Proper design of high performance industrial heat transfer equipment relies on accurate knowledge and prediction of the thermal boundary conditions. In order to enhance the overall gas turbine efficiency, advancements in cooling technology for gas turbines and related applications are continuously investigated to increase the turbine inlet temperature without compromising the durability of the materials used. For detailed design, local distributions are needed in addition to bulk quantities. Detailed local distributions require advanced experimental techniques whereas they are readily available using numerical tools. Numerical predictions using a computational fluid dynamics approach with popular turbulence models are benchmarked against a semi-empirical correlation for the friction in a circular channel with repeated-rib roughness to demonstrate some shortcomings of the models used. Numerical predictions varied widely depending on the turbulence modelling approach used. The need for a compatible experimental dataset to accompany numerical simulations was discussed. An exact, closed-form analytical solution to the enhanced lumped capacitance model is derived. The temperature evolution in a representative 2D turbulated surface is simulated using Fluent to validate the model and its exact solution. A case including an interface contact resistance was included as well as various rib sizes to test the validity of the model over a range of conditions. The analysis was extended to the inter-rib region to investigate the extent and magnitude of the influence of the metallic rib features on the apparent heat transfer coefficients in the inter-rib region. It was found that the thermal contamination is limited only to the regions closest to the base of the rib feature. An experimental setup was developed, capable of measuring the local heat transfer distributions on all four channel walls of a rectangular channel (with aspect ratios between 1 and 5) at Reynolds numbers up to 150,000. The setup utilizes a transient thermochromic liquid crystals technique using narrow band crystals and a four camera setup. The setup is used to test a square channel with ribs applied to one wall. Using the transient thermochromic liquid crystals technique and applying it underneath high conductivity, metallic surface features, it is possible to calculate the heat transfer coefficient using a lumped heat capacitance approach. The enhanced lumped capacitance model is used to account for heat conduction into the substrate material. Rohacell and aluminum ribs adhered to the surface were used to tandem to validate the hybrid technique against the standard technique. Local data was also used to investigate the effect of thermal contamination. Thermal contamination observed empirically was more optimistic than numerical predictions. Traditional transient thermochromic liquid crystals technique utilizes the time-to-arrival of the peak intensity of the green color signal. The technique has been extended to utilize both the red and green color signals, increasing the throughput by recovering unused data while also allowing for a reduction in the experimental uncertainty of the calculated heat transfer coefficient. The over-determined system was solved using an un-weighted least squares approach. Uncertainty analysis of the multi-color technique demonstrated its superior performance over the single-color technique. The multi-color technique has the advantage of improved experimental uncertainty while being easy to implement.

Shape memory alloys when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as shape memory. This strain recovery can occur against large forces, resulting in their use as actuators. The goal of this project is to lower the operating temperature range of shape memory alloys in order for them to be used in cryogenic switches, seals, valves, fluid-line repair and self-healing gaskets for space related technologies. The Ni-Ti-Fe alloy system, previously used in Grumman F-14 aircrafts and activated at 120 K, is further developed through arc-melting a range of compositions and subsequent thermo-mechanical processing. A controlled atmosphere arc-melting facility and vertical vacuum quench furnace facility was commissioned to fabricate these alloys. The facility can create a vacuum of 10-7 Torr and heat treat samples up to 977 °C. High purity powders of Ni, Ti and Fe in varying ratios were mixed and arc-melted into small buttons weighing 0.010 kg to 0.025 kg. The alloys were subjected to solutionizing and aging treatments. A combination of rolling, electro-discharge machining and low-speed cutting techniques were used to produce strips. Successful rolling experiments highlighted the workability of these alloys. The shape memory effect was successfully demonstrated at liquid nitrogen temperatures through a constrained recovery experiment that generated stresses of over 40 MPa. Differential scanning calorimetry (DSC) and a dilatometry setup was used to characterize the fabricated materials and determine relationships between composition, thermo-mechanical processing parameters and transformation temperatures.

The purpose of this study was to contribute to the understanding of the effects of aphasia couples therapy (ACT) in a person with conduction aphasia. ACT is a social therapeutic approach that involves facilitating conversations between the person with aphasia (PWA) and their spouse, or caregiver. The participants in this study involved one pair. The dependent variables included conveyance of main concepts, use of intentional gestures, reflections and summary statements per conversation. Miscellaneous measures were also counted and analyzed including the PWA’s frequency of paraphasias, fillers (e.g. um, uh), and disfluencies. Baseline sessions involved the PWA watching a video clip, and then providing a verbal summary of the main concept of the clip to his non-aphasic spouse within a 10-minute conversation. Therapy treatment sessions followed the same format as the baseline sessions, however, therapy sessions also included the aide of the researcher to coach the participants to use their pre-selected communication strategies to improve the balance in their conversations. The ability to accurately convey the main concept of a video clip in conversation served as the primary dependent variable in this study. Follow-up sessions were also conducted in similar fashion to baseline and probe sessions to determine maintenance and validity of results by dividing the total number of main concepts by the total number of utterances per conversation. Furthermore, ratings of the PWA’s quality of life and confidence in his ability to communicate were gathered and compared. The results of this study indicated that ACT yielded improved effects for the couple with regards to the communication of main concepts per conversation. A decrease in the use of all included miscellaneous measures were also observed. However, no significant changes were noted with regards to use of intentional gestures, reflections, and summary statements.

No description available.

<p> Working within the framework of the linearized Boltzmann equation for the conduction electrons the existing theoretical treatments of ultrasonic attenuation in metals are extended to include realistic descriptions of the electronic structure and electron-lattice interaction. A variational solution of the Boltzmann equation which allows the inclusion of phonon drag effects is derived. An anisotropic scattering time solution is also presented. Both of these solutions are applied to calculation of the attenuation coefficient in pure metals and dilute alloys. </p> <p> The theory of the effects of electron-electron collisions on the ultrasonic attenuation in metals is also examined. </p> / Thesis / Doctor of Philosophy (PhD)

In niobium oxide-based capacitors non-linear switching characteristics can be observed if the oxide properties are adjusted accordingly. Such non-linear threshold switching characteristics can be utilized in various non-linear circuit applications, which have the potential to pave the way for the application of new computing paradigms. Furthermore, the non-linearity also makes them an interesting candidate for the application as selector devices e.g. for non-volatile memory devices. To satisfy the requirements for those two areas of application, the threshold switching characteristics need to be adjusted to either obtain a maximized voltage extension of the negative differential resistance region in the quasi-static I-V characteristics, which enhances the non-linearity of the devices and results in improved robustness to device-to-device variability or to adapt the threshold voltage to a specific non-volatile memory cell. Those adaptations of the threshold switching characteristics were successfully achieved by deliberate modifications of the niobium oxide stack. Furthermore, the impact of the material stack on the dynamic behavior of the threshold switches in non-linear circuits as well as the impact of the electroforming routine on the threshold switching characteristics were analyzed. The optimized device stack was transferred from the micrometer-sized test structures to submicrometer-sized devices, which were packaged to enable easy integration in complex circuits. Based on those packaged threshold switching devices the behavior of single as well as of coupled relaxation oscillators was analyzed. Subsequently, the obtained results in combination with the measurement results for the statistic device-to-device variability were used as a basis to simulate the pattern formation in coupled relaxation oscillator networks as well as their performance in solving graph coloring problems. Furthermore, strategies to adapt the threshold voltage to the switching characteristics of a tantalum oxide-based non-volatile resistive switch and a non-volatile phase change cell, to enable their application as selector devices for the respective cells, were discussed.:Abstract I Zusammenfassung II List of Abbrevations VI List of Symbols VII 1 Motivation 1 2 Basics 5 2.1 Negative differential resistance and local activity in memristor devices 5 2.2 Threshold switches as selector devices 8 2.3 Switching effects observed in NbOx 13 2.3.1 Threshold switching caused by metal-insulator transition 13 2.3.2 Threshold switching caused by Frenkel-Poole conduction 18 2.3.3 Non-volatile resistive switching 32 3 Sample preparation 35 3.1 Deposition techniques 35 3.1.1 Evaporation 35 3.1.2 Sputtering 36 3.2 Micrometer-sized devices 36 3.3 Submicrometer-sized devices 37 3.3.1 Process flow 37 3.3.2 Reduction of the electrode resistance 39 3.3.3 Transfer from structuring via electron beam lithography to structuring via laser lithography 48 3.3.4 Packaging procedure 50 4 Investigation and optimization of the electrical device characteristic 51 4.1 Introduction 51 4.2 Measurement setup 52 4.3 Electroforming 53 4.3.1 Optimization of the electroforming process 53 4.3.2 Characterization of the formed filament 62 4.4 Dynamic device characteristics 67 4.4.1 Emergence and measurement of dynamic behavior 67 4.4.2 Impact of the dynamic device characteristics on quasi-static I-V characteristics 70 5 Optimization of the material stack 81 5.1 Introduction 81 5.2 Adjustment of the oxygen content in the bottom layer 82 5.3 Influence of the thickness of the oxygen-rich niobium oxide layer 92 5.4 Multilayer stacks 96 5.5 Device-to-device and Sample-to-sample variability 110 6 Applications of NbOx-based threshold switching devices 117 6.1 Introduction 117 6.2 Non-linear circuits 117 6.2.1 Coupled relaxation oscillators 117 6.2.2 Memristor Cellular Neural Network 121 6.2.3 Graph Coloring 127 6.3 Selector devices 132 7 Summary and Outlook 138 8 References 141 9 List of publications 154 10 Appendix 155 10.1 Parameter used for the LT Spice simulation of I-V curves for threshold switches with varying oxide thicknesses 155 10.2 Dependence of the oscillation frequency of the relaxation oscillator circuit on the capacitance and the applied source voltage 156 10.3 Calculation of the oscillation frequency of the relaxation oscillator circuit 157 10.4 Characteristics of the memristors and the cells utilized in the simulation of the memristor cellular neural network 164 10.5 Calculation of the impedance of the cell in the memristor cellular network 166 10.6 Example graphs from the 2nd DIMACS series 179 11 List of Figures 182 12 List of Tables 194

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24872号 / 理博第4982号 / 新制||理||1711(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 北川 宏, 教授 有賀 哲也, 教授 堀毛 悟史 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

In narrow electron bands in which the Coulomb interaction energy becomes comparable to the bandwidth, interactions can drive new quantum phases. In this dissertation, we achieve narrow bands by twisting two atomically thin layers of the semiconducting van der Waals material WSe₂. The resulting moiré potential from the twist angle modulates the electronic bands, yielding minibands of tens of meV on the valence band. We perform transport measurements at cryogenic temperatures and observe signatures of collective phases over twist angles that range from 4 to 5.1°. At half-band filling, a correlated insulator appeared that is tunable with both twist angle and displacement field. Near the boundary between ordered and disordered quantum phases, several experiments have demonstrated metallic behaviour that defies the Landau Fermi paradigm. We find that the metal-insulator transition as a function of both density and displacement field is continuous. At the metal–insulator boundary, the resistivity displays strange metal behaviour at low temperatures, with dissipation comparable to that at the Planckian limit. Further into the metallic phase, Fermi liquid behaviour is recovered at low temperature, and this evolves into a quantum critical fan at intermediate temperatures, before eventually reaching an anomalous saturated regime near room temperature. An analysis of the residual resistivity indicates the presence of strong quantum fluctuations in the insulating phase. We further show via magnetotransport measurements that new correlated electronic phases can exist independent of moiré commensurability, and are instead driven by weak interactions in twisted WSe₂. The first of these phases is an antiferromagnetic metal that is driven by proximity to the van Hove singularity (vHS), which trails a range of incommensurate dopings. The temperature, magnetic field and density dependence of the Hall effect carry signatures of the reconstructed Fermi surface due to itinerant magnetic ordering. The second is an excitonic metal-insulator phase that exists at high external magnetic field in the vicinity of half-filling of the moiré superlattice. For a 4.2° sample, magnetic field dependence of the longitudinal resistance shows metallic behavior at fields above 5 T, but transitions to an insulating state above ∼ 24 T. A detailed analysis of of the Landau fans and the high field 𝝆_𝜘𝛾 near the gap rules out the possibility of a trivial insulator. We propose an Ising excitonic insulator as the most likely scenario. Moreover, in the electron-imbalanced excitonic metal, a set of correlated Landau levels emerge. The observation of tunable collective phases in a simple band, which hosts only two holes per unit cell at full filling, establishes twisted bilayer transition metal dichalcogenides as an ideal platform to study correlated physics in two dimensions on a triangular lattice.

The company Kanthal produces electric heating elements that require high temperature treatment in one production step. In this process step, called sintering, the amount of heat received by the sintered material is in direct correlation to the product’s outcome.  It is therefore of interest for the company to gather information about how heat transfer happens in an electrical furnace. This study examines two different possible scenarios of how the heat transfer in the furnace could look like and which amount of heat the sintered material would receive. The relation between a gaseous ambience at a certain temperature and the temperature an object submerged into this ambience is assuming is studied in the process called "transient heat conduction".  Two models were built in Matlab, representing transient heat conduction effects on two different geometries: a plane wall and a short cylinder.  It could be shown that transient heat conduction effects turned out differently for the two models. The conclusion drawn from the results was that the wall model was susceptible to horizontal heat transfer effects, whereas the cylinder model was affected from all directions equally. Further, an analysis of the heat transfer channels within the furnace revealed that the heat leakage through the furnace muffle edges, which are in contact with air, causes a multiple in heat loss compared to the overall heat leakage.

Regional anestesi kan anses mindre fördelaktigt eftersom patienten är vaken under operationen, något som patienten kan ha en förutfattad mening om och känna sig främmande för. Även om det finns flertalet fysiologiska fördelar med anestesimetoden. Anestesisjuksköterskan har en viktig roll i det perioperativa vårdandet och det anses därför av gagn att förstå patienters upplevelse av att vara vaken under operation. Det för att få möjlighet att främja upplevelsen och undvika oönskade konsekvenser så som lidande i upplevelsen intraoperativt. Syftet var att undersöka patientens upplevelse av att vara vaken under operation med regional anestesi. För att undersöka upplevelsen användes en systematisk litteraturöversikt. Det resulterade i fyra huvudteman. Sensationer, att navigera i det okända, Det främmande landskapet och närvarons betydelse. Resultatet berör upplevda känslor och förnimmelser av operationen. Det beskriver vikten av en professionell vårdrelation och hur det kan påverka måendet negativt av att inte bli sedd. Miljön på operationen är på flera sätt annorlunda och främmande. Slutligen framkommer det hur patienten kunde uppleva olika grader av kontroll samt hur kroppen upplevs främmande med regional anestesi. Resultatet speglar olika delar av patientens upplevelse intraoperativt. Genom att förstå den perioperativa patientens upplevelser, kan den perioperativa sjuksköterskan nyttja den perioperativa dialogen för att kunna lindra patientens lidande. / Regional anesthesia can be considered disadvantageous since the patient is awake during surgery, something, the patient may have preconceived notions, and be nervous about. However, there are several physiological benefits associated with this anesthesia method. The nurse anesthetist plays a crucial role in the perioperative care, and therefore it is beneficial to understand patients experiences of being awake during surgery. This to promote positive experiences and avoid unwanted consequences such as suffering in the intraoperative phase. The aim was to investigate the patient’s experience of being awake during surgery with regional anesthesia. A systematic literature review was employed to investigate the experience. Four main themes emerged: sensations, navigating the unknown, the unfamiliar landscape and the importance of presence. The result discusses emotions and sensations experienced during surgery. It describes the importance of a professional care relationship and how negative effects can occur from not being accepted. The environment in surgery is in many ways different and unfamiliar. Finally, it emerged how the patient might experience varying degrees of control and how the body felt unknown with regional anesthesia. The result reflects various aspects of the patient’s intraoperative experiences. By understanding the perioperative patients experience, the perioperative nurse can utilize the perioperative dialogue to alleviate the patients suffering.