• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.493-500
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• 1999

In 1990's, two types of land consolidation has been widely carried out to enforce competativeness of rice production in Korea. One is so called large-scale land consolidation for resizing paddy field and farm road, the other is general land consolidation for changing both size and shape of field, water channel and farm road. This study was conducted to evaluate how much effect on fm mechanization the land consolidation had. To evaluate the influence of the land consolidation, theoretical analysis and surveys were accomplished. Land consolidation was analyzed to increase field efficiency by 180 to 670% depending on the type of land consolidation and machine selection. Also, land consolidation brought increment of real working time ratio by reducing traveling time on farm road. Trends of large scale mechanization and increment of custom work were observed to be accelerated by land consolidation. It also gave effect on the pattern of machine troubles. Farmers were conscious of the influence of land consolidation on machine utilization, however, in plains level of satisfaction was shown to be low.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.57-58
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• 2017

This paper proposes a high efficiency hybrid generator which has a winding and PM(Permanent Magent) field together. The PM field can supply the enough flux to generate the no-load output voltage, and the field winding current can supply the flux to compensate the voltage drop from the load. Furthermore, the PM exciter can supply the enough power for the field of the generator. The detailed design and the FEM analysis are presented to verify the proposed hybrid generator. Then the experimental results shows the effectiveness of the proposed system.

• ETRI Journal
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• v.28 no.6
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• pp.761-769
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• 2006

In this paper, we address the problem of closely spaced source localization using sensor array processing. In particular, the performance efficiency (measured in terms of the root mean square error) of the unconditional maximum likelihood (UML) algorithm for estimating the direction of arrival (DOA) of near-field sources is evaluated. Four parameters are considered in this evaluation: angular separation among sources, signal-to-noise ratio (SNR), number of snapshots, and number of sources (multiple sources). Simulations are conducted to illustrate the UML performance to compute the DOA of sources in the near-field. Finally, results are also presented that compare the performance of the UML DOA estimator with the existing multiple signal classification approach. The results show the capability of the UML estimator for estimating the DOA when the angular separation is taken into account as a critical parameter. These results are consistent in both low SNR and multiple-source scenarios.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1319-1327
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• 2001

The results of stand and field testing of a combustion chamber for a heavy-duty 150 MW gas turbine are discussed. The model represented one of 14 identical segments of a tubular multican combustor constructed 1:1 scale. The model experiments were executed at a lower pressure than that in a real gas turbine. Combustion efficiency, pressure loss factor, pattern factor, liner wall temperature, flame radiation, fluctuating pressure and NOx emission were measured at partial and full loads for both model and on-site testing. The comparison of these items in the stand and field test results led to has the development of a method of calculation and the improvement of gas turbine combustors.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.5-10
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• 2011

Recently, small hydropower attracts attention because of its renewable, clean and abundant energy resources to develop. Therefore, a tubular type hydro turbine is proposed for small hydropower in this study because the turbine has relatively simple structure and high possibility of applying to small hydropower. The purpose of this study is to investigate the performance characteristics of the turbine by field test. Field test iss conducted using one tubular turbine system as well as serial arrangement system by two tubular turbines taking into consideration of actual operation conditions. The results show that efficiency of test turbine changes considerably by the runner vane angle. Best efficiency of one turbine arrangement is higher than that of two turbine serial arrangement.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.9
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• pp.752-760
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• 1991

The computer aided analysis is performed to investigate the influence of physical parameters (thickness and doping concentration, etc.) in the window, emitter, base on the efficiency characteristics of a uniformly doped hetroface cell. A field aided heteroface cell is newly designed on a basis of optimum data obtained from the theoretical analysis. The field aided heteroface cell fabricated using MOCVD exhibits a total/active area conversion efficiency of EFF. (tot) = 18.9% /EFF. (act.) = 21.4% under the natural incident light of 56.2 mW/cm\ulcorner having a low series resistance of Rs = 0.94 \ulcornercm\ulcornerand a high spectral response of S.R. (ext) > 90% in a range of $7700{\AA}$ < $8500{\AA}$.

• Journal of Biosystems Engineering
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• v.9 no.2
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• pp.19-26
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• 1984

This study intended to develop the prediction models of the traction and field performance of two-wheel tractors by using the principles which were applied for predicting those of the four-wheel tractors. The traction model developed in this study consists of the net traction coefficient, rolling resistance coefficient and traction efficiency, Which are expressed as functions of both wheel numeric and slip. A computer program on the field performance of two-wheel tractors is also developed to predict the drawbar horsepower, traction force, traction efficiency, rotational speed of engine and engine horsepower if the characteristics of the engine performance and operational condition of the two-wheel tractor are known. Based on the developed models, the conditions of basic variables to maximize the field performance were analyzed so as to assess the existing two-wheel tractor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.2
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• pp.131-137
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• 2003

We have performed computer simulation to obtain electro-optic chracteristics of reflective liquid crystal display (LCD) using wide viewing angle LC mode, fringe field switching(FFS). Unlike other reflective LCD modes, in the FFS mode, the LC director in plance so an application to reflective display consisted of polarizer, LC layer and reflector is possible. when an incident light is 550mm, the optimal cell retardation value is 0.1365${\mu}$m and the efficiency of reflectivity is high over 90% with very little wavelength dispersion. Further, we have studied a new reflective display with polarizer, optical compensation film with half plate, LC plus reflector. The display with optimized cell parameters shows high contrast ratio (CR) over 130 with high light efficiency over 90% at normal direction and the CR greater than 5 exists over 60$^{\circ}$ of polar angle in all directions.

• Journal of Power Electronics
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• v.19 no.3
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• pp.625-636
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• 2019

This paper proposes an active leakage magnetic field (LMF) suppression scheme, which uses the dual-transmitter (DT) topology, for EV wireless charging systems (EVWCS). The two transmitter coils are coplanar, concentric and driven by separate inverters. The LMF components generated by the three coils cancel each other out to reduce the total field strength. This paper gives a detailed theoretical analysis on the operating principles of the proposed scheme. Finite element analysis is used to simulate the LMF distribution patterns. Experimental results show that when there is no coil misalignment, 97% of the LMF strength can be suppressed in a 1kW prototype. These results also show that the impact on efficiency is small. The trade-off between LMF suppression and efficiency is revealed, and a control strategy to balance these two objectives is presented.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.119-128
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• 1993

Effective machine capacity is affected by the physical and geometrical conditions of the fields. In the small and scattered farmland structure field efficiency is greatly influenced by plot geometry. In this paper, a method for estimating field efficiency and effective machine capacity was developed . The developed method was applied to Korean paddy cultivation. Various time elements related to farm operations for small and scattered plots are discussed in this paper . Available working time is divided into two parts, viz. the preparation time for machine operation and actual working time. Two kinds of machine efficiencies, namely , Machine Efficiency 1, applicable on a single large plot or set of well consolidated plots ; and Machine Efficiency 2, applicable on small and scattered multiple plots, are considered. Based assumptions made and steps followed to construct the model are discussed. Effective capacity of each machine based on different plot geometries are calculated y the model. Machine efficiency on a single plot increases with increase in the dimension of longer side of the plot . Low speed, low theoretical capacity machines have higher machine efficiency which is only slightly influenced by plot geometry. As plot geometry is improved , the machine efficiency of high speed, high capacity machines increases rapidly. The effects of short side length and plot size on machine efficiency on a single plot depend on the type of farm operation. For a particular plot shape, as plot size increases, machine efficiency on multiple plots increases rapidly. The effects of consolidation on machine efficiency is highly significant if the plot size is small and/or machine size is large.