用极移数据直接测算钱德勒摆动Q值

运用已经发展起来的共振激发和参数共振模型,在频率调制的基础上,对IERS极移数据测算出钱德勒摆动的Q值,得到平均值为63,并以每百年0.8的速率在增大。这一结果与Q的滞弹性PREM模型理论值69十分接近,表明共振激发模型和参数共振模型完全与钱德勒摆动滞弹理论相容。     

椎管内肿瘤的高场MRI诊断

目的：观察市场ＭＲＩ地椎管内病变的诊断价值和影像特点。方法：回顾分析２５例椎客内肿瘤（髓内肿瘤７便,髓外人肿瘤１１例,硬膜外肿瘤７例）。结果：肿瘤最长径０．３￣１１ｃｍ,改天在颈胸段肿瘤（１７例）定位准确率为１００％,但马尾部肿瘤起地髓内外的判断有有一定的困难（７５％）,对椎管内肿瘤及明确病史转移瘤的定性确率达８４％。增强扫描有助于反映出椎管肿瘤特征及与周围结构关系。：结论：高场ＭＲ濉有更高的组织     

地面核磁共振感应系统(NUMIS)及其在找水中的应用

地面核磁共振找水技术是一种新的地球物理勘探技术,具有直接找水的特点.本文简述了该方法的原理、仪器及工作过程,并给出了两个应用实例来说明该方法的应用效果.     

Some Observations on the Changes of Physico-Chemical and Biological Factors in Victoria Harbour and Vicinity, Hong Kong, 1988–1996

This study analysed monthly physico-chemical and biological data collected from 18 marine monitoring stations in Victoria Harbour and its vicinity in Hong Kong, from 1988 to 1996. Cluster analysis based on all water quality parameters measured shows that the 18 monitoring stations can be grouped into four clusters: Cluster I consists of stations located in the Harbour proper; Cluster II consists of stations located west of the Harbour and along the Rambler Channel; Cluster III consists of stations located east of the Harbour near Junk Bay and Cluster IV consists of stations located west of the Harbour and near the Ma Wan, Kap Shui Mun and Western Fairways. Factor analysis shows high positive loadings for nutrients in the first two factors of the four clusters. This suggests that effluents from the 11 outfalls of sewage screening plants influence the water quality of Victoria Harbour and its vicinity. Other factors such as storm water runoff, marine traffic, construction and industrial activities and the Pearl River discharges also appear to play an important role in determining local water quality. Five stations located along an east–west transect across the Harbour were selected for trend analysis. The three stations located in the Harbour exhibit an increasing trend for temperature and levels of total phosphorus (TP), ortho-phosphate phosphorous (PO₄-P) and faecal bacteria and a decreasing trend for pH and levels of total nitrogen (TN), total kjeldahl-nitrogen (TKN), 5-day biochemical oxygen demand (BOD₅) and chlorophyll a. For the station located east of the Harbour, an increasing trend is observed for levels of TP, PO₄-P, but no decreasing trend in TN and TKN is detected. For the station located west of the Harbour, no decreasing trend in TN, TKN and chlorophyll a is observed. Changes in levels of phosphorus and nitrogen in Victoria Harbour and the immediate vicinity have led to significant increases in the ratios of Total Silica (TSi) to TN, as well as a decrease in TN to TP and TSi to TP in most stations. Results of the present study show that Victoria Harbour and its immediate vicinity remain polluted.     

Red-Pelaged Harbour Seals, in Humboldt County, California: why some Seals Rust

In this paper we present data on the occurrence of red-pelaged harbour seals, Phoca vitulina, at a haul-out in Humboldt County, California. Density of red seals ranged from 4% to 17.5% (n=21) and was comparable to that reported for San Francisco Bay, being the highest documented worldwide. The red colouration is the result of natural inorganic iron oxide/hydroxide pigments (limonite), which are present in small patches on the beach sand of the seals haul-out at the mouth of the Mad River. Thorough analysis of the river water and ocean water excluded these as possible sources for the iron oxide/hydroxide pigments. We found that the manmade reinforcement of the river bank adjacent to the haul-out consisted of greenshist boulders with a very high iron content. Weathering of these rocks produces red iron oxide/hydroxide particles which are then redeposited by rain or river action in small patches across the haul-out. Seals receive their red colouration through direct physical contact with these patches. SEM examination showed that these particles can adhere lastingly to the seals’ hair. Other studies provide reason for concern that this situation may detrimentally impact the seals’ health.     

Analytical Solution of the Kozai Resonance and its Application

When Kozai (1962) studied the secular resonance of asteroids, he found the so-called Kozai resonance and expressed the analytical solution with the use of Weierstrass ℘. Here we discuss the case where the disturber is outside a disturbed body and give the analytical solution of the eccentricity, the inclination and the argument of pericenter with the use of the Jacobi elliptic functions, which are more familiar than the Weierstrass ℘. Then we derive the Fourier expansion of the longitude of node and the mean anomaly. The analytical expressions obtained here can be used for any value of the eccentricity and the inclination. Finally we applied these analytical expressions to several dynamical systems – Nereid, that is a highly eccentric satellite of Neptune, and newly discovered retrograde satellites of Uranus. This revised version was published online in July 2006 with corrections to the Cover Date.     

Applications of the Mild-Slope Equation to Tidal Computations in the Taiwan Strait

Employing harmonic analysis of tidal data in the Taiwan Strait, the cross-strait tidal characteristics are completely illustrated. Based on the two dimensional mild-slope equation which can be reduced to the shallow-water wave equation, a finite element model (Tsay et al., 1989) is applied to investigate the characteristics of tides in the Taiwan Strait. The co-range and equi-phase charts of major tidal constituents, such as M₂, S₂, N₂, and K₁, are reproduced. Anomalous amplification of semidiurnal tides in the Taiwan Strait is verified. With rotation effects neglected and by applying a non-reflective condition on the open boundaries, the numerical results of phase-lag and co-range distributions show very good agreement with observed data for semidiurnal tides in the Taiwan Strait. Due to crude representation of the topography at two ends along the China coast, computed tidal distributions deviate from the observations. However, both computed amplitudes and phase-lags compare very well with observed data along the central half of the China coast.     

The 2/1 and 3/2 Resonant Asteroid Motion: A Symplectic Mapping Approach

A comparative study is made between the 2/1 and the 3/2 resonant asteroid motion, with the aim to understand their different behaviour (gap in the 2/1 resonance, group in the 3/2 resonance). A symplectic mapping model is used, for each of these two resonances, assuming the asteroid is moving in the three-dimensional space under the gravitational perturbation of Jupiter. It is found that these resonances differ in several points, and although there is, in general, more chaos in the phase space close to the 3/2 resonance, even in the model of circular orbit of Jupiter, there are regions, close to the secondary resonances, which are less chaotic in the 3/2 resonance compared to the 2/1 resonance, and consequently trapping can take place.     

共振在近地小行星轨道演化中的作用

本文采用了合理的力学模型和可靠的计算方法,研究了近地小行星轨道运动,揭示了共振（轨道共振和长期共振）在其轨道演化中的作用,并初步探讨了近地小行星的起源问题。     

冥王星轨道运动中的共振

在冥王星的运动中存在着三个共振（３：２平运动共振、Ｋｏｚａｉ共振以及１：１超级共振）。这三个共振保证了冥王星运动的稳定性。我们通过大量的数值模拟来探索三个共振在轨道根数空间的区域分布以及几颗大行星对它们的影响。结果证实了１：１超级共振为Ｋｏｚａｉ共振的次数共振,并表明了３：２共振是三者中最重要的,木星对三个共振的影响最大。