• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 309
  • 264
  • 117
  • 74
  • 49
  • 27
  • 24
  • 13
  • 12
  • 12
  • 12
  • 12
  • 10
  • 9
  • 9
  • Tagged with
  • 1075
  • 289
  • 118
  • 90
  • 73
  • 70
  • 70
  • 64
  • 52
  • 52
  • 50
  • 49
  • 49
  • 48
  • 42
  • 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.
481

A Study on High-linearity and Low-hysteresis Capacitive Humidity Microsensors

Hsieh, Chia-hsu 27 August 2008 (has links)
People for long term exposed to an air-conditioned but highly humid environment are vulnerable to hyper-sensitivity or asthma triggered by fungi or dust mites. This thesis aims to develop a high-linearity and low-hysteresis capacitive relative humidity (RH) microsensor to more precisely accommodate the humidity of living spaces. To reduce the hysteresis and enhance the linearity, this research uses not only one polyimide (PI) thin film as a humidity sensing layer but also utilizes another PI thin film as a protecting layer of the top electrodes. To improve further the RH sensitivity and responding speed, interlacing out-of-plane electrodes are designed in the RH microsensor. The main processing steps of the RH sensor developed in this study involve at least five photolithographic and four thin film deposition processes. The influences of sensing area, number of electrode pairs and testing temperature on the sensitivity and sensing linearity of humidity microsensors were investigated. Based on the measurement results, the sensitivity apparently increase as well as the sensing area (2 mm ¡Ñ 2 mm: 0.12 pF/%RH, 3 mm ¡Ñ 3 mm: 0.48 pF/%RH, 5 mm ¡Ñ 5 mm: 1.09 pF/%RH), and decrease with the number of electrode pairs (40 pairs: 0.51 pF/%RH, 20 pairs: 0.4 pF/%RH) and increase with the testing temperature. The thesis has demonstrated that the capacitance of the RH sensor vary from the relative humidity with a very linear relationship (linearity: 98.8%~99.99%) over the range of 30~70%RH. Finally, to increase effectively the surface area and to reduce further the hysteresis, three-dimensional (3D) moisture entrances and exits were designed and a very low hysteresis value (0.5%RH) can be achieved.
482

The relationship between team-level aggression and basketball performance

Wright, Mary Ann 12 November 2009 (has links)
Previous research has indicated that aggression is generally detrimental to performance in the occupational domain (Campbell, 1990; James et al., 2005; Sackett, 2002; Viswesvaran et al., 1999). In certain athletic contexts, however, aggression may serve to enhance performance at the team level. For this analysis, team-level aggression is hypothesized to be positively related to team performance in basketball. Aggression in this context is defined as "the desire to inflict harm on another individual, group, or entity" (James, 2005, p.71). Both implicit (CRT-A) and explicit (NEO-PI-R) aggression were measured, and team performance was represented primarily by team scores. The data demonstrate that team-level implicit aggression is significantly and positively related to team performance, however team-level explicit aggression does not have a significant relationship with team performance.
483

Hydroxy cruciforms and bis(hydroxystyryl)benzenes: synthesis, structure, and photophysical properties of novel π-systems

McGrier, Psaras Lamar 15 June 2010 (has links)
This thesis examines the synthesis, photophysical properties, and sensory responses of hydroxy-substituted 1,4-distyryl-2,5-bis(arylethynyl)benzenes (Cruciforms, XFs). These two-dimensional cross-conjugated materials possess spatially separated frontier molecular orbitals (FMOs). This spatial separation allows the HOMO and LUMO to be addressed independently by analytes, which leads to significant changes in their absorption and emission. These properties allow XFs to be utilized for the detection of various analytes. These studies highlight the benefits of utilizing XFs for the development of advanced functional solid state materials for sensory applications.
484

Developing mobile agents through a formal approach

Barbu, Andreea Best, Eike Pelz, Elisabeth January 2005 (has links) (PDF)
Thèse de doctorat : Informatique : Paris 12 : 2005. Thèse de doctorat : Informatique : Oldenburg, Carl v. Ossietzky Universität : 2005. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. p. 166173. Index.
485

Elucidation of the Cation−π Interaction in Small-Molecule Asymmetric Catalysis

Lin, Song 14 October 2013 (has links)
The cation&ndash;&pi; interaction has been long-established to play an important role in molecular recognition, supramolecular chemistry, and molecular biology. In contrast, its potential application in small-molecule catalysis, especially as a selectivity-determining factor in asymmetric synthesis has been overlooked until very recently. This dissertation begins with an extensive literature review on the state-of-the-art research on the application of cation&ndash;&pi; interactions in non-enzymatic catalysis of organic and organometallic transformations. The research in this field has been largely inspired and guided by the related biosynthetic systems incorporating the same type of interactions.</p> / Chemistry and Chemical Biology
486

Magneto-Optic Polymers and Devices

Lopez Santiago, Alejandra January 2014 (has links)
For several decades, the field of magneto-optics (MO) has demonstrated applications that have impact on every day applications such as in optical data storage, magnetic field sensing, crucial for magnetoencephalography and magnetocardiography; and compact and efficient optical isolators, among others. In the past, many of these applications and the devices designed for them have heavily relied on inorganic materials. Organic materials with a high MO response represent an interesting alternative to the inorganic equivalent by not only being a more cost efficient solution, but also by allowing the user to modify a number of variables to control and optimize the MO performance depending on the application and level of performance desired. In this dissertation I discuss the MO properties of novel organic materials, starting with polythiophene, which has been of interest due to the strong relationship between its high MO performance and its lamellar structure and regioregularity. I will also be discussing another material system that provides several degrees of MO tunability: magnetite based nanocomposites. A unique and novel synthetic approach described in this dissertation yields both highly transparent and MO responsive polymer films. I will be describing a systematic approach that indicates a strong influence of the size of the nanoparticle as well as the nanoparticle concentration in the MO performance of the bulk polymer, while maintaining high optical quality with minimal scattering and absorption in the visible and near infrared. Finally, I will be discussing the implementation of both a magnetite nanocomposite and a cobalt ferrite based nanocomposite in a free space magnetic field system and demonstrate the proof-of-principle operation of a sensing system.
487

Psi-calculi: a framework for mobile process calculi : Cook your own correct process calculus - just add data and logic

Johansson, Magnus January 2010 (has links)
A psi-calculus is an extension of the pi-calculus with nominal data types for data structures, logical assertions, and conditions. These can be transmitted between processes and their names can be statically scoped as in the standard pi-calculus. Expressiveness and therefore modelling convenience significantly exceed those of other formalisms: psi-calculi can capture the same phenomena as other extensions of the pi-calculus, and can be more general, e.g. by allowing structured channels, higher-order formalisms such as the lambda calculus for data structures, and predicate logic for assertions. Ample comparisons to related calculi are provided and a few significant applications are discussed. The labelled operational semantics and definition of bisimulation is straightforward, without a structural congruence. Minimal requirements on the nominal data and logic are established in order to prove general algebraic properties of psi-calculi. The purity of the semantics is on par with the pi-calculus. The theory of weak bisimulation is established, where the tau actions are unobservable. The notion of barb is defined as the output label of a communication action, and weak barbed equivalence is bisimilarity for tau actions and preservation of weak barbs in all static contexts. It is proved that weak barbed equivalence coincides with weak bisimulation equivalence. A symbolic transition system and bisimulation equivalence is presented, and shown fully abstract with respect to bisimulation congruence in the non-symbolic semantics. The symbolic semantics is necessary for an efficient implementation of the calculus in automated tools exploring state spaces, and the full abstraction property means processes are bisimilar in the symbolic setting if they are bisimilar in the original semantics. Psi-calculi remove the necessity of proving general properties every time a new mobile process calculus is defined. By properly instantiating the framework the properties are guaranteed to hold, thus removing the need to do tedious and error-prone proofs.
488

Supramolecular chemistry of aryl extended calix [4] pyrroles

Gil Ramírez, Guzmán 19 November 2009 (has links)
La presente tesis consta de dos vertientes interrelacionadas. La primera se centra en intentar cuantificar experimentalmente la contribución energética en disolución de la interacción anión-&#61552;, mediante el uso de calix[4]pirroles aril substituidos en las posiciones meso- como moléculas modelo. El trabajo realizado muestra que la interacción anión-&#61552; es repulsiva para anillos con valores de ESP negativos y a medida que el efecto electrón atrayente de los sustituyentes aumenta la interacción se vuelve menos repulsiva, hasta que, cuando el valor de ESP en el centro del anillo aromático es positivo la interacción se vuelve ligeramente atractiva. La segunda en el uso de estos receptores simples para obtener arquitecturas supramoleculares más complejas, y su autoensamblaje en capsulas. Los estudios muestran que calix[4]pirroles sustituidos con grupos urea en sus anillos aromáticos se autoemsamblan en capsulas diméricas en presencia de un huesped adecuado como los N-óxidos de alquil aminas y piridinas en disolventes apolares. / This thesis consists of two interrelated aspects. The first one pretends to quantify experimentally the energetic contribution in solution of the anion-&#61552; interaction, using aryl extended calix[4] pyrroles substituted in their meso- positions as a model system. The work performed shows that the anion-&#61552; interaction is repulsive for aromatic rings with negative ESP values, as the electron withdrawing character of the substituent increases the interaction becomes less repulsive, until eventually, when the ESP value in the center of the aromatic ring is positive the interaction turns into slightly attractive.The second one is based on the use of these simple receptors as scaffolds to obtain complex structures and their self-assembly into capsules. The studies performed show that aryl extended calix[4]pyrroles substituted with urea functions on their upper rim self-assemble into dimeric capsules in the presence of a suitable guest like the N-oxides of alkyl amines and pyridines in non-polar solvents.
489

A COMPARISON OF THE REISS PROFILE WITH THE NEO PI-R ASSESSMENT OF PERSONALITY

Boyd, Sara E. 01 January 2010 (has links)
The purpose of this thesis was to determine whether the NEO Personality Inventory-Revised (NEO PI-R) could account for significant variance within a measure of personality developed for the intellectually disabled (i.e., the Reiss Profile of Fundamental Motives), as well as to consider their comparative validity. The NEO PI-R and the Reiss Profile of Fundamental Motives were administered to 127 undergraduate students in conjunction with the Personality Research Form (PRF) and the Behavior Report Form (BRF). The NEO PI-R was able to account for a substantial amount of variance in the Reiss Profile scales, and the Reiss and the NEO accounted for approximately equivalent amounts of variance in the PRF and BRF. Implications for general personality research as well as additional research with a sample of adults with intellectual disability are discussed.
490

PARTIALLY FLUORINATED POLYCYCLIC AROMATIC COMPOUNDS: SYNTHESIS AND SUPRAMOLECULAR BEHAVIOR

Cho, Don Mark 01 January 2007 (has links)
The field of organic electronics has received much attention over the last few years, and engineering of organic crystals to grow with pi-electron systems arranged in a face-to-face motif has been shown to be beneficial in electronic devices. The effects of combining aromatic and perfluorinated aromatic derivatives have shown that the intramolecular stacking pattern can be changed from an edge-to-face arrangement to that of a face-to-face motif. Before the work described herein, there were no reported studies of the supramolecular behavior of fused polycyclic aromatic compounds with partial peripheral fluorination, inducing the desired face-to-face behavior. This is the main focus of the thesis. Furthermore, by exploiting the interactions between the fluorinated and non-fluorinated faces of the molecule, columnar liquid crystalline behavior can be achieved through variations of the alkyl substituents on the molecule.

Page generated in 0.0298 seconds