Bent Strip Research Articles

Strip-coupling circularly polarized antenna and its same-sense bidirectional array

A strip-coupling antenna and its bidirectional array with the same-sense circular polarization are introduced. By placing a bending strip above a narrow slot, circular polarization is obtained by combing the electric and magnetic currents. An array consisting of a three-element long slot and coupled strips on both sides of the slot is then constructed for bidirectional radiations with high gain. The fabricated antenna array shows wide bandwidth of 16.6% (2.16–2.55 GHz) for |S11| < −10 dB and 5.8% (2.33–2.47 GHz) for axial ratio <3 dB. In addition, same-sense bidirectional radiation patterns are also achieved with a high gain over 6.5 dBic.

Orientational Coherent Effects of High-Energy Particles in a LiNbO3 Crystal.

A bent lithium niobate strip was exposed to a 400-GeV/c proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (LiNbO3) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), LiNbO3 shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration (10(4) per cm2) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per cm2). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations.

The effects of forming parameters on the cold roll forming of channel section

Cold roll forming is one of the complex forming processes which quality of products is highly dependent on the process parameters. In this study the effect of some roll forming parameters of channel section are investigated on the edge longitudinal strain and bow defect of products. These parameters are bending angle increment, strip thickness, flange width of section, web width of section, friction in the roll and strip contact, speed of roll, and distance between the roll stands. It is important to consider these parameters for roll forming process design. Longitudinal bow is one of the main defects in the cold roll forming products which is affected by the bending angle increment. Experimental and numerical results of this study show that bow defect increase with the bending angle increasing. Results of present study show that peak of longitudinal strain in the edge of channel section increases with the bending angle increment and strip thickness increase, but decreases with the flange width, web width and distance between the roll stands increasing. Results show that friction in the roll-strip contact and speed of roll stand does not have any effect on the edge longitudinal strain.

Channeling efficiency dependence on bending radius and thermal vibration amplitude of the model for the channeling of high-energy particles in straight and bent crystals implemented in Geant4

Monte Carlo simulations of the interaction of particles with matter are usually done with downloadable toolkits such as Geant4. A model suitable for the implementation into Geant4 for the interaction of high-energy particles in straight and bent crystals was developed and implemented. The model relies on the continuum potential approximation. The variation of the Geant4 model for the description of the orientational effect as a function of the physical parameters for the calculation of the interplanar potential is presented. The simulations are capable of reproducing the variation of the efficiency of channeling as a function of the thermal vibration amplitude and the bending radius of a bent Si strip. The study can be useful for the simulation of the channeling effect in experiments at GeV/c energies.

Note: design and development of improved indirectly heated cathode based strip electron gun.

An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor the non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length.

Deflection of high energy protons by multiple volume reflections in a modified multi-strip silicon deflector

The effect of multiple volume reflections in one crystal was observed in each of several bent silicon strips for 400GeV/c protons. This considerably increased the particle deflections. Some particles were also deflected due to channeling in one of the subsequent strips. As a result, the incident beam was strongly spread because of opposite directions of the deflections. A modified multi-strip deflector produced by periodic grooves on the surface of a thick silicon plate was used for these measurements. This technique provides perfect mutual alignment between crystal strips. Such multi-strip deflector may be effective for collider beam halo collimation and a study is planned at the CERN SPS circulating beam.

Pulsed electrohydraulic springback calibration of parts stamped from advanced high strength steel

Electrohydraulic calibration (EHC) of springback is a novel method of removing springback from stamped sheet metal panels and is based upon the electro-hydraulic effect: a complex phenomenon related to the discharge of high voltage electrical current through a liquid. The EHC process involves clamping a stamped panel against a female die with the desired part shape and then applying several pulses of pressure onto and through the thickness of the sheet, in a process somewhat similar to conventional coining operations. However, in EHC the pressure is applied by a fluid and through the use of the electrohydraulic effect, and not with a matching hard tool as done in coining. In EHC, electrical energy is stored in a bank of capacitors and is converted into kinetic energy within the liquid by rapidly discharging the stored energy across a pair of electrodes submerged in a fluid. The objective of this paper is to describe the newly developed EHC process, to report the results of early proof-of-concept experiments, to present the results of more advanced experiments using a more industrial tool and actual part geometry, and to describe how numerical modeling techniques were used to optimize the design of the larger and more industrial tool. The developed concept of electrohydraulic stress relieving calibration is based upon clamping a stamped panel to the calibration die surface with the target shape and then applying pulses of pressure to eliminate internal stresses in the stamped panel. When a stamped blank is removed from a forming die, allowed to springback, and then clamped to a calibration die, the internal elastic stresses within the panel in such a configuration serve as a memory of the shape of the blank after springback, and it is these residual stresses that EH calibration is intended to remove from the panel. The developed concept of stress relieving calibration was initially validated by a simple experiment consisting of submerging a bent strip of aluminum into the fluid within an EH chamber, so that both the outer and inner surfaces of the strip (where the internal stresses from bending are located) were exposed to the fluid and the pressure pulse. This experiment served as an initial confirmation that impact with the tool is not necessary to achieve the calibration effect. The sheet metal materials used in this study, and for which springback was eliminated after forming, include DP 980 at 1.0mm and 1.4mm thick, and also DP600 at 1.0mm thick.

Mechanical behaviour of bending bucky-gel actuators and its representation

Bucky-gel actuators are ionic electromechanically active materials that bend in response to a low-voltage excitation. While bending actuators may offer new approaches in engineering solutions, the characterization of bending poses many challenges in comparison to conventional rotary motion. It is often desired to reduce the bending behaviour to a single parameter, which may lead to the loss of accuracy in modelling. A high-speed laser profilometer is utilized to characterize the bending response of different bucky-gel actuators at their full length and to critically compare the applicability of existing representation tools for bending. The best analytical representation of the bending of a bucky-gel actuator is found to be in the form of a power function. It is also observed that, along the length of the actuator, sections closer to the electrical input clamp exhibit back-relaxation (a common drawback for bending ionic actuators) already when the far end of the bending strip is still in forward motion.

Deflection of ultrahigh energy particle beams by repeated reflections in bent monocrystals

Bent silicon monocrystals are used today in the planar channeling mode for beam extraction and collimation at large accelerators. Volume reflection is more efficient than channeling, though it has a small deflection angle. A device for repeated deflection of a proton beam using a few bent silicon strips in the reflection mode is described in this paper. Sequential silicon strips on the surface of a thick plate are bent by internal stresses in the crystal material resulting from the Twyman effect. As shown by the Monte Carlo calculations, this method for deflecting the beam is optimal for the teraelectronvolt energy range.

Highly bent (110) Ge crystals for efficient steering of ultrarelativistic beams

Thanks to the effective electrostatic potential generated by the ordered atomic structure, bent crystals can efficiently deflect ultra relativistic charged beams by means of planar and axial channeling phenomena as well as of the recently discovered volume reflection effect. Most of the experimental knowledge about these phenomena has been gathered with Si crystals, but it has been recently demonstrated that the steering performance can be improved by using high quality Ge materials which have a larger atomic number. In this paper, we investigate channeling and volume reflection of 400 GeV protons from (110) lattice planes in highly bent Ge strips crystals. Both production and characterization of the strips are presented. Herein, the experimental results on deflection are compared with theoretical predictions, with previous published data and with the expected performances of Si crystals in similar experimental conditions.

A new design of indirectly heated cathode based strip type electron gun

A new design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The design issue addressed is the uniformity of temperature on the solid cathode using (a) a multi-segmented filament with variable height as the primary heat source and (b) trapezoidal shaped single long filament as the primary heat source. The proposed design in this paper is based on computer simulation and validated by extensive experimentations. The design emphasis is on maintaining uniform temperature on the solid cathode. The designed multi-segment filament and the single long filament provide a temperature uniformity on the solid cathode of about 250 K and 110 K, respectively. The better temperature uniformity inspite of the thermal expansion, in case of a single long filament tightly clamped at two ends, has been possible due to shaping of the single filament with a number of constituent sections such that the thermal expansion of different sections forming the actual filament takes care of not only the mechanical stability but also does not affect the emitting surface of the filament. Experiments show that the modified design achieves a one to one correspondence of the solid cathode length and the electron beam length emitted from the solid cathode.

Broadband Square Slot Circularly Polarized Antenna for Wimax and Wlan Applications

ABSTRACTA compact coplanar waveguide‐fed circularly polarized antenna with corner truncated ground for broadband wireless applications is presented. The antenna is designed to have a U‐shaped feedline in conjunction with an inverted L‐strip and a 45° bent strip to cover a fractional bandwidth of more than 103% (2.69–8.83 GHz) and fractional 3‐dB axial ratio bandwidth of 58.93% (2.92–5.36 GHz). Triangle shaped pieces are removed from top corners of the antenna to excite circular polarization. The antenna is manufactured and its parameters are measured. It has been shown that there is a good agreement between simulated and experimental results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2191–2195, 2013

Materials and technological aspects of gilded buckles from a North Eastern Medieval Italian context

This study concerns the archaeometric characterization of two artefacts from the medieval site of San Rocco (Castelfranco Veneto, Italy). Both of them belong to a larger set of metallic objects, some being part of tomb ornaments belonging to two very well distinct periods of frequentation of the site. Both items are buckles and they have been selected as representative of two very well-known and established typologies. The older one, at the end of the sixth—beginning of the seventh century AD, is made of silver, although relicts of gold have been found. A number of relevant counterparts of this item have been found in different sites of the Longobard Italy. The main body of the second artefact (second half of the fourteenth century AD) consists of a bent strip of a copper rich alloy, coated on one side with a nearly continuous, decorated, gold layer. This is a so-called lyre-buckle, with a widespread diffusion not only in Italian, but also North European contexts. From the results of the analyses carried out using low-vacuum scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry, information on manufacturing, gilding technology and materials have been obtained that will be an useful benchmark for the archaeometric characterization of similar items from selected collections. In this way, the already established typological affinity of these two classes of items will be extended to technological and materials aspects, also.

Isogeometric rotation-free bending-stabilized cables: Statics, dynamics, bending strips and coupling with shells

An isogeometric cable formulation is derived from a 3D continuum, where large-deformation kinematics and the St. Venant–Kirchhoff constitutive law are assumed. It is also assumed that the cable cross-sections remain circular, planar, and orthogonal to the cable middle curve during the deformation. The cable geometry representation reduces to a curve in 3D space, and, because only displacement degrees of freedom are employed, only membrane and bending effects are accounted for in the modeling. Torsion is neglected and bending is confined to an osculating plane of the curve. In the case structural loading and response are confined to a plane, the formulation is reduced to a 2D Euler–Bernoulli beam of finite thickness. Bending terms also stabilize the cable formulation in the presence of compressive forces. The resulting cable formulation is validated in the regime of linear and nonlinear statics, and nonlinear dynamics. The concept of bending strips is extended to the case of multiple cables, and cable-shell coupling is also investigated. The formulation is presented in sufficient mathematical detail for straightforward computer implementation.

Seismic performance of structures with pre-bent strips as a damper

In this study, a new type of structural damper in the form of braces based on pre-bent strips has been proposed. In designing the structures, parameters that support the safety of structures like base shear, acceleration and displacement are so important. To create safe conditions in structures some new technologies like vibration control and isolation have been considered. Vibration control has been studied by dissipation of the seismic energy which contains vibration isolator like dampers. In this paper a new kind of energy dissipative devices has been utilized and simulated by FEM in ABAQUS. According to other studies, investigation on experimental methods to prove some features of pre bent struts as column, one of which was about per bent strips as damper on brace but as experimental study which contains parametric investigation about pre bent strips with simple prototype was studied. In this paper, pre bent steel strips have been studied by FEM in various structural models under different dynamic loading. Some seismic responses of structures like base shear, acceleration and displacement have been investigated to prove the efficiency of this damper. In order to compare the results for models with damper and without damper and achieve accurate result and approximation, a rational approach to the performance of pre bent steel strips in structure with various spans and stories, the average responses of 3 different dynamic loading like Palm Sprins, Northridge, Fruili has been demonstrated which functioned as a bilinear inelastic stress-strain model for mild steel simulation in ABAQUS. Key words: Pre bent strips, response of structure, damper, energy-dissipation.

Trapped modes in finite quantum waveguides

The Laplace operator in infinite quantum waveguides (e.g., a bent strip or a twisted tube) often has a point-like eigenvalue below the essential spectrum that corresponds to a trapped eigenmode of finite L2 norm. We revisit this statement for resonators with long but finite branches that we call "finite waveguides". Although now there is no essential spectrum and all eigenfunctions have finite L2 norm, the trapping can be understood as an exponential decay of the eigenfunction inside the branches. We describe a general variational formalism for detecting trapped modes in such resonators. For finite waveguides with general cylindrical branches, we obtain a sufficient condition which determines the minimal length of branches for getting a trapped eigenmode. Varying the branch lengths may switch certain eigenmodes from non-trapped to trapped states. These concepts are illustrated for several typical waveguides (L-shape, bent strip, crossing of two stripes, etc.). We conclude that the well-established theory of trapping in infinite waveguides may be incomplete and require further development for being applied to microscopic quantum devices.

A simple method for studying internal migration of liquids in rubber

When swollen rubber sheets are bent, they swell more on the tension side and less on the compression side. When the bending constraint is removed, immediate recovery towards the flat state is only partial, followed by slow further recovery as the swelling liquid migrates internally. The rate of this slow recovery is directly related to the internal diffusion rate of the swelling liquid [1]. Experiments are described here for sharply bent sheets of lightly-crosslinked natural rubber, swollen with decane. The initial recovery when the bending constraint was removed was determined from the angle θ between the two arms of a bent strip. Slow further recovery was followed as liquid migrated internally and the strip straightened (θ increased towards 180°). The amount of “set” following release from bending was in reasonable accord with swelling theory and the time dependence of slow further recovery was consistent with the observed rate of diffusion of decane into rubber. Thus, recovery from “fold-back” bending appears to be a simple way of studying the internal mobility of absorbed liquids in polymers, provided that the amount of liquid absorbed depends on applied strain and that the polymer is reasonably elastic.

An Ultra-Wideband Antenna for Mobile Handset Applications

A printed open-ended slot antenna is designed for mobile phone application. The slot has a hybrid structure of a rectangle and a circle cut out of a 60mm×115mm ground plane, and fed by a microstrip line with a circular patch connected to a bent strip on the upper part of the patch. The proposed antenna provides a wide -6dB bandwidth covering 1.73-11GHz. It can be used in DCS1800, PCS1900, UMTS2000, TD-SCDMA, Bluetooth, LTE2.5GHz, WiMax, and UWB

Research on Divinable Characters of Rock Burst and Movement of Strata and Ground

Large-scale separation terrane in bending strip upside cranny strip is brought by un-consistency of overlying strata subsidence movement due to underground mining. Different characters of movement and deformation of overlying strata and ground include periodic caving of separation terrane interspace along with work face mining. Conglomerate rock layer movement is the main power fountain of rock burst on the basis of locale observation. And rock burst moves periodically adapt to movement of deep conglomerate rock layer which had similar characters with main roof. Practice indicates this method that forecasting and prediction using correlation information of movement of strata and ground is feasible and has reference meaning for similar stope.

Estimation of the bending rigidity and spontaneous curvature of fluid membranes in simulations

Several numerical methods for measuring the bending rigidity and the spontaneous curvature of fluid membranes are studied using two types of meshless membrane models. The bending rigidity is estimated from the thermal undulations of planar and tubular membranes and the axial force of tubular membranes. We found a large dependence of its estimate value from the thermal undulation analysis on the upper-cutoff frequency q(cut) of the least-squares fit. The inverse power-spectrum fit with an extrapolation to q(cut)→0 yields the smallest estimation error among the investigated methods. The spontaneous curvature is estimated from the axial force of tubular membranes and the average curvature of bent membrane strips. The results of these methods show good agreement with each other.