Preface: The Chang'e-3 lander and rover mission to the Moon     

Wing-Huen Ip  Jun Yan  Chun-Lai Li  Zi-Yuan Ouyang 《中国天文和天体物理学报》2014,(12)

The Chang'e-3(CE-3) lander and rover mission to the Moon was an intermediate step in China's lunar exploration program, which will be followed by a sample return mission. The lander was equipped with a number of remote-sensing instruments including a pair of cameras(Landing Camera and Terrain Camera) for recording the landing process and surveying terrain, an extreme ultraviolet camera for monitoring activities in the Earth's plasmasphere, and a first-ever Moon-based ultraviolet telescope for astronomical observations. The Yutu rover successfully carried out close-up observations with the Panoramic Camera, mineralogical investigations with the VIS-NIR Imaging Spectrometer, study of elemental abundances with the Active Particle-induced X-ray Spectrometer, and pioneering measurements of the lunar subsurface with Lunar Penetrating Radar. This special issue provides a collection of key information on the instrumental designs, calibration methods and data processing procedures used by these experiments with a perspective of facilitating further analyses of scientific data from CE-3 in preparation for future missions.  相似文献   

Cosmic Rays and Clusters of Galaxies     

W.-H. Ip  W.I. Axford 《Astrophysics and Space Science》1998,264(1-4):437-442

The presence of a significant population of relic relativistic electrons - created at an early epoch of the Universe - has been invoked to explain the diffuse EUV emission excess observed in a number of galaxy clusters. While the postulated inverse Compton scattering of the 3° K background radiation by cosmic ray electrons might indeed be utilized as an important diagnostic tool for the physical nature of the intracluster cosmic rays, it is shown here that continuous generation plus reacceleration would be necessary if the conditions on the observed energy spectral distribution and energy supply rate are to be met in the case of clusters with large radio halos. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The spatial and temporal distribution of heavy metals in sediments of Victoria Harbour, Hong Kong   总被引：2，自引：0，他引：2  

Tang CW  Ip CC  Zhang G  Shin PK  Qian PY  Li XD 《Marine pollution bulletin》2008,57(6-12):816-825

Victoria Harbour has received substantial loadings of pollutants from industrial and municipal wastewater discharged since the 1950s. Inputs of contaminants have declined dramatically during the last two decades as a result of better controls at the source and improved wastewater treatment facilities. To assess the spatial and temporal changes of metal contaminants in sediments in Victoria Harbour, core and grab sediments were collected. The central harbour areas were generally contaminated with heavy metals. The spatial distribution of trace metals can probably be attributed to the proximity of major urban and industrial discharge points, and to the effect of tidal flushing in the harbour. In the sediment cores, the highest concentrations of trace metals were observed to have accumulated during the 1950s-1980s, corresponding with the period of rapid urban and industrial development in Hong Kong. From the late 1980s, there has been a major decline in the concentrations of trace metals, due to a reduction in industrial activities and to the enactment of wastewater pollution controls in the territory. The Pb isotopic compositions of the sediments revealed the anthropogenic inputs of Pb to the harbour. The (206)Pb/(207)Pb ratios varied from 1.154 to 1.190, which were lower than those of background geological materials in Hong Kong ((206)Pb/(207)Pb: 1.201-1.279). The data also indicated that the Pb in the harbour sediments most likely originated from mixed sources, including the leaded gasoline used in the past and other anthropogenic sources.  相似文献   

Extreme Ultraviolet Photon-Induced Chemical Reactions in the C₂H₂-H₂O Mixed Ices at 10 K     

C.Y. Robert WuD.L. Judge  Bing-Ming ChengWen-Hao Shih  Tai-Sone YihW.H. Ip 《Icarus》2002,156(2):456-473

Experimental results on the spectral identification of new infrared absorption features and the changes of their absorbances produced through vacuum ultraviolet-extreme ultraviolet (VUV-EUV) photon-induced chemical reactions in the C₂H₂-H₂O mixed ices at 10 K are obtained. To the best of our knowledge, this is the first time that EUV photons have been employed in the study of the photolysis of ice analogues. Two different compositions, i.e., C₂H₂:H₂O=1:4 and 1:1, were investigated in this work. A tunable intense synchrotron radiation light source available at the Synchrotron Radiation Research Center, Hsinchu, Taiwan, was employed to provide the required VUV-EUV photons. In this study, the photon wavelengths selected to irradiate the icy samples corresponded to the prominent solar hydrogen, helium, and helium ion lines at 121.6 nm, 58.4 nm, and 30.4 nm, respectively. The photon dosages used were typically in the range of 1×10¹⁵ to 2×10¹⁷ photons. Molecular species produced and identified in the ice samples at 10 K resulting from VUV-EUV photon irradiation are mainly CO, CO₂, CH₄, C₂H₆, CH₃OH, and H₂CO. In addition to several unidentified features, we have tentatively assigned several absorption features to HCO, C₃H₈, and C₂H₅OH. While new molecular species were formed, the original reactants, i.e., H₂O and C₂H₂, were detectably depleted due to their conversion to other species. The new chemical species produced by irradiation of photons at 30.4 nm and 58.4 nm can be different from those produced by the 121.6-nm photolysis. In general, the product column density of CO reaches saturation at a lower photon dosage than that of CO₂. Furthermore, the production yield of CO is higher than that of CO₂ in the photon irradiation. In the present study, we also observe that the photon-induced chemical reaction yields are high using photons at 30.4 and 58.4 nm. The results presented in this work are essential to our understanding of chemical synthesis in ice analogues, e.g., the cometary-type ices and icy satellites of planetary systems.  相似文献   

An search for X-ray emission from comet Bradfield (1979l)     

H. S. Hudson  W. -H. Ip  D. A. Mendis 《Planetary and Space Science》1981,29(12)

X-radiation may result from active plasma phenomena in the interactions of comets with the solar wind. We have carried out a limited but sensitive search for soft X-radiation from Comet Bradfield (1979 ), on 1980 Feb. 5. No X-radiation was detected at a level (3σ) of 1.7 × 10⁻¹³ erg(cm²sec keV)⁻¹ in the 0.2 – 4.0 kev range. This corresponds to a limit on the power dissipated in the comet by non-thermal electrons of approximately 10¹⁹ ergs sec⁻¹, averaged over the 2568-sec exposure to the comet. This energy deposition is near the magnitude suggested by simple theoretical ideas, and further searches of appropriate comets both in soft X-radiation and at radio wavelengths seem warranted.  相似文献   

Some dynamical aspects of the accretion of Uranus and Neptune: The exchange of orbital angular momentum with planetesimals     

J.A. Fernández  W.-H. Ip 《Icarus》1984,58(1):109-120

The final stage of the accretion of Uranus and Neptune is numerically investigated. The four Jovian planets are considered with Jupiter and Saturn assumed to have reached their present sizes, whereas Uranus and Neptune are taken with initial masses 0.2 of their present ones. Allowance is made for the orbital variation of the Jovian planets due to the exchange of angular momentum with interacting bodies (“planetesimals”). Two possible effects that may have contributed to the accretion of Uranus and Neptune are incorporated in our model: (1) an enlarged cross section for accretion of incoming planetesimals due to the presence of extended gaseous envelopes and/or circumplanetary swarms of bodies; and (2) intermediate protoplanets in mid-range orbits between the Jovian planets. Significant radial displacements are found for Uranus and Neptune during their accretion and scattering of planetesimals. The orbital angular momentum budgets of Neptune, Uranus, and Saturn turn out to be positive; i.e., they on average gain orbital angular momentum in their interactions with planetesimals and hence they are displaced outwardly. Instead, Jupiter as the main ejector of bodies loses orbital angular momentum so it moves sunward. The gravitational stirring of planetesimals caused by the introduction of intermediate protoplanets has the effect that additional solid matter is injected into the accretion zones of Uranus and Neptune. For moderate enlargements of the radius of the accretion cross section (2–4 times), the accretion time scale of Uranus and Neptune are found to be a few 10⁸ years and the initial amount of solid material required to form them of a few times their present masses. Given the crucial role played by the size of the accretion cross section, questions as to when Uranus and Neptune acquired their gaseous envelopes, when the envelopes collapsed onto the solid cores, and how massive they were are essential in defining the efficiency and time scale of accretion of the two outer Jovian planets.  相似文献   

Seemingly unrelated intervention time series models for effectiveness evaluation of large scale environmental remediation     

Ryan H.L. Ip  W.K. Li  Kenneth M.Y. Leung 《Marine pollution bulletin》2013

Large scale environmental remediation projects applied to sea water always involve large amount of capital investments. Rigorous effectiveness evaluations of such projects are, therefore, necessary and essential for policy review and future planning. This study aims at investigating effectiveness of environmental remediation using three different Seemingly Unrelated Regression (SUR) time series models with intervention effects, including Model (1) assuming no correlation within and across variables, Model (2) assuming no correlation across variable but allowing correlations within variable across different sites, and Model (3) allowing all possible correlations among variables (i.e., an unrestricted model). The results suggested that the unrestricted SUR model is the most reliable one, consistently having smallest variations of the estimated model parameters. We discussed our results with reference to marine water quality management in Hong Kong while bringing managerial issues into consideration.  相似文献   

Source dependency of exospheric sodium on Mercury     

Y.-C. Wang  W.-H. Ip 《Icarus》2011,216(2):387-402

Due to a large solar radiation effect, the sodium exosphere exhibits many interesting effects, including the formation of an extended corona and a tail-like structure. The current suite of observations allows us to study some physical properties of the sodium exosphere, such as the source rates and the interaction with the surface, both experimentally and theoretically. In order to quantify the complex variations in the sodium exosphere in more detail, we use an exospheric model with the Monte-Carlo method to examine the surface interactions of a sodium atom, including the surface thermal accommodation rate and the sticking coefficient. The source rates from different components, such as the photon stimulated desorption (PSD), the meteoroid impact vaporization (MIV), and the solar wind ion sputtering (IS), can be constrained by comparing our exospheric model calculations with the published observational data. The detected terminator to limb (TL) ratio on the disk and the tail production rate can be explained with no sticking effect and small thermal accommodation rates. We also examine the best fit of the MIV source evolution, through comparison with the disk-averaged emission. The resultant discrepancy between the observations and the model fit may reflect the surface variation in the sodium abundance. A comprehensive mapping of the surface geochemical composition of the surface by the MESSENGER and Bepi-Colombo missions should give us more information about the nature of this surface-bound exosphere.  相似文献   

Evolution of anisotropy with saturation and its implications for the elastoplastic responses of clay rocks     

Sabrina C.Y. Ip  Ronaldo I. Borja 《国际地质力学数值与分析法杂志》2022,46(1):23-46

Many clay rocks have distinct bedding planes. Experimental studies have shown that their mechanical properties evolve with the degree of saturation (DOS), often with higher stiffness and strength after drying. For transversely isotropic rocks, the effects of saturation can differ between the bed-normal (BN) and bed-parallel (BP) directions, which gives rise to saturation-dependent stiffness and strength anisotropy. Accurate prediction of the mechanical behavior of clay rocks under partially saturated conditions requires numerical models that can capture the evolving elastic and plastic anisotropy with DOS. In this study, we present an anisotropy framework for coupled solid deformation-fluid flow in unsaturated elastoplastic media. We incorporate saturation-dependent strength anisotropy into an anisotropic modified Cam-Clay (MCC) model and consider the evolving anisotropy in both the elastic and plastic responses. The model was calibrated using experimental data from triaxial tests to demonstrate its capability in capturing strength anisotropy at various levels of saturation. Through numerical simulations, we demonstrate the role of evolving stiffness and strength anisotropy in the mechanical behavior of clay rocks. Plane strain simulations of triaxial compression tests were also conducted to demonstrate the impacts of material anisotropy and DOS on the mechanical and fluid flow responses.  相似文献