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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

XIII. Internationales Oberflächenkolloquium

16 March 2012 (has links) (PDF)
Das 13. Internationale Oberflächenkolloquium war das erste Treffen in der neuen Veranstaltungsreihe Industry meets standardization and science (IMSAS), mit dem ein Forum für Entwickler, Fertigungstechniker, Normungsexperten und Wissenschaftlern geschaffen werden soll. Vom 12. bis zum 14. März 2012 haben wir in diesem Rahmen über das Thema Kanten und Radien informiert. Viele internationale Normen existieren bereits zur Spezifikation und Verifikation. In einigen Bereichen sind diese Festlegungen jedoch noch lückenhaft. Kanten und Radien sind dafür ein perfektes Beispiel. Default Angaben zu Toleranzzonen und Verifikationsfestlegungen zur Extraktion, Filterung und Assoziation werden benötigt, um Spielräume bei der Interpretation und Bewertung auszuschließen und die Funktion eindeutig beschreiben zu können. Unsere Ziele für das Kolloquium waren die Einführung der neuen Veranstaltungsreihe IMSAS, die Information der Teilnehmer über den aktuellen Stand der Normung auf dem Gebiet von Kanten und Radien, die Präsentation von Problemstellungen und aktuell verfügbaren Lösungen zu diesem Thema und die Ableitung des zukünftigen Normungs- und Entwicklungsbedarfs auf diesem Gebiet. Das Kolloquium wurde vom Institut für Fertigungsmesstechnik und Qualitätssicherung IFMQ (Prof. M. Dietzsch und Dr.-Ing. Sophie Gröger ) der Technischen Universität Chemnitz in Zusammenarbeit mit dem Normungsauschuss Technische Grundlagen (NA 152) (J. Zymnossek) des Deutschen Instituts für Normung (DIN) organisiert.
2

A Study of Radii of Curvature by Fusing Process and Improvement of Coupling Efficiency in Hyperbola Fiber Microlens

Lin, Yong-Shian 15 August 2012 (has links)
This study is to improve the coupling efficiency between 980nm high-power pump laser diode and single-mode fiber. In this study, we use the third generation of fiber grinding machine which is designed by Cheng Shiu University, professor Ying-Chien Tsai. This machine is fully automatic. we use it to fabricate the hyperbola microlenses. The advantages about hyperbola microlenses structure are a single-step fabrication, grinding steps to simplify, reduce the grinding time and will greatly reduce the offset of fiber. In the fusing procedure, the slight arc fusion was mainly applied for fine polishing merely instead of reshaping for the reason that the fabricated hyperbola fiber endface was very close to the ideal shape. The fabrication reproducibility and yield increase, and can reduce the cost of grinding. The fiber end shape is similar to the math on the hyperboloid, and the length of the axis of the hyperboloid profile shows a hyperbola. By mathematical properties of hyperbola, we derivation the parameter of radius of curvature for hyperbola microlenses. The definition of the radius of curvature of the hyperbolic vertex and the mode field diameter (the MFD) = 4.2£gm point of intersection with the hyperbola, the characteristics of the formation of this three o'clock round the curvature is the radius of curvature we have said. The radius of curvature (R) is a semi-consistent axial length (a) and two progressive line angle (£c) function, it means we can through the control of ¡§a¡¨ and £c to control the R, but £c is fixed after grinding process. So we choose control parameter ¡§a¡¨ by fusing process, via control ¡§a¡¨ to achieve the purpose of the control R. By various fusing parameters to adjust the gain of ¡§a¡¨, we can control the R in an ideal 2.6-2.8£gm. This process indeed improves the coupling efficiency. This method gives a low offset of the fiber it easier for more than 80%. And larger offset of the fiber by this method can achieve to 70% even 80%.
3

Discovery and Characterization of Hot Stars and their Cool, Transiting Companions

Stevens, Daniel Joseph 07 November 2018 (has links)
No description available.
4

Developments of the ISOLDE RILIS for radioactive ion beam production and the results of their application in the study of exotic mercury isotopes

Day Goodacre, Thomas January 2017 (has links)
This work centres around development and applications of the Resonance Ionization Laser Ion Source (RILIS) of the ISOLDE radioactive ion beam facility based at CERN. The RILIS applies step-wise resonance photo-ionization, to achieve an unparalleled degree of element selectivity, without compromising on ion source efficiency. Because of this, it has become the most commonly used ion source at ISOLDE, operating for up to 75% of ISOLDE experiments. In addition to its normal application as an ion source, the RILIS can be exploited as a spectroscopic tool for the study of nuclear ground state and isomer properties, by resolving the influence of nuclear parameters on the atomic energy levels of the ionization scheme. There are two avenues of development by which to widen the applicability of the RILIS: laser ionization scheme development, enabling new or more efficient laser ionized ion beams and the development of new laser-atom interaction regions. New ionization schemes for chromium, tellurium, germanium, mercury and radium have been determined. Additionally, for the first time, the anode cavity of the VADIS, ISOLDE's variant of the FEBIAD type arc discharge ion source was used as the laser-atom interaction region. A new element selective RILIS mode of operation was established, enabling the ISOLDE RILIS to be coupled with molten targets for the first time, increasing the flexibility of ISOLDE operation and opening a direction for future developments. This combined ion source was termed the VADLIS or Versatile Arc Discharge and Laser Ion Source. A combination of the developments presented in this thesis: an improvement of the laser ionization efficiency and the ability to couple the RILIS with molten targets, satisfied the pre-requisites for the long-awaited extension of the laser spectroscopy studies of exotic mercury isotopes. A sudden onset of extreme shape staggering in the neutron deficient mercury isotopes was revealed by optical pumping and laser spectroscopy experiments at ISOLDE in the 1970s and 1980s, with measurements conducted down to 181Hg. Despite this being one of the most remarkable examples of shape coexistence in the nuclear chart, in the intervening decades the cessation point of this odd-even staggering had yet to be unambiguously determined through measurements of nuclear ground state charge radii. This open question was successfully resolved using the ISOLDE RILIS for in-source resonance ionization spectroscopy. The experiment was performed as part of a large collaboration, using the Leuven Windmill system for alpha-detection; direct ion counting with the ISOLTRAP multi-reflection time-of-fight mass spectrometer (MR-ToF MS); and ion beam current measurements using the ISOLDE Faraday cups. The sensitivity of the technique enabled the measurements to be extended down to 177Hg, providing a definitive answer, that the extreme shape staggering stops at 180Hg. In addition to extending the measurements at the neutron deficient end of the mercury isotope chain, the relative mean square charge radii of both 207Hg and 208Hg was determined. This extended the measurements beyond the N = 126 shell closure, enabling the characterization of the "kink" in the trend of the isotope shifts.
5

Sizing Up the Stars

Boyajian, Tabetha Suzanne 17 July 2009 (has links)
For the main part of this dissertation, I have executed a survey of nearby, main sequence A, F, and G-type stars with the CHARA Array, successfully measuring the angular diameters of forty-four stars to better than 4% accuracy. The results of these observations also yield empirical determinations of stellar linear radii and effective temperatures for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale isochrones to constrain the masses and ages of the stars. These quantities are compared to the results found in Allende Prieto & Lambert (1999), Holmberg et al. (2007), and Takeda (2007), who indirectly determine these same properties by fitting models to observed photometry. I find that for most cases, the models underestimate the radius of the star by ~12%, while in turn they overestimate the effective temperature by ~ 1.5 - 4%, when compared to my directly measured values, with no apparent correlation to the star's metallicity or color index. These overestimated temperatures and underestimated radii in these works appear to cause an additional offset in the star's surface gravity measurements, which consequently yield higher masses and younger ages, in particular for stars with masses greater than ~ 1.3 M_sol. Alternatively, these quantities I measure are also compared to direct measurements from a large sample of eclipsing binary stars in Andersen (1991), and excellent agreement is seen within both data sets. Finally, a multi-parameter solution is found to fit color-temperature-metallicity values of the stars in this sample to provide a new calibration of the effective temperature scale for these types of stars. Published work in the field of stellar interferometry and optical spectroscopy of early-type stars are presented in Appendix D and E, respectively.
6

Approximation Algorithms for Clustering Problems

Behsaz, Babak Unknown Date
No description available.
7

Radii and neutron correlations of (6,8)He within the Gamow Shell Model

Papadimitriou, Georgios 01 December 2011 (has links)
We study the spatial correlations between halo neutrons in 6,8He within the complex-energy Gamow Shell Model (GSM). To this end, we calculate the neutron and proton radii, and two-neutron correlations in a large shell model space consisting of the 0p3/2 resonance and non-resonant p-sd scattering continuum. We use schematic forces and the finite-range Modified Minnesota interaction.The calculated charge radii, corrected for the core polarization and spin-orbit effects, are compared to the values extracted from measured atomic isotope shifts.We find that the charge radius of 6He primarily depends on the two-neutron separation energy and the shell-model occupation of the 0p3/2 orbit.We confirm that the ground-state GSM wave function of 6Heis dominated by the S=0 component representing a di-neutron structure. On the other hand, the correlation density of the 2+ resonance in 6He indicates a very weak di-neutron correlations in this state. We study the effect of pairing correlations on the neutron and charge radii of 6He and we confirm the presence of the Pairing-Anti-Halo effect in this light system.Finally, we calculate the charge radius of 8He in the full GSM space with the help of the Density Matrix Renormalization Group (DMRG) technique. The results of our realistic GSM+DMRG studies presented in this work show promise for extending the reach of the realistic complex-energy shell model to heavier halo systems.
8

XIII. Internationales Oberflächenkolloquium: 1. Treffen ”Industry meets standardization and science” - IMSAS: Kanten und Radien

Dietzsch, Michael, Gröger, Sophie 16 March 2012 (has links)
Das 13. Internationale Oberflächenkolloquium war das erste Treffen in der neuen Veranstaltungsreihe Industry meets standardization and science (IMSAS), mit dem ein Forum für Entwickler, Fertigungstechniker, Normungsexperten und Wissenschaftlern geschaffen werden soll. Vom 12. bis zum 14. März 2012 haben wir in diesem Rahmen über das Thema Kanten und Radien informiert. Viele internationale Normen existieren bereits zur Spezifikation und Verifikation. In einigen Bereichen sind diese Festlegungen jedoch noch lückenhaft. Kanten und Radien sind dafür ein perfektes Beispiel. Default Angaben zu Toleranzzonen und Verifikationsfestlegungen zur Extraktion, Filterung und Assoziation werden benötigt, um Spielräume bei der Interpretation und Bewertung auszuschließen und die Funktion eindeutig beschreiben zu können. Unsere Ziele für das Kolloquium waren die Einführung der neuen Veranstaltungsreihe IMSAS, die Information der Teilnehmer über den aktuellen Stand der Normung auf dem Gebiet von Kanten und Radien, die Präsentation von Problemstellungen und aktuell verfügbaren Lösungen zu diesem Thema und die Ableitung des zukünftigen Normungs- und Entwicklungsbedarfs auf diesem Gebiet. Das Kolloquium wurde vom Institut für Fertigungsmesstechnik und Qualitätssicherung IFMQ (Prof. M. Dietzsch und Dr.-Ing. Sophie Gröger ) der Technischen Universität Chemnitz in Zusammenarbeit mit dem Normungsauschuss Technische Grundlagen (NA 152) (J. Zymnossek) des Deutschen Instituts für Normung (DIN) organisiert.
9

An Evaluation of QuikSCAT UHR Wind Product's Effectiveness in Determining Selected Tropical Cyclone Characteristics

Said, Faozi 23 November 2009 (has links) (PDF)
While the standard wind product (L2B) available operationally in near-real time from SeaWinds on QuikSCAT is only 25 km in resolution, QuikSCAT data can be enhanced to yield a 2.5 km ultra-high resolution (UHR) product. The latter can be used to help estimate Tropical Cyclone (TC) characteristics such as TC eye center and wind radii. Two studies are conducted in this thesis, in which QuikSCAT UHR wind product's effectiveness in estimating these TC characteristics is evaluated. First, a comparison is made between the analyst's choice of eye location based on UHR images and interpolated best-track position. In this analysis, the UHR images are divided into two categories, based on the analyst's confidence level of finding the eye center location. In each category, statistical error quantities are computed. UHR images within the high confidence category can provide, for a given year and basin, mean error distance as small as 19 km with a 10 km standard deviation. Second, a visual comparison of QuikSCAT's performance in estimating wind radii is made. QuikSCAT's performance is gauged against H*wind dataset and the Extended Best-Track (EBT) dataset. Results show that QuikSCAT UHR data yields a correct 34-kt wind radius most of the time regardless of the TC category when compared to both H*wind and EBT, whereas the 50- and 64-kt wind radii visual estimates do not always agree with H*wind and EBT. A more sophisticated method is also implemented to automatically estimate wind radii based on a model fit to QuikSCAT data. Results from this method are compared with EBT wind radii. Wind radii obtained from QuikSCAT model fit are generally highly correlated with EBT estimated wind radii. These two studies show that QuikSCAT UHR wind products are helpful in estimating TC eye location and wind radii, thus improving TC forecasting and analysis.
10

Caput Radii Fractures : - Epidemiology, Classification and Treatment

Landergren, Lina January 2022 (has links)
Introduction Caput radii fractures vary from non-dislocated to complex comminuted fractures and are oftenclassified by the Mason Classifications system from 1954. Most caput radii-fractures aresuccessfully treated non-surgical although some need surgery. Several surgical methods havebeen developed and surgical treatment is increasing. Aim Primary aim is to assess the Mason classification correlation to choice of treatment.Secondary aims are to describe the epidemiology, treatment frequency including surgical andnon-surgical as well as reoperation rate. Results Correlation between Mason classification and surgical/non-surgical treatment showed asignificant positive correlation (rs=0.403, p<0.001). Of 315 patients 95.2% were treated nonsurgical,4,8% received acute surgery. The estimated incidence was 3.25 per 10 000 per year,for women 4.09 and men 2.41 per 10 000 per year. Median age was 49 years (IQR 33-60), 54for women and 36 years for men respectively. Of the patients with Mason I did 0.4% receiveacute surgery, Mason II 3.4%, Mason III 66.7% and Mason IV 36.4%. Multiple surgicalmethods were used, Open reduction and internal fixation with plate and screw was mostfrequent. Four patients in the surgical treatment-group (23.5%) were reoperated. Two patients(0.7%) had late surgery due to complications. Conclusions Surgical treatment was more often used in more advanced fractures according to the Masonclassification although the correlation was fair and there were patients in each class that weresurgery treated. Surgical methods varied and reoperation rate was high. Women had higherincidence and a higher median age then men at time of injury.

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