23,478 research outputs found
Challenges of Primary Frequency Control and Benefits of Primary Frequency Response Support from Electric Vehicles
As the integration of wind generation displaces conventional plants, system inertia provided by rotating mass declines, causing concerns over system frequency stability. This paper implements an advanced stochastic scheduling model with inertia-dependent fast frequency response requirements to investigate the challenges on the primary frequency control in the future Great Britain electricity system. The results suggest that the required volume and the associated cost of primary frequency response increase significantly along with the increased capacity of wind plants. Alternative measures (e.g. electric vehicles) have been proposed to alleviate these concerns. Therefore, this paper also analyses the benefits of primary frequency response support from electric vehicles in reducing system operation cost, wind curtailment and carbon emissions
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
Quantum asymmetric cryptography with symmetric keys
Based on quantum encryption, we present a new idea for quantum public-key
cryptography (QPKC) and construct a whole theoretical framework of a QPKC
system. We show that the quantum-mechanical nature renders it feasible and
reasonable to use symmetric keys in such a scheme, which is quite different
from that in conventional public-key cryptography. The security of our scheme
is analyzed and some features are discussed. Furthermore, the state-estimation
attack to a prior QPKC scheme is demonstrated.Comment: 8 pages, 1 figure, Revtex
Preparation and In vitro Digestibility of Corn Starch Phosphodiester
Purpose: To optimize the process conditions and analyze in vitro digestibility of corn starch phosphodiester prepared by sodium trimetaphosphate (STMP).Methods: By using response surface method, the effects of STMP concentration, pH, esterification temperature, and urea addition on digestion resistance of corn starch phosphodiester were investigated and optimal conditions were determined. Corn starch phosphodiester was identified by Fourier transform infrared spectroscopy (FT-IR) and an in vitro digestibility method was applied to investigate starch digestion performances of corn starch phosphodiester.Results: The optimum conditions for the preparation of corn starch phosphodiester were as follows: STMP, 3.3 %; pH 9.07; esterification temperature, 42 °C; and urea, 2.3 %. Under these conditions, corn starch phosphodiester with a digestion resistance of 66.02 % ± 1.63 % was obtained. Compared with corn starch, the digestible starch content of corn starch phosphodiester decreased sharply (from 86.6 to 10.9 %), while digestion-resistance starch content increased significantly from 1.9 to 66.0 % (p < 0.05), and its digestibility was reduced. FTIR spectrum showed new absorption peaks at 1028 cm-1 indicating that an esterification cross-linking reaction occurred between corn starch and sodium trimetaphosphate.Conclusion: The corn starch phosphodiester obtained has a lower digestbility and therefore, can potentially be used as a medium glycemic index food for diabetic patients.Keywords: Corn starch phosphodiester, Digestion resistance, Sodium trimetaphosophate, In vitrodigestibility, Glycemic inde
A minimal model for excitons within time-dependent density-functional theory
The accurate description of the optical spectra of insulators and
semiconductors remains an important challenge for time-dependent
density-functional theory (TDDFT). Evidence has been given in the literature
that TDDFT can produce bound as well as continuum excitons for specific
systems, but there are still many unresolved basic questions concerning the
role of dynamical exchange and correlation (xc). In particular, the role of the
long spatial range and the frequency dependence of the xc kernel
for excitonic binding are still not very well explored. We present a minimal
model for excitons in TDDFT, consisting of two bands from a one-dimensional
Kronig-Penney model and simple approximate xc kernels, which allows us to
address these questions in a transparent manner. Depending on the system, it is
found that adiabatic xc kernels can produce a single bound exciton, and
sometimes two bound excitons, where the long spatial range of is
not a necessary condition. It is shown how the Wannier model, featuring an
effective electron-hole interaction, emerges from TDDFT. The collective,
many-body nature of excitons is explicitly demonstrated.Comment: 12 pages, 11 figure
Circular quantum secret sharing
A circular quantum secret sharing protocol is proposed, which is useful and
efficient when one of the parties of secret sharing is remote to the others who
are in adjacent, especially the parties are more than three. We describe the
process of this protocol and discuss its security when the quantum information
carrying is polarized single photons running circularly. It will be shown that
entanglement is not necessary for quantum secret sharing. Moreover, the
theoretic efficiency is improved to approach 100% as almost all the instances
can be used for generating the private key, and each photon can carry one bit
of information without quantum storage. It is straightforwardly to utilize this
topological structure to complete quantum secret sharing with multi-level
two-particle entanglement in high capacity securely.Comment: 7 pages, 2 figure
Entanglement in the dispersive interaction of trapped ions with a quantized field
The mode-mode entanglement between trapped ions and cavity fields is
investigated in the dispersive regime. We show how a simple initial preparation
of Gaussian coherent states and a postselection may be used to generate
motional non-local mesoscopic states (NLMS) involving ions in different traps.
We also present a study of the entanglement induced by dynamical Stark-shifts
considering a cluster of N-trapped ions. In this case, all entanglement is due
to the dependence of the Stark-shifts on the ions' state of motion manifested
as a cross-Kerr interaction between each ion and the field.Comment: 10 pages, 5 figures, corrected typo
Demonstrating anyonic fractional statistics with a six-qubit quantum simulator
Anyons are exotic quasiparticles living in two dimensions that do not fit
into the usual categories of fermions and bosons, but obey a new form of
fractional statistics. Following a recent proposal [Phys. Rev. Lett. 98, 150404
(2007)], we present an experimental demonstration of the fractional statistics
of anyons in the Kitaev spin lattice model using a photonic quantum simulator.
We dynamically create the ground state and excited states (which are six-qubit
graph states) of the Kitaev model Hamiltonian, and implement the anyonic
braiding and fusion operations by single-qubit rotations. A phase shift of
related to the anyon braiding is observed, confirming the prediction of
the fractional statistics of Abelian 1/2-anyons.Comment: revised version 3, revTex, 4.3 pages, 4 figures, notes and reference
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Formation of a Double Diamond Cubic Phase by Thermotropic Liquid Crystalline Self-Assembly of Bundled Bolaamphiphiles
A quaternary amphiphile with swallow-tail side groups displays a new bicontinuous thermotropic cubic phase with symmetry Pn3‾ m and formed by two interpenetrating networks where cylindrical segments are linked by H bonds at tetrahedral junctions. Each network segment contains two bundles, each containing 12 rod-like mesogens, lying along the segment axis. This assembly leads to the first thermotropic structure of the "double diamond" type. A quantitative geometric model is proposed to explain the occurrence of this rare phase
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