• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.189-197
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• 2012

The cold-formed steel stud, which has been used as a load-bearing member of wall panels for steel houses, poses a significant problem in insulation due to heat bridging of the web. Therefore, some additional thermal insulating materials are required. In order to solve this problem, the cold-formed steel thermal stud with slits in the web was developed. However, estimating the structural strength of thermal studs is very difficult because of the arrangement of perforations. In this paper, an analytical and experimental research on thermal studs is described. Three types of studs with different length, pitch and arrangement of slits were tested to failure. A simple design approach was proposed based on the test results. The proposed method adopted the direct strength method, based on the elastic local and distortional buckling stress of plain studs with equivalent thickness in the web instead of thermal studs. The predictions using the proposed method were compared with test results for verification and the adequacy of the proposed method was confirmed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.183-184
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• 2015

Recent structural approach of the House of Commons has been an increase in demand for dry wall light due to a change in load bearing composite structure of a flat plate type structure under the name of long-life housing, attach the attachment to the wall as the needs of the residents of reserved space increases things that are on the rise. However, depending on the strength of collapse accidents is shown wall and recent wall deposits are required, a load resistance evaluation method of the deposit of the need is the situation. Therefore, in this study, for the evaluation of the evaluation of dry lightweight wall as widely used gypsum board and ALC lightweight wall of two types of laboratory the wall through the previous studies to be installed in direct co-housing to the target and field experiments I want to evaluate the different points.

• Advances in concrete construction
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• v.10 no.3
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• pp.195-209
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• 2020

This study investigates the behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) with hybrid macro-micro steel and macro steel-polypropylene (PP) fibers. Compression, direct and indirect tension tests were carried out on cubic and cylindrical, dogbone and prismatic specimens, respectively. Three types of macro steel fibers, i.e., round crimped (RC), crimped (C), and hooked (H) were combined with micro steel (MS) and PP fibers in overall ratios of 2% by volume. Additionally, numerical analyses were performed to validate the test results. Parameters studied included, fracture energy, tensile strength, compressive strength, flexural strength, and residual strength. Tests showed that replacing PP fibers with MS significantly improves all parameters particularly flexural strength (17.38 MPa compared to 37.71 MPa). Additionally, the adopted numerical approach successfully captured the flexural load-deflection response of experimental beams. Lastly, the proposed regression model for the flexural load-deflection curve compared very well with experimental results, as evidenced by its coefficient of correlation (R²) of over 0.90.

• Journal of Power Electronics
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• v.4 no.3
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• pp.152-160
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• 2004

This paper presents analysis, modeling, and design of a low-harmonic, isolated, active-clamped SEPIC for future avionics applications. Simpler converter dynamics, high switching frequency, zero voltage-Transition-PWM switching, and a single-layer transformer construction result. This paper describes complete design of a digital controller for a high-frequency switching power supply. Guidelines for the minimum required resolution of the analog-to-digital converter, the pulse-width modulator, and the fixed-point computational unit is derived. A design example based on a SEPIC converter operating at the high switching frequency is presented. The controller design is based on direct digital design approach and standard root-locus techniques.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.148-153
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• 2008

An inflow of daylight to the room offers comfortable view environment, psychological and physical security to people in the room and there are merits such as a work efficiency and energy saving. But, it has many problems as an excessive direct sunlight, cooling and heating. We can expect to have energy saving effect for illumination with comfortable view environment creation through control on height of roller shade. This study will be a used a fundamental approach to control on height of roller shade to changing daylight.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.987-992
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• 1992

In recent years, induction motor is applied for several industrial actuatung parts instead of direct current motor because of the robust construction, nonexpensive and maintenance-free actuator etc. and having capability of speed control according to development of power electrounics and microprocessor techniques. In the paper, a microprocessor-based digital control approach for spped control of induction motor system is presented by considering a simple modelling equation as the system expression equation of induction motor and using the self tuning control and torque effdforward control method. As the model equation of the induction motor system, we use a second order differential equation which is well known in the modeling equation is induced form the control theory stand point such tath we can describe usually the motor system connected by inverter, generator and load etc. The effectiveness of the control system composed by the above mentioned design concept is illustrated by the expermental result in the presence of step reference change and generator load variation.

• Computers and Concrete
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• v.20 no.1
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• pp.23-29
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• 2017

In this study engineered steel fibres used as reinforcement for concrete were characterized by number of key mechanical and spatial parameters, which are easy to measure and quantify. Such commonly used parameters as length, diameter, fibre intrinsic efficiency ratio (FIER), hook geometry, tensile strength and ductility were considered. Effective classification of various fibres was demonstrated using simple multivariate computations involving principal component analysis (PCA). Contrary to univariate data mining approach, the proposed analysis can be efficiently adapted for fast, robust and direct classification of engineered steel fibres. The results have revealed that in case of particular spatial/geometrical conditions of steel fibres investigated the FIER parameter can be efficiently replaced by a simple aspect ratio. There is also a need of finding new parameters describing properties of steel fibre more precisely.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1193-1198
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• 2004

This paper describes the lightning protection system for railway signaling equipments installed at subway car depots in Seoul metropolitan Rapid Transit Cooperation. Several measures for improving lightning protection performance are adopted; newly organized grounding system for neutral line of power system, rolling method to minimize damages induced by direct lightning strike, new measures to reduce voltage differences between the signaling equipments and the ground, and improvement of grounding system. The proposed system has greatly reduced the grounding resistance and also the voltage difference between the signaling equipments and the ground, and has prevented the accident related with lightning surges since it was installed. The proposed approach can be viewed as a useful alternative of dealing with lightning protection for railway signaling equipments.

• Advances in concrete construction
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• v.5 no.4
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• pp.377-390
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• 2017

This study proposes a mix design method for geopolymer concrete (GPC) using low calcium fly ash and alccofine, with the focus on achieving the required compressive strength and workability at heat and ambient curing. Key factors identified and nine mixes with varied fly ash content (350, 375 and $400kg/m^3$) and different molarity (8, 12 and 16M) of NaOH solutions were prepared. The cubes prepared were cured at different temperatures ($27^{\circ}C$, $60^{\circ}C$ and $90^{\circ}C$) and tested for its compressive strength after 3, 7 and 28 days of curing. Fly ash content has been considered as the direct measure of workability and strength. The suggested mix design approach has been verified with the help of the example and targets well the requirements of fresh and hardened concrete.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2005.05a
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• pp.259-262
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• 2005

Since the importance of early education has been emphasized the Reggio preschools based on the philosophy of open education has been recreated in Korean culture. The Reggio Emilia approach to education is committed to the creation of conditions for learning that will enhance and facilitate children's construction of their own powers of thinking. Dream and hope of children are reflected in every where of the Reggio preschools that great attention is given to the look and feel of the classroom and environment is considered the‘third teacher.’ The results of the kindergarten design as a way of expressing direct, indirect and eclectic images using nature, that natural elements can become the elements of design in any form, and that nature's images are expressed by not only natural and artificial materials. In addition, safety and harmony with adjacent outdoors are also importantly considered in kindergarten design. Even though there were some limitations on this planning, the findings can be utilized as a basis for generating interior environmental recommendations for planning a better quality of kindergarten.