Analysis of multicomponent seismic data from the Hydrate Ridge, offshore Oregon

textMulticomponent seismic data can be used to derive P- and S-wave velocity structures of the subsurface, which can be used further to estimate rock and reservoir properties. Most seismic analysis methods and algorithms assume that the earth is isotropic. In many geologic situations, however, sedimentary rocks exhibit anisotropic behavior, and the isotropic assumption will introduce errors in the estimates of the elastic properties of the subsurface. With the goal of analyzing multicomponent seismic data from complex regions (which may show anisotropic behavior), I have developed new algorithms for 1) seismic modeling based on a ray-Born approximation and 2) traveltime computation in tilted transversely isotropic media based on Fermat’s principle. This new traveltime computation algorithm is tested on prestack depth migration of a physical model dataset. Such algorithms are essential for estimating subsurface rock properties in complex areas such as the Hydrate Ridge area, offshore Oregon. viii I participated in the acquisition of multicomponent seismic data (summer 2002), at the Hydrate Ridge of the Cascadia convergent margin. The primary goal of the experiment was to map the gas hydrates and free gas, and to understand the mechanism of fluid migration. Gas hydrate is an ice-like substance that contains low molecular weight gases (mostly methane) in a lattice of water molecules. Gas hydrates and free-gas are generally detectable with seismic methods because the seismic velocity increases in the presence of gas hydrates, and it decreases in the presence of free-gas. My analysis results in estimates of P- and S-wave interval velocities and anisotropic parameters with the final goal of relating these parameters to the presence and quantification of gas hydrate and free gas. I performed interval velocity analysis in the τ-p (intercept time - ray parameters) domain following three main steps: 1) P-wave velocity analysis, 2) P- to S-wave (converted PS-wave) event correlation, and 3) S-wave velocity analysis. P- to Swave event correlation is done using synthetic seismograms and traveltime tables. Seismic velocities are correlated to gas hydrate and free gas saturation using a Modified Wood equation. I find that Hydrate Ridge is heterogeneous and is weakly anisotropic (maximum of 10%) in some regions caused possibly by the hydrate veins. The P-wave velocity is more sensitive to the saturation of gas hydrates (maximum of 7% of rock volume) and free gas than the S-wave velocity. The S-wave velocity does not show an anomalous increase in the hydrate-bearing sediments. Thus, I conclude that hydrate does not cement sediment grains enough to affect shear properties. It is more likely that the hydrates are formed within the pore space in this region.Geological Science

Crescimento e caracterização de grafeno de grande área e de dissulfureto de molibdénio por deposição química em fase de vapor (CVD)

Doutoramento em Nanociências e NanotecnologiaThe present work is aimed to provide description of experimental part of graphene and two-dimensional structures. State-of-the-art techniques employing chemical vapor deposition (CVD) were used to deposit graphene and two-dimensional structures for their multidisciplinary applications including nano-electronics and semi-conducting industries. All the problems, suggestions and other important issues related to the growth and parameterizing the optimum condition for strictly monolayer to few layers have been briefly discussed. This may give double benefits such as realizing 2D electronic devices with high carrier motilities and understanding the behaviour of these 2D materials upon small ion intercalation. The as synthesized graphene grown on copper (Cu) substrate showed the ideal Raman spectrum with least defect concentration. The presence of very small D peaks confirmed the high quality of graphene crystals with strictly monolayer to few layers. Moreover, High Resolution X-rays Spectroscopy (HR-XPS) analysis showed the high quality graphene with C 1s in sp2 configuration (with binding energy at ~284.8 eV). The absence of other components resembled the purity of graphene and again reconfirmed the good quality of synthesized graphene. The Raman image mapping, demonstrated the full coverage of large area graphene on copper substrate. Additionally, the High Resolution Transmission Electron Microscopy (HRTEM) results reconfirmed that the high crystalline nature with two-type of rotational planes, which may attributed to the presence of wrinkles formed during the transfer of graphene sheet on TEM grids. This thesis is also devoted to the heteroatom doping in order to tune the electronic properties of graphene. Ammonia (NH3) was used herein to provide nitrogen (N) as a source for foreign atom for the doping of pure graphene. Here again, efforts were made to discuss all the problems, suggestions and other important issues related to growth and parameterizing the optimum conditions for in-situ ammonia doping of graphene on Cu. The substrate (thickness of films) playing role in the defect creations was also discussed. Raman results showed the enhanced D and D’ peaks, which confirmed the doping of graphene by NH3. HRXPS showed the C 1s core level centred at a BE of 284.5 eV, ascribed to C sp2 can be co-related with the good quality of C. Thus, in context with the XPS, the graphene grown on 20 µm Cu substrate showed the better nitrogen intercalation in the graphene sheets under the same growing conditions. Two components (substitutional at BE of 401.7 eV and pyridinic at BE of 398.5 eV) were clearly distinguished in the respective N 1s core level. The doping with substitutional type of configuration, involves three nitrogen valence electron forming three σ– bonds, one electron filling the π–states, and the fifth electron entering the π*–states of the conduction band, and altogether provide a strong doping effect. The presented work also reported a study demonstrating an in-situ method for the quantitative characterization of nanoscale electrostatic properties of as-grown multilayer-graphene (MLG) sheets on nickel (Ni) by combining atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). Large area epitaxial MLG sheets were grown on Ni by using CVD technique. The high crystalline nature of MLG sheets on Ni was confirmed by Raman spectroscopy with the FWHM value as low as ~20 cm-1 for G peak. We performed the charge injection (and subsequent charge diffusion over time) on the as synthesized graphene on Ni. The results unveiled that: (i) MLG surface can be either positively or negatively charged through injection process using Pt coated Si-based AFM probes; (ii) the charges can be accumulated and eventually reached to saturated concentrations of (+4.45±0.1) μC/m2 and (−1.3±0.1) μC/m2 , respectively; and (iii) the charge diffusion coefficients on graphene surface were measured to be (1.50±0.05) × 10−16 m2 /s and (0.64±0.05) × 10−16 m2 /s for the positive and the negative charges, respectively. The concerned experiment related to the discovery of charge injection in MLG may pave the way for designing a new class of energy harvesting devices. In addition to this, study also demonstrated a technique for nano-patterning/charge lithography of surface charges by contact electrification, which could be a promising application to create charged nanostructures for next generation graphene based nano-electronic devices. A brief description on the quality of transferred substrate has also been noted. Various substrates such as SiO2/Si and Au substrate have been used. A relative quality comparison between before and after transfer of graphene has been critically described. Results from HRXPS show the iron monolayer interaction with graphene. Lastly, this research also showed the major parameterizing and synthesizing steps, and the work flow for the high quality TMDs materials (such as MoS2) by modifying the current CVD equipment. A thorough review of the fundamental properties as well as methods of synthesis, properties and problems related to the growth of 2D materials was also highlighted. The effect of pressure and other conditions for the growth of high quality were fully described. This study found 50mbar as an optimum pressure for the growth of large area MoS2 having a direct bandgap of 1.6eV. Micro-Raman results clearly showed distinguish E1 2g and A1 g peaks and HRXPS re-confirmed its high quality by the different Mo and S core-level peaks. Additionally, employing Focused ion beam equipped with SEM (scanning electron microscopy) technique (FIB), the present study prepared platinum (Pt) electrodes required for the electrical measurements. The result showed: (i) the ohmic and semi-conducting behavior of the crystals; (ii) the importance of high-quality singlelayer (SL) MoS2 in the semi-conducting industries; and (iii) the potential of high quality SL MoS2 for replacing graphene in near future.O presente trabalho, tem com objetivo promover a descrição da parte experimental da síntese de grafeno e de estruturas bidimensionais (2D). Foram usadas as técnicas já existentes, que aplicam deposição química na fase de vapor (CVD), para a síntese de grafeno e estruturas bidimensionais com aplicações multidisciplinares, como indústrias de nano-eletrónicos e de semicondutores. Todos os problemas, sugestões e questões importantes relacionados com o crescimento e parametrização da condição ótima para formação de estritamente monocamadas a pequenas camadas foram brevemente discutidas. Isto pode trazer benefícios duplos como a produção de dispositivos eletrónicos 2D com altas motilidades de transporte e o entendimento do comportamento dos materiais 2D sujeitos a intercalação iónica. Os grafenos sintetizados no substrato cobre (Cu) apresentaram um espectro ideal de Raman com uma concentração de defeitos menor. A presença de pequenos picos D confirmou a elevada qualidade dos cristais de grafeno com estritamente monocamadas a pequenas cadeias. Além disso, a espectroscopia de Raios-X de alta resolução (HR-XPS) mostrou o grafeno de elevada qualidade com C 1s em configuração sp2 (com energia de ligação a ~284.8 eV). A ausência de outros componentes reforça a pureza e a qualidade do grafeno sintetizado. As imagens de mapping Raman demonstraram a cobertura total do grafeno de elevada área no substrato cobre. Adicionalmente, os resultados de microscopia de transmissão eletrónica de alta resolução (HRTEM) confirmaram a elevada natureza cristalina com dois tipos de planos rotacionais que podem ser atribuídos à presença de rugas durante a transferência de folhas de grafeno nas grelhas de TEM. Esta tese dedica-se também à dopagem heteroatómica do grafeno com o objetivo de alterar as suas propriedades eletrónicas. A amónia (NH3) foi usada como fonte de azoto (N) como átomo externo para a dopagem do grafeno puro. Mais uma vez, foram feitos esforços para discutir todos os problemas, sugestões e outras questões importantes relacionadas com o crescimento e parametrização das condições ótimas para a dopagem in-situ de amónia do grafeno no cobre. O papel do substrato (espessura do filme) na criação de defeitos foi também discutida. Os resultados de Raman mostram o aumento dos picos D e D’, o que confirma a dopagem do grafeno por NH3. Os dados de HRXPS mostraram o pico C 1s centrado a uma energia de ligação (BE) de 284.5 eV, atribuído ao C sp2 que pode ser correlacionado com a boa qualidade do C. Então, de acordo com o XPS, o grafeno que cresceu no substrato Cu 20 µm apresentou uma melhor intercalação do azoto nas folhas de grafeno sob as mesmas condições de crescimento. As duas componentes (substitucional a BE de 401.7 eV e piridínica de 398.5 eV) foram claramente distinguidas no respetivo pico N 1s. A dopagem com o tipo de configuração substitucional envolve três eletrões de valência do nitrogénio formando três ligações σ, um eletrão a preencher os estados π e o quinto eletrão no estado π* da banda de condução que conduzem, no total, a um forte efeito de doping. O presente trabalho também reporta um método in-situ para a caraterização quantitativa das propriedades eletrostáticas na escala nano das folhas de grafeno multicamada (MLG) crescidas no níquel (Ni) por combinação de dados de microscopia de força atómica (AFM) e microscopia de força atómica Kelvin (KPFM). Folhas MLG de larga área epitaxial cresceram no Ni usando a técnica CVD. A elevada natureza cristalina das folhas MLG no níquel foi confirmada por espectroscopia Raman com valor de FWHM tão baixo como ~20 cm-1 para o pico G. Foi feita a injeção de carga (e subsequente difusão de carga com o tempo) no recém sintetizado grafeno no Ni. Os resultados revelaram que : (i) a superfície MLG pode ser carregada quer positivamente quer negativamente pelo processo de injeção usando sondas de Si revestidas de Pt; (ii) as cargas podem ser acumuladas e eventualmente atingir concentrações de saturação de (+4.45±0.1) μC/m2 e (−1.3±0.1) μC/m2 , respetivamente; e (iii) os coeficientes de difusão de carga na superfície medidos foram de (1.50±0.05) × 10−16 m2 /s e (0.64±0.05) × 10−16 m2 /s para as cargas positivas e negativas, respetivamente. As experiências relacionadas com a descoberta de injeção de carga no MLG podem conduzir a uma maneira de desenhar uma nova classe de dispositivos de recolha de energia. Além disso, este estudo também demonstra uma técnica para nano-modelação/litografia de carga das superfícies de carga por eletrificação do contacto, que pode vir a ser uma aplicação promissora para criar nanoestruturas carregadas para a próxima geração de dispositivos nanoeletrónicos baseados em grafeno. Uma breve descrição da qualidade dos substratos transferidos foi também explorada. Foram usados vários substratos, como SiO2/Si e Au. Uma comparação qualitativa da qualidade entre a transferência do grafeno antes e depois foi criticamente descrita. Os resultados de HRXPS mostram a interação da camada de ferro com o grafeno. Por fim, esta pesquisa também mostrou as principais etapas de parametrização e síntese, e o fluxo de trabalho para materiais de elevada qualidade TMDs (como MoS2), por modificação do actual aparelho de CVD. Uma revisão completa das propriedades fundamentais, assim como do método de síntese, propriedades e problemas relacionados com o crescimento de materiais 2D foram também salientados. O efeito da pressão e outras condições para o crescimento de elevada qualidade foram completamente descritos. Este estudo indica que a pressão ótima para o crescimento de uma larga área MoS2 com uma bandgap direta de 1.6 eV é de 50 mbar. Os resultados de micro-Raman mostram claramente a distinção de picos E1 2g e A1 g picos e os dados de HR-XPS reconfirmam a sua elevada qualidade através de diferentes picos de nível interno de Mo and S. Além disso, através do uso da técnica microscopia eletrónica de varrimento (SEM) com feixe de iões focalizados (FIB), foram preparados elétrodos de platina necessários para medidas elétricas. O resultado mostrou: (i) o comportamento óhmico e semi-condutor dos cristais; (ii) a importância das monocamadas de elevada qualidade (SL) MoS2 nas indústrias de semi-condutores e (iii) o potencial das SL MoS2 de elevada qualidade para substituir o grafeno num futuro próximo

Fabrication of Pd/Pd-Alloy Films by Surfactant Induced Electroless Plating for Hydrogen Separation from Advanced Coal Gasification Processes

Dense Pd, Pd-Cu and Pd-Ag composite membranes on microporous stainless steel substrate (MPSS) were fabricated by a novel electroless plating (EP) process. In the conventional Pd-EP process, the oxidation-reduction reactions between Pd-complex and hydrazine result in an evolution of NH{sub 3} and N{sub 2} gas bubbles. When adhered to the substrate surface and in the pores, these gas bubbles hinder uniform Pd-film deposition which results in dendrite growth leading to poor film formation. This problem was addressed by introducing cationic surfactant in the electroless plating process known as surfactant induced electroless plating (SIEP). The unique features of this innovation provide control of Pd-deposition rate, and Pd-grain size distribution. The surfactant molecules play an important role in the EP process by tailoring grain size and the process of agglomeration by removing tiny gas bubbles through adsorption at the gas-liquid interface. As a result surfactant can tailor a nanocrystalline Pd, Cu and Ag deposition in the film resulting in reduced membrane film thickness. Also, it produces a uniform, agglomerated film structure. The Pd-Cu and Pd-Ag membranes on MPSS support were fabricated by sequential deposition using SIEP method. The pre- and post-annealing characterizations of these membranes (Pd, Pd-Cu and Pd-Ag on MPSS substrate) were carried out by SEM, EDX, XRD, and AFM studies. The SEM images show significant improvement of the membrane surface morphology, in terms of metal grain structures and grain agglomeration compared to the membranes fabricated by conventional EP process. The SEM images and helium gas-tightness studies indicate that dense and thinner films of Pd, Pd-Cu and Pd-Ag membranes can be produced with shorter deposition time using surfactant. H{sub 2} Flux through the membranes fabricated by SIEP shows large improvement compared to those by CEP with comparable permselectivity. Pd-MPSS composite membrane was subjected to test for long term performance and thermal cycling (573 - 723 - 573 K) at 15 psi pressure drop for 1200 hours. Pd membranes showed excellent hydrogen permeability and thermal stability during the operational period. Under thermal cycling (573 K - 873 K - 573 K), Pd-Cu-MPSS membrane was stable and retained hydrogen permeation characteristics for over three months of operation. From this limited study, we conclude that SIEP is viable method for fabrication of defect-free, robust Pd-alloy membranes for high-temperature H{sub 2}-separation applications

Detection of Sybil attack in vehicular ad hoc networks by analyzing network performance

Vehicular ad hoc network (VANET) is an emerging technology which can be very helpful for providing safety and security as well as for intelligent transportation services. But due to wireless communication of vehicles and high mobility it has certain security issues which cost the safety and security of people on the road. One of the major security concerns is the Sybil attack in which the attacker creates dummy identities to gain high influence in the network that causes delay in some services and fake voting in the network to misguide others. The early detection of this attack can prevent people from being misguided by the attacker and save them from getting into any kind of trap. In this research paper, Sybil attack is detected by first applying the Poisson distribution algorithm to predict the traffic on the road and in the second approach, analysis of the network performance for packet delivery ratio (PDR) is performed in malign and benign environment. The simulation result shows that PDR decreases in presence of fake vehicles in the network. Our approach is simple and effective as it does not require high computational overhead and also does not violate the privacy issues of people in the network

Simulation of Field Oriented Control Variable Frequency Induction Motor Drive

now days replacing the DC motor with Induction motors are requirement of each plant due to very high operating cost associated with DC motors. To achieve the better dynamic response like as DC motors IM drives are developed. Field Oriented Control based drives with pulse width modulation technique for operation of inverter. In field oriented control method whole induction motor is converted into mathematical DC motor model and control like a dc motor. by Feedback control loop system a gate pulse is generated for the pulse width modulated inverter and according to that voltage and frequency to be controlled. These new technique improve the torque speed characteristics and reduced the response time. This results a very good speed controlling of induction motor and required speed torque characteristic

Nutritional assessment of rural children (6–12 years) of north bihar: A cross-sectional study

Objective: Malnutrition is one of the most common causes of morbidity and mortality among children and adolescent throughout the world. The present study was undertaken to assess the nutritional status in terms of the prevalence of stunting and thinness among rural children of North Bihar. Methods: The present community-based cross-sectional study was conducted on 1263 rural children (674 male and 589 female) with the age group of 6–12 years, during the period from January 2018 to March 2018. Age was recorded in completed year; height and weight were measured in centimeter and kilogram, respectively. Body mass index (BMI) was calculated using standard equation. Results: The nutritional status in terms of the prevalence of stunting and thinness was found to be 18.2% and 23.8%, respectively, among studied children. Stunting was significantly higher among girls (23.1%) in comparison to boys (13.9%). BMI was significantly associated with age, socioeconomic status and mother’s literacy. Conclusions: Anthropometric assessment indicates that the malnutrition is still a major problem among children (6–12 years) of North Bihar. The major factors identified for this problem is illiteracy of mother and socioeconomic status of the family

Optimazation and performance analysis of gas turbine blade by implimenting cooling techniques

Gas turbine are extensively used for aircraft propulsion, land-based power generation, thermal efficiency and power output of gas turbine increase with increasing turbine rotor inlet temperature (RIT) the current RIT level in advanced gas turbine is far above the melting point of the blade material. Therefore, along with high temperature material developed a sophisticated cooling scheme must be developed for continuous safe operation of gas turbine with high performance ,gas turbine blades are cooled internally and externally for increase the life of blade turbine. This paper is focused on internal cooling of blade and vanes on gas turbine, internal cooling is achieved by passing the coolant through several enhanced serpentine passages inside the blade and extracting the heat from the outside of the blade. Jet impingement cooling, rib tabulators, dimple and pin fin cooling are all utilized as method of internal cooling, which are presented in this article. Due to the different heat transfer enhancement and pressure drop, they are used in specific part of the blades and vanes on the gas turbine

A CROSS-SECTIONAL STUDY TO ESTIMATE THE PREVALENCE OF HYPERTENSION IN URBAN FIELD PRACTICE AREA OF MEDICAL COLLEGE IN METROPOLITAN CITY OF INDIA

Objectives: The objectives of the study were to estimate the prevalence of hypertension in people above 35 years and to study the sociodemographic profile of the study subjects. Methods: The study was a cross-sectional study conducted in urban field practice area of medical college. Five chawls were selected by simple random sampling out of 42 chawls. Males and females above 35 years of age living in study area formed a sample frame. Sample size was calculated and it was 667. As per the protocol, informed written consent and demographic details with clinical data were obtained from the patients. Results: A total of 667 participants were included from five chawls. Maximum number of participants, that is, 37%; were from the age group of 35 to 44, consisting of 41% males and 59% females. Around 67% of study respondents belonged to the age group of 35–54 years. Around 3/4th of study respondents had studied up to primary school and secondary and high school. Out of 263 males, 37%, that is, 98 respondents were hypertensive, and out of 404 females, 152, that is, 38% were hypertensive. Hence, the total prevalence of hypertension in this study was 37.5%. Conclusion: Hypertension is the new era pandemic which is the leading cause of morbidity and mortality in the world and is ranked third as a cause of disability-adjusted life years. To control hypertension, it is imperative to identify and modify its risk factors