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[en] A magnetic nozzle leads the ion beam accelerated by the adiabatic expansion of plasma electrons in the expanding magnetic field for thrust. This concept has the advantage that the expanding electrons can be directly used for the neutralization of the ion beam without additional installation of a cathode for neutralizing the ion beam. Then, it is discussed as the next generation electric thruster. The efficiency of the magnetic nozzle apparatus in terms of ion beam acceleration energy is determined by the relationship between electron cooling and plasma potential gradient via a polytropic equation that can represent the adiabatic expansion in magnetically expanding plasma. Thus, previous studies have been conducted with the importance that a clear understanding of the electron thermodynamics in the magnetic nozzle contributes to the thrust efficiency. For the analysis of the electron thermodynamic state in the magnetic nozzle plasma, it describes the magnetically expanding plasma by introducing a total energy conservation law in which changes in the internal energy of the electron gas system work on magnetic and electric fields defined as flexible surroundings. The experiment and modeling results for the electron thermodynamics indicate that the system is enable to be classified based on the electron group trapped by the electric potential barrier or constant maximum magnetic moment. In the case of electrically trapped electrons, the adiabatic expansion of the electrons contributes to the formation of the electric field structure, while escaping electrons may work to cause a change in the magnetic field structure regardless of the electric field formation. Hence, in the electron thermodynamics of the magnetic nozzle plasma, it implies that consideration of the electrostatic confinement is essential. Previous studies focused on the identification of the electron thermodynamic states based on a clear definition of the electron gas system have been the basis for studying the relationship between the electron thermodynamics and the efficiency of magnetic nozzles, and require refined study that reflect complex plasma physics. Notice that the plasma generation in the magnetic nozzle apparatus is achieved by the electron energy and directional selective heating on them, it is emphasized that the study on the plasma potential gradient formation due to the change of the thermodynamic state of the electrons should be carried out based on the diagnosis considering the directional orientation of the electrons. The electron energy distribution function (EEDF) of each directional component is measured, while increasing the applied power to the plasma source by electron cyclotron resonance (ECR), and selectively changing the perpendicular electron energy. Interestingly, the increase in the perpendicular energy of the electrons at the nozzle throat did not contribute to the formation of the plasma potential gradient, which is interpreted because most of the power applied for the electron heating contributed to the rise in the perpendicular energy of the escaping electrons. In the case of the electron energy in the parallel direction, the electron heating in the far-field region of the nozzle is observed as the applied power increased, and this heating induces the synergistic effect of the absolute value of the plasma potential, resulting in the attenuation of the ambipolar electric field generated by the trapped electron group in the perpendicular direction. The correlation between the plasma potential gradient change and the change of electron cooling and energy transfer from perpendicular to parallel component of the trapped electrons according to the applied power proves that the trapped electrons contribute to the electric field formation through the adiabatic expansion and suggests the following points. First, heating of trapped electrons directly contributes to the build-up of an electric field for ion acceleration in a magnetic nozzle utilizing ECR heating. Second, the change in the paraxial thermal energy of the trapped electrons and the change in the electric field are demonstrated by the adiabatic expansion of which the polytropic index is close to 5/3. Third, the electron energy transfer between the perpendicular and parallel directions can interrupt formation of the electric field in far-field region. Therefore, modeling and device design in the magnetic nozzle research that reflects the above perspectives are essential. This study is the first to emphasize that the anisotropy of electron temperature can directly affect the magnetic nozzle efficiency when generating magnetic nozzle plasma by wave heating. From the engineering point of view, it is important that the ratio of trapped electrons should be prioritized to abundant via plasma potential control for efficient increase of ion energy. Through the further research on the plasma generation method such as parallel electron energy heating in the plasma generation region, this suggests that energy conversion from the perpendicular to the parallel direction due to magnetic expansion in the far-field region can be minimized
[en] The exposure of pediatric patients to ionizing radiation from medical procedures is becoming increasingly worrying, given the increasing use of technologies that use this type of radiation. The high radiosensitivity of the developing cells of pediatric patients makes the analysis of the amount of dose received by these patients in each exam performed extremely important, aiming to evaluate and optimize the exams in order to reduce the risk of occurrence of biological effects. The objective of this work was to evaluate the radiation dose received in conventional pediatric radiology exams. The chest (Antero-Posterior and Profile), skull (Antero-Posterior, Profile and Towne), abdomen (Antero-Posterior and Antero-Posterior standing), pelvis (Antero-Posterior and Frog) and sinuses examinations were evaluated (Antero-Posterior, Profile and Waters). To estimate the entrance skin dose, for each exam, the value of the X-ray tube output and the technical parameters used for the exams were used. Anthropometric data were collected from patients, radiographic technique data and exam classification data. The results were used for a descriptive statistical analysis of the entrance skin dose and also for the elaboration of a statistical modeling showing the correlation between the variables used in the exams and their significance in the radiation dose received by the patient. The variables were separated between equipment and patient parameters. The estimated dose values resulted mostly in values above international recommendations and similar studies, but allowed, along with the modeling, a better understanding of the dose distribution for each equipment, examination projection and gender studied. In view of the results obtained, an optimization study can be carried out to improve the doses received by patients, in compliance with the aforementioned principle of radioprotection. (author)
[en] The human identification process represents one of the most relevant aspects of the forensic sciences field. Few studies related to sex dimorphism have evaluated the accuracy of linear measurements of frontal and maxillary sinuses on multislice computed tomography (MCT). This investigation aimed to: (1) evaluate parameters of accuracy in sex estimation of maxillary and frontal sinuses on MCT of Brazilian adult individuals; (2) develop and cross-validate a new formula for discriminating males and females. Two-phase cross-sectional research was conducted with a statistically estimated sample of 140 MCTs: phase 1) development of a formula based on both sinuses (50 males and 50 females); phase 2) validation study (20 males and 20 females). Frontal and maxillary sinuses linear measurements (height, width, and diameter) were assessed using the RadiAnt DICOM software. Based on a multivariate statistical approach, a new formula combining both paranasal sinuses was developed and further validated. Receiver operating characteristic (ROC) curves, the area under the curve (AUC), sensitivity, specificity, positive and negative predictive values, accuracy, and likelihood ratio were obtained. Also, the influence of age was evaluated by subgroup statistical analysis. Men showed higher mean values of width, height, and diameter of the studied paranasal sinuses (p<0.05). The maxillary sinuses were a better predictor of sex estimation than frontal sinus (accuracy between 61-74% and 58-69%, respectively). The highest accuracy was found with the distance between the right and left maxillary sinuses (74%).The formula for sex estimation showed a sensitivity of 80%, specificity of 95.5%, and an accuracy of 87.5%. In individuals aged > 30 years, there was a 63.1% reduction in predictive values for sex estimation. Frontal and maxillary sinuses measurements were adequate predictors for sexual dimorphism in a Brazilian sample. Both paranasal sinuses showed a better estimation of males, and the most significant accuracy occurred with maxillary sinuses. High precision was found with the distance between the right and left maxillary sinuses. The multivariate statistics-based formula provided a better precision in discriminating males and females. (author)
[en] We present extensions and new developments of the in-medium no-core shell model (IMNCSM), which is a novel ab initio many-method that merges the multi-reference in-medium similarity renormalization group (MR-IM-SRG) with the no-core shell model (NCSM) - two complementary and successful ab initio many-body methods. Within the IM-NCSM framework, the MR-IM-SRG employs a correlated NCSM reference state and unitarily transforms observables such that the reference state is decoupled. Consequently, the model-space convergence of a subsequent NCSM calculation is substantially accelerated - demonstrating the power of the IM-SRG decoupling scheme - and the IM-NCSM can treat nuclei that are out of reach for traditional NCSM calculations. In earlier applications we already employed the IM-NCSM for addressing scalar observables w.r.t. ground and excited states in even open-shell nuclei, however, this initial formulation of the IM-NCSM had several restrictions that we eliminate in this work. Due to the spherical formulation of the IM-SRG equations - which is mandatory from a computational point of view - the total angular momentum of the reference state is required to vanish and, thus, the IM-NCSM was restricted to the treatment of even nuclei. The particle-attached/particle-removed extension overcomes this restriction and makes odd nuclei accessible. Furthermore, the spherical formulation of the IM-SRG equations did not account for non-scalar operators and, therefore, the consistent transformation of electromagnetic observables was not possible. By deriving and implementing the IM-SRG equations corresponding to non-scalar observables, we open up the possibility to calculate electromagnetic observables from the IM-NCSM. These observables are sensitive to different aspects of the wave functions and, therefore, ideal for validating theoretical models and new opportunities for fruitful collaborations with experimentalists are opened up. For the transformation of observables we implemented a Magnus-type transformation, which determines the generator for the IM-SRG transformation and greatly reduces the computational effort. Considering numerical applications, we employ the IM-NCSM for the calculation of groundstate energies, excitation energies, radii, magnetic dipole moments, electric quadrupole moments, B(M1) transitions, and B(E2) transitions, where we study various medium-mass nuclei up to calcium isotopes. These calculations are already converged at very small model-space sizes-showing the great advantage of the IM-NCSM - and the results are compatible with large-scale NCSM calculations. These applications demonstrate that the IM-NCSM is now capable of addressing the full range of nuclear structure observables - including spectroscopic and electromagnetic observables - in fully open-shell nuclei.
[en] Mixed convection occurs in a Passive Cooling System (PCS), Small Modular Reactors (SMR), Very High Temperature Gas-cooled Reactor (VHTGR) and Super-Critical Water Reactor (SCWR) due to buoyancy influence. This can lead to local impairment of the cooling performance and affect the heat transfer performance. Mixed convection is the flow phenomenon that occurs when the flow is driven by both forced convection and natural convection in similar magnitudes. Depending on the direction of forced convection, it is divided into buoyancy-aided flow and buoyancy-opposed flow. In laminar mixed convection, buoyancy-aided flow shows enhanced heat transfer compared to the pure forced convection due to the velocity increase by the addition of buoyancy force. However, in turbulent mixed convection, for small buoyance, buoyancy-aided flow shows impaired heat transfer compared with that of forced convection under the same flow condition. This is caused by the reduction of the turbulence production by decreased turbulent shear stress near the heated wall. When buoyance increases, the mixed convection heat transfer recovers and then enhances compared with the forced convection of similar flow condition. The behavior of mixed convection heat transfer is non-monotonous, depending on the forced flow direction, the flow conditions, and the geometry of the system. The existing correlations for turbulent mixed convection heat transfer are not applicable to other systems as they have been developed to fit their specific systems. Therefore, it is necessary to develop a more generalized heat transfer correlation considering the height of the system through the phenomenological analysis of turbulent mixed convection. In this study, the buoyancy-aided turbulent mixed convection experiments were performed on the circular heating and non-circular heating conditions. To achieve high buoyancy, mass transfer experiments utilizing the copper sulfate-sulfuric acid electroplating system, were performed replacing heat transfer ones based on the analogy concept. The local average heat transfers were measured varying the axial position (χ), the total height of the heated wall (H), the hydraulic diameter (D) and the flow rate (ν). In order to compare the mixed convection heat transfer with that of the forced convection including the thermal entry effect, the forced convection experiments were performed and the modified turbulent forced convection correlation was developed based on the correlation of Gnelinski and Petukhov et al. The local heat transfer of the mixed flow were lower than that of the forced convection and behaved non-monotonously along the axial position due to the buoyancy influences. This is the result of the interaction between the natural convection flow development near the wall and forced convection in the core region of the channel. As the total height of the heated wall increases, the local heat transfer decreases due to the influence of the system buoyancy. The local heat transfer was increasingly impaired with the decreased hydraulic diameter. Because the magnitude of the buoyancy influence increases as the heated perimeter increases with respect to the flow surface area. The double dip behavior was observed: one from deteriorated regime and the other one from transition flow regime. The Particle Image Velocimetry (PIV) measurements of the velocity and turbulent shear stress backed up these observations. Non-monotonous behaviors of the mixed convection along x/D were discussed. We observed that the thickness of the viscous sublayer increased and distorted velocity profile with the buoyancy effect. We concluded that the mixed convection heat transfer is affected by the magnitude of turbulent shear stress at the edge of the viscous sublayer and buffer layer. The buoyancy coefficient was derived through the scale analysis and through the comparisons of the results of the existing studies and the current experiments. The turbulent mixed convection heat transfer correlations were developed for both non-circular heating and circular heating conditions by considering the buoyant flow development (χ/D), heated perimeter to flow surface area (D/H), system buoyancy ((H-χ)/D). These correlations were compared with the experimental results of other studies and are more general, which expand the applicability of the correlations to other systems with different heating length and can contribute to enhancement of the fundamental understanding of the mixed convection phenomena and detailed analysis on the cooling performance analysis and safety system design
[en] Natural essential oils are complex mixtures containing several compounds of structural similarity. They are well known for their wide range of applications in different areas, from medicine to cosmetics. One of the conventional methods for their quantitative analysis is gas chromatography (GC). Despite the numerous advantages of GC as an analytical tool, some aspects such as structure determination cannot be addressed with it. Another technique which is applicable to the volatile essential oil components is rotational spectroscopy. It is a powerful method for the structure determination not only of the respective compounds, but also of their different isomers and conformers. Rotational spectroscopy thus complements the information obtained with GC, which is necessary for a comprehensive study on the molecular systems of interest. In the first part of this thesis, some of the main constituents of peppermint and thyme oils were analyzed with rotational spectroscopy. Structure determination of several oil components including menthol, thymol, linalool, and pulegone was performed. The internal dynamics of trans-thymol-B, linalool, pulegone, and menthyl acetate, resulting from the internal rotation of their methyl groups were studied. The conformational landscape of menthyl acetate was characterized both experimentally and computationally. All these key points help to better understand the functionality of the chemical substances discussed here, and their mode of interaction in our body. Additionally, a semi-quantitative analysis of thyme oil was performed. The results were compared to the GC study for benchmarking purposes, showing a good agreement. Many of the essential oil constituents are chiral. Chirality is of utmost importance in the biological context. There is a high demand for reliable methods for a detailed characterization of chiral molecules. Recent developments in rotational spectroscopy have enabled the exploration of molecules in a chirality-sensitive way by applying the microwave three-wave mixing (M3WM) technique. The M3WM makes use of the advantages of rotational spectroscopy such as conformer selectivity and mixture compatibility. It was successfully applied in the scope of this thesis to differentiate between the enantiomers of some essential oil constituents. The M3WM was recently extended to allow coherent population transfer (CPT) of the enantiomers to rotational states of choice. This approach is discussed in the second part of the present work. It may pave the way for enantioseparation in future experiments. Finally, M3WM and CPT were combined in the experiment to manipulate the chiral conformers of a molecule, which has no stereogenic center (cyclohexylmethanol). Such a procedure significantly widens the range of molecular systems available for chiral analysis with rotational spectroscopy.
[en] In this work the calculation of the resonance’s decay parameters with N = 2 + 1 + 1 flavour lattice QCD is presented. The calculation is performed based on gauge configuration ensembles produced by the ETM collaboration which were generated with three different lattice spacing values and pion masses ranging from 230 MeV to 500 MeV. The calculation of resonance parameters with Lattice QCD requires correlation functions of all relevant decay channels in multiple moving reference frames. In this work operators resembling a meson as well as a -system are used. The boost to moving frames breaks rotational symmetry and thereby causes a level splitting. Operators which transform like basis states of the reduced symmetry groups’ irreducible representations are constructed to determine each energy level individually. Aided by the stochastic Laplacian Heaviside method correlation functions are calculated for all lattice momenta up to (0, 0, 2) and all irreducible representations that emerge. From these correlation functions energy levels are determined under consideration of systematic error sources. Most notably the effect of thermal pollutions and bias from fit range selection are taken into account. By applying the Lüscher method the energy spectra are translated into phase shift curves on each ensemble separately. From a Breit-Wigner fit to the phase shift curves the meson mass and width on all ensembles are determined. The results are fed into a combined fit of mass and width and extrapolated to the chiral and continuum limit. The main result of this thesis are the continuum extrapolated values of M and at the physical point which were determined to M = 769(19) MeV, = 129(7) MeV. Lattice artefacts could not be resolved within the statistical uncertainties of this work. While the -meson massis in very good agreement with experiment the corresponding decay width differs by about two standard deviations from its experimental counterpart. The results of this thesis were pre-published in .
[en] In this thesis, the first experimental determination of the running of the top quarkmass is presented. The running is extracted from a measurement of the differentialtop quark-antiquark () production cross section as a function of the invariant mass of the system, m. The analysis is performed using proton-proton collision data recorded by the CMS detector at the CERN LHC in 2016, corresponding to an integrated luminosity of 35.9 fb. Candidate events are selected in the final state with an electron and a muon of opposite charge, and the differential cross section dσ/dm is determined at the parton level by means of a maximum-likelihood fit to multidifferential final-state distributions. The value of the top quark mass in the modified minimal subtraction () renormalization scheme, m(μ), is determined as a function of the scale μ=m by comparing the measured dσ/dm to theoretical predictions at next-to-leading order, and the resulting scale dependence is interpreted as the running of the top quark mass. The observed running is found to be compatible with the one-loop solution of the corresponding renormalization group equation, up to a scale of the order of 1 TeV.
[en] A measurement of the top quark mass using LHC proton-proton collision data with an integrated luminosity of 35.9fb is presented. The dataset has been recorded with the CMS detector in LHC Run 2 at a center-of-mass energy of 13 TeV in the 2016 data taking period. Events are selected in which a top quark and a top antiquark are produced and both decay exclusively to jets. This t all-jets final state is characterized by six jets in the detector and therefore contaminated by multijet background, which is estimated from data in a control region. A kinematic fit is utilized to reconstruct the full t system, improving the invariant mass resolution for the top quark candidates and at the same time reducing the multijet background by requiring a goodness-of-fit criterion. The top quark mass is extracted using the ideogram method, simultaneously constraining an additional jet energy scale factor (JSF) to reduce systematic uncertainties. The top quark mass is found to be m=172.34±0.20 (stat+JSF)±0.70 (syst) GeV, agreeing well with previous measurements. Furthermore, a combined top quark mass measurement using the all-jets and lepton+jets final states simultaneously is performed. For this, a combined likelihood including the events of both final states is constructed and the same mass extraction is applied as for the all-jets final state. The resulting measurement is m=172.26±0.07 (stat+JSF)±0.61 (syst) GeV. This is the first time a top quark mass measurement combining both final states in a single likelihood function is presented. The result is consistent with other measurements at the LHC. A global electroweak fit employing this measurement shows the importance of the top quark mass for consistency checks of the standard model of particle physics.
[en] The Standard Model of particle physics is a very successful theory, but it leaves some open questions. Especially the topic of dark matter is a very active field of research and the discovery of dark matter candidates might be accessible to modern collider experiments. Answering open questions of the Standard Model is one of the greater goals of this work. The dark matter candidates might interact with the recently discovered Higgs boson and would appear invisible to a particle detector. This motivates a search for invisible decays of the Higgs boson produced in vector-boson fusion. The search is looking for a pair of wellseparated, highly energetic jets and missing transverse energy in the final state. The analysisuses 36.1 fb of proton–proton collision data recorded at a centre-of-mass energy of 13 TeV in 2015 and 2016 with the ATLAS experiment at the LHC. The main backgrounds are leptonically decaying vector bosons. These backgrounds are constrained in dedicated data control regions. The multijet background is small, since it can only result from mismeasurements of the jet transverse momentum, but it is challenging to quantify. The jet response is a measure for the mismeasurement of jet transverse momenta. To study how well it is simulated in areas of extreme mismeasurements the non-Gaussian tails of these distributions are quantified in a comparison between data and simulation. This is achieved by modelling the Gaussian core with fits. In order to see the effect in data the momentum balance of jet pairs is considered by using an extrapolation to pure dijet events. The effort is undertaken with a new jet definition, particle flow jets, as well as topocluster jets. For both of them simulation and data are in good agreement. This leads to systematic uncertainties small enough to have a negligible impact on the analysis. The systematic uncertainty resulting from the jet energy resolution is one of the main limitations to the sensitivity of the search. This is addressed with the global sequential calibration (GSC), a simulation-driven method that removes the dependencies of jet momenta on a selection of detector variables in order to improve the jet resolution. The calibration leads to a jet resolution improvement of up to 20%. The GSC is fully derived for particle flow jets for the first time, allowing performance comparisons between different kinds of jet reconstruction algorithms. The search is able to derive a new observed (expected) limit on the Higgs to invisible branching fraction of 0.37 (0.28) at 95% confidence level. The results are also interpreted considering a Higgs portal model, treating the invisible decay products as dark matter candidates. The resulting limits on the cross-section for the DM candidate to interact with an atomic nucleus is between 10 cm and 10 cm at 90% confidence level depending on the DM mass and spin..