• International Journal of Aeronautical and Space Sciences
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• 제16권3호
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• pp.407-417
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• 2015

Recently, piezo-aeroelastic energy harvesting has received greater attention. In the present study, a piezo-aeroelastic energy harvester using a nonlinear trailing-edge flap is proposed, and its nonlinear aeroelastic behaviors are investigated. The energy harvester is modeled using a piezo-aeroelastic model of a two-dimensional typical section airfoil with a trailing-edge flap (TEF). A piezo-aeroelastic analysis is carried out using RL and time-integration methods, and the results are verified with the experimental data. The linearizing method using a describing function is used for the frequency domain analysis of the nonlinear piezo-aeroelastic system. From the linear and nonlinear piezo-aeroelastic analysis, the limit cycle oscillation (LCO) characteristics of the proposed energy harvester with the nonlinear TEF are investigated in both the frequency and time domains. Finally, the authors discuss the air speed range for effective piezo-aeroelastic energy harvesting.

• Advances in Computational Design
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• 제1권2호
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• pp.155-173
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• 2016

This paper presents a method of design for the energy harvesting of a piezoelectric cantilever beam. Vibration modes have strain nodes where the strain distribution changes in the direction of the beam length. Covering the strain nodes of the vibration modes with continuous electrodes effects a cancellation of the voltages outputs. The use of segmented electrodes avoids cancellations of the voltage for multi-mode vibration. The resistive load affects the voltage and generated power. The optimum resistive load is considered for segmented and continuous electrodes, and then the power output is verified. One of the effective parameters on energy harvesting performance is the existence of concentrated mass. This topic is studied in this paper. Resonance and off-resonance cases are considered for the harvester. In this paper, both theoretical and experimental methods are used for satisfactory results.

• Journal of Communications and Networks
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• 제14권2호
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• pp.151-161
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• 2012

This paper considers a two-user Gaussian interference channel with energy harvesting transmitters. Different than conventional battery powered wireless nodes, energy harvesting transmitters have to adapt transmission to availability of energy at a particular instant. In this setting, the optimal power allocation problem to maximize the sum throughput with a given deadline is formulated. The convergence of the proposed iterative coordinate descent method for the problem is proved and the short-term throughput maximizing offline power allocation policy is found. Examples for interference regions with known sum capacities are given with directional water-filling interpretations. Next, stochastic data arrivals are addressed. Finally, online and/or distributed near-optimal policies are proposed. Performance of the proposed algorithms are demonstrated through simulations.

• 세라미스트
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• 제22권2호
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• pp.110-121
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• 2019

Triboelectric nanogenerators and piezoelectric nanogenerators are a spotlighted energy harvesting method that converts the wasted mechanical energy from the environment into usable electrical energy. In the case of triboelectric nanogenerators, researches have been mainly focused on high permittivity and flexible polymer materials, and in the case of piezoelectric nanogenerators, researches have been focused on ceramic materials exhibiting high polarization characteristics. Recently, many researches have been conducted to improve durability and power in various environments by using composite materials which have flexible properties of polymer, high permittivity, thermal resistance and high polarization properties of ceramics. This article reviews the energy harvesting studies reported about composites materials using ceramics and polymers.

• KSBB Journal
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• 제26권2호
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• pp.143-150
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• 2011

The aim of the study was to optimize harvesting method for concentrating microalgae from microalgae mass culture. It is well known that the mass density of microalgae is usually very low and these are small size (5-20 ${\mu}m$) in the culture medium. It is essential that microalgae is harvested and concentrated economically for economical biodiesel production from microalgae. In this study, to determine optimized conditions for microalgae harvesting by chemical flocculation. Flocculation of three algae, Chlorella ellipsoidea, Dunaliella bardawil, and Dunaliella tertiolecta, was performed using various chemical flocculants, such as inorganic flocculants (aluminium sulfate, aluminium potassium sulfate, ferrous sulfate, ferric sulfate, ferric chloride, calcium hydroxide, sodium carbonate, sodium nitrite, and sodium aluminate), organic flocculant (polyacrylamide), and biopolymer flocculants (chitosan and starch). The results indicated that aluminium based inorganic flocculants is suitable for microalgae harvesting such as Chlorella ellipsoidea, Dunaliella bardawil, and Dunaliella tertiolecta. The results also recommended that flocculant doses, agitation speed, agitation time, sedimentation time for economical microalgae harvesting method using chemical flocculants.

• ETRI Journal
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• 제45권3호
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• pp.519-533
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• 2023

This paper implements a simultaneous solar and thermal energy harvesting system, as a hybrid energy harvesting (HEH) system, to convert ambient light into electrical energy through photovoltaic (PV) cells and heat absorbed in the body of PV cells. Indeed, a solar panel equipped with serially connected thermoelectric generators not only converts the incoming light into electricity but also takes advantage of heat emanating from the light. In a conventional HEH system, the diode block is used to provide the path for the input source with the highest value. In this scheme, at each time, only one source can be handled to generate its output, while other sources are blocked. To handle this challenge of combining resources in HEH systems, this paper proposes a method for collecting all incoming energies and conveying its summation to the load via the current mirror cells in an approach similar to the maximum power point tracking. This technique is implemented using off-the-shelf components. The measurement results show that the proposed method is a realistic approach for supplying electrical energy to wireless sensor nodes and low-power electronics.

• 농업과학연구
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• 제50권3호
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• pp.357-364
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• 2023

In this study, we propose a ripe tomato bunch localization method based on convolutional neural networks, to be applied in robotic harvesting systems. Tomato images were obtained from a smart greenhouse at the Rural Development Administration (RDA). The sample images for training were extracted based on tomato maturity and resized to 128 × 128 pixels for use in the classification model. The model was constructed based on four-layer convolutional neural networks, and the classes were determined based on stage of maturity, using a Softmax classifier. The localization of the ripe tomato bunch region was indicated on a class activation map. The class activation map could show the approximate location of the tomato bunch but tends to present a local part or a large part of the ripe tomato bunch region, which could lead to poor performance. Therefore, we suggest a recursive method to improve the performance of the model. The classification results indicated that the accuracy, precision, recall, and F1-score were 0.98, 0.87, 0.98, and 0.92, respectively. The localization performance was 0.52, estimated by the Intersection over Union (IoU), and through input recursion, the IoU was improved by 13%. Based on the results, the proposed localization of the ripe tomato bunch area can be incorporated in robotic harvesting systems to establish the optimal harvesting paths.

• Journal of Communications and Networks
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• 제14권2호
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• pp.169-178
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• 2012

In this paper, we study the advantages of using range extension cooperative transmission (CT) in multi-hop energy harvesting wireless sensor networks (EH-WSNs) from the network layer perspective. EH-WSNs rely on harvested energy, and therefore, if a required service is energy-intensive, the network may not be able to support the service successfully. We show that CT networks that utilize both range extension CT and non-CT routing can successfully support services that cannot be supported by non-CT networks. For a two-hop toy network, we show that range extension CT can provide better services than non-CT. Then, we provide a method of determining the supportable services that can be achieved by using optimal non-CT and CT routing protocols for EH-WSNs. Using our method and network simulations, we justify our claim that CT networks can provide better services than nonCT networks in EH-WSNs.

• 한국연초학회지
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• 제19권1호
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• pp.29-32
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• 1997

This study was carried out to develop a new stalk curing of the horizontal hanging method that would reduce the harvesting and curing labor, and improve its quality of cured leaf than the conventional stalk curing method in burley tobacco. The horizontal hanging stalk-curing method designed from 1988 was compared with the conventional method. The horizontal method shortened the curing Period for 7 days and reduced to 0.3%, while it occurred 9.4% in the vertical method. In the horizontal method, the quality of cured leaf improved 9%, but the contents of chemical components and physical properties were similar to those of vertical method. The labor of stalk-cut and loading in curing facility reduced 28% by the horizontal method. In harvesting and curing process, the horizontal method resulted 12% of labor saving as compared with the vertical method. Key words : horizontal hanging stalk-curing method, vertical method, stalk-curing.

• 한국환경과학회지
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• 제24권2호
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• pp.197-205
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• 2015

This study was performed to identify the effect of fertilizer application and planting method on growth and yield of 'Seolhyang' strawberry during seedling raising. According to the concentration of fertilizer applied, the height of daughter plants was the highest at an EC of $0.8dS{\cdot}m^{-1}$. Leaf number and crown diameter were greatest at an EC of $0.6-0.8dS{\cdot}m^{-1}$. In the first measurement, root number was highest in non-fertilizer application, while root weight was heaviest in non-fertilizer application and EC $0.4dS{\cdot}m^{-1}$. The higher the concentration of fertilizer applied as culture media, the lower the growth rate. Thirty days after planting on the main field, plant height and number of new leaf were highest at an EC of $0.8dS{\cdot}m^{-1}$. However, no significant difference was found in leaf length and width and chlorophyll content according to fertilizer application. Marketable yield of 25 g or higher was greatest in EC $0.6dS{\cdot}m^{-1}$. In contrast, no significance was found in total marketable yield at an EC of $0.4-0.8dS{\cdot}m^{-1}$. Aconsistent pattern was exhibited in the growth of 1-5 harvesting flower clusters according to planting method. The length of leaf and flower cluster was short and chlorophyll content was low, when bed soil was removed 100% in harvesting of the first flower cluster. In all treatment, leaf length was shortened until harvesting of the second and third flower cluster, but rapidly lengthened in harvesting of the third and fourth flower clusters. Moreover, the length of flower cluster had a increasing tendency from harvesting of the third flower cluster. However, chlorophyll content was reduced continuously until harvesting of the fifth flower cluster, and was lowest in harvesting of the fourth flower cluster without removal of bed soil. Total yield was greatest in treatment of crown removal in bed soil between November and May. Late marketable yield between March and May was highest in treatment of 100% bed soil removal, followed by treatment of crown removal. Marketable yield of 25 g or higher was greatest in treatment of crown removal between December and February, while greatest in treatment of 100% bed soil removal between March and May.