• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.1032-1043
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• 1989

The heat transfer characteristics of the drag reducing polymer solutions are investigated experimentally in the thermal entrance region of circular tube flows. Fluids used in experiments are the aqueous solutions of high molecular polymer, polyacrylamide Separan AP-273 and the range of polymer concentrations is from 20 to 1000 wppm. Two stainless steel tubes with inside diameter 8.5mm(L/D=712) and 10.3mm(L/D=1160) are used for the heat transfer flow loops. The flow loop is set up to measure friction factors and heat transfer coefficients of test sections in two different modes; the recirculating flow system and once-through flow system. The test tubes are heated directly by electricity to apply the constant heat flux boundary conditions to the wall. Three different types of adaptors are used to observe the effects of the upstream flow conditions of the heat transfer test sections. The viscosity and characteristic relaxation time of the test fluids circulating in the flow system are measured by the capillary tube viscometer and falling ball viscometer at regular time intervals. The installed adaptors exhibit slight effect on the entrance heat transfer of Newtonian fluid. However, no noticeable effects are observed for the entrance heat transfer of the drag reducing fluids. The order of magnitude of the thermal entrance lengths of the drag reducing fluids which follow the minimum friction asymptote is much longer than that of Newtonian fluids in turbulent flows. A new dimensionless parameter, the viscoelastic Graetz number, is defined and all the experimental data are recasted in terms of the viscoelastic Graetz number. The local Nusselt number of the viscoelastic fluids is represented as a function of flow behavior index n and the viscoelastic Graetz number. As degradation continues the viscosity and the characteristic relaxation time of the testing fluids decrease. Weissenberg number defined by the relaxation time and D/V appears to be a proper dimensionless parameter in describing degradation effects on heat transfer of the viscoelastic fluids.

• Journal of Energy Engineering
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• v.27 no.4
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• pp.27-35
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• 2018

The passive containment cooling system (PCCS) has been designed to remove the released decay heat during the accident by means of the condensation heat transfer phenomenon to guarantee the safety of the nuclear power plant. The heat removal performance of the PCCS is mainly governed by the condensation heat transfer of the steam-air mixture. In this study, the heat removal performance of the PCCS was evaluated by using the MARS-KS code with a new empirical correlation for steam condensation in the presence of a noncondensable gas. A new empirical correlation implemented into the MARS-KS code was developed as a function of parameters that affect the condensation heat transfer coefficient, such as the pressure, the wall subcooling, the noncondensable gas mass fraction and the aspect ratio of the condenser tube. The empirical correlation was applied to the MARS-KS code to replace the default Colburn-Hougen model. The various thermal-hydraulic parameters during the operation of the PCCS follonwing a large-break loss-of-coolant-accident were analyzed. The transient pressure behavior inside the containment from the MARS-KS with the empirical correlation was compared with calculated with the Colburn-Hougen model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.10-19
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• 2019

Management plan with repairing is essential for RC structures exposed to chloride attack since durability problems occur with extended service life. Conventionally deterministic method is adopted for evaluation of service life and repair cost, however more reasonable repair cost can be obtained through continuous repair cost from probabilistic maintenance technique. Unlike the previous researches considering only normal distribution of life time, PLTFs (Probabilistic Life Time Function) which can be capable of handling log and normal distributions are attempted for initial and repair service life, and repair cost is evaluated for OPC and GGBFS concrete. PLTF with log distributions in initial service life is more effective to save repair cost since it is more dominant after average than normal distribution. Repair cost in GGBFS concrete decreases to 30% of OPC concrete due to longer initial service life and lower repairing event. The proposed PLTF from the work can handle not only normal distributions but also log distributions for initial and repair service life, so that it can provide more reasonable repair cost evaluation.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.4
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• pp.222-231
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• 2020

To use the external connection implant (EXT) appropriately, the inter-implant distance should be carefully considered during placement, and the bones raised above the implants should be trimmed during the second surgery. The hex abutment is more useful than the non-hex abutment. EXT is particularly useful when the inter-arch space is limited. The tissue level (TL, internal butt connection) implant has a biomechanical advantage of coronal wall thickness and a biological advantage of an inherent transmucosal smooth surface. During TL implant restoration, an abutment can be selected using the abutment and fixture margins with considerations for the inter-arch space. Since no single type of implant can satisfy all the cases, it is necessary to select the appropriate type, considering the occlusal force and the bone condition.

• The Journal of the Korea Contents Association
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• v.22 no.6
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• pp.638-651
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• 2022

Last year, a new perception of the right to peace on the Korean Peninsula was adopted: DMZ Yanggu Peace Declaration 2021. The Declaration reflects that there is a raising of necessity for a new perception and approach from the perspective of DMZ-related laws, sustainable ecological environment and security. Gangwon is making considerable efforts to make the border area in DMZ as an area of peace by continuously enhancing publicity on the establishment of the 'Peace Special Self-Governing Province'. This study suggests the necessity of a paradigm shift towards the significance of the interkorean border region that it should function as a passage between the South and the North rather than a dam. For, to be renewed as a sustainably developing region through newly constructed flow of communication, the wall of hostility must preliminarily fall dawn. Then a question arises about how Gangwon is, out of other border region, most eligible for the reconsideration of its significance as a border area. The answer relies on the newly established agenda and understandings towards the right to peace in the perspective of founding the policy for the Unification of the Korean Peninsula. Furthermore, the conservation of DMZ ecological environment through enlistment of UNESCO Biosphere Reserve should go hand in hand with the ultimate value of global agenda of the conservation and protection of the environment. The study insists that the peace zone is a prerequisite for the adaption of the era of future-oriented glocalization featured by the Fourth Industrial Revolution. Up to this date, the border area was an area of pain and agony. It is time for Gangwon to be reborn as an area of peace and coexistence. The aim of this study is to point a direction for Gangwon to become a sustainably developing region by illuminating the value of the Gangwon border area as a new area of peace.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.25-32
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• 2007

Because of the increasing use of clayey soil as the backfill in reinfurced soil structures and embankments, nonwoven geotextiles of drain capability have been receiving much attention. However, there are few studies on the deformation behavior analysis of nonwoven geotextiles in reinforced soil structures in the site because nonwoven geotextiles which have low tensile stiffness and higher deformability than geogrids and woven geotextiles, are difficult to measure their deformation by using strain gauges. In this study, it was suggested that a new and more convenient method could measure the deformation behaviour of nonwoven geotextile using a strain gauge and examine the availability of the method by conducting laboratory tests and applying to two geosynthetics reinforced soil (GRS) walls in the site. The result of wide-width tensile test conducted under confining pressure of 70 kPa shows that the local deformation of nonwoven geotextile to be measured with strain gauges has a similar pattern to the total deformation measured with LVDT. In the GRS walls, nonwoven geotextile shows a larger deformation range than the woven geotextile and geogrid. However, the deformation patterns of these three reinforcement materials are similar. The function of strain gauges attached to nonwoven geotextile in the walls works normally for 16 months. Therefore, the method proposed in this study for measuring nonwoven geotextile deformation using a strain gauge has proved useful.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.6
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• pp.41-51
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• 2015

The purpose of the Follies that were constructed for the Gwangju-Biennale were for urban regeneration, to activate the empty old-town areas, and to strengthen the tradition and sense of place of the city. However, the ten Follies constructed around the wall of the old castle reveal many problems including that of leaving Follies alone instead of actively using them, damage to shop-keepers nearby, and pedestrian inconvenience, which is different from the original purposes. This study is meant to help understand the source of the negative phenomena, and to offer plans that will be conductive to the role of urban regeneration through activating the Follies and the spaces around them. As results of the investigation, there was no context giving uniformity among the various Follies. Also, the study showed that the insufficience of designers' understanding of the circumference near the Follies and lack of a consensus between the citizens and designers in the process of making the Follies. The crucial solution for solving these problems, and bringing to life the original purpose of creating the Follies was derived as applying "human activity" to the Follies. This study suggested 'street performance' as an effective device for application to human activity. While a Folly has no fixed function, the development of space program categories based on the applied characteristics of each Folly, and the simulation thereof showed effective potential for attracting people and activating those stagnated spaces. Recently, Gwangju city depicted the second Follies in applications such as reading roon, toilet, and movable food cart, which have clear purpose and different characteristics from the first ones. However, the first Follies will not be moved or demolished. As they are located around the National Asia Culture Center, some of them are supposed to be used to view the center. Consequently, a counterplan for the continuous and efficient use of those Follies is needed. Gwangju has a plan for the installation of 100 Follies throughout the city and it is expected that this study will be a meaningful guide line for improved Follies in the future.

• Journal of Chest Surgery
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• v.32 no.6
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• pp.536-542
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• 1999

Background: The purpose of this study is to improve the quality of the diagnostic procedures in the preoperative evaluation so as to reduce the unnecessary thoracotomy and to ensure resectability in non-small cell lung cancer. Material and Method: Of 616 patients who underwent thoracotomy for primary lung cancer from January 1990 to December 1996, 59 patients(9.6%) turned out to have inoperable lesions after the thoracotomy. We reprospectively reviewed the bronchoscopic findings, methods of tissue diagnosis, CT scans, pulmonary function test and lung perfusion scan, reasons for nonresectability, and adjuvant therapy, and then followed up on the survival rate after exploratory thoracotomy. Result: The cell types were squamous cell carcinoma in 38, adenocarcinoma in 15, large cell carcinoma in 3 and others in 3. Primary loci were RUL in 20, RML in 6, RLL in 8, LUL in 13, LLL in 4 and others in 8. The reasons for non-resectability were various; direct tumor invaison to mediastinal structures(n=41), seeding on pleural cavity(n=8), poor pulmonary function(n=2), invasions to extranodal mediastinal lymph node(n=2), technical non- resectability due to extensive chest wall invasion (n=3), small cell carcinoma (n=1), malignant lymphoma(n=1), and multiple rib metastases(n=1). In the follow-up of 58 patients, 1-year survival rate was 55.2% and 2-year survival rate was 17.2% and the mean survival time was 14 months. When compared according to cell types or postoperative adjuvant therapeutic modalities, no significant difference in the survival rates were found. The squamous cell carcinoma was frequently accompanied by local extension to contiguous structures and was the main cause of non-resectability. In adenocarcinoma, pleural seeding with malignant effusion was frequently encountered, and was the major reason for non-resectability. Conclusion: These data revealed that if appropriate preoperative diagnostic tools had been available, many unnecessary thoracotomies could have been avoided. Both the use of thoracoscopy in selected cases of adenocarcinoma and the more aggressive surgical approach to the locally advanced tumor could reduce the incidence of unnecessary thoracotomies for non-small cell lung cancers.

• Tuberculosis and Respiratory Diseases
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• v.60 no.3
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• pp.297-303
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• 2006

Background : Pulmonary tuberculosis is frequently accompanied with complications such as bronchiectasis, cavities, fibrosis and a deterioration of the lung function. However, there is little information available on the pathogenesis of these complications in pulmonary tuberculosis. Among the many factors involving in tissue remodeling, transforming growth factor-${\beta}1$ ($TGF-{\beta}1$) is a potent stimulus of the extracellular matrix fomation and a mediator of potential relevance for airway wall remodeling. Therefore, this study examined the relationship between the radiological changes and the $TGF-{\beta}1$ level in patients with pulmonary tuberculosis. Methods : Serum and bronchoalveolar lavage fluid (BALF) were collected from total of 35 patients before treating them for active pulmonary tuberculosis, and the $TGF-{\beta}1$ levels were measured using an enzyme-linked immunosorbent assay (ELISA). The BALF levels were recalculated as the epithelial lining fluid (ELF) levels using the albumin method. pulmonary function test (PFT) and high resolution computed tomography (HRCT) were performed before and after treatment. Results : There was a strong correlation between the serum $TGF-{\beta}1$ level and the presence of cavities (r=0.404, p=0.006), even though the BAL $TGF-{\beta}1$ level showed a weak correlation with complications. In addition, there was no correlation between the $TGF-{\beta}1$ levels before treatment and the changes in the PFT and HRCT during treatment. Conclusion : There is a correlation between the serum $TGF-{\beta}1$ level and cavity formation in pulmonary tuberculosis before treatment. However, further study will be needed to confirm this.

• Journal of fish pathology
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• v.8 no.2
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• pp.119-134
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• 1995

To induce an overpopulated melanomacrophage centers(MMCs) within spleen and kidney in tilapias, two methods were applied through the intraperitoneal inoculation of V. anguillarum FKC with a repeated dose of saline(the 1st induction group), and of colloidal carbon (the 2nd induction group). In the 1st group, both number and size of MMCs were slightly increased in spleen and head kidney. However in the 2nd group the two hemopoietic tissues were nearly occupied with quite a large number of MMCs. Regardless of induction groups, many of MMCs were confined within the walls of blood vessels in the spleen. Especially in the 2nd group, the MMCs without fibrous capsules often had concentrically or eccentrically located, thin-walled lumens of vessels, which strongly suggests to be ellipsoids. In head kidney, nearly all MMCs were located within or just around the lymphocytic areas but the precise relationship to blood vessel wall was not obvious. Despite of such overpopulated MMCs, no histopathological degenerative findings in hemopoetic parenchymas of both organs were recognized. To evaluate the effect on defensive function, tilapias of the 2nd group were challenged with E. tarda. Susceptabilities to E. tarda were never increased but rather significantly decreased compared to control. Weekly antibody titres in sera were determined for all induction groups, in which the titres in the 1st and 2nd groups were 4 or 8 times higher than in the control, and then remained high until the 4th week. Also with the hemopoietic function, cellular compositions of peripheral blood were analyzed at weekly intervals but no significant changes resulted. From those results, it is suggested that overcrowding of MMCs would not lead to any morphological as well as functional deteriorations of spleen and head kidney but have an intimate association with enhancement of protective immune system in tilapias.