• 대한환경공학회지
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• 제39권1호
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• pp.1-8
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• 2017

식수부족문제는 지표수와 지하수의 오염, 수처리의 어려움, 기반시설의 부재로 인해 많은 개발도상국에서 주로 발생하고 있다. 이에 빗물을 모아 식수로 이용하는 빗물식수화시설(RFD)이 매우 효과적인 대안으로 떠오르고 있으며, 전 세계적으로 빗물식수화시설 사업이 진행되고 있다. 대부분의 빗물식수화시설은 지역주민이 사업 종료 후부터 스스로 시설을 운영하도록 하기 때문에 빗물식수화시설 사업에 대한 지역주민의 인식이 매우 중요하다. 따라서 본 연구에서는 베트남에서 빗물식수화시설을 사용하는 총 209명의 현지 지역주민을 대상으로 설문조사와 면담을 실시하여 지역주민의 인식을 조사하였다. 지역주민들은 빗물식수화시설 사업의 효과성에 긍정적인 인식을 가지고 있으며(41.9%), 빗물식수화시설 사업에 참여의향이 있는 것으로 나타났다(58.9%). 지역주민이 빗물식수화시설 사업에서 가장 기대하는 세가지 요소는 '안전한 식수의 공급', '마을공동체의 활성화', '빗물식수화시설의 확산'순으로 나타나 빗물식수화시설 사업에의 참여를 통해 안전한 식수를 공급받는 것을 가장 기대하는 것으로 파악되었다. 빗물식수화시설 사업에서 가장 우려하는 세가지 요소로는 '빗물의 수질', '빗물식수화시설의 설치 기술', '지역주민의 참여도'순으로 나타났으며, 특히 빗물식수화시설 사업의 종료 후의 빗물 수질과 시설의 유지관리를 우려하는 것으로 파악되었다. 빗물식수화시설 사업의 종료 후에도 지역주민이 성공적으로 빗물식수화시설을 운영하기 위해서는 빗물식수화시설의 수질을 용이하게 측정할 수 있는 간편한 수질 측정 도구의 개발과 지역주민 스스로가 빗물식수화시설에 관심을 가지고 유지관리를 할 수 있도록 빗물식수화시설에 대한 정기적인 교육을 진행하는 것이 필요할 것이다.

• Journal of information and communication convergence engineering
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• 제9권3호
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• pp.305-309
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• 2011

This paper proposes a new rotational frequency detector (RFD) for phase-locked loop (PLL) or clock and data recovery (CDR) applications for fast frequency acquisition. The proposed RFD uses the four states finite state machine (FSM) model to accelerate the frequency acquisition time. It is modeled and simulated with MATLAB Simulink. The functionalities of the proposed RFD are examined and the results are compared to those of a conventional RFD. The proposed RFD's frequency acquisition time is four times faster than that of a conventional one. The proposed RFD incorporated with a phase detector (PD) in PLL or CDR is expected to improve the frequency and phase acquisition performance later greatly.

• Journal of Communications and Networks
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• 제9권4호
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• pp.490-498
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• 2007

BGP route flap damping(RFD) was anecdotally considered to be a key contributor to the stability of the global Internet inter-domain routing system. However, it was recently shown that RFD can incorrectly suppress for substantially long periods of time relatively stable routes, i.e., routes that only fail occasionally. This phenomenon can be attributed to the complex interaction between BGP path exploration and how the RFD algorithm identifies route flaps. In this paper we identify a distinct characteristic of BGP path exploration following a single network event such as a link or router failure. Based on this characteristic, we distinguish BGP route updates during BGP path exploration from route flaps and propose a novel BGP route flap damping algorithm, RFD+. RFD+ has a number of attractive properties in improving Internet routing stability. In particular, it can correctly suppress persistent route flaps without affecting routes that only fail occasionally. In addition to presenting the new algorithm and analyzing its properties, we also perform simulation studies to illustrate the performance of the algorithm.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 추계학술대회 논문요약집
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• pp.52-52
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• 2003

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.526-531
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• 1998

본 논문은 농축도 0.9%의 순환우라늄 핵연료(CANFLEX-RU)에 대한 축방향 출력분포(AFD) 및 반경방향 출력분포(RFD) 특성을 조사하고 CANFLEX-RU 다발이 장전된 CANDU줄 채널의 예비 열수력 해석을 수행하였다. CANFLEX-RU 다발의 4 bundle shift 핵연료 교체 방법에 따라 AFD 분포 특성은 정점(Peak) 열속이 채널 상류쪽으로 이동하였고 채널 중심 부근에서 평탄하거나 다소 오목한 형상을 보여주었다. RFD 분포를 표현하는 적절한 변수로서 국부 다발열유속비를 정의하고, 이 비와 국부 표면열유속비의 상호 관계식을 도출하였다. 연소도에 따른 최외환봉의 국부 다발열유속비 변화를 조사한 결과로서, CANFLEX-RU 다발의 최대 국부 다발열유속비는 초기 연소도에서 발생되었고 이 값 CANFLEX-NU 다발 보다는 크고 37-핵연료봉다발 보다는 작았다. CCP 계산시에 RFD 분포 효과를 고려하는 방안으로서 최외환봉 열유속을 다발의 국부 열유속으로 가정하였다 이는 임계열유속이 -10.2% 감소한 조건을 사용하여 CCP를 계산하는 결과가 되었다. 다발-블균형 계수를 이용한 CCP 민감도 결과와 본 계산에서 얻은 CCP 결과에 의하면, CANFLEX-RU의 CCP 는 CANFLEX-NU에 비교해서 土1.0% 이내로 근사한 분포가 예상되었으며 이는 AFD 분포 효과가 RFD 분포에 의한 CCP 감소를 보상하기 때문이다. 결론적으로, CANFLEX-RU는 열수력적 설계 관점에서 CANFLEX-NU에 비교해서 열적 성능이 저하되지 않았고 따라서 기존 37-핵연료봉다발에 대한 CANFLEX-NU의 열여유도 증가와 같은 장점을 유지할 것으로 예상되었다.

• 한국작물학회지
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• 제50권2호
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• pp.105-107
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• 2005

A field study was conducted to investigate and ascertain the effects of boron and molybdenum with recommended N P K S Zn fertilizers (RFD) for sustained sugarcane yield in the sandy acidic soil in Old Himalayan Piedmont Plain of Bangladesh. Results revealed that the treatment $T_7$ having recommended fertilizers of N 120, P 35, K 100, S 25 and Zn 2kg $ha^{-1}$ + B 2kg $ha^{-1}$ + Mo 2 kg $ha^{-1}$ produced significantly higher number of millable cane (126.96\times10^3\;ha^{-1})$ except in $T_9$ with RFD + B 2 kg $ha^{-1}$ + Mo 4kg $ha^{-1}$, and higher cane yield (92.83 Mg $ha^{-1}$) among all except in $T_3$ with RFD + B2 kg $ha^{-1}$, $T_5$ with RFD + Mo 2kg $ha^{-1}$ and $T_9$ where the effects were statistically identical. The increase in cane yield by $T_7$ was $164.6\%$ over control. The treatment $T_7$ having RFD + B 2kg $ha^{-1}$ + Mo 2kg $ha^{-1}$ further gave the highest additional net economic benefit of Taka 16, 500.00 for added Band Mo at 2kg $ha^{-1}$ among all the treatments in the study.

• 한국농공학회논문집
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• 제57권1호
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• pp.69-78
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• 2015

The objective of this study was to investigate characteristics of irrigation return flow from paddy block in a reservoir irrigated district during growing seasons. The irrigation return flow was divided into three parts, quick return flow from irrigation canal (RFI), quick return flow from drainage canal (RFD), and delayed return flow (DRF). The RFI was calculated from water level and stage-discharge relationships at the ends of the irrigation canals. The DRF was estimated using measured infiltration amount from paddy fields of the irrigated district. A combined monitoring and modeling method was used to estimate the RFD by subtracting surface runoff from surface drainage. The paddy block irrigated from the Idong reservoir was selected to study the irrigation return flow components. The results showed that daily agricultural water supply (AWS), the RFI, and the RFD were $27.4mm\;day^{-1}$, $4.9mm\;day^{-1}$, and $19.8mm\;day^{-1}$, respectively in May, which were greater than other months (p<0.05). The return flow ratio of the RFI and the RFD were the greatest in July (34.6%) and May (72.3%), respectively. The daily AWS was closely correlated with the RFD (correlation coefficients of 0.76~0.86) in except for July with, while correlation coefficient with the RFI were 0.56 and 0.42 in June and July, respectively (p<0.01). The total irrigation return flow was 1,965 mm in 2011, and 1,588 mm in 2012, resulting in total return flow ratio of 84.6% and 79.1%, respectively. This results indicate that substantial amounts of agricultural water were returned to streams as irrigation return flow. Thus, irrigation return flow should be fully considered into the agricultural water resources planning in Korea.

• Steel and Composite Structures
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• 제47권2호
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• pp.167-184
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• 2023

In this study, a new recentering friction device (RFD) to retrofit steel moment frame structures is introduced. The device provides both self-centering and energy dissipation capabilities for the retrofitted structure. A hybrid performance-based seismic design procedure considering multiple limit states is proposed for designing the device and the retrofitted structure. The design of the RFD is achieved by modifying the conventional performance-based seismic design (PBSD) procedure using computational intelligence techniques, namely, genetic algorithm (GA) and artificial neural network (ANN). Numerous nonlinear time-history response analyses (NLTHAs) are conducted on multi-degree of freedom (MDOF) and single-degree of freedom (SDOF) systems to train and validate the ANN to achieve high prediction accuracy. The proposed procedure and the new RFD are assessed using 2D and 3D models globally and locally. Globally, the effectiveness of the proposed device is assessed by conducting NLTHAs to check the maximum inter-story drift ratio (MIDR). Seismic fragilities of the retrofitted models are investigated by constructing fragility curves of the models for different limit states. After that, seismic life cycle cost (LCC) is estimated for the models with and without the retrofit. Locally, the stress concentration at the contact point of the RFD and the existing steel frame is checked being within acceptable limits using finite element modeling (FEM). The RFD showed its effectiveness in minimizing MIDR and eliminating residual drift for low to mid-rise steel frames models tested. GA and ANN proved to be crucial integrated parts in the modified PBSD to achieve the required seismic performance at different limit states with reasonable computational cost. ANN showed a very high prediction accuracy for transformation between MDOF and SDOF systems. Also, the proposed retrofit showed its efficiency in enhancing the seismic fragility and reducing the LCC significantly compared to the un-retrofitted models.

• 한국CDE학회논문집
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• 제12권5호
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• pp.354-365
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• 2007

We present novel methods to generate a sequence of shapes that represents the pattern of morphological development or transformation of Bezier curves. The presented methods utilize the intrinsic geometric structures of a Bezier curve that are derived from rib and fan decomposition (RFD). Morphological development based on RFD shows a characteristic pattern of structural growth of a Bezier curve, which is the direct consequence of development path defined by fans. Morphological transformation based RFD utilizes development patterns of source and target curves to mimic the theory of evolutionary developmental biology: although the source and target curves are quite different in shapes, we can easily find similarities in their younger shapes, which makes it easier to set up feature correspondences for blending them. We also show that further controls on base transformation for intensity of feature blending, and extrapolation can compensate the immaturity of blended curves. We demonstrate the experimental results where transformation patterns are smoother and have unique geometric style that cannot be generated using conventional methods based on multi-linear blending.

• Earthquakes and Structures
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• 제25권4호
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• pp.223-234
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• 2023

The use of displacement-dependent rotational friction dampers (RFD) as fuses or interchangeable elements in the moment-resisting frames (MRF) is one of the newest methods for improving seismic performance. In the present study, the performance of rotational friction dampers in MRF has been investigated. Evaluation of MRF with and without RFD models was performed using the finite element method by ABAQUS. For validation, an MRF and MRF with rotational friction dampers were modeled that had been experimentally tested and reported in previous experimental research and a good agreement was observed. The behavior of these dampers in frames of 3-, 6-, and 9-story was studied by modeling the damper directly. Nonlinear time history dynamic analysis was used. It was observed that by increasing the number of stories in the buildings, rotational friction dampers should be used to perform properly against earthquakes. The installation of rotational friction dampers in steel moment-resisting frames shows that the drift ratio between the floors is reduced and the seismic performance of these frames is improved.