• Journal of Navigation and Port Research
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• v.44 no.4
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• pp.305-311
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• 2020

Rising sea levels along the coast from global warming causes the increase of wave energy along the coast. This rise in sea levels results in relatively deep water levels, which would incur the loss of sand that had not occurred in the past from erosion in coastal areas. Generally, it has been challenging to protect against coastal erosion, and the slope, cross-sectional shape, and materials are selected for the site conditions depending on the change in external forces. However, the application of counter measures based on insufficient understanding of the phenomenon is causing various damage, indicating the need for technological development and converging technologies to improve credibility. In this study, we developed eco-friendly permeable biopolymer concrete blocks to control the coastal erosion by using the Bio-Coast, an effective porous structure that mitigates the destructive erosion caused by the rising sea levels. The hexagonal design of Bio-Coast was derived from the honeycomb, columnar joints, and clover, which are durable and stable structures in nature, and the design was changed to apply bumps on the Bio-Coast filling in the form of a clover to reduce wave overtopping and run-up. Applying the field condition of beaches on the east coast of Korea, the block weight and size were decided and the prototype blocks were manufactured and are ready for field placement. In particular, it is intended to protect coastal areas from destructive erosion by natural and artificial external forces, and to extend the design to river,s lakes, and natural walking trails, to improve the efficiency of quality control and process control through the use of blocks.

• Smart Structures and Systems
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• v.20 no.5
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• pp.549-562
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• 2017

The US railroad network carries 40% of the nation's total freight. Railroad bridges are the most critical part of the network infrastructure and, therefore, must be properly maintained for the operational safety. Railroad managers inspect bridges by measuring displacements under train crossing events to assess their structural condition and prioritize bridge management and safety decisions accordingly. The displacement of a railroad bridge under train crossings is one parameter of interest to railroad bridge owners, as it quantifies a bridge's ability to perform safely and addresses its serviceability. Railroad bridges with poor track conditions will have amplified displacements under heavy loads due to impacts between the wheels and rail joints. Under these circumstances, vehicle-track-bridge interactions could cause excessive bridge displacements, and hence, unsafe train crossings. If displacements during train crossings could be measured objectively, owners could repair or replace less safe bridges first. However, data on bridge displacements is difficult to collect in the field as a fixed point of reference is required for measurement. Accelerations can be used to estimate dynamic displacements, but to date, the pseudo-static displacements cannot be measured using reference-free sensors. This study proposes a method to estimate total transverse displacements of a railroad bridge under live train loads using acceleration and tilt data at the top of the exterior pile bent of a standard timber trestle, where train derailment due to excessive lateral movement is the main concern. Researchers used real bridge transverse displacement data under train traffic from varying bridge serviceability levels. This study explores the design of a new bridge deck-pier experimental model that simulates the vibrations of railroad bridges under traffic using a shake table for the input of train crossing data collected from the field into a laboratory model of a standard timber railroad pile bent. Reference-free sensors measured both the inclination angle and accelerations of the pile cap. Various readings are used to estimate the total displacements of the bridge using data filtering. The estimated displacements are then compared to the true responses of the model measured with displacement sensors. An average peak error of 10% and a root mean square error average of 5% resulted, concluding that this method can cost-effectively measure the total displacement of railroad bridges without a fixed reference.

• Korean Journal of Social Welfare
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• v.1
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• pp.51-71
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• 1979

During last five years several workshops and seminars among social work educators, in and out country, has taken place. In those gatherings there has been, criticism on American model on which curriculum of social work in Korea has mainly based, and many proposals which most developing countries should consider and adopt for developing their own curriculums. The proposals could be summarized as follows; 1. Specification of developmental functions of social work should be made so that the curriculum could involve. It also must come from own societal needs and own national development task. 2. Social work should participate and make contribution to plan and solve the main social problems in own countries. 3. Clarification of educational objective in undergraduate level should be made and one of them must be related to the first professional degree. 4. There should be the courses which provide the content of macro level participation. How much of the proposals are reflected in the current curriculum of Korea? What are the problems Korean social work education has been faced in connection with reflecting the proposals? What kinds of task we should or could perform in order to adopt the proposals? These are the questions which deserved to be studied. The followings are the answers to the questions; 1. The new courses such as social welfare policy and planning, Social Development, Population Dynamics and Family Planning, Social problems, Special Issues in Social Welfare, etc, are placed in the curriculum. 2. Though the new courses are added the courses of case work, group work, and community organization are strongly remained it means that integrative method is not quite adopted and that conflicts are taking place between new and old fashion. 3. Fieldwork placement policy has been changes from concurrent to block and from social work method oriented to social problem oriented. 4. There are lack of integration among the all courses, of consistency between pre and post courses and connection among the related courses. 5. Establishment of image of social worker with B, A. degree should be urgently taken place. It can't be done by social work field alone but by cooperation with all the forces related to the social work practice. 6. B. A. graduate should have a common base of knowledge and competence. It could be come from the clear and specified objectives of undergraduate level education. And agreement among the member schools on the objectives can call on the fundamental similarities in each curriculums. Different programs from one school to another can be tolerated as long as there are fundamental similarities among the schools. Basic concepts and framework of social work should be kept clearly. It is a slow and long process to make social work recognized as a profession in the developing countries. Korea can't be and exception. Failure of having social work be indegenous can't be the reason to refuse an change the basic concepts of social work. One of he most important task which social work education in Korea must achieve in the near future is to establish the minimum requirement courses in the curriculum. Social work field, on the other hand, must find the positions for the social works in the various settings and institute. Clear role and image of social worker can be obtained by doing that.

• Journal of the Korean Institute of Landscape Architecture
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• v.24 no.4
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• pp.1-22
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• 1997

This paper was focused on the efficient management of landscape woody plants, and concerned itself with their important role in the urban environment. Based on the philosophy that there is nothing that can be done without an inventory, the purpose of this study was to develop an inventory system and iris proper application to a site for establishing a management plan Two different approaches were used, The first was to make a newly structured inventory system through collecting, analyzing, and evaluating various types of inventories used in Korea, the U. S. A., and Japan. The second approach was to apply a newly designed inventory system to the case study area. using GIS 'as a tool of spacial analysis and statistics for making decisions. The results could be summarized as follows; 1. In Korea, most of the Landscape Woozy Plants Inventories had datas which represented possession of trees, and only the work which they had done according to their traditional ways, There was no data related to the conditions, management needs, and site conditions of individual trees, This is essential information for organizing an inventory system . 2. There needs to be data which is balanced, containing tree characteristics and site characteristics. Through such information the management needs could be adjusted properly. The inventory list described in this paper was determined by botanical identity, placement condition, condition of tree, and types of work for maintaining as well as improving the condition of each tree One of the most important things was to determine the location data of each tree so as to compare data with other trees. The data gained from the field survey still had some problems because of lack of scientific method for supporting objective views, and because of actual situations, especially in the field of evaluating site conditions and management needs. All data should be revised to fit a computer data management system , if possible 3. The GIS(Geographic Information System) application showed good performance in handling inventory data for decision making. All the data used for the GIS application was divided into location and non-spatial data. Using the location data, it was easy to find the exact location of each tree on the monitor and on the maps generated by the computer even in the actual managed trite, along with various attribute data. Therefore it could be said that the entire management plan should start from data of individual trees with their exact locations, for making concrete management goals through actual budget planning.

• Journal of Chest Surgery
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• v.31 no.5
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• pp.509-512
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• 1998

Although posterolateral thoracotomy(PLT) has been a standard thoracic incision in resection surgery of the lung for surgeons to achieve a good surgical field, there remains concern about severing a group of thoracic muscles remains. Muscle-sparing vertical thoracotomy (MVT) is an alternative to PLT, which gives cosmetic result and may preserve motion of the shoulder girdle as well as respiratory function of the patient in the early postoperative period. However, surgeons tend not to perfer it because of limited surgical field from the vertical wound made on the lateral thoracic wall. The purpose of this study is to compare the surgical outcomes of PLT versus MVT. We retrospectively reviewed 29 patients(15 who had PLT and 14 who had MVT, organized into those two groups) who had undergone lung resection surgery in our institute. There were no clinical differences between the two groups in terms of operation time, estimated amount of blood loss during the operation, amount of chest drainage on the first and the second postoperative day, duration of chest tube placement, incidence and amount of transfusion, and postoperative complications. We conclude that, from our limited experience, MVT can be applied to lung resection surgery as safely as PLT and that it may have a beneficial role for the patient with compromised lung function in addition to cosmetic effect.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.55 no.1
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• pp.76-82
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• 2010

Experiments were conducted to investigate seed persistence of Chinese milk vetch(CMV) in naturally reseeded rice field in 2007~2009. The seed and pods with seeds were buried in rice field at 0, 5 and 10 cm depths and retrieved from the field at one to three month intervals from July to the following year March and determined change of seed dormancy and viability. In the second experiment, persistence of the CMV seeds in the naturally reseeded rice field at different tillage methods and soil depths were also investigated after rice harvest in autumn. Burial depths and durations affected recovery rate, dormancy and viability of CMV seed. The viability loss was faster and greater in the seed than the pod with seeds and on the soil surface than the 5 or 10 cm burial depths. The recovery rate of CMV seed was decreased starting from one month as seed burial and it was significantly decreased to 52~65% for the seed in September. However, unlike the seed burial, the nearly 100% CMV seeds were recovered for burial as pod with seeds even after four months burial in both 0 and 5 cm depths. However, the recovery rate was sharply declined to below 30% at October in 2007 in both seed and pods with seeds and in the 2008/2009 experiment. the 15~47% of CMV seeds still remained even after October. The CMV had high seed dormancy of 95%, showing only 4~5% germination at the beginning in June but the seed germination increased to 25 to 35% in seed and 55 to 61% in pod with seeds in September due to breakage of hard seed dormancy. The viability loss was faster in the seed than in the pod with seeds regardless of depths of placement in the soil base on decayed seeds. Also the seed placed on the soil surface lost viability faster than the 5~10 burial depths. On the other hand, field observation in the naturally reseeded CMV rice field showed that as many as 917~2,185 CMV seeds $m^2$ were from the 0~15 cm soil depth in the rotary tillage and 250~10,105 CMV seeds in minimum tillage treatmints. The recovered seed germinated 25~33%, 23~43% but still had high percentage of hard seed having 64~72% and 51~77% even after rice harvest in autumn. These results indicate that freshly harvested CMV seeds had high level of primary dormancy and the dormancy was gradually broken in soil with time during rice cultivation periods and appreciable number of CMV seeds remained even 4 month after burial in soil. CMV plant regenerated naturally from the remained seed bank at rice harvest time in autumn. The CMV seedling still emerged even after 2 years of continuous destructive killing of emerged CMV plant by rotary tillage in naturally reseeded CMV plant in rice field, indicating that CMV seeds do persistent as least two years in soil.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.2
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• pp.137-142
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• 1998

Assessment of N release pattern from hairy vetch (Vicia villosa Roth) residue is an important step for the efficient use of the residue as a green manure and the specific management strategy development. Objective of this research was to determine the changes of chemical composition, especially in light of the N release, when the residues of hairy vetch were applied in the soil. hairy vetch was harvested at different growth stages (April 23, May 9, and May 28) and the residues were encapsulated in the nylon mesh (1 mm) bag. The bags were placed on the surface of no-tillage plots and buried at 15cm in depth in conventional tillage plots of the corn field in early June. The bags were removed for measurements of dry matter and N content at 1, 2, 3. 5, 8 and 12 weeks after placement. Dry matter and N content of hairy vetch were higher when harvested closer to maturity, as also found in C/N ratio, cellulose and hemicellulose contents. The rate of N releases from hairy vetch residue under conventional tillage condition was greater than that under no-tillage condition. Percentages of N remaining in residue over the initial N contents under conventional tillage condition were in average 40, 23, and 15% for 1, 2, and 3 weeks after placement of mesh bag, respectively, compared with respective values of 71, 31, and 21% under no-tillage condition. The rate of N release was slower as the harvest time was closer to maturity of hairy vetch under both tillage conditions. Most of N in residue was released within 3 and 5 weeks, under conventional and no-tillage conditions, respectively. Results indicated that amounts of N released from hairy vetch residue were more closely related to the variability of N contents in residue due to the harvest time than changes of chemical composition of plant or soil management.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.196-203
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• 2003

The application of sealants is a highly technique-sensitive procedure, requiring an extremely dry field prior to placement. Moisture contamination of the etched enamel surface before sealant placement is cited as the main reason for sealant failure. The purpose of this study was to evaluate the effects of different methods of sealant application on the shear bond strength of sealants to enamel. In groups 1, 2, 3, 4 Teethmate(unfilled sealant) was used, while Ultraseal XTplus(filled sealant) was used in groups 5, 6, 7, 8. Groups 1 and 5(control) were acid etched for 15 seconds using 35% phosphoric acid, washed and then dried. In groups 2, 6 drying agents were applied, and in groups 3, 7 bonding agents were applied and light cured. In groups 4 and 8 both drying agent and bonding agent were applied. Then sealant was cured to the specimen using molds 3mm in diameter and 2mm in height. Thermocycling was performed and shear bond strength was finally measured. The following results were obtained : 1. Groups using filled sealant(groups 5, 6, 7, 8) showed higher shear bond strengths compared to groups using unfilled sealant(groups 1, 2, 3, 4). 2. Among groups using unfilled sealant(groups 1, 2, 3, 4), groups 2, 3, 4 showed significantly higher shear bond strength compared to group 1(p<0.05). There were no significant differences among groups 2, 3 and 4. 3. There were no significant differences(p>0.05) among groups using filled sealant(groups 5, 6, 7, 8). 4. When modes of fracture were examined, cohesive failure was observed in groups 2, 3 and 4.

• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.55-62
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• 2006

Transverse cracks in continuously reinforced concrete pavement (CRCP) occur at early ages due to temperature and moisture variations. The width and spacing of transverse cracks have a significant effect on pavement performance such as load transfer efficiency and punchout development. Also, crack widths in CRCP depend on 'zero-stress temperature,' which is defined as a temperature where initial concrete stresses become zero, as well as drying shrinkage of concrete. For good long-term performance of CRCP, transverse cracks need to be kept tight. To keep the crack widths tight throughout the pavement life, zero-stress temperature must be as low as practically possible. Thus, temperature control at early ages is a key component In ensuring good CRCP performance. In this study, concrete temperatures were predicted using PavePro, a concrete temperature prediction program, for a CRCP construction project, and those values were compared with actual measured temperatures obtained from field testing. The cracks were also surveyed for 12 days after concrete placement. Findings from this study can be summarized as follows. First, the actual maximum temperatures are greater than the predicted maximum temperature in the ranges of 0.2 to 4.5$^{\circ}C$. For accurate temperature predictions, hydration properties of cementitious materials such as activation energy and adiabatic constants, should be evaluated and accurate values be obtained for use as input values. Second, within 24 hours of concrete placement, temperatures of concrete placed in the morning are higher than those placed in the afternoon, and the maximum concrete temperature occurred in the concrete placed at noon. Finally, from the 12 days of condition survey, it was noted that the rate of crack occurrence in the morning placed section was 25 percent greater than that in the afternoon placed section. Based on these findings, it is concluded that maximum concrete temperature has a significant effect on crack development, and boner concrete temperature control is needed to ensure adequate CRCP performance.

• Korean Journal of Heritage: History & Science
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• v.46 no.1
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• pp.318-345
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• 2013

This study was carried out with a focus on the factor on the periodical space organization of Daebodan (大報壇: the altar of great recompense) in Changdeok Palace, which is significant in terms of political history in the late Chosun Dynasty, and consider the factors in the formation of the structural system through historical records and drawings. Daebodan has the ideology of righteousness to the Ming Dynasty which the hierarchy of the Joseon Dynasty. who felt the crisis of the domination order, imposed as a solution after the Manchu war of 1636. In addition, Daebodan was built by complex factors that entailed the self-esteem of the 'Joseon Centralism Ideology (朝鮮中華)' and the desire of the sacrificial rituals for Heaven that were imminent to the kings of Joseon. Superficially, Daebodan has the spatial organization of the Sajik (社稷) Altar and the placement of an annex building, but had the applied placement due to limited topography and access to the backyard. Furthermore, the lateral structure of Daebodan multiply accepted various factors of the nine step's stairs, the hight of five cheok (尺), the circumstance of two floors that were showed in the altar and platform with small fences and an imperial order including the internal form of Hwangjangbang (黃帳房). Moreover, the name of the alter came from 'the Jiaote Sheng Book of Rites(禮記 郊特牲)' representing 'the suburban sacrifice ritual for Heaven (郊天)', and it was built by not only combining the system of the Sajik Altar in the Joseon Dynasty and China but also avoiding 'excessive etiquette (僭禮).' The point is a remarkable feature shown by the structural system of Daebodan. Thus, it is considered that the 'Notion of Confucian-Cultural Succession (中華繼承意識)' and the desire of the sacrificial rituals for Heaven were expressed by the structure and form of altar. This study examined the process of the creation, expansion, decline and disposal of Daebodan in a chronological order, and found that the ruling ideology of the governing elite by the political and cultural background of the era at each transitional point was reflected in the spatial formation of the altar. On the other hand, as a result of performing a field survey to find the location in accordance with Daebodan in drawing materials, there remains items such as worked stones from Daebodan, precast pavers and fragments of proof tile discovered in the surrounding of tora vine (Actinidia arguta) which is a natural monument of Changdeok Palace. As such, verification through future excavation and investigation is required.