Fuel mixture formation and spray characteristics are crucial for the advancement of Gasoline Compression Ignition (GCI) engine. For investigations of spray characteristics, a high-pressure high-temperature spray chamber with constant volume has been designed, tested and commissioned at CCRC, KAUST. Back light illumination technique has been applied to investigate the macroscopic spray properties of an outwardly opening piezoelec- tric injector. Three parameters including injection pressure, ambient pressure, and ambient temperature have been involved. A total of 18 combinations of experimental conditions were tested under non-reactive conditions. Through qualitative analysis of spray morphology under different operating conditions, an apparent distinction of spray morphology has been noticed. Spray morphology and propagation have shown strong dependencies on ambient pressure and ambient tempera- ture while injection pressure has a negligible effect on spray shape. Increasingly compact and bushier spray patterns were observed in the cases of high ambient pressure due to in- creasing aerodynamic drag force on spray boundary. It should also be noted that ambient temperature plays a fairly important role in fuel evaporation rate. At 200 °C, oscillating and considerably short spray shape was produced. Also, circumferential ring-like vortices and distinctive string-like structures have been identified for the fuel spray exiting this hollow cone injector. It has been observed that high ambient pressure conditions (Pamb = 4 bar and 10.5 bar) are favorable to the vortices generation, which has also been reported in previous literature. The quantitative description of macroscopic spray properties reveals that ambient pres- sure and ambient temperature are found to be the most influential parameters on liquid penetration length. The rise of ambient pressure results in considerably shorter liquid pen- etration length. Ambient temperature also appears to be a very effective factor of reducing penetration length. Injection pressure contributes to a notable increase of liquid penetra- tion length under ambient pressure of 1 atm. However, the influence of injection pressure is substantially reduced under ambient pressures of 4 bar and 10.5 bar, which indicates that ambient pressure exerts much stronger influence than injection pressure on liquid penetra- tion length. Furthermore, it has been revealed that the increase of injection pressure and ambient pressure are the predominant sources contributing to the enlargement of spray cone angle. The effect of injection pressure on spray cone angle has been amplified by the increase of ambient pressure. With increasing ambient pressure, the penetration of injected fuel tends to propagate axially in a much slower manner that leads to wider fuel distribution in the radial direction. Ambient temperature exerts a similar influence on spray cone angle as on liquid penetration length. The spray cone angle experiences a noticeable decline when ambient gas is increased to 200 °C.

Macroscopic fundamental diagrams (MFD) reveal the relations among flow, speed and density in a large geographic region. After literature review on macroscopic analysis, the similar methodology is applied in this thesis. The purpose of the thesis is to find the evidence that is able to prove MFD existing in Stockholm urban region. Both floating car data (FCD) based on global positioning system (GPS) data from taxis travelling in Stockholm region and traffic data from fixed detectors data source are used to construct the fundamental diagrams. Geographically, the usage of data is extended from single link to multiple links, then to the entire study region. The temporal phase is restricted in one weekday and weekend. The diagram of flow vs. speed based on single detector is found disordered, by contrast, the diagrams of cumulative flow, speed and density for all detectors represent orderly. MFD diagrams proposed in Yokohama case study by Geroliminis and Daganzo are reproduced with cumulative data in this thesis.  Therefore, it can be proved that MFD exists when using data from multiple links. However, the cumulative data from fixed detectors only represents the traffic on links where they locate, not the entire region. To overcome it, GPS data from taxis, which covers the whole region, is analyzed with same method. Because full taxis travel in the same manner as normal vehicles, they are selected to approximate traffic in whole region. A neat curve of flow vs. speed is produced and it coincides with corresponding diagram in the reference paper. It enhances the conclusion that MFD exists in the entire study region. Moreover, based on the constant ratio between average link flow and region exit flow, a controlling density policy is discussed in aiming for maximizing trip completion.

Fire is a primary driver of environmental change that can originate from natural or human ignition. Macroscopic charcoal (>125 "m) deposited into lake sediment is a record of a local fire event, whereas microscopic charcoal indicates fire activity on a broad landscape scale. Patterns of charcoal deposition may shed light on both human activities and climate history over long-time scales. Whether lowland Caribbean forests have experienced natural fire regimes over the long-term is unknown. Laguna Limón is a little-studied, large, freshwater lake on the northeastern coast of the Dominican Republic. We extracted four overlapping sediment cores totaling 315 cm in depth, and conducted analysis of macroscopic charcoal (2-cm), microscopic charcoal (16-cm), and loss-on-ignition (1-cm) to examine the long-term fire and environmental history of the area. Loss-on-ignition data established that the lake has only recently become organic rich, and was likely open to the sea as a low energy bay until 1400 Cal. Yr BP. The lake existed briefly as a wetland before transitioning to the modern freshwater lake 1200 Cal. Yr BP. Macroscopic charcoal was most abundant in the freshwater section of the core while microscopic charcoal peaked near the bottom of the core, and aligns well with other regional microscopic charcoal records. Overall the charcoal record reflects a combination of climatic and anthropogenic related charcoal deposition suggesting that fire has played an active role in the environmental history Laguna Limón. / Master of Science

No description available.

Various theories have been proposed to describe vehicular traffic flow in cities on an aggregate level. This dissertation work shows that a number of MFDs exist in an urban network. The number of MFDs basically indicate the existence of different levels of service on different network routes. It also demonstrate that the modification of control strategy can optimize the signal timing plan for the links with high congestion and spillbacks. With the proposed control strategy, the location of points are shifted from lower MFDs to upper MFDs which means the congestion are reduced and the overall network traffic flow operation is improved. In this thesis, the emergency vehicle preemption (EVP) operation is also evaluated by using the MFDs. The concept of MFD can help to illustrate the effect on various types of roads due to EVP operation. The results show that the volume of links along the emergency route is increased and the volume of other links closed to the emergency route is decreased due to preemption. The researchers and practitioners can apply the proposed approach to identify the affected links and minimize the total network delay during EVP. / Master of Science

Side friction factors are defined as all those actions related to the activities taking place by the sides of the road and sometimes within the road, which interfere with the traffic flow on the travelled way. They include but not limited to pedestrians, bicycles, non-motorised vehicles, parked and stopping vehicles. These factors are normally very frequent in densely populated areas in developing countries, while they are random and sparse in developed countries making it of less interest for research and consequently there is comparatively little literature about them. The objective of this thesis is to analyze the effect of these factors on traffic performance measures on urban roads. To carry out this work, a research design was formulated including specific methods and prescribed limitations. An empirical case study methodology was adopted where Dar-es-salaam city in Tanzania was chosen as a representative case. The scope was limited to include only road-link facilities. A sample of these facilities including two-lane two-way and four-lane two-way roads were selected and studied. The study was conducted in two parts, of which each involved a distinctive approach. Part one involved a macroscopic approach where traffic and friction data were collected and analyzed at an aggregated level, whereas part two involved a microscopic approach where data of individual frictional elements were collected and analysed individually. Data collection was mainly performed by application of video method, which proved to be effective for simultaneous collection of traffic and side friction data. Data reduction was conducted chiefly by computer, using standard spreadsheet and statistical software packages, mainly SPSS and some computer macros. The analysis part was based on statistical methods, chiefly regression analysis. In the macroscopic approach, traffic and friction data from all sites were adjusted through a process called ‘normalization’, which enabled the data from the different sites to be merged, and consequently to obtain speed-flow curves for each road type. The individual friction factors through regression analysis were weighted and combined into one unit of measure of friction called "FRIC". The effect of "FRIC" on speed-flow curves was analyzed. The results showed significant impact on speed for both road types. Impact on capacity was identified on two-lane two-way roads while field data on four-lane two-way roads did not allow this. In the microanalysis approach, effect of individual side friction factors on speed was analyzed. The results showed that on two-lane two-way roads, all studied factors exhibited statistically significant impact on speed, while on four-lane two-way roads, only one factor showed the same. The results also identified impact values characteristic to the individual friction factors on some roads. Recommendations were made based on these results that highway capacity studies particularly in developing countries, should include the friction variable, though in the form suitable to their own particular circumstances. Further recommendations were made that these results should be applied to formulate management programs seeking to limit levels of side friction on high mobility urban arterial streets in order to improve traffic safety and operation efficiency. / <p>QC 20100701</p>

Doctor of Philosophy / Department of Physics / Chii-Dong Lin / In this thesis, we establish the theoretical tools to investigate high-order harmonic generation (HHG) by intense infrared lasers in a gaseous medium. The macroscopic propagation of both the fundamental and the harmonic fields is taken into account by solving Maxwell’s wave equations, while the single-atom (or single-molecule) response is obtained by quantitative rescattering theory. The initial spatial mode of the fundamental laser is assumed either a Gaussian or a truncated Bessel beam. On the examples of Ar, N[subscript]2 and CO[subscript]2, we demonstrate that the available experimental HHG spectra with isotropic and aligned target media can be accurately reproduced theoretically even though the HHG spectra are sensitive to the experimental conditions. We show that the macroscopic HHG can be expressed as a product of a macroscopic wave packet and a photorecombination cross section, where the former depends on laser and experimental conditions while the latter is the property of the target only. The factorization makes it possible to retrieve the single-atom or single-molecule structure information from experimental HHG spectra. As for the multiple molecular orbital contribution in HHG, it causes the disappearance of the minimum in the HHG spectrum of aligned N[subscript]2 with the increase of laser intensity, and the position of minimum in HHG spectrum of aligned CO[subscript]2 depending on many factors is also attributed to it, which could explain why the minima observed in different laboratories may differ. For an important application of HHG as ultrashort light source, we show that measured continuous harmonic spectrum of Xe due to the reshaping of the fundamental laser field can be used to produce an isolated attosecond pulse by spectral and spatial filtering in the far field. For on-going application of using HHG to ionize aligned molecules, we present the photoelectron angular distribution from aligned N[subscript]2 and CO[subscript]2 in the laboratory frame, which can be compared directly with future experiments.

Este sumário apresenta o resumo e os resultados deste estudo experimental do Fechamento do Coto Duodenal, em um e dois planos de sutura, realizado em 48 cães submetidos a uma gastrectomia Billroth II, com a finalidade de estudar comparativamente, o processo de cicatrização, macro e microscópico da sutura deste Coto. Os aspectos mais relevantes deste estudo de cicatrização de feridas macroscópicas e microscópicas no coto duodenal foram os seguintes: A) Estudo macroscópico: Com o objetivo de realizar um estudo macroscópico de fechamento do coto duodenal, foi realizada uma gastrectomia BII, em 48 cães, divididos em dois grupos: Grupo 1 - composto por 24 cães em que a sutura do coto duodenal foi realizada em um plano extra-mucoso. Estes animais foram divididos em dois subgrupos de 12 animais cada: i1 - cães sacrificados no período pós-operatório imediato, ou seja, no primeiro, quarto e sétimo dia após a operação; e M1 - cães sacrificados em um período pós-operatório mais tardio, ou seja, no décimo quarto, vigésimo primeiro e vigésimo oitavo dia, após a operação. Grupo 2 - Composto por 24 animais, em que a sutura do coto duodenal foi realizada em 2 planos (total e seromuscular). Também estes animais foram distribuídos em subgrupos, i2 e M2, de forma idêntica como no Grupo 1. Um estudo comparativo foi feito quanto aos resultados de fechamento do coto duodenal em 1 e 2 planos, levando em consideração seus aspectos macroscópicos, obtendo-se as seguintes conclusões: o Em nenhum dos cães, em ambos os grupos, ocorreu deiscência do coto duodenal ou quaisquer outras complicações pós-operatórias; o O diâmetro externo do coto duodenal ao nível da sutura foi significativamente maior no grupo com 2 planos de sutura. No entanto, a 5 e 10 cm distalmente à sutura do coto, esta medida foi semelhante em ambos os grupos. o Aderências ao coto duodenal foram semelhantes em ambos os métodos de sutura, exceto por uma incidência significativamente maior de aderências de epíplon no grupo com um plano de sutura, durante os primeiros 7 dias. o A inflamação da mucosa foi significativamente maior no grupo com 2 planos de sutura, durante os primeiros 7 dias; o O esporão formado no fechamento do coto em 2 planos de sutura foi significativamente maior que o formado em um plano de sutura. o A distância entre a superfície mucosa do coto duodenal e a papila maior e papila menor do duodeno, foi significativamente maior nos cotos fechados com 1 plano de sutura. B) O estudo histológico: Um estudo histológico de fechamento do coto duodenal foi feito, após gastrectomia Billroth II em 48 cães, divididos em dois grupos iguais. No Grupo 1, o fechamento foi realizada em um plano, enquanto no Grupo 2 foi feito em dois planos (total e seromuscular). Em cada grupo, os animais foram divididos em dois subgrupos; i1 - cães sacrificados no início do período pós-operatório, ou seja, no primeiro, quarto e sétimo dias; e M1 - cães sacrificados no pós-operatório tardio, ou seja, no décimo quarto, vigésimo primeiro e vigésimo oitavo dia. Não houve um único caso de deiscência em qualquer animal. As conclusões relativas aos aspectos histológicos mostraram os seguintes aspectos: o Houve um esporão invertido para o lúmen do intestino, em todos os animais do grupo 2, enquanto que um pseudoesporão foi observado em apenas 37% nos animais do Grupo 1 ; o Sinais inflamatórios agudos foram mais intensos no grupo 2, na primeira semana de pós-operatório; o A formação de neofibrose do tecido conjuntivo e a regeneração da \"muscularis mucosae\" foi semelhante nos dois grupos. No entanto, a regeneração da mucosa ocorreu mais precocemente no grupo 1 , ao passo que a regeneração das fibras musculares ocorreu mais precocemente no grupo 2 / An experimental study of duodenal stump closure in one and two suture layers was performed in 48 dogs submitted to a Billroth II Gastrectomy, in order to study comparatively Macroscopic and Histological wound healing aspects. The most relevant aspects of this Macroscopic and Histological wound healing study in the duodenal stump, were the following ones: A) Macroscopic study: A comparative study was made as to the results of duodenal stump closure in 1 and 2 layers, taking in consideration its macroscopic aspects. Billroth II gastrectomy was performed in 48 dogs divided in two groups: a. Group 1 - consisted of 24 dogs in which the duodenal stump suture was performed in one extra-mucous layer. These animals were distributed into 2 subgroups of 12 animals each: i1 - dogs sacrificed in the early postoperative period, that is, on the first, fourth and seventh day after the operation; and M1 - dogs sacrificed at a later postoperative period, that is, on the fourteenth, twenty-first and twenty-eighth day after the operation. b. Group 2 - consisted of 24 dogs, in which the suture of the duodenal stump was performed in 2 layers (total and seromuscular ones). Also these animals were distributed in i2 and M2 sub-groups, identically as in group 1. The following conclusions were obtained, concerning the macroscopic aspects: o Dehiscence of the duodenal stump or any other postoperative complications occurred in none of the dogs in both groups; o The external diameter of the duodenal stump at the level of the suture was significantly larger in the group with 2 suture layers. However, at 5 and 10 cm distally from the suture, this measure was similar in both groups. o Adherences to the duodenal stump were similar in both suturing methods, except for a significantly higher incidence of epiplon adherence in the 1 layer group during the first 7 days. o Mucosal inflammation was significantly greater in the 2 suture layers group during the first 7 days; o The spurs formed in the 2 layers stump closure was significantly larger than that formed in 1 layer suture. o The distance from the mucosal surface of the stump suture to the Major and Minor papilla of the duodenum was significantly greater in the stumps closed with 1 layer sutures. B) Histological study: A histological study of duodenal stump closure was made, following a Billroth II gastrectomy in 48 dogs, divided in two equal groups (1 and 2) and its subgroups (i1 and M1; i2 and M2), as mentioned above. The conclusions concerning to histological aspects showed the following characteristics: o There was an inverted spur toward the lumen of the bowel, in all group 2 animals, whereas a pseudo- spur was also observed in only 37% in group 1 animals; o Acute inflammatory signs were more intense in group 2 in the first week of recovery; o The formation of young connective tissue fibrosis and muscularis mucosae fibers regeneration was similar in both groups. However, mucosal regeneration occurred earlier in group 1, while regeneration of muscle fibers occurred more precociously in group 2

Perturbações ambientais foram detectadas em sistema de turfeira no sul da Bacia do Paraná (Mina de Faxinal, Formação Rio Bonito) durante o Eopermiano (idade radiométrica 291 ± 1.3 Ma, topo do Sakmariano) sob vigência de período climático pós-glacial da Idade do Gelo do Neopaleozoico. Além da detecção de incêndios recorrentes, foi identificado um evento de incêndio autóctone/hipoautóctone em vegetação arbórea em um horizonte no carvão contendo grandes fragmentos de lenhos queimados comprimidos (21,8 x 13.4 cm). A influência de vulcanismo está registrada sob a forma de uma camada de tonstein (cinza vulcânica sedimentada) intercalada ao carvão, onde estão incluídas abundantes compressões de folhas glossopterídeas. A análise do carvão consistiu em determinação de refletância sob óleo de macerais do grupo inertinita em blocos polidos para confirmar a identificação de carvão vegetal macroscópico e ocorrência de incêndios na turfeira. Adicionalmente, a observação da matéria orgânica sob fluorescência nos blocos revelou que os incêndios não afetaram a microflora, mas alteração na fluorescência evidenciou dessecação ambiental, verificada também em lâminas palinofaciológicas. Sob microscopia eletrônica de varredura, o carvão vegetal apresentou paredes celulares homogeneizadas, indicando temperaturas de queima acima de 325ºC, mas não superiores a 400ºC devido aos baixos resultados de refletância e à preservação de tecido vegetal delicado. A preservação de floema secundário, em associação orgânica com xilema tipo Agathoxylon, é registrada ineditamente. A observação sob microscopia de luz transmitida das cutículas foliares extraídas do tonstein permitiu descrição detalhada de padrões xeromórficos que ocorrem de forma endêmica nas epidermes de glossopterídeas de Faxinal e foram atribuídos a respostas adaptativas às frequentes perturbações ambientais que afetaram a floresta turfosa, tais como incêndios recorrentes por dessecação ambiental cíclica ou influência de vulcanismo regional. Esses fatores, em conjunto ou alternativamente, garantiram a dominância monotípica de Glossopteris pubescens nom. nov. na comunidade. O conjunto de evidências indicou que os incêndios foram de superfície, em baixas temperaturas, o transporte do carvão vegetal foi praticamente inexistente no horizonte de grandes fragmentos de lenhos queimados e que os demais incêndios recorrentes tiveram pouco efeito na comunidade proximal, ocorrendo regularmente nas áreas de entorno da turfeira dado o aporte de carvão vegetal macroscópico fragmentário. Durante a fase de aquecimento pós-glacial no Permiano, os ambientes de turfeira no Gondwana eram altamente suscetíveis à ocorrência de incêndios dos quais as glossopterídeas se beneficiavam para manter sua dominância e abundância nessas comunidades, por possuírem eficiente plasticidade adaptativa para sobreviver a condições extremas em ambientes altamente perturbados. / Environmental disturbances were detected in a peat-forming environment from the southern Brazilian Paraná Basin (Faxinal Coalfield, Rio Bonito Formation) during the lower Permian (radiometric age 291 ± 1.3 Ma, late Sakmarian) under post-glacial conditions in the Late Paleozoic Ice Age. In addition to recurrent wildfires, an autochthonous/hypauthochthonous wildfire event was identified in the woody vegetation from a coal horizon containing compressed, large-sized logs (21,8 x 13.4 cm). Volcanic influence is recorded in a tonstein layer (sedimentary volcanic ash) interbedded in the coal, where abundant compressed glossopterid leaves are entombed. The coal analysis consisted of reflectance measurements in polished blocks under oil of macerals of the inertinite group to confirm the macroscopic charcoal identification and wildfire occurrence in the peatland. Additionally, the observation of the organic matter in the polished block under fluorescence showed that the microflora has not been affected by the wildfires, but altered fluorescence evidenced environmental dryness, verified in palynofacies slides as well. Under scannin electron microscopy, the charcoal showed homogenized cell walls, indicating burning temperatures higher than 325ºC, but not higher than 400ºC given the low reflectance values and the preservation of fragile plant tissue. The preservation of secondary phloem in organic association with Agathoxylon wood-type is a first paleobotanical record. Observation under transmitted light of the leaf cuticles extracted from the tonstein allowed for the detailed description of xeromorphic patterns, which have been attributed to adaptative responses to the frequent environmental disturbances affecting the peat forest, such as recurrent wildfires due to environmental dryness or regional volcanic activity. These factors, collectively or in an alternating way, ensured the monotypic dominance of Glossopteris pubescens nom. nov. in the plant community. The set of evidences indicated low temperature surface fires, virtually inexistent charcoal transport in the charcoalified log horizon and that the other wildfire events had little effect in the proximal community, occurring regularly in the surrounding areas of the peatland given the fragmentary macroscopic charcoal input. During the postglacial warming in the Permian, the Gondwanan peatlands were highly susceptible to wildfires from which the glossopterids benefited to maintain their dominance and abundance in these communities due to efficient adaptative plasticity to survive under extreme conditions in highly disturbed environments.

Une analyse exhaustive de la piézoélectricité a été réalisée par la modélisation moléculaire basée sur l'application des principes de la mécanique quantique. La calibration de la méthode et des paramètres du calcul est d'abord examinée en comparant les résultats calculés concernant les oxydes de silicium et de Germanium à leurs homologues expérimentaux. Ensuite, les paramètres microscopiques qui influencent chaque contribution de cette propriété macroscopique de réponse sont distinctement rationalisés. Enfin, après la rationalisation de la propriété piézoélectrique, la conception de matériaux montrant un effet piézoélectrique élevé a été tentée. Nous avons montré que la grande piézoélectricité induite par un dopage dans le plan du graphène tendra vers une valeur unique, ni nulle ni infinie, et de façon indépendante de la nature physique ou chimique particulière du défaut. L'induction d'une piézoélectricité hors du plan du graphène en brisant sa planéité selon la direction-z est également étudiée. La réponse piézoélectrique obtenue est largement améliorée par rapport à la limite finie de la piézoélectricité dans le plan, mais aux grandes concentrations du défaut seulement. En effet, contrairement à la composante dans le plan de la piézoélectricité, la composante hors du plan, dépend de la nature du défaut et diminue jusqu'à tendre vers zéro à dilution infinie. / An exhaustive analysis of the technologically important piezoelectric phenomena is here done by applying quantum chemical simulations. At first, the calibration of the assumed computational scheme is examined by comparing our calculated piezoelectric properties of the well-known piezoelectric quartz to their experimental counterparts. Secondly, the microscopic parameters that influence each contribution of piezoelectric macroscopic property are distinctly rationalized. After the rationalization of the piezoelectric property, the design of materials that exhibiting a high piezoelectric effect has been attempted. It has been shown that a large in-plane piezoelectricity induced in graphene by doping can be acquired by including any in-plane defect(s). Moreover, in the limit of vanishing defect concentration, the piezoelectric response tends toward a unique value, neither null nor infinite, regardless of the particular chemical or physical nature of the defect. The induction of an out-of-plane piezoelectricity in graphene by breaking its planarity through the non-periodic z-direction is stated, where the obtained piezoelectric response is largely improved compared to the finite in-plane piezoelectric limit, at however higher concentration of the defect. Contrarily to what has been discussed for the in-plane piezoelectric effect, the out-of-plane one eventually vanishes as far as the limit of infinite defect dilution is reached, and so it relies ultimately on the nature of the defect.