• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.353-358
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• 2011

In this paper, we describe a process for optimally designing a ring-type permanent magnet thrust bearing. The bearing consists of two sets of permanent magnet rings. One set is located inside the other set. An axial offset between the two sets creates axial force, which results in a thrust bearing function. In order to realize an optimal design of the bearing where the required load capacity of the bearing is achieved with the least magnet volume, we derived analytical design equations by adopting the equivalent current sheet (ECS) method. We considered the following two types of magnet arrays: axial arrays and Halbach arrays. These two types of arrays are optimized using the analytical design equations. The results of the optimization are verified using three dimensional (3D) finite element analyses (FEA). The results show that the Halbach array can achieve the required load capacity with less amount of permanent magnet than the axial array does. The efficacy of the ECS method is also verified by using 3D FEA. It is found that the accuracy of ECS method is more sensitive to the underlying assumptions for the Halbach array than for the axial array.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.737-742
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• 2015

Course correction munition are a weapson system for precision attacks and are assembled by applying a ballistic control system to existing projectiles. The roll control system is a subsystem of the ballistic control system and is placed between the guidance and control units inside of the projectile, which undergoes a 5000g lateral acceleration. Thus, it is very important to design the system to endure this load. Many developed countries evaluate the performance and safety of course correction munitions' parts using live-fire gun launch tests or a soft recovery system. However, these methods are expensive and slow. Thus, in this study, we develop impact analysis model of the roll control system using CAE. We apply the code to simulate impact phenomenon and use Johnson-Cook material model for modeling the high strain rate effect on the materials. We also design bearings in detail to analyze their behavior and verify the reliability of CAE model through gas-gun impact tests of the roll control system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1757-1763
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• 2010

Flywheel energy storage system (FESS) is defined as a high speed rotating flywheel system that can save surplus electric power. The FESS is proposed as an efficient energy storage system because it can accumulate a large amount of energy when it is operated at a high rotating speed and no mechanical problems are encountered. The FESS consists of a shaft, flywheel, motor/generator, bearings, and case. It is difficult to simulate rotor dynamics using common structure simulation programs because these programs are based on the 3D model and complex input rotating conditions. Therefore, in this paper, a program for the FESS based on the 2D FEM was developed. The 2D FEM can model easier than 3D, and it can present the multi-layer rotor with different material each other. Stiffness changing of the shaft caused by shrink fitting of the hub can be inputted to get clear solving results. The results obtained using the program were compared with those obtained using the common programs to determine any errors.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.3
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• pp.86-91
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• 2009

Purpose: The whole body scan in Nuclear Medicine is a widely accepted examination and procedure. Especially, it is mainly used in bone, I-131, MIBI, and HMPAO WBC scans. The diverse uses of the whole body scan range from the HMPAO WBC scan with a speed of 13cm/min, to a whole body bone scan using the Onco. Flash technique with a speed of 30cm/min. The accuracy of table movement has a strong correlation with the image quality, and inaccuracy of speed could negatively affect the image quality. The purpose of this study is to evaluate the accuracy of the table movement while considering the influence of the age of the equipment and the variability in the weight of the patients. Material and Methods: The study was conducted using two of Seoul Asan Medical Center's SIEMENS gamma cameras which are commonly used in our whole body study. The first one is the oldest gamma camera, an ECAM plus (installed in 2000), and the last is brand new one, a SYMBIA T2 (installed in 2008). Three trials were conducted with the tables moving at a different speed each time; 10, 15 and 30 cm/min. The tables' speeds were measured by checking how long it took for the table to move 10cm, and this was repeated every 10cm until the table reached 100 cm. With an average body weight of the patients of about 60~70 kg, the table speed was measured with weights of 0 kg, 66 kg and 110 kg placed on the table, then compared among conditions. Results: The coefficient of variance (CV) of the ECAM plus showed 1.23, 1.42, 2.02 respectively when the table movement speeds were set at 10, 15, and 30 centimeters per minute. Under the same conditions, the SYMBIA T2 showed 1.23, 1.83 and 2.28 respectively. As table movement speed more, the variance of CV as the speed increases. When the patient body weight was set to 0, 66 and 110kg, the CV values of both cameras showed 0.96, 1.45, 2.08 (0 Kg), 1.32, 1.72, 2.27 (66 Kg) and 1.37, 1.73, 2.14 (110 Kg). There was no significant difference (p>0.05) in 95 percent of confidence intervals and measured CV values were acceptable. However, the CV value of the SYMBIA T2 was relatively larger than the ECAM plus. Conclusion: The scan speed of the whole body scan is predetermined based on which examination is being performed. It is possible for the accuracy of the speed to be affected, such as the age of the equipment, the state of the bearings or the weight of a patient. These factors can have a negative impact on the diagnostic consistency and the image quality. Therefore, periodic quality control should be needed on the gamma cameras currently being used, focusing on the table movement speed in order to maintain accuracy and reproducibility.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.30 no.2
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• pp.119-129
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• 2012

Yongdoseo and Guimunwon are described in "Bokgeo(卜居, fixabode)" of "Sanlimkyengje(山林經濟)" written by Manseon Hong. This record is a unique garden conceptual idea applying the principles of Hetu(河圖) and Luoshu(洛書), fanciful gardens which have not been actually constructed. Here, two garden types were concretely described respectively, however the underlying meaning therein cannot be apprehended without exact understanding about Sangsu studies. Therefore, the purpose of this study is to illuminate the meaning contained in Garden illustration and the historical meaning of landscape therein through considering this text. To achieve the purpose of this study, the writer and the compiler who are the background of this writing and the outline of Sangsu studies were investigated. Also, the principles of Saengsu(生數), Seongsu(成數), Yin Yang(陰陽), Four Bodies(四象), Palgwedo(八卦圖), etc. which are in Hetu and Luoshu were considered. The result of this study went through this research process is summarized as follows. First, Hetu Luoshu are conceptual definitions which wholly abstracted the basic propositions of Sangsu philosophy such as the universe change principle, etc., while Yongdoseo and Guimunwon can be said to be operational definitions which apply those as garden composition principle, enabling to experience the meaning contained therein concretely and explain it in a replicable way. This attempt is a unique example, unprecedented in Chinaas well. Second, as a livingspace, garden was selected as a means to concretize operational definitions about the meaning of Hetu Luoshu, and as the property to reproduce the bearings concept, the location and the number, etc. of Hetu Luoshu, Taegukjeong(太極亭), Shipjagak(十字閣), Dondae(墩臺), well, pond as well as various kinds of trees were used. Third, the main motif of Yongdoseo and Guimunwon is the relation between Apriority(先天) and Posterior(後天), and the relation between Constitution(體) and Use(用) of Hetu and Luoshu respectively. That is, Yongdoseo planted evergreen trees such as Shipjangcheong(十長靑) in order to symbolize the universe creation principle which Hetu stands for, i.e. silent, harmonious, orderly and win-win image. In Guimunwon, flowering trees(花木) and fruit trees(果木) were planted freely to express the change of Posterior which Luoshu stands for, thatis, dynamic, disharmonious, disorderly, incompatible(相剋) and changing image. The effects intended to be attained through such planting were, 'freshness and cheerfulness(淸爽)' of Yongdoseo and 'splendidness' of Guimunwon respectively. Sangsu studies based on Hetu and Luoshu is a unique thinking system to the Orient which came from the accumulated wisdom of several scholars from various schools through a long period since ancient times. Therefore, the concept and the theory thereof are profound and huge, and its viewpoints of interpretation are diverse. It is a limit of this study that more in-depth and various consideration was not performed. As a further research project, more empirical study of Orientalism such as Sangsu studies, etc. inherent in Traditional Garden is necessary.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.245-253
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• 2021

RC slab bridges account for the largest portion of deteriorated bridges in Korea. However, most RC slabs are not included in the first and second classes of bridges, which are subject to bridge safety management and maintenance. The highest damaged components in highway bridges are the subsidiary facilities including expansion joints and bearings. In particular, leakage through expansion joints causes deterioration and cracks of concrete and exposure of reinforced bars. Therefore, this study analyzed the effect of adhesion damage at expansion joints on the response of the deck in RC slab bridges. When the spacing between the expansion joints at both ends was closely adhered, cracks occurred in the concrete at both ends of the deck due to the resistance rigidity at the expansion joints. Based on the response results, the correlation analysis between displacements in the longitudinal direction of the expansion joint and concrete stress at both ends of the deck for each damage scenario was performed to investigate the effect of the occurrence of damage on the bridge behavior. When expansion joint devices at both sides were damaged, the correlation between displacement and stress showed a low correlation of 0.18 when the vehicles proceeded along all the lanes. Compared with those in the intact state, the deflections of the deck in the damaged case at both sides showed a low correlation of 0.34 to 0.53 while the vehicle passed and 0.17 to 0.43 after the vehicle passed. This means that the occurrence of cracks in the ends of concrete changed the behavior of the deck. Therefore, data-deriven damage detection could be developed to manage the damage to expansion joints that cause damage and deterioration of the deck.

• The Korean Journal of Archival Studies
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• no.14
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• pp.153-190
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• 2006

Externally, business environment in public institution has being changed as government business reference model(BRM) appeared and business management systems for transparency of a policy decision process are introduced. After Records Automation System started its operation, dissatisfaction grows because of inadequacy in system function and the problems about authenticity of electronic records. With these backgrounds, National Archives and Records Service had carried out 'Information Strategy Planning for Reform to Records Management System' for 5 months from September, 2005. As result, this project reengineers current records management processes and presents the world-class system model. After Records and Archives Management Act was made, the records management in public institution has propelled the concept that paper records are handled by means of the electric data management. In this reformed model, however, we concentrates on the electric records, which have gradually replaced the paper records and investigate on the management methodology considering attributes of electric records. According to this new paradigm, the electric records management raises a new issue in the records management territory. As the major contents of the models connecting with electric records management were analyzed and their significance and bounds were closely reviewed, the aim of this paper is the understanding of the future bearings of the management system. Before the analysis of the reformed models, issues in new business environments and their records management were reviewed. The government's BRM and Business management system prepared the general basis that can manage government's whole results on the online and classify them according to its function. In this points, the model is innovative. However considering the records management, problems such as division into Records Classification, definitions and capturing methods of records management objects, limitations of Records Automation System and so on was identified. For solving these problems, the reformed models that has a records classification system based on the business classification, extended electronic records filing system, added functions for strengthening electric records management and so on was proposed. As regards dramatically improving the role of records center in public institution, searching for the basic management methodology of the records management object from various agency and introducing the detail design to keep documents' authenticity, this model forms the basis of the electric records management system. In spite of these innovations, however, the proposed system for real electric records management era is still in its beginning. In near feature, when the studies is concentrated upon the progress of qualified classifications, records capturing plans for foreign records structures such like administration information system, the further study of the previous preservation technology, the developed prospective of electric records management system will be very bright.

• Progress in Medical Physics
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• v.18 no.3
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• pp.118-125
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• 2007

In this study we estimated a geometric correlation among digitally reconstructed radiographic image (DRRI), kV x-ray image (kVXI) from the On-Board Imager (OBI) and electric portal image (EPI). To verify geometric correspondence of DRRI, kVXI and EPI, specially designed phantom with indexed 6 ball bearings (BBs) were employed. After accurate setup of the phantom on a treatment couch using orthogonal EPIs, we acquired set of orthogonal kVXIs and EPIs then compared the absolute positions of the center of the BBs calculated at each phantom plane for kVXI and EPI respectively. We also checked matching result for obliquely incident beam (gantry angle of $315^{\circ}$) after 2D-2D matching provided by OBI application. A reference EPI obtained after initial setup of the phantom was compared with 10 series of EPIs acquired after each 2D-2D matching. Imaginary setup errors were generated from -5 mm to 5 mm at each couch motion direction. Calculated positions of all center positions of the BBs at three different images were agreed with the actual points within a millimeter and each other. Calculated center positions of the BBs from the reference and obtained EPIs after 2D-2D matching agreed within a millimeter. We could tentatively conclude that the OBI system was mechanically quite reliable for image guided radiation therapy (IGRT) purpose.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.32 no.2
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• pp.27-41
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• 2014

This study aims to investigate the history, cultural values prototype through literature analysis, characteristics of construction, location, space structure and landscape characteristics by Arc-GIS on the Munam pavilion(聞巖亭) in Changnyeong. The results were as follows. First, Shin-cho((辛礎, 1549~1618) is the builder of the Munam pavilion and builder's view of nature is to go back to nature. The period of formation of Munam pavilion is between 1608-1618 as referred from document of retire from politics and build a pavilion. Secondly, Munam pavilion is surrounded by mountains and located at the top of steep slope. Pavilion was known as scenic site of the area. But damaged in a past landscape is caused by near the bridge, agricultural facilities, town, the Kye-sung stream of masonry and beams. Thirdly, Munam pavilion is divided into the main space, which is located on the pavilion, space in located on the pavilion east and west and the orient space, which is located on the Youngjeonggak. Of these, original form of Munam pavilion is a simple structure composed of pavilion and Munam rock, thus at the time of the composition seems to be a direct entry is possible, unlike the current entrance. Fourth, Spatial composition of Munam pavilion is divided into vegetation such as Lagerstroemia indica trees in Sa-ri in Changnyeong, ornament such as letters carved on the rocks and pavilion containing structure. The vegetation around the building is classified as precincts and outside of the premises. Planting of precincts was limited. Outside of area consists of front on the pavilion, which is covered with Lagerstroemia Indica forest and Pinus densiflora forest at the back of the pavilion. Ofthese,LargeLagerstroemiaIndicaforestcorrespondstothenaturalheritageasHistoricalrecordsofrarespeciesresourcesthatareassociated withbuilder. Letterscarvedontherocksrepresenttheboundaryof space, which is close to the location of the Munam pavilion and those associated with the builder as ornaments. Letters carved on the rocks front on the pavilion are rare cases that are made sequentially with a constant direction and rules as act of record for families to honor the achievements. Fifth, 'The eight famous spots of Munam' is divided into landscape elements that have nothing to do with bearing 4 places and landscape elements that have to do with bearing 4 places. Unrelated bearings of landscape elements are Lagerstroemia indica trees in Sa-ri in Changnyeong, Pinus densiflora forest at the back of the pavilion, Okcheon valley, Gwanryongsa temple and Daeheungsa temple. Bearing that related element of absolute orientation, which is corresponding to the elements are Daeheungsa temple, Hwawangsan mountain, Kye-sung stream and Yeongchwisan mountain. Relative bearing is Gwanryongsa temple, Yeongchwisan mountain and Kye-sung stream Gongjigi hill. At Lagerstroemia indica trees in Sa-ri in Changnyeong, Pinus densiflora forest at the back of the pavilion, Kye-sung stream and Okcheon valley, elements are exsting. Currently, it is difficult to confirm the rest of the landscape elements. Because, it is a generic element that reliable estimate of the target and locations are impossible for element. Munam pavilion is made for turn to nature by Shin-cho(辛礎). That was remained a record such as Munamzip(聞巖集) and Munamchungueirok(聞巖忠義錄) that is relating to construction of pavilion. Munam pavilion located in a unique form, archival culture through the letters carved on the rocks and Large Lagerstroemia indica forest and through eight famous spots, cultural landscape elements can be assumed that those elements are remained.