• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.1
• /
• pp.72-78
• /
• 2008

In this study, advanced (fluid-structure interaction (FSI)) analysis system has been developed in order to predict turbine cascade performance with blade deformation effect due to aerodynamic loads. Intereference effects due to the relative movement of the rotor cascade with respect to the stator cascade are also considered. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation k-ω SST turbulence models are solved to accurately predict fluid dynamic loads considering flow separation effects. A fully implicit time marching scheme based on the (coupled Newmark time-integration method) with high artificial damping is efficiently used to compute the complex fluid-structure interaction problem. Predicted aerodynamic performance considering structural deformation effect of the blade shows somewhat different results compared to the case of rigid blade model. Cascade performance evaluations for different elastic axis positions are importantly presented and its aeroelastic effects are investigated.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.2 no.1
• /
• pp.9-25
• /
• 1994

In the present study, the Reynolds-averaged Navier-Stokes equations, together with the equations of the $k-{\varepsilon}$ model of turbulence, were solved numerically in a general body-fitted coordinate system for three-dimensional turbulent flows around the six basic shapes of the magnetically levitated train(MAGLEV). The numerical computations were conducted on the MAGLEV model configurations to provide information on shapes of this type very near the elevated track at a constant Reynolds number of $1.48{\times}10^{6}$ based on the body length. The coordinate system was generated by numerically solving a set of Poisson equations. The convective transport equations were discretized using the finite-analytic scheme which employed analytic solutions of the locally-linearized equations. A time marching algorithm was employed to enable future extensions to be made to handle unsteady and fully-elliptic problems. The pressure-velocity coupling was treated with the SIMPLER-algorithm. Of particular interests were wall effect by the elevated track on the aerodynamic forces and flow characteristics of the six models calculated. The results indicated that the half-circle configuration with extended sides and with smooth curvature of sides was desirable because of the low aerodynamic forces and pitching moment. And it was found that the separation bubble was occured at wake region in near the elevated track.

• 한국연소학회:학술대회논문집
• /
• 2002.06a
• /
• pp.123-132
• /
• 2002

A numerical study was conducted to investigate the combustion phenomena of normal start and unstart processes based on ISL's RAMAC 30 experiments with different diluent amounts and fill pressures in a ram accelerator. The initial projectile launching speed was 1.8 km/s which corresponded to the superdetonative speed of the stoichiometric $H_2/O_2$ mixture diluted with 5 $CO_2$ or 4 $CO_2$. Experiments with same condition except for projectile surface material demonstrated that ignition was successful with an aluminum projectile, but no combustion was observed in case of a steel projectile. In this study, it was found that neither shock nor viscous heating was sufficient to ignite the mixture at a low speed of 1.8 km/s, as was found in the experiments using a steel projectile. However, we could succeed in igniting the mixtures by imposing a minimal amount of additional heat to the combustor section and simulate the normal start and unstart processes found in the experiments with an aluminum projectile. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations coupled with a Baldwin-Lomax turbulence model and detailed chemistry reaction equations of $H_2/O_2/CO_2$ suitable for high-pressure gaseous combustion were considered. The governing equations were discretized by a high order accurate upwind scheme and solved in a fully coupled manner with a fully implicit, time accurate integration method. The numerical results matched almost exactly to the experimental results. As a result, it was found that the normal start and unstart processes depended on the strength of gas mixture, development of shock-induced combustion wave stabilized by the first separation bubble, and its size and location.

• The Journal of the Korea Contents Association
• /
• v.18 no.8
• /
• pp.102-108
• /
• 2018

The existing data transmission technology applied between the non-secure external internet and the secure internal business network has various problems when applied to the building facility management SCADA system control network. Traditional inter-network data transfer technologies involve high complexity and high costs because blacklist-based security techniques are applied to all data. However, whitelist-based security techniques can be applied to data distributed in Building Facility Management SCADA control systems because a small number of structured control data are repeatable and periodic. This simplifies the security technology applied to inter-network data transmission, enabling building facility management SCADA system control network deployment at low cost. In this paper, we proposed building control networks specialized in building facility management SCADA control systems by providing solutions to address and address these problems.

• Journal of the Korean Institute of Rural Architecture
• /
• v.20 no.3
• /
• pp.19-26
• /
• 2018

There are still a number of "olles" existing with traditional alley characteristics in the inner city of Jeju. As a matter of fact, the renovation of old buildings and the protection of alley space are facing a dilemma due to the existence of less than 4m-width-roads in the area of "Mu-geun-sung". This study examines the current status of alley space in "Mu-geun-sung" area; and puts forward to the potential possibility and limitation of alley space regeneration via exploring the applicable scheme of building agreement. In the field survey, a number of regions in inner city of Jeju witnesses the existing majority of invaluable, conventional olles. So as to grasp the feasibility in "Mu-geun-sung" area, we designs a simulating experiment to carry out the Building Agreement; and compares with the current development model in this area. Building Agreement implies to establish gradually a separation of land ownership under the existing unified development of landowners and users, thus to explore a variety of land exploitation systems by separating land ownership and right to use land. As a result, the deterioration of the street landscape results from the increase of building storey numbers. The damages to the surrounding environment brought by the newly built buildings will be minimized as well as keeping the maximum building volume rate. Obviously, these measures will alleviate infringement to the traditional residential sunlight and privacy space effectively, and reduce the pressure from high-rise buildings to the alley space, so that the landscape of the alley will enhance to form a more comfortable alley environment.

• International Journal of Contents
• /
• v.14 no.3
• /
• pp.7-16
• /
• 2018

The extent and depth of the event plan determines the scope of pedagogical experience in situations and consequently the quality of immersive learning based on our simulated world. In contrast to planning in conventional narrative-based systems mainly pursuing dramatic interests, planning in virtual world-based pedagogical systems strive to provide realistic experiences in immersed situations. Instead of story plot comprising predetermined situations, our inter-event planning method aims at simulating diverse situations that each involve multiple events coupled via their associated agents' conditions and meaningful associations between events occurring in a background world. The specific techniques to realize our planning method include, two-phase planning based on inter-event search and intra-event decomposition (down to the animated action level); autonomous and independent agents to behave proactively with their own belief and planning capability; full-blown background world to be used as the comprehensive stage for all events to occur in; coupling events via realistic association types including deontic associations as well as conventional causality; separation of agents from event roles; temporal scheduling; and parallel and concurrent event progression mechanism. Combining all these techniques, diverse exogenous events can be derived and seamlessly (i.e., semantically meaningfully) integrated with the original event to form a wide scope of situations providing chances of abundant pedagogical experiences. For effective implementation of plan execution, we devise an execution scheme based on multiple priority queues, particularly to realize concurrent progression of many simultaneous events to simulate its corresponding reality. Specific execution mechanisms include modeling an action in terms of its component motions, adjustability of priority for agent across different events, and concurrent and parallel execution method for multiple actions and its expansion for multiple events.

• Journal of Digital Contents Society
• /
• v.18 no.7
• /
• pp.1323-1331
• /
• 2017

Despite the fact that the copyright has grown into a large-scale business, there are many constant problems especially in image copyright. In this study, we propose an automatic object extraction and classification system for the scanned educational book image by combining document image processing and intelligent information technology like deep learning. First, the proposed technology removes noise component and then performs a visual attention assessment-based region separation. Then we carry out grouping operation based on extracted block areas and categorize each block as a picture or a character area. Finally, the caption area is extracted by searching around the classified picture area. As a result of the performance evaluation, it can be seen an average accuracy of 83% in the extraction of the image and caption area. For only image region detection, up-to 97% of accuracy is verified.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.4
• /
• pp.629-635
• /
• 2009

The FSK duplex remote controlling wireless transmission units with a common local oscillator circuit for transmitter and receiver are designed and implemented in this paper. In the FSK full-duplex the channel frequency for Tx/Rx is allocated, a common switching oscillator circuit for Tx/Rx is designed in the FSK half-duplex scheme. Both of FSK units get functions of automatic channel detection for busy channels and channel configuration for an idle channel in order to reduce the RF channel interference and are designed as a remote controller with small-sized low power of 10mW and the 400MHz-colpitz type PLL configuration of 50kHz channel separation. The full-duplex Tx/Rx link frequency gets frequency difference of 42.8MHz, which is double of 21.4MHz IF frequency.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.55 no.7
• /
• pp.303-312
• /
• 2006

This paper proposes the architecture and protocol of a data communication network for the safety system in nuclear power plants. First, we establish four design criteria with respect to determinability, reliability, separation and isolation, and verification/validation. Next we construct the architecture of the safety network for the following systems: PPS (Plant Protection System), ESF-CCS (Engineered Safety Features-Component Control System) and CPCS (Core Protection Calculator System). The safety network consists of 12 sub-networks and takes the form of a hierarchical star. Among 163 communication nodes are about 1600 origin-destination (OD) pairs created on their traffic demands. The OD pairs are allowed to exchange data only during the pre-assigned time slots. Finally, the communication protocol is designed in consideration of design factors for the safety network. The design factors include a network topology of star, fiber-optic transmission media, synchronous data transfer mode, point-to-point link configuration, and a periodic transmission schedule etc. The resulting protocol is the modification of IEEE 802.15.4 (LR-WPAN) MAC combined with IEEE 802.3 (Fast Ethernet) PHY. The MAC layer of IEEE 802.15.4 is simplified by eliminating some unnecessary (unctions. Most importantly, the optional TDMA-like scheme called the guaranteed time slot (GTS) is changed to be mandatory to guarantee the periodic data transfer. The proposed protocol is formally specified using the SDL. By performing simulations and validations using Telelogic Tau SDL Suite, we find that the proposed safety protocol fits well with the characteristics and the requirements of the safety system in nuclear power plants.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.7 no.4
• /
• pp.33-38
• /
• 2003

The Physics of the Plume-induced shock and separation Particularly at a high Plume to exit pressure ratio and supersonic speeds up to Mach 3.0 with and without a passive control method, porous extension, were studied using computational techniques. Mass-averaged Navier-Stokes equations with the RNG $\kappa$-$\varepsilon$ turbulence model were solved using a fully implicit finite volume scheme and a 4-stage Runge-Kutta method. The control methodology for plume-afterbody interactions is to use a perforated wall attached at either the nozzle exit or the edge of the missile base. The Effect of porous wall length on plume interference is also investigated The computational results show the main effect of the porous extension on plume-afterbody interactions is to restrain the plume from strongly underexpanding during a change in flight conditions. With control, a change in porous extension length has no significant effect rut plume interference.