• Journal of the Korean Magnetics Society
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• v.11 no.2
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• pp.72-77
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• 2001

Top spin valve films with PtMn antiferromagnetic layers were deposited using a multi-target dc magnetron sputtering in (100)Si substrates overcoated with 500 $\AA$ of Al$_2$O$_3$. Firstly, the post-deposition annealing was performed at 270$\^{C}$ in a unidirectional magnetic field of 3 kOe to induce the crystallographic transformation of the PtMn layer from a fcc (111) to a fct (111) structure. Secondly, the spin valve films were annealed without magnetic fields and magnetic properties were measured. In Si/A1$_2$O$_3$ (500$\AA$)/Ta(50$\AA$)NiFe(40$\AA$)/CoFe(17$\AA$)/Cu(28$\AA$)/CoFe (30$\AA$)PtMn(200$\AA$)Ta(50$\AA$) top spin valve samples, the MR ratio decreased slowly with increasing annealing temperature up to 325$\^{C}$. But above 325$\^{C}$, the MR ratio decreased rapidly to 1%, due to a collapse of the exchange coupling between a antiferromagnetic layer and a pinned layer with increasing annealing temperature. Also above 325$\^{C}$, the exchange biased field rapidly decreased and the interlayer coupling field rapidly increased with increasing annealing temperature. A change in the interlayer coupling field was resulted from the increase in interface roughness due to Mn-interdiffusion through the grain boundaries. We confirmed the temperature in changing magnetic properties agreed well with the blocking temperature of PtMn based spin valve structure.

• The Journal of the Acoustical Society of Korea
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• v.35 no.1
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• pp.74-82
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• 2016

In this paper, a new automatic speech recognition (ASR) was proposed where ultrasonic doppler signals were used, instead of conventional speech signals. The proposed method has the advantages over the conventional speech/non-speech-based ASR including robustness against acoustic noises and user comfortability associated with usage of the non-contact sensor. In the method proposed herein, 40 kHz ultrasonic signal was radiated toward to the mouth and the reflected ultrasonic signals were then received. Frequency shift caused by the doppler effects was used to implement ASR. The proposed method employed multi-channel ultrasonic signals acquired from the various locations, which is different from the previous method where single channel ultrasonic signal was employed. The PCA(Principal Component Analysis) coefficients were used as the features of ASR in which hidden markov model (HMM) with left-right model was adopted. To verify the feasibility of the proposed ASR, the speech recognition experiment was carried out the 60 Korean isolated words obtained from the six speakers. Moreover, the experiment results showed that the overall word recognition rates were comparable with the conventional speech-based ASR methods and the performance of the proposed method was superior to the conventional signal channel ASR method. Especially, the average recognition rate of 90 % was maintained under the noise environments.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.15-15
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• 1999

In chip plating, several parameters must be taken into consideration. Current density, solution concentration, pH, solution temperature, components volume, chip and media ratio, barrel geometrical shape were most likely found to have an effect to the process yields. The 3 types of barrels utilized in chip plating industry are the conventional rotating barrel. vibrational barrel (vibarrel), and the centrifugal type. Conventional rotating barrel is a close type and is commonly used. The components inside the barrel are circulated by the barrel's rotation at a horizontal axis. Process yield has known to have higher thickness deviation. The vibrational barrel is an open type which offers a wide exposure to electrolyte resulting to a stable thickness deviation. It rotates in a vertical axis coupled with multi-vibration action to facilitate mixed up and easy transportation of components, The centrifugal barrel has its plated work centrifugally compacted against the cathode ring for superior electrical contact with simultaneous rotary motion. This experiment has determined the effect of barrel vibration intensity to the plating thickness distribution. The procedures carried out in the experiment involved the overall plating process., cleaning, rinse, Nickel plating, Tin-Lead plating. Plating time was adjusted to meet the required specification. All other parameters were maintained constant. Two trials were performed to confirm the consistency of the result. The thickness data of the experiment conducted showed that the average mean value obtained from higher vibrational intensity is nearer to the standard mean. The distribution curve shown has a narrower specification limits and it has a reduced variation around the target value, Generally, intensity control in vi-barrel facilitates mixed up and easy transportation of components, However, it is desirable to maintain an optimum vibration intensity to prevent solution intrusion into the chips' internal electrode. A cathodic reaction can occur in the interface of the external and internal electrode. $2HD{\;}+{\;}e{\;}{\rightarrow}20H{\;}+{\;}H_2$ Hydrogen can penetrate into the body and create pressure which can cause cracks. At high intensity, the chip's motion becomes stronger, its contact between each other is delayed and so plating action is being controlled. However, the strong impact created by its collision can damage the external electrode's structure thereby resulting to bad plating condition. 1 lot of chip was divided into two equal partion. Each portion was loaded to the same barrel one after the other. Nickel plating and tin-lead plating was performed in the same station. Portion A maintained the normal barrel vibration intensity and portion B vibration intensity was increased two steps higher. All other parameters, current, solution condition were maintained constant. Generally, plating method find procedures were carried out in a best way to maintained the best plating condition. After plating, samples were taken out from each portion. molded and polished. Plating thickness was investigated for both. To check consistency of results. 2nd trial was done now using different lot of another characteristics.

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.35-44
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• 1998

An integrated system of GIS and water quality model was suggested including the pollutant loads from the watershed. The developed system consists of two parts. First part is the GIS module. The geographic information system of the study area was built to provide the information on landuse and several surface factors concerning the overland flow processes of water and pollutants. Second part is the modeling modules which include storm event pollutant load model(SEPLM)., non-storm event pollutant load model(NSPLM), and river water quality simulation model(RWQSM). Models can calculate the pollutant load from the study area. The databases and models are linked through the interface modules resided in the overall system, which incorporate the graphical display modules and the operating scheme for the optimal use of the system. The developed system was applied to the Chungju multi-purpose reservoir to estimate the pollutant load during the four selected rainfall events between 1991 and 1993,. based upon monthly basis and seasonal basis in drought flow, low flow, normal flow and wet flow.

• Journal of Biosystems Engineering
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• v.28 no.6
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• pp.517-524
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• 2003

There have been worldwide research and development efforts to automate various processes of bio-production and those efforts will be expanded with priority given to tasks which require high intensive labor or produce high value-added product and tasks under hostile environment. In the field of bio-production capabilities of the versatility and robustness of automated system have been major bottlenecks along with economical efficiency. This paper introduces a new concept of automation based on tole-operation, which can provide solutions to overcome inherent difficulties in automating bio-production processes. Operator(farmer), computer, and automatic machinery share their roles utilizing their maximum merits to accomplish given tasks successfully. Among processes of greenhouse watermelon cultivation tasks such as pruning, watering, pesticide application, and harvest with loading were chosen based on the required labor intensiveness and functional similarities to realize the proposed concept. The developed system was composed of 5 major hardware modules such as wireless remote monitoring and task control module, wireless remote image acquisition and data transmission module, gantry system equipped with 4 d.o.f. Cartesian type robotic manipulator, exchangeable modular type end-effectors, and guided watermelon loading and storage module. The system was operated through the graphic user interface using touch screen monitor and wireless data communication among operator, computer, and machine. The proposed system showed practical and feasible way of automation in the field of volatile bio-production process.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.1
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• pp.58-62
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• 2007

Digital communication is important for reliability and mobilization of the multi-channel communication systems. Transmitting and receiving data for the mobilization should be possible in anywhere and in anytime. And this system must be designed light weight small size and low power. One are essential technology for implementing the mobile wireless communication system on the age of ubiquotos. Requirements in constructing such communication field are followings. At first data transmitting and receiving should be carried out by a simple command. Second, the device should be designed as hand-hold type and low power consumption. Third, data communication should be reliable. As one of examples, car to car system which is popular in the market is introduced here, All traffic information in highway is transmitted from one car to another by using this system which can prevent possible traffic accident. This paper shows the design of a digital data communication system with CC1020 chip. This CC1020 makes easy frequency selection and easy switch from the transmit mode to the receive mode by simple setting of a memory register in the chip. The transmit power of this system is designed 10dBm and its communication range is about 100m. The power supplied this system is 3V considered as low power. The sleep mode can be easily entered during transmit mode or receive mode. We shows the program algorithm of CC1020 and interface circuit between MCU and CC1020. We shows the Photo of the CC1020 Module and Atmega128 Module.. We analysed the receiver rate with this system.

• Geophysics and Geophysical Exploration
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• v.9 no.2
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• pp.139-147
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• 2006

We had conducted a numerical modeling to investigate seismic properties of gas hydrate with field parameters acquired over the East sea in 1998. We used a 2-D staggered grid finite difference method to generate synthetic elastic seismograms for multi-channel seismic survey, OBC (Ocean Bottom Cable) survey and VCS (Vertical Cable Seismic) survey. The results of this study showed that the method using staggered grid yielded stable results and could be used to seismic imaging. We could find out the high amplitude anomaly and the phase reversal phenomenon of reflection wave at interface between the gas hydrate layer and free gas layer such a BSR (Bottom Simulating Reflector) which is the evidence for existence of gas hydrate in seismic reflection data. And we computed the reflection coefficients at the incident angles corresponding to offset distance with the synthetic seismograms. The reflection coefficients acquired from the numerical modeling were nearly consistent with the reflection coefficient computed by Shuey's equation.

• Journal of the Korean Society for Railway
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• v.19 no.5
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• pp.617-628
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• 2016

This paper proposes the structure of a smart transformer to improve the performance of the 60Hz main power transformer for rolling stock. The proposed smart transformer is a kind of solid state transformer that consists of semiconductor switching devices and high frequency transformers. This smart transformer would have smaller size than the conventional 60Hz main transformer for rolling stock, making it possible to operate AC electrified track efficiently by power factor control. The proposed structure employs a cascade H-Bridge converter to interface with the high voltage AC single phase grid as the rectifier part. Each H-Bridge converter in the rectifier part is connected by a Dual-Active-Bridge (DAB) converter to generate an isolated low voltage DC output source of the system. Because the AC voltage in the train system is a kind of medium voltage, the number of the modules would be several tens. To control the entire smart transformer, the inner DC voltage of the modules, the AC input current, and the output DC voltage must be controlled instantaneously. In this paper, a control algorithm to operate the proposed structure is suggested and confirmed through computer simulation.

• The Transactions of the Korea Information Processing Society
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• v.5 no.12
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• pp.3047-3062
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• 1998

This paper deseribes the desihn and the implementation of the Realtime Transport Protocol(RTP)/ Rdaltime Control Protocol(RTCP) (RFC 1889,1890) that is used to transmit the audio/video data to any destination and to feedback the Quality of Service (QoS) information of the received media data to the sender, in the teleconferencing systems proposed by ITU-T. These protocols are implemented with multi thead technique and run on top of UDP/IP-Multicast through the socket interface as the underlying protocol. The upper layer is impelmented such that in can be accessed by the H245 comference control protocol. The RTP packetizes the digitized audio/video data from the encoder info a fixed format, and multieast to the participants. The RTCP monitors RTP packets and extracts the QoS values from it such as round-trip delay, jiter and packet loss to form RTCP packets and non periokically sends them to the sender site. In this Paper, we also descritx the study of measurement and analysis for QoS factors that observed on performing teleconferencing system over Internet. The results from this experiment is indicate that RTT and Jitter value are acceptable even entwork load is high. However, it appears that packet loss rate is high in daytime and most losses periods have length one or two.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.572-579
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• 2009

A monitoring system needs many parameters to increase devices for monitoring data and to support various services. In particular, monitoring the status of a device in a wireless mobile environment has a difficulty in displaying multi data in a limited screen size, and transfer of the status data of a device into a network is largely related with network traffic. The research aims at designing a control board that collects data in order to effectively manage a greenhouse environment system. Also, the research tries to appropriately operate devices, environment data monitoring, and the control of each device by realizing a multiplexed interface based on a web. Thus, in the case in which a distributed client was a computer, monitoring and control were obtained with a web browser through the Lab VIEW web server of a server or local control module in order to effectively monitor and control according to the status of a user. In the case in which a client was a PDA, application of a wireless mobile considering the scale and data processing capacity of a displayer was connected. As a result of the research, we could confirm a satisfactory outcome from the viewpoint of a human-centered design by supplying adaptability and mobility according to the environment of a user.