Computational modelling of fracture with local maximum entropy approximations

The key objective of this research is to study fracture with a meshfree method, local maximum entropy approximations, and model fracture in thin shell structures with complex geometry and topology. This topic is of high relevance for real-world applications, for example in the automotive industry and in aerospace engineering. The shell structure can be described efficiently by meshless methods which are capable of describing complex shapes as a collection of points instead of a structured mesh. In order to find the appropriate numerical method to achieve this goal, the first part of the work was development of a method based on local maximum entropy (LME) shape functions together with enrichment functions used in partition of unity methods to discretize problems in linear elastic fracture mechanics. We obtain improved accuracy relative to the standard extended finite element method (XFEM) at a comparable computational cost. In addition, we keep the advantages of the LME shape functions,such as smoothness and non-negativity. We show numerically that optimal convergence (same as in FEM) for energy norm and stress intensity factors can be obtained through the use of geometric (fixed area) enrichment with no special treatment of the nodes near the crack such as blending or shifting. As extension of this method to three dimensional problems and complex thin shell structures with arbitrary crack growth is cumbersome, we developed a phase field model for fracture using LME. Phase field models provide a powerful tool to tackle moving interface problems, and have been extensively used in physics and materials science. Phase methods are gaining popularity in a wide set of applications in applied science and engineering, recently a second order phase field approximation for brittle fracture has gathered significant interest in computational fracture such that sharp cracks discontinuities are modeled by a diffusive crack. By minimizing the system energy with respect to the mechanical displacements and the phase-field, subject to an irreversibility condition to avoid crack healing, this model can describe crack nucleation, propagation, branching and merging. One of the main advantages of the phase field modeling of fractures is the unified treatment of the interfacial tracking and mechanics, which potentially leads to simple, robust, scalable computer codes applicable to complex systems. In other words, this approximation reduces considerably the implementation complexity because the numerical tracking of the fracture is not needed, at the expense of a high computational cost. We present a fourth-order phase field model for fracture based on local maximum entropy (LME) approximations. The higher order continuity of the meshfree LME approximation allows to directly solve the fourth-order phase field equations without splitting the fourth-order differential equation into two second order differential equations. Notably, in contrast to previous discretizations that use at least a quadratic basis, only linear completeness is needed in the LME approximation. We show that the crack surface can be captured more accurately in the fourth-order model than the second-order model. Furthermore, less nodes are needed for the fourth-order model to resolve the crack path. Finally, we demonstrate the performance of the proposed meshfree fourth order phase-field formulation for 5 representative numerical examples. Computational results will be compared to analytical solutions within linear elastic fracture mechanics and experimental data for three-dimensional crack propagation. In the last part of this research, we present a phase-field model for fracture in Kirchoff-Love thin shells using the local maximum-entropy (LME) meshfree method. Since the crack is a natural outcome of the analysis it does not require an explicit representation and tracking, which is advantageous over techniques as the extended finite element method that requires tracking of the crack paths. The geometric description of the shell is based on statistical learning techniques that allow dealing with general point set surfaces avoiding a global parametrization, which can be applied to tackle surfaces of complex geometry and topology. We show the flexibility and robustness of the present methodology for two examples: plate in tension and a set of open connected pipes

Mestring forbi selvskading . Hvordan kan «Opplevelse av Sammenheng» påvirke mestringsstrategi hos ungdom som selvskader?

I masteroppgaven valgte jeg å bruke kvalitativ metode fordi det kan være med på å belyse temaet og hvordan prosessen oppleves av selvskadere. Gjennom metoden intervju, lå interessen i utviklingen av livssituasjon og selvskading. Jeg valgte å foreta semistrukturert intervju, hvor to informanter lot seg intervjue, disse informantene er en av kildene til masteroppgaven. I utviklingen av spørsmål for intervjuet, var referansegrunnlaget litteratur om selvskading, resiliens og selvskading som mestringsstrategi. Litteraturen står som bakteppe for intervjuguiden. Etter å ha kontaktet mulige informanter, var det to informanter som var villige til å la seg intervjues. Disse to individene ble intervjuet hver for seg, på to ulike tidspunkter. Det var en intervjuguide som førte intervjuet delvis, men informanten hadde også muligheten til å føre intervjuet. Det var ved begge tilfeller semistrukturert intervju, ved hjelp av lydopptaker og notathefte tilgjengelig. Under intervju situasjonen, slo det meg at informantene var bevisste på at selvskadingen var en måte å mestre smerte på. Om dette er fordi selvskading er et tilbakelagt kapittel eller om informantene var klar over det tidligere, er uklart. Informantene virket bevisste på at det var noe som fungerte, og selvskading ble brukt for å erstatte smerte med synlig smerte. Hva slags resultater kan man ta med seg fra dette? Informantene bekreftet tendensen beskrevet i litteraturen, ungdom som er mest utsatt for å bruke selvskading som mestringsstrategi er de som kommer fra ustabile hjem, hvor traumer har forekommet. Det virket som informanten opplevde lite støtte og forståelse og kommunikasjon var svak, dette økte trangen for å unnslippe uro i det indre, gjennom å visualisere det på det ytre. Kokepunktet kan være forskjellig, det varierer alt fra noe konkret som skjer i en situasjon til noe som bygger seg opp i løpet av en periode, men begge informantene meddelte følelsen av lettelse. Lettelse over at smerten kan skylles bort sammen med blodet, ned i vasken. Etter hvert, gikk livet videre med skole, venner, endring av miljø. Utvikling av sosiale ferdigheter og en klarere opplevelse av egen identitet, fører til selvskading som en mindre prioritert mestringsstrategi og tjener ikke lenger som en kommunikasjonsplattform. Informantene synes til å ha gått fra en tilstand som Antonovsky ville kalt svak opplevelse av sammenheng, til en sterkere opplevelse av sammenheng. Ved nærmere undersøkelse ville det vært interessant å se om informantene hadde skåret høyt på spørsmål som måler begripelighet, håndterbarhet og meningsfullhet. Hvordan kan opplevelse av sammenheng (OAS) påvirke mestringsstrategi hos ungdom som selvskader? Muligens kan man gå bort fra et patogent syn på selvskading, og anvende det salutogene tilnærmingen, ved å studere på hva som predikerer et godt utfall. Hva predikerer et godt utfall i tilfellet med selvskading. Ved å fokusere på mestringsstrategi, kan fagfolk prøve å bli fortrolig med type situasjon som øker lysten til selvskading, muligens trene opp til en OAS inspirert tankegang for å unngå selvskading. I stedet for å fokusere kun på selvskading, kan det forsøkes å skape en bakgrunnshistorie på eventuelle traumer og vonde opplevelser som har ført til økt lyst til å skade selvet. Målet med problemstillingen er ikke å åpne gamle sår, og dermed gjøre disse individene sårbare for tilbakefall for å selvskade, men å ha en åpen dialog. Jeg anser dette som en mulighet for å øke forståelsen av selvskading og informantenes opplevelse av selvskading. Oppgaven er et forsøk på å belyse behovet for kompetanse innenfor dette temaet hos fagfolk som jobber med barn og ungdom som muligens er selvskadere, og forhåpentligvis bidra til felles refleksjon over prosessen disse ungdommene går gjennom

The knowledge, attitude, and action of Northern Iranian women about cervical cancer and screening

Background: Cervical cancer is one of the most prevalent cancers in the world among women which its early diagnosis plays an important role in the prognosis. There are many factors that contribute to the participation in the screening programs, most notably the level of knowledge and attitude of people towards cancer. Understanding the level of these factors in the female population and its association with participation in screening programs is important. Therefore, the aim of this study was to determine the knowledge, attitude and practice of women in the north of Iran to compare these factors between two groups with different baseline knowledge.Methods: This cross-sectional study was carried out among female medical clients and healthcare staff in a healthcare center in the north of Iran. All the eligible patients were interviewed and were asked to fill a questionnaire containing the demographic data, knowledge, attitude, and action about cervical cancer and screening. The data were analyzed by SPSS v24.Results: A total of 283 females entered our study of which 156(55.1%) were clients of the healthcare center and 127(44.9%) were non-physician healthcare staff. Ninety (60.8%) of clients and 39(56.5%) of the staff have performed pap smear at least once (p=0.556). The levels of knowledge and attitude were significantly lower in the clients (p < 0.001 and p=0.003, respectively). There were no significant differences regarding the level of knowledge and attitude between those who performed pap smear and those who did not (0.621 and 0.788, respectively).Conclusions: Increasing awareness, especially improving attitudes in the female population, should be the focus of the health care system to encourage more women to participate in screening programs

Antecedents and consequences of preferred customer status

Suppliers have evolved to become significant stakeholders in any companies’ business. Suppliers might seem hands-down or be taken for granted because of the vast number of available options nowadays, and buyers might consider the process of procurement to be simple and trivial. That might be true for the majority of purchased products, however, there are situations in which lack of supply resources or scarcity of certain products results in competition between customers to secure their access to the scarce goods or services offered by competent suppliers. In these situations, these highly demanded suppliers can pick and choose, giving birth to the concept of preferred customer status. Preferred customer status is a level of customer attractiveness in which the buying firm has become the preferred and chosen customer of a certain supplier and will benefit from exclusive offers like early access to innovations and the best brainpower from the supplier. The objective of this study is to investigate how buying firms can become more attractive and gain this preferred status and to analyse the benefits a buyer gains by being an attractive or preferred customer. The drivers and consequences are explored from the available literature and a model of preferred customer status is constructed to be tested. In this study, three antecedents and two consequences are tested using data from a survey study. Statistical equation modeling is used to form a model and partial least square method is used to test the model using SmartPLS software. The results of this study show that the bridging capability of a buyer or its ability to connect suppliers to interesting new markets or interesting potential partners has a significant effect on customer attractiveness. It also shows that both customer attractiveness and preferred customer status are positively influenced by the performance feedback that the buyer provides to the supplier. Furthermore, the study shows that common goals and strategic fit of the two parties has a positive effect on the chance of gaining preferred status but has no effect on customer attractiveness. Moreover, testing the consequences, it is found out that customer attractiveness and preferred customer status both increase the supplier’s willingness to share information with the customer and improve the mutual performance of the two companies. These results are strong indications of the benefits of being a preferred customer. They show that becoming more attractive leads to valuable information that suppliers share with the buyer and the supplier’s commitment and efforts to improve the mutual relationship. The results also show that in order to gain attractiveness, buyers can leverage their network of partners and to connect the target supplier to interesting markets. It is also observed that developing an effective feedback system and having regular discussions with supplier about the relationship is very desirable to suppliers and buyers should take it into account in order to gain preferred status. Finally, buyers should consider the strategic fit between the two parties when thinking about becoming closer and gaining preferred status

Error analysis in academic writing: a case of international postgraduate students in Malaysia

This paper examines the different types of writing errors performed by 16 international postgraduate students undertaking an intensive English course at a public university in Malaysia. It was mandatory for international postgraduate students who obtained less than IELTS Band 6 to undertake an Intensive English Course (IEC) offered by the University, prior to entering their respective faculties’ academic programs. The students were required to write a 3-5 page term paper assignment on a topic related to their field of study. Mixed methodology approach was employed to examine and analyze corpus of students’ term papers. The errors in the term papers were identified and classified accordingly. The results of the study revealed that four most common English language errors committed by the participants were sentence structure, articles, punctuation and capitalization. This study also shed light on the manner in which students assumed the rules of English to that of their native language. Such insight is useful for both instructors and students because it provides significant information on the building blocks experienced by English language learners in academic writing

Physiological and Morphological Responses of the ‘Dargazi’ Pear (Pyrus communis) to in vitro Salinity

Salinity is one of the most important factors limiting growth and production of plants worldwide. Improving tolerance to salinity in plants is the most effective way to increase performance. Influence of salinity on growth, physiological and biochemical responses of Pyrus communis ‘Dargazi’ explants was investigated in in vitro conditions. Explants were cultured on Murashige and Skoog (MS) medium containing 1 mg L-1 BAP (6-banzyl amino purine) and 0.1 mg L-1 NAA (Naphthaline acetic acid) supplemented with different sodium chloride (NaCl) concentrations 0 (control), 40, 80, 120 and 160 mM. With increased salinity, the fresh weight, dry weight, the number of leaves, shoot length, chlorophyll index, multiplication index, leaf relative water content and total protein decreased. In contrast, proline, soluble sugar and activity of catalase increased