• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2172-2194
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• 2023

A variational nodal method (VNM) with unstructured-mesh is presented for solving steady-state and dynamic neutron diffusion equations. Orthogonal polynomials are employed for spatial discretization, and the stiffness confinement method (SCM) is implemented for temporal discretization. Coordinate transformation relations are derived to map unstructured triangular nodes to a standard node. Methods for constructing triangular prism space trial functions and identifying unique nodes are elaborated. Additionally, the partitioned matrix (PM) and generalized partitioned matrix (GPM) methods are proposed to accelerate the within-group and power iterations. Neutron diffusion problems with different fuel assembly geometries validate the method. With less than 5 pcm eigenvalue (k_eff) error and 1% relative power error, the accuracy is comparable to reference methods. In addition, a test case based on the kilowatt heat pipe reactor, KRUSTY, is created, simulated, and evaluated to illustrate the method's precision and geometrical flexibility. The Dodds problem with a step transient perturbation proves that the SCM allows for sufficiently accurate power predictions even with a large time-step of approximately 0.1 s. In addition, combining the PM and GPM results in a speedup ratio of 2-3.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2678-2686
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• 2023

This work demonstrates the results of full-scale numerical experiments of a hybrid thorium-containing fuel plant operating in a state close to critical due to a controlled source of D-T neutrons. The proposed facility represented a level of generated power (~10-100 MW_t) in a small pilot. In this work, the simulation of the D-T neutron plasma source operation in conjunction with the facility blanket was performed. The fission of fuel nuclei and the formation of spatial-energy release were studied in this simulation, in pulsed and stationary modes of the facility operation. The optimization results of neutronic and fluid dynamics studies to level the emerging offsets of the radial energy formed in the volume of the facility multiplying part due to the pulsed operation of the D-T neutron plasma source were presented. The results will be useful in improving the power control-based subcriticality monitoring method in coupled systems of the "pulsed neutron source-subcritical fuel assembly" type.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.613-620
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• 2021

A flow channel shape of PEMFC has an influence on the internal flow uniformity. If the reactant distribution in a flow path is not uniform during operation, both catalyst deactivation and mechanical damage of membrane could occur resulting in decreasing the membrane electrode assembly (MEA) durability. Numerous studies concerning flow design have been conducted to make smooth supply and uniform distribution of reactants in fuel cells. The baffle of flow path could improve fuel cell performance through the forced convection effect. A sub-channel, as an additional air flow path, could increase the reactant concentration and reduce the mass transfer loss via a smooth water discharge. In this study, computational fluid dynamics (CFD) was used to analyze the effect of blocks and sub-channels on the current density and oxygen concentration of the fuel cell. As a result, the limit current density and oxygen concentration at a rear block increased when using blocks and sub-channels in a flow channel. In particular, the current density increased significantly when the sub-channel was placed between two blocks. Also, the sub-channel position was optimized by analyzing the oxygen concentration, and the oxygen concentration was recovered at a rear block in the fuel cell.

• Transactions of Materials Processing
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• v.22 no.5
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• pp.275-279
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• 2013

The tube hydroforming process has received much attention in the automotive industry because of its advantages compared to conventional manufacturing technologies. A wide range of products such as sub-frames, camshafts, radiator frames, axles and crankshafts are made by hydroforming process. The hydroformed parts often need to be structurally joined to other components during assembly. Therefore, these automotive parts need to be manufactured with a localized attachment flange. In this study, FE forming analyses of a part with a rectangular flanged shape was performed with Dynaform 5.5. Using the optimized conditions determined numerically, hydroforming experiments were performed. Then, the characterization of defects was analyzed. Finally, the accuracy of the optimized internal pressure condition as well as that of the initial ram position were evaluated. The results demonstrated that flanged parts can be successfully produced using the tube hydroforming process.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.4
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• pp.1-8
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• 2011

Injection molding machine is the assembly of many kinds of mechanical and fluid power part and electro-electronic control system. From in these, fluid power is a part where becomes the first core of this machine. Fluid power systems of injection molding machine are modelled and analyzed using a commercial program AMESim. The analysis model which is detailed about the parts applied a publishing catalog data. Sub system models which is divided according to functional operation are made and its analysis results shows how design parameters work on operational characteristics like displacement, pressure, flow rates at each node and so on. Total fluid power circuit model is also made and analyzed. The results made by analysis will be used design of fluid power circuit of injection molding machine.

• Korean Journal of Computational Design and Engineering
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• v.11 no.1
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• pp.11-19
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• 2006

For several years, a research about the simulation for shipyard and shipbuilding has been performed. This research is based on the concept of PLM (Product Lifecycle Management) and DM (Digital Manufacturing). Global leading companies and research center are trying to get a good position of PLM, especially M&S field. Digital shipbuilding is to computerize shipyard facilities and shipbuilding processes, and to simulate expected scenarios of shipbuilding processes using a computer model in order to resolve a potential problem such as a bottleneck processes, and over loaded resources. In this paper, simulation methodology for shipbuilding is described. In addition, a local and global strategy for the use of simulation methodology is suggested. Finally, case studies about an indoor shop and an outdoor shop are described.

• Journal of Welding and Joining
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• v.14 no.1
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• pp.30-37
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• 1996

조선에서 추진되어온 용접로봇의 적용은 주로 대조립 용접공정의 자동화로서, 갠트리(Gantry)에 용접토치를 장착한 로봇을 설치하여 구성하였다. 이러한 시스템에 서의 용접은 로봇을 용접부위까지 이송시킨 후 로봇의 구동으로 용접을 수행하거나, 또는 로봇과 캔트리의 동시 구동으로 용접을 수행하기도 한다. 또한 이 공정은 복잡 한 용접구조물을 OLP(Off-Line Programming)를 이용하여 교시하므로서 효과적인 자동 화 시스템의 구성이 가능할 수 있었다. 소조립 공정은 대조립공정과 비교하면 더 간단 한 부재의 용접이라 할 수 있으나 공정과 공장의 생산방법에 따라 자동화의 어려움은 따른다. 적용되는 매니프레이타는 소조립 공정의 특성에 맞게 그 형태가 설계되어야 하고 이를 운용하는 시스템은 소조립 생산방법에 맞게 통합, 개발되는 Task-Based System"이 되어야 한다. 특히 소조립 공정은 대조립 공정과 달리 여러가지 용접 판넬 을 동시에 이송시킨 후 용접함으로서 OLP의 직접 적용을 어렵게 하는 요인이 있어 이것을 해결하는 것이 생산성을 증가시키는데 적지 않은 영향을 미친다 하겠다. 이 글에서는 소조립 용접 자동화를 구성하기 위해 필요한 젓으로서 소조립 용접 공정을 소개하고, 공정의 특성에 맞도록 설계된 매니퓰레이타 시스템과, OLP, 판넬인식, 자동 교시 모들로 이루어지는 작업인식 시스템에 관해 기술한다.기술한다.

• Journal of Korean Institute of Industrial Engineers
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• v.25 no.1
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• pp.21-34
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• 1999

We consider a scheduling problem arising in a shipyard subassembly welding process. There are four welding robots of gantry type, which perform the welding process for the subassemblies. Because the robots perform the welding operations at the same time, there is a possibility of collision between adjacent robots depending on the welding schedule. In this paper, we propose a heuristic method to find a welding schedule which does minimize the welding completion time while avoiding collision among the robots. The method consists of two phases: assignment and scheduling. In the assignment phase, we assign each welding line to a proper robot. In the scheduling phase, we determine the welding schedules for the robots so that collision is avoided. Computational experiences with the data which reflect the real situation are reported.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1138-1141
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• 1995

An arc sensor for seam tracking is developed to automate sub-assembly welding in shipbuilding. We utilize a moving average method, which produces an effect of low-pass filter, to generate the position compensation. Therefore the sensor is able to modify the path of the weld seam in real time. By simplifying the compension process, the tunning time is reduced so that operators react quickly. It turns out that this sensor is highly reliable and it is installed and being used in SHI Keoje shipbuilding yard.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.201-207
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• 2004

High speed rotating airflow inside a HDD chamber causes sub-micron scale disk vibration that could generate significant TMR problems in most of current HDD products. Many publications are presented for the reduction of airflow excitation. One of the most effective methods widely adopted in high-end HDD products is SqueezeAir Bearing Plate (SABP). However, because of its tight assembly clearance between the damper and disk, this method could not be easily implemented in volume production. This article presents a disk damper design that is modified to be feasible for volume production by virtue of a new airflow modeling method.