• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.17-23
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• 2006

In this paper, Adjacent Channel Power Ratio (ACPR) of wireless Orthogonal Frequency Division Multiplexed (OFDM) system interconnected with Radio over Fiber (RoF) link is analyzed for broadband convergence network applications. Unlike previous results, ACPR of the total link, which is involved with Radio Frequency (RF) amplifier as well as ROF link, at 5.8 GHz in IEEE 802.11a environment is simulated and compared at both system ends.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1087-1094
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• 2010

With recent growth of population and industry, urban development grows into grand scheme of excavation and construction in urban area. As the development progress advanced, the developments get large and deepen. With a progress of technology development in geotechnical engineering in Korea, most our grand scheme of projects follows great progress. On the other hand, some excavation in construction site caused direct or indirect event that affects the adjacent or surrounding structures by excavation from time to time. This event usually happens around residential and commercial area where underground tunnel, subway station, commercial building, and high-rises excavation site is, could lead great damage on economy as well as personal injury or human casualties. In order to prevent this event, the study has to be done with analysis on various events of excavation and its cause. In this paper, the research has collected the various excavation events and their causes to analyze on each site and event to define emphasis on surrounding environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.11
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• pp.2923-2931
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• 1996

In this paper, the symbol error probability for orthogonal frequency division multiplexing (OFDM) in the multipath fading environment is obtained analytically. In the analysis, OFDM signals with and without the guard interval are considered, and the two-ray fading model is used for the multi-path fading channel. From the analysis results, it is found that the adjacent subchannel interfernce increases the symbol error rate when the guard interval is not employed or shorter than the length of the delay. It is also shown that the adjacent subchannel interference is a Gaussian random variable and its variance depends on the subchannel location and the number of subchannels. Finally, it is found that the variance of the subchannel interference also increases as the power of the signal increases for the OFDM with insufficient guard interval, yieldin an irreducible error at high signal to noise ratio.

• KIEAE Journal
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• v.9 no.1
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• pp.61-68
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• 2009

In this study, computer simulation program was using to identify the effects of road traffic noise propagation depending on the road types which are very variable in dense city. To achieve this goal, the roads should adjacent to housing complex were categorized into 7 types and propagation noise level should predicted then after simulation of noise exposure population calculation are carried out. Followings the results. First, the road types producing the higher noise level are R1, R2, R3 and R7. The lowest one is R6. And R4, R5 showed that some amount of noise level reduction. Second. the R6 road type which is tunnel shaped showed the highest noise level reduction in vertical distance gap. Last, the order of noise exposure population ratio is R1>R2>R7 and R6 showed the lowest.

• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.364-371
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• 2012

Currently, CMMB(China Mobile Multimedia Broadcasting) and the conventional analog TV broadcasting have transmitted by using UHF(Ultra High Frequency : 474MHz~754MHz) band. Normally, the transmission power of the digital TV broadcasting is lower than the conventional analog TV broadcasting to protect the reception quality of the conventional analog TV broadcasting. The reception sensitivity of CMMB receiver has severely deteriorated due to adjacent the conventional analog TV broadcasting signals which called ACI (Adjacent Channel Interference). To improve the reception sensitivity of a CMMB receiver on ACI environment, this paper proposed a simple method which is tuning a cut off frequency of LPF (Low Pass Filter). From the experiment, the reception sensitivity of CMMB receiver was improved as 11.3dB.

• Structural Engineering and Mechanics
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• v.51 no.2
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• pp.277-297
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• 2014

Since the isolation bearings undergo large displacements in base-isolated structures, impact with adjacent structures is inevitable. Therefore, in this investigation, the effect of impact on seismic response of isolated structures mounted on double concave friction pendulum (DCFP) bearings subjected to near field ground motions is considered. A non-linear viscoelastic model of collision is used to simulate structural pounding more accurately. 2-, 4- and 8-story base-isolated buildings adjacent to fixed-base structures are modeled and the coupled differential equations of motion related to these isolated systems are solved in the MATLAB environment using the SIMULINK toolbox. The variation of seismic responses such as base shear, displacement in the isolation system and superstructure (top floor) is computed to study the impact condition. Also, the effects of variation of system parameters: isolation period, superstructure period, size of seismic gap between two structures, radius of curvature of the sliding surface and friction coefficient of isolator are contemplated in this study. It is concluded that the normalized base shear, bearing and top floor displacement increase due to impact with adjacent structure. When the distance between two structures decreases, the base shear and displacement increase comparing to no impact condition. Besides, the increase in friction coefficient difference also causes the normalized base shear and displacement in isolation system and superstructure increase in comparison with bi-linear hysteretic behavior of base isolation system. Totally, the comparison of results indicates that the changes in values of friction coefficient have more significant effects on 2-story building than 4- and 8-story buildings.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.71-80
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• 2013

Before and after the test constructions, and after an 11-month hiatus from the pilot pile installations, the in-situ tests (CPT, SPT) were carried out at the ground adjacent to the noise- and vibration-free screw concrete piles installed by 2 kinds of construction methods (i.e., the toe-jetting shoe type, the pre-digging type). In the toe-jetting shoe type construction methods, after construction, the soil strength within 3.5D (where, D = pile diameter) from the pile center decreased greatly by about 46% of the original ground and, after an 11-month hiatus, a strength recovery adjacent to the piles appeared about 71% of the original ground. In the pre-digging type construction methods, a strength recovery adjacent to the piles appeared 100% of the strength of the original ground.

• Journal of the Korean Geotechnical Society
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• v.22 no.2
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• pp.19-28
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• 2006

Long-term field observations were performed in three excavation sites in order to investigate the displacement behavior of adjacent ground during overall excavation procedure, where the depths of deep excavations were 15 m$\∼$29 m. In this study, ground settlements and lateral displacements of braced wall measured during installation of retaining wall and removal of bracing were specially focused to evaluate the behavior quantitatively according to three-stage-divided procedure, i.e. pre-excavation, main excavation, and removal of bracing. Through field measurements on three excavation sites, lateral displacements induced during removal of bracing are approximate to 40$\%$ of the amount found during main excavation stage and additional adjacent ground deformation during post-excavation procedure ranges from 18$\%$ to 33$\%$ of that found during main excavation stage, based on the settlement volume. In conclusion, it was quantitatively identified in this study that the deformations of adjacent ground during pre- and post-excavation stage were not negligible.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.121-131
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• 2007

This study is to investigate the damage assessment of adjacent structures due to excavation in urban environment. Model tests were carried out for 2 story masonry building and frame structures in various shapes and locations. The damage level of adjacent structures were very differently estimated in accordance with the shape ratio (L/h) of structures, construction stages, and various locations. Therefore the most weak part (bay) of structure must be heavily instrumented and monitored in more details at early stage of constructions. The progressive crack development mechanism at various construction stages was revealed through model tests and crack size indicated more conservative side of damage level on the damage level graph.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.863-870
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• 2022

Unsatisfactory urban walking environment stresses urban residents, and may cause mental illness and chronic diseases by reducing walking activities. Therefore, establishing a high-quality walking environment that can promote walking activities in urban residents has emerged as an important issue. The walking environment consists of various components, such as trees, stairs, streetlights, benches, signs, fences, and facilities, and it is essential to understand which components and their settings act as satisfiers or dissatisfiers for pedestrians, to create a better quality walking environment. Therefore, this study investigated pedestrian satisfaction and dissatisfaction as a function of various environmental components through a survey using walking environment images. The results revealed that most of the walking environment components except the braille block and treezone exhibited significant correlations with pedestrian satisfaction. Particularly, safety-related component (e.g., adjacent roads, parked cars, traffic cushions, and car separation), and landscape-related components (e.g., trees and green), as well as the material settings of landscape facilities (e.g., wooden fences, benches, stairs, and walkway surfaces) correlated with pedestrian satisfaction. The results of this study can contribute to the extraction of useful features to evaluate pedestrian satisfaction as a function of the walking environment. The research outcome is expected to assist in the effective arrangement of walking environment components and their settings, which will ultimately contribute to significantly satisfactory walking environment and encourage walking activities.