24,779 research outputs found
Compact and High Performance Dual-band Bandpass Filter Using Resonator-embedded Scheme for WLANs
A compact microstrip dual-band bandpass filter (DBBPF) with high selectivity and good suppression for wireless local area networks (WLANs) is proposed utilizing a novel embedded scheme resonator. Two passbands are produced by a pair of embedded half-wavelength meandered stepped-impedance resonator (MSIR) and a quadwavelength short stub loaded stepped-impedance resonator (SIR) separately. The resonator is fed by folded Tshaped capacitive source-load coupling microstrip feed line, and four transmission zeros are obtained at both sides of the bands to improve selectivity and suppression. Simultaneously, the size of the filter is extermely compact because embedding half-wavelength MSIR only changes the interior configuration of quad-wavelength SIR. To validate the design method, the designed filter is fabricated and measured. Both simulated and measured results indicate that good transmission property has been achieved
B\"{a}cklund transformations for high-order constrained flows of the AKNS hierarchy: canonicity and spectrality property
New infinite number of one- and two-point B\"{a}cklund transformations (BTs)
with explicit expressions are constructed for the high-order constrained flows
of the AKNS hierarchy. It is shown that these BTs are canonical transformations
including B\"{a}cklund parameter and a spectrality property holds with
respect to and the 'conjugated' variable for which the point
belongs to the spectral curve. Also the formulas of m-times
repeated Darboux transformations for the high-order constrained flows of the
AKNS hierarchy are presented.Comment: 21 pages, Latex, to be published in J. Phys.
Angular momentum and energy structure of the coherent state of a 2D isotropic harmonic oscillator
The angular momentum structure and energy structure of the coherent state of a 2D isotropic harmonic oscillator were investigated. Calculations showed that the average values of angular momentum and energy (except the zero point energy) of this nonspreading 2D wave packet are identical to those of the corresponding classical oscillator moving along a circular or an elliptic orbit
Financial Hedging, Corporate Cash Policy, and the Value of Cash
We study the implications of financial hedging for corporate cash policy and the value of cash holdings. Using a web crawler program to collect data on the use of financial derivatives between 1993 and 2016, we find that US public firms with financial hedging programs have smaller cash reserves but a higher value of cash than firms without hedging contracts in place. Our empirical results are robust when controlling for potential endogeneity issues, corporate governance, cash regimes, and alternative measures of cash holdings. Further, we find that financial hedging not only increases the investment sensitivity to internal cash, but also has a positive effect on investment efficiency. The positive effect of financial hedging on the value of cash is more pronounced for firms with more financial constraints, higher information asymmetry, and weaker corporate governance. Collectively, our paper highlights the importance of corporate cash policy as a channel through which financial risk management increases firm value
B\"{a}cklund transformations for the KP and mKP hierarchies with self-consistent sources
Using gauge transformations for the corresponding generating
pseudo-differential operators in terms of eigenfunctions and adjoint
eigenfunctions, we construct several types of auto-B\"{a}cklund transformations
for the KP hierarchy with self-consistent sources (KPHSCS) and mKP hierarchy
with self-consistent sources (mKPHSCS) respectively. The B\"{a}cklund
transformations from the KPHSCS to mKPHSCS are also constructed in this way.Comment: 22 pages. to appear in J.Phys.
Self-Synchronized Universal Droop Controller
In this paper, a self-synchronization mechanism is embedded into the universal droop controller
(UDC), which is applicable to inverters having an impedance angle between −π/2 rad and π/2 rad,
to form a self-synchronized UDC (SUDC). Both the voltage loop and the frequency loop of the UDC are
modified to facilitate the standalone and grid-connected operation of inverters. Importantly, the dedicated
phase-locked-loop that is often needed for grid-connected or parallel-operated converters is removed. The
inverter is able to achieve synchronization before and after connection without the need of a dedicated
synchronization unit. Since the original structure of the UDC is kept in the SUDC, the properties of the
UDC, such as accurate power sharing and tight output voltage regulation, are well maintained. Extensive
experimental results are presented to demonstrate the performance of the proposed SUDC for a gridconnected
single-phase inverter
Generalized Darboux transformations for the KP equation with self-consistent sources
The KP equation with self-consistent sources (KPESCS) is treated in the
framework of the constrained KP equation. This offers a natural way to obtain
the Lax representation for the KPESCS. Based on the conjugate Lax pairs, we
construct the generalized binary Darboux transformation with arbitrary
functions in time for the KPESCS which, in contrast with the binary Darboux
transformation of the KP equation, provides a non-auto-B\"{a}cklund
transformation between two KPESCSs with different degrees. The formula for
N-times repeated generalized binary Darboux transformation is proposed and
enables us to find the N-soliton solution and lump solution as well as some
other solutions of the KPESCS.Comment: 20 pages, no figure
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