• Journal of Power System Engineering
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• v.17 no.3
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• pp.89-98
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• 2013

In this paper, the authors consider control system design problem of barge type surface vessel. It is based on the Dynamic Positioning System(DPS) design problem. The main role of barge ship is to carry and supply the materials to the floating units and other places. To carry out this job, it should be positioned in the specified area. Even though sometimes the thrust systems are installed on it, in general the mooring winch system with the rope is used. It may be difficult to compare the control performances of two types. But, if we consider this problem in point of usefulness, we can easily find out that the winch control system is more useful and applicable to the real field than the thrust control system except a special use. Therefore, in this paper we consider a single type mooring winch system and control system design problem in which accurate position control is needed. Because this result can be extended to the general type mooring system in which a number of winch are installed. At first, a mathematical model of winch is obtained and evaluated to verify the usefulness for control system design by experiment. Also, the disturbance model is extracted from experiment data to evaluate the strength of the uncertainty. Based on this results, the robust control system is designed and control performance is evaluated by simulation.

• The Journal of the Acoustical Society of Korea
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• v.39 no.1
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• pp.8-15
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• 2020

In this paper, we propose a frame synchronization algorithm for robust to the combined effects of large Doppler fluctuations and extended, time-varying multipath in the underwater acoustic communication. From the algorithm, we can recover a high timing error which is occurred from an acoustic propagation delay and uncertainty of oscillator between transmitter and receiver. In order to verify the performance of the synchronization algorithm, the lake trial results are used. The lake experiments are performed in a Gyeongcheonho located in Mungyeong-si, Gyeongsangbuk-do. We can see that the start position of frame is adjusted after the frame synchronization while the receiver moving.

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.281-290
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• 2010

In geographic forwarding algorithms, traditional route maintenance requires mobile nodes periodically exchange beacon messages with their neighbors. In beacon message based forwarding scheme, a longer interval reduces the number of beacons needed, but may result in significant location errors. Conversely, a shorter interval guarantees more accurate location information, but induces control overheads.Therefore, the fixed or dynamic interval scheme based forwarding schemes cannot adapt well to different mobility environments. Also, existing schemes result in the uncertainty of neighbor node's position in the forwarding table of mobile node. Therefore, this paper presents a self-adaptive location checking mechanism based proactive geo-routing algorithm for beacon-based geographic routing. Simulation results show that the proposed routing algorithm not only significantly increases the relay transmission rate but also guarantees the high end-to-end packet delivery in low and high mobility environments.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.88-97
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• 2013

This paper presents a robust air-to-fuel ratio (AFR) control algorithm for managing exhaust gas recirculation (EGR) systems. In order to handle production tolerance, deterioration and parameter-varying characteristics of the EGR system, quantitative feedback theory (QFT) is applied for designing the robust AFR control algorithm. A plant model of EGR system is approximated by the first order transfer function plus time-delay (FOPTD) model. EGR valve position and AFR of exhaust gas are used as input/output variables of the plant model. Through engine experiments, parameter uncertainty of the plant model is identified in a fixed engine operating point. Requirement specifications of robust stability and reference tracking performance are defined and these are fulfilled by the following steps: during loop shaping process, a PID controller is designed by using a nominal loop transmission function represented on Nichols chart. Then, the frequency response of closed-loop transfer function is used for designing a prefilter. It is validated that the proposed QFT-based AFR control algorithm successfully satisfy the requirements through experiments of various engine operating points.

• Korean Security Journal
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• no.12
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• pp.291-308
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• 2006

A regular aperture occurs between persons controlled and a person governing the society according to national formation and development. A ruler is subdivided into a king, the President, or the highest controller who can feel the uncertainty of ruler's position. To protect those people, it is called guard that used all possible means and ways to protect those people or remove the danger. An opening of guard was related to enhancement of royal authority or centralism. Firstly a military organization had acted for this, but the organization gradually became independent according to it's subdivision and systematization. During the period of the Three States and Unified Silla, the guard was needed new management system by enhancement of royal authority, expansion of the territory, and establishment of centralism. The new management system that organized the group of vassal and Siweebu take charge of guarding the king or serving as private soldiers. In the end of Silla, as a wide range of reformation of government organization, the organization of vassal like Jungsasung and Sunkyosung that developed as not only guard the king and prince but also hold the business writing.

• Journal of Technology Innovation
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• v.13 no.2
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• pp.97-131
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• 2005

This paper has discussed several issues regarding the barriers and opportunities for technological catch-up by the late-comer countries and firms. As one of the barriers to technological catch-up, the paper emphasizes the uncertainty involved with the third stage of learning how to design. The barriers arise because as the forerunner firms refuse to sell or give license to successful catching-up firms who thus have to design the product by themselves. The paper discusses how to overcome this barrier. It also notes that if the crisis of design technology is a push factor for leapfrogging, arrival of new techno-economic paradigm can serve as a pull factor for leapfrogging, serving as a winder of opportunity. The, it emphasized the two risks with leapfrogging, namely the risk of choosing right technology or standards and the risk of creating initial markets, and how to overcome these risks. It discusses how to overcome these risks in leapfrogging, and differentiates diverse forms of knowledge accesses. Then, the paper takes up the issue of whether there can be a single common or several models for catch-up. A common element of catching-up is to enter new markets segments quickly, to manufacture with high levels of engineering excellence, and to be first-to-market by means of the best integrative designs. This observation is supported by the fact that Korea and Taiwan has achieved higher levels of technological capabilities in such sectors as featured by short cycle time of technology. The possibility of two alternative models for catch-up is also discussed in terms of the key difference between Korean and Taiwan, especially in the position toward the source of foreign knowledge and the paths taken toward the final goal of OBM. Taiwan followed the sequential steps of OEM, ODM and OBN, in collaboration or integration with the MNCs. Korean chaebols jumped from OEM directly to OBM even without consolidating design technology.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.674-681
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• 2011

The increasing number of orbital debris objects is a risk for satellite operations due to space activities over past 50 years since launched Sputnik. The GEO (Geostationary Earth Orbit), where COMS-1 is being operated since last June 2010, has more and more risks that collide with space debris or another satellites. In this paper, as a preliminary study about GEO satellite collision probability and operations environment, collision probability between COMS-1 and RADUGA 1-7 that is one of Russian military communication satellites is investigated and analyzed. Indeed, the space environment including space debris of COMS-1 is presented. As a result, it is noted that collision probability between two satellites using NORAD TLEs on 14th Jan. 2011 was 2.8753E-07 in case that position uncertainty was assumed 10km. Particularly, the largest proportion of space debris around COMS-1's mission orbit is meteoroids.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.3 s.303
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• pp.115-120
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• 2005

In this paper, we propose a new robust content-based musical genre classification algorithm using multi-feature clustering(MFC) method. In contrast to previous works, this paper focuses on two practical issues of the system dependency problem on different input query patterns(or portions) and input query lengths which causes serious uncertainty of the system performance. In order to solve these problems, a new approach called multi-feature clustering(MFC) based on k-means clustering is proposed. To verify the performance of the proposed method, several excerpts with variable duration were extracted from every other position in a queried music file. Effectiveness of the system with MFC and without MFC is compared in terms of the classification accuracy. It is demonstrated that the use of MFC significantly improves the system stability of musical genre classification performance with higher accuracy rate.

• Journal of The Korean Astronomical Society
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• v.52 no.6
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• pp.227-233
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• 2019

We report the performance of the 13.7-meter Taeduk Radio Astronomy Observatory (TRAO) radio telescope. The telescope has been equipped with a new receiver, SEQUOIA-TRAO, a new backend system, FFT2G, and a new VxWorks operating system. The receiver system features a 16-pixel focal plane array using high-performance MMIC preamplifiers; it shows very low system noise levels, with system noise temperatures from 150 K to 450 K at frequencies from 86 to 115 GHz. With the new backend system, we can simultaneously obtain 32 spectra, each with a velocity coverage of 163 km s^-1 and a resolution of 0.04 km s^-1 at 115 GHz. The new operating system, VxWorks, has successfully handled the LMTMC-TRAO observing software. The main observing method is the on-the-fly (OTF) mapping mode; a position-switching mode is available for small-area observations. Remote observing is provided. The antenna surface has been newly adjusted using digital photogrammetry, achieving a rms surface accuracy better than 130 ㎛. The pointing uncertainty is found to be less than 5" over the entire sky. We tested the new receiver system with multi-frequency observations in OTF mode. The aperture efficiencies are 43±1%, 42±1%, 37±1%, and 33±1%, the beam efficiencies are 45±2%, 48±2%, 46±2%, and 41±2% at 86, 98, 110, and 115 GHz, respectively.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.4
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• pp.304-309
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• 2013

This paper proposes a intelligent approach on range decision of figure of merit. Unknown range of the underwater target and the non-fixed signal excess make the uncertainty for the tracking process. Using the input data of signal excess related to the range, we establish the rule of the fuzzy set and the original data acquired by sonar can be transformed to the fuzzified data set. To reduce the error arisen from the unexpected data, we use the new data transformed in fuzzy set. The piecewise relations of the min value, max one, and the mean one are calculated. The three values are used for the expected range of the underwater target. By analysing the fluctuation of the data, we can expect the target's position and the characteristics of the maneuvering. The examples are presented to show the performance and the effectiveness of the proposed method.