School-based environmental education in the context of a research and development project on integrated water resources management: experiences from Mongolia     

Daniel Karthe  Tobias Reeh  Michael Walther  Steffen Niemann  Alexander Siegmund 《Environmental Earth Sciences》2016,75(18):1286

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HARP/ACSIS: a submillimetre spectral imaging system on the James Clerk Maxwell Telescope     

J. V. Buckle  R. E. Hills  H. Smith  W. R. F. Dent  G. Bell  E. I. Curtis  R. Dace  H. Gibson  S. F. Graves  J. Leech †  J. S. Richer  R. Williamson ‡  S. Withington  G. Yassin †  R. Bennett  P. Hastings  I. Laidlaw  J. F. Lightfoot  T. Burgess  P. E. Dewdney  G. Hovey  A. G. Willis  R. Redman  B. Wooff  D. S. Berry  B. Cavanagh  G. R. Davis  J. Dempsey  P. Friberg  T. Jenness  R. Kackley  N. P. Rees §  R. Tilanus  C. Walther  W. Zwart  T. M. Klapwijk  M. Kroug  T. Zijlstra 《Monthly notices of the Royal Astronomical Society》2009,399(2):1026-1043

This paper describes a new Heterodyne Array Receiver Program (HARP) and Auto-Correlation Spectral Imaging System (ACSIS) that have recently been installed and commissioned on the James Clerk Maxwell Telescope. The 16-element focal-plane array receiver, operating in the submillimetre from 325 to 375 GHz, offers high (three-dimensional) mapping speeds, along with significant improvements over single-detector counterparts in calibration and image quality. Receiver temperatures are ∼120 K across the whole band, and system temperatures of ∼300 K are reached routinely under good weather conditions. The system includes a single-sideband (SSB) filter so these are SSB values. Used in conjunction with ACSIS, the system can produce large-scale maps rapidly, in one or more frequency settings, at high spatial and spectral resolution. Fully sampled maps of     size can be observed in under 1 h.
The scientific need for array receivers arises from the requirement for programmes to study samples of objects of statistically significant size, in large-scale unbiased surveys of galactic and extra-galactic regions. Along with morphological information, the new spectral imaging system can be used to study the physical and chemical properties of regions of interest. Its three-dimensional imaging capabilities are critical for research into turbulence and dynamics. In addition, HARP/ACSIS will provide highly complementary science programmes to wide-field continuum studies and produce the essential preparatory work for submillimetre interferometers such as the Submillimeter Array (SMA) and Atacama Large Millimeter/Submillimeter Array (ALMA).  相似文献   

Characterising and visualizing spatio-temporal patterns in hourly precipitation records     

Agne Burauskaite-Harju  Anders Grimvall  Christine Achberger  Alexander Walther  Deliang Chen 《Theoretical and Applied Climatology》2012,109(3-4):333-343

We develop new techniques to summarise and visualise spatial patterns of coincidence in weather events such as more or less heavy precipitation at a network of meteorological stations. The cosine similarity measure, which has a simple probabilistic interpretation for vectors of binary data, is generalised to characterise spatial dependencies of events that may reach different stations with a variable time lag. More specifically, we reduce such patterns into three parameters (dominant time lag, maximum cross-similarity, and window-maximum similarity) that can easily be computed for each pair of stations in a network. Furthermore, we visualise such three-parameter summaries by using colour-coded maps of dependencies to a given reference station and distance-decay plots for the entire network. Applications to hourly precipitation data from a network of 93 stations in Sweden illustrate how this method can be used to explore spatial patterns in the temporal synchrony of precipitation events.  相似文献   

Effects of mixed physical barrier on residual saltwater removal and groundwater discharge in coastal aquifers     

Mingpeng Gao  Tianyuan Zheng  Qinpeng Chang  Xilai Zheng  Marc Walther 《水文研究》2021,35(7):e14263

Physical barriers are widely used to control seawater intrusion (SWI). Amongst different kinds of physical barriers, mixed physical barriers (MPBs) are shown to be an effective approach to prevent SWI. However, the system may hinder the discharge of fresh groundwater and the removal of residual saltwater trapped in the inland aquifers of MPBs. Herein, using the validated numerical model, for the first time, we investigated the dynamics of residual saltwater and groundwater discharge after the installation of MPBs. For examining the applicability of MPB and its response to structural variations and hydraulic gradient, the comparison with traditional physical barriers and sensitivity analysis was also carried out. The MPB increased the mixing area of freshwater and saltwater at the beginning of the removal process, resulting in the reduction of the saltwater wedge length (R_L) by 74.6% and the removal of total salt mass (R_M) by 62.6% within the 4% of the total removal time. Meanwhile, the groundwater discharge (Q') rose rapidly after a sharp decline from 100% to 40% in the first stage. As the residual saltwater wedge was retreated, the mixing intensity and removal efficiency decreased substantially in the second stage. Similarly, Q' raised with a declining rate at this stage. The removal efficiency was positively correlated with wall depth and hydraulic gradient and there were optimal distance of the middle spacing and height of lower dam to reach the highest efficiency. The groundwater discharge reduced monotonously with the increase of dam height and wall depth as well as the decrease of barrier spacing and hydraulic gradient. Under certain conditions, the efficiency of MPB in removing residual saltwater could be 40%–100% and 0%–56% higher than that of traditional subsurface dam and cutoff wall, respectively. The laboratory scale conclusions provide valuable physical insight for the real field applications regarding dynamic mechanism and regularity. These findings will always help decision makers choose proper engineering measures and protect groundwater resources in coastal areas.  相似文献   

Far from equilibrium enstatite dissolution rates in alkaline solutions at earth surface conditions     

Sougata Halder  John V. Walther 《Geochimica et cosmochimica acta》2011,75(23):7486-7493

Far from equilibrium enstatite dissolution rates both open to atmospheric CO₂ and CO₂ purged were measured as a function of solution pH from 8 to 13 in batch reactors at room temperature. Congruent dissolution was observed after an initial period of incongruent dissolution with preferential Si release from the enstatite. Steady-state dissolution rates in open to atmospheric CO₂ conditions decrease with increase in solution pH from 8 to 12 similar to the behavior reported by other investigators. Judging from the pH 13 dissolution rate, rates increase with pH above pH 12. This is thought to occur because of the increase in overall negative surface charges on enstatite as Mg surface sites become negative above pH 12.4, the pH of zero surface charge of MgO.Steady-state dissolution rates of enstatite increase above pH 10 when CO₂ was purged by performing the experiments in a N₂ atmosphere. This suggests inhibition of dissolution rates above pH 10 when experiments were open to the atmosphere. The dissolved carbonate in these solutions becomes dominantly CO₃²⁻ above pH 10.33. It is argued that CO₃²⁻ forms a >Mg₂-CO₃ complex at positively charged Mg surface sites on enstatite, resulting in stabilization of the surface Si-O bonds. Therefore, removal of solution carbonate results in an increase in dissolution rates of enstatite above pH 10. The log rate of CO₂-purged enstatite dissolution in moles per cm² per s as a function of increasing pH above pH 10 is equal to 0.35. This is consistent with the model of silicate mineral dissolution in the absence of surface carbonation in alkaline solutions proposed earlier in the literature.  相似文献   

Geologie und Erdöl von Comodoro Rivadavia (Patagonien)     

Walther Schiller 《International Journal of Earth Sciences》1919,10(1-3):14-31

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Bücher- und Zeitschriftenschau     

Walther Penck  E. Kayser  Sal 《International Journal of Earth Sciences》1912,3(7):512-518

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Über die Ursachen der vulkanischen Ausbrüche     

Walther Karmin 《International Journal of Earth Sciences》1914,5(1):47-53

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Beobachtungen am Ostende des Erstfeldermassivs     

Walther Staub 《International Journal of Earth Sciences》1912,3(5-6):310-319

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Über Schichten-Zusammensinken in Patagonien infolge von Unterwaschung     

Walther Schiller 《International Journal of Earth Sciences》1924,15(3):215-223

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