Using P(Pressure)-T(Temperature) Path to Control the Foaming Cell Sizes in Microcellular Injection Molding Process

Microcellular injection molding technology (MuCell) using supercritical fluid (SCF) as a foaming agent is one of the important green molding solutions for reducing the part weight, saving cycle time, and molding energy, and improving dimensional stability. In view of the environmental issues, the successful application of MuCell is becoming increasingly important. However, the molding process encounters difficulties including the sliver flow marks on the surface and unstable mechanical properties that are caused by the uneven foaming cell sizes within the part. In our previous studies, gas counter-pressure combined with dynamic molding temperature control was observed to be an effective and promising way of improving product quality. In this study, we extend this concept by incorporating additional parameters, such as gas pressure holding time and release time, and taking the mold cooling speed into account to form a P(pressure)-T(temperature) path in the SCF PT diagram. This study demonstrates the successful control of foaming cell size and uniformity in size distribution in microcellular injection molding of polystyrene (PS). A preliminary study in the molding of elastomer thermoplastic polyurethanes (TPU) using the P-T path also shows promising results.

Sources of error in open-path FTIR measurements of N₂O and CO₂ emitted from agricultural fields

Open-path Fourier transform infrared spectroscopy (OP-FTIR) is susceptible to environmental variables which can become sources of errors for gas quantification. In this study, we assessed the effects of water vapour, temperature, path length, and wind speed on quantitative uncertainties of nitrous oxide (N2O) and carbon dioxide (CO2) derived from OP-FTIR spectra. The presence of water vapour in spectra underestimated N2O mole fractions by 3 % and 12 %, respectively, from both lab and field experiments using a classical least squares (CLS) model when the reference and sample spectra were collected at the same temperature (i.e. 30 ∘C). Differences in temperature between sample and reference spectra also underestimated N2O mole fractions due to temperature broadening and the increased interferences of water vapour in spectra of wet samples. Changes in path length resulted in a non-linear response of spectra and bias (e.g. N2O and CO2 mole fractions were underestimated by 30 % and 7.5 %, respectively, at the optical path of 100 m using CLS models). For N2O quantification, partial least squares (PLS) models were less sensitive to water vapour, temperature, and path length and provided more accurate estimations than CLS. Uncertainties in the path-averaged mole fractions increased in low-wind conditions (<2 m s−1). This study identified the most common interferences that affect OP-FTIR measurements of N2O and CO2, which can serve as a quality assurance/control guide for current or future OP-FTIR users.

Pressure-to-depth conversion models for (ultra-)high-pressure metamorphic rocks: review and application

&lt;p&gt;Pressure estimated from metamorphic rocks is one of the main tools for geodynamic reconstructions. The pressure-temperature path of UHP metamorphic rocks typically shows a linear increase of P and T followed by a rapid drop of Pressure at near-constant temperature. The geological history can be reconstructed by using the metamorphic pressure as a proxy for depth. Researchers often base their geodynamic reconstruction on a simple linear mapping of pressure to depth, by considering that the pressure is the weight of the overlying column of rock or lithostatic pressure. In recent years, an increasing corpus of evidence demonstrates that rocks can experience pressures that deviate from the lithostatic state on the order of GPa. These deviations can be at the scale of the orogen (Petrelli and Podladchikov, 2002), the outcrop (Jamtveit et al., 2018; Luisier et al., 2019); or even at the grain-scale (Tajcmanova, 2015). Thus, these studies raise the concern that metamorphic pressures may not be reliable proxies for depth, and therefore could not be used for geodynamic reconstructions. The objective of this contribution (1) to review the various models proposed in the literature for metamorphic pressure, (2) to formulate analytical models with simple assumptions that can be used to convert metamorphic pressure to depth even in the case where pressure deviates significantly from the lithostatic pressure. We use our pressure-to-depth conversion models to estimate the depth of ~60 samples from various orogens worldwide. The prediction of the different models varies widely. Some models predict depth as deep as 160km for specific samples, while other models predict depth $&lt;75$ km (i.e. deepest depth of the Moho) for all data points.&amp;#160; We discuss the limits of applicability and the geodynamic implications of each model.&amp;#160;&lt;/p&gt;

Sources of error in open-path FTIR measurements of N₂O and CO₂ emitted from agricultural fields

Open-path Fourier transform infrared spectroscopy (OP-FTIR) is susceptible to environmental variables which can become sources of errors for gas quantification. In this study, we assessed the effects of water vapour, temperature, path length, and wind speed on the uncertainty of nitrous oxide (N2O) and carbon dioxide (CO2) concentrations derived from OP-FTIR spectra. The presence of water vapour resulted in underestimating N2O in both lab (−3 %) and field (−12 %) experiments at 30 °C using a classical least squares (CLS) model. Differences in temperature between the sample and reference spectra also underestimated N2O concentrations due to temperature broadening and the increased interferences of water vapour in spectra of wet samples. Changes in path length resulted in a non-linear response of spectra and bias (e.g. N2O and CO2 concentrations were underestimated by 30 % and 7.5 %, respectively, at the optical path of 100-m using CLS models). For N2O quantification, partial least squares (PLS) models were less sensitive than CLS to the influence of water vapour, temperature, and path length, and provided more accurate estimations. Uncertainties in the path-averaged concentrations increased in low wind conditions (

Influence of the Scanning Temperature on the Classification of Whisky Samples Analysed by UV-VIS Spectroscopy

The definition of the optimal temperature and its effects (either increasing or variations) during analysis of alcoholic beverages are of importance to develop protocols based in spectroscopy. Although several reports have been published on the use of spectroscopy combined with chemometrics to classify and authenticate alcoholic beverages (e.g., wine, tequila, whisky), few reports deal with issues related with the spectra collection (e.g., temperature, path length) and its effect on the classification performances. The objective of this study was to evaluate the effect of increasing temperature on both the UV-VIS spectra of whisky and on the classification results of the samples according to country of origin. Whisky samples from different commercial labels were analysed at different temperatures (25, 35, 45, 55 °C) using a UV-VIS instrument (Agilent, Cary 3500). Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) models based in cross validation were used to classify whisky samples according to scanning temperature and origin. The results of this study indicated that temperature did not affect the classification of whisky samples according to country of origin. Overall, well defined protocols need to be defined for routine use of these methods in research and by the industry.

A phase equilibrium investigation of selected source controls on the composition of melt batches generated by sequential melting of an average metapelite

The ability of Rcrust software to conduct path-dependent phase equilibrium modelling with automated changing bulk compositions allows for a phase equilibrium approach to investigate an array of source controls for their effect on the bulk compositions of melts produced by sequential melting events. The following source controls of the rock system are considered: (1) initial magnesium and iron content; (2) initial sodium and calcium content; (3) pressure–temperature path followed by the system; and (4) threshold by which melt extractions in the system are triggered. These source controls are investigated in a water-restricted system and a water-in-excess system. The permutation of these cases resulted in 128 different modelled pressure–temperature bulk composition paths investigating the melting of an average pelite composition. The resultant melt compositions are compared to that of a natural granite dataset and provide a good fit for the incompatible elements Na2O and K2O with the allowance that granites most likely form as magmas consisting of melt and ferromagnesian-rich crystals. The fluid state of the system is shown to have the strongest control on melt compositions, with the pressure–temperature path having subordinate control on the volume and composition of melts produced.