• Smart Structures and Systems
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• 제31권4호
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• pp.421-436
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• 2023

This paper presents a vibration displacement measurement and damage identification method for a space truss structure from its vibration videos. Features from Accelerated Segment Test (FAST) algorithm is combined with adaptive threshold strategy to detect the feature points of high quality within the Region of Interest (ROI), around each node of the truss structure. Then these points are tracked by Kanade-Lucas-Tomasi (KLT) algorithm along the video frame sequences to obtain the vibration displacement time histories. For some cases with the image plane not parallel to the truss structural plane, the scale factors cannot be applied directly. Therefore, these videos are processed with homography transformation. After scale factor adaptation, tracking results are expressed in physical units and compared with ground truth data. The main operational frequencies and the corresponding mode shapes are identified by using Subspace Stochastic Identification (SSI) from the obtained vibration displacement responses and compared with ground truth data. Structural damages are quantified by elemental stiffness reductions. A Bayesian inference-based objective function is constructed based on natural frequencies to identify the damage by model updating. The Success-History based Adaptive Differential Evolution with Linear Population Size Reduction (L-SHADE) is applied to minimise the objective function by tuning the damage parameter of each element. The locations and severities of damage in each case are then identified. The accuracy and effectiveness are verified by comparison of the identified results with the ground truth data.

• Structural Engineering and Mechanics
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• 제86권3호
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• pp.291-309
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• 2023

This paper addresses the finite element modeling of functionally graded porous (FGP) beams for free vibration and buckling behaviour cases. The formulated finite element is based on simple and efficient higher order shear deformation theory. The key feature of this formulation is that it deals with Euler-Bernoulli beam theory with only three unknowns without requiring any shear correction factor. In fact, the presented two-noded beam element has three degrees of freedom per node, and the discrete model guarantees the interelement continuity by using both C⁰ and C¹ continuities for the displacement field and its first derivative shape functions, respectively. The weak form of the governing equations is obtained from the Hamilton principle of FGP beams to generate the elementary stiffness, geometric, and mass matrices. By deploying the isoparametric coordinate system, the derived elementary matrices are computed using the Gauss quadrature rule. To overcome the shear-locking phenomenon, the reduced integration technique is used for the shear strain energy. Furthermore, the effect of porosity distribution patterns on the free vibration and buckling behaviours of porous functionally graded beams in various parameters is investigated. The obtained results extend and improve those predicted previously by alternative existing theories, in which significant parameters such as material distribution, geometrical configuration, boundary conditions, and porosity distributions are considered and discussed in detailed numerical comparisons. Determining the impacts of these parameters on natural frequencies and critical buckling loads play an essential role in the manufacturing process of such materials and their related mechanical modeling in aerospace, nuclear, civil, and other structures.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.242-249
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• 2009

High-rise construction sites, especially those situated in spatially constrained urban areas, have difficulties in timely delivery of materials. Modern techniques such as Just-in-time delivery, and use of information technology such as Project Management Information System (PMIS), are targeted to improve the efficiency of the logistics. Such IT-driven management techniques can be further benefited from state-of-the-art devices such as Radio Frequency Identification (RFID) tags and Ubiquitous Sensor Networks (USN), which has resulted in notable achievements in automated logistics management at the construction sites. Based on those achievements, this research develops USN hardware toolkits for construction lifts, which aims to be automated the vertical material delivery by sensing the material information and routing it automatically to the right place. The gathered information from the sensors can also be used for monitoring the overall status. The developed system will be tested in the actual high-rise construction sites to assess the system's feasibility. The proposed system is being implemented using Zigbee communication modules and RFID sensor networks which will communicate with the intelligent palette system (previously developed by the authors). To support the system, a lift-mountable intelligent toolkit is under development. Its feasibility test will be conducted by applying the implemented system to a test bed and then analyzing efficiency of the system and the toolkit. The collected test data will be provided as a basis of autonomous vertical transport equipment development. From this research, efficient management of the material lift is expected with increased accuracy, as well as better management of overall construction schedule benefited from the system. Further research will be expected to develop a smart construction lift, which will eliminate the need for human supervision, thus enabling a real 'autonomous' operation of the system.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.136-144
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• 2022

Construction sites are characterized by dangerous situations and environments that cause fatal accidents. Potential risk detection needs to be improved by continuously monitoring site conditions. However, the current labor-intensive inspection practice has many limitations in monitoring dangerous conditions at construction sites. Computer vision technology that can quickly analyze and collect site conditions from images has been in the spotlight as a solution. Nonetheless, inspection results obtained via computer vision are still stored and managed in centralized systems vulnerable to tampering with information by the central node. Blockchain has been used as a reliable and efficient decentralized information management system. Despite its potential, only limited research has been conducted integrating computer vision and blockchain. Therefore, to solve the current safety management problems, the authors propose a framework for construction site inspection that integrates object detection and blockchain network, enabling efficient and reliable remote inspection. Object detection is applied to enable the automatic analysis of site safety conditions. As a result, the workload of safety managers can be reduced with inspection results stored and distributed reliably through the blockchain network. In addition, errors or forgery in the inspection process can be automatically prevented and verified through a smart contract. As site safety conditions are reliably shared with project participants, project participants can remotely inspect site conditions and make safety-related decisions in trust.

• KNOM Review
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• 제22권2호
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• pp.29-38
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• 2019

4차 산업혁명의 핵심 기술 중의 하나로서 사물인터넷 (Internet of Things)은 무선 네트워크, 통신모듈 및 센서, 스마트 단말 등의 기술 발전 및 보급 확산으로 그 영향력이 의료, 교통, 제조, 유통, 교육 등의 산업분야를 넘어 과학기술 및 공공분야로까지 확대되고 있다. 특히 과학기술 분야에서도 점차 IoT 기술 연구 및 활용 연구가 증가하고 있으며, 이를 통해 기존의 이론 및 실험 중심의 연구에서 데이터 중심의 연구로의 연구 패러다임이 변환되고 있다. 이와 같이 다양한 데이터를 수집하는 인프라스트럭처 환경 구축의 필요성이 커지고 있으며, 수집된 데이터의 전송·처리·분석을 위한 유·무선 통합 네트워크 환경을 위해 국가과학기술연구망 (KREONET)에서는 저전력 장거리 통신기술 LPWAN (Low Power Wide Area Network) 기반의 국가과학기술무선사물인터넷연구망 (ScienceLoRa) 프로젝트를 시작하였다. ScienceLoRa는 기존의 백본망 위주의 유선망인 KREONET를 활용하여 LoRa/LoRaWAN 기술을 활용한 무선망을 구축함으로써 과학기술 및 공공분야에서 다양한 센서들로부터 데이터를 수집하여 이를 전송, 활용 및 분석에 이용하고자 한다. 본 논문에서는 ScienceLoRa 소개, 현재 진행상황, 활용 및 발전 가능성에 대하여 살펴보기로 한다.

• Nutrition Research and Practice
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• 제17권2호
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• pp.330-340
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• 2023

BACKGROUND/OBJECTIVES: Emotional eating is one of the eating behaviors in which negative emotions affect eating. During the luteal phase, premenstrual syndrome (PMS) and its associated psychological and physical symptoms can appear in some women, and a few of them suffer from premenstrual dysphoric disorder (PMDD), a severe form of PMS. Some women diagnosed with PMS/PMDD experience emotional eating during the luteal phase, which may be a coping mechanism for psychological stress. This study aimed to investigate how PMS/PMDD and negatively perceived stress are related to emotional eating. SUBJECTS/METHODS: A total of 409 women aged 20 to 39 yrs with a body mass index (BMI) ranging from 18.5 to 29.9 kg/m² participated in this study. Participants who responded to all the questions of the Shortened Premenstrual Assessment Form, Negative Perceived Stress Scale, and Emotional Eater Questionnaire were divided into a PMDD and a non-PMDD group according to the cut-off value for PMDD diagnosis. Independent t-tests and mediation analyses were performed to compare the 2 groups. RESULTS: No significant differences between the 2 groups were found in terms of BMI; however, the average values for emotional eating, PMS, and negative perceived stress of the PMDD group were significantly higher than those of the non-PMDD group. Only negative perceived stress had a significant effect on emotional eating in the non-PMDD group. In the PMDD group, PMS was statistically significant for both negative perceived stress and emotional eating mediated by negative perceived stress. Consequently, it appeared to have a partial or complete mediation depending on the independent variable for the PMDD group. CONCLUSIONS: This study highlights the importance of managing negative perceived stress to control emotional eating in PMS/PMDD for improved women's health.

• 한국광학회지
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• 제34권2호
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• pp.45-52
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• 2023

본 연구에서는 다양한 파장의 저출력 light-emitting diode (LED)를 이용한 photobiomodulation (PBM)이 각막 상처 치유에 미치는 영향을 분석하였다. 각막상피세포에 623 nm에서 940 nm 범위의 파장의 LED를 조사한 결과, 유의미한 세포독성 영향을 미치지 않는 것을 확인하였다. PBM의 세포이동 촉진 효과를 세포 이동능 평가 시험을 통해 분석한 결과 623 nm 파장의 광조사에 의한 PBM이 세포이동을 크게 증가시키고 상처 치유를 촉진하는 것으로 나타났다. 또한, 세포이동 및 상처 치유와 관련된 유전자의 발현을 분석한 결과, 623 nm 파장의 광조사에 의한 PBM이 세포 증식과 세포 외 기질 분해를 촉진하는 것으로 알려진 FGF-1과 MMP2 유전자의 발현을 상향 조절한다는 사실을 발견했다. 이러한 연구 결과는 특정 파장, 특히 623 nm 파장의 저출력 빛을 이용한 PBM이 각막 손상 치료에 활용될 수 있는 가능성을 시사한다.

• 품질경영학회지
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• 제51권1호
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• pp.131-154
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• 2023

Purpose: The purpose of this paper is to design an integrated informatization system that can manage quality & KPI by integrating management systems in the aerospace and defense industry, and study the effect on KPI when applied to related companies. Methods: The 7 management systems required for integration in the AS&D industry were studied, and an empirical analysis was conducted for H company in South Korea for the application of e-QMS integrated informatization & KPI system based on security environment and open quality. Results: The results of this study were analyzed to have an effect on the improvement of customer satisfaction and the positive improvement of quality failure cost in the aerospace and defense industry. And it was analyzed that it works to continuously comply with ethical management and environmental laws and prevent safety accidents. Conclusion: The greatest significance of this study is that it attempted to build an e-QMS integrated system in the aerospace and defense industry. Considering that the case of integrated management system and integrated operation of KPI in related industries has not been introduced in the existing literature, the results of this study will be shared as a meaningful preceding study in the era of digital quality information. In addition, the fact that the open-quality quality innovation methodology emphasizing measurement(M), tracking(T), and connection(C) was actually applied in an AS&D company and its effectiveness was objectively proven. It is expected that it will be a good paper for follow-up research.

• Smart Structures and Systems
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• 제31권2호
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• pp.101-111
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• 2023

Structural health monitoring (SHM) covers a range of damage detection strategies for buildings. In real-time, SHM provides a basis for rapid decision making to optimise the speed and economic efficiency of post-event response. Previous work introduced an SHM method based on identifying structural nonlinear hysteretic parameters and their evolution from structural force-deformation hysteresis loops in real-time. This research extends and generalises this method to investigate the impact of a wide range of flag-shaped or pinching shape nonlinear hysteretic response and its impact on the SHM accuracy. A particular focus is plastic stiffness (K_p), where accurate identification of this parameter enables accurate identification of net and total plastic deformation and plastic energy dissipated, all of which are directly related to damage and infrequently assessed in SHM. A sensitivity study using a realistic seismic case study with known ground truth values investigates the impact of hysteresis loop shape, as well as added noise, on SHM accuracy using a suite of 20 ground motions from the PEER database. Monte Carlo analysis over 22,000 simulations with different hysteresis loops and added noise resulted in absolute percentage identification error (median, (IQR)) in K_p of 1.88% (0.79, 4.94)%. Errors were larger where five events (Earthquakes #1, 6, 9, 14) have very large errors over 100% for resulted K_p as an almost entirely linear response yielded only negligible plastic response, increasing identification error. The sensitivity analysis shows accuracy is reduces to within 3% when plastic drift is induced. This method shows clear potential to provide accurate, real-time metrics of non-linear stiffness and deformation to assist rapid damage assessment and decision making, utilising algorithms significantly simpler than previous non-linear structural model-based parameter identification SHM methods.

• Fisheries and Aquatic Sciences
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• 제26권2호
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• pp.158-168
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• 2023

The global output of Pyropia yezoensis (dried seaweed or laver, also called 'Gim' in Korea) has been reduced over the half-decade due to the wide spread of red rot disease, a serious algal disease affecting P. yezoensis. Recently, Gold 1 (G1), which is a resistant strain of P. yezoensis to red rot disease, was developed and commercialized in South Korea, yet its physiological activity has not been investigated. In this study, a comparative study was performed on G1 and commercially available strain of P. yezoensis (CP) for their antioxidative activities. Aqueous extract of G1 showed more marked 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity compared to that of CP. In 293T cells, antioxidant activity against H₂O₂-induced reactive oxygen species (ROS) formation was only observed in G1 extract. In addition, G1 extract showed more potent inhibitory effect on H₂O₂-induced apoptotic cell death than CP extract, as examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and fluorescence microscopy. Expression levels of various apoptosis-related genes, including B-cell lymphoma 2-associated X protein, p53, capase-3, and inflammatory cytokines, in H₂O₂-treated cells were significantly decreased by the treatment of G1. Taken together, the present study suggests that a new strain of red seaweed G1 can recover oxidative stress effectively by improving the imbalance of ROS generation and has a potential to be used a functional ingredient as an antioxidant source.