• Journal of Digital Convergence
• /
• v.15 no.7
• /
• pp.223-229
• /
• 2017

Europe, the US and Japan have acquired test results on impact coefficient for a long time and applied it to equipment design to secure safety of structures. However, Korean enterprises use the impact factor held by advanced business to design equipment as it is difficult for them to obtain it through tests. In this paper, NX/NASTRAN, was used to perform static load analysis and impact load analysis of a PCB Handler, semiconductor test equipment, and the result was employed to study how to calculate the impact coefficient with the finite element analysis. The calculation method was applied to the JIS(Japanese Industrial Standard), and the impact coefficient of the PCB handler was calculated as 1.27 for the sudden start or stop. The impact coefficient generated by the analysis is expected to make a great contribution to the industry as it can be used to improve the equipment structure and develop on existing equipment in the future.

• Computational Structural Engineering
• /
• v.10 no.2
• /
• pp.225-232
• /
• 1997

Material properties of a new composite composed of components with known material properties are usually investigated through experiments. Elastic modulus and Poisson's ratio are measured at various volume fractions of mixed components and utilized as the base information on an analytical model for predicting the mechanical behaviors of a structure constructed by the composite. Elastic material properties of a composite at various volume fractions are numerically estimated by minimizing the error between the static displacements computed from a model for the composite and those computed from a model of homogeneous and isotropic material. A finite element model for a composite is proposed to distribute different types of material components easily into the model depending on the volume fraction. Then, the material properties of a composite filled with solid mircospheres are predicted numerically through a sample study and the estimated results are compared with experimental results and some theoretical equations.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.713-721
• /
• 2004

Variable air intake and variable exhaust nozzle of hypersonic engines are designed and tested in this study. Dimensions for variable geometry air intake, ram combustor and variable geometry exhaust nozzle are defined based on the requirements of a pre-cooled turbojet engine. Hypersonic Ramjet Engine is designed as a scaled test bed for each component. Actuation forces of moving parts for variable intake and variable nozzle are reduced by balancing the other force in the opposite direction. A demonstrator engine which includes variable intake and variable nozzle is designed and the components are fabricated. Composite material with silicone carbide is applied for high temperature parts under oxidation environment such as leading edge of the variable intake and combustor liner. Internal cooling structure is adopted for both moving and static parts of the variable nozzle. Pressure recovery and mass capture ratio of the variable intake at Mach 5 is obtained by a hypersonic wind tunnel test. Flow characteristics of the variable nozzle are obtained by a low temperature flow test. Wall temperature and heat flux of the nozzle at Mach 3 is obtained by a firing test. As results, the intake and the nozzle are proved to be used at designed pressure and temperature environment.

• Journal of the Society of Naval Architects of Korea
• /
• v.35 no.1
• /
• pp.72-79
• /
• 1998

Static deformation theory of elastoplastic structures can be applied only if the magnitude of loading is less than the plastic collapse force $F_c$. However, with impact or explosive blast loading, the structure can be subjected to an intense but short-duration force pulse that exceeds the plastic collapse force and initiates structural collapse. In this paper, the dynamic response of a rigid-perfectly plastic cantilever subject to intense impact loading is examined in terms of the plastic collapse force. When a step loading is applied, the motion of the beam is calculated and analyzed through the non-dimensionalization of variables. It is concluded that the motion of a beam can be characterized as a function of the nondimensionalized force parameter, $f{\equiv}F/F_c$, where $F_c$ represents the critical force for plastic collapse. This result is used to the analysis of the beam motion subject to rectangular force pulse.

• Journal of the Korea Society of Computer and Information
• /
• v.4 no.3
• /
• pp.67-72
• /
• 1999

The neural network is a static network that consists of a number of layer: input layer, output layer and one or more hidden layer connected in a feed forward way. The popularity of neural network appear to be its ability of learning and approximation capability. The Elman Neural Network proposed the J. Elman. is a type of recurrent network. Is has the feedback links from hidden layer to context layer. So Elman Neural Network is the better performance than the neural network. In this paper. we propose the Modified Elman Neural Network. The structure of a MENN is based on the basic ENN. The recurrency of the network is due to the feedback links from the output layer and the hidden layer to the context layer. In order to certify the usefulness or the proposed method. the MENN apply to the multi target system. Simulation shows that the proposed MENN method is better performance than the multi layer neural network and ENN.

• Journal of the Korea Convergence Society
• /
• v.8 no.6
• /
• pp.17-27
• /
• 2017

Recently, as cyber attacks have been activated, many such attacks have come into contact with various media. Research on security engineering and reverse engineering is active, but there is a lack of research that integrates them and applies attack systems through cost effective attack engineering. In this paper, security - enhanced information systems are developed by security engineering and reverse engineering is used to identify vulnerabilities. Using this vulnerability, we compare and analyze lifecycle models that construct or remodel attack system through attack engineering, and specify structure and behavior of each system, and propose more effective modeling. In addition, we extend the existing models and tools to propose graphical attack specification models that specify attack methods and scenarios in terms of models such as functional, static, and dynamic.

• The Journal of Korean Academy of Prosthodontics
• /
• v.31 no.3
• /
• pp.303-316
• /
• 1993

The purpose of this study was to analysis the stress distribution induced by three unit PFM bridges and various cantilever bridges replacing maxillary latersal incisor. The simplified two-dimensional photoelastic models used for this study was contructed in the folio- wing way. CR/R ratio was designed to be 1 : 1, 1 : 1.25 and 1 : 1.5. The pontics of cantilever bridge supported by maxillary canines consisted of wrap-around type, rest-extension type, and simple type. 3-unit PFM bridge was constructed with traditional method. 1kg vertical static load was applied on the center of the incisal edge of the pontic. The stress pattern was examined and recorded by photography. The results obtained were as follows ; 1. The magnitude of stress on the abutment root apex area of a traditional 3-unit bridge was the lowest. 2. The model of cantilevered pontic with a rest showed the relatively well distributed stress around the abutment tooth. The model with simple pontic generated the greatest stress concentration in the supporting structure of the abutment tooth. 3. As the height of bone level reduced, the rotational and vertical force increased around the abutment tooth. 4. The stress concentration of the 3-unit bridges occured on the root apex and stress concentration of the cantilever briage occured on the root apex and cervix area, 5. In the case of the cantilever bridge, stress concentrated distally on the root apex area of the abutment tooth and additional stress was observed mesially on the upper part of the root. Especially in the case of the simple pontic, was phenomenon was more apparent than the others. 6. Force applied to cantilevered pontic was transmitted to the adjacent central incisor through the contact surface. Stress was markedly observed on the mesial cervix area in the case of simple pontic and on the root apex area in the case of wrap-around type and rest-extension type.

• The KIPS Transactions:PartA
• /
• v.18A no.2
• /
• pp.61-68
• /
• 2011

Memory error debugging is one of the most critical processes in improving software quality. However, due to the extensive time consumed to debug, the enhancement often leads to a huge bottle neck in the development process of mobile devices. Most of the existing memory error detection tools are based on static error detection; however, the tools cannot be used in mobile devices due to their use of large working memory. Therefore, it is challenging for mobile device vendors to deliver high quality mobile devices to the market in time. In this paper, we introduce "PinMemcheck", a pin-based memory error detection tool, which detects all potential memory errors within $1.5{\times}$ execution time overhead compared with that of a baseline configuration by applying the Pin's binary instrumentation process and a simple data structure.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.9
• /
• pp.775-780
• /
• 2016

In this paper, a computational algorithm of an improved and versatile structural analysis applicable for large-size flexible nonlinear structures is developed. In more detail, nonlinear finite element based on the co-rotational (CR) framework is developed. Then, a finite element tearing and interconnecting method using local Lagrange multipliers (FETI-local) is combined with the nonlinear CR finite element. The resulting computational algorithm is presented and applied for nonlinear static analyses, i.e., cantilevered beam and multibody structure. Finally, the proposed analysis is evaluated with regard to its parallel computation performance, and it is compared with those obtained by serial computation using the sparse matrix linear solver, PARDISO.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.15 no.2
• /
• pp.134-141
• /
• 2010

Small PEM (Proton Exchange Membrane) fuel cell systems do not require humidification and have great commercialization possibilities. However, methods for controlling small PEM fuel cell stacks have not been clearly established. In this paper, a control method for small PEM fuel cell systems using a dual closed loop with a static feedforward structure is defined and realized using a DSP (Digital Signal Processor). The fundamental elements that need to be controlled in fuel cell systems include the supply of air and hydrogen, water management inside the stack, and heat management of the stack. For small PEM fuel cell stacks operated without a separate humidifier, fans are essential for air supply, heat management, and water management of the stack. A purge valve discharges surplus water from the stack. The proposed method controls the fan using double control loops to quicken transient response of the fan thereby improving the supply rate of air. Feedback control to compensate for the voltage change in fuel cell stack improves the response characteristics in fuel cell to load variations. The feasibility of proposed method was proved by the experiments with a 60W small PEM fuel cell system and operation of a notebook computer using this system.