• Journal of Information Processing Systems
• /
• v.13 no.5
• /
• pp.1071-1088
• /
• 2017

For dual-hop multiple-input multiple-output (MIMO) decode-and-forward relaying systems, we propose a selective relaying scheme that uses orthogonal space-time block code (OSTBC) and transmit antenna selection with maximal-ratio combining (TAS/MRC) or vice versa at the first and second hops, respectively. The aim is to achieve an asymptotically identical performance to the dual-hop relaying system with only TAS/MRC, while requiring lower feedback overhead. In particular, we give the selection criteria based on the antenna configurations and the average channel powers for the first and second hops, assuming Rayleigh fading channels. Also, the numerical results are shown for the outage performance comparison between the dual-hop DF relaying systems with the proposed scheme, only TAS/MRC, and only OSTBC.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2022.11a
• /
• pp.32-33
• /
• 2022

팬데믹이후 온라인 커뮤니케이션이 가속화되면서 개인화의 현상이 두드러지고 있는 가운데 도시의 정보시스템의 많은 부분들이 디지털 트윈으로 가고 있다. 때문에 오프라인의 사이니지 등은 이미 개인화에 익숙한 사용자에게 만족도나 낮고 이를 반영하여 다양화시키기에는 많은 예산이 소요되며 물리적 한계가 있다. 본 연구는 사용자 중심 프로세스의 기술 융합 연구를 통해 이러한 오프라인 정보 표기와 전달 등의 문제점을 해결하고자 하였다. 본 논문은 이러한 목적을 가지고 개인화 기반 도시 인포메이션 시스템의 물리적 사이니지와의 정보 데이터 간의 상호운용을 실현화하는 연구를 진행하였다. QR 코드 등 비쥬얼 코드-기반 기존의 인터랙션 기술들의 장점을 활용하고 AI 기반의 필터 시스템을 도입하여 도시 복합정보데이터와 개인데이터와의 연동 및 변별 시스템을 설계하여 AR서비스 환경을 디자인 하였다. 개인화 서비스를 위하여 'Personal Data'와 타사용자의 'Feedback Data를 기존의 클라우드 정보와 AI-Analytic-Process에 개입시켜서 개인화 기반의 서비스 시스템 모델로 개발하였다.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1995.05b
• /
• pp.1027-1032
• /
• 1995

To develop operation scenarios of KT-2 tokamak, 3 operation modes(OH, high ${\beta}$ and high bootstrap) deduced from zero dimensional steady-state power balance are examined with TSC(Tokamak Simulation Code) time-dependent transport .ode. Plasma profiles are evaluated self consistently during simulations and plasma shapes are maintained by feedback control on PF coil currents. Simulations show operation modes which are typical of KT-2 expected discharges are compatible with the KT-2 PF system design specifications[1].

• The Journal of Korean Association of Computer Education
• /
• v.18 no.6
• /
• pp.13-22
• /
• 2015

The purpose of this research is to develop scratch code analysis system about scratch project for assessment in computational thinking(CT) education. Recently, scratch which is event-based language is used actively in K-12 SW education but it is difficult to understand the structure of scratch project. Therefore, in this study, we developed the system that students can use it to debug their scratch project and teachers can give feedback to students or evaluate students' projects through this system, and verified its usability. We are able to use this system to facilitate students' debugging process and to evaluate students' project in K-12 SW education.

• Nuclear Engineering and Technology
• /
• v.12 no.4
• /
• pp.267-273
• /
• 1980

The quasistatic approximation is incorporated in HEXKIN, a 2-group, 2-dimensional reactor kinetics code specially developed for a hexagonal lattice-type reactor. The code allows maximum 15 delayed neutron groups, 279 lattice points, and 500 different driving functions to be able to initiate perturbation at each lattice point. Reactivity feedback due to power-dependent fuel temperature change is also involved. To check the accuracy of the code, a result of numerical experiment is compared with the measurement at the Savannah River Laboratory. The experiment was specifically designed to emphasize delayed neutron holdback. The calculated flux tilts agree with the measured flux tilts within the small uncertainty of the measurements.

• Journal of The Korean Astronomical Society
• /
• v.47 no.3
• /
• pp.87-98
• /
• 2014

We develop a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order Lagrangian perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature uctuations at the initial particle position are assigned according to the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We test the code in several standard cases such as one-dimensional Riemann problems, Kelvin-Helmholtz, and Sedov blast wave instability. Star formation on the galactic disk is investigated to check whether the Schmidt-Kennicutt relation is properly recovered. We also study global star formation history at different simulation resolutions and compare them with observations.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.7C
• /
• pp.666-674
• /
• 2005

A hybrid multicarrier CDMA/FDM system with a truncated adaptive transmission scheme is analyzed in forward link based on the feedback information from the mobile station. In the single cell environment, the prop(mea scheme outperforms the adaptive FH/DS system as well as the MC DS/CDMA system when orthogonal signature sequences are used. In the multiple cell environment also, the proposed scheme has better performance characteristics than the adaptive FH/DS system when orthogonal and random codes are used as spreading sequences.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.5C
• /
• pp.265-275
• /
• 2011

In this paper, we propose a Multi-Strata Space Time Code(MSSTC) for MIMO retransmissions. Since MSSTC is constructed by superimposing two OSTBC matrices, there are no intra-stratum interferences, but there exist inter-strata interferences. In MIMO retransmission environment, the transmitter switches adaptively the phases of strata at each transmission by using 1-bit feedback sent from the receiver in order to reduce the inter-strata interferences efficiently. We also propose a power allocation scheme between strata to improve error performance. Simulation results show that the proposed scheme achieves better performance than other conventional schemes.

• Nuclear Engineering and Technology
• /
• v.54 no.7
• /
• pp.2670-2689
• /
• 2022

STREAM - a lattice transport calculation code with method of characteristics for the purpose of light water reactor analysis - has been developed by the Computational Reactor Physics and Experiment laboratory (CORE) of the Ulsan National Institute of Science and Technology (UNIST). Recently, efforts have been taken to develop a photon module in STREAM to assess photon heating and the influence of gamma photon transport on power distributions, as only neutron transport was considered in previous STREAM versions. A multi-group photon library is produced for STREAM based on the ENDF/B-VII.1 library with the use of the library-processing code NJOY. The developed photon solver for the computation of 2D and 3D distributions of photon flux and energy deposition is based on the method of characteristics like the neutron solver. The photon library and photon module produced and implemented for STREAM are verified on VERA pin and assembly problems by comparison with the Monte Carlo code MCS - also developed at UNIST. A short analysis of the impact of photon transport during depletion and thermal hydraulics feedback is presented for a 2D core also from the VERA benchmark.

• Nuclear Engineering and Technology
• /
• v.54 no.5
• /
• pp.1813-1824
• /
• 2022

This paper shows the verification work of SARAX code system in the reactor core transient calculation based on the simplified EBR-II Benchmark. The SARAX code system is an analysis package developed by Xi'an Jiaotong University and aims at the advanced reactor R&D. In this work, a neutron-photon coupled power calculation model and a spatial-dependent reactivity feedback model were introduced. To verify the models used in SARAX, the EBR-II SHRT-45R test was simplified to an ULOF transient with an input flowrate change curve by fitting from reference. With the neutron-photon coupled power calculation model, SARAX gave close results in both power fraction and peak power prediction to the reference results. The location of the hottest assembly from SARAX and reference are the same and the relative power deviation of the hottest assembly is 2.6%. As for transient analysis, compared with experimental results and other calculated results, SARAX presents coincident results both in trend and absolute value. The minimum value of core net reactivity during the transient agreed well with the reported results, which ranged from -0.3$ to -0.35$. The results verify the models in SARAX, which are correct and able to simulate the in-core transient with reliable accuracy.