• Smart Structures and Systems
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• v.33 no.4
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• pp.313-323
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• 2024

Deterioration of buildings is one of the biggest problems in modern society, and the importance of a safety diagnosis for old buildings is increasing. Therefore, most countries have legal maintenance and safety diagnosis regulations. However, the reliability of the existing safety diagnostic processes is reduced because they involve subjective judgments in the data collection. In addition, unstructured tasks increase rework rates, which are time-consuming and not cost-effective. Therefore, This paper proposed the method that can calculate the safety grade of deterioration automatically. For this, a DNN structure is generated by using existing precision inspection data and precision safety diagnostic data, and an objective building safety grade is calculated by applying status evaluation data obtained with a UAV, a laser scanner, and reverse engineering 3D models. This automated process is applied to 20 old buildings, taking about 40% less time than needed for a safety diagnosis from the existing manual operation based on the same building area. Subsequently, this study compares the resulting value for the safety grade with the already existing value to verify the accuracy of the grade calculation process, constructing the DNN with high accuracy at about 90%. This is expected to improve the reliability of aging buildings in the future, saving money and time compared to existing technologies, improving economic efficiency.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2090-2100
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• 2011

Railway rail fastening system is the critical device which gives big influences to not only the vehicle driving stability and the orbit's structural stability against the impulsive load, but also the noise vibration and the ride comfort. As a part of the low-carbon green growth, the importance of the railroad industry is getting highlights on its excellent energy-efficiency and eco-friendliness. However, so far the Korea's domestic rail fastening system technology is not so good and the technical reliance to abroad is very heavy. In this study, we conducted comparative analysis on the rail fastening system with new and used one of the same type. And those systems are imported by Seoul Metro and are being used by it. With this basis, we developed the components and the materials and then, established the durability assessment methods appropriate to the Korean domestic circumstances. And through the reliability qualification test on the 7 parts of the rail fastening system, we've improved the reliability and guaranteed the 15 years of service lifetime. ($B_{10}Life15$) Establishment and standardization of Reliability Standard on the parts of the rail fastening system such as anti-vibration pads, guide-plate, screw spike made it possible to perform the internationally fair assessment. And it is thought that we can satisfy the manufactures' and consumers' needs of cost-cutting and qualification security by shortening of assessment period on rail fastening system.

• Earthquakes and Structures
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• v.16 no.3
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• pp.279-293
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• 2019

The overall seismic performance of existing pre 1960-70s reinforced concrete (RC) structures is significantly affected by the inadequate length of columns' lap-spliced reinforcement. Due to this crucial structural deficiency, the cyclic response is dominated by premature bond - slip failure, strength and stiffness degradation, poor energy dissipation capacity and low ductility. Recent earthquakes worldwide highlighted the importance of improving the load transfer mechanism between lap-spliced bars, while it was clearly demonstrated that the failure of lap splices may result in a devastating effect on structural integrity. Extensive experimental and analytical research was carried out herein, to evaluate the effectiveness and reliability of strengthening techniques applied to RC columns with lap-spliced reinforcement and also accurately predict the columns' response during an earthquake. Ten large scale cantilever column subassemblages, representative of columns found in existing pre 1970s RC structures, were constructed and strengthened by steel or RC jacketing. The enhanced specimens were imposed to earthquake-type loading and their lateral response was evaluated with respect to the hysteresis of two original and two control subassemblages. The main variables examined were the lap splice length, the steel jacket width and the amount of additional confinement offered by the jackets. Moreover, an analytical formulation proposed by Tsonos (2007a, 2019) was modified appropriately and applied to the lap splice region, to calculate shear stress developed in the concrete and predict if yielding of reinforcement is achieved. The accuracy of the analytical method was checked against experimental results from both the literature and the experimental work included herein.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.5
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• pp.1303-1317
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• 2024

The development of high-performance underwater propulsion devices has gained importance with the expansion of recreational and industrial diving applications. This study aims to develop and validate a waterjet-type diver propulsion system capable of achieving a top speed of 3.8 knots and an operational time of over 120 minutes. Utilizing advanced modeling and simulation techniques, the design focuses on minimizing hydrodynamic resistance and optimizing buoyancy. Structural and fluid dynamic analyses were conducted to ensure the device's stability and performance under 20 atm pressure at a depth of 200 meters. The propulsion system employs a sensorless BLDC motor and a 36V lithium-ion battery pack to enhance efficiency and reliability. Field tests confirmed an average speed of 3.88 knots and a continuous operation time of 150 minutes, exceeding the initial targets. This research demonstrates significant advancements in diver propulsion technology, providing valuable insights for future underwater equipment development. The outcomes are poised to enhance the safety, efficiency, and usability of diver propulsion devices, with broader applications in marine research, environmental monitoring, and resource exploration.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.4
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• pp.171-182
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• 2017

Most people seek a happy life and happiness positively affects sentiment, satisfaction with life, creativity, human relationship, business productivity, and even health and life extension. However, according to a survey in 2013, subjective happiness of adolescents (including university students) was very low compared to other age groups in Korea. Therefore this paper examined the effects of job-seeking stress, appearance recognition, financial situation, trust in government, and locus of control on university students' happiness using SEM (structural equation modeling). 207 university students in Seoul, Korea have been surveyed. At first, an initial experimental SEM model among these variables has been set up and reliability analysis has been conducted. Then multiple regression analyses on job-seeking stress and happiness as well as SEM analysis have been conducted. As a result of these analyses, the SEM model has been revised two times. The final SEM model passed the goodness-of-fit test (using RMR, GFI, NFI, CFI, and IFI indices). The final SEM model showed the followings. First, Higher job-seeking stress (especially sentimental part, rather than environment or action related parts) negatively affects happiness. Second, Trust in government also affects happiness both directly and indirectly. Third, Locus of control is affected both by trust in government and financial situation. Fourth, appearance recognition heavily affects job-seeking stress. In addition, appearance importance is higher than appearance interest, meaning that students who are not very interested in appearance usually recognize the importance of appearance. Finally, happiness is affected neither financial situation nor appearance recognition. Therefore, even either they are in a poor financial situation or not happy with their appearance, they can be happy if they have firm locus of control.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.4
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• pp.153-162
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• 2022

Nostalgia advertising is one of the key and effective tools for marketers to capture the attention of consumers. Prior studies have identified two types of nostalgia, personal and historical. The aim of this research is to learn more about historical nostalgia and its influence on consumer brand purchase intentions. A convenience sampling technique was used to obtain a sample of 182 respondents via Google forms. The study then used partial least square structural equation modeling. In PLS-SEM, we applied a measurement model to obtain the results related to reliability, validity, and model fitness. Once the desired results are achieved, the study proceeded to the structural model where results related to hypotheses were obtained. The study's findings corroborated the literature, revealing that historical nostalgia advertisements have a significant impact on consumers' cognition and emotions, leading to an effect on attitudes. The serial process has the effect of influencing consumer buying intentions. Hence, the importance of nostalgia advertising proposed in the study was established through empirical evidence. Policymakers, organizations, and advertising agencies in Pakistan are recommended to implement nostalgia advertising techniques based on the findings and are encouraged to do so for immediate benefits.

• Journal of Wellbeing Management and Applied Psychology
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• v.7 no.3
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• pp.43-53
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• 2024

Purpose: his study aims to explore how healthcare provider service characteristics in telemedicine services, which have become more common since the pandemic, affect rapport formation and service satisfaction with healthcare providers. Research design, data and methodology: A group of actual telemedicine users underwent data collection and empirical analysis. After analyzing reliability and validity, hypotheses were tested using a structural equation model. Results: Key perceived attributes of healthcare providers in telemedicine services were identified as doctor effort, doctor listening, and doctor expertise. Each of these variables had a significant positive impact on trust in telemedicine. Moreover, these attributes significantly positively impacted rapport formation and user service satisfaction, which was mediated by trust. However, the direct impact of rapport formation on service satisfaction was not supported. Conclusions: The study's findings have academic and practical implications for expanding telemedicine services. As an initial empirical study on telemedicine services, it confirms the importance of trust and rapport formation even in non-face-to-face medical situations. In order to overcome the limitations of non-physical contact, telemedicine services should strive to develop UI/UX designs that are more interoperable and boost trust in service apps.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.387-390
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• 2008

The importance of the life cycle cost analysis for construction projects of bridge has been recognized over the last decades. Accordingly, theoretical models, guidelines, and supporting softwares have been developed for the life cycle cost analysis of bridges. However, it is difficult to predict life cycle cost considering uncertainties precisely. This paper presents methodology for optimal design of substructure for a steel box bridge. Total life cycle cost for the service life is calculated as sum of initial cost, damage cost considering uncertainty, maintenance cost, repair and rehabilitation cost. The optimization method is applied to design of a bridge substructure with minimal cost, in which the objective function is set to life cycle cost and constraints are formulated on the basis of Korean Bridge Design Specification. Initial cost is calculated based on standard costs of the Korea Construction Price Index and damage cost on the damage probabilities to consider the uncertainty of load and resistance. An advanced first-order second moment method is used as a practical tool for reliability analysis using damage probability. Maintenance cost and cycle is determined by a stochastic method and user cost includes traffic operation costs and time delay costs.

• Earthquakes and Structures
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• v.16 no.5
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• pp.523-532
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• 2019

Different types of gas reservoir such as Liquid Natural Gas (LNG) are among the strategic infrastructures, and have great importance for any government or their private owners. To keep the tank and its contents safe during earthquakes especially if the contents are of hazardous or flammable materials; using seismic protection systems such as base isolator can be considered as an effective solution. However, the major deficiency of this system can be the large deformation in the isolation level which may lead to the failure of bearing system. In this paper, as a solution, the efficacy of an optimally designed combined vibration control system, the combined laminated rubber isolator and rotational friction damper, is investigated to evaluate the enhancement of an existing metal tank response under both far- and near-field earthquakes. Responses like impulsive and convective accelerations, base shear, and sloshing height are studied herein. The probabilistic framework is used to consider the uncertainties in the structural modeling, as well as record-to-record variability. Due to the high calculation cost of probabilistic methods, a simplified structural model is used. By using the Mont-Carlo simulation approach, it is revealed that this combined isolation system is a highly reliable system which provides considerable enhancement in the performance of reservoir, not only leads to the reduction of probability of catastrophic failure of the tank but also decrease the reservoir damage during the earthquake. Moreover, the relative displacement of the isolation level is controlled very well by this combined system.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.7
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• pp.269-277
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• 2020

Bao Loc City is the new tourism destination in Lam Dong province, Vietnam, where more and more tourists have been drawn to pay a visit. This study aims to test the correlative impact of tourism service quality factors on satisfaction of the tourists who have visited Bao Loc City. The key theory used in this study is SERVQUAL scale. The survey sample consists of 350 tourists who stayed overnight in Bao Loc City in the last quarter of 2019; 315 valid survey questionnaires could be used for the analysis. The research applied Cronbach's Alpha, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), structural equation modeling (SEM), and bootstrap test. The results show that the satisfaction of the tourists who have visited Bao Loc City has been affected statistically by three factors: (1) Responsiveness; (2) Reliability; and (3) Empathy, which were ranked by descending importance. Surprisingly, the research found that Tangibles and Assurance do not have an impact on tourists' satisfaction towards Bao Loc City. The research formulates some suggestions to the city policy-makers and the tourism businesses management in Bao Loc City in order to enhance tourists' satisfaction through improving the tourism service quality at Bao Loc City.