• Smart Structures and Systems
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• 제25권3호
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• pp.311-322
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• 2020

This paper studies the influence of parameters of a novel SMA helical spring energy dissipation brace on the seismic resistance of a frame structure. The force-displacement relationship of the SMA springs is established mathematically based on a multilinear constitutive model of the SMA material. Four SMA helical springs are fabricated, and the force-displacement relationship curves of the SMA springs are obtained via tension tests. A numerical dynamic model of a two-floor frame with spring energy dissipation braces is constructed and evaluated via vibration table tests. Then, two spring parameters, namely, the ratio of the helical spring diameter to the wire diameter and the pre-stretch length, are selected to investigate their influences on the seismic responses of the frame structure. The simulation results demonstrate that the optimal ratio of the helical spring diameter to the wire diameter can be found to minimize the absolute acceleration and the relative displacement of the frame structure. Meanwhile, if the pre-stretch length is assigned a suitable value, excellent vibration reduction performance can be realized. Compared with the frame structure without braces, the frames with spring braces exhibit highly satisfactory seismic resistance performance under various earthquake waves. However, it is necessary to select an SMA spring with optimal parameters for realizing optimal vibration reduction performance.

• 패션비즈니스
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• 제25권4호
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• pp.151-160
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• 2021

The purpose of this study was to investigate whether there were improvements on balance when both ankle-jointed calf muscles and hip muscles, which affect balance capabilities, were activated through taping techniques and EMS. In this study, the One Leg Standing Test, a static balance test, was conducted by experimenting on a flat floor, foam pad, and a stretching board with a gradient of 20 degrees, respectively, to study static balance capabilities in different situations. Nine healthy men in their 20s were measured five times every five minutes considering muscle fatigue, and the difference between each variable was analyzed through post-test using nonparametric statistical analysis. Our results showed an equal increase in static balance capability was similar when EMS was applied only to calf muscles and only to hip muscles. Notably most improvements were seen when wearing calf supporters and taping technology pants, and applying EMS together. It was also found that the difference between EMS electric stimulation and balance capability was greater when wearing and applying supporters and taping technology pants. Based on the results of the present study, a muscle support band and EMS of taping techniques can improve balance capabilities. These findings are expected to form a basis for solutions Improving the balance capabilities

• Smart Structures and Systems
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• 제23권3호
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• pp.227-242
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• 2019

Seismic isolation systems employ structural control that protect both buildings and vibration-sensitive contents from destructive effects of earthquakes. Structural control is divided into three main groups: passive, active, and semi-active. Among them, semi-active isolation systems, which can reduce floor displacements and accelerations concurrently, has gained importance in recent years since they don't require large power or pose stability problems like active ones. However, their seismic performance may vary depending on the variations that may be observed in the mechanical properties of semi-active devices and/or seismic isolators. Uncertainties relating to isolators can arise from variations in geometry, boundary conditions, material behavior, or temperature, or aging whereas those relating to semi-active control devices can be due to thermal changes, inefficiencies in calibrations, manufacturing errors, etc. For a more realistic evaluation of the seismic behavior of semi-active isolated buildings, such uncertainties must be taken into account. Here, the probabilistic behavior of semi-active isolated buildings under historical pulse-like near-fault earthquakes is evaluated in terms of their performance in preserving structural integrity and protecting vibration-sensitive contents considering aforementioned uncertainties via Monte-Carlo simulations of 3-story and 9-story semi-active isolated benchmark buildings. The results are presented in the form of fragility curves and probability of failure profiles.

• 국제초고층학회논문집
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• 제8권2호
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• pp.117-123
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• 2019

Tall buildings are prone to wind-induced vibrations due to their slenderness whereby peak structural accelerations may be higher than the recommended maximum value. The common countermeasure is the installation of a tuned mass damper (TMD) near the highest occupied floor. Due to the extremely large modal mass of tall buildings and because of the narrow to broad band type of wind excitation the TMD mass may become inacceptable large - in extreme cases up to 2000 metric tons. It is therefore a need to develop more efficient TMD concepts which provide the same damping to the building but with reduced mass. The adaptive TMD concept described in this paper represents a solution to this problem. Frequency and damping of the adaptive TMD are controlled in real-time by semi-active oil dampers according to the actual structural acceleration. The resulting enhanced TMD efficiency allows reducing its mass by up to 20% compared to the classical passive TMD. The adaptive TMD system is fully fail-safe thanks to a smart valve system of the semi-active oil dampers. In contrast to active TMD solutions the adaptive TMD is unconditionally stable and its power consumption on the order of 1 kW is negligible small as controllable oil dampers are semi-active devices. The adaptive TMD with reduced mass, stable behavior and lowest power consumption is therefore a preferable and cost saving damping tool for tall buildings.

• 한국지열·수열에너지학회논문집
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• 제16권4호
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• pp.9-15
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• 2020

In this study, effect of reinforced insulation on heating and cooling loads were studied due to installation of PV panels on factory building roof with a floor area of 12,960 m². For PV panel installation, combination of aluminum, polyurethane, air, polystyrene and steel materials were added to the original roof, which increased thermal insulation performance. Half of the roof were covered with PV panel and the other half without. Temperature and relative humidity were measured for 8 days during summer season for both indoor spaces. PV panel showed the effect of lowering the indoor space temperature by 0.6℃. TRNSYS dynamic simulation showed that with PV panel, cooling load per area is reduced by 1.7 W/m² and heating by 10.0 W/m². PV panels installed on building roof not only generate electricity but also can save energy by reducing cooling and heating loads.

• International Journal of Internet, Broadcasting and Communication
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• 제15권1호
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• pp.97-112
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• 2023

The purpose of this study is to design and test a new way of public transportation route guidance system for persons with disabilities, including wheelchair users. The guidance system is smartphone app-based, using, routes that involve disabled-friendly facilities in the vicinity can be searched. A database that contains publicly available data on low-floor bus services, location and extent of disabled-friendly facilities, and suitable subways and stations, was developed for this purpose. The app uses the database to access and query the required information. A pilot study was conducted to test the effectiveness of the guidance system. It was found that the system was able to convey information about the disabled-friendly routes and related guidance information even inside subway stations, effectively. The performance of the system was compared with route guidance services that do not explicitly use data on disabled-friendly services. A notable difference was observed in the travel time estimated by this program and other guidance services. The difference was around 4 to 15 minutes. This is significant savings for persons with disabilities if they use the app and service. The study thus shows that exclusive use of disabled-friendly data in route guidance will bring more benefits for persons with disabilities.

• 한국전기전자재료학회논문지
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• 제35권2호
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• pp.155-159
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• 2022

Smart livestock, which combines information and communication technology (ICT) with livestock, can be said to be an effective solution to existing livestock problems such as productivity improvement, odors, and diseases. So far, it has hardly been universalized; thus, it is necessary to develop automation devices to reduce labor by localizing automation devices to expand the distribution of ICT technology to farms, and to advance precise specifications and health management technology using biometric information. Weighing scales currently being used in livestock farms are to prevent the spread of diseases by diagnosis and preparation for AI and other diseases in advance, using information on the growing weight of duck breeding. However, accurate values cannot be obtained due to poor breeding conditions. In this paper, we developed a separate data transmission system kit for the weighing scale and placed the sensor on top of the weighing scale so that the sensor wire is not affected by pollutants or ducks on the floor. A display function was provided, and a method of receiving and analyzing the serial port data of the weighing device, and then transmitting them to the data collection server was implemented.

• 로봇학회논문지
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• 제19권3호
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• pp.311-317
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• 2024

Large-scale three-wheeled cleaning robots are utilized to clean large spaces such as warehouses and manufacturing plants where significant floor contamination occurs. Although there are autonomous cleaning robots, user-operated cleaning robots are often preferred because they are easy to repair and inexpensive. Therefore, workers have to spend extra time on cleaning, which reduces work efficiency. In this paper, we propose an autonomous driving system designed to automate the operation while maintaining the structure of existing cleaning robots. The contributions of this paper are as follows: 1) Hardware modules that control the driving and steering components. 2) A LiDAR-based autonomous driving system and path point generation system considering the mechanical characteristics of the cleaning robot. 3) The proposed system is implemented on an actual cleaning robot and driving tests are performed. As a result, when path planning is performed to cover the cleaning area, the average RMSE for each straight path is 0.0802 m, which is smaller than the minimum cleaning overlap of 0.3 m that occurs during the straight cleaning of the robot. This shows that the proposed system effectively covers the entire cleaning area.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 춘계학술대회
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• pp.209-212
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• 2013

교육부가 중점 추진하는 누리과정은 교육과 보육에 대한 국가차원의 표준화된 교육과정으로서 취학전 교육의 질을 제고하고, 생애 초기의 공정한 출발선을 보장하며 전 영역에서 창의 인성 교육을 강조하고 있다. 영유아기 누리과정의 창의교육을 위한 곤충로봇을 개발하여 흥미와 교육효과를 높였다. 기존의 지면을 사용한 조립도와 온라인 홈페이지를 이용한 교육용 로봇의 조립과 학습에 VR을 이용하여 조립과 교육내용학습에 효과를 높였다. 유아들이 로봇을 학습하기 위해서는 적극적인 관심과 학습의 동기가 필요하며 정보기반사회에서의 정보기술을 활용한 창의적인 학습 또한 필요하다. 증강현실에서 사용될 마커는 로봇에 관한 3차원의 모델정보를 연계하여 증강하고, 이는 마커를 통하여 증강현실의 대상 마커와 카메라와의 상대 좌표계 변환을 구하고, 그 마커내의 패턴을 이용하여 미리 정의된 패턴 중 무엇인지에 대한 결정을 할 수 있도록 한다. 본 논문을 통하여 교육용 조립로봇의 현실세계에서의 창의교육과 증강 가상환경으로 표현되는 스마트교육을 융합하여 새로운 형태의 첨단 스마트교육을 제시하여 국가인재의 조기육성을 통한 인재대국의 기초를 마련하고자 한다.

• Smart Structures and Systems
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• 제21권4호
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• pp.479-491
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• 2018

Shape memory alloys (SMA) exhibit superelasticity which refers to the capability of entirely recovering large deformation upon removal of applied forces and dissipating input energy during the cyclic loading reversals when the environment is above the austenite finish temperature. This property is increasingly favored by the earthquake engineering community, which is currently developing resilient structures with prompt recovery and affordable repair cost after earthquakes. Compared with the other SMAs, NiTi SMAs are widely deemed as the most promising candidate in earthquake engineering. This paper contributes to evaluate the seismic performance of properly designed concentrically braced frames (CBFs) equipped with NiTi SMA braces under earthquake ground motions corresponding to frequently-occurred, design-basis and maximum-considered earthquakes. An ad hoc seismic design approach that was previously developed for structures with idealized SMAs was introduced to size the building members, by explicitly considering the strain hardening characteristics of NiTi SMA particularly. The design procedure was conducted to compliant with a suite of ground motions associated with the hazard level of design-basis earthquake. A total of four six-story CBFs were designed by setting different ductility demands for SMA braces while designating with a same interstory drift target for the structural systems. The analytical results show that all the designed frames successfully met the prescribed seismic performance objectives, including targeted maximum interstory drift, uniform deformation demand over building height, eliminated residual deformation, controlled floor acceleration, and slight damage in the main frame. In addition, this study indicates that the strain hardening behavior does not necessarily impose undesirable impact on the global seismic performance of CBFs with SMA braces.