• 한국수산과학회지
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• 제19권3호
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• pp.274-280
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• 1986

대, 소조기에 마산만에서 연속관측한 자료를 사용하여 만구 단면의 유속 변동특성을 구명하기 위하여 net velocity와 RMS속도의 등양선 및 순 유출입량을 계산하여 검토하였다. 최강유속은 수도 중앙과 서부의 4m 이하의 표층에서 나타나고, 최대 유입속도 24cm/sec 최대 유출속도는 15 cm/sec이다. 최강유속 시간임에도 불구하고 4m 이심에서는 유속이 약하여 $0{\sim}2cm/sec$에 불과하다. 만구 단면의 가장자리의 상층에 역류가 존재한다. net velocity는 비가 오지 않은 대조기의 경우 유출유속은 만구단면 서부에서 나타나며, 유입유속은 단면 동부에서 나타난다. 비온 직후의 소조기에는 이와 정반대로 흐른다. RMS속도의 최대 세기는 대조기에 $11.3{\sim}15.0cm/sec$, 소조기에 $7{\sim}10.3cm/sec$로서 단면 서부의 표층에 있으며, 매 조석주기마다 거의 동일위치에서 계속 존재한다. 순 통과유량은 건기에 $-39.7m^3/sec$, 우기 $-170m^3/sec$로서 유출이 탁월하다. 항유성분은 건기에는 조석잔차류가 우세하지만, 소조기의 강우시에는 밀도류가 우세한 것으로 추리된다.

• 정보처리학회논문지C
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• 제12C권1호
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• pp.19-28
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• 2005

최근 알려지지 않은 공격(unknown attack)으로부터 네트워크를 보호하기 위한 네트워크 트래픽 어노멀리(anomaly) 검출에 대한 관심이 고조되고 있다. 본 논문에서는 캠퍼스 네트워크의 보드라우터(border router)의 NetFlow 데이터로 제공되는 초당비트수(bits per second)와 초당플로수(flows per second)의 상관관계를 단순회귀분석을 통하여 새로운 어노멀리 검출 기법을 제시하였다. 새로이 제안된 기법을 검증하기 위해 실지 캠퍼스 네트워크에 적용하였으며 그 결과론 Holt-Winters seasonal(HWS) 알고리즘과 비교하였다. 특히, 제안된 기법은 기존 RRDtool에 통합시켜 실시간 검출이 가능하도록 설계하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권6호
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• pp.1981-1995
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• 2021

When a person tries to conceal emotions, real emotions will manifest themselves in the form of micro-expressions. Research on facial micro-expression recognition is still extremely challenging in the field of pattern recognition. This is because it is difficult to implement the best feature extraction method to cope with micro-expressions with small changes and short duration. Most methods are based on hand-crafted features to extract subtle facial movements. In this study, we introduce a method that incorporates optical flow and deep learning. First, we take out the onset frame and the apex frame from each video sequence. Then, the motion features between these two frames are extracted using the optical flow method. Finally, the features are inputted into an improved MobileNetV2 model, where SVM is applied to classify expressions. In order to evaluate the effectiveness of the method, we conduct experiments on the public spontaneous micro-expression database CASME II. Under the condition of applying the leave-one-subject-out cross-validation method, the recognition accuracy rate reaches 53.01%, and the F-score reaches 0.5231. The results show that the proposed method can significantly improve the micro-expression recognition performance.

• International Journal of Aeronautical and Space Sciences
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• 제8권2호
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• pp.126-131
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• 2007

In this paper, Monte Carlo Simulation (MCS) method was used as an uncertainty assessment tool for air flow, net thrust measurement. Uuncertainty sources of the net thrust measurement were analyzed, and the probability distribution characteristics of each source were discussed. Detailed MCS methodology was described including the effect of the number of simulation. Compared to the conventional sensitivity coefficient method, the MCS method has advantage in the uncertainty assessment. The MCS is comparatively simple, convenient and accurate, especially for complex or nonlinear measurement modeling equations. The uncertainty assessment result by MCS was compared with that of the conventional sensitivity coefficient method, and each method gave different result. The uncertainties in the net thrust measurement by the MCS and the conventional sensitivity coefficient method were 0.906% and 1.209%, respectively. It was concluded that the first order Taylor expansion in the conventional sensitivity coefficient method and the nonlinearity of model equation caused the difference. It was noted that the uncertainty assessment method should be selected carefully according to the mathematical characteristics of the model equation of the measurement.

• Fisheries and Aquatic Sciences
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• 제16권2호
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• pp.101-108
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• 2013

An active stimulating device (ASD) consisting of a net panel or ropes fluttering in the turbulence inside the cod end was effective in driving fish near the cod end to reduce juvenile by-catch. The fluttering characteristics of the rope and net panel were examined by video observations and analyzed for fluttering amplitude and period in a water channel and in field experiments with a bottom trawl. The amplitude ratio of the fluttering ropes or nets in the tank test increased with the fluttering index as the diameter of the twine, mesh size, flexibility, and flow velocity changed, whereas the period decreased with the above factors. In bottom trawl experiments, the range of mean depth difference in the fluttering net panel was 12-17% of the length of the fluttering net, and the period of depth difference or three-dimensional (3D) tilt was revealed, with shorter ones ranging from 2 to 6 s. The amplitude as depth difference and period from field measurements were similar to those of nets in tank experiments and also to the period of 3D flow velocity inside the cod end. These results could be used to design an ASD that could be used for to the cod end of actual towed fishing gear to reduce juvenile by-catch.

• 한국수산과학회지
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• 제33권6호
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• pp.514-519
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• 2000

우리형 그물에 작용하는 유수저항을 그 도면으로부터 정확하게 계산하기 위하여 그물실을 원형 실린더로 단순화하여 실린더를 통과한 흐름의 속도 감소에 대한 수치 해석 결과와 상자 구조의 모형 우리 그물에 대한 수리 모형실험을 행하여 저항계수 및 그물감을 통과기 전과 후의 속도 감소비에 대한 관계를 검토하였으며, 속도 감소비를 고려하여 흐름에 의한 그물의 변형 유무에 따른 모형 우리 그물에 작용하는 유수저항을 측정하였다. 실험에서 얻어진 결과를 요약하면 다음과 같다. 1. 그물감을 통과하기 전의 유속 U와 통과한 후의 유속 u의 비인 속도 감소비와 그물감의 $S_n/S$ 값과의 관계는 다음과 같이 나타났다. 나일론 랏쉘 그물감의 경우: $$\frac{u}{U}=1-1.54(\frac{S_n}{S})^(1.47)$$ 나일론 막매듭 그물감의 경우: $$\frac{u}{U}=1-0.97(\frac{S_n}{S})^(1.24)$$ 2. 변형을 고려하지 않는 그물의 경우는 후류의 영향을 고려하여 각각의 그물감에 작용하는 유수저항을 독립적으로 계산하고 그들을 합산하여 전체 저항으로 채택해도 된다는 것을 확인하였다. 3. 흐름에 의한 변형이 있는 그물의 경우는 유수저항 R이 유속 U의 제곱에 비례하지 않고 $R={\kappa}U^(1.76{\~}1.83)$으로 나타났다. 4. 유속이 1 m/s인 때의 A, B 및 C 그물의 유수저항은 그들에 생긴 변형으로 인해 변형이 없는 경우의 저항에 비해 각각 $63{\%}, 71.2{\%}$ 및 $73.2{\%}$로 나타났다.

• 한국산학기술학회논문지
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• 제12권3호
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• pp.1439-1443
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• 2011

본 연구에서는 지중 매설관 주변의 지하수 흐름을 이론적으로 규명해 보았다. 지하수 흐름에 있어서는 비압축, 비회전 흐름을 고려하였다. 지하수 흐름 해석시 복소 포텐셜을 이용하여 흐름을 정의하였는데 지중 매설관이 없는 경우의 균등흐름을 먼저 고려하였고 원 정리에 의해 지중 매설관의 영향을 기존의 균등흐름에 추가하였다. 복소 포텐셜의 선형성에 근거하여 두 개의 흐름을 중첩시킬 수 있으나 이때 특이점의 위치를 고려하여 적절한 복소 포텐셜을 적용함으로써 추가적인 특이점의 이미지를 삽입하지 않도록 하는 효율적인 해석이 필요하다. 최종적으로는 순환을 동반하는 지중 매설관 주변의 흐름을 복소 포텐셜 중첩을 통해 살펴보았고 그 경우 흐름에 의해 지중 매설관에 작용하는 작용력을 유도해 보았다.

• 대한안전경영과학회지
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• 제15권4호
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• pp.435-448
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• 2013

The aim of this study is to investigate and develop the extended models for Economic Cash Amount(ECA), Cash Break Even-Point(BEP), and Cash Flow Statement(CFS) by referencing systematic literature review in the field. The study develops three extended models to determine the optimal cash amount: ECA model with interest opportunity cost, financing transaction cost and financing fail cost, ECA model with daily cash supply and interest opportunity cost, ECA model with financing fail cost and interest opportunity cost. Earnings Before Interests, Tax, Depreciation and Amortization(EBITDA) is obtained by subtracting noncash depreciation costs from Earning Before Interest and Tax(EBIT), which is efficient metric to evaluate operating cash flow. The research also develops two extended Cash BEP models, considered as interest and corporate tax, in order to indentify the break-even point as EBITDA equals zero. Furthermore, this paper proposes the modified version of CFS by introducing the reclassification of operating and financing accounts in the statement of financial position. In addition, the study also present the reclassification of five types of profit, such as gross profit, EBIT, ordinary profit, special profit, and net profit within the statement of comprehensive income. In order to provide a better understanding of the proposed cash flow models, numerical examples, such as two-sample t test and Analysis of Variance(ANOVA), are presented to demonstrate the statistical significance according to the industrial types for net working capital(i.e cash-to-cash), net profit, operating cash flow and free cash flow.

• 설비공학논문집
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• 제17권6호
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• pp.544-551
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• 2005

The flow characteristics have been numerically investigated for various shapes of the diffuser/nozzles which are used for a valveless micro-pump. The important parameters considered in this study are the throat width ($15\~120\mu$m), the taper angle ($3.15\~25.2^{\circ}$), and the diffuser length ( $600\~4,800\mu$m), and the size of the middle chamber ($1\~16mm^2$). To find the optimal values for these parameters, steady state calculations have been performed assuming the constant pressure difference between the inlet and exit of the flow For the taper angle and the throat width, it is found that there exists an optimum at which the net flow rate is the greatest. The optimal taper angle is in the range of $10\~20^{\circ}$ for all the pressure differences; and the throat width indicates an optimal value near $75\mu$m for the case of 35 kPa pressure difference. The net flow rate is also influenced by the size of the middle chamber. With decreasing chamber size, the net flow rate is reduced because of the interference between two streams flowing into the middle chamber. The unsteady pulsating flow characteristics for a micro-pump with a given diffuser/nozzle shape have been also investigated to show the validity of the steady state parametric study.

• 수산해양기술연구
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• 제59권2호
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• pp.164-171
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• 2023

This study analyzed the flow inside floating seedling equipment for Scapharca subcrenata. Due to the aging society of fishing villages, it is impossible to continuously input the labor force. Therefore, it is necessary to improve efficiency. Scapharca subcrenata has high per capita consumption. It serves as an important aquatic food resource. Scapharca subcrenata culture tends to be highly dependent on the natural environment. Production of Scapharca subcrenata is difficult to predict with low stability. In the past, manpower directly installed bamboo nets in mudflats. The seedling equipment devised in this study is a floating type and can be freely moved on the sea according to the prediction of Scapharca subcrenata generation. The flow around the floating seedling equipment was analyzed by numerical analysis. The physical phenomena of the flow around the net inside the floating seedling equipment were visualized. As a result, the space between the floating seedling equipment and the bottom net and the space between the net groups showed a lower flow rate than the inlet flow rate. It is expected that the low flow rate of the floating seedling equipment will have a positive effect on the attachment of Scapharca subcrenata.