• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.4
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• pp.620-626
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• 1997

Annual biomasses of the hairtail, Trichiurus lepturus, were estimated from the biomass-based cohort analysis (Zhang, 1987), using data of annual catch in weight at age during $1970\~1988$ in Korean waters. Annual biomass of the hairtail was peaked at about 240,000 mt in 1975, and thereafter declined with a slight fluctuation. Adult biomass showed a peak in 1978 with about 55,000 mt. However, it has continuously decreased untill 1980 to the level of 9,000 mt and remained at this level till 1988. Age compositions of the hairtail in the 1980s differed greatly from those in the 1970s. The proportions of older hairtail (>4 years) were very low in the 1980s and even the biomasses of young hairtail $(1\~3\;years)$ were at a low evel in the 1980s compared with the level in 1970s. The 1973 and 1974 year classes appeared to be relatively dominant. The mean value of instantaneous rate of fishing mortality (F) in the 1980s was significantly different from that of the 1910s (P<0.05). Recruitment of the hairtail exhibited a similar trend with stock biomass until 1974, indicating the density-dependent Ricker curve.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.138-152
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• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Journal of the Korean Ceramic Society
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• v.29 no.5
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• pp.347-356
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• 1992

Various kaolin samples with different alumina content were prepared from calcined admixture of kaolin and ammonium sulfate by varying the treatment time in sulfuric acid. Samples were nitridated under N2 or N2-H2 atmosphere with changing the amount of added carbon, the reaction time and temperature. As the alumina content lowered, the size of kaolin particles decreased and the specific surface area increased. XRD analysis indicated that ${\alpha}$-quartz remained by decomposition of halloysite and meta-halloysite. Experimental results of nitridation behavior are summerized as follows; 1) Nitridation under N2 atmosphere. With the increase of C/SiO2 ratio and with the decrease of Al2O3 content, disappearance of XRD pattern peaks of mullite, ${\alpha}$-quartz and ${\alpha}$-Al2O3 were accelerated at 1300$^{\circ}C$. SiC was the main phase in the reaction product of acid-treated kaolin samples nitridated at 1300$^{\circ}C$ for 10 hours regardless of C/SiO2 ratio. But the XRD peak intensities of ${\beta}$-Si3N4, ${\beta}$-sialon and SiC did not show much difference when untreated raw kaolin was fired at the same condition. When the ratio of C/SiO2 was 3.5, ${\beta}$-sialon and ${\beta}$-Si3N4 existed in the reaction product of about 22% alumina containing kaolin sample fired at 1350$^{\circ}C$ for 7 hours. Only ${\beta}$-sialon existed in the same sample fired at 1400$^{\circ}C$ for 10 hours. ${\beta}$-sialon was obtained from all of the acid-treated kaolin samples fired at 1400$^{\circ}C$ for 40 hours, but AlN and SiC remained in the untreated kaolin sample. Z value of the ${\beta}$-sialon obtained from the 22% alumina containing kaolin sample fired at 1400$^{\circ}C$ for 40 hours was about 1.3(XRD) and 1.5(EDS). 2) Nitridation under 80N2+2OH2 mixed gas atmosphere with the C/SiO2 ratio of 1 Mullite was not found, but ${\alpha}$-Si3N4, and ${\beta}$-sialon were present in the reaction product of about 22% alumina containing kaolin sample fired at 1300$^{\circ}C$ for 10 hours. When untreated kaolin sample was nitridated at the same condition, mullite remained. AlN and SiC were not found in the reaction product of about 22% alumina containing kaolin sample fired at 1350$^{\circ}C$ for 5 hours. On the other hand, AlN and SiC remained in the product of untreated kaolin fired at the same condition.

• Journal of Korean Neurosurgical Society
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• v.61 no.1
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• pp.81-88
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• 2018

Objective : Spondylitis is often chemotherapy resistant and requires long-term treatment. Without adequate chemotherapy, the outcome can be fatal or result in severe neurologic damage. Therefore, differentiating the etiology of spondylitis is very important, particularly in spontaneous cases. As the prevalence of tuberculosis in Korea has decreased in recent years, updated clinical research about spondylitis is warranted. Methods : From April 2010 to March 2016, data from spondylitis patients were collected retrospectively. In total, 69 patients (51 with pyogenic spondylitis and 18 with tuberculous spondylitis) were included. Clinical data, laboratory findings including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level, measurements of Cobb angles at the initial and final follow-up, and radiologic features on magnetic resonance imaging (MRI) scans were evaluated. To test differences between the pyogenic and tuberculous groups, numerical data were compared using the student's t-test and Mann-Whitney U test, and categorical data were compared using the chi-square test and Fisher's exact test. Results : The patients' mean age was 60.0 years. Male sex was slightly predominant (56.5%). There was no difference in mean age and sex between the two groups. The pyogenic group had a relatively higher proportion of immunocompromised patients. The peak CRP value was higher in the pyogenic group than in the tuberculous group (14.08 mg/dL and 8.50 mg/dL, respectively, p=0.009), whereas the ESR was not significantly different between the groups (81.5 mm/h and 75.6 mm/h, respectively, p=0.442). Radiologically, the presence of disc space sparing and vertebral body collapse differed between the groups. In the tuberculous group, the disc was more commonly preserved on contrast-enhanced MRI (50% and 23.5%, respectively, p=0.044), and vertebral body collapse was more common (66.6% and 15.7%, respectively, p<0.001). The mean length of hospitalization was longer in the pyogenic group (56.5 days and 41.2 days, respectively, p=0.001). Four mortality cases were observed only in the pyogenic group. The most commonly isolated microorganism in the pyogenic group was Staphylococcus aureus(S. aureus) (methicillin susceptible S. aureus and methicillin resistant S. aureus [MRSA] in 8 and 4 cases, respectively). Conclusion : The clinical and radiological manifestations of spontaneous spondylitis differ based on the causative organism. Pyogenic spondylitis patients tend to have a higher CRP level and a more severe clinical course, whereas tuberculous spondylitis patients present with destruction of the vertebral body with disc sparing more frequently. The presence of MRSA is increasing in community-acquired spondylitis cases.

• Journal of Korean Neurosurgical Society
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• v.63 no.3
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• pp.386-396
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• 2020

Objective : To generate synthetic spine magnetic resonance (MR) images from spine computed tomography (CT) using generative adversarial networks (GANs), as well as to determine the similarities between synthesized and real MR images. Methods : GANs were trained to transform spine CT image slices into spine magnetic resonance T2 weighted (MRT2) axial image slices by combining adversarial loss and voxel-wise loss. Experiments were performed using 280 pairs of lumbar spine CT scans and MRT2 images. The MRT2 images were then synthesized from 15 other spine CT scans. To evaluate whether the synthetic MR images were realistic, two radiologists, two spine surgeons, and two residents blindly classified the real and synthetic MRT2 images. Two experienced radiologists then evaluated the similarities between subdivisions of the real and synthetic MRT2 images. Quantitative analysis of the synthetic MRT2 images was performed using the mean absolute error (MAE) and peak signal-to-noise ratio (PSNR). Results : The mean overall similarity of the synthetic MRT2 images evaluated by radiologists was 80.2%. In the blind classification of the real MRT2 images, the failure rate ranged from 0% to 40%. The MAE value of each image ranged from 13.75 to 34.24 pixels (mean, 21.19 pixels), and the PSNR of each image ranged from 61.96 to 68.16 dB (mean, 64.92 dB). Conclusion : This was the first study to apply GANs to synthesize spine MR images from CT images. Despite the small dataset of 280 pairs, the synthetic MR images were relatively well implemented. Synthesis of medical images using GANs is a new paradigm of artificial intelligence application in medical imaging. We expect that synthesis of MR images from spine CT images using GANs will improve the diagnostic usefulness of CT. To better inform the clinical applications of this technique, further studies are needed involving a large dataset, a variety of pathologies, and other MR sequence of the lumbar spine.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.543-552
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• 1994

A series of drained plane strain compression tests was performed on dried samples of dense Toyoura sand and Silver Leighton Buzzard sand prepared by air-pluviation method to find out the deformation and strength characteristics on the value of confining pressure ${\sigma}{_3}^{\prime}({\sigma}{_3}^{\prime}=0.05{\sim}4.0kgf/cm^2)$. The axial and lateral strains measured in this apparatus ranged from $10^{-6}$ up to the failure of the specimen. So the stress-strain characteristics would be investigated from very small to very large strain levels. It was found that the change of the angle of internal friction ${\phi}^{\prime}{_{max}}=arcsin\{({\sigma}{_1}^{\prime}-{\sigma}{_3}^{\prime})/({\sigma}{_1}^{\prime}+{\sigma}{_3}^{\prime})\}_{max}$ with the change of ${\sigma}{_3}^{\prime}$ is very small when ${\sigma}{_3}^{\prime}$ is lower than higher. Furthermore, the effect of confining pressure on stiffness of sands was evaluated. It was also found that for the range of shear strain ${\gamma}$ from $10^{-6}$ to those at peak, the Rowe's stress-dilatancy relation seems to be a good approximation for air-dried Toyoura sand and Silver Leighton Buzzard sand, irrespective of the change of ${\sigma}{_3}^{\prime}$.

• The Korean Journal of Nuclear Medicine
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• v.26 no.1
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• pp.40-48
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• 1992

Gated blood pool scan is frequently used for evaluating the change in cardiac function in various cardiac diseases. But resting gated blood pool scan using only LVEF as a cardiac index has been consitently shown to have a low sensitivity, which is about 50%, in detecting coronary artery disease. So it is recommended to compare exercise gated blood pool scan to resting gated blood pool scan. Exercise tests, however, are not always possible, especially in patients with musculoskeletal diseases, recent myocardial infarction and in elderly persons. We studied the usefulness of resting gated blood pool scan using multiple indices in evaluating the patients with coronary artery disease. Studied cases were 185 patients with coronary artery disease (angina pectoris 31, myocardial infarction 154) and 25 normals with low likelihood of coronary artery disease. We used $^{99m}Tc-labeled$ RBC, 740 MBq labeled by in vivo method. The data were evaluated by Micro DELTA computer program. The results were as following: 1) The ejection rates (PER, AER) and filling rates (PFR, AFR) were different in normls and patients with angina pectoris or myocardial infarction. 2) Mean phase angle, ejection rates and filling rates could separate normals from coronary artery disease patients with normal LVEF. 3) Regional ejection fraction was decreased at the site of the infarct in patients with myocardial infarction. 4) Peak filling rate was the the most detectable index in evaluation of cardiac function in patients with coronary artery disease. 5) The threshold at 1.5 standard deviation of normal range was considered as the most reliable cut-off value from ROC analysis. These data suggest that the resting gated blood pool scan has an important role in the evaluation of cardiac functional changes using various cardiac indices in patients with coronary artery disease.

• Research in Plant Disease
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• v.6 no.1
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• pp.23-26
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• 2000

Effects of infection time of the clubroot pathogen, Plasmodiophora brassicae, on yield loss of Spring-sown Chinese cabbage plants were examined in field experiments. Yield loss of Chinese cabbage plants increased as the infection time becomes early. Plants infected at 20 days after transplanting or earlier were completely killed before harvest, and those infected at 30 days after transplanting were healthy in appearance but their head weights were reduced to 59% with poor commodity value. The plants infected 40 days after transplanting were not affected in yield. Development of root hairs in diseased plants was greatly reduced as the infection progressed, and root length was reduced to 1/2 to 1/3 of that of healthy plants. root galls were first developed 20 days after inoculation and rapidly enlarged to reach the peak in size 20 days from initial development, and decayed thereafter. Development and decay of root galls tended to be faster at later season as air temperature became high, regardless of the infection time. Diseased plants started to wilt approximately 10 days after root gall development. Root galls began to decay 10 days after initial plant wilting, and then were completely rotten within following 10 days. Based on the results, root gall development stages on spring-sown Chinese cabbage plants could be grouped into 20 days of root gall enlargement period, and 10 days of root gall decay period, followed by survival period in soil.

• 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.29 no.1
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• pp.1-6
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• 1996

We developed an experimental model of brain death using dogs. Brain death was induced by increasing the intracranial pressure (ICP) gradually by continuous Infusion of saline through an epidural Foley catheter in 5 mongrel dogs (weight, 18~22kg). Hemodynamic and electrocardiographic changes were evaluated continuously during the process of brain death and obtained the following results. 1. The average volume and time required to induce brain death was 4.8$\pm$1.0ml and 143.0$\pm$30.9minutes respectively. 2. There was a steady rise of the ICP after starting the constant infusion of saline, and ICP rised continuously until the brain death (122.0$\pm$62.5mmHg). After reaching to the maximal value (125.0$\pm$47.7mmHg) at 30 minutes after brain death, the ICP dropped and remained approximately constant at the slightly higher level than the mean arterial pressure (MAP). 3. MAP showed no change until the establishment of brain death and it declined gradually. The peak heart rate reached to 172.6$\pm$35.3/min at 30 minutes after the brain death. 4. Even though the body temperature and all hemodynamic variables, such as cardiac output, mean pulmonary arterial pressure, left ventricular (LV) end-diastolic pressure and LV maximum + dp/dt, were slightly greater than those of basal state, at the point of brain death, there was no statistically significant change during t e process of brain death. 5. There was no remarkable arrhythmias during the experiment except ventricular premature beats which was observed transiently in one dog at the time of brain death. Hemodynamic changes in the brain death model induced by gradual ICP increment were inconspicuous, and arrhythmias were rarely seen. Hyperdynamic state, which was observed at the point of brain death in another brain death model caused by abrupt ICP increase, was not observed.