• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2009.11a
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• pp.89-94
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• 2009

The purpose of this study is to provide a fundamental data for reducing energy consumption and greenhouse gas emission of detached houses by investigating the energy consumption characteristic of detached houses in Daegu. Although the ratio of the detached houses decreases, the detached houses are common dwelling form next to apartments. Nevertheless the study about the energy consumption of detached houses has been insufficient compared apartments. There is a necessity which will investigate the energy consumption characteristic of detached houses. Because that with the building quality which is various form is different from apartments. This study investigate construction and equipment conditions and analyzing effective factors on energy consumption of detached houses. And this study draw up the energy consumption unit and emission factors unit for greenhouse gas of detached houses. This study represent a basic report for energy consumption reduction and helps effective use of energy.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.1
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• pp.43-55
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• 2001

A continuously variable transmission(CVT) mechanism composed of one differential gear unit and one continuously variable unit(CVU) can be classified according to the coupling of CVU and the direction of power flows. The mechanism has many advantages which are the decrease of CVT size, the increase of overall efficiency, the extension of speed ratio range and generation of geared neutral. The CVT mechanism considered here is the input coupled type which combines the functions of a 2K-H I type differential gear unit and a V-belt type CVU. One shaft of the CVU is connected directly to the input shaft and another shaft of it is linked to the differential gear unit. It is shown that some fundamental relations(speed ratios, power flows and efficiencies) for twelve mechanisms previously described are valid by various experimental studies, six of them produce a power circulation and the others produce a power split. Some useful comparisons between theoretical analysis and experimental results are presented. General properties also are discussed, which connect following power flow modes : (a) power circulation mode; (b) power split mode.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.742-745
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• 2009

This paper proposes a wireless LAN antenna system that tracks an object automatically by using image-based tracking. The proposed system consists of a camera and a pan-tilt unit in addition to a directional wireless LAN antenna. The camera and the directional antenna are set in same direction and they are set on the pan-tilt unit. A target object which has a wireless LAN receiver is tracked by using images captured by the camera. And the directional antenna faces in same direction as the camera by the pan-tilt unit. Therefore, the directional antenna keeps pointing the receiver, and a transmitting efficiency is improved. A result of a fundamental experiment shows that a receiver attached to a flying airship was tracked by a prototype of the proposed antenna system. The airship flied about, and the proposed antenna system was set on a roof of a building. The experimental result indicates an effectiveness of the proposed system compared to the conventional directional LAN antenna.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.422-429
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• 2008

The objective of the present study is to develope a propultion unit cooling system for the next-generation High-speed EMU. The propulsion power control unit consists of some IGBT semiconductors. In general, those power semiconductors are very sensitive to temperatures and need a cooling system to keep them at a proper operational conditions in the range of $50{\sim}100^{\circ}C$. In this first year of study, we tried to focuss on the understanding of fundamental technologies for each of the two different cooling systems and collecting basic data for design and manufacturing for both cases. For the water cooling system, a heat sink with multi channels of liquid flow was considered and a model unit was designed and performance test was conducted. For the heat pipe cooling system, a Loop Heat Pipe(LHP) was considered as an element to transport heat from IGBT to environment air flow and a model unit was designed and performance test was conducted. The analysis using SINDA/FLUINT showed that those design parameters are good enough for the LHP to properly operate under a heat load up to around 360W.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.912-915
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• 1998

As a fundamental study on the development of porous concrete for planting, this study is designed to present the properties of porous concrete by varying the kinds of cement, paste to aggregate ratio and dosage of AE admixture. As the results of experiment, the void volumes show 30~33%, 25~ 28% and 17~22% respectively, with paste to aggregate ratio of 20%, 30% and 40%. And unit weight is 1700~1900kg/㎥ while compressive strengths 40~60, 8 0~100 and 120~150kg/$\textrm{cm}^2$. pH of concrete shows a sufficient value at which the plant could grow, when the concrete is permeated in Ammonium Phosphate Dibasic for more than 1 hour. In brief, it shows a possibility of development of porous concrete if the concrete is permeated with permeating in Ammonium Phosphate Dibasic for more than 1 hour when the blast furnace slag cement is used.

• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.3
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• pp.10-16
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• 1986

This paper deals with a simple, approximate formula to predict the natural frequencies of the sagged cable structures. Assuming that the propagation velocity of the lateral wave is dependent only on the local mass per unit length and local tension, the explicit simple formula to predict the fundamental period is newly derived. The modified form of these formula is also presented for the prediction of the fundamental period of general shaped cable structures. The results of comparison shows fairly good agreements with experimental results and with theoretical ones. This formula is also used to predict the natural frequencies of a long vertical cable and the derived approximate formula in that case, becomes identical to the exact solution.

• East Asian mathematical journal
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• v.37 no.1
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• pp.41-77
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• 2021

Let M be a semi-invariant submanifold of codimension 3 with almost contact metric structure (��, ξ, η, g) in a complex space form Mn+1(c), c ≠ 0. We denote by Rξ = R(·, ξ)ξ and A(i) be Jacobi operator with respect to the structure vector field ξ and be the second fundamental form in the direction of the unit normal C(i), respectively. Suppose that the third fundamental form t satisfies dt(X, Y ) = 2��g(��X, Y ) for certain scalar ��(≠ 2c)and any vector fields X and Y and at the same time Rξ is ��∇ξξ-parallel, then M is a Hopf hypersurface in Mn(c) provided that it satisfies RξA(1) = A(1)Rξ, RξA(2) = A(2)Rξ and ${\bar{r}}-2(n-1)c{\leq}0$, where ${\bar{r}}$ denotes the scalar curvature of M.

• Journal of Korea Water Resources Association
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• v.44 no.1
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• pp.41-49
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• 2011

This study is a research based on an existing analysis that peak values of unit hydrograph are variant according to rainfall intensity in a watershed. Differently from the fundamental assumption that an unit hydrograph is time-invariant in a watershed a variant unit hydrograph to rainfall intensity by storms is defined and applied into rainfall events, which produces out runoff hydrograph for an examination. Peak flow and time to peak of unit hydrograph used for an application are obtained from the relation equation with rainfall intensity developed by a previous study reviewed, and its shape is made by Nash unit hydrograph which is determined by the peak values. For the purpose of a comparison an invariant unit hydrograph is defined as Nash model obtained from averaged peak values of unit hydrograph which is derived by 26 rainfall storms. Peak flow and time to peak of flood hydrograph developed respectively by variant unit hydrograph with rainfall intensity and an averaged unit hydrograph are compared to those of the observed hydrograph. With comparing both hydrographs calculated by averaged unit hydrograph and revised unit hydrograph to observed hydrograph it is shown the peak flow and time to peak of hydrograph calculated by time-invariant unit hydrograph revised in this study are closer to those of observed hydrograph than those calculated by averaged unit hydrograph.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.53-54
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• 2015

As the result of uniaxial compression strength test on the CLMS mixing BFS and SS with BFS 4000, it required to determine the desired strength through increasing unit quantity of cement in mixing process because of dramatic strength deterioration of strength according to increasing replacing rate. In this study's result, regardless of differences in fine aggregates used, in order to get uniaxial compression strength in the scope exceeding criteria of minimum strength for applying to the field, the most reasonable combination was to mix replacing BFS with fineness of 6000 in 30%. For the CLMS mixing BFS and SS, in order to improve flow ability by securing quantity of minimum unit and to repress bleeding rate with securing uniaxial compress strength considering the field applicability, regardless of differences in fine aggregates used, to mix BFS over 6000 in 30% was most effective.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.3
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• pp.27-36
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• 2004

This paper has been conducted to design for pressure regulation system. to simulate for performance of turbo pump unit using AMESim(Advanced Modeling Environment for Simulation of Engineering Systems). With optimized of system, pressure regulation system has been confirmed dynamic characteristics of transient and steady states range based on static modeling of open type turbo pump fed engine system. These results can be utilized to verify for performance test facility of propulsion control system for analysis on control valves, review of the fundamental principle on the control logic and certificating engine feeding system.