Grundlagen des Selektiven Elektronenstrahlschmelzens von Eisenaluminiden

The Additive Manufacturing process (AM) of Selective Electron Beam Melting (SEBM) is, due to its near-net shape character, particularly suitable for materials with a poor machinability, such as iron aluminides. These materials, which belong to the class of intermetallic phases, are assigned a high potential for high-temperature applications. The reason for this is the high melting point of iron aluminides paired with their excellent resistance to oxidation. Due to the high process temperatures of SEBM, the risk of cracking, as it is the case with iron aluminides that tend to be brittle, is significantly reduced. The resulting material properties are rather determined by the remaining porosity. In the absence of a ductile response to stress concentrations, brittle intermetallic phases are predominantly affected hereby. In addition to multi-layer binding faults and single layer binding faults, which can be reliably avoided by correct melting parameters, gas pores can have a negative influence, too. Gas pores have their origin in the used gas atomized powder and their fraction is only slightly depending on the melting parameters. Neither the processing of iron aluminides via SEBM, nor an influence of the atomizing gas during powder production on the remaining gas porosity, have been investigated so far. The aim of the present work is the development of the SEBM process for iron aluminides. In addition, the influence of the atomizing gas used during powder production on said SEBM process is investigated. For this purpose, a FeAl28Ti5B1.3 alloy atomized with nitrogen and a FeAl28Ti5B0.7 alloy atomized with argon are processed via SEBM. The process windows for the generation of dense material show a direct influence of the used atomizing gas. In addition to the remaining gas porosity, its influence can also be seen in the width of the process window and the generated microstructure. The processed iron aluminides show, depending on the alloy, a coarsely or finely crystalline structure which is an effect of the underlying boron content. Via the selected melting parameters, the size of the microstructural components, as well as the chemical composition, can be influenced. The resulting mechanical properties show advantages of a fine crystalline microstructure and a reduced gas porosity. Finally, a comparison with other AM methods is carried out regarding the mechanical properties.Das additive Fertigungsverfahren (AM) des Selektiven Elektronenstrahlschmelzens (SEBM) eignet sich infolge seines endkonturnahen Charakters besonders für Materialien mit einer geringen Spanbarkeit, wie es zum Beispiel für Eisenaluminide der Fall ist. Diesen zu den intermetallischen Phasen gehörenden Werkstoffen wird ein hohes Potenzial für eine Anwendung im Hochtemperaturbereich zugeschrieben. Grund hierfür ist der hohe Schmelzpunkt von Eisenaluminiden gepaart mit einer herausragenden Beständigkeit gegen Oxidation. Durch die erhöhten Prozesstemperaturen ist die Rissgefahr, wie sie bei zu sprödem Verhalten neigenden Eisenaluminiden gegeben ist, im SEBM deutlich reduziert. Vielmehr bestimmen die im additiv aufgebauten Material verbleibenden Konsolidierungsfehler dessen resultierende Eigenschaften. Spröde intermetallische Phasen sind hierbei in Ermangelung einer duktilen Antwort auf Spannungskonzentrationen besonders betroffen. Neben Tunnelkavitäten und Schichtanbindungsfehlern, welche prozesssicher über die Einstellung richtiger Schmelzparameter vermieden werden können, können Gasporen einen negativen Einfluss zeigen. Diese Poren finden ihren Ursprung im verwendeten gasverdüsten Pulver. Deren Anteil reagiert nur bedingt auf die verwendeten Schmelzparameter. Weder die Verarbeitung von Eisenaluminiden im SEBM noch der Einfluss des bei der Pulverherstellung verwendeten Verdüsungsgases auf die in solchen SEBM-Bauteilen verbleibende Gasporosität wurden bisher im Rahmen einer größeren Studie untersucht. Das Ziel der vorliegenden Monografie ist die Entwicklung des SEBM Prozesses für Eisenaluminide. Darüber hinaus soll der Einfluss des bei der Pulverherstellung verwendeten Verdüsungsgases untersucht werden. Hierzu wird neben einer mit Stickstoff verdüsten FeAl28Ti5B1,3-Legierung auch eine mit Argon verdüste FeAl28Ti5B0,7-Legierung mittels SEBM verarbeitet. Die Prozessfenster für die Erzeugung dichten Materials zeigen hierbei einen direkten Einfluss des verwendeten Verdüsungsgases. Dessen Einfluss ist neben der verbleibenden Gasporosität auch in der Breite der erzeugten Prozessfenster und der Mikrostruktur ersichtlich. Die prozessierten Eisenaluminide zeigen je nach Legierung grob- oder feinkristallines Gefüge, welches sich gut mit dem verwendeten Borgehalt erklären lässt. Neben der Größe der verschiedenen Gefügebestandteile lässt sich über die gewählten Schmelzparameter auch die chemische Zusammensetzung beeinflussen. Die Betrachtung der resultierenden mechanischen Eigenschaften zeigt die Vorteile des feinkristallinen Mikrogefüges sowie einer verringerten Gasporosität. Zur Bewertung der mechanischen Eigenschaften erfolgt abschließend ein Vergleich mit anderen AM-Verfahren

Cold Spray metal powder deposition with 9 %Cr-steel applied for the HCPB First Wall fabrication: Proof of concept and options for ODS steel processing

At the KIT a hybrid manufacturing concept for nuclear fusion First Walls is developed combining aspects of conventional and Additive Manufacturing (AM) technologies. The state of the art for ITER does not cover all specifications of a DEMO relevant First Wall. Thus, additional R&D-work has been initiated in terms of manufacturing. The AM technology basis used in the presented process combination is Cold Spray metal powder deposition applied in alternation with machining including the feature of filling grooves temporarily with a water-soluble granulate for creation of closed channels and cavities. Thus, the technology provides the option to manufacture shells with a thin gas tight membrane on top of previously machined structures. This membrane is used as pressure seal and makes the joining of shells by Hot Isostatic Pressing (HIP) into one monolithic body possible. This paper describes the manufacturing process and recalls differences and common aspects with regard to conventional concepts of First Wall manufacturing. The achievement of Technology Readiness Level TRL 3 by mechanical qualification and comparison of the results to other HIP joint experiments is also demonstrated. Finally, an outlook is given concerning integration options of the technology into manufacturing of shells with cooling channel structures using Oxide Dispersion Strengthened (ODS) materials

Rationale, design, and implementation protocol of an electronic health record integrated clinical prediction rule (iCPR) randomized trial in primary care

<p>Abstract</p> <p>Background</p> <p>Clinical prediction rules (CPRs) represent well-validated but underutilized evidence-based medicine tools at the point-of-care. To date, an inability to integrate these rules into an electronic health record (EHR) has been a major limitation and we are not aware of a study demonstrating the use of CPR's in an ambulatory EHR setting. The integrated clinical prediction rule (iCPR) trial integrates two CPR's in an EHR and assesses both the usability and the effect on evidence-based practice in the primary care setting.</p> <p>Methods</p> <p>A multi-disciplinary design team was assembled to develop a prototype iCPR for validated streptococcal pharyngitis and bacterial pneumonia CPRs. The iCPR tool was built as an active Clinical Decision Support (CDS) tool that can be triggered by user action during typical workflow. Using the EHR CDS toolkit, the iCPR risk score calculator was linked to tailored ordered sets, documentation, and patient instructions. The team subsequently conducted two levels of 'real world' usability testing with eight providers per group. Usability data were used to refine and create a production tool. Participating primary care providers (n = 149) were randomized and intervention providers were trained in the use of the new iCPR tool. Rates of iCPR tool triggering in the intervention and control (simulated) groups are monitored and subsequent use of the various components of the iCPR tool among intervention encounters is also tracked. The primary outcome is the difference in antibiotic prescribing rates (strep and pneumonia iCPR's encounters) and chest x-rays (pneumonia iCPR only) between intervention and control providers.</p> <p>Discussion</p> <p>Using iterative usability testing and development paired with provider training, the iCPR CDS tool leverages user-centered design principles to overcome pervasive underutilization of EBM and support evidence-based practice at the point-of-care. The ongoing trial will determine if this collaborative process will lead to higher rates of utilization and EBM guided use of antibiotics and chest x-ray's in primary care.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov Identifier <a href="http://www.clinicaltrials.gov/ct2/show/NCT01386047">NCT01386047</a></p

Migrant networks, language learning and tourism employment

This paper examines the relationship between migrants’ social networks, the processes of language acquisition and tourism employment. Data collected using netnography and interviews are used to identify the strategies that Polish workers in the UK use to develop their language skills. The paper highlights the roles played by co-workers, co-nationals and customers in migrants’ language learning, both in the physical spaces of work and the virtual spaces of internet forums. It also shows how migrant workers exchange knowledge about the use of English during different stages of their migration careers: prior to leaving their country of origin and getting a job, during their employment and after leaving their job. Implications for academic inquiry and human resource management practice are outlined

Dynamic star formation in the massive DR21 filament

The formation of massive stars is a highly complex process in which it is not clear whether the star-forming gas is in global gravitational collapse or in an equilibrium state, supported by turbulence. By studying one of the most massive and dense star-forming regions in the Galaxy at a distance of less than 3 kpc, the filament containing the well-known sources DR21 and DR21(OH), we expect to find observational signatures that allow to discriminate between the two views. We use molecular line data from our 13CO 1-0, CS 2-1, and N2H+ 1-0 survey of the Cygnus X region obtained with the FCRAO and high-angular resolution observations of CO, CS, HCO+, N2H+, and H2CO, obtained with the IRAM 30m telescope. We observe a complex velocity field and velocity dispersion in the DR21 filament in which regions of highest column-density, i.e. dense cores, have a lower velocity dispersion than the surrounding gas and velocity gradients that are not (only) due to rotation. Infall signatures in optically thick line profiles of HCO+ and 12CO are observed along and across the whole DR21 filament. From modelling the observed spectra, we obtain a typical infall speed of 0.6 km/s and mass accretion rates of the order of a few 10^-3 Msun/yr for the two main clumps constituting the filament. These massive (4900 and 3300 Msun) clumps are both gravitationally contracting. All observed kinematic features in the DR21 filament can be explained if it is formed by the convergence of flows at large scales and is now in a state of global gravitational collapse. Whether this convergence of flows originated from self-gravity at larger scales or from other processes can not be settled with the present study. The observed velocity field and velocity dispersion are consistent with results from (magneto)-hydrodynamic simulations where the cores lie at the stagnation points of convergent turbulent flows.Comment: Astronomy and Astrophysics, in pres

Novel focused OCT-LIF endoscope

Combined optical coherence tomography (OCT) and laser-induced fluorescence (LIF) endoscopy has shown higher sensitivity and specificity for distinguishing normal tissue from adenoma when compared to either modality alone. Endoscope optical design is complicated by the large wavelength difference between the two systems. A new high-resolution endoscope 2 mm in diameter is presented that can create focused beams from the ultraviolet to near-infrared. A reflective design ball lens operates achromatically over a large wavelength range, and employs TIR at two faces and reflection at a third internal mirrored face. The 1:1 imaging system obtains theoretically diffraction-limited spots for both the OCT (1300 nm) and LIF (325 nm) channels

Comportamento dos poluentes do ar durante e após lockdown em uma cidade de médio porte

The COVID-19 Pandemic is undoubtedly the greatest public health problem of the century, to date. Among the actions sanctioned by governments to curb the spread of the virus are blocking and confinement measures, known as lockdown. Several locations around the world have shown an improvement in air quality due to reduced urban mobility during periods of lockdown. However, results in Brazil are still scarce. The aim of the study was to evaluate the behavior of air pollutants in a short-term lockdown (64 hours) in the city of Pelotas, RS.&nbsp;The concentrations of O3, CO, PM2.5 NO2 and SO2 were measured during and after (up to 35h) the lockdown using satellite data and the average concentrations of the previous seven days were compared.&nbsp;With the exception of NO2, all pollutants were reduced during the lockdown period and levels maintained even 35 hours after its end. The reduction in ozone levels during the lockdown is widely questioned worldwide, and seems to be related to less populated cities and with low concentrations of NO2. The study showed that a short period of confinement is sufficient to reduce the levels of pollutants in the air.&nbsp;A Pandemia da COVID-19 é, sem dúvida, o maior problema de saúde pública do século, até o momento. Entre as ações sancionadas pelos governos para conter a propagação do vírus estão as medidas de bloqueio e confinamento, conhecidas como lockdown. Vários locais do mundo mostraram melhoria da qualidade do ar decorrente da redução da mobilidade urbana durante os períodos de confinamento. No entanto, os resultados no Brasil ainda foram escassos. O objetivo do estudo foi avaliar o comportamento dos poluentes do ar em um lockdown de curta duração (64 horas) no município de Pelotas, RS. As concentrações de O3, CO, PM2,5 NO2 e SO2 foram medidas durante e após (até 35h) o lockdown por meio de dados de satélite e foram comparadas a média dos sete dias anteriores. Com exceção do NO2, todos os poluentes foram reduzidos durante o período do lockdown e os níveis mantidos mesmo após 30 horas do fim do bloqueio. A redução dos níveis de ozônio durante o lockdown é bastante questionada, em nível mundial, e parece estar relacionada a cidades menos populosas e com baixas concentrações de NO2. O estudo mostrou que um curto período de confinamento é suficiente para reduzir os níveis de poluentes no ar

Evolutionary biology and anthropology suggest biome reconstitution as a necessary approach toward dealing with immune disorders

Industrialized society currently faces a wide range of non-infectious, immune-related pandemics. These pandemics include a variety of autoimmune, inflammatory and allergic diseases that are often associated with common environmental triggers and with genetic predisposition, but that do not occur in developing societies. In this review, we briefly present the idea that these pandemics are due to a limited number of evolutionary mismatches, the most damaging being ‘biome depletion’. This particular mismatch involves the loss of species from the ecosystem of the human body, the human biome, many of which have traditionally been classified as parasites, although some may actually be commensal or even mutualistic. This view, evolved from the ‘hygiene hypothesis’, encompasses a broad ecological and evolutionary perspective that considers host-symbiont relations as plastic, changing through ecological space and evolutionary time. Fortunately, this perspective provides a blueprint, termed 'biome reconstitution', for disease treatment and especially for disease prevention. Biome reconstitution includes the controlled and population-wide reintroduction (i.e. domestication) of selected species that have been all but eradicated from the human biome in industrialized society and holds great promise for the elimination of pandemics of allergic, inflammatory and autoimmune diseases

A participação do investigado no Inquérito Policial

Busca-se por meio deste artigo fazer uma análise crítica sobre a participação do investigado no Inquérito Policial à luz da Constituição Federal de 1988. Para tanto, faz-se necessário perpassar pelos principais sistemas processuais adotados no ordenamento jurídico diante do atual Estado Democrático de Direito, bem como analisar a abrangência do art. 5°, inciso LV da CRFB/88 e do art. 14 do Código de Processo Penal, visando propiciar uma reflexão sobre a atual forma de participação do investigado na fase pré processual Palavras-chaves: DIREITOS FUNDAMENTAIS, INQUÉRITO POLICIAL, PARTICIPAÇÃO DO INVESTIGADO THE INVESTIGATED PARTICIPATION IN POLICE INVESTIGATION ABSTRACT The aim is to through this article make a critical analysis of the participation of the police inquiry investigated in the light of the 1988 Federal Constitution Therefore, it is necessary to pervade the main procedural systems adopted in the legal system before the current democratic state and to examine the scope of art. 5 °, item LV CRFB / 88 and the art. 14 of the Criminal Procedure Code, in order to provide a reflection on the current form of participation of the investigation in the pre procedural stage. Keywords: FUNDAMENTAL RIGHTS, POLICE INVESTIGATION, INVESTIGATED PARTICIPATION Data da submissão: 31/03/2015 Data da aceitação: 27/07/201