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Two-phase viscoelastic jetting

Description: A coupled finite difference algorithm on rectangular grids is developed for viscoelastic ink ejection simulations. The ink is modeled by the Oldroyd-B viscoelastic fluid model. The coupled algorithm seamlessly incorporates several things: (1) a coupled level set-projection method for incompressible immiscible two-phase fluid flows; (2) a higher-order Godunov type algorithm for the convection terms in the momentum and level set equations; (3) a simple first-order upwind algorithm for the convection term in the viscoelastic stress equations; (4) central difference approximations for viscosity, surface tension, and upper-convected derivative terms; and (5) an equivalent circuit model to calculate the inflow pressure (or flow rate) from dynamic voltage.
Date: December 10, 2008
Creator: Yu, J.-D.; Sakai, S. & Sethian, J. A.
Partner: UNT Libraries Government Documents Department

Effect of Electrode Composition and Microstructure on Impedancemetric Nitric Oxide Sensors based on YSZ Electrolyte

Description: The role of metal (Au, Pt, and Ag) electrodes in YSZ electrolyte-based impedancemetric nitric oxide (NO) sensors is investigated using impedance spectroscopy and equivalent circuit analysis. The test cell consists of a rectangular block of porous YSZ with two metal wire loop electrodes, both exposed to the same atmosphere. Of the electrode materials, only Au was sensitive to changes in NO concentration. The impedance behavior of porous Au electrodes in a slightly different configuration was compared with dense Au electrodes and was also insensitive to NO. Ag showed no sensitivity to either O{sub 2} or NO, and the measured impedances occurred at frequencies > 10 kHz, which are typically associated with ionic conduction in YSZ. Pt and porous Au showed sensitivity to O{sub 2}, which was quantified using power-law exponents that suggest electrochemical rate-determining mechanisms occurring at the triple phase boundary. The behavior of the dense Au suggests different rate-determining processes (e.g., diffusion or adsorption) for the O{sub 2} reaction. Although the exact mechanism is not determined, the composition and microstructure of the metal electrode seem to alter the rate-limiting step of the interfering O{sub 2} reaction. Impedance behavior of the O{sub 2} reaction that is limited by processes occurring away from the triple phase boundary may be crucial for impedancemetric NO sensing.
Date: April 2, 2007
Creator: Woo, L Y; Martin, L P; Glass, R S; Wang, W; Jung, S; Gorte, R J et al.
Partner: UNT Libraries Government Documents Department

An equivalent circuit model and power calculations for the APS SPX crab cavities.

Description: An equivalent parallel resistor-inductor-capacitor (RLC) circuit with beam loading for a polarized TM110 dipole-mode cavity is developed and minimum radio-frequency (rf) generator requirements are calculated for the Advanced Photon Source (APS) short-pulse x-ray (SPX) superconducting rf (SRF) crab cavities. A beam-loaded circuit model for polarized TM110 mode crab cavities was derived. The single-cavity minimum steady-state required generator power has been determined for the APS SPX crab cavities for a storage ring current of 200mA DC current as a function of external Q for various vertical offsets including beam tilt and uncontrollable detuning. Calculations to aid machine protection considerations were given.
Date: March 21, 2012
Creator: Berenc, T.
Partner: UNT Libraries Government Documents Department

Coupling interaction between the power coupler and the third harmonic superconducting cavity

Description: Fermilab has developed a third harmonic superconducting cavity operating at the frequency of 3.9 GHz to improve the beam performance for the FLASH user facility at DESY. It is interesting to investigate the coupling interaction between the SRF cavity and the power coupler with or without beam loading. The coupling of the power coupler to the cavity needs to be determined to minimize the power consumption and guarantee the best performance for a given beam current. In this paper, we build and analyze an equivalent circuit model containing a series of lumped elements to represent the resonant system. An analytic solution of the required power from the generator as a function of the system parameters has also been given based on a vector diagram.
Date: June 1, 2007
Creator: Li, Jianjian; Solyak, Nikolay & Wong, Thomas
Partner: UNT Libraries Government Documents Department

Including Internal Losses In The Equivalent Circuit Model Of The SLAC Damped Detuned Structure (DDS)

Description: In the equivalent circuit model for the DDS originally presented no losses were explicitly included in the cell circuits or the manifold circuits. Damping via the manifolds was effected by imposing matching conditions (including the possibility of reflection) on the ends of the manifolds. In this paper we extend the circuit theory to include lossy circuit elements. We discuss and compare shunt conductance and series resistance models for the cells. Manifold damping is modeled by introducing a shunt conductance per unit length in the transmission line elements of the manifolds. We apply the theory to the mitigation of performance degradation associated with fabricationally desirable decoupling of several cells at the ends of the structure from the manifolds.
Date: April 1, 1999
Creator: Jones, Roger M
Partner: UNT Libraries Government Documents Department

Equivalent circuit analysis of the RHIC injection kicker

Description: The RHIC injection kicker is built as a traveling wave structure in order to assure the required 95 nsec risetime in the deflection strength. The kicker is constructed from 14 cells, each 7.5 cm long, with alternating ferrite and high-permittivity dielectric sections. The cell structure permits an analysis of the electrical properties of the kicker using lumped L, C, and R circuit elements. Their values are obtained directly from impedance measurements of the full-length kicker, the inductance and shunt capacitance values by measuring the input impedance at 1 MHz with the output shorted and open, respectively. A lossy series resonance circuit in each cell is found to reproduce the measured input impedance of the terminated kicker up to {approximately}100 MHz. The validity of the equivalent circuit was confirmed by comparing the measured output current pulse shape time with that computed by the P-Spice program.
Date: July 1, 1997
Creator: Hahn, H. & Ratti, A.
Partner: UNT Libraries Government Documents Department

Identifying high-level components in combinational circuits

Description: The problem of finding meaningful subcircuits in a logic layout appears in many contexts in computer-aided design. Existing techniques rely upon finding exact matchings of subcircuit structure within the layout. These syntactic techniques fail to identify functionally equivalent subcircuits that are differently implemented, optimized, or otherwise obfuscated. The authors present a mechanism for identifying functionally equivalent subcircuits that can overcome many of these limitations. Such semantic matching is particularly useful in the field of design recovery.
Date: July 1, 1998
Creator: Doom, T.; White, J.; Wojcik, A. & Chisholm, G.
Partner: UNT Libraries Government Documents Department

Equivalent circuit analysis of the SLAC damped detuned structure

Description: An accelerating structure designed as described previously is nearing completion. An equivalent circuit analysis, elaborated to take account of both the lower two dipole bands and the nonuniform properties of the damping manifolds, has been carried out. The equivalent circuit has nine parameters per cell, determined by matching the dispersion curves of the three lowest modes (two dipole modes plus the manifold mode) as computed by MAFIA. This procedure is carried out for eleven selected cells, after which interpolation is used to determine the parameters for the remaining 195 cells. Because the manifold-cell coupling is strong, a numerically challenging non-perturbative treatment is required. Wakefield and other results are presented.
Date: June 1, 1996
Creator: Jones, R.M.; Ko, K.; Kroll, N.M.; Miller, R.H. & Thompson, K.A.
Partner: UNT Libraries Government Documents Department

Identification of functional components in combinational circuits

Description: Identifying the subcircuits in a detailed circuit description is a fundamental operation in both circuit validation and design recovery. Existing identification techniques rely on finding an exact match for a subcircuit structure within the description. These techniques fail to identify subcircuits that are functionally equivalent but have been obfuscated because a different technology is being used or because the design has been optimized. This report presents a mechanism for identifying subcircuits that are functionally equivalent, irrespective of obfuscating details. It also describes the initial progress made in transforming detailed circuit descriptions into corresponding descriptions based on subcircuits. Such progress depends on enumerating all of the candidate subcircuits within the original detailed description and functionally matching each candidate. The report presents unique solutions for reducing the amount of computation needed for this enumeration.
Date: January 1, 1998
Creator: Doom, T.E.; White, J.L.; Wojcik, A.S. & Chisholm, G.H.
Partner: UNT Libraries Government Documents Department

Reactive Robinson instability in the NSLS X-ray ring

Description: The theory of the reactive Robinson instability is formulated in terms of the terminal variables, its stopband structure is analysed, and the results are applied to the X-ray ring of the NSLS. The reactive Robinson instability for the case of multiple cavities in the storage ring is also studied.
Date: January 22, 1996
Creator: Broome, W.A. & Wang, J.M.
Partner: UNT Libraries Government Documents Department

Wakefield and Beam Centering Measurements of a Damped and Detuned X-Band Accelerator Structure

Description: In the Next Linear Collider (NLC) design, X-Band (11.4 GHz) accelerator structures are used to accelerate multibunch beams to several hundred GeV. Although these structures allow for high gradient operation, their strong deflecting modes impose a number of operational constraints. In particular, the long-range transverse wakefields generated by the bunches need to be reduced by about two orders of magnitude to prevent significant beam breakup. During the past five years, a reduction scheme that employs both detuning and damping of the structure dipole modes has been developed to meet this requirement. Several prototype Damped and Detuned Structures (DDS) have been built to test and refine this scheme. The wakefield of the latest version, DDS3, has recently been measured in the Accelerator Structure Setup (ASSET) facility at SLAC. In this paper, we present these results together with predictions based on an equivalent circuit model of the structure. We also present ASSET studies in which the beam-induced dipole signals that are coupled out for damping purposes are used to center the beam in the structure.
Date: September 14, 1999
Creator: Adolphsen, Chris
Partner: UNT Libraries Government Documents Department

Impedancemetric NOx Sensing Using Yttria-Stabilized Zirconia (YSZ) Electrolyte and YSZ/Cr2O3 Composite Electrodes

Description: An impedancemetric method for NO{sub x} sensing using an yttria-stabilized zirconia (YSZ) based electrochemical cell is described. The sensor cell consists of a planar YSZ electrolyte and two identical YSZ/Cr{sub 2}O{sub 3} composite electrodes exposed to the test gas. The sensor response to a sinusoidal ac signal applied between the two electrodes is measured via two parameters calculated from the complex impedance, the modulus |Z| and phase angle {Theta}. While either of these parameters can be correlated to the NO{sub x} concentration in the test gas, {Theta} was found to provide a more robust metric than |Z|. At frequencies below approximately 100 Hz, {Theta} is sensitive to both the NO{sub x} and O{sub 2} concentrations. At higher frequencies, {Theta} is predominantly affected by the O{sub 2} concentration. A dual frequency measurement is demonstrated to compensate for changes in the O{sub 2} background between 2 and 18.9%. Excellent sensor performance is obtained for NO{sub x} concentrations in the range of 8-50 ppm in background. An equivalent circuit model was used to extract fitting parameters from the impedance spectra for a preliminary analysis of NO{sub x} sensing mechanisms.
Date: November 1, 2006
Creator: Martin, L P; Woo, L Y & Glass, R S
Partner: UNT Libraries Government Documents Department

Creating dynamic equivalent PV circuit models with impedance spectroscopy for arc-fault modeling.

Description: Article 690.11 in the 2011 National Electrical Code{reg_sign} (NEC{reg_sign}) requires new photovoltaic (PV) systems on or penetrating a building to include a listed arc fault protection device. Currently there is little experimental or empirical research into the behavior of the arcing frequencies through PV components despite the potential for modules and other PV components to filter or attenuate arcing signatures that could render the arc detector ineffective. To model AC arcing signal propagation along PV strings, the well-studied DC diode models were found to inadequately capture the behavior of high frequency arcing signals. Instead dynamic equivalent circuit models of PV modules were required to describe the impedance for alternating currents in modules. The nonlinearities present in PV cells resulting from irradiance, temperature, frequency, and bias voltage variations make modeling these systems challenging. Linearized dynamic equivalent circuits were created for multiple PV module manufacturers and module technologies. The equivalent resistances and capacitances for the modules were determined using impedance spectroscopy with no bias voltage and no irradiance. The equivalent circuit model was employed to evaluate modules having irradiance conditions that could not be measured directly with the instrumentation. Although there was a wide range of circuit component values, the complex impedance model does not predict filtering of arc fault frequencies in PV strings for any irradiance level. Experimental results with no irradiance agree with the model and show nearly no attenuation for 1 Hz to 100 kHz input frequencies.
Date: June 1, 2011
Creator: Johnson, Jay Dean; Kuszmaul, Scott S.; Strauch, Jason E. & Schoenwald, David Alan
Partner: UNT Libraries Government Documents Department

{open_quotes}Secure Bus{close_quotes} disturbance-free power at the utility substation level

Description: Over the last 18 months Public Service Company of New Mexico (PNM), El Camino Real Engineering, Inc. (CRE), Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL) have worked on the development of disturbance-free power at the medium voltage substation level. The work resulted in the Secure Bus concept, a system in which a medium voltage bus in a substation is immune to power outages and voltage sags on the utility source. The Secure Bus voltage is also immune to voltage sags resulting from faults on any distribution feeder connected to the bus. The Secure Bus concept originated from work conducted to improve power quality for large high-tech manufacturing facilities, in particular for large semiconductor manufacturing plants. For the demands on quality power of a modern facility conventional equipment is not adequate for protecting the end user. For example, the operation of conventional vacuum breakers during short circuit conditions on a feeder circuit, requiring 3 to 5 cycles for breaker opening, does not allow for fast enough current interruption to avoid a voltage dip on the main bus. A sever voltage sag could result in a shut down of sensitive equipment being supplied by the other feeder circuits, which are connected to the main bus. The circumvent the problem, a fast breaker was introduced which interrupts the short circuit before the current causes a significant voltage disturbance. To make the bus immune also to power disturbances caused by power outages, energy storage is introduced to provide the necessary energy back-up in case the primary source is not available.
Date: December 1, 1996
Creator: Boenig, H. J. & Jones, W. H.
Partner: UNT Libraries Government Documents Department

A spectral function method applied to the calculation of the wake function for the NLCTA

Description: The equivalent circuit representation of the dipole modes of the SLAC damped detuned structure (DDS) which is being fabricated at LAC has been analyzed by three different methods. The first two are based upon a modal analysis: in the first, damped modes are found by a first order perturbation in the cell to damping manifold coupling strength; while in the second, preferred when the coupling strength is large (as is the case for the SLAC structure) they are determined exactly (a time consuming procedure). The third method, which the authors report here, expresses the wake as a modal sum for modes whose frequencies place them outside the propagation bands of the manifolds (a minor contribution) plus a Fourier like integral of a spectral function over the propagation band of the manifolds (the major contribution). They will present comparisons to previous calculations, assessment of appropriate domains of applicability, and applications to the SLAC structure with matched and mismatched manifold terminations.
Date: September 1, 1996
Creator: Jones, R.M.; Kroll, N.M.; Ko, K. & Miller, R.H.
Partner: UNT Libraries Government Documents Department

Equivalent circuit study of beam-loading using a moment method

Description: In this work, we present a formalism by considering the perturbations in the moments of a bunched beam for the equivalent circuit model to include all harmonics of the synchroton oscillation in a beam-cavity interaction system. The linear coupling among all longitudinal modes under the influence of narrow-band impedance can be naturally incorporated in this new approach. We used this method to re-examine the coupling between the dipole and the quadrupole modes. The dispersion relation obtained by this new method was compared with that derived from the linearized Vlasov equation up to the second harmonic of the synchrotron motion. We found excellent qualitative agreements between two approaches.
Date: August 1, 1997
Creator: Wang, T.F.; Machida, S.; Mori, Y. & Ohmori, C.
Partner: UNT Libraries Government Documents Department

Analysis and application of mainfold radiation in DDS 1: First experiences

Description: The cells in the SLAC DDS are designed in such a way that the transverse modes excited by the beam are detuned in a Gaussian fashion so that destructive interference causes the wake function to decrease rapidly and smoothly. Moderate damping provided by four waveguide manifolds running along the outer wall of the accelerator is utilized to suppress the reappearance of the wake function at long ranges where the interference becomes constructive again. The newly developed spectral function method, involving a continuum of frequencies, is applied to analyze the wake function of the DDS 1 design and to study the dependence of the wake function on manifold termination. The wake function obtained with the actually realized manifold terminations is presented and compared to wake function measurements recently carried out at the ASSET facility installed in the SLAC LINAC.
Date: October 1, 1996
Creator: Jones, R.M.; Kroll, N.M. & Seidel, M.
Partner: UNT Libraries Government Documents Department

MEASUREMENTS OF THE COUPLING IMPEDANCE OF THE SNS EXTRACTION KICKERS.

Description: The Spallation Neutron Source (SNS) Accumulator ring extraction system includes 14 modules of ferrite kicker magnets with window-frame geometry. Among all ring components, the extraction kickers make the single largest contribution to the coupling impedance budget. A prototype was constructed and various design options impacting the transverse coupling impedance have been thoroughly studied. Bench as well as system measurements were performed to determine the benefits from an external circuit resistance, from using different ferrites material, and from adding a novel ferrite winding. The results presented in this paper confirm that a resistive termination in the external circuit yields a solution with sufficiently reduced transverse coupling impedance. In order to determine the total contribution of all modules, an equivalent circuit and a simple scaling law was derived from measurements of full and half size magnets.
Date: June 3, 2002
Creator: DAVINO,D.; HAHN,H. & LEE,Y.Y.
Partner: UNT Libraries Government Documents Department

Equivalent circuit analysis of sled

Description: A direct application of equivalent circuit concepts leads to: (1) confirmation of Perry Wilson's SLED (SLAC Linac Energy Doubler) equation; (2) an equation that applies to a SLED device with input and output waveguides of different characteristic impedances; and (3) an equation that results if we demand that no power be lost by reflection from SLED. If the incident voltage is tailored as prescribed by this equation, the cavity voltage tracks the incident voltage and the reflected voltage is zero.
Date: May 1, 1986
Creator: Lippmann, B.A.
Partner: UNT Libraries Government Documents Department

Comparison of the domain and frequency domain state feedbacks

Description: In this paper, we present explicitly the equivalence of the time domain and frequency domain state feedbacks, as well as the dynamic state feedback and a modified frequency domain state feedback, from the closed-loop transfer function point of view. The difference of the two approaches is also shown.
Date: January 1, 1986
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

A variable current bypass shunt for electromagnets

Description: An IGBT is used to control the current in bypass circuits that vary the relative strength of magnets connected in series. Each circuit consists of a water cooled assembly rated for continuous operation at 70 Volts and 0--50 Amperes DC, with 1 KV insulation between control/monitoring elements and magnets. The circuit operates as a 10KHz PWM switcher that includes filters and transient protection.
Date: November 1, 1992
Creator: Berndt, M. M. & Lipari, J. J.
Partner: UNT Libraries Government Documents Department

Manifold damping of the NLC detuned accelerating structure

Description: In order to investigate the reappearance of the HOM wakefield of a detuned accelerator structure and relax tolerance requirements, we propose to provide low level damping by coupling all cavities to several identical and symmetrically located waveguides (manifolds) which run parallel to each accelerator structure and are terminated at each end by matched loads. The waveguides are designed such that all modes which couple to the acceleration mode are non-propagating at the acceleration mode frequency. Hence the coupling irises can be designed to provide large coupling to higher frequency modes without damping the acceleration mode. Because the higher order modes are detuned, they are localized and have a broad spectrum of phase velocities of both signs. They are therefore capable of coupling effectively to all propagating modes in the waveguides. Methods of analyzing and results obtained for the very complex system of modes in the accelerating structure and manifolds are presented.
Date: September 1, 1994
Creator: Kroll, N.; Thompson, K.; Bane, K.; Ko, K.; Miller, R.; Ruth, R. et al.
Partner: UNT Libraries Government Documents Department

Detailed Performance Model for Photovoltaic Systems: Preprint

Description: This paper presents a modified current-voltage relationship for the single diode model. The single-diode model has been derived from the well-known equivalent circuit for a single photovoltaic cell. The modification presented in this paper accounts for both parallel and series connections in an array.
Date: July 1, 2012
Creator: Tian, H.; Mancilla-David, F.; Ellis, K.; Muljadi, E. & Jenkins, P.
Partner: UNT Libraries Government Documents Department