• Horticultural Science & Technology
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• v.29 no.1
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• pp.29-35
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• 2011

Individual ion concentrations and ionic contributions to EC reading in the circulated nutrient solution are the important factors to be considered for stable EC-based closed-loop soilless culture. This study was conducted to determine appropriate ion-analysis intervals of the circulated nutrient solutions based on ion concentration, ion balance, and ion electrical conductivity under different renewal intervals in EC-based nutrient control systems for sweet peppers (Capsicum annum L. 'Fiesta') in early growth stage. Average node numbers of the plants were 13 and 18 when the experiment started and finished, respectively, and three plants were grown in each rockwool slab. Four different renewal intervals of circulated nutrient solutions such as 1, 2, 3, and 4 weeks were used as treatment. Nutrient solutions were supplied to the plants based on integrated radiation. Drainage was collected into drain tanks after irrigation ended in the day and then mixed with fresh water until the EC reaches 2.69 $dS{\cdot}m^{-1}$. The replenished nutrient solution was supplied to the plants in the next day. Ion concentrations of the individual ions periodically analyzed in the circulated nutrient solutions showed no significant differences among the treatments during the experimental period. Ion concentrations of $K^+$, $Ca^{2+}$, $Mg^{2+}$, $Na^+$, $NO_3{^-}$, ${SO_4}^{2-}$, ${PO_4}^{3-}$, and $Cl^-$ varied within 5-8, 11-14, 2.0-2.7, 0.5-0.6, 14-19, 4-5, 1-4, and 0.3-0.5 $meq{\cdot}L^{-1}$, respectively. Ion balance showed a consistent tendency over all the treatments and especially $K^+$ : $Ca^{2+}$ and ${SO_4}^{2-}$ : ${PO_4}^{3-}$ played great roles in the cation and anion balances in the nutrient solutions, respectively. Activity coefficients of ions such as $K^+$, $NO_3{^-}$, and $H_2PO_4{^-}$ varied within 0.8-0.9 and those of $Ca^{2+}$, $Mg^{2+}$, ${SO_4}^{2-}$ varied within 0.5-0.6, showing little changes with time. Ionic contributions of $K^+$ and $NO_3{^-}$ to EC reading were the greatest followed by $Ca^{2+}$, ${SO_4}^{2-}$, and $Mg^{2+}$ in the order. From the results, we thought that allowable ranges in ion concentration, ion balance, and subsequent individual ionic contributions to EC reading would be obtained within 4-week renewal interval of nutrient solution in EC-based closed-loop soilless culture for sweet pepper plants.

• Survey Research
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• v.10 no.2
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• pp.97-114
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• 2009

Even the importance and necessity of a basic national statistical survey, the population and housing census is facing with some practical difficulties such as higher survey cost, decrease of survey information and much longer survey period. As an alternative to the traditional census for tackling such difficulties, a rolling census has been introduced. The rolling census has some advantages such as improved timeliness with much more frequent data and evenly distributed survey cost over several years. On the contrary, the rolling census has also some disadvantages such as the lost of snapshot feature of the population and increasing risk of outside influence on field work. In this paper we reviewed the French rolling census and the American community survey as roiling surveys, and then investigated some factors like balanced sample selection, population update, synthetic estimation, and the operation of rolling survey, which are to be checked carefully in case of introducing a rolling census as an alternative to the current census.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2007.11a
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• pp.225-226
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• 2007

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.333-333
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• 2004

• Proceedings of the Korea Technology Innovation Society Conference
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• 2016.10a
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• pp.113-120
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• 2016

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.49-49
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• 2020

하천 보 상류영역에서 발생하는 박리 흐름을 분석하기 위해 실험수로에 하천보 모형을 설치하고, 보 주변에서 발생하는 흐름 구조를 입자 영상 유속계(PIV)로 이용하여 정밀하게 측정하였다. 본 연구에 사용된 보는 하천 설계기준을 따른, 전방 수직벽과 하류 경사램프가 있는 유한한 마루 길이 보이다. 실험 조건은 보 상·하류부 수심으로 인한 4가지 흐름(Hydraulic jump, Plunging jet, Surface wave, Surface jet)을 기반으로 설정하여 수리조건에 따른 유속 특성을 규명하였다. 실험에서 측정한 수직-수평방향 평균 유속·유선도를 분석한 결과, 보 전방의 하부에서 재순환 흐름이 관측되었고, 역방향 흐름도 이 지역에서 발견되었다. 유속 편차의 제곱 평균(Root Mean Square) 흐름장에서 보 전방과 재순환 흐름 영역에 불안전한 흐름이 강하게 발견되었다. 역방향 흐름은 박리 흐름에서 발견되는 주요 특성으로, 역방향 흐름의 전체 면적을 매 관측마다 측정하여 이를 분석한 결과, 재순환 흐름의 면적은 오른쪽으로 기울어진 분포를 가지고, 항상 0보다 큰 값을 가지는 것으로 나타났다. 재순환 면적에 따른 흐름 특성은 역방향 흐름 면적에 대한 조건부 평균을 이용하여 파악했는데, 조건부 평균의 구간은 재순환 흐름의 중심에서 지배적인 주기값을 이용했다. 역방향 흐름이 작은 영역에선, 보 상류의 흐름이 재순환 흐름으로 말려들어가는 열린 박리흐름이 나타나며, 역방향 흐름이 큰 경우에는 재순환 영역의 흐름은 보 상류의 흐름과 분리되는 닫힌 박리흐름이 발생하였다. 역방향 흐름이 가장 큰 경우, 보 전방의 박리흐름은 보의 상단을 넘는 것으로 관찰되었다. 이러한 결과를 통해 보 마루에서 발생하는 박리흐름이 보 전방에 박리흐름에 영향을 미치는 것으로 파악되었다. 조건부 평균된 역방향 흐름의 면적과 박리 지점(separation point)의 관계를 분석한 결과, 역방향 흐름의 오른쪽으로 기울어진 분포와 대규모 흐름 방출 현상이 관측되었다. 박리 지점의 위치와 수리 매개변수의 관계를 분석한 결과, 상류의 수심 증가에 따라 증가하는 경향이 나타났다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.41-43
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• 2000

멀티미디어 시스템에서는 미디어 데이터의 연속성을 보장하는 것이 중요한 문제이다. 90년대에 제안된 구역분할 디스크에서 연속성을 보장하면서 멀티미디어를 효과적으로 저장, 전송하기 위하여 새로운 스케줄링 방식과 데이터 블록의 배치가 제안되었다. 이 방식은 구역을 순환하면서 데이터 블록을 배치시키고 SCAN 알고리즘으로 데이터를 읽어 들이는 방식이다. 이 경우 SCAN 알고리즘으로 데이터를 읽어 들이므로 이중 버퍼링(double buffering) 방법을 사용하게 된다. 이중 버퍼링의 데이터를 읽어 들이는 주기와 서비스 주기의 불일치성으로 인하여 새로운 스트림의 요청이 있을 때 기존의 서비스 스트림에 주기시간의 증가로 인한 데이터의 지연문제(jitter)가 발생한다. 본 논문에서는 구역분할 디스크를 이용하는 비디오 서버에서 새로운 요구의 도착으로 인하여 발생하는 데이터 지연 문제(jitter)를 해결하기 위하여 선행 버퍼링이란 기법을 제시한다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.1
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• pp.1-18
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• 2023

The East Sea, one of the regions where the most rapid warming is occurring, is known to have important implications for the response of the ocean to future climate changes because it not only reacts sensitively to climate change but also has a much shorter turnover time (hundreds of years) than the ocean (thousands of years). However, the processes underlying changes in seawater characteristics at the sea's deep and abyssal layers, and meridional overturning circulation have recently been examined only after international cooperative observation programs for the entire sea allowed in-situ data in a necessary resolution and accuracy along with recent improvement in numerical modeling. In this review, previous studies on the physical characteristics of seawater at deeper parts of the East Sea, and meridional overturning circulation are summarized to identify any remaining issues. The seawater below a depth of several hundreds of meters in the East Sea has been identified as the Japan Sea Proper Water (East Sea Proper Water) due to its homogeneous physical properties of a water temperature below 1℃ and practical salinity values ranging from 34.0 to 34.1. However, vertically high-resolution salinity and dissolved oxygen observations since the 1990s enabled us to separate the water into at least three different water masses (central water, CW; deep water, DW; bottom water, BW). Recent studies have shown that the physical characteristics and boundaries between the three water masses are not constant over time, but have significantly varied over the last few decades in association with time-varying water formation processes, such as convection processes (deep slope convection and open-ocean deep convection) that are linked to the re-circulation of the Tsushima Warm Current, ocean-atmosphere heat and freshwater exchanges, and sea-ice formation in the northern part of the East Sea. The CW, DW, and BW were found to be transported horizontally from the Japan Basin to the Ulleung Basin, from the Ulleung Basin to the Yamato Basin, and from the Yamato Basin to the Japan Basin, respectively, rotating counterclockwise with a shallow depth on the right of its path (consistent with the bottom topographic control of fluid in a rotating Earth). This horizontal deep circulation is a part of the sea's meridional overturning circulation that has undergone changes in the path and intensity. Yet, the linkages between upper and deeper circulation and between the horizontal and meridional overturning circulation are not well understood. Through this review, the remaining issues to be addressed in the future were identified. These issues included a connection between the changing properties of CW, DW, and BW, and their horizontal and overturning circulations; the linkage of deep and abyssal circulations to the upper circulation, including upper water transport from and into the Western Pacific Ocean; and processes underlying the temporal variability in the path and intensity of CW, DW, and BW.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.889-896
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• 2006

The crest factor distribution of orthogonal frequency division multiplexing (OFDM) symbol sequences is evaluated and it is shown that OFDM symbol sequences with a short period are expected to have a high crest factor. The crest factor relationship between two input symbol sequences, Hamming distance D apart is also derived. Using these two results, we propose two criteria for a phase sequence set of the selected mapping (SLM) scheme and suggest the rows of the cyclic Hadamard matrix constructed from an m-sequence as the near optimal phase sequence set of the SLM scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.846-852
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• 2006

The ${\kappa}$-error linear complexity is a ky measure of the stability of the sequences used in the areas of communication systems, stream ciphers in cryptology and so on. This paper introduces an efficient algorithm to determine the ${\kappa}$-error linear complexity and the corresponding error vectors of $p^m$-periodic binary sequences, where : is a prime and 2 is a primitive root modulo $p^2$. We also give a new sense about the ${\kappa}$-error linear complexity in viewpoint of coding theory instead of cryptographic results. We present an efficient algorithm for decoding binary cyclic codes of length $p^m$ and derive key properties of the minimum distance of these codes.