• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 326
  • 196
  • 109
  • 55
  • 51
  • 39
  • 39
  • 18
  • 16
  • 11
  • 8
  • 8
  • 6
  • 5
  • 3
  • Tagged with
  • 1023
  • 175
  • 164
  • 158
  • 113
  • 103
  • 102
  • 93
  • 93
  • 89
  • 80
  • 75
  • 75
  • 73
  • 68
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Harmonic Analysis of a Static VAR Compensated Mixed Load System

Ruckdaschel, James David 01 May 2009 (has links)
As power electronic based controllers and loads become more prevalent in power systems, there is a growing concern about how the harmonics generated by these controllers and loads affect the power quality of the system. One widely used power electronic based load is the Variable Frequency Drive (VFDs) used to vary the speed of an induction motor; whereas a common example of a power electronic based controller used in power systems is the Static VAR Compensator (SVC) for improving a system’s power factor. In this thesis, the harmonic content and overall performance of a system including both a VFD and a SVC will be studied and analyzed. Specifically, the cases of no compensation, static capacitor compensation, and power electronic based static VAR compensation are examined. A small-scale model of a system for study was constructed in lab. Several cases were then performed and tested to simulate a system which contained both fixed and power electronic based harmonic generating loads. The performance of each case was determined by total harmonic current and voltage distortions, true power factor, and RMS current levels at different points in the system.
62

A Longitudinal Exploration of Drive for Leanness: Potential Uniqueness, Sex Neutrality, Adaptive Nature, and Sociocultural Fit

Lang, Brittany 18 October 2018 (has links)
Historically disordered eating research has been gendered with models focusing on women’s pursuit of a thin ideal, as well as men’s attempts to obtain a muscular ideal. The motivations to achieve these ideals are called the drive for thinness (DT) and drive for muscularity (DM). More recently, a cultural shift has been noted in that ideal bodies are converging across sexes to a lean ideal, with the associated motivation being labeled the drive for leanness (DL). As DL is a nascent construct, little is known about its relationships with DT and DM, or if it predicts or is predicted by the same variables that are associated with DT and DM. This study aimed to expand what is known about DL in four ways: 1) ascertain the uniqueness of DL from DT and DM; 2) explore whether DL is sex neutral; 3) investigate the extent to which DL is more or less adaptive than DT and/or DM in terms of health-related outcomes; and 4) explore associations between DL and established predictors from sociocultural models of disordered eating. Analyses evidenced support for DL’s distinctiveness from DT and DM, partial support for DL’s sex neutrality, partial support discerned via relationships with health-related outcomes for DL’s adaptive nature in comparison to DT or DM, and support for DL’s relationships with sociocultural predictors being similar to that seen between these predictors with DT and DM. This study adds to the literature by broadening what is known about DL’s uniqueness, sex neutrality, adaptive nature, and sociocultural fit in relation to the other drives within a theory based framework, providing a potential basis for future DL model building and research in general.
63

Understanding and Modeling the Behavior of a Harmonic Drive Gear Transmission

Tuttle, Timothy D. 01 May 1992 (has links)
In my research, I have performed an extensive experimental investigation of harmonic-drive properties such as stiffness, friction, and kinematic error. From my experimental results, I have found that these properties can be sharply non-linear and highly dependent on operating conditions. Due to the complex interaction of these poorly behaved transmission properties, dynamic response measurements showed surprisingly agitated behavior, especially around system resonance. Theoretical models developed to mimic the observed response illustrated that non-linear frictional effects cannot be ignored in any accurate harmonic-drive representation. Additionally, if behavior around system resonance must be replicated, kinematic error and transmission compliance as well as frictional dissipation from gear-tooth rubbing must all be incorporated into the model.
64

X chromosome drive in Drosophila testacea

Keais, Graeme 01 May 2018 (has links)
Selfish genes that bias their own transmission during gametogenesis can spread rapidly in populations, even if they contribute negatively to the fitness of their host. Driving X chromosomes provide a clear example of this type of selfish propagation. These chromosomes, which are found in a broad range of taxa including plants, mammals, and insects, can have important evolutionary and ecological consequences. In this thesis, I report a new case of X chromosome drive (X drive) in a widespread woodland fly, Drosophila testacea. I show that males carrying the driving X (SR males) sire 80-100% female offspring, and that the majority of sons produced by SR males are sterile and appear to lack a Y chromosome. This suggests that meiotic defects involving the Y chromosome may underlie X drive in this species. Abnormalities in sperm cysts of SR males reflect that some spermatids are failing to develop properly, confirming that drive is acting during gametogenesis. Further, I show that SR males possess a diagnostic X chromosome haplotype that is perfectly associated with the sex ratio distortion phenotype. Phylogenetic analysis of X-linked sequences from D. testacea and related species strongly suggests that the driving X arose prior to the split of D. testacea and its sister species, D. neotestacea and D. orientacea. Suppressed recombination between the XST and XSR due to inversions on the XSR likely explains their disparate evolutionary histories. By screening wild-caught flies using progeny sex ratios and a diagnostic X-linked marker, I demonstrate that the driving X is present in wild populations at a frequency of ~10% and that autosomal suppressors of drive are segregating in the same population. Both SR males and homozygous females for the driving X have reduced fertility, which helps to explain the persistence of the driving X over evolutionary timescales. The testacea species group appears to be a hotspot for X drive, and D. testacea is a promising model to compare driving X chromosomes in closely related species, some of which may even be younger than the chromosomes themselves. / Graduate / 2019-04-16
65

Nové přístupy ke konstrukci produktů pojištění automobilů / New approaches to construction of vehicles insurance

Čápová, Markéta January 2009 (has links)
This thesis describes new possibilities that can occur at construction of motor-vehicle insurance on the worldwide market. In Czech republic there has been insurance liability for damage incurred running vehicles and wrecking crane insurance till now. Abroad indeed begins extend unprecedented product of motor-vehicle insurance known as Pay As You Drive that derives benefits from absolutely new methods at construction insurance.Insurance is invoiced on the basis of real mileage.For data gathering there are exploited different counter circuit functional mainly on the basis of GPS navigation.Aim of diploma work was analysis of this new kind of insurance, evaluation of its fruitfulness, serviceability and possibilities of its aplication in Czech republic.At the end of my thesis there was effected analysis of GAP insurance that can be negotiate in Czech republic already. GAP Insurance there has been like form of additional insurance to all-risk insurance. It covers difference in acquisition price of new vehicle and its actual market price that the classical all-risk insurance doesn't cover.
66

Disková pole RAID a jejich budoucnost v éře SSD / Future of disk arrays in SSD era

Sládek, Petr January 2012 (has links)
The thesis aims at verification of using emerging Solid-State drives in disk arrays. The advent of SSD disks caused a small revolution in area of data storage, because the growth performance of hard drives has been slow compared to other PC components. But an entirely different principle of operation could mean compatibility problems between SSD and related technologies, such as RAID. This thesis aims at analyzing all the relevant technologies, mainly HDD, SSD and RAID. To achieve this objective, information from literature, articles and other appropriate sources will be used. Other objectives of this thesis are to determine how much are the SSDs suitable for use in the disk array, because low performance RAID controllers or different principles of operation could limit their efficiency. This question should be answered by submission of selected types of storage arrays to synthetic and practical tests of performance. The final goal is to use financial analysis of the test solutions as a shared file storage. Today, remote access to data is used by a wide range of job positions. Slow storage could mean inefficient use of working time and therefore unnecessary financial costs. The goal of my work is primarily to provide answers to the questions mentioned above. Currently it is very hard to find tests of more complex forms of disk arrays based on solid-state drives. This article can be also very useful for companies where fileservers are used to share user data. Based on the result of cost analysis, the company can then decide what type of storage is best for its purpose.
67

Development and Implementation of Drive Away Release Function for a Vehicle

Astré, Gustav, Edman, Joakim January 2020 (has links)
As autonomy increases in today’s vehicles, the demands increase on both safety and comfort functions. Vehicle Hold, which holds the vehicle stationary without requiring the driver to press the brake pedal, is an example of such as function. This thesis aims to develop a concept for a Drive Away Release from this hold state, following several requirements regarding such as rollback, comfort, manual and autonomous drive mode, driving direction, road inclinations, with or without a trailer, and following the safety standard ISO 26262. In order to develop the concept function, a study of the state-of-the-art was made, followed by modeling the dynamics and control. The control algorithm was validated and tested first by running co-simulations between Matlab/Simulink and CarMaker. It was then implemented in a test vehicle. The test vehicle did not have all systems which are usually provided, demanding estimations to be made, such as the road inclination and vehicle mass. For manual drive mode, the driver controls the propulsion torque, and the control algorithm is based on releasing the brakes depending on estimations of the gravitational and propulsion torques. For autonomous drive mode, the vehicle is supposed to follow an acceleration reference. The control algorithm for autonomous drive mode is then extended with two feedforward compensators, one from reference and one from the gravitational torque, which is regarded as a disturbance, and with a feedback PI controller. To ensure that rollback do not occur at drive away release, a rollback prevention safety feature was also developed. The results of both the simulations and the test drives show that the concept function provides comfortable drive-off for most inclinations, drive modes and directions, without causing an undesired rollback
68

Design vozidla se spirálním pohonem / Design of car with spiral drive

Uhlíř, Filip January 2009 (has links)
Annotation Following work deals with the design proposal of the screw drive vehicle designed for the rescue and evacuation from the places which are unavailable to reach with usual vehicles. The intention was to diversify the current drive to design an innovative concept which will be in line with today‘s technological knowledge and modern trends. The main objective of the thesis is to solve the design and the shape of the vehicle which implements the requirements for an emergency car not only in terms of the appearance, but also in the way of functionality and variability of the interior. The thesis is divided into three general parts. The first one includes the historical development, the analysis and the description of technologies. The second part deals with the design, options and their ergonomic and technical solutions. In the last part is the end-point analysis of the proposal.
69

Alternativy řešení plošinového zvedáku / Solution alternatives of lifting platform

Hájek, Ondřej January 2010 (has links)
The aim of this thesis is to analyze the possibility of mechanical design platform lifts. Proposal lifting platform with mechanical and hydraulic drive with a capacity of 3500 kg and lift 600 mm. The work is mainly focused on design and strength calculation mechanism and structure. Proposal hydraulic circuits and the development drawings for both types of drive.
70

Control and Drive Quality Refinement of a Parallel-Series Plug-in Hybrid Electric Vehicle

Yard, Matthew Alexander January 2014 (has links)
No description available.

Page generated in 0.0453 seconds