209 research outputs found
Evanescent-field Q-switched Yb:YAG Channel Waveguide Lasers with Single- and Double-pass Pumping
No full textA femtosecond-laser inscribed Yb:YAG surface channel waveguide (WG) laser with single-walled carbon nanotubes deposited on the top surface of the WG was passively Q-switched by evanescent field interaction. Q-switched operation of the 14-mm-long compact Yb:YAG WG laser was achieved near 1031 nm with two different pumping schemes (single- and double-pass pumping) with an output coupling transmission of 91%. The Q-switched pulse characteristics depending on the absorbed pump power were investigated for both pumping geometries and analyzed in detail based on theoretical modeling. The best performances (energy/pulse duration) for each configuration were 204.4 nJ/75 ns at a repetition rate of 1.87 MHz, and 201.1 nJ/81 ns at 1.75 MHz for single- and double-pass pumping, respectively.
Episode 095 : Cathrine Hasse
No full textCliff Anderson is Vanderbilt’s associate university librarian for research and digital strategy, and he’s back on the podcast interviewing another author of a fascinating book Cliff read recently. This time, he speaks with Cathrine Hasse, professor of Learning at Aarhus University in Denmark, author of the 2020 book Posthumanist Learning: What Robots and Cyborgs Teach Us about Being Ultra-Social from Routledge Press.
Cliff and Cathrine have a wide-ranging conversation, covering such topics as posthumanism, Lev Vygotsky’s learning theories, why teaching humans is harder than teaching gorillas, and cyborgs
The wronskian and its derivatives
No full textArticolo testo di una conferenza tenuta presso l'Accademia Peloritana dei Pericolanti (Messina
FRA JOURNALIST TIL „BIG MAMMA“: Om sociale rollers betydning for antropologers datagenerering
No full textCathrine Hasse: From Journalist to „big
mamma“. On the Meaning of Social
Roles in Anthropological Data Generation
The article takes up the question of the different
social roles the anthropologist utilizes in
the field, the interchange between the field
and the anthropologist’s personal social
equipment, and how this can be used to get
data from selected groups of informants. As
an example of this approach the author describes
how she herself went from being „
journalist", which frightened her informants,
to the much more socially accepted role as
„ig mamma“, which opened for a more
emotional relationship between herself and
the people in the small Sardinian village,
Mamoiada, where the fieldwork took place
Femtosecond-laser writing and selective etching of laser crystals for laser applications
No full textIn dieser Arbeit wurde erstmals eine systematische Analyse des selektiven Ätzprozesses fs-lasergeschriebener Strukturen in kristallinem Y_3Al_5O_12 (YAG) für verschiedene Ätz- und Strukturierungsparameter durchgeführt. In Hinblick auf die Herstellung von Mikrokanälen hoher Aspektverhältnisse von Länge zu Breite für zukünftige Laseranwendungen in seltenerddotiertem YAG wurden die Parameter optimiert.
Funktionelle Zusammenhänge von Ätztiefe und Kanalbreite mit der Zeit wurden gefunden, welche zusammen mit der Selektivität das Ätzverhalten charakterisieren. Zumeist zeigen die Ätztiefe d und der Zuwachs der Kanalbreite einen Quadratwurzelzusammenhang d = (2 · D · t)^(1/2) mit der Zeit, welcher von der Brownschen Diffusion bekannt ist, denn der Austausch der Reaktionsprodukte im Mikrokanal findet über Diffusion statt. Der Fitparameter D entspricht der Diffusionskonstanten. Der höchste Wert D = 3,69 μm^2/s wurde mit 43%H_3PO_4 48%H_2SO_4 als Ätzsubstanz bei einer Ätztemperatur von 105 °C erreicht. Mit dieser Ätzsubstanz wurde bei 83 °C (D = 3,13 μm^2/s) auch die höchste Selektivität von 1200 ± 750 gemessen.
Für die Verdünnung des Gemischs zu 22%H_3PO_4 24%H_2SO_4 wird der Ätzprozess viel schneller. Die Ätztiefe zeigt statt des Quadratwurzelzusammenhangs den zeitlichen Verlauf d = 0,0028 μm/s · t + (2 · 2,24 µm^2/s · t)^(1/2). Folglich könnten mit dieser Ätzsubstanz die in dieser Arbeit mit 85%H_3PO_4 bei 83 °C innerhalb von 9 Monaten (D = 0,53 µm^2/s) bisher längsten selektiv in kristallinem YAG geätzten Mikrokanäle von 8,9 mm Länge und 15 μm Durchmesser theoretisch innerhalb von < 10 d geätzt werden. In Bezug auf die Strukturierungsparameter erwiesen sich eine Fokussierlinse der Brennweite 4,5 mm, eine Repetitionsrate von 10 MHz (von den untersuchten 1 kHz und 10 MHz), Schreibgeschwindigkeiten zwischen 30 mm/s und 100 mm/s, Pulsenergien zwischen 75 nJ und 108 nJ und eine Polarisation des Strukturierungslasers senkrecht zur Schreibrichtung als optimal.
Für zukünftige kombinierte Anwendungen fs-lasergeschriebener Wellenleiter und selektiv geätzter Strukturen wurde auch das Schreiben von Wellenleitern in Kristallen, nämlich Yb(7 %):YAG und Yb(8,1 %):CaGdAlO_4, erstmals bei 10 MHz Pulsrepetitionsrate und rekordhohen Schreibgeschwindigkeiten bis zu 100 mm/s untersucht. Gepumpt mit einem Ti:Saphir-Laser bei 913,4 nm bzw. einem optisch gepumpten Halbleiterlaser bei 967 nm war in den hergestellten Doppelspurwellenleitern Wellenleiterlaserbetrieb mit einem differentiellen Wirkungsgrad von 40% und maximaler Ausgangsleistung P_Aus = 528 mW in Yb:YAG und einem differentiellen Wirkungsgrad von 67% sowie P_Aus = 3,9 W in Yb:CaGdAlO_4 möglich.In this work selective etching of fs-laser written structures in crystalline Y_3Al_5O_12 (YAG) is analyzed systematically concerning structuring and etching parameters for the first time. The fabrication process is optimized aiming for future laser applications of large-scale hollow microstructures in rare-earth doped YAG.
For the etched depth d and the change of the channel width a square-root-dependency on time, which is d = (2 · D · t)^(1/2), similar to Brownian diffusion, was found for most parameters, since the exchange of the reaction products is based on diffusion. The etching parameter D corresponds to the diffusion constant. Thus, the selective etching process is characterized by the temporal change of etched depth and channel width as well as the selectivity of the process, which is defined as the ratio of etched depth and the change of the channel width over this length. The highest value of D = 3.69 μm^2/s was reached with a 43%H_3PO_4 48%H_2SO_4 mixture at 105 °C. For the same etching agent, we observed the highest selectivity of 1200 ± 750 at a temperature of 83 °C (D = 3.13 μm^2/s).
Diluting the mixture with 50% water changes the temporal dependency of the etching depth to d = 0,0028 μm/s · t + (2 · 2,24 µm^2/s · t)^(1/2) and thus, fastens the etching significantly. Using this etching agent, the longest selectively etched microchannel of 8.9 mm long and 15 μm diameter in YAG up to now, which was etched in this work with 85%H_3PO_4 at 83 °C within 9 months (D = 0.53 μm^2/s), could be fabricated in less than 10 days. Concerning the structuring parameters, a focusing lens of 4.5 mm focal length, a pulse repetition rate of 10 MHz, writing velocities between 30 mm/s and 100 mm/s, pulse energies between 75 nJ and 108 nJ as well as a structuring laser beam polarization perpendicular to the writing direction showed the best results concerning aspect ratio and etching behaviour.
For future combined applications of fs-laser inscribed waveguides and selectively etched structures in crystals fast inscription at 10MHz repetition rate and writing velocities up to 100 mm/s was investigated in Yb(7 %):YAG and Yb(8.1 %):CaGdAlO_4 for the first time. In both materials double-track waveguide laser operation with slope efficiencies of 40 %, maximum output power P_Aus = 528 mW and slope efficiencies of 67 %, P_Aus = 3.9 W could be reached pumping with a Ti:sapphire laser at 913.4 nm and an optically pumped semiconductor laser at 967 nm, respectively
O arquivo pessoal Fiama Hasse Pais Brandão
No full textConsiste no estudo do Arquivo Pessoal Fiama Hasse Pais Brandão, desenvolvido na modalidade de relatório de estágio no âmbito do mestrado na área de Ciências da Documentação e Informação, com o intuito de entender o objeto de estudo e o seu enquadramento contextual na sociedade da sua época.
Tem como objetivos: elaborar um estudo biográfico de Fiama Hasse Pais Brandão (que permite identificar as diferentes funções/facetas exercidas pela biografada); criar uma proposta de macroestrutura para um quadro de classificação; e descrição (parcial) de documentos relativos à correspondência.
A elaboração do estudo biográfico de Fiama Hasse Pais Brandão é o método que permite a identificação das diferentes facetas (papéis e funções) exercidas pela biografada. As facetas identificadas são a base para a proposta de macroestrutura para a elaboração de um quadro de classificação que poderá no futuro ser utilizado para a organização do arquivo pessoal.
Procura-se delimitar as problemáticas referentes à noção de arquivo pessoal e ao seu desenvolvimento ao longo da história. Neste sentido a revisão de literatura permite a discussão com estudiosos da área sobre as noções referentes a arquivo pessoal, enquadrando o estudo neste contexto de investigação.
Utiliza-se como métodos de investigação a investigação documental e o método biográfico, servindo este de base para a organização e representação da informação do arquivo pessoal.
Conclui que um arquivo pessoal necessita de estar sempre enquadrado no contexto em que foi elaborado porque apenas desse modo a informação que integra pode ser compreendida e utilizada corretamente de forma a produzir novos conhecimentos e a ampliar os horizontes de investigação.The proposal of this work consists in the study of the Personal Archives Fiama Hasse Pais Brandão. This report was developed within the scope of the master's degree in Documentation and Information Sciences to understand the object of study and its contextual framework in the society of its time.
It’s objectives are: to elaborate a biographical study of Fiama Hasse Pais Brandão (which allows to identify the different functions performed by the biographed); create a macrostructural proposal for a classification framework; and (partial) description of documents relating to correspondence.
The elaboration of the biographical study of Fiama Hasse Pais Brandão is the method that allows the identification of the different facets (roles and functions) exercised by the biographed. The facets identified are the basis for the macrostructural proposal of a classification framework that may in the future be used for the organization of the personal archive.
The author delimits the problems related to the notion of personal archives and its development throughout history. In this sense, the documentary research allows the discussion with scholars of the area about the notions related to personal archive, framing the study in this context of investigation.
The research methods are the documentary research for the literature review, and the biographical method and for the organization and representation of the information of the personal archive.
It concludes that personal archives needs to be always framed in the context in which it was elaborated because only in this way can the information contained by them be understood and used correctly to produce new knowledge and broaden the horizons of the research
O arquivo pessoal Fiama Hasse Pais Brandão
No full textConsiste no estudo do Arquivo Pessoal Fiama Hasse Pais Brandão, desenvolvido na modalidade de relatório de estágio no âmbito do mestrado na área de Ciências da Documentação e Informação, com o intuito de entender o objeto de estudo e o seu enquadramento contextual na sociedade da sua época.
Tem como objetivos: elaborar um estudo biográfico de Fiama Hasse Pais Brandão (que permite identificar as diferentes funções/facetas exercidas pela biografada); criar uma proposta de macroestrutura para um quadro de classificação; e descrição (parcial) de documentos relativos à correspondência.
A elaboração do estudo biográfico de Fiama Hasse Pais Brandão é o método que permite a identificação das diferentes facetas (papéis e funções) exercidas pela biografada. As facetas identificadas são a base para a proposta de macroestrutura para a elaboração de um quadro de classificação que poderá no futuro ser utilizado para a organização do arquivo pessoal.
Procura-se delimitar as problemáticas referentes à noção de arquivo pessoal e ao seu desenvolvimento ao longo da história. Neste sentido a revisão de literatura permite a discussão com estudiosos da área sobre as noções referentes a arquivo pessoal, enquadrando o estudo neste contexto de investigação.
Utiliza-se como métodos de investigação a investigação documental e o método biográfico, servindo este de base para a organização e representação da informação do arquivo pessoal.
Conclui que um arquivo pessoal necessita de estar sempre enquadrado no contexto em que foi elaborado porque apenas desse modo a informação que integra pode ser compreendida e utilizada corretamente de forma a produzir novos conhecimentos e a ampliar os horizontes de investigação.The proposal of this work consists in the study of the Personal Archives Fiama Hasse Pais Brandão. This report was developed within the scope of the master's degree in Documentation and Information Sciences to understand the object of study and its contextual framework in the society of its time.
It’s objectives are: to elaborate a biographical study of Fiama Hasse Pais Brandão (which allows to identify the different functions performed by the biographed); create a macrostructural proposal for a classification framework; and (partial) description of documents relating to correspondence.
The elaboration of the biographical study of Fiama Hasse Pais Brandão is the method that allows the identification of the different facets (roles and functions) exercised by the biographed. The facets identified are the basis for the macrostructural proposal of a classification framework that may in the future be used for the organization of the personal archive.
The author delimits the problems related to the notion of personal archives and its development throughout history. In this sense, the documentary research allows the discussion with scholars of the area about the notions related to personal archive, framing the study in this context of investigation.
The research methods are the documentary research for the literature review, and the biographical method and for the organization and representation of the information of the personal archive.
It concludes that personal archives needs to be always framed in the context in which it was elaborated because only in this way can the information contained by them be understood and used correctly to produce new knowledge and broaden the horizons of the research
Dissipative Range Scaling of Higher Order Structure Functions for Velocity and Passive Scalars
No full textDifferently to Kolmogorov's second similarity hypothesis, we find that the 2n-th order velocity and scalar structure functions scale with n-th order moment of the energy dissipation and the scalar dissipation, respectively. The origins of this scaling are analyzed by the transport equations of the fourth order velocity and scalar increment moments and by direct numerical simulations
- …
