No description available.

Biomolecular structure and interactions in aqueous environment are determined by a complicated interplay between physical and chemical forces including solvation, electrostatics, van der Waals forces, the hydrophobic effect and covalent bonding. Among them, electrostatics has been of particular interest due to its long-range nature and the tradeoff between desolvation and interaction effects [1]. In addition, electrostatic interactions play a significant role within a biomolecule as well as between biomolecules, making the balance between the two vital to the understanding of macromolecular systems. As a result, much effort has been devoted to accurate modeling and simulation of biomolecule electrostatics. One important application of this work is to compute the structure of electrostatic interactions for a biomolecule in an electrolyte solution, as well as the potential that the molecule generates in space. There are two valuable uses for these simulations. First, it provides a full picture of the electrostatic energetics of a biomolecular system, improving our understanding of how electrostatics contributes to stability, specificity, function, and molecular interaction [2]. Second, these simulations serve as a tool for molecular design, since electrostatic complementarity is an important feature of interacting molecules. Through examination of the electrostatics and potential field generated by a protein molecule, for example, it may be possible to suggest improvements to other proteins or drug molecules that interact with it, or perhaps even design new interacting molecules de novo [3]. There are two approaches in simulating a protein macromolecule in an aqueous solution with nonzero ionic strength. Discrete/atomistic approaches based on Monte-Carlo or molecular dynamics simulations treat the macromolecule and solvent explicitly at the atomic level. Therefore, an enormous number of solvent molecules are required to provide reasonable accuracy, especially when electric fields far away from macroscopic surface are of interest, leading to computational infeasibility. In this work, we adopt instead an approach based on a continuum description of the macromolecule and solvent. Although the continuum model of biomolecule electrostatics is widely used, the numerical techniques used to evaluate the model do not exploit fast solver approaches developed for analyzing integrated circuit interconnect. I will describe the formulation used for analyzing biomolecule electrostatics, and then derive an integral formulation of the problem that can be rapidly solved with precorrected-FFT method [4]. / Singapore-MIT Alliance (SMA)

The structure of direct-current microdischarges is investigated using a detailed two-dimensional multi-species continuum model. Microdischarges are directcurrent discharges that operate at a relatively high pressure of about 100 Torr and geometric dimensions in the 10-100 micrometer range. Our motivation for the study of microdischarges comes from a potential application of these devices in microthrusters for small satellite propulsion. The Micro Plasma Thruster (MPT) concept consists of a direct-current microdischarge in a geometry comprising a constant area flow section followed by a diverging exit nozzle. A detailed description of the plasma dynamics inside the MPT including power deposition, ionization, coupling of the plasma phenomena with high-speed flow, and propulsion system performance is reported in this study. A two-dimensional model is developed as part of this study. The model consists of a plasma module coupled to a flow module and is solved on a hybrid unstructured mesh framework. The plasma module provides a self-consistent, multispecies, multi-temperature description of the microdischarge phenomena while the flow module provides a description of the low Reynolds number compressible flow through the system. The plasma module solves conservation equations for plasma species continuity and electron energy, and Poisson’s equation for the self-consistent electric field. The flow module solves mass, bulk gas momentum and energy equations. The coupling of energy from the electrostatic field to the plasma species is modeled by the Joule heating term which appears in the electron and heavy species energy equations. Discretization of the Joule heating term on unstructured meshes requires special attention. We propose a new robust method for the numerical discretization of the Joule heating term on such meshes using a cell-centered, finite volume approach. A prototypical microhollow cathode discharge (MHCD) is studied to guide and validate the modeling effort for theMPT. Computational results for the impedance characteristics as well as electrodynamic and chemical features of the discharge are reported and compared to experimental results. At low current (< 0.1 mA), the plasma activity is localized inside the cylindrical hollow region of the discharge operating in the so-called “abnormal regime”. For larger currents, the discharge expands over the outer flat surface of the cathode and operates in the “normal regime”. Transient relaxation oscillations are predicted in the plasma properties for intermediate discharge currents ranging from 0.1 mA to 0.3 mA; a phenomenon that is reported in experiments. The MPT, in its present configuration, is found to operate as an electrothermal, rather than as an electrostatic thruster. A significant increase in specific impulse, compared to the cold gas micronozzle, is obtained from the power deposition into the expanding gas. For a discharge voltage of 750 V, a power input of 650 mW, and an argon mass flow rate of 5 sccm, the specific impulse of the device is increased by a factor of 1.5 to a value of 74 s. The microdischarge remains mostly confined inside the micronozzle and operates in an abnormal regime. Gas heating, primarily due to ion Joule heating, is found to have a strong influence on the overall discharge behavior. The study provides crucial understanding to aid in the design of direct-current microdischarge based thrusters. / text

No description available.

The behavior of large and tightly interconnected power systems resembles, in certain circumstances, the behavior of a continuously distributed system. This resemblance motivated the derivation of continuum models, which were used to explain and predict disturbance propagation, un-damped power oscillations, and the stability of power systems. In this dissertation, we propose a one-dimensional continuum representation suitable for meshed power systems. Previous continuous representations of meshed power systems used two-dimensional spatial domains. Thus our approach has the potential to provide better resolution for comparable computational burden. It is important to note that, the computational burden required to obtain solutions for PDEs involved in the continuum representation varies notably with the solver implementation. The contributions of this dissertation are: a) Reviewing a previous continuum model and providing a detailed derivation for the one-dimensional version of it. b) Providing and describing in detail a parameter distribution technique adequate for the continuum approach. c) Identifying and documenting limitations on the continuum model voltage calculation. e) Providing a procedure to simulate the behavior of meshed power systems using the one dimensional continuum model. And f) Identifying and applying a numerical PDE solver for the continuum approach. / Ph. D.

Abstrakt   Den snabba tekniska utvecklingen har lett till ökad produktion av digitala handlingar/records och transaktioner. Inom e-arkivens domäner, har detta medfört ett ökat tryck på det tekniska området för att kunna garantera autenticitet av bevarad information över tid.          Tidsstämplingstekniker är ett sätt att säkerställa digital information för en särskild tidpunkt och kan användas för att garantera autenticitet av digital information över tid. Denna magisteruppsats undersöker funktionen tidsstämpling inom e-arkivens domäner genom en kvalitativ metod med fem semistrukturerade intervjuer av fem svenska organisationer. I undersökningen ingår också en fallstudie av det svenska innovationsföretaget Enigio Time AB för att ge en förståelse av tidsstämplingstekniker och av deras tjänst time:stamp. Den teoretiska utgångspunkten i denna magisteruppsats är records continuum model med dels dess syn på kontinuitet i handlingar/records och dels dess belysande av skapelseögonblicket av handlingar/records. Den internationella standarden OAIS (Open Archival Information System) används för att hantera digital information och är, i denna uppsats, använd för att analysera hanteringen i dokumenthanteringssystem inom de fem organisationerna.                       Resultaten visar att denna snabba tekniska utveckling har komplicerat dels hanteringen i att säkerställa att digitala handlingar/records inte kan bli manipulerade eller ändrade och dels för att fortsatt kunna garantera autenticitet i ett långtidsperspektiv.                       Undersökningen visar även att organisationerna kan garantera att det bevarade materialet inte kommer att ändras när det väl är inne i arkivet men dess autenticitet, innan de kommer innanför arkivens trösklar, kan aldrig bekräftas. I och med att den moderna tiden producerar och bevarar enorma mängder data så bör detta starta med skapelsen av ett digitalt record tillsammans med bättre strukturerad metadatascheman som är säkrade i tid. / Abstract   The rapid ongoing technical development has led to increased production of digital records and transactions. In the domain of electronic archives, this has put pressure on the technical area in order to guarantee authenticity of preserved information over time. Time stamping techniques are one way to secure digital information at a certain point in time and can be employed to guarantee authenticity of digital information over time. This study examines the function of time stamping within the domain of electronic archives and is conducted with a qualitative method using semi-structured interviews on five Swedish organisations. The study is complemented with a case-study of the Swedish innovation company Enigio Time AB in order to gain understanding in time stamping techniques and their service time:stamp.                       The theoretical framework in this study is the records continuum model with the view of the continuity in records and its illumination of the point of creation. The international standard OAIS (Open Archival Information System) is used by several electronic models to manage digital information and is, in this study, used to analyse the management in record keeping within the five organisations.                       The conclusion is that this rapid technological development has complicated the management of secure digital records from manipulation and guaranteeing the authenticity in a long term perspective.                       The study further shows that organisations may guarantee that records will not change once they are received into the archive but the authenticity of them, before they were delivered, can never be confirmed. Since the modern information era produces and preserves enormous amounts of data, this has to start with the creation of the digital record where better structured metadata schemes are secured in time.

Philosophiae Doctor - PhD / South Africa has placed emphasis on evidence-based decision-making for justifying service delivery improvement decisions. Evidence-based decision-making entails decisions made by referring to verifiable facts and figures available from a variety of sources of evidence such as organizational records. Records are created or received during the conduct of business and contain evidence of organizational activities. Their use as sources of evidence is continuous. Most records management scholars hypothesize that the use of records as sources of evidence for decision-making contributes to improved service delivery. In the same breath, some scholars lament their minimal use as sources of evidence for decision-making in the South African public sector due to poor records management. This descriptive, positivist quantitative study used a cross-sectional survey to determine the extent to which records as sources of evidence were used for evidence-based decision-making by senior managers in Western Cape governmental bodies,

Most rock masses encountered in civil and mining engineering projects contain pre-existing discontinuities. These discontinuities weaken the rock masses to an extent, which depends very much on the size of engineering structure relation to discontinuity spacing. The strength and deformability of rock mass is controlled not only by the intact portion of rock, but by the characteristic of the joints that break up the mass, particularly their pattern and their orientation with respect to the in-situ stresses. In considering the effect of joints, the discrete approach emerged as an efficient tool and advocated since 1970s (Cundall, 1971). However, the numerical approach with modelling the joints explicitly has the limitation of computational complexity for modelling large-scale problems with extremely large number of joints. As an alternative to this limitation, the equivalent continuum approach models the jointed rock masses as a continuum with the equivalent properties that represent implicitly the effects of the joints. Several numerical methods have been developed by various researchers to model jointed rock masses as equivalent continuum, using various techniques. However, the existing equivalent continuum models are complicated and need more input data from experimental or field testing in order to carry out the analysis. Present approach attempts to use statistical relations, which are simple and obtained after analyzing a large data from the literature on laboratory test results of jointed rock masses. Systematic investigations were done including laboratory experiments to develop the methodologies to determine the equivalent material properties of rock mass and their stress-strain behaviour, using a hyperbolic approach (Duncan and Chang, 1970). Present study covers the development of equivalent continuum model for rock mass right from developing statistical correlations to find out equivalent material properties based on experimental results, to the implementation of the model in FLAC3D for 3-dimensional applications and subsequently verification leading to real field application involving jointed rocks. Experimental work carried out to study the strength and deformation characteristics of jointed rock by using standard laboratory tests on cylindrical specimens of plaster of Paris by introducing artificial joints. The objective was to derive the compressive strength and elastic modulus of rock mass as a function of intact rock strength/modulus and joint factor. The obtained experimental results and developed relations were compared with the previous experimental data on jointed rocks. Further, a failure criterion as proposed by Ramamurthy (1993) has been validated from these experimental results of intact and jointed rock specimens. Empirical relationships similar to Ramamurthy’s relations are established for the prediction of rock mass strength and were compared with proposed equation by Ramamurthy (1993) and are found comparable. However, the equations by Ramamurthy were based on different variety of rocks and therefore recommended for further use and were used in numerical models. For efficient application to the field problems the equivalent continuum model is implemented in the program Fast Lagrangian analysis of continua (FLAC3D). The model was rigorously validated by simulating jointed rock specimens. Element tests were conducted for both uniaxial and triaxial cases and then compared with the respective experimental results. The numerical test program includes laboratory tested cylindrical rock specimens of different rock types, from plaster of Paris representing soft rock to granite representing very hard rock. The results of the equivalent continuum modelling were also compared with explicit modelling results where joints were incorporated in the model as interfaces. To represent highly discontinuous system, the laboratory investigation on block jointed specimens of gypsum plaster (Brown and Trollope, 1970) was modelled numerically using equivalent continuum approach. To extend the applicability of the model to field applications, investigation were done by undertaking numerical modelling of two case studies underground caverns, one Nathpa Jhakri hydroelectric power cavern in Himachal Pradesh, India, and the other one Shiobara hydroelectric power cavern in Japan. This study verifies the efficiency of the present approach in estimating ground movement and stress distribution around the excavations in jointed rock masses. The modelling results were also compared with six other computation models as presented by Horii et al. (1999) for the Shiobara power house cavern. An attempt has also been made to numerically model the support system for the cavern and investigate the efficiency of reinforcements using FLAC3D. The model was also used for analyzing large scale slope in jointed rocks using the equivalent continuum model by undertaking numerical modelling of Anji bridge abutment slopes, in Jammu and Kashmir, India. Slope stability analysis is done using equivalent continuum approach for both, the original profiles as well as with the pier loads on cut profiles. Attempt was also made to exhibit the shear strength dependency of the strain though the hyperbolic stress- strain model. The shear strain developed in the slope increases with reducing the shear strength. The relationship between the shear strength reduction ratio ‘R’ and axial strain ‘ε’, for different values of failure ratio ‘Rf’ was studied and it was observed that, the value of ‘ε’ increases, as the value of ‘R’ increases especially it increases rapidly when the value ‘R’ approaches certain critical value, which varies with the value of ‘Rf’. This critical value of R is known as the critical shear strength reduction factor Rc and is highly sensitive to the confining stress. As the value of Rf increases, representing a transition from linear elastic nature to nonlinear nature, the value of critical shear strength reduction ratio also decreases. Relationship between the critical shear strength reduction ratio and the safety factor were examined to elucidate their physical meaning. It was observed that at critical value of the shear strength reduction ratio, a well defined failure shear zone developed from the toe to the crest of the slope. Intelligent models using ANNs were also developed to predict the elastic modulus of jointed rocks as an alternative to empirical equations and without predefining a mathematical model to correlate the properties.

Digital preservation is a relatively new subject to Swedish archives. Alhough computers have been used for a long time, preservation has been made on paper and stored on shelves. These days a lot of cities in Sweden have investigated how to best secure the digital information for the future through electronic archiving, e-archives. One option is to hand in the information as soon as possible, but to let the producer keep the information ownership yet some time. The idea is to let the producers of the information answer questions and hand out material, since they are more competent on their field. This thesis analyzes how five different cities have organized the submission of information. I have used archiving models and interviews. For comparison the cities creating their e-archives have been set against Stockholm. There archive has been up and running for some time. The conclusion is that the solution using a transfer archive could be useful, if the material has got a lot of secrecy and one needs specific knowledge to handle the questions. The theoretical framework has been the life cycle model versus the records continuum model. Swedish city archives embrace the continuum approach early in the creation of the information, but the archivists believe in the life cycle model where all long term preservation comes to the point where no further changes can be done, to protect the authenticity of the information. Two years master’s thesis in Archive, Library and Museum studies. Archival science.

This study concerns the contracting of digital archives for Swedish municipalities and the needs and requirements that govern this. Since the early 2000s, the Swedish government has been interested in expanding the utilization of digital information management. In order to preserve “born digital” official documentation, digital archives are increasingly becoming a necessity for Swedish municipalities. This study considers what the requirements and requests are explicated in formal requirement specifications for such systems. Tobias Edvardssons framework from the book chapter “Kommersiella IT-avtal” (commercial IT-contracts)  in the book “Rättsinformatik” edited by Cecilia Magnusson Sjöberg, as well as grounded theory, is used to discern pertinent categories of requirements. The study finds that the main areas of interest while negotiating a new digital archive can be divided into functional-, qualitative-, governing-, and economic requirements (in accordance with Edvardsson). Archival specifications and technical considerations are also central, as per findings using grounded theory with the support of such models as OAIS and Records Continuum Model.  The study concludes that there still are considerable steps to take before reaching an e-archive solution that can be used on a broad scale to accommodate many different needs and restrictions. However, at the same time, the development of long-term preservation systems for digital records would benefit from more standardized guidelines on a national scale.