Symmetric Loop Research Articles

Research on zero-sum magnetic field integral technology of optical current sensors

An architecture based on the Faraday effect to minimize the crosstalk effect in optical current sensors (OCSs) is proposed. It was demonstrated that the magnetic field integral along a discrete loop can meet Ampere’s law under certain conditions, and the mathematical model of zero-sum points was given. Based on it, a zero-sum OCS (ZOCS) was proposed, which consists of several OCSs forming a symmetrical discrete loop. Ideally, the currents that flow outside the ZOCS do not contribute to the measurement of the currents inside it. The experimental results showed that the magnetic crosstalk-induced errors of ZOCS were less than 0.2%, and the influence of external current was reduced one order compared with conventional OCSs.

Low cycle fatigue behavior under asymmetric loading of two AZ31B magnesium alloys with different microstructures and textures

Abstract Low cycle fatigue experiments under asymmetric loading on differently prepared AZ31 alloys show that the alloy with fine grains exhibits higher stress amplitudes than those of the alloy with coarse grains at the same strain amplitudes. The elastic strain in the tensile process is higher than that in the compressive process for both alloys, but the difference is much smaller for the alloy with fine grains. The microstructure with fine grains exhibits a symmetrical hysteresis loop and cyclic strain softening at the early fatigue stage at low strain amplitude.

Bulk Synthesis of Monodisperse Magnetic FeNi<SUB>3</SUB> Nanopowders by Flow Levitation Method

In this work, a novel bulk synthesis method for monodisperse FeNi3 nanoparticles was developed by flow levitation method (FL). The Fe and Ni vapours ascending from the high temperature levitated droplet was condensed by cryogenic Ar gas under atmospheric pressure. X-ray diffraction was used to identify and characterize the crystal phase of prepared powders exhibiting a FeNi3 phase. The morphology and size of nanopowders were observed by transmission electron microscopy (TEM). The chemical composition of the nanoparticles was determined with energy dispersive spectrometer (EDS). The results indicated that the FeNi3 permalloy powders are nearly spherical-shaped with diameter about 50-200 nm. Measurement of the magnetic property of nanopowders by a superconducting quantum interference device (SQUID, Quantum Design MPMS-7) showed a symmetric hysteresis loop of ferromagnetic behavior with coercivity of 220 Oe and saturation magnetization of 107.17 emu/g, at 293 K. At 5 K, the obtained saturation magnetization of the sample was 102.16 emu/g. The production rate of FeNi3 nanoparticles was estimated to be about 6 g/h. This method has great potential in mass production of FeNi3 nannoparticles.

Stable multi-wavelength PM-EDF linear cavity laser employing a TCF fiber comb filter and an SNOLM

We propose and demonstrate a stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) linear cavity laser by using a twin-core fiber (TCF) comb filter and a symmetric nonlinear optical loop mirror (SNOLM). Using a homemade TCF, we fabricate a TCF comb filter with a channel spacing of 0.29 nm. By adjusting the polarization controllers (PCs) carefully, the polarization hole-burning effect in the PM-EDF is enhanced and intensity-dependent loss is produced by a nonlinear polarization rotation effect in the SNOLM. As a result, the homogeneous broadening gain medium is effectively reduced, and the mode competition of the EDF is distinctly suppressed. With only 100 mW pump power, up to 52-wavelength stable outputs with channel spacing of 0.29 nm have been achieved at room temperature. The power fluctuation and wavelength shift for each lasing wavelength are less than 0.1 dB and 0.02 nm in an hour, respectively. Experimental results illustrate that the proposed structure of a fiber laser can realize multi-wavelength outputs with high stability at lower pump power.

Experimental investigation of natural circulation in a symmetrical loop under large scale rolling motion conditions

In ocean environment, the ship motion significantly affects the natural circulation behavior in ship-based integrated-type reactor. This paper theoretically and experimentally investigated natural circulation characteristics in symmetrical loops under rolling condition. Experiments were carried out on a test loop with a symmetrical configuration by simulating the structure of an accrual reactor. The theoretical results revealed that only angular acceleration contributes to the resultant force under zero power rolling condition. In a closed circuit with a uniform cross-section area, the angular acceleration force integral is proportional to the angular acceleration and the area enclosed by the circuit. The integral value varies over time and causes flow oscillations. However, the angular acceleration force does not influence the flow status in the shared part of the two symmetrical neighbor circuits due to force interactions. Rolling experiments with a zero power load confirmed these results. Full power experiments under rolling condition exhibited observable flow rate and temperature oscillations in each branch of the flow channel. The oscillations in the side flow channels had the same values for both the period and the phase with the variation of rolling angle. The angular acceleration force was the main cause of this. The oscillations in the middle channel had a period half the value of the rolling period. The periodical variation of the vertical component of gravity caused this. The horizontal component of gravity was out-phasing with angular acceleration. Therefore, it alleviated oscillation in the side channels. The experimental results showed that for the same rolling period, as the rolling angle increased, the average flow rate decreased and oscillation amplitudes increased. Also, as the power load increased, the oscillations in the middle channel increased and the oscillation in the side channel decreased.

THE IMPORTANCE OF GEOMETRIC EFFECTS IN CORONAL LOOP MODELS

We systematically investigate the effects of geometrical assumptions in one-dimensional (1D) models of coronal loops. Many investigations of coronal loops have been based on restrictive assumptions, including symmetry in the loop shape and heating profile, and a uniform cross-sectional area. Starting with a solution for a symmetric uniform-area loop with uniform heating, we gradually relax these restrictive assumptions to consider the effects of nonuniform area, nonuniform heating, a nonsymmetric loop shape, and nonsymmetric heating, to show that the character of the solutions can change in important ways. We find that loops with nonuniform cross-sectional area are more likely to experience thermal nonequilibrium, and that they produce significantly enhanced coronal emission, compared with their uniform-area counterparts. We identify a process of incomplete condensation in loops experiencing thermal nonequilibrium during which the coronal parts of loops never fully cool to chromospheric temperatures. These solutions are characterized by persistent siphon flows. Their properties agree with observations (Lionello et al.) and may not suffer from the drawbacks that led Klimchuk et al. to conclude that thermal nonequilibrium is not consistent with observations. We show that our 1D results are qualitatively similar to those seen in a three-dimensional model of an active region. Our results suggest that thermal nonequilibrium may play an important role in the behavior of coronal loops, and that its dismissal by Klimchuk et al., whose model suffered from some of the restrictive assumptions we described, may have been premature.

Theoretical and experimental study on single-phase natural circulation under inclined conditions

The natural circulation reactor is widely used in marine environments where thermo-hydraulic performance is heavily affected by the heaving, pitching, and inclining of a ship. This paper theoretically and experimentally investigated steady-state single-phase natural circulation under inclined conditions. Results showed that energy transported by natural circulation was proportional to 1.5 times the power of the temperature difference between the hot leg and the cold leg. Furthermore, a parameter, k, was presented that revealed the comprehensive influence of working fluid properties, resistance characteristics, gravity fields, and loop configurations. k was treated as the criterion for the circulation ability of a loop and it also acted as the basis for evaluating and optimizing different designs. Analysis under the guidance of k was confirmed by a series of experiments performed on a symmetrical two-circuit loop. Both theoretical and experimental results showed that the inclination restrained overall circulation due to the decrease in average altitude difference between the steam generators and the electric heater. The disparity in branch circulations increased with the increase in the inclined angle. A loop design consisting of a large altitude difference and a small width was preferable to confine the influence of inclination. However, if the loop width was too small, it caused a severe reduction in the circulation ability for large angle inclinations.

The Characterization of the Variational Minimizers for Spatial RestrictedN+1-Body Problems

We use Jacobi's necessary condition for the variational minimizer to study the periodic solution for spatial restrictedN+1-body problems with a zero mass on the vertical axis of the plane forNequal masses. We prove that the minimizer of the Lagrangian action on the anti-T/2 or odd symmetric loop space must be a nonconstant periodic solution for any2≤N≤472; hence the zero mass must oscillate, so that it cannot be always in the same plane with the other bodies. This result contradicts with our intuition that the small mass should always be at the origin.

Dynamic mechanism of turbulent flow in meandering channels: considerations for deflection angle

To find turbulent flow structure inside meandering channels, three physical models of river meanders representing strongly curved bend, mild bend and elongated symmetrical meander loop were tested in this paper. Instantaneous velocity data in three dimensions were measured using Micro-ADV at different cross sections of these models. Depth averaged velocity vectors, streamwise velocity, secondary currents, turbulent and mean flow kinetic energy were investigated with respect to the sediment deposition pattern. In order to gain more regarding the force acting the sediment particles, three dimensional velocity fluctuations were analyzed in detailed inside the elongated symmetrical meander loop. Occurrence frequency, transition probability and angle of attack for different events were also computed for the points close to the bed. Of the present results, the importance of sweeps and ejections on sediment deposition can be detected. Further, distribution of bursting events is presented through the water column and compared the results with the previous works. Importantly, occurrence of fluctuating velocities in three dimensions at different locations inside the river meanders in addition to the effect of mean flow and turbulent components is responsible for sediment transport. Streamwise velocity distribution through the depth is also compared with some previous mathematical models. Researchers seeking the better control over the river morphology can apply this method without sacrificing much time and cost. This study is also included some insights to be pursued by future works.

Effect of thermal cycle on the interfacial antiferromagnetic spin configuration and exchange bias in Ni-Mn-Sb alloy

Effect of thermal cycle on the interfacial antiferromagnetic (AFM) spin configuration and exchange bias in Ni50Mn36Sb14 alloy has been investigated. The results indicate thermal cycle can induce further martensitic transition from part of arrested FM phase to AFM phase, leading to the reconstruction of interfacial antiferromagnetic spin configuration. The shape of hysteresis loops at 5 K after cooling back can be tuned from a single-shifted loop to a nearly symmetric double-shifted loop gradually accompanied with exchange bias field increasing to peak value and then decreasing. The evolutions can be illustrated intuitively by a simple AFM bidomain model.

Synthesis and properties of magnetic FeNi3 alloyed microchains obtained by hydrothermal reduction

In this paper, stoichiometric FeNi3 alloyed microchains were successfully synthesized via a simple hydrothermal method without surfactants or external magnetic fields. The effect of synthetic parameters, including citrate concentration, the reactant molar ratio and reaction time, on the formation and morphologies of the FeNi3 assemblies were investigated. The as-prepared chain-like structures were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Furthermore, magnetic measurements by superconducting quantum interference device were also carried out to explore their magnetic properties, which confirmed that the as-prepared samples had the symmetric hysteresis loop behavior of ferromagnetic materials.

THREE-DIMENSIONAL SIMULATIONS OF GYROSYNCHROTRON EMISSION FROM MILDLY ANISOTROPIC NONUNIFORM ELECTRON DISTRIBUTIONS IN SYMMETRIC MAGNETIC LOOPS

Microwave emission of solar flares is formed primarily by incoherent gyrosynchrotron radiation generated by accelerated electrons in coronal magnetic loops. The resulting emission depends on many factors, including pitch-angle distribution of the emitting electrons and the source geometry. In this work, we perform systematic simulations of solar microwave emission using recently developed tools (GS Simulator and fast gyrosynchrotron codes) capable of simulating maps of radio brightness and polarization as well as spatially resolved emission spectra. A 3D model of a symmetric dipole magnetic loop is used. We compare the emission from isotropic and anisotropic (of loss-cone type) electron distributions. We also investigate effects caused by inhomogeneous distribution of the emitting particles along the loop. It is found that effect of the adopted moderate electron anisotropy is the most pronounced near the footpoints and it also depends strongly on the loop orientation. Concentration of the emitting particles at the loop top results in a corresponding spatial shift of the radio brightness peak, thus reducing effects of the anisotropy. The high-frequency (around 50 GHz) emission spectral index is specified mainly by the energy spectrum of the emitting electrons; however, at intermediate frequencies (around 10-20 GHz), the spectrum shape is strongly dependent on the electron anisotropy, spatial distribution, and magnetic field nonuniformity. The implications of the obtained results for the diagnostics of the energetic electrons in solar flares are discussed.

멀티미디어단말기용 상하대칭 루프 안테나

본 연구는 얇은 유전체기판 위에 프린트 패턴으로 구현하는 상/하 대칭 루프안테나에 관한 것으로서, 유전체기판 상/하에 대칭으로 루프안테나용 동박패턴을 제작하여 기판의 상/하에 프린트된 루프패턴 간에서 방사되는 전자계가 서로 충돌하지 않게 방사되는 위상제어형 상/하 대칭 루프안테나에 관한 것이다. 이 방법으로 상/하에 프린트된 각 루프코일이 서로 동위상으로 보완적으로 배치되어 전자계가 원만하게 방사되어, 방사 손실이 없고 방사 효율이 뛰어나게 된다. 앓은 유전체기판의 상/하에 프린트하여 안테나를 구현함으로 연해 경박/소형화가 가능해지며, 이로 인하여 크기 <TEX>$40mm{\times}6mm$</TEX> 이하의 사이즈에, 두께 0.2mm 이하의 박막의 유전체가판에 제 3세대 휴대폰대역인 WCDMA 안테나를 구현하여 액티브 시험에서 평균게인 -3dBi 이상 방사효율 50~70% 정도의 안테나특성이 얻어졌으며, 상용되는 이동형 멀티미디어단말기에 부착하여 액티브 시험결과 평균게인 -4dBi, 송/수신 효율이 43% 얻어졌다. The paper is for top and bottom symmetrical phase controlled loop antenna using for multi-media devices. We developed a top and bottom phase control loop pattern arrangement methods for loop antenna in mobile devices like as a cell phone and PCS, WCDMA. In the loop antenna pattern, arrange close adhesive the loop antenna pattern <TEX>$180^{\circ}$</TEX> cycle in wave length, the radiated electro-magnetic wave from close adhesive loop pattern in <TEX>$180^{\circ}$</TEX> become to coherent wave than the phase controlled loop antenna has high efficiency and high radiation gain. To acquire a wide band width on phase controlled loop antenna, we arrange a top and bottom symmetrical architecture loop pattern that bas a <TEX>$180^{\circ}$</TEX> wave length in each layer. Top and bottom each layer bas a U form pattern separated <TEX>$90^{\circ}$</TEX> wave length each other. This architecture cause a well balanced electro-magnetic flow control that acquired wide bandwidth resonance response in loop pattern antenna. In experiment, we designed a WCDMA mobile multi-media antenna in <TEX>$40mm{\times}6mm$</TEX> area thickness 0.2mm, in that passive experiment the radiation efficiency is over 50% and over 0dBi radiation average gain was acquired, in the active experiment in real multi-media device we acquired -4dBi average gain and 43% transmit/receive efficiency.

The Effect of Monovalent Cations on the Thermal Stability of Small DNA Oligomers with Internal Loops

Although the effect of monovalent cations on the thermal stability of nucleic acid duplexes has been studied for many years, relatively little is known about cation effects on the stability of DNAs or RNAs with internal loops. We have therefore investigated the thermal stability of the DNA analog of the let-7 microRNA::lin-41 messenger RNA complex from C. elegans, which contains an asymmetric internal loop that kinks the helix backbone1. A DNA construct containing a symmetric internal loop at the same site was also studied, as well as a fully base-paired control. The melting temperatures of the two oligomers with internal loops are equal at low ionic strengths in solutions containing Na+ ions. However, the melting temperature of the oligomer with the asymmetric loop is ∼2°C higher in solutions with Na+ ion concentrations greater than ∼100 mM. The melting temperature of the oligomer with the asymmetric loop is also ∼2°C higher than the oligomer with the symmetric loop when the solution contains K+ ions. Binding studies indicate that both oligomers with internal loops, as well as the duplex control, bind Na+ ions weakly, with an average dissociation constant of 150 ± 10 mM. Hence, high concentrations of Na+ ions appear to stabilize DNAs with asymmetric internal loops, most likely because of electrostatic screening of the closely spaced phosphate groups near the kink site. Surprisingly, none of the oligomers bind K+ ions over the concentration range tested. Supported in part by the Analytical and Surface Chemistry Program of the National Science Foundation. 1 M. Cevec, C. Thibaudeau, J. Plavec (2008) Nucleic Acids. Res. 36, 2330-2337.

THE ROLE OF ACTIVE REGION LOOP GEOMETRY. II. SYMMETRY BREAKING IN THREE-DIMENSIONAL ACTIVE REGION: WHY ARE VERTICAL KINK OSCILLATIONS OBSERVED SO RARELY?

We present numerical results of simulations of kink oscillations of coronal loops in an idealized active region (AR) that is initialized as a potential dipole magnetic configuration with gravitationally stratified density. We consider loops, with density higher than the surrounding plasma, embedded into the dipolar AR. We study the excitation of kink oscillations of such loops by velocity pulses at different positions, of a given duration and amplitude. The position of the pulse varies in the parametric studies. For a central (symmetric) loop within the AR, we find that the amplitude of vertical kink oscillations is significantly amplified in comparison to horizontal kink oscillations for exciters located centrally (symmetrically) below the loop. For pulses initiated further from such a symmetric loop a combination of vertical and horizontal oscillations is excited. The scenario changes significantly when we study an inclined loop (non-symmetric within a dipole field). In this case, we do not see vertical kink oscillations of any significant amplitude being excited, while horizontal ones can be easily detected. These results indicate that the reason why vertical kink oscillations are observed so rarely is that their excitation requires a set of conditions to occur simultaneously: the exciting pulse must be located roughly below the loop apex and the loop itself must be located symmetrically within the group of loops. The new findings of the present study show the importance of not only the position of the pulse, but mainly of the location of the loop within the set of field lines having the same magnetic connectivity. We find that the slow propagating wave is excited in all the studied loops and its excitation does not depend either on the geometry of the loop or the pulse. We discuss TRACE observations of coronal loop oscillations in view of our findings and find that our results can be used for identifying the polarization of the kink mode based on the location of the loop within the set of field lines of the same connectivity and the position of the flare.

Fabrication and properties of solution processed all polymer thin‐film ferroelectric device

AbstractA ferroelectric device, making use of a flexible plastic, polyethylenterephtalate (PET), as a substrate was fabricated by all solution processes. PET was globally coated by a conducting polymer, poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) acid (PEDOT/PSSH), which is used as bottom electrode. The ferroelectric copolymer, poly(vinylidenefluoride–trifluoroethylene) (PVDF–TrFE), thin film was deposited by spin‐coating process from solution. The top electrode, polyaniline, was coated by solution process as well. The ferroelectric properties were measured on this all solution processed all polymer ferroelectric thin‐film devices. A square and symmetric hysteresis loop was observed with high‐polarization level at 15‐V drive voltage on a all polymer device with 700 Å (PVDF–TrFE) film. The relatively inexpensive conducting polyaniline electrode is functional well and therefore is a good candidate as electrode material for ferroelectric polymer thin‐film device. The remnant polarization Pr was 8.5 μC/cm2 before the fatigue. The ferroelectric degradation starts after 1 × 103 times of switching and decreases to 4.9 μC/cm2 after 1 × 105 times of switching. The pulse polarization test shows switching take places as fast as a few micro seconds to reach 90% of the saturated polarization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Hysteresis effects in the magnetic-field-induced reverse martensitic transition in magnetic shape-memory alloys

We study the mechanism of magnetic-field-induced reverse martensitic transformations by considering the field-induced temperature-shifts in the thermal hysteresis loop of the magnetization and critical fields determined from magnetization isotherms. We consider first the temperature-shifts in a symmetric thermal hysteresis loop and extend the discussion to the case of the Heusler-based Ni50Mn34In16 magnetically superelastic alloy having a nonsymmetric thermal hysteresis loop. We obtain two different temperature-behaviors for the critical field depending on whether the initial measurement temperature lies on the forward or on the reverse transformation path of the thermal hysteresis.

Flat broadband erbium-doped fiber ASE source based on symmetric nonlinear optical loop mirror

A new type of flat broadband Erbium-doped fiber (EDF) amplified spontaneous emission source is proposed and demonstrated. The intensity-dependent loss induced by a symmetric nonlinear optical loop mirror is used to flatten the spectrum and broaden the bandwidth. The 3 dB bandwidth over 50 nm has been obtained with 15 m EDF and 100 mW pump power based on the single-pass forward pump configuration. This spectrum flattening and broadening method is quite effective over a large range both in pump power and EDF length.

Solution structure of the cap-independent translational enhancer and ribosome-binding element in the 3' UTR of turnip crinkle virus.

The 3(') untranslated region (3(') UTR) of turnip crinkle virus (TCV) genomic RNA contains a cap-independent translation element (CITE), which includes a ribosome-binding structural element (RBSE) that participates in recruitment of the large ribosomal subunit. In addition, a large symmetric loop in the RBSE plays a key role in coordinating the incompatible processes of viral translation and replication, which require enzyme progression in opposite directions on the viral template. To understand the structural basis for the large ribosomal subunit recruitment and the intricate interplay among different parts of the molecule, we determined the global structure of the 102-nt RBSE RNA using solution NMR and small-angle x-ray scattering. This RNA has many structural features that resemble those of a tRNA in solution. The hairpins H1 and H2, linked by a 7-nucleotide linker, form the upper part of RBSE and hairpin H3 is relatively independent from the rest of the structure and is accessible to interactions. This global structure provides insights into the three-dimensional layout for ribosome binding, which may serve as a structural basis for its involvement in recruitment of the large ribosomal subunit and the switch between viral translation and replication. The experimentally determined three-dimensional structure of a functional element in the 3(') UTR of an RNA from any organism has not been previously reported. The RBSE structure represents a prototype structure of a new class of RNA structural elements involved in viral translation/replication processes.

MULTIBAND FOLDED LOOP ANTENNA FOR SMART PHONES

This paper presents a multiband folded loop antenna for smart phone applications. The proposed antenna with a symmetric loop pattern generates four resonance modes in the design bands. The current distributions of the excited resonance modes are analyzed to conflrm the mode characteristic. Using a pair of tuning elements near the feed port, the impedance bandwidth is broadened to cover GSM850/GSM900/DCS/PCS/UMTS bands. This research performed simulation by a high frequency structure simulator (HFSS) to optimally design the antenna, and a practical structure was constructed to test. The current study measured the antenna parameters including re∞ection coe-cient, radiation characteristics, peak gain, and radiation e-ciency to validate the proposed antenna.