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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.
51

Finanční podpory hospodaření v zemědělském družstvu

LIBÍNSKÁ, Dana January 2019 (has links)
The aim of this thesis was to evaluate the impact of financial support on farming in a chosen agricultural cooperative. In the theoretical part, the overall state of agriculture in the conditions of the Czech Republic, the current situation on the market with milk, beef and pork and the situation on the market with plant commodities were assessed.
52

Cálculo autoconsistente de estrutura eletrônica no espaço direto. / Self-consistent calculation of electronic structure in direct space.

Peduto, Pascoal Roberto 25 October 1990 (has links)
Neste trabalho, propusemos um método autoconsistente de espaço direto para o calculo de estrutura eletrônica. O método se baseia no formalismo LNTO -ASA na representação fortemente ligada (light-binding) e no método de recorrência aliado ao terminador de Beer & Pettifor. Neste método o custo computacional cresce linearmente com o numero de átomos não equivalentes na cela primitiva sendo, portanto, ideal para tratar sistemas complexos que não apresentam periodicidade ou que possuem um grande numero de átomos não equivalentes por cela primitiva. Podemos, por exemplo, estudar de forma autoconsistente a estrutura eletrônica das vizinhanças de uma impureza com um custo computacional apenas cinco ou seis vezes maior que o de um metal puro. O método aqui proposto tem a vantagem adicional de ser fisicamente transparente. Para avaliarmos a eficácia do método, comparamos nossos resultados autoconsistentes obtidos para a liga cristalina ZR IND.2FE com os resultados obtidos pelo processo autoconsistente de espaço reciproco. O material em questão tem uma estrutura cristalina simples com seis átomos por cela primitiva e o calculo de estrutura eletrônica pode ser resolvido por métodos usuais de espaço reciproco. A presença do FE com sua banda d estreita e com uma alta densidade de estados no nível de Fermi tornara o processo de convergência não trivial. / In this work we have proposed a first-principles selfconsistent method which allows us to perform electronic structure calculations in real space. The scheme, based on the LNTO ASA formalism and the Recursion Method, enables us to evaluate the electronic structures of complex systems, with good degree of precision and low computational costs. Using Zr 2 Fe as test case, we compare our real-space results with those obtained in reciprocal space using the standard LMTO - ASA procedure. The agreement is very good showing the efficiency of the real-space approach. We note that the real-space method developed here presents advantages for the evaluation of local properties and can be applied for non-periodic systems. For instance, we can describe the electronic structure in a large region around a substitutional impurity with very little cost. lf we consider five shells around the impurity the cost in real-space will be about seven times the cost of the calculation for a mono atomic system.
53

Automated analysis and validation of chemical literature

Townsend, Joseph A. January 2008 (has links)
Methods to automatically extract and validate data from the chemical literature in legacy formats to machine-understandable forms are examined. The work focuses of three types of data: analytical data reported in articles, computational chemistry output files and crystallographic information files (CIFs). It is shown that machines are capable of reading and extracting analytical data from the current legacy formats with high recall and precision. Regular expressions cannot identify chemical names with high precision or recall but non-deterministic methods perform significantly better. The lack of machine-understandable connection tables in the literature has been identified as the major issue preventing molecule-based data-driven science being performed in the area. The extraction of data from computational chemistry output files using parser-like approaches is shown to be not generally possible although such methods work well for input files. A hierarchical regular expression based approach can parse > 99.9% of the output files correctly although significant human input is required to prepare the templates. CIFs may be parsed with extremely high recall and precision, contain connection tables and the data is of high quality. The comparison of bond lengths calculated by two computational chemistry programs show good agreement in general but structures containing specific moieties cause discrepancies. An initial protocol for the high-throughput geometry optimisation of molecules extracted from the CIFs is presented and the refinement of this protocol is discussed. Differences in bond length between calculated and experimentally determined values from the CIFs of less than 0.03 Angstrom are shown to be expected by random error. The final protocol is used to find high-quality structures from crystallography which can be reused for further science.
54

Local Nucleic Acid Base Conformation Study by Guanine Fluorescent Analogue 6- Methyl Isoxanthopterin (6-MI) Labeled DNA

Ji, Huiying 30 April 2019 (has links)
Understanding the local conformations of DNA at the level of individual nucleic acid bases is important for the study of the mechanism of DNA sequence-dependent behavior. Here we apply linear absorption, circular dichroism (CD), and fluorescence spectroscopy to study the DNA local base conformation using 6-methyl Isoxanthopterin (6-MI) labeled DNA. We interpret excitation–emission peak shift (EES) measurements of the 6-MI, both as a ribonucleotide monophosphate in solution and as a site-specific substituent for guanine in various DNA constructs, by implementing a simple two-state model. We show that the spectroscopic properties of the 6-MI probe in DNA can be used to obtain detailed information about local base conformations and conformational heterogeneity and fluctuations. Based on these findings, we apply a simple theoretical model to calculate CD of 6-MI substituted DNA constructs. We find that our model can be used to extract basesequence- dependent information about the local conformation of the 6-MI probe as modulated by the local base or base-pair environment. We next apply 6-MI to probe the ligand insertion of small molecules to duplex DNA, further extending the potential of 6- MI as a useful reporter of local nucleic acid base conformation. These studies served to establish a new level of sophistication in qualitatively analyzing 6-MI structural behavior in terms of local base stacking and unstacking conformations. v This dissertation contains previously published and unpublished co-authored material.
55

Áreas e volumes : de Eudoxo e Arquimedes a Cavalieri e o cálculo diferencial e integral / Areas and volumes : from Eudoxo and Arquimedes from Cavalieri and differential and integral calculus

Kurokawa, Cecilia Yumi, 1965- 11 September 2018 (has links)
Orientador: Maria Lúcia Bontorim de Queiroz / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica / Made available in DSpace on 2018-09-11T21:24:47Z (GMT). No. of bitstreams: 1 Kurokawa_CeciliaYumi_M.pdf: 2968759 bytes, checksum: 5b4c2abc6c3e05e7bb90da7d96a80067 (MD5) Previous issue date: 2015 / Resumo: O cálculo de áreas e volumes foi um tema que desafiou os matemáticos desde os primeiros registros encontrados. Desde as formas rudimentares e práticas sem embasamento teóricos dos babilônicos e egípcios até o desenvolvimento do Cálculo Diferencial e Integral, inúmeros matemáticos contribuíram para o desenvolvimento e formalização dos conceitos e maneiras de cálculo de áreas e volumes. Neste trabalho apresentaremos conceitos formais e também aspectos históricos no desenvolvimento do cálculo de áreas e volumes, através das contribuições dos matemáticos ao longo da história da Matemática. Em especial, analisaremos os trabalhos de Cavalieri, que utilizou a ideia dos indivisíveis, ampliando conceitos utilizados pelo método da exaustão e Pappus, que contribuiu formalizando o cálculo de áreas e volumes dos sólidos de revolução através do centro de gravidade. Também destacamos a contribuição das ideias de Newton e Leibniz no desenvolvimento do Cálculo Diferencial e Integral, que permitiu significativo avanço no cálculo de áreas e volumes. Finalizamos este trabalho com algumas aplicações didáticas, visando um melhor entendimento dos alunos sobre este tema / Abstract: The volume and area calculation were a theme that challenged mathematicians since the first registers that they found out. From rudimental shapes and practices without theoretical support of Babylonians and Egyptians until Differential and Integral Calculus development, a vast number of mathematicians contributed for development and systematization of concepts and forms of areas and volume calculation. In this paper has as an objective to show formal concepts and historical aspects about area and volume calculation through mathematicians¿ contributions over the Mathematic history. Particularly, it will be analyzed Cavalieri¿ projects who used the indivisible idea. He extended concepts that used exhaustion method and Pappus that contributed about formalization of area and volume calculation of solids of revolution through gravity center. Other aspect pointed in this paper are the contributions of Newton and Leibniz about Differential and Integral Calculus development that to make possible a meaningful advance about area and volume calculation. To finish this paper, some didactic applications it will be presented with the aim to make students have a clear understanding about the theme / Mestrado / Matemática em Rede Nacional / Mestra em Matemática em Rede Nacional
56

Analýza nákladů v podniku Jihočeská zelenina, a.s. / Analysis of costs in the company called Jihočeská zelenina, a.s.

Čadková, Hana January 2011 (has links)
The Master's thesis with the title the analysis of costs in the company called Jihočeská zelenina a.s. The work is divided into theoretical and practical part. The theoretical part prepared the basis for the subsequent practical part. The aim of this thesis was to evaluate financial and managerial accounting system in controlling costs in Jihočeská zelenina a.s. and propose solutions for their effectiveness. First was described the organizational structure of the company and its range of products and was mapped his previous work with information at all levels of management. The way of preparing calculations and their current form was solved then. A new possibility how to prepare the calculation was proposed after it. At the conclusion was written about the technical aspect of the topic. They were designed different software solutions in the existing enterprise accounting software, in application MS Excel or the possibility of purchasing a new software programme.
57

Cálculo autoconsistente de estrutura eletrônica no espaço direto. / Self-consistent calculation of electronic structure in direct space.

Pascoal Roberto Peduto 25 October 1990 (has links)
Neste trabalho, propusemos um método autoconsistente de espaço direto para o calculo de estrutura eletrônica. O método se baseia no formalismo LNTO -ASA na representação fortemente ligada (light-binding) e no método de recorrência aliado ao terminador de Beer & Pettifor. Neste método o custo computacional cresce linearmente com o numero de átomos não equivalentes na cela primitiva sendo, portanto, ideal para tratar sistemas complexos que não apresentam periodicidade ou que possuem um grande numero de átomos não equivalentes por cela primitiva. Podemos, por exemplo, estudar de forma autoconsistente a estrutura eletrônica das vizinhanças de uma impureza com um custo computacional apenas cinco ou seis vezes maior que o de um metal puro. O método aqui proposto tem a vantagem adicional de ser fisicamente transparente. Para avaliarmos a eficácia do método, comparamos nossos resultados autoconsistentes obtidos para a liga cristalina ZR IND.2FE com os resultados obtidos pelo processo autoconsistente de espaço reciproco. O material em questão tem uma estrutura cristalina simples com seis átomos por cela primitiva e o calculo de estrutura eletrônica pode ser resolvido por métodos usuais de espaço reciproco. A presença do FE com sua banda d estreita e com uma alta densidade de estados no nível de Fermi tornara o processo de convergência não trivial. / In this work we have proposed a first-principles selfconsistent method which allows us to perform electronic structure calculations in real space. The scheme, based on the LNTO ASA formalism and the Recursion Method, enables us to evaluate the electronic structures of complex systems, with good degree of precision and low computational costs. Using Zr 2 Fe as test case, we compare our real-space results with those obtained in reciprocal space using the standard LMTO - ASA procedure. The agreement is very good showing the efficiency of the real-space approach. We note that the real-space method developed here presents advantages for the evaluation of local properties and can be applied for non-periodic systems. For instance, we can describe the electronic structure in a large region around a substitutional impurity with very little cost. lf we consider five shells around the impurity the cost in real-space will be about seven times the cost of the calculation for a mono atomic system.
58

Experimental and theoretical studies of electronic and mechanical properties of two-dimensional (2D) WSe₂

Zhang, Rui January 2018 (has links)
Two-dimensional (2D) transition metal dichalcogenides (TMDs) with intrinsic band gaps are considered to be prospective alternatives for graphene in the applications of emerging nano-semiconductor devices. As a significant member of the TMDs family, WSe₂ with superior optical properties attracts increasing attention, especially in the optoelectronics. In this thesis, the electronic and mechanical properties of 2D WSe₂ have been studied experimentally and theoretically. Firstly, the fabrication of substrate-supported and suspended pre-patterned WSe₂ FETs with the low-cost optical lithography and vapour HF etching technology have been realised. The subsequent electrical measurement of the fabricated WSe₂ FETs indicates that the WSe₂/dielectric interface can affect the electrical performance of 2D WSe₂ negatively. To gain more insights on the impact of field-effect on 2D WSe₂, first-principle calculations have been conducted in this research to study the evolutions of the crystal structure, electronic band structure, conductive channel size, and electrical transport property of WSe2 under various levels of field-effect. Furthermore, a layer thinning and chemical doping method of 2D WSe₂ by vapour XeF₂ exposure featured with good air-stability, scalability, and controllability has been developed to enable the layer engineering of 2D WSe₂ and integration of 2D WSe₂ to logic circuits, solar cells, and light-emitting diodes (LED). The thinning and doping mechanism has been investigated with a combination of Raman spectroscopy, photoluminescence (PL) spectroscopy, and Xray photoelectron spectroscopy (XPS) characterization techniques. Afterwards, the inplane elastic properties (including the Young's modulus, breaking strain, and etc.) of 2D WSe₂ have been measured with nanoindentation experiments implemented by atomic force microscopy (AFM). The results prove the suitability of 2D WSe₂ in the applications of flexible devices and nanoelectromechanical systems (NEMS) operating in the audio resonance frequency, such as acoustic sensors and loudspeakers. To provide a comprehensive understanding of the strain engineering of 2D WSe₂, the strain induced variations of the crystal structure, electronic band structure, and electrical transport property of 2D WSe₂ have been further studied with first-principle calculations, which paves the way for the performance tuning of 2D WSe₂ devices via strain and applications of 2D WSe₂ in strain sensors.
59

Error Propagation Dynamics of PIV-based Pressure Field Calculation

Pan, Zhao 01 May 2016 (has links)
Particle Image Velocimetry (PIV) based pressure field calculation is becoming increasingly popular in experimental fluid dynamics due to its non-intrusive nature. Errors propagated from PIV results to pressure field calculations are unavoidable, and in most cases, non-negligible. However, the specific dynamics of this error propagation process have not been unveiled. This dissertation examines both why and how errors in the experimental data are propagated to the pressure field by direct analysis of the pressure Poisson equation. Error in the pressure calculations are bounded with the error level of the experimental data. The error bounds quantitatively explain why and how many factors (i.e., geometry and length scale of the flow domain, type of boundary conditions) determine the resulting error propagation. The reason that the type of flow and profile of the error matter to the error propagation is also qualitatively illustrated. Numerical and experimental validations are conducted to verify these results. The results and framework introduced in this research can be used to guide the optimization of the experimental design, and potentially estimate the error in the reconstructed pressure field before performing PIV experiments.
60

Verification of dose calculations in radiotherapy

Nyholm, Tufve January 2008 (has links)
External radiotherapy is a common treatment technique for cancer. It has been shown that radiation therapy is a both clinically and economically effective treatment for many types of cancer, even though the equipment is expensive. The technology is in constant evolution and more and more sophisticated and complex techniques are introduced. One of the main tasks for physicists at a radiotherapy department is quality control, i.e. making sure that the treatments are delivered in accordance with the dosimetric intentions. Over dosage of radiation can lead to severe side effects, while under dosage reduces the probability for patient cure. The present thesis is mainly focused on the verification of the calculated dose. Requirements for independent dose calculation software are identified and the procedures using such software are described. In the publications included in the thesis an algorithm specially developed for verification of dose calculations is described and tested. The calculation uncertainties connected with the described algorithm are investigated and modeled. A brief analysis of the quality assurance procedures available and used in external radiotherapy is also included in the thesis. The main conclusion of the thesis is that independent verification of the dose calculations is feasible in an efficient and cost effective quality control system. The independent calculations do not only serve as a protection against accidents, but can also be the basis for comparisons of the dose calculation performance at different clinics.

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