• 대한원격탐사학회지
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• 제36권2_1호
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• pp.139-153
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• 2020

본 연구는 전산유체역학(computational fluid dynamics, CFD) 모델을 이용하여 도시 지역에 위치한 도시 대기측정소의 대기질 대표성을 평가하고, 측정 목적에 따른 측정소 위치 선정에 대한 방법론을 제시하였다. 이를 위하여 대상 지역을 은평구 도시대기측정소(air quality monitoring system, AQMS)로 선정하였고 두 가지배출 시나리오(대기오염물질이 배경에서 수송되는 경우, 도로에서 배출되는 경우에 대한 수치 실험을 수행하였다. 대기 흐름은 대상 지역의 북동쪽과 남동쪽에 위치한 산악 지형의 영향을 크게 받고, 건물이 밀집한 지역에서는 2차 순환에 의한 복잡한 흐름이 나타났다. 대기오염물질이 배경에서 수송되는 경우에, 대기오염물질 분포는 지형(산)의 영향을 크게 받았다. 선오염(도로)에서 배출되는 경우에는 도로 위치와 건물 분포/높이 영향을 크게 받았다. 은평구 AQMS 위치에서 수치 모의된 농도는 지형보다 건물의 영향이 크게 나타났다. 배출 시나리오 결과를 이용하여 은평구 AQMS가 대상 지역의 대기질을 대표할 수 있는지에 대하여 평가하였다. 은평구 AQMS 위치에서 모의되는 농도는 두 시나리오의 층 평균 농도와 유사한 크기를 가지고 있어 측정 높이에서의 대기질을 대표할 수 있다고 판단된다. 대기오염물질은 시·공간적으로 비균질적이기 때문에 측정 목적에 따른 고도 별 측정망 위치 선정에 대한 가이드라인을 제시하였다. 측정망을 고농도가 나타나는 지역(hot spot)과 청정 지역(clean zone), 각 층의 평균 농도가 나타나는 지역(average zone), 건물/지형에 가로막혀 흐름의 유입과 유출이 활발하지 않는 안락처 지역(shelter zone), 외부에서 수송되는 배경 농도를 대표할 수 있는 지역(equi-background zone) 등 총 5가지로 분류하여 조사하였다.

• 토지주택연구
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• 제8권1호
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• pp.13-22
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• 2017

In this study, triggering mechanism of ground sinking was analyzed through groundwater flow analysis on the basis of a case of the ground sinking occurred in Yongsan in 2015. The results of geotechnical investigation performed before and after the ground sinking were analyzed for the accurate understanding of geological features in the study area. The numerical groundwater flow analysis was performed to evaluate the influence of the flow behavior from the surrounding area toward the excavated site using software of Visual MODFLOW. As a result, it was found from the geotechnical analysis that the strata of sedimentary layer along the sunken area in the vertical direction was mixed significantly after the ground sinking compared with the status of the soil condition before the ground sinking. Piping was occurred at the toe of cut-off wall in the sandy gravel layer, and this phenomenon was predicted by the numerical flow analysis. Sequential ground displacement scenario of the ground sinking was derived from the geotechnical in situ test and numerical flow analysis performed in this study.

• Journal of Information Processing Systems
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• 제18권3호
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• pp.443-456
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• 2022

An efficient and reasonable resource allocation strategy can greatly improve the service quality of Internet of Vehicles (IoV). However, most of the current allocation methods have overestimation problem, and it is difficult to provide high-performance IoV network services. To solve this problem, this paper proposes a network resource allocation strategy based on deep learning network model DDQN. Firstly, the method implements the refined modeling of IoV model, including communication model, user layer computing model, edge layer offloading model, mobile model, etc., similar to the actual complex IoV application scenario. Then, the DDQN network model is used to calculate and solve the mathematical model of resource allocation. By decoupling the selection of target Q value action and the calculation of target Q value, the phenomenon of overestimation is avoided. It can provide higher-quality network services and ensure superior computing and processing performance in actual complex scenarios. Finally, simulation results show that the proposed method can maintain the network delay within 65 ms and show excellent network performance in high concurrency and complex scenes with task data volume of 500 kbits.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.89-92
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• 2000

In this paper, we consider the interworking methods for Internet layer 3 protocols. The legacy protocol for Internet is IPv4(IP version 4). The ability of IPv4 is not enough for modern real time multimedia communication services. So IPv6(IP version 6) protocol was suggested to resolve the problems of IPv4. 6Bones(IPv6 Backbones) have also constructed from 1996 in many countries. The 6Bones should be interoperatable to the legacy internet. To support all data services including voice and video, IP protocol should be enhanced because the characteristics of modern network services are requiring QoS(Quality of Service) functions, plug and play, security, mobility and so on. So a new IP protocol, IPv6, has been developing to meet the requirements. In this paper, some migration methods for internets are described. We first describe the protocol compatibility problems and suggest some solutions and scenario to solve the problems.

• 대한임베디드공학회논문지
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• 제9권6호
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• pp.353-360
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• 2014

In cognitive radio networks (CRNs), SU (secondary user)'s transmissions are frequently disrupted by PU (primary user)'s transmission. Therefore SU expereiences consecutive retransmission timeout and its exponential backoff, and subsequently, the TCP of SU does not proceed with the transmission even after the disruption is over or the SU succeeds to hold an idle channel. In order to solve this problem, we propose a cross-layer approach called TCP-Freeze-CR. Moreover we consider a practical scenario where either secondary transmitter (ST) or secondary receiver (SR) detects PU's transmission, which results in the need of spectrum synchronization mechanism. All of our proposals are implemented and verified with a real CRN testbed consisting of 6 software radios called USRP. The experimental results illustrate that standard TCP suffers from significant performance degradation and show that TCP-Freeze-CR greatly mitigates the degradation.

• ETRI Journal
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• 제38권5호
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• pp.934-940
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• 2016

In this paper, secure multicasting with the help of cooperative decode-and-forward relays is considered for the case in which a source securely sends a common message to multiple destinations in the presence of a single eavesdropper. We show that the secrecy rate maximization problem in the secure multicasting scenario under an overall power constraint can be solved using semidefinite programing with semidefinite relaxation and a bisection technique. Further, a suboptimal approach using zero-forcing beamforming and linear programming based power allocation is also proposed. Numerical results illustrate the secrecy rates achieved by the proposed schemes under secure multicasting scenarios.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.223-230
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• 1999

The seismic damage assessment to the postulated earthquake is attempted for the buildings in the model district of Seoul City. The capacity spectrum method is employed in which the vulnerability functions are expressed as functions of the spectral displacement. the database of the building stock is constructed and managed using Geographic Information System software. The model district is selected to represent the typical structural and residential characteristics of Seoul City The structural properties were collected from the design documents. The field inspections were carried out to find out the current status of the building. They are classified into 11 structural types. The fragility curves in HazUS are employed, The ground motions from the postulated earthquakes are simulated using the Boor's methods, The surface soil in the district is classified into 3 profiles using the depth as the parameter. The one-dimensional wave propagation method is used to calculate he filtered ground motion through surface soil layer. The average spectrum of this sample time histories is used as the demand curves. The calculated results are expressed in maps using GIS software ArcView 3.0a

• ETRI Journal
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• 제44권6호
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• pp.925-935
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• 2022

In this study, we propose a limited feedback-based frequency divided group beamforming with sparse space-frequency transmit diversity coded orthogonal frequency division multiplexing (OFDM) system for ultrareliable low latency communication (URLLC) scenario. The proposed scheme has several advantages over the traditional hybrid beamforming approach, including not requiring downlink channel state information for baseband precoding, supporting distributed multipoint transmission structures for diversity, and reducing beam sweeping latency with little uplink overhead. These are all positive aspects of physical layer characteristics intended for URLLC. It is suggested in the system to manage the multipoint transmission structure realized by distributed panels using a power allocation method based on cooperative game theory. Link-level simulations demonstrate that the proposed scheme offers reliability by achieving both higher diversity order and array gain in a nonline-of-sight channel of selectivity and limited spatial scattering.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2007년도 추계학술발표대회
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• pp.1003-1005
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• 2007

WCDMA서비스가 본격적으로 활성화됨에 따라 WCDMA와 WLAN을 동시에 연결할 수 있는 단말들의 출시도 늘어나고 있다. Multi-home은 Transport Layer에서 이러한 연동을 지원하게 해주는 기능이다. 본 논문에서는 Multi-home을 지원하는 TCP-MH와 SCTP 프로토콜을 WCDMA-WLAN 연동 시나리오에 적용시켜 분석하였다. SCTP는 TCP-MH에 비해 폭넓은 활용도를 보여주었다.

• 한국습지학회지
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• 제17권3호
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• pp.273-282
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• 2015

본 연구는 RCP 4.5와 RCP 8.5 기후변화 시나리오를 이용하여 서울시 온량지수 변화를 추정하였으며, 이에 따른 적응 가능한 식물종을 제안하였다. 기후변화 시나리오에 따라 서울시의 온량지수 변화의 차이는 있었으나 냉온대 남부림에서 난온대림으로 변화할 것으로 예상된다. 2010년부터 2099년까지 서울시 온량지수 분포변화를 예측한 결과에 따른 적응 가능한 식물종은 교목층에 졸참나무, 굴참나무, 소나무, 상수리나무, 때죽나무, 곰솔 등 6종이었으며, 관목층에는 쥐똥나무, 조록싸리, 개옻나무, 작살나무, 산딸기, 찔레꽃, 초피나무 등 7종이었고, 초본층은 주름조개풀, 고사리, 닭의 장풀 등 3종, 덩굴성식물에는 청미래덩굴, 댕댕이덩굴, 담쟁이덩굴, 인동, 계요등, 노박덩굴, 사위질빵, 멍석딸기, 마, 으름, 마삭줄 등, 등 11종을 포함하여 총 27종이 공통적으로 기후변화 시나리오에 따라 온량지수의 변화에도 적응 가능할 것으로 예상된다.