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The synthesis of 17-hydroxy-oleic acid based oligomeric esters was investigated with immobilized Pseudozyma antarctica Lipase B and hexanediol as co-substrate. The effects of different reaction parameters on velocity and product composition at equilibrium conditions were analyzed. The synthesis of oleic acid esters was used as a reference system for initial evaluation of reaction parameters. The reaction with oleic acid and hexanediol was fastest at an enzyme concentration of 5% at 60 °C and high conversions of > 90 % were achieved in non-polar solvents in the presence of molecular sieves. In heptane an oleic acid conversion of 96 % was reached with a final diester to monoester ratio of > 4:1. In syntheses trials with 17-hydroxy-oleic acid the formation of oligomers was verified with GPC, however; conversion was generally lower than with oleic acid. Removal of hydroxyl fatty acid monomers and dimers and the formation ester functionalities could be verified by GC analysis. An increase of the degree of oligomerization was observed simultaneously by GPC analysis. The number-average molecular weight was around 1400 in the best trials corresponding to a degree of oligomerization of around 4 units of hydroxyl-fatty acid attached to a hexanediol core. Though transformations were not complete, the final oligomer size was in the lower range of polyester diols used for polyurethane manufacturing.
Risk-based authentication (RBA) is an adaptive security measure to strengthen password-based authentication. RBA monitors additional implicit features during password entry such as device or geolocation information, and requests additional authentication factors if a certain risk level is detected. RBA is recommended by the NIST digital identity guidelines, is used by several large online services, and offers protection against security risks such as password database leaks, credential stuffing, insecure passwords and large-scale guessing attacks. Despite its relevance, the procedures used by RBA-instrumented online services are currently not disclosed. Consequently, there is little scientific research about RBA, slowing down progress and deeper understanding, making it harder for end users to understand the security provided by the services they use and trust, and hindering the widespread adoption of RBA.
In this paper, with a series of studies on eight popular online services, we (i) analyze which features and combinations/classifiers are used and are useful in practical instances, (ii) develop a framework and a methodology to measure RBA in the wild, and (iii) survey and discuss the differences in the user interface for RBA. Following this, our work provides a first deeper understanding of practical RBA deployments and helps fostering further research in this direction.
Online services such as social networks, online shops, and search engines deliver different content to users depending on their location, browsing history, or client device. Since these services have a major influence on opinion forming, understanding their behavior from a social science perspective is of greatest importance. In addition, technical aspects of services such as security or privacy are becoming more and more relevant for users, providers, and researchers. Due to the lack of essential data sets, automatic black box testing of online services is currently the only way for researchers to investigate these services in a methodical and reproducible manner. However, automatic black box testing of online services is difficult since many of them try to detect and block automated requests to prevent bots from accessing them.
In this paper, we introduce a testing tool that allows researchers to create and automatically run experiments for exploratory studies of online services. The testing tool performs programmed user interactions in such a manner that it can hardly be distinguished from a human user. To evaluate our tool, we conducted - among other things - a large-scale research study on Risk-based Authentication (RBA), which required human-like behavior from the client. We were able to circumvent the bot detection of the investigated online services with the experiments. As this demonstrates the potential of the presented testing tool, it remains to the responsibility of its users to balance the conflicting interests between researchers and service providers as well as to check whether their research programs remain undetected.
The southeast of Córdoba province used to be originally covered by hundreds of wetlands that got heavily modified or drained in the last few decades. Since wetlands provide various important ecosystem services (ESS) for human well-being, their degradation created several problems in La Picasa basin, among which floods are the most obvious one. The wise use of wetlands is increasingly acknowledged to be part of nature-based solution approaches reducing disaster risk. However, in the study area these approaches remain a relatively new concept to decision makers and the lack of knowledge on their effectiveness and implementation process poses a serious barrier to their adoption.
To overcome this obstacle, this dissertation applies an ESS perspective on the current problems of La Picasa basin and sets it in a context of socio-ecological system (SES) theory. A comprehensive analysis of (1) the role wetlands have played in the historic development of the SES, (2) important stakeholder dynamics that create opportunities or restrictions for the conservation of wetlands and (3) possible management approaches to inverse negative ESS trade-offs and feedback loops, was performed.
Results demonstrate that the current problems of floods have both natural and anthropogenic causes. In this regard, wetlands hold a vital role in the complex historic interactions between the social and ecological drivers of changes in the water balance. Although a social network between stakeholders exists, several conflicts prevent a proper functioning of a basin-wide integrated management concept based on wetland restoration. Nature-based solution approaches, putting wetlands in the center of attention of future management strategies, were found to hold a high potential to reduce the risk of floods and, as a side-effect boost biodiversity and habitat quality in the study area.
Grasping and manipulation with anthropomorphic robotic and prosthetic hands presents a scientific challenge regarding mechanical design, sensor system, and control. Apart from the mechanical design of such hands, embedding sensors needed for closed-loop control of grasping tasks remains a hard problem due to limited space and required high level of integration of different components. In this paper we present a scalable design model of artificial fingers, which combines mechanical design and embedded electronics with a sophisticated multi-modal sensor system consisting of sensors for sensing normal and shear force, distance, acceleration, temperature, and joint angles. The design is fully parametric, allowing automated scaling of the fingers to arbitrary dimensions in the human hand spectrum. To this end, the electronic parts are composed of interchangeable modules that facilitate the echanical scaling of the fingers and are fully enclosed by the mechanical parts of the finger. The resulting design model allows deriving freely scalable and multimodally sensorised fingers for robotic and prosthetic hands. Four physical demonstrators are assembled and tested to evaluate the approach.
This contribution deals with the topic of the consistent further development of a wheel hub motor for battery electric vehicles (BEV) based on the principle of an outer rotor switched reluctance machine (SRM). The research work presented in this paper was founded by the ERDF.NRW program, Investment for Growth and Employment and the European Regional Development Fund. The R&D project was named Switched - Reluctance fo(u)r wheel (SR4Wheel). Based on the experience made by first prototype Evolution 0 (EVO 0), developed in the Laboratory for Automation Engineering, Power Electronics and Electrical Drives of the Cologne University of Applied Sciences (CUAS), the test results of EVO 1, as well as the redesign, EVO 2 is presented in this paper.
The prototype EVO 0, a first proof of concept leads to several optimizations and lessons learned for the predecessor model EVO 1. The overall target of developing such a gearless outer rotor wheel hub motor is the full integration of the complete machine including its power electronics into the given space between the original friction brake and the rim. Furthermore, due to the additional integration of the power electronics, great opportunities in terms of new vehicle design as well as retrofitting capabilities of already existing vehicle platforms can be achieved. Thereby, further drive train assembly space like the engine compartment is no longer necessary. The SRM does not require magnets for torque production which leads to independence from the changeable commodity prices on the rare earth element markets. This paper presents the developing process, testing, and verification of the innovative drive train concept starting with the final CAD of EVO 1. During the testing and verification process a machine characteristic mapping is performed on a drive train test bench and subsequently the results of a finite element analysis (FEA) are plausibility checked by the test bench results. The process continues with energy conversion test scenarios of the project demonstrator vehicle on a roller test bench focused on noise vibrationharshness (NVH) behavior and efficiency. As a conclusion, the gained knowledge by evaluating two EVO 1 prototypes on the rear axle of the test vehicle, and the design for the front axle drive train EVO 2 will be presented. As a major task on the front axle, the limited space due to the large disc brake can be identified and solved.
Aerobic microbial cultivations are industrially important group of processes and pose challenges for the reactor design. In particular, estimation of industrial scale conditions is difficult from laboratory and pilot scale data. Due to complex interaction of gas/liquid phase hydrodynamics, mass transfer parameters and microbial metabolism, both improvement of modelling tools and reactor design are desired. We present an approach to estimate growth conditions in industrial scale reactor by combining black-box metabolic models with CFD-model.
The reactor type used here is Outotec OKTOP9000®, which is used in the industrial hydrometallurgical processes at 900 m3 scale. It is adopted to a laboratory setting and compared to stirred tank reactor (STR) in gas dispersion, mass transfer and yeast cultivation experiments. In addition, a kinetic model for the yeast growth is developed based on literature sources and validated by the laboratory scale batch cultivations. This kinetic model is used along with CFD-model that is developed to describe the flow and mass transfer conditions in the industrial scale reactor.
The laboratory scale experiments show the feasibility of OKTOP9000® reactor when compared to STR, particularly with improved gas handling capacity. The modelling approach shows qualitatively similar behavior in the large scale simulations when compared to laboratory scale cultivations.
In the degradation of ammonia (NH4+) to gaseous nitrogen (N2), the nitrification is one of the two reaction steps. The nitrification itself is divided in two steps and is performed by two different types of bacteria. Current literature has shown that there are types of bacteria, which have the genetic equipment to perform both steps in one bacteria. Nevertheless, in wastewater and landfill leachate treatment, ammonia-oxidizing organisms (AOO) and nitrite-oxidizing organisms (NOO) occur as a symbiosis. The intermediate of the two consecutive reaction steps (NO2-, nitrite) is toxic. For this reason, both steps are necessary for the two bacterial groups. To determine the ratio of AOO, NOO and heterotrophic bacteria (which use organic compounds as carbon and energy source) the oxygen uptake rate (OUR) with selective inhibition with N-allylthiourea (ATU) and azide is used. In the inflow of a pilot plant in one street a step by step increased amount of a process water out of a fermentation plant was added to the landfill leachate. For comparison, the other street was supplied only with landfill leachate with the same amount of nitrogen. As a result, comparable values for the different bacterial groups and reproducible results were measured and lead to a better understanding of the analysed nitrification sludge. Deeper understanding of the behavior of the different groups will result in a reduce risk of malfunctions and a more stable operation in the wastewater or landfill leachate treatment plant.
Due to the worldwide shortage of petrochemical based resources, the usage of renewable bio-based raw materials for established and novel products becomes increasingly important.[1] Such bio-based resources are already used for the fabrication of a variety of products, e. g. paper, lubricants, detergents or cosmetics. In the future they are expected to emerge in many more applications in industry and household.[1]
A very promising approach relies on the use of glycolipids as a source of hydroxy-oleic acid.[2] Microbial glycolipids are produced for instance via fermentation from natural resources such as plant oils and sugar.[3] After fermentation complex product mixtures are obtained with the composition depending on the microorganism, substrate and fermentation time.[3] The successful use of microbial glycolipids and hydroxy-oleic acid (HOA) derived therefrom as bio-based intermediates requires reliable analytical methods as well as robust manufacturing processes for the synthesis and cleavage of bio-based molecules. In order to obtain hydroxy-oleic acids as bio-based intermediates, the acidic cleavage of microbial derived sophorolipid was investigated. In addition the implementation of HOA in polyurethane (PU) systems was explored.
In the Mesoamerican forest Selva Maya, multiple driving forces create an imbalance in the sensitive human-nature relation and demand for innovative management strategies for its re-establishment. Within the Guatemalan Maya Biosphere Reserve (MBR), core areas are under strict protective legislation and agricultural activity is permitted only within a bordering buffer zone (BZ), which covers great part of the Guatemalan department Petén. Here, the implementation of agroecological practices by multiple stakeholders aims at tackling the principle driving forces of environmental degradation and thus at reducing the pressure on Central America’s largest tropical forest area. Since 2011, the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) has assisted local stakeholders by carrying out the project “Conservation and sustainable use of the Selva Maya”. This project has offered technical support, cooperated with national institutions, and assisted multiple target groups to nudge agroecological transitions at the household and community level. As the establishment of agroecological systems face main obstacles stemming from the socio-ecological setting of the respective area, the following work presents a context specific analysis for the adaption of established strategies in the MBR BZ. Therefore, it raises the following research questions: What are the current properties of the socio-ecological system that describes the BZ? How has the GIZ’s project nudged and guided agroecological transitions? Which factors have favored or limited the turn to agroecological farming? And finally: Which recommendations derive for the navigation of agroecological transitions? The overall research approach is orientated on the framework of ecosystem stewardship1 and incorporates elements of system theory and resilience science. The framework has been adapted by combining two approaches on different management levels. The social-ecological system approach2 is used to describe the socio-ecological system of the BZ, while the evaluation of the pilot groups‘ AESs follows the Mexican MESMIS3 approach for sustainability assessments. By the integration of both approaches, it is revealed that the socio-economic context impedes or hinders the implementation of agroecological strategies for the majority of farmers. The application of the MESMIS framework has revealed that the installed monitoring mechanism is dysfunctional. Findings further indicate that there is potential for transitions of individual AESs, but they demand investments and support with the current circumstances of reducing farmers’ vulnerability. The rapidly decreasing social and environmental conditions for family farmers in the BZ are most likely not addressed by solutions that the agroecological approach tackles. Recommendations for the immediate improvement of the strategy include adjustments of the project’s proceedings as well as fundamental changes in conservation paradigm and governance to maintain the necessary functionality of the socio-ecological system.