• Smart Structures and Systems
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• 제24권3호
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• pp.333-343
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• 2019

The possibility of adopting vibration-powered wireless nodes has been largely investigated in the last years. Among the available technologies based on the piezoelectric effect, the most common ones consist of a vibrating beam covered by electroactive layers. Another energy harvesting strategy is based on the use of piezoelectric strips attached to a hosting structure subjected to dynamic loads. The hosting structure, for example, can be the system to be equipped with wireless nodes. Such strategy has received few attentions so far and no analytical studies have been presented yet. Hence, the original contribution of the present paper is concerned with the development of analytical solutions for the electrodynamic analysis and design of piezoelectric polymeric strips attached to relatively large linear elastic structural systems subjected to random vibrations at the base. Specifically, it is assumed that the dynamics of the hosting structure is dominated by the fundamental vibration mode only, and thus it is reduced to a linear elastic single-degree-of-freedom system. On the other hand, the random excitation at the base of the hosting structure is simulated by filtering a white Gaussian noise through a linear second-order filter. The electromechanical force exerted by the polymeric strip is negligible compared with other forces generated by the large hosting structure to which it is attached. By assuming a simplified electrical interface, useful new exact analytical expressions are derived to assess the generated electric power and the integrity of the harvester as well as to facilitate its optimum design.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2019년도 춘계학술대회
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• pp.618-620
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• 2019

농업과 ICT융합 기술이 접목된 스마트팜은 우리나라에서 타 산업보다 낮은 단계에 머물러 있지만 가장 활발한 연구개발이 추진되는 분야이기도 하다. 스마트팜은 농업과 ICT기술 간의 융합을 통해 농업 분야의 각종 정보를 수집하고 가공, 분석하여 단계별 효율성 향상을 높이는데 목적이 있다. 이 연구에서는 원예작물인 딸기의 스마트팜 구성을 위해 수확기에 수확이 가능한 딸기를 색상으로 구분할 수 있는 영상 처리 방법에 대해 연구를 진행 하였다. 딸기 재배 과정에서 딸기 수확은 많은 노동력을 필요로 한다. 이 연구에서는 딸기 수확기에 노동력 절감에 필요한 정보 수집을 목표로 하고 있다. 그 선행 연구로서 빛의 조사 방향 및 밝기 값에 따라 색 온도가 변화하는 형태를 파이썬을 이용한 OpenCV 색상 검출을 통해 구현 해 볼 계획이다. 향후에는 색 온도 변화에 보상 값을 적용하여 수확에 적합한 딸기색상 값을 찾는 연구를 계획하고 있다.

• 한국기계가공학회지
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• 제18권3호
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• pp.14-25
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• 2019

From 2019 onwards, more stringent regulations (from Stage 4 to Stage 5) are to be implemented in Europe in order to reduce the air pollutant emissions. In South Korea, the government authorities started to make new regulation to meet the European regulation. As a first step, the air pollutant emissions such as CO, NOx, SOx, TSP, $PM_{10}$, $PM_{2.5}$, VOC, $NH_3$ by agricultural machinery were analyzed based on CAPSS inventory along with the analysis in the general aspect in this study. Three levels of analysis was conducted each in agricultural machinery aspect along with in the general aspect. Per agricultural tractor, all kinds of the air pollutant emissions decreased by 25, 25, 99, 25, 25, 25, 25% for the CO, NOx, SOx, TSP, $PM_{10}$, VOC, $NH_3$ emissions each from the year 2000 to the year 2014. Per combine harvester, all kinds of the air pollutant emissions decreased by 63, 63, 91, 63, 63, 63, 63% for the CO, NOx, SOx, TSP, $PM_{10}$, VOC, $NH_3$ emissions each from the year 2000 to the year 2014.

• Journal of Forest and Environmental Science
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• 제38권4호
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• pp.239-248
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• 2022

Forestry crane work in a forest harvester or forwarder is regarded as one of most hard work requiring a very high level of operation skill. The operator must handle two or more multi-axes joysticks simultaneously to control the multiple manipulators for maneuvering the crane-tip to its intended location. This study has been carried out to develop a crane-tip controller which can intuitively maneuver the crane-tip, resulting in improving the productivity by decreasing the technical difficulty of control as well as reducing the workload. The crane-tip controller consists of a single 2-axis joystick and a control algorithm run on microcontroller. Lab-scale forestry crane was constructed using electric cylinders. The crane-tip control algorithm has the crane-tip follow the waypoints generated on the given path considering the dead band region using LBO (Lateral Boundary Offset). A speed control gain to change the speed of relevant cylinders relatively is applied as well. By the P (Proportional) control within the control interval of 20 msec, the average error of crane-tip control on the predefined straight path turned out to be 14.5 mm in all directions. When the joystick is used the waypoints are generated in real time by the direction signal from the joystick. In this case, the average error of path control was 12.4 mm for straight up, straight forward and straight down movements successively at a certain constant speed setting. In the slant movement of crane-tip by controlling two axes of joystick simultaneously, the movement of crane-tip was controlled in the average error of 15.9 mm when the crane-tip is moved up and down while moving toward forward direction. It concluded that the crane-tip control was possible using the control algorithm developed in this study.

• 한국전기전자재료학회논문지
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• 제35권2호
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• pp.119-128
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• 2022

Recent advancement of Internet of Things (IoT) and energy harvesting technology enable realization of flexible thermoelectric energy harvester (f-TEH), with technological prowess for use in biomedical monitoring system integrated applications. To expand a flexible thermoelectric energy harvesting platform, the f-TEH must be required for optimized flexible thermoelectric materials and device structure. In response to these demands related to thermoelectric energy harvesting, many research groups have investigated various f-TEHs applied as a power source for wearable electronics. As a key member of the f-TEH, film-based f-TEHs possess significant applicability in research to realize self-powered wearable electronics, owing to their excellent flexibility, low thermal conductivity, and convenient fabrication process. Thus, based on the rapid growth of thermoelectric film technology, this review aims to overview comprehensively the f-TEH made of various inorganic/organic thermoelectric materials including developed fabrication methods, high thermoelectric performance, and wide-range applications.

• 농업과학연구
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• 제49권2호
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• pp.269-284
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• 2022

The development of radish collectors has the potential to increase radish yields while decreasing the time and dependence on human labor in a variety of field activities. Stress and fatigue analyses are essential to ensure the optimal design and machine life of any agricultural machinery. The objectives of this research were to analyze the stress and fatigue of major components of a tractor-mounted radish collector under dynamic load conditions in an effort to increase the design dependability and dimensions of the materials. An experiment was conducted to measure the shaft torque of stem-cutting and transferring conveyor motors using rotary torque sensors at different tractor ground speeds with and without a load. The Smith-Watson-Topper mean stress equation and the rain-flow counting technique were utilized to determine the required shear stress with the distribution of the fatigue life cycle. The severity of the operation was assessed using Miner's theory. All running conditions produced more than 10⁷ of high cycle fatigue strength. Furthermore, the highest severity levels for motor shafts used for stem cutting and transferring and for transportation joints and cutting blades were 2.20, 4.24, 2.07, and 1.07, and 1.97, 3.81, 1.73, and 1.07, respectively, with and without a load condition, except for 5.24 for a winch motor shaft under a load. The stress and fatigue analysis presented in this study can aid in the selection of the most appropriate design parameters and material sizes for the successful construction of a tractor-mounted radish collector, which is currently under development.

• 한국전기전자재료학회논문지
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• 제36권3호
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• pp.292-297
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• 2023

Triboelectric devices are attracting attention from researchers as self-powered electronic systems that can instantly convert mechanical input into electrical energy output. To improve triboelectric energy harvesting performance, increasing the number of contacts as well as the contact area has been carried out by numerous researchers. In this study, we design a shaker-type energy harvester which is called as maracas triboelectric generator (M-TEG), inspired by the structure of maracas, one of the musical percussion instruments. A tripod frame is inserted to the inside of a cylindrical case, which is a device with the electrodes of aluminum and copper. Then, the triboelectric energy harvesting characteristics between polypropylene (PP) balls and the electrodes are measured. The M-TEG with the frame generates the energy harvesting signals up to ~100 V and ~2.5 ㎂ due to larger contact area and numbers, which enhances the voltage and current output by 250% and 610% compared to that without the frame, respectively. This study presents the feasibility of self-powered sensors and toys using improved triboelectric energy performance with a low-cost and simple manufacturing process in the interesting structure.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.106-111
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• 2024

A triboelectric nanogenerator is a promising energy harvester operated by the combined mechanism of electrostatic induction and contact electrification. It has attracting attention as eco-friendly and sustainable energy generators by harvesting wasting mechanical energies. However, the power generated in the natural environment is accompanied by low frequencies, so that the output power under such input conditions is normally insufficient amount for a variety of industrial applications. In this study, we introduce a non-contact rotational triboelectric nanogenerator using pedaling and gear systems (called by P-TENG), which has a mechanism that produces high power by using rack gear and pinion gear when a large force by a pedal is given. We design the system can rotate the shaft to which the rotor is connected through the conversion of vertical motion to rotational motion between the rack gear and the pinion gear. Furthermore, the system controls the one directional rotation due to the engagement rotation of the two pinion gears and the one-way needle roller bearing. The TENG with a 2 mm gap between the rotor and the stator produces about the power of 200 ㎼ and turns on 82 LEDs under the condition of 800 rpm. We expect that P-TENG can be used in a variety of applications such as operating portable electronics or sterilizing contaminated water.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.112-117
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• 2024

The Internet of Things (IoT) device is a key component for Industry 4.0, which is the network in homes, factories, buildings, and infrastructures to monitor and control the systems. To demonstrate the IoT network, batteries are widely utilized as power sources, and the batteries inevitably require repeated replacement due to their limited capacity. Magneto-mechano-electric (MME) generators are one of the candidate to develop self-powered IoT systems since MME generators can harvest electricity from stray alternating current (AC) magnetic fields arising from electric power cables. Herein, we report a magneto-mechano-triboelectric generator enabled by a ferromagnetic-ferroelectric composite. In the triboelectric nylon matrix, a ferromagnetic carbonyl iron powder (CIP) was introduced to induce magnetic force near the AC magnetic field for MME harvesting. Additionally, a ferroelectric ceramic powder was also added to the MME composite material to enhance the charge-trapping capability during triboelectric harvesting. The final ferromagnetic-ferroelectric composite-based MME triboelectric harvester can generate an open-circuit voltage and a short-circuit current of 110 V and 8 μA, respectively, which were enough to turn on a light emitting diode (LED) and charge a capacitor. These results verify the feasibility of the MME triboelectric generator for not only harvesting electricity from an AC magnetic field but also for various self-powered IoT applications.

• 생물환경조절학회지
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• 제7권3호
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• pp.226-236
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• 1998

본 연구는 오이수확기 개발을 위하여 오이의 인식에 장해가 되는 잎의 부분적인 제거 및 기계화를 위한 재배방식이 오이의 생육과 수량에 미치는 영향을 구명하고자 하였다. 세가지 형태의 잎제거 방식과 두가지 형태의 정식간격, 그리고 3가지 형태의 줄기 유인방식을 정하여 오이의 전장, 수량과 1등급비율을 측정한 결과를 요약하면 다음과 같다. 1. 잎제거 형태에 따른 오이의 생육을 관찰하기 위해서 전장을 측정한 결과, 관행적인 제거방식의 경우, 일정 실험기간동안 평균 52.2cm 생장하였다. 또한, 2일마다 하부잎 하나를 제거한 경우에는 평균 51.5cm 생장하였다. 수확한 오이가 있는 경우 하부의 잎을 모두 제거한 경우에는 평균 51cm가 생장한 것으로 보아 평균 3% 이내의 차이를 보였다. 또한, 24cm, 30cm의 주간간격에 따라서는 각각 평균 50.8cm, 51.8cm의 약 2%정도 생장에 차이를 보였다. 따라서 부분적인 잎제거는 오이의 생장에 큰 영향을 미치지 않는 것으로 판단되었다. 2. 판별변수의 하나인 수량과 1등급비율을 잎제거 형태에 따라 비교해 보면, 관행적인 제거방식의 경우, 평균 한주당 2.6개/일 를 수확하였다. 1등급 비율은 56.7%로 나타났다. 또한 2일마다 하부잎 하나를 제거한 경우에는 평균 한주당 2.47개/일의 수확이 있었으며, 1등급 비율은 53.1%로 나타났다. 마지막으로 수확한 오이가 있는 경우 하부의 잎을 모두 제거한 경우에는 한주당 평균 2.48개/일 를 수확하였으며, 1등급 비율이 56.3%로 나타났다. 따라서 수량의 차이는 약 6%정도이고 1등급 비율도 10% 이내로 큰 영향은 없는 것으로 판단되었다. 3. 오이의 주간간격에 따른 수량과 1등급비율을 측정한 결과, 24cm의 경우 한주당 2.3개/일의 평균수확이 되었다. 1등급비율은 59.8%, 30cm의 경우 한주당 평균 2.5개/일을 수확하였으며, 1등급은 57.2%로 나타났다. 따라서 수량은 24cm의 경우가 약간 적었지만 1등급의 비율로 환산하면 크게 차이가 없는 것을 알 수 있다. 따라서 농가전체 수량을 기준으로 한다면 24cm가 유리하다고 판단되었다. 4. 줄기유인 형식에 따라 수량과 1등급비율을 살펴보면, 관행적인 방법은 평균 한주당 2.9개/일, 42.8%, 직립후횡유인은 평균 한주당 2.2개/일, 61.3%, 직립후 가로줄유인은 평균 한주당 2.2개/일, 54.1%로 나타났다. 따라서 수량과 1등급을 동시에 고려하면, 큰 차이는 없지만, 직립후 횡유인방법과 직립후 가로줄유인의 경우는 오이가 지면에서 상대적으로 상부에 위치하므로 영상인식과 기계화 측면에서 유리할 것으로 생각되었다.