Decision Making in a Hybrid Two-Step Problem of Dynamic Control with Three Participants

The equations of motion of a control system in a two-step problem on a fixed time interval contain the controls of either the first player, or the first and second players, or the first and third players, or all players simultaneously. At the first step (stage) of the control process (from the initial time up to a certain predefined moment), the system is controlled only by the first player, who solves an optimal control problem with a given terminal functional. At the beginning of the second step (stage) of the process, the first player decides whether the other players will participate in the control process for the remaining time period. If yes, then the participants play a nonantagonistic differential game with given terminal functionals, and it can be a game of two or three persons. A Pareto-optimal Nash equilibrium is taken as a solution in this game. If no, then the first player continues to solve the optimal control problem until the end of the process. © 2020 Krasovskii Institute of Mathematics and Mechanics. All rights reserved

Altruistic and Aggressive Types of Behavior in a Non-Antagonistic Positional Differential Two-Person Game

A non-antagonistic positional differential two-person game is considered in which each of the two players, in addition to the usual normal (nor) type of behavior oriented toward maximizing own functional, can use other types of behavior. In particular, it is altruistic (alt), aggressive (agg) and paradoxical (par) types. It is assumed that in the course of the game players can switch their behavior from one type to another. In this game, each player along with the choice of positional strategy also chooses the indicator function defined over the whole time interval of the game and taking values in the set {nor, alt, agg, par}. Player's indicator function shows the dynamics for changing the type of behavior that this player adheres to. The concept of BT-solution for such game is introduced. Using players types of behavior other than normal, can lead to outcomes more preferable to them than in a game with only a normal type of behavior. An example of a game with the dynamics of simple motion in the plane and phase constraints illustrates the procedure for constructing BT-solutions. © 201

Altruistic and Aggressive Types of Behavior in a Non-Antagonistic Differential Game

An example of a non-antagonistic positional (feedback) differential two-person game (NPDG) is considered in which each of two players, in addition to the normal type of behavior, oriented toward maximizing own functional, can use other types of behavior. In particular, it can be altruistic and aggressive types. In the course of the game players can switch their behavior from one type to other. The use by players of types of behavior other than normal can lead to outcomes more preferable for them than in a game with only normal behavior. The example with the dynamics of simple motion on a plane and phase constraints illustrates the procedure of constructing new solutions

Decomposition of light hydrocarbons on a Ni-containing glass fiber catalyst

The work is devoted to the study of the novel process of catalytic decomposition of light hydrocarbons on a catalyst at temperatures of 550 °С and 600 °C at various pressures. The CVD process is a new COx-free approach for hydrogen production. A glass fiber fabric was used as a catalyst, which was preliminarily modified by the application of additional outer layers of NiO and porous silica. A technical mixture of propane and butane was used as feedstock. The main purpose is to investigate the effects of pressure and temperature on the production of hydrogen and carbon nanofibers over a glass-based catalyst. As a result of the decomposition of the mixture, the yield of hydrogen was 266–848 L/gcat, and that of carbon nanofibers was 3–10 g/gcat. Increasing the pressure of propane-butane mixture decomposition led to an increase of the catalyst lifetime. The highest yield of hydrogen and carbon nanofibers was achieved at 1 bar and 600 °C

In situ surface analysis in selective oxidation catalysis: n-Butane conversion over VPP

In-situ analysis of the surface of a working selective oxidation catalyst is an essential yet rarely conducted experiment in attempts to derive structure-function relationships. The case study of n-butane oxidation over vanadyl pyrophosphate (VPP) is used to develop a general working hypothesis and to illustrate that the molecular properties of the substrate set boundary conditions on the surface chemical properties of the catalyst. Experiments using in-situ X-ray photoelectron spectroscopy (XPS) and in-situ low energy X-ray absorption spectroscopy are used to derive compositional, electronic, and geometric structural information of the surface of the working VPP. These data allow the conclusion that a surface phase different from VPP must be present covering at least part of the active material. The recent data together with literature observations are used to derive a scenario explaining the function of VPP as a unique catalytic system

Dynamic surface behaviour of VPO catalysts under reactive and non-reactive gas compositions: an in-situ XAS study

The surface of an activated vanadium phosphorus oxide (VPO) catalyst was investigated by means of in situ X-ray absorption spectroscopy in the total electron yield mode. We observed significant changes of the V L3-near edge X-ray absorption fine structure (NEXAFS) when the material was transferred from room temperature to working conditions at 400°C in the reaction atmosphere. We studied the same VPO material under different gas compositions comprising the reaction mixture of n-butane and oxygen, pure oxygen and vacuum to elucidate the influence of the gas-surface interaction and the effect of the temperature. The results of this extensive study indicate a dynamic response of the catalyst surface to the applied conditions

Adsorbate coverages and surface reactivity in methanol oxidation over Cu(110): An in situ photoelectron spectroscopy study

The adsorbate species present during partial oxidation of methanol on a Cu(110) surface have been investigated in the 10–5 mbar range with in situ x-ray photoelectron spectroscopy and rate measurements. Two reaction intermediates were identified, methoxy with a C 1s binding energy (BE) of 285.4 eV and formate with a C 1s BE of 287.7 eV. The c(2×2) overlayer formed under reaction conditions is assigned to formate. Two states of adsorbed oxygen were found characterized by O 1s BE's of 529.6 and 528.9 eV, respectively. On the inactive surface present at low T around 300–350 K formate dominates while methoxy is almost absent. Ignition of the reaction correlates with a decreasing formate coverage. A large hysteresis of 200 K occurs in T-cycling experiments whose correlation with adsorbate species was studied with varying oxygen and methanol partial pressures. The two branches of the hysteresis differ mainly in the amount of adsorbed oxygen, the methoxy species, and a carbonaceous species. Methoxy covers only a minor part of the catalytic surface reaching at most 20%. Above 650 K the surface is largely adsorbate-free

Combined in situ XPS and PTRMS study of ethylene epoxidation over silver

Ethylene epoxidation over silver was investigated by combined in-situ X-ray photoelectron spectroscopy (XPS) and proton-transfer reaction mass-spectrometry (PTRMS) at temperatures from 300 to 520 K and in the pressure range from 0.07 to 1 mbar. Ethylene oxide was present among the reaction products at T 420 ≥ K and P ≥ 0.3 mbar. The catalytically active surface contains two oxygen species – nucleophilic and electrophilic oxygen. The observed correlation between the abundance of electrophilic oxygen and the yield of ethylene oxide expressed as C2H4O partial pressure indicates that namely this oxygen species oxidizes ethylene to ethylene oxide. Opposite trend is observed for nucleophilic oxygen: the higher is the abundance of this species, the lower is the yield of ethylene oxide. This result is in line with the known fact that nucleophilic oxygen due to its oxidic nature is active in total oxidation of ethylene to CO2 and H2O. The low activity of silver at T < 420 K is caused by the presence of carbonates and carbonaceous residues at the silver surface that reduce the available silver surface area for the catalytic reaction. Reduction of the surface area available for the formation of active species due to accumulation of the embedded oxygen species explains also the decrease of the rate of ethylene oxide formation with time observed for T 470 ≥ K

High-pressure X-ray photoelectron spectroscopy of palladium model hydrogenation catalysts. Part 2: Hydrogenation of trans-2-pentene on palladium

We have performed the first “high-pressure” X-ray photoelectron spectroscopy (XPS) study on the palladium, hydrogen, and olefin (trans-2-pentene) system to gain better insight into the hydrogenation reaction. We report here data collected with the use of a Pd(111) single crystal and a polycrystalline foil. Hydrogenation was observed on polycrystalline foil (RT and 373 K) but not on Pd(111) single crystal, as revealed by on-line mass spectrometry. We observed the reaction in the presence of a huge amount of carbon (up to 73%) in the information depth of XPS. Mainly graphite was present on Pd(111), whereas other components, C–H and C–Pd, were also formed on the foil to a much greater extent. C–Pd characterizes a carbon species in the interaction with palladium, whereas C–H represents hydrogenated carbon, including chemisorbed species. The d-band of the foil showed a remarkable upshift toward EFERMI compared with Pd(111). We concluded that the differences found in the valence and the C1s region are indicators of different electronic structures that contribute to the variation in activity. The palladium foil lost its activity at an elevated temperature (523 K), most probably because of desorption of hydrogen. From additional UPS measurements, we concluded that trans-2-pentene is hydrogenated in σ-bonded chemisorption modus, at least in UHV conditions