• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.4
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• pp.55-62
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• 2004

In this paper, we have developed a portable acceleration measurement system to measure acceleration signals during walking and a gait analysis algorithm which can evaluate gait regularity and symmetry and estimate gait parameters automatically. Portable acceleration measurement system consists of a biaxial accelerometer, amplifiers, lowpass filter with cut-off frequency of 16Hz, one-chip microcontroller, EEPROM and RF(TX/RX) module. The algerian includes FFT analysis, filter processing and detection of main peaks. In order to develop the algorithm, eight hemiplegic patients for training set and the other eight hemiplegic patients for test set are participated in the experiment. Acceleration signals during 10m walking were measured at 60 samples/sec from a biaxial accelerometer mounted between L3 and L4 intervertebral area. The algorithm, detected foot contacts and classified right/left steps, and then calculated gait parameters based on these informations. Compared with video data and analysis by manual, algorithm showed good performance in detection of foot contacts and classification of right/left steps in test set perfectly. In the future, with improving the reliability and ability of the algerian so that calculate more gait Parameters accurately, this system and algerian could be used to evaluate improvement of walking ability in hemiplegic patients in clinical practice.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.3
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• pp.271-278
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• 2014

In spite of that stop line and crosswalk should be aware of the most basic objects in transportation system, its features extracted are very limited. In addition to image-based recognition technology, laser and RF, GPS/INS recognition technology, it is difficult to recognize. For this reason, the limited research in this area has been done. In this paper, the algorithm to recognize the stop line and crosswalk is designed and implemented using image-based recognition technology with the images input through a vision sensor. This algorithm consists of three functions.; One is to select the area, in advance, needed for feature extraction in order to speed up the data processing, 'Region of Interest', another is to process the images only that white color is detected more than a certain proportion in order to remove the unnecessary operation, 'Color Pattern Inspection', the other is 'Feature Extraction and Recognition', which is to extract the edge features and compare this to the previously-modeled one to identify the stop line and crosswalk. For this, especially by using case based feature comparison algorithm, it can identify either both stop line and crosswalk exist or just one exists. Also the proposed algorithm is to develop existing researches by comparing and analysing effect of in-vehicle camera installation and changes in recognition rate of distance estimation and various constraints such as backlight and shadow.

• Journal of Internet Computing and Services
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• v.12 no.1
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• pp.55-70
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• 2011

In this paper, we propose a policy-driven RFID data management event definition language, which is possibly applicable as a partial standard for SSI (Software System Infrastructure) Part 4 (Application Interface, 24791-4) defined by ISO/IEC JTC 1/SC 31/WG 4 (RFID for Item Management). The SSI's RFID application interface part is originally defined for providing a unified interface of the RFID middleware functionality―data management, device management, device interface and security functions. However, the current specifications are too circumstantial to be understood by the application developers who used to lack the professional and technological backgrounds of the RFID middleware functionality. As an impeccable solution, we use the concept of event-constraint policy that is not only representing semantic contents of RFID domains but also providing transparencies with higher level abstractions to RFID applications, and that is able to provide a means of specifying event-constraints for filtering a huge number of raw data caught from the associated RF readers. Conclusively, we try to embody the proposed concept by newly defining an XML-based RFID event policy definition language, which is abbreviated to rXPDL. Additionally, we expect that the specification of rXPDL proposed in the paper becomes a technological basis for the domestic as well as the international standards that are able to be extensively applied to RFID and ubiquitous sensor networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.6
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• pp.457-465
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• 2014

This paper introduces a test bed for communication protocol schemes of underwater acoustic sensor network, and also shows experimental results obtained from the test bed. As a testing protocol, carrier sense multiple access/collision avoidance (CSMA/CA) is evaluated on underwater acoustic channel. A sensor node is equipped with a DSP control board of ATmega2560 and a commercial underwater modem produced by Benthos. The control board not only manipulates a GPS signal to acquire the information of location and time, but also controls the underwater modem to operate according to the procedure designed for a given testing protocol. Whenever any event takes place such as exchanging control/data packets between underwater modems and acquiring location and timing information, each sensor node reports them through radio frequency (RF) air interface to a central station located on the ground. The four kinds of packets for CSMA/CA, RTS(Request To Send), CTS(Clear to Send), DATA, ACK(Acknowledgement) are designed according to the underwater communication environment and are analyzed through the lake experiment from the point of feasibility of CSMA/CA in underwater acoustic communications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.27-30
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• 2022

The plasma process, which has many advantages in terms of efficiency and environment compared to conventional process methods, is widely used in semiconductor manufacturing. Plasma Sheath is a dark region observed between the plasma bulk and the chamber wall surrounding it or the electrode. The Plasma Sheath Monitoring Sensor (PSMS) measures the difference in voltage between the plasma and the electrode and the RF power applied to the electrode in real time. The PSMS data, therefore, are expected to have a high correlation with the state of plasma in the plasma chamber. In this study, a model for predicting the state of nitrogen ions in the plasma chamber is training by a deep learning machine learning techniques using PSMS data. For the data used in the study, PSMS data measured in an experiment with different power and pressure settings were used as training data, and the ratio, flux, and density of nitrogen ions measured in plasma bulk and Si substrate were used as labels. The results of this study are expected to be the basis of artificial intelligence technology for the optimization of plasma processes and real-time precise control in the future.

• Geophysics and Geophysical Exploration
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• v.8 no.4
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• pp.270-279
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• 2005

Under the research project supported by Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), we have conducted the development of GPR systems for landmine detection. Until 2005, we have finished development of two prototype GPR systems, namely ALIS (Advanced Landmine Imaging System) and SAR-GPR (Synthetic Aperture Radar-Ground Penetrating Radar). ALIS is a novel landmine detection sensor system combined with a metal detector and GPR. This is a hand-held equipment, which has a sensor position tracking system, and can visualize the sensor output in real time. In order to achieve the sensor tracking system, ALIS needs only one CCD camera attached on the sensor handle. The CCD image is superimposed with the GPR and metal detector signal, and the detection and identification of buried targets is quite easy and reliable. Field evaluation test of ALIS was conducted in December 2004 in Afghanistan, and we demonstrated that it can detect buried antipersonnel landmines, and can also discriminate metal fragments from landmines. SAR-GPR (Synthetic Aperture Radar-Ground Penetrating Radar) is a machine mounted sensor system composed of B GPR and a metal detector. The GPR employs an array antenna for advanced signal processing for better subsurface imaging. SAR-GPR combined with synthetic aperture radar algorithm, can suppress clutter and can image buried objects in strongly inhomogeneous material. SAR-GPR is a stepped frequency radar system, whose RF component is a newly developed compact vector network analyzers. The size of the system is 30cm x 30cm x 30 cm, composed from six Vivaldi antennas and three vector network analyzers. The weight of the system is 17 kg, and it can be mounted on a robotic arm on a small unmanned vehicle. The field test of this system was carried out in March 2005 in Japan.

• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.14-18
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• 2020

This study investigates the nitrogen dioxide (NO₂) sensing characteristics of an Si MOSFET gas sensor with a tungsten trioxide (WO₃) sensing layer deposited using the sputtering method. The Si MOSFET gas sensor consists of a horizontal floating gate (FG) interdigitated with a control gate (CG). The WO₃ sensing layer is deposited on the interdigitated CG-FG of a field effect transistor(FET)-type gas sensor platform. The sensing layer is deposited with different thicknesses of the film ranging from 100 nm to 1 ㎛ by changing the deposition times during the sputtering process. The sensing characteristics of the fabricated gas sensor are measured at different NO₂ concentrations and operating temperatures. The response of the gas sensor increases as the NO₂ concentration and operating temperature increase. However, the gas sensor has an optimal performance at 180℃ considering both response and recovery speed. The response of the gas sensor increases significantly from 24% to 138% as the thickness of the sensing layer increases from 100 nm to 1 ㎛. The sputtered WO₃ film consists of a dense part and a porous part. As reported in previous work, the area of the porous part of the film increases as the thickness of the film increases. This increased porous part promotes the reaction of the sensing layer with the NO₂ gas. Consequently, the response of the gas sensor increases as the thickness of the sputtered WO₃ film increases.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.339-339
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• 2012

지난 몇 년 동안, 투명 비정질 산화물 반도체는 유기 발광 다이오드, 플렉서블 전자 소자, 솔라 셀, 바이오 센서 등 많은 응용분야에 연구되고 있다. 투명 비정질 산화물 반도체 그룹들 중, 특히 비정질 IGZO 박막 트랜지스터는 비정질 상태임에도 불구하고 높은 이동도와 낮은 동작 전압으로 훌륭한 소자 특성을 보인다. 이러한 고성능의 IGZO 박막 트랜지스터는 RF 마그네트론 스퍼터링이나 pulsed laser deposition과 같은 고진공 장비를 이용하여 이미 여러 그룹에서 제작되고 발표되었다. 하지만 진공 증착 시스템은 제조 비용의 절감이나 디스플레이 패널의 대면적화에 큰 걸림돌이 되고 있고, 이러한 문제점을 극복하기 위해서 용액 공정은 하나의 해결책이 될 수 있다. 용액 공정의 가장 큰 장점으로는 저온 공정이 가능하기 때문에 글라스나 플라스틱 기판에서 대면적으로 제작할 수 있고 진공 장비가 필요없기 때문에 제조 비용을 획기적으로 절감시킬 수 있다. 본 연구에서는 high-k 게이트 절연막과 IGZO 채널 층을 용액 공정을 이용하여 박막 트랜지스터를 제작하고 그에 따른 전기적 특성을 분석하였다. IGZO의 몰 비율은 In, Ga, Zn 순으로 각각 0.2 mol, 0.1 mol, 0.1 mol로 제작하였고, high-k 게이트 절연막으로는 Al2O3, HfO2, ZrO2을 제작하였다. 또한, 용액 공정 IGZO TFT를 제작하기 전, 용액 공정 high-k 게이트 절연막 캐패시터를 제작하여 그 특성을 분석하였다. 다양한 용액 공정 high-k 게이트 절연막 중, 용액공정 HfO2를 이용한 IGZO TFT는 228.3 [mV/dec]의 subthreshold swing, 18.5 [$cm^2/V{\cdot}s$]의 유효 전계 이동도, $4.73{\times}106$의 온/오프 비율을 보여 매우 뛰어난 전기적 특성을 확인하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.57.2-57.2
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• 2010

투명전도 산화막(Transparent conducing oxide: TCO)은 태양 전지, 터치패널, 가스 센서 등 여러 분야에 적용할 수 있는 물질로서 전기 전도성과 광 투과성을 동시에 가진다. 높은 전기 전도성과 광 투과성을 가지는 Sb:$In_2O_3$(ITO)는 투명전도 산화막 재료로써 가장 일반적으로 사용되고 있으나 인듐의 매장량 한계로 인해 가격이 높다는 단점이 있다. 본 연구에서는 ITO 대체 TCO 물질인 Al doped ZnO(AZO)를 rf magnetron sputter를 이용하여 최적의 수소 도핑량을 찾아 ITO의 전기적 광학적 성질과 비교하였다. AZO 박막은(ZnO:Al2O3 2wt.%)타겟을 이용하여 heater 온도 250도에서 슬라이드 글래스 및 코닝 글래스에 증착시켰고 비교군인 ITO박막은 (In2O3:$SnO_2$ 10wt.%)타겟을 이용하여 수소 도핑 없이 350도로 증착시켰다. AZO 및 ITO 박막의 전기적 특성은 hall measurement를 이용하여 측정하였고, UV-VIS spectrophotometer로 광학적 특성을 측정하였다. 수소 도핑량이 증가함에 따라 AZO 박막의 캐리어 농도가 증가하여 전기적 특성이 향상되었고, 가시광 영역에서 높은 평균 투과도를 유지 하였다. AZO 박막과 ITO 박막의 전기적 및 광학적 특성을 비교한 결과, 최적 수소 도핑량을 가진 AZO 박막은 ITO 박막에 준하는 특성을 보였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1277-1282
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• 2016

In the next generation wireless communication systems, an energy harvesting from radio frequency signals is considered as a method to solve the lack of power supply problem for sensors. In this paper, we try to propose an efficient algorithm for simultaneous wireless information and power transfer in energy harvesting networks with channel estimation error. At first, we find an optimal channel training interval using one-dimensional exhaustive search, and estimate a channel using MMSE channel estimator. Based on the estimated channel, we propose a power allocation and splitting algorithm for maximizing the data rate while guaranteeing the minimum required harvested energy constraint, The simulation results confirm that the proposed algorithm has an insignificant performance degradation less than 10%, compared with the optimal scheme which assumes a perfect channel estimation, but it can improve the data rate by more than 20%, compared to the conventional scheme.