Survey on performance of vertical slot and nature-like fishways at Angu hydropower station, Southwest China

To restore dam-blocked natural fish migratory passages,a growing number of artificial fishways have been built in water conservancy and hydropower projects in China.The Angu hydropower station involved diverse important fish habitats in the lower reaches of the Daduhe River in Southwest China.Therefore,a vertical slot fishway(VSF)and a nature-like fishway(NLF)were built near the backwater area of the reservoir to connect the upstream and downstream habitats.Hydrodynamic and aquatic ecological surveys were conducted after the completion of the project to estimate the fish passing effect of the two fishways.The results indicated that both fishways were in effective operation and could maintain the desired hydrodynamic conditions and be used by several local fish species.During the survey,149 fish from 15 species and 111 fish from 17 species were captured by the traps in the VSF and NLF,respectively,while 1263 fish from 27 species were found in the downstream area.Some species captured in the VSF were not found in the NLF,and vice versa,which implied the different preferences of fish.Meanwhile,3789 signals including 2099 upward ones and 1690 downward ones were monitored with an ultrasonic fish detector at the inlet of the VSF.These findings revealed the characteristics of fish species observed in and near the fishways and provided valuable insights into the different fish passing capabilities of VSFandNLF.

V-Shaped Monopole Antenna with Chichena Itzia Inspired Defected Ground Structure for UWB Applications

Due to rapid growth in wireless communication technology,higher bandwidth requirement for advance telecommunication systems,capable of operating on two or higher bands with higher channel capacities and minimum distortion losses is desired.In this paper,a compact Ultra-Wideband(UWB)V-shaped monopole antenna is presented.UWB response is achieved by modifying the ground plane with Chichen Itzia inspired rectangular staircase shape.The proposed V-shaped is designed by incorporating a rectangle,and an inverted isosceles triangle using FR4 substrate.The size of the antenna is 25 mm×26 mm×1.6 mm.The proposed V-shaped monopole antenna produces bandwidth response of 3 GHz Industrial,Scientific,and Medical(ISM),Worldwide Interoperability for Microwave Access(WiMAX),(IEEE 802.11/HIPERLAN band,5G sub 6 GHz)which with an additional square cut amplified the bandwidth response up to 8 GHz ranging from 3.1 GHz to 10.6 GHz attaining UWB defined by Federal Communications Commission(FCC)with a maximum gain of 3.83 dB.The antenna is designed in Ansys HFSS.Results for key performance parameters of the antenna are presented.The measured results are in good agreement with the simulated results.Due to flat gain,uniform group delay,omni directional radiation pattern characteristics and well-matched impedance,the proposed antenna is suitable for WiMAX,ISM and heterogeneous wireless systems.

RIGID-PLASTIC MECHANICAL MODEL FOR THE FORGING METHOD WITH HORIZONTAL V-SHAPED ANVIL

In order to decrease the anisotropy of mechanical properties, the rigid-plastic mechanical model for the forging method with horizontal V-shaped anvil is presented. The forging method, through the change of anvils shape, is able to control fibrous tissue direction, to improve the anisotropy of mechanical properties of axial forgings, to realize uniform forging. Therefore, the forging method can overcome the defect that conventional forging methods produce. The mechanism of the forging method with horizontal V-shaped anvil and the process of metal deformation are analyzed. The agreement of theoretical analysis with experimental study verifies the fact that the forging method with horizontal V-shaped anvil can control effectively the mechanical properties of axial forgings.

An experimental investigation of the fracturing behaviour of rock-like materials containing two V-shaped parallelogram flaws

The distribution characteristics and evolution law of rock mass fissures induced by mining are a key scientific issue in the study of deep rock mechanics.In this study,a series of uniaxial compression experiments was conducted on rock-like specimens containing double V-shaped prefabricated fissures at dip angles ofα=β=45°,α=45°<b=60°,α=β=60°,andα=60°<β=75°with a rock mechanics servocontrolled testing system.According to the experimental results,the effects of the dip angles of the double V-shaped prefabricated flaws with the same area on the mechanical parameters and fracturing process of the specimens were analysed in detail.Additionally,the crack initiation stress presented a nearly linear growth trend,which is generally similar to that of the crack peak stress with increasing flaw dip angle.By applying photographic monitoring to the crack initiation,propagation,coalescence,and failure modes in rock-like specimens,it was easily seen that the V-shaped flaw properties slightly influence the crack initiation positions but significantly influence the crack trajectories.The crack failure modes can be summarized into two distinct types.The study reported herein can provide a better understanding of the evolution of double V-shaped prefabricated fissures induced by coal mining.

Scattering of SH waves induced by a symmetrical V-shaped canyon: a unified analytical solution

This paper reports a series solution of wave functions for two-dimensional scattering and diffraction of plane SH waves induced by a symmetrical V-shaped canyon with different shape ratios. A half-space with a symmetrical V-shaped canyon is divided into two sub-regions by using a circular-arc auxiliary boundary. The two sub-regions are represented by global and local cylindrical coordinate systems, respectively. In each coordinate system, the wave field satisfying the Helmholtz equation is represented by the separation of variables method, in terms of the series of both Bessel functions and Hankel functions with unknown complex coefficients. Then, the two wave fields are described in the local coordinate system using the Graf addition theorem. Finally, the unknown coefficients are sought by satisfying the continuity conditions of the auxiliary boundary. To consider the phase characteristics of the wave scattering, a parametric analysis is carried out in the time domain by assuming an incident signal of the Ricker type. Surface and subsurface transient responses demonstrate the characteristics and mechanisms of wave propagating and scattering.

Seismic analysis of high-speed railway irregular bridge–track system considering V-shaped canyon effect

To explore the effect of canyon topography on the seismic response of railway irregular bridge-track system that crosses a V-shaped canyon, seismic ground motions of the horizontal site and V-shaped canyon site were simulated through theoretical analysis with 12 earthquake records selected from the Pacific Earthquake Engineering Research Center(PEER) Strong Ground Motion Database matching the site condition of the bridge.Nonlinear seismic response analyses of an existing 11-span irregular simply supported railway bridge-track system were performed under the simulated spatially varying ground motions. The effects of the V-shaped canyon topography on the peak ground acceleration at bridge foundations and seismic responses of the bridge-track system were analyzed. Comparisons between the results of horizontal and V-shaped canyon sites show that the top relative displacement between adjacent piers at the junction of the incident side and the back side of the V-shaped site is almost two times that of the horizontal site, which also determines the seismic response of the fastener. The maximum displacement of the fastener occurs in the V-shaped canyon site and is 1.4 times larger than that in the horizontal site. Neglecting the effect of V-shaped canyon leads to the inappropriate assessment of the maximum seismic response of the irregular high-speed railway bridge-track system. Moreover, engineers should focus on the girder end to the left or right of the two fasteners within the distance of track seismic damage.

New Methods of Determining the Mixed Mode Stress Intensity Factors for V-Shaped Notch

In this paper, on the basis of the stress field given by D.H.Chen, three new photoelastic methods are developed for determining the stress intensity factors K1 and K2 of V-shaped notch. Some photoelastic experiments are performed on a skew -symmetric 45° notch. Measurements of the coordinates components of r,θand fringe order N are made for progressively smaller fringes and used in the proposed methods to solve K1 and K2.Plots of apparent K vs. r/l are made and extrapolated to the notch tip to yield the true values of K1 and K2.The results obtained by the three methods are very close to each other. When the notch problem is simplified as a crack problem, the corresponding equation is identical to the one proposed by D.G. Smith, which shows that the proposed methods are applicable for both notch and crack problems.

Light-extraction efficiency and forward voltage in GaN-based light-emitting diodes with different patterns of V-shaped pits

We present a new method of making a textured V-pit surface for improving the light extraction efficiency in GaN- based light-emitting diodes and compare it with the usual low-temperature method for p-GaN V-pits. Three types of GaNbased light-emitting diodes （LEDs） with surface V-pits in different densities and regions were grown by metal-organic chemical vapor deposition. We achieved the highest output power and lowest forward voltage values with the p-InGaN V-pit LED. The V-pits enhanced the light output power values by 1.45 times the values of the conventional LED owing to an enhancement of the light scattering probability and an effective reduction of Mg-acceptor activation energy. Moreover, this new technique effectively solved the higher forward voltage problem of the usual V-pit LED.

Wave Pressure Acting on V-Shaped Floating Breakwater in Random Seas

Wave pressure on the wet surface of a V-shaped floating breakwater in random seas is investigated. Considering the diffraction effect, the unit velocity potential caused by the single regular waves around the breakwater is solved using the finite-depth Green function and boundary element method, in which the Green function is solved by integral method. The Response-Amplitude Operator(RAO) of wave pressure is acquired according to the Longuet-Higgins' wave model and the linear Bernoulli equation. Furthermore, the wave pressure's response spectrum is calculated according to the wave spectrum by discretizing the frequency domain. The wave pressure's characteristic value corresponding to certain cumulative probability is determined according to the Rayleigh distribution of wave heights. The numerical results and field test results are compared, which indicates that the wave pressure calculated in random seas agrees with that of field measurements. It is found that the bigger angle between legs will cause the bigger pressure response, while the increase in leg length does not influence the pressure significantly. The pressure at the side of head sea is larger than that of back waves. When the incident wave angle changes from 0? to 90?, the pressure at the side of back waves decreases clearly, while at the side of head sea, the situation is more complicated and there seems no obvious tendency. The concentration of wave energy around low frequency(long wavelength) will induce bigger wave pressure, and more attention should be paid to this situation for the structure safety.

Electronic and transport properties of V-shaped defect zigzag MoS_2 nanoribbons

Based on the nonequilibrium Green＇s function （NEGF） in combination with density functional theory （DFT） calcu- lations, we study the electronic structures and transport properties of zigzag MoS2 nanoribbons （ZMNRs） with V-shaped vacancy defects on the edge. The vacancy formation energy results show that the zigzag vacancy is easier to create on the edge of ZMNR than the armchair vacancy. Both of the defects can make the electronic band structures of ZMNRs change from metal to semiconductor. The calculations of electronic transport properties depict that the currents drop off clearly and rectification ratios increase in the defected systems. These effects would open up possibilities for their applications in novel nanoelectronic devices.

Construction of a 3D Co(Ⅱ) Framework Based on Two Types of V-shaped Bidentate Ligands

A three-dimensional （3D） coordination polymer {[Co（bdc）（dpb）]·H2O}n （1） was prepared by solvothermal reaction of 1,3-dipyridyl benzene （dpb） with deprotonated 1,3-benzene- dicarboxylate （H2bdc）, and was characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. It crystallizes in the monoclinic system, space group C2/c with α = 15.478（6）, b = 12.865（5）, c = 24.091（10） ？, β = 95.599（5）°, V = 4774（3） ？3, C24H18CoN2O5, Mr = 473.34, Dc = 1.267 g/cm3, F（000） = 1864.0, μ = 0.748 mm-1 and Z = 8. Each Co（II） ion links three bdc2- anions to form an infinitely 1D ladder-shaped chain containing binuclear [（COO）Co]2 cluster, and dpb links adjacent 1D chains to form a 3D pcu framework. In addition, the UV-vis of 1 was also studied.

Carrier transport via V-shaped pits in InGaN/GaN MQW solar cells

Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths for the photo-generated carriers. Due to the thin barrier thickness and low indium composition of the MQW on V-pit sidewall, the carriers entered the sidewall QWs can easily escape and contribute to the photocurrent. This forms a parallel escape route for the carries generated in the fiat quantum wells. As the barrier thickness of the fiat MQW increases, more carriers would transport via the V-pits. Furthermore, it is found that the V-pits may reduce the recombination losses of carriers due to their screening effect to the dislocations. These discoveries are not only helpful for understanding the carrier transport mechanism in the InGaN/GaN MQW, but also important in design of the structure of solar cells.

Study on a W-band modified V-shaped microstrip meander-line traveling-wave tube

The study on a miniaturized, low-voltage, wide-bandwidth, high-efficiency modified V-shaped microstrip meander-line slow-wave structure is presented. This structure is evolved from the original U-shaped microstrip meander-line slow-wave structure, combining the advantages of a traditional microstrip and a rectangular helix. In this paper, simulations of the electromagnetic characteristics and the beam-wave interaction of this structure are carried out. Our study shows that when the design voltage and the current of a sheet electron beam are set to be 4700 V and 100 mA, respectively, this miniature millimeter-wave power amplifier is capable of delivering 160-W output power with a corresponding gain of 37.3 dB and a maximum interaction efficiency of 34% at 97 GHz.

Stress release mechanism of deep bottom hole rock by ultra-high-pressure water jet slotting

To solve the problems of rock strength increase caused by high in-situ stress,the stress release method with rock slot in the bottom hole by an ultra-high-pressure water jet is proposed.The stress conditions of bottom hole rock,before and after slotting are analyzed and the stress release mechanism of slotting is clarified.The results show that the stress release by slotting is due to the coupling of three factors:the relief of horizontal stress,the stress concentration zone distancing away from the cutting face,and the increase of pore pressure caused by rock mass expansion;The stress concentration increases the effective stress of rock along the radial distance from O.6R to 1R(R is the radius of the well),and the presence of groove completely releases the stress,it also allows the stress concentration zone to be pushed away from the cutting face,while significantly lowering the value of stresses in the area the drilling bit acting,the maximum stress release efficiency can reach 80%.The effect of slotting characteristics on release efficiency is obvious when the groove location is near the borehole wall.With the increase of groove depth,the stress release efficiency is significantly increased,and the release range of effective stress is enlarged along the axial direction.Therefore,the stress release method and results of simulations in this paper have a guiding significance for best-improving rock-breaking efficiency and further understanding the technique.

Construction of a 2D Cd(II) Coordination Polymer Based on a V-shaped Bidentate Ligand

A two-dimensional（2D）coordination polymer{[Cd（bdc）（dpb）]·H2O}n（1）has been prepared by solvothermal reaction of 1,3-dipyridyl benzene（1,3-dpb）with deprotonated1,4-benzenedicarboxylate（H2bdc）,and was characterized by elemental analysis,IR spectroscopy,and X-ray single-crystal diffraction.It crystallizes in the monoclinic system,space group C2/c with a=15.1839（12）,b=20.7585（17）,c=7.2989（6）,β=117.3450（10）°,V=2043.5（3）3,C24H18N2O5Cd,Mr=526.81,Dc=1.712 g/cm3,F（000）=1056.0,μ=1.110 mm-1and Z=4.The neighboring Cd（II）ions link the bdc2-anions and 1,3-dpb to form an infinite 2D sheet,and such two2D sheets are interlocked with each other to form a 2D→2D sheet.Two groups of interlocked sheets are further linked together by intermolecularπ···πinteraction,giving a 3D supramolecular network.In addition,the fluorescence property of 1 was also studied.

Enhanced optical transmission by V-shaped nanoslit in metal film

In this paper, we reveal that the enhanced transmission through a perforated metal film can be further boosted up by a V-shaped nanoslit, which consists of two connected oblique slits. The maximum transmission at resonance can be enhanced significantly by 71.5% in comparison with the corresponding vertical slit with the same exit width. The value and position of transmission resonance peak strongly depend on the apex angle of the V-shaped slit. The optimum apex angle, at which the transmission is maximal, is sensitive to the slit width. Such phenomena can be well explained by a concrete picture in which the incident wave drives free electrons on the slit walls. Moreover, we also simply analyze the splitting of the transmission peak in the symmetry broken V-shaped slit, originating from the resonances of different parts of the V-shaped slit. We expect that our findings will be used to design the nanoscale light sources based on the metal nanoslit structures.

Effect of Mg-Preflow for p-AlGaN Electron Blocking Layer on the Electroluminescence of Green LEDs with V-Shaped Pits

In GaN-based green light-emitting diodes（LEDs） with and without Mg-preflow before the growth of p-Al GaN electron blocking layer（EBL） are investigated experimentally.A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment,effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures.However,unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature.Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions.Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to pGaN side through the（8-plane rather than the V-shape pits,which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN.Within this framework,apparently disparate experimental observations regarding electroluminescence properties,in this work,are well reconciled.

Joint Slot Scheduling and Power Allocation in Clustered Underwater Acoustic Sensor Networks

Dear Editor, This letter deals with the joint slot scheduling and power allocation in clustered underwater acoustic sensor networks(UASNs),based on the known clustering and routing information, to maximize the network's energy efficiency(EE). Based on the block coordinated decent(BCD) method, the formulated mixed-integer non-convex problem is alternatively optimized by leveraging the KuhnMunkres algorithm.

Effect of an Inclined Slots on the Power Consumption and Vortices Size in a Rushton Turbine Agitated Tank

Mechanical agitation in baffled vessels with turbines plays a vital role in achieving homogeneous fluid mixing and promoting various transfer operations.Therefore,designing vessels with optimal energy efficiency and flow dynamics is essential to enhance operational performance and eliminate flow perturbations.Hence,the present research focuses on a numerical investigation of the impact of inclined slots with different angles installed at the side-wall of a cylindrical vessel equipped with a Rushton turbine.This study explores power consumption and vortex size while considering various rotation directions of the impeller with different rotation speeds.The numerical simulations are conducted for Reynolds numbers ranging from 104 to 105,using the RANS k-εturbulence model to govern the flow inside the stirred vessel,accounting for mass and momentum balances.The results have shown that the installation of slots reduces power consumption and vortex size compared to conventional vessel configu-rations.Moreover,increasing the slot angle from 0 to 32.5°further reduces energy consumption and vortex size,especially with negative rotation speeds.On the other hand,increasing the Reynolds numbers leads to a decrease in power consumption and an increase in vortex size.The present research therefore proposes a design for con-structing Rushton-turbine stirred vessels offering optimal operation,characterized by reduced energy consumption and minimized vortex size.

Numerical Study on Mechanism of Blast-Induced Damage Considering Guiding Effect of Water Jet Slot

Damage is one of the most important characteristics of rock failure.Studying the damage mechanism of rock blasting under the guiding effect of the water jet slot and revealing the mechanism of controlled blasting with water jet assistance are crucial.In this study,a rock-like material was chosen as the research object for the calibration experiment of the numerical model.The numerical simulation models were then established by ANSYS/LS-DYNA,and the blastinduced damage mechanism under the guiding effect of the water jet slot was analyzed according to the blasting theory.The results indicated that explosive energy accumulates toward the direction of the slot as the guiding effect of the water jet slot,which allows the rock mass in the direction of the slot bear more damage.Meanwhile,the rock mass in the middle of the connection line between two blast-holes bears more damage under the combination of the effect of the explosion stress wave and guiding effect of water the jet slot on the detonation gas during double-slotted borehole blasting,which results in the formation of a gourd-shaped blast-induced damage area.In addition,the influence of the water jet slot on blast-induced damage varies depending on the blasting-process stage.