• Journal of the Society of Naval Architects of Korea
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• v.61 no.5
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• pp.312-323
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• 2024

This study aims to evaluate the safe operating envelope (SOE) for light aircraft carriers using a computational fluid dynamics (CFD) modeling database of flight deck air-wake. Assessing the SOE is crucial for ensuring the safe operation of carrier-based aircraft, particularly during take-off and landing maneuvers. Traditional methods that only consider relative wind envelopes (RWE) provide basic information but fail to account for the complex airflow patterns over the flight deck. To address this limitation, this research utilizes CFD to analyze the air-wake and integrate these findings into the SOE assessment. Various studies on CFD modeling of airflow around naval ships and aircraft carriers were reviewed, confirming the importance of accurate airflow databases for operational safety. This study employs the KRISO-CVX1 model, a light aircraft carrier designed by the Korea Research Institute of Ships & Ocean Engineering (KRISO), to demonstrate the application of CFD data in SOE evaluations. The methodology involves a detailed analysis of turbulent flow and thermal fields around the carrier deck under different wind speed, direction, and ship speed conditions. The results indicate significant variations in air-wake characteristics depending on the relative wind speed and direction, impacting the operational safety of carrier-based aircraft. This study emphasizes the need for incorporating CFD-based airflow data into SOE assessments to enhance the accuracy and reliability of operational safety evaluations for aircraft carriers. In conclusion, the integration of CFD air-wake modeling databases provides a more comprehensive approach to assessing the SOE, offering improved safety margins for carrier-based aircraft operations. This research is expected to contribute to the development of more robust and precise operational guidelines for naval aviation.

• Journal of the Korea Society of Computer and Information
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• v.14 no.5
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• pp.149-156
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• 2009

Korean WiBro becomes international standard to IEEE 802.16e, and We are carrying out a WiBro network business from capital regions. We executed eavesdropping about voices and messenger program and the VoIP which frequently happened in WiBro networks at these papers. We have a lot in common with the Wireshark which is a packet collection and an analyzer, and We execute eavesdropping, and We reproduce eavesdropping data with bases to a SIP, H.263, TCP, UDP protocol through packets. In time of a copy of a packet negative the VoIP which verify time with bases, and was eavesdropped on integrity packet and a X-Lite call record, be matched that a packet is counterfeit forgery did not work, and We demonstrate, and verify integrity. The data which integrity was verified put in a seaming envelope, and we prepare so as it is to a liver of investigator, and execute, and to be able to do use to proof data after seaming in courts in order to utilize as criminal investigation data.

• Journal of Korea Port Economic Association
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• v.27 no.3
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• pp.135-146
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• 2011

A voluminous research on efficiency employs the DEA(Data Envelope Analysis) models. There are, however, only very few that have an interest in the factors influencing such efficiencies. We, furthermore, do not see any studies which analyze the long-term efficiency of the logistics providers using the panel cointegration techniques. The purpose of this paper, hence, is to evaluate the efficiency, analyse its determinants and show a long-term relationship between turnover and the other variables employing the SBM(Slack Based Measure) model, Tobit model, the panel procedure and the FMOLS(Fully Modified OLS). The panel data are composed of 9 individuals and 6 years. The panel cointegrating vectors show that the group coefficient of asset and employees is not only significant but has expected signs, while some of the individual coefficients are insignificant or/and exhibit wrong signs. The panel cointegrating vectors from fully modified OLS also indicate that the estimated coefficients of the panel analysis tend to be overvalued and the asset influences the turnover far greater than the employee does.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.148-159
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• 1998

Spot welding palys a key role in increasing productivity and weight reduction of the final products. This paper proposes a systematic approach on the design of spot weld configuration, dealing with the requried number and location of spot weld joints under the given design parameters, such as the applied loads, lap area, and individual spot weld strength. The optimal design of a spot-welded joint is postulated as a state when the safety factors of all spot weld points (i) are evenly distributed and (ii) reach maximum value. A CAD program is developed to arrange the optimal location of each spot weld based on the derived objective function and constraints. The CAD tool integrates the optimization procedure with Finite Element Analysis (FEA) code through an interface. The interface automatically provides geometrical data and mesh configuration for different spot weld locations to FEA model. It also extracts the transmitted load of each spot weld from the FEA code, and allows the optimization code predict an improved arrangement of spot weld locations. The feasibility of the developed approach is demonstrated by the selected examples.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.41.3-41.3
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• 2015

As part of the Herschel key program "Water in Star-forming Regions with Herschel (WISH)", PACS imaging spectroscopy data have been taken toward ten massive young stellar objects (YSOs): four high mass protostellar objects (HMPOs), two hot molecular cores (HMCs), and four ultracompact HII regions (UCHIIs). The spectra cover a broad range of wavelengths (55 to 210 micron) presenting various atomic and molecular lines as well as excellent dust thermal continua. By fitting the continua utilizing a modified black-body formula we estimate mass-weighted temperature and column density distributions of warm dust and find that UCHII regions are warmer and HMCs are more deeply embedded than the other types. We also estimate rotational temperature and column density distributions of warm CO gas using the rotational diagram analysis. In addition, based on the comparison of high J CO line fluxes to the RATRAN estimates of central heating envelope models, we find that majority of warm CO is originated from bipolar outflow shocks.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1133-1140
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• 2011

Current design process for the Hall effect thruster has relied on expensive experimental method based on the limited historical data. In this study, a proper design space for the Hall effect thruster is chosen and associated design space exploration is conducted based on a recently proposed numerical method in order to improve current design process. According to the results of the design space exploration, performance envelope is determined for the given design space and the correlations between performance metrics are analyzed. Further analysis shows that main factors in performances for the Hall effect thruster are the anode mass flow rate and the discharge voltage.

• Geomechanics and Engineering
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• v.9 no.1
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• pp.115-124
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• 2015

Determination of mobilized shear strength parameters (that identify stresses on the failure plane) is required for analyzing the stability by limit equilibrium method. Generalized Hoek-Brown (GHB) and Mohr-Coulomb (MC) failure criteria are usually used for obtaining stresses on the plane of failure. In the present paper, the applicability of these criteria for determining the stresses on failure plane is investigated. The comparison is based on stresses on the real failure plane which are obtained from the Mohr stress circle. To do so, 18 sets of data (consist of principal stresses and angle of failure plane) presented in the literature are used. In addition, the values account for (VAF) and the root mean square error (RMSE) indices were calculated to check the determination performance of the obtained results. Values of VAF and RMSE for the normal stresses on the failure plane evaluated from MC are 49% and 31.5 where for GHB are 55% and 30.5, respectively. Also, for the shear stresses on failure plane, they are 74% and 36 for MC, 76% and 34.5 for GHB. Results show that the obtained stresses and angles of failure plane for each criterion differ from real ones, but GHB results are closer to the empirical results. Also, it is inferred that results are affected by the failure envelope not real failure plane. Therefore, obtained shear strength parameters are not mobilized. Finally, a multivariable regressed relation is presented for determining the stresses on the failure plane.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4
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• pp.18-23
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• 1996

Fluctuation statistics of scattering strength are not only important because they impact the performance of active sonar systems, but also because they may provide insight into the major scattering process. In this article, analysis of the statistical characteristics of bottom backscattering, measured in shallow water, are presented. The slowly moving experimental sonar was operated at 30kHz to gather data over the bottom. Spatial and temporal correlation functions of the signal amplitudes were measured. The distribution function and probability of false alarm function of the detected envelope of widebeam and narrowbeam signals were measured. An attempt was made to compare the results with existing theoretical models. The result suggests that the statistical characteristics of bottom backscattering fluctuation of moving source is differ from that of fixed source.

• Journal of Surface Science and Engineering
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• v.55 no.6
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• pp.398-402
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• 2022

Vacuum Insulation Panel (VIP) is an high energy efficient insulation system that facilitate slim but high insulation performance, based on based on a porous core material evacuated and encapsulated in a multi-barrier envelope. Although VIP has been on the market for decades now, it wasn't until recently that efforts have been initiated to propose a standard on aging testing. One of the issues regarding VIP is its durability and aging due to pressure and moisture dependent increase of the initial low thermal conductivity with time. It is hard to visually determine at an early stage. Recently, a method of analyzing the damage on the a material surface by applying image processing technology has been widely used. These techniques provide fast and accurate data with a non-destructive way. In this study, the surface VIP images were analyzed using the Harris corner detection algorithm. As a result, 171,333 corner points in the normal packaging were detected, whereas 32,895 of the defective packaging, which were less than the normal packaging. were detected. These results are considered to provide meaningful information for the determination of VIP condition.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.413-427
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• 2006

It is necessary to study and develop guidelines for providing comfort and health indoor air quality for office workers since air-tight envelope system of current office building may cause poor indoor air quality. The purpose of this study is to propose guideline for volatile organic compounds in office base on the field study, human health risk assessment and cost-benefit analysis. The field study was conducted to survey the concentrations of volatile organic compounds in indoor air of 69 offices from June to September, 2005 in Seoul and Gyeonggi-do. The rate of excess to guideline of volatile organic compounds in indoor air of new apartment on the Ministry of Environment in Korea(MOE) was surveyed 37.6% for benzene, 6.8% for toluene, and 1.5% for ethylbenzene. As the result of human health risk assessment, mean cancer risk did not exceed 10-6 which is guideline of US.EPA. Also, total hazard index did not exceed 1 which is guideline of US.EPA. Through the cost-benefit analysis of angle on the social-economics to verify the necessary to establish the standards of volatile organic compounds for improvement and development of indoor air quality in office, the present value of benefit was higher than the present value of cost. With the above considerations in mind, it is suggested that the field study for indoor air quality in offices should be expanded and human health risk assessment and cost-benefit analysis be performed th offer scientific data for decision-making of policy for improvement and management of indoor air quality in office.