Physical-Mathematical Model for Fixed-Bed Solid Fuel Gasification Process Simulation

Phycial-mathmatical model for fixed-bed coal gasification process simulation is proposed. The heterogeneous carbon oxidation chemical reactions were simulated via Arrhenius equation while homogeneous reactions in gas phase were calculated using Gibbs free energy minimization procedure. The syngas component concentration field and fuel conversion distribution as well as syngas final temperature and composition were defined for fixed bed gasification of T-grade coal of Kuznetskiy deposit. The optimal fuel residence time and gasifyer specific productivity were defined. The prevail reactions in oxidizing and reduction zones together with its height were defined

Interplay Between Time-Temperature-Transformation and the Liquid-Liquid Phase Transition in Water

We study the TIP5P water model proposed by Mahoney and Jorgensen, which is closer to real water than previously-proposed classical pairwise additive potentials. We simulate the model in a wide range of deeply supercooled states and find (i) the existence of a non-monotonic ``nose-shaped'' temperature of maximum density line and a non-reentrant spinodal, (ii) the presence of a low temperature phase transition, (iii) the free evolution of bulk water to ice, and (iv) the time-temperature-transformation curves at different densities.Comment: RevTeX4, 4 pages, 4 eps figure

Advanced embedded systems for autonomous robots control

In recent years, Autonomous Underwater Vehicles (AUVs) and Remotely Operated Underwater Vehicles (ROUVs) have become essential for various underwater missions, including environmental monitoring, offshore resource exploration, structural inspection, and rescue operations. A primary challenge in these missions is precise underwater navigation, particularly during structure inspections, where acoustic and optical systems offer complementary benefits. These tasks require building a local 3D map of the object using inertial systems, a process complicated by the fact that global navigation methods like LBL (Long Base Line) or USBL (Ultra-Short Base Line) are often impractical due to acoustic signal transmission limitations from surface beacons. While optical systems deliver detailed object information, they are hindered by issues like stereo vision distortions, lighting variability, and noise from suspended particles. Conversely, Forward Looking Sonar (FLS) provides robustness against environmental noise but operates at lower resolution and in polar coordinates, complicating data alignment with optical data devices like stereo camera. At the first part of our research we developed a nonlinear model of the ROUV in Computer-Aided Design (CAD) application and identified essential parameters, such as hydrostatic and hydrodynamic coefficients, through Computational Fluid Dynamics (CFD) simulations. These findings enabled accurate modeling of dynamic behaviors, including Coriolis effects and damping forces, forming the basis of the vehicle’s control equations. Additionally, a fractional-order PI controller was designed for yaw control, derived from a 6 DoF nonlinear model of the ROUV. The integration of Robot Operating System (ROS) and the Gazebo simulator allowed testing of control algorithms and sensor interactions within a digital twin environment, which included an Inertial Measurement Unit (IMU), FLS, Doppler Velocity Log (DVL) and stereo camera. This setup facilitated a smooth transition of navigation, computer vision, and path-planning functionalities from simulation to real-world deployment. Based on the designed nonlinear model of the ROUV and the developed control algorithm, we integrated a multimodal inertial-visual mapping and navigation system. This system enabled us to analyze the impact of the vehicle’s movement on the accuracy and stability of the visual-inertial system in a dynamically changing environment. Mapping, navigation, and control of the underwater vehicle equipped with a visual-inertial system that merges multimodal data from FLS, DVL, IMU, and a stereo camera devices through unsupervised deep-learning detector and descriptor algorithm is a core study of this research. Our research focuses on the geometric and computational integration of optical and sonar images. Given that a classical computer vision and supervised deep-learning feature matching algorithms is inadequate for opti-acoustic data fusion, we introduce an unsupervised feature matching approach tailored to sonar and optical datasets. This novel method enhances motion estimation by utilizing a hybrid direct and indirect matching strategy together with opti-acoustic epipolar constrains, where sonar data refines the depth of optical visual features. Both Sonar-to-Optical and Optical-to-Sonar mappings are employed to improve feature matching reliability under varying lighting and turbidity conditions. In our research, we introduced opti-acoustic image processing, including a calibration approach for each device and both devices the sonar and stereo camera, along with imaging enhancements to improve data fusion quality. To further enhance degraded optical images, we implemented a method combining stereo calibration in air and further data improving via physically guided underwater image enhancement framework based on synthetic and real images integration. By integrating unsupervised deep learning algorithm we was able to map sonar features onto optical images, enhancing image depth estimation while preserving key details. Testing across various scene geometries showed substantial improvements in visual odometry accuracy, which is crucial for effective navigation and inspection in challenging underwater conditions. Lastly, this research presents a robust framework for simulating underwater missions by combining CFD-based dynamics modeling, control algorithms, and sensor fusion techniques with optical and acoustic data. This comprehensive platform addresses underwater navigation and 3D mapping complexities, providing a unified system for testing and optimizing ROUV operations in diverse environments

When management myths collide? : case study of management control systems in two Norwegian companies, operating in Russia

Masteroppgave i bedriftsøkonomi - Universitetet i Nordland, 2011In this case study I have described two companies: Norwegian-Russian joint venture Rossnor and Reinertsen NWR, founded as a foreign direct investment of a parent company. I have analyzed management control systems of both companies with focus on challenges, arising in cross-cultural settings. This research indentifies and questions differences in myths of Russian and Norwegian management and shows how they can be resolved through the use of management control. Pursuing the goal of establishing links between different types of myths, challenges for managers and design of management control system a model of process relationship has been developed. The contribution of this model is that it emphasizes the necessity of two types of organizational learning as tools for reconsidering beliefs and assumptions of managers and redesigning management control systems, based on changes and new myths, with purpose to handle new challenges. Case of Rossnor proved that double-loop learning is critical for joint ventures and should supplement single-loop learning

Segue Between Favorable and Unfavorable Solvation

Solvation of small and large clusters are studied by simulation, considering a range of solvent-solute attractive energy strengths. Over a wide range of conditions, both for solvation in the Lennard-Jones liquid and in the SPC model of water, it is shown that the mean solvent density varies linearly with changes in solvent-solute adhesion or attractive energy strength. This behavior is understood from the perspective of Weeks' theory of solvation [Ann. Rev. Phys. Chem. 2002, 53, 533] and supports theories based upon that perspective.Comment: 8 pages, 7 figure

Field exposed water in a nanopore: liquid or vapour?

We study the behavior of ambient temperature water under the combined effects of nanoscale confinement and applied electric field. Using molecular simulations we analyze the thermodynamic causes of field-induced expansion at some, and contraction at other conditions. Repulsion among parallel water dipoles and mild weakening of interactions between partially aligned water molecules prove sufficient to destabilize the aqueous liquid phase in isobaric systems in which all water molecules are permanently exposed to a uniform electric field. At the same time, simulations reveal comparatively weak field-induced perturbations of water structure upheld by flexible hydrogen bonding. In open systems with fixed chemical potential, these perturbations do not suffice to offset attraction of water into the field; additional water is typically driven from unperturbed bulk phase to the field-exposed region. In contrast to recent theoretical predictions in the literature, our analysis and simulations confirm that classical electrostriction characterizes usual electrowetting behavior in nanoscale channels and nanoporous materials.Comment: 20 pages, 6 figures + T.O.C. figure, in press in PCC

Pre-collectivization peasantry social dynamics: retroprognosis: application of alternative modells

Anfang der 30er Jahre endete in der UdSSR die 'Neue Politische Ökonomie' und es begann die Phase der Zwangskollektivierung der sowjetischen Landwirtschaft. Der vorliegende Beitrag versucht durch ein Simulationsmodell einer nicht kollektivierten Bauernschaft die verloren gegangenen Möglichkeiten der 'Neuen Politischen Ökonomie' retrospektiv in Erinnerung zu bringen. Die Modellparameter stützen sich auf Erhebungen Mitte der 20er Jahre. Die Ergebnisse der Simulation zeigen, daß bei Fortsetzung der 'freien Marktwirtschaft' die Bauernschaft nicht wie vorausgesagt und befürchtet in sich bekämpfende Gruppen zerfallen wäre, sondern eine Nivellierung hin auf Mittellagen eingetreten wäre. (pmb)'The events that occurred in the USSR at the end of the 1920s - beginning of the 1930s were given the name 'great break'. It was the end of NEP - New Economic Policy. This work applies simulation to retroprognosis of the pre-collectivization peasantry social structure dynamics to 'prolong' the NEP rural population social mobility tendencies up to the late 30ies, which offers an opportunity to disclose distinctly the nature of social processes in the countryside before the collectivization, to detect the directions and extent of the social differentiation. Simulation based on Markovs chains allows to assess a theory that market economy inevitably entails rural population differentiation and antagonistic social groups formation from the formerly homogeneous mass of petty commodity producers. The model's parameters were estimated by using the data on the rural social processes, recorded by dynamic censuses of the mid-20ies. The results of simulation indicate that if the NEP economic conditions had been sustained, the peasantry wouldn't have splitted into opposed group, on the contrary, the position of medium strata would have grown stronger against the background of the overall economic growth.' (author's abstract

Modeling of Pyrolysis in a Stage Scheme of Low‐Grade Solid Fuel Gasification

This paper is concerned with the development of a model of wood pyrolysis in a screw reactor as the first stage of the multistage gasification process. In terms of design, the pilot pyrolyzer represents a recuperative heat exchanger where the heat carrier is represented by a mixture of exhaust and recirculation gases. To prevent clinkering of particles and thermal inhomogeneities, screw‐type transportation is used to transport fuel. In order to describe kinetics of pyrolysis and transport of volatiles within the wood particles and their transition to the gas phase, we carried out the studies using a complex of synchronous thermal analysis. The original techniques for the interpretation of measurements were developed for this complex, including the techniques for technical analysis of fuels and identification of detailed kinetics and mechanism of pyrolysis. A detailed numerical modeling of pyrolyzer was performed using the Comsol Multiphysics software, which makes it possible to optimize the design and operating parameters of the pyrolysis process in a screw reactor

GASFLOW-MPI: A Scalable Computational Fluid Dynamics Code for Gases, Aerosols and Combustion. Band 1 (Theory and Computational Model (Revision 1.0) und Band 2 (Users\u27 Manual). (KIT Scientific Reports ; 7710 und 7711)

Karlsruhe Institute of Technology (KIT) is developing the parallel computational fluid dynamics code GASFLOW-MPI as a best-estimate tool for predicting transport, mixing, and combustion of hydrogen and other gases in nuclear reactor containments and other facility buildings. GASFLOW-MPI is a finite-volume code based on proven computational fluid dynamics methodology that solves the compressible Navier-Stokes equations for three-dimensional volumes in Cartesian or cylindrical coordinates