We present our estimate of pole shift caused by the recent 31 largest earthquakes of magnitude over 8.0. After reviewing theory of perturbation in the Earth’s rotation, each co-seismic as well as post-seismic pole shifts by the earthquakes are acquired and illustrated. A total co-seismic excitation due to these earthquakes is (x1, x2)=(−3.35, 5.89) milliarcsec, which increased about twice the initial estimation when the post-seismic deformation is considered. The single largest co-seismic excitation by 2011 Japan earthquake was (x1, x2)=(−2.06, 2.36) milliarcsec, which corresponds to 9.7 cm pole shift on the surface of the Earth.

The purpose of this study was to investigate the effects of active and passive postural perturbation on ankle dorsiflexor responses in stroke patients. The subjects consisted of 13 stroke patients. Using wireless electromyography, the patients’ ankle dorsiflexor muscle responses were measured under the following conditions: active dorsiflexion (AD), active perturbation (AP), and passive perturbation (PP). Tibialis anterior muscle activity increased most significantly during PP of the affected side (118.64±56.28). The most significant increase for the non-affected side was in AD (72.64±24.56). Tibialis anterior muscle activity was compared under each condition. The affected side showed significant differences between PP and AD and between PP and AP (p<.05). The non-affected side showed not significant differences between each condition. The ratios of tibialis anterior muscle activity under AP to that under AD were 1.00 on the affected side and .75 on the non-affected side and the difference was not significant (p>.05). The ratios of tibialis anterior muscle activity under PP to that under AD were 3.30 on the affected side and 1.14 on the non-affected side and the difference was significant (p<.05). Passive perturbation improved tibialis anterior muscle activity on the affected side, and training based on this approach may have the potential to improve the ankle dorsiflexion of people with stroke.

카울라에 의해 완성되었던 인공위성궤도이론과 케플러의 법칙을 다시 다루었다. 카울라의 원문에서는 생략되었던 부분을 포함한 모든 수식유도과정을 상세히 기술하였다. 특히 15개의 독립적인 라그랑지 괄호들을 계산하는 데에 변환행렬의 직교성을 사용하여, 간결성과 명확성을 이루었다. 여러 중간단계에서 중요한 물리적인 개념들에 대한 설명도 추가하였다. 카울라의 개념적 오류 한 개를 정정하였다.

Cosmological linear perturbation theory has fundamental importance in securing the current cosmological paradigm by connecting theories with observations. Here we present an explanation of the method used in relativistic cosmological perturbation theory and show the derivation of basic perturbation equations.

The purpose of this study was to compare the onset times of muscle activities and the order of muscle firing in erector spinae, multifidus, rectus abdominis and biceps brachii during perturbation between subjects with and without work-related chronic low back pain (LBP). Twenty-nine subjects, 14 with and 15 without LBP, participated in this study. The muscle responses were measured by surface EMG (electromyography) during perturbation in eye opened and eye closed conditions. The EMG onset times of the erector spinae, multifidus, rectus abdominis and biceps brachii were similar between groups in eye closed condition. But the onset times of the erector spinae, multifidus, rectus abdominis were significantly delayed in subjects with LBP in eye opened condition. The results provide an evidence for impaired feed-forward control of the trunk muscles in subjects with LBP. Further studies are needed to identify whether the impaired feed-forward control of the trunk muscles is the contributing factor to LBP.

High temperature dielectric constants of the various ceramic materials have been measured using cavity perturbation method. The measurements were applied to refractory, traditional and fine ceramic powder compacts from room temperature to . Calibration constant in the equation suggested by Hutcheon et al., was determined from the dielectric constants of reference specimen (teflon and alumina) at room temperature. From these results, informations on the refectory materials were obtained for the microwave kiln design and understanding of the microwave heating effects of ceramics have been improved.

사각형 유체저장 탱크내에 저장되어 있는 유체의 비선형 유동거동을 섭동법을 사용하여 해석하였다. 제시된 방법에 의한 비선형 해석결과는 기존의 연구결과와 잘 일치하였다. 지반특성과 탱크형상에 따른 유체 표면의 비선형 거동 특성을 분석하여 비선형 해석의 중요성을 입증하였다. 유체의 비선형 거동은 토사지반에서 크게 나타나며 특히 Broad Tank에서의 응답은 대단히 크게 나타났다. 일반적으로 유체표면 유동의 비선형 해석결과는 선형해석결과 보다 크게 나타났다. 유체저장탱크의 설계시 선형해석 만으로는 최대응답을 과소평가할 수 있으므로 비선형 해석을 반드시 수행할 필요가 있다.

The collision effects in particles of the accretion disk are examined by the use of small perturbation. The collision force is assumed to be equal to 2 vV. From the equations governing collisions of such particles the local dispersion relation is obtained.

구조물의 손상전후에 나타나는 고유진동수와 모드 형상으로 부터 Inverse Modal Perturbation기법을 이용하여 잔교식 부두나 돌핀과 같은 대규모 항만구조물의 손상도 추정을 위한 모드 기여도 계수를 근사적으로 직접 구하는 방법을 제시하였다. 잔교식 항만구조물의 고유치 해석을 통해 구조물의 강성 변화량과 구조물의 고유진동수와 모드 형상의 변화량과 요소 손상도 계수를 도입하여 Inverse Modal Perturbation의 2차항을 고려한 관계식을 유도하고 손상전후에 구조물의 강성 감소로 나타나는 구조물의 손상도를 추정하여 수렴정도를 고찰하였다.

COBE's results on the anisotropy of the cosmic microwave background radiation (CMBR) is discussed. Some ambiguities in the linear GI cosmic perturbation theory are clarified. The problem of the last scattering surface and the deficiencies of the linear cosmic perturbation theory are mentioned. The possible ways to overcome the theoretical difficulties are discussed also.

교량, 발전소, 해양구조물과 같은 토목구조물은 사용기간중에 지진, 바람, 파랑하중등에 의해 구조적 손상을 받기 쉽다. 장기간에 걸쳐 구조물에 손상이 누적되면 구조물 전체의 파괴를 초래할 수도 있다. 따라서 현존하는 구조물의 안전성을 분석하기 위한 구조물의 손상도를 추정하는 방법이 필요하다. 본 논문에서는 Inverse Modal Perturbation기법을 이용하여 구조물의 손상도를 추정하는 방법에 대하여 연구하였다. Perturbation식은 구조물의 강성 및 질량행렬의 변화량과 구조물의 고유진동수와 모우드형상의 변화량의 식으로 구성된다. 또한 구조물의 손상은 강성행렬의 변화량으로 표현하였다. 본 연구에서는 구조물의 손상도추정의 효율성을 증대시키기 위하여 2차-Perturbation식을 구성하고, 이것을 반복적인 절차를 거쳐 해를 구하는 방법에 대하여 연구하였다. 제안된 방법의 효율성은 일련의 예제해석을 통하여 검증하였으며, 추정된 결과로 부터 본 방법이 구조물의 손상을 적절히 산정함을 알 수 있었다.

The purpose of this study is to get analytic solution of space truss using homotopy perturbation. A homotopy perturbation was derived by formulating a governing equation for a space truss, and a semi analytical solution was obtained by homotopy perturbation. In conclusion, the analytical solution of the simple nonlinear model using the homotopy perturbation was compared with the numerical analysis result.

The purpose of this study is to investigate the applicability of multi-stage homotopy perturbation method to shallow arches in order to obtain a semi-analytical solution. For this research purpose, a nonlinear governing equation of the arches was formulated and a homotopy equation was derived using the formulated differential equation. The result of a dynamic analysis on a symmetric mode and an asymmetric one was compared with the classical homotopy perturbation method and the 4th order Runge-Kutta method.

This study aims to apply multistage homotopy perturbation method (MHPM) to SDOF space truss to obtain a semi-analytical solution. For the purpose, a nonlinear governing equation is derived in consideration of geometrical nonlinearity, and homotopy equation is formulated. The result of carrying out dynamic analysis on a simple model is compared to a numerical method of 4th order Runge-Kutta method (RK4), and the dynamic response by MHPM concurs with the numerical result.

This paper presents a new method for conveniently estimating static displacements of a structure based on its vibration data. In the proposed method, structural static displacements can be obtained using a normalized modal flexibility matrix assisted by a known mass perturbation method in order to overcome several shortcomings of existing displacement sensors such as the limitation on installation due to surrounding environments and the inconvenience to the public during static loading tests. For validating the feasibility of the proposed method, experimental validation was carried out on a simply-supported beam model. It was found that the proposed method can be an effective alternative to conventional static displacement estimation.

In spite of the difficulties and uncertain characteristic of cable driven method, surgical robot instrument has adopted it as driving mechanism for various reasons. To overcome the problem of cable system, previous research applied SMCSPO (sliding mode control with sliding perturbation observer) algorithm as robust controller to control the instrument and found that the value of SPO (sliding perturbation observer) followed force disturbance, reaction force loaded on the tip very similarly. Thus, this paper confirms that the perturbation observer is sufficient estimator which finds out the mount of loaded force on the surgical robot instrument. To prove the proposition, simulation using the similar model with an actual instrument and experimental evaluation are performed. The results show that it is possible to substitute SPO for sensors to measure the reaction force. This estimated reaction force will be used to realize haptic function by sending the reaction force to a master device for a surgeon. The results will contribute to create surgical benefit such as shortening the practice time of a surgeon and giving haptic information to surgeon by using it as haptic signal to protect an organ by making force boundary.