Дисертації з теми "NVC parametres"
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1
Браге, Ксенія Сергіївна. "Метод вимірювання НВЧ- параметрів матеріалів на основі тонкого діелектричного резонатора". Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/22979.
Повний текст джерелаАнотація:
В даній роботі розглянуто питання загальних теоретичних відомостей з складених та тонких діелектричних резонаторів та методів вимірювання вимірювання НВЧ параметрів діелектричних матеріалів. Досліджено метод тонкого діелектричного резонатора та наведено результати експерементальних досліджень. При досліджені тонких діелектричних плівок виникають труднощі, тому що методи не забезпечують достатньої точності. При дослідженні метода тонких плівок результати показали, що при зменшенні товщини базового резонатора, збільшується точність. Тому метою роботи є адаптація методу складеного діелектричного резонатора для вимірювання параметрів тонких плівок.
Для досягнення поставленої мети необхідно було вирішити наступні задачі:
1. Проаналізувати існуючи методи вимірюваняя НВЧ – параметрів діелектричних матеріалів.
2. Проаналізувати властивості тонкого діелектричного резонатора (ТДР).
3. Запропонувати метод дослідження параметрів тонких плівок на основі ТДР.
4. Експерементально перевірити метод тонких плівок на основі ТДР.
Предметом і об’єктом даної робот є:
Об’єкт: тонкий діелектричний резонатор
Предмет: електродинамічні властивості тонкого діелектриного резонатора
Наукова новизна:
Теоретичне та експериментальне дослідження електро-динамічних властивостей ТДР показує, що на основі ТДР можна з достатньою точністю вимірювати НВЧ – властивості тонких діелектричних плівок.In the given work, the nutritional pockets of the teoretical publications are stored in those thin dielectric resonators and the method of determining the NVH parameters in the power electronics. The method of a thin dielectric resonator is applied to the result of the experimental data. When study slim dielectric films arise difficulties, to that method do not gave accuracy. When the method of thin plots is used, the results have been shown, when the basic resonator is changed, the accuracy is determined. To the method of robotics is adaptation to the method of the stored dielectric resonator for the parameterization of thin cells. For achivment it's delivered goal it was necessary to solve the problem: 1. Analyze existing methods 2. Analyze power of a thin dielectric resonator (TDR). 3.Propose method of study parameters in the small films on the basis of the TDR. 4. Experimentally check method of thin plvok on the basis of the TDR. The subject і objective of this work is: Ob'ekt: thin dielectric resonator Subject: Electrodynamic power of a thin dielectric resonator Science novelty: Theoretically, this experiment is complementary to the electric-dynamical authorities of the TDR, but on the basis of the TDR, it is possible to obtain the accuracy of the NVCH - the power of subtle electrical add-ons.
2
Belák, Kristián. "Určení NVH parametrů skříně převodovky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378021.
Повний текст джерелаАнотація:
This master’s thesis deals with determination of NVH parameters of the gearbox housing. Introductory part is focused on the necessary theoretical knowledge. Subsequently, it contains the modal analysis with the computational and experimental approach, which are being compared to each other. In the case of the computational approach, analysis of the influence of bolt pretension on the modal properties is also involved. The thesis continues with the harmonic analysis with the computational and experimental approach, including their mutual comparison. Based on these analyses, design modifications for improvement of the NVH parameters are designed at the end of the thesis, which are being compared to each other and to the original geometry, using the computational approach.
3
David, Jan. "NVH převodového ústrojí pro elektromobily." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-433548.
Повний текст джерелаАнотація:
This master’s thesis deals with determination of NVH parameters of the gearbox housing for electric vehicle. The introduction part is focused on the theoretical knowledge of this issue. Subsequently, the deviations of geometry on the gearbox were measure by 3D scan method. The next part of thesis is focused on the modal analysis, which is solved by numerical approach and followed by experimental verification. During the numerical calculation solving, the influence of the screw preloading on the modal properties of the structure, was also taken into account. Numerical harmonic analysis was then performed and the results were compared with the experimental approach. The conclusion is devoted to material damping and comparison of the individual results.
4
Bouchner, Michal. "Určení NVH parametrů rovinné desky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378142.
Повний текст джерелаАнотація:
The aim of this thesis is examination and verification of numeric model for solving acoustics and vibration problems. Specifically, we are speaking about cast iron plate machined from gearbox. Main objectives of this work is set of experimental and numerical analysis at this simplified part with follow-up numerical model, where same analyses examining not only structure, but especially acoustic space around were performed. Due to this we were able to compare data between experimental and numerical analyses and to be able to prove or disprove functionality and limitation of numerical model.
5
Coelho, Paula Rodrigues Teixeira. "Determinação de parâmetros atmosféricos de estrelas em NGC 6528 e NGC 6553 - aglomerados globulares de referência para o estudo de populações ricas em metais." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-08052002-153720/.
Повний текст джерелаАнотація:
Os aglomerados globulares ricos em metais do bojo são uma peça chave na compreensão da história evolutiva da nossa Galáxia e o estudo dessas populações estelares simples pode fornecer vínculos importantes aos modelos de formação do bojo galáctico. Neste trabalho apresentamos o estudo feito com 22 estrelas dos aglomerados globulares NGC 6528 e NGC 6553, aglomerados representativos da população estelar do bojo. Através do uso de dados fotométricos e espectroscópicos determinamos a velocidade radial, temperatura efetiva, gravidade superficial e metalicidade das estrelas. Encontramos parâmetros que cobrem os intervalos 3200 <= Tef <= 5000K e -0.5 <= log g <= 2.4, representando portanto uma faixa de estágios evolutivos do aglomerado. O valor médio de [Fe/H] para os dois aglomerados foi estimado em -0.5dex, tanto pelo uso de índices de metalicidade de Lick, de calibrações de larguras equivalentes de TiO W(TiO) em função de parâmetros atmosféricos e principalmente através de espectros sintéticos. Foram encontrados também indícios de sobreabundância de elementos a. Essas estrelas estudadas são estrelas de referência para o estudo de populações estelares velhas e ricas em metais, de modo que testar e calibrar os espectros sintéticos com esses espectros estelares é um importante passo para garantir a qualidade dos espectros sintéticos na síntese de populações estelares.The metal-rich bulge globular clusters are a keystone for the understanding of the evolutionary history of our Galaxy and the study of the bulge stellar populations provides constraints to models of bulge formation. In this work we present the study of 22 stars in the globular clusters NGC 6528 and NGC 6553, templates of the metal-rich populations of the bulge. With the use of photometric and spectroscopic data, we have found the radial velocities, effective temperatures, gravities and metallicities of these stars. The parameters found are in the range 3200 <= Tef <= 5000K and -0.5 <= log g <= 2.4, covering from the Horizontal Branch to the tip of the Red Giant Branch evolutionary stages. The mean metallicity determined was [Fe/H] = -0.5 dex, from the Lick indices, calibrations of equivalent widths of TiO as a function of stellar parameters and comparisons to the synthetic spectra. A trend is found for an overabundance of a elements. These stars are templates for the study of old metal-rich stellar populations and the fitting of the synthetic spectra to the observed stellar spectra is an important check of the quality of the synthetic spectra for stellar population synthesis.
6
Otipka, Václav. "Konstrukční návrh zkušebního stavu s uzavřenou smyčkou toku momentu pro experimentální ověření parametrů převodových ústrojí." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-378013.
Повний текст джерелаАнотація:
The thesis deals with the design of the experimental testing rig. Test rig is designed to measure NVH transmission parameters. First, basic knowledge of vibro-acoustic measurement is discussed. This is followed by an evaluation of the most commonly used power devices to derive real loads on measured gearboxes. In more detail, a back-to-back test rig is disassembled among other things. In the thesis are described two main components, which are composed of a connecting element and a test bench. Both components were optimized during the design due to their modal properties. Numerical modal analysis was performed in ANSYS Workbench software. The thesis also includes strength calculations performed using both numerical and analytical approaches. The indispensable result of the design work is the complete drawing documentation. Finally, measurements of vibrations and noise on the physically made connecting element assembly have been performed and subsequently evaluated.
7
Hatna, Abdelmadjid. "Investigation of pre-processing approaches for NC machining of sculptured surfaces." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324767.
Повний текст джерела
8
Koshida, Shintaro, Yuzuru Yoshii, Yukiyasu Kobayashi, Takeo Minezaki, Keigo Enya, Masahiro Suganuma, Hiroyuki Tomita, Tsutomu Aoki, and Bruce A. Peterson. "Calibration of AGN Reverberation Distance Measurements." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624678.
Повний текст джерелаАнотація:
In Yoshii et al., we described a new method for measuring extragalactic distances based on dust reverberation in active galactic nuclei (AGNs), and we validated our new method with Cepheid variable stars. In this Letter, we validate our new method with Type Ia supernovae (SNe Ia) that occurred in two of the AGN host galaxies during our AGN monitoring program: SN 2004bd in NGC 3786 and SN 2008ec in NGC 7469. Their multicolor light curves were observed and analyzed using two widely accepted methods for measuring SN distances, and the distance moduli derived are m= 33.47 +/- 0.15 for SN 2004bd and 33.83 +/- 0.07 for SN 2008ec. These results are used to obtain independently the distance measurement calibration factor, g. The g value obtained from the SN Ia discussed in this Letter is gSN= 10.61 +/- 0.50, which matches, within the range of 1s uncertainty, gDUST = 10.60, previously calculated ab initio in Yoshii et al. Having validated our new method for measuring extragalactic distances, we use our new method to calibrate reverberation distances derived from variations of Ha emission in the AGN broad-line region, extending the Hubble diagram to z approximate to 0.3 where distinguishing between cosmologies is becoming possible.
9
Bharadwaj, Shashank. "Investigation of oxide thickness dependence of Fowler-Nordheim parameter B." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000251.
Повний текст джерела
10
Gruyters, Pieter. "Exploring the Chemical Evolution of Globular Clusters and their Stars : Observational Constraints on Atomic Diffusion and Cluster Pollution in NGC 6752 and M4." Doctoral thesis, Uppsala universitet, Observationell astrofysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-230182.
Повний текст джерелаАнотація:
Through the cosmic matter cycle, the chemical evolution of the Milky Way is imprinted in the elemental abundance patterns of late-type stars (spectral types F to K). Due to their long lifetimes ( 1 Hubble time), these stars are of particular importance when it comes to studying the build-up of elements during the early times of our Galaxy. The chemical composition of the atmospheric layers of such stars is believed to resemble the gas from which they were formed. However, recent observations in globular clusters seem to contradict this assumption. The observations indicate that processes are at work that alter the surface compositions in these stars. The combined effect of processes responsible for an exchange of material between the stellar interior and atmosphere during the main sequence lifetime of the star, is referred to as atomic diffusion. Yet, the extent to which these processes alter surface abundances is still debated. By comparing abundances in unevolved and evolved stars all drawn from the same stellar population, any surface abundance anomalies can be traced. The anomalies, if found, can be compared to theoretical predictions from stellar structure models including atomic diffusion. Globular clusters provide stellar populations suitable to conduct such a comparison. In this thesis, the results of three independent analyses of two globular clusters, NGC 6752 and M4, at different metallicities are presented. The comparison between observations and models yields constraints on the models and finally a better understanding of the physical processes at work inside stars.
11
Burke, Christopher J. "Survey for transiting extrasolar planets in stellar systems stellar and planetary content of the Open Cluster NGC 1245 /." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1132168623.
Повний текст джерела
12
Zhang, Meijing. "Quantifying high-resolution hydrologic parameters at the basin scale using InSAR and inverse modeling, Las Vegas Valley, NV." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50833.
Повний текст джерелаАнотація:
The overall goal of this dissertation is to determine and develop optimal strategies for inversely calibrating transmissivities (T), elastic and inelastic skeletal storage coefficients (Ske and Skv) of the developed-zone aquifer and conductance (CR) of the basin-fill faults for the entire Las Vegas basin, and to investigate future trends of land subsidence in Las Vegas Valley.
This dissertation consists of three separate stand-alone chapters. Chapter 2 presents a discrete adjoint parameter estimation (APE) algorithm for automatically identifying suitable hydraulic parameter zonations from hydraulic head and subsidence measurements. Chapter 3 compares three different inversion strategies to determine the most accurate and computationally efficient method for estimating T and Ske and Skv at the basin scale: the zonation method (ZM), the adaptive multi-scale method and the Differential Evolution Adaptive Metropolis Markov chain Monte Carlo scheme (DREAM MCMC). Chapter 4 outlines a fine-scale numerical model capable of capturing far more hydrologic detail than any previously developed model of Las Vegas Valley The new model is calibrated using high-resolution InSAR data and hydraulic head data from 1912 to 2010. The calibrated model is used to investigate the influence of faults and their potential role on influencing clay thicknesses and land subsidence distributions, and to investigate future trends of land subsidence in Las Vegas Valley.Ph. D.
13
Schledde, Dominik [Verfasser]. "Modellbasierte Identifikation von physikalischen Parametern zur Bestimmung der Veränderung charakteristischer Eigenschaften einer C/NMC Lithium-Ionen-Zelle durch Alterungsmechanismen zur Anwendung in Batteriemanagementsystemen / Dominik Schledde." Kassel : Kassel University Press, 2018. http://d-nb.info/1162712759/34.
Повний текст джерела
14
Ustuntepe, Bulent. "A Novel Two-parameter Modulation And Neutral Point Potential Control Method For The Three-level Neutral Point Clamped Inverter." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606928/index.pdf.
Повний текст джерелаАнотація:
In this thesis, the neutral point potential drift/fluctuation of the three-level neutral
point clamped inverter is analyzed and a novel control algorithm, the two-parameter
PWM method is proposed to confine the neutral point potential variation to a very
small range. The two-parameter PWM method provides superior neutral point
potential control performance even with small DC bus capacitors. The method is
based on PWM pulse pattern modification and requires no additional hardware.
Detailed analytical models of the neutral point current and potential as a function of
the modulation parameters are established and the neutral point potential behavior is
thoroughly investigated. Based on the study, the deficiency of the known methods is
illustrated and the two-parameter PWM method is developed and its superior
performance demonstrated. The performance of the two-parameter PWM method is
verified by means of computer simulations utilizing both the per-PWM-cycle
average model and the detailed model of the inverter. The results are supported by
laboratory experiments involving both an R-L load and an induction motor drive.
15
Morganti, Lucia [Verfasser], and Ortwin [Akademischer Betreuer] Gerhard. "Made-to-measure particle models of intermediate-luminosity elliptical galaxies : regularization, parameter estimation, and the dark halo of NGC 4494 / Lucia Morganti. Betreuer: Ortwin Gerhard." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1027669425/34.
Повний текст джерела
16
Zhang, Peipei. "Diffuse response surface model based on advancing latin hypercube patterns for reliability-based design optimization of ultrahigh strength steel NC milling parameters." Compiègne, 2011. http://www.theses.fr/2011COMP1949.
Повний текст джерелаАнотація:
Puisque les incertitudes des paramètres de systèmes mécaniques entrainent la variabilité de la performance du produit, les systèmes optimisés sans prendre en compte les incertitudes peuvent présenter le risque de défaillance. L'optimisation fiabiliste (RBDO) focalise ainsi l'attention des ingénieurs et des chercheurs. Cependant, les méthodes habituelles de RBDO présentent un coût informatique excessif. Donc, afin d'améliorer l'efficacité informatique de la résolution de problèmes de RBDO, il est naturel de faire appel à des approches basées sur les surfaces de réponse (RSM). Dans ce travail, nous nous concentrons sur une Méthodologie de Surface de Réponse adaptée à la conception optimale dans le contexte fiabiliste. Nous proposons une variante de l'Approximation Diffuse, basée sur un modèle d'échantillonnage progressif et couplée à l'estimation de la fiabilité par FORM. La méthode proposée utilise simultanément des points dans l'espace normal standard U ainsi que dans l'espace physique X. Les deux réseaux forment un « plan d'expériences virtuel » défini par deux jeux de points dans les deux espaces de conception, qui sont évalués seulement quand nécessaire pour réduire au minimum le nombre d'évaluations « exactes » et ainsi diminuer le coût informatique. Dans chaque nouvelle itération, le pattern de points est mis à jour avec des points du design virtuel convenablement choisis afin d'effectuer l'approximation. Nous étendons ici l'idée d'Hypercube Latin (LHS) pour réutiliser au maximum des points précédemment calculés en ajoutant un nombre minimal de nouveaux points voisins à chaque étape, nécessaires pour l'approximation au voisinage du design actuel. Nous proposons des opérateurs de translation, de zoom avant et arrière, étendant ainsi le modèle LHS et le rendant récursif tout en contrôlant la qualité d'exploration de l'espace de conception et en maximisant le conditionnement de l'approximation. Dans la partie applicative de ce travail, nous examinons l'optimisation des paramètres du processus de fraisage à commande numérique (NC) de l'acier à haute limite élastique. Le succès de l'opération d'usinage dépend de la sélection des paramètres tels que le taux d'alimentation, la vitesse de coupe, les profondeurs axiales et radiales de coupe. Les contraintes d'optimisation sont exprimées comme des fonctions des indices de fiabilité calculés par FORM diffusSince variances in the input parameters of engineering systems cause subsequent variations in the product performance, and deterministic optimum designs that are obtained without taking uncertainties into consideration could lead to unreliable designs. Reliability-Based Design Optimization (RBDO) is getting a lot of attention recently. However, RBDO is computationally expensive. Therefore, the Response Surface Methodology (RSM) is often used to improve the computational efficiency in the solution of problems in RBDO. In this work, we focus on a Response Surface Methodology (RSM) adapted to the Reliability-Based Design Optimization (RBDO). The Diffuse Approximation (DA), a variant of the well-known Moving Least Squares (MLS) approximation based on a progressive sampling pattern is used within a variant of the First Order Reliability Method (FORM). The proposed method simultaneously uses points in the standard normal space (U-space) as well as the physical space (X-space). The two grids form a “virtual design of experiments” defined by two sets of points in the two design spaces, that are evaluated only when needed in order to minimize the number of ‘exact’ thus computationally expensive function evaluations. In each new iteration, the pattern of points is updated with points appropriately selected from the “virtual design of experiments”, in order to perform the approximation. As an original contribution, we introduce the concept of « advancing Latin Hypercube Sampling (LHS) » which extends the idea of Latin Hypercube Sampling (LHS) to maximally reuse previously computed points while adding a minimal number of new neighboring points at each step, necessary for the approximation in the vicinity of the current design. We propose panning, expanding and shrinking Latin hypercube patterns of sampling points and we analyze the influence of this specific kind of patterns on the quality of the approximation. Next we calculate the minimal number of data points required in order to get a well-conditioned approximation system. In the application part of this work, we investigate the optimization of the process parameters for Numerical Control (NC) milling of ultrahigh strength steel. The success of the machining operation depends on the selection of machining parameters such as the feed rate, cutting speed, and the axial and radial depths of cut. A variant of the First Order Reliability Method (FORM) is chosen to calculate the reliability index. The optimization constraints are expressed as functions of the computed reliability indices
17
Joner, Michael Deloss. "High-Quality Broadband BVRI Photometry of Benchmark Open Clusters." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2495.
Повний текст джерелаАнотація:
Photometric techniques are often used to observe stars and it can be demonstrated that fundamental stellar properties can be observationally determined using calibrated sets of photometric data. Many of the most powerful techniques utilized to calibrate stellar photometry employ the use of stars in clusters since the individual stars are believed to have many common properties such as age, composition, and approximate distance. Broadband photometric Johnson/Cousins BVRI observations are presented for several nearby open clusters. The new photometry has been tested for consistency relative to archival work and shown to be both accurate and precise. The careful use of a regular routine when making photometric observations, along with the monitoring of instrumental systems and the use of various quality control techniques when making observations or performing data reductions, will enhance an observer's ability to produce high-quality photometric measurements. This work contains a condensed review of the history of photometry, along with a brief description of several popular photometric systems that are often utilized in the field of stellar astrophysics. Publications written by Taylor or produced during the early Taylor and Joner collaboration are deemed especially relevant to the current work. A synopsis of seven archival publications is offered, along with a review of notable reports of VRI photometric observations for the nearby Hyades open star cluster. The body of this present work consists of four publications that appeared between the years 2005 and 2008, along with a soon to be submitted manuscript for a fifth publication. Each of these papers deals specifically with high-quality broadband photometry of open clusters with new data being presented for the Hyades, Coma, NGC 752, Praesepe, and M67. It is concluded that the VRI photometry produced during the Taylor and Joner collaborative investigations forms a high-quality data set that has been: 1) stable for a period of more than 25 years; 2) monitored and tested several times for consistency relative to the broadband Cousins system, and 3) shown to have well-understood transformations to other versions of broadband photometric systems. Further work is suggested for: 1) the transformation relationships for the reddest stars available for use as standards; 2) the standardization of more fields for use with CCD detectors; 3) a further investigation of transformations of blue color indices for observations done using CCD detectors with enhanced UV sensitivity, and 4) a continuation of work on methods to produce high-quality observations of assorted star clusters (both open and globular) with CCD-based instrumentation and intermediate-band photometric systems.
18
Bello, Filipe de Oliveira. "Assessing the sustainability of a public pension system : the case of Brazil." Master's thesis, Instituto Superior de Economia e Gestão, 2020. http://hdl.handle.net/10400.5/20922.
Повний текст джерелаАнотація:
Mestrado em Actuarial ScienceO Brasil experimentou um aumento de quase sete pontos na Razão de Dependência de Idosos, de 7,0 em 1990 para 13,8 em 2020. As projeções estimam que suba para 36,2 em 2050, o que significa que haverá aproximadamente 36 indivíduos com 65 anos ou mais por 100 indivíduos em idade produtiva. Em 2019, a situação das finanças públicas brasileiras era muito grave e, pelo sexto ano consecutivo, estava deficitária. O desequilíbrio foi causado principalmente pelo déficit previdenciário. As dúvidas sobre a sustentabilidade do sistema previdenciário são muito pertinentes nos dias de hoje, uma reforma foi aprovada e começou a ser implementada em 2019. O objetivo é projetar a receita e os benefícios até 2100, no âmbito de alterações alternativas de pensões paramétricas e também no âmbito de uma reforma sistemática, nomeadamente a passagem para um sistema de CD. Os custos de transição e outras despesas, e os custos relacionados com a pensão mínima garantida, também são contabilizados. Os achados comprovaram que a reforma iniciada em 2019 melhora o equilíbrio e permite que o déficit do RGPS diminua nos próximos dez anos, mas um aumento será observado a partir de então - embora em valor bem menor do que seria em um cenário de reforma pré-2019. Portanto, é muito provável que a discussão sobre a sustentabilidade do sistema volte a estar na ordem do dia em alguns anos. Explorarando as alternativas propostas, mudar para o esquema NDC parece resolver o problema a longo prazo.
Brazil has experienced an increase of nearly seven points in the Old-Age Dependency Ratio, from 7.0 in 1990 to 13.8 in 2020. Projections estimate it will rise to 36.2 in 2050, which means that there will be approximately 36 individuals aged 65 and over per 100 individuals of working age. In 2019, the condition of the Brazilian public finance was very serious and for the sixth year in a row it was in deficit. The imbalance was mainly caused by the social security deficit. Doubts about the sustainability of the pension system are very pertinent nowadays and a reform was approved and started to be implemented in 2019. The goal is to project the revenue and the benefits until 2100, under alternative parametric pension changes and also under a systematic reform, namely the shift to a DC system. Transition costs and other expenses, and the costs related to the minimum guaranteed pension, are also accounted for. The findings proved that the reform started in 2019 improves the balance and allows the deficit in RGPS to decrease for the next ten years, but an increase will be observed from that time on - although of a much less amount than it what would be in pre-2019 reform scenario. Therefore, it is very likely that the discussion about the sustainability of the system will be again the order of the day in a few years. Exploring the proposed alternatives, switch to NDC scheme seems to solve the problem in the long run.
info:eu-repo/semantics/publishedVersion
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Luong, David, and Ibrahim Salloum. "Investigation of electromagnetic compatibility (EMC) of low-voltage (<60V) DC electric motors in construction machinery application." Thesis, Linköpings universitet, Fysik och elektroteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-162160.
Повний текст джерелаАнотація:
The brushed DC motor is a source of electromagnetic emission that may cause interference. The main issues with brushed DC motor are arcing, which occurs between the brushes and commutator, and inrush current. It is possible to decrease the electromagnetic emissions by addressing the source (brushed dc motor) and the installation. The source may be addressed by using filters in the form of X2Y-capacitors on the terminals or ferrites on the cables. The installation does not produce any emission, but it is possible to lower its contribution. This is done by altering the installation like changing the placement of cables and provide good coupling. An effective way of decreasing inrush currents is by using negative-thermal-coefficient (NTC) thermistors. Another measure to improve the EMC properties of the brushed DC motor is to design the motor so that it can trap EM emissions. Some of these parameters are motor house material, end-cap material, vent holes or slots on motor housing, placement of power terminals, crimping tabs and motor enclosure.
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Sebastianutti, Marco. "Geodesic motion and Raychaudhuri equations." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18755/.
Повний текст джерелаАнотація:
The work presented in this thesis is devoted to the study of geodesic motion in the context of General Relativity. The motion of a single test particle is governed by the geodesic equations of the given space-time, nevertheless one can be interested in the collective behavior of a family (congruence) of test particles, whose dynamics is controlled by the Raychaudhuri equations. In this thesis, both the aspects have been considered, with great interest in the latter issue. Geometric quantities appear in these evolution equations, therefore, it goes without saying that the features of a given space-time must necessarily arise. In this way, through the study of these quantities, one is able to analyze the given space-time. In the first part of this dissertation, we study the relation between geodesic motion and gravity. In fact, the geodesic equations are a useful tool for detecting a gravitational field. While, in the second part, after the derivation of Raychaudhuri equations, we focus on their applications to cosmology. Using these equations, as we mentioned above, one can show how geometric quantities linked to the given space-time, like expansion, shear and twist parameters govern the focusing or de-focusing of geodesic congruences. Physical requirements on matter stress-energy (i.e., positivity of energy density in any frame of reference), lead to the various energy conditions, which must hold, at least in a classical context. Therefore, under these suitable conditions, the focusing of a geodesics "bundle", in the FLRW metric, bring us to the idea of an initial (big bang) singularity in the model of a homogeneous isotropic universe. The geodesic focusing theorem derived from both, the Raychaudhuri equations and the energy conditions acts as an important tool in understanding the Hawking-Penrose singularity theorems.
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Wu, Chen-Yao, and 吳正堯. "Optimization of Cutting Parameters and Machining Time Estimation for NC Machining." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/64162850836331871049.
Повний текст джерелаАнотація:
碩士國立臺北科技大學
機電整合研究所
92
The rough and finish cutting parameters (i. e. cutting speed, feed rate and depth of cut etc.) of the metal-cutting operations are almost set by experiences or in the ranges of suggestion from cutting tool factory owner which usually are conservative and disable to develop the function of the tools and the machines completely. In this thesis, the problems to find the optimal cutting parameters are formulated as an optimization problem. The minimum production cost or maximum production rate (or minimum production time) are considered as the objective function of the optimization problem. The design variables of the objective function are the cutting parameters. The optimization problem subjected to the functional or circumstantial constraints such as the horsepower of machine tool or cutting tool strength. We adopted the augmented Lagrange multiplier method (ALMM) as the optimization method of the cutting parameters design. ALMM to solve constrained optimization problems by the use of penalty functions. While this methods are easy to program and considered efficient, the optimization process can be significantly improved by including the Lagrange multipliers into the algorithm. The Pro/E CAD/CAM system is applied to construct the optimization examples of cutting operations, the cutting operations including face milling, end milling, and drilling process. Firstly, the CL (cutter location) data or the tool-path is generated by the Pro/E CAD/CAM system (only for two dimensional machining in this paper) as the given and remains unchanged tool-path data, and then to find the optimal cutting speed, feed rate, and the cutting depth of rough and finish cutting using ALMM. Based on the solution of the optimum values of cutting parameters, go back to alter the values of cutting parameter commands in the original CL data, and the modified CL data become formal optimum numerical control process program through post processor. The example analyzing results show the optimum cutting parameters design procedure is fit to the rough and finish cutting of CNC or synthesize cutting of the optimum process program, and effectively promote production efficiency and reduce production cost. Furthermore, this paper also investigates the responses of cutting feed rate of the CNC machine tool. The appearance of delay in the actual cutting feed rate compares with the program feed rate commands (owing to the acceleration after starting and the deceleration before stopping the tool) are inescapable. The average feed rate lower, to make actual cutting time is longer than that computed by the CAD/CAM system. For predicting the real cutting time of the CNC machine tool, here we measured the delay time of feed rate directly on the CNC machining center by several different feed rate and moving length conditions. Using the fitted curves of these measured data, the actual feed rate of a variety of feed rate and moving length commands of a CNC machining center can be approached. Through some analytical examples, the predicted machining times using the present machining time estimation algorithm are in agreement with the measured actual machining time on three axes CNC machine tool. To know the actual machining time of a part program in advance, the estimation of production planning and machining cost will be more correct. The last part research of this thesis attempts to plan an ideal feed rate in pocket milling operation of each tool movement by applying the CAD/CAM system machining data file (according to the moving length of every NC program block and the removing material volume data) in order to modify the suitable tool feed rate commands subjected to un-surpass tool loading. This application can effectively shorten time of parts machining and make CNC program more excellent.
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Sun, Shao-En, and 孫紹恩. "A Parametric Interpolator with Minimal Contouring Position Errors for NC Machining." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/89978767152158908242.
Повний текст джерелаАнотація:
碩士國立交通大學
機械工程系所
94
In modern CAD/CAM systems profiles or curves for parts like dies, vanes, aircraft turbines, shoes, mobile phones, etc., are usually represented in parametric forms. As conventional CNC machines only provide linear and circular interpolators. The parametric curve is approximated by a lot of line segments and sent to CNC systems. It causes a lot of computer memories. Thus, it is necessary to embed the parametric interpolation inside CNC machine to achieve real-time parametric interpolation. There are a lot of researches about parametric curves, like position interpolation, constant speed interpolation, acceleration and deceleration control, reducing the chord error, and or concerning about the arc length of the curves. But these researches didn’t consider the issues of both achieving minimal chord error and maintaining the constant speed. This article proposes a method to decrease the chord errors while maintaining a constant speed under a radial error. The simulation and the experimental results show that the proposed method effectively improves the interpolation accuracy in terms of the contouring position error and maintains speed accuracy at the specified level.
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詹金來. "Result presentation for feature parametric input of NC machining of mechanical parts." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/53296826930025668153.
Повний текст джерелаАнотація:
碩士國立中興大學
機械工程學系
87
Through the input of feature parameters, the interface makes NC code generation of mechanical part much more efficient and easier than manual programming. But the danger of machining errors still exists due to the human input errors to the generated NC code. In order to reduce the high cost of erroneous machining, consequentially, most of the NC coding errors will be checked, found and corrected that tremendous time, effort and material can be saved. It is expected that the input errors are easily detected from the drawing and illustrations presented as the result of machining. The result presentation is intended to capture the geometry, dimensions, tolerances, surface roughness and other manufacturing feature which are supposed to be produced by executing the NC code generated using the feature parametric input. Executing NC code makes NC machines perform designated tool movements with speed and feedrate. For example, tool paths produce geometry, dimensions and tolerances; different feedrates and speeds affect surface roughness
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Hu, Chuan-cheng, and 胡全成. "Parameter Design and 3+1-axis NC Machining of Overlapped Fan-blades." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/2br8gy.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
自動化及控制研究所
94
ABSTRACT This thesis uses Pro/ENGINEER and Pro/Toolkit to develop a computer-aided system for part modeling and NC machining of overlapped fan-blades. The major research issues include: (1) Automatic design change of fan-blades: The Pro/ENGINEER part model of fan-blades can be automatically created by input of the following design parameters: parameters of fan-blade sections, setting angle, twist angle, number of fan-blades and parameters for other geometric features. (2) Automatic determination of cutting-tool orientations for machining of fan-blades: Through the geometric analysis of CAD model of fan-blade, the rotational angles to adjust the orientations of the cutting-tools can be found, so that the fan-blades can be machined without any collision with the cutting-tools. (3) Practical fan-blade machining: The process plan for NC machining of the fan-blades is firstly created and NC programs are then generated using Pro/ENGINEER. The machining geometry and its corresponding NC tool paths and NC programs can be automatically revised once the design parameters of fan-blade are changed.
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Chang, Wen-Chou, and 張文洲. "A Practical Tuning Method of CNC Parameters to Improve Cutting Efficiency for NC Machine Tools." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/89187701142908229698.
Повний текст джерелаАнотація:
碩士逢甲大學
材料與製造工程所
93
High efficiency machining concept has been used in die and mold industry. The machining program often composes with numerous short segments, which were generated by the CAM software. With constantly changing tool path, machine vibration, overshoot and extra long machining time may occur if the acceleration/deceleration characteristics were not properly tuned. Therefore, high acceleration capability and proper acceleration/deceleration servo functions are the key prerequisites for a high efficiency machine tool for mold machining. Commercial CNC controllers provide many acceleration/deceleration functions to meet the above requirements. If these functions are used properly, they could make the machine tool move fast and smooth, so that a high efficiency machining process could be realized. This dissertation investigates the characteristics of acceleration/deceleration parameters experimentally to find out the rules of parameters setting for suitable acceleration and deceleration during high efficiency machining. We design a simulation program according to the Fanuc’s patent and simulate the axes deceleration behaviors under various conditions. In this study, We also design a special tool path, run it on a machine tool and simultaneously measure the 2D profile error, vibration and speed with Heidenhain Grid Encoders, accelerometers and Fanuc’s Servo Guide software. A series of experiments have been completed to verify the effect of acceleration/deceleration behaviors on machine vibration and profile error. Consequently, a method for controller parameters tuning has been proposed and illustrated by real cutting examples.
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Mokilane, Paul Moloantoa. "The application and empirical comparison of item parameters of Classical Test Theory and Partial Credit Model of Rasch in performance assessments." Diss., 2014. http://hdl.handle.net/10500/18362.
Повний текст джерелаАнотація:
This study empirically compares the Classical Test Theory (CTT) and the Partial Credit Model
(PCM) of Rasch focusing on the invariance of item parameters. The invariance concept which is
the consequence of the principle of specific objectivity was tested in both CTT and PCM using the
results of learners who wrote the National Senior Certificate (NSC) Mathematics examinations in
2010. The difficulty levels of the test items were estimated from the independent samples of learn-
ers. The same sample of learners used in the calibration of the difficulty levels of the test items in
the PCM model were also used in the calibration of the difficulty levels of the test items in CTT
model. The estimates of the difficulty levels of the test items were done using RUMM2030 in the
case of PCM while SAS was used in the case of CTT. RUMM2030 and SAS are both the statistical
softwares. The analysis of variance (ANOVA) was used to compare the four different design groups
of test takers. In cases where the ANOVA showed a significant difference between the means of the
design groups, the Tukeys groupings was used to establish where the difference came from.
The research findings were that the test items' difficulty parameter estimates based on the CTT theoretical framework were not invariant across the different independent sample groups. The over-
all findings from this study were that the CTT theoretical framework was unable to produce item
difficulty invariant parameter estimates. The PCM estimates were very stable in the sense that for
most of the items, there was no significant difference between the means of at least three design
groups and the one that deviated from the rest did not deviate that much. The item parameters of
the group that was representative of the population (proportional allocation) and the one where the
same number of learners (50 learners) was taken from different performance categories did not differ
significantly for all the items except for item 6.6 in examination question paper 2. It is apparent
that for the test item parameters to be invariant of the group of test takers in PCM, the group of
test takers must be heterogeneous and each performance category needed to be big enough for the proper calibration of item parameters.
The higher values of the estimated item parameters in CTT were consistently found in the sample
that was dominated by the high proficient learners in Mathematics ("bad") and the lowest values
were consistently calculated in the design group that was dominated by the less proficient learners. This phenomenon was not apparent in the Rasch model.Mathematical Sciences
M.Sc. (Statistics)
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Lilly, Thomas. "Exploring the formation histories of galaxies - globular clusters and beyond." Doctoral thesis, 2007. http://hdl.handle.net/11858/00-1735-0000-0006-B46B-7.
Повний текст джерела