• Journal of Chest Surgery
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• v.17 no.4
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• pp.593-606
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• 1984

With the ligation of patent ductus arteriosus by Gross in 1938, surgeons first entered the field of congenital heart disease. Interruption of a ductus is one of the most satisfactory and curative operations in the field of surgery for congenital heart disease. 27 cases of isolated patent ductus arteriosus were operated from Jan. 1978 to July 1984 at the Department of Thoracic & Cardiovascular Surgery in Kyung-Hee University Hospital. Retrospective clinical analysis of these patients were: 1. Sex ratio, female: male, was 2:1. 2. Mean age at operation was 9.85\ulcorner.58 years. The youngest patient was a 23 month-old girl and the oldest one was a 24 year-old male. 3. More than half of the patients had less than 50 percentile of growth retardation. 4. Chief complaints of the patients were frequent URI [52%], dyspnea on exertion [33%], generalized weakness [22%], palpitation [7%], but 7 patients [26%] had no subjective symptoms. 5. Continuous machinery murmur could be heard at the 2nd or 3rd intercostal space on the left sternal border in 22 patients [81%]. The other S patients made systolic murmur with accentuation of the second heart sound and those were associated with pulmonary hypertension. 6. Radiologic findings of Chest P-A were cardiac enlargement in 15 patients [55%], enlargement of pulmonary conus and/or increasing density of pulmonary vascularity in 20 patients [74%]. 7. Electrocardiographic findings of the patients were within normal limit in 13 patients [48%], LVH in 4 patients [15%], biventricular hypertrophy in 3 patients [11%]. 8; echocardiogram was obtained from 11 patients. Ductus was directly visualized in 7 patients. Left atrial enlargement is the secondary change of left to right shunt, 10 patients had LA/Ao ratio more than 1.2. 9. Cardiac catheterization performed in 25 patients. The mean value of the results were:SO2[PA-RV]= 14.72\ulcorner6.01%, Qp/Qs=2.22\ulcorner.80, peak systolic pulmonary arterial pressure=48.28\ulcorner1.60 mmHg. 10. 26 patients were operated through the left posterolateral thoracotomy: closure of ductus by double ligation in 14 cases, triple ligation in 5 cases, and division with suture in 8 cases. One patient suffer from aneurysmal rupture of main pulmonary artery, endocarditis, hemopericardium was treated with cardiopulmonary bypass via median sternotomy and closure of ductus through the ruptured main pulmonary artery. 11.There was no death associated with the operation, but 3 cases were experienced with intraoperative rupture around the ductus resulting in massive bleeding. The other complications were transient hoarseness in one patient, atelectasis in left lower lobe in 3 patients, and postoperative systemic hypertension in 4 patients with unknown etiology. 12. Pulse pressure was reduced, 11.47+5.92 mmHg, postoperatively, as compare to preoperative status. 13. Intraoperative wedge lung biopsy from lingular segment for the evaluation of the pulmonary vascular disease was taken in S patients with severe pulmonary hypertension. The result was Heath-Edward grade I in one case, grade II in two cases, and grade III in two cases.

• Journal of Chest Surgery
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• v.32 no.8
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• pp.702-708
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• 1999

Background: Surgical closure of the PDA in premature infants with complications or contraindications to indomethacin use, or recurrence of symptomatic PDA is a safe and effective procedure with low operative risk and minimal complications. Material and Method: From April 1996 to August 1998, 11 premature infants with body weight under 1.5 kg at operation underwent operation for a symptomatic PDA (male:5, female: 6). Associated dise ases were congenital heart disease(7), hyaline membrane disease(6), intraventricular hemor rhage(4), pneumonia(4), pneumothorax(3), hyperbilirubinemia(2), necrotizing enterocolitis(2), renal failure(1), epilepsy(1), and hydrocephalus(1). Surgical techniques are hemoclipping(8) and ligation(3). The size of PDA was 3~6 mm (5.0$\pm$1.2). Result: Systolic and diastolic blood pressure rised and heart rates decreased after PDA closure. ABGA improved postoperatively. There were no surgical complications. Six infants with improved ABGA data were weaned from mechanical ventilatory support. The follow-up durations after discharge were 3 month to 12 month. Five deaths were not related to operation. The causes of death were hyaline membrane disease(2), bronchopulmonary dysplasia with pneumonia(1), sepsis(1), and con gestive heart failure with respiratory distress syndrome(1). Conclusion: Early operative closure is the treatment of choice in most premature infants with a hemodynamically significant shunt(PDA), recurrence of symptomatic PDA, complications of Indomethacin, or contraindi cations to Indomethacin.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2484-2490
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• 2012

This study reports on the development and performance verification of cell simulation boards of simulator and the embedded program for board control of the battery management system (BMS) of electric vehicle (EV) cars, which manages the next-generation automotive lithium-ion battery pack. Here, we have improved the speed of the simulator by using operational (OP) amplifier and transistors that were connected in series. In addition, using a digital analog converter (DAC) in each channel, we have improved the performance by channel-to-channel isolation (isolation) as compared to the traditional methods. Furthermore, by constructing a current-limiting protection circuit, one can be protected from disturbance and, by utilizing a precision shunt resistor for the current sensor, we have increased the precision of the current control. In order to verify the performance of the developed simulator, we have performed the experiment 10 times, with values ranging from 0.5 V to 5 V, and a voltage drop step of 0.5 V. Significance analysis of experimental data, and repeatability tests were performed, showing an average standard deviation of 0.001~0.004 V, indicating high repeatability and high statistical significance of the current method and system.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.348-351
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• 1999

We investigated current limiting properties for an SFCL of YBCO thin film coated with an Au layer. The YBCO film of 1 mm wide and 400 nm thick could carry the current 9.6 A$_{peak}$ without quench. The SFCL limited the fault current below 7.6 A$_{peak}$, which otherwise increases above 65 A$_{peak}$ and melted down at the potential fault current of about 100 A$_{peak}$ which is 10 times greater than the quench current. This means that the Au layer successfully protected the superconducting film by dispersing the heat generated at hot spots and electrically shunting the YBCO film.

• Korean Journal of Bronchoesophagology
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• v.5 no.2
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• pp.130-137
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• 1999

Background and Objectives : Provox, a recently developed tracheoesophageal prosthesis, had been widely used for voice rehabilitation after total laryngectomy for its low resistance and easiness of speech ability. But, long-term use of Provox resulted in many complications and resulted in cessation of Provox as a primary method of vocal rehabilitation. The aim of this study is to report Provox-related problems and the long-term results of Provox voice prosthesis. Materials and Methods : Medical records from patients who had undergone total laryngectomy with Provox insertion at seoul National University Hospital between January 1993 and December 1998 were reviewed retrospectively. Results : 36 patients had used 79 Provox voice prostheses during the observed period. The most common complication causing prosthesis change or removal was leakage and/or aspiration, followed by granulation formation, crusting and/or obstruction, and non-function. Median in situ lifetime of Provox was 274 days and 1-year-in situ rate was 31.0% Among 36 patients, 17 patients had undergone tracheoesophageal shunt closure at the last follow-up visit. 10 patients had complications but got along without further treatments, and 1 patient changed to Blom-Singer voice prosthesis. Only 8 patients experienced no complication, and 5 out of whom had several times of Provox change. Conclusion : long-term use of Provox resulted in discontinuation of its use due to complications in many cases. A better voice prosthesis with lower complication rate and longer in situ lifetime is needed.

• Journal of Chest Surgery
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• v.29 no.10
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• pp.1118-1122
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• 1996

From January 1990 through December 1995, 43 patients underwent diaphragmatic plication for the management of phrenic nerve palsy .complicating various pediatric cardiovascular surgery. Their mean age at plication was 11.1 months and sex ratio was 31 males to 12 females. In order of decreasing incidence, the primary cardiovascular procedures included modified Blalock-Taussig shunt (7), total correction for the Tetralogy of Falloff (7), arterial switch operation (6), unifocalization for the pulmonary atresia with VSD (3), modified Fontan operation (3), VSD patch closure (3) and others. The involved sides of diaphragm were right in 17, left in 2) and bilateral in 3. Extensive pericardial resection with electocauterization of resected margin was thought to be the most common cause of phrenic nerve palsy (20). The interval between primary operation and plication ranged from the day of operation to 98 days (median 11 days). The methods of plication were central pleating technique(plication with phrenic nerve branch preservation) in 41, and other technique In 2. 10 patients died after plication (7: early, 3; late), and the causes of death were thought to be unrelated to plication itself. Among the 36 early survivors, extubation or cessation of positive pressure ventilation could be accomplished between 1 and 24 days postoperatively(mean : 4.5). Cumulative follow-up was 92 patient years without major complications. Postoperative follow-up fluoroscopy was performed in 6 patients, and the location and movement of plicated diaphragms were satisfactory in 5 patients. We concluded that diaphragmatic plication with preservation of phrenic n rve branch could lead to cessation of positive pressure ventilation and complete recovery of diaphragmatic function in the long term, unless the phrenic nerve was irreversibly damaged.

• Journal of Chest Surgery
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• v.32 no.6
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• pp.532-535
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• 1999

Background: The purpose of this study was to evaluate and analyze the surgical techniques and postoperative complications in patients undergoing operations for descending thoracic aortic aneurysms. Material and Method: The data of 22 major operations between March 1987 and August 1997 were retrospectively reviewed. Result: There were 18 men and 4 women with a mean age of 49 years (range 33 years to 82 years). The cause of the aneurysm was aortic dissection in 13 patients, atherosclerosis in 3, mycotic in 3, trauma in 2 and uncertain in 1. The operative techniques were resection and graft replacement in 16, axillofemoral bypass graft in 2, femorofemoral bypass graft in 2, exclusion, aneurysmorrhaphy in 1 and transfemoral stent insertion in 1. During the operation, 16 cases were performed under total aortic clamp. Among the 16 patients, femorofemoral bypass was used in 14 cases and previously made shunt in 2 cases. The mean total aortic clamp time was 91 minutes and the mean extracorporeal circulation time was 116 minutes. One death occurred in an excluded patient on the 52 postoperative day due to a rupture of the aneurysm. Postoperative complications were paraplegia in 1 case, acute renal failure in 1 case and acute respiratory failure in 1 case. Conclusion: Although surgical treatment of the descending thoracic aneurysm has many postoperative complications, good surgical results can be achieved with a proper patient selection and fine surgical techniques.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.10 s.352
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• pp.1-9
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• 2006

In this paper, a couple of 10Gb/s transimpedance amplifiers are realized in a 0.18um standard CMOS technology for optical communication applications. First, the voltage-mode inverter TIA(I-TIA) exploits inverter input configuration to achieve larger effective gm, thus reducing the input impedance and increasing the bandwidth. I-TIA demonstrates $56dB{\Omega}$ transimpedance gain, 14GHz bandwidth for 0.25pF photodiode capacitance, and -16.5dBm optical sensitivity for 0.5A/W responsivity, 9dB extinction ration and $10^{-12}$ BER. However, both its inherent parasitic capacitance and the package parasitics deteriorate the bandwidth significantly, thus mandating very judicious circuit design. Meanwhile, the current-mode RGC TIA incorporates the regulated cascade input configuration, and thus isolates the large input parasitic capacitance from the bandwidth determination more effectively than the voltage-mode TIA. Also, the parasitic components give much less impact on its bandwidth. RGC TIA provides $60dB{\Omega}$ transimpedance gain, 10GHz bandwidth for 0.25pF photodiode capacitance, and -15.7dBm optical sensitivity for 0.5A/W responsivity, 9dB extinction ration and $10^{-12}$ BER. Main drawback is the power dissipation which is 4.5 times larger than the I-TIA.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.121-128
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• 2010

This paper presents a design of a 100 W high-efficiency power amplifier, whose operational frequency band expands from 30 to 512 MHz, using negative feedback network, push-pull structure, broadband RF choke, and transmission line transformer for balun configuration. The push-pull amplifier has been tuned for higher output power using a shunt capacitor as a matching component at its load especially for high-frequency region. The implemented power amplifier exhibited a very flat power gain of $18.34{\pm}0.9\;dB$ throughout the operating frequency band and very high power-added efficiency(PAE) of greater than 40% at an output power of 100 W. It also showed second- and third-harmonic distortion levels of below -34 dBc and -12 dBc, respectively, through the entire operating frequency band.

• Advances in pediatric surgery
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• v.1 no.1
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• pp.18-26
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• 1995

For the prevention of later contralateral hernia as well as unnecessary contralateral exploration in pediatric patients with unilateral inguinal hernias, a reasonable indication of contralateral exploration is required. To examine the contralateral positivity, a prospective selective contralateral exploration has been performed by the author from Sept. 1985 to Dec. 1993, at Pediatric Surgical Section of the Department of Surgery, Kangnam St. Mary's Hospital, Catholic University Medical College. Among the total 1200 cases of pediatric inguinal hernias, 580 cases of contralateral side were explored at hernia operations, by the indications as; male with infant onset, 2)female of all age, 3)prematurity, 4)profuse ascites due to cirrhosis, nephrotic syndrome, and ventriculoperitoneal shunt, and 5)remarkable silk sign. Overall positive rate was 71.4%, and positive rates of each indication were 80.7%, 70.4%, 73.1%, 66.7%, and 72.0%, respectively. Right side hernia showed 67.0%, left s ide 75.7%, and positive familial history 71.8% of contralateral positivities. In male, getting older revealed lower positive rates and the rate suddenly dropped after 12 years of age. Birth order, mother's age at delivery, postmaturity did not show any significant differences between the rates. Recurrence was seen in 3(0.5%) ipsilateral and 2(0.3%) contralateral, both of which were negative esplorations on previons operations. Overall complication rate was 3.8%, including 1 infection, 14 fluid or blood accumulation, 5 edemas, 3 temporary testicular edemas, 2 persisting fevers, 2 enures is and one delayed recovery from anesthesia. Among 38 cases with contralateral hernias developed after unilateral surgery by authors(6 cases) or surgeons in other institutions, 14 were males with infant onset, 4 were prematurities and 9 were females. Therefore, 27(71.7%) cases were originally under the contralateral exploration indications. The primary site of the hermia was right in 25 and left in 13. With above results, the following indications for contralateral exploration could be suggested ; 1)under one year of age, both sex, 2)prematurity, 3) remarkable silk sign, 4)in the double checked suspicions among males with infant onset, all age females, ascites, left hernia and familial history. After 12 years of age, exploration is not required. Considering complications, contralateral explorations could be considered only in the following situations; 1)expert, experienced pediatric surgeon, 2)experienced pediatric anesthesiologist, 3)operations could be done smoothly in an hour, 4)good general condition of the patient.