• Nuclear Engineering and Technology
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• v.47 no.6
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• pp.766-775
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• 2015

The integrity assessment of reactor vessel internals should be conducted in the design process to secure the safety of nuclear power plants. Various loads such as self-weight, seismic load, flow-induced load, and preload are applied to the internals. Therefore, the American Society of Mechanical Engineers (ASME) Code, Section III, defines the stress limit for reactor vessel internals. The present study focused on structural response analyses of the upper guide structure upper flange. The distributions of the stress intensity in the flange body were analyzed under various design load cases during normal operation. The allowable stress intensities along the expected sections of stress concentration were derived from the results of the finite element analysis for evaluating the structural integrity of the flange design. Furthermore, seismic analyses of the upper flange were performed to identify dynamic behavior with respect to the seismic and impact input. The mode superposition and full transient methods were used to perform time-history analyses, and the displacement at the lower end of the flange was obtained. The effect of the damping ratio on the response of the flange was also evaluated, and the acceleration was obtained. The results of elastic and seismic analyses in this study will be used as basic information to judge whether a flange design meets the acceptance criteria.

• Journal of KIBIM
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• v.5 no.4
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• pp.11-22
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• 2015

Government efforts for green growth policy initiatives demand low-carbon technologies in the road construction industry. The purpose of this paper is to develop an algorithm of a road alignment design solution for establishing the multi-dimensional information, and to calculate carbon emission quantity due to the geometric design elements in the planning phase of road alignment. The paper developed a calculation method for carbon emission quantity by drawing a speed profile reflected in the operating speed, acceleration and deceleration, which are majors factor of carbon emissions while driving and by applying a carbon emission factor. From this effort, it enabled alignment planning to reduce carbon emission. Object-based parametric design methods of the cross-sections were proposed for alignment planning, and the paper demonstrated a BIM-based road alignment planning solution. The proposed solutions can provide multi-dimensional information on carbon emission quantity and cross section elements through driving simulation. It is expected to allow construction of eco-friendly roads by deriving optimal road alignment to minimize environmental costs.

• Steel and Composite Structures
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• v.31 no.5
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• pp.437-452
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• 2019

In this study, in-situ static and dynamic tests of four pre-stressed concrete (PC) track beams with different span lengths and curvatures in a straddle monorail transit system were reported. In the static load tests, the strain and deflection at critical sections of the PC track beams were measured to determine the load bearing capacity and stiffness. The dynamic responses of strain, deflection, acceleration, and displacement at key positions of the PC track beams were measured under different train speeds and train loads to systematically study the dynamic behaviors of the PC track beams. A three-dimensional finite element model of the track beam-vehicle coupled vibration system was established to help understand the dynamic behavior of the system, and the model was verified using the test results. The research results show that the curvature, span length, train speed, and train loads have significant influence on the dynamic responses of the PC track beams. The dynamic performance of the PC track beams in the curve section is susceptible to dynamic loads. Appropriate train loads can effectively reduce the impact of the train on the PC track beam. The PC track beams allow good riding comfort.

• Steel and Composite Structures
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• v.52 no.6
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• pp.673-693
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• 2024

An advanced numerical method is proposed in this paper for the second-order inelastic dynamic analysis of cable-stayed bridges using rectangular concrete-filled steel tubular (CFST) columns under earthquake loadings for the first time. The proposed method can exactly predict the nonlinear response of the bridges by using only one element per member in simulating the structural model. This comes from considering both the geometric and material nonlinearities in a fiber beam-column element and a catenary cable element. In the fiber beam-column element, the geometric nonlinearities are captured by applying the stability functions, whereas the material nonlinearities are evaluated by tracing the uniaxial cyclic stress-strain curves of each fiber on the cross-sections, which are located at the integration points along the member length. A computer program was developed based on Newmark's average acceleration algorithm to solve the nonlinear equations of motion. The accuracy and computational efficiency of the proposed program were verified by comparing the predicted results with the experimental results, and the results obtained from the commercial software SAP2000 and ABAQUS. The proposed program is promising as a useful tool for practical designs for the nonlinear inelastic dynamic analysis of cable-stayed bridges.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.6
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• pp.66-83
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• 2021

Vehicles experience changes in driving behavior due to the various facilities on the freeway. These sections may cause repetitive traffic congestion when the traffic volume increases, so safety issues may be raised. Therefore, the purpose of this study is to perform microscopic traffic analysis on these sections using drone images and to identify the causes of traffic problems. In the case of drone image, since trajectory data of individual vehicles can be obtained, empirical analysis of driving behavior is possible. The analysis section of this study was selected as the weaving section of Pangyo IC and the sag section of Seohae Bridge. First, the trajectory data was extracted through the drone image. And the microscopic traffic analysis performed on the speed, density, acceleration, and lane change through cell-unit analysis using Generalized definition method. This analysis results can be used as a basic study to identify the cause of the problem section in the freeway. Through this, we aim to improve the efficiency and convenience of traffic analysis.

• Korean Journal of Applied Biomechanics
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• v.17 no.4
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• pp.17-25
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• 2007

The purpose of the study is to give basic data for the improvement of the skill and to show an exemplary position for squash club members or trainers thru a comparative analysis on the kinematics and kinetics variables on the forehand drive motion in playing squash. The objects of the research are divided into two sections, skilled group(n=8) and unskilled group(n=8). The skilled group is composed of professional players currently working and unskilled group is career of six month, both of lives in B city. In this research, to gather the data 3D motion analysis and test result analysis using force platform was used. The variables are duration, position, segment velocity, segment acceleration and etc. in using force platform. The results are as follows: 1. The duration per phase of the skilled is 0.18sec P1(DS) while that of unskilled is 0.32sec. in P2(FT), the duration of the skilled is 0.29sec, that of unskilled is 0.34sec. Average of the duration of the skilled is 0.48sec, while the unskilled, 0.66sec. 2. Regarding positional movements per event, the unskilled has a relatively higher position in center of gravity, shoulder joint, elbow joint compared with that of the skilled. Generally speaking, positions of the unskilled is higher than the skilled. 3. In segment velocity per event, R-shank, R-upper arm, R-forearm and racket. The skilled is faster than the unskilled. we found a big dig difference in shank. 4. In acceleration per event, there was a big difference in upper-arm and fore-arm of the impact. 5. The skilled group on the force platform shows relatively stable and regular changes while the unskilled shows unstable from the touch down to initial 20% the force value of central support period after the impact moment decreases rapidly and the center of gravity is not moved well. 6. The maximum force value of the skilled is 1019.7N. it is found 19.86% of the total duration. That of the unskilled is 639.2N, it is found 20.67% of total duration.

• Journal of Korean Neurosurgical Society
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• v.29 no.4
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• pp.461-470
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• 2000

Objective : Many investigators have demonstrated the protective effects of hypothermia following traumatic brain injury(TBI) in both animals and humans. It has long been recognized that mild to moderate hypothermia improves neurologic outcomes as well as reduces histologic and biochemical sequelae after TBI. In this study, two immunohistochemical staining using terminal deoxynucleotidyl-transferase-mediated biotin dUTP nick end labeling(TUNEL), staining of apoptosis, and ${\beta}$-amyloid precursor protein(${\beta}$-APP), a marker of axonal injury, were done and the authors evaluated the protective effects of hypothermia on axonal and neuronal injury after TBI in rats. Material and Method : The animals were prepared for the delivery of impact-acceleration brain injury as described by Marmarou and colleagues. TBI is achieved by allowing of a weight drop of 450gm, 1 m height to fall onto a metallic disc fixed on the intact skull of the rats. Fourty Sprague-Dawley rats weighing 400 to 450g were subjected to experimental TBI induced by an impact-acceleration device. Twenty rats were subjected to hypothermia after injury, with their rectal temperatures maintained at $32^{\circ}C$ for 1 hour. After this 1-hour period of hypothermia, rewarming to normothermic levels was accomplished over 30-minute period. Following 12 hours, 24 hours, 1 week and 2 weeks later the animals were killed and semiserial sagittal sections of the brain were reacted for visualization of the apoptosis and ${\beta}$-APP. Results : The density of ${\beta}$-APP marked damaged axons within the corticospinal tract at the pontomedullary junction and apoptotic cells at the contused cerebral cortex were calculated for each animal. In comparison with the untreated controls, a significant reduction in ${\beta}$-APP marked damaged axonal density and apoptotic cells were found in all hypothermic animals(p<0.05). Conclusion : This study shows that the posttraumatic hypothermia result in substantial protection in TBI, at least in terms of the injured axons and neurons.

• Journal of the Korean GEO-environmental Society
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• v.20 no.7
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• pp.5-10
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• 2019

In recent Gyeongju and Pohang earthquakes, motions that exceed the design ground motion were recorded. This has led to adjustments to the design earthquake intensity in selected design guidelines. An increment in the design intensity requires reevaluation of all associated facilities, requiring extensive time and cost. Firstly, the seismic factor of safety of built concrete retaining walls are calculated. Secondly, the seismic margin of concrete retaining walls is evaluated. The design sections of concrete walls built at power plants and available site investigation reports are utilized. Widely used pseudo-static analysis method is used to evaluate the seismic performance. It is shown that all concrete walls are safe against the adjusted design ground motion. To determine the seismic margin of concrete walls, the critical accelerations, which is defined as the acceleration that causes the seismic factor of safety to exceed the allowable value, are calculated. The critical acceleration is calculated as 0.36g~0.8g. The limit accelerations are significantly higher than the design intensity and are demonstrated to have sufficient seismic margin. Therefore, it is concluded that the concrete retaining walls do not need to be reevaluated even if the design demand is increased up to 0.3g.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.3
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• pp.310-317
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• 2014

The Next-generation High-speed Rail Technology Development Project was started in 2007 by the Korean Government with the aim of developing the core technologies for a high-speed electric multiple unit (EMU) railway system. This is the first attempt to develop a high-speed EMU railway. High-speed EMU trains have superior acceleration and deceleration compared to push-pull high-speed railways such as KTX(Korean Train eXpress). A prototype train was developed and tested on a high-speed line starting in 2012. The new train must maintain running safety during the test. Generally, the international standard (UIC518) is adopted to evaluate the running safety of trains. This method suggests that the test zone must have over 25 sections, and the length of each section must be 500 m. However, it is difficult to implement these test conditions for a real high-speed line. In this study, we analyzed the running safety using several test section lengths (100 m to 500 m) and compared the results. The results of this study will be used to establish a running safety evaluation method for high-speed EMU railways.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.43-49
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• 2015

By the trends of electronic package to be smaller, thinner and more integrative, organic printed circuit board is required to be finer Cu trace pitch. This paper reports on a study of failure mechanism for PCB with fine Cu trace pitch using biased HAST. In weibull analysis of the biased HAST lifetime, it is found that the acceleration factor (AF) of between $135^{\circ}C/90%RH/3.3V$ and $130^{\circ}C/85%RH/3.3V$ is 2.079. A focused ion beam (FIB) was used to polish the cross sections to reveal details of the microstructure of the failure mode. It is found that $Cu_xO/Cu(OH)_2$ colloids and Cu dendrites were formed at anode (+) and at cathode (-), respectively. Thus, this gives the evidence that Cu dendrites formed at cathode by $Cu^{2+}$ ion migration lead to a short failure between a pair of Cu nets.