Computer simulation studies of recombination of ions in multi ion-pair ensembles—II. Processes characterized by long mean free paths of charged species

The problem of the recombination of charged species for the case in which initially one or more non-separable pairs of oppositely charged ions are present in the system is treated by means of computer simulation method.The calculations of the electron–cation recombination in the systems characterized by long mean free path (MFP) of an electron between the scattering events were performed. The calculations of the recombination kinetics and escape probability for single pairs were compared with the Debye–Smoluchowski–Onsager theory. It was found that for large MFPs, of above 10–20% of the Onsager distance in the medium, the theory based on the diffusion model is no longer valid, even for isolated ion pairs.The multi-pair effects were investigated by simulation of the electron–cation recombination in clusters composed of up to ten pairs. The deviations of the multi-pair kinetics and escape probability from the corresponding single-pair results are significant.In a series of preliminary calculations it was found that, in contrast to the processes characterized by short MFPs, the mechanism of the energy and momentum transfer during the electron scattering process influences very significantly both the recombination kinetics and the escape probability.     

SimKnowledge—Analyzing impact of knowledge management measures on team organizations with multi agent-based simulation

Even though there is abundant literature on successful cases of organizations applying knowledge management (KM) measures, many KM initiatives have failed to achieve their knowledge and business goals. In order to foster decisions about the design of such initiatives, information is required on success factors and barriers when selecting KM measures. Multi agent-based simulation (MABS) is suggested as instrument to investigate potential effects of KM measures on dependent variables such as sharing of knowledge in organizations or business performance. For such a simulation, the concept of knowledge sharing, influencing factors and their impact on business and knowledge goals are modeled based on an extensive multi-disciplinary literature survey. An extensive domain model is operationalized in a simulation model which is then further simplified and implemented in a MABS tool used for a series of experiments contrasting results with/without KM measures, specifically skill and experience management. Skill management is found highly sensitive with respect to conditions of application and has no significant impact on knowledge or business goals. Experience management positively impacts knowledge and business goals. Personal documentation leads to specialist, project debriefings to generalist knowledge workers. Finally, the paper discusses the simulation’s limitations and further areas of application.     

PREOPT-W: Off-line optimization of binary gradient separations in HPLC by simulation—IV. Phase 3

Off-line gradient optimization by means of the PREOPT-W simulation program is described and illustrated with examples based on real data. The influence of the main factors such as the type of simplex strategy used, optimization objective function and gradient duration as well as other minor, although important, factors like the definition of initial gradient shape and advances used in the design of the initial simplex are discussed. Additional features of the simulation program such as vertex revision and gradient manipulator are also outlined, emphasizing the multiple possibilities at the hands of the chromatographer when developing a gradient separation for very complex mixtures with the help of PREOP-W.     

Moltw: A program for conformational studies using empirical functions—I. Description and general evaluation

A Fortran V (Univac) program is described which calculates molecular conformational energies on the basis of user-selected intramolecular potential energy functions. The algorithm presented here is designed to perform the computation of the conformational partition and therefore it can be used for the prediction of experimentally available quantities such as NMR chemical shifts and coupling constants. The program is efficient in the sense that only dihedral angles and pseudorotational coordinates are handled in the first steps thus allowing a rapid sampling of a great number of points through the entire conformational space. The program provides options to choose between grid searches, energy minimization or both, using a reasonable amount of computer time.     

MASAS—A user-friendly simulation tool for modeling the fate of anthropogenic substances in lakes

MASAS is a computer simulation tool to investigate anthropogenic organic compounds in lakes. Models included are based on a dynamic one-dimensional vertical lake model describing the time-dependent concentration of a compound in the water column and in the sediment. Provision of data is ensured by library files. Interactive specification of transport and transformation processes yields models of different complexity, suitable for the initial assessment of chemicals and for chemodynamic studies. A hypothetical spill of an insecticide (disulfoton) serves as an illustration. Aspects relevant to the development of user-friendly software in the environmental sciences are discussed. User-friendliness is found to depend more on program concepts than on a particular user interface. The management of data sets on lakes and compounds, and the implementation of transport and transformation processes in MASAS exemplify the significance of modularization, program data structures, the use of metaphors, and the distinction between automatic and user-controlled program functions.     

Diffusivities in liquid and fcc Al–Mg–Si alloys and their application to the simulation of solidification and dissolution processes

The experimental viscosities and diffusivities in Al–Mg–Si melts as well as the experimental diffusivities in fcc Al–Mg–Si alloys available in the literature were first critically reviewed. The Sutherland equation was then employed to convert the experimental viscosity data into self-/tracer diffusivity data in Al–Mg–Si melts. Based on the experimental diffusivities together with the converted ones, the atomic mobilities in liquid and fcc phases of the Al–Mg–Si system were assessed by means of DIffusion-Controlled TRAnsformation (DICTRA) software package. Comprehensive comparisons showed that most of the measured and converted diffusivities in liquid and fcc Al–Mg–Si system can be reasonably reproduced by the currently obtained atomic mobilities. Moreover, the reliability of the established atomic mobilities of liquid and solid phases were further verified by two typical cases in Al–Mg–Si alloys during solidification and dissolution processes. The simulation results agree well with the experimental information, not only validating the reliability of the atomic mobilities, but also demonstrating the importance of the accurate atomic mobility database in quantitative simulation of microstructure during various preparation processes.     

Parallel processing of chemical information in a local area network — I. HYDRA: Concept,configuration, and implementation of parallel applications

Sophisticated software packages put an increasing demand on computer hardware. In local area networks, computational intensive programs can lower the performance of individual workstations to an unacceptable level. However, utilizing in a coarse grained sense the computing power of all hosts in such networks, offers the potential to achieve considerable improvements in execution speed within reasonable cost limits. Since conventional workstations are not designed to be used in a parallel configuration, the program HYDRA is developed to control and synchronize parallel processing in a local area network. Part I of this paper focuses on the technical aspects of HYDRA, i.e. configuration and implementation. The second and third parts describe two applications of the HYDRA package in the field of chemistry: using parallel genetic algorithms for the conformational analysis of nucleic acids, and parallel cross-validation of artificial neural networks.     

Predictive computations of intermetallic σ phase evolution in duplex steel. II) Thermo-kinetic simulation in duplex and hyper duplex stainless steels

Kinetic simulations of σ phase precipitation in duplex and hyper duplex stainless steels were carried out by employing mean field approach. For duplex and hyper duplex steels, time-temperature-precipitation (TTP) curves were calculated and compared with experimental results. Thermokinetic predictions confirm that segregation of Cr and especially Mo at grain boundaries of ferrite plays an important role for the nucleation of σ phase in ferrite. This is also reflected by the concentration change of dissolved Mo in σ phase from early nucleation stage to precipitation after long-term isothermal aging of several hours. From the present results, predictive simulations of modified alloy compositions are presented and discussed.     

Simulation of soil chemistry and nutrient availability in a forested ecosystem of southern Quebec — I. Reconstruction of the time-series files of nutrient cycling using the Makedep model

The Makedep model is used to reconstruct the time-series input files of deposition, forest growth, uptake and litterfall needed to run the dynamic biogeochemical model SAFE. The amounts and timing of N made available for tree growth is what determines most of the model output. In this paper, the sensitivity of Makedep to various amounts and timing of N availability, including increased supplies of N prior to air pollution assuming increased biological N₂ fixation, was assessed in a small hardwood stand of southern Quebec. The scenarios of N cycling were validated for burned and unburned conditions based on the simulated tree growth and N leaching rates as well as the model’s ability to recreate the trends in atmospheric deposition of major ions in northeastern North America. The N leaching rates were calculated as the residual component of all simulated processes acting as sources and sinks of N. The N availability scenarios that subtracted/added 5 mmol m⁻² yr⁻¹ of NH₄ in the unburned and burned conditions, respectively, recreated N leaching rates and tree biomass with the most precision. Modifying the amounts of N made available prior to air pollution was also necessary for the trees to grow to reasonable values before 1900. Historical trends of deposition were linked to the changes in the continental emissions in northeastern North America. Observational data for 30 years at the Hubbard Brook Experimental Forest, New Hampshire, showed convergent trends for most ions with the deposition trends simulated with Makedep.     

Application of robotics in onshore oil and gas industry—A review Part I

With ever increasing global demand and depleting resources for fossil fuels, oil and gas industry is now positively looking for advanced robotic solutions to increase their productivity and safety. With time easy resources of the fossil fuels are shrinking and newly searched reservoirs, to feed supply demands of global consumption, are mostly located in extreme environmental conditions such as hot deserts, deep water and arctic zone etc. Production of the fossil fuels, in such inhospitable environmental conditions, poses difficult challenges to health, safety and environment (HSE). Tragic incidents like Exxon Valdez and Deepwater Horizon oil spills are examples of such challenges. Therefore, oil and gas industry has lot to learn from successful implementation of robotics and automation for dull, dirty and dangerous (3D) tasks of manufacturing industry. Most of the robotics technologies, currently used in the oil and gas industry, are mainly focused on inspection, maintenance and repair (IMR) of plant facilities with higher frequency and accuracy. Fundamental idea, involved in the automatization of these processes, is based on the principle of teleoperation with skilled operator. Automation of 3D tasks not only improves HSE standards but also lead to much needed economic efficiency by reducing production cycle, floor space and number of staff members required for continuous inspection and manipulation of plant facilities. Considering the risks involved in this industry usage of completely autonomous robots, first without achieving very high reliability, is still a far fetch choice. Therefore, semi-autonomous robots, where actions are performed by robots but cognitive decisions are still taken by skilled operator, is an excellent choice for this industry as a near future solution. In the onshore oil and gas industry robotic solutions are used both in upstream and downstream processes, such as site survey, drilling, production and transportation, mainly focused in the form of in-pipe inspection robots (IPIRs), tank inspection robots (TIRs), unmanned aerial vehicles (UAVs) and wireless sensor networks (WSNs) etc. This paper presents the state of art robotic solutions currently used in onshore oil and gas facilities.     

Structures,hypergraphs, and knowledge representation in chemical engineering science. I — Problem formulation

It is shown how algebraic structure theory — a tool developed in the last two decades to describe chemical engineering systems — fits into the conceptual framework of hypergraph theory. A new type of structure — actually a special hereditary hypergraph — is introduced in order to lay the foundations for knowledge representation in expert systems designed for chemical engineering problems. Sketchy algorithms are proposed to solve the problems. An existing expert system called FOREST which is applied in the Hungarian chemical industry is mentioned and it is shown how it has been built upon the theoretical basis outlined here. Several very simple mathematical examples are shown, and a real-life example including chemical reactions, mass and heat transport between not more than two phases are treated in detail in the Appendix. A large set of open problems in modelling, mathematics and computation are presented and possible further directions are outlined.     

How I deciphered a Robert E. Lee letter—and a note on the power of context in short polyalphabetic ciphers

We decrypt a message from Robert E. Lee, which is possibly too short for efficient analysis by classical cryptanalytic techniques, by exploiting the mistake of not encrypting the full contents of the message.     

Why adoption and use behavior of IT/IS cannot last?—two studies in China

It is often observed in China that the user acceptance of a new information technology starts satisfactorily well when it is strongly promoted or even enforced to be used, but declines sharply after the initial stage. Based on an extended model derived from the Technology Acceptance Model (TAM), this paper presents two studies in academic and governmental contexts respectively to analyze such phenomena from a post-adoption perspective. Results from structured equation model (SEM) analyses demonstrate the ability of the model to interpret the IT acceptance behavior of Chinese users both during and after the initial stage. It is then inferred that the initial rise of user acceptance is usually driven by mandatory instructions due to the managerial characteristics of long power distance in Chinese organizations, while the drop in the second period is caused by changes that occur in some of the recognition factors in the model, which may reflect the lack of fit between technology and work style. In the two specific cases studied in the paper, the lack of compatibility and facilitating conditions made the user acceptance decline after the initial period when the effects of training and mandatory instructions faded away.     

A program for calculation and graphic representation of conditional constants—I. Complex formation constants

A BASIC program (CONSCOND) is described. Given the stability constants values of metal and ligand, concentration of metal and stoichiometry it calculates and draws the conditional constant diagram vs pH.