¹H and ¹³C NMR Data on Hydroxy/methoxy Flavonoids and the Effects of Substituents on Chemical Shifts

Yoon, Hyuk,Eom, Sung-Lock,Hyun, Ji-Ye,Jo, Geun-Hyeong,Hwang, Do-Seok,Lee, Sun-Hee,Yong, Yeon-Joong,Park, Jun-Cheol,Lee, Young-Han,Lim, Yoong-Ho Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.6

Moxifloxacin-Containing Triple Therapy as Second-Line Treatment for <i>Helicobacter pylori</i> Infection: Effect of Treatment Duration and Antibiotic Resistance on the Eradication Rate

Yoon, Hyuk,Kim, Nayoung,Lee, Byoung Hwan,Hwang, Tae Jun,Lee, Dong Ho,Park, Young Soo,Nam, Ryoung Hee,Jung, Hyun Chae,Song, In Sung Blackwell Publishing Ltd 2009 HELICOBACTER -CAMBRIDGE USA- Vol.14 No.5

<P>Abstract</P><P>Background and Aim: </P><P>The aim of this study was to evaluate the efficacy of a moxifloxacin-containing triple therapy as second-line treatment for <I>Helicobacter pylori</I> infection. We also investigated the effect of treatment duration and antibiotic resistance on the eradication rate of this therapy.</P><P>Methods: </P><P>We prospectively enrolled patients found to have persistent <I>H. pylori</I> infections after failure of first-line proton-pump inhibitor-based triple therapy. Patients took moxifloxacin (400 mg q.d.), amoxicillin (1000 mg b.i.d.), and esomeprazole (20 mg b.i.d.). The eradication rate, drug compliance, and adverse event rates were evaluated. Minimal inhibitory tests were performed for moxifloxacin and amoxicillin by the agar dilution method.</P><P>Results: </P><P>In 2004, 41 patients were treated for 7 days. The intention-to-treat and per-protocol eradication rates (ITT/PP) were 75.6/83.8%. Moxifloxacin resistance was 5.6%. Therapy was extended to 10 days during 2005–2006 and 139 patients were treated. The ITT/PP eradication rates were 71.9/82.6%; moxifloxacin resistance had increased to 12%. The final group of 181 patients in 2007–2008 who were treated for 14 days also had low eradication rates (68/79.9%), but there was no statistical significance in the efficacy among the treatment periods. Moxifloxacin resistance in 2007–2008 was 28.2%. Side-effect increased with treatment duration (i.e., 9.8, 12.2, and 25.4% at 7, 10, and 14 days, respectively, <I>p</I> = .001).</P><P>Conclusion: </P><P>The 7-day moxifloxacin-containing triple therapy produced an unacceptably low eradication rate. Increasing the duration of therapy was expected to increase the eradication rate, but the expected increased did not materialize, most likely because of coincident marked increase in the prevalence of resistance to moxifloxacin. Tailored treatment based on antibiotic susceptibility testing might be more effective in the achievement of high eradication rate when rapid antibiotic resistance such as moxifloxacin is occurring.</P>

Diffraction Behaviors of New Photopolymers and their Diffuser Properties

Yoon, Hyuk,Kim, Jae-Hong,Lee, Seung-Hwan,Paek, Sang-Hyon,Choi, Dong-Hoon The Korean Infomation Display Society 2004 Journal of information display Vol.5 No.1

Photopolymers are quite promising candidates for holographic data storage and diffusers because of their high sensitivity and high refractive index modulation. New photopolymers were prepared using the cellulose ester binder bearing different kinds of monomer. The holographic gratings were elaborated successfully in these photopolymer samples by conventional optical interference method. We investigated the dynamic behavior of the diffraction efficiency and the effect of the functionality of the monomer doped into the polymer binder. Triacrylate monomer doped photopolymer showed the highest diffraction efficiency of around 80-90 %, even under low intensity of writing beam (I=2 mW/$cm^2$). We inscribed the gratings of the glass diffuser on the surface of the photopolymer and investigated their diffusion properties.

Coordinated Simultaneous Attitude Pointing for Multiple Satellites Under Formation Flying

Yoonhyuk Choi,Henzeh Lee,Hyochoong Bang 한국항공우주학회 2007 International Journal of Aeronautical and Space Sc Vol.8 No.1

In this paper, attitude control laws for simultaneous pointing of multiple spacecrafts are considered under a formation flying scenario. The basic approach lies in adaptive feedback gains using relative attitude information or maneuver time approximation for coordinated attitude control. Each control law is targeted to balancing mean motion or to correcting system response to the slowest satellite. The control gain adaptation is constructed by two approaches. The first one is using variable damping gain to manipulate speed of a fast system response, and the second one uses alternate natural frequency of the system under control. The validity and stability of the proposed approaches are examined analytically and tested through numerical simulations.

Dynamic Control Allocation for Shaping Spacecraft Attitude Control Command

Yoonhyuk Choi,Hyochoong Bang 한국항공우주학회 2007 International Journal of Aeronautical and Space Sc Vol.8 No.1

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.<SUP>1-2</SUP> The CA technique deals with a problem of distributing a given control demand to available sets of actuators.<SUP>3-4</SUP> There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.<SUP>1-2</SUP> In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.? Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.? Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm?, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Harkegard, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

Predictive Filter를 이용한 인공위성 자세결정 연구

최윤혁(YoonHyuk Choi),방효충(Hyochoong Bang) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.11

Predictive 필터는 Kalman 필터의 단점을 보완하고 모델 오차를 동시에 추정할수 있는 최근에 제시된 기법이다. 한 단계 앞의 추정 오차를 최소화하기 위한 최적화된 필터의 형태가 Predictive 필터이다. 본 필터의 주요 장점은 상태변수와 함께 모델오차를 파악할 수 있다는데 있다. 본 연구에서는 Predictive 필터를 이용한 인공위성의 자세추정 내용을 소개하도록 한다. 기존에 제시된 Predictive 필터 이론을 적용하여 자이로 바이어스 신호를 추정할수 있는 수식을 유도하고 또한 벡터 관측 정보를 이용한 자세추정 결과를 소개하도록 한다. 본 연구결과를 통해 향후 Predictive 필터의 확장 가능성을 예상할수 있다. Predictive filter theory proposed recently can be characterized by inherent advantages of estimating modelling error and overcoming the disadvantage of the Kalman filter theory. A one-step ahead error is minimized to produce optimized filter performance in the form of the predictive filter. The main advantage of this filter lies in the ability to estimate both state vector and system model error. In this paper, attitude estimation results based upon the predictive filter theory addressed. Mathematical formulation for estimating bias signal is peformed by using the predictive filter theory, and attitude estimation based upon vector observation is presented. From the results of this study, the potential applicability of the predictive filter is highlighted.

반작용 휠의 최대 가용 토크 분배법칙

최윤혁(Yoonhyuk Choi),이현재(Henzeh Lee),방효충(Hyochoong Bang) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.7

본 논문에서는 저사양의 반작용 휠을 이용하여 토크 가용성을 높이는 두 가지 기법이 제안 하였다. 첫 번째는 기존의 의사역행렬을 이용한 토크 제어 분배 법칙 대신 가중치가변 의사역행렬과 모멘텀을 최소화하는 제어 분배 법칙을 제안하여 반작용 휠의 토크, 모멘텀 제한 조건 내의 해를 찾도록 했다. 두 번째는 휠의 장착각을 변경하여 토크가 많이 필요한 축의 토크 가용성 자체를 증가시키는 방법을 제안하였다. 제안된 법칙들은 위성체의 자세 천이에 적용되었으며, 시뮬레이션을 통하여 성능 향상과 실제 위성의 적용 가능성을 기술했다. A new approach for maximizing torque capability of low efficient reaction wheel assembly is addressed in this paper. At first, to find out a solution in constrainted field, weighted pseudo-inverse and momentum minimized allocation are suggested instead of a general control allocation called pseudo-inverse. The second method is a structural manner to enlarge torque capability of specific axis by changing installed skew angle of wheels. Two proposed methods are applied to large angle maneuvers of satellite. Improvement of control performance and feasibility for applying to commercial satellite attitude control are demonstrated by numeric simulations.

기하학적 형상 및 경계조건의 변화에 대한 공진 기반 생화학 센서의 감도 특성 분석

신윤혁(Yoonhyuk Shin),임시형(Si-Hyung Lim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

For the micromechanical structure having the bio-chemical molecular adsorption like alkanethiol self assembly monolayer formation, the origin of resonance shifts has been analyzed for different physical dimensions, materials, and boundary conditions using numerical analysis. When the bio-chemical substances are adsorbed on the one side of the micromechanical structure, both material layer addition and adsorption induced surface stress change occur simultaneously. For the microcantilever structure having the fixed-free boundary condition, the effect of the surface stress change on the resonance shift was negligible. However, that of the material layer addition was more dominant. On the other hand, in the microbridge structure having the fixed-fixed boundary condition, the effect of the surface stress change was more dominant compared to that of the material layer addition. Furthermore, it was found that the microbridge structure has one or two order higher sensitivity than the microcantilever structure for the same bio-chemical adsorption stimulus. The analysis results can provide some insights and good basis for the high sensitive resonance based bio-chemical sensor design.

다중 우주쓰레기 제거 시연 시나리오 설계

최윤혁(Yoonhyuk Choi),임성민(Seongmin Lim),이승엽(Seungyup Lee),나경수(Kyung-Su Na),김경근(Kyeong Keun Kim) 한국항공우주학회 2022 한국항공우주학회 학술발표회 논문집 Vol.2022 No.11

안드로이드 Monkey를 이용한 매크로 탐지 연구

정윤혁(YoonHyuk Jung) 한국정보과학회 2015 한국정보과학회 학술발표논문집 Vol.2015 No.12