• Smart Structures and Systems
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• 제25권3호
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• pp.285-299
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• 2020

Long term structural health monitoring has gained wide attention among civil engineers in recent years due to the scale and severity of infrastructure deterioration. Establishing effective damage indicators and proposing enhanced monitoring methods are of great interests to the engineering practices. In the case of bridge health monitoring, long term structural vibration measurement has been acknowledged to be quite useful and utilized in the planning of maintenance works. Previous researches are majorly concentrated on linear time series models for the measurement, whereas nonlinear dependences among the measurement are not carefully considered. In this paper, a new bridge health monitoring method is proposed based on the use of long term vibration measurement. A combination of the fundamental ARMA model and copula theory is investigated for the first time in detecting bridge structural damages. The concept is applied to a real engineering practice in Japan. The efficiency and accuracy of the copula based damage indicator is analyzed and compared in different window sizes. The performance of the copula based indicator is discussed based on the damage detection rate between the intact structural condition and the damaged structural condition.

• The Korean Journal of Pain
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• 제32권2호
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• pp.120-128
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• 2019

Background: We aimed to explore the American College of Rheumatology (ACR) 1990 and 2011 fibromyalgia (FM) classification criteria's items and the components of Fibromyalgia Impact Questionnaire (FIQ) to identify features best discriminating FM features. Finally, we developed a combined FM diagnostic (C-FM) model using the FM's key features. Methods: The means and frequency on tender points (TPs), ACR 2011 components and FIQ items were calculated in the FM and non-FM (osteoarthritis [OA] and non-OA) patients. Then, two-step multiple logistic regression analysis was performed to order these variables according to their maximal statistical contribution in predicting group membership. Partial correlations assessed their unique contribution, and two-group discriminant analysis provided a classification table. Using receiver operator characteristic analyses, we determined the sensitivity and specificity of the final model. Results: A total of 172 patients with FM, 75 with OA and 21 with periarthritis or regional pain syndromes were enrolled. Two steps multiple logistic regression analysis identified 8 key features of FM which accounted for 64.8% of variance associated with FM group membership: lateral epicondyle TP with variance percentages (36.9%), neck pain (14.5%), fatigue (4.7%), insomnia (3%), upper back pain (2.2%), shoulder pain (1.5%), gluteal TP (1.2%), and FIQ fatigue (0.9%). The C-FM model demonstrated a 91.4% correct classification rate, 91.9% for sensitivity and 91.7% for specificity. Conclusions: The C-FM model can accurately detect FM patients among other pain disorders. Re-inclusion of TPs along with saving of FM main symptoms in the C-FM model is a unique feature of this model.

• 한국방재안전학회논문집
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• 제12권2호
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• pp.35-45
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• 2019

인위적인 하도의 확대 및 축소는 유수의 흐름을 변화시킬 뿐만 아니라 침퇴적 양상에 변화를 가져와 홍수의 원활한 소통에 지장을 초래할 수 있다. 이에 본 연구는 하도의 급확대가 하상의 변화와 하천 흐름의 변화에 미치는 영향을 분석하는데 목적이 있다. 이를 위하여 고향의 강 조성사업으로 하도의 일부 구간이 2~3배 이상 확폭 된 지방하천인 경포천을 대상으로 RMA-2 및 SED-2D모형을 이용하여 하도의 확폭으로 인한 흐름특성의 변화와 하상변동을 모의하였다. 연구결과, 경포천 하도의 확폭은 확폭 전에 비해 치수적 안정성을 확보하고 있는 것으로 나타났으나, 연구대상 구간의 침수빈도는 연중 1회 이상으로 향후 유지관리에 많은 비용과 시간이 필요할 것으로 분석되었다.

• 한국치위생학회지
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• 제19권5호
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• pp.731-742
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• 2019

Objectives: To analyze the association between sleep duration and the number of remaining teeth in people aged 65 years or older in order to provide basic data for improving sleep quality and developing oral health programs for teeth maintenance. Methods: The raw data for the analysis were obtained from the sixth Korean National Health and Nutrition Examination Survey (KNHANES) dataset, conducted between 2013 and 2015. The 4,340 subjects included in the study underwent oral examinations and then proceeded to answer related questions. The collected data were analyzed using SPSS (ver 23.0) program via composite samples, with the calculations for mean, standard deviation, chi-square test, and logistic return analysis being performed. Results: An analysis of the effect of sleep duration on the number of remaining teeth among people aged >65 years old showed that if the confounding variables were not corrected for, the risk of having less than 9 hours of sleep was 1.40 times higher (95% CI: 1.06-1.86). However, this was not statistically significant in models that corrected for gender, age, and other confounding variables (p>0.05). Conclusions: The association between sleep duration among the elderly with their number of remaining teeth was confirmed. Therefore, measures to improve sleep quality and oral care practices to maintain the remaining teeth in people over 65 years old should be developed.

• International Journal of Computer Science & Network Security
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• 제21권9호
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• pp.118-124
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• 2021

The article examines the formation of a competitive paradigm of economic security of industrial enterprises in the formation of a circular economy. The basic laws of industrial enterprises are formed, which determined the characteristics of competitive positions and threats. The basic competitive concepts and their application at maintenance of economic safety of the industrial enterprises in the conditions of formation of circular economy are described. Thus, the technological approach to the formation of a competitive paradigm is based on production technologies, opportunities for technological modernization and development of infrastructure and intellectual competencies. The institutional concept reveals the regulatory mechanisms for ensuring competitiveness through the protectionism of national industrial enterprises, standardization and regulation of market imbalances. The innovation-investment approach within the competitive paradigm is also manifested in the creation of competitive advantages due to the presence of active innovative developments and their commercialization, knowledge and competencies of staff, capitalization of intelligence and communications, constant updating of infrastructure and technologies. Collectively, innovation and investment effects on the level of economic security allow industrial enterprises to ensure resilience to increasing competition, the emergence of new market challenges in the formation of a circular economy. A strategic approach to the application of a competitive paradigm to ensure the economic security of industrial enterprises allows you to justify the prospects for development and design behavioral models to predict and assess potential threats. The concept of system management is based on the complexity of threat analysis, the integrity of the economic security system, system-forming functions and patterns of implementation of industrial development tasks in the formation of a circular economy. The application of the described concepts is formalized by the authors through the definition of the basic patterns, directions and characteristics of their impact on the elements of the security system of industrial enterprises in the formation of a circular economy.

• 농촌지도와개발
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• 제29권3호
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• pp.131-142
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• 2022

This study aims to develop a curriculum for nurturing experts who perform agricultural safety and health management tasks. This study was conducted in three stages. First, job definitions and job models of agricultural safety and health managers were derived through job analysis using the DACUM technique. Second, job demand analysis was conducted by conducting a survey on the difficulty, importance, and frequency of each task. Third, IPA analysis was performed as the first priority tasks of job demand analysis to present the courses and subjects of the training course for safety and health managers in agricultural work. The job of the agricultural safety and health manager was defined as "to conduct guidance and advice on safety and health education, risk factors, and evaluation and management of harmful factors to protect farmers' professional health and safety." The job model consisted of 4 tasks, 31 core tasks, and 67 detailed tasks. As a result of job demand analysis, there were 39 tasks in the 1st priority, 22 in the 2nd priority, and 6 in the 3rd priority. As a result of the IPA analysis, there were 13 'capacity development focused areas', 4 'capacity development effort areas', 11 'low priority areas', and 3 'continuous maintenance areas'.

• 천문학회지
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• 제55권4호
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• pp.111-121
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• 2022

Based on the light an exoplanet blocks from its host star as it passes in front of it during a transit, the mid-transit time can be determined. Periodic variations in mid-transit times can indicate another planet's gravitational influence. We investigate 83 transits of TrES-1 b as observed from 6-inch telescopes in the MicroObservatory robotic telescope network. The EXOTIC data reduction pipeline is used to process these transits, fit transit models to light curves, and calculate transit midpoints. This paper details the methodology for analyzing transit timing variations (TTVs) and using transit measurements to maintain ephemerides. The application of Lomb-Scargle period analysis for studying the plausibility of TTVs is explained. The analysis of the resultant TTVs from 46 transits from MicroObservatory and 47 transits from archival data in the Exoplanet Transit Database indicated the possible existence of other planets affecting the orbit of TrES-1 and improved the precision of the ephemeris by one order of magnitude. We now estimate the ephemeris to be (2 455 489.66026 BJD_TDB ± 0.00044 d) + (3.0300689 ± 0.0000007) d × epoch. This analysis also demonstrates the role of small telescopes in making precise midtransit time measurements, which can be used to help maintain ephemerides and perform TTV analysis. The maintenance of ephemerides allows for an increased ability to optimize telescope time on large ground-based telescopes and space telescope missions.

• 한국항공우주학회지
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• 제50권2호
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• pp.111-118
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• 2022

전기-기계식 구동기(EMA)는 전기 모터와 기계적 동력전달 요소를 결합한 것으로 설계 자유도와 유지보수 측면에서 도심 항공 모빌리티(UAM)에 적합하다. 본 논문에서는 UAM의 로터 블레이드 피치각을 조종하는 EMA에 대한 연구 결과를 제시한다. 구동기는 역구동형 롤러 스크류를 기반하며, 2절 링크를 통하여 블레이드 피치각을 조종한다. 구동기만의 동역학과 이것을 포함한 블레이드 피치운동의 동역학 방정식을 유도하였다. 블레이드 피치 동역학 방정식의 경우 링크의 영향으로 등가 관성모멘트는 링크 각도에 따라 변한다. 넛트 운동의 관점과 블레이드 피치 운동의 관점에서 등가 관성모멘트의 변동을 분석·비교하는 과정을 제시하였다. 사례로 선정한 모델의 경우에 전자의 등가 관성모멘트 변동이 후자에 비하여 작았으며, 그래서 넛트 운동의 관점에서 유도한 모델이 제어기 설계에 적합하다고 판단한다.

• 대한조현병학회지
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• 제24권2호
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• pp.60-67
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• 2021

Objectives: The optimal duration of maintenance treatment for patients with first-episode schizophrenia (FES) remains unclear. We examined the first antipsychotic treatment duration and its association with re-initiation of treatment using a nationwide claim database. Methods: Data from the Health Insurance Review and Assessment Service database in South Korea for 2007-2016 were used. Linear regression analysis and Cox proportional hazard models were used to evaluate the associations between the duration of the first antipsychotic treatment, time to re-initiation of treatment, and occurrence of treatment re-initiation. Results: Of 30,143 patients with FES, 80.4% (n=24,231) received <2 years of the first antipsychotic treatment. In patients who discontinued treatment (n=23,030), the rate of treatment re-initiation was 74.2% (n=17,086). As the duration of the first antipsychotic treatment increased, the time to re-initiation of treatment decreased (β=-0.146, p<0.001); however, the rate of treatment reinitiation was relatively constant (hazard ratio=1.001, p<0.001). Conclusion: Long-term antipsychotic treatment was not significantly associated with the rate of treatment re-initiation but showed a negative association with the time to re-initiation of treatment. Further research is needed to better understand the optimal treatment duration for FES.

• Design & Manufacturing
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• 제16권4호
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• pp.1-6
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• 2022

Fine blanking is a press processing technology that can process most of the product thickness into a smooth surface with a single stroke. In this fine blanking process, shear is an essential step. The punches and dies used in the shear are subjected to impacts of tens to hundreds of gravitational accelerations, depending on the type and thickness of the material. Therefore, among the components of the fine blanking mold (dies), punches and dies are the parts with the shortest lifespan. In the actual production site, various types of tool damage occur such as wear of the tool as well as sudden punch breakage. In this study, machine learning algorithms were used to predict these problems in advance. The dataset used in this paper consisted of the signal of the vibration sensor installed in the tool and the measured burr size (tool wear). Various features were extracted so that artificial intelligence can learn effectively from signals. It was trained with 5 features with excellent distinguishing performance, and the SVM algorithm performance was the best among 33 learning models. As a result of the research, the vibration signal at the time of imminent tool replacement was matched with an accuracy of more than 85%. It is expected that the results of this research will solve problems such as tool damage due to accidental punch breakage at the production site, and increase in maintenance costs due to prediction errors in punch exchange cycles due to wear.