• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권11호
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• pp.3950-3969
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• 2021

Radio Frequency (RF)-based indoor localization technologies play significant roles in various Internet of Things (IoT) services (e.g., location-based service). Most such technologies require that all the devices comply with a specified technology (e.g., WiFi, ZigBee, and Bluetooth). However, this requirement limits its application scenarios in today's IoT context where multiple devices complied with different standards coexist in a shared environment. To bridge the gap, in this paper, we propose a cross-technology localization approach, which is able to localize target nodes using a different type of devices. Specifically, the proposed framework reuses the existing WiFi infrastructure without introducing additional cost to localize Non-WiFi device (i.e., ZigBee). The key idea is to leverage the interference between devices that share the same operating frequency (e.g., 2.4GHz). Such interference exhibits unique patterns that depend on the target device's location, thus it can be leveraged for cross-technology localization. The proposed framework uses Principal Components Analysis (PCA) to extract salient features of the received WiFi signals, and leverages Dynamic Time Warping (DTW), Gradient Boosting Regression Tree (GBRT) to improve the robustness of our system. We conduct experiments in real scenario and investigate the impact of different factors. Experimental results show that the average localization accuracy of our prototype can reach 1.54m, which demonstrates a promising direction of building cross-technology technologies to fulfill the needs of modern IoT context.

• 한국인터넷방송통신학회논문지
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• 제23권4호
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• pp.29-34
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• 2023

본 논문에서는 마이크로스트립-도파관 전이구조의 임피던스 해석 모델을 바탕으로 설계 방법을 제안하였다. 제안한 구조는 크게 세 부분으로 마이크로스트립-SIW (Substrate Integrated Waveguide) 구조, 기판 두께의 유전체로 쌓인 구조 및 게단형 도파관 구조로 구성되어 있다. 전이구조의 형상은 임피던스 변화에 따라 변화하게 된다. 유전체 변화를 통한 두 가지 형태의 동일한 특성을 가진 전이구조를 제시하였다. 두 Ka대역 전이구조의 설계 방법은 도파관의 크기와 상관없이 모든 응용 분야에 적용가능하다. 제안한 전이구조의 back-to-back 특성은 29.8 ~ 38.2 GHz 대역에서 1.2 dB 이하의 삽입손실 및 15 dB 이상의 반사손실을 가짐을 확인하였다.

• International Journal of Computer Science & Network Security
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• 제23권7호
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• pp.155-164
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• 2023

Machine learning with its high precision algorithms, Precision agriculture (PA) is a new emerging concept nowadays. Many researchers have worked on the quality and quantity of PA by using sensors, networking, machine learning (ML) techniques, and big data. However, there has been no attempt to work on trends of artificial intelligence (AI) techniques, dataset and crop type on precision agriculture using internet of things (IoT). This research aims to systematically analyze the domains of AI techniques and datasets that have been used in IoT based prediction in the area of PA. A systematic literature review is performed on AI based techniques and datasets for crop management, weather, irrigation, plant, soil and pest prediction. We took the papers on precision agriculture published in the last six years (2013-2019). We considered 42 primary studies related to the research objectives. After critical analysis of the studies, we found that crop management; soil and temperature areas of PA have been commonly used with the help of IoT devices and AI techniques. Moreover, different artificial intelligence techniques like ANN, CNN, SVM, Decision Tree, RF, etc. have been utilized in different fields of Precision agriculture. Image processing with supervised and unsupervised learning practice for prediction and monitoring the PA are also used. In addition, most of the studies are forfaiting sensory dataset to measure different properties of soil, weather, irrigation and crop. To this end, at the end, we provide future directions for researchers and guidelines for practitioners based on the findings of this review.

• 한국인터넷방송통신학회논문지
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• 제23권5호
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• pp.103-108
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• 2023

본 논문에서는 미사일의 눈 역할을 하는 탐색기에 적용할 수 있는 AESA 안테나의 성능 고도화 연구를 진행하고 실제 측정을 통해 안테나 성능을 검증하였다. AESA 안테나 설계 시에는 필연적으로 발생하는 복사소자 간의 상호간섭 영향으로 송신 시 능동반사계수의 최적화를 고려해야하며, 탐색기의 공간 제한을 극복할 수 있는 소형/경량화가 적용된 복사소자의 선정이 중요한 설계 고려 사항이다. 이에 탐색기용 AESA 구조에 적용하기 위한 배열안테나 연구를 통해 전기적 성능 및 Low-profile 구조 측면에서 최적화가 필요하다. 본 논문에서 설계하고 측정한 복사소자는 일반적인 비발디 안테나의 성능을 고도화시키면서 Low-profile 구조를 만족할 수 있는 Step Flared Notch(SFN)를 설계하였다. 본 논문을 통해 SFN은 일반적인 비발디 안테나와 동일하게 광대역 특성을 가지며 AESA 안테나에 필요한 특성들이 최적화 된 특성을 보유함을 확인 할 수 있었다. 시뮬레이션을 통해 최적화 된 구조는 실제 프로토타입 안테나 제작을 통해 패턴 특성과 능동반사계수 특성을 확인하였다.

• 한국진공학회지
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• 제16권5호
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• pp.359-365
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• 2007

본 논문에서는 zinc oxide (ZnO)와 gallium이 도핑 된 zinc oxide (GZO)를 이용하여 radio frequency (RF) magnetron sputtering 방법에 의해 상온에서 제작된 bottom-gate 박막 트랜지스터의 특성을 평가하고 분석하였다. 게이트 절연층 물질로서 새로운 물질을 사용하지 않고 열적 성장된 $SiO_2$를 사용하여 게이트 누설 전류를 수 pA 수준까지 줄일 수 있었다. ZnO와 GZO 박막의 표면 제곱평균제곱근은 각각 1.07 nm, 1.65 nm로 측정되었다. 그리고 ZnO 박막은 80% 이상, GZO 박막은 75% 이상의 투과도를 가지고 있었고, 박막의 두께에 따라 투과도가 달라졌다. 또한 두 시료 모두 (002) 방위로 잘 정렬된 wurtzite 구조를 가지고 있었다. 제작된 ZnO 박막 트랜지스터는 2.5 V의 문턱 전압, $0.027\;cm^2/(V{\cdot}s)$의 전계효과 이동도, 104의 on/off ratio, 1.7 V/decade의 gate voltage swing 값들을 가지고 있었고, enhancement 모드 특성을 가지고 있었다. 반면에 GZO 박막 트랜지스터의 경우에는 -3.4 V의 문턱 전압, $0.023\;cm^2/(V{\cdot}s)$의 전계효과 이동도, $2{\times}10^4$의 on/off ratio, 3.3 V/decade의 gate voltage swing 값들을 가지고 있었고, depletion 모드 특성을 가지고 있었다. 우리는 기존의 ZnO와 1wt%의 Ga이 도핑된 ZnO를 이용하여 두 가지 모드의 트랜지스터 특성을 보이는 박막 트랜지스터를 성공적으로 제작하고 분석하였다.

• Radiation Oncology Journal
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• 제7권2호
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• pp.247-257
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• 1989

절제 불가능한 원발성 간암은 여러 가지 다양한 치료법의 시도에도 불구하고 그 예후는 극히 불량하다. 이에 본 저자들은 온열요법에 대한 축적된 경험을 바탕으로 1988년 4월부터 7월까지 본과에 내원한 30명 의 절제 불가능한 원발성 간암 환자들에 대하여 온열 및 방사선 병용요법을 시행하였다. 방사선치료는 일일 조사량 180 cGy씩 3. 5주에 3060 cGy를 조사하였고 온열요법은 8 MHz 유전형온열치료기 (Thermotron RF-8, Cancermia)를 사용하여 주 2회씩 총 5회 시행하되 순서는 방사선 치료를 먼저 한 후 30분 이내에 온열요법이 30~60분간 시행되었다. 그 결과 부분반응이 12예에서 관찰되었고(40%), 증상의 호전이 28예 중 22예에서 관찰되었다(78.6%), 종양의 반응을 예측할 수 있는 인자로서는 형태학적 유형이 가장 유의하게 나타났다(single massive: 10/14, 71.4%, diffuse infiltrative: 2/10, 20% : multinodular : 0/6, 0%, p<0.005). 치료로 인한 심각한 부작용은 관찰되지 않았다. 1년 생존율은 34%였고 정중앙 생존기 간은 6.5개월이었다. 부분반응을 보인 환자군의 생존율 및 정중앙 생존 기간은 각각 50%, 11개월로서 반응을 보이지 않은 환자군의 22%, 5개월과 비교해 볼 때 정중앙 생존기간의 차이가 통계적으로 유의하였다.(p<0.05). 결론적으로 온열 및 방사선 병용요법은 절제 불가능한 원발성 간암의 증상호전 및 국소적 치료에 효과가 있는 것으로 생각되며 생존율 및 부작용 등에 관해서는 앞으로 연구가 더 진행되어야 할 것으로 생각된다.

• Journal of Ginseng Research
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• 제37권3호
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• pp.332-340
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• 2013

In this study, gamma rays were used to irradiate embryogenic calli induced from cotyledon explants of Panax ginseng Meyer. After the embryogenic calli were irradiated, they were transferred to adventitious roots using an induction medium; next, mutated adventitious root (MAR) lines with a high frequency of adventitious root formations were selected. Two MAR lines (MAR 5-2 and MAR 5-9) from the calli treated with 50 Gy of gamma rays were cultured on an $NH_4NO_3$-free Murashige and Skoog medium with indole-3-butyric acid 3 mg/L. The expression of genes related to ginsenoside biosynthesis was analyzed using reverse transcription polymerase chain reaction with RNA prepared from native ginseng (NG), non-irradiated adventitious root (NAR) and 2 MAR lines. The expression of the squalene epoxidase and dammarenediol synthase genes was increased in the MAR 5-2 line, whereas the phytosterol synthase was increased in the MAR 5-9 line. The content and pattern of major ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rf, and Rg1) were analyzed in the NG, NAR, and 2 MAR lines (MAR 5-2 and MAR 5-9) using TLC and HPLC. In the TLC analysis, the ginsenoside patterns in the NG, NAR, and 2 MAR lines were similar; in contrast, the MAR 5-9 line showed strong bands of primary ginsenosides. In the HPLC analysis, compared with the NG, one new type of ginsenoside was observed in the NAR and 2 MAR lines, and another new type of ginsenoside was observed in the 2 MAR lines irradiated with gamma rays. The ginsenoside content of the MAR 5-9 line was significantly greater in comparison to the NG.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.115-116
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• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.

• 한국전자파학회논문지
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• 제21권5호
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• pp.475-485
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• 2010

본 논문에서는 여파기와 안테나 기능을 동시에 수행할 수 있는 새로운 개념의 마이크로스트립 공진기를 제안하고자 한다. 제안한 구조는 바깥쪽 링, 안쪽 링, 원형 패치, 그리고 3개의 포트로 이루어져 있다. 제안하는 구조가 여파기와 안테나로 동작하는 주파수는 각각 주로 안쪽 링과 원형 패치의 반지름에 의해 결정된다. 측정 결과를 통해 마이크로스트립 공진기가 여파기로 동작할 경우 공진 주파수는 0.69 GHz에서 3 dB 대역폭 15.1 %에 삽입 손실이 -1.4 dB의 특성을 보였다. 이 때, 통과 대역 아래 부분에 전달 영점은 0.52 GHz에, 윗부분의 전달 영점은 1.14 GHz와 2.22 GHz에 위치하였다. 위쪽 저지 대역에서 바깥쪽 링의 스터브에 의한 교차 결합(cross coupling)과 안쪽 링에 의해 각각 1개의 전달 영점이 형성된다. 원형 패치는 이중 모드(dual-mode) 특성을 형성하며, 또 다른 전달 영점을 유도한다. 제안한 구조가 안테나로 동작하는 주파수는 2.7 GHz이고, 이득은 3.8 dBi 였다. 여파기와 안테나의 공진 주파수에서 격리도 특성(isolation)이 각각 -25 dB 이하의 좋은 특성을 나타내었다.

• Radiation Oncology Journal
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• 제12권2호
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• pp.191-199
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• 1994

Purpose : This study was undertaken to show the clinical results of combined radiotherapy and hyperthermia in primary hepatoma Materials and Methods : Between December 1989 and March 1993, 50 patients with hepatomas were treated by combined radiotherapy and hyperthermia. Among them, we analyzed retrospectively 33 patients who received the complete course of treatment. The ages of the patients ranged from 36 to 75(mean age: 55.5 years). Twenty-six patients ($78.8\%$) were men, and 7 ($21.2\%$ were women. According to Child's classification, nine patients ($27.3{\%}$) were A group, 9 ($27.3\%$) were B group, 15 ($45.4\%$) were C group. Radiation therapy was done by a 6 MV and 15 MV linear accelerator. Patients were treated with daily fractions of 150-180 cCy to doses of 2550 cGy -4950 cGy (median : 3000 cGy). Local hyperthermia was done by 8 MHZ RF capacitive heating device (Cancermia. Green Cross Co., Korea), 50-60 min/session, 1-2 sessions/wk, and 8.5 sessions (median number)/patient. We analyzed the prognostic factors including age, sex, tumor type, Child's classification, $\alpha$-fetoprotein, liver cirrhosis, ascites, portal vein invasion, esophageal varix, number of hyperthermia, chemotherapy, total bilirubin level, Karnofsky perfomance status. Results : The overall 1-year survival was $24.2\%$, with a mean survival of 10months. Of 33 patients, tumor regression (PR+MR) was seen in $30.4\%$, no response was seen in $52.2\%,\;17.4\%$ patient was progressed. In patients who had tumor regression, the overall 1-year survival was $42.1\%$ with a mean survival of 14 months. Factors influencing the survival were sex (p=0.05), tumor type (p=0.0248), Child's classification (p=0.0001), liver cirrhosis (p=0.0108), ascites (p=0.0009), and Karnofsky perfomance status (p=0.0028). Complications developed in 28 patients, including 18 hot pain,5 fat necrosis, 3 transient fever, 2 nausea and vomiting. Conclusion : In this study, the results suggests that combined radiotherauy and hyperthermia may improve the survival rate of hepatoma.