• New & Renewable Energy
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• v.10 no.2
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• pp.5-11
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• 2014

Squirrel cage induction motor is the main driving system of industrial field and familiar with its use in a large variety of applications. The structure and operating characteristics of induction generator is almost identical to induction motor, but the induction generator part is used restrictively from hydropower power and wind power development etc. Recently induction generator is commonly used for micro & small hydro power applications due to its simplicity, reliability, low cost and robustness. Input and output of induction motor has turned against at the induction generator operation. Rotation speed of induction generator is small faster than synchronous speed of induction motor. As output of induction machines increases with the increasement of speed, so loss is same. Actually, generator efficiency is lower than motor at this condition. If induction generator is connected with mechanical load such as increaser, total efficiency is decreased. Consequently the quality in compliance with an induction motor parameter applying like that in the generator is a possibility of having the error of some. In this paper, we analyzed that input, output, torque and efficiency of induction machine is different from each other above and below synchronous speed.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.155-161
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• 2006

This paper introduces a new type of mechanical tape feeder for chip mounter. The mechanical feeder is composed of a pneumatic linear actuator and a linear feeding module with the application of a cam-slider. As semiconductor chips are getting smaller, PCB assembly makers require the feeder to position the chip with high accuracy. The linear feeding system improves the positioning accuracy of the chip by getting rid of the index error, which brings into existence on the sprocket rotating feeder. It also can make greatly reduce the dumping rate. The dumping error is caused by the impact occurred as the pawl to interrupt ratchet wheel rotation. The paper discusses its mechanism and mechanical performance. The positioning accuracy and the dynamic characteristic were measured for long time operation and analyzed. As a result, the feeder showed very good performance. However, the feeding system was dynamically unstable due to the cover film eliminator that is required to be modified

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5624-5638
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• 2016

A novel method based on Surf points is proposed to detect and lock-track single ground target in aerial videos. Videos captured by moving cameras contain complex motions, which bring difficulty in moving object detection. Our approach contains three parts: moving target template detection, search area estimation and target tracking. Global motion estimation and compensation are first made by grids-sampling Surf points selecting and matching. And then, the single ground target is detected by joint spatial-temporal information processing. The temporal process is made by calculating difference between compensated reference and current image and the spatial process is implementing morphological operations and adaptive binarization. The second part improves KALMAN filter with surf points scale information to predict target position and search area adaptively. Lastly, the local Surf points of target template are matched in this search region to realize target tracking. The long-term tracking is updated following target scaling, occlusion and large deformation. Experimental results show that the algorithm can correctly detect small moving target in dynamic scenes with complex motions. It is robust to vehicle dithering and target scale changing, rotation, especially partial occlusion or temporal complete occlusion. Comparing with traditional algorithms, our method enables real time operation, processing $520{\times}390$ frames at around 15fps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.12C
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• pp.1299-1305
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• 2002

Tx/Rx dual microstrip array antennas for satellite communications are designed, fabricated, and measured in this paper. They have a Right Handed Circular Polarization (RHCP) for Tx and Left Handed Circular Polarization (LHCP) for Rx. Two stacked patches are used for wideband characteristics and corner-truncated square patches are adopted for a circular polarization. To enhance bandwidth characteristics of a circular polarization, 2${\times}$1 sequential rotation mays are applied. From the measured results, 8${\times}$1 microstrip may antennas have a good agreement with those of the simulation. Therefore the array antennas are applicable to satellite communication antennas, active phased may antennas, and radiators in other antennas.

• 연구논문집
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• s.28
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• pp.73-87
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• 1998

A pneumatic control system of compressed air as a working fluid has a variety of advantages such as low price, high respondence, non-explosion and good control performance and thus has many applications in the field of automobile, electronic and semiconductor industry. However, it has a difficulty in contolling a precise position due to quick response of system and compressibility of working fluid and. in particular, shock stress may occur due to an external load, resulting in fracture of a cylinder cap unless cushion device is equipped in the linear actuator. To avoid this, a cushion device should be installed for damping effect of the external load and the supply pressure as well as for decreasing shock stress and vibration caused by high speed rotation. Previous studies include dimensionless analyses and computer simulations of cushion capability and experiments of horizontally-mounted cylinder performances. A new attempt is experimentally made in this study using a vertically-mounted cylinder under an operation condition of 4, 5 and 6 (bar) as supply pressure and 40, 70 and 100 (kgf) as external load. It turns out that the cushion pressure is mainly a function of the external load rather than the supply pressure. The cushion characteristics was also revealed in the meter-in circuit.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.77-80
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• 2013

SURF algorithm is an algorithm to extract feature points and to generate descriptors from input images. It is robust to change of environment such as scale, rotation, illumination and view points. Because of these features, it is used for many image processing applications such as object recognition, constructing panorama pictures and 3D image restoration. But there is disadvantage for real time operation because many recognition algorithms such as SURF algorithm requires a lot of calculations. In this paper, we propose a design of feature extractor and descriptor generator based on SURF for high memory efficiency. The proposed design reduced a memory access and memory usage to operate in real time.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.55-62
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• 2011

Although the performance of the commercial vessel has been dramatically improved through innovations, there has been no big changes on the traditional anchoring method of commercial vessels, both on design and operation until now. In this paper, two cases of design modifications were introduced for optimized design of pocket type anchor handling, which resulted in improved performance of the vessel's anchoring. From the first time fully balanced type anchors were applied on vessels in Korean shipyard, main design problem on this application was that the anchor doesn't normally slide into the pocket when the anchor fluke is not in line with pocket, as the anchor freely rotates by the swivel on forerunner. In order to prevent the problem, swivel has been deleted on the forerunner to prevent anchor rotation until now, but this solution caused problems such as twist lock of anchor chain, restriction of windlass direction, etc. On this paper, one of the solution is introduced to overcome the design problem by tilting the hawse pipe to some extent, which makes anchor turned at the time anchor ring touches the pocket skirt and that it properly slides into the pocket. Secondly, one of the solution is introduced to overcome misalignment problem between anchor chain cable and roller of chain compressor, which has been frequently occurred, by modification of roller design.

• Journal of Korea Foundry Society
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• v.24 no.5
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• pp.273-280
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• 2004

Vibrational motions of the compaction table were investigated to select the optimal operation conditions of sand filling and compaction for the EPC process. Their modes were measured at the nine points of the table with changing the relative rotation angles between the two eccentric mass vibrators which were attached parallel beneath the table. Well-defined vibration modes were measured at the center of the table but those of left and right sides of the table were distorted regardless of rotational angle differences. The distortion of vibration modes at both sides of the table were caused by the moment generated by offset positions of two eccentric masses. It was found that the uniform vibration modes would be gathered by controlling the relative distances between the rotating axis and the center of gravity in the compaction system at the various conditions of vibration modes and rotational angle differences.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.350-353
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• 2013

In this paper, a hardware implementation of phase calculator for extracting 3D depth image from TOF(Time-Of-Flight) sensor is proposed. The designed phase calculator, which adopts redundant binary number systems and a pipelined architecture to improve throughput and speed, performs arctangent operation using vectoring mode of DCORDIC algorithm. Fixed-point MATLAB simulations are carried out to determine the optimized bit-widths and number of iteration. The designed phase calculator is verified by emulating the restoration of virtual 3D data using MATLAB/Simulink and FPGA-in-the-loop verification, and the estimated performance is about 7.5 Gbps at 469 MHz clock frequency.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.1
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• pp.43-48
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• 2001

In conventional wind generation systems, since the blade rotates at low speed when the velocity of wind decreases their operations are possible only under limited conditions. Therefore they are in trouble of self-generation without the help of auxiliary generation devices outside. In addition, most of them have very low usage efficiency because of the characteristic changes of wind. For the solution of these problems and for enough generation regardless of districts and geographical features the rotation energy stored in a spring drives a compact generator and then electric power is stored at battery and supplied to the load continuously according to the lack of wind force. In this paper, the fabricated system consisting of a wind generator and power storage apparatus was introduced and its operation characteristics were analyzed.