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 & Computer science. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.

Keep me Updated: An Empirical Study of Third-Party Library Updatability on Android

Abstract: Third-party libraries in Android apps have repeatedly been shown to be hazards to the users' privacy and an amplification of their host apps' attack surface. A particularly aggravating factor to this situation is that the libraries' version included in apps are very often outdated. This paper makes the first contribution towards solving the problem of library outdatedness on Android. First, we conduct a survey with 203 app developers from Google Play to retrieve first-hand information about their usage of libraries and requirements for more effective library updates. With a subsequent study of library providers' semantic versioning practices, we uncover that those providers are likely a contributing factor to the app developers' abstinence from library updates in order to avoid ostensible re-integration efforts and version incompatibilities. Further, we conduct a large-scale library updatability analysis of 1,264,118 apps to show that, based on the library API usage, 85.6% of the libraries could be upgraded by at least one version without modifying the app code, 48.2% even to the latest version. Particularly alarming are our findings that 97.8% out of 16,837 actively used library versions with a known security vulnerability could be easily fixed through a drop-in replacement of the vulnerable library with the fixed version. Based on these results, we conclude with a thorough discussion of solutions and actionable items for different actors in the app ecosystem to effectively remedy this situation.

2D mapping of cluttered indoor environments by means of 3D perception

Abstract: This paper presents a combination of a 3D laser sensor and a line-base SLAM algorithm which together produce 2D line maps of highly cluttered indoor environments. The key of the described method is the replacement of commonly used 2D laser range sensors by 3D perception. A straightforward algorithm extracts a virtual 2D scan that also contains partially occluded walls. These virtual scans are used as input for SLAM using line segments as features. The paper presents the used algorithms and experimental results that were made in a former industrial bakery. The focus lies on scenes that are known to be problematic for pure 2D systems. The results demonstrate that mapping indoor environments can be made robust with respect to both, poor odometry and clutter.

MOF-in-COF molecular sieving membrane for selective hydrogen separation.

Abstract: Covalent organic frameworks (COFs) are promising materials for advanced molecular-separation membranes, but their wide nanometer-sized pores prevent selective gas separation through molecular sieving. Herein, we propose a MOF-in-COF concept for the confined growth of metal-organic framework (MOFs) inside a supported COF layer to prepare MOF-in-COF membranes. These membranes feature a unique MOF-in-COF micro/nanopore network, presumably due to the formation of MOFs as a pearl string-like chain of unit cells in the 1D channel of 2D COFs. The MOF-in-COF membranes exhibit an excellent hydrogen permeance (>3000 GPU) together with a significant enhancement of separation selectivity of hydrogen over other gases. The superior separation performance for H2/CO2 and H2/CH4 surpasses the Robeson upper bounds, benefiting from the synergy combining precise size sieving and fast molecular transport through the MOF-in-COF channels. The synthesis of different combinations of MOFs and COFs in robust MOF-in-COF membranes demonstrates the versatility of our design strategy.

A quadratically convergent procedure for the calculation of stability points in finite element analysis

Abstract: In this paper a new finite element formulation is given for the analysis of nonlinear stability problems. The introduction of extended systems opens the possibility to compute limit and bifurcation points directly. Here, the use of the directional derivative yields a quadratically convergent iteration scheme. The combination with arc-length and branch-switching procedures leads to a global algorithm for path-following.