Displacement Prediction of Tunnel Surrounding Rock: A Comparison of Support Vector Machine and Artificial Neural Network

Displacement prediction of tunnel surrounding rock plays an important role in safety monitoring and quality control tunnel construction. In this paper, two methodologies, support vector machines (SVM) and artificial neural network (ANN), are introduced to predict tunnel surrounding rock displacement. Then the two modes are texted with the data of Fangtianchong tunnel, respectively. The comparative results show that solutions gained by SVM seem to be more robust with a smaller standard error compared to ANN. Generally, the comparison between artificial neural network (ANN) and SVM shows that SVM has a higher accuracy prediction than ANN. Results also show that SVM seems to be a powerful tool for tunnel surrounding rock displacement prediction

Dynamic properties and optical phase conjugation of two-photon pumped ultrashort blue stimulated emission in a chromophore solution

The dynamic properties of two-photon pumped blue lasing (~470 nm) in the solution of an organic chromophore [2-acetyl-6-(dimethylamino)naphthalene], excited by ~160-fs laser pulses at ~775 nm, have been studied. Both the forward and backward stimulated emission are enhanced by feedback from the reflection at the two optical windows of the solution filled cuvette. Under current experimental conditions, the lasing wavelengths in the forward and backward directions were almost the same, but both blueshifted compared to the fluorescence peak wavelength of the sample solution. The temporal behavior of the lasing output was recorded by a high-speed streak camera system. The multipulse structure and spectral properties of the output lasing are semiquantitatively explained. In addition, excellent optical phase-conjugation properties of the backward stimulated emission were observed; the aberration influences from an aberrator on the backward lasing beam were automatically removed

Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study

Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe

Application of flow field decomposition and reconstruction in studying and modeling the characteristics of a cartridge valve

In modeling the characteristics of a cartridge valve with traditional methods, it is commonly required to determine the value of flow area and other coefficients such as discharge coefficient and jet angle, etc. However, these parameters often rely heavily on empirical or experimental data and often involve some uncertainties, especially with the variation of the spool displacement (valve opening). To avoid these uncertainties, this paper proposes a modeling method which calculates spool force and flow rate directly through the distribution of fluid field. Transient 3D flow field simulation with dynamic mesh technique is conducted using commercial code FLUENT, and Proper Orthogonal Decomposition (POD) method is introduced to simplify fluid field data. The results showed that the POD method can capture the main features of the fluid field while significantly reducing the amount of data. With reconstructed pressure field and velocity field, spool force and flow rate can be calculated directly without using traditional formulas which contain uncertain coefficients. Valve characteristics calculated with this method agree with Computational Fluid Dynamics (CFD) and experimental data well, which confirms the validity and effectiveness of this method

Experimental Determination of the Standard Gibbs Energy of Formation of Fe_3–xV_xO₄ at 1473 K

In the present study, an approach of determining the standard Gibbs energy of formation of Fe3–xVxO4 was proposed firstly, then the standard Gibbs energies of formation of a variety of Fe3–xVxO4 were determined experimentally, and finally, a calculating model of the standard Gibbs energy of formation of Fe3–xVxO4 was established. The detailed results are as follows: (1) the standard Gibbs energy of formation of Fe3–xVxO4 can be determined successfully by two steps; the first is to measure the chemical potential of Fe in Fe3–xVxO4 under fixed oxygen partial pressure, the second is to derive the chemical potential of V in Fe3–xVxO4 by Gibbs–Duhem relation; (2) the standard Gibbs energies of formation of Fe3–xVxO4 are mainly decided by the Fe/V molar ratio, and almost not influenced by the oxygen partial pressure in the range from 2.39 × 10−12 to 3.83 × 10−11 atm; (3) in this oxygen partial pressure range, the standard Gibbs energies of formation of Fe3–xVxO4 can be calculated satisfactorily by the following model: ΔfGFe3−xVxO4θJ/mol=1−x/2ΔfGFe3O4θ+x/2ΔfGFeV2O4θ+1−x/2RTln1−x/2+x/2RTlnx/2 − 168627.481−x/2x/2

Rapid and efficient removal of methylene blue by freshly prepared manganese dioxide

Freshly prepared manganese dioxide was employed as an adsorbent to remove methylene blue (MB) from water. It was demonstrated that the obtained MnO2 outperformed several adsorbents previously reported in the literatures for a rapid and effective removal of MB. The time required to reach adsorption equilibrium was as short as 2 min. The Langmuir isotherm fit well into the experimental data with a linear correlation coefficient (R2) of 0.997. The maximum adsorption capacity was 627.1 mg/g. The removal efficiency of MB increased along with increasing MnO2 dose, whereas decreased over pH 3.0–6.0. The adsorption mechanism was primarily attributed to electrostatic attraction