Anomalously Strong Effect of the Ion Sign on the Thermochemistry of Hydrogen Bonded Aqueous Clusters of Identical Chemical Composition

The sign preference of hydrogen bonded aqueous ionic clusters X±(H2O)i (n =1–5, X = F; Cl; Br) has been investigated using the Density Functional Theory and ab initio MP2 method. The present study indicates the anomalously large difference in formation free energies between cations and anions of identical chemical composition. The effect of vibrational anharmonicity on stepwise Gibbs free energy changes has been investigated, and possible uncertainties associated with the harmonic treatment of vibrational spectra have been discussed

Effect of Ammonia on the Gas-Phase Hydration of the Common Atmospheric Ion HSO4−

Hydration directly affects the mobility, thermodynamic properties, lifetime and nucleation rates of atmospheric ions. In the present study, the role of ammonia on the formation of hydrogen bonded complexes of the common atmospheric hydrogensulfate (HSO4−) ion with water has been investigated using the Density Functional Theory (DFT). Our findings rule out the stabilizing effect of ammonia on the formation of negatively charged cluster hydrates and show clearly that the conventional (classical) treatment of ionic clusters as presumably more stable compared to neutrals may not be applicable to pre-nucleation clusters. These considerations lead us to conclude that not only quantitative but also qualitative assessment of the relative thermodynamic stability of atmospheric clusters requires a quantum-chemical treatment

Automated visual inspection algorithm for the reflection detection and removing in image sequences

Specular reflections are undesirable phenomena that can impair overall perception and subsequent image analysis. In this paper, we propose a modern solution to this problem, based on the latest achievements in this field. The proposed method includes three main steps: image enhancement, detection of specular reflections, and reconstruction of damaged areas. To enhance and equalize the brightness characteristics of the image, we use the alpha-rooting method with an adaptive choice of the optimal parameter alpha. To detect specular reflections, we apply morphological filtering in the HSV color space. At the final stage, there is a reconstruction of damaged areas using adversarial neural networks. This combination makes it possible to quickly and effectively detect and remove specular reflections, which is confirmed by a series of experiments given by the experimental section of this work

Estimating the Lower Limit of the Impact of Amines on Nucleation in the Earth’s Atmosphere

Amines, organic derivatives of NH3, are important common trace atmospheric species that can enhance new particle formation in the Earth’s atmosphere under favorable conditions. While methylamine (MA), dimethylamine (DMA) and trimethylamine (TMA) all efficiently enhance binary nucleation, MA may represent the lower limit of the enhancing effect of amines on atmospheric nucleation. In the present paper, we report new thermochemical data concerning MA-enhanced nucleation, which were obtained using the DFT PW91PW91/6-311++G (3df, 3pd) method, and investigate the enhancement in production of stable pre-nucleation clusters due to the MA. We found that the MA ternary nucleation begins to dominate over ternary nucleation of sulfuric acid, water and ammonia at [MA]/[NH3] > ~10−3. This means that under real atmospheric conditions ([MA] ~ 1 ppt, [NH3] ~ 1 ppb) the lower limit of the enhancement due to methylamines is either close to or higher than the typical effect of NH3. A very strong impact of the MA is observed at low RH; however it decreases quickly as the RH grows. Low RH and low ambient temperatures were found to be particularly favorable for the enhancement in production of stable sulfuric acid-water clusters due to the MA

Study on the Formation Mechanism of Cutting Dead Metal Zone for Turning AISI4340 with Different Chamfering Tools

Tools with chamfered edges are often used in high speed machining of hard materials because they provide compelling cutting toughness and reduced tool wear. Chamfered tools are also responsible for the dead metal zone (DMZ). Through numerical simulation of orthogonal cutting with AISI 4340 steel, this paper examines the mechanism of the DMZ, the cutting speed, the impacts of the chamfer angle, and the coefficient of friction on the generation of the DMZ. The analysis is based upon the Arbitrary Lagrangian-Eulerian (ALE) finite element method (FEM) for the continuous process of chip formation. The different chamfered angles, cutting speeds, and friction coefficient conditions are utilized in the simulation. The research demonstrates that a zone of trapped material called DMZ has been formed beneath the chamfer and serves as an effective cutting edge of the tool. Additionally, the dead metal zone DMZ becomes smaller while the cutting speed increases or the friction coefficient decreases. The machining forces rise with increasing chamfer angles, rise with increasing friction coefficients, and fall with increasing cutting speed in both the cutting and thrust directions. In this paper, the effect of different chamfering tools on AISI 4340 steel using carbide tools in the simulation environment is studied. It has certain reference significance for studying the formation mechanism of the dead zone of difficult-to-machine materials such as AISI4340 and improving the processing efficiency and workpiece surface quality

Ab intio Investigation of the Thermochemistry and Kinetics of the SO2 + O3− → SO3− + O2 Reaction in Aircraft Engines and the Environment

In the present work, the mechanisms, thermochemistry and kinetics of the reaction of SO2 with O3− have been studied using the CCSD(T)/6-31G(d) + CF method. It has been shown that there exist two possible pathways A and B of the SO2 + O3− → SO3− + O2 reaction. The two pathways’ A and B barrier heights are 0.61 kcal mol−1 and 3.40 kcal mol−1, respectively, while the energy of the SO2 + O3− → SO3− + O2 reaction is −25.25 kcal mol−1. The canonical variational transition state theory with small-curvature tunneling (CVT/SCT) has been applied to study the reaction kinetics. The CVT/SCT study shows that the rate constants K for pathways A and B, KA = 1.11 × 10−12exp(−2526.13/T) and KB = 2.7 × 10−14exp(−1029.25/T), respectively, grow as the temperature increases and are much larger than those of the SO2 + O3 → SO3 + O2 reaction over the entire temperature range of 200–1500 K. This indicates that ionization of O3 and high temperatures are favorable for the SO2 oxidation via the reaction with ozone. The new data obtained in the present study can be utilized directly for the evaluation of experiments and model predictions concerning SO2 oxidation and kinetic modeling of gas-phase chemistry of pollutants/nucleation precursors formed in aircraft engines and the Earth’s atmosphere

Amines in the Earth’s Atmosphere: A Density Functional Theory Study of the Thermochemistry of Pre-Nucleation Clusters

The impact of organic species which are present in the Earth’s atmosphere on the burst of new particles is critically important for the understanding of the molecular nature of atmospheric nucleation phenomena. Amines have recently been proposed as possible stabilizers of binary pre-nucleation clusters. In order to advance the understanding of atmospheric nucleation phenomena, a quantum-chemical study of hydrogen-bonded complexes of binary sulfuric acid-water clusters with methyl-, dimethyl- and trimethylamines representing common atmospheric organic species, vegetation products and laboratory impurities has been carried out. The thermochemical stability of the sulfuric acid-amines-water complexes was found to be higher than that of the sulfuric acid-ammonia-water complexes, in qualitative agreement with the previous studies. However, the enhancement in stability due to amines appears to not be large enough to overcome the difference in typical atmospheric concentrations of ammonia and amines. Further research is needed in order to address the existing uncertainties and to reach a final conclusion about the importance of amines for the atmospheric nucleation

Electromagnetic Radiation and Heat Transfer in Disperse Systems Consisting of Spherical and Cylindrical Particles

The article deals with the electromagnetic radiation transfer in systems of spherical disperse particles with different optical characteristics. A model of the electromagnetic radiation transfer in cylindrical particles containing a small volume of different chemical substance is developed. The substance differs substantially from that of the particle in a radiation absorption coefficient for the wavelength under study in the long wave approximation. The finite element method is used to calculate the temperature field for the system of spherical particles in a two-dimensional approximation. The configurations of particle packing is chosen on a random basis, which significantly complicated the calculations, the longitudinal and transverse diameters of particle clusters, the distance between centers of two largest particles, and similar natural geometric properties have been considered as characteristic system dimensions.The possibility of controlling heat transfer in such systems is studied. It follows from our model calculations that both electromagnetic and thermal interaction of dispersed particles can be noticeable at large distances between their centers; that near the boundary of the dispersed particle there is a thermal surface layer of the particle, where the temperature distribution is essentially heterogeneous. It is concluded that the thermal mechanism of destruction of a weakly absorbing particle due to a strong increase in temperature because of electromagnetic resonance in a neighboring particle with a strong absorption. It is established that the effect of collective influences in polydisperse system can change temperature by more than 1,5 times

Restoration of the lost volume of bone tissue with use data of the computed tomography

The paper deals with the issue of bone tissue restoration. To assist the specialist, we developed the SmartAssistantConstructor software package. The recovery process is based on finding a mirror copy of a piece of bone tissue. The article describes the algorithm for finding the missing part of the bone. The paper shows examples of this operation