• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.179-184
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• 2018

In this study, we compared the measured values of the effective beam size of standard gamma irradiator with the simulation results to provide a useful means to the effective beam area determination. Results of the simulation and measured using ion chamber was distributed in a relative error of 4.5 ~ 7.3% of the case of air kerma rate. The size of the effective beam area is when the simulation was implemented in the horizontal direction 27cm, 21.6cm vertical direction, the measured result using a film was obtained similar results with the horizontal direction 26.5cm, 21.9cm vertical direction. The relative error in the horizontal direction is 1.85% and 1.38% vertical effective beam area was also similarly distributed around the field gamma rays. As a result of the study, it was confirmed that the effectiveness of the simulation was sufficient for the gamma irradiation system. In particular, it is small relative errors in the effective beam size than the air kerma rate is considered to be due to the size of the beam is determined by geometric factors rather than the capacity of the standard source. A further study is needed to improve the reliability of the photon energy distribution diagram using simulation.

• Asia pacific journal of information systems
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• v.17 no.2
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• pp.29-47
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• 2007

Owing to the rapid growth of using the Internet, not only click-and-mortar companies but also brick-and-mortar ones have been expanding their distribution channels into online, Moreover, since online channels are more attractive than offline ones in control and maintenance, switching customers into online ones is emerged as one of very important managerial issues in a view of reduction of cost as well as expansion of services. However, the switched customers should be faced by uncertainties which could not have been experienced in offline. Specifically, in online channels, buyers and sellers are separated temporally and spacially and there are always so many kinds of threat for security as well as not enough systems and conventions for them yet. Therefore, trust has been considered as one of the most critical mechanisms for resolution of such uncertainties in online transactions. However, it is not easy to build and maintain the relationships in online since most of them are virtual and indirect generally. Therefore, in order to switch offline customers into online ones, it is very important to make strategies based on identification of the relationship between online transaction and offline trust which has been built in offline business. Generally offline trust, which has been built independent of online, could not include trust for online-dependent activities such as payment security during or after transactions, while most of online trust include it. Therefore, a customer with high offline trust does not always perceive high security and assure safe transactions. Accordingly, while online trust, where technical capabilities for online security is one of main bases, includes control trust implicitly or explicitly, offline trust does not. However. in spite of such clear discrimination and independence between offline trust and perceived security, there can be the significant dependency between these two beliefs. The customers with high offline trust believe that the company would do some activities for online security for customers' safe transactions since it has been believed of doing well for customers' trust. Theoretically, users' perception of security is interpreted as a kind of control trus, which is trust for company's technical control capacities in order to resolve technical uncertainties in online. Therefore, the relationship between two beliefs can be considered as transference from offline trust to another type trust. that is, control trust. The objective of this study is to analyze the effect of offline trust on online transaction uses mediated by perceived security. For this purpose, we suggest a research model based on technology acceptance model (TAM). Reuse intention is adopted as a dependent variable and TAM is modified by adding perceived risk (PR) as well as two beliefs of using Internet banking, perceived usefulness (PU) and perceived ease of use (PEOU). Moreover, perceive security (PS) is adopted as an external variable for PR and PU, while offline trust (OT) is an antecedent of PS. For an empirical test, sampling from 108 visitors to the banks in Daegu, Korea, we analyze our model by partial least square (PLS) approach. In result, our model is shown to explain 51.4% of the variance in reuse intention and all hypothesis are supported statistically. A theoretical implication of this study is to identify a role of PS between offline trust and reuse intention of using online transaction services. According to our result, PS can be considered as a mediation variable for bridging between two different concepts: trust that explains social aspects of customers and companies, and TAM that explains customers' reuse intention.

• Weed & Turfgrass Science
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• v.6 no.2
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• pp.117-123
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• 2017

Invasive alien species (IAS) can affect agricultural ecosystem negatively and critically. The geographical distributions of nine IAS plants in Korean orchards and uplands were investigated. Ambrosia artemisiifolia distributed widely in Korean peninsula and Ambrosia trifida distributed intensively in Gyeonggi-do. Aster pilosus distributed in Gyeonggi-Gangwon region and Lactuca scariola distributed linear region from the north-western to south-eastern part of Korea. Hypochaeris radicata distributed mainly in Jeju-do and Solanum carolinense distributed in eastern Gyeonggi-do. Rumex acetosella and Sicyos angulatus sporadically occurred in Korean croplands and Eupatorium rugosum was found in one region only. The distribution of IAS plants in croplands was very similar to that in non-croplands suggesting that ecological position of arable lands is not different from that of non-arable lands. Therefore, IAS plants in the croplands should be managed for not only prevention of yield reduction, but also protection or maintenance of original ecosystem. Development of management methods apposite to current Korean status are required to control IAS plants in croplands.

• Journal of the Korean Society of Food Culture
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• v.17 no.5
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• pp.578-583
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• 2002

The purposes of this study were to a) find out the operational characteristics of the contract-managed highschool foodservice in Seoul, b) investigate the expected level of meal-price and facilities investment cost perceived by contract-managed highschool foodservice managers c) compare the present level and expected level of meal-price and facilities investment cost. From October 12 to November 13 in 2001, the questionnaires were mailed to 249 high schools which was managed by contract foodservice company with respondent rate 40.2%. Data were analyzed using SPSS Win(10.0) for descriptive analysis and one group paired t-test. The results of this study were as follows ; 1. The student enrollment of highschools run by contract-managed foodservice was 1,243 with 72.6% participation rate of school lunch program. The average meal-price was 2,138 won. The average annual period of school foodservice operation was 156.78 days per year. The average contracting period was about 3 years. 2. The average cost concerned in the facilities investment amounts 169,578,180 won at the initial investment and 25,204,092 won at the repairs and maintenance cost in the course of operation. 3. The present level of meal-price and facilities investment cost were respectively 2,136won/meal and 171,157,336.72 won. And expected level of meal-price and amount of facilities investment cost were 2,418.75 won and 121,353,215.19 won. Comparing the present level with the expected level of the meal- price and facilities investment cost, expected level of meal-price was significantly higher than the present level of meal-price(p<.001) and expected level of facilities investment cost was significantly lower than present level of facilities investment cost(p<.001).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5964-5970
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• 2013

The recent budget planning for highway infrastructure implied that the investments for Operation & Maintenance(O&M) became greater than that for new construction. This circumstance made many stakeholders pay attention to the O&M of road infrastructure and adopt other countries' policies and system for effective management. In other countries, most O&M for road infrastructure have been done by private entities using long-term contract and Korea is about to shift from one year contract to long-term contract. The most important parts for the expansion of the long-term O&M contract for road infrastructure are valuation of the O&M contract based on accurate prediction of O&M costs and instrument for proper risk sharing between contracting parties. Thus, this study provides a methodology to estimate a reasonable O&M contract price and a framework to share contract risk between contracting parties using real option. The analysis results showed that the contract price and ceiling and floor conditions for the 20 year-contract of 20 km-highway project were 45.7, 60 and 42.3 billion won, respectively.

• International Journal of Highway Engineering
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• v.4 no.3 s.13
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• pp.43-49
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• 2002

Asphalt pavements have to perform under the conditions of heavily-loaded vehicles due to the industrialization and large temperature variance between the summer and the winter. Due to these factors, a characteristics change of early permanent deformation becomes a big issue, and to remedy this problem many research to use modified asphalt are being widely conducted. However, most of the modified asphalt is being paved after milling the surface course and applying tackcoating, and it is being used mostly for the repair and maintenance purpose rather than pavement of new national road. The purpose of this investigation is to obtain some fundamental data for the evaluation of the performance and long-term performance of the construction material mixtures by the laboratory test and field experiments. For the field experiment, 200m of two-lanes national road, that is being paved for the new national road under the direction of Pusan Regional Construction Management Office, was paved with SBS PMA and PSMA asphalt mixtures, which are an modified asphalt mixtures used for the surface course, on top of the base course paved with other modified asphalt mixtures. The remaining section of the new national road was paved with dense grade mixture. The laboratory tests assessed and analyzed the mixture characteristics by Marshall's stability test, strength tests and wheel-tracking test. On the basis of the evaluation result of the temperature control and roughness of the newly constructed road at the field experiment site, it is desired to evaluate and identify the most economic modified asphalt mixtures by long-term performance evaluation and LCC(Life Cycle Cost) analysis in order to apply the test result to the design of new road construction in the future.

• Journal of Korean Society on Water Environment
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• v.22 no.5
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• pp.757-767
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• 2006

Biological assessments are the primary tool for evaluating the biological condition of a water body and makes it possible to understand accumulative and long-term effect of stressors. They also provide reliable biological information for which disturbed systems are to be restored. Sustainable water environment is not enough with attaining only the clean water, but it should sustain healthy and diverse aquatic life. Aquatic organisms are affected by various factors, including not only water quality but also habitat condition and stressors, and thus good condition of both physical and chemical water quality is prerequisite for sustaining healthy organisms. Therefore, biological assessment, along with other physical and chemical assessments, are crucial for evaluating the health of a water body. Overall, sustainability of water environment demands the attainment and maintenance of ecological integrity, which is resulted from the combination of physical, chemical and biological integrity. The biological criteria will play very important role in the water resource management and policy issues, and thus bioassessment program should be fully implemented and supported eventually by the law. To keep ecosystem health of water environment safely from the toxic pollutants and other stressors, the following suggestions need to be considered in environmental quality standards in Korea. For the first step, the biological indicators need to be introduced in evaluating river quality condition; they provide a qualitative description of biological condition of water body. Secondly, the biological water quality standards using biotic indices should be developed and implemented under the consideration of characteristics of Korean river systems. Lastly, the ecological status classification regime (ESCR) should be developed and introduced; it could be used in quality assessment of the water environment in general. In developing ESCR, integration of physico-chemical, biological, and habitat parameters should be taken into account.

• Journal of Korea Water Resources Association
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• v.43 no.11
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• pp.967-976
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• 2010

AFDA (Approximate Full Distribution Approach) model of FORM (First-Order Reliability Model) which can quantitatively calculate the probability that storm sewer reach to performance limit state was developed in this study. It was defined as a failure if amount of inflow exceed the capacity of storm sewer. Manning's equation and rational equation were used to determine the capacity and inflow of reliability function. Furthermore, statistical characteristics and distribution for the random variables were analyzed as a reliability analysis. It was found that the statistical distribution for annual maximum rainfall intensity of 10 cities in Korea is matched well with Gumbel distribution. Reliability model developed in this study was applied to Y shaped storm sewer system to calculate the probability that storm sewer may exceed the performance limit state. Probability of failure according to diameter was calculated using Manning's equation. Especially, probability of failure of storm sewer in Mungyeong and Daejeon was calculated using rainfall intensity of 50-year return period. It was found that probability of failure can be significantly increased if diameter is decreased below the original diameter. Therefore, cleaning the debris in sewer pipes to maintain the original pipe diameter should be one of the best ways to reduce the probability of failure of storm sewer. In sewer system, two sewer pipes can flow into one sewer pipe. For this case, probability of system failure was calculated using multiple failure mode. Reliability model developed in this study can be applied to design, maintenance, management, and control of storm sewer system.

• Land and Housing Review
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• v.5 no.4
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• pp.225-234
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• 2014

Because of their nature as public facilities, demands that former military facilities be utilized for the public welfare are increasing, thereby leading to an increase in cases in which these military facilities are reestablished as parks. Cases in which former military bases were reestablished as public parks were analyzed; as a result, several implications were derived. First, the objectives of public park projects should be examined from the perspective of the concept of urban regeneration and regional revitalization. Moreover, it is necessary that profits are yielded and that regional identity and history are reproduced through reusing existing facilities as much as possible rather than entirely remodeling former military sites. As parks become larger in size, bases should be reorganized into complexes rather than single facilities or programs. It is also necessary that parks be established in stages considering the enormous expenses required for building public parks. Consequently, because the special characteristics of military facilities can lead to insufficient on-site investigation in the process of establishing parks, thereby incurring a vast amount of costs for design adjustment and contamination disposal, this should be considered in advance. A method of delegating the development rights to partial sites to private businesses and supplementing the costs of park establishment and maintenance with development benefits should be examined. In addition, given that there are various interests and stakes in former military bases, a method of operating a public-private cooperative decision-making organization during project execution should be considered. Finally, policies related to urban parks need to be improved in order to raise funds, expand profitable businesses, facilitate social services and sponsorship, and encourage the participation of trusts and non-profit organizations in park operation and management.

• Journal of Cadastre & Land InformatiX
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• v.49 no.2
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• pp.57-66
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• 2019

Recently, as a part of the production of spatial information by smart cities, three-dimensional reproduction of structures for reverse engineering has been attracting attention. In particular, terrestrial LiDAR is mainly used for 3D reproduction of structures, and 3D reproduction research by UAS has been actively conducted. However, both technologies produce blind spots due to the shooting angle. This study deals with vertical structures. 3D model implemented through SfM-based image analysis technology using UAS and reproducibility and effectiveness of 3D models by terrestrial LiDAR-based laser scanning are examined. In addition, two 3D models are merged and reviewed to complement the blind spot. For this purpose, UAS based image is acquired for artificial rock wall, VCP and check point are set through GNSS equipment and total station, and 3D model of structure is reproduced by using SfM based image analysis technology. In addition, Through 3D LiDAR scanning, the 3D point cloud of the structure was acquired, and the accuracy of reproduction and completeness of the 3D model based on the checkpoint were compared and reviewed with the UAS-based image analysis results. In particular, accuracy and realistic reproducibility were verified through a combination of point cloud constructed from UAS and terrestrial LiDAR. The results show that UAS - based image analysis is superior in accuracy and 3D model completeness and It is confirmed that accuracy improves with the combination of two methods. As a result of this study, it is expected that UAS and terrestrial LiDAR laser scanning combination can complement and reproduce precise three-dimensional model of vertical structure, so it can be effectively used for spatial information construction, safety diagnosis and maintenance management.