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This report is based on the discussions, presentations, and reflections on the Workshop on Sustainable Software Sustainability (wosss.org/wosss21/home) that took place in October 2021 (WoSSS21). The workshop brought together leaders, managers, and specialists in software sustainability. The topics covered included Open Science, FAIR software, human and technical infrastructure, advances in research software and software aspects of cultural heritage. The report captures the state of the art for a range of software sustainability topics according to those who attended. It contains featured sections (where authors provided information beyond a summary), summaries, discussions, and where applicable links to videos of the talks, slides and transcripts. This is the 4th report in the WoSSS report series (wosss.org).

Various beliefs are common about the extraction of soluble compounds from leaf tea, suggesting that cold brewed tea or tea brewed for a shorter time than usual may contain a higher polyphenol-to-caffeine ratio, a selling point due to the potential health benefits of polyphenolic compounds. To test these beliefs, we investigated the effect of brewing time and temperature on the colour intensity and caffeine content of the extract of one type of black tea. Results showed that the extraction of the two components of interest had different half-lives, with an initial large variation of the ratio between them rapidly reaching a quite constant value. At different temperatures, a significantly different ratio between caffeine and colour compounds was observed. Although the difference in relative concentration was small, the range of brewing temperatures tested was only 20 Kelvin, so it seems possible to increase this difference. A difference in total extraction efficiency of both components together was noted too. To effectively change the ratio of the components using the extraction time would require using accurate times of less than 3 minutes and accurate temperatures unusual in a home environment.

Rapid advancements in technology has led to urgent requirement for mobile and portable power sources. Achieving self-sustainability using renewable energy sources using such devices provide an added advantage. Electrode materials play a critical role in performance of these devices, while the surface morphology of the electrode material play a crucial role in performance of electrodes themselves. Here we report fabrication of a flexible, all-solid state high performance hybrid supercapacitor using the 3D dendritic cell like nanostructures of Ni–Co LDH@rGO as cathode and novel crumpled leaf like rGO nano porous networks as anode. PVA-KOH gel is used as solid-state gel electrolyte. The fabricated supercapacitor is incorporated with a solar cell to demonstrate a self sustainable power pack The working potential window obtained is ∼1.4–1.8V. The asymmetric and hybrid assembly of the device enables in achieving high energy and power density. The energy and power density of the assembled supercapacitor is ∼58.4 Wh/Kg and ∼374 W/kg respectively at a current density of 0.5 A/g. The Coulombic efficiency is approximately 100% and suggests superior performance of the supercapacitor. Our experiments demonstrate the potential use of graphene based materials for powering wearable and portable electronic devices in a self sustainable manner.

Research software has become a central asset in academic research. It optimizes existing and enables new research methods, implements and embeds research knowledge, and constitutes an essential research product in itself. Research software must be sustainable in order to understand, replicate, reproduce, and build upon existing research or conduct new research effectively. In other words, software must be available, discoverable, usable, and adaptable to new needs, both now and in the future. Research software therefore requires an environment that supports sustainability. Hence, a change is needed in the way research software development and maintenance are currently motivated, incentivized, funded, structurally and infrastructurally supported, and legally treated. Failing to do so will threaten the quality and validity of research. In this paper, we identify challenges for research software sustainability in Germany and beyond, in terms of motivation, selection, research software engineering personnel, funding, infrastructure, and legal aspects. Besides researchers, we specifically address political and academic decision-makers to increase awareness of the importance and needs of sustainable research software practices. In particular, we recommend strategies and measures to create an environment for sustainable research software, with the ultimate goal to ensure that software-driven research is valid, reproducible and sustainable, and that software is recognized as a first class citizen in research. This paper is the outcome of two workshops run in Germany in 2019, at deRSE19 - the first International Conference of Research Software Engineers in Germany - and a dedicated DFG-supported follow-up workshop in Berlin.

Tailoring of surface-enhanced materials is vital towards achieving enhanced energy storage. In order to achieve this, hybrid material combinations often used in traditional vertically stacked morphologies. However, the inherent nature of poor conductivity and aggregation results in a bottleneck in exploiting such materials' full potential. In particular, the hybrid composites of layered double hydroxide (LDH) architectures suffer from restacking and results in poor charge transport. To mitigate these issues, the rational design of a graphene-based interlinked framework is vital. The interfacial phenomena associated with graphene's charge transport properties are also of considerable interest for manoeuvring graphene-based hybrid material architectures. Herein, we report the synthesis of Co-Mn LDH coronal hybrids with radially aligned LDH lamellae on graphene-based core shells. The synthesis process involves spherical graphene oxide core shells obtained from GO encapsulated SiO2 spheres to prepare hollow coronal LDH hybrids. Without any harsh reagents, self-sacrificial removal of the SiO2 core occurs. The process also helps formulate open porous graphene channels, which help in an efficient charge transfer process. The charge transfer efficiency of LDH becomes superior by incorporating the electrically conductive graphene-based nano core framework. The battery type hybrid material shows an enhanced energy storage capacity of ~770 Cg−1 at a current density of 1 Ag−1.

The use of battery-powered electric commuter trains instead of those which are propelled by internal combustion engines on only partially (or non) electrified railway lines can save considerable amounts of energy and can avoid exhaust emissions to a large extent with comparatively low investment costs. As path to these goals, the railway line, the operating and the trains are modeled for a particularly interesting, real-life example. Then, for the generated models, it is shown how the energy demands of model-compliant (battery) electric commuter trains can be calculated and how their energy storages can be designed. The models and the procedure can also be applied for a large number of comparable dimensioning cases when defining further railway lines, operating and commuter train models, corresponding parameterization as well as the occasionally necessary addition of slope and curvature resistances. The calculation of energy demands and the design of energy storages, however, show that there are a large number of different alternatives for technical specifications as well as decisions relevant to energy efficiency and business management, too. To determine the most suitable solutions, further measures such as the investigation of the effects of intelligent modifications to the underlying models, the development and implementation of computer-aided simulations as well as the construction and testing of real (battery) electric commuter trains make sense.

The discovery of graphene oxide (GO) has made a profound impact on varied areas of research due to its excellent physicochemical properties. However, surface engineering of these nanostructures holds the key to enhanced surface properties. Here, we introduce surface engineering of reduced GO (rGO) shells by radially grafting Ni-Co layered double hydroxide (LDH) lamella on rGO shells to form Ni-Co LDH@rGO. The morphology of synthesized Ni-Co LDH@rGO mimics dendritic cell-like three-dimensional (3D) hierarchical morphologies. Silica nanospheres form self-sacrificial templates during the reduction of GO shells to form rGO shells during the template-assisted synthesis. The radial growth of LDH lamellae during hydrothermal process on GO shells provides access to a significantly larger number of additional active redox sites and overcompensates the loss of pseudocapacitive charge storage centers during the reduction of GO to form rGO shells. This enables in the synthesis of novel surface-engineered rGO nanoshells, which provide large surface area, enhanced redox sites, high porosity, and easy transport of ions. These synthesized 3D dendritic cell-like morphologies of Ni-Co LDH@rGO show a high capacitance of ∼2640 F g

Functionalization of graphene-based materials using chemical moieties not only modify the electronic structure of the underlying graphene but also enable in limited enhancement of targeted properties. Surface modification of graphene-based materials using other nanostructures enhances the effective properties by minimally modifying the properties of pristine graphene backbone. In this pursuit, we have synthesized bio-inspired hierarchical nanostructures based on Ni–Co layered double hydroxide on reduced graphene oxide core–shells using template based wet chemical approach. The material synthesized have been characterized structurally and electrochemically. The fabricated dendritic morphology of the composite delivers a high specific capacity of 1056 Cg−1. A cost effective solid state hybrid supercapacitor device was also fabricated using the synthesized electrode material which shows excellent performance with high energy density and fast charging capability. A nanostructure consisting of Ni-Co layered double hydroxide dendrites on a reduced graphene oxide shell offers a high specific capacity for energy devices. Transition metal layered double hydroxides are attractive electrode materials for energy storage devices. However, slow ionic diffusion and poor electrical conductivity limits their use. Now, an international team from India and Germany, led by Sumit Saxena, demonstrate the synthesis of Ni-Co layered double hydroxide dendrites grown radially on reduced graphene oxide shells. This morphology creates a large a number of active sites, enabling a high specific capacity of 1056 Cg−1. They also fabricate a solid state hybrid supercapacitor with their material as the cathode, achieving an energy density of 35 Wh kg−1 with fast charging. Further tuning of the morphology of the material may enable higher performance.

Search and rescue of people in need after catastrophic events is dangerous and challenging for the rescue personnel. Limited resources and reduced accessibility to danger zones even prevent rescue attempts at all. New technologies to assist and keep safe the search and rescue teams while maintaining maximal success rate are therefore desired.

Simulation is a helpful tool for analysing and optimising certain problems in various different scenarios. In urban area, traffic simulation could help optimising the placement of the traffic lights or traffic signs. Typically, the simulation based mostly on the linear approximation of the distance and speed. However, drivers’ behaviour could also influence the traffic situation resulting in traffic jam which lead to delay on the arrival time on other drivers. In this work, a simulation framework that focusses on the drivers’ behaviour is presented. Each driver is modelled as an agent which has some driving attitude. The simulation model a daily activity of each agent, where it has a place to live and an office to work. The agents will then do their daily activities which can be an ordinary day or some free day by visiting friends, cinema or shopping center. Based on the daily activity situation the driving style will be influenced from a patient driver which drives carefully to an angered driver that tends to become more careless.

The rational design and fabrication of nanostructured materials with desired electrochemical performance is highly demanded for energy storage applications. Functionalization of graphene based materials using chemical moieties not only alter the electronic structure of the underlying graphene but also enable in only limited enhancement of targeted properties. Surface modification of graphene based materials using other nanostructures enhances the effective properties by minimally modifying the properties of pristine graphene backbone. In this pursuit we have fabricated bio-inspired hierarchical nanostructures based on Ni-Co layered double hydroxide on the reduced graphene oxide core shells using template based wet chemical approach. The as-obtained materials with tuned morphology have been characterized structurally and electrochemically. The results show that the charge storage capability of the synthesized material is 3 fold higher than that of pristine materials. These characterizations confirm that the obtained material has large effective surface and has promising applications in catalysis and energy storage. This surface modification strategy is not limited to only transition metal based hydroxides but also may pave a way for the fabrication of many other nanostructured materials.

The quantum phase diagram of disordered quantum wires in a strong magnetic field is reviewed. For uncorrelated disorder potential the 2-terminal conductance, as calculated with the numerical transfer matrix method, shows zero temperature discontinuous transitions between exactly integer plateau values and zero. This is explained by the dimensional crossover of the bulk localisation length, which drives a transition from delocalised to localised edge states. In the thermodynamic limit, fixing the aspect ratio of the wire, there is a transition from the one dimensional chiral metal of extended edge states to localisation along the wire. In the vicinity of this chiral metal insulator transition (CMIT), states are identified which are superpositions of edge states with opposite chirality. The bulk contribution of such states is found to decrease with increasing wire width. Based on exact diagonalisation results for the eigenstates and their participation ratios, we conclude that these states are characteristic for the CMIT, and have the appearance of nonchiral edges states. Thereby these states are distinguishable from other states in the quantum Hall wire, namely, extended edge states, two-dimensionally (2D) localized, quasi-1D localized, and 2D critical states. In the presence of spatially correlated random potential we find with the numerical transfermatrix method that the potential correlation results in a shift of quantized conductance plateaus in long wires proportional to the strength of the random potential. This shift is found to be insensitive to the strength of magnetic fields and the same for all plateaus. A semiclassical explanation of this effect is proposed. We conclude with an outlook on modfications of the quantum phase diagram due to the spin degree of freedom of the electrons and their interactions. We discuss the stability of the phase diagram at finite temperature. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The two-terminal conductance of quantum Hall wires in the presence of spatially correlated disorder is investigated numerically. It is found that the conductance plateau transitions shift to higher energies than the corresponding Landau subband centers. By performing the analysis on individual samples, it is found that the critical energy of the plateau transition depends on the disorder realization, but the distance between successive critical energies is independent of the sample and is equal to the bulk Landau level separation.

Modelling, simulation and optimal control for a lithium-ion battery cell is discussed. The model involves ionic concentrations, currents and potentials in the electrodes and the separator together with the battery temperature as state variables. The resulting system is a nonlinear PDAE system with 10 partial, 1 ordinary differential and 4 algebraic equations involving the Butler-Volmer kinetics for describing the interaction of ionic currents and potentials. Time-optimal charging of the battery subject to age-preventing leads to a state-constrained optimal control problem which is solved in two ways. A first-discretize-then-optimize approach leads to a high-dimensional nonlinear optimization problem which is solved by an efficient solver. As an alternative, a feedback control law along an active arc of the state constraint of order 1 is derived to formulate and solve the corresponding so-called induced optimization problem. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

Im Artikel werden laufende Arbeiten und Ergebnisse der Forschergruppe Wissensmanagement beschrieben. Diese entstanden vor allem durch die am Lehrstuhl Wissensmanagement angesiedelten Projekte Europeana v2.0, Digitised Manuscripts to Europeana (DM2E) sowie von Teilprojekten des vor kurzem gestarteten DFG-Exzellenzclusters Bild Wissen Gestaltung. Die Projekte befassen sich mit Spezialisierungen des Europeana Data Model, der Umwandlung von Metadaten in RDF und der automatisierten und nutzerbasierten semantischen Anreicherung dieser Daten auf Basis eigens entwickelter oder modifizierter Anwendungen sowie der Modellierung von Forschungsaktivitäten, welche derzeit auf die digitale Geisteswissenschaft zugeschnitten ist. Allen Projekten gemeinsam ist die konzeptionelle oder technische Modellierung von Informationsentitäten oder Nutzeraktivitäten, welche am Ende im Linked Data Web repräsentiert werden.

In this paper the simulation of hybrid processes containing membrane units will be discussed. For this purpose a user-defined module for simulation and design of membrane processes was implemented into the simulation program AspenPlus. The advantages can be summarized as follows: –any combination of membrane processes with all other units already implemented in AspenPlus is possible, including internal recycle streams –utilization of the physical property models and data bases of AspenPlus is possible – cost and sensitivity analysis can be performed. These benefits are demonstrated in detail for a membrane vapor recovery unit for the treatment of tank farm off -gas, for a two-stage reverse osmosis plant for organic/-organic separations and for a combination of distillation and pervaporation for the separation of a dimethylcarbonate/methanol mixture.

We propose a new local, deterministic and parameter-free algorithm that detects fuzzy and crisp overlapping communities in a weighted network and simultaneously reveals their hierarchy. Using a local fitness function, the algorithm greedily expands natural communities of seeds until the whole graph is covered. The hierarchy of communities is obtained analytically by calculating resolution levels at which communities grow rather than numerically by testing different resolution levels. This analytic procedure is not only more exact than its numerical alternatives such as LFM and GCE but also much faster. Critical resolution levels can be identified by searching for intervals in which large changes of the resolution do not lead to growth of communities. We tested our algorithm on benchmark graphs and on a network of 492 papers in information science. Combined with a specific post-processing, the algorithm gives much more precise results on LFR benchmarks with high overlap compared to other algorithms and performs very similar to GCE., 25 pages, 10 figures

We analyze the fermion density of the one-dimensional Hubbard model using bosonization and numerical density matrix renormalization group calculations. For finite systems we find a relatively sharp crossover even for moderate short-range interactions into a region with 4kF density waves as a function of density. The results show that the unstable fixed point of a spin-incoherent state can dominate the physical behavior in a large region of parameter space in finite systems. The crossover may be observable in ultracold fermionic gases in optical lattices and in finite quantum wires.

The local density of states (LDOS) in finite quantum wires is calculated as a function of discrete energies and position along the wire. By using a combination of numerical density matrix renormalization group (DMRG) calculations and analytical bosonization techniques it is possible to obtain a good understanding of the local spectral weights along the wire in terms of the underlying many-body excitations., 5 pages, 4 figures. v2 with additional data. The most recent version can be found at http://www.physik.uni-kl.de/eggert/papers/

Quantum transport properties in quantum Hall wires in the presence of spatially correlated random potential are investigated numerically. It is found that the potential correlation reduces the localization length associated with the edge state, in contrast to the naive expectation that the potential correlation increases it. The effect appears as the sizable shift of quantized conductance plateaus in long wires, where the plateau transitions occur at energies much higher than the Landau band centers. The scale of the shift is of the order of the strength of the random potential and is insensitive to the strength of magnetic fields. Experimental implications are also discussed., Comment: 5 pages, 4 figures

The quantum phase diagram of disordered wires in a strong magnetic field is studied as a function of wire width and energy. The two-terminal conductance shows zero-temperature discontinuous transitions between exactly integer plateau values and zero. In the vicinity of this transition, the chiral metal-insulator transition (CMIT), states are identified that are superpositions of edge states with opposite chirality. The bulk contribution of such states is found to decrease with increasing wire width. Based on exact diagonalization results for the eigenstates and their participation ratios, we conclude that these states are characteristic for the CMIT, have the appearance of nonchiral edges states, and are thereby distinguishable from other states in the quantum Hall wire, namely, extended edge states, two-dimensionally (2D) localized, quasi-1D localized, and 2D critical states., replaced with revised version

The compressibility of a two-dimensional electron system with spin in a spatially correlated random potential and a quantizing magnetic field is investigated. Electron-electron interaction is treated with the Hartree-Fock method. Numerical results for the influences of interaction and disorder on the compressibility as a function of the particle density and the strength of the magnetic field are presented. Localization-delocalization transitions associated with highly compressible region in the energy spectrum are found at half-integer filling factors. Coulomb blockade effects are found near integer fillings in the regions of low compressibility. Results are compared with recent experiments., Comment: 4 pages, 2 figures, replaced with revised version

We implemented three recently proposed approaches to the identification of overlapping and hierarchical substructures in graphs and applied the corresponding algorithms to a network of 492 information-science papers coupled via their cited sources. The thematic substructures obtained and overlaps produced by the three hierarchical cluster algorithms were compared to a content-based categorisation, which we based on the interpretation of titles and keywords. We defined sets of papers dealing with three topics located on different levels of aggregation: h-index, webometrics, and bibliometrics. We identified these topics with branches in the dendrograms produced by the three cluster algorithms and compared the overlapping topics they detected with one another and with the three pre-defined paper sets. We discuss the advantages and drawbacks of applying the three approaches to paper networks in research fields., Comment: 18 pages, 9 figures