49,893 research outputs found
Bifurcation Boundary Conditions for Switching DC-DC Converters Under Constant On-Time Control
Sampled-data analysis and harmonic balance analysis are applied to analyze
switching DC-DC converters under constant on-time control. Design-oriented
boundary conditions for the period-doubling bifurcation and the saddle-node
bifurcation are derived. The required ramp slope to avoid the bifurcations and
the assigned pole locations associated with the ramp are also derived. The
derived boundary conditions are more general and accurate than those recently
obtained. Those recently obtained boundary conditions become special cases
under the general modeling approach presented in this paper. Different analyses
give different perspectives on the system dynamics and complement each other.
Under the sampled-data analysis, the boundary conditions are expressed in terms
of signal slopes and the ramp slope. Under the harmonic balance analysis, the
boundary conditions are expressed in terms of signal harmonics. The derived
boundary conditions are useful for a designer to design a converter to avoid
the occurrence of the period-doubling bifurcation and the saddle-node
bifurcation.Comment: Submitted to International Journal of Circuit Theory and Applications
on August 10, 2011; Manuscript ID: CTA-11-016
A theoretical analysis of the current-voltage characteristics of solar cells
The correlation of theoretical and experimental data is discussed along with the development of a complete solar cell analysis. The dark current-voltage characteristics, and the parameters for solar cells are analyzed. The series resistance, and impurity gradient effects on solar cells were studied, the effects of nonuniformities on solar cell performance were analyzed
Entropic Regularization Approach for Mathematical Programs with Equilibrium Constraints
A new smoothing approach based on entropic perturbationis proposed for solving mathematical programs withequilibrium constraints. Some of the desirableproperties of the smoothing function are shown. Theviability of the proposed approach is supported by acomputationalstudy on a set of well-known test problems.mathematical programs with equilibrium constraints;entropic regularization;smoothing approach
A theoretical analysis of the current-voltage characteristics of solar cells
The following topics are discussed: (1) dark current-voltage characteristics of solar cells; (2) high efficiency silicon solar cells; (3) short circuit current density as a function of temperature and the radiation intensity; (4) Keldysh-Franz effects and silicon solar cells; (5) thin silicon solar cells; (6) optimum solar cell designs for concentrated sunlight; (7) nonuniform illumination effects of a solar cell; and (8) high-low junction emitter solar cells
Entropic regularization approach for mathematical programs with equilibrium constraints
A new smoothing approach based on entropic perturbation is proposed for solving mathematical programs with equilibrium constraints. Some of the desirable properties of the smoothing function are shown. The viability of the proposed approach is supported by a computational study on a set of well-known test problems.Entropic regularization;Smoothing approach;Mathematical programs with equilibrium constraints
The radial abundance gradient of oxygen towards the Galactic anticentre
We present deep optical spectroscopy of eight HII regions located in the
anticentre of the Milky Way. The spectra were obtained at the 10.4m GTC and
8.2m VLT. We determined Te([NII]) for all objects and Te([OIII]) for six of
them. We also included in our analysis an additional sample of 13 inner-disc
Galactic Hii regions from the literature that have excellent T_e
determinations. We adopted the same methodology and atomic dataset to determine
the physical conditions and ionic abundances for both samples. We also detected
the CII and OII optical recombination lines in Sh 2-100, which enables
determination of the abundance discrepancy factor for this object. We found
that the slopes of the radial oxygen gradients defined by the HII regions from
R_25 (= 11.5 kpc) to 17 kpc and those within R_25 are similar within the
uncertainties, indicating the absence of flattening in the radial oxygen
gradient in the outer Milky Way. In general, we found that the scatter of the
O/H ratios of Hii regions is not substantially larger than the observational
uncertainties. The largest possible local inhomogeneities of the oxygen
abundances are of the order of 0.1 dex. We also found positive radial gradients
in Te([O III]) and Te([N II]) across the Galactic disc. The shapes of these
temperature gradients are similar and also consistent with the absence of
flattening of the metallicity distribution in the outer Galactic disc.Comment: 20 pages, 11 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
On the finite termination of an entropy function based smoothing Newton method for vertical linear complementarity problems
By using a smooth entropy function to approximate the non-smooth max-type function, a vertical linear complementarity problem (VLCP) can be treated as a family of parameterized smooth equations. A Newton-type method with a testing procedure is proposed to solve such a system. We show that the proposed algorithm finds an exact solution of VLCP in a finite number of iterations, under some conditions milder than those assumed in literature. Some computational results are included to illustrate the potential of this approach.Newton method;Finite termination;Entropy function;Smoothing approximation;Vertical linear complementarity problems
Amplification of Reynolds number dependent processes by wave distortion
A system using a hot-wire transducer as an analog of a liquid droplet of propellant was employed to investigate the ingredients of the acoustic instability of liquid-propellant rocket engines. It was assumed that the combustion process was vaporization-limited and that the combustion chamber was acoustically similar to a closed-closed right-circular cylinder. Before studying the hot-wire closed-loop system (the analog system), a microphone closed-loop system, which used the response of a microphone as the source of a linear feedback exciting signal, was investigated to establish the characteristics of self-sustenance of acoustic fields. Self-sustained acoustic fields were found to occur only at resonant frequencies of the chamber. In the hot-wire closed-loop system, the response of hot-wire anemometer was used as the source of the feedback exciting signal. The self-sustained acoustic fields which developed in the system were always found to be harmonically distorted and to have as their fundamental frquency a resonant frequency for which there also existed a second resonant frequency which was approximately twice the fundamental frequency
Process feasibility study in support of silicon material task 1
Initial results for gas thermal conductivity of silicon tetrafluoride and trichlorosilane are reported in respective temperature ranges of 25 to 400 C and 50 to 400 C. For chemical engineering analyses, the preliminary process design for the original silane process of Union Carbide was completed for Cases A and B, Regular and Minimum Process Storage. Included are raw material usage, utility requirements, major process equipment lists, and production labor requirements. Because of the large differences in surge tankage between major unit operations the fixed capital investment varied from 11,138,000 for Cases A and B, respectively. For the silane process the original flowsheet was revised for a more optimum arrangement of major equipment, raw materials and operating conditions. The initial issue of the revised flowsheet (Case C) for the silane process indicated favorable cost benefits over the original scheme
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