Leibniz University of Hanover

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.

Contextual classification of lidar data and building object detection in urban areas

Abstract: In this work we address the task of the contextual classification of an airborne LiDAR point cloud. For that purpose, we integrate a Random Forest classifier into a Conditional Random Field (CRF) framework. It is a flexible approach for obtaining a reliable classification result even in complex urban scenes. In this way, we benefit from the consideration of context on the one hand and from the opportunity to use a large amount of features on the other hand. Considering the interactions in our experiments increases the overall accuracy by 2%, though a larger improvement becomes apparent in the completeness and correctness of some of the seven classes discerned in our experiments. We compare the Random Forest approach to linear models for the computation of unary and pairwise potentials of the CRF, and investigate the relevance of different features for the LiDAR points as well as for the interaction of neighbouring points. In a second step, building objects are detected based on the classified point cloud. For that purpose, the CRF probabilities for the classes are plugged into a Markov Random Field as unary potentials, in which the pairwise potentials are based on a Potts model. The 2D binary building object masks are extracted and evaluated by the benchmark ISPRS Test Project on Urban Classification and 3D Building Reconstruction. The evaluation shows that the main buildings (larger than 50 m 2 ) can be detected very reliably with a correctness larger than 96% and a completeness of 100%.

High-Flux Membranes Based on the Covalent Organic Framework COF-LZU1 for Selective Dye Separation by Nanofiltration.

Abstract: Covalent organic frameworks (COFs) are attractive candidates for advanced water-treatment membranes owing to their high porosity and well-organized channel structures. Herein, the continuous two-dimensional imine-linked COF-LZU1 membrane with a thickness of only 400 nm was prepared on alumina tubes by in situ solvothermal synthesis. The membrane shows excellent water permeance (ca. 760 L m-2 h-1 MPa-1 ) and favorable rejection rates exceeding 90 % for water-soluble dyes larger than 1.2 nm. The water permeance through the COF-LZU1 membrane is much higher than that of most membranes with similar rejection rates. Long-time operation demonstrates the outstanding stability of the COF-LZU1 membrane. As the membrane has no selectivity for hydrated salt ions (selectivity <12 %), it is also suitable for the purification of dye products from saline solutions. The excellent performance and the outstanding water stability render the COF-LZU1 membrane an interesting system for water purification.

Quantum-Fluctuation-driven crossover from a dilute bose-einstein condensate to a macrodroplet in a dipolar quantum fluid

Abstract: Experiments with ultracold magnetic atoms reveal liquid-like quantum droplets that are 20 times larger than previously observed droplets.

Oriented Zeolitic Imidazolate Framework-8 Membrane with Sharp H2/C3H8 Molecular Sieve Separation

Abstract: A highly oriented zeolitic imidazolate framework 8 (ZIF-8) composite membrane was prepared by seeding and secondary growth. By dip-coating, preformed ZIF-8 nanocrystals were attached to the surface of a porous α-alumina support using polyethyleneimine as the coupling agent. After solvothermal treatment, a continuous and well-intergrown ZIF-8 layer was obtained. X-ray diffraction analysis of the membrane showed preferred orientation of the {100} plane parallel to the support. Further time-dependent investigations by scanning and transmission electron microscopy as well as X-ray diffraction indicated that the preferred orientation develops during an evolutionary growth process. In gas mixture permeation experiments, the membrane showed good performance in H2/hydrocarbon separation. A sharp molecular sieve separation is observed for an equimolar H2/C3H8 mixture with a separation factor above 300.