Optimizing decomposition of software architecture for local recovery

Cataloged from PDF version of article.The increasing size and complexity of software systems has led to an amplified number of potential failures and as such makes it harder to ensure software reliability. Since it is usually hard to prevent all the failures, fault tolerance techniques have become more important. An essential element of fault tolerance is the recovery from failures. Local recovery is an effective approach whereby only the erroneous parts of the system are recovered while the other parts remain available. For achieving local recovery, the architecture needs to be decomposed into separate units that can be recovered in isolation. Usually, there are many different alternative ways to decompose the system into recoverable units. It appears that each of these decomposition alternatives performs differently with respect to availability and performance metrics. We propose a systematic approach dedicated to optimizing the decomposition of software architecture for local recovery. The approach provides systematic guidelines to depict the design space of the possible decomposition alternatives, to reduce the design space with respect to domain and stakeholder constraints and to balance the feasible alternatives with respect to availability and performance. The approach is supported by an integrated set of tools and illustrated for the open-source MPlayer software

Cracking and Failure Characteristics of Flame Cut Thick Steel Plates

The manufacturing of thick wear-resistant steel plates commonly leads to a layered structure and non-uniform properties in the thickness direction which makes the processing and utilization of the plates problematic. The processing steps of thick plates include flame cutting, which generates a heat-affected zone and high residual stresses into the cut edge. In the worst case, the cutting causes cracking. However, the residual stress level alone is not high enough to break a wear-resistant steel plate that behaves normally. Therefore, high-tensile stress also requires a microstructurally weak factor for crack initiation. For this reason, the main objective of this study is to reveal the main microstructural reasons behind the cracking of plates in flame cutting. To achieve this, plate samples containing cracks are mechanically tested and analyzed by electron microscopy. The results show that cracks are commonly formed horizontally into the tempered region of the heat-affected zone. Cracks initiate in the segregations, which typically have a higher amount of impurity and alloying elements. Increased impurity and alloying content in the segregations decreases the cohesion of the prior austenite grain boundaries. These weakened grain boundaries combined with high-residual tensile stress generate the cracks in the flame-cutting process.publishedVersionPeer reviewe

Does dental hygienist professional education meet the needs of working life?:educators’ views

Abstract Objective: The aim of this study was to describe the compatibility of dental hygienist education with working life from the perspective of their educators. Methods: We conducted a qualitative study among principal educators of dental hygienists in Finland in 2012–2013. The participants were leading educators of dental hygienists (n = 13) from the four Finnish education units. We used semi-structured interviews based on previous Nordic studies to collect the data and analysed them using inductive content analysis. Results: According to the educators, dental hygienists’ skills at work are neither fully nor effectively utilized, even though their education meets the needs of working life quite well. The educators felt that hygienists’ professional competence would prove more useful in health promotion and orthodontic measures and that the division of labour should be clearer. Clarifying this distinction in periodontal therapy could be improved. Conclusion: Fully utilizing dental hygienists’ competence in clinical work would benefit from further development. The content of dental hygienists’ clinical work should be reassessed so as to utilize their skills more fully. The compatibility of dental hygienist education corresponds largely to the needs of future working life

Comparative study of additively manufactured and reference 316 L stainless steel samples:effect of severe shot peening on microstructure and residual stresses

Abstract The as-built selective laser melted (SLM) austenitic stainless steel 316 L components are characterized by presence of quality related concerns such as tensile residual stresses, poor surface finish, etc. These issues may prove to be detrimental during the actual usage of components and could result in poor mechanical performance. Therefore, it is important to perform the apt post processing such as heat treatment and shot peening to tailor such problems and facilitate improved mechanical performance. In the present work, additively manufactured (AM) 316 L samples were subjected to shot peening with different parameters including the severe shot peening (SSP) procedure. The identical shot peening protocol was also applied to reference samples to evaluate the comparable response. Both the shot peened reference and AM samples were studied for residual stresses, surface topography, microhardness, and the corresponding microstructure. The results indicated, that SSP induced higher values of compressive residual stresses deeper into the samples. This was accompanied by reduced surface roughness, increased grain refinement depth, and higher microhardness near the surface. The SSP resulted in transformation of original austenite to martensite near the surface in the reference samples

Characterization of Flame Cut Heavy Steel : Modeling of Temperature History and Residual Stress Formation

Heavy steel plates are used in demanding applications that require both high strength and hardness. An important step in the production of such components is cutting the plates with a cost-effective thermal cutting method such as flame cutting. Flame cutting is performed with a controlled flame and oxygen jet, which burns the steel and forms a cutting edge. However, the thermal cutting of heavy steel plates causes several problems. A heat-affected zone (HAZ) is generated at the cut edge due to the steep temperature gradient. Consequently, volume changes, hardness variations, and microstructural changes occur in the HAZ. In addition, residual stresses are formed at the cut edge during the process. In the worst case, unsuitable flame cutting practices generate cracks at the cut edge. The flame cutting of thick steel plate was modeled using the commercial finite element software ABAQUS. The results of modeling were verified by X-ray diffraction-based residual stress measurements and microstructural analysis. The model provides several outcomes, such as obtaining more information related to the formation of residual stresses and the temperature history during the flame cutting process. In addition, an extensive series of flame cut samples was designed with the assistance of the model.acceptedVersionPeer reviewe