Many chemical processes need large computation time to simulate. It has been observed that the speed of a process simulation depends to a large extent on evaluation of certain important functions in the system to be simulated. One such function is K-value estimation function which involves heavy vapor-liquid equilibrium calculations. Because of large number of K-value calculations, there can be a bottleneck in simulation convergence. Thus within process simulation applications computational speed is often emphasized and accuracy is compromised. In situ adaptive tabulation or ISAT, a storage and retrieval technique is proposed for speeding up K-value estimation in a process simulator (CHEMCAD®) using the input-output data. C language code is developed to implement ISAT algorithm for this application. The C code is then converted into Dynamic link library to be able to be used vii by main CHEMCAD® code as required. The overall testing with different K-value databases gave promising results improving computational time while maintaining accuracy. / text

Large-scale processes that are modeled using differential algebraic equations based on mass and energy balance calculations at times require excessive computation time to simulate. Depending on the complexity of the model, these simulations may require many iterations to converge and in some cases they may not converge at all. Application of a storage and retrieval technique, named in situ adaptive tabulation or ISAT is proposed for faster convergence of process simulation models. Comparison with neural networks is performed, and better performance using ISAT for extrapolation is shown. In particular, the requirement of real-time dynamic simulation is discussed for operating training simulators (OTS). Integration of ISAT to a process simulator (CHEMCAD®) using the input-output data only is shown. A regression technique based on partial least squares (PLS) is suggested to approximate the sensitivity without accessing the first-principles model. Different record distribution strategies to build an ISAT database are proposed and better performance using the suggested techniques is shown for different case studies. A modified ISAT algorithm (mISAT) is described to improve the retrieval rate, and its performance is compared with the original approach in a case study. State estimation is a key requirement of many process control and monitoring strategies. Different nonlinear state estimation techniques studied in the past are discussed with their relative advantages/disadvantages. A robust state estimation technique like moving horizon estimation (MHE) has a trade-off between accuracy of state estimates and the computational cost. Implementation of MHE based ISAT is shown for faster state estimation, with an accuracy same as that of MHE. Flowsheet optimization aims to optimize an objective or cost function by changing various independent process variables, subject to design and model constraints. Depending on the nonlinearity of the process units, an optimization routine can make a number of calls for flowsheet (simulation) convergence, thereby making the computation time prohibitive. Storage and retrieval of the simulation trajectories can speed-up process optimization, which is shown using a CHEMCAD® flowsheet. Online integration of an ISAT database to solve the simulation problem along with an outer-loop consisting of the optimization routine is shown using the sequential-modular approach. / text

The presented work is intended to develop a geometrically reduced order (homogenized) model for a large antenna space structure with flexible joints. An energy equivalence concept is employed to find the continuum model for the system. The kinetic and strain energy expressions of the fundamental elements are found based on the assumptions of the micropolar elasticity theory. Necessary assumptions are made to reduce the order of the strain variables while retaining the effects of the micro-rotations that are coupled to the primary strain terms. As a result, a micropolar-based continuum model is found for the structure with torsional joints. The vibrations equations of motion for various coordinates of the one dimensional equivalent model are presented. Subsequently, the relations between the physical parameters of the distributed parameter model and the radar structure are introduced. The effect of the asymmetric mass distribution as a result of the addition of the radar panel to the truss system is studied. For the purpose of the experimental validation of the suggested model a planar truss structure with Pratt Girder configuration was built and tested in the laboratory. The results for the experimental frequency response functions are shown to be in good agreement with the theory. Finally, the continuum model is used to quantify the effects of the thermally induced disturbances on the satellite system during the eclipse transition. / Ph. D.

Doctor of Philosophy(PhD) / This body of research uses numerical and experimental investigative techniques to further the understanding of autoignition. Hydrogen/nitrogen and methane/air fuel configurations of turbulent lifted flames in a vitiated coflow burner are used as model flames for this investigation. Characterisation was undertaken to understand the impact of controlling parameters and the overall behaviour of the flames, and to provide a body of data for modelling comparisons. Modelling of the flames was conducted using the PDF-RANS technique with detailed chemistry incorporated using In-situ Adaptive Tabulation (ISAT) within the commercial CFD package, FLUENT 6.2. From these investigations, two numerical indicators for autoignition were developed: convection-reaction balance in the species transport budget at the mean flame base; and the build-up of ignition precursors prior to key ignition species. These indicators were tested in well defined autoignition and premixed flame cases, and subsequently used with the calculated turbulent lifted flames to identify if these are stabilised through autoignition. Based on learnings from the modelling, a quantitative, high-resolution simultaneous imaging experiment was designed to investigate the correlations of an ignition precursor (formaldehyde: CH2O) with a key flame radical (OH) and temperature. Rayleigh scattering was used to measure temperature, while Laser Induced Fluorescence (LIF) was used to measure OH and CH2O concentrations. The high resolution in the Rayleigh imaging permitted the extraction of temperature gradient data, and the product of the OH and CH2O images was shown to be a valid and useful proxy for peak heat release rate in autoigniting and transient flames. The experimental data confirmed the presence of formaldehyde as a precursor for autoignition in methane flames and led to the identification of other indicators. Sequenced images of CH2O, OH and temperature show clearly that formaldehyde exists before OH and peaks when autoignition occurs, as confirmed by images of heat release. The CH2O peaks decrease later while those of OH remain almost unchanged in the reaction zone.

Doctor of Philosophy(PhD) / This body of research uses numerical and experimental investigative techniques to further the understanding of autoignition. Hydrogen/nitrogen and methane/air fuel configurations of turbulent lifted flames in a vitiated coflow burner are used as model flames for this investigation. Characterisation was undertaken to understand the impact of controlling parameters and the overall behaviour of the flames, and to provide a body of data for modelling comparisons. Modelling of the flames was conducted using the PDF-RANS technique with detailed chemistry incorporated using In-situ Adaptive Tabulation (ISAT) within the commercial CFD package, FLUENT 6.2. From these investigations, two numerical indicators for autoignition were developed: convection-reaction balance in the species transport budget at the mean flame base; and the build-up of ignition precursors prior to key ignition species. These indicators were tested in well defined autoignition and premixed flame cases, and subsequently used with the calculated turbulent lifted flames to identify if these are stabilised through autoignition. Based on learnings from the modelling, a quantitative, high-resolution simultaneous imaging experiment was designed to investigate the correlations of an ignition precursor (formaldehyde: CH2O) with a key flame radical (OH) and temperature. Rayleigh scattering was used to measure temperature, while Laser Induced Fluorescence (LIF) was used to measure OH and CH2O concentrations. The high resolution in the Rayleigh imaging permitted the extraction of temperature gradient data, and the product of the OH and CH2O images was shown to be a valid and useful proxy for peak heat release rate in autoigniting and transient flames. The experimental data confirmed the presence of formaldehyde as a precursor for autoignition in methane flames and led to the identification of other indicators. Sequenced images of CH2O, OH and temperature show clearly that formaldehyde exists before OH and peaks when autoignition occurs, as confirmed by images of heat release. The CH2O peaks decrease later while those of OH remain almost unchanged in the reaction zone.

Permeability surface layer of concrete is engaged in many research institutes around the world, because the surface layer is the weakest link in the entire concrete structure. This dissertation followed on the issue of global solutions and broadens the horizon of the covercrete issues. The aim of this work was to create the conversion relations between the methods for evaluating the permeability of concrete surface layer allow approximate evaluation of the surface layer of concrete depending on the current moisture. In practice mostly occur concrete, which surface mass of moisture is equal to 3 %, so this amount of moisture is selected as the reference. For comparison were used: the device TPT (Torrent Permeability Tester), device GWT (Germanns Water Permeability Tester) and methods ISAT (Initial Surface Absorption Test). A secondary aim was to create a unified methodology for measuring the device.

The reliance on information systems in daily operations in organizations made these systems and the security thereof a vital asset that must be protected. Traditionally, technical solutions were thought to be the critical factor in achieving security requirements. However, this has changed with research advancements into information security, suggesting that users are the root cause of the majority of information security incidents. It is widely accepted that an integral part of the methodology of securing information systems is end-user Information Security Awareness Train-ing (ISAT). The goal of ISAT is described to be a change in user behavior. As a result, research into the area has been steadily improving the ways ISAT is carried out. Yet, information security incidents are still on the rise with no indication of slowing down. Previous research has mainly examined users’ experience in relation to ISAT with very little focus on the organizational per-spective. In this study, the organizational perspective on the preferences and expectations of ISAT is examined by inviting all Nordic municipalities to participate in an online survey. The survey consisted of two parts; the first part focused on the current state of ISAT in Nordic municipalities. The second part examined the ideal design of ISAT according to participants. The results obtained from the survey revealed that the participating Nordic municipalities are well aware of recent developments in ISAT. Furthermore, their preferences and expectations of ISAT and what they consider an ideal design of ISAT conform to what is suggested in the literature—with some ex-ceptions. However, there seems to be a gap between knowing about recent developments and having a desired ideal design that conforms to the literature on one side, and actually applying these in production on the other side.

The master thesis dealing with problematic about durability of concrete, with use of recycled concrete and addition of silica additions. Predominant for resistance of concrete constructions is surface layer, through which aggressive gasses and liquids penetrate from surrounding environment. The most important indicator of concrete durability is ability of surface layer transmissions of aggressive substants. In experimental part will be defined the actual state of surface layer by normal testing methods. The transmissions of surface layer will be tested on concrete cubes. Tests for transmissions of air (method TORRENT), of water (method ISAT), of acid gases (dept of carbonation by quick test in 98% CO2) will be carried out and also strength tests. Assessment of positive or negative influence of additions and amount of cement on durability and mechanical properties of concrete will be discussed in conclusion.