• Journal of the Korean Wood Science and Technology
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• v.40 no.2
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• pp.78-90
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• 2012

Soybean hull is an attractive feedstock for glucose production. To increase the glucose conversion in acid hydrolysis, a pretreatment method combined steam explosion with alkali pretreatment for soybean hull was studied. For first step pretreatment, steam explosion conditions (log Ro 2.45) were optimized to obtain maximum solid recovery and cellulose content. In the second step pretreatment, the conditions for potassium hydroxide pretreatment of steam exploded soybean hull were optimized by using RSM (response surface methodology). The optimum conditions for minimum lignin content were determined to be 0.6% potassium hydroxide concentration, $70^{\circ}C$ reaction temperature and 198 min reaction time. The predicted lignin content was 2.2% at the optimum conditions. Experimental verification of the optimum conditions gave the lignin content in similar value with the estimated value of the model. Finally, glucose conversion of pretreated soybean hull using acid hydrolysis resulted in $97.1{\pm}0.4%$. This research of two-step pretreatment was a promising method for increasing the glucose conversion in the cellulose-to-glucose process.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.118-126
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• 2000

An optimum structural design system for double hull oil tankers is developed based on the generalized slope deflection method which was previously proposed by the authors. For the optimization technique, the Hooke & Jeeves direct search method is applied to the minimum weight design problems with discrete design variables. A minimum weight design program is developed for the longitudinal members by the classification rules and for the transverse frames and the bulkhead members by the generalized slope deflection method. By this program, a minimum hull weight design of double hull oil tankers considering tank arrangement is performed and the design results are compared with existing ship. It is possible to find optimum tank arrangement and efficient types of hull structures for the minimum weight design of double hull oil tankers.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.246-255
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• 2017

The proposed design methodology represents a new approach to optimize the propeller-hull system simultaneously. In this paper, two objective functions are considered, the first objective function is Lifetime Fuel Consumption (LFC) and the other one is cost function including thrust, torque, open water and skew efficiencies. The variables of the propeller geometries (Z, EAR, P/D and D) and ship hull parameters (L/B, B/T, T and $C_B$) are considered to be optimized with cavitation, blades stress of propeller. The well-known evolutionary algorithm based on NSGA-II is employed to optimize a multi-objective problem, where the main propeller and hull dimensions are considered as design variables. The results are presented for a series 60 ship with B-series propeller. The results showed that the proposed method is an appropriate and effective approach for simultaneously propeller-hull system design and is able to minimize both of the objective functions significantly.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.5
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• pp.466-474
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• 2016

The model tests results for the original lines of an 10000TEU container vessel show that the delivered power is higher and could not satisfy the requirement of energy saving effects and design targets. In this paper, the lines optimization of the 10,000 twin-skeg container vessel was carried out by parametric modeling and CFD simulations. At first, the CFD methods for twin-skeg hull form were validated by the comparison with the experimental results. Then more than one hundred parameters were adopted for the establishment of the fully parametric model. Based on the parametric model of the twin-skeg container vessel, the preliminary optimization was carried out by tight coupling of FRIENDSHIP-FRAMEWORK with potential flow of SHIPFLOW. Then several important parameters related to the after part of twin-skeg vessel were investigated by viscous flow computation. The final optimized variant PM11, which the total resistance was reduced by about 8.3% in model scale, is obtained within the constraints of general arrangement. And the model tests for variant PM11 was carried out in CSSRC, which shows that the resistance of optimized variant PM11 is decreased by about 8.6%.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.558-570
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• 2015

A study on the green ship design for Ultra Large Container Ship (ULCS, 18,000 TEU Class Container Ship) was performed based on the four step procedures of the initial design and hull form optimization to maximize economic and propulsive performance. The first, the design procedure for ULCS was surveyed with economic evaluation considering environmental rules and regulations. The second, the characteristics of single and twin skeg container ships were investigated in view of initial design and performances. The third, the hull form optimization for single and twin skeg ships with the same dimensions was conducted to improve the resistance and propulsive performances at design draught and speed by several variations and the results of the optimization were verified by numerical calculations of CFD and model test. The last, for the estimated operating profile of draught and speed, the hull forms of single and twin sked ships were optimized by CFD. From this study, the methodologies to optimize the hull form of ULCS were proposed with considerations during the green ship design and the improvement of the energy efficiency for the optimized hull forms was confirmed by the proposed formula of the total energy considering design conditions, operating profile and fuel oil consumption.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.82-96
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• 2019

A semi-submersible structure has been widely used for offshore drilling and production of oil and gas. The small water plane area makes the structure very sensitive to weight increase in terms of payload and stability. Therefore, it is necessary to lighten the substructure from the early design stage. This study aims at an optimization of hull structure based on a sophisticated yield and buckling strength in accordance with classification rules. An in-house strength assessment system is developed to automate the procedure such as a generation of buckling panels, a collection of required panel information, automatic buckling and yield check and so on. The developed system enables an automatic yield and buckling strength check of all panels composing the hull structure at each iteration of the optimization. Design variables are plate thickness and stiffener section profiles. In order to overcome the difficulty of large number of design variables and the computational burden of FE analysis, various methods are proposed. The steepest descent method is selected as the optimization algorithm for an efficient search. For a reduction of the number of design variables and a direct application to practical design, the stiffener section variable is determined by selecting one from a pre-defined standard library. Plate thickness is also discretized at 0.5t interval. The number of FE analysis is reduced by using equations to analytically estimating the stress changes in gradient calculation and line search steps. As an endeavor to robust optimization, the number of design variables to be simultaneously optimized is divided by grouping the scantling variables by the plane. A sequential optimization is performed group by group. As a verification example, a central column of a semi-submersible structure is optimized and compared with a conventional optimization of all design variables at once.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1231-1237
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• 2022

In the present study, the optimization of the main particulars of a ship using AI-based design search techniques was investigated. For the design search techniques, the SHERPA algorithm by HEEDS was applied, and CFD analysis using STAR-CCM+ was applied for the calculation of resistance performance. Main particulars were automatically transformed by modifying the main particulars of the ship at the stage of preprocessing using JAVA script and Python. Small catamaran was chosen for the present study, and the main dimensions of the length, breadth, draft of demi-hull, and distance between demi-hulls were considered as design variables. Total resistance was considered as an objective function, and the range of displaced volume considering the arrangement of the outfitting system was chosen as the constraint. As a result, the changes in the individual design variables were within ±5%, and the total resistance of the optimized hull form was decreased by 11% compared with that of the existing hull form. Throughout the present study, the resistance performance of small catamaran could be improved by the optimization of the main dimensions without direct modification of the hull shape. In addition, the application of optimization using design search techniques is expected for the improvement in the resistance performance of a ship.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.225-228
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• 2004

The generalized knapsack problem, or gknap is the combinatorial optimization problem of optimizing a nonnegative linear functional over the integral hull of the intersection of a polynomially separable 0 - 1 polytope and a knapsack constraint. Among many potential applications, the knapsack, the restricted shortest path, and the restricted spanning tree problem are such examples. We prove via the ellipsoid method the equivalence between the fully polynomial approximability and a certain pseudo-polynomial separability of the gknap polytope.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.1
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• pp.118-126
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• 2024

In this paper, the research contents and results related to the automation of the hull-form optimal design of container ships are summarized. A container ship is a ship that generally operates near Froude number of 0.26. To implement hull-form optimal design automation for ships operating at this speed, an optimization algorithm, a hull-form change algorithm, a ship performance prediction algorithm, an automation algorithm, and an iterative calculation technique were applied to develop a numerical analysis computer program that enables hull-form optimal design automation of the container ship, and it was named HOTCONTAINER. In this study, a sensitivity analysis algorithm was developed and applied to appropriately set design variables for hull-form optimal design. To understand the reliability and real ship applicability of the developed algorithm, a numerical analysis was performed on KCS(KRISO Container Ship), a container ship that has been studied in various ways worldwide. Consequently, the optimal ship was derived, and the wave resistance, wave pattern, and wave height of the target and optimal ship were compared. In conclusion, compared the target ship, the optimal ship a 47.63% decrease in wave resistance, and the displacement and wet surface area decreased by 0.50% and 0.39%, respectively.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.47-52
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• 2003

지금까지의 선형 최적화에 대한 연구는 고전적인 최적화 기법인 비선형계획법과 유동해석법을 중심으로 생물의 진화 알고리즘을 바탕으로 한 유전자 알고리즘과 인공지능에 기초를 둔 신경망이론 등이 이용되어 왔다. 또한 최근 컴퓨터의 성능이 급속도로 향상됨에 따라 전산유체역학에 기초한 시뮬레이션 평가기법도 사용되고 있다. 본 논문에서는 유전자 알고리즘을 이용한 선형 최적화 방법을 제시하였다. 그리고 광역 최적해의 효과적인 검색과 빠른 접근을 위한 방법으로 네트워크 시스템을 기반으로 한 병렬분산 유전자 알고리즘 시스템(PDGAS)을 개발하였으며 그 성능을 기존의 진화 알고리즘과 비교${\cdot}$분석함으로써 선형 최적화의 가능성을 확인하였다.