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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.
91

Hassel (Corylus avellana) som indikator på markanvändningshistorik

Wallstedt, Lennart January 2015 (has links)
Hazel (Corylus avellana L.) is a common feature of meadows and pastures where it can grow in large populations and become very old. Is it possible to use the size of hazel stools for age determination and is it possible to use the size distribution of a population to provide information about how the land has been used? Hazel populations on ground where the lake-water level had been lowered, has been studied to validate an already developed growth model of hazel clones. Different hazel populations, on wooded meadows affected by mowing or grazing or overgrown meadows, were studied to evaluate the method utilizing hazel as land use indicator. The growth model was used to compare the size distributions of hazel populations with historical periods, which has been important for changes in agriculture or demography. The results show that the current growth model needs to be refined, but the method itself with a growth model based on the circumference of hazel bushes seems feasible. Additional studies about the influence of, for example, soils of different fertility are needed. The results also show that the size distribution in a population depends on how much meadows have been affected by mowing or grazing and that areas with similar land use have similar size distribution. Finally, some examples are reported about how a growth model can be used to compare historical periods of changes in agriculture, for example reduced livestock, with variations of the size distribution in a hazel population.
92

Process measurements and kinetics of unseeded batch cooling crystallization

Li, Huayu 08 June 2015 (has links)
This thesis describes the development of an empirical model of focus beam reflectance measurements (FBRM) and the application of the model to monitoring batch cooling crystallization and extracting information on crystallization kinetics. Batch crystallization is widely used in the fine chemical and pharmaceutical industries to purify and separate solid products. The crystal size distribution (CSD) of the final product greatly influences the product characteristics, such as purity, stability, and bioavailability. It also has a great effect on downstream processing. To achieve a desired CSD of the final product, batch crystallization processes need to be monitored, understood, and controlled. FBRM is a promising technique for in situ determination of the CSD. It is based on scattering of laser light and provides a chord-length distribution (CLD), which is a complex function of crystal geometry. In this thesis, an empirical correlation between CSDs and CLDs is established and applied in place of existing first-principles FBRM models. Built from experimental data, the empirical mapping of CSD and CLD is advantageous in representing some effects that are difficult to quantify by mathematical and physical expressions. The developed model enables computation of the CSD from measured CLDs, which can be followed during the evolution of the crystal population during batch cooling crystallization processes. Paracetamol, a common drug product also known as acetaminophen, is selected as the model compound in this thesis study. The empirical model was first established and verified in a paracetamol-nonsolvent (toluene) slurry, and later applied to the paracetamol-ethanol crystallization system. Complementary to the FBRM measurements, solute concentrations in the liquid phase were determined by in situ infrared spectra, and they were jointly implemented to monitor the crystallization process. The framework of measuring the CSD and the solute concentration allows the estimation of crystallization kinetics, including those for primary nucleation, secondary nucleation, and crystal growth. These parameters were determined simultaneously by fitting the full population balance model to process measurements obtained from multiple unseeded paracetamol-ethanol crystallization runs. The major contributions of this thesis study are (1) providing a novel methodology for using FBRM measurements to estimate CSD; (2) development of an experimental protocol that provided data sets rich in information on crystal growth and primary and secondary nucleation; (3) interpretation of kinetics so that appropriate model parameters could be extracted from fitting population balances to experimental data; (4) identification of the potential importance of secondary nucleation relative to primary nucleation. The protocol and methods developed in this study can be applied to other systems for evaluating and improving batch crystallization processes.
93

Μελέτη κατανομών μεγέθους συστάδας για επιγενή Poisson και συναφείς ασυμπτωτικές κατανομές

Κουσίδης, Σωκράτης 09 October 2008 (has links)
Σε προβλήματα ερμηνείας βιολογικών δεδομένων όπου οι υπό μελέτη μονάδες εμφανίζονται κατά συστάδες (cluster) τυχαίου μεγέθους και πλήθους, ιδιαίτερο ρόλο παίζουν οι επιγενείς κατανομές. Συγκεκριμένα ως επιγενής Poisson κατανομή μπορεί να παρασταθεί κάθε μονοδιάστατη διακριτή κατανομή η οποία είναι άπειρα διαιρετή. Έχει μελετηθεί, η περίπτωση στην οποία η κατανομή του μεγέθους της συστάδας (csd) είναι μια γενικευμένη (εισάγεται νέα παράμετρος) εξαρτώμενη μεγέθους (gsb) λογαριθμική κατανομή. Παίρνοντας τα όρια αυτής της παραμέτρου ως οριακές κατανομές προκύπτουν η ΝΝΒD και η Pόlya-Aeppli. Στη παρούσα διπλωματική μελετάται η κατανομή που προκύπτει όταν ως csd χρησιμοποιείται η gsb μιας οιασδήποτε κατανομής. Δίνεται η πιθανογεννήτρια και προσδιορίζονται οι ασυμπτωτικές κατανομές στη γενικότερη περίπτωση. Μελετώνται επίσης, οι ιδιότητες της κατανομής και δίνονται εκτιμητές με τις μεθόδους των ροπών και της μέγιστης πιθανοφάνειας. Ειδικότερα, παρουσιάζεται η περίπτωση της ακρότμητης Poisson που δίνει ως οριακές κατανομές τις Νeyman και Thomas και προσομοιώνονται δεδομένα. Εξάγονται επίσης, ως ειδική περίπτωση των γενικών τύπων, τα αποτελέσματα που έχουν αποδειχθεί για τη λογαριθμική κατανομή. Στη συνέχεια αναπτύσσονται αντίστοιχα γενικευμένα διδιάστατα μοντέλα τέτοιων κατανομών. Δίνονται επίσης οι περιθώριες και οι δεσμευμένες κατανομές τους, υπολογίζονται οι ροπές, και χρήσιμες σχέσεις για τα διδιάστατα μοντέλα. Τέλος, παρουσιάζονται ειδικές περιπτώσεις, όπως οι Sum-Symmetric Power-Series και δίνονται εφαρμογές των διδιαστάτων κατανομών που μελετήθηκαν. / In biological data interpretation domains, where the units we exam come along as clusters of random size and number, generalized distributions have a very major role. In particular, every univariate discrete distribution that is infinite divisible can be formed like a generalized Poisson distribution. The case where the cluster-size distribution is a generalized (a new parameter has been inserted) size-biased log-series distribution has been studied. Taking the limits of this parameter, as limited cases we have the NNBD and Polya-Aeppli distribution. In this diplomatic work, we study the distribution which arises when as a csd we use the gsb of a random distribution. We give the pgf and we see the asymptotic distributions in the general case. We also see the attributes of the distribution and we give estimators with the method of moments and maximum likelihood estimators. Specially, we report the case of Truncated Poisson, which gives Neyman and Thomas as limiting cases and we simulate some data. Likewise, we also see the results that have been proofed for the Log-Series distribution as a special case of the general formulas. Then, we see correspond generalized Bivariate models of these distributions. We also give the marginals and the conditional distributions, we find the moments and some useful relations about the Bivariate models. Final, we present special cases, like Sum-Symmetric Power-Series and we give applications of the Bivariate distributions that we saw. In biological data interpretation domains, where the units we exam come along as clusters of random size and number, generalized distributions have a very major role. In particular, every univariate discrete distribution that is infinite divisible can be formed like a generalized Poisson distribution. The case where the cluster-size distribution is a generalized (a new parameter has been inserted) size-biased log-series distribution has been studied. Taking the limits of this parameter, as limited cases we have the NNBD and Polya-Aeppli distribution. In this diplomatic work, we study the distribution which arises when as a csd we use the gsb of a random distribution. We give the pgf and we see the asymptotic distributions in the general case. We also see the attributes of the distribution and we give estimators with the method of moments and maximum likelihood estimators. Specially, we report the case of Truncated Poisson, which gives Neyman and Thomas as limiting cases and we simulate some data. Likewise, we also see the results that have been proofed for the Log-Series distribution as a special case of the general formulas. Then, we see correspond generalized Bivariate models of these distributions. We also give the marginals and the conditional distributions, we find the moments and some useful relations about the Bivariate models. Final, we present special cases, like Sum-Symmetric Power-Series and we give applications of the Bivariate distributions that we saw.
94

Theoretical and Experimental Behavior of Suspension Pressurized Metered Dose Inhalers

Sheth, Poonam January 2014 (has links)
Pressurized metered dose inhalers (pMDIs) are widely utilized to manage diseases of the lungs, such as asthma and chronic obstructive pulmonary disease. They can be formulated such that the drug and/or nonvolatile excipients are dissolved or dispersed in the formulation, rendering a solution or suspension formulation, respectively. While the formulation process for solution pMDIs is well defined, the formulation process of pMDIs with any type of suspended entity can be lengthy and empirical. The use of suspended drug or the addition of a second drug or excipient in a suspension pMDI formulation may non-linearly impact the product performance of the drug of interest in the formulation; this requires iterative testing of a series of pMDIs in order to identify a formulation with the most potential for success. One of the primary attributes used to characterize the product performance and quality control of inhaled medications is the residual aerodynamic particle size distribution (APSD) of the aerosolized drug. Along with clinical factors, formulation and device parameters have a significant impact on APSD. In this study, a computational model was developed using the principles of statistics and physical chemistry to predict the residual APSD generated by suspension pMDIs based on formulation, device, and raw drug or excipient substance considerations. The formulations modeled and experimentally evaluated consist of a suspended drug or excipient with/without a dissolved drug or excipient in a cosolvent-propellant system. The in silico model enables modeling a process that is difficult to delineate experimentally and contributes to understanding the link between pMDI formulation and device to product performance. The ability to identify and understand the variables that affect atomization and/or aerosol disposition , such as initial droplet size, suspended micronized drug or excipient size, and drug or excipient concentration, facilitates defining the design space for suspension pMDIs during development and improves recognizing the sensitive of the APSD is on each hardware and formulation variable. This model can later be applied to limit batch-to-batch variation in the manufacturing process and selecting plausible suspension pMDI formulations with quality design as the end goal.
95

Effect of Near-Wall Turbulence on Selective Removal of Particles from Sand Beds Deposited in Pipelines

Zeinali, Hossein Unknown Date
No description available.
96

Characterization of Athabasca asphaltenes separated physically and chemically using small-angle X-ray scattering

Amundarain, Jesus Unknown Date
No description available.
97

A New Concept On Sampling Systems By Air Cannon Application

Yunel, Ufuk 01 January 2004 (has links) (PDF)
The most important criterion in industrial production processes is to control the required product quality and comply with the standards pre-described for the application during any stage of the process. This control begins from the entry of raw material to the plant and continues with pre-determined points. Mainly two different types of inspection and analyses are used to examine the material quality and content. These are physical and chemical analysis.In most of the production plants above mentioned analyses are made in related laboratories of the plant. Therefore, it is necessary to have &amp / #65533 / sample&amp / #65533 / to be analyzed. This &amp / #65533 / sample&amp / #65533 / should have a real &amp / #65533 / representative&amp / #65533 / property, which must carry all of the physical and chemical characteristics of the material at the point where this &amp / #65533 / sample&amp / #65533 / is taken.The present methods and systems used to take samples from any required point have some disadvantages and present some problems especially for not being &amp / #65533 / representative&amp / #65533 / . These problems are discussed in detail within this thesis study and aimed to reach a new concept and system with: - Low cost of investment - Low cost of operation - Less requirement of maintenance and calibration - The achievement of &amp / #65533 / correct&amp / #65533 / and &amp / #65533 / representative&amp / #65533 / sample As a result of the theoretical studies together with practical application works and experiments, a new concept in sampling, namely &amp / #65533 / Sampling System with Air Cannons&amp / #65533 / was introduced. The new system of sampling was tested to give better performance and practical use.
98

Characterization of Athabasca asphaltenes separated physically and chemically using small-angle X-ray scattering

Amundarain, Jesus 11 1900 (has links)
Athabasca asphaltenes were characterized using small-angle X-ray scattering (SAXS) with synchrotron radiation. Two methods were used to separate asphaltenes from Athabasca bitumen. Conventional chemical separation by precipitation with n-pentane, and physical separation realized by passing bitumen through a zirconia membrane with a 20 nm average pore size. The Athabasca permeates and chemically separated samples were dispersed in 1-methylnaphtalene and n-dodecane, with temperature and asphaltene concentration ranges of 50-310 C and 1-8 wt. %, respectively. Two approaches were also taken in the analysis of the SAXS emissions. A model-independent approach provided radii of gyration and scattering coefficients. A model-dependent fit provided size distributions for asphaltenes aggregates assuming that they are dense and spherical. Physically and chemically separated asphaltenes showed significant differences in nominal size and structure, and their structural properties exhibited different temperature dependencies. The results challenge the merits of using chemically separated asphaltene properties as a basis for asphaltene property prediction in crude oil/bitumen.
99

Optimal Estimation Retrieval of Aerosol Microphysical Properties in the Lower Stratosphere from SAGE II Satellite Observations

Wurl, Daniela January 2007 (has links)
A new retrieval algorithm has been developed based on the Optimal Estimation (OE) approach, which retrieves lognormal aerosol size distribution parameters from multiwavelength aerosol extinction data, as measured by the Stratospheric Aerosol and Gas Experiment (SAGE) II in the lower stratosphere. Retrieving these aerosol properties becomes increasingly more difficult under aerosol background conditions, when tiny particles (« 0.1 µm) prevail, to which the experiment is nearly or entirely insensitive. A successful retrieval algorithm must then be able (a) to fill the 'blind spot' with suitable information about the practically invisible particles, and (b) to identify 'the best' of many possible solutions. The OE approach differs from other previously used aerosol retrieval techniques by taking a statistical approach to the multiple solution problem, in which the entire range of possible solutions are considered (including the smallest particles) and characterized by probability density functions. The three main parts of this thesis are (1) the development of the new OE retrieval algorithm, (2) the validation of this algorithm on the basis of synthetic extinction data, and (3) application of the new algorithm to SAGE II measurements of stratospheric background aerosol. The validation results indicate that the new method is able to retrieve the particle size of typical background aerosols reasonably well, and that the retrieved uncertainties are a good estimate of the true errors. The derived surface area densities (A), and volume densities (V ) tend to be closer to the correct solutions than the directly retrieved number density (N), median radius (R), and lognormal distribution width (S). Aerosol properties as retrieved from SAGE II measurements (recorded in 1999) are observed to be close to correlative in situ data. In many cases the OE and in situ data agree within the (OE and/or the in situ ) uncertainties. The retrieved error estimates are of the order of 69% (σN), 33% (σR), 14% (σS), 23% (σA), 12% (σV), and 13% (σReff ). The OE number densities are generally larger, and the OE median particle sizes are generally smaller than those N and R retrieved by Bingen et al. (2004a), who suggest that their results underestimate (N) or overestimate (R) correlative in situ data due to the 'small particle problem'. The OE surface area estimates are generally closer to correlative in situ profiles (courtesy of T. Deshler, University of Wyoming), and larger than Principal Component Analysis (PCA) retrieval solutions of A (courtesy of L. W. Thomason, NASA LaRC) that have been observed to underestimate correlative in situ data by 40-50%. These observations suggest that the new OE retrieval algorithm is a successful approach to the aerosol retrieval problem, which is able to add to the current knowledge by improving current estimates of aerosol properties in the lower stratosphere under low aerosol loading conditions.
100

Influência do tamanho da amostra na determinação da curva de retenção da água no solo / Sample size effect on the determination of the soil water retention curve

Maria Laiane do Nascimento Silva 25 May 2016 (has links)
A curva de retenção da água no solo é um dos principais instrumentos para avaliar a qualidade física dos solos e possibilitar seu manejo adequado. Por meio da Teoria da Capilaridade vários equipamentos foram desenvolvidos para determinar a intensidade com que a água está retida ao solo, porém, pouco se tem dado atenção para verificar se os pressupostos para o real funcionamento da teoria estão sendo atendidos. Um aspecto refere-se ao tamanho da amostra utilizada para determinar a curva de retenção, de modo que haja continuidade dos feixes capilares na amostra e placa porosa. Desta forma, este trabalho propõe avaliar diferentes tamanhos de amostra indeformada para a determinação da curva de retenção. Para isso, coletaram-se amostras em anéis volumétricos cilíndricos de três tamanhos (altura) diferentes (T1 - 0,075 m; T2 - 0,05 m; T3 - 0,025 m;) e mesmo diâmetro interno (0,07 m), dos horizontes diagnósticos de um Latossolo e um Nitossolo em áreas experimentais da Escola Superior de Agricultura Luiz de Queiroz (Esalq/USP), Piracicaba - SP. Realizou-se a caracterização física destes solos, por meio da análise granulométrica, densidade do solo, densidade de partículas, porosidade total e teor de carbono orgânico. As curvas foram determinadas para cada tamanho de amostra, utilizando-se o Funil de Haines, para as tensões 0,5, 1, 4, 6 e 10 kPa, e a Câmara de Pressão de Richards para 33, 100 e 500 kPa. As curvas de retenção foram ajustadas pelo modelo utilizado por van Genuchten. Estimadas as curvas, avaliou-se a distribuição de poros do solo das amostras, determinando-se a curva de frequência acumulada de poros em função do logaritmo do raio e, depois pela diferenciação das equações de ajuste das curvas de retenção, a curva diferencial de frequência acumulada de poros. Os resultados mostram que o Latossolo, por ter textura arenosa no horizonte estudado, não apresentou diferença significativa nas curvas de retenção para os tamanhos das amostras estudadas. Verificou-se pouca modificação na distribuição dos poros deste solo, que possui teor elevado das frações areia fina e muito fina, e desenvolveram papel importante para a retenção de água. O Nitossolo, por sua vez, apresentou diferença significativa da curva obtida pela amostra de menor tamanho (T3), havendo maior retenção de água com a diminuição do tamanho da amostra. Devido a sua textura muito argilosa, o arranjo estrutural deste solo foi diferenciado ao se utilizar as amostras maiores, com provável interrupção e descontinuidade dos feixes capilares. Consequentemente, houve também alteração na distribuição dos poros, com redução dos mesoporos e aumento dos microporos. Desta forma, pode-se concluir que o tamanho da amostra influenciou a curva de retenção da água devido à complexidade estrutural do solo, que provavelmente é diferente nas amostras maiores por causa da continuidade dos feixes capilares, principalmente no Nitossolo. Em outras palavras, quanto menor o tamanho da amostra há menor diferenciação no arranjo de poros, ou seja, maior proximidade da real condição do solo e, assim, uma interpretação da retenção de água \"mais correta\" por meio da Teoria da Capilaridade. / The soil water retention curve is one of main tools to assess the physical quality of the soil and to make possible its adequate management. By means of the Capillary Theory, many instruments have been developed to determine the water retention forces in soil, but, little attention has been given to check whether the assumptions for the application of the theory are being attended. One aspect relates to the sample size used to determine the retention curve, so that there is capillary continuity of the sample and porous plate. Thus, this study aimed to evaluate different sizes of undisturbed cylindrical samples for determination of the retention curve. The samples were collected from diagnostic horizons of Latosol and a Nitosol, in experimental areas of the Escola Superior de Agricultura Luiz de Queiroz (Esalq/USP), Piracicaba - SP. Three volumetric rings with three different heights (T1 - 0,075 m; T2 - 0,05 m; T3 - 0,025 m;), were used the diameter of the rings were the same for the three sizes (0,07 m). The physical characterization soils were made by the granulometric analysis, bulk density, particle density, porosity and organic carbon. The curves were determined for each sample size, using the Haine\'s funnel, for tensions 0.5, 1, 4, 6 and 10 kPa, and Richard\'s pressure chamber for 33, 100 and 500 kPa. The pore size distribution of the soil was evoluated first by determining the cumulative frequency curve of pore radius, and then, by differentiating fitling equation of fluis curve to obtain a differential curve of pore cumulative frequency. The retention curves were fitted by the model used by Van Genuchtem. The results showed that in the Latosol there was no significant difference in retention curves for the sizes of the samples studied. There was little change in pore distribution of the fluis soil with high content of fractions fine and very fine sand, that developes significant role in soil water retention. The Nitosol exhibited significant difference of the curve obtained by the smallest size sample (T3), with greater water retention with the decreasing of the sample size. Because of its very clayey texture, the structural arrangement of this soil was different when larger samples were used, with probable interruption and discontinuity of capillaries. Consequently there was also a change in the pore distribution, with reduction of mesopores and an increase of micropores. Thus, itean be conclude that the sample size influenced the soil water retention curve due to the structural complexity of the soil that probably is different in the bigger sample because of the continuity of the capillary budles fluit was more affected in the Nitosol. In other words, the smaller the sample size, the smaller the difference in the arrangement of pores, that is, more closeness of the actual condition of the soil and so a \"more correct\" interpretation of soil water retention by capillary theory.

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