• Title/Summary/Keyword: FEAS

Search Result 58, Processing Time 0.02 seconds

Impact parameter prediction of a simulated metallic loose part using convolutional neural network

  • Moon, Seongin;Han, Seongjin;Kang, To;Han, Soonwoo;Kim, Kyungmo;Yu, Yongkyun;Eom, Joseph
    • Nuclear Engineering and Technology
    • /
    • v.53 no.4
    • /
    • pp.1199-1209
    • /
    • 2021
  • The detection of unexpected loose parts in the primary coolant system in a nuclear power plant remains an extremely important issue. It is essential to develop a methodology for the localization and mass estimation of loose parts owing to the high prediction error of conventional methods. An effective approach is presented for the localization and mass estimation of a loose part using machine-learning and deep-learning algorithms. First, a methodology was developed to estimate both the impact location and the mass of a loose part at the same times in a real structure in which geometric changes exist. Second, an impact database was constructed through a series of impact finite-element analyses (FEAs). Then, impact parameter prediction modes were generated for localization and mass estimation of a simulated metallic loose part using machine-learning algorithms (artificial neural network, Gaussian process, and support vector machine) and a deep-learning algorithm (convolutional neural network). The usefulness of the methodology was validated through blind tests, and the noise effect of the training data was also investigated. The high performance obtained in this study shows that the proposed methodology using an FEA-based database and deep learning is useful for localization and mass estimation of loose parts on site.

Numerical Investigation of Residual Strength of Steel Stiffened Panel Exposed to Hydrocarbon Fire

  • Kim, Jeong Hwan;Baeg, Dae Yu;Seo, Jung Kwan
    • Journal of Ocean Engineering and Technology
    • /
    • v.35 no.3
    • /
    • pp.203-215
    • /
    • 2021
  • Current industrial practices and approaches are simplified and do not describe the actual behavior of plated elements of offshore topside structures for safety design due to fires. Therefore, it is better to make up for the defective methods with integrated fire safety design methods based on fire resistance characteristics such as residual strength capacity. This study numerically investigates the residual strength of steel stiffened panels exposed to hydrocarbon jet fire. A series of nonlinear finite element analyses (FEAs) were carried out with varying probabilistic selected exposures in terms of the jet fire location, side, area, and duration. These were used to assess the effects of exposed fire on the residual strength of a steel stiffened panel on a ship-shaped offshore structure. A probabilistic approach with a feasible fire location was used to determine credible fire scenarios in association with thermal structural responses. Heat transfer analysis was performed to obtain the steel temperature, and then the residual strength was obtained for the credible fire scenarios under compressive axial loading using nonlinear FEA code. The results were used to derive closed-form expressions to predict the residual strength of steel stiffened panels with various exposure to jet fire characteristics. The results could be used to assess the sustainability of structures at risk of exposure to fire accidents in offshore installations.

A Study on the Influence of the Inclined Angle and Depth of the Substrate on Thermal and Residual Stress Characteristics in the Vicinity of the Repaired Region by a Directed Energy Deposition Process (기저부 경사각과 깊이가 에너지 제어형 용착 공정으로 보수된 영역의 열 및 잔류응력 특성에 미치는 영향 고찰)

  • Kim, Dan-A;Lee, Kwang-Kyu;Ahn, Dong-Gyu
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.21 no.6
    • /
    • pp.50-59
    • /
    • 2022
  • The design of the substrate significantly affects the thermal history and the residual stress formation in the vicinity of a repaired region by a directed energy deposition (DED) process. The occurrence of defects in the repaired region depends on the thermal history and residual stress formation. The objective of this study was to investigate the influence of the inclined angle and depth of the substrate on the thermal and residual stress characteristics in the vicinity of a repaired region by a DED process through two-dimensional finite element analyses (FEAs). The temperature and residual stress distributions in the vicinity of the repaired region were predicted according to the combination of the inclined angle and depth of the substrate. The effects of the inclined angle and depth on the depth of the heat affected zone and the maximum value of the residual stress were examined. A proper combination of the inclined angle and depth of the substrate was estimated to decrease the residual stress in the vicinity of the repaired region.

Enhanced Electron Emission of Carbon Nanotube Arrays Grown Using the Resist-Protection-assisted Positioning Technique

  • Ryu, Je-Hwang;Kim, Ki-Seo;Yu, Yi-Yin;Lee, Chang-Seok;Lee, Yi-Sang;Jang, Jin;Park, Kyu-Chang
    • Journal of Information Display
    • /
    • v.9 no.4
    • /
    • pp.30-34
    • /
    • 2008
  • Field emitter arrays (FEAs) were developed using carbon nanotubes (CNTs) as electron emission sources. The CNTs were grown using a selective-positioning technique with a resist-protection layer. The light emission properties were studied through the electron emission of the CNTs on patterned islands, which were modulated with island diameter and spacing. The electron emission of CNT arrays with $5{\mu}m$ diameters and $10{\mu}m$ heights increased with increased spacing (from $10{\mu}m$ to $40{\mu}m$). The electron emission current of the $40-{\mu}m$-island-spacing sample showed a current density of 1.33 mA/$cm^2$ at E = 11 V/${\mu}m$, and a turn-on field of 7 V/${\mu}m$ at $1{\mu}A$ emission current. Uniform electron emission current and light emission were achieved with $40{\mu}m$ island spacing and $5{\mu}m$ island diameter.

Model-based localization and mass-estimation methodology of metallic loose parts

  • Moon, Seongin;Han, Seongjin;Kang, To;Han, Soonwoo;Kim, Munsung
    • Nuclear Engineering and Technology
    • /
    • v.52 no.4
    • /
    • pp.846-855
    • /
    • 2020
  • A loose part monitoring system is used to detect unexpected loose parts in a reactor coolant system in a nuclear power plant. It is still necessary to develop a new methodology for the localization and mass estimation of loose parts owing to the high estimation error of conventional methods. In addition, model-based diagnostics recently emphasized the importance of a model describing the behavior of a mechanical system or component. The purpose of this study is to propose a new localization and mass-estimation method based on finite element analysis (FEA) and optimization technique. First, an FEA model to simulate the propagation behavior of the bending wave generated by a metal sphere impact is validated by performing an impact test and a corresponding FEA and optimization for a downsized steam-generator structure. Second, a novel methodology based on FEA and optimization technique was proposed to estimate the impact location and mass of a loose part at the same time. The usefulness of the methodology was then validated through a series of FEAs and some blind tests. A new feature vector, the cross-correlation function, was also proposed to predict the impact location and mass of a loose part, and its usefulness was then validated. It is expected that the proposed methodology can be utilized in model-based diagnostics for the estimation of impact parameters such as the mass, velocity, and impact location of a loose part. In addition, the FEA-based model can be used to optimize the sensor position to improve the collected data quality in the site of nuclear power plants.

Knowledge and Attitudes of Medical and Non-Medical Turkish University Students about Cervical Cancer and HPV Vaccination

  • Borlu, Arda;Gunay, Osman;Balci, Elcin;Sagiroglu, Mehmet
    • Asian Pacific Journal of Cancer Prevention
    • /
    • v.17 no.1
    • /
    • pp.299-303
    • /
    • 2016
  • Background: This study was conducted to determine knowledge, attitudes and practices about cervical cancer and HPV vaccination of students studying in various faculties of Erciyes University. Materials and Methods: The study was performed among the first and fourth grade students of Medicine, Theology, Education and Economics and Administrative Sciences (FEAS) faculties of Erciyes University. It was aimed to reach 1,073 students and 718 were evaluated. A questionnaire consisting of 48 questions related to the socio-demographic characteristics, knowledge, attitude and practices about cervical cancer and HPV vaccination was administered to the students. The chi-square test and logistic regression were used for the statistical analyses. Results: Of the students, 78.3% were aware of cervical cancer, while 36.1% of them were aware of the HPV vaccine. The percentage hearing about cervical cancer and HPV vaccination was significantly higher among the students of the medical faculty than the others and among fourth grade students comparing with the first grade. The marital status and the presence of a health worker in the family had no significant impact on the knowledge level of the students. The acceptability of the HPV vaccination was low among all students. Conclusions: The knowledge levels of the university students about cervical cancer and HPV vaccination are inadequate. This deficiency is more pronounced among the non-medical students and there is no significant increase during the faculty years. Non-medical students must be provided with information about important public health issues by elective courses. HPV vaccination could provide many benefits for men and women by decreasing the morbidity and mortality of cervical, anal, and penile cancers.

Effects of Geometry and Imperfection of a Small-sized Groove on Stress Distributions in the Vicinity of the Joined Region of an ABS Part with a Thin Wall (기저부에 생성된 작은 홈 형상과 결함이 박벽이 포함된 ABS 재료로 제작된 제품의 결합 영역 응력 분포에 미치는 영향)

  • Ahn, Dong-Gyu;Hassan, Humayun;Baek, Sun Ho;Kim, Ho
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.19 no.7
    • /
    • pp.81-88
    • /
    • 2020
  • The geometry and the defect of the groove of the part provoke a sudden change of stress in a local region. The objective of this paper is to investigate the effects of the geometry and the imperfection of a small groove on stress distributions in the vicinity of the joined region for the ABS part with a thin wall using a three-dimensional finite element analysis (FEA). Several types of groove are designed to improve joining characteristics in the vicinity joined region. The imperfection model of the small-sized groove is obtained from observation of deposition characteristics of a fused deposition modeling process. Local stress distributions in the vicinity of the joined region are predicted by the FE model with refined meshes. The influence of the angle and the imperfection of the groove on appearance regions of the maximum stress and distributions of the defined principal stress for different loading conditions is examined using the results of FEAs. Finally, a proper design of the groove is proposed to improve joining characteristics between the substrate and the ABS part.

Residual Longitudinal Strengths of Asymmetrically Damaged Ships (비대칭 손상 선박의 잔류 종강도 평가)

  • Choung, Joon-Mo;Lee, Min-Seong;Jeon, Sang-Ik;Nam, Ji-Myung;Ha, Tae-Bum
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.48 no.3
    • /
    • pp.246-253
    • /
    • 2011
  • This paper presents estimation of deterministic damage extents and locations due to collision and grounding which are defined by ABS guideline and DNV ship rules. It is noted that the overall extents of damages from DNV are larger than those from ABS. Nonlinear FEAs are carried out to predict residual longitudinal strength of hull girder with asymmetric severe damages. The accuracy of the applied FEA procedure is proved by comparing FEA result with test result of a 1/3-scaled frigate. The investigated vessels are a VLCC and a large-sized bulker for which evenly distributed heeling angles from $0^{\circ}$(sagging) to $180^{\circ}$(hogging) by $30^{\circ}$ due to damage-induced flooding are taken into account. The reduction ratios of the ultimate residual strength for the damaged cases to those for the intact sagging case are shown. It is proved that the grounding damage case under DNV assumption reveals most critical the residual strength. The design formulas are presented to assure minimum residual ultimate moment after damage.

Finite element simulations on the ultimate response of extended stiffened end-plate joints

  • Tartaglia, Roberto;D'Aniello, Mario;Zimbru, Mariana;Landolfo, Raffaele
    • Steel and Composite Structures
    • /
    • v.27 no.6
    • /
    • pp.727-745
    • /
    • 2018
  • The design criteria and the corresponding performance levels characterize the response of extended stiffened end-plate beam-to-column joints. In order to guarantee a ductile behavior, hierarchy criteria should be adopted to enforce the plastic deformations in the ductile components of the joint. However, the effectiveness of thesecriteria can be impaired if the actual resistance of the end-plate material largely differs from the design value due to the potential activation of brittle failure modes of the bolt rows (e.g., occurrence of failure mode 3 in the place of mode 1 per bolt row). Also the number and the position of bolt rows directly affect the joint response. The presence of a bolt row in the center of the connection does not improve the strength of the joint under both gravity, wind and seismic loading, but it can modify the damage pattern of ductile connections, reducing the gap opening between the end-plate and the column face. On the other hand, the presence of a central bolt row can influence the capacity of the joint to resist the catenary actions developing under a column loss scenario, thus improving the joint robustness. Aiming at investigating the influence of these features on both the cyclic behavior and the response under column loss, a wide range of finite element analyses (FEAs) were performed and the main results are described and discussed in this paper.

Fabrication and characterization of silicon field emitter array with double gate dielectric (이중 게이트 절연막을 가지는 실리콘 전계방출 어레이 제작 및 특성)

  • 이진호;강성원;송윤호;박종문;조경의;이상윤;유형준
    • Journal of the Korean Vacuum Society
    • /
    • v.6 no.2
    • /
    • pp.103-108
    • /
    • 1997
  • Silicon field emitter arrays (FEAs) have been fabricated by a novel method employing a two-step tip etch and a spin-on-glass (SOG) etch-back process using double layered thermal/tetraethylortho-silicate (TEOS) oxides as a gate dielectric. A partial etching was performed by coating a low viscous photo resist and $O_2$ plasma ashing on order to form the double layered gate dielectric. A small gate aperture with low gate leakage current was obtained by the novel process. The hight and the end radius of the fabricated emitter was about 1.1 $\mu\textrm{m}$ and less than 100$\AA$, respectively. The anode emission current from a 256 tips array was turned-on at a gate voltage of 40 V. Also, the gate current was less than 0.1% of the anode current.

  • PDF