3,658 research outputs found
Real-time microdamage and strain detection during micromechanical testing of single trabeculae
No full textFor the assessment of local deformations, we recently combined mechanical testing of trabecular bone with high-speed photography. In a previous study on cuboids of human vertebral trabecular bone we found strained trabeculae to whiten, and scanning electron microscopy showed excessive microdamage in whitened zones. In the presented study we tested single trabeculae from bovine femur and tibia in a three-point-bending geometry. Whitening was detected in the form of an ellipsoid zone on the tension side on tested trabeculae. Upon crack formation the whitening fades and a whitened zone following the propagating crack tip can be seen In addition to whitening/microdamage assessment we use ink marks applied to the samples and a modified digital image correlation to obtain the local strains involved in whitening and formation. In the presented loading case the tensile strain along the long axis of the trabecula qualitatively correlates best with the whitening zones seen. Whitening and thus microdamage initiates around a local tensile strain of 3%, whereas crack initiation occurs at strains around 13%. Our results allow for the first time to correlate microdamage and local strains directly, which is direly needed for the development of realistic damage models used in finite element analyses
Design and input shaping control of a novel scanner for high-speed atomic force. [In special section on Optimized System Performances Through Balanced Control Strategies, The 4th IFAC Symposium on Mechatronic Systems – Mechatronics 2006]
No full textA novel design of a scanning unit for atomic force microscopy (AFM) is presented that enables scanning speeds three orders of magnitude faster than compared to conventional AFMs. The new scanner is designed for high mechanical resonance frequencies, based on a new scanner design, which is optimized using finite element analysis. For high-speed scanning a new controller, based on input-shaping techniques, has been developed that reduces imaging artifacts due to the scanner’s dynamics. The implementation of the new AFM system offers imaging capabilities of several thousand lines per second with a scanning range of 13 ?m in both scanning directions, and the freedom to choose the fast scan-axis in any arbitrary direction in the X–Y-plane
Georg Hermann.
No full textThe internationally renowned author of numerous novels, essays, and articles, Georg Hermann, was born as Georg Borchardt in Berlin-Friedenau on October 7, 1871, the youngest of six children in a well-established Jewish family. Later in life he used his father’s first name Hermann as his surname when writing. Contrary to the expectations for a young man from a reputable family, Hermann did not pursue the Abitur exam in a Gymnasium (secondary school), but instead received a one-year certificate in 1890, leaving school to become an apprentice salesman at a tie company. From 1896 until 1899 he worked in the Statistical Office of Berlin, at the same time attending literature and art history lectures at the University of Berlin. Afterwards he worked as a freelance writer and art critic.His first book, 'Spielkinder', was published in 1896, but he did not become well-known until 1906, with the publication of 'Jettchen Gebert', followed by its sequel, 'Henriette Jacoby'. These novels told the story of the life of a young woman living in Jewish Berlin during the Biedermeier period of the 1820s and 1830s. Politically active, Georg Hermann was also a member of the Central-Verein deutscher Staatsbürger jüdischen Glaubens.Having become known for his pacifist tendencies through his writing, and because of his Jewish heritage, Georg Hermann and his family fled to Holland shortly after the burning of the Reichstag in 1933. Although the rest of his family was saved from the Nazis after their occupation of Holland in 1943, Georg Hermann was sent to the Dutch concentration camp of Westerbork. On November 16, 1943 he was transported to Auschwitz and either died during transport or shortly after his arrival.Digital ImageRecord added to DigiTool. Aleph record suppressed. J. Palmisano 09/15/2010
On recent developments for high-speed atomic force microscopy
No full textThe atomic force microscope (AFM) is limited in imaging speed by the bandwidth and dynamic behavior of the actuators and mechanical parts. For high-speed imaging all AFM components have to be optimized in performance. Here, we present improvements of the force sensor, the scanner, the controller, and the data acquisition system. By combining all these improvements, the next generation AFMs will enable imaging speeds more than two orders of magnitude faster than current commercial AFM systems
Sammlung von Merckwürdigkeiten der Natur und Alterthümern des Erdbodens, welche petrificirte Cörper enthält
No full textaufgewiesen und beschrieben von Georg Wolffgang KnorrVorlageform des Erscheinungsvermerks: Nürnberg, zu finden bey dem Author. Gedruckt bey Andreas Bieling
A new technique for imaging mineralized fibrils on bovine bone fracture surfaces by atomic force microscopy
No full textGeorg Trakl and melancholy
No full textThis paper identifies some of the decisive aspects of Georg Trakl’s poetry, taking as the starting point the author’s awareness about God’s death, from Nietzsche’s approach. Emphasis is placed on melancholy, support of the creation, testimony and acknowledgement of failure and grief of mankind, from which the author was able to express his discouragement upon the downfall and decline of the West.Se identificaron algunos aspectos determinantes de la obra poética de Georg Trakl, tomando como punto de partida la conciencia del escritor acerca de la muerte de Dios, desde la perspectiva de Nietzsche. Se hizo un énfasis sobre la melancolía, soporte de la creación, testimonio y reconocimiento del errar y el duelo del hombre, a partir de la cual el autor pudo expresar el desconsuelo por la ruina y el ocaso de Occidente
Tractatio Jvridica De Concursu Novercæ Cum Privignis
No full textZugl.: Basel, Univ., Jur. Diss., 1728[Hermann Georg Krohn]A new edition, revised by the author, of his inaugural dissertation, Basel, 1728, published by G.C. Overbeck, with a conspectus of the chapters. Cf. prefIncludes bibliographical referencesWith: Rösener, Andreas Christoph. Andreae Christophori Röseneri j.u.d. Tractatus juridicus de libris mercatorum. Lipsiae : Sumptibus haeredum Friderici Lanckisii, literis Christiani Scholvini, [1694]. Copy 2. Bound together subsequent to publicationAutopsie nach Ex. der ULB Sachsen-AnhaltVorlageform des Erscheinungsvermerks: Lubecæ, Sumtibus Jonae Schmidt. MDCCXLVII
Wellenfrontkompensation mit adaptiver Optik
No full textDie Verwendung von Interferometern zur exakten Distanzbestimmung ist vor allem in der Hoch-Präzisions-Industrie, wie etwa der Halbleiterfertigung, nicht mehr wegzudenken. Das berührungslose und nanometer-genaue Messprinzip auf Basis des Michelson Interferometers wird beispielsweise zur Positionierung von Waferstages bei deren Belichtung verwendet. Durch die steigenden Anforderungen bei immer höheren Taktraten auch entsprechend hohe Beschleunigungen zu erreichen, besteht die Gefahr von Luftverwirbelungen entlang des offenen Interferometer-Messpfades. Diese Luftverwirbelungen können dazu führen, dass durch unterschiedlich dichte Luft die ebene Wellenfront des verwendeten Lasers gestört wird. Da alle Aberrationen der Wellenfront im Messpfad bei der Interferenz mit dem Referenzpfad zu einem unerwünschten Inteferenzmuster führen und dadurch die Signalstärke am Ausgang des Interferometers geschwächt wird, wird die exakte Positionierung erheblich erschwert. Um diese Fehlerquelle einerseits zu bestimmen und andererseits auch zu kompensieren, wird in dieser Arbeit ein adaptives optisches System untersucht welches in ein Michelson Interferometer integriert wird. Die Aberration wird dabei mit einem Shack-Hartmann Wellenfront-Sensor gemessen und mittels eines deformierbaren Spiegels in einem Regelkreis kompensiert. In dem vorgeschlagenen Aufbau werden jeweils für das Interferometer als auch für das adaptive optische System handelsübliche Komponenten verwendet was die Praxistauglichkeit und somit die einfache Integrierbarkeit in bestehende Systeme zeigen soll. Das realisierte System ist in der Lage Störungen niedriger Ordnung zu kompensieren und eine durchschnittliche Verbesserung des Ausgangssignal um den Faktor 5,7 konnte erreicht werden.Precise distance measurement is crucial for the high-precision industry as the semiconductor manufacturing is one. Measurement devices based on the concept of a Michelson interferometer are widely used to implement a very accurate and non-contact distance measurement with nanometer resolution. Interferometers are often applied in environments where the optical path is uncovered and influenceable by air turbulences such as caused by fast moving targets. Air turbulences cause aberrations in the wavefront, deteriorate the interference pattern and lead to a smaller peak-to-valley intensity signal which cause problems in the determination of the traveling distance. To determine as well as to compensate for aberrated wavefronts this thesis investigates the integration of an adaptive optics system into a Michelson interferometer. The aberrated wavefront is measured with a Shack-Hartmann wavefront sensor and compensated by a deformable mirror. A feedback controller is implemented that computes the signals for the deformable mirror. The proposed setup comprises off-the-shelf products for the interferometer and the adaptive optics setup. The implemented system is capable of compensating low order aberrations, resulting in an average improvement of 5,7 of the peak-to-valley signal
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