Creep Behavior of a Ti-based Multi-Principal Element Alloy

Abstract The understanding of microstructural damage mechanisms is the foundation of better understanding existing materials and future material development. There are significant challenges to measuring these damage mechanisms in-situ as continuous observation of the state of the microstructure is difficult or impossible for many experimental setups. This thesis presents a method for measuring grain boundary sliding (GBS) and local strain concentrations in-situ via a Heaviside function based algorithm. GBS is the shearing of two grains along their shared grain boundary and is a common damage mechanism in creep which presents as a discontinuity that can be measured with a Heaviside function. Multi-principal element alloys (MPEAs) have potential to be the future of alloy design as there are limitless compositions possible which could exceed the capabilities of conventional alloys. MPEAs are a new class of alloys with a loose definition that they are made of multiple principal elements, generally with ≥5 at% of each principal element. Ti80(AlCrNb)20 is the alloy used in this thesis due to its potential as a lightweight MPEA (LMPEA) and its solid solution β titanium phase composition which is well suited for strong creep resistance. High resolution digital image correlation (HRDIC) enabled creep tests are performed to measure the GBS and other localized slip of Ti80(AlCrNb)20. The GBS analysis code developed in this thesis utilizes the HRDIC creep data captured via optical microscope to measure GBS. Microstructural maps from electron backscatter diffraction (EBSD) are aligned with HRDIC creep imaging using fiducial markers to identify grain boundary locations, and the discontinuity across the grain boundary due to GBS was measured via a Heaviside function based algorithm. Measurement of GBS in-situ using an optical microscope is an advancement over existing methods by providing continuous data. This method also requires significantly less scanning electron microscope (SEM) time and access as the only SEM usage is an initial EBSD scan to identify the microstructure. Current methods utilize multiple or continuous SEM scans that can require the creep test to be stopped temporarily. As creep testing is typically at elevated temperatures, this induces thermic cycling in the sample which prevents a pure creep test. Being able to run a pure creep test without thermic cycling or interruptions while taking continuous measurements will improve the data analysis capabilities and informativity of future testing on microstructure damage

Factors affecting youth entrepreneurship in Tõrva parish

Magistritöö Ökonoomika ja ettevõtluse õppekavalMagistritöö eesmärk on Tõrva valla noorte ettevõtlusvalmiduse ning kohaliku omavalitsuse võimaluste välja selgitamine noorte ettevõtlikkusele suunamisel ja ettevõtluskeskkonna arendamisel. Eesmärgi saavutamiseks koguti esmaseid andmeid, korraldades Tõrva valla noorte seas ankeetküsitlus ning viies läbi individuaalintervjuud kohaliku omavalitsuse ja Tõrva avatud noortekeskuse juhiga. Analüüsi tulemustest selgus, et uuritavatest üle poole ei oska hinnata võimalusi uue äritegevuse alustamiseks piirkonnas. Väitega, et Tõrva vallas pakutakse häid võimalusi äritegevuse alustamiseks nõustus 12,4% uuritavatest ja 34,5% ei pea piirkonna võimalusi ettevõtlust soodustavaks. Ettevõtlusega alustamise juures tajutakse peamiselt rahalisi takistusi – üle 70 protsendi uuritavatest märkisid, et takistuseks võib saada piisavate ressursside puudumine või ettevõtte finantseerimine. Üle poole vastanutest märkis, et Tõrva vallas pole piisavalt kvalifitseeritud töötajaid ning üle kolmandiku noortest leidsid, et ettevõtte loomist ja selle arengut Tõrva vallas võivad takistada tegurid nagu tööjõupuudus, probleemid toodetele või teenustele turu leidmisega ja vähene piirkonna tuntus. Noored ootavad kohalikult omavalitsuselt ja selle allasutustelt rohkemate meetmete rakendamist, näiteks ettevõtlusalaste koolituste ja ettevõtluspäevade korraldamist. Magistritöö on praktilise väärtusega, sest uurimistöö tulemusi saab kasutada kohaliku omavalitsuse ja piirkonna ettevõtjate vahelise koostöö soodustamise planeerimisel.The aim of the master’s thesis is to identify the entrepreneurial readiness among youth in Tõrva Parish and local government opportunities to encourage entrepreneurship among young people and develop the business environment. To achieve the purpose, primary data was collected by conducting a questionnaire among youth in Tõrva Parish and carrying out individual interviews with the local Government Mayor and the director of the Youth Centre. The results of the analyses showed that more than a half of the respondents could not estimate the chances of starting a business in Tõrva Parish. 12,4% of respondents agreed with the statement that Tõrva Parish offers good business opportunities and 34,5% of respondents do not think that entrepreneurship is encouraged here. Financial obstacles were mostly pointed out – more than 70% of respondents mentioned insufficient financial resources or financing the business. More than a half of the respondents referred to the shortage of skilled workers in Tõrva Parish and more than a third pointed out a labour shortage, problems in finding the market for products and services and that the area is not widely known. Young people are expecting the local government and its subordinate establishments to implement more measures, such as organizing entrepreneurship training and entrepreneurial days. The Master’s thesis has a practical value as the results of the survey can be used to encourage cooperation between the local government and the entrepreneurs of the area

HACCP based food safety management system implementation in example Estonian dairy industry

Magistritöö Majandusarvestuse ja finantsjuhtimise õppekavalHACCP (Hazard Analysis Critical Control Points), ohtude analüüs ja kriitiliste kontrollpunktide ohje on süsteem, mida laialdaselt kasutatakse toiduainete käitlemise valdkondades toidu ohutuse tagamiseks. Magistritöö eesmärk on välja selgitada HACCP põhise toiduohutuse juhtimise süsteemi olemus ja rakendamine Eesti piimatööstusettevõtete näitel, millised probleemid on rakendamisega kaasnenud. Empiiriliste andmete kogumise meetodiks valiti kvalitatiivne meetod, täpsemalt juhtumianalüüs. HACCP põhist toiduohutuse juhtimise süsteemi saab käsitada praktilise vahendina, mis aitab kontrollida toidutootmiskeskkonda ja -protsessi ning tagada toodete ohutuse. Toiduohutuse juhtimise süsteem on terviklik süsteem, milles on ühendatud ennetus, valmisolek ja enesekontrollitoimingud, et tagada toidukäitlemisettevõttes toiduohutus ja toiduhügieen. Ohutu toit tagatakse HACCP süsteemi rakendamisega, kui on täidetud eeltingimuste programmid ja tagatud toidu jälgitavus. HACCP põhise toiduohutuse juhtimise süsteemi rakendamisega on valimisse kuulunud piimatööstusettevõtetel kaasnenud probleemid. Probleemid on seotud HACCP põhise süsteemi riskijuhtimisega, eeltingimuste programmidega, märgistusega, toidu tagasikutsumisega. Igal piimatööstusel on oma enesekontrolli plaani osas fikseeritud, kuidas toodete tagasikutsumine käib, kui selline olukord tekib ja igal toidukäitlejal on kohustus teavitada pädevat asutust kui ta teab, või kui tal on põhjust arvata, et ta on turule viinud inimese tervisele ohtlikku toitu. Mittevastavuste käsitlemise korral on oluline välja selgitada kõrvalekallete tekkepõhjused, et hoida ära mittevastavuste kordumine. Edaspidistes uuringutes on oluline analüüsida HACCP põhist toiduohutuse juhtimise süsteemi ka teistes toidutööstuse valdkondades.The hazard analysis and critical control points (HACCP) system is widely recognized as a management tool capable of ensuring food safety. The aim of the master's thesis is to determine the implementation of the HACCP based food safety management system on the example of Estonian dairy companies and which problems have occurred with its implementation. A qualitative method, namely a case study, was selected as the method of collecting empirical data. The HACCP based food safety management system is a holistic system of prevention, preparedness and own-check activities to manage food safety and hygiene in a food business. The HACCP based food safety management system should be seen as a practical tool to control the food production environment and process and ensure the products are safe. Food hygiene and safety is the result of the implementation by food businesses of prerequisite programs and procedures based on the HACCP principles and traceability. The problems of Estonian dairy companies are related to the HACCP based system risk management, prerequisite programmes, labelling, and food recall. Each dairy industry has a record in HACCP plan of how to recall products when such a situation arises, and each food handler has an obligation to inform a competent authority if it knows or has any reason to believe that it has placed food dangerous to human health on the market. When dealing with non-conformities, it is important to determine the causes of deviations in order to prevent recurrence of nonconformities. The results of this Master's thesis can be used at the national, professional association, support structure and company levels. In future studies, it is important to analyse the HACCP based food safety management system in other food industry sectors as well

Creating a multi-level e-learning course by example of robotics

Käesoleva magistritöö peamiseks eesmärgiks oli luua kvaliteetne mitmetasemeline robootikateemaline e-kursus olemasoleva e-kursuse baasil. Töös uuriti esmalt kvaliteetsete e-kursuste loomise probleeme, misjärel anti ülevaade olemasolevast e-kursusest. Seejuures viidi läbi põhjalik analüüs selgitamaks välja olemasoleva e-kursuse puudujääke ja probleeme. Analüüsi käigus jõuti tõdemusele, et olemasolev kursus sisaldab puudujääke nii sisulises kui ka tehnilises pooles ega vasta suures osas kvaliteedinõuetele [6]. Analüüsi tulemustest lähtuvalt, defineeriti enne uue kursuse loomist täpsed nõuded ja selgitati välja vajadused, mida uus kursus rahuldama peab. Kursuse loomise protsessi raames uuriti ka erinevaid Moodle’i vahendeid õppematerjalide esitamiseks ja kursuse korraldamiseks ning anti ülevaade mitmetasemelise kursuse loomise võimalustest Moodle keskkonda. Töö tulemusena valmis õpikeskkonda Moodle LEGO MINDSTORMS NXT kursus, mis on korraga kasutatav erinevate sihtrühmade poolt ning mille loomisel on täielikult järgitud e-õppe kvaliteedinõudeid. Töö lisadena valmisid ka kursusele materjalide lisamise juhendid. Lisaks on tööga kaasas näited endise ning uue e-kursuse hinnatavatest ülesannetest ning käesoleva magistritöö autori poolt väljapakutud LEGO MINDSTORMS NXT algkursuse ajakava.The purpose of this thesis is to create a high-quality, thoughtfully designed new multi-level e-learning robotics course which could be used by different target groups at the same time and which could be expandable in the future perspective. The new course is created on a basis of existing e-learning course “LEGO MINDSTORMS NXT course for beginners”, which did not comply to e-learning quality criteria [6]. Within the thesis, an extensive analysis of the existing course is done, to map all problem areas the existing course has. Also exact new requirements for the new course are specified. In addition, review of different tools of Moodle learning management system is done to determine which suit the best for implementing the new course. Significant part is devoted to aspects of multilevel course creation. During the creation process of the new e-learning course, all necessary prerequisites are satisfied for claiming an e-learning quality label. This thesis consists of four parts. In the first part, the description of exact problem to be solved is provided. The second part addresses the problems of creating a high-quality e-learning course. The third part concentrates on an overview of the existing course structure, and describes the results of the analysis. The fourth part deals with the process of creating a new e-learning course and gives an extensive overview of tools which can be used to create a multilevel e-learning course in Moodle learning management system. In order to keep sustainability and manageability of the new course, manuals for adding new materials to the course have been created as well. These are provided as annexes 1, 2 and 3 of the current thesis. Also an example of old e-learning course’s assessment and the assessment created for the new e-learning course has been provided as annex 4. In the annex 5, the proposed time schedule and acceptance conditions of the LEGO MINDSTORMS NXT course for the beginners are given

СУЧАСНІ ТЕНДЕНЦІЇ РОЗВИТКУ ВИЩОЇ ОСВІТИ У СФЕРІ ПІДГОТОВКИ МЕНЕДЖЕРІВ

The article highlights the predictable conditions of the development of the society that influence the higher managers' education

A workflow for accurate metabarcoding using nanopore MinION sequencing

1. Metabarcoding has become a common approach to the rapid identification of the species composition in a mixed sample. The majority of studies use established short‐read high‐throughput sequencing platforms. The Oxford Nanopore MinION™, a portable sequencing platform, represents a low‐cost alternative allowing researchers to generate sequence data in the field. However, a major drawback is the high raw read error rate that can range from 10% to 22%. 2. To test if the MinION™ represents a viable alternative to other sequencing platforms we used rolling circle amplification (RCA) to generate full‐length consensus DNA barcodes for a bulk mock sample of 50 aquatic invertebrate species with at least 15% genetic distance to each other. By applying two different laboratory protocols, we generated two MinION™ runs that were used to build error‐corrected consensus sequences. A newly developed Python pipeline, ASHURE, was used for data processing, consensus building, clustering, and taxonomic assignment of the resulting reads. 3. Our pipeline achieved median accuracies of up to 99.3% for long concatemeric reads (>45 barcodes) and successfully identified all 50 species in the mock community. The use of RCA was integral for increasing consensus accuracy but was also the most time‐consuming step of the laboratory workflow. Most concatemeric reads were skewed towards a shorter read length range with a median read length of up to 1262bp. 4. Our study demonstrates that Nanopore sequencing can be used for metabarcoding, but exploration of other isothermal amplification procedures to improve consensus accuracy is recommended

The onset and solidification path of a basaltic melt by in situ differential scanning calorimetry (DSC) and ex situ investigations

The in situ differential scanning calorimetry (DSC) technique has been applied to investigate the solidification paths of a basaltic liquid. The starting glass was heated up to 1300◦C, kept at this superliquidus temperature for 2 h and cooled at rates (∆T/∆t) of 7, 60, 180, 1000, and 1800◦C/h, down to 800 and 600◦C. Glass transition temperature (Tg), crystallization temperature (Tx_HR) and melting temperature (Tm) were measured by in situ DSC spectra on heating. Tx measured along the cooling paths (Tx_CR) shows exothermic peaks that change from a single symmetric shape (7 and 60◦C/h) to multi-component patterns (180, 1000, and 1800◦C/h). The recovered products characterized by field emission gun source of the scanning electron microscopy and electron probe micro-analyzer-wavelength dispersive spectrometers show a phase assemblage of spinel (sp), clinopyroxene (cpx), melilite (mel), plagioclase (plg), and glass. Moreover, crystal size distributions (CSDs) and growth rates (Gmax and GCSD) were also determined. The crystal content slightly increases from 7 to 1800◦C/h. Faceted sp are present in all the run products with an amount always <2 area%. Cpx increases from 7 to 1800◦C/h, changing its texture from almost faceted to dendritic between 60 and 180◦C/h. The area% of mel follows an asymmetric Gaussian trend, while plg nucleates only at 7◦C/h with a content <2 area%. The coupling of DSC and SEM outcomes indicate that sp nucleate first, followed by cpx and mel (and/or plg). The increment of ∆T/∆t causes an increase of the CSD slope (m) and crystal population density per size (n0 ), as well as a decrease of the crystal size, for both cpx and sp. The log-linear CSD segments with different slopes at 7 and 60◦C/h suggest multiple nucleation events and crystal growth by coarsening. Gmax and GCSD for cpx and sp directly measured on the actual crystallization time by DSC spectra, both increase with the increasing of ∆T/∆t. The onset temperature of crystallization (Txi ) decreases as ∆T/∆t increases, following an exponential trend that defines the uppermost portion of a time-transformation-temperature-like curve. This analytical model allows us to quantitatively model the kinetic crystallization paths of dry basalts

Riparian forests can mitigate warming and ecological degradation of agricultural headwater streams

1. Riparian forests are commonly advocated as a key management option to mitigate the effects of agriculture on headwater stream biodiversity and ecosystem func tions. However, the benefits of riparian forests might be reduced by uninterrupted catchment-scale pollution. 2. We studied the effects of riparian land use on multiple ecological endpoints in head water streams in an agricultural landscape. We studied stream habitat characteristics, water temperature and algal accrual, and macrophyte, benthic macroinvertebrate and fish communities in 11 paired forested and open agricultural headwater stream reaches that differed in their extent of riparian forest cover but had similar water quality. 3. Hydromorphological habitat quality was higher in forested reaches than in open reaches. Riparian forest had a strong effect on the summer water temperature regime, with maximum and mean water temperatures and temperature variation in forested reaches substantially lower than in open reaches. 4. Macrophyte communities differed between forested and open reaches. The mean abundance of bryophytes was higher in forested reaches but the difference to open reaches was only marginally significant, whereas graminoids were significantly more abundant in open reaches. Within-stream dissimilarity of benthic macroinvertebrate community structure was significantly related to the difference in riparian land use between reach pairs. The relative DNA sequence abundance of pollution-sensitive Ephemeroptera, Plecoptera, and Trichoptera species tended to be higher in forested reaches than in open reaches. Finally, fish densities were not significantly different be tween forested and open reaches, although densities were higher in forested reaches. 5. This unequivocal evidence for the ecological benefits of forested riparian reaches in agricultural headwater streams suggests that riparian forest can partly mitigate the adverse impacts of agricultural diffuse pollution on biota. The strong effect of forests on stream water temperature suggest that riparian forest could also miti gate harmful effects on headwater stream biodiversity and ecosystem functions of the predicted more frequent high summer temperatures