• Transactions of the Korean Society of Automotive Engineers
• /
• v.17 no.1
• /
• pp.114-119
• /
• 2009

The authors have investigated the NVH problems of drive system in full vehicle test. However it is difficult to define the NVH problems of driveline system. Since it is hard to measure the rotating part and it is vague that only the drive system induces the NVH problem. Vibration in a driveline is presented in this paper. In the experiment, the rear sub-frame and propeller shafts and axle were composed and mounted with rubber each other. For applying the vibration input instead of the torsional vibration effect of an engine, the shaker was taken. In particular, torsional vibration due to fluctuating forced vibration excitation across the joint between driveline and rear sub-frame was carefully examined. Accordingly, the joint response was checked from experiments and the FE-simulation using FRF (frequency response function) analysis was performed. All test results were signal processed and validated against numerical simulations. In present study, the new test bench for measuring the vibration signal and simulating the vehicle chassis system was proposed. The modal value and the mode shape of components were analyzed using the CAE model to identify the important components affecting driveline noise and vibration. It could be reached that the simplified test bench could be well established and be used for design guide and development of the vehicle chassis components.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.1
• /
• pp.26-32
• /
• 2005

In this paper, the effect of various regression models is investigated on structural optimization using the central composite method. Three bar truss and the upper platform of a satellite are optimized using various regression models that are polynomial, exponential and log functions. Response surface method is non-gradient, semi-global, discrete and fast converging in optimization problem. Sampling points are extracted by the design of experiments using the central composite method. Response surface is generated using the various regression functions. Structural analysis for calculating constraints is executed to find static and dynamic responses. From this study, it is verified that the response surface method has advantage in optimum value and computation time in comparison to other optimization methods.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.7
• /
• pp.92-97
• /
• 2005

In this paper, the performance of the KOMPSAT-1 GPS receiver on orbit was analyzed. OD (Orbit Determination) accuracy using GPS navigation solutions and GPS visibility were investigated with respect to the configuration of the GPS receiver. Indeed, the problem such as ‘3D Fix Loss’ observed during the mission was presented. As a result, the OD accuracy of ‘Best-of-4’ Position Fix Algorithm with 0 degree of mask angle was slightly better than that of ‘N-in-View’ Position Fix Algorithm. On the other hand, the GPS visibility under ‘N-in-View’ Algorithm is better than that of ‘Best-of-4’ Algorithm. The occurrence of temporal 3D Fix Loss is reduced when the ‘N-in-View’ Position Fix Algorithm was selected.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.7
• /
• pp.629-639
• /
• 2016

Batch process TRN(Terrain Relative Navigation) using an altimeter is a technique to correct position by correlating a series of periodically measured terrain height profile and terrain height candidate profile of the DEM(Digital Elevation Map). However, it is generally known that the performance of TRN is degraded when measured terrain height profile and terrain height candidate profiles of the DEM are similar at hill or repetitive terrain. In this paper, area based terrain slope roughness index[11] is applied and area based terrain curvature roughness index which can detect similarity of terrain in ROI(Region Of Interest) is proposed to overcome this problem. Applying terrain roughness indexes to terrain relative navigation system of lunar lander, it is shown that TRN using area based terrain roughness results in improved performance compared to conventional trajectory based method through simulation.

• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.1
• /
• pp.28-40
• /
• 2015

This paper aims to address the intelligent active vibration control problem of a flexible rectangular plate vibration involving parameter variation and external disturbance. An adaptive sliding mode (ASM) MIMO control strategy and smart piezoelectric materials are proposed as a solution, where the controller design can deal with problems of an external disturbance and parametric uncertainty in system. Compared with the current 'classical' control design, the proposed ASM MIMO control strategy design has two advantages. First, unlike existing classical control algorithms, where only low intelligence of the vibration control system is achieved, this paper shows that high intelligent of the vibration control system can be realized by the ASM MIMO control strategy and smart piezoelectric materials. Second, the system performance is improved due to two additional terms obtained in the active vibration control system. Detailed design principle and rigorous stability analysis are provided. Finally, experiments and simulations were used to verify the effectiveness of the proposed strategy using a hardware prototype based on NI instruments, a MATLAB/SIMULINK platform, and smart piezoelectric materials.

• Journal of Broadcast Engineering
• /
• v.22 no.1
• /
• pp.70-77
• /
• 2017

Among available people counting methods, map-based approaches based on moving interest points have shown good performance. However, the stationary people counting is challenging in such methods since all static points of interest are considered as background. To include stationary people in counting, it is needed to discriminate between the static points of stationary people and the background region. In this paper, we propose a people counting method based on using both moving and static points. The proposed method separates the moving and static points by motion information. Then, the static points of the stationary people are classified using foreground mask processing and point pattern analysis. The experimental results reveal that the proposed method provides more accurate count estimation by including stationary people. Also, the background updating is enabled to solve the static point misclassification problem due to background changes.

• Journal of Energy Engineering
• /
• v.26 no.4
• /
• pp.7-13
• /
• 2017

As environmental problems become a problem of survival, interest in eco-friendly energy is increasing to improve the environment. So, demand for eco-friendly fuels such as hydrogen, LPG and CNG is increasing. In particular, Korea, which relies on imports of most fuels, is investing in the development of hydrogen energy, which is favorable in terms of high production volume and energy independence. However, As demand grows every year, a variety of accidents occur in various ways, ranging from small leak incidents to massive fires and explosion, thus research needs to be done. So, in this study, compared and analyzed cases of hydrogen, LPG, CNG accidents occurring at domestic and overseas refueling stations. and various programs were used for assessing risk, estimated the flame length due to gas leakage and evaluated the dangerous distance.

• Journal of Elementary Mathematics Education in Korea
• /
• v.9 no.2
• /
• pp.181-200
• /
• 2005

The purpose of this thesis was to analyze communicational means of mathematical communication in perspective of languages and behaviors. Research questions were as follows; First, how are the characteristics of mathematical languages in communicating process of mathematical small group learning? Second, how are the characteristics of behaviors in communicating process of mathematical small group learning? The analyses of students' mathematical language were as follows; First, the ordinary language that students used was the demonstrative pronoun in general, mainly substituted for mathematical language. Second, students depended on verbal language rather than mathematical representation in case of mathematical communication. Third, quasi-mathematical language was mainly transformed in upper grade level than lower grade, and it was shown prominently in shape and measurement domain. Fourth, In mathematical communication, high level students used mathematical language more widely and initiatively than mid/low level students. Fifth, mathematical language use was very helpful and interactive regardless of the student's level. In addition, the analyses of students' behavior facts were as follows; First, students' behaviors for problem-solving were shown in the order of reading, understanding, planning, implementing, analyzing and verifying. While trials and errors, verifying is almost omitted. Second, in mathematical communication, while the flow of high/middle level students' behaviors was systematic and process-directed, that of low level students' behaviors was unconnected and product-directed.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.15 no.2
• /
• pp.31-40
• /
• 2012

The Environmental Conservation Value Assessment Map (ECVAM) is a five grade assessment map created with nationally integrated environmental information and environmental values. The map is made through the evaluation of 65 items, including greenbelt area and naturalness. Naturalness means original state of nature, and it is one of the most important evaluation items for conserving nature. The criteria of naturalness includes the Degree of Green Naturality (DGN) made by MOE. Using the data which has been not updated is a problem of accuracy for ECVAM. Therefore, this study would like to improve the criteria of naturalness. To improve the criteria, the study examined the effectiveness of DGN using field survey. The results of analysis the naturalness without DGN, some area changed grade of naturalness have been already damaged or cleared for agriculture and industrial purposes. The grade of naturalness should be included the concept of vegetation transition like DGN. The study suggested a improved method using vegetation type (natural and planted forest), forest age, and the grade of vegetation conservation. The method was reviewed by experts and field survey. After applying the method in South Korea, the grade of naturalness were distributed evenly like GradeI is 38.87%, GradeII is 37.62%, GradeIII is 23.51%, respectively. From the results of field survey, over 4 grade of forest age in natural forest showed similar pattern of structure and composition in original forests. Therefore, the improved criteria explained the naturalness better than existing criteria, and the accuracy of ECVAM has been improved more.

• School Mathematics
• /
• v.5 no.4
• /
• pp.477-506
• /
• 2003

In this paper, we analyze nine-grade students' conceptions of parameters, their relation to unknowns and variables and the process of understanding of letters in problem solving of equations and functions. The roles of letters become different according to the letters-used contexts and the meaning of letters Is changed in the process of being used. But, students do not understand the meaning of letters correctly, especially that of parameter. As a result, students operate letters in algebraic expressions according to the syntax without understanding the distinction between the roles. Therefore, the parameter of learning should focus on the dynamic change of roles and the flexible thinking of using letters. We develop a self-regulation model based on the monitoring working question in teaching-learning situations. We expect that this model helps students understand concepts of letters that enable to construct meaning in a concrete context.