• Nuclear Engineering and Technology
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• 제37권6호
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• pp.587-594
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• 2005

In an effort to develop a thermal-hydraulic (TH) safety analysis code for Gas-cooled Reactors (GCRs), the MARS code, which was primarily developed for TH analysis of water reactor systems, has been extended here for application to GCRs. The modeling requirements of the system code were derived from a review of major processes and phenomena that are expected to occur during normal and accident conditions of GCRs. Models fur code improvement were then identified through a review of existing MARS code capability. Among these, the following priority models necessary fur the analysis of limiting high and low pressure conduction cooling events were evaluated and incorporated in MARS-GCR/V1 : 1) Helium (He) and Carbon Dioxide ($CO_2$) as main system fluids, 2) gas convection heat transfer, 3) radiation heat transfer, and 4) contact heat transfer models. Each model has been assessed using various conceptual problems for code-to-code benchmarks and it was demonstrated that MARS-GCR/V1 is capable of capturing the relevant phenomena. This paper describes the models implemented in MARS-GCR/V1 and their verification and validation results.

• Journal of Communications and Networks
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• 제10권1호
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• pp.5-9
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• 2008

Researchers have investigated many upper bound techniques applicable to error probabilities on the maximum likelihood (ML) decoding performance of turbo-like codes and low density parity check (LDPC) codes in recent years for a long codeword block size. This is because it is trivial for a short codeword block size. Previous research efforts, such as the simple bound technique [20] recently proposed, developed upper bounds for LDPC codes and turbo-like codes using ensemble codes or the uniformly interleaved assumption. This assumption bounds the performance averaged over all ensemble codes or all interleavers. Another previous research effort [21] obtained the upper bound of turbo-like code with a particular interleaver using a truncated union bound which requires information of the minimum Hamming distance and the number of codewords with the minimum Hamming distance. However, it gives the reliable bound only in the region of the error floor where the minimum Hamming distance is dominant, i.e., in the region of high signal-to-noise ratios. Therefore, currently an upper bound on ML decoding performance for turbo-like code with a particular interleaver and LDPC code with a particular parity check matrix cannot be calculated because of heavy complexity so that only average bounds for ensemble codes can be obtained using a uniform interleaver assumption. In this paper, we propose a new bound technique on ML decoding performance for turbo-like code with a particular interleaver and LDPC code with a particular parity check matrix using ML estimated weight distributions and we also show that the practical iterative decoding performance is approximately suboptimal in ML sense because the simulation performance of iterative decoding is worse than the proposed upper bound and no wonder, even worse than ML decoding performance. In order to show this point, we compare the simulation results with the proposed upper bound and previous bounds. The proposed bound technique is based on the simple bound with an approximate weight distribution including several exact smallest distance terms, not with the ensemble distribution or the uniform interleaver assumption. This technique also shows a tighter upper bound than any other previous bound techniques for turbo-like code with a particular interleaver and LDPC code with a particular parity check matrix.

• 인터넷정보학회논문지
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• 제7권5호
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• pp.95-108
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• 2006

국가 경쟁력 제고를 위해서도 디지털콘텐츠에서 확대하여 소프트웨어 소스 코드에 대한 지적재산권 제도와 기술의 정비는 매우 중요한 의미를 지닌다. 이러한 지적재산권 중에서 특히 소프트웨어 보호에 대한 인지는 매우 낮은 편이다. 소프트웨어 소스코드의 소유권 분쟁이 발생 시 소유권을 증명하기 위해서는 원본의 소프트웨어 소스코드를 판별해야만 하는 문제점을 갖고 있다. 또한 소프트웨어가 복제되어도 복잡성과 독해 능력 부족으로 정확한 판정을 내리기가 쉽지 않다. 본 논문에서는 이러한 소프트웨어 복제에 대한 판별을 하나의 개별 코드 단위로 시행하지 않고, 전체 소스가 가지는 구조적 일치성을 기반으로 복제를 판별할 수 있는 XMI 타입의 디지털 라이센스 프로토타입을 개발하였다. 소프트웨어는 구조적으로 Context Free Grammar 기반이며, 그러므로 BNF표기 형태로 표현할 수 있고, 이는 다시 계층 구조로 표현할 수 있기 때문에 가능한 것이다. 그러므로 소프트웨어 소스코드의 구조적 일치성을 비교하기 위한 계층구조를 갖는 소스코드의 아키텍처를 표현할 수 있다.

• International Journal of Aeronautical and Space Sciences
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• 제15권4호
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• pp.374-382
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• 2014

This paper presents the computational aerodynamic analysis of a long-endurance UAV that was developed by the Korea Aerospace Research Institute (KARI), named EAV-2. EAV-2 is a technical demonstrator of aerodynamically efficient design, as well as a hybrid electric-propulsion system for future long-endurance UAVs. We evaluated the aerodynamic characteristics of six low-Reynolds number airfoils, using a panel method code, XFOIL, to select an optimal airfoil for the long-endurance mission of EAV-2. The computational results by a CFD code, FLUENT, suggested that the aerodynamic performance of EAV-2 would be notably improved after adopting SG6043 airfoil, and modifying the fuselage design. This reduced the total drag by 43%, compared to that of a previous KARI model, EAV-1, at the target lift of $C_L=1.0$. Also, we achieved a drag reduction of approximately 14% by means of the low-drag fuselage configuration.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권4호
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• pp.252-256
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• 2006

A low-power ECC check bit generator is presented with competent DRAM implementation with minimal speed loss, area overhead and power consumption. The ECC used in the proposed scheme is a variant form of the minimum weight column code. The spatial and temporal correlations of input data are analyzed and the input paths of the check bit generator are ordered for the on-line adaptable power savings up to 24.4% in the benchmarked cases. The chip size overhead is estimated to be under 0.3% for a 80nm 1Gb DRAM implementation.

• 음성과학
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• 제11권2호
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• pp.259-269
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• 2004

In this paper, we propose a new excitation enhancement technique to improve the speech quality of low bit-rate code-excited linear prediction (CELP) coders. The proposed technique is based on a harmonic model and it is employed only in the decoding process of speech coders without any additional bits. We develop the procedure of harmonic model parameter estimation and harmonic generation, and apply this technique to a current state-of-the-art low bit rate speech coder, ITU-T G.729 Annex D. Also, its performance is measured by using the ITU-T P.862 PESQ score and compared to those of the phase dispersion filter and the long-term postfilter applied to the decoded excitation. It is shown that the proposed excitation enhancement technique can improve the quality of decoded speech and provide better quality for male speech than other techniques.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.397-397
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• 2011

In a low aspect ratio (LAR) tokamak reactor with a superconducting toroidal field (TF) coil, the radial build of TF coil and the shield play a key role in determining the size of a reactor. For self-consistent determination of the reactor components and physics parameters, a system analysis code is coupled with one-dimensional radiation transport code. Conceptual design study of a compact superconducting LAR tokamak reactor with aspect ratio less than 2.5 was conducted and the optimum radial build was identified. It is shown that the use of an improved shielding material and high temperature superconducting magnets with high critical current density opens up the possibility of a fusion power plant with compact size and small re-circulating power simultaneously at low aspect ratio, and that by using an inboard neutron reflector instead of breeding blanket, tritium self-sufficiency is possible with outboard blanket only and thus compact sized reactor is viable.

• 전기학회논문지
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• 제61권12호
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• pp.1880-1885
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• 2012

Nonlinear dynamical behaviors in thermionic low pressure discharge are investigated using a particle-in-cell(PIC) simulation. An electrostatic PIC code is developed to model the plasma discharge system including the kinetic effects. The elastic collision, excitation collision, ionization collision, and electron-ion recombination collision are considered in this code. The generated electrons and ions are traced to analyze physical characteristics of the plasma. The simulation results show that the nonlinear oscillation structures are observed for cold plasma in the system and the similar structures are observed for warm plasma with a shift in values of the bifurcation parameter. The detailed oscillation process can be subdivided into three distinct mode; anode-glow, temperature-limited, and double-layer modes.

• Journal of Information Processing Systems
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• 제14권3호
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• pp.600-606
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• 2018

Smart city is currently the main direction of development. The automatic management of instrumentation is one task of the smart city. Because there are a lot of old instrumentation in the city that cannot be replaced promptly, how to makes low-cost transformation with Internet of Thing (IoT) becomes a problem. This article gives a low-cost method that can identify code wheel instrument information. This method can effectively identify the information of image as the digital information. Because this method does not require a lot of memory or complicated calculation, it can be deployed on a cheap microcontroller unit (MCU) with low read-only memory (ROM). At the end of this article, test result is given. Using this method to modify the old instrumentation can achieve the automatic management of instrumentation and can help build a smart city.

• Nuclear Engineering and Technology
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• 제22권4호
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• pp.359-370
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• 1990

이 논문은 원자력발전소의 안전사고해석에 흔히 이용되는 중성자 다군확산 동특성방정식의 저차원(0차원 및 1차원) 수치해를 3차원 수치해와 비교함으로써 저차원 수치해법에 요구되는 동특성해석 입력자료를 체계적으로 유도하기 위한 것이다. 이 목적으로 이 논문에서는 수정형 Borresen 소격모형에 의한 3차원 동특성 해석코드인 CMSNACK 전산코드로 LRA-BWR 경수로 동특성 시범문제의 3차원해를 구하고 이 해를 기준으로 삼아 중성자 다군확산 동특성방정식의 1차원 유한차분해와 3차 Hermit 다항식 전개해법에 의한 점운동방정식의 0차원 수치해를 비교하고자 했다. 중성자 다군확산방정식의 1차원 유한차분해와 점운동방정식의 0차원 수치해를 구하기 위해 ODTRAN 전산코드와 POTRAN 전산코드를 개발하였고 이들 코드의 입력자료는 ODTRAN 코드의 경우 중성자속 체적가중법을 POTRAN의 경우 단열근사법을 수정하여 마련하였다. 이같이 마련한 입력자료를 써서 LRA-BWR 동특성문제에 대한 1차원 및 0차원 해를 구했으며 그 결과를 CMSHACK코드에 의한 3차원 해와의 비교를 통해서 저차원 수치해의 계산효율성과 안전해석코드에 요구되는 계산결과의 보수성 등을 조사했다. 이같은 비교결과를 토대로 저차원 수치해법의 입력자료 마련에 이 논문에서 제시한 방법이 유용하게 이용될 수 있음을 보였다.