BER Analysis of FSO System with Airy Beam as Carrier Over Exponentiated Weibull Channel Model

Average Bit Error Rate (BER) expression of free-space optical (FSO) communication links with Airy beam as signal carrier under weak atmospheric turbulence and on-off keying (OOK) modulation scheme is derived based on scintillation index of Airy beam and Exponentiated Weibull (EW) channel model. The average BER has been evaluated at different transverse scale factors and exponential decay factors of Airy beam and link distances. And comparison of the average BER of FSO links with Airy beam and Gaussian beam as signal carrier has been carried out. The simulation results show that the average BER of FSO links with Airy beam as carrier decreases with the increase of mean signal to noise ratio (SNR) and increases with the increase of transmission distance. When the transverse scale factor is about 1.5cm, a lower average BER can be obtained. And the smaller the exponential decay factor is, the lower the average BER is. Under the same atmospheric turbulence condition, the average BER of FSO links with Airy beam as carrier is obviously better than that of FSO links with Gaussian beam as carrier. The results of this research have some significance for the application of Airy beam in FSO system.

Conventional Partial and Complete Solutions of the Fundamental Equations of Fluid Mechanics in the Problem of Periodic Internal Waves with Accompanying Ligaments Generation

The problem of generating beams of periodic internal waves in a viscous, exponentially stratified fluid by a band oscillating along an inclined plane is considered by the methods of the theory of singular perturbations in the linear and weakly nonlinear approximations. The complete solution to the linear problem, which satisfies the boundary conditions on the emitting surface, is constructed taking into account the previously proposed classification of flow structural components described by complete solutions of the linearized system of fundamental equations without involving additional force or mass sources. Analyses includes all components satisfying the dispersion relation that are periodic waves and thin accompanying ligaments, the transverse scale of which is determined by the kinematic viscosity and the buoyancy frequency. Ligaments are located both near the emitting surface and in the bulk of the liquid in the form of wave beam envelopes. Calculations show that in a nonlinear description of all components, both waves and ligaments interact directly with each other in all combinations: waves-waves, waves-ligaments, and ligaments-ligaments. Direct interactions of the components that generate new harmonics of internal waves occur despite the differences in their scales. Additionally, the problem of generating internal waves by a rapidly bi-harmonically oscillating vertical band is considered. If the difference in the frequencies of the spectral components of the band movement is less than the buoyancy frequency, the nonlinear interacting ligaments generate periodic waves as well. The estimates made show that the amplitudes of such waves are large enough to be observed under laboratory conditions.

Fluid model of the plasma flow in the magnetic tail of a planet

<p>All planets of the solar system with an active internal dynamo have a their magnetic dipole oriented perpendicularly or nearly perpendicularly to the solar wind during all or part of their orbit  around the Sun. If, in addition, the planetary rotation is slow, or if the angle between dipole and rotation axis is large, planetary field lines crossing the antisolar axis can become stretched to large distances downstream of the planet. Examples where this may occur are Mercury and Uranus at solstice time, respectively. </p><p>Inspired by these examples, we present a tentative one-dimensional magnetohydrodynamic model of the plasma flowing along the antisolar direction. </p><p>Assuming that the radius of curvature R(z) of the planetary field lines is defined locally as R=D/D', where D(z) is a characteristic  transverse scale of the magnetosphere at a distance z downstream of the planet,  we obtain that the plasma velocity u(z) obeys to a Hugoniot type equation  (M<sup>2</sup>-1) u'/u =  D'/D,  where M=u/v<sub>A</sub> is the Alfvén Mach number. </p><p>The solution for a typical profile D(z) will be discussed. </p>

Rhodeus flaviventris, a new bitterling (Teleostei: Cyprinidae: Acheilognathinae) from China

Rhodeus flaviventris, a new species, is described from the Le-An River, a tributary flowing into Poyang Lake in the Yangtze River basin, in Jiangxi Province, China. It is distinguished from all congeners by the combination of characters: branched dorsal-fin rays 9 (9–10); branched anal-fin rays 9 (9–10); longest simple rays of dorsal and anal fins thick and stiff; longitudinal scale series 33–34; transverse scale series 11 (10–12); pored scales 4–7; vertebrae 32–34; spindle-shaped eggs with major axis of 3.1–3.7 mm; color pattern of nuptial males (iris yellowish, belly yellow, central part of caudal fin orange, dorsal and anal fins with reddish-orange stripe).

Parapercis annamalai sp. nov., a new sandperch from southwestern India (Family Pinguipedidiae)

A new sandperch is described from 3 specimens from off Parangipettai, southeastern India. It can be separated from its congeners in having a combination of dorsal-fin rays V, 21‒22; anal-fin rays I, 17‒18; pectoral-fin rays 17‒18; pored lateral-line scales 53‒54; median predorsal scales 7; transverse scale rows 4/13; gill rakers on 1st gill arch 15‒17; single row of stout teeth on vomer; no teeth on palatine; 3 pairs of enlarged canines at front of lower jaw; opercle uniformly dark brownish; blade-like patch on cheek, the patch orange dorsally and reddish ventrally, fading entirely in preservative; dorsal fins light grayish with 2 rows of spots; a whitish longitudinal band just above lateral axis of body; dorsal surface of body with 8 irregular blackish saddles and lower half with 7 reddish bars and black dots on upper half of each bar; lower half of anal fin reddish; caudal fin grayish with upper and lower portion darker and vertical rows of orange dots on yellowish bands. The new species is most similar to Parapercis somaliensis and Parapercis kentingensis morphologically and genetically, but differs in coloration, serrations on the opercle, and body proportions. The establishment of the new species is also supported by DNA barcoding analysis.

A new species of the codlet genus Bregmaceros from the western Pacific Ocean (Gadiformes: Bregmacerotidae)

Bregmaceros retrodorsalis sp. nov., a new codlet species is described based on specimens from shallow to deep waters off Japan and Melanesia. It differs from all congeners by having the origin of second dorsal-fin well posterior, above bases of 5th to 7th anal-fin rays and combination of the following characters: a pointed snout distinctly longer than eye diameter; upper lobe of opercle branched distally; body relatively slender, its depth 10.0‒13.0% SL; 13 principal caudal-fin rays (middle 11 branched); 52‒57 second dorsal-fin rays; 58‒63 anal-fin rays; 16‒18 transverse scale rows below dorsal-fin origin; 86‒93 longitudinal scale rows along body axis; vertebrae 55‒58; entire body evenly covered with melanophores, those on lateral sides forming regular longitudinal rows, one melanophores per scale; head and isthmus entirely, but loosely, covered with variably sized melanophores.

Controlling and leveraging small-scale information in tomographic galaxy–galaxy lensing

ABSTRACT The tangential shear signal receives contributions from physical scales in the galaxy–matter correlation function well below the transverse scale at which it is measured. Since small scales are difficult to model, this non-locality has generally required stringent scale cuts or new statistics for cosmological analyses. Using the fact that uncertainty in these contributions corresponds to an uncertainty in the enclosed projected mass around the lens, we provide an analytic marginalization scheme to account for this. Our approach enables the inclusion of measurements on smaller scales without requiring numerical sampling over extra free parameters. We extend the analytic marginalization formalism to retain cosmographic (shear-ratio) information from small-scale measurements that would otherwise be removed due to modelling uncertainties, again without requiring the addition of extra sampling parameters. We test the methodology using simulated likelihood analysis of a Dark Energy Survey Year 5-like galaxy–galaxy lensing and galaxy clustering datavector. We demonstrate that we can remove parameter biases due to the presence of an unmodelled one-halo contamination of the galaxy–galaxy lensing signal, and use the shear-ratio information on small scales to improve cosmological parameter constraints.

Channa brunnea, a new species of snakehead (Teleostei: Channidae) from West Bengal, India

Channa brunnea, a new species of snakehead fish lacking pelvic fins, from West Bengal, India, is distinguished from its pelvic fin-less congeners by possessing an uniform dark brown body, ochre to bright-orange blotches on the caudal fin, fewer dorsal and anal-fin rays (35–37 vs. 47–51 and 24 vs. 28–32, respectively), fewer vertebrae (43 vs. 45–57), and fewer lateral-line scales (43–46 vs. 51–63). Though Channa brunnea superficially resembles C. bleheri, it can be distinguished from the latter by possessing dark-brown oblique markings on the upper half of the body; transverse scale rows (4½–5½ vs. 3½); pre-anal scales (22–26 vs. 17–20); 2 rows of teeth in the fifth ceratobranchial, the outer row with 16 large conical teeth (vs. 3 rows of teeth, the outer row with 13 large conical teeth); dentary with 20 large, stout, conical teeth in the inner row (vs. 32 medium-sized conical teeth); and a Kimura’s two parameter (K2P) distance of 9.8–10.6%.

A new species of Dibamus Duméril & Bibron, 1839 (Squamata: Dibamidae) from Pulau Manado Tua, Northern Sulawesi, Indonesia

Based on three adult specimens, viz. two males and a female that form the type series, a new species of blind or worm-like lizards is described from Pulau (= Island) Manado Tua, a little volcanic island located off the northern tip of the Minahassa Peninsula of Sulawesi, Indonesia. Dibamus manadotuaensis sp. nov. differs from all congeneric species in the following unique combination of characters: maximum snout-vent length 135 mm; tail length up to 14.2 mm (i.e., 12–13% of SVL); labial and nasal sutures present and complete; four (three) postoculars; four to six scales on posterior edge of infralabial; 26–28 midbody scale rows; 30–33 transverse scale rows posterior to head; 25 transverse scale rows anterior to vent; 218–232 ventral scales; 39 subcaudal scales; relative size of frontal to frontonasal 0.68–0.73; relative size of interparietal to surrounding scales 0.67–1.43; 132–135 presacral and 21–24 postsacral vertebrae. Morphologically, D. manadotuaensis is most similar to D. celebensis, which occurs on mainland Sulawesi.Dibamus manadotuaensis sp. nov. represents the twenty-fourth species of Dibamus and the third species of this genus recorded from the Sulawesi region. At the same time, it is the only squamate species considered endemic for the islands of the Bunaken Marine National Park, to which Manado Tua belongs.

A new species of Rhinogobius (Pisces: Gobiidae), with analyses of its DNA barcode

The genus Rhinogobius Gill 1859 is widely distributed in fresh waters along the Western Pacific coast of tropical and temperate Asia. A new species, Rhinogobius maxillivirgatus, is described from Anhui Province in Eastern China. This species can be differentiated from all congeners by a combination of the following characters: up to 6 longitudinal brown to black stripes along the side of the body; pectoral-fin rays modally 14; predorsal scale series 5–9; lateral scale series 28–30; transverse scale series 6–7; branchiostegal membrane with about 20 red round spots in males; and 2 black oblique stripes parallel along the upper jaw on the anterior portion of the cheek. Analyzing sequences of cytochrome c oxidase subunit I revealed that the new species is closely related to, but distinct, from Rhinogobius wuyanlingensis.