• 한국환경과학회지
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• 제21권3호
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• pp.289-296
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• 2012

The purpose of this study was to identify the irrigation intervals and the amount of suitable growing substrate needed to achieve the desired shallow-extensive green roof system during a dry summer in Korea. In terms of treatment, three types (SL, $P_6P_2L_2$, $P_4P_4L_2$) with varying soil mixture ratios and two types (15 cm, 25 cm) with varying soil depths were created. The results have been analyzed after measuring growth and soil water contents. The difference of growth by treatment was significant in terms of green coverage, height, leaf width and photosynthesis. In measurement of chlorophyll content, no difference was detected when measured against soil depth. According to the growth measurement of Zoysia japonica with respect to differing soil mixture ratios in the 15 cm-deep treatment, a statistical difference was detected at the 0.05 significance level in photosynthesis. In case of green coverage, height, chlorophyll content and leaf width, no statistical significance was observed. In case of the 25 cm-deep treatment, a statistical significance was observed in height and photosynthesis. In terms of green coverage, chlorophyll content and leaf width, no statistical significance was detected. In comparisons of soil moisture tension and soil water contents, the irrigation interval and amount were 8 days and 14.9 L in the SL (15 cm) treatment, respectively. The irrigation interval showed for 10 days a 1.3-fold increase, and the irrigation amount was 27.4 L 1.8-fold more than SL (25 cm), respectively. For $P_6P_2L_2$ (15 cm) treatment, the irrigation interval and amount were 12 days and 20.7 L, respectively. However, an irrigation interval under $P_6P_2L_2$ (25 cm) was for 15 days 1.3 times longer than $P_6P_2L_2$ (15 cm), and an irrigation amount of 40 L was 1.9 times more than that under $P_6P_2L_2$ (15 cm). In $P_4P_4L_2$ (15 cm) treatment, it was indicated that the irrigation interval was 15 days, and the irrigation amount was 19.2 L. It was not needed to irrigate for 16 days under $P_4P_4L_2$ (25 cm) treatment during the dry summer and the longest no-rain periods. The irrigation interval and amount under $P_4P_4L_2$ were 1.8-fold and 1.3-fold, respectively, more than SL treatment as affected by soil mixture ratio. Comparatively $P_4P_4L_2$ had more 1.3-fold and 0.9-fold in irrigation interval and amount more than $P_6P_2L_2$. Therefore, it can be noted that different soil depth and soil mixture ratios had a significant effect on the irrigation interval and amount.

• 한국정보처리학회논문지
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• 제4권3호
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• pp.880-894
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• 1997

본 논문에서는 양자화 계수가 0이 되는 위치를 예측하여 축소된 영역내에서 DCT (Discrete Cosine Trans-form)를 수행하는 새로운 알고리즘을 제안한다. 이 제안한 알고 리즘은 FDCT(Forward DCT)와 IDCT(Inverse DCT)의 계산량을 줄여 부호와 시간과 복호 화 시간을 감소시킬 뿐만 아니라, 허프만(huffiman) 부호화시에도 각각의 불럭에 대하여 분류된 블럭 크기에 따라 각기 다른 수평 수직 지그재그 스캔을 수행함으로써 압축률 을 증가시킨다. 기존의 영상 부호화 방법은 모든 블럭에 대하여 똑같은 DCT 계산과 지그재그 스캔을 행한다. 그렇지만, 제안한 알고리즘은 부호화시에 분류된 블럭 크기 밖의 양자화 계수에 대해 FDCT를 계산하는 대신 0을 대입함FDCT 계산 시간을 줄인다. 또한, 복호화시에는 분류된 블럭 크기내에 존재하는 역양자화 계수만 가지고 IDCT를 수행함으로써 IDCT 계산 시간을 줄인다. 추가하여, 제안한 알고리즘은 분류된 블럭 특성에 적합한 수평 수직 지그재그 스캔을 수행함으로써 Run-length를 줄여서, 향상된 압축률을 제공한다. 한편, 제안한 알고리즘은 DCT에서 압축률과 화질면에서는 최적이지만 부호와 시간과 복호화 시간이 많이 걸리는 16*16 블럭의 처리에도 적용되어질 수 있다. 또한, 실시간을 요구하는 동영상 부호화로 확장되어 질 수 있다.

• 한국통신학회논문지
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• 제25권8B호
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• pp.1460-1468
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• 2000

본 논문에서는 고정소수점 DSP인 TMS320C6201을 이용하여 MPEG-1 Layer III 오디오 디코더를 실시간으로 동작하도록 구현하였다 음질의 손실 없이 부동소수점 연산을 고정소수점 연산으로 변환하였으며 적은 메모리를 사용하여 동작하도록 소스프로그램을 최적화하였다 특히 연산의 정확성을 위해서 Descaling 모듈에서 중점적으로 부동소수점 연산을 고정소수점 연산으로 변환하여UT고 연산량과 프로그램 크기를 줄이기 위해서 IMDCT 모듈과 Synthesis Polyphase Filter Bank 모듈에 대해서 최적화 작업을 수행하였다 그 결과 구현된 디코더는 TMS320C6201 DSP가 수행할 수 있는 최대 연산량의 26% 만으로 실시간 동작이 가능하여UT으며 사용된 프로그램 ROM의 크기는 3.13 kWord 데이터 RAM의 크기는 9.94 kWord 이었다 부동소수점 프로그램의 최종 출력 PCM값과 구현된 고정소수점 연산의 최종 출력 PCM값을 비교하여 60 dB 이상의 높은 SNR를 가짐을 확인함으로써 고정소수점 연산의 정확성을 검증하였다. 또한 EVM 보드에서 사운드 입출력과 호스트(PC) 통신을 이용하여 실시간으로 동작함을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.731-734
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• 1998

A scalable parallel algorithm is proposed for efficient image component labeling with local operatos on a mesh connected SIMD computer. In contrast to the conventional parallel labeling algorithms, where a single pixel is assigned to each PE, the algorithm presented here is scalable and can assign m$\times$m pixel set to each PE according to the input image size. The assigned pixel set is converted to a single pixel that has representative value, and the amount of the required memory and processing time can be highly reduced. For N$\times$N image, if m$\times$m pixel set is assigned to each PE of P$\times$P mesh, where P=N/m, the time complexity due to the communication of each PE and the computation complexity are reduced to O(PlogP) bit operations and O(P) bit operations, respectively, which is 1/m of each of the conventional method. This method also diminishes the amount of memory in each PE to O(P), and can decrease the number of PE to O(P2) =Θ(N2/m2) as compared to O(N2) of conventional method. Because the proposed parallel labeling algorithm is scalable, we can adapt to the increase of image size without the hardware change of the given mesh connected SIMD computer.

• 전기학회논문지
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• 제67권7호
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• pp.846-853
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• 2018

In this paper, an improved model predictive control (MPC) method is proposed, which reduces the amount of calculations caused by the increased number of candidate voltage vectors with the increased voltage level in multi-level inverters. When the conventional MPC method is used for multi-level inverters, all candidate voltage vectors are considered to predict the next-step current value. However, in the case that the sampling time is short, increased voltage level makes it difficult to consider the all candidate voltage vectors. In this paper, the improved MPC method which can get a fast transient response is proposed with a small amount of the computation by adding new candidate voltage vectors that are set to find the optimal vector. As a result, the proposed method shows faster transient response than the method that considers the adjacent vectors and reduces the computational burden compared to the method that considers the whole voltage vector. the performance of the proposed method is verified through simulations and experiments.

• 한국정보통신학회논문지
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• 제13권8호
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• pp.1497-1504
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• 2009

본 논문에서는 JPEG2000의 연산 시간을 줄일 수 있는 방법을 제안한다. 제안한 방법은 웨이블릿 변환의 특성인 상관관계를 기반으로 상위 부대역에서 예측한 계수들의 정보를 이용하여 하위 부대역의 탐색 횟수를 줄인다. 이 방법은 컨텍스트 추출을 위한 연산량과 출력 데이터양이 줄어드나 화질의 열화가 심해지는 연산량과 화질 또는 데이터량간의 상보적 관계가 성립된다. 실험결과 제안한 알고리즘을 적용하였을 경우 표준에 비해 탐색 횟수가 35% 이상 감소함을 보여 수용할 만한 화질의 열화를 대가로 상당한 연산량 감소를 얻을 수 있을 것으로 판단된다.

• 한국자동차공학회논문집
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• 제16권6호
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• pp.19-25
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• 2008

Selective Catalytic Reduction is effective in the reduction of NOx emission. This research focused to evaluate the performance of a urea-SCR system and was conducted in two procedures. One is SCR reactor test using model gas in order to provide an optimal injection condition itself. In this step, some parametric study on emission temperature, space velocity, aspect ratio and the formation of urea spray were made by using flow visualization and Computation Fluid Dynamics techniques. The basic simulation results contributed in determining the layout for an actual engine test. The other is an engine performance and emission test. The urea injector was placed at the opposite direction of exhaust gases emitted into an exhaust duct and an optimal amount of a reducing agent is estimated accurately under different engine loads and speeds. Furthermore, the variation of NOx emission and applied amount of urea was investigated in terms of modes under the condition of with and without SCR, and other emissions such as PM, CO and NMHC were evaluated quantitatively as well. This research may provide fundamental data for the practical use of urea-SCR in future.

• 한국게임학회 논문지
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• 제13권6호
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• pp.43-52
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• 2013

경로 탐색은 인공지능의 매우 중요한 요소 중의 하나이며, 여러 분야에서 두루 쓰이는 과정이다. 경로 탐색은 매우 많은 연산이 필요하기 때문에 성능에 매우 중대한 영향을 미친다. 이를 해결하기 위해서 연산량을 줄이는 방식의 연구가 많이 진행되었고, 대표적으로 A* 알고리즘이 있으나 불필요한 연산이 있어 효율성이 떨어진다. 본 논문에서는 A* 알고리즘 중 연산 비용이 높은 노드 탐색 수 등 연산량을 줄이기 위해서 가중치 기반의 선수행 A* 알고리즘을 새롭게 제안한다. 제안한 알고리즘의 효율성을 측정하기 위해 시뮬레이션을 구현하였으며, 실험 결과 가중치를 이용하는 방법이 일반적인 방법보다 약 1~2배 높은 효율을 보였다.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.448-456
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• 2016

Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies themass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The $H_2O$ content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of $CO_2$ necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core-concrete interaction analysis.

• Journal of Information Processing Systems
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• 제16권6호
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• pp.1359-1371
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• 2020

In transmitting and receiving such a large amount of data, reliable data communication is crucial for normal operation of a device and to prevent abnormal operations caused by errors. Therefore, in this paper, it is assumed that an error correction code (ECC) that can detect and correct errors by itself is used in an environment where massive data is sequentially received. Because an embedded system has limited resources, such as a low-performance processor or a small memory, it requires efficient operation of applications. In this paper, we propose using an accelerated ECC-decoding technique with a graphics processing unit (GPU) built into the embedded system when receiving a large amount of data. In the matrix-vector multiplication that forms the Hamming code used as a function of the ECC operation, the matrix is expressed in compressed sparse row (CSR) format, and a sparse matrix-vector product is used. The multiplication operation is performed in the kernel of the GPU, and we also accelerate the Hamming code computation so that the ECC operation can be performed in parallel. The proposed technique is implemented with CUDA on a GPU-embedded target board, NVIDIA Jetson TX2, and compared with execution time of the CPU.