• 수산해양기술연구
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• 제56권2호
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• pp.163-171
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• 2020

Engaged in trawling in limited fishing grounds with a number of fish schools could cause collisions between fishing vessels. Therefore, providing accurate maneuver information according to the situation could be regarded as essential for improving seafarers safety and fishing efficiency as well as safety of navigation. It is difficult to obtain all maneuver information through sea trial tests only, so a method through empirical formula is necessary. Since most empirical formulas are developed for merchant ship types, especially the characteristics of hull shape parameter like C_bB/L and dC_b/B etc. are clearly different between fishing vessels and merchant ships, this could occur estimation errors. Therefore, in this study, the authors have selected target fishing vessels and merchant ships and analyzed the characteristics of hull shape parameter according to the ship types. Based on this analysis, the empirical formula developed for the merchant ship type has applied to the target fishing vessels; it has verified through the turning motion simulation that the estimation error could be generated. In conclusion, it is necessary to include the characteristics of the hull shape parameter of fishing vessels in the empirical formula in order to apply the empirical formula has developed for merchant ship types to fishing vessel types.

• 한국항해항만학회지
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• 제45권3호
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• pp.165-172
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• 2021

쇄파는 연안류, 표사이동, 충격파압, 에너지소산 등과 같은 연안에서 발생하는 다양한 물리현상과 직접적인 관계가 있으므로 항만 구조물의 설계시 반드시 고려되어야 하는 중요한 설계인자 중 하나이다. 쇄파에 대한 연구들은 쇄파가 가진 고유의 복잡성으로 인해 주로 수리모형실험을 통해 쇄파파고와 쇄파수심 등과 같은 쇄파지표를 예측하기 위한 많은 경험식이 제안되어 왔다. 하지만, 기존의 쇄파지표에 대한 경험식은 일정한 방정식의 가정하에 자료의 통계적 분석을 통해 가정한 방정식의 계수들을 결정하고 있다. 본 연구에서는 회귀 혹은 분류문제와 관련된 다양한 연구분야에 있어서 높은 예측성능을 보여주는 대표적인 선형기반의 머신러닝 기법을 적용하여 천수변형에 의해 발생하는 쇄파의 한계파고를 산정하기 위한 새로운 Munk형식의 경험식을 제안하였다. 새롭게 제안된 쇄파지표식은 단순한 형태의 다항식에도 불구하고 기존의 경험공식과 유사한 예측성능을 보였다.

• 한국수자원학회논문집
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• 제54권12호
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• pp.1305-1316
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• 2021

본 연구에서는 과거 추적자실험결과를 이용하여 2차원 횡분산계수에 대한 새로운 추정식을 개발하고 추정식을 이용한 횡 분산계수 산정결과의 정확도를 검증했다. 다수의 추적자실험이 하폭 대 수심비가 50보다 작은 조건에서 수행되었기 때문에 기존 추적자실험결과만을 이용하여 개발한 추정식은 하폭 대 수심비가 50보다 큰 조건의 하천에 적용하는데 한계를 보인다. 따라서 특정 수리조건에 편중된 횡 분산계수 자료로부터 횡 분산계수 추정식을 개발하기 위해 SMOTE (Synthetic Minority Oversampling TEchnique)를 적용하여 기존 자료의 특성을 반영한 새로운 데이터를 생성했다. SMOTE 기법으로 하폭 대 수심비가 50보다 큰 조건에 대한 수리량과 횡 분산계수 데이터를 생성하였으며, ROC (Receiver Operating Characteristic) 곡선으로부터 생성된 데이터의 신뢰성을 검증했다. 새롭게 생성된 데이터를 포함하여 횡 분산계수 추정식을 개발했고, 추정식을 이용하여 계산한 횡 분산계수의 R²(결정계수)를 계산하여 기존 연구에서 제안한 추정식과의 정확도를 비교했다. 그 결과, 본 연구에서 개발한 추정식을 이용하여 계산한 횡 분산계수의 R²가 W/H < 50인 조건에서 0.81, 50 < W/H 인 조건에서 0.92를 나타내어 기존 추정식과 비교하여 향상된 정확도를 나타냈다.

• 대한조선학회논문집
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• 제56권4호
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• pp.316-326
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• 2019

In this paper, a methodology is presented for determining the optimal lamination of composite cylindrical structures subject to hydrostatic pressure. The strength criterion in association with the process of optimal design is the buckling collapse of composite cylinders under hydrostatic pressure loads. An empirical formula expressed in the form of the Merchant-Rankine equation is used to calculate the ultimate strength of filament-wound composite cylinders where genetic algorithm is applied for determining the optimized stacking sequences. It is shown that the optimized lamination provides improved collapse pressure loads. It is concluded that the developed method would be useful for the optimal lamination design of composite cylindrical structures.

• 소성∙가공
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• 제8권5호
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• pp.520-526
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• 1999

In this study a practical formula based on the experime수 랙 the estimation of load in the non-circular tube extrusion with the mandrel is proposed by using the effective extrusion ratio. Through some experiments for the several shaped sections, the coefficients of the empirical equation are determined by ticine as a model material at room temperature. The proposed empirical formula for the estimation of extrusion load will be applicable to the non-steady state as well as steady state for the extrusion of various shaped tubes from hollow billets.

• 한국지반공학회논문집
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• 제37권6호
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• pp.5-20
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• 2021

본 연구에서는 풍화암에 근입된 강관 매입말뚝의 지지력 공식 제안을 위하여 정재하시험 20본과 확인지반조사를 수행하였다. 기존 공식의 표준관입저항치를 50으로 제한하는 문제를 극복하기 위해 지반 현장 상태를 고려할 수 있도록 확장된 표준관입저항치를 기반으로 새로운 지지력 공식을 제안하였다. 재하시험 데이터는 통계적 처리를 수행하였다. 이때, 통계적 처리를 수행하여 얻어진 지지력과 기존공식을 이용한 지지력을 비교한 결과 기존공식이 지지력을 보수적으로 평가하고 있는 것으로 나타났다. 제안된 공식은 기존공식에 비해 지지력은 선단 15%, 주면 20% 더 높게 (q_t=230P_driven(kN/m²), f_max=3.0N_s^E(kN/m²)) 평가되는 것으로 확인되었다. 제안식은 여타 현장에 대해 재하시험 결과와 검증을 수행하였으며, 검증 과정에서 제안된 공식이 기존 공식보다 정확히 평가하는 것으로 나타났다.

• Water Engineering Research
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• 제5권4호
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• pp.185-193
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• 2004

Estimates of annual actual evapotranspiration are needed in water balance studies, water resources management projects, and many different types of hydrologic studies. This study validated a set of 5 empirical equations of estimating annual actual evapotranspiration with climate data on 11 watersheds, and evaluated the further applicability of these forms in estimating annual runoff on watershed level. Five empirical equations generally overestimated annual evapotranspiration, with relative errors ranging $3.3\%$ to $47.2\%$. The results show that Schreiber formula can be applicable in determining annual evapotranspiration in sub-humid region that is classified by aridity index, while Zhang equation gave better results than the remaining methods in humid region. The mean differences for annual evapotranspiration bias over 11 watersheds are Zhang, Schreiber, Budyko, Pike, and Ol'dekop formula from lowest to highest. The empirical equations provide a practical tool to help water resources managers in estimating regional water resources on ungauged large watershed.

• Wind and Structures
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• 제21권1호
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• pp.85-103
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• 2015

Aerodynamic forces of vortex-induced vibration and galloping are going to be coupled when their onset velocities are close to each other, which will induce the cross-wind amplitudes of the structures increased continuously with ever-increasing wind velocities. The main purpose of the present work is going to propose an empirical formula to predict the response amplitude of VIV-galloping interaction. Firstly, two typical mathematical models for the coupled oscillations, i.e., Tamura & Shimada model and Parkinson & Corless model are comparatively summarized. Then, the key parameter affecting response amplitude is determined through comparative numerical simulations with Tamura & Shimada model. For rectangular cylinders with the side ratio from 0.5 to 2.5, which are actually prone to develop the VIV and galloping induced interaction responses, an empirical amplitude prediction formula is proposed after regression analysis on comprehensively collected experimental data with the predetermined key parameter.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.80-87
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• 2002

We predict the unknown cannon tube erosion rate by using observed values of the standard cannon, 155mm Howitzer Ml85. We know the standard cannon's ten erosion observation values each 400 rounds. An approximate formula fitting the erosion values of the standard cannon has been derived. Numerical simulation applying this formula to the Rauf Imam's erosion equations is presented.

• Communications for Statistical Applications and Methods
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• 제25권3호
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• pp.321-328
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• 2018

In clinical trials with repeated measurements, the time-averaged difference (TAD) may provide a more powerful evaluation of treatment efficacy than the rate of changes over time when the treatment effect has rapid onset and repeated measurements continue across an extended period after a maximum effect is achieved (Overall and Doyle, Controlled Clinical Trials, 15, 100-123, 1994). The sample size formula has been investigated by many researchers for the evaluation of TAD in two treatment groups. For the evaluation of TAD in multi-arm trials, Zhang and Ahn (Computational Statistics & Data Analysis, 58, 283-291, 2013) and Lou et al. (Communications in Statistics-Theory and Methods, 46, 11204-11213, 2017b) developed the sample size formulas for continuous outcomes and count outcomes, respectively. In this paper, we derive a sample size formula to evaluate the TAD of the repeated binary outcomes in multi-arm trials using the generalized estimating equation approach. This proposed sample size formula accounts for various correlation structures and missing patterns (including a mixture of independent missing and monotone missing patterns) that are frequently encountered by practitioners in clinical trials. We conduct simulation studies to assess the performance of the proposed sample size formula under a wide range of design parameters. The results show that the empirical powers and the empirical Type I errors are close to nominal levels. We illustrate our proposed method using a clinical trial example.