• Nuclear Engineering and Technology
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• 제56권5호
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• pp.1562-1573
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• 2024

This study rigorously examined uncertainty in the TMI-1 benchmark within the Uncertainty Analysis in Modeling (UAM) benchmark suite using the STREAM/RAST-K two-step method. It presents two pivotal advancements in computational techniques: (1) Development of an uncertainty quantification (UQ) module and a specialized library for the pin-based pointwise energy slowing-down method (PSM), and (2) Application of Principal Component Analysis (PCA) for UQ. To evaluate the new computational framework, we conducted verification tests using SCALE 6.2.2. Results demonstrated that STREAM's performance closely matched SCALE 6.2.2, with a negligible uncertainty discrepancy of ±0.0078% in TMI-1 pin cell calculations. To assess the reliability of the PSM covariance library, we performed verification tests, comparing calculations with Calvik's two-term rational approximation (EQ 2-term) covariance library. These calculations included both pin-based and fuel assembly (FA-wise) computations, encompassing hot zero-power and hot full-power operational conditions. The uncertainties calculated using both the EQ 2-term and PSM resonance treatments were consistent, showing a deviation within ±0.054%. Additionally, the data compression process yielded compression ratios of 88.210% and 92.926% for on-the-fly and data-saving approaches, respectively, in TMI fuel assembly calculations. In summary, this study provides a comprehensive explanation of the PCA process used for UQ calculations and offers valuable insights into the robustness and reliability of newly developed computational methods, supported by rigorous verification tests.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2006년도 추계학술발표대회
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• pp.321-324
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• 2006

인터넷과 인트라넷의 확산에 따라, 스트림 데이터 처리 (stream data processing) 와 같은 새로운 분야가 등장하게 되었다. 스트림 데이터의 특징은 실 시간적이고 연속적으로 생성된다는 것이다. 따라서 기존의 질의 처리와는 달리 질의 또한 연속적으로 처리된다. 본 논문에서는 시간에 따라서 예측할 수 없게 특성이 바뀌는 데이터 스트림에 대한 처리에 대하여 다룬다. 특별히, 본 논문에서는 스트림 데이터에 대한 질의문을 구성하는 연산자들 간의 효율적인 수행 순서 생성 기법을 제안한다. 본 논문에서 제안하는 방법은 시스템의 부담을 적게 주면서도 데이터의 변화에 따라 수행 순서를 변화시킨다. 또한 본 논문에서는 고정 연산자 순서와 비교하여 제안한 기법의 우수성을 보였다.

• 한국환경복원기술학회지
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• 제17권1호
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• pp.45-64
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• 2014

This study was carried out to offer the ecological data for restoring and maintaining a local stream by analyzing the vegetation and flora in Geumsan Stream and Gisa Stream, Geumsan-gun, Chungcheongnam-do, Korea. As a result of comparison of realities of land use near Geumsan Stream and Gisa Stream, in Geumsan Stream, the ratio of residential areas, commercial and business places, and places of transportation facilities was high. With these types of land use aggregating densely in the center, farmlands were formed on both sides. On the other hand, in Gisa Stream, farmlands were distributed evenly in all sections. As a result of comparison of flora of the two streams, Geumsan Stream had a total of 166 taxons including 53 families, 131 genuses, 139 species, 23 varieties, and 4 forms, and Gisa Stream had a total of 142 taxons including 42 families, 111 genuses, 116 species, 21 varieties, and 5 forms. As a result of calculation of the Naturalization Index and Urbanization Index, the indices were analyzed to be 23.5% and 12.1% in Geumsan Stream and to be 21.8% and 9.7% in Gisa Stream, respectively. Hence, Geumsan Stream showed higher figures in both evaluation indices than those of Gisa Stream. In addition, as a result of calculation of the Actual Urbanization Index, which is the index supplemented by considering the species pool and area, it could be known that Geumsan Stream (0.0285) was urbanized more than Gisa Stream (0.0107) by about 2.7 times. A total of 18 plant communities were classified in Geumsan Stream and Gisa Stream. In Geumsan Stream, 14 vegetation types were identified, and it was analyzed that there are various vegetation types including Phalaris arundinacea community, Zoysia japonica community, Phragmites japonica-Phalaris arundinacea community, etc. evenly distributed. 11 vegetation types were identified in Gisa Stream, and it was examined that Phragmites japonica community is widely distributed in all sections.

• International Journal of Computer Science & Network Security
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• 제22권2호
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• pp.406-412
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• 2022

Storing large amounts of data has always been a big problem from the beginning of computing history. Big Data has made huge advancements in improving business processes by finding the customers' needs using prediction models based on web and social media search. The main purpose of big data stream processing frameworks is to allow programmers to directly query the continuous stream without dealing with the lower-level mechanisms. In other words, programmers write the code to process streams using these runtime libraries (also called Stream Processing Engines). This is achieved by taking large volumes of data and analyzing them using Big Data frameworks. Streaming platforms are an emerging technology that deals with continuous streams of data. There are several streaming platforms of Big Data freely available on the Internet. However, selecting the most appropriate one is not easy for programmers. In this paper, we present a detailed description of two of the state-of-the-art and most popular streaming frameworks: Apache Ignite and Hazelcast. In addition, the performance of these frameworks is compared using selected attributes. Different types of databases are used in common to store the data. To process the data in real-time continuously, data streaming technologies are developed. With the development of today's large-scale distributed applications handling tons of data, these databases are not viable. Consequently, Big Data is introduced to store, process, and analyze data at a fast speed and also to deal with big users and data growth day by day.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.356-368
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• 2019

This paper presents the verification and validation (V&V) of the STREAM/RAST-K 2.0 code system for a pressurized water reactor (PWR) analysis. A lattice physics code STREAM and a nodal diffusion code RAST-K 2.0 have been developed by a computational reactor physics and experiment laboratory (CORE) of Ulsan National Institute of Science and Technology (UNIST) for an accurate two-step PWR analysis. The calculation modules of each code were already verified against various benchmark problems, whereas this paper focuses on the V&V of linked code system. Three PWR type reactor cores, OPR-1000, three-loop Westinghouse reactor core, and APR-1400, are selected as V&V target plants. This code system, for verification, is compared against the conventional code systems used for the calculations in nuclear design reports (NDRs) and validated against measured plant data. Compared parameters are as follows: critical boron concentration (CBC), axial shape index (ASI), assembly-wise power distribution, burnup distribution and peaking factors. STREAM/RAST-K 2.0 shows the RMS error of critical boron concentration within 20 ppm, and the RMS error of assembly power within 1.34% for all the cycles of all reactors.

• 한국환경생태학회지
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• 제29권2호
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• pp.292-303
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• 2015

The objective of this study is to evaluate the spatial restoration of Hampyeong Stream and to analyze the determinants of demand for the multi-functionalities of the stream. A Contingent Valuation Method (CVM) was used to estimate the multi-functional public benefits of restored stream area, and major determinants were scrutinized by establishing a demand model. The research data was collected by conducting a survey intended for Hampyeong's local residents, resulting in 284 valid samples. In terms of determinants that affect willingness to pay (WTP), 'physical factor of waterfront area' and 'experience factor of stream space' showed a significantly positive influence on WTP. As a result of applying a double-bounded CVM, the willingness to pay for the restored Hampyeong Stream area indicated a potential contribution of 22,523 won (17,362~27,459 won, 95% confidence interval). When multiplying the number of households in Hampyeong-gun, the total annual value of Hampyeong Stream spatial restoration is approximately 302million won.

• 한국수자원학회논문집
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• 제40권7호
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• pp.503-510
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• 2007

현재 하천정비는 하천생태계에 초점을 맞추고 자연하천에 근접할 수 있는 공법을 사용하는 자연 친화적인 하천정비가 비약적으로 늘어나고 있다. 하지만 자연 친화적인 하천정비는 아직까지 많은 기술이 축적되지 않아 어떤 공법이 하천환경에 적합한 공법인지가 확립되어 있지 않은 상태이다. 또한, 값비싼 공법을 적용하여 하천을 자연 친화적으로 정비하였다. 하더라도 하천정비에 대한 종합적인 평가방법이 확립되어있지 않아 자연 친화적 하천정비에 대한 타당성을 객관화하지 못하고 있다. 따라서 하천환경기능을 포함한 종합적이고 다양한 평가방법을 개발하여 정비하천에 대한 평가를 수행할 필요가 있다. 본 연구에서는 자연 친화적으로 정비된 하천에 대해 정비의 타당성과 효율성을 평가하는 평가방법에 대해 연구하였다. 전라북도 순창읍에 있는 경천을 대상으로 2000년${\sim}$2000년 월별로 모니터링을 수행하여 자료를 수집하였으며, 수집된 자료를 분석하여 하천환경기능을 종합적으로 고려할 수 있는 방법으로서 하천자연도 평가, 전 과정 평가, 어메니티 평가, 경제적 편익 평가 등의 평가방법을 개발하였다. 본 연구에서 개발한 4가지의 평가방법은 하천정비사업의 종합적이고 정량적인 평가를 수행할 수 있는 방법으로 판단된다. 하지만 하나의 하천을 대상으로 개발된 방법을 적용하였기 때문에 차후 각 하천마다 갖는 특성을 고려하여 하천정비의 평가방법이 요구된다.

• 환경생물
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• 제42권2호
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• pp.207-218
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• 2024

Food webs have received global attention as next-generation biomonitoring tools; however, it remains challenging because revealing trophic links between species is costly and laborious. Although a link-extrapolation method utilizing published trophic link data can address this difficulty, it has limitations when applied to construct food webs in domestic streams due to the lack of information on endemic species in global literature. Therefore, this study aimed to develop a link extrapolation-based food web model adapted to Korean stream ecosystems. We considered taxonomic similarity of predation and dominance of generalists in aquatic ecosystems, designing taxonomically higher-level matching methods: family matching for all fish (Family), endemic fish (Family-E), endemic fish playing the role of consumers (Family-EC), and resources (Family-ER). By adding the commonly used genus matching method (Genus) to these four matching methods, a total of five matching methods were used to construct 103 domestic food webs. Predictive power of both individual links and food web indices were evaluated by comparing constructed food webs with corresponding empirical food webs. Results showed that, in both evaluations, proposed methods tended to perform better than Genus in a data-poor environment. In particular, Family-E and Family-EC were the most effective matching methods. Our model addressed domestic data scarcity problems when using a link-extrapolation method. It offers opportunities to understand stream ecosystem food webs and may provide novel insights into biomonitoring.

• 한국물환경학회지
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• 제37권4호
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• pp.249-262
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• 2021

This study investigated the pollution characteristics of the main pollution zone in the Hwangguji watershed and the influence of the tributary on the main stream. The characteristics of the main pollution zone, including, the water quality index (WQI), stream rating, load duration curve (LDC), delivery load density (DLD), and contribution of the tributary to the mainstream, were evaluated by time-series visual heatmap. The WQI of the mainstream of Hwangguji was lowered to the poor (IV) level from the inflow point of Suwon stream (SW) and the LDC excess rate in the T-P was higher than that of BOD₅, especially for the wet season, suggesting that management of non-point source with T-P is preferred. The contribution (%) of the tributaries in the upstream section of Hwangguji watershed were BOD₅ 14.54%, TOC 15.67%, T-N 5.43%, and T-P 6.97%. In particular, the Suwon sewage treatment plant located in the mainstream showed a high contribution of BOD₅ (64.40%) and T-P (53.54%), respectively, due to the high discharge rate (6.019 m³/sec). Meanwhile, Sammi and Gal stream have a large impact on the mainstream with high DLD and poor WQI. Thus, both streams were considered as pollution hot spots. These results provide useful basic data for preparing more effective water quality improvement and management plans in the watershed.

• ALGAE
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• 제34권1호
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• pp.23-33
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• 2019

Freshwater red algal diversity and the relationship with water conditions in 22 stream segments in the area around Khao Luang National Park, Nakhon Si Thammarat province, southern Thailand, were studied during a period of twelve months (May 2014 to April 2015). Sixteen species of freshwater red algae, belonging to eight genera (Audouinella, Balliopsis, Batrachospermum, Caloglossa, Compsopogon, Kumanoa, Sirodotia, and Thorea) were identified, which were all reported earlier for the country. Thorea clavata (Thoreaceae) was the most common species occurring in eight stream segments. Caloglossa beccarii sensu lato (Delesseriaceae) and Sirodotia huillensis Skuja (Batrachospermaceae) had the highest percent cover with up to 40% and 20% per stream segment, respectively. The water quality showed most sites to be unpolluted or ultra-oligotrophic to oligotrophic. Canonical Correspondence Analysis revealed some trends in occurrence of individual species with stream environmental variables: Batrachospermum sp.with strong current velocity; Kumanoa hirosei with high turbidity, total dissolved solid and alkalinity; Caloglossa beccarii with high conductivity; Kumanoa tabagatenensis with high ammonia-nitrogen and Thorea siamensis with high calcium and magnesium. In view of the scarce studies on the stream ecology of freshwater red algae in Philippines and neighbouring countries, it is expected that the data presented here would be helpful in more critical further studies in south-east Asia in general.