• Wind and Structures
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• 제18권3호
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• pp.253-265
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• 2014

The platform and floating structure of spar type offshore wind turbine systems should be designed in order for the 6-DOF motions to be minimized, considering diverse loading environments such as the ocean wave, wind, and current conditions. The objective of this study is to optimally design the platform and substructure of a 3MW spar type wind turbine system with the maximum postural stability in 6-DOF motions as well as the minimum material cost. Therefore, design variables of the platform and substructure were first determined and then optimized by a hydrodynamic analysis. For the hydrodynamic analysis, the body weight of the system was considered, and the ocean wave conditions were quantified to the wave forces using the Morison's equation. Moreover, the minimal number of computation analysis models was generated by the Design of Experiments (DOE), and the design variables of the platform and substructure were finally optimized by using a genetic algorithm with a neural network approximation.

• Steel and Composite Structures
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• 제29권2호
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• pp.175-186
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• 2018

The plastic hinge method and the plastic zone method are extensively adopted in displacement-based elements and force-based elements respectively for second-order inelastic analysis. The former enhances the computational efficiency with relatively less accurate results while the latter precisely predicts the structural behavior but generally requires more computer time. The displacement-based elements receive criticism mainly on plasticity dominated problems not only in accuracy but also in longer computer time to redistribute the forces due to formation of plastic hinges. The multi-element-per-member model relieves this problem to some extent but will induce a new problem in modeling of member initial imperfections required in design codes for direct analysis. On the contrary, a force-based element with several integration points is sufficient for material yielding. However, use of more integration points or elements associated with fiber section reduces computational efficiency. In this paper, a new force-based element equipped with stress-resultant plasticity model with minimal computational cost is proposed for second-order inelastic analysis. This element is able to take the member initial bowing into account such that one-element-per-member model is adequate and complied with the codified requirements of direct analysis. This innovative solution is new and practical for routine design. Finally, several examples demonstrate the validity and accuracy of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.79-84
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• 1992

Path planning is an important task for optimal motion of a robot in structured or unstructured environment. The goal of this paper is to plan the optimal collision-free path in 3D, when a robot is navigated to pick up some tools or to repair some parts from various locations. To accomplish the goal, the Path Coordinator is proposed to have the capabilities of an obstacle avoidance strategy and a traveling salesman problem strategy (TSP). The obstacle avoidance strategy is to plan the shortest collision-free path between each pair of n locations in 2D or in 3D. The TSP strategy is to compute a minimal system cost of a tour that is defined as a closed path navigating each location exactly once. The TSP strategy can be implemented by the Hopfield Network. The obstacle avoidance strategy in 2D can be implemented by the VGraph Algorithm. However, the VGraph Algorithm is not useful in 3D, because it can't compute the global optimality in 3D. Thus, the Path Coordinator is used to solve this problem, having the capabilities of selecting the optimal edges by the modified Genetic Algorithm and computing the optimal nodes along the optimal edges by the Recursive Compensation Algorithm.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권4호
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• pp.450-457
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• 2018

The determination of assembly sequence in general mechanical assemblies plays an important role in terms of manufacturing cost, duration and quality. In the production of ships and offshore plants, the consideration of productivity factors and welding deformation is crucial in determining the optimal assembly sequence. In shipbuilding and offshore industries, most assembly sequence planning has been done according to engineers' decisions based on extensive experience. This may result in error-prone planning and sub-optimal sequence, especially when dealing with unfamiliar block assemblies composed of dozens of parts. This paper presents an assembly sequence planning method for block assemblies. The proposed method basically considers geometric characteristics of blocks to determine feasible assembly sequences, as well as assembly process and productivity factors. Then the assembly sequence with minimal welding deformation is selected based on simplified welding distortion analysis. The method is validated using an asymmetric assembly model and the results indicate that it is capable of generating an optimal assembly sequence.

• 한국소음진동공학회논문집
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• 제16권9호
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• pp.964-970
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• 2006

Micro gas turbine(MGT) has received attention recently as small-scale distributed power sources. With characteristics such as their small size, lightweight, low maintenance cost and minimal vibrations during operation, they are expected to become widespread in a wide range of ' applications, including residential and small-scale industrial use. It is very easier to start-up and stop the MGT system which is the friendly environmental power system has just below the 9ppm NOx emmission and good quality of noise level. The exhaust heat emitted by the MGT is in the form of about $300^{\circ}C$ clean exhaust gas. The exhaust gas is suitable for absorption chiller/heater system. 1 has researched performance characteristics of the 60 kW class MGT-absorption chiller-heater system in the local condition. Variations of heat recovery from exhaust gas has measured according to micro gas turbine output of 15, 30, 45, 60kW. From those results, the performance of the MGT-absorption chiller/heater system has been evaluated.

• Membrane and Water Treatment
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• 제4권4호
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• pp.237-249
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• 2013

Ultra-pure water (UPW), a highly treated water free of colloidal material and of a conductivity less than 0.06 ${\mu}S$, is an essential component required by modern industry. One of the methods for UPW production is the electrodialysis-ion exchange (ED/IE) system, in which the electrodialysis (ED) process is used as a preliminary demineralization step. The IE step can be replaced with electrodeionization (EDI) to decrease the volume of post-regeneration lyes. In this paper, the electrodialysis process carried out to relatively low diluate conductivity was investigated and the costs of UPW production were calculated. The optimal value of desalination degree by ED in the ED/IE and ED/EDI systems was estimated. UPW unit costs for integrated ED/IE and ED/EDI systems were compared to simple ion exchange and other methods for UPW production (RO-IE, RO-EDI). The minimal UPW unit costs in ED/EDI integrated system were estimated as $0.37/$m^3$ for feed TDS 600 mg/L and $0.36/$m^3$ for feed TDS 400 mg/L at 64 $m^3/h$ capacity, which was lower than in the comparable ED/IE integrated system ($0.42-0.44/$m^3$). The presented results suggest that an ED/EDI integrated system may be economically viable.

• 로봇학회논문지
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• 제11권3호
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• pp.163-171
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• 2016

A modular manipulator in serial-chain structure usually consists of a series of modularized revolute joint and link modules. The geometric shapes of these modules affect the number of possible configurations of modular manipulator after assembly. Therefore, it is important to design the geometry of the joint and link modules that allow various configurations of the manipulators with minimal set of modules. In this paper, a new 1-DoF(degree of freedom) joint module and simple link modules are designed based on a methodology of joint configurations using a series of Rotational(type-R) and Twist(type-T) joints. Two of the joint modules can be directly connected so that two types of 2-DoFs joints could be assembled without a link module between them. The proposed geometries of joint and link modules expand the possible configurations of assembled modular manipulators compared to existing ones. Modular manipulator system of this research can be a cornerstone of user-centered markets with various solution but low-cost, compared to conventional manipulators of fixed-configurations determined by the provider.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.75-78
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• 2014

MLCC is one of the most frequently used component in high-tech device like smart phone. Because of dynamic characteristic of piezoelectric materials which is main ingredient of MLCC, its vibration leads to acoustic noise from pcb. To solve this problem at minimal cost, company has to change only the main noise-generating MLCC to low noise-generating MLCC. To find the main noise source, this study approached to solution from a vibration point of view. From mode shapes of pcb at particular frequencies, two groups can be obtained; MLCCs soldered at where maximum deformation occurs and where anti-phase with respect to the other group appears. When the MLCC belongs to 1st group does not working, amplitude at where maximum deformation occurs decreases compared to when all MLCCs are working. This tendency also appears in noise measurement. This analysis can be put to use in various fields where require noise reduction or noise source identification.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.127-141
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• 2009

While the ever-increasing complexity of automotive software systems can be effectively managed through the adoption of a reliable real-time operating system (RTOS), it may incur additional resource usage to a resultant system. Due to the mass production nature of the automotive industry, reducing physical resources used by automotive software is of the utmost importance for cost reduction. OSEK OS is an automotive real-time kernel standard specifically defined to address this issue. Thus, it is very important to develop and exploit kernel mechanisms such that they can achieve minimal resource usage in the OSEK OS implementation. In this paper, we analyze the task subsystem, resource subsystem, application mode and conformance classes of OSEK OS as well as the OSEK Implementation Language (OIL). Based on our analysis, we in turn devise and implement kernel mechanisms to minimize the dynamic memory usage of the OSEK OS implementation. Finally, we show that our mechanisms effectively reduce the memory usage of OSEK OS and applications.

• 한국축산시설환경학회지
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• 제20권1호
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• pp.15-20
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• 2014

The present study was conducted to develop a milk filtering system for decreasing somatic cell count (SCC) in bulk tank milk. The pore sizes of the filter were 0.1, 0.3, 0.4, 0.5 and $0.8{\mu}m$. The rate of SCC reduction of $1^{st}$ grade milk on $0.1{\mu}m$ filter was 76% and significantly higher than other treatments. The rates of SCC reduction for 0.3, 0.4, 0.5 and $0.8{\mu}m$ were 35, 32, 18 and 6.4%, respectively. The effects of the milk filtering system on bacterial count and milk fat content were minimal. The milk flow rates per minute between the filter sizes were similar. But discharge pressures were increased as the pore size of the filter decreased. In conclusion, Considering the rate of SCC reduction, discharge pressure and cost, $0.4{\mu}m$ filter could be recommended.