• Steel and Composite Structures
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• 제51권4호
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• pp.441-456
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• 2024

This paper aims to develop Machine Learning (ML) algorithms to predict the buckling resistance of cold-formed steel (CFS) channels with restrained flanges, widely used in typical CFS sheathed wall panels, and provide practical design tools for engineers. The effects of cross-sectional restraints were first evaluated on the elastic buckling behaviour of CFS channels subjected to pure axial compressive load or bending moment. Feedforward multi-layer Artificial Neural Networks (ANNs) were then trained on different datasets comprising CFS channels with various dimensions and properties, plate thicknesses, and restraining conditions on one or two flanges, while the elastic distortional buckling resistance of the elements were determined according to the Finite Strip Method (FSM). To develop less biased networks and ensure that every observation from the original dataset has the chance of appearing in the training and test set, a K-fold cross-validation technique was implemented. In addition, the hyperparameters of the ANNs were tuned using a grid search technique to provide ANNs with optimum performances. The results demonstrated that the trained ANNs were able to predict the elastic distortional buckling resistance of CFS flange-restrained elements with an average accuracy of 99% in terms of coefficient of determination. The developed models were then used to propose a simple ANN-based design formula for the prediction of the elastic distortional buckling stress of CFS flange-restrained elements. Finally, the proposed formula was further evaluated on a separate set of unseen data to ensure its accuracy for practical applications.

• Composites Research
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• 제37권2호
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• pp.132-138
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• 2024

본 연구에서는 분자동역학 전산모사를 통해 육방정계 단일벽 질화붕소 나노튜브(BNNT)의 반경 변화에 따른 압전탄성 변화를 규명하였다. 질화붕소의 거동을 비교적 잘 모사하는 Tersoff 포텐셜과 기계적 하중인가에 따른 질소 및 붕소원자의 상대변위로 인한 분극의 정량화를 위해 강체 이온 근사를 채택하였다. 선형 압전탄성 구성방정식을 기반으로 각각의 질화붕소에 변형률을 인가하고 이에 따른 전기적 변위와 응력을 산출하여 압전상수와 영률을 각각 예측하였다. 그 결과, BNNT의 압전상수는 반경이 증가함에 따라 점진적으로 감소하는 양상을 보였다. 반면 탄성계수의 경우 불연속적 구조를 가지는 질화붕소를 등가의 연속체 구조로 등가시키는 방법에 따라 증가 또는 감소하는 경향을 보였다. BNNT의 곡률변화에 따른 물성변화를 가상실험에 기반한 경험적 모델로 근사하기 위해 BNNT의 튜브반경-압전탄성물성 간 상관관계식을 제안하였다. 또한 BNNT의 반경변화에 따른 물성을 곡률의 관점에서 설명하기 위해, BNNT와 질화붕소 나노시트(BNNS)의 결합에너지와 탄성변형에 따른 원자간 결합길이 변화가 각각의 구조의 변형에너지 증가에 기여하는 정도를 상호 비교하였다.

• 정보관리학회지
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• 제41권3호
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• pp.411-429
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• 2024

본 연구는 사서교사의 근골격계질환 자각증상과 관련 요인을 파악하여, 사서교사의 건강과 안전에 대한 인식을 높이고, 근골격계질환 예방을 위한 기초자료를 제공하고자 한다. 초·중·고등학교 학교도서관에서 근무하는 사서교사를 대상으로 온라인 설문조사를 실시하여 204명의 응답을 수집했다. 근골격계질환 자각증상을 분석하기 위해 KOSHA에서 제공하는 조사표를 활용하였으며, 수집된 자료는 SPSS 29.0 프로그램을 이용하여 분석하였다. 204명의 사서교사 중 92.6%가 지난 1년 동안 작업과 관련하여 통증, 쑤심, 찌릿찌릿함 등의 근골격계질환 증상을 경험한 것으로 나타났으며, 증상에 따라 20.6%가 정상, 44.1%가 관리대상자, 35.3%가 통증호소자로 분류되었다. 신체 부위별로 살펴보면 손 부위에서 근골격계 자각증상 비율이 가장 높았고 이어 허리, 어깨, 목, 팔, 다리 순으로 나타났다.

• 소성∙가공
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• 제33권5호
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• pp.348-353
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• 2024

The S355NL steel has garnered attention as a structural material for applications in extremely challenging environments owing to its excellent mechanical properties. This study investigated the hot deformation behavior of S355NL steel through compression tests conducted in a temperature range of 900-1200℃ and a strain rate range of 10^-3-1 s^-1 to explore the optimal processing parameters. The flow behaviors consisted of an initial rapid increase and subsequent plateau with a marginal decrease in stress. This phenomenon was interpreted in terms of microstructural evolution, such as dislocation density and dynamic recrystallization. The efficiency of power dissipation and instability domains were derived using the dynamic material model based on the compression test dataset, providing a series of processing maps. In contrast to conventional processing maps plotted for a single strain value, this study has established ten maps at a strain interval of 0.1. This approach allowed for the consideration of continuously variable strain parameters, which is inherent to an actual metal-forming process. The efficiency of power dissipation was strongly governed by the high temperatures (≥ 1100℃). The strain rates barely affected the efficiency, but it primarily contributed to the instability domains. The application of high strain rates (≥ 10^-1s^-1) generated a region of negative instability due to the absence of dynamic recrystallization and the presence of cracks at grain boundaries.

• Clinical Nutrition Research
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• 제11권4호
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• pp.264-276
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• 2022

Hemodialysis (HD) patients can experience appetite alterations that affect meals and nutritional status. Few qualitative studies have assessed the chronic impact of HD on the everyday diet. This study aimed to characterise comprehensively the experiences of HD patients adapting to appetite alteration. Semi-structured, face-to-face interviews were conducted in a unit of a tertiary hospital to understand patient experiences with appetite alteration. An interview guide was used to consider adaptive processes developed after reviewing the literature and based on the researchers' clinical experiences. A single researcher conducted all interviews to maintain consistency in data collection. The interview content was analysed using Nvivo 11 based on grounded theory and constant comparison analysis. As a results, the mean age and HD vintage of 14 participants were 60 and 5.8 years, respectively. We developed a self-care model based on HD patient experiences with appetite alteration based on axial and selective coding. Differences in urea sensitivity, taste alteration, and social support could be explained by timing of transitions, life events, and responses to stress. Self-care processes are adapted through the processes of "self-registration" and "self-reconstruction," starting with "disruption." At the stage of adjustment, 4 self-management types were derived based on pattern of self-care: self-initiator, follower, realist, and pessimist. The results of this study provide unique qualitative insight into the lived experiences of HD patients experiencing appetite alteration and their self-care processes. By recognising dietary challenges, health teams can better support HD patients in the transition from dietary education to self-care.

• 대한예방한의학회지
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• 제28권2호
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• pp.99-111
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• 2024

Objectives : Anxiety is an important mental health symptom associated with healthcare utilization. This research aims to identify the demographic, socio-economic, and health-related factors associated with the use of Korean medicine (KM) treatments in adults experiencing anxiety. Methods : We conducted a cross-sectional analysis using the Korea Health Panel Annual Data 2019. Logistic regression models were employed to examine the relationships between KM utilization and various factors such as economic activity, perceived stress levels, and presence of physical discomfort. The study sample included 552 adults experiencing anxiety. Results : Among the subjects, 19.20% were using both conventional treatment and KM treatment. The analysis revealed that individuals engaged in economic activities were more likely to use KM treatments compared to those who were not (odds ratio [OR] = 2.207, 95% confidential interval [CI] = 1.316 to 3.699). Additionally, individuals reporting high levels of pain or discomfort showed a significantly higher likelihood of using both KM and conventional medical services (OR = 2.933, 95% CI = 1.645 to 5.231). Musculoskeletal conditions were the most common reason for KM utilization among the study participants. Conclusion : The findings suggest that economic activity and the severity of physical discomfort significantly influence the use of KM treatments among adults with anxiety. These insights could inform healthcare policy and the integration of KM services into broader health management strategies for anxiety.

• Advances in concrete construction
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• 제17권3호
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• pp.151-158
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• 2024

The calculation of the natural frequencies versus Young's modulus of carbon nanotubes with modified continuum shell is the subject of current research. When designing these tubes, it is important to understand their frequencies because excessive vibrations might cause fatigue. These tubes are designed and built to meet specific needs and have been suitably modified to investigate their vibratory response. There are numerous uses for carbon nanotube free vibration analysis in the mechanical sciences. The fundamental frequency with Young's modulus for clamped-free and simply supported end conditions, which is connected to the carbon nanotubes, is calculated theoretically for chiral single carbon nanotubes. When Young's modulus rises, so does the frequency curve pattern. Young's modulus influences the single-walled carbon nanotube's dynamic response by simulating it as a modified continuum shell. The Young's modulus of chiral tube and the value of frequency increased as the chiral tube's index increased. The results are checked against past studies to ensure the problem's validity and are determined to be accurate.

• 보건의료생명과학 논문지
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• 제9권2호
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• pp.373-381
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• 2021

본 연구는 SUKI 대체요법의 유효성과 두피마사지의 상관관계를 살펴보고, 헤어SUKI 대체요법 적용 및 활성화에 기여하는 것을 목적으로 문헌연구를 실시하였다. 연구 방법은 첫째, SUKI 대체요법의 개념, SUKI 대체요법 특징, SUKI 대체요법 시술시 주의할 점 등을 통해 SUKI 대체요법의 이해를 살펴보았고, 둘째, SUKI 대체요법 적용 실태 및 두피마사지요법에 관한 선행연구 등을 고찰하여, SUKI 대체요법과 두피마사지의 효과를 알아보았다. 그 결과 SUKI 대체요법은 스트레스나 우울증, 고혈압, 근육통증, 피부주름과 탄력 등 유의한 효과가 있었고, 두피마사지는 현대인들의 스트레스와 불면증과 같은 심리적, 정신적인 증상과 더불어 탈모와 두통 등의 신체적인 치료에 영향을 미치는 것으로 나타났다. 이에 헤어SUKI 대체요법에 대한 효과연구와 프로그램 활성화 통해 현대인들의 건강과 삶의 질을 향상시키는데 긍정적으로 활용될 수 있을 것으로 기대된다.

• Safety and Health at Work
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• 제15권3호
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• pp.245-254
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• 2024

Background: In recent years, the rise of workplace racial discrimination and microaggressions has decreased the efficiency and productivity of organizations and institutions, and realization of organizational goals globally. Accordingly, it was decided to conduct a systematic review and meta-analysis in the present study with the aim of investigating the prevalence of microaggression and racial discrimination in the workplace. Methods: The PubMed, Scopus, Web of Science, ScienceDirect and Google Scholar databases were systematically searched for studies that had reported the effects of work stress among managers. The search did include a lower time limit and was conducted in June 2023. The heterogeneity of the studies was investigated using the I² index, and accordingly random effects method was adopted for meta-analysis. Data analysis was conducted with the Comprehensive Meta-Analysis (v.2) software. Results: In the review of seven studies with a sample size of 2998 people, the overall prevalence of microaggression and racial discrimination in the workplace was found to be 73.6% and 18.8%, respectively. Publication bias within the selected studies was examined with the Egger's test, which indicated the absence of publication bias for the pooled prevalence of workplace microaggression (p: 0.264) and for the pooled prevalence of workplace racial discrimination (p: 0.061). Conclusion: The results obtained from this report indicate the high impact of micro-aggression and racial discrimination in the workplace. Considering the negative effects of such behaviours, the findings from this study will be helpful to managers and health policymakers.

• Steel and Composite Structures
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• 제52권6호
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• pp.621-626
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• 2024

The work researched the application of artificial intelligence to the design and analysis of advanced nanoplates, with a particular emphasis on size and surface effects. Employing an integrated theoretical framework, this study developed a more accurate model of complex nanoplate behavior. The following analysis considers nanoplates embedded in a Pasternak viscoelastic fractional foundation and represents the important step in understanding how nanoscale structures may respond under dynamic loads. Surface effects, significant for nanoscale, are included through the Gurtin-Murdoch theory in order to better describe the influence of surface stresses on the overall behavior of nanoplates. In the present analysis, the modified couple stress theory is utilized to capture the size-dependent behavior of nanoplates, while the Kelvin-Voigt model has been incorporated to realistically simulate the structural damping and energy dissipation. This paper will take a holistic approach in using sinusoidal shear deformation theory for the accurate replication of complex interactions within the nano-structure system. Addressing different aspectsof the dynamic behavior by considering the length scale parameter of the material, this work aims at establishing which one of the factors imposes the most influence on the nanostructure response. Besides, the surface stresses that become increasingly critical in nanoscale dimensions are considered in depth. AI algorithms subsequently improve the prediction of the mechanical response by incorporating other phenomena, including surface energy, material inhomogeneity, and size-dependent properties. In these AI- enhanced solutions, the improvement of precision becomes considerable compared to the classical solution methods and hence offers new insights into the mechanical performance of nanoplates when applied in nanotechnology and materials science.