• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1560
  • 574
  • 7
  • 5
  • 5
  • 4
  • 4
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 4259
  • 4259
  • 2000
  • 1611
  • 678
  • 395
  • 232
  • 225
  • 188
  • 185
  • 175
  • 164
  • 162
  • 151
  • 148
  • 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.
31

Applications of Operations Research in Domestic Electric Utilities

Myers, Jametta 11 December 2008 (has links)
Since its inception in the 1950s, operations research has been used in a number of industries, including the energy industry. Documentation of its use in exploration, production, gasoline blending, oil spill management, coal mining, coal handling, and coal mixing is extensive. However, considerably less documented research exists for one significant customer of many of these products: the electric utility. This work reviews refereed literature from United States operations research journals that document the use of operations research in United States electric utility operations. Applications that centered specifically on the areas of thermal energy generation, transmission, distribution, capacity planning, electric power service options, and other general operations-related activities were included. Applications solely related to plant siting, general energy policy, or work that focused on electricity as a commodity and primarily investigated the use of financial instruments, were not included.
32

Fabrication of surface amine gradients by controlled-rate infusion for chromatographic applications

Kannan, Balamurali 23 July 2013 (has links)
Surface gradients are materials that exhibit a variation in properties such as chemical composition, topography etc., in a continuous and/or discrete fashion. They are broadly classified as chemical and physical gradients depending upon the properties that gradient exhibits. Among those, chemical gradients on various surfaces have been a great interest in materials research for the last two decades. This is due to the applications of gradients in various fields such as biological sciences, separation science, etc. There have been several different approaches developed for the preparation of chemical gradients. Silane-based approaches are among those that are widely used because of the straightforwardness of the chemistry involved and also the availability of silanes with various chemical functionalities. A few of these silane based approaches such as the vapor-diffusion method and liquid diffusion method have been used for various applications so far. Most of these methods were only able to prepare surface chemical gradients for a specific application mainly because of their limitations in terms of gradient-length scale and chemistry involved. Hence, there is a need to develop additional procedures for the preparation of chemical gradients that can be adaptable to different substrates and use them to form gradients at various length-scales such as few hundred microns to tens of centimeters. Using 3-aminopropyltriethoxysilane (APTEOS) as the precursor, a simple method was developed to prepare surface amine gradients termed ‘controlled-rate infusion (CRI). The CRI method involves the infusion of an organoalkoxysilane solution into a container with a substrate mounted vertically so that time-based exposure along the substrate forms a gradient in chemical functionality. The most important attribute of this method is that the local steepness of the gradient can be systematically controlled by simply changing the rate of infusion. The steepness of the gradient can also be changed at predefined positions along its length by programming the rate of infusion. The ability to manipulate the gradient profile is particularly important for applications that rely on mass transport and/or those that require spatial control of gradient properties. CRI can also be used to study the reactivity of aminoalkoxysilanes that contain mono, di and tri amino groups and also amines with various substitutions (secondary and tertiary amines). The gradient profiles in each case were different and correlated to their reactivity with surface silanols. Among those aminoalkoxysilanes, ethylenediamine and diethlenetriamine were found to be very good chelating agents to bind with metal ions. Thus, gradients prepared with diamine and triamine were used as ligand density gradients for the investigation of metal-amine complex formation using two different metal ions (Cu2+ and Zn2+). The above mentioned work formed the first part of this dissertation (up to Chapter 5). The latter part concentrates on fabrication and application of surface gradients for stationary phases for chromatographic separation. For the demonstration of proof-of-principle of the application of gradient stationary phases, the CRI approach was employed to prepare continuous stationary phase gradients on HP-TLC plates for planar chromatography. The SiOH groups on the activated HP-TLC plates were reacted with 3-aminopropyltriethoxysilane (APTEOS) in a time dependent fashion by using a programmable syringe pump to control the rate of APTEOS infusion into the deposition reservoir. The shape (profile) of the gradient was controlled by the rate of infusion and the gradients were visualized by utilizing a concentration-dependent color formation reaction between amine groups and ninhydrin. The advantages of such gradients in optimizing the retention and separation of various components in different mixtures was illustrated using mixtures of (i) four weak acids and bases and (ii) three widely-used over-the-counter drugs. Thus, the gradient stationary phase was successfully fabricated and applied as a planar chromatographic support. The next step of this research was to prepare continuous amine gradients on silica capillaries as these would be useful in open-tubular capillary electrochromatography for separation of complex mixtures and also to study the retention behavior of various components. This was achieved by carefully infusing micro-volumes of APTEOS solution into the activated silica capillaries. To characterize these gradients, a unique set-up was developed to measure streaming potential and zeta potential along the gradient capillary. Since surface amine groups exist as positively charged groups at acidic and neutral pHs, the measured zeta potential increased from the low amine end to the high amine end of the capillary. In summary, this dissertation work focuses mainly on the development of a simple, rapid and cost-effective method for the preparation of surface chemical gradients. CRI has incredible flexibility and adaptability, which was confirmed by extending it to different substrates such as silica TLC plates and capillary tubes for various applications. The CRI approach is not just helpful in preparing gradients for chromatographic separations; it can be a stable platform to study the reactivity of various precursors which could be a useful tool to develop high-throughput surface modification procedures.
33

SYNTHESIS OF NANOCOMPOSITES BY LASER ABLATION

MUTISYA, STEPHEN 12 May 2011 (has links)
Immunoglobulin E (IgE)-conjugated gold nanoparticles were produced via in situ conjugation of gold nanoparticles with immunoglobulin E by laser ablation of Au in a liquid solution. The colloidal stability and the size distribution of the resulting bio-nanoconjugates were examined with UV-Visible spectroscopy (UV-Vis), dynamic light scattering (DLS), and transmission electron microscopy (TEM). These techniques showed that the Au nanoparticles in aqueous solutions were highly monodispersed spherical particles with a very narrow size distribution. The particles net diameter using TEM, was found to be D5 =3.8±0.9nm and D10 =4.7±1.3nm while the hydrodynamic diameter obtained with DLS was found to be h5 D =171±12nm , h10 D =164±18nm for 5min and 10min laser ablation time respectively. Enzyme-Linked immunosorbent Assay (ELISA) and flow cytometry measurements of the conjugates confirmed that the gold-bound protein remained biologically active, thus paving the way for the application of these nanoparticles in immuno-diagnostics, particularly in tumor-targeted drug delivery.
34

Ordinal indexing of the class of strictly singular operators

stevenson, craig 01 May 2009 (has links)
The Schreier families are a collection of finite subsets of N and have been used to provide refinements of the following Banach space notions: unconditional basic sequences, convergent sequences, spreading model and strictly singular operators to name a few. We use the Schreier families to study subclasses of strictly singular operators on Banach spaces. We also provide a sufficient condition on the strictly singular operators implying every operator falls into one of these subclasses.
35

NONCOVALENT INTERACTION OF PLATINUM PLANAR AMINE COMPOUNDS WITH TRYPTOPHAN: A STRATEGY TO INTERFERE WITH P53-MDM2 INTERACTIONS AND TARGETING RETROVIRAL ZN FINGER-DNA INTERACTION (HIV NCP7)

Bate, Aaron 01 January 2009 (has links)
Non-covalent interactions involving π-π stacking play an essential role in self-assembly and molecular recognition processes such as protein folding and DNA/RNA-protein selective recognition. The knowledge gained from these studies could provide insight into possible site recognition complexes, inhibiting or mimicking protein-protein or protein-DNA interactions. Based on molecular modeling as well as HOMO and LUMO energies, several chromophores were selected with a variety of ∆ε values (∆ε= |εHOMO,NAcTrp – εLUMO,chromophores|), high and low, to establish a correlating trend with the modeling and experimental data. The corresponding Pt(dien) compounds were synthesized and their ability to stack to N-acetyl tryptophan was evaluated by fluorescence quench experiments. Attaching a strong electron donating/withdrawing group or extending the π system of pyridine or thiazole by means of a benzene ring (quinoline and benzothiazole) was found to enhance the π-π interaction with N-acetyl tryptophan.
36

Development of Quasi-Likelihood Techniques for the Analysis of Pseudo-Proportional Data

Elder, Jennifer A. 01 January 1996 (has links)
In certain experimental situations, the data observed are pseudo-proportional. By this, we observe the numerator, the number of responders, but the denominator, the total number, is random and, possibly, unobserved. In such situations, the data often exhibit "extra" variability due to the randomness of the denominator. Analysis of these data should account for this overdispersion. Several authors have proposed parametric approaches to this problem. Finney [Biometrika (1949) 36, 239-256] proposed the use of a mixture of the binomial and Poisson distributions. Anscombe [Annals of Applied Biology (1949) 36, 203-205] discussed the use of a mixture of the binomial and negative binomial distributions. Margolin et al. [Proceedings of the National Academy of Sciences (1981) 78, 3779-3783] suggested the use of a gamma mixture of Poisson distributions. While it is true that these approaches provide a means of handling overdispersion, the choice of the distributions used often is based on mathematical convenience. To avoid making full distributional assumptions, Kim [Unpublished Ph.D. dissertation (1991), UCLA] applied quasi-likelihood methodology to overdispersed binomial data. In his method, he assumed that the conditional mean and variance of the numerator was that of a binomial distribution, and that the mean of the distribution of the denominator was known, but that its variance was unknown. Using conditional arguments, he arrived at the unconditional mean and variance of the numerator. With the form of the first two moments of the numerator, Kim used quasi-likelihood method of moments estimation to get estimates of the unknown parameters. In this dissertation, Kim's results are generalized to allow the denominator to have an unknown mean and variance, and estimation is achieved using a generalized quasilikelihood method of moments technique. In addition, methodology is developed that allows for overdispersion in both the numerator and denominator. Here, extended quasilikelihood techniques are used for estimation of any unknown parameters. Properties of the estimators were studied via a simulation study which suggests the extended quasilikelihood estimates are not asymptotically normally distributed. Also, goodness-of-link testing is described for use in maximum likelihood, as well as, quasi-likelihood estimation. The methods developed here are illustrated by the analysis of data from a colony formation assay involving serial dilutions.
37

Simulations of the inuence of atomic vibrations on the magneticsignal observed in scattering of electron vortex beams on bcc ironcrystal

Löfgren, André January 2019 (has links)
No description available.
38

Multivariate modeling improves quality grading of sawn timber

Wendel, Charlotta January 2019 (has links)
The quality grades are what determines the value of sawn timber. Therefore the grading process is essential for the profitability of a sawmill. At a modern sawmill in northern Sweden, a CT Log Computed Tomography is used in the saw line to optimize the cutting solutions by virtual 3D reconstruction of the log features. By adjusting the position of the log according to the optimal solution before cutting, the aim is to increase the quality and final resale value of the sawn timber. However, measurement errors in the virtual and final grading systems cause inconsistencies that decrease the agreement in grading. The grading process uses a rule-based system based on the Nordic Timber Grading Rules, which depends strongly on the size and shape of knots. If knots are measured incorrectly they could falsely exceed the allowed value for a certain quality, resulting in an inaccurate quality grade. The results from this initial project, show that using multivariate modeling instead of the traditional rule-based grading system improves the agreement between the virtual and final grading. The accuracy in grading increases with up to 19%, resulting in an agreement of 73%. A better agreement between the two systems would allow the process to take advantage of the full potential of the CT, increasing the profitability of the sawmill. The results are promising, but before implementing the method in the sawmill further testing and development have to be done to ensure optimal improvement.
39

- “Om det är damm på kommer det gå mycket fortare”. : En designbaserad studie om hur barn förklarar fenomenet luftmotstånd / ”It will go faster if there is dust on it” : A design-based study of how children explains the phenomena of air resistance

Gunnarsson, Alva, Pohjonen, Emma January 2019 (has links)
No description available.
40

Implementing a One Qubit Holonomic Quantum Gate in aBosonic Environment

de Castro Portugal, Pedro Vinicius January 2019 (has links)
No description available.

Page generated in 0.0811 seconds