224 research outputs found
Design of Energy-Efficient Artificial Noise for Physical Layer Security in Visible Light Communications
This paper studies the design of energy-efficient artificial noise (AN)
schemes in the context of physical layer security in visible light
communications (VLC). Two different transmission schemes termed
and
are examined and
compared in terms of secrecy energy efficiency (SEE). In the former, the
closest LED luminaire to the legitimate user (Bob) is the information-bearing
signal's transmitter. At the same time, the rest of the luminaries act as
jammers transmitting AN to degrade the channels of eavesdroppers (Eves). In the
latter, the information-bearing signal and AN are combined and transmitted by
all luminaries. When Eves' CSI is unknown, an indirect design to improve the
SEE is formulated by maximizing Bob's channel's energy efficiency. A
low-complexity design based on the zero-forcing criterion is also proposed. In
the case of known Eves' CSI, we study the design that maximizes the minimum SEE
among those corresponding to all eavesdroppers. At their respective optimal
SEEs, simulation results reveal that when Eves' CSI is unknown, the selective
AN-aided SISO transmission can archive twice better SEE as the AN-aided MISO
does. In contrast, when Eves' CSI is known, the AN-aided MISO outperforms by
30%
Nature of phase transition in magnetic thin films
We study the critical behavior of magnetic thin films as a function of the
film thickness. We use the ferromagnetic Ising model with the high-resolution
multiple histogram Monte Carlo (MC) simulation. We show that though the 2D
behavior remains dominant at small thicknesses, there is a systematic
continuous deviation of the critical exponents from their 2D values. We observe
that in the same range of varying thickness the deviation of the exponent
is very small from its 2D value, while exponent suffers a larger
deviation. Moreover, as long as the film thickness is fixed, i. e. no finite
size scaling is done in the direction perpendicular to the film, the 3D
values of the critical exponents cannot be attained even with very large (but
fixed) thickness. The crossover to 3D universality class cannot therefore take
place without finite size scaling applied in the direction, in the limit of
numerically accessible thicknesses. From values of exponent obtained
by MC, we estimate the effective dimension of the system. We conclude that with
regard to the critical behavior, thin films behave as systems with effective
dimension between 2 and 3.Comment: 8 pages, 17 figures, submitted to Phys. Rev.
Morphological characteristics and genetic diversity of <em>Terapon jarbua</em> (Forrskäl, 1775) in Central, Vietnam
Many environmental factors affect the morphology of migratory fish species, such as salinity, water flow rate, and temperature. However, studies on changes in fish morphology under environmental variations from salt water to brackish water are still limited in many fish species, especially in *Terapon jarbua*. This study aims to investigate the differences in the morphological parameters of *T. jarbua* between the coastal sea (seawater) and lagoon (brackish water); and between male and female fish based on a landmark morphological approach. Additionally, the genetic diversity of *T. jarbua* populations in Central Vietnam was elucidated using the mitochondrial DNA cytochrome oxidase subunit I (mtDNA COI) sequence as a molecular marker. The analytical results indicated no sexual dimorphism in the *T. jarbua* population, yet conformational differences exist between the two studied aquatic species. The analysis of 42 mtDNA COI sequences collected from Central Vietnam identified 13 haplotypes with medium genetic diversity and low genetic differentiation between the Tam Giang lagoon and Thua Thien Hue coastal (Fst = 0.028) and not significant (p = 0.126). Most haplotypes obtained are present in reference populations, indicating a high genetic exchange between populations. We proposed that the *T. jarbua* population in Central Vietnam has a stable connection with neighboring populations (China, Taiwan, Philippines, Indonesia, Malaysia, Bangladesh, India, and Pakistan)
ANOVA_robust: A SAS Macro for Parametric Tests of Mean Differences in One-Factor ANOVA Models
Testing the equality of several independent group means is a common statistical practice in the social sciences. The traditional analysis of variance (ANOVA) is one of the most popular methods. However, the ANOVA F test is sensitive to violations of the homogeneity of variance assumption. Many alternative tests have been developed in response to this problem of the F test. These tests include some modifications of the ANOVA F test and others based on the structured means modeling technique. This paper provides a SAS macro for testing the equality of group means using thirteen methods including the regular ANOVA F test. In addition, this paper summarizes the results of a simulation study that compares the performance of these tests in terms of their Type I error rate under different conditions, especially under violations of the homogeneity of variance assumption
Designing a novel heterostructure AgInS<sub>2</sub>@MIL-101(Cr) photocatalyst from PET plastic waste for tetracycline degradation
Semiconductor-containing porous materials with a well-defined structure could be unique scaffolds for carrying out selective organic transformations driven by visible light. We herein introduce for the first time a heterostructure of silver indium sulfide (AgInS(2)) ternary chalcogenide and a highly porous MIL-101(Cr) metal–organic framework (MOF) synthesised from polyethylene terephthalate plastic waste. Our results demonstrate that AgInS(2) nanoparticles were uniformly attached to each lattice plane of the octahedral MIL-101(Cr) structure, resulting in a nanocomposite with a high distribution of semiconductors in a porous media. We also demonstrate that the nanocomposite with up to 40% of AgInS(2) doping exhibited excellent catalytic activity for tetracycline degradation under visible light irradiation (∼99% tetracycline degraded after 4 h) and predominantly maintained its performance after five cycles. These results could promote a new material circularity pathway to develop new semiconductors that can be used to protect water from further pollution
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