• Journal of Institute of Control, Robotics and Systems
• /
• v.21 no.8
• /
• pp.729-734
• /
• 2015

Improvement in the control strategy for continuous casting is a crucial requirement to enhance the slab's quality and to increase productivity. The mold oscillator adopts the dual cylinders due to its heavy weight, so the synchronized motion of two cylinders is an important aspect when precise control is needed. The conventional method uses the master-slave control applied to the valve input reference, but the synchronization performance should still be improved. This paper proposes a novel synchronization algorithm for dual cylinders used in a mold oscillator. The master-slave concept is applied to the target reference position, that is, the slave target reference position is controlled to match the slave cylinder's position with the master cylinder's position. In the simulation based on a Simulink model, the proposed algorithm shows a better synchronization performance in aspect of the mean of the absolute error and the peak synchronization error.

• The Journal of the Korean bone and joint tumor society
• /
• v.20 no.2
• /
• pp.94-98
• /
• 2014

Osteoid osteoma can occur in all parts of the skeletal system. More than half occur in lower extremity and rare in wrist. Clinically pain is almost the only symptom worse at night and which is characterized by a rapid improvement by NSAID. We report the cases of osteoid osteoma which shows the characteristic symptoms and got a good results with appropriate imaging work up and surgical treatment.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.45-48
• /
• 2008

This study is for proposing the shape of hollow and evaluating the structural performance of hollow reinforced concrete (RC) half slabs. The two-phase experimental works were carried out, and styrofoam was used for reduction of dead load and vibration. From the Phase I test result, the shape and spacing of the hollow were determined to obtain the high deduction ratio of the concrete and the desirable failure mode of the hollow RC half slabs. In the Phase II test, two slab specimens were tested in flexure to evaluate the flexural capacity of the hollow RC half slabs with the proposed hollow shape. In the result of the test, all the specimens having the proposed hollow shape showed sufficient flexural capacity.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.12 no.2
• /
• pp.21-28
• /
• 1998

A new technique for shaping the line current and reducing the total hannonic distortion in a threephase rectifier is introduced. A review of the problems inherent in a three-phase diode rectifier feeding capacitive load and the possible solutions are first presented. The proposed 3 bidirectional switches and their operation are presented. The main features of this paper are low cost, high efficiency and simplicity. A simulation and experiment results show its good action.action.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.10a
• /
• pp.290-294
• /
• 2001

Satellite data, with Sea Surface Temperature(SST) by NOAA and Sea Level(SL) by Topex/poseidon, are used to estimate characteristics on the variations and correlations of SST and SL in the East Asian Seas from January 1993 through May 1998. In the oceanic climate, the variations of SL shown the high values in the main current of Kuroshio and the variations of SST shown not the remarkable seasonal variations because of the continuos compensation of warm current by Kuroshio. In the continental climate, SL shown high variations in the estuaries(the Yellow River, the Yangtze River) with the mixing the fresh water in the mouth of estuaries of the saline water in the coasts of continent and SST shown highly the seasonal variations due to the climatic effect of continents. In the steric variations in summer, the eastern sea of Japan, the East China Sea and the western sea of Korea shown the increment of sea level with 10~20cm. But the Bohai bay in China shown relatively the high values of 20~30cm due to the continental climate. Generally the trends of SST and SL increased during all periods. That is say, the slopes of SST and SL presented 0.29$^{\circ}C$/year and 0.84cm/year, respectively. The annual and semi-annual amplitudes shown a remarkable variations in the western sea of Korea and the eastern sea of Japan.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.12
• /
• pp.1173-1178
• /
• 2007

Ubiquitous sensor network (USN) is composed of many sensor nodes which are one of the simplest form of embedded system. In developing the sensor network system, a debugging tool is necessary to test and verify the system. Recently, a so-called packet analyzer has been developed for this purpose, and it supports IEEE 802.15.4 which is considered as the standard for the sensor network protocols. The major function of the packet analyzer is to take RF packets from sensor nodes and show the structure and the data of the packets graphically to the user. However, the conventional packet analyzers do not support remote control because they require a USB interface along with a personal computer. To make it available for remote control, we propose a new packet analyzer based on a server-client scheme in which a server program is implemented on embedded Linux and a client program is implemented on Windows for convenient use.

• Journal of Institute of Control, Robotics and Systems
• /
• v.16 no.2
• /
• pp.164-171
• /
• 2010

We have studied the port-automation system which is requested by the steep increment of cost and complexity for processing the freight. This paper will introduce a new algorithm for navigating and controlling the autonomous Guided Vehicle (AGV). The camera has the optical distortion in nature and is sensitive to the external ray, the weather, and the shadow, but it is very cheap and flexible to make and construct the automation system for the port. So we tried to apply to the AGV for detecting and tracking the lane using the CCD camera. In order to make the error stable and exact, this paper proposes new concept and algorithm for obtaining the error is generated by the Virtual Photo-Sensor Array (VPSA). VPSAs are implemented by programming and very easy to use for the various autonomous systems. Because the load of the computation is light, the AGV utilizes the maximal performance of the CCD camera and enables the CPU to take multi-tasks. We experimented on the proposed algorithm using the mobile robot and confirmed the stable and exact performance for tracking the lane.

• Korean Journal of Materials Research
• /
• v.12 no.1
• /
• pp.94-99
• /
• 2002

The electrical properties of porous $SiO_2/ITO$ nano thin film were studied by complex impedance and conductive mechanisms were analyzed. According to the results of complex impedance, the activation energy of $SiO_2/ITO$ and $Zn-SiO_2/ITO$ were 0.309 eV, 0.077 eV in below $450^{\circ}C$ and 0.147 eV in over $450^{\circ}C$, respectively. In case of $SiO_2/ ITO$, slightly direct tunneling occurred at room temperature. The contribution for conduction was very tiny because of high barrier of silica. However, the conductivity abruptly increased in over $300^{\circ}C$ by Thermally assisted tunneling. In case of $Zn-SiO_2/ITO$, high conductivity in 1.26 ${\Omega}^{ -1}{cdot}cm^{-1}$ at room temperature appeared by space charge conduction or Frenkel-poole emission that Zn ions play a role as localized electron states.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.116-116
• /
• 2000

질화물 반도체는 LED, LD, Transistor, 그리고 Photodetector 등 광소자 및 전자소자를 실현할 수 있는 소재로써 최근에 각광 받고 있으며, 또한 국·내외적으로 연구가 활발히 진행되고 잇다. 질화물 발광 다이오드 제작에는 소자의 효율과 수명시간의 향상을 위하여 질화물 반도체와 금속과의 접합시 고 품질의 오믹 접합이 필수적이다. 특히 p-형 GaN의 경우에는 높은 정공 농도를 갖는 p-형 GaN를 얻기가 어렵고 GaN의 일함수에 비하여 높은 일함수를 갖는 금속이 없기 때문에 매우 낮은 접합 저항을 가지며 안정성이 매우 우수한 금 접합을 얻기가 어렵다고 알려져 있다. 또한, GaN 계열의 발광 다이오드는 일반적으로 표면 발광 다이오드 형태로 제작되기 때문에 p-형 GaN 층의 오믹 접촉으로 사용되는 금속의 전기적 특성뿐만 아니라 발광 다이오드의 활성층에서 발광되어 나오는 빛에 대한 투과도 또한 우수하여야 발광 다이오드의 효율이 우수해진다. 본 연구에서는 p-형 GaN층의 접합 금속으로 Pt(80nm)과 Ni(5nm)/Au(7nm)를 사용하여 InGaN/GaN 다중양자우물 구조의 발광 다이오드를 제작하여 전기적 특성 및 발광효율을 측정하였다. 그리고, Pt(80nm)과 p-형 GaN와의 접합시 온도 변화에 따른 전기적 특성을 TLM 방법으로 조사하고, 가시광선 영역에서의 빛에 대한 투과도를 UV/VIS spectrometer, X-ray reflectivity, 그리고 Atomic Force Microscopy 등을 이용하여 분석하였다.

• Transactions of Materials Processing
• /
• v.14 no.6 s.78
• /
• pp.527-532
• /
• 2005

Among the failure modes which can occur in tube hydroforming such as wrinkling, bursting or buckling, the bursting by local instability under excessive tensile stresses is irrecoverable phenomenon. Thus, the accurate prediction of bursting condition plays an important role in producing the successfully hydroformed part without any defects. As the classical forming limit criteria, strain-based forming limit diagram (FLD) has widely used to predict the failure in sheet metal forming. However, it is known that the FLD is extremely dependant on strain path throughout the forming process. Furthermore, The application of FLD to hydroforming process, where strain path is no longer linear throughout forming process, may lead to misunderstanding for fracture initiation. In this work, stress-based forming limit diagram (FLSD), which is strain path-independent and more general, was applied to prediction of forming limit in tube hydroforming. Combined with the analytical FLSD determined from plastic instability theory, finite element analyses were carried out to find out the state of stresses during hydroforming operation, and then FLSD is utilized as forming limit criterion. In addition, the approach is verified by a series of bulge tests in view of bursting pressure and shows a good agreement. Consequently, it is shown that the approach proposed in this paper will provide a feasible method to satisfy the increasing practical demands for judging the forming severity in hydroforming processes.