• Land and Housing Review
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• v.15 no.2
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• pp.29-37
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• 2024

This study investigates the thermal conductivity and density of expanded polystyrene insulation materials collected from buildings under going energy retrofit projects. Due to the absence of initial thermal conductivity data, determining precise long-term patterns was challenging. Analysis based on design documents revealed that expanded polystyrene insulation maintained consistent performance over ten years. Notably, the thermal conductivity measurements of insulation samples of the same grade and age varied significantly. Additionally, the insulation density was found to be substantially below the standard specified in the design documents. The results of the experiment indicate that performance management during both construction and operation phases is lacking. It is crucial to apply building commissioning, which involves performance verification throughout the building's life cycle, to properly evaluate building energy performance improvements, such as building energy retrofit projects.

• Journal of the Korea Society of Computer and Information
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• v.29 no.1
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• pp.121-130
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• 2024

In this paper, we propose an installation approach for Naval Combat Management System(CMS) software that identifies potential data anomalies during installation. With the popularization of wireless communication methods, such as Low Earth Orbit(LEO) satellite communications, various utilization methods using wireless networks are being discussed in CMS. One of these methods includes the use of wireless network communications for installation, which is expected to enhance the real-time performance of the CMS. However, wireless networks are relatively more vulnerable to security threats compared to wired networks, necessitating additional security measures. This paper presents a method where files are transmitted to multiple nodes using encryption, and after the installation of the files, a validity check is performed to determine if there has been any tampering or alteration during transmission, ensuring proper installation. The feasibility of applying the proposed method to Naval Combat Systems is demonstrated by evaluating transmission performance, security, and stability, and based on these evaluations, results sufficient for application to CMS have been derived.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.339-346
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• 2012

The pre-evaluation of the current-collection performance is an important issue for high-speed railway vehicles. In this paper, using flexible multibody dynamic analysis techniques, a simulation model of the dynamic interaction between the catenary and pantograph is developed. In the analysis model, the pantograph is modeled as a rigid body, and the catenary wire is developed using the absolute nodal coordinate formulation, which can analyze large deformable parts effectively. Moreover, for the representation of the dynamic interaction between these parts, their relative motions are constrained by a sliding joint. Using this analysis model, the contact force and loss of contact can be calculated for a given vehicle speed. The results are evaluated by EN 50318, which is the international standard with regard to analysis model validation. This analysis model may contribute to the evaluation of high-speed railway vehicles that are under development.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.12
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• pp.943-947
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• 2009

To support an efficient management of software verification and validation activities, many defect prediction models have been proposed based on object oriented metrics. In order to apply defect prediction models, we need to determine a threshold value. Because we cannot know actually where defects are, it is difficult to determine threshold. Therefore, we performed a series of experiments to explore the issue of determining a threshold. In the experiments, we applied defect prediction models to other systems different from the system used in building the prediction model. Specifically, we have applied three models - Olague model, Zhou model, and Gyimothy model - to four different systems. As a result, we found that the prediction capabilities varied considerably with a chosen threshold value. Therefore, we need to perform a study on the determination of an appropriate threshold value to improve the applicably of defect prediction models.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.316-323
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• 2016

A UAV(Unmanned Aerial Vehicle) flies along pre-programed navigation points(in-flight, take-off, or landing) automatically without pilot input. Even though UAVs fly differently from general piloted aircraft as the pilot controls the aircraft from a ground station through means of a data-link system. Occasionally, the data-link connection can be lost for any number of reasons, in which case, the FLCC(Flight control Computer) must automatically switch to autopilot to continue flying. Hence, the FLCC is a flight-critical component that must be throughly tested and validated. This paper discusses the development of a HILS(Hardware in the Loop Simulation) test environment designed to simulate real flight conditions to verify the FLCC satisfies flying quality requirements and maintains robustness despite any potential malfunctions or emergency situations.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.196-202
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• 2017

A very long test track is required for high-speed operation test of the real-scale Linear Synchronous Motor (LSM) for ultra-high-speed trains. The required length results in huge construction cost and economic loss if any error occurs during development. Therefore, validation study of the LSM design technology using a low-cost small-scale model must be carried out in the early research stages. It is possible to deduce an optimal winding method for the armature and determine the mechanical properties of the LSM through a performance tester that applies a rotary-type small-scale LSM model. In addition, it is possible to utilize previous research on LSM control systems. Therefore, a basic design model, comprising a rotary-type LSM tester that meets the requirements for the propulsion of 600km/h-class ultra-high-speed trains, is derived in this study. Finally, an optimal model, which has a stable structure under the condition of 1500rpm or more high-speed rotation, is derived by electromagnetic and mechanical stiffness analysis.

• Atmosphere
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• v.23 no.4
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• pp.443-452
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• 2013

The original Fog Stability Index (FSI) is formulated as FSI=$2(T-T_d)+2(T-T_{850})+WS_{850}$, where $T-T_d$ is dew point deficit (temperature-dew point temperature), $T-T_{850}$ is atmospheric stability measure (temperature-temperature at 850 hPa altitude) and $WS_{850}$ is wind speed at 850 hPa altitude. As a way to improve fog prediction at Incheon International Airport (IIA), we develop the modified FSI for IIA, using the meteorological data at IIA for two years from June 2011 to May 2013, the first one year for development and the second one year for validation. The relative contribution of the three parameters of the modified FSI is 9: 1: 0, indicating that $WS_{850}$ is found to be a non-contributing factor for fog formation at IIA. The critical success index (CSI) of the modified FSI is 0.68. Further development is made to consider the fact that fogs at IIA are highly influenced by advection of moisture from the Yellow Sea. One added parameter after statistical evaluation of the several candidate parameters is the dew point deficit at a buoy over the Yellow Sea. The relative contribution of the four parameters (including the new one) of the newly developed FSI is 10: 2: 0.5: 6.4. The CSI of the new FSI is 0.50. Since the developmental period of one year is too short, the FSI should be refined more as the data are accumulated more.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.9
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• pp.814-821
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• 2015

The STEP Cube Lab. classified as a pico-class satellite has been successfully developed as a flight model(FM) to be launched in 2015. Its mission objective is to perform the on-orbit verification of fundamental space core-technologies. In this study, a thermal design concept based on the passive method to achieve the mission objective is introduced. The effectiveness of the thermal design and performance of the satellite has been verified through the acceptance level thermal vacuum test. In addition, to improve the reliability of thermal mathematical model, correlation was performed using the results of thermal balance test. This paper describes a series of process for the thermal vacuum test on the STEP Cube Lab. FM.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.421-426
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• 2017

In this study, we propose a method for predicting the mechanical properties of the printed circuit board (PCB) that has transversely isotropic characteristics. Unlike the isotropic material, there is no specific test standard for acquisition of the transversely isotropic properties. In addition, common material test methods are not readily applicable to that type of laminated thin plate. Utilizing the natural frequency obtained by a modal test and the sizing optimization technique provided in $OptiStruct^{(R)}$, the mechanical properties of a PCB were derived to minimize the difference between test and analysis results. In addition, the validity of the predicted mechanical properties was confirmed by the MAC (Modal Assurance Criteria) value of each of the compared mode shapes. This proposed approach is expected to be extended to the structural analysis for the design verification of the top product that includes a PCB.

• Journal of the Korea Society for Simulation
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• v.21 no.3
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• pp.11-16
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• 2012

Simulation is the imitation of the operation of a real-world process or system over time. It concerns the study of the operating characteristics of real systems. Typically, a simulation project consists of several steps such as data collection, coding, model verification, model validation, experimental design, output data analysis, and implementation. Among these steps of a simulation study this paper focus on statistical analysis methods of simulation output data. Specially, we explain how to develop confidence interval estimators for mean ${\mu}$ in terminating and non-terminating simulation cases. We, then, explore the estimation techniques for $f({\mu})$, where the function $f({\bullet})$ is a nonlinear that is continuously differentiable in a neighborhood of ${\mu}$ with $f'({\mu}){\neq}0$.