49,086 research outputs found
Secure Quantum Secret Sharing Based on Reusable GHZ States as Secure Carriers
We show a potential eavesdropper can eavesdrop whole secret information when
the legitimate users use secure carrier to encode and decode classical
information repeatedly in the protocol [proposed in Bagherinezhad S and
Karimipour V 2003 Phys. Rev. A \textbf{67} 044302]. Then we present a revised
quantum secret sharing protocol by using Greenberger-Horne-Zeilinger state as
secure carrier. Our protocol can resist Eve's attack
Field study on adaptive thermal comfort in typical air conditioned classrooms
This study investigates adaptive thermal comfort in air conditioned classrooms in Hong Kong. A field survey was conducted in several typical classrooms at the City University of Hong Kong. This survey covered objective measurement of thermal environment parameters and subjective human thermal responses. A total of 982 student volunteers participated in the investigation. The results indicate that students in light clothing (0.42 clo) have adapted to the cooler classroom environments. The neutral temperature is very close to the preferred temperature of approximately 24 °C. Based on the MTSV ranging between −0.5 and + 0.5, the comfort range is between 21.56 °C and 26.75 °C. The lower limit is below that of the ASHRAE standard. Of the predicted mean vote (PMV) and the University of California, Berkeley (UCB) model, the UCB model predictions agree better with the mean thermal sensation vote (MTSV). Also, the respective fit regression models of the MTSV versus each of the following: operative temperature (Top), PMV, and UCB were obtained. This study provides a better understanding of acceptable classroom temperatures
The effect of parental opportunism, IJV's autonomy and tacit knowledge on IJV instability: A comparison of multi-variate regression and fuzzy-set qualitative comparative analysis
This study uses an agency theory perspective to examine how the factors that influence principal (IJV parents) and agent (IJV) relationship may affect IJV instability in China. The study proposes a framework that bridges knowledge-based theory (of tacit knowledge) and agency theory (of parental opportunism) by incorporating reactance theory (of autonomy). By comparing the empirical results of fuzzy-set qualitative comparative analysis (fsQCA) and multiple regression analysis, using a sample of 203 Chinese-foreign IJVs, the study add further evidence to growing methodological consideration regarding complexity theory. The results from multiple regressions show that parental opportunism and IJV’s autonomy has a positive effect on IJV’s instability, and that the interaction of autonomy and tacit knowledge moderates the effect of parental opportunism on IJV instability. However, fsQCA uncovers more causal paths than findings from multiple regression analysis
An unexpectedly low-redshift excess of Swift gamma-ray burst rate
Gamma-ray bursts (GRBs) are the most violent explosions in the Universe and
can be used to explore the properties of high-redshift universe. It is believed
that the long GRBs are associated with the deaths of massive stars. So it is
possible to use GRBs to investigate the star formation rate (SFR). In this
paper, we use Lynden-Bell's method to study the luminosity function and
rate of \emph{Swift} long GRBs without any assumptions. We find that the
luminosity of GRBs evolves with redshift as with
. After correcting the redshift evolution through
, the luminosity function can be expressed as
for dim GRBs and for bright GRBs, with the break point
. We also find that the formation
rate of GRBs is almost constant at for the first time, which is
remarkably different from the SFR. At , the formation rate of GRB is
consistent with the SFR. Our results are dramatically different from previous
studies. Some possible reasons for this low-redshift excess are discussed. We
also test the robustness of our results with Monte Carlo simulations. The
distributions of mock data (i.e., luminosity-redshift distribution, luminosity
function, cumulative distribution and distribution) are in good
agreement with the observations. Besides, we also find that there are
remarkable difference between the mock data and the observations if long GRB
are unbiased tracers of SFR at .Comment: 33 pages, 10 figures, 1 table, accepted by ApJ
Angle-of-Arrival Estimation Using Difference Beams in Localized Hybrid Arrays.
Angle-of-arrival (AoA) estimation in localized hybrid arrays suffers from phase ambiguity owing to its localized structure and vulnerability to noise. In this letter, we propose a novel phase shift design, allowing each subarray to exploit difference beam steering in two potential AoA directions. This enables the calibration of cross-correlations and an enhanced phase offset estimation between adjacent subarrays. We propose two unambiguous AoA estimation schemes based on the even and odd ratios of the number of antennas per subarray N to the number of different phase shifts per symbol K (i.e., N/K), respectively. The simulation results show that the proposed approach greatly improves the estimation accuracy as compared to the state of the art when the ratio N/K is even
Analytical Solution to Transport in Brownian Ratchets via Gambler's Ruin Model
We present an analogy between the classic Gambler's Ruin problem and the
thermally-activated dynamics in periodic Brownian ratchets. By considering each
periodic unit of the ratchet as a site chain, we calculated the transition
probabilities and mean first passage time for transitions between energy minima
of adjacent units. We consider the specific case of Brownian ratchets driven by
Markov dichotomous noise. The explicit solution for the current is derived for
any arbitrary temperature, and is verified numerically by Langevin simulations.
The conditions for vanishing current and current reversal in the ratchet are
obtained and discussed.Comment: 4 pages, 3 figure
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