• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.680-690
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• 2022

Vibrations in the pipe system trigger fatigue-related issues and lead to fatal other problems caused by pipe damage. There are numerous studies to analyze and reduce the cause of pipe vibration, among which a small number of studies are being conducted on pipe vibration reduction using friction supports. The study of friction supports, however, focused only on predicting and evaluating the performance of the friction supports and seldomly considered the design perspective of the install location of the supports. Therefore, this study intends to suggest the optimization process for finding the best installation region of friction support to attenuate the vibration of entire piping system. The optimal position of the friction support is predicted only by linear analysis to guarantee optimization efficiency in the design process. The designed friction support location is verified by time domain analysis.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.131-137
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• 2024

Aerodynamic noise generated by the surrounding flow of a train traveling at high speed affects both outdoor and indoor noise. This study's goal is to develop a test method to measure and quantitatively evaluate aerodynamic noise through pressure perturbation data on the train surface. To accurately evaluate aerodynamic noise, it is important to separate and evaluate the compressive and incompressible pressure fluctuations mixed in the acquired surface pressure fluctuation data. This is because the noise transmission characteristics of the two pressure fluctuations are different. First, the installation length and interval of the microphone were determined to acquire surface pressure fluctuation data, and wavenumber-frequency analysis was performed to separate incompressible pressure fluctuation and compressible pressure fluctuation to obtain a sound pressure level spectrum. Finally, as a result of comparing the test results measured in the train head and trail, It was confirmed that the pressure fluctuation on the train head surface was greater than that on the tail.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.465-470
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• 2024

Kitchen cabinets are widely used for their spacious storage and efficient use of space, but their high installed location makes it difficult for the elderly and disabled to access. Therefore, in this paper, we propose a new height-adjustable kitchen cabinet that can be used more easily and safely. The lift-down range of cabinet was set considering the installation location of cabinet for efficient use of kitchen space and the maximum height accessible to the elderly and disabled, and the link geometry and driving method of the complex link mechanism were determined through the mechanism design procedure to ensure that the selected floor come down safely along the optimal descend path. In addition, the appropriate motor and control algorithm were added to allow the user to descend to the desired height with a simple button operation. It was confirmed through actual production that the proposed linkage mechanism performs the desired lift-down motion.

• Steel and Composite Structures
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• v.50 no.5
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• pp.515-529
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• 2024

Cold-formed steel (CFS) is a popular choice for construction due to its low cost, durability, sustainability, resistance to high environmental and seismic pressures, and ease of installation. The beam-column connections in residential and medium-rise structures are formed using self-drilling screws that connect two CFS channel sections and a gusset plate. In order to increase the moment capacity of these CFS screwed beam-column connections, stiffeners are often placed on the web area of each single channel. However, there is limited literature on studying the effects of stiffeners on the moment capacity of CFS screwed beam-column connections. Hence, this paper proposes a new test approach for determining the moment capacity of CFS screwed beam-column couplings. This study describes an experimental test programme consisting of eight novel experimental tests. The effect of stiffeners, beam thickness, and gusset plate thickness on the structural behaviour of CFS screwed beam-column connections is investigated. Besides, nonlinear elasto-plastic finite element (FE) models were developed and validated against experimental test data. It found that there was reasonable agreement in terms of moment capacity and failure mode prediction. From the experimental and numerical investigation, it found that the increase in gusset plate or beam thickness and the use of stiffeners have no significant effect on the structural behaviour, moment capacity, or rotational capacity of joints exhibiting the same collapse behaviour; however, the capacity or energy absorption capacities have increased in joints whose failure behaviour varies with increasing thickness or using stiffeners. Besides, the thickness change has little impact on the initial stiffness.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.35 no.1
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• pp.68-82
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• 2017

Strengthening surveillance, one of the most important factors in the crime prevention environment of cultural heritages, has difficulty in evaluating and diagnosing the site. For this reasons, surveillance enhancement has been assessed by modelling the shape of cultural heritage, topography, and trees digitally. The purpose of this study is to develop the evaluation method of crime prevention environment for cultural heritage by using the 3D visual exposure index (3DVE) which can quantitatively evaluate the surveillance enhancement in three dimensions. For the study, the evaluation factors were divided into natural, organizational, mechanical, and integrated surveillance. To conduct the analysis, the buildings, terrain, walls, and trees of the study site were modeled in three dimensions and the analysis program was developed by using the Unity 3D. Considering the working area of the person, it is possible to analyze the surveillance point by dividing it into the head and the waist position. In order to verify the feasibility of the 3DVE as the analysis program, we assessed the crime prevention environment by digitally modeling the Donam Seowon(Historic Site No. 383) located in Nonsan. As a result of the study, it was possible to figure out the problems of patrol circulation, the blind spot, and the weak point in natural, mechanical, and organizational surveillance of Donam Seowon. The results of the 3DVE were displayed in 3D drawings, so that the position and object could be identified clearly. Surveillance during the daytime is higher in the order of natural, mechanical, and organizational surveillance, while surveillance during the night is higher in the order of organizational, mechanical, and natural surveillance. The more the position of the work area becomes low, the more it is easy to be shielded, so it is necessary to evaluate the waist position. It is possible to find out and display the blind spot by calculating the surveillance range according to the specification, installation location and height of CCTV. Organizational surveillance, which has been found to be complementary to mechanical surveillance, needs to be analyzed at the vulnerable time when crime might happen. Furthermore, it is note that the analysis of integrated surveillance can be effective in examining security light, CCTV, patrol circulation, and other factors. This study was able to diagnose the crime prevention environment by simulating the actual situation. Based on this study, consecutive researches should be conducted to evaluate and compare alternatives to design the crime prevention environment.

• Journal of Energy Engineering
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• v.27 no.2
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• pp.1-13
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• 2018

The proportion of natural gas-fueled power generation is expanding due to the change of domestic energy policy pursuing reduction of dust and increasing clean energy consumption. Natural gas fuels used for the combined-cycle power plants and the district-heating power plants are operated at high temperature and high pressure in the fuel supply system. Accidents due to leakage of the gas such as fire and explosion should be prevented by applying risk management techniques. In this study, risk assessment was performed on the natural gas fuel supply system of a combined power plant based on the API RP 581 RBI code. For the application of the API RBI code, lines and segments of the evaluation target system were identified. Operational data and input information were analyzed for the calculations of probability of failure and consequence of failure. The results of the risk assessment were analyzed over time from the initial installation time. In the code-based evaluation, the gas fuel supply system was mainly affected by thinning, external damage, and mechanical fatigue damage mechanisms. As the operating time passes, the risk is expected to increase due to the external damage caused by the CUI(Corrosion Under Insulation).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.106-111
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• 2017

In this study, the stiffness of an LMU (Leg Mating Unit), which is a device required for installing the top side part of an offshore structure, was examined through structural analysis. This unit is mounted on the supporting point of the structure and is used to absorb the shock at installation. It is a cylindrical structure with an empty center. To support the vertical load, elastomeric bearings (EBs) and iron plates are laminated in layers. The stiffness of the EBs is basically influenced by the size of the bearings, but it varies with the number of laminated sheets inside the same sized structure. The relationship between the stiffener and the compressive stiffness is investigated, and its design is suggested. The stiffness of the EBs is analyzed by calculating the reaction force, while controlling the displacement. First, the relationship between the size of the reinforcing plate and the compressive stiffness is considered. Next, the relationship between the number of stacked reinforcing plates and the compression stiffness is considered. Different loads are required for each installed point. The goal is to design the compression stiffness in such a way that the same deformation occurs at each point in the analysis. In this study, ANSYS is used to perform the FE analysis.

• Korean Journal of Construction Engineering and Management
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• v.18 no.3
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• pp.33-41
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• 2017

A modular specification is a contract document that specifies the requirements of production, transformation and installation in a modular construction. A problem of the currently used specification is that it does not guarantee the level of performance required by the modular construction and fails to accommodate unique characteristics of each construction because it widely uses the standard specification as it is. This study proposes a specification that reflects the unique feature of modular construction in order to improve the quality of modular construction. Research focuses on the leakage in waterproof and mechanical equipment because it is the area with the highest rate of defects. This study suggests ways to improve the modular specification as follows: 1)Descriptive specifying (following MasterFormat) 2)Propose leakage verification method and test clause 3) Reflect characteristic of modular construction. Proposed modifications to modular specification are reviewed by experts for validation and their opinion verifies suggested improvements as a way to secure the quality of modular construction and to promise characteristics of the modular specification. This improvement will be used for reference when writing construction project specification, which can be an important contract document, so that it could lower occurrence rate of the modular defects.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.1
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• pp.1-7
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• 2013

Structural design and analysis of a coiling arm unloading machine for submarine cable have been originally conducted in this study. Three-dimensional CAD modeling process is practically applied for the structural design in detail. Finite element method(FEM) and multi-body dynamics(MBD) analyses are also used to verify the safety and required motions of the designed coiling arm structure. The effective moving functions of the designed coiling arm with respect to rotational and radial motions are achieved by adopting bearing-roller mechanical parts and hydraulic system. Critical design loading conditions due to its self weight, carrying cables, offshore wind, and hydraulic system over operation conditions are considered for the present structural analyses. In addition, possible inclined ground conditions for the installation of the designed coiling arm are also considered to verify overturn stability. The present hydraulic type coiling arm system is originally designed and developed in this study. The developed coiling arm has been installed at a harbor, successfully tested its operational functions, and finished practical unloading mission of the submarine cable.

• Journal of Aerospace System Engineering
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• v.14 no.3
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• pp.42-50
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• 2020

For calibration of the non-uniformity characteristics of the space-borne infrared (IR) sensor, a black body system shall provide estimated representative surface temperature at various reference temperatures by using the limited number of temperature sensors. The black body system proposed in this study has an I/F flange integrated on the rear side of the black body for installation of the heat pipe to transfer the residual heat after the black body heat-up. This design allows for obtaining a circular symmetric thermal contour of black body with low surface temperature gradient, leading to much easier representative temperature estimation. Additionally, this provides mechanically stable thermal I/F under launch and on-orbit environmental loads, as well as allowing a fail safe design by using the two heat pipes. Also, a highly accurate temperature estimation is possible even if the temperature sensors are attached on the surface on the rear side of the black body. The effectiveness of the thermal design of the proposed black body has been verified through the on-orbit thermal analysis. Based on the results, the representative surface temperature was estimated according to the number and position of the temperature sensors.