On the Development of Hierarchical Real-Time Systems

Hierarchical scheduling (also referred to as resource reservation) is a hot topic within the research of real-time systems. It has many advantages such that it can facilitate software integration, fault isolation, structured analysis, legacy system integration etc. The main idea is to partition resources into well defined slots and the resource itself may be the processor, memory etc. This technique is rarely used in real-time applications, however, it is well adopted in the avionics industry in order to isolate error propagation between system parts, and facilitate analysis of the system.Much of the research within resource reservation deals with theoretical schedulability analysis of partitioned systems, including shared resources (other than the processor). We will in this thesis address more practical issues related to resource reservation. We focus on implementation and prototyping aspects, as well as verification and instrumentation. One of our assumptions is that we deal only with fixed-priority preemptive scheduling (FPPS).The first part in this thesis deals with individual software systems that may have its own tasks as well as a scheduler and it is assumed to be part of another larger system, hence, we refer to this individual system as a subsystem. The subsystem is assumed to be integrated together with other subsystems, but at a early stage, we make it possible to simulate the subsystem running together with the rest of the subsystems. This "simulation`` does not require the actual resource reservation mechanism, the only requirement is an operating system with support for FPPS. This pre-study may be a natural step towards the "real`` integration, since each individual subsystem can be test executed within its assigned partition. All subsystems are assumed to run together using a resource reservation mechanism (during the actual integration). We have developed two prototypes of this mechanism. The first prototype is hand-crafted and it is equipped with a program tracer for partitoned based schedulers. This instrumentation is useful for debugging and visualization of program traces for this type of scheduling. The second prototype is developed using timed automata with tasks (task automata). This model-based scheduler is verified for correctness and it is possible to automatically generate source code for the scheduler. We have successfully synthesized this scheduler for the real-time operating system VxWorks. However, it can easily be executed on most other platforms. Both prototypes has pros and cons. The first version has good performance while the second can guarantee its correctness, hence, there is a trade-off between performance and correctness

Enhancing the Interactivity in the Classroom via Smartphone

In order to enrich the interactivity in the classroom a digital survey system can be employed to enable teachers to enquire questions to the students and review the answers in a quick and effortless way. Today at Uppsala University a commercial survey system is in use that consists of; handheld devices used by students to submit an answer, Wi-Fi adapters that receive the answers from the devices and software that creates and presents survey sessions. This report is concerned about finding an alternative to that system and is aimed primarily to improve the economical factor. The approach is to make use of the increasing amount of Smartphone devices that flourish among students today. This resulted into a solution that holds the basic features of the original system. The design employs a Smartphone application which lets the students select a survey from a content manager and then fill it out by interacting with an online survey service. The outcome of a survey can, similarly to the original system, be presented in an integrated fashion within a presentation slide to reduce the need of switching windows when showing a presentation. In conclusion there is a basic and free alternative to the current system assuming every student has a Smartphone available. One of the advantages beside the economical factor include being easier to manage for the teachers as there is no need to administer response devices to the students prior to a survey session

筑前国 福岡藩札 為替手形 金1朱

日本銀行金融研究所所蔵藩札等資料番号：ⅢAエドa1-63-2-15科学研究費助成事業（研究成果公開促進費）で電子化を実施データベースの名称：藩札等に関する統合データベース課題番号：19HP8033利用に関するお問い合わせ：画像の転載（出版物・HP等）に際しては、日本銀行貨幣博物館への申請手続きが必要です。詳しくは貨幣博物館ホームページ（http://www.imes.boj.or.jp/cm/service/）をご覧ください

Synthesis and Synchronization Support for Hierarchically Scheduled Real-Time Systems

A piece of software, that we define as a software system, can consist of anything from a few lines of program code or the entire software stack in a vehicle. Software systems can be divided into smaller and partially independent parts called subsystems/partitions (we use the words partition and subsystem interchangeably). The non-functional isolation of subsystems, that appears when the software system is hierarchically divided, has great advantages when it comes to preventing fault propagation between subsystems. The hierarchical division, that we refer to as hierarchical scheduling, has other advantages as well. It facilitates re-usability and it makes timing analysis of software systems easier. Hierarchical scheduling has been shown to be a useful tool in counteracting the verification challenges that comes from the growing complexity in software. For example, the avionics-specification ARINC653 and the safety-critical operating systems seL4 and PikeOS safely divide resources for independent safety-critical applications by using hierarchical scheduling. Hierarchical scheduling can be implemented in many different ways, depending on what resource that is supposed to be shared among applications. The resource could be the CPU, memory, network etc. The work in this thesis is focused on the practical aspects of timing isolation among subsystems, i.e., sharing of the CPU resource. Hence, this work elaborates on how to adapt and extend the operating-system task-scheduler to support hierarchical scheduling. We have focused on both independent and semi-dependent subsystems. Independent subsystems only share general resources such as the CPU and memory. Semi-independent subsystems share not only the general resources, but also other logical resources that can only be accessed in a mutually exclusive way, i.e., by one subsystem at a time. An example of such a resource could be a shared memory-space, e.g., a database, a memory-mapped device etc. This thesis has two main parts related to hierarchical scheduling: scheduler synthesis, and synchronization. Scheduler synthesis is related to implementation and design strategies when adding support for hierarchical scheduling in an operating system. We have focused on various operating systems that were lacking the feature of hierarchical scheduling. The two most interesting operating systems that we worked on was Linux and seL4. These two operating systems represent two extremes, where Linux is more focused towards soft real-time systems and seL4 towards pure hard real-time (safety-critical) systems. Linux-based systems have in general less strict demands on correctness and more requirements on usability. Usability implies less installation efforts and less limitations in the usage of the available Linux functionality. The usability aspect is especially important for Linux systems since kernel updates occur much more frequently compared to any other operating system. Hence, extending/modifying the functionality of Linux must be done in a way that does not require any modifications to the kernel. seL4 on the other hand has strict requirements on safety, i.e., functional and non-functional correctness, but also performance efficiency. Guaranteeing correctness implies a potential loss of performance due to the added overhead that the verified software can bring. The correctness aspect includes strategies on how to verify hierarchical schedulers, but also how to minimize the scheduler overhead and achieve as good run-time performance as possible. Conclusively, there are many challenges when it comes to scheduler synthesis. There are requirements on performance, usability, correctness etc. The contribution in the synthesis part includes a scheduler framework called ExSched (External Scheduler). We have also contributed with a novel approach to verify hierarchical schedulers, and a code generator called TAtoC (Timed Automata to C) which contributes to the effective run-time performance of synthesized timed-automata models. The second part of this thesis, synchronization, is an important general aspect of hierarchically scheduled systems since the isolation of subsystems makes resource sharing among subsystems more challenging. We have advanced the state-of-the-art in this research area by introducing a new synchronization protocol called RRP (Rollback Resource Policy) that improves on the robustness and run-time performance compared to the existing protocols. We have also conducted a large scale experimental evaluation of all existing protocols that we have implemented in the widely used real-time operating system VxWorks

Jämförelse av Oracle och MySQL med fokus på användning i laborationer för universitetsutbildning

Syftet med arbetet som beskrivs i denna rapport var att undersöka om den Oracle-baserade laborationsmiljö som användes hos ADIT gick att överföra till MySQL. Oracle är ett komplext system som är krävande att administrera, något som ADIT ansvarat för med egen personal och egen hårdvara och detta var inte idealiskt. I kombination med ett stort intresse från studenter att använda just MySQL vid laborationer hos ADIT beslutades det att man skulle undersöka om MySQL nu var moget att axla den roll som Oracle tidigare haft. Utifrån detta går rapporten igenom vad som behövde göras med det befintliga laborationsmaterialet. En introduktion till relations¬modellen och SQL samt förklaringar av skillnader i features mellan Oracle och MySQL som hade betydelse för laborationerna återfinns också. Det visade sig att överföringen var enkel att göra och sist i rapporten sammanställs våra erfarenheter

Enhancing the Interactivity in the Classroom via Smartphone

In order to enrich the interactivity in the classroom a digital survey system can be employed to enable teachers to enquire questions to the students and review the answers in a quick and effortless way. Today at Uppsala University a commercial survey system is in use that consists of; handheld devices used by students to submit an answer, Wi-Fi adapters that receive the answers from the devices and software that creates and presents survey sessions. This report is concerned about finding an alternative to that system and is aimed primarily to improve the economical factor. The approach is to make use of the increasing amount of Smartphone devices that flourish among students today. This resulted into a solution that holds the basic features of the original system. The design employs a Smartphone application which lets the students select a survey from a content manager and then fill it out by interacting with an online survey service. The outcome of a survey can, similarly to the original system, be presented in an integrated fashion within a presentation slide to reduce the need of switching windows when showing a presentation. In conclusion there is a basic and free alternative to the current system assuming every student has a Smartphone available. One of the advantages beside the economical factor include being easier to manage for the teachers as there is no need to administer response devices to the students prior to a survey session

Enhancing the Interactivity in the Classroom via Smartphone

In order to enrich the interactivity in the classroom a digital survey system can be employed to enable teachers to enquire questions to the students and review the answers in a quick and effortless way. Today at Uppsala University a commercial survey system is in use that consists of; handheld devices used by students to submit an answer, Wi-Fi adapters that receive the answers from the devices and software that creates and presents survey sessions. This report is concerned about finding an alternative to that system and is aimed primarily to improve the economical factor. The approach is to make use of the increasing amount of Smartphone devices that flourish among students today. This resulted into a solution that holds the basic features of the original system. The design employs a Smartphone application which lets the students select a survey from a content manager and then fill it out by interacting with an online survey service. The outcome of a survey can, similarly to the original system, be presented in an integrated fashion within a presentation slide to reduce the need of switching windows when showing a presentation. In conclusion there is a basic and free alternative to the current system assuming every student has a Smartphone available. One of the advantages beside the economical factor include being easier to manage for the teachers as there is no need to administer response devices to the students prior to a survey session

The effect of self-care and participation in dialysis care at home, the impact on everyday life : A qualitative literature review

Bakgrund: Kronisk njursvikt är en vanlig förekommande sjukdom och andelen patienter i behov av dialys är hög. Patienten har idag möjlighet att behandlas i hemmet med antingen hemodialys eller peritonealdialys. För att patienten ska kunna utföra sin behandling i hemmet är egenvård och delaktighet centralt. Att sjuksköterskor arbetar personcentrerat är också en viktig aspekt, där patientberättelsen är utgångspunkten i hur vården ska utformas. Syfte: Beskriva patienters upplevelser av dialysvård i hemmet. Metod: Då syftet var att beskriva patienters upplevelse av sin dialysbehandling utfördes en kvalitativ litteraturöversikt bestående av 11 vetenskapliga artiklar med patientperspektiv. Resultat: Resultatet visar att patienten i början av behandlingen upplever en osäkerhet kring lärandet av hemdialys, men tryggheten ökar med tiden. Behovet av stöd ifrån sjuksköterskor och närstående beskrivs som en viktig faktor då det bidrar till en ökad trygghet för patienten i sin behandling. Efter en tid kan patienten anpassa sin behandling inom den terapeutiska ordinationen för att kunna styra sin behandling utifrån vardagliga aktiviteter. Konklusion: Hemdialys medför stora krav på patientens delaktighet och egenvård. Sjuksköterskans stöd leder till trygghet i behandlingen. När en god egenvård uppnås och behandlingen fungerar medför hemdialys flexibilitet och frihet där patienten upprätthåller en önskvärd livsstil.Background: Chronic kidney disease is a common disease, and the numbers of patients in need of dialysis are high. The patient today has the opportunity to do dialysis at home with either hemodialysis or peritoneal dialysis. Self-care and participation are essential and central for the patient to cope with the treatment method at home. It's also important that the nurse operate person-centered. The patient's own story is the focal point in how the care is designed. Purpose: Describe patients experience on dialysis at home. Method: Qualitative articles with a patient perspective were analyzed. Results: The patient was initially uncertain about learning the treatment, but security comes with time. The need for support by relatives and nurses were described as necessary in the security of their treatment. With time the patient learned to adjust the treatment within the therapeutic ordination to fit with everyday activities. Conclusion: Home dialysis involves requisites on the patient. Self-care and participation are central. Support of the nurse gives the patient security in their treatment. When a good self-care is reached, the treatment method enables flexibility and freedom, and the patient can live a more desirable life

Effect of preheating temperature on the porosity and microstructure of martensitic hot work tool steel manufactured with L-PBF

Additive manufacturing (AM) brings the possibility to produce tools with a complex design of the cooling channels to achieve desired properties in the working piece. However, AM of tool steels can be challenging due to the residual stresses and crack formation which may be mitigated by optimizing process parameters. In this study, process parameters development in the laser powder bed fusion (L-PBF) of a martensitic hot work tool steel was under investigation. Having power, scanning speed and hatch distance as variables, a design of experiment was performed to map a process window to produce dense components. In addition, the same sets of process parameters were applied at different preheating temperatures to study and discuss the effect of three preheating temperatures on the porosity, microstructure and hardness of the manufactured components. The characterization of the parts was done using optical and scanning electron microscopy, x-ray diffraction and micro-hardness test. The results showed that the martensitic hot work tool steel can be manufactured with L-PBF with high densities above 99.95%. © 2022 The Authors. Published by Elsevier B.V

Process quality assessment with imaging and acoustic monitoring during Laser Powder Bed Fusion

Acoustic monitoring of laser powder bed fusion (LPBF) has shown a high sensitivity to stochastic defects, e.g., cracks, pores and lack of fusion (LOF), and melting instability. The advantage of this method is the possibility to filter raw data and extract acoustic signal features for the data analysis, thus minimizing data and computing time. In this research during the build of components from hot work tool steel powder, acoustic signals and powder bed images were acquired for post-process data analysis and search for correlations with LOF. Different densities caused by LOF were obtained by changing the shielding gas velocity. In the analysis, selected combinations of features with the relationship between the build phases and the final properties such as density and surface roughness, were investigated. For the current dataset prediction of the optimal state showed an accuracy of 98%. This investigation suggests the applicability of the smart data-centric machine learning method to predict the relationship of process parameters, monitoring signals, and material properties. © 2022 The Authors. Published by Elsevier B.V