• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 854
  • 777
  • 184
  • 149
  • 107
  • 82
  • 31
  • 22
  • 20
  • 16
  • 15
  • 11
  • 11
  • 10
  • 9
  • Tagged with
  • 2585
  • 545
  • 216
  • 178
  • 166
  • 154
  • 140
  • 131
  • 124
  • 123
  • 122
  • 113
  • 100
  • 98
  • 95
  • 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.
21

Perlite expansion and evaluation using a laboratory furnace

Allen, M. J. January 1999 (has links)
No description available.
22

Mathematical modelling of human skin as a membrane in tension : derivation of finite element solutions for the geometrically and materially nonlinear membrane equations and the consideration of their application to reconstructive surgery

Sun, Ding-Fook January 1988 (has links)
No description available.
23

Electronic spectroscopy of unstable species in free jet expansions

Moxey, S. R. January 1988 (has links)
No description available.
24

Haemoglobin E-β thalassaemia

Premawardhena, A. P. January 2002 (has links)
No description available.
25

The role of Sir Roderick Murchison in promoting the geographical and geological exploration of the British Empire and its sphere of influence, 1855-1871

Stafford, R. A. January 1985 (has links)
No description available.
26

Investigación sobre la expansión territorial del modelo de negocios radicales a lo largo de Chile

Garay Pulgar, Tahya, Las Heras Olivares, Mónica 12 1900 (has links)
Seminario para optar al título de Ingeniero Comercial, Mención Administración / Drygrass Group es una empresa que nace en el año 2010 de la mano de Andrés Arias y Patricio Mora, con la finalidad de desarrollar el primer Bar The Clinic en Santiago, ubicado en el barrio Bellas Artes. Esta idea, que se basaba en plasmar la línea de pensamiento del diario tanto en las paredes como en la oferta entregada al público, no tardó mucho tiempo en volverse un ícono exitoso tanto de la ciudad como de la idiosincrasia chilena. Con el pasar del tiempo y debido al gran éxito que estaba teniendo, sus dueños se dieron cuenta que la oferta del bar no alcanzaba a cubrir todas las necesidades de su público, siendo necesario expandirse e integrar nuevos espacios para potenciar la experiencia entregada a sus clientes. Es así, como en el año 2014, nace Radicales, una apuesta complementaria para el edificio, que en sus inicios integraba un bar, un cine, un club de baile y tiendas residentes como un centro de tatuajes y un sex shop. En el año 2015, tras romper los lazos con la marca The Clinic y coincidiendo con un viaje personal de los dueños hacia Puerto Varas, fue donde se dieron cuenta del gran atractivo que tenía ésta ciudad para el modelo de Radicales. Es así, tras una extensa búsqueda del lugar y de conversaciones con el municipio sobre el proyecto, que se llegó a la empresa INVIA de Ferrocarriles del Estado, quienes presentaron no sólo el lugar perfecto para llevar a cabo la realización del modelo en la ciudad, sino que estaban abiertos a poner a disposición de Radicales las estaciones de todo el sur de Chile, para que éste actuara como agente revitalizador de estos espacios patrimoniales. En el siguiente informe, se desarrolla la investigación realizada sobre la expansión territorial del modelo de negocios de Radicales a lo largo de Chile. Ésta, tiene por objetivo principal analizar y reconocer cuáles son las estaciones ferroviarias, actualmente pertenecientes a la Empresa de Ferrocarriles del Estado (EFE), que poseen mayor potencial para implementar y desarrollar alguno de los distintos modelos de negocio que opera Radicales. Dentro de los objetivos específicos de este proyecto, se encuentran el revitalizar espacios patrimoniales y ponerlos al servicio de los ciudadanos en las comunidades en las que están inmersos, así, facilitar y apoyar el desarrollo de múltiples actividades relacionadas con la industria creativa, cultural y turística. Junto con ello, otro objetivo es el de, a través de la implementación del modelo Radicales, mejorar la imagen que EFE tiene ante la comunidad dado que estos inmuebles se han convertido en focos negativos por la delincuencia y el abandono. Finalmente, otro objetivo, es llevar a cabo la implementación de forma eficiente y rentable tanto en lo económico como en lo social, con buenos estándares de calidad para así funcionar como un integrador de la actividad ciudadana en sus áreas comerciales.
27

Covariance and Gramian matrices in control and systems theory

Fernando, Kurukulasuriya Vicenza January 1983 (has links)
Covariance and Gramian matrices in control and systems theory and pattern recognition are studied in the context of reduction of dimensionality and hence complexity of large-scale systems. This is achieved by the removal of redundant or 'almost' redundant information contained in the covariance and Grarrdan matrices. The Karhunen-Loeve expansion (principal component analysis) and its extensions and the singular value decomposition of matrices provide the framework for the work presented in the thesis. The results given for linear dynamical systems are based on controllability and observability Gramians and some new developments in singular perturbational analysis are also presented.
28

The Russian advance in Central Asia and the British response 1834-1884

Tealakh, Gali Oda January 1991 (has links)
No description available.
29

Thermoreponsive behaviour of AM₂O₈ materials

Allen, Simon January 2003 (has links)
This thesis investigates the synthesis and structural characterisation of AM(_2)O(_8) phases, many of which show negative thermal expansion (NTE); relevant literature is reviewed in Chapter One. Chapter Two describes the synthesis, structure solution, and mechanistic role of a new family of low-temperature (LT) orthorhombic AM(_2)O(_8) polymorphs (A(^TV) = Zr, Hf; M(^VI) = Mo, W). These materials are key intermediates in the preparation of cubic AM(_2)O(_8) phases from AM(_2)O(_7)(OH)(_2)(H(_2)O)(_2). The structure of LT-AM(_2)O(_8) has been elucidated by combined laboratory X-ray and neutron powder diffraction. Variable temperature X-ray diffraction (VTXRD) studies have shown LT- AM(_2)O(_8) phases exhibit anisotropic NTE. LT-ZrMo(_2)O(_8) has been shown to undergo spontaneous rehydration, allowing preparation of ZrMo(_2)O(_7)(OD)(_2)(D(_2)O)(_2) and assignment of D(_2)O/OD positions within the structure by neutron diffraction. Using this result, a reversible topotactic dehydration pathway from AM(_2)O(_7)(OH)(_2)(H(_2)O)(_2) to LT-AM(_2)O(_8)s is proposed. Chapter Three investigates the order-disorder phase transition with concurrent oxygen mobility in cubic AM(_2)O(_8) materials; studies include comprehensive VT neutron diffraction of cubic ZrMo(_2)O(_8) to reveal a static to dynamic transition at 215 K, and novel quench-anneal/quench-warm variable temperature/time diffraction experiments on ZrMo(_2)O(_8) which lead to an activation energy of 40 kJmol(^-1) for oxygen migration. In Chapter Four (^17)O-labelled cubic ZrW(_2)O(_8) has been prepared to understand the oxygen migration process by VT MAS NMR. In situ hydrothermal studies of cubicZrMo(_2)O(_8) using synchrotron radiation have shown direct hydration to ZrMo(_2)O(_7)(OH)(_2)(H(_2)O)(_2).. In Chapter Five VTXRD of trigonal a-AMo(_2)O(_8) phases reveals a previously unknown second-order phase transition at 487 K (A = Zr) or 463 K (A = Hf) from P31c to P3ml. Rigid-body Rietveld refinements have shown this is due to alignment of apical Mo-O groups with the c axis in the high-temperature, a' phase.
30

Development of Lewis Acid Catalyzed Asymmetric Ring Expansion Reactions and Catalysis of Etherification Reactions with sp3 Electrophiles

Rendina, Victor L. January 2013 (has links)
Thesis advisor: Marc L. Snapper / Chapter 1: Over the past 100 years, ring expansion chemistry with non-stabilized diazoalkanes has grown slowly. While the intrinsic hazards and stigma associated with the use of diazoalkanes has been a serious impediment to more widespread development, a number of groups have made significant advances over the years. This chapter aims to provide a brief historical account of the most significant developments related to diazoalkane- based ring expansion methods. Chapter 2: The construction of stereogenic centers adjacent to ketones remains a challenging synthetic problem for chemists. Deficiencies with regard to reaction scope, efficiency, and generality remain. In contrast to the majority of other methods in the literature, stereoselective insertion of diazoalkanes provides a pathway to directly access enantiomerically enriched α-substituted cycloalkanones. In this chapter, an account of how we developed the first catalytic asymmetric diazoalkane-based ring expansion reactions is presented. Ring expansion of unfunctionalized cycloalkanones with diazoalkanes efficiently affords α-aryl substituted cycloalkanones with high enantiopurity. Additionally, this work led to the synthesis of new chiral bis(oxazoline) ligands and the discovery of a rapid method to assay the concentration of diazoalkane solutions. Chapter 3: Single-carbon ring expansion is a powerful synthetic disconnection, allowing chemists to construct or purchase the lower homologue of a ring system before expanding to the target ring size. Starting from a smaller ring size can often allow access to a broader array of transformations that proceed with greater stereoselection. In our approach to a class of natural products bearing a cis-decalin core, we successfully implemented a catalytic regioselective single-carbon ring expansion reaction in the context of an advanced synthetic intermediate. This chapter describes the experimental details behind the first catalytic single carbon cyclopentanone homologations and how we extended the method to more complex substrates. Chapter 4: Catalytic activation of sp2 hybridized electrophiles by nucleophilic catalysts has been studied extensively and proceeds through a well-defined mechanistic pathway. In constrast, activation of sp3 hybridized electrophiles in a similar fashion with small-molecule organocatalysts remains an elusive endeavor for chemists. This chapter describes prelimi- nary studies towards this lofty goal and how we discovered a new class of imidazole-based catalysts. Thorough mechanistic studies with the newly discovered catalysts ultimately proved that the reactions proceeded through a pathway that does not involve electrophile activation. However, inexpensive and commercially available imidazolium salts were found to catalyze Williamson etherification reactions under mild conditions through a mechanism that involves an unusual imidazolium alkoxide ion-pair. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Page generated in 0.0854 seconds