Historical development in soil micromorphological imaging     

A.R.Mermut 《山地科学学报》2009,6(2):107-112

The book ＂micropedolog＂ by Kubieana and a large number of publications has induced many people to practice soil micromorphology. Quantification of the soil fabric and its components was a major challenge. The use of the image analyses in soil science was a breakthrough. Attempts to make soil thin sections go back to the beginning of the 2oth century. Microscopic techniques and recently high resolution electron microscope and use of computer assisted imaging techniques enabled the in vitro study of soils in three dimensional levels. It is now possible to store and process massive amounts of data. Micro- morphological concepts and techniques are applied in paleopedological, ecological, and archaeological studies. The aim of this work was to examine soil micromorphological imaging in historical perspective.  相似文献   

The Monitor project: rotation of low-mass stars in the open cluster NGC 2516     

Jonathan Irwin  Simon Hodgkin  Suzanne Aigrain  Leslie Hebb  Jerome Bouvier  Cathie Clarke  Estelle Moraux  D. M. Bramich 《Monthly notices of the Royal Astronomical Society》2007,377(2):741-758

  相似文献   

Magnetic fields in massive star-forming regions     

R. L. Curran  A. Chrysostomou 《Monthly notices of the Royal Astronomical Society》2007,382(2):699-716

We present the largest sample of high-mass star-forming regions observed using submillimetre imaging polarimetry. The data were taken using the Submillimetre Common User Bolometer Array (SCUBA) in conjunction with the polarimeter on the James Clerk Maxwell Telescope (JCMT) in Hawaii. In total, 16 star-forming regions were observed, although some of these contain multiple cores. The polarimetry implies a variety of magnetic field morphologies, with some very ordered fields. We see a decrease in polarization percentage for seven of the cores. The magnetic field strengths estimated for 14 of the cores, using the corrected Chandrasekhar and Fermi (CF) method, range from <0.1 mG to almost 6 mG. These magnetic fields are weaker on these large scales when compared to previous Zeeman measurements from maser emission, implying the role of the magnetic field in star formation increases in importance on smaller scales. Analysis of the alignment of the mean field direction and the outflow directions reveals no relation for the whole sample, although direct comparison of the polarimetry maps suggests good alignment (to at least one outflow direction per source) in seven out of the 15 sources with outflows.  相似文献   

Laboratory simulation experiments on the solid-state greenhouse effect in planetary ices     

Erika Kaufmann  Norbert I. Kömle  Günter Kargl 《Icarus》2006,185(1):274-286

Icy surfaces like the polar caps of Mars, comets, Edgeworth-Kuiper belt objects or the surface areas of many moons in the outer Solar System behave different than rock and soil surfaces when irradiated by solar light. The latter ones absorb and reflect incoming solar radiation immediately at the surface. In contrast, ices are partially transparent in the visible spectral range and opaque in the infrared. Due to this fact it is possible for the solar radiation to reach a certain depth and increase the temperature of the sub-surface layers directly. This internal temperature rise is called “solid-state greenhouse effect,” in analogy to the classical greenhouse effect in an atmosphere. It may play an important role in the energy balance of various icy bodies in the Solar System. Within the scope of a project conducted at the Space Research Institute of the Austrian Academy of Sciences in Graz the solid-state greenhouse effect was investigated experimentally and theoretically. A number of experiments with diverse materials, focussing mainly on layered samples with a surface cover consisting of transparent H₂O-ice, were performed. The samples were irradiated under cryo-vacuum conditions by a solar simulator. The temperature distributions inside the samples were measured and compared with the results of numerical model calculations. We found that the predicted sub-surface temperature maximum is very clearly measurable in glass beads samples with various particle size distributions, but can also be detected in transparent compact surface ice layers. However, in the latter case it is less distinct than originally expected. Measuring the effect by laboratory methods turned out to be a difficult task due to the shallow depth where the temperature maximum occurs.  相似文献   

站式全景遥感影像展示方法与应用技术研究     

梁冰  杜萌  姚远  刘建华  杜明义 《地理信息世界》2015,(1):86-90

虚拟漫游技术已成功应用到社会各个领域,传统漫游技术如VRML(Virtual Reality Modeling Language)、Quick Time、PTGui(Panorama Tools)等存在集成难度大、建模时间长、投入成本高等问题。本文基于全景相机以及Pano2vr、Dynamic-Photo HDR、Photoshop等软硬件环境,研发搭建了一整套旅游景区全景影像采集与展示平台。该平台具有良好的沉浸性、多视角浏览、实现方法简单、搭建快速等优点,为旅游景点、酒店、历史文化名胜等场景的360度实景展示提供了有效地工程化解决途径。  相似文献   

A uvbyβ photometric analysis of the Monoceros star‐forming field     

N. Kaltcheva  A. Kuchera  C. Hathaway 《Astronomische Nachrichten》2010,331(4):384-396

This investigation presents a new analysis of the spatial distribution of the bright early‐type stars in the field of Northern Monoceros. A database of all O–B9 stars with available uvbyβ photometry is collated and a homogeneous distance scale is established for the clusters and layers of field stars. We provide revised distances for NGC 2264 and NGC 2244 of 833±38 (s.e.) pc and 1585±60 (s.e.) pc, respectively. We present arguments that there might be substructures in the clusters projected along the line of sight. According to the present sample the classical Mon OB2 association at 1.6 kpc is represented by a relatively compact group at 1.26 kpc in the vicinity of NGC 2244 and a layer of massive stars located between 1.5 and 3 kpc (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

High‐fidelity spectroscopy at the highest resolutions     

D. Dravins 《Astronomische Nachrichten》2010,331(5):535-540

High‐fidelity spectroscopy presents challenges for both observations and in designing instruments. High‐resolution and high‐accuracy spectra are required for verifying hydrodynamic stellar atmospheres and for resolving intergalactic absorption‐line structures in quasars. Even with great photon fluxes from large telescopes with matching spectrometers, precise measurements of line profiles and wavelength positions encounter various physical, observational, and instrumental limits. The analysis may be limited by astrophysical and telluric blends, lack of suitable lines, imprecise laboratory wavelengths, or instrumental imperfections. To some extent, such limits can be pushed by forming averages over many similar spectral lines, thus averaging away small random blends and wavelength errors. In situations where theoretical predictions of lineshapes and shifts can be accurately made (e.g., hydrodynamic models of solar‐type stars), the consistency between noisy observations and theoretical predictions may be verified; however this is not feasible for, e.g., the complex of intergalactic metal lines in spectra of distant quasars, where the primary data must come from observations. To more fully resolve lineshapes and interpret wavelength shifts in stars and quasars alike, spectral resolutions on order R = 300 000 or more are required; a level that is becoming (but is not yet) available. A grand challenge remains to design efficient spectrometers with resolutions approaching R = 1 000 000 for the forthcoming generation of extremely large telescopes (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

EST Adaptive optics performance estimations     

T. Berkefeld  D. Soltau 《Astronomische Nachrichten》2010,331(6):640-643

We give a short overview of the Adaptive Optics (AO) and Multi‐conjugate Adaptive Optics (MCAO) system of the planned 4 m European Solar Telescope (EST). The optimization process of the AO / MCAO parameters is shown, including the parameters and layout of the Shack‐Hartmann wavefront sensor setup and the DMs. We show the expected performance of the AO and MCAO system (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

A synoptic program for large solar telescopes: Cyclic variation of turbulent magnetic fields     

L. Kleint  S.V. Berdyugina  D. Gisler  A.I. Shapiro  M. Bianda 《Astronomische Nachrichten》2010,331(6):644-647

Upcoming large solar telescopes will offer the possibility of unprecedented high resolution observations. However, during periods of non‐ideal seeing such measurements are impossible and alternative programs should be considered to best use the available observing time. We present a synoptic program, currently carried out at the Istituto Ricerche Solari Locarno (IRSOL), to monitor turbulent magnetic fields employing the differential Hanle effect in atomic and molecular lines. This program can be easily adapted for the use at large telescopes exploring new science goals, nowadays impossible to achieve with smaller telescopes. The current, interesting scientific results prove that such programs are worthwhile to be continued and expanded in the future. We calculate the approximately achievable spatial resolution at a large telescope like ATST for polarimetric measurements with a noise level below 5 × 10^‐5 and a temporal resolution which is sufficient to explore variations on the granular scale. We show that it would be important to optimize the system for maximal photon throughput and to install a high‐speed camera system to be able to study turbulent magnetic fields with unprecedented accuracy (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Quantitative solar spectroscopy     

K. Wilhelm 《Astronomische Nachrichten》2010,331(5):502-511

Quantitative solar spectroscopy must be based on calibrated instrumentation. The basic requirement of a calibration, i.e., a comparison between the instrument under test and a primary laboratory standard through appropriate procedures, will be briefly reviewed, and the application to modern space instruments will be illustrated. Quantitative measurements of spectral radiances with high spectral and spatial resolutions as well as spectral irradiances yield detailed information on temperatures, electron densities, bulk and turbulent motions, element abundances of plasma structures in various regions of the solar atmosphere – from the photosphere to the outer corona and the solar wind. The particular requirements for helioseismology and magnetic‐field observations will not be covered in any depth in this review. Calibration by a laboratory standard is necessary, but not sufficient, because an adequate radiometric stability can only be achieved together with a stringent cleanliness concept that rules out a contamination of the optical system and the detectors as much as possible. In addition, there is a need for calibration monitoring through inter‐calibration and other means (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献