Liquid-propellant droplet vaporization and combustion in high pressure environments

In order to correct the deficiencies of existing models for high-pressure droplet vaporization and combustion, a fundamental investigation into this matter is essential. The objective of this research are: (1) to acquire basic understanding of physical and chemical mechanisms involved in the vaporization and combustion of isolated liquid-propellant droplets in both stagnant and forced-convective environments; (2) to establish droplet vaporization and combustion correlations for the study of liquid-propellant spray combustion and two-phase flowfields in rocket motors; and (3) to investigate the dynamic responses of multicomponent droplet vaporization and combustion to ambient flow oscillations

Nonlinear analysis of pressure oscillations in ramjet engines

Pressure oscillations in ramjet engines have been studied using an approximate method which treats the flow fields in the inlet and the combustor separately. The acoustic fields in the combustor are expressed as syntheses of coupled nonlinear oscillators corresponding to the acoustic modes of the chamber. The influences of the inlet flow appear in the admittance function at the inlet /combustor interface, providing the necessary boundary condition for calculation of the combustor flow. A general framework dealing with nonlinear multi-degree-of-freedom system has also been constructed to study the time evolution of each mode. Both linear and nonlinear stabilities are treated. The results obtained serve as a basis for investigating the existence and stabilities of limit cycles for acoustic modes. As a specific example, the analysis is applied to a problem of nonlinear transverse oscillations in ramjet engines

Overview of Combustion Instabilities in Liquid-Propellant Rocket Engines

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Metal-organic frameworks as chemical sensors

Metaloorganske mreže su posebna klasa spojeva u kemiji materijala koja predstavlja najbolju simbiozu kemije organskih i anorganskih spojeva u jednom. Građeni su od više metalnih centara ili metalnih klastera povezanih međusobno organskim ligandima koji se u terminologiji metaloorganskih mreža nazivaju linkerima tvoreći pritom mrežu koja ovisno o veličini svojih pora može selektivno propuštati samo one molekule koje su svojim proporcijama manje od spomenutih pora. Zbog već navedenih specifičnosti u strukturi, metaloorganske mreže su pronašle primjenu u raznim područjima znanosti i tehnologije od kojih se zasigurno najviše izdvaja primjena kao kemijskih senzora. Metaloorganske mreže mogu se nadograđivati čime se postiže pojačavanje signala. Takvi spregnuti kemijski senzori svojom specifičnom građom omogućavaju selektivnost i smanjenje koncentracije analita potrebne za detekciju. S obzirom da su metaloorganske mreže dio kemije materijala čiji razvoj je novijeg datuma, do sada su uspješno razvijeni mnogi kemijski senzori bazirani na sustavima u kojima glavnu ulogu prepoznavanja signala imaju metaloorganske mreže. Najbolje istraženi kemijski senzori su MOF-ovi čije se djelovanje bazira na interferometriji, površinski lokaliziranoj plazmatskoj rezonanciji, luminescenciji i koloidnim kristalima. Očekuje se kako će daljnjim razvojem znanosti zasada samo velik potencijal metaloorganskih mreža u budućnosti imati veću primjenu koja se neće bazirati samo na specifičnoj selektivnosti i poboljšanjima starijih tehnika detekcije, već i u primjeni koja će biti korisnija za cijelokupno područje prirodnih i tehničkih znanosti

Antibody targeted nanoparticles for imaging and therapy of cancer

The central hypothesis for this thesis is that antibody-targeted superparamagnetic iron oxide nanoparticles (SPIONs) can be used for diagnosis and therapy of cancer. The hypothesis is based on the knowledge that firstly, recombinant single chain Fv antibody fragments (scFv) are effective targeting reagents and second, SPIONs can substantially improve the sensitivity of magnetic resonance imaging (MRI). Furthermore, SPIONs can be induced to generate heat when subjected to an alternating magnetic field (AMF). The aim of the thesis was to test the cancer imaging and therapeutic potential scFvfunctionalised nanoparticles by: (1) Generating scFvs reactive with carcinoembryonic antigen (CEA) a cell surface tumour marker. (2) Developing conjugation methods to attach the scFv, in functional form, to SPIONs. (3) Evaluating the cellular interaction (targeting and specificity) of functionalised SPIONs and (4) Measuring the imaging and therapeutic heating effect of the targeted SPIONs. ScFvs reactive to CEA were generated in Pichia pastoris and conjugation chemistries optimised for attachment of purified scFv to SPION surface. Targeting efficacy of the scFv functionalised SPIONs was tested by ELISA, cellular uptake, confocal microscopy and MRI. Results demonstrated unequivocal CEA-specific cellular uptake and CEAspecific MRI, using SPIONs conjugated with Sm3E, a high affinity humanized anti- CEA scFv. Cellular interaction of the Sm3E-SPIONs was found to be influenced by size and surface properties; neutrally charged Sm3E functionalised dextran SPIONs localised preferentially to the outside of the cell membrane, whilst negatively charged Sm3E functionalised PEGylated SPIONs showed evidence of intracellular uptake. The SPIONs were shown to be effective generators of heat when exposed to AMF of 150V, 0.74A and 1MHz. AMF treatment of Sm3E-SPION targeted cells was found to induce expression of the stress protein HSP70 and lead to hyperthermic cell death in vitro. These results indicate that scFv-SPION conjugates have potential for selective tumour imaging and therapy

Minimising biases in Full Configuration Interaction Quantum Monte Carlo

We show that Full Configuration Interaction Quantum Monte Carlo (FCIQMC) is a Markov Chain in its present form. We construct the Markov matrix of FCIQMC for a two determinant system and hence compute the stationary distribution. These solutions are used to quantify the dependence of the population dynamics on the parameters defining the Markov chain. Despite the simplicity of a system with only two determinants, it still reveals a population control bias inherent to the FCIQMC algorithm. We investigate the effect of simulation parameters on the population control bias for the neon atom and suggest simulation setups to in general minimise the bias. We show a reweighting scheme to remove the bias caused by population control commonly used in Diffusion Monte Carlo [J. Chem. Phys. 99, 2865 (1993)] is effective and recommend its use as a post processing step.Comment: Supplementary material available as 'Ancillary Files

Lox droplet vaporization in a supercritical forced convective environment

A systematic investigation has been conducted to study the effects of ambient flow conditions (i.e. pressure and velocity) on supercritical droplet gasification in a forced-convective environment. The model is based on the time-dependent conservation equations in axisymmetric coordinates, and accommodates thermodynamic nonidealities and transport anomalies. In addition, an efficient scheme for evaluating thermophysical properties over the entire range of fluid thermodynamic states is established. The analysis allows a thorough examination of droplet behavior during its entire lifetime, including transient gasification, dynamic deformation, and shattering. A parametric study of droplet vaporization rate in terms of ambient pressure and Reynolds number is also conducted