• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1021-1029
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• 2013

In this paper, we propose a new indoor location estimation method which combines the fingerprint technique with the propagation prediction model. The wireless LAN (WLAN) access points (APs) deployed indoors are divided into public APs and private APs. While the fingerprint method can be easily used to public APs usually installed in fixed location, it is difficult to apply the fingerprint scheme to private APs whose location can be freely changed. In the proposed approach, the accuracy of user location estimation is improved by simultaneously utilizing public and private APs. Specifically, the fingerprint method is used to the received signals from public APs and the propagation prediction model is employed to the signals from private APs. The performance of the proposed method is compared with that of conventional indoor location estimation schemes through measurements and numerical simulations in WLAN environments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.769-777
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• 2015

In this paper, a damage assessment technique using a moving load test and optical sensors was studied to overcome the deficiency of measurement information in bridge maintenance. Continuous displacements by applying the reciprocal theorem to the test can make the assessment simpler and more practical. Numerical and experimental studies were performed to show the efficiency and accuracy of the proposed technique as well as the possibility of a more realistic assessment for large infrastructure. The results showed that the assessed damage levels are quite accurate, and similar to the exact values in actual damage locations, even in the experiments. The proposed technique is useful and practical for both detecting damage locations and damage quantities.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.5 s.122
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• pp.405-414
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• 2007

In recent years, experimental and theoretical studies show that turbulent flows looking disordered have a definite structure produced repetitively with visible order. As a core structure of turbulence, hairpin vertices are believed to play a major role in developing and sustaining the turbulence process in the near wall region of turbulent boundary layers and may be regarded as the simplest conceptual model that can account for the essential features of the wall pressure fluctuations. In this work, fully developed typical hairpin vortices are focused and the associated surface pressure distributions and their corresponding spectra are estimated. On the basis of the attached eddy model, the overall surface pressure spectra are represented in terms of the eddy size distribution. The model is validated by comparison of predicted wavenumber spectra with existing empirical models, the results of direct numerical simulation (DNS) and also spatial correlations with experimental measurements.

• 한국해양학회지
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• v.22 no.1
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• pp.9-18
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• 1987

A number of hydrographic studies and some recent current measurements around Chejudo Island suggest an existence of a clockwise residual flow in the west and north coasts of the island all the year round. On the eastern side of the island the Tsushinma Current flows northward and northeastward. The contribution of tide-induced residual currents to the observed residual. flow around the island was examined here through numerical solution of the two-dimensional nonlinear shallow-water equations. The calculated tide-induced residual currents show a clockwise circulation around the island. Significant residuals of 2-4cms$\^$-1/are confined over sloping bottom topography around t he island and the far-field residuals are negligibly small. The inclusion of a permanent current into the model was also attempted in order to see the effects of the Tsushima Current system on the residual circulation around the is land. It was found that combined effects of tide-induced residuals and the permanent current field associatedwith the Tsushima Current explain qualitatively not only the observed clock wise residuals in the west and north coasts but also the northward flow on the eastern side of the island.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.1
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• pp.53-62
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• 2006

Structural measurements obtained from accelerometers, strain gauges. and tilt meters at Ieodo ocean research station was analyzed. In the acceleration signals, dynamic characteristics of the station were round by using the measured dynamic responses under different wave attacks and were compared with those by numerical analysis. Data from strain gauges and tilt-meters were also analyzed to identify the present state of dynamic response. Effect of wave height on the dynamic characteristics were investigated. The present results and those which will be measured and analyzed later can be used to identify and to assess the state of the station whether it is health or not.

• Industrial Engineering and Management Systems
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• v.7 no.3
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• pp.189-196
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• 2008

This paper proposes a way of designing of a global logistics system for "the international cooperative global complementary production system" (ICGCPS) constructed in ASEAN region. ICGCPS is a global production system with several production bases located in a number of countries. In order to assemble the final products and sell them in the domestic market, each production base produces only special kinds of components and parts with the total demand required all the participating countries, and supplies them to the other production bases each other. In the ICGCPS, there are a number of important decision-making problems such as identifying which countries are suitable to produce specified components and parts, and deciding how to transport components and parts between the production bases. In the initial period of this system, each production base focused on its domestic market so that the final products it produced were sold only in the country where the base was located. Recently, some production bases have expanded sales to overseas markets. Taking this fact into account, we propose a production and transportation planning model in this paper that takes into account the export quantity of the final products, formulating it into a mathematical programming problem. Using this, we propose a way for managing the supply chain processes of the ICGCPS in order to improve performance measurements such as the total lead-time, the inventory quantity at the depot and the average rate of loading. A numerical example is presented to clarify the procedure proposed in this paper.

• Structural Engineering and Mechanics
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• v.40 no.4
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• pp.471-488
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• 2011

The Ting Kau Bridge in Hong Kong is a cable-stayed bridge comprising two main spans and two side spans. The bridge deck is supported by three towers, an end pier and an abutment. Each of the three towers consists of a single reinforced concrete mast strengthened by transverse cables and struts. The bridge deck is supported by four inclined planes of cables emanating from anchorages at the tower tops. In view of the heavy traffic on the bridge, and threats from typhoons and earthquakes originated in areas nearby, the dynamic behaviour of long-span cable-supported bridges in the region is always an important consideration in their design. Baseline finite element models of various levels of sophistication have been built not only to match the bridge geometry and cable forces specified on the as-constructed drawings but also to be calibrated using the vibration measurement data captured by the Wind and Structural Health Monitoring System. This paper further describes the analysis of axle loading data, as well as the generation of random axle loads and simulation of vibrations of the bridge using the finite element models. Various factors affecting the vehicular loading on the bridge will also be examined.

• Wind and Structures
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• v.19 no.3
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• pp.249-270
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• 2014

Through comparing the mean wind profiles observed overland during the passages of four typhoons, and the gradient wind speeds calculated based on the sea level pressure data provided by a numerical model, the present paper discusses, (a) whether the gradient balance is a valid assumption to estimate the wind speed in the height range of 1250 m ~ 1750 m, which is defined as the upper-level mean wind speed, in a tropical cyclone over land, and (b) if the super-gradient feature is systematically observed below the height of 1500 m in the tropical cyclone wind field over land. It has been found that, (i) the gradient balance is a valid assumption to estimate the mean upper-level wind speed in tropical cyclones in the radial range from the radius to the maximum wind (RMW) to three times the RMW, (ii) the super-gradient flow dominates the wind field in the tropical cyclone boundary layer inside the RMW and is frequently observed in the radial range from the RMW to twice the RMW, (iii) the gradient wind speed calculated based on the post-landfall sea level pressure data underestimates the overall wind strength at an island site inside the RMW, and (iv) the unsynchronized decay of the pressure and wind fields in the tropical cyclone might be the reason for the underestimation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.3
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• pp.247-260
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• 2002

This paper presents the design case of the 3-arch tunnel under Daejeon railroad station building. The original construction method was the underpinning method supported by pipe-roof, but it was changed to the mined tunnelling method because of the complex construction condition and the safety problem. This 3-arch tunnel has a width of 28 meters and a height of 10 meters. Overburden is only 23m and the ground around the tunnel is a weathered rock. The allowable settlements for the station building and some railroads are very strict. Accordingly, various measurements for the tunnel stability and the settlement minimization was applied and they were reviewed by 2-D and 3-D numerical analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.3
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• pp.183-197
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• 2004

The introduction of geodetic methods of absolute displacement monitoring in tunnels has significantly improved the value of the measurements. Structurally controlled behavior and influences of an anisotropic rock mass can be determined, and the excavation and support adjusted accordingly. Three-dimensional finite element simulations of different weakness zone properties, thicknesses, and orientations relative to the tunnel axis were carried out and the function parameters were evaluated from the results. The results were compared to monitoring results from Alpine tunnels in heterogeneous rock. The good qualitative correlation between trends observed on site and numerical results gives hope that by a routine determination of the function parameters during excavation the prediction of rock mass conditions ahead of the tunnel face can be improved. Implementing the rules developed from experience and simulations into the monitoring data evaluation program allows to automatically issuing information on the expected rock mass quality ahead of the tunnel.