• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.351-353
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• 2017

To realize large-format compact array detectors covering a wide far-infrared wavelength range up to 200 µm, we have been developing Blocked-Impurity-Band (BIB) type Ge detectors with the room-temperature surface-activated wafer bonding technology provided by Mitsubishi Heavy Industries. We fabricated various types of $p^+-i$ junction devices which possessed a BIB-type structure, and evaluated their spectral response curves using a Fourier transform spectrometer. From the Hall effect measurement, we also obtained the physical characteristics of the $p^+$ layers which constituted the $p^+-i$ junction devices. The overall result of our measurement shows that the $p^+-i$ junction devices have a promising applicability as a new far-infrared detector to cover a wavelength range of $100-200{\mu}m$.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.2
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• pp.76-84
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• 2009

In this review an attempt is made to give the background to the current trends in foreign developments in the ceramic matrix composites for space vehicles. The lightweight and high temperature specific modulus properties of ceramic composites have continued to develop for designing advanced propulsion structures and for increasing space vehicle performances. Those applications require advanced materials with good resistance to high temperatures, to oxidation environments and to mechanical stresses. The advantages of ceramic matrix composites are the low specific weight, the high specific strength over a wide temperature ranges, and their good damage tolerance compared to tungsten, pyrographites and polycrystalline graphites. Due to these advantages ceramic matrix composites are currently used in rocket engine chamber, nozzle, solar array, radar antenna, mirror support structures, hypersonic leading edge articles, heat shields, reentry vehicle nose tips, and radiators for spacecraft. Various processes are discussed together with examples of current application so that some of the advanced technologies can be possibly applied to Korean space technology.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.318-325
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• 2015

Pico satellite has limited surface to install the solar cells due to its extremely limited size. Also, the sun incidence angle with respect to the solar panel continuously varies according to the attitude control strategy and its important parameter for the power generation. In this study, a concentrating photovoltaic system for pico satellite application has been proposed that can enhance the power generation efficiency in case of the unfavorable condition of the sun incidence angle with respect to the solar panel of the satellite using the fresnel lens. To prove the possibility of maximizing the power generation efficiency of the proposed concentrating power system, we have performed the power measurement test using a solar simulator and commercial fresnel lens. And on-orbit analysis of the power generation efficiency using the STK which is a commercial S/W has also been performed based on the test results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.988-995
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• 2014

Two axis gimbal type X-band antenna system has been widely used to effectively transmit the real time image data from the observation satellite to the ground station. The micro-vibration generated by stepping motor actuation and imperfect intermeshed gear configuration of the antenna is one of the sources to degrade the image quality. To guarantee a high quality image of high resolution observation satellite, micro-vibration isolation of X-band antenna is required. In this paper, the X-band antenna vibration isolation system using pseudoelastic SMA(Shape Memory Alloy) mesh washer has been newly suggested. The basic characteristics of the SMA mesh washer isolator proposed in this study has been measured through static load tests and its effectiveness has been demonstrated by the micro-vibration isolation test of the X-band antenna.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.274-280
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• 2016

Hinge driving type holding and release mechanism based on the burn wire release for application of cubesat is main payload of STEP Cube Lab. (Cube Laboratory for Space Technology Experimental Project) to be launched at 2015. It has high constraint force, low shock level as well as surmounting drawbacks of conventional nichrome burn wire release method that has relatively low constraint force and system complexity for application of multi-deployable systems. In this paper, we have proposed a flight model of holding and release mechanism for the verification of the constraint force and deployment status signal acquisition. To validate the effectiveness of the flight model, launch and on-orbit environment verification test have been performed.

• Journal of Biosystems Engineering
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• v.30 no.5 s.112
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• pp.261-267
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• 2005

In order to save labor and cost, direct seeding has been considered as an important alternative to the machine transplanting in rice cultivation. As current seeders for direct seeding of rice seeds drill irregular amount of seeds under various operating conditions, conventional drilling should be turned to precision planting which enables accurate placement of proper amount of rice seeds at equal intervals within rows. In this study, design, construction and performance evaluation of a precision seed metering device for planting of rice seeds were carried out. As prototype, the conventional roller type seed metering device was modified for planting: increasing diameter of metering roller, setting 2 or 4 seed cells on metering roller, adding seed discharging lid and its driving cam mechanism. Through performance tests for prototype and the current seed metering device, number of seeds in a hill, planting space and its error ratio, coefficient of variation of planting space (planting accuracy), and seeding length of $90\%$ of seeds in a hill divided by planting space (planting precision) at setting planting spaces of 15, and 20cm, seeding heights of 10, and 20cm, and seeding speeds of 0.1, 0.2, and 0.5m/s were investigated. Prototype showed better seed planting performance than the current seed metering devices. When setting planting space of 15 cm and seeding height of 10cm, prototype with 2 seed cells showed that variations of planting space and seeding lengths of $90\%$ of seeds in a hill at up to seeding speed of 0.5m/s were within 0.9cm, and 3.6cm, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1140-1148
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• 2014

Due to Seoul city population growth, urbanization and industrial structure change, apartment type factory was introduced. The purpose of this study, by analyzing the relationship between land shape of apartment type factory and privately owned public space, draw the elements to increase publicness. Draw land shape and private owned public space layout plan elements with advanced research and analysis through cases. As a result of analysis, land shape of the square and the front-side connected arrangement of the privately owned public space are good for the increase of publicness, rectangular land shape good that front-side connected arrangement and front-back arrangement, to consider in terms of user identification and access via the link should be good.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.9
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• pp.1041-1048
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• 2019

Recently, social demands on atypical buildings and building spaces are increasing, and examples of atypical buildings are easily seen in major cities around the world. This study investigates the user behaviors in the typical atypical buildings currently constructed and analyzes the characteristics of human behavior in the atypical building space. Ultimately, this study aims to develop human behavior simulation technology for reviewing residential performance of atypical building space design, and the results of this study can be used for user behavior modeling and simulation technology development. This is because it is difficult to find an investigation or analysis of what behavioral characteristics occur in the atypical building space in previous studies. This study derives the characteristics of human behavior in the atypical architectural space that has been overlooked in the existing human behavior simulation tools. In other words, the site visits and surveys typical atypical buildings to investigate user behaviors in typical spaces and other atypical buildings.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3544-3564
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• 2022

With the development of the NB-IoT (Narrow band Internet of Things) and smart cities, coupled with the emergence of smart smoke sensors, new requirements and issues have been introduced to study on the deployment of sensors in large spaces. Previous research mainly focuses on the optimization of wireless sensors in some monitoring environments, including three-dimensional terrain or underwater space. There are relatively few studies on the optimization deployment problem of smart smoke sensors, and leaving large spaces with obstacles such as libraries out of consideration. This paper mainly studies the deployment issue of smart smoke sensors in large spaces by considering the fire probability of fire areas and the obstacles in a monitoring area. To cope with the problems of coverage blind areas and coverage redundancy when sensors are deployed randomly in large spaces, we proposed an optimized deployment strategy of smart smoke sensors based on the PSO (Particle Swarm Optimization) algorithm. The deployment problem is transformed into a multi-objective optimization problem with many constraints of fire probability and barriers, while minimizing the deployment cost and maximizing the coverage accuracy. In this regard, we describe the structure model in large space and a coverage model firstly, then a mathematical model containing two objective functions is established. Finally, a deployment strategy based on PSO algorithm is designed, and the performance of the deployment strategy is verified by a number of simulation experiments. The obtained experimental and numerical results demonstrates that our proposed strategy can obtain better performance than uniform deployment strategies in terms of all the objectives concerned, further demonstrates the effectiveness of our strategy. Additionally, the strategy we proposed also provides theoretical guidance and a practical basis for fire emergency management and other departments to better deploy smart smoke sensors in a large space.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.595-602
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• 2015

The rotor configuration of the brushless doubly fed induction generator (BDFIG) plays an important role in its performance. In order to make the magnetomotive force (MMF) space vector in one set rotor windings to couple both magnetic fields with different pole-pair and have low resistance and inductance, this paper presents a novel wound rotor type for BDFIG with low space harmonic contents. In accordance with the principles of slot MMF harmonics and unequal element coils, this novel rotor winding is designed to be composed of three-layer unequal-pitch unequal-turn coils. The optimal design process and rules are given in detail with an example. The performance of a 700kW 2/4 pole-pair prototype with the proposed wound rotor is analyzed by the finite element simulation and experimental test, which are also carried out to verify the effectiveness of the proposed wound rotor configuration.