• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.430-433
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• 2006

Wireless sensor network plays a prominent role in tracking the location of the target outdoor and indoor. This paper describes the implementation of the passive indoor location tracking system using ultrasonic and RF technologies that provides accurate location in the form of user space and position in three dimensions. Our system used a combination of RF and ultrasonic technologies to provide a location-support service to users and applicants. Ceiling-mounted beacons were spread through the building, publishing location information on an RF signal. The person carried a listener and the listener determined the location by calculating the distance from three beacons using triangulation algorithm.

• Journal of Appropriate Technology
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• v.6 no.2
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• pp.136-145
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• 2020

Agriculture is the backbone of the economy of most developing countries. In these countries, agriculture or farming is mostly done manually with little integration of machinery, intelligent systems and data monitoring. Irrigation is an essential process that directly influences crop production. The fluctuating amount of rainfall per year has led to the adoption of irrigation systems in most farms. The absence of smart sensors, monitoring methods and control, has led to low harvests and draining water sources. In this research paper, we introduce a 433 MHz Radio Frequency and 2G based Smart Irrigation Meter System and a water prepayment system for rural areas of Tanzania with no reliable internet coverage. Specifically, Ngurudoto area in Arusha region where it will be used as a case study for data collection. The proposed system is hybrid, comprising of both weather data (evapotranspiration) and soil moisture data. The architecture of the system has on-site weather measurement controllers, soil moisture sensors buried on the ground, water flow sensors, a solenoid valve, and a prepayment system. To achieve high precision in linear and nonlinear regression and to improve classification and prediction, this work cascades a Dynamic Regression Algorithm and Naïve Bayes algorithm.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.217-227
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• 2010

To apply active RFID technology in the various kinds of industry, it needs to quickly transmit a large amount of data. ISO/IEC 18000-7 standard uses the 433.92MHz as single channel system and its transmit rate is just 27.8kbps, that is insufficient for a large amount of data transmission. To solve this problem, we designed a new data transmission protocol using 2.4GHz band. The feature of designed protocol is not only making over 255bytes data messages using the Burst Read UDB but also efficiently transmitting it. To implement this protocol, we use Texas Instruments's SmartRF04 develop kit and CC2500 transceiver as RF module. As an evaluation of 63.75kbytes data transmission, we demonstrate that transmission time of Burst Read UDB has improved as 17.95% faster than that of Read UDB in the ISO/IEC 18000-7.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.532-541
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• 2009

The RFID technology has attracted much attention these days due to the far better efficiency than the bar-code and magnetic card system. As an important usage, the 433 MHz active RFID tag was already adopted to the container ports in the United States and Europe for container loading/unloading automation and equipment location. However, there is one problem to be solved for the complete automation. RFID readers support only the direct communication with tags within their RF communication range. Then there are a lot of containers and equipments such as crane, yard tractor, and forklift in ports; and because they are made of metal, they interfere the RF communication, resulting in the occurrence of the dead-zone. In the dead-zone, RFID tags cannot receive any signal from readers. There may be several solutions to resolve the dead-zone problem. Among them, this paper suggests the most economical solution where RFID tags in the dead-zone can communicate with readers via neighbor tags in the multi-hop manner The new RFID communication architecture should be carefully designed in order to maintain the compatibility with the previous standard. Our experiment shows that the proposed architecture works well even in the case where some tags are out of the RF range of reader.

• Journal of the Korean Society of Food Culture
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• v.20 no.4
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• pp.433-437
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• 2005

The characteristic properties of rice breads produced from several conditions were investigated. The rice bread made in control condition (wheat flour), RF 3 (rice and wheat flour mixing) condition and RF 1 (rice, gluten and modified starch mixing) showed relatively higher volumethan others. The crust and crumb color were measured by Humter colory meter. The rice breads making on RF 5 and RF 6 condition showed higher crust L-value and the crumb L-value of the bread from RF 1 condition was higher than that from other condition. On the texture measuring by texture analyzer, hardness of the bread made from RF 1 and RF 2 conditions and cohesiveness of that from RF 3 condition were lower than control. However the significant higher level of the springiness and chewiness were showed in the bread from RF 1, RF 2 and RF 3 condition. The bread containing 85% of rice, 5% of rice, 5% of gluten and 10% of modified starch which was made in RF 1 condition obtained significant high overall acceptance score by sensory evaluation.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2005.11a
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• pp.343-346
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• 2005

유비쿼터스 시대의 도래로 인해 많은 IT업체는 유비쿼터스 핵심기술을 기반으로 발전하고 있다. 이러한 유비쿼터스 핵심기술의 상당부분은 무선통신기술 RF를 이용한 것이며 이를 활용하여 RFID 시스템 및 Ubiquitous Sensor Network 등을 구축할 수 있다. 본 논문에서는 이에 적합한 400/800MHz ISM/SRD 밴드대역을 사용하는 무선 트렌시버 단일 칩인 CC1020을 이용하여 하드웨어를 구성 하였다. CC1020칩을 사용하면 저전력, 고감도, 적은 주변회로 구성 등 많은 이점이 있으며 주파수원 고정과 필터링 및 전원공급상태 그리고 PC와의 interface등의 하드웨어를 쉽게 구현할 수 있다. 따라서 이러한 각 주변회로 구성에 대해 설명하고 실제 구현을 통해 DATA의 송수신실험을 통해 하드웨어의 특성을 확인 하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.7
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• pp.433-437
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• 2014

Transparent thin film transistors were fabricated on $n^+$-Si wafers coated by $Al_2O_3/SiO_2$. Zinc tin oxide (ZTO) films deposited by rf magnetron sputtering were employed for active layers. The mobility (${\mu}s$), threshold voltage ($V_T$), and subthreshold swing (SS) dependances on ZTO thickness were analyzed. The $V_T$ decreased with increasing ZTO thickness. The ${\mu}s$ raised from $5.1cm^2/Vsec$ to $27.0cm^2/Vsec$ by increasing ZTO thickness from 7 nm to 12 nm, and then decreased with ZTO thickness above 12 nm. The SS was proportional to ZTO thickness.

• Journal of the Korean institute of surface engineering
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• v.38 no.1
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• pp.7-13
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• 2005

Bismuth thin films were prepared on glass substrate with RF magnetron sputtering and effects of substrate temperature on surface morphology and their electrical transport properties were investigated. Grain growth of bismuth after nucleation and the onset of coalescense of grains at 393 K were observed with field emission secondary electron microscopy. Continuous thin films could not be obtained above 473 K because of grain segregation and island formation. Hall effect measurements showed that substrate heating yields the decrease of carrier density and the increase of mobility. Resistivity of bismuth film has its minimum (about 0.7 x 10/sup -3/ Ωcm) in range of 403～433 K. Annealing of bismuth films deposited at room temperature was carried out in a radiation furnace with flowing hydrogen gas. The change of resistivity was not significant due to cancellation of the decrease of carrier density and the increase of mobility. The abrupt change of electrical properties of film annealed above 523 K was found to be caused by partial oxidation of bismuth layer in x-ray diffraction analysis.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.36 no.6
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• pp.433-442
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• 2018

The reservoir area is defined as the area surrounded by the planned flood level of the dam or the land under the planned flood level of the dam. In this study, supervised classification based on RF (Random Forest), which is a representative machine learning technique, was performed to detect cropland in the reservoir area. In order to classify the cropland in the reservoir area efficiently, the GLCM (Gray Level Co-occurrence Matrix), which is a representative technique to quantify texture information, NDWI (Normalized Difference Water Index) and NDVI (Normalized Difference Vegetation Index) were utilized as additional features during classification process. In particular, we analyzed the effect of texture information according to window size for generating GLCM, and suggested a methodology for detecting croplands in the reservoir area. In the experimental result, the classification result showed that cropland in the reservoir area could be detected by the multispectral, NDVI, NDWI and GLCM images of UAV, efficiently. Especially, the window size of GLCM was an important parameter to increase the classification accuracy.

• Korean Journal of Remote Sensing
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• v.35 no.6_1
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• pp.987-997
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• 2019

Recently the demand for drones is rapidly increasing, as developing Unmanned Aerial Vehicle (UAV) and growing interest in them. Compared to traditional satellite and aerial imagery, it can be used for various researches (environment, geographic information, ocean observation, and remote sensing) because it can be managed with low operating costs and effective data acquisition. However, there is a disadvantage in that only a small area is acquired compared to the satellite and an aircraft, which is a traditional remote sensing method, depending on the battery capacity of the UAV, and the distance limit between Ground Control System (GCS) and UAV. If remote control at long range is possible, the possibility of using UAV in the field of remote sensing can be increased. Therefore, there is a need for a communication network system capable of controlling regardless of the distance between the UAV and the GCS. The distance between UAV and GCS can be transmitted and received using simple radio devices (RF 2.4 GHz, 915 MHz, 433 MHz), which is limited to around 2 km. If the UAV can be managed simultaneously by improving the operating environment of the UAV using a Long-Term Evolution (LTE) communication network, it can make greater effects by converging with the existing industries. In this study, we performed the maximum straight-line distance 6.1 km, the test area 2.2 ㎢, and the total flight distance 41.75 km based on GCS through LTE communication. In addition, we analyzed the possibility of disconnected communication through the base station of LTE communication.