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Duty Ratio (duty + ratio)

Distribution by Scientific Domains
Polymers and Materials Science42%
Engineering42%

Selected Abstracts

High speed sliding of axonemal microtubules produced by outer arm dynein

CYTOSKELETON, Issue 2 2005
Raviraja N. Seetharam
Abstract To study dynein arm activity at high temporal resolution, axonemal sliding was measured field by field for wild type and dynein arm mutants of Tetrahymena thermophila. For wt SB255 cells, when the rate of data acquisition was 60 fps, about 5× greater than previously published observations, sliding was observed to be discontinuous with very high velocity sliding (average 196 ,m/sec) for a few msec (1 or 2 fields) followed by a pause of several fields. The sliding velocities measured were an order of magnitude greater than rates previously measured by video analysis. However, when the data were analyzed at 12 fps for the same axonemes, consistent with previous observations, sliding was linear as the axonemes extended several times their original length with an average velocity of ,10 ,m/sec. The pauses or stops occurred at approximately 200 and 300% of the initial length, suggesting that dynein arms on one axonemal doublet were initially active to the limit of extension, and then the arms on the next doublet became activated. In contrast, in a mutant where OADs are missing, sliding observed at 60 fps was continuous and slow (5 ,m/sec), as opposed to the discontinuous high-velocity sliding of SB255 and of the mutant at the permissive temperature where OADs are present. High-velocity step-wise sliding was also present in axonemes from an inner arm dynein mutant (KO6). These results indicate that the high-speed discontinuous pattern of sliding is produced by the mechanochemical activity of outer arm dynein. The rate of sliding is consistent with a low duty ratio of the outer arm dynein and with the operation of each arm along a doublet once per beat. Cell Motil. Cytoskeleton 60:96,103, 2005. © 2004 Wiley-Liss, Inc. [source]

Tailored Plasmonic Gratings for Enhanced Fluorescence Detection and Microscopic Imaging

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
Xiaoqiang Cui
Abstract The ability to precisely control the pattern of metallic structures at the micro- and nanoscale for surface plasmon coupling has been demonstrated to be essential for signal enhancement in fields such as fluorescence and surface-enhanced Raman scattering. In the present study, a series of silver coated gratings with tailored duty ratio and depth and a periodical pitch of 400,nm are designed and implemented. The influence of the grating profile on plasmonic properties and the corresponding enhancement factor are investigated by angular scanning measurement of reflectivity and fluorescence intensity and by finite difference time domain simulation. The application of the substrate in the enhanced fluorescence imaging detection of labeled protein is also investigated. This substrate has a wide range of potential applications in areas including biodiagnostics, imaging, sensing, and photovoltaic cells. [source]

A simple PWM method for improving lamp current crest factor of valley-filled electronic ballast

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 3 2010
Zhi-Ren Lee
Abstract In this paper, a PWM method to improve the lamp current crest factor (CCF) of the valley-filled electronic ballast (VFEB) is presented. The VFEB has merits of high power factor, simple structure, and low cost. However, it results in an excessive CCF, which will shorten the lifetime of low-pressure discharge lamp. The proposed method controls switching duty ratio by feeding forward the dc-link voltage waveform of VFEB. It decreased the duty ratio with rising of dc-link voltage. Therefore, the proposed method could restrain the lamp peak current and improve the lamp CCF. The control block diagram and basic theory are introduced to improve the CCF. The computer simulations verify the proposed method and derive a minimum lamp CCF. The experimental results demonstrate that the lamp CCF was reduced from 1.9 to 1.58, the ac line power factor is 96%, and the input current THD is 29.3%. The fixed switching frequency operation gains a satisfactory power quality. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Global Model of He/O2 and Ar/O2 Atmospheric Pressure Glow Discharges

PLASMA PROCESSES AND POLYMERS, Issue 6 2008
Ganyoung Park
Abstract Atmospheric pressure glow discharges (APGDs) have widespread applications, including sterilization, cancer cell treatment, deposition, and surface modification due to their rather simple configurations, thanks to no need for vacuum system and their great capability to generate reactive species such as radical oxygen species. Helium and argon are widely used as feeding gases, achieving stable operations for wide ranges of parameters in atmospheric pressure, and oxygen is added into these gases to generate more reactive oxygen species (ROS), which play a significant role in sterilization. As the measurements of species densities and electron temperature in APGDs are difficult, we have developed the zero-dimensional global model of He/O2 and Ar/O2 APGDs to calculate the densities of several kinds of species and electron temperature. It was shown that even though small fraction of oxygen less than 1% was added to helium or argon, electrons dissipated most of their energy through collisions with oxygen molecules rather than helium or argon atoms. The densities of electron, atomic oxygen, and ozone of Ar/O2 were higher than those of He/O2; however, the electron temperature of He/O2 was higher than that of Ar/O2. When the pulsed power is applied, the time-averaged electron temperature for the shorter pulse period and the larger duty ratio increased, and the electron density decreased as the duty ratio increased. [source]

Nonlinear Controller Design for PWM,Controlled Converters

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
A. Kugi Prof. Dr. techn.
This contribution is concerned with the nonlinear controller design for a certain class of PWM (pulse width modulation) , controlled converter systems. It will be shown that under certain assumptions the SSA (state space averaging) , model of the PWM,controlled converter with the duty ratio as the plant input has a very special mathematical structure. Based on this mathematical model a modified version of the nonlinear H2,design where an integral term is systematically included in the nonlinear controller will be presented. [source]

Small-signal analysis of interleaved dual boost converter

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 6 2001
Mummadi Veerachary
Abstract This paper presents a systematic development of steady-state, small-signal models of interleaved dual boost converter operating in a continuous current mode. These models are derived by employing the well-known signal flow graph method. This signal flow graph approach provides a means to directly translate the switching converter into its equivalent graphic model, from which a complete behaviour of the converter can easily be studied. Steady-state performance, small-signal characteristic transfer functions are derived using Mason's gain formula. The bode plots of audiosusceptibility, input impedance, output impedance, and control-to-output transfer functions are determined and illustrated using MATLAB for different values of load resistances, duty ratios. Small-signal frequency responses obtained from the signal flow graph method are validated with PSPICE simulator results. To validate the signal flow graph modelling equations, sample steady-state experimental results are provided. Copyright © 2001 John Wiley & Sons, Ltd. [source]