• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.999-1005
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• 2007

In case of an abnormal condition of control surface, the real-time estimation of aerodynamic derivatives are required for the reconfigurable control system to be flight for missions or return to the head office. The goal of this paper is to represent a technique of fault detection to the control surface as a base research to the fault tolerant control system for safety improvement of UAV. The real-time system identification for the fault detection to the control surface was applied with the recursive Fourier Transform and verified through the HILS and flight test. The failures of the control surface are detected by comparing the control derivatives in fault condition with the normal condition. As a result from the flight test, we have confirmed that the control derivatives of fault condition less than about 50% in the normal condition.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.425-436
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• 2015

This paper presents the procedures used for estimating the stability and control derivatives of a general aviation canard aircraft from flight data. The maximum likelihood estimation method which accounts for both process and measurement noise was used for the flight data analysis of a four seat canard aircraft, the Firefly. Without relying on the parameter estimation method, several aerodynamic derivatives were obtained by analyzing the steady state flight data. A wind tunnel test, a flight test of a 1/4 scaled remotely controlled model aircraft, and the prediction of aerodynamic coefficients using the USAF Stability and Control Digital Data Compendium (DATCOM), Advanced Aircraft Analysis (AAA), and Computer Fluid Dynamics (CFD) were performed during the development phase of the Firefly and the results were compared with flight determined derivatives of a full scaled flight prototype. A correlation between the results from each method could be used for the design of the canard aircraft as well as for building the aerodynamic database.

• Archives of Pharmacal Research
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• v.13 no.1
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• pp.14-18
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• 1990

The carbinols, hydrazide, Schiff's bases and acryloyl derivatives of 2-thiobenzethiazole were prepared. The acid and nitrile of 20thiobenzothiazole were also obtained. The derivatives were tested for their antibacterial activities. Some derivatives showed the highest antifungal and activity.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1094-1097
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• 1999

This paper presents a new PID control scheme based on the feedback of averaged derivatives to realize a noise-free differential control. The PID(Proportional, Integral and Differential) control is still one of the control methods in most wide use. In the paper, the conventional PID control adopting filtering technique is analyzed with new interpretation of filtering function. In order to overcome the drawbacks of the conventional PID control, this paper introduces the feedback of averaged derivatives in the noisy environment, and suggests a new PID control scheme using delay components to realize a noise-free differential control. The proposed PID control yields good performance much similar to the original system response in case of no noises. The proposed control scheme has been tested for the load frequency control of power systems.

• Journal of the Korean Applied Science and Technology
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• v.26 no.1
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• pp.29-37
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• 2009

This study is focused on the synthesis of urea and amide derivatives particularly, since the amide moiety is an essential binding group at the binding site. Urea derivatives 3-7 and 13-14 were obtained by reaction of 2-aminopyrimidines and other amines with diverse isocyanates in pyridine as a solvent under reflux. The urea derivatives were obtained in low yield because of the highly electron deficient nature of the amino group of the 2-aminopyrimidine. Amide derivatives 8-10 were obtained in moderate yields by reaction of compound 1 with aryl chloride derivatives. Also, arylamine 11 was synthesized by Buchwald-Hartwig amination in moderate yields. Most of the compound did not show good activity against A375P melanoma cells, compared with Sorafenib as control compound.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.27-28
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• 2006

Chromatographic separation of enantiomers by high-performance liquidchromatography (HPLC) has considerably advanced in the past two, and many optically active polymers have been developed to be usedaschiral stationary phases (CSP). Among many CSPs, cellulose-andamylose-based CSPs are most attractive from the viewpoints of theirwide applicability and easy availability. The polysaccharides are readily modified to ester and carbamates. The derivatives have been used as CSPs after being coated on macroporus silica gel. Here, the CSPs based on phenylcarbamate derivatives of these two polysaccharides will be mainly discussed. The immobilization of the derivatives on silica gel will also be discussed.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.1
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• pp.38-44
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• 1998

The modified maximum likelihood estimation method is used to estimate the nondimensional aerodynamic derivatives of a single turbo-prop aircraft at a specified flight condition for the best deduction of the dynamic characteristics. In wind axes the six degree of freedom equations are algebraically linearized so that the linear state equation contains aerodynamic derivatives in a state-space form and is used in the maximum likelihood method. The simulated data added with the measurement noise is used as a flight test data which is necessary to the estimation of nondimensional aerodynamic derivatives. It is obtained by implementing the 6-DOF nonlinear flight simulation. In the flight simulation, the effects of several control input types, control deflection amplitudes, and the turbulence intensities on the statistical convergence criteria are also examined and quantitative analysis of the results is discussed.

• Journal of Korea Trade
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• v.24 no.1
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• pp.1-34
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• 2020

Purpose - In this study, we investigate determinants of hedging with derivatives and its effect on firm value and firm risk for Korean firms. Design/methodology - To avoid the endogeneity problem pointed out in previous studies, we use a two-stage analysis by using gains and losses from derivatives as instrument variable for hedging with derivatives. Findings - Our analysis on the determinants of hedging shows that firms that are more leveraged and less profitable, and with more growth opportunities are likely to hedge through derivatives. Additionally, large firms, firms less diversified into industry, and firms more diversified geographically are likely to use derivatives. Our two-stage analysis shows that indicators of hedging with derivatives have an insignificant effect on firm value, and the indicator of futures/forwards use and of swaps use have significant negative effect on firm value. Whereas, the extent of hedging with derivatives has positive effect on firm value for all types of foreign currency derivatives, which suggests that moderately low hedgers use derivatives inefficiently, but extensive hedgers use derivatives properly. With regard to firm risk, hedging with derivatives increases market-based risk, but decreases accounting-based risk. Thus, we conclude that Korean firms use derivatives to manage operational volatility rather than to manage market risk, and accounting-based risk reduction through hedging is not directly translated into higher firm value. Originality/value - This is not the first study to investigate hedging behavior of Korean firms, but the sample period that that this study analyzed is the longest and various method are used to control the endogeneity problem. We investigate not only total foreign currency derivatives but also by types of derivatives, including futures/forwards, options, and swaps.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1663-1666
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• 1997

The purpose of this paper is to find how to determine the controllability and stability derivatives form flight test and to display the stability of the Twinbee aircraft. There are various methods developed to find the derivatives : wind tunnel testing, predicted result from empirical data, flight test and so on. Among those methods, the estimation form flight test of real aricraft is the most reliable. We performed the flight test of Twinbee and recorded the states of aorcraft. Using those states and parameter setimation algorithem based on the Maximum Likdlihood(MMLE) criterion, we can estimate the controllability and stability derivatives. In this paper, wel will show the process form designing the proper flight test input to estimation of derivatives.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.44-53
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• 2009

In this paper, Recursive Least Squares (RLS) and Fourier Transform Regression (FTR) methods for estimating stability and control derivatives of small unmanned helicopter are evaluated together with MMLE technique. Flight data simulated by using a commercial small-scale helicopter model are exploited to estimate the parameters with accuracies for hover and cruise modes. The performances of the system identification methods are also compared by analyzing the responses of the reconstructed systems using estimated derivatives.