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Institution

Leibniz University of Hanover

EducationHanover, Niedersachsen, Germany
About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Population. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.


Papers
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Journal ArticleDOI
TL;DR: This paper applied various unit root tests to a panel of wage data and found that firm and industry wages both possess a unit root in the autoregressive representation of the distribution of hourly wages.
Abstract: Theoritical considerations suggest that spillover forces equalize wages for similar jobs Thus, it is expected that firm wages are cointegrated with the corresponding wage rates on an industrial level In this paper we apply various unit root tests to a panel of wage data We show that the familiar techniques can be adopted to this type of data allowing for unobserved heterogeneity and common time effects Our results suggest that firm and industry wages both possess a unit root in the autoregressive representation However, ther is only weak evidence for a cointegration realtionship

247 citations

Journal ArticleDOI
TL;DR: The authors aim to devise a simple and efficient implementation of phase-field model for the modelling of quasi-static and dynamic fracture in the general purpose commercial software developer, COMSOL Multiphysics.

247 citations

Journal ArticleDOI
TL;DR: The authors show that Anak Krakatau exhibited an elevated state of activity several months prior to the collapse, including precursory thermal anomalies, an increase in the island’s surface area, and a gradual seaward motion of the southwestern flank.
Abstract: Flank instability and sector collapses, which pose major threats, are common on volcanic islands. On 22 Dec 2018, a sector collapse event occurred at Anak Krakatau volcano in the Sunda Strait, triggering a deadly tsunami. Here we use multiparametric ground-based and space-borne data to show that prior to its collapse, the volcano exhibited an elevated state of activity, including precursory thermal anomalies, an increase in the island’s surface area, and a gradual seaward motion of its southwestern flank on a dipping decollement. Two minutes after a small earthquake, seismic signals characterize the collapse of the volcano’s flank at 13:55 UTC. This sector collapse decapitated the cone-shaped edifice and triggered a tsunami that caused 430 fatalities. We discuss the nature of the precursor processes underpinning the collapse that culminated in a complex hazard cascade with important implications for the early detection of potential flank instability at other volcanoes. On 22 December 2018, the western flank of Anak Krakatau collapsed into the sea of the Sunda Strait triggering a tsunami which killed approximately 430 people and displaced 33,000. Here, the authors show that Anak Krakatau exhibited an elevated state of activity several months prior to the collapse, including precursory thermal anomalies, an increase in the island’s surface area, and a gradual seaward motion of the southwestern flank.

246 citations

Journal ArticleDOI
TL;DR: The results show that the echo amplitude as well as two features computed from the radiometric calculation of full-waveform data, namely the cross-section and the backscatter coefficient, significantly contribute to the high classification accuracies reported in this paper.
Abstract: Full-waveform lidar data are increasingly being available. Morphological features can be retrieved from the echoes composing the waveforms, and are now extensively used for a large variety of land-cover mapping issues. However, the genuine contribution of these features with respect to those computed from standard discrete return lidar systems has been barely theoretically investigated. This paper there- fore aims to study the potential of full-waveform data through the automatic classification of urban areas in building, ground, and vegetation points. Two waveform processing methods, namely a non-linear least squares method and a marked point process approach, are used to fit the echoes both with symmetric and asymmetric modeling functions. The performance of the extracted full-waveform features for the classification problem are then compared to a large variety of multiple-pulse features thanks to three fea- ture selection methods. A support vector machines classifier is finally used to label the point cloud according to various scenarios based on the rank of the features. This allows to find the best classification strategy as well as the minimal feature subsets allowing to achieve the highest classification accuracy possible for each of the three feature selection methods. The results show that the echo amplitude as well as two features computed from the radiometric cal- ibration of full-waveform data, namely the cross-section and the backscatter coefficient, significantly contribute to the high classification accuracies reported in this paper (around 95%). Conversely, features extracted from the non Gaussian modelling of the echoes are not relevant for the discrimination of veg- etation, ground, and buildings in urban areas. � 2011 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS) Published by Elsevier

246 citations

Journal ArticleDOI
TL;DR: The covalent post-functionalization of MOF molecular sieve membranes to increase the selectivity of a ZIF-90 membrane is presented.
Abstract: Metal–organic frameworks (MOFs) are being evaluated for several applications, such as gas adsorption, molecular separation, drug delivery, and catalysis owing to their welldefined, adjustable, and open pore framework structures. Apart from the use of MOFs as powders, supported MOF layers are of interest for various potential applications as separating membranes, sensors, and other functional layers. Among the reported MOFs, the subfamily of zeolitic imidazolate frameworks (ZIFs), which are based on transition metals (Zn, Co) and imidazolate linkers, have emerged as candidates for the fabrication of molecular sieve membranes owing to their zeolite-like permanent porosity, uniform pore size, and exceptional thermal and chemical stability. Recently, a few ZIF membranes have shown promising molecular sieve performances that are better than the Knudsen mechanism.*** [16–21] However, there is still a long way ahead before robust synthetic strategies can be developed. Normally, the organic linkers of MOFs cannot form covalent bonds with surface OH groups of the supports, which causes problems in the heterogeneous nucleation of MOFs on support surface. Furthermore, similar to zeolite membranes, most of the MOF layers are polycrystalline with intercrystalline grain boundaries, which are detrimental to the membrane selectivity. Therefore, post-modification, such as chemical vapor deposition (CVD) or covalent functionalization, is helpful to minimize the non-selective transport through the intercrystalline gaps. The post-synthetic modification of MOFs has turned out to be an effective and versatile strategy to improve and fine-tune their physical and chemical properties. Herein, we present the covalent post-functionalization of MOF molecular sieve membranes to increase the selectivity of a ZIF-90 membrane. Recently, we have prepared the molecular sieve ZIF-90 membranes by using 3-aminopropyltriethoxysilane (APTES) as covalent linker between the ZIF-90 layer and the Al2O3 support by an imine condensation reaction. The ZIF-90 membrane is thermally and hydrothermally stable and shows molecular sieve performance, with a H2/CH4 selectivity of more than 15. On the other hand, the H2/CO2 selectivity was found to be only 7.2, as the pore size of ZIF-90 (0.35 nm) is larger than the kinetic diameter* of CO2 (0.33 nm). The separation of H2 and CO2 is important for example, for the hydrogen production by steam reforming of methane including the water gas-shift strategy. As reported by Yaghi and co-workers, the free aldehyde groups in the ZIF-90 framework allow the covalent functionalization with amine groups by an imine condensation reaction. Based on this reaction (Supporting Information, Figure S1), in the present work we report the covalent post-functionalization of a ZIF-90 membrane by ethanolamine to enhance its H2/CO2 selectivity (Figure 1). Two

246 citations


Authors

Showing all 14621 results

NameH-indexPapersCitations
Hyun-Chul Kim1764076183227
Peter Zoller13473476093
J. R. Smith1341335107641
Chao Zhang127311984711
Benjamin William Allen12480787750
J. F. J. van den Brand12377793070
J. H. Hough11790489697
Hans-Peter Seidel112121351080
Karsten Danzmann11275480032
Bruce D. Hammock111140957401
Benno Willke10950874673
Roman Schnabel10858971938
Jan Harms10844776132
Hartmut Grote10843472781
Ik Siong Heng10742371830
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023221
2022520
20212,280
20202,210
20192,105
20181,959