• Steel and Composite Structures
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• 제32권6호
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• pp.807-819
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• 2019

In recent earthquakes, the failure of ceiling systems has been one of the most widely reported damage and the major cause of functionality interruption in some buildings. In an effort to mitigate this damage, some scholars have studied a series of ceiling systems including plaster ceilings and mineral wool ceilings. But few studies have involved the backdrop metal ceiling used in some important constructions with higher rigidity and frequency such as the main control area of nuclear power plants. Therefore, in order to evaluate its seismic performance, a full-scale backdrop metal ceiling system, including steel runners and metal panels, was designed, fabricated and installed in a steel frame in this study. And the backdrop metal ceiling system with two perimeter attachments variants was tested: (i) the ends of the runners were connected with the angle steel to form an effective lateral constraint around the backdrop metal ceiling, (ii) the perimeter attachments of the main runner were retained, but the perimeter attachments of the cross runner were removed. In the experiments, different damage of the backdrop metal ceiling system was observed in detail under various earthquakes. Results showed that the backdrop metal ceiling had good integrity and excellent seismic performance. And the perimeter attachments of the cross runner had an adverse effect on the seismic performance of the backdrop metal ceiling under earthquakes. Meanwhile, a series of seismic construction measures and several suggestions that need to be paid attention were proposed in the text so that the backdrop metal ceiling can be better applied in the main control area of nuclear power plants and other important engineering projects.

• Steel and Composite Structures
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• 제31권1호
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• pp.13-25
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• 2019

Reactive powder concrete (RPC) is a type of ultra-high strength concrete that has a relatively high brittleness. However, its ductility can be improved by confinement, and the use of RPC in composite RPC filled steel tube columns has become an important subject of research in recent years. This paper aims to present an experimental study of axial capacity calculation of RPC filled circular steel tube columns. Twenty short columns under axial compression were tested and information on their failure patterns, deformation performance, confinement mechanism and load capacity were presented. The effects of load conditions, diameter-thickness ratio and compressive strength of RPC on the axial behavior were further discussed. The experimental results show that: (1) specimens display drum-shaped failure or shear failure respectively with different confinement coefficients, and the load capacity of most specimens increases after the peak load; (2) the steel tube only provides lateral confinement in the elastic-plastic stage for fully loaded specimens, while the confinement effect from steel tube initials at the set of loading for partially loaded specimens; (3) confinement increases the load capacity of specimens by 3% to 38%, and this increase is more pronounced as the confinement coefficient becomes larger; (4) the residual capacity-to-ultimate capacity ratio is larger than 0.75 for test specimens, thus identifying the composite columns have good ductility. The working mechanism and force model of the composite columns were analyzed, and based on the twin-shear unified strength theory, calculation methods of axial capacity for columns with two load conditions were established.

• Nuclear Engineering and Technology
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• 제50권7호
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• pp.1138-1147
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• 2018

Delayed hydride cracking (DHC) is an important failure mechanism for Zircaloy tubes in the demanding environment of nuclear reactors. The threshold stress intensity factor, $K_{IH}$, and critical hydride length, $l_C$, are important parameters to evaluate DHC. Theoretical models of them are developed for Zircaloy tubes undergoing non-homogenous temperature loading, with new stress distributions ahead of the crack tip and thermal stresses involved. A new stress distribution in the plastic zone ahead of the crack tip is proposed according to the fracture mechanics theory of second-order estimate of plastic zone size. The developed models with fewer fitting parameters are validated with the experimental results for $K_{IH}$ and $l_C$. The research results for radial cracking cases indicate that a better agreement for $K_{IH}$ can be achieved; the negative axial thermal stresses can lessen $K_{IH}$ and enlarge the critical hydride length, so its effect should be considered in the safety evaluation and constraint design for fuel rods; the critical hydride length $l_C$ changes slightly in a certain range of stress intensity factors, which interprets the phenomenon that the DHC velocity varies slowly in the steady crack growth stage. Besides, the sensitivity analysis of model parameters demonstrates that an increase in yield strength of zircaloy will result in a decrease in the critical hydride length $l_C$, and $K_{IH}$ will firstly decrease and then have a trend to increase with the yield strength of Zircaloy; higher fracture strength of hydrided zircaloy will lead to very high values of threshold stress intensity factor and critical hydride length at higher temperatures, which might be the main mechanism of crack arrest for some Zircaloy materials.

• Physical Therapy Rehabilitation Science
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• 제8권1호
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• pp.8-14
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• 2019

Objective: Degenerative knee arthritis is the most common disease that occurs in older people. Constriction-induced movement therapy (CIMT) has been reported to be as an effective treatment for the impairments, such as asymmetric weight-bearing and reduced balance that occurs after receiving a total knee replacement (TKR). Game-based rehabilitation training for persons with TKR is interesting and provides a variety of feedback. Design: Randomized controlled trial. Methods: Thirty-six subjects with TKR were randomly assigned to either the CIMT game training (n=12), general game training (n=12), or the control (n=12) group. Each group underwent twelve sessions (30 min/d, 3 d/wk for 4 weeks). In the CIMT game training group, the application of CIMT adjusted the weight of the pressure delivered from the two boards used in Wii games. In the general game training group, the game was played without adjusting the weight of pressure. The game training used the Wii Fit's Ski Slalom application. Subjects were assessed with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Activities-specific Balance Confidence (ABC) Scale. Results: All three groups showed significant improvements in pain, stiffness and physical function, total WOMAC scores, and ABC scores after the intervention (p<0.05). Significant differences were observed in physical function, total WOMAC scores, and ABC scores of the CIMT game training group compared with the other groups (p<0.05). Conclusions: The CIMT game training and general game training exhibited improvements on stiffness, but the CIMT game training exhibited a larger effect on lower extremity function and balance confidence levels.

• 한국전문물리치료학회지
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• 제28권1호
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• pp.84-91
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• 2021

Background: A hip fracture may occur spontaneously prior to the hip impact, due to the muscle pulling force exceeding the strength of the femur. Objects: We conducted falling experiments with humans to measure the activity of the hip muscles, and to examine how this was affected by the fall type. Methods: Eighteen individuals fell and landed sideways on a mat, by mimicking video-captured real-life older adults' falls. Falling trials were acquired with three fall directions: forward, backward, or sideways, and with three knee positions at the time of hip impact, where the landing side knee was free of constraint, or contacted the mat or the contralateral knee. During falls, the activities of the iliopsoas (Ilio), gluteus medius (Gmed), gluteus maximus (Gmax) and adductor longus (ADDL) muscles were recorded. Outcome variables included the time to onset, activity at the time of hip impact, and timing of the peak activity with respect to the time of hip impact. Results: For Ilio, Gmed, Gmax, and ADDL, respectively, EMG onset averaged 292, 304, 350, and 248 ms after fall initiation. Timing of the peak activity averaged 106, 96, 84, and 180 ms prior to the hip impact, and activity at the time of hip impact averaged 72.3, 45.2, 64.3, and 63.4% of the peak activity. Furthermore, the outcome variables were associated with fall direction and/or knee position in all but the iliopsoas muscle. Conclusion: Our results provide insights on the hip muscle activation during a fall, which may help to understand the potential injury mechanism of the spontaneous hip fracture.

• 디지털산업정보학회논문지
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• 제18권4호
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• pp.97-110
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• 2022

The purpose of this study is to analyze the level of public data convergence capabilities of administrative organizations and to explore important variables in data-based organizational capabilities. The theoretical background was summarized on public data and use activation, joint use, convergence, administrative organization, and convergence constraints. These contents were explained Public Data Act, the Electronic Government Act, and the Data-Based Administrative Act. The research model was set as the data-based organizational capabilities effect by a data-based administrative capability, public data operation capabilities, and public data operation constraints. It was also set whether there is a capabilities difference data-based on an organizational operation by the level of data convergence capabilities. This study analysis was conducted with hierarchical cluster analysis and multiple regression analysis. As the research result, First, hierarchical cluster analysis was classified into three groups. It was classified into a group that uses only public data and structured data, a group that uses public data on both structured and unstructured data, and a group that uses both public and private data. Second, the critical variables of data-based organizational operation capabilities were found in the data-based administrative planning and administrative technology, the supervisory organizations and technical systems by public data convergence, and the data sharing and market transaction constraints. Finally, the essential independent variables on data-based organizational competencies differ by group. This study contributed. As a theoretical implication, this research is updated on management information systems by explaining the Public Data Act, the Electronic Government Act, and the Data-Based Administrative Act. As a practical implication, the activity reinforcement of public data should be promoting the establishment of data standardization and search convenience and elimination of the lukewarm attitudes and Selfishness behavior for data sharing.

• 한국지반공학회논문집
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• 제22권10호
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• pp.173-181
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• 2006

본 논문에서는 정적 및 액상화와 같은 동적하중을 받는 흙의 거동해석을 위한 두 개의 활성면을 가진 구성모델을 제안하였다. 이 모델은 두 개의 활성면에 기초하고 있으며, 첫번째면은 회전하는 최대전단면을 나타내며 두 번째면은 고정된 수평면을 나타낸다. 이와 같은 두 개의 활성면을 이용하여 본 모델은 초기의 다른 응력상태하에 있는 시료의 직접단순전단시에 발생하는 주응력회전현상을 모델링할 수 있다. 제안된 모델은 초기의 응력비에 관계없이 평균유효응력이 동일할 경우에 유사한 거동을 보이는 흙의 실내실험결과를 묘사할 수 있다 그리고, 배수시 반복 직접단순전단으로 발생하는 흙의 거동 즉 제하시에 나타나는 체적감소 및 대변형에서 발생하는 체적팽창을 묘사할 수 있다. 비배수시의 흙의 정적 및 동적 거동은 배수거동에서 흙 골격사이에 존재하는 물의 구속력을 고려함으로써 해석하였다. 본 모델의 구성관계식은 응력-물의 상관관계를 동시에 묘사할 수 있는 FLAC을 이용하여 구현하였다. 배수 직접단순전단 시험을 이용한 Fraser River Sand의 실험결과를 이용하여 모델을 먼저 검증하였으며, 동일한 입력변수를 이용한 Fraser River Sand 비배수 거동의 예측치와 실험치를 비교하여 검증하였다.

• Steel and Composite Structures
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• 제50권6호
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• pp.659-674
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• 2024

Casting Ultra High-Performance Concrete (UHPC) on an orthotropic steel deck and forming a composite action by connectors could improve the steel deck fatigue performance. This study presents the mechanical performance of a proposed post-combination connection between UHPC and steel, which had a low constraint effect on UHPC shrinkage. A total of 10 push-out tests were conducted for static and fatigue performance investigations. And the test results were compared with evaluation methods in codes to verify the latter's applicability. Meanwhile, nonlinear simulation and parametric works with material damage plasticity models were also conducted for the static and fatigue failure mechanism understanding. The static and fatigue test results both showed that fractures at stud roots and surrounding local UHPC crushes were the main failure appearances. Compared with normally arranged studs, group arrangement could result in reductions of static stud shear stiffness, strength, and fatigue lives, which were about 18%, 12%, and 27%, respectively. Compared with the test results, stud shear capacity and fatigue lives evaluations based on the codes of AASHTO, Eurocode 4, JSCE and JTG D64 could be applicable in general while the safety redundancies tended to be smaller or even insufficient for group studs. The analysis results showed that arranging studs in groups caused obviously uneven strain distributions. The severer stress concentration and larger strain ranges caused the static and fatigue performance degradations of group studs. The research outcome provides a very important basis for establishing a design method of connections in the novel post-combination steel-UHPC composite deck.

• 대한방사선치료학회지
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• 제22권2호
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• pp.105-111
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• 2010

목 적: 세기변조방사선치료(intensity modulated radiation therapy; IMRT) 계획에는 여러 가지 beam parameter가 적용되어 치료계획을 수립하게 된다. 본 연구에서는 세기변조방사선치료 계획 시 선량율(dose rate) 변화가 이하선 선량에 미치는 영향을 알아보고자 한다. 대상 및 방법: 두경부암 환자 중 비인강암(nasopharyngeal carcinoma, NPC) 세기변조방사선치료를 시행한 10명의 환자를 대상으로 하였다. 동일한 조건하에 환자의 CT영상을 3 mm 두께로 획득하고 치료계획시스템은 Eclipse (Ver 7.1, Varian, Palo Alto, USA)를 사용하였다. 치료계획은 6 MV 에너지, 8개의 조사면, 그리고 동일한 dose volume constraint를 적용하였고, 선량율을 300, 400, 500 MU/min으로 각각 다르게 적용하였다. 수립된 세 개의 치료계획을 통해 이하선 mean dose를 산출하여 10명의 환자 평균치로 분석하였고, 2D diode array (MapCheck from Sun Nuclear Corporation, Melbourne, Florida)를 사용하여 이하선 부위의 선량을 검증하였다. 그리고 총 Monitor Unit (MU)과 조사시간을 비교하였다. 결 과: 선량율 변화에 따른 이하선 mean dose는 선량율을 300 MU/min에서 400, 500 MU/min 변화 시켰을 때 평균 0.8, 2.0% 증가하였고, 총 MU 또한 평균 5.4, 10.6% 증가하였다. 2D diode Array를 사용한 이하선 부위의 선량측정에서도 증가 추세가 나타났으며 총 조사시간의 차이는 1-2분 정도로 선량율에 따라 큰 변화가 없었다. 결 론: 본 연구결과 선량율이 증가하면 총 MU가 현저히 늘어났고 그에 따라 이하선 선량도 증가하는 유의한 상관관계를 보였으나, 치료시간 단축효과는 크지 않았다. 그러므로 세기변조방사선치료 계획 시 적절한 선량율을 적용하여 이하선 선량을 줄인다면 방사선치료로 인한 이하선의 후기 부작용(late side effect)을 줄일 수 있을 것으로 사료된다.

• 한국콘텐츠학회논문지
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• 제20권6호
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• pp.326-341
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• 2020

본 연구는 국내 온라인 커뮤니티 이용 공중(public)이 한국과 일본의 관계 악화에 따른 민간주도의 불매운동 이슈에 대하여 그 중요성을 인식하고 관련된 커뮤니케이션 행위에 관여하는 과정을 문제해결 상황이론(Situational Theory of Problem Solving, STOPS)의 적용을 통해 분석하였다. 이를 위해 지난 2019년 7월 일본의 경제보복 성격의 수출규제 조치로 인해 촉발된 일본산 제품 불매운동을 사회적 쟁점으로 선정하여, 온라인 커뮤니티에서 활동하는 공중 524명을 대상으로 설문조사를 실시했다. 연구결과, 불매운동 이슈에 대한 공중의 높은 문제인식과 준거지침은 문제해결을 위한 상황적 동기에 정(+)적 영향을 주는 것으로 나타났다. 제약인식과 관여도는 정(+)적 영향을 주었으나 통계적으로 유의하지 않았다. 매개변인인 상황적 동기는 정보선별, 정보수용, 정보전달, 정보공유, 정보추구, 정보주목으로 구성된 문제해결 커뮤니케이션 행위에 모두 정(+)적 영향을 주고 있는 것으로 나타났다. 즉, 사회적 쟁점인 불매운동에 대해 중요성을 느끼고 있으며, 이에 대한 배경지식과 의지를 지닌 온라인 공중은 보다 적극적으로 문제해결을 위한 다양한 커뮤니케이션 행위에 참여함을 확인하였다. 또한 연구결과의 이론적 함의와 더불어 향후 연구의 방향성에 대해 기술하였으며, 특히 실무적으로는 정부의 공공PR 전략이 이러한 온라인 공중의 능동성과 파급력을 감안하여, 정교하게 구분된 공중의 특성에 맞는 섬세하고 효과적인 커뮤니케이션 전략을 수립-실행해야 함을 논하였다.