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  • Articles  (136)
  • Geosciences  (135)
  • Architecture, Civil Engineering, Surveying  (3)
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  • Articles  (136)
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  • 1
    Publication Date: 2016-05-12
    Description: This paper describes a new genus Liaous , with L. shaiwensis He and Chen n. gen. n. sp. as the type species, from the Xinyuan Formation of Anisian age in Ziyun, southern Guizhou, China. The phylogenetic tree revealed by the parsimony analysis shows that Liaous is closely allied to both Mentzelia Quenstedt, 1871 and Paramentzelia Xu, 1978 of the subfamily Mentzeliinae. A new classification scheme for the Spiriferinoidea is also proposed based on a phylogenetic tree of the superfamily indicated by parsimony analysis. The Spiriferinoidea includes three families and nine subfamilies. Three new subfamilies—Madoinae He and Chen, new subfam., Qinghaispiriferininae He and Chen, new subfam., and Triadispirinae He and Chen, new subfam. are proposed. Liaous shaiwensis He and Chen n. gen. n. sp. is found in the Posidonia wengensis - Liaous shaiwensis (P-L) paleocommunity, which is dominated by r-strategists (i.e., organisms defined by a fauna with a high dominance and small body sizes) and has a low diversity and high dominance. The P-L paleocommunity therefore has little similarity to its coeval communities from the Anisian Stage of South China and instead it appears more similar to the Lower Triassic shelly faunas in community structures. This paleocommunity is interpreted to have inhabited a relatively deep, low-energy, dysaerobic offshore basin/slope setting with the influence of episodic storms.
    Print ISSN: 0022-3360
    Electronic ISSN: 1937-2337
    Topics: Geosciences
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  • 2
    Publication Date: 2011-03-30
    Description: The capability of Weather Research and Forecasting (WRF) model in the simulation of cirrus clouds has been examined, with a focus on the effects of radiative processes and vertical model resolution. We incorporate in WRF a new radiation module, referred to as the Fu-Liou-Gu scheme, which is an improvement and refinement based on the Fu-Liou scheme, particularly in reference to parameterization of the single-scattering properties of ice crystal size and shape. We conducted a number of real-time WRF simulations for cirrus cases that were observed in the coastal and western United States on 29–30 March 2007, and we compared these with available observations from Moderate Resolution Imaging Spectroradiometer (MODIS) and GOES visible and IR images over the same areas. Simulation results show that WRF is capable of generating reasonable cirrus cloud fields and their movement and dissipation processes, especially those associated with the large-scale frontal system. Radiative processes are important in cirrus cloud simulations by affecting the vertical thermal structure and hence convection. The newly implemented radiation module, the Fu-Liou-Gu scheme, has been demonstrated to work well in WRF and can be effectively used for studies related to cirrus cloud formation and evolution and aerosol-cloud-radiation interactions. With the newly implemented radiation scheme, the simulations of cloud cover and cloud and ice water path (CWP and IWP) have been improved for cirrus clouds, with a more consistent comparison with the corresponding MODIS observations in terms of CWP and IWP means and CWP frequency distribution, especially for optically thin cirrus with an improvement of about 20% in simulated mean IWP. The model-simulated ice crystal sizes have also been shown to be comparable to those determined from MODIS cloud products. Finally, we have demonstrated that model vertical resolution plays a significant role in cirrus cloud simulation in terms of altering vertical velocity field and the associated regional circulation.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Publication Date: 2019
    Description: Abstract Severe geomagnetic storms caused by the solar wind disturbances have harmful influences on the operation of modern equipment and systems. The modeling and forecasting of AE index are extremely useful to understand the geomagnetic substorms. This study presents a novel cloud‐nonlinear autoregressive with exogenous input (NARX) model to predict AE index 1 hr ahead. The cloud‐NARX model provides AE index forecasting results, with a correlation coefficient of 0.87 on the data of whole year 2015. The benchmarks on the data of the two interested periods of 17–21 March 2015 and 22–26 June 2015 are presented. The presented model uses uncertainty “cloud” model and cloud transformation to quantify the uncertainty throughout the structure detection, parameter estimation, and model prediction. The new predicted band can be generated to forecast AE index with confidence interval. The proposed method provides a new way to evaluate the model based on uncertainty analysis, revealing the reliability of model, and visualize the bias of model prediction.
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
    Publication Date: 2019
    Description: Abstract Severe geomagnetic storms caused by the solar wind disturbances have harmful influences on the operation of modern equipment and systems. The modeling and forecasting of AE index are extremely useful to understand the geomagnetic substorms. This study presents a novel cloud‐nonlinear autoregressive with exogenous input (NARX) model to predict AE index 1 hr ahead. The cloud‐NARX model provides AE index forecasting results, with a correlation coefficient of 0.87 on the data of whole year 2015. The benchmarks on the data of the two interested periods of 17–21 March 2015 and 22–26 June 2015 are presented. The presented model uses uncertainty “cloud” model and cloud transformation to quantify the uncertainty throughout the structure detection, parameter estimation, and model prediction. The new predicted band can be generated to forecast AE index with confidence interval. The proposed method provides a new way to evaluate the model based on uncertainty analysis, revealing the reliability of model, and visualize the bias of model prediction.
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
    Publication Date: 2016-11-22
    Description: Nowadays, with the development of high resolution remote sensing image and the wide application of laser point cloud data, proceeding objected-oriented remote sensing classification based on the characteristic knowledge of multi-source spatial data has been an important trend on the field of remote sensing image classification, which gradually replaced the traditional method through improving algorithm to optimize image classification results. For this purpose, the paper puts forward a remote sensing image classification method that uses the he characteristic knowledge of multi-source spatial data to build the geographic ontology semantic network model, and carries out the objected-oriented classification experiment to implement urban features classification, the experiment uses protégé software which is developed by Stanford University in the United States, and intelligent image analysis software—eCognition software as the experiment platform, uses hyperspectral image and Lidar...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 6
    Publication Date: 2014-06-03
    Description: A stochastic approach has been developed to model the positions of BC/dust internally mixed with two snow-grain types: hexagonal plate/column (convex) and Koch snowflake (concave). Subsequently, light absorption and scattering analysis can be followed by means of an improved geometric-optics approach coupled with Monte Carlo photon tracing to determine BC/dust single-scattering properties. For a given shape (plate, Koch snowflake, spheroid, or sphere), the action of internal mixing absorbs substantially more light than external mixing. The snow-grain shape effect on absorption is relatively small, but its effect on asymmetry factor is substantial. Due to a greater probability of intercepting photons, multiple inclusions of BC/dust exhibit a larger absorption than an equal-volume single inclusion. The spectral absorption (0.2 – 5  μ m) for snow grains internally mixed with BC/dust is confined to wavelengths shorter than about 1.4  μ m, beyond which ice absorption predominates. Based on the single-scattering properties determined from stochastic and light absorption parameterizations and using the adding/doubling method for spectral radiative transfer, we find that internal mixing reduces snow albedo substantially more than external mixing and that the snow-grain shape plays a critical role in snow albedo calculations through its forward scattering strength. Also, multiple inclusion of BC/dust significantly reduces snow albedo as compared to an equal-volume single sphere. For application to land/snow models, we propose a two-layer spectral snow parameterization involving contaminated fresh snow on top of old snow for investigating and understanding the climatic impact of multiple BC/dust internal mixing associated with snow grain metamorphism, particularly over mountain/snow topography.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
    Publication Date: 2019
    Description: Abstract The United Nations has reported that 55% of the global population resides in urban areas, and 68% of the population is expected to be urban dwellers by 2050. Urbanization has critical implications for global land cover. Relevant literature has provided evidence attributing climatic effects to urban expansion; however, few studies have investigated the effect on public health and pollutant sensitivity to emissions. This study aimed to characterize the effect of urbanization‐induced changes in regional climate on ozone (O3), to evaluate ozone sensitivity to nitrogen oxide (NOx) and volatile organic compound (VOC) emissions, and to estimate premature mortalities due to O3 exposure. We employed atmospheric models with the higher‐order decoupled direct method (HDDM) to simulate effects of urbanization on O3 and to determine O3 sensitivity to NOx and VOC emissions. China‐specific concentration response functions were utilized to estimate cardiovascular and respiratory mortalities due to ozone exposure. Urbanization increased O3, which translated to a 39.6% increase in O3‐induced premature mortality (1,100 deaths). Moreover, O3 has become less/more sensitive to unit changes in NOx and VOC emissions in various cities. Urban greening may reduce urban temperature, but it may increase O3 in some cities due to the additional VOC emissions of greening. These findings highlight the strong interactions between land‐use policies, urban climate adaptation strategies, and air quality policies, suggesting the need of cobeneficial strategies and policies. We proposed a “precision environmental management” concept that emphasizes the importance of considering the specific atmospheric condition and composition of a city when formulating its environmental policies.
    Print ISSN: 2169-897X
    Electronic ISSN: 2169-8996
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 49-55 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A procedure combining direct methods and solvent flattening to break the phase ambiguity intrinsic to the single isomorphous replacement (SIR) technique has been tested with the experimental SIR data of the known protein RNase Sa at 2.5 Å resolution. The use of direct methods provided better initial phases for the solvent-flattening procedure, while the solvent-flattening procedure greatly improved direct-method phases leading to a traceable Fourier map. A small subset of known phases at low resolution makes direct phasing of SIR data much easier. Accordingly a method for extending low-resolution phases to high-resolution ones is proposed making use of additional SIR information. This reduces the problem of finding a value in the range of 0–2π for each unknown phase to that of just making a choice between two possible values. Tests with the known protein RNase Sa showed that the method is able to extend phases from a resolution of 6 to 2.5 Å leading to an easily traceable Fourier map. The solvent-flattening technique and the combination of which with direct methods were used for the phase extension. Either procedure yielded reasonably good results, but on the whole, the result from the combination of direct methods with solvent flattening is better. Results of the latter procedure were further compared with that from direct phasing of the 2.5 Å SIR data and with that from phase extension by solvent flattening without SIR information. An improvement gained by the use of SIR information is evident.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 1114-1118 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Any distribution is completely defined by its moments. It is shown that a process of phase refinement can be carried out, based on Fourier transforms, which modifies the moments of electron density, separately in the protein and solvent regions, towards target values. Tests have been carried out on two moderate-sized proteins with 800–900 atoms in the asymmetric unit, one containing heavy atoms and the other not. It has been found that refinement using the third moment about zero in the protein region is most effective and that refinement with higher moments, or in the solvent region, adds nothing useful. Two kinds of weights are necessary in the method. One is for giving a weighted mixture of new phase indications with original phase estimates from, say, multiple isomorphous replacement. The other weights are applied to the Fourier coefficients of density maps to give the best possible signal:noise ratio. These weights have been explored empirically and the best ones found are described. It is concluded that since the moments method, which changes phases in reciprocal space, is independent of other histogram-matching procedures, which change density in real space, it has something to offer in a refinement package containing several procedures.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 792-794 
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new procedure for combining direct methods with the solvent-flattening technique is proposed for phasing single isomorphous replacement (SIR) or one-wavelength anomalous scattering (OAS) data of proteins. The new procedure differs from the previous one [Zheng, Zheng, Gu, Mo, Fan & Hao (1997). Acta Cryst. D53, 49–55] in that the direct method not only provides input phases to but also accepts feedback phases from solvent flattening, thus forming an iterative process for breaking the ambiguities and refining the values of phases. The new procedure was tested with the experimental SIR data of the known structure ribonuclease Sa. For the strongest 1000 of the total 7264 refelctions, the mean Fobs-weighted phase error is 7.5 and 9.4° lower than that of the previous procedure and that of solvent flattening alone, respectively.
    Type of Medium: Electronic Resource
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