博士（経済学） / 甲第99号 / 155p / Hitotsubashi University

Syftet med studien har varit att undersöka vilka utmaningar utvecklare upplever vidgenomförande av enhetstester. Enhetstester är testkod som skrivs för att verifiera att produktionskod eller så kallad vanlig kod fungerar på ett bra sätt och uppfyller sitt syfte. Detta är den typ av testning vilket görs först i en utvecklingsprocess för att garantera att koden håller god kvalitét. Studien genomfördes genom att 5 utvecklare på ett IT konsultföretag i Luleå medverkat i individuella öppna kvalitativa intervjuer där de fått svara på frågor kring deras upplevelser av att arbeta med enhetstest. De slutsatser som studien har kommit fram till är att många av de identifierade problem som framkommit i denna studie stämmer överens med tidigare forskning inom detta ämne. Huvudsakligen var dessa problem av teknisk natur, där exempelvis underhåll, att veta vad som ska testas och att veta när en har testat tillräckligt, hörde till de vanligast förekommande gemensamma. Detta visar att denna problematik finns kvar än i dag. Vad som även framkommit i denna studie är att det är vanligt med avsaknad avutbildning gällande enhetstest. Även avsaknad av någon gemensam metod är något vi, speciellt i kombination med avsaknad av utbildning, anser förvärrar problematiken som redan existerar. Med hjälp av studiens kvalitativa ansats så har det identifierats en del potentiellabidragande faktorer för dessa upplevda problem. Utifrån dessa slutsatser har det formulerats rekommendationer för organisationer och för vidare forskning. / The purpose of the study has been to investigate what challenges developers experience when working with unit tests. Unit tests are test code written to verify that production code or so-called regular code works well and fulfills its purpose. This is the type of testing which is done first in a development process to guarantee that the code maintains good quality. The study was carried out by having 5 developers at an IT consulting company in Luleå participate in individual open qualitative interviews where they had to answer questions about their experiences of working with unit tests. The conclusions that the study has reached are that many of the identified problems that emerged in this study are consistent with previous research on this topic. Mainly these problems were of a technical nature, where, for example, maintenance, knowing what to test and knowing when one has tested enough, were among the most commonly occurring ones. This shows that these problems still exist today. What also emerged in this study is that it is common to lack education regarding unit tests. Also the lack of a common method is something we, especially in combination with the lack of education, consider to worsen the problems that already exist. With the help of the study's qualitative approach, some potential contributing factors for these perceived problems have also been identified. Based on these conclusions, recommendations have been formulated for organizations and for further research.

A vast amount of goods and products are transported in bulk as palletized unit loads, where the pallet is the base of the unit load. Material handling systems represent the physical environment in which unit loads are transported through supply chains. Material handling systems include different transportation modes and storage conditions, many of which are well researched. While industrial forklifts are paramount to material handling systems, the physical effect they have on load systems is not well understood. The weight of the unit load causes the pallets to deflect, and previous research has revealed that forklift vibration amplifies pallet deflection. The effects of forklift vibration on pallet deflection are not considered in international standards used to determine pallet load capacities. Standards such as ISO 8611 and ASTM D1185 provide deflection limits that are used to determine pallet load capacities, yet there is a lack of understanding and justification on these deflection limits related to forklift support conditions. A comprehensive understanding of the effects of forklift vibration on unit load performance is necessary to produce accurate and safe load capacity ratings. In this research, two studies were completed to gain further understanding on unit load performance and stability in forklift handling conditions. The first study evaluated pallet deflection and unit load stability of unbound unit loads designed with a 20 mm. performance limit (ISO 8611, 2011). Common forklift handling factors were investigated and included fork tine angle (level and 4-degree incline) and pallet orientation (racked across the width and across the length). The results showed that the dynamic environment of forklift handling created unstable unit loads. The second study of this research project investigated unit load performance against unit load design factors of load capacity (500 lbs., 750 lbs., 900 lbs.) and box size (8 in., 12 in., 16 in.). The results showed that unit load instability occurred at all load levels and all box sizes. Additionally, an increase in box size decreased load bridging for unit loads under fork tine support conditions. Furthermore, the time to instability was used to calculate projected forklift travel distances that can be used to further optimize material handling systems. / Master of Science / Many goods and products are transported across the world every day using a multitude of transportation modes and systems. The use of pallets to transport goods in bulk optimizes efficiency of the supply chain system. The physical transportation environment pallets are exposed to is used to determine their load capacity. While pallets are commonly handled by industrial forklifts, the environment the forklift creates for the pallet is not well understood. The mechanical stressors that forklifts create play a vital role in pallet performance and have been found to cause unit load instability.  Vibration represents one mechanical stressor that creates a hazard for material handling.  The goal of this research was to evaluate the performance of pallets in relation to the vibration imposed by industrial forklifts.   Previous studies measured forklift vibration and developed test procedures to replicate the forklift handling environment in a laboratory setting. Previous research investigated unit load performance where the pallet load capacity was determined using a 4.5-degree performance limit (ISO 8611, 2021). This study expanded on previous research by further investigating unit load performance against various load capacities and design parameters. This study included two experiments. The first experiment investigated the effect of common material handling factors on unit loads designed with a 20 mm. performance limit (ISO 8611, 2011). The second experiment investigated the effect of unit load design parameters such as load capacity and box size on unit load performance.   This study found that forklift vibration creates a hazardous environment where pallet deflection combined with magnified vibration caused unbound unit loads to become unstable. The data also revealed that larger boxes decrease unit load bridging in the fork tine support condition. Additionally, projected forklift travel distances were determined for various pallet testing standards. This data can be used to further optimize material handling systems.

The contributions of this research are a scalable formulation and solution method for decentralized unit commitment, experimental results comparing decentralized unit commitment solution times to conventional unit commitment methods, a demonstration of the benefits of faster unit commitment computation time, and extensions of decentralized unit commitment to handle system network security constraints. We begin with a discussion motivating the shift from centralized power system control architectures to decentralized architectures and describe the characteristics of such an architecture. We then develop a formulation and solution method to solve decentralized unit commitment by adapting an existing approach for separable convex optimization problems to the nonconvex domain of unit commitment. The potential computational speed benefits of the novel decentralized unit commitment approach are then further investigated through a rolling-horizon framework that represents how system operators make decisions and adjustments online as new information is revealed. Finally, the decentralized unit commitment approach is extended to include network contingency constraints, a crucial function for the maintenance of system security. The results indicate decentralized unit commitment holds promise as a way of coordinating system operations in a future decentralized grid and also may provide a way to leverage parallel computing resources to solve large-scale unit commitment problems with greater speed and model fidelity than is possible with conventional methods.

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