It is generally accepted that the fatigue crack growth depends on the stress intensity factor range (ΔK) and the maximum stress intensity factor (K_max). Numerous driving forces were introduced to analyze fatigue crack growth for a wide range of stress ratios. However, it appears that the effect of the crack tip stresses and strains need to be included into the fatigue crack growth analysis as well. Such an approach can be successful as long as the stress intensity factors are correlated with the actual elastic-plastic crack tip stress-strain field. Unfortunately, the correlation between the stress intensity factors and the crack tip stress-strain field is often altered by residual stresses induced by reversed plastic deformations. A two-parameter model (ΔK_tot, K_max,tot) based on the elastic-plastic crack tip stress-strain history has been proposed. The applied stress intensity factors (ΔK_appl, K_max,appl) were modified and converted into the total stress intensity factors (ΔK_tot, K_max,tot) in order to account for the effect of local crack tip stresses and strains on the fatigue crack growth. The fatigue crack growth was regarded as a process of successive crack re-initiations in the crack tip region and predicted by simulating the stress-strain response in the material volume adjacent to the crack tip and estimating the accumulated fatigue damage. The model was developed to predict the mean stress effect for steady-state fatigue crack growth and to determine the fatigue crack growth under simple variable amplitude loading histories. Moreover, the influence of the applied compressive stress on fatigue crack growth can be explained with the proposed two-parameter model. A two-parameter driving force in the form of: Δκ = K_max,tot^p ΔK_tot^(1-p) was derived based on the local stresses and strains at the crack tip using the Smith-Watson-Topper (SWT) fatigue damage parameter: D = σ_maxΔε/2. The parameter p is a function of material cyclic stress-strain properties and varies from 0 to 0.5 depending on the fatigue crack growth rate. The effects of the internal (residual) stress induced by the reversed cyclic plasticity manifested themselves in the change of the resultant (total) stress intensity factors driving the crack. Experimental fatigue crack growth data sets for two aluminum alloys (7075-T6 and 2024-T351), two steel alloys (4340 and 4140), and one titanium alloy (Ti-6Al-4V) were used for the verification of the model under constant amplitude loading. This model was also capable of predicting variable-amplitude fatigue crack growth. Experimental fatigue crack growth data sets after single overloads for the aluminum alloy 7075-T6, steel alloy 4140, and titanium alloy Ti-6Al-4V were also used for the verification of the model. The results indicate that the driving force Δκ can successfully predict the stress ratio R effect and also the load-interaction effect on fatigue crack growth.

With the growth of population and development of the global economy, the unrestrained use of natural and energy resources have seriously influenced environment and economy of world. Many people start to realize the serious environmental problems that come from the high energy utilizations, especially of high carbon dioxide (CO2) emissions. So Low-Carbon Economy has become focus of attention around the world; it also has become every country‟s strategic goals for future development under this global situation.As the biggest country of CO2 emissions in the world, China‟s development of Low-Carbon Economy is increasingly influencing the economy and environmental development in the world, and the country has faced more and more pressure after United Nations Climate Change Conference, 2009. Transition to Low-Carbon Economy is essential road for China, whether respond to the threat of climate change or balance domestic economic development with environmental sustainability. However, China also faces lots of challenges and pressure in the process of transition to Low-Carbon Economy.This thesis combines quantitative method with qualitative methods to do a research about driving force and challenges of developing Low-Carbon Economy in China. Firstly, it discusses the driving forces for China to develop Low-Caron Economy from two aspects-pressures and benefits. Secondly, it investigates challenges that China is likely to face in Low-Carbon Economy development from energy and economic aspect. Finally, it uses cause and effect diagram to explain the bottlenecks of Low-Carbon Economy development in China.Our conclusion is that China faces the bottleneck between challenges and driving force to develop Low-Carbon Economy. And this situation was caused by national actual situations and conditions in China. This explains also why China requested in Copenhagen Conference that “developing countries take appropriated measures to emission control and reduction in terms of receiving the funding and technology support from developed countries. Those emission reduction actions should be done according to the national actual situations and conditions.”

It is generally accepted that the fatigue crack growth depends on the stress intensity factor range (ΔK) and the maximum stress intensity factor (K_max). Numerous driving forces were introduced to analyze fatigue crack growth for a wide range of stress ratios. However, it appears that the effect of the crack tip stresses and strains need to be included into the fatigue crack growth analysis as well. Such an approach can be successful as long as the stress intensity factors are correlated with the actual elastic-plastic crack tip stress-strain field. Unfortunately, the correlation between the stress intensity factors and the crack tip stress-strain field is often altered by residual stresses induced by reversed plastic deformations. A two-parameter model (ΔK_tot, K_max,tot) based on the elastic-plastic crack tip stress-strain history has been proposed. The applied stress intensity factors (ΔK_appl, K_max,appl) were modified and converted into the total stress intensity factors (ΔK_tot, K_max,tot) in order to account for the effect of local crack tip stresses and strains on the fatigue crack growth. The fatigue crack growth was regarded as a process of successive crack re-initiations in the crack tip region and predicted by simulating the stress-strain response in the material volume adjacent to the crack tip and estimating the accumulated fatigue damage. The model was developed to predict the mean stress effect for steady-state fatigue crack growth and to determine the fatigue crack growth under simple variable amplitude loading histories. Moreover, the influence of the applied compressive stress on fatigue crack growth can be explained with the proposed two-parameter model. A two-parameter driving force in the form of: Δκ = K_max,tot^p ΔK_tot^(1-p) was derived based on the local stresses and strains at the crack tip using the Smith-Watson-Topper (SWT) fatigue damage parameter: D = σ_maxΔε/2. The parameter p is a function of material cyclic stress-strain properties and varies from 0 to 0.5 depending on the fatigue crack growth rate. The effects of the internal (residual) stress induced by the reversed cyclic plasticity manifested themselves in the change of the resultant (total) stress intensity factors driving the crack. Experimental fatigue crack growth data sets for two aluminum alloys (7075-T6 and 2024-T351), two steel alloys (4340 and 4140), and one titanium alloy (Ti-6Al-4V) were used for the verification of the model under constant amplitude loading. This model was also capable of predicting variable-amplitude fatigue crack growth. Experimental fatigue crack growth data sets after single overloads for the aluminum alloy 7075-T6, steel alloy 4140, and titanium alloy Ti-6Al-4V were also used for the verification of the model. The results indicate that the driving force Δκ can successfully predict the stress ratio R effect and also the load-interaction effect on fatigue crack growth.

Abstract This study aims to measure the flow field distribution in a microchannel with different heights adjusted. Two different materials, PDMS and Coverglass, were used to observe the flow velocity distribution change resulting from the difference in Zeta potential. The velocity distribution data were also obtained. In the experiment, 1¡Ñ TBE buffer solution with viscosity of 1 cp was used with the electric field intensity controlled under 5, 7.5 and 10 kV/m, respectively. Micrometer resolution Particle Image Velocimetry (£gPIV) was used to measure partial velocity distribution in order to explore the hydrodynamic stretch effect on DNA molecules when the microchannel, where the solution was placed, was adjusted to different heights. This study also statistically analyzed the stretch length distribution of DNA molecules in the microchannel and calculated the time of DNA molecule deformation and stress relaxation time in order to understand the stretch condition under different heights as well as the stretch and deformation of DNA molecules in microchannels.

The background to this bachelor thesis is an on-going project within the VINN Excellence Center Hero-m. The task in this thesis is to perform a literature survey about the martensite transformation and investigate how the resulting fraction depends on cooling below the Ms-temperature. Instead of calculating the undercooling for each of the known fractions of martensite the driving force will be evaluated. Several efforts have been made through the years to describe the relationships between fraction transformed austenite and temperature. The approaches to the first models were empirical and derived from collections of data regarding the amount of retained austenite at different quenching temperatures. Lately, studies have been made to derive a thermodynamical relationship using how the Gibbs energy is affected by increments in volume transformed austenite. Two equations are derived by calculating the resulting driving force at different known quenching temperatures and the respective percentage transformed martensite found in previous works. The data for the steels used show a characteristic slope when linearised. A trend for the steels which have a high characteristic slope is that they also have a high Ms temperature, and the steels which have a low characteristic slope tend to have a low Ms. Previous relationships which describe the martensitic transformation have considered the importance of the Ms temperature only in it being a starting temperature for the transformation. To further incorporate the Ms temperature in the equations presented, further research of the martensitic transformation is required. The approach in this thesis of using thermodynamically calculated data is a base for further investigation of the range of the martensite transformation.

Building Information Modeling, abbreviated BIM, is a process of information sharing which enhances communication and which helps in visualizing complex problems in the building industry. BIM has not been used in a larger extent in the production phase of civil works. The purpose of the study is therefore to investigate driving forces behind the use of BIM and the resistors against it and to investigate in what ways BIM could be used in the production phase. The theoretical framework is based on one licentiate thesis, two degree projects, three research papers and three books. A qualitative method with semi-structured interviews was used. The interviews were made with a calculator, a supervisor and a CAD planner from Skanska, a constructor and project manager from ELU, a Project Information Officer from Tyréns and a VDC coordinator and VDC business developer from Veidekke who all have been working with BIM. This was to get a good representation from different actors and people with different professional roles. The study shows that the driving forces behind a use of BIM are that it enhances collaboration and communication between the actors, it makes it easier to visualize the project and the scope, and it provides a higher degree of accuracy of coordination’s. BIM also makes the work more effective and results in fewer errors. Above all, BIM give a possibility for a shorter production phase, shorter total project duration and a lower total cost. The study also shows that the resistors against the use of BIM are employee’s negative attitude against administrative work, that it is hard to measure profitability of using BIM, the uncertainty of who has the legal ownership of the data, and who has the responsibility of the accuracy of it. 3 That the implementation cost and the design phase are more expensive is also a resistor against a use of BIM. BIM could be used in visualization with 3D models in collision controls and co-reviews in meetings, work preparations and at site. A workplace outline could also be printed from the 3D model to be placed on the site for visualization. 4D scheduling and 4D animations could be used for visualization in meetings, work preparations and at site. The study showed that quantity takeoff and cost estimation with 5D is only reconciled in the meetings in the production phase and that the programs for it are not needed in this phase. RFID tags could be used at site for logistics and tracking materials, and field verifications could be used to verify that a work task is executed according to exact coordination’s in the 3D model. Furthermore tablet computers could be used for bringing the technique of BIM to the site which enables a better understanding of complex work tasks for the workers. A BIM coordinator who understands the process of working with BIM and who could work as a bridge between the users and the technical development team is important in a successful implementation. The study also shows that the focus of BIM should lie on how to make use of the technique. The examples of how BIM could be used in the production phase of civil works have to be useful and meet the needs and demands of the users. The processes of using 3D models, 4D scheduling, 4D animations, RFID tags, field verifications and tablet computers should therefore be studied thoroughly to find how the technique could be applicable at site, in meetings and work preparations and how it could enhance the daily activities and work tasks. If the demands are met it will be accepted by both the user and the organization. Further research should therefore lie on how 3D models, 4D scheduling, 4D animations, RFID tags, field verifications and tablet computers could be useful in the production phase. These BIM techniques should then be tested on a real project to investigate how the processes could be useful at site, in meetings and in work preparations. Further research should also be made on how countries like Norway, Finland and USA have made use of BIM in the production of civil works.

The objective of this research based on both the theory and experimentation was to prove that the total pressure difference is the primary driving force during the vacuum drying. The theoretical drying rates of diffusion, free water bulk flow and water vapor bulk flow were calculated and compared. The concept of equilibrium moisture content under the vacuum was developed. The theoretical maximum moisture content drop in one cycle was calculated using energy balance. The model was developed for the vacuum drying to understand the mechanism of the vacuum drying including the boiling front and its movement. To evaluate the effect of the sample size on the drying rate, four different thicknesses (1, 1.5, 2, 2.5 inches) and three different lengths (5, 10, 15 inches) were used. In the cyclic drying, the specimens were heated to the 60 C. The vacuum was pulled to about 18 mm Hg. The vacuum pump was kept running for 140 minutes. It was found that in cyclic vacuum drying, drying rate was not affected by the thickness. However, it was affected by the length. The cyclic drying curve consisted of two distinct parts. The fast drying period lasted about 10 to 20 minutes. The slow drying period occurred next when the pressure inside wood got close to the ambient pressure. In end grain vacuum drying, the specimens were coated with wax, wrapped in the plastic film and inserted into a rubber tube to prevent the moisture loss from the side surfaces during drying. The specimen size was 1×1×10 inches. Red oak and white oak were sealed and dried in both cyclic and continuous vacuum drying. The results showed that sealed specimens dried almost as fast as unsealed specimen. There was little moisture loss from the side surfaces. There was a moisture gradient along the length in both cyclic drying and continuous vacuum drying. Red oak specimens of 2.5×1.5×10 inches were used to study the boiling front in the vacuum drying. In order to detect the boiling phenomenon, the saturation pressures were calculated and were compared with the pressures at the same time and the same location. Boiling occurred during drying and the boiling front retreated to the center of wood as drying proceeded. The retreating speed depended on the heat supply and the permeability. Vacuum drying at room temperature was investigated. The specimens were dried at 20 C and pressure near 18 mm Hg. The results showed that wood can be vacuum dried at room temperature with little or no degrade at a reasonable drying rate. All experimental results support the objective of this study that the primary driving force is the total pressure difference. / Ph. D.

Syfte: Att studera hur tidigare kariesaktiva patienter har ändrat sina vanor med resultatet minskad kariesaktivitet. Frågeställningen var: ”Hur lyckas tidigare kariesaktiva patienter ändra sina vanor?”. Material och metod: Studien genomfördes på Tandvårdshögskolan i Malmö med ett slutgiltigt urval som bestod av sex informanter varav fyra var patienter på Tandvårdshögskolan och två på Folktandvården i Malmö. Inklusionskriterierna var tidigare kariesaktiva med nu avstannad kariessjukdom, fyllda 18 år och som talade flytande svenska. För datainsamlingen genomfördes kvalitativa semistrukturerade intervjuer med efterföljande dataanalys med kvalitativ innehållsanalys.     Resultat: Den ena kategorin som identifierades var: Den varierande drivkraften som omfattade subkategorierna den positiva drivkraften och den negativa drivkraften. Den andra kategorin var: Det externa stödets vara eller icke vara omfattande externt positivt inflytande och en önskan om externt stöd (under sårbara tider).  Slutsats: Informanterna lyckades med en beteendeförändring som initierades av stöd, i form av information, eller drivkrafter, i form av funktion, estetik eller rädsla. När informanterna kände sig lyssnade på, involverade, motiverade och handlingskraftiga kunde de förstå hur de skulle kunna förändras från att vara kariesaktiva till kariesinaktiva. / Aim: To study how previously caries-active patients have changed their habits with the result reduced caries activity. The research question was, "How does previous caries-active patients manage to change their habits?" Material and method: The study was conducted at The Faculty of Odontology at Malmö University with a final sample of six informants, of whom four were patients at the faculty and two at the Public Dental Health Service in Malmö. The inclusion criteria were previously caries-active with now arrested caries disease, 18 years and above and fluent in Swedish. For data collection, qualitative semi-structured interviews were conducted with subsequent data analysis using qualitative content analysis. Results: One category that was identified was: The varied driving force which included the subcategories the positive driving force and the negative driving force. The second category was: The presence or absence of external support including external positive influence and a desire for external support (during vulnerable times). Conclusion: The study showed that the informants managed a behavioral change which was initiated by support, in the form of information, or by driving force, in the form of function, aesthetics or fear. When the informants felt listened to, involved, motivated and driven, they could understand how they could change from being caries-active to caries-inactive.

Please read the abstract in the section 00front of this document / Thesis (PhD)--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / PhD / Unrestricted

We study the time evolution of driven quantum systems using analytic, algebraic, and numerical methods. First, we obtain analytic solutions for driven free and oscillator systems by shifting the coordinate and phase of the undriven wave function. We also factorize the quantum evolution operator using the generators of the Lie algebra comprising the Hamiltonian. We obtain coupled ODE's for the time evolution of the Lie algebra parameters. These parameters allow us to find physical properties of oscillator dynamics. In particular we find phase-space trajectories and transition probabilities. We then search for chaotic behavior in the Lie algebra parameters as a signature for dynamical chaos in the quantum system. We plot the trajectories, transition probabilities, and Lyapunov exponents for a wide range of the following physical parameters: strength and duration of the driving force, frequency difference, and anharmonicity of the oscillator. We identify conditions for the appearance of chaos in the system.