Literatura académica sobre el tema "Internal filed NMR"
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Artículos de revistas sobre el tema "Internal filed NMR"
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Bernal, O. O., M. E. Moroz, H. G. Lukefahr, D. E. MacLaughlin, J. A. Mydosh, A. A. Menovsky y C. Ortiz. "Ambient-pressure NMR in URu2Si2: internal-field anisotropy". Journal of Magnetism and Magnetic Materials 272-276 (mayo de 2004): E59—E60. http://dx.doi.org/10.1016/j.jmmm.2003.11.159.
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XIE, Ran-Hong y Li-Zhi XIAO. "NMR Logging Probing the Internal Magnetic Field Gradients of Rocks". Chinese Journal of Geophysics 52, n.º 3 (mayo de 2009): 650–56. http://dx.doi.org/10.1002/cjg2.1386.
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AKAY, Cengiz y Handan ENGİN KİRİMLİ. "NMR Spectroscopy in the Earth's Magnetic Field". Bitlis Eren Üniversitesi Fen Bilimleri Dergisi 12, n.º 2 (22 de mayo de 2023): 428–34. http://dx.doi.org/10.17798/bitlisfen.1232239.
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Magnetic imaging systems used today are quite expensive and are generally used for medical purposes. Apart from this purpose, there are many scientific fields of study whose internal structure is desired to be displayed. Especially in science, different from the techniques used to understand the internal structure of matter, magnetic imaging techniques are also needed. Therefore, the interest in more useful and smaller magnetic imaging systems is increasing. For this purpose, studies on magnetic particle imaging and magnetic resonance imaging techniques have gained momentum. The magnetic resonance imaging technique, which is one of the magnetic imaging systems based on the NMR phenomenon, has passed through numerous stages and has become smaller and more useful. This study examines the basic components of the NMR images made in the earth's magnetic field for different liquids, the T1 and T2 proton relaxation parameters, and the technique of the obtained two-dimensional images with the EFNMR system.
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Isaac-Lam, Meden F. "Determination of Alcohol Content in Alcoholic Beverages Using 45 MHz Benchtop NMR Spectrometer". International Journal of Spectroscopy 2016 (17 de agosto de 2016): 1–8. http://dx.doi.org/10.1155/2016/2526946.
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Alcohol or ethanol is considered the most widely used recreational drug worldwide, and its production, consumption, and sale are strictly regulated by laws. Alcohol content of alcoholic beverages (wine, beers, and spirits) is about 3–50% v/v. Analytical methods to determine the alcohol content must be reliable, precise, and accurate. In this study, the amount of ethanol in several alcoholic beverages was determined using a 45 MHz low-field benchtop NMR (nuclear magnetic resonance) spectrometer. Internal standard and standard addition analytical methods were utilized to quantify ethanol. For both methods, acetic acid or acetonitrile was used as internal standard to quantify alcohol content by using the peak area corresponding to the methyl peaks of ethanol, acetic acid, or acetonitrile. Results showed that internal standard method gave values of percent alcohol that are in close agreement with the indicated label as confirmed by running the samples in a 400 MHz high-field NMR spectrometer using acetic acid as internal standard. This study demonstrates the utility of a benchtop NMR spectrometer that can provide an alternative technique to analyze percent alcohol in alcoholic products.
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Kirkland, Catherine M., Julia R. Krug, Frank J. Vergeldt, Lenno van den Berg, Aldrik H. Velders, Joseph D. Seymour, Sarah L. Codd, Henk Van As y Merle K. de Kreuk. "Characterizing the structure of aerobic granular sludge using ultra-high field magnetic resonance". Water Science and Technology 82, n.º 4 (27 de julio de 2020): 627–39. http://dx.doi.org/10.2166/wst.2020.341.
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Abstract Despite aerobic granular sludge wastewater treatment plants operating around the world, our understanding of internal granule structure and its relation to treatment efficiency remains limited. This can be attributed in part to the drawbacks of time-consuming, labor-intensive, and invasive microscopy protocols which effectively restrict samples sizes and may introduce artefacts. Time-domain nuclear magnetic resonance (NMR) allows non-invasive measurements which describe internal structural features of opaque, complex materials like biofilms. NMR was used to image aerobic granules collected from five full-scale wastewater treatment plants in the Netherlands and United States, as well as laboratory granules and control beads. T1 and T2 relaxation-weighted images reveal heterogeneous structures that include high- and low-density biofilm regions, water-like voids, and solid-like inclusions. Channels larger than approximately 50 μm and connected to the bulk fluid were not visible. Both cluster and ring-like structures were observed with each granule source having a characteristic structural type. These structures, and their NMR relaxation behavior, were stable over several months of storage. These observations reveal the complex structures within aerobic granules from a range of sources and highlight the need for non-invasive characterization methods like NMR to be applied in the ongoing effort to correlate structure and function.
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Nestle, Nikolaus, Asal Qadan, Petrik Galvosas, Wolfgang Süss y Jörg Kärger. "PFG NMR and internal magnetic field gradients in plant-based materials". Magnetic Resonance Imaging 20, n.º 7 (septiembre de 2002): 567–73. http://dx.doi.org/10.1016/s0730-725x(02)00529-5.
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Johnson, Andrew y Hugh Daigle. "Nuclear magnetic resonance secular relaxation measurements as a method of extracting internal magnetic field gradients and pore sizes". Interpretation 4, n.º 4 (1 de noviembre de 2016): T557—T565. http://dx.doi.org/10.1190/int-2015-0127.1.
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Nuclear magnetic resonance (NMR) has been used as a common and powerful tool for petrophysical investigation of fluid-bearing porous media. A major complication of NMR analysis occurs, however, when diffusion of fluid protons through magnetic field heterogeneities becomes nonnegligible. A quantity called the secular relaxation rate ([Formula: see text]) has been defined as the difference in transverse and longitudinal relaxation rates ([Formula: see text]-[Formula: see text]) and can be shown to isolate the effects of diffusion as a function of pore system parameters. We have developed results that extract internal magnetic field gradient strengths based on changes in [Formula: see text] as a function of the NMR interecho spacing. We also indicated that an optimization algorithm can be used to invert for volumetrically weighted mean pore sizes. The benefit of these types of analyses is to provide simple methodologies for inferring the average strengths of internal magnetic field gradients and pore sizes from NMR measurements without the need for independent measurements of pore size, such as from mercury injection porosimetry. In addition, secular relaxation analysis removes complicating effects provided by bulk fluid and other nondiffusion relaxation mechanisms.
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Boddenberg, B. y G. Neue. "Spin I = 1 NMR Patterns for the Case of Twofold Internal Spin Interactions". Zeitschrift für Naturforschung A 42, n.º 9 (1 de septiembre de 1987): 948–56. http://dx.doi.org/10.1515/zna-1987-0907.
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An operator formalism is developed which allows a convenient calculation of high field spin I = 1 solid state NMR powder spectra for the case that the spins are acted on not only electrically via an electric field gradient tensor but also magnetically via a shielding tensor. Examples of practical applications in the field of surface science are given.
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Brox, Timothy I., Mark L. Skidmore y Jennifer R. Brown. "Characterizing the internal structure of laboratory ice samples with nuclear magnetic resonance". Journal of Glaciology 61, n.º 225 (2015): 55–64. http://dx.doi.org/10.3189/2015jog14j133.
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AbstractDue to solute impurities and freezing-point depression in polycrystalline ice, a complicated and dynamic network of liquid water forms within the solid ice matrix at the boundaries between ice crystal grains. Impurity concentrations, temperature and pressure influence this network structure and impact physical, transport and rheological properties of ice. However, the nature of this internal network structure is not fully understood. Here we utilize nuclear magnetic resonance (NMR) measurements of diffusion and magnetic relaxation to study the geometry and interconnectivity of the liquid-filled network in laboratory ice, formed from a 7 g L−1 NaCl solution, and its evolution due to recrystallization processes. Additionally, we apply these NMR measurements to observe the impact on ice microstructure of an ice-binding protein (IBP) excreted by the V3519-10 organism (Flavobacteriaceae family) isolated from the Vostok ice core in Antarctica. Recrystallization inhibition was observed as a function of IBP concentration. This work demonstrates the utility of advanced NMR techniques for applications to ice microstructure and has broader implications for understanding geophysical properties of cryospheric systems.
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Mohnke, O. y N. Klitzsch. "Microscale Simulations of NMR Relaxation in Porous Media Considering Internal Field Gradients". Vadose Zone Journal 9, n.º 4 (noviembre de 2010): 846–57. http://dx.doi.org/10.2136/vzj2009.0161.
Texto completoTesis sobre el tema "Internal filed NMR"
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Van, Zyl Derrick Steven. "SQUID detected low-field NMR for the evaluation of internal fruit quality". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5208.
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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Assessing the quality of fruit has become vitally important for farmers and growers. With retailers placing ever stricter requirements on fresh produce, growers have to spend a greater amount of time and effort sorting and grading their harvest. Increasingly, vendors are placing requirements not only on external factors like colour, and firmness, but on internal quality factors such as sugar content and acidity, because, although consumers buy fruit based on their external appearances, the taste of the fruit is what determines whether the consumer will buy again. Different techniques exist that probe the internal quality of fruit non-destructively. The technique most widely used today is Near Infrared Spectroscopy. This technique is powerful, but has certain limitations such as poor reliability and the need for constant recalibration. This thesis suggests an alternative method for evaluating internal fruit quality based on low-field nuclear magnetic resonance detected by superconducting quantum interference devices. It introduces the theory of SQUIDs and NMR, and evaluates the use of SQUID detected NMR spectroscopy as a method for determining the internal quality of fruit. The fabrication techniques and processes are explained in detail and a design for a SQUID detected NMR spectrometer is given. Relevant simulations and simulation results are also given. No working SQUID could be fabricated and, as such, no working NMR spectrometer was demonstrated. This thesis serves as a reference work for future research.
AFRIKAANSE OPSOMMING: Bepaling van die gehalte van vrugte het vir boere uiters belangrik geword. Met kleinhandelaars wat al strenger vereistes plaas op vars produkte moet boere meer tyd en inspanning bestee met die sortering en gradering van hul oes. Handelaars plaas nie net vereistes op eksterne kwaliteitsfaktore soos kleur en fermheid nie, maar begin al hoe strenger vereistes plaas op interne kwaliteitsfaktore soos suikerinhoud en suurgehalte, want, hoewel verbruikers vrugte koop op grond van hul eksterne kwaliteitsfaktore, is dit die smaak van die vrug wat bepaal of die verbruiker weer die vrug sal koop. Verskillende tegnieke bestaan wat die interne kwaliteit van vrugte op ’n nie-destruktiewe manier kan bepaal. Die mees algemene tegniek is Naby Infrarooi Spektroskopie. Hierdie tegniek is kragtig maar het sekere beperkings soos swak betroubaarheid en die noodsaaklikheid van konstante herkalibrasie. Hierdie tesis stel ’n alternatiewe metode vir die evaluering van interne vrugkwaliteit gebaseer op lae-veld kernmagnetiese resonans waargeneem deur supergeleidende kwantum inmenging toestelle voor. Dit stel die teorie van SKWITs en KMR bekend, en evalueer die gebruik van SKWIT-bespeurde KMR spektroskopie as ’n metode vir die bepaling van die interne kwaliteit van vrugte. Die fabrikasie tegnieke en prosesse word in detail verduidelik en ’n ontwerp vir ’n SWKIT opgevangde KMR spektrometer word gegee. Toepaslike simulasies en simulasie resultate word ook gegee. Geen werkende SKWIT kon vervaardig word nie en as gevolg daarvan kon geen werkende KMR spektrometer gedemonstreer word nie. Hierdie tesis dien as ’n naslaan werk vir toekomstige navorsing.
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Andreev, Andrey. "Résonance Magnétique Nucléaire du 59Co en champ interne, application aux catalyseurs et à des structures similaires". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066371/document.
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Du fait de leur ferromagnétisme, les nanoparticules de Cobalt se prêtent à la réalisation d’expérience de Résonance Nucléaire Magnétique en Champ Interne du 59Co (RMN-CI). Dans ce manuscrit, nous présentons tout d’abord une description générale de la RMN-CI dans le cadre du modèle de Bloch. Concernant plus précisément le Co(0), passant en revue la littérature, nous insistons sur les aspects controversés et les progrès récents en la matière. Une attention particulière est portée à la caractérisation du Co dans les catalyseurs Fischer-Tropsch (FT) qui représente aujourd’hui un champ majeur d’application de la technique ; l’histoire de la catalyse FT et une brève revue de la synthèse et de la structure de ces catalyseurs sont donc présentées. Concernant le travail expérimental, celui-ci est structuré de la façon suivante. Tout d’abord, des échantillons modèles sont étudiés afin de mettre en place un modèle interprétatif basé sur les contributions structurales (fcc, hcp, sfs) et magnétiques (domaines, parois de domaines, mono-domaines) à la résonance. Nous passons ensuite à l’étude in situ par RMN-CI de la stabilité thermique de nanoparticules supportées sur du β-SiC. La transition hcp/fcc est observée dans la gamme de température 600-650 K. Ceci étant posé, des structures plus complexes ont été étudiées. Nous avons révélé la structure de la partie métallique de céramiques modifiées Co-Al-O. Finalement, la structure et la stabilité de particules de Cobalt métallique déposées sur et dans des nanotubes de carbone ont été étudiées. Ces structures hybrides originales ont été examinées par RMN-CI, microscopie électronique en transmission et DRX synchrotron in situThis manuscript is devoted to the study of different catalysis-related materials by Internal Field 59Co Nuclear Magnetic Resonance (IF-NMR). The principles of IF-NMR are stated, based on the Bloch model, which gives a good insight into the internal field NMR mechanism. Further, a short description of the possible range of materials than can be studied by IF-NMR is provided with a particular emphasis on Co Fischer-Tropsch synthesis catalysts. The study of a model sample used to assess our understanding of IF-NMR spectra is included. This model is based on separating the structural (fcc, hcp, and sfs) and magnetic (domains, domain walls, and single-domain particles) contributions. Our experimental work uncovers the thermal stability of small Co nanoparticles probed in situ by IF-NMR. Co(0) supported on β-SiC is studied within the 300-850 K temperature range. The line position and width are mainly determined by magnetic properties, whereas the absolute and relative NMR intensities give crucial information regarding the Co particle stability. A study of Fischer-Tropsch catalysts synthesized by non-conventional co-precipitation routes on different modified aluminum oxides is presented. The IF-NMR application to Co-Al-O ceramic materials provided unique information on the metallic cermet part of the sample. The structure and stabilization of different size Co(0) nanoparticles on multi-walled carbon nanotubes have been studied. These hybrid structures were examined by IF-NMR, HRTEM, and in situ synchrotron XRD, which provide crucial information on Co particles reduction, stability and structures
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Pu, Mingming. "Investigations of the Mechanism for Activation of Bacillus Thuringiensis Phosphatidylinositol-specific Phospholipase C". Thesis, Boston College, 2009. http://hdl.handle.net/2345/1179.
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Thesis advisor: Mary F. RobertsThesis advisor: Steven D. Bruner
The bacterial phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis is specifically activated by low concentrations of a non-substrate lipid, phosphatidylcholine (PC), presented as an interface. However, if the PC concentration in the interface is too high relative to substrate, the enzyme exhibits surface dilution inhibition. Understanding this bacterial enzyme, which shares many kinetic features with the larger and more complex mammalian PI-PLC enzymes, requires elucidating the mechanism for PC activation and inhibition. Various techniques were applied to study the interaction of the protein with vesicles composed of both the activator lipid PC and the substrate lipid (or a nonhydrolyzable analogue). Fluorescence correlation spectroscopy (FCS), used to monitor bulk partitioning of the enzyme on vesicles, revealed that both the PC and the substrate analogue are required for the tightest binding of the PI-PLC to vesicles. Furthermore, the tightest binding occurred at low mole fractions of substrate-like phospholipids. Field cycling 31P NMR (fc-P-NMR) spin-lattice relaxation studies provided information on how bound protein affects the lipid dynamics in mixed substrate analogue/PC vesicles. The combination of the two techniques could explain the enzyme kinetic profile for the PC activation and surface dilution inhibition: small amounts of PC in an interface enhanced PI-PLC binding to substrate-rich vesicles while high fractions of PC tended to sequester the enzyme from the bulk of its substrate leading to reduced specific activity. FCS binding profiles of mutant proteins were particularly useful in determining if a specific mutation affected a single or both phospholipid binding modes. In addition, an allosteric PC binding site was identified by fc-P-NMR and site directed spin labeling. A proposed model for PC activation suggested surface-induced dimerization of the protein. Experiments in support of the model used cysteine mutations to create covalent dimers of this PI-PLC. Two of these disulfide linked dimers, formed from W242C or S250C, exhibited higher specific activities and tighter binding to PC surfaces. In addition, single molecule total internal reflection fluorescence microscopy was used to monitor the off-rate of PI-PLC from surface tethered vesicles, providing us with a direct measure of off-rates of the protein from different composition vesicles
Thesis (PhD) — Boston College, 2009
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Zhang, Qian. "NMR formulation evaluation: Hydrogen index, wettability and internal field gradients". Thesis, 2001. http://hdl.handle.net/1911/18055.
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Nuclear Magnetic Resonance (NMR) well logging is finding wide use in formation evaluation. In most cases, it is adequate to use default parameters and interpretation methods to get formation properties. In this work, we will investigate three exceptional cases: The departure of the hydrogen index ( HI) of live crude oils from unity due to high solution gas:oil ratio; The wettability alteration from water-wet condition to some degree of mixed wettability for sandstones; Significant diffusion effect on NMR spin-spin relaxation time (T2) measurements due to internal field gradients.
A new correlation is proposed to express HI as a function of density and hydrogen:carbon ratio. The HI of live crude oils can be calculated from PVT data and ambient measurements.
Wettability alteration is interpreted for sandstones from NMR analysis. Bentheim and Berea were water-wet with refined oil but became mixed-wet with SMY crude oil and brine at Swir after aging. North Burbank sandstones were even mixed-wet with refined oil due to the pore lining chlorite clay flakes. NMR wettability analysis is consistent with other quantitative wettability alteration indicators.
Strong internal field gradients are measured for both chlorite-coated North Burbank sandstones and chlorite slurries. The distributions of internal field gradients are analytically solved through potential theory. High gradients are concentrated around the tips of the clay flakes. Mean gradient values from analytical solutions using a clay width of 0.2 mum are close to the experimental results.
The combined effects of diffusion, constant gradient, and restricted 1-D geometry on Carr-Purcell_Meiboom_Gill (CPMG) measurement are evaluated numerically. The parameter space that defines the relaxation process is reduced to only two dimensionless groups: D* and tau*. The hypothesis that the dimensionless normalized magnetization relaxes as a single exponential with a constant dimensionless relaxation time T*2 is justified for most regions of the parameter space. The location of the boundaries between different relaxation regimes defined in the analytical analysis is challenged by the numerical results. After adjustment of boundaries, numerical simulation results and analytical solutions match each other for every relaxation regime except for near the boundaries. A procedure to estimate fluid diffusivity and system length is illustrated.
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Rohilla, Neeraj. "Transverse relaxation in sandstones due to the effect of internal field gradients and characterizing the pore structure of vuggy carbonates using NMR and Tracer analysis". Thesis, 2013. http://hdl.handle.net/1911/72033.
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Nuclear magnetic resonance (NMR) has become an indispensable tool in petroleum industry for formation evaluation. This dissertation addresses two problems.
• We aim at developing a theory to better understand the phenomena of
transverse relaxation in the presence of internal field gradients.
• Chracterizing the pore structure of vuggy carbonates.
We have developed a two dimensional model to study a system of claylined pore. We have identified three distinct relaxation regimes. The interplay of three time parameters characterize the transverse relaxation in three different regimes. In future work, useful geometric information can be extracted from from SEM images
and the pore size distribution analysis of North Burbank sandstone to simulate transverse relaxation using our 2-D clay flake model and study diffusional coupling in the presence of internal field gradients.
Carbonates reservoirs exhibit complex pore structure with micropores and macropores/vugs. Vuggy pore space can be divided into separate-vugs and touching-vugs, depending on vug interconnection. Separate vugs are connected only through interparticle pore networks and do not contribute to permeability.
Touching vugs are independent of rock fabric and form an interconnected pore
system enhancing the permeability. Accurate characterization of pore structure of carbonate reservoirs is essential for design and implementation of enhanced
oil recovery processes. However, characterizing pore structure in carbonates is a complex task due to the diverse variety of pore types seen in carbonates and extreme pore level heterogeneity. The carbonate samples which are focus of this
study are very heterogeneous in pore structures. Some of the sample rocks are breccia and other samples are fractured. In order to characterize the pore size in
vuggy carbonates, we use NMR along with tracer analysis. The distribution of porosity between micro and macro-porosity can be measured by NMR. However, NMR cannot predict if different sized vugs are connected or isolated. Tracer analysis is used to characterize the connectivity of the vug system and matrix.
Modified version of differential capacitance model of Coats and Smith (1964) and a solution procedure developed by Baker (1975) is used to study dispersion and
capacitance effects in core-samples. The model has three dimensionless groups:
1) flowing fraction (f), 2) dimensionless group for mass transfer (NM) characterizing
the mass transfer between flowing and stagnant phase and 3) dimensionless group for dispersion (NK) characterizing the extent of dispersion. In order to obtain
unique set of model parameters from experimental data, we have developed an algorithm which uses effluent concentration data at two different flow rates to
obtain the fitted parameter for both cases simultaneously. Tracer analysis gives
valuable insight on fraction of dead-end pores and dispersion and mass transfer
effects at core scale. This can be used to model the flow of surfactant solution
through vuggy and fractured carbonates to evaluate the loss of surfactant due to
dynamic adsorption.
Libros sobre el tema "Internal filed NMR"
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Takahashi, Shinnosuke. The Translocal Island of Okinawa. Bloomsbury Publishing Plc, 2024. http://dx.doi.org/10.5040/9781350411555.
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The Translocal Island of Okinawa reveals the underrepresented memories, visions and actions that are involved in the making of Okinawan resistance against its subordinated status under the US-Japan security system beyond the narrowly defined political, cultural and geographical borders of locality. As Okinawa’s base politics is a problem deeply rooted in the context of East Asia, so is the history of the people’s protest movement. The issue examined in this book is the arbitrary distinction of scale between ‘local’, which tends to be employed for a particular territory demarcated by a cohesive culture, and ‘regional’, a larger area that consists of myriad localities. Locality, Shinnosuke Takahashi here argues, is neither self-evident, fixed nor homogenous but is established through historical processes that involve interaction, conflict and negotiation of individuals and communities across territorial and cultural boundaries. This book reveals the novel concept of Okinawa as a translocal island which offers a way to understand locality in the context of Okinawan activism as a product of multiple cultural and human flows, as opposed to the conventional way of framing the local community as fixed, internally cohesive and rigidly bordered. It makes an exciting contribution to the field of modern Japanese and East Asian studies by stimulating discussions on the richness and scale of local civic activism that is increasingly becoming a key political feature of the East Asian region
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Radu, Roxana. Negotiating Internet Governance. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198833079.001.0001.
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What is at stake for how the Internet continues to evolve is the preservation of its integrity as a single network. In practice, its governance is neither centralized nor unitary; it is piecemeal and fragmented, with authoritative decision-making coming from different sources simultaneously: governments, businesses, international organizations, technical and academic experts, and civil society. Historically, the conditions for their interaction were rarely defined beyond basic technical coordination, due at first to the academic freedom granted to the researchers developing the network and, later on, to the sheer impossibility of controlling mushrooming Internet initiatives. Today, the search for global norms and rules for the Internet continues, be it for cybersecurity or artificial intelligence, amid processes fostering the supremacy of national approaches or the vitality of a pluralist environment with various stakeholders represented. This book provides an incisive analysis of the emergence and evolution of global Internet governance, unpacking the complexity of more than 300 governance arrangements, influential debates, and political negotiations over four decades. Highly accessible, this book breaks new ground through a wide empirical exploration and a new conceptual approach to governance enactment in global issue domains. A tripartite framework is employed for revealing power dynamics, relying on: (a) an extensive database of mechanisms of governance for the Internet at the global and regional level; (b) an in-depth analysis of the evolution of actors and priorities over time; and (c) a key set of dominant practices observed in the Internet governance communities. It explains continuity and change in Internet-related negotiations, opening up new directions for thinking and acting in this field.
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Chong, Wu-Ling. Chinese Indonesians in Post-Suharto Indonesia. Hong Kong University Press, 2018. http://dx.doi.org/10.5790/hongkong/9789888455997.001.0001.
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This book examines the complex situation of ethnic Chinese Indonesians in post-Suharto Indonesia, focusing on Chinese in two of the largest Indonesian cities, Medan and Surabaya. The fall of Suharto in May 1998 led to the opening up of a democratic and liberal space to include a diversity of political actors and ideals in the political process. However, due to the absence of an effective, genuinely reformist party or political coalition, predatory politico-business interests nurtured under the New Order managed to capture the new political and economic regimes. As a result, corruption and internal mismanagement continue to plague the bureaucracy in the country. The indigenous Indonesian population generally still perceives the Chinese minority as an alien minority who are wealthy, selfish, insular and opportunistic; this is partially due to the role some Chinese have played in perpetuating corrupt business practices. As targets of extortion and corruption by bureaucratic officials and youth/crime organisations, the Chinese are neither merely passive bystanders of the democratisation process in Indonesia nor powerless victims of corrupt practices. By focusing on the important interconnected aspects of the role Chinese play in post-Suharto Indonesia, via business, politics and civil society, this book argues, through a combination of Anthony Giddens’s structure-agency theory as well as Pierre Bourdieu’s notion of habitus and field, that although the Chinese are constrained by various conditions, they also have played an active role in shaping these conditions.
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Sahay, Sundeep, T. Sundararaman y Jørn Braa. Public Health Informatics. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780198758778.001.0001.
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Rapid and unpredictable developments in health policies, technologies, disease profiles, institutional environments, and their inter-connections have significant implications on how we design, develop, implement, and use health information systems (HIS) in low and middle-income countries (LMICs). Our current systems have heightened expectations but have proven largely incapable of meeting these new challenges. Nor have they been able to effectively leverage upon the new opportunities that are emerging, such as through the cloud, big data, the proliferation of mobile devices and the Internet of Things, and also the increasing array of new open source software solutions being made available through global development communities. What is required to try and address these challenges and opportunities? This book proposes the ‘Expanded PHI’ (public health informatics) perspective as a way forward, and through the various chapters first seeks to define it, and then apply it to analyse the following key problematics facing public health informatics in the domains of research, practice, and policy: use of information; integration of systems; leveraging cloud computing and big data; design and building of institutions that facilitate; managing complexity; evolving governance mechanisms and standards; responding to the new challenges thrown up by universal health coverage and Sustainable Development Goals; and building synergies between health systems strengthening and health information strengthening efforts. In defining the scope of Expanded PHI, the field of public health informatics is first situated within an informatics context, and then within public health and finally within the context of changing global health policies. Drawing from these contextualizations, the design principles for Expanded PHI are elucidated, based primarily on a social systems perspective, where the health of populations is kept as the central purpose and a participatory and incremental nature of change as the primary strategy.
Capítulos de libros sobre el tema "Internal filed NMR"
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Echeverría, Gabriel. "Differently Similar: The Quest for Migration Control in the Netherlands and Spain". En IMISCOE Research Series, 149–65. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-26002-5_8.
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AbstractIn relation to migration controls, the perceptions of the public opinion, but also the accounts of a good part of the specialized literature in this field, have often portraited the Netherlands and Spain as opposite examples. The Northern European country has been imagined as a paradigmatic case of strong control enforcement, while the Southern as one of weak control measures. Because of this type of analysis, a more general idea of a North/South divide, which sums up in a dichotomic picture the different approaches to migration in the continent, has become the hegemonic interpretative framework. However, whereas dichotomic pictures may be of help when the goal is to produce clear-cut and simple representations (or political and moral judgements), they are invariably misguiding when the goal is to understand reality. Migration policies and their enforcement are neither clear-cut, nor simple. Countries display in this field a very dynamic and fragmented conduct that may generate at times convergences or divergences with the others. This chapter will focus on internal control policies in the Netherlands and Spain. The analysis will show an ambiguous reality, complex enough to escape a dichotomist description in terms of opposites.
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Ali, S. S. "Superconductors for Medical Applications". En Superconductors, 211–29. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644902110-12.
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Superconductivity plays a vital role in advanced medical diagnostic as well as in treatment of cancer. Smaller sized superconducting cyclotrons are developing as efficient techniques with carbon ions and protons for external beam therapy. This equipment further gives benefits of less cost and due to smaller size it is far easier to handle. Nowadays, superconductivity has been used commercially in numerous applications in medical sciences including low-temperature superconducting (LTS) materials and high field magnets in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), magnetic gene transfer, magnetic drug delivery system and cancer and internal hemorrhages detection. Almost all commercial medical systems based on superconductivity use LTS and the majority uses NbTi wires or superconducting quantum interference device (SQUID) made of LTS material.
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Minear, Roger A. y Mark A. Nanny. "Solution and Condensed Phase Characterization". En Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0012.
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Improvements in nuclear magnetic resonance (NMR) instrumentation, magnetic field strength, pulse sequences, and computer technology and software have increased the range of applications and specific elements available for study by NMR. The five chapters in this Part clearly indicate the benefits of these advances, especially regarding studies of aquatic, environmental significance. Each of the studies focuses on environmentally significant issues. For example, chlorination is widely used to disinfect drinking waters, a method that can produce undesirable disinfection by-products. This was first recognized in 1974 with the discovery of trihalomethanes in most finished drinking waters where hypochlorite was used for disinfection. Chapter 7 examines the chlorination of alanine and relates it to the chlorination reactions of acetaldehyde and ammonia, a topic of importance with respect to drinking water disinfection. Aluminum is also widely used in drinking water treatment, and understanding its hydrolysis chemistry and complexation behavior is of great importance to aquatic chemistry. In addition, the aquatic chemistry of aluminum is important because acid rain can release soluble aluminum ions from clay into soil water, possibly damaging terrestrial plant life. Aluminum may eventually reach and accumulate in hydrological systems where it can be toxic to aquatic life. Chapters 8 and 9 focus on 27Al NMR in defining aqueous aluminum speciation in a mildly acidic solution or in the presence of complexing organic compounds. Furthermore, aluminum is of environmental and geochemical significance since it is an integral component of clays, another ubiquitous constituent of natural waters (surface and ground). Interaction between clays, cations, and internal water molecules can be significant in understanding the fate and transport of chemicals through the environment. Since colloidal suspensions of clay materials frequently represent challenges to water and wastewater treatment, understanding of physical and chemical processes are of tantamount importance to the environmental scientist and engineer. Chapter 10 explores cation behavior in clay matrices by using “uncommon” nuclei such as 7Li, 23Na, and 133Cs as probes. This is unique in that many NMR studies of complexation in clay have focused primarily upon the nuclei 27A1 and 29Si.
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Merwe, Peter Van Der. "British Origins of the Blues". En Origins of the Popular Style, 171–83. Oxford University PressOxford, 1992. http://dx.doi.org/10.1093/oso/9780198163053.003.0021.
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Abstract It must be understood that the third is not a fixed note in the folk-scale, as it is in both of the modern scales. The English folk-singer varies the intonation of this particular note very considerably. His major third is never as sharp as the corresponding interval in the tempered scale, to which modern ears are attuned. On the other hand, it is often so flat that it is hardly to be distinguished from the minor third. Frequently, too, it is a ‘neutral’ third, i.e., neither major nor minor, like the interval between the two notes of the Cuckoo’s song, when the Spring is waning. Apparently, the folk-singer, not having any settled notions with regard to the pitch of the third note of the scale, varies it according to the character of the phrase in which it happens to occur.
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Cranley, Nicola y Liam Murphy. "Incorporating User Perception in Adaptive Video Streaming Systems". En Multimedia Technologies, 1491–507. IGI Global, 2008. http://dx.doi.org/10.4018/978-1-59904-953-3.ch108.
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There is an increasing demand for streaming video applications over both the fixed Internet and wireless IP networks. The fluctuating bandwidth and time-varying delays of best-effort networks makes providing good quality streaming a challenge. Many adaptive video delivery mechanisms have been proposed over recent years; however, most do not explicitly consider user-perceived quality when making adaptations, nor do they define what quality is. This chapter describes research that proposes that an optimal adaptation trajectory through the set of possible encodings exists, and indicates how to adapt transmission in response to changes in network conditions in order to maximize user-perceived quality.
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Cranley, Nicola y Liam Murphy. "Incorporating User Perception in Adaptive Video Streaming Systems". En Digital Multimedia Perception and Design, 244–65. IGI Global, 2006. http://dx.doi.org/10.4018/978-1-59140-860-4.ch012.
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There is an increasing demand for streaming video applications over both the fixed Internet and wireless IP networks. The fluctuating bandwidth and time-varying delays of best-effort networks makes providing good quality streaming a challenge. Many adaptive video delivery mechanisms have been proposed over recent years; however, most do not explicitly consider user-perceived quality when making adaptations, nor do they define what quality is. This chapter describes research that proposes that an optimal adaptation trajectory through the set of possible encodings exists, and indicates how to adapt transmission in response to changes in network conditions in order to maximize user-perceived quality.
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Lalic, Danijela, Ugljesa Marjanovic y Bojan Lalic. "The Influence of Social Networks on Communication Satisfaction within the Organizations". En Handbook of Research on Business Social Networking, 545–66. IGI Global, 2012. http://dx.doi.org/10.4018/978-1-61350-168-9.ch029.
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Today, technological achievements that significantly influence communication management are Social Networks in virtual environment. The latest research clearly indicates that this trend is going to last in the future. It is considered as a fact that there are many changes and innovations in the field of information and communication technologies during the past few decades. Development of communication technologies has provided a new framework for organizing corporate communication processes, both internally and externally. Channels for the transfer of relevant information had been faced with huge technological improvement, but fact analysis and former research do not provide insight into specific motivation patterns for usage of Social Networks among employees, nor into their influence on Communication Satisfaction within the organizations.
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Gelder, Timothy van. "The Dynamical Alternative". En The Future of the Cognitive Revolution, 227–44. Oxford University PressNew York, NY, 1997. http://dx.doi.org/10.1093/oso/9780195103335.003.0017.
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Abstract What is cognition? Contemporary orthodoxy maintains that it is computation: the mind is a special kind of computer, and cognitive processes are the internal manipulation of symbolic representations. This broad idea has dominated the philosophy and the rhetoric of cognitive science-and even, to a large extent, its practice-ever since the field emerged from the postwar cybernetic melee. Many arguments have been advanced in its favor, and perhaps equally many against it. For a number of years, the situation has been one of stalemate, for generally neither computationalists nor their opponents have found each other’s arguments convincing. There is no doubt, however, that for a long time computationalists maintained a strategic advantage, for their opponents were unable to provide an alternative conception that could match computationalism in empirical scope and theoretical well-foundedness. Computationalists could thus always fall back on what has become known as the “what else could it be?” argument.
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Hussein, Ersin. "Ancient and Modern World Views". En Revaluing Roman Cyprus, 1–22. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198777786.003.0001.
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This chapter brings together the few geographical surveys of Cyprus written by outsiders (i.e. non-Cypriots) during the Roman Empire. The accounts of Strabo, Pliny the Elder, Claudius Ptolemy, Pausanias, Ammianus Marcellinus, and the anonymous Expositio totius mundi et gentium represent the culmination and transmission of ideas about the island based on key events, scenarios, and anecdotes. Situating the key passages within the motivations and themes of these authors’ works reveals how and why particular ideas about the island and its space came to fruition, what purpose these served, and what the perceived status and role of Cyprus in relation to Rome and to the wider Empire was. Discussion of the wider research-context study of the Roman provinces and the current ‘state of the field’ for the study of Roman Cyprus follows. In Cyprus no colonies were founded by the Romans, nor were any existing towns given colonial status; the island did not receive benefits, nor was it awarded any special status by Rome, despite being taxed. Furthermore, its inhabitants did not engage in aggressive military action to resist Roman control of the island, nor is its Roman period characterized by internal turmoil because of the Roman government, in contrast to some other provincial case studies. Therefore, this investigation draws upon a range of studies and models, utilizing vocabulary that acknowledges identity, culture, and experience as fluid, nuanced, and situational. It also emphasizes the importance of geography, geology, space, and place as active in the formation of local identity
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Coakley, Sarah. "Why Three? Some Further Reflections on the Origins of the Doctrine of the Trinity". En The Making and Remaking of Christian Doctrine, 29–56. Oxford University PressOxford, 1993. http://dx.doi.org/10.1093/oso/9780198267393.003.0003.
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Abstract In a justly famous article, ‘Some Reflections on the Origins of the Doctrine of the Trinity’, Maurice Wiles sets out to foil attempts to give a rational defense to the doctrine of the Trinity based on religious (Christian) experience. His conclusion is that once the triadic baptismal formula became fixed, quite early in the church’s life, it exercised a strongly authoritative-but ultimately ‘arbitrary’-clamp on more properly critical reflection. Attempts in the modern period, then, to provide ex post facto justifications for the doctrine of the Trinity out of the church’s early experience are in Wiles’s view fatally flawed: we find in the ante-Nicene Fathers, he shows, neither any consistent allocation of different activities to the three ‘persons’, nor (the epistemological correlate of this) any distinctive set of experiences associated with each of the three. And indeed-for here Wiles produces his Cappadocian coup de grace to look for such would, from the perspective of achieved fourth-century ‘orthodoxy’, be intrinsically suspect. The homoousion principle should debar any such possibility, since only ‘internal relations’ distinguish the divine hypostases; in their experiential effects all arc found to work together co-operatively.
Actas de conferencias sobre el tema "Internal filed NMR"
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Hursan, Gabor, Mohammed Sahhaf y Wala’a Amairi. "Utilizing NMR Workflow to Optimize Power Water Injector Placement in the Presence of Tar Barriers". En SPE Middle East Oil & Gas Show and Conference. SPE, 2021. http://dx.doi.org/10.2118/204565-ms.
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Abstract The objective of this work is to optimize the placement of horizontal power water injector (PWI) wells in stratified heterogeneous carbonate reservoir with tar barriers. The key to successful reservoir navigation is a reliable real-time petrophysical analysis that resolves rock quality variations and differentiates tar barriers from lighter hydrocarbon intervals. An integrated workflow has been generated based on logging-while drilling (LWD) triple combo and Nuclear Magnetic Resonance (NMR) logging data for fluid identification, tar characterization and permeability prediction. The workflow has three steps; it starts with the determination of total porosity using density and neutron logs, the calculation of water-filled porosity from resistivity measurements and an additional partitioning of porosity into bound and free fluid volumes using the NMR data. Second, the total and water-filled porosity, the NMR bound fluid and NMR total porosity are used as inputs in a hydrocarbon compositional and viscosity analysis of hydrocarbon-bearing zones for the recognition of tar-bearing and lighter hydrocarbon intervals. Third, in the lighter hydrocarbon intervals, NMR logs are further analyzed using a multi-cutoff spectral analysis to identify microporous and macroporous zones and to calculate the NMR mobility index. The ideal geosteering targets are highly macroporous rocks containing no heavy hydrocarbons. In horizontal wells, the method is validated using formation pressure while drilling (FPWD) measurements. The procedure has been utilized in several wells. The original well path of the first injector was planned to maintain a safe distance above an anticipated tar-bearing zone. Utilizing the new real-time viscosity evaluation, the well was steered closer to the tar zone several feet below the original plan, setting an improved well placement protocol for subsequent injectors. In the water- or lighter hydrocarbon-bearing zones, spectral analysis of NMR logs clearly accentuated micro- and macroporous carbonate intervals. The correlation between pore size and rock quality has been corroborated by FPWD mobility measurements. In one well, an extremely slow NMR relaxation may indicate wettability alteration in a macroporous interval. An integrated real-time evaluation of porosity, fluid saturation, hydrocarbon viscosity and pore size has enhanced well placement in a heterogeneous carbonate formation where tar barriers are also present. The approach increased well performance and substantially improved reservoir understanding.
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Gaunkar, N. Prabhu, R. Weber, M. Mina y D. Jiles. "Design and implementation of a low frequency pulsed magnetic field generator applicable to unilateral NMR". En 2017 IEEE International Magnetics Conference (INTERMAG). IEEE, 2017. http://dx.doi.org/10.1109/intmag.2017.8007647.
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Friedemann, Karen. "Internal post-curing of hydrating cement pastes of high performance concretes studied by low-field NMR relaxometry". En International RILEM Conference on Volume Changes of Hardening Concrete: Testing and Mitigation. RILEM Publications, 2006. http://dx.doi.org/10.1617/2351580052.016.
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Kabiyev, Y., R. Manakhayev y M. Kazhgaliyev. "Field Trial of LWD NMR Tool for Accurate Estimation of Effective Porosity in Deviated HPHT Wells: A Viable Alternative to Wireline-Based NMR Tools". En SPE Caspian Technical Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/217647-ms.
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Abstract The Tengiz reservoir is known for its substantial bitumen content, requiring careful differentiation during formation evaluation processes. To accurately estimate the effective porosity, wireline nuclear magnetic resonance (NMR) tools were used in conjunction with other logging tools. However, the increasing number of deviated wells drilled in Tengiz posed conveyance challenges for the wireline-based NMR tool due to high deviation angles. In light of this, TCO (Tengizchevroil) geoscientists sought opportunities to acquire NMR data using logging-while-drilling (LWD) technology in the reservoir section. Although the LWD NMR tool was not previously available for the required hole size, recent commercialization made it feasible. A team of geoscientists at TCO meticulously planned and executed a field trial of the LWD NMR tool to assess its potential future utilization in situations where the conveyance of wireline NMR tools may encounter difficulties. The LWD NMR tool was successfully deployed in a deviated well during drilling operations, followed by a subsequent measurement after drilling (MAD) pass to ensure log quality control. To verify and compare the acquired data, wireline-based NMR measurements were also conducted in the same well. The results of the field trial demonstrated the successful acquisition of high-quality LWD NMR data, corroborated by the MAD pass data and wireline log data. Furthermore, we revised and tested internal NMR data processing workflows, which conclusively established LWD NMR as a viable alternative to wireline-based NMR tools. Notably, the acquisition of NMR data while drilling offers additional benefits, as the near wellbore zone is not fully flushed with drilling mud, potentially enhancing fluid typing techniques (T1 and T2 distribution). This promising outcome opens up new avenues for more efficient and reliable estimation of effective porosity in deviated wells, as well as in wells with potential restrictions to run WL tools within the Tengiz reservoir and beyond, contributes to improved reservoir characterization and decision-making processes in asset development.
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de Oliveira, Lucas Abreu Blanes, Leonardo Gonçalves, Bernardo Coutinho Camilo dos Santos, Willian Andrighetto Trevizan y Rodolfo Araujo Victor. "Improving the Calculation of Petrophysical Properties in Vugular Carbonates Using Logs and Rock Samples: A Case Study in a Brazilian Pre-salt Well". En 2022 SPWLA 63rd Annual Symposium. Society of Petrophysicists and Well Log Analysts, 2022. http://dx.doi.org/10.30632/spwla-2022-0019.
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Calculating log-scale petrophysical properties is essential in formation evaluation, since it directly impacts the estimates of hydrocarbon reserves and reservoir flow capacity. These calculations traditionally use the nuclear magnetic resonance (NMR) log through cutoffs in the transverse relaxation time (T2) in the Brazilian pre-salt carbonates. T2 values above and below 100 ms are associated with free and irreducible fluids, respectively. Above the oil-water contact, free fluid is interpreted as oil when calculating saturation and permeability, assuming the rock has only water and oil. As the NMR readings are influenced by oil-based mud invasion, the free fluid is also related to the oil in the mud filtrate. The filtrate and formation oil present T2 bulk values of 500 ms, and the traditional interpretation calculates reliable properties in intervals with matrix porosity. Nevertheless, this interpretation does not hold in formations with vugular porosity. The wide pore throats prevent mudcake formation, and therefore mud invades the vugs with the solid particulates as well. The mud particles decrease the mud bulk T2 to 50 ms, being misinterpreted as irreducible fluid by the traditional approach, and therefore artificially increasing the water saturation and decreasing permeability estimates. Additionally, mud has hydrogen index below one, decreasing total porosity estimated from the NMR measurements. In this work we present a workflow for calculating petrophysical properties on the Brazilian pre-salt carbonates, integrating laboratory analyses and well logs. The chosen well was drilled with oil-based mud, has an extensive core interval, and a complete wireline suite. First, NMR and Dean-Stark distillation were performed on preserved core plugs with matrix and vugular porosities. These analyses allowed the mud T2 signal identification in vugs by decomposing the T2 spectrum into base functions. Then, the samples' porosity and permeability were measured. The mud signal was propagated to the NMR logs in intervals dominated by vugs. These intervals were defined using photoelectric factor and acoustic image. The T2 spectrum was decomposed into base functions, which allowed identifying and quantifying the irreducible fluids, mud-filled vugs, and free fluid. The last two were interpreted as the pore volume initially filled by formation oil, redefining the saturation and permeability calculations. Finally, the NMR total porosity was corrected using the mud hydrogen index. Our workflow showed a better agreement with laboratory analyses. Estimated average water saturation decreased by 0.18 v/v, average permeability increased by 408 mD, and average porosity increased by 0.02 v/v compared to the traditional interpretation. The importance of correctly interpreting the different types of fluid and pores when analyzing the T2 spectrum becomes evident, especially in complex formations like the Brazilian pre-salt carbonates.
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Pawandeep Singh, Bagga y Vardhan Harsh. "Formation Evaluation Using LWD NMR, LWD Electrical Imaging and Triple Combo Data - A Case Study from India". En SPE Conference at Oman Petroleum & Energy Show. SPE, 2024. http://dx.doi.org/10.2118/218793-ms.
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Abstract Logging While Drilling (LWD) Nuclear Magnetic Resonance (NMR), LWD Electrical Imaging along with Conventional Triple Combo LWD services were deployed in Mumbai Offshore field in India. LWD NMR data gives a rock independent porosity measurement which seem to verify the other measurements which in turn increases the data confidence. Depending on rock quality and wettability NMR data might give some good insight in fluid saturations. Furthermore, NMR data gives a permeability Index (also while drilling) which can be useful for selecting pressure stations while drilling, it might also be useful for completion design and production/injection rate calculations. LWD Electrical Imaging tool from provides detailed reservoir characterization, structural classification, and wellbore integrity management in Realtime. In this well, The NMR permeability seemed to be related to total porosity; high porosity gave high permeability and low porosity gave low permeability, i.e., a synthetic perm curve based on Neutron density aligned quite well with NMR perm. The Hydrocarbon saturation appeared to be highest in the upper part of the section but both Archie saturation and NMR saturation indicate a nearly monotonically decreasing Hydrocarbon saturation towards end of well. In the upper part the T2 peak was positioned at around 1000ms but gradually moved towards a shorter T2 time with depth. Towards bottom the T2 peak had moved down to about 2-300ms and water saturation appeared to be high. Electrical imaging was used to demarcate the bed boundaries, Dip Picking and Fracture identification. Quick-Look Interpretation of the image data provides evidence of vuggy carbonaceous formation with presence of continuous conductive fractures scattered across the drilled interval. This made the use of permeability model and saturation calculation more complicated. The conventional triple combo helped to steer the well and be in the zone of interest. The paper in depth discusses the deployments of LWD NMR and LWD Electrical Imaging in the field, Associated challenges, and value these services brought to the operator.
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Gao, Jun, Hyung T. Kwak y Marwah AlSinan. "Accurate Carbonate Pore System Characterization by Nuclear Magnetic Resonance and Micro-CT Techniques". En SPE Middle East Oil & Gas Show and Conference. SPE, 2021. http://dx.doi.org/10.2118/204659-ms.
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Abstract Carbonate reservoir rocks usually have complex pore systems of broad size distributions, which determine many aspects of oil exploitation, from petrophysical properties to oil/water displacements. An accurate and complete description of these pore systems remains a challenge. A single technique often gives one measurement of complicated microscopic pore space. The new techniques (i.e., micro-CT and NMR) are utilized together with conventional methods (e.g., MICP, BET) to capture a more accurate and complete picture of pore structures. MICP measures the pore throat while the NMR T2 mainly measures the pore body. Micro-CT provides a 3D image of a limited sample size. Recently, NMR DDIF (decay due to diffusion in the internal field) for direct pore body size is extended from high to low magnetic field, which overcomes many limitations in pore system characterization. This study obtains pore throat size distributions from in-situ centrifuge capillary pressure and pore body size distributions from low field DDIF measurement and verifies them with micro-CT and BET/T2 in different types of carbonate rocks. The pore throat size distribution of the conventional sample is obtained from in-situ centrifuge capillary pressure. The major features of both macro and micro pore throat size distributions are captured. Pore size distributions are directly obtained from glass beads and carbonate rocks without calibration. Combined analysis of the pore size distribution from two methods reveals the underlying causes of their different petrophysical properties. The pore throat size distribution from in-situ centrifuge capillary pressure and pore size distribution from NMR DDIF can be employed to obtain a better understanding of conventional carbonate pore systems.
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Hursan, Gabor, Wei Shao, Ron Balliet y Yasir Farooq. "Eliminating Diffusion Effects from NMR Logging Data for Enhanced Carbonate Pore Typing". En SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206233-ms.
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Abstract Transverse relaxation (T2) times measured by multi-frequency, multi-gradient nuclear magnetic resonance (NMR) logging tools are affected by diffusion-induced enhanced relaxation which reduces the sensitivity to pore size in slow-relaxing formations such as macroporous carbonates and complicates the integration with zero-gradient core NMR data. We propose a solution for eliminating the diffusion-related uncertainties using intrinsic T2 distributions, obtained by a new inversion-forward modeling-inversion (IFMI) method, for carbonate pore typing applications. The NMR logs presented in this paper are based on data measured at five frequencies where the static magnetic field gradient varies from 26 to 55 G/cm. The high-quality echo signals are processed using a three-step IFMI differential signal analysis approach which nullifies diffusion effects due to the tool gradient and the potentially present internal gradient caused by paramagnetic minerals in the formation. The resulting diffusion-free intrinsic T2 distribution accentuates fine pore size variations and allows better discernment of micro-, meso-, and macropore systems of complex carbonate reservoirs. Multi-frequency NMR data, acquired in multiple wells, were processed and analyzed in several ways. First, apparent T2 distributions were obtained separately for individual frequencies. Discrepancies between the results of different frequencies clearly indicated that in macro- and mesoporous carbonates the diffusion effect is significant even with TE=0.3ms. This leads a peak broadening observed in the apparent T2 spectrum from conventional NMR processing, where echo trains from different frequencies are averaged in time-domain prior to the inversion. With the IFMI processing, individual-frequency echo trains are first pre-processed using a 2D NMR inversion whose results are used to forward model a diffusion-free echo train without prior assumptions on reservoir fluid diffusivity D. A second inversion, applied on the diffusion-free echo train, yields the intrinsic T2 distribution. The intrinsic T2 distribution has a noticeably higher spectral resolution in carbonate formations where diffusion effect is significant. The intrinsic T2 logs are expected to be more consistent with other gradient-free NMR measurements such as core NMR or LWD NMR data sets.
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Bordakov, G. A., S. Utsuzawa, D. F. Allen, Y. Karpekin, D. Rose, W. Troyer, R. J. Laronga y H. N. Bachman. "New NMR Porosity Correction Algorithm for Steady-State Buildup Effect in Unconventional Reservoirs". En SPE Annual Technical Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/214766-ms.
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Abstract Nuclear magnetic resonance (NMR) logging for subsurface exploration is gaining acceptance as an everyday measurement for conventional and unconventional reservoirs, as well as new energy applications such as carbon storage and geothermal formation evaluation. Out of many NMR sensor designs, ones with a saddle-point magnetic field profile have gained broad acceptance because of their short echo spacing and many operational advantages. Despite bringing advantages, the saddle-point design can lead to systematic overestimation of porosity in combination with T1-T2 logging, which has been especially observed in unconventional reservoirs. We have developed a multiphysics tool model—a digital twin—that quantifies the recently discovered steady-state buildup (SSB) of the NMR signal in a multivalued gradient magnetic field. This effect arises mostly from off-resonance signals. The model incorporates the static and dynamic fields of the NMR sensors, associated physics, and the transmitter and receiver electronics. It is validated by laboratory experiments. This SSB effect has been found to be the key cause of the observed porosity overestimation, which is most significant in unconventional and carbonate reservoirs. The application of the digital twin has allowed us to improve the tool forward modeling accuracy by calculating the correction factors for each combination of T1, T2, pulse sequence, and environment. A new kernel-corrected NMR inversion has been developed. The novelty of the inversion includes not only a forward modeling correction, but also post-inversion correction for the bias caused by regularization and an additional procedure for the reduction of the artifacts particularly evident at short relaxation time constants. The overall improved inversion delivers accurate, higher-definition T1-T2 maps that were not attainable before. Validation of the new inversion has been performed on field datasets. Results demonstrate reconciliation of kernel-corrected NMR porosity with independent porosity measurements in unconventional and conventional formations. High-definition maps enable better segregation of different fluid types in unconventional reservoirs and delineation of producible intervals with increased clarity and confidence.
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Huo, Yan, W. K. Chow y Ye Gao. "Internal Fire Whirls Induced by Pool Fire in a Vertical Shaft". En ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44477.
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Internal fire whirls induced by a pool fire in a square vertical shaft were studied by experiments and numerical simulations. The burning behaviour of two pool fires in the vertical shaft and in open air was compared. The gap width of the rig is a key factor in onsetting fire whirls. Air flow field in the vertical square shaft of different gap widths were studied experimentally with nine tests. A fire whirl would not be onsetted when the gap is too narrow nor too wide. Whirling flame is not clearly observed near to the bottom of the vertical shaft when the gap width was small.