• 천문학회지
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• 제27권1호
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• pp.13-29
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• 1994

We have constructed a 3-dim hydrodynamics code called BTSPH. The fluid dynamics part of the code is based on the smoothed particle hydrodynamics (SPH), and for its Poisson solver the binary tree (BT) scheme is employed. We let the smoothing length in the SPH algorithm vary with space and time, so that resolution of the calculation is considerably enhanced over the version of SPH with fixed smoothing length. The binary tree scheme calculates the gravitational force at a point by collecting the monopole forces from neighboring particles and the multipole forces from aggregates of distant particles. The BTSPH is free from geometric constraints, does not rely on grids, and needs arrays of moderate size. With the code we have run the following set of test calculations: one-dim shock tube, adiabatic collapse of an isothermal cloud, small oscillation of an equilibrium polytrope of index 3/2, and tidal encounter of the polytrope and a point mass perturber. Results of the tests confirmed the code performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권7호
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• pp.1293-1310
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• 2011

A simple modification of well known Low Energy Adaptive Clustering Hierarchy (LEACH) protocol is proposed to exploit cooperative diversity. Instead of selecting a single cluster-head, we propose M cluster-heads in each cluster to obtain a diversity of order M. The cluster-heads gather data from all the sensor nodes within the cluster using same technique as LEACH. Cluster-heads transmit gathered data cooperatively towards the destination or higher order cluster-head. We propose a code combining based cooperative diversity protocol which is similar to coded cooperation that maximizes the performance of the proposed cooperative LEACH protocol. The implementation of the proposed cooperative strategy is analyzed. We develop the upper bounds on bit error rate (BER) and frame error rate (FER) for our proposal. Space time block codes (STBC) are also a suitable candidate for our proposal. In this paper, we argue that the STBC performs worse than the code combining cooperation.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권8호
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• pp.491-494
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• 2000

A scheme is proposed for measuring similarities between the binary pulse signals in the pulse-code modulation using the Integra-Normalizer. The Integra-Normalizer provides a better interpretation of the relationship between the pulse signals by removing redundant codes, which maps all possible observed signals to one of the codes to be received with relative similarities between each pair of compared signals. The proposed method provides better error tolerance than L2 metric, such as Hamming distance, since the distances between pulse signals are measured not useful for the time-delay detection in the pulse-code modulation.

• Nuclear Engineering and Technology
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• 제28권3호
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• pp.320-330
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• 1996

The streaming rays(SR) method is improved and extended to multigroup, anisotropic scattering, and three-dimensional angular space(x-y-z(infinite))problems. This method is applied to the shielding problems in which the ray effect occurs seriously. For verification, the results of MORSE-CG code are used as reference solution and the results of TWODANT code are compared. The results show that solutions of the SR method are much better than those of the TWODANT code and are in good agreement with those of the MORSE-CG code. Also, to reduce computing time, two acceleration algorithms are implemented in the SR method : the standard coarse-mesh rebalance and a new angular two-grid acceleration.

• Journal of electromagnetic engineering and science
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• 제6권2호
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• pp.83-91
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• 2006

In this paper, we develop space-time(ST) Rake receivers for Time Division Synchronous Code Division Multiple Access(TD-SCDMA) base stations(BS). The beamforming of BS transforms the uplink MIMO channel space into many sub-sectors' channels to be nearly orthogonal, thus, well established 1-D Rake technology can be used to TD-SCDMA base station to construct ST Rake, which simplified the system's implementation as well as enlarged users' capacity by the beamforming. The construction and capacity of MIMO sub-sectors by multi-beamforming have been presented. The proposed ST Rake algorithm include the multi-beamforming algorithm for MIMO sub-sectors and classical 1-D Rake algorithm. The calculating formulas for interference plus noise ratio(SINR) and bit error rate(BER) have been derived. Simulations verify that the proposed ST Rake receiver for BS is effective, and the BS systems can get higher system capacity and can be of better performance than presented TD-SCDMA systems.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.843-847
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• 2005

The development of distributed application in the standardized CORBA(Common Object Request Broker Architecture) environments reduces the developing time and maintaining cost of the systems. Because of these advantages, the development of application is being progressed in the several fields using the CORBA environments. The programmers in the CORBA environments usually develop the application programs using the CORBA IDL(Interface Definition Language). The IDL files are compiled by IDL compiler and translated into the stubs and skeleton codes which are mapped onto particular target language. The stubs produced by IDL compilers processes the marshaling a data into message buffer. Before a stub can marshal a data into its message buffer, the stub must ensure that the buffer has at least enough free space to contain the encoded representation of the data. But, the stubs produced by typical IDL compilers check the amount of free buffer space before every atomic data is marshaled, and if necessary, expand the message buffer. These repeated tests are wasteful and incidence of overheads, especially if the marshal buffer space must be continually expanded. Thus, the performance of the application program may be poor. In this paper, we suggest the way that the stub code is maintain the enough free space before marshaling the data into message buffer. This methods were analyzes the overall storage requirements of every message that will be exchanged between client and server. For these analysis, in the Front End of compiler has maintain the information that the storage requirements and alignment constraints for data types. Thus, stub code is optimized and the performance of application program is increased.

• 한국항행학회논문지
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• 제15권6호
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• pp.1068-1074
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• 2011

본 논문에서는 고속 무선 데이터 전송에서 높은 데이터 전송의 신뢰성을 얻기 위해 MIMO(multi-input multi-output) 기술 중 하나인 시공간 블록 코드(STBC: space-time block codes)와 채널코딩 중 하나인 컨볼루션 코드(convolution code)를 연계한 시스템을 제안한다. 또한 이 시스템은 전송한 데이터를 복원하며 높은 시스템 이득을 가지기 위해 수정된 비터비 알고리즘을 사용한다. 제안한 시스템은 시공간 블록 코드와 컨볼루션 코드를 연계하였기 때문에 시스템의 복잡도는 다소 높지만 STBC의 최대 다이버시티 이득과 컨볼루션 코드의 높은 부호화 이득을 동시에 얻을 수 있는 큰 장점이 있다. 수정된 비터비 알고리즘은 기존의 비터비 알고리즘과 달리 브랜치 매트릭스를 구하기 위해 해밍 거리를 사용하지 않고 수신 심볼과 레퍼런스 심볼 사이의 유클리디안 거리를 사용한다. 제안한 시스템을 시뮬레이션 한 결과 기존의 시스템보다 7.5 dB(STBC 2Tx-2Rx $BER=10^{-3}$ )의 성능이 향상됨을 확인 할 수 있었다. 이 결과를 통해 STBC와 컨볼루션 코드를 연계할 때 본 논문에서 제안한 알고리즘을 사용하면 향상된 전송 신뢰성과 전송 효율로 데이터를 전송 할 수 있다.

• 한국항공우주학회지
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• 제35권8호
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• pp.685-692
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• 2007

본 연구에서는 헬리콥터 하중 해석을 위한 통합해석코드에서 사용되는 에어포일의 공력 성능 테이블 작성 자동화를 위한 GUI 프로그램을 개발하였다. 개발 후 상용화를 위해 PC환경에서 사용이 보편화 되어 있는 윈도우 운영체제 기반으로 프로그램을 개발하였다. 또한, 별도의 과정을 거치지 않고도 계산 과정 및 생성된 격자 표시등의 결과를 확인할 수 있는 후처리 기능을 포함하여 사용자의 편의를 도모하였다. 기 검증된 기존의 전산유체역학 코드를 기본으로 하여 다양한 받음각과 마하수 영역에서 공력해석이 자동적으로 수행되도록 하였으며, 계산 격자는 에어포일 표면 좌표가 입력되면 자동으로 생성되도록 하였다. FORTRAN 으로 작성된 전산유체역학 코드를 별도의 변환 과정 없이 C++ 기반의 GUI 프로그램과 연동시키기 위하여 Mixed-Language 기법을 사용하였다.

• 한국항행학회논문지
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• 제15권6호
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• pp.1053-1058
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• 2011

본 논문에서는 비정형 궤도를 따라 이동하며 통신하는 비행체들 간의 데이터 전송 신뢰성을 보장하기 위해 컨볼루션 코드를 연접한 연접 단일 안테나 다이버시티 시스템을 제안하고 이 시스템의 성능을 분석하였다. 제안한 시스템은 단일 안테나를 사용하면서도 다이버시티 이득을 얻을 수 있고 컨볼루션 코드를 연접하였기 때문에 부호화 이득 또한 동시에 얻을 수 있다. 제안한 시스템의 비트 오율 성능(BER: bit error rate)을 시뮬레이션하여 컨볼루션 코드와 비교한 결과 BER $10^{-4}$에서 약 9.5dB 우수하였고, 최대 다이버시티 이득을 갖는 시공간 블록코드와 비교한 결과 BER $10^{-3}$에서 약 14dB 우수함을 확인 하였다. 마지막으로 부호화 이득과 다이버시티 이득을 동시에 갖는 시공간 트렐리스 코드와 그 성능을 비교하였을 때 $10^{-5}$의 BER에서 약 4dB 우수하였다. 따라서 비정형 궤도를 따라 이동하며 통신하는 비행형 에어노드간의 신뢰성 있는 통신을 위해서는 연접 단일 안테나 다이버시티 시스템의 적용이 필요하다.

• 대한임베디드공학회논문지
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• 제14권2호
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• pp.103-111
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• 2019

The IoT-driven large-scaled systems consist of connected things with on-chip executable embedded software. These light-weighted embedded things have limited hardware space, especially small size of on-chip flash memory. In addition, on-chip embedded software in flash memory is not easy to update in runtime to equip with latest services in IoT-driven applications. It is becoming important to develop light-weighted IoT devices with various software in the limited on-chip flash memory. The remote instruction execution in cloud via IoT connectivity enables to provide high performance software execution with unlimited software instruction in cloud and low-power streaming of instruction execution in IoT edge devices. In this paper, we propose a Cloud-IoT asymmetric structure for providing high performance instruction execution in cloud, still low power code executable thing in light-weighted IoT edge environment using remote instruction execution. We propose a simulated approach to determine efficient partitioning of software runtime in cloud and IoT edge. We evaluated the instruction cloudification using remote instruction by determining the execution time by the proposed structure. The cloud-connected instruction set simulator is newly introduced to emulate the behavior of the processor. Experimental results of the cloud-IoT connected software execution using remote instruction showed the feasibility of cloudification of on-chip code flash memory. The simulation environment for cloud-connected code execution successfully emulates architectural operations of on-chip flash memory in cloud so that the various software services in IoT can be accelerated and performed in low-power by cloudification of remote instruction execution. The execution time of the program is reduced by 50% and the memory space is reduced by 24% when the cloud-connected code execution is used.