• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.1
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• pp.121-131
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• 1999

Automatic Rudder Trim System(ARTS) is a device to reduce the pilot's work load for rudder trimming greatly required in varying abruptly aircraft's engine power. This paper represents a technical analysis and a design of control law of the ARTS. The control law of the ARTS is designed based on the analysis of aircraft's characteristics, system's requirements, and limitations. The control law is comprised of open loop control using the rudder trim map for a specific aircraft and closed loop control to compensate the error of the open loop control system. flight test results show that the ARTS can reduce pilot's work load for rudder trimming dramatically and can compensate the aircraft's transient yaw motion.

• Journal of Broadcast Engineering
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• v.16 no.6
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• pp.1009-1017
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• 2011

Fast generation of digital hologram is of importance for real-time holography broadcasting. In this paper, we propose such a method that parallelizes the Computer-Generated Holography (CGH) algorithm for digital hologram generation and make it faster using Multi Graphic Processing Unit (Multi-GPU) with help of the Compute Unified Device Architecture (CUDA) and the Open Multi-Processing (OpenMP). In addition, we propose optimization methods such as fixation variable, vectorization, and loop unrolling for making the CGH algorithm much faster. Experimental results show that our method is about 9,700 times faster than a CPU-based one.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.2
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• pp.52-60
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• 2020

This paper deals with an optimal output tracking control for open-cycle liquid propellant rocket engine. For this purpose, we modeled simplified mathematical model of open-cycle liquid propellant rocket engine and designed optimal output feedback control system using combustion chamber pressure. For design the closed-loop system of open-cycle liquid propellant rocket engine, we designed optimal output feedback linear quadratic tracking control system using the linearized model and demonstrated the performance of the controller through numerical simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.171-176
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• 2005

This study designed and fabricated a multi-purpose planar antenna for base stations that are accessible to DCS, WiBro, and ISM. The proposed antenna was designed into an open loop form from the existing monopole structure. The capacitance of the multi-purpose antenna was increased by the coupling of open parts. This makes the use of MMIC and LTCC convenient and the antenna is smaller and has a larger gain than existing antennas. The resonance distance and bandwidth can be adjusted by changing the open gap and the height of the loop of the antenna. The bandwidth of the designed antenna satisfies DCS, IMT-2000, WiBro, Bluetooth, wireless LAN and ISM bands based on VSWR 2. The entire frequency bandwidth is $58.75\%$ of $1.575GHz\~2.985GHz(1.41GHz)$. Also, the radiation pattern of the antenna displayed co-polarization and cross-polarization characteristics at 1.6GHz, 2.3GHz and 2.8GHz.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.89.1-89.1
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• 2011

We have investigated a coronal jet near the limb on 2010 June 27 by Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), Solar Optical Telescope (SOT), SDO/Atmospheric Imaging Assembly (AIA), and STEREO. From EUV (AIA and EIS) and soft X-ray (XRT) images we identify the erupting jet feature in cool and hot temperatures. It is noted that there was a small loop eruption in Ca II images of the SOT before the jet eruption. Using high temporal and multi wavelength AIA images, we found that the hot jet preceded its associated cool jet. The jet also shows helical-like structures during the rising period. According to the spectroscopic analysis, the jet structure changes from blue shift to red one with time, implying the helical structure of the jet. The STEREO observation, which enables us to observe this jet on the disk, shows that there was a dim loop associated with the jet. Comparing the observations from the AIA and STEREO, the dim loop corresponds to the jet structure which implies the heated loop. Considering that the structure of its associated active region seen in STEREO is similar to that in AIA observed 5 days before, we compared the jet morphology on the limb with the magnetic fields extrapolated from a HMI vector magnetogram observed on the disk. Interestingly, the comparison shows that the open field corresponds to the jet which is seen as the dim loop in STEREO. Our observations (XRT, SDO, SOT, and STEREO) are well consistent with the numerical simulation of the emerging flux reconnection model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.47-56
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• 2005

This paper presents a performance improvement result with the aid of closed feedback controller loop to a micro gyroscope. The dynamic model of a micro gyroscope is derived and a conventional proportional and derivative controller is designed via frequency domain analysis. The proposed control loop is implemented using several analog devices and applied to the SNU-Bosch MEMS gyroscope to check its performance improvement in real environment. The experiments demonstrated the performance improvement with the proposed feedback control loop. The bandwidth, linearity, and bias stability are improved to 78 Hz, 0.504 %, and 0.043 deg/sec, respectively, from 35 Hz, 2.07 %, and 0.066 deg/sec of open loop system.

• Journal of the Korean Operations Research and Management Science Society
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• v.40 no.1
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• pp.5-19
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• 2015

Literatures on open innovation have two major limitations. First, either on a firm level or on an industry level did they analyze the open innovation issues. The results of a firm's innovation can be diffused through the whole network and the firm can learn back from the network knowledge. Prior literatures did not consider the feedback loop among firms and network in which the firms are involved. Second, most open innovation research had a static perspective on firm's innovation performance. Since the diffusion, spill-over and learning among network members are involved over time, the open innovation is intrinsically dynamic. From the dynamic perspective, we can appreciate the fundamental attributes of the open innovation network which involves diverse firms, research institutes, and universities. In order to overcome the limitations, we suggest a dynamic model for open innovation network. We build an agent-based model which consists of heterogeneous firms. The firms are connected through a scale-free network which is formed by preferential attachment. Through the diverse scenario of simulation, we collect massive data on the firm level and analyze them both on firm and industry level. From the analysis, we found that, on industry level, the overall performance of open innovation increases as the internal research capability, absorptive capacity, and learning curve coefficient increase. Noticeably, as the deprecation rate of knowledge increases, the variability of knowledge increases. From the firm level analysis, we found that the industry-level variables had a significant effect on the firm's innovation performance lasting through all the time, whereas the firm-level variables had only on the early phase of innovation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1074-1079
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• 1999

A high performance CMOS receiver for 155.52 Mbps STM-1 digital communication has been designed and fabricated. The ASIC operates properly with 155.52 MHz clock frequency in case of the data loss due to some system error such as transmission line open or data transfer fail. Also it operates properly in case the system starts after the power failure or system maintenance. The designed circuit has especially PLL based self oscillation loop which operates on abnormal environment which is added to main oscillation loop. The measured results show that the circuit operates well with 153.52 MHz clock frequency not only on normal environment but also on abnormal environment. Rms jitter of the PLL loop is about 23 ps.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.39-56
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• 2009

Vibration is an undesirable phenomenon in a dynamic system like lightly damped aerospace structures and active vibration control has gradually been employed to suppress vibration. The objective of the current investigation is to introduce an active torsional magneto-rheological (MR) fluid based damper for vibration control of a typical nose landing gear. They offer the adaptability of active control devices without requiring the associated large power sources. A torsional damper is designed and developed based on Bingham plastic shear flow model. The numerical analysis is carried out to estimate the damping coefficient and damping force. The designed damper is fabricated and an experimental setup is also established to characterize the damper and these results are compared with the analytical results. A typical FE model of Nose landing gear is developed to study the effectiveness of the damper. Open loop response analysis has been carried out and response levels are monitored at the piston tip of a nose landing gear for various loading conditions without damper and with MR-damper as semi-active device. The closed-loop full state feedback control scheme by the pole-placement technique is also applied to control the landing gear instability of an aircraft.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.4
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• pp.313-319
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• 2000

As the interest of flexible manufacturing systems and computer integrated manufacturing systems increase, the distribution of centralized control systems using industrial control networks is getting more attention. In this paper, we investigate the rate-based traffic control of industrial control networks to improve the performance regarding the throughput, fairness, and error rates. Especially, we consider the protocol of Lon-$Works^{(TM)}$ which consists of all OSI 7-layers and supports various communication media at a low cost. Basically, the proposed rate-based traffic control system is closed loop by utilizing the feedback channel errors, which shows improved performance when compared with other industrial control networks commonly operated in open loop. To this end, an additional network node called monitoring node is introduced to check the channel status without increasing the channel load. The Proposed control loop is in effect whenever the feedback channel error becomes greater than an admittable value. We demonstrate the improved performance of the controlled network system in view of throughput and fairness measures by implementing the lab-scale network system based on LonWorks and through the experimentation upon it.