• Journal of Digital Contents Society
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• v.18 no.5
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• pp.803-810
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• 2017

Currently, every person possesses a smart phone due to the development of the IT industry. There is an improper situation in which a smart phone is not set in silent mode, such as a lecture room, a library, and a theatre hall. The proposed system automatically automates the function of smart phones where they are designated as a public place or etiquette area and automatically return the function of the smartphone if they deviate from the location of the site. It is also equipped with a combination of autonomous devices and services, based on Bluetooth communications, which are applied to ultra-light low-power IoT(Internet of Things) devices, and has features that allow diverse types of features and services to be added without requiring deformation of the hardware.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.523-526
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• 2010

In this study, we demonstrated a development of a non-releasing bolt which is fastened with a target by expanding a certain area of a bolt body. Being released a bolt causes many problems in a field where bolts are used. In order to figure out the problems, currently, many types of a non-releasing bolt have been developed and have been using. Unfortunately, however, they do not perfectly function not to be released. Therefore, the structures builded with bolts have many problems caused by external stress such as vibration and shock, and thus the bolts have to be regularly tightened for maintenance. With the important factors of internal geometry, the amount of explosive, and the firing pin, we developed a technology which could control the expansion degree of a certain area on a bolt body. Based on the results, it was founded that the performance of non-releasing was linearly proportional to the degree of body expansion.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.10-11
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• 1997

고체 추진제를 사용하는 추진 시스템을 개발하는데 가장 커다란 문제로 인식되고 있는 것은 추진제의 연소 특성을 이해하는 일이다. 그 중에서도 연소실의 압력 진동과 추진제 벽면으로 흡수되는 복사 열전달에 의한 연소율(burning rate)의 변화로 인하여 발생하는 연소 불안정에 대한 이해는 아직도 완전히 규명되지 않고 있다. 고체 추진제의 연소 불안정에 대한 이론적 해석은 준-정상 1차원 해석(Quasi-Steady Homogeneous One-Dimension) 방법에 의하여 단순화된 지배방정식을 해석하는 것이 일반적으로 잘 알려져 있는 방법이다. 이 가정은 고체 추진제가 연수되는 영역을 두께가 매우 얇은 영역의 표면반응영역(surface reaction layer)과 화학반응이 없는 응축상태영역(condensed phase zone) 그리고 기체상태의 연료와 화염이 존재하는 기체상태영역(gas phase zone) 등의 3영역으로 구분하며, 기체상태영역에서 발생하는 교란에 대한 응축상태영역의 반응시간 크기(response time scale)가 매우 크기 때문에 응축상태영역의 반응은 준 정상적으로 일어난다고 가정하는 것이다.그러나, 연소실의 온도가 $3000^{\circ}K$ 정도의 높은 온도이어서 복사 열전달에 의한 고체 추진제의 가열이 중요한 열전달 방법으로 작용하게 되므로 이를 무시한 이론적 해석은 물리적인 중요성이 약하여질 수밖에 없다. 본 연구에서는 기체영역으로부터 전달되는 복사 열전달은 투명(transparent)한 표면반응영역을 통과하여 응축상태영역에서 모두 흡수되며 추진제 표면에서의 복사열방출(emission)을 고려하였다. 또한 연소불안정 현상을 해석하기 위하여 표면반응영역에서의 경계조건은 선형교란량으로 대치하는 Zn(Zeldovich-Novozhilov) 방법을 사용하였다. 이 방법은 기체상태영역에 대한 구체적인 해석없이도 연소불안정 현상을 해석할 수 있는 장점이 잇다. 즉 응축상태영역에서의 연소율과 표면온도는 각각 기체영역으로부터 전달되는 온도구배와 연소압력, 그리고 복사 열전달의 함수관계이므로 선형교란에 의한 추진제표면에서의 교란경계조건을 얻을 수 잇으며, 응축영역의 교란지배방정식과 함께 사용하여 압력교란과 복사 열전달의 교란에 대한 연소율의 교란 증감 여부를 판단하여 연소 불안정 현상을 해석할 수 있다.

• Computational Structural Engineering
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• v.10 no.2
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• pp.233-242
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• 1997

The main purpose of this paper is to investigate the dynamic optimal design of continuous beams. The computer-aided optimization technique is used to obtain the near-optimal parameters of continuous beam. The computer program is developed to obtain the natural frequency parameters and the forced vibration responses to a transit point load for the continuous beam with variable support spacing, mass and stiffness. The model test data is in good agreement with the computer calculation, which serves to validate the mathematical analysis. The optimization function to describe the design efficiency is defined as a linear combination of four dimensionless span characteristics; the maximum dynamic stress; the stress difference between span segments; the rms deflection under the transit point load; and the total span mass. Studies of three span beams show that the beam with near-optimal parameters can improve design efficiency when compared to a uniform beam with even spacing of the same total span length.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.228-231
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• 2017

The surface temperature of a combustor such as an aircraft engine is one of the important measuring factors related to the combustion performance. However, a conventional temperature measurement technique have a large measurement error due to a bad environment such as a combustion flame, vibration, and dust. In order to solve this problem, a technology has been developed which can measure the surface temperature of the combustor in real time using the wavelength change or attenuation time change according to the temperature of the phosphor. In this study, we developed a technique that can measure surface temperature of scram-jet combustor using phosphor thermometry. The calibration curve was obtained according to the temperature from $200^{\circ}C$ to $800^{\circ}C$ in the calibrated temperature chamber. So, we confirmed that phosphor thermometry can be used for measuring surface temperature of scram-jet combustor.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.845-852
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• 2007

An OWC-type Wave Energy Conversion passes through 3 steps energy conversion process. This paper deal with the impulse turbine with staggered blade to improved performance by numerical analysis using commercial CFD code, FLUENT Maximum value of axial airflow velocity during exhalation is higher than that during inhalation This paper deal with special-type of Impulse Turbine so-called "Staggered Blade" for more efficiency to making air flow direct to on pressure side. Also, this paper has proposed special-type turbine with self-pitched blade more efficient.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.165-174
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• 2004

This research develops a technique which uses energy dissipation ratio in order to monitor the structural health on real time basis. For real-time monitoring, we employ the NExT and the ERA which enable us to obtain real-time data. Energy dissipation ratio is calculated from those data only with the damping and natural frequency of the structure, and from the calculated values we develop an algorithm (Energy dissipation method) which decides the damage degree of structure. The Energy dissipation method developed in this research is proved to be valid by comparison with other methods like the eigenparameter method and the MAC. Especially this method enables us to save measuring time and data which are the most important in real-time monitoring, and its use of the ambient vibration also makes it easy to monitor the whole structure and its damage points.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.38-47
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• 1995

The three-dimensional multi-layer computer simulation technology for tidal current developed in the previous study is updated to a new version. many improvements are achieved by following changes : (1) No-reflection condition is adopted instead of no-gradient condition as an open boundary condition. (2) Time marching algorithm is changed so that velocity and pressure(surface movement) might be salved in turn at different time step (3) Convection term in equation of motion is estimated by upwind differencing scheme instead of central differencing. The stability is improved considerably and the steady state is achieved within 2 tidal periods which is about 3 times shorter than that of the old version. Moreover, fluctuations in time disappeared by introducing the new time marching technique. An application to the real near shore area(near Inchon harbor) is performed by the new version. Simulated results are compared with those by the simulation total developed in the University of Tokyo. Validity and effectiveness of the two simulation technologies are chocked through the comparative research works.

• Journal of the Korean Society for Railway
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• v.11 no.6
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• pp.543-549
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• 2008

The ride comfort is more important according to train speedup. Generally it is defined as the vehicle vibration. There are many studies on evaluation method of ride comfort for railway. But the ride comfort for Korean high speed train (HSR 350x) has been assessed by statistical method according to UIC 5l3R. In this paper, the ride indices, which were measured in the Korean high speed train. have been analyzed and reviewed by using the inferential statistics such as t-test, variance analysis (ANOVA) and regression analysis.

• Journal of the Korea Society of Computer and Information
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• v.25 no.6
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• pp.143-154
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• 2020

In this study, four types of bodice patterns of elderly males in their 70s and 80s were made, and appearance evaluation was conducted through 3D simulation. For objective evaluation, airgap, cross section, color distribution, etc. were analyzed to compare differences between patterns. The pattern shape of bodice for elderly males was a pattern without darts except for the L pattern. As a result of appearance evaluation for 3D simulation, the elderly males' pattern was found to have a significant difference among the patterns on the front, side, and back items, and the H pattern was analyzed as the best pattern in all items except the armhole shape on the side. As a result of evaluating the airgap, color distribution, and cross-section, the most suitable pattern for the elderly male's body type was analyzed as the H pattern. Based on the H pattern, it is thought that the development of a pattern suitable for the upper body shape of elderly male should be made.