• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.314-321
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• 2007

Recently, multi-dimensional joint inversion of geophysical data based on fundamentally different physical properties is being actively studied. Joint inversion can provide a way to obtaining much more accurate image of the subsurface structure. Through the joint inversion, furthermore, it is possible to directly estimate non-geophysical material properties from geophysical measurements. In this study, we developed a new algorithm for jointly inverting dc resistivity and seismic traveltime data based on the multiple constraints: (1) structural similarity based on cross-gradient, (2) correlation between two different material properties, and (3) a priori information on the material property distribution. Through the numerical experiments of surface dc resistivity and seismic refraction surveys, the performance of the proposed algorithm was demonstrated and the effects of different regularizations were analyzed. In particular, we showed that the hidden layer problem in the seismic refraction method due to an inter-bedded low velocity layer can be solved by the joint inversion when appropriate constraints are applied.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.606-611
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• 2007

Pulsation is an inherent phenomenon in reciprocating compressors. It interacts with piping to cause vibrations and performance problems. Indiscriminately connecting to a compressor can be dangerous and cost money in the form of broken equipment and piping, poor performance, inaccurate metering, unwanted vibration, and sometimes noise. Piping connected to a compressor can materially affect the performance and response. To minimize these detrimental effects, reciprocating compressor system should be equipped by pulsation suppression system. This study discusses pressure pulsation phenomena occurred in a reciprocating compressor system. An experiment applied air compressor unit, as pulsating pressure generator, has been done. The compressor was connected sequentially to a snubber model and pressure tank. Sensor probes were placed on the inlet and outlet pipes of snubber. Compressor was driven by a motor controlled by a frequency regulator. The experiment was conducted by adjusting the regulator at 40Hz. General information about an internal gas flow can be achieved by numerical analysis approach. Information of the velocity, pressure and turbulence kinetic energy distribution are presented in this paper. Based on this result, the design improvement might be done.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.49-54
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• 1990

In this paper, a simple model is presented for the gate-voltage dependence of the parasitic resistance in MOSFETs with the lightly-doped drain (LDD) structure. At the LDD region located under the gate electrode, an accumulation layer is formed due to the gate voltage. The parasitic resistance of the source side LDD in the channel is treated as a parallel combination of the resistance of the accumulation layer and that of the bulk LDD, which is approximated as a spreading resistance from the end of the channel inversion layer to the ${n^+}$/LDD junction boundary. Also the effects of doping gradients at the junction are discussed. As result of the model, the LDD resistance decreases with increasing the gate voltage at the linear regime, and increase quasi-linearly with the gate voltage at the saturation regime, considering th velocity saturation both in the channel and in the LDD region. The results are in good agreement with experimental data reported by others.

• Journal of the Korea Society of Computer and Information
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• v.25 no.2
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• pp.189-195
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• 2020

In this study, the inlet duct and guide vane of the gas floating absorption tower were redesigned to improve the desulfurization efficiency so that the exhaust gas can be uniformly introduced into the absorption tower. In order to reduce the sulfur oxide pollutants among the main sources of air pollutants in industrial boilers, the existing equipment is redesigned and solved. For this purpose, change the exhaust gas, the slurry and recycling the adsorbent to improve the removal efficiency of SOx component in the exhaust gas inside the gas floating absorption tower so as to uniformly contact. And the initial design value and CFD value for the pressure loss from the boiler outlet to the gas floating absorption tower outlet are verified. Also, the velocity distribution of the exhaust gas, the concentration distribution of the recycled adsorbent, the liquid slurry behavior, and the pressure loss were compared. The results confirmed that the desulfurization efficiency was improved because the pressure loss from the boiler outlet to the absorption tower outlet was reduced and the deflection of the exhaust gas was minimized.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2A
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• pp.51-60
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• 2005

In this paper, we propose an enhanced SIR measurement algorithm for WCDMA mobile station modem. The proposed algorithm minimizes processing delay by applying velocity estimation-based channel estimator with IIR filter and reduces measured SIR offset by compensating attenuated signal power by using pilot channel(CPICH) in fading channel environment. To improve stability of SIR measurement, we also adopt an IIR filter which can properly reflect variation of fading channel in signal and interference power measurement. We prove that the proposed algorithm outperforms conventional SIR measurement algorithm in mean and jitter of measured SIR. Computer simulation shows that performance results using the proposed algorithm have improvement of approximately 8dB for measured mean and 2dB for measured jitter in the wireless mobile channel, especially in fast mobile speed environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.7-15
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• 2008

In this paper, it is investigated that the limitation due to the asymmetry of optical power with respect to optical phase conjugator(OPC) in mid-span spectral inversion(MSSI) for compensating optical signal distortion due to group velocity dispersion(GVD) and nonlinearities generated in fiber by combining with lumped dispersion management(DM) technique into MSSI. Two kinds of lumped DM configuration(configuration A and configuration B) are considered and compared each other in this research. Configuration A consists of two dispersion compensating fiber(DCF) span positioned after transmitter and before receiver, respectively. Configuration B consists of two dispersion compensating fiber(DCF) span positioned before and after OPC placed at middle of total transmission link, respectively. It is confirmed that the transmission performances are more improved by the configuration A combined with MSSI than configuration B. Also, it is confirmed that the best performance of overall channels are obtained by making net residual dispersion(NRD) to have positive value in self phase modulation(SPM)-limited WDM transmission systems, irrelevant to the configuration of DM.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.362-370
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• 2011

This paper presents a K-band radar system installed on the ground moving vehicle to detect and track a high-speed target. The presented radar is separated into three search regions to satisfy a wide area detection and a limitation of the installing space of the radar, and each region performs detecting the target independently and tracking the detected target automatically. The presented radar radiating K-band FMCW waveform acquires range and velocity information of the target at the every dwell and receiving antenna of the radar is applied the multiple baseline interferometer to extract the precise angle information of the target. 3-dimensional tracking accuracy of the radar is 0.25 m RMSE measured actually through a fire experiment of an imitation target.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1509-1513
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• 2003

The autopilot system of vessel is proposed to take service safety and security, to elevate service efficiency, to decrease labor and to improve working environment. Ultimate purpose of the proposed system is to minimize the number of crew by guaranteeing economical efficiency of shipping service. Recently, the research is being achieved to compensate various nonlinear parameters of vessel and apply it to course keeping control, track keeping control, roll-rudder stabilization, dynamic ship positioning and automatic mooring control etc. using optimizing control technique. Relation between rudder angle controlled by steering machine of vessel and ship-heading angle, and load condition of ship is nonlinear, which affects various parameters of shipping service. The speed and direction of waves, velocity and quantity of wind, which also cause the non-linearity of it. Therefore the autopilot system of ship requires the robust control algorithm can overcome various non-linearity. On this paper, we design the autopilot system of ship, which overcomes nonlinear Parameters and disturbance of it using Fuzzy Algorithm, evaluate the proposed algorithm and its excellence through simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.673-676
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• 2005

In this paper, we propose a improved control performance for autonomous mobile robot using the embeded system. The proposed PID(PPID) control method removes steady state error, and has good performance in transient response. The integral term in the proposed method accumulates error in increment section, inverses errors in decrement section, and increases the effect of integral coefficient around target. Therefore, the PPID control method decreases the overshoot, and makes settling time faster than general PID(GPID) control method. In order to verify the effectiveness of the proposed method(PPID), we simulated the position control of DC motor, and experimented the velocity control of autonomous mobile robot. The PPID control method demonstrated good control performance that decrease overshoot and settling time in simulation and experiments.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.277-282
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• 2006

It is well known that Kalman filtering is an optimal real-time data fusion method for GPS/INS integration. However, it has some limitations in terms of stability, adaptability and observability. A Kalman filter can perform optimally only when its dynamic model is correctly defined and the noise statistics for the measurement and process are completely known. It is found that estimated Kalman filter states could be influenced by several factors, including vehicle dynamic variations, filter tuning results, and environment changes, etc., which are difficult to model. Neural networks can map input-output relationships without apriori knowledge about them; hence a proper designed neural network is capable of learning and extracting these complex relationships with enough training. This paper presents a GPS/INS integrated system that combines Kalman filtering and neural network algorithms to improve navigation solutions during GPS outages. An Extended Kalman filter estimates INS measurement errors, plus position, velocity and attitude errors etc. Kalman filter states, and gives precise navigation solutions while GPS signals are available. At the same time, a multi-layer neural network is trained to map the vehicle dynamics with corresponding Kalman filter states, at the same rate of measurement update. After the output of the neural network meets a similarity threshold, it can be used to correct INS measurements when no GPS measurements are available. Selecting suitable inputs and outputs of the neural network is critical for this hybrid method. Detailed analysis unveils that some Kalman filter states are highly correlated with vehicle dynamic variations. The filter states that heavily impact system navigation solutions are selected as the neural network outputs. The principle of this hybrid method and the neural network design are presented. Field test data are processed to evaluate the performance of the proposed method.