• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.92-97
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• 2003

By using a centerbody injection, an effort to reduce shock assoicated noise is made in an underexpanded sonic nozzle with an exit diameter of 10mm. The centerbody or micro nozzle, aligned with the axis of the main jet has an o.d. of 2mm and i.d. of 1.5mm. When measured at 90$^{\circ}$ relative to the main jet the farfield noise spectra showed that the screech tones and broadband shock associated noise can be significantly reduced simply by varying the length of the centerbody and/or mass fraction of the microjet. The maximum reduction in overall sound pressure level (OASPL) was as much as 9 and 4 ㏈ at fully expanded jet Mach numbers Mi of 1.3 and 1.5, respectively, when the length of the centerbody was varied from 0 to 4 main nozzle diameters without blowing. With the aid of the blowing, the maximum reduction in OASPL increased to 12 and 7 ㏈ at M$\sub$j/=1.3 and 1.5, respectively. The impact pressure field in the main jet plume strongly suggested that the reduced periodic pressure distribution in the shear layers and/or centerline is responsible for the reduced screech and broadband shock associated noise. Therefore, the steady blowing by a micro centerbody is a promising technique for shock noise reduction in a supersonic jet.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.195-203
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• 2017

A 2U cube satellite called SNUGLITE has been developed by GNSS Research Laboratory in Seoul National University. Its main mission is to perform actual operation by mounting dual-frequency global positioning system (GPS) receivers. Its scientific mission aims to observe space environments and collect data. It is essential for a cube satellite to control an Earth-oriented attitude for reliable and successful data transmission and reception. To this end, an attitude estimation and control algorithm, Attitude Determination and Control System (ADCS), has been implemented in the on-board computer (OBC) processor in real time. In this paper, the Extended Kalman Filter (EKF) was employed as the attitude estimation algorithm. For the attitude control technique, the Linear Quadratic Gaussian (LQG) was utilized. The algorithm was verified through the processor in the loop simulation (PILS) procedure. To validate the ADCS algorithm in the ground, the experimental verification via a single axis Hardware-in-the-loop simulation (HILS) was used due to the simplicity and cost effectiveness, rather than using the 3-axis HILS verification (Schwartz et al. 2003) with complex air-bearing mechanism design and high cost.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1042-1048
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• 2012

A 2-axis gimbal system is one of main disturbance sources affecting image jitter response of a satellite. The gimbal system comprises azimuth stage and elevation stage, and these pointing mechanism can be rotated by stepping motors about its azimuth and elevation axes simultaneously. Because of the complex and coupled dynamic motion of the gimbal system, its moment of inertia and structural modes can be changed according to the system configuration, and thus the gimbal system generates complicated and non-linear disturbance characteristics. In order to improve the jitter response of a spacecraft, it is an indispensable process to reduce the micro-vibration disturbance level of the antenna system. In the present research, a 2-axis gimbal system was manufactured and then its micro-vibration test was performed in terms of two types of stepping motors(2-phase and 5-phase). The test results show that the disturbance level of the gimbal system can be reduced by replacing the 2-phase stepping motor with the 5-phase one, and the average disturbance attenuation ratio is 56 % in peak level and 48 % in standard deviation level. The experimental results confirm that it is an efficient jitter reduction method to adopt a high-phase stepping motor.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.293-298
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• 2007

The aged are faced with increasing risk for falls. The aged have more fragile bones than others. When falls occur, it is important to detect this emergency state because such events often lead to more serious illness or even death. A implementation of PDA system, for detection of emergency situation, was developed using 3-axis accelerometer in this paper as follows. The signals were acquired from the 3-axis accelerometer, and then transmitted to the PDA through a Bluetooth module. This system can classify human activity, and also detect an emergency state like falls. When the fall occurs, the system generates the alarm on the PDA. If a subject does not respond to the alarm, the system determines whether the current situation is an emergency state or not, and then sends some information to the emergency center in the case of an urgent situation. Three different studies were conducted on 12 experimental subjects, with results indicating a good accuracy. The first study was performed to detect the posture change of human daily activity. The second study was performed to detect the correct direction of fall. The third study was conducted to check the classification of the daily physical activity. Each test lasted at least 1 min. in the third study. The output of the acceleration signal was compared and evaluated by changing various postures after attaching a 3-axis accelerometer module on the chest. The newly developed system has some important features such as portability, convenience and low cost. One of the main advantages of this system is that it is available at home healthcare environment. Another important feature lies in its low cost of manufacture. The implemented system can detect the fall accurately, so it will be widely used in emergency situations.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.12 no.1
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• pp.71-81
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• 2017

Objectives : It is important to develop a new Chuna manual therapy as a representative of Chuna manual therapy technique at the time of KSCMM's (Korean Society of Chuna manual medicine) joining a $F{\acute{e}}d{\acute{e}}ration$ Internationale de $M{\acute{e}}decine$ Manuelle (FIMM). Therefore, Sunu manual therapy (SMT) will be introduced as a purely new Chuna manual therapy. Main subject : Sunu manual therapy (SMT) was discovered about two decade ago by a Korean Medicine doctor who wanted to develop a new manual therapy to treat a internal disease. It is very important to make the best use of four powers such as a compression force, a torsion force, a bending force, a tension force using a resonance principle and to experience a feeling of spine axis. SMT is different from Chiropractic technique and Osteopathy technique, in that SMT could treat so many disease using only one technique, but other manual therapy could utilize so many technique to treat only one disease. Discussion : Because SMT utilize a power of a moving in silience, it will take several years to totally master a SMT which will make a patient and a doctor experience a feeling of spine axis. As a feeling of spine axis is deeper, a nerve could be excited and treated by a SMT. Also as a feeling of spine axis is shallower, a muscle could be excied and treated by a SMT. Conclusions : SMT could be classed as a craniosacral chuna therapy or visceral chuna therapy to treat a internal disease considering SMT's action and purpose.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.3
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• pp.198-204
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• 2022

In this paper, the 5kW and 50kW vertical axis wind turbines were studied using the ANSYS flow analysis simulation program. The 5 kW vertical shaft wind turbine has 30 units of the number of main blades and sub-blades and the electrical characteristics were analyzed by changing the tip speed ratio (TSR) from 0.2 to 06. A 50kW vertical axis wind turbine was designed based on the electrical characteristics of a 5kW vertical axis wind turbine. When the tip speed ratio was 0.5, the 5 kW wind power generation showed the maximum output of 9.5 kW and the efficiency of 0.28. The calculation of the power current(Ip) and the power voltage(Ep) show that, as the tip speed ratio increases, the power current(Ip) decreases and the power voltage(Ep) increases. And even if the tip speed ratio was changed, 5kW wind power generation was measured for output of 5 kW or higher. When the tip speed ratio was changed from 0.3 to 0.6, 50 kW wind power generation was output more than 50 kW. When the tip speed ratio of 50kW wind power generation was 0.4, the output was 58.37 [kW] and the efficiency was 0.318, and it was confirmed that the proposed 50kW wind power generation satisfies the design conditions.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.34 no.1
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• pp.18-39
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• 2016

The study pertains to reviewing and discussing of the master plan of the main buildings in the palaces of Joseon Dynasty regarding on a Feng Shui concept that has been implemented on the palace axis that is originated from the main mountain. Gyeongbokgung (景福宮) Palace is located on the northwest coner of Hanyang (漢陽) and on the tip of the main mountain which is in contrast a quite distinguishable from the location of the Fobidden city in Beijing located in the middle of a vast basin. Changdeokgung (昌德宮) Palace as well is also located on the tip of Eungbong (鷹峯), a part of Samkaksan (三角山) mountain, of which the locations were designed for the palaces to receive the benevolent force from the main mountain. The same concept was also applied to appointing the ideal location of the maJor buildings such as Jungjeon (正殿: The throne hall), Pyunjeon (便殿: The king's office) and Chimjeon (寢殿: The king and queen's residence) in the palace that must receive the benevolent force from the qui stream also originated from the main mountain, as such that the buildings have in close relationship with the king. Amisa (蛾眉砂) had been considered as an important geographical milestone of the estate where the palace is located, especially as the guiding landmark for other buildings that must be on the land axis. The land axis with the Amisa as the starting point attributed the Feng Shui as an important measure that determines the location and the shape of other buildings. The buildings location was appeared as having the conceptual buildings location as 'front office-back bedroom building (前朝後寢)' and 'three gates-three sectors (三問三朝)' as per the Rites of Zhou (周禮). On both palaces, Amisa is located on the benevolent point of the land, and the king's bed room buildings are located near the Amisa. The main offices were located on the south of the king's bed room buildings. By practicing this type of concept, consequently the king can receive the pure benevolent force first. In the case of the clearly distinguished locations of the buildings in Gyeongbokgung Palace, Chimjeon, Pyunjeon and Jungjeon were located on the same main qui stream. However, in Changdeokgung Palace where scattered qui stream is observed, the buildings are located on the scattered qui stream. The study found that the type of location of Jungjeon receives least amount of benefit from the Feng Shui but reflects primarily the king's authority rather than order and formality of the space.

• Journal of the Korean Institute of Rural Architecture
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• v.15 no.1
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• pp.39-46
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• 2013

There have been numerous researches on Nak-An village in Jeollanamdo, one of the most representative traditional castle village in Korea. Most of them have dealt with general and physical architectural scale and features separately. Therefore this study aims to understand the compositional characteristics of building layout and exterior space and the relations between street system and dwelling unit of folk houses in Nak-An village. The study examined houses of ordinary people in Nak-An village constructed before the village was not affected by foreign influences. 36 folk houses in Nak-An built from nineteenth century to early twentieth century and believed to have few physical changes from the original floor plans and architectural forms were the subjects to be analyzed. The most popular types in building layout are "Open L"and "Open U". The most typical orientation of main building is Southwest. The favorable entry into the dwelling lot is from the side. The street system in the village consists of main streets of South-North, resulting in dwelling lots with North-South axis most general. This site condition forces the entry into the lot from North main street and the side access to the main building. From these findings, the building layout and the entry into the dwelling lot of folk houses in Nak-An are strongly related with street system and conditions of dwelling lot.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.36-42
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• 2022

Whereas the necessity for recycling and reuse is being emphasized owing to the depletion of resources and waste disposal problems caused by the continuous development of the industry, the importance of remanufacturing has been highlighted recently. Re-manufacturing involves a series of processes in which failed disposal or aging goods are recovered to a state similar to that of a new product. In this regard, machine tools, which are large structures, can achieve the effect of remanufacturing. Among the various elements constituting the machine tool, the main spindle portion that affects the processing precision is critical. Therefore, this study is conducted to derive improvement measures for the main axis of an old Miller planner via reverse engineering and central composite design, which is one of the core processes of remanufacturing.

• Journal of the Korean Chemical Society
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• v.42 no.1
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• pp.135-140
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• 1998

High oxygen pressures appear an important tool in Solid State Chemistry. Two main routes can be developed: (i) the stabilization of thermally unstable oxides, used as precursors, in order to open the synthesis of new materials, (ii) the stabilization of the highest oxidation states of transition metals. This paper is essentially devoted to this second research axis. The methodology developed for preparing new oxides containing Fe(Ⅴ), Ir(Ⅵ), high spin Fe(Ⅳ) and Cu(Ⅲ) is described.