• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.1
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• pp.25-33
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• 2021

With the development of machine learning techniques, various types of data such as vibration, temperature, and flow rate can be used to detect and diagnose abnormalities in machine conditions. In particular, in the field of the state monitoring of rotating machines, the fault diagnosis of machines using vibration data has long been carried out, and the methods are also very diverse. In this study, an experiment was conducted to collect vibration data from normal and abnormal compressors by installing accelerometers directly on rotary compressors used in household air conditioners. Data segmentation was performed to solve the data shortage problem, and the main features for the fault classification model were extracted through the chi-square test after statistical and physical features were extracted from the vibration data in the time domain. The support vector machine (SVM) model was developed to classify the normal or abnormal conditions of compressors and improve the classification accuracy through the hyperparameter optimization of the SVM.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.168-178
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• 2022

In this study, the resistance test, the vertical static angle of the attack test and VPMM test will be conducted to estimate the maneuverability of underwater vehicles with ahead propeller. The vertical static test will be conducted within the range of -40deg to 40deg, to investigate the cross-flow drag at high incidence angles. The tests will be conducted by dividing the propeller rotation into a case in which the propeller rotates at a specific rpm, and a case in which the propeller rotates naturally, according to the towing speed. Hydrodynamic coefficients of vertical direction will be estimated by the captive model tests. Additionally, the vertical dynamic stability index based on estimated hydrodynamic coefficients will be calculated and the impact of the propeller revolution state on the index will be investigated. The results are expected to be used as reference test data for underwater vehicles with ahead propeller.

• Journal of Convergence for Information Technology
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• v.11 no.4
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• pp.130-136
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• 2021

This study investigated the general characteristics of mobility disadvantaged persons with disabilities, and to suggest implications to ensure personal mobility with the greatest possible independence for the physically disabled in community. The survey questionnaire included the categories as follows: the general characteristics of the participants, the status of outing and mobility, usage of low-floor buses & taxi for the disabled, service improvement, and mobile support center. Data collected from 219 with physical disabilities were analyzed for this purpose by using descriptive statistics. The study results showed that 54.6% of the total tended to go out everyday, and 17.0% rarely. 53.4% could go out without any assistance, and the major obstacles not to go out were stairs and inconvenience of public transportation. 26.9% used low-floor buses, and 71.1% preferred to use taxi for the disabled. The average waiting time for the usage of low-flow buses and taxi was 66.57 minute and 42.65 minute, separately. 78.7% insisted that the function of mobile support center in the community should be expanded, whereas only 49.8% recognized the role of mobile support center. Based on the study results, the researchers suggested to facilitate access by persons with disabilities to mobility aids, and to improve the actual state of pedestrian environment. In addition, the function of mobile support center should be expanded to help the mobility disadvantaged persons live independently in community, thereby contributing to the promotion of their quality of life.

• Korean Association of Arts Management
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• no.59
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• pp.73-99
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• 2021

Free admission policies have been gradually extended for the public to use cultural facilities free of charge, which lowered the barriers to use those facilities and has a great effect on increasing visitor demands. However, the annual number of visitors which is open to the public isn't quite accurate and varies from institution to institution, which means just a head count. Especially people counter overestimates the number of visitors because it counts visitors in duplicate. Therefore, the purpose of this study is to prepare effective way of grasping the number of visitors using cultural infrastructure. First, comparable number of visitors should be measured by defining the notion of visitor clearly, which has been measured vaguely. Secondly, the problem of duplicate count, which is considered the most problematic, should be solved. Thirdly, the various analysis of visitor behavior should be conducted to provide a high-quality service. To work out the problems above, new measurement will be presented here. This study suggests a state-of-the-art wireless signal-based measurement that could eliminate the duplicate data by collecting MAC address -smart device's distinct signal value. And it also could analyze diverse visitor behaviors by understanding a flow of visitor traffic, duration of stay and revisitation. I would like to examine the possibility and effectiveness of this new measurement by testing it.

• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.24-29
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• 2022

This paper is a purpose to Analyze and study the failure examples for a engine oil leakage of camshaft bearing seal, poor contact by computer connector fin damage and vaporizer inferiority on LPG automotive. The first example, when the researcher disassembled the cylinder head of engine to establish the cause for oil leakage, he confirmed the engine oil leakage by damaged between the engine intake camshaft bearing and seal part. The second example, the connector fin of power source line that control the starting of a car supplied with engine computer. As a result, it found the fact that the engine operation stopped because of cutting of the power source by connector fin damage. The third example, it verified the engine incongruity phe cutting of the power source by connector fin damage. The third example, it verified the engine incongruity phenomenon as thd gas didn't flow the vaporizer by foreign substance deposit. Finally, it supplied a small quantity gas from vaporizer to mix. As the computer controlling mix opening condition supplied a air as opening signal, the air and fuel became rarefied state. it knew that the engine didn't produce prpper power. Therefore, a car have to throughtly inspect not in order to arise the failure symptoms.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.643-659
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• 2022

Geologic sequestration technologies such as CCS (carbon capture and storage), EGS (enhanced geothermal systems), and EOR (enhanced oil recovery) have been widely implemented in recent years, prompting evaluation of the mechanical stability of storage sites. As fluid injection can stimulate mechanical instability in storage layers by perturbing the stress state and pore pressure, poroelastic models considering various injection scenarios are required. In this study, we calculate the pore pressure, stress distribution, and vertical displacement along a surface using commercial finite element software (COMSOL); fault slips are subsequently simulated using PyLith, an open-source finite element software. The displacement fields, are obtained from PyLith is transferred back to COMSOL to determine changes in coseismic stresses and surface displacements. Our sequential use of COMSOL-PyLith-COMSOL for poroelastic modeling of fluid-injection and induced-earthquakes reveals large variations of pore pressure, vertical displacement, and Coulomb failure stress change during injection periods. On the other hand, the residual stress diffuses into the remote field after injection stops. This flow pattern suggests the necessity of numerical modeling and long-term monitoring, even after injection has stopped. We found that the time at which the Coulomb failure stress reaches the critical point greatly varies with the hydraulic and poroelastic properties (e.g., permeability and Biot-Willis coefficient) of the fault and injection layer. We suggest that an understanding of the detailed physical properties of the surrounding layer is important in selecting the injection site. Our numerical results showing the surface displacement and deviatoric stress distribution with different amounts of fault slip highlight the need to test more variable fault slip scenarios.

• Journal of Science Education
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• v.47 no.1
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• pp.52-62
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• 2023

This study examines how prospective earth science teachers perceive the concept of "equilibrium" and "interaction between Earth's spheres" in understanding Earth's radiative equilibrium and tries to identify their misconceptions. For this purpose, a questionnaire was designed and put to them to look into their thought flow based on the items that appeared in the national level evaluation. As a result of analyzing their answers, even though all the prospective teachers correctly described the concept of radiative equilibrium, about 90% of them did not apply the concept of radiative equilibrium to the new environment of the Earth without atmosphere. They do not seem to be able to smoothly derive the concept of a new 'interaction' between the changed regions and a new 'equilibrium' that will be reached over a long period of time. In this respect, it is likely that the textbooks had some influence on the formation of their concepts. In particular, high school Earth Science textbooks describe the Earth's radiation equilibrium in a quantitative manner, focusing on the heat budget of the equilibrium state rather than the process of reaching radiation equilibrium. Such an approach of textbooks might be an obstacle to fostering students into creative convergence-type talents pursued in the 2015 revised curriculum. Meanwhile, in order to eliminate the misconceptions of students often found in the understanding of Earth's radiation equilibrium, this study suggests that the core concepts need to be dealt with more attention even in college courses for training prospective teachers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.53-62
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• 2008

A constitutive model, which can simulate the effect of principal stress rotation associated with direct simple shear test, is proposed in this study. The model is based on two mobilized planes. The plastic strains occur from the two mobilized planes, and depend on stress state, and they are added. The first plane is a plane of maximum shear stress, which rotates about the horizontal axis, and the second plane is a horizontal plane which is spatially fixed. The second plane is used to consider the effect of principal stress rotation on simple shear tests under different stress states. The soil skeleton behavior observed in drained simple shear tests is captured in the model. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program FLAC. The model is first calibrated with drained simple shear tests on loose Fraser River sand. The measured shear stress and volume change are partially induced by principal stress rotation and compared with model calculations. The model is verified by comparing predicted and measured settlements due to rigid footing resting on loose sands. Settlements predicted by the proposed model were very similar to measured settlements. Mohr-Coulomb model can not consider the effect of principal stress rotation and its prediction was only 20% of measured settlements.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.161-168
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• 2023

Converter slag is a by-product generated by refining the pig iron produced into molten steel in the blast furnace, occupying about 15 % of the weight of steel production. It has a high free-CaO content that can generate expansion cracks when used for concrete aggregate. This is the main reason to make it difficult to recycle. To solve this problem, government guideline requires that converter slag has to be aged in an open yard for 90 days. However, aging can not be perfectly performed because it entails time and cost. In this study, we tried to investigate the applicability of converter slag as a cementitious material rather than an aggregate by mixing converter slag with mortar formulations. According to the EDS results of the converter slag in the experiment, we found that screening in the aggregate phase was more effective than that in the powder phase. When the particles separated by a magnet in the aggregate state were pulverized and used for concrete up to a 15 % replacement ratio, various engineering characteristics, such as flow, length change, and compressive strength, showed engineering characteristics similar to those of the control mix.

• Journal of Service Research and Studies
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• v.13 no.4
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• pp.113-130
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• 2023

This study is a single case study of the application of service design in a regional emergency medical centre of a senior general hospital, focusing on the experiences of patients and medical staff. It aims to measure and improve the experience of healthcare services using service design techniques and to verify their effectiveness. A qualitative case study centred on ethnography and design workshops was conducted to collect in-depth experience data from patients and medical staff. The study identified key experiential differences between patients and healthcare workers, with a particular focus on the challenges faced in emergency medical services. The qualitative data collected through patient and healthcare worker interviews and design thinking workshops were analysed and incorporated into the design in order to understand the complex dynamics of the regional emergency medical centre environment. The results of the study highlighted the need to improve communication, manage patient flow, and improve the environment in three main aspects of the current state of design reflecting the needs of patients and medical staff. By analysing the differences in the specific needs of the two groups of patients and medical staff, a design-led implementation process can be applied to improve the services of the regional emergency medical centre. This study highlights the role and importance of design in healthcare and provides an efficient way to bridge the gap between theoretical research and practical design implementation. This will contribute to creating a faster, more effective, and more satisfying healthcare experience. It is hoped that this will be a new opportunity to see service design as a key to a new innovation process for the satisfaction of both patients and medical staff.