System Quality Factors Research Articles

Ultra-smooth microcylindrical resonators fabricated from the silicon optical fiber platform

High quality hydrogenated amorphous silicon microcylindrical resonators are fabricated using the recently developed semiconductor optical fiber platform. The resonators are shown to have ultra-smooth surfaces that minimize the effects of scattering losses and exhibit localized whispering gallery modes with loaded quality factors of up to ∼2.8 × 104. Coupled mode theory indicates that the system quality factor is limited by both the bulk material loss of the resonator and the tapered fiber coupling scheme. The large extinction ratios and thermal nonlinearities measured in these microcylindrical resonators suggest that they should find application for low-power all-optical processing.

Subharmonic Resonant Optical Excitation of Confined Acoustic Modes in a Free-Standing Semiconductor Membrane at GHz Frequencies with a High-Repetition-Rate Femtosecond Laser

We propose subharmonic resonant optical excitation with femtosecond lasers as a new method for the characterization of phononic and nanomechanical systems in the gigahertz to terahertz frequency range. This method is applied for the investigation of confined acoustic modes in a free-standing semiconductor membrane. By tuning the repetition rate of a femtosecond laser through a subharmonic of a mechanical resonance we amplify the mechanical amplitude, directly measure the linewidth with megahertz resolution, infer the lifetime of the coherently excited vibrational states, accurately determine the system's quality factor, and determine the amplitude of the mechanical motion with femtometer resolution.

An empirical study on information system quality factors that affect job satisfaction of call center agents

An empirical study on information system quality factors that affect job satisfaction of call center agents

Increasing Gas Turbine Blade Damping Through Cavities Filled with Viscoelastic Materials

To evaluate the effectiveness of high-damping materials as candidate fill materials for hollow fan blades, test specimens in the form of flat trapezoidal plates were designed and mounted as cantilevers. An open-ended cavity of uniform thickness comprised 71% of the planform area. Two viscoelastic materials were developed and used as fillers. Each was modified for reduced density and then aged after application to simulate the influence of 4000 service hours at a characteristic mission profile. Values of the loss factor (reciprocal of the system quality factor) determined from the resonant responses of the filled plates in the first bending, first torsion, and second bending modes at 75° C (170°F) were found to be in the range of q = 0.025-0.045 (Q = 22-40), η = 0.06 (Q = 16), and q = 0.09-0.11 (Q = 9-11) for the three modes, respectively, which is an improvement of 1.5 to 2 orders of magnitude over values measured with the unfilled specimens. A finite element analysis, using temperature and frequency dependent properties of the filler material as determined by separate tests, showed satisfactory agreement with the observed values for temperatures up to 120° C (250°F). This study confirmed that the addition of viscoelastic filler to a hollow plate can increase damping significantly and that the system response could be predicted by finite element analysis. Through appropriate selection of the filler material, such systems can be designed to have maximum damping at a desired specific combination of temperature and frequency.

Quality factor concept in piezoceramic transformer performance description

A new general approach based on the quality factor concept to piezoceramic transformer (PT) performance description is proposed. The system's quality factor, material elastic anisotropy, and coupling factors of the input and output sections of an electrically excited and electrically loaded PT fully characterize its resonance and near-resonance behavior. The PT efficiency, transformation ratio, and input and output power were analytically analyzed and simulated as functions of the load and frequency for the simplest classical Langevin-type and Rosen-type PT designs. A new formulation of the electrical input impedance allows one to separate the power consumed by PT from the power transferred into the load. The system's PT quality factor takes into account losses in each PT "input-output-load" functional components. The loading process is changing PT input electrical impedance on the way that under loading the minimum series impedance is increasing and the maximum parallel impedance is decreasing coincidentally. The quality-factors ratio, between the states of fully loaded and nonloaded PT, is one of the best measures of PTs dynamic performance--practically, the lower the ratio is, the better PT efficiency. A simple and effective method for the loaded PT quality factor determination is proposed. As was found, a piezoceramic with low piezoelectric anisotropy is required to provide maximum PT efficiency and higher corresponding voltage gain. Limitations on the PT output voltage and power, caused by nonlinear effects in piezoceramics, were established.

All-optical logic performance of quantum-dot semiconductor amplifier-based devices

The performances of all-optical logic gates AND, OR, XOR, and NOT, based on quantum-dot semiconductor optical amplifier (QD-SOA) devices, are simulated. The saturation power, optical gain, and optical phase response of a QD-SOA is analyzed numerically using a rate-equation model of quantum dots embedded in a wetting layer. The calculated response is used to model the performance of the logic gates. The impact of the injection current and the input-signal power on the system's quality factor are studied. For the parameters used in this paper, all-optical logic gates using QD-SOA are capable of operating at speeds of ∼250 Gb/s. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 29–35, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21252

An Exploratory Investigation of System Success Factors in Data Warehousing

Despite the increasing role of the data warehouse as a strategic information source for decision makers, academic research has been lacking, especially from an organizational perspective. An exploratory study was conducted to improve general understanding of data warehousing issues from the perspective of IS success. For this, the effect of variables pertaining to system quality, information quality, and service quality on user satisfaction for the data warehouse was studied. Additional characterization was made on data warehouse users, their organizational tasks, and data warehouse usage. Empirical data were gathered at a large enterprise from three different information sources: a survey, unstructured group interviews with end-users, and informal interviews with an IT manager who was in charge of the data warehouse. Data analysis showed that user satisfaction with the data warehouse was significantly affected by such system quality factors as data quality, data locatability, and system throughput. Interviews also supported the existence of system design and management issues that have to be addressed to optimize the utility of the data warehouse as an effective decision support environment. In the meantime, data analysis indicated that first-line (or lower) and middle managers were the main users of the system. Managers and knowledge workers were taking advantage of the system to perform complex tasks, to support decision making, and to seek information critical for enhanced productivity. The group interviews revealed additional benefits of the data warehouse and major roadblocks in its successful usage.

An Empirical Investigation of the Factors Affecting Data Warehousing Success

The IT implementation literature suggests that various implementation factors play critical roles in the success of an information system; however, there is little empirical research about the implementation of data warehousing projects. Data warehousing has unique characteristics that may impact the importance of factors that apply to it. In this study, a cross-sectional survey investigated a model of data warehousing success. Data warehousing managers and data suppliers from 111 organizations completed paired mail questionnaires on implementation factors and the success of the warehouse. The results from a Partial Least Squares analysis of the data identified significant relationships between the system quality and data quality factors and perceived net benefits. It was found that management support and resources help to address organizational issues that arise during warehouse implementations; resources, user participation, and highly-skilled project team members increase the likelihood that warehousing projects will finish on-time, on-budget, with the right functionality; and diverse, unstandardized source systems and poor development technology will increase the technical issues that project teams must overcome. The implementation's success with organizational and project issues, in turn, influence the system quality of the data warehouse; however, data quality is best explained by factors not included in the research model.

Explicit Realization of Chaos Control in an NMR-Laser Experiment

Abstract The usefulness of the Ott-Grebogi-Yorke control method is demonstrated by stabilizing a chaotic NMR-laser system around an unstable period-one orbit. We have used a six-dimensional delay-coordinate embedding technique in order to fully determine the stability properties of the orbit controlled. Our analysis yields small time-dependent perturbations of the system quality factor capable to perform real-time control.

System quality factors for LPI communications

Quality factors are developed for low-probability-intercept (LPI) communication systems in order to provide a quantitative technique that allows the system engineer to evaluate LPI effectiveness in the presence of jammers and intercept receivers. LPI quality factors are derived from the system link equations, which describe the signal power gains and losses as a function of system link parameters. Quality factors for the essential components of the LPI system that provide some advantage to the cooperative transmitter and receiver over the jammer and intercept receiver are described. These include quality factors for the antennas, type of modulation, atmospheric propagation conditions, and interference rejection capability.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>