Thematische Bibliographien / Hydrated crystal

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Auswahl der wissenschaftlichen Literatur zum Thema „Hydrated crystal“

Autor: Grafiati

Veröffentlicht am 4. Juni 2021

Zuletzt aktualisiert am 1. Februar 2022

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Zeitschriftenartikel zum Thema "Hydrated crystal"

Zorin, Dmitriy, und Ivan Burlov. „Morphology of ettringite crystal of sulfoferrite clinker“. E3S Web of Conferences 244 (2021): 04008. http://dx.doi.org/10.1051/e3sconf/202124404008.

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This paper deals with the composition and properties of solid solution of calcium sulfoferrite. It was studied an influence of calcium s sulfoferrite on structure and properties cement phases. Study of the hydration processes of the calcium sulfoferrite mineral are observed only short prismatic crystals. Prismatic crystals of ferruginous ettringite are always formed from sulfoferrite mineral of any fraction. it was found that the smaller the initial hydrating grains of minerals, the faster they are hydrated. Analyse polyfractional compound hydration showed that fine fractions provide formation of crystallization centres, and particles less than 45 microns, with constant interaction with the liquid phase, cause a gradual growth of crystals. Expansion of hydrated minerals of certain fractions was analysed to check the dependence of the expansion on the morphology of ettringite crystal hydrates. During the hardening of the samples, expansion was observed along with a drop in strength.

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Oyama, Hironaga, Takashi Miyamoto, Akiko Sekine, Ilma Nugrahani und Hidehiro Uekusa. „Solid-State Dehydration Mechanism of Diclofenac Sodium Salt Hydrates“. Crystals 11, Nr. 4 (12.04.2021): 412. http://dx.doi.org/10.3390/cryst11040412.

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Salt formation is a useful technique for improving the solubility of active pharmaceutical ingredients (APIs). For instance, a nonsteroidal anti-inflammatory drug, diclofenac (DIC), is used in a sodium salt form, and it has been reported to form several hydrate forms. However, the crystal structure of the anhydrous form of diclofenac sodium (DIC-Na) and the structural relationship among the anhydrate and hydrated forms have not yet been revealed. In this study, DIC-Na anhydrate was analyzed using single-crystal X-ray diffraction (XRD). To determine the solid-state dehydration/hydration mechanism of DIC-Na hydrates based on both the present and previously reported crystal structures (4.75-hydrate and 3.5-hydrate), additional experiments including simultaneous powder XRD and differential scanning calorimetry, thermogravimetry, dynamic vapor sorption measurements, and a comparison of the crystal structures were performed. The dehydration of the 4.75-hydrate form was found to occur in two steps. During the first step, only water molecules that were not coordinated to Na+ ions were lost, which led to the formation of the 3.5-hydrate while retaining alternating layered structures. The subsequent dehydration step into the anhydrous phase accompanied a substantial structural reconstruction. This study elucidated the complete landscape of the dehydration/hydration transformation of DIC-Na for the first time through a crystal structure investigation. These findings contribute to understanding the mechanism underlying these dehydration/hydration phenomena and the physicochemical properties of pharmaceutical crystals.

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FÜREDI-MILHOFER, H., M. SIKIRIĆ, L. TUNIK, N. FILIPOVIĆ-VINCEKOVIĆ und N. GARTI. „INTERACTIONS OF ORGANIC ADDITIVES WITH IONIC CRYSTAL HYDRATES: THE IMPORTANCE OF THE HYDRATED LAYER“. International Journal of Modern Physics B 16, Nr. 01n02 (20.01.2002): 359–66. http://dx.doi.org/10.1142/s0217979202009871.

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The interactions of two groups of hydrated model crystals, calcium hydrogenphosphate dihydrate (DCPD) vs. octacalcium phosphate (OCP) and calcium oxalate monohydrate (COM) vs. calcium oxalate dihydrate (COD) with different organic additives are considered. DCPD precipitates as platelet-like crystals with the dominant faces shielded by hydrated layers and charged lateral faces. In the second system COM has charged surfaces, while all faces of COD are covered with layers containing water molecules. The organic molecules tested include negatively charged, flexible and rigid small and macromolecules (glutamic and aspartic acid, citrate, hexaammonium polyphosphate, phytate and polyaspartate) and anionic surfactants (sodium dodecyl sulphate, SDS, sodium diisooctyl sulfosuccinate, AOT, sodium cholate NaC and disodium oleoamido PEG-2 sulfosuccinate, PEG). Two types of effects have been demonstrated: (1) Effect on crystal growth morphology: Flexible organic molecules with high charge density and anionic surfactants affected the growth morphology of DCPD and COM by selectively interacting with the charged lateral faces while rigid molecules (phytate, polyaspartate) specifically recognized the dominant (010) face of DCPD due to structural and stereochemical compatibility. (2) Effect on phase composition: Anionic surfactants at concentrations above the cmc promoted growth of OCP and COD respectively by selectively adsorbing at, and inhibiting growth oif nuclei of DCPD and/or COM, which were dominant in the respective control systems. The effect was especially pronounced in the calcium oxalate precipitation system, where in some cases complete reversal of the phase composition occurred. The important role of the hydrated layer, as part of the structure of the investigated crystal hydrates, in the above crystal additive interactions is discussed.

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Braun, Doris, und Ulrich Griesser. „Insights into hydrate formation and stability of morphinanes“. Acta Crystallographica Section A Foundations and Advances 70, a1 (05.08.2014): C991. http://dx.doi.org/10.1107/s2053273314090081.

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The formation of multi-component crystals with water (hydrates) is a widespread phenomenon among organic molecules. Hydrate formation is of high practical relevance for industrially used materials, as it affects their physicochemical properties. [1,2] To exclude water or moisture in industrial processes is often difficult. Therefore knowledge about the existence and stability of hydrates and the understanding and control of the anhydrate/hydrate balance is mandatory for avoiding manufacturing problems. In order to improve our understanding of hydrate formation we selected representative substances (morphine, codeine, ethylmorphine) from a class of molecules (morphinanes), which are prone to crystallize along with water. Stable hydrates of both, free bases and HCl salts, have been observed in this important class of drug compounds. This allowed us to investigate the influence of different functional groups, the role of water and the Cl– counterion on the structure and properties of these morphinanes. A crystallization screen on the six compounds considerably extended the total number of known solid forms from twelve [3] to 17 and the number of crystal structures from five to twelve. Anhydrous polymorphs were detected for all compounds except ethylmorphine (one anhydrate) and its HCl salt (no anhydrate). The relative stabilities of the hydrated and anhydrous forms differ considerably, which was evaluated by moisture sorption studies and thermal analytical experiments. Two different hydrates, a tri- and dihydrate, were found for morphine HCl. In the free bases, the substituents define the number of hydrogen bond donor groups and lead to differences in the sterical hindrance around polar groups, influencing the intermolecular interactions, packing and stability. Hydrate formation results in higher dimensional hydrogen bond networks, whereas salt formation decreases the packing variability of the structures among the different compounds. Calorimetric measurements and lattice energy calculations were employed to estimate the heat of hydrate/anhydrate phase transformation, showing an enthalpic stabilization of the hydrates over the anhydrates. The combination of a variety of experimental techniques with computational modelling allowed us to generate sufficient kinetic, thermodynamic and structural information to understand the principles of hydrate formation of morphinanes.

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Zhang, Ziming, Qiang Cai, Jiadan Xue, Jianyuan Qin, Jianjun Liu und Yong Du. „Co-Crystal Formation of Antibiotic Nitrofurantoin Drug and Melamine Co-Former Based on a Vibrational Spectroscopic Study“. Pharmaceutics 11, Nr. 2 (30.01.2019): 56. http://dx.doi.org/10.3390/pharmaceutics11020056.

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The co-crystallization of active pharmaceutical ingredients (APIs) has received increasing attention due to the modulation of the relative physicochemical properties of APIs such as low solubility, weak permeability and relatively inferior oral bioavailability. Crystal engineering plays a decisive role in the systematic design and synthesis of co-crystals by means of exerting control on the inter-molecular interactions. The characterization and detection of such co-crystal formations plays an essential role in the field of pharmaceutical research and development. In this work, nitrofurantoin (NF), melamine (MELA) and their hydrated co-crystal form were characterized and analyzed by using terahertz time-domain spectroscopy (THz-TDS) and Raman vibrational spectroscopy. According to the experimental THz spectra, the hydrated co-crystal form has characteristic absorption peaks at 0.67, 1.05, 1.50 and 1.73 THz, while the THz spectra for the two raw parent materials (NF and MELA) are quite different within this spectral region. Similar observations were made from the experimental Raman vibrational spectra results. Density functional theory (DFT) calculation was performed to help determine the major vibrational modes of the hydrated co-crystal between nitrofurantoin and melamine, as well as identify the structural changes due to inter- and/or intra-molecular hydrogen bonding motifs between NF and MELA. The results of the theoretical frequency calculations corroborate the THz and Raman experimental spectra. The characteristic bands of the NF–MELA-hydrated co-crystal between nitrofurantoin and melamine were also determined based on the DFT simulated calculation. The reported results in this work provide us with a wealth of structural information and a unique vibrational spectroscopic method for characterizing the composition of specific co-crystals and inter-molecular hydrogen bonding interactions upon pharmaceutical co-crystallization.

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Kersten, Kortney, Ramanpreet Kaur und Adam Matzger. „Survey and analysis of crystal polymorphism in organic structures“. IUCrJ 5, Nr. 2 (25.01.2018): 124–29. http://dx.doi.org/10.1107/s2052252518000660.

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With the intention of producing the most comprehensive treatment of the prevalence of crystal polymorphism among structurally characterized materials, all polymorphic compounds flagged as such within the Cambridge Structural Database (CSD) are analysed and a list of crystallographically characterized organic polymorphic compounds is assembled. Classifying these structures into subclasses of anhydrates, salts, hydrates, non-hydrated solvates and cocrystals reveals that there are significant variations in polymorphism prevalence as a function of crystal type, a fact which has not previously been recognized in the literature. It is also shown that, as a percentage, polymorphic entries are decreasing temporally within the CSD, with the notable exception of cocrystals, which continue to rise at a rate that is a constant fraction of the overall entries. Some phenomena identified that require additional scrutiny include the relative prevalence of temperature-induced phase transitions among organic salts and the paucity of polymorphism in crystals with three or more chemical components.

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Zimakova, Galina, Valentina Solonina, Marina Zelig und Viktor Orlov. „Effect of fine-grained components on concrete properties and structure formation“. MATEC Web of Conferences 143 (2018): 02004. http://dx.doi.org/10.1051/matecconf/201814302004.

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The paper investigates the influence of fine-grained components on the synthesis of new formations and structure of cellular concrete. Grain size composition was defined with the aid of a laser diffraction analyzer of particles ANALYSETTE 22 NanoTecplus. The composition of the obtained hydrated phases was studied using electron microscopy and X-ray phase analysis. The introduction of silica and aluminosilicate components with the specific surface area >350 m2/kg enabled to directly influence the mechanism of the hydrated phases formation. Complex hydrated calcium aluminosilicates of the frame structure of zeolite type and non-permanent composition were identified in the hydration products. The formation of the total set of properties is attributed to the morphological features of the hydrated phases, the nature of connections between the crystalline hydrates, and their location in the material structure. X-ray phase analysis showed that ultra-micro-dispersed components have the stimulating impact on the processes of silicate formation. With the increase in the amount of hydrated new formations and decrease in the liquid phase volume the conditions for building of strong crystal intergrowth contacts were created.

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Bétourné, E., und M. Touboul. „Crystallographic data about hydrated and anhydrous lithium monoborates“. Powder Diffraction 12, Nr. 3 (September 1997): 155–59. http://dx.doi.org/10.1017/s0885715600009635.

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The anhydrous and hydrated lithium monoborates have been studied. The most hydrated phase is LiBO2·8H2O; its structural formula in the P3 space group is Li(H2O)4B(OH)4·2H2O. Refinement of the cell parameters yielded the following results: a=6.5483(5) Å, c=6.1692(7) Å with F(30)=64(0.015, 32), Z=1, and Dx=1.402 g/cm3. This phase gives LiB(OH)4 by spontaneous dehydration. An X-ray powder diffraction study of LiB(OH)4 as a function of temperature indicated three poorly crystallized hydrates. Two of these hydrates have the formula LiBO2·0.3H2O; the other, LiBO2·xH2O, has an undetermined water content. Crystal data for α-LiBO2 have been obtained: a=5.8473(10) Å, b=4.3513(6) Å, c=6.4557(10) Å, β=115.08(1)°, F(27)=58.5(0.001, 41); space group P21/c, Z=4, and Dx=2.18 g/cm3. β-LiBO2 does not exist but corresponds to the α-LiBO2 form observed at 600 °C. Numerous other LiBO2 forms reported recently have not been found.

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Gallois-Montbrun, Delphine, Geneviève Le Bas, Sax A. Mason, Thierry Prangé und Sylviane Lesieur. „A highly hydrated α-cyclodextrin/1-undecanol inclusion complex: crystal structure and hydrogen-bond network from high-resolution neutron diffraction at 20 K“. Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 69, Nr. 2 (26.02.2013): 214–27. http://dx.doi.org/10.1107/s2052519213001772.

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The monoclinicC2 crystal structure of an α-cyclodextrin/1-undecanol host–guest inclusion complex was solved using single-crystal neutron diffraction. Large high-quality crystals were specially produced by optimizing temperature-controlled growth conditions. The hydrate crystallizes in a channel-type structure formed by head-to-head dimer units of α-cyclodextrin molecules stacked like coins in a roll. The alkyl chain of the guest lipid is entirely embedded inside the tubular cavity delimited by the α-cyclodextrin dimer and adopts an all-transplanar zigzag conformation, while the alcohol polar head group is outside close to the α-cyclodextrin primary hydroxyl groups. The cyclodextrin dimer forms columns, which adopt a quasi-square arrangement much less compact than the quasi-hexagonal close packing already observed in the less hydrated α-cyclodextrin channel-type structures usually found with similar linear guests. The lack of compactness of this crystal form is related to the high number of interstitial water molecules. The replacement of 1-undecanol by 1-decanol does not modify the overall crystal structure of the hydrate as shown by additional X-ray diffraction investigations comparing the two host–guest assemblies. This is the first study that analyses the entire hydrogen-bonding network involved in the formation of a cyclodextrin dimer surrounded by its shell of water molecules.

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Mackay, Maureen F., Robert W. Gable, James D. Morrison und Lothar O. Satzke. „Structure of Hydrated Copper(II) Colchiceine“. Australian Journal of Chemistry 52, Nr. 4 (1999): 333. http://dx.doi.org/10.1071/c98162.

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Hydrated crystals of copper(II) colchiceine belong to the tetragonal space group P 432I2 with a 13·415(1), c 50·169(8) Å and Z 8. The structure has been refined to a conventional R factor of 0·077 for 4560 observed data. The tropolonic oxygens from two colchiceine molecules are coordinated to the copper atom in this bis-chelated complex to form a square planar arrangement. The sites of three of the waters are clearly defined, but the others are disordered over seven partially occupied sites. An intricate hydrogen-bonding system links the complex and water molecules into a three-dimensional network in the crystal.

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Dissertationen zum Thema "Hydrated crystal"

Pedesseau, Laurent. „Modélisation atomique à l'équilibre de phases, périphases et interphases : vers l'application à des cristaux hydratés“. Toulouse 3, 2004. http://www.theses.fr/2004TOU30286.

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La prise et le durcissement des matériaux de Génie Civil (plâtre, C-S-H) reposent sur des interactions entre cristaux et solutions ioniques. Ces interactions mettent en jeu des équilibres entre phases, leurs frontières (dites périphases) et des phases confinées entre périphases (dites interphases). La partie 1 "Concepts, méthodes et outils" introduit tout d'abord le concept phéno-corpusculaire proposé pour l'étude de ces équilibres, irréductibles à une approche macroscopique via la physique statistique, et d'autre part encore inabordables par la seule voie corpusculaire. Parmi les méthodes originales présentées, la méthode SASP ouvre la voie phéno-corpusculaire en physico-chimie; puis est proposée la méthode OPTASYM pour définir les positions d'atomes H inconnus dans certaines cristaux; enfin est exposée la méthode CAC exploitant simultanément expérience et simulation AFM. Quant aux outils numériques originaux, ils sont essentiellement dévolus au traitement conjoint cristal/solution, encore embryonnaire en modélisation moléculaire. La partie 2 "Equilibre massique de phases, périphases et interphases" s'attache tout d'abord à l'élaboration de structures atomiques complètes de cristaux (gypse, ettringite, thaumasite), de structures de molécules et ions, et de structure de solution grâce à la méthode SASP qui débouche numériquement sur la relation fondamentale concentrations/potentiels chimiques. Ces structures étant définies, leurs interactions sont d'abord traitées par docking entre faces cristallines et molécules ou ions. Puis l'interaction cristal/solution/cristal est présentée via SASP dans le cas d'une solution saturée de gypse. D'où, pour la première fois, l'obtention de la structure d'une interphase d'épaisseur < 1 nm. La partie 3 " Equilibre mécanique de phases, périphases et interphases " présente, tout d'abord, une étude critique de l'estimation par modélisation moléculaire des contraintes totales de cristaux et solutions ioniques. L'introduction du calcul des contraintes partielles, inabordable expérimentalement, est fort prometteuse pour relier résistance à rupture macroscopique et structure atomique. L'équilibre mécanique entre phases, périphases et interphases est tout d'abord examiné en déplacement normal jusqu'à rupture d'adhésion, pour divers couples de faces (120), (010) ou (-101), la solution interphase (CaSO4, CaCl2 ou Na2SO4) étant en situation ionique non équilibrée (pour simuler des états transitoires ou isolés) avec éventuellement de l'acide citrique. Puis cette étude est reprise en situation ionique équilibrée, via la méthode SASP, pour les faces (120) du gypse en solution saturée. Enfin une première illustration de cisaillement est donnée dans le cas d'interphase (120), en solution CaSO4 non équilibrée avec acide citrique. La conclusion souligne les avancées de ce travail en modélisation atomique de solution en présence de cristal, ainsi que ses perspectives placées dans l'optique générale phéno-corpusculaire
The setting and hardening of materials used in civil engineering (plaster, C-S-H) are based on interactions between crystals and ionic solutions. These interactions involve equilibriums between phases, their boundaries (referred to as periphases) and phases confined between periphases (referred to as interphases). Part 1, "Concepts, methods and tools", first introduces the pheno-corpuscular concept proposed for the study of these equilibriums that cannot be addressed in a macroscopic approach via the statistical physics or in a corpuscular approach alone. Among the original methods presented, the SASP method opens up the pheno-corpuscular pathway in physicochemistry; then is presented the OPTASYM method using molecular modelling to propose positions of H atoms unknown in certain crystalline structures; finally is exposed the CAC method based on a simultaneous use of AFM experiment and simulation. The original numerical tools are mainly devoted to joint crystal/solution processing, an area that is still at its beginnings in molecular modelling. Part 2, "Mass equilibrium of phases, periphases and interphases" first addresses the build-up of complete crystal atomic structures (gypsum, ettringite and thaumasite), of molecules and ions structures and of solution structures, the SASP method leading numerically, in this last case, to the fundamental relation between concentrations and chemical potentials. Once these structures have been defined, their interactions are first handled by docking between the crystalline faces and molecules or ions. The crystal/solution/crystal interaction is then presented using SASP, in the case of a saturated solution of gypsum. Whence, for the first time, the structure of an interphase of thickness < 1 nm. Part 3, "Mechanical equilibrium of phases, periphases and interphases", consists, first of all, of a critical study of estimation by molecular modelling of the total stresses of ionic crystals and solutions. The introduction of calculation of partial stresses, which cannot be performed by experiment, is particularly promising for linking macroscopic failure strength and atomic structure. Mechanical equilibrium between phases, periphases and interphases is first examined in normal displacement of various pairs of faces (120), (010) or (-101) until adhesion failure, the solution interphase (CaSO4, CaCl2 or Na2SO4) being in a non-equilibrium ionic situation (to simulate transitory or isolated states), possibly with citric acid. The study is then repeated in an equilibrium ionic situation using the SASP method for the gypsum faces (120) in a saturated solution. Finally, a first illustration of an interphase shearing is given in the case of faces (120), with a non-equilibrated solution of CaSO4 and citric acid. The conclusion underlines the progress made in this work on crystal/solution atomic modelling and its prospects within the overall pheno-corpuscular approach

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Vladu, Maria-Camelia. „Calcium sulphoaluminate hydrates : crystal growth, stability and flow properties“. Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/11506.

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The calcium sulphoaluminate hydrates are important components of Portland cement and constitute the principal matrix formers of some sulphoaluminate cements. Their practical importance lies in the involvement as intermediates and products of the hydration of portland cements under geothermal conditions. Ettringite is a complex mineral (Ca₆[Al(OH)₆]₂(SO₄)₃.26H₂O) formed during the initial stages of Portland cement hydration at ambient temperature, by reaction of sulphate ions released by gypsum (CaSO₄.2H₂O) with tricalcium aluminate (Ca₃Al₂O₆). After exhaustion of gypsum, the remaining tricalcium aluminate in solution reacts with already formed ettringite transforming to monosulphate (Ca₄Al₂(SO₄)(OH)₁₂.xH₂O). At higher temperature (>100°C), ettringite is unstable and transforms to monosulphate. Monosulphates are known to exist is at least four different hydrate forms (x = 8,10,12,14). In this study the stability of calcium sulphoaluminate hydrates were mapped in various environments (variable relative humidity, temperature and alkalinity). The monosulphate hydrates were obtained by hydrothermal synthesis using microwave radiation at 120°C. Their formation is via ettringite thermal decomposition in autoclave conditions under autogenous pressure. It has been shown that a series of calcium sulphoaluminate hydrates can be obtained depending on temperature and water activity. The interconversion of the calcium sulphoaluminate hydrates was found to be an easy and rapid process, whereby metastable phase are readily formed, indicating the lability of Ca-OH-Al-SO₄ system. The kinetics and the mechanism of growth of calcium sulphoaluminate hydrates are known to influence the development of mechanical properties and the characteristics of cements. The ettringite crystal growth process was evaluated from the point of view of its influence on crystal morphology. General crystallisation methods for ettringite synthesis were developed starting from supersaturated solutions of pure phases and its morphology was found to vary with crystallisation factors (temperature for instance); ettringite crystals are generally hexagonal rods with different aspect ratios.

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Motie, Richard Edward. „Crystal growth and inhibition mechanisms of natural gas hydrates“. Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441228.

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Klironomou, Sophia. „Crystal growth and phase equilibria studies of clathrate hydrates“. Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417619.

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Angeles, Eloisa. „Computational prediction of hydrate formation in organic crystal structures“. Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708136.

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Valyashko, Elena. „Synthesis and crystal chemistry of ferric hydrogen sulfate hydrate“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22411.pdf.

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Skyner, Rachael Elaine. „Hydrate crystal structures, radial distribution functions, and computing solubility“. Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/11746.

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Solubility prediction usually refers to prediction of the intrinsic aqueous solubility, which is the concentration of an unionised molecule in a saturated aqueous solution at thermodynamic equilibrium at a given temperature. Solubility is determined by structural and energetic components emanating from solid-phase structure and packing interactions, solute–solvent interactions, and structural reorganisation in solution. An overview of the most commonly used methods for solubility prediction is given in Chapter 1. In this thesis, we investigate various approaches to solubility prediction and solvation model development, based on informatics and incorporation of empirical and experimental data. These are of a knowledge-based nature, and specifically incorporate information from the Cambridge Structural Database (CSD). A common problem for solubility prediction is the computational cost associated with accurate models. This issue is usually addressed by use of machine learning and regression models, such as the General Solubility Equation (GSE). These types of models are investigated and discussed in Chapter 3, where we evaluate the reliability of the GSE for a set of structures covering a large area of chemical space. We find that molecular descriptors relating to specific atom or functional group counts in the solute molecule almost always appear in improved regression models. In accordance with the findings of Chapter 3, in Chapter 4 we investigate whether radial distribution functions (RDFs) calculated for atoms (defined according to their immediate chemical environment) with water from organic hydrate crystal structures may give a good indication of interactions applicable to the solution phase, and justify this by comparison of our own RDFs to neutron diffraction data for water and ice. We then apply our RDFs to the theory of the Reference Interaction Site Model (RISM) in Chapter 5, and produce novel models for the calculation of Hydration Free Energies (HFEs).

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Carver, Timothy John. „A study of kinetic inhibition of natural gas hydrates by polyvinylpyrrolidone“. Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339491.

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Yoslim, Jeffry. „The effect of surfactant on the morphology of methane/propane clathrate hydrate crystals“. Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3415.

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Considerable research has been done to improve hydrate formation rate. One of the ideas is to introduce mechanical mixing which later tend to complicate the design and operation of the hydrate formation processes. Another approach is to add surfactant (promoter) that will improve the hydrate formation rate and also its storage capacity to be closer to the maximum hydrate storage capacity. Surfactant is widely known as a substance that can lower the surface or interfacial tension of the water when it is dissolved in it. Surfactants are known to increase gas hydrate formation rate, increase storage capacity of hydrates and also decrease induction time. However, the role that surfactant plays in hydrate crystal formation is not well understood. Therefore, understanding of the mechanism through morphology studies is one of the important aspects to be studied so that optimal industrial processes can be designed. In the present study the effect of three commercially available anionic surfactants which differ in its alkyl chain length on the formation/dissociation of hydrate from a gas mixture of 90.5 % methane – 9.5% propane mixture was investigated. The surfactants used were sodium dodecyl sulfate (SDS), sodium tetradecyl sulfate (STS), and sodium hexadecyl sulfate (SHS). Memory water was used and the experiments for SDS were carried out at three different degrees of under-cooling and three different surfactant concentrations. In addition, the effect of the surfactant on storage capacity of gas into hydrate was assessed. The morphology of the growing crystals and the gas consumption were observed during the experiments. The results show that branches of porous fibre-like crystals are formed instead of dendritic crystals in the absence of any additive. In addition, extensive hydrate crystal growth on the crystallizer walls is observed. Also a “mushy” hydrate instead of a thin crystal film appears at the gas/water interface. Finally, the addition of SDS with concentration range between 242ppm – 2200ppm (ΔT =13.10C) was found to increase the mole consumption for hydrate formation by 14.3 – 18.7 times. This increase is related to the change in hydrate morphology whereby a more porous hydrate forms with enhanced water/gas contacts.

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Aldiwan, Nawaf Hisham. „Crystal growth and inhibition studies of hydrocarbon hydrates and n-alkanes“. Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431705.

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Buchteile zum Thema "Hydrated crystal"

Irvin, G., S. Li, B. Simmons, V. John, G. McPherson und C. J. O’Connor. „Crystal -Growth Restriction Through Clathrate Hydrate Formation: Applications to Nanoparticle Synthesis“. In Advances in Crystal Growth Inhibition Technologies, 255–65. Boston, MA: Springer US, 2002. http://dx.doi.org/10.1007/0-306-46924-3_18.

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Spohr, E., und G. Pálinkás. „Computer Simulations of Water Interactions Near Single Crystal Surfaces“. In Interactions of Water in Ionic and Nonionic Hydrates, 221–24. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72701-6_40.

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Lutz, H. D., und J. Henning. „Uncoupled HDO Modes Caused by Metal Guest Ions in Crystal Matrices“. In Interactions of Water in Ionic and Nonionic Hydrates, 69–70. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72701-6_13.

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Füredi-Milhofer, H., D. Škrtić, V. Hlady, L. Komunjer, M. Marković, N. Filipović-Vinceković und J. Miculinić. „The Influence of Additives on Nucleation, Crystal Growth, and Aggregation of Calcium-Oxalate Hydrates“. In Urolithiasis, 259. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4899-0873-5_80.

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Stöber, Stefan, und Herbert Pöllmann. „Crystal Chemistry of Lamellar Calcium Aluminate Sulfonate Hydrates: Fixation of Aromatic Sulfonic Acid Anions“. In Minerals as Advanced Materials II, 115–30. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-20018-2_11.

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Ji, G. L. „Electrostatic Adsorption of Anions“. In Chemistry of Variable Charge Soils. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097450.003.0007.

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Electrostatic adsorption of anions is one of the important characteristics of variable charge soils. This is caused by the fundamental feature that these soils carry a large quantity of positive surface charge. However, because these soils carry positive as well as negative surface charges, they may exert both attractive and repulsive forces on anions. Therefore, the situation in the adsorption of anions by these soils may be quite complex. There may also be the occurrence of negative adsorption of anions. Besides, for some anion species both electrostatic force and specific force may be involved during their interactions with variable charge soils. As shall be seen in this chapter, such specific force may be operative even for some anion species such as chloride that are generally considered as solely electrostatic in nature during adsorption. Because of historical reasons, the literature on electrostatic adsorption of anions by soils is very limited. Nevertheless, as shall be seen in this chapter, the topic is of interest in both theory and practice. In the present chapter, adsorption of anions shall be discussed mainly from the viewpoint of electrostatic adsorption. The other type of adsorption, specific adsorption or coordination adsorption, shall be dealt with in Chapter 6. The radius of anions is generally much larger than that of cations. Thus, the charge density on anions would be low. When hydrated, because of the smaller ion-dipole force exerted on water molecules, anions are less hydrated than cations. This can be seen in Table 4.1. The rH/rc ratio for cations ranges from 2.22 to 6.37, while that for anions is smaller than 2 except for F-. The orientation of water molecules around anions, especially in the primary hydration region, is also different from that around cations (Conway, 1981). Because of the small rH/rc ratio, hydration does not induce the change in order of size when anions of the same valency are compared. For example, the crystal radii of Cl-, NO3-, and ClO4- are 0.181, 0.264, and 0.292 nm, respectively, while the hydrated radii of these ions are 0.332, 0.335, and 0.338, respectively.

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Bethke, Craig M. „Activity Coefficients“. In Geochemical Reaction Modeling. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195094756.003.0011.

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Among the most vexing tasks for geochemical modelers, especially when they work with concentrated solutions, is estimating values for the activity coefficients of electrolyte species. To understand in a qualitative sense why activity coefficients in electrolyte solutions vary, we can imagine how solution concentration affects species activities. In the solution, electrical attraction draws anions around cations and cations around anions. We might think of a dilute solution as an imperfect crystal of loosely packed, hydrated ions that, within a matrix of solvent water, is constantly rearranging itself by Brownian motion. A solution of uncharged, nonpolar species, by contrast, would be nearly random in structure. The electrolyte solution is lower in free energy G than it would be if the species did not interact electrically because of the energy liberated by moving ions of opposite charge together while separating those of like charge. The chemical potentials of the species, for the same reason, are smaller than they would be in the absence of electrostatic forces.

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Bernstein, Joel. „Polymorphism of pharmaceuticals“. In Polymorphism in Molecular Crystals, 342–75. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780199655441.003.0007.

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Chapter 7 deals with polymorphism in pharmaceuticals. Following a discussion of the problem of determining the statistics of the occurrence of polymorphism in pharmaceuticals, I present a discussion and examples of the connection between polymorphism and the rate of dissolution and solubility, bioavailability, and the importance of phase changes and mixtures of forms in pharmaceutical preparations. I survey some of the considerations and techniques involved in screening for crystal forms: solvent selection, specific screening for solvates and hydrates, gel crystallization, crystallization in ionic liquids, the challenge of difficult to obtain stable forms and unstable new forms, and the outlook on new techniques and conditions for crystallization. The chapter also deals with polymorphism in pharmaceutical co-crystals, excipients, and amorphous forms and the importance and utility of chemical microscopy in the study of polymorphism of pharmaceuticals.

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Nangia, Ashwini. „Water Clusters in Crystal Hydrates“. In Encyclopedia of Supramolecular Chemistry, 1–9. CRC Press, 2004. http://dx.doi.org/10.1081/e-esmc-120023838.

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Wu, Qiang, Fuliang Zhu, Xia Gao und Baoyong Zhang. „Effect of hydrate crystal type on mechanical properties of gas hydrate-bearing coal“. In Progress in Mine Safety Science and Engineering II, 1029–32. CRC Press, 2014. http://dx.doi.org/10.1201/b16606-194.

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Konferenzberichte zum Thema "Hydrated crystal"

Nielsen, James L., Syed Y. Nahri, Wei Zhao, Panfeng Wei und Yuanhang Chen. „Effect of LCM Fibers on the Rate of THF-Water Clathrate Hydrate Growth in Water-Based Drilling Fluids“. In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96682.

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Abstract This study investigates how different sized fibers used commonly as Lost Circulation Material (LCM) change the time required for induction and agglomeration of natural gas hydrates in drilling fluids using laboratory experimentally obtained data. Three different sizes of LCM fibers, fine, medium and coarse, were studied to observe how the size of each type of fiber affects the rate of hydrates growth. THF-Water clathrate hydrates were used as a model for hydrate growth at standard pressure conditions using a 20:80 molar ratio of THF to water. The concentrations of LCM fibers tested varied between 1–3% by weight. Each type of fiber was tested individually at −6 °C, −3 °C, and 0 °C and monitored for changes in hydrate induction and agglomeration rates. Tests were repeated using water-based drilling fluids using bentonite as the primary viscosifier and barite as a weighting agent to test 10, 12, and 14 ppg fluids. Fibers were tested under static conditions to identify changes in the nucleation and agglomeration rates for each. The rates of hydrate nucleation between samples of THF-Water and LCM fibers and each sample of water-based drilling fluid with LCM fibers was found to be consistent with no statistically significant change in rate being observed due to the fibers present. However, we observed a significant change in the rate of agglomeration that was dependent on the size and concentration of the fiber particles. We identified that fine fibers provided the most significant increase in the rate of agglomeration followed by medium and coarse fibers, respectively, with increasing LCM fiber concentrations. Compared to control samples, using fibers produced initial hydrate agglomeration around the freely suspended fibers. Due to their proximity to other fibers with hydrates developing around them, the hydrates were able to form very large free moving crystals in the solution before completely agglomerating and forming a solid plug. The results and conclusions provide new insights and guidance in drilling fluids and LCM design for offshore deep-water drilling. Gas hydrates can potentially develop and agglomerate along in the BOP and kill/choke lines during a well control event, as what is suspected as what happened in Macondo blowout where a considerable amount LCMs were used during drilling and as a spacer during a negative pressure test.

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Yuanyuan, Li, Pan Xiaoqiang, Huang Xiulin, Wu Ying und Yang Jing. „Study on Preparation Process and Properties of High Hydrogen Content Concrete for Neutron Shielding“. In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16631.

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Abstract A series of concrete samples with high hydrogen content were prepared by pressing process with aluminum hydroxide, boron carbide and aluminate cement as raw materials. the mechanical performance of the shielding material was examined by flexural strength tester and compression strength tester. Thermogravimetric analyzer was used to test the weight loss performance of the shielding material, hydrated cement and Al(OH)3. The thermal stability of the concrete at working temperature were investigated by bake the samples at 210°C for 90 hours and at 300°C for 5 hours. The shielding performance against neutron from 241Am-Be source were examined by neutron penetration tests. The test results show that the mechanical properties of the shielding material decrease with the increase of the content of aluminum hydroxide, the compression strength of the shielding material reached above 10MPa. The decomposition temperature of conc is 220°C, the weight loss curve tends to be plateau after baking at 210°C for 20 hours. Most of the crystal water lost after holding at 300°C for 5 hours, but the dimensions of the samples show no obvious change. The shielding performance of the material against neutron from 241Am-Be source is comparable to that of lead-boron polyethylene.

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Odukoya, Adedoyin, und Greg F. Naterer. „Entropy Production of Hydrate Transport in Subsea Multiphase Pipeline Flows“. In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-42272.

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A numerical model is developed to examine the flow conditions of multiphase heat transfer and entropy production during hydrate formation in subsea pipelines. The temperature and pressure gradients of the oil and gas flow in subsea pipelines lead to entropy generation. This paper examines the impacts and effects of thermodynamic irreversibilities on the nucleation and growth processes of hydrate crystals in the pipeline flows. The effects of heat transfer ratio, internal diameter of the pipe, molar gas density, and environment temperature on entropy production in subsea pipelines are predicted and discussed in this paper. The numerical model accounts for the temperature distribution along the axial length of the pipe, reaction kinetics, and mass transfer between the solid and fluid layer. The kinetic energy of the hydrate particles during the coagulation process is analyzed in the numerical model. The results indicate that entropy production is highest at the beginning of the nucleation process. Pipelines with smaller internal radii have a lower rate of hydrate formation in subsea pipelines. The results from the numerical model are verified by comparison with experimental results for structure type II natural gas hydrates.

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Kwon, Jinhyeong, Hyunmin Cho, Inho Ha, Habeom Lee, Sukjoon Hong und Seung Hwan Ko. „Mechano-thermo-chromic device with supersaturated salt hydrate crystal for next-generation smart window applications“. In Emerging Liquid Crystal Technologies XV, herausgegeben von Liang-Chy Chien und Dirk J. Broer. SPIE, 2020. http://dx.doi.org/10.1117/12.2542731.

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Yu, Feng, Yongchen Song, Weiguo Liu, Yanghui Li und Jiafei Zhao. „Study on Shear Strength of Artificial Methane Hydrate“. In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-21174.

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The production of methane from hydrate reservoir may induce deformation of the hydrate-bearing strata. The research on mechanical properties of methane hydrate and establishing an efficient methane exploitation technology appear very important. In this paper, a low-temperature high-pressure triaxial test system including pressure crystal device (sample preparation system) was developed. A series of triaxial shear tests were carried out on artificial methane hydrate samples. The mechanical behavior was analyzed. The preliminary results show that the shear strength of methane hydrate increases with the increase of confining pressure and strain rate. While it increases with the decrease of temperature. Moreover, the secant modulus increases with the enhancement of strain rate and the decrease of confining pressure.

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Yao, Lei, Jiafei Zhao, Chuanxiao Cheng, Yu Liu und Yongchen Song. „Formation and Dissociation of Tetrahydrofuran Hydrate in Porous Media“. In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-21176.

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Tetrahydrofuran hydrate has long been used as a proxy of methane hydrate in laboratory studies. This paper investigates the formation and dissociation characters of tetrahydrofuran hydrate in porous media using the magnetic resonance imaging (MRI) technology. Various sized quartz glass beads are used to simulate the sediment. The formation and dissociation processes of THF hydrate are observed. The hydrate saturation during the formation is calculated based on the MRI data. The experimental result indicates that the third surface has an important effect on hydrate formation process. THF hydrate crystals begin to form on the glass beads and in their adjacent area as well as from the wall of the sample container. Furthermore, as the pore size increases, or the formation temperature decreases, the formation rate of THF hydrate gets faster. However, the dissociation rate is mostly dependent on the dissociation temperature rather than the pore size.

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de Matos Gomes, Etelvina, Cristina F. Goncalves, Michael S. Belsley, Flavio Ferreira, M. Margarida R. Costa, Victor H. Rodrigues und Alberto Criado. „Crystal structure and second harmonic generation in cesium hydrogen malate hydrate“. In Optics & Photonics 2005, herausgegeben von Ravindra B. Lal und Donald O. Frazier. SPIE, 2005. http://dx.doi.org/10.1117/12.614096.

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Ninagawa, Chikako, Hirohiko Niioka, Tsutomu Araki und Mamoru Hashimoto. „Observation of anhydrated and hydrated DAST crystals using multiplex fourth order Raman microscope“. In JSAP-OSA Joint Symposia. Washington, D.C.: OSA, 2014. http://dx.doi.org/10.1364/jsap.2014.18a_c3_11.

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Bourg, P., P. Glénat und M. L. Bousque. „Selection Of Commercial Kinetic Hydrate Inhibitors Using A New Crystal Growth Inhibition Approach Highlighting Major Differences Between Them.“ In SPE Middle East Oil and Gas Show and Conference. Society of Petroleum Engineers, 2013. http://dx.doi.org/10.2118/164258-ms.

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Chakraborty, Suvra, Vandad Talimi, Mohammad Haghighi, Yuri Muzychka und Rodney McAffee. „Thermal Analysis of Offshore Buried Pipelines Through Experimental Investigations and Numerical Analysis“. In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65441.

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Modeling of heat loss from offshore buried pipelines is one of the prime concerns for Oil and Gas industries. Offshore Oil and Gas production and thermal modeling of buried pipelines in arctic regions are challenging tasks due to environmental conditions and hazards. Flow properties of Oil and Gas flowing through the pipelines in arctic regions are also affected due to freezing around pipelines. Solid formation in the production path can have serious implications on production. Heavy components of crude oil start to precipitate as wax crystal when the fluid temperature drops. Gas hydrates also form when natural gas combines with free water at high pressure and low temperature. Pipeline burial and trenching in some offshore developments are now one of the prime methods to avoid ice gouge, ice cover, icebergs, and other threats. Long pipelines require more thermal management to deliver production to the sea surface. Significant heat loss may occur from offshore buried pipelines in the forms of heat conduction and natural convection through the seabed. The later can become more prominent where the backfill soil is loose or sandy. The aim of this paper is to provide an insight of modeling and conducting the experiments using different parameters with numerical analysis results support to investigate the heat loss from offshore buried pipelines. This paper also provides validation of the outputs from benchmark tests with analytical models available for theoretical shape factor at constant temperature and constant heat flux boundary conditions. These theoretical models have limitations such as the assumption of uniform soil properties around the buried pipeline, isothermal outer surface of the buried pipeline and soil surface. Degree of saturation of surrounding medium can play a significant role in the thermal behavior of fluid travelling through the backfill soil. This paper presents several steady states and transient response analysis describing some influential geotechnical parameters along with test procedures and numerical simulations using CFD to model the heat loss for different parameters such as burial depth, backfill soil, trench geometries etc. This paper also shows the transient response for several shutdown (cooldown) tests performed in the saturated sand medium. The statistical and uncertainty analysis performed from the experimental outputs also ensure the legitimacy of the experimental model. The outcomes of this research will provide valuable experimental data and numerical predictions for offshore pipeline design, heat loss from buried pipelines in offshore conditions, and efficient model to mitigate the flow assurance issues e.g. wax and hydrates.

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Berichte der Organisationen zum Thema "Hydrated crystal"

Miller, M. L., und R. C. Ewing. The crystal chemistry and structural analysis of uranium oxide hydrates. Final report, May 15, 1995--December 31, 1997. Office of Scientific and Technical Information (OSTI), November 1998. http://dx.doi.org/10.2172/665932.

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