An Agency-Directed Approach to Test Generation for Simulation-based Autonomous Vehicle Verification

Simulation-based verification is beneficial for assessing otherwise dangerous or costly on-road testing of autonomous vehicles (AV). This paper addresses the challenge of efficiently generating effective tests for simulation-based AV verification using software testing agents. The multi-agent system (MAS) programming paradigm offers rational agency, causality and strategic planning between multiple agents. We exploit these aspects for test generation, focusing in particular on the generation of tests that trigger the precondition of an assertion. On the example of a key assertion we show that, by encoding a variety of different behaviours respondent to the agent's perceptions of the test environment, the agency-directed approach generates twice as many effective tests than pseudo-random test generation, while being both efficient and robust. Moreover, agents can be encoded to behave naturally without compromising the effectiveness of test generation. Our results suggest that generating tests using agency-directed testing significantly improves upon random and simultaneously provides more realistic driving scenarios.Comment: 18 pages, 8 figure

An Agency-Directed Approach to Test Generation for Simulation-based Autonomous Vehicle Verification

Simulation-based verification is beneficial for assessing otherwise dangerous or costly on-road testing of autonomous vehicles (AV). This paper addresses the challenge of efficiently generating effective tests for simulation-based AV verification using software testing agents. The multi-agent system (MAS) programming paradigm offers rational agency, causality and strategic planning between multiple agents. We exploit these aspects for test generation, focusing in particular on the generation of tests that trigger the precondition of an assertion. On the example of a key assertion we show that, by encoding a variety of different behaviours respondent to the agent's perceptions of the test environment, the agency-directed approach generates twice as many effective tests than pseudo-random test generation, while being both efficient and robust. Moreover, agents can be encoded to behave naturally without compromising the effectiveness of test generation. Our results suggest that generating tests using agency-directed testing significantly improves upon random and simultaneously provides more realistic driving scenarios.Comment: 18 pages, 8 figure

On Determinism of Game Engines used for Simulation-based Autonomous Vehicle Verification

Game engines are increasingly used as simulation platforms by the autonomous vehicle (AV) community to develop vehicle control systems and test environments. A key requirement for simulation-based development and verification is determinism, since a deterministic process will always produce the same output given the same initial conditions and event history. Thus, in a deterministic simulation environment, tests are rendered repeatable and yield simulation results that are trustworthy and straightforward to debug. However, game engines are seldom deterministic. This paper reviews and identifies the potential causes of non-deterministic behaviours in game engines. A case study using CARLA, an open-source autonomous driving simulation environment powered by Unreal Engine, is presented to highlight its inherent shortcomings in providing sufficient precision in experimental results. Different configurations and utilisations of the software and hardware are explored to determine an operational domain where the simulation precision is sufficiently low i.e.\ variance between repeated executions becomes negligible for development and testing work. Finally, a method of a general nature is proposed, that can be used to find the domains of permissible variance in game engine simulations for any given system configuration.Comment: 17 pages, 9 figures, 1 tabl

Diagnostik von Beinödemen

Ödeme der unteren Extremitäten entsprechen immer einem pathologischen Zustand, der insbesondere bei Betroffenen mit chronischen Wunden einer Therapie bedarf. Weil die Ursachen dieser Ödeme sehr unterschiedlich und teilweise auch komplex sein können, sollte zuerst eine klinische und ggf. apparative Diagnostik erfolgen. Oft kann nach einer klinischen Untersuchung mit Testung des Stemmer- und Godet-Zeichens bereits eine klinische Verdachtsdiagnose gestellt werden. Als weiterführende apparative Diagnostik kann eine sonographische Untersuchung erfolgen. Messtechniken wie beispielsweise die Wasserplethysmographie gelten derzeit zwar als Goldstandard für Volumenmessungen, sind aber sehr aufwendig und fehleranfällig, sodass sie in der klinischen Routine heute kaum angewendet werden. Zusammenfassend wird empfohlen, für die Ödemdiagnostik eine klinische Untersuchung möglichst in Kombination mit einer Sonographie durchzuführen. Insbesondere zu Beginn der Entstauungsphase sollten regelmäßig Umfangsmessungen durchgeführt und dokumentiert werden. Diese Dokumentation ist für die Bewertung des therapeutischen Erfolgs von hoher Aussagekraft. // Edema of the lower extremities is always associated with a pathological condition that should be treated, especially in patients with chronic wounds. Because the underlying causes of edema can vary greatly and sometimes be complex, clinical and, if necessary, various diagnostic tests should also be performed. Often, a suspected clinical diagnosis can already be made after clinical inspection with testing of Stemmer's and Godet's signs. Sonographic examination should then be performed as the next diagnostic test. Although measurement techniques such as water plethysmography are currently considered gold standard for volume measurements, they are very complex and prone to error, so that they are rarely used in clinical routine today. In summary, it is recommended to perform a clinical examination, if possible in combination with sonography, for edema diagnosis. Especially at the beginning of the decongestion phase, regular circumferential measurements should be performed and documented. This documentation is of high relevance for evaluation of therapeutic success

Adsorption and Ultrafiltration as Techniques for Value Addition to Plant-Based By-Products

The growth of the global population to 8.5 – 10 billion people by 2050 entails an increased demand for food in the forthcoming decades. Our incumbent world food system is marked by tremendous inefficiencies in the utilization of agricultural commodities for food production. The accumulation of vast quantities of solid and liquid food processing by products along the food supply chain poses a serious environmental burden. The expansion of food production to cope with the growing demand for food proliferates the generation of by products and exacerbates the adverse externalities associated with existing by product management strategies. Hence, the food system faces the conflicting pressure to deliver the predicted demand for food by means of an environmentally sustainable development. In this context, efforts focusing on the exploitation and valorization of underutilized natural resources become of utmost importance. However, the specificity of food by products in accordance with the processed commodities depicts a central challenge for the design of reutilization processes to derive added value from unused material. This work shows applications of adsorption and ultrafiltration processes aimed at the complete utilization of diverted resources and the recovery of higher added value compounds that capitalize on the unique properties of the by products studied. Pigeon pea husk (PPH) possessed promising merits as low cost adsorbent for the removal of atenolol (ATN) and trimethoprim (TMP) that are among the most abundantly occurring pharmaceuticals in Indian water bodies. Detailed investigations of the mass transfer mechanism using the external mass transfer model (EMTM) and description of adsorption equilibrium state based on the Akaike information criterion (AIC) revealed the governing mechanisms of the adsorption processes. Moreover, olive pit derived activated carbon (OPAC) exhibited the technological suitability for the adsorption of hydroxytyrosol (HT), a potent antioxidant found in olive mill wastewater (OMWW), by matching the adsorption capacity of a commercial activated carbon (CAC). The rigorous examination of the adsorption behavior of HT onto OPAC, including the description of adsorption kinetics by means of the pore volume and surface diffusion model (PVSDM), demonstrated a promising complementary approach for the exploitation of solid and liquid by products arising during the production of olive oil. Ultrafiltration of polysaccharides with distinct conformation in aqueous solutions and comparable molecular weight, namely rigid rod like and randomly coiled pullulan, differed significantly in terms of their rejection yield, illustrating a decisive effect of polysaccharide conformation on ultrafiltration separation performance. Additionally, the observations indicated that molecular weight cut off (MWCO) offers limited suitability as selection criteria for membranes intended for polysaccharide filtrations. Overall, the presented applications of adsorption and ultrafiltration processes provide encouraging prospects for their incorporation into integrated processes aimed at the valorization of various food by products. Further collaborative efforts from diverse research fields, such as physics, chemical engineering, food science and process engineering, will facilitate the development of holistic valorization concepts to expedite the complete reutilization of food by products

Pigeon Pea Husk for Removal of Emerging Contaminants Trimethoprim and Atenolol from Water

The pace of industrialization and rapid population growth in countries such as India entail an increased input of industrial and sanitary organic micropollutants, the so-called emerging contaminants (EC), into the environment. The emission of EC, such as pharmaceuticals, reaching Indian water bodies causes a detrimental effect on aquatic life and ultimately on human health. However, the financial burden of expanding sophisticated water treatment capacities renders complementary, cost-efficient alternatives, such as adsorption, attractive. Here we show the merits of washed and milled pigeon pea husk (PPH) as low-cost adsorbent for the removal of the EC trimethoprim (TMP) and atenolol (ATN) that are among the most detected pharmaceuticals in Indian waters. We found a linear increase in adsorption capacity of PPH for TMP and ATN at concentrations ranging from 10 to 200 μg/L and from 50 to 400 μg/L, respectively, reflecting the concentrations occurring in Indian water bodies. Investigation of adsorption kinetics using the external mass transfer model (EMTM) revealed that film diffusion resistance governed the adsorption process of TMP or ATN onto PPH. Moreover, analysis of the adsorption performance of PPH across an extensive range of pH and temperature illustrated that the highest adsorption loadings achieved concurred with actual conditions of Indian waters. We anticipate our work as starting point towards the development of a feasible adsorbent system aiming at low-cost water treatment.ISSN:1420-304

Mass Transfer Mechanism and Equilibrium Modelling of Hydroxytyrosol Adsorption on Olive Pit–Derived Activated Carbon

The rise in olive oil production coincides with an increase in olive oil side-streams, such as olive mill wastewater and olive pits, enabling the exploitation of higher value-added products through proper processes. Adsorption techniques, common in wastewater treatment, facilitate the recovery of valuable compounds found in these by-products, such as the strong natural antioxidant hydroxytyrosol present in olive mill wastewater. Owing to their chemical composition, olive pits are a promising precursor for activated carbon production intended for adsorption purposes. However, a complementary side-stream strategy requires an in-depth analysis of the equilibrium state and the governing mass transfer mechanism based on sophisticated mathematical models for a reliable investigation of the processes occurring during hydroxytyrosol adsorption on olive pit–derived activated carbon (OPAC). Here we show the technological suitability of OPAC for adsorption of hydroxytyrosol in comparison to an existing commercial activated carbon (CAC). We found that the removal efficiency of OPAC was superior to CAC with increasing initial concentrations of hydroxytyrosol. The Redlich-Peterson isotherm provided the best fit to the adsorption equilibrium data based on the Akaike Information Criterion (AIC). Elucidation of the adsorption kinetics by means of the pore volume and surface diffusion model (PVSDM) showed that intraparticle diffusion resistance dominated hydroxytyrosol adsorption on OPAC. In addition, investigations over a broad temperature and pH range revealed the versatile applicability of OPAC and indicated a physisorption governed interaction. Our results demonstrate the fundamental parameters associated with hydroxytyrosol adsorption on OPAC, crucial for the development of adsorption systems to convert by-products into opportunities.ISSN:0300-9467ISSN:1385-8947ISSN:1873-3212ISSN:0923-046

On Determinism of Game Engines used for Simulation-based Autonomous Vehicle Verification

Game engines are increasingly used as simulation platforms by the autonomous vehicle (AV) community to develop vehicle control systems and test environments. A key requirement for simulation-based development and verification is determinism, since a deterministic process will always produce the same output given the same initial conditions and event history. Thus, in a deterministic simulation environment, tests are rendered repeatable and yield simulation results that are trustworthy and straightforward to debug. However, game engines are seldom deterministic. This paper reviews and identifies the potential causes of non-deterministic behaviours in game engines. A case study using CARLA, an open-source autonomous driving simulation environment powered by Unreal Engine, is presented to highlight its inherent shortcomings in providing sufficient precision in experimental results. Different configurations and utilisations of the software and hardware are explored to determine an operational domain where the simulation precision is sufficiently low i.e.\ variance between repeated executions becomes negligible for development and testing work. Finally, a method of a general nature is proposed, that can be used to find the domains of permissible variance in game engine simulations for any given system configuration.Comment: 16 pages, 9 figures, 1 tabl

Effect of Polysaccharide Conformation on Ultrafiltration Separation Performance

The manifold array of saccharide linkages leads to a great variety of polysaccharide architectures, comprising three conformations in aqueous solution: compact sphere, random coil, and rigid rod. This conformational variation limits the suitability of the commonly applied molecular weight cut-off (MWCO) as selection criteria for polysaccharide ultrafiltration membranes, as it is based on globular marker proteins with narrow Mw and hydrodynamic volume relation. Here we show the effect of conformation on ultrafiltration performance using randomly coiled pullulan and rigid rod-like scleroglucan as model polysaccharides for membrane rejection and molecular weight distribution. Ultrafiltration with a 10 kDa polyethersulfone membrane yielded significant different recoveries for pullulan and scleroglucan showing 1% and 71%, respectively. We found deviations greater than 77-fold between nominal MWCO and apparent Mw of pullulan and scleroglucan, while recovering over 90% polysaccharide with unchanged Mw. We anticipate our work as starting point towards an optimized membrane selection for polysaccharide applications.ISSN:0144-8617ISSN:1879-134