• Polymer(Korea)
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• v.33 no.6
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• pp.561-568
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• 2009

Small injection molded articles are generally molded by multi-cavity injection molding. The most important thing in multi-cavity molding is flow imbalance among the cavities because it affects the physical property and the quality of products. The cavity filling balance can be achieved by flow balance in the runner through the thermal balance. In this study, novel screw type runner or helical type runner has been developed for the flow balance in the runner and performed experiment and computer simulation. Flow balance has been observed using various screw type runners for several resins such as amorphous and crystalline polymers including low and high viscosities grades. Flow balance experiments have been performed for various injection speeds since the flow balance can be affected by injection speed among the injection conditions. Experimental results have been compared with computational results and they showed good agreement. The cavity filling balance can be achieved by the screw runner where the temperature distribution is uniform through the circulation flow along the screw channel in the screw runner. It has been verified that the novel screw runner is very effective device in flow balance in the multi-cavity injection molding. cavity filling imbalance, multi-cavity injection molding, runner design, screw runner, thermal balance.

• Convergence Security Journal
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• v.24 no.1
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• pp.35-42
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• 2024

Multi-tenancy architecture plays a crucial role in cloud-based services and applications, and data isolation within such environments has emerged as a significant security challenge. This paper investigates various data isolation methods including schema-based isolation, logical isolation, and physical isolation, and compares their respective advantages and disadvantages. It evaluates the practical application and effectiveness of these data isolation methods, proposing security considerations and selection criteria for data isolation in the development of multi-tenant websites. This paper offers important guidance for developers, architects, and system administrators aiming to enhance data security in multi-tenancy environments. It suggests a foundational framework for the design and implementation of efficient and secure multi-tenant websites. Additionally, it provides insights into how the choice of data isolation methods impacts system performance, scalability, maintenance ease, and overall security, exploring ways to improve the security and stability of multi-tenant systems.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.129-132
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• 2002

The practical virtual compensator, which uses a dynamic multi-leaf collimator (dMLC) and three-dimensional radiation therapy planning (3D RTP) system, was designed. And the feasibility study of the virtual compensator was done to verify that the virtual compensator acts a role as the replacement of the physical compensator. Design procedure consists of three steps. The first step is to generate the isodose distributions from the 3D RTP system (Render Plan, Elekta). Then isodose line pattern was used as the compensator pattern. Pre-determined compensating ratio was applied to generate the fluence map for the compensator design. The second step is to generate the leaf sequence file with Ma's algorithm in the respect of optimum MU-efficiency. All the procedure was done with home-made software. The last step is the QA procedure which performs the comparison of the dose distributions which are produced from the irradiation with the virtual compensator and from the calculation by 3D RTP. In this study, a phantom was fabricated for the verification of properness of the designed compensator. It is consisted of the styrofoam part which mimics irregular shaped contour or the missing tissues and the mini water phantom. Inhomogeneous dose distribution due to the styrofoam missing tissue could be calculated with the RTP system. The film dosimetry in the phantom with and without the compensator showed significant improvement of the dose distributions. The virtual compensator designed in this study was proved to be a replacement of the physical compensator in the practical point of view.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.507-514
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• 2022

This study proposes an optimal design process for a high-frequency transformer that has a large leakage inductance for dual-active-bridge converters. Notably, conventional design processes have large errors in designing leakage transformers because mathematically modeling the leakage inductance of such transformers is difficult. In this work, the geometric parameters of a shell-type transformer are identified, and finite element analysis(FEA) simulation is performed to determine the magnetization inductance, leakage inductance, and copper loss of various shapes of shell-type transformers. Regression models for magnetization and leakage inductances and copper loss are established using the simulation results and the machine learning technique. In addition, to improve the regression models' performance, the regression models are tuned by adding featured parameters that consider the physical characteristics of the transformer. With the regression models, optimal high-frequency transformer designs and the Pareto front (in terms of volume and loss) are determined using NSGA-II. In the Pareto front, a desirable optimal design is selected and verified by FEA simulation and experimentation. The simulated and measured leakage inductances of the selected design match well, and this result shows the validity of the proposed design process.

• Journal of Korean Physical Therapy Science
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• v.9 no.2
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• pp.133-141
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• 2002

This purpose of this study was to design the effect of recovering of a hand amputees by Myoelectronic hand. It was designed with 2 degree of freedom in the laboratory. Myoelectronic hand had only one degree of freedom and one movement until now. Also this myoelectronic hand had multi-joint and it could move widely. Wire was used in transmission. Myoelectronic hand data was obtained by analyzing hand anatomically and measuring and that data was applied when it was designed. PID controller of Myoelectronic hand was used to it. Displacement control was applied the first link. Experiment was accomplished in Tip grasp, Power grasp and Hook grasp modes. Displacement control was good in low frequency. Velocity control was applied to each mode. The objective of the study was to develop more better multifunction myoelectronic control strategies. A myoelectronic hand with a hand amputees could do some jobs such as grasping materials, lifting weighting, holding cup and etc. As a result of this study, all subjects with hand amputees significantly improved in ADL. Further studies were needed to evaluate the effect of a myoelectronic hand with more precise laboratory equipment.

• Korean Journal of Computational Design and Engineering
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• v.15 no.3
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• pp.167-177
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• 2010

In recent years, the use of high-resolution tiled display system which does not have restrictions on the size of the screen and implements various layout of tile is increasing in order to evaluate the digital mock-up in physical scale or explore large engineering data set in detail. In this study, we developed multi-channel distributed visualization system which provides a virtual reality-based visual contents using 3D open-source graphics engine. Efficient data structures and exchange methods were proposed as a scene synchronization technology in PC cluster environments. DLP-Cube based tiled visualization system which provides $5{\times}2$ layout of display wall was developed and we validated our approach using this system. In addition, we introduced integrated control program that administrates PC cluster environment in remote and controls the layout of display channels.

• Korean Journal of Computational Design and Engineering
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• v.8 no.3
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• pp.175-183
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• 2003

This paper introduces a Web-based vibration analysis system for rotary-type refrigerator compressors. Concern for vibration reduction in compressors has been growing for many years. What is important in vibration reduction is to easily predict the vibration without using a physical compressor. The dynamic model of the compressor is represented as a multi-body dynamic system. Solving the dynamic model is run on a high-performance server. The interfaces of the system are accessible via Web browsers, such as Netscape or Explorer. Anyone who wants to analyze the vibration of the rotary compressor or share the results data can access the system over the Internet regardless of their OS, platform, or location.

• Journal of Electrical Engineering and information Science
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• v.3 no.3
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• pp.292-299
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• 1998

Placement of multiple dies on an MCM or high-performance VLSI substrate is a non-trivial task in which multiple criteria need to be considered simultaneously to obtain a true multi-objective optimization. Unfortunately, the exact physical attributes of a design are not known in the placement step until entire design process is carried out. When the performance issues are considered, crosstalk noise constraints in the form of net separation and via constraint become important. In this paper, for better performance and wirability estimation during placement for MCMs, several performance constraints are taken into account simultaneously. A graph-based wirability estimation along with the Genetic placement optimization technique is proposed to minimize crosstalk, crossing, wirelength and the number of layers. Our work is significant since it is the first attempt at bringing the crosstalk and other performance issues into the placement domain.

• Journal of the Semiconductor & Display Technology
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• v.13 no.1
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• pp.73-81
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• 2014

In this paper, high-speed Hybrid MAC (Medium Access Control layer) implementation suitable for smart grid applications is researched. MB-OFDM (Multi-Band Orthogonal Frequency Division Multiplexing) is considered for high-speed communication method in smart grid application. In this paper, the MAC adopts the distributed network managing method. Also, the MB-OFDM merit of high-speed transfer rate of up to 480Mbps must be supported. Hence, this paper presents an efficient hardware-software integration (co-design) method in order to realize a high- speed transmission, and a realizing method of distribution network. Finally, MAC performance and reliability based on MB-OFDM PHY (PHYsical layer) are confirmed through simulation and emulation.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.5
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• pp.227-237
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• 2019

Ultra-low latency control is one of the characteristics of 5G cellular network services, which means that the control loop is handled in milliseconds. To achieve this, it is necessary to identify time delay factors that occur in all components related to CPS control loop, including new 5G cellular network elements such as MEC, and to optimize CPS control loop in real time. In this paper, a novel CPS architecture for ultra-low latency control of CPS is designed. We first define the ultra-low latency characteristics of CPS and the CPS concept model, and then propose the design of the control loop performance monitor (CLPM) to manage the timing information of CPS control loop. Finally, a case study of MEC-based implementation of ultra-low latency CPS reviews the feasibility of future applications.