Thesis resolvs proposal punches in the sheet metal for heat transfer solar panels. Shapes of punches are selected – piramidal shape and lengwise shape. It is reviewed their possible production and the selected method of Guérin is described. Sheet metal from austenitic stainless 17 240 is selected for the manufacturing. Forming tool is designed with interchangeable punches and elastic medium for various modifications and comparing shapes of punches. It is used hydraulic press CZR 600 for a experimental production.

This master thesis is consisted of literature search and practise part with focusing on the theme of abrasive water jet cutting. Introductory chapters deal with various methods and principles water jet cutting. Following chapters deal with quality of cutting surface by abrasive water jet cutting. After these chapters is introduced machine equipment of water jet cutting technology. At the end of this theoretical part are listed advantages and comparison with other unconventional technologies. In the practical part is solved design of machinery with regard to manufacturing technology of component flange in series 630 000 pieces per year. Last chapter describes economic evaluation of production.

Unconventional technologies and their continual development brings along new possibilities in the manufacturing process. The submitted project is focused on solving problems in the procession of sheet metals in the manufacture of special parts of roller and conveyor chains. In the assessment of the technology of components, laser cutting was evaluated as the most optimal technology. With this goal, there was a public tender in terms of the purchase of a new machine designed for the manufacturing operations of the company of RETEZY Vamberk. This company ranks among the most major manufacturers of conveyor, roller and special chains in Europe.

In this thesis, the electronic properties in superconducting LiFeAs single crystal are investigated using low temperature scanning tunneling microscopy and spectroscopy (STM/S) at various temperatures. For this purpose, the differential conductance (dI/dV) measured by STS which is directly proportional to the local density of states (LDOS) of the sample to the sub-atomic precision, is used together with the topography information. The dI/dV spectra within the ±1 V energy range reveal a characteristic feature at around -350 mV to -400 mV in stoichiometric LiFeAs. This feature seems to be a universal property among all the Fe-based high temperature superconductors, because it is also found in Fe0.965Se1.035 and NaFe0.975Co0.025As single crystals at the energy of -210 mV and -200 mV, respectively. The temperature dependent spectroscopy data averaged over a spatially fixed clean area of 2 nm × 2 nm are successfully executed between 5 K and 20 K. The two distinct superconducting phases with critical temperatures Tc = 16 K and 18 K are observed. In addition, the distance between the dip position outside the superconducting gap and the superconducting coherence peak in the spectra remains temperature independent which confirms that it is not connected to an antiferromagnetic (AFM) spin resonance. The temperature dependent spectra have been measured between 5 K and 61 K within the energy range of ±100 mV as well. The hump structure at 42 mV tends to disappear around 60 K from unknown origin. The temperature dependent quasiparticle interference (QPI) has been studied within the temperature range between 6.7 K and 25 K and analyzed by the Fourier transformation of the measured spectroscopic maps. The dispersion plots in momentum space as a function of temperature show an enhancement of QPI intensity (±5.5 mV) within the superconducting gap at the Fermi level at 6.7 K near q ~ 0. This is interpreted on the basis of Andreev bound state. In both polarities outside of this, a depletion of QPI intensity is noticed between 5.5 mV and around 9 mV. At positive energies, the QPI intensity becomes very rich above 9 mV. The size of the enhanced QPI intensity near the Fermi level, and the edge of the rich QPI intensity beyond 9 mV are found to behave like superconducting order parameter with rising of temperature. Furthermore, an energy mode peaked at around 14 mV appears in the integrated QPI intensity below superconducting Tc (6.7 K). This is consistent with the observed peak at 1st derivative of the dI/dV spectra. In both of these cases, such 14 mV peak is suppressed at normal state (25 K). This mode is therefore directly related to superconductivity in LiFeAs. The off-stoichiometric LiFeAs single crystal with superconducting Tc of 6.5 K has a 10 mV rigid band shift of the Fermi level towards electron doping. The absence of the rich QPI intensity between 9 mV and 17 mV is found compared to the stoichiometric LiFeAs, and hence the 14 mV mode is absent here. This brings us to conclude once more time that such 14 mV energy mode is relevant for superconductivity in LiFeAs.

CeCu_2Si_2 was the first heavy-fermion compound showing signatures of bulk superconductivity (T_c = 0.5 K). Further observations have put in evidence the correlations between superconductivity, magnetic order, Kondo physics, and quantum critical phenomena. In spite of the interest generated, a systematic study of such correlations was hampered by strong sample dependences. Fortunately, the inherent complexity associated to the stoichiometric composition has been recently understood. The availability of single-crystals with well-defined properties has thus reignited the interest in CeCu_2Si_2 as a window to novel phenomena, such as unconventional superconductivity. The present work summarizes the results of my doctoral research. It exemplifies the importance not only of high-quality materials, but also of suitable experimental techniques. A first step in this project involved the design of angle-dependent techniques in the milli-kelvin range, namely: electrical resistivity and thermal conductivity. It comprised the development of a rotational stage, the construction of sample holders, and the implementation of controlling and measuring components. In the second part of the project, electrical- and thermal-transport measurements on CeCu_2Si_2 were performed. Power-law behavior below T_c in the thermal conductivity suggests the presence of lines of nodes in the gap function. Also, the non-vanishing extrapolated residual terms (k_00/T ) support the presence of a residual density of states. The nodes are broadened by potential scattering, which appears to be significant in CeCu_2Si_2. The scattering hinders the determination of the symmetry of the order parameter and might be responsible for the observed isotropic angle dependence of the thermal conductivity. In contrast, angle-dependent measurements of the upper critical field exhibit a four-folded behavior, which also points towards the presence of nodes. By comparing with a weak-coupling model including the effects of Pauli limiting and anisotropic Fermi velocity, the results point towards a d_xy-wave symmetry of the order parameter. Such results represent the first angle-dependent measurements supporting a d-wave symmetry in CeCu_2Si_2.

In this thesis, an extended periodic Anderson model with an additional local Coulomb repulsion U f c between localized f electrons and conduction electrons is investigated by use of the projector-based renormalization method (PRM). First, it is shown that the model in one dimension shows a valence transition, which becomes sharper, when the energy of the f level approaches the Fermi level. The transition becomes also enhanced, when the hybridization V between the localized and conduction electrons decreases, for the case that the total number of electrons is fixed. In the two-dimensional case, one finds a similar valence transition behavior. However, in the valence transition regime also a superconducting phase may occur. To investigate this phase, we start from an Hamiltonian which includes small gauge symmetry breaking fields. We derive renormalization equations, from which the superconducting pairing functions are self-consistently determined. Our analytical and numerical results show that d- wave superconductivity becomes dominant in the valence transition regime. This confirms the suggestion by Miyake that valence fluctuations may lead to superconductivity in the Ce based heavy-fermion systems under high pressure. / In dieser Arbeit wird mit Hilfe der projektiven Renormierungsmethode (PRM) ein erweitertes periodische Anderson Modell untersucht, das zusätzlich eine Coulomb-Abstoßung zwischen den lokalisierten f-Elektronen und den Leitungselektronen enthält. In einer Dimension zeigt das Modell einen Valenzübergang, wenn sich die Energie des f-Niveaus der Fermienergie nähert. Der Übergang wird ebenfalls schärfer, wenn bei festgehaltener Gesamtelektronenzahl die Hybridisierung V zwischen den lokalisierten und den Leitungselekronen abnimmt. In zwei Dimensionen findet man ein ähnliches Valenzübergangsverhalten. Allerdings kann zusätzlich eine supraleitende Phase im Valenzübergangsgebiet auftreten. Um die supraleitende Phase zu untersuchen, betrachten wir einen Hamiltonoperator mit kleinen zusätzlichen Feldern, die die Eichsymmetrie brechen. Wir leiten Renormierungsgleichungen her, aus denen sich die supraleitenden Paarfunktionen selbstkonsistent bestimmen lassen. Unsere analytischen und numerischen Resultate zeigen, dass im Valenzübergangsgebiet d-Wellen-Supraleitung dominiert. Dies bestätigt eine Vermutung von Miyake, dass Valenzfluktuationen in Ce-basierten Schwerfermionensystemen bei hohen Drücken zur Supraleitung führen können.

La presente investigación tuvo como prioridad resolver el problema de congestión vehicular en el cruce de la Panamericana Norte con la avenida Próceres de Huandoy, ubicado en el distrito de los Olivos, Lima, Perú. Para resolver los problemas que aquejan a los usuarios de la intersección mencionada anteriormente se propuso implementar una intersección innovadora llamada Giro a la Izquierda Desplazada (DLT). El estudio se realizó teniendo en cuenta los principios microscópicos de simulación con el programa Vissim; con el fin de evaluar a detalle el comportamiento vehicular y peatonal de manera independiente, ya que el comportamiento de uno influye en las acciones de los demás. La intersección estudiada posee grandes aforos vehiculares y peatonales, y la relación entre vehículo y peatón se encuentra latente, ya que interactúan en medio de la calzada. Para realizar el estudio, se requirió dos visitas a campo con el fin de obtener datos para, posteriormente, evaluar la situación del tránsito actual y proponer las mejoras que los aforos demanden. Asimismo, se buscó que la solución propuesta sea perdurable en el tiempo. Por tal motivo, se analizaron los escenarios con proyecciones a un horizonte de 15 años en el futuro. Los tiempos de viajes vehiculares y las velocidades peatonales fueron los parámetros que ayudaron a la investigación calibrar y validar el modelo para que, finalmente, se obtenga las demoras vehiculares y peatonales. / The present investigation had as a priority to solve the problem of vehicular congestion at the intersection of the Panamericana Norte with Próceres de Huandoy avenue, located in the Los Olivos district, Lima, Peru. To solve the problems afflicting the users of the intersection, it was proposed to implement an innovative intersection called Displaced Left Turn (DLT). The study was carried out considering the microscopic principles of simulation with the Vissim program; to evaluate in detail, the vehicular and pedestrian behavior independently. Since the behavior of one influence the actions of others. The intersection studied has large vehicular and pedestrian traffic, and the relationship between vehicle and pedestrian is latent since they interact in the middle of the road. To carry out the study, two field visits were required to obtain data to subsequently evaluate the current traffic situation and propose the improvements that the gauges demand. Likewise, it was sought that the proposed solution is lasting over time. For this reason, the scenarios with projections for a horizon of 15 years in the future were analysed. Vehicle travel times and pedestrian speeds were the parameters that helped the investigation calibrate and validate the model so that, finally, vehicular and pedestrian delays were obtained. / Tesis

Emergent electronic phenomena in iron-based superconductors have been at the forefront of condensed matter physics for more than a decade. Much has been learned about the origins and intertwined roles of ordered phases, including nematicity, magnetism, and superconductivity, in this fascinating class of materials. In recent years, focus has been centered on the peculiar and highly unusual properties of FeSe and its close cousins. This family of materials has attracted considerable attention due to the discovery of unexpected superconducting gap structures, a wide range of superconducting critical temperatures, and evidence for nontrivial band topology, including associated spin-helical surface states and vortex-induced Majorana bound states. Here, we review superconductivity in iron chalcogenide superconductors, including bulk FeSe, doped bulk FeSe, FeTe1−xSex, intercalated FeSe materials, and monolayer FeSe and FeTe1−xSex on SrTiO3. We focus on the superconducting properties, including a survey of the relevant experimental studies, and a discussion of the different proposed theoretical pairing scenarios. In the last part of the paper, we review the growing recent evidence for nontrivial topological effects in FeSe-related materials, focusing again on interesting implications for superconductivity.

No description available.

The past decade has offered up some fintech innovations that are gradually reshaping the financial sector. Phasing out of paper currencies together with the populatization of the private digital currencies has propelled central banks to consider issuance of their digital currencies – so called Central Bank Digital Currency (CBDC). In particular, the Central Bank of Sweden has started its e-krona project in 2017. Despite the rising interest in the study of CBDC among the academic, as well as tech and policy practitioners’ communities all over the world, the research of the CBDC remains fragmented and limited. Therefore, this thesis aims to study the impact of CBDC on the conduct of monetary policy and for the preservation of financial and monetary stability that is an important, but underresearched topic. As such, the purpose of this research is to explore how the Central Bank of Sweden plans to use CBDC for addressing the central banks’ main objectives of monetary and financial stability. To reach this purpose, an exploratory qualitative case study has been conducted. The results are based on six semi-structured interviews conducted with the practitioners from the Central Bank of Sweden, Finansinspektionen, Swedish Bankers’ Association, and the Swedish House of Finance. The results of this study show that the Central Bank of Sweden has started studying the possibilities and implications of CBDC in the spring of 2017. The analysis focusses on the need of CBDC for Sweden, as well as the possibilities it opens up and implications it entails for the financial system. At the moment of the conduction of this study, the Central Bank of Sweden has been working on solving two next challenges – examining legal issues and existing technology. As such, a pilot project to test the e-krona concept for the general public and diverse security challenges has been planned for 2020-2021. Next, this study has also investigated the possible impact of the introduction of CBDC on the conduction of monetary policy and preservation of monetary and financial stability. First, this study has shown that the impact of the introduction of CBDC on quantitative easing would depend on the design of the CBDC. As such, if CBDC would be interest-bearing, it would have no impact on quantitative easing. If CBDC would, however, have no interest rate, the effectiveness of quantitative easing would be put in jeopardy. As such, a zero interest rate on CBDC would be a lower bound for policy rate and would make setting a negative policy rate impossible. Some economists argue that introducing CBDC would be a replacement for quantitative easing. The introduction of interest-bearing CBDC, however, would ease the setting of a negative policy rate and might enhance the operation of monetary policy. However, this research has shown that introduction of CBDC with a negative interest rate is unlikely. Second, this study has concluded that the necessity and the effectiveness of the helicopter money concept are widely questioned by scholars and practitioners. It is agreed that introducing CBDC would help to distribute the helicopter money, but the concept itself is often inapplicable. Thus, this research has concluded that helicopter money remains just an idea that is vastly supported by scholars and is a no-go policy for practitioners. Third, the study has also shown that CBDC’s impact on the transmission mechanism is still not clear. As such, scholars argue that CBDC would have a big impact on interest rate channel, as it will increase a pass-through to the to lending rates, as well as on the assets’ channel, as CBDC might become an alternative to bank deposits if it offers a higher interest rate. Practitioners agree that the introduction of interest-bearing CBDC would strengthen the transmission mechanism of the interest rate channel and would lead to the direct and almost instant correlation between the policy rate and the CBDC account interest rate. Some practitioners, however, believe that under the condition of the positive policy rate the transmission mechanisms would not be affected other than marginally. Lastly, an interest-bearing CBDC is considered to be dangerous for financial stability in the scholarly research. It is expected to compete with bank deposits and lead to bank runs, which would result in the drain of the funding from the banking system. Some practitioners agree with these conclusions, however, the majority disagrees and perceives CBDC to be an asset to diversify the savings portfolio, which would potentially bring more deposits to commercial banks and extend the banking system. It is agreed that CBDC would entail risks for financial stability if people lose trust in the whole banking sector and move all of their assets to the Central Bank accounts. However, if the Central Bank puts these assets back into the financial system, CBDC would not entail any risks. / Under det senaste decenniet har nya högteknologiska innovationer skapats som gradvist har förändrat den finansiella sektorn i grunden. Utfasning av pappersvalutor i kombination med populariseringen av privata digitala valutor har drivit och inspirerat centralbanker att skapa egna digitala valutor, så kallade CBDC (central bank digital currency). 2017 startade den svenska centralbanken, Sveriges riksbank, sitt e-krona projekt. Trots ökat intresset för studier av digital centralbanksvaluta, både bland akademiker men även inom experter och poltitiker över hela världen, saknas mycket forskning. Denna uppsats kommer att studera effekterna av digital centralbanksvaluta på penningpolitiken i relation till det finansiella och monetära systemets stabilitet. Syftet är att undersöka hur Sveriges riksbank planerar att använda en digital centralbanksvaluta för att vidare kunna uppfylla sitt primära syfte, som är att stabilisera ekonomin. För att uppnå detta, har en kvalitativ studie genomförts. Resultaten är baserade på sex stycken semistrukturerade intervjuer med anställda i olika beslutsfattande positioner inom Riksbanken, Finansinspektionen, Svenska Bankföreningen och Finanshuset. Resultaten av denna studie visar att Riksbanken har börjat undersöka möjligheterna och långvariga implikationerna av en digital centralbanksvaluta. För tillfället arbetar man med två utmaningar: att undersöka det juridiska ramverket samt tillgänglig teknologi. Pilottesterna av e-krona har påbörjats 2020, ytterligare tester har planerats för 2020 - 2021. Ytterligare har denna studie undersökt införandet av digital centralbanksvaluta möjliga effekter på penningpolitiken och långsiktig finansiell stabilitet. Inverkan av en digital centralbanksvaluta på den kvantitativa lättnaden skulle variera beroende på utformningen av den digitala valutan. Om den digitala valutan skulle vara räntebärande så skulle den inte ha någon effekt på den kvantitativa lättnaden, däremot om den var det skulle detta kunna påverka Riksbankens möjligeter att köpa statsobligationer. Det finns också diskussion hurvida man kan använda en digital centralbanksvaluta för att underlätta genomförandet av negativ styrränta. Dessutom visar denna studie också att nödvändighet och positiva effekter av så kallade helikopterpengar är starkt ifrågasatt, även om en digital centralbanksvaluta skulle kunna användas för att distribuera sådana monetära medel. Denna studie visar även att det är oklart om digital centralbanksvaluta skulle ha en effekt på den penningspolitiska transmissionsmekanismen. Många är dock övertygade att det skulle ha effekt på räntekanalen då det skulle öka genomströmningen mellan styrräntan och räntan på CBDC-kontot. Slutligen skulle en räntebärande digital centralbanksvaluta kunna vara farlig för finansiell stabilitet, då det kan stimulera snabba variationer i värde och sätta igång stora uttag från bankkonton. Dock, är detta farlig bara om människor tappar förtroende för hela banksektorn. Om inte är fallet, medför digital centralbanksvaluta inga risker och skulle kunna istället ses som en finansiell tillgång och öka insättningar på privata banker.