• Journal of Korean Society of Environmental Engineers
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• v.31 no.11
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• pp.997-1006
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• 2009

Organic removal efficiency and methane production rate, a feasibility of power generation from biogas, and the optimum conditions for membrane operation were evaluated for the pilot scale (5 tons/day) two-phase anaerobic digestion coupled with ultra filtration (TPADUF) system fed with garbage leachate. The TPADUF system is consisted of a thermophilic acidogenic reactor, a mesophilic methanogenic reactor, and an UF membrane. When garbage leachate with 150 g/L of TCOD was fed to the TPADUF up to organic loading rate (OLR) of 11.1 g COD/L/d, the effluent TCOD was lower than 6 g/L and the average removal efficiencies of TCOD and SCOD were higher than 95%. The methane composition of the gas was 65%, and the methane yield was 39 $m^3/m^3$ garbage leachatefed, 260 $m^3$/tons $COD_{added}$, or 270 $m^3$/tons $COD_{removed}$, even there was some gas leak. The power production per consumed gas was 0.96 kWh/$m^3$ gas or 1.49 kWh/$m^3$ methane. This lower power production efficiency mainly due to the small capacity of gas engine (15 kW class). The membrane was operated at the average flux of 10 L/$m^2$/hr. When the flux decreased, washing with water and chemical (NaOCl) was conducted to restore the flux. In the TPADUF system, optimum pH could be maintained without alkali addition by recycling the membrane concentrate or mixed liquor of the methanogenic digester to the acidogenic reactor. Also, partial production of methane in the acidogenic reactor had a positive effect on lowering the OLR of the methanogenic reactor.

• Journal of Chest Surgery
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• v.43 no.4
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• pp.404-408
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• 2010

Background: Pleural symphysis is regarded as an important treatment option in reducing recurrence rates after surgical treatment of spontaneous pneumothorax. However, there is much debate over the best method for achieving pleural symphysis. We retrospectively compared apical pleurectomy (AP) with mechanical pleural abrasion (MPA). Material and Method: Between January 2000 and December 2007, 83 patients underwent video-assisted thoracoscopic surgery (VATS) for spontaneous pneumothorax. In addition to wedge resection of bullae, MPA was performed in 21 patients (group A) and AP in 62 patients (group B). Result: There were no significant differences in age, gender and site of pneumothorax between the two groups. Operative time was $97{\pm}44$ minutes in group A and $77{\pm}18$ minutes in group B (p>0.05). The mean amount of pleural drainage through the chest tube on the first postoperative day was $156{\pm}87 cc$ in group A and $147{\pm}87 cc$ in group B (p>0.05). There was no mortality or significant morbidity in all patients with the exception of reoperation for bleeding in two patients in group B. In the postoperative course, there were no statistical differences between the two groups in the rate of residual air space, air leak and indwelling time of chest tube, and hospital stay. Mean follow up time was $31.7{\pm}25.3$ months, and the recurrence rate of pneumothorax was 9.5% (2/21) in group A and 6.5% (4/62) in group B, without statistical significance. Conclusion: AP was no more advantageous than MPA in terms of operative time, postoperative course and prevention of recurrent pneumothorax. Therefore, complete resection of bullae and existence of residual bullae are more important factors in reducing the incidence of recurrent pneumothorax than pleural symphysis.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.94-101
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• 2015

To mitigate the greenhouse gas emission, many carbon capture and storage projects are underway all over the world. In Korea, many studies focus on the storage of $CO_2$ in the offshore sediment. Assurance of safety is one of the most important issues in the geological storage of $CO_2$. Especially, the assessment of possibility of leakage and amount of leaked $CO_2$ is very crucial to analyze the safety of marine geological storage of $CO_2$. In this study, the leakage of injected $CO_2$ through fault was numerically studied. TOUGH2-MP ECO2N was used to simulate the subsurface behavior of injected $CO_2$. The storage site was 150 m thick saline aquifer located 825 m under the continental shelf. It was assumed that $CO_2$ leak was happened through the fault located 1,000 m away from the injection well. The injected $CO_2$ could migrate through the aquifer by both pressure difference driven by injection and buoyancy force. The enough pressure differences made it possible the $CO_2$ to migrate to the bottom of the fault. The $CO_2$ could be leaked to seabed through the fault due to the buoyancy force. Prior to leakage of the injected $CO_2$, the formation water leaked to seabed. When $CO_2$ reached the seabed, leakage of formation water stopped but the same amount of sea water starts to flow into the underground as the amount of leaked $CO_2$. To analyze the effect of injection rate on the leakage behavior, the injection rate of $CO_2$ was varied as 0.5, 0.75, and $1MtCO_2/year$. The starting times of leakage at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 11.3, 15.6 and 23.2 years after the injection, respectively. The leakage of $CO_2$ to the seabed continued for a period time after the end of $CO_2$ injection. The ratios of total leaked $CO_2$ to total injected $CO_2$ at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 19.5%, 11.5% and 2.8%, respectively.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.382-393
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• 2020

The engineered barrier system of high-level radioactive waste disposal must maintain its performance in the long term, because it must play a role in slowing the rate of leakage to the surrounding rock mass even if a radionuclide leak occurs from the canister. In particular, it is very important to clarify gas dilation flow phenomenon clearly, that occurs only in a medium containing a large amount of clay material such as a bentonite buffer, which can affect the long-term performance of the bentonite buffer. Accordingly, DECOVALEX-2019 Task A was conducted to identify the hydraulic-mechanical mechanism for the dilation flow, and to develop and verify a new numerical analysis technique for quantitative evaluation of gas migration phenomena. In this study, based on the conventional two-phase flow and mechanical behavior with effective stresses in the porous medium, the hydraulic-mechanical model was developed considering the concept of damage to simulate the formation of micro-cracks and expansion of the medium and the corresponding change in the hydraulic properties. Model verification and validation were conducted through comparison with the results of 1D and 3D gas injection tests. As a result of the numerical analysis, it was possible to model the sudden increase in pore water pressure, stress, gas inflow and outflow rate due to the dilation flow induced by gas pressure, however, the influence of the hydraulic-mechanical interaction was underestimated. Nevertheless, this study can provide a preliminary model for the dilation flow and a basis for developing an advanced model. It is believed that it can be used not only for analyzing data from laboratory and field tests, but also for long-term performance evaluation of the high-level radioactive waste disposal system.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.67-76
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• 2013

Landfill require special care due to the dangers of nearby surface water and underground water pollution caused by leakage of leachate. The leachate does not leak due to the installation of the geomembrane but sharp wastes or landfill equipment can damage the geomembrane and therefore a means of protecting the geomembrane is required. In Korea, in accordance with the waste control act being modified in 1999, protecting the geosynthetics liner on top of the slope of landfill and installing a drainage layer to fluently drain leachate became mandatory, and technologies are being researched to both protect the geomembrane and quickly drain leachate simultaneously. Therefore, this research has its purpose in studying the drainage functions of leachate and protection functions of the geomembrane in order to examine the application possibilities of Geo-Multicell-Composite (GMC) as a Leachate Collection Removal and Protection System (LCRPs) at the slope on top of the geomembrane of landfill by observing methods of inserting filler with high-quality water permeability at the drainage net. GMC's horizontal permeability coefficient is $8.0{\times}10^{-4}m^2/s$ to legal standards satisfeid. Also crash gravel used as filler respected by vertical permeability is 5.0 cm/s, embroidering puncture strength 140.2 kgf. A result of storm drain using artificial rain in GMC model facility, maxinum flow rate of 1,120 L/hr even spray without surface runoff was about 92~97% penetration. Further study, instead of crash gravel used as a filler, such as using recycled aggregate utilization increases and the resulting construction cost is expected to savings.

• Advances in pediatric surgery
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• v.1 no.2
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• pp.149-161
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• 1995

The first national survey on esophageal atresia and tracheoesophageal fistula was conducted to access the current status of its incidence, clinical manifestation, preoperative diagnosis and management, type of its anomaly, associated anomalies, and surgical results and course. The 43 members of the Korea Association of Pediatric Surgeons received questionnaires and registration forms to be filled out on each patient who were born during the three years from January 1, 1992 through December 31, 1994. Questionnaires composed of six broad areas which include 1) preoperative diagnosis and management, 2) surgical technic, 3) long gap, 4) postoperative management, and 5) complications and courses. A total of 148 cases was returned by 28 members working at 23 institutions and 27 members returned questionnaires. We obtained the following results by analysis of the 148 cases of tracheoesophageal anomalies. The incidence of tracheoesophageal anomaly was about 1/10,000-11,000 in 1994, which is one third of that of anorectal malformations in Korea and the distribution of the patients was almost proportionate to the size of each province. Both sexes are about equally affected. Majority of the members make diagnosis of tracheoesophageal anomaly by taking a simple infantogram with a radiopaque tube in upper pouch and a little under half(46%) prefers to perform echocardiography as a part of preoperative management to identify congenital heart disease and lateralize the aorta. Esophageal atresia with distal TEF(87.5%) was by far the most common and there were pure esophageal atresia(5.6%), H-type TEF(2.1%), and so on. About half(49%) of the patients had one or more associated anomalies in addition to tracheoesophageal anomalies. Congenital heart disease was associated in 46 cases(31%), anorectral malfomations in 19 cases(13%), musculoskeletal anomalies in 15 cases(10%), genitourinary anomalies in 10 cases(7%) and gastrointestinal anomalies in 7 cases(5%). Postoperatively, parenteral nutrition and assisted ventilation were given in 66% and 52% of patients respectively. Ninety three(74%) of 126 cases who underwent sugical procedure, experienced one or more complications such as respiratory complication(65%), leak(22%), stricture(21%) and so on. The survival rates related to the Waterston risk categories were 90.2% in group A, 71.4-75% in $B_1$, $B_2$, and $C_1$, groups, and 28% in group $C_2$, and the overall survival rate was 71.4%. Thirty six(28.6%) of 126 cases died of pneumonia/sepsis(12 cases), respiratory failure(12 cases), and congenital heart disease(4 cases). With short term follow-up, 69% of patients have been excellent whereas remainders of the cases have suffered from some sort of morbidity related to gastroesophageal reflux, recurrent respiratory infection, and esophageal stricture.

• Tuberculosis and Respiratory Diseases
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• v.44 no.5
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• pp.975-991
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• 1997

Background : Many patients with isoniazid and rifampin-resistant pulmonary tuberculosis have organisms that are also resistant to other first-line drugs. Despite of aggressive retreatment chemotherapy, the results are often unsuccessful, with a failure rate approaching 40%. Recently, there has been a revival of resectional surgery for the treatment of multidrug-resistant pulmonary tuberculosis. Methods : A retrospective analyses of the case records and radiographic findings were done. Between January 1991 and December 1995, 14 human immunodeficiency virus (HIV)-seronegative patients with multidrug-resistant pulmonary tuberculosis were selected for resection to supplement chemotherapy. All patients had organisms resistant to many of the first-line drugs, including both isoniazid and rifampin. Results : Despite of aggressive therapy for median duration of 9.5 months, 12 of the 14 patients (86%) were still sputum smear and/or culture positive at the time of surgery. The disease was generally extensive. Although main lesions of the disease including thick-walled cavities were localized in one lung, lesser amounts of contralateral disease were demonstrated in 10 of 14 (71%). Types of surgery performed were pneumonectomy including extrapleural pneumonectomy in six patients, lobectomy or lobectomy plus in six patients, and segmentectomy in two patients. The resected lung appeared to have poor function ; preoperative perfusion lung scan showed only 4.8% of the total perfusion to the resected portion of the lung. There were no operative deaths. Two patients had major postoperative complications including empyema with bronchopleural fistula and prolonged air leak, respectively. Of the 14 patients, 13 (93%) remained sputum-culture-negative for M. tuberculosis for a median duration of 23 months and one remained continuously sputum smear and culture positive for M. tuberculosis. Conclusion : On the basis of comparison with historical controls, adjunctive resectional surgery appears to play a significant beneficial role in the management of patients with multidrug-resistant pulmonary tuberculosis if the disease is localized and there are adequate reserve in pulmonary function.

• Journal of Korean Neurosurgical Society
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• v.29 no.10
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• pp.1309-1315
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• 2000

Objectives : We performed an in vivo experiment to investigate the effect of $^{166}Holmium$ and $^{166}Holmium$-chitosan complex($^{166}Ho$-CHICO) on the normal brain of rats and to determine the sublethal dose of $^{166}Ho$-CHICO. Materials and Methods : $^{166}Ho$ is a beta and gamma ray emitter. $^{166}Ho$-CHICO is a novel radio-pharmaceutical complex with chitosan to facilitate the transport of $^{166}Ho$ obtained from Korea Atomic Energy Research Center(Taejon, Korea). It is in acidic form and becomes gel state at alkaline pH. One hundred and seventy consecutive rats were divided into four groups : $^{166}Ho$ treated(n＝50), $^{166}Ho$-CHICO treated(n＝57), saline treated(n＝5) and chitosan treated(n＝5) groups. $^{166}Ho$ and $^{166}Ho$-CHICO were injected into the rat brain stereotactically with various doses of 0.1mCi/$20{\mu}l$, 0.2mCi/$20{\mu}l$, 0.3mCi/$20{\mu}l$, and 0.4mCi/$20{\mu}l$ using an automated microinjector. Nuclear imaging, histopathological and hematological studies were performed in 10 rats in each group at 1 day, 3days, 7 days, 1 month and 3 months after the injections. Results : An infiltration of inflammatory cells and necrotic changes were noted in $^{166}Ho$ treated group at 1 week after the injection. A wedge-shaped tissue defect due to necrosis, lined with infiltrated glial cells in $^{166}Ho$ treated group and a cystic defect lined with reactive astroglial cells in $^{166}Holmium$-CHICO treated group at 3 months after the injection were observed. $^{166}Ho$ alone without chitosan leaked out and caused necrotic lesion on the cerebral surface but $^{166}Holmium$-CHICO treated group did not show this feature. As the dose of $^{166}Ho$ increased, the mortality rates were also increased. The mortality rate of the $^{166}Holmium$-CHICO group was higher than the $^{166}Ho$ treated group at a dose of 0.4mCi/$20{\mu}l$/300g. There was no detectable radioactivity due to the leakage or extravasation from the injected site of the brain on the scintigraphy performed at 1 hour, 24 hours and 48 hours after the injection. There was also no detectable activity of $^{166}Holmium$-CHICO in other organs including spleen, liver and kidney. Conclusions : $^{166}Ho$-CHICO did not leak out to the critical cortical surface of the brain from the injection site and induced radiation changes of the parenchyma around the injection site without cortical damage. The sublethal dose of $^{166}Ho$-CHICO for the normal brain in rats was determined to be 0.2mCi/$20{\mu}l$/300g.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.05
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• pp.27-47
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• 1992

Engineers have developed new instruments that aid in diagnosis and therapy Ultrasonic imaging has provided a nondamaging method of imaging internal organs. A complex transducer emits ultrasonic waves at many angles and reconstructs a map of internal anatomy and also velocities of blood in vessels. Fast computed tomography permits reconstruction of the 3-dimensional anatomy and perfusion of the heart at 20-Hz rates. Positron emission tomography uses certain isotopes that produce positrons that react with electrons to simultaneously emit two gamma rays in opposite directions. It locates the region of origin by using a ring of discrete scintillation detectors, each in electronic coincidence with an opposing detector. In magnetic resonance imaging, the patient is placed in a very strong magnetic field. The precessing of the hydrogen atoms is perturbed by an interrogating field to yield two-dimensional images of soft tissue having exceptional clarity. As an alternative to radiology image processing, film archiving, and retrieval, picture archiving and communication systems (PACS) are being implemented. Images from computed radiography, magnetic resonance imaging (MRI), nuclear medicine, and ultrasound are digitized, transmitted, and stored in computers for retrieval at distributed work stations. In electrical impedance tomography, electrodes are placed around the thorax. 50-kHz current is injected between two electrodes and voltages are measured on all other electrodes. A computer processes the data to yield an image of the resistivity of a 2-dimensional slice of the thorax. During fetal monitoring, a corkscrew electrode is screwed into the fetal scalp to measure the fetal electrocardiogram. Correlations with uterine contractions yield information on the status of the fetus during delivery To measure cardiac output by thermodilution, cold saline is injected into the right atrium. A thermistor in the right pulmonary artery yields temperature measurements, from which we can calculate cardiac output. In impedance cardiography, we measure the changes in electrical impedance as the heart ejects blood into the arteries. Motion artifacts are large, so signal averaging is useful during monitoring. An intraarterial blood gas monitoring system permits monitoring in real time. Light is sent down optical fibers inserted into the radial artery, where it is absorbed by dyes, which reemit the light at a different wavelength. The emitted light travels up optical fibers where an external instrument determines O2, CO2, and pH. Therapeutic devices include the electrosurgical unit. A high-frequency electric arc is drawn between the knife and the tissue. The arc cuts and the heat coagulates, thus preventing blood loss. Hyperthermia has demonstrated antitumor effects in patients in whom all conventional modes of therapy have failed. Methods of raising tumor temperature include focused ultrasound, radio-frequency power through needles, or microwaves. When the heart stops pumping, we use the defibrillator to restore normal pumping. A brief, high-current pulse through the heart synchronizes all cardiac fibers to restore normal rhythm. When the cardiac rhythm is too slow, we implant the cardiac pacemaker. An electrode within the heart stimulates the cardiac muscle to contract at the normal rate. When the cardiac valves are narrowed or leak, we implant an artificial valve. Silicone rubber and Teflon are used for biocompatibility. Artificial hearts powered by pneumatic hoses have been implanted in humans. However, the quality of life gradually degrades, and death ensues. When kidney stones develop, lithotripsy is used. A spark creates a pressure wave, which is focused on the stone and fragments it. The pieces pass out normally. When kidneys fail, the blood is cleansed during hemodialysis. Urea passes through a porous membrane to a dialysate bath to lower its concentration in the blood. The blind are able to read by scanning the Optacon with their fingertips. A camera scans letters and converts them to an array of vibrating pins. The deaf are able to hear using a cochlear implant. A microphone detects sound and divides it into frequency bands. 22 electrodes within the cochlea stimulate the acoustic the acoustic nerve to provide sound patterns. For those who have lost muscle function in the limbs, researchers are implanting electrodes to stimulate the muscle. Sensors in the legs and arms feed back signals to a computer that coordinates the stimulators to provide limb motion. For those with high spinal cord injury, a puff and sip switch can control a computer and permit the disabled person operate the computer and communicate with the outside world.

• Journal of Chest Surgery
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• v.32 no.6
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• pp.567-572
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• 1999

Background: Surgical correction of the full spectrum of esophageal atresia with tracheoesophageal fistula has improved over the years, but the mortality and morbidity assoiated with repair of these anomalies still remains high. Material and Method: We retrospectively analyzes 27 surgically treated patients with esophageal atresia and tracheoesophageal fistula at Dong-A University Hospital between January 1992 and March 1997. Result: There were 21 male and 6 female patients. Mean birth weight was 2.62$\pm$.385 kg(2.0~3.4 kg). Twenty- four(88.9%) had esophageal atresia with distal tracheoesophageal fistula, and 3(11.1%) had pure esophageal atresia. Four(14.8%) infants were allocated to Waterston risk group A, 18(66.7%) to group B, and 5(18.5%) to group C. In eighteen(66.7%) infants with associated anomalies, cardiovascular anomalies were the most common. Three had a gap length of 3.5 cm or greater(ultra-long gap) between esophageal segments, 7 had 2.0 to 3.5 cm(long gap), 8 had 1.0 to 2.0 cm(medium gap), and 9 had 1 cm or less(short gap) gap length. Among 27 neonates, 3 cases underwent staged operation, late colon interposition was done in 2, and all other 24 cases underwent primary esophageal anastomosis. Oerative mortality was 2/27(7.4%). Causes of death included acute renal failure(n=1), empyema from anastomotic leak(n=1), necrotizing enterocolitis(n=1), sepsis(n=1), insulin-dependent diabetus mellitus(n=1 . There were 4 anastomosis- related complications including stricture in 3, leakage in 1. Mortality was related to the gap length(p<.05). Conclusion: Although the complication rate associated with surgical repair of these anomalies is high, this does not always implicate the operative mortality. The overall survival can be improved by effective treatment for combined anomalies and intensive postoperatve care.