• Journal of Astronomy and Space Sciences
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• v.28 no.3
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• pp.217-223
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• 2011

Precise point positioning (PPP) is increasingly used in several parts such as monitoring of crustal movement and maintaining an international terrestrial reference frame using global positioning system (GPS) measurements. An accuracy of PPP data processing has been increased due to the use of the more precise satellite orbit/clock products. In this study we developed PPP algorithm that utilizes data collected by a GPS receiver. The measurement error modelling including the tropospheric error and the tidal model in data processing was considered to improve the positioning accuracy. The extended Kalman filter has been also employed to estimate the state parameters such as positioning information and float ambiguities. For the verification, we compared our results to other of International GNSS Service analysis center. As a result, the mean errors of the estimated position on the East-West, North-South and Up-Down direction for the five days were 0.9 cm, 0.32 cm, and 1.14 cm in 95% confidence level.

• Architectural research
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• v.19 no.1
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• pp.1-6
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• 2017

Over the past decade, building information modeling (BIM) has gained a foothold in the construction sector. However, as digital data generated in the virtual space of a computer environment, BIM-based data have an inherent limitation in their application efficacy under field conditions. To overcome this, the present study employs augmented reality (AR) to reduce the discrepancy between the digital data generated in virtual spaces and real-world conditions. We assessed the potential applicability of an AR-based interface by analyzing existing examples of Apple, Google, and Facebook, which reflect the recent developments of technologies focusing on user experience. We then proceeded with an AR study, restricting the scope of application to a mobile environment in which an efficient information transmission between a digital model and real life can take place. Object-oriented software engineering was employed to ensure an efficient implementation of a BIM-based AR system for campus space management (CSM) in a mobile environment. Finally, we conducted a module test to check the reliability of the CSM method by using an AR-based mobile system with a prototype of the model used in university campuses, and extracted and itemized the supplementary requirements for CSM by using BIM tools for running AR applications.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.1
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• pp.44-50
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• 2008

In this study a turboshaft engine for a helicopter propulsion system was modeled using SIMULINK and the components' maps were generated from the limited performance deck data provided by engine supplier using a hybrid method with the genetic algorithms and the system identification method. In order to verify the SIMULINK performance model and the component maps generated by the hybrid method, the steady-state performance analysis results were compared with the performance data provided by engine manufacturer. In this investigation, it was confirmed that the analysis results by the proposed model are closely met with those by engine manufacturer's data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.3
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• pp.482-490
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• 2002

This paper presents modelling and analyzing method of centrifugal chiller which has a rated capacity of 200 RT(703 kW) through on-site performance test. Field performance data of a chiller installed in a research building of KIST have been collected. Simple models were developed for predicting the heat exchanger and system performances by regression of chiller operation data during 5 days in August. The models proposed here account for the effect of variations of cooling capacity, temperatures and flew rates of secondary fluids. The proposed models can predict the actual performance data from June to September within $\pm$ 5% error. The COP of centrifugal chiller are estimated under the standard rating conditions and reduced mass flow rates of chilled and cooling water.

• Nuclear Engineering and Technology
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• v.29 no.3
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• pp.201-210
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• 1997

A thermal conductivity correlation has been proposed which can be applied to high turnup fuel by considering both of thermal conductivity with turnup across fuel pellet and additional degradation at pellet rim due to very high porosity. In addition, a correlation has been developed that can estimate the porosity of rim region as a function of rim burnup under the assumptions that all the produced fission gases are retained in the in porosity and threshold pellet average burnup required for the formation of rim region is 40 MWD/㎏U. Rim width is correlated to rim burnup using measured data. For the RISO experimental data obtained at pellet average turnup of 43.5 MWD/㎏U for three linear heat generation rates of 30, 35 and 40 ㎾/m, radial temperature distributions ore calculated using the present correlation and compared with the measured ones. This comparison shows that the present correlation gives the best agreement with the measured data when it is combined with the HALDEN's correlation for thermal conductivity considering its degradation with burnup. Another comparison with the HALDEN's measured fuel centerline temperature as a function of burnup at 25 ㎾/m up to about 44 MWD/㎾U also suggest that the present correlation yields the best agreement when it is combined with the HALDEN's thermal conductivity.

• Journal of the Korean Data and Information Science Society
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• v.23 no.1
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• pp.131-142
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• 2012

Since Korea is moving towards the aged society, increasing is the social attention on overall life satisfaction of the elderly. The purpose of this study is to find the factors affecting the life satisfaction of the elderly among demographic characteristics of aged people, categorized satisfactions and sources of income, based on the 2008 national survey data of the actual living condition of the elderly and welfare need. We found that many factors have significant impact on the life satisfaction of the elderly, such as demographic characteristics, the level of physical and mental health, the economic level.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.12-20
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• 1991

The informations of ship structural design have been represented as the form various drawing plants, but to enhance the design productivity, it is necessary to utilize the advanced technologies such as CAD system and database management system. In this study, efforts are focused on the data modelling of those informations of midship configuration and attribute for the integration of ship structural design programs through database system. As actual example, midship configuration of bulk carrier was visualized by computer graphics. Relational data model is employed and topological informations is used for the best treatment of geometries representing structural arrangement. RDBMS 'ORACLE' was used for the implementation of the results.

• Computers and Concrete
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• v.25 no.2
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• pp.181-192
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• 2020

Nowadays, steel fiber reinforced concretes (SFRCs) are widely used in practical applications. Significant experimental research has thus been carried out to determine the constitutive equations that represent the behavior of SFRCs under multiaxial loadings. However, numerical modelling of SFRCs via FEM has been challenging due to the complexities of the implementation of these constitutive equations. In this study, following the literature, a plasticity model is constructed for the behavior of SFRCs that involves the Willam-Warnke failure surface with the relevant evolution laws and a non-associated flow rule for determining the plastic deformations. For the precise (yet rapid) integration of the constitutive equations, an explicit substepping scheme consisting of yield intersection and drift correction algorithms is employed and thus implemented in ABAQUS via UMAT. The FEM model includes various material parameters that are determined from the experimental data. Three sets of parameters are used in the numerical simulations. While the first set is from the experiments that are conducted in this study on SFRC specimens with various contents of steel fibers, the other two sets are from the experiments reported in the literature. The response of SFRCs under multiaxial compression obtained from various numerical simulations are compared with the experimental data. The good agreement between numerical results and the experimental data indicates that not only the adopted plasticity model represents the behavior of SFRCs very well but also the implemented integration scheme can be employed in practical applications of SFRCs.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.151-151
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• 2018

The present study is aimed to quantifying the uncertainty in the general circulation model (GCM) selection and its impacts on hydrology studies in the basins. For this reason, 13 GCMs was selected among the 26 GCM models of the Fifth Assessment Report (AR5) scenarios. Then, the climate data and hydrologic data with two Representative Concentration Pathways (RCPs) of the best model (INMCM4) and worst model (HadGEM2-AO) were compared to understand the uncertainty associated with GCM models. In order to project the runoff, the Precipitation-Runoff Modelling System (PRMS) was driven to simulate daily river discharge by using daily precipitation, maximum and minimum temperature as inputs of this model. For simulating the discharge, the model has been calibrated and validated for daily data. Root mean square error (RMSE) and Nash-Sutcliffe Efficiency (NSE) were applied as evaluation criteria. Then parameters of the model were applied for the periods 2011-2040, and 2070-2099 to project the future discharge the five large basins of South Korea. Then, uncertainty caused by projected temperature, precipitation and runoff changes were compared in seasonal and annual time scale for two future periods and RCPs compared to the reference period (1976-2005). The findings of this study indicated that more caution will be needed for selecting the GCMs and using the results of the climate change analysis.

• The Journal of Industrial Distribution & Business
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• v.12 no.2
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• pp.19-27
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• 2021

Purpose: This study investigated the impact of key factors such as service quality, perceived benefit and brand familiarity on a consumer's intention to order online food delivery (OFD). In addition, mediating effect of electronic word of mouth (e-WOM) between relationships among selected key variables and OFD purchase intention is also assessed. Research design, data and methodology: This explanatory, quantitative study employed convenience sampling and collected data through online structured questionnaire from 304 respondents who are users of OFD apps based in greater Klang valley region of Malaysia. The data was then subjected to normality and reliability assessment followed by confirmatory factor analysis, validity assessment and structural equation modelling using IBM SPSS AMOS 24.0. Results: Findings revealed that service quality, perceived benefits and brand familiarity affects purchase intention positively and significantly. Perceived benefits demonstrated highest impact on purchase intention followed by brand familiarity and service quality. Findings also suggest that e-WOM fully mediates relationship between brand familiarity and purchase intention, however, the same was not observed for remaining two variables. Conclusions: The study has enriched OFD literature by investigating impact of selected key factors on purchase intention in the context of OFD. Implications, limitations and future research avenues are then discussed.