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Narongwit Nakwan,Thidarat Ruklerd,Pattarawadee Taptawee 대한결핵및호흡기학회 2022 Tuberculosis and Respiratory Diseases Vol.85 No.3
Background: The use of low-dose inhaled corticosteroid-formoterol as reliever monotherapy has recently been recommended in the asthma treatment guidelines. However, the efficacy of this treatment strategy has not yet been determined during the stepping-down period in moderate asthma. This study aimed to evaluate the feasibility of reducing treatment to as-needed budesonide-formoterol (BFM) in moderate asthma with complete remission.Methods: We randomly assigned 31 patients (8 males and 23 females with a mean age of 57.2 years) with complete remission of asthma by inhaled BFM (160/4.5 μg) twice daily to receive BFM (160/4.5 μg) as needed (16 patients), or budesonide (BUD) (200 μg) twice daily (15 patients). The study was an open-label study done for 48 weeks, with the primary outcome as the cumulative percentages of patients with treatment failure (asthma exacerbation or loss of asthma control or lack of satisfaction after using medications) in the two groups.Results: Six patients (42%) using as-needed BFM had treatment failure, as compared with three patients (21.4%) using BUD maintenance (hazards ratio for as-needed BFM, 1.77; 95% confidential interval, 0.44–7.12; p=0.41). The changes in forced expiratory volume in 1 second were −211.3 mL with as-needed BFM versus −97.8 mL with BUD maintenance (difference, 113.5 mL; p=0.75) and the change in fractional exhaled nitric oxide was significantly higher in both groups, at 8.68 parts per billion (ppb) in the as-needed BFM group and 2.5 ppb. in the BUD maintenance group (difference, 6.18 ppb; p=0.049).Conclusion: Compared with BUD maintenance, there were no significant differences in treatment failure rate in patients who received as-needed BFM during the stepping down period in moderate asthma. However, they showed reduced lung function and relapsed airway inflammation. The results are limited by imprecision, and further large RCTs are needed.
김낙완(Nakwan Kim),유창선(Chang Sun Yoo),강영신(Young Shin Kang) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.6
적응제어신호를 저역필터에 통과시켜 점근적 추종과 과도구간 성능을 동시에 보장하는 £₁ 적응제어 기법과 비선형 시스템을 선형 시불변 형태로 변환하는 피드백 선형화 기법을 결합하여 £₁ 적응제어 기법의 적용가능 범위를 확대하였다. Barbalat의 보조정리를 이용하여 추종오차가 0으로 수렴함을 증명하고 과도구간의 추종오차도 원하는 크기로 감소시킬 수 있음을 보였다. This paper presents an approach to combine £₁ adaptive controller with feedback linearization, which extends the applicability of the £₁ adaptive controller to a wider class of systems. The £₁ adaptive controller guarantees the asymptotic tracking convergence and the transient performance of the tracking error. The feedback linearization transforms a nonlinear plant into a linear time invariant form. The asymptotic tracking convergence is shown by the use of Lyapunov stability analysis and Barbalat’s lemma.
신경회로망 기존제어기의 접합기법을 이용한 유도무기 제어
김낙완(Nakwan Kim) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.3
불확실성과 비선형성은 비선형시스템의 제어기 설계에 중요하게 고려할 요소이다. 본 논문에서는 기존 제어기와 신경회로망을 접합하여 불확실성과 비선형성에 대처하는 기법을 소개한다. 이 기법은 기존의 제어기를 사용하기 때문에 신경회로망을 사용하기 위해 역변환 제어기와 같은 새로운 형태의 제어기를 설계할 필요가 없다. 이 기법은 유도무기의 수직 가속도 제어에 적용하여 그 효용성을 제시하였다. The effect of uncertainty and nonlinearity is an important aspect in a control design of a highly nonlinear plant. This paper presents an approach to address uncertainty and nonlinearity by augmenting an existing controller with a neural network based adaptive element. The approach has advantage in the sense that augmentation of neural network does not require to design a new controller architecture like an inversion controller. The approach is illustrated in an application of normal acceleration control for guided munitions.
김낙완(Nakwan Kim),김병수(Byoung-Soo Kim),유창선(Chang Sun Yoo),강영신(Young Sin Kang) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.12
A design of attitude controller for a tiltrotor is presented augmenting L1 adaptive control, neural networks, and feedback linearization. The neural networks compensate for the modeling error caused by the lack of knowledge of tiltrotor dynamics while the L1 adaptive control allows high adaptation gains in adaptation laws thereby, satisfying tracking performance requirement. The efficacy of this control methodology is illustrated in high-fidelity nonlinear simulation of a tiltrotor by flying the tiltrotor in different flight modes from where the L1 adaptive controller with neural networks is originally designed for.
Dynamics modeling of a semi-submersible autonomous underwater vehicle with a towfish towed by cable
Jinmo Park,Nakwan Kim 대한조선학회 2015 International Journal of Naval Architecture and Oc Vol.7 No.2
In this paper, we employ a dynamics modeling method for investigating a multi-body dynamics system of semi-submersible autonomous underwater vehicles consisting of a towing vehicle operated near the water surface, a tow cable, and a towfish. The towfish, which is towed by a marine cable for the purposes of exploration or mine hunting, is modeled with a Six-Degree-of-Freedom (6-DOF) equation of motion that reflects its hydrodynamics characteristics. The towing cable, which can experience large displacements and deformations, is modeled using an absolute nodal coordinate formulation. To reflect the hydrodynamic characteristics of the cable during motion, the hydrodynamic force due to added mass and the drag force are imposed. To verify the completeness of the modeling, a few simple numerical simulations were conducted, and the results confirm the physical plausibility of the model.
Integrated dynamics modeling for supercavitating vehicle systems
Seonhong Kim,Nakwan Kim 대한조선학회 2015 International Journal of Naval Architecture and Oc Vol.7 No.2
We have performed integrated dynamics modeling for a supercavitating vehicle. A 6-DOF equation of motion was constructed by defining the forces and moments acting on the supercavitating body surface that contacted water. The wetted area was obtained by calculating the cavity size and axis. Cavity dynamics were determined to obtain the cavity profile for calculating the wetted area. Subsequently, the forces and moments acting on each wetted part-the cavitator, fins, and vehicle body-were obtained by physical modeling. The planing force-the interaction force between the vehicle transom and cavity wall-was calculated using the apparent mass of the immersed vehicle transom. We integrated each model and constructed an equation of motion for the supercavitating system. We performed numerical simulations using the integrated dynamics model to analyze the characteristics of the supercavitating system and validate the modeling completeness. Our research enables the design of high-quality controllers and optimal supercavitating systems.
Design of an adaptive backstepping controller for auto-berthing a cruise ship under wind loads
Park, Jong-Yong,Kim, Nakwan The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.2
The auto-berthing of a ship requires excellent control for safe accomplishment. Crabbing, which is the pure sway motion of a ship without surge velocity, can be used for this purpose. Crabbing is induced by a peculiar operation procedure known as the push-pull mode. When a ship is in the push-pull mode, an interacting force is induced by complex turbulent flow around the ship generated by the propellers and side thrusters. In this paper, three degrees of freedom equations of the motions of crabbing are derived. The equations are used to apply the adaptive backstepping control method to the auto-berthing controller of a cruise ship. The controller is capable of handling the system non-linearity and uncertainty of the berthing process. A control allocation algorithm for a ship equipped with two propellers and two side thrusters is also developed, the performance of which is validated by simulation of auto-berthing.