scholarly journals Basic Physical and Chemical Information Needed for Development of Monte Carlo Codes

Author(s):  
Mitio Inokuti
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hiroto Yamashita ◽  
Rei Sonobe ◽  
Yuhei Hirono ◽  
Akio Morita ◽  
Takashi Ikka

AbstractSpectroscopic sensing provides physical and chemical information in a non-destructive and rapid manner. To develop non-destructive estimation methods of tea quality-related metabolites in fresh leaves, we estimated the contents of free amino acids, catechins, and caffeine in fresh tea leaves using visible to short-wave infrared hyperspectral reflectance data and machine learning algorithms. We acquired these data from approximately 200 new leaves with various status and then constructed the regression model in the combination of six spectral patterns with pre-processing and five algorithms. In most phenotypes, the combination of de-trending pre-processing and Cubist algorithms was robustly selected as the best combination in each round over 100 repetitions that were evaluated based on the ratio of performance to deviation (RPD) values. The mean RPD values were ranged from 1.1 to 2.7 and most of them were above the acceptable or accurate threshold (RPD = 1.4 or 2.0, respectively). Data-based sensitivity analysis identified the important hyperspectral regions around 1500 and 2000 nm. Present spectroscopic approaches indicate that most tea quality-related metabolites can be estimated non-destructively, and pre-processing techniques help to improve its accuracy.


1981 ◽  
Vol 6 ◽  
Author(s):  
Paul G. Huray ◽  
M. T. Spaar ◽  
S. E. Nave ◽  
J. M. Legan ◽  
L. A. Boatner ◽  
...  

The electronic charge states and site symmetries of the radioactive ions incorporated in nuclear waste forms are of considerable importance in determining the physical and chemical properties of these materials. An in situ characterization of these ions is, unfortunately, often difficult – especially when a mixture of charge states and local crystal symmetries exist. The application of Mbssbauer spectroscopy represents a powerful technique for obtaining solid state chemical information.


A survey is given on typical ‘top-down’ and ‘bottom-up’ approaches to design nanostructured sensors which monitor different physical and chemical quantities. Particular emphasis is put on new materials and transducers for molecular recognition by chemical sensors. These convert chemical information into electronic signals by making use of suitable ‘key-lock’ structures. This requires the control of surface structures of chemically sensitive materials down to the molecular scale under thermodynamically or kinetically controlled conditions. This in turn requires the molecular understanding of sensor mechanisms which is deduced from comparative microscopic, spectroscopic and sensor test studies on ‘prototype materials’. Selected case studies illustrate the common mechanisms of molecular recognition with electron conductors, ion conductors, mixed conductors, molecular cages, polymers and selected biomolecular function units.


2003 ◽  
Vol 36 (2) ◽  
pp. 230-238 ◽  
Author(s):  
Angela Altomare ◽  
Rocco Caliandro ◽  
Carmelo Giacovazzo ◽  
Anna Grazia Giuseppina Moliterni ◽  
Rosanna Rizzi

Theab initiocrystal structure solution from powder diffraction data can be attemptedviadirect methods. If heavy atoms are present, they are usually correctly located; then some crystal chemical information can be exploited to complete the partial structure model. Organic structures are more resistant to direct methods; as an alternative, their molecular geometry is used as prior information for Monte Carlo methods. In this paper, a new procedure is described which combines the information contained in the electron density map provided by direct methods with a Monte Carlo method which uses simulated annealing as a minimization algorithm. A figure of merit has been designed based on the agreement between the experimental and calculated profiles, and on the positions of the peaks in the electron density map. The procedure is completely automatic and has been included inEXPO; its performance has been validated and tested for a set of known molecular structures.


Author(s):  
M. A. Yakhyaev ◽  
V. S. Gutenkov ◽  
Yu. A. Pisarenko

Mesityl oxide is an important product of organic synthesis, which is used in the manufacture of pharmaceuticals and as a solvent. The demand for mesityl oxide is growing, which determines the need for further improvement of its production. The disadvantages of the traditional methods of obtaining mesityl oxide are low values of reagent conversion and selectivity. To eliminate them, it is proposed to obtain mesityl oxide in a combined reaction-rectification process. The combination of chemical transformation and separation of the resulting reaction mixture by means of rectification in one apparatus allows for a continuous withdrawal of the formed products from the reaction zone, which increases the rate of the target reaction, conversion and selectivity. In accordance with the modern strategy for the development of chemical-technological processes, the collection and processing of physical and chemical information on the properties of the components and mixtures contained in the reaction system was performed. Based on the experimental data, the parameters of the phase equilibrium model are determined, and its adequacy is estimated. The phase equilibrium model was used to construct a distillation diagram, to verify its consistency, and to conduct computational studies of the reaction-rectification process. The thermochemical parameters of the target reactions are calculated, the equilibrium constants are determined, and their temperature dependence is established. On the basis of the analysis of the literature data, a kinetic model of the process is proposed, and the conditions favorable for the course of the desired chemical transformation are determined with the use of this model. The obtained data are necessary for carrying out the analysis of the statics, constructing the basic technological scheme and calculating its static parameters.


2021 ◽  
Vol 9 ◽  
Author(s):  
Nikolaos Cheimarios ◽  
Deifilia To ◽  
George Kokkoris ◽  
George Memos ◽  
Andreas G. Boudouvis

Monte Carlo (MC) and kinetic Monte Carlo (kMC) models are widely used for studying the physicochemical surface phenomena encountered in most deposition processes. This spans from physical and chemical vapor deposition to atomic layer and electrochemical deposition. MC and kMC, in comparison to popular molecular methods, such as Molecular Mechanics/Dynamics, have the ability to address much larger time and spatial scales. They also offer a far more detailed approach of the surface processes than continuum-type models, such as the reaction-diffusion models. This work presents a review of the modern applications of MC/kMC models employed in deposition processes.


2020 ◽  
Author(s):  
An-Sheng Lee ◽  
Dirk Enters ◽  
Sofia Ya Hsuan Liou ◽  
Bernd Zolitschka

<p>Sediment facies provide vital information for the reconstruction of past environmental variability. Due to rising interest for paleoclimate data, sediment surveys are continually growing in importance as well as the amount of sediments to be discriminated into different facies. The conventional approach is to macroscopically determine sediment structure and colour and combine them with physical and chemical information - a time-consuming task heavily relying on the experience of the scientist in charge. Today, rapidly generated and high-resolution multiproxy sediment parameters are readily available from down-core scanning techniques and provide qualitative or even quantitative physical and chemical sediment properties. In 2016, an interdisciplinary research project WASA (Wadden Sea Archive) was launched to investigate palaeo-landscapes and environments of the Wadden Sea. The project has recovered 92 up to 5 m long sediment cores from the tidal flats, channels and off-shore around the island of Norderney (East Frisian Wadden Sea, Germany). Their facies were described by the conventional approach into glacioflucial sands, moraine, peat, tidal deposits, shoreface sediments, etc. In this study, those sediments were scanned by a micro X-ray fluorescence (µ-XRF) core scanner to obtain high-resolution records of multi-elemental data (2000 µm) and optical images (47 µm). Here we propose a supervised machine-learning application for the discrimination of sediment facies using these scanning data. Thus, the invested time and the potential bias common for the conventional approach can be reduced considerably. We expect that our approach will contribute to developing a more comprehensive and time-efficient automatic sediment facies discrimination.</p><p>Keywords: the Wadden Sea, µ-XRF core scanning, machine-learning, sediment facies discrimination</p>


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