V-shaped Array Research Articles

The investigation of V-shaped arrays with non-uniform diameter cylinders for high performance hydrokinetic energy conversion

Harnessing hydrokinetic energy through vortex-induced vibration (VIV) is of great significance. The energy capture efficiency of VIV cylindrical arrays still has great potentials for making further progress. This paper investigates the energy conversion performance of cylinder cluster arrays with non-uniform diameter positioned at the upstream, midstream, and downstream locations, utilizing the downstream VIV enhancement effect. The cylinder arrays consist of five cylinders with non-uniform diameters of 2, 3, and 4 cm, resulting in a total of eight different V-shaped configuration scenarios. Through numerical simulation, it is found that the optimal flow velocity for maximizing the cylinder vibration amplitude is 0.8 m/s. In the condition of 0.8 m/s flow velocity, this study investigates the impact of cylinder diameter and the array arrangement on lift force, amplitude response, vortex shedding frequency, converted power, and efficiency. If the diameter of a cylinder is smaller than that of its upstream cylinder, cylinder experiences an enhanced amplitude, and the magnitude of this enhancement increases with the difference in diameters between the two cylinders. The blocking effect in the cylinder array occurs at a distance of two times the diameter. It has been observed that the small diameter cylinder demonstrates exceptional performance, achieving the highest converted power of 6.58 W (88% higher than the single cylinder) and the highest conversion efficiency of 68 % (75% higher than the single cylinder) in the convergent V-shaped array. The divergent V-shaped array achieves a maximum total converted power of 17.12 W (14% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders), while the convergent V-shaped array achieves a maximum total conversion efficiency of 44% (24% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders). This study presents an innovative perspective on the VIV enhancement effect in energy conversion, specifically focusing on multi-cylinder arrays with non-uniform diameters.

Transmission polarization converter based on V-shaped metasurface in terahertz region

Metasurfaces have attracted extensive attention due to their powerful functions, especially the manipulation of the polarization state of electromagnetic wave in many different areas, which have aroused a lot of research interest. In this work, a broadband transmission polarization converter based on V-shaped element array in terahertz band is designed and analyzed, which consists of grating-V-shaped metasurface-grating. The top layer and bottom layer form a pair of crossed gratings, and the middle layer is a V-shaped metasurface, and the layers are separated by polyimide. The structure parameters of the polarization converter are optimized by CST microwave studio, changes of which can result in narrow band or low transmission. Cross-polarization transmission rate and polarization conversion rate can reach more than 80% and 99%, respectively, in a frequency range from 0.35 THz to 1.11 THz. By studying the electric field distribution in the substrate under the V-shaped metasurface , it is found that the real part of the cross-polarization electric field between adjacent V-shaped metasurfaces presents similar values in a frequency range from 0.35 THz to 1.11 THz, resulting in high cross-polarization transmission. However, the real part of the cross-polarization electric field between adjacent V-shaped metasurfaces presents opposite values, resulting in low cross-polarization transmission at 1.40 THz. At the same time, the responses of the single layer structure of the V-shaped array and the bi-layer structure of the grating placed behind the V-shaped array to vertically incident x-polarized terahertz waves are investigated respectively, and the results show that the single-layer V-shaped array can convert part of linearly polarized incident light into cross-polarization light, however, in the bi-layer structure, Fabry-Perot cavity is formed between the V-shaped array and the grating, and the cross polarization transmission increases. This indicates that the V-shaped array provides the capability of polarization conversion, and the existence of the grating makes the F-P cavity inside the structure create the conditions for the back and forth reflection of terahertz waves. The combined action of the V-shaped metasurface and orthogonal grating results in a high polarization conversion rate.

On the Performance of L- and V-Shaped Arrays of Cardioid Microphones for Direction Finding

The L-shaped and V-shaped arrays of first-order cardioid microphones for direction finding are presented in this paper. A comparative study of the direction of arrival estimation performance of the arrays was carried out by analytically deriving, in closed-form, and comparing the Cramér-Rao bounds of an incident signal's direction-of-arrival (DoA) azimuth and polar angles for these arrays. The maximum-likelihood estimator is used to verify the correctness of derived bounds. This investigation reveals that for direction finding, the L-shaped array of cardioid microphones would generally outperform the V-shaped array of cardioid microphones in more sub-regions of the DoA polar-azimuth angle space. However, in regions where the V-shaped array of cardioid microphones outperforms the L-shaped array of cardioid microphone, the variance ratios are usually higher in favor of the V-shaped array.

基于V形孔阵结构薄膜的光学与磁光特性研究

基于V形孔阵结构薄膜的光学与磁光特性研究

An Optimum Volumetric Array Design Approach for Both Azimuth and Elevation Isotropic DOA Estimation

In this study, a new volumetric array design approach is presented for both azimuth and elevation isotropic direction of arrival (DOA) estimation. The presented method uses a minimum number of additional sensors to extend the given arrays to a volumetric array which has equal values for the Cramér-Rao lower bound (CRLB) for the entire azimuth and elevation angles. This approach can be applied to all arbitrary linear and planar arrays. Moreover, the design approach also takes into account the electromagnetic mutual coupling (MC) effect between the array elements and both the azimuth and elevation angular ambiguity uncertainties in an optimum manner while extending the array. It has been verified both analytically and with simulations that the designed volumetric arrays satisfy the two dimensional (2-D) isotropic DOA estimation conditions. The proposed approach is applied to Uniform Linear Arrays (ULA), Uniform Circular Arrays (UCA), V-shaped Arrays, and an arbitrary planar array to extend to optimum volumetric arrays with considerable results.

Grating ridged waveguide V‐shaped slot array antenna for SATCOM applications

This Letter presents a grating ridged waveguide V-shaped slot array antenna for satellite communication (SATCOM) receiving antenna applications. A special grating ridged waveguide, V-shaped slots and a matching section are applied in the proposed antenna design, so that the antenna provides an extra filtering response with a high radiation polarisation purity in a compact structure. For demonstration, a referential normal ridged waveguide V-shaped slot array antenna is designed and compared. The simulation results show that the proposed antenna not only operates well in the working frequencies (12.25–12.75 GHz) but also provides the antenna gains of lower than − 17.8 dB compared with those of the referential antenna in the interference frequencies (14.0–14.5 GHz).

A New Species of Nectar-Feeding Bat of the GenusHsunycteris(Phyllostomidae: Lonchophyllinae) from Northeastern Peru

ABSTRACT A new species of the nectarivorous bat genus Hsunycteris is described from lowland Amazonian forest in northeastern Peru. The new species, H. dashe, can be distinguished from other congeners by its larger size; V-shaped array of dermal chin papillae separated by a wide basal cleft; metacarpal V longer than metacarpal IV; broad rostrum; lateral margin of infraorbital foramen not projecting beyond rostral outline in dorsal view; well-developed sphenoidal crest; large outer upper incisors; weakly developed lingual cusp on P5; and well-developed, labially oriented M1 parastyle. A phylogenetic analysis of cytochrome-b sequence data indicates that H. dashe is sister to a clade that includes all other species of the genus including H. cadenai, H pattoni, and a paraphyletic H. thomasi. We provide a key based on craniodental and external characters of all four known species of Hsunycteris.

The Ocean Cleanup raises $22 million

The Ocean Cleanup, a Dutch nonprofit founded in 2013 by then-17-year-old Boyan Slat, has raised $22 million from Silicon Valley investors including Marc and Lynne Benioff and Peter Thiel. The Dutch chemical firm DSM is also a funder. The nonprofit developed a V-shaped array of long, floating booms designed to trap plastics and other debris carried by ocean currents. It plans to launch a pilot version in the Pacific Ocean later this year. Some marine scientists question how well the array will hold up under harsh ocean conditions.

Surface nanopattern formation due to current-induced homoepitaxial nanowire edge instability

Physical nanopatterning based on a precise control of macroscopic forcing is an essential tool of nanoscale science and technology. Using an externally applied electric field as the macroscopic force, we report here a computational study on the formation of surface nanopatterns consisting of single-layer homoepitaxial islands as a result of a morphological instability that can occur under edge electromigration conditions on the straight edge of a single-layer nanowire grown epitaxially on a crystalline substrate. Direct dynamical simulations based on a model that has been validated experimentally for the Ag/Ag system show that the current-induced nanowire edge instability causes the breakup of the nanowire and leads to the formation of uniformly distributed islands, arranged in linear or V-shaped arrays, which are uniformly sized with nanoscale dimensions. The simulation results are supported by linear stability theory and demonstrate that the geometrical features of the island patterns and the island sizes can be controlled precisely by controlling the electric field direction with respect to the nanowire axis and the electric field strength. Our findings have important implications for developing physical nanopatterning approaches toward enabling future nanofabrication technologies.

An Artificial Light-Harvesting Array Constructed from Multiple Bodipy Dyes

An artificial light-harvesting array, comprising 21 discrete chromophores arranged in a rational manner, has been synthesized and characterized fully. The design strategy follows a convergent approach that leads to a molecular-scale funnel, having an effective chromophore concentration of 0.6 M condensed into ca. 55 nm(3), able to direct the excitation energy to a focal point. A cascade of electronic energy-transfer steps occurs from the rim to the focal point, with the rate slowing down as the exciton moves toward its ultimate target. Situated midway along each branch of the V-shaped array, two chromophoric relays differ only slightly in terms of their excitation energies, and this situation facilitates reverse energy transfer. Thus, the excitation energy becomes spread around the array, a situation reminiscent of a giant holding pattern for the photon that can sample many different chromophores before being trapped by the terminal acceptor. At high photon flux under conditions of relatively slow off-load to a device, such as a solar cell, electronic energy transfer encounters one or more barriers that hinder forward progress of the exciton and thereby delays arrival of the second photon. Preliminary studies have addressed the ability of the array to function as a sensitizer for amorphous silicon solar cells.

Continuous Concentration and Separation of Microparticles Using Dielectrophoretic Force in a V-Shaped Electrode Array

Continuous Concentration and Separation of Microparticles Using Dielectrophoretic Force in a V-Shaped Electrode Array

2J1612 V字型電極アレイを用いた誘電泳動力による微粒子の連続的濃縮分離(計測、その他,第49回日本生物物理学会年会)

2J1612 V字型電極アレイを用いた誘電泳動力による微粒子の連続的濃縮分離(計測、その他,第49回日本生物物理学会年会)

Optimum Ambiguity-Free Directional and Omnidirectional Planar Antenna Arrays for DOA Estimation

This paper studies the antenna array geometry impact on both direction of arrival (DOA) estimation accuracy and array rank ambiguity. Some restrictions are imposed on the array geometry that guarantee first-order ambiguity-free arrays and, at the same time, reduce the cost of a global systematic optimization. The subsequently derived Cramer-Rao bound (CRB) on the DOA estimates shows to be attractive for numerical evaluation. Depending on whether the DOA estimation accuracy is desired to be uniform in all possible directions or is to be enhanced in a given aperture around some privileged direction, two optimization problems are formulated and solved by exhaustive search to compute the optimal array geometries. The obtained optimal arrays significantly outperform their circular counterparts and tend to have a form close to the V shape. We study in details V-shaped arrays and derive asymptotic performance measures that apply for large sized arrays where exhaustive search is unaffordable.

Design and fabrication of electrothermal nickel microgripper

In order to bring about industrialization in mi- cro-electro-mechanical systems(MEMS), the microgripper applied in microoperation and microassembly is developed. It is based on electrothermal principle. V-shaped beam array elec- trothermal microactuators is adoped to generate displacement for microgriper,and the microgripper is designed by topology optimization. Niclel is selected for fabricating the electrother- mal microgripper,and UV-LIGA process is used to fabricate the electrothermal microgripper. The optimized parameters for SU-8 mold are obtained through orthogonal experiment. All factors influenced process are discussed in detail and the re- solved methods are given. And an electrothermal nickel micro- griper with whole dimension in a millimeter magnitude, depth 30 μm and minimum character size 10 μm. Final dynamic per- formance of the nickel microgripper is experimented within 0~2.5 V range. The maximum tweezing displacements of up to 67 μm is recorded for this nickel microgripper, and the maximum clamping force can reach 0.8 N. This microgeipper can satisfy microoperation in MEMS.

Cramer-Rao bounds for antenna array design

We study the impact of the geometry of the (planar) antenna array on the accuracy of the estimated direction(s) of arrivals of an emitting source. We develop explicit Cramer-Rao bounds (CRBs) of the azimuth and elevation angles that show a simple structure. In particular, for a fixed elevation angle, the CRBs are cosine functions of the source azimuth, and so, regardless of the array geometry. The amplitude and extremes of these functions depend on the array geometry. Hence, the array configuration can be chosen in order to ensure a desired (an)isotropic behavior. To do so, we propose a pragmatic methodology that also takes into account the array ambiguity problem. The array design problem is simplified by limiting the array search within a family of V-shaped arrays that are advantageously characterized by a single parameter, the angle between the two branches. A performance measure is proposed, then analytically expressed, to assess the array directivity and gain with respect to the more standardly used uniform circular array.

Furrow microtubules and localized exocytosis in cleaving Xenopus laevis embryos.

In dividing Xenopus eggs, furrowing is accompanied by expansion of a new domain of plasma membrane in the cleavage plane. The source of the new membrane is known to include a store of oogenetically produced exocytotic vesicles, but the site where their exocytosis occurs has not been described. Previous work revealed a V-shaped array of microtubule bundles at the base of advancing furrows. Cold shock or exposure to nocodazole halted expansion of the new membrane domain, which suggests that these microtubules are involved in the localized exocytosis. In the present report, scanning electron microscopy revealed collections of pits or craters, up to approximately 1.5 micro m in diameter. These pits are evidently fusion pores at sites of recent exocytosis, clustered in the immediate vicinity of the deepening furrow base and therefore near the furrow microtubules. Confocal microscopy near the furrow base of live embryos labeled with the membrane dye FM1-43 captured time-lapse sequences of individual exocytotic events in which irregular patches of approximately 20 micro m(2) of unlabeled membrane abruptly displaced pre-existing FM1-43-labeled surface. In some cases, stable fusion pores, approximately 2 micro m in diameter, were seen at the surface for up to several minutes before suddenly delivering patches of unlabeled membrane. To test whether the presence of furrow microtubule bundles near the surface plays a role in directing or concentrating this localized exocytosis, membrane expansion was examined in embryos exposed to D(2)O to induce formation of microtubule monasters randomly under the surface. D(2)O treatment resulted in a rapid, uniform expansion of the egg surface via random, ectopic exocytosis of vesicles. This D(2)O-induced membrane expansion was completely blocked with nocodazole, indicating that the ectopic exocytosis was microtubule-dependent. Results indicate that exocytotic vesicles are present throughout the egg subcortex, and that the presence of microtubules near the surface is sufficient to mobilize them for exocytosis at the end of the cell cycle.

Role of Myosin VI in the Differentiation of Cochlear Hair Cells

The mouse mutant Snell's waltzer (sv) has an intragenic deletion of the Myo6 gene, which encodes the unconventional myosin molecule myosin VI (K. B. Avraham et al., 1995, Nat. Genet. 11, 369–375). Snell's waltzer mutants exhibit behavioural abnormalities suggestive of an inner ear defect, including lack of responsiveness to sound, hyperactivity, head tossing, and circling. We have investigated the effects of a lack of myosin VI on the development of the sensory hair cells of the cochlea in these mutants. In normal mice, the hair cells sprout microvilli on their upper surface, and some of these grow to form a crescent or V-shaped array of modified microvilli, the stereocilia. In the mutants, early stages of stereocilia development appear to proceed normally because at birth many stereocilia bundles have a normal appearance, but in places there are signs of disorganisation of the bundles. Over the next few days, the stereocilia become progressively more disorganised and fuse together. Practically all hair cells show fused stereocilia by 3 days after birth, and there is extensive stereocilia fusion by 7 days. By 20 days, giant stereocilia are observed on top of the hair cells. At 1 and 3 days after birth, hair cells of mutants and controls take up the membrane dye FM1-43, suggesting that endocytosis occurs in mutant hair cells. One possible model for the fusion is that myosin VI may be involved in anchoring the apical hair cell membrane to the underlying actin-rich cuticular plate, and in the absence of normal myosin VI this apical membrane will tend to pull up between stereocilia, leading to fusion.

Formation of the primitive myo- and endocardial tubes in the chicken embryo

The morphogenesis of the mesenchymal cardiogenic plate, the formation of the bilateral heart primordia leading to the primitive heart tube, and also the genesis of the endocardial tube, have been studied in 1 to 13 somite chick embryos. The morphological data were compared with those obtained in electrophysiological studies of the development of the cardiac action potentials (Fujii et al., 1981a). The primordia of the consecutive heart chambers are definable before the appearance of myosin-type filaments and primitive Z bands, which occurs simulataneously with the first spontaneous action potentials in the 7 somite embryo. At the 8 to 9 somite stage, fusion of the lateral heart primordia proceeds to include the outflow tract and atrial primordia; the pacemaker site migrates into the atrial wall and subsequently into the sinus venosus, this process occurring simultaneously with the progressive transformation of mesenchymal cells into cardiomyocytes. Proendocardial cells are first detected detaching individually or in small groups from the cardiogenic plate to become attached by fine filamentous material to the basal surface of the foregut endoderm, on which they “stream”, establishing an anastomosing V-shaped array with respect to the ventral mesoderm. This array coalesces first at the atrioventricular groove to form double endocardial tubes, which in turn fuse into a single tube with the establishment of the single myocardial tube. Evidence suggests a key role for the ventral mesocardium and its transient attachment zone with the foregut, in providing a line focus for migration of proendocardial cells and primitive capillaries from the lateral splanchnic mesoderm, from which they derive.