• Journal of Trauma and Injury
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• v.23 no.2
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• pp.134-141
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• 2010

Purpose: A classic approach to abdominal stab wounds has been a routine laparotomy for the purpose of diagnosis or treatment. However, management protocols for abdominal stab wounds are still contentious in most trauma centers. We examined the relationship between the character of the stab wound and the injured intraabdominal organs by retrospectively analyzing the medical records of patients with abdominal stab wounds admitted to Gil hospital, and the findings for our patients are then confronted with a review of the literature. We aimed to propose proper management protocols to approach abdominal stab wounds. Methods: The medical records of all 80 patients sustaining abdominal stab wounds, admitted at the Department of Surgery, Gil Hospital, Gachon Medical School, from January 2004 to December 2008 were retrospectively reviewed. All the abdominal stab wounds were collated based on the site and the character of the injury, investigations performed on admission, results of investigations, operations performed and findings at the time of the operation. Results: The most prevalent age group was patients in their forties and the average age of the patients was 41 years for both genders. The stab wounds were most commonly located at the periumbilical area (16.9%), followed by the epigastric area (15.6%), and 18.2% of the patients had multiple wounds. The most commonly eviscerated organ was the omentum (9 out of 16 cases); 61.7% of non-eviscerated patients underwent a therapeutic laparotomy while 81.3% of eviscerated patients underwent a therapeutic laparotomy. The small bowel was the most commonly injured organ (22.7%, 17 out of 75 injuries). The review revealed a relatively common diaphragmatic injury in abdominal stab wound patients (8 cases, 10.5%). The average hospital stay was 11 days. Conclusion: This review revealed commonly eviscerated and injured intraabdominal organs in abdominal stab wound patients and their relationship with a therapeutic laparotomy. Although the management is still controversial, the authors suggest indications for an immediate laparotomy and a protocol for managing abdominal stab wounds. Hemodynamic instability and peritoneal irritation signs are definite indicators for an immediate laparotomy, but the review revealed intraabdominal organ evisceration alone not to be a statistically significant factor. In addition, the authors suggest that abnormal CT findings can be valuable for making a decision on management of hemodynamically stable stab wound patients. Further study may clarify a role for a more selective approach to operative intervention and for a more extensive use of selective observation.

• Journal of Chest Surgery
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• v.34 no.6
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• pp.485-489
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• 2001

Background: The most important factor in preventing sternal complications is stable sternal approximation. We have tried to find the most effective sternal closure method by examining the incidence of sternal dehiscence with or without infection in patients with cardiac surgery through median sternotomy. Material and Method: This study was performed in 489 patients over 45 years of age with median sternotomy for open cardiac surgery. Simple closure with interrupted 6 wires was performed in 159 patients, figure-of-8 closure technique in 119, overlapping interrupted closure using 10 wires in 150, and combined closure technique of interrupted simple closure and figure-of-8 suture closure in 61. Two hundred thirty-four patients underwent valve and aortic operations and 213 patients coronary artery bypass surgery. Result: Sternal dehiscence with or without infection occurred in 12 (2.5 %) patients. The complication developed in 5 of 159 patients (3.1%) with six interrupted simple closure, in 4 of 119 patients (3.4%) with figure-of-8 closure, and in 3 of 150 patients (2.0%) with overlapping interrupted closure using 10 wires, but there was no complication in 61 patients with combined closure technique (relative risk for other closure techniques, p<0.05). There was no significant difference in the incidence of the sternal complication between valve and aortic operation group and coronary artery bypass group (3.0% vs 2.3%, not significant), but diabetes mellitus was a significant independent risk factor (odds ratio and multivariate analysis, p<0.05). Conclusion: The sternal closure technique that combines simple interrupted suture closure and figure-of-8 suture closure may be a more useful technique to enhance sternal stabilization compared to other closure techniques, such as simple interrupted closure, 8-figure closure, and overlapping interrupted closure.

• Journal of Chest Surgery
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• v.29 no.12
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• pp.1323-1328
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• 1996

The obstructive diseases involving the left main coronary artery(LMCA) are serious. Surgical treatment is generally regarded as much more effective than medical therapy in terms of long-term survival and relief of symptoms. This study represents an attempt to present an analysis of early surgical results in 21 cases conducted at Chonnam University Hospital between October 1992 And August 1995. The subject. 12 males and 9 female, ranged in age from 25 to 67 years with a mean age of 49.3${\pm}$12.5 years. As for indications for operation, unstable angina was reported on 66.7% of the subjects, while stable angina and acute myocardial infarction in 4 and 3 cases, respectively. There were also 2 cases of Takayasu's aortitis and 1 case of failed percutaneous translumlnal coronary angioplasty(PTCA). Eleven subjects had isolated LMCA diseases compared to 10 subjects with associated LMCA diseases. Of the patients with ass;3ciated LMCA diseases, 4 subjects had single coronary artery disease, 3 had double coronary artery disease, remaining 3 suffered from triple coronary artery disease. As for the group with isolated LMCA disease, ostidl angioplasty llsing autopericardium was conducted with 5 subjects. The remaining subjects with the isolated diseases and all of the patients with associated LMCA disease underwent aortocoronary bypass grafts. The left internal mammary artery was used in all patients and the average number of anastomoses was 3.13 ${\pm}$0.93. One subject died of low cardiac output syndrome at the second postoperative day. There were 5 instances of postoperative complication including reoperation for bleeding in two patients, wound infection in two, and arrhythmia in one. Follow-up coronary angiogram were conducted with eights patients, including five patients who underwent ostial angioplasty. In these cases, the patients showed surf. ficient enlargement of the left coronary ostium and the grafted vessels kept their patency. In our experience, surgical treatment of the LMCA diseases has not shown a higher rAte of operative mortAlity or morbidity than other obstructive coronary artery diseases. To patients with ostial stenosis, which is frequently observed among young female, angioplasly utilizing autopericardium seems to be a desirable choice considering the cosmetic effect, chances of reoperation and hemodynamic characteristics.

• Economic and Environmental Geology
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• v.35 no.3
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• pp.221-227
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• 2002

Column experiments were performed to evaluate the removal efficiency of soil vapor extraction (SVE) iota TCE (trichloroethylene) and toluene in soil. Homogeneous Ottawa sands and real soils collected from contaminated area were used to investigate the effect of soil properties and SVE operation conditions on the removal efficiency. In column teats with two different sizes of Ottawa sand, the maximum effluent TCE concentration in a coarse sand column was 442 mg/L and 337 mg/L in a fine sand column. However, after 20 liter gas flushing, the effluent concentrations were very similar and more than 90% of initial TCE mass were removed from the column. For two real contaminated soil columns, the maximum effluent concentration decreased 50% compared with that in the homogeneous Ottawa coarse sand column, but 99% of initial TCE mass were extracted from the column within 40 liter air flushing, suggesting that SVE is very available to remove volatile NAPLs in the contaminated soil. To investigate the effect of contaminant existing time on the removal efficiency, an Ottawa sand column was left stable for one week after TCE was injected and the gas extraction was applied into the column. Its effluent concentration trend was very similar to those for other Ottawa sand columns except that the residual TCE after the air flushing showed relatively high. Column tests with different water contents were performed and results showed high removal efficiency even in a high water content sand column. Toluene as one of BTEX compounds was used in an Ottawa sand column and a real soil column. Removal trends were similar to those in TCE contaminated columns and more than 98% of initial toluene mass were removed with SVE in both column.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.3
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• pp.60-68
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• 2009

This work proposes a 10b 200MS/s 65nm CMOS ADC for high-definition video systems such as HDTV requiring high resolution and fast operating speed simultaneously. The proposed ADC employs a four-step pipeline architecture to minimize power consumption and chip area. The input SHA based on four capacitors reduces the output signal range from $1.4V_{p-p}$ to $1.0V_{p-p}$ considering high input signal levels at a low supply voltage of 1.2V. The proposed three-stage amplifiers in the input SHA and MDAC1 overcome the low output resistance problem as commonly observed in a 65nm CMOS process. The proposed multipath frequency-compensation technique enables the conventional RNMC based three-stage amplifiers to achieve a stable operation at a high sampling rate of 200MS/s. The conventional switched-bias power-reduction technique in the sub-ranging flash ADCs further reduces power consumption while the reference generator integrated on chip with optional off-chip reference voltages allows versatile system a locations. The prototype ADC in a 65nm CMOS technology demonstrates a measured DNL and INL within 0.19LSB and 0.61LSB, respectively. The ADC shows a maximum SNDR of 54.BdB and 52.4dB and a maximum SFDR of 72.9dB and 64.8dB at 150MS/S and 200MS/s, respectively. The proposed ADC occupies an active die area of $0.76mm^2$ and consumes 75.6mW at a 1.2V supply voltage.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2E
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• pp.30-45
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• 2001

This study considers the environmental factors affecting propagation loss and sonar performance in the continental regions of the East Coast Sea of Korea. Water mass distributions appear to change dramatically in a few weeks. Simple calculation with the case when the NKCW (North Korean Cold Water) develops shows that the difference in propagation loss may reach in the worst up to 10dB over range 5km. Another factor, an eddy, has typical dimensions of 100-200km in diameter and 150-200m in thickness. Employing a typical eddy and assuming frequency to be 100Hz, its effects on propagation loss appear to make lower the normal formation of convergence zones with which sonars are possible to detect long-range targets. The change of convergence zones may result in 10dB difference in received signals in a given depth. Thermal fronts also appear to be critical restrictions to operating sonars in shallow waters. Assuming frequency to be 200Hz, thermal fronts can make 10dB difference in propagation loss between with and without them over range 20km. An observation made in one site in the East Coast Sea of Korea reveals that internal waves may appear in near-inertial period and their spectra may exist in periods 2-17min. A simulation employing simple internal wave packets gives that they break convergence zones on the bottom, causing the performance degradation of FOM as much as 4dB in frequency 1kHz. An acoustic experiment, using fixed source and receiver at the same site, shows that the received signals fluctuate tremendously with time reaching up to 6.5dB in frequencies 1kHz or less. Ambient noises give negative effects directly on sonar performance. Measurements at some sites in the East Coast Sea of Korea suggest that the noise levels greatly fluctuate with time, for example noon and early morning, mainly due to ship traffics. The average difference in a day may reach 10dB in frequency 200Hz. Another experiment using an array of hydrophones gives that the spectrum levels of ambient noises are highly directional, their difference being as large as 10dB with vertical or horizontal angles. This fact strongly implies that we should obtain in-situ information of noise levels to estimate reasonable sonar performance. As one of non-stationary noise sources, an eel may give serious problems to sonar operation on or under the sea bottoms. Observed eel noises in a pier of water depth 14m appear to have duration time of about 0.4 seconds and frequency ranges of 0.2-2.8kHz. The 'song'of an eel increases ambient noise levels to average 2.16dB in the frequencies concerned, being large enough to degrade detection performance of the sonars on or below sediments. An experiment using hydrophones in water and sediment gives that sensitivity drops of 3-4dB are expected for the hydrophones laid in sediment at frequencies of 0.5-1.5kHz. The SNR difference between in water and in sediment, however, shows large fluctuations rather than stable patterns with the source-receiver ranges.

• KDI Journal of Economic Policy
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• v.12 no.1
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• pp.111-125
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• 1990

For the last several years, considerable criticism has been leveled against Korea's exchange rate management. While Korea was designated a currency manipulator by the U.S., domestically it is often complained that the won/dollar rate did not adequately reflect changes in Korea's export competitiveness and fluctuations in the exchange rates of major currencies. In view of this situation, Korea changed its exchange regime at the beginning of March this year from the dual currency basket system to a more flexible one, called a "market average rate regime". Under this new regime, the won rate is determined in the exchange market based upon the supply of and demand for foreign exchange and is allowed to freely fluctuate each day within a + 0.4 % range. This paper, first, seeks to evaluate Korea's exchange rate management under the dual basket regime of the 1980s, and then to construct an optimal currency basket for the won which could provide a proper indicator for exchange market intervention under the new market average rate regime. The analysis of fluctuations in the real effective exchange rate (REER) of the won indicates that the won rates in the 1980s failed not only to offset changes in relative prices between home and trading partner countries, but also to properly respond to variations in major exchange rates as further evidenced by sizable fluctuations in the nominal effective rates of the won. In other words, the currency basket regime which was adopted in 1980 for the stabilization of the REER of the won has not been operated properly, mainly because authorities often resorted to policy considerations in determining the won's rate. In the second part of the paper, an optimal currency basket for Korea is constructed, designed to minimize the fluctuations in the REER of the won without including policy considerations as a factor. It is recognized, however, that both domestic and foreign price data are not available immediately for the calculation of the REER. For this problem, the approach suggested by Lipschitz (1980) is followed, in which optimal weights for currencies in the basket are determined based upon the past correlation between price and exchange rates. When the optimal basket is applied to Korea since the mid-80s, it is found that the REER of the won could have been much more stable than it actually was. We also argue for the use of variable weights rather than fixed ones, which would be determined by the changing relationship between exchange rates and relative prices. The optimal basket, and the optimal basket exchange rate based on that basket, could provide an important medium- or long-term reference for proper exchange market intervention under the market average rate regime, together with other factors, such as developments in the current account balance and changes in productivity.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.642-650
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• 2020

In general, the circulation path of the fluidized particles in a CFB (Circulating Fluidized Bed) boiler is such that the particles entrained from a combustor are collected by a cyclone and recirculated to the combustor via a sealpot which is one of non-mechanical valves. However, when a fluidized bed heat exchanger (FBHE) is installed to additionally absorb heat from the fluidized particles, some particles in the sealpot pass through the FBHE and then flow into the combustor. At this time, in the FBHE operated in the bubbling fluidization regime, if the heat flow is not evenly distributed by poor mixing of the hot particles (800~950 ℃) flowing in from the sealpot, the heat exchanger tubes would be locally heated and then damaged, and the agglomeration of particles could also occur by formation of hot spot. This may affect the stable operation of the circulating fluidized bed. In this study, the unevenness of heat flow arising from structural problems of the FBHE of the domestic D-CFB boiler was found through the operating data analysis and the CPFD (Computational Particle Fluid Dynamics) simulation using Barracuda VR. Actually, the temperature of the heat exchanger tubes in the FBHE showed the closest correlation with the change in particle temperature of the sealpot. It was also found that the non-uniformity of the heat flow was caused by channeling of hot particles flowing in from the sealpot. However, it was difficult to eliminate the non-uniformity even though the fluidizing velocity of the FBHE was increased enough to fluidize hot particles vigorously. When the premixing zone for hot particles flowing in from the sealpot is installed and when the structure is changed through the symmetrization of the FBHE discharge line for particles reflowing into the combustor, the particle mixing and the uniformity of heat flow were found to be increased considerably. Therefore, it could be suggested that the structural modification of the FBHE, related to premixing and symmetric flow of hot particles, is an alternative to reduce the non-uniformity of the heat flow and to minimize the poor particle mixing.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.1
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• pp.14-20
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• 2006

In this study, the feasibility of simultaneous removal of organic materials and nitrogen in the waste-water from fisheries processing plant was evaluated using entrapped mixed microbial cell technique(EMMC) process. The experiment was performed using activated sludge from municipal sewage treatment plant which was immobilized with gel matrix by cellulose triacetate. It was found that the stable operation at the treatment system which is composed of anoxic and oxic tank, was possible when the organic and nitrogen loading rates were increased stepwise. The organic and nitrogen loading rates were applied from 0.65 to $1.72kgCOD/m^3/d$ and from 0.119 to $0.317kgT-N/m^3$ with four steps, respectively. The maximum nitrogen loading rate which could satisfy the regulated effluent standard of nitrogen concentration, was $0.3kgT-N/m^3/d$. The removal efficiency of total nitrogen was decreased apparently as increasing nitrogen loading rates, whereas the removal efficiency of ammonium nitrogen was effective at the all tested nitrogen loading rates. Therefore, it was concluded that nitrification was efficient at the system. Nitrate removal efficiency ranged from 98.62% to 99.51%, whereas the nitrification efficiency at the oxic tank ranged 94.0% to 96.9% at the tested loading rates. The removal efficiencies of chemical oxygen demand(COD) and those of total nitrogen at the entire system ranged from 94.2% to 96.6% and 73.4% to 83.4%, respectively.

• Clean Technology
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• v.18 no.4
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• pp.390-397
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• 2012

Removal characteristics of lead-contaminated soil at the military shooting range located in the Changwon city were studied experimentally using soil washing process. As a washing solution, hydrogen chloride (HCl) concentrations of 0.001, 0.01, 0.1 and 0.2 N were used, and soil : solution ratios were 1 : 2, 1 : 3, 1 : 4, and 1 : 5. Particle diameter of contaminated soil of 4-0.075 mm, and washing period of 5, 10, 15, 20, 30, 60, and 120 min were used as operating parameters. The optimum concentration of HCl solution was 0.1 N (56.3% of Pb removal efficiency) with 15 minutes operation period in views of economics, and the optimum soil : solution ratio was determined as 1 g : 3 mL for 69.7% of Pb removal efficiency with 0.1 N HCl and 15 minutes washing period. As washing period increased, removal efficiency was increased until 20 min of the removal efficiency of 75.3%, and then almost stable. Pb removal efficiency in soil particle diameters of 0.075 mm or more was ranged from 77.0% to 82.0%, but it was decreased to 52.8% in diameter of less than 0.075 mm. Therefore, the optimum cut-off size of the soil particle diameter was found less than 0.075 mm. Combined HCl solution and ultrasonic washing method showed better removal efficiency compared to only water or HCl washing method for particle sizes above 0.075 mm.