• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.9
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• pp.896-902
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• 2012

For most applications of the vibration energy harvesting technology as in wireless sensor networks for smart buildings and plants, the evaluation of DC output performance of vibration energy harvesters is typically required. However, there is no dedicated algorithm for the evaluation. The lack of a dedicated algorithm results from difficulties in the direct incorporation of nonlinear rectifying and regulating circuitry into finite element models of piezoelectric vibration energy harvesters. In this study, we develop a dedicated algorithm and present software based on it for the evaluation of not only AC but also DC electrical quantities. Here, an equivalent electrical circuit model is employed. The COMSOL multiphysics simulation tool is adopted for extracting equivalent electrical circuit parameters of a piezoelectric vibration energy harvester and MATLAB is used to make a graphical user interface. The AC voltage and power outputs calculated by the proposed algorithm under various conditions are compared with those by a traditional finite element analysis. The DC output voltage and power through a rectifier are obtained for varying values of smoothing capacitance and external resistance.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.71-72
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• 2015

본 논문에서는 전자기유도현상을 이용한 에너지 하베스터의 AC 출력 전압을 DC 전압으로 바꾸는 고효율 정류회로를 제안한다. 하베스터에서 다이오드의 문턱전압보다 낮은 전압이 생산될 수도 있을 뿐더러, 더 높은 전압이 생산된다 해도 결국 다이오드 정류를 거치면 엄청난 손실이 생기기 때문에 기존의 다이오드를 이용한 정류회로는 작은 AC 전압을 생산해내는 전자기유도현상을 이용한 에너지 하베스터와는 맞지 않다. 따라서 제안하는 정류회로는 별도의 전원을 필요로 하지 않는 스위치 회로를 갖추어 MOSFET과 LC공진을 이용하여 부스팅 후 정류를 그 목적으로 한 고효율 정류회로이다. 본 논문에서는 MOSFET과 LC공진회로의 특성을 이용한 고효율 정류회로를 설계, 동작원리를 설명하고, PSIM 시뮬레이션을 통하여 그 유용성을 검증한다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.73-74
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• 2015

본 논문에서는 인체의 움직임에서 발생하는 낮은 주파수의 진동 에너지를 전기 에너지로 수확하는 전자기유도 현상 기반의 고효율 에너지 하베스터를 제작하였다. 제안된 하베스터는 기어모듈을 이용하여 사람이 인가하는 직선운동을 회전운동으로 바꾸는 방식으로 동작한다. 회전수를 늘리기 위해서 증속기어모듈을 달아 높은 회전비를 갖게 한다. 그리고 발전부의 자석들은 할바흐 배열을 통해 불필요한 곳의 자속을 최소한으로 하고 필요한 곳의 자속은 최대한으로 하여 높은 효율을 낼 수 있게 하였다. 제작된 전자기 에너지 하베스터의 출력전압은 230.9 mV이며 $18{\Omega}$에서 2.96 mW의 최대 피크 전력을 전달한다.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1998.05a
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• pp.45-53
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• 1998

농산물 수입개방으로 외국산 농산물의 대량 유입은 우리 농업의 기반을 흔들고 있는 실정이다. 가격 면에서 여러 가지 어려운 점을 감안한다면 국민의 감정에 국내산 농산물 애용을 호소하기에는 시대적으로 쉬운 일은 아니다. 따라서 농산물의 고품질화 및 생산비 절감으로 대외 경쟁력을 높일 수밖에 없는 실정이다. 이를 위해서 농산물의 적기 수확은 재배기술 못지 않게 중요하다. (중략)

• Journal of Biosystems Engineering
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• v.32 no.6
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• pp.395-402
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• 2007

This study was carried out as basic researches to develop the leaf vegetable harvester. This study was conducted to investigate physical and rheological properties of bundled leaf vegetables with stem (Chinese leek, Crown daisy and Chamnamul) as test materials held and picked-up by a machine. Stress-strain behavior, stress relaxation, and strain recovery for the bundled materials were analyzed using simple Maxwell model. Physical and rheological properties of the materials were investigated by measuring rupture load, deformation and stress experimentally. Also, strain recovery time when unloading was measured using super high speed camera. Recorded recovery time for stress-strain behavior was0.026 s for Chinese leek with liner strain recovery, 0.046 s for Crown daisy and 0.05 s for Chamnamul with non-linear strain recovery. Furthermore, the strain recovery time for permanent deformation was 0.026 s, 0.046 s, and 0.05 s for Chinese Leek, Crown daisy and Chamnamul, respectively. Finally, strain recovery time and strain recovery ratio for the test materials were 0.17 s, 60.4% in Chinese leek, 0.12 s, 55.3% in Crown daisy, 0.15 s, 58.7% in Chamnamul. Here strain recovery time means that how fast the test materials are recovered from initial deformation and strain recovery ratio means how much the test materials are recovered from initial deformation. The above results show that the test materials can be held enough and moved by the belts.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.544-547
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• 2002

According to the rising of national economic level. domestic consumption of vegetables having high additive values is increased continuously due to increased consumption of meat in last decade. These vegetables are produced almost in this country and are limited to import from neighbor countries in due of high transportation expenses for storing in refrigerated container. It is very important to mechanize the harvest work, forming more than 30% for their production cost, in order to cultivate variable vegetables at the same time according to their harvesting seasons. In this state its former harvest methods, with using of human power or semi-automatic harvest, caused to increase their production cost due to high labor cost and low working efficiency. The former onion harvest being operated almost by semi-automatic plant distributer mechanism have many limit and troublesome for cultivation spaces, vinyle mulched ridge, gravel mixture in soil. Therefore, it is necessary to develope a fully automatic and self-running situation and overcome above handicaps, even in the farm covered with vinyle house or mulch sheets. This newly developed onion harvest can be applied to plant various young trees and will be able to export together with onion haying their competition in the worldwide market in which the culinary vegetable method or farm conditions is similar to our country.

• Journal of Biosystems Engineering
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• v.29 no.3
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• pp.281-286
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• 2004

The end-effector is the one of the important factors on development of the cucumber robot to harvester a cucumber. Three end-effectors were designed the single blade end-effector with one blade, the double blade end-effector with two blades and the triple blade end-effector with three blades. Performance tests of the end-effector, the fully integrated system, were conducted to determine the cutting rate by using two different kinds of cucumber. The success rates of cucumber cutting ratio of single end-effector, double end-effector and triple end-effector in laboratory. were 61.7%, 95%, 86.7%, respectively. The cutting rate of single blade or double blade was a little difference with respect to the different diameters of cucumber stem. However, the success cutting rate of the end-effector with triple blade was 61.7% under 29mm diameter of a grabbing stem section. The triple end-effector was not suitable for harvesting a cucumber, but was considered to be suitable for harvesting a grape, an apple and a tomato. The success rate of cucumber cutting ratio of triple end-effectors in greenhouse was 84%. The failure cutting rate was 16% which are due to abnormal shape of cucumber fruit.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.4
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• pp.397-404
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• 2010

The use of equivalent circuit models of piezoelectric energy harvesters is inevitable when power circuitry including rectifying and smoothing circuit elements is connected to them for evaluating DC electrical outputs. This is because it is difficult to incorporate the electro-mechanical coupling resulting from the additional circuitry into the conventional finite element analysis. Motivated by this observation, we propose a method to accurately extract the equivalent circuit parameters by using commercially available FEM software such as ANSYS which provides three-dimensional AC piezoelectric analysis. Then the equivalent circuit can be analyzed by circuit simulators such as $SimPowerSystems^{TM}$ of MATLAB. While the previous works have estimated the circuit parameters by experimental measurements or by analytical solutions developed only for limited geometries and boundary conditions, the proposed method has no such limitation because piezoelectric energy harvesters of any shapes and boundary conditions can be treated in FEM software. For the verification of the proposed method, multi-modal AC electrical power output by using a corresponding equivalent circuit is compared with that by ANSYS. The proposed method is then shown to be very useful in the subsequent evaluation of DC electrical output which is obtained by attaching a bridge diode and a storage capacitor to a piezoelectric energy harvester.

• Korean Journal of Plant Resources
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• v.15 no.1
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• pp.72-76
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• 2002

This study was carried out to determine an effective mechanical harvester for rhizomes of Rehmannia glutinosa Libosch. Labor-saving efficiency showed 69∼76% by using tillage operations with power tiller, digger attached to power tiller, and digger attached to tractor compared with manual harvest. Loss percentage of rhizomes by mechanical harvesters was 3.1∼ 9.3% higher, and fresh rhizome yield was 2∼6％ lower than that by manual harvest, respectively. Although it showed higher loss percentage of rhizomes and lower fresh rhizome yield compared with manual harvest, mechanical harvest using digger attached to power tiller or digger attached to tractor was effective in labor-saving for rhizomes of Rehmannia glutinosa Libosch.

• Journal of Magnetics
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• v.16 no.3
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• pp.271-275
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• 2011

This paper proposes a magnetoelectric (ME) composite transducer structure consisting of a magnetostrictive H-type Fe-Ni fork substrate and piezoelectric PZT plates. The fork composite structure has a higher ME voltage coefficient compared to other ME composite structures due to the higher quality (Q) factor. The ME sensitivity of the fork structure reaches 12 V/Oe (i.e., 150 V/cm Oe). The fork composite with two PZT plates electrically connected in series exhibits over 5 times higher ME voltage coefficient than the output of the rectangle structure in the same size. The experiment shows the composite of a Fe-Ni fork substrate and PZT plates has a significantly enhanced ME voltage coefficient and a higher ME sensitivity relative to the prior sandwiched composite laminates. By the use of a lock-in amplifier with 10 nV resolution, this transducer can detect a weak magnetic field of less than $10^{-12}$ T. This transducer can also be designed for a magnetoelectric energy harvester due to its passive high-efficiency ME energy conversion.