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Mobile apps are nowadays the preferred means to accomplish ubiquitous tasks like messaging, e-commerce and even playing games. Often, there exist multiple apps for the same purpose, and it is the choice of the end user to pick an appropriate app. Apps that behave unexpected, e.g., crash frequently, are sooner or later replaced, which isundesirable for the companies developing such apps. Thus, it is essential to tests apps properly before they are released onto the market. However, testing manually is often not only too cost-intensive but also too time-consuming in the short development phase, thus an automated solution is preferred. Testing mobile apps automatically received increased attention in the last decade from primarily people in academia, and several testing techniques evolved. One technique that yielded promising results, especially in different domains, is search-based software testing in which a metaheuristic, e.g., a genetic algorithm, is applied to solve an optimisation problem, e.g., test generation. A main objective of test generation is to produce tests that reveal as many faults as possible.
This in turn requires the generation of tests that deeply explore the tested app. The core metric to quantify how much code tests cover is the measurement of code coverage, which can be computed at different levels of granularity ranging from determining the fraction of covered activities to a very fine-grained measurement that calculates the percentage of covered lines. This coverage information is then often used to guide the search of the employed metaheuristic.
However, current automated test generation approaches produce tests with a rather low code coverage. Thus, a substantial part of tested apps remains unexplored, which in turn misses revealing deeply residing faults. We identified three core issues that are directly related to the generation of low-coverage tests. First, the applicability of current test generators is often limited. This comprises the fact that current state-of-the-art code coverage tools are incapable of instrumenting a substantial number of apps and consequently, test generators cannot utilise detailed coverage information during exploration.
In addition, test generators are often only equipped with a primitive set of actions that are insufficient to simulate system events and complex user inputs. Second, the test execution is extremely time-consuming. This includes among other things the overhead associated with executing individual actions, intermediate restart operations as well as fitness evaluations. Since search-based algorithms require a substantial number of test executions to play out their strengths, the slow test execution impedes the effectiveness of the search. Third, the guidance offered by search-based algorithms is often hampered by applying inadequate fitness functions or by using non-representation-specific variation operators.
In this thesis we address the problem of low-coverage tests in the Android domain by proposing several enhancements for the three identified core issues. Concerning the applicability problem, we provide the implementation of a robust code coverage tool that is capable of measuring coverage at different levels of granularity and requires no access to the source code. We also propose to include actions that can simulate system events as well as complex user inputs. Regarding the performance issue, we suggest the integration of a surrogate model that is capable of predicting the outcome of individual actions or complete tests over time in order to reduce the overall test execution costs. With respect to the lack of guidance offered by traditional search-based algorithms, we suggest alternative search strategies. In the case of a deceptive fitness landscape, we propose using novelty search algorithms. Alternatively, we suggest utilising estimation of distribution algorithms that require no crossover or mutation perators to sample new tests. While all those enhancements had a positive impact on the Android test generation process, the individual empirical studies highlighted that further research is necessary to unleash the full power of the proposed search-based algorithms. In particular, exploring complex user interfaces meaningfully requires more attention whether by introducing additional actions or by extracting valuable hints to infer reasonable text inputs. In addition, the guidance offered by fitness functions is often limited because they are either designed too coarse at all or do not accurately reflect the search objectives.
Migration plays a significant role in Ghanaian society, particularly in rural areas where its impact is inextricably linked to socio-economic dynamics. In March 2023, a student field research field research project was conducted in Amedzofe as part of the international research project “Migration and Translocality in West Africa”, shedding light on various aspects of rural life through the lens of translocality. The field research aimed to address a wide range of topics related to rural livelihoods, focusing on migration and translocal aspects of everyday life. Six working groups embarked on a 10-day field research journey, employing mixed methods encompassing both quantitative and qualitative approaches. This extensive fieldwork followed a semester of intensive preparation, ensuring the thoroughness and depth of the study.
The survey results were meticulously analysed and presented, providing valuable insights into the patterns, drivers and impacts of migration in the region. Additionally, the findings of the six working groups offered nuanced perspectives on various facets of rural life, including economic activities, social networks, cultural practices, education and gender aspects.
This endeavour aims at fostering a deeper understanding of the complexities surrounding migration and translocality in rural Ghana. It is a testament to the dedication and vision of the late Prof. Dr. Malte Steinbrink, whose leadership and guidance were instrumental in the preparation and realisation of this study.
With recent progresses in the field of artificial intelligence (AI), algorithms can support more complex tasks (Frey and Osborne, 2017) that seemed safe from automation a few years ago (Brynjolfsson and McAfee, 2012). They can even outperform human decision-making in many task domains (Meehl, 1954; Dawes et al., 1989). The prominent defeat of Garry Kasparov, the world champion in chess, in 1997 is a milestone for the potentials of algorithms, increasing the value of IBM’s stock increased by $18 billion (Norvig and Russell, 2010). More recently, universal chatbots such as ChatGPT and the Bing Chatbot Sydney can influence millions of users and provide them answers to a broad range of tasks.
To gain a competitive edge, companies invest heavily in algorithmic systems (Kappelman et al., 2021), which are considered as one of the most important drivers of today’s economy (Brynjolfsson and McAfee, 2011; Hogharth and Makridakis, 1981; Önkal et al., 2019). Particularly in management accounting, an algorithmic data analysis offers the potential to support a high decision quality, making their usage a key factor for success.
However, algorithms can not only support, but also manipulate human decision-making (Roose et al., 2023). Algorithmic advice can lead to overtrust, i.e. to the heuristic replacement of vigilant information seeking and processing in favor of the advice provided (Mosier et al., 2001). The implementation of algorithmic decision support systems is thus no panacea to improve human decision-making. In contrast, they can entail new risks, such as the uncritical use of these algorithms (Boden, 2016). Yet, this ‘dark side’ of algorithms is not sufficiently investigated in the field of management accounting. With advances in machine learning, algorithmic support can become even more of a black box, blurring the reference points for evaluating its advice quality and thus increasing the risk of overtrust. Stephen Hawking even warns that AI will be “either the best, or the worst thing, ever to happen to humanity” (Alex Hern in: The Guardian: Stephen Hawking: AI will be 'either best or worst thing' for humanity, 19th October 2016). Interacting with such algorithmic systems therefore requires data literacy skills for an appropriate use. They seem to be a crucial prerequisite in today’s data-driven world to reap of the benefits of algorithmic systems. If no reflective and critical interaction between human and algorithm can be ensured, the trend towards a digitalized world will be a race against the algorithm (Brynjolfsson and McAfee, 2011).
This dissertation takes this understudied critical perspective on the increasing implementation of algorithmic systems and sheds light on different aspects of human-algorithm interaction, ranging from the ability to use data visualization tools to trust calibrations and critical evaluations of algorithmic advices. Study I investigates an adequate information representation of subjective multiple criteria decision problems, an important task in management accounting, to support human decision-making. Study II distinguishes different designs of the human-algorithm interaction investigated in the trust in automation literature and compiles factors influencing the calibration of trust and behavior toward the true capabilities of the algorithm. Study III examines the role of performance feedback on trust and advice usage in a forecasting task for a better understanding of the recently observed phenomenon ‘algorithm aversion’. Finally, Study IV focusses on the risk of overtrust in advice in repeated interactions with a forecasting advisor and investigates the calibration of advice usage. Each study thereby represents an independent contribution and contains all information relevant to the respective research questions asked in the study.
Offering solutions impose manifold challenges on suppliers. To master these challenges, suppliers need excellent commercial capabilities. This thesis considers these challenges and opportunities in sales, contracting, and pricing of complex B2B solutions in three essays:
Essay 1 addresses the increased complexity for solution salespeople, who represent an essential strategic asset in solution selling. In-depth interviews with solution sales managers in study 1 and survey data from matched sales manager-salesperson dyads in study 2, reveal nine specific equifinal configurations of key personal and procedural competencies that qualify individual salespeople in their role and thus determine their solution sales success.
The focus of essay 2 lies on B2B export relationships for complex product-service combinations in an international context. A regression analysis based on a survey study with 198 responses shows several direct and indirect effects of contractual and cultural constructs. The results give insights under which cultural framework conditions contract specificity serves as a safeguarding mechanism against uncertainty and opportunism.
Essay 3 examines how the bidirectional agency relationship between suppliers and customers and the performance uncertainty of a solution influence B2B customers’ acceptance of performance-based pricing (PBP). Drawing on a cross-industry survey with 196 managers of B2B firms, this study contributes to extend PBP literature by showing how bidirectional agency relationships shape customers’ acceptance of PBP.
In sum, this thesis contributes to a better understanding on how to optimize commercial capabilities in the context of national and international solution selling. It thereby focuses on addressing recently identified causes that hinder B2B firms from increasing their margins through solution selling by
(1) optimizing the sales force through a better understanding of important resources and capabilities for solution selling,
(2) optimizing their contractual set-up through a better understanding of cultural factors and the interplay with contract specificity, and
3) optimizing price policy through a better understanding of framework conditions, which have an impact on customers’ acceptance of PBP.
Coastal flooding events pose an existential threat to populations around the world, particularly in the Global South. As a result of climate change and other, direct forms of anthropogenic interference, the magnitude and frequency of such floodings is predicted to continuously increase in the near future. Therefore, it is important to understand the vulnerability of affected people to implement appropriate measures. This research presents a case study on coastal flooding and its impact on livelihoods in the Volta Region of Ghana. The paper utilizes a vulnerability framework that focuses on exposure, susceptibility, as well as the capacities to anticipate, cope with, and recover from the effects of natural hazards. Based on a qualitative approach, the study focusses on those households who were directly affected of a severe tidal flood in November 2021, leading to a total destruction of their property. The research was conducted in March, July and August 2022. It revealed that the studied group had low capacity to anticipate and had no contingency plans in case of relocation. Further, we discovered different strategies that people applied to deal with the situation eight months after the flood event. Most households applied (short term) coping strategies to reestablish their former marine-based livelihood systems. Adaption in terms of long-term adjustment of their livelihoods played only a minor role and could be found in form of out-migration in a limited number of households.
Climate change as a driver of migration? A comparative case study in eastern and northern Ghana
(2024)
Academic studies and media reports have pointed to climate change as a dominant factor responsible for future mass migrations from and within the Global South. In response to the deterministic nature of their estimates and predictions, this research explores the link that migrants establish between the environmental changes they experience and migration as a climate adaptation strategy. Furthermore, the overlaps between the profile and migratory behavior of those who manifest a greater presence of climate change in their migratory processes and their counterparts are analysed to identify potential unique climate migration patterns and practices. The quantitative analysis of data gathered in the context of the Mitra|WA project in Ghana's Eastern and Northern Regions in 2022 reveals that, while migration is not predominantly propelled by climate change climate, it does not constitute a new form of mobility demarcated from existing migration patterns and practices. This paper provides an opportunity to redirect future research towards the factors that determine the agency of individuals in response to climate hazards and to explore the role of climate change in a set of drivers of migration in a West African setting.
This study explores American folk horror as a mode of inquiry into the literary, cultural, filmic, ecological, and political histories of the United States. By using ecofeminist theory to read American folk horror against its roots in the frontier gothic, a genre concerned with the realities and afterlives of American settler colonialism, in turn inextricably linked with the U.S.' founding myths and national narratives that developed since the arrival of the first European settlers, my approach uncovers the dual and simultaneous exploitation of women and nature since 1492, focusing on the ways human and non-human Others continue to be at the mercy of anthropocentric and capitalocentric systems.
American folk horror as genre, and the frontier gothic as its archive, allows us to see the ways American founding narratives serve as and word like folklore, contributing to the perpetuation of discrimination against underprivileged groups, especially those who are seen as nature, like women.
This book offers a lengthy theorization of the genre as well as both ecofeminist readings of select texts of American folk horror (Darren Aronofsky's mother!, Shirley Jackson's We Have Always Lived in the Castle, Robert Eggers's The VVitch: A New-England Folktale) and a first discussion of a potential corpus of the genre ranging from frontier gothic literature and contemporary film to video games of the 2020s.
The thesis addresses a current topic related to the foreign policy of Serbia whereby Serbian foreign policy is analysed with reference to its domestic factors - in particular national identity - and also with regards to Serbia’s foreign factors, such as the Europeanization process and the nature of the international system. The overarching focus of the thesis is laid on the following puzzle: in spite of not attaining self-declared foreign policy goals and changing dynamics at the systemic level, Serbia’s foreign policy appear to be stable over time. In each of the five publications comprising the thesis, a narrower aspect of this puzzle is addressed.
In ständiger Rechtsprechung sanktioniert das Bundesarbeitsgericht fehlerhafte Massenentlassungsverfahren mit der Unwirksamkeit der Entlassungen, § 134 BGB i. V. mit § 17 KSchG. Die Arbeit untersucht anhand einer dreistufigen Prüfung, ob und wie geschehene Fehler zu sanktionieren sind.
1) Fehler sind immer dann zu sanktionieren, wenn sie den Sinn und Zweck des Verfahrens tangieren, wenn sie also relevant sind. 2) Arbeitnehmer:innen können sich auf einen Fehler nur berufen, wenn sie von diesem betroffen sind. 3) Erscheint eine Sanktion im konkreten Einzelfall als unangemessen, ist eine Ausnahme vom Unwirksamkeitsverdikt zu gewähren – andere, ggf. weniger weitreichende Rechtsfolgen kommen dann aber ebenfalls nicht in Betracht.
Protection blinding is a challenging issue in renewables-penetrated distribution grids and refers to a situation where a circuit breaker may not trip due to fault current contribution from distributed generation. This research addresses how the distributed generation location and capacity impact the operation of the circuit breaker in terms of the response time of the circuit breakers. The relative electrical distances of the faults and distributed generation to the circuit breakers are considered. The impact of distributed generation capacity considering the fault location is characterized using a new index called the heterogeneity index. The electrical distance between distributed generations and circuit breakers and the electrical distance between fault and circuit breaker is considered by a second new index called the electrical distance ratio. Data analysis on simulation results shows that these indices capture the phenomena of protection blinding caused by distributed generation.
Results show that a higher distributed generation penetration and faults that are electri
cally further away from a circuit breaker show severe cases of protection blinding captured by the indices. Furthermore, it is demonstrated how these indices can identify the worst impacted locations in the distribution grid. A key result is that protection blinding does not necessarily occur solely due to the presence of distributed generation between a circuit breaker and a fault, but is dependent on factors such as distributed generation location in the distribution grid, fault level, fault level distribution across the generation units and fault location.