• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1325-1332
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• 2009

In this paper, we design a 2.4 GHz bio-radar system that can detect human heartbeat and respiration signals with small size and improved noise performance using single circular-polarized antenna and phase-locked loop. The demonstrated bio-radar system consists of single circular-polarized antenna with $90^{\circ}$ hybrid, low-noise amplifier, power amplifier, voltage-controlled oscillator with phase-locked loop circuits, quadrature demodulator and analog circuits. To realize compact size, the printed annular ring stacked microstrip antenna is integrated on the transceiver circuits, so its dimension is just $40\times40mm^2$. Also, to improve signal-to-noise-ratio performance by phase noise due to transmitter leakage signal, the phase-locked loop circuit is used. The measured results show that the heart rate and respiration accuracy was found to be very high for the distance of 50 cm without the additional digital signal processing.

• Journal of Korean Neurosurgical Society
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• v.61 no.1
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• pp.51-59
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• 2018

Objective : The feasibility and usefulness of transradial catheterization for coronary and neuro-intervention are well known. However, the anatomical change in the catheterized radial artery (RA) is not well understood. Herein, we present the results of ultrasonographic observation of the RA after routine transradial cerebral angiography (TRCA). Methods : Patients who underwent routine TRCA with pre- and post-procedure Doppler ultrasonography (DUS) of the catheterized RA were enrolled. We then recorded and retrospectively reviewed the diameter and any complicated features of the RA observed on DUS, and the factors associated with the diameter and complications were analyzed. Results : A total of 223 TRCAs across 181 patients were enrolled in the current study. The mean RA diameter was 2.48 mm and was positively correlated with male gender (p<0.001) and hypertension (p<0.002). The median change in diameter after TRCA was less than 0.1 mm (range, -1.3 to 1.2 mm) and 90% of changes were between -0.8 and +0.7 mm. Across 228 procedures, there were 12 cases (5.3%) of intimal hyperplasia and 22 cases (9.6%) of asymptomatic local vascular complications found on DUS. Patients with abnormal findings on the first procedure had a smaller pre-procedural RA diameter than that of patients without findings (2.26 vs. 2.53 mm, p=0.0028). There was no significant difference in the incidence of abnormal findings for the first versus subsequent procedures (p=0.68). Conclusion : DUS identified the pre- and post-procedural diameter and local complications of RA. Routine TRCA seems to be acceptable with regard to identifying local complications and changes in RA diameter.

• Archives of Plastic Surgery
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• v.36 no.3
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• pp.336-340
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• 2009

Purpose: The wound of a patient who has chronic venous insufficiency is easy to recur. Also they develop a complication even after the conservative therapy or skin graft. We have to diagnose the venous stasis ulcer correctly and remove the cause to improve the effectiveness of treatment. We operated endoscopic perforating vein ligation and splitt thickness skin graft on a patient with venous stasis ulceration on right leg. Methods: A 26 year old male patient who had a scalding burn on his right leg in July 2005 checked into our hospital in March 2008. Even though he got three operations - the split thickness skin graft - at different clinics, the wound did not heal. The size of the wound was 12 by $8cm^2$ and granulation with edema and fibrosis had been formed. We kept observation on many collateral vessels and perforating vein through venogram and doppler sonography and firmly get to know that the wound came with chronic venous insufficiency. After a debridement and an application of VAC$^{(R)}$ for two weeks, the condition of granulation got better. So we proceeded with the operation using subfascial endoscopic perforating surgery and split thickness skin graft. Results: Through the venogram after the operation, we found out that the collateral vessels had been reduced compared to the previous condition and the widened perforating vein disappeared. During a follow up of 6 months, the patient did not develop recurrent stasis ulcer and postoperative complications. Conclusion: Subfascial endoscopic perforator ligation is relatively simple technique with a low complication rate and recurrence rate. Split thickness skin graft with subfascial endoscopic perforator surgery can be valuable method for treating severe venous stasis ulcers.

• Annals of Clinical Neurophysiology
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• v.11 no.2
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• pp.54-58
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• 2009

Background: Obstructive sleep apnea (OSA) is associated with several cardiovascular diseases. However, the mechanisms are not completely understood. The measure of common carotid artery intima-media thickness (IMT) has been extensively used as an early marker of atherosclerosis. The aim of this study was to test the hypothesis that early signs of atherosclerosis are present in patients with OSA and correlate with OSA severity Methods: Eleven male patients with OSA were studied by using full standard overnight polysomnography and high-definition echo-tracking device to measure intima-media thickness and carotid artery diameter. Eight healthy volunteers matched for age and sex were studied by portable respiratory monitoring device. All participants were free of hypertension, diabetes, and were not on any medications. Patients with OSA were naive to treatment. Results: All patients and normal controls were male. There was no significant difference of age between patients and controls ($48.4{\pm}8.85$ and $48.0{\pm}9.77$). Significant differences existed between control subjects and patients with mild to moderate and severe OSA (apnea-hypopnea index, $1.51{\pm}1.15$ and $38.51{\pm}19.13$ respectively) in intima-media thickness ($0.59{\pm}0.064$ and $0.93{\pm}0.16$; P=0.0023), and carotid diameter ($5.79{\pm}0.44$ and $6.47{\pm}0.51$; P=0.0227). Multivariate analyses showed that the apnea-hypopnea index correlated independently with intima-media thickness and carotid diameter (r=0.79, P=0.0008, and r=0.47, P=0.0482). Conclusions: Middle-aged patients with OSA who are free of overt cardiovascular diseases have early signs of atherosclerosis, which further supports the hypothesis that OSA plays an independent role in atherosclerosis progression.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.361-370
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• 2004

The DSN(Deep Space Network) measurement model for interplanetary navigations which is essential for precise orbit determination has been developed. The DSN measurement model produces fictitious DSN observables such as range, doppler and angular data, containing the potential observational errors in geometric data obtained from orbit propagator. So the important part of this research is to model observational errors in DSN observation and to characterize the errors. The modeled observational errors include the range delay effect caused by troposphere, ionosphere, antenna offset, and angular refraction effect caused by troposphere. Non-modeled errors are justified as the parameters. All of these results from developed models show about $10\%$ errors compared to the JPL's reference results, that are within acceptable error range.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.8
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• pp.84-87
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• 2017

Cerebral hyperperfusion syndrome (CHS) is a rare complication that can occur when conducting stent insertion or endarterectomy in patients with carotid artery stenosis and is known to be caused by various mechanisms when the blood volume abruptly increases. The main clinical symptoms are unilateral headache, hypertension, seizure, and focal neurologic deficit. Subarachnoid hemorrhage and parenchymal hemorrhage may lead to permanent impairment or death in severe cases. CHS can be predicted by using transcranial Doppler, perfusion magnetic resonance imaging, and single photon emission computed tomography. In our case report, a patient developed CHS subsequent to significant venous congestion caused by carotid artery stent insertion. The patient had preexisting, symptomatic bilateral carotid artery stenosis. Venous congestion occurs when the direction of blood flow changes because of increased blood volume in patients with well-developed collateral vessels. We believe that CHS can be predicted from this finding. This study reports the possibility that CHS could be confirmed by cerebral angiography after insertion of the internal carotid stent.

• Clinical and Experimental Pediatrics
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• v.46 no.12
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• pp.1207-1211
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• 2003

Purpose : This study was performed to observe the relationship of plasma L-arginine level and the severity of disease and pulmonary artery pressure in respiratory distress syndrome of premature infants. Methods : Peripheral blood samples were obtained at 1st, 3rd and 7th day from 21 premature infants with respiratory distress syndrome to analyze the L-arginine concentration. Oxygenation index (OI), an indicator of the severity of the disease, was calculated at the same time of the blood sampling. And pulmonary artery pressure was measured by Doppler echocardiography at each period. Plasma L-arginine level, OI and right ventricular systolic time interval(RVSTI) were analyzed. Results : Plasma L-arginine concentration of the 1st day was lower than 3rd and 7th day. OI and RVSTI were significantly correlated with each other(r=0.772, P<0.01). Plasma L- arginine level was correlated with oxygenation index(r=-0.346, P<0.01) and RVSTI(r=-0.416, P<0.01). Conclusion : Plasma L-arginine level was lowest in the 1st day during the study period. Plasma L-arginine concentration correlated significantly with the severity of respiratory distress syndrome and pulmonary artery pressure in premature infants.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.99-104
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• 2012

The United States will proceed with the effort to modernize the GPS system, and one of its main content is to provide L5 signal. L5 will be transmitted in a radio band reserved exclusively for aviation safety services. And, L5, in combination with L1, will improve the position accuracy via ionospheric correction and robustness via signal redundancy. However, The acquisition processing time of L5 takes longer than that of L1 as the code length of L5 is 10 times longer than that of L1. To reduce this acquisition processing time, a higher number of correlators in the aquisition module should be used. However, there is a problem that this causes increase in the complexity of the correlator configuration and the computation power. So, in this paper, we propose L5 signal tracking scheme using tracking results in the GPS L1/L5 receiver. The proposed scheme could reduce the hardware complexity as the GPS L5 signal acquisition module is not needed, and provide fast and stable tracking of L5 signal by aiding L1 tracking results such as PRN, the code phase synchronization, and the Doppler frequency. The feasibility of the proposed scheme is demonstrated through simulation results.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.1
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• pp.43-50
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• 2012

The safety of cosmetics or cosmetic ingredients on human skin is generally evaluated by visual assessment but some early subtle skin changes may not be noticed by the naked eyes. Thus, the present study was conducted to detect skin reactions induced by mildly irritating cosmetic ingredients by using a laser Doppler perfusion imager (LDPI) method that measures blood flow, a $Vapometer^{(R)}$ that measure strans epidermal water loss (TEWL), and a spectrophotometer that measures the skin color as the erythema values ($a^*$). Visual assessment showed that all tested oils and humectants except propylene glycol belong to the low skin irritation ranges (grades 0+ to 2.9+) while all tested surfactants and propylene glycol belong to the moderate-to strong-skin irritation ranges (grades 3+ to 5+). Among three instrumental methods, TEWL assessment appeared to be more sensitive than spectrophotometric or LDPI method and suitable for the detection of subtle skin response invisible to the naked eye (grades 0+ to 2.9+). Skin reactions of grade 3+ to 5+ could be detected by all three instrumental methods. In conclusion, the current study suggested that the sub-clinical skin reactions due to mild irritants contained in cosmetics can be best assessed by TEWL measurements.

• Journal of Korea Water Resources Association
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• v.53 no.4
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• pp.313-322
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• 2020

There is always a risk of water disasters due to sudden storms in mountainous regions in Korea, which is more than 70% of the country's land. In this study, a radar-based risk prediction technique for sudden downpour is applied in the mountainous region and is evaluated for its applicability using Mt. Biseul rain radar. Eight local heavy rain events in mountain regions are selected and the information was calculated such as early detection of cumulonimbus convective cells, automatic detection of convective cells, and risk index of detected convective cells using the three-dimensional radar reflectivity, rainfall intensity, and doppler wind speed. As a result, it was possible to confirm the initial detection timing and location of convective cells that may develop as a localized heavy rain, and the magnitude and location of the risk determined according to whether or not vortices were generated. In particular, it was confirmed that the ground rain gauge network has limitations in detecting heavy rains that develop locally in a narrow area. Besides, it is possible to secure a time of at least 10 minutes to a maximum of 65 minutes until the maximum rainfall intensity occurs at the time of obtaining the risk information. Therefore, it would be useful as information to prevent flash flooding disaster and marooned accidents caused by heavy rain in the mountainous area using this technique.