• Journal of Korean Society of Water and Wastewater
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• v.28 no.6
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• pp.635-645
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• 2014

The changes of rainfall pattern and impervious covers have increased disaster risks in urbanized areas. Impervious covers such as roads and building roofs have been dramatically increased. So, it is falling the ability safety of flood defense equipments to exist. Runoff coefficient means ratio of runoff by whole rainfall which is able to directly contribute at surface runoff during rainfall event. The application of accurate runoff coefficients is very important in sewer pipelines design. This study has been performed to estimate runoff characteristics change which are applicable to the process of sewer pipelines design or various public facilities design. It has used the SHER model, a long-term runoff model, to analyze the impact of a rising impervious covers on runoff coefficient change. It thus analyzed the long-term runoff to analyze rainfall basins extraction. Consequently, it was found that impervious surfaces could be a important factor for urban flood control. We could suggest the application of accurate runoff coefficients in accordance to the land Impervious covers. The average increase rates of runoff coefficients increased 0.011 for 1% increase of impervious covers. By having the application of the results, we could improve plans for facilities design.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.6
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• pp.503-512
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• 2020

Identifying the water circulation status is one of the indispensable processes for watershed management in an urban area. Recently, various water circulation models have been developed to simulate the water circulation, but it takes a lot of time and cost to make a water circulation model that could adapt the characteristics of the watershed. This paper aims to develop a water circulation state estimation model that could easily calculate the status of water circulation in an urban watershed by using multiple linear regression analysis. The study watershed is a watershed in Seoul that applied the impermeable area ratio in 1962 and 2000. And, It was divided into 73 watersheds in order to consider changes in water circulation status according to the urban characteristic factors. The input data of the SHER(Similar Hydrologic Element Response) model, a water circulation model, were used as data for the urban characteristic factors of each watershed. A total of seven factors were considered as urban characteristic factors. Those factors included annual precipitation, watershed area, average land-surface slope, impervious surface ratio, coefficient of saturated permeability, hydraulic gradient of groundwater surface, and length of contact line with downstream block. With significance probabilities (or p-values) of 0.05 and below, all five models showed significant results in estimating the water circulation status such as the surface runoff rate and the evapotranspiration rate. The model that was applied all seven urban characteristics factors, can calculate the most similar results such as the existing water circulation model. The water circulation estimation model developed in this study is not only useful to simply estimate the water circulation status of ungauged watersheds but can also provide data for parameter calibration and validation.

• Korean Journal of Logic
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• v.17 no.1
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• pp.71-109
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• 2014

Gila Sher believes that Tarskian definition of logical consequence is a conceptually and extensionally adequate explanation. She has tried to show this on the basis of Mostowskian conceptions of generalized quantifiers as being invariant under isomorphic structures and her own conceptions of models. In this paper I try to show that her attempt to justify the Tarskian definition is only partially successful. I admit that her conceptions of the logical as being invariant under isomorphic structures are enough to show the logical formality of logical consequence relations. But I think that since her conceptions of meanings of terms are quite inadequate for dealing with the problem of empty predicates, she fails to distinguish logically necessary truths from other kinds of truths.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.9
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• pp.1225-1228
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• 2006

A total of 1,367 first lactation records of daughters of 81 sires, having 5 or more progeny were used to evaluate sires by 3 different methods viz., least squares (LS), best linear unbiased prediction (BLUP) and derivative free restricted maximum likelihood (DFREML) method. The highest and lowest overall average breeding value of sires for first lactation 305 days or less milk yield was obtained by BLUP (1,520.72 kg) and LS method (1,502.22 kg), respectively. The accuracy, efficiency and stability of different sire evaluation methods were compared to judge their effectiveness. The error variance of DFREML method was lowest ($191,112kg^2$) and its coefficient of determination of fitting the model was highest (33.39%) revealing that this method of sire evaluation was most efficient and accurate as compared to other methods. However, the BLUP method was most stable amongst all the methods having coefficient of variation (%) very near to unadjusted data (18.72% versus 19.89%). The higher rank correlations (0.7979 to 0.9568) between different sire evaluation methods indicated that there was higher degree of similarity of ranking sires by different methods ranging from about 80 to 96 percent. However, the DFREML method seemed to be the most effective sire evaluation method as compared to other methods for the present set of data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5572-5595
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• 2016

Multi-server authentication enables the subscribers to enjoy an assortment of services from various service providers based on a single registration from any registration centre. Previously, a subscriber had to register from each service provider individually to avail respective services relying on single server authentication. In the past, a number of multi-server authentication techniques can be witnessed that employed lightweight and even computationally intensive cryptographic operations. In line with this, Zhu has presented a chaotic map based multi-server authentication scheme recently, which is not only vulnerable to denial-of-service attack, stolen-verifier attack, but also lacks anonymity. This research aims at improving the Zhu's protocol in terms of cost and efficiency. Moreover, the comparative study is presented for the performance of improved model against the existing scheme, and the security of proposed model is formally proved using BAN Logic.

• Advances in aircraft and spacecraft science
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• v.10 no.4
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• pp.303-315
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• 2023

The primary goal of this research is to investigate flow separation phenomena using various turbulence models. Also investigated are the effects of free-stream turbulence intensity on the flow over a NACA 0018 airfoil. The flow field around a NACA 0018 airfoil has been numerically simulated using RANS at Reynolds numbers ranging from 100,000 to 200,000 and angles of attack (AoA) ranging from 0° to 18° with various inflow conditions. A parametric study is conducted over a range of chord Reynolds numbers for free-stream turbulence intensities from 0.1 % to 0.5 % to understand the effects of each parameter on the suction side laminar separation bubble. The results showed that increasing the free-stream turbulence intensity reduces the length of the separation bubble formed over the suction side of the airfoil, as well as the flow prediction accuracy of each model. These models were used to compare the modeling accuracy and processing time improvements. The K- SST performs well in this simulation for estimating lift coefficients, with only small deviations at larger angles of attack. However, a stall was not predicted by the transition k-kl-omega. When predicting the location of flow reattachment over the airfoil, the transition k-kl-omega model also made some over-predictions. The Cp plots showed that the model generated results more in line with the experimental findings.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5529-5552
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• 2016

Mobile cloud computing (MCC) has revolutionized the way in which the services can be obtained from the cloud service providers. Manifold increase in the number of mobile devices and subscribers in MCC has further enhanced the need of an efficient and robust authentication solution. Earlier, the subscribers could get cloud-computing services from the cloud service providers only after having consulted the trusted third party. Recently, Tsai and Lo has proposed a multi-server authenticated key agreement solution for MCC based on bilinear pairing, to eliminate the trusted third party for mutual authentication. The scheme has been novel as far as the minimization of trusted party involvement in authenticating the user and service provider, is concerned. However, the Tsai and Lo scheme has been found vulnerable to server spoofing attack (misrepresentation attack), de-synchronization attack and denial-of-service attack, which renders the scheme unsuitable for practical deployment in different wireless mobile access networks. Therefore, we have proposed an improved model based on bilinear pairing, countering the identified threats posed to Tsai and Lo scheme. Besides, the proposed work also demonstrates performance evaluation and formal security analysis.

• Advances in aircraft and spacecraft science
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• v.9 no.2
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• pp.131-148
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• 2022

The paper presents the surface-modified NACA 2412 airfoil performance with variable cavity characteristics such as size, shape and orientation, by numerically investigated with the pre-validation study. The study attempts to improve the airfoil aerodynamic performance at 30 m/s with a variable angle of attack (AOA) ranging from 0° to 20° under Reynolds number (R_e) 4.4×10⁵. Through passive surface control techniques, a boundary layer control strategy has been enhanced to improve flow performance. An intense background survey has been carried out over the modifier orientation, shape, and numbers to differentiate the sub-critical and post-critical flow regimes. The wall-bounded flows along with its governing equations are investigated using Reynolds Average Navier Strokes (RANS) solver coupled with one-equational transport Spalart Allmaras model. It was observed that the aerodynamic efficiency of cavity airfoil had been improved by enhancing maximum lift to drag ratio ((l/d) max) with delayed flow separation by keeping the flow attached beyond 0.25C even at a higher angle of attack. Detailed investigation on the cavity distribution pattern reveals that cavity depth and width are essential in degrading the early flow separation characteristics. In this study, overall general performance comparison, all the cavity airfoil models have delayed stalling compared to the original airfoil.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1614-1618
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• 2007

분포형 수문모형은 유역을 격자단위로 세분화하여 매개변수를 부여하고, 증발산, 침투, 지표면유출, 중간유출, 지하수유출, 하도흐름 등 여러 가지 수문요소를 해석하는 종합적인 수문모형이다. 지표면에 내린 강우의 증발 및 침투, 유출은 토양수분의 함량에 크게 의존하게 된다. 따라서 토양수분에 대한 적절한 모의가 분포형 수문모형의 정확도를 좌우하는 핵심이라 할 수 있다. 토양수분은 식물의 생장 및 가용수자원 산정 등에 있어서 중요한 요소로서 토양층 상부의 수 미터 내에 존재하는 수분의 양을 일컫는다. 토양수분의 공간적 시간적 특성들은 증발, 침투, 지하수 재충전, 토양침식, 식생분포 등을 지배하는 매우 중요한 요소라 할 수 있다. 강우로 인한 지면과 지표하에서의 순간적인 포화공간의 형성 및 유출의 생성을 포함하는 과정과 증발산 등은 모두 비포화대(vadose zone) 혹은 토양층에서의 토양수분의 함량에 크게 의존하게 된다(이가영 등, 2005) 본 연구에서는 토양수분에 대한 정밀측정 자료가 있는 설마천 유역 범륜사 사면에 대하여 분포형 수문모형의 토양수분 해석 능력을 평가하고자 하였다. 토양수분 모의에 사용된 격자기반의 분포형 수문모형은 미공병단에서 개발한 GSSHA(USACE, 2006) 모형이다. 모형의 입력자료는 정밀토양도와 현장측정에 의한 토양매개변수를 반영하여 구축하였고, 강우 및 기상자료는 2003년 1월 1일 ${\sim}$ 2004년 12월 31일의 1시간 자료를 이용하였다. 모의기간 중 2003년은 초기 토양수분값 등 초기조건의 영향을 줄이기 위한 웜업 (Warm-up)기간으로 설정하였고, 2004년의 모의결과를 토양수분 관측값과 비교하였다.업지역, 상업지역 등과 같이 지형적 특성에 따른 유량측정망을 구축하는 것이다.의 의사결정 지원 도구가 될 것이다. 따라서, 본 연구에서는 도시유역의 물순환 해석을 위한 일련의 과정, 즉 자료의 조사 및 취득에서부터 물순환 해석 모형을 이용한 정량적 현황파악, 물순환 개선 기법 및 평가를 수행함에 있어 주요 착안점 및 실무에서의 기술적 가이드를 제공하고자 하였으며, 보다 세밀한 도시유역의 물순환 해석을 위하여 우리나라와 일본에서 적용이 활발한 물리적 기반의 분포형 모형(WEP, SHER, SWMM)의 적용사례를 통하여 국내 도시하천의 물순환 해석에 활용함에 있어서의 실질적인 적용절차 등을 제시하고자 하였다. 한다.호강유역의 급격한 수질개선을 알 수 있다.世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와 동년대에 동일한 목적으로 찬술되었음을 알 수 있다. $\ulcorner$경상도실록지리지$\lrcorner$(慶尙道實錄地理志)에는 $\ulcorner$세종실록$\lrcorner$(世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와의 비교를 해보면 상 중 하품의 통합 9개소가 삭제되어 있고, $\ulcorner$동국여지승람$\lrcorner$(東國與地勝覽) 에서는 자기소와 도기소의 위치가 완전히 삭제되어 있다. 이러한 현상은 첫째, 15세기 중엽 경제적 태평과 함께 백자의 수요 생산이 증가하자 군신의 변별(辨別)과 사치를 이유로 강력하게 규제하여 백자의 확대와 발전에

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1076-1080
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• 2007

최근 국내에서는 하천변 생태계를 대상으로 생태구조 및 서식처 평가 등 많은 연구가 진행되었음에도 불구하고 생태적 변화를 예측하고 예측된 결과에 따라 생태복원 대책을 수립할 수 있는 연구는 현재까지 미흡하다고 볼 수 있으며, 이는 생태복원 연구에 있어 주요과제라고 할 수 있다. 이에 반해 유럽과 미국에서는 수문학적 서식처 조건에 따른 식생 반응 예측 등 수문생태 모형에 대한 연구가 꾸준히 이루어져 왔으며, 최근에는 습지, 홍수터 등을 대상으로 생태보전 복원분야에 널리 응용되고 있다. 본 연구에서는 국외의 수문생태모형 적용사례를 분석하여 국내 적용가능성 및 문제점에 대한 타당성을 제시하고자 하였다. 그 대상으로는 유역 내에 홍수량 분담을 위한 천변저류지를 적용하였으며, 의미상으로 홍수터(범람원), 습지 역시 해당 범위에 포함할 수 있다. 천변저류지는 홍수기와 비홍수기에 따라 활용 측면을 구분할 수 있으며, 이런 맥락에서 천변저류지의 수위변화는 식생 변화의 중요한 요소(factor)가 될 수 있다. 그 외 범람시기, 범람일수, 건조기간 등을 포함한 수문요소 역시 수문생태 모델의 예측 변수인 식생 성장에 영향을 미치게 된다. 이러한 수문/생태시스템의 상호관계를 활용하고 모형의 형태를 국내 식생에 대한 생리학적 특성에 맞게 변화시킬 수 있다면 국내 천변저류지에도 충분히 적용 가능할 것으로 판단된다. 또한 잠재적으로 식생 성장에 영향을 줄 수 있는 다양한 환경조건 예를 들면 영양물질, 토양구조, 토사 퇴적 등을 적용대상지 환경에 맞게 포함하거나 고려할 수 있다면 모형의 재현성을 더욱 높일 수 있을 것이다.의 기대효과를 가져올 수 있으리라 생각되며 분석된 인자들은 수달 서식지를 위한 하천정비의 기초자료에 유용할 것으로 보인다.따른 유량측정망을 구축하는 것이다.의 의사결정 지원 도구가 될 것이다. 따라서, 본 연구에서는 도시유역의 물순환 해석을 위한 일련의 과정, 즉 자료의 조사 및 취득에서부터 물순환 해석 모형을 이용한 정량적 현황파악, 물순환 개선 기법 및 평가를 수행함에 있어 주요 착안점 및 실무에서의 기술적 가이드를 제공하고자 하였으며, 보다 세밀한 도시유역의 물순환 해석을 위하여 우리나라와 일본에서 적용이 활발한 물리적 기반의 분포형 모형(WEP, SHER, SWMM)의 적용사례를 통하여 국내 도시하천의 물순환 해석에 활용함에 있어서의 실질적인 적용절차 등을 제시하고자 하였다. 한다.호강유역의 급격한 수질개선을 알 수 있다.世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와 동년대에 동일한 목적으로 찬술되었음을 알 수 있다. $\ulcorner$경상도실록지리지$\lrcorner$(慶尙道實錄地理志)에는 $\ulcorner$세종실록$\lrcorner$(世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와의 비교를 해보면 상 중 하품의 통합 9개소가 삭제되어 있고, $\ulcorner$동국여지승람$\lrcorner$(東國與地勝覽) 에서는 자기소와 도기소의 위치가 완전히 삭제되어 있다.