A combined theory for zonal harmonic and resonance perturbations of a near-circular orbit with applications to COSMOS 1603 (1984-106A)

Theory for the motion of a satellite in a near-circular orbit and perturbed by zonal and resonance terms in the Earth's gravity field is developed. Commensurability with respect to both primary and secondary terms is considered with the solution dependent on the depths of the resonances. The theory is applied to the motion of COSMOS 1603 (1984-106A) which approached 14 : 1 resonance in 1987. Values of lumped harmonics derived from least-squares analysis are in close agreement with previous studies of 1984-106A and global gravity field models. The theory is finally extended to incorporate the effects of air drag.     

The integrable cases of the three-body problem at second-order resonance under the high oblateness of the central body

For the general and restricted elliptic spatial three-body problems under the high oblateness of the central body and at both second-order orbital and secondary resonances, an analytical solution is obtained by the use of the Weierstrass functions and with an accuracy of the fourth-degree terms in the eccentricities and in the inclinations. The behavior of solutions is studied on the phase plane.     

云南地区震前舒曼谐振异常初步分析

There is a good correlation between anomalous Schumann resonance and seismic activities. Pre-earthquake anomalous Schumann resonance is an important manifestation of LAIC (Lithosphere-Atmosphere-Ionosphere Coupling), which is probably associated with seismic ionospheric disturbance. The observation system parameters of the Yunnan Schumann resonance monitoring stations and the results of statistical and seismic cases analysis are introduced in this paper. Three days before the March 10, 2011 MS5.8 Yingjiang earthquake, anomalous Schumann resonance in the By component (E-W) was observed by Yongsheng station, and two days before the Lincang MS4.0 earthquake of January 23, 2011, anomalous Schumann resonance in the By component was detected by the same station. Spectrum analysis results on the By component observations of Tonghai station show that strong disturbances were observed in spectral density corresponding to the first three Schumann resonant frequencies on the very day of the MS4.2 Honghe earthquake of May 22, 2011. Research shows that Schumann resonance monitoring is a feasible method for seismic-electromagnetic precursors monitoring.     

乳腺钼靶上含钙化占位性病变的动态增强MRI研究

目的:探讨动态增强MRI对乳腺钼靶上含钙化占位性病变的诊断价值。资料与方法:回顾性分析101例乳腺含钙化占位性病变的钼靶及MRI检查资料。其中,乳腺恶性占位性病变56例,包括浸润性导管癌46例,导管原位癌3例,小叶原位癌2例,粘液腺癌3例,基底细胞癌1例,肌上皮癌1例;乳腺良性占位性病变45例,包括乳腺纤维腺瘤39例,乳腺囊肿4例,乳腺纤维囊性增生2例。根据钼靶上钙化形态对于良恶性病变的判断标准,将钙化分为典型良性、可疑恶性、高度可能恶性三类。将钼靶和MRI的诊断结果与病理诊断结果进行对照。以病理结果为金标准,对钼靶与MRI的诊断结果进行配对四格表χ2检验统计学分析。结果:本组85例患者(84.2%)根据钼靶所见做出正确诊断。16例患者(15.8%)钼靶提示可疑恶性钙化但未能确诊或误诊,其中14例在MRI检查后做出正确诊断。MRI检查做出正确诊断99例(98.0%)。钼靶和MRI检查对本组含钙化乳腺占位性病变的诊断准确率差异有统计学意义(P=0.0005,P<0.O5)。结论:当钼靶上钙化信息不能明确乳腺占位性病变的性质,特别在钙化归为BI-RADS3和BI-RADS4级乳腺疾病时,动态增强MRI可以提高诊断准确性。     

The elliptic restricted problem at the 3 : 1 resonance

Four 3 : 1 resonant families of periodic orbits of the planar elliptic restricted three-body problem, in the Sun-Jupiter-asteroid system, have been computed. These families bifurcate from known families of the circular problem, which are also presented. Two of them, I _c , II _c bifurcate from the unstable region of the family of periodic orbits of the first kind (circular orbits of the asteroid) and are unstable and the other two, I _e , II _e , from the stable resonant 3 : 1 family of periodic orbits of the second kind (elliptic orbits of the asteroid). One of them is stable and the other is unstable. All the families of periodic orbits of the circular and the elliptic problem are compared with the corresponding fixed points of the averaged model used by several authors. The coincidence is good for the fixed points of the circular averaged model and the two families of the fixed points of the elliptic model corresponding to the families I _c , II _c , but is poor for the families I _e , II _e . A simple correction term to the averaged Hamiltonian of the elliptic model is proposed in this latter case, which makes the coincidence good. This, in fact, is equivalent to the construction of a new dynamical system, very close to the original one, which is simple and whose phase space has all the basic features of the elliptic restricted three-body problem.     

Site Effect and its Relationship to the Intensity and Damage Observed in the June 27, 1998 Adana-Ceyhan Earthquake

The site response at 15 stations in the Adana-Ceyhan region (Southern Turkey) is calculated from the recordings of aftershocks of June 27, 1998 Adana-Ceyhan earthquake (M_S=6.2) by using the Standard Spectral Ratio (SSR) and the Horizontal-to-Vertical Spectral Ratio (HVSR) methods. While the two methods are in good harmony at a few stations in determining the site effects, they show differences on the estimated amplifications or on the site resonance frequencies at most stations. It was not clear which one of the two methods underestimates or overestimates the amplification values. We observe that at some stations, where the local site conditions are rather complex, the vertical component records are strongly influenced from the local soil conditions. Thus, the HVSR method fails at these stations. The SSR method underestimates the amplifications at some stations since the rock site, selected as reference site, has its own site response and/or the path correction we applied, considering the geometrical spreading factor only, is insufficient. At the sites where high intensity values were observed, we found high amplifications. The fundamental soil frequencies characterize the damage properties observed in the Adana-Ceyhan earthquake. The fundamental soil frequency is nearly at 1.1 Hz at the Ceyhan site, where severe damage was observed in the 5–6 story buildings, while the fundamental soil frequency is between 3–6 Hz at the Adana site, where damage was in the low-story buildings. Therefore, in addition to inefficient construction practices, it is clear that the resonance effects have also contributed to the observed damage.     

Stacking gravity tide observations in central Europe for the retrieval of the complex eigenfrequency of the nearly diurnal free-wobble

We have used tidal gravity measurements from six stations in central Europe to investigate the resonance in the diurnal tidal band, caused by inertial coupling between the mantle and outer core of the Earth. By the use of stacking it was possible to determine the eigenfrequency and quality factor of this eigenmode, commonly called the 'nearly diurnal free-wobble'. We assessed the effect of systematic errors from the ocean correction to the tidal measurements employing a Monte-Carlo method. The observed eigenfrequency is 1 + 1/(434 ± 7) cycles per sidereal day, and is significantly higher than predicted by theories. The observed quality factor is (2.8 ± 0.5) × 10³.     

Stability of resonant planetary orbits in binary stars

This paper contains a numerical study of the stability of resonant orbits in a planetary system consisting of two planets, moving under the gravitational attraction of a binary star. Its results are expected to provide us with useful information about real planetary systems and, at the same time, about periodic motions in the general four-body problem (G4) because the above system is a special case of G4 where two bodies have much larger masses than the masses of the other two (planets). The numerical results show that the main mechanism which generates instability is the destruction of the Jacobi integrals of the massless planets when their masses become nonzero and that resonances in the motion of planets do not imply, in general, instability. Considerable intervals of stable resonant orbits have been found. The above quantitative results are in agreement with the existing qualitative predictions     

The problem of critical inclination combined with a resonance in mean motion in artificial satellite theory

In this paper the two-degree of freedom problem of a geosynchronous artificial satellite orbiting near the critical inclination is studied. First a local approach of this problem is considered. A semi-numerical method, well suited to describe the perturbations of a non-trivial separable system, is then applied such that surfaces of section illustrating the global secular dynamics are obtained. The results are confirmed by numerical integrations of the full Hamiltonian.Research Assistant for the Belgian National Fund for Scientific Research