Metal Screen Research Articles

Cooperation in rats playing the iterated Prisoner's Dilemma game

Humans and animals show cooperative behaviour, but our understanding of cooperation among unrelated laboratory animals is limited. A classic test of cooperation is the iterated Prisoner's Dilemma (IPD) game, where two players receive varying payoffs for cooperation or defection in repeated trials. To determine whether unrelated rats cooperate in the IPD, we tested pairs of rats making operant responses to earn food reward in 25 trials/day. The operant chamber was bisected by a metal screen with a retractable lever and pellet dispenser on each side. When levers extended, rats had 2 s to respond. Mutual cooperation (Reward) delivered three pellets each, mutual defection (Punishment) provided no pellets, and unilateral defection (Temptation) gave five pellets to the defector, while the partner (Sucker) received none. In eight pairs of males (RM-) and females (RF-), cooperation was defined by withholding a response. In seven pairs of RM+ males, cooperation was defined by responding on the lever. In males, food restriction significantly inhibited both cooperation and pellets received. There was no effect of dominance status. Males and females made similar numbers of responses under ad libitum feeding. However, neither food restriction nor dominance status affected responses in females. Rats were subsequently tested for reciprocity in 24 alternating trials/day. A response on the lever within 5 s delivered three pellets to the partner. Females made significantly more responses for their cage-mate than males. Responses within pairs were significantly correlated for males, but not for females. For both sexes, responses declined significantly when paired with an unfamiliar partner who never reciprocated ('bad stooge'). These results demonstrate that rats working for food show cooperation in IPD and direct reciprocity. Their responses depend on food availability and responses of their partner.

Catenary nanostructures as compact Bessel beam generators

Non-diffracting Bessel beams, including zero-order and high-order Bessel Beams which carry orbital angular momentum (OAM), enable a variety of important applications in optical micromanipulation, sub-diffraction imaging, high speed photonics/quantum communication, etc. The commonly used ways to create Bessel beams, including an axicon or a digital hologram written to a spatial light modulator (SLM), have great challenges to operate at the nanoscale. Here we theoretically design and experimentally demonstrate one kind of planar Bessel beam generators based on metasurfaces with analytical structures perforated in ultra-thin metallic screens. Continuous phase modulation between 0 to 2π is realized with a single element. In addition, due to the dispersionless phase shift stemming from spin-orbit interaction, the proposed device can work in a wide wavelength range. The results may find applications in future optical communication, nanofabrication and super-resolution imaging, etc.

Experimental Evidence of a Strong Image Force between Highly Charged Electrosprayed Molecular Ions and a Metal Screen

ABSTRACTWe investigated the capturing mechanisms of highly charged macromolecular ions of polyethylene glycol electrosprayed onto a metal screen. Our experiments assessed how the charge state, size of the macromolecular ions, and filtration velocity affected the penetration of the ions through the metal screen. The single fiber efficiencies were plotted as functions of the Peclet number and image force parameter. Highly charged molecular ions had much higher collection efficiencies than neutralized macromolecules, suggesting the presence of a strong image force between the ions and metal surface. The single fiber efficiency by image force was proportional to the square root of an image force parameter predicted by theory. When using the prefactor of 9.7 proposed by Alonso et al. (2007), we found fair agreement between the experimental data and theoretical predictions on the collection efficiency of highly charged molecular ions with mobility diameters from 2.6 to 4.8 nm and numbers of electrical charges from 2 to 7. The experimental evidence from our study reveals that image force contributes strongly to the collection of multicharged macromolecular ions by a metal wire screen.

Electrolytic Removal of Cadmium, Lead and Copper from Wastewater

The respective compounds of copper, cadmium and lead, owing to their strong toxic potential, as a result of industrial effluent, have left a trail of contamination in humans and the environment. This paper aimed to study the electrode position on the removal of aqueous solutions of cadmium, lead and copper, using an electrolytic cell with a metallic screen cathode of carbon steel and platinum anode. Removal efficiencies were obtained by analysis of the solutions before and after treatment, using the methodology of cathodic-stripping voltammetry with a mercury drop electrode to quantify the concentrations of Cd2+, Pb22+ and Cu2+. Removal efficiencies were obtained of 94.07% for cadmium, 94.71% for lead and 96.19% for copper, demonstrating that electrolytic removal is an effective technique for the removal of these metals from simulated industrial wastewater.

All-dielectric reciprocal bianisotropic nanoparticles

The study of high-index dielectric nanoparticles currently attracts a lot of attention. They do not suffer from absorption but promise to provide control on the properties of light comparable to plasmonic nanoparticles. To further advance the field, it is important to identify versatile dielectric nanoparticles with unconventional properties. Here, we show that breaking the symmetry of an all-dielectric nanoparticle leads to a geometrically tunable magneto-electric coupling, i.e. an omega-type bianisotropy. The suggested nanoparticle exhibits different backscatterings and, as an interesting consequence, different optical scattering forces for opposite illumination directions. An array of such nanoparticles provides different reflection phases when illuminated from opposite directions. With a proper geometrical tuning, this bianisotropic nanoparticle is capable of providing a $2\pi$ phase change in the reflection spectrum while possessing a rather large and constant amplitude. This allows creating reflectarrays with near-perfect transmission out of the resonance band due to the absence of an usually employed metallic screen.

Nonreciprocal Horn Antennas Using Angular Momentum-Biased Metamaterial Inclusions

In this work, we apply angular momentum-biased metamaterials to break the intrinsic reciprocity of antenna systems, with potential applications to satellite communications. We focus our attention on a conical horn antenna exhibiting nonreciprocal response for left-handed and right-handed circularly polarized fields. A metallic screen with an annular aperture is placed between the feeding waveguide and the horn. This inclusion is loaded with modulated capacitors to achieve a nonreciprocal transmittance for circularly polarized fields impinging from opposite sides. We present the analysis of the nonreciprocal annular inclusion and explain its nonreciprocal response, obtained through proper spatiotemporal modulation, with the help of an equivalent transmission-line representation. A possible practical implementation of the modulation circuit based on band-pass and band-stop filters is also discussed. The electrical and radiating performance of the conical horn is numerically evaluated, showing the ability of the proposed antenna to filter signals with same polarization in two separate bands, e.g., uplink and downlink bands of a satellite link, depending on the propagation direction of the signal. These results may pave the way to several interesting applications of nonreciprocal radiators in satellite and radar systems.

ANALYSIS OF THE PROCESSES IN AN INDUCTOR SYSTEM WITH AN ATTRACTING SCREEN EXCITED BY THE EXTERNAL CIRCULAR SOLENOID

Introduction. Developments in the field of magnetic-pulse treatment of metals (MPTM) are increasingly used in the modern technologies of production and repair of the aviation, automotive and other machinery, as they are environmentally friendly and energy-efficient in comparison with classical approaches. One of the main components of the device MPTM is a tool – inductor or the inductor system with an attractive screen (ISAS). The calculated dependences to calculate the inductor system with an attractive screen were taken from previous works. The ratios were obtained for the low-frequency mode of the excited fields, when is place their significant penetration through a thin-walled metal screen and a deformed workpiece. As it was shown earlier this mode is the most efficient from point of view of a force action on the object of a processing. Purpose . The theoretical analysis of the spatial-temporal distributions of the induced currents and forces of an attraction in the inductor system with an attractive screen excited by a flat circular solenoid located on the outside of the auxiliary screen. Methodology . The calculations are shown that the induced currents both in the screen and the workpiece are unidirectional and their interaction, in accordance with the law of Ampere determines the amplitudes of excited forces of attraction. Let’s note the effective validity of the considered inductor system excited by an external circular solenoid. With sufficient simplicity of the design take place rather high values of the developed forces of attraction and their averages. Results . Physically, a higher power efficiency of the system with an «external» coil in comparison with a system where coil is located in the internal cavity, can be accounted for lade of «failure» in the radial distribution of the excited forces. This «failure» in the design with a coil between the sheet metal is caused by its screening action against the forces of attraction between the induced currents. Practical value. It is shown that the inductor system with an attractive screen when it is excited by outer circular solenoid with a current of 50 kA ~ provides attractive power rates to about 1400 N on an area of sheet metal ~ 0.004 m 2 . The sufficiently high efficiency of the proposed options of an inductor system allows us to recommend it as a tool of the external straightening dents in the bodycar surfaces of vehicles.

Simulation of a plasma antenna by PIC method

The numerical model of a plasma asymmetric dipole antenna is studied in this paper. This antenna consists of a dielectric tube with discharge plasma and a metal screen. The plasma in the tube is simulated by Particle-in-cell (PIC) method. The spectra of the electromagnetic field components were studied in the plasma and the near antenna field for various antenna operating modes. The operating modes depend on a ratio of a plasma frequency and a frequency of radiated electromagnetic wave. Langmuir frequency component was found in spectra within plasma for all antenna operating modes. The amplitude of this spectral component is greater than the amplitude of the component at the carrier frequency for nonradiative and non-linear modes. The biggest amplitude of the radiated signal spectrum is at the carrier frequency in the linear mode.

Mathematical modeling of nonstationary processes of heat and mass transfer in a rectangular cable channel

This work is devoted to solving the problem of heat and mass transfer in a rectangular cable channel laid in the earth mass, taking into account the electric and magnetic dynamics processes in the metal elements of the power cable. The current load of power cables depends on the temperature field in the cable construction, which in turn the following factors influence: the conditions of heat transfer, thermal characteristics of the materials used, the induced currents in a metal screen of power cables, etc. The proposed mathematical model of the processes of complex heat and mass transfer is based on the laws of conservation of mass, momentum, and energy. For the electrodynamics problem, equations of current density and a magnetic potential vector based on Maxwell equations are used. The problem was solved numerically under conditions of natural convection with taking into account the radiant energy by the finite element method in the Ansys Fluent software package. As a result, the power of heat losses in the metal structural elements of the power cable and the velocity and temperature fields in the cable channel were calculated. The temperature fields in the cable channel are presented and analyzed depending on the location of power cables. The different operating modes of the cable line are discussed. To analyze the heat processes in the cable channel, the nonstationary problem defining the heating time of cable lines to the limit values is solved. The heating curves of the cable lines operating in unsteady mode are obtained. The maximum operating time of the cable line in an overload and short circuit is determined.

Control of the domain structure and stray fields of MEMS magnetic elements by electron microscopy

Experimental research into the possibilities of visualizing the distribution of magnetic stray fields near the surface of uniaxial highly anisotropic magnets and working fields of permanent thin-film magnets for microelectromechanical systems is performed. The possibility of visualizing the magnetic-field distribution near the basal and prismatic planes of uniaxial crystals caused by 180-degree-type domain structure is demonstrated. A method of the segmentation of magnetic contrast by removing the topographic component from the full image using a movable metallic screen is proposed.

New approach for extraordinary transmission through an array of subwavelength apertures using thin ENNZ metamaterial liners.

Extraordinary transmission (ET) through a periodic array of subwavelength apertures on a perfect metallic screen has been studied extensively in recent years, and has largely been attributed to diffraction effects, for which the periodicity of the apertures, rather than their dimensions, dominates the response. The transmission properties of the apertures at resonance, on the other hand, are not typically considered 'extraordinary' because they may be explained using more conventional aperture-theoretical mechanisms. This work describes a novel approach for achieving ET in which subwavelength apertures are made to resonate by lining them using thin, epsilon-negative and near-zero (ENNZ) metamaterials. The use of ENNZ metamaterials has recently proven successful in miniaturizing circular waveguides by strongly reducing their natural cutoff frequencies, and the theory is adapted here for the design of subwavelength apertures in a metallic screen. We present simulations and proof-of-concept measurements at microwave frequencies that demonstrate ET for apertures measuring one-quarter of a wavelength in diameter and suggest the potential for even more dramatic miniaturization simply by engineering the ENNZ metamaterial dispersion. The results exhibit a fano-like profile whose frequency varies with the properties of the metamaterial liner, but is independent of period. It is suggested that similar behaviour can be obtained at optical frequencies, where ENNZ metamaterials may be realized using appropriately arranged chains of plasmonic nanoparticles.

Imaging Functions of Quasi-Periodic Nanohole Array as an Ultra-Thin Planar Optical Lens

In this paper, the lensing functions and imaging abilities of a quasi-periodic nanohole array in a metal screen have been theoretically investigated and demonstrated. Such an optical binary mask with nanoholes designed in an aperiodic arrangement can function as an ultra-thin planar optical lens, imaging complex structures composed of multiple light sources at tens of wavelengths away from the lens surface. Via resolving two adjacent testing objects at different separations, the effective numerical aperture (N.A.) and the effective imaging area of the planar optical lens can be evaluated, mimicking the imaging function of a conventional lens with high N.A. Furthermore, by using the quasi-periodic nanohole array as an ultra-thin planar optical lens, important applications such as X-ray imaging and nano-optical circuits may be found in circumstances where conventional optical lenses cannot readily be applied.

Frequency-Independent Response of Self-Complementary Checkerboard Screens.

This research resolves a long-standing problem on the electromagnetic response of self-complementary metallic screens with checkerboardlike geometry. Although Babinet's principle implies that they show a frequency-independent response, this unusual characteristic has not been observed yet due to the singularities of the metallic point contacts in the checkerboard geometry. We overcome this difficulty by replacing the point contacts with resistive sheets. The proposed structure is prepared and characterized by terahertz time-domain spectroscopy. It is experimentally confirmed that the resistive checkerboard structures exhibit a flat transmission spectrum over 0.1-1.1THz. It is also demonstrated that self-complementarity can eliminate even the frequency-dependent transmission characteristics of resonant metamaterials.

Modulated heat transfer tube with short conical-mesh inserts: A linking from microflow to macroflow

This paper creates new method that uses microflows through mesh pores to modulate flow and temperature fields. Modulated heat transfer tube (MHTT) was constructed by suspending consecutive conical-mesh inserts in a tube. Because there are too many 3D mesh pores (10–100μm size) for a conical mesh insert, numerical simulations in laminar flow regime were performed by an 3D to 2D conversion of mesh pores applying equal equivalent diameter criterion and total flow area criterion of mesh pores. The multiscale grid generation linked micron scale of mesh pores and macroscale of the tube. Covering the present data ranges, MHTT had Nusselt numbers which are 1.4–4.1 times of that in a bare tube, PEC (performance evaluation criterion) was up to 2.2, demonstrating excellent heat transfer enhancement at low flow rate pumping cost. The perfect MHTT performance comes from the distinct flow field: an attached hydraulic boundary layer having large velocity and its gradient near the tube wall, a weak circulating flow region upstream of the mesh insert and a weakly positive flow region downstream of the mesh insert. A thin thermal boundary layer on the tube wall was reached to enhance heat transfer. The periodic unit length S and diameter of the conical mesh insert δ were optimized. The varied slopes of Nu versus Re were found and explained while increasing Re. There are best matches of PPI (pores per inch) and Re (Reynolds number). Low PPI mesh insert was suggested at low Re, high PPI mesh insert deformed streamlines to deviate from the perfect flow and temperature fields. Meanwhile, high PPI mesh insert had better performance at high Re. Low PPI mesh insert had good performance, which can be further improved by raising PPI. Because metallic mesh screen is commercialized and cheap, MHTT has wide potential engineering applications.

Electromagnetic wave transmission through a subwavelength nano-hole in a two-dimensional plasmonic layer.

An integral equation is formulated to describe electromagnetic wave transmission through a subwavelength nano-hole in a thin plasmonic sheet in terms of the dyadic Green's function for the associated Helmholtz problem. Taking the subwavelength radius of the nano-hole to be the smallest length of the system, we have obtained an exact solution of the integral equation for the dyadic Green's function analytically and in closed form. This dyadic Green's function is then employed in the numerical analysis of electromagnetic wave transmission through the nano-hole for normal incidence of the incoming wave train. The electromagnetic transmission involves two distinct contributions; one emanates from the nano-hole, and the other is directly transmitted through the thin plasmonic layer itself (which would not occur in the case of a perfect metal screen). The transmitted radiation exhibits interference fringes in the vicinity of the nano-hole, and they tend to flatten as a function of increasing lateral separation from the hole, reaching the uniform value of transmission through the sheet alone at large separations.

Analytical Multimodal Network Approach for 2-D Arrays of Planar Patches/Apertures Embedded in a Layered Medium

A fully analytical multimodal equivalent circuit is presented for the modeling of the scattering of an obliquely incident plane wave by a two-dimensional (2-D) periodic array of metallic patches (or apertures in a metallic screen) embedded in a layered medium. The topology of the equivalent network is rigorously derived in the analysis and all the network parameters are given in closed form. In contrast with the previously reported explicit circuit models, the proposed approach accounts for dynamical effects over a very wide frequency range, which enables the application of the model to a great variety of situations. The key advantages of the reported multimodal network representation are its analytical nature, its extremely low-computational cost and that the physical phenomena involved in the scattering can be easily understood in terms of transmission line and lumped circuital reasonings.

Diffusion deposition of submicron aerosol particles in screen filters

The deposition of submicron aerosol particles on metal screens has been studied at small Reynolds numbers. The obtained experimental data have been compared with theoretical estimates of the deposition of Brownian particles in a model fibrous filter with allowance for a finite particle size and the existence of a Knudsen boundary layer on a wire surface, with the thickness of the layer being, under normal conditions, comparable with particle sizes. The possibility of using screen diffusion batteries for determining the average diffusion coefficient of submicron particles and as test filters has been discussed.

Matching and radiation characteristics of a phased array based on quasi-Yagi planar antennas with an additional screen

This article presents the results of numerical investigation and optimization of matching and radiation characteristics for a single planar quasi-Yagi antenna and for a planar phased antenna array (PAA) with size 11×11 elements, which is designed based on these radiators. The research has been performed utilizing the finite difference time domain technique. The calculations have taken into account the presence of an additional metal screen behind the radiating curtain and the feeding of each array’s element via the coaxial-to-microstrip transition, that has made the model of an array as close as possible to the real PAA design and to its performance under real conditions. The levels of electromagnetic coupling between adjacent array elements have been investigated, the variations of operating characteristics of elements in its structure have been demonstrated in the case of in-phase excitation and in the scanning mode. It has been found that the possible scanning sector of this screened PAA falls within the range ±45° for the reflection coefficient of any array’s element, which is less than −10 dB in the frequency range not less than 10%, and for the central element of an array the corresponding operation frequency range exceeds 30% for the scanning in E-plane and it is larger than 17% for the scanning in H-plane.

Multiband shorted monopole antenna for handset applications

A compact, multiband, shorted monopole antenna is presented for ultraslim mobile handsets. The proposed antenna is formed by a simple structure of three radiating strips of different length namely, λ/4 C–shaped radiating strip, 3λ/8 meandered line radiating strip, and a λ/4 shorting strip. Which results in proposed antenna that covers GSM850/900/1800/1900/UMTS/Wi-Fi/LTE2300/2500/WiMAX bands with respect to −6 dB impedance bandwidth. The measured peak realized gain is observed between 1.2 and 4.2 dBi while simulated total radiation efficiency is between 60 to 93% in the operating bands. The proposed antenna is investigated in free space as well as in actual mobile environment consisting of mobile plastic housing along with large metallic display screen and battery. Specific absorption rate computation is also carried out on human head phantom in vicinity of the proposed antenna and obtained well below the specified limit. The parametric analysis is also carried out to understand the effect of the shape parameters of the antenna. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1459–1466, 2015

Sound energy harvesting using an acoustic grating

A sound energy harvester with an acoustic grating and a piezoelectric plate has been demonstrated. The acoustic grating consists of a metal slit grating and a thin flat metal screen. The metal slit grating can squeeze an incident acoustic wave into the air gap between the slit grating and metal screen, thus giving rise to high sound pressure and causing the metal screen to vibrate. Using the direct piezoelectric effect, the “squeezed” acoustic energy is harvested efficiently by a piezoelectric component that is mounted on the back of the metal screen.