We investigate the effect of thermal expansion and gravity on the propagation and stability of flames in inhomogeneous mixtures. We focus on laminar flames in the simple configuration of an infinitely long channel with rigid porous walls in order to understand the effect of inhomogeneities on these fundamental structures. The first part of the thesis is concerned with premixed flames propagating against a prescribed parallel (Poiseuille) flow and subject to thermal expansion. We show that in a narrow channel (corresponding to a relatively thick flame), if the Peclet number is fixed and of order unity, a premixed flame propagating against a parallel flow is governed by the equation for a planar premixed flame with an effective diffusion coefficient. The enhanced diffusion is shown to correspond to Taylor dispersion, or shear-enhanced diffusion. Several important applications of the results are discussed. One of the topics of relevance is the bending effect of turbulent combustion. The results of our analysis show that, for a large flow intensity, the effective propagation speed of the premixed flame for depends only on the Peclet number (which is equal to the Reynolds number if the Prandtl number is unity). This mimics the behaviour of the turbulent premixed flame when the effective propagation speed is plotted versus the turbulence intensity for fixed values of the Reynolds number. The second part of the thesis is concerned with triple flames, subject to thermal expansion and buoyancy. A study is undertaken to investigate the stability of a diffusion flame subject to these effects, which gives rise to a problem analogous to the classical Rayleigh--B\'nard convection problem. A linear stability analysis in the Boussinesq approximation is performed, which leads to analytical results showing that the Burke-Schumann flame is unstable if the Rayleigh number is above a critical value which is determined. Numerical results confirm and complement the analytical results. A full numerical investigation of the effects of gravity and thermal expansion on triple flames propagating in a direction perpendicular to the direction of gravity is then carried out. This configuration does not seem to have received dedicated attention in the literature. It is found that the well-known monotonic relationship between the propagation speed $U$ and the flame-front thickness $\epsilon$, which exists in the constant density case when the Lewis numbers are of order unity or larger, persists for triple flames undergoing thermal expansion. Under strong enough gravitational effects, however, the relationship is no longer found to be monotonic, exhibiting hysteresis if the Rayleigh number is large enough. Finally, the initiation of triple flames from a hot two-dimensional ignition kernel is investigated. Particular attention is devoted to the energy required for ignition and the transient evolution of triple flames after initiation. Steady, non-propagating, two-dimensional solutions representing "flame tubes" are determined; their thermal energy is used to define a minimum ignition energy for the two-dimensional triple flame in the mixing layer. The transient behaviour of triple flames following "energy-increasing" or "energy-decreasing" perturbations to the flame tube solutions is described in situations where the underlying diffusion flame is either stable or unstable.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第21874号 / 人博第903号 / 新制||人||215(附属図書館) / 2018||人博||903(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)准教授 小林 純也, 教授 宮下 英明, 准教授 三浦 智行 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

No description available.

Diploma thesis deals in the first part with recent knowledge of cold spray, its mechanism and parameters of deposition, advanced coatings made by cold spray and their applications, knowledge of Ti-6Al-4V coatings and their heat treatment. Deposit of Ti- 6Al-4V powder was made by cold spray process. In experimental part, microstructure and mechanical properties of supplied and its heat treated material were observed and examined. Mechanical properties and microstructure remained unchanged by annealing at 600 °C as in the case of supplied material. Recrystallization occured in microstructure of and phases by annealing at 800 °C. Grains were emerged in microstructure and mechanical properties were decreased. Mechanical properties were improved by annealing at 900 °C due to quenching. Microstructure consists of and ’ phases. Mechanical properties were the worst for annealed material at 1000 °C because of coarsed grains. Material which was annealed at 800 °C, quenched and precipitation hardened had the best microstructure and mechanical properties.

L’objet de la présente thèse porte sur le rôle de la monnaie, en particulier bancaire, dans la détermination du niveau général d’activité chez le fondateur de la théorie quantitative contemporaine, Irving Fisher (1867–1947). Nous y montrons comment évolue sa conception des fluctuations et de l’instabilité en confrontant sa théorie des cycles de crédit (1911) à la déflation par la dette (1932, 1933). Notre objectif est de retracer la manière dont l’essor de la monnaie bancaire à partir de la fin du 19ème siècle, puis des marchés financiers dans l’entre-deux-guerres, sont intégrés dans la pensée de Fisher et, à travers lui, dans la conception libérale de la neutralité monétaire. Nous dégageons ainsi les structures logiques de ses deux analyses, en faisant valoir qu’elles s’appuient sur des mécanismes qualitativement différents, l’un bancaire, l’autre financier, mettant en jeu des variables et des processus de nature distincte. Cependant, une fois cette hétérogénéité mise en avant, il est possible de rapprocher les deux théories de Fisher en soulignant une invariance plus profonde portant sur le caractère déstabilisant de la monnaie. C’est pourquoi les deux grands projets de réformes qu’il défend au cours de sa vie, le dollar-compensé (1911, 1920) puis le 100% Monnaie (1935), sont construits en vue de répondre au même objectif : stabiliser la valeur de la monnaie. Le chapitre 1, introductif, présente les ressorts de la déflation par la dette afin d’en discuter l’articulation à la théorie des cycles de crédit au chapitre 2. Dans celui-ci, nous faisons apparaître que cette analyse de Fisher constitue un cas particulier d’un modèle plus général dans lequel, contrairement à ce qu’il pense alors, la stabilité de l’équilibre n’est pas garantie. Au chapitre 3, nous abordons les solutions qu’il propose pour lutter contre les désordres monétaires. Plus spécifiquement, nous précisons les liens entre sa perception de l’instabilité et les réformes qu’il suggère pour neutraliser l’influence de la monnaie sur les grandeurs économiques réelles. Dans le chapitre 4, nous poursuivons notre étude de la vision de l’instabilité de Fisher en examinant les fondements logiques et historiques de la notion « d’effet Fisher » au sens que lui donne James Tobin (1980). Enfin, le chapitre 5 traite de la réception et de la postérité des idées de Fisher en matière d’analyse de l’instabilité financière. Nous y montrons que la déflation par la dette n’est ni ignorée, ni totalement rejetée par les économistes dans les années 1930 et 1940, puis qu’elle occupe une place importante à partir des années 1970 dans la constitution des programmes de recherche néo-keynésien et post-keynésien. / The purpose of this thesis is to examine the role of money, especially of bank deposits,in Irving Fisher’s (1867–1947) analysis of the general level of activity determination, which constitutes nowadays the foundation of the contemporary quantitative theory.We show how his explanation of monetary instability evolves by comparing his credit cycle theory (1911) with the debt-deflation (1932, 1933). Our aim is to highlight the influence of the development of bank currency (from the end of the 19th century) and financial markets (during the interwar period) on Fisher’s economic thought, and through him, on the liberal conception of monetary neutrality. In this way, we draw the logical structures of its two analyses, by pointing out that they are based on qualitatively different mechanisms, one banking, and the other one financial, involving variables and processes of different nature. However, once this heterogeneousness advanced, it is possible to reconcile the two theories of Fisher by underlining a deeper invariance concerning the destabilizing character of money. That is why his two big reforms projects, the compensated-dollar (1911, 1920), and then the 100% Money (1935), are intended to answer at the same purpose: stabilize the value of money.Chapter 1 introduces the dynamic of the debt-deflation to discuss his relation with thecredit cycle theory in the chapter 2. In the latter, we assert that this analysis of Fisher is only a particular case of a more general model in which, contrary to what he thinks at the time, the stability of the equilibrium is not guaranteed. In the chapter 3, we discuss the solutions he proposed to solve the monetary disorders. More precisely, we specify the links between his perception of instability and the reforms he suggests to neutralize the influence of money on the real economic variables. In the chapter 4, we pursue our study of Fisher’s conception of instability by examining the logical and historical foundations of the notion of “Fisher effect” in the meaning given by James Tobin (1980). Finally, the chapter 5 deals with the reception and the posterity of Fisher’s ideas regarding financial instability. We show that the debt-deflation is neither ignored, nor totally rejected by the economists in the 1930s and 1940s, then that it occupies an important place from 1970s in the constitution of the neo-Keynesian and post-Keynesian research program.

Electric field can be a viable method in controlling various combustion properties. Comparing to traditional actuators, an application of electric field requires very small power consumption. Especially, alternating current (AC) has received attention recently, since it could modulate flames appreciably even for the cases when direct current (DC) has minimal effects. In this study, the effect of AC electric fields on small coflow diffusion flames is focused with applications of various laser diagnostic techniques. Flow characteristics of baseline diffusion flames, which corresponds to stationary small coflow diffusion flames when electric field is not applied, were firstly investigated with a particular focus on the flow field in near-nozzle region with the buoyancy force exerted on fuels due to density differences among fuel, ambient air, and burnt gas. The result showed that the buoyancy force exerted on the fuel as well as on burnt gas significantly distorted the near-nozzle flow-fields. In the fuels with densities heavier than air, recirculation zones were formed very close to the nozzle exit. Nozzle heating effect influenced this near-nozzle flow-field particularly among lighter fuels. Numerical simulations were also conducted and the results showed that a fuel inlet boundary condition with a fully developed velocity profile for cases with long fuel tubes should be specified inside the fuel tube to obtain satisfactory agreement in both the flow and temperature fields with those from experiment. With sub-critical AC applied to the baseline flames, particle image velocimetry (PIV), light scattering, laser-induced incandescence (LII), and laser-induced fluores- cence (LIF) techniques were adopted to identify the flow field and the structures of OH, polycyclic aromatic hydrocarbons (PAHs), soot zone. Under certain AC condi- tions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered from the baseline case, leading to the formation of toroidal vortices. Increased residence time and heat recirculation inside the vortex resulted in appreciable formation of PAHs and soot near the nozzle exit. Decreased residence time along the jet axis through flow acceleration by the vortex led to a reduction in the soot volume fraction in the downstream sooting zone. Electromagnetic force generated by AC was proposed as a viable mechanism for the formation of the toroidal vortex. By varying applied AC in a wide range of frequency and voltage, several insta- bility modes were observed, including flicking flames, partial pinch-off of flames, and spinning flames. High speed imaging together with Mie scattering techniques were combined to reveal the flame dynamics as well as the flow structure inside the flames. Original steady toroidal vortices triggered by AC were noted to exhibit axisymmetric axial instability in the flicking and partial pinch-off modes and non-axisymmetric azimuthal instability in the spinning mode. Electrical measurements were also conducted simultaneously to identify the voltage, current, and electrical power responses. Integrated power was noted to be sensitive to indicate subtle variation of flames properties and to the occurrence of axial instability. Under low frequency AC forcing with electrical conditions not generating toroidal vortices, responses of flames were further investigated. Several nonlinear flame responses, including frequency doubling and tripling phenomena, were identified. Spectral analysis revealed that such nonlinear responses were attributed to the combined effects of triggering buoyancy-induced oscillation of the flame as well as the Lorenz force generated by applying AC. Phase delay behaviors between the applied voltage and the heat release rate (or flame size) were also studied to explore the potential of applying AC in controlling flame instability. It was found that the phase delay had large variations for AC frequency smaller than 80 Hz and became saturated at over 80 Hz, which has been explained based on the interaction between the buoyancy and ionic wind. Electrical measurement showed the power consumed by the AC was smaller than 0.01% of the heat release rate from the flame. To improve the understanding on the electric current resulting from applying electric field on flames, a simplified one-dimensional model was developed in that the reaction zone was modeled as a thin ionized layer. Model governing equations were derived from species equations by implementing mobility differences depending on the type of charged particles, especially between ions and electrons. The result showed that the sub-saturated current along with field intensity was significantly influenced by the polarity of DC due to the combined effect of non-equal mobility of charged particles as well as the position of the ionized layer in a gap relative to two electrodes. Experiments with quasi-one-dimensional flames under DC were conducted to substantiate the model and measured currents agreed qualitatively well with the model predictions.

Heavy rains and El Nio phenomenon are recurring natural phenomena at a national level. These can cause floods due to the overflowing of rivers, which, when close to cities, can cause both human and material losses. The district of Catacaos, located in the city of Piura, was the one with the highest number of injuries due to the flood caused by El Nio phenomenon in 2017. This phenomenon causes a large amounts of rainfalls due to the presence of abnormally warm waters along the northern coast of Peru [1]. It is for this reason that the need arose to carry out an analysis of the physical vulnerability due to instability of people through static equilibrium, in said district, in order to present maps of unsafe areas in the face of this phenomenon. In this investigation, flood hazard maps are generated simulating the one presented in 2017, using 2D hydraulic modeling. For the generation of vulnerability curves, the instability analysis is performed by moment and drag force. Finally, maps with unsafe areas are made using ArcGis software. Where the results obtained indicate that 29.37% of the city was flooded. Likewise, the vulnerability maps generated show us that women and men over 18 years of age in the city of Catacaos would be vulnerable to dragging and overturning in the face of floods in 16.54% and 13.21%, respectively, of the total studied area. This information will be useful for the development of future evacuation plans during floods, carried out by national entities. © Published under licence by IOP Publishing Ltd.

Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder that is caused by a point mutation in the LMNA gene, resulting in production of a truncated farnesylated-prelamin A protein (progerin).We previously reported that XPAmislocalized to the progerin-inducedDNAdouble-strand break (DSB) sites, blocking DSB repair, which led to DSB accumulation,DNA damage responses, and early replication arrest inHGPS. In this study, the XPA mislocalization to DSBs occurred at stalled or collapsed replication forks, concurrent with a significant loss of PCNA at the forks, whereas PCNA efficiently bound to progerin. This PCNA sequestration likely exposed ds-ssDNA junctions at replication forks for XPA binding. Depletion of XPA or progerin each significantly restored PCNAat replication forks.Our results suggest that although PCNAismuchmore competitive than XPAin binding replication forks, PCNA sequestration by progerin may shift the equilibrium to favor XPA binding. Furthermore, we demonstrated that progerin-induced apoptosis could be rescued by XPA, suggesting that XPAreplication fork binding may prevent apoptosis in HGPS cells. Our results propose a mechanism for progerininduced genome instability and accelerated replicative senescence in HGPS. - Hilton, B. A., Liu, J., Cartwright, B.M.,Liu,Y.,Breitman,M.,Wang,Y., Jones,R.,Tang, H.,Rusinol,A.,Musich,P.R.,Zou,Y.Progerin sequestrationof PCNApromotes replication fork collapse andmislocalization ofXPAin laminopathy-related progeroid syndromes.

This thesis is dedicated to developing a concept that allows for predicting the magnitude of political instability periods. To that end existing literature is consulted to explore the most appropriate definitions and explanatory models for creating a elaborated approach to political instability. On the basis of this refined concept, that defines political instability as a latent condition rather than an occurrence, hypotheses are devised. These hypotheses are tested by employing a exploratory correlation analysis on a limited sample, which yields results that encourage confidence in the predictive potential of the developed concept. As suggested in the explanatory framework the analysis finds that the magnitude of conflict, resulting from political instability, is positively correlated with social fragmentation and individual deprivation, while being negatively correlated to military professionalism. A fourth explanatory component - viable alternatives to conflict - was not found to have any effect.

Parametric resonance is a particular type of resonance in which a parameter in a system changes with time. A particularly interesting case is when the parameter changes in a periodic way, which can lead to very intricate behavior. This di↵ers from periodic forcing in that solutions are not necessarily periodic. A system in which parametric resonance is realized is when a fluid bath is shaken periodically, which leads to an e↵ective time dependent gravitational force. This system will be used to study the onset of surface waves in a bath with non-uniform topography. A linear model for the surface waves is derived from the Euler equations in the limit of shallow waves, which includes the geometry of the bottom and surface tension. Experiments are performed to compare with the proposed model and good qualitative agreement is found. Another experiment which relies on a shaking fluid bath is that of bouncing fluid droplets. In the case of two droplets the shaking allows for a larger bouncing droplet to attract a smaller moving droplet in a way that creates a bound system. This bound system is studied and shows some analogous properties to quantum systems, so a quantum mechanical model for a two dimensional atom is studied, as well as a proposed model for the droplet-wave system in terms of equations of fluid mechanics.