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Kimberlitic olivineBrett, Richard Curtis 05 1900 (has links)
Kimberlite hosts two populations of olivine that are distinguished on the basis of grain size and morphology; the populations are commonly described genetically as xenocrysts and phenocrysts. Recent studies of zoning patterns in kimberlitic olivine phenocrysts have cast doubt on the actual origins of the smaller olivine crystals. Here, we elucidate the nature and origins of the textural and chemical zonation that characterize both populations of olivine. Specifically, we show that both olivine-I and olivine-II feature chemically distinct overgrowths resulting from magmatic crystallization on pre-existing olivine xenocrysts. These results suggest that the total volume of olivine crystallized during transport is substantially lower (≤5%) than commonly assumed (e.g. ~25%), and that crystallization is dominantly heterogeneous. This reduces estimates of the Mg# in primitive kimberlite melt to more closely reconcile with measured phenocryst compositions.
Several additional textures are observed in olivine, and include: sealed cracks, healed cracks, phases trapping in cracks, rounded grains, overgrowths and phase trapping in overgrowths. These features record processes that operate in kimberlite during ascent, and from these features we create a summary model for kimberlite ascent:
• Olivine is incorporated into kimberlitic melts at great depths as peridotitic mantle xenoliths.
• Shortly after the incorporation of these xenocrysts the tensile strength of the crystals within xenoliths is reached at a minimum of 20 km from its source. Disaggregation of mantle xenoliths producing xenocrysts is facilitated by expansion of the minerals within the xenoliths.
• The void space produced by the failure of the crystals is filled with melt and crystals consisting of primary carbonate (high-Sr), chromite and spinel crystals. The carbonate later crystallizes to produce sealed fractures.
• Subsequent decompression causes cracks that are smaller than the sealed cracks and are preserved as healed cracks that crosscut sealed cracks.
• Mechanical rounding of the xenocrysts post-dates, and/or occurs contemporaneously with decompression events that cause cracking.
• Saturation of olivine produces rounded overgrowths on large xenocrysts, euhedral overgrowths on smaller xenocrysts, and a volumetrically minor population of olivine phenocrysts. Olivine growth traps fluid, solid and melt inclusions.
Calculations based on these relationships suggest that the melt saturates with olivine at a maximum depth of 20 km and a minimum depth of 7 km.
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Investigation of How Different Fat Systems and Other Ingredients Affect the Properties of Whipping Creams Based on Vegetable FatLundin, Josefin January 2013 (has links)
Whipping creams are oil-in-water emulsion which by whipping can be formed to a foam by the incorporation of air into the system. Traditionally whipping creams are made out of milk but today imitation whipping creams based on vegetable fat has gained a large share of the marked due to their many benefits compared to traditionally whipping creams. Imitation whipping creams are both cheaper and more flexible than traditionally creams. By vary the characteristics of the fat system and the cream recipe the properties of the imitation creams can be adapted to fit the purpose of a specific product. The aim of this thesis was to increase the understanding of how different types of fat systems and other ingredients affect the properties of imitation whipping creams based on vegetable fat. This was done by studying three vegetable fat systems with different physicochemical properties. The properties of the fat systems were characterized and the three fat systems were then used for making different imitation whipping creams. The properties of the creams were characterized and the properties of the fat systems and the creams were assessed and compared with each other. The study showed that the fat characteristics that generally seem to have the highest impact on the properties of whipping creams are the structure, the solid fat content and the crystallization temperature of the fat. A fat solution with a hard structure, a high crystallization temperature and a high solid fat content at a wide range of temperatures overall seem to provide the whipping creams with the best properties. This as these fat properties provide the creams with a high foam stability, a high overrun and a short whipping time. This study has also shown that other ingredients than the fat systems provide the creams with diverging properties. This is best shown by the results of the freeze-thaw stability which indicate that a recipe with a high amount of sugar seem to provide the whipping creams with good freeze-thaw stability. Other properties of the whipping creams also seem to be very much influenced by other ingredients than the fat systems but further studies are needed to provide clarity to the complexity of the interplay of the ingredients in whipped creams.
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Crystallizing Application ConfigurationsZhang, Zanqing January 2006 (has links)
Software applications have both static and dynamic dependencies. Static dependencies are those derived from the source code. Dynamic runtime dependencies are established at runtime and may be based on information external to the source code, such as configuration files. Flexible applications commonly rely on configuration to adapt to diverse environments. An application's configuration encodes runtime dependencies between the various parts of the application. Reverse engineering tools have traditionally been based solely on static dependencies extracted from the source code. Neglecting dynamic dependencies encoded in an application's configuration can result in incorrect or incomplete program comprehension. Unfortunately, many applications store their configuration in an ad hoc, unstructured format from which it is not feasible to extract runtime dependencies by traditional reverse engineering. Our work takes advantage of well structured, published configuration formats, such as that of J2EE applications. Using these formats we are able to extend reverse engineering to analyse this previously neglected information. We introduce a technique called crystallization, which extracts configuration facts that encode dynamic dependencies. We use these recovered facts to predict and validate dynamic dependencies. Crystallizing configurations has the potential to increase developer productivity by providing better program comprehension.
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Modeling and control of a continuous crystallization process using neural networks and model predictive controlAshobi, Mohammad 01 January 1996 (has links)
Continuous crystallizers are distributed dynamical systems. Physical modeling of these systems using basic principles results in partial and integro-differential equations. To exploit the physical models, in the analysis of the system behavior and the design of an appropriate controller, requires complicated measurement techniques especially in the spatial domain (crystal size distribution or crystal population density). Therefore, obtaining a lumped model structure is desirable. The lumped model of a continuous crystallizer can be obtained either from the physical model, using conventional techniques such as the discretization or function separation methods, or from input and output measurements using system identification approaches. Studies of the crystallization process have indicated that in order to improve the control performance, expressing the process dynamics using single-input, single-output models is insufficient. The aim of this thesis was to investigate the process behavior in a multivariable framework. In this regard, the dynamics of a continuous cooling KCl crystallizer were identified using three-input, three-output linear and nonlinear model structures. The autoregressive exogenous model structures were employed in linear modeling of the process. The nonlinear modeling was performed using several architectures of feedforward and recurrent neural networks. Simulation results demonstrated that the linear modeling, using a single model for the entire dynamics, is not adequate. Either multi-model or nonlinear modeling is recommended. The performance of different neural network structures in the nonlinear modeling of the process was illustrated and, based on the results, some comparisons were made between these networks. The next step in the study of the crystallization process as a multivariable system was to design and apply a multivariable control scheme. Simulation results from the modeling of the process indicated that strong interactions are present among different loops of the system. The process is nonlinear and some of the outputs exhibit inverse or non-minimum-phase responses. The model predictive control strategy is known to perform well in the control of the systems with the behaviors found in the crystallization process. To ensure a feasible solution, the feasible sequential quadratic optimization algorithm was successfully exploited in a model predictive controller. Computer simulations of the controller were performed in order to demonstrate control of the crystal size distribution, crystal purity, and production rate. The effects of different control parameters were illustrated using the simulation results. A brief discussion on how to select these parameters was also provided. Robustness of the model predictive controller was studied in the presence of mismatch between the model and the process.
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Structure-property relationships in copolyester fibers and composite fibersMa, Hongming 12 April 2004 (has links)
Polyethylene terephthalate is one of the most important engineering thermal plastics used for fibers, films and bottles. Despite its wide applications and vast global market, PET has shortcomings, which limits it usage in many
areas. PET has a glass transition temperature (Tg) of 80 DEGREE Celsius, this temperature
is too low for certain applications. Increase in glass transition temperature, high temperature mechanical properties, and dimensional stability is of great importance to further expand the applications of PET. Significant research efforts have been made toward this goal, using a variety of approaches.
In this work, we attempt to improve the properties of PET melt spun filament. Three strategies has been investigated (i) copolymerization of more rigid comonomer, 4, 4' bibenzoate unit into the PET structure, (ii) UV crosslinking of functionalized PET fiber, and (iii) Reinforcing PET matrix with carbon
nanofibers.
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Nonisothermal Crystallization and Thermal Degradation Behaviors of Poly(butylene succinate) and its Copolyesters with Minor Amounts of Propylene SuccinateLu, Shih-fu 15 August 2010 (has links)
Poly(butylene succinate) (PBSu) and two poly(butylene succinate-co-propylene succinate)s (PBPSu 95/5 and PBPSu 90/10) were synthesized via the direct polycondensation reaction. The copolyesters were characterized as having 7.0 and 11.5 mol% propylene succinate (PS) units, respectively, by 1H NMR. Copolyesters were characterized as random, based on 13C NMR spectra. They were fully investigated during nonisothermal crystallization and thermal degradation through various approaches in this study. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) adopted to study the nonisothermal crystallization of these polyesters at a cooling rate of 1, 2, 3, 5, 6 and 10 ºC/min. Morphologies and the isothermal growth rates of spherulites under PLM experiments were monitored and obtained by curve-fitting, respectively. These continuous rate data were analyzed with the Lauritzen-Hoffman equation. A transition of regime II ¡÷ III was found at 95.6, 84.4, and 77.3 ºC for PBSu, PBPSu 95/5, and PBPSu 90/10, respectively.
DSC exothermic curves show that all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Ozawa, Mo, Friedman and Vyazovkin equations. Ozawa equation does not accurately describe the nonisothermal crystallization kinetics of this polyester because part of the crystallization is secondary crystallization. All the results of PLM and DSC measurements indicate that incorporation of minor PS units into PBSu markedly inhibits the crystallization of the resulting polymer. The melting behavior of nonisothermally crystallized samples presents a continuous melting¡Vrecrystallization¡Vremelting process. Additionally, three absorption bands during the nonisothermal crystallization were identified for PBSu and two PBPSu copolyesters, namely, 916, 955, 1045 cm-1 in the attenuated total reflectance FTIR spectra.
Thermogravimetric analysis (TGA)-FTIR was heated at 5 ºC/min under N2 to monitor the degradation products of these three polyesters. FTIR spectra revealed that the major products were anhydrides, which were obtained following two cyclic intramolecular degradation mechanisms by breaking the weak O-CH2 bonds around a succinate group. Thermal stability at heating rates of 1, 3, 5, and 10 ºC/min under N2 was investigated using TGA. The model-free methods of Friedman and Ozawa equations are useful for studying the activation energy of degradation in each period of mass loss. The results reveal that the random incorporation of minor PS units into PBSu did not markedly affect their thermal resistance. Two model-fitting mechanisms were used to determine the loss mass function f(£\), the activation energy and the associated mechanism. The mechanism of autocatalysis nth-order, with f(£\)=£\m(1-£\)n, fitted the experimental data much more closely than did the nth-order mechanism given by f(£\)=(1-£\)n. The obtained activation energy was used to estimate the failure temperature (Tf). The values of Tf for a mass loss of 5% and an endurance time of 60,000 hr are 160.7, 155.5, and 159.3 ºC for PBSu and two the copolyesters, respectively.
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Nonisothermal Crystallization and Thermal Degradation Behaviors of Poly(butylene succinate) and its Copolyesters with Minor Amounts of 2-methyl-1,3-Propylene SuccinateLu, Jin-Shan 11 August 2012 (has links)
Poly(butylene succinate) (PBSu), poly(2-methyl-1,3-propylene succinate) (PMPSu), and their two novel poly(butylene succinate-co-2-methyl-1,3-propylene succinate)s (PBMPSu 95/05 and PBMPSu 90/10) were synthesized by a two-stage esterification reaction. PBMPSu 95/05 and PBMPSu 90/10 were characterized as having 6.5 and 10.8 mol% 2-methyl-1,3-propylene succinate (MPS) units, respectively, by 1H NMR. These copolymers were characterized to be random from the 13C NMR spectra. In this study, the nonisothermal crystallization and thermal degradation behaviors of the polyesters were investigated via different approaches. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) were employed to investigate the nonisothermal crystallization of these copolyesters and neat PBSu. Morphology and the isothermal growth rates of spherulites under PLM experiments at three cooling rates of 1, 2.5 and 5 ¢XC/min were monitored and obtained by curve-fitting. These continuous rate data were analyzed with the Lauritzen-Hoffman equation. A transition of regime II ¡÷ III was found at 96.2, 83.5, and 77.9 ¢XC for PBSu, PBMPSu 95/05, and PBMPSu 90/10, respectively. DSC exothermic curves at five cooling rates of 1, 2.5, 5, 10 and 20 ¢XC/min show that almost all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Tobin, Ozawa, Mo, Friedman and Vyazovkin equations. All the results of PLM and DSC measurements reveal that incorporation of minor MPS units into PBSu markedly inhibits the crystallization of the resulting polymer. The nonisothermal crystallization behavior of these polyesters was also investigated using a Fourier-transform infrared spectrometer (FTIR) with an attenuated total reflection (ATR). The absorbance peaks of crystals for the £\ form (918, 955, and 1045 cm-1) of PBSu and PBMPSu copolyesters were observed by ATR-FTIR under nonisothermal crystallization. When these semicrystalline polyesters started to be solidified from the melt state, these characteristic absorption bands for PBSu and its copolyesters crystals have been detected.
In this study, the thermal degradation mechanisms of PBSu, PMPSu, PBMPSu 95/05, and PBMPSu 90/10 were investigated using a thermogravimetric analyzer combined Fourier-transform infrared spectrometer (TGA-FTIR) and a pyrolysis-gas chromatography¡Vmass spectrometry (Py-GC-MS). The volatile products evolved from the thermal degradation of these two copolyesters were identified to be anhydride, ether, ester, alcohol, alkene, aldehyde, and CO2. FTIR spectra displayed that the main degradation products for these four polymers were anhydrides. Moreover, PBSu-rich PBMPSu copolymers exhibited the same thermal degradation mechanism as that of PBSu at lower thermal degradation temperatures (< 403 ºC) and as that of PMPSu at higher thermal degradation temperatures (> 403 ºC) by the TGA-FTIR analysis. The results of the TGA-FTIR analysis clearly demonstrates that the influence of MPS units on the thermal degradation process is gradually increased as the temperature increases for PBMPSu copolymers. The degradation mechanism of PBMPSu at lower thermal degradation temperatures and PBSu mainly follows the £]-hydrogen bond scission mechanism and the back-biting process from the polymer chains. Moreover, the degradation mechanism of PBMPSu at higher thermal degradation temperatures and PMPSu occurred mainly through the £]-hydrogen bond scission and secondarily through £\-hydrogen bond scission.
Finally, the thermal stability and degradation kinetics of these polyesters were investigated using a TGA at heating rates of 1, 3, 5, and 10 ºC/min under dynamic nitrogen. The activation energies of thermal degradation in elective conversions were estimated using the Friedman and Ozawa methods. The results clearly demonstrated that the thermal stabilities of these PBMPSu copolyesters were slightly reduced with the incorporation of minor MPS units into PBSu. Two model-fitting methods of nth-order and autocatalysis nth-order reaction mechanisms were adopted to determine the mass loss function f(£\), the activation energy and the associated degradation parameters. The results revealed that the mechanism of autocatalysis nth-order fitted the experimental data much more closely than did the nth-order mechanism for PBSu, PMPSu and PBMPSu copolymers.
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Heat of Fusion, Isothermal Crystallization Kinetics and Morphology of Poly(ethylene-co-trimethylene terephthalate) CopolyestersChang, Chih-wei 13 July 2004 (has links)
The crystallization kinetics and the melting behavior of a random copolyester with equal amounts of ethylene- and trimethylene- terephthalate units were studied by using a modulated differential scanning calorimeter in both conventional mode (DSC) and modulated mode (TMDSC). Polarizing light microscope (PLM) was used to study the spherulite growth rates and spherulite patterns. Isothermal crystallization was performed at temperatures (TC) between 115 and 142¢J. The Avrami exponents, n1, were found to increase from 3.00 to 3.22 with an increasing TC. At the highest TC, it should be a sporadic nucleation with spherical growth, i.e. n1 = 4. The value of n1 less than 4 and the slow rate of crystallization indicate that both primary and secondary crystallization occurs in parallel rather than in series. Triple- and double- melting peaks were observed for the melting behavior of DSC at 10¢J/min and of TMDSC at 2¢J/min. The results of WAXD, DSC and TMDSC indicate the coexistence of two melting mechanisms, i.e., dual morphologies and the recrystallization process. The Hoffman-Weeks plot gave an equilibrium melting temperature of 176.6¢J from the reversing curves of TMDSC. In this study, the regime II¡÷III transition temperature can be estimated from the inverse of the half-time of crystallization as overall growth rate and the growth rate. Meanwhile, a clear change in morphology from negative regular to banded spherulites was also observed around 132¢J by using PLM.
The heat of fusion of polymer is customarily evaluated through the melting point depression measurements with the thermodynamic melting points. Application of the Flory equation to the PET/PTT random copolyesters diluted with di-n-butyl phthalate gave the values of the heat of fusion to be 4.48, 3.43 and 3.07 kcal/mole, respectively, for the random copolyesters containing 28, 38 and 50 mole % of ethylene terephthalate unit. The corresponded values of the interaction energy of mixing at infinite dilution were 3.90, 2.85 and 2.75 cal/cc.
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Amorphization and Nanocrystallization Behavior in Mg-Cu-Y Alloy by Adding BoronCheng, Yu-ting 19 July 2005 (has links)
The glass forming ability (GFA) of the lightweight Mg65Cu25Y10 alloy has been widely studied. This alloy contains a medium sized Mg matrix (0.16 nm in atomic radius), a small sized Cu (0.14 nm) and a large sized Y (0.18 nm). The glass transition temperature Tg, supercooled temperature range
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Characterization, Crystallization, Melting and Morphology of Poly(ethylene succinate), Poly(trimethylene succinate) and their CopolyestersChang, Wei-che 03 July 2006 (has links)
Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters (PETSAs) with various compositions were used to investigate the structure-property relationship. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The chemical compositions and the sequence distribution of co-monomers in the copolyesters were determined by NMR spectroscope. The distributions of ES unit and TS unit were found to be random. Their thermal properties were characterized using differential scanning calorimeter (DSC). The thermal stability of polyesters was analyzed by thermogravimeter (TGA) and polarized light microscope (PLM) under nitrogen. The results of TGA show that all of the samples have similar thermal stability (Tstart : 246¡Ó3 ¢XC), but the thermal
degradation temperature of PES and PETSA(95/05) are 213 and 200 ¢XC, respectively,
estimated from the isothermal growth rates after pre-melting at various temperatures.
The degradation temperature analyzed by PLM is more sensitive than that obtained
from TGA. The incorporation of 5 mol% of TS units into PES significantly reduces
the thermal stability of PES. In addition, wide-angle X-ray diffractograms (WAXD)
were obtained for polyesters which were crystallized isothermally at a temperature
5~10 ¢XC below their melting temperatures. The results of WAXD and DSC indicate
that the incorporation of TS units into PES significantly inhibit the crystallization
behavior of PES.
In the second part of this study, PES and PETSA(95/05) were studied in detail.
The crystallization kinetics and the melting behavior were investigated by using DSC
in both conventional mode and modulated mode (TMDSC). The reversing, total, and
non-reversing heat flow curves were analyzed. The Hoffman-Weeks plots gave an
equilibrium melting temperature of 112.7 and 108.3 ¢XC for PES and PETSA(95/05),
XI
respectively. Only one crystal form was found from WAXD for specimens crystallized
isothermally at various temperatures. Based on the WAXD patterns, DSC and
TMDSC thermograms, multiple endothermic melting peaks can be explained by two
mechanisms, melting-recrystallization-remelting and dual morphologies. PLM was
used to study the growth rates and morphology of the spherulites. The growth rates
measured in isothermal conditions were very well comparable with those measured by
the non- isothermal procedure. In addition, the temperature range of growth rates
detected by the non- isothermal procedure is wider than that by the isothermal method,
which is time consuming. The regime II®III transition of PES was estimated at ~ 71
¢XC which is very close to the literature values, and that of PETSA(95/05) was found at
~ 65 ¢XC.
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