A Comparison between WCS and OPeNDAP for Making Model Results and Data Products Available through the Internet

Numerical models produce output with a large number of variables, grid cells and time steps. The same applies to algorithms that produce gridded datasets from sparse or abundant raw data. Further use of the resulting data products has been challenging, especially for dissemination outside the institute of origin. Due to the gradually increasing size of data products, simply downloading copies of them is becoming impossible. A gradual transition from traditional download methods to web services is therefore observed. Web services allow for on‐the‐fly access to subsets of data that were hitherto considered as indivisible granules. Here we compare the most mature candidates to serve gridded data through the web: the Open‐source Project for a Network Data Access Protocol (OPeNDAP) and Web Coverage Service (WCS) protocols. In the framework of the new Dutch National Model and Data Centre (NMDC.eu) a distributed data storage has been created by coupling OPeNDAP servers. A WCS service layer is provided for the same data. This allows us to compare OPeNDAP and WCS. Using several use cases, we compare the usability, performance and features of the two protocols.     

地球重力模型及中国大陆重力场的计算

融多颗卫星数据、地面重力值和其它资料一起的地球重力模型EGM 96 ,为研究中国大陆的重力场及相关问题提供了一个高精度 36 0阶的球谐系数。在分析EGM 96的基础上 ,计算并简单解释了中国大陆的自由空气异常和布格重力异常。计算所得重力场的精度和分辨率大大高于常用的1∶140 0 0 0 0 0自由空气异常图及布格重力图     

Wrench tectonics flip at oblique subduction. A model from New Zealand

In eastern North Island New Zealand, oblique subduction of the Pacific Plate beneath the Australian Plate is associated with strain partitioning. Dextral along-strike component of displacement occurred first at Early Miocene major faults within the eastern fore-arc domain. These faults were active from Early Miocene to Pliocene times. Since Pliocene times, most of the movement occurs at western faults such as the Wellington Fault. The latter joins the back-arc domain to the north. The jump of wrench faulting is related to the oblique opening of the back-arc domain. Both phenomena are impeded southwards by the Hikurangi oceanic plateau entering the subduction zone. To cite this article: J. Delteil et al., C. R. Geoscience 335 (2003).     

Times of sand: Sedimentary history and archaeology at the Sigatoka Dunes,Fiji

The orthodox archaeological sequence at the Sigatoka Dunes site (VL 16/1) in Fiji proposes three phases of occupation spanning Fijian prehistory, each associated with a period of dune stability. It has been taken as the standard model of Fijian prehistory for more than 30 years. Recently, however, it has been argued that there is no stratigraphic support for three discrete levels and that the occupation history was fragmented, complex, and continuous within a volatile dune system. We present new data, from optical and radiocarbon dating, to argue that a three‐phase model, although somewhat more complex in detail, remains the most robust interpretation of site history. The longest stable phase (Level 2) began 2500–2300 cal yr B.P. and is possibly associated with relatively low ENSO frequency. Substantial sand dune accumulation began after ˜1300 cal yr B.P. © 2006 Wiley Periodicals, Inc.     

国际冰芯与气候环境研究新进展--关于国际冰芯与气候会议

2001年8月19～23日, 在格陵兰举行了规模空前的冰芯与气候国际盛会, 会议展示了冰芯与气候环境研究的最新进展. 文中介绍这次会议并概括了近年来的主要研究进展. 与南北极地区的冰芯研究相比, 中低纬度地区冰芯研究是近年来国际冰芯研究中发展最快的. 在这一研究中, 中国科学家做出了重要贡献并得到了国际同行的高度评价.     

Polycyclic aromatic hydrocarbon lifetime in cometary environments

Observations of cometary comae in the infrared and in the near-ultraviolet suggest that polycyclic aromatic hydrocarbons (PAHs) are present in these environments. However, the chemical identity and abundance of these molecules are not clearly determined yet. Some species are probably more stable than others when submitted to the solar radiation field, and are therefore more likely to be observed. The photophysics of gas-phase PAHs in cometary environments is modelled. Photodissociation occurs when the heating by absorption of UV photons is more efficient than the radiative cooling. The lifetime of the molecules is found to depend on their size: small molecules being more stable than large ones. Furthermore, at 1 AU from the Sun, the lifetime of PAHs is found to be very short (20s for phenanthrene). This suggests that, if observed in the gas phase in cometary environments, these molecules should be produced by an extended source.     

An OLS regression model for context-aware tile prefetching in a web map cache

The increasing popularity of web map services has motivated the development of more scalable services in the spatial data infrastructures. Tiled map services have emerged as a scalable alternative to traditional map services. Instead of rendering map images on the fly, a collection of pre-generated image tiles can be served very fast from a server-side cache. However, during the start-up of the service, the cache is initially empty and users experience a poor quality of service. Tile prefetching attempts to improve hit rates by proactively fetching map images without waiting for client requests.

While most popular prefetching policies in traditional web caching consider only the previous access history to make predictions, significant improvements could be achieved in web mapping by taking into account the background geographic information.

This work proposes a regressive model to predict which areas are likely to be requested in the future based on spatial cross-correlation between an unconstrained catalog of geographic features and a record of past cache requests. Tiles that are anticipated to be most frequently requested can be pre-generated and cached for faster retrieval. Trace-driven simulations with several million cache requests from two different nation-wide public web map services in Spain demonstrate that accurate predictions and performance gains can be obtained with the proposed model.     

DEPENDENCE BETWEEN FUSION TEMPERATURES AND CHEMICAL COMPONENTS OF A CERTAIN TYPE OF COAL USING CLASSICAL,NON-PARAMETRIC AND BOOTSTRAP TECHNIQUES

A statistical study of the dependence between various critical fusion temperatures of a certain kind ofcoal and its chemical components is carried out.As well as using classical dependence techniques(multiple,stepwise and PLS regression,principal components,canonical correlation,etc.)together withthe corresponding inference on the parameters of interest,non-parametric regression and bootstrapinference are also performed.     

Segmentation and kinematics of the North America‐Caribbean plate boundary offshore Hispaniola

We explored the submarine portions of the Enriquillo–Plantain Garden Fault zone (EPGFZ) and the Septentrional–Oriente Fault zone (SOFZ) along the Northern Caribbean plate boundary using high‐resolution multibeam echo‐sounding and shallow seismic reflection. The bathymetric data shed light on poorly documented or previously unknown submarine fault zones running over 200 km between Haiti and Jamaica (EPGFZ) and 300 km between the Dominican Republic and Cuba (SOFZ). The primary plate‐boundary structures are a series of strike‐slip fault segments associated with pressure ridges, restraining bends, step overs and dogleg offsets indicating very active tectonics. Several distinct segments 50–100 km long cut across pre‐existing structures inherited from former tectonic regimes or bypass recent morphologies formed under the current strike‐slip regime. Along the most recent trace of the SOFZ, we measured a strike‐slip offset of 16.5 km, which indicates steady activity for the past ~1.8 Ma if its current GPS‐derived motion of 9.8 ± 2 mm a^?1 has remained stable during the entire Quaternary.     

A review of new interpretations of the tectonostratigraphy,geochemistry and evolution of the Onverwacht Suite,Barberton Greenstone Belt,South Africa

The Paleoarchean (ca. 3.5–3.3 Ga) Onverwacht Suite (OS) of the Barberton Greenstone Belt consists of a 15‐km thick imbricate tectonic stack of seven complexes consisting predominantly of volcanic rocks and intrusions. Tectonostratigraphically from base to top they are the Sandspruit, Theespruit, Komati, Hooggenoeg, Noisy, Kromberg and Mendon Complexes. The Hooggenoeg and Noisy Complexes in the middle of the OS are separated by a significant unconformity resulting from the uplift of the submarine lavas and deep erosion, demonstrating the onset of tectonic accretion prior to 3455 Ma. The basic lavas of the tectonostratigraphic lower (Theespruit, Sandspruit and Komati) and upper (Mendon) complexes are composed of komatiite, komatiitic basalt and high-MgO basalt, whereas those in the middle part (Hooggenoeg and Kromberg) are predominantly high- to low-MgO tholeiitic basalts. Felsic volcanic rocks and intrusions are important in two of the complexes (Theespruit and Noisy). The ultramafic to basaltic lavas show REE patterns that are almost flat and resemble those of modern MORB, whereas those of the felsic rocks are flat from Lu to Gd and moderately to strongly enriched in LREE, similar to modern arcs. Average ε_{Nd (T)} values are close to depleted mantle growth curves. In MORB-normalised multi-element diagrams, the komatiitic to basaltic rocks exhibit flat patterns from Lu through La and consistent relative enrichment in the elements Pb, U, Th, Ba and Cs. Apart from the Komati Complex, the majority of the lavas show significant negative Nb and Ta anomalies. Enrichment in non-conservative incompatible elements (Cs, Ba, Th, LREE) relative to conservative elements (Ta, Nb, Zr, Hf, Ti, Y, HREE) shows that the komatiitic to basaltic magmas were generated from metasomatised mantle above subducting altered oceanic crust. The geochemistry of the felsic rocks indicates an origin by melting of subducted amphibolite and eclogite. The tectonostratigraphy and the geochemical characteristics of the lavas and intrusions are consistent with successive obduction and accretion of segments of oceanic crust formed in back-arc basins and volcanic arcs.