to the G-band filter images. As results, we found the followings. (1) Darkness of pores is positively correlated with magnetic flux density. (2) Downflows always exist inside and around the pores. (3) The speed of downflows inside the pores is negatively correlated with their darkness. (4) The pores are surrounded by strong downflows. (5) Brightness changes of the pores are correlated with the divergence of mass flow (correlation coefficient > 0.9). (6) The pores in the growing phase are associated with the converging flow pattern and the pores in the decay phase with the diverging flow pattern. Our results support the idea that a pore grows as magnetic flux density increases due to the convergence of ambient mass flow and it decays with the decrease of the flux density due to the diverging mass flow.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.29.2-29.2
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• 2010

The Extreme ultraviolet Imaging Spectrometer (EIS) on board Hinode provide us with excellent imaging spectroscopic data with very good spatial and spectral resolutions, which can be used for detecting Doppler flows in transition region and coronal lines as well as diagnosing plasma properties such as temperature, density, and non-thermal velocity. In this study we have made an EUV-imaging spectroscopic study of the source region of a partial halo coronal mass ejection (CME) that occurred on 2007 July 9 in NOAA 10961. Dopplergrams are obtained before and after the CME eruption using 12 EIS spectral lines (Log T= 4.9~7.2). Major results are summarized as follows. First, it is noted that either red shifts disappeared or blue shifts newly appeared for all spectral lines lower than Log T =6.0. Second, there were significant intensity increases for all wavelengths. Third, there were no significant variations in non-thermal motions for all wavelengths. We found one interesting bright point that newly appeared after the CME eruption. We discuss the implication on the results in terms of the CME eruption.

• Archives of Plastic Surgery
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• v.35 no.2
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• pp.193-196
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• 2008

Purpose: TRAM flap reconstruction has settled down as a common method for breast reconstruction after mastectomy. There are a few surgical contraindication in TRAM flap surgery. Previous abdominal liposuction has been a relative contraindication in TRAM flap surgery. The authors present 2 patients of successful breast reconstruction using pedicled TRAM flaps, who previously underwent abdominal liposuction. Methods: Case 1: A 48-year-old woman with a right breast cancer visited for mastectomy and breast reconstruction. Her past surgical history was notable for abdominal liposuction 15 years ago. Skin sparing mastectomy and breast reconstruction with a pedicled TRAM flap was performed. Case 2: A 45-year-old woman with a left breast cancer visited us for mastectomy and autologous breast reconstruction. 3 years ago, she had an abdominal liposuction and augmentation mammaplasty in other hospital. Nipple sparing mastectomy and breast reconstruction was done using pedicled TRAM flap. Results: One year after the reconstruction, partial fat necrosis was developed in one case but there was no skin necrosis or donor site complication in both patients. Conclusion: As aesthetic surgery becomes more popular, increasing numbers of patients who have a prior abdominal liposuction history want for autologous tissue breast reconstruction. In these patients, TRAM flap surgery will be also used for breast reconstruction. But, the warning of fat necrosis and the use of preoperative Doppler tracing to evaluate the abdominal perforator may be beneficial to patients who had abdominal liposuction recently.