• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 319
  • 78
  • 73
  • 41
  • 37
  • 19
  • 15
  • 14
  • 10
  • 8
  • 8
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 702
  • 422
  • 213
  • 135
  • 126
  • 118
  • 111
  • 110
  • 108
  • 104
  • 80
  • 68
  • 67
  • 64
  • 59
  • 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.
271

Factors that Facilitate and Inhibit Engagement of Registered Nurses: An Analysis and Evaluation of Magnet versus Non-Magnet Designated Hospitals

Wonder, Amy C. 16 March 2012 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / Work engagement of registered nurses (RNs) has gained attention in health care, as an organizational process that is requisite to promoting optimal patient outcomes. Improving patient outcomes has caused a movement to examine what can be done to bridge the disparity between good and excellent care. Standards that enhance RN engagement to promote professional care are seen as vital to excellence. Magnet designation, awarded by the American Nurses Credentialing Center, signifies an organization meets such standards. Therefore, the purpose of this study was to evaluate whether a correlation exists between RN engagement and the organizational structures common to Magnet designation. This study also evaluated the influence of social and institutional demographics on the relationship between engagement and Magnet designation. The variables in this study included: age (generation), gender, nursing degree, years of RN experience, years of unit longevity, shift, hours scheduled and worked per week, percentage of time in direct patient care, nursing unit, and shared governance council participation. Finally, this study evaluated the influence of RN perception related to organizational support for work on the relationship between engagement and Magnet designation. A total of 370 RNs in Magnet (n = 220) and non-Magnet (n = 150) designated hospitals completed a 17-item engagement survey and a 15-item demographic survey. Major findings of the study indicated no significant difference in RN engagement between nurses who work at Magnet versus non-Magnet designated hospitals. Within the Magnet sample, significant relationships were found between engagement and shift, years of RN experience in any clinical setting, and RN perceptions related to organizational support for work. Scatter plots for nursing experience showed positive slopes for total engagement, vigor, dedication, and absorption. Post-hoc results for RN perception related to organizational support for work identified the significant areas of engagement were total engagement, vigor, and absorption. No significant post-hoc results were noted for the variable of shift. Through significant and non-significant findings, several insights were gained about engagement. As a result of this study, leadership can better assess the needs of the RN workforce to provide what RNs perceive to be important to professional practice and RN engagement.
272

Designing a New SPS Injection System With Numerical Optimisation

Waagaard, Elias January 2022 (has links)
The Super Proton Synchrotron (SPS) injection system plays a fundamental role to preserve the quality of injected high-brightness beams for the LHC physics program and to maintain the maximum storable intensity. The present set-up is the result of years of upgrades and patches of a system that was not conceived for such intensities and beam qualities. In this study, we propose the design of a completely new injection system based on multi-level numerical optimisation of the different constraints, including realistic hardware assumptions. We present the different algorithms and procedures applied in the optimisation process, and we also outline how this generic optimisation framework can be adapted to other situations for optimal accelerator system design.
273

OPEN SOURCE NMR RELAXOMETRY PLATFORM

Twieg, Michael D. 12 March 2013 (has links)
No description available.
274

Cogging Torque, Torque Ripple and Radial Force Analysis of Permanent Magnet Synchronous Machines

Islam, Mohammed Rakibul 09 June 2009 (has links)
No description available.
275

A Descriptive Study of the Organizational Attributes of Exemplar Tennessee Hospitals.

Grindstaff, Sharron Rutledge 01 May 2002 (has links) (PDF)
Tennessee's registered nurse vacancy rate is the highest in five years and the nursing shortage has dramatically impacted all portions of the state. The purpose of this study was to describe organizational attributes of exemplar Tennessee hospitals, as perceived by Chief Nurse Executives, which may influence the recruitment and retention of registered nurses. In this study, 52 Tennessee hospitals were identified as exemplars of quality patient care, organizational policy, and administration. Their Chief Nurse Executive's were surveyed utilizing a Hospital Characteristics Questionnaire and the Organizational Support Subscale from the Nursing Workforce Index Revised (NWI-R). The hospital characteristics and organizational attributes were then compared with those found in American Nurses Credentialing Center (ANCC) magnet hospitals, which have a reputation for retaining and recruiting nurses. The study demonstrated that the exemplar Tennessee hospitals were not comparable with the ANCC magnet hospitals and the findings suggest that Tennessee hospitals must develop strategies related to staffing, professional autonomy, respect for nursing, and positive work environments in order to recruit and retain nurses to preserve a nursing workforce now, and in the future.
276

The Effect of a Lingual Magnet on Fricative Production: An Acoustic Evaluation of Placement and Adaptation

Weaver, Andrea Lynn 29 August 2005 (has links) (PDF)
Much of speech kinematics research is conducted by attaching a device to the articulators. However very little research has been conducted to determine what influence these devices may have on the perceptual and acoustic characteristics of speech. This study examined the effect of placing a small magnet on the tongue of ten normal adult speakers while reading a sentence containing /s/ and "sh" in initial, medial and final position. Two different placements of 10 and 15 mm from the tip of the tongue were analyzed. Data were taken before magnet placement, immediately after magnet placement, after 5 minutes of conversation, and after an additional 10 minutes of conversation. The acoustic output was analyzed using spectral moments analysis (spectral mean, variance, skewness, and kurtosis). Changes in spectral mean and variance were found for "sh" as a result of magnet placement, which was characterized by an interaction effect between condition and the word position of the target fricative. In addition, significant changes in spectral mean were found for /s/ and "sh" as a result of magnet position. Although results from the present study indicated that there were some acoustic changes in fricative productions with a marker attached at midline, the spectral changes were not consistent or pervasive, and speakers were able to adapt to the presence of the magnet in a relatively short amount of time.
277

Multi-pole permanent magnet motor design and control for high performance electromechanical actuation in all electric aircraft

Bindl, Jared C. 01 January 2010 (has links)
The evolution of aircraft has led into a large increase in the demand for electrically integrated subsystems. Part of this demand is the transformation of a centralized hydraulic systems to independently operated electrical subsystems. The result of this overhaul will decrease aircraft weight, increase reliability, reduce aircraft lifetime maintenance and cost, and help to increase the control of power distribution. This thesis proposes the design methodology of a multi-pole permanent magnet (PM) motor with a capability to operate at high temperature. High temperature capability is one of the key requirements to implement electromechanical actuation for aircraft flight control, replace hydraulic actuation system, especially in tactical military aircraft, due to the hot environment and lack of heat sink. Temperature effects on motor materials are reviewed. The need for high power density is considered in the design. The motor design is confirm by ANYSYS RMXprt software. Along with the motor design, a voltage control method is also designed for the motor. Integrated electrical simulation results of the motor and controller to follow highly dynamic flight profiles are provided to show the stroke tracking, input power (including regenerative power), and winding copper loss. Experimentation set-up of EMA and experimental uncertainties are also discussed.
278

Super High-speed Miniaturized Permanent Magnet Synchronous Motor

Zheng, Liping 01 January 2005 (has links)
This dissertation is concerned with the design of permanent magnet synchronous motors (PMSM) to operate at super-high speed with high efficiency. The designed and fabricated PMSM was successfully tested to run upto 210,000 rpm The designed PMSM has 2000 W shaft output power at 200,000 rpm and at the cryogenic temperature of 77 K. The test results showed the motor to have an efficiency reaching above 92%. This achieved efficiency indicated a significant improvement compared to commercial motors with similar ratings. This dissertation first discusses the basic concept of electrical machines. After that, the modeling of PMSM for dynamic simulation is provided. Particular design strategies have to be adopted for super-high speed applications since motor losses assume a key role in the motor drive performance limit. The considerations of the PMSM structure for cryogenic applications are also discussed. It is shown that slotless structure with multi-strand Litz-wire is favorable for super-high speeds and cryogenic applications. The design, simulation, and test of a single-sided axial flux pancake PMSM is presented. The advantages and disadvantages of this kind of structure are discussed, and further improvements are suggested and some have been verified by experiments. The methodologies of designing super high-speed motors are provided in details. Based on these methodologies, a super high-speed radial-flux PMSM was designed and fabricated. The designed PMSM meets our expectation and the tested results agree with the design specifications. 2-D and 3-D modeling of the complicated PMSM structure for the electromagnetic numerical simulations of motor performance and parameters such as phase inductors, core losses, rotor eddy current loss, torque, and induced electromotive force (back-EMF) are also presented in detail in this dissertation. Some mechanical issues such as thermal analysis, bearing pre-load, rotor stress analysis, and rotor dynamics analysis are also discussed. Different control schemes are presented and suitable control schemes for super high- speed PMSM are also discussed in detail.
279

Mathematical Modeling and Computer Control of a Two-Phase Permanent-Magnet Stepping Motor

Wong, Richard C. S. 02 1900 (has links)
<p> The analysis of stepping motors using linear models has been simplified through identifications of the constants. Though the existing nonlinear models assuming a smooth air-gap machine may, in some cases, yield a fairly close prediction of the characteristics of a stepping motor, the models do not represent the actual motors which are essentially salient-pole motors. A new salient-pole nonlinear model is introduced. The analysis of permanent-magnet stepping motors using the nonlinear models has been simplified by assuming constant current sources. Dynamic behaviors of a permanent -magnet stepping motor are shown by phase-plane plots and step by step transient response plots.</p> <p> Computer control of stepping motors in both open-loop and closed-loop is discussed. The open-loop control has been demonstrated to be successful and a closed-loop control system using light-sensors as feedback has been designed.</p> / Thesis / Master of Engineering (MEngr)
280

DESIGN OF V-SHAPED INTERIOR PERMANENT MAGNETMACHINES FOR HVAC APPLICATIONS

Carlos Andres Castillo Ruiz (17593320) 10 December 2023 (has links)
<p dir="ltr">Recent regulatory changes have been proposed to phase down the use of hydrofluorocarbon</p><p dir="ltr">(HFC)-based refrigerants in air conditioning and refrigeration systems. The proposed</p><p dir="ltr">low global warming potential alternatives (low-GWP) are characterized by lower volumetric</p><p dir="ltr">capacities, which require either higher displacements or higher speeds to meet compressor</p><p dir="ltr">loads. In order to address this, the coupled optimization of a compressor system and its electric</p><p dir="ltr">drive has been proposed. The primary goal of this thesis is to establish tools that can be</p><p dir="ltr">used to assess the impact that alternative low-GWP refrigerants have on the sizing and performance</p><p dir="ltr">of electrically driven compressors. Toward this goal, a method-of-moments-based</p><p dir="ltr">model has been established and structured to enable rapid evaluation of the electromagnetic</p><p dir="ltr">performance of V-shaped interior magnet machines. Contributions to the model formulation</p><p dir="ltr">include the use of a judicious combination of point and pulse basis functions to evaluate</p><p dir="ltr">machine behavior under saturation of stator and rotor steels. Also included is a straightforward</p><p dir="ltr">means to include multiple operating points with minimal additional computational</p><p dir="ltr">expense. Coupled to the electromagnetic model is a thermal equivalent circuit model that</p><p dir="ltr">includes conductive heat transfer between slot winding bundles and stator steel. It also includes</p><p dir="ltr">convective heat transfer from the stator to the rotor through the airgap. The proposed</p><p dir="ltr">models have been validated using commercial finite-element based software. Subsequently,</p><p dir="ltr">they have been applied in design optimization studies used to compare the efficiency and size</p><p dir="ltr">(mass) between machines designed for a common HFC refrigerant (R410A) and a proposed</p><p dir="ltr">alternative (R454B).</p>

Page generated in 0.0366 seconds