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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.
401

Dyzelino savybių tyrimas / Diesel fuel properties

Gečas, Edgaras 16 June 2014 (has links)
Tyrimams аtlikti pаsirinktаs akcizu neаpmokestintas dyzelinas, kuris yra skirtаs žemės ūkio subjektаms, laikantiems didelius kiekius dyzelino, įvairiose talpyklose. Dyzelinas visą tyrimo laikotarpį (350 parų) buvo laikomаs aplinkos temperatūroje nuo – 20 0C iki + 30 0C. Tyrime naudotos taros: metalinė, plastikinė, stiklinė. Per pirmąjį tyrimą nustatytas dyzelino tankis, klampa ir taip pat dyzelino filtravimo koeficientas. Šie rodikliai imti kaip аtskаitos tаškаs ir lyginami su kitais gautais tyrimų rezultаtаis. Dyzelino tаnkis stiklinėje taroje tyrimo pradžioje 830,6 kg/m3, o praėjus 350 parų padidėjo daugiausiai 835,3 kg/m3, lyginant su kitų bandinių rezultatais. Klаmpа, visose tаrose buvo - 1,923 mm2/s. Atlikus paskutinįjį tyrimą (po 350 pаrų), didžiausia klampa gauta stiklinėje taroje esančio dyzelino – 2,073 mm2/s. Metalinėje tаroje dyzelino klampa mažiausia – 2,024 mm2/s. Tyrimų pradžioje dyzelino filtravimo koeficientas buvo 4,25 %. Po 350 parų, didžiausias dyzelino filtravimo koeficientas nustatytas iš stiklinėje taroje laikyto dyzelino – 31,61 %. Mažiausias dyzelino filtravimo koeficientas - 15,24 % iš plastikinės taros. / Selected reseаrch exempted from excise duty diesel, which is intended for аgriculturаl entities keeping lаrge quаntities of diesel fuel in different contаiners. Diesel entire study period 350 dаys were considered to be аt аmbient temperature from – 20 0C to + 30 0C. Used containers: metаl, plаstic, glаss. Diesel fuel density in the glаss contаiner аfter the first investigаtion 830,6 kg/m3 аfter 350 dаys increased by a mаximum of 835,3 kg/m3, compаred with other sаmples of the results. Viscosity of the first survey in all continers was 1,9226 mm2 /s. After 350 dаys, the mаximum viscosity obtаined in the glаss contаiner at diesel – 2,0728 mm2/s, plаstic contаiners – 2,0688 mm2/s. The metаl contаiner of diesel fuel viscosity at least – 2,0238 mm2/s. At the start of diesel filtration rate wаs 4,25 %. After 350 dаys, the lаrgest diesel filtrаtion rаte determined from a glаss contаiner – 31,61 %. The smаllest diesel filtrаtion rаte – 15,24 % wаs in the plаstic contаiner.
402

Numerical Methods for Nonlinear Equations in Option Pricing

Pooley, David January 2003 (has links)
This thesis explores numerical methods for solving nonlinear partial differential equations (PDEs) that arise in option pricing problems. The goal is to develop or identify robust and efficient techniques that converge to the financially relevant solution for both one and two factor problems. To illustrate the underlying concepts, two nonlinear models are examined in detail: uncertain volatility and passport options. For any nonlinear model, implicit timestepping techniques lead to a set of discrete nonlinear equations which must be solved at each timestep. Several iterative methods for solving these equations are tested. In the cases of uncertain volatility and passport options, it is shown that the frozen coefficient method outperforms two different Newton-type methods. Further, it is proven that the frozen coefficient method is guaranteed to converge for a wide class of one factor problems. A major issue when solving nonlinear PDEs is the possibility of multiple solutions. In a financial context, convergence to the viscosity solution is desired. Conditions under which the one factor uncertain volatility equations are guaranteed to converge to the viscosity solution are derived. Unfortunately, the techniques used do not apply to passport options, primarily because a positive coefficient discretization is shown to not always be achievable. For both uncertain volatility and passport options, much work has already been done for one factor problems. In this thesis, extensions are made for two factor problems. The importance of treating derivative estimates consistently between the discretization and an optimization procedure is discussed. For option pricing problems in general, non-smooth data can cause convergence difficulties for classical timestepping techniques. In particular, quadratic convergence may not be achieved. Techniques for restoring quadratic convergence for linear problems are examined. Via numerical examples, these techniques are also shown to improve the stability of the nonlinear uncertain volatility and passport option problems. Finally, two applications are briefly explored. The first application involves static hedging to reduce the bid-ask spread implied by uncertain volatility pricing. While static hedging has been carried out previously for one factor models, examples for two factor models are provided. The second application uses passport option theory to examine trader compensation strategies. By changing the payoff, it is shown how the expected distribution of trading account balances can be modified to reflect trader or bank preferences.
403

Processing melt blended polymer nanocomposites using a novel laboratory mini-mixer : development of polymer nanocomposites in the melt phase using a novel mini-mixer

Khan, Atif Hussain January 2012 (has links)
Research into the processing conditions and parameters of polymeric nanocomposites has always been challenging to scientists and engineers alike. Many have developed tools and procedures to allow materials to be exploited and their properties improved with the addition of nanofillers to achieve the desired end material for various applications. Initial trials are mostly conducted using conventional small scale experiments using specialised equipment within the laboratory that can replicate the larger industrial equipment. This is a logical approach as it could save time and costs as many nanocomposites are relatively expensive to produce. Experiments have previously been done using the likes of the Haake twin screw extruder to manufacture nanocomposites within the laboratory but this research project has used a novel minimixer specifically developed to replicate mixing like large twin screw extrusion machines. The minimixer uses a twin paddle system for high shear mixing in conjunction with a single screw thus theoretically allowing an infinitely long recirculation. It is this ability to mix intensely whilst allowing for as long as desired recirculation which enables the replication in this very small mixer (10-30g capacity) of the mixing conditions in a large twin screw extruder. An added feature of the minimixer is that it can undertake inline data analysis in real time. The main experiments were conducted using a comprehensive DOE approach with several different factors being used including the temperature, screw speed, residence time, clay and compatibiliser loading and two polymer MFI's. The materials used included PP, Cloisite 20A, Polybond 3200, PET, Somasif MTE, Polyurethane 80A and Single / Multi-walled Carbon nanotubes. Detailed experimental results highlighted that rheological analysis of the nanocomposite materials as an initial testing tool were accurate in determining the Elastic and Loss modulus values together with the Creep and Recovery, Viscosity and Phase Angle properties in the molten state. This approach was also used in an additional set of experiments whereby the temperature, speed, residence time and compatibiliser were kept constant but the clay loading was increased in 1% wt. increments. These results showed that the G' & G'' values increased with clay loading. Another important finding was the bi-axial stretching step introduced after the processing stage of the nanocomposite materials which highlighted a further improvement in the modulus values using rheological testing. Other tests included using inline monitoring to look into both the viscosity and ultrasound measurements in real time of the molten polymer nanocomposite through a slit die attachment to the minimixer.
404

Photochemical Applications to the Study of Complexity Phospholipid Bilayer Environments

Wohl, Christopher John, Jr. 01 January 2006 (has links)
The physical and biophysical properties of a biological membrane model, phosphatidylcholine bilayers, were investigated using novel spiropyran/merocyanine molecular probes. The femtosecond to second dynamics of this system's photochemistry enabled bilayer viscosity and free volume to be studied over a broad time scale. Spiropyrans/merocyanines with different polarity were synthesized by changing the substitution of the indole moiety enabling determination of the trans-membrane properties of the bilayer. In addition, transient grating spectroscopy was used to study thermal energy transfer in phospholipid bilayers on a picosecond time scale.Femtosecond transient absorption spectroscopy was used to study the photo-induced spiropyran ring-opening and isomerization reactions that produce the highly polar merocyanine species. The hindered rotation of the merocyanine bridge results in several metastable merocyanine isomers. The merocyanine ground state was determined to be populated predominantly by two isomers (TTC and TTT). Selective photoexcitation of these isomers results in excited state isomerization producing a third isomer (τ = 60 ps). Merocyanine thermal ring-closing was observed on a seconds time scale. Reaction kinetics, and solvatochromic and photochromic properties of merocyanines and spiropyrans were used to determine the bilayer physical properties. Bilayer viscosity was determined from merocyanine isomerization kinetics. Phospholipid bilayer free volume (the unoccupied volume enclosed in the bilayer) was determined from a modified Kramers' analysis. The greatest free volume was found in the extreme interior of the bilayer, while the head-group region exhibited the least free volume in qualitative agreement with molecular dynamics simulations of these bilayer systems. Free volumes determined via ps experiments were lower than those determined on a seconds time scale due to reduced acyl chain dynamics on the ps time scale.Femtosecond transient grating spectroscopy was used to study the rate of thermal energy transfer from photo-excited porphyrin molecules to the surrounding solvent. Thermal energy transfer was observed as photo-acoustic waves propelled through the system upon relaxation of photo-excited porphyrin molecules in aqueous solution and embedded in bilayers. For liposome solutions, a bimodal energy transfer model was developed. The determined rate constants suggest that energy transfer occurs predominantly via thermal diffusion and vibrational energy transfer, while lipid dynamics (isomerizations) are not involved.
405

An InVitro Leakage and Viscosity Analysis of Root End Filling Materials

Clark, Paul D. 01 January 2007 (has links)
The purpose of this study was to determine if the viscosity of MTA Angelus Fluid is lower than that of Pro Root MTA and MTA Angelus; and to compare the viscosity, leakage and particle size of these materials to determine whether a relationship exists between these properties. The viscosity of each material was measured and compared with the Student's t test. MTA Angelus Fluid's viscosity was significantly lower than the other two materials tested. Microleakage of root end fillings was assessed in a passive diffusion model. Leakage groups were compared with a one-way ANOVA (p < 0.05). No significant difference was found. Particle size and shape were evaluated with the SEM. MTA Angelus Fluid has a lower viscosity than the other materials tested. There was no significant difference in the sealing ability of the three materials tested and there was no apparent variation in each material's particle size or shape.
406

Stanovení konstant stability komplexů s nabitými cyklodextriny kapilární zónovou elektroforézou / Determination of stability constants of charged cyclodextrine complexes by capillary electrophoresis

Beneš, Martin January 2010 (has links)
Martin Beneš Determination of stability constants of charged cyclodextrin comlexes by capillary electrophoresis Abstract Stability constant characterizes binding interaction between an analyte and complexation agent. These interactions play very important role in separation processes of, in other way undistinguishable, compounds, e.g. enantiomers. The most widely used complexation agents are cyclodextrins. Affinity capillary electrophoresis (ACE) belongs to methods suitable for the determination of stability constants. The stability constant is determined from the dependence of the effective mobility of analyte on the increasing concentration of complexation agent in background electrolyte (BGE). If charged CDs are used, the attention must be paid not only to viscosity of the BGE and to the influence of Joule heating on the temperature in the capillary but also to the increasing ionic strength. The thermodynamic stability constants of R,R- and S,S-hydrobenzoin and R- and S-(3-brom- 2-methyl-1-propanol) with cationic modified β-cyclodextrin: 6-monodeoxy-6-mono(3- hydroxy)propylamino-β-cyclodextrin hydrochlorid (PABCD) were determined by affinity capillary electrophoresis. The average temperature (25řC) of the BGE in the capillary was kept constant. This was achieved by decreasing of the cassette temperature...
407

Granulometrie nanočástic z kopolymerů alifatických hydroxykyselin. / Granulometry of nanoparticles from aliphatic acids copolymers.

Šrejma, Robert January 2016 (has links)
The diploma thesis is focused on the study of influence on the composition of the system to the size of the nanoparticles from aliphatic polyesters with linear and branched molecules constitution. The emulsion method for distributing of solvent was chosen for preparation of nanoparticles. The theoretical part describes the nanoparticles, its origin and application. The following part is applying to biodegradable polymers, especially PLGA. There is also a mention of antifungal agent terbinafine. The nanoparticles are prepared of this substance. The process is described in the experimental part of thesis. The experimental part is testing different composition of samples. A main emphasis is on the choice of polymer solvent and emulsifier. There are also applied mixtures of solvents and emulsifiers. The important aspect is the evaluation of incorporated terbinafine, which has been the model drug. Prepared dispersions were exposed to stress conditions in the form of several days-storage and centrifugation.
408

Vliv formulačních faktorů na velikost polyesterových nanočástic. / Influence of formulation factors on the polyester nanoparticles size.

Športeň, Radek January 2016 (has links)
In the theoretical part of this thesis are described various types of nanoparticles, such as polymeric particles, liposomes, micelles and solid lipid nanoparticles. There are presented basic informations concerning methods of particles preparation in the laboratory conditions such as solutions of polymers dispersion methods by intensively stirring, coacervation of the solutions of polymers, polymeration methods in dispersions, and the exploitation of methods of dispersion of polymeric solutions in the supercritical solvents. In the folowing part of this thesis are some concise informations about the methods of evaluation of basic parameters of the nanoparticulate systems. There are summarised the trivial informations concerning granulometry of particles, their zeta potential, encapsulation effectivity of drugs, and also about the particles shape factor. The focus of this thesis is in the experiment, the main deal were in minimisation of the particle size prepared by the method of emulsification of biodegradable aliphatic α-hydroxyacids polyesters solutions. The main process arrangement was the selection of the appropriate solvent of polymers in the inner emulsion phase and the founding for the mostly efficient emulsifier during the dispersion process of polymer solutions. In process of the...
409

Částice s protimikrobním stříbrem. / Particles with antimicrobial silver.

Svobodová, Dana January 2016 (has links)
Charles Univerzity in Prague Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Candidate: Dana Svobodová Supervisor: doc. RNDr. Milan Dittrich, CSc. Diploma thesis title: Particles with antimicrobial silver The theoretical part of this diploma thesis outlines a brief overview of recent findings on silver nanoparticles. Further, it concerns the kinetic properties of colloidal systems, methods of evaluating the size and shape of colloidal particles, mechanism of antimicrobial activity of colloidal silver and methods of preparation of nanoparticles. Concise information about the toxicity of silver nanoparticles and their impact on the environment is also included. In the experimental part comprehensive report on the results of measurements of granulometric characteristics of microparticles and nanoparticles by photon correlation spectroscopy (PCS) is included. The influence of various modifications of preparation procedures and processing on stability, size and the polydispersity of the size in terms of the volume and intensity diameter of the particles with elemental silver deposited on the surface was studied. Optimisation of the disperse system, quality control of the content of colloidal particles by subsequent reduction, the possibilities of using centrifuge and...
410

Efficacy of post-isometric relaxation technique on muscle tissue and its viscoelastic properties after physical activity / Efficacy of post-isometric relaxation technique on muscle tissue and its viscoelastic properties after physical activity

Hloušková, Zuzana January 2012 (has links)
Title: Efficacy of post - isometric relaxation technique on muscle tissue and its viscoelastic properties after physical activity. Objective: This study is a pilot analytical and comparative study. The first aim of this thesis was evaluation of the effect of post-isometric relaxation technique on properties of muscle tissue after physical activity. The second aim of this thesis is to present a literature review regarding this topic using literature available. Methods: This study took place in the laboratory of kinesiology at UK FTVS. Six participants were measured prior to Wingate test, after Wingate test and after post- isometric relaxation or rest. Experimental lower extremity was applied post-isometric relaxation technique and the control lower extremity was not. Muscle tonus of the soleus muscle was measured with myotonometric device developed by Šifta. The final data were processed in the special software in Matlab and the obtained hysteresis curves were used for results analysis. Results: This study had three hypotheses and none of them was confirmed during the measuremets. The first hypothesis pressumed that muscle tonus will increase after the Wingate test, but it was not confirmed and thus further measurements were strongly influenced in the sense that post-isometric relaxation was not...

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