• The KIPS Transactions:PartC
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• v.8C no.1
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• pp.68-74
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• 2001

This paper mentions a centralized approach based on SNMP protocol and distributed approach based on mobile agent in network management s system. And it presents a few Quantitative models for systematically evaluating those two different approaches. To do this, we propose model m that is applicable under a uniform network environment, and compare network execution times of each paradigms based on parameters from s simulation. The model is then refined to take into account non-uniform networks. We show that it can reduce overall network execution times b by determining the best interaction patterns to perfo$\pi$n network management operations from this model. We believe that the model proposed h here should help us to decide appropriate paradigms and interaction patterns for developing network management applications.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.205-207
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• 2012

무선 센서 네트워크에서 에너지 효율적인 네트워크 구성을 위해 데이터를 수집하는 싱크 노드에 이동성을 적용시킨 모바일 싱크를 이용한 데이터 수집 기법이 활발하게 연구되고 있다. 하지만 최근 모바일 싱크를 적용한 데이터 수집 기법에서는 무선 센서 노드들의 에너지 소모를 분산시켜 네트워크의 수명은 증가시켰지만 고정적인 경로를 기반으로 하여 이벤트 데이터의 신속한 수집이 불가능하거나 이동성을 갖는 모바일 싱크로의 동적 라우팅 패스의 빈번한 설정으로 인해 최적화된 에너지 효율을 제공하지 못한다. 본 논문에서는 이와 같은 문제점을 해결하기 위해 모바일 싱크 기반의 무선 센서 네트워크 환경에서 에너지 효율성을 고려하여 이벤트 데이터를 우선 수집하는 데이터 수집 기법을 제안한다. 제안하는 기법은 특정 이벤트가 발생할 경우, 모바일 싱크의 이동성을 이용하여 특정 이벤트 데이터를 빠르게 수집하며 일반적인 모니터링 데이터의 압축과 전송 주기를 변경함으로써 전반적인 QoS를 향상시킨다. 성능평가 결과, 제안하는 기법은 기존 기법에 비해 이벤트 데이터에 대한 응답시간이 평균 57% 감소하였고, 네트워크의 수명이 평균 19% 증가하였다.

• Journal of Labour Economics
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• v.35 no.2
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• pp.79-115
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• 2012

In the study, we try to get reliable estimates of intergenerational income mobility in Korea. At first, we show that the low estimates of previous studies are mainly due to sample selection problem. The direct estimations using OLS after correcting this problem show higher values than previous estimates. We also compute the attenuation bias by decomposing the variances of earnings into the variances of permanent and transitory components of earnings by the results of the regression. Additionally, we try to estimate the range of intergenerational mobility by comparing the OLS results with the results of the two samples instrumental variable estimation and the three samples instrumental variable estimation. The results of these estimations are a little higher than or similar to OLS results.

• Journal of Satellite, Information and Communications
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• v.2 no.1
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• pp.27-34
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• 2007

A mobile satellite broadcasting service including an ancillary terrestrial component (ATC) takes advantage of the satellite's inherent capability to provide broadcast service over global coverage. We consider the downlink transmission concept using ATC with space=time code (STC) for the mobile satellite communication. We do not regard ATC as simply a repeater but consider it as an antenna for STC. First transmission scenarios for an application of STC are represented. Next, we apply STC in the mobile satellite system including ATC and compare the system performance in the proposed architecture of ATC to that in the conventional structure. The simulation results are compared to the conventional downlink transmission concept for the mobile satellite broadcasting service.

• The KIPS Transactions:PartC
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• v.14C no.2
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• pp.171-178
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• 2007

In mobile ad hoc networks, an application scenario requires mostly group mobility behavior in the mix of group moving nodes and individually moving nodes. The nodes of those applications tend to belong to the movement group with similar movement behavior. Group mobility is one of the good methods to improve scalability, and reduces the protocol overhead. In this paper, we propose the multicast architecture which regards nodes that have equal group mobility in the heterogeneous group mobility network as the single entity with the multiple interfaces and composes multicast tree, The logical cooperative entity-based multicast architecture accommodates the scalability, the multicast tree simplification, and the protocol overhead reduction which arc obtained from the hierarchical multicast architecture, while it maintains the nat multicast architecture for the data transmission. It also prevents the concentration of the energy consumption dispersing data forwarding load into the several ingress/egress nodes. Results obtained through simulations show that logical cooperative entity based multicast protocol with multiple interfaces offers the protocol scalability and the efficient data transmission.

• Convergence Security Journal
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• v.8 no.1
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• pp.35-42
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• 2008

While an information system and administration for an application that a user contacts with raise a head by an important problem, a system approach and methodology for administration are mentioned. Authentication technology of various configuration is used, but non-efficiency by complicated authentication administration and operation inappropriate use are for a successful expansion of various and new business of wire/wireless environment. In addition, under the mobile computer environment with different authentic method each other, it is difficult at all to expect flexible and continuous service. Under the ubiquitous computing environment, It is very important thing plan to research and develop compatibility and the side of variance authentication plan that preservation characteristics are helped. Hereby, This paper look around an requirement items and authority mechanism for the administration and the operation mechanism of the distributed authentication considering expansion possibility of the ubiquitous computing environment not only fixed computing environment but also mobile computing. In future, we expect it by can guide positive participation about distributed authentication technique of the genuine ubiquitous environment.

• Geotechnical Engineering
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• v.10 no.1
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• pp.7-18
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• 1994

A new model for describing the behavior of clay under monotonic and cyclic loading is proposed. This model uses the hyperbolic representation for the stress -strain relationship in overconsolidated state and it describes undrained effective stress path on the basis of the critical state theory. The developed constitutive model by using an energy dissipation equation can describe the behavior of clay in heavily overconsolidated state as u.ell as lightly overconsolidated state under monotonic loading. In order to extend the model for the behavior of clay under cyclic loading, a shift function of undrained stress spacing ratio is introduced in the constitutive model developed for monotonlc loading. A single additional parameter is required to represent the cyclic effect and it can be reasonably deter mined from the test results. The measured behavior in undrained cyclic triaxial tests has been easily and precisely predicted by the newly developed constitutive model.

• Journal of KIISE:Information Networking
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• v.41 no.4
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• pp.167-176
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• 2014

In this paper, we discuss the implementation and experimentations of a new future Internet architecture for mobile-oriented environments, named Mobile Oriented Future Internet (MOFI). The MOFI architecture is featured by the host identifier and local locator for identifier-locator separation, Query-First Data Delivery (QFDD), and Distributed Mapping System (DMS) for identifier-locator mapping control. In the existing study on MOFI, we examined the intra-domain mobility control, the implementation of MOFI over Linux platform, and the performance analysis over the small-scale testbed. In this paper, we describe how to implement the MOFI architecture for inter-domain mobility control by using the OpenFlow and Click Modular Router platform. From the experimentations over the KOREN testbed, we can see that the MOFI scheme can give better performance than the existing Proxy Mobile IP scheme.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.171-171
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• 2017

전산유체역학(CFD: Computational Fluid Dynamics)를 이용한 스마트팜 환경 내부의 정밀 제어 연구가 진행 중이다. 시계열 데이터의 난해한 동적 해석을 극복하기위해, 비선형 모델링 기법의 일종인 인공신경망을 이용하는 방안을 고려하였다. 선행 연구를 통하여 환경 데이터의 비선형 모델링을 위한 Tensorflow활용 방법이 하드웨어 가속 기능을 바탕으로 월등한 성능을 보임을 확인하였다. 그럼에도 오프라인 일괄(Offline batch)처리 방식의 한계가 있는 인공신경망 모델링 기법과 현장 보급이 불가능한 고성능 하드웨어 연산 장치에 대한 대안 마련이 필요하다고 판단되었다. CFD 해석을 위한 Solver로 SU2(http://su2.stanford.edu)를 이용하였다. 운영 체제 및 컴파일러는 1) Mac OS X Sierra 10.12.2 Apple LLVM version 8.0.0 (clang-800.0.38), 2) Windows 10 x64: Intel C++ Compiler version 16.0, update 2, 3) Linux (Ubuntu 16.04 x64): g++ 5.4.0, 4) Clustered Linux (Ubuntu 16.04 x32): MPICC 3.3.a2를 선정하였다. 4번째 개발환경인 병렬 시스템의 경우 하드웨어 가속는 OpenCL(https://www.khronos.org/opencl/) 엔진을 이용하고 저전력 ARM 프로세서의 일종인 옥타코어 Samsung Exynos5422 칩을 장착한 ODROID-XU4(Hardkernel, AnYang, Korea) SBC(Single Board Computer)를 32식 병렬 구성하였다. 분산 컴퓨팅을 위한 환경은 Gbit 로컬 네트워크 기반 NFS(Network File System)과 MPICH(http://www.mpich.org/)로 구성하였다. 공간 분해능을 계측 주기보다 작게 분할할 경우 발생하는 미지의 바운더리 정보를 정의하기 위하여 3차원 Kriging Spatial Interpolation Method를 실험적으로 적용하였다. 한편 병렬 시스템 구성이 불가능한 1,2,3번 환경의 경우 내부적으로 이미 존재하는 멀티코어를 활용하고자 OpenMP(http://www.openmp.org/) 라이브러리를 활용하였다. 64비트 병렬 8코어로 동작하는 1,2,3번 운영환경의 경우 32비트 병렬 128코어로 동작하는 환경에 비하여 근소하게 2배 내외로 연산 속도가 빨랐다. 실시간 CFD 수행을 위한 분산 컴퓨팅 기술이 프로세서의 속도 및 운영체제의 정보 분배 능력에 따라 결정된다고 판단할 수 있었다. 이를 검증하기 위하여 4번 개발환경에서 운영체제를 64비트로 개선하여 5번째 환경을 구성하여 검증하였다. 상반되는 결과로 64비트 72코어로 동작하는 분산 컴퓨팅 환경에서 단일 프로세서 기반 멀티 코어(1,2,3번) 환경보다 보다 2.5배 내외 연산속도 향상이 있었다. ARM 프로세서용 64비트 운영체제의 완성도가 낮은 시점에서 추후 성공적인 실시간 CFD 모델링을 위한 지속적인 검토가 필요하다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.197-200
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• 2008

A GNSS augmentation system provides precise position information using corrected GNSS pseudorange measurements. Common bias errors are corrected by PRC (Pseudorange Correction) between reference stations and a rover. However non-common errors (Ionospheric and Tropospheric noise error) are not corrected. Using position error variance this paper analyzes non-common errors (noise errors) of ionosphere and troposphere wet vapor.