• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5955-5962
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• 2014

Generally, the frame design of a vehicle is a critical technology that plays an important role in the racing and high performance sports car market. The high performance of race car frame means that it requires high torsional stiffness because it directly affects the cornering behavior of the race car. The optimal design for the frame of a low-cost single seat race car was carried out using the DOE (Design Of Experiments) with Taguchi's orthogonal array and FEM (Finite Element Method) analysis to secure sufficient torsional stiffness in this paper. According to the results by DOE and FEM analysis, the optimal design case produced improved 10.7% and 14.5% improvement in each stiffness-to-weight ratio and frame weight than in the early design step. Therefore, this paper shows that the optimal design with Taguchi's orthogonal array is very useful and effective for designing a tubular space frame of a low-cost single seat race car in the early design step.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.361-374
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• 2008

Recently, satellite formation flying has been a topic of significant research interest in aerospace society because it provides potential benefits compared to a large spacecraft. Some techniques have been proposed to design optimal formation trajectories minimizing fuel consumption in the process of formation configuration or reconfiguration. In this study, a method is introduced to build fuel-optimal trajectories minimizing a cost function that combines the total fuel consumption of all satellites and assignment of fuel consumption rate for each satellite. This approach is based on collocation and nonlinear programming to solve constraints for collision avoidance and the final configuration. New constraints of nonlinear equality or inequality are derived for final configuration, and nonlinear inequality constraints are established for collision avoidance. The final configuration constraints are that three or more satellites should form a projected circular orbit and make an equilateral polygon in the horizontal plane. Example scenarios, including these constraints and the cost function, are simulated by the method to generate optimal trajectories for the formation configuration and reconfiguration of multiple satellites.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.407-412
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• 2010

Software reusability is one of key factors which impacts cost and schedule on a software development project. It is very crucial also in satellite simulator development since there are many commercial simulator models related to satellite and dynamics. If these models can be used in another simulator platform, great deal of confidence and cost/schedule reduction would be achieved. Simulation model portability (SMP) is maintained by European Space Agency and many models compatible with SMP/simulation model interface (SMI) are available. Korea Aerospace Research Institute (KARI) is developing hardware abstraction layer (HAL) supported satellite simulator to verify on-board software of satellite. From above reasons, KARI wants to port these SMI compatible models to the HAL supported satellite simulator. To port these SMI compatible models to the HAL supported satellite simulator, simulation scheduler is preliminary designed according to the SMI standard.

• Journal of applied mathematics & informatics
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• v.4 no.1
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• pp.83-108
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• 1997

Chebysheff-Halley methods are probably the best known cubically convergent iterative procedures for solving nonlinear equa-tions. These methods however require an evaluation of the second Frechet-derivative at each step which means a number of function eval-uations proportional to the cube of the dimension of the space. To re-duce the computational cost we replace the second Frechet derivative with a fixed bounded bilinear operator. Using the majorant method and Newton-Kantorovich type hypotheses we provide sufficient condi-tions for the convergence of our method to a locally unique solution of a nonlinear equation in Banach space. Our method is shown to be faster than Newton's method under the same computational cost. Finally we apply our results to solve nonlinear integral equations appearing in radiative transfer in connection with the problem of determination of the angular distribution of the radiant-flux emerging from a plane radiation field.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.84-90
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• 2006

The formation flying of satellites has been identified as an enabling technology for many future space missions. The application of conventional thrusters for formation flying usually results in high cost, limited life-time, and a large weight penalty. Various methods including the use of coulomb forces have been considered as an alternative to the conventional thrusters. In the present investigation, we investigate the feasibility of achieving the desired formation using Coulomb forces. This method has several advantages including low cost, light weight and no contamination. A simple controller based on the relative position and velocity errors between the leader and follower satellites is developed. The proposed controller is applied to circular formations considering the effects of disturbances in initial formation conditions as well as system nonlinearity. Results of the numerical simulation state that the proposed controller is successful in establishing circular formations of leader and follower satellites, for a formation size below 100 m.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.266-273
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• 2012

In conventional direct torque control (DTC) using space-vector modulation (SVM) of induction machine (IM) drives, at least three current sensors are needed. In this paper, a low-cost SVM-DTC strategy is proposed, in which only a single current sensor is used. The position of the voltage space vector is divided into two areas: effective and non-effective area. If it is located in the non-effective area, the voltage space vector will be shifted into the effective area with minimum distortion. Further, the switching frequency remains constant. The simulation is carried out on a MATLAB/Simulink platform and the simulated results verify the effectiveness of the proposed strategy.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1024-1026
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• 2003

The purpose of establishing GPS networks of continuously operating reference stations (CORS) is aimed to assist land surveying or crustal deformation in the early stage. However, with a fast evolving and improving path the GPS technique has been extended to accurately measure atmospheric precip itable water vapor as a core objective of many projects developed in many countries and regions such as the SuomiNet (U.S., UNAVCO), COST716 (European, COST), GEONET (Japan, GSI), ...etc. In this paper, we present the current progress of the being-set-up GPS network in Taiwan whose atmospheric profile observations mainly count on the traditional radiosonde soundings as typically seen in any other part of the world. The GPS data collected from the Taiwan dense GPS network primarily supported by Central Weather Bureau are processed using the Bernese software version 4.2. Precipitable water vapor is then derived with the auxiliary surface meteorological measurements. Time series of precipitable water are examined and analyzed. A focus on the extreme weather cases is shown as an example.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.131-136
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• 2018

Research on space development and satellites is being actively pursued. An interesting field is the study of reliable low-cost space launch vehicles. Since chemical fuel-based launching systems are expensive and take a lot of time and cost to maintain, the EML system, which is an electromagnetic force launching apparatus, is attracting attention. The EML system converts electrical energy stored in a capacitor into magnetic energy, and converts magnetic energy into mechanical kinetic energy, thereby accelerating the projectile. Although studies are actively conducted in the field, it is difficult to solve the equation because the impedance and speedance change with time and the nonlinearity is strong. Many researchers have solved this equation in a variety of methods. In this paper, the velocity analysis of the projectile was carried out by FEM (finite element method) using the commercial electromagnetic analysis program MAXWELL.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.5
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• pp.436-444
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• 2018

The purpose of this research is to assess the efficiency of the airline's route. The revenue source of low cost airline carriers is not various unlike regular airline carriers, because they are operating only domestic and international flights for a country of close proximity. In particular, domestic low-cost airlines in Korea can't provide cargo transport services but rely on passengers and additional services to generate profits. Therefore, it is absolutely important to maintain a low cost and effective passenger transport line. This study will suggest the way to improve efficiency of route operated by low-cost airlines. Analysis method is DEA. The input parameters and output results were selected by existing research. Based on the results of this study, it will be able to assist establishing routes and selling strategies of the low-cost airlines.

• Structural Engineering and Mechanics
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• v.6 no.5
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• pp.543-554
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• 1998

Space truss structures may be fabricated in any of several common grid configurations. With different configurations, the truss performance varies considerably affecting both its competitiveness and suitability for specific applications. The work presented in this paper is an assessment of the most commonly adopted truss configurations and their effect on truss characteristics such as the stiffness/weight value, member stress distribution, number of joints and members, degree of redundancy and cost. The study is parametric and covers wide variations of truss aspect ratios, boundary conditions and span/depth ratios. The results of this study could be of significant value to the design of space truss structures.