• Tribology and Lubricants
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• v.37 no.4
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• pp.117-124
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• 2021

In this study, we perform a 3D CFD conjugate analysis according to the shape of the foil ramp of the air foil thrust bearing, analyze the flow characteristics inside the bearing, and compare the results corresponding to the two shapes. Air has a lower viscosity than lubricating oil. Therefore, the thrust runner of the bearing must rotate at high speed to support the load. The gap between thrust runner and foil is significantly smaller than that of the oil bearing. Hence, it is crucial to analyze the complex flow characteristics inside the bearing to predict the complex flow inside the bearing and performance of the bearing. In addition, flow characteristics may appear differently depending on the ramp shape of the bearing foil, which may affect bearing performance. In this study, we numerically analyze the main flow path of air flowing into the bearing and the secondary flow path used for cooling the bearing using the commercial CFD software ANSYS CFX and compare the flow characteristics for straight and curved foil ramp shapes. Notably, there is a difference in the speed of the flowing air according to the shape of the ramp, which affects the bearing performance.

• International Journal of Computer Science & Network Security
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• v.21 no.1
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• pp.143-151
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• 2021

The enormous prevalence of transferring official confidential digital documents via the Internet shows the urgent need to deliver confidential messages to the recipient without letting any unauthorized person to know contents of the secret messages or detect there existence . Several Steganography techniques such as the least significant Bit (LSB), Secure Cover Selection (SCS), Discrete Cosine Transform (DCT) and Palette Based (PB) were applied to prevent any intruder from analyzing and getting the secret transferred message. The utilized steganography methods should defiance the challenges of Steganalysis techniques in term of analysis and detection. This paper presents a novel and robust framework for color image steganography that combines Linear Congruential Generator (LCG), simulated annealing (SA), Cesar cryptography and LSB substitution method in one system in order to reduce the objection of Steganalysis and deliver data securely to their destination. SA with the support of LCG finds out the optimal minimum sniffing path inside a cover color image (RGB) then the confidential message will be encrypt and embedded within the RGB image path as a host medium by using Cesar and LSB procedures. Embedding and extraction processes of secret message require a common knowledge between sender and receiver; that knowledge are represented by SA initialization parameters, LCG seed, Cesar key agreement and secret message length. Steganalysis intruder will not understand or detect the secret message inside the host image without the correct knowledge about the manipulation process. The constructed system satisfies the main requirements of image steganography in term of robustness against confidential message extraction, high quality visual appearance, little mean square error (MSE) and high peak signal noise ratio (PSNR).

• Korean Journal of Social Welfare Studies
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• v.42 no.1
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• pp.433-461
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• 2011

This study investigated changes and determinants of public pension generosity and pension spending in welfare states during the last retrenchment period. Path-dependency thesis, industrialization theory and power resources model were examined with the twelve welfare states from 1980 to 2007. The main results are as follows. First, the developments of benefit generosity and pension spending have been differently presented according to pension structure. Second, the cross-national pooled-time series analysis confirmed that pension structure is the most significant factors to determine the level of benefit generosity and pension spending. Third, the positive effect of population ageing on pension spendings were proved even without any changes of pension generosity. New social risks, however, have restrained the pension spending. Fourth, the power of the left party and labor union did not affect the pension policy, which implies that power resources theory cannot explain the development of pension policy in this retrenchment period.

• The Journal of Korean Medicine
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• v.44 no.1
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• pp.38-55
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• 2023

Objectives: The purpose of this study was to provide direction for future research in the field of Korean medicine by analyzing microbiome based technologies emerging as a new diagnostic and treatment paradigm. Methods: To achieve the purpose of the study intellectual property data was used. After establishing citation network from registered microbiome-related US patents, citation network was analyzed by knowledge persistence-based main path approach to understanding technological trajectories. Furthermore, community detection algorithms were used to quantitatively identifying specific technological domain in a particular time period. Results: Results shows that early technologies in livestock industry contribute most to the recent patents. Knowledge in the patents flow through the path of food and beverage technological domain, and finally are inherited to the recent development of diagnosis, treatment and prevention technic. Conclusions: This study indicate that developing diagnostic tools which can link the composition of microbiome to specific diseases should be given high priority. Researches should lead to novel therapeutic strategies. Specifically, improving reliability of pattern identification and finding effective therapeutic compositions based on principles of Korean medicine is necessary.

• Journal of the Economic Geographical Society of Korea
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• v.26 no.2
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• pp.73-95
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• 2023

The purpose of this study is to analyze the industrial structural changes and types of specialized in the shipbuilding cities, which are representative sectors of industrial city decline, and explore regional responses. Most cities designated as special areas for industrial crisis response in 2018 are specialized in shipbuilding. While the shift from prosperity to recession since the 2010s is the main factor, each city has responded differently to the industrial crisis. The analysis, targeting seven shipbuilding cities, shows that regions where large shipyards of major corporations with high industrial competitiveness are located have relatively less decline during business fluctuations, and there is a tendency for a decrease in industrial structural diversity during prosperous periods and an increase during recessionary periods. Based on the resistance and recoverability to industrial crises, the industrial paths of shipbuilding cities are classified into four types. Considering regional industrial structure and competitiveness, it is necessary to develop customized support strategies such as maintaining and declining shipbuilding industries and fostering new alternative industries.

• Journal of the Korean Society for Library and Information Science
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• v.54 no.3
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• pp.209-236
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• 2020

This study describes a set of user experience indicators developed for the evaluation of knowledge and information resource systems. The user experience perspectives had emerged as a new analysis standard in the field of information media and information service research. The study included a survey conducted to verify the derived experience factors and developed them as indicators. The survey data was gathered from 158 participants in the preliminary and 480 participants in the main study. The applied analysis techniques were descriptive statistics, the exploratory factor analysis, the confirmatory factor analysis, the correlation analysis, and the path analysis. The results introduced seven user experience factors, 37 detailed user experience factors, and 105 system perception factors as the final user experience indicators. The developed and verified indicators should measure the degree of user experience perceived by users of the knowledge and information resource system and conduct effective evaluations that reflect correlation rather than a simple comparison of each experience factor.

• Geotechnical Engineering
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• v.1 no.2
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• pp.17-26
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• 1985

This study was carried out for the purpose of comparing in reference to sand drain in the next three different cases. First, The case of drain material (sand pile) has some rigidity during embankment and consolidation. Second, In usual case of no rigidity as a paper drain without permeability during embankment and consolidation Third, Check up clay behavior when above the two cases carried out respectively. This FEM analysis is consisted with Biot's consolidation equation when it is used for Christian Boehmer's numerical technique. The main results are obtained from above the Analysis When sand drain has some rigidity, the lateral and vertical deformation of clay foundation is restrained considerable amount and .exhibited bearing capacity of load as a pile According to the foundation in drained condition and untrained condition, the results are much variable in this analysis method. Also, The behaviors of stress path and pore water pressure met our expectation during , consolidation. This analysis should be considered to put into use of sand drain and design in future.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.222-226
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• 2008

The construction industry has remained stagnant for a long time. So many researchers have wanted to solve this problem not only focusing on enhancement of construction process, but also introducing the culture of cooperation. The Last Planner System(LPS), one of the elementary techniques of Lean Construction, aims for improving the work reliability and reducing variability by measuring and managing the daily or weekly performance for overcoming the weakness of recent complex schedule management tools such as Critical Path Method. This research propose a framework for implementation of LPS conducted by owner focused on construction stage and introduce optimal owner participation model in plant construction, based on needs analysis for construction participants. Furthermore, this research introduce a modified needs analysis, so called IPBA(Importance-Performance-Betterment Analysis), and an advanced LPS procedure which add the needs analysis during pre-LPS and(or) main LPS stages.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.289-299
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• 2008

Based on the case study on the causes for the failure of cutting slope composed of weathered rock and soil, the factors influencing the design of a cutting slope have been examined, This type of rock and soil is widely distributed on the region whose parent rock is granite. To analyze the stability of the cutting slope, the following series of progress has been conducted: (1) ground characterization by geological survey and ground investigation, (2) the safety factor examination by limit equilibrium analysis and numerical analysis and (3) the comparison and analysis of rainfall and failure history. As a result, the main factors to cause the failure is determined to be the decrease of shear strength in the upper parts whose ground condition is weakened during localized heavy rain. Moreover, the analysis indicates the failure is also closely related to the groundwater inflow path. On the base of this investigation, a reinforcement method is proposed to ensure the stability of the cutting slope.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.37-48
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• 2023

In this study, performance analysis modeling of two spool mixed flow type turbofan engine according to steady-state and transient is performed. The target engine is selected as F100-PW-229 from Pratt & Whitney, and main engine components including fan, high pressure compressors, combustion, high pressure turbines, low pressure turbines, mixer, convergent-divergent nozzle are modeled. The cooling effect of turbine through secondary flow path are considered in engine simulation model. We develop in-house Matlab/Simulink-based engine performance analysis program capable of analyzing internal engine state and compare it with GASTURB which is generally used as a commercial engine analysis program.