Home About us Contact
|
Home About us Contact | ||
|
|
||
Isothermal Conditions (isothermal + condition)
Selected AbstractsCombustion behavior of a falling sodium droplet: Burning rate-constant and drag coefficientHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2005Atsushi Makino Abstract The combustion behavior of a single sodium droplet has been studied experimentally, by use of a falling droplet. It was found that D2 -law can hold for the sodium droplet combustion after the ignition, which can be observed to occur through an increase in the droplet temperature under a condition without a gaseous flame, suggesting that a surface reaction plays an important role in the ignition of sodium. It was also found that the burning rate-constant without forced convection has nearly the same value as those for conventional hydrocarbon droplets, although it is considered that the sodium combustion proceeds in an oxidizer-rich environment even in the air. This can be judged by comparing a temporal variation of the flame/droplet diameter ratio for the sodium droplet with that for the hydrocarbon droplet. A micro-explosion of the burning droplet is also observed when oxygen concentration in the ambience exceeds 0.33 in mass fraction. As for the falling velocity and/or distance of the burning droplet, it turned out that the use of the drag coefficient for solid sphere under isothermal condition is inappropriate in obtaining accurate values. It was also found in another experiment that when Re > 500, the drag coefficient of the falling droplet undergoing combustion is as high as 2 depending on combustion situation and/or droplet temperature, while that of the solid sphere under an isothermal condition is 0.44. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(7): 481,495, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20084 [source] Flashing characteristics in a pipe downstream from a depressurizing tank and temperature fluctuation characteristics at a mixing tee junction with cold water injectionHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2003Koji Shiina Abstract The flashing characteristics in a pipe downstream from a depressurizing tank were experimentally and analytically investigated on the basis of the transient test and two-phase flow analysis. The following conclusions were obtained. (1) When the pressure margin of the pump inlet side and the distance to obtain an isothermal condition were sufficient, flashing phenomena did not occur in spite of the decreasing pressure. (2) When the ratio of the cold water injection flow rate to the hot water flow rate Mc/Mh increased, the peak distance of the water temperature fluctuation moved from L/D = 1 to 0, and the maximum water temperature fluctuation ratio was about 40% of the temperature difference between hot and cold water near the mixing tee junction. Because no problem occurred regarding the pipe material thermal fatigue, reliability of the mixing tee junction was assured. (3) Due to suppression of flashing phenomena of the mixing pipe system, the decision diagram on the flashing occurrence was obtained from the test and the analytical results, taking into consideration three factors: the depressurizing ratio in the tank; the cold water injection flow rate due to remaining subcooling; and the delay time of thermal mixing. The simplified analytical equation was used to decrease the cold water injection flow rate by the optimized pipe length between the mixing tee junction and the drain pump. The cold water injection flow rate was minimized when the pipe length was about 15 to 20 times the pipe inner diameter. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(5): 411,429, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10096 [source] Studies on pyrolysis of vegetable market wastes in presence of heat transfer resistance and deactivationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2005Ruby Ray Abstract In the present investigation, the pyrolysis of predried vegetable market waste (dp=5.03 mm) has been studied using a cylindrical pyrolyser having diameter of 250 mm under both isothermal and non-isothermal conditions within the temperature range of 523,923 K with an intention to investigate the effective contribution of different heat transfer controlling regime namely intra-particle, external along with kinetically control regime on the overall global rate of pyrolysis. Thermogravimetric method of analysis was utilized to obtain experimental data for both isothermal and non-isothermal cases by coupling a digital balance with the pyrolyser. The pyrolysis of vegetable market waste has been observed to exhibit deactivated concentration independent pyrolysis kinetics, analogous to catalytic poisoning, throughout the entire range of study. The deactivation is of 1st order up to 723 K and follows the 3rd order in the temperature range of 723 Loop-mediated isothermal amplification targeting the apxIVA gene for detection of Actinobacillus pleuropneumoniaeFEMS MICROBIOLOGY LETTERS, Issue 1 2009Wang Yang Abstract Loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method performed under isothermal conditions with high specificity and efficiency. We developed a diagnostic method based on LAMP for detection of Actinobacillus pleuropneumoniae. Using six specific primers targeting the apxIVA gene, the LAMP assay rapidly amplified the target gene within 30 min, requiring only a laboratory water bath for the reaction to occur. The resulting amplificon was visualized by adding SYBR Green I to the mixture. The results obtained from testing 15 A. pleuropneumoniae reference strains and other seven bacterial species strains showed that the LAMP was as specific as and 10 times more sensitive than nested PCR. Sixty-five tonsil samples were collected from 65 healthy pigs. All the samples were negative for A. pleuropneumoniae by immunomagnetic separation-based (IMS) bacterial isolation, nested PCR and LAMP, respectively. Meanwhile, 115 tonsil samples were also collected from 115 pigs with apparent respiratory problems. Twenty-two were positive by IMS bacterial isolation. All the samples that were positive by IMS bacterial isolation were also positive by nested PCR and LAMP. The LAMP assay demonstrated exceptionally higher sensitivity than nested PCR by picking up 14 additional positive cases (,2 test, P<0.0001); we concluded that LAMP was a highly sensitive and reliable method for detection of A. pleuropneumoniae infection. [source] Safety evaluation of sewage-sludge-derived fuels by comparison with other fuelsFIRE AND MATERIALS, Issue 4 2009Xin-Rui Li Abstract The utility of sewage sludge as a biomass fuel is taken as a new approach to recycle unwanted wastes as renewable energy and deal with global warming. However, safety caring of this new type of fuel is a premise before it is practically used in boilers. Thermal behaviors of four sludge-derived fuels which are under development were examined by several calorimeters (such as thermogravimetry/differential thermal analysis, C80 and thermal activity monitor) at temperature ramp and isothermal conditions. Heat generation at relatively low temperatures was observed. The corresponding spontaneous ignition was detected in an adiabatic spontaneous ignition tester at 80,C in some sludge species. Moreover, a certain amount of gaseous evolution was accompanied when the sludge fuels were stored at room temperature and at 60,C. Oxidation is mainly responsible for the heat and gas release from the sludge fuels. The hazards of the sewage sludge fuels were also compared with a bituminous coal and a refuse-derived fuel, which have the main feature of spontaneous ignition. Copyright © 2009 John Wiley & Sons, Ltd. [source] Rapid detection of metastasis of gastric cancer using reverse transcription loop-mediated isothermal amplificationINTERNATIONAL JOURNAL OF CANCER, Issue 5 2007Daisuke Horibe Abstract Tailor-made surgeries for patients with solid malignancies have been under consideration on the basis of the development of new approaches for minor metastatic foci of malignant tumors. Accurate and reliable methods to detect metastases in biopsy specimens with certain rapidity are essential for the performance of these surgeries. The aim of this study was to develop a rapid and practical method to detect metastasis in specimens from patients with gastric carcinoma with the use of reverse transcription loop-mediated isothermal amplification (RT-LAMP) reaction, a novel technique for detecting mRNA expressions of targeted sequences with high sensitivity, specificity and rapidity under isothermal conditions. RT-LAMP primers to detect cytokeratin19 (CK19) mRNA were generated and 92 lymph nodes (LNs) obtained from 9 patients with gastric cancer were tested for tumor metastases with this technique. Among 92 LNs, 15 were metastasis-positive by routine histopathological examination. RT-LAMP reaction detected CK19 expression in all of the pathologically positive LNs and in 16 of 77 negative LNs. Nested RT-PCR assay for CK19 expression was also performed on 2 of the 9 cases including 32 LNs. The agreement rate of CK19 expression detection by RT-LAMP and RT-PCR analysis was 31/32 (97%). The RT-LAMP technique showed similar sensitivity to detect metastases as nested RT-PCR assay, with a rapidity comparable to that of intraoperative histopathological examination with frozen sectioning and hematoxylin and eosin staining. This method is expected to play an essential role in the performance of tailor-made surgeries in the near future. © 2006 Wiley-Liss, Inc. [source] Studies on pyrolysis of vegetable market wastes in presence of heat transfer resistance and deactivationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2005Ruby Ray Abstract In the present investigation, the pyrolysis of predried vegetable market waste (dp=5.03 mm) has been studied using a cylindrical pyrolyser having diameter of 250 mm under both isothermal and non-isothermal conditions within the temperature range of 523,923 K with an intention to investigate the effective contribution of different heat transfer controlling regime namely intra-particle, external along with kinetically control regime on the overall global rate of pyrolysis. Thermogravimetric method of analysis was utilized to obtain experimental data for both isothermal and non-isothermal cases by coupling a digital balance with the pyrolyser. The pyrolysis of vegetable market waste has been observed to exhibit deactivated concentration independent pyrolysis kinetics, analogous to catalytic poisoning, throughout the entire range of study. The deactivation is of 1st order up to 723 K and follows the 3rd order in the temperature range of 723 Curing mechanisms and kinetic analysis of DGEBA cured with a novel imidazole derivative curing agent using DSC techniquesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Li Liu Abstract A novel imidazole derivative, 2MI- g -CA, was obtained through the reaction of 2-methylimidazole (2MI) and cyanuric acid (CA) and characterized by means of elemental analysis, FTIR spectroscopy, 1H NMR spectroscopy, and mass spectrometric analysis. The curing mechanisms and kinetics of diglycidyl ether of bisphenol A (DGEBA) using 2MI and 2MI- g -CA as curing agents were studied with differential scanning calorimetry (DSC) under dynamic and isothermal conditions. Both dynamic and isothermal DSC thermograms of DGEBA/2MI system showed two distinct exothermic peaks, whereas those of DGEBA/2MI- g -CA system showed only one distinct exothermic peak. These results indicated that the two systems have different initiation curing mechanisms. The apparent activation energies (Ea) obtained from DSC scanning runs using the Kissinger and Ozawa methods were 79.0, 83.0 kJ/mol and 84.2, 88.8 kJ/mol for DGEBA/2MI and DGEBA/2MI- g -CA systems, respectively. These values suggested the novel curing agent 2MI- g -CA exhibited greater levels of latency during cure or increased the pot life of epoxy resin system. In addition, under the same curing condition, the Tg values of DGEBA/2MI- g -CA system were about 25°C higher than those of DGEBA/2MI system, exhibiting a better thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Kinetic study of the thermal degradation of poly(aryl ether ketone)s containing 2,7-naphthalene moietiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Si-Jie Liu Abstract The degradation of poly(aryl ether ketone) containing 2,7-naphthalene moieties was subjected to dynamic and isothermal thermogravimetry in nitrogen and air. The dynamic experiments showed that the initial degradation temperature, temperature for 5% weight loss, and temperature corresponding to the maximum degradation rate of poly(aryl ether ketone) containing 2,7-naphthalene moieties were a little higher than those of poly(ether ether ketone) and almost independent of the 2,7-naphthalene moiety content. The thermal stability of poly(aryl ether ketone) containing 2,7-naphthalene moieties in air was substantially less than that in nitrogen, and the degradation mechanism was more complex. The results obtained under the isothermal conditions were in agreement with the corresponding results obtained in nitrogen and air under the dynamic conditions. In the dynamic experiments, the apparent activation energies for the degradation processes were 240 and 218 kJ/mol in nitrogen and air for the second reaction stage as the heating rate was higher than 5°C/min. In the isothermal experiments, the apparent activation energies for the degradation processes were 222 and 190 kJ/mol in nitrogen and air, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis, characterization, and electrical properties of diazophenylene bridged Co, Ni, Cu, Ce, and Er phthalocyanine polymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Cemil Alkan Abstract In this research, diazophenylene bridged metal-phthalocyanine (Pc) polymers were produced from diazonium salt of 1,4-diaminophenylene and presynthesized 1,8,15,22-tetraamino metal-Pcs. 1,8,15,22-Tetraamino metal-Pc complexes of Co, Ni, Cu, Ce, and Er were obtained by reducing 1,8,15,22-tetranitro metal-Pc complexes synthesized from 3-nitrophthalic anhydride, urea, metal salt, and ammonium molybdate catalyst. Complexes and polymers were characterized by Fourier transform infrared (FTIR), ultraviolet,visible (UV,vis), and X-ray powder diffraction spectroscopes. X-ray analysis of the polymers showed that there were short-range orientations in the polymers. Thermal analysis of the complexes and the polymers were done by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA) at a heating rate of 10°C min,1 under nitrogen atmosphere. Ash analysis was performed to determine the metal content of the polymers. Viscosimetry and ebullioscopy measurements of the soluble part of the polymers were done for molecular weight analysis of the soluble part in tetrahydrofuran (THF) at 25°C. Four-probe conductivity measurements on isothermal conditions revealed that the polymer samples showed 104 fold increases in their electrical conductivities when doped with iodine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Detection of koi herpesvirus in common carp, Cyprinus carpio L., by loop-mediated isothermal amplificationJOURNAL OF FISH DISEASES, Issue 10 2004I Gunimaladevi Abstract Loop-mediated isothermal amplification (LAMP) is a novel method that amplifies DNA with high specificity and rapidity under isothermal conditions. In this study, using the LAMP method, a protocol for koi herpes virus (KHV) detection in common carp was designed. A set of four primers, two inner and two outer, were designed based on the sequence of the thymidine kinase (tk) gene of KHV. Time and temperature conditions for detection of KHV were optimized for 60 min at 65 °C. The detection limit using LAMP was found to be similar to that by polymerase chain reaction. In this study, we have developed a highly sensitive and rapid diagnostic procedure for detection of KHV infection in common carp. [source] GROWTH KINETICS OF CLOSTRIDIUM PERFRINGENS IN COOKED BEEF,JOURNAL OF FOOD SAFETY, Issue 2 2003LIHAN HUANG ABSTRACT The objective of this work was to investigate the growth kinetics of a three-strain cocktail of Clostridium perfringens in cooked beef. The study was conducted by growing the heat-activated spores in ground beef under isothermal conditions between 17,50C. A four-parameter Gompertz equation was used as a primary model to fit the growth curves along with a modified Ratkowsky model to analyze the temperature dependence of the bacterial growth. Results indicated that the Gompertz model could accurately describe the growth of C. perfringens in cooked beef. The estimated theoretical minimum, optimum, and maximum growth temperatures of this organism in cooked beef were 9.8, 47.1, and 50.8C, respectively. A linear relationship between the durations of the lag and exponential phases of growth curves was observed in this study. Such a linear relationship can be used to generate a linear isothermal growth curve complete with the lag, exponential, and stationary phases without complex mathematical computation. The kinetic models and growth parameters obtained from this study potentially can be applied to the food industry to design appropriate cooling schedules and estimate the growth of C. perfringens in thermally processed beef products under temperature abuse conditions. [source] Reduction of Acrylamide and Its Kinetics by Addition of Antioxidant of Bamboo Leaves (AOB) and Extract of Green Tea (EGT) in Asparagine,Glucose Microwave Heating SystemJOURNAL OF FOOD SCIENCE, Issue 2 2008Yu Zhang ABSTRACT:, This study investigated the effect of antioxidant of bamboo leaves (AOB) and extract of green tea (EGT) on the formation and kinetics of acrylamide in an equimolar asparagine,glucose model system. The substrates spiked with AOB and EGT were microwave-heated at 180 °C and the acrylamide content in final reaction products was quantified by ultra-performance liquid chromatography,tandem mass spectrometry (UPLC-MS/MS). The results showed that both AOB and EGT could effectively reduce the formation of acrylamide in an asparagine,glucose microwave heating model system and achieved a maximum reduction rate when the addition levels of AOB and EGT were both 10,6 mg/mL reaction solution. To describe the kinetic behavior of acrylamide, a simplified kinetic model was optimized and relative kinetic rate constants were evaluated under isothermal conditions. The results indicated that the reduction effect of AOB and EGT on the acrylamide formation may partly be ascribed to the decrease of the formation rate constant (kF) in both AOB and EGT-spiked systems (43.4% and 32.3% of decrease, respectively, P < 0.05). The kinetic parameter kE, which represents the elimination rate of acrylamide in both AOB and EGT-spiked systems, was not significantly different (6.9% of increase and 10.9% of decrease, respectively, P > 0.05). The results of the kinetic study indicated that addition of AOB and EGT could significantly reduce the formation rate constant (kF) of acrylamide, but could not significantly affect the elimination rate constant (kE) of acrylamide. [source] Dynamic Predictive Model for Growth of Salmonella Enteritidis in Egg YolkJOURNAL OF FOOD SCIENCE, Issue 7 2007V. Gumudavelli ABSTRACT:,Salmonella Enteritidis (SE) contamination of poultry eggs is a major human health concern worldwide. The risk of SE from shell eggs can be significantly reduced through rapid cooling of eggs after they are laid and their storage under safe temperature conditions. Predictive models for the growth of SE in egg yolk under varying ambient temperature conditions (dynamic) were developed. The growth of SE in egg yolk under several isothermal conditions (10, 15, 20, 25, 30, 35, 37, 39, 41, and 43 °C) was determined. The Baranyi model, a primary model, was fitted with growth data for each temperature and corresponding maximum specific growth rates were estimated. Root mean squared error (RMSE) values were less than 0.44 log10 CFU/g and pseudo- R2 values were greater than 0.98 for the primary model fitting. For developing the secondary model, the estimated maximum specific growth rates were then modeled as a function of temperature using the modified Ratkowsky's equation. The RMSE and pseudo- R2 were 0.05/h and 0.99, respectively. A dynamic model was developed by integrating the primary and secondary models and solving it numerically using the 4th-order Runge,Kutta method to predict the growth of SE in egg yolk under varying temperature conditions. The integrated dynamic model was then validated with 4 temperature profiles (varying) such as linear heating, exponential heating, exponential cooling, and sinusoidal temperatures. The predicted values agreed well with the observed growth data with RMSE values less than 0.29 log10 CFU/g. The developed dynamic model can predict the growth SE in egg yolk under varying temperature profiles. [source] Synthesis of heat exchanger networks with nonisothermal phase changesAICHE JOURNAL, Issue 4 2010M. M. Faruque Hasan Abstract Most literature on the synthesis of heat exchanger networks via mathematical programming methods has dealt with phase changes by assuming nearly isothermal conditions. Many multicomponent phase changes of practical interest (e.g., those in sub-ambient processes) occur over ranges of temperatures and exhibit nonlinear temperature-enthalpy relations (T-H curve). In such cases, isothermal approximations may lead to inferior or unacceptable networks. In this article, we propose a mixed-integer nonlinear programming formulation and a solution algorithm to incorporate nonisothermal phase changes in heat exchanger network synthesis. We approximate the nonlinear T-H curves via empirical cubic correlations, and propose a procedure to ensure minimum temperature approach at all points in the exchangers. Our approach successfully solves two industry examples and shows promise for significant cost reductions when compared with existing processes. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] In situ high temperature microscopy study of the surface oxidation and phase transformations in titanium alloysJOURNAL OF MICROSCOPY, Issue 3 2002S. Malinov Summary Two popular commercial titanium alloys, Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.08Si, were used for in situ high temperature microscopy study. The experiments were performed on an optical microscope equipped with high temperature stage using both normal and florescence lights. Two kinds of experiments were performed, at continuous heating/cooling with different rates and in isothermal conditions at different temperatures. The changes taking place on the sample surface during the experiments were monitored. The morphology of the ,,,,, phase transformation was recorded at different heat treatment conditions using the effect of thermal etching. An effect of sample surface oxidation and deoxidation was observed during continuous heating. The appearance and disappearance of ordered titanium oxides Ti3O and Ti2O are discussed based on the phase equilibrium diagram. The kinetics of the surface oxidation was monitored in both isothermal and continuous cooling conditions. [source] Parameters of gas dissolution in liquids obtained by isothermal pressure decayAICHE JOURNAL, Issue 1 2009Maurice L. Rasmussen Abstract A rapid and effective data analysis and interpretation approach is developed and validated for simultaneous determination of the film-mass-transfer and diffusion coefficients from time-limited experimental data obtained by dissolving gas in liquids by the pressure-decay method under isothermal conditions. Whereas previous approaches require experimental data until equilibrium and only determine the diffusion coefficient, accurate and rapid estimation of both parameters are achieved using a shorter set of time-limited data, thereby reducing the errors owing to swelling by significant gas dissolution at later times. The equilibrium conditions can be predicted theoretically stemming from an analysis of the time-limited data. This provides the estimates of the equilibrium pressure and gas solubility. This methodology not only yields accurate parameter values, but also alleviates the sufficiently large-time collection of pressure-decay data needed to essentially achieve equilibrium. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Nonstationary model of the semicontinuous depolymerization of polycarbonateAICHE JOURNAL, Issue 12 2006Raúl Piñero-Hernanz Abstract The experimental work for the depolymerization process of Bisphenol A polycarbonate pellets and CD/DVD wastes in a semicontinuous reactor and a novel nonstationary model to describe the process is presented. The different steps of the process to develop the model are analyzed thoroughly. The kinetics of the alkali-catalyzed methanolysis of polycarbonate was determined. The reactor and kinetic models were validated by a series of 21 experiments performed in a laboratory semicontinuous tubular reactor at isothermal conditions from 90 to 180°C and pressures from 1.0 to 20.0 MPa in liquid phase, with and without NaOH concentrations of 1 × 10,3 to 5 × 10,3 kg/L, flow rates from 2.3 × 10,3 to 10.2 × 10,3 L/min, and CO2 molar fractions from zero to 0.374. The effects of temperature, pressure, catalyst amount, mass transfer (solvent flow rate), and CO2 addition in kinetics were investigated. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Wide-ranging molecular mobilities of water in active pharmaceutical ingredient (API) hydrates as determined by NMR relaxation timesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008Sumie Yoshioka Abstract In order to examine the possibility of determining the molecular mobility of hydration water in active pharmaceutical ingredient (API) hydrates by NMR relaxation measurement, spin,spin relaxation and spin,lattice relaxation were measured for the 11 API hydrates listed in the Japanese Pharmacopeia using pulsed 1H-NMR. For hydration water that has relatively high mobility and shows Lorentzian decay, molecular mobility as determined by spin,spin relaxation time (T2) was correlated with ease of evaporation under both nonisothermal and isothermal conditions, as determined by DSC and water vapor sorption isotherm analysis, respectively. Thus, T2 may be considered a useful parameter which indicates the molecular mobility of hydration water. In contrast, for hydration water that has low mobility and shows Gaussian decay, T2 was found not to correlate with ease of evaporation under nonisothermal conditions, which suggests that in this case, the molecular mobility of hydration water was too low to be determined by T2. A wide range of water mobilities was found among API hydrates, from low mobility that could not be evaluated by NMR relaxation time, such as that of the water molecules in pipemidic acid hydrate, to high mobility that could be evaluated by this method, such as that of the water molecules in ceftazidime hydrate. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4258,4268, 2008 [source] FTIR Microanalysis and Phase Behaviour of Ethylene/1-Hexene Random CopolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2007Mariano Pracella Abstract Ethylene/1-hexene random copolymers with 1-hexene content in the range of 1,5 mol-%, synthesised in the presence of new heterogeneous catalyst systems based on bis-carboxylato and -bis-chloro-carboxylato titanium chelate complexes, have been characterised by FTIR microspectroscopy (FTIR-M), DSC calorimetry and X-ray scattering. The co-monomer content and sequence distribution in the various samples were determined by means of both FTIR-M and 13C NMR spectroscopy. The deformation bands of methyl groups in the region of 1,400,1,330 cm,1 were used for the structural analysis of these copolymers. The effect of composition on the crystallinity and phase transitions of copolymers was analysed both in 1,500,1,300 and 760,690 cm,1 frequency ranges as a function of the annealing temperature. A neat variation of the absorbance ratio of methyl band at 1,378 cm,1 was recorded between 110 and 130,°C corresponding to the melting range of the copolymer crystals. The crystallisation behaviour of the copolymers was examined by DSC in dynamic and isothermal conditions; the isothermal kinetics were analysed according to the Avrami model. A marked decrease in the bulk crystallisation rate, accompanied by changes in the nucleation and growth of crystals, was found with an increase in the co-monomer content. The melting behaviour of isothermally crystallised samples was also investigated and the melting temperatures of the copolymers at equilibrium conditions were related to the composition; the experimental data were consistent with the Flory exclusion model of side branches from the crystalline phase. The lowering of crystal growth rate in the copolymers has been accounted for by an increase in the free energy of formation of critical size nuclei due to the effect of the side branches. [source] Thermal Behavior of Isotactic Poly(propylene)/Maleated Poly(propylene) BlendsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2007Catalin Vîlcu Abstract This paper analyzes the thermal and thermo-oxidative degradation behavior, phase separation, melting, and crystallization of blends consisting of isotactic poly(propylene) (IPP) and poly(propylene) grafted with maleic anhydride (PP- g -MA). It has been established that, depending on the blend composition and crystallization/preparation procedure, the blends of IPP and PP- g -MA can either co-crystallize or evidence phase separation. This conclusion has been attained by comparing the DSC results of crystallization under dynamic and isothermal conditions with X-ray diffraction results. On the basis of the obtained results, the optimum mixing ratios have been established as 95,85 wt.-% IPP/5,15 wt.-% PP- g -MA. Thermo-oxidative behavior has been studied by thermogravimetry and differential thermal analysis. [source] Influence of heat flux and surface temperature on the intergranular corrosion of stainless steelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2005T. Pro Abstract The exposure tests followed by metallographic evaluation and the electrochemical reactivation measurements in double-loop (DL-EPR) modification were used for investigation of the influence of non-boiling heat transfer on initiation and rate of propagation of intergranular corrosion (IGC) of sensitized austenitic stainless steel EN 1.4301 (AISI 304) in sulfuric acid solutions. The influence of heat flux and surface temperature was ascertained separately. The susceptibility to IGC and the rate of crack propagation increased with the surface temperature. Heat flux from metal to solution at constant surface temperature facilitated the IGC initiation, but at the same time it caused a drop of the corrosion attack depth in the metal. The increase of the heat flux by 10 kW m,2 in a range from 0 to 42 kW m,2 led to a drop of the maximum depth of cracks formed after subsequent bending the specimen, in average by 8%. The overall danger of corrosion was lower at positive heat flux between metal and solution than under isothermal conditions at constant surface temperature of the metal. The intensification of heat flux by 10 kW m,2 had the same effect on the IGC as a change of the surface temperature by less than 2 K. Therefore, the effect of the heat flux on IGC of the heat exchangers operating under non-boiling conditions may be considered as relatively less important than the effect of the surface temperature. [source] Initiation and propagation of stainless steel pitting corrosion under heat fluxMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2003T. Pro nichtrostender Stahl; Lochkorrosion; Wärmeübergang; Wärmefluss Abstract An effect of heat flux on initiation and propagation of pitting corrosion of austenitic stainless steel in chloride environment has been studied using electrochemical and exposure methods. The experiments were performed at constant surface temperature of 60°C and heat flux from , 15 to + 74 kW m,2. The presence of heat flux from metal to solution shifted the breakdown potential towards noble values and lowered the pit density, whereas the pit propagation rate increased. Presence of maximum heat flux caused, in comparison with isothermal conditions, increase of the breakdown potential by approx. 100 mV, reduction of pit density by 30% and increase of the average pit depth by 40%. The positive effect of heat flux from metal to solution was given mainly by improving the protective ability of the passive film, as the amount of oxygen available at the metal surface increased. With a smaller significance, the effect of intensified mass transfer, which made accumulation of the chloride ions on the surface more difficult, occurred. Entstehung und Fortschreiten der Lochkorrosion von nichtrostendem Stahl bei Wärmefluss Der Einfluss von Wärmefluss auf die Entstehung und das Fortschreiten der Lochkorrosion bei austenitischen nichtrostenden Stählen in chloridhaltiger Umgebung wurden unter Verwendung elektrochemischer Methoden und in Auslagerungsversuchen untersucht. Die Versuche wurden bei einer konstanten Oberflächentemperatur von 60°C und einem Wärmefluss von , 15 bis 74 kWm2 durchgeführt. Ein Wärmefluss vom Metall hin zur Lösung verschob das Durchbruchspotential hin zu edleren Werten, es verringerte sich die Lochdichte, während eine Zunahme der Lochbildungsrate erfolgte. Ein Maximum des Wärmeflusses bewirkte im Vergleich mit isothermen Bedingungen eine Zunahme des Potentials um ca. 100 mV, eine Verringerung der Lochdichte um 30% und eine Zunahme des Wertes für die Lochtiefe um 40%. Der positive Einfluss des Wärmeflusses in Richtung vom Metall zur Lösung ergab im wesentlichen eine Verbesserung der Schutzwirkung des Passivfilms, da sich die verfügbare Menge Sauerstoff an der Metalloberfläche erhöhte. Weniger signifikant war der Effekt eines erhöhen Stofftransportes, der eine Akkumulation von Chlorid-Ionen an der Oberfläche erschwerte. [source] The dynamics of transition layers in solids with discontinuous chemical potentialsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 5 2006T. Blesgen Abstract We derive a two-phase segregation model in solids under isothermal conditions where due to plastic effects the number of vacancies changes when crossing a transition layer, i.e. a reconstitutive phase transition. We show the thermodynamic correctness of the model and review the existence of weak solutions in suitable spaces. By a formal asymptotic analysis we study the dynamics of the interface and its dependence on the unsymmetric vacancy distribution. Copyright © 2006 John Wiley & Sons, Ltd. [source] Rapid, sensitive and simple detection method for koi herpesvirus using loop-mediated isothermal amplificationMICROBIOLOGY AND IMMUNOLOGY, Issue 7 2009Manabu Yoshino ABSTRACT New methods were developed for the detection of koi herpesvirus (KHV, CyHV-3) by LAMP, which were compared with the PCR for specificity and sensitivity. We designed two primer sets targeting a specific sequence within the 9/5 PCR amplicon (9/5 LAMP) and the upper region of the SphI-5 PCR amplicon (SphI-5 LAMP), including a sequence highly conserved among the strains. The amplification was monitored in real-time based on the increase in turbidity, with magnesium pyrophosphate as the by-product. The reactions were carried out under isothermal conditions at 65°C for 60 min. The detection limit of both LAMP was six copies, equal to the modified SphI-5 PCR. No cross-reactivity with other fish pathogenic viruses and bacteria was observed. SphI-5 LAMP was found to have a quicker response in terms of the reaction velocity than 9/5 LAMP. Therefore, we consider SphI-5 LAMP to be superior for routine use. Additionally, LAMP was found applicable to crude extract from gills and other organs. LAMP methods are superior in terms of sensitivity, specificity, rapidity and simplicity, and are potentially a valuable diagnostic tool for KHV infections. [source] An analytical model for steady coextrusion of viscoplastic fluids in thin slit dies with wall slipPOLYMER ENGINEERING & SCIENCE, Issue 4 2010Dilhan M. Kalyon Coextrusion is widely used to fabricate multilayered products with each layer providing a separate functionality, including barrier resistance to gases, strength, and printability. Here an analytical model of the coextrusion die flow of two incompressible, viscoplastic fluids in a slit die, subject to nonlinear wall slip and under fully developed and isothermal conditions, is developed to allow the prediction of the steady-state velocity and shear stress distributions and the flow rate versus pressure gradient relationship. The resulting model is applied to the coextrusion of two layers of viscoplastic fluids in a thin rectangular slit die (slit gap, h , slit width, W). The analytical solution recognizes a number of distinct flow conditions (eleven cases) that need to be treated separately. The solutions for all eleven cases are provided along with an apriori identification methodology for the determination of the applicable case, given the shear viscosity and wall slip parameters of the two viscoplastic fluids, the slit geometry and the flow conditions. Simplifications of the model would provide the solutions for the fully developed and isothermal coextrusion flows of any combination of Hershel-Bulkley, Bingham, power-law and Newtonian fluids with or without wall slip at one or both walls of the slit die. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Modelling of viscoelastic material behaviour close to the glass transition temperaturePROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Michael Johlitz In this contribution we investigate the mechanical behaviour of polyurethane over a range of different but constant temperatures from the glass to the viscoelastic state. Therefore uniaxial tension tests are performed on dogbone specimens under different isothermal conditions. In this manner an experimental data set is provided. As a theoretical basis we present the well known thermomechanically coupled one dimensional linear viscoelastic material model which is able to display the experimentally observed material behaviour. For this we adopt temperature dependent relaxation times. The introduced model parameters are identified via a standard parameter identification tool. Finally, the experimental results are compared with the ones of simulations of the identified model parameters. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Morphology in Immiscible Polymer Blends During Solidification of an Amorphous Dispersed Phase under ShearingTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Yves Deyrail Abstract Solidification under shear of dispersed polycarbonate (PC) fibers in copolymer polyethylene-methyl acrylate matrix (EMA) was investigated using a hot optical shear device. First, the deformation of PC droplets and its modeling under isothermal conditions were studied for comprehension purposes. Overall agreement with literature models was found and the main influence of the viscosity ratio has been stressed. Second, the morphology control through dynamic quenching was experimented. It consists of solidifying the amorphous PC dispersed phase under shear flow. Break-up times of PC fibers were taken into account. Shear rate and quenching-time balance was demonstrated. Thus, during dynamic solidification, a fibrillar morphology could be obtained through rapid quenching. Long quenching times allow nodular morphology, whose size depends on the shear rate used. PC rods can be obtained by adjusting the shear rate during dynamic quenching. La solidification sous cisaillement du polycarbonate (PC) dispersé dans une matrice copolymère éthylène-acétate de vinyle (EMA) a été suivie à l'aide d'un microscope et d'une platine de cisaillement chauffante. Dans un premier temps la déformation isotherme de billes de PC pour différentes températures a été étudiée, ainsi que sa modélisation. Une bonne corrélation avec les modèles issus de la littérature a été obtenue. L'importance du rapport des viscosités a été ainsi soulignée. Dans un second temps le contrôle de la morphologie par le procédé de « refroidissement dynamique » a été expérimenté. Celui-ci consiste à solidifier le PC sous cisaillement pendant le refroidissement. Les temps de rupture des fibres de PC ont été considérés et l'importance du couple gradient de cisaillement-temps de refroidissement sur le contrôle de la morphologie a été mis en évidence. Pendant la solidification, un refroidissement rapide permet d'obtenir une morphologie fibrillaire. [source] Nonisothermal Bioreactors in the Treatment of Vegetation Waters from Olive Oil: Laccase versus Syringic Acid as Bioremediation ModelBIOTECHNOLOGY PROGRESS, Issue 3 2005Angelina Attanasio Laccase from Trametes versicolor was immobilized by diazotization on a nylon membrane grafted with glycidil methacrylate, using phenylenediamine as spacer and coupling agent. The behavior of these enzyme derivatives was studied under isothermal and nonisothermal conditions by using syringic acid as substrate, in view of the employment of these membranes in processes of detoxification of vegetation waters from olive oil mills. The pH and temperature dependence of catalytic activity under isothermal conditions has shown that these membranes can be usefully employed under extreme pH and temperatures. When employed under nonisothermal conditions, the membranes exhibited an increase of catalytic activity linearly proportional to the applied transmembrane temperature difference. Percentage activity increases ranging from 62% to 18% were found in the range of syringic acid concentration from 0.02 to 0.8 mM, when a difference of 1°C was applied across the catalytic membrane. Because the percentage activity increase is strictly related to the reduction of the production times, the technology of nonisothermal bioreactors has been demonstrated to be an useful tool also in the treatment of vegetation waters from olive oil mills. [source] Modeling of Kinetic Expressions for the Reduction of NOx by Hydrogen in Oxygen-Rich Exhausts Using a Gradient-Free Loop ReactorCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2003E. Frank Abstract The reduction of NOx by hydrogen under lean conditions is investigated in a gradient-free loop reactor. Using this computer-controlled reactor, the reaction rates can be measured under exact isothermal conditions. Systematic variation of the input concentrations of hydrogen, nitric oxide, oxygen as well as reaction temperature provides a complete data set of reaction rates for the given reaction system. A number of kinetic rate expressions were evaluated for their ability to fit the experimental data by using toolboxes of MATLAB. The temperature influence on reaction rate constants and adsorption equilibrium constants were correlated simultaneously using Arrhenius and van't Hoff equations, respectively. The kinetic rate expression based on a Langmuir-Hinshelwood-type model describes the data and the model can be improved by introducing a correction term in square root of hydrogen partial pressure over the range of conditions investigated. [source]
| | ||||||||||||||||||||||||||||||||||||