3,545 research outputs found
A Two-Step Quantum Direct Communication Protocol Using Einstein-Podolsky-Rosen Pair Block
A protocol for quantum secure direct communication using blocks of EPR pairs
is proposed. A set of ordered EPR pairs is used as a data block for sending
secret message directly. The ordered EPR set is divided into two particle
sequences, a checking sequence and a message-coding sequence. After
transmitting the checking sequence, the two parties of communication check
eavesdropping by measuring a fraction of particles randomly chosen, with random
choice of two sets of measuring bases. After insuring the security of the
quantum channel, the sender, Alice encodes the secret message directly on the
message-coding sequence and send them to Bob. By combining the checking and
message-coding sequences together, Bob is able to read out the encoded messages
directly. The scheme is secure because an eavesdropper cannot get both
sequences simultaneously. We also discuss issues in a noisy channel.Comment: 8 pages and 2 figures. To appear in Phys Rev
Parametric Analysis of Energy Absorption in Micro-particle Photophoresis in Absorbing Gaseous Media
The study deals with photophoresis of a spherical micro-particle suspended in absorbing gaseous media. Photophoretic motion of the particle stems from the asymmetric distribution of absorbed energy within the particle. By evaluating the so-called heat source function at various conditions, the study focuses on the effects of governing parameters on the energy distribution within the particle and their potential influences to the photophoresis. The results reveal that the increase in either particle size or absorptivity enhances the energy intensity on the illuminated (leading) side and tends to generate positive photophoresis. For a particle of low absorptivity, the energy distribution is dominated by particle refraction. Enhancing particle refractivity, the energy tends to be focused onto a certain spot area on the shaded (trailing) side and leads to a tendency of negative photophoresis. Increasing medium absorptivity significantly degrades the level of energy absorbed by the particle and in turn weakens the driving force of the particle photophoresis.Defence Science Journal, 2010, 60(3), pp.233-237, DOI:http://dx.doi.org/10.14429/dsj.60.34
Parity violation in nuclear systems
Parity violation in nuclear systems is reviewed. A few ingredients relevant
to the description of the parity-violating nucleon-nucleon force in terms of
meson exchanges are reminded. Effects in nuclear systems are then considered.
They involve pp scattering, some complex nuclei and the deuteron system.Comment: 4 pages, to be published in the proceedings of the worksho
Quantum secure communication scheme with W state
Recently, Cao et al. proposed a new quantum secure direct communication
scheme using W state. In their scheme, the error rate introduced by an
eavesdropper who takes intercept-resend attack, is only 8.3%. Actually, their
scheme is just a quantum key distribution scheme because the communication
parties first create a shared key and then encrypt the secret message using
one-time pad. We then present a quantum secure communication scheme using
three-qubit W state. In our scheme, the error rate is raised to 25% and it is
not necessary for the present scheme to use alternative measurement or Bell
basis measurement. We also show our scheme is unconditionally secure.Comment: Comments are welcom
Dynamic Analysis of a Rotating Shaft Subject to the Double Cutting Force and Time-varying Mass Effects of the Rod
AbstractThis paper investigates the dynamic behaviors of a rotating shaft subjected to the double cutting force and time-varying mass effects. The Timoshenko beam theory is used to model the rotating shaft, and the general boundary condition is assumed as the clamped-hinged supports. This system is used to simulate the manufacture process of the double turret CNC lathes, and the mass of the rod which is reduced gradually in cutting process. The system equations of motion are derived based on the global assumed mode method, and the dynamic responses of the system are obtained by Runge-Kutta numerical method. The transformation matrix is derived to make the equation of motion completing the boundary geometric constraints. The numerical results compare the dynamic response in different moving speeds and skew angles of the cutting forces with/without the time-varying mass effects. Additionally, this paper compares the response with single cutting force and double force. The results show that the double moving force system can reduce not only the machining time but also the amplitude of shaft vibration
Parity nonconservation in deuteron photoreactions
We calculate the asymmetries in parity nonconserving deuteron
photodisintegration due to circularly polarized photons gamma+d to n+p with the
photon laboratory energy ranging from the threshold up to 10 MeV and the
radiative capture of thermal polarized neutrons by protons n+p to gamma+d. We
use the leading order electromagnetic Hamiltonian neglecting the smaller
nuclear exchange currents. Comparative calculations are done by using the
Reid93 and Argonne v18 potentials for the strong interaction and the DDH and
FCDH "best" values for the weak couplings in a weak one-meson exchange
potential. A weak NDelta transition potential is used to incorporate also the
Delta(1232)-isobar excitation in the coupled-channels formalism.Comment: 14 pages, 13 figures (18 eps files), LaTeX2
Design and Setup of the Micro-Turboexpander Transcritical CO2 System
As the potential Eco-friendly refrigerant, CO2 regains more and more attentions. It has various advantages over conventional refrigerants, such as non-flammability, non-toxicity, high volumetric refrigerant capacity and excellent heat transfer properties. Because the heat rejection temperature in a transcritical CO2 heat pump or a transcritical CO2 refrigeration system is higher than the critical temperature of CO2, the transcritical vapor compression cycle becomes the best choice for transcritical CO2 systems. However, the relative low COP caused by the throttle valve limited the further development. The replacement of a throttle valve with a turboexpander, an ejector or a vortex tube is leading to the way for improving the COP of a transcritical CO2 system. With the advantages of high efficiency, high compactness, high reliability and long-life time, turboexpanders have been widely used in gas lique faction devices (below 120K) and most of the reverse Brayton refrigeration systems. It is also one of the most ideal expansion devices for transcritical CO2 systems. However, its applications are limited by the difficulties of high pressure and super high rotating speed operation. With the development of manufacturing technology and gas bearing technology, it becomes possible to use turboexpanders in transcriticalCO2 systems. In this paper, two turboexpanders with 10 mm radial reaction turbine wheel and 9 mm rotor diameter were designed for the 15 kW transcritical CO2 refrigeration system, and the rotating speed is about 200 krpm.The proposed turboexpanders outlet states are CO2 two-phase flow and subcooled CO2 liquid flow, respectively. This study will lay a foundation for the application of turboexpanders in transcritical CO2 systems
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