Dependence Of Rate Research Articles

Linear analysis of whistler mode instability in anisotropic q-nonextensive distributed plasmas: a numerical approach

Due to the occurrence of nonextensive particle distributions in different space plasma environments, an analytical and numerical studies of electron temperature anisotropy-driven whistler instability (WI) in the nonextensive magnetized plasma are performed within the framework of kinetic theory for both superextensive (q < 1) and subextensive (q > 1) cases. By taking the nonextensive character of electrons into account (distinguished to nearly all existing studies), the dispersion relation for WI is derived and solved numerically to examine the characteristics of growth rate against the allowed domain of wave number. The effect of various physical parameters such as electron plasma beta , temperature anisotropy (Λ e ), and nonextensivity (q) on the growth rate and frequency of whistler mode are investigated. The growth rate of WI displays a significant dependence on these parameters, i.e. the growth rate increases by taking smaller values of nonextensive parameter q and for the large initial electron plasma beta and temperature anisotropy magnitudes. It is observed that the variation in the frequency of whistler mode is more sensitive to the temperature anisotropy (Λ e ) compared with other physical parameters, i.e. plasma beta and nonextensivity. The present findings also validate the large impact of electron temperature anisotropy on altering the dispersion properties of whistler mode. A detailed comparison of parametric dependence of the growth rate of WI for both superextensive and subextensive plasmas is also presented. Furthermore, a comparative analysis of whistler mode instability in anisotropic q-nonextensive and bi-Maxwellian plasmas is also the part of our present findings.

Regulations of the Influence of External Thermal Influences on Speed and Explosive Safe Combustion Modes of Pyrotechnic Nitrate-Metallized Mixtures with Metal Fluoride

A study was made of the regularities of the influence of the main parameters of external thermal effects (elevated heating temperatures and external pressures) on the rate and explosive modes of combustion development of compacted mixtures of magnesium, aluminum and sodium nitrate with fluoride additives metals for different values of technological parameters (excess ratio of the oxidizing agent, nature and content of the additive, dispersion of the components). The effect of technological parameters (ratio and dispersion of components, compaction coefficient, charge diameter, shell material, etc.) on the dependence of the burning rate of mixtures on elevated heating temperatures and external pressures was established; critical ranges of changes in these parameters are determined, the excess of which leads to premature explosive development of combustion of mixtures and fire hazardous destruction of products. On the basis of the research, methods were developed to prevent these destructions of products by regulating technological parameters at the stage of preparation of charge mixtures, which increases the stability of the combustion process of mixtures to external thermal influences. A database has been obtained on the burning rates of compacted mixtures of metal powders (Mg, Al), nitrate-containing oxidizer (NaNO3 ) and additives of inorganic substances (metal fluorides (LiF, NaF, BaF2 , SiF2 , SrF2 , AlF3 )) under conditions elevated heating temperatures and external pressures for various values of technological parameters, which makes it possible to determine the explosive modes of their combustion.

Controlling Bowing and Narrowing in SiO2 Contact-Hole Etch Profiles Using Heptafluoropropyl Methyl Ether as an Etchant with Low Global Warming Potential

Heptafluoropropyl methyl ether (HFE-347mcc3), as a lower-GWP (global warming potential) alternative to PFCs (perfluorocarbons), was used to etch SiO2 contact holes. The etch profiles of the SiO2 contact holes in HFE-347mcc3/O2/Ar plasmas showed more bowing at lower flow rate ratios of HFE-347mcc3 to Ar, whereas more narrowing occurred at higher ratios. The measurements of the angular dependences of the deposition rates of fluorocarbon films on the surface of SiO2 and the etch rates of SiO2 showed that the shape evolution of contact-hole etch profiles at different HFE-347mcc3/Ar ratios was attributed to an increase in etch resistance and a decrease in etch ability of the sidewalls of the contact hole with the increasing HFE-347mcc3/Ar ratio. This resulted in determining the optimum ratio of HFE-347mcc3 to Ar to achieve the maximum anisotropy of the contact hole etched in HFE-347mcc3/O2/Ar plasmas. By carefully selecting the specific flow rates of HFE-347mcc3/O2/Ar (9/2/19 sccm), a highly anisotropic and bowing-free SiO2 contact hole, with a 100 nm diameter and an aspect ratio of 24, was successfully achieved.

On paradoxes between optimal growth, metabolic control analysis, and flux balance analysis

In Microbiology it is often assumed that growth rate is maximal. This may be taken to suggest that the dependence of the growth rate on every enzyme activity is at the top of an inverse-parabolic function, i.e. that all flux control coefficients should equal zero. This might seem to imply that the sum of these flux control coefficients equals zero. According to the summation law of Metabolic Control Analysis (MCA) the sum of flux control coefficients should equal 1 however. And in Flux Balance Analysis (FBA) catabolism is often limited by a hard bound, causing catabolism to fully control the fluxes, again in apparent contrast with a flux control coefficient of zero. Here we resolve these paradoxes (apparent contradictions) in an analysis that uses the ‘Edinburgh pathway’, the ‘Amsterdam pathway’, as well as a generic metabolic network providing the building blocks or Gibbs energy for microbial growth. We review and show that (i) optimization depends on so-called enzyme control coefficients rather than the ‘catalytic control coefficients’ of MCA's summation law, (ii) when optimization occurs at fixed total protein, the former differ from the latter to the extent that they may all become equal to zero in the optimum state, (iii) in more realistic scenarios of optimization where catalytically inert biomass is compensating or maintenance metabolism is taken into consideration, the optimum enzyme concentrations should not be expected to equal those that maximize the specific growth rate, (iv) optimization may be in terms of yield rather than specific growth rate, which resolves the paradox because the sum of catalytic control coefficients on yield equals 0, (v) FBA effectively maximizes growth yield, and for yield the summation law states 0 rather than 1, thereby removing the paradox, (vi) furthermore, FBA then comes more often to a ‘hard optimum’ defined by a maximum catabolic flux and a catabolic-enzyme control coefficient of 1. The trade-off between maintenance metabolism and growth is highlighted as worthy of further analysis.

A dynamic parameterization of sulfuric acid–dimethylamine nucleation and its application in three-dimensional modeling

Abstract. Sulfuric acid (SA) is a governing gaseous precursor for atmospheric new particle formation (NPF), a major source of global ultrafine particles, in environments studied around the world. In polluted urban atmospheres with high condensation sinks (CSs), the formation of stable SA–amine clusters, such as SA–dimethylamine (DMA) clusters, usually initializes intense NPF events. Coagulation scavenging and cluster evaporation are dominant sink processes of SA–amine clusters in urban atmospheres, yet these loss processes are not quantitatively included in the present parameterizations of SA–amine nucleation. We herein report a parameterization of SA–DMA nucleation, based on cluster dynamic simulations and quantum chemistry calculations, with certain simplifications to greatly reduce the computational costs. Compared with previous SA–DMA nucleation parameterizations, this new parameterization was able to reproduce the dependences of particle formation rates on temperature and CSs. We then incorporated it in a three-dimensional (3-D) chemical transport model to simulate the evolution of the particle number size distributions. Simulation results showed good consistency with the observations in the occurrence of NPF events and particle number size distributions in wintertime Beijing and represented a significant improvement compared to that using a parameterization without coagulation scavenging. Quantitative analysis shows that SA–DMA nucleation contributes significantly to nucleation rates and aerosol population during the 3-D simulations in Beijing (&gt;99 % and &gt;60 %, respectively). These results broaden the understanding of NPF in urban atmospheres and stress the necessity of including the effects of coagulation scavenging and cluster stability in simulating SA–DMA nucleation in 3-D simulations. Representing these processes is thus likely to improve model performance in particle source apportionment and quantification of aerosol effects on air quality, human health, and climate.

DRGEP-based mechanism reduction considering time dependency of reaction rate

Importance of the method to determine interaction coefficient in the DRGEP method is explored by considering the pyrolysis reaction with time variation of temperature. To take into account time dependency, the interaction coefficients were determined using four different methods: the original method and three alternative methods. Two of the three alternative methods use the overall interaction coefficient computed from direct interaction coefficient determined by maximum value of ratio of production rate in each time, and the overall interaction coefficient computed from direct interaction coefficient determined by the averaged value of ratio of production rate in each time, respectively. The other method considers overall interaction coefficient computed from time-dependent direct interaction coefficient. The analytical condition for the mechanism reduction and the assessment of reduction accuracy are the pyrolysis of the gas composed of C2H2, C2H4, and N2 at 1000–1600 K and 0.1 MPa. The concentration of benzene during the simulation by the reduced mechanism was compared with original mechanism. In case of the DRGEP with method, the smallest reduced mechanism with accuracy has 60 species. In contrast, the reduced mechanisms constructed by the DRGEP with the latter two methods of the four accurately predict the concentration with only 45 species. In particular, the method that takes into account the time dependence of the reaction rate was able to describe the behavior in which the formation rate of the target chemical species, benzene, gradually approaches zero near equilibrium, even when the number of chemical species is 40.

Quantum rate theory and electron-transfer dynamics: A theoretical and experimental approach for quantum electrochemistry

Quantum rate theory is based on a first-principle quantum mechanical rate concept that comprises with the Planck–Einstein relationship E=hν, where ν=e2/hCq is a frequency associated with the quantum capacitance Cq and E=e2/Cq is the energy associated with ν. For a single state mode of transmittance, e2/Cq corresponds to the chemical potential differences Δμ between donor and acceptor state levels comprising an electrochemical reaction. A statistical mechanic treatment of E is required to compute the contribution of the thermal dynamics at finite temperature. The Arrhenius equation for the temperature dependence of the reaction rate was obtained, as well as Marcus’s Arrhenius-type electron-transfer rate constant as a particular setting of the quantum rate ν. Consequently, this ν concept provides the quantum mechanical foundations for electrochemical reactions at room temperature. The present work also demonstrates that the electron-transfer rate of heterogeneous (diffusionless) reactions can be studied in detail within this theory by measuring Cq using time-dependent electrochemical methods. Since the electron transfer follows a statistical mechanics version of the Planck–Einstein E=hν relationship, the electrochemical reaction dynamics cannot be appropriately modeled using non-relativistic Schrödinger wave mechanics, which is the ongoing quantum approach to electrochemistry. Accordingly, a relativistic analysis that takes into account the spin dynamics of the electron is more appropriate. The latter assumption implies quantum electrodynamics within a particular quantum transport mode intrinsically coupled to the electron-transfer rate of electrochemical reactions that have not been considered thus far. Here it is demonstrated that the consideration of this inherent quantum transport is key to obtaining an in-depth understanding of the electron transfer phenomenon. Finally, the theory is validated through its description of electron transfer, quantum conductance, and capacitance in different electro-active molecular films.

Shelf-life prediction of fresh ginseng packaged with plastic films based on a kinetic model and multivariate accelerated shelf-life testing

The purpose of this study was to monitor changes in the quality of ginseng and predict its shelf-life. As the storage period of ginseng increased, some quality indicators, such as water-soluble pectin (WSP), CDTA-soluble pectin (CSP), cellulose, weight loss, and microbial growth increased, while others (Na2CO3-soluble pectin/NSP, hemicellulose, starch, and firmness) decreased. Principal component analysis (PCA) was performed using the quality attribute data and the principal component 1 (PC1) scores extracted from the PCA results were applied to the multivariate analysis. The reaction rate at different temperatures and the temperature dependence of the reaction rate were determined using kinetic and Arrhenius models, respectively. Among the kinetic models, zeroth-order models with cellulose and a PC1 score provided an adequate fit for reaction rate estimation. Hence, the prediction model was constructed by applying the cellulose and PC1 scores to the zeroth-order kinetic and Arrhenius models. The prediction model with PC1 score showed higher R2 values (0.877-0.919) than those of cellulose (0.797-0.863), indicating that multivariate analysis using PC1 score is more accurate for the shelf-life prediction of ginseng. The predicted shelf-life using the multivariate accelerated shelf-life test at 5, 20, and 35°C was 40, 16, and 7 days, respectively.

Depth dependence of the photocatalytic reaction rate. kinetic model generalization

The model for photodegradation with a modified rate constant that was developed and presented in previous study, was generalized for the application of ZnO-based photocatalyst in both thin film and powder form. The applicability of the model was proved on methylene blue discoloration on both types of photocatalysts. The photocatalytic reaction rate was found to be dependent on the depth of the solution in case of small depths for this photocatalyst. This correlataion was valid in both high and low transparency. In addition, the impact of the solution pH on the model pollutant decomposition rate was defined.

Large-Area Niobium Titanium Nitride Superconducting Microstrip Single-Photon Detector Fabricated Using a Photolithography Process

In this paper, we present a large-area niobium titanium nitride (NbTiN) superconducting microstrip single-photon detector (SMSPD) fabricated using a photolithography process. We fabricated a 1-μm-wide NbTiN-SMSPD covering 420 × 420 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> active area with a filling factor of 20% using an i-line stepper. The detector is cooled down to approximately 2.2 K, and its performance is evaluated at the wavelengths from visible to near-infrared. The detector operates stably without a shunt resistor and shows single-photon sensitivity for photons with a wavelength of 1550 nm. The bias current dependence of the detection count rate is measured at the wavelengths from 406 to 1550 nm. The saturation of the detection count rate with increasing the bias current was successfully observed at wavelengths below 850 nm, suggesting an internal detection efficiency approaching 100%. Furthermore, we evaluated the timing jitter performance using the femtosecond pulse laser with a wavelength of 1550 nm. Consequently, we achieved a system timing jitter of 85 ps for a light spot diameter of 100 µm.

Ai-guided proportioning and evaluating of self-compacting concrete based on rheological approach

Self-Compacting Concrete (SCC) has gained significant popularity due to its exceptional workability performance. However, designing SCC poses more challenges than ordinary concrete, as it must fulfill requirements for filling ability, passing ability, and segregation resistance. Regrettably, existing test techniques lack the ability to simultaneously evaluate all these properties, and relying on experiential knowledge and cognition without tangible physical meaning. Although rheology examines the flow and deformation of fluid materials and is closely related to SCC’s properties, the relationship between SCC composition, rheology, and properties remains unclear due to the complexity of the factors involved and the absence of effective tools. This study introduces a novel approach by utilizing a random forest algorithm to create multiple interpretable machine learning models for predicting the rheology, workability, and mechanical properties of SCC. Additionally, SHapley Additive exPlanation (SHAP) and Partial Dependence Plot (PDP) methods were integrated with the models to analyze how SCC composition impacts its properties by altering the rheology of the mixture. The models exhibit high accuracy in predicting both rheology and SCC properties (R2 = 0.93 ∼ 0.98, Index of Agreement = 0.92 ∼ 0.99). According to the SHAP and PDP analysis, yield stress and plastic viscosity were negatively correlated with slump flow, L-box ratio, and segregation rate, while exhibiting a positive correlation with V-funnel time and strength. Furthermore, the dependence of the segregation rate on yield stress was observed to be stronger at relatively low yield stress levels (below 40 Pa). These models provide valuable insights for designing and evaluating SCC mixtures tailored to specific requirements. Additionally, the study explores underlying mechanisms and offers guidelines for proportioning SCC in different design scenarios. The findings contribute to the advancement of SCC technology and have significant implications for the construction industry.

Association, Conformational Rearrangements and the Reverse Process of Aggregates Dissociation during Apomyoglobin Amyloid Formation

Amyloid formation is linked with serious human diseases that are currently incurable. Usually, in the study of amyloid aggregation, the description of the protein’s association is in focus. Whereas the mechanism of the cross-β-structure formation, and the presence of aggregation reversibility, remain insufficiently explored. In this work, the kinetics of amyloid aggregation of apomyoglobin (ApoMb) have been studied using thioflavin fluorescence, electron microscopy, and non-denaturing electrophoresis. An analysis of the concentration dependence of the aggregation rates allows the conclusion that ApoMb amyloid formation includes the stages of conformational rearrangements in the aggregates, followed by their association and the fibril formation. The study of the mutant variants aggregation kinetics showed that the association rate is determined by the amino acids’ hydrophobicity, while the rate of conformational rearrangements is affected by the localization of the substitution. An unexpected result was the discovery that ApoMb amyloid formation is reversible, and under native-like conditions, the amyloid can dissociate, producing monomers. A consequence of the reversibility of amyloid aggregation is the presence of the monomer after aggregation completion. Since the aggregation reversibility indicates the possibility of dissociation of already formed fibrils, presented data and approaches can be useful in finding ways for amyloid diseases treatment.

Exploration of spatiotemporal heterogeneity and socio-demographic determinants on COVID-19 incidence rates in Sarawak, Malaysia

BackgroundIn Sarawak, 252 300 coronavirus disease 2019 (COVID-19) cases have been recorded with 1 619 fatalities in 2021, compared to only 1 117 cases in 2020. Since Sarawak is geographically separated from Peninsular Malaysia and half of its population resides in rural districts where medical resources are limited, the analysis of spatiotemporal heterogeneity of disease incidence rates and their relationship with socio-demographic factors are crucial in understanding the spread of the disease in Sarawak.MethodsThe spatial dependence of district-wise incidence rates is investigated using spatial autocorrelation analysis with two orders of contiguity weights for various pandemic waves. Nine determinants are chosen from 14 covariates of socio-demographic factors via elastic net regression and recursive partitioning. The relationships between incidence rates and socio-demographic factors are examined using ordinary least squares, spatial lag and spatial error models, and geographically weighted regression.ResultsIn the first 8 months of 2021, COVID-19 severely affected Sarawak’s central region, which was followed by the southern region in the next 2 months. In the third wave, based on second-order spatial weights, the incidence rate in a district is most strongly influenced by its neighboring districts’ rate, although the variance of incidence rates is best explained by local regression coefficient estimates of socio-demographic factors in the first wave. It is discovered that the percentage of households with garbage collection facilities, population density and the proportion of male in the population are positively associated with the increase in COVID-19 incidence rates.ConclusionThis research provides useful insights for the State Government and public health authorities to critically incorporate socio-demographic characteristics of local communities into evidence-based decision-making for altering disease monitoring and response plans. Policymakers can make well-informed judgments and implement targeted interventions by having an in-depth understanding of the spatial patterns and relationships between COVID-19 incidence rates and socio-demographic characteristics. This will effectively help in mitigating the spread of the disease.

Quantification of macromolecule crowding at single-molecule level.

Macromolecule crowding has a prominent impact on a series of biochemical processes in the cell. It is also expected to promote macromolecular complexation induced by excluded volume effects, which conflicts with recent advances in the thermodynamic interaction between inert, synthetic polymers, and nucleic acids. Along this line, a method combining high-resolution magnetic tweezers and extended crowder-oxDNA model was applied to resolve these discrepancies by systematically studying the kinetics and thermodynamics of the folding-unfolding transition for an individual DNA hairpin in a crowded environment. More specifically, from the magnetic tweezers-based experiments, the linear dependence of the critical force of the DNA hairpin on the polyethylene glycol (PEG) concentration was demonstrated, which is consistent with the results based on the crowder-oxDNA model in which the Lennard-Jones potential was adopted to express the interaction between the crowders and the DNA hairpin. These consistencies highlight that the excluded volume effects are mainly responsible for the interaction between PEG and the DNA hairpin, which is different from the interaction between dextran and the DNA hairpin. In the meantime, the dependence of the folding rate on the molecule weight of PEG, which was different from fluorescence resonance energy transfer-based results, was identified. The proposed method opens a path to detect the interaction between an inert, synthetic molecule, and the DNA hairpin, which is important to accurately mimic the cytosolic environments using mixtures of different inert molecules.

On the onset of long-wavelength three-dimensional instability in the cylinder wake

We study the onset of the three-dimensional mode A instability in the near wake behind a circular cylinder. We show that long-wavelength perturbations organise in a time-shifting pattern such that the in-plane velocity in each streamwise slice corresponds to the base flow solution at shifted times. This observation introduces an additional unifying characteristic for certain mode A type instabilities. We then analyse the mechanisms which control the growth or decay of these perturbations and highlight the crucial role played by the tilting mechanism which operates via non-local interactions in a manner similar to Biot–Savart induction. We characterise its domain of influence using a Green's function-based approach which allows us to rationalise the non-trivial dependence of the growth rate on the spanwise wavenumber. We connect this behaviour to the subtle balance between the local growth of the perturbations as they are swept along by the flow and the feedback on the perturbations that are generated during the next period of the time-periodic base flow. Finally, we discuss generalisations of our findings to other types of flows.

Evaluation of a compact 3 T MRI scanner for patients with implanted devices

Access to high-quality MR exams is severely limited for patients with some implanted devices due to labeled MR safety conditions, but small-bore systems can overcome this limitation. For example, a compact 3 T MR scanner (C3T) with high-performance gradients can acquire exams of the head, extremities, and infants. Because of its reduced bore size and the patient being advanced only partially into the bore, the associated electromagnetic (EM) fields drop off rapidly caudal to the head, compared to whole-body systems. Therefore, some patients with MR conditional implanted devices can safely receive 3 T brain exams on the C3T using its strong gradients and a multiple-channel receive coil, while a corresponding exam on whole-body MR is precluded. The purpose of this study is to evaluate the performance of a small-bore scanner for subjects with MR conditional spinal or sacral nerve stimulators, or abandoned cardiac implantable electronic device (CIED) leads. The spatial dependence of specific absorption rate (SAR) on the C3T was compared to whole-body scanners. A device assessment tool was developed and applied to evaluate MR safety individually on the C3T for 12 subjects with implanted devices or abandoned CIED leads. Once MR safety was established, the subjects received a C3T brain exam along with their clinical, 1.5 T exam. The resulting images were graded by three board-certified neuroradiologists. The C3T exams were well-tolerated with no adverse events, and significantly outperformed the whole-body 1.5 T exams in terms of overall image quality.

Morbidity of the population in the Orenburg region with viral hepatitis for the period from 2016–2020.

Introduction. Hepatitis B is one of the urgent problems of modern medicine and is included in the list of socially significant diseases [1, 3, 4]. According to WHO, about 4 million cases of acute hepatitis B are detected annually in the world, which can turn into a chronic form with the subsequent development of adverse outcomes, and also requires significant financial costs. In 2016, the 69th session of the World Health Assembly approved a strategy to combat viral hepatitis until 2030. In the Orenburg region, preventive measures carried out within the framework of the National Priority Project in the field of healthcare (section Vaccination prevention) for many years have significantly reduced the number of primary infections with viral hepatitis B.Target. To show the effectiveness of preventive immunization against hepatitis B and to assess the dependence of the incidence rate on the coverage of the population with hepatitis B vaccination on the example of the Orenburg region. Materials and methods. Data from the Federal statistical observation forms No. 2 “Information on infectious and parasitic diseases”, No. 6 “Information on the contingents of children and adults vaccinated against infectious diseases” in the Orenburg region for 2016–2020.Results. The coverage of vaccination against viral hepatitis B in the Orenburg region was analyzed, during the analyzed period, the coverage of vaccination increased significantly, as a result of which there is a tendency to decrease the incidence of acute viral hepatitis by 3,4 times.Conclusion. This article shows the effectiveness of preventive immunization against viral hepatitis B and evaluates the dependence of the incidence rate on the coverage of the population with vaccination against viral hepatitis B for the period from 2016 to 2020 on the example of the Orenburg region.

Analysis of Bandwidth Narrowing in Wavelength Selective Switch Enabled DP-64QAM Systems With Transceiver Noise

The impact of filtering impairments resulting from cascaded, wavelength selective switches is investigated for 32 Gbaud dual-polarization 64-ary quadrature amplitude modulation in the presence of transceiver noise. Training-sequence based adaptive equalization and pilot-aided carrier phase estimation are employed to cope with the combined effects of the transceiver-imposed limitation in achievable signal-to-noise ratio and the filtering-induced signal distortion. For a given level of amplified spontaneous emission noise, transceiver noise reduces the total signal-to-noise ratio resulting in an increased dependence of the bit-wise achievable information rate on filtering-induced bandwidth narrowing. The implications of statistical variations in the overall filter frequency response are also assessed by considering randomly selected responses for each of the individual filters in a cascade. Further, the impact of the frequency response of the demultiplexing filter at the receiver is investigated by considering a 3-channel 32 Gbaud wavelength division multiplexed system with a channel spacing of 37.5 GHz.

Oxidation Effects on Short-Term Creep Response in Air of Commercially Pure Titanium (CP-2 Ti)

The creep response in the air of commercially pure titanium was investigated at 550, 600, and 650 °C to assess the effect of oxidation on the mechanical response. Experiments demonstrated that prolonged exposures at high temperatures produced a marked reduction in the minimum creep rate under a given applied stress. Microhardness measurements showed that a hardened zone formed in proximity to the surface due to oxygen penetration into the metal. A simplified composite model was then used to describe the creep response. In this model, the sample consisted of two zones, the hard case that was enriched in oxygen and the soft pure-titanium core, both creeping with similar strain rates. Calculations led to an estimation of the dependence of the minimum creep rate on stress and temperature for the hard high-oxygen zone. The simplified composite model presented here provided a good description of the experimental creep data for pure titanium, tested in its air, and a reliable picture of the effect of oxidation on complex Ti alloys.

Prediction of water vapor permeation and desiccant saturation in vacuum insulation panels with a glass fiber core

The permeation of dry air in vacuum insulation panels (VIPs) with a glass fiber core has been often prevented using laminated films with metallized ethylene vinyl alcohol copolymer (EVOH) layers; meanwhile, desiccants are incorporated to control the increasing pressure due to the permeation of water vapor. Previously proposed models can predict the changes in long-term performance caused by dry-air permeation, but a method that accounts for water-vapor permeation and desiccant saturation has not been reported before. Predicting the long-term performance of VIPs when exposed to outdoor temperature and humidity is essential for using it as a building insulation material. In this study, we investigated the dependence of the water-vapor transmission rate (WVTR) of metallized EVOH film on temperature and relative humidity, and the effect of ambient water-vapor pressure on the WVTR of metallized EVOH film. To reduce the measurement time of WVTR, we developed a new measurement method using a small sensor device and confirmed that its accuracy is equivalent to that of the conventional method. We measured the water-vapor transmission coefficient of glass fiber core VIPs under various temperature and humidity conditions using this measurement method. For the same water-vapor pressure, the amount of transmission significantly depended on the temperature and humidity conditions. Therefore, the WVTR of metallized EVOH films should be more concerned with the effect of relative humidity than that of the water vapor pressure of the ambient air. Based on these results, a new model that accounts for desiccant saturation was proposed and validated based on the conventional model to predict the long-term performance under permeation of mixed gases. The new model accurately evaluated the long-term performance of VIPs with confirmed desiccant saturation, supporting the long-term performance of glass fiber core VIPs.