• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.1
• /
• pp.9-16
• /
• 2019

In the present study, to investigate flows around space launch vehicles at mid-high altitudes efficiently, a three-dimensional unstructured mesh Navier-Stokes solver employing a Maxwell slip boundary condition was developed. Validation of the present flow solver was made for a blunted cone-tip configuration by comparing the results with those of the DSMC simulation and experiment. It was found that the present flow solver works well by capturing the velocity slip and the temperature jump on the solid surface more efficiently than the DSMC simulation. Flow simulations of space launch vehicles were conducted by using the flow solver. Mach number of 6 at the mid-high altitude around 86km was considered, and the flow phenomena at the mid-high altitude was discussed.

• Journal of Broadcast Engineering
• /
• v.26 no.2
• /
• pp.132-142
• /
• 2021

The purpose of this study is to present an effective methodology that can measure heart rate, heart rate variability, oxygen saturation, respiration rate, mental stress level, and blood pressure using mobile front camera that can be accessed most in real life. Face recognition was performed in real-time using Blaze Face to acquire facial image data, and the forehead was designated as ROI (Region Of Interest) using feature points of the eyes, nose, and mouth, and ears. Representative values for each channel of the ROI were generated and aligned on the time axis to measure vital signs. The vital signs measurement method was based on Fourier transform, and noise was removed and filtered according to the desired vital signs to increase the accuracy of the measurement. To verify the results, vital signs measured using facial image data were compared with pulse oximeter contact sensor, and TI non-contact sensor. As a result of this work, the possibility of extracting a total of six vital signs (heart rate, heart rate variability, oxygen saturation, respiratory rate, stress, and blood pressure) was confirmed through facial images.

• Journal of Advanced Navigation Technology
• /
• v.22 no.2
• /
• pp.57-63
• /
• 2018

In the case of aircraft-launched guided weapons, various interface tests such as MIL-STD-1760 based power source, discrete signal, MUX communication as well as BIT of missile can verify system safety and reliability. The purpose of this case study is to develop a test bench based on MIL-STD-1760E for interoperability testing between aircraft and weapons. We proposed a testing method of the launch sequence based on the defined TIME LINE in the development phase of the missile system from the application of the power of the missile to the targeting, the transfer order, and the missile separation process. Furthermore, it will be a reference model that can maximize the verification scope in the development phase of the air to surface missile system by simulating abnormal situation to the inert missile using the error insertion function.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.18 no.3
• /
• pp.155-162
• /
• 2008

In this paper we proposed a video watermarking algorithm based on a three dimension discrete wavelet transform (3D DWT) and direct spread spectrum (DSS). In the proposed method, the information watermark is embedded into followed frames, after sync watermark is embedded into the first frame. Input frames are divided into sub frames which are located odd row and even row. The sub frames are arranged as 3D frames, and transformed into 3D wavelet domain. In this domain the watermark is embedded using DSS. Existing video watermarking using 3D DWT is non-blind method but, proposed algorithm uses blind method. The experimental results show that the proposed algorithm is robust against frame cropping, noise addition, compression, etc. acquiring BER of 10% or below and sustains level of 40dB or above on the average.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.20 no.6
• /
• pp.15-21
• /
• 2010

In the recent years, various researches about the signal processing have been presented to improve the performance of power analysis. Among these signal processing techniques, the research about the signal compression is not enough than a signal alignment and a noise reduction; even though that can reduce considerably the computation time for the power analysis. But, the existing compression method can sometimes reduce the performance of the power analysis because those are the unsophisticated method not considering the characteristic of the signal. In this paper, we propose the new PCA (principal component analysis)-based signal compression method, which can block the loss of the meaningful factor of the original signal as much as possible, considering the characteristic of the signal. Also, we prove the performance of our method by carrying out the experiment.

• Composites Research
• /
• v.34 no.4
• /
• pp.264-268
• /
• 2021

In this study, we propose a method for fabricating hydrophobic coatings/films with three-dimensional (3D) hierarchical nanostructured organic/inorganic composite surfaces. An epoxy-based, large-area 3D ordered nanoporous template is first prepared through an advanced photolithography technique called Proximity-field nanoPatterning (PnP). Then, a hierarchically structured surface is generated by densely impregnating the template with silica nanoparticles with an average diameter of 22 nm through dip coating. Due to the coexisting micro- and nano-scale roughness on the surface, the fabricated composite film exhibits a higher contact angle (>137 degrees) for water droplets compared to the reference samples. Therefore, it is expected that the materials and processes developed through this study can be used in various ways in the traditional coating/film field.

• Journal of Advanced Navigation Technology
• /
• v.26 no.3
• /
• pp.179-184
• /
• 2022

The accurate wing flexure model is required to improve the transfer alignment performance of guided weapon system mounted on a wing of fighter aircraft or armed helicopter. In order to solve this problem, mechanical or stochastical modeling methods have been studying, but modeling accuracy is too low to be applied to weapon systems. The deep learning techniques that have been studying recently are suitable for nonlinear. However, operating fighter aircraft for deep-learning modeling to secure a large amount of data is practically difficult. In this paper, it was used to generate amount of flexure data samples that are similar to the actual flexure data. And it was confirmed that generated data is similar to the actual data by utilizing "measures of similarity" which measures how much alike the two data objects are.

• Composites Research
• /
• v.22 no.2
• /
• pp.30-36
• /
• 2009

In this paper, we propose the design method for the composite torque link of a landing gear for a helicopter. The composite torque link has to be light weighted and very stiff to keep the shock absorber in the landing gear of helicopter. The configuration and structural shape has to be designed in consideration of the RTM (Resin Transfer Molding) manufacturing process which is adopted to minimize the manufacturing cost. The mechanical properties are obtained through the coupon tests with the specimens made by the same manufacturing process for the composite structure. The optimal design process was performed through iterative modifications of the models which were verified by stress analysis using FEM. The composite torque link has lug-shaped parts and is very thick, so 3D Layered solid elements of ABAQUS were used to get the stress field including the stress components in thickness direction and non-linear static analysis using contact B.C. of rigid-deform condition was used to get the optimal design.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.16 no.2
• /
• pp.109-115
• /
• 2023

In this paper, we demonstrated the orientation characteristics of liquid crystals using UV-treated FSAM as alignment layer. Moreover we confirmed the FSAM properties before and after UV treatment on indium tin oxide (ITO) glass substrates using physicochemical analysis. The hydrophobic property of the FSAM surface is change to hydrophilic through UV treatment. After UV treatment the LC molecules also were uniformly and horizontally aligned on the FSAM surfaces and the pretilt angle was obviously changed 90° degrees to 0° degrees. EO characteristic of TN cell which was fabricated with UV-treated FSAM was faster response time compare to conventional PI layer. The FSAM before and after UV treatment has a superior application potential as the LC alignment layer for LCD, potentially replacing the conventional polyimide layer.

• The Transactions of the Korea Information Processing Society
• /
• v.13 no.3
• /
• pp.130-139
• /
• 2024

Artificial intelligence models are being used to detect facility anomalies using physics data such as vibration, current, and temperature for predictive maintenance in the manufacturing industry. Since the types of facility anomalies, such as facility defects and failures, anomaly detection methods using autoencoder-based unsupervised learning models have been mainly applied. Normal or abnormal facility conditions can be effectively classified using the reconstruction error of the autoencoder, but there is a limit to identifying facility anomalies specifically. When facility anomalies such as unbalance, misalignment, and looseness occur, the facility vibration frequency shows a pattern different from the normal state in a specific frequency range. This paper presents an N-segmentation anomaly detection method that performs anomaly detection by dividing the entire vibration frequency range into N regions. Experiments on nine kinds of anomaly data with different frequencies and amplitudes using vibration data from a compressor showed better performance when N-segmentation was applied. The proposed method helps materialize them after detecting facility anomalies.